Abstract:

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.

Key words: ore-hosting rock, volcanic rock, zircon U-Pb dating, Gangcha, Western Qinling Mountains