湘中曹家坝大型钨矿床的主要矽卡岩矿物学特征及其地质意义  

Mineralogical characteristics of skarns of Caojiaba large tungsten deposit in central Hunan Province and their geological significance

作　　者：张志远[1] 谢桂青[2] 朱乔乔[2] 李伟[2] 韩颖霄 王凤兰[3] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质科学院矿产资源研究所,国土资源部成矿作用和资源评价重点实验室,北京100037 [3]河北省地矿局第五地质大队,河北唐山063000

出　　处：《矿床地质》2016年第2期335-348,共14页Mineral Deposits

基　　金：国家重点基础研究发展计划“973”课题(编号:2014CB440902)资助

摘　　要：矽卡岩矿物特征是确定矽卡岩矿床成因的关键证据之一。曹家坝钨矿床是湘中盆地新探明的大型钨矿床,矿体呈似层状产于中泥盆统棋梓桥组灰岩与跳马涧组碎屑岩之间硅钙界面附近。矿区内发育大量矽卡岩矿物,但是未见到岩浆岩。文章通过钻孔编录、矿物的显微特征和电子探针分析,确定了曹家坝钨矿床的成因类型。研究表明曹家坝钨成矿作用与矽卡岩关系密切;石榴子石存在早、晚2个阶段,早阶段石榴子石以钙铝榴石和钙铁榴石为主,晚阶段以钙铝榴石和铁铝榴石-锰铝榴石为主;辉石以钙铁辉石为主;绿泥石主要是铁镁绿泥石。根据矽卡岩的矿物特征,结合发育磁黄铁矿和伴生金矿化等特征,提出曹家坝钨矿床可能是还原性远端矽卡岩型钨矿床。Skarn minerals can provide important information about the type of skarn deposit. The Caojiaba tungsten deposit is a newly discovered large tungsten deposit in central Hunan Province, and its orebodies occurring in stratiform-like form are hosted within the contact zone between Middle Devonian Qiziqiao Formation limestone and Tiaomajian Formation clastic rocks. This deposit is characterized by the plenty of skarn minerals, in spite of the absence of intrusions in the mining area. In this paper, the drill hole logging, microscopic study and electron microprobe analysis were conducted to constrain the origin of the Caojiaba tungsten deposit. The results show that tungsten mineralization is genetically associated with skarn, and the garnets have two distinct stages, i. e., early stage garnets are dominated by grossular with subordinate andradite, and late stage garnets are grossular with minor almandine and spessortite. The pyroxene consists of mainly hedenbergite, with minor diopside, and the chlorites at Caojiaba belong to brunsvigite. Two stages of scheelite were identified; it is shown that early fined disseminated scheelite is intergrowth with prograde skarn, and late stage coarse grained scheelite coexists with quartz as veinlets. Based on studies of compositions of garnet, pyroxene and chlorite together with modes of occurrence of pyrrhotite and gold by-product, the authors infer that the Caojiaba tungsten deposit is a distal reduced skarn tungsten deposit.

关 键 词：地质学 矽卡岩矿物 还原性矽卡岩钨矿床 曹家坝 湖南 

分 类 号：P618.67[天文地球—矿床学]