【作者】 张凯；

【导师】 王智琳；

【作者基本信息】 中南大学 ， 矿产普查与勘探， 2023， 硕士

【摘要】 东昆仑成矿带是我国西部重要的金、铜、铁、钴、镍多金属成矿带,矿床类型多样。驼路沟钴（金）矿床是西北发现的首例大型独立钴矿床,然而关于该矿床中钴的成矿过程还存在争议。本文以驼路沟钴（金）矿床为研究对象,利用TIMA、EBSD、EPMA、LA-ICP-MS和LA-MC-ICP-MS等现代测试手段开展了详细的矿相学和元素地球化学工作,得出如下认识:（1）驼路沟钴（金）矿床中钴的成矿过程分为喷流沉积期和叠加改造期两个成矿期。其中,喷流沉积期形成了细粒黄铁矿（Py I）;叠加改造期从早到晚进一步划分为细粒黄铁矿（Py II）+辉砷钴矿+辉砷镍矿+硫镍钴矿+少量白铁矿+少量磁黄铁矿+少量黄铜矿阶段和粗粒黄铁矿（Py III）+自然金阶段。（2）驼路沟钴（金）矿床中钴的赋存形式主要有两种:以类质同象形式替换铁赋存于黄铁矿中和形成钴的独立矿物辉砷钴矿、辉砷镍矿以及硫镍钴矿。（3）三个世代黄铁矿具有不同化学成分。第一世代黄铁矿（Py I）中的Co、Ni、As的含量范围依次为0.03～4.86 wt.%（平均0.42 wt.%）、≤1.46 wt.%（平均0.09 wt.%）、≤3.26 wt.%（平均0.20wt.%）;第二世代黄铁矿（Py II）中的Co、Ni、As的含量范围依次为0.38～4.75 wt.%（平均2.19 wt.%）、≤1.87 wt.%（平均0.33 wt.%）、≤4.59 wt.%（平均0.51 wt.%）;第三世代黄铁矿（Py III）中的Co、Ni、As的含量范围依次为0.04～4.62 wt.%（平均0.19 wt.%）、≤0.69wt.%（平均0.02 wt.%）、0.34～4.42 wt.%（平均1.53 wt.%）。黄铁矿复杂的成分和结构特征揭示Py I为喷流沉积成因,Py II则是通过溶解再沉淀机制形成,Py III为增生或直接从溶液中沉淀形成。（4）不同世代黄铁矿的硫同位素结果不同。Py I的δ³⁴S_V-CDT值为—1.68‰～+0.99‰,Py II的δ³⁴S_V-CDT值为+3.36‰～+10.67‰,而Py III中的δ³⁴S_V-CDT值为+2.99～+6.66‰。Py I的硫同位素组成接近零,暗示其来源为深部地幔;Py II、Py III的硫同位素值为较低的正值,与东昆仑区域三叠纪造山型金矿的硫同位素组成范围接近。（5）结合以往研究,建立了驼路沟钴（金）矿床中钴的富集成矿过程,具体如下:喷流沉积期形成了细粒黄铁矿Py I;叠加改造期早阶段,区域韧性剪切变形活动导致了定向排列的Py II和独立含钴矿物的形成,Py II呈不规则状、丝带状和环带状交代Py I或发生静态重结晶恢复;叠加改造期晚阶段,随着韧-脆性转变,形成了粗粒Py III,自然金分布于Py III裂隙。因此,喷流沉积成矿作用和叠加改造作用均是驼路沟钴（金）矿床中钴富集成矿的两个重要过程,叠加改造期早阶段的变形作用使钴流体活化再富集,提升了黄铁矿中钴含量并形成了独立钴矿物。图23幅,表6个,参考文献162篇更多还原

【Abstract】 East Kunlun Orogen is a significant Au-Cu-Fe-Co-Ni polymetallic metallogenic belt in western China and there are diverse deposit types.The Tuolugou Co(Au)deposit has a great reputation as the first discovered independent Co deposit in northwestern China.It is still debatable over the Co mineralization process in the Tuolugou Co(Au)deposit.The detailed mineralogical and sulfur isotopic studies on Tuolugou Co(Au)deposit using the integrated TIMA,EBSD,EPMA,LA-ICP-MS,In-situ sulfur isotope analyses revealed five understandings as follows:(1)The Co mineralization process in the Tuolugou Co(Au)deposit can be divided into two metallogenic periods,including sedimentary exhalative mineralization and superimposed reworking process.The sedimentary exhalative mineralization formed the fine-grained pyrite(Py I).The superimposed reworking process consists of two mineralizing stages,that is,fine-grained pyrite(Py II)+ cobaltite + gersdorffite + siegenite +minor marcasite + minor pyrrhotite + minor chalcopyrite stage and coarsegrained pyrite(Py III)+ native Au stage.(2)There are two forms of Co occurrence in the Tuolugou Co(Au)deposit.1)Exists in the pyrite lattice by stoichiometric substitution of Fe.2)Occurs as either independent minerals(e.g.,cobaltite,gersdorffite and siegenite)or cobaltiferous pyrite.(3)Three generations of pyrite have different chemical compositions.The contents of Co,Ni,and As in Py I ranged from 0.03 ～ 4.86 wt.%(avg.0.42 wt.%),≤1.46 wt.%(avg.0.09 wt.%),≤3.26 wt.%(avg.0.20 wt.%),respectively.The Content ranges of Co,Ni,and As in Py II are 0.38 ～ 4.75 wt.%(avg.2.19 wt.%),≤1.87 wt.%(avg.0.33 wt.%),≤4.59 wt.%(avg.0.51 wt.%),respectively.Variation ranges of Co,Ni,and As in Py III are0.04 ～ 4.62 wt.%(avg.0.19 wt.%),≤0.69 wt.%(avg.0.02 wt.%),0.34 ～4.42 wt.%(avg.1.53 wt.%),respectively.The complex composition and structural characteristics of pyrite revealed their formation mechanism.Py I is formed by sedimentary exhalative mineralization.Py II is formed by dissolution and reprecipitation mechanisms.Py III is formed by overgrowth or direct precipitation from solution.(4)The sulfur isotopes display distinct fractionation patterns,varying from —1.68‰ ～ +0.99‰ of Py I and +3.36‰ ～ +10.67‰ of Py II and +2.99～ +6.66‰ of Py III.The sulfur isotope composition of Py I is close to zero,suggesting that the source of Py I is deep mantle.The sulfur isotope values of Py II and Py III are lower positive range,which are close to the range of sulfur isotope composition of Triassic orogenic Au deposits in East Kunlun region.(5)In combination with the previous work,the process of Co enrichment and mineralization in the Tuolugou Co(Au)deposit is established as follows.Fine-grained Py I was formed in the sedimentary exhalative mineralization.At the early stage of the superimposed reworking process,regional ductile shear deformation led to the formation of orientated Py II and independent Co minerals,Py II presented irregular,ribbonlike and ringlike metasomatic Py I or static recrystallization recovery.At the late stage of the superimposed reworking process,coarse-grained Py III and native Au were formed in the ductile-brittle transitional environment.Therefore,both the sedimentary exhalative mineralization and superimposed reworking process contributed to Co mineralization in the Tuolugou Co(Au)deposit.Among them,the shear deformation effect in the early stage of superimposed reworking process reenriched Co fluid,increased the Co content in pyrite and formed independent Co minerals.更多还原