Anwangshan Au deposit, Feng County, Baoji, Shaanxi, Chinai

Regional Level Types
Anwangshan Au deposit	Deposit
Feng County	County
Baoji	Prefecture-level City
Shaanxi	Province
China	Country

The two northwest-trending Wuxingtai–Nianziba and Miaoping–Kangjialiang faults are parallel to each other, and crosscut by the late northeast-trending Yujiayao–Weijiawan fault. Under the influence of the two northwest-trending faults, three strong mylonitic zones with a width of 20–50 m are distributed between them. Silicification, sericitation, potassization, and pyritization are developed within the mylonitic zone.
The magmatic rocks are highly related to the gold mineralization in the Anwangshan deposit, including the pyroxenite and the quartz syenite veins. Minor granite porphyry veins display no spatial relation with gold mineralization and will not be discussed here. The pyroxenite is mainly exposed in the area sandwiched between the Jiangjiagou and Hujiagou river, which is 100–200 m in width and approximately 1 km in length. The quartz syenite veins intruded into the pyroxenite and Ols tuffaceous siltstone. The quartz syenite veins vary from 0.5 to 30 m in width and from 10 to 1000 m in length, showing obvious structural control, with a general northwest trending.
Four gold ore bodies (No.1, 2, 3, and 4) have been identified within the mining area, with gold grades peaking at 62.3 g/t. They share a strong spatial relationship with quartz syenite veins, either enclosed within the veins or situated within contact zones between the veins and the Ols. Importantly, ore grades within the veins generally exceed those in the Ol sediments. The ores can be divided into altered quartz–syenite type and altered sandstone type. Silicification, sericitization, carbonatization, epidotization, pyritization, and chloritization are widely developed in the mining area.
The paragenesis of the Anwangshan gold deposit have been divided into three stages. The quartz–sericite-pyrite (Py1) stage I is characterized by hydrothermal veins comprising coarse-grained quartz, sericite, and sparsely distributed euhedral Py1. The quartz–polymetallic sulfide–early calcite stage II is characterized by anhedral pyrite (Py2) occurring in association with sphalerite. Minor chalcopyrite presents as solid solutions within sphalerite. Additionally, early calcite veins crosscutting stage I quartz veins are widely distributed. The epidote–late calcite stage III is characterized by epidote predominantly developing along fissures. The epidote veins cut through early calcite veins and are subsequently cut by even later calcite veins, with minimal to no association with gold mineralization.

Other Regions, Features and Areas containing this locality

References