广东大宝山北部层状矿体硫化物Re-Os测年及指示

Re-Os dating of sulfides in the north stratiform ore body in Dabaoshan,Guangdong Province and its indication

广东省大宝山铜多金属矿,近年来在北部新发现层状铜硫矿体,新增铜资源量20.6万吨,与采区内层状铜硫主矿体特征基本一致。为解决层状铜硫矿体的成矿时代问题,采集北部层状矿体的块状硫化物矿石样品,首次直接对黄铜矿和磁黄铁矿开展Re-Os测年,探讨成矿时代,并分析矿床成因。黄铜矿样品的Re-Os等时线年龄为(243±41)Ma(MSWD=3.1),磁黄铁矿样品的Re-Os等时线年龄为(410±16)Ma(MSWD=15),指示黄铜矿的形成可能晚于磁黄铁矿,加里东期是否存在成矿事件仍需进一步研究。黄铜矿与磁黄铁矿的矿石学研究表明,黄铜矿交代磁黄铁矿,前者形成晚于后者,结合采区地质填图结果,认为大宝山矿区及外围属于一个大的岩浆成矿系统,存在多期次岩浆侵位,主体可能属于燕山期与岩浆热液有关的成岩成矿事件。

The Dabaoshan copper polymetallic deposit, has increased its copper metal resources about 206000 tons owing to the north stratiform copper orebody found in recent years which is similar to the main stratiforrn copper-sulfur orebody in the pit. In order to solve the mineralization time issue of this stratiform copper orebody, massive sulfide ore samples were collected from this north copper orebody. Re-Os dating of chalcopyrite and pyrrhotite was carried out to determine the mineralization time and analyze the genesis of copper ore deposit. Re-Os isochron age of chalcopyrite is 243±41 Ma （MSWD=3. 1） and isochron age of pyrrbotite is 410± 16 Ma （MSWD= 15）, indicating the formation of chalcopyrite may be later than that of pyrrhotite. But whether there is a mineralization event in the Caledonian should be considered more carefully with more study. The ore mineralogic study of chaleopyrite and pyrrhotite shows that the chalcopyrite had replaced pyrrhotite, which suggests that the chalcopyrite was formed later than pyrrhotite. Combined with geological mapping in the pit, there may have been a large magmatic and mineralization system beneath Dabaoshan area and its periphery and multiple intrusions have occurred. This belongs to the Jurassic mineralization event related to the magmatie hydrothermal origin.