江西王坞斑岩型Mo-Cu矿床花岗斑岩锆石U-Pb和辉钼矿Re-Os同位素测年及地质意义

王坞斑岩型Mo-Cu矿床位于北武夷地区,地处钦杭构造岩浆成矿带北段。目前钻孔信息显示,该矿床的矿体主要由网脉状石英-辉钼矿-黄铜矿矿石组成,也含少量的浸染状和细脉浸染状Cu-Mo矿化,主要的蚀变作用包括硅化、绢英岩化和绿泥石化。矿区内隐伏燕山期的花岗斑岩脉及石英闪长玢岩脉。本文对该矿床的花岗斑岩进行了LA-ICP-MS锆石U-Pb测年,对主要矿石类型(网脉状石英-辉钼矿矿石)中的辉钼矿进行了Re-Os同位素测年。结果显示,花岗斑岩的锆石U-Pb年龄为136. 7±2. 2Ma,辉钼矿的Re-Os同位素模式年龄为132. 6±1. 8Ma~134. 5±2. 0Ma,加权平均值为133. 7±0. 94Ma,对应的Re-Os等时线年龄为134. 8±2. 1Ma。花岗斑岩的锆石U-Pb年龄和辉钼矿的Re-Os年龄在误差范围内基本一致,且花岗斑岩和矿体之间具有密切的空间关系,指示王坞Mo-Cu矿床的Mo矿化可能与矿区内的花岗斑岩存在密切的成因联系。北武夷地区主要的斑岩-矽卡岩和岩浆热液脉型Cu-Mo多金属矿床的成岩成矿年龄数据的统计结果显示,北武夷地区的Cu-Mo-Pb-ZnAg成矿作用主要集中在燕山期,可被划分为150~165Ma和140~125Ma两个阶段。结合区域构造背景资料,王坞Mo-Cu矿床形成于早白垩纪伸展的构造背景下。

Zircon U-Pb dating of granite porphyry and Re-Os isotopic dating of molybdenite from Wangwu porphyry Mo-Cu deposit, Jiangxi Province, and their geological significance

The Wangwu Mo-Cu deposit, located in the northern part of the Qin-Hang tectonic magmatic metallogenic Belt (QHB), is a middle tonnage porphyry type deposit. The orebodies of the deposit are mainly composed of quartz-molybdenite-chalcopyrite veins, with minor disseminated mineralization. Yanshanian granite porphyry and quartz diorite porphyrite dykes are cryptoplasmic in the area. In this paper, we present LA-ICP-MS U-Pb zircon age data for the granite porphyry and Re-Os isotope age data for molybdenite from the quartz-molybdenite veins. The U-Pb age of zircons from the granite porphyry is 136.7±2.2Ma, and Re-Os dating of molybdenite yields an isochron age of 134.8±2.1Ma. Re-Os isotopic model ages of molybdenite range from 132.6±1.8Ma to 134.5±2.0Ma, with a weighted average age of 133.7±0.94Ma. The results show that the ages of granite porphyry and molybdenite mineralization are the same within errors. Furthermore, geological and geochronological evidence indicate that the granite porphyry and molybdenite mineralization have very close genetic relationships. The integrating results of this study with published data and regional tectonic setting suggest that the Wangwu molybdenum-copper deposit was formed in an extensional tectonic setting at Early Cretaceous. The regional diagenetic and metallogenic age data show that the Cu-Mo-Pb-Zn-Ag mineralization of North Wuyi area were mainly occured in Yanshanian and can be grouped into two stages of 150~165Ma and 140~125Ma, respectively.