Trace elements mineral chemistry of sulfides from the Woxi Au‐Sb‐W deposit, southern China

Abstract

The Woxi Au‐Sb‐W deposit is one of the largest polymetallic ore deposits in the Xuefengshan Range, southern China, hosted in low‐grade metamorphosed Neoproterozoic volcaniclastic rocks. The orebodies of the deposit are predominantly composed of banded quartz veins, which are strictly controlled by bedding and faults. Petrographic observations and geochemical results are reported on the occurrence of Au and properties of the ore‐forming processes for different stages in the deposit. The veins extend vertically up to 2 km without obvious vertical metal zoning. The ore‐forming process can be subdivided into four mineralization stages: Pre‐ore stage; Early stage (scheelite‐quartz stage); Middle stage (pyrite‐stibnite‐quartz stage); and Late stage (stibnite‐quartz sage). Four types of pyrite (Py0, Py1, Py2, and Py3) were identified in the ores and host‐rock: Py0 occurs as euhedral grains with voids in the core, ranging in size from 50 to 100 μm and formed mainly in the Pre‐ore stage and Early stage; Py1 occurs as subhedral grains. Small grains (around 10 μm) of Py1 form irregularly shaped clusters of variable size ranging from tens to hundreds of μm and mainly formed in the Middle stage; Euhedral‐subhedral fine‐grained Py2 formed in the Late stage; Minor subhedral fine‐grained Py3 was deposited in the Late‐stage. Stibnite is widely distributed in the Middle and Late stage ore veins. No systemic difference was recognized in mineralogical features among stibnite formed in different stages. In addition to native gold, the lattice bound Au+1 widely exists in Py1 and Py2 in the deposit, and widespread Py1 is considered as the main Au‐bearing mineral with the highest Au contents. Most elements (such as Co, Ni, Cu, As, Sb, Ba, and Pb) are considered to occur as solid solution within the crystal lattice and/or invisible nanoparticles in sulfides minerals. The Co/Ni ratio of most pyrite is lower than 1, suggesting that the metals in the ore‐forming fluid are sourced from sedimentary rocks. The coupled behavior between Au and As; Au and Sb suggests that the substitution of As and Sb in pyrite can enhance the incorporation of Au. Variation of trace elements in pyrites of different stages suggests some information on the mineralization processes: Large ion lithophile elements (such as Ba and Pb) are enriched in Py0 indicating that water‐rock reaction occurred in the Early stage; Fine‐grained Py1 with a heterogeneous distribution of elements suggests fast crystallization of pyrite in the Middle stage.

Primary source of placer gold in the Luk Ulo Metamorphic Complex, Central Java, Indonesia

“…However, Iftiqar et al (2017) reported the occurrence of native gold inclusions in pyrite from the quartz‐carbonate veins found in the Loning River, Karangsambung area. High contents of minor and trace elements such as As, Pb, Cu, Sb, Au, and Ag in hydrothermal pyrite are common feature for sediment‐hosted or orogenic gold‐type mineralization, in which these metals occur as either solid solution in crystal lattice or nano particle inclusions (e.g., Large et al, 2011; Zhou et al, 2022). Theoretically, Au content of pyrite is constrained by As content (Reich et al, 2005).…”

A Fluid Inclusion and Critical/Rare Metal Study of Epithermal Quartz-Stibnite Veins Associated with the Gerakario Porphyry Deposit, Northern Greece

“…The acquisition dwell time was set to 0.02 s for 74 Ge, 82 Se, 115 In, 125 Te, and 202 Hg, to 0.03 s for 107 Ag, to 0.04 s for 197 Au, and to 0.01 s for all other elements. The monitored isotopes include: 27 Al, 31 P, 34 S, 49 Ti, 51 V, 53 Cr, 55 Mn, 57 Fe, 59 Co, 60 Ni, 65 Cu, 66 Zn, 71 Ga, 73 Ge, 74 Ge, 75 As, 77 Se, 93 Nb, 95 Mo, 107 Ag, 111 Cd, 115 In, 118 Sn, 121 Sb, 125 Te, 139 La, 140 Ce, 146 Nd, 147 Sm, 157 Gd, 182 W, 1 85 Re, 197 Au, 202 Hg, 205 Tl, 208 Pb, 209 Bi, 232 Th, and 238 U. The targeted areas in the polished sections were predefined to try and avoid mineral inclusions.…”

“…In addition, the depletion of Au +1 as solid solutions in stibnite and the presence of native gold in interstices of the quartz-stibnite veins [45] indicate that Au precipitation slightly followed Sb precipitation. Thus, it could be suggested that the precipitation of massive stibnite depleted the H 2 S content of the mineralizing fluids, and enhanced the precipitation of native gold (Au 0 ) in the quartz-epithermal veins [65].…”

North-South Differences of Xuefeng Mountain Metallogenic Belt and Fluid Inclusion and Isotope Evidences of Ore-Forming Hydrothermal Solution Source

“…For many typical deposits, such as Bake Gold Deposit, Pingqiu Gold Deposit, Mobin Gold Deposit, Zhazixi Antimony Tungsten Deposit, Woxi Gold Antimony Tungsten Deposit, and Longshan Gold Antimony Tungsten Deposit, many researchers have carried out tracer study of the source of gold, antimony, tungsten ore-forming minerals and hydrothermal solution using geochemical methods, such as trace elements, rare earth elements, S isotopes, Pb isotopes, H-O-C isotopes, and Sr isotopes, and formed different views accordingly. In terms of the source of ore-forming materials, Liu et al believed that the gold and antimony ore-forming materials came from the ore-hosting strata [6][7][8]; Peng et al believed that the gold deposits may come from the deep strata, instead of the ore-hosting strata [9,10]; Yang et al [11] believed that the ore-forming materials of large-scale deposits, such as Woxi, Zhazixi, and Longshan, came from the ore-hosting strata, deep strata and even katathermal solution. In terms of the ore-forming hydrothermal solution source, Gu [12] believed through rockwater interaction simulation experiments that the ore-forming hydrothermal solution of gold deposits in southwestern Hunan was groundwater heated by magmatic rocks and tectonic forces; Gu et al [13] believed that the ore-forming hydrothermal solution of the Woxi Gold Antimony Tungsten Deposit was mainly seawater, after studying the geology and fluid inclusions of the deposit and the geochemical characteristics of trace and rare earth elements; Zhu et al [14] studied the noble gas isotopes of fluid inclusions using the laser Raman spectrometry, and the research results showed that the ore-forming hydrothermal solution of the Woxi Gold Antimony Tungsten Deposit was mainly deep hydrothermal solution, mixed with a small amount of atmospheric precipitation or groundwater; Zeng et al [15] believed that the ore-forming hydrothermal solution of the Zhazixi Antimony Tungsten Deposit was a mixture of metamorphic and magmatic water after the isotope tracer study of H, O, and S; Liu [16] studied C, H, O, He-Ar, S and Pb of gold deposits in the Jiangnan orogenic belt, and the research results showed that the ore-forming hydrothermal solution mainly came from metamorphic and/or magmatic water, and also mantle fluids in the late ore-forming stage.…”