Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the northern Great Xing’an Range, NE China

Accepted Manuscript Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the Northern Great Xing’an Range, NE China Zhiqiang Feng, Yongjiang Liu, Yanrong Li, Weimin Li, Quanbo Wen, Binqiang Liu, Jianping Zhou, Yingli Zhao PII: DOI: Reference:

S1367-9120(16)30406-0 http://dx.doi.org/10.1016/j.jseaes.2016.12.006 JAES 2875

To appear in:

Journal of Asian Earth Sciences

Received Date: Revised Date: Accepted Date:

6 June 2016 7 December 2016 7 December 2016

Please cite this article as: Feng, Z., Liu, Y., Li, Y., Li, W., Wen, Q., Liu, B., Zhou, J., Zhao, Y., Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the Northern Great Xing’an Range, NE China, Journal of Asian Earth Sciences (2016), doi: http://dx.doi.org/10.1016/j.jseaes.2016.12.006

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Ages, geochemistry and tectonic implications of the Cambrian igneous rocks in the Northern Great Xing’an Range, NE China Zhiqiang Feng

a, b, c

, Yongjiang Liu

b, c,

*, Yanrong Li a, Weimin Li

b, c

, Quanbo

Wen b, c, Binqiang Liu b, c, Jianping Zhou b, c, Yingli Zhao b, c a

Department of Earth science and Engineering, Taiyuan University of Technology,

Taiyuan 030024, China b

College of Earth Sciences, Jilin University, Jianshe Str. 2199, Changchun 130061,

Jilin, China c

Key laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of

Land and Resources, China Abstract: The Xinlin–Xiguitu suture zone, located in the Great Xing’an Range, NE China, in the eastern segment of the Central Asian Orogenic Belt (CAOB), represents the boundary between the Erguna and Xing’an micro-continental blocks. The exact location of the Xinlin-Xiguitu suture zone has been debated, especially, the location of the northern extension of the suture zone. In this study, based on a detailed field, geochemical, geochronological and Sr–Nd–Hf isotope study, we focus our work on the Cambrian igneous rocks in the Erguna-Xing’an block. The Xinglong granitoids, mainly include ~520 Ma diorite, ~470 Ma monzogranite and ~480 Ma pyroxene diorite. The granitoids show medium to high-K calc-alkaline series characteristics with post-collision granite affinity. The circa 500 Ma granitoids have low εHf (t) values (–16.6 to +2.2) and ancient two-stage model (TDM2) ages between 1317 Ma and 2528

Ma. These results indicate the primary magmas of the Xinglong granitoids were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials, and formed in a post-collision tectonic setting after the amalgamation of the Erguna and Xing’an blocks. Compared with the Xinglong granitoids, the Duobaoshan igneous rocks are consisted of the approximately coeval rhyolitic tuffs (491 ± 5 Ma) and ultramafic intrusions (497 ± 5 Ma) within the Duobaoshan Formation. They are generally enriched in large ion lithophile elements (LILEs) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), consistent with the geochemistry of igneous rocks from island arcs or active continental margins. The ultramafic have high positive εHf (t) values (+1.3 to +15) and εNd (t) (+1.86 to +2.28), and relatively young two-stage model (TDM2) ages and low initial 87Sr/86Sr ratios (0.70628–0.70853), indicating the partial melting of a depleted mantle source from a subducted slab in the ocean basin between the Erguna-Xing’an and Songliao blocks. The rhyolitic tuffs contain a group of Phanerozoic zircons with εHf (t) values (–4.6 to +15.0), suggesting that the rhyolitic tuffs were derived from juvenile lower crustal material with some ancient crustal material. Coupled with our previous geochemical and isotopic studies on Early Paleozoic igneous rocks, we proposed that the collision of the Erguna and Xing’an blocks at least took place ca. 500 Ma ago, and that there exist in a westward subduction of an oceanic plate between the Eruguna-Xing’an and Songliao blocks, took place during the Early Ordovician. Up to now, there are more evidences and constraints that the

northern extension location of the Xinlin-Xiguitu suture zone is located in the Jifeng–Xinglong areas.

Key words: Great Xing’an Range; Early Paleozoic; Igneous rocks; Sr–Nd–Hf isotopes; Xinlin–Xiguitu suture zone; Central Asian Orogenic Belt

1. Introduction

The Central Asian Orogenic Belt (CAOB) (also known as the Altaids, Central Asian Mobile Belt, or Central Asian Orogenic System) (Jahn et al., 2004), is located between the Siberian and Russian Cratons to the north, and the Tarim and North China Cratons to the south (Sengör et al., 1993; Sengör and Natal’in, 1996; Fig. 1a). It is one of the largest complex accretionary orogens on Earth and considered to records the breakup of the Rodinia supercontinent and the creation of the Eurasian continent over a period of some 800 million years (Li et al., 2006; Kröner et al., 2010, 2014), through accretion of ophiolitic mélanges, arc/back-arc systems, and microcontinental fragments (Sengör et al., 1993). Despite abundant and new studies published on the CAOB, our understanding is still limited due to insufficiently detailed studies throughout the vast area. Especially, both the correlations of blocks and sutures and the tectonic relationships between different divisions remain uncertain (Zheng et al. 2009; Sun et al. 2011; Zhang et al.,

2013; Xu et al., 2014, 2015; Han et al., 2015; Liu et al., 2016). At present, tectonic division of the CAOB, two huge oroclines, the Tuva-Mongolia and Kazakhstan oroclines are remarkably displayed in the western part of the CAOB (Fig.1a; Sengör et al., 1993). A long structural belt, which extends along the outside margin of the Tuva-Mongolian orocline and was named as South Mongolia-Da Xing’an suture (also called the Main Mongolian Lineament in some references, e.g. Huang et al., 1977; Ren et al., 1999a, 1999b; Badarch et al., 2002) separates Mongolian portion of the CAOB into two tectonic domains, with an Early Paleozoic one to north and a Late Paleozoic one to south. The eastern extension to China of the Main Mongolian Lineament, also known as the Xinlin-Xiguitu suture zone, which was considered as the Early Paleozoic suture between the Erguna and Xing’an blocks by most geologists in NE China (Fig.1a; Ge et al. 2005; Wang et al. 2008; Zhang et al. 2008; Miao et al., 2004, 2007, 2015; Wu et al. 2011; Xu et al., 2013; Liu et al. 2010, 2016; Zhou et al. 2009, 2011a, b, 2015; Han et al. 2011, 2012a, b, 2015; Xu et al., 2014, 2015; Feng et al., 2014, 2015, 2016). In this suture, high-pressure blueschists with ca. 520 Ma were found at Toudaoqiao (Zhou et al., 2015; Miao et al., 2015), post-orogenic migmatites with ca. 490 Ma crop out at Tahe (Ge et al., 2005; Wu et al., 2005) and SSZ-type ophiolitic mélanges with ca. 650 Ma were exposed at Jifeng-Huyuan-Gaxian (IMBGMR, 1985b; Li, 1991; She et al., 2012; Feng et al., 2014, 2015, 2016). Although the collision time between the Erguna and Xing’an blocks occurred in the Cambrian, no high quality geochronological data are currently available for the Cambrian igneous rocks around

the Xinlin-Xiguitu suture zone, which makes it difficult to place the terrane in a reliable tectonic context. To resolve these issues, we present new whole-rock geochemical data and zircon U-Pb ages and Sr-Nd-Hf isotope compositions for the Cambrian igneous rocks in the northern Great Xing’an Range (GXR), which will place important constraints on the location and age of the Xinlin–Xiguitu Suture zone.

2.1 General geological setting

The study area situated in the northern GXR is an important tectonic unit in the eastern section of the Central Asia Orogenic belt (CAOB) (Zonenshain et al., 1990; Sengör et al., 1993). The northern GXR consists of the Erguna, Xing’an and Songliao blocks, from northwest to southeast. The Erguna block is located in the west of the Xinlin-Xiguitu suture zone and is linked with the Ereendavaa block in Mongolia (Fig.1a; Badarch et al., 2002). The Erguna block is an ancient microcontinent of Precambrian crystalline basement that consists mainly of amphibolite and greenschist facies metamorphic rocks of the Xinghuadukou Group and the Jiageda Group, respectively, and Neoproterozoic granitic rocks (Tang et al. 2013; Sun et al. 2012; Zhou et al., 2011a; Zhang et al., 2013). Paleozoic and Mesozoic granites dominate the main body of the Erguna block and are covered by Mesozoic sediments (ca. 150 Ma; Wu et al., 2011) and volcanic rocks of the Mohe and Labudalin–Genhe basins (Zhou et al., 2011a; Zhang et al., 2013; HBGMR, 1993; Wu et al., 2005; Ge et al., 2005, 2007; Wu et al., 2011).

The Xing’an block is one of the major microcontinental blocks in the GXR and sits adjacent to the southeast of the Erguna block (Fig. 1b). It is characterized by a huge volume of Mesozoic volcanic rocks and granitoids, and minor thicknesses of Paleozoic sedimentary strata. Metamorphic rocks in the study area that were previously considered to be Proterozoic in age (i.e., the Xinkailing, Wolegen, and Fengshuigouhe groups; see IMBGMR, 1996) have now been shown to be metamorphic complexes related to late Paleozoic to early Mesozoic orogenic processes (Miao et al., 2004, 2007; Xu et al., 2012). In the north of the Xing’an block, at Duobaoshan, an Ordovician island arc with coeval porphyry Cu mineralization has been identified, while early Paleozoic limestones, late Paleozoic clastic sedimentary rocks, and Mesozoic volcanic rocks are present across the entire region (HBGMR, 1993; Ge et al., 2007; Zhang et al., 2008; 2010). A small number of Neoproterozoic granitoids have been found in the south Mongolian microcontinent, which is the western extension of the Xing’an block in Mongolia (Badarch et al., 2002). The Songliao block is represented by the Mesozoic Songliao Basin and the Zhangguangcai Mountains in the east (Fig. 1b). Petrographic examination of drill cores obtained during petroleum exploration reveal that most of the basement rocks are weakly deformed and metamorphosed Phanerozoic granites and Paleozoic strata (Wu et al., 2011; Pei et al., 2007). The Zhangguangcai Mountains was mainly consist of Phanerozoic granites and lenses of amphibolite facies metamorphic rocks (Dongfengshan Group) occur in the northern part of the Zhangguangcai Mountains (HBGMR, 1993; Liu et al., 2008; Wu et al., 2011).

2.2 Sample locations and description

The samples analyzed during this study were collected from the Xinglong and Duobaoshan areas (Fig. 2). Samples of diorite (HJY01-a–d) were collected in the Beixili region, ~2 km northeast of Huibaogou (Fig.2a; 51°58′59.2″N, 125°42′3.7″E). The diorite has been previously mapped as Carboniferous, with a K–Ar age of 328 Ma (1:200,000 Regional Geological Survey) (HBGMR, 1993). It is dark grey in color, with a massive structure and a hypidiomorphic granular texture. It contains plagioclase (60%–70%), hornblende (20%–30%), and quartz (5%–10%), as well as accessory zircon, magnetite, and apatite (~2%). The majority of crystals range from 0.2 to 3 mm in size. The plagioclase is andesine in composition and has been partly altered to sericite and epidote. The quartz has an allotriomorphic granular texture and occurs in interstices among the plagioclase crystals (Fig. 3g). Samples of monzogranite (HJY02-a–d) were collected at a site located ~8 km northeast of the Beixili forest (Fig.2a; 51°53′15.6″N, 125°41′35.7″E). The samples have undergone greenschist-facies metamorphism and are pale yellow in color, with a blastoporphyritic texture and schistose structure. They contain 25%–50% phenocrysts, mostly plagioclase and perthite, set in a groundmass (50%–75%) of quartz, K-feldspar, and chlorite (Fig. 3f). Samples of pyroxene diorite (HJY03-a–d) were collected from a set of E–W trending outcrops located northeast of the Beixili forest (Fig.2a; 51°5245.9N, 125°3910.2E). The pyroxene diorites are black and massive, and contain plagioclase

(65%–75%, An = 38%–48%) and hornblende (10%–15%), plus minor amounts of clinopyroxene. The plagioclase crystals are euhedral and 0.2–2 mm in length. The clinopyroxene typically occurs as relics, variably replaced by hornblende (Fig. 3h, l). Samples DBS01(ultramafic rock) and DBS02 (rhyolitic tuff) were collected southwest of Sanfengshan in Nenjiang County, along the highway between Woduhe and Duobaoshan (Fig. 2b; 50°20′45.0″N, 125°40′01.8″E). In the Duobaoshan area, the Early Ordovician Duobaoshan Formation is characterized by gray–black, fine- to medium-bedded siltstone that grades downward into gray–yellowish tuffaceous slate and then into alternating sandstone, siltstone, rhyolitic tuff, and claystone, with locally interbedded andesite (HBGMR, 1993). Importantly, the sample DBS01 (ultramafic rock) is taken from an ultramafic intrusion within the Duobaoshan Formation. It is dark green with a schistose structure and lepidoblastic texture, and is dominated by serpentine (50%–70%), chlorite (44%), and talc (8%), plus minor opaque minerals (Fig. 3a, b). Sample DBS02 (rhyolitic tuff) is from a dark yellow rhyolitic tuff layer within the Duobaoshan Formation. It has a schistose structure and consists predominantly of cryptocrystalline minerals that have been carbonatized (~98%), along with minor plagioclase, quartz, and crystal pyroclasts (~2%) (Fig. 3c, d).

2. Analytical methods

2.1. LA-ICP-MS zircon U-Pb dating

Zircons were selected from the whole-rock samples with standard density and magnetic separation techniques in the Laboratory of Langfang Regional Geological

Survey, Hebei Province. Over 500 zircons were handpicked under binocular microscope, then mounted in epoxy resin and polished until the grain centers were exposed. To remove lead contamination, the surface was cleaned using 3% HNO 3 prior to analyses. Cathodoluminescence (CL) images were obtained using a Mono CL3+ microprobe, in order to characterize internal structures and choose potential target sites for U-Pb dating. Laser ablation ICP-MS zircon U-Pb analyses were conducted on an Agilent 7500a ICP-MS equipped with a ComPex 102 (193 nm ArF-excimer laser, Lambda Physik) and an optical system (MicroLas), housed at the State Key Laboratory of Continental Dynamics of Northwest University in Xi’an. Detailed analytical methods were described by Liu et al. (2007). A 44 μm-spot size was adopted in this study with a laser repetition rate of 10 Hz and energy up to 90 MJ. Helium was used as a carrier gas to enhance transport efficiency of ablated material. The age calculations and concordia plots were made using Isoplot (version 3.0) (Ludwig. 2003). Zircon U-Pb age data are presented in Table 1.

2.2. Major and Trace elements

After petrographic examination, 15 samples were selected and powdered in agate mill. The geochemical analyses were conducted at the Institute of geology and geophysics, Chinese academy of science (IGGCAS) in Beijing, China. Major element compositions of bulk-rock samples were determined by using XRF, with analytical uncertainties ranging from 2 to 3 %. Bulk-rock trace element concentrations were determined using ICP-MS (Agilent 7500a) with acid digestion of samples in Teflon

bombs and dilution in 2 % HNO3 in the same laboratory. During analysis, the data quality was monitored by repeated analyses of five rocks reference materials (RGW-2, GSR-1, AGV-2, BCR-2 and W-2), and the accuracy is generally above 10 % for trace and rare earth element (REE). The analytical results of major and trace elements in the Cambrian igneous rocks are listed in Table 2.

2.3. Zircon Hf isotopes

In-situ zircon Hf isotopic analyses were carried out with a Neptune MC-ICPMS, equipped with a 193-nm laser, at the Institute of Geology and Geophysics, Chinese Academy of Sciences in Beijing, China. Zircon Hf isotope analysis was carried out on a Neptune multi-Collector ICP-MS equipped with a Geolas 193 laser ablation system. During Hf isotope analysis, spot size of 60 μm a laser repetition rate of 8 Hz at 15 J/cm2 was used and raw count rates for

172

Yb,

173

Yb,

175

Lu,

176

(Hf + Yb + Lu),

177

Hf, 178 Hf, 179 Hf, 180 Hf and 182 W were collected and isobaric interference corrections for

176

Lu and

176

Yb on

176

Hf must be determined precisely; the detailed analytical

technique is described in Wu et al. (2005). Further external adjustment was not applied to the unknowns because our determined

176

Hf/177 Hf ratios of 0.282303 ±

0.000020 for zircon standard 91500 are in good agreement with the reported values. The analytical results are listed in Table 3.

2.4. Sr-Nd isotopes

The Rb, Sr, Sm, and Nd isotopic compositions were determined at the

Laboratory of Beijing Research Institute of Uranium Geology on an ISOPROBE-T thermal ionization mass spectrometer, operating in static mode, using the procedures described by Chen et al. (2000). Total procedure blanks were 0.2 ng for Rb and Sr and <0.05 ng for Sm and Nd. The precision for Rb, Sr, Sm, Nd, Nd was ± 0.2% (2σ), and the precision for

87

Sr/86 Sr and

in Table 4. The mass fractionation correction for were normalized against whereas the reported NBS-987 standard

87

87

86

Sr/88 Sr = 0.1194 and

Sr/86 Sr and

143

87

146

143

87

Rb/86 Sr, and 147 Sm/144

Nd/144 Nd (2σ) is shown

Sr/86 Sr and

143

Nd/144 Nd ratios

Nd/144 Nd = 0.7219, respectively,

Nd/144 Nd ratios were adjusted relative to the

Sr/86 Sr = 0.710250 ± 0.000007 (2σ) and the JMC standard

Nd/144 Nd = 0.512109 ± 0.000003 (2σ). Measured were used to calculate initial

87

87

Sr/86 Sr and

87

Rb/86 Sr ratios

Sr/86 Sr ratios, taking the decay constant for

1.42 × 10-11 year-1 (Steiger and Jager, 1977), and Measured Sm/144 Nd ratios were used to calculate initial

143

143

143

87

Rb as

Nd/144 Nd and

147

Nd/144 Nd ratios, taking the decay

constant for 147 Sm as 6.54 × 10-12 year-1 (Lugmair and Marti, 1978). εNd (t), TDM1(Nd), and TDM2(Nd) were calculated using present-day values for chondritic uniform reservoir (CHUR): 143 Nd/144 Nd = 0.512638 (Goldstein et al., 1984) and 147 Sm/144 Nd = 0.1967 (Jacobsen and Wasserburg, 1980); and for depleted mantle (DM):

143

Nd/144

Nd = 0.513151 and 147 Sm/144 Nd = 0.2137 (Liew and Hofmann, 1988).

3. Analytical results

3.1. Zircon U–Pb dating

In this study, five samples from different intrusions and one volcanic rock

collected in Xinglong-Duobaoshan areas were chosen for zircon U-Pb dating by LA-ICP-MS. The CL images of representative zircons are shown in Fig. 4 and the U–Pb dating are listed in Table 1. Samples HJY01, HJY02, HJY03, DBS01, and DBS02 were collected from rocks previously mapped as late Paleozoic or Neoproterozoic in age (HBGMR, 1993). The zircon crystals from samples (HJY02, DBS02) are mostly euhedral to subhedral, and have short (50–150 μm), prismatic habits, with aspect ratios of 1:1–2:1. They are transparent, but have a pale–dark brown hue, and exhibit oscillatory zoning (Fig. 4a and 4e). However, most of the zircon grains from other samples studied (HJY01, HJY03 and DBS01) are rounded or oval, and display straight rhythmic stripes in the CL images (Fig. 4b, 4c and 4d).

3.1.1. Xinglong granitoids

The Xinglong granitoids consist of diorite (HJY01), monzogranite (HJY02) and pyroxene diorite (HJY03). The LA–ICP–MS U–Pb analyses of 15 zircon grains from sample HJY01 (diorite) yield a weighted mean

206

Pb/238 U age of 523 ± 2 Ma (2,

MSWD = 0.71) (Fig. 4a), which is interpreted as the crystallization age of the diorite. For sample HJY02 (monzogranite), the

206

Pb/238 U ages from 13 analytical spots

range from 469 to 476 Ma, and they yield a weighted mean 206 Pb/238 U age of 473 ± 2 Ma (2, MSWD = 0.7) (Fig. 4b), which is inferred to represent the crystallization age of the monzogranite. The other age (503 Ma) represent the crystallization ages of inherited or captured zircons entrained by the monzogranite. Zircons from sample

HJY03 show typical straight rhythmic zoning, and 23 spot analyses yielded

206

Pb/238

U ages of 481–488 Ma with a weighted mean 206 Pb/238 U age of 483 ± 2 Ma (MSWD = 0.41; Fig. 4c). This is interpreted as representing the emplacement age of the pyroxene diorite.

3.1.2. Duobaoshan igneous rocks

The Duobaoshan igneous rocks, composed of ultramafic intrusion (DBS01) and rhyolitic tuff samples (DBS02). The DBS01 samples (from the ultramafic rock intrusion) have variable Thorium (23–422 ppm) and Uranium (33–378 ppm) concentrations, with moderate to high Th/U ratios (0.4–1.2). The LA–ICP–MS U–Pb analyses of 20 zircons yielded 206 Pb/238 U ages ranging from 480 ± 10 Ma to 520 ± 13 Ma, and the data form a tight cluster on the concordia plot (Fig. 4), with a weighted mean

206

Pb/238 U age of 497 ± 6 Ma (2, MSWD = 1.3) (Fig. 4d). The zircons from

the DBS02 samples are euhedral–subhedral and display oscillatory zoning, which together with their Th/U ratios (0.1–1.0) are indicative of a magmatic origin (Pupin, 1980). The LA–ICP–MS zircon U–Pb analyses of 15 zircon grains give ages ranging from 475 ± 9 Ma to 507 ± 10 Ma, and the data form a tight cluster on the concordia plot, with a weighted mean

206

Pb/238 U age of 491 ± 5 Ma (2, MSWD = 0.8) (Fig.

4e). Thus, the results of the LA–ICP–MS zircon U–Pb dating analyses of the studied suite of igneous rocks provide a consistent set of crystallization ages (within error), indicating the presence of Cambrian igneous rocks in the northern GXR (Fig. 4f).

3.2. Whole-rock geochemical analyses

3.2.1. Major and trace elements of the Xinglong granitoids

They contain 50.72–73.18 wt.% SiO2, 0.06–1.08 wt.% TiO2, 1.24–1.75 wt.% total Fe2O3, 0.93–6.20 wt.% MgO, 13.50–20.96 wt.% Al2O3, and they have Na2O/K2O ratios of 0.93–4.04 (Table 2). They fall within the subalkalic region on a total alkali versus SiO2 diagram (TAS; Fig. 5a; Irvine and Baragar, 1971) and range from medium-K to high-K calc-alkaline region on a K2O versus SiO2 diagram (Fig. 5c; Peccerillo and Taylor, 1976). Their A/CNK [molar Al2O3/ (CaO + K2O + Na2O)] values range from 1.19 to 1.77, indicating transitional characteristics from metaluminous to weakly peraluminous (Fig. 5b; Maniar and Piccoli, 1989). As listed in Table 2 and shown Fig. 5, the Xinglong granitoids all have similar trace element characteristics. On the chondrite-normalized rare earth element (REE) diagram (Fig. 6a), they are enriched in light rare earth elements (LREEs), with (La/Yb)

N

ratios of

4.53–21.58. The ca. 520 Ma diorite and ca. 470 Ma monzogranite show pronounced negative Eu anomalies ((Eu/Eu*)

N

= 0.53–0.85), whereas the ca. 480 Ma pyroxene

diorite has no obvious Eu anomalies ((Eu/Eu*) intensely fractionated, with (La/Yb)

N

N=

0.73–1.06). These granitoids are

and (Gd/Yb)

N

ratios of 4.53-21.58 and

1.37-2.20. In the PM (primary mantle)-normalized (Fig. 6b; Sun and McDonough, 1989) trace element diagram, they are enriched in large ion lithophile elements (LILEs; e.g., Rb, Th, and U) and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, Ti, and P).

3.2.2. Major and trace elements of the Duobaoshan igneous

The ultramafic intrusion (DBS01) shows low SiO2 (40.68–41.18 wt.%) and Al2O3 (0.41–2.20 wt.%) contents, and high MgO (29.48–37.90 wt.%) contents. The Na2O (0.01–0.13 wt.%) and TiO2 (0.01–0.05 wt.%) contents are variable (Fig. 5a). They have Co contents of 88.63–94.00 ppm and Ni contents of 1563–2060 ppm. The REE contents of the serpentinites are so low that some HREE are almost below the level of detection; e.g., ∑LREE = 0.87–2.78 ppm (average of 1.88 ppm) and ∑HREE = 0.23–0.39 ppm (average of 0.33 ppm). Their (La/Yb)

N

ratios vary from 3.21 to 6.3,

and they have strong positive Eu anomalies, with (Eu/Eu*)

N

ratios of 1.59–2.22,

thereby recording the fractional crystallization of plagioclase (Fig. 6c). In primitive-mantle-normalized spider diagram, they show enrichment in U, P and light depletion in Th, Nb, and Ti (Fig. 6d). The ca. 490 Ma rhyolitic tuff samples (DBS02) are characterized by high Na2O (1.76–1.78 wt.%) and SiO2 (68.59–68.77 wt.%) contents, with low TiO2 (0.33–0.34 wt.%), K2O (0.70–0.71 wt.%), and total Fe2O3 (5.34–5.38 wt.%) contents, and moderate Al2O3 (7.91–8.01 wt.%) contents. These samples plot in the sub-alkaline region on the total alkali versus SiO2 diagram, and belong to the low-K tholeiitic (Fig. 5c) and metaluminous group of rocks (Fig. 5b). They are enriched in LREEs, depleted in heavy rare earth elements (HREEs) and HFSEs, and exhibit strong negative Eu anomalies ((Eu/Eu*) N

N

= 0.70–0.74) (Fig. 6c). Their LREE/HREE ratios and (La/Yb)

ratios range from 4.92 to 5.15 and 4.24 to 4.47, respectively. These rhyolitic tuffs

have negative Nb/Ta anomalies and are enriched in LILE, which are analogous to the

island-arc basalt-andesite from the Duobaoshan Formation (Fig. 6d; Wu et al., 2015).

3.3. Zircon Hf isotopes

Some of the zircon U–Pb dating spots in five of the samples (one sample for each of the rock types studied: diorite, monzogranite, pyroxene diorite, ultramafic intrusion, and rhyolitic tuff) were also selected for in situ Hf isotopic analyses (Table 3; Fig. 7).

3.3.1. Zircon Hf isotopes of the Xinglong granitoids

Zircons from the ca. 520 Ma diorite (HJY01) have homogeneous

176

Hf/177 Hf

ratios of 0.281978–0.282058, with εHf (t) values of –16.6 to –13.8 (Fig. 7c), TDM1 ages of 1665–1768 Ma, and TDM2 ages of 2359–2536 Ma. In contrast to the ca. 520 Ma diorite (HJY01), the 176 Hf/177 Hf ratios for zircons from the ca. 470 Ma monzogranite (HJY02) and pyroxene diorite (HJY03) range from 0.282390 to 0.282512 and 0.282410 to 0.282558, respectively. In the monzogranite, εHf (t) values and TDM1 and TDM2 ages vary from –3.5 to +0.6, 1068 to 1240 Ma, and 1407 to 1673 Ma, respectively. In the pyroxene diorite, εHf (t) values, TDM1 ages, and TDM2 ages range from –2.4 to +2.2, 1033 to 1197 Ma, and 1317 to 1606 Ma, respectively.

3.3.2. Zircon Hf isotopes of the Duobaoshan igneous rocks

Zircons from the ca. 490 Ma ultramafic intrusions (DBS01) have homogeneous 176 Hf/177 Hf ratios (0.282523–0.282922), with εHf (t) values of +1.3 to +15.0, TDM1 ages of 493–1043 Ma, and TDM2 ages of 499–1368 Ma, indicating that their parent magmas

were produced from relatively depleted mantle nature. Zircons from the ca. 490 Ma rhyolitic tuffs (DBS02) possess relatively homogeneous Hf isotopic compositions. Their initial 176 Hf/177 Hf ratios vary from 0.282329 to 0.282900, and their εHf(t) values and TDM1 ages range from –4.6 to +15.0 and 504 to 1275 Ma, respectively (Table 3 and Fig. 7). All of the analyzed zircons of the Xinglong granitoids have similar Hf isotopic compositions to those of zircons from the Phanerozoic igneous rocks in the Erguna block (Fig. 7a; Sui et al., 2006; Ge et al., 2007; Zhang et al., 2010; Zhao et al., 2014), but they differ from those of the Phanerozoic zircons in the Duobaoshan igneous rocks (Fig. 7b).

3.4. Sr–Nd isotopes

The results of Sr–Nd isotope analyses are presented in Table 4. The initial 87 Sr/86 Sr ratios for two samples from the Duobaoshan ultramafic rocks range from 0.70628 to 0.70853. Their εNd (t) values range from 1.86 to 2.28, and their depleted mantle Nd single-stage (TDM1 (Nd)) and two-stage model ages (TDM2 (Nd)) range from 959 to 1038 Ma and 1045 to 1072 Ma, respectively (Fig. 8).

4. Discussion

5.1. Depositional age and source of the Duobaoshan Formation

Field studies show that the Duobaoshan Formation consists of intermediate–acidic lava, volcanic breccia, rhyolitic tuff, slate, and marble, and was deposited in an

island-arc environment (HBGMR 1993). The depositional age of the Duobaoshan Formation has previously been estimated using the age relationships of fossils, porphyry copper deposits, and intrusions, and regarded as Middle–Late Ordovician in age. Ge et al. (2007), Cui et al. (2008), Xiang et al. (2012), and Zeng et al. (2014) published zircon SHRIMP and LA–ICP–MS U–Pb ages of ~475 Ma for the granodiorite intrusions related to the Duobaoshan Formation. Xiang et al. (2012), Liu et al. (2012), and Zeng et al. (2014) also reported an age of ~475 Ma for the intrusions, based on Re–Os dating of molybdenite. In addition, fossils in sediments of the Duobaoshan Formation indicate that it was deposited during the Ordovician. Wu et al. (2015) showed that the volcanic rocks of the Duobaoshan Formation were erupted during the Late Ordovician, based on ages of 479 ± 2 Ma obtained for granodiorite intrusions and 447 ± 2 Ma for volcanic rocks in the Tongshan ore district. In this study, we obtained a zircon LA–ICP–MS U–Pb age of 491 ± 5 Ma for the rhyolitic tuffs in the Duobaoshan Formation. The sedimentary rocks that host the Duobaoshan ultramafic intrusions yield reliable ages of 497 ± 6 Ma (MSWD = 0.8; Fig. 4e), further constraining the timing of volcanism to the Early Ordovician. In addition, the rhyolitic tuffs contain a group of Phanerozoic zircons with εHf (t) values (–4.6 to +15.0), that of εHf (t) values (+0.4 to +15) similar to the igneous zircons extracted from island-arc intrusive rocks of the Xing’an block (Fig. 7b; Ge et al., 2007; Zeng et al., 2014; Wu et al., 2015), indicates that one possible source for the rhyolitic tuffs are from partial melting of juvenile lower crustal material. However, some Phanerozoic zircons extracted from the rhyolitic tuffs have negative εHf(t) (-4.6 to -2.3) values and

older crustal Hf model ages (Fig. 7c), suggesting that another potential source is an ancient crustal material beneath the Erguna block. Therefore, the Duobaoshan Formation were derived from a mixed source, such as juvenile lower crustal material with ancient crustal material from the Xing’an and Erguna blocks. In summary, it has the sedimentation character of island-arc in the active continental margin and was formed in the Early Ordovician, rather than the Middle-Late Ordovician.

5.2. Origin of the Duobaoshan ultramafic rocks

The Duobaoshan ultramafic rocks are characterized by low SiO 2 and TiO2, and high Fe2O3T contents, along with high Mg# (91.4 to 93.7), distinct from those of any crustal materials or crustally derived melts, implying a mantle source. These ultramafic rocks are depleted in HREE, slight in enriched in LREE, and show negative Nb and Ti anomalies, which are similar to Alaskan-type Quetico mafic-ultramafic intrusions (Fig.6d; Pettigrew and Hattori, 2006). Although depletion in HFSEs (e.g., Nb and Ti) is normally interpreted as reflecting magma generation in a subduction-related environment (Pearce, 1983), it could also be related to contamination with relatively old continental crust (Wilson, 1989). Compared with the isotopic compositions of average crust, N-type MORBs, ocean island basalts (OIBs), and primitive mantle, the Duobaoshan ultramafic intrusion has a lower Nb/U ratio and higher La/Nb and Ba/Nb ratios. Thus, the trace element ratios of the Duobaoshan ultramafic intrusion cannot be a result of crustal contamination of the mantle end-member; instead, they must reflect the attributes of the mantle source. As

mentioned earlier, they have positive εHf (t) values (+3.0 to +15.0, avg. +10.78) and very young Hf single-stage and two-stage model ages (TDM1 = 493–1043 Ma, avg. 673 Ma; TDM2 = 499–1368 Ma, avg. 777 Ma). Similar to above Hf isotopic compositions, the ultramafic rocks also exhibit positive εNd (t) values (+1.86 to +2.28), low initial 87 Sr/86 Sr ratios (0.70628–0.70853), and young Nd single-stage and two-stage model ages (TDM1 = 959–1038 Ma; TDM2 = 1045–1072 Ma), indicating that they were derived from a depleted mantle source that was metasomatized by subduction-related fluids (Pearce, 1983; Wilson, 1989). In Fig. 7c and Fig. 8, all of the samples fall into the mantle array. Taken all these data into account, it is likely that the ultramafic rocks were generated from the partial melting of a depleted mantle source metasomatized by fluids derived from a subducted slab in the ocean basin between the Erguna-Xing’an and Songliao blocks.

5.3. Petrogenesis and tectonic setting of the Xinglong granitoids

5.3.1. Petrogenesis

The ca. 480 Ma Xinglong granitoids, including ~520 Ma diorites, ~480 Ma monzogranites and ~470 Ma pyroxene diorites, have high SiO2 (50.72–73.18 wt.%) and low MgO (0.93–6.20 wt.%), and Ni (0.01–54.96 ppm) concentrations, indicating a crustal source. The ~520 Ma diorites have relatively low

176

Hf/177 Hf ratios of

0.2821978-0.282058 with Hf two-stage model ages of 2359-2536 Ma (Table 3), suggesting that the primary magma of these rocks could have originated from the partial melting of a dominantly “old” source of Paleoproterozoic age. Importantly,

there are the Gneissic monogranite from the drill (NO. ZK6301, Depth: 226 m) with U-Pb age of ~2607 Ma in the southwestern Derbugan country (Shao et al., 2015), However, several zircons in the ~480 Ma monzogranite and most of the zircons in the ~470 Ma pyroxene diorites have positive εHf (t) values (+0.1 to +2.2) and plot between the depleted mantle and CHUR line in the εHf (t) vs. t diagram (Table 3; Fig. 7c), implying that some juvenile components, such as juvenile crust or depleted mantle sources, could be involved in the origin of these rocks. This interpretation is further supported by the zircon Hf isotopic study of the Early Paleozoic post-collision granitoids in the Shibazhan-Neihe-Chalabanhe-Baiyinna areas from the Erguna block (Fig. 7a; Sui et al., 2006; Ge et al., 2007; Zhang et al., 2010; Wu et al., 2005, 2015). Therefore, we conclude that the primary magmas of the ca. 480 Ma Xinglong granitoids were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials.

5.3.2. Tectonic setting

Clarifying the tectonic setting of the ca. 480 Ma Xinglong granitoids in the northern GXR can provide important insights into understanding of the early Paleozoic tectonic evolution of the Erguna-Xing’an Block. Firstly, the ca. 480 Ma Xinglong granitoids have high SiO2 and K2O contents with K2O/Na2O ranging from 0.93 to 4.04 (Table 2). They belong to the medium- to high-K calc-alkaline series (Fig. 5c) and are characterized by enrichment in LREEs and LILEs, and depletion in

HREEs and HFSEs (Fig. 5 and 6). These geochemical characteristics indicate that the ~480 Ma Xinglong granitoids have affinity to those of A-type graitoids, implying that they could have formed in a post-collisional or post-orogenic extensional setting. This conclusion is further favored by the following evidence: all samples fall into the field of Post-COLG field in Fig. 9. Secondly, these geochemical characteristics are similar to that of the Early Paleozoic post-collision granitoids in the Erguna block (Fig. 6a, b), which are mainly distributed in the northern Xinglong area, including ~500 Ma monzogranites and syenogranites at Shibazhan-Neihe (Ge et al., 2007), ~480 Ma granodiorite at Halabaqi-Chalabanhe (Sui et al., 2006), and ~480 Ma granitic complex at Tahe (Ge et al., 2005; Zhang et al., 2010). Thirdly, as mentioned earlier, the Erguna and Xing’an block had amalgamated before ~500 Ma by most geologists in NE China (Ge et al. 2005; Liu et al. 2010, 2016; Zhou et al. 2009, 2011a, b, 2015; Han et al. 2011, 2012a, b, 2015; Xu et al., 2014, 2015; Feng et al., 2014, 2015, 2016). The Early Paleozoic post-collision granitoids are related to the collision between the Erguna and Xing’an blocks (Sui et al., 2006; Ge et al., 2007; Zhang et al., 2010; Wu et al., 2005, 2015). In summary, we conclude that the ca. 480 Ma Xinglong granitoids most likely formed in a post-collisional setting related to the collision between the Erguna and Xing’an blocks.

5.4. Tectonic implications

The tectonic construction of NE China is interpreted to have involved the amalgamation of the several micro-continental blocks associated with the closure of

the Paleo-Asian Ocean. The Xinlin–Xiguitu suture zone between the Xing’an and Erguna blocks (Fig. 1b), is one of the most important suture zones for discussing the evolution of the western segment of NE China (Liu et al., 2016, in press). Its location was determined based on the presence of: (1) a NE-striking zone containing the Xinlin–Jifeng–Gaxian ophiolites (Li et al. 1991; Hu et al. 1995, 2001, 2003; Li et al. 2002; She et al. 2012; Feng et al., 2015) and the Toudaoqiao blueschists (Ye et al., 1994; Zhou et al. 2015; Miao et al., 2015); and (2) a stark contrast in the nature of the magmatic

and

basement

rocks

on

either

side

of

the

Toudaoqiao–Xiguitu–Jifeng–Xinlin belt. Proterozoic to early Paleozoic magmatic intrusions occur mainly to the northwest of the suture zone, where significant crustal growth occurred during the Mesoproterozoic to Neoproterozoic. In contrast, the late early Paleozoic to the late Paleozoic magmatic intrusions occur extensively to the northeast of the suture zone in the Xing’an block (Fig. 4f). Furthermore, it was shown that the εHf(t) value of the Xing’an block is very different to that of the Erguna block (Fig. 7a, b; Zhou et al., 2005; Ge et al., 2007a; Zhang et al., 2008, 2010a,b, 2011b, 2013; Sui et al., 2009a,b; Zhao et al., 2010a; Sun et al., 2012; Tang et al., 2013). Therefore, the Xinlin–Xiguitu suture zone is inferred to be the boundary between the blocks, and it extends from central Mongolia eastwards through Toudaoqiao, via Jifeng and Gaxian, to Xinlin, in the region between Mohe and Heihe (Han et al., 2015; Miao et al., 2015; Zhou et al., 2015; Feng et al., 2016). However, the nature of the northern extension location of the Xinlin–Xiguitu suture zone has been debated. The early studies suggested that the northern extension

of the suture zone ran from Alihe to Tayuan, based on studies of ophiolites and mafic rocks in the area (HBGMR, 1993). Ye et al. (1994) emphasized that the Tayuan gabbros and Xinlin Ophiolite are important features for demarcating the suture zone’s northern limit. In contrast, recent studies have indicated that the Tayuan gabbros do not possess the characteristics of ophiolites, and thus cannot be used as suture zone markers (Wu et al., 2011; Feng et al., 2014, 2015). In addition, Early Paleozoic granitic plutons are poorly exposed in the Tahe–Mohe area in the northern part of the GXR, where the Tahe pluton, characterized by porphyritic syenogranite and monzogranite is exposed. These post-orogenic granitoids formed between 480 Ma and 494 Ma, suggesting that the Tahe pluton is not only an important marker for the location of the suture zone, but also reveal collision time between the Erguna and Xing’an blocks (Ge et al., 2005, 2007). Most recently, Xu et al. (2014, 2015) extended the suture zone northward from Xinlin to Tahe, but did not give the details of its precise location. Although the Xinlin ophiolites are used as a marker (Li, 1991), its ages remain unclear due to the difficult in dating of the mafic rocks. Zhou et al. (2011, 2015) proposed that the zone extends from Xinlin, via Tahe, to Hanjiayuan, based on the distribution of a ca. 500 Ma high-grade metamorphic belt. The new data from our study may be significant in helping to accurately identify the location of the Xinlin–Xiguitu suture zone. Firstly, the Xinglong granitoids show medium to high-K calc-alkaline series characteristics and were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials, whereas the Duobaoshan

ultramafic rocks and rhyolitic tuffs were mainly derived from the juvenile materials with some ancient crustal material; Secondly, the ca. 480 Ma Xinglong granitoid rocks possess the geochemical characteristics of post-collision granite affinity, supported by the identification of the Early Paleozoic post-collision granitoids (Sui et al., 2006; Ge et al., 2007; Zhang et al., 2010; Wu et al., 2005, 2015), whereas the similar-aged rhyolitic tuffs and ultramafic intrusion from the Duobaoshan Formation show the geochemical characteristics of island-arc igneous rock and occurred in an island-arc tectonic setting; Thirdly, the previous studies have proved that the εHf (t) of the Xing’ an and Erguna blocks yield obvious differences, which are shown in in Fig. 7 (Han et al., 2015; Feng et al., 2016). The εHf (t) values yielded by the ca. 480 Ma Xinglong granitoids range from –16.6 to +2.2, showing an affinity to the Erguna block (Fig. 7a). However, the εHf (t) values of the coeval Duobaoshan ultramafic rocks and rhyolitic tuffs rang from –4.6 to +15, thus showing more of an affinity to the Xing’an block (Fig. 7b), and indicating that the two groups of rocks studied were derived from two different magmatic basement sources along the Xinlin-Xiguitu suture zone; Fourthly, metamorphic rocks in the Xing’an block previously were considered to be the Proterozoic in age (i.e., the Xinkailing, Wolegen, Fengshuigouhe, Luomahu, Ergunahe and Zhalantun Groups), but now are considered to be the metamorphic complexes related to late Paleozoic to early Mesozoic orogenic processes (Miao et al., 2015; Sun et al., 2014; Cui et al., 2015). Finally, new evidence supports the recognition that the closing process of the Xinlin-Xiguitu ocean along the north margin of the Erguna block before ca. 500 Ma marks the suture of an arc-continent

soft-collision, rather than continental collision, based on the SSZ-type ophiolitic melanges (ca. 650 Ma; She et al., 2012; Feng et al., 2015, 2016) and ca. 520 Ma Toudaoqiao blueschist with OIB affinity (Ye et al., 1994; Zhou et al., 2015; Miao et al., 2015). According to regional data and the discussion above, we further suggest that there are probably subduction-accretionary complexes between Erguna-Xing’an and Songliao blocks during the Cambrian to Early Ordovician (Fig. 10). The representative of this complexes is the Duobaoshan arc and hosts large-scale porphyry-type Cu-Mo deposits (Fig. 10). The northern extension location of the Xinlin-Xiguitu suture zone is located in the Jifeng-Xinglong areas.

6. Conclusions

(1) The Xinglong granitoids (including ~520 Ma diorite, ~470 Ma monzogranite and ~480 Ma pyroxene diorite), show medium to high-K calc-alkaline series characteristics and were probably derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials. (2) Zircon crystals within the rhyolitic tuffs from the Duobaoshan Formation yield a weighted mean 206 Pb/238 U age of 492 ± 5 Ma, whereas the sedimentary rocks intruded by the Duobaoshan ultramafic rock were dated at 497 ± 6 Ma. These data constrain the timing of the Duobaoshan Formation to the Early Ordovician. (3) The ca. 480 Ma Xinglong granitoid rocks possess the geochemical

characteristics of post-collision granite affinity, whereas the Early Ordovician rhyolitic tuffs and ultramafic intrusion from the Duobaoshan Formation show the geochemical characteristics of island-arc igneous rock and occurred in an island-arc tectonic setting. (4) The collision of the Erguna and Xing’an blocks at least took place ca. 500 Ma ago, and that there exist in a westward subduction of an oceanic plate between the Eruguna-Xing’an and Songliao blocks, took place during the Early Ordovician. There are more evidences and constraints that the northern extension location of the Xinlin-Xiguitu suture zone is located in the Jifeng–Xinglong areas.

Acknowledgments

We are grateful to Prof. Bei Xu, and the anonymous reviewers for their critical review and helpful suggestions. We thank the staff of the Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, and the State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, China, for assistance during the zircon LA-ICP-MS U-Pb dating, CL imaging and major and trace element analysis, Hf isotopes analysis. The study was funded by the 973 Program (Grant 2013CB429802), NSFC (Grant 41602235, 41502207, 41302175), Special/Youth Foundation of TYUT (Grant 1205-04020202), Regional Geology of Heilongjiang Province Summary (Grant 12120114033501).

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Fig. 2.

Geological map of the Hanjiayuanzi-Xinglong and Sanfengshan-Duobaoshan

areas, with sample location shown (modified after HBGMR, 1993)

Fig. 3. Photographs and microphotographs showing field relationships and textures. (a) contact relationship between the ultramafic rock (DBS01) and rhyolitic tuffs (DBS02); (b) outcrop of the ultramafic rocks in the Duobaoshan area; (c) ultramafic rocks (DBS01) with serpentinization was intruded into the tuffs (DBS02) of the Duobaoshan Formation, cross-polarized light; (d) back scatter images of c; (e) outcrop of monzogranite (HJY02); (f) monzogranite (HJY02) (cross polarized light); (g) diorites (HJY01) (cross polarized light); (h) outcrop of pyroxene diorites (HJY03); (i) pyroxene diorite (HJY03) (cross polarized light); Bi= biotite; Cpx = clinopyroxene; Hb= hornblende; Or= orthoclase; Pl = plagioclase; Q = quartz.

Fig. 4. Cathodoluminescence (CL) images of the representative zircon grains and concordia plots of the samples from the Xinglong and Duobaoshan areas. The solid and dashed circles indicate the locations of the LA-ICP-MS U-Pb dating and Hf analyses, respectively. The scale bar length in CL image is 50 μm (a-e). Relative probability plot of the granitoid intrusions in the Erguna and Xing’an blocks, respectively , with data from this study and from Qu et al., 2011; Cui et al., 2013; Li et al., 2013; Zhang et al., 2011; Zhang et al., 2013; Wu et al., 2002, 2011; Zhang et al., 2010; Feng et al., 2015, 2016) (f)

Fig. 5. (a) SiO2 versus (Na2O+K2O diagram); (b) Plot of A/CNK versus A/NK; (c) SiO2 versus K2O diagram;

Fig. 6. Chondrite–normalized REE patterns and Primitive–mantle–normalized trace element spidergrams for the samples in the northern GXR (Peccerillo et al., 1976; Boynton 1984; Sun McDonough 1989).

Fig. 7. Compilation diagram of ɛHf (t) versus U-Pb ages, (a, b) data from the Erguna and Xing’an blocks (Zhou et al., 2005; Ge et al., 2007; Zhang et al., 2008, 2010a,b, 2011b; Sui et al., 2009a, 2009b; Zhao et al., 2010; Sun et al., 2012; Tang et al., 2013; Han et al., 2015), (c) data from our samples. Dashed line areas show typical composition plotting for different blocks.

Fig. 8. εNd (t) versus (87 Sr/86 Sr)i plot for the unltramafic rocks in the Duobaoshan area. DM, EM I, EM II, HIMU, and PM are mantle end members defined by Hart (1984). DM, depleted mantle; EM I, I-type enriched mantle; EM II, II-type enriched mantle; HIMU, high-l mantle; PM, primitive mantle. Gray solid squares indicate data from Wu et al. (2015).

Fig. 9. Tectonic discrimination diagrams of the granodiorites from the Duobaoshan area. (a) Nb versus Y diagram (after Pearce et al., 1984); (b) Rb versus Y + Nb

diagram (after Pearce, 1996); Syn-COLG, syn-collisional granites; VAG, volcanic arc granites; WPG, within-plate granites; Post-COLG, post-collisional granites.

Fig. 10. Schematic sections through the northern Great Xing’an Range showing the tectonic evolution from the Cambrian to Early Ordovician. Modified after Xiao et al. (2003) and Windley et al. (2007).

Table captions Table 1 LA-ICP-MS U-Pb-Th data for zircons of the Early Paleozoic intrusive rock and rhyolitic tuffs from the Xinglong and Duobaoshan areas

Table 2 Whole-rock major, trace element data of the Early Paleozoic intrusive rock and rhyolitic tuffs from the Xinglong and Duobaoshan areas

Table 3 Hf isotopic data from the Early Paleozoic intrusive rocks and rhyolitic tuffs from the Xinglong and Duobaoshan areas

Table 4 Sr-Nd isotopic compositions for the Early Paleozoic ultramafic rocks in the Duobaoshan area.

Table 1 Sample no.

Pb*

Th

U

（×10-6）

Sample DBS01

LA-ICP-MS U-Pb-Th data for zircons of the Early Paleozoic intrusive rock and tuffs from the Xinglong and Duobaoshan areas 207

Th/U

Pb/206 Pb

207

Pb/235 U

206

Pb/238 U

ratio

（±1σ）

ratio

（±1σ）

ratio

（±1σ）

207

Pb/206 Pb

（Ma）

（±1σ）

207

Pb/235 U

（Ma）

（±1σ）

206

Pb/238 U

（Ma）

（±1σ）

the ultramafic rocks

DBS01-01

25

203

225

0.9

0.06433

0.00277

0.73176

0.02626

0.08243

0.00174

753

88

558

15

511

10

DBS01-02

7

35

69

0.5

0.05771

0.00461

0.65988

0.04947

0.08287

0.00222

519

167

515

30

513

13

DBS01-03

6

32

63

0.5

0.06114

0.00444

0.69885

0.04723

0.08284

0.00211

644

149

538

28

513

13

DBS01-04

4

25

44

0.6

0.05850

0.00490

0.65358

0.05163

0.08098

0.00221

548

173

511

32

502

13

DBS01-05

30

226

304

0.7

0.05669

0.00256

0.61899

0.02374

0.07915

0.00169

479

97

489

15

491

10

DBS01-06

4

23

33

0.7

0.05386

0.00465

0.62358

0.05119

0.08393

0.00219

365

184

492

32

520

13

DBS01-07

13

53

132

0.4

0.05947

0.00309

0.65418

0.03002

0.07974

0.00178

584

109

511

18

495

11

DBS01-08

10

61

105

0.6

0.06020

0.00337

0.64256

0.03225

0.07739

0.00178

611

116

504

20

481

11

DBS01-09

8

37

88

0.4

0.05919

0.00333

0.65887

0.03331

0.08071

0.00186

574

118

514

20

500

11

DBS01-10

10

56

102

0.5

0.05219

0.00308

0.56955

0.03049

0.07914

0.00183

294

129

458

20

491

11

DBS01-11

14

141

129

1.1

0.05796

0.00282

0.66685

0.02828

0.08343

0.00184

528

104

519

17

517

11

DBS01-12

35

348

339

1.0

0.06033

0.00268

0.64621

0.02431

0.07769

0.00168

615

93

506

15

482

10

DBS01-13

30

296

277

1.1

0.05752

0.00248

0.64079

0.02330

0.08080

0.00173

511

93

503

14

501

10

DBS01-14

18

95

195

0.5

0.05750

0.00279

0.63281

0.02679

0.07983

0.00176

510

104

498

17

495

11

DBS01-15

35

259

366

0.7

0.05850

0.00256

0.62475

0.02316

0.07749

0.00168

548

93

493

14

481

10

DBS01-16

23

207

225

0.9

0.06105

0.00257

0.66690

0.02346

0.07926

0.00171

641

88

519

14

492

10

DBS01-17

37

357

378

0.9

0.05551

0.00212

0.59122

0.01827

0.07730

0.00163

433

83

472

12

480

10

DBS01-18

5

23

50

0.5

0.06216

0.00481

0.71212

0.05172

0.08316

0.00223

680

157

546

31

515

13

DBS01-19

12

74

126

0.6

0.06334

0.00373

0.70819

0.03790

0.08115

0.00197

720

120

544

23

503

12

DBS01-20

37

422

343

1.2

0.05794

0.00234

0.63285

0.02108

0.07929

0.00170

527

86

498

13

492

10

0.2

0.05879

0.00191

0.64123

0.01479

0.07906

0.00158

559

69

503

9

491

9

Sample DBS02 the rhyolitic tuffs DBS02-01

142

329

1624

DBS02-02

7

38

66

0.6

0.05737

0.00385

0.64424

0.04002

0.08141

0.00197

505

142

505

25

505

12

DBS02-03

4

2

48

0.1

0.08708

0.00580

0.96537

0.05879

0.08037

0.00213

1362

123

686

30

498

13

DBS02-04

24

209

233

0.9

0.05380

0.00279

0.58420

0.02679

0.07872

0.00176

363

112

467

17

489

10

DBS02-05

6

25

69

0.4

0.06804

0.00455

0.74778

0.04607

0.07969

0.00201

870

133

567

27

494

12

DBS02-06

35

134

385

0.3

0.05933

0.00228

0.64886

0.01999

0.07930

0.00166

579

81

508

12

492

10

DBS02-07

6

36

62

0.6

0.05950

0.00513

0.65600

0.05353

0.07995

0.00226

585

177

512

33

496

13

DBS02-08

211

2043

2134

1.0

0.05926

0.00193

0.62423

0.01468

0.07639

0.00155

577

69

493

9

475

9

DBS02-09

110

669

1139

0.6

0.06261

0.00225

0.68641

0.01909

0.07951

0.00165

695

75

531

11

493

10

DBS02-10

39

127

453

0.3

0.05757

0.00275

0.61747

0.02562

0.07779

0.00172

513

102

488

16

483

10

DBS02-11

25

160

255

0.6

0.05719

0.00238

0.63547

0.02205

0.08058

0.00172

498

90

500

14

500

10

DBS02-12

24

139

246

0.6

0.07443

0.00303

0.83100

0.02788

0.08099

0.00176

1053

80

614

15

502

10

DBS02-13

48

326

495

0.7

0.05966

0.00221

0.66239

0.01938

0.08053

0.00169

591

78

516

12

499

10

DBS02-14

30

251

314

0.8

0.05973

0.00285

0.63544

0.02638

0.07717

0.00173

594

100

500

16

479

10

DBS02-15

48

114

551

0.2

0.05943

0.00237

0.67082

0.02196

0.08190

0.00176

583

84

521

13

507

10

Sample HJY01 the diorites HJY01-01

10

62

83

0.8

0.05780

0.00124

0.67076

0.01299

0.08417

0.00060

522

46

521

8

521

4

HJY01-02

11

73

92

0.8

0.05800

0.00111

0.68723

0.01163

0.08594

0.00059

529

42

531

7

532

3

HJY01-03

8

52

69

0.7

0.05789

0.00131

0.66938

0.01390

0.08386

0.00061

526

49

520

8

519

4

HJY01-04

14

80

125

0.6

0.05776

0.00099

0.67128

0.00987

0.08430

0.00055

520

37

522

6

522

3

HJY01-05

19

130

157

0.8

0.06031

0.00120

0.70064

0.01239

0.08426

0.00059

615

42

539

7

522

4

HJY01-06

13

87

104

0.8

0.05781

0.00134

0.67857

0.01439

0.08513

0.00062

522

50

526

9

527

4

HJY01-07

12

73

108

0.7

0.05777

0.00111

0.67094

0.01145

0.08423

0.00057

521

42

521

7

521

3

HJY01-08

11

64

95

0.7

0.05820

0.00150

0.67435

0.01610

0.08403

0.00066

537

56

523

10

520

4

HJY01-09

12

91

97

0.9

0.05789

0.00121

0.67391

0.01269

0.08443

0.00060

525

46

523

8

523

4

HJY01-10

11

59

99

0.6

0.05843

0.00111

0.68329

0.01137

0.08481

0.00057

546

41

529

7

525

3

HJY01-11

12

51

114

0.4

0.05797

0.00162

0.67266

0.01766

0.08416

0.00062

528

60

522

11

521

4

HJY01-12

8

49

71

0.7

0.05804

0.00159

0.68159

0.01757

0.08518

0.00064

531

59

528

11

527

4

HJY01-13

17

92

145

0.6

0.05799

0.00112

0.67585

0.01154

0.08453

0.00054

529

42

524

7

523

3

HJY01-14

17

94

151

0.6

0.05787

0.00099

0.67677

0.00985

0.08482

0.00054

525

37

525

6

525

3

HJY01-15

20

103

179

0.6

0.05778

0.00118

0.67076

0.01220

0.08419

0.00058

521

44

521

7

521

3

Sample HJY02 the monzogranites HJY02-01

30

97

313

0.3

0.05663

0.00095

0.59716

0.00858

0.07648

0.00048

476

37

475

5

475

3

HJY02-02

32

150

324

0.5

0.05668

0.00101

0.59088

0.00926

0.07561

0.00048

478

40

471

6

470

3

HJY02-03

32

128

332

0.4

0.05807

0.00091

0.60505

0.00794

0.07557

0.00049

532

35

480

5

470

3

HJY02-04

24

102

243

0.4

0.05664

0.00115

0.59407

0.01085

0.07607

0.00051

477

45

474

7

473

3

HJY02-05

34

128

349

0.4

0.05681

0.00089

0.59718

0.00779

0.07623

0.00048

484

34

475

5

474

3

HJY02-06

46

269

462

0.6

0.05649

0.00092

0.58761

0.00815

0.07545

0.00049

471

36

469

5

469

3

HJY02-07

42

234

424

0.6

0.05674

0.00088

0.59377

0.00776

0.07589

0.00047

481

34

473

5

472

3

HJY02-08

34

105

352

0.3

0.05669

0.00092

0.59884

0.00824

0.07662

0.00048

479

36

477

5

476

3

HJY02-09

25

94

257

0.4

0.05663

0.00089

0.59760

0.00787

0.07653

0.00049

477

35

476

5

475

3

HJY02-10

31

95

320

0.3

0.05664

0.00080

0.59850

0.00679

0.07663

0.00047

477

31

476

4

476

3

HJY02-11

45

183

462

0.4

0.05663

0.00117

0.59754

0.01122

0.07653

0.00049

476

45

476

7

475

3

HJY02-12

30

103

321

0.3

0.05648

0.00081

0.58926

0.00691

0.07567

0.00047

470

32

470

4

470

3

HJY02-13

34

205

355

0.6

0.05675

0.00108

0.59463

0.01010

0.07599

0.00048

481

42

474

6

472

3

Sample HJY03 the pyroxene diorite HJY03-01

26

124

277

0.4

0.05604

0.00091

0.60706

0.00845

0.07857

0.00053

453

35

482

5

488

3

HJY03-02

33

215

340

0.6

0.05759

0.00079

0.61606

0.00683

0.07758

0.00049

514

30

487

4

482

3

HJY03-03

16

59

175

0.3

0.05680

0.00098

0.60843

0.00908

0.07766

0.00053

483

38

483

6

482

3

HJY03-04

60

349

612

0.6

0.05584

0.00068

0.59874

0.00534

0.07774

0.00046

446

26

476

3

483

3

HJY03-05

28

171

277

0.6

0.05606

0.00087

0.59876

0.00782

0.07742

0.00050

455

34

476

5

481

3

HJY03-06

39

234

397

0.6

0.05713

0.00087

0.60932

0.00774

0.07732

0.00049

496

33

483

5

480

3

HJY03-07

38

184

387

0.5

0.05560

0.00097

0.59364

0.00899

0.07740

0.00052

436

38

473

6

481

3

HJY03-08

37

154

381

0.4

0.05665

0.00075

0.60620

0.00628

0.07757

0.00047

477

29

481

4

482

3

HJY03-09

26

141

283

0.5

0.05702

0.00156

0.60977

0.01576

0.07766

0.00071

492

60

483

10

482

4

HJY03-10

132

1379

1212

1.1

0.05694

0.00123

0.60871

0.01214

0.07763

0.00063

489

47

483

8

482

4

HJY03-11

16

69

173

0.4

0.05743

0.00203

0.61792

0.02088

0.07814

0.00083

508

76

489

13

485

5

HJY03-12

123

1122

1191

0.9

0.05741

0.00092

0.61362

0.00854

0.07756

0.00057

507

35

486

5

482

3

HJY03-13

43

289

443

0.7

0.05498

0.00135

0.59083

0.01357

0.07798

0.00067

411

53

471

9

484

4

HJY03-14

68

391

726

0.5

0.05707

0.00108

0.61622

0.01048

0.07836

0.00060

494

41

488

7

486

4

HJY03-15

23

133

244

0.5

0.05643

0.00170

0.60553

0.01727

0.07788

0.00074

469

65

481

11

483

4

HJY03-16

24

97

269

0.4

0.05743

0.00162

0.61452

0.01641

0.07767

0.00072

508

61

486

10

482

4

HJY03-17

14

59

161

0.4

0.05699

0.00207

0.60912

0.02124

0.07758

0.00083

491

79

483

13

482

5

HJY03-18

62

372

647

0.6

0.05663

0.00110

0.61273

0.01081

0.07855

0.00061

476

43

485

7

488

4

HJY03-19

145

1897

1238

1.5

0.05571

0.00104

0.59600

0.00996

0.07767

0.00059

440

40

475

6

482

4

HJY03-20

27

132

286

0.5

0.05646

0.00154

0.61114

0.01575

0.07859

0.00071

470

60

484

10

488

4

HJY03-21

16

75

171

0.4

0.05806

0.00199

0.62129

0.02035

0.07770

0.00082

532

74

491

13

482

5

HJY03-22

34

262

349

0.7

0.05812

0.00177

0.62066

0.01793

0.07753

0.00076

534

66

490

11

481

5

HJY03-23

29

149

311

0.5

0.05689

0.00165

0.60955

0.01678

0.07779

0.00073

487

64

483

11

483

4

Table 2 Whole-rock major, trace element data of the Early Paleozoic intrusive rock and rhyolitic tuffs from the Xinglong and Duobaoshan areas Sample no.

DBS01-a

DBS01-b

DBS01-c

DBS02-a

DBS02-b

DBS02-c

HJY01-a

HJY01-b

HJY01-c

HJY02-a

HJY02-b

HJY02-c

HJY03-a

HJY03-b

Major oxides (wt.%) SiO2

41.18

40.68

41.01

68.61

68.77

68.59

58.03

62.48

56.55

71.36

73.18

72.27

53.18

50.72

Al2O3

0.41

2.20

1.60

8.00

7.91

8.01

15.92

15.43

16.27

13.50

13.51

13.50

17.12

20.96

TFe2O3

5.50

5.05

5.17

5.38

5.35

5.34

6.81

5.24

6.01

2.25

1.24

1.75

8.17

8.67

MgO

29.48

37.90

37.65

7.90

7.87

7.90

6.20

2.29

4.02

1.46

0.93

1.20

3.97

3.14

CaO

6.28

0.43

0.52

3.70

3.66

3.69

2.88

3.18

7.26

0.31

0.79

0.55

5.14

7.26

Na2O

0.01

0.13

0.09

1.77

1.76

1.78

3.15

4.18

3.60

4.56

3.34

3.95

4.56

3.61

K2O

0.01

0.21

0.21

0.71

0.70

0.72

3.38

2.87

2.82

3.38

5.61

4.49

1.13

1.00

TiO2

0.01

0.05

0.05

0.33

0.33

0.34

0.14

0.96

0.49

0.06

0.25

0.16

1.13

1.08

P2O5

0.01

0.05

0.05

0.09

0.08

0.10

0.86

0.35

0.18

0.33

0.07

0.20

0.20

0.53

MnO

0.12

0.10

0.07

0.19

0.19

0.19

0.34

0.08

0.20

0.07

0.06

0.07

0.26

0.13

LOI

15.23

12.34

12.17

2.11

2.16

2.12

0.73

2.20

0.69

1.36

0.74

1.05

3.82

2.20

Total

99.41

100.94

100.17

99.74

99.72

99.71

99.32

99.84

98.76

98.99

99.86

99.43

99.75

100.27

Mg#

91.40

93.70

93.51

74.41

74.44

74.54

64.33

46.42

56.99

56.31

59.74

57.59

49.05

41.76

Trace elements (ppm) Ba

6.33

13.80

8.17

451.00

455.00

464.00

1125.33

856.00

1020.00

1036.00

901.00

968.50

455.33

158.40

Sr

501.33

17.70

14.00

114.00

113.00

114.00

835.83

783.00

750.00

241.67

195.00

218.33

674.00

752.80

Sc

3.67

6.12

7.60

12.00

11.00

12.00

12.01

14.24

13.13

1.86

2.84

2.03

20.67

14.24

Ni

1563.00

2060.00

1920.00

0.07

0.06

0.06

3.40

12.50

7.95

0.50

3.30

1.90

0.01

54.96

Co

88.63

94.00

93.00

36.80

39.30

37.40

14.70

13.70

14.20

2.03

1.91

1.97

21.23

47.34

Cs

2.37

0.37

1.28

1.10

1.30

1.30

0.80

1.88

1.34

1.80

3.01

2.41

2.80

0.28

Ga

0.50

9.55

9.80

8.50

8.80

8.30

19.57

20.30

19.93

17.77

15.30

16.53

18.87

12.50

Hf

0.10

2.26

1.72

2.00

2.10

2.10

7.80

5.29

6.55

5.80

4.84

5.32

2.53

2.23

Nb

0.10

1.89

1.09

3.10

3.10

2.90

10.17

11.80

10.98

15.77

12.80

14.28

4.80

2.08

Rb

0.20

1.22

1.58

9.50

9.60

9.30

71.30

56.70

64.00

96.03

203.00

149.52

51.70

11.73

Ta

0.10

0.50

0.50

0.10

0.10

0.10

0.63

0.65

0.64

2.30

1.06

1.68

0.17

0.18

Th

0.20

0.10

0.14

2.60

2.50

2.50

6.23

2.65

4.44

14.13

21.00

17.57

4.57

0.34

U

0.10

0.05

0.05

1.20

1.20

1.00

1.30

0.55

0.93

1.63

2.66

2.15

1.50

0.09

V

13.33

19.30

19.40

60.00

62.00

64.00

152.67

103.00

127.83

12.00

16.50

14.25

248.67

343.20

Zr

0.83

51.70

41.50

75.70

74.20

74.40

338.87

205.00

271.93

226.00

157.00

191.55

93.07

19.60

Y

0.10

0.41

0.44

15.00

15.20

14.50

20.87

12.40

30.50

21.07

14.00

17.53

13.77

55.80

La

0.27

0.58

0.39

10.00

10.50

10.60

44.60

19.60

33.10

70.20

44.70

57.45

16.97

28.90

Ce

0.20

1.26

0.88

21.60

22.30

22.20

90.37

36.40

72.50

130.77

72.90

101.83

34.47

49.90

Pr

0.02

0.14

0.10

2.67

2.65

2.72

9.96

3.84

9.95

12.73

7.77

10.25

4.20

8.42

Nd

0.30

0.60

0.46

11.60

11.80

11.40

38.07

16.10

41.90

42.67

25.30

33.98

17.40

42.40

Sm

0.05

0.12

0.10

2.41

2.47

2.40

6.78

3.12

7.98

6.04

3.51

4.77

3.36

10.10

Eu

0.04

0.08

0.05

0.59

0.58

0.61

1.76

0.54

1.77

0.97

0.82

0.90

1.16

2.50

Gd

0.05

0.14

0.09

2.62

2.53

2.65

5.58

2.45

7.11

4.92

3.27

4.09

3.20

10.80

Tb

0.01

0.02

0.02

0.40

0.42

0.43

0.69

0.37

1.00

0.64

0.42

0.53

0.46

1.70

Dy

0.05

0.07

0.08

2.57

2.56

2.81

3.89

2.65

5.19

3.79

2.04

2.91

2.72

9.75

Ho

0.02

0.02

0.02

0.53

0.50

0.54

0.77

0.49

1.01

0.73

0.43

0.58

0.51

1.91

Er

0.03

0.06

0.06

1.59

1.57

1.62

2.16

1.39

2.95

2.16

1.36

1.76

1.46

5.33

Tm

0.01

0.01

0.01

0.25

0.26

0.25

0.33

0.24

0.40

0.32

0.21

0.26

0.21

0.70

Yb

0.05

0.06

0.08

1.57

1.67

1.60

2.27

1.44

2.61

2.19

1.44

1.82

1.45

4.30

Lu

0.01

0.01

0.01

0.26

0.25

0.25

0.34

0.21

0.38

0.33

0.24

0.29

0.22

0.61

δEu

2.22

1.77

1.59

0.71

0.70

0.74

0.85

0.58

0.70

0.53

0.73

0.60

1.06

0.73

LREE

0.87

2.78

1.98

48.87

50.30

49.93

191.54

79.60

167.20

263.37

155.00

209.19

77.55

142.22

HREE

0.23

0.39

0.37

9.79

9.76

10.15

16.02

9.24

20.65

15.07

9.41

12.24

10.24

35.10

LREE/HREE

3.80

7.08

5.34

4.99

5.15

4.92

11.95

8.61

8.10

17.48

16.47

17.09

7.58

4.05

(La/Yb)N

3.60

6.31

3.21

4.29

4.24

4.47

13.25

9.18

8.55

21.58

20.93

21.32

7.89

4.53

∑REE

1.10

3.17

2.35

60.06

60.08

207.56

88.84

187.85

278.44

164.41

221.43

87.78

177.32

58.66 2+

2+

2+

Note: LOI = loss on ignition; Mg# = 100×Mg / (Mg +TFe ); δEu = 2*(Eu/0.0735)/ ((Sm/0.195)+(Gd/0.259)); (La/Yb)N = (La/0.310)/(Yb/0.209). LREE = La + Ce + Pr + Nd + Sm + Eu; HREE = Gd + Tb + Dy + Ho + Er + Tm + Yb + Lu; ∑REE = LREE + HREE; (La/Yb)N = (La/0.687)/ (Yb/0.493).

Sample no.

t (Ma)

Table 3 Hf isotopic data from the Early Paleozoic intrusive rocks and rhyolitic tuffs from the Xinglong and Duobaoshan areas 176 177 176 177 176 Yb/ Hf Lu/ Hf Hf/177Hf 2σ εHf(0) εHf(t) 2σ TDM1(Hf)

TDM2(Hf-average)

fLu/Hf

Sample DBS01 the ultramafic rocks DBS02-01

502

0.0946

0.0033

0.282850

0.000021

2.77

12.8

0.74

607

659

-0.90

DBS02-02

495

0.0565

0.0019

0.282825

0.000024

1.88

12.2

0.84

620

690

-0.94

DBS02-03

481

0.0850

0.0029

0.282922

0.000024

5.32

15.0

0.85

493

499

-0.91

DBS02-04

491

0.0283

0.0009

0.282718

0.000020

-1.91

8.6

0.71

756

915

-0.97

DBS02-05

501

0.0920

0.0029

0.282905

0.000025

4.69

14.8

0.88

519

529

-0.91

DBS02-06

481

0.0409

0.0014

0.282523

0.000058

-8.80

1.3

2.04

1043

1368

-0.96

Sample DBS02 the rhyolitic tuffs DBS01-01

491

0.0279

0.0010

0.282521

0.000030

-8.87

1.6

1.06

1035

1359

-0.97

DBS01-02

505

0.0029

0.0001

0.282329

0.000017

-15.66

-4.6

0.62

1275

1762

-1.00

DBS01-03

498

0.0569

0.0020

0.282860

0.000021

3.12

13.4

0.74

571

612

-0.94

DBS01-04

492

0.0332

0.0010

0.282409

0.000016

-12.84

-2.3

0.58

1192

1610

-0.97

DBS01-05

496

0.0359

0.0013

0.282900

0.000023

4.51

15.0

0.81

504

508

-0.96

DBS01-06

475

0.0579

0.0019

0.282416

0.000028

-12.60

-2.7

0.98

1212

1623

-0.94

DBS01-07

493

0.0282

0.0010

0.282355

0.000024

-14.76

-4.2

0.84

1267

1730

-0.97

DBS01-08

500

0.0321

0.0010

0.282481

0.000023

-10.30

0.4

0.82

1093

1445

-0.97

DBS01-09

502

0.0985

0.0034

0.282428

0.000041

-12.15

-2.2

1.46

1243

1610

-0.90

DBS01-10

499

0.0945

0.0032

0.282832

0.000029

2.11

12.1

1.03

634

701

-0.90

DBS01-11

479

0.0194

0.0007

0.282785

0.000026

0.45

10.8

0.91

658

767

-0.98

Sample HJY01 the diorites HJY01-01

521

0.0162

0.0006

0.281988

0.000022

-27.72

-16.5

0.79

1759

2519

-0.98

HJY01-02

532

0.0176

0.0006

0.282058

0.000019

-25.25

-13.8

0.66

1665

2359

-0.98

HJY01-03

519

0.0144

0.0005

0.282008

0.000024

-27.02

-15.8

0.86

1729

2476

-0.99

HJY01-04

522

0.0207

0.0007

0.281995

0.000020

-27.47

-16.2

0.69

1755

2506

-0.98

HJY01-05

522

0.0166

0.0006

0.281996

0.000022

-27.46

-16.2

0.80

1751

2504

-0.98

HJY01-06

527

0.0173

0.0006

0.281983

0.000026

-27.91

-16.5

0.90

1768

2528

-0.98

HJY01-07

521

0.0176

0.0006

0.281991

0.000022

-27.62

-16.4

0.78

1757

2514

-0.98

HJY01-08

520

0.0175

0.0006

0.282021

0.000028

-26.55

-15.3

1.01

1717

2449

-0.98

HJY01-09

523

0.0138

0.0005

0.282018

0.000026

-26.68

-15.3

0.91

1716

2452

-0.99

HJY01-10

525

0.0205

0.0007

0.282022

0.000022

-26.51

-15.2

0.77

1718

2444

-0.98

HJY01-11

521

0.0146

0.0005

0.282016

0.000023

-26.73

-15.4

0.83

1718

2457

-0.98

HJY01-12

527

0.0114

0.0004

0.281978

0.000021

-28.09

-16.6

0.73

1766

2536

-0.99

HJY01-13

523

0.0124

0.0004

0.282035

0.000022

-26.05

-14.7

0.78

1689

2411

-0.99

HJY01-14

525

0.0166

0.0006

0.282011

0.000020

-26.92

-15.6

0.71

1728

2467

-0.98

HJY01-15

521

0.0192

0.0007

0.282008

0.000023

-27.02

-15.8

0.83

1737

2478

-0.98

Sample HJY02 the monzogranites HJY02-01

475

0.0262

0.0009

0.282414

0.000021

-12.67

-2.5

0.74

1183

1608

-0.97

HJY02-02

470

0.0906

0.0029

0.282418

0.000028

-12.51

-3.1

0.97

1240

1638

-0.91

HJY02-03

470

0.0417

0.0014

0.282463

0.000025

-10.92

-1.0

0.90

1127

1509

-0.96

HJY02-04

473

0.0546

0.0018

0.282414

0.000026

-12.68

-2.8

0.91

1211

1626

-0.95

HJY02-05

474

0.0359

0.0012

0.282490

0.000023

-9.99

0.1

0.81

1086

1445

-0.96

HJY02-06

469

0.0529

0.0017

0.282512

0.000025

-9.21

0.6

0.87

1068

1407

-0.95

HJY02-07

472

0.0524

0.0018

0.282453

0.000020

-11.27

-1.4

0.70

1153

1537

-0.95

HJY02-08

476

0.0317

0.0011

0.282408

0.000025

-12.86

-2.7

0.87

1196

1622

-0.97

HJY02-09

475

0.0773

0.0021

0.282490

0.000024

-0.2

0.87

1113

1462

-0.94

HJY02-10

476

0.0460

0.0016

0.282390

0.000025

-13.51

-3.5

0.88

1238

1673

-0.95

HJY02-11

475

0.0537

0.0017

0.282479

0.000019

-10.37

-0.5

0.69

1116

1478

-0.95

HJY02-12

470

0.0439

0.0015

0.282503

0.000021

-9.51

0.4

0.76

1073

1421

-0.96

HJY02-13

472

0.0334

0.0012

0.282497

0.000025

-9.74

0.3

0.87

1074

1428

-0.97

-9.99

Sample HJY03 the pyroxene diorites HJY03-01

488

0.0299

0.0012

0.282476

0.000025

-10.48

-0.1

0.89

1104

1467

-0.96

HJY03-02

482

0.0548

0.0021

0.282465

0.000035

-10.86

-0.9

1.24

1147

1512

-0.94

HJY03-03

482

0.0722

0.0028

0.282446

0.000032

-11.53

-1.8

1.12

1197

1569

-0.92

HJY03-04

483

0.0212

0.0008

0.282444

0.000021

-11.61

-1.2

0.73

1139

1534

-0.97

HJY03-05

481

0.0183

0.0008

0.282493

0.000024

-9.88

0.5

0.86

1068

1424

-0.98

HJY03-06

480

0.0265

0.0011

0.282466

0.000026

-10.84

-0.6

0.91

1115

1491

-0.97

HJY03-07

481

0.0358

0.0014

0.282522

0.000037

-8.85

1.3

1.31

1045

1372

-0.96

HJY03-08

482

0.0335

0.0013

0.282451

0.000021

-11.35

-1.1

0.75

1142

1527

-0.96

HJY03-09

482

0.0337

0.0013

0.282471

0.000025

-10.63

-0.4

0.88

1114

1482

-0.96

HJY03-10

482

0.0266

0.0011

0.282485

0.000023

-10.15

0.1

0.81

1088

1447

-0.97

HJY03-11

485

0.0174

0.0007

0.282410

0.000020

-12.82

-2.4

0.71

1182

1606

-0.98

HJY03-12

482

0.0379

0.0015

0.282503

0.000024

-9.51

0.6

0.86

1075

1415

-0.95

HJY03-13

484

0.0761

0.0028

0.282558

0.000025

-7.57

2.2

0.89

1033

1317

-0.92

HJY03-14

486

0.0282

0.0011

0.282413

0.000022

-12.68

-2.3

0.79

1188

1605

-0.97

HJY03-15

483

0.0304

0.0012

0.282468

0.000026

-10.76

-0.5

0.92

1116

1488

-0.96

HJY03-16

482

0.0272

0.0011

0.282418

0.000022

-12.53

-2.3

0.76

1183

1598

-0.97

HJY03-17

482

0.0215

0.0009

0.282467

0.000020

-10.80

-0.5

0.71

1107

1484

-0.97

HJY03-18

488

0.0266

0.0011

0.282444

0.000018

-11.61

-1.2

0.63

1146

1536

-0.97

HJY03-19

482

0.0408

0.0015

0.282466

0.000020

-10.81

-0.7

0.70

1128

1498

-0.95

HJY03-20

488

0.1156

0.0041

0.282480

0.000026

-10.34

-0.9

0.92

1191

1517

-0.88

Table 4 Sr-Nd isotopic compositions for the Early Paleozoic ultramafic rocks in the Duobaoshan area Sample

t

Rb

Sr

no.

(Ma)

(ppm)

(ppm)

87

Rb/86S r

DBS01-a

497

4.28

19.51

0.6340

DBS01-b

497

3.92

21.36

0.5310

87

Sr/86S r

2s

ISr

0.7062

0.0000

0.70179

8

6

0

0.7085

0.0000

0.70476

3

6

9

Sm

Nd

(ppm)

(ppm)

147

Sm/144N d

143

Nd/144N d

0.09124

0.54290

0.1016

0.512445

0.08801

0.46921

0.1134

0.512462

2s

TDM1

0.00001

TDM2

εNd(0

εNd(t

fSm/N

)

)

d

-3.8

2.28

-0.48

-3.4

1.86

-0.42

103

0

959

8

0.00000

104

107

9

5

2

Highlights: 1. The Xinglong granitoids were derived from the partial melting of a dominantly Paleo-Mesoproterozoic “old” crustal source with possible different degrees of addition of juvenile materials. 2. These data constrain the timing of the Duobaoshan Formation to the Early Ordovician, rather than Middle-Late Ordovician. 3. The ca. 480 Ma Xinglong granitoid rocks possess the geochemical characteristics of post-collision granite affinity, whereas the similar-aged rhyolitic tuffs and ultramafic intrusion from the Duobaoshan Formation show the geochemical characteristics of island-arc igneous rock and occurred in an island-arc tectonic setting. 4. There are more evidences and constraints that the northern extension location of the Xinlin-xiguitu suture zone is located in the Jifeng–Xinglong areas.