Middle Neoarchean magmatism in western Shandong, North China Craton: SHRIMP zircon dating and LA-ICP-MS Hf isotope analysis

Precambrian Research 255 (2014) 865–884

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Middle Neoarchean magmatism in western Shandong, North China Craton: SHRIMP zircon dating and LA-ICP-MS Hf isotope analysis Yusheng Wan a,b,∗ , Chunyan Dong a , Shijin Wang c , Alfred Kröner a , Hangqiang Xie a , Mingzhu Ma a , Hongying Zhou d , Shiwen Xie a , Dunyi Liu a a

Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China State Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China c Shandong Geological Survey Institute, Jinan 250013, China d Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China b

a r t i c l e

i n f o

Article history: Received 6 December 2013 Received in revised form 30 June 2014 Accepted 26 July 2014 Available online 4 August 2014 Keywords: Neoarchean Granitoids SHRIMP zircon dating Hf-in-zircon isotopes Shandong Province North China Craton

a b s t r a c t Western Shandong Province is a typical area of the North China Craton (NCC) where Neoarchean plutonic and supracrustal rocks are widely distributed. Early studies documented that ∼2.7 Ga and ∼2.5 Ga magmato-tectono-thermal events are well developed in the area. Here we report SHRIMP U–Pb ages and Hf-in-zircon isotopic data from ten samples of different magmatic rock types including hornblendite, gneissic tonalite, gneissic trondhjemite and gneissic granite. Magmatic zircon grains have 207 Pb/206 Pb ages ranging from 2667 to 2598 Ma. Some rocks contain ∼2.5 Ga metamorphic rims and ∼2.7 Ga zircon cores. The magmatic zircon grains have εHf (t) values and Hf crustal model ages of −1.1 to +11.3 and 3.02–2.4 Ga, respectively. Combined with an earlier study, our main conclusions are that the middle Neoarchean rocks mainly occur together with early Neoarchean rocks in the northeastern portion of the central belt. Juvenile additions to continental crust and crustal recycling played important roles in the middle Neoarchean of western Shandong Province, and the entire Neoarchean tectonic evolution can be divided into middle to early Neoarchean (2.75–2.6 Ga) and late Neoarchean (2.6–2.5 Ga) events. © 2014 Elsevier B.V. All rights reserved.

1. Introduction The Neoarchean appears to have been an important period for global formation of continental crust (Condie et al., 2009; Condie and Aster, 2010). Compared with the late Neoarchean (2.6–2.5 Ga), the early Neoarchean (2.8–2.7 Ga) was a more important period for crust formation. At around 2.7 Ga, juvenile additions from mantle sources as well as crustal recycling played significant roles worldwide during these magmato-tectono-thermal events as indicated by whole-rock Nd and zircon Hf isotopic studies (Ayer and Dostal, 2000; Belousova et al., 2010; Condie and Aster, 2010; Griffin et al., 2004; Guitreau et al., 2012; Halla, 2005; Henry et al., 1998; Kovalenko et al., 2005). It would appear that global major magmato-tectono-thermal events were more extensive in the middle Neoarchean (2.7–2.6 Ga) than in the late Neoarchean (Fig. 1a). The North China Craton (NCC) is characterized by widespread late Neoarchean (mainly 2.55–2.5 Ga) tectono-thermal events,

∗ Corresponding author at: Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China. Tel.: +86 10 68999762. E-mail address: [email protected] (Y. Wan). http://dx.doi.org/10.1016/j.precamres.2014.07.016 0301-9268/© 2014 Elsevier B.V. All rights reserved.

which resulted in the formation of supracrustal and magmatic rocks as a result of juvenile additions to the continent and reworking of older continental material (Diwu et al., 2010, 2011; Dong et al., 2012a; Geng et al., 2012; Jian et al., 2012; Kröner et al., 2005a, 2005b; Liu et al., 2009; Ma et al., 2013; Shen et al., 2005; Wan et al., 2010a, 2011a; Wang and Liu, 2012; Wu et al., 2005; Wilde et al., 2005; Zhao et al., 2002; Zhai and Santosh, 2011). Such events occurred only in a few areas on other cratons such as southern India, Antarctica, Brazil and northwestern Australia (Clark et al., 2009; Condie et al., 2005; Druppel et al., 2009; Jayananda et al., 2000; Veevers and Saeed, 2009). Recent studies have revealed that, similar to many other cratons, the NCC also experienced its main period of crustal growth in the late Mesoarchean to early Neoarchean (mainly 2.85–2.7 Ga) (Dong et al., 2012b; Han et al., 2012; Jahn et al., 2008; Jiang et al., 2010; Kröner et al., 2005a, 2005b; Lu et al., 2008; Ma et al., 2013; Wan et al., 2010b, 2011b, 2014; Yang et al., 2013; Zhu et al., 2013). Middle Neoarchean (2.7–2.6 Ga) tectono-thermal events were so far recorded only in a few areas of the NCC, including Zhongtiaoshan, Hebi and western Shandong Province (WSP) (Cao, 1996; Lu et al., 2008; Zhang et al., 2012; Zheng et al., 2012). It is uncertain how strong the middle Neoarchean event was and what the relationship was between the middle and early Neoarchean

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Fig. 1. Histograms showing distribution of magmatic zircon ages. (a) Worldwide (simplified after Condie and Aster, 2010), the detrital ancient sediment database is multiplied by two for comparative purposes and (b) North China Craton (Wan et al., 2011a).

events. We report SHRIMP U–Pb ages and Hf-in-zircon isotopic data for various magmatic rocks of middle Neoarchean age in the WSP, indicating that this event may also be widespread in the NCC, whereas the ∼2.6 Ga tectono-thermal event may have been a final phase in a long evolution from 2.75 to 2.6 Ga. 2. Geological background The WSP is located in the eastern NCC and is an area where Neoarchean magmatic rocks (mainly granitoids) and supracrustal assemblages are widely distributed, constituting the WSP granitegreenstone terrane, with a total area of ∼10,000 km2 (Fig. 2). Based on numerous studies, great progress on understanding the Archean geology of the WSP have been made (Cao, 1996; Cheng et al., 1977; Du et al., 2003, 2005, 2010; Jahn et al., 1988; Jiang et al., 2010; Lu et al., 2008; Peng et al., 2012; Polat et al., 2006; Wan et al., 2010a, 2011b, 2012; Wang et al., 2008, 2009a, 2013a, 2013b; Zhang et al., 1998, 2001; Zhuang et al., 1997) which we briefly summarize below. (1) The WSP granite–greenstone belt extends roughly in a northwest-southeast direction and is truncated by the huge Tanlu Strike-Slip Fault in the east. Based on formation ages and rock types, the WSP can be divided into three belts: a late Neoarchean crustally derived granite belt in the northeast that consists predominantly of 2525–2490 Ma monzogranite and syenogranite and banded gneisses (Belt A), a middle to early Neoarchean belt in the center which is mainly composed of 2.75–2.60 Ga TTGs and supracrustal rocks (Belt B), and a late Neoarchean belt of juvenile rocks in the southwest that is dominated by granodiorite, gabbro, quartz diorite and tonalite, with some monzogranite and syenogranite (Belt C). (2) Supracrustal rocks of the Taishan “Group” were once considered to have formed in the early Neoarchean (we use the terms “group” and “formation” with quotation marks since these are not lithopstratigraphic terms and refer to Wan et al. (2006) for discussion of this issue). However, contrary to earlier opinion, zircon dating has revealed that the Shancaoyu “Formation” and the upper part of the Liuhang “Formation” of the Taishan “Group” were deposited in the late Neoarchean (2.55–2.525 Ga), and not in the early Neoarchean (2.8–2.7 Ga). Also, the Jining “Group” was deposited in the late Neoarchean (2.55–2.525 Ga) and not in the early Paleoproterozoic (∼1.8 Ga). The WSP is currently the only terrane in the NCC where both early and late Neoarchean supracrustal rocks have been identified. The early Neoarchean supracrustal rocks, named

the Yanlingguang-Liuhang succession, include the original Yanlingguang “Formation” and the lower part of the Liuhang “Formation” of the Taishan “Group” and the Mengjiatun “Formation”. They mainly occur in Belt B and consist of amphibolite and meta-ultramafic rocks with a few clastic metasedimentary layers. Some meta-ultramafic rocks show spinifix textures, and some amphibolites show massive or pillow structures. Most amphibolites are similar in composition to MORB. (3) The late Neoarchean supracrustal rocks, named the ShancaoyuJining succession, include the original Shancaoyu “Formation” and the upper part of the Liuhang “Formation” of the Taishan “Group” and the Jining“Group” and occur in all three belts and consist mainly of fine-grained biotite gneiss, conglomerate, BIF and felsic metavolcanic rocks. Metasedimentary rocks show bedding with interlayered coarse-grained and fine-grained sandstone or fine-grained sandstone and pelitic siltstone. There are three potential sources for the late Neoarchean supracrustal rocks. (1) Intrusive late Neoarchean rocks which are represented by granitoids and minor gabbro in Belt C; (2) the middle to early Neoarchean basement in Belt B provided detritus containing zircon grains older than 2.6 Ga; (3) late Neoarchean volcanic rocks have the same ages as the intrusive rocks. (4) The WSP is the largest area within the NCC where early Neoarchean (mainly 2.75–2.7 Ga) rocks have been identified, with a total area up to 500 km2 . This is the main evidence that the NCC is similar to many other cratons worldwide where magmato-tectono-thermal events of the early Neoarchean are well developed. The early Neoarchean magmatic rocks are mainly composed of TTGs and quartz diorite, occurring at different scales, with some intruding the Yanlingguang-Liuhang succession as veins. They commonly underwent significant metamorphism and deformation, resulting in local anatexis, due to ∼2.6 Ga and ∼2.5 Ga overprinting. More work is required to further determine the spatial relationship and relative proportion of the early and middle Neoarchean TTGs. (5) The late Neoarchean magmatic rocks have zircon ages between 2560 and 2480 Ma. Rocks formed during the first phase (2560–2525 Ma) include gabbro, quartz diorite, granodiorite, tonalite, monzonite, quartz monzonite and syenogranite that are significantly deformed and metamorphosed. In contrast, similar rock associations formed during the second phase (2525–2480 Ma) are undeformed or only weakly deformed. This change suggests that the tectonic regime in the WSP changed from compression to extension between 2530 and 2520 Ma, a period when the magmatic activity reached a peak.

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Fig. 2. Geological map of the early Precambrian Taishan-Xintai area, western Shandong Province, modified after RGSSP (1991, 2003, 2008), Cao (1996) and Wan et al. (2010a, 2011b, 2012). Insets (a) and (b) show the study area and the early Precambrian geological distribution in western Shandong Province. Also shown are sample locations of this study and previous work.

(6) Magmatic zircon from most early Neoarchean (2.75–2.7 Ga) supracrustal and granitoid rocks shows high initial εHf values (+4.5 to +9.7), suggesting that their protoliths were derived from depleted mantle sources and that continental crust was mainly formed during the early Neoarchean. However, more ancient continental basement should exist at depth, as indicated by negative εHf (t) values (down to −15) in zircon from some granitoid rocks. On the other hand, most late Neoarchean (2.55–2.5 Ga) crustally derived granites have whole-rock Nd and magmatic Hf-in-zircon depleted mantle model ages of 2.9–2.7 Ga (our unpublished data), suggesting that reworking of early Neoarchean to late Mesoarchean continental material

played an important role in the late Neoarchean tectonothermal event. (7) The widespread late Neoarchean plutonic and supracrustal rocks were probably generated in an arc environment. Sanukitoids and high-SiO2 adakites have been identified. The deformed juvenile rocks represent products of the first phase of arc evolution (2560–2525 Ma), whereas the undeformed and weakly deformed magmatic rocks are considered to have formed as a result of magmatic underplating during a later phase involving arc collapse (2525–2480 Ma). The spatial distribution of the different magmatic rocks suggests that subduction was from southwest to northeast.

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3. Sampling and petrography

3.4. Gneissic trondhjemite (SY0335A, N36◦ 15 28 , E117◦ 04 25 )

3.1. Hornblendite (S1144, N36◦ 22 42 , E117◦ 16 47 )

This sample was taken from Caishixi, Taishan (Fig. 2c). In the outcrop, felsic veins cut amphibolite (Fig. 3e). The protolith of the amphibolite is uncertain (intrusive or volcanic) due to metamorphism and deformation, but it should be magmatic in origin because of its homogeneous appearance. Zircon from the amphibolite records an age of 2678 ± 27 Ma (Lu et al., 2008). The zircon underwent strong recrystallization, and original textures cannot be easily observed, so the age may limit the youngest formation age of the mafic rock if the zircon is of magmatic origin. The felsic veins are trondhjemitic in composition, show anatectic features and are cut by 2.5 Ga monzogranite veins (Fig. 3f). The dated trondhjemite is composed of plagioclase and quartz, with a few grains of biotite and epidote. Some plagioclase grains show polysynthetic twinning, with many being altered to sericite and epidote. Some quartz grains are oriented as aggregates.

Pyroxenite–hornblendite are widely distributed in ∼2.7 Ga tonalite–trondhjemite–granodiorite (TTG) plutons of Belt B and in ∼2.5 Ga gneissic granodiorite of Belt C, with some isolated bodies with large scales occurring and extending in a northwest–southeast direction (Fig. 2c). These commonly show a gneissic and coarsegrained structure and are mainly composed of clinopyroxene and hornblende; both show large variations in minerasl content, and the latter is considered to mainly be a result of retrogression of the former. Their protoliths are of magmatic origin as a result of accumulation of clinopyroxene and hornblende, but their origin and formation age, which was considered to be ∼2.7 (Cao, 1996), is uncertain. Sample S1144 was taken from a large ultramafic body in ∼2.7 Ga TTG rocks southwest of Qixingtai (Fig. 2c). It shows a gneissic structure and is almost completely composed of coarsegrained hornblende (Fig. 3a). At the sampling location, felsic veins of unknown age cut the hornblendite. 3.2. Mylonitized tonalite (S0722, N35◦ 44 08 , E117◦ 45 47 ) In the Panchegou area, the late Neoarchean ShancaoyuJining succession in the northeast and the early Neoarchean Yanlingguang-Liuhang succession in the southwest have a tectonic contact (Wan et al., 2012). In the southwestern portion of the Yanlingguang-Liuhang succession, there are strongly deformed felsic rocks, from which an age of 2.70 Ga has been obtained for zircon with magmatic zoning. The felsic rock was originally considered to be a mylonitized supracrustal rock (fine-grained biotite gneiss, Wan et al., 2011b, 2012). However, further observation revealed that it is homogeneous and contains feldspar porphyroclasts, suggesting a mylonitized 2.70 Ga trondhjemite. On the southwest side of the trondhjemite, ∼2.6 Ga tonalite is widely distributed. Sample S0722 was taken in the west of Panchegou (Fig. 2c). It shows strong deformation (Fig. 3b), with foliation being parallel to that of the 2.70 Ga trondhjemite and 2.75–2.52 Ga supracrustal rocks. Around the outcrop there are light felsic veins that also display strong deformation with some showing complex folding (Fig. 3c). The tonalite mainly comprises plagioclase, quartz and biotite, and four domains can be identified in thin section: (1) fine-grained plagioclase + quartz + biotite aggregates, (2) oriented biotite aggregates, (3) oriented quartz aggregates showing undulose extinction, and (4) plagioclase porphyroclasts with or without polysynthetic twinning. 3.3. Gneissic tonalite (S1028, N36◦ 11 15 , E118◦ 38 25 ) In the northeastern portion (Belt A) of the WSP granite–greenstone belt, anatexis is well developed and resulted in the formation of ubiquitous ∼2.5 Ga granites (Wan et al., 2010a). Sample S1028 was taken from Yishan (Fig. 2b), a typical area of anatectic rocks (migmatites). In this area, older rocks, mainly including TTG and amphibolite, occur as enclaves at different scales in anatectic rocks. The dated sample was from a tonalite enclave that shows partial melting (Fig. 3d), but the sample contains no leucosome. The tonalite shows a gneissic structure and is composed of plagioclase, quartz, biotite, hornblende and a few microcline and opaque minerals. Microcline commonly occurs in small grains between other minerals and is considered to have formed during anatexis. More work is required to identify the dark minerals, but they seem to be transformed from biotite and hornblende during anatexis in terms of textural features because the dark minerals commonly occur together with biotite and hornblende.

3.5. Gneissic trondhjemite (S0726, N36◦ 24 11 , E117◦ 20 02 ) In the Qixingtai-Dawangzhuang area, both the early Neoarchean Yanlingguang-Liuhang succession (in the west) and late Neoarchean Shancaoyu-Jining succession (in the east) extend roughly in a south-north direction (Fig. 2c). The YanlingguangLiuhang succession is cut by ∼2.7 Ga trondhjemite and tonalite veins (Wang et al., 2009b; Y.S. Wan, unpublished data). Gneissic tonalite, ∼2.7 Ga in age, occurs as a narrow belt between the early to late Neoarchean supracrustal rocks and the ∼2.6 Ga gneissic trondhjemite that is widely exposed in the west (Fig. 2c, RGSSP, 1991; Wan et al., 2011b; this study). Sample S0726 was taken near the center of the trondhjemite intrusive (Fig. 2c) where the rock shows a gneissic and medium- to coarse-grained texture (Fig. 3g) and locally contains small biotite-rich aggregates. The dated sample excludes the aggregates and consists of quartz, plagioclase and a little biotite. Plagioclase grains show euhedual or subeuhedual shapes and are commonly altered to sericite and epidote in the center. Some quartz grains occur as banded aggregates and show undulose extinction. 3.6. Gneissic trondhjemite (CY002-TM1, N36◦ 19 14 , E117◦ 22 56 ) This sample was taken at a location southeast of sample S0726 (Fig. 2c). The foliation at the outcrop extends in a southeastnorthwest direction, similar to the regional tectonic trend of the area. It is similar in appearance (Fig. 3h) and mineral assemblage to sample S0726 but shows stronger deformation and alteration. 3.7. Gneissic trondhjemite (SY0301, N36◦ 04 44 , E117◦ 34 30 ) The typical early Neoarchean Yanlingguang-Liuhang succession occurs in the Yanlingguan area (Cao, 1996; Cheng et al., 1977; Wan et al., 2012). In the east of Yanlingguan, ∼2.6 Ga trondhjemite and granodiorite are widely exposed and extend in a southeast–northwest direction. However, their spatial distribution and relationship are uncertain. It was observed near Yanlingguan village that the Yanlingguang-Liuhang succession is cut by trondhjemite veins which are considered to be derived from 2.6 Ga TTGs. Sample SY0301 was taken from the north of Yanlingguan, several hundred meters away from the boundary of the Yanlingguang-Liuhang succession and TTG rocks. It shows a gneissic but homogeneous structure (Fig. 3i) and is composed of plagioclase, quartz and a few microcline and biotite. Some plagioclase occurs as phenocrysts with polysynthetic twinning, partly altered to epidote and sericite. Some quartz grains are oriented as

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Fig. 3. Field photographs of middle Neoarchean magmatic rocks. (a) Hornblendite (S1144), southwest of Qixingtai; (b) mylonitized tonalite (S0722), west of Panchegou; (c) gneissic tonalite (S1028), Yishan; (d) gneissic trondhjemite (SY0335A), Caishixi, Taishan; (e) gneissic trondhjemite (S0726), southwest of Qixingtai; (f) gneissic trondhjemite (CY002-TM1), northwest of Dawangzhuang; (g) gneissic trondhjemite (SY0301), north of Yanlingguan; (h) mylonitized trondhjemite (S0834), southeast of Huamawan; (i) gneissic trondhjemite (TS1204), east of Xintai; (j) gneissic granite (S1136), northwest of Panchegou.

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banded aggregates. There are a few microcline phenocrysts containing small plagioclase grains. 3.8. Mylonitized trondhjemite (S0834, N36◦ 05 10 , E117◦ 26 42 ) This sample was taken from Fushan trondhjemite that intrudes the early Neoarchean Yanlingguang-Liuhang succession (Fig. 2c). It shows strong deformation (Fig. 3j) and mainly consists of plagioclase, quartz and biotite, with some epidote, sericite and tourmaline of alteration origin. It is similar in structure to sample S0722 but contains less biotite and plagioclase and more quartz. 3.9. Gneissic trondhjemite (TS1204, N35◦ 54 04 , E117◦ 53 04 ) This sample was taken from a huge enclave in ∼2.5 Ga massive monzogranite east of Xintai (Fig. 2c). An intrusive relationship between the enclave and monzogranite has been observed. The gneissic trondhjemite shows anatectic features (Fig. 3k) and locally contains amphibolite enclaves. It mainly contains plagioclase, quartz and biotite. Quartz occurs as aggregates and shows undulose extinction. There are epidote and sericite as a result of alteration of plagioclase.

TS1204, analyses were carried out using a MC-ICP-MS (Neptune) coupled with an excimer laser ablation system (New Wave 193 nm FX) at the Tianjin Institute of Geology and Mineral Resources, Tianjin. The analytical procedure is similar to those described by Geng et al. (2011). All Lu–Hf isotopic results are reported with 95% confidence limits. Whenever possible, the Hf analyses were done on the same spots analyzed for U–Pb on SHRIMP II. The calculation of Hf model ages was based on a depleted-mantle source with a present-day 176 Hf/177 Hf = 0.28325, using a 176 Lu decay constant of 1.865 × 10−11 year−1 (Scherer et al., 2001) and assuming that the evolution of the Hf isotopic composition of the depleted mantle with time was linear. 176 Hf/177 Hf and 176 Lu/177 Hf ratio of the modern depleted mantle is 0.28325 and 0.0384, respectively (Nowell et al., 1998; Vervoort and Blichert, 1999). Calculation of Hf crustal model ages (tDM2(CC) ) is based on the assumption of a mean 176 Lu/177 Hf ratio of 0.01 (Vervoort and Patchett, 1996; Kröner et al., 2014), for the average continental crust. The calculation of εHf (t) values was based on zircon ages and the chondritic values (176 Hf/177 Hf = 0.282785, 176 Lu/177 Hf = 0.0336, Bouvier et al., 2008). 5. SHRIMP zircon dating

3.10. Gneissic granite (S1136, N35◦ 46 29 , E117◦ 41 20 )

5.1. Hornblendite (S1144)

This sample was taken from the northwest of tonalite sample S0722 mentioned above (Fig. 2c), but is granitic in composition. It displays a gneissic and prophyritic structure (Fig. 3l) and mainly contains quartz, plagioclase, microcline and biotite. Some quartz grains are oriented as aggregates, some plagioclase grains occur as porphyroclasts, and many show alteration to sericite and epidote. Biotite contains needle-like dark minerals (ilmenite?). The gneissic granite occurs only locally in the area.

The zircon grains are stubby or elongate in shape and show banded zonation in cathodoluminescence (CL) images with some grains displaying oscillatory zoning in outer domains (Fig. 4a and b). Overgrowth or recrystallization occur in some zircon grains. Twelve analyses were performed on 11 magmatic zircon grains (Table 1). The magmatic and recrystallized or overgrowth domains show similar age variations, with the analyses showing slightly reverse discordance (Fig. 5a) and displaying U contents and Th/U ratios ranging from 17 to 85 ppm and 0.67 to 1.28, respectively. Ten analyses yielded a weighted mean 207 Pb/206 Pb age of 2597 ± 19 Ma (MSWD = 1.4), which is interpreted to approximate the formation age of the ultramafic rock. Recrystallized or overgrowth domains have the same age as the magmatic domains. This means that the former most probably formed during a process of retrogression to hornblendite from pyroxenite during cooling and soon after formation of the ultramafic rock. The magmatic zircon is relatively large and probably grew during slow cooling of the magma.

4. Analytical techniques All zircon dating was carried out using the SHRIMP II instrument at the Beijing SHRIMP Center, Chinese Academy of Geological Sciences (CAGS). Age measurements were carried out over a period of more than ten years, and the analytical procedures and conditions were described by Williams (1998). The intensity of the primary O2− ion beam was 3.5–5.0 nA, the spot size was 30–35 ␮m, and each analytical site was rastered for 2.5–3.0 min prior to analysis to remove surface common Pb. Five scans through the mass stations were made for each age determination of zircon. Reference zircon SL13 (U = 238 ppm, Williams, 1998), M257 (U = 840 ppm, Nasdala et al., 2008) and TEMORA 1 (206 Pb/238 U age = 417 Ma, Black et al., 2003) were used for elemental abundance and calibration of 206 Pb/238 U, respectively. Common lead corrections were applied using the measured 204 Pb abundances. Data processing was carried out using the SQUID and ISOPLOT programs (Ludwig, 2001, 2003). Uncertainties in the isotopic ratios of individual analyses in Table 2 and on the concordia diagrams are given at 1, whereas uncertainties for weighted mean ages in the text are quoted at the 95% confidence level. Hf-in-zircon analyses from samples S0834, S1028, S1136, S1144 and CY002-TM1 were carried out using a Newwave UP213 laserablation microprobe, attached to a Neptune multicollector ICP-MS at the Institute of Mineral Resources, CAGS, Beijing. Instrumental conditions and data acquisition were described in Hou et al. (2007). For samples SY0301, SY0335A, S0722, and S0726, analyses were carrried out using a 193 nm UVArF excimer laser ablation system, attached to a Neptune multi-collector ICP MS at the State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing. Details of the analytical procedure were described by Wu et al. (2006). For sample

5.2. Mylonitized tonalite (S0722) The zircon is stubby in shape and show oscillatory zoning in CL images (Fig. 4c and d). It seems likely that recrystallization more commonly occurred in the outer domains of some grains, but their composition and age are similar to the magmatic domains. Twelve analyses yielded U contents and Th/U ratios of 74–309 ppm and 0.63–0.72 (Table 1). Ten concordant analyses have a weighted mean 207 Pb/206 Pb age of 2615 ± 8 Ma (MSWD = 0.57) (Fig. 5b) that is interpreted as recording the crystallization age of the tonalite magma. Analysis 12.1 shows strong lead loss due to high U and Th contents and was not considered in the age calculation. 5.3. Gneissic tonalite (S1028) The zircon grains are elongate in shape, and most show banded or oscillatory zoning in CL images, some with recrystallization (Fig. 4e and f). Eleven analyses were performed on 9 zircon grains (Table 1). Six analyses on magmatic domains have 165–326 ppm U contents and 0.64–1.14 Th/U ratios; the recrystallized domains are commonly higher in U contents (276–1440) and lower in Th/U ratios (0.10–0.53). They show lead loss to variable degrees, but four analyses on magmatic domains are positioned close to concordia

Table 1 SHRIMP U–Pb data for zircons from middle Neoarchean rocks in western Shandong. Spot

206

Pbc (%)

206

Pb*/206 Pb*

±%

±%

Err corr

206

0.524 0.546 0.551 0.527 0.535 0.528 0.529 0.522 0.526 0.517 0.528 0.552

3.3 2.5 4.3 2.8 2.6 2.7 2.7 3.1 2.8 2.8 2.8 2.8

0.94 0.96 0.88 0.89 0.94 0.91 0.92 0.83 0.90 0.89 0.91 0.89

2718 2809 2828 2728 2761 2734 2738 2707 2725 2687 2734 2835

±72 ±57 ±98 ±62 ±59 ±61 ±60 ±69 ±62 ±62 ±62 ±65

2612 2596 2605 2583 2564 2633 2587 2618 2633 2611 2573 2534

±20 ±12 ±39 ±23 ±16 ±21 ±19 ±35 ±22 ±24 ±22 ±24

−4 −8 −9 −6 −8 −4 −6 −3 −3 −3 −6 −12

2.7 2.4 2.4 2.6 2.5 2.6 2.5 2.5 2.5 2.5 2.5 2.3

0.485 0.475 0.473 0.494 0.494 0.495 0.498 0.477 0.501 0.536 0.486 0.353

2.5 2.3 2.3 2.4 2.3 2.4 2.4 2.3 2.3 2.4 2.4 2.2

0.91 0.97 0.96 0.92 0.94 0.93 0.95 0.94 0.95 0.96 0.96 0.97

2551 2504 2497 2588 2588 2594 2607 2513 2616 2768 2554 1950

±52 ±47 ±48 ±51 ±49 ±52 ±50 ±49 ±50 ±54 ±50 ±38

2607 2625 2612 2619 2610 2619 2630 2618 2605 2605 2601 2607

±19 ±9 ±11 ±17 ±13 ±17 ±12 ±15 ±12 ±11 ±12 ±9

2 5 4 1 1 1 1 4 0 −6 2 25

11.90 7.49 8.79 5.38 7.43 10.35 12.31 7.33 12.95 12.22 3.60

2.0 1.9 4.5 2.3 2.2 1.9 2.1 2.0 2.2 1.9 3.3

0.4849 0.3204 0.350 0.2529 0.3106 0.4234 0.4885 0.3046 0.517 0.4928 0.1698

1.9 1.8 4.3 2.1 2.1 1.9 2.0 1.9 2.1 1.9 2.7

0.97 0.97 0.96 0.92 0.97 0.97 0.96 0.95 0.97 0.98 0.83

2549 1791 1936 1454 1744 2276 2564 1714 2686 2583 1011

±40 ±29 ±72 ±28 ±32 ±36 ±43 ±28 ±47 ±39 ±26

2633.7 2553 2671 2394 2590.7 2627.3 2678 2601.6 2667.8 2651.9 2387

±8.6 ±8.0 ±20 ±15 ±9.2 ±7.7 ±9.6 ±9.7 ±9.3 ±6.4 ±31

3 30 27 39 33 13 4 34 −1 3 58

13.16 13.00 3.39 10.30 8.37 11.18 11.87 10.40 4.54 8.90 10.03

2.1 2.4 2.1 2.1 2.9 2.3 2.6 2.2 2.4 2.1 2.1

0.531 0.526 0.151 0.423 0.349 0.462 0.484 0.428 0.206 0.370 0.407

2.0 2.3 2.0 2.0 2.5 2.1 2.6 2.1 2.1 2.1 2.1

0.95 0.97 0.96 0.98 0.89 0.92 0.98 0.96 0.87 0.97 0.96

2746 2726 906 2275 1930 2447 2546 2298 1207 2028 2202

±46 ±51 ±17 ±39 ±42 ±43 ±54 ±40 ±23 ±36 ±39

2650 2645 2487 2620 2595 2612 2632 2617 2455 2603 2641

±11 ±10 ±10 ±8 ±21 ±15 ±10 ±10 ±20 ±9 ±10

−4 −3 64 13 26 6 3 12 51 22 17

207

Pb*/235 U

±%

Th/U

Hornblendite (S1144) 0.05 1.1MA 0.03 2.1RC 0.38 2.2MA 0.23 3.1MA 0.10 4.1MA 0.20 5.1MA 6.1MA 0.09 0.34 7.1MA 8.1MA 0.12 9.1MA 0.31 0.08 10.1MA 0.16 11.1MA

49 135 17 53 85 56 63 26 46 42 49 45

48 67 17 44 103 60 71 17 50 43 35 55

1.02 0.52 0.99 0.86 1.25 1.11 1.17 0.67 1.14 1.04 0.74 1.28

22 63 8 24 39 26 29 12 21 19 22 21

0.1756 0.1740 0.1748 0.1726 0.1706 0.1778 0.1730 0.1761 0.1778 0.1755 0.1715 0.1675

1.2 0.72 2.3 1.4 0.96 1.3 1.2 2.1 1.3 1.5 1.3 1.4

12.70 13.10 13.28 12.54 12.58 12.95 12.62 12.68 12.90 12.52 12.49 12.76

3.5 2.6 4.9 3.1 2.8 3.0 2.9 3.8 3.1 3.2 3.1 3.2

Mylonitized tonalite (S0722) 0.43 1.1 0.18 2.1 0.37 3.1 1.33 4.1 0.43 5.1 0.49 6.1 7.1 0.24 8.1 0.43 9.1 0.48 10.1 0.15 0.21 11.1 12.1 0.52

74 179 120 102 151 78 125 132 123 141 107 309

48 104 74 66 100 53 75 84 85 95 66 187

0.67 0.60 0.64 0.67 0.69 0.70 0.63 0.66 0.72 0.69 0.64 0.63

31 73 49 44 65 33 54 54 53 65 45 94

0.1751 0.1770 0.1756 0.1763 0.1754 0.1763 0.1775 0.1763 0.1749 0.1749 0.1745 0.1751

1.10 0.57 0.69 1.00 0.81 0.99 0.74 0.88 0.74 0.67 0.73 0.56

11.72 11.59 11.46 12.01 11.94 12.04 12.20 11.59 12.07 12.93 11.70 8.53

209 780 276 1056 362 333 165 326 213 287 1440

163 137 93 111 312 154 135 334 133 316 739

0.81 0.18 0.35 0.11 0.89 0.48 0.85 1.06 0.64 1.14 0.53

87.1 215 84.7 231 96.8 121 69.3 85.7 94.7 121 213

0.17793 0.16952 0.1819 0.1543 0.17339 0.17725 0.1827 0.1745 0.1816 0.17990 0.1536

0.52 0.48 1.2 0.88 0.55 0.46 0.58 0.58 0.56 0.38 1.8

Gneissic trondhjemite (SY0335A) 0.22 423 1.1 0.24 217 2.1 0.28 664 3.1 4.1 0.21 380 5.1 0.03 502 6.1 0.32 180 0.28 228 7.1 8.1 0.11 244 0.16 805 9.1 10.1 0.23 488 0.25 253 11.1

24 32 54 21 17 20 36 108 38 39 21

0.06 0.15 0.08 0.06 0.04 0.12 0.16 0.46 0.05 0.08 0.09

194 98 86 139 151 72 95 90 143 156 89

0.1797 0.1792 0.1630 0.1764 0.1738 0.1756 0.1778 0.1762 0.1599 0.1747 0.1787

0.65 0.60 0.60 0.47 1.30 0.90 0.57 0.57 1.20 0.55 0.58

206

Pb*/238 U

Pb/238 U Age (Ma)

207 Pb/206 Pb Age (Ma)

Discordance (%)

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

Th (ppm)

Gneissic tonalite (S1028) 1.1MA 0.13 2.1RC 0.20 3.1RC 1.95 0.69 3.2RC 0.30 4.1MA 5.1MA + RC 0.09 5.2MA 0.09 0.51 6.1MA 0.03 7.1MA 0.06 8.1MA 1.57 9.1RC

Pb* (ppm)

207

U (ppm)

871

872

Table 1 (Continued) Spot

206

Pbc (%)

U (ppm)

Th (ppm)

Th/U

206

Pb* (ppm)

207

Pb*/206 Pb*

±%

207

Pb*/235 U

±%

206

Pb*/238 U

±%

Err corr

206 Pb/238 U Age (Ma)

207 Pb/206 Pb Age (Ma)

Discordance (%)

13 25 93 22 37 70 84 8 20 73 19 34 88

0.29 0.52 0.60 0.60 0.72 1.52 1.32 0.48 0.23 1.08 0.13 0.86 0.75

20 22 69 15 22 20 28 7 40 30 63 17 50

0.1804 0.1793 0.1823 0.1787 0.1762 0.1764 0.1759 0.1786 0.1834 0.1766 0.1823 0.1775 0.1762

0.94 0.84 0.42 1.10 0.79 0.84 0.65 1.70 0.60 0.63 0.51 0.97 0.52

12.57 12.88 12.52 11.66 11.80 11.79 11.93 12.18 12.69 12.14 12.40 12.21 11.66

2.6 2.6 2.3 2.8 2.5 2.6 2.5 3.3 2.4 2.4 2.4 2.7 2.4

0.505 0.521 0.498 0.473 0.486 0.485 0.492 0.495 0.502 0.499 0.493 0.499 0.480

2.4 2.4 2.3 2.5 2.4 2.4 2.4 2.9 2.3 2.3 2.3 2.5 2.3

0.93 0.94 0.98 0.91 0.95 0.95 0.96 0.86 0.97 0.97 0.98 0.93 0.97

2636 2704 2605 2497 2552 2549 2579 2590 2622 2608 2585 2609 2527

±53 54 49 52 51 51 51 62 50 50 49 53 48

2657 2646 2674 2641 2617 2619 2615 2640 2684 2621 2674 2629 2618

16 14 7 19 13 14 11 28 10 10 9 16 9

1 −2 3 5 2 3 1 2 2 0 3 1 3

Gneissic trondhjemite (CY002-TM1) 0.13 483 1.1MA 1.2C 1.04 44 0.12 84 1.3MA 2.1MA 0.37 86 102 0.23 3.1MA 0.09 527 4.1MA 0.08 438 5.1MA 0.44 117 6.1MA 7.1C 0.16 233 0.45 522 7.2MA 8.1C 1.16 36 0.23 149 9.1MA 10.1MA 0.42 87 11.1MA 0.44 84 0.41 202 12.1MA 0.09 103 13.1C 14.1MA 0.43 98 0.36 74 15.1MA 129 0.27 16.1C 0.23 77 17.1C 0.13 76 17.2MA 0.44 94 18.1MA 0.21 104 18.2C 19.1MA 0.56 46 0.37 59 20.1C 0.10 461 20.2MA

26 14 11 17 18 23 19 17 85 25 20 24 15 20 11 21 15 16 96 32 14 17 49 19 37 17

0.06 0.33 0.13 0.20 0.18 0.04 0.05 0.15 0.38 0.05 0.57 0.17 0.18 0.24 0.06 0.21 0.16 0.23 0.77 0.43 0.18 0.19 0.49 0.44 0.64 0.04

147 20 38 35 46 230 132 0 94 115 16 46 32 36 69 45 39 28 57 34 33 40 46 20 26 135

0.1803 0.1836 0.1832 0.1809 0.1829 0.1829 0.1802 0.1825 0.1870 0.1794 0.1838 0.1805 0.1827 0.1788 0.1780 0.1848 0.1786 0.1837 0.1837 0.1823 0.1841 0.1797 0.1825 0.1824 0.1841 0.1806

0.50 2.1 0.82 1.2 0.85 0.33 0.43 0.81 0.51 0.76 2.5 0.75 0.98 1.0 0.72 0.70 0.95 0.99 0.71 0.90 0.84 1.1 0.75 1.3 1.3 0.41

8.81 13.23 13.16 11.70 13.00 12.81 8.73 12.37 12.05 6.32 12.56 8.93 10.60 12.16 9.64 12.93 11.38 10.97 12.98 12.91 12.67 12.16 12.99 12.65 13.11 8.47

1.5 3.1 2.0 2.2 1.9 1.5 1.5 1.9 1.6 2.2 3.4 1.9 3.5 2.1 1.7 1.9 2.3 2.1 2.1 2.1 2.0 2.1 1.9 2.5 2.3 1.5

0.3544 0.5230 0.5209 0.4689 0.5155 0.5080 0.3516 0.4917 0.4674 0.2554 0.4960 0.3586 0.4211 0.4933 0.3930 0.5076 0.4621 0.4330 0.5121 0.5139 0.4991 0.4907 0.5162 0.5032 0.5160 0.3403

1.4 2.4 1.8 1.8 1.7 1.4 1.4 1.7 1.5 2.1 2.3 1.7 3.4 1.8 1.6 1.8 2.0 1.8 2.0 1.9 1.8 1.8 1.7 2.1 2.0 1.4

0.95 0.75 0.91 0.83 0.90 0.97 0.96 0.90 0.95 0.94 0.68 0.91 0.96 0.88 0.91 0.93 0.91 0.88 0.94 0.91 0.91 0.86 0.91 0.84 0.84 0.96

1956 2712 2703 2479 2680 2648 1942 2578 2472 1466 2596 1976 2264 2585 2137 2646 2449 2319 2667 2673 2610 2574 2683 2627 2684 1888

±24 ±52 ±40 ±37 ±38 ±31 ±24 ±36 ±31 ±27 ±50 ±29 ±65 ±39 ±29 ±38 ±42 ±35 ±44 ±42 ±38 ±39 ±38 ±45 ±43 ±23

2656 2685 2682 2661 2679 2679 2655 2675 2716 2648 2687 2658 2677 2642 2634 2696 2640 2686 2687 2673 2690 2650 2676 2674 2690 2658

±8.2 ±34 ±14 ±20 ±14 ±5 ±7 ±13 ±9 ±13 ±42 ±12 ±16 ±17 ±12 ±12 ±16 ±16 ±12 ±15 ±14 ±18 ±12 ±22 ±21 ±7

26 −1 −1 7 0 1 27 4 9 45 3 26 15 2 19 2 7 14 1 0 3 3 0 2 0 29

32 83 213 135 349 199 339 63 74 40 327 191

0.54 0.43 0.61 0.41 0.61 0.51 0.24 0.64 0.54 0.51 0.16 0.97

24 51 103 99 204 148 90 40 58 29 113 62

0.1953 0.1749 0.1659 0.1753 0.1737 0.1756 0.1671 0.1790 0.1809 0.1748 0.1918 0.1778

2.00 1.20 1.10 0.76 0.52 0.77 1.60 1.10 1.30 1.30 2.50 1.20

12.03 7.17 7.53 8.19 9.53 10.15 1.61 11.34 11.62 10.02 1.61 8.51

4.4 3.8 3.8 3.7 3.6 3.7 4.0 3.8 3.9 3.9 4.4 4.0

0.447 0.297 0.329 0.339 0.398 0.419 0.070 0.460 0.466 0.416 0.061 0.347

3.9 3.7 3.7 3.6 3.6 3.6 3.6 3.7 3.7 3.7 3.6 3.8

0.89 0.95 0.96 0.98 0.99 0.98 0.91 0.96 0.94 0.94 0.82 0.95

2381 1679 1835 1881 2160 2257 437 2438 2466 2241 381 1922

±78 ±54 ±59 ±59 ±66 ±69 ±15 ±75 ±75 ±71 ±13 ±63

2787 2605 2516 2609 2593 2612 2528 2643 2660 2604 2756 2632

±34 ±20 ±19 ±13 ±9 ±13 ±28 ±19 ±22 ±22 ±42 ±21

15 36 27 28 17 14 83 8 7 14 86 27

Gneissic trondhjemite (SY0301) 1.30 61 1.1 198 0.19 2.1 1.09 360 3.1 0.34 340 4.1 0.27 596 5.1 0.85 406 6.1 7.1 2.87 1435 0.65 102 8.1 1.68 142 9.1 0.42 80 10.1 2.39 2086 11.1 1.43 204 12.1

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

Gneissic trondhjemite (S0726) 0.59 47 1.1 2.1 0.68 50 0.24 161 3.1 0.51 38 4.1 0.41 53 5.1 0.50 47 6.1 0.32 66 7.1 1.04 17 8.1 9.1 0.50 92 0.31 70 10.1 0.15 149 11.1 0.44 40 14.1 0.12 122 15.1

385 136 104 127 124 112

0.93 0.45 0.58 0.81 0.57 0.60

83 60 55 67 69 67

0.1729 0.1755 0.1800 0.1787 0.1771 0.1772

1.10 2.80 3.90 1.20 0.98 1.10

5.35 5.38 8.40 11.81 8.66 9.79

3.8 4.7 5.7 3.9 3.8 3.8

0.225 0.223 0.339 0.479 0.355 0.401

3.6 3.7 4.1 3.7 3.7 3.7

0.96 0.80 0.72 0.95 0.97 0.96

1306 1295 1880 2524 1957 2172

±43 ±44 ±67 ±77 ±62 ±68

2585 2610 2652 2641 2626 2627

±18 ±48 ±66 ±20 ±16 ±18

49 50 29 4 25 17

221 310 114 543 148 265 531 370 107 294 520 420

81 59 2 156 5 2 290 196 33 92 479 254

0.38 0.20 0.02 0.30 0.04 0.01 0.56 0.55 0.32 0.32 0.95 0.63

94 77 48 103 61 80 111 93 30 110 71 71

0.1744 0.1770 0.1816 0.1724 0.1757 0.1740 0.1723 0.1742 0.1684 0.1751 0.1648 0.1682

0.49 0.54 0.71 0.67 0.60 0.66 0.46 1.60 1.20 0.51 1.40 1.20

11.95 7.07 12.24 5.22 11.67 8.40 5.75 6.97 7.52 10.48 3.60 4.54

2.6 2.7 2.7 2.6 2.7 2.6 2.6 3.0 3.0 2.6 2.9 2.8

0.497 0.290 0.489 0.220 0.482 0.350 0.242 0.290 0.324 0.434 0.158 0.196

2.6 2.6 2.6 2.5 2.6 2.6 2.5 2.6 2.8 2.6 2.6 2.6

0.98 0.98 0.97 0.97 0.97 0.97 0.98 0.85 0.91 0.98 0.87 0.91

2601 1640 2565 1280 2535 1935 1397 1643 1809 2325 947 1152

±55 ±38 ±55 ±29 ±54 ±43 ±32 ±37 ±44 ±50 ±22 ±27

2600 2625 2668 2581 2613 2597 2580 2599 2541 2607 2506 2540

±8 ±9 ±12 ±11 ±10 ±11 ±8 ±27 ±21 ±9 ±24 ±19

0 38 4 50 3 25 46 37 29 11 62 55

Gneissic trondhjemite (TS1204) 1.1RC 0.15 77 2.1R 0.22 871 3.1R 0.22 100 4.1RC 0.00 114 5.1RC 0.04 957 6.1MA 0.03 322 6.2RC 0.06 243 7.1RC 0.10 187 7.2R 0.07 317 8.1MA 0.02 445 9.1R 0.06 1044 10.1MA 0.00 74 11.1R 0.07 456 12.1RC 0.00 115 13.1RC 13.25 47 14.1R 0.09 126 15.1RC 0.26 32 16.1RC 0.38 639 17.1RC 0.00 85 18.1RC 0.37 373 19.1R 0.11 285 20.1RC 0.04 317 21.1R 0.40 214 22.1RC 0.32 627

38 62 34 34 75 427 39 52 32 355 56 32 97 32 26 5 2 157 46 209 40 45 29 166

0.51 0.07 0.35 0.31 0.08 1.37 0.17 0.28 0.11 0.82 0.06 0.45 0.22 0.29 0.57 0.04 0.06 0.25 0.56 0.58 0.14 0.15 0.14 0.27

32.6 201 42.6 43.9 276 111 105 70.4 96.5 165 221 31.6 121 50.3 19.6 53.3 11.8 129 37.5 142 108 138 86.5 127

0.1767 0.16197 0.1717 0.1721 0.16830 0.17761 0.17918 0.1759 0.15938 0.17294 0.14558 0.1783 0.16240 0.1808 0.171 0.1707 0.1758 0.15672 0.1793 0.1744 0.16247 0.17985 0.1703 0.15697

2.1 1.4 1.9 1.8 1.3 1.5 1.5 1.6 1.6 1.4 1.4 2.0 1.4 1.7 11 1.7 3.0 1.5 1.8 1.5 1.5 1.4 1.6 1.4

0.4938 0.2686 0.4925 0.4497 0.3352 0.4024 0.5048 0.4369 0.3542 0.4317 0.2464 0.4980 0.3100 0.5097 0.418 0.4907 0.434 0.2335 0.5142 0.4403 0.4423 0.5074 0.4692 0.2356

1.7 1.3 1.6 1.6 1.3 1.4 1.4 1.5 1.5 1.4 1.3 1.7 1.3 1.6 4.0 1.5 2.6 1.3 1.6 1.3 1.4 1.4 1.4 1.3

1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1

2587 1534 2581 2394 1863 2180 2634 2337 1955 2313 1420 2605 1741 2655 2252 2574 2325 1353 2675 2352 2361 2646 2480 1364

±36 ±18 ±34 ±31 ±21 ±25 ±30 ±29 ±26 ±27 ±16 ±37 ±20 ±34 ±76 ±32 ±51 ±16 ±35 ±27 ±28 ±29 ±29 ±16

2622 2476 2574 2578 2541 2631 2645 2615 2449 2586 2295 2637 2481 2661 2564 2564 2613 2421 2646 2601 2482 2652 2561 2423

±19 ±8.7 ±16 ±14 ±5 ±9 ±9 ±12 ±9 ±7 ±7 ±16 ±9 ±13 ±170 ±12 ±25 ±10 ±14 ±10 ±10 ±7 ±12 ±10

1 38 0 7 27 17 0 11 20 11 38 1 30 0 12 0 11 44 0 10 5 0 3 44

Gneissic granite (S1136) 1.1 0.57 1.2 0.10 2.1 0.00 0.28 3.1 5.1 1.30 6.1 0.02 7.1 0.10 8.1 2.18 8.2 1.19 9.1 0.19 10.1 1.23 11.1 0.12 10.2 0.51

378 80 84 216 180 79 66 141 245 81 373 154 188

0.62 0.44 1.06 0.63 0.48 0.69 0.61 0.52 0.76 0.73 0.74 0.70 0.41

160 84.5 39.3 118 102 51.2 48.7 48.5 102 43.2 94.8 92.0 112

0.1750 0.1740 0.1738 0.1735 0.1724 0.1742 0.1752 0.1724 0.1704 0.1713 0.1688 0.1721 0.1695

2.2 2.5 3.8 2.2 2.3 2.4 2.4 2.8 2.2 2.4 2.2 2.2 2.2

0.2958 0.525 0.562 0.3879 0.3042 0.503 0.504 0.1962 0.3498 0.4389 0.2093 0.4705 0.2732

2.1 2.4 3.6 2.1 2.1 2.2 2.2 2.1 2.1 2.2 2.1 2.1 2.1

0.96 0.96 0.95 0.96 0.92 0.94 0.93 0.78 0.93 0.92 0.92 0.96 0.95

1670 2721 2873 2113 1712 2626 2631 1155 1934 2346 1225 2486 1557

±31 ±53 ±84 ±37 ±32 ±48 ±48 ±23 ±35 ±43 ±23 ±43 ±29

2606 2597 2595 2591 2581 2599 2608 2580 2561 2570 2545 2578 2553

±11 ±11 ±20 ±10 ±15 ±14 ±14 ±29 ±14 ±15 ±15 ±10 ±11

0.47 1.42 1.70 0.51 0.18 0.07

Gneissic trondhjemite (S0834) 1.1 0.13 2.1 0.31 3.1 0.27 4.1 0.78 5.1 0.12 6.1 0.62 7.1 0.19 8.1 0.51 9.1 0.78 10.1 0.15 11.1 0.55 12.1 0.64

626 187 82 354 384 119 112 280 334 114 519 227 476

1.1 0.47 0.97 0.82 0.32 0.53 0.55 0.70 0.55 0.43 0.40 0.97 0.53 0.76 10 0.73 1.5 0.61 0.84 0.60 0.61 0.44 0.71 0.60 0.64 0.67 1.2 0.59 0.91 0.82 0.85 1.8 0.86 0.91 0.89 0.60 0.67

12.03 5.999 11.66 10.67 7.78 9.85 12.47 10.60 7.78 10.29 4.945 12.24 6.941 12.71 9.8 11.55 10.53 5.045 12.71 10.59 9.91 12.58 11.02 5.100 7.14 12.60 13.46 9.28 7.23 12.08 12.18 4.66 8.21 10.36 4.87 11.16 6.39

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

427 310 185 161 224 195

13.1 14.1 15.1 16.1 17.1 18.1

36 −5 −11 18 34 −1 −1 55 24 9 52 4 39

873

Notes: (1) Age in Ma; (2) * means radiogenic Pb, measured 204 Pb was used for the common lead correction; (3) 206 Pbc represents common lead; and (4) for samples S1144, S1028, CY002-TM1 and TS1204, MA, RC, R and C represent magmatic zircon, recrystallized zircon, rim (metamorphic) and core domains, respectively. Zircons from other samples are magmatic in origin.

874

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

Table 2 Lu–Hf isotope compositions of middle Neoarchean rocks in western Shandong Hornblendite (S1144). Hf spot

Age (Ma)

176

±2

εHf (0)

εHf (t)

2

tDM1 (Ga)

2

tDM2(CC) (Ga)

2

fLu/Hf

1-1MA 2-2MA 3-1MA 4-1MA 5-1MA 6-1MA 7-1MA 8-1MA 9-1MA 10-1MA 11-1MA

2597 2597 2597 2597 2597 2597 2597 2597 2597 2597 2597

0.067362 0.123408 0.038939 0.059953 0.087362 0.106812 0.078588 0.045869 0.096504 0.079186 0.0891

0.001193 0.002272 0.000768 0.001272 0.001696 0.002097 0.001633 0.000946 0.001869 0.001686 0.001723

0.281312 0.281476 0.281243 0.281345 0.281361 0.281388 0.281375 0.28121 0.281358 0.281316 0.281354

0.000025 0.000027 0.000021 0.000021 0.000024 0.000025 0.000025 0.000022 0.000022 0.000021 0.000022

−51.6 −45.8 −54.1 −50.5 −49.9 −48.9 −49.4 −55.2 −50.0 −51.5 −50.2

4.6 8.6 2.9 5.7 5.5 5.7 6.1 1.4 5.1 3.9 5.2

0.9 1.0 0.7 0.7 0.9 0.9 0.9 0.8 0.8 0.8 0.8

2.72 2.57 2.78 2.68 2.69 2.68 2.66 2.84 2.71 2.75 2.70

0.07 0.08 0.06 0.06 0.07 0.07 0.07 0.06 0.06 0.06 0.06

2.76 2.56 2.84 2.71 2.72 2.70 2.68 2.92 2.74 2.79 2.73

0.11 0.12 0.09 0.09 0.10 0.11 0.11 0.10 0.10 0.09 0.09

−0.96 −0.93 −0.98 −0.96 −0.95 −0.94 −0.95 −0.97 −0.94 −0.95 −0.95

Mylonitized tonalite (S0722) 1-1 2615 0.011243 2-1 2615 0.020457 3-1 2615 0.016176 2615 0.017946 4-1 2615 0.015983 5-1 2615 0.009937 6-1 2615 0.008805 7-1 8-1 2615 0.013391 2615 0.014495 9-1 2615 0.009338 10-1 2615 0.029125 11-1 2615 0.017401 12-1

0.000515 0.000967 0.000749 0.000784 0.00075 0.000468 0.000402 0.000653 0.000685 0.000457 0.001297 0.000839

0.281273 0.281327 0.281288 0.281302 0.281244 0.28125 0.281257 0.281277 0.281261 0.281299 0.281343 0.281311

0.000016 0.000016 0.000014 0.000018 0.000016 0.000016 0.000015 0.000015 0.000017 0.000023 0.000017 0.000016

−53.0 −51.1 −52.5 −52.0 −54.0 −53.8 −53.6 −52.9 −53.4 −52.1 −50.5 −51.7

4.8 6.0 5.0 5.4 3.4 4.1 4.5 4.8 4.1 5.9 5.9 5.6

0.6 0.6 0.5 0.6 0.6 0.6 0.5 0.5 0.6 0.8 0.6 0.6

2.73 2.68 2.72 2.70 2.78 2.75 2.74 2.73 2.75 2.69 2.69 2.70

0.04 0.05 0.04 0.05 0.04 0.04 0.04 0.04 0.05 0.06 0.05 0.05

2.76 2.71 2.76 2.73 2.83 2.80 2.78 2.77 2.80 2.71 2.71 2.72

0.07 0.07 0.06 0.08 0.07 0.07 0.07 0.06 0.08 0.10 0.07 0.07

−0.98 −0.97 −0.98 −0.98 −0.98 −0.99 −0.99 −0.98 −0.98 −0.99 −0.96 −0.97

Gneissic tonalite (S1028) 2662 1-1MA 2662 8-1MA 2662 11-1MA 2662 12-1MA 2662 14-1MA 15-1MA 2662 2662 16-1MA 17-1MA 2662 18-1MA 2662 2662 19-1MA

0.0012 0.0005 0.0004 0.0007 0.0006 0.0009 0.0015 0.0007 0.0011 0.0008

0.281308 0.281326 0.281234 0.281291 0.281121 0.281281 0.281281 0.281275 0.281258 0.281273

0.000027 0.000023 0.000081 0.000027 0.000077 0.000026 0.000021 0.000019 0.000015 0.000045

−51.8 −51.1 −54.4 −52.4 −58.4 −52.7 −52.7 −52.9 −53.5 −53.0

5.9 7.8 4.8 6.2 0.3 5.6 4.4 5.6 4.4 5.3

1.0 0.8 2.9 1.0 2.7 0.9 0.7 0.7 0.6 1.6

2.73 2.65 2.77 2.72 2.94 2.74 2.79 2.74 2.79 2.75

0.07 0.06 0.22 0.07 0.02 0.07 0.06 0.05 0.04 0.12

2.75 2.65 2.80 2.73 3.03 2.76 2.82 2.76 2.82 2.78

0.12 0.10 0.35 0.12 0.33 0.11 0.09 0.08 0.07 0.19

−0.96 −0.98 −0.99 −0.98 −0.98 −0.97 −0.95 −0.98 −0.97 −0.97

Gneissic trondhjemite (SY0335A) 1-1 2626 0.015986 2626 0.017918 2-1 3-1 2626 0.019286 2626 0.019912 4-1 2626 0.018105 5-1 2626 0.018295 6-1 2626 0.014831 7-1 8-1 2626 0.017209 2626 0.015375 9-1 10-1 2626 0.014192 2626 0.026783 11-1 2626 0.015394 12-1 2626 0.015373 13-1 2626 0.01347 14-1 2626 0.023845 15-1 2626 0.013247 16-1 2626 0.024022 17-1 2626 0.010739 18-1 2626 0.019356 19-1 2626 0.000251 20-1

0.000589 0.000674 0.00077 0.000772 0.00069 0.000658 0.000516 0.000603 0.000558 0.000495 0.000937 0.000534 0.000587 0.00046 0.000827 0.000482 0.000862 0.000392 0.000682 0.000006

0.28115 0.281226 0.281237 0.281223 0.281217 0.281204 0.281244 0.281276 0.28119 0.281207 0.281222 0.281185 0.281134 0.2812 0.281243 0.281185 0.281228 0.281184 0.281239 0.281173

0.000022 0.00002 0.000017 0.000019 0.00002 0.000016 0.00002 0.000018 0.00002 0.00002 0.000018 0.000019 0.00002 0.000019 0.000018 0.00002 0.00002 0.000018 0.000023 0.00001

−57.4 −54.7 −54.3 −54.8 −55.0 −55.5 −54.1 −52.9 −56.0 −55.3 −54.8 −56.1 −57.9 −55.6 −54.1 −56.1 −54.6 −56.2 −54.2 −56.6

0.6 3.2 3.4 2.9 2.8 2.4 4.1 5.0 2.1 2.8 2.5 1.9 0.0 2.6 3.5 2.0 2.9 2.2 3.6 2.5

0.8 0.7 0.6 0.7 0.7 0.6 0.7 0.6 0.7 0.7 0.6 0.7 0.7 0.7 0.6 0.7 0.7 0.6 0.8 0.4

2.90 2.80 2.79 2.81 2.81 2.83 2.76 2.73 2.84 2.81 2.82 2.84 2.92 2.82 2.79 2.84 2.81 2.84 2.78 2.82

0.06 0.06 0.05 0.05 0.05 0.04 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.05 0.05 0.06 0.05 0.5 0.06 0.03

2.98 2.86 2.85 2.87 2.87 2.89 2.81 2.76 2.91 2.87 2.89 2.92 3.01 2.88 2.84 2.91 2.87 2.91 2.83 2.89

0.10 0.09 0.07 0.08 0.09 0.07 0.08 0.08 0.09 0.09 0.08 0.08 0.09 0.08 0.08 0.09 0.09 0.08 0.10 0.05

−0.98 −0.98 −0.98 −0.98 −0.98 −0.98 −0.98 −0.98 −0.98 −0.99 −0.97 −0.98 −0.98 −0.99 −0.98 −0.99 −0.97 −0.99 −0.98 −1

Gneissic trondhjemite (S0726) 2623 0.01359 1-1 2623 0.019058 2-1 3-1 2623 0.040829 2623 0.046833 4-1 2623 0.042779 5-1 2623 0.037667 6-1 2623 0.038709 7-1 2623 0.01786 8-1 2623 0.023978 9-1 2623 0.030022 10-1 2623 0.029989 11-1 2623 0.079528 12-1 2623 0.041198 13-1 2623 0.036227 14-1

0.000579 0.000797 0.001662 0.002178 0.00206 0.001627 0.001824 0.000765 0.00114 0.001209 0.001268 0.00321 0.001879 0.001702

0.281279 0.281246 0.281371 0.281404 0.281369 0.281338 0.281342 0.28128 0.281294 0.28134 0.281292 0.281377 0.281359 0.281334

0.000014 0.000017 0.000017 0.000018 0.000019 0.000018 0.000019 0.000012 0.000018 0.000015 0.000017 0.000015 0.000021 0.000021

−52.8 −54.0 −49.5 −48.4 −49.6 −50.7 −50.6 −52.8 −52.3 −50.6 −52.3 −49.3 −50.0 −50.8

5.2 3.6 6.5 6.7 5.7 5.4 5.1 4.8 4.7 6.2 4.4 3.9 5.7 5.1

0.5 0.6 0.6 0.6 0.7 0.6 0.7 0.4 0.6 0.5 0.6 0.6 0.8 0.7

2.72 2.78 2.67 2.66 2.70 2.72 2.72 2.73 2.74 2.68 2.75 2.78 2.70 2.73

0.04 0.05 0.05 0.05 0.05 0.05 0.05 0.03 0.05 0.04 0.05 0.05 0.06 0.06

2.75 2.83 2.69 2.67 2.73 2.74 2.75 2.77 2.78 2.70 2.79 2.81 2.73 2.76

0.06 0.07 0.07 0.08 0.08 0.08 0.08 0.05 0.08 0.06 0.07 0.07 0.09 0.09

−0.98 −0.98 −0.95 −0.93 −0.94 −0.95 −0.95 −0.98 −0.97 −0.96 −0.96 −0.9 −0.94 −0.95

Yb/177 Hf

0.0431 0.0175 0.0161 0.0298 0.0251 0.0305 0.0545 0.0304 0.0412 0.0373

176

Lu/177 Hf

176

Hf/177 Hf

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

875

Table 2 (Continued) Hf spot

Age (Ma)

176

Yb/177 Hf

176

Lu/177 Hf

176

Hf/177 Hf

±2

εHf (0)

εHf (t)

2

tDM1 (Ga)

2

tDM2(CC) (Ga)

2

fLu/Hf

Gneissic trondhjemite (CY002-TM1) 2667 0.0284 1-1MA 2685 0.0172 1-2C 1-3MA 2667 0.0471 2-1MA 2667 0.047 2667 0.054 3-1MA 4-1MA 2667 0.0586 2667 0.0677 5-1MA 2667 0.0703 6-1MA 2716 0.0205 7-1C 7-2MA 2667 0.0314 2687 0.0923 8-1C 2667 0.0383 9-1MA 2667 0.0246 10-1MA 2667 0.0216 11-1MA 2667 0.0401 12-1MA 2696 0.046 13-1C 2667 0.0519 14-1MA 2667 0.0539 15-1MA 2687 0.0485 16-1C 2673 0.062 17-1C 17-2MA 2667 0.0362 2667 0.0292 18-1MA 2676 0.0713 18-2C 2667 0.0929 19-1MA 2690 0.0532 20-1C 20-2MA 2667 0.0751

0.0007 0.0005 0.0012 0.0012 0.0013 0.0015 0.0016 0.0018 0.0005 0.0008 0.0023 0.001 0.0006 0.0006 0.0009 0.0011 0.0013 0.0013 0.0013 0.0016 0.0009 0.0008 0.0018 0.0023 0.0014 0.0018

0.281267 0.281208 0.281302 0.281272 0.281289 0.281297 0.281331 0.281418 0.281327 0.281318 0.281342 0.281339 0.281235 0.281222 0.281222 0.281293 0.281361 0.281375 0.281268 0.281358 0.281278 0.281294 0.281408 0.281355 0.28128 0.28128

0.000016 0.000022 0.000022 0.000019 0.000019 0.00002 0.000018 0.000017 0.000022 0.000021 0.000025 0.000021 0.00002 0.000018 0.000018 0.000017 0.000018 0.00002 0.000024 0.000023 0.000018 0.000019 0.000023 0.000021 0.000026 0.000024

−53.2 −55.3 −52.0 −53.0 −52.5 −52.2 −51.0 −47.9 −51.1 −51.4 −50.6 −50.7 −54.4 −54.8 −54.8 −52.3 −49.9 −49.4 −53.2 −50.0 −52.8 −52.3 −48.3 −50.1 −52.8 −52.8

5.4 4.2 5.9 4.8 5.1 5.2 6.1 8.9 9.0 7.1 5.7 7.5 4.5 4.1 3.5 6.3 7.7 8.2 5.0 7.2 5.5 6.3 8.7 5.8 5.2 4.0

0.6 0.8 0.8 0.7 0.7 0.7 0.7 0.6 0.8 0.7 0.9 0.7 0.7 0.6 0.6 0.6 0.7 0.7 0.8 0.8 0.7 0.7 0.8 0.8 0.9 0.8

2.75 2.81 2.73 2.76 2.76 2.76 2.73 2.62 2.66 2.68 2.76 2.69 2.79 2.80 2.82 2.74 2.66 2.64 2.79 2.69 2.75 2.71 2.63 2.74 2.78 2.81

0.04 0.06 0.06 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.07 0.06 0.06 0.05 0.05 0.05 0.05 0.05 0.07 0.06 0.05 0.05 0.06 0.06 0.07 0.07

2.76 2.85 2.75 2.81 2.79 2.79 2.74 2.60 2.63 2.69 2.78 2.67 2.82 2.84 2.87 2.75 2.66 2.64 2.82 2.69 2.77 2.73 2.62 2.76 2.80 2.85

0.07 0.10 0.09 0.08 0.08 0.09 0.08 0.07 0.10 0.09 0.11 0.09 0.09 0.09 0.08 0.07 0.08 0.09 0.10 0.10 0.08 0.08 0.10 0.09 0.11 0.10

−0.98 −0.99 −0.96 −0.96 −0.96 −0.96 −0.95 −0.95 −0.98 −0.98 −0.93 −0.97 −0.98 −0.98 −0.97 −0.97 −0.96 −0.96 −0.96 −0.95 −0.97 −0.98 −0.95 −0.93 −0.96 −0.95

Gneissic trondhjemite (SY0301) 2663 0.028251 1-1 2663 0.021375 2-1 2663 0.021381 3-1 2663 0.025911 4-1 5-1 2663 0.020028 2663 0.02087 6-1 7-1 2663 0.026385 2663 0.014902 8-1 2663 0.025107 9-1 2663 0.045153 10-1 2663 0.031413 11-1 12-1 2663 0.004995 2663 0.014076 13-1 14-1 2663 0.012691 2663 0.019636 15-1

0.001133 0.000898 0.000795 0.001009 0.000729 0.000874 0.001039 0.00053 0.00095 0.001731 0.00109 0.000177 0.000546 0.0005 0.000796

0.281287 0.28131 0.281292 0.281296 0.28128 0.28133 0.281343 0.281289 0.281313 0.281337 0.281307 0.281286 0.281266 0.281319 0.281319

0.000017 0.000018 0.000014 0.000016 0.000016 0.00002 0.00002 0.000015 0.000022 0.000021 0.000017 0.000012 0.000017 0.000017 0.000015

−52.5 −51.7 −52.4 −52.2 −52.8 −51.0 −50.5 −52.4 −51.6 −50.7 −51.8 −52.6 −53.3 −51.4 −51.4

5.3 6.6 6.1 5.9 5.8 7.3 7.5 6.5 6.6 6.0 6.1 7.0 5.7 7.6 7.1

0.6 0.6 0.5 0.6 0.6 0.7 0.7 0.5 0.8 0.8 0.6 0.4 0.6 0.6 0.5

2.75 2.70 2.72 2.73 2.73 2.67 2.67 2.70 2.70 2.72 2.72 2.68 2.74 2.66 2.68

0.05 0.05 0.04 0.05 0.04 0.06 0.06 0.04 0.06 0.06 0.05 0.03 0.05 0.05 0.04

2.78 2.71 2.74 2.75 2.75 2.68 2.67 2.72 2.71 2.74 2.74 2.69 2.76 2.66 2.69

0.07 0.08 0.06 0.07 0.07 0.09 0.09 0.06 0.09 0.09 0.07 0.05 0.07 0.07 0.07

−0.97 −0.97 −0.98 −0.97 −0.98 −0.97 −0.97 −0.98 −0.97 −0.95 −0.97 −0.99 −0.98 −0.98 −0.98

Mylonitized trondhjemite (S0834) 9-1S 2605 0.036 13-1S 2605 0.0376 2605 0.0803 14-1S 2605 0.0563 15-1S 2605 0.0534 16-1S 2605 0.0475 17-1S 20-1S 2605 0.0354 2605 0.0758 21-1S 2605 0.0753 24-1S 2605 0.0519 25-1S 2605 0.037 28-1S 2605 0.0366 29-1S 2605 0.0807 30-1S

0.0011 0.001 0.0023 0.0015 0.0015 0.0011 0.001 0.0017 0.0019 0.0016 0.001 0.0011 0.0021

0.281357 0.281298 0.281368 0.281306 0.28131 0.281242 0.281376 0.281383 0.281421 0.281419 0.281235 0.281368 0.281385

0.000068 0.000066 0.00005 0.000059 0.000038 0.000084 0.000084 0.000122 0.000038 0.000101 0.000044 0.000083 0.000088

−50.0 −52.1 −49.7 −51.8 −51.7 −54.1 −49.4 −49.1 −47.8 −47.8 −54.4 −49.7 −49.1

6.6 4.7 4.9 4.0 4.3 2.4 7.4 6.4 7.5 8.0 2.4 6.9 5.8

2.4 2.4 1.8 2.1 1.4 3.0 3.0 4.3 1.3 3.6 1.6 3.0 3.1

2.65 2.72 2.72 2.75 2.74 2.81 2.62 2.66 2.62 2.60 2.81 2.64 2.68

0.19 0.18 0.14 0.16 0.11 0.23 0.23 0.34 0.11 0.28 0.12 0.23 0.25

2.66 2.76 2.75 2.80 2.78 2.88 2.63 2.68 2.62 2.60 2.88 2.65 2.70

0.29 0.28 0.22 0.26 0.17 0.36 0.36 0.53 0.16 0.44 0.19 0.36 0.38

−0.97 −0.97 −0.93 −0.95 −0.96 −0.97 −0.97 −0.95 −0.94 −0.95 −0.97 −0.97 −0.94

Gneissic trondhjemite (TS1204) 1-1MA 2650 0.006222 2650 0.006949 4-1MA 2650 0.015224 5-1MA 6-1MA 2650 0.032405 2650 0.007067 6-2MA 2650 0.016898 7-1MA 2650 0.047426 8-1MA 2650 0.015591 10-1MA 12-1MA 2650 0.009352 2650 0.010269 13-1MA 2650 0.006134 15-1MA 2650 0.012302 16-1MA 2650 0.013148 17-1MA 2650 0.010425 18-1MA 2650 0.010826 20-1MA 2650 0.017812 22-1MA 2565 0.0133 2-1R

0.000191 0.000226 0.000434 0.000891 0.000223 0.000459 0.001177 0.000403 0.000354 0.000269 0.00018 0.000439 0.000489 0.00037 0.000402 0.000711 0.00047

0.281211 0.2812 0.281154 0.281218 0.281176 0.281183 0.281282 0.281166 0.281178 0.281219 0.28113 0.281228 0.281213 0.281126 0.281184 0.28121 0.281217

0.000015 0.000016 0.000014 0.000017 0.000012 0.000015 0.000018 0.000017 0.000013 0.000016 0.000014 0.000013 0.00002 0.000018 0.000019 0.000029 0.000013

−55.2 −55.6 −57.2 −55.0 −56.5 −56.2 −52.7 −56.8 −56.4 −54.9 −58.1 −54.6 −55.1 −58.2 −56.2 −55.3 −55.0

4.0 3.6 1.6 3.0 2.7 2.5 4.8 2.0 2.6 4.2 1.2 4.2 3.6 0.7 2.7 3.1 1.8

0.5 0.6 0.5 0.6 0.4 0.5 0.6 0.6 0.5 0.6 0.5 0.5 0.7 0.7 0.7 1.1 0.5

2.79 2.80 2.88 2.83 2.83 2.84 2.76 2.86 2.84 2.78 2.89 2.78 2.80 2.91 2.84 2.82 2.80

0.04 0.04 0.04 0.05 0.03 0.04 0.05 0.05 0.03 0.04 0.04 0.04 0.05 0.05 0.05 0.08 0.04

2.83 2.85 2.95 2.88 2.90 2.91 2.79 2.93 2.90 2.82 2.97 2.82 2.85 3.00 2.90 2.88 2.87

0.06 0.07 0.06 0.07 0.05 0.07 0.08 0.07 0.06 0.07 0.06 0.06 0.09 0.08 0.08 0.13 0.06

−0.99 −0.99 −0.99 −0.97 −0.99 −0.99 −0.96 −0.99 −0.99 −0.99 −0.99 −0.99 −0.99 -0.99 -0.99 -0.98 -0.99

876

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

Table 2 (Continued) Hf spot

Age (Ma)

176

3-1R 7-2R 9-1R 11-1R 14-1R 19-1R 21-1R

2565 2565 2565 2565 2565 2565 2565

0.007563 0.006432 0.00946 0.013126 0.007401 0.013071 0.011187

0.000221 0.000221 0.000509 0.00043 0.000208 0.000443 0.000381

0.073913 0.039833 0.044065 0.035365 0.051013 0.057004 0.032401 0.043176 0.063408 0.061643 0.036347

0.001331 0.000715 0.000715 0.000704 0.000897 0.000867 0.000511 0.000716 0.001085 0.001083 0.000756

Gneissic granite (S1136) 1-2 2600 2-1 2600 3-1 2600 6-1 2600 2600 7-1 2600 8-1 2600 8-2 2600 9-1 2600 10-1 2600 10-2 2600 11-1

Yb/177 Hf

176

Lu/177 Hf

±2

εHf (0)

εHf (t)

2

tDM1 (Ga)

0.281247 0.281188 0.281139 0.281232 0.281184 0.28122 0.281182

0.000016 0.000013 0.000026 0.000015 0.000016 0.000017 0.000021

−53.9 −56.0 −57.8 −54.5 −56.2 −54.9 −56.2

3.3 1.2 −1.1 2.4 1.1 2.0 0.7

0.6 0.5 0.9 0.5 0.6 0.6 0.7

2.74 2.82 2.90 2.77 2.82 2.79 2.84

0.281301 0.281227 0.281305 0.281318 0.281309 0.281317 0.281228 0.281206 0.281383 0.281417 0.281281

0.000023 0.000024 0.000018 0.000022 0.000026 0.000031 0.000024 0.000027 0.000021 0.000017 0.000022

−52.0 −54.6 −51.9 −51.4 −51.8 −51.4 −54.6 −55.4 −49.1 −47.9 −52.8

4.1 2.5 5.3 5.8 5.1 5.5 2.9 1.8 7.4 8.6 4.4

0.8 0.9 0.7 0.8 0.9 1.1 0.9 1.0 0.7 0.6 0.8

2.75 2.80 2.70 2.68 2.70 2.69 2.79 2.83 2.62 2.57 2.73

176

Hf/177 Hf

2

tDM2(CC) (Ga)

2

fLu/Hf

0.04 0.04 0.07 0.04 0.04 0.04 55.00

2.80 2.90 3.02 2.84 2.91 2.87 2.93

0.07 0.06 0.11 0.07 0.07 0.07 0.09

-0.99 -0.99 −0.98 −0.99 −0.99 −0.99 −0.99

0.06 0.07 0.05 0.06 0.07 0.08 0.07 0.07 0.06 0.05 0.06

2.79 2.87 2.73 2.70 2.74 2.72 2.85 2.90 2.62 2.56 2.77

0.10 0.11 0.08 0.10 0.11 0.13 0.11 0.12 0.09 0.07 0.10

−0.96 −0.98 −0.98 −0.98 −0.97 −0.97 −0.98 −0.98 −0.97 −0.97 −0.98

Note: (1) Excepting for samples S0834 and S1028, LA-ICPMS Hf isotope spots are same as those for SHRIMP U–Pb dating and (2) tDM2(CC) represents Hf crustal model age.

Fig. 4. Cathodoluminescence images of representative zircons from middle Neoarchean magmatic rocks in western Shandong. (a) and (b) Hornblendite (S1144); (c) and (d) mylonitized tonalite (S0722); (e) and (f) gneissic tonalite (S1028); (g) and (h) gneissic trondhjemite (SY0335A); (i) and (j) gneissic trondhjemite (S0726); (k) and (l) gneissic trondhjemite (CY002-TM1); (m) and (n) gneissic trondhjemite (SY0301); (o) and (p) mylonitized trondhjemite (S0834); (q) and (r) gneissic trondhjemite (TS1204); (s) and (t) gneissic granodiorite (S1136). For samples S1144, S1028, CY002-TM1 and TS1204, MA, RC, R and C represent magmatic zircon, recrystallized zircon, rim (metamorphic) and core (inherited) domains, respectively. Zircons from other samples are magmatic in origin.

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

877

Fig. 4. (Continued .)

(Fig. 5c) with three of these yielding a weighted mean 207 Pb/206 Pb age of 2662 ± 9 Ma (MSWD = 2.8). This is interpreted as representing the formation age of the tonalite. 5.4. Gneissic trondhjemite (SY0335A) The zircon is elongate in shape and show oscillatory zoning in CL images (Fig. 4g and h). Some grains are homogeneous or show broadly banded zoning in their centers, suggesting that the physico-chemical conditions (including water content) in the magma chamber changed from stable to unstable during the magmatic process when zircon crystallized. Eleven analyses on 11 zircon grains (Table 1) show variable degrees of lead loss but form a linear array on a concordia diagram (Fig. 5d). Three analyses yielded a weighted mean 207 Pb/206 Pb age of 2642 ± 12 Ma (MSWD = 0.81) that is considered to represent the formation age of the trondhjemite. The U contents and Th/U ratios are 180–805 ppm and 0.04–0.16 (0.46 for grain 8.1), respectively. These low Th/U ratios are uncommon for magmatic zircon. 5.5. Gneissic trondhjemite (S0726) The zircon grains are stubby or elongate in shape and show oscillatory zoning in CL images (Fig. 4i and j). It appears likely that some zircon grains underwent recrystallization with narrow overgrowth rims. Fifteen analyses on 15 zircon grains yielded U contents and Th/U ratios of 17–496 ppm and 0.13–1.52 (Table 1), respectively. Except for spots 12.1 and 13.1, the remaining data are concentrated on or close to concordia (Fig. 5e) and define a weighted mean 207 Pb/206 Pb age of 2647 Ma with a large error (±17 Ma) and MSWD value (3.42). Excluding three analyses with older 207 Pb/206 Pb ages (3.1, 9.1 and 11.1), some of which may be partly on inherited cores (e.g. Fig. 4j, grain 11), the remaining 9 analyses yielded a weighted mean 207 Pb/206 Pb age of 2623 ± 9 Ma (MSWD = 0.69) that is interpreted as representing the emplacement age of the trondhjemite.

5.6. Gneissic trondhjemite (CY002-TM1) The zircon is stubby in shape, and some show core-rim structures in CL images (Fig. 4k and l). The rims display oscillatory zoning and are considered to be magmatic in origin, and the cores commonly show recrystallization and are interpreted to be inherited. Twenty-six analyses were performed on 20 zircon grains (Table 1). Eighteen analyses on magmatic domains have U contents and Th/U ratios ranging from 46 to 527 ppm and 0.04–0.44 (mostly <0.20), respectively, and show lead loss to different degrees (Fig. 5f). Nine analyses on or close to concordia yielded a weighted mean 207 Pb/206 Pb age of 2667 ± 10 Ma (MSWD = 1.14) that is interpreted as the time of formation of the trondhjemite. Eight analyses on cores have U contents and Th/U ratios of 36–233 ppm and 0.21–0.77. Their 207 Pb/206 Pb ages range from 2716 to 2673 Ma, but the younger ages may not represent the true crystallization ages but are due to recrystallization. 5.7. Gneissic trondhjemite (SY0301) The zircon grains are elongate in shape and show oscillatory zoning in CL images (Fig. 4m and n). Rims with high-U and oscillatory zoning are developed on some zircon grains and are considered to have formed at a late stage of magma crystallization. Some domains show recrystallization but have the same age as the magmatic domains (Fig. 4n, grain 9). Eighteen analyses on 18 zircon grains yielded U contents of 61–2086 ppm and Th/U ratios of 0.16–0.97 (Table 1) and commonly show strong lead loss (Fig. 5g). Analyses closest to concordia have a weighted mean 207 Pb/206 Pb age of 2663 ± 11 Ma (MSWD = 2.10) that is considered to represent the emplacement age of the trondhjemite. Analysis 1.1 has an older 207 Pb/206 Pb age and is considered to be on an inherited domain. 5.8. Mylonitized trondhjemite (S0834) The zircon is clear with euhedral, prismatic faces and pyramidal terminations and show oscillatory zoning in CL images

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Fig. 5. Concordia diagrams for SHRIMP U–Pb zircon analyses from middle Neoarchean magmatic rocks in western Shandong. (a) Hornblendite (S1144); (b) mylonitized tonalite (S0722); (c) gneissic tonalite (S1028); (d) gneissic trondhjemite (SY0335A); (e) gneissic trondhjemite (S0726); (f) gneissic trondhjemite (CY002-TM1); (g) gneissic trondhjemite (SY0301); (h) mylonitized trondhjemite (S0834); (i) gneissic trondhjemite (TS1204); (j) gneissic granite (S1136). For samples S1144, S1028, CY002-TM1 and TS1204, MA, RC, R and C represent magmatic zircon, recrystallized zircon, rim (metamorphic) and core (inherited) domains, respectively. Zircons from other samples are magmatic in origin.

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

879

Fig. 6. Age versus εHf diagram of zircons from middle Neoarchean magmatic rocks in western Shandong. (a) Hornblendite (S1144); (b) mylonitized tonalite (S0722); (c) gneissic tonalite (S1028); (d) gneissic trondhjemite (SY0335A); (e) gneissic trondhjemite (S0726); (f) gneissic trondhjemite (CY002-TM1); (g) gneissic trondhjemite (SY0301); (h) mylonitized trondhjemite (S0834); (i) gneissic trondhjemite (TS1204); and (j) gneissic granite (S1136).

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Fig. 7. (a) Summary age versus εHf diagram and (b) crustal Hf model age histogram for zircon from middle to early Neoarchean magmatic rocks in western Shandong. In (a) the Hf isotopic data of ∼2.7 Ga zircons are from Wan et al. (2011) and this study. For sample S0741 the Hf isotopic analyses on zircon are from two experiments with similar results. See text for further interpretation.

Table 3 Summary of middle Neoarchean magmatic rocks in western Shandong. Dating techenique

εHf (t)

19 8 9 12 9 10 11 12 10

SHRIMP SHRIMP SHRIMP SHRIMP SHRIMP SHRIMP SHRIMP SHRIMP SHRIMP

15 18 16 50 27 32 22

SHRIMP SHRIMP SHRIMP SHRIMP LA-ICPMS LA-ICPMS LA-ICPMS

No.

Sample no.

Rock type

Location

Age (Ma)

1 2 3 4 5 6 7 8 9

S1144 S0722 S1028 SY0335A S0726 CY002-TM1 SY0301 S0834 TS1204

Hornblendite Mylonitized tonalite Gneissic tonalite Gneissic trondhjemite Gneissic trondhjemite Gneissic trondhjemite Gneissic trondhjemite Mylonitized trondhjemite Gneissic trondhjemite

Southwest of Qixingtai West of Panchegou Yishan Caishixi, Taishan Southwest of Qixingtai Northwest of Dawangzhuang North of Yanglingguan Southeast of Huamawan East of Xintai

2597 2615 2662 2642 2623 2667 2663 2605 2650

± ± ± ± ± ± ± ± ±

S1136 SD0502 SD0503 SD0512 SD0601 SD0602 SD0604

Gneissic granite Gneissic tonalite Gneissic trondhjemite Felsic vein Amphibolite Felsic vein Gneissic tonalite

Northwest of Panchegou Lihang, Taishan Taishan Lihang, Taishan Caishixi, Taishan Caishixi, Taishan Taishan

2600 2627 2620 2607 2678 2660 2637

± ± ± ± ± ± ±

10 11 12 13 14 15 16

(Fig. 4o and p). Many zircon grains display recrystallization to variable degrees but are identical in age to the magmatic domains. This may suggest that recrystallization occurred soon after crystallization of the zircon. Twelve analyses on 12 zircon grains yielded U contents of 107–543 ppm and large variations in Th/U from 0.02 to 0.95 (Table 1). Most grains show strong lead loss, but two analyses plot on corcondia and yielded a weighted mean 207 Pb/206 Pb age of 2605 ± 12 Ma (MSWD = 0.97) (Fig. 5h). This is interpreted to represent the emplacement age of the trondhjemite. Analysis 3.1 on an inherited domain has an older 207 Pb/206 Pb age. 5.9. Gneissic trondhjemite (TS1204) The zircon grains are stubby or elongate in shape and display oscillatory zoning in CL images but commonly with recrystallization and overgrowth (Fig. 4q and r). The recrystallized domains are identical in age to the magmatic domains but different from the overgrowth rims. Twenty-three analyses were carried out on 21 zircon grains (Table 1). Fifteen analyses on magmatic or recrystallized domains yielded U contents and Th/U ratios ranging from 32 to 957 ppm and 0.06 to 1.37, respectively, with the recrystallized domains commonly lower in Th/U ratios. They show variable lead loss (Fig. 5i), and four analyses plotting closest to concordia have a weighted mean 207 Pb/206 Pb age of 2650 ± 10 Ma (MSWD = 0.63). This is considered to be the emplacement age of the trondhjemite. Eight analyses on the rims have U contents and Th/U ratios of 100–1044 ppm and 0.04–0.22 (0.35 for 3.1R), respectively, with Th/U ratios commonly lower than those of the magmatic or

tDM2(CC) (Ga)

Reference

1.4–8.6 3.4–6.0 6.2–11.3 0.0–5.0 3.6–6.7

2.92–2.56 2.83–2.71 2.73–2.47 3.01–2.76 2.83–2.67

5.3–7.6

2.78–2.66

0.7–4.8 −1.1 to 3.3 1.8–11.1

3.00–2.79 3.02–2.80 2.90–2.44

This study This study This study This study This study This study This study This study This study This study Lu et al. (2008) Lu et al. (2008) Lu et al. (2008) Lu et al. (2008) Lu et al. (2008) Lu et al. (2008)

recrystallized domains. The rims also show lead loss to different degrees, and three analyses on or close to concordia yielded a weighted mean 207 Pb/206 Pb age of 2565 ± 15 Ma (MSWD = 0.21), which may be slightly older than the metamorphic and anatectic event that these overgrowths represent, due to the analytical spot partly overlapping onto the recrystallized domain during analysis. 5.10. Gneissic granite (S1136) The zircon grains are stubby or elongate in shape and show oscillatory zoning in CL images (Fig. 4s and t). Some grains appear to contain inherited cores (Fig. 4s, grain 1), but these have the same age as the magmatic domains. Some grains have narrow overgrowth rims (Fig. 4s, grain 5). Thirteen analyses were carried out on 10 magmatic zircon grains (Table 1), yielding U contents of 82–626 ppm and Th/U ratios of 0.41–1.06. Although most analyses show lead loss to variable degrees, some are located on or near concordia (Fig. 5j) and yielded a weighted mean 207 Pb/206 Pb age of 2600 ± 15 Ma (MSWD = 0.23). This is taken to approximate the time of crystallization of the granite. 6. Hf-in-zircon isotopic signatures Hf-in-zircon isotopic compositions have been obtained on all samples dated in this study (Table 2). In most cases the Hf isotopic analyses were carried out on the spots previously analyzed on SHRIMP. Exceptions are samples S0834 and S1028 for which most Hf isotopic analyses were made on undated grains because

Y. Wan et al. / Precambrian Research 255 (2014) 865–884

these magmatic zircon grains are uniform in age. In a Hf isotopic evolution diagram (Fig. 6) magmatic zircon from all samples has εHf (t) values (t is the weighted mean 207 Pb/206 Pb age of magmatic zircon from each sample) varying between the CHUR and depleted mantle lines. Magmatic zircon from seven samples (S1144, S1028, S0726, CY002-TM1, SY0301, S0834, and S1136) has εHf (t) values up to or above the depleted mantle line, and some show large variations in their εHf (t) values down to 0 (Fig. 6a, c, e–h, and j). Their Hf crustal model ages are 3.0–2.6 Ga. Compared with the magmatic zircon mentioned above, magmatic zircon from the other three samples (S0722, SY0335A, and TS1204) shows relative enrichment with εHf (t) values varying from 0.0 to 6.0. Their crustal model ages are 3.0–2.7 Ga. Metamorphic zircon from sample TS1204 is similar in Hf isotope composition to magmatic zircon from the same sample, having ␧Hf (t) (t = 2.6 Ga) and Hf crustal model ages varying from 3.3 to −1 and 3.0 to 2.8 Ga, respectively. Inherited cores from sample CY002-TM1 have ␧Hf (t) and Hf crustal model ages of 4.2–9.0 and 2.9–2.6 Ga, respectively.

881

Fig. 8. Age histogram of zircon from Neoarchean magmatic rocks in western Shandong Province. Data are from Du et al. (2003), Jiang et al. (2010), Lu et al. (2008), Peng et al. (2012), Wan et al. (2010a, 2011b) and this study.

7. Discussion Sixteen samples of middle Neoarchean age dated in this study and in previous work (Lu et al., 2008) include metamorphosed mafic-ultramafic rocks, gneissic tonalite, gneissic trondhjemite, gneissic granodiorite and gneissic granite. Their zircon ages and Hf-in-zircon isotopic data are summarized in Table 3. Compared with the early Neoarchean, the rock types in the middle Neoarchean are more complex, but trondhjemite and tonalite are still the main components, whereas potassium-rich granodiorite and granite are rare. Gnessic trondhjemites occur widely in the west of the Qixingtai-Dawangzhuang belt, but zircon dating of two samples (S0726 and CY002-TM1) indicated that these trondhjemites formed at different times (2623 ± 9 Ma and 2667 ± 10 Ma). The middle Neoarchean rocks mainly occur in the northeastern portion of Belt B and show a close spatial relationship with the early Neoarchean rocks. However, they have also been identified as enclaves in 2.5 Ga granites and anatectic rocks in Belt A as revealed by zircon dating of samples S1028 and TS1204 from Yishan and the northeast of Xintai. This supports the conclusion of Wan et al. (2010a) that the widely distributed ∼2.5 Ga granites in Belt A originated through crustal recycling of >2.6 Ga rocks. In this study, only a meta-ultramafic sample (S1144) was taken from Belt B for zircon dating and yielded a magmatic age of 2.60 Ga. However, we cannot conclude from this that all the ultramafic rocks in the WSP (especially in Belt C) formed during this period, although they are similar in appearance. It appears that the middle Neoarchean rocks are slightly smaller in areal extent than the early Neoarchean rocks if considering the WSP basement as a whole. Early studies indicated that magmatic zircon from most ∼2.7 Ga rocks in the WSP has depleted Hf isotopic compositions, but gneissic granodiorite sample S0741 contains magmatic zircon with εHf (t) values from 1.8 to −13.9, showing Hf isotope enrichment (Wan et al., 2011b). The latter is verified by new Hf isotope analysis on zircon from the same sample. The zircon Hf isotope enrichment of sample S0741 (Fig. 7a) indicates the existence of >2.8 Ga continental material in the WSP. On the other hand, it is clear that both juvenile additions from the depleted mantle and crustal recycling played important roles during different magmatic events of the middle Neoarchean (Fig. 7a). Based on the comparison of Hf-in-zircon isotopic compositions, we speculate that some middle Neoarchean trondhjemitic rocks with high SiO2 contents may be derived from the early Neoarchean rocks or at least were influenced by the early Neoarchean rocks in their formation processes. This is consistent with the phenomenon that magmatic zircon from trondhjemite sample CY002-TM1 contains ∼2.7 Ga inherited cores

and zircon from samples S0335A and CY002-TM1 shows oscillatory zoning but is commonly low in Th/U ratios, being similar to anatectic zircon. It is notable that magmatic zircon from ultramafic rock S1144 has a similar Hf isotopic composition as those of the early Neoarchean rocks. It is uncertain whether this is due to contamination with crustal material during its formation process or represents a compositional feature of the mantle source. Juvenile additions to the WSP continental crust occurred in the early, middle and late Neoarchean. However, it seems likely that crustal recycling played an increasingly more important role than juvenile addition of mantle material with time from the early to late Neoarchean in terms of the variations of rock associations and zircon Hf isotope compositions (this study; Wan et al., 2010a, 2011b; Y.S. Wan, unpublished data). The Hf crustal model ages of magmatic zircon from the middle Neoarchean rocks mainly vary from 2.9 to 2.6 Ga (Fig. 7b). Some middle Neoarchean trondhjemites have magmatic zircon with εHf (t) values close to 0 and Hf crustal model ages >2.9 Ga (Table 2). This also supports the conclusion that there are >2.8 Ga continental rocks in the WSP although their scale and distribution are unknown. The WSP is the only area in the NCC where early to late Neoarchean rocks are widely distributed at present leves of exposure, giving us a chance to understand the Neoarchean tectonic evolution of the entire craton. We suggest that the Neoarchean tectonic evolution of the WSP can be divided into two events, namely middle to early Neoarchean (or simply, early Neoarchean, 2.75–2.6 Ga) and late Neoarchean (2.6–2.5 Ga). The main reasons are as follows: (1) Geological records are almost continuous from the early to middle Neoarchean (Figs. 8 and 9); (2), there is no ∼2.7 Ga metamorphism, but ∼2.6 Ga metamorphism has been widely identified (Du et al., 2003, 2005; Y.S. Wan, unpublished data); (3) ∼2.7 Ga supracrustal rocks occur widely (Lu et al., 2008; Wan et al., 2011) but ∼2.6 Ga supracrustal rocks have not been identified; (4) it appears that there was a “quiet period” between 2.60 and 2.56 Ga (Fig. 8) because most zircon ages between 2.60 and 2.56 Ga are only slightly younger than 2.60 Ga or older than 2.56 Ga, or have large errors or result from discordant analyses; (5) ∼2.6 Ga ultramafic rocks are widely distributed in the area. The 2.60 Ga hornblendite (sample S1144) is a meta-pyroxenite with a coarsegrained texture and contains large magmatic zircon grains. Crystal accumulation may have played an important role in the formation of this ultramafic rock, probably suggesting a stable and extensional environment. This division is important for understanding geological evolution of the NCC during the Neoarchean period. If

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Fig. 9. Zircon age variation diagram (with error bars) for early to middle Neoarchean magmatic rocks in western Shandong Province. Data are from Du et al. (2003), Jiang et al. (2010), Lu et al. (2008), Wan et al. (2011b) and this study.

a plate regime similar to the present one played a role in the late Neoarchean NCC geological evolution, as suggested by some geologists, it was necessary that several blocks with relatively high rigidity had been formed at the end of early Neoarchean (∼2.6 Ga). Middle Neoarchean rocks have only been identified in a few areas in the NCC until now. However, as revealed in the WSP, rocks of this age may be more widespread and occur in more areas in the NCC after more work is carried out, similar to the early Neoarchean rocks which have now been identified in many areas of the NCC (Wan et al., 2014; references therein). It may also be appropriate to consider 2.6 Ga as the boundary between the early and late Neoarchean periods in the entire NCC, although more work is required to confirm this conclusion. In some other areas such as southern Africa, North America, southern India and Western Australia, metamorphism and crustally derived granites were emplaced at around 2.6 Ga, and granitoid magmatism was continuous from ∼2.7 Ga to ∼2.6 Ga (Bagai et al., 2002; Bennett et al., 2005; Jayananda et al., 2006; Kramers and Mouri, 2011; Van Kranendonk et al., 2013). This is consistent with the idea to treat 2.6 Ga as a boundary between the early and late Neoarchean geological periods. 8. Conclusions (1) Several compositional variations in middle Neoarchean magmatic rocks have been identified in the WSP, including metamorphosed mafic-ultramafic rocks and gneissic tonalite, trondhjemite, granodiorite and granite. These rock types mainly occur together with early Neoarchean rocks in the northeastern portion of Belt B.

(2) Both juvenile additions from a depleted mantle source and crustal recycling played important roles in the middle Neoarchean. It seems likely that crustal recycling became increasingly important compared to juvenile additions with time from the early to late Neoarchean. (3) The Neoarchean tectonic evolution of the WSP can be divided into two periods, namely early Neoarchean (2.75–2.6 Ga) and late Neoarchean (2.6–2.5 Ga). This may also be the case for the entire NCC.

Acknowledgements We thank Chun Yang, Hua Tao, Jianhui Liu, Liqing Zhou and Ning Li for mount making and zircon CL imaging, and Chunli Ge, Kejun Hou, Jinghui Yang and Yueheng Yang for Hf-in-zircon isotopic analysis. Zircon standards were provided by Ian Williams, Lance Black and Lutz Nasdala. We are grateful to C. Friend, an anonymous reviewer, and guest editor A. Nutman for their valuable comments. This research was financially supported by the Major State Basic Research Program of the People’s Republic of China (2012CB416600), the National Natural Science Foundation of China (40672127) and the Key Program of the Ministry of Land and Resources of China (12120114021301, 12120113013700, and 1212010811033).

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