东天山东戈壁钼矿床辉钼矿Re-Os年龄及印支期成矿事件

Molybdenite Re-Os isotope age of the Donggebi Mo deposit and the Indosinian metallogenic event in eastern Tianshan

东戈壁超大型钼矿床位于新疆境内的东天山觉罗塔格成矿带。8件辉钼矿样品Re-Os同位素年龄介于228.7±2.7Ma～241.7±0.9Ma,等时线年龄为231.9±6.5Ma(95%置信度,MSWD=0.71),加权平均年龄为238.5±3.7Ma(95%置信度,MSWD=5.8)。其中,最小的辉钼矿Re-Os年龄与矿区内斑状花岗岩年龄(227.6±1.3Ma)一致,表明成岩和成矿作用发生在三叠纪。7件辉钼矿样品Re含量为26.51×10-6～91.34×10-6,指示成矿物质主要来自古生代增生作用形成的不成熟大陆壳。已有成矿年龄显示了印支期成矿事件在东天山地区非常显著,发生于大陆碰撞造山体制。

The Donggebi giant Mo deposit is located in the Qoltag metallogenic belt, eastern Tianshan, Xinjiang. Eight molybdentie samples from the deposit yield Re-Os isotope ages ranging from 228.7±2.7Ma to 241.7±0.9Ma, with an isochron age of 231.9±6.5Ma （95% confidence, MSWD=0.71）, and a weighted mean age of 238.5±3.7Ma （95% confidence, MSWD=5.8）. The lowest molybdenite Re-Os age （228.7±2.7Ma） agrees well with the age （227.6±1.3Ma） of the parental porphyritic granite at the deposit, indicating that the magmatism and Mo-mineralization occurred in Triassic. The Re contents in seven molybdenite samples range from 26.51×10^-6 to 91.34×10^-6, suggesting that the ore-forming metals were mainly sourced from an immature continental crust which was likely formed in Paleozoic subduction-related accretion. Compiling of the available isotope ages obtained from the mineral systems in eastern Tianshan area shows that the Indosinian mineralization was significant in the eastern Tianshan orogenic belt. The Indosinian mineralization occurred in continental collision regime.