云南省墨江金矿床成矿时代探讨

Discussion on Metallogenic Ages of Mojiang Gold Deposit in Yunnan Province

在系统研究墨江金矿床地质事件的基础上 ,以富金石英脉中的石英流体包裹体为测定对象 ,获得Rb_Sr等时线年龄为 (1 35± 3)Ma。上三叠统地层中含金石英脉旁侧发育的铬水云母脉K_Ar法年龄为 (1 0 9.5± 1 .7)Ma。结合前人的研究资料 ,认为墨江金矿床经历了多期次成矿作用 ,其中构成本矿床的主体———富金石英脉的形成时代可能为 1 35～ 90Ma。

The Mojiang gold deposit, one of the most important large gold deposits in the “Sanjiang' gold mineralization area of Yunnan Province, has great potential in increasing its gold reserves. Knowledge of its metallogenic age is very insufficient, which has restricted the study of its origin and the ore prognosis. Based on systematical analysis of geological events in this area, this paper deals with metallogenic ages of the Mojiang gold deposit. The samples studied were taken from quartz in gold-rich quartz veins at various levels, and the fluid inclusion Rb-Sr isochronal ages are (135±3) Ma. The K-Ar isotopic age of Cr-hydromuscovite from gold-bearing quartz veins in Upper Triassic Waigucun Formation is (109.52±1.69) Ma. According to regional geological characteristics and geochronological investigations, the authors consider that the Mojiang gold deposit has undergone repeated polymetallic ore-forming activities, and that the main orebodies of the ore deposit, i.e., the gold-rich quartz veins, might have been formed at 135～90Ma.