西秦岭岗岔金矿赋矿围岩成岩时代及其地质意义

岗岔金矿是在西秦岭西段北缘发现的中型金矿床，有潜力达到大型。该金矿目前发现的5条金矿脉明显受断裂控制，赋矿围岩浅部主要是一套火山岩和火山碎屑岩。该套火山岩长期以来被认为是侏罗系郎木寺组。采用锆石U-Pb法对其中的凝灰岩进行定年测试，结果显示年龄为(245±2) Ma，说明该火山岩不是侏罗系而应该属于三叠系。矿区内与金矿脉空间关系密切的花岗闪长岩和石英闪长岩锆石U-Pb定年结果显示，二者年龄也分别为(242±2) Ma和(246±3) Ma。这说明矿区内侵入体与赋矿围岩属于近乎同时代(印支期)岩浆活动的产物。上述测年结果进一步限定了岗岔金矿形成时间为三叠纪早期，即构造岩浆活动之期后的热液期。该结论为深入认识矿床成因、总结成矿规律和指导勘查方向提供了新的依据。

Dating for Ore-hosting Rock of the Gangcha Gold Deposit in Western Qinling Mountains and Its Geological Significance

Gangcha gold deposit is a new medium-sized gold deposit which was found in the northern margin along western segments of Western Qinling Mountains, and it is expected to be a larger scale. There are five ore veins in the deposit, which are limited by the fault zones. The shallow part of host rocks are the volcanic and volcanic clastic rock group. The sets of the volcanic rock groups have been identified as Lower Jurassic Langmusi Formation for a long time before. In fact, those are confirmed as Triassic with the age of (245±2) Ma by zircon U-Pb dating method applied to the tuffs in the group this time. Also, there are two kinds of intruded rocks which are granodiorites and quartz diorites in the deposit, and the both ages are confirmed as (242±2) Ma and (246±3) Ma by zircon U-Pb dating method, respectively. That means that those intrusive bodies and ore-hosting volcanic rock group are same magmatic activity products in Indo-Chinese epoch. Above results limited that the Gangcha gold deposit was formed under magmatic hydrothermal activities after tectonic magmatic activity of Early Triassic period. The study conclusion can provide new facts for advancing gold deposit genesis research and clearing exploration direction.