东天山白山铼钼矿区燕山期成岩成矿作用同位素年代学证据

Isotopic Chronological Evidence for Yanshanian Diagenetic Mineralization in Baishan Rhenium-Molybdenum Mine,E. Tianshan Mountains

近年来对东天山地区有色、贵金属矿床成矿年代学研究表明,成矿作用主要发生于海西期—印支期,成矿作用高峰期为晚石炭世—早二叠世。笔者最近对白山铼钼矿区南西1.2 km处出露的黑云母斜长花岗岩和含矿石英脉作了系统的年代学研究,分别获得岩体SHRIMP锆石微区原位U - Pb和谐年龄为181±3Ma(n=13,MSWD=1.10 ) ,含矿石英脉石英的Rb- Sr等时线年龄为187±7Ma(95 %可信度;MSWD=3.5 2 ) ,4 0 Ar- 39Ar坪年龄为182±1.6 Ma,三种不同定年方法所获得的年龄值基本一致,表明东天山地区存在燕山期成岩成矿事件,矿化作用可能与矿区内出露的黑云母斜长花岗岩岩浆活动有关。

Chronological research of recent years shows that nonferrous and precious metallic mineralization in E. Tianshan Mountains mainly happened during Hercynian^Indosinian Period with Late Carboniferous and Early Permian to be mineralization peak. Systematical chronologic dating shows that biotite plagiogranite body 1.2km southwestern to the Baishan Rhenium-Molybdenum Mine has a zircon SHRIMP U-Pb age of 181±3Ma(n=13,MSWD=1.10)and ore-bearing quartz veins in the orefield have a Rb-Sr isochron age of 187±7 Ma(95% confidence;MSWD=3.52) and a 40Ar- 39Ar plateau age of 182±1.6Ma. The fact that three ages are in accordance within dating errors indicates that there exists Yanshanian diagenetic mineralization events in E. Tianshan area and the mineralization might be related to magmatism of the biotite plagiogranite body outcropped in the orefield.