Zircon evidence for the Eoarchean (~3.7 Ga) crustal remnant in the Sulu Orogen, eastern China

Journal Pre-proofs Zircon evidence for the Eoarchean (∼3.7 Ga) crustal remnant in the Sulu Orogen, eastern China Kun Zhou, Yi-Xiang Chen, Shao-Bing Zhang, Yong-Fei Zheng PII: DOI: Reference:

S0301-9268(19)30193-7 https://doi.org/10.1016/j.precamres.2019.105529 PRECAM 105529

To appear in:

Precambrian Research

Received Date: Revised Date: Accepted Date:

28 March 2019 4 October 2019 5 November 2019

Please cite this article as: K. Zhou, Y-X. Chen, S-B. Zhang, Y-F. Zheng, Zircon evidence for the Eoarchean (∼3.7 Ga) crustal remnant in the Sulu Orogen, eastern China, Precambrian Research (2019), doi: https://doi.org/10.1016/ j.precamres.2019.105529

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Zircon evidence for the Eoarchean (~3.7 Ga) crustal remnant in

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the Sulu Orogen, eastern China

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Kun Zhou1, Yi-Xiang Chen*1,2, Shao-Bing Zhang1,2, Yong-Fei Zheng1,2

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1. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China

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2. CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei 230026, China

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Corresponding author. Email: [email protected]; Tel./Fax: +86 551 63600105.

Abstract

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Zircon provides one of the best records of the formation and reworking of continental

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crust in the early Earth. However, Hadean to Eoarchean zircons are relatively scarce

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worldwide. Here we present the first report of relict Eoarchean magmatic zircons in granitic

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gneisses from the Sulu Orogen, eastern China. Based on internal structures, trace element

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contents, and U–Pb ages, we identified four groups of zircon domains with U–Pb ages of ~3.7

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Ga (Group I), ~2.1 Ga (Group II), ~790 Ma (Group III), and ~720 Ma (Group IV). Group I

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domains exhibit variable Th/U ratios, steep HREE patterns, and negative Eu anomalies. They

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yield lower intercept U–Pb ages of 1.82–1.95 Ga and discordia upper intercept ages of

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3.65–3.69 Ga that are similar to the oldest concordant spot age of 3680 ± 29 Ma. This

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indicates their growth from an Eoarchean magma and reworking during the Paleoproterozoic.

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The oldest Eoarchean domains with U–Pb ages of 3606 ± 28 to 3680 ± 29 Ma have low P

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contents of 216–563 ppm and high (Y + REE)/P molar ratios of 1.13–3.34, consistent with an

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igneous source. They show εHf(t) values of –2.8 to –0.9 at 3.67 Ga and TCHUR2 ages of 3.7–4.0

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Ga, suggesting the growth of juvenile crust during the early Eoarchean. Group II to IV

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domains have consistent TDM2 ages of 2.6–3.0 Ga, suggesting that they grew during multiple

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reworkings of the Archean crust. Group II domains have variable Th/U ratios and steep to

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flattened HREE patterns that suggest growth during Paleoproterozoic crustal anatexis. Groups

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III and IV zircon domains have Th/U ratios and trace element contents that indicate growth

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from magmas that formed during Neoproterozoic continental rifting. In view of the unique

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feature of Neoproterozoic rifting magmatism in South China, the relict Eoarchean magmatic

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zircons would have originated in the Yangtze Craton and then undergone multiple phases of

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reworking during the Paleoproterozoic and Neoproterozoic. The results indicate the presence

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of ~3.7 Ga relict magmatic zircons in the Sulu Orogen, and they represent the oldest remnants

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of crustal material in the Yangtze Craton.

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Keywords: Eoarchean; zircon; Hf isotopes; Sulu Orogen; Yangtze Craton; continental crust

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1. Introduction

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Hadean to Eoarchean crustal rocks and mineral relics are important in decoding the

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physical and chemical properties of early Earth (e.g., Cavosie et al., 2006, 2019; Harrison,

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2009; Bauer et al., 2017; Harrison et al., 2017; Trail et al., 2018). They provide direct records

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on the formation conditions and geochemical compositions of the earliest continental crust.

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However, such samples are rarely preserved, and among the few found worldwide are those in

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the Anshan area of the North China Craton (Liu et al., 1992, 2008; Wan et al., 2019), the

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Aktash Gneiss Complex in the Tarim Craton of northwestern China (Lu et al., 2008; Ge et al.,

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2018), the Itsaq Gneiss Complex of Greenland (Nutman et al., 1996), and the Acasta Gneiss

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Complex in northwestern Canada (Bowring et al., 1999; Bauer et al., 2017). Therefore, it is

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essential to obtain more samples that represent the early Earth, and compare the material from

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as many different locations as possible to gain insights into the nature of the early continental

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crust (e.g., Burnham and Berry, 2017; Harrison et al., 2017; Boehnke et al., 2018; Trail et al.,

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2018).

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The ancient rocks, once formed, would have undergone complex deformation,

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metamorphism, and anatexis during the evolution of the continental lithosphere (e.g., Nutman

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et al., 2007; Lu et al., 2008; Bauer et al., 2017). Thus it is difficult to retrieve information on

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the sources and formation conditions of such rocks (e.g., Bell et al., 2016). Zircon is a robust

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accessory mineral and resistant to later modification by metamorphism and anatexis. With

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advances in U–Pb dating and trace element and O–Hf isotope analyses, the mineral zircon has

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become a valuable target for elucidating the growth and reworking of continental crust,

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especially that of early Earth for which records of actual rocks are scarce (e.g., Wilde et al.,

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2001; Harrison et al., 2005; Zhang et al., 2006a; Hoffmann et al., 2014; Valley et al., 2014;

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Bauer et al., 2017). However, care is needed when using detrital zircons to reconstruct the

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growth and reworking of continental crust due to the loss of information on the provenance of

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these zircons.

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The Yangtze and North China cratons are the two largest Precambrian blocks in China

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(Zhao and Cawood, 2012; Zheng et al., 2013). Eoarchean to Paleoarchean rocks, as well as

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rare occurrences of Hadean to Eoarchean detrital zircons, have been identified in China (Liu

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et al., 1992, 2008; Zhang et al., 2006b; Wu et al., 2008a; Wan et al., 2019). Compared with

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the widespread Archean rocks and crustal remnants in the North China Craton, only a few

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pieces of Archean basement are exposed in the Yangtze Craton, such as the Kongling

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Complex (e.g., Gao et al., 1999; Zhang et al., 2006a; Guo et al., 2014), the Yudongzi

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Complex (e.g., Hui et al., 2017; Zhou et al., 2018), the Zhongxiang Complex (e.g., Wang et

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al., 2018a; Wang et al., 2018b), and the Douling Complex (e.g., Wu et al., 2014). The records

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of Archean crust in the Yangtze Craton are preserved as Archean rocks, relict zircon cores in

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magmatic and metamorphic rocks, and detrital zircons in sedimentary rocks. A detrital zircon

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with a U–Pb age of 3802 ± 8 Ma, found in the Yangtze Gorge, is the oldest detrital mineral

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recorded in the Yangtze Craton (Zhang et al., 2006b). The existence of Eoarchean continental

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crust is indicated by Hf model ages of a few Paleoarchean zircons within orthogneisses and

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migmatites in the Kongling Complex (Zhang et al., 2006a; Jiao et al., 2009; Gao et al., 2011;

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Guo et al., 2014). However, the crustal evolution of the Yangtze Craton during the Eoarchean

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or earlier is still poorly constrained (e.g., Wu et al., 2008; Zhang and Zheng, 2013).

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In this paper, we present the results of a combined study of whole-rock geochemistry,

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zircon U–Pb ages, trace elements, and Lu–Hf isotope compositions for the granitic gneisses

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from Yangkou in the Sulu Orogen, which was formed during the Triassic continental collision

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between the North China and Yangtze cratons (Zheng et al., 2003, 2009, 2019). Our results

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show the presence of ~3.7 Ga relict magmatic zircons, the oldest in the Sulu Orogen. Our

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results also point to the exposure of a new area of Archean basement along the northern

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margin of the Yangtze Craton.

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2. Geological setting and samples

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The Sulu Orogen is the eastern part of the Dabie–Sulu orogenic belt, which formed

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during the northwards subduction of the South China Block (SCB) beneath the North China

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Craton (NCC) in the Triassic (Cong, 1996; Zheng et al., 2003; Zhang et al., 2009). The

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orogen is bounded by the Jiashan–Xiangshui Fault (JXF) to the south and the Wulian–Yantai

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Fault (WYF) to the north (Fig. 1a). According to previous petrological and geochemical

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studies it can be divided into a high-pressure (HP) metamorphic zone in the south and an

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ultrahigh-pressure (UHP) metamorphic zone in the north (Xu et al., 2006; Zheng et al., 2019).

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The HP zone is composed mainly of schist, paragneiss, orthogneiss, and marble along with

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minor blueschist, while the UHP zone is predominantly granitic orthogneiss with minor

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eclogite, paragneiss, quartzite, marble, and garnet peridotite. Both zones are intruded by

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Mesozoic granites and overlain by Jurassic clastic strata with a covering of Cretaceous

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volcaniclastics (Zhang et al., 1995; Zhao and Zheng, 2009). Previous geochronological and

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geothermobarometric studies indicated that the protoliths of the gneiss and eclogite were

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mostly of Neoproterozoic age along with some of Paleoproterozoic age (Tang et al., 2008;

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Katsube et al., 2009; Zhang et al., 2009).

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For our study, we collected four gneiss samples from the UHP metamorphic zone in the

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Yangkou region, on the east coast of the Laoshan District (GPS: N36°13'21", E120°40'38";

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Fig. 1b). The Yangkou region belongs to the central part of the Sulu Orogen and is well

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known for its outcrops of UHP metamorphic rocks (Liou and Zhang, 1996; Ye et al., 2000;

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Wang et al., 2014). The region is composed mainly of metagabbro, coesite-bearing eclogite,

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serpentinized peridotite, and granitic gneiss, all of which are cut by lamprophyre and quartz

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porphyry dikes of Cretaceous age (Zhang and Liou, 1997; Chen et al., 2002; Xia et al., 2018).

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Most of the relict magmatic zircons in the eclogite and granitic gneiss yield middle

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Neoproterozoic U–Pb ages of 770–780 Ma (Zheng et al., 2004; Wang et al., 2014; Wang et al.,

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2017). Our samples (15Q35, 19Q03, 19Q04, and 19Q08) were collected from an outcrop of

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granitic gneiss (see Fig. 1b for the location) that is exposed over an area of ~50 m2 close to

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General Hill (Wang et al., 2014) and the Yangkou Unit (Zhang and Liou, 1997). All samples

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are weakly deformed, have similar mineral textures and contents, and are composed of

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30%–40% quartz, 25%–35% K-feldspar, 20%–25% plagioclase, and 10%–15% biotite

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together with minor titanite, rutile/ilmenite, apatite, and zircon (Fig. 2). The biotite in these

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samples generally shows a preferred orientation, and it has undergone retrogression so that it

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shows irregular margins in thin sections. The mineral abbreviations used here are after

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Whitney and Evans (2010).

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3. Analytical methods

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3.1. Whole-rock major and trace elements

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Whole-rock major element compositions were measured at ALS Chemex, Guangzhou,

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China. Sample powders (200 mesh) were fused with a lithium borate flux in an auto fluxer at

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1050–1100 °C. A flat molten glass disc was prepared from the resulting melt and then

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analyzed using X-ray fluorescence spectrometry (XRF). Whole-rock trace element

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compositions were measured on an Agilent 7700e ICP–MS at SampleSolution Analytical

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Technology, Wuhan, China. Sample powders were digested using HNO3/HF (1 ml: 1 ml) in a

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Teflon bomb. After the initial digestion and evaporation to dryness, samples were then

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refluxed with concentrated HNO3, and finally diluted in 2% HNO3. The final solutions were

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analyzed by inductively coupled plasma–mass spectrometer (ICP–MS). Relative standard

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deviations (RSD) were within ±1–2% for major element oxides, and the precision and

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accuracy for most trace elements were better than ±5%.

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3.2. Whole-rock oxygen isotopes

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Whole-rock O isotope compositions were measured using the laser fluorination

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technique at the CAS Key Laboratory of Crust–Mantle Materials and Environments in the

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University of Science and Technology of China (USTC), Hefei, China. A sample of 1.2–2.0

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mg was reacted with BrF5 under vacuum and a MIR-10 CO2 laser was used to extract O2. The

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O2 was then transferred to a Finnigan MAT-253 mass spectrometer for oxygen isotope

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measurements. The data are reported in standard δ18O notation relative to the reference

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standard VSMOW. Two reference minerals, National Standard of China GBW04409 quartz

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with 18O = 11.1‰ (Zheng et al., 1998) and in-house standard 04BXL07 garnet with 18O =

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3.7‰ (Gong et al., 2007), were used for quality control. Reproducibility for measurements of

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each standard on any given day was better than ±0.1‰ (1σ).

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3.3. Zircon U–Pb ages and trace elements

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Zircon grains were hand-picked, mounted in epoxy, and then polished to expose internal

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domains. Cathodoluminescence (CL) images were obtained using a MIRA3 TESCAN

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scanning electron microscope at the CAS Key Laboratory of Crust–Mantle Materials and

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Environments in USTC, Hefei. Zircon U–Pb dating and trace element analyses were

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conducted at the same laboratory using an Agilent 7900 ICP–MS connected to a GeoLas HD

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193 nm ArF-excimer laser-ablation system. A laser beam diameter of 24 μm was used with a

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repetition frequency of 4 Hz. The procedures followed those of Liu et al. (2008). Offline data

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processing was performed using the Excel-based software ICPMSDataCal (Liu et al., 2008,

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2010). During raw data processing, the time-resolved signal was checked carefully to avoid

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mixing different zircon domains. Zircon standard 91500 was used as an external standard for

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U–Pb dating calibration. During the analyses, zircon GJ-1 gave a concordia age of 602 ± 2

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Ma (2σ, n = 36; Fig. S1), which is within analytical uncertainty of published results (e.g.,

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Jackson et al., 2004). For trace element calibration, NIST610 was used as an external standard.

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The analytical precision and accuracy were better than 10% for most trace elements. The spot

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ages are presented with 1σ errors, and intercept ages from concordia diagram and weighted

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means of spot ages are presented with 2σ errors.

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3.4. Zircon Lu–Hf isotopes

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Zircon Lu–Hf isotope compositions were measured using a Neptune Plus MC–ICP–MS

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in combination with a Geolas HD excimer ArF laser ablation system at Wuhan Sample

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Solution Analytical Technology, Hubei, China. The laser spot was 32 μm in diameter with an

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ablation frequency of 8 Hz. The operating conditions for the laser ablation system and the

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MC–ICP–MS instrument and analytical methods were the same as those described by Hu et al.

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(2012). Off-line selection and integration of analytic signals, and mass bias calibrations were

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performed using ICPMSDataCal (Liu et al., 2010). During the analytical sessions, zircon

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standards GJ-1 and Temora-2 gave mean 176Hf/177Hf ratios of 0.282004 ± 0.000011 (2σ; n = 8)

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and 0.282689 ± 0.000010 (2σ; n = 8), respectively (Fig. S1), which agree well with previous

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results (e.g., Wu et al., 2006; Yuan et al., 2008). Initial Hf isotope ratios were calculated using the following parameters: 1.867 × 10–11

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year–1 for the decay constant of

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the

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calculation of the depleted mantle Hf model ages, we used depleted mantle with a present-day

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176Hf/177Hf

ratio of 0.28325 and

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176Lu/177Hf

ratio of 0.015 for average continental crust (Griffin et al., 2002). The spot Hf

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isotope compositions and model ages are quoted with 1σ errors, and weighted means are

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quoted with 2σ errors.

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176Hf/177Hf

and

176Lu/177Hf

176Lu

(Söderlund et al., 2004), and 0.282785 and 0.0336 for

ratios of chondrite, respectively (Bouvier et al., 2008). For

176Lu/177Hf

ratio of 0.0384 (Griffin et al., 2000), and a

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4. Results

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4.1. Whole-rock geochemistry

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The whole-rock major and trace element compositions of the samples are presented in

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Table 1. All four samples have similar granitic compositions with high contents of SiO2

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(71.9–75.1 wt%) and K2O (4.72–6.16 wt%), and high K2O/Na2O ratios of 1.41–2.09. The

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rocks are weakly peraluminous with A/CNK = 1.05–1.09 (Fig. 3). The trace element

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compositions display negative anomalies of the high field strength elements (HFSEs) such as

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Nb, Ta, Ti, and P, and there are no positive Eu anomalies (Fig. 3). They have Th/U ratios of

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5.29–9.75 and Nb/Ta ratios of 10.2–15.9. Zircon saturation temperatures of 742–760 °C were

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obtained following the experimental calibration of Watson and Harrison (1983). Their O

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isotope compositions are generally homogeneous, with δ18OWR values of 5.4–6.1‰ (Table 1).

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4.2. Zircon U–Pb ages and trace elements Zircons from all four samples were analyzed (Tables 2–3; Supplementary Tables S1–S2),

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and they yielded apparent U–Pb ages that varied from 3680 ± 29 to 665 ± 8 Ma. Based on CL

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images, trace element compositions (especially Th and U contents, and Th/U ratios), and

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U–Pb ages, the zircon domains can be categorized into four groups (Figs. 4–9), as follows.

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Group I zircon domains are relict cores that are present in all four granitic gneiss samples, 207Pb/206Pb

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and they have apparent

ages of 3680 ± 29 to 2383 ± 46 Ma (Table 2). These

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zircons yield discordia upper intercept ages of 3671 ± 58, 3655 ± 66, 3652 ± 59, and 3688 ±

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140 Ma, and lower intercept ages of 1822 ± 64, 1941 ± 70, 1820 ± 83, and 1947 ± 100 Ma

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(Fig. 5). These domains show variable contents of Th (53.7–453 ppm) and U (120–1192 ppm),

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with Th/U ratios of 0.07–0.85. They exhibit negative Eu anomalies with Eu* = 0.03–0.39 and

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variable (Yb/Gd)N ratios of 10.6–104. They have Hf contents of 8554–12587 ppm and P

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contents of 183–728 ppm. Their Ti contents are 6.93–38.3 ppm and the Ti-in-zircon

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temperatures are 709–874 °C (average 780 °C). Six zircon domains (35#14, 35#57, 35#60,

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03#16, 04#19, and 08#05) yielded the oldest concordant spot ages of 3680 ± 29 to 3606 ± 28

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Ma, close to the discordia upper intercept ages (Figs. 4–5). These domains display relatively

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small ranges in Th/U ratios (0.43–0.85) and (Yb/Gd)N ratios (10.6–23.1) (Table 3). They

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contain 8556–10261 ppm Hf, 216–563 ppm P, 0.32–4.05 ppm Al, and 15.6–37.0 ppm Ti with

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Ti-in-zircon temperatures of 773–871 °C (average 808 °C).

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Group II zircon domains were found in the zircons from three samples (15Q35, 19Q03, 207Pb/206Pb

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and 19Q04), and they yield apparent

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S1). Nine spots in zircons from sample 15Q35 gave an upper intercept age of 2118 ± 75 Ma

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(MSWD = 1.19). Group II zircon domains contain 14.6–452 ppm Th and 61.2–904 ppm U,

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and yield a large range of Th/U ratios from 0.08 to 7.38 and negative Eu anomalies (Eu* =

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0.15–0.80). They generally have low contents of trace elements such as P (74.9–389 ppm), Ti

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(4.73–16.6 ppm), and Y (44.3–770 ppm). Six concordant spots (35#20, 35#21, 35#23, 35#50,

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03#09, and 04#12) display relatively homogeneous trace element contents with 2.00–3.46

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ppm Al, 196–372 ppm P, 5.73–10.9 ppm Ti, 279–770 ppm Y, and (Yb/Gd)N ratios of

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16.0–24.1.

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ages of 2199 ± 84 to 1851 ± 70 Ma (Table

Group III domains display oscillatory zoning in CL images (Fig. 4). Most domains yield 206Pb/238U

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Neoproterozoic

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Ma (MSWD = 4.4). They have Th contents of 30.5–1535 ppm, U contents of 43.0–1703 ppm,

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and Th/U ratios of 0.26–1.82 (Table S1; Fig. 7). They show negative Eu anomalies (Eu* =

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0.01–0.71) and steep REE patterns with (Yb/Gd)N ratios of 15.5–53.1 (Table S2; Fig. 6).

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These domains have variable contents of Al (0.14–35.2 ppm), P (151–785 ppm), Y

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(291–3177 ppm), Nb (0.43–18.0 ppm), and Ti (1.83–12.1 ppm). Their Ti-in-zircon

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temperatures range from 611 to 758 °C with an average of 660 °C.

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ages of 836 ± 9 to 751 ± 11 Ma with a weighted mean of 790 ± 6

Group IV domains occur in the outer rims of zircon grains and they have dark CL

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features with weak oscillatory zoning (Fig. 4). In comparison to Group III domains, they gave

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younger

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(MSWD = 4.4), except for three analyses that possibly indicate Pb loss (Table S1). They have

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high contents of Th (704–5277 ppm) and U (664–2951 ppm), and Th/U ratios of 0.92–2.14

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(Table S1; Fig. 7). These domains are characterized by high contents of trace elements such

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as Al (10.3–562 ppm), P (424–2029 ppm), Y (2111–7469 ppm), and Nb (8.18–35.0 ppm).

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They also exhibit steep REE patterns and negative Eu anomalies (Eu* = 0.19–0.35). Their Ti

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contents are 4.17–38.5 ppm, corresponding to Ti-in-zircon temperatures of 669 to 875 °C with

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an average of 774 °C.

206Pb/238U

ages of 748 ± 11 to 695 ± 11 Ma with a weighted mean of 720 ± 6 Ma

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4.3. Zircon Lu–Hf isotopes

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Ninety-eight Lu–Hf isotope analyses were made by LA–MC–ICP–MS on the same spots

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as used for the LA–ICP–MS U–Pb dating (Table 4, Figs. 10–11). The U–Pb ages used in the

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calculation of εHf(t) values and Hf model ages for Groups I–IV zircon domains are 3.67 Ga,

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2.10 Ga, 790 Ma, and 720 Ma, respectively.

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Group I zircon domains (n = 37) have

176Hf/177Hf

ratios of 0.280376–0.280533 and

ratios of 0.000466–0.002384 (Table 4). Their εHf(t) values range from –3.8 to 0.6

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176Lu/177Hf

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with an average of –1.6 ± 0.3 (Fig. 11a). They yield two-stage chondrite Hf model ages

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(TCHUR2) of 3624–3960 Ma with an average of 3794 ± 22 Ma (Fig. 11b), and two-stage

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depleted mantle Hf model ages (TDM2) of 3899–4166 Ma with an average of 4034 ± 18 Ma

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(Fig. 11c). The six spots with the oldest Eoarchean U–Pb ages have εHf(t) values of –2.8 to

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–0.9. They yield TCHUR2 ages of 3.74–3.96 Ga and TDM2 ages of 4.00–4.17 Ga. Because it is

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still highly debatable whether there was any depleted mantle during the Hadean and

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Eoarchean (e.g., Fisher and Vervoort, 2018), the calculated TCHUR2 ages may be more

267

appropriate for Group I domains. Notably, the TCHUR2 ages are significantly lower than the

268 269

TDM2 ages. Group II domains (n = 11) exhibit higher 176Lu/177Hf

271

(Fig. 10b) with TDM2 ages of 2.7–3.0 Ga. Group III domains (n = 26) have high

176Hf/177Hf

ratios of 0.281733–0.281933 and

ratios of 0.000804–0.004143 (Table 4). Their εHf(t) values are –20.0 to –13.9 and

273

176Lu/177Hf

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TDM2 ages are 2.5–2.9 Ga (Fig. 10b).

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ratios of 0.281316–0.281464 and

ratios of 0.000018–0.001642 (Table 4). Their εHf(t) values range from –5.4 to –1.2

270

272

176Hf/177Hf

Group IV zircon domains (n = 24) have 176Hf/177Hf ratios of 0.281743–0.281975 that are 176Lu/177Hf

276

similar to those of the Group III domains, but they exhibit much higher

ratios of

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0.001577–0.006012, consistent with their high HREE contents. Their εHf(t) values are –22.0

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to –15.2 and the TDM2 ages are 2.6–3.0 Ga (Table 4; Fig. 10b).

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5. Discussion

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5.1. The presence of Eoarchean (~3.7 Ga) crustal remnants

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Many studies have been devoted to understanding the formation and evolution of the

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Yangtze Craton in the South China Block. The oldest U–Pb age of 3802 ± 8 Ma was obtained

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for a detrital zircon from sandstone of the Neoproterozoic Liantuo Formation, thus providing

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the oldest age for any mineral in the Yangtze Craton (Zhang et al., 2006b). However, whether

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this detrital zircon originated from within the Yangtze Craton is uncertain. Neither Eoarchean

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rocks nor Eoarchean relict magmatic zircons that clearly originated in the Yangtze Craton

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have been found in magmatic, sedimentary, or metamorphic rocks of the craton. A relict

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zircon with a U–Pb age of 3.53 Ga was found in the granulite at Huangtuling in the Dabie

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Orogen (Wu et al., 2008), suggesting the presence of a Paleoarchean crustal remnant. Guo et

291

al. (2014) identified 3.45 Ga granitic gneiss in the Kongling Complex, pre-dating the earlier

292

reported 3.3 Ga trondhjemitic gneiss (Gao et al., 2011) by 150 Myr. These Paleoarchean rocks

293

show Eoarchean Hf model ages, yet no Eoarchean rocks have been found to date (Gao et al.,

294

2011; Guo et al., 2014).

295

Group I zircon domains show mostly high Th/U ratios of >0.1 and steep REE patterns

296

with marked negative Eu anomalies (Figs. 6 and 7), suggesting a magmatic origin (Rubatto,

297

2002; Chen and Zheng, 2017). The following three lines of evidence indicate that these

298

Eoarchean zircons are not detrital zircons derived from some other continent or terrane: (1)

299

the oldest zircon domains in the samples have concordant Eoarchean U–Pb ages of 3.61–3.68

300

Ga (n = 6); (2) Group I zircons in all four gneiss samples show very good discordant lines

301

with upper intercept ages of 3.65–3.69 Ga, consistent with the oldest concordant spot age of

302

3680 ± 29 Ma, which clearly indicates these zircon domains underwent Pb loss rather than

303

formed at different times under different conditions; and (3) these zircon domains show

304

almost constant

305

that they formed from the same magma source but underwent Pb loss during the

306

Paleoproterozoic. Therefore, it is confident that these Eoarchean magmatic zircons are not

307

recycled Eoarchean detrital minerals from unknown continents or terranes, and the data

308

strongly suggest that they are all from the same magma source. The zircons indicate the

309

presence of an Eoarchean (~3.7 Ga) crustal remnant in this region, which would be the oldest

310

known crustal remnant in the Yangtze Craton. These Eoarchean zircons have negative εHf(t)

311

values of –2.8 to –0.9 and TCHUR2 ages of 3.62 to 3.96 Ga, indicating their derivation from

312

juvenile crust during the early Eoarchean.

176Hf/177Hf

ratios with variable U–Pb ages (Fig. 10a), which also indicates

313

It is essential to clarify if these Archean zircons originated from the Yangtze Craton

314

rather than elsewhere (e.g., the North China Craton). The North China Craton was formed by

315

the accretion and amalgamation of Archean micro-continents, and it is characterized by an

316

Archean to Paleoproterozoic basement that is overlain by Mesoproterozoic to Cenozoic

317

sedimentary rocks (Zhai and Santosh, 2011; Zhao and Cawood, 2012; Zheng et al., 2013).

318

The South China Block is composed of the Yangtze Craton in the northwest and the

319

Cathaysia terrane in the southeast, which collided to form the Jiangnan Orogen during the

320

Neoproterozoic (Zheng et al., 2013). Magmatic rocks of middle Neoproterozoic age are

321

widespread in the periphery of the Yangtze Craton, but they are absent from the North China

322

Craton (Tang et al., 2007, 2008; Zheng and Zhang, 2007; Zhang and Zheng, 2013; Zhang et

323

al., 2014). In the four studied gneiss samples, the zircon domains with Eoarchean to

324

Paleoproterozoic U–Pb ages have coherent rims with middle Neoproterozoic U–Pb ages.

325

Group II domains exhibit Paleoproterozoic U–Pb ages of 1.9–2.2 Ga, which are

326

indistinguishable from the ages of ancient crustal rocks in the North China Craton.

327

Nevertheless, Groups III and IV domains show Neoproterozoic U–Pb ages of 790 ± 6 to 720

328

± 6 Ma, which are characteristic of the magmatism that accompanied a period of continental

329

rifting in the periphery of the Yangtze Craton (Zheng et al., 2004; Zhang and Zheng, 2013).

330

Therefore, the studied granitic gneiss has a tectonic affinity with the Yangtze Craton, and its

331

Eoarchean to Paleoarchean zircons were probably derived from the Archean basement of the

332

Yangtze Craton. Because the Sulu Orogen was produced during the northwards subduction of

333

the Yangtze Craton beneath the North China Craton during the Triassic, the protoliths of the

334

granitic gneiss must have been located along the northeastern margin of the Yangtze Craton.

335

Due to the scarcity of hydrous minerals in the protoliths of the granitic gneisses, no Triassic

336

zircon domains grew during this period of Triassic continental subduction (Zheng, 2009). For

337

this reason, the youngest U–Pb age of zircon rims in our samples is Neoproterozoic rather

338

than Triassic.

339

The trace element compositions of zircon can constrain the characteristics of the source,

340

thus helping our understanding of early Earth. It has been demonstrated experimentally that

341

apatite is more soluble in peraluminous than in metaluminous melts, which means that

342

peraluminous melts contain higher amounts of P (e.g., London, 1992; Pichavant et al., 1992).

343

The P contents of zircons in S-type granites are generally much higher than those of zircons in

344

I-type granites. Xenotime substitution (REE3+ + P5+ = Zr4+ + Si4+) in zircon from S-type

345

granites always leads to a strong correlation between the molar concentrations of P and (REE

346

+ Y), whereas an additional vacancy-related mechanism in zircon from I-type granites may

347

decouple this correlation to result in (REE + Y) > P (Burnham and Berry, 2017). The P

348

contents of zircon and the ratios of P to REE have been used as discriminants between I- and

349

S-type sources for Hadean zircons from Jack Hills, which were considered to have

350

crystallized mainly from I-type magmas formed by the melting of a reduced, garnet-bearing

351

igneous crust (Burnham and Berry, 2017). The Eoarchean zircons in our samples have low P

352

contents of 216–563 ppm and low P/(Y + REE) molar ratios of 1.13–3.34, consistent with

353

zircons from typical I-type granites (Fig. 8). Similarly, the Al in zircons can be used as

354

evidence for growth from peraluminous or metaluminous melts, regardless of their ages, as

355

the zircons from peraluminous rocks yield higher Al concentrations (mostly >4 ppm) than

356

those from metaluminous rocks (Trail et al., 2017). The Al contents in our Eoarchean zircons

357

range from 0.32 to 4.05 ppm, mostly lower than 4 ppm, indicating derivation from a

358

metaluminous source (Fig. 7f). Taken together, the trace element characteristics of our

359

Eoarchean zircon domains indicate they crystallized from the magma of a metaluminous

360

I-type granite.

361 362

5.2. Crustal growth and reworking during the Archean and Paleoproterozoic

363

Although the Yangtze Craton is generally considered to be much younger than the North

364

China Craton, more and more studies of zircon U–Pb geochronology indicate the presence of

365

Archean crustal remnants in the Yangtze Craton. In particular, the zircon age data exhibit two

366

peaks of Archean ages at 2.9–3.0 Ga and 2.5 Ga (Zhang and Zheng, 2013). The zircon U–Pb

367

ages record the times of crustal reworking through either magmatism or metamorphism, but

368

the zircon εHf(t) values and Hf model ages can be used to decode the nature of the source. In

369

the Yangtze Craton, both positive and negative εHf(t) values are associated with the Archean

370

U–Pb ages, indicating the growth of juvenile crust and reworking of ancient crust during the

371

Archean (e.g., Zhang et al., 2006a; Zhao et al., 2010; Zhang and Zheng, 2013). Our examples

372

of Eoarchean zircons have negative εHf(t) values of –2.8 to –0.9 and TCHUR2 ages of 3.74 to

373

3.96 Ga, indicating the growth and rapid reworking of juvenile crust during the early

374

Eoarchean.

375

So far, no positive Hf(t) values have been obtained for Paleoproterozoic zircons from the

376

Yangtze Craton (Zhang et al., 2006c; Wu et al., 2008; Wu et al., 2012; Yin et al., 2013; Zhang

377

and Zheng, 2013; Li et al., 2014; Chen and Xing, 2016). In terms of their Archean Hf model

378

ages, the Paleoproterozoic reworking of Archean crust by either magmatism or

379

metamorphism is indicated, with a possible link to the assembly of the supercontinent

380

Columbia (Zhang and Zheng, 2013). Our Group II zircons yield Paleoproterozoic U–Pb ages

381

of 1.94–2.20 Ga with TDM2 ages of 2.77–3.03 Ga, consistent with previous studies of zircons

382

in the Paleoproterozoic crustal rocks of the Yangtze Craton. The Archean Hf model ages are

383

consistent with the exposed Archean basements in the Kongling, Yudongzi, and Douling

384

complexes of the Yangtze Craton (Gao et al., 1999; Zheng et al., 2006; Wu et al., 2014; Hui et

385

al., 2017; Zhou et al., 2017; Zhou et al., 2018).

386

Two analytical spots on the Group II domains (35#13 and 35#47) gave low Th/U ratios

387

of 0.13–0.33, flat HREE patterns, weak negative Eu anomalies (Eu* = 0.67–0.80), and

388

apparent 207Pb/206Pb ages of 2039 ± 46 and 2028 ± 44 Ma. These characteristics are similar to

389

those of the zircons that formed during the granulite-facies metamorphism in the middle

390

Paleoproterozoic (e.g., Wu et al., 2008). Thus, these ages probably record the metamorphic

391

event at ~2.0 Ga. The other Group II zircon domains with concordant U–Pb ages of 1.94–2.15

392

Ma exhibit high Th/U ratios of 0.31–7.38, high (Yb/Gd)N ratios of 16.0–24.1, and steep

393

HREE patterns with negative Eu anomalies, indicating growth from granitic magmas.

394

Therefore, the Group II zircons record Paleoproterozoic tectonothermal events of

395

granulite-facies metamorphism and granitic magmatism in the Yangtze Craton.

396 397 398

5.3. Crustal reworking during the Neoproterozoic The two populations of zircons in our samples with U–Pb ages of 790 ± 6 Ma (Group III)

399

and 720 ± 6 Ma (Group IV) record crustal reworking by Neoproterozoic magmatic events

400

(Fig. 9). Both groups of Neoproterozoic magmatic zircons have TDM2 ages of 2.6–3.0 Ga (Fig.

401

10), suggesting that the reworked crust was generated in the Archean. The final emplacement

402

age for the protolith of the granitic gneiss is ca. 720 Ma, which is constrained by the youngest

403

group of Neoproterozoic zircon U–Pb ages. Based on the whole-rock diagram of total alkalis

404

vs. SiO2, all the samples fall in the granite field (Fig. 3a). Trace element compositions of these

405

samples show strong enrichments in large ion lithophile elements (LILEs) and depletions in

406

high field strength elements (HFSEs) (Fig. 3c). Considering their high SiO2 contents and the

407

moderate Zr/Hf and low Nb/Ta ratios, these samples share some of the features of fractionated

408

granites (Wu et al., 2007). The δ18O values of 5.4–6.1‰ indicate that their magmatic source

409

was not significantly affected by water–rock interaction or the incorporation of sediments.

410

The Neoproterozoic magmatism in the South China Block has been intensively studied

411

based on zircon U–Pb ages and Hf–O isotopes, which provide robust constraints on its

412

relationship with the assembly and breakup of the supercontinent Rodinia (e.g., Li et al., 1999;

413

Zheng and Zheng, 2007; Zheng et al., 2008a, 2008b; Zhang and Zheng, 2013; He et al., 2018).

414

The Neoproterozoic magmatic rocks commonly show two groups of U–Pb age peaks at

415

830–800 and 780–740 Ma (Zhang and Zheng, 2013). Both felsic and mafic intrusions with

416

U–Pb ages ranging from 860 to 750 Ma crop out along the western margin of the South China

417

Block (Zhao et al., 2018), and they indicate a series of continuous processes from oceanic

418

subduction through arc–continent collision to post-collisional reworking (Zhang and Zheng,

419

2013). In particular, the post-collisional reworking may have been caused by continental

420

rifting along preexisting suture zones (Zheng and Chen, 2017; Zheng and Zhao, 2017; He et

421

al., 2018; Zheng et al., 2019).

422

Continental rifting was extensive in the South China Block during the period of 830–720

423

Ma, as indicated by the occurrence of bimodal volcanic rocks, A-type granites, and

424

sedimentary basins in the periphery of the Yangtze Craton (Wang and Li, 2003; Li et al., 2005;

425

Zheng et al., 2008, 2009; Wang et al., 2010, 2012, 2018c). Group III and IV zircon domains

426

in our sample are probably the products of continental-rifting magmatism during the middle

427

Neoproterozoic. Nevertheless, there are large differences between the two groups of zircon

428

domains in their CL images and trace element compositions (Figs. 4–7). Group III domains

429

show bright CL images, a low average Ti-in-zircon temperature of ~660 °C, low U and Al

430

contents, and low Th/U ratios that average 0.92. In contrast, Group IV domains exhibit dark

431

CL images, high U contents, an elevated Th/U ratio of 1.48, a high average Ti-in-zircon

432

temperature of ~770 °C, and much higher Al contents. These differences may have been

433

dictated by differences in the compositions of the parental rocks and differences in the

434

conditions of crustal anatexis (e.g., Trail et al., 2017). During continental rifting, multiple

435

episodes of high-temperature metamorphism and anatexis may occur (Zheng and Chen, 2017;

436

He et al., 2018), which could be recorded by both groups of zircons. Whatever the details, it is

437

clear that both groups of zircons record distinctive magmatic events that occurred during

438

continental rifting in the middle Neoproterozoic.

439 440

6. Conclusions

441

Relict magmatic zircons with Eoarchean U–Pb ages of ~3.7 Ga are described for the first

442

time from the granitic gneisses at Yangkou in the Sulu Orogen. They show negative εHf(t)

443

values of –2.8 to –0.9 and two-stage chondrite Hf model ages of 3.74–3.96 Ga, indicating the

444

existence of Eoarchean crustal remnants along the northeastern margin of the Yangtze Craton

445

and the growth of juvenile crust during the early Eoarchean. The low P contents, high (Y +

446

REE)/P molar ratios, and low Al contents of these zircons suggest the melting of

447

metaluminous granite rocks. Three other groups of zircon domains have younger U–Pb ages

448

at ~2.1 Ga, ~790 Ma, and ~720 Ma. Their two-stage depleted Hf model ages of 2.6–3.0 Ga

449

suggest derivation through the episodic reworking of Archean crust. The Paleoproterozoic

450

zircon domains may have grown during magmatism in response to the assembly of the

451

Columbia supercontinent. The two groups of Neoproterozoic zircon domains show large

452

differences in their trace element characteristics, such as the Th/U ratios and the contents of

453

Ti, Al, P, and REEs, and they may have grown during repeated magmatism in response to the

454

continental rifting that took place during the breakup of Rodinia. Our study demonstrates the

455

presence of Eoarchean crustal remnants in the Yangtze Craton and multiphase reworking of

456

Archean crust during the Paleoproterozoic and Neoproterozoic.

457 458

Acknowledgements

459

This study was supported by funds from the Natural Science Foundation of China

460

(41622302, 41590624, and 41773021), the Strategic Priority Research Program (B) of CAS

461

(XDB18020303), the Youth Innovation Promotion Association of CAS (2014300), and the

462

Fundamental Research Funds for the Central Universities. Thanks are due to Zi-Fu Zhao, Fei

463

Zheng, Guo-Chao Sun, Chun Sun, He-Zhi Ma, Jia-Wei Xiong and Yong-Jie Yu for their

464

assistance with sample collection, and to Ting Liang for her assistance with LA–ICP–MS

465

zircon dating and trace element measurements. Comments by two anonymous reviewers and

466

editors (Guochun Zhao and Xianhua Li) have greatly improved the presentation of the

467

manuscript.

469

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470

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773

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776

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777

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779

Figure captions

780

Figure 1. (a) Simplified geological map of the Sulu Orogen. Abbreviations: WYF =

781

Wulian–Yantai Fault; JXF = Jiashan–Xiangshui Fault. (b) Sketch map of the Yangkou region

782

on the east coast of the Laoshan district within the central Sulu belt, showing the location of

783

granitic gneiss samples (yellow star with red outline).

784 785

Figure 2. Field photographs and photomicrographs of granitic gneisses in the Yangkou region.

786

(a) Field outcrop of granitic gneiss. (b) Hand specimen of granitic gneiss sample 15Q35. (c–f)

787

Petrographic characteristics of granitic gneiss samples 15Q35 (c and d) and 19Q04 (e and f).

788

Panels (c) and (e) are under plane-polarized light, and (d) and (f) under cross-polarized light.

789

Mineral abbreviations are after Whitney and Evans (2010).

790 791

Figure 3. Whole-rock major and trace element compositions of the granitic gneisses from

792

Yangkou in the Sulu Orogen. (a) Total alkalis vs. SiO2 diagram. The classifications are after

793

Middlemost (1994) and Irvine and Baragar (1971). (b) A/NK vs. A/CNK diagram, where

794

A/CNK = Al2O3/(CaO + Na2O + K2O) molar ratio. (c) Primitive-mantle-normalized trace

795

element patterns. (d) Chondrite-normalized REE patterns. Chondrite values are after Sun and

796

McDonough (1989), and primitive mantle values are after McDonough and Sun (1995).

797 798

Figure 4. CL images of zircons from the granitic gneisses at Yangkou showing their apparent

799

U–Pb ages (Ma) and εHf(t) values. The red circles denote the U–Pb age spots, and the circles

800

in sky blue denote the Lu–Hf isotope spots. Scale bar = 100 μm.

801 802 803

Figure 5. Zircon U–Pb concordia diagrams for the granitic gneisses at Yangkou.

804

Figure 6. Chondrite-normalized REE patterns for zircons from the granitic gneisses of

805

Yangkou. Chondrite REE values are after Sun and McDonough (1989).

806 807

Figure 7. Trace element vs. U–Pb age diagrams for zircons from the granitic gneisses of

808

Yangkou. In (a), the Ti-in-zircon temperature (°C) was calculated using the calibration of

809

Watson et al. (2006). For each panel, we only considered concordant ages with discordance

810

<10%.

811 812

Figure 8. The relationship between the molar concentrations of REE + Y and P in zircons

813

from the granitic gneisses of Yangkou. Only concordant ages with discordance <10% were

814

considered. The spots in cyan and light-yellow are data for zircons from the granites of the

815

Lachlan Fold Belt (LFB) (Burnham and Berry, 2017). The solid lines (after Burnham and

816

Berry, 2017) are considered to be the boundary lines for the discrimination of magmatic

817

zircons from I- and S-type granites.

818 819

Figure 9. U–Pb ages and Hf isotope compositions of zircons from the granitic gneiss at

820

Yangkou. (a) Histogram of all zircon U–Pb ages for the granitic gneiss samples. Note that

821

only concordant ages are plotted. The data in the light gray color are for Archean igneous

822

zircons in the TTG rocks of the Yangtze Craton. Literature data: Zhang et al. (2006b), Zheng

823

et al. (2006), Jiao et al. (2009), Gao et al. (2011), Chen et al. (2013), Guo et al. (2014), Wu et

824

al. (2014), Hui et al. (2017), Wang et al. (2018a), Wang et al. (2018b), Zhou et al. (2018), and

825

Chen et al. (2019). (b) Histogram of Neoproterozoic U–Pb ages of zircons (Groups III and IV)

826

from the Yangkou granitic gneiss samples.

827 828

Figure 10. (a) Plot of

176Hf/177Hf

vs. U–Pb age for zircons from the granitic gneisses at

829

Yangkou. (b) Plot of εHf(t) vs. U–Pb age for zircons from the granitic gneiss at Yangkou.

830

Archean igneous zircons from the TTG rocks of the Yangtze Craton are also shown on the

831

plot in a light gray color.

832 833

Figure 11. The Lu–Hf isotope compositions of Group I domains of zircons from the granitic

834

gneiss samples of Yangkou. Histograms of (a) εHf(t) values and (b–c) two-stage Hf model

835

ages (TCHUR2 & TDM2). The value of t(Ma) used in the calculations was 3.67 Ga.

Supporting Information

837 838 839

Table S1. U–Pb isotope data for Group II to IV zircons from the granitic gneisses at Yangkou

840

in the Sulu Orogen

841 842

Table S2. Trace element compositions (ppm) of Group II to IV zircons from the granitic

843

gneisses at Yangkou in the Sulu Orogen

844 206Pb/238U

845

Figure S1. (a) Concordia diagram and (b) weighted mean

846

GJ-1 calibrated against 91500. (c–d) 176Hf /177Hf ratios of zircon standard GJ-1 and Temora-2

847

measured during the analytical sessions.

848 849

age for zircon standard

850 851 852 853

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

854 855 856

857 858 859 860 861 862

Figure 10

863

864 865 866

867 868

Figure 11

869 870 871

Table 1. Whole-rock major and trace element as well as oxygen isotope compositions of granitic gneisses from Yangkou in the Sulu Orogen Sample 15Q35 Major elements (wt%) SiO2 72.78

19Q03

19Q04

19Q08

19Q03R

71.91

75.11

74.93

72.28

TiO2

0.14

0.15

0.23

0.15

0.15

Al2O3

13.98

14.38

12.81

13.45

14.48

Fe2O3T MnO MgO CaO Na2O

1.52 0.03 0.31 0.85 2.95

1.50 0.02 0.21 1.05 3.18

1.80 0.04 0.37 0.89 3.33

1.37 0.02 0.21 0.98 3.32

1.51 0.02 0.21 1.06 3.21

K2O

6.16

6.05

4.72

4.72

6.07

P2O5 0.05 LOI 0.70 Total 99.47 A/CNK 1.07 Trace elements (ppm) Rb 125 Sr 288 Y 27.4 Zr 114 Nb 4.87 Cs 0.91 Ba 3766 La 102 Ce 105 Pr 12.3 Nd 36.9 Sm 5.27 Eu 1.40 Gd 4.09 Tb 0.72 Dy 4.16 Ho 0.85 Er 2.47 Tm 0.36 Yb 2.26 Lu 0.34 Hf 2.93 Ta 0.41 Pb 13.3 Th 9.33 U 1.37 Sr/Y 10.5 (La/Yb)N 32.4 Eu* 0.92 TZr(°C) 760

0.05 0.72 99.22 1.05

0.05 0.72 100.07 1.05

0.05 0.86 100.06 1.09

0.05 0.74 99.78 1.05

120 306 29.1 102 5.15 0.86 3828 96.2 107 12.5 38.3 5.61 1.43 4.52 0.71 4.28 0.84 2.58 0.40 2.62 0.39 2.66 0.51 14.4 10.0 1.89 10.5 26.3 0.87 749

107 200 12.1 111 8.82 0.81 2528 40.3 57.0 5.10 15.2 2.09 0.72 1.75 0.24 1.57 0.35 1.20 0.21 1.61 0.30 3.05 0.56 11.7 8.80 1.19 16.5 17.9 1.15 760

95.6 287 9.32 103 3.98 0.71 3030 45.4 78.1 5.52 15.8 1.90 0.83 1.28 0.23 1.36 0.30 0.98 0.17 1.15 0.20 2.66 0.36 14.0 9.94 1.02 30.8 28.3 1.63 757

120 305 28.9 93.4 5.09 0.87 3787 97.2 106 12.7 38.6 5.80 1.49 4.66 0.70 4.36 0.87 2.56 0.39 2.58 0.41 2.44 0.52 14.9 10.0 1.95 10.5 27.0 0.88 742

5.9

5.8

6.1

δ18OWR (‰)

5.4

872 873 874

Note: Eu* = EuN/(SmN*GdN)0.5, and the subscript N denotes the normalization to the chondrite values of Sun and McDonough (1989). The calculation of zircon saturation temperature TZr(°C) is after the equation of Watson and Harrison (1983). 19Q03R denotes the replicate analysis of the sample 19Q03.

875 876 877 878

h (ppm) 　

Table 2 U-Pb isotope data for Group I zircons in the Yangkou granitic gneisses from Yangkou in the Sulu Orogen

U (ppm) 　

Th/U 　

207Pb/206Pb

1σ

207Pb/235U

Isotopic ratios 1σ

115 54.3 220 53.7 172 164 213 121 172 82.4 139 92.4 65.9 64.2 94.2 70.0 232 222 61.0 282 74.2 89.3 140 93.3 193

182 121 257 143 245 423 376 267 506 468 446 162 171 721 500 369 952 388 726 584 1054 945 1127 556 388

0.63 0.45 0.85 0.38 0.70 0.39 0.57 0.45 0.34 0.18 0.31 0.57 0.39 0.09 0.19 0.19 0.24 0.57 0.08 0.48 0.07 0.09 0.12 0.17 0.50

0.34381 0.34051 0.33159 0.32258 0.31554 0.30676 0.30313 0.30113 0.29965 0.28907 0.28377 0.26487 0.26151 0.25888 0.23952 0.23357 0.22104 0.20668 0.20655 0.18765 0.17778 0.17379 0.17309 0.16474 0.15318

0.00779 0.00744 0.00824 0.00976 0.00676 0.00709 0.00764 0.00832 0.00653 0.00736 0.00614 0.00599 0.00802 0.01168 0.00659 0.00670 0.00679 0.00652 0.00449 0.00509 0.00450 0.00694 0.00447 0.00493 0.00416

34.69865 35.24113 31.38921 32.57752 29.28191 29.17624 29.21932 24.70462 24.65630 22.60951 21.79237 21.16996 19.66073 16.07262 18.06706 16.40198 13.39438 13.20733 12.85976 10.78594 9.38539 9.01887 9.23150 8.66435 7.73282

69.0 136 119 125 295 162 371 300

120 318 810 319 468 253 665 1192

0.58 0.43 0.15 0.39 0.63 0.64 0.56 0.25

0.3304 0.2937 0.2747 0.2255 0.2229 0.2219 0.1790 0.1770

0.0078 0.0071 0.0065 0.0098 0.0083 0.0100 0.0064 0.0199

34.0454 25.0344 21.6931 15.3436 14.5662 14.7907 11.7840 10.0353

879 880 881

1σ

207Pb/206Pb

0.78052 0.90816 0.68992 0.96148 0.61660 0.69626 0.75040 0.64994 0.56245 0.53984 0.48066 0.50147 0.48284 0.36218 0.55767 0.47484 0.45230 0.44627 0.28164 0.30287 0.24744 0.23300 0.22842 0.22588 0.20391

0.72574 0.74411 0.68763 0.72290 0.66583 0.68473 0.69086 0.58893 0.59122 0.56461 0.55100 0.57389 0.53736 0.44860 0.53598 0.50475 0.43310 0.45681 0.44910 0.41339 0.37762 0.37737 0.38220 0.38260 0.36448

0.00754 0.01134 0.00812 0.00889 0.00606 0.00934 0.00836 0.00685 0.00800 0.00727 0.00638 0.00675 0.00639 0.00442 0.00795 0.00693 0.00658 0.00643 0.00409 0.00490 0.00422 0.00434 0.00398 0.00447 0.00404

3680 3665 3624 3582 3550 3505 3486 3476 3468 3413 3384 3276 3257 3240 3117 3077 2989 2880 2879 2722 2632 2595 2588 2505 2383

29 33 38 47 32 36 39 43 34 40 34 35 48 71 44 45 49 52 35 45 42 67 44 51 46

3630 3645 3531 3568 3463 3459 3461 3297 3295 3210 3175 3146 3075 2881 2993 2901 2708 2695 2669 2505 2376 2340 2361 2303 2200

0.8023 0.6661 0.4978 0.5244 0.3594 0.3984 0.2993 0.2844

0.7388 0.6120 0.5761 0.4894 0.4676 0.4784 0.4399 0.4051

0.0105 0.0098 0.0076 0.0078 0.0060 0.0060 0.0054 0.0050

3620 3439 3333 3020 3002 2995 2644 2625

36 38 37 69 60 73 59 189

3611 3310 3170 2837 2787 2802 2587 2438

206Pb/238U

1σ

22 26 22 29 21 24 25 26 22 23 22 23 24 22 30 28 32 32 21 26 24 24 23 24 24

3518 3586 3374 3507 3290 3363 3386 2985 2994 2886 2829 2924 2772 2389 2767 2634 2320 2425 2391 2230 2065 2064 2087 2088 2003

28 42 31 33 24 36 32 28 32 30 27 28 27 20 33 30 30 28 18 22 20 20 19 21 19

23 26 22 33 24 26 24 26

3566 3078 2933 2568 2473 2520 2350 2193

39 39 31 34 27 26 24 23

Table 2 (continued)

Th (ppm) 　

U (ppm) 　

Th/U 　

207Pb/206Pb

1σ

362 189 224 96.7

713 584 665 852

0.51 0.32 0.34 0.11

0.3277 0.2700 0.2573 0.1796

0.0060 0.0071 0.0091 0.0118

33.7023 20.4699 18.3691 9.8785

453 281 195 76.8 111 139 95.8

1044 840 963 199 1037 636 242

0.43 0.33 0.20 0.39 0.11 0.22 0.40

0.3387 0.3144 0.2312 0.2016 0.1909 0.1744 0.1599

0.0063 0.0113 0.0133 0.0091 0.0170 0.0039 0.0042

34.1182 27.2857 15.4133 11.7972 11.4182 10.2185 8.3556

882 883 884

Apparent ages (Ma) 1σ 207Pb/235U 1σ

206Pb/238U

Isotopic ratios 207Pb/235U 1σ

Apparent ages (Ma) 1σ 207Pb/235U 1σ

206Pb/238U

1σ

207Pb/206Pb

0.6046 0.5326 0.3810 0.2547

0.7398 0.5458 0.5143 0.3975

0.0069 0.0073 0.0056 0.0041

3606 3306 3231 2650

28 41 56 109

3601 3114 3009 2424

0.6647 0.6482 0.4309 0.2861 0.3463 0.2065 0.1922

0.7435 0.6385 0.4783 0.4242 0.4199 0.4215 0.3895

0.0085 0.0060 0.0052 0.0048 0.0060 0.0044 0.0040

3657 3543 3061 2839 2750 2611 2454

28 55 92 73 152 37 44

3613 3394 2841 2588 2558 2455 2270

206Pb/238U

1σ

18 25 20 24

3570 2808 2675 2157

26 31 24 19

19 23 27 23 28 19 21

3584 3183 2520 2279 2260 2267 2121

31 24 23 22 27 20 18

Note: ‘Conc.’ indicates age concordance, defined as (206Pb/238U age)/(207Pb/206Pb age)*100%.

51

2 2 5 1 1 4 7 3 1 4 3 6 5

4 2 7 4 3 5 5 9 7 3 6

8 4 6 1

6 8 5

886 887 888 889

Table 3 Trace element compositions (in ppm) for Group I zircons in the Yangkou granitic gneisses from Yangkou in the Sulu Orogen

P

Ti

Y

Hf

Nb

Ta

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

T (°C)

E

414 216 563 231 543 493 401 370 464 358 559 466 313 183 231 360 521 728 326 542 522 512 248 421 592

14.3 16.4 15.6 15.9 11.6 15.8 13.3 11.6 9.57 19.6 21.3 10.0 13.4 27.1 13.1 11.2 10.6 8.47 13.8 11.0 21.2 11.3 15.5 12.2 10.1

1143 506 1847 517 1745 1512 1259 1202 1228 757 1415 1031 782 368 443 723 904 1527 634 1602 1017 820 649 1000 1311

8937 9283 8556 9500 8554 9344 10132 8751 11027 11148 10020 9377 9161 11380 10550 9866 10843 9510 11072 10230 10708 11721 12587 10641 9860

3.53 3.39 3.83 3.97 3.58 9.27 10.0 5.72 6.68 8.31 7.44 3.63 4.35 9.37 6.96 10.9 5.07 9.13 11.7 8.18 6.70 17.9 13.5 11.9 4.88

1.81 1.66 2.07 1.89 1.91 7.74 10.3 3.80 3.79 9.88 5.54 2.08 2.38 7.20 4.78 9.20 5.83 4.35 14.0 5.76 11.1 37.6 22.6 6.96 2.46

0.02 0.00 0.08 0.01 0.02 0.12 0.02 0.02 0.04 0.02 0.03 0.00 0.22 0.02 0.03 0.01 0.04 0.01 0.04 0.04 0.15 0.06 0.02 0.10 0.04

7.67 5.99 10.4 6.43 9.07 9.53 10.2 7.10 11.5 6.21 9.00 7.96 6.87 5.91 14.2 8.50 13.0 15.5 6.44 17.1 4.42 5.03 19.4 13.3 12.7

0.13 0.02 0.37 0.03 0.23 0.20 0.09 0.11 0.06 0.03 0.09 0.03 0.04 0.01 0.11 0.03 0.05 0.08 0.04 0.08 0.09 0.05 0.03 0.07 0.06

2.46 0.54 5.43 0.68 3.73 3.40 1.24 2.19 0.88 0.57 1.69 0.94 0.74 0.21 1.48 0.73 0.61 1.55 0.77 1.05 0.52 0.50 0.26 1.48 1.11

4.18 1.17 10.1 1.74 7.53 6.46 3.03 4.02 2.37 1.39 4.19 3.05 2.19 0.29 2.74 1.87 1.21 3.97 1.40 3.21 0.88 0.82 0.72 3.66 3.38

0.55 0.10 0.86 0.15 0.67 0.54 0.16 0.49 0.20 0.18 0.48 0.31 0.23 0.09 0.30 0.17 0.08 0.28 0.27 0.27 0.10 0.07 0.17 0.41 0.31

24.7 8.26 49.1 8.84 41.9 31.6 22.6 25.3 19.1 10.7 26.2 20.5 15.2 3.40 13.7 11.3 12.4 31.6 9.59 30.5 7.00 5.45 6.96 24.0 27.1

8.62 3.21 15.8 3.47 13.7 10.8 8.57 8.83 7.59 4.42 9.52 7.52 5.43 1.50 3.91 4.30 5.08 11.0 3.61 11.0 3.95 2.73 2.98 8.04 9.49

103 42.1 178 43.1 162 135 110 106 103 57.6 122 90.2 68.6 24.7 40.7 57.3 68.0 136 49.7 140 66.1 47.6 43.5 86.7 113

39.6 17.2 64.2 17.5 60.1 51.5 42.4 40.8 42.6 24.8 48.8 34.9 26.3 11.2 14.0 23.9 29.0 52.4 19.9 55.3 33.5 25.7 19.5 33.6 44.5

169 80.5 270 81.2 258 229 197 180 194 118 226 156 119 63.4 62.9 116 146 229 96.8 247 194 149 105 157 195

33.4 16.9 53.1 17.2 49.6 46.4 40.8 35.9 40.9 27.4 48.4 30.9 24.6 16.5 13.6 25.8 32.6 45.9 20.9 49.8 53.2 40.6 27.0 33.4 38.1

308 158 456 162 433 425 386 319 367 270 472 283 228 175 139 254 308 397 218 446 603 435 300 306 337

57.4 31.0 83.6 32.0 80.2 83.3 77.6 62.4 72.4 57.8 95.2 54.5 45.3 40.3 29.2 54.1 62.7 74.1 46.0 88.0 134 96.6 70.3 61.6 64.6

773 786 781 783 754 783 767 754 737 804 812 741 767 837 765 751 746 726 770 749 811 751 781 759 742

0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

336 387 265 407 600 562 635 431

17.0 16.1 22.8 9.80 21.0 7.29 10.2 19.6

1507 1272 532 869 1460 1520 1855 1041

8827 8939 10897 9544 8770 9197 8863 11378

4.00 5.79 7.93 5.10 5.54 5.46 8.91 13.4

2.02 2.67 2.90 2.44 2.17 2.61 4.20 12.4

0.04 0.01 0.01 0.03 0.04 0.01 0.02 0.05

4.83 6.32 14.9 13.3 14.2 11.8 16.9 11.9

0.32 0.17 0.01 0.05 0.11 0.07 0.06 0.03

4.04 2.37 0.35 1.22 2.18 1.57 1.94 0.63

8.07 4.87 0.61 3.44 4.96 4.69 4.97 1.99

1.48 0.86 0.08 0.30 0.28 0.42 0.40 0.16

40.0 26.8 4.24 20.5 32.5 31.0 36.6 15.0

13.0 9.09 1.80 6.79 11.5 11.1 13.0 5.54

147 112 29.1 75.6 130 135 161 75.7

53.1 43.2 14.4 29.0 48.3 52.5 62.7 32.2

218 187 85.5 129 208 226 279 160

41.7 37.6 24.5 26.5 40.8 44.8 55.0 37.1

352 335 282 229 349 398 484 368

66.3 65.2 74.9 45.1 68.3 74.8 92.3 78.7

790 784 819 739 810 714 743 804

0. 0. 0. 0. 0. 0. 0. 0.

890 891 892 893 894

Table 3 (continued)

P

Ti

Y

Hf

Nb

Ta

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

T (°C)

E

6 7 9 8

538 412 456 309

37.0 13.2 38.3 16.6

2098 1048 1238 710

10261 9774 11071 11165

8.95 7.99 9.0 16.3

6.30 6.21 7.06 19.8

0.01 0.11 1.02 0.53

16.1 10.3 16.2 7.11

0.24 0.10 0.28 0.15

4.01 1.38 2.62 1.17

7.93 3.03 3.64 0.96

0.27 0.19 0.31 0.32

46.3 18.2 23.3 6.53

15.4 6.84 8.39 2.96

189 86.2 102 46.6

71.8 34.1 41.0 21.5

317 160 187 117

63.2 33.9 39.2 28.7

553 314 362 293

105 64.3 73.2 62.6

871 766 874 787

0. 0. 0. 0.

0 3 3 5

402 267 692 581 429 554 542

30.4 26.7 27.2 14.9 19.5 12.4 6.91

2886 1441 1109 1026 886 1054 1034

9815 10307 11203 9900 9964 10041 9842

13.4 13.2 27.0 5.72 12.1 14.2 5.78

7.57 7.45 36.0 2.89 8.69 8.34 2.69

0.19 0.51 0.01 0.03 2.54 0.02 0.02

22.2 18.2 15.0 8.21 14.5 13.4 10.1

0.35 0.27 0.02 0.06 0.10 0.06 0.05

6.50 2.65 0.59 0.80 0.29 0.93 1.70

11.6 4.86 0.98 2.07 1.04 3.10 4.07

0.27 0.19 0.14 0.29 0.15 0.30 0.32

59.3 26.5 9.2 18.1 8.88 21.8 22.0

21.5 9.93 4.50 6.59 4.09 7.78 7.52

264 125 71.0 85.3 59.8 93.7 89.2

101 49.2 33.8 33.8 27.5 35.9 35.5

434 217 183 156 144 161 151

83.5 43.7 44.5 32.5 33.4 32.3 31.1

703 381 452 297 324 287 292

128 70.1 97 58.1 67.6 56.5 57.8

849 835 837 777 803 760 709

0. 0. 0. 0. 0. 0. 0.

1 5

895 896 897

Note: Eu* = EuN/(SmN*GdN)0.5, and N denotes the normalization to the chondrite values of Sun and McDonough (1989). The calculation of Ti-in-zircon temperature is after the equation of Watson et al. (2006), assuming the activity of SiO2 and TiO2 to be 1. 52

898 899

53

901 902 903 904

No. -Pb)

Group

60 14 57 38 69 54 18 19 27 06 70 67 30 07 45 33 41 31 56 15 28 21 13 47 23 34 42 11 46 32 53 65 52 12 09

I I I I I I I I I I I I I I I I I I I I II II II II II II III III III III III III III IV IV

Table 4 Zircon Lu–Hf isotope compositions for the Yangkou granitic gneisses from Yangkou in the Sulu Orogen 176Yb/177Hf

1σ

176Lu/177Hf

1σ

176Hf/177Hf

1σ

εHf(t)

1σ

TDM1 (Ma)

1σ

TDM2 (Ma)

1σ

TCHUR1 (Ma)

1σ

0.031631 0.017956 0.040866 0.014622 0.034921 0.040846 0.029539 0.021479 0.022979 0.021271 0.033695 0.025657 0.013427 0.015180 0.022608 0.033578 0.065612 0.036206 0.037386 0.032309 0.015073 0.013060 0.011510 0.000647 0.015549 0.049990 0.047364 0.026390 0.067705 0.065840 0.038960 0.025173 0.022936 0.064552 0.175255

0.000227 0.000099 0.000671 0.000272 0.000393 0.000470 0.000262 0.000181 0.000362 0.000236 0.000821 0.000325 0.000127 0.000123 0.000367 0.000446 0.002619 0.000573 0.000210 0.000203 0.000222 0.000123 0.000244 0.000023 0.000101 0.000379 0.001365 0.001516 0.001462 0.001627 0.001108 0.000526 0.000704 0.000925 0.001211

0.001012 0.000571 0.001373 0.000466 0.001137 0.001358 0.000966 0.000732 0.000765 0.000709 0.001087 0.000849 0.000505 0.000550 0.000798 0.001076 0.002384 0.001449 0.001265 0.001014 0.000547 0.000446 0.000415 0.000018 0.000524 0.001642 0.001580 0.000941 0.002367 0.002500 0.001486 0.000972 0.000893 0.002248 0.006012

0.000010 0.000005 0.000021 0.000007 0.000010 0.000012 0.000005 0.000007 0.000009 0.000005 0.000027 0.000006 0.000003 0.000003 0.000017 0.000008 0.000083 0.000024 0.000012 0.000010 0.000006 0.000003 0.000010 0.000001 0.000002 0.000015 0.000047 0.000044 0.000044 0.000046 0.000044 0.000015 0.000021 0.000033 0.000024

0.280396 0.280416 0.280456 0.280384 0.280401 0.280451 0.280393 0.280389 0.280403 0.280376 0.280403 0.280426 0.280388 0.280419 0.280413 0.280457 0.280533 0.280475 0.280423 0.280447 0.281417 0.281384 0.281316 0.281389 0.281428 0.281464 0.281852 0.281755 0.281756 0.281795 0.281799 0.281826 0.281807 0.281791 0.281877

0.000013 0.000015 0.000016 0.000012 0.000014 0.000014 0.000011 0.000011 0.000012 0.000012 0.000012 0.000015 0.000013 0.000012 0.000015 0.000014 0.000013 0.000011 0.000016 0.000018 0.000011 0.000011 0.000017 0.000017 0.000017 0.000013 0.000017 0.000013 0.000014 0.000013 0.000014 0.000014 0.000012 0.000013 0.000012

-2.8 -0.9 -1.5 -1.8 -2.9 -1.7 -2.8 -2.3 -1.9 -2.7 -2.7 -1.3 -1.8 -0.8 -1.6 -0.8 -1.4 -1.0 -2.4 -0.9 -1.7 -2.7 -5.0 -1.9 -1.2 -1.6 -16.2 -19.3 -20.0 -18.7 -18.0 -16.8 -17.4 -20.2 -18.9

0.8 0.9 0.9 0.8 0.9 0.9 0.8 0.8 0.8 0.8 0.8 0.9 0.8 0.8 0.9 0.9 0.8 0.8 0.9 0.9 0.9 0.9 1.0 1.0 1.0 0.9 0.6 0.5 0.5 0.5 0.5 0.5 0.4 0.5 0.4

3940 3869 3896 3901 3946 3902 3939 3921 3906 3935 3939 3883 3899 3864 3896 3866 3895 3878 3929 3872 2533 2570 2660 2535 2517 2542 1997 2096 2176 2129 2065 2000 2021 2118 2224

18 20 21 16 19 19 15 15 16 15 17 20 17 16 19 19 21 15 21 24 15 14 23 22 23 18 24 18 20 18 20 19 17 19 19

4101 3992 4027 4045 4109 4037 4101 4074 4050 4097 4099 4013 4041 3983 4033 3982 4017 3999 4082 3993 2801 2863 3009 2814 2774 2794 2689 2881 2924 2844 2801 2725 2764 2881 2802

33 37 38 32 35 35 30 30 31 31 32 36 33 32 36 35 36 30 38 42 32 32 43 43 43 35 38 29 31 29 32 31 27 30 26

3789 3710 3737 3747 3795 3743 3789 3769 3751 3785 3788 3725 3745 3704 3739 3703 3731 3716 3776 3711 2173 2217 2320 2181 2154 2170 1539 1663 1736 1679 1620 1551 1577 1671 1735

20 23 24 19 22 22 17 17 18 18 19 22 20 19 22 22 24 17 24 27 17 16 26 26 27 21 28 21 23 21 23 22 20 22 22

176Yb/177Hf

905 906 907

No. U-Pb) #55 #01 #02 #51 #04

Group IV IV IV IV IV

#16 #26 #02 #35 #15 #33 #30 #08 #09 #13 #23

I I I I I I I I II II III

Table 4 (continued) 1σ

0.6 0.4 0.5 0.7 0.5

TDM1 (Ma) 2146 2096 2124 2141 2102

1.2 1.2 1.4 1.0 1.1 0.9 1.0 1.2 1.1 1.0 1.0

3879 3901 3836 3849 3813 3866 3861 3926 2662 2686 2155

1σ

176Lu/177Hf

1σ

176Hf/177Hf

1σ

εHf(t)

1σ

0.052206 0.087386 0.069020 0.046261 0.091413

0.000384 0.000778 0.000780 0.000378 0.000455

0.001766 0.003013 0.002536 0.001612 0.003161

0.000007 0.000018 0.000023 0.000009 0.000016

0.281752 0.281838 0.281799 0.281750 0.281840

0.000018 0.000012 0.000014 0.000019 0.000013

-21.3 -18.9 -20.0 -21.3 -18.9

0.039807 0.034703 0.024409 0.025738 0.030550 0.033185 0.050147 0.028092 0.045034 0.035072 0.050946

0.000346 0.000942 0.000157 0.000376 0.000368 0.000238 0.000386 0.000357 0.001997 0.000400 0.000442

0.001223 0.001111 0.001035 0.000854 0.000979 0.001063 0.001609 0.001011 0.001615 0.001316 0.001869

0.000011 0.000028 0.000009 0.000015 0.000011 0.000006 0.000012 0.000007 0.000069 0.000013 0.000013

0.280458 0.280433 0.280476 0.280452 0.280489 0.280455 0.280500 0.280407 0.281376 0.281343 0.281750

0.000026 0.000025 0.000031 0.000016 0.000019 0.000014 0.000017 0.000024 0.000023 0.000018 0.000018

-1.1 -1.7 0.0 -0.4 0.6 -0.8 -0.6 -2.4 -4.6 -5.4 -20.0

54

1σ

25 18 20 26 19

TDM2 (Ma) 2953 2801 2872 2953 2800

1σ

39 27 30 41 29

TCHUR1 (Ma) 1710 1634 1673 1706 1638

35 33 41 22 26 19 24 32 32 25 25

4002 4038 3935 3958 3899 3983 3971 4078 2984 3029 2921

60 56 68 40 46 37 42 55 54 44 43

3718 3744 3669 3686 3644 3704 3696 3773 2310 2341 1719

41 38 47 25 30 22 27 37 36 29 29

29 21 23 30 23

#27 #11 #17 #03 #28 #18 #32 #14 #07 #19 #04 #29 #12 #01 #34

III III III III III III III III IV IV IV IV IV IV IV

0.060055 0.081598 0.044215 0.020990 0.048981 0.041102 0.069736 0.057762 0.043416 0.090011 0.068022 0.067899 0.080565 0.094586 0.085483

0.000615 0.000872 0.000577 0.000234 0.000331 0.000789 0.000969 0.000914 0.002233 0.000546 0.000972 0.000547 0.000387 0.001286 0.001734

0.002189 0.002894 0.001433 0.000804 0.001782 0.001546 0.002499 0.001996 0.001577 0.003158 0.002409 0.002387 0.003808 0.004148 0.003278

0.000020 0.000024 0.000015 0.000010 0.000012 0.000029 0.000030 0.000025 0.000075 0.000023 0.000027 0.000013 0.000021 0.000044 0.000063

0.281827 0.281817 0.281863 0.281733 0.281764 0.281829 0.281802 0.281797 0.281744 0.281869 0.281821 0.281768 0.281826 0.281884 0.281755

0.000019 0.000019 0.000020 0.000019 0.000018 0.000023 0.000019 0.000017 0.000018 0.000021 0.000019 0.000018 0.000015 0.000018 0.000032

-17.4 -18.1 -15.7 -20.0 -19.4 -17.0 -18.5 -18.4 -21.5 -17.9 -19.2 -21.1 -19.7 -17.8 -22.0

1.0 1.0 1.0 1.0 1.0 1.1 1.0 0.9 1.0 1.0 1.0 1.0 0.9 0.9 1.3

2065 2119 1972 2118 2131 2026 2118 2096 2148 2059 2085 2161 2161 2094 2233

27 28 28 26 25 32 27 24 26 31 28 25 23 27 48

2763 2806 2658 2924 2888 2736 2828 2822 2967 2736 2820 2937 2850 2732 2991

46 47 48 46 44 54 45 42 46 50 47 43 38 43 74

1610 1662 1513 1691 1692 1573 1667 1649 1714 1588 1630 1718 1697 1614 1790

31 33 32 30 29 37 31 28 29 36 33 29 27 32 56

#19 #04 #10

I I I

0.035975 0.025894 0.040366

0.000187 0.000167 0.000483

0.001181 0.000891 0.001449

0.000006 0.000005 0.000019

0.280460 0.280437 0.280479

0.000016 0.000022 0.000017

-0.9 -1.0 -0.9

1.0 1.1 1.0

3872 3873 3874

21 30 23

3991 3996 3992

40 52 41

3710 3713 3711

25 34 26

1σ

1σ 57 44 57 48 44 47 45 47 44 46 43 43 49 39

TCHUR1 (Ma) 2319 2206 2316 1556 1457 1512 1680 1532 1582 1574 1636 1636 1518 1547

1σ

33 23 33 27 26 29 26 28 25 28 25 25 32 22

TDM2 (Ma) 3006 2849 3002 2726 2545 2602 2857 2651 2722 2698 2810 2834 2569 2703

23 21 24 29 26 32 30 33 35 30 28 57 31 19 24

4166 4059 4043 4043 4001 3950 2749 2662 2718 2709 2997 2716 2744 2581 2959

42 39 44 50 47 56 47 52 54 49 46 85 50 36 41

3837 3760 3747 3749 3717 3680 1640 1569 1629 1575 1771 1592 1616 1434 1756

27 24 28 34 30 37 35 39 41 36 32 66 37 22 28

908 909 910 911

No. U-Pb) #12 #15 #18 #03 #17 #11 #05 #06 #07 #08 #16 #09 #01 #13

Group II II II III III III III III III III IV IV IV IV

#05 #21 #14 #24 #18 #02 #08 #22 #19 #07 #04 #11 #01 #20 #15

I I I I I I III III III IV IV IV IV IV IV

912 913 914 915

Table 4 (continued) 1σ

176Lu/177Hf

1σ

176Hf/177Hf

1σ

εHf(t)

1σ

0.019394 0.002297 0.016513 0.029121 0.072621 0.095755 0.059786 0.066935 0.065534 0.075027 0.078537 0.068368 0.123619 0.078103

0.000409 0.000119 0.000905 0.000125 0.000758 0.001138 0.000308 0.000760 0.002399 0.000902 0.001091 0.000706 0.002564 0.000922

0.000617 0.000074 0.000567 0.001142 0.002687 0.003200 0.002196 0.002453 0.002310 0.002694 0.002862 0.002257 0.005425 0.002635

0.000011 0.000004 0.000034 0.000006 0.000034 0.000031 0.000016 0.000032 0.000074 0.000029 0.000034 0.000021 0.000089 0.000020

0.281326 0.281376 0.281325 0.281828 0.281933 0.281914 0.281784 0.281881 0.281847 0.281863 0.281832 0.281813 0.281975 0.281877

0.000024 0.000017 0.000024 0.000019 0.000018 0.000020 0.000018 0.000020 0.000018 0.000019 0.000017 0.000017 0.000020 0.000015

-5.0 -2.4 -4.9 -16.8 -13.9 -14.8 -18.9 -15.6 -16.8 -16.4 -19.0 -19.4 -15.2 -17.3

1.2 1.0 1.2 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.9 1.0 1.0 0.9

TDM1 (Ma) 2661 2558 2658 2006 1940 1995 2126 2001 2042 2041 2096 2089 2032 2017

0.049497 0.047690 0.031686 0.051529 0.031103 0.026657 0.091785 0.078512 0.092629 0.070706 0.079768 0.088409 0.085659 0.055128 0.086109

0.001163 0.001182 0.000116 0.000604 0.000189 0.000155 0.000874 0.001533 0.001244 0.000977 0.000479 0.000365 0.000913 0.000925 0.000713

0.001416 0.001538 0.000972 0.001574 0.000924 0.000861 0.003673 0.003588 0.004143 0.003462 0.002614 0.003855 0.003895 0.001755 0.003030

0.000030 0.000033 0.000007 0.000017 0.000005 0.000008 0.000021 0.000056 0.000034 0.000016 0.000015 0.000013 0.000058 0.000023 0.000023

0.280395 0.280453 0.280420 0.280463 0.280437 0.280456 0.281855 0.281893 0.281876 0.281886 0.281743 0.281887 0.281875 0.281921 0.281766

0.000017 0.000015 0.000018 0.000022 0.000020 0.000024 0.000020 0.000022 0.000023 0.000021 0.000019 0.000038 0.000021 0.000014 0.000017

-3.8 -2.1 -1.8 -1.8 -1.1 -0.2 -17.2 -15.8 -16.7 -17.4 -22.0 -17.5 -18.0 -15.3 -21.4

1.0 1.0 1.0 1.1 1.1 1.2 1.0 1.0 1.1 1.0 1.0 1.5 1.0 0.9 0.9

3984 3917 3903 3907 3877 3845 2110 2049 2107 2052 2209 2072 2093 1908 2201

176Yb/177Hf

Note: The “t” used for calculation of εHf(t) and Hf model ages for Group I, II, III and IV zircon domains are 3.67 Ga, 2.10 Ga, 790 Ma and 720 Ma, respectively.

916 917

55

38 26 37 31 31 33 30 33 29 32 30 29 38 26

Highlights

918 919 920



Eoarchean zircons as old as 3.7 Ga are found in Neoproterozoic granitic gneisses;

921



The Eoarchean zircons show negative εHf(t) values of -2.8 to -0.9 and CHUR Hf model ages of 3.74-3.96 Ga;

922 923



The Eoarchean zircons were derived from reworking of the early Eoarchean crust;

924



Paleoproterozoic to Neoproterozoic zircons were derived from reworking of the Archean crust;

925 926 927



The relict zircons of Eoarchean age record the growth and reworking of the most ancient crust in the Yangtze Craton.

928 929 930

Conflict of Interest

931 932 933 934

I, on behalf of all the authors, declare that we have no conflict of interest of our

935

present work.

936 937

Yi-Xiang Chen

938

October 4, 2019

939

56