Eoarchean to Mesoarchean crustal evolution in the Dharwar craton, India: Evidence from detrital zircon U-Pb and Hf isotopes

Gondwana Research 72 (2019) 1–14

Contents lists available at ScienceDirect

Gondwana Research journal homepage: www.elsevier.com/locate/gr

Eoarchean to Mesoarchean crustal evolution in the Dharwar craton, India: Evidence from detrital zircon U-Pb and Hf isotopes Jing-Yi Wang a, M. Santosh a,b,c,⁎ a b c

School of Earth Sciences and Resources, China University of Geosciences, Beijing, 29 Xueyuan Road, Beijing 100083, China Centre for Tectonics, Resources and Exploration, Department of Earth Sciences, University of Adelaide, SA 5005, Australia Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea

a r t i c l e

i n f o

Article history: Received 10 January 2019 Received in revised form 19 February 2019 Accepted 19 February 2019 Available online 18 March 2019 Handling Editor: T. Tsunogae Keywords: Dharwar craton Crustal evolution Zircon geochronology and Lu-Hf isotopes Detrital zircon Southern India

a b s t r a c t The formation and evolution of continental crust in the Early Earth are of fundamental importance in understanding the emergence of continents, their assembly into supercontinents and evolution of life and environment. The Dharwar Craton in southern India is among the major Archean cratons of the world, where recent studies have shown that the craton formation involved the assembly of several micro-continents during Meso- to Neoarchean through subduction-accretion-collision processes. Here we report U-Pb-Hf isotope data from detrital zircons in a suite of metasediments (including quartz mica schist, fuchsite quartzite and metapelite) from the southern domain of the Chitradurga suture zone that marks the boundary between the Western and Central Dharwar Craton. Morphology and internal structure of the zircon grains suggest that the dominant population was derived from proximal granitic (felsic) sources. Zircon U-Pb data are grouped into Paleo-Mesoarchean and Neoarchean to Paleoproterozoic with peaks at 3227 Ma and 2575 Ma. The age spectra of detrital zircon grains, in combination with the Lu-Hf isotopic analyses indicate sediment provenance from magmatic sources with model ages in the range of ca. 3.67 to 2.75 Ga. A transition from dominantly juvenile to a mixture of juvenile and recycled crustal components indicate progressive crustal maturity. The results from this study suggest major crustal growth events during ca. 3.2 Ga and 2.6 Ga in Dharwar. Our study provides insights into continental emergence, weathering and detrital input through river drainage systems into the trench during Eoarchean to Mesoarchean. © 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction The formation and evolution of continental crust on the early Earth, its incorporation into cratons and building of supercontinents, as well as destruction along convergent plate margins constitute important themes in understanding the evolution of Earth as a habitable planet with major implications on resources, environment and life (e.g., Maruyama et al., 2013, 2018; Nance et al., 2014; Santosh et al., 2009; Spencer et al., 2017a; Hawkesworth et al., 2018). The time of initiation of modern-style plate tectonics and the emergence of continental crust above sea level are debated, with recent geological and numerical models marking the Archean Era as an important timeframe that witnessed a major transition through secular cooling of the mantle (Szilas et al., 2016; Maruyama and Ebisuzaki, 2017; Spencer et al., 2017a). Recent zircon U-Pb-Hf-O isotope data on the Mesoarchean magmatic rocks from the Coorg Block in southern India illustrate felsic crust formation at 3.5-Ga, followed by further pulses at 3.37–3.27 and 3.19–3.14 Ga, comprising both reworked crust and juvenile material, ⁎ Corresponding author at: School of Earth Sciences and Resources, China University of Geosciences, Beijing, 29 Xueyuan Road, Beijing 100083, China. E-mail address: [email protected] (M. Santosh).

indicating successive crustal maturation (Roberts and Santosh, 2018). The elevation in δ18O through time was interpreted to indicate an increase in the amount of sediment recycling reflecting crustal thickening, as well as progressive emergence of continental crust. Archean cratons on the globe provide important windows to gain insights on the nature and history of continental growth and emergence in the early Earth, as many of these preserve Eoarchean to Mesoarchean geological and tectonic imprints (e.g., Van Kranendonk, 2010; Santosh et al., 2015; Roberts and Santosh, 2018). The Paleo- to Neoarchean granitegreenstone terranes in ancient cratons display geological and geochemical imprints of distinct magmatic pulses and crust building events at 3.8 Ga, 3.5–3.2 Ga, 2.8–2.7 and 2.6–2.5 Ga through vertical and lateral accretion of juvenile crustal materials as well as crustal recycling (Smithies et al., 2009; Manikyamba and Kerrich, 2012; Manikyamba et al., 2015, 2017; Santosh et al., 2015; Tang and Santosh, 2018). The Dharwar Craton in southern India (Fig. 1) is a composite collage of Archean microcontinents that preserve important records of continental growth and recycling during distinct thermal and tectonic events ranging from 3.8 to 2.5 Ga (Jayananda et al., 2018; Santosh and Li, 2018; Li et al., 2018b). The ancient continental nuclei in the craton incorporates volcano-sedimentary successions of Archean greenstone belts that range in age from 3.6 to 2.5 Ga (Peucat et al., 1995; Chadwick

https://doi.org/10.1016/j.gr.2019.02.006 1342-937X/© 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

2

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Fig. 1. Geological framework of the Dharwar Craton in southern India (after Li et al., 2018b). Abbreviations: ChSZ—Chitradurga Shear Zone, KolSZ— Kolar Suture Zone; McSZ—Mercara Shear zone; SSZ— Salem Suture Zone; KoSZ—Kollegal Shear Zone; MeSZ—Mettur Shear Zone, NLSZ—Nallamalai Shear Zone, MSZ—Moyar Shear Zone, SASZ—Salem-Attur Shear Zone; BSZ—Bhavani Shear Zone, CaSZ—Cauvery Shear Zone, PCSZ—Palghat-Cauvery Shear Zone; KKPTSZ—Karur-Kambam-Painavu—Trichur Shear Zone; ASZ—Achankovil Shear Zone; WDC— Western Dharwar Craton; CDC—Central Dharwar Craton; EDC—Eastern Dharwar Craton; EGMB—Eastern Ghats Mobile Belts; KB—Karwar Block; CB—Coorg Block; BRB—Billigiri Rangan Block; SB—Shevaroy Block; MdB—Madras Block; NB—Nilgiri Block; NkB—Namakkal Block; MB—Madurai Block; TB—Trivandrum Block. Inset figure shows the major cratons in Peninsular India. AC- Aravalli Craton; BC- Bastar Craton; BKC- Bundelkhand Craton; DC – Dharwar Craton; SC- Singbhum Craton.

et al., 2000; Jayananda et al., 2006, 2008; Manikyamba et al., 2017). Although several previous studies have focused on the basement TTG (tonalite-trondhjemite-granodiorite) gneisses and associated granitoids of Dharwar, as well as the greenstone belts, and proposed models ranging from plume-arc accretion to modern-style plate tectonic processes involving subduction-accretion collision (e.g., Manikyamba and Kerrich, 2012; Jayananda et al., 2018, an references there in; Santosh and Li, 2018; Li et al., 2018b), only few investigations have so far addressed the detrital zircon record from ancient metasediments. As detrital zircon grains offer a potential archive to trace the evolution of continental crust, in this study we investigate a suite of metasediments from the collisional margin of two major crustal blocks in the Dharwar Craton to gain insights on the early crustal evolution history. We present U-Pb-Hf data that suggest major crustal growth events during ca. 3.2 Ga and 2.6 Ga, followed by metamorphism at ca. 2.4 Ga (Li et al., 2018a). Our results also have important implications for continental emergence during Eoarchean to Mesoarchean and detrital input through drainage systems.

2. Geological background and sampling 2.1. Regional geological background The Precambrian basement of India is composed of the northern and southern domains separated by the Central Indian Tectonic Zone (Radhakrishna and Naqvi, 1986). The southern domain is dominantly composed of Archean cratonic nuclei such as the Dharwar, Bastar and Singhbhum which are welded together by Archean – Proterozoic collisional sutures. The Dharwar Craton (DC) in the south is bordered by the Southern Granulite Terrane to the south and covered by Deccan basalts in the north (Fig. 1). The Southern Granulite Terrane is composed of several crustal blocks including Coorg, Biligiri Rangan, Shevaroy (including Salem), Madras, Madurai, Trivandrum and Nagercoil with distinct evolutionary history and preserving evidence for subductionaccretion-collision processes ranging in age from Mesoarchean to Late Neoproterozoic (e.g., Samuel et al., 2014; Santosh et al., 2009, 2015, 2017). The DC is dominantly made up of Archean granite-gneiss

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

greenstone sequences and has figured prominently in the paleogeographic reconstructions of Precambrian supercontinents as one of the oldest cratonic nuclei on the globe (e.g., Rogers and Santosh, 2003; Meert et al., 2011). Previous studies subdivided the craton into two major domains: the Western Dharwar Craton (WDC) and Eastern Dharwar craton (EDC) largely based on the nature and age of the greenstone belts, degree of metamorphism and crustal thickness (e.g., Swami Nath and Ramakrishnan, 1981; Jayananda et al., 2000). The WDC and EDC are separated by a transitional zone between Gadag-Mandya shear zone and Closepet granite along the eastern side of Chitradurga schist belt (Sengupta and Roy, 2012). This zone was designated as the Central Dharwar Province based on isotope geochronological data (Chardon et al., 2011; Dey and Sukanta, 2013; Peucat et al., 2013). Geologically, the WDC is dominated by 3.4 to 2.7 Ga greenstone belts together with 3.35 to 3.0 Ga tonalite–trondhjemite–granodiorite (TTG) suites which preserve evidence for reworked crustal material (e.g., Dey and Sukanta, 2013). The EDC incorporates 2.7 Ga Kolar-type greenstone belts and 2.7–2.5 Ga calc-alkaline felsic plutonic and volcanic rocks (Jayananda et al., 2000; Chardon et al., 2002; Dey et al., 2012; Jayananda et al., 2013). These greenstone belts comprise greenschist to amphibolite facies metabasalts with subordinate felsic volcanic rocks and metasediments (e.g., Manikyamba and Kerrich, 2012; Jayananda et al., 2013). Younger granitoids including TTG gneisses, high Mg diorites or sanukitoids, and ‘Closepet-type’ granitoid and Krich leucogranites are also present (e.g., Jayananda et al., 2000). Older granitoids (3.3–3.0 Ga) and metasediments are now present only as remnants. Following the accretion of the EDC onto the WDC at ~2.5 Ga, widespread platformal basins (1.9–0.6 Ga) were generated such as the Cuddapah basin in the east (e.g., Saha and Mazumder, 2012). The schist belts of DC were sub-divided into the older Sargur group and younger Dharwar Supergroup (Swami Nath and Ramakrishnan, 1981). Jayananda et al. (2008) proposed that the komatiite volcanism in the Sargur group represents melt extraction from the mantle at ca. 3.35 Ga. Only limited studies have so far been conducted on detrital zircon population in the metasediments of the DC. Based on detrital zircon geochronology of Sargur Group metasediments, Nutman et al. (1992) inferred that the WDC is older than 3.5 Ga and that the Sargur Group accumulated prior to 3 Ga. In the EDC, sericitic and fuchsitic quartzites, metapelites, calc-silicate rocks and banded manganiferous iron formations occurring as enclaves in orthogneisses were correlated with the Sargur Group of the WDC (Swami Nath and Ramakrishnan, 1981). Lancaster et al. (2015) investigated detrital zircon grains in quartzites and related rocks and reported significant juvenile crustal extraction events at ~3.3 and 2.7 Ga, with crustal reworking in the western block at 2.55–2.50 Ga. Sarma et al. (2012) studied detrital zircons in metagreywackes from the Gadag Greenstone Belt in the WDC and reported several age populations ranging from ca. 3.34 to 2.55 Ga. Based on Lu-Hf isotopic data, they traced major crust forming events at ca. 3.6 and 3.36 Ga, with juvenile addition at ca. 2.6 Ga. Based on available geochronological data (e.g., Dey et al., 2012; Jayananda et al., 2000, 2013), the WDC was considered as an Archean nucleus to which the Late Archean to early Paleoproterozoic (2.7–2.5 Ga) EDC was accreted. Chadwick et al. (2000) suggested that the WDC and EDC are separated by a shear zone that can be traced along the eastern boundary of the Chitradurga schist belt (Fig. 1). The Chitradurga greenstone belt is dominantly composed of 2.7–2.5 Ga metabasalts, BIFs, amphibolite and metagabbros (Chardon et al., 2011). The magmatic emplacement events in the CDC are constrained as 3.2–2.9 Ga for the basement and 2.6–2.5 Ga for the granite and greenstones (Chardon et al., 2011; Santosh and Li, 2018). In recent studies, based on Isotopic age provinces defined from precise geochronological data, the DC has been further divided into the Western, Central and East Blocks (Peucat et al., 2013; Jayananda et al., 2018). Recent studies along the Chitradurga shear zone and adjacent domains confirm this zone to be a collisional suture that amalgamated the WDC and the CDC during late Neoarchean. Santosh and Li (2018)

3

reported a suite of gabbro-anorthosites from the eastern part of the suture and presented zircon U-Pb age data that indicate emplacement of this suite at ca. 2.6 Ga. Based on geochemical features and Lu-Hf isotopes, they demonstrate that the parent magmas of this were derived from subduction-related depleted mantle source that also incorporated continental crustal components. The time of emplacement of this suite also broadly correlates with widespread arc magmatism and crust production as well as recycling in other domains of the Dharwar Craton. In another study, Li et al. (2018a) investigated high-pressure, upper amphibolite- and granulite-facies meta-igneous and metasedimentary rocks from the southern part of the Chitradurga shear zone, and reported minimum peak metamorphic conditions of ~820–875 °C at ~10 kbar, and suggested that the metamorphism occurred at the base of thickened continental crust. From zircon U-Pb data, they suggested microblock amalgamation in the Dharwar Craton during ca. 2.48–2.44 Ga at the Archean-Proterozoic boundary. They also proposed a tectonic model where the WDC, CDC, and EDC are envisaged to have accreted synchronously, driven by two separate eastward-dipping ocean-continent convergent plate margins. 2.2. Geology of the study area and sampling We carried out systematic field investigations and sampling of representative metasediments around the Chitradurga suture zone and surrounding regions along the eastern margin of the WDC. Our samples include metapelite, muscovite schist, and fuchsite quartzite. The sample locations are shown in Fig. 2, and Representative field photographs are shown in Fig. 3. The location, co-ordinates and salient details of the six representative samples from various rocks types used in this study are given in Table 1. A brief description of their field setting is given below. 2.2.1. Metapelite (MY-2/1) and muscovite schist (MY-2/3) Samples MY-2/1 and MY-2/3 were collected from Nodekoppallu (12°30′52.09″N, 76°45′38.45″E). A hillock ridge here exposes bands of medium grade gabbro, BIF (banded iron formation), muscovite schist, metapelite, and quartzite. The muscovite schist ranges in color from brownish to bluish and milky white. The samples used in this study from this locality are medium grained and highly schistose muscovite quartz schist and metapelite. 2.2.2. Fuchsite quartzite Sample MY-13/1 was collected at 12°25′22.85″N, 76°43′08.28″ from Karighatta hill. Hill forms folded bands of fuchsite quartzite in ground level exposures and along road cuttings. Several tens to few 100 m thick of crystalline quartzite with greenish tinge occur in this locality. The quartzite bands show folding and prominent lineation. Muscovite is also present in the bedding planes of quartzite. Sample MY-14/1, MY-14/2, MY-14/3 were collected at Karighatta hill top (12°25′30.25″N, 76°43′07.29″E). Large rocky exposures of thick-bedded quartzite are exposed on the hill top. The rock is schistose with greenish fuchsite in association with white muscovite. Some exposures also show typical fuchsite quartzite with green colored “aventurine” quartzite grains. Sporadic tiny garnet crystals are observed in some domains. 3. Analytical techniques A summary of the analytical techniques employed in this study relating to petrography, zircon U-Pb and Lu-Hf isotopic analyses is given below. 3.1. Petrography Six samples used in this study were used for the petrographic and thin sections studies. Polished thin sections for petrographic studies were prepared at the School of Earth and Space Sciences, Peking

4

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Fig. 2. Geological map of the study area showing sample locations (base map modified from Geological Survey of India, 2008).

University. Petrographic and thin section studies were carried out at the Institute of Earths Sciences, China University of Geosciences Beijing. 3.2. Zircon geochronology Zircon separation from the crushed rocks was performed at the Yu'neng Geological and Mineral Separation Survey Centre, Langfang City, Hebei Province, China using magnetic and density separation methods, followed by handpicking under a binocular microscope. The grain morphology was studied using a binocular microscope under reflected light. The zircon grains were mounted onto an epoxy resin disk and then polished to expose the internal texture and were examined under transmitted and reflected light. The internal zircon textures were studied using Cathode Luminescence (CL) images acquired on a scanning electron microscope (SEM) (JSM510) equipped with a Gatan CL probe at the Beijing Geoanalysis Centre. U-Pb dating of zircon was conducted by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) at the Beijing Geoanalysis Co., Ltd. Detailed operating conditions for the laser ablation system and the ICP-MS instrument and data reduction followed those in Zong et al. (2017). Laser sampling was performed using a GeolasPro laser ablation system that consists of a COMPexPro 102 ArF excimer laser (wavelength of 193 nm and maximum energy of 200 mJ) and a MicroLas optical system. An 80 mJ laser energy was used in this study. An Agilent 7700e ICP-MS instrument was used to acquire ion-signal intensities. Helium was used as carrier gas and argon as make-up gas and mixed with the carrier gas via a T-connector before entering the ICP. A “wire” signal smoothing device is included in this laser ablation system (Hu et al., 2015). The spot size and frequency of the laser were set to 32 μm and 8 Hz respectively in this study according to the size and the U content of the zircon. Each analysis incorporated a background acquisition of approximately 20–30 s followed by 50 s of data acquisition from the sample. Zircon 91500 and glass NIST610 were used as external standards for U-Pb dating, respectively. Time-dependent drifts of U-Th-Pb isotopic ratios were corrected using a linear interpolation (with time)

for every ten analyses according to the variations of the 91,500 zircon standard and the U-Th-Pb isotopic ratios used for 91,500 are from Wiedenbeck et al. (1995). The weighted mean 206Pb/238U age for standard for 91,500 is 1062.4 ± 2.4/21 Ma (n = 90, MSWD = 0.0027). Zircon standards GJ-1 (Jackson et al., 2004) and Plešovice (Sláma et al., 2008) were used as unknown samples to monitor the stability and accuracy of acquired U-Pb data. The obtained concordia U-Pb ages of GJ-1 (weighted mean 206Pb/238U age = 600.3 ± 2.6/12 Ma, n = 16, MSWD = 0.020) and Plešovice (weighted mean 206Pb/238U age = 337.3 ± 1.6/7 Ma, n = 16, MSWD = 0.013) are consistent within error with the recommended values. However, the uncertainties of standards could be overestimated according to the very low MSWD of weighted mean age from 91,500 standards. An Excel-based software ICPMSDataCal (ver. 10.7) was used to perform off-line data reduction and integration of background and analyzed signals, time-drift correction and quantitative calibration for trace element analysis and U-Pb dating (Liu et al., 2008, 2010). Final assessment of uncertainty and data visualization were calculated by Isoplot software (Ludwig, 2003). All ages are reported as concordia ages (Ludwig, 1998). Errors are quoted at the 2σ level. Full isotopic data are given in Supplementary Table 1. 3.3. Zircon Lu-Hf analysis In situ zircon Lu-Hf analyses were performed on the same domains of the grains that are large enough for analyses from where U-Pb data were collected. The analysis was conducted using an ESI NWR193 laser-ablation microprobe, attached to a Neptune plus multi-collector ICP–MS at the Beijing CreaTech Testing International Co., Ltd., Beijing, China. Instrumental conditions and data acquisition were as described by Wu et al. (2006) and Hou et al. (2007). The beam diameter was 40 μm depending on the size of ablated domains. Helium was used as carrier gas to transport the ablated sample from the laser-ablation cell to the ICP-MS torch via a mixing chamber mixed with Argon. In order to correct the isobaric interferences of 176Lu and 176Yb on 176Hf,

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

5

Fig. 3. Representative field photographs: (a) metapelite (MY-2/1) and (b) Muscovite schist (MY-2/3). (c)–(f) Fuchsite quartzite (MY-13/1, 14/1, 14/2, 14/3). 176

Lu/175Lu = 0.02658 and 176Yb/173Yb = 0.796218 ratios were determined (Chu et al., 2002). For instrumental mass bias correction, Yb isotope ratios were normalized to 172 Yb/ 173 Yb of 1.35274 (Chu et al., 2002) and Hf isotope ratios to 179Hf/177Hf of 0.7325 using an exponential law. The mass bias behavior of Lu was assumed to follow that of Yb, mass bias correction protocols followed those described in Wu et al. (2006) and Hou et al. (2007). Zircon GJ1 was used as the reference standards during our analyses, with a weighted mean 176 Hf/177Hf ratio of 0.282007 ± 0.000007 (2σ, n = 36). This value is not distinguishable from a weighted mean 176 Hf/ 177 Hf ratio of 0.282000 ± 0.000005 (2σ) using a solution analysis method by Morel et al. (2008). The Hf depleted mantle model ages and Hf crustal model ages were also computed. The Lu-Hf analytical results are reported in Supplementary Table 2.

4. Results 4.1. Petrography The samples analyzed in this study include metapelite, muscovite schist, and fuchsite quartzite. A summary of their petrographic features is given below. Representative photomicrographs are shown in Fig. 4.

4.1.1. Metapelite Sample MY-2/1 metapelite is composed of quartz (~40%) biotite (~30%), muscovite (~25%) and minor zoisite, sericite and zircon (~5%) (Fig. 4a). The rock shows prominent schistosity and compositionally corresponds to quartz mica schist.

Table 1 Sample numbers, rock types, localities, and GPS reading. Serial no.

Sample no.

Locality

Rock type

Coordinates

1 2 3 4 5 6

MY-2/1 MY-2/3 MY-13/1 MY-14/1 MY-14/2 MY-14/3

North of Nodekoppallu North of Nodekoppallu Karighatta hill Karighatta hill top Karighatta hill top Karighatta hill top

Metapelite Muscovite schist Fuchsite quartzite Fuchsite quartzite Fuchsite quartzite Fuchsite quartzite

N 12°30′52.09″, E 76°45′38.45″ N 12°30′52.09″, E 76°45′38.45″ N 12°25′22.85″, E 76°43′08.28″ N 12°25′30.25″, E 76°43′07.29″ N 12°25′30.25″, E 76°43′07.29″ N 12°25′30.25″, E 76°43′07.29″

6

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Fig. 4. Representative photomicrographs of thin sections. (a) Metapelite showing quartz + biotite assemblage (sample MY-2/1). (b) Muscovite schist showing muscovite + quartz assemblage (sample MY-2/3). (c)–(f) Fuchsite quartzite showing fuchsite + quartz assemblage (sample MY-13/1, 14/1, 14/2, 14/3). Mineral abbreviations: Qtz-quartz; Bt-biotite; Msmuscovite; Mrp-fuchsite.

4.1.2. Muscovite schist Sample MY-2/3 is a well-foliated mica schist. The rock is composed of muscovite (80–85%) and quartz (10–20%) with minor epidote and magnetite (~3–5%) (Fig. 4b). The rock exhibits foliation both in hand specimen and in the thin section defined by aggregates of muscovite with width: length ratio of 1:3 to 1:12 and elongated grayish ribbon quartz with width: length ratio of 1:3 to 1:5.

4.1.3. Fuchsite quartzite Sample MY-13/1 fuchsite quartzite composed primarily of greenish quartz (90%) and fuchsite mica (5–10%) with accessory zircon (Fig. 4c). The quartz (0.05–1.0 mm) and fuchsite (0.05–0.6 mm) are relatively coarse grained and show preferred orientation. Sample MY-14/1 fuchsite quartzite is composed of quartz (85%) and fuchsite (13–15%) with accessory zircon (Fig. 4d). Compared with sample MY-13/1, the quartz is more coarse-grained (0.2–1.2 mm) along with greenish fuchsite flakes (0.1–0.4 mm), both showing orientation and defining prominent schistosity. Sample MY-14/2 fuchsite quartzite is a foliated rock containing quartz (70–85%) and fuchsite (10–15%) with accessory zircon (Fig. 4e). The quartz grains are elongated and fuchsite laths also show preferred orientation.

Sample MY-14/3 fuchsite quartzite is similar to sample MY-14/2. It contains less quartz (70–80%) compared with the other quartzites and more fuchsite (10–20%) with accessory zircon (Fig. 4f). The quartz elongated parallel to the foliation. 4.2. Zircon morphology 4.2.1. Metapelite (sample MY-2/1) Zircon grains from the metapelite are euhedral to subhedral, prismatic or stumpy (Fig. 5). They show a size range of 50–150 μm with aspect ratios of 3:1 to 1:1. Most of the grains display clear zoning, and some grains possess core-rim texture, with inherited angular cores surrounded by thin overgrowth rim. Some of the cores are surrounded by thin and bright metamorphic rims. Heterogeneous grains are also present, indicating diffusion and recrystallization. Some grains contain abundant inclusions. 4.2.2. Muscovite schist (sample MY-2/3) The detrital zircons from muscovite schist sample MY-2/3 are mostly colorless or brownish, and transparent to translucent. They are irregular and mostly euhedral to subhedral, with elongated prismatic to stumpy morphology. Some grains are nearly euhedral suggesting a short distance transportation. The grains range from 30–100 × 30–130 μm in

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

7

Fig. 5. Representative Cathodoluminescence (CL) images of zircon grains from metapelite (MY-2/1), muscovite schist (MY-2/3), and fuchsite quartzite (MY-13/1, 14/1, 14/2, 14/3). Zircon U-Pb ages (Ma) and εHf(t) values are also shown. The smaller yellow circles indicate spots of LA-ICP-MS U-Pb dating, whereas the larger red circles represent locations of Hf isotopic analyses.

size with aspect ratios of 3.5:1–1:1 (Fig. 5). Most grains display clear oscillatory zoning or bright luminescence band. Some grains possess a bright domain of low-U contents. Some grains display a bright core surrounded by a thin dark rim, suggesting recrystallization or overgrowth. 4.2.3. Fuchsite quartzite (sample MY-13/1) In CL images, the zircon grains from sample MY-13/1 are colorless or dark brownish, and transparent to translucent. Most grains are irregular

euhedral to anhedral and show prismatic or stumpy morphology (Fig. 5). The zircon grains show a size range of 30–120 μm × 80–220 μm with aspect ratios of 2.5:1 to 1:1. Many grains display core-rim texture. The detrital cores mostly show clear oscillatory zoning, with some showing patchy zoning, and are surrounded by a thin (up to10 μm) dark overgrowth rim. The metamorphic rims are sometimes surrounded by another dark rim, suggesting recrystallization or overgrowth from fluids. Few grains show dark cores without structure. Some grains show abundant inclusions.

8

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

4.2.4. Fuchsite quartzite (sample MY-14/1) Zircon grains from sample MY-14/1 are colorless or dark brownish, transparent to translucent. They are irregular, subhedral to anhedral. They show prismatic to sub-rounded and sometimes elliptical or elongated morphology. The grain size shows a range of 80–200 μm × 100–210 μm with aspect ratios of 2.5:1–1:1. They show typical corerim structure (Fig. 5). The detrital cores show oscillatory zoning or patchy zoning and are surrounded by a bright metamorphic rim or thin luminescent boundary. The metamorphic rims show width up to 10 μm. Several grains in this sample carry mineral/fluid inclusions. 4.2.5. Fuchsite quartzite (sample MY-14/2) Zircons from sample MY-14/2 are mostly brownish or colorless, transparent and some are cracked. They show euhedral to anhedral morphology and are prismatic or elliptical in habit (Fig. 5) with a size range of 40–100 μm × 60–200 μm and aspect ratios of 2.5:1–1:1. In CL images, the core-rim structure is marked by a thin luminescence rim or band. The metamorphic rims are mostly narrow but in some cases, they range up to 20 μm in width. Cores of many grains display oscillatory zoning. 4.2.6. Fuchsite quartzite (sample MY-14/3) In CL images, zircons from this fuchsite quartzite are transparent to translucent and colorless or dark brownish color, with prismatic or elongated morphology (Fig. 5). They show a size range of 30–100 mm × 50–160 mm and aspect ratios of 3:1–1:1. Some grains display corerim texture with the detrital cores showing oscillatory zoning or luminescent banding and are surrounded by bright metamorphic rims. In some grains, the oscillatory cores are surrounded by a dark overgrowth rim. 4.3. Zircon U-Pb data 4.3.1. Metapelite (sample MY-2/1) Twenty seven spots were analyzed from twenty seven grains in this sample and the data can be divided into two groups. Three grains from the older group yield weighted mean 207Pb/206Pb age of 3343 ± 160 Ma. The oldest grain from this group shows 207Pb/206Pb age of 3411 ± 56 Ma, with Th and U contents of 93 ppm and 160 ppm, and Th/U ratio of 0.59. Another grain shows 207Pb/206Pb age of 3027 ± 80 Ma. The remaining 23 spots form one coherent group and their Th, U

contents range from 53–1495 ppm to 71–1228 ppm together with Th/ U ratios of 0.59–2.17. They define an upper intercept age of 2651 ± 33 Ma (MSWD = 2.4; n = 23). In age data histogram, the zircon grains define 207Pb/206Pb age peaks at 2606 Ma, 3027 Ma and 3342 Ma (Fig. 6). 4.3.2. Muscovite schist (sample MY-2/3) Twenty seven grains from this rock define an upper intercept age of 2566 ± 17 Ma (MSWD = 0.74; n = 27). The Th, U contents show a range of 81–1835 ppm, 114–1667 ppm with Th/U values in the range of 0.38–1.23. The 207Pb/206Pb age peaks show 2525 Ma, 2563 Ma and 2593 Ma (Fig. 6). 4.3.3. Fuchsite quartzite (sample MY-13/1) Fifty one grains were analyzed from sample MY-13/1. The data define an upper intercept age of 3377 ± 85 Ma (MSWD = 2.0; n = 51). Their Th, U contents range from 25 ppm to 410 ppm and 56 ppm to 546 ppm, with Th/U ratio of 0.14–1.65. Zircon grains with 207Pb/206Pb age peaks are also observed at 2985 Ma, 3206 Ma and 3306 Ma (Fig. 7). 4.3.4. Fuchsite quartzite (sample MY-14/1) Sixty one spots were analyzed from 56 zircon grains from this sample and the results show Th and U contents and Th/U ratios in the range of 24–447 ppm, 30–638 ppm, and 0.14–2.05 (Supplementary Table 1). Sixty one analyses define an upper intercept age of 3247 ± 11 Ma (MSWD = 2.1; n = 61). The age data show a unimodal distribution with a single peak of 207Pb/206Pb age at 3234 Ma (Fig. 7) suggesting a single Meso- to early Paleoarchean source. 4.3.5. Fuchsite quartzite (sample MY-14/2) A total of 66 spots from 55 zircon grains from this sample show Th and U contents and Th/U ratios in the range of 5–309 ppm, 40–592 ppm, and 0.06–0.97, respectively (Supplementary Table 1). Sixty six analyses define an upper intercept age of 3266 ± 14 Ma (MSWD = 2.5; n = 66). The grains show 207Pb/206Pb single age peak at 3235 Ma (Fig. 8), which is similar to the age peak in sample MY-14/1. 4.3.6. Fuchsite quartzite (sample MY-14/3) A total of 48 analyses were performed on the different domains from 47 zircon grains in this sample. The Th and U contents range from 1 to 547 ppm and 25–511 ppm respectively with Th/U ratios ranging from 0.04 to 1.36. The data define an upper intercept age of 3269 ± 22 Ma

Fig. 6. (a) U-Pb concordia plots of zircon U-Pb analyses from metapelite sample MY-2/1. Zircon U-Pb data processed using the kernel density distribution approach (Spencer et al., 2017b) for the metapelite sample MY-2/1. (b) U-Pb concordia plots of zircon U-Pb analyses from muscovite schist sample MY-2/3. Kernel density distribution is also shown.

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

9

Fig. 7. (a) U-Pb concordia plots of zircon U-Pb analyses from fuchsite quartzite sample MY-13/1. Kernal density distribution of ages for the fuchsite quartzite sample MY-13/1. (b) U-Pb concordia plots and kernel density distribution of zircon U-Pb analyses from fuchsite quartzite sample MY-14/1.

(MSWD = 2.3; n = 48). The 207Pb/206Pb data show a prominent age peak at 3225 Ma (Fig. 8). 4.4. Zircon Lu-Hf results In situ Hf isotope analyses were carried out on zircons on the same spots or immediately adjacent domains from where the U-Pb data were gathered. A total of 32 zircon grains were analyzed for Lu-Hf isotopes and the results are presented in Supplementary Table 2 and plotted in Fig. 9. The salient features are briefly evaluated below. 4.4.1. Metapelite (sample MY-2/1) Only two zircons were analyzed from sample MY-2/1 for Lu-Hf isotopes because the grains are either small or rare in this rock. The results show initial 176Hf/177Hf ratios in the range of 0.281110 to 0.281278 and both negative and positive εHf(t) values ranging from −1.2 to 4.7, as

computed from 207Pb/206Pb ages of individual zircon spots (2622–2631 Ma). The Hf depleted model ages (TDM) are between 2746 Ma and 2960 Ma, and Hf crustal model ages (TCDM) range from 2891 to 3391 Ma. The data indicate a mixed Paleoarchean to Mesoarchean source involving both juvenile mantle and reworked crustal components (Fig. 9).

4.4.2. Muscovite schist (sample MY-2/3) Due to the small size of zircons, only three grains were analyzed from this sample for Lu-Hf isotopes. The results show initial 176 Hf/177Hf ratios of 0.281006 to 0.281105 and negative εHf(t) values in the range of −3.1 to −7.1 with an average value of −5.7, based on the 207Pb/206Pb age of individual age spots (2527–2619 Ma). The Hf depleted model ages (TDM) are between 3039 Ma and 3117 Ma (mean 3084 Ma), and Hf crustal model ages (TCDM) range from 3553 to

Fig. 8. (a) U-Pb concordia plots and kernel density distribution of zircon U-Pb data from fuchsite quartzite sample MY-14/2. (b) U-Pb concordia plots and kernel density distribution of zircon U-Pb data from fuchsite quartzite sample MY-14/3.

10

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Fig. 9. (a) Zircon Hf isotopic evolution diagram. Error bars represent 2σ uncertainties. CHUR-chondritic uniform reservoir. New crust line is after Dhuime et al. (2011). Crustal model ages TCDM were calculated using representative bulk crustal value 176Lu/177Hf = 0.015 (Griffin et al., 2002). (b) Zircon TDM age data using the kernel density distribution approach (Spencer et al., 2017b) for all samples in this study.

3847 Ma (mean 3738 Ma). The data suggest that the detritus was derived from Eoarchean to Paleoarchean reworked crust (Fig. 9).

that the source rocks were derived from Eoarchean to Paleoarchean juvenile components (Fig. 9).

4.4.3. Fuchsite quartzite (sample MY-13/1) Nine zircons were analyzed from this sample and the results show initial 176Hf/177Hf ratios of 0.280585 to 0.280915. Both negative and positive εHf(t) values are in the range of −1.4 to 4.4 with an average value of 1.9 computed using the 207Pb/206Pb age of individual zircon spots (3202–3442 Ma). The Hf depleted model ages (TDM) are between 3291 Ma and 3672 Ma (mean 3433 Ma), and Hf crustal model ages (TCDM) range from 3367 to 3964 Ma (mean 3592 Ma). The data indicate a mixed Eoarchean to Paleoarchean source involving both juvenile mantle and reworked crustal components (Fig. 9).

5. Discussion

4.4.4. Fuchsite quartzite (sample MY-14/1) Six zircons were analyzed from this sample for Lu-Hf isotopes and the results show initial 176Hf/177Hf ratios of 0.28850 to 0.280943 and positive εHf(t) values ranging from 2.4 to 4.7 with a mean at 3.4, computed using 207Pb/206Pb age of individual zircon spots (3200–3261 Ma). The Hf depleted model ages (TDM) are between 3246 Ma and 3354 Ma (mean 3305 Ma), and Hf crustal model ages (TCDM) range from 3295 to 3488 Ma (mean 3404 Ma). The data suggest that Paleoarchean juvenile sources (Fig. 9). 4.4.5. Fuchsite quartzite (sample MY-14/2) Eight zircon grains were analyzed in this sample and the results show initial 176Hf/177Hf ratios of 0.280774 to 0.280921. The data also show positive εHf(t) values in the range of 1.6 to 4.6 with an average value of 2.8, as computed from the 207Pb/206Pb age of individual zircon spots (3202–3310 Ma). The Hf depleted model ages (TDM) are between 3254 Ma and 3441 Ma (mean 3360 Ma), and Hf crustal model ages (TCDM) rage from 3299 to 3612 Ma (mean 3485 Ma). The data suggest that the parent magma of the source rocks was derived from Eoarchean to Paleoarchean juvenile components (Fig. 9). 4.4.6. Fuchsite quartzite (sample MY-14/3) Only four zircon crystals were analyzed for Lu-Hf isotopes from this sample because of the small size of the zircon grains. The results show initial 176Hf/177Hf ratios of 0.280768 to 0.280894 and positive εHf (t) values in the range of 0.7 to 2.3 with an average value of 1.6, when computed using the 207Pb/206Pb ages of individual zircon spots (3221–3294 Ma). The Hf depleted model ages (TDM) are between 3349 Ma and 3460 Ma (mean 3415 Ma), and Hf crustal model ages (TCDM) range from 3504 to 3677 Ma (mean 3595 Ma). The data suggest

5.1. Age constraints The age data from sample MY-2/1 are compiled in Fig. 6, where the Pb/206Pb ages define age peak at 2606 Ma and two sub-peaks at 3027 Ma and 3342 Ma. Zircon grains in the older group of the metapelite (MY-2-1) yielded a weighted mean 207Pb/206Pb age of 3343 ± 160 Ma (MSWD = 5.6; n = 3). Twenty three analyses define an upper intercept age of 2651 ± 33 Ma (MSWD = 2.4; n = 23). Zircon grains from the muscovite schist (MY-2/3) define an upper intercept age of 2566 ± 17 Ma (MSWD = 0.74; n = 27), and those from sample MY-13/1 define an upper intercept age of 3377 ± 85 Ma (MSWD = 2.0; n = 51) with the lower intercept at 2686 ± 200 Ma. Sixty one analyses of zircon grains in sample MY-14/1 define an upper intercept age of 3247 ± 11 Ma (MSWD = 2.1; n = 61). Sixty six analysis from MY-14/2 define an upper intercept age of 3266 ± 14 Ma (MSWD = 2.5; n = 66) and forty eight analysis of zircon grains in MY-14/3 define an upper intercept age of 3269 ± 22 Ma (MSWD = 2.3; n = 48). Our results from the detrital zircons in the metapelite, mica schist and fuchsite quartzites, representing a suite of continental margin sedimentary succession, date two discrete crust forming events at the source: one at 3.2 Ga corresponding to the formation of the basement TTG rocks and the other representing the 2.6 Ga event of the granitegreenstone sequence (e.g., Chardon et al., 2011; Santosh and Li, 2018). Recent tectonic models divide the Dharwar Craton into two distinct crustal blocks: the 3.3–2.7 Ga Meso- to Neo- Archean granitegreenstone sequences of the WDC and the 2.5 Ga Neoarchean granitoids and greenstone belts in the EDC (Borah et al., 2014; Lancaster et al., 2015). Jayananda et al. (2015), based on SHRIMP zircon U-Pb ages of TTG gneisses from WDC, suggested two major crustal growth events at 3.35–3.28 Ga and 3.23–3.2 Ga with both positive and negative εNd signature (t = 3.3 Ga, −2.8 to +3.0; t = 3.2 Ga, −3.4 to +9.8), indicating that the magmas were sourced from juvenile sources contaminated with crustal components. Felsic volcanic sequences from the WDC and EDC investigated by Jayananda et al. (2013) show 2.7–2.6 Ga juvenile crustal growth along the eastern margin of the WDC. These ages broadly correlate with those from detrital zircon grains in the metapelite and muscovite schist in our study. Compiled age data histograms using the kernel density distribution approach (Spencer et al., 2017b) for the WDC are shown in Fig. 10, 207

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

11

3.34 to 2.55 Ga (Fig. 10c). The Hf isotopic evolution of the detrital zircons also shows two major crust-forming events at ca. 3.6 and 3.36 Ga, with some indication of juvenile addition to the crust at ca. 2.6 Ga. Jayananda and colleagues (see recent review in Jayananda et al., 2018) identified two major periods (3350–3280 Ma and 3230–3200 Ma) of crustal growth (Fig. 10d) through TTG accretion sub-contemporaneous with greenstone volcanism. They invoked magmatism from depleted shallow and deep mantle reservoirs during 3350–3280 Ma magmatism with mantle differentiation during an earlier episode of crust formation at around 3800–3600 Ma. It is obvious in Fig. 10 that the zircon age data from the WDC reported by Lancaster et al. (2015), Sarma et al. (2012), Jayananda et al. (2015) and those from this study all have two similar major age peaks at ~2.45–2.6 Ga and ~3.2 Ga. We also compile zircon 207Pb/206Pb ages from the DC in Fig. 11, following the data presented in Santosh and Li (2018) and Jayananda et al. (2018). The data clearly indicate age peaks at ~ 2.5–2.7 Ga, ~2.9–3.0 Ga and ~3.1–3.4 Ga, corresponding to major crustal growth and recycling events. Age data from basement rocks of the Dharwar Craton as compiled by Jayananda et al. (2018) display five major peaks in felsic crust formation at ca. 3450–3300 Ma, 3230–3150 Ma, 3000–2960 Ma, 2700–2600 Ma, and 2560–2520 Ma which are considered to be broadly coeval with the episodes of greenstone volcanism. The zircon U-Pb data also suggest at least four major reworking events (Fig. 11) during ca. 3200 Ma, 3000 Ma, 2620–2600 Ma, and 2530–2500 Ma corresponding to lower crustal melting. The age data also allow the sub-division of the TTGs into the older (3450–3000 Ma) TTGs and the younger (2700–2600 Ma) transitional TTGs (Jayananda et al., 2018). Previous studies reported an emplacement age of 2.6 Ga for the Chitradurga granite (Taylor et al., 1984; Rao et al., 1992). Also, ~2.61 Ga potassic granitic plutons were reported from either side of the central domain of the Chitradurga belt (Jayananda et al., 2006). Together with the new age data reported by Santosh and Li (2018) and Li et al. (2018b), as well as those in the present study, the 2.6 Ga magmatism is inferred to be widespread in the Dharwar Craton. 5.2. Provenance and implications on crustal evolution

Fig. 10. Zircon U-Pb ages using the kernel density distribution approach (Spencer et al., 2017b) for (a) metapelite, schist and quartzite (this study); (b) quartzite (Lancaster et al., 2015); (c) Gadag greenstone (Sarma et al., 2012); (d) TTG (Jayananda et al., 2015) from Western Dharwar Craton.

and compared with the data from the present study. The time of construction of the crust in the arc basement coincides with the age peak reported by Lancaster et al. (2015), Sarma et al. (2012) and Jayananda et al. (2015). Lancaster et al. (2015) proposed significant juvenile crustal extraction events at ~3.3 and 2.7 Ga, and continuous extraction from 3.7 to 3.3 Ga based on U–Pb-Hf analyses of detrital zircons in quartzites from the WDC. The age data (Fig. 10b) show reworking in the western block at 2.55–2.50 Ga which is correlated to accretion of the two terranes and final cratonization. Sarma et al. (2012) reported detrital zircons from two metagreywacke samples from the Gadag Greenstone Belt in the WDC and the data show multiple age populations ranging in age from ca.

The initial 176Hf/177Hf values of zircon grains in metapelite (MY-2/1) show a range of 0.281110 to 0.281383 and corresponding εHf(t) values of −1.2 to 8.1, indicating a heterogeneous source involving both depleted mantle and older continental crust. The initial 176Hf/177Hf values of zircon grains from muscovite schist (MY-2/3) range from 0.281006 to 0.281105 and yield negative εHf(t) values in the range of −3.1 to −7.1, indicating that the source material was derived from Eoarchean reworked crust. The initial 176Hf/177Hf values from fuchsite quartzite (MY-13/1) show a range of 0.280585 to 0.280915 with εHf(t) values of −1.4 to 4.4, indicating a mixed Paleoarchean to Eoarchean source involving both juvenile mantle and reworked crustal components. The initial 176Hf/177Hf values from fuchsite quartzite (MY-14/1) show a range of 0.28850 to 0.280943 and corresponding εHf(t) values of 2.4 to 4.7, indicating that the magma was sourced Eoarchean juvenile sources. The initial 176Hf/177Hf values of zircon grains from fuchsite quartzite (MY-14/2) range from 0.280774 to 0.280921 and yield negative εHf(t) values in the range of 1.6 to 4.6, indicating that the magma was sourced Eoarchean juvenile sources. The initial 176Hf/177Hf values from fuchsite quartzite (MY-14/3) show a range of 0.280768 to 0.280894 with positive εHf(t) values in the range of 0.7 to 2.3, suggesting Eoarchean juvenile sources. The data presented in our study yield Hf depleted mantle model ages (TDM) of 2703–3672 Ma and Hf crustal residence model ages (TCDM) ranging from 2667 Ma to 3964 Ma (Supplementary Table 2, Fig. 9a). Most of the data fall below the depleted mantle line as well as between the CHUR line and the depleted mantle line. The data indicate that the

12

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Fig. 11. Histogram of zircon 207Pb/206Pb ages (Ma) from the Dharwar Craton, as compiled from Santosh and Li (2018) and Jayananda et al. (2018).

zircons from the rocks in present study were derived from both juvenile and reworked components of Paleoarchean to Eoarchean. The peak age of TDM age (Fig. 9b) is 3363 Ma. A compilation of Lu-Hf data from previous studies from the Mesoarchean Coorg Block and surrounding regions (Santosh et al., 2015, 2016) also show mixed sources from both reworked crustal components and juvenile components ranging in age from Eo- to Paleoarchean. Fig. 12 shows a compiled zircon Hf isotopic evolution diagram from this study, Lancaster et al. (2015) and Santosh and Li (2018), which

reveal three distinct clusters. The data of Santosh and Li (2018) from the gabbro-anorthosite complex representing suprasubduction zone magmatism along the eastern margin of the WDC show both negative and positive εHf(t) values of −5.3 to +0.9, suggesting a heterogeneous source of mixed depleted mantle and continental crustal material (Fig. 12). Santosh and Li (2018) proposed a continental arc setting with magma emplaced at the root of a Mesoarchean arc, as also supported by the zircon age and Lu-Hf data from the basement TTG gneiss. Data from Lancaster et al. (2015) show more negative εHf values and correlate with younger U-Pb ages and a transition to overgrowths on existing cores, recording U-Pb ages between 2550 and 2450 Ma. The εHf values plot very close to CHUR until ~3000 Ma, followed by a shift to negative values overlapping with the data from ~2550 Ma detrital zircon grains from greywackes of the Gadag greenstone belt (Sarma et al., 2012). Both negative and positive εHf(t) values in the zircon grains also suggest a source of mixed depleted mantle and continental crustal material. In summary the U-Pb-Hf data from detrital zircon grains in our study trace distinct pulses of magmatism and crustal growth during early to late Archean with increasing contribution of recycled components during the younger phase indicating crustal maturity. 6. Conclusions

Fig. 12. Combined Zircon Hf isotopic evolution diagram from this study, Lancaster et al. (2015) and Santosh and Li (2018). Error bars represent 2σ uncertainties. CHURchondritic uniform reservoir. New crust line is after Dhuime et al. (2011). Crustal model ages TCDM were calculated using representative bulk crustal value 176Lu/177Hf = 0.015 (Griffin et al., 2002).

(1) The morphology and internal structure of detrital zircon grains in our study suggest that the dominant population was derived from proximal granite (felsic) sources. Our data suggest continental emergence, weathering and detrital input through river drainage systems into trench were initiated during Eoarchean to Mesoarchean. (2) Detrital zircon U-Pb data from metasediments in the Dharwar Craton show dominant Paleoarchean to early Paleoproterozoic ages (2429–3442 Ma), with peaks at 2575 Ma and 3227 Ma.

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

(3) The age spectra of detrital zircons, in combination with the Lu-Hf isotopic data, indicate sediment provenance from magmas derived from ca. 3.67 to 2.70 Ga juvenile and reworked material with the younger magmatic pulses involving more reworked components signaling crustal maturity. (4) The protocrust formation in Dharwar was achieved by ca. 3.2 Ga, followed by another major crust formation and recycling event at ca. 2.6 and final cratonization.

Supplementary data to this article can be found online at https://doi. org/10.1016/j.gr.2019.02.006. Acknowledgments We thank Editor Prof. T. Tsunogae and two anonymous referees for helpful comments that improved our manuscript. This work forms part of the research project of Jingyi Wang at CUGB. M. Santosh is supported as Foreign Expert by China University of Geosciences Beijing, China, and in Professorial position at the University of Adelaide, Australia for supporting this work. We also thank Dr. K. Sajeev and team members for help during the field work. References Borah, K., Rai, S.S., Gupta, S., Prakasam, K.S., Kumar, S., Sivaram, K., 2014. Preserved and modified mid-Archean crustal blocks in Dharwar craton: seismological evidence. Precambrian Research 246, 16–34. Chadwick, B., Vasudev, V.N., Hegde, G.V., 2000. The Dharwar craton, southern India, interpreted as the result of late Archaean oblique convergence. Precambrian Research 99, 91–111. Chardon, D., Peucat, Jean-Jacques, Jayananda, M., Choukroune, P., Fanning, C.M., 2002. Archean granite-greenstone tectonics at Kolar (South India): interplay of diapirism and bulk inhomogeneous contraction during juvenile magmatic accretion. Tectonics 21 (3), 7–1-7-17. Chardon, D., Jayananda, M., Peucat, J.J., 2011. Lateral constrictional flow of hot orogenic crust: Insights from the Neoarchean of south India, geological and geophysical implications for orogenic plateaux. Geochemistry, Geophysics, Geosystems 12, 1–24. Chu, N.C., Taylor, R.N., Chavagnac, V., Nesbitt, R.W., Boella, R.M., Milton, J.A., German, C.R., Bayon, G., Burton, K., 2002. Hf isotope ratio analysis using multi-collector inductively coupled plasma mass spectrometry: an evaluation of isobaric interference corrections. Journal of Analytical Atomic Spectrometry 17, 1567–1574. Dey, Sukanta, 2013. Evolution of archaean crust in the dharwar craton: the nd isotope record. Precambrian Research 227, 227–246. Dey, S., Pandey, U.K., Rai, A.K., Chaki, A., 2012. Geochemical and nd isotope constraints on petrogenesis of granitoids from nw part of the eastern dharwar craton: possible implications for late archaean crustal accretion. Journal of Asian Earth Sciences 45 (4), 40–56. Dhuime, B., Hawkesworth, C., Cawood, P., 2011. When continents formed. Science 331, 154–155. Geological Survey of India, 2008. Geological quadrangle map: Mysore quadrangle. Karnataka. Geological Survey of India, Calcutta. Griffin, W.L., Wang, X., Jackson, S.E., Pearson, N.J., O'Reilly, S.Y., Xu, X., Zhou, X., 2002. Zircon chemistry and magma mixing, SE China: in-situ analysis of Hf isotopes, Tonglu and Pingtan igneous complexes. Lithos 61, 237–269. Hawkesworth, C., Cawood, P.A., Dhuime, B., 2018. Rates of generation and growth of the continental crust. Geoscience Frontiers https://doi.org/10.1016/j.gsf.2018.02.004. Hou, K.J., Li, Y.H., Zou, T.R., Qu, X.M., Shi, Y.R., Xie, G.Q., 2007. Laser ablation-MC-ICPMS technique for Hf isotope microanalysis of zircon and its geological applications. Acta Petrologica Sinica 23, 2595–2604 (In Chinese with English abstract). Hu, Z.C., Zhang, W., Liu, Y.S., Gao, S., Li, M., Zong, K.Q., Chen, H.H., Hu, S.H., 2015. “Wave” signal smoothing and mercury removing device for laser ablation quadrupole and multiple collector ICP-MS analysis: application to lead isotope analysis. Analytical Chemistry 87, 1152–1157. Jackson, S.E., Pearson, N.J., Griffin, W.L., Belousova, E.A., 2004. The application of laser ablation inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology. Chemical Geology 211, 47–69. https://doi.org/10.1016/j.chemgeo.2004.06.017. Jayananda, M., Moyen, J.F., Martin, H., Peucat, J.J., Auvray, B., Mahabaleswar, B., 2000. Late Archaean (2550–2520 Ma) juvenile magmatism in the Eastern Dharwar craton, southern India: constraints from geochronology, Nd-Sr isotopes and whole rock geochemistry. Precambrian Research 99, 225–254. 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 Research 150, 1–26. Jayananda, M., Kano, T., Peucat, J.J., Channabasappa, S., 2008. 35 Ga komatiite volcanism in the western Dharwar craton, southern India: Constraints from Nd isotopes and whole-rock geochemistry. Precambrian Research 162 (3), 160–179. Jayananda, M., Peucat, J., Chardon, D., Krishna Rao, B., Fanning, C., Corfu, F., 2013. Neoarchean greenstone volcanism and continental growth, dharwar craton, southern

13

India: constraints from sims u-pb zircon geochronology and nd isotopes. Precambrian Research 227, 55–76. 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 Research 268, 295–322. Jayananda, M., Santosh, M., Aadhiseshan, K.R., 2018. Formation of Archean (3600–2500 Ma) continental crust in the Dharwar Craton, southern India. EarthScience Reviews 181, 12–42. Lancaster, P.J., Dey, S., Storey, C.D., Mitra, A., Bhunia, R.K., 2015. Contrasting crustal evolution processes in the dharwar craton: insights from detrital zircon u–pb and hf isotopes. Gondwana Research 28 (4), 1361–1372. Li, S.S., Santosh, M., Palin, R.M., 2018a. Metamorphism during the archean– paleoproterozoic transition associated with microblock amalgamation in the dharwar craton, India. Journal of Petrology 59 (12), 2435–2462. Li, S.S., Santosh, M., Ganguly, S., Thanooja, P.V., Sajeev, K., Pahari, A., et al., 2018b. Neoarchean microblock amalgamation in southern India: evidence from the nallamalai suture zone. Precambrian Research. S030192681830127X. Liu, Y.S., Hu, Z.C., Gao, S., Günther, D., Xu, J., Gao, C.G., Chen, H.H., 2008. In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard. Chemical Geology 257 (1–2), 34–43. Liu, Y.S., Gao, S., Hu, Z.C., Gao, C.G., Zong, K.Q., Wang, D.B., 2010. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen: U-Pb dating, Hf isotopes and trace elements in zircons of mantle xenoliths. Journal of Petrology 51 (1&2), 537–571. Ludwig, K.R., 1998. On the treatment of concordant uranium-lead ages. Geochimica et Cosmochimica Acta 62 (885), 676. Ludwig, K.R., 2003. ISOPLOT 3.00: A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center. Berkeley, California, p. 39. Manikyamba, C., Kerrich, R., 2012. Eastern Dharwar Craton, India: Continental lithosphere growth by accretion of diverse plume and arc terranes. Geoscience Frontiers 3, 225–240. Manikyamba, C., Ganguly, S., Santosh, M., Saha, A., Chatterjee, A., Khelen, A.C., 2015. Neoarchean arc–juvenile back-arc magmatism in eastern Dharwar Craton, India: geochemical fingerprints from the basalts of Kadiri greenstone belt. Precambrian Research 258, 1–23. Manikyamba, C., Ganguly, S., Santosh, M., Subramanyam, K.S.V., 2017. Volcanosedimentary and metallogenic records of the Dharwar greenstone terranes, India: Window to Archean plate tectonics, continent growth, and mineral endowment. Gondwana Research 50, 38–66. Maruyama, S., Ebisuzaki, T., 2017. Origin of the Earth: a proposal of new model called ABEL. Geoscience Frontiers 8 (2), 253–274. https://doi.org/10.1016/j.gsf.2016.10.005. Maruyama, S., Ikoma, M., Genda, H., Hirose, K., Yokoyama, T., Santosh, M., 2013. The naked planet earth: most essential pre-requisite for the origin and evolution of life. Geoscience Frontiers 4 (2), 141–165. Maruyama, S., Santosh, M., Azuma, S., 2018. Initiation of plate tectonics in the hadean: eclogitization triggered by the abel bombardment. Geoscience Frontiers 9, 1033–1048 S1674987116302079. Meert, J.G., Pandit, M.K., Pradhan, V.R., Kamenov, G., 2011. Preliminary report on the paleomagnetism of 1.88 ga dykes from the bastar and dharwar cratons, peninsular India. Gondwana Research 20 (2), 335–343. Morel, M.L.A., Nebel, O., Nebel-Jacobsen, Y.J., 2008. Hafnium isotope characterization of the GJ-1 zircon reference material by solution and laser-ablation MC-ICPMS. Chemical Geology 255, 231–235. Nance, R.D., Murphy, J.B., Santosh, M., 2014. The supercontinent cycle: a retrospective essay. Gondwana Research 25 (1), 4–29. 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. Journal of the Geological Society of India 39, 367–374. 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). The Journal of Geology 103, 701–710. Peucat, J.J., Jayananda, M., Chardon, D., Capdevila, R., Fanning, C.M., Paquette, J.L., 2013. The lower crust of the Dharwar Craton, Southern India: Patchwork of Archean granulitic domains. Precambrian Research 227, 4–28. Radhakrishna, B.P., Naqvi, S.M., 1986. Precambrian continental crust of India and its evolution. Journal of Geology 94 (2), 145–166. Rao, Y.J.B., Sivaraman, T.V., Pantulu, V.C., Gopalan, S., Naqvi, S.M., 1992. Rb-Sr ages of late Archean metavolcanics and granites, Dharwar craton, South India and evidence for early Proterozoic thermotectonic event (s). Precambrian Research 59, 145–170. Roberts, N.M.W., Santosh, M., 2018. Capturing the Mesoarchean emergence of continental crust in the Coorg Block, southern India. Geophysical Research Letters 45, 7444–7453. https://doi.org/10.1029/2018GL078114. Rogers, J.J.W., Santosh, M., 2003. Supercontinents in earth history. Gondwana Research 6 (3), 357–368. Saha, D., Mazumder, R., 2012. An Overview of the Palaeoproterozoic Geology of Peninsular India, and Key Stratigraphic and Tectonic Issues. Palaeoproterozoic of India. 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 Research 245, 146–173. Santosh, M., Li, S.S., 2018. Anorthosites from an Archean continental arc in the Dharwar Craton, southern India: Implications for terrane assembly and cratonization. Precambrian Research 308, 126–147. Santosh, M., Maruyama, S., Sato, K., 2009. Anatomy of a Cambrian suture in Gondwana: Pacific-type orogeny in southern India? Gondwana Research 16 (2), 321–341.

14

J.-Y. Wang, M. Santosh / Gondwana Research 72 (2019) 1–14

Santosh, M., Yang, Q.-Y., Shaji, E., Tsunogae, T., Ram Mohan, M., Satyanarayanan, M., 2015. An exotic Mesoarchean microcontinent: the Coorg Block, southern India. Gondwana Research 27 (1), 165–195. https://doi.org/10.1016/j.gr.2013.10.005. Santosh, M., Yang, Q.-Y., Shaji, E., Ram Mohan, M., Tsunogae, T., Satyanarayanan, M., 2016. Oldest rocks from Peninsular India: evidence for Hadean to Neoarchean crustal evolution. Gondwana Research 29 (1), 105–135. https://doi.org/10.1016/j. gr.2014.11.003. Santosh, M., Hu, C.N., He, X.F., Li, S.S., Tsunogae, T., Shaji, E., et al., 2017. Neoproterozoic arc magmatism in the southern Madurai block, India: subduction, relamination, continental outbuilding, and the growth of gondwana. Gondwana Research 45, 1–42. 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 Research 22 (3–4), 843–854. Sengupta, S., Roy, A., 2012. Tectonic amalgamation of crustal blocks along gadag-mandya shear zone in dharwar craton of southern India. Journal of the Geological Society of India 80 (1), 75–88. Sláma, J., Košler, J., Condon, D.J., Crowley, J.L., Gerdes, A., Hanchar, J.M., Horstwood, M.S.A., Morris, G.A., Nasdala, L., Norberg, N., Schaltegger, U., Schoene, B., Tubrett, M.N., Whitehouse, M.J., 2008. Plešovice zircon – a new natural reference material for UPb and Hf isotopic microanalysis. Chemical Geology 249, 1–35. https://doi.org/ 10.1016/j.chemgeo.2007.11.005. Smithies, R.H., Champion, D.C., Van Kranendonk, M.J., 2009. Formation of Paleoarchean continental crust through infracrustal melting of enriched basalt. Earth and Planetary Science Letters 281, 298–306. Spencer, C.J., Roberts, N.M.W., Santosh, M., 2017a. Growth, destruction, and preservation of Earth's continental crust. Earth-Science Reviews 172, 87–106. https://doi.org/ 10.1016/j.earscirev.2017.07.013.

Spencer, C.J., Yakymchuk, C., Ghaznavi, M., 2017b. Visualising Data Distributions with Kernel Density Estimation and Reduced Chi-squared Statistic. Geoscience. vol. 8. Frontiers, pp. 1–6. Swami Nath, J., Ramakrishnan, M. (Eds.), 1981. Early Precambrian Supracrustals of Southern Karnataka. Geological Survey of India 112, 79–81. Szilas, K., Maher, K., Bird, D.K., 2016. Aluminous gneiss derived by weathering of basaltic source rocks in the Neoarchean Storø Supracrustal Belt, southern West Greenland. Chemical Geology 441, 63–80. https://doi.org/10.1016/j.chemgeo.2016.08.013. Tang, L., Santosh, M., 2018. Neoarchean granite-greenstone belts and related ore mineralization in the North China Craton: an overview. Geoscience Frontiers 8, 751–768. Taylor, P.N., Chadwick, B., Moorbath, S., Ramakrishnan, M., Viswanatha, M.N., 1984. Petrography, chemistry and isotopic ages of Peninsular Gneiss, Dharwar acid volcanic rocks and the Chitradurga granite with special reference to the late Archean evolution of the Karnataka craton, southern India. Precambrian Research 23, 349–375. Van Kranendonk, M.J., 2010. Two types of Archean continental crust: Plume and plate tectonics on early Earth. American Journal of Science 310 (10), 1187–1209. https://doi. org/10.2475/10.2010.01. Wiedenbeck, M., Alle, P., Corfu, F., Griffin, W.L., Meier, M., Oberli, F., Quadt, A.V., Roddick, J.C., Spiegel, W., 1995. Three natural zircon standards for U-Th-Pb, Lu-Hf, trace element and REE analyses. Geostandards and Geoanalytical Research 19 (1), 1–23. Wu, F.Y., Yang, Y.H., Xie, L.W., 2006. Hf isotopic compositions of the standard zircons and baddeleyites used in U-Pb geochronology. Chemical Geology 234, 105–126. Zong, K.Q., Klemd, R., Yuan, Y., He, Z.Y., Guo, J.L., Shi, X.L., Liu, Y.S., Hu, Z.C., Zhang, Z.M., 2017. The assembly of Rodinia: the correlation of early Neoproterozoic (ca. 900 Ma) high-grade metamorphism and continental arc formation in the southern Beishan Orogen, southern Central Asian Orogenic Belt (CAOB). Precambrian Research 290, 32–48.