青海西部祁漫塔格山卡尔却卡铜多金属矿床似斑状黑云二长花岗岩LA-ICP-MS锆石U-Pb年龄

祁漫塔格卡尔却卡铜多金属矿体主要产于花岗闪长岩、似斑状黑云母二长花岗岩体与寒武纪—奥陶纪滩间山群接触部位的矽卡岩带和二长花岗岩中。本次对矿区Ⅶ号带矽卡岩与矿体紧邻的似斑状黑云母二长花岗岩体进行LA-ICP-MS锆石U-Pb测年,获得年龄为410.1Ma±2.6Ma。结合前人获得的花岗闪长岩SHRIMP锆石U-Pb年龄（237 Ma±2Ma）和矿石矿物辉钼矿Re-Os模式年龄（239Ma）,认为岩体成岩和成矿时代都发生在印支期,卡而却卡铜多金属矿成矿作用不仅与印支期中酸性侵入岩有关,也与加里东晚期酸性侵入岩有关。祁漫塔格地区矿床形成时代主要集中于加里东中晚期和印支晚期,尽管加里东期岩体在地表出露规模远没有印支期岩体规模宏大,但是加里东晚期岩体对成矿作用的贡献也应该引起足够的重视。

Zircon LA-ICP-MS U-Pb age of monzogranites in the Kaerqueka copper-polymetallic deposit of Qimantag,western Qinghai Province

The Kaerqueka copper-polymetallic ore bodied in Qimantage region can mainly be found in monzonitic granite and skarn belts located in the contact zones between granodiorite,porphyritic biotitic monzogranite and Cambrian-Ordovician strata.Based on LA-ICP-MS U-Pb chronological study of zircons,the authors obtained the age（410.1Ma±2.6Ma） of biotitic monzogranite close to Ⅶ ore belt.Nevertheless,other researchers hold that the rock-forming and ore-forming processes took place in Indo-Chinese period based on the age of granodiorite（237Ma±2Ma） and the Re-Os model age（239Ma）of molybdenite.A comparison of the geochemical characteristics between the two rock bodies has led the authors to reach the conclusion that the mineralization was related not only to the Indo-Chinese intermediate-acid intrusive rocks but also to the late Caledonian acid intrusive rocks,and there existed a difference in magma origin between porphyritic biotitic monzogranite and granodiorite,suggesting that they were formed in different periods of tectonic evolution.Ore deposits in Qimantag region were formed in late Caledonian and in Indo-Chinese period.Although the outcrop of late Caledonian period is not so apparent as the one of Indo-Chinese period,due attention should be paid to the contribution of late Caledonian intrusives to mineralization.