广东大宝山多金属矿床两期成矿:来自黑色炭质泥岩和辉钼矿Re-Os同位素定年的证据

Two Phases of Mineralization in the Dabaoshan Polymetallic Deposit, Guangdong Province: Constraints from Re-Os Geochronology of Black Carbonaceous Mudstone and Molybdenite

广东省大宝山多金属矿床位于南岭成矿带中段南侧,为多因复成矿床,包括喷流沉积型Cu-Pb-Zn矿床和叠加斑岩-矽卡岩型W-Mo矿床。系统的野外考察发现,喷流沉积型Cu-Pb-Zn矿床主要以层状-似层状、透镜状和角砾状矿体赋存于中泥盆统棋梓桥组,具有典型喷流沉积型矿床特征;斑岩-矽卡岩型W-Mo矿床主要以斑岩型和矽卡岩型矿体围绕大宝山燕山期花岗闪长(斑)岩产出或叠加在喷流沉积形成的层状-似层状矿体之上。对矿区内斑岩-矽卡岩型W-Mo矿床中辉钼矿和喷流沉积型Cu-Pb-Zn矿床中炭质泥岩进行Re-Os同位素定年研究表明,辉钼矿Re-Os等时线年龄为163.6?1.0 Ma(MSWD=0.58),代表了斑岩-矽卡岩型矿床的形成年龄;炭质泥岩Re-Os等时线年龄为387.6?9.9 Ma(MSWD=56),代表同沉积矿床即喷流沉积矿床形成年龄。这反映大宝山多金属矿床至少存在两期重要的成矿事件:斑岩-矽卡岩型W-Mo矿床形成与燕山期中酸性岩浆活动相关,层状-似层状Cu-Pb-Zn矿床形成与海西期海底热液喷流沉积相关。

The Dabaoshan polymetallic deposit is a polygenetic composite ore deposit located at south of the Qinhang(Qinzhou-Hangzhou)Metallogenic Belt,which is composed mainly of SEDEX type Cu-Pb-Zn and porphyry-skarn type W-Mo orebodies.Systematic field study shows that the W-Mo mineralization exhibits as quartz-vein type and skarn type orebodies around the granodioritic porphyry,or superimposes on the SEDEX type Cu-Pb-Zn orebody,while the Cu-Pb-Zn mineralization occurs mainly in the Qiziqiao Formation as stratiform-substratiform type and breccia type orebodies with typical SEDEX-type characteristics.Re-Os dating of five molybdenite separates from porphyry-skarn type W-Mo orebodies yielded isochron ages of 163.6±1.0 Ma(MSWD=0.58),which represents the age of W-Mo mineralization.Re-Os dating of seven black carbonaceous mudstone samples from a Cu-Pb-Zn orebody yielded isochron age of 387.6±9.9 Ma(MSWD=56),which is interpreted to be the age of SEDEX-type Cu-Pb-Zn mineralization.These ages indicate that there are at least two stages of ore mineralization in the Dabaoshan polymetallic deposit.The W-Mo mineralization is related to the Yanshanian intermediated-acidic intrusions,while the stratiform-substratiform SEDEX-type Cu-Pb-Zn mineralization is associated with the Hercynian seafloor hydrothermal activities.