湖南新田岭钨矿床白钨矿矿物学特征及其地质意义

Mineralogical Characteristics and Geological Significance of Scheelites in the Xintianling Tungsten Deposit,Hunan Province

新田岭钨矿床地处南岭钨锡成矿带,为接触交代作用形成的超大型夕卡岩型白钨矿床。目前,针对矿体的具体形成阶段以及矿化类型仍存在一定的争议。本研究在野外和矿相学研究基础上,选取新田岭钨矿床中不同类型的代表性白钨矿颗粒,开展微区原位微量元素定量分析,通过矿相学和地球化学特征探讨研究区内白钨矿的成因。研究表明,矿床经历了早期夕卡岩阶段、晚期夕卡岩阶段、氧化物阶段、早期硫化物阶段和晚期硫化物阶段的完整成矿阶段,退变质作用显著。成矿夕卡岩经历了氧逸度升高然后降低的过程,成矿流体中的Mo元素因为被REE元素占据了晶格空位而无法进入白钨矿中,进一步指示夕卡岩在变质作用中发生了显著的退变质成矿。未来的找矿勘查应更多聚焦于退变质作用显著部位,退变质矿物(如绿帘石、阳起石等)可以作为在深边部寻找隐伏白钨矿体的找矿标志。

Located in Nanling tungsten-tin metallogenic belt,Xintianling tungsten deposit is a super-large skarn scheelite deposit formed by contact metasomatism.There are still some disputes about the specific formation stage and mineralization type of ore bodies.On the basis of field and mineralogical research,we selected different types of representative scheelite particles in Xintianling tungsten deposit to carry out quantitative analysis of trace elements in micro-area,and discussed the genesis of scheelite in the study area through mineralogical and geochemical characteristics.The results show that:the deposit has experienced the complete mineralization stages of early skarn stage,late skarn stage,oxide stage,early sulfide stage and late sulfide stage,and the retrogression is remarkable.The ore-forming skarn experienced the process of oxygen fugacity increasing and then decreasing,and Mo element in ore-forming fluid could not enter scheelite because it was occupied by REE element,which further indicated that skarn had undergone significant retrogressive mineralization during metamorphism.Future prospecting exploration should focus more on the prominent parts of retrogressive metamorphism,and retrogressive minerals(such as epidote and actinolite)can be used as prospecting indicators for searching for concealed scheelite bodies in the deep edge.