赣北梅子坑钼矿床辉钼矿Re Os 同位素年龄及其地质意义

摘要

The forming age of the Meizikeng molybdenum deposits located in Jiuling Zhanggongshan ploymetallic metallogenic belt,northern Jiangxi Province,has been determined by the Re Os isotopic dating method in this paper.The Re Os dating of 5 molybdenite samples yielded average model ages from 148.2 to 150.7 Ma,with a weighted average of (150±1)Ma,and an isochron age of (148.9±4.4)Ma.Evidently,we can constrain the forming age of Meizikeng deposits at ca.150 Ma.The geological characteristics of the deposit show that the molybdenum mineralization in this deposit is closely related to the Late Jurassic magmatic activities,which accounted for the constant pressure triggered by the simultaneous subduction of the Pacific plate.The forming ages of some deposits in the metallogenic belt allows further inference about the existence of different mineralization processes.The molybdenum polymetallic mineralization was caused by the extension and reduction of the lithosphere (135 Ma ± ). Moreover, the Late Jurassic mineralization was also found in this metallogenic belt,which was formed by the convergence of lithosphere plate in East Asia since the Late Middle Jurassic period (150 Ma±).The accurate ore-forming age will contribute to mineral exploration in Jiuling Zhanggongshan polymetallic metallogenic belt,northern Jiangxi Province.%运用 Re Os 同位素定年对赣北九岭鄣公山多金属成矿带梅子坑钼矿床进行成矿年龄的厘定，获得5件钼矿石样品的 Re Os 模式年龄为148．2～150．7 Ma，加权平均值为（150±1）Ma（MSWD＝0．66），对应的等时线年龄为（148．9±4．4）Ma，指示该矿床的成矿时限为150 Ma 左右，表明其形成与晚侏罗世中晚期的岩浆活动有关，可能与该时期由太平洋板块的俯冲而导致的持续挤压作用有关。结合该成矿带上的成岩成矿年龄，可推断该成矿带的形成不仅包括与岩石圈伸展减薄背景有关（约135 Ma）的钨多金属成矿作用，应该还存在中侏罗世晚期以来（约150 Ma）由东亚岩石圈板块汇聚作用而形成的一定规模和强度的晚侏罗世成矿作用。该年龄的精确测定将对赣北九岭鄣公山多金属成矿带找矿起到很好的指示作用。