TTG and Potassic Granitoids in the Eastern North China Craton ...

JOURNAL OF PETROLOGY

Journal of Petrology, 2016, Vol. 57, No. 9, 1775–1810 doi: 10.1093/petrology/egw060 Original Article

TTG and Potassic Granitoids in the Eastern North China Craton: Making Neoarchean Upper Continental Crust during Micro-continental Collision and Post-collisional Extension Downloaded from http://petrology.oxfordjournals.org/ at Peking University on December 2, 2016

Chao Wang1, Shuguang Song1*, Yaoling Niu2,3, Chunjing Wei1 and Li Su4 1

MOE Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China; 2Department of Earth Sciences, Durham University, Durham DH1 3LE, UK; 3 Institute of Oceanology, Chinese Academy of Science, Qingdao 266071, China and 4Institute of Earth Sciences, Chinese University of Geosciences, Beijing 100083, China *Corresponding author. E-mail: [email protected] Received January 7, 2016; Accepted September 8, 2016

ABSTRACT As the major component, Archean granitoids provide us with an insight into the formation of the early continental crust. We report the study of a series of Neoarchean granitoids, including tonalite–trondhjemite–granodiorite (TTG) and potassic granitoids, in the Xingcheng region of the eastern North China Craton. Zircon U–Pb dating shows that the TTG granitoids were emplaced in the Neoarchean within a 75 Myr period (2595–2520 Ma), with coeval mafic magmatic enclaves, followed by intrusion of potassic granitoids. The geochemistry of the TTG granitoids is consistent with partial melting of Mesoarchean enriched mafic crustal sources at different depths (up to 10–12 kbar equivalent pressure) during a continental collision event. The potassic granitoids are derived from either low-degree melting of Mesoarchean enriched mafic crustal sources or remelting of Mesoarchean TTGs in response to post-collisional extension, and were hybridized with Neoarchean mantle-derived mafic melts to various degrees. The TTG and potassic granitoids in the Xingcheng region record the evolution from collision of micro-continental blocks to post-collisional extension, consistent with other studies, suggesting that the amalgamation of micro-continental blocks is what gave rise to the cratonization of the North China Craton at the end of the Archean. The rock assemblage of these granitoids resembles those of syn- and post-collisional magmatism in Phanerozoic orogenic belts, and the estimated average composition is similar to that of the present-day upper continental crust, suggesting that a prototype upper continental crust might have been developed at the end of the Archean from a mixture of TTG and potassic granitoids. Together with concurrent high-grade metamorphism in the North China Craton, we conclude that collisional orogenesis is responsible for continental cratonization at the end of the Archean in the North China Craton. Key words: TTG; potassic granitoids; cratonization; micro-continental collision; prototype upper continental crust; North China Craton

INTRODUCTION Our knowledge of when and how the mature continental crust may have developed remains incomplete. As the main components of Archean terranes or primary

architecture of the continental crust, sodic granitoids of varying composition, collectively called tonalite– trondhjemite–granodiorite (TTG) suites, have been extensively studied with the aim of understanding the

C The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: [email protected] V

1775

1776

Neoarchean remains controversial; some researchers have suggested a mantle plume-related setting (e.g. Zhao et al., 2001, 2005; Yang et al., 2008), whereas others have argued for a subduction-related environment (e.g. Liu et al., 2010, 2011; Wan et al., 2010, 2011; Nutman et al., 2011; Wang et al., 2011, 2012, 2013). We present results of in situ zircon U–Pb dating, bulk-rock geochemistry, including Nd isotopes, and in situ zircon Hf isotopes for the TTG granitoids and their mafic magmatic enclaves (MMEs) as well as the associated potassic granites in the eastern NCC. We show that these granitoids are products of partial melting of proto-crust during micro-continental collision and postcollisional extension at the end of the Archean. Therefore, a prototype upper continental crust might have been already developed by the end of the Archean in the NCC.

REGIONAL GEOLOGY The NCC is the largest and oldest craton in China and preserves records of 38 Ga crustal remnants (Liu et al., 1992; Song et al., 1996; Wan et al., 2005). It is suggested to have formed by collision between the Eastern Block and the Western Block along the TransNorth China Orogen (TNCO) at 185 Ga (Fig. 1a; Zhao et al., 2001, 2005; Guo et al., 2002) or at 195 Ga as argued by Qian et al. (2013), Zhang et al. (2013) and Wei et al. (2014). The Eastern Block underwent Paleoproterozoic intra-continental rifting along its eastern continental margin in the period 22–19 Ga and the rift system was finally terminated by subduction and continental collision at 19 Ga, leading to the formation of the Jiao–Liao–Ji Belt (Fig. 1a; Li & Zhao, 2007; Tam et al., 2011). The Western Block comprises two Archean micro-blocks, the Yinshan Block in the north and the Ordos Block in the south, which were amalgamated along the east–west-trending Khondalite Belt at 195 Ga (Fig. 1a; Santosh et al., 2007a, 2007b; Zhao et al., 2010). The exposures of Precambrian basement rocks of the Eastern Block are shown in Fig. 1a, except for a few outcrops in the central part (Western Shandong and Eastern Shandong). These are mainly distributed in the northern part in three major regions: Jidong (Eastern Hebei), Northern Liaoning–Southern Jilin and Western Liaoning. These Archean terranes contains 38 Ga tonalites (Song et al., 1996; Wan et al., 2005) and experienced a complex evolutionary history from 38 to 25 Ga (Nutman et al., 2011; Zhai & Santosh, 2011). Our study area is in the northwestern part of the Eastern Block, one of the key regions with well-exposed Precambrian basement rocks of the NCC (Fig. 1a). It mainly consists of the Jidong–Jianping high-grade gneiss terrane, which has varying protoliths and metamorphic ages (26–25 Ga; Kro¨ner et al., 1998; Zhao et al., 2001, 2005; Nutman et al., 2011), and the Suizhong granitic terrane (e.g. Yang et al., 2008), which includes some low- to medium-grade greenstones in

Downloaded from http://petrology.oxfordjournals.org/ at Peking University on December 2, 2016

evolution of the Earth and constraining the differentiation processes of the continental crust (Barker 1979; Jahn et al., 1981; Martin, 1999; Smithies, 2000; Condie, 2005b, 2014; Martin et al., 2005; Moyen, 2011; Moyen & Martin, 2012). Many studies suggest that TTGs are generated by partial melting of mafic rocks under either amphibolite-facies conditions (less than 15 kbar; e.g. Foley et al., 2002) or eclogite-facies conditions (more than 15–20 kbar; e.g. Rapp et al., 2003). The compositional similarity between the Archean TTGs and Phanerozoic subduction-related adakites (e.g. Defant & Drummond, 1990; Castillo, 2012) has led to the popular acceptance that TTGs may have formed in Archeantype subduction settings (e.g. Condie, 2005b; Martin et al., 2005; Niu et al., 2013). Potassic granitoids are also an important crustal component, closely associated with the TTGs, especially in Neoarchean terranes. They have been previously interpreted as products of remelting of pre-existing TTGs (Sylvester, 1994; Moyen et al., 2001, 2003; Bleeker, 2003; Whalen et al., 2004; Watkins et al., 2007), and as a marker for the final consolidation of the cratonic continental crust (Frost et al., 1998; Whalen et al., 2004; Martin et al., 2005). However, the role of potassic granitoids in the growth of the continental crust has been less studied than that of TTGs. The present-day upper continental crust is relatively rich in K2O and heavy rare earth elements (HREE) [K2O/ Na2O ¼ 086, (La/Yb)N ¼ 11; Rudnick & Gao, 2003], significantly different from Archean TTGs [K2O/ Na2O ¼ 035, (La/Yb)N ¼ 32; Moyen & Martin, 2012]. It is therefore important to explore how the present-day upper continental crust may have evolved from the Archean TTG-dominated upper continental crust over the Earth’s history. Condie (1993, 2014) proposed that after the Archean the TTG-dominated upper continental crust was gradually replaced by other calc-alkaline granitoids with geochemical features distinct from those of Archean TTGs, to form the mature, presentday, upper continental crust. As there are coeval calcalkaline granitoids and TTGs reported from some Archean terranes (e.g. Samsonov et al., 2005) and potassic granitoids are widely distributed in Archean cratons worldwide (Bleeker , 2003; Moyen et al., 2003), there exists the possibility that in some cases the Archean upper continental crust might have already achieved the present-day upper continental crust composition. The formation and evolution of the North China Craton (NCC) has been the focus of research for decades, with extensive investigations carried out to decipher its Precambrian history (e.g. Zhao et al., 1998, 1999, 2001, 2005; Zhai et al., 2010; Nutman et al., 2011; Zhai & Santosh, 2011; Zhao & Cawood, 2012). The widely distributed Neoarchean to Paleoproterozoic igneous rocks of the NCC offer insights into its Archean to Paleoproterozoic crustal growth and its geodynamic evolution (e.g. Compston et al., 1983; Jahn & Ernst, 1990; Kro¨ner et al., 1998; Yang et al., 2008). However, the geodynamic regime of the NCC during the

Journal of Petrology, 2016, Vol. 57, No. 9


1777

the Fuxin region (Fig. 1b; Liu et al., 2010; Wang et al., 2011, 2012, 2015b). These units are partially obscured by Paleoproterozoic to Paleozoic platform strata and Mesozoic volcano-sedimentary sequences, and are intruded by Late Paleozoic to Mesozoic igneous rocks. The Suizhong granitic terrane, previously termed ‘Suizhong granitoids’, is dominated by granitoids with the TTG assemblage plus minor monzogranite and potassic granite (Fig. 1b and c). Their precise ages and geochemical characteristics have not been well studied. The Qinhuangdao granitoid in the southern part of the Suizhong granitic terrane has long been treated as part of the Eastern Hebei Archean terrane, which has a rock assemblage of diorite, granodiorite and monzogranite emplaced at 2526–2515 Ma and metamorphosed at 2500–2490 Ma, subsequently intruded by K-feldspar granite (2440 Ma) (Fig. 1b; Yang et al., 2008; Nutman et al., 2011).

FIELD OCCURRENCE AND SAMPLES The Xingcheng region lies in the central part of the Suizhong granitic terrane. Several outcrops of Neoarchean granitoid are exposed along the west coast of the Bohai Sea (Fig. 1b). Samples were collected from four representative locations: Taili, Xingcheng, Juhuadao and Huludao (Fig. 1c). The lithologies present in these four representative locations include gneissic granite, tonalite, trondhjemite, granodiorite with MMEs, red-colored potassic granite and locally red pegmatite dykes, which encompass almost all the rock types observed within the Suizhong granitic terrane. Owing to the extensive sedimentary cover, the field relationships between most of these lithologies are difficult to determine and map on outcrop scales. Nevertheless, study of samples from these representative outcrops can provide insightful information about the petrogenetic history of the Suizhong granitic terrane.


Fig. 1. (a) Schematic map showing major Precambrian tectonic units of the NCC [modified after Zhao et al. (2005)]. EH, Eastern Hebei; WL, Western Liaoning; NL-SJ, Northern Liaoning–Southern Jilin; WS, Western Shandong; ES: Eastern Shandong. (b) Simplified geological map of the northern part of the Eastern Block of the NCC. (c) Simplified geological map of the Xingcheng region; black stars indicate sampling locations.

1778


Taili gneissic tonalite–granites All the Archean granitoids from Taili are strongly deformed with an east–west foliation. They are intruded by 230–220 Ma adakitic plutons (Wang et al., 2015a), 155 Ma undeformed granites (our unpublished data) and as yet undated mafic dykes (Fig. 2a). The adakitic plutons show the same deformation character as the gneisses that they intrude (Fig. 2a), indicating that the Taili Archean granitoids experienced their latest deformation between 220 and 155 Ma.

Two Archean rock types have been identified in Taili, gneissic tonalite and porphyritic gneissic granite, which are interleaved with each other (Fig. 2b). The gneissic tonalites are dark grey, homogeneous and medium- to fine-grained without porphyroblasts. They have a mineral assemblage of plagioclase (50–60%), K-feldspar (10–20%), quartz (10–20%), amphibole (5%), minor biotite and accessory zircon, magnetite and titanite. The porphyritic gneissic granites are pale grey, medium- to coarse-grained with feldspar phenocrysts in a matrix of


Fig. 2. Field photographs of the Neoarchean TTG and potassic granitoids in the Xingcheng region. (a) Neoarchean gneissic tonalite–granite at Taili intruded by Triassic adakitic pluton; (b) gneissic tonalite and gneissic granite at Taili; mafic sills are also shown; (c, d) tonalite–trondhjemite with MMEs at Xingcheng; (e) tonalite–trondhjemite, MMEs and syn-plutonic dyke at Xingcheng, intruded by pegmatite dyke; (f) tonalite–trondhjemites at Xingcheng intruded by potassic granite; both are intruded by a pegmatite dyke; (g) granodiorite and MMEs at Juhuadao; (h) potassic granite at Huludao, unconformably overlain by the Paleoproterozoic sedimentary rocks of the Changcheng formation (Pt2c).


K-feldspar (40–50%), plagioclase (20–30%), quartz (20– 30%), amphibole (5%), minor biotite and accessory zircon, magnetite and titanite. Strongly deformed mafic dyke (sills) are present (Fig. 2b), but difficult to sample.

Xingcheng porphyritic tonalite–trondhjemites and potassic granites

Juhuadao granodiorites The granodiorites from Juhuadao are pale grey in color with a medium to coarse grain size and also contain MMEs. They are intruded by Mesozoic plutons (Fig. 1c). The granodiorites have the mineral assemblage quartz, plagioclase, hornblende, minor K-feldspar and accessory zircon, magnetite and titanite. The MMEs are fineto medium-grained with the mineral assemblage hornblende, plagioclase, minor biotite and accessory zircon, magnetite and titanite, showing clear contacts with the host granodiorites (Fig. 2g).

Huludao potassic granites The potassic granites from Huludao have a pinkish red color, fine- to medium-grained texture and are dominated by quartz, K-feldspar, minor biotite and accessory zircon, magnetite and titanite. They are unconformably overlain by Paleoproterozoic sedimentary rocks of the Changcheng formation (Pt2c) (Figs 1c and 2h).

ANALYTICAL TECHNIQUES In situ zircon U–Pb dating Zircon grains were extracted from crushed samples by standard heavy liquid and magnetic techniques, and subsequently purified by hand-picking under a

binocular microscope. The selected grains were embedded in epoxy resin discs and polished down to about half-sections to expose the grain interiors. Cathodoluminescence (CL) images were acquired using a Garton Mono CL3þ spectrometer installed on a Quanta 200F ESEM at Peking University; scanning conditions were 15 kV and 120 nA. Measurements of U, Th and Pb in zircons were carried out by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on an Agilent-7500a quadrupole ICP-MS system coupled with a New Wave UP-193 solid-state LA system in the Geological Lab Center, China University of Geosciences, Beijing (CUGB) following the analytical procedures of Song et al. (2010a). A laser spot size of 36 lm, laser energy density of 85 J cm–2 and a repetition rate of 10 Hz were used for analysis. The ablated sample material was carried into the ICP-MS system by high-purity helium gas. NIST 610 glass and Harvard standard zircon 91500 (Wiedenbeck et al., 1995) were used as external standards, Si as the internal standard and the standard zircon TEMORA (417 Ma) from Australia (Black et al., 2003) as a secondary standard. The software GLITTER (version 4.4, Macquarie University) was used for data reduction. The common lead correction was made following Andersen (2002). Age calculations and concordia diagrams were made using Isoplot (version 3.0) (Ludwig, 2003).

Bulk-rock major and trace element analyses All the samples are fresh cuttings sampled away from late veinlets, with any surface contaminants trimmed off before being thoroughly cleaned. Fresh portions of the trimmed samples were crushed to 1–2 cm size chips using a percussion mill. These rock fragments were then ultrasonically cleaned in Milli-Q water, dried and powdered in a thoroughly cleaned agate mill to 200 mesh in the clean laboratory at the Langfang Regional Geological Survey, China. Bulk-rock major and trace element analysis was carried out at CUGB, following Song et al. (2010b). Major elements were analyzed on a Leeman Prodigy inductively coupled plasma-optical emission spectroscopy (ICP-OES) system with high-dispersion Echelle optics. Based on USGS (US Geological Survey) rock standards AGV-2 and W-2, and CNGR (Chinese National Geological Reference) materials GSR-1 and GSR-3, the analytical precision (1r) for most major element oxides is better than 1%, with the exception of TiO2 (15%) and P2O5 (20%). Loss on ignition (LOI) was determined by placing 1 g of sample in a furnace at 1000 C for a few hours and then reweighing the cooled samples. Bulk-rock trace elements were analyzed by ICP-MS using an Agilent-7500a quadrupole ICP-MS system. About 35 mg powder of each sample was dissolved in a distilled acid mixture (1:1 HF þ HNO3) in Teflon digesting vessels and heated on a hot plate at 195 C for 48 h


The tonalite–trondhjemites from Xingcheng are grey, medium- to coarse-grained with plagioclase phenocrysts and contain some MMEs and syn-plutonic dykes. They have a porphyritic texture and consist of quartz, plagioclase, K-feldspar, minor hornblende and accessory zircon, magnetite and titanite (Fig. 2c–f). The MMEs are dark grey to black and irregular in shape, ranging in size from several to tens of centimeters, with relatively clear boundaries but no chilled margins (Fig. 2c–e). They have a fine- to medium-grained texture with plagioclase phenocrysts; their matrix consists of hornblende, plagioclase, minor biotite and accessory zircon, magnetite and titanite. The syn-plutonic dykes are darker in color than, and display clear boundaries with, their host; together with irregularly layered MMEs, this may suggest a cumulate origin (Fig. 2e). The tonalite–trondhjemites were intruded by later potassic granites with sharp intrusive contacts (Fig. 2f). The potassic granites are pinkish red, medium- to coarse-grained and are composed of quartz, K-feldspar, minor biotite and accessory zircon, magnetite and titanite. Both the tonalite–trondhjemites and the potassic granites are intruded by parallel, red-colored pegmatite dykes (Fig. 2e and f).

1779

1780

using high-pressure bombs for digestion. The sample was then evaporated to incipient dryness, refluxed with 1 ml of 6N HNO3 and heated again to incipient dryness. The sample was again dissolved in 2 ml of 3N HNO3 and heated at 165 C for further 24 h to guarantee complete digestion–dissolution. The sample was finally diluted with Milli-Q water to a dilution factor of 2000 in 2% HNO3 solution for analysis. Rock standards USGS AGV-2, W-2 and BHVO-2 were used to monitor the analytical accuracy and precision. Analytical accuracy is indicated by a relative difference between measured and recommended values better than 5% for most elements, and 10–15% for Cu, Zn, Gd, and Ta.

Bulk-rock Nd isotope analyses

In situ zircon Hf isotope analyses In situ zircon Lu–Hf isotope analysis of dated samples from the Xingcheng region was carried out using a Neptune multi-collector ICP-MS system with an attached New Wave UP-213 LA system (LA-MC-ICP-MS) at the MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing. Analytical details have been given by Wu et al. (2006) and Hou et al. (2007). A laser spot size of 40 lm was used for analysis and helium gas was used as the carrier gas to transport the laser ablated sample from the LA cell to the ICP-MS torch via a mixing chamber where it was mixed with argon gas. Correction for the isobaric

interferences of 176Lu and 176Yb on 176Hf was after Wu et al. (2006) and Hou et al. (2007). Before the analysis, standard zircons (TEMORA, GJ1 and FM02) were analyzed and the efficacy of the correction method of isobaric interferences of Wu et al. (2006) and Hou et al. (2007) was shown to be efficient. Zircon GJ1 was used as the reference standard to monitor data quality during analysis, giving a weighted mean 176Hf/177Hf ratio of 0282007 6 7 (2r, n ¼ 36), which is in accordance with the weighted mean 176Hf/177Hf ratio of 0282000 6 5 (2r) measured by the solution analysis method (Morel et al., 2008).

RESULTS Geochronology Eight samples were selected for zircon U–Pb analysis, including gneissic granite (10TL13), tonalite–trondhjemite (10XC02), granodiorite (12XC22 and 12XC28), MMEs (11XC03 and 12XC15) and potassic granite (10XC05 and 10XC08) from the four outcrops in the Xingcheng region: Taili, Xingcheng, Juhuadao and Huludao (see Fig. 1c for sampling locations). CL images of representative zircons are shown in Fig. 3 and the in situ LA-ICP-MS U–Pb data are given in Table 1 and plotted in Fig. 4. Zircon grains from all the eight dated samples are euhedral–prismatic, and have varying sizes (50–250 lm) with a length:width of 2:1–5:1. They show typical oscillatory growth zoning of magmatic origin in CL images (Fig. 3), suggesting that these zircons from the granitoids and their MMEs were crystallized from magmas parental to the host-rocks. Most of the zircon grains have Th/U ratios varying from 03 to 18; some are less than 03 possibly as a result of late-stage alteration.

Taili gneissic tonalite–granite Sample 10TL13 is a gneissic granite from Taili (Figs 1 and 2a, b). U–Pb analysis for 25 zircon grains yielded 207 Pb/206Pb ages ranging from 2581 6 21 to 2525 6 21 Ma (1r), apart from two strongly discordant ages, which may be due to lead loss (2285 6 47 and 2463 6 47 Ma) (Table 1). The data form a discordant line with an upper intercept age of 2558 6 16 Ma (MSWD ¼ 050) (Fig. 4a). Nineteen analyses on or close to the concordia give a weighted mean 207Pb/206Pb age of 2551 6 9 Ma (MSWD ¼ 053), which is in accordance with the upper intercept age. Therefore, the Taili gneissic granites were emplaced at 2558 Ma.

Xingcheng tonalite–trondhjemites and MMEs Sample 10XC02 is a tonalite from Xingcheng (Figs 1 and 2c–f). Twenty-five zircon grains were analyzed and give a wide 207Pb/206Pb age range of 2578 6 22 to 2388 6 23 Ma (1r) (Table 1). They fall on a discordant line with an upper intercept with the concordia at 2559 6 23 Ma (MSWD ¼ 088) (Fig. 4b). Seven near-concordant analyses of zircon grains give a weighted mean


Separation and purification of Nd were carried out using conventional two-column ion exchange procedures in the ultraclean laboratory of the MOE Key Laboratory at Peking University. Approximately 250 mg powder of each sample was dissolved with a distilled acid mixture (HF þ HClO4) in a sealed Savillex beaker on a hot plate for 168 h. The ion exchange procedures include: (1) group separation of light rare earth elements (LREE) through a cation-exchange column (1 75 cm2, packed with 200 mesh AG50W resin); (2) purification of Nd through a second cation-exchange column (05 55 cm2, packed with 200 mesh P507 resin), conditioned and cleaned with dilute HCl. Nd isotopic ratios were measured by thermal ionization mass spectrometry (TIMS) using a Thermo-Finnigan Triton system at the Isotope Laboratory of the Tianjin Institute of Geology and Mineral Resources. The 147Sm/144Nd ratios were calculated using ICP-MS analyzed Sm and Nd concentrations. Mass fractionation was corrected for by normalizing the measured 143Nd/144Nd against a 146 Nd/144Nd ratio of 07219. Rock standard USGS BCR-2 was used to evaluate the separation and purification process of Nd, which yielded a weighted mean 143 Nd/144Nd ratio of 0512632 6 4 (2r, n ¼ 100). To monitor the data quality during the period of data acquisition, the LRIG Nd standard was analyzed and gave a weighted mean 143Nd/144Nd ratio of 0512206 6 6 (2r, n ¼ 100).



1781

207

Pb/206Pb age of 2548 6 17 Ma (MSWD ¼ 105), agreeing well with the upper intercept age. Thus, the Xingcheng tonalite–trondhjemites crystallized at 2559 Ma. Sample 11XC03 is an MME hosted in the Xingcheng tonalite–trondhjemites (Fig. 2c–e). Ten zircon grains were analyzed and give a 207Pb/206Pb age range of 2487 6 27 to 2236 6 26 Ma (1r) (Table 1). They are extremely discordant owing to lead loss and lie along a discordant line under the concordia with a projected upper intercept age of 2546 6 55 Ma (MSWD ¼ 061) (Fig. 4c). Thus, the crystallization age of the MMEs in Xingcheng is 2546 Ma and coeval with the host tonalite–trondhjemites within error.

Juhuadao granodiorites and MMEs Sample 12XC22 is a granodiorite from Juhuadao (Figs 1 and 2g). Thirty zircon grains were analyzed and give a wide 207Pb/206Pb age range of 2660 6 17 to 2145 6 18 Ma (1r) owing to lead loss (Table 1). They define a discordant line and intercept the concordia at 2595 6 14 Ma (MSWD ¼ 120), which is in accordance with the weighted mean 207Pb/206Pb age of nine analyses indistinguishable from concordia (2587 6 11 Ma; MSWD ¼ 086) (Fig. 4d). Another granodiorite sample 12XC28 was also selected for dating. Thirty zircon grains were analyzed, which give a wide 207Pb/206Pb age range of 2582 6 24 to 1822 6 58 Ma (1r) resulting from lead loss (Table 1). They are strongly discordant and form a discordant line intercepting the concordia at 2573 6 28 Ma (MSWD ¼ 290) (Fig. 4e). Therefore, the timing of

emplacement of the Juhuadao granodiorites is between 2595 and 2574 Ma. Sample 12XC15 is an MME hosted in the Juhuadao granodiorites (Fig. 2g). Twenty-four zircon grains were analyzed and gave a wide 207Pb/206Pb age range of 2583 6 26 to 1626 6 95 Ma (1r), showing the effects of lead loss (Table 1). They fall on a discordant line with an upper intercept age of 2568 6 13 Ma (MSWD ¼ 280) (Fig. 4f). Thus, the MMEs crystallized at 2568 Ma, coeval with the host granodiorite within error.

Xingcheng and Huludao potassic granites Sample 10XC05 is a potassic granite intruding the Xingcheng tonalite–trondhjemites (Figs 1 and 2f). Fifteen zircon grains were analyzed, giving a 207 Pb/206Pb age range of 2573 6 16 to 2327 6 15 Ma (1r), in addition to two strongly discordant ages owing to lead loss (1985 6 51 and 2021 6 15 Ma) (Table 1). They define a discordant line intercepting the concordia at 2545 6 20 Ma (MSWD ¼ 098) (Fig. 4g), in accordance with the weighted mean 207Pb/206Pb age of eight analyses (2531 6 23 Ma; MSWD ¼ 27) near or close to the concordia. Therefore, the crystallization age of the Xingcheng potassic granites is 2545 Ma, slightly younger than that of the intruded tonalite–trondhjemites; this is consistent with field observations of their relative ages (Fig. 2f). Sample 10XC08 is a potassic granite from Huludao (Figs 1 and 2h). Nineteen zircon grains were analyzed giving a 207Pb/206Pb age range of 2544 6 41 to 2334 6 19 Ma (1r) (Table 1). They are also strongly discordant


Fig. 3. Cathodoluminescence (CL) images of representative zircons from the Neoarchean TTG and potassic granitoids in the Xingcheng region. The continuous-line and dashed-line circles on the CL images are the spots of in situ zircon U–Pb dating and Hf isotope analyses, respectively. Also shown are the 207Pb/206Pb ages and eHf(t) values of the zircons. The scale bar represents 100 lm.

1782


Table 1: In situ LA-ICP-MS zircon U–Pb data for the Neoarchean TTG and potassic granitoids in the Xingcheng region Spot Concentrations (ppm) Pb

207

Pb/

Th

206

Isotopic ages (Ma)

Pb* 61r

207

Pb/

235

U 61r

206

238

Pb/

U 61r

207

Pb/206Pb 61r

207

Pb/235U 61r

206

Pb/238U 61r

177 179 207 146 226 224 411 160 110 133 120 138 129 164 1148 95 224 163 117 120 163 476 339 333 257

107 194 113 114 190 152 250 124 92 87 111 135 101 121 445 79 164 142 92 89 110 189 227 194 237

061 108 055 078 084 068 061 077 083 065 092 098 078 074 039 083 073 087 078 074 068 040 067 058 093

016836 016833 016066 016696 016832 016840 016693 016988 016851 016884 016989 017010 017160 017020 014477 016799 017127 016905 017235 016772 017129 016901 016856 016937 016670

000343 000344 000437 000349 000344 000348 000342 000357 000361 000360 000370 000368 000373 000369 000390 000378 000373 000374 000390 000379 000384 000377 000381 000380 000382

1052913 1089588 829389 1104128 1031485 1083504 965213 1103919 1110818 1108213 1079382 1127141 1105388 1037456 323391 1108530 1088441 1061618 1066542 1100906 1113181 741609 929889 1096702 738636

021126 021918 020021 022674 020728 021987 019466 022775 023368 023205 023040 023877 023550 022019 007766 024351 023169 022949 023563 024262 024374 016140 020505 024015 016455

045337 046925 037441 047943 044427 046645 041919 047111 047793 047588 046064 048044 046705 044196 016201 047846 046080 045536 044871 047595 047125 031819 040006 046957 032131

000541 000560 000469 000578 000527 000555 000496 000565 000580 000575 000561 000581 000566 000533 000197 000589 000553 000552 000552 000583 000571 000383 000485 000566 000391

2541 2541 2463 2527 2541 2542 2527 2556 2543 2546 2557 2559 2573 2560 2285 2538 2570 2548 2581 2535 2570 2548 2543 2551 2525

18 18 47 19 18 19 19 19 20 19 20 20 20 20 47 21 20 20 21 21 21 21 21 21 21

2482 2514 2264 2527 2463 2509 2402 2526 2532 2530 2506 2546 2528 2469 1465 2530 2513 2490 2494 2524 2534 2163 2368 2520 2159

19 19 22 19 19 19 19 19 20 20 20 20 20 20 19 20 20 20 21 21 20 19 20 20 20

2410 2480 2050 2525 2370 2468 2257 2488 2518 2509 2442 2529 2471 2359 968 2521 2443 2419 2390 2510 2489 1781 2169 2482 1796

24 25 22 25 24 24 23 25 25 25 25 25 25 24 11 26 24 24 25 25 25 19 22 25 19

513 621 409 418 376 558 462 147 222 477 169 152 379 529 356 78 449 373 668 484 209 82 123 718 171

349 547 270 280 276 367 339 171 202 390 151 229 249 432 453 55 554 248 612 360 124 58 99 1067 80

068 088 066 067 074 066 074 116 091 082 089 150 066 082 127 070 123 066 092 074 059 070 080 149 047

016152 015966 016568 016672 015971 015649 016239 016580 016783 016619 017213 016893 016705 015875 017124 016661 017132 016754 015520 016186 016208 017140 016915 015375 016934

000343 000340 000354 000358 000347 000473 000356 000372 000374 000368 000393 000386 000377 000360 000389 000394 000395 000386 000359 000375 000502 000415 000406 000365 000408

766776 660013 858031 840999 651651 672745 761619 1047853 870800 752882 1135416 1048996 783094 580663 803153 1098751 918680 925327 628863 753594 935390 1142870 1109244 475209 1049423

016588 014342 018705 018412 014394 018198 016948 023825 019705 016913 026233 024256 017913 013317 018475 026222 021420 021551 014687 017654 026030 027872 026829 011375 025435

034424 029976 037552 036579 029587 031179 034008 045828 037623 032850 047830 045028 033993 026522 034010 047820 038884 040048 029382 033761 041855 048349 047552 022412 044935

000439 000382 000479 000467 000379 000421 000436 000595 000486 000422 000625 000587 000439 000342 000440 000632 000505 000518 000380 000437 000572 000642 000626 000292 000591

2472 2452 2514 2525 2453 2418 2481 2516 2536 2520 2578 2547 2528 2442 2570 2524 2571 2533 2404 2475 2478 2571 2549 2388 2551

20 20 20 20 21 53 21 21 21 21 22 22 22 22 22 23 22 22 23 23 54 23 23 23 23

2193 2059 2294 2276 2048 2076 2187 2478 2308 2176 2553 2479 2212 1947 2235 2522 2357 2363 2017 2177 2373 2559 2531 1776 2479

19 19 20 20 19 24 20 21 21 20 22 21 21 20 21 22 21 21 20 21 26 23 23 20 22

1907 1690 2055 2010 1671 1750 1887 2432 2059 1831 2520 2396 1886 1516 1887 2519 2117 2171 1661 1875 2254 2542 2508 1304 2392

21 19 22 22 19 21 21 26 23 20 27 26 21 17 21 28 23 24 19 21 26 28 27 15 26

467 624 656 501 641 440 558 439 635 580

319 638 538 545 571 292 236 281 841 523

068 102 082 109 089 066 042 064 132 090

015943 014072 015778 016152 014793 016300 015907 016278 015695 015582

000387 000344 000390 000404 000374 000421 000425 000450 000433 000432

653596 444205 728731 787504 528056 834632 810277 962657 632256 695868

016490 011277 018710 020438 013827 022332 022405 027455 018013 019924

029730 022891 033494 035358 025887 037132 036940 042886 029214 032387

000401 000309 000453 000479 000352 000507 000507 000595 000404 000448

2450 2236 2432 2472 2322 2487 2446 2485 2423 2411

25 26 26 26 27 27 28 30 30 30

2051 1720 2147 2217 1866 2269 2243 2400 2022 2106

22 21 23 23 22 24 25 26 25 25

1678 1329 1862 1952 1484 2036 2027 2301 1652 1809

20 16 22 23 18 24 24 27 20 22

479 216 283 228 249 240 126 383 383 485 425 730 251 361 518 541 296 382

175 141 166 86 116 195 59 169 211 460 228 408 146 184 246 297 168 228

037 065 059 038 047 081 047 044 055 095 054 056 058 051 047 055 057 060

016121 017516 015599 016640 016698 017383 017199 017227 017360 017407 016626 015666 017382 016889 015947 016291 017420 016983

000436 000334 000605 000461 000482 000334 000338 000323 000328 000330 000321 000297 000335 000321 000304 000311 000337 000328

544924 1201575 671794 896332 819624 1186304 1166775 945201 819718 670082 805266 433220 1112443 826141 589199 625067 899370 713564

012452 024544 023728 021062 020223 024359 024360 019081 016635 013612 016577 008813 022895 016827 012031 012759 018537 014716

024516 049750 031236 039067 035600 049493 049197 039790 034244 027916 035126 020054 046413 035473 026795 027825 037441 030470

000355 000716 000502 000575 000531 000714 000719 000566 000489 000398 000506 000285 000669 000506 000382 000396 000538 000437

2468 2608 2413 2522 2528 2595 2577 2580 2593 2597 2520 2420 2595 2547 2450 2486 2598 2556

47 17 67 48 50 17 17 16 17 17 17 17 17 17 17 17 17 17

1893 2606 2075 2334 2253 2594 2578 2383 2253 2073 2237 1700 2534 2260 1960 2012 2337 2129

20 19 31 21 22 19 20 19 18 18 19 17 19 18 18 18 19 18

1413 2603 1752 2126 1963 2592 2579 2159 1898 1587 1941 1178 2458 1957 1530 1583 2050 1715

18 31 25 27 25 31 31 26 23 20 24 15 29 24 19 20 25 22

(continued)


10TL13 1.1 99 2.1 114 3.1 96 4.1 89 5.1 130 6.1 132 7.1 214 8.1 97 9.1 68 10.1 80 11.1 74 12.1 89 13.1 78 14.1 93 15.1 225 16.1 59 17.1 131 18.1 97 19.1 68 20.1 73 21.1 97 22.1 181 23.1 170 24.1 191 25.1 107 10XC02 1.1 216 2.1 232 3.1 187 4.1 188 5.1 135 6.1 215 7.1 191 8.1 88 9.1 109 10.1 195 11.1 102 12.1 92 13.1 157 14.1 170 15.1 162 16.1 46 17.1 223 18.1 183 19.1 251 20.1 202 21.1 108 22.1 49 23.1 74 24.1 207 25.1 90 11XC03 1.1 159 2.1 179 3.1 269 4.1 220 5.1 204 6.1 200 7.1 239 8.1 226 9.1 235 10.1 232 12XC22 1.1 134 2.1 129 3.1 126 4.1 104 5.1 106 6.1 147 7.1 72 176 8.1 9.1 155 10.1 162 11.1 175 12.1 172 13.1 138 14.1 150 15.1 161 16.1 176 17.1 131 18.1 138

U

Th/U Isotopic ratios


1783

Table 1: Continued Spot Concentrations (ppm) Pb

207

Pb/

Th

206

Isotopic ages (Ma)

Pb* 61r

207

Pb/

235

U 61r

206

238

Pb/

U 61r

207

Pb/206Pb 61r

207

Pb/235U 61r

206

Pb/238U 61r

200 195 274 280 1604 410 167 238 506 237 203 164

86 101 79 196 1379 263 87 288 325 239 108 97

043 052 029 070 086 064 052 121 064 101 053 059

017159 017290 018079 016735 013350 017172 017254 017530 016234 017232 017009 017389

000345 000343 000359 000328 000260 000336 000360 000352 000320 000343 000350 000355

1156417 1173715 1166874 948389 207408 849988 1174836 1206470 629619 1045083 1141264 1189487

024587 024693 024544 019790 004300 017671 025692 025644 013164 022031 024684 025567

048874 049230 046806 041098 011267 035895 049377 049911 028125 043982 048658 049605

000720 000719 000682 000592 000161 000515 000740 000730 000404 000636 000718 000728

2573 2586 2660 2531 2145 2574 2582 2609 2480 2580 2559 2595

18 17 17 17 18 17 18 18 18 17 18 18

2570 2584 2578 2386 1140 2286 2585 2609 2018 2476 2557 2596

20 20 20 19 14 19 20 20 18 20 20 20

2565 2581 2475 2219 688 1977 2587 2610 1598 2350 2556 2597

31 31 30 27 9 24 32 31 20 28 31 31

702 664 980 209 850 786 691 655 726 729 506 383 767 755 1526 1143 811 685 710 938 707 157 558 761 814 143 308 654 964 752

177 77 164 140 95 108 424 174 407 94 377 531 218 129 171 261 207 184 371 135 162 119 315 430 256 101 82 218 120 272

025 012 017 067 011 014 061 027 056 013 074 139 028 017 011 023 025 027 052 014 023 076 056 057 031 070 027 033 012 036

015749 015763 014414 016829 014002 014569 015780 014801 014500 015079 015900 016842 014456 014210 011135 012939 016375 015379 014720 013386 014381 017235 015949 014892 013665 017250 016206 014271 013135 015105

000354 000436 000412 000388 000428 000418 000537 000449 000526 000445 000377 000398 000455 000436 000350 000427 000394 000481 000529 000426 000461 000455 000397 000553 000466 000447 000515 000503 000436 000388

425413 419575 306494 1004039 298320 330925 518964 426626 388751 409197 572963 831480 422683 291957 183570 274263 582444 441219 434966 237363 388840 1161222 705721 579619 271613 1081478 762506 432520 264876 411604

009912 009872 007522 023893 007960 008147 015676 011223 012692 010423 013937 020211 011665 007816 005079 008033 014367 012072 014051 006652 010962 031000 017930 019417 008233 028425 021176 013669 007807 010747

019587 019304 015422 043263 015453 016474 023852 020906 019444 019682 026129 035799 021206 014902 011957 015373 025791 020808 021430 012861 019610 048852 032084 028228 014416 045457 034125 021981 014625 019757

000289 000282 000226 000648 000230 000243 000374 000316 000307 000293 000392 000536 000320 000224 000177 000234 000386 000316 000338 000195 000298 000787 000486 000450 000224 000710 000526 000345 000224 000302

2429 2430 2277 2541 2227 2296 2432 2323 2288 2355 2445 2542 2283 2253 1822 2090 2495 2389 2314 2149 2274 2581 2450 2334 2185 2582 2477 2260 2116 2358

21 48 50 21 54 50 59 53 64 52 22 22 55 54 58 59 22 55 63 57 56 24 23 65 61 24 55 62 60 25

1685 1673 1424 2439 1403 1483 1851 1687 1611 1653 1936 2266 1679 1387 1058 1340 1950 1715 1703 1235 1611 2574 2119 1946 1333 2507 2188 1698 1314 1657

19 19 19 22 20 19 26 22 26 21 21 22 23 20 18 22 21 23 27 20 23 25 23 29 22 24 25 26 22 21

1153 1138 925 2318 926 983 1379 1224 1145 1158 1496 1973 1240 895 728 922 1479 1219 1252 780 1154 2564 1794 1603 868 2416 1893 1281 880 1162

16 15 13 29 13 13 19 17 17 16 20 25 17 13 10 13 20 17 18 11 16 34 24 23 13 31 25 18 13 16

233 877 250 200 1385 313 533 670 709 1266 1351 496 305 402 384 496 670 829 376 1043 1111 1252 780 858

58 552 239 139 981 144 293 432 345 1132 1173 246 163 231 190 685 392 434 222 698 960 1194 426 637

025 063 096 069 071 046 055 064 049 089 087 050 053 057 050 138 058 052 059 067 086 095 055 074

016849 013624 017028 017261 010011 016634 016029 014498 014603 011452 012223 016362 016766 016757 016568 016001 015262 014563 016639 015276 013723 012114 015022 014900

000452 000369 000467 000474 000498 000456 000635 000402 000409 000324 000348 000463 000477 000479 000478 000464 000446 000430 000492 000286 000260 000232 000285 000285

907919 264930 1110899 1172069 082149 711234 546886 308874 366606 152724 140299 642534 978540 819642 746622 558246 349685 299452 883543 327716 235245 159781 331450 237305

024599 007242 030718 032434 003835 019669 019698 008621 010328 004338 004005 018276 027948 023509 021596 016212 010227 008846 026155 006602 004784 003275 006745 004854

039069 014099 047300 049231 005952 031001 024745 015446 018202 009669 008322 028470 042315 035462 032672 025294 016611 014908 038496 015558 012432 009566 016001 011550

000607 000219 000748 000778 000102 000485 000409 000242 000286 000152 000131 000449 000670 000561 000519 000403 000266 000239 000618 000221 000177 000136 000228 000165

2543 2180 2560 2583 1626 2521 2459 2288 2300 1872 1989 2493 2534 2534 2514 2456 2375 2295 2522 2377 2193 1973 2348 2334

25 27 26 26 95 26 69 27 27 29 29 27 27 27 28 28 29 29 29 17 17 18 17 17

2346 1314 2532 2582 609 2126 1896 1430 1564 941 890 2036 2415 2253 2169 1913 1527 1406 2321 1476 1228 969 1484 1235

25 20 26 26 21 25 31 21 22 17 17 25 26 26 26 25 23 22 27 16 14 13 16 15

2126 850 2497 2581 373 1741 1425 926 1078 595 515 1615 2275 1957 1822 1454 991 896 2099 932 755 589 957 705

28 12 33 34 6 24 21 14 16 9 8 23 30 27 25 21 15 13 29 12 10 8 13 10

842 178 46 64 197 89 1103 603 65 207 67 618 833

338 151 55 85 217 111 435 613 69 219 80 996 615

040 085 121 132 110 125 039 102 106 106 119 161 074

012195 016770 016654 017154 016952 016296 012443 016041 016668 016345 016324 015538 014837

000344 000281 000316 000307 000284 000294 000210 000268 000308 000661 000641 000271 000256

229081 987753 1090193 1114555 1079594 833760 224319 651598 1055981 978188 886819 542702 406905

005725 017427 021369 020811 019075 015663 003983 011480 020220 036635 031933 009896 007352

013624 042709 047467 047115 046180 037100 013072 029455 045939 043405 039401 025327 019887

000177 000532 000620 000602 000573 000470 000162 000364 000588 000661 000617 000315 000246

1985 2535 2523 2573 2553 2487 2021 2460 2525 2492 2490 2406 2327

51 14 17 16 14 16 15 15 16 70 68 15 15

1209 2423 2515 2535 2506 2268 1195 2048 2485 2414 2325 1889 1648

18 16 18 17 16 17 12 16 18 35 33 16 15

823 2293 2504 2489 2448 2034 792 1664 2437 2324 2141 1455 1169

10 24 27 26 25 22 9 18 26 30 29 16 13

(continued)


19.1 128 20.1 113 21.1 144 22.1 134 23.1 217 24.1 177 25.1 97 26.1 156 27.1 169 28.1 133 29.1 115 30.1 97 12XC28 1.1 152 2.1 139 3.1 165 4.1 109 5.1 148 6.1 141 7.1 201 8.1 154 9.1 175 10.1 160 11.1 163 12.1 187 13.1 186 14.1 126 15.1 199 16.1 201 17.1 232 18.1 163 19.1 186 20.1 135 21.1 157 22.1 95 23.1 203 24.1 266 25.1 135 26.1 80 27.1 119 28.1 171 29.1 159 30.1 168 12XC15 1.1 101 2.1 145 3.1 151 4.1 120 5.1 100 6.1 111 7.1 167 8.1 121 9.1 147 10.1 149 11.1 138 12.1 166 13.1 153 14.1 171 15.1 147 16.1 146 17.1 123 18.1 141 19.1 172 20.1 190 21.1 168 22.1 146 23.1 145 24.1 118 10XC05 1.1 141 2.1 96 3.1 29 4.1 42 5.1 119 6.1 44 7.1 161 8.1 224 9.1 39 10.1 147 11.1 39 12.1 224 13.1 203

U


1784


Table 1: Continued Spot Concentrations (ppm) Pb

U

207

Pb/

Th

206

Isotopic ages (Ma)

Pb* 61r

207

Pb/

235

206

U 61r

238

Pb/

U 61r

207

Pb/206Pb 61r

207

Pb/235U 61r

206

Pb/238U 61r

58 49

76 73

132 150

016384 016306

000326 000346

1056115 1005910

021597 021772

046742 044733

000611 000600

2496 2488

18 19

2485 2440

19 20

2472 2383

27 27

574 489 213 297 491 230 288 246 307 843 115 206 637 275 266 356 288 617 138

534 215 145 65 415 159 456 261 240 767 139 45 302 181 131 250 259 361 92

093 044 068 022 085 069 158 106 078 091 121 022 047 066 049 070 090 058 067

015301 016173 016370 016862 015945 015997 016692 016492 015665 014897 016320 016451 015189 015633 016685 016426 015999 015951 016004

000536 000309 000326 000405 000308 000318 000332 000549 000503 000300 000340 000425 000432 000477 000462 000346 000529 000643 000512

552864 812081 868478 1049582 687381 678309 671287 957308 775313 382223 1088160 772400 441524 763884 873500 758397 742654 618658 737588

017666 016040 017764 021520 013699 013850 013709 028803 022443 007887 023183 017328 011113 020851 021284 016286 022209 023235 021230

026205 036410 038469 045146 031260 030747 029161 042100 035897 018605 048347 034052 021082 035440 037970 033480 033666 028129 033426

000377 000458 000492 000566 000393 000390 000370 000599 000496 000235 000622 000436 000278 000482 000502 000428 000473 000409 000466

2380 2474 2494 2544 2450 2455 2527 2507 2420 2334 2489 2503 2367 2416 2526 2500 2456 2451 2456

61 17 18 41 18 18 18 57 56 19 19 44 50 53 48 20 57 70 55

1905 2245 2305 2480 2095 2084 2074 2395 2203 1597 2513 2199 1715 2189 2311 2183 2164 2003 2158

27 18 19 19 18 18 18 28 26 17 20 20 21 25 22 19 27 33 26

1500 2002 2098 2402 1753 1728 1650 2265 1977 1100 2542 1889 1233 1956 2075 1862 1871 1598 1859

19 22 23 25 19 19 18 27 24 13 27 21 15 23 23 21 23 21 23

*Corrected ratios.

and define a discordant line intercepting the concordia at 2520 6 25 Ma (MSWD ¼ 104) (Fig. 4h). Therefore, the crystallization ages of the potassic granites in the Xingcheng region range from 2545 to 2520 Ma.

Summary The emplacement age of Neoarchean granitoids in the studied region is between 2595 and 2520 Ma. The TTG granitoids were emplaced during the period 2595– 2558 Ma, which is coeval with the hosted MMEs of 2568–2546 Ma, followed by intrusion of potassic granites at 2545–2520 Ma.

Geochemistry Bulk-rock major and trace elements Forty-eight fresh or least altered samples from four representative outcrops of Neoarchean granitoids in the Xingcheng region, including gneissic granite, tonalite– trondhjemite, granodiorite, MMEs and potassic granite, were selected for bulk-rock major and trace element analyses; the data are reported in Table 2. The samples vary in composition from diorite to granodiorite to quartz monzonite and granite. Most of these samples are sub-alkaline, although some plot in the alkaline field (Fig. 5a). Taili gneissictonalite–granite. The gneissic granite samples from Taili are characterized by enrichment in K2O over Na2O (K2O/Na2O ¼ 096–241) and relatively high total alkali contents (Figs 5a, d and 6a), and show a relatively large compositional range in terms of other major elements (Table 2; Figs 5 and 6). They are all metaluminous, plotting in the granite field in the An–Ab–Or diagram (Table 2; Fig. 5b and c). The Taili gneissic granite samples with lower SiO2 contents have elevated P2O5 and TiO2 contents (Fig. 6b and c). They also have low concentrations of Cr and Ni but relatively high Y

and variable Sr abundances (Table 2; Fig. 6e and f). They are all enriched in LREE with varying (La/Yb)N ratios of 8–51 (Table 2; Fig. 7a). They have obvious negative Eu anomalies (Eu/Eu* ¼ 050–093) and superchondritic heavy rare earth element (HREE) abundances (Fig. 7a). Primitive mantle (PM)-normalized trace element patterns (Fig. 8a) are relatively enriched in large ion lithophile elements (LILE; e.g. Cs, Rb, Ba and Th), with limited variation, and depleted in high field strength elements (HFSE; negative Nb anomalies, but no Zr and Hf depletion). They also show a large range of Sr/Y ratios of 7–62. The Taili gneissic tonalite samples have relatively high SiO2 and K2O/Na2O (071–082) (Table 2; Fig. 5d). They are all metaluminous and fall near the TTG field in the An–Ab–Or diagram (Table 2; Fig. 5b and c). They also have low concentrations of Cr, Ni and Y but relatively high Sr (Table 2; Fig. 6e and f). They show the typical fractionated REE patterns of TTGs (or adakites), with high (La/Yb)N ratios of 72–74 without negative Eu anomalies (Eu/Eu* ¼ 111–119) (Table 2; Fig. 7a). In the PM-normalized trace element diagram (Fig. 8a), they are enriched in LILE, with significant negative anomalies of some HFSE (e.g. Nb and Ti) without Zr and Hf depletion. They have positive Sr anomalies with high Sr/Y ratios of 161–172. Xingchengtonalite–trondhjemites and MMEs. The tonalite–trondhjemite samples from Xingcheng are intermediate to felsic in composition (Table 2). They are relatively enriched in Na2O relative to K2O (K2O/ Na2O ¼ 020–067) (Fig. 5d), and all plot in or near the trondhjemite field in the An–Ab–Or diagram (Fig. 5b). They also have low Cr, Ni and Y, but relatively high Sr (Table 2; Fig. 6e and f). They have uniform REE patterns with moderate depletion in HREE [(La/Yb)N ¼ 25–47] and weakly negative to positive Eu anomalies (Eu/Eu* ¼


14.1 36 15.1 31 10XC08 1.1 208 2.1 207 3.1 101 4.1 152 5.1 185 6.1 86 7.1 102 8.1 141 9.1 146 10.1 191 11.1 74 12.1 80 13.1 162 14.1 123 15.1 121 16.1 146 17.1 128 18.1 265 19.1 59



1785


Fig. 4. U–Pb concordia diagrams for the Neoarchean TTG and potassic granitoids.

076–116) (Fig. 7b). In PM-normalized trace element patterns (Fig. 8b), they are enriched in LILE and depleted in Nb, Ta and Ti, and show positive Sr anomalies with high Sr/Y ratios of 83–145. The MMEs hosted within the Xingcheng tonalite– trondhjemites are mafic to intermediate in composition (Table 2). In contrast to their host, the MMEs have higher TiO2, Al2O3, total Fe2O3, MgO and CaO, similar

Cr, Ni, Sr and K2O/Na2O (042–087) (Fig. 5d), but lower Ba, Th and U (Table 2; Fig. 6). They have higher HREE with lower (La/Yb)N ratios of 11–13 than their host and show weakly negative Eu anomalies (Eu/Eu* ¼ 068– 094) (Fig. 7b). In PM-normalized trace element patterns (Fig. 8b), the MMEs are relatively depleted in some LILE (e.g. Ba and Th) and show depletion of HFSE with negative anomalies of Nb, Zr, Hf and Ti and

Major elements (wt %) 7322 SiO2 031 TiO2 1302 Al2O3 157 Fe2O3T MnO 002 MgO 045 CaO 112 319 Na2O 586 K2O P2O5 013 LOI 024 Total 9914 183 K2O/Na2O A/CNK 096 Mg# 400 Trace elements (ppm) Li 1805 P 721 K 43100 Sc 177 Ti 2054 V 1848 Cr 598 Co 159 Ni 349 Cu 1001 Zn 3242 Ga 1336 Rb 176 Sr 313 Y 1937 Zr 194 Nb 1607 Cs 178 Ba 760 La 7546 Ce 12282 Pr 1154 Nd 3806 Sm 584 Eu 098 Gd 457 Tb 060 Dy 317 Ho 058 Er 163 Tm 024 Yb 139 Lu 019 Hf 396 Ta 109 Pb 17 Th 1177 U 097 RREE 267 Eu/Eu* 056 39 (La/Yb)N Sr/Y 16 DRb 304 DTh –48 DSr 777 DY 109 DNb 87

10TL08 GG TL 6801 063 1475 335 004 066 175 309 746 021 028 10023 241 090 313 2664 1845 53340 741 3980 4238 1475 321 709 2692 5352 1714 271 255 3408 322 3112 202 779 5166 12366 1544 5802 983 144 738 098 525 097 281 041 248 034 583 212 25 706 116 281 050 15 7 1510 –69 –844 191 219

3624 1994 42220 896 3910 4370 1960 508 970 1614 6516 1738 227 316 3294 272 2980 225 884 6648 15630 1719 6242 1000 155 747 096 514 094 270 039 243 033 499 211 18 1061 148 334 053 20 10 1141 –27 –510 163 201

10TL10 GG TL

6666 063 1478 405 006 112 206 369 594 034 040 9973 161 091 391

10TL09 GG TL

877 876 44500 109 1209 1561 528 116 283 785 3530 1601 140 516 828 138 855 099 1415 4666 6938 620 1974 274 076 208 025 128 023 069 010 065 010 269 069 24 641 073 151 093 51 62 142 –82 2008 –52 –02

6923 021 1625 138 003 033 166 454 617 009 042 10032 136 095 359

10TL13 GG TL

3345 986 47880 479 3243 3867 3393 537 1655 1159 7762 1837 189 450 2707 253 2378 224 1117 7841 17122 1897 6493 1025 164 752 095 512 097 282 041 273 039 615 142 30 1636 206 366 055 21 17 683 23 1122 122 146

6809 050 1450 332 004 097 196 334 588 024 062 9947 176 094 404

12XC09 GG TL

2388 722 43360 405 2902 3346 1140 417 658 1298 5410 1798 187 353 2350 265 1936 174 1175 5212 13054 1520 5344 867 152 641 082 444 085 244 035 234 034 613 118 21 946 148 279 060 16 15 579 –55 516 109 108

6992 043 1448 254 003 061 178 381 511 017 052 9940 134 096 357

12XC10 GG TL

3400 802 42760 256 2970 3596 1153 419 600 941 5788 1876 168 370 2652 283 2348 165 1080 3126 8718 1176 4490 831 139 633 086 482 094 271 040 268 039 674 165 21 739 213 204 056 8 14 486 –66 288 115 143

6796 046 1532 292 004 073 198 407 524 020 054 9946 129 096 369

12XC11 GG TL

3708 1117 42180 701 3874 4530 1872 607 940 2176 7480 1893 191 349 3608 353 2757 242 1095 7692 19316 2302 8060 1294 208 952 124 674 129 371 053 348 048 821 186 21 1055 173 416 055 16 10 752 –31 –69 201 181

6720 060 1484 379 005 104 216 368 520 028 062 9947 141 095 391

12XC12 GG TL

6488 2416 49880 1051 5456 8432 1762 1067 1087 3002 8870 2234 210 390 2490 280 3350 310 1417 6534 15502 1748 6108 960 203 718 086 467 089 248 035 239 035 639 204 19 1483 236 330 072 20 16 1124 31 –391 44 227

6357 085 1515 588 006 153 247 383 507 055 071 9968 133 093 378

13TL07 GG TL

6264 3224 44520 1212 7028 10200 2216 1280 1408 1486 11054 2428 228 687 3020 382 3954 458 1127 6596 17674 2070 7452 1192 257 885 106 565 107 298 042 282 042 826 244 21 1113 207 376 073 17 23 1410 04 2145 69 280

6137 110 1530 678 008 197 321 411 440 072 070 9974 107 088 404

13TL08 GG TL

— 4377 49477 1035 8285 9440 1858 1696 1626 3443 9536 2691 162 555 2498 281 2707 128 1254 7172 15114 1906 6321 979 211 718 094 463 090 235 033 215 031 646 162 17 758 154 336 073 24 22 700 –36 1012 29 159

6232 090 1394 638 008 182 359 349 427 071 221 9970 122 083 399

15TL01 GG TL 6943 033 1421 316 005 122 257 361 386 012 061 9920 107 096 473 — 831 40759 882 2765 4004 3158 884 1694 1106 5269 2085 164 423 1208 163 1258 256 950 3400 5708 648 2042 333 089 272 038 205 042 115 017 112 017 397 083 15 1893 186 130 087 22 35 370 42 1112 –11 39

— 5067 40718 1241 9563 12029 2298 1818 1738 3234 10462 2920 192 695 3246 315 4359 383 870 7642 17781 2241 7453 1181 247 867 114 581 114 306 044 289 042 738 243 16 945 147 389 071 19 21 1086 –09 2084 83 318

15TL03 GG TL

6066 108 1458 812 010 212 418 381 367 087 073 9992 096 082 379

15TL02 GG TL


No.: Lithology: Location:

Table 2: Major and trace element data for the Neoarchean TTG and potassic granitoids in the Xingcheng region

— 5429 48851 1554 10307 12675 2526 1934 2013 4350 9670 3070 196 853 3349 386 4323 359 1048 7797 17390 2281 7644 1208 260 897 116 584 113 298 042 275 040 831 306 13 807 143 389 073 20 25 1150 –20 3567 87 313

6016 108 1499 796 009 225 410 389 392 087 067 9997 101 083 398

15TL05 GG TL

2302 1142 30300 333 1875 2844 2686 395 1215 110 3310 1608 126 761 443 144 878 175 1609 2900 4924 498 1706 238 082 166 017 078 013 034 005 028 004 271 050 17 451 130 107 119 74 172 –53 –106 4644 –79 03

7018 031 1478 223 003 112 195 491 401 011 029 9993 082 093 540

10TL12 GT TL

(continued)

2310 1103 27140 339 1810 2764 3358 387 1398 1234 3878 1582 100 720 447 132 848 132 1321 2958 5158 506 1739 246 079 173 018 079 013 035 005 029 004 252 048 18 476 127 110 111 72 161 –325 –105 4301 –74 02

7051 030 1481 225 003 113 209 526 372 015 033 10058 071 090 539

10TL11 GT TL

1786 Journal of Petrology, 2016, Vol. 57, No. 9

10XC02 TT XC

10XC03 TT XC

11XC02 TT XC

12XC04 TT XC

11XC01-1 MME XC

11XC01-2 MME XC

11XC03 MME XC

11XC06 MME XC

10XC05 PG XC

11XC07 PG XC

12XC01 PG XC

12XC02 PG XC


12XC14 GD JHD

12XC17 GD JHD

12XC18 GD JHD

12XC19 GD JHD

(continued)

Major elements (wt %) 7084 6470 7148 6500 5747 5834 5366 5613 7357 7611 7380 7361 6440 6621 6533 6495 SiO2 047 039 042 043 078 076 087 077 027 009 021 021 044 041 046 040 TiO2 1444 1563 1386 1636 1642 1583 1515 1683 1297 1154 1340 1303 1820 1543 1527 1617 Al2O3 Fe2O3T 309 344 351 396 862 820 1186 842 170 086 153 147 335 444 489 438 MnO 003 005 004 005 009 010 018 012 003 001 003 003 005 007 008 007 MgO 149 131 215 145 377 362 447 307 033 014 037 035 121 158 176 151 249 067 322 287 336 596 538 088 090 090 117 222 375 421 385 CaO 076 Na2O 649 591 385 492 462 457 307 453 319 356 320 340 500 413 420 445 130 393 172 316 212 194 266 242 566 535 528 545 303 235 194 271 K2O 023 022 020 025 043 042 025 048 011 001 006 006 014 015 018 015 P2O5 LOI 132 124 126 066 206 210 115 111 053 058 052 054 143 085 106 077 Total 10047 9931 9916 9947 9925 9925 9929 9925 9923 9916 9931 9932 9947 9938 9939 9943 020 067 045 064 046 042 087 053 178 150 165 160 061 057 046 061 K2O/Na2O A/CNK 107 084 147 094 109 101 081 085 100 087 106 096 117 096 092 094 Mg# 529 470 588 461 505 507 468 460 314 280 358 360 457 454 456 446 Trace elements (ppm) 1211 1934 2982 3722 3528 3631 2270 966 379 829 895 1830 4090 4536 3990 Li 1355 P 1542 1343 888 1007 1855 1937 1061 2084 1007 94 236 252 527 615 730 591 K 10338 27220 16250 26080 19886 19450 24276 22580 39160 46560 41940 44480 24880 19466 16101 21700 Sc 514 491 505 564 1682 1879 2203 1443 263 138 235 205 484 893 1026 783 Ti 2984 2422 2976 2782 5614 5924 6017 5510 1575 575 1311 1298 2830 2650 2882 2530 V 4124 4494 3352 5702 13420 13044 18675 11348 1582 636 1505 13144 2362 6378 6835 6158 1195 2126 1399 2144 1366 3022 485 396 1114 1419 514 849 1972 2297 2154 Cr 1277 Co 615 617 704 871 1695 1673 2343 1605 128 082 184 174 489 994 1051 953 Ni 950 887 1473 1134 2424 1813 3316 1314 216 542 1111 282 456 1021 1108 1065 3384 59580 64460 53227 43760 705 1474 2994 553 1012 1963 764 2998 516 Cu 3696 3456 Zn 7290 4628 7640 9012 16060 12660 13406 12196 3224 3332 7932 4754 5562 6640 7193 6358 Ga 1346 1673 1294 2046 2354 2412 2223 2396 1522 1368 1622 1668 2056 1815 1874 1799 Rb 46 86 41 150 143 130 107 122 271 151 228 246 135 167 166 138 Sr 732 931 1117 1064 650 750 958 1251 230 259 213 241 384 457 472 452 1000 1580 1901 1715 1458 940 541 1580 1575 670 1708 2179 1511 Y 887 729 770 Zr 133 124 140 127 121 115 136 133 190 85 215 164 214 169 181 131 Nb 880 669 1074 677 1337 1627 1515 1238 2296 930 1611 1578 925 997 1242 927 Cs 026 077 028 353 149 136 359 308 130 135 131 148 174 501 549 435 Ba 447 1768 435 1431 283 280 362 449 537 424 570 575 755 704 504 937 2202 2414 2026 1597 2912 1970 6072 5350 3826 3540 3285 2874 2852 La 2886 2134 3512 Ce 5838 4224 6932 6126 5930 7062 6161 4706 6848 3662 12024 10300 6836 6750 6572 5634 Pr 703 506 811 768 894 1091 905 737 597 362 1116 1064 700 735 754 627 3900 4776 3662 3336 2014 1145 3458 3414 2318 2620 2819 2264 Nd 2758 1955 3000 2928


Table 2: Continued

Journal of Petrology, 2016, Vol. 57, No. 9 1787

Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U RREE Eu/Eu* (La/Yb)N Sr/Y DRb DTh DSr DY DNb


453 098 300 033 157 026 072 009 056 008 248 060 9 483 106 134 076 37 83 –877 –106 4492 –26 06

10XC02 TT XC

318 106 224 025 121 021 057 008 050 007 229 044 11 336 077 98 116 31 128 –177 –90 5247 –118 –37

10XC03 TT XC

479 110 320 035 166 028 076 010 061 008 310 074 8 742 099 155 081 41 145 –959 –83 8465 –29 28

11XC02 TT XC

494 139 351 041 200 036 098 013 083 011 301 040 18 638 138 141 097 25 106 454 –61 6642 –87 –35

12XC04 TT XC

734 157 517 061 311 055 148 020 122 016 291 085 18 174 052 151 074 13 41 757 –70 997 –124 05

11XC01-1 MME XC

891 194 630 075 377 066 177 024 146 019 264 123 18 184 056 179 075 12 39 579 –73 2164 –81 37

11XC01-2 MME XC

637 178 492 062 327 060 163 021 138 019 323 099 11 158 062 149 094 11 56 591 –53 3313 –158 09

11XC03 MME XC

668 134 490 058 293 051 137 017 108 014 315 085 18 172 056 123 068 11 86 610 –63 6731 –153 –10

11XC06 MME XC

324 055 222 030 168 031 099 016 118 017 410 202 25 2380 335 135 059 18 25 1234 70 18 14 157

10XC05 PG XC

168 037 127 016 086 017 053 008 063 011 275 076 26 5294 393 77 074 22 48 –91 349 811 06 29

11XC07 PG XC

529 082 393 052 289 056 168 026 180 027 558 102 48 4546 492 245 052 24 13 792 286 –108 80 89

12XC01 PG XC

544 084 403 053 292 056 166 025 173 025 456 109 43 4036 472 219 052 22 15 979 236 129 78 85

12XC02 PG XC


Table 2: Continued

340 113 264 029 140 025 067 009 055 009 517 057 16 973 090 147 111 50 57 333 –25 –278 –128 –12

12XC14 GD JHD

467 120 397 054 312 062 182 027 182 028 431 067 20 1003 200 155 083 14 27 558 –31 811 –02 01

12XC17 GD JHD

401 113 338 046 269 054 160 024 162 024 328 064 19 926 186 130 091 13 30 336 –32 510 –37 –10

12XC19 GD JHD

(continued)

530 119 463 066 385 078 230 034 232 035 455 081 19 984 1197 156 072 10 22 598 –28 790 35 23

12XC18 GD JHD


12XC20 GD JHD

Major elements (wt %) 6315 SiO2 046 TiO2 1672 Al2O3 518 Fe2O3T MnO 009 MgO 163 CaO 440 416 Na2O 232 K2O 017 P2O5 LOI 097 Total 9925 056 K2O/Na2O A/CNK 096 Mg# 423 Trace elements (ppm) Li 4760 P 734 K 21280 Sc 1109 Ti 3558 V 8052 Cr 2960 Co 1195 Ni 1419 Cu 927 Zn 7044 Ga 2142 Rb 164 Sr 564 Y 2102 Zr 181 Nb 1132 Cs 431 Ba 799 La 3460 Ce 6910 Pr 780 Nd 2872 Sm 529 Eu 140


6473 047 1539 508 008 186 411 428 210 018 113 9941 049 092 460 4840 705 17426 1118 3090 7242 6588 1128 3064 908 7430 1899 191 486 2098 159 1224 617 532 3396 6706 761 2822 525 126

3774 648 26260 959 2706 7654 2274 801 1078 725 8428 2262 239 404 2174 163 1374 514 876 4240 7948 860 3066 540 113

3652 811 13186 1044 3164 6420 2640 859 1440 933 8580 2374 155 566 2232 182 1838 402 254 2944 6036 698 2636 498 119

12XC23 GD JHD

6445 042 1625 461 009 113 382 422 314 016 115 9944 074 094 364

12XC22 GD JHD

6299 050 1639 460 013 174 513 503 162 021 110 9943 032 085 468

12XC21 GD JHD

2176 463 22280 820 3550 2986 893 510 569 511 6558 2008 147 331 791 148 1235 259 832 2544 3652 473 1635 278 115

6600 057 1721 381 006 109 199 447 278 012 132 9942 062 123 401

12XC24 GD JHD

2496 825 21660 1074 4554 1774 1027 533 490 1382 8768 1963 133 294 1343 121 2001 388 743 3092 6068 683 2472 453 111

6689 073 1540 459 008 114 308 360 274 022 091 9936 076 106 367

12XC25 GD JHD

2564 456 25140 727 2980 1502 795 396 512 897 5720 1835 130 248 1007 283 1110 295 875 5608 10336 1064 3516 502 129

6872 044 1481 385 006 094 189 444 295 011 117 9938 066 106 363

12XC27 GD JHD

2284 742 20740 966 3842 1795 966 462 479 904 7544 1946 121 304 1317 145 1727 306 672 3434 7018 742 2634 462 108

6769 061 1552 398 007 097 311 369 253 019 097 9933 069 107 362

12XC28 GD JHD

5564 1061 24100 2770 4674 22320 1034 2614 1046 8496 15666 2462 312 485 4034 118 1377 1046 228 2328 6070 864 3702 833 214

5206 064 1813 1025 019 345 604 441 273 025 155 9969 062 086 439

12XC15 MME JHD

3588 962 16164 2460 4118 20860 1189 2346 1046 7768 11636 2216 159 495 3260 123 1104 579 171 1850 4994 714 3024 658 207

5383 058 1769 947 019 312 695 459 187 023 100 9954 041 080 434

12XC16 MME JHD

1029 730 33880 281 1308 2314 1296 233 544 2250 4342 1761 165 307 520 135 620 472 1089 2686 4642 475 1618 232 064

7178 022 1474 192 002 070 047 415 484 007 094 9985 117 114 457

10XC08 PG HLD

7003 033 1505 182 001 042 032 238 768 016 126 9945 323 118 349 1129 641 64620 333 2184 2522 1756 353 770 1961 7592 1912 246 157 747 214 1260 357 1798 2880 5636 603 2080 327 086

1153 577 73895 333 2057 2958 2196 287 1017 283 8030 1847 251 61 902 222 997 432 1322 4423 8548 896 2989 453 106

12XC30 PG HLD

6969 035 1498 165 001 063 045 088 967 015 103 9948 1104 118 470

12XC29 PG HLD


Table 2: Continued

1195 386 68000 306 1371 2544 1981 142 609 414 9972 2032 258 157 517 131 881 310 1470 24 45 463 15 232 064

7145 020 1499 106 001 047 030 220 777 009 088 9941 354 119 506

12XC31 PG HLD

709 328 79220 287 1423 2324 1204 214 792 264 6416 1728 258 50 1117 134 984 381 1084 45 88 938 31 477 106

7150 023 1375 199 001 048 025 042 977 008 098 9944 2304 117 360

12XC33 PG HLD

(continued)

658 685 58760 387 2644 2838 457 654 1201 2130 12956 1597 207 71 997 249 1860 457 789 34 65 681 22 341 076

7232 041 1337 236 003 043 036 172 713 017 108 9937 416 120 299

12XC32 PG HLD

Journal of Petrology, 2016, Vol. 57, No. 9 1789

450 062 358 073 214 032 222 034 406 067 21 936 236 161 085 11 27 678 –22 1274 00 04

12XC20 GD JHD

431 061 358 075 228 036 254 040 452 117 42 865 303 144 077 8 25 600 –28 1263 11 74

12XC21 GD JHD 468 064 371 075 217 033 227 035 416 083 48 1170 400 183 067 13 19 1365 –05 –73 23 33

12XC22 GD JHD 455 064 371 075 222 033 227 034 399 083 21 971 199 158 077 11 23 876 –27 801 19 19

12XC23 GD JHD 259 032 170 031 077 009 057 009 348 073 39 524 071 93 129 32 42 369 –78 –495 –96 24

12XC24 GD JHD 411 052 278 052 135 017 097 014 304 123 16 750 066 139 077 23 22 182 –59 –683 –29 104

12XC25 GD JHD 400 045 221 039 101 013 084 014 667 062 13 1190 102 221 085 48 25 68 –25 –776 –40 21

12XC27 GD JHD 404 051 270 051 133 017 101 015 359 101 15 842 077 154 075 24 23 26 –54 –420 –22 80

12XC28 GD JHD 728 109 658 137 414 064 454 070 260 086 57 370 943 166 082 4 12 2719 –23 –1739 54 –10

12XC15 MME JHD 579 088 531 111 335 052 363 056 274 071 39 228 946 136 100 4 15 1099 –46 –1282 –01 –31

12XC16 MME JHD 164 018 084 015 042 006 042 006 268 045 9 773 119 101 095 46 59 257 –82 426 –51 –17

10XC08 PG HLD 324 038 190 035 094 014 090 014 509 061 13 2089 221 182 081 35 7 1230 60 –2450 –39 14

12XC29 PG HLD


246 028 139 027 078 012 083 014 489 079 12 922 182 122 088 25 21 1160 –58 –1426 –50 41

12XC30 PG HLD

179 021 105 019 056 009 064 011 338 053 14 2242 156 97 092 27 30 1209 67 –1144 –55 08

12XC31 PG HLD

268 035 192 037 109 017 116 019 620 120 20 1646 226 140 074 21 7 652 03 –1827 04 109

12XC32 PG HLD

358 044 227 041 111 015 097 014 333 061 14 2672 151 189 075 33 4 1201 110 –2205 05 19

12XC33 PG HLD

GG, gneissic granite; GT, gneissic tonalite; TT, tonalite–trondhjemite; MME, mafic magmatic enclave; PG, potassic granite; GD, granodiorite; TL, Taili; XC, Xingcheng; JHD, Juhuadao; HLD, Huludao. For X as any given element, DX ¼ X – (aSiO2 þ b); for Rb, a ¼ 5, b ¼ –220; for Th, a ¼ 05, b ¼ –20; for Sr, a ¼ –20, b ¼ 1700; for Y, a ¼ –125, b ¼ 100; for Nb, a ¼ –035, b ¼ 33 (Moyen et al., 2010).

Gd Tb Dy Ho Er Tm Yb Lu Hf Ta Pb Th U RREE Eu/Eu* (La/Yb)N Sr/Y DRb DTh DSr DY DNb


Table 2: Continued



1791

moderate positive Sr anomalies with relatively high Sr/ Y ratios of 39–86. Juhuadao granodiorites and MMEs. The granodiorite samples from Juhuadao are compositionally intermediate to felsic (Table 2), with high Na2O and thus lower K2O/Na2O (032–076), similar to the Xingcheng tonalite–trondhjemites (Table 2; Fig. 5d). They fall in the tonalite–trondhjemite–granodiorite field in the An–Ab– Or diagram (Fig. 5b), and have intermediate Y and Sr abundances. They are all enriched in LREE with significantly varying HREE depletion, thus giving varying (La/ Yb)N (8–50) (Fig. 7c). They have varying Eu/Eu* (067– 129) and an inverse Yb–SiO2 correlation (Table 2; figure not shown). In PM-normalized trace element patterns (Fig. 8c), they are enriched in LILE and depleted in Nb, Ta and Ti, with varying Sr/Y ratios (19–57). The MMEs in the Juhuadao granodiorites are mafic with relatively low SiO2 and high K2O/Na2O (041–062), consistent with the host granodiorite (Table 2; Fig. 5d). They have low TiO2, MgO, Cr, Ni, and Sr (Table 2; Fig. 6). In contrast to their host, they have flat LREE patterns with

high HREE and thus weak REE fractionation [(La/Yb)N 4], lower Sr/Y ratios (12–15), and no obvious Eu anomaly (Fig. 7c). In PM-normalized trace element patterns (Fig. 8c), they are depleted in some LILE (e.g. Th and U) and have negative anomalies of HFSE (Nb, Ta, Zr, Hf and Ti). Xingcheng and Huludao potassic granites. The potassic granites intruding the Xingcheng tonalite–trondhjemites have high SiO2, and are metaluminous to slightly peraluminous (Table 2; Fig. 5c), enriched in K2O (K2O/ Na2O ¼ 150–178; Fig. 5d), and fall in the granite field in the An–Ab–Or diagram (Fig. 5b). They have relatively low Cr, Ni, Y and Sr concentrations (Table 2; Fig. 6e and f). They have fractionated REE patterns [(La/Yb)N ¼ 18– 24] with negative Eu anomalies (Eu/Eu* ¼ 052–074) and concave HREE patterns (Fig. 7d). In PM-normalized trace element patterns (Fig. 8d), they are enriched in LILE and depleted in some HFSE such as Nb and Ti, but with no depletion of Zr and Hf. They are also depleted in Sr, with moderate Sr/Y ratios of 13–48 (Fig. 12b). The potassic granite samples from Huludao are peraluminous (Fig. 5c) and are strongly enriched in K2O, with


Fig. 5. (a) (Na2O þ K2O)–SiO2 diagram, (b) normative An–Ab–Or triangle (Barker, 1979), (c) A/NK–A/CNK diagram and (d) Na2O vs K2O for the Neoarchean TTG and potassic granitoids in the Xingcheng region. Grey fields are the fields of experimental metabasalt melts at 1–4 GPa, which are constructed using data from Sen & Dunn (1994), Rapp & Watson (1995), Rapp et al. (1999, 2002, 2003), ~ o Douce (2002) and references therein. Skjerlie & Patin

1792


Fig. 7. Chondrite-normalized REE patterns for the Neoarchean TTG and potassic granitoids in the Xingcheng region. The chondrite values are from Sun & McDonough (1989).


Fig. 6. Harker diagrams for the Neoarchean TTG and potassic granitoids in the Xingcheng region. (a) K2O–SiO2; (b) P2O5–SiO2; (c) TiO2–SiO2; (d) MgO–SiO2; (e) Y–SiO2; (f) Sr–SiO2. Grey fields are for experimental metabasalt melts at 1–4 GPa. Data sources are the same as for Fig. 5. The fields of slab-derived adakites and lower crust-derived adakitic rocks in (d) are after Wang et al. (2006). The dividing line between high-Sr and low-Sr series in (f) is from Moyen et al. (2007). Legends are the same as in Fig. 5.


1793

Table 3: Bulk-rock Nd isotopic compositions of the Neoarchean TTG and potassic granitoids in the Xingcheng region Sample

Lithology Location Sm Nd (ppm) (ppm)

13TL07 13TL08 11XC02 11XC04 11XC05 12XC04 11XC01-1 11XC01-2 11XC03 11XC06 11XC07 12XC01 12XC19 12XC20 12XC24 12XC27 12XC15 12XC16 12XC29 12XC30

GG GG TT TT TT TT MME MME MME MME PG PG GD GD GD GD MME MME PG PG

TL TL XC XC XC XC XC XC XC XC XC XC JHI JHI JHI JHI JHI JHI HLD HLD

960 1192 479 306 353 494 734 891 637 668 168 529 401 529 278 502 833 658 453 327

6108 7452 3000 2608 2733 2928 3900 4776 3662 3336 1145 3458 2264 2872 1635 3516 3702 3024 2989 2080

147

Sm/144Nd

143

00997 01015 01013 00744 00819 01070 01194 01184 01104 01270 00930 00971 01124 01168 01081 00907 01428 01380 00962 00998

Nd/144Nd 2r eNd(0) (143Nd/144Nd)i* eNd(t)* TDM1 TDM2 fSm/Nd (Ma) (Ma)

0511007 0511032 0511020 0510621 0510733 0511055 0511312 0511303 0511114 0511434 0510963 0510923 0511258 0511166 0511136 0510859 0511714 0511552 0510926 0510971

7 4 5 4 5 4 5 8 15 5 6 4 10 9 10 5 5 4 16 5

–318 –313 –316 –394 –372 –309 –259 –261 –297 –235 –327 –335 –269 –287 –293 –347 –180 –212 –334 –325

0509325 0509320 0509310 0509364 0509351 0509248 0509307 0509314 0509261 0509302 0509403 0509294 0509335 0509167 0509302 0509321 0509295 0509215 0509328 0509313

–02 –02 –04 06 03 –16 –07 –06 –17 –08 10 –11 10 –23 –02 01 –04 –19 –11 –14

2848 2859 2871 2752 2778 2975 2951 2936 2983 2996 2745 2892 2829 3099 2887 2821 3067 3194 2866 2897

2903 2911 2926 2841 2861 3023 2945 2935 3018 2954 2798 2968 2843 3106 2920 2892 2937 3063 2945 2969

–049 –048 –048 –062 –058 –046 –039 –040 –044 –035 –053 –051 –043 –041 –045 –054 –027 –030 –051 –049

*Calculated at zircon U–Pb ages GG, gneissic granite; TT, tonalite–trondhjemite; MME, mafic magmatic enclave; PG, potassic granite; GD, granodiorite; TL, Taili; XC, Xingcheng; JHD, Juhuadao; HLD, Huludao. Parameters used in the calculation are as follows: 147Sm decay k ¼ 654 1012 a1; (147Sm/144Nd)CHUR ¼ 01967; (143Nd/144Nd)CHUR ¼ 0512638; (147Sm/144Nd)DM ¼ 02137; (143Nd/144Nd)DM ¼ 051315.

elevated K2O/Na2O (117–2304; Fig. 5d). They have low Cr, Ni, Y and Sr abundances (Table 2; Fig. 6e and f). They have fractionated REE patterns [(La/Yb)N ¼ 21–46] and negative Eu anomalies (Eu/Eu* ¼ 074–095), with HREE patterns being flat to concave (Fig. 7d). In PM-normalized trace element patterns (Fig. 8d), they are enriched in LILE and depleted in Nb, Ta and Ti. They are strongly depleted in Sr with moderate Sr/Y ratios of 4–59.

Bulk-rock Nd isotopic compositions Bulk-rock Sm–Nd isotopic data for the Neoarchean TTG and potassic granitoids in the Xingcheng region are given in Table 3 and plotted in Fig. 9. Two Taili gneissic granite samples have uniform initial 143Nd/144Nd ratios (0509320–0509325) with eNd(t) values of –02 and twostage depleted mantle Nd model ages (TDM2) of 291– 290 Ga. Four Xingcheng tonalite–trondhjemite samples


Fig. 8. Primitive mantle (PM)-normalized trace element patterns for the Neoarchean TTG and potassic granitoids in the Xingcheng region. The values of PM are from Sun & McDonough (1989).

1794


DISCUSSION Fig. 9. eNd(t)–t diagram for the Neoarchean TTG and potassic granitoids in the Xingcheng region. It should be noted that the MMEs and their host TTG have overlapping eNd(t) values. The eNd(t) values of the potassic granitoids are also indistinguishable from those of the TTG granitoids. Legends are the same as in Fig. 5.

have a narrow range of initial 143Nd/144Nd ratios (0509248–0509364), with eNd(t) values from –16 to –06 and two-stage depleted mantle Nd model ages (TDM2) of 302–284 Ga. The MMEs within the Xingcheng tonalite– trondhjemites exhibit homogeneous initial 143Nd/144Nd ratios (0509261–0509314), with eNd(t) values of –17 to – 06 and TDM2 model ages of 302–294 Ga, essentially the same as their host. Four Juhuadao granodiorite samples have initial 143Nd/144Nd ratios of 0509167–0509335, with eNd(t) values from –23 to þ 10 and TDM2 model ages of 310–284 Ga. The MMEs contained within the Juhuadao granodiorites have uniform 143Nd/144Nd ratios (0509295–0509313), with eNd(t) values of –19 to –04 and TDM2 model ages of 306–294 Ga. The Xingcheng potassic granite samples have initial 143Nd/144Nd ratios of 0509313–0509403, with eNd(t) values of –14 to þ 10 and TDM2 ages of 297–280 Ga. The Huludao potassic granite samples show narrow ranges of initial 143 Nd/144Nd ratios (0509313–0509328), with eNd(t) values of –14 to –11 and TDM2 ages of 297–295 Ga.

Zircon Hf isotopic compositions Zircon Hf isotopic data for these Neoarchean granitoids are given in Table 4 and plotted in Figs 10 and 11. Zircons of the Taili gneissic granite (sample 10TL13) have a narrow range of initial 176Hf/177Hf ratios (0281207–0281277), with eHf(t) values of þ 20 to þ 73 and two-stage depleted mantle Hf model ages (TDM2) of 285–259 Ga, slightly younger than the Nd model ages. Zircons of the Xingcheng tonalite–trondhjemite (sample 10XC02) have uniform initial 176Hf/177Hf ratios of

Petrogenesis of Neoarchean TTG granitoids and MMEs TTG granitoids: partial melting of Mesoarchean enriched mafic crust at varying depths Even though exposed in different locations and showing large compositional variation from sodic tonalite–trondhjemite-granodiorites (the Xingcheng tonalite–trondhjemites and the Juhuadao granodiorites) to potassic gneissic tonalites (the Taili gneissic tonalites), the age and isotopic data (Tables 3 and 4; Figs 9– 11) suggest that the TTG granitoids in the Xingcheng region were emplaced contemporaneously and thus should share similar magma sources. The Neoarchean TTG granitoids in the Xingcheng region have relatively high SiO2 and low MgO, Cr and Ni contents, indicating a crustal source rather than being directly derived from the mantle (Table 2; Fig. 6d). They have bulk-rock eNd(t) values of –23 to 10 and Nd TDM2 model ages of 310–284 Ga (Table 3 and Fig. 9), and their zircons have positive eHf(t) values of 11–77 and Hf TDM2 ages of 289–262 Ga (Table 4 and Figs 10 and 11), pointing to a Mesoarchean (31–29 Ga) crustal source without the involvement of Paleo- to Eoarchean crustal materials (Fig. 11). Additionally, their major element compositions are similar to those of experimental metabasalt melts (Figs 5, 6 and 12c). However, Mesoarchean rocks in the eastern NCC are mainly TTG and to date no mafic magmatism has been reported. Some of the Mesoarchean TTG are characterized by negative zircon eHf(t) values (e.g. Tiejiashan granites in the Anshan area; Wan et al., 2007; Fig. 11), which is consistent with an origin by reworking of Paleo- to Eoarchean crustal materials, and cannot act as the sources of the Neoarchean TTG granitoids in the Xingcheng region. Some Mesoarchean TTG exhibit depleted zircon Hf isotopic compositions (e.g. Mesoarchean TTG in Eastern Shandong; Liu et al., 2013a; Wang et al., 2014b; Wu et al., 2014; Xie et al., 2014; Fig. 11), which are best


0281179–0281242, eHf(t) values of 11–33 and TDM2 model ages of 289–279 Ga. Zircons from the Juhuadao granodiorite (samples 12XC22 and 12XC28) have initial 176 Hf/177Hf ratios of 0281192–0281356, with eHf(t) values of 19–77 and TDM2 ages of 287–258 Ga. Zircons from the MMEs hosted within the Juhuadao granodiorite (sample 12XC15) have uniform initial 176Hf/177Hf ratios of 0281276–0281320, eHf(t) values of 48–63 and TDM2 model ages of 272–265 Ga. Zircons from the Xingcheng potassic granite (sample 10XC05) have homogeneous Hf isotopic compositions with initial 176 Hf/177Hf ratios of 0281165–0281261, eHf(t) values of 02–37 and TDM2 model ages of 292–276 Ga. Zircons from the Huludao potassic granite (sample 10XC08) have relatively large range of initial 176Hf/177Hf ratios from 0281175 to 0281301, eHf(t) values from 00 to þ 67 and TDM2 model ages of 291–257 Ga.


1795

Table 4: Zircon Hf isotopic compositions of the Neoarchean TTG and potassic granitoids in the Xingcheng region Spot t (Ma)

Yb/177Hf 2r

176

Lu/177Hf 2r

176

Hf/177Hf 2r

(176Hf/177Hf)i eHf(0) eHf(t) TDM1 (Ma) TDM2 (Ma) fLu/Hf

0021396 0010755 0017761 0034066 0021570 0025856 0021523 0038337 0022314 0034304 0025556 0024173 0026668 0024650 0030324

0000256 0000088 0000150 0000382 0000583 0000203 0000138 0001641 0000333 0000401 0000157 0000354 0000325 0000132 0000237

0000813 0000417 0000629 0001098 0000717 0000896 0000738 0001248 0000807 0001183 0000815 0000810 0000913 0000850 0001115

0000010 0000003 0000005 0000009 0000016 0000005 0000007 0000055 0000005 0000014 0000007 0000008 0000005 0000008 0000014

0281317 0281261 0281269 0281321 0281301 0281314 0281391 0281307 0281311 0281308 0281316 0281286 0281301 0281313 0281262

0000019 0000017 0000021 0000021 0000021 0000018 0000019 0000016 0000017 0000018 0000021 0000019 0000018 0000019 0000020

0281277 0281240 0281238 0281267 0281266 0281271 0281355 0281246 0281272 0281250 0281276 0281247 0281256 0281272 0281207

–515 –534 –532 –513 –520 –515 –488 –518 –517 –518 –515 –525 –520 –516 –534

45 32 31 42 41 43 73 34 43 36 45 34 38 43 20

2687 2734 2738 2701 2701 2695 2581 2730 2694 2724 2687 2728 2715 2693 2783

2724 2788 2792 2742 2743 2735 2588 2778 2733 2771 2725 2777 2760 2733 2846

–098 –099 –098 –097 –098 –097 –098 –096 –098 –096 –098 –098 –097 –097 –097

0028273 0035514 0030472 0049514 0025117 0023294 0012761 0021480 0032504 0015687 0040625 0025134 0028017 0027675 0014526

0001198 0000231 0000438 0000909 0000266 0000466 0000269 0000293 0001190 0000427 0001890 0000254 0000446 0000357 0000375

0001057 0001230 0001098 0001464 0000940 0000857 0000489 0000737 0001182 0000588 0001573 0000957 0001170 0001067 0000569

0000040 0000006 0000014 0000021 0000007 0000013 0000014 0000008 0000039 0000014 0000067 0000016 0000018 0000012 0000014

0281269 0281280 0281233 0281263 0281277 0281269 0281238 0281277 0281266 0281226 0281281 0281273 0281278 0281294 0281252

0000016 0000018 0000014 0000016 0000015 0000016 0000016 0000018 0000015 0000018 0000019 0000016 0000014 0000014 0000017

0281217 0281220 0281179 0281191 0281231 0281227 0281214 0281240 0281208 0281198 0281204 0281226 0281221 0281242 0281224

–532 –528 –544 –534 –529 –532 –543 –529 –533 –547 –527 –530 –528 –523 –538

25 25 11 15 29 28 23 33 21 17 20 27 25 33 27

2769 2766 2821 2807 2749 2755 2770 2735 2782 2793 2790 2756 2765 2735 2757

2828 2823 2894 2873 2803 2811 2834 2787 2844 2862 2851 2812 2822 2785 2816

–097 –096 –097 –096 –097 –097 –099 –098 –096 –098 –095 –097 –096 –097 –098

0045424 0057298 0072076 0041675 0043004 0043223 0079776 0053140 0016274 0026392 0038235 0058734 0064034 0054779 0033663

0002526 0001655 0006100 0002943 0000431 0004240 0005050 0003457 0000590 0001510 0001065 0003600 0006086 0003951 0001252

0001131 0001421 0001732 0001115 0001058 0001096 0001970 0001266 0000413 0000714 0000974 0001420 0001720 0001378 0000914

0000071 0000040 0000155 0000082 0000013 0000102 0000129 0000078 0000017 0000038 0000027 0000079 0000139 0000099 0000067

0281366 0281369 0281384 0281357 0281350 0281365 0281416 0281382 0281235 0281331 0281353 0281399 0281410 0281397 0281338

0000027 0000018 0000026 0000026 0000021 0000024 0000025 0000026 0000024 0000025 0000024 0000024 0000028 0000024 0000021

0281310 0281299 0281298 0281301 0281297 0281311 0281319 0281319 0281215 0281296 0281305 0281328 0281324 0281329 0281293

–497 –496 –491 –501 –503 –498 –479 –492 –543 –510 –502 –486 –482 –486 –507

66 62 62 63 62 66 69 69 32 61 64 73 71 73 60

2641 2657 2659 2653 2659 2640 2630 2629 2768 2660 2648 2616 2622 2616 2664

2654 2674 2675 2670 2677 2653 2639 2638 2821 2679 2663 2622 2629 2621 2684

–097 –096 –095 –097 –097 –097 –094 –096 –099 –098 –097 –096 –095 –096 –097

0037577 0044263 0044736 0045870 0041565 0035079 0028076 0043964 0053367 0045096 0047215 0052082 0029177 0028390 0026413

0004067 0007510 0002953 0003312 0003475 0003813 0001309 0002386 0002264 0003187 0006264 0003416 0000996 0001213 0002856

0001080 0001136 0001145 0001274 0001159 0001051 0000762 0001256 0001378 0001354 0001410 0001520 0000791 0000855 0000759

0000162 0000198 0000109 0000064 0000117 0000094 0000064 0000044 0000112 0000141 0000228 0000067 0000058 0000067 0000122

0281372 0281381 0281359 0281326 0281249 0281369 0281345 0281364 0281423 0281391 0281406 0281388 0281360 0281384 0281324

0000022 0000028 0000023 0000062 0000105 0000029 0000021 0000099 0000034 0000029 0000044 0000048 0000029 0000048 0000025

0281319 0281325 0281302 0281263 0281192 0281318 0281307 0281302 0281356 0281324 0281337 0281313 0281321 0281342 0281287

–495 –492 –500 –512 –539 –496 –505 –498 –477 –488 –483 –489 –499 –491 –512

64 67 58 44 19 64 60 58 77 66 71 62 65 73 53

2630 2621 2653 2707 2804 2631 2645 2653 2580 2622 2605 2638 2627 2598 2673

2646 2635 2675 2744 2868 2648 2666 2676 2581 2636 2614 2655 2642 2605 2702

–097 –097 –097 –096 –097 –097 –098 –096 –096 –096 –096 –095 –098 –097 –098

0037806 0038547 0062136 0070345 0076301

0004644 0001917 0004203 0007137 0007758

0001049 0000931 0001484 0001647 0002049

0000133 0000039 0000089 0000162 0000218

0281344 0281359 0281368 0281401 0281377

0000021 0000021 0000022 0000030 0000020

0281293 0281314 0281295 0281320 0281276

–505 –500 –497 –485 –493

54 61 55 63 48

2665 2637 2664 2630 2691

2693 2657 2689 2646 2722

–097 –097 –096 –095 –094

(continued)


10TL13 1.1 2558 2.1 2558 3.1 2558 4.1 2558 5.1 2558 6.1 2558 7.1 2558 8.1 2558 9.1 2558 10.1 2558 11.1 2558 12.1 2558 13.1 2558 14.1 2558 15.1 2558 10XC02 1.1 2559 2.1 2559 3.1 2559 4.1 2559 5.1 2559 6.1 2559 7.1 2559 8.1 2559 9.1 2559 10.1 2559 11.1 2559 12.1 2559 13.1 2559 14.1 2559 15.1 2559 12XC22 1.1 2595 2.1 2595 3.1 2595 4.1 2595 5.1 2595 6.1 2595 7.1 2595 8.1 2595 9.1 2595 10.1 2595 11.1 2595 12.1 2595 13.1 2595 14.1 2595 15.1 2595 12XC28 1.1 2573 2.1 2573 3.1 2573 4.1 2573 5.1 2573 6.1 2573 7.1 2573 8.1 2573 2573 9.1 10.1 2573 11.1 2573 12.1 2573 13.1 2573 14.1 2573 15.1 2573 12XC15 1.1 2568 2.1 2568 3.1 2568 4.1 2568 5.1 2568

176

1796


Table 4: Continued Spot t (Ma)

Yb/177Hf 2r

176

Lu/177Hf 2r

176

Hf/177Hf 2r

(176Hf/177Hf)i eHf(0) eHf(t) TDM1 (Ma) TDM2 (Ma) fLu/Hf

0060050 0039128 0033227 0081032 0064137 0058328 0051725 0039231 0060534

0001087 0000571 0000641 0007512 0004769 0008839 0003568 0000797 0003153

0001464 0000972 0000862 0002283 0001570 0001662 0001352 0001054 0001451

0000026 0000016 0000024 0000219 0000111 0000240 0000081 0000019 0000066

0281364 0281328 0281330 0281395 0281374 0281359 0281357 0281340 0281379

0000021 0000019 0000023 0000033 0000028 0000031 0000021 0000022 0000023

0281292 0281280 0281287 0281283 0281297 0281278 0281291 0281289 0281308

–498 –511 –510 –487 –494 –500 –500 –506 –493

54 49 52 50 55 48 53 52 59

2668 2682 2672 2683 2661 2688 2669 2671 2645

2694 2715 2702 2710 2685 2720 2696 2700 2666

–096 –097 –097 –093 –095 –095 –096 –097 –096

0026440 0022417 0060909 0027440 0042667 0042172 0024619 0040373 0035771 0045724 0019801 0041392 0067286 0029115 0082453

0000521 0000499 0001075 0000169 0001063 0000970 0001694 0000296 0000697 0000515 0000175 0000277 0001685 0000116 0001516

0000659 0000568 0001205 0000599 0000995 0001071 0000582 0000916 0001051 0001042 0000451 0000834 0001300 0000570 0001588

0000012 0000013 0000016 0000003 0000021 0000021 0000037 0000008 0000021 0000011 0000005 0000005 0000029 0000003 0000018

0281204 0281213 0281294 0281260 0281227 0281313 0281216 0281223 0281275 0281233 0281251 0281258 0281228 0281270 0281313

0000028 0000023 0000026 0000024 0000025 0000021 0000024 0000023 0000018 0000020 0000022 0000025 0000025 0000023 0000025

0281172 0281185 0281236 0281231 0281179 0281261 0281188 0281178 0281224 0281182 0281229 0281218 0281165 0281242 0281235

–555 –551 –523 –535 –546 –516 –550 –548 –529 –544 –538 –535 –546 –531 –516

05 10 28 26 07 37 11 07 23 09 25 21 02 30 27

2828 2809 2745 2748 2821 2709 2805 2821 2760 2816 2749 2767 2842 2733 2747

2912 2888 2800 2809 2900 2756 2883 2901 2821 2893 2811 2831 2924 2789 2801

–098 –098 –096 –098 –097 –097 –098 –097 –097 –097 –099 –097 –096 –098 –095

0056771 0030677 0033572 0052554 0031436 0025497 0044377 0036333 0051620 0046460 0024366 0049782 0056384 0135431 0033383 0053345 0112112 0056625 0066692

0000951 0000956 0000340 0001893 0001854 0000282 0000628 0001111 0001260 0000272 0001238 0000379 0000961 0002583 0000407 0000302 0001007 0001730 0001562

0001237 0000675 0000786 0000990 0000638 0000561 0000849 0000799 0001077 0000993 0000539 0001058 0001097 0002276 0000673 0001074 0002057 0001038 0001128

0000017 0000024 0000012 0000026 0000035 0000007 0000005 0000024 0000016 0000003 0000025 0000006 0000021 0000027 0000007 0000010 0000013 0000015 0000030

0281360 0281239 0281294 0281340 0281270 0281279 0281309 0281240 0281227 0281291 0281248 0281300 0281243 0281473 0281301 0281352 0281354 0281289 0281238

0000022 0000023 0000026 0000023 0000023 0000022 0000022 0000025 0000026 0000022 0000023 0000024 0000023 0000024 0000020 0000024 0000030 0000023 0000025

0281301 0281206 0281256 0281293 0281239 0281252 0281268 0281201 0281175 0281243 0281222 0281249 0281190 0281364 0281269 0281300 0281255 0281239 0281183

–499 –542 –523 –506 –531 –528 –517 –542 –546 –524 –539 –521 –541 –459 –520 –502 –501 –525 –543

45 11 29 42 23 28 33 10 00 25 17 27 05 67 33 45 29 23 03

2657 2782 2716 2667 2738 2720 2699 2789 2827 2734 2760 2726 2807 2572 2698 2656 2724 2740 2817

2695 2860 2773 2709 2802 2780 2751 2868 2913 2795 2832 2785 2888 2584 2751 2695 2775 2803 2900

–096 –098 –098 –097 –098 –098 –097 –098 –097 –097 –098 –097 –097 –093 –098 –097 –094 –097 –097

a

Calculated at zircon U–Pb ages. Parameters used in the calculation are as follows: 176Lu decay k ¼ 1867 1011 a1; average continental crust 176Lu/177Hf ¼ 0015; 176 ( Lu/177Hf)CHUR ¼ 00332; (176Hf/177Hf)CHUR ¼ 0282772; (176Lu/177Hf)DM ¼ 00384; (176Hf/177Hf)DM ¼ 028325.

explained as resulting from melting of mantle-derived basaltic materials of Mesoarchean age. This would point to the existence of Mesoarchean juvenile mafic magmatism in the eastern NCC. Furthermore, the wide range of SiO2 contents of the Neoarchean TTG granitoids and their MMEs required a mafic precursor instead of felsic sources like TTG. All these observations and inferences indeed suggest that the Neoarchean TTG granitoids in the Xingcheng region must have been derived from Mesoarchean juvenile mafic crustal sources. The Neoarchean TTG granitoids in the Xingcheng region show large major and trace element compositional variation, with enrichment of LILE (e.g. Rb, Ba and Sr) and depletion of HFSE (e.g. Nb, Ta and Ti) (Figs 5–9). As suggested previously (e.g. Moyen et al., 2007, 2010), the compositions of TTG are mainly controlled by the source

compositions and the pressures or depths of melting. The enrichment of LILE (Figs 6a and 8) and relatively higher K2O/Na2O of the studied TTG granitoids suggest that their Mesoarchean juvenile mafic sources should be more enriched than those of the typical sodic TTG (typical Archean TTG K2O/Na2O ¼ 035; Moyen & Martin, 2012; Fig. 5d). Therefore, the Neoarchean TTG granitoids in the Xingcheng region are probably derived from Mesoarchean mafic crustal rocks that are more enriched than the present-day mid-ocean ridge basalt (MORB) [enriched (E)-MORB-like?] (Smithies, 2000; Qian & Hermann, 2013). An enriched mafic source has also been proposed to explain the compositions of TTG in other Archean cratons (e.g. Champion & Smithies, 2007; Moyen et al., 2007; Smithies et al., 2009). In addition, most Archean mafic magmatic rocks are characterized


6.1 2568 7.1 2568 8.1 2568 9.1 2568 10.1 2568 11.1 2568 12.1 2568 13.1 2568 14.1 2568 10XC05 1.1 2545 2.1 2545 3.1 2545 4.1 2545 5.1 2545 6.1 2545 7.1 2545 8.1 2545 9.1 2545 10.1 2545 11.1 2545 12.1 2545 13.1 2545 14.1 2545 15.1 2545 10XC08 1.1 2520 2.1 2520 3.1 2520 4.1 2520 5.1 2520 6.1 2520 7.1 2520 8.1 2520 9.1 2520 10.1 2520 11.1 2520 12.1 2520 13.1 2520 14.1 2520 15.1 2520 16.1 2520 17.1 2520 18.1 2520 19.1 2520

176


1797

by somewhat enriched trace element signatures (Jahn et al., 1980; Condie, 2005a; Hollings & Kerrich, 2006; Moyen & Martin, 2012; van Hunen & Moyen, 2012). It should be noted that to accurately determine the nature and the enrichment mechanism of the Mesoarchean enriched mafic crustal rocks is not straightforward because no Mesoarchean mafic magmatism has been reported in the eastern NCC. It is possible that the enrichment reflects a prior mantle source metasomatism caused by recycled even earlier crustal components (Smithies et al., 2009). The Xingcheng tonalite-trondhjemites, the Taili gneissic tonalites and some of the Juhuadao granodiorites are characterized by high (La/Yb)N and Sr/Y ratios and thus plot in the TTG–adakite field in the (La/Yb)N– (Yb)N and Sr/Y–Y diagrams (Fig. 12a and b), suggesting the presence of garnet as a residual phase in the magma source region. They all have positive or slightly negative Eu anomalies and belong to the high-Sr series defined by Moyen et al. (2007), implying that there was

no or little plagioclase left in the magma sources (Fig. 7). In Fig. 13, the pressure-controlled DX parameters on the vertical axes for these samples suggest that they were formed at higher pressures than the other samples, reflecting the presence or absence of some pressure-sensitive minerals such as garnet, plagioclase and rutile in the magma sources (Moyen et al., 2010). Thus these samples were most probably derived from mafic crustal sources at relatively high pressures (10– 12 kbar), with garnet and amphibole present as residual phases with little or no plagioclase (Rapp et al., 1991; Sen & Dunn, 1994; Qian & Hermann, 2013). Geochemical modeling illustrated in Fig. 12a shows that they could be generated by 10–25% partial melting of a mafic crustal source (E-MORB-like) with varying proportions of garnet. Thus, the appropriate source lithology for samples with high Sr/Y and (La/Yb)N ratios is likely to be garnet amphibolite rather than eclogite. These samples should correspond to the medium-pressure group of TTGs defined by Moyen (2011).


Fig. 10. Histograms of eHf(t) values for the zircons from the Neoarchean TTG and potassic granitoids in the Xingcheng region. It should be noted that the eHf(t) values of zircons from the Taili gneissic granite and the Xingcheng tonalite–trondhjemite are similar. The same goes for the Juhuadao granodiorite and the hosted MMEs; their eHf(t) values are slightly higher than those of the the Taili gneissic granite and the Xingcheng tonalite–trondhjemite. The eHf(t) values of zircons from the Xingcheng potassic granites are similar to those of the Huludao potassic granites.

1798

In contrast, other samples of the Juhuadao granodiorites are distinct in having lower Sr, Sr/Y and (La/Yb)N, higher Y, and negative Eu and Sr anomalies (Fig. 6e and f), plotting in the field of typical arc rocks in (La/ Yb)N–(Yb)N and Sr/Y–Y diagrams (Fig. 12a and b). However, they are similar to samples with high Sr/Y and (La/Yb)N ratios in terms of major elements and bulk-rock Nd and zircon Hf isotopic compositions. Thus, they may be derived from a similar Mesoarchean mafic crustal source, but at lower pressures ( 1) was a liquidus phase; (2) crystallization of garnet from TTG magmas needs a high-pressure condition over 14 kbar (e.g. Adam et al., 2012; Hoffmann et al., 2014; Song et al., 2014); (3) in partial melts (usually tonalitic) of mafic rocks, as calculated by Hoffmann et al. (2014), the potential of garnet as a fractionating phase is limited. Therefore, low-pressure (30 Ga) sources were involved in their genesis. All zircons from these rocks have positive eHf(t) and fall between the evolution lines of the depleted mantle and CHUR in the eHf(t)–t diagram (Fig. 11), distinct from those from the Early Archean rocks in the NCC (Wu et al., 2005a), again pointing to more juvenile crustal sources compared with the Paleo- to Eoarchean crustal sources. Many studies have shown that the Archean basement rocks in


Experimental investigations have suggested that low degrees of partial melting (