新疆西天山阿尔恰勒铅锌铜矿床磁铁矿、黑柱石成因及地质意义OA

[Objective]The Arqiale Pb-Zn-Cu deposit is situated on the southwestern margin of the Yishijilik metallogenic belt in the western Tianshan Orogen,Xinjiang,northwestern China.The ore bodies occur as stratiform-stratoid bodies within limestone of the Lower Carboniferous Akshak Formation.No ore-related intrusive bodies have been identified in surface exposures or drill cores in the mining area.Two competing genetic models,i.e.,sedimentary exhalative(SEDEX)and distal skarn-type origins,have long been proposed for this deposit.The genetic link between mineralization and magmatism remains unclear,restricting exploration targeting at depth and along the periphery of the deposit.This work aims to resolve this genetic controversy by elucidating mineral-forming mechanisms,constraining ore-forming physicochemical conditions,and determining deposit genesis,providing mineralogical evidence for regional prospecting.[Methods]Two generations of magnetite(granular and radial aggregates)and abundant ilvaite in the skarn ores were selected for integrated research.Systematic petrographic observations were conducted using transmitted-and reflected-light microscopy,and the major-element compositions of magnetite and ilvaite were determined by electron probe microanalysis(EPMA).Multiple geochemical thermometers,including the Al+Mn-Ti+V discrimination diagram and Mg-in-magnetite geothermometer,were applied to estimate ore-formation temperatures,and major-element ratios in ilvaite were used to evaluate the redox state of ore-forming fluids.[Results]Both granular and radial magnetite showed geochemical signatures typical of hydrothermal skarn magnetite,characterized by low Ti and V contents and elevated Al and Mn concentrations.The Al+Mn-Ti+V diagram yielded mineralization temperatures ranging from 200 to 300℃,whereas the Mg-in-magnetite geothermometer showed average temperatures of 381-392℃,collectively indicating a moderate-to low-temperature hydrothermal mineralization environment.Ilvaite in the ores was classified as a manganiferous ilvaite variety characterized by low Fe2+and high Mn2+.Its TFeO/(TFeO+MnO)ratios varied from 0.86 to 0.93,indicating relatively oxidizing conditions of ore-forming fluids.Petrographic observations revealed well-developed skarn mineral assemblages of garnet-hedenbergite-ilvaite-actinolite and pervasive metasomatic ore textures.A distinct vertical metal-zoning pattern was recognized.Shallow levels were dominated by Pb-Zn mineralization,whereas Cu-dominated mineralization prevailed at deeper parts.[Conclusion]Integrated mineralogical and geochemical evidence indicates that the Arqiale deposit is a distal skarn-type Pb-Zn-Cu deposit genetically linked to concealed intermediate-acid intrusions at depth.The metasomatic textures and skarn paragenesis contradict the typical features of SEDEX deposits.According to the observed metal zonation,the deep northern part of the mining area possesses favorable prospecting potential for concealed contact-zone Fe-Cu ore bodies related to hidden magmatic intrusions.