Textural and Compositional Characteristics of Pyrite in the Tuolugou Cobalt-gold Deposit in East Kunlun and Its Implications for Cobalt Mineralization
The Tuolugou cobalt gold deposit is a rare large-scale hydrothermal type independent cobalt deposit in China.Few previous studies are focused on the cobalt-bearing minerals in this deposit,which hinder the further understanding of the mineralization process.To address this problem,detailed petrography,mineral assemblage,pyrite textural,trace elements,and S isotopic composition analyses are conducted in the Tuolugou deposit in order to reveal the characteristics of ore-forming fluid,evolution process,source of ore-forming material,and ore-form-ing process,and the indicative role of pyrite in cobalt mineralization is explained.The Tuolugou cobalt-bearing pyrite can be divided into three generations:the core with good crystal shape and occasional pores,the mantle with an oscillating ring and symbiosis with thionickelite and arsonite,and the well-crystallized pyrite rim.Among them,the pyrite core is rich in Co,Ni and other elements,the mantle is rich in Co,Ni and As,and the rim has higher As and Se content and slightly higher Au content.Comparisons of the three generations of pyrite show that the core has the highest Co content,the mantle has the high As content,and the edge contains high Au content.The ω(Co)/ω(Ni)ratios in the three generations of pyrite are mostly greater than 1,indicating the hydrothermal origin.From the core to the mantle to the rim,the Co and Ni contents gradually decrease,and the Se content grad-ually increases,which indicates the fluid temperature gradually decreases.The 834S value of pyrite is-1.43‰～0.48‰,which indicates that the ore-forming material mainly comes from magma.The textural,trace element char-acteristics and S isotope composition of the pyrite show that the ore-forming fluid is a low-temperature hydrothermal fluid rich in Co,Ni,As and other elements.This study is of great significance for revealing the mineralization process of sedimentary exhalative and hydrothermal reworking cobalt deposit and guiding the prospecting of similar deposits.
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