Paleoarchean and Neoarchean Tonalite–Trondhjemite–Granodiorite (TTG) and granite magmatism in the Western Dharwar Craton, southern India: Implications for Archean continental growth and geodynamics

Journal Pre-proofs Paleoarchean and Neoarchean Tonalite–Trondhjemite–Granodiorite (TTG) and granite magmatism in the Western Dharwar Craton, southern India: implications for Archean continental growth and geodynamics Sameer Ranjan, Dewashish Upadhyay, Kumar Abhinay, Chikkahydegowda Srikantappa PII: DOI: Reference:

S0301-9268(19)30381-X https://doi.org/10.1016/j.precamres.2020.105630 PRECAM 105630

To appear in:

Precambrian Research

Received Date: Revised Date: Accepted Date:

1 July 2019 10 January 2020 21 January 2020

Please cite this article as: S. Ranjan, D. Upadhyay, K. Abhinay, C. Srikantappa, Paleoarchean and Neoarchean Tonalite–Trondhjemite–Granodiorite (TTG) and granite magmatism in the Western Dharwar Craton, southern India: implications for Archean continental growth and geodynamics, Precambrian Research (2020), doi: https:// doi.org/10.1016/j.precamres.2020.105630

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2020 Published by Elsevier B.V.

Paleoarchean and Neoarchean Tonalite–Trondhjemite–Granodiorite (TTG) and granite magmatism in the Western Dharwar Craton, southern India: implications for Archean continental growth and geodynamics

Sameer

Ranjan1,

Dewashish

Upadhyay1,

Kumar

Abhinay1,

Chikkahydegowda

Srikantappa2

1

Department of Geology and Geophysics, Indian Institute of Technology (IIT) Kharagpur, India

2

DOS in Earth Science, Manasagangotri, Mysore-570006, India

*Corresponding author: Dewashish Upadhyay Address: Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, 721302 Kharagpur, West Bengal, India Phone: +91–3222–283398 Fax: +91–3222–283372

1

Abstract The Western Dharwar Craton in southern India is underlain by Paleoarchean to Neoarchean granitoids. Here, we use major-trace element chemistry and zircon U-Pb-Hf isotopic composition to identify major components of the crust, constrain the timing of juvenile crust extraction, and discuss the implications for Archean tectonic processes. The granitoids are metaluminous to weakly peraluminous, magnesian and calcic. They were derived from basaltic protoliths with minor components sourced from pre-existing felsic crust. Low La/Yb and Sr/Y indicate shallow garnet-free plagioclase-bearing amphibolitic sources. The granitoids display large variations in concentration of trace elements, attributed to plagioclase accumulation or fluid-assisted mobilization of REEs during metamorphism. Zircon ages help to constrain four major episodes of granitoid crust formation at 3.43–3.41 Ga, 3.36–3.34 Ga, 3.29–3.26 Ga, and 2.66–2.65 Ga. The 3.43–3.41 Ga, 3.36–3.34 Ga, and 3.29–3.25 Ga granitoid suites have positive εHfi (2.7–4.5) and plot on a common εHfi vs. time trend consistent with repeated granitoid extraction at 3.43– 3.41 Ga, 3.36–3.34 Ga, and 3.29–3.25 Ga from mafic sources that separated from model depleted mantle between 3.55 Ga and 3.35 Ga. The εHfi (0.4–0.69) of the 2.66–2.65 Ga Neoarchean granitoids can be explained by melting of similar 3.35 Ga mafic crust or by mixing between juvenile magmas and preexisting granitoids. Uranium-Pb ages from metamorphic zircons indicate polyphase metamorphism of the granitoids at 3353–3329 Ma, 3264–3256 Ma, 3187–3141 Ma, 3083–3062 Ma, and 2574–2526 Ma. Hf-isotopic data from zircons in granitoids from several cratons indicate that prior to c. 3.5 Ga most granitoids have chondritic or crust-like εHfi explained by repeated granitoid extraction from long-lived mafic crusts with limited interaction with juvenile magmas. Juvenile εHfi and short protolith residence times of the Western Dharwar Craton Paleoarchean granitoids is suggestive of a tectonic setting with rapid recycling

2

of basalts as in subduction zones. In contrast, greater protolith residence times and crust-like signature of granitoids older than 3.5 Ga in the crustal record indicate a tectonic setting where basalts persisted for prolonged periods of times such as in an oceanic plateau.

Keywords Western Dharwar Craton; Paleoarchean-Neoarchean; low-P TTG; Granodiorite-granite; U-Pb-Hf isotope

1. Introduction The continental crust is the primary archive of the Earths geological history. Its formation and growth has been a protracted process that affected mantle composition, the evolution of the ocean and atmosphere system, and the emergence of life. Considerable debate exists on when and how the first continents formed, and how the processes of crust formation have changed over time (e.g., Stern, 2005; Harrison et al., 2008; Kemp et al., 2010; Hawkesworth et al., 2010; Condie and Kröner, 2013; Shirey and Richardson, 2011; Korenaga, 2013; Dhuime et al., 2015). Very little of the ancient continental crust survives today, preserved as Archean cratons in the cores of present-day continents. More than 50% of the existing Archean crust comprises Na rich tonalite-trondhjemite-granodiorites (TTGs) and K-rich granite-granodiorite-monzogranites, which represent the oldest felsic components of continents (e.g., Barker and Arth, 1976; Martin, 1987; Moyen, 2011; Moyen and Martin, 2012; Condie, 2014; Laurent et al., 2014). The geodynamic models of Archean TTG formation are controversial and invoke melting of subducted oceanic crust or arc crust in a subduction zone (e.g., Martin, 1986; Drummond et al., 1990; Nagel et al., 2012; Hoffmann et al., 2014), or melting of basalts at the base of thickened

3

oceanic plateaus (e.g., Smithies et al., 2009; Martin et al., 2014; Johnson et al., 2017). There is also increasing realization that Archean TTG formation was a complex process involving melting of metabasalt sources at multiple depths contemporaneously and under a range of geodynamic settings related to both subduction as well as non-subduction processes (Halla et al., 2009, Moyen, 2011; Moyen and Martin, 2012). The K-rich granite-granodiorite-monzogranites are hybrid granitoids that formed through mingling/mixing between magmas derived from TTGs, sanukitoids, and biotite- and two-mica granites (e.g., Laurent et al., 2014; Halla et al., 2017). The sparse preservation of the early granitic crust and the polyphase nature of its magmatic and metamorphic history with multiple components intricately intermixed/interlayered on centimeter to decimeter scale make the extraction of pristine petrological and isotopic information from it challenging. Owing to these inherent complexities, extrapolation of whole rock geochemical and isotope data back to primary magmatic compositions have remained a challenging task (e.g., Moorbath and Whitehouse, 1996; Moorbath et al, 1997; Vervoort et al., 1999; Kemp, 2018). However, micro-analytical techniques such as laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS), which allow spatially-resolved measurements of elemental and isotopic composition of targeted mineral growth domains such as those observed in zircon, is widely used for extracting crystallization age and petrogenetic information from granitoids with complex geological histories. The usefulness of zircon lies in its ability to preserve the chemical and isotopic record of multiple growth and reequilibration phases and its resilience to complete chemical and isotopic resetting even under high-grade conditions. The combination of U-Pb geochronology, Hf isotopic composition, and trace element chemistry of zircon from ancient TTGs or their remnants (as detrital zircon) can be used to constrain aspects of continental evolution, such as the timing of crustal growth/recycling, the tectonothermal

4

history, and the nature and age of the protoliths (e.g., Bowring et al., 1989; Nutman et al., 1996; Amelin et al., 1999; Mojzsis et al., 2001; Wilde et al., 2001; Iizuka et al., 2006; Harrison et al., 2008; Kemp et al., 2010; Bell et al., 2014; Reimink et al., 2014; 2016a, b; 2018a, b; 2019; Fisher and Vervoort, 2018; Kemp et al., 2019; Vezinet et al., 2018; Vezinet et al., 2019). The Western Dharwar Craton (WDC) in southern India (Fig. 1) is underlain by TTG gneisses and granodiorite-granites (Beckinsale et al., 1980; Taylor et al., 1984; Radhakrishna and Naqvi, 1986; Dhoundial et al., 1987; Meen et al., 1992; Peucat et al., 1993, 2013; Jayananda et al., 2008, 2015, 2018; Naqvi et al., 2009). Although the Paleoarchean to Neoarchean ancestry of the granitoids has been established (e.g., Beckinsale et al., 1980; Bhaskar Rao et al., 1991; Meen et al., 1992; Peucat et al., 1993, 2013; Naqvi et al., 2009; Jayananda et al., 2015; 2018; Guitreau et al., 2017), there is no clarity on the timing of major crust forming episodes, the nature and age of the crustal protoliths, and the broader implications for Archean geodynamics. In this study, we use zircon U-Pb isotopes, Hf isotopic composition, and trace element characteristics together with whole rock major and trace element measurements on TTG gneisses and granites from the WDC to identify the major components of the granitoid crust, constrain the nature of their protoliths (juvenile vs. recycled), and the timing of major crust extraction events in the craton. We also discuss the implications for Archean tectonic processes using a compilation of Hf isotope data on zircons in granitoids from several Archean cratons.

2. Geologic setting of the Dharwar Craton The Dharwar Craton is the largest cratonic nuclei of the Indian shield and hosts a typical Archean rock association comprising grey-gneisses, potassic granites and greenstone belt successions (Fig.1) (Beckinsale et al., 1980; Taylor et al., 1984; Radhakrishna and Naqvi, 1986;

5

Dhoundial et al., 1987; Meen et al., 1992; Peucat et al., 1993, 2013; Naqvi et al., 2009; Jayananda et al., 2008, 2015, 2018). The craton is subdivided into two units, namely the Western and the Eastern Dharwar Cratons separated by the Chitradurga Shear Zone (e.g., Jayananda et al., 2006; Chardon et al., 2008, 2011).

2.1. The Western Dharwar Craton The gneissic basement of the WDC, commonly referred to as the Peninsular Gneisses, comprises Paleo- to Mesoarchean (3.4–3.0 Ga) TTG suites and granites (Beckinsale et al., 1980; Taylor et al., 1984; Dhoundial et al., 1987; Meen et al., 1992; Peucat et al., 1993, 2013; Jayananda et al., 2008, 2015, 2018) (Fig. 1). The oldest (c. 3.40–3.28 Ga; Beckinsale et al., 1982; Meen et al., 1992; Peucat et al., 1993; Jayananda et al., 2015; Guitreau et al., 2017) components of the gneissic crust are exposed in the Gorur-Holenarsipur region. The basement gneisses are associated with two greenstone-type volcano-sedimentary successions that are sub-divided into an older amphibolite- to granulite-facies Sargur Group of Paleo- to Mesoarchean (c. 3.3–3.1 Ga) age, and a younger greenschist-facies Dharwar Supergroup of Neoarchean age (c. 3.0–2.6 Ga) (Swami Nath et al., 1976; Janardhan et al., 1979; Nutman et al., 1992; Bouhallier et al., 1993, 1995; Peucat et al., 1995; Ramakrishnan and Vaidyanadhan, 2008; Maibam et al., 2016, Lancaster et al., 2015; Jayananda et al., 2008, 2015). The Sargur-type greenstone sequences are well-preserved in the central and south-central parts of the craton and comprise quartzite, banded iron formation, metapelite, metacarbonate, metakomatiite and layered ultramafic-mafic igneous complexes. They are intensely deformed and metamorphosed at amphibolite to granulite facies conditions and display dome- and basin-like structures with the Peninsular Gneisses (Bouhallier et al., 1993, 1995; Chardon et al., 1996). Komatiites of the Sargur greenstone belts define an

6

imprecise Sm-Nd whole rock isochron age of 3352±110 Ma (MSWD=3.1) (Jayananda et al., 2008) while zircons in inter-bedded rhyolitic flows give an age of 3298±7 Ma (Peucat et al., 1995). Zircons from quartzites/pelites of the Sargur Group have U-Pb ages between 3.6 Ga and 3.2 Ga (Ramakrishnan et al., 1994; Maibam et al., 2011; Nutman et al., 1992; Hokada et al., 2013; Lancaster et al., 2015; Wang et al., 2019). The TTG-greenstone association is intruded by the 3.15 Ga Chikmagalur granite, the c. 3.0 Ga Bukkapatna granite (Chardon et al., 2011), and the 2.6–2.56 Ga Arsikere-Banavara, Chitradurga and Gadag potassic granites (Jayananda et al., 2006; Chardon et al., 2011; Mohan et al., 2014) which are thought to represent intracrustal melts of the older TTGs and lower crust (Taylor et al., 1984; Rogers, 1988; Jayananda et al., 2006, 2015, 2018). The Peninsular Gneisses and the Sargur Group supracrustal rocks are unconformably overlain by the Dharwar Supergroup deposited between c. 2.8 and 2.6 Ga (Nutman et al., 1996; Trendall et al., 1997a, b; Jayananda et al., 2013b). The Dharwar succession has been sub-divided into an older Bababudan Group and younger Chitradurga Group, the two being separated by a disconformity (Swami Nath and Ramakrishnan, 1981). The Bababudan Group has a basal oligomict conglomerate layer overlain by metabasalt interlayered with quartzite, phyllite, felsic volcanic rocks and banded iron formation. The basalts define whole-rock Sm-Nd isochron ages of c. 2.91–2.85 Ga (MSWD = 0.02–0.56) (Drury et al., 1983; Kumar et al., 1996) while zircons from volcanic tuff layers in the higher stratigraphic levels give an age of 2720±7 Ma (Trendall et al., 1997a). The Chitradurga Group begins with polymictic conglomerate followed by basalt, intermediate to felsic volcanic rocks and metasedimentary sequences including carbonate-greywacke-orthoquartzite-conglomerate-banded iron formation-phyllite. The basaltic

7

flows define whole-rock Sm-Nd isochron age of 2747±15 Ma (MSWD=0.62) (Kumar, 1996), while zircon from the felsic volcanic units give an age of 2677±2 Ma (Jayananda et al., 2013b).

2.2. The Eastern Dharwar Craton The Eastern Dharwar Craton is divided into two sub-provinces, the Central Dharwar Province and the Eastern Dharwar Province (Peucat et al., 2013; Jayananda et al., 2013a, 2018). The Eastern Dharwar province comprises 2700–2520 Ma TTGs, sanukitoids, calc-alkaline granites, and K-rich anatectic biotite granites interleaved with narrow c. 2.7 Ga greenstone belts dominated by greenschist to amphibolite facies metabasalts with subordinate komatiites and felsic volcanic rocks interlayered with iron formation, greywacke and pelite. The province lies to the east of the Kolar greenstone belt/Anantapur shear zone. The Central Dharwar Province comprises the area between the WDC and the Eastern Dharwar Province and is dominated by mixed older (3400–3200 Ma) and younger (2700–2520 Ma) crust that was remobilized at 2.56– 2.51 Ga. The three crustal provinces of the Dharwar Craton amalgamated at c. 2.5 Ga synchronously with the emplacement of the Closepet granite batholith in the Central Dharwar Province (Peucat et al., 1993, 2013; Jayananda et al., 2013a, 2018). The emplacement of mafic dyke swarms at c. 2.4 Ga, 2.2–2.0 Ga and c. 1.8 Ga mark the final phase of igneous activity in the craton (French and Heaman, 2010; Kumar et al., 2012a, b, 2014, 2015; Belica et al., 2014; Nagaraju et al., 2018a, b; Söderlund et al., 2019). The Dharwar Craton exposes an oblique tilted crustal section with low-grade greenschist facies granite-greenstone terrane in the north transitioning into amphibolite and granulite facies gneisses and supracrustal sequences to the south. The P-T conditions vary from about 4 kbar, 450°C in the north to 8 kbar, 800°C at the southern margin (Raith et al., 1983; Hansen et al.,

8

1984a, 1995; Raase et al., 1986). The amphibolite to granulite facies transition is marked by the orthopyroxene isograd followed by the development of massive charnockites to the south. The transition zone is characterized by the occurrence of migmatitic gneisses with orthopyroxene-bearing patches formed by dehydration melting in the presence of CO2-rich fluids (incipient charnockites) from lower crustal or mantle sources (Pichamuthu, 1960; Janardhan et al., 1979a, 1982; Hansen et al., 1984a, b, 1995; Stähle et al., 1987; Newton, 1990, 1992; Srikantappa et al., 1992; Peucat et al., 2013).

2.3 The marginal high-grade terranes and the Biligirirangan Hills The southern boundary of the Dharwar Craton is girdled by a series of complexly amalgamated microblocks. From west to east, these blocks include the Coorg Block, the Nilgiri Block, the Biligirirangan Block, and the Shevaroy Block (including Salem) (Samual et al., 2014; Santosh et al., 2015; Ratheesh-Kumar et al., 2016; Vijaya Kumar et al., 2017; Li et al., 2018a, b). They were welded together along a number of crustal-scale suture zones such as the Mercara, Moyar, Mettur, and the Nallamalai shear zones (Drury et al., 1984; Raith et al., 1999; Chetty et al., 2012; Santosh et al., 2015; Li et al., 2018b). The Biligirirangan Block comprises large charnockitic massifs with typical TTG affinities emplaced between 3.4 and 3.0 Ga. The charnockites record peak P-T conditions of 6.0–8.5 kbar and 750-850°C (Janardhan et al., 1982; Buhl, 1987; Peucat et al., 1989a, b; Mahabaleswar et al., 1995; Jayananda et al., 2000; Bhaskar Rao et al., 2003; Friend and Nutman, 1991; Mojzis et al., 2003; Chardon et al., 2011; Peucat et al., 2013; RatheeshKumar et al., 2016, Vijaya Kumar et al., 2017, Li et al., 2018a, b). The 2.56–2.51 Ga granulite

9

facies metamorphic overprint in the region was synchronous with the amalgamation of the Western and Eastern Dharwar Cratons.

3. Analytical techniques The granitoids were analyzed for their whole-rock major and trace element composition. Zircons were separated and analyzed for U-Pb-Hf isotopes and trace element composition. The details of the instrumentation, analytical conditions and data reduction protocols are described in the online supplementary material.

4. Results 4.1. Sample description and petrography Representative samples of TTGs and granites were collected from the Gorur-Holenarsipur region (WDS-18, 23A, 24, 26, 27, 28, 29, 30A, B, 31, 32) in the central part and the Sargur region (WDS-8, 10A, 10B) in the south central part of the Western Dharwar Craton. In addition, samples of granitoids and charnockitic gneisses were collected from the transition zone of the Central Dharwar Province (WDS-11A, B, C,) and the Biligirirangan Hills (WDS-16, 17) respectively, at the southern margin of the craton (Fig. 1). The sample details including their location, mineralogy, and petrographic description is given in Table 1 and illustrated in Figure 2. A detailed summary of the petrographic features of the granitoids from the four regions is given below.

4.1.1. Granitoids from the Gorur-Holenarsipur region

10

The granitoids of the Gorur-Holenarsipur region are finely-banded grey tonalitic and granodioritic gneisses. They are intruded by or interlayered with lighter deformed/folded trondhjemitic veins which give them a coarse banded appearance. The gneissic rocks are intruded by late grey granites and whitish grey and pink pegmatites. At places, they are interlayered with mafic rocks (amphibolite), or contain them as boudins and enclaves. In general, the granitoids comprise K-feldspars, plagioclase, quartz, biotite, muscovite, epidote, apatite, ilmenite, titanite, clinozoisite, zircon and allanite (Table 1). The tonalites from this region are characterized by a biotite-defined tectonic fabric that is overgrown by epidote/clinozoisite, titanite, and muscovite (Fig. 2a). The zircons associated with epidote show evidence of recrystallization with the igneous zones replaced by patchy recrystallized domains. The primary growth zoning often survives as small patches while the remaining parts of the grains display diffuse patchy zoning (Fig. 2a, inset). The trondhjemites have biotite- and muscovite-defined foliation that overgrows K-feldspar, plagioclase, quartz and ilmenite/iron oxide (Figs. 2b, c, d). The mica-defined fabric is overgrown by epidote, and titanite (Figs. 2b, d). Plagioclase shows textural evidence of metasomatic alteration with the altered patches appearing pitted and porous and albitic in composition (Fig. 2e). They are extensively replaced by K-feldspar, clinozoisite/epidote, titanite, and sericite (Figs. 2e, f, g). Apatites and ilmenites are replaced by allanite, zircon and HREE-rich Y-Yb oxide with fine veins of allanite within epidote (Figs. 2h, i, and d, i insets). The apatites and zircons are pitted and porous in nature (Fig. 2d). The granodiorites also possess a biotite-defined tectonic fabric which replaces K-feldspar, plagioclase, quartz and iron oxides. Anhedral zircons are closely associated with iron oxides and monazites (Fig. 2j, inset). Zircons usually have cores with traces of oscillatory zoning which are truncated by broad featureless metamorphic rims (Fig. 2j, inset). Plagioclase shows patchy

11

alteration and replacement by K-feldspar. The salient petrographic features of individual granitoid samples from the region are listed in Table 1.

4.1.2. Granitoids from the Sargur region The Sargur region is dominated by an association of tonalitic and trondhjemitic gneisses intruded by late-stage coarse pink granites. These granitoids contain plagioclase, quartz, hornblende (only in WDS-8), K-feldspar, apatite, allanite, epidote, titanite, zircon, monazite and iron oxides (Table 1). The tonalites have a gneissic layering defined by segregations of quartz- and feldspar-rich layers and hornblende-rich layers and often contain enclaves of amphibolites. The amphiboles grow as small patches in the plagioclase and quartz matrix (Fig. 2k). The high-grade gneissic fabric is overprinted by greenschist facies minerals such as epidote, titanite, allanite, K-feldspar, and sodic plagioclase. The cores of some zircons appear pitted/porous with the oscillatory zoning being partially erased (Fig. 2k inset). The trondhjemites from the Sargur region are weakly gneissic and lack any prominent banding. The tectonic fabric is defined by biotite which overgrows patchy K-feldspar, plagioclase, quartz and ilmenite. Titanite also replaces ilmenite (Fig. 2l). The trondhjemites are intruded by a network of coarse-grained pink granite and finegrained mafic dykes. The petrographic details of the individual samples studied from the region are listed in Table 1.

4.1.3. Granitoids from the transition zone of the Central Dharwar Province The trondhjemites from the transition zone of the Central Dharwar Province are strongly deformed and folded with a biotite-defined foliation. They contain plagioclase, K-feldspar, quartz, biotite, rare garnet, muscovite, epidote, allanite, clinozoisite, zircon and monazite. Biotite

12

and epidote/clinozoisite replace K-feldspar, plagioclase, and ilmenite (Fig. 2m). Plagioclase is pitted and porous and altered to albite along grain boundaries and fractures. The biotite-epidoteclinozoisite alteration is commonly associated with patches of allanite (Fig. 2m). The trondhjemites are intruded by coarse, deformed pink granite which also have a biotite-defined fabric. Apatites are often rimmed by secondary zircon and allanite (Fig. 2n). Fine veins or patches of allanite are seen in the vicinity of monazite and apatite (Fig. 2n). Further petrographic details of the samples are provided in Table 1.

4.1.4 Granitoids from the Biligirirangan Hills The Biligirirangan Hills in the southern part of the craton exposes an association of maficultramafic granulites, charnockites with TTG affinities, and meta-sedimentary rocks. The main rock types in the area are charnockites, granites, garnet-bearing gneisses, meta-gabbros and quartzites. The charnockites are trondhjemitic to granodioritic coarse-grained banded rocks comprising plagioclase, quartz, K-feldspar, orthopyroxene, biotite, zircon, monazite and iron oxides (Table 1). The banding in the granodiorites is defined by leucocratic layers rich in quartz, perthitic K-feldspar and plagioclase alternating with orthopyroxene-rich layers. Fine fibrous biotite overgrows the banding (Fig. 2o). Enclaves of amphibolites are common within the charnockitic gneisses. The trondhjemites from the region are strongly deformed, plagioclase feldspars are altered, and elongate quartz grains show recrystallization. The coarse plagioclase and quartz grains are extensively recrystallized to fine-grained aggregates along the grain boundaries. The petrographic detail of the individual samples from the Biligirirangan Hills is summarized in Table 1.

13

4.2. Major and trace element geochemistry On the basis of normative Ab-An-Or contents, the WDC granitoids are grouped as tonalites, trondhjemites, granodiorites and granites (Fig. 3a). The majority are trondhjemites (WDS-10A, 11B, 17, 24, 26, 27, 28, 29, 30A), with subordinate tonalites (WDS-8, 23A), granodiorites (WDS-16, 18, 31, 32), and granites (WDS-10B, 11A, 11C, 30B) (Fig. 3a). In Harker diagrams, the granitoids define trends with MgO, CaO, Al2O3, FeO, TiO2, Ni, La, and La/Yb decreasing with increasing SiO2 (Fig. 4, Table 2). The K2O is positively correlated with SiO2. The geochemistry of the granitoids is described in detail below in terms of their grouping into tonalite, trondhjemite, granodiorite, and granite.

4.2.1. Tonalites The tonalites have high SiO2 (71.7–72.7 wt. %), low to medium Na2O (2.21–3.84 wt. %) and K2O (0.26–1.43 wt. %) and low K2O/Na2O (0.12–0.37). The Al2O3 (13.3–14.28 wt. %) is slightly lower than typical sodic TTGs (Moyen and Martin, 2012). On the basis of their ASI [(Al2O3/CaO-3.33×P2O5+Na2O+K2O) = 0.86–0.95], A/CNK [Al2O3 (A)/ CaO (C) + Na2O (N) + K2O (K) = 0.84–0.94], Fe-number (0.71–0.73) and modified alkali-lime index (MALI), the tonalites are classified as metaluminous, magnesian and calcic (Fig. 3c, d, e). Their compositions plot in the field of melts derived from low-K mafic sources (Laurent et al., 2014) (Fig. 3b). The MgO (1.10–1.22 wt. %), Ni (11.2–24.9 ppm) and Cr (10.7–48.7 ppm) concentrations are low but show some variation (Table 2; Fig. 4a, e). The chondrite normalized REE patterns are enriched in the light-REEs (La = 21.7–33.4 ppm) and lack heavy-REE depletion (Yb = 1.27–1.41 ppm), resulting in moderately fractionated REE patterns (LaN/YbN = 11.6–16.1) (Fig. 5a). Europium anomalies are subtle but negative (Eu/Eu* = 0.77–0.80) (Fig. 4f; 5a). The REE patterns are

14

similar to the high-HREE Archean TTGs (Halla et al, 2009; Moyen and Martin, 2012). In multielement spider diagram, the rocks are characterized by negative Nb, Ta and Ti anomalies and positive Th anomalies (Fig. 5b). The Nb (5.69–6.75 ppm), Ta (0.41–0.61 ppm), and Y (13.0– 17.7 ppm) concentrations are high and the Nb/Ta ratios (11.1–13.8) are largely sub-chondritic. The La/Yb (17.1–23.7) and Sr/Y (14.7–16.0) is low and similar to low-P, high-HREE TTGs (Figs. 5a, b; 6a, b, c).

4.2.2. Trondhjemites The trondhjemites have high SiO2 (73.9–79.7 wt. %), moderate Na2O (4.41–5.11 wt. %), low K2O (0.89–2.72 wt. %), low K2O/Na2O (0.18–0.60) and variable Al2O3 (11.1–15.4 wt. %). They are magnesian and metaluminous to slightly peraluminous (ASI = 0.98–1.05; A/CNK = 0.97– 1.04) and calcic (Figs. 3c, d, e). They mostly plot in the field of melts derived from low-K mafic source with a few samples plotting in the field of melts derived from tonalites (Fig. 3b). The MgO (0.11–0.47 wt. %), Ni (2.1–6.6 ppm), and Cr (5.5–18.7 ppm) concentrations are low (Fig. 4a, e; Table 2). The REE patterns are moderately fractionated (LaN/YbN= 1.74–46.79) with large variation in REE concentrations (La = 4.14–127 ppm; Yb = 0.18–7.54) (Fig. 5c). The patterns are generally parallel to each other except for one sample which is concave upward and unusually enriched in the heavy REE (Fig. 5c; sample 11B). The LREE concentrations of some samples are significantly lower than those for typical TTGs/granites. The HREE contents span the entire range of low to high HREE TTGs (Halla et al., 2009) with some even more depleted than the low-HREE Archean TTGs (Fig. 5c; sample 10A, 27). Both positive and negative Euanomalies are observed (Eu/Eu*=0.68–3.11) and they are correlated with the REE concentrations, varying from highly negative to highly positive with decreasing REE (Fig. 5c, 5h

15

inset). In primitive mantle normalised multi-element spider diagram, most rocks display distinct negative anomalies in Nb, Ta and Ti and positive anomalies in Pb (Fig. 5d). The concentrations of Nb (1.1–26.6 ppm), Ta (0.14–2.22 ppm), and Y (2.1–100 ppm) are high but variable. The Nb/Ta (7.95–47.67) and the Sr/Y ratios (2.08–541) are also highly variable but within the range of low- to medium-P, high to transitional-HREE TTGs (Figs. 5c, d; 6a, b, c).

4.2.3. Granodiorites The granodioritic rocks have high SiO2 (72.9–75.4 wt. %), and moderate Na2O (3.41–3.75 wt. %) and K2O (2.95–3.43 wt. %). The K2O/Na2O ratios (0.80–0.93) and the Al2O3 (12.72–14.13 wt. %) are fairly low (Table 2). The A/CNK (0.94–1.02) and ASI (0.95–1.04) are moderate making them metaluminous to weakly peraluminous (Fig. 3e). On the basis of their Fe-number and MALI, they are classified as magnesian and calcic (Fig. 3c, d). They plot in the field of melts derived from high-K mafic sources (Fig. 3b). The MgO (0.45–0.77 wt. %), Ni (6.04–9.68 ppm), and Cr (7.7–14.9 ppm) concentrations are low (Fig. 4a, e; Table 2). The REE patterns are moderately fractionated (LaN/YbN = 11.6–42.0) and characterized by enrichment in the light REE (La = 19.1–35.9 ppm) (Fig. 5e). The LREE concentrations are similar to those of typical TTGs while the HREE (Yb = 0.38–1.12 ppm) show large variations bracketed between the low- and high-HREE TTG types (Fig. 5e). Europium anomalies are non-existent to slightly positive (Eu/Eu* = 0.96–1.24) (Fig. 5e, h inset). In multi-element spider diagram, the rocks are characterised by distinct negative anomalies in Nb, Ta, and Ti and positive anomalies in Pb (Fig. 5f). The Nb (2.33–6.74 ppm), Ta (0.08–0.23 ppm), and Y (8.05–9.13 ppm) concentrations are low and the Nb/Ta ratios (5.76–29.86) are variable. The La/Yb (17.1–61.8) and Sr/Y ratios

16

(19.3–84.4) are variable but within the range of low- and high-P, transitional to high-HREE TTGs (Fig. 6a, b, c).

4.2.4. Granites The granites have high SiO2 (75.1–79.7 wt. %), low to moderate Na2O (2.47–4.20 wt. %), moderate to high K2O (3.09–5.20 wt. %) and high K2O/Na2O (0.79–2.11). The Al2O3 (11.1–13.7 wt. %) is low, and the A/CNK (0.97–0.99) and ASI (0.98–1.00) values moderate, making them metaluminous (Fig. 3e; Table 2). On the basis of their Fe-number and MALI, they are magnesian and calcic (Fig. 3c, d). Their compositions plot in the field of melts produced from tonalitic source (Fig. 3b). The MgO (0.08–0.37 wt. %), Ni (2.29–3.39 ppm) and Cr (3.65–11.24 ppm) concentrations are low (Fig. 4a, e; Table 2). The REE patterns are weakly fractionated (LaN/YbN = 2.97–19.61) with the LREE concentrations of some granites being lower than those of typical TTGs (La = 6.76–19.2 ppm) (Fig. 5g). There is no depletion of the HREE (Yb = 0.67–2.43 ppm) with some samples being more enriched in the HREE compared to even the low-HREE TTGs (Fig. 5g). Both positive as well as negative Eu anomalies (Eu/Eu* = 0.37–1.59) are seen (Figs. 4f; 5g, h inset). In multi-element spider diagram, the granites are characterised by distinct negative anomalies in Nb, Ta, and Ti and positive anomalies in U and Pb (Fig. 5h). The Nb (1.28–5.43 ppm), Ta (0.17–0.73 ppm), and Y (7.63–20.76 ppm) concentrations are relatively low and the Nb/Ta (7.14–14.9) is subchondritic. The La/Yb (4.4–28.9) and the Sr/Y ratios (8.71– 40.2) are low and similar to those of low-P, high-HREE TTGs (Fig. 6a, b and c).

4.3. Zircon geochronology and Hf isotopic composition 4.3.1. U–Pb ages and Hf isotope composition

17

In this section, we describe the U-Pb ages, Hf isotope composition and trace element characteristics of different textural domains of zircons from individual samples. Both concordant as well as discordant ages were obtained from most samples. The discordant analyses are usually from recrystallized domains of grains affected by Pb-loss or represent mixed analyses of multiple age domains during the ablation process and are therefore not considered further for the discussion. Only the key trace element characteristics of the zircons are described here with further details on the composition of the oscillatory and recrystallized domains and the chemical screening procedure for identifying them being provided in the online supplementary file (Subsection 1.5.2).

4.3.1.1. WDS-8: Zircons in this tonalite from the Sargur region furnish five concordant age populations at 3414±5 Ma, 3353±6 Ma, 3264±10 Ma, 3154±11 Ma and 3065±14 Ma (Figs. 9a, b; Table 3). The 3414±5 Ma population corresponds to analyses from oscillatory-zoned cores or from domains with well-developed oscillatory growth zoning (Fig. 7 grain 1, 2, 3). These domains have strongly fractionated REE patterns with low LREE concentrations. The c. 3.35 Ga, 3.26 Ga, 3.15 Ga, 3.06 Ga dates were obtained from recrystallized/altered domains which are both bright with patchy appearance and erased oscillatory zoning, or have relatively low luminescence and appear porous and pitted in CL images (Fig. 7 grain no. 2, 3, 4, 5). These domains are enriched in LREEs and non-formula cations such as Ca, Fe, Sr and others (Fig. 8, Supplementary Fig. S5, Table S3). Only the oscillatory zoned domains were analyzed for their Hf isotopic compositions and the initial

176

Hf/177Hf, calculated at 3414 Ma, range between

0.280696 and 0.280719 (n=17) and define a single population with weighted mean of

18

0.280675±18 (2σ) (MSWD=5.1). The εHfi varies between 0.8 and 5.2 with a weighted mean value of 3.6±0.6 (2σ) (MSWD=4.3) (Table 3; Supplementary Fig. S3a, Tables S1a, S2a).

4.3.1.2. WDS-10A: The U-Pb dates from zircons in this trondhjemite from the Sargur region define four concordia age populations at 3420±8 Ma, 3329±8 Ma, 3256±9 Ma and 3156±63 Ma. A single analysis, possibly from a xenocrystic core, gives an older discordant 207Pb/206Pb date of 3606±24 (Fig. 7 grain 9; Fig. 9c, d; Table 3). The 3.42 Ga age populations correspond to domains preserving oscillatory zoning (Fig. 7 grain no. 6, 7, 8; Fig. 9d). The c. 3.33 Ga, 3.25 Ga, 3.15 Ga dates were obtained from domains showing evidence of recrystallization and alteration as seen from the lacking any clear oscillatory zoning and the diffuse or very bright CL response (Fig. 7 grain no. 7, 9, 10; Table 3). The oscillatory-zoned domains have strongly fractionated LREE-depleted REE patterns (Fig. 8a) and low concentrations of Fe, Ca, Sr and other nonformula cations. In contrast, the recrystallized domains have higher concentrations of LREE and non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). The initial

176

Hf/177Hf of the

zircons calculated at 3420 Ma varies between 0.280650 and 0.280746 (n=27) and define a weighted mean of 0.280694±13 (2σ) (MSWD=6.3). The εHfi ranges between 2.8 and 6.3 with a weighted mean value of 4.4±0.5 (2σ) (MSWD=4.7) (Table 3; Supplementary Fig. S3b, Tables S1b, S2b).

4.3.1.3. WDS-17: This is a trondhjemitic sample collected from the Biligirirangan Hills region. The U-Pb isotope ratios of zircons define concordia age populations at 3425±29 Ma, 3337±15 Ma, 3269±9 Ma, 3154±13 Ma, 3067–2947 Ma, 2773±32 Ma and 2562–2532 Ma (Fig. 10a, b; 19

Table 3). The 3425±29 Ma ages are from rounded inherited cores which appear dark in CL images (e.g. Fig. 7 grain 15). The 3337±15 Ma concordant population is from oscillatory-zoned domains (Fig. 7 grain no. 13, 15). The c. 3.26 Ga, 3.15 Ga, 3.06–2.94 Ga, 2.7 Ga, 2.56–2.53 Ga ages were obtained from recrystallized domains, characterized by chaotic, patchy zoning or faint partially-erased oscillatory zoning in CL images (Fig. 7 grain no. 11, 12, 14, 15). The trace elements compositions of the oscillatory-zoned domains are typical of igneous zircons while the recrystallized domains show slight enrichment in LREEs and other non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). The initial

176

Hf/177Hf of the oscillatory-zoned domains

(calculated at 3337 Ma) show slight variation (0.280606–0.280778, n=13) with a weighted mean value of 0.280703±26 (2σ) (MSWD=11.9). The εHfi varies from -0.7 to 5.4 with a weighted mean value of 2.7±0.9 (2σ) (MSWD=8.4), (Table 3; Supplementary Fig. S3c, Tables S1c, S2c).

4.3.1.4. WDS-28: This is a trondhjemite from the Gorur-Holenarsipur region. Zircons furnish concordant age populations at 3353±4 Ma, 3268±7 Ma, 3187±31 Ma, and 3083±16 Ma (Fig. 10c, d). The 3353±4 Ma age population was measured on oscillatory-zoned domains of the grains (Fig. 7 grain no. 16, 17, 18, 19) and was used for the calculation of initial 176Hf/177Hf and εHfi. The c. 3.26 Ga, 3.18 Ga and 3.08 Ga ages were obtained from recrystallized/altered domains. The recrystallized/altered domains have patchy distribution of bright and relatively dark domains. In some grains, irregular porous and pitted replacement fronts can be seen to have progressed inward from the grain margins (Fig. 7 grain no. 17, 18, 19). These domains are characterized by high LREE concentrations and enrichment in non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). The initial

176

Hf/177Hf ranges between 0.280667 and

0.280761 (n=11) with a weighted mean value of 0.280724±20 (2σ) (MSWD=3.5). The ɛHfi varies 20

between 1.9 and 5.4 with weighted mean value of 3.9±0.7 (2σ) (MSWD=3.1) (Table 3; Supplementary Fig. S3d, Tables S1d, S2d).

4.3.1.5. WDS-30B: Uranium-Pb analyses of zircons from this granite from the GorurHolenarsipur region furnish concordant age populations at 3334±11 Ma, 3221±37 Ma, 3150±21 Ma and 2638±32 Ma (Fig. 10c, d). The domains with oscillatory growth zoning correspond to the 3334±11 Ma age population (Fig. 7 grain no. 20, 21). The c. 3.22 Ga, 3.15 Ga and 2.63 Ga ages were calculated from analyses obtained from recrystallized and altered domains characterised by high concentrations of LREE and other non-formula cations. Such domains appear bright, and have chaotic and patchy zoning (Fig. 7 grain no. 22; Fig. 8, Supplementary Fig. S5, Table S3). The initial

176

Hf/177Hf (calculated at 3334 Ma) from oscillatory-zoned

domains vary between 0.280667 and 0.280777 (n=14) and define a population with weighted mean value of 0.280726±16 (2σ) (MSWD=3.4). The ɛHfi varies between 1.4 and 5.4 with a weighted mean value of 3.5±0.5 (2σ) (MSWD=2.9), (Table 3; Supplementary Fig. S3e, Tables S1e, S2e).

4.3.1.6. WDS-31: This is a granodiorite from Gorur-Holenarsipur region. The U-Pb spot ages define concordia age populations at 3342±10 Ma, 3258±10 Ma, 3153±38 Ma, and a relatively younger population at 2971±40 Ma (Fig. 10e, f; Table 3). The 3342±9 Ma ages were from the core parts of grains (Fig. 7 grain 23, 24) while the c. 3.25 Ga, 3.15 Ga, and 2.97 Ga age are from the rims or recrystallized domains (Fig. 7 grain no. 23, 24, 25). The recrystallized domains usually have higher LREEs and relatively flatter REE patterns, low luminescence and preserve ghost zoning. Such zones replace the oscillatory-zoned domains with irregular contacts (Fig. 7

21

grain no. 23, 24, 25, Fig. 8, Supplementary Fig. S5, Table S3). The initial

176

Hf/177Hf ratios

calculated at 3342±9 Ma varies between 0.280644 and 0.280797 (n=20) with a weighted mean value of 0.280742±23 (2σ) (MSWD=13). The ɛHfi varies between 0.80 and 6.3 with a weighted mean value of 4.2±0.8 (2σ) (MSWD=10.6) (Table 3; Supplementary Fig. S3f, Tables S1f, S2f).

4.3.1.7. WDS-32: This is a granodiorite collected from the Gorur-Holenarsipur region. The U-Pb spot ages define concordia populations at 3355±17 Ma, 3237±18 Ma, 3141±10 Ma, and a relatively younger population at c. 2927–3062 Ma (Fig. 10e, f; Table 3). The 3355±9 Ma ages are from core regions of the grains usually characterized by oscillatory zoning (Fig. 7 grain 26, 27, 28). The c. 3.23 Ga, 3.15 Ga, and 2.97–3.06 Ga ages were obtained either from rim regions or from altered/recrystallized domains as seen from their CL images and trace element compositions (Fig. 7 grain no. 26, 27, 28; Fig. 8, Supplementary Fig. S5, Table S3). These domains either constitute rims of grains with low CL response and no clear oscillatory zoning or form porous inclusion-rich domains in the interior of grains. The initial 176Hf/177Hf ratio at 3355 Ma range between 0.280644 and 0.280797 (n=12) with a weighted mean of 0.280731±34 (2σ) (MSWD=21). The ɛHfi varies between 0.80 and 6.25 with a weighted mean value of 4.1±1 (2σ) (MSWD=14), (Table 3; Supplementary Fig. S4a, Tables S1g, S2g).

4.3.1.8. WDS-18: Zircons from this granodiorite of the Gorur-Holenarsipur region define a single concordia age of 3289±6 Ma (Fig. 7 grain 29, 30, 31; Fig. 11a, b; Table 3). These ages correspond to domains with oscillatory zoning and with trace element compositions typical of igneous zircon with fractionated REEs patterns, low LREE concentrations and low concentrations of non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). The initial

22

176

Hf/177Hf calculated at 3289±6 Ma varies between 0.280706 and 0.280808 (n=20) with a

weighted mean of 0.280745±13 (2σ) (MSWD=3.5). The ɛHfi varies between 1.8 and 5.4 with a weighted mean value of 3.2±0.5 (2σ) (MSWD=3.0), (Table 3; Supplementary Fig. S4b, Tables S1h, S2h).

4.3.1.9. WDS-24: Zircons in this trondhjemite from the Gorur-Holenarsipur region furnish concordant age populations at 3343±20 Ma, 3263±8 Ma, and 3154±21 Ma (Fig. 11c, d; Table 3). The 3343±20 Ma age is from a single zircon core possibly of xenocrystic origin. The 3263±8 Ma ages were obtained from domains having oscillatory zoning (Fig. 7 grain no. 33; Fig. 11d). The c. 3.15 Ga ages are from altered and recrystallized domains having high concentrations of LREEs, Ca, Fe, Sr and Y. The CL response of such zones is low and they appear porous and pitted in CL images (Fig. 7 grain no. 32, 33; Fig. 8, Supplementary Fig. S5, Table S3). The initial 176

Hf/177Hf (calculated at 3268 Ma) varies between 0.280699 and 0.280826 (n=14) and defines a

weighted mean value of 0.280761±22 (2σ) (MSWD=6.6). The ɛHfi ranges between 0.9 and 5.4 with a weighted mean value of 3.1±0.8 (2σ) (MSWD=5.7), (Table 3; Supplementary Fig. S4c, Tables S1i, S2i).

4.3.1.10. WDS-27: This is a trondhjemite from the Gorur-Holenarsipur region. The concordant ages calculated from the U-Pb isotope ratios are 3260±13 Ma, 3149±15 Ma, and 3073–3009 Ma (Fig. 11c, d; Table 3). The 3260±13 Ma is the major concordant population and was measured on domain with oscillatory zoning (Fig. 7 grain no. 34, 35; Fig. 11d). The c. 3.15 Ga, and 3.07–3.0 Ga ages were obtained from altered/recrystallized domains having relatively high concentrations of LREEs and other non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). In CL 23

images these domains appear as patchily zoned and chaotic (Fig. 7 grain no. 34, 35). The initial 176

Hf/177Hf of the zircons at 3260 Ma vary between 0.280741 and 0.280853 (n=13) and furnish a

weighted mean value of 0.280800±24 (2σ) (MSWD=5.3) .The ɛHfi varies between 2.3 and 6.3 with a weighted mean value of 4.4±0.8 (2σ) (MSWD=4.3) (Table 3; Supplementary Fig. S4d, Tables S1j, S2j).

4.3.1.11. WDS-23A: This is a tonalite from the Gorur-Holenarsipur region. The U-Pb spot ages define populations at 3268±6 Ma, 3167±11 Ma, and c. 3082 Ma (Fig. 11c, d; Table 3) of which the 3266±5 Ma population defines a major peak in age probability density/histogram plot. This population corresponds to domains having oscillatory zoning and trace element characteristics typical of igneous zircon (Fig. 7, 36, 37; Fig. 11d). The c. 3.16 Ga, 3.08 Ga ages were obtained from recrystallized/altered domains having relatively high LREE, Ca, Fe, and Sr (Fig. 8; Supplementary Fig. S5, Table S3). The recrystallized/altered parts are porous and pitted and have low cathodoluminescence with fuzzy and patchy zoning (Fig. 7 grain no. 37, 38). The initial 176

Hf/177Hf at 3268 Ma varies between 0.280674 and 0.280837 (n=14) with a weighted mean

value of 0.280770±26 (2σ) (MSWD=7). The ɛHfi varies between 0.08 and 5.9 with a weighted mean value of 3.5±0.9 (2σ) (MSWD=6.1), (Table 3; Supplementary Fig. S4e, Tables S1k, S2k).

4.3.1.12. WDS-16: The zircons in this granodiorite from near the Biligirirangan Hills furnish concordant ages of 2935±24 Ma, 2831±25 Ma, 2660±4 Ma, and 2526±24 Ma (Table 3). The 2660±4 Ma is the most prominent age peak in the concordia and relative age probability density/histograms plot and were largely derived from oscillatory-zoned igneous domains (Fig. 7 grain no. 39, 40; Fig. 12a, b). The c. 2.52 Ga ages were obtained from grain rims which appear

24

bright in BSE images (Fig. 7 grain no. 41). The oscillatory-zoned zircons have fractioned REE patterns with low LREE concentrations (Fig. 8, Supplementary Fig. S5, Table S3). Hafnium isotope analyses on the oscillatory-zoned domains furnish initial

176

Hf/177Hf (calculated at 2660

Ma) between 0.281050 and 0.281149 (n=13) which define a weighted mean value of 0.281095±18 (2σ) (MSWD=3.8). The ɛHfi ranges from 2.6 to -0.9 with a weighted mean value of 0.7±0.7 (2σ) (MSWD=3.3) (Table 3; Supplementary Fig. S4f, Tables S1l, S2l).

4.3.1.13. WDS-10B: The zircons in this granitic sample from the Sargur region are highly altered. Most spot analyses are discordant (118 out of 128 spots are discordant). The few concordant analyses define two concordia age populations at 2649±13 Ma and 2574±15 Ma. Several of the discordant analyses have 207Pb/206Pb ages close to 2.4 Ga (Fig. 7 grain no. 42, 43, 44, 45; Fig. 12c, d; Supplementary Table S1m). The least altered domains corresponding to the 2649±13 Ma age population have REE patterns like igneous zircons. In contrast the altered/recrystallized domains show enrichment in LREEs and other non-formula cations (Fig. 8, Supplementary Fig. S5, Table S3). In BSE images two types of domains can be identified, one appears bright and the other relatively dark. The original oscillatory zoning show replacement by altered domains at some places (Fig. 7 grain no 42, 43, 44, 45). A single concordant age of 3343±34 Ma was obtained from the core of one grain (Fig. 7 grain no. 42, 43). This is possibly of xenocrystic origin has ɛHfi (calculated at 3.3 Ga) of 2.7±1.8, identical to those of zircons from the 3.29–3.25 Ga granitoid suite (Fig. 13). The initial

176

Hf/177Hf (calculated at 2649 Ma) shows

a large variation (0.281201–0.280992, N=7) with a weighted mean of 0.281093±70 (2σ) (MSWD=21). The ɛHfi values range from 4.2±1.2 to -3.2±1.4 (weighted mean =0.4±2.5, 2σ,

25

MSWD=19) (Fig. 13). Most of these zircons have relatively high 176

176

Yb/177Hf (0.09–0.45) and

Lu/177Hf (0.002–0.008) ratios (Table 3; Supplementary Fig. S4g, Tables S1m, S2m).

5. Discussion 5.1. Major and trace element constraints on the petrogenesis of the TTGs and granites The WDC granitoids display large variations in SiO2, Al2O3, REEs, and other trace element concentrations. In general, all are metaluminous to weakly peraluminous and therefore derived from the protoliths similar to I-type granitoids. The majority of the granitoids plot in the field of melts derived from mafic protoliths which suggests that they were largely derived from juvenile sources (Fig. 3b). The well correlated trends of major oxide with SiO2 and the low MgO, Ni, and Cr concentrations indicate that the parental magmas underwent significant fractional crystallization (Fig. 4) with tonalites representing the most primitive end members. Some of the granites and trondhjemites are possibly the products of fractionated tonalitic magma. The tonalites have REE patterns typical of high-HREE TTGs (Halla et al., 2009) with slight negative Eu anomalies which suggests that their parental magmas were derived by shallow-level partial melting of a garnet-free plagioclase-bearing amphibolitic source. This is generally true for the other granitoids which are characterized by moderately fractionated REE patterns, low La/Yb, low to moderate Nb/Ta, and low Sr/Y ratios. Similar REE patterns with large variation in the HREE concentrations in the granitoids from the WDC have been reported by earlier studies (Dhoundial et al., 1987; Bhaskar Rao et al., 1991; Devaraju et al., 2007; Naqvi et al., 2009; Jayananda et al., 2015) (Fig. 5). Several of the granitoids, particularly from amongst the trondhjemites and the granites, are unusually depleted in the REEs and other incompatible elements (e.g., samples WDS-24, 26,

26

11B, 27, 10B, 30B). Their REE and multielement patterns are not typical of Paleoarchean granitoids. Jayananda et al. (2015) reported similar poorly fractionated relatively flat REE patterns for several gneisses from the Gorur-Holenarsipur region which they attributed to LREEand LILE-depleted source and a significant role of plagioclase as residue or fractionating phase. These authors also reported the presence of granitoids with anomalously low LREE, and with HREE enrichment, similar to what we see in our trondhjemite, which they attributed to depleted source without any significant role of plagioclase and garnet in the residue. In summary, Jayananda et al. (2015) attributed the variable and anomalous trace element signatures of the WDC granitoids to be the effects of fractional crystallization or residual mineralogy of the source. In the studied TTGs and granites, the degree of REE depletion correlates with the extent of positive Eu anomaly (Fig. 5h inset) and the SiO2 (Fig. 4f), which indicates that the unusual trace element depletion in some of the granitoids may be due to alteration of the primary TTG melt signature by variable amounts of feldspar accumulation (Fig. 6d). Laurent et al. (2019) invoke a similar process of variable extents of plagioclase accumulation to explain the large compositional range of co-genetic and coeval Paleoarchean trondhjemites from the Barberton terrane, southern Africa. These authors use textural and geochemical evidence to show that the Barberton granitoids represent a plagioclase-rich silicic crystal mush containing interstitial granitic liquid and are therefore not melt compositions. Some of the LREE-depleted trondhjemites show unusual HREE enrichment resulting in concave upward REE patterns (e.g., sample WDS-11B, Fig. 5c), a feature noted by Jayananda et al. (2015) as well. Others are unusually enriched in the REE. The petrographic features described earlier indicate that several of these granitoids are affected by post-emplacement metasomatic

27

alteration which may have caused extensive fluid-assisted mobilization of REE from the rocks as evidenced by the extensive alteration of apatite, ilmenite, and zircon, and the precipitation of secondary allanite, zircon and Y-Yb oxide (Fig. 2). The unusual REE patterns shown by some of these granitoids are therefore attributed to open system alteration of the rocks under lowtemperature fluid-rich conditions.

5.2. U-Pb-Hf isotope constraints on the formation and evolution of the Archean granitoid crust in the Western Dharwar Craton The U-Pb isotopic measurements furnish concordant as well as discordant dates. Given that the zircons show microtextural evidence for recrystallization and fluid-induced reequilibration, only concordant analyses from oscillatory-zoned domains with igneous zircon-like trace element characteristics were used for constraining emplacement ages and retrieval of Hf-isotopic petrogenetic information. The granitoids do not show any systematic correlation between chemical composition (major and trace elements)/granitoid type and emplacement ages. Therefore, the age and Hf isotope data is discussed by clubbing the granitoids into different age groups based on their inferred crystallization ages. The 3414±5 Ma and 3420±8 Ma ages obtained on oscillatory-zoned domains/zircon grains with igneous zircon-like trace element characteristics from the tonalite (WDS-8) and trondhjemite (WDS-10A) respectively of the Sargur region are inferred to date their emplacement. (Fig. 7 grain no. 1, 2, 3, 7, 8, 9, 10; Fig. 9; Table 3). These granitoids are therefore considered to be a part of the 3.43–3.41 Ga TTG suite. Zircons from the trondhjemite (WDS-28), granodiorites (WDS-31, 32), and granite (WDS-30B) from the Gorur-Holenarsipur region and trondhjemite (WDS-17) from transition

28

zone of the Central Dharwar Province furnish ages of 3353±4 Ma (WDS-28), 3342±10 Ma (WDS-31), 3355±17 Ma (WDS-32), 3334±11 Ma (WDS-30B) and 3337±15 Ma (WDS-17) from oscillatory-zoned domains (Fig. 7 grain no 15, 16, 21, 23, 27, 28; Fig. 10; Table 3). Such domains are characterized by trace element signatures typical of igneous zircons. These granitoids are grouped together as part of the 3.36–3.34 Ga TTG and granite suite. An age of 3425±29 Ma from a CL-dark rounded core of a zircon from WDS-17 of this suite is interpreted to be of inherited origin (Fig. 7 grain no. 15). Oscillatory-zoned domains in zircons from the tonalite (WDS-23A), trondhjemite (WDS24, 27), and granodiorite (WDS-18) from the Gorur-Holenarsipur region furnish ages of 3268±6 Ma (WDS-23A), 3263±8 Ma (WDS-24), 3260±13 Ma (WDS-27), and 3289±6 Ma (WDS-18). The ages correspond to igneous domains and are interpreted as the crystallization ages of the granitoids (Fig. 7 grain no. 29, 30, 31, 33, 35, 36, 37; Fig. 11a–d; Table 3). Accordingly, these granitoids are grouped together as members of the 3.29–3.25 Ga TTG and granite suite. An age of 3343±20 Ma from a zircon from the trondhjemite WDS-24 is interpreted as inherited. The 2.67–2.65 Ga TTG and granite suite includes the granite WDS-10B from the Sargur region and a granodiorite WDS-16 from the transition zone of the Central Dharwar Province. The zircons from the Central Dharwar Province granodiorite preserve igneous cores that are truncated by metamorphic rims which are CL-bright and display chaotic and patchy zonation (Fig. 7 grain 39, 40, 41). In contrast, the zircons from the Sargur region granite are highly altered, with the majority being discordant (118 out of 128 spot analyses are discordant). The 2660±4 Ma and 2649±13 Ma zircon ages from WDS-16 and WDS-10B respectively represent the predominant populations recovered from relatively pristine oscillatory-zoned domains and are interpreted as their emplacement ages. The c. 2.93 Ga and 2.83 Ga ages are from xenocrystic

29

cores in the granodiorite. A single older age of 3343±34 Ma from a zircon in the granite is also from an inherited core (Fig. 7 grain 42, 43). In summary, the zircon U-Pb ages from the granitoids help to constrain four major phases of granitoid magmatism at 3.43–3.41 Ga, 3.36– 3.34 Ga, 3.29–3.25 Ga, and 2.66–2.65 Ga in the Western Dharwar Craton. Zircons in granitoids from the 3.43–3.41 Ga, 3.36–3.34 Ga, and 3.29–3.25 Ga suites have positive εHfi which suggests that the basaltic sources of these granitoids had little crustal residence time (<250–100 Ma). The εHfi of the 3.43–3.41 Ga suite (3.6–4.4), 3.36–3.34 Ga suite (2.7–4.1), and of the 3.29–3.26 Ga (3.1–4.5) Paleoarchean suites plot on a common εHfi vs. time trend which can be explained by repeated partial melting and granitoid extraction at 3.43–3.41 Ga, 3.36–3.34 Ga, and 3.29–3.25 Ga from mafic sources that separated from the depleted mantle at c. 3.55 Ga (Fig. 13b). The 3.29–3.25 Ga suite also contains granitoids with more radiogenic εHfi (3.1–4.5) which requires a juvenile component extracted from the depleted mantle at c. 3.35 Ga. The εHfi of the 2.66–2.65 Ga Neoarchean granitoids (0.4–0.69) can be explained by melting of the same mafic crust that was the source of the more radiogenic members of the 3.29–3.26 Ga suite at c. 2.66 Ga. Alternatively, the chondritic εHfi of these granitoids may be due to mixing between juvenile magmas and melts derived from the preexisting Paleoarchean granitoids (Fig. 13a, b).

5.3. Comparison with existing Nd-Hf isotope data from the TTGs and granites The whole rock initial

143

Nd/144Nd of the Paleoarchean (3.35–3.20 Ga) granitoids of the WDC

show relatively large variations in εNdi (+3.0 to -2.8 at 3.3 Ga; Jayananda et al., 2015). The excursion to negative values has been interpreted to be reflecting the involvement of pre-existing granitoid crustal contamination in the source of these TTGs (Jayananda et al., 2015). The

30

depleted mantle-like εHfi of the 3.43–3.25 Ga granitoids described above, and the absence of negative values precludes any significant recycling of felsic crustal material during their formation. Any minor TTG contaminant most likely had too short crustal residence ages to affect the Hf isotope compositions. The reason for the discrepancy between the earlier Nd-isotope data and our zircon Hf-isotope data is not clear. A number of other studies (e.g., Meen et al., 1992; Bhaskar Rao et al 2008; Guitreau et al., 2017) have also argued for the involvement of ancient crustal precursors in the origin of the TTG suites in the Gorur-Holenarsipur area. It appears that there is considerable heterogeneity in the mineralogy and chemistry of the granitoid suites and that we may not have sampled granitoids affected by crustal contamination/recycling. There is very little Hf isotopic data on the granitoids of the WDC except for the study by Guitreau et al. (2017), who reported limited U-Pb ages and Hf isotope compositions of zircons from granitic and trondhjemitic gneisses and biotite-rich enclave from the Holenarsipur area. These authors measured εHfi of 2.2 ± 0.6 for c. 3.41 Ga granite gneiss which is identical to the values reported by us for the 3.43–3.41 Ga granitoid suite. Guitreau et al. (2017) chose to interpret these gneisses to have formed by reworking of a felsic precursor with short crustal residence time based on the presence of muscovite and the peraluminous nature of the gneiss. However, none of granitoids from the Gorur-Holenarsipur belt studied by us (ten in total) are peraluminous. They are metaluminous to weakly peraluminous in nature. Moreover, detailed petrographic studies using an SEM (Fig. 2b, c, d, g and h) reveals that muscovite is a secondary phase that grew during greenschist facies overprint of these rocks. Therefore, we consider the positive εHfi of the 3.43–3.41 Ga granitoids to be reflecting the juvenile nature of their protoliths, rather that reworking of a felsic precursor with short crustal residence.

31

Guitreau et al. (2017) reported unusually high εHfi (up to +10.4) for 3.41 Ga inherited zircons in 3.18 Ga trondhjemitic gneisses which they attributed to a strongly depleted mantle source for the protoliths of the 3.41 Ga granitoids. However, zircons from the 3.43–3.41 Ga granitoids that we studied have significantly lower mean εHfi (3.6–4.4), similar to those of the model DM which does not support the extreme mantle depletion postulated by Guitreau et al. (2017). Rather, the moderately positive εHfi of the 3.43–3.25 Ga granitoids point towards moderate mantle depletion during the Paleoarchean, consistent with the highest εNdi of c. 3.0 reported for some of the granitoids (Dey et al., 2013; Jayananda et al., 2015). The Nd-Hf isotope data from TTGs of the nearby Singhbhum Craton in eastern India also support only moderate depletion of the Paleoarchean mantle (Dey et al, 2017, 2019; Pandey et al., 2019; Upadhyay et al., 2019). The unusually high εHfi of the 3.41 Ga inherited zircons, which were markedly different from the younger Paleoarchean granitoids, led Guitreau et al. (2017) to postulate a rather complicated model for the growth and accretion of the WDC involving formation of 3.41– 3.20 Ga cratonic nuclei in a remote location away from continental crust followed by accretion at c. 3.20 Ga with a crustal block containing >3.41 Ga zircons. The Hf isotopic data that we present does not require any such exotic model for the growth of the WDC granitoid crust. Rather, our dataset attests to a far simpler evolution of the WDC continental crust involving two major episodes of Paleoarchean juvenile mafic crust extraction events from the mantle between 3.55 Ga and 3.35 Ga and repeated granitoid extraction from these mafic sources at 3.43–3.41 Ga, 3.36– 3.34 Ga, 3.29–3.25 Ga, and 2.66–2.65 Ga (Fig. 13). Recycling of felsic crust during the Paleoarchean granitoid forming events was minor as seen from the positive εHfi of the zircons and the scarce occurrence of inherited zircons within the granitoids.

32

Our Hf isotope data and the existing Nd isotope data from TTGs and granites indicate that most of the felsic crust in the WDC formed after c. 3.43 Ga. However, the presence of 3.61 Ga inherited zircon with εHfi of -2.3 in trondhjemites from Holenarsipur and some of the negative ɛNdi values reported for c. 3.3 Ga granitoids (Jayananda et al., 2015; Guitreau et al., 2017) points towards the existence of an earlier Eoarchean granitic crust whose protoliths were extracted from the depleted mantle between 3.7 Ga and 4.0 Ga. The report of 3.60–3.56 Ga detrital zircons in metasediments (Nutman et al., 1992; Bhaskar Rao et al., 2008; Sarma et al., 2012; Lancaster et al., 2015) from the Western Dharwar Craton also support the existence of an earlier felsic crust. However, this earlier crust did not contribute in any significant way to the formation of the Paleoarchean granitoids.

5.4. Zircon textures, U-Pb ages, and trace element constraints on metamorphic overprint on the granitoids There is ample evidence for recrystallization and neo-crystallization of metamorphic zircon in the TTGs and the granites (Fig. 2). The newly crystallized metamorphic zircons appear as micron-sized grains distributed throughout the rock matrix but mostly associated with amphiboles, epidote, ilmenite, apatite, monazite, allanite and Y-Yb oxide phases (Fig. 2, a, d, h, j and n). The growth of such zircons is attributed to the expulsion of Zr, REEs and other trace elements during metamorphic reequilibration/fluid-induced alteration of magmatic minerals like amphiboles, pyroxene, apatite, and ilmenite which commonly incorporate significant amounts of these elements in their structure at higher temperature (Fraser et al., 1997; Degeling et al., 2001; Bingen et al., 2004; Ayers et al., 2012; Ewing et al., 2013, Hermann and Rubatto, 2014; Kohn et al., 2015).

33

Several of the zircons analyzed exhibit complex recrystallization/reequilibration and alteration textures (Fig. 7) which is also reflected in their widely variable REE and trace element chemistries

(Fig.

8,

Supplementary

Fig.

S5,

Table

S3).

The

recrystallized

and

altered/pitted/porous domains are usually discordant and have significantly elevated LREE concentrations (Fig. 8a, b) and show enrichment in non-formula cations such as Na, Ca, Sr, Al, Fe, Nb, Ta and Ca (Supplementary Fig. S5, Table S3). Their REE patterns are flat to concave upward, typical of altered/recrystallized zircons (e.g., Long et al., 2012; Zeh et al., 2014; Kovaleva et al., 2017; Ranjan et al., 2018) (Fig. 8a, b). Such textures and chemistries are indicative of extensive fluid-induced alteration of radiation-damaged metamict zircon (e.g., Fig. 7 grain no. 5, 19, 38, 40, 44, 45) (Geisler et al., 2003a, b, 2007) through a diffusion-controlled recovery recrystallization process in the presence of aqueous fluids (Geisler et al., 2003c; Romano et al., 2004; Rayner et al., 2005; Nasdala et al., 2010). Such fluids appear to have played a key role in the alteration of zircons in the WDC granitoids and the precipitation of micro- to nanometer-sized inclusions of thorite, coffinite, xenotime, thortveitite, (Sc2Si2O7), keiviite, yttrialite (Y2Si2O7) etc. in them. They were also responsible for the alteration of apatite and ilmenite and precipitation of secondary allanite, monazite, and Y-Yb oxide phases (Fig. 2) (e.g., Spandler et al., 2004; Xie et al., 2005; Soman et al., 2006). Majority of the U-Pb isotopic analyses from the recrystallized domains furnish discordant ages. This is attributed to partial loss of radiogenic Pb or sampling of mixed pristine and reequilibrated domains during the ablation process and therefore has no geological significance. However, concordant dates were recovered from recrystallized and reequilibrated domains in several samples. These are possibly from metamorphic grains/domains where the U-Pb isotopic system was completely reset during metamorphism or fluid-induced alteration. Such dates,

34

whenever found to be consistent across several samples, are considered to be geologically meaningful and interpreted to date the timing of metamorphism/fluid-induced alteration. Recrystallized/altered zircon domains furnish concordant ages of 3353–3329 Ma, 3264– 3256 Ma, 3187–3141 Ma, 3083–3062 Ma, c. 2638 Ma and 2574–2526 Ma from different samples studied across the WDC (Figs. 9, 10, 11, 12; Table 3). The 3353–3329 Ma and 3264– 3256 Ma metamorphic events were contemporaneous with the emplacement of the 3.36–3.34 Ga and 3.29–3.25 Ga granitoids and komatiite magmatism and therefore represent the thermal imprint of granitoid emplacement on the prior formed crust (Figs. 9, 10, 11, 12, Table 3). The 3190–3158 Ma and the 3084–3062 Ma ages can be correlated to the 3.14–3.10 Ga Mesoarchean upper amphibolite facies metamorphism of the WDC rocks reported from the Holenarsipur greenstone belt (Jayananda et al., 2013a, 2015; Dasgupta et al., 2019) and the 3.21–3.16 Ga amphibolite to granulite facies overprint in the Biligirirangan Hills region of the Central Dharwar Province (Jayananda et al., 2013a; Peucat et al., 2013). This event was of regional extent and contemporaneous with fluid fluxing and emplacement of the protoliths of the Gunjur gneisses and the Chikmagalur granite (Meen et al., 1992, Jayananda et al., 2015, 2018). The c. 2.64 Ga metamorphic ages represents the thermal imprint of the emplacement of the 2.66–2.65 Ga Neoarchean TTG/granite suite and is contemporaneous with felsic magmatism in the Chitradurga greenstone belt (emplacement of high-K plutons of Arsikere-Banavara and Chitradurga granites: Jayananda et al., 2006; Chadwick et al., 2007). Similar ages (2.64–2.61 Ga) have been reported from the Central Dharwar Province and interpreted to be dating high-temperature thermal imprint (Jayananda et al., 2013a; Peucat et al., 2013). The c. 2.53 Ga ages is prominent in the gneisses from the transition zone of the Central Dharwar Province in the Biligirirangan Hills region. These ages can be correlated with c. 2.5–2.4 Ga major felsic crust formation,

35

migmatization, CO2 fluxing and charnockite formation, and granulite facies metamorphism in the Central and Eastern Dharwar Provinces (Jayananda et al., 2013a; Peucat et al., 2013; Rateesh-Kumar et al., 2016; Li et al., 2018a, b). This event led to the amalgamation of the Eastern Dharwar Province with the Western Dharwar Craton marking the final stage of cratonization of the Dharwar Craton (Jayananda et al., 2018).

5.5. Comparison with other Archean granitoid suites and implications for Archean tectonics A compilation of Hf isotopic data on zircons in TTGs/granites from several Archean cratons indicates that prior to c. 3.5 Ga most granitoids have chondritic or crust-like εHfi (Fig. 13b). This suggests that their protoliths were sufficiently long-lived to evolve to crust-like Hf isotopic compositions. This signature of the long-term storage and reprocessing of Hadean/Eoarchean mafic crust is preserved in the gneisses of the Acasta Gneiss Complex (AGC), the Isua region in south west Greenland (Iizuka et al., 2009; Kemp et al., 2009; Hiess et al., 2009; Nærra et al., 2012; Reimink et al., 2016a, 2019; Bauer et al., 2017; Fisher and Vervoort, 2018) and the Singhbhum Craton in India (Chaudhuri et al., 2018). The Hf isotopic record of the pre 3.5 Ga TTGs in the AGC, the Singhbhum Craton, and elsewhere can by and large be explained by repeated granitoid extraction from long-lived mafic crustal sources with limited/variable interaction with juvenile magmas. In the AGC, a transition to juvenile Hf-isotopic composition is noted at about 3.55 Ga (Fig. 13) (Reimink et al., 2019), accompanied by increasing SiO2, Na2O, La/Yb, Sr/Y, increasing negative Nb-Ta anomalies, increase in fractionation between the light and heavy REE, and decreasing Nb/Th of the granitoids. These changes in the chemistry of the AGC granitoids are usually attributed to a shift from shallow level melting of anhydrous metabasalts in an iceland-like tectonic setting in the Hadean to deeper levels of melting of

36

hydrated metabasalts by about 3.6 Ga in some form of a subduction-like regime involving horizontal tectonics (Reimink et al., 2014; 2016a, b; 2018a, b; 2019).. A similar transition at c. 3.6 Ga to more juvenile source of the TTGs is evident from Paleoarchean magmatic and Hadean/Eoarchean xenocrystic zircons in TTGs from the Singhbhum Craton (Dey et al., 2017, 2019; Chaudhuri et al., 2018; Pandey et al., 2019) (Fig. 13). Nӕraa et al. (2012) also documented a transition from an array characterized by crustal reworking to more juvenile protoliths by c. 3.2 Ga in TTG gneisses from the Isua region. The mantle-like εHfi of the Paleoarchean TTGs/granites of the Western Dharwar Craton indicate that their mafic protoliths had relatively short crustal incubation times. The general scarcity of inherited zircons (with near complete absence of any >3.6 Ga inherited zircon) in them rules out the involvement of older crustal basement either in the form of mafic or preexisting felsic crust. The short crustal residence time of the protoliths of the Western Dharwar Craton granitoids is suggestive of a tectonic setting characterized by rapid recycling of basalts while the greater crustal residence times of the mafic protoliths of the older than 3.5 Ga TTGs indicate a tectonic setting where basalts could persist for more prolonged periods of times. The juvenile signature of the Western Dharwar Craton TTGs, and the lack of evidence for assimilation of older crust in any significant amounts, is easily explained by lateral, rather than vertical, growth of the crust (e.g., Reimink et al., 2019) in a plate tectonic regime and is consistent with recent models involving subduction of oceanic slab to generate island arc crust and remelting of the base of the thickened island arc crust to produce the TTGs of the Western Dharwar Craton (Jayananda et al., 2015). In contrast, the long-term persistence of mafic sources with repeated episodes of granitoid extraction and crustal assimilation is more likely in a tectonic scenario involving TTG production by melting of a thickened mafic pile/oceanic plateau

37

(Bédard, 2006, 2018; Smithies et al., 2009; Martin et al., 2014; Johnson et al., 2014, 2017) in a stagnant-lid-like convective regime. It therefore appears that a transition from a stagnant lid to a plate tectonic regime may have taken place in several cratons by 3.5–3.6 Ga. This transition marks the initiation of prolific juvenile Paleoarchean TTG crust formation in many Archean cratons such as the Western Dharwar Craton, the Slave Craton and the Singhbhum Craton (Dey et al., 2017; Chaudhuri et al., 2018; Pandey et al., 2019; Reimink et al., 2019). In the Western Dharwar Craton, the juvenile crust extraction broadly continued until c. 3.2 Ga by which time the continental crust had attained enough thickness to undergo extensive intracrustal melting to generate potassic granites by melting preexisting TTGs accompanied by juvenile input. This would explain the chondritic to crust-like Hf isotopic compositions of late stage (c. 3.0 Ga to 2.5 Ga) K-granites in the Western Dharwar Craton.

6. Summary and conclusions The major findings of this study can be summarized as follows: (1) The granitoid crust of the Western Dharwar Craton formed in four episodes at 3.43–3.41 Ga, 3.36–3.34 Ga, 3.29–3.26 Ga, and 2.66–2.65 Ga. (2) The TTGs and granites were subject to polyphase metamorphism at 3353–3329 Ma, 3264–3256 Ma, 3187–3141 Ma, 3083–3062 Ma, c. 2638 Ma and c. 2574–2526 Ma. (3) The Paleoarchean (3.43–3.41 Ga, 3.36–3.34 Ga, and 3.29–3.25 Ga) granitoid suites have positive εHfi and plot on a common εHfi vs. time trend. Their Hf-isotopic compositions are consistent with repeated partial melting and granitoid extraction at 3.43–3.41 Ga, 3.36– 3.34 Ga, and 3.29–3.25 Ga from mafic sources that separated from the depleted mantle between 3.55 Ga and 3.35 Ga.

38

(4) The Neoarchean (2.66–2.65 Ga) granitoids have chondritic to slightly negative εHfi and formed by melting of the same 3.35 Ga mafic crust that was the source of the 3.29–3.25 Ga suite or by mixing between juvenile magmas and pre-existing TTGs. (5) The TTGs were derived from a shallow garnet-free plagioclase-bearing amphibolitic source with minor components derived from pre-existing tonalites. (6) Many of the granitoids are unusually depleted in several incompatible elements or have unusually fractionated REE patterns which is attributed either to variable amounts of plagioclase accumulation or fluid-assisted mobilization of REEs during greenschist facies alteration of the rocks. (7) The juvenile εHfi and the short crustal residence time of the protoliths of the Western Dharwar Craton granitoids is suggestive of a tectonic setting characterized by rapid recycling of basalts such as in subduction zones. In comparison, TTGs older than c. 3.5 Ga from a number of Archean cratons have chondritic to crust-like εHfi involving longterm persistence of mafic sources and repeated episodes of granitoid extraction and crustal assimilation, a tectonic scenario consistent with TTG generation at the base of thickened mafic pile/oceanic plateau.

Acknowledgement The U–Pb, Hf and trace element data were generated at the Diamond Jubilee Radiogenic Isotope Facility of the Department of Geology and Geophysics, IIT Kharagpur. DU acknowledges financial support from IIT Kharagpur for setting up the laboratory. The research work was partly funded by the Department of Science and Technology (DST), New Delhi through an extra mural research grant (Grant no. EMR/2015/002165) to DU. SR acknowledges the Council of Scientific

39

and Industrial Research (CSIR), New Delhi for a PhD fellowship (09/081(1278)/2016-EMR-1). The manuscript benefitted from constructive comments by Adrien Vezinet and an anonymous reviewer. Editorial handling by G Zhao is gratefully acknowledged.

References Amelin, Y., Lee, D.C., Halliday, A.N., Pidgeon, R.T., 1999. Nature of the Earth's earliest crust from hafnium isotopes in single detrital zircons. Nature 399, 252–255. Ayers, J.C., Zhang, L., Luo, Y and. Peters, T.J, 2012. Zircon solubility in alkaline aqueous fluids at upper crustal conditions, Geochim. Cosmochim. Acta, 96, 18–28. Barker, F., 1979. Trondhjemite: Definition, environment and hypotheses of origin. In: Barker, F. (Ed.), Trondhjemite. Dacite and Related Rocks Elsevier, Amsterdam, pp. 1–12. Barker, F., Arth, J.G., 1976. Generation of trondhjemite–tonalite liquids and Archaean bimodal trondhjemite–basalt suites. Geology 4, 596–600. Bauer, A.M., Fisher, C.M., Vervoort, J.D., Bowring, S.A., 2017. Coupled zircon Lu–Hf and U– Pb isotopic analyses of the oldest terrestrial crust, the>4.03 Ga Acasta Gneiss Complex. Earth Planet. Sci. Lett. 458, 37–48. Beckinsale, R.D., Drury, S.A., Holt, R.W., 1980. 3360 M.Y. old gneisses from south Indian craton. Nature 283, 469–470. Beckinsale, R.D., Reeves-Smith, G., Galen, H., Holt, R.W., Thompson, B., 1982. Rb-Srand PbPb whole rock isochron ages and REE data for Archaean gneisses and granites, Karnataka State, South India. In: Indo-US Workshop on Precambrians of South India, Abstracts of the Papers. DD. 35–36. National Geophys. Res. Inst., Hyderabad, India.

40

Bédard, J.H., 2006. A catalytic delamination-driven model for coupled genesis of Archaean crust and sub-continental lithospheric mantle. Geochim. Cosmochim. Acta 70, 1118–1124. Bédard, J.H., 2018. Stagnant lids and mantle overturns: implications for Archaean tectonics, magma genesis, crustal growth, mantle evolution, and the start of plate tectonics. Geosci. Front. 9, 19–49. Belica, M.E., Piispa, E.J., Meert, J.G., Pesonen, L.J., Plado, J., Pandit, M.K., Kamenov, G.D., Celestino, M., 2014. Paleoproterozoic mafic dyke swarms from the Dharwar craton; paleomagnetic poles for India from 2.37 to 1.88 Ga and rethinking the Columbia supercontinent. Precambrian Res. 244, 100–122. Bell, E.A., Harrison, T.M., Kohl, I.E., Young, E.D., 2014. Eoarchean crustal evolution of the Jack Hills zircon source and loss of Hadean crust. Geochim. Cosmochim. Acta 146, 27– 42. Bhaskar Rao, Y.J., Griffin, W.L., Ketchum, J., Pearson, N.J., Beyer, E., O'Reilly, S.Y., 2008. An outline of juvenile crust formation and recycling history in the Archaean western Dharwar craton, from zircon in situ U–Pb dating and Hf-isotopic compositions goldschmidt conference. Geochim. Cosmochim. Acta 72, A81. Bhaskar Rao, Y.J., Janardhan, A.S., Vijaya Kumar, T., Narayana, B.L., Dayal, A.M., Taylor, P.N., Chetty, T.R.K., 2003. Sm-Nd model ages and Rb-Sr isotopic systematics of charnockite gneisses across the Cauvery shear zone, south India: implication for Archean, Neoproterozoic terrane boundary in the granulite terrane. In: Ramakrishnan, M. (Ed.), Tectonics of the Southern Granulite Terrane. vol. 50. Kuppam-Palani Geotransect: Geol. Soc. of India Memoir, pp. 297–317.

41

Bhaskar Rao, Y.J., Naha, K., Srinivasan, R., Gopalan, K., 1991. Geology, geochemistry and geochronology of Peninsular gneisses around Gorur, Hassan district, Karnataka. Proc. Indian Acad. Sci (Earth Planet. Sci.) 100, 399–412. Bingen, B., Austrheim, H., Whitehouse, M.J., Davis, W.J., 2004. Trace element signature and U– Pb geochronology of eclogite-facies zircon, Bergen Arcs, Caledonides of W Norway. Contrib. Mineral. Petrol. 147, 671–683. Blichert-Toft, J., Albarede, F., 2008. Hafnium isotopes in Jack Hills zircons and the formation of the Hadean crust. Earth Planet. Sci. Lett. 265, 686–702. Bouhallier, H., Choukroune, P., Ballèvre, M., 1993. Diapirism, bulk homogeneous shortening and Trans current shearing in the Archaean Dharwar Craton: the Holenarsipur area, Southern India. Precambrian Res. 63, 43–58. Bouhallier, H., Chardon, D., Choukroune, P., 1995. Strain patterns in Archaean domeand-basin structures: the Dharwar Craton (Karnataka, South India). Earth Planet. Sci. Lett. 135, 57– 75. Bowring, S.A., Williams, I.S. and Compston, W., 1989. 3.96 Ga gneisses from the Slave province, Northwest Territories, Canada. Geology 17, 971–975. Buhl, D., 1987. U–Pb und Rb–Sr Altersbestimmungen und Untersuchungen zum strontium isotopenaustausch an granuliten Südindiens. Ph.D. Thesis. University of Nürberg, Germany, 197 pp. Chadwick, B., Vasudev, V., Hegde, G.V., Nutman, A.P., 2007. Structure and SHRIMP U-Pb zircon ages of granites adjacent to the Chitradurga schist belt: implications for Neoarchean convergence in the Dharwar craton, southern India. J. Geol. Soc. India 69, 5– 24.

42

Chardon, D., Choukroune, P., Jayananda, M., 1996. Strain patterns, de'collement and incipient sagducted greenstone terrains in the Archaean Dharwar craton (south India). J. Struct. Geol. 18, 991–1004. Chardon, D., Jayananda, M., Chetty, T.R.K., Peucat, J.-J., 2008. Precambrian continental strain and shear zone patterns: the South Indian case. J. Geophys. Res. 113, B08402. Chardon, D., Jayananda, M., Peucat, J.-J., 2011. Lateral contrictional flow of hot orogenic crust: insights from the Neoarchean of South India, geological and geophysical implications for orogenic plateaux. Geochem. Geophys. Geosyst. 12, Q02005. Chaudhuri, T., Wan, Y., Mazumder, R., Ma, M., Liu, D., 2018. Evidence of enriched, Hadean mantle reservoir from 4.2–4.0 Ga zircon xenocrysts from Paleoarchean TTGs of the Singhbhum Craton, Eastern, India. Sci. Rep. 8, 7069. Chetty, T.R.K., Mohanty, D.P., Yellappa, T., 2012. Mapping of shear zones in the Western Ghats, Southwestern part of Dharwar Craton. J. Geol. Soc. India 79, 151–154. Condie, K.C., and Kröner, A., 2013. The building blocks of continental crust: Evidence for a major change in the tectonic setting of continental growth at the end of the Archean. Gondwana Res. 23, no. 2, 394–402. Condie, K.C., 2014. How to make a continent: thirty-five years of TTG research. In: Dilek, Y., Furnes, H. (Eds.), Evolution of Archean Crust and Early Life, Modern Approaches to Solid Earth Sciences, vol. 7. Springer Science, Dordrecht, pp. 179-193. Dasgupta, A., Bhowmik, S.K., Dasgupta, S., Avila, J., Ireland, T.R., 2019. Mesoarchean clockwise metamorphic P-T path from the Western Dharwar Craton. Lithos 342–343, 270–290.

43

Degeling, H., Eggins, S., and Ellis, D.J, 2001. Zr budgets for metamorphic reactions, and the formation of zircon from garnet breakdown, Mineral. Mag. 65, 749–758. Devaraju, T.C., Huhma, H., Sudhakara, T.L., Kaukonen, R.J., Alapieti, T.T., 2007. Petrology, geochemistry, model Sm-Nd ages and petrogenesis of the granitoids of the northern block of western Dharwar Craton. J. Geol. Soc. India 70, 889–911. Dey, S., 2013. Evolution of Archaean crust in the Dharwar craton: the Nd isotope record. Precambrian Res. 227, 227–246. Dey, S., Nandy, J., Choudhary, A.K., Liu, Y., Zong, K., 2014. Origin and evolution of granitoids associated with the Kadiri greenstone belt, eastern Dharwar Craton: a history of orogenic to anorogenic magmatism. Precambrian Res. 246, 64–90. Dey, S., Topno, A., Liu, Y., Zong, K., 2017. Generation and evolution of Palaeoarchaean continental crust in the central part of the Singhbhum craton, eastern India. Precambrian Res. 298, 268–291. Dey, S., Mitra, A., Nandy, J., Mondal, S., Topno, A., Liu, Y., Zong, K., 2019. Early crustal evolution as Recorded in Granitoids of the Singhbhum and Western Dharwar Cratons. Earth’s Oldest Rocks (Second Edition), 741–792. Dhoundial, D.P., Paul, D.K., Sarkar, A., Trivedi, J.R., Gopalan, K., Potts, P.J., 1987. Geochronology and geochemistry of Precambrian granitic rocks of Goa, SW India. Precambrian Res. 36, 287–302. Dhuime, B., Wuestefeld, A., Hawkesworth, C.J., 2015. Emergence of modern continental crust about 3 billion years ago. Nat. Geosci., 8, 552–555.

44

Drummond, M.S., Defant, M.J., 1990. A model from trondhjemite–tonalite–dacite genesis and crustal growth via slab melting: Archaean to modern comparisons. J. Geophys. Res. 95, 21503–21521. Drury, S.A., Holt, R.W., Van Calastren, P.C. and Beckinsale, R.D., 1983. Sm-Nd and Rb-Sr ages for Archaean rocks in western Karnataka, South India. J. Geol. Soc. India, 24, 454–460. Drury, S.A., N.B. Harris, R.W. Holt, Reeves-Smith, G.J., Wightman, R. T, 1984. Precambrian tectonics and crustal evolution in South India, J. Geol. 92, 3–20. Ewing, T.A., Hermann, J., Rubatto, D., 2013. The robustness of the Zr-in-rutile and Ti-in zircon thermometers during high-temperature metamorphism (Ivrea-Verbano Zone, northern Italy). Contrib. Mineral. Petrol. 165, 757–779. Fisher, C.M., Vervoort, J.D., 2018. Using the magmatic record to constrain the growth of continental crust-The Eoarchean zircon Hf record of Greenland. Earth Planet. Sci. Lett. 488, 79–91. Fraser, G., Ellis, D., Eggins, S., 1997. Zirconium abundance in granulite-facies minerals, with implications for zircon geochronology in high-grade rocks. Geology 25 (7), 607– 610. French, J.E., Heaman, L.M., 2010. Precise U–Pb dating of Paleoprotoerozoic mafic dyke swarms of the Dharwar craton India: implications for the existence of the Neoarchean supercraton Sclavia. Precambrian Res. 183, 416–441. Friend, C.R.L., Nutman, A.P., 1991. SHRIMP U-Pb geochronology of the closepet granite and Peninsular gneisses Karnataka, South of India. J. Geol. Soc. India 38, 357–368. Geisler, T., Pidgeon, R.T., Kurtz, R., van Bronswijk, W., Schleicher, H., 2003a. Experimental hydrothermal alteration of partially metamict zircon. Am. Mineral. 88, 1496–1513.

45

Geisler, T., Rashwan, A.A., Rahn, M.K.W., Poller, U., Zwingmann, H., Pidgeon, R.T., Schleicher, H., Tomaschek, F., 2003c. Low-temperature hydrothermal alteration of natural metamict zircons from the Eastern Desert, Egypt. Mineral. Mag. 67, 485–508. Geisler, T., Schaltegger, U., Tomaschek, F., 2007. Re-equilibration of zircon in aqueous fluids and melts. Elements 3, 43–50. Geisler, T., Trachenko, K., Ríos, S., Dove, M.T., Salje, E.K.H., 2003b. Impact of self-irradiation damage on the aqueous durability of zircon (ZrSiO4): implications for its suitability as nuclear waste form. J. Physic.: Condensed Matter 15, L597–L605. Geng, Y.S., Du, L.L., Ren, L.D., 2012. Growth and reworking of the early Precambrian continental crust in the North China Craton: constraints from zircon Hf isotopes. Gondwana Res. 21, 517–529. Griffin, W.L., Pearson, N.J., Belousova, E., Jackson, S.E., van Achterbergh, E., O'Reilly, S.Y., Shee, S.R., 2000. The Hf isotopic composition of the cratonic mantle: LAM-MCICPMS analysis of zircon megacrysts in kimberlites. Geochim. Cosmochim. Acta 64, 133–147. Guitreau, M., Mukasa, B.S., Loudin, L., Krishnan, S., 2017. New constrains on the early formation of the Western Dharwar Craton (India) from igneous zircon (U-Pb) and Lu-Hf isotopes. Precambrian Res. 302, 33–49. Halla, J., van Hunen, J., Heilimo, E., Hölttä, P., 2009. Geochemical and numerical constraints on Neoarchean plate tectonics. Precambrian Res. 174, 155–162. Halla, J., Whitehouse, M.J., Ahmad, T., Bagai, Z., 2017. Archaean granitoids: an overview and significance from a tectonic perspective. Geol. Soc. Lond. Spec. Publ. 449, 1–18.

46

Hansen, E.C., Newton, R.C., Janardhan, A.S., 1984a. Pressures, temperatures and metamorphic fluids across an unbroken amphibolite facies to granulite facies transition in Southern Karnataka. In: Kröner, A. (Ed.), Archaean Geochemistry. , pp. 161–181. Hansen, E.C., Newton, R.C., Janardhan, A.S., 1984b. Fluid inclusions in rocks from the amphibolite-facies gneiss to charnockite progression in southern Karnataka, India: direct evidence concerning the fluids of granulite metamorphism. J. Metamorph. Geol. 2, 249– 264. Hansen, E.C., Newton, R.C., Janardhan, A.S., Lindenberg, S., 1995. Differentiation of late Archean crust in the eastern Dharwar craton, Krishnagiri–Salem area, South India. J. Geol. 103, 629–651. Harrison, T.M., Schmitt, A.K., McCulloch, M.T., Lovera, O.M., 2008. Early (4.5 Ga) formation of terrestrial crust: Lu-Hf, δ18O, and Ti thermometry results for Hadean zircons. Earth Planet. Sci. Lett. 268, 476–486. Hawkesworth, C.J., Dhuime, B., Pietranik, A.B., Cawood, P.A., Kemp, A.I.S, Storey, C.D., 2010. The generation and evolution of the continental crust. Journal of the Geological Society of London, 167, 229–248. Henderson, D.R., Long, L.E., Barton Jr., J.M., 2000. Isotopic ages and chemical and isotopic composition of the Archaean Turfloop Batholith, Pietersburg granite–greenstone terrane, Kaapvaal Craton, South Africa. S. Afr. J. Geol. 103 (1), 38–46. Hermann, J., Rubatto, D., 2014. Subduction of continental crust to mantle depth: Geochemistry of ultrahigh-pressure rocks. In: Rudnick R (ed) The Crust vol 4. Elsevier Amsterdam pp 309–340.

47

Hiess, J., Bennett, V.C., 2016. Chondritic Lu/Hf in the early crust–mantle system as recorded by zircon populations from the oldest Eoarchean rocks of Yilgarn Craton, West Australia and Enderby Land, Antarctica. Chem. Geol.427, 125–143. Hiess, J., Bennett, V.C., Nutman, A.P., Williams, I.S., 2009. In situ U–Pb, O and Hf isotopic compositions of zircon and olivine from Eoarchaean rocks, West Green-land: new insights to making old crust. Geochim. Cosmochim. Acta 73 (15), 4489–4516. Hoffmann, J.E., Kröner, A., Hegner, E., Viehmann, S., Xie, H., Iaccheri, L. M., Schneider, K. P., Hofmann, A., Wong, J., Geng, H., Yang, J., 2016. Source composition, fractional crystallization and magma mixing processes in the 3.48–3.43 Ga Tsawela tonalite suite (Ancient Gneiss Complex, Swaziland)-Implications for Palaeoarchaean geodynamics. Precambrian Res. 276, 43–66. Hoffmann, J.E., Münker, C., Næraa, T., Rosing, M.T., Herwartz, D., Garbe-Schönberg, D., Svahnberg, H., 2011. Mechanisms of Archean crust formation inferred from highprecision HFSE systematics in TTGs. Geochim. Cosmochim. Acta 75, 4157–4178. Hoffmann, J.E., Münker, C., Polat, A., Rosing, M.T., Schulz, T., 2011. The origin of decoupled Hf–Nd isotope compositions in early Archean rocks from southern West Greenland. Geochim. Cosmochim. Acta 75, 6610–6628. Hoffmann, J.E., Nagel, T.J., Münker, C., Næraa, T., Rosing, M.T., 2014. Constraining the process of Eoarchean TTG formation in the Itsaq Gneiss Complex, southern West Greenland. Earth Planet. Sci. Lett. 388, 374–386. Hokada, T., Horie, K., Satish-Kumar, M., Ueno, Y., Nasheeth, A., Mishima, K., Shiraishi, K., 2013. An appraisal of Archaean supracrustal sequences in Chitradurga Schist Belt, western Dharwar craton, southern India. Precambrian Res. 227, 99–119.

48

Iizuka, T., Horie, K., Komiya, T., Maruyama, S., Hirata, T., Hidaka, H., Windley, B., 2006. 4.2 Ga zircon xenocryst in an Acasta gneiss from northwestern Canada: evidence for early continental crust. Geology 34, 245–248. Iizuka, T., Komiya, T., Johnson, S.P., Kon, Y., Maruyama, S., Hirata, T., 2009. Reworking of Hadean crust in the Acasta gneisses, northwestern Canada: evidence from in-situ Lu–Hf isotope analysis of zircon. Chem. Geol. 259, 230–239. Iizuka, T., Nakai, S., Sahoo, Y.V., Takamasa, A., Hirata, T., Maruyama, S., 2010. The tungsten isotopic composition of Eoarchean rocks: Implications for early silicate differentiation and core–mantle interaction on Earth. Earth Planet. Sci. Lett. 291, 189–200. Janardhan, A.S., Newton, R.C. Smith, J.V., 1979a. Ancient crustal metamorphism at low P H2O: charnockite formation at Kabbaldurga, South India. Nature 278, 511–514. Janardhan, A.S., Newton, R.C., Hansen, E.C., 1982. The transformation of amphibolite facies gneisses to charnockite in southern Karnataka and Tamil Nadu. Contrib. Mineral. Petrol. 79, 139–149. Jayananda, M., Chardon, D., Peucat, J.J., Capdevila, R., 2006. 2.61 Ga potassic granites and crustal reworking in the western Dharwar craton, southern India: tectonic, geochronologic and geochemical constraints. Precambrian Res. 150, 1–26. Jayananda, M., Kano, T., Peucat, J.-J., Channabasappa, S., 2008. 3.35 komatiite volcanism in the western Dharwar craton, southern India: constraints from Nd isotopes and whole-rock geochemistry. Precambrian Res. 162, 160–179. Jayananda, M., Peucat, J.-J., Chardon, D., Krishna Rao, B., Corfu, F., 2013a. Neoarchean greenstone volcanism, Dharwar craton, Southern India: Constraints from SIMS zircon geochronology and Nd isotopes. Precambrian Res. 227, 55–76.

49

Jayananda, M., Santosh, M., Aadhiseshan, K.R., 2018. Formation of Archean (3600–2500 Ma) continental crust in the Dharwar Craton, southern India. Earth-Sci. Rev. 181, 12–42. Jayananda, M., Tsutsumi, Y., Miyazaki, T., Gireesh, R.V., Kapfo, Kowe-u, Tushipokla, Hidaka, H., Kano, 2013b. Geochronological constraints on Meso-neoarchean regional metamorphism and magmatism in the Dharwar craton, southern India. J. Asian Earth Sci. 78, 18–38. Jayananda, M., Moyen, J.F., Martin, H., Peucat, J.J., Auvray, B., Mahabaleswar, B., 2000. Late Archaean (2550–2520 Ma) juvenile magmatismin the Eastern Dharwar Craton, southern India: constraints from geochronology, Nd–Sr isotopes and whole rock geochemistry. Precambrian Res. 99, 225–254. Jayananda, M., Chardon, D., Peucat, J.J, Tushipokla, Fanning, C.M, 2015. Paleo-to Mesoarchean TTG accretion and continental growth in the western Dharwar craton, Southern India: Constraints from SHRIMP U-Pb zircon geochronology, whole rock geochemistry and Nd-Sr isotopes Precambrian Res. 268, 295–322. Johnson, T.E., Brown, M., Gardiner, N.J., Kirkland, C.L., and Smithies, R.H., 2017, Earth's first stable continents did not form by subduction: Nature 543, 239–242. Johnson, T.E., Brown, M., Kaus, B.J.P., Van Tongeren, J.A., 2014. Delamination and recycling of Archaean crust caused by gravitational instabilities. Nat. Geosci. 7, 47-52. Kamber, B.S., Ewart, A., Collerson, K.D., Bruce, M.C., McDonald, G.D., 2002. Fluid-mobile trace element constraints on the role of slab melting and implications for Archaean crustal growth models. Contrib. Mineral. Petrol. 144, 38-56. Kaur, P., Zeh, A., Chaudhri, N., Eliyas, N., 2016a. Unravelling the record of Archaean crustal evolution of the Bundelkhand Craton, northern India using U-Pb zircon monazite ages,

50

Lu-Hf isotope systematics, and whole-rock geochemistry of granitoids. Precambrian Res. 281, 384–413. Kaur, P., Zeh, A., Chaudhuri, N., 2014. Characteristic of U-Pb–Hf isotope record of the 3.55 Ga felsic crust from the Bundelkhand Craton, Northern India. Precambrian Res. 255, 236– 244. Kaur, P., Zeh, A., Chaudhri, N., 2019. Archean crustal evolution of the Aravalli Banded Gneissic Complex, NW India: Constraints from zircon U-Pb ages, Lu-Hf isotope systematics, and whole-rock geochemistry of granitoids. Precambrian Res. 327, 81–102. Kemp, A.I.S., 2018. Early earth geodynamics: cross examining the geological testimony. Phil. Trans. R. Soc. A 376, 20180169. Kemp, A.I.S., Foster, G.L., Scherstén, A., Whitehouse, M.J., Darling, J., Storey, C., 2009. Concurrent Pb–Hf isotope analysis of zircon by laser ablation multi-collector ICP-MS, with implications for the crustal evolution of Greenland and the Himalayas. Chem. Geol. 261 (3–4), 244–260. Kemp, A.I.S., Wilde, S.A., Hawkesworth, C.J., Coath, C., Nemchin, A.A., Pidgeon, R.T., Vervoort, J.D., DuFrane, S.A., 2010. Hadean crustal evolution revisited: new constraints from Pb-Hf isotope systematics of the Jack Hills zircons. Earth Planet. Sci. Lett. 296, 45– 56. Kemp, A. I. S., Whitehouse, M. J., Vervoort, J. D., 2019. Deciphering the zircon Hf isotope systematics of Eoarchean gneisses from Greenland: Implication for ancient crust-mantle differentiation and Pb isotope controversies. Geochim. Cosmochim. Acta, 250, 76–97. Kohn, M. J., Corrie, S. L. and Markley, C., 2015. The fall and rise of metamorphic zircon, Am. Mineral. 100, 897–908.

51

Korenaga, J., 2013. Initiation and evolution of plate tectonics on Earth: theories and observations. Annu. Rev: Earth Planet. Sci. Lett. 41, 117–151.

Kovaleva, E., Klötzil, U., Habler, G., Huet, B., Guan, Y., Rhede, D., 2017. The effect of crystalplastic deformation on isotope and trace element distribution in zircon: combined BSE, CL, EBSD, FEG-EMPA and NanoSIMS study. Chem. Geol. 450, 183–198. Kröner, A., Elis Hoffmann, J., Xie, H., Wu, F., Münker, C., Hegner, E., Wong, J., Wan, Y., Liu, D., 2013. Generation of early Archaean felsic greenstone volcanic rocks through crustal melting in the Kaapvaal, craton, southern Africa. Earth Planet. Sci. Lett.381, 188–197. Kröner, A., Hoffmann, J.E., Xie, H., Münker, C., Hegner, E., Wan, Y., Hofmann, A., Liu, D.,Yang, J., 2014. Generation of early Archaean grey gneisses through crustal melting of older crust in the eastern Kaapvaal craton, southern Africa. Precambrian Res. 255, 833– 846. Kröner, A., Jaeckel, P., Brandl, G., 2000. Single zircon ages for felsic to intermediate rocks from the Pietersburg and Giyani greenstone belts and bordering granitoid orthogneisses, northern Kaapvaal Craton, South Africa. J. Afr. Earth Sci. 30 (4), 773–793. Kumar, A., Bhaskar Rao, Y.J., Sivaraman, T.V., Gopalan, K., 1996. Sm-Nd ages of Archaean metavolcanic of the Dharwar craton, South India. Precambrian Res. 80, 206–215. Kumar, A., Hamilton, M.A., Halls, H.C., 2012a. A Paleoproterozoic giant radiating dyke swarm in the Dharwar Craton, southern India. Geochem. Geophys. Geosyst. 7, Q02011. Kumar, A., Nagaraju, E., Besse, J., Bhaskar Rao, Y.J., 2012b. New age, geochemical and paleomagnetic data on a 2.21 Ga dyke swarm from southern India: constraints on Paleoproterozoic reconstruction. Precambrian Res. 220–221, 123–138.

52

Kumar, A., Nagaraju, E., Srinivasa Sarma, D., Davis, D.W., 2014. Precise Pb baddeleyite geochronology by the thermal extraction-thermal ionization mass spectrometry method. Chem. Geol. 372, 72–79. Kumar, A., Parashuramulu, V., Nagaraju, E., 2015. A 2082 Ma radiating dyke swarm in the Eastern Dharwar Craton, southern India and its implications to Cuddapah basin formation. Precambrian Res. 266, 490–505. Lancaster, P. J., Dey, S., Storey, C.D, Mitra, A., Bhunia, R.K., 2015. Contrasting crustal evolution process in the Dharwar craton: Insights from detrital zircon U-Pb and Hf isotopes Gondwana Res 28, 1361–1372. Laurent, O., 2012. Les changements géodynamiques à la transition Archéen- Protérozoïque: étude des granitoïdes de la marge Nord du craton du Kaapvaal (Afrique du Sud). Unpublished Ph.D. thesis, University Blaise Pascal, Clermont- Ferrand II, 512 pp (in French). Laurent, O., Bjornsen, J., Bretcher, S., Wotzlaw, J., Silva, P.M., Moyen, J., Ulmer, P., Bachmann, O., 2019. Linking volcanic and plutonic records in the early Earth : TTG and silicic crystal mushes. Goldschmidt2019 abstract. Laurent, O., Martin, H., Moyen, J.F., Doucelance, R., 2014. The diversity and evolution of lateArchean granitoids: evidence for the onset of “modern-style” plate tectonics between 3.0 and 2.5 Ga. Lithos 205, 208–235. Laurent, O., Zeh, A., 2015. A linear Hf isotope-age array despite different granitoid sources and complex Archean geodynamics: example from the Pietersburg block (South Africa). Earth Planet. Sci. Lett. 430, 326–338.

53

Li, S.S., Santosh, M., Ganguly, S., Thanooja, P.V., Sajeev, K., Pahari, A., Manikyamba, C., 2018b. Neoarchean microblock amalgamation in southern India: Evidence from the Nallamalai Suture zone. Precambrian Res. 314, 1–27. Li, S.S, Santosh, M., m Palin, R.M., 2018a. Metamorphism during the Archean-Paleoproterozoic Transition Associated with Microblock Amalgamation in the Dharwar craton, India. J. Petro 59, 2435–2462. Long, X.P., Sun, M., Yuan, C., Kröner, A., Hu, A.Q., 2012. Zircon REE patterns and geochemical characteristics of Paleoproterozoic anatectic granite in the northern Tarim Craton, NW China: implications for the reconstruction of the Columbia supercontinent. Precambrian Res. 222–223, 474–487 Ludwig, K.R., 2003. User's Manual for ISOPLOT 3.00: A Geochronological Toolkit for Microsoft Excel, Special Publication No. 4. Berkeley Geochronology Center, pp. 1–70. Mahabaleswar, B., Jayananda, M., Peucat, J.J., Shadakshara Swamy, N., 1995. Archaean highgrade gneiss complex from Satnur-Halagur-Sivasamudram areas, Karnataka, southern India: petrogenesis and crustal evolution. J. Geol. Soc. India 45, 33–49. Maibam, B., Goswami, J.N., Srinivasan, R., 2011. Pb-Pb zircon ages of Archean metasediments and gneisses from the Dharwar craton, southern India: implications for the antiquity of the eastern Dharwar craton. J. Earth Syst. Sci. 120, 643–661. Maibam, B., Gerdes, A., Goswami, J.N., 2016. U-Pb and Hf isotope records in detrital and magmatic zircon from eastern and western Dharwar Craton, southern India: evidence for coeval Archean crustal evolution. Precambrian Res. 275, 496–512. Martin, H., 1986. Effect of steeper Archean geothermal gradient on geochemistry of subduction zone magmas. Geology 14, 753–756.

54

Martin, H., 1987. Petrogenesis of Archaean trondhjemites, tonalites and granodiorites from eastern Finland; major and trace element geochemistry. J. Petrol. 28, 921–953. Martin, H., Moyen, J.F., Guitreau, M., Blichert-Toft, J., Le Pennec, J.L., 2014. Why Archean TTG cannot be generated by MORB melting in subduction zones. Lithos 198–199, 1–13. McDonough, W.F., and Sun, S.S., 1995. The composition of the Earth. Chem. Geol. 120, 223– 253. Meen, J.K., Rogers, J.J., Fullagar, P.D., 1992. Lead isotopic composition of the western Dharwar craton, southern India: evidence for distinct middle Archaean terrenes in a late Archaean craton. Geochim. Cosmochim. Acta 56, 2455–2470. Mohan, M.R., Sarma, D.S., Mc Naughton, N.J., Fletcher, I.R., Wilde, S.A., Siddiqui, M.H., Rasmussen, B., Krapez, B., Gregory, C.J., Kamo, S.L., 2014. SHRIMP zircon and titanite U-Pb ages, Lu-Hf isotope signatures and geochemical constraints for 2.56 Ga granite magmatism in western Dharwar craton, southern India: evidence for short lived Neoarchean episodic crustal growth. Precambrian Res. 243, 197–220. Mojzis, S.J., Devaraju, T.C., Newton, R.C., 2003. Ion microprobe U–Pb age determinations on zircon from the late Archean granulite facies transition zone of southern India. J. Geol. 111, 407–425. Mojzsis, S.J., Cates, N.L., Caro, G., Trail, D., Abramov, O., Guitreau, M., Blichert-Toft, J., Hopkins, M.D., Bleeker, W., 2014. Component geochronology in the polyphase ca. 3920 Ma Acasta Gneiss. Geochim. Cosmochim. Acta 133, 68–96. Mojzsis, S.J., Harrison, T.M., Pidgeon, R.T., 2001. Oxygen-isotope evidence from ancient zircons for liquid water at the earth’s surface 4300 Myr ago. Nature 409, 178–181.

55

Moorbath, S., Whitehouse, M.J., 1996. Sm-Nd Idotopic data and Earth Evolution. Science 273, 1878. Moorbath, S., Whitehouse, M.J., Kamber, B.S., 1997. Extreme Nd-isotope heterogeneity in the early Archaean-fact or fiction? Case histories from northern Canada and West Greenland. Chem. Geol. 135, 213–231. Moyen, J.F., 2011. The composite Archaean grey gneisses, petrological significance, and evidence for a non–unique tectonic setting for Archaean crustal growth. Lithos 123, 21– 36. Moyen, J.F., Martin, H., 2012. Forty years of TTG research. Lithos 148, 312–336. Naeraa, T., Schersten, A., Rosing, M.T., Kemp, A., Hoffmann, J.E., Kokfelt, T.F., Whitehouse, M.J., 2012. Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2 Gyr ago. Nature 485, 627–630. Nagaraju, E., Parashuramulu, V., Kumar, A., Srinivas Sarma, D., 2018b. Paleomagnetism and geochronological studies on a 450 km long 2216 Ma dyke from the Dharwar craton, southern India. Phys. Earth Planet. Inter. 274, 222–231. Nagaraju, E., Parashuramulu, V., Ramesh Babu, N., Narayana, A.C., 2018a. A 2207 Ma radiating mafic dyke swarm from eastern Dharwar craton, Southern India: drift history through Paleoproterozoic. Precambrian Res. 317, 89–100. Nagel, T.J., Hoffmann, J.E., Münker, C., 2012. Melting of Eoarchaean TTGs from thickened mafic arc crust. Geology 40, 375–378. Naqvi, S.M., Ram Mohan, M., Rana Prathap, J.G., Srinivasa Sarma, D., 2009. Adakite–TTG connection and fate of Mesoarchaean basaltic crust of Holenarsipur nucleus, Dharwar Craton, India. J. Asian Earth Sci. 35, 416–434. 56

Nasdala, L., Hanchar, J.M., Rhede, D., Kennedy, A.K., Vaczi, T., 2010. Retention of uranium in complexly altered zircon: an example from Bancroft, Ontario. Chem. Geol. 269, 290– 300. Newton, R.C., 1990. The late Archean high-grade terrain of South India and the deep structure of the Dharwar Craton. In: Fountain, D.M. (Ed.), Exposed Cross-sections of the Continental Crust. Kluwer Academic, Salisbury, pp. 305–326. Newton, R.C., 1992. Charnockitic alteration: evidence for CO2 infiltration in granulite facies metamorphism. J. Metamorph. Geol. 10, 383–400. Nutman, A.P., Chadwick, B., Krishna Rao, B., Vasudev, V.N., 1996. SHRIMP U/Pb zircon ages of acid volcanic rocks in the Chitradurga and Sandur groups, and granites adjacent to the Sandur Schist belt, Karnataka. J. Geol. Soc. India 47, 153–164. Nutman, A.P., Chadwick, B., Ramakrishnan, M., Viswanatha, M.N., 1992. SHRIMP U–Pb ages of detrital zircon in Sargur supracrustal rocks in western Karnataka, southern India. J. Geol. Soc. India 39, 367–374. Nutman, A.P., Mcgregor, V.R., Friend, C.R., Bennett, V.C., Kinny, P.D., 1996. The Itsaq Gneiss Complex of southern West Greenland; the world's most extensive record of early crustal evolution (3900-3600 Ma). Precambrian Res. 78, 1–39. Nutman, P.A., Bennett, C.V., Friend, L.C.R., Norman, D.M., 1999. Meta-igneous (non-gneissic) tonalites and quartz-diorites from an extensive ca. 3800 Ma terrain south of the Isua supracrustal belt, southern West Greenland: constraints on early crust formation. Contrib. Mineral. Petrol. 137, 364–388.

57

O’Neil, J., Boyet, M., Carlson, R.W., Paquette, J.L., 2013. Half a billion years of reworking of Hadean mafic crust to produce the Nuvvuagittuq Eoarchean felsic crust. Earth Planet. Sci. Lett.379, 12–25. Pandey, O.P., Mezger, K., Ranjan, S., Upadhyay, D., Villa, I.M. Villa, Nägler, T.F., Vollstaedt, H., 2019. Genesis of the Singhbhum Craton, eastern India; implications for Archean crust-mantle evolution of the Earth. Chem. Geol. 512, 85–106. Peucat, J.-J., Bouhallier, H., Fanning, C.M., Jayananda, M., 1995. Age of the Holenarsipur greenstone belt, relationships with the surrounding gneisses (Karnataka, South India). J. Geol. 103, 701–710. Peucat, J.-J., Jayananda, M., Chardon, D., Capdevila, D., Capdevila, R., Fanning, C.M., Paquette, J.-L., 2013. The lower crust of the Dharwar Craton, southern India: patchwork of Archean granulite domains. Precambrian Res. 227, 4–28. Peucat, J.-J., Mahabaleswar, B., Jayananda, M., 1993. Age of younger tonalitic magmatism and granulitic metamorphism in the South Indian transition zone (Krishnagiri area): comparison with older Peninsular gneisses from the Gorur-Hassan area. J. Metamorph. Geol. 11, 879–888. Peucat, J.-J., Vidal, P., Bernard-Griffiths, J., Condie, K.C., 1989a. Sr, Nd and Pb systems across the amphibolite to granulite facies transition in southern India. Terra. Cognita. 7, 333. Peucat, J.J., Vidal, P., Bernard-Griffiths, J., Condie, K.C., 1989b. Sr, Nd and Pb isotopic systematics in the Archaean low- to high-grade transition zone of southern India: Synaccretion vs. post-accretion granulites. J. Geol. 97, 537–550. Pichamuthu, C.S., 1960. Charnockite in the making. Nature 188, 135–136.

58

Raase, P., Raith, M., Ackermand, D., Lal, R.K., 1986. Progressive metamorphism of mafic rocks from greenschist to granulite facies in the Dharwar craton of South India. J. Geol. 94, 261–282. Radhakrishna, B.P., Naqvi, S.M., 1986. Precambrian continental crust of India and its evolution. J. Geol. 94, 145–166. Raith, M., Raase, P., Ackermand, D., Lal, R.K., 1983. Regional geothermobarometry in the granulite facies terrane of South India. Transactions of the Royal Society of Edinburgh, Earth Sciences 73, 221–244. Raith, M., Srikantappa, C., Buhl, D. and Köhler, H., 1999. The Nilgiri enderbites, South India: Nature and age constraints on protolith formation, high-grade metamorphism and cooling history, Precambrian Res. 98, 129–150. Ramakrishnan, M., Moorbath, S., Taylor, P.N., Anantha Iyer, G.V., Viswanatha, M.N., 1984. Rb-Sr and Pb-Pb whole-rock isochron ages of basement gneisses in Karnataka craton. J. Geol. Soc. India 25, 20–34. Ramakrishnan, M., Vaidyanadhan, R., 2008. Geology of India. Publications of the Geological Society of India, Bangalore 1, 556p. Ramakrishnan, M., Venkata Dasu, S.P., Kroner, A., 1994. Middle Archean age of Sargur Group by single grain zircon dating and geochemical evidence of clastic origin of metaquartzite from J.C. Pura greenstone belt, Karnataka. J. Geol. Soc. India 44, 605–616. Ranjan S., Upadhyay, D., Abhinay, K., Pruseth, K.L., & Nanda, J.K., 2018. Zircon geochronology of deformed alkaline rocks along the Eastern Ghats Belt margin: India– Antarctica connection and the Enderbia continent. Precambrian Res. 310, 407–424.

59

Ratheesh Kumar, R.T., Santosh, M., Yang, Q.-Y., Iswar Kumar, C., Chen, N.S., Sajeev, K., 2016. Archean tectonics and crustal evolution of the Biligiri Rangan block, southern India. Precambrian Res. 275, 406–428. Rayner, N., Stern, R.A., Carr, D., 2005. Grain scale variations in trace element composition of fluid-altered zircon, Acasta Gneiss Complex, northwestern Canada. Contrib. Mineral. Petrol. 148: 721–734. Reimink, J.R., Bauer, A.M., Chacko. T., 2018b, The Acasta Gneiss complex: Earth’s Oldest Rocks (second edition) P. 329–347. Reimink, J.R., Chacko, T., Carlson, R.W., Shirey, S.B., Liu, J., Stern, R.A., Bauer, A.M., Pearson, D.G., Heaman, L.M., 2018a. Petrogenesis and tectonics of the Acasta Gneiss Complex derived from integrated petrology and

142

Nd and

182

W extinct nuclide-

geochemistry. Earth Planet. Sci. Lett. 494, 12–22. Reimink, J.R., Chacko, T., Stern, R.A., Heaman, L.M., 2014. Earth’s earliest evolved crust generated in an Iceland-like setting. Nat. Geosci. 7, 529–533. Reimink, J.R., Chacko, T., Stern, R.A., Heaman, L.M., 2016a. The birth of a cratonic nucleus: lithogeochemical evolution of the 4.02–2.94 Ga Acasta Gneiss Complex. Precambrian Res. 281, 453–472. Reimink, J.R., Davies, J.H.F.L., Chacko, T., Stern, R.A., Heaman, L.M., Sarkar, C., Schaltegger, U., Creaser, R.A., Pearson, D.G., 2016b. No evidence for Hadean continental crust within Earth's oldest evolved rock unit. Nat. Geosci. 9, 777–780. Reimink, J.R., Pearson, D.G., Shirey, S.B., Carlson, R.W., Ketchum, J.W.F., 2019. Onset of new, progressive crustal growth in the central Slave craton at 3.55 Ga. Geochem. Persp. Let. 10, 8–13.

60

Rogers, J.J.W., 1988. The Arsikere granite of southern India: magmatism and metamorphism in a previously depleted crust. Chem. Geol. 67, 55–163. Romano, S.S., Dörr, W., Zulauf, G., 2004. Cambrian granitoids in pre-Alpine basement of Crete (Greece): evidence from U-Pb dating of zircon. Int. J. Earth Sci. 93, 844–859. Saha, L., Frei, D., Gerdes, A., Pati, J.K., Sarkar, S., Patoke, V., Bhandari, A., Nasipur, P., 2016. Crustal geodynamics from the Archaean Bundelkhand Craton, India: constraints from zircon U-Pb-Hf isotope studies. Geol. Mag. 153, 179–192. Sambridge, M.S., Compston, W., 1994. Mixture modeling of multicomponent datasets with application to ion-probe zircon ages. Earth Planet. Sci. Lett. 128,373–390. Santosh, M., Yang, Q.Y., Shaji, E., Tsunogae, T., Mohan, M.R., Satyanarayanan, M., 2015. An exotic Mesoarchean microcontinent: the Coorg Block, southern India. Gondwana Res. 27, 165–195. Sarma, D.S., McNaughton, N.J., Belusova, E., Ram Mohan, M., Fletcher, I.R., 2012. Detrital zircon U–Pb ages and Hf-isotope systematics from the Gadag Greenstone Belt: Archean crustal growth in the western Dharwar Craton, India. Gondwana Res. 22, 843–854. Samuel, V.O., Santosh, M., Liu, S.W., Wang, W., Sajeev, K., 2014. Neoarchean continental growth through arc magmatism in the Nilgiri Block, southern India. Precambrian Res. 245, 146–173. Shirey, S.B., and Richardson, S.H., 2011. Start of the Wilson Cycle at 3 Ga shown by diamonds from subcontinental mantle. Science, 333, 434–436.

61

Smithies, R.H., Champion, D.C., van Kranendonk, M.J., 2009. Formation of continental crust through infracrustal melting of enriched basalt. Earth Planet. Sci. Lett. 281(3–4), 298– 306. Söderlund, U., Bleeker, W., Demirer, K., Srivastava, R.K., Hamilton, M., Nilsson, M., Pesonen, J.L., Samal, K.A., Jayananda, M., Ernst, E.R., Srinivas, M., 2019. Emplacement ages of Paleoproterozoic mafic dyke swarm in eastern Dharwar craton, India: Implication for paleo reconstructions and support for a ̴30° change in dyke trends from south to north. Precambrian Res 329, 26–43. Soman, A., Tomaschek, F., Berndt, J., Geisler, T., Scherer, E. 2006. Hydrothermal reequilibration of zircon from an alkali pegmatite of Malawi. Beihefte zum. Euro. J. Mineral. 18, 132. Spandler, C., Hermann, J., Rubatto, D., 2004. Exsolution of thortveitite, yttrialite, and xenotime during low-temperature recrystallization of zircon from New Caledonia, and their significance for trace element incorporation in zircon. Am. Mineral. 89, 1795–1806. Srikantappa, C., Raith, M., Touret, J., 1992. Synmetaorphic high-density carbonic fluids in the lowercrust: evidence from the Nilgiri granulites, southern India. J. Petro. 33, 733–760. Stähle, H.J., Raith, M., Hoernes, S., Delfs, A., 1987. Element mobility during incipient granulite formation at Kabbaldurga, Southern India. J. Petro 28, 803–834. Stern, R.J., 2005. Evidence from ophiolites, blueschists, and ultra-high pressure metamorphic terranes that the modern episode of subduction tectonics began in Neoproterozoic time. Geology, 33, 557–560. Swami Nath, J., Ramakrishnan, M., 1981. Early Precambrian supracrustals of Southern Karnataka. Memoirs of the Geological Survey of India 112, 308p.

62

Swami Nath, J., Ramakrishnan, M., Viswanatha, M.N., 1976. Dharwar stratigraphic model and Karnataka craton evolution. Records of the Geological Survey of India 107, 149–175. Taylor, P.N., Chadwick, B., Moorbath, S., Ramakrishanan, M., Viswanatha, M.N., 1984. Petrography, chemistry and isotopic ages of Peninsular Gneisses, Dharwar acid volcanics and Chitradurga granite with special reference to Archaean evolution of Karnataka craton, Southern India. Precambrian Res. 23 (3–4), 349–375. Trendall, A.F., de Laeter, J.R., Nelson, D.R., Bhaskar Rao, Y.J., 1997b. Further zircon U-Pb age data for the Daginikatte formation, Dharwar Supergroup, Karnataka craton. J. Geol. Soc. India 50, 25–30. Trendall, A.F., de Laeter, J.R., Nelson, D.R., Mukhopadhyay, D., 1997a. A precise U–Pb age for the base of Mulaingiri formation (Bababudan Group, Dharwar Supergroup) of the Karnataka craton. J. Geol. Soc. India 50, 161–170. Upadhyay, D., Chattopadhyay, S., Mezger, K., 2019. Formation of Paleoarchean-Mesoarchean Na-rich (TTG) and K-rich granitoid crust of the Singhbhum craton, eastern India: Constraints from major and trace element geochemistry and Sr-Nd-Hf isotope composition. Precambrian Res. 327, 255–272. Vervoort, J.D., Blichert-Toft, J., Patchett, P.J., Albarède, F., 1999. Relationships between Lu–Hf and Sm–Nd isotopic systems in the global sedimentary system. Earth Planet. Sci. Lett. 168, 79–99. Vezinet, A., Pearson, D. G., Thomassot, E., Stern, R. A., Sarkar, C., Luo, Y., and Fisher, C. M., 2018. Hydrothermally altered mafic crust as source for early Earth TTG: Pb/Hf/O isotope and trace element evidence in zircon derived from TTG of the Eoarchean Saglek Block, N. Labrador. Earth Planet. Sci. Lett. 503, 95–107.

63

Vezinet, A., Thomassot, E., Pearson, G. D., Stern, A. R., Luo, Y., Sarkar, C., 2019. Extreme δ18O signatures in zircon from the Saglek Block (North Atlantic Craton) document reworking of mature supracrustal rocks as early as 3.5 Ga. Geology, 47, 605–608. Vijaya Kumar, T., Bhaskar Rao, Y.J., Plavsa, D., Collins, A.S., Tomson, J.K., Vijaya Gopal, B., Babu, E.V.S.S.K., 2017. Zircon U-Pb ages and Hf isotopic systematics of Charnockites gneisses from the Ediacaran- Cambrian high grade metamorphic terranes, southern India: constraints on crust formation, recycling, and Gondwana correlations. Geol. Soc. Am. Bull. 129 5/6, 625–648. Wan, Y., Liu, D., Nutman, A., Zhou, H., Dong, C., Yin, X., Ma, M., 2012. Multiple 3.8–3.1 Ga tectono-magmatic events in a newly discovered area of ancient rocks (the Shengousi Complex), Anshan, North China Craton. J. Asian Earth Sci. 54–55, 18–30. Wan, Y., Liu, D., Song, B., Wu, J., Yang, C., Zhang, Z., Geng, Y., 2005. Geochemical and Nd isotopic compositions of 3.8 Ga meta-quartz dioritic and trondhjemitic rocks from the Anshan area and their geological significance. J. Asian Earth Sci. 24, 563–575. Wang, Y., Li, X., Jin, W., Zhang, J., 2015. Eoarchean ultra-depleted mantle domains inferred from ca. 3.81 Ga Anshan trondhjemitic gneisses, North China Craton. Precambrian Res. 263, 88–107. Wang, J., Santosh, M., 2019. Eoarchean to Mesoarchean crustal evolution in the Dharwar craton, India: Evidence from detrital zircon U-Pb and Hf isotopes. Gondwana Res. 72. 1–14. Wilde, S.A., Valley, J.W., Peck, W.H., Graham, C.M., 2001. Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature 409, 175– 178.

64

Whitney, D.L., Evans, B.W., 2010. Abbreviations for names of rock-forming minerals. Am. Miner. 95, 185–187. Xie, L., Wang, R. Chen, X., Qiu, J. and Wang D., 2005. Th‐ rich zircon from peralkaline A‐ type granite: Mineralogical features and petrological implications. Chin. Sci. Bull. 50, 809–817. Zeh, A., Gerdes, A., Barton, J.M., Wu, D., 2009. Archean accretion and crustal evolution of the Kalahari Craton—the zircon age and Hf isotope record of granitic rocks from Barberton/Swaziland to the Francistown Arc. J. Petrol.50, 933–966. Zeh, A., Gerdes, A., Millonig, L., 2011. Hafnium isotope record of the Ancient Gneiss Complex, Swaziland, southern Africa: evidence for Archaean crust–mantle formation and crust reworking between 3.66 and 2.73 Ga. J. Geol. Soc. Lond. 168, 953–963. Zeh, A., Stern, R.A., Gerdes, A., 2014. The oldest zircon of Africa. Their U-Pb-Hf-O isotope and trace element systematics and implication for Hadean to Archean crust-mantle evolution. Precambrian Res. 241, 203–230.

Figure captions

Figure 1: Geological map of the Western Dharwar Craton and surrounding regions (modified from Jayananda et al., 2018; Ratheesh-Kumar et al., 2016). Sample locations are indicated by filled stars. The blue stars mark location of samples used for U-Pb geochronology and Hf isotope analyses in addition to major and trace element measurements. The high grade terranes and different microblocks indicated on the map are as follows: CB=Coorg Block, NB=Nilgiri Block, BRB=Biligirirangan Block and SB=Shevaroy Block. The inset is a generalized geological map

65

of peninsular India showing the major lithotectonic divisions. (Abbreviations: WDC=Western Dharwar Craton; EDC=Eastern Dharwar Craton; CDC=Central Dharwar Craton; CB= Cuddapah Basin; BSC=Bastar Craton; SC= Singhbhum Craton; CGC= Chhotanagpur Gneiss Complex; CITZ= Central Indian Tectonic Zone; BC= Bundelkhand Craton; DT= Deccan Traps; SP=Shillong Plateau; BR= Biligirirangan).

Figure 2: Back scattered electron images illustrating salient microtextural relations in granitoids from the Gorur-Holenarsipur belt (a-j), Sargur belt (k-l), transition zone of the Central Dharwar Province (m-n), and Biligirirangan Hills (o). (a) biotite-defined tectonic fabric overgrown by epidote/clinozoisite, titanite, and muscovite in tonalite. The inset contains images of a zircon with the igneous zones partially replaced by patchy recrystallized domains, (b, c, d) biotite- and muscovite-defined foliation that overgrows K-feldspar, plagioclase, and ilmenite/iron oxide in trondhjemites. The mica-defined fabric is overgrown by epidote, and titanite, (e, f, g) fluidinduced replacement of plagioclase by albite with the altered patches appearing pitted and porous. The plagioclase is extensively replaced by K-feldspar, clinozoisite/epidote, titanite, and sericite, (h, i, and d, i insets) alteration and replacement of apatites and ilmenites by allanite, zircon and HREE-rich Y-Yb oxide. Fine veins of allanite are associated with epidote. The apatite and zircon are pitted and porous (d). The granodiorites also possess a biotite-defined metamorphic fabric which replaces K-feldspar and iron oxides, (j) anhedral reequilibrated zircons closely associated with iron oxides and monazites. The cores preserve traces of oscillatory zoning which are truncated by broad featureless metamorphic rims (j inset). Plagioclase shows patchy alteration and replacement by K-feldspar, (k) patches of amphibole overgrowing the plagioclase and quartz matrix with the high-grade gneissic fabric overprinted by

66

greenschist facies minerals such as epidote, titanite, allanite, K-feldspar, and sodic plagioclase. The uranium-rich cores of some zircons appear pitted/porous with the igneous zoning being partially erased (k inset), (l) biotite-defined tectonic fabric which overgrows patchy K-feldspar, plagioclase, and ilmenite in trondhjemite. Titanite is seen to replace ilmenite, (m) biotite-defined foliation in trondhjemites from the transition zone of the Central Dharwar Province. Biotite and epidote/clinozoisite replace K-feldspar, plagioclase, and ilmenite. Plagioclase is pitted and porous and altered to albite along grain boundaries and fractures. Patches of allanite are associated with biotite-epidote-clinozoisite, (n) apatites rimmed by secondary zircon and allanite. Fine veins or patches of allanite are seen in the vicinity of monazite and apatite, (o) coarse banding in granodiorite from the BR Hills. The banding is defined by leucocratic layers rich in of quartz, perthitic K-feldspar and plagioclase alternating with orthopyroxene-rich layers. Fine fibrous biotite overgrows the earlier fabric.

Figure 3: Classification diagram of granitoids from the Western Dharwar Craton based on their (a) normative Albite (Ab)–Anorthite (An)–Orthoclase (Or) (after Barker, 1979), (b) Al2O3/(FeOt+MgO)–3*CaO–5*(K2O/Na2O) with fields representing the composition of melts derived from a range of potential sources (after Laurent et al., 2014), (c) FeOt/(FeOt+MgO) vs. SiO2 (wt. %), (c) Na2O+K2O-CaO vs. SiO2 (wt. %) and (d) A/NK vs. A/CNK. Previously published (Ramakrishnan et al., 1984; Dhoundial et al., 1987; Bhaskar Rao et al., 1991; Devaraju et al., 2007; Naqvi et al., 2009; Jayananda et al., 2015; Guitreau et al., 2017) data on granitoids from the Western Dharwar Craton are also plotted for comparison.

67

Figure 4: Harker diagrams illustrating the variations in concentration of selected major and trace elements/ratios from the TTGs and granites of the Western Dharwar Craton. Data from Ramakrishnan et al. (1984), Dhoundial et al. (1987), Bhaskar Rao et al. (1991), Devaraju et al. (2007), Naqvi et al. (2009), Jayananda et al. (2015) and Guitreau et al. (2017) on the Western Dharwar Craton granitoids are also plotted.

Figure 5: Chondrite normalized REE and primitive mantle normalized multi-element diagrams for tonalites (a, b), trondhjemites (c, d), granodiorites (e, f) and granites (g, h) from the Western Dharwar Craton. Eu/Eu* vs. La (ppm) plot (h inset). The REE patterns for 4.0–3.6 Ga TTGs from the Acasta Gneiss Complex (Reimink et al., 2014, 2016a) and high-, medium- and lowHREE Archean TTGs (Moyen and Martin, 2012) are also shown for comparison. Gray fields mark the range in the variation of REE and other trace element concentrations in the dataset of Naqvi et al. (2009) and Jayananda et al. (2015). The chondrite and primitive-mantle normalizing values are after McDonough and Sun (1995).

Figure 6: (a) La/Yb vs. Yb (ppm), (b) Sr/Y vs. Y (ppm) bivariate plots for TTGs. The WDC granitoids show a large variation in trace element concentrations/ratios but mostly plot in the field of medium- to low-P TTGs (Moyen, 2011). (c) Sr/Y vs. Y (ppm) field of high-HREE TTG, low-HREE TTG, and transitional (enriched) TTG after Dey et al. (2014). The WDC granitoids plot in the field of high-HREE to transitional (enriched) TTG. (d) Sr/Y vs. Sr/La plot showing higher Sr/Y and Sr/La for the granitoids with anomalous REE depletion/enrichment. These granitoids plot along modeled plagioclase addition trend assuming the tonalites as the most primitive member of granitoid suite. Published data from TTGs and granites in the Western

68

Dharwar Craton (Bhaskar Rao et al., 1991; Devaraju et al., 2007; Naqvi et al., 2009; Jayananda et al., 2015), Acasta Gneiss Complex (AGC) (Iizuka et al., 2010; Mojzsis et al., 2014; Reimink et al., 2014, 2016a), southwest Greenland (GL) (Nutman et al., 1996, 1999; Kamber et al., 2002; Nærra et al., 2012; Hoffmann et al., 2011, 2014) Kaapvaal Craton (KC) (Kröner et al., 2000, 2014; Henderson et al., 2000; Laurent et al., 2012; Hoffmann et al., 2016), North China Craton (NCC) (Wan et al., 2005, 2012; Wang et al., 2015), are plotted for comparison.

Figure 7: Representative cathodoluminescence and back scattered electron images documenting the internal structures of zircons from the studied TTGs and granites (see text for description). The laser ablation spots and the corresponding

207

Pb/206Pb ages are marked (not to scale) as

dotted circles (discordant analyses are marked by a “d” after the age).

Figure 8: Chondrite-normalized REE patterns of magmatic and recrystallized/reequilibrated or metamorphic zircons from (a) 3.43–3.41 Ga and 3.36–3.34 Ga, and (b) 3.29–3.25 Ga and 2.67– 2.65 Ga granitoids of the WDC. The recrystallized/reequilibrated and metamorphic zircons show variable degrees of enrichment in LREEs, and loss of positive Ce anomalies.

Figure 9: U-Pb concordia and

207

Pb/206Pb age relative probability density/histogram plots for

zircons from the 3.43–3.41 Ga TTG suite: (a-b) tonalite, WDS-8, (c-d) trondhjemite, WDS-10A, both from the Sargur region. The probability density plots were constructed using only the concordant analyses. The ages of the populations corresponding to the peaks in the probability density plots here and elsewhere were computed using the unmix function (Sambridge and Compston, 1994) in Isoplot 4.15 (Ludwig, 2003).

69

Figure 10: U-Pb concordia and

207

Pb/206Pb age relative probability density histogram plots for

zircons from the 3.36–3.34 Ga granitoids. This group includes trondhjemite (WDS-28), granodiorites (WDS-31, 32) and granite (WDS-30B) from the Gorur-Holenarsipur region and trondhjemite (WDS-17) from transition zone of the Central Dharwar Province.

Figure 11: U-Pb concordia and 207Pb/206Pb age relative probability density diagram for the 3.29– 3.25 Ga TTG and granite suite. These comprise tonalite (WDS-23A), trondhjemite (WDS-24, 27), and granodiorite (WDS-18) from the Gorur-Holenarsipur region.

Figure 12: U-Pb concordia and 207Pb/206Pb age relative probability density plots showing the age data from the Neoarchean (2.67–2.65 Ga) granitoids. This group includes granite (WDS-10B) from the Sargur region and granodiorite (WDS-16) from the transition zone of the Central Dharwar Province.

Figure 13: The initial

176

Hf/177Hf (a) and εHfi (b) vs. age for the WDC TTGs and granites

(plotted points are the weighted means of individual samples). The evolution curve for model depleted mantle (DM) (176Lu/177Hf=0.0384, Griffin et al., 2000) is plotted assuming silicate Earth differentiation of the Earth at 4.55 Ga. Evolution line for mafic crust (176Lu/177Hf=0.022) and TTG crust (176Lu/177Hf=0.005) are from Blichert-Toft and Albarède (2008). εHfi values from zircons in TTGs/granites from several Archean cratons worldwide are also plotted for comparison. The yellow, red and green curves roughly mark the temporal trends in the εHfi of zircons from TTGs of the Singhbhum Craton, Acasta Gneiss Complex/Slave Craton, and the Isua

70

region of southwest Greenland respectively [Data compilation: Southwest Greenland (SWG) (Kemp et al., 2009; Hiess et al., 2009; Nærra et al., 2012; Fisher and Vervoort, 2018); (AGC+SC) Acasta Gneiss Complex + Slave craton; northwest Canada (Iizuka et al., 2009; Reimink et al., 2014, 2016a, 2019; Bauer et al., 2017); Napier Complex (NC); Antarctica (Hiess and Bennett, 2016); Yilgarn Craton (YC); Australia (Kemp et al., 2010; Hiess and Bennett, 2016); Nuvvuagittuq Greenstone Belt (NGB); eastern Canada (O’Neil et al., 2013); Kaapvaal Craton (KC); Africa (Zeh et al., 2009, 2011; Kröner et al., 2013; Laurent and Zeh, 2015; Hoffmann et al., 2016); North China Craton (NCC); China (compilation of Hf isotope data for felsic meta-igneous rocks after Geng et al., 2012; Wang et al., 2015); Singhbhum Craton (SC); India (Dey et al., 2017, 2019; Chaudhuri et al., 2018; Pandey et al., 2019); Bundelkhand Craton (BC), India (Kaur et al., 2014; 2016a; Saha et al., 2016); Aravalli Banded Gneissic Complex (ABGC); India (Kaur et al., 2019); Western Dharwar Craton (WDC); India (Mohan et al., 2014; Ratheesh-Kumar et al., 2016; Guitreau et al., 2017)].

Declaration of interests The authors declare that they have no competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.

71

Table 1. Summary of petrographic characteristics of the granitoids samples used in this study Rock type/sample number

Co-ordinates (spatial extent)

Mineralogy*

Tonalite (WDS23A)

12°50'0.36"N, 76°13'57.59"E (Gorur-Holenarsipur region)

Pl, Bt, Qz, Ep, Ap, Ms, Ttn, Zrn

Trondhjemite (WDS-26)

12°50'56.06"N, 76°9'31.4"E (Gorur-Holenarsipur region)

Pl, Kfs, Qz, Ms, Bt, Ep, Ap, Ttn, Ilm, Zrn

Trondhjemite (WDS-28)

12°52'52.97"N, 76°4'40.66"E (Gorur-Holenarsipur region)

Pl, Kfs, Qz, Bt, Ms, Ep, Ap, Aln, Ttn, Czo, Zrn

72

Petrographic description Bt-defined tectonic fabric overgrown by Ep, Ttn, Ms (Fig. 2a). Finegrained Pl-rich matrix shows high temperature annealing forming a granoblastic mosaic. Bt- and Msdefined tectonic fabric that overgrows Kfs, Pl, and Ilm. Pl is extensively altered to sericite and is replaced by Kfs (2b, c). Ms and Bt define a weak fabric (Fig. 2d) and are overgrown by Ep and Ttn. Kfs replaces Pl. Veins and patches of Aln are associated with Ep and secondary zircon (Fig. 2d). Ap is altered / pitted and replaced by Aln and YYb oxide (Fig. 2d, inset).

Trondhjemite (WDS-24)

12°51'51.5"N, 76°15'0.16"E (Gorur-Holenarsipur region)

Pl, Kfs, Qz, Bt, Ep, Ap, Ms, Ttn, Zrn, Czo

Trondhjemite (WDS-27)

12°49'42.26"N, 76°4'4.07"E (Gorur-Holenarsipur region)

Pl, Kfs, Qz, Bt, Ep, Ilm, Ap, Ms, Zrn, Rt, Mnz

Trondhjemite (WDS-29)

12°55'41.17"N, 76°5'28.12"E (Gorur-Holenarsipur region)

Pl, Qz, Kfs, Bt, Ms, Zrn, Ep, Iron oxide

Trondhjemite (WDS-30A)

12°55'47.1"N, 76°4'48.25"E (Gorur-Holenarsipur region)

Pl, Kfs, Bt, Qz, Ttn, Iron oxide, Zrn

73

No tectonic foliation. Pl extensively altered/pitted/p orous and replaced by Kfs, Czo and Ab. (Fig. 2e, f). Late-stage Bt and Ms replace Kfs/ Pl (Fig. 2f). Pl replaced by Kfs, Ms, and Bt along margins (Fig. 2g, h). Micronsized metamorphic zircons occur near larger Ap, Ilm, and Y-Yb oxide (Fig. 2 h). Weak fabric defined by Bt and Ms. Bimodal distribution of grain size. Pl and Qz show bulging grain boundary migration recrystallizatio n. Bt shows replacement by Ep and Aln. Evidence of neo-zircon formation is present. Absence of strong tectonic fabric. Scattered Bt show weak alignment. Pl extensively altered.

Granodiorite (WDS-18)

12°42'44.01"N, 76°18'24.97"E (Gorur-Holenarsipur region)

Kfs, Pl, Mc, Qz, Bt, Zrn

Granodiorite (WDS-31)

12°51'29.96"N, 75°41'43.79"E (Gorur-Holenarsipur region)

Kfs, Pl, Qz, Bt, Zrn

Granodiorite (WDS-32)

12°50'47.51"N, 75°41'13.51"E (Gorur-Holenarsipur region)

Kfs, Pl, Qz, Bt, Zrn

Granite (WDS30B)

12°55'47.1"N, 76°4'48.25"E (Gorur-Holenarsipur region)

Kfs, Qz, Pl, Mc, Ms, Bt, Zrn

74

Bt weakly aligned producing a crude foliation. Microcline is a major phase. Pl grains show grain boundary migration by bulging and sub-grain formation. Weak alignment of Bt which overgrows Kfs and Fe-oxides. Pl, Kfs together with Qz form the main matrix. Micron-sized zircon distributed throughout the rock matrix, and also associated with Fe-oxide and Mnz (Fig. 2j, inset). Bt is weakly aligned. Pl, Kfs together with Qz form the main matrix. Micron-sized zircon distributed throughout the rock matrix. Stretched Qz, Ms and Kfs define a weak fabric. Pl is extensively altered. Myrmekitic intergrowth present. The minerals show

Tonalite (WDS8)

11°55'41.39"N, 76°34'21.32"E (Sargur region)

Pl, Amp, Qz, Ttn, Ap, Ep, Aln, Zrn

Trondhjemite (WDS-10A)

11°57'23.33"N, 76°39'33.49"E (Sargur region)

Pl, Qz, Bt, Kfs, Ilm, Zrn, Mnz, Iron oxide

Granite (WDS10B)

11°57'23.33"N, 76°39'33.49"E (Sargur region)

Kfs, Qz, Pl, Bt, Zrn

75

bulging grain boundary migration recrystallizatio n. Pl-rich rock. Amphiboles are anhedral and skeletal in nature, and commonly associated with Qz and Pl (Fig. 2k). Secondary Aln and Ep grow near Amp rims (Fig. 2k). Zircons are mostly associated with Ttn and Ap (Fig. 2k). Altered zircon cores appear bright in BSE images (Fig. 2k inset). Pl-rich rock with only minor Kfs. Biotite defines a weak fabric replacing ilmenite. Kfs occurs as patches along Pl, Qz grain boundaries (Fig. 2l). Coarsegrained (pegmatitic) granite with mm-sized crystals of Pl, Kfs and Qz. Pl and Kfs are extensively altered.

Trondhjemite (WDS-11B)

12°8'2.96"N, 77°1'24.63"E (transition zone of Central Dharwar Province)

Pl, Qz, Kfs, Grt, Bt, Aln, Ep, Czo

Granite (WDS11A)

12°8'2.96"N, 77°1'24.63"E (transition zone of Central Dharwar Province)

Kfs, Pl, Qz, Bt, Grt, Ttn, Ap, Zrn, Aln, Mnz

Granite (WDS11C)

12°8'2.96"N, 77°1'24.63"E (transition zone of Central Dharwar Province)

Kfs, Pl, Qz, Bt, Ms

76

Lack of any preferred mineral alignment. Pl and Kfs altered to Bt, Czo, and Ep, (Fig. 2m). Bt-Ep-Czo alteration is commonly associated with patches of Aln (Fig. 2m). Bt defines the fabric in the rock. Pl, Kfs, and Qz grains are stretched parallel to the foliation. Bimodal grain size distribution with coarsegrained bands alternating with fine-grained recrystallized matrix. Micronsized zircons grow near Bt, Mnz, Ap and Aln vein association (Fig. 2n). Coarsegrained banded rock with bimodal distribution of grain size; mm-sized crystals of Pl, Kfs and Qz, recrystallized to fine aggregates along grain boundaries. Pl shows alteration

along the cleavages and fractures.

Trondhjemite (WDS-17)

11°59'52.30"N, 77°8'19.95"E (Biligirirangan Hills region)

Pl, Qz, Kfs, Bt, Zrn

Granodiorite (WDS-16)

12°1'40.03"N, 77°6'42.43"E (Biligirirangan Hills region)

Pl, Kfs, Qz, Opx, Zrn, Mnz, Iron oxide

*Mineral abbreviation are after Whitney and Evans (2010)

77

Pl and Qz are stretched and aligned. The rock has a banded appearance defined by alternate coarse-grained and finegrained layers. Strongly deformed and banded rock. The banding is defined by leucocratic layers rich in Qz, Kfs, and Pl alternating with Opx-rich layers. Fine fibrous biotite overgrows the banding (Fig. 2o).

Table 2. Major element composition (in wt. %) and trace element concentrations (in ppm) of the rocks from the TTG suite and granites of the Western Dharwar Craton Rock Type Sample no.

Ton alite WD S23 A

Trondh *

Trondh

Trondh

Trondh

Trondh

Trondh

Granod **

Granod

Grano d

Granite

WDS2 4

WDS26

WDS2 7

WDS28

WDS29 A

WDS3 0A

WDS 18

WDS 31

WDS 32

WDS 30B

75.6

74.5

79.7

75.1

74.9

75.7

73.8

72.9

76.2

13.9

14.2

11.1

13.5

13.8

12.7

13.9

14.1

13.2

0.67

1.47

1.83

1.23

1.41

2.11

1.74

1.82

0.41

0.04

0.03

0.08

0.09

0.03

0.09

0.08

0.03

0.06

0.25

0.47

0.34

0.41

0.41

0.47

0.54

0.77

0.13

1.70

2.73

1.33

2.13

1.98

2.13

2.10

2.73

1.59

4.89

4.78

4.35

4.41

4.43

3.41

3.70

3.75

3.73

2.64

1.30

0.96

2.66

2.59

2.95

3.43

3.01

4.23

0.08

0.18

0.13

0.20

0.18

0.09

0.22

0.36

0.04

0.04

0.03

0.03

0.07

0.08

0.02

0.15

0.17

0.05

0.10

0.12

0.01

0.02

0.07

0.16

0.25

0.25

0.19

0.05

0.05

0.01

0.01

0.04

0.03

0.05

0.08

0.08

0.03

0.11

0.14

0.12

0.06

0.06

0.06

0.03

0.08

100.0

99.9

99.9

100.0

99.9

99.9

99.9

100.0

99.9

0.986 651 10.1 11.9 130 2.10 1.10 19.1 60.8 617 4.55 78.5 3.40 2.45 501 6.42 12.4 1.56 6.01 1.32

1.49 1299 16.7 11.9 249 4.79 24.8 18.9 36.8 455 3.14 66.5 2.25 0.483 95.8 15.6 30.8 3.34 12.4 2.02

2.12 825 12.4 18.7 371 6.57 40.0 21.4 15.6 208 100 164 18.2 0.24 302 126 277 38.5 160 29.3

2.00 1233 18.7 11.1 244 4.58 1.42 20.6 77.9 390 12.9 108 26.6 3.42 477 32.5 61.1 6.47 23.2 4.09

1.91 1293 17.4 7.72 223 3.40 2.51 19.7 73.1 332 8.66 119 6.88 2.06 371 24.9 46.4 4.93 18.0 3.30

3.09 1097 14.1 7.70 218 6.56 1.95 16.8 43.7 160 8.29 72.3 2.33 0.102 506 27.8 49.9 5.06 17.7 2.77

1.95 1637 35.1 7.84 237 6.04 2.83 18.1 63.9 414 8.05 114 3.68 0.27 824 35.9 65.8 6.88 24.5 4.07

1.89 1853 44.5 9.68 174 9.04 8.35 18.0 64.7 432 5.13 101 3.28 0.41 1004 21.5 42.4 4.65 17.6 2.94

0.865 289 6.02 3.65 219 2.29 1.09 16.2 78.2 306 7.63 45.6 3.03 1.01 711 7.07 14.3 1.53 5.81 1.30

Oxide (Wt. %) 71. 74.8 7 14. 14.4 Al2O3 3 2.9 0.82 FeOt 8 0.0 0.08 MnO 9 1.1 0.21 MgO 0 4.0 1.35 CaO 2 3.8 5.11 Na2O 4 1.4 2.72 K2O 3 0.3 0.08 TiO2 2 0.0 0.03 P2O5 9 0.0 0.21 ZnO 9 0.0 0.03 BaO 2 0.0 0.09 LOI 5 10 100.0 Total 0.0 Trace elements (ppm) 1.07 Sc 5.96 340 Ti 2244 7.79 V 53.2 5.53 Cr 10.7 274 Co 207 2.95 Ni 11.2 0.54 Cu 8.01 18.6 Ga 16.9 64.7 Rb 62.3 456 Sr 274 4.78 Y 17.2 45.3 Zr 101 2.12 Nb 6.75 0.96 Cs 4.42 469 Ba 206 2.11 La 33.4 4.23 Ce 59.9 0.573 Pr 6.13 2.40 Nd 21.0 0.684 Sm 3.48 SiO2

78

Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U

0.923 3.55 0.480 2.68 0.495 1.42 0.200 1.41 0.222 2.47 0.609 8.69 7.05 0.932

0.315 0.753 0.132 0.827 0.159 0.48 0.076 0.565 0.089 1.24 0.205 13.4 0.670 0.394

0.480 1.23 0.168 0.883 0.154 0.451 0.067 0.484 0.075 2.15 0.295 16.1 3.43 1.51

0.535 1.59 0.158 0.643 0.105 0.313 0.043 0.330 0.052 1.49 0.234 6.18 2.01 0.393

3.34 28.7 4.13 21.6 3.61 9.21 1.20 7.54 1.07 5.31 1.00 11.2 16.1 1.91

1.04 3.84 0.508 2.70 0.466 1.33 0.189 1.37 0.200 2.66 2.22 18.4 9.58 7.14

0.822 3.02 0.383 1.85 0.307 0.838 0.114 0.821 0.125 2.87 0.608 14.0 7.85 1.85

1.06 2.62 0.303 1.57 0.303 0.924 0.138 1.10 0.191 1.84 0.078 14.8 6.53 0.272

1.22 3.71 0.428 1.94 0.302 0.769 0.089 0.581 0.088 2.59 0.232 12.7 11.93 0.504

1.11 2.56 0.281 1.22 0.191 0.498 0.057 0.385 0.060 2.83 0.154 10.0 7.93 0.418

0.695 1.37 0.226 1.39 0.298 0.818 0.134 1.03 0.166 1.38 0.424 16.8 3.12 1.48

*Trondh=trondhjemite, Granod**=granodiorite, †= international rock standards Table 2 continued. Major element composition (in wt. %) and trace element concentrations (in ppm) of the rocks from the TTG suite and granites of the Western Dharwar Craton Rock Type

Tonalit e

Trondh

Granite

Trondh

Granite

Granite

Trondh

Granod

Basalt†

Andesite †

Sample no.

WDS8

WDS1 0A

WDS 10B

WDS1 1B

WDS 11A

WDS 11C

WDS1 7

WDS 16

JB-3 (N=3)

JA-2 (N=4)

Gran ite† JG-2 (N=4 )

Oxide (Wt. %) SiO2

72.7

73.9

77.6

78.2

75.1

79.7

74.2

74.9

53.34

60.07

Al2O3

13.3

15.4

12.7

13.0

13.7

11.1

13.8

13.1

16.61

15.17

0.53 0.01 0.20 1.67 3.90 3.09 0.08 0.04 0.08 0.00 0.15 100.0

0.36 0.01 0.11 2.38 4.57 0.99 0.06 0.05 0.19 0.02 0.09 100.0

1.03 0.02 0.37 2.00 4.20 3.24 0.13 0.05 0.06 0.03 0.06 100.0

0.16 0.03 0.08 0.85 2.47 5.20 0.03 0.04 0.23 0.02 0.12 100.0

1.98 0.09 0.50 2.56 4.86 1.39 0.26 0.14 0.07 0.01 0.04 99.9

1.88 0.06 0.45 2.53 3.65 3.00 0.15 0.06 0.14 0.04 0.06 100.0

10.03 0.17 4.96 9.58 2.63 0.74 1.35 0.32

5.37 0.22 6.99 6.40 2.96 1.76 0.63 0.21

78.7 2 11.4 4 0.71 0.01 0.05 0.92 3.16 4.63 0.06 0.02

99.7

99.7

99.7

1.02 332 7.66 11.2 228 3.27

0.983 150 8.83 14.9 296 3.30

1.39 952 16.7 5.16 173 2.80

0.753 168 6.33 8.25 287 3.39

4.17 2124 16.4 8.49 196 4.82

2.99 1423 26.8 14.9 419 8.72

26.2 7349 311 53.6 32.1 35.4

18.4 3984 118 424 28.8 136

2.14 219 4.04 2.83 4.08 1.69 0.78 4 18.1 289 13.9 84.8

1.02 FeOt 2.96 0.06 MnO 0.11 0.33 MgO 1.22 3.06 CaO 6.52 5.02 Na2O 2.21 0.89 K2O 0.26 0.18 TiO2 0.30 0.07 P2O5 0.11 0.01 ZnO 0.21 0.02 BaO 0.01 0.04 LOI 0.09 100.0 Total 100.0 Trace elements (ppm) 0.979 Sc 6.43 1074 Ti 1836 12.0 V 43.6 6.30 Cr 48.7 196 Co 302 2.92 Ni 24.9 Cu

40.0

6.28

2.00

7.78

21.46

3.15

7.21

4.72

185

28.5

Ga Rb Sr Y

15.0 2.22 191 13.0

16.0 29.4 1135 2.10

16.8 115 337 11.6

13.2 8.46 402 6.86

18.6 57.1 291 8.68

12.0 118 181 20.8

26.4 22.5 622 11.1

19.8 101 229 9.13

17.1 8.62 310 21.5

16.6 71.1 244 15.7

79

Zr Nb Cs Ba La Ce Pr Nd Sm

46.7 5.69 0.05 38.9 21.7 41.1 4.46 16.4 3.07

39.2 1.18 1.82 99.0 12.2 27.5 3.10 11.8 1.89

55.7 5.43 2.25 156 6.76 15.8 1.80 6.77 1.64

41.7 1.30 0.09 94.8 4.14 6.96 0.77 2.66 0.43

91.1 3.74 0.22 437 19.2 36.6 3.93 14.6 2.93

41.0 1.28 0.43 292 13.0 31.3 3.59 13.6 3.30

94.5 8.78 0.02 145 27.9 55.0 6.17 21.1 3.96

102 6.74 6.38 377 19.0 41.4 4.40 15.7 2.70

76.4 1.84 0.63 205 6.32 17.8 2.65 13.2 3.54

109 8.90 5.12 316 14.7 33.4 3.67 14.4 3.08

Eu

0.782

0.565

0.381

0.444

0.851

0.412

0.862

0.822

1.08

0.91

Gd Tb

3.14 0.441

1.39 0.128

1.71 0.335

0.443 0.076

2.82 0.386

3.44 0.501

3.78 0.392

2.46 0.315

3.72 0.627

3.21 0.498

Dy

2.46

0.474

2.28

0.719

1.91

3.23

2.28

1.67

3.85

2.99

Ho Er Tm Yb Lu Hf Ta Pb Th U

0.454 1.28 0.180 1.27 0.196 1.29 0.414 2.74 4.58 0.429

0.072 0.208 0.026 0.177 0.026 0.81 0.139 4.29 1.58 1.05

0.451 1.38 0.213 1.55 0.226 2.04 0.734 23.7 9.90 31.56

0.222 0.926 0.185 1.62 0.269 1.63 0.163 5.26 0.222 0.274

0.305 0.784 0.099 0.666 0.099 2.40 0.252 17.4 7.50 1.21

0.618 1.88 0.312 2.43 0.379 1.51 0.173 15.1 9.01 3.98

0.386 1.05 0.112 0.780 0.116 2.33 0.184 14.5 5.30 0.309

0.312 0.949 0.145 1.12 0.182 2.68 1.17 17.0 7.73 1.45

0.735 2.09 0.300 2.13 0.327 2.02 0.238 4.07 0.950 0.345

0.571 1.65 0.240 1.74 0.272 2.51 0.743 17.6 4.64 2.03

*Trondh=trondhjemite, Granod**=granodiorite, †= international rock standards

80

106 15.4 7.01 51.6 19.7 48.4 6.20 25.9 7.96 0.09 4 8.53 1.65 11.0 5 2.24 6.86 1.08 8.03 1.25 4.99 2.20 31.6 30.8 10.8

Table 3. Summary of zircon Hf isotope and U-Pb ages presented in this study Sample Name

Wt. mean Hf isotope 176Hf/177Hf

i(Wt.m)

U-Pb zircon ages (Ma)

ɛHfi (Wt.m)

Magmatic

Metamorphic

Inherited NA

Tonalite (WDS-8)

0.280675±18

3.6±0.6

3414±5

3353±6 3264±10 3154±11 3065±14

Trondhjemite (WDS-10A)

0.280694±13

4.4±0.5

3420±8

3329±8 3256±9 3156±63

3606±24*

3425±29

Trondhjemite (WDS-17)

0.280703±26

2.7±0.9

3337±15

3269±9 3154±13 3067±19 2999±13 2947±15 2773±32 2562±7 2532±13

Trondhjemite (WDS-28)

0.280724±20

3.9±0.7

3353±4

3268±7 3187±31 3083±16

NA

Granite (WDS-30B)

0.280726±16

3.5±0.6

3334±11

3221±37 3150±28 2638±32

NA

Granodiorite (WDS-31)

0.280742±23

4.2±0.8

3342±10

3258±10 3153±38 2971±40

NA

3237±18 3141±10 3062±18 2987±13 2927±28

NA

Granodiorite (WDS-32)

0.280731±34

4.1±1.2

3355±17

Granodiorite (WDS-18)

0.280745±13

3.2±0.5

3289±6

Trondhjemite (WDS-24)

0.280761±22

3.1±0.8

3263±8

3154±21

3343±20

Trondhjemite (WDS-27)

0.280800±24

4.4±0.8

3260±13

3149±15 3073±15 3009±18

NA

Tonalite (WDS-23A)

0.280770±26

3.5±0.9

3268±6

3167±11 3082±23

NA

Granodiorite (WDS-16)

0.281095±18

0.69±0.7

2660±4

2526±24

2831±25 2935±24

Granite (WDS-10B)

0.281093±70

0.4±2.5

2649±13

2574±15

3343±34

NA

wt.m =weighted mean; 176Hf/177Hfi=initial ratio; ɛHfi= initial epsilon Hafnium; Ages other than 81

those marked by * are concordia age (* denotes 207Pb/206Pb age)

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

Highlights 

West Dharwar Craton granitoid crust formed at c. 3.43Ga, 3.36Ga, 3.29Ga, and 2.66Ga



Paleoarchean granitoids with juvenile εHfi extracted from 3.55–3.35Ga mafic sources



Neoarchean granitoids with chondritic εHfi have mixed juvenile-crustal signature



TTG parental magmas derived from garnet-free plagioclase-bearing amphibolites



Juvenile εHfi, short protolith ages suggest formation by rapid recycling of basalts

101