Antimony isotope fractionation in stibnite – constraints from δ123Sb values and infrared microthermometric data of stibnite-hosted fluid inclusions“Antifrac”

锑(Sb)是一种“关键”元素。作为辉锑矿(Sb2S3)，Sb高度集中在不同类型的矿床中：-低硫化浅成热液脉型-温泉矿床，一些斑岩和钼-部分造山金或沉积-卡林型金矿-沉积物-热液石英-辉锑矿脉-一些Sedex类型-或大量交代碳酸盐交代在一些矿床中，辉锑矿的矿化还与相当多的金、汞、银、锡、钨或贱金属(例如，Gumiel和Arrias 1987；Dill 1998；Peng等)有关。2002年；瓦格纳和博伊斯2003年；哈格曼和L 2003年；杨等人。2006年；Buchholz等人。2007年；Bortnikov等人。2010年；Voudouris等人。2019年；Pohl，2020)。热液矿床中Sb的来源(S)往往没有得到很好的约束，仍然是一个有争议的问题。S结壳中Sb的平均丰度为0.2ppm(Taylor和McLennan，1995年)。据报道，黑色页岩中的Sb平均浓度较高，约为5ppm(Ketris和Yudovich，2009年)，因此，黑色页岩的蚀变可能构成热液石英-辉锑矿中Sb的潜在来源(例如，Wagner和Boyes，2003年，SośNicka等人)。2021年)。辉锑矿也与长英质岩浆岩有关。在这种情况下，并不总是清楚Sb的富集度是否与岩浆流体或热液蚀变作用直接相关(Krolop等人。2018年)。以往对辉锑矿同位素组成的研究表明，不同产状的辉锑矿中的~(123)Sb/~(121)Sb比值可能为解释辉锑矿矿床的来源(S)提供了一种手段(翟某等)。2021年及其参考文献)。然而，到目前为止，大多数关于Sb同位素分馏的结论是基于观察到的某些δ123Sb值在矿床或矿石类型内的移动，以及关于Sb(III)Sb(V)氧化还原反应的实验数据(例如Lobo等人)。2012年；Dillis等人。2019年)。Sb(III)在高温热液流体中的迁移依赖于流体中的ph值和硫化物浓度，并以HS-或OH-络合物的形式发生(例如，Krupp 1988；Olsen等人。2019年)，而氯化锑络合物仅在强盐酸性流体中稳定(例如Obolensky等人)。2007)。然而，在不同温度下从卤水或低盐度流体中沉淀出来的辉辉石中Sb同位素分馏的相关性至今还没有得到研究。由于辉锑矿在近红外光下表现出极好的透明度(L 2017年)，可以在使用红外显微测温时常规研究辉锑矿中的流体包裹体，从而获得有关辉锑矿形成流体的T-x的信息。结合辉锑矿流体包裹体的显微测温资料，对所选矿床中辉锑矿的Sb同位素体系进行详细的研究，将为Sb同位素体系在矿床研究中的适用性提供新的见解。

Antimony (Sb) is a “critical” element. As Stibnite (Sb2S3), Sb is highly concentrated in different types of deposits: - Low-sulfidation epithermal vein-type - hot spring deposits, some porphyry and molybdenum - parts of orogenic gold or sediment-hosted Carlin-type gold - sediment-hosted hydrothermal quartz-stibnite veins - some SEDEX-type - or massive metasomatic carbonate replacement In some deposits, stibnite mineralization is also associated with considerable concentrations of gold, mercury, silver, tin, tungsten, or base metals (e.g., Gumiel and Arribas 1987; Dill 1998; Peng et al. 2002; Wagner and Boyce 2003; Hagemann and Lüders 2003; Yang et al. 2006; Buchholz et al. 2007; Bortnikov et al. 2010; Voudouris et al. 2019; Pohl, 2020). The source(s) of Sb in hydrothermal ore deposits are often not well constrained and still a matter of debate. The average abundance of Sb in the Earth´s crust is 0.2 ppm (Taylor and McLennan 1995). Higher average Sb concentrations of about 5 ppm are reported from black shales (Ketris and Yudovich 2009) and thus, alteration of black shales may constitute a potential source for Sb in hydrothermal quartz-stibnite deposits (e.g. Wagner and Boyes 2003, Sośnicka et al. 2021). Stibnite deposits are also associated with felsic magmatic rocks. In this case is not always clear whether Sb enrichment is directly related to magmatic fluids or hydrothermal alteration processes (Krolop et al. 2018). Previous studies of isotope compositions of stibnite have shown that the 123Sb/121Sb ratios in stibnite from various occurrences may provide a means to decipher the source(s) of stibnite deposits (Zhai et al. 2021 and references therein). However, most of the conclusions about Sb isotope fractionation that are drawn so far are based on observed shifts of some δ123Sb values within a deposit or ore types, and experimentally data on Sb(III) Sb(V) redox reactions (e.g. Lobo et al. 2012; Dillis et al. 2019). The transport of Sb (III) in hydrothermal fluids at high temperatures is dependent on ph and the sulfide concentration in the fluid and occurs in from of HS- or OH- complexes (e.g. Krupp 1988; Olsen et al. 2019) whilst Sb chloride complexes are only stable in strong saline acidic fluids (e.g. Obolensky et al. 2007). However, the dependence of Sb isotope fractionation in stibnites that precipitated from either brines or low-salinity fluids at different temperatures has not been studied so far. Since stibnite shows extremely good transparency in near IR light (Lüders 2017) fluid inclusions hosted in stibnite can be studied routinely when using IR microthermometry and information about T-x of the stibnite-forming fluids can be obtained. Studying Sb isotopic systematics in stibnite in detail in selected ore deposits in combination with microthermometric data of stibnite-hosted fluid inclusions will provide new insights for the applicability of the Sb isotope system for questions related to ore deposit research.