Geochronology, petrogenesis and tectonic implication of Late Paleozoic volcanic rocks from the Dashizhai Formation in Inner Mongolia, NE China

    Geochronology, petrogenesis and tectonic implication of Late Paleozoic volcanic rocks from the Dashizhai Formation in Inner Mongolia, NE China Qian Yu, Wen-Chun Ge, Jian Zhang, Guo-Chun Zhao, Yan-Long Zhang, Hao Yang PII: DOI: Reference:

S1342-937X(16)30002-8 doi: 10.1016/j.gr.2016.01.010 GR 1580

To appear in:

Gondwana Research

Received date: Revised date: Accepted date:

23 January 2015 30 January 2016 31 January 2016

Please cite this article as: Yu, Qian, Ge, Wen-Chun, Zhang, Jian, Zhao, Guo-Chun, Zhang, Yan-Long, Yang, Hao, Geochronology, petrogenesis and tectonic implication of Late Paleozoic volcanic rocks from the Dashizhai Formation in Inner Mongolia, NE China, Gondwana Research (2016), doi: 10.1016/j.gr.2016.01.010

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ACCEPTED MANUSCRIPT Geochronology, petrogenesis and tectonic implication of Late Paleozoic volcanic

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rocks from the Dashizhai Formation in Inner Mongolia, NE China

Qian Yu a, Wen-Chun Ge a*, Jian Zhang a, Guo-Chun Zhao b, Yan-Long Zhang a, Hao

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Yang a

College of Earth Sciences, Jilin University, Changchun 130061, China

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Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong

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*Corresponding author:

College of Earth Sciences Jilin University No. 2199 Jianshe Street Changchun, 130061, China

Tel.:

86-0431-88502278

Fax:

86-0431-88584422

E-mail:

[email protected]

ACCEPTED MANUSCRIPT Abstract In this paper we report on geochemical, zircon U–Pb and Hf isotopic data for the late

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Paleozoic volcanic rocks of the Dashizhai Formation, which are exposed along the

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northwestern margin of the Songnen terrane in eastern Inner Mongolia. Our aim is to

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constrain the petrogenesis and tectonic setting of the volcanic rocks and to unravel the late Paleozoic tectonic evolution of the northwestern part of the Songnen terrane, along the eastern segment of the Central Asian Orogenic Belt. Lithologically, the

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Dashizhai Formation is composed mainly of rhyolitic tuff, rhyolite, dacite, andesite, basaltic andesite and basalt, with minor basaltic trachyandesite. The zircons separated

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from these rocks are euhedral–subhedral, have high Th/U ratios (0.2–1.6), and display broad oscillatory growth zoning, indicating a magmatic origin. The results of zircon U–Pb dating indicate the volcanic rocks formed during the early Permian (295–283

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Ma). Geochemically, these volcanic rocks belong to the mid–K to high–K

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calc-alkaline series and are characterized by an enrichment in large ion lithophile elements (LILEs) and a depletion in high field strength elements (HFSEs, such as Nb,

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Ta, and Ti), similar to igneous rocks that form in active continental margin settings. Most magmatic zircons of the rhyolites show positive εHf(t) values (+3.65–+13.0) and two–stage model ages (TDM2) of 1396–551 Ma. These geochemical characteristics

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indicate that the acidic volcanic rocks of the Dashizhai Formation were most likely derived from the partial melting of dominantly juvenile crustal components with a possible addition of “old” materials. In contrast, the basic to intermediate volcanic rocks were derived from the partial melting of a depleted lithospheric mantle that had been metasomatized by fluids derived from a subducted slab. These data, together with regional geological investigations, suggest that the generation of the early Permian volcanic rocks of the Dashizhai Formation was related to the southward subduction of the Paleo–Asian oceanic plate beneath the Songnen terrane. This also implies that the terminal collision between the Songnen and Xing’an terranes did not occur before the early Permian. Keywords: Late Paleozoic; Volcanic rocks; Zircon U–Pb geochronology;

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Geochemistry; Dashizhai Formation; Inner Mongolia

ACCEPTED MANUSCRIPT 1. Introduction The Central Asian Orogenic Belt (CAOB), one of the world’s largest accretionary orogens (Sengör et al., 1993; Windley et al., 2007), evolved over ~800

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Myr, involving multiple episodes of subduction and long continuous periods of accretion (Coleman, 1989; Kovalenko et al., 2004; Kröner et al., 2007, 2014; Rytsk et

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al., 2007; Windley et al., 2007; Xiao and Santosh, 2014). The CAOB is situated between the Siberian, Tarim, North China, and East European cratons, and was the remarkable site of Phanerozoic crustal growth (Kovalenko et al., 1996, 2004; Kröner

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et al., 2014; Sengör et al., 1993; Xiao and Santosh, 2014). The architecture and amalgamation history of the CAOB are closely associated with the closing of the

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Paleo–Asian Ocean, and have attracted wide interest from the international tectonics community (Cawood et al., 2009; Mossakovsky et al., 1993; Windley et al., 2007;

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Xiao et al., 2013; Zonenshain et al., 1990).

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Many researchers have studied the tectonic history of the CAOB based on its sutures, which represent the boundaries between accreted blocks and the sites of

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closure of the Paleo–Asian Ocean (Li, 2006; Sengör, 1992; Wu et al., 2011; Xiao et al., 2013, 2014). It is well established that the terminal collision of the western segment of the CAOB (e.g., the Junggar and Tianshan orogens) occurred by the late Permian to

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Triassic (Han et al., 2015; Scheltens et al., 2015; Xiao et al., 2013, 2014; Xiao and Santosh, 2014). However, the tectonic evolution and timing of amalgamation along the eastern CAOB are debated (Badarch et al., 2002; Chen et al., 2000, 2009; Jian et al., 2008, 2010, 2012; Miao et al., 2007, 2008; Wang and Liu, 1986; Xiao et al., 2003, 2009). This paper focuses on late Paleozoic magmatism in the Songnen terrane, which occurred in the NE China segment of the eastern CAOB. This region of NE China saw the amalgamation of microcontinental blocks (from NW to SE, the Erguna, Xing’an, Songnen, and Jiamusi–Khanka blocks) during the Paleozoic (Li, 2006; Sengör et al., 1993; Wu et al., 2011) and was affected by circum–Pacific tectonism during the Mesozoic (Wu et al., 2007; Xu et al., 2009; Yu et al., 2012). Several sutures have been recently discovered in this region; i.e., the Solonker–Xra Moron and Hegenshan ophiolite belts. Most previous studies have identified the Solonker–Xra

ACCEPTED MANUSCRIPT Moron ophiolite belt as the final suture that represents closure of the Paleo–Asian Ocean between the North China and Siberian blocks (Huang, 1983; Li and Wang, 1983; Wang and Liu, 1986; Wang et al., 1991; Wu et al., 2011). Although many

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studies have helped constrain the geochronology and tectonic setting of the Hegenshan ophiolite belt, which marks the zone of collision between the Xing’an and

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Songnen terranes, questions remain regarding the late Paleozoic tectonic setting of the Xing’an and Songnen terranes (Eizenhöfer et al., 2014; Jian et al., 2012; Miao et al., 2008; Xiao et al., 2003, 2009; Zhang et al., 2014) and the timing of their terminal

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collision (Bao et al., 1994; Miao et al., 2008; Nozaka and Liu, 2002; Robinson et al., 1999; Tang, 1990).

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These uncertainties arise from the lack of precise geochronological and geochemical data for the late Paleozoic volcanic rocks of the Xing’an and Songnen

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terranes. To examine the geochronology, petrogenesis, and tectonic implications along

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this segment of the eastern CAOB, we present whole–rock geochemical data, zircon U–Pb ages, and in situ Hf isotopic compositions for late Paleozoic volcanic rocks in

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the Songnen terrane.

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2. Geological background and sample descriptions

Tectonically, the Songnen terrane is considered as a part of the eastern CAOB, located between the Siberian and North China blocks (Jahn et al., 2000; Li, 2006; Sengör et al., 1993). The Songnen terrane is bounded by the Solonker–Xra Moron suture zone to the south, the Jiamusi–Khanka block to the east, and the Xing’an terrane to the north (Fig. 1). The Hegenshan ophiolite belt is generally believed to have resulted from the middle Paleozoic collision between the Songnen and Xing’an terranes (Bao et al., 1994; Nozaka and Liu, 2002; Robinson et al., 1999; Tang, 1990) and was subsequently affected by asthenospheric upwelling and lithospheric extension in the late Paleozoic (Jian et al., 2012; Zhang et al., 2008; Zhang et al., 2014). Recent studies have argued that this tectonism occurred during the Permian and led to a supra-subduction setting for the Songnen terrane (Eizenhöfer et al., 2014; Miao et al.,

ACCEPTED MANUSCRIPT 2008; Xiao et al., 2003, 2009). To resolve the timing of these events, we studied the volcanic rocks of the Dashizhai Formation, which are exposed along the northwestern margin of the

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Songnen terrane. The Dashizhai Formation was first recognized in central–eastern Inner Mongolia (BGMRIM, 1965), and the outcropping strata contain basic to acid

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volcanic rocks and tuffs intercalated with marine sedimentary rocks (Figs. 1a and b; BGMRIM, 1991). These volcanic rocks play an important role to reveal the tectonic evolution of the Songnen terrane during the late Paleozoic, but their geochronology

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and geochemistry are poorly understood. We measured a stratigraphic section of the Dashizhai Formation (Fig. 2) from N46°21'19.6", E121°23'19.6" to N46°17'21.0",

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E121°21'3.3" (Fig. 1b), and confirmed that it consists mainly of rhyolitic tuffs, rhyolites, dacites, andesites, basalts, and sedimentary rocks. The formation is

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conformably overlain by the neritic-facies Zhesi Formation that consists mainly of

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clastic rocks and limestone (Fig. 2; BGMRIM, 1991). Granitoids in the study area were emplaced mainly during the middle–late Triassic, early–middle Jurassic, and

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early Cretaceous (Ge et al., 2005).

The analyzed samples from the Dashizhai Formation include rhyolite tuff, rhyolite, dacite, andesite, basaltic andesite, basaltic trachyandesite, and basalt. The

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rhyolitic tuff is gray–white and contains ~60% volcanic ash, ~30% rhyolite detritus, and ~10% crystal fragments (including plagioclase, alkali feldspar, and quartz) (Fig. 3a). The rhyolite is gray–white and has a porphyritic texture and flow structures; it contains phenocrysts (~10%) of alkali feldspar and quartz in aphanitic and felsitic groundmass (Fig. 3b). The dacite is massive and gray, and contains ~5% phenocrysts of plagioclase and minor quartz. The andesite is massive and dark gray, containing phenocrysts (dominated by plagioclase and amphibole) that make up ~30% of the rock; the groundmass is pilotaxitic (Fig. 3c). The basaltic andesite is also dark gray in color, and is massive or vesicular; it contains phenocrysts (mainly plagioclase and pyroxene) that make up ~15% of the rock, with an intersertal groundmass texture. The basaltic trachyandesite is dark gray, porphyritic, and massive, containing alkali feldspar and pyroxene phenocrysts that make up ~30% of the rock, and the

ACCEPTED MANUSCRIPT groundmass has an intergranular texture. The basalt is dark gray and is either aphyric or porphyritic, and either massive or vesicular; pyroxene phenocrysts make up ~5% of

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the rock, and the groundmass has an intersertal texture (Fig. 3d).

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3. Analytical methods

3.1. Zircon U–Pb dating

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Zircons from five volcanic rocks were extracted using a combination of magnetic and heavy liquid methods, and then handpicked under a binocular microscope at the

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Langfang Regional Geological Survey, Hebei Province, China. The selected zircons were examined under transmitted and reflected light with an optical microscope, and

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cathodoluminescence (CL) images (Fig. 4) were collected on a CAMECA SX51

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under conditions of 50 kV and 15 nA at the Institute of Geology and Geophysics, Chinese Academy of Sciences (Beijing), China. The CL images were used to examine

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the internal textures and choose potential targets for U–Pb dating. To avoid any impact on the dating results from inherited material and other mineral inclusions, homogeneous zircons with no bright cores, inclusions, or fissures were chosen for

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analysis, based on their CL images (Fig. 4). Samples were analyzed for geochronology on an Agilent 7500 ICP–MS (inductively coupled plasma–mass spectrometer) equipped with a 193 nm laser (New Wave Research Inc.), and housed at the Institute of Geology and Geophysics, Chinese Academy of Sciences (Beijing). Zircon 91500 was used as the external standard, and a standard silicate glass Nist 610 was used to optimize the instrument. The zircon standard TEMORA (417 Ma) from Australia (Black et al., 2003) was also used as a secondary standard when examining the deviations in age measurements and calculations. The diameter of the laser spot was 60 m throughout the analyses. Isotopic ratios and element contents were calculated using the GLITTER program (ver. 4.4, Macquarie University). Correction for common Pb was made following Andersen (2002). The age calculations and concordia plots were made using Isoplot (ver. 3.0) (Ludwig, 2003). Errors on

ACCEPTED MANUSCRIPT individual analyses by laser ablation (LA)–ICP–MS are quoted at the 1level, while errors on pooled ages are quoted at the 95% confidence level. The U–Pb dating results for the zircons from the volcanic rocks of the Dashizhai Formation are presented in

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Table 1.

3.2. Major and trace element analysis

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For geochemical analyses, altered rock surfaces were first removed, then whole–rock samples were crushed in an agate mill to ~200 mesh. An X–ray

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fluorescence spectrometer (XRF; Rigaku RIX 2000) using fused glass beads and an ICP–MS (PerkinElmer Sciex ELAN 6000) were used to measure the major and trace element compositions, respectively, at the Institute of Geochemistry, Chinese

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Academy of Sciences (Guangzhou), China. A set of USGS and Chinese national rock

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standards, including BHVO–1, W–2, AGV–1, G–2, GSR–1, and GSR–3, was chosen for calibrating element concentrations of unknowns. Analytical precision was better

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than 5% for major elements and 10% for trace elements (Rudnick et al., 2004). The results of the geochemical analyses are listed in Table 2.

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3.3. Hf isotope analysis

In situ zircon Hf isotopic analyses were carried out on a Neptune multi-collector ICP–MS equipped with a 193 nm laser at the Institute of Geology and Geophysics, Chinese Academy of Sciences (Beijing), China. Hf isotopic analyses were performed using a spot diameter of 63 m, a laser repetition rate of 10 Hz, and a laser beam energy density of 10 J/cm2. For details of the analytical procedure, see Wu et al. (2006). Correction for the isobaric interference of measuring the intensity of the interference-free

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Lu on

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Hf was performed by

Lu isotope plus a recommended

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Lu/175Lu ratio of 0.02655 (Machado and Simonetti, 2001) to calculate the

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Lu/177Hf ratios. Isobaric interference of

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Yb on 176Hf was corrected by measuring

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Yb isotope and using a

2006). During the analyses, the measured

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Lu/172Yb ratio of 0.5886 (Wu et al.,

Hf/177Hf ratio of the standard zircon

91500 was 0.282295 ± 0.000027, which agrees well with the low peaks of the Hf/177Hf ratio of 0.282284 ± 0.000022 measured by Griffin et al. (2006). Measured

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Hf/177Hf and

Lu/177Hf ratios were used to calculate initial

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Hf/177Hf ratios,

present-day chondritic ratios of

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taking the decay constant for 176Lu as 1.865 × 10−11 year−1 (Scherer et al., 2001). The Hf/177Hf = 0.282772 and

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Lu/177Hf = 0.0332

(Blichert–Toft and Albarède, 1997) were adopted to calculate εHf(t) values. Hf model

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ages were calculated as described by Amelin et al. (2000), Griffin et al. (2000), and

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Nowell et al. (1998). The results of our Hf isotope analyses are presented in Table 3.

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4. Analytical results

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4.1. Zircon U–Pb ages

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Five representative volcanic samples were collected from the Dashizhai Formation for zircon U–Pb dating by LA–ICP–MS. CL images of the representative zircons are presented in Fig. 4 and concordia plots are shown in Fig. 5.

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Sample DS005 is a rhyolitic tuff that consists mainly of plagioclase, alkali–feldspar, and quartz. The zircons are mostly euhedral to subhedral elongate prisms of 110–150 m in length, with length: width ratios of 1.5:1 to 2:1. These zircons show oscillatory growth zoning and have high Th/U ratios (0.7–1.6), indicating a magmatic origin (Koschek, 1993). The 206Pb/238U ages from 24 analytical spots range from 300 to 275 Ma (Table 1), most of which are concordant, and they gave a weighted mean

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Pb/238U age of 292 ± 2 Ma (n = 18, MSWD = 0.55) that is

interpreted to be the time of eruption of the rhyolitic tuff (Fig. 5a). Zircons from sample DS019, a rhyolite, are mostly stubby to elongate euhedral prismatic crystals of 70–130 m in length, with length: width ratios of 1.1:1–2:1. They display clear oscillatory zoning and high Th/U ratios (0.4–1.4), indicating a magmatic origin. The

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Pb/238U ages from 22 spots vary from 290 to 275 Ma (Table

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Pb/238U age of 284 ± 3 Ma (n = 21, MSWD =

0.39), which is interpreted to be the timing of rhyolite eruption (Fig. 5b). Sample DS042, also a rhyolite, contains euhedral to subhedral zircons with a

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long prismatic habit. Their lengths vary from 100 to 150 m, and length: width ratios are 1.1:1 to 2:1. In CL images, most of the zircons show oscillatory zoning, typical of

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an igneous origin. Twenty-one analyses yielded high Th/U ratios of 0.5 to 1.1, Pb/238U ages between 307 and 281 Ma (Table 1), and a weighted mean

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Pb/238U

age of 290 ± 2 Ma (n = 20, MSWD = 2.5), interpreted to represent the time of

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formation of the rhyolite (Fig. 5c).

Sample DS070 is a rhyolitic tuff, and it consists mainly of rhyolite detritus,

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crystal fragments, and volcanic ash. Zircons are mostly euhedral to subhedral, 110–150 m in length, and with aspect ratios of 1.1:1 to 2.5:1. These zircons are

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characterized by oscillatory zoning and high Th/U ratios (0.2–1.6), indicative of a 206

Pb/238U ages of 330 to 271

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magmatic origin. Twenty-two analytical spots yielded

Ma (Table 1), with age populations at 330 ± 11 Ma (n = 1) and 283 ± 3 Ma (n = 21,

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MSWD = 3.5) (Fig. 5d). The younger age is considered as the time of eruption of the rhyolitic tuff, whereas the older age is interpreted to be the age of crystallization of inherited or captured zircons entrained by the rhyolitic tuff.

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Zircons in sample DS079, a rhyolite, are mostly euhedral and elongate prisms, 130–160 m in length and with aspect ratios of 2:1 to 3:1. These zircons show oscillatory growth zoning and yield high Th/U ratios (0.2–1.0), indicating a magmatic origin. Twenty-three analyses produced a

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Pb/238U age range of 922 to 279 Ma

(Table 1), and yielded two concordant groups of ages at 909 ± 34 Ma (n = 5) and 295 ± 4 Ma (n = 18, MSWD = 3.9) (Figs. 5e and f). These data indicate that the rhyolite formed at 295 ± 4 Ma, with the older age representing inherited or captured zircons entrained by the rhyolite.

4.2. Geochemistry

4.2.1. Major and trace elements

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The major and trace element geochemistry of forty-three late Paleozoic volcanic samples is given in Table 2. Lithologically, the rocks consist of rhyolite, dacite,

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andesite, basaltic andesite, basaltic trachyandesite, and basalt (Fig. 6a; Peccerillo and Taylor, 1976). They plot within the subalkaline series on the TAS chemical

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classification diagram (Fig. 6a), and mainly fall in the field of mid–K to high–K calc-alkaline volcanic rocks on the K2O versus SiO2 diagram (Fig. 6b; Richwood, 1989).

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As shown in Table 2, the basalts are high in SiO2 (49.68–51.50 wt.%) and contain 6.49–8.28 wt.% MgO, 16.20–17.03 wt.% Al2O3, and 6.81–8.93 wt.% CaO.

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They are low in TiO2 (1.40–1.91 wt.%), P2O5 (0.17–0.25 wt.%), Na2O (2.51–3.27 wt.%), and K2O (0.28–0.93 wt.%), with quite low K2O/Na2O ratios of 0.10–0.31. In

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the chondrite-normalized REE diagram (Fig. 7a; Boynton, 1984), these basalts show

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smooth chondrite-normalized REE patterns, with slight enrichments in light rare earth elements (LREEs) (LaN/YbN = 2.19–3.49) and weak positive Eu anomalies (Eu/Eu* =

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1.06–1.23). In the PM (primitive mantle)–normalized trace element diagram (Fig. 7b; Sun and McDonough, 1989), they show a depletion in high field strength elements (HFSEs; e.g., Th, U, Nb, Ta, Zr, and P) and an enrichment in large ion lithophile

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elements (LILEs; e.g., Ba, K, and Sr). The basaltic trachyandesites, basaltic andesites, and andesites have variable SiO2 (51.07–59.68 wt.%), MgO (0.49–6.30 wt.%), Al2O3 (14.96–18.69 wt.%), CaO (1.96–10.33 wt.%), and Ti2O (0.88–2.00 wt.%) contents, with K2O/Na2O = 0.05–0.50 (1.74 and 2.46 for individual andesites). These samples have relatively flat REE patterns (Fig. 7c), an enrichment in LREEs (LaN/YbN = 3.48–10.53), and weak Eu anomalies (Eu/Eu* = 0.79–1.29). In addition, they are enriched in LILEs (e.g., Rb, Ba, and K) and depleted in HFSEs (e.g., Nb, Ta, and Ti) (Fig. 7d). The dacites have SiO2 = 63.86–69.30 wt.%, MgO = 1.16–2.58 wt.%, TiO2 = 0.53–0.63 wt.%, Al2O3 = 14.72–15.63 wt.%, and K2O/Na2O = 0.09–0.93. Additionally, these samples are characterized by a depletion in HFSEs (e.g., Nb, Ta, and Ti), an enrichment in LILEs (e.g., Rb, Ba, and K) (Fig. 7e), and minor negative or positive

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0.06–0.29 wt.%, Al2O3 = 7.32–13.96 wt.%, and CaO = 0.03–1.38 wt.%. These rhyolites are enriched in LREEs and LILEs (e.g., Rb, Ba, U, and K) and depleted in

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HREEs and HFSEs (e.g., Nb, Ta, Sr, P, and Ti) (Figs. 7e and f). Their LaN/YbN ratios and Eu/Eu* values vary from 4.15 to 20.29 and from 0.24 to 0.81, respectively. On a Harker diagram (Fig. 8), Al2O3, CaO, Fe2O3, MgO, P2O5, and TiO2 show

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negative linear correlations with SiO2 (Figs. 8a–c, f–h), whereas K2O shows a positive correlation (Fig. 8d); Na2O shows large variations without a clear trend (Fig. 8e). The

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strong correlations between SiO2 and the other major elements suggest that fractional

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crystallization played an important role in the magmatic process.

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4.2.2. In situ zircon Hf isotopic compositions

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All the zircon U–Pb spots used for dating the rhyolites (DS005, DS019, DS042, DS070, and DS079) were chosen for in situ zircon Hf isotopic analysis (Table 3). Zircons from the early Permian rhyolites possess relatively homogeneous Hf isotopic

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compositions. Their initial 176Hf/177Hf ratios vary from 0.282714 to 0.282981. At 280 Ma, the calculated εHf(t) values range from +3.65 to +13.0 and the two-stage model ages (TDM2) vary from 1396 to 551 Ma. All the analyzed zircon spots plot between depleted mantle and the CHUR line on the εHf(t) versus age diagram (except for six points for inherited or captured zircons; Fig. 9), and they have similar Hf isotopic compositions to zircons from the Phanerozoic igneous rocks of the CAOB (Chen et al., 2009; Xiao et al., 2004).

5. Discussion

5.1. Ages of the volcanic rocks from the Dashizhai Formation

ACCEPTED MANUSCRIPT The volcanic rocks of the Dashizhai Formation are widely distributed along the northwestern margin of the Songnen terrane. Previous geochronological data indicate that these volcanics formed in the early or middle Permian (BGMRIM, 1965, 1991;

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Liu, 2009; Tao et al., 2003; Wang, 1987). However, most studies have focused on the volcanics of central Inner Mongolia. The volcanic rocks of eastern Inner Mongolia

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have been dated based on stratigraphic relationships and fossils (Zhao, 2008), but their ages have not been well constrained by zircon age data.

For this study, only zircons from the acidic volcanic rocks were collected for

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U–Pb dating, since it was too difficult to obtain zircons from the basic to intermediate rocks. All the zircons from the analyzed samples of the Dashizhai Formation display

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typical oscillatory growth zoning, and have high Th/U ratios (0.2–1.6), indicating a magmatic origin. We conclude, therefore, that the LA–ICP–MS U–Pb ages for these 206

Pb/238U

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zircons represent the eruption ages of the magmas. The weighted mean

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ages for 5 rhyolite and rhyolitic tuff samples are in the range 295 ± 4 to 283 ± 3 Ma (Figs. 10 and 11a). As shown in the measured stratigraphic section (Fig. 2), the

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Dashizhai Formation consists mainly of acidic volcanic rocks interlayered with minor basic to intermediate volcanic rocks, and the rock sequence mostly ranges from acidic to basic volcanics in ascending stratigraphic order. Moreover, precise radiometric age

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data for the Dashizhai Formation in central Inner Mongolia yield early Permian ages for the basic to intermediate volcanic rocks (Gao and Jiang, 1998; Tao et al., 2003; Zhu et al., 2001; Zhang et al., 2008). Based on the above, we consider that the basic to intermediate volcanic rocks formed coevally with the acidic volcanic rocks. This conclusion is also consistent with paleontological evidence (BGMRIM, 1965, 1991). To understand the spatial and temporal distribution of the Dashizhai Formation, we compiled the results of geochronological studies from other regions, which are summarized as follows. (1) Wang (1987) suggested that volcanic rocks from the Dashizhai Formation in the Huanggangliang region, in the southern segment of Daxing’anling, formed at 280 Ma according to whole-rock K–Ar isotope ages (Fig. 11f); (2) Tao et al. (2003) discovered 285 Ma basic to intermediate volcanics in the Dashizhai Formation of the Mandula area, in the middle part of Inner Mongolia (Fig.

ACCEPTED MANUSCRIPT 11g); (3) Gao and Jiang (1998) reported a 281 Ma andesite from the Dashizhai Formation of the Sonid Left Banner area, using Rb–Sr isotope dating (Fig. 11h); (4) Zhu et al. (2001) documented early Permian magmatic activity in the Mongolian

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orogenic zone, based on Rb–Sr isochron dating of the basic to intermediate volcanic rocks (Fig. 11e); (5) Zhang et al. (2008) suggested that basaltic andesite and rhyolite,

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collected from the Dashizhai Formation in Xilinhot, formed at 281 Ma and 279 Ma, respectively (Figs. 11b and d); (6) Liu (2009) reported an age of 271 Ma for a rhyolite from the Dashizhai Formation in the Xiwuqi area (Fig. 11c). Taken together, these

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dating results for volcanic rocks from the Dashizhai Formation lead us to conclude that an important magmatic event occurred in central–eastern Inner Mongolia along

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the northwestern margin of the Songnen terrane during the early Permian.

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5.2. Petrogenesis of volcanic rocks from the Dashizhai Formation

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5.2.1. Origin of the basic–intermediate volcanic rocks

The early Permian basalts of the Dashizhai Formation have retained their primary minerals, have low LOI values, and have consistent variations in both

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immobile and mobile elements in PM-normalized trace element patterns (Fig. 7b), all of which indicate no significant alteration or change to their original chemical compositions. Therefore, we assume that the analytical data for major and trace elements in the basalts preserve the primary compositions. As mentioned above, the distinctive features of the basalts (e.g., negative Nb–Ta anomalies; Fig. 7) might have resulted from continental contamination or have been derived from their subduction-related sources (Davidson and Arculus, 2006; Rudnick and Gao, 2003). Nevertheless, all of the studied basalts are also characterized by negative Zr–Hf anomalies (Fig. 7b), whereas rocks affected by continental contamination do not display such anomalies for the reason that crustal materials are relatively rich in these two elements. Therefore, we conclude that crustal

ACCEPTED MANUSCRIPT contamination did not play a significant role during the evolution of the magma. The basalts of the Dashizhai Formation are high in SiO2 (49.68–51.50 wt%) and low in MgO (6.49–8.28 wt%), Cr (189–324 ppm), Co (36.8–42.4 ppm), and Ni

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(99.4–142 ppm), relative to primitive-mantle-derived magmas, suggesting they were derived from relatively evolved melts (Frey and Prinz, 1978). The Harker diagrams

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(Fig. 8) show that the basic to intermediate volcanics possess a fractional crystallization trend, indicating varying degrees of fractional crystallization, as also supported by the fractional crystallization trend shown in the Cr versus Th diagram

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(Fig. 12a).

The basic to intermediate volcanic rocks of the Dashizhai Formation belong to

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the subalkaline series, and mainly plot within the mid-K calc-alkaline fields on the K2O versus SiO2 diagram (Fig. 6). Furthermore, they are characterized by selective

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enrichment in LREEs and LILEs, and depletion in HFSEs, with relatively high La/Nb

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(1.58–2.02) and low La/Ba (0.02–0.07) values (Fig. 12b). These features are similar to those of volcanic rocks from an active continental margin (Eiler et al., 2000; Gill,

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1981; Grove and Kinzler, 1986; Grove et al., 2003), suggesting that their mantle source could be a depleted mantle wedge that had been metasomatized before partial melting. This view is also consistent with the previous published Sr-Nd-Hf isotopic

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data for the early Permian volcanic rocks and plutons of the central Inner Mongolia, e.g., the mafic samples of the volcanic-plutonic sequence in the Mandula area have high (143Nd/144Nd)i (0.51262–0.51270) and positive εNd(t) (+3.4–+8.0), implying that they were likely derived from the depleted mantle source (Chen et al., 2012); and the diabase dikes from the Linxi area display low (87Sr/86Sr)i (0.70315–0.70362), positive εNd(t) (+6.8–+7.4) and positive zircon εHf(t) (+14.7–+19.1), suggesting their generation from a depleted mantle (Li et al., 2015). Meanwhile, the Sr-Nd-Hf isotopic evidence leads to a scenario that a highly depleted mantle source once existed in the central Inner Mongolia through the late Paleozoic as the incompatible elements depleting progressively, due to the extraction of juvenile continental crust during the evolution of CAOB (Sengör et al. 1993; Wu et al. 2011; Li et al., 2015). Sediment and altered oceanic crust of a subducted slab are the most potential

ACCEPTED MANUSCRIPT materials, which would be introduced into the mantle wedge through partial melting and/or dehydration in subduction zones. Generally, both slab-derived fluids and hydrous melts from the subducted sediments or the altered oceanic crust will modify

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the overlying mantle wedge. Slab-derived fluids commonly have a high capacity to transport water-soluble elements but are low in water-insoluble elements, whereas

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hydrous melts have the capacity to transport both (Zheng, 2012). Hence, the Ba content and Rb/Y ratio will be sensitive to slab dehydration fluids, and the Nb/Y ratio is indicative of hydrous melts. In Figure 13a, the basalts exhibit high Ba

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concentrations coupled with constant Nb/Y ratios, which is consistent with fluid-induced enrichment. Also, the increase in Rb/Y ratios with generally low Nb/Y

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ratios, which is consistent with increasing slab dehydration fluids metasomatism, is shown in Figure 13b. These trace element characteristics are commonly interpreted as

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a slab-derived fluid addition to a sub-arc mantle source (Kepezhinskas et al., 1997).

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Taken together, it is likely that the basic to intermediate volcanic magma originated from the partial melting of a depleted mantle wedge that had been metasomatized by

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subduction-related fluids. Moreover, the basaltic trachyandesites, basaltic andesites, and andesites were produced by fractional crystallization of the basaltic magma.

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5.2.2. Origin of the dacites and rhyolites

As shown by the zircon U–Pb dating results, the Dashizhai Formation basalts, basaltic trachyandesites, basaltic andesites, andesites, dacites, and rhyolites possess similar early Permian ages, indicating that they all formed nearly coevally. It is important to determine whether the acidic rocks were derived from the basaltic magma. First, considering the much greater abundance of exposed acidic volcanic than basic to intermediate volcanic rocks (Fig. 2), we infer that the acidic volcanics were unlikely to have been directly derived from basic magma. Moreover, Fig. 7 shows that LREE abundance and geochemical features are similar between the acidic and basic to intermediate volcanic rocks, further indicating that the acidic volcanics

ACCEPTED MANUSCRIPT have an origin that is independent of the basic magma. Considering characteristics of the acidic rocks from the Dashizhai Formation, which are marked by high SiO2, low MgO, Cr, and Ni contents, significant negative

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Nb, Ta, P, and Ti anomalies, positive Th, Zr, and Hf anomalies, and pronounced moderate negative Eu anomalies, we infer that the felsic lava may derive from the

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continental crust produced by chemical differentiation of arc-derived magmas (Guo et al., 2014). Combine with the nature of calc-alkaline shown in the K2O versus SiO2 diagram (Fig. 6b), these acidic volcanic rocks probably define an arc volcanic rocks

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that related to subduction, and were produced by partial melting of arc-type crustal rocks with the enrichment of plagioclase but absence of garnet in the residual phase

176

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(Rapp and Watson, 1995). Isotopically, the rhyolites have relatively high initial Hf/177Hf ratios of 0.282714 to 0.282981 and positive εHf(t) values of +3.65 to +13.0,

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with Hf two-stage model ages of 551 Ma to 1396 Ma. Most magmatic zircons of the

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rhyolites plot between the depleted mantle and CHUR line (Fig. 9), indicating that the primary magma could have originated from the partial melting of dominantly juvenile

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crustal materials and Cambrian–Mesoproterozoic was a major period of crust growth in the Songnen terrane. In addition, the captured or inherited zircons of rhyolites from the Dashizhai Formation have low εHf(t) values of -0.4 to -17. Five analytical spots of

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them possess εHf(t) values of -16 to -17 at a weighted age of 909 Ma, while the other spot shows εHf(t) value of -0.4 at the age of 330 Ma, suggesting a contribution from “old” crust components involved in the source region of the felsic lavas. In summary, we conclude that the primary magma of the acidic rocks probably originated from the partial melting of dominantly juvenile crustal components with a possible addition of “old” materials, induced by the heat provided by the passage of contemporaneous basaltic magma derived from the underlying mantle wedge.

5.3. Tectonic implications

The Songnen and Xing’an terranes are considered as part of the eastern CAOB, but the timing of their collision, as well as their tectonic setting during the late

ACCEPTED MANUSCRIPT Paleozoic, remains controversial. Geochronological studies of the Hegenshan suture indicate that the terminal collision occurred during the middle Paleozoic and caused lithospheric extension of the northwestern Songnen terrane in the late Paleozoic (Bao

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et al., 1994; Nozaka and Liu, 2002; Robinson et al., 1999; Tang, 1990). However, recent SHRIMP age data obtained from gabbros and mafic dikes in the Hegenshan

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suture indicate that the final amalgamation took place in the latest Permian to earliest Triassic (Miao et al., 2008). Therefore, the late Paleozoic volcanic rocks along the

Paleozoic tectonic evolution of this area.

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northwestern margin of the Songnen terrane provide important insights into the late

The geochemical data presented in this paper show that the early Permian

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volcanic rocks from the Dashizhai Formation, which consist mainly of rhyolites, dacites, andesites, basaltic andesites, basaltic trachyandesites, and basalts, belong to

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the mid–K or high–K calc-alkaline series. All of the analyzed samples are

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characterized by enrichment in LREEs and LILEs, and depletion in HREEs and HFSEs (e.g., Nb, Ta, and Ti), with positive εHf(t) values. Such geochemical features

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indicate that the early Permian volcanic rocks formed in an active continental margin setting (Gill, 1981; Grove and Kinzler, 1986; Grove et al., 2003; Pearce, 1982). This conclusion is also supported by the following observations.

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(1) The acidic volcanic rocks, which are widely distributed throughout the Dashizhai Formation, display enrichment in LILEs and depletion in HFSEs, with prominent Nb, Ta, Sr, P, and Ti troughs. These geochemical features indicate a subduction setting of the northwestern Songnen terrane similar to that of the modern Andes. All of the basalt samples from the Dashizhai Formation plot within the calc-alkaline basalt field in the tectonic setting discrimination diagrams of Ti/100–Zr–Sr/2 (Fig. 14a; Pearce and Cann, 1973) and TiO2–10MnO–10P2O5 (Fig. 14b; Mullen, 1983). (2) The Permian strata in this region are characteristic of regressive sequences, shifting from marine to continental facies and indicating that deposition occurred in a remnant sea or along an active continental margin (BGMRIM, 1991; Li, 2006). (3) Finally, late Paleozoic igneous rocks in central Inner Mongolia also have

ACCEPTED MANUSCRIPT geochemical affinities to active continental margin volcanics. Tao et al. (2003) considered the rocks from the Dashizhai Formation in the Mandula region to have been derived from island arc magma, based on a study of their petrology,

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petrochemistry, and geochemistry. In addition, Zhao (2008) proposed that volcanic rocks from the Dashizhai Formation in the Dashizhai district formed along an active

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continental margin.

Taken together, we propose that the late Paleozoic Dashizhai Formation formed along an active continental margin, closely related to the southward subduction of the

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remnant Paleo-Asian oceanic plate beneath the Songnen terrane. This conclusion also

occur before the early Permian.

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indicates that the terminal collision between the Songnen and Xing’an terranes did not

Based on the discussion above, we reconstruct the late Paleozoic tectonic

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evolution of the eastern segment of CAOB in the Inner Mongolia section. During the

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Carboniferous to early Permian, a large scale of continental arc volcanic rocks (e.g. Dashizhai Formation), I-type granites, island arc magmatic rocks, and some

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subduction-accretion complexes exposed in the Xing’an and Songnen terranes (Blight et al., 2008, 2010; Chen et al., 2000, 2009; Liu et al., 2013). In the late Permian to earliest Triassic, the final collision between the Xing’an and Songnen terrane occurred

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with formation of the Hegenshan granodiorite dike (Miao et al., 2008). The granodiorite dike has LREE-enriched, chondrite-normalized REE patterns with high εNd(t) values (+6.3 to +6.8) and low (87Sr/86Sr)i (0.70412 to 0.70450), suggesting a derivation from partial melting of thickened oceanic crust (Miao et al., 2008). Thus, the volcanic association of our study, together with the previous researches reflects a tectonic transition from a subduction-related island-arc setting to an extension-related syn- and/or post-collisional setting occurred between late Permian and earliest Triassic.

6. Conclusions

Based on whole-rock geochemistry, zircon U–Pb dating, and in situ Hf isotopic

ACCEPTED MANUSCRIPT analyses of volcanic rocks from the Dashizhai Formation, combined with geological field investigations, we draw the following conclusions. 1. LA–ICP–MS zircon U–Pb dating indicates that volcanic rocks of the Dashizhai

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Formation in eastern Inner Mongolia formed in the early Permian (295–283 Ma). 2. The primary magma for the basic to intermediate volcanic rocks was derived from

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the partial melting of a depleted mantle wedge that had been metasomatized by subduction-related fluids, whereas the acidic rocks were generated by the partial melting of dominantly juvenile crustal components with a possible addition of

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“old” materials.

3. The volcanic rocks of the Dashizhai Formation formed along an active continental

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margin related to the southward subduction of the Paleo–Asian Oceanic plate, indicating that the terminal collision between the Songnen and Xing’an terranes did

Acknowledgements

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not occur before the early Permian.

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We thank the staff of the Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, for their advice and assistance during zircon U-Pb dating by LA–ICP–MS and in situ zircon Hf isotopic data. We also appreciate the Institute of

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Geochemistry, Chinese Academy of Sciences, Guangzhou, China, for their assistance in the major and trace element analysis. This work was financially supported by the National Natural Science Foundation of China (41272076), Research Fund for the Doctoral Program of Higher Education of China (20120061110050), and Graduate Innovation Fund of Jilin University (Project 2015136).

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Zhu, Y.F., Sun, S.H., Gu, L.B., Ogasawara, Y., Jiang, N., Honma, H., 2001. Permian volcanism in the Mongolian orogenic zone, northeast China: geochemistry, magma sources and petrogenesis. Geological magazine 138, 101–115.

Figure captions Figure 1. (a) Tectonic sketch map of northeastern (NE) China (after Wu et al., 2011); (b) Geological sketch map of the studied area (after BGMRIM, 1991). Abbreviations: F1 = Xiguitu-Tayuan Fault; F2 = Hegenshan–Heihe Fault; F3 = Solonker–Xar Moron–Changchun zone; F4 = Chifeng–Bayan Fault; F5 = Dunhua-Mishan Fault; F6 = Yitong-Yilan Fault; F7 = Jiayin-Mudanjiang Fault. Figure 2. Measured section for the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia.

ACCEPTED MANUSCRIPT Figure 3. Representative photomicrographs for the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia; (a) rhyolitic tuff, cross polarized light; (b) rhyolite, cross polarized light; (c) andesite, cross polarized light; (d) basalt, cross

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polarized light. Cpx = clinopyroxene; Hb = hornblende; Or = orthoclase; Pl = plagioclase; Q = quartz.

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Figure 4. Representative cathodoluminescence (CL) images of zircons for the volcanic rocks from the Dashizhai Formation. White circles show the locations of LA–ICP–MS U–Pb analyses, and the scale bar in all CL images is 60 μm in length.

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Figure 5. Zircon LA–ICP–MS U–Pb concordia diagrams for the volcanic rocks from the Dashizhai Formation. The weighted mean age and MSWD are shown in each

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figure (including samples of DS005, DS019, DS042, DS070, and DS079). Figure 6. (a) Plots of TAS chemical classification diagram (after Peccerillo and Taylor,

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1976); (b) Plots of K2O versus SiO2 diagram (after Richwood, 1989).

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Figure 7. Chondrite-normalized REE patterns (a, c and e), and primitive mantle (PM) normalized trace element patterns (b, d and f) for the volcanic rocks from the

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Dashizhai Formation in eastern Inner Mongolia. Chondrite-normalized and primitive mantle-normalized values are from Boynton (1984) and Sun and McDonough (1989), respectively.

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Figure 8. Harker variation diagrams for major oxides vs. SiO2 content for the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia. Figure 9. εHf(t) vs. t diagram of the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia. CAOB = the Central Asian Orogenic Belt; YFTB = the Yanshan Fold and Thrust Belt (after Yang et al., 2006). Figure 10. Relative probability diagram for the forming time of the volcanic rocks from the Dashizhai Formation. Figure 11. The sketch map for the distribution of the volcanic rocks from the Dashizhai Formation in central-eastern Inner Mongolia (a, after this article; b and d, after Zhang et al., 2008; c, after Liu, 2009; e, after Zhu et al., 2001; f, after Wang, 1987; g, after Tao et al., 2003; h, after Gao and Jiang, 1998). Figure 12. (a) Plots of Cr contents versus Th contents diagram; (b) Plots of La/Ba

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Figure 13. (a) Plots of Ba vs. Nb/Y; (b) Plots of Rb/Y vs. Nb/Y.

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1992), DM are from (McKenzie and O’Nions, 1991).

Figure 14. (a) Zr–Ti–Sr discrimination diagram (after Pearce and Cann, 1973). OFB =

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ocean floor basalts; CAB = calc-alkaline basalts; IAB = island arc basalts. (b) MnO–TiO2–P2O5 discrimination diagram (after Mullen, 1983). CAB = calc-alkaline basalts; IAT = island arc tholeiites; MORB = mid ocean ridge basalts; OIT = ocean

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island tholeiites; OIA = ocean island alkaline basalts.

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ACCEPTED MANUSCRIPT Table 1. LA-ICP-MS zircon U-Pb dating data for the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia Isotopic ratios

Sample No.

Th

U

Pb Th/U

Pb/ Pb

207

235

Pb/ U

206

238

Pb/ U

207

Pb/206Pb

207

Pb/235U

206

Pb/238U

Ratio

1σ

Ratio

1σ

Ratio

1σ

Ages

1σ

Ages

1σ

Ages

1σ

34

268

7

284

7

DS005-01

481.3 415.0 24.3

0.9

0.0487

0.00165

0.30241

0.00953

0.04504

T

ppm ppm

Ages (Ma)

206

133

DS005-02

340.9 318.2 18.5

0.9

0.0521

0.00159

0.32359

0.0092

0.04504

0.00109

290

29

285

7

284

7

DS005-03

156.5 152.1 8.7

1.0

0.05315

0.002

0.33584

0.01169

0.04583

0.00119

335

37

294

9

289

7

DS005-04

590.1 492.5 29.3

0.8

0.07025

0.00174

0.42229

DS005-05

138.4 164.9 9.6

1.2

0.05491

0.00128

0.35729

DS005-06

147.9 166.8 9.7

1.1

0.05259

0.00153

0.33643

DS005-07

261.4 242.7 14.5

0.9

0.063

0.00165

0.39128

DS005-08

617.7 469.1 28.7

0.8

0.05197

0.0014

0.32536

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ppm

207

DS005-09

506.5 340.1 22.1

0.7

0.05433

0.0015

DS005-10

107.1 171.6 9.4

1.6

0.05471

0.00141

DS005-11

172.8 196.6 11.6

1.1

0.05332

0.00113

DS005-12

214.3 228.1 13.4

1.1

0.06373

DS005-13

202.1 222.5 13.1

1.1

0.05156

DS005-14

165.1 186.7 10.8

1.1

0.05493

DS005-15

285.1 249.1 15.4

0.9

0.05422

DS005-16

250.8 240.0 14.5

1.0

DS005-17

166.9 177.0 10.1

DS005-18

296.9 279.2 17.0

DS005-19

326.6 258.5 17.0

DS005-20

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0.00112

0.0436

0.00102

936

22

358

7

275

6

0.00791

0.04719

0.00106

409

23

310

6

297

7

0.00913

0.0464

0.00111

311

28

294

7

292

7

0.00948

0.04505

0.00106

708

23

335

7

284

7

0.00818

0.04541

0.00106

284

26

286

6

286

7

0.34742

0.00895

0.04638

0.0011

385

26

303

7

292

7

0.35271

0.00856

0.04676

0.00108

400

24

307

6

295

7

0.34827

0.00703

0.04738

0.00105

342

22

303

5

298

6

0.00112

0.40511

0.00683

0.04611

0.00101

733

22

345

5

291

6

0.0011

0.33829

0.00688

0.04759

0.00106

266

23

296

5

300

7

0.00121

0.3511

0.00734

0.04636

0.00104

409

22

306

6

292

6

0.00105

0.35501

0.00657

0.04749

0.00104

380

22

308

5

299

6

0.05372

0.00104

0.34751

0.00646

0.04692

0.00103

359

22

303

5

296

6

1.1

0.0547

0.00164

0.34645

0.00968

0.04594

0.00111

400

28

302

7

290

7

0.9

0.05542

0.00107

0.36003

0.00666

0.04712

0.00104

429

22

312

5

297

6

0.8

0.06894

0.00579

0.42907

0.0342

0.04514

0.00119

897

179

363

24

285

7

193.6 188.7 11.3

1.0

0.05588

0.00146

0.35977

0.0088

0.0467

0.0011

448

24

312

7

294

7

DS005-21

188.0 174.8 10.6

0.9

0.06376

0.00219

0.40498

0.01271

0.04607

0.00119

734

30

345

9

290

7

DS005-22

250.5 216.5 13.4

0.9

0.06372

0.00234

0.4012

0.01347

0.04567

0.00122

732

33

343

10

288

8

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AC

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0.00958

DS005-23

174.4 203.5 11.6

1.2

0.0564

0.00209

0.36349

0.01242

0.04675

0.00122

468

35

315

9

295

8

DS005-24

293.7 248.6 15.2

0.8

0.05628

0.00121

0.36144

0.00732

0.04658

0.00105

463

22

313

5

293

6

DS019-01

281.1 482.8 25.0

0.6

0.05309

0.00132

0.33309

0.00778

0.04549

0.00106

333

24

292

6

287

7

DS019-02

248.4 506.7 25.7

0.5

0.05076

0.00116

0.32112

0.00697

0.04587

0.00104

230

24

283

5

289

6

DS019-03

200.4 461.8 23.2

0.4

0.05232

0.00144

0.32958

0.00849

0.04568

0.00109

299

26

289

6

288

7

DS019-04

183.8 438.5 21.6

0.4

0.05102

0.00107

0.3192

0.0064

0.04537

0.00102

242

23

281

5

286

6

DS019-06

363.1 595.2 30.3

0.6

0.05374

0.0013

0.33189

0.00753

0.04478

0.00104

360

24

291

6

282

6

DS019-07

309.8 553.8 28.3

0.6

0.05489

0.00106

0.34238

0.0063

0.04523

0.00101

408

23

299

5

285

6

DS019-08

171.2 333.8 17.1

0.5

0.05254

0.00154

0.3327

0.00907

0.04592

0.00111

309

28

292

7

289

7

DS019-09

196.9 446.7 22.2

0.4

0.05332

0.00111

0.33306

0.00661

0.04529

0.00102

342

23

292

5

286

6

DS019-10

426.8 621.0 33.0

0.7

0.05744

0.00113

0.35925

0.00671

0.04536

0.00102

508

22

312

5

286

6

DS019-11

169.8 350.0 17.3

0.5

0.05274

0.00191

0.32637

0.01096

0.04488

0.00116

318

36

287

8

283

7

DS019-12

626.1 688.2 37.2

0.9

0.05927

0.00134

0.36015

0.00766

0.04407

0.00101

577

22

312

6

278

6

DS019-13

235.1 428.9 21.6

0.5

0.05348

0.00146

0.33133

0.00843

0.04493

0.00107

349

26

291

6

283

7

DS019-14

330.4 596.0 30.0

0.6

0.05885

0.00119

0.35902

0.00689

0.04424

0.001

562

22

311

5

279

6

DS019-15

228.7 277.3 15.1

0.8

0.05713

0.00268

0.35636

0.01527

0.04523

0.00133

497

47

309

11

285

8

DS019-16

348.1 417.9 22.3

0.8

0.05278

0.00147

0.33038

0.00859

0.04539

0.00108

319

26

290

7

286

7

DS019-17

345.2 355.1 19.9

1.0

0.06186

0.00232

0.37515

0.01283

0.04398

0.00119

669

34

323

9

277

7

DS019-18

1990

1453 87.3

1.4

0.06851

0.00096

0.42116

0.0058

0.04458

0.00096

884

23

357

4

281

6

DS019-19

389.4 606.6 31.2

0.6

0.05422

0.00133

0.33576

0.00776

0.04491

0.00104

380

24

294

6

283

6

DS019-20

576.9 608.4 33.5

0.9

0.05356

0.00175

0.34017

0.0103

0.04606

0.00115

353

31

297

8

290

7

DS019-22

219.1 395.5 19.8

0.6

0.05479

0.00212

0.33838

0.01207

0.04478

T

404

38

296

9

282

7

DS019-23

302.7 495.7 24.1

0.6

0.05314

0.00263

0.31977

0.01454

0.04363

0.0013

335

53

282

11

275

8

DS019-24

350.7 515.5 26.7

0.7

0.05196

0.00142

0.32927

0.00846

0.04596

0.00109

284

26

289

6

290

7

DS042-01

547.5 753.2 40.3

0.7

0.04631

0.00082

0.29464

DS042-02

186.0 266.6 14.1

0.7

0.05149

0.00144

0.32267

DS042-04

171.4 263.0 14.0

0.7

0.05196

0.00427

0.33218

DS042-05

347.0 407.5 22.6

0.9

0.05301

0.00116

0.33715

DS042-06

182.2 325.2 17.8

0.6

0.0479

0.00114

0.32203

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DS042-08

589.9 538.6 28.5

1.1

0.06172

0.0013

DS042-09

184.5 337.9 17.5

0.5

0.05918

0.00204

DS042-10

187.6 346.4 18.1

0.5

0.0509

0.0012

DS042-11

205.8 314.8 16.6

0.7

0.05197

DS042-12

193.1 296.4 15.3

0.7

0.04839

DS042-13

158.9 205.9 11.1

0.8

0.05388

DS042-14

455.7 691.1 35.9

0.7

0.04967

DS042-15

144.2 189.5 10.2

0.8

DS042-16

198.8 268.1 14.7

DS042-17

187.1 295.9 17.3

DS042-18

162.3 322.1 16.3

DS042-19

IP

0.0012

0.04615

0.00103

14

23

262

4

291

6

0.00835

0.04545

0.00111

263

27

284

6

287

7

0.02493

0.04636

0.00193

284

98

291

19

292

12

0.00689

0.04613

0.00106

329

23

295

5

291

7

0.00719

0.04875

0.00113

94

25

283

6

307

7

0.36215

0.00707

0.04255

0.00098

664

22

314

5

269

6

0.37046

0.01164

0.04539

0.00119

574

31

320

9

286

7

0.33045

0.00727

0.04708

0.00109

236

24

290

6

297

7

0.00133

0.33326

0.00795

0.04649

0.0011

284

25

292

6

293

7

0.00134

0.30282

0.00784

0.04537

0.00108

118

27

269

6

286

7

0.00174

0.33829

0.01004

0.04553

0.00115

366

30

296

8

287

7

0.00094

0.31441

0.00568

0.0459

0.00103

180

24

278

4

289

6

0.05648

0.0029

0.35587

0.0166

0.04569

0.00143

471

52

309

12

288

9

0.7

0.05329

0.00372

0.34483

0.02193

0.04692

0.00177

341

79

301

17

296

11

0.6

0.07295

0.00524

0.45591

0.03019

0.04533

0.00126

1012

150

381

21

286

8

0.5

0.05865

0.00185

0.36058

0.01047

0.04458

0.00112

554

28

313

8

281

7

304.2 356.7 18.8

0.9

0.05689

0.00166

0.35162

0.00945

0.04482

0.0011

487

26

306

7

283

7

DS042-20

290.7 394.8 21.3

0.7

0.052

0.0012

0.33686

0.0073

0.04697

0.00108

285

24

295

6

296

7

DS042-21

323.9 407.8 22.4

0.8

0.05169

0.00122

0.33244

0.00736

0.04664

0.00107

272

24

291

6

294

7

MA

D

TE

CE P

AC

NU

0.00498

DS042-22

451.2 414.7 22.9

1.1

0.05642

0.00178

0.34636

0.01008

0.04452

0.00112

469

29

302

8

281

7

DS042-23

256.9 377.0 19.7

0.7

0.05431

0.00224

0.33441

0.01267

0.04466

0.00123

384

41

293

10

282

8

DS042-24

112.4 179.3 9.5

0.6

0.05314

0.00192

0.34004

0.01132

0.0464

0.00121

335

35

297

9

292

7

DS070-01

180.0 175.6 10.1

1.0

0.05558

0.00249

0.34699

0.01428

0.04527

0.00128

436

45

302

11

285

8

DS070-02

345.6 575.6 30.3

0.6

0.04865

0.00116

0.3104

0.00696

0.04627

0.00105

131

24

274

5

292

6

DS070-03

770.9 473.9 29.7

1.6

0.05735

0.00232

0.34409

0.01272

0.04351

0.00119

505

39

300

10

275

7

DS070-04

264.3 425.8 22.0

0.6

0.05277

0.00187

0.33366

0.01092

0.04585

0.00118

319

34

292

8

289

7

DS070-05

231.1 366.6 19.7

0.6

0.0508

0.00137

0.32136

0.0081

0.04587

0.00107

232

26

283

6

289

7

DS070-06

277.6 603.5 30.2

0.5

0.05098

0.00208

0.30767

0.01157

0.04376

0.00118

240

42

272

9

276

7

DS070-07

358.0 267.4 16.5

1.3

0.05228

0.00252

0.31811

0.01412

0.04412

0.00128

298

52

280

11

278

8

DS070-08

754.6 1043 55.7

0.7

0.05323

0.00104

0.33308

0.00617

0.04538

0.001

339

22

292

5

286

6

DS070-09

196.8 341.7 18.1

0.6

0.05341

0.00153

0.33728

0.00896

0.0458

0.00109

346

27

295

7

289

7

DS070-10

326.4 463.9 24.8

0.7

0.05384

0.00187

0.33961

0.01086

0.04574

0.00117

364

33

297

8

288

7

DS070-11

472.7 572.2 31.1

0.8

0.05429

0.00196

0.3332

0.0111

0.0445

0.00115

383

35

292

8

281

7

DS070-12

306.4 405.2 21.4

0.8

0.05508

0.00156

0.33408

0.00877

0.04399

0.00105

415

26

293

7

278

6

DS070-13

635.2 392.3 26.2

1.6

0.04936

0.00162

0.30908

0.00942

0.04541

0.00112

165

32

273

7

286

7

DS070-14

312.3 400.7 22.3

0.8

0.05355

0.00136

0.3393

0.00804

0.04595

0.00106

352

24

297

6

290

7

DS070-15

300.9 689.4 34.0

0.4

0.05241

0.00182

0.31979

0.01026

0.04425

0.00112

303

34

282

8

279

7

DS070-16

228.3 185.4 9.9

1.2

0.06419

0.00274

0.38363

0.01482

0.04334

0.00123

748

39

330

11

274

8

DS070-17

100.3 239.6 12.3

0.4

0.05087

0.00232

0.31367

0.01317

0.04471

0.00127

235

49

277

10

282

8

DS070-18

193.8 544.9 26.5

0.4

0.04867

0.00197

0.30045

0.01125

0.04476

0.00119

132

43

267

9

282

7

DS070-19

118.8 213.5 11.5

0.6

0.05098

0.00196

0.32427

0.01152

0.04613

T

240

39

285

9

291

7

DS070-20

328.6 428.5 22.4

0.8

0.06346

0.00185

0.37557

0.01003

0.04292

0.00105

724

25

324

7

271

6

DS070-21

264.7 569.1 28.9

0.5

0.05419

0.00142

0.33355

0.00812

0.04463

0.00104

379

25

292

6

281

6

DS070-22

205.5 311.2 16.8

0.7

0.05421

0.00143

0.34065

DS070-23

312.3 349.2 19.3

0.9

0.05541

0.00159

0.33365

DS070-24

54.1

0.2

0.05316

0.00221

0.38561

DS079-01

104

143

7.9

0.7

0.05252

0.00249

0.34639

DS079-02

147

214

11.3

0.7

0.05764

0.00256

0.36126

SC R

ACCEPTED MANUSCRIPT

DS079-03

88

130

7.1

0.7

0.05843

0.00284

DS079-04

88.7

155.0 8.3

0.6

0.06268

0.00068

DS079-05

244

1070 168

0.2

0.07183

0.00292

DS079-06

89.8

156.9 8.6

0.6

0.07042

DS079-07

82.6

145.1 7.6

0.6

0.07964

DS079-08

119.0 168.7 9.0

0.7

0.06482

DS079-09

192.6 229.7 13.7

0.8

0.07078

DS079-10

215.2 749.4 124

0.3

DS079-12

132.9 186.1 11.1

DS079-13

206.6 214.3 11.8

DS079-14

68.2

137.9 7.2

DS079-15

IP

0.00121

0.04557

0.00106

380

25

298

6

287

7

0.00887

0.04366

0.00105

429

26

292

7

275

6

0.01475

0.0526

0.00144

336

42

331

11

330

9

0.01509

0.04784

0.00142

308

50

302

11

301

9

0.01459

0.04546

0.00134

516

42

313

11

287

8

0.38205

0.01678

0.04742

0.00147

546

47

329

12

299

9

1.3183

0.01496

0.15254

0.00331

697

27

854

7

915

19

0.48419

0.01754

0.04889

0.00143

981

34

401

12

308

9

0.0031

0.46711

0.01852

0.0481

0.00144

941

38

389

13

303

9

0.00703

0.51461

0.04242

0.04686

0.00148

1188

181

422

28

295

9

0.00079

1.41335

0.01748

0.1581

0.00344

768

26

895

7

946

19

0.00215

0.47623

0.01315

0.04878

0.00125

951

25

395

9

307

8

0.05499

0.0021

0.35769

0.01257

0.04716

0.00127

412

37

310

9

297

8

0.7

0.05766

0.00248

0.36184

0.01422

0.04549

0.00129

517

42

314

11

287

8

1.0

0.07596

0.00097

1.52368

0.01959

0.14542

0.00316

1094

24

940

8

875

18

0.5

0.07441

0.00291

0.50397

0.01767

0.0491

0.0014

1053

32

414

12

309

9

524.2 1346 219

0.4

0.06691

0.00084

1.41941

0.01804

0.15379

0.00333

835

25

897

8

922

19

DS079-16

128.3 166.9 9.1

0.8

0.07096

0.00625

0.47066

0.03907

0.0481

0.00141

956

186

392

27

303

9

DS079-17

316.8 591.1 98.1

0.5

0.07318

0.0074

0.46439

0.04453

0.04602

0.00148

1019

213

387

31

290

9

AC

MA

D

TE

CE P

285.8 15.7

NU

0.00841

DS079-18

86.6

126.8 7.2

0.7

0.05673

0.00313

0.35377

0.01782

0.04522

0.00146

481

58

308

13

285

9

DS079-19

502.1 976.2 166

0.5

0.06791

0.00269

0.42934

0.01543

0.04585

0.00128

866

35

363

11

289

8

DS079-20

145.0 177.2 10.9

0.8

0.05408

0.00397

0.35254

0.02372

0.04727

0.00179

374

85

307

18

298

11

DS079-21

223.6 251.9 16.2

0.9

0.05872

0.0031

0.3691

0.0178

0.04559

0.00142

557

54

319

13

287

9

DS079-22

173.1 201.9 10.8

0.9

0.07747

0.00314

0.49592

0.01807

0.04643

0.00132

1133

34

409

12

293

8

DS079-23

137.6 166.4 9.2

0.8

0.07741

0.0009

1.58359

0.01895

0.1484

0.00316

1132

24

964

7

892

18

DS079-24

149.0 195.5 11.0

0.8

0.08014

0.00487

0.48917

0.02643

0.04428

0.00162

1200

53

404

18

279

10

ACCEPTED MANUSCRIPT Table 2. Major (wt.%), and trace (ppm) elements for the volcanic rocks sample JS012 DS125 DS139 DS118 JS011 SiO2

###

###

JS008

DS107 JS002

from the Dashizhai Formation in eastern Inner Mongolia

JS013

DS085 JS001

JS003

JS004

DS055 JS005

DS029 JS009

DS065 DS032 JS010

50.90

51.07

51.50

51.70

52.22

52.94

52.95

53.27

53.30

53.55

54.05

55.74

56.36

57.31

58.81

59.68

###

###

DS038 DS028 68.70

###

1.68

1.91

1.58

1.76

1.40

2.00

1.38

1.10

1.48

1.32

1.32

1.05

1.38

1.07

1.17

1.50

1.34

0.88

0.88

0.93

0.53

0.53

Al2O3

16.29

17.03

16.99

16.20

16.81

17.66

18.51

18.14

17.09

18.69

16.50

18.05

18.36

16.56

16.06

14.96

18.96

17.11

14.72

15.02

15.63

14.88

TFe2O3

10.81

11.06

10.26

10.76

9.69

11.00

10.07

9.71

9.54

8.59

9.66

9.34

9.13

10.20

11.28

8.56

6.29

7.26

5.81

3.78

3.46

MnO

0.14

0.16

0.14

0.14

0.13

0.16

0.21

0.14

0.14

0.12

0.15

0.10

MgO

8.28

7.51

6.87

8.13

6.49

4.50

4.99

5.69

6.30

5.24

4.77

4.14

CaO

8.93

8.18

8.48

6.81

8.82

5.02

6.74

7.55

6.82

4.30

Na2O

2.85

2.51

2.82

3.27

3.00

5.03

3.43

3.10

3.67

5.20

K2O

0.28

0.51

0.55

0.62

0.93

0.33

1.11

0.80

0.81

0.58

P2O5

0.19

0.23

0.17

0.25

0.17

0.21

0.45

0.19

0.20

0.14

LOI

0.57

0.75

0.95

0.71

0.77

2.12

0.58

0.34

0.72

2.30

T

TiO2

IP

7.35

0.16

7.41

9.14

4.08

6.45

8.89

4.71

1.96

10.33

4.39

3.09

2.17

2.24

3.76

3.54

4.26

2.74

3.12

4.15

2.28

0.81

3.29

5.14

3.52

3.61

1.07

0.17

2.15

0.82

1.28

0.99

3.98

2.00

0.99

0.47

2.10

3.37

0.35

0.19

0.28

0.11

0.18

0.21

0.10

0.12

0.15

0.10

0.12

0.10

1.42

0.44

0.91

2.47

0.89

1.17

2.31

1.93

1.89

0.43

1.98

1.00

0.17

0.17

0.05

0.13

0.12

0.12

0.06

0.07

4.94

3.43

4.24

3.28

1.43

0.49

2.19

2.58

1.35

1.16

NU

SC R

0.17

99.70

99.70

99.71

99.71

99.70

99.74

99.70

99.70

99.71

99.75

99.72

99.70

99.71

99.77

99.71

99.73

99.78

99.77

99.75

99.70

99.95

99.71

Sc

29.4

28.5

31.3

29.1

27.7

30.2

24.6

20.2

23.1

22.7

29.4

19.5

23.3

24.3

22.4

28.5

21.3

15.5

19.2

16.4

10.6

9.07

V

223

232

224

221

218

237

206

Cr

324

209

189

314

200

153

103

Co

42.4

41.6

38.6

41.9

36.8

34.0

29.7

Ni

142

122

102

140

99.4

100

67.8

Cu

35.1

31.4

36.5

59.3

26.6

61.3

Zn

87.1

95.6

91.9

91.9

74.6

142

Ga

18.8

19.5

19.7

18.5

18.0

Rb

4.97

9.63

15

10

19

Sr

551

590

Y

26.2

27.0

Nb

4.82

5.68

Ge

1.41

1.23

Cs

3.16

5.89

Ba

104.4

La

MA

Total

197

185

234

229

184

244

179

235

118

74.9

157

101

75.1

59.5

132

164

59.50

27

108

138

17.7

86.5

0.40

128

0.53

5.58

71.5

0.34

7.03

35.0

30.4

25.5

20.6

28.1

26.8

27.8

15.2

27.5

20.4

3.14

16.20

15.8

9.28

6.34

91.10

102

###

18.3

81.30

65.1

17.50

38.0

13.80

###

2.63

9.83

25.3

1.70

11.2

D

190

26.6

8.0

34.5

48.7

57.9

32.5

37.10

6.01

69.8

29.4

4.76

28.1

7.97

15.9

9.27

97.6

82.0

74.0

86.2

83.4

60.0

88.8

86.0

74.8

111

72.1

###

71.8

46.8

50.2

50.2

20.7

22.3

19.9

18.5

19.0

19.7

22.6

21.5

15.4

18.8

19.7

23.2

49.9

14.7

14.5

15.2

15.4

7.13

26

17

25

16

23

3.66

71

25

35

33

98

60

33

18

50

76

CE P

TE

35.7

501

597

252

1190

785

588

496

572

970

643

865

527

208

233

1563

638

337

483

335

26.8

26.5

20.5

23.6

27.4

12.5

20.1

16.2

21.5

14.0

16.4

18.2

24.4

22.5

40.8

34.0

18.9

13.1

19.2

18.3

4.43

4.71

3.81

4.92

7.37

2.12

3.98

5.63

6.95

2.11

7.28

2.29

6.61

3.93

8.88

6.36

3.10

3.08

4.61

5.07

1.36

1.44

1.41

1.57

1.60

1.22

1.17

1.25

1.55

1.65

0.20

1.32

1.46

0.99

1.17

4.69

1.05

1.96

1.49

1.01

11.0

7.92

3.17

3.78

6.31

6.01

24.3

2.44

3.15

1.47

20.6

2.2

7.29

4.19

11.3

3.84

2.52

8.64

2.10

3.64

153.4

199.6

168.5

###

108.8

717.4

###

164

173.1

543.3

140.2

###

306.7

###

295.9

###

###

313.4

80.9

743.2

805.3

7.61

9.43

8.23

8.63

7.68

11.7

30.0

8.63

11.2

16.0

17.0

9.38

27.7

10.8

28.7

15.1

40.5

24.2

14.0

9.31

19.7

20.9

Ce

21.2

25.3

21.9

23.1

20.4

27.6

65.6

20.2

26.6

35.2

45.1

21.7

58.5

25.2

61.8

34.2

89.1

52.9

31.1

19.8

41.7

42.8

Pr

3.41

3.85

3.44

3.56

3.07

4.02

8.54

2.74

3.67

4.62

7.13

3.01

7.31

3.64

7.88

4.82

11.45

6.97

4.37

2.60

5.18

5.11

Nd

16.7

18.8

16.9

17.5

14.6

18.3

34.7

12.1

15.9

18.6

31.7

13.9

28.4

16.2

30.9

21.3

47.5

29.1

18.1

11.0

20.1

19.1

Sm

4.35

4.65

4.48

4.44

3.74

4.19

6.64

2.66

3.58

3.66

6.58

3.08

4.75

3.66

5.79

4.83

9.15

6.24

3.85

2.34

3.93

3.64

Eu

1.52

1.71

1.58

1.63

1.35

1.67

1.95

0.99

1.38

1.29

1.87

1.12

1.83

1.15

2.30

1.36

2.43

1.56

1.12

0.95

1.04

0.99

Gd

4.29

4.6

4.48

4.40

3.63

3.98

5.70

2.35

3.39

3.15

5.06

2.75

3.80

3.27

4.89

4.13

7.93

5.7

3.31

2.18

3.38

3.01

Tb

0.76

0.82

0.79

0.77

0.66

0.68

0.90

0.37

0.61

0.50

0.78

0.42

0.53

0.56

0.81

0.69

1.29

0.9

0.54

0.38

0.53

0.52

Dy

4.60

4.93

4.73

4.66

3.78

4.16

4.97

2.16

3.44

2.84

4.07

2.43

2.85

3.29

4.44

4.09

7.36

5.70

3.15

2.29

3.26

3.05

Ho

0.93

0.97

0.96

0.94

0.76

0.85

0.98

0.42

0.70

0.57

0.78

0.46

0.57

0.68

0.85

0.83

1.50

1.17

0.63

0.47

0.67

0.63

Er

2.61

2.72

2.66

2.70

2.18

2.45

2.80

1.22

2.07

1.66

2.21

1.36

1.66

1.92

2.28

2.46

4.36

3.47

1.87

1.39

1.99

1.96

Tm

0.37

0.39

0.38

0.37

0.30

0.35

0.40

0.18

0.30

0.25

0.31

0.18

0.25

0.28

0.32

0.37

0.64

0.51

0.27

0.21

0.30

0.29

Yb

2.35

2.49

2.50

2.50

1.97

2.27

2.60

1.15

1.97

1.72

2.07

1.22

1.77

1.78

2.14

2.47

4.27

3.31

1.85

1.48

2.10

2.09

Lu

0.37

0.39

0.38

0.37

0.30

0.35

0.41

0.17

0.31

0.27

0.32

0.19

0.28

0.28

0.33

0.38

0.67

0.54

0.29

0.22

0.34

0.35

AC

491

ACCEPTED MANUSCRIPT 0.32

0.40

0.30

0.33

0.28

0.35

0.47

0.14

0.27

0.37

0.45

0.14

0.47

0.15

0.40

0.27

0.65

0.46

0.21

0.21

0.38

0.42

Pb

3.62

4.3

4.2

3.52

4.59

13.0

11.0

5.4

7.19

5.44

8.92

7.74

14.80

10.7

12.8

7.87

12.50

###

10.6

7.21

13.7

13.6

Th

0.45

0.64

0.57

0.63

0.63

0.49

2.94

1.26

1.48

2.53

3.43

1.30

2.58

2.21

2.33

3.43

5.77

7.38

3.25

1.65

6.28

7.22

U

0.14

0.18

0.16

0.17

0.18

0.13

0.83

0.38

0.45

0.73

1.20

0.48

0.62

0.67

0.72

1.05

1.91

2.21

0.97

0.48

1.57

1.98

Zr

164

184

153

170

139

175

247

85.2

152

192

242.5

83.7

234

80.1

222

132

277

227

114

132

130

152

Hf

3.47

3.81

3.28

3.55

3.15

3.49

5.22

2.00

3.29

4.11

6.15

1.95

5.00

2.12

3.39

6.49

5.56

2.76

2.71

3.44

4.00

T

Ta

IP

4.42

sample DS111 DS079 DS134 DS133 DS017 DS050 DS057 DS115 DS021 DS039 DS022 DS042 DS069 DS054 DS019 DS044 DS043 DS040 DS046 DS031 DS052 74.36

75.51

76.34

76.60

76.86

76.94

77.47

77.80

77.84

78.24

TiO2

0.29

0.25

0.06

0.06

0.27

0.13

0.14

0.13

0.13

0.09

Al2O3

13.82

13.61

13.95

13.84

13.96

12.84

12.61

12.77

12.38

12.35

TFe2O3

1.52

1.47

0.46

0.19

1.29

0.92

0.91

0.47

0.61

0.53

MnO

0.02

0.02

0.02

0.01

0.02

0.03

0.03

0.00

0.01

0.03

MgO

0.39

0.05

0.22

0.16

0.62

0.20

0.34

0.07

0.17

0.12

CaO

0.33

0.48

0.24

0.20

0.04

0.55

0.37

0.08

0.11

Na2O

3.64

4.32

4.00

4.52

0.10

3.27

2.61

3.25

2.48

K2O

3.96

3.25

3.67

3.58

4.51

4.10

4.22

P2O5

0.07

0.07

0.07

0.07

0.07

0.06

0.07

LOI

1.30

0.67

0.67

0.44

2.21

0.66

0.96

Total

99.70

99.70

99.70

###

99.85

99.70

99.71

Sc

2.51

7.07

2.02

1.99

4.13

2.23

V

24.9

7.20

5.96

7.45

25.7

6.71

Cr

0.10

0.08

0.22

0.50

0.56

Co

2.69

0.45

0.32

0.42

0.57

Ni

2.85

0.19

Cu

2.29

2.85

Zn

28.5

39.3

Ga

17.9

10.9

Rb

107

62.4

Sr

257

Y

79.12

79.70

80.12

80.18

SC R

SiO2

###

###

83.74

84.65

85.49

86.55

###

0.10

0.09

0.14

0.14

0.08

0.08

0.11

0.06

0.13

0.07

11.93

11.19

11.47

11.83

11.38

12.04

9.42

8.96

9.64

7.53

7.32

0.21

0.89

0.43

0.76

0.42

0.28

0.29

0.19

0.14

0.58

0.38

0.01

0.03

0.02

0.01

0.01

0.02

0.02

0.02

0.02

0.01

0.02

0.20

0.09

0.18

0.29

0.15

0.17

0.07

0.07

0.16

0.22

0.16

0.78

0.08

1.38

0.09

0.32

0.08

0.03

0.08

0.28

0.03

0.09

0.03

2.86

1.76

2.22

1.83

3.34

2.18

0.10

2.13

2.90

0.10

1.03

0.10

MA

NU

0.11

5.10

4.04

5.56

3.38

4.27

1.74

3.71

4.95

3.13

1.84

2.88

2.69

2.21

0.07

0.06

0.06

0.06

0.06

0.07

0.08

0.06

0.07

0.06

0.07

0.06

0.07

0.07

0.83

0.84

0.59

0.68

0.70

1.09

1.02

0.91

1.35

0.67

0.60

1.35

0.79

1.15

99.70

99.71

99.71

99.72

99.73

99.67

99.71

99.74

99.79

99.70

###

###

99.70

###

D

4.22

1.09

2.76

1.85

2.33

1.83

1.84

2.34

2.65

2.07

1.43

1.11

1.46

1.25

2.13

9.36

15.9

8.39

5.27

6.19

9.98

9.89

7.67

8.98

3.68

9.02

6.80

1.41

8.09

22.8

0.26

0.80

0.16

833

8.12

0.22

0.24

0.76

0.25

0.86

0.65

0.95

0.41

0.48

0.07

0.07

0.59

0.63

0.62

0.20

0.21

0.21

0.42

0.35

0.19

0.43

0.08

0.49

0.21

0.00

0.03

0.58

CE P

TE

1.85

0.13

0.76

0.56

0.55

0.01

1.42

0.62

5.29

0.99

0.02

0.91

2.41

0.41

0.49

0.20

0.92

0.22

0.87

6.81

5.52

5.78

3.10

1.94

1.75

1.67

2.27

0.99

1.05

1.64

2.85

2.43

1.16

1.61

2.20

0.78

0.88

1.58

16.7

14.6

22.8

24.3

26.4

15.5

18.3

12.8

12.4

11.9

13.0

12.8

14.0

23.1

10.8

29.1

5.49

7.65

14.2

15.8

16.0

16.9

10.4

12.3

15.1

10.2

8.79

10.5

9.33

8.66

9.42

10.5

12.9

5.94

5.93

11.5

7.49

7.64

79.4

75.0

148.7

99.4

117

127

130

81.7

148

84.3

123

55.2

110

152

79.1

40.4

110

81.7

69.0

213

72.5

67.6

22.4

126

117

101.8

71.4

222

93.6

362

58.8

55.0

86.3

26.6

68.2

99.2

2.7

33.1

4.9

6.63

20.8

11.8

14.3

15.8

11.2

12.1

3.17

14.6

13.6

13.1

8.89

14.0

7.18

14.4

15.4

5.41

6.46

11.4

7.76

8.26

Nb

4.46

10.0

10.3

11.0

7.15

5.24

5.37

3.01

6.99

5.84

5.53

3.70

6.16

4.16

6.62

6.30

3.23

3.51

5.31

3.45

3.00

Ge

1.03

0.93

1.33

1.60

1.85

0.87

1.18

0.85

0.76

0.68

0.80

0.95

0.75

0.64

0.87

0.68

0.64

0.72

0.81

0.73

0.78

Cs

4.24

3.03

4.05

4.52

25.2

2.94

3.83

3.92

6.25

1.87

6.32

1.77

4.86

4.44

3.85

6.83

2.19

0.95

4.84

2.94

3.65

Ba

513

1514

390

358

990

830

784

288

936

865

989

666

634

424

755

550

743

679

98.2

419

273

La

15.0

25.7

14.9

16.2

31.7

20.8

27.1

13.1

15.4

27.0

16.9

26.7

23.2

9.20

30.1

13.7

13.5

12.9

8.44

9.20

14.8

Ce

30.4

53.4

32.5

34.5

64.3

38.9

48.9

22.8

31.9

51.8

34.6

42.5

45.7

17.7

56.5

28.8

26.1

23.4

18.2

19.5

27.7

Pr

3.44

6.67

3.99

4.35

7.41

4.09

5.08

2.32

3.80

5.54

3.97

4.06

4.93

2.00

6.00

3.41

2.89

2.57

2.26

2.30

2.98

Nd

12.0

25.3

14.0

15.4

25.9

13.3

16.2

7.51

13.0

18.5

13.6

12.7

16.9

6.74

20.1

11.7

9.78

8.56

7.86

8.36

10.0

Sm

1.97

4.70

2.77

3.06

4.09

2.06

2.35

1.16

2.36

2.88

2.34

1.72

2.69

1.18

3.17

2.44

1.49

1.33

1.73

1.50

1.67

Eu

0.43

1.16

0.45

0.51

0.65

0.36

0.41

0.24

0.33

0.41

0.29

0.31

0.26

0.21

0.36

0.21

0.24

0.28

0.13

0.26

0.26

Gd

1.52

3.77

2.03

2.43

2.60

1.82

1.97

0.87

2.03

2.37

1.93

1.46

2.04

1.02

2.49

2.06

1.10

1.12

1.59

1.22

1.34

Tb

0.21

0.64

0.35

0.44

0.42

0.29

0.32

0.11

0.36

0.36

0.32

0.21

0.35

0.17

0.39

0.39

0.16

0.18

0.29

0.20

0.23

Dy

1.12

3.75

2.06

2.47

2.64

1.79

1.93

0.52

2.34

2.07

1.97

1.22

2.20

1.11

2.30

2.44

0.95

1.04

1.84

1.31

1.36

AC

3.53

ACCEPTED MANUSCRIPT 0.20

0.80

0.40

0.49

0.54

0.39

0.40

0.10

0.51

0.44

0.45

0.28

0.48

0.26

0.48

0.54

0.20

0.22

0.39

0.29

0.28

Er

0.62

2.44

1.21

1.42

1.68

1.28

1.33

0.33

1.68

1.38

1.39

0.92

1.52

0.86

1.51

1.67

0.67

0.75

1.20

0.94

0.83

Tm

0.10

0.39

0.19

0.22

0.27

0.22

0.22

0.05

0.28

0.23

0.22

0.15

0.26

0.15

0.25

0.28

0.12

0.12

0.19

0.16

0.13

Yb

0.70

2.67

1.26

1.48

1.82

1.60

1.65

0.43

2.06

1.68

1.74

1.19

1.87

1.16

1.86

1.97

0.92

0.88

1.37

1.14

0.96

Lu

0.12

0.44

0.18

0.21

0.29

0.27

0.27

0.08

0.35

0.27

0.29

0.20

0.30

0.20

0.30

0.31

0.16

0.15

0.21

0.18

0.14

Ta

0.54

0.77

0.93

1.01

0.61

0.58

0.58

0.34

0.79

0.62

0.62

0.40

0.66

0.46

0.68

0.37

0.37

0.59

0.34

0.33

Pb

9.01

16.7

3.88

6.93

7.85

22.7

22.6

8.06

10.0

11.7

8.53

12.4

5.87

9.06

9.83

13.2

12.6

13.9

9.87

4.15

6.93

Th

12.9

8.67

8.89

10.9

14.1

11.2

10.5

12.8

11.2

10.5

9.03

8.12

11.9

8.22

10.1

8.22

6.23

6.11

6.72

5.79

5.21

U

2.86

2.20

1.26

1.60

3.84

2.57

2.62

1.86

2.94

2.38

Zr

127

266

64.8

71.0

156

94.8

97.9

75.1

92.7

75.0

Hf

3.72

6.78

2.67

2.94

4.40

2.97

2.98

2.69

3.08

2.45

SC R

IP

0.68

2.80

1.96

3.20

1.96

2.74

2.84

1.15

1.81

2.44

1.41

2.70

74.1

76.0

70.2

65.8

81.2

61.1

67.6

63.7

49.8

67.6

35.3

2.52

2.17

2.32

2.13

2.51

2.23

2.06

1.86

1.73

1.91

1.13

NU MA D TE CE P AC

T

Ho

ACCEPTED MANUSCRIPT Table 3. In situ zircon Hf isotopic data for the volcanic rocks from the Dashizhai Formation in eastern Inner Mongolia 176

Lu/177Hf(corr)

176

Hf/177Hf

Hf(0) Hf(t)  TDM1(Hf)

DS005-01

280

0.040

0.0018

0.282917 0.000024

5.14

11.0 0.85

485

734

-0.95

DS005-02

280

0.056

0.0025

0.282914 0.000024

5.02

10.7 0.84

499

755

-0.93

DS005-03

280

0.046

0.0020

0.282918 0.000033

5.15

10.9 1.18

487

736

-0.94

DS005-04

280

0.053

0.0022

0.282864 0.000022

T

Yb/177Hf(corr)

t (Ma)

9.01 0.79

568

910

-0.93

DS005-05

280

0.025

0.0011

0.282842 0.000022

2.47

8.41 0.79

584

964

-0.97

DS005-06

280

0.044

0.0019

0.282936 0.000028

5.81

11.6 0.99

459

675

-0.94

DS005-07

280

0.050

0.0022

0.282859 0.000026

3.09

8.83 0.91

576

927

-0.93

DS005-08

280

0.041

0.0018

0.282881 0.000023

3.87

9.69 0.81

537

849

-0.95

DS005-09

280

0.046

0.0020

0.282830 0.000027

2.05

7.83 0.96

616

1018

-0.94

DS005-10

280

0.020

0.0009

0.282840 0.000027

2.39

8.38 0.95

584

968

-0.97

DS005-11

280

0.029

0.0013

SC R

176

Sample

0.282917 0.000024

5.14

11.1 0.85

478

725

-0.96

DS005-12

280

0.028

0.0012

0.282839 0.000025

2.38

8.31 0.89

589

974

-0.96

DS005-13

280

0.031

0.0014

0.282824 0.000026

1.85

7.75 0.92

613

1024

-0.96

DS005-14

280

0.037

0.0018

0.282943 0.000034

6.03

11.9 1.22

448

652

-0.95

DS005-15

280

0.064

0.0028

0.282895 0.000030

4.36

10.0 1.05

531

821

-0.92

DS005-16

280

0.052

0.0023

0.282870 0.000030

3.46

9.18 1.05

562

895

-0.93

DS005-17

280

0.026

0.0012

0.282861 0.000022

3.15

9.09 0.78

557

903

-0.97

DS005-18

280

0.048

0.0021

0.282947 0.000033

6.18

12.0 1.18

445

643

-0.94

DS005-19

280

0.065

0.0028

0.282954 0.000025

6.44

12.1 0.88

443

632

-0.92

DS005-20

280

0.049

0.0021

0.282906 0.000028

4.74

10.5 1.00

506

776

-0.94

DS005-21

280

0.040

0.0017

0.282961 0.000027

6.70

12.5 0.95

421

591

-0.95

DS005-22

280

0.043

0.0019

0.282924 0.000028

5.39

11.2 0.99

476

712

-0.94

DS005-23

280

0.049

0.0021

0.282913 0.000025

4.98

10.7 0.90

496

753

-0.94

DS005-24

280

0.063

0.0027

0.282907 0.000029

4.77

10.4 1.03

513

782

-0.92

DS019-01

280

0.057

0.0022

0.282841

0.000020

2.44

8.19 0.72

602

985

-0.93

3.27

IP

NU

MA D

TE

CE P

AC

2m

TDM2(Hf) fLu/Hf

DS019-02

280

0.041

0.0018

0.282835

0.000013

2.22

8.05 0.48

604

998

-0.95

DS019-03

280

0.033

0.0014

0.282840

0.000016

2.40

8.29 0.56

591

976

-0.96

DS019-04

280

0.039

0.0017

0.282849

0.000014

2.73

8.56 0.48

583

952

-0.95

DS019-06

280

0.050

0.0021

0.282832

0.000015

2.11

7.87 0.53

615

1014

-0.94

DS019-07

280

0.047

0.0021

0.282821

0.000015

1.72

7.49 0.53

630

1049

-0.94

DS019-08

280

0.051

0.0022

0.282847

0.000019

2.64

8.38 0.67

594

967

-0.93

DS019-09

280

0.043

0.0019

0.282828

0.000018

1.97

7.78 0.64

616

1022

-0.94

DS019-10

280

0.055

0.0024

0.282874

0.000019

3.59

9.31 0.69

557

883

-0.93

DS019-11

280

0.043

0.0019

0.282850

0.000015

2.77

8.56 0.55

584

951

-0.94

DS019-12

280

0.050

0.0022

0.282895

0.000017

4.35

10.1 0.60

523

812

-0.93

DS019-13

280

0.041

0.0018

0.282825

0.000016

1.86

7.68 0.56

619

1031

-0.95

DS019-14

280

0.055

0.0024

0.282835

0.000015

2.22

7.94 0.53

614

1008

-0.93

DS019-15

280

0.047

0.0021

0.282834

0.000017

2.20

7.97 0.60

610

1005

-0.94

DS019-16

280

0.064

0.0028

0.282812

0.000020

1.41

7.05 0.72

655

1088

-0.92

DS019-17

280

0.048

0.0021

0.282844

0.000018

2.54

8.30 0.65

597

975

-0.94

DS019-18

280

0.192

0.0076

0.282948

0.000026

6.23

11.0 0.91

523

732

-0.77

ACCEPTED MANUSCRIPT 280

0.076

0.0033

0.282901

0.000022

4.55

10.1 0.77

531

812

-0.90

DS019-20

280

0.064

0.0027

0.282838

0.000019

2.32

7.97 0.66

616

1004

-0.92

DS019-22

280

0.057

0.0022

0.282863

0.000023

3.20

8.94 0.81

571

917

-0.93

DS019-23

280

0.049

0.0021

0.282846

0.000018

2.62

8.38 0.64

594

968

-0.94

DS019-24

280

0.062

0.0026

0.282871

0.000020

3.49

9.16 0.70

565

897

-0.92

DS042-01

280

0.048

0.0021

0.282858

0.000016

DS042-02

280

0.033

0.0014

0.282806

0.000016

DS042-04

280

0.048

0.0022

0.282835

0.000036

DS042-05

280

0.062

0.0027

0.282832

DS042-06

280

0.030

0.0013

DS042-08

280

0.059

DS042-09

280

DS042-10

8.80 0.58

576

930

-0.94

1.19

IP

7.08 0.58

640

1085

-0.96

2.23

7.98 1.28

611

1004

-0.93

0.000019

2.13

7.78 0.66

624

1022

-0.92

0.282817

0.000016

1.58

7.48 0.58

623

1049

-0.96

0.0026

0.282858

0.000020

3.04

8.71 0.70

584

938

-0.92

0.036

0.0016

0.282820

0.000016

1.68

7.53 0.56

624

1044

-0.95

280

0.033

0.0015

0.282833

0.000016

2.14

8.01 0.58

603

1001

-0.95

DS042-11

280

0.032

0.0014

0.282823

0.000016

1.82

7.70 0.56

615

1029

-0.96

DS042-12

280

0.040

0.0018

0.282856

0.000018

2.97

8.80 0.64

574

930

-0.95

DS042-13

280

0.040

0.0017

0.282858

0.000020

3.03

8.86 0.69

571

924

-0.95

DS042-14

280

0.058

0.0026

0.282840

0.000019

2.42

8.09 0.66

609

993

-0.92

DS042-16

280

0.039

0.0018

0.282873

0.000020

3.57

9.39 0.72

549

876

-0.95

DS042-17

280

0.031

0.0014

0.282849

0.000016

2.71

8.60 0.56

579

948

-0.96

DS042-18

280

0.035

0.0016

0.282818

0.000017

1.63

7.49 0.59

625

1048

-0.95

DS042-19

280

0.049

0.0022

0.282902

0.000020

4.59

10.3 0.72

514

791

-0.93

DS042-20

280

0.053

0.0024

0.282823

0.000021

1.82

7.53 0.75

631

1044

-0.93

DS042-21

280

0.054

0.0024

0.282842

0.000018

2.46

8.16 0.63

606

988

-0.93

DS042-22

280

0.046

0.0021

0.282881

0.000018

3.84

9.61 0.62

542

856

-0.94

DS042-23

280

0.053

0.0024

0.282858

0.000020

3.04

8.76 0.72

580

933

-0.93

DS042-24

280

0.031

0.0014

0.282819

0.000016

1.65

7.55 0.56

621

1043

-0.96

DS070-01

280

0.076

0.0033

0.282905

0.000037

4.70

10.2 1.30

525

799

-0.90

MA D

TE

CE P

AC

SC R

3.04

NU

T

DS019-19

DS070-02

280

0.065

0.0029

0.282845

0.000023

2.57

8.18 0.83

609

986

-0.91

DS070-03

280

0.093

0.0038

0.282950

0.000031

6.28

11.7 1.10

464

665

-0.88

DS070-04

280

0.057

0.0025

0.282908

0.000024

4.81

10.5 0.86

508

775

-0.92

DS070-05

280

0.040

0.0019

0.282869

0.000023

3.42

9.22 0.81

557

892

-0.94

DS070-06

280

0.052

0.0024

0.282837

0.000022

2.31

8.02 0.77

611

1000

-0.93

DS070-07

280

0.070

0.0030

0.282946

0.000027

6.14

11.7 0.96

459

663

-0.91

DS070-08

280

0.082

0.0036

0.282899

0.000028

4.47

9.96 1.01

539

824

-0.89

DS070-09

280

0.037

0.0018

0.282868

0.000021

3.38

9.21 0.76

557

893

-0.95

DS070-10

280

0.041

0.0018

0.282890

0.000025

4.16

9.98 0.88

526

823

-0.95

DS070-11

280

0.052

0.0023

0.282932

0.000019

5.67

11.4 0.68

470

694

-0.93

DS070-12

280

0.065

0.0030

0.282921

0.000023

5.27

10.9 0.80

495

741

-0.91

DS070-13

280

0.105

0.0044

0.282883

0.000028

3.91

9.25 0.99

576

889

-0.87

DS070-14

280

0.061

0.0028

0.282907

0.000028

4.78

10.4 0.98

514

783

-0.92

DS070-15

280

0.056

0.0026

0.282896

0.000022

4.38

10.1 0.79

528

816

-0.92

DS070-16

280

0.055

0.0025

0.282832

0.000030

2.11

7.81 1.05

621

1019

-0.93

DS070-17

280

0.036

0.0016

0.282878

0.000026

3.74

9.59 0.94

540

858

-0.95

ACCEPTED MANUSCRIPT 280

0.051

0.0024

0.282887

0.000019

4.07

9.79 0.69

537

840

-0.93

DS070-19

280

0.028

0.0013

0.282890

0.000026

4.18

10.1 0.91

518

813

-0.96

DS070-20

280

0.040

0.0018

0.282897

0.000022

4.43

10.2 0.78

515

799

-0.95

DS070-21

280

0.052

0.0024

0.282913

0.000020

4.98

10.7 0.72

499

758

-0.93

DS070-22

280

0.076

0.0033

0.282832

0.000026

2.12

7.66 0.93

635

1033

-0.90

DS070-23

280

0.074

0.0031

0.282981

0.000024

DS070-24

330

0.029

0.0013

0.282593

0.000023

DS079-01

280

0.065

0.0026

0.282739

0.000029

DS079-02

280

0.052

0.0021

0.282769

DS079-03

280

0.037

0.0015

DS079-04

909

0.040

DS079-05

280

DS079-06

13.0 0.85

407

551

-0.91

-6.33

IP

-0.4 0.83

941

1762

-0.96

-1.15

4.52 1.03

759

1317

-0.92

0.000027

-0.10

5.66 0.96

706

1214

-0.94

0.282802

0.000030

1.08

6.95 1.05

647

1097

-0.95

0.0016

0.282135

0.000022

-22.5

-17

0.77

1602

3217

-0.95

0.037

0.0015

0.282889

0.000031

4.14

10.0 1.11

522

820

-0.95

280

0.029

0.0012

0.282870

0.000029

3.47

9.40 1.03

545

875

-0.96

DS079-07

280

0.055

0.0022

0.282741

0.000030

-1.09

4.65 1.04

749

1305

-0.93

DS079-08

909

0.031

0.0013

0.282163

0.000022

-21.5

-16

0.78

1548

3123

-0.96

DS079-09

280

0.058

0.0024

0.282714

0.000023

-2.07

3.65 0.81

792

1396

-0.93

DS079-10

280

0.031

0.0013

0.282730

0.000020

-1.47

4.43 0.70

747

1325

-0.96

DS079-12

280

0.041

0.0017

0.282774

0.000023

0.06

5.90 0.80

691

1192

-0.95

DS079-13

909

0.030

0.0012

0.282144

0.000020

-22.2

-16

0.70

1572

3182

-0.96

DS079-14

280

0.055

0.0023

0.282837

0.000029

2.30

8.02 1.04

610

1000

-0.93

DS079-15

909

0.059

0.0023

0.282155

0.000025

-21.8

-16

0.87

1602

3164

-0.93

DS079-16

280

0.042

0.0017

0.282803

0.000023

1.11

6.94 0.82

649

1098

-0.95

DS079-17

280

0.079

0.0031

0.282791

0.000030

0.66

6.24 1.06

693

1162

-0.91

DS079-18

280

0.060

0.0024

0.282775

0.000035

0.12

5.82 1.24

703

1199

-0.93

DS079-19

280

0.070

0.0028

0.282784

0.000034

0.41

6.05 1.21

697

1178

-0.92

DS079-20

280

0.033

0.0014

0.282718

0.000025

-1.92

3.97 0.88

766

1367

-0.96

DS079-21

280

0.050

0.0021

0.282808

0.000034

1.27

7.04 1.19

648

1089

-0.94

MA D

TE

CE P

AC

SC R

7.39

NU

T

DS070-18

DS079-22

280

0.044

0.0018

0.282758

0.000033

-0.51

5.30 1.18

717

1246

-0.95

DS079-23

909

0.043

0.0018

0.282140

0.000029

-22.4

-17

1601

3205

-0.95

1.03

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

TE

D

MA

NU

SC R

Graphical abstract

ACCEPTED MANUSCRIPT Highlights 1. The volcanics along northwestern margin of Songnen terrane formed in 295–283

AC

CE P

TE

D

MA

NU

SC R

IP

T

Ma. 2. The volcanic rocks formed in an active continental margin setting. 3. The terminal collision did not occur before the early Permian.