Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China

Accepted Manuscript Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China

Wen-Sheng Li, Pei Ni, Jun-Yi Pan, Guo-Guang Wang, Li-Li Chen, Yu-Long Yang, Jun-Ying Ding PII: DOI: Reference:

S0375-6742(17)30462-4 doi:10.1016/j.gexplo.2017.11.013 GEXPLO 6041

To appear in:

Journal of Geochemical Exploration

Received date: Revised date: Accepted date:

28 June 2017 28 October 2017 21 November 2017

Please cite this article as: Wen-Sheng Li, Pei Ni, Jun-Yi Pan, Guo-Guang Wang, Li-Li Chen, Yu-Long Yang, Jun-Ying Ding , Fluid inclusion characteristics as an indicator for tungsten mineralization in the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Gexplo(2017), doi:10.1016/ j.gexplo.2017.11.013

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ACCEPTED MANUSCRIPT Title:

Fluid inclusion characteristics as an indicator for tungsten mineralization in

the Mesozoic Yaogangxian tungsten deposit, central Nanling district, South China

Authors: Wen-Sheng Li a, Pei Nia,* , Jun-Yi Pan a,*, Guo-Guang Wang a, Li-Li Chena, a

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Yu-Long Yang a，Jun-Ying Ding a State Key Laboratory for Mineral Deposits Research, Institute of Geo-Fluids, School of Earth Sciences and

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Engineering, Nanjing University, Nanjing 210023, China

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*Corresponding authors.

E-mail addresses: [email protected] (P. Ni), [email protected] (J. -Y. Pan)

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Tel.: +86 25 89680883; fax: +86 25 89682393.

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Abstract

The giant Yaogangxian tungsten deposit, situated in the central Nanling region of

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South China, is one of the largest tungsten deposits in China. It comprises both

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large-scale wolframite–quartz vein-type and scheelite–skarn mineralization. The

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wolframite–quartz vein-type mineralization can be divided into three successive

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hydrothermal vein-forming stages, based on mineral paragenesis and crosscutting relationships: stage 1 (early) wolframite–cassiterite–quartz veins, also termed

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“main-stage” veins, characterized by significant wolframite deposition; stage 2 sulfide–quartz veins, where abundant sulfide minerals were introduced during vein formation; and stage 3 fluorite–carbonate–quartz veins that resulted from the latest hydrothermal event and commonly crosscut earlier veins. Fluid inclusion petrographic, microthermometric and Raman spectroscopic analyses were carried out on wolframite, quartz and fluorite. Three types of fluid inclusions were recognized in wolframite, quartz

ACCEPTED MANUSCRIPT and fluorite: two-phase liquid-rich (type L), two-phase CO2-bearing (type CB), and CO2-rich fluid inclusions (type C). Secondary type L fluid inclusions were also recorded in wolframite. In main-stage veins, primary type L and CB inclusions occur in both

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wolframite and quartz crystals, whereas type C only occurs in quartz and coexists with

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type L. Type L and CB inclusions in wolframite exhibit homogenization temperatures of

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280 to 360 °C and 321 to 355 °C, with salinities of 2.2 to 7.6 and 2.8 to 3.6 wt. % NaCl

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equivalent (NaCl equiv.), respectively. Secondary type L inclusions in wolframite have homogenization temperatures of 204 to 256 °C, with salinities of 1.4 to 5.7 wt. % NaCl

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equiv.), which similar to type L inclusions in quartz coexisting with sulfides, indicating

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that the sulfide-forming fluid is preserved as secondary inclusions in wolframite.

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Coexisting type L and C inclusions in quartz display similar homogenization temperature ranges (244 to 317 °C) but contrasting salinity ranges of 4.2 to 7.3 and 0.2 to 2.8 wt. %

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NaCl equiv., respectively, suggesting fluid immiscibility during stage 1 quartz formation.

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In stage 2 veins, type L inclusions in quartz that coexists with sulfides have lower

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homogenization temperatures (219 to 276 °C) and salinities (2.1 to 5.7 wt. % NaCl equiv.). Type L inclusions in fluorite from stage 3 veins show the lowest homogenization temperatures (183 to 205 °C) and salinities (1.1 to 3.0 wt. % NaCl equiv.). The significantly higher homogenization temperatures of fluid inclusions in wolframite than in coexisting quartz, and their observed paragenesis, indicates that wolframite was precipitated earlier than most of the coexisting quartz. H–O isotopic data, the presence of primary CO2-bearing inclusions in wolframite, and the temperature vs. salinity trends of

ACCEPTED MANUSCRIPT fluid-inclusion data indicate that wolframite was most likely deposited during cooling from an initial CO2-bearing magmatic fluid; while subsequent fluid immiscibility and mixing resulted in massive quartz precipitation and sulfide mineralization. Combining the

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spatial distribution characteristics of vein mineralization, our study results provide new

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guide lines for mineral exploration. The veins containing fluid inclusions that are

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characterized by high homogenization temperatures and high salinities are dominated by

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magmatic water. Therefore in the areas where abundant sulfides and carbonates occur, the

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potential for tungsten-rich ore-veins is in the deeper part of the deposit.

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Key words: Wolframite; Quartz; Fluid inclusion; Yaogangxian; Central Nanling

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1. Introduction

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Wolframite–quartz vein-type tungsten deposits, generally related to granitic

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intrusions, play a significant role in tungsten production in China, and the world in general (Hsu, 1943; Kelly, 1979; Tonelli, 1982; Tan, 1985; RGNTD., 1985; Mao et al.,

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2007; Ni et al., 2015). The ores comprise mainly wolframite and quartz, with variable quantities

of

base-metal

sulfides

and

carbonates.

In

recent

years,

infrared

micro-thermometric studies of fluid inclusions in wolframite have provided information about ore-forming fluids in wolframite–quartz vein-type deposits (Campbell and Panter, 1990; Lueders, 1996; Bailly et al., 2002; Ni et al., 2006, 2015; Wei et al., 2012). The results indicate that only two-phase aqueous inclusions occur in wolframite, and that the

ACCEPTED MANUSCRIPT ore-forming fluid is a simple H2O–NaCl solution without detectable CO2 or CH4 component (Campbell and Robinson, 1987; Campbell and Panter, 1990; Lueders, 1996; Bailly et al., 2002; Ni et al., 2006, 2015). However, a large amount of CO2-rich fluid

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inclusions have been reported in the quartz coexisting with wolframite (Higgins, 1985;

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Noronha et al., 1992; Macey and Harris, 2006; Wang et al., 2012). Thus, it remains

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uncertain whether CO2-rich inclusions are present in wolframite but undiscovered.

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There are two opinions on the role of CO2 in tungsten mineralization. One is that CO2 is an essential component of the hydrothermal fluid of wolframite–quartz vein–type

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tungsten deposits (Macey and Harris, 2006; Wang et al., 2010; Naumov et al., 2011), as

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reflected by CO2-rich fluid inclusions commonly preserved in quartz (Higgins, 1980,

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1985; Giuliani, et al., 1988; Wang et al., 2010). According to this view, CO2 plays an important role in metal transport under high pressure (Higgins, 1980), and its loss from

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immiscibility, as indicated by the petrography and micro-thermometry of CO2-rich

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inclusions in associated quartz, leads to the precipitation of metals (Quilez et al., 1990;

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So and Yun, 1994; Wang et al., 2013b; Mohamed, 2013). The other view is that CO2 is unlikely to be responsible for tungsten mineralization, because there are no CO2-rich fluid inclusions in wolframite (Campbell and Panter, 1990; Lueders, 1996; Ni et al., 2015). It is therefore necessary to further elucidate the role of CO2 in the formation of wolframite–quartz vein–type tungsten deposits. China is the world’s largest producer of tungsten, accounting for 57% of the total known reserves worldwide (USGS, 2016). More than 60% of China’s tungsten resources

ACCEPTED MANUSCRIPT are in the Nanling region, South China (Tang et al., 2016). The tungsten deposits in Nanling region mainly include wolframite–quartz vein–type, skarn–type, greisen–type, and porphyry type (Tanelli, 1982; Lu, 1986). The wolframite–quartz vein–type tungsten

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deposits are predominant in geological exploration and mineral exploitation and most

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widely distributed in Nanling region (Xu et al., 1959; Tan, 1985; Chen et al., 2008). The

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geological setting and characteristics of the wolframite–quartz vein-type tungsten

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deposits in the central Nanling area have been relatively well studied and documented (Hsu., 1943; GDNU., 1981; Lu, 1986; Liu et al., 1993; Feng et al., 2011), with most

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research indicating that the ore-forming fluid was derived from multi-stage magmatic

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activity, related to particularly during the Yanshanian (Late Mesozonic) period (Hsu.,

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1943; Lu, 1986; Hu et al., 2012; Li et al., 2011). The Yaogangxian deposit is one of the largest deposits in the Nangling region (Hu

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and Zhou, 2012), and comprises both large-scale wolframite–quartz vein-type

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mineralization (>200,000 tonne WO3) and scheelite–skarn mineralization (310,000 tonne

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WO3) (Zhu et al., 2015). In recent decades, numerous studies have examined the formation of the Yaogangxian deposit, focusing on geological features (Hsu, 1957; Chen, 1981; Guo et al., 2010), the age of mineralization (Peng et al., 2006; Wang et al., 2009), and the ages of different stages of the Yaogangxian composite granitic pluton (Dong et al., 2014). Although features of fluid inclusions from different minerals at Yaogangxian were also reported by several authors in recent years (i.e., Wang et al., 2007; Cao et al., 2009; Dong et al., 2011), the genetic interpretations of the sources of ore-forming fluids and

ACCEPTED MANUSCRIPT mechanisms of ore deposition are still poorly constrained. The preliminary description of fluid inclusion characteristics in quartz from the Yaogangxian deposit were first reported by Wang et al. (2007), in which fluid inclusion types and their microthermometric

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properties were roughly constrained. Subsequently, Cao et al. (2009) and Dong et al.

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(2011) carried out similar studies on fluid inclusions microthermometry from both

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wolframite and their coexisting quartz. Both studies concluded that the fluid inclusion in

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wolframite exhibits higher homogenization temperature and salinity than those hosted by coexisting quartz. Nevertheless, all of these studies were built on poorly described

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samples and field geology, in which the paragenetic sequence of ore veins has never been

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constrained. As for fluid inclusion, the significance of CO2 in the ore-forming fluids at

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Yaogangxian has been largely ignored and none of these studies have included discussion on temporal or spatial evolution of ore-forming fluids which may provide valuable

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indication on mineral exploration.

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The present study examines fluid inclusions in wolframite, quartz, and fluorite from

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temporally defined successive hydrothermal veins of the Yaogangxian deposit based on a systematic field geology. Through petrography and detailed microthermometry, combined with stable-isotope analyses, the study aims to (1) define the roles of CO2-bearing fluids in wolframite formation and the source of ore-forming fluids, (2) delineate fluid processes in the precipitation of wolframite, and (3) explore the implications of studying fluid inclusions from the different ore-forming stages for exploration of vein type tungsten deposits.

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2. Geological setting

The central Nanling region is located in the south of China, mainly within the southern Jiangxi, northern Guangdong, and southeastern Hunan regions (Fig. 1B). It is

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part of the South China Block (Shu et al., 2006), which was formed by collision between

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the Yangtze Block to the northwest and the Cathaysian Block to the southeast (Fig.1A), along the Shi–Hang tectonic zone during the Neoproterozoic (Zhou et al., 2002; Zheng et

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al., 2008; Zhao et al., 2011).

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Strata exposed in the central Nanling region are mainly metamorphic basement and

argillaceous

sandstones

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sedimentary cover rocks. The basement comprises Neoproterozoic metamorphic interbedded

with

volcanic

rocks

and

Sinian–Silurian

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metamorphic sedimentary flysch (slate), siliceous rocks, pyroclastic rocks, and

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intermediate–basic volcanic rocks. These are overlain by Late Devonian to Early Triassic

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mudstone, sandstone, and neritic facies carbonate rocks that formed in the littoral and neritic marine environments. Triassic–Paleogene volcanoclastic rocks, clastic rocks, and

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volcanic rocks and terrigenous red-bed sandstones occur in faulted basins (Fig.1B) (Shu et al., 2006; Mao et al., 2007; Wang et al., 2012). Concentrations of tungsten in the widespread Sinian–Ordovician and Devonian strata are several times higher than equivalents elsewhere, and are generally considered be the W source for the Yanshanian W-bearing granite and the related tungsten deposits (Li, 1991; Wei et al., 2006). The central Nanling region experienced multiple tectonic events, resulting in the

ACCEPTED MANUSCRIPT formation of E–W and N–E trending fault systems, which controlled regional-scale magmatic activity and mineralization. The sedimentary cover and basement have been subjected to strong intracontinental deformation under the influence of the Indosinian

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(early Mesozoic) orogeny, causing deep faulting and upwelling of magma, and forming

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numerous Indosinian granites (Shu et al., 2006; Zhou et al., 2006). Subsequently, the

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Nanling region has undergone tectonic shift from Tethysian to Pacific regimes and the

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Yanshanian orogeny began (Zhou et al., 2006). During the Yanshanian (late Mesozoic) orogeny, the tectonic environment of the Nanling region changed from compression to

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extensional tectonism, with extensive magmatism, producing abundant calc-alkaline

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granites (Zhou, 2003; Mao et al., 2004; Hua et al, 2005).

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The central Nanling region is characterized by different periods granitoids from early Paleozoic to late Mesozoic time and related tungsten–tin mineralization (Fig. 1B)

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(Zhou et al., 2006; Mao et al., 2007; Hu et al., 2012; Chen et al., 2013). The Caledonian

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(early Paleozoic) granites are mainly strongly peraluminous S-type, with some associated

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with tungsten mineralization (Zhang et al., 2011).The Indosinian granites formed in a post-collision extensional tectonic environment after Indosinian collision (Sun et al., 2003), and some of these granites have a genetic relationship with ore deposits (Liang et al., 2011). The Yanshanian cycle represents the most important period of magmatic activity, and the Yanshanian granites are associated with the most important tungsten and tin deposits in the central Nanling region (Zhou et al., 2006; Chen et al., 2013). Most of tungsten–tin deposits in China are distributed within the Central Nanling

ACCEPTED MANUSCRIPT region (Xu and Zhu, 1988; Chen et al., 2008), including the Shizhuyuan W–Sn–Mo–Bi polymetallic deposit, Xintianling tungsten deposit, and Xianghualing skarn-type tin deposit in southern Hunan Province, the Xihuashan, Piaotang, and Dajishan tungsten

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deposits in southern Jiangxi Province, and the Jubankeng and Meiziwo tungsten deposits

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3. Ore geology of the Yaogangxian deposit

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in northern Guangdong Province (Fig. 1B).

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The Yaogangxian tungsten deposit is located within the Cathaysia Block in the central Nanling area (Fig. 1B). Several NE- and WNW-trending second-order faults are

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developed in the deposit, and WNW-trending faults control the wolframite–quartz veins

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(Fig. 2). The stratigraphic sequence at Yaogangxian includes Cambrian meta-sandstone

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and slate, Devonian medium–fine sandstone, Carboniferous shale and limestone, and Jurassic sandy shale (Fig. 2).

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The Yaogangxian composite granitic pluton (a Yanshanian granite intrusion), with an

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exposed surface area of 1.2 km2 (Figs. 2 and 3), intruded Cambrian and Devonian strata along the axis of the Yaogangxian anticline (Chen, 1981; Hu et al., 2012). The pluton consists of biotite granite and muscovite granite, both with medium–coarse and medium–fine grain sizes, representing highly differentiated magma products of high-K calc-alkaline series granite (Dong et al., 2014; Zhu et al., 2016). Zircon U–Pb age determinations of igneous rocks in the Yaogangxian tungsten deposit indicate that

ACCEPTED MANUSCRIPT magmatic activity occurred mainly at 156 and 158 Ma (Li et al., 2011). The age is consistent with that obtained by Re–Os dating of molybdenite from the ores (156 Ma; Peng et al., 2006), confirming that tungsten mineralization in the Yaogangxian deposit is

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related to the early Yanshanian composite granitic pluton.

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The ore-bearing quartz veins occur mainly in or near the granite (Figs. 2 and 3). Ore

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veins are a set of NW- to NNW-trending and south dipping quartz veins and a set of

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NWW-trending and south dipping quartz veins. Individual veins are generally approximately 500–1400 meters long vertically. The width and mineral composition of

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veins show a zonation from bottom to top. In the lower part of the vein system, the width

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of these veins ranged from 0.8 to 1.3 m (average 1.0 m) and predominantly contain quartz.

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In the middle part of the vein system, Veins are commonly 0.5 to 1 meter wide (average 0.6 m) (Fig. 4D), and contain the most important orebodies. The minerals include

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wolframite and quartz, with minor sphalerite, chalcopyrite bismutinite, chalcopyrite,

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pyrite, fluorite, and calcite (Figs. 4B, E, F and G). The veins are narrower near the

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surface. These veins are composed of fluorite, quartz and calcite, with minor wolframite, sphalerite, chalcopyrite, pyrite, arsenopyrite (Figs. 4C, I). Our field investigations of mineral assemblages and textures indicate that mineralization can be divided into three stages: wolframite–cassiterite–quartz of stage 1, sulfide–quartz of stage 2 and fluorite–carbonate–quartz of stage 3 (Figs. 4C, D, I and 5). The early wolframite–cassiterite–quartz stage is characterized by abundant tabular crystals of wolframite (Figs. 4A, E, H), smaller amounts of cassiterite and molybdenite

ACCEPTED MANUSCRIPT (usually enclosed in massive quartz), and minor pyrite and chalcopyrite (Fig. 5). Wolframite is intergrown with cassiterite commonly along vein edges (Fig. 4A), and occurs as lath-shaped, columnar, and irregular crystals (Figs. 4E, G and H). Most

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wolframite crystals enclosed by massive quartz show signs of deformation, except for

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free-standing crystals in cavities. Notably, wolframite crystals usually show an earlier

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paragenetic sequence than their intimately coexisting quartz (Figs. 4A, F, and G). Such

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relationship is more convincingly observed in miarolitic cavities, where most quartz crystals grew on the base of crystalized wolframite crystal (Fig. 4E). The early stage ore

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veins are mainly distributed in the lower part of the deposit and are directly linked to the

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granitic intrusion.

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The sulfide–quartz stage is dominated by abundant polymetallic sulfides such as pyrite, arsenopyrite, molybdenite, chalcopyrite, rare wolframite, galena, and sphalerite

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(Fig. 5). Gangue minerals are mainly quartz and sericite. Locally, sulfide–quartz veins cut

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across wolframite–cassiterite–quartz veins (Figs. 4C), indicating that the sulfides are

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younger than the wolframite stage. These veins mostly occur in the shallow part of the deposit and are generally above the early stage veins. The fluorite–carbonate–quartz stage comprises mainly fluorite, calcite and quartz, with trace amounts of pyrite and arsenopyrite (Figs. 4I and 5). Minerals of this stage can either form independent veins crosscutting early stage veins (Fig. 4D) or grow into euhedral crystal covers coating early stage minerals in miarolitic cavities (Fig. 4H). Fluorite is the index mineral of this stage and were commonly observed as free-standing

ACCEPTED MANUSCRIPT cubic crystals (Fig. 4H) or massive veins (Fig. 4I).

4. Sampling and analytical methods

wolframite

and

coexisting

quartz

crystals

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crystallized

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We undertook a microthermometric fluid inclusions study on undeformed, well from

stage

1

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wolframite–cassiterite–quartz veins (Figs. 4D, E, F), and quartz crystals associated with

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sulfides in stage 2 sulfide–quartz veins (Fig. 4C). The cubic fluorite crystals exhibits as a

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clearer index mineral of stage 3 than quartz and were thus chose for fluid inclusion study (Figs. 4H, I). Over two hundreds representative samples were collected from several

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locations in the Yaogangxian quartz-vein tungsten deposit. Twenty-six double polished

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thin sections (200 μm thick) were prepared for analyses of fluid inclusions in quartz and

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fluorite. The ten wolframite section was made thinner (~100 μm thick) to achieve better visual under near-infrared light.

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The microthermometric measurements were carried out with a Linkam THMS600

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heating–freezing stage with a temperature range of −195 to +600 °C mounted on a DMLB Leica microscope, at the State Key Laboratory for Mineral Deposit Research, Nanjing University. The stage was calibrated by measuring the ice melting points of pure-water inclusions (0 °C), pure-CO2 inclusions (−56.6 °C), and potassium dichromate (398 °C). The accuracy of measured temperatures was ± 0.2 °C during cooling, about ± 0.2 °C between 0 to 100°C and about ± 2 °C at 100 to 600 °C. Fluid inclusions trapped in

ACCEPTED MANUSCRIPT wolframite are invisible due to the opacity of wolframite. Consequently, a BX51 infrared microscope (Fluid Inc., USA) was used. Salinities of NaCl–H2O inclusions were calculated from the final melting temperature of ice for two-phase inclusions, using

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equations published by Bodnar (1993).

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The three-phase CO2-rich inclusions (type C) were cooled to freezing of the

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carbonic component at −95 to −100 °C. The phase changes of CO2 melting, gas hydration,

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homogenization, and total homogenization were observed during heating. Salinities of CO2-rich inclusions were calculated from the melting temperature of clathrate (Collins,

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1979).

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The compositions of individual fluid inclusions in quartz were determined using a

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Raman microprobe (RM2000; Renishaw) with a 5 mW (514.5 nm) Ar-ion laser. The scanning band was set to 1000–4000 cm–1, with a buildup time of 30 s for each scan. The

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charge-coupled detector (CCD) area was 20.

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Representative samples of quartz from all three stages and wolframite from stage 1

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were selected for oxygen and hydrogen isotopic analyses. Free-standing euhedral wolframite and quartz crystals grew in miarolitic cavities were hand-picked from mineralized vein samples for analysis to avoid secondary hydrothermal modification and deformation to the most extent. Oxygen was liberated by reaction with BrF5 (Clayton et al., 1972) and converted to CO2 on a platinum-coated carbon rod. Isotopic ratios (δ18O) were determined using a MAT-253 mass spectrometer at the Laboratory of Stable Isotope Geochemistry (LSIG), Institute of Mineral Resources, Chinese Academy of Geological

ACCEPTED MANUSCRIPT Sciences, Beijing, China. All values are reported relative to the VSMOW standard, with an uncertainty of ±0.2‰. Hydrogen isotopic analyses were conducted with the same samples as for fluid inclusions hosted in quartz and wolframite. The samples were first

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degassed of labile volatiles by heating under vacuum at 150 °C for 3 h. The temperature

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was then gradually increased to 500 °C causing the fluid inclusions to decrepitate, and the

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liberated water was collected. The water was converted to hydrogen by passage over

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heated zinc powder at 410 °C (Friedman, 1953), and its isotopic composition was determined using a MAT-252 mass spectrometer at the LSIG. Analyses of standard water

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samples indicated a precision for δD of ±3‰ (1σ).

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5. Fluid inclusions 5.1. Fluid inclusion petrography

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Through phase relationships at room temperature and phase transitions during

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heating and cooling (Roedder, 1984; Lu et al., 2004), three types of fluid inclusions were

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recognized in wolframite, quartz and fluorite: two-phase liquid-rich inclusions (type L), two-phase CO2-bearing inclusions (type CB), and three-phase CO2-rich fluid inclusions (type C). The type CB inclusions do not show obvious liquid CO2 phase at room temperature, but were distinguished from type L by observing clathrate during cooling. The type C inclusions show both aqueous and liquid CO2 phases and a vapor bubble at room temperature. All inclusion types were further subdivided by their hosted minerals into “Q” for quartz, “W” for wolframite and “F” for fluorite.

ACCEPTED MANUSCRIPT Petrographical criteria suggested by Roedder (1984) and Goldstein & Reynolds (1994) were used to distinguish primary and secondary fluid inclusions. Fluid inclusions occur in the growth zones or isolated clusters in the crystal cores are regarded as primary.

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In addition to primary fluid inclusions in these minerals, secondary fluid inclusions in

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wolframite were also investigated whereas those in quartz and fluorite were neglected

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despite their abundance.

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Wolframite

Fluid inclusions in wolframite from the Yaogangxian deposit are not as numerous as

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in quartz from the same samples. Inclusions hosted in wolframite are circular, elongated,

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or negative-crystal shaped. Type LW and CBW inclusions were identified in wolframite

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(Figs. 6E, F), both contain an aqueous phase and a vapor bubble at room temperature, and homogenize by vapor disappearance.

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Primary type LW inclusions were recognized in wolframite growth planes (Figs. 6A,

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C, and E). They have long-prismatic, plate-prismatic (negative-crystal), or elliptic forms,

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and are typically 10 to 75 μm in diameter. The vapor phase typically occupies 20 to 40 vol. %. Some inclusions are isolated and some are linearly distributed along striations that formed during crystal growth. Primary type CBW inclusions contain a dark vapor bubble (25 to 35 vol. %) and a liquid phase. Clathrates were detected during freezing runs and are thus considered to be CO2-bearing fluid inclusions. They have long or elliptic forms, and are typically 8 to 25 μm in diameter. These inclusions are often distributed along crystal growth plane which

ACCEPTED MANUSCRIPT indicates their primary origin (Figs. 6A and F). Secondary type LW inclusions are always distributed along healed trans-granular fractures in wolframite and thus are considered to be secondary in origin. They

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commonly have round or irregular shapes, and sizes of 5 to 15 μm (Figs. 6B, I, G and K).

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Secondary inclusions are relatively rare in wolframite crystals from deformed massive

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quartz veins and are nearly absent in free-standing wolframite crystals from miarolitic

Quartz and fluorite

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(1) Quartz associated with wolframite

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cavities.

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Type L fluid inclusions are prevalent in quartz associated with wolframite (Fig. 7B).

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They are variable in shape, including irregular, negative-crystal, and elongated, with typical size of 5 to 45 μm. The vapor phase normally occupies between 25 and 35 vol. %.

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Type L inclusions occurred along mineral growth zones or isolated clusters in crystal

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cores are interpreted to be primary inclusions, while those linearly distributed along

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healed intragranular fractures are considered to be secondary. Secondary fluid inclusions are abundant in massive quartz samples from deformed veins but were not further studied owing to their ambiguous genesis. CO2-rich three-phase fluid inclusions (type C) generally have high CO2 phase volumetric proportions (VCO2 ＞ 70%). Type C inclusions are commonly of negative-crystal, ellipse, and round shape and are 10 to 55 μm in size. They occur in clusters with type L inclusions in quartz associated with wolframite (Figs. 7C, D). Type CB inclusions in quartz are two-phase CO2-bearing

ACCEPTED MANUSCRIPT inclusions with vapor proportion between 30% and 45%. They appear the same to L type inclusion at room temperature, but were distinguished by the occurrence of liquid CO2 phase during cooling runs. They are typically 15 to 35 μm in diameter and have nearly

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ellipsoidal or irregular shapes (Fig. 7A). Only few type CB inclusions were observed in

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quartz associated with wolframite during microthermometry measurement and no data

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were obtained from them owing to their rareness and less significance.

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(2) Quartz in the sulfides stage

Type L inclusions are abundant in quartz in the sulfides stage (Fig. 7E), whereas both

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type CB and C are absent in these veins. The vapor phase of type L normally occupies

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between 10 and 20 vol.%. They are commonly of irregular, ellipse, and round shape and

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are 7 to 23 μm in size. (3) Fluorite in the last stage

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Studied fluorites are free-standing single euhedral crystals from vein cavities which

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are almost undeformed and have much less chance of trapping secondary inclusions

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(Goldstein and Reynolds, 1994). Only type L inclusions were recognized in fluorite of the stage 3 ore-barren fluorite carbonate quartz veins. The vapor phase generally occupies between 5 and 15 vol.% (Fig. 7F). These inclusions are commonly of ellipse and irregular shape, with 5 to 13 μm in size. 5.2. Fluid inclusion microthermometry The microthermometric studies were conducted on type LW, CBW, LQ and CQ

ACCEPTED MANUSCRIPT inclusions from stage 1 wolframite-cassiterite-quartz veins, type LQ inclusions from stage 2 sulfide-quartz veins and type LF inclusion from stage 3 fluorite-carbonate-quartz veins. In this study, microthermometry measurements were conducted based on the concept of

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fluid inclusion assemblage (FIA, Goldstein and Reynolds, 1994; Chi and Lu, 2008). In

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petrographically defined assemblage, fluid inclusions of similar phase proportion were

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selected for microthermometry to avoid fluid inclusions that formed by heterogenetic

in Table 1, and shown in Figures 9 and 10.

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Wolframite

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entrapment or necking down process. Fluid inclusion microthermometric results are listed

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Homogenization temperatures for type LW fluid inclusions are in the range 280 to

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360 °C, peaking at around 300 to 340 °C (Fig. 9A). Their final ice-melting temperatures range from −1.3 to −4.8 °C, corresponding to salinities from 2.2 to 7.6 wt. % NaCl equiv.

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(Fig. 9B). Secondary LW type inclusions were homogenized to liquid phase at 204 to

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256 °C (Fig. 9A). Their freezing points ranged from −0.8 to −3.5 °C, with salinities of 1.4

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to 5.7 wt. % NaCl equiv. (Fig. 9B). Very few type CB inclusions were found in wolframite and their CO2 clathrate-melting temperatures range from 8.1 to 8.6 °C. Correspondingly, the salinities of the aqueous phase in these inclusions ranged from 2.8 to 3.6 wt. % NaCl equiv. (Fig. 9B). Upon heating, these inclusions finally homogenized to the liquid phase at temperatures from 321 to 355°C (Fig. 9A). The existence of CO2 in type CBW inclusions was indicated by the detection of clathrates during freezing runs (Fig. 8). Phase changes of primary type CBW inclusion during cooling and heating

ACCEPTED MANUSCRIPT process show that the inclusion was frozen at −120°C (Fig. 8A) and the clathrate causes the bubble to deform (Fig. 8C). Quartz and fluorite

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(1) Quartz associated with wolframite

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During stage 1 mineralization, primary type L fluid inclusions in quartz associated

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spatially with wolframite yielded ice-melting temperatures from −2.5 to −4.6 °C, with

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salinities ranging from 4.2 to 7.3 wt. % NaCl equiv. (Fig. 10B). They were homogenized to the liquid phase at temperatures of have homogenization 244 to 308 °C (Fig. 10A).

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Type C inclusions in quartz are completely homogenized to CO2 phase at temperatures of

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276 to 317 °C (Table 1; Fig. 9C). The CO2 phase homogenizes to liquid (Quantity is 5),

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to vapor (Quantity is 11), and by critical behavior (Quantity is 4) at temperatures of 28.5 to 30.7 °C for type C inclusions. The melting temperature range of solid CO2 is −56.6 to

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−59 °C, below the triple point (−56.5 °C) of CO2, indicating minor amounts of dissolved

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components in the carbonic phase (Lu et al., 2004). This is consistent with Raman

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analyses indicating minor amounts of CH4 occur in fluid inclusions. The melting of CO2 clathrate (Tm, clath) in the presence of CO2 liquid occurred between 8.6 and 9.9 °C, with the calculated salinities of the aqueous phase ranging from 0.2 to 2.8 wt.% NaCl equiv. (Fig. 9D). (2) Quartz in the sulfides stage In stage 2, primary type L fluid inclusions in quartz coexisting with sulfide yield homogenization temperature values of 219 to 276 °C, peaking at 230 to 260 °C (Fig.

ACCEPTED MANUSCRIPT 10C), with salinities of 2.1 to 5.7 wt.% NaCl equiv. (Fig. 10D). These data are similar to secondary type L inclusions in wolframite, indicating that the wolframite was overprinted by the fluid associated with base sulfide mineralization.

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(3) Fluorite in the last stage

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In stage 3, primary type L inclusions in fluorite from fluorite carbonate quartz veins

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have ice-melting temperatures from −0.6 to −1.7 °C, with salinities of 1.1–3.0 wt. %

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NaCl equiv. (Fig. 10F). They were homogenized to the liquid phase at temperatures of

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183 to 205 °C (Fig. 10E). 5.3. Raman spectroscopy

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Representative inclusions were measured using Raman spectroscopy to constrain

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their gas compositions. Type LQ inclusions from stage 1 wolframite-cassiterite-quartz veins are dominated by H2O with minor amounts of CO2 (Fig. 11A). By contrast, only

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CO2 and minor amounts of CH4 (± N2) was detected in type CQ inclusions coexisting with

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type LQ inclusions in stage 1 wolframite-cassiterite-quartz veins(Figs. 11B). Type CBQ

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inclusions from stage 1 wolframite-cassiterite-quartz veins are dominated by H2O and CO2 (Fig. 11C). In the stage 2 sulfide-quartz veins, the Raman analyses of type LQ inclusions showed that H2O is the dominant composition, without other compressive volatile compositions (Figs. 11D). The Raman results show that NaCl–H2O–CO2 is the dominant composition of the fluid in quartz associated with wolframite, with variable volatile components (i.e., CH4 and N2).

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6. H and O isotopes

The δ D values of the extracted waters for wolframite and quartz samples in stage 1 ranged from −45‰ to −67‰ and −56‰ to −64‰, respectively (Table 2 and Fig. 13).

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The δ D of quartz from stage 2 and 3 has relatively low values, which ranged from -66‰

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to −76‰ and −64‰ to −73‰, respectively (Table 2 and Fig. 13).

Measured δ18O values of coexisting quartz and wolframite from stage 1

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mineralization are relatively restricted, with ranges of 11.9‰ to 17.6‰ and 2.6‰ to

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5.4‰, respectively (Table 2 Fig. 13). Using the equations of Clayton (1972) and Zhang

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Li-Gang (1994), and corresponding fluid inclusion homogenization temperature data, the δ18O values for fluids from coexisting quartz and wolframite from stage 1 were calculated

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to be 3.7‰ to 8.5‰ and 4.7‰ to 7.6‰, respectively (Table 2). The same calculation

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method applied to stage 2 and 3 quartz yielded δ18O values of 2.1‰ to 2.7‰ and −1.2‰

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to 0.2‰, respectively (Table 2). Since the homogenization temperature of fluid inclusion can only provide a lower limit of trapping temperature unless the fluid inclusions were

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entrapped from an immiscible or boiling fluid (Roedder, 1984). δ18O values of stage 2 and 3 fluids calculated using fluid inclusion homogenization temperatures may have been underestimated. Notably, secondary fluid inclusions of lower temperature and different source may also occur in the analyzed samples and thus caused shifts of H and O isotopic compositions. In this study, quartz and wolframite samples used for H and O isotope

ACCEPTED MANUSCRIPT analysis were euhedral crystals collected from miarolitic cavities which may well prevent post-ore modification and deformation. Therefore, the isotopic shifts resulted from mixing of secondary fluid inclusions are suggested to be minor in our case and the

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reported data are reliable to a large extent.

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7. Discussion

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7.1 The roles of CO2-bearing fluid inclusions in wolframite formation Carbon dioxide is a common volatile component of ore-forming fluids and plays a

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significant role in the formation of various types of deposits, such as orogenic gold

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deposits (Ridley and Diamond, 2000; Xu et al., 2016) and porphyry molybdenum

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deposits (Ni et al., 2015b; Ni et al., 2017). Similarly, CO2-rich ore fluids are commonly present in the Nanling wolframite–quartz vein-type tungsten deposit belt, including in

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the Pangushan (Wang et al., 2010), Dajishan (Wang et al., 2013b), and Xihuashan

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(Giuliani et al., 1988) tungsten deposits of Jiangxi Province.

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Many type C inclusions occur in coexisting quartz (Figs. 7C, D) but only few type CB inclusions in wolframite (Fig. 6F) in the Yaoganxian tungsten deposit, suggesting that the ore-forming fluid was a CO2-bearing solution. Possible functions of CO2 in the ore-forming process are discussed here. The early view regarding the influence of carbonate species on tungsten transport was given by Higgens (1980) based on investigation of CO2-rich inclusions in quartz coexisting with wolframite. Carbonate and bicarbonate complexes were suggested to

ACCEPTED MANUSCRIPT have contribution on tungsten transport at very high fluid pressures (Higgens, 1980), and are conducive to tungsten precipitation (Higgens, 1985; Polya, 1988; So and Yun, 1994). However, further studies argue that tungsten exists in ore-forming fluids mainly as

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H2WO4, HWO4–, and WO42–, which implies that carbonate complexes probably play a

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negligible role in hydrothermal tungsten transport (Wood and Samson, 2000).

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Nevertheless, the carbonate species may have indirect effects on tungsten precipitation.

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For example, immiscibility may lead to the loss of CO2 and results in pH increase, which in turn reduces the stability of tungsten in the hydrothermal fluid system (e.g., Fig.

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15 in Wood and Samson, 2000), causing its precipitation (Polya, 1988; So and Yun,

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1994; Wood and Samson, 2000; Sushchevskaya, 2010). A similar process was also

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suggested to have contribution on gold precipitation in orogenic gold deposits (Phillips and Evans, 2004).

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The possible effects of immiscible CO2 on tungsten deposition seem to be

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reasonable since CO2-rich fluid inclusions were commonly observed in quartz that

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coexisting with wolframite (Higgins, 1980, 1985; Giuliani, et al., 1988; Macey and Harris, 2006; Wang et al., 2012; Naumov et al., 2011). However, by using infrared microscopy in the recent decades, no CO2-bearing inclusions were found in wolframite, which again leads to that CO2 plays only a minor role in tungsten migration (Campbell and Robinson, 1987; Campbell and Panter, 1990; Lueders, 1996; Rios et al., 2003; Ni et al., 2015). In the present study, carbonic fluid inclusions were found present in wolframite

ACCEPTED MANUSCRIPT crystals growth planes and were thus identified as primary in origin (Figs. 6 and 8). The detection of minor CO2 in wolframite-hosted inclusions may indicate that wolframite was precipitated from a low- to moderately-saline aqueous fluid containing minor

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amounts of CO2. However, the role of CO2 in wolframite formation is still unclear from

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our present result. In general, type LW inclusions are the dominated primary fluid

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inclusions in all studied wolframite samples. The microthermometric results for LW type

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inclusions indicate a decreasing trend in temperature (Figs.9A and 12), suggesting that a simple cooling process could have caused the deposition of wolframite in the

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Yaoganxian tungsten deposit (Heinrich, 1990; Wood and Samson, 2000; Ni et al., 2015).

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7.2 Relationship between fluids associated with wolframite and coexisting quartz

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The analyses of fluid inclusions in ore minerals such as wolframite, pyrite, tetrahedrite and rutile using infrared microscopy for microthermometric analysis can

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provide reliable information about ore-forming fluids (Campbell and Panter, 1990;

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Lindaas et al., 2002; Ni et al., 2008; Moritz, 2006). Previous fluid inclusion studies of

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quartz vein-type tungsten deposits indicate that inclusion fluids in wolframite have a relatively high salinity and homogenization temperature compared with those in coexisting quartz (Campbell and Panter, 1990; Ni et al., 2006, 2015; Wei et al., 2012). In the present study, the homogenization temperature and salinity of two-phase aqueous inclusions in wolframite and quartz are remarkably different, indicating that the two minerals were precipitated separately (Figs. 9 and 12). This view is consistent with our

ACCEPTED MANUSCRIPT field observation that wolframite always occur along vein walls and show earlier paragenetic sequence than coexisting quartz (Figs. 4A, E and F). As discussed above, wolframite at Yaogangxian was most likely to be precipitated

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by simple cooling of a low- to moderately-saline aqueous fluid with minor amounts of

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CO2. In contrast, fluid characteristics recorded in their coexisting quartz showed different

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processes. The large number of type C inclusions occurs in quartz (Figs. 7C, D) indicates

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that the quartz-forming fluid contains significant higher amounts of CO2 comparing to the parental fluids that formed wolframite (Fig. 6F). However, given the earlier paragenetic

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sequence of wolframite than coexisting quartz, it is confusing to conclude that the later

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fluid pulse is more CO2–rich that the early one if both generated from a single

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crystalizing magma. Considering the fact that CO2 tends to exsolve from magma during early stage of emplacement (Holloway, 1976; Giggenbach, 1997; Lowenstern, 2001), a

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possible explanation is that the relatively later CO2–rich fluid was derived from an

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additional CO2–bearing magma. Nevertheless, explanation to this question has beyond

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the scope of our current study and additional work is required before a complete understanding can be reached. As recorded by fluid inclusions in quartz from stage 1 veins, fluid immiscibility had occurred during quartz crystallization. The occurrence of fluid immiscibility is supported by the following evidence from inclusions in quartz: (1) type L and C inclusions in stage 1 quartz have intimate spatial relationship (Figs. 7C, D); (2) they display different homogenization modes and (3) these inclusions exhibit similar homogenization

ACCEPTED MANUSCRIPT temperature ranges but contrasting salinities (Figs. 9C, D). Significantly, the homogenization temperatures of type C inclusions (276 to 317°C) are slightly higher than those from coexisting type L inclusions (244 to 308°C). The elevated temperature of type

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C inclusions is best explained by the heterogenetic entrapment of small amount of

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H2O–dominated phase into the CO2–rich endmember due to preferential surface wetting

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of quartz by aqueous phase (Roedder, 1984). Similar criteria indicating fluid

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immiscibility was suggested in many other fluid inclusion studies (e.g., Fan et al., 2003; Ramboz et al., 1982; Roedder, 1984; Xu et al., 2016).

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Additionally, from stage 1 to stage 3, the Th vs. salinity plots for type L fluid

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inclusions in quartz and fluorite (Figs. 10 and 12) show a trend of dilution, which can be

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interpreted as mixing between a hot, saline fluid and a cooler dilute fluid (e.g., Chi and Savard, 1997). Mixing of fluids is also indicated by the oxygen isotopic composition of

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stage 2 and 3 fluids, although δ18O values may be underestimated by using fluid inclusion

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homogenization temperatures. During the sulfide-quartz veins stage (stage 2), δ D and

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δ18O values in quartz are relatively low (Fig. 13), and decreasing salinities are likely due to mixing. It appears, therefore, that the fluid precipitating quartz had undergone immiscibility and mixing processes, whereas only simple fluid cooling was recorded in wolframite. 7.3 Pressure estimation and metallogenic process The three-phase CO2-rich inclusions in the immiscible assemblages in quartz of

ACCEPTED MANUSCRIPT stage 1 can be used to estimate pressure because assemblage end-members form adjacent to the solvus and can indicate trapping pressures (Roedder and Bodnar, 1980). Using microthermometric data and estimated petrographic volume fractions of CO2, the

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trapping pressures of type C inclusions were estimated using Flincor software (Brown

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and Hagemann, 1995) based on the criteria of Bowers and Helgeson (1983). The

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estimated trapping pressure of type C inclusions in stage 1 quartz is 72 to 94 MPa, at

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temperatures of 290 to 300 °C, representing the trapping pressure in the process of fluid immiscibility during quartz formation. Field observations, together with the

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homogenization temperature values of wolframite and coexisting quartz indicate that

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wolframite formed earlier than quartz, prior to fluid immiscibility. Thus, the estimated

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pressure from type C inclusions in quartz gives a lower limit of wolframite formation. During the precipitation of tungsten in the Yaogangxian deposit, it can be inferred that

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the hydrothermal system was initially in a relatively closed setting probably under

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lithostatic pressure where simple cooling of mineralizing fluids was responsible for

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wolframite deposition. As the system progressively cooled, the rocks can fracture in a more brittle way at temperature lower than 400°C (Fournier, 1999); regional uplifting and paleosurface erosion may cause transition from lithostatic to hydrostatic environment which probably results in fluid immiscibility and mixing with meteoric water. Similar conclusions can also be concluded from the microthermometric information of primary inclusions in wolframite from quartz vein-type deposits in the Gannan metallogenic belt (Ni et al., 2015) and worldwide (Campbell and Robinson,

ACCEPTED MANUSCRIPT 1987; Campbell and Panter, 1990; Lueders, 1996). 7.4 Source of ore-forming fluid Ore-forming fluids of wolframite–quartz vein deposits are mainly of magmatic

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origin (Pirajno, 1992; Burnham 1979; Jackson et al., 2000; Li et al., 2011), although

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mixing of magmatic and meteoric water was also indicated (Zhang 1988; Taylor, 1997).

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Fluids precipitating wolframite show δ D and δ18O values range from −45‰ to

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−67‰ and 4.7‰ to 7.6‰, respectively. These values plot within the magmatic water region of the δ D–δ18O diagram (Fig. 13), indicating a primary magmatic origin for the

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mineralization process (Burnham 1979; Jackson et al., 2000). The H–O isotopic data of

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wolframite from the Yaogangxian deposit are consistent with many wolframite–quartz

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vein-type tungsten deposits (Zhang, 1988; Burnham 1997; Jackson et al., 2000; Zhang et al., 1997; Li et al., 2014), indicating that magmatic fluids generally play a key role in this

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type of mineralization. Calculated fluid δD and δ18O values of coexisting quartz also plot

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in the magmatic water region of the δD–δ18O diagram (Fig. 13), indicating a primary

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magmatic origin for the quartz-forming fluid in stage 1 mineralization. From stage 2 to stage 3, the δD–δ18O diagram of fluids precipitating quartz (Fig. 13) shows a trend of dilution caused by magmatic water being mixed with meteoric water. Considering a possible underestimate of δ18O values using fluid inclusion homogenization temperatures, the mixing degree of meteoric water into magmatic fluid is probably less than expected. However, the input of a low-temperature and low-salinity

ACCEPTED MANUSCRIPT meteoric fluid is strongly indicated by the slanting trend of microthermometric data for stages 2 and 3 in the homogenization temperature vs salinity diagram (Fig. 12). In general, our study of stable isotopes in wolframite and quartz demonstrated that ore-forming

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fluids in the Yaogangxian deposit were possibly directly evolved from an initial

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magmatic fluid, with gradual mixing of exogenic fluid occurring after the formation of

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wolframite, and possibly resulting in the deposition of sulfides and carbonates. Similar

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processes were also reported at the Brandberg West area Sn–W vein deposits (Macey and Harris, 2006), Kalguty Mo–W (Be) deposit (Borovikov et al., 2016) and tin-tungsten

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deposits of Panasqueira (Kelly and Rye, 1979).

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7.5 Interpretation of secondary fluid inclusions in wolframite

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Wolframite–quartz vein–type deposits commonly show multiple stages of mineralization, including early oxide stage, sulfide stage, and late carbonate stage

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(Shepherd and Waters, 1984; Shelton et al., 1987; So and Yun, 1994; Wood and

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Samson, 2000). Since wolframite forms mainly in the oxide stage, superimposition and

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reworking by later stage fluids can be naturally expected. However, a number of recent researches on wolframite-quartz vein type deposits indicate no record of secondary fluids in wolframite (Wei et al., 2012; Ni et al., 2015). Huang et al. (2012) suggested that wolframite crystals are relatively more plastic and less dissolvable, which give wolframite stronger resistance against brittle fracturing and thus are not preferential for trapping secondary fluid inclusion (Roedder, 1984). Consequently, fluid inclusions in

ACCEPTED MANUSCRIPT wolframite were generally considered as primary in many case studies of wolframite-quartz vein type deposits in the Nanling region (Wei et al., 2012; Huang et al., 2012; Ni et al., 2015).

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Nevertheless, our infrared petrographic studies of fluid inclusions in wolframite

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crystals from the Yaogangxian deposit indicate that secondary L type inclusions,

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although very rare, may still be entrapped in the wolframite (Figs. 6B, I, K). These

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secondary fluid inclusions yielded variable Th values of 204 to 256 °C (Fig. 9A) and salinities of 1.4 to 5.7 wt.% NaCl equiv. (Fig. 9B), which are also distinguishable from

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primary fluid inclusions. Significantly, the microthermometric results of secondary

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inclusions in wolframite are similar to those primary inclusions in quartz coexisting

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with sulfides (Fig. 10C, D), implying that sulfide stage fluids may be trapped in early wolframite as secondary inclusions. It is therefore suggested that superimposition of

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later stage fluids can also be recorded in wolframite and a more cautious petrographic

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observation is required for their recognition.

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8. Implications for exploration of quartz vein-type tungsten deposits

Spatially, the quartz vein-type tungsten deposits commonly root into the underlying intrusive rocks (Hsu, 1943; Tanelli, 1982), and the wolframite-quartz veins can extend hundreds to over thousand meters, such as the NO.39 ore-vein of Pangushan deposit (Ren et al., 1986), the NO.21 ore-vein of Dajishan deposit (Wang et al., 2013b) and NO.49-501

ACCEPTED MANUSCRIPT ore-vein of Yaogangxian deposit (Chen, 1981). However, there are significant differences in mineralization fashion at different elevation of single ore veins, which is best summarized by the famous “Five–floor” model of the quartz vein-type tungsten deposits

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in the Nanling region (Liu., 1980; Wei et al., 2008). Based on the vertical scale of the

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“Five-floor” model, the tungsten grade is higher near the deep granite, and sulfides are

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rich in the middle zone, whereas carbonates are mainly distributed in the shallow part of

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ore veins. Therefore, the determination of the location of W-rich parts in the ore-veins combined with fluid inclusions and isotope analysis can be very important for mineral

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exploration and exploitation.

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The study of characteristics of ore-forming fluids can establish the deposit model

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and guide ore prospecting (Hedenquist et al., 1998; Redmond et al., 2004; Wang et al., 2013).The fluid inclusions and isotope evidence in the Yaogangxian tungsten deposit

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demonstrate that the ore-forming fluid responsible for wolframite crystallization was

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mainly composed of magmatic water with high temperature and moderate salinity.

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Ore-fluids responsible for sulfide and carbonate formation are featured by mixture of magmatic water with meteoric water and by relatively low temperature and salinity. Therefore, veins that contain fluid inclusions that are characterized by high temperature, high salinity and dominated by magmatic water are suggested to be a preferred prospecting target area. In addition, in levels where abundant sulfides and carbonates exist, the search for potential tungsten-rich ore should be concentrated in deeper parts of the vein system.

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9. Conclusions

The following conclusions are derived from our study of the Yaogangxian tungsten deposit.

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(1) Fluid inclusion results show that wolframite was precipitated from a

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low-moderately saline fluid containing trace amounts of CO2 and CH4. The CO2 may play a positive role in tungsten transport but has negligible influence on tungsten

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precipitation.

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(2) The homogenization temperature of fluid inclusions in wolframite is higher than

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in coexisting quartz and indicates that wolframite was precipitated earlier than most of the coexisting quartz. The coexisting quartz in stage 1 has experience fluid immiscibility

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whereas only a simple cooling process was recorded in wolframite.

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(3) The prevalence of aqueous fluid inclusions in wolframite, and the scarcity of

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carbonic inclusions, indicates that the simple cooling of CO2-poor, H2O-dominated fluid was responsible for tungsten mineralization. While subsequent fluid immiscibility and

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mixing resulted in massive quartz precipitation and sulfide mineralization. (4) δD and δ18O values obtained from wolframite indicate a chear magmatic source of ore fluid. However, δD and δ18O values of quartz imply a signature of meteoric water mixing during sulfide and late carbonate stages. (5) Infrared microscopy studies of fluid inclusions in wolframite crystals show that secondary liquid-rich inclusions were entrapped in the wolframite and may correspond to

ACCEPTED MANUSCRIPT the fluid associated with sulfide stage. (6) From an exploration viewpoint, veins that show high temperature, moderate salinity fluids with a magmatic isotopic signature indicate a preferred prospecting target

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area whereas the regions with abundant sulfides and carbonates suggest shallower levels

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and potential for deeper-seated W mineralization.

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Acknowledgements

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The authors would like to thank reviewers for their constructive comments which significantly improve the manuscript. We are grateful to Fan Ming-Sen, Zhang Xin, Liu

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Zheng, and Wei Tao from Nanjing University for the help of fieldwork work, Zhang

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Zeng-Jie form Chinese Academy of Geological Sciences for helping measuring hydrogen

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isotopes, He Xiao-Ping and Wang Ping-Ping from the Yaogangxian mine in Hunan province for their help during fieldwork. This study is supported by the National Key R&

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D Program of China (NO.2016YFC0600205) and the China National Basic Research

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Program (Grant NO. 2012CB416706).

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Bailly, L., Grancea, L., Kouzmanov, K., 2002. Infrared microthermometry and chemistry of wolframite from the Baia Sprie epithermal deposit, Romania. Economic Geology 97, 415–423. Bodnar, R.J., 1993. Revised equation and table for determining the freezing point depression of H2O-NaCl solutions. Geochimica et Cosmochimica Acta 57, 683–684. Borovikov, A. A., Goverdovskiy, V. A., Borisenko, A.S., Bryanskiy, N.V., Shabalin, S. I., 2016. Composition and metal contents of ore-forming fluids of the Kalguty Mo–W(Be) deposit (Gorny Altai). Russian Geology & Geophysics 57, 507–518. Bowers, T. S., Helgeson, H. C., 1983. Calculation of the thermodynamical consequences of nonideal mixing in the system H2O-CO2-NaCl on phase relations in geologic systems: metamorphic equilibria at high pressures and temperatures. American Mineralogist 68, 1059–1075. Brown, P. E., Hagemann, S. G., 1995. Macflincor and its application to fluids in archean lode-gold deposits. Geochimica et Cosmochimica Acta 59, 3943–3952. Burnham, C. W., 1979. Magmas and hydrothermal fluids. Geochemistry of Hydrothermal pp. 71–136. Campbell, A. R., Panter, K. S., 1990. Comparison of fluid inclusions in coexisting (cogenetic?) wolframite, cassiterite, and quartz from St. Michael's Mount and Cligga Head, Cornwall, England. Geochimica et Cosmochimica Acta 54, 673–681. Campbell, A. R., Robinson, C. S., 1987. Infrared fluid inclusion microthermometry on coexisting wolframite and quartz. Economic Geology 82, 1640–1645. Cao, X. F., Lv, X. B., He, M. C., Niu, H., Du, B. F., Mei, W., 2009. An infrared microscope investigation of fluid inclusions in coexisting quartz and wolframite: A case dtudy of Yaogangxian quartz-vein wolframite deposit. Mineral Deposits 28, 611–620 (in Chinese with English abstract). Chen, J., Lu, J. J., Chen, W. F., Wang, R. C., Ma, D. S., Zhu, J., Zhang, W. L., Ji, J. F., 2008.W–Sn–Nb–Ta-bearing granites in the Nanling Range and their relationship to metallogengesis. Geological Journal of China Universities 14, 459–473 (in Chinese with English abstract). Chen, J., Wang, R. C., Zhu, J., Lu, J. C., Ma, D. S., 2013. Multiple-aged granitoids and related tungsten-tin mineralization in the Nanling Range, South China. Science China Earth Sciences 56, 2045–2055. Chen, Y. R., 1981. Geological characteristics and symbols of Yaogangxian tungsten deposit. Geology and Exploration 2, 25–30 (in Chinese). Chi, G. X., Savard, M. M. 1997. Sources of basinal and mississippi valley-type mineralizing brines: mixing of evaporated seawater and halite-dissolution brine. Chemical Geology 143, 121–125. Chi, G. X., Lu, H. Z., 2008. Validation and representation of fluid inclusion microthermometric data using fluid inclusion assemblage (FIA) concept. Acta Petrologica Sinica 24, 1945–1953 (in Chinese with English abstract). Clayton, R. N., O'Neil, J. R., Mayeda, T. K. 1972. Oxygen isotope exchange between quartz and water. Journal of Geophysical Research Atmospheres 77, 3057–3067. Collins, P. L. F. 1979. Gas hydrates in CO2-bearing fluid inclusions and the use of freezing data for estimation of salinity. Economic Geology 74, 1435–1444. Dong, S. H., Bi X. W., Hu, R. Z. Chen, Y. W., Chen, H., 2011.Characteristics of ore-forming fluid in Yaogangxian quartz-vein wolframite deposit, Hunan province. Journal of Mineralogy and Petrology 31, 54–60 (in Chinese with English abstract). Dong, S. H., Bi X. W., Hu, R. Z. Chen, Y. W., 2014. Petrogenesis of the Yaogangxian granites and implications for W mineralization, Hunan Province. Acta Petrologica Sinica 30, 2749–2765(in

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Chinese with English abstract). Fan, H. R., Zhai, M. G., Xie, Y. H., Yang, J. H., 2003. Ore-forming fluids associated with granitehosted gold mineralization at the Sanshandao deposit, Jiaodong gold province, China. Mineralium Deposita 38, 739–750. Feng, C. Y., Zeng, Z. L., Zhang, D. Q., Qu, W. J., Du, A. D., Li, D. X., She, H. Q., 2011. SHRIMP zircon U-Pb and molybdenite Re–Os isotopic dating of the tungsten deposits in the Tianmenshan-Hongtaoling W-Sn orefield, southern Jiangxi Province, China, and geological implications. Ore Geology Reviews 43, 8–25. Friedman, I., 1953. Deuterium content of natural waters and other substances. Geochimica et Cosmochimica Acta 4, 89–103. Fournier, R. O., 1999. Hydrothermal processes related to movement of fluid from plastic into brittle rock in the magmatic-epithermal environment: Economic Geology 94, 1193−1211. Geology Department, Nanjing Uinversity, 1981. Granites of Different Ages of South China and their Metallogenetic Relations. Beijing: Science Press, pp. 1–195(in Chinese). Giggenbach, W.F., 1997. The origin and evolution of fluids in magmatic–hydrothermal systems. Geochemistry of Hydrothermal Ore Deposits 3, 737–796. Giuliani, G., Li, Y. D., Sheng, T. F., 1988. Fluid inclusion study of Xihuashan tungsten deposit in the southern Jiangxi province, China. Mineralium Deposita 23, 24–33. Goldstein, R. H., Reynolds, T. J., 1994. Systematics of fluid inclusions in diagenetic minerals: SEPM short course. Society for Sedimentary Geology 31, 1–199. Guo, W. G., Jiang, J. Z., Gan, X. P., 2010. Geological characteristics and metallogenic model of Yaogagnxian tungsten deposit in Hunan. Mineral Resources and Geology 24, 309–313 (in Chinese with English abstract). Hedenquist, J. W., Arribas, A., Reynolds, T. J., 1998. Evolution of an intrusion-centered hydrothermal system; Far Southeast-Lepanto porphyry and epithermal Cu-Au deposits, Philippines. Economic Geology 93, 373–404. Heinrich, C. A., 1990. The chemistry of hydrothermal tin (-tungsten) ore deposition. Economic Geology 85, 457–481. Higgins, N., 1980. Fluid inclusion evidence for the transport of tungsten by carbonate complexes in hydrothermal solutions. Canadian Journal of Earth Sciences 17, 823–830. Higgins, N., 1985. Wolframite deposition in a hydrothermal vein system; the Grey River tungsten prospect, Newfoundland, Canada. Economic Geology 80, 1297–1327. Holloway, J.R., 1976. Fluids in the evolution of granitic magmas: consequences of finite CO 2 solubility. Geological Society of America Bulletin 87, 1513–1518. Hsu, K. C., 1943. Tungsten deposits of southern Kiangsi, China. Economic Geology 38, 431–474. Hsu, K. C., 1957. Discovery of pyrometasomatic scheelite deposits near a wolframite-producing district in Southern China, and a discussion about the origin of these two classes of deposits. Acta Geologica Sinica 37, 117–151 (in Chinese with English abstract). Hu, R. Z., Zhou, M. F., 2012. Multiple Mesozoic mineralization events in South China—an introduction to the thematic issue. Mineralium Deposita 47, 579–588. Hu, R. Z., Bi, X. W., 2012. Mantle-derived noble gases in ore-forming fluids of the granite-related Yaogangxian tungsten deposit, Southeastern China. Mineralium Deposita 47, 623–632. Huang, H. L., Chang, H. L., Li, F., Zhang, C. H., Tan, J., Zhou, Y., 2012. A comparative study of fluid inclusions from coexisting transparent minerals and opaque minerals in Xihuashan tungsten deposit. Mineral deposits 31, 171–1183 (in Chinese with English abstract). Hua, R. M., Chen, P. R., Zhang, W. L., Yao, J. M., Lin, J. F., Zhang, Z. S., 2005. Metallogeneses and their geodynamic settings related to Mesozoic granitoids in the Nanling range. Geological Journal of China Universities 11, 291–304 (in Chinese with English abstract). Jackson, P., Changkakoti, A., Krouse, H. R., Gray, A. J., 2000. The origin of greisen fluids of the foley's zone, Cleveland tin deposit, Tasmania, Australia. Economic Geology 95, 227–236. Kelly, W. C., Rye, R. O., 1979. Geologic, fluid inclusion and stable isotope studies of the tin tungsten deposits of Panasqueira, Portugal. Economic Geology 74, 1721–1822.

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Li, G. L., Hua, R. M., Zhang, W. L., Hu, D. Q., Wei, X. L., Huang, X. E., Xie, L., Yao, J. M., Wang, X. D., 2011. He-Ar isotope composition of pyrite and wolframite in the Tieshanlong tungsten deposit, Jiangxi, China: Implications for fluid evolution. Resource Geology 61, 356–366. Li, G. L., Hua R. M., Wang, X. D., Zhou, L. Q., Tang, A., 2014. H-O isotope study of Pangushan tungsten deposit in Southern Jiangxi. Journal of East China Institute of Technology (Natural Science Edition) 37, 164–169 (in Chinese with English abstract). Li, S. T., Wang, J. B., Zhu, X. Y., Wang, Y. L., Han, Y., Guo, L. L., 2011. Chronological characteristics of the Yaogangxian composite pluton in Hunan Province. Geology and Exploration 47, 143–15 (in Chinese with English abstract). Li, Y. Q., 1991. Mineralogy of tungsten deposits in Nanling and neighboring area, China. China University of Geosciences press pp, 1–455 (in Chinese). Liang, H. Y., Wu, J., Sun, W. D., Mo, J. H., Huang, W. T., 2011. Discussion on Indosinian metallogenic in Southern China. Acta mineralogica Sinica 31, 53–54 (in Chinese with English abstract). Lindaas, S. E., Kulis, J., Campbell, A. R., 2002. Near-infrared observation and microthermometry of pyrite-hosted fluid inclusions. Economic Geology 97, 603–618. Liu, Y. J., Ma, D. S., 1993. Vein-type tungsten deposits of China and adjoining regions. Ore Geology Reviews 8, 233–246. Liu, Z. Q., 1980. Metallogenic forecasting theory of quartz-vein type wolframite deposits. Science Press, Beijing, pp. 1–150 (in Chinese). Lowenstern, J. B., 2001. Carbon dioxide in magmas and implications for hydrothermal systems. Mineralium Deposita 36, 490 –502. Lueders, V., 1996. Contribution of infrared microscopy to fluid inclusion studies in some opaque minerals (wolframite, stibnite, bournonite); metallogenic implications. Economic Geology 91, 1462–1468. Lu, H. Z., 1986. The origin of tungsten mineral deposits in South China. Chongqing Publishing House, Chongqing, pp. 1–232 (in Chinese). Lu, H. Z., Fan, H. R., Ni, P., Ou, G. X., Shen, K., Zhang, W. H., 2004. Fluid inclusions. Science Press, Beijing, pp. 1–487 (in Chinese). Macey, P., Harris, C., 2006. Stable isotope and fluid inclusion evidence for the origin of the Brandberg West area Sn–W vein deposits, NW Namibia. Mineralium Deposita 41, 671–690. Mao, J. W., Xie, G. Q., Li, X. F., 2004. Mesozoic large scale mineralization and multiple lithospheric extension in South China. Earth Science Frontiers 11, 45–55. Mao, J. W., Xie, G. Q., Guo, C. L., Chen, Y. C., 2007. Large–scale tungsten–tin mineralization in the Nanling region, South China: metallogenic ages and corresponding geodynamic processes. Acta Petrologica Sinica 23, 2329–2338 (in Chinese with English abstract). Mohamed, A. M., 2013. Evolution of mineralizing fluids of cassiterite–wolframite and fluorite deposits from Mueilha tin mine area, Eastern Desert of Egypt, evidence from fluid inclusion. Arabian Journal of Geosciences 6, 775–782. Moritz, R., 2006. Fluid salinities obtained by infrared microthermometry of opaque minerals: Implications for ore deposit modeling–a note of caution. Journal of Geochemical Exploration 89, 284–287. Naumov, V. B., Dorofeev, V. A., Mironova, O. F., 2011. Physicochemical parameters of the formation of hydrothermal deposits: a fluid inclusion study. I. tin and tungsten deposits. Geochemistry International 49, 1002. Ni, P., Huang, J. B., Wang, X. D., Jiang, S. Y., Ling, H. F., 2006. Infrared fluid inclusion microthermometry on coexisting wolframite and quartz from Dajishan tungsten deposit, Jiangxi province, China. Geochimica et Cosmochimica Acta 70, A444. Ni, P., Pan, J. Y., Wang, G. G., Chi, Z., Qin, H., Ding, J. Y., Chen, H., 2017. A CO2-rich porphyry ore-forming fluid system constrained from a combined cathodoluminescence imaging and fluid inclusion studies of quartz veins from the Tongcun Mo deposit, South China. Ore Geology Reviews 81, 856–870. Ni, P., Wang, X. D., Wang, G. G., Huang, J. B., Pan, J. Y., Wang, T. G., 2015. An infrared

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microthermometric study of fluid inclusions in coexisting quartz and wolframite from Late Mesozoic tungsten deposits in the Gannan metallogenic belt, South China. Ore Geology Reviews 65, 1062–1077. Ni, P., Wang, G. G., Yu, W., Chen, H., Jiang, L. L., Wang, B. H., Xu, Y. F., 2015b. Evidence of fluid inclusions for two stages of fluid boiling in the formation of the giant Shapinggou porphyry Mo deposit, Dabie Orogen, Central China. Ore Geology Reviews 65, 1078–1094. Ni, P., Zhu, X., Wang, R. C., Shen, K., Zhang, Z. M., Qiu, J. S., Huang, J. P., 2008. Constraining ultrahigh-pressure (UHP) metamorphism and titanium ore formation from an infrared microthermometric study of fluid inclusions in rutile from Donghai UHP eclogites, Eastern China. Geological Society of America Bulletin 120, 1296–1304. Noronha, F., Doria, A., Dubessy, J., Charoy, B., 1992. Characterization and timing of the different types of fluids present in the barren and ore-veins of the W–Sn deposit of Panasqueira, Central Portugal. Mineralium Deposita 27, 72–79. Peng, J. T., Zhou, M. F., Hu, R. Z., Shen, N. P., Yuan, S. D., Bi, X. W., Du, A. D., Qu, W. J., 2006. Precise molybdenite Re–Os and mica Ar–Ar dating of the Mesozoic Yaogangxian tungsten deposit, Central Nanling District, South China. Mineralium Deposita 41, 661–669. Phillips, G. N., Evans, K. A., 2004. Role of CO2 in the formation of gold deposits. Nature 429, 860. Pirajno, F., 1992. Hydrothermal mineral deposits. Springer Berlin Heidelberg, New York, pp. 101–155. Polya, D. A. 1988. Compositional variation in wolframites from the Barroca Grande mine, Portugal: Evidence for fault-controlled ore formation. Mineralogical Magazine 52, 497–503. Quilez, E., Sierra, J., Vindel, E., 1990. A fluid-inclusion study and genetic model of wolframite-bearing quartz veins, Garganta de los Montes, Spanish central system. Mineralogical Magazine 54, 267–278. Ramboz, C., Pichavant, M., Weisbrod, A., 1982. Fluid immiscibility in natural processes: Use and misuse of fluid inclusion data: II. Interpretation of fluid inclusion data interms of immiscibility. Chemical Geology 37, 29–48. Redmond, P. B., Einaudi, M. T., Inan, E. E., Landtwing, M. R., Heinrich, C. A., 2004. Copper deposition by fluid cooling in intrusion-centered systems: new insights from the Bingham porphyry ore deposit, Utah. Geology 32, 217–220. Ren, Y. C., Cheng, M. Q., Wang, C. C., 1986. Characteristics and vertical zoning of tungsten-bismuth minerals in the Pangushan quartz-vein type tungsten deposit of Jiangxi Province. Mineral Deposits, 5, 63–74 (in Chinese with English abstract). RGNTD. (Research Group for Nanling Tungsten Deposits, Chinese Ministry of Metallurgy), 1985. Tungsten Deposits in South China. Publishing House of Metallurgical Industry, Beijing, pp. 1–496 (in Chinese). Ridley, J. R., Diamond, L. W., 2000. Fluid chemistry of orogenic lode gold deposits and implications for genetic models. Reviews in Economic Geology 13, 141–162. Rios, F. J., Villas, R. N., Fuzikawa, K., 2003. Fluid evolution in the Pedra Preta wolframite ore deposit, Paleoproterozoic Musa granite, eastern Amazon craton, Brazil. Journal of South American Earth Sciences 15, 787–802. Roedder, E., Bodnar, R., 1980. Geologic pressure determinations from fluid inclusion studies. Annual Review of Earth and Planetary Sciences 8, 263–301. Roedder, E., 1984. Fluid inclusions. Reviews in Mineralogy 12, 1–644. Shelton, K. L., Taylor, R. P., So, C. S., 1987. Stable isotope studies of the Dae Hwa tungsten-molybdenum mine, Republic of Korea; evidence of progressive meteoric water interaction in a tungsten-bearing hydrothermal system. Economic Geology 82, 471–481. Shepherd, T. J., Waters, P., 1984. Fluid inclusion gas studies, Carrock Fell tungsten deposit, England: Implications for regional exploration. Mineralium Deposita 19, 304–314. Shu, L. S., Zhou, X. M., Deng, P., Yu, X. Q., 2006. Principal Geological Features of Nanling Tectonic Belt, South China. Geological Review 52, 251–265 (in Chinese with English abstract). So, C. S., Yun, S. T., 1994. Origin and evolution of W-Mo-producing fluids in a granitic hydrothermal system; geochemical studies of quartz vein deposits around the Susan Granite, Hwanggangri

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District, Republic of Korea. Economic Geology 89, 246–267. Sun, T., Zhou, X. M., Chen, P. R., Li, H. M., Zhou, H. Y., Wang, Z. C., Shen, W. Z., 2003. Genesis and tectonic significance of Mesozoic strong peraluminous granites in Eastern Nanling region. Science in China (Series D) 33, 1209–1218. Sushchevskaya, T. M., Bychkov, A. Y., 2010. Physicochemical mechanisms of cassiterite and wolframite precipitation in the granite-related hydrothermal system: thermodynamic modeling. Geochemistry International 48, 1246–1253. Tanelli, G., 1982. Geological setting, mineralogy and genesis of tungsten mineralization in Dayu district, Jiangxi (People's Republic of China): An outline. Mineralium Deposita 17, 279–294. Tan, Y. J., 1985. Geochemical types of vein wolframite deposits in Nanling region. Geochemistry 4, 236–244. Tang, P. Z., Wang, J., Zhou, Y. Y., 2016. Analysis of the present situation and development strategy of tungsten ore resources. China mining industry 25, 9–12 (in Chinese with English abstract). USGS., 2016. Mineral Commodity Summary. 1996–2016. Taylor, H. P., 1997. Oxygen and hydrogen isotope relationships in hydrothermal mineral deposits. Geochemistry of Hydrothermal Ore Deposits 3, 229–302. Wang, D. H., Li, H. Q., Qin, Y., Mei, Y. P., Cheng, Z. H., Qu, W. J., Wang, Y. B., Cai, H., Gong, S. Q., He, X. P., 2009. Study on the chronology of diagenesis and mineralization of Yaogangxian tungsten deposit in Hunan. Rock and Mineral Analysis 28, 201–208 (in Chinese with English abstract). Wang, D. Z., Shu, L. S., 2012. Late Mesozoic basin and range tectonics and related magmatism in Southeast China. Geoscience Frontiers 3, 109–124. Wang, G. G., Ni, P., Wang, R. C., Zhao, K. D., Chen, H., Ding, J. Y., Zhao, C., Cai, Y. T., 2013. Geological, fluid inclusion and isotopic studies of the Yinshan Cu–Au–Pb–Zn–Ag deposit, South China: Implications for ore genesis and exploration. Journal of Asian Earth Sciences 74, 343–360. Wang, Q, Y., Hu, R. Z., Peng, J. T., Bi, X. W., Wu, L. Y., Liu, H., Su, B. X., 2007. Characteristics and significance of the fluid inclusions from Yaogangxian tungsten deposit in south of Hunan. Acta Petrologica Sinica 23, 2263–2273 (in Chinese with English abstract). Wang, X. D., Ni, P., Zhang, B. S., Wang, T. G., 2010. Fluid inclusion studies of the Pangushan quartz-vein type tungsten deposit in Southern Jiangxi province. Acta Petrologica et Mineralogica 29, 539–550 (in Chinese with English abstract). Wang, X. D., Ni, P., Yuan, S. D., Wu, S. H., 2012. Fluid inclusion studies of the Huangsha quartz-vein type tungsten deposit, Jiangxi province. Acta Petrologica Sinica 28, 122–132 (in Chinese with English abstract). Wang, X. D., Ni, P., Yuan, S. D., Wu, S. H., 2013b. Fluid inclusion studies of Dajishan tungsten deposit in Jiangxi Province. Mineral Deposits 32, 308–322(in Chinese with English abstract). Wei, L. M., Lin, J. F., Li, W. Q., Wang, J. C., Zhu, W. F., 2008. Discussion on “five stored” super posed mode1 of Meiziwo tungsten deposit, Guangdong. Acta Geological Sinica 82, 888–893 (in Chinese with English abstract). Wei, S. L., Jia, B. H., Zeng, Q. W., 2006. Metallogenic mechanism of tungsten deposit in Nanling area. Resources Survey & Environment 27, 103–109 (in Chinese with English abstract). Wei, W. F., Hu, R. Z., Bi, X. W., Peng, J. T., Su, W. C., Song, S Q., Shi, S. H., 2012. Infrared microthermometric and stable isotopic study of fluid inclusions in wolframite at the Xihuashan tungsten deposit, Jiangxi province, China. Mineralium Deposita 47, 589–605. Wood, S. A., Samson, I. M., 2000. The hydrothermal geochemistry of tungsten in granitoid environments: I. Relative solubilities of ferberite and scheelite as a function of T, P, pH, and mNaCl Economic Geology 95, 143–182. Xu, K, Q., Liu, Y. J., Yu S Y., 1959. Types and distribution of Chinese tungsten mine. Journal of Nanjing University: Natural Science 2, 31–54 (in Chinese with English abstract). Xu, K. Q., Zhu, J. C., 1988. Time and space distribution of tin/tungsten deposits in South China and controlling factors of mineralization. In: Hutchison, C. S. (Ed.), Geology of Tin Deposits in Asia and the Pacific. Springer-Verlag, New York, pp. 265–277.

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Xu, Y. F., Ni, P., Wang, G. G., Pan, J. Y., Guan, S. J., Chen, H., 2016. Geology, fluid inclusion and stable isotope study of the Huangshan orogenic gold deposit: implications for future exploration along the Jiangshan-Shaoxing fault zone, South China. Journal of Geochemical Exploration 171, 37–54. Zhang, G. X., Xie, Y. N., Yu, F. J., Zhang, H. B., 1997., Stable Isotope Geochemistry of Distinct Metallogenic Stages of Tungsten Deposits in Dajishan Mine. Acta geoscientia sinica 18, 197–199 (in Chinese with English abstract). Zhang, L., 1988. Oxygen isotope studies of wolframite in tungsten ore deposits of South China. Acta Geochimica 7, 109–119(in Chinese with English abstract). Zhang, L. G., Liu, J., Chen, Z., Zhou, H., 1994. Experimental investigations of oxygen isotope fractionation in cassiterite and wolframite. Economic Geology 89, 150–157. Zhang, W. L., Wang, R. C., Lei, Z. H., 2011.The found of containing scheelite Penggongmiao Caledonian aplite in southern Hunan. China Science Bulletin 56, 1448–1454. Zhao, J. H., Zhou, M. F., Yan, D. P., Zheng, J. P., Li, J. W., 2011. Reappraisal of the ages of Neoproterozoic strata in South China: no connection with the Grenvillian orogeny. Geology 39, 299–302. Zheng, Y. F., Wu, R. X., Wu, Y. B., Zhang, S. B., Yuan, H., Wu, F. Y., 2008. Rift melting of juvenile arc-derived crust: geochemical evidence from Neoproterozoic volcanic and granitic rocks in the Jiangnan Orogen, South China. Precambrian Research 163, 351–383. Zhou, M. F., Yan, D. P., Kennedy, A. K., Li, Y. Q., Ding, J., 2002. SHRIMP U-Pb zircon geochronological and geochemical evidence for Neoproterozoic arc-magmatism along the western margin of the Yangtze Block, South China. Earth and Planetary Science Letters 196, 51–67. Zhou, X. M., 2003. My thinking about granite geneses of South China. Geological Journal of China Universities 9, 556–565 (in Chinese with English abstract). Zhou, X. M., Sun, T., Shen, W. Z., Shu. L. S., Niu, Y. L., 2006. Petrogenesis of Mesozoic granitoids and volcanic rocks in South China: A response to tectonic evolution. Episodes 29, 26–33. Zhu, X. Y., Wang, Y. L., Cheng, X. Y., Tian, Y., Fu, Q. B., Li, S. T., 2015. Metallogenic system of Yaogangxian quartz vein type tungsten ore deposit in Hunan. Mineral deposit 34, 874–894. (in Chinese with English abstract). Zhu, X. Y., Wang, Y. L., Cheng, X. Y., Tian, Y., 2016. Geological and geochemical characteristics of xenoliths in Yaogangxian granite, Hunan Province. Acta Petrologica et Mineralogica 35, 16–32 (in Chinese with English abstract).

ACCEPTED MANUSCRIPT Figure Captions Figure 1. (A) Location of the Central Nanling in the South China Block. (B) Sketch map of Central Nanling and spatial distribution of the main tungsten and tin deposits in the

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region. (modified from Hu and Zhou, 2012 and Mao et al., 2007).

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Figure 2. Simplified geological map of the Yaogangxian tungsten deposit (modified after Hunan Yaogangxian Mining CO., LTD, unpublished report; location is indicated in Fig.

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1B).

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Figure 3. Cross sections along the main prospecting line in Yaogangxian deposit, showing

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the spatial relationship between veins and granite (modified after Hunan Yaogangxian

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Mining CO., LTD, unpublished report; location is indicated in Fig. 2).

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Figure 4. Photographs showing mineralization and ore textures in Yaogangxian tungsten deposit. (A) Wolframite is intergrown with cassiterite commonly along vein edges; (B)

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The typical rich wolframite branch vein from stage 1 wolframite−cassiterite−quartz veins; (C) Stage 2 sulfide−quartz veins cutting the stage 1 wolframite−cassiterite−quartz veins; (D)

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wolframite−cassiterite−quartz veins; (E) Quartz crystals grew on the base of fully crystalized wolframite crystal; (F) Wolframite crystal shows an earlier paragenetic sequence than their intimately coexisting quartz; (G) Mineralized hand-specimen sample

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Qtz–quartz, Py–pyrite, Ccp–chalcopyrite, Apy–arsenopyrite, Cal–calcite, Flu–fluorite.

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Figure 5. Paragenetic sequence of minerals in the Yaogangxian tungsten Deposit.

Figure 6. Photomicrographs showing characteristics of different types of fluid inclusions

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in wolframite from Yaogangxian tungsten Deposit. (A) Distribution of different type fluid

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inclusions in a wolframite tabular crystal; (B) and (G) Secondary type LW inclusions are

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always distributed along healed trans-granular fractures in wolframite; (C) and (D) Primary type LW inclusions distribute in wolframite growth planes, showing irregular

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features and long-prismatic; (E) Primary type Lw plate-prismatic (negative-crystal) fluid

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inclusions in the wolframite crystal; (F) Primary type CBw inclusions distribute along

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crystal growth plane; (H) and (J) Primary type Lw fluid inclusions in wolframite of massive wolframite−cassiterite−quartz vein; (G) and (K) Secondary type LW inclusions in wolframite of massive wolframite−cassiterite−quartz vein; (L) Wolframite crystal from massive wolframite−cassiterite−quartz vein; Abbreviations: L–aqueous liquid phase; V–aqueous vapor phase; VCO2–CO2 vapor phase.

Figure 7. Photomicrographs showing characteristics of different types of fluid inclusions

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immiscibility fluid inclusions assemblage in stage 1 wolframite−cassiterite−quartz veins;

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(E) Type LQ inclusions in quartz from stage 2 sulfide−quartz veins; (F) Type LF fluid

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inclusions in fluorite from stage 3 fluorite−carbonate−quartz veins. Abbreviations:

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vapor phase.

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Figure 8. Photomicographs showing the phase changes of primary type CBW inclusion

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during the microthermometric cooling and heating process. (A) The inclusion is frozen at −120°C; (B) The ice in the liquid is melting at −6°C; (C) The clathrate causes the bubble

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to deform at 1°C; (D) Bubble is returning to the original state at 7°C; (E) The bubble has

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completely returned to its original state; (F) The bubble is getting smaller at 150°C.

Figure 9. (A)and(B) Histograms of homogenization temperatures (Th) and salinities for primary type Lw, primary type CBw and secondary type Lw inclusions in wolframite from stage 1 wolframite−cassiterite−quartz veins; (C) and (D) Histograms of homogenization temperatures (Th) and salinities for primary type LQ and CQ inclusions in quartz from stage 1 wolframite−cassiterite−quartz veins.

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inclusions in quartz from stage 2 sulfide-quartz veins; (E) and (F) Histograms of

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homogenization temperatures (Th) and salinities for type LF inclusions in fluorite from

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stage 3 fluorite-carbonate-quartz veins.

Figure 11. Raman spectra of fluid inclusions in quartz from Yaogangxian tungsten

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deposit. (A) H2O spectrum of vapor in type LQ inclusions from stage 1

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wolframite−cassiterite−quartz veins; (B) CO2, CH4 spectrum of vapor in type CQ

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inclusions from stage 1 wolframite−cassiterite−quartz veins; (C) H2O，CO2 spectrum of vapor in type CBQ inclusions from stage 1 wolframite−cassiterite−quartz veins; (D) H2O

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spectrum of vapor in type LQ inclusions from stage 2 sulfide-quartz veins.

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Figure 12. Temperature-salinity diagram for typical inclusions in wolframite, quartz and fluorite of the Yaogangxian tungsten deposit.

Figure 13. δD and δ18O values of the fluids from the Yaogangxian tungsten deposit. Also shown in boxes are the isotopic fields for common metamorphic and magmatic waters.

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Table Captions Table.1. Microthermometric data of fluid inclusions in the Yaogangxian tungsten deposit.

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TmCO2: melting temperature of the carbonic phase; Tmice: temperature of final ice melting;

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Tmclath: melting temperature of the CO2 clathrate; ThCO2: partial homogenization

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temperature of carbonic inclusion and the mode of homogenization (L: Liquid; V: Vapor;

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Ch: Critical homogenization); Thtotal: temperature of total homogenization and mode (L: Liquid; C: CO2); (N): number of measured fluid inclusions.

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All temperatures in °C. Salinity expressed as wt. % NaCl equiv.

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Table 2 Oxygen and hydrogen isotopes for quartz from wolframite−cassiterite−quartz

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tungsten deposit.

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veins, sulfide−quartz veins and fluorite−carbonate−quartz veins in the Yaogangxian

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Figure 9

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Figure 10

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Figure 11

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Figure 12

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Figure 13

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Stage

FI types (N)

Origin

Size (μm)

V（CO2）%

1

Lw（97）

P

10 to 75

20 to 40

1

CBw（5）

P

8 to 25

25 to 35

1

Lw（28）

S

5 to 15

10 to 25

−0.8 to −3.5

1

LQ（45）

P

5 to 45

25 to 35

−2.5 to −4.6

1

CQ（20）

P

10 to 55

70 to 95

2

LQ（29）

P

7 to 23

10 to 20

−1.2 to −3.5

3

LF（28）

P

5 to 13

5 to 15

−0.6 to −1.7

TmCO2 (°C )

Tm ice (°C )

Tmclath (°C )

−1.3 to −4.8

T P

8.1 to 8.6

8.6 to 9.9

-56.6 to -59

ice:

I R

28.5 to 30.7 (L / V/ Ch)

C S

U N

Table 1 Microthermometric data of fluid inclusions in the Yaogangxian tungsten deposit. TmCO2: melting temperature of the carbonic phase; Tm

ThCO2 (°C ) (Mode)

Thtotal (°C ) (Mode)

Salinity (wt. %)

280 to 360 (L)

2.2 to 7.6

321 to 355 (L)

2.8 to 3.6

204 to 256 (L)

1.4 to 5.7

244 to 308 (L)

4.2 to7.3

276 to 317 (C)

0.2 to 2.8

219 to 276 (L)

2.1 to 5.7

183 to 205 (L)

1.1 to 3.0

temperature of final ice melting; Tmclath: melting temperature of the CO2 clathrate; ThCO2: partial homogenization

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temperature of carbonic inclusion and the mode of homogenization (L: Liquid; V: Vapor; Ch: Critical homogenization); Thtotal: temperature of total homogenization and mode (L: Liquid; C: CO2); (N): number of measured fluid inclusions.

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T P

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Sample No.

Vein descriptions

Minerals

δDfluid‰

18

OV-SMOW‰

Th(°C)

δ18OH2O‰

Wolframite-cassiterite-quartz veins

Wolframite

−65

2.6

330

﹢4.7

ygx29

Wolframite-cassiterite-quartz veins

Wolframite

−50

2.9

330

﹢5.0

ygx141

Wolframite-cassiterite-quartz veins

Wolframite

−45

5.2

340

﹢7.4

ygx35

Wolframite-cassiterite-quartz veins

Wolframite

−67

4.7

340

﹢7.0

ygx32-1

Wolframite-cassiterite-quartz veins

Wolframite

−49

5.4

340

﹢7.6

ygx16

Wolframite-cassiterite-quartz veins

Quart

−56

17.6

250

﹢8.5

ygx29-1

Wolframite-cassiterite-quartz veins

Quart

−56

14.4

270

﹢6.2

ygx141-1

Wolframite-cassiterite-quartz veins

Quart

−59

11.9

270

﹢3.7

−62

Wolframite-cassiterite-quartz veins

Quart

16.4

260

﹢7.7

Wolframite-cassiterite-quartz veins

Quart

−64

12.8

270

﹢4.6

ygx717

Sulfide-quartz veins

Quart

−76

12.6

220

﹢2.1

ygx241

Sulfide-quartz veins

Quart

-70

13.6

225

﹢3.1

ygx243

Sulfide-quartz veins

Quart

-66

13.7

225

﹢2.3

ygx242

Sulfide-quartz veins

Quart

-67

13.2

225

﹢2.7

ygx744

Fluorite-carbonate-quartz veins

Quart

-73

11.5

185

﹣1.2

ygx18

Fluorite-carbonate-quartz veins

Quart

-64

12.7

185

﹣0.3

ygx60

Fluorite-carbonate-quartz veins

Quart

-65

13

185

﹢0.2

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ygx10 ygx32-1

CR

IP

T

ygx21

ED

Table 2 Oxygen and hydrogen isotopes for quartz from wolframite-cassiterite-quartz veins, sulfide-quartz veins and

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CE

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fluorite-carbonate-quartz veins in the Yaogangxian tungsten deposit.

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Highlights

1. CO2-bearing fluid inclusions are reported in wolframite.

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2. Wolframite was precipitated earlier than most of the coexisting quartz.

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3. Wolframite was formed by simple cooling of CO2-poor, H2O-dominated fluid.

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4. Secondary inclusions in wolframite record late-stage fluids.

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5. The study of fluid inclusion provides target areas for mineral exploration.