江西大湖塘北段石门寺钨铜钼矿化关系研究

A study of the relationship of W-Cu-Mo mineralization features of the Shimensi ore district in northern Dahutang,Jiangxi Province

江南造山带中段的赣北大湖塘矿集区是我国近年查明的世界级超大型钨矿产地,并伴生大型铜矿。本文对该区北段石门寺矿区燕山期不同岩石单元的W、Cu、Mo矿化特征与成矿年龄进行了系统研究。白钨矿多呈细脉浸染状产于似斑状花岗岩及其与围岩的外接触带;黄铜矿与辉钼矿多呈浸染状共生于似斑状黑云母花岗岩、细粒黑云母花岗岩、黑云母花岗斑岩及其围岩中。矿石矿物化学研究表明,似斑状黑云母花岗岩、细粒黑云母花岗岩和黑云母花岗斑岩中的硫化物成分较均一,黄铜矿中Cu 34.215%～35.161%、Fe 29.206%～30.721%、S 34.388%～35.520%,辉钼矿中Mo 59.44%～60.54%、S 40.067%～40.370%;似斑状黑云母花岗岩、细粒黑云母花岗岩、黑云母花岗斑岩和石英大脉中的辉钼矿Re-Os同位素模式年龄均值分别为143.3 Ma、145.2 Ma、144.5 Ma、143.6Ma,在误差范围内基本相同,指示该矿区内的Cu、Mo矿化为一期成矿作用形成,由此给出辉钼矿Re-Os同位素等时线年龄145.1±1.0 Ma （MSWD=0.46）,代表Cu、Mo矿化时间。结合前人岩浆岩研究结果,石门寺矿区白钨矿与Cu、Mo矿化是两期成矿作用的产物,前者与似斑状黑云母花岗岩密切相关,而后者可能与燕山晚期黑云母花岗斑岩有成因联系,成矿物质由斑岩向其他岩石单元迁移逐渐成矿。

Located in the middle Jiangnan orogenic belt, the Dahutang ore concentration area in northern Jiangxi Province is famous for producing world-class superlarge tungsten ore deposits and large copper ore deposits, thus serving as one of the largest discovered tungsten producing base area in recent years. This study is aimed at investigating the W, Cu and Mo mineralization features and ore-forming age in different rock units of Yanshanian period in the Shimensi ore district. Scheelite mainly occurs in porphyritic granite and the external contact zone of the wall rock with veinlet-disseminated granite. Chalcopyrite and molybdenite are mainly existent in porphyritic granite, fine-grained granite, granite porphyry and the contact zone of wall rock with disseminated granite. Ore chemical composition indicates that the components of sulfides are relatively uniform in three sets of rock units with the following data：chalcopyrite （Cu 34.215%～35.161%, Fe 29.206%～30.721%, S 34.388%～35.520%） and molybdenite （Mo 59.44%～60.54%, S 40.067%～40.370%）. The molybdenite Re-Os isotopic model average ages are 143.3 Ma, 145.2 Ma, 144.5 Ma, 143.6 Ma respectively in porphyritic biotite granite, fine-grained biotite granite, biotite granite porphyry and thick-vein quartz, which are basically identical within the error range, indicating that Cu, Mo mineralization were formed in one metallogenic epoch. Therefore the molybdenite Re-Os isotopic isochron age of 145.1±1.0 Ma （MSWD=0.46） could represent the mineralization time of Cu, Mo. Combined with the previous study of granites in Dahutang, the authors hold that the mineralization of scheelite and Cu, Mo took place in two metallogenic epochs in the Shimensi ore district. The former was closely related to the porphyritic granite and the latter probably had metallogenic relationship with the granite porphyry of late Yanshanian period. The ore-forming materials were delivered from granite porphyry to other rock units to cause mineralization gradually.