Elsevier

Chemical Geology

Volume 607, 30 September 2022, 121020
Chemical Geology

A general ore formation model for metasediment-hosted Sb-(Au-W) mineralization of the Woxi and Banxi deposits in South China

https://doi.org/10.1016/j.chemgeo.2022.121020Get rights and content

Highlights

  • Late-stage Sb mineralization received more metals and ligands from granitic magmatic than the early-stage Au mineralization.

  • Metasediment-hosted Sb-(Au-W) deposits possess similarities with both orogenic-type and intrusion-related gold systems.

  • A complex compound Au-W-Sb mineralization sequence was proposed in the Woxi and Banxi deposits.

Abstract

Metasediment-hosted Sb-(Au-W) deposits occur widely in the Jiangnan Orogen (South China), but their complicated metallogenic histories are still under debate. Ore formation models such as syngenetic (SEDEX), granitoid-related, and orogenic scenarios have been proposed by previous studies, but their metal provenance and fluid evolutionary processes are still uncertain. In this study, two typical Sb-(Au-W) deposits (Woxi and Banxi) from this region were studied by in-situ geochemical and geochronological analyses of sulfides to establish a general ore formation model for this type of deposit. Two stages of gold-related pyrite (Py1 and Py2) and one stage of stibnite in the Woxi Sb-(Au-W) deposit, and two stages of arsenopyrite (Apy1 and Apy2) and stibnite (Stb1 and Stb2) in the Banxi Sb deposit were differentiated. Compared to Py1, Py2 is depleted in V but enriched in Au, As, Bi, Pb and Ag, with more negative δ34Sv-CDT and lower Pb isotopic values. Compared with stibnite at Woxi, stibnite at Banxi has higher but more variable contents of most trace elements (e.g., Li, Mg, Al, Si, Cu, Pb, Co, Ni, Fe, Sr and Mn, except for As) and lower Pb isotopic ratios. At Banxi, Stb2 has lower Fe, Cu, Pb, Co, Ni, Sr and Mn contents than Stb1, and Apy2 has higher Co, Ni, Zr, Ti, and Nb contents than Apy1. Analyses of Re-Os isotopes in four samples yielded an isochron age of 439 ± 3.4 Ma (2σ) for Apy1, with an initial 187Os/188Os of 0.3373 ± 0.0009. The above results indicate that early-stage Au mineralization at Woxi may have been orogeny-related, and that ore metals were derived mainly from local epimetamorphic sedimentary rocks with limited input from magmatic fluids. In contrast, the late-stage Sb mineralization at Banxi may have been influenced by deep granitic magmatism. We propose that the common temporal and spatial mineralization sequence of the metasediment-hosted Sb-(Au-W) ores is: orogenic-type gold (early stage; at deep levels of the ore field) → orogenic + magmatic-hydrothermal W (middle stage; at middle levels) → magmatic-hydrothermal + meteoric water Sb (late stage; at shallow levels). Both local metasedimentary rocks and granite magmatism provide metals and ligands for mineralization, with magmatic fluids playing an essential role in late-stage ore formation. Metasediment-hosted Sb-(Au-W) ores in this region exhibit similarities to both orogenic-type and intrusion-related gold systems.

Introduction

Metasedimentary rock-hosted (= “metasediment-hosted”) Sb-(Au-W) ores occur widely, e.g., in the Tombstone gold belt of Canada (Mair et al., 2006), the La Belliere district of the French Armorican Massif (Cheval-Garabédian et al., 2020), the Western Lachlan Orogen of southeastern Australia (Voisey et al., 2019), Caledonian shear zones in Greenland (Kolb et al., 2016; Steenfelt et al., 2016), West Qinling of North China (Liu et al., 2015; Qiu et al., 2020), the Yellow Pine district of central Idaho (Stewart et al., 2017; Winzter, 2019), and the Jiangnan Orogen of South China (Fig. 1; Gu et al., 2012; Li et al., 2018, Li et al., 2019a). These deposits represent huge Sb, Au, W and Ag resources that have attracted much attention from economic geologists (Neiva et al., 2008; Kontak and Kyser, 2011; MacKenzie et al., 2015; Zhou et al., 2018). However, the metallogenic histories of these metasediment-hosted Sb-(Au-W) deposits are still controversial, with debate centering on their metal and ligand sources (sediment-derived vs. intrusion-originated; Pitcairn et al., 2015; Fusswinkel et al., 2017; Rice et al., 2018; Jia et al., 2019), metallogenic mechanisms (orogenic vs. anorogenic; MacKenzie et al., 2007; Li et al., 2014a; Zhu and Peng, 2015; Lee et al., 2019), fluid compositions and evolution (magmatic fluid, metamorphic water vs. basinal brine; Couto and Roger, 2017; Adomako-Ansah et al., 2018; Krolop et al., 2019; Qiu et al., 2020), and ore emplacement history (single stage vs. multi-stage; Konyshev, 2020; Li et al., 2019a, Li et al., 2020a, Li et al., 2020b, Li et al., 2020c). Thus, a systematic study of such deposits would be helpful in gaining new insights into the origin of metasediment-hosted Sb-(Au-W) ores.

The Xuefeng Mountains in the Jiangnan Orogen (South China) contain >100 Sb-(Au-W) deposits with total proven metal reserves of 1.67 Mt. Sb @ 6%, >100 t Au @ 5–10 g/t, and 0.25 Mt. WO3 @ 0.2–0.8% (Fig. 2; Gu et al., 2007; Li et al., 2018). The main point of controversy concerning the genesis of Sb-(Au-W) deposits in the Xuefeng Mountains is whether they are granite intrusion-related or not (Peng and Frei, 2004; Peng, 2006; Gu et al., 2012; Liang et al., 2015; Zhu and Peng, 2015; Li et al., 2018). Sb-(Au-W) mineralization in the Xuefeng Mountains mainly occurred during three periods: ~420 Ma, ~220 Ma, and ~ 130 Ma (Peng et al., 2003; Wang et al., 2012; Li et al., 2018; Li et al., 2020a, Li et al., 2020b, Li et al., 2020c). Similarly, granitic intrusions were also emplaced in and around the Xuefeng Mountains during three periods: 450–420 Ma, 240–220 Ma, and 160–140 Ma (Fig. 2; Wang et al., 2007b; Xu et al., 2014; Li et al., 2014b; Fu et al., 2015; Kong et al., 2021). However, within the study area, granitic rocks are rarely exposed. Thus, the link between granitic magmatism and Sb-(Au-W) mineralization is still uncertain.

The Upper Silurian to Lower Cretaceous Woxi and Banxi deposits in northwestern Hunan Province (Xuefeng Mountains), South China (Fig. 1) are representative metasediment-hosted Sb-(Au-W) deposits. The Woxi and Banxi deposits share many similarities with regard to orebody setting, host rock lithology, ore mineralogy and geochemistry, and history. These two deposits are hosted by metasedimentary rocks (mainly schist, slate, marble, quartzite, and conglomerate), occur dominantly as quartz vein-type mineralization, contain stibnite, native gold, scheelite, pyrite, arsenopyrite, and quartz as major ore and gangue minerals, and exhibit several stages of mineralization that coincided with local tectonic and magmatic events (Peng et al., 2003; Peng and Frei, 2004; Li et al., 2018; Fu et al., 2020b). These similarities provide an excellent opportunity to study the ore genesis and metallogeny of Sb-(Au-W) deposits on a comparative basis. Though some geochemical and geochronological studies have been carried out for these two deposits, the following issues still need to be resolved: 1) The precise metallogenic age. Previous scheelite Sm-Nd and quartz Ar-Ar dating have constrained the mineralization age at Woxi to 420–402 Ma (Peng et al., 2003), but it is not clear whether this stage of metallogenesis occurred in the Banxi deposit. 2) The ore formation model. Previous studies have proposed several models to explain the genesis of Sb-(Au-W) mineralization for these two deposits, such as syngenetic (SEDEX) (Gu et al., 2007, Gu et al., 2012), Mesozoic granitoid-related (Peng and Frei, 2004; Li et al., 2018), and orogenic scenarios (Zhu and Peng, 2015), but the metal and ligand sources and fluid evolutionary processes are still uncertain, and the mineralization sequence in each deposit is under debate. Thus, a comprehensive study combining new geochronological and in situ beam geochemical analysis is urgently needed.

This paper presents original in-situ major- and trace-element concentration, S-Pb isotope, and Re-Os geochronological data for stibnite, pyrite, and arsenopyrite from the Woxi and Banxi Sb-(Au-W) deposits, South China. The main research objectives of this work are 1) determining similarities and differences between the Banxi and Woxi deposits, 2) reconstructing their detailed metallogenetic histories, and 3) developing a general ore formation model for metasediment-hosted Sb-(Au-W) deposits.

Section snippets

Regional geology

The Woxi (28°27′45″-28°34′00”N, 110°48′30″-110°57′45″E) and Banxi (28°21′03″-28°22′14”N, 110°54′22″-111°56′19″E) Sb-(Au-W) deposits are located in northwestern Hunan Province, South China, within the Xuefeng Mountains (Fig. 1). These mountains are part of the larger Jiangnan Orogen, which marks the boundary between the Yangtze Block to the northwest and the Cathaysia Block to the southeast, recording the Early Neoproterozoic continent-arc-continent collision that formed the South China Craton (

Ore deposit geology

The Woxi Sb-Au-W deposit is located in the central part of the Xuefeng Mountains (Fig. 2). It contains significant Sb (220,000 t), Au (>50 t), and WO3 (25,000 t) reserves, with average grades of 2.84%, 9.8 g/t, and 0.3% for Sb, Au, and W, respectively (Zhu and Peng, 2015). The Banxi Sb deposit lies on the southeastern margin of the Jiangnan Orogenic Belt, a transitional region between the Xuefeng Mountains and the Xiangzhong Basin (Fig. 2). It possesses a total Sb metal reserve of up to

Sampling and methods

Representative ore samples of the major mineralization stages of the Woxi and Banxi deposits were collected in underground mine tunnels at several elevations (see Table 1 for detailed sample information). A part of each sample was prepared as a polished section, and the remaining part was used for mineral separation (i.e., stibnite, pyrite, and arsenopyrite).

Back-scattered electron (BSE) images were taken at State Key Laboratory of Geological Processes and Mineral Resources, China University of

BSE imaging

The BSE images of pyrite and stibnite from the Woxi deposit are shown in Fig. 11. It can be seen that both Py1 and Py2 possess core-rim textures: the core of Py1 is characterized by porous textures that are filled by quartz and feldspar (Fig. 11a, b), whereas the core of Py2 possesses an oscillatory zoning texture (Fig. 11d-e). The rims of both Py1 and Py2 are relatively clear and homogeneous in textures on the BSE images (Fig. 11a-f). Thus, the cores of Py1 and Py2 are noted as Py1a and Py2a,

Sources of ore metals and ligands

The concentrations and ratios of trace elements (such as Co and Ni) in pyrite have been used to determine the source of ore-forming fluids (Thomas et al., 2011; Large et al., 2013; Franchini et al., 2015; Adam et al., 2020). The Co/Ni ratio is widely used to reveal the genesis of pyrite and to reveal the source of ore metals. Pyrite with Co/Ni < 1 is considered to be of sedimentary origin, whereas pyrite with Co/Ni > 1 (especially between 1 and 5) is considered to be of magmatic-hydrothermal

Conclusions

Early-stage Au mineralization at Woxi may have been orogeny-related, and ore metals were derived mainly from local epimetamorphic sedimentary rocks with limited inputs from magmatic fluids. In contrast, late-stage Sb mineralization at Banxi may have received more ore metals and ligands from deep granitic magmatism.

The shift in mineralization from gold to stibnite at Woxi can be described as: Py1 + native gold + fluid (Au) (aq) → Py2 + Stb + Gn + Ccp + fluid (As3+, Sb3+, Pb2+, Cu2+) (aq). The Sb

Declaration of Competing Interest

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.

Acknowledgments

This research benefited from the financial support provided by the National Key Research and Development Plan (Grant No. 2018YFC0603902) and the Central South University (Grant No. 218059). Prof. Balz Kamber is thanked for efficient editorial handling. Two anonymous reviewers are also acknowledged for their careful reviews that resulted in an improved manuscript.

References (143)

  • T. Deng et al.

    Caledonian (early Paleozoic) veins overprinted by Yanshanian (late Mesozoic) gold mineralization in the Jiangnan Orogen: a case study on gold deposits in northeastern Hunan, South China

    Ore Geol. Rev.

    (2020)
  • M. Franchini et al.

    Trace metals in pyrite and marcasite from the Agua Rica porphyry-high sulfidation epithermal deposit, Catamarca, Argentina: Textural features and metal zoning at the porphyry to epithermal transition

    Ore Geol. Rev.

    (2015)
  • J. Fu et al.

    In situ sulfur isotopes (δ34S and δ33S) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by laser ablation MC-ICP-MS

    Anal. Chim. Acta

    (2016)
  • S. Fu et al.

    Trace element composition of stibnite: Substitution mechanism and implications for the genesis of Sb deposits in southern China

    Appl. Geochem.

    (2020)
  • S. Fu et al.

    Trace element chemistry of hydrothermal quartz and its genetic significance: a case study from the Xikuangshan and Woxi giant Sb deposits in southern China

    Ore Geol. Rev.

    (2020)
  • T. Fusswinkel et al.

    Fluid evolution of the Neoarchean Pampalo orogenic gold deposit (E Finland): Constraints from LA-ICPMS fluid inclusion microanalysis

    Chem. Geol.

    (2017)
  • X.X. Gu et al.

    Rare earth element geochemistry of the Woxi W-Sb–Au deposit, Hunan Province, South China

    Ore Geol. Rev.

    (2007)
  • X.X. Gu et al.

    The Woxi W–Sb–Au deposit in Hunan, South China: An example of Late Proterozoic sedimentary exhalative (SEDEX) mineralization

    J. Asian Earth Sci.

    (2012)
  • W. He et al.

    Deformation evolution of Eastern Sichuan–Xuefeng fold-thrust belt in South China: Insights from analogue modelling

    J. Struct. Geol.

    (2018)
  • Z. Hu et al.

    A “wire” signal smoothing device for laser ablation inductively coupled plasma mass spectrometry analysis

    Spectrochim. Acta Part B At. Spectrosc.

    (2012)
  • R. Hu et al.

    The giant South China Mesozoic low-temperature metallogenic domain: Reviews and a new geodynamic model

    J. Asian Earth Sci.

    (2017)
  • X.-W. Huang et al.

    Re-Os and S isotopic constraints on the origins of two mineralization events at the Tangdan sedimentary rock-hosted stratiform Cu deposit, SW China

    Chem. Geol.

    (2013)
  • S. Jia et al.

    Geology, fluid inclusions and isotope geochemistry of the Herenping gold deposit in the southern margin of the Yangtze Craton, China: a sediment-hosted reduced intrusion-related gold deposit?

    Ore Geol. Rev.

    (2019)
  • M. Keith et al.

    Pyrite chemistry: a new window into Au-Te ore-forming processes in alkaline epithermal districts, Cripple Creek, Colorado

    Geochim. Cosmochim. Acta

    (2020)
  • J. Kolb et al.

    Metallogeny of Greenland

    Ore Geol. Rev.

    (2016)
  • H. Kong et al.

    Early Paleozoic tectonic evolution of the South China Block: Constraints from geochemistry and geochronology of granitoids in Hunan Province

    Lithos

    (2021)
  • P. Krolop et al.

    Antimoniferous vein-type mineralization of the Berga Antiform, Eastern-Thuringia, Germany: a fluid inclusion study

    Chem. Geol.

    (2019)
  • R.R. Large et al.

    Trace element content of sedimentary pyrite as a new proxy for deep-time ocean–atmosphere evolution

    Earth Planet. Sci. Lett.

    (2014)
  • M. Lee et al.

    LA-ICP-MS trace element analysis of arsenopyrite from the Samgwang gold deposit, South Korea, and its genetic implications

    Ore Geol. Rev.

    (2019)
  • H. Li et al.

    Zircon morphology, geochronology and trace element geochemistry of the granites from the Huangshaping polymetallic deposit, South China: Implications for the magmatic evolution and mineralization processes

    Ore Geol. Rev.

    (2014)
  • H. Li et al.

    Geochemistry of A-type granites in the Huangshaping polymetallic deposit (South Hunan, China): Implications for granite evolution and associated mineralization

    J. Asian Earth Sci.

    (2014)
  • H. Li et al.

    Geochemistry and geochronology of the Banxi Sb deposit: Implications for fluid origin and the evolution of Sb mineralization in Central-Western Hunan, South China

    Gondwana Res.

    (2018)
  • H. Li et al.

    Genesis of the Banxi Sb deposit, South China: Constraints from wall-rock geochemistry, fluid inclusion microthermometry, Rb–Sr geochronology, and H–O–S isotopes

    Ore Geol. Rev.

    (2019)
  • H. Li et al.

    Ore-forming material sources of the Jurassic Cu–Pb–Zn mineralization in the Qin–Hang ore belt, South China: Constraints from S–Pb isotopes

    Geochemistry

    (2019)
  • H. Li et al.

    Geochronology and geochemistry of tuffaceous rocks from the Banxi Group: Implications for Neoproterozoic tectonic evolution of the southeastern Yangtze Block, South China

    J. Asian Earth Sci.

    (2019)
  • H. Li et al.

    Fluid-zircon interaction during low-temperature hydrothermal processes: Implications for the genesis of the Banxi antimony deposit, South China

    Ore Geol. Rev.

    (2019)
  • H. Li et al.

    Integrated U–Pb, Lu–Hf and (U–Th)/He analysis of zircon from the Banxi Sb deposit and its implications for the low-temperature mineralization in South China

    Geosci. Front.

    (2020)
  • H. Li et al.

    Fluid inclusion, H–O–S isotope and rare earth element constraints on the mineralization of the Dong’an Sb deposit, South China

    Ore Geol. Rev.

    (2020)
  • Y. Liu et al.

    In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard

    Chem. Geol.

    (2008)
  • L. Liu et al.

    Geometry and timing of Mesozoic deformation in the western part of the Xuefeng Tectonic Belt, South China: Implications for intra-continental deformation

    J. Asian Earth Sci.

    (2012)
  • J. Liu et al.

    Geological characteristics and ore-forming process of the gold deposits in the western Qinling region, China

    J. Asian Earth Sci.

    (2015)
  • J. Liu et al.

    Indium mineralization in the Xianghualing Sn-polymetallic orefield in southern Hunan, Southern China

    Minerals

    (2017)
  • Q. Liu et al.

    Insights into the genesis of orogenic gold deposits from the Zhengchong gold field, northeastern Hunan Province, China

    Ore Geol. Rev.

    (2019)
  • X. Lu et al.

    Temporal record of osmium concentrations and 187Os/188Os in organic-rich mudrocks: Implications for the osmium geochemical cycle and the use of osmium as a paleoceanographic tracer

    Geochim. Cosmochim. Acta

    (2017)
  • D.J. MacKenzie et al.

    Mineralogy, geochemistry, and structural controls of a disseminated gold-bearing alteration halo around the schist-hosted Bullendale orogenic gold deposit, New Zealand

    J. Geochem. Explor.

    (2007)
  • R. Mathur et al.

    Different crustal sources for Au-rich and Au-poor ores of the Grasberg Cu-Au porphyry deposit

    Earth Planet. Sci. Lett.

    (2000)
  • A.M.R. Neiva et al.

    Antimony quartz and antimony–gold quartz veins from northern Portugal

    Ore Geol. Rev.

    (2008)
  • P. Ni et al.

    An early Paleozoic orogenic gold belt along the Jiang−Shao Fault, South China: evidence from fluid inclusions and Rb–Sr dating of quartz in the Huangshan and Pingshui deposits

    J. Asian Earth Sci.

    (2015)
  • I.K. Pitcairn et al.

    Mobility of gold during metamorphism of the Dalradian in Scotland

    Lithos

    (2015)
  • L. Qiu et al.

    Mesozoic geology of southwestern China: Indosinian foreland overthrusting and subsequent deformation

    J. Asian Earth Sci.

    (2016)
  • Cited by (21)

    View all citing articles on Scopus
    View full text