第七届青年地学论坛

The Zhangjiakou-Xuanhua district is one of the most important-gold producing areas in the middle part of the northern North China Craton (Fig. 1a). There are many Te-Au deposits in this district, such as the Dongping, Huangtuliang, Zhongshangou, Hougou and Xiaoyingpan deposits (Fig. 1b). These deposits are mainly distributed in the boundaries of the Devonian Shuiquangou syenite complex and the Archean Sanggan metamorphic rock. No or minor Te-Au mineralization exists in other geology bodies. All of the Te-Au deposits are controlled by the NWW-SEE and NW-SE trending faults that formed because of remobilization of the Shangyi-Chongli-Chicheng mantle−penetrating fault. For example, the Dongping and Hougou deposits are controlled by the NWW-SEE trending Xisanjianfang-Womakeng fault, and the Xiaoyingpan and Hougou deposits are controlled by the NW-SE trending Hanjiagou-Guzuizi-Changdi fault (Fig. 1b). In addition to the close relationship of distribution, the Te-Au deposits in the Zhangjiakou-Xuanhua district have many common features in mineral and geochemical compositions, including enriched in tellurides, negative sulfur isotopes and coincident lead isotopes, low-sulfide deposits and As-free in pyrite (Wang et al., 2019). δD values of the Te-Au deposits in the Zhangjiakou-Xuanhua district vary from ‑1.7‰ to 8.9‰, δ¹⁸O_H2O values range from –109.1‰ to –50.5‰. The Dongping and Zhongshangou deposits have wider ranges of δ¹⁸O_H2O values compared with the δD values, indicating the mixture of magmatic and meteoric waters with different Proportions. The Xiaoyingpan, Dabaiyang and Shuijingtun deposits have narrower δ¹⁸O_H2O ranges, and plotted between magmatic water and the Sanggan group metamorphic rocks in the H-O diagram, indicating an intensive water-rock reaction between ore-forming fluids and wallrocks. δ³⁴S values of the Te-Au deposits range from –20 to +2. The various δ³⁴S values are resulted from high oxygen fugacity and boiling of the ore-forming fluids, and the sulfur mainly derived from the deep-seated magma. The ³He/⁴He ratios of the Te-Au deposits vary from 0.13 to 5.2 Ra, indicating the mixture of crustal and mantle fluids. ⁴⁰Ar/³⁶Ar ratios of the Dongping and Zhongshangou deposits are 309–2200, close to the atmospheric Ar. The Dabaiyang and Xiaoyingpan deposits have higher ⁴⁰Ar/³⁶Ar ratios, ranging from 3489 to 21824. The contents of radiogenic ⁴⁰Ar range from 1.92 × 10⁻⁶ to 17.13 × 10⁻⁶ ccSTP/g and account for 91.5% to 98.5% of the total ⁴⁰Ar, indicating the high radiogenic ⁴⁰Ar values were likely derived from the metamorphic wallrocks.
Based on geology characteristic and isotope compositions, the Te-Au deposits in the Zhangjiakou-Xuanhua district can be divided into two groups, and they are: (1) the intrusion-related deposit, including the Dongping, Hougou and Zhongshangou deposits; (2) the metamorphic rock related deposit, including the Xiaoyingpan, Dabaiyang and Shuijingtun deposits. The common features of these two deposit types include containing tellurides and negative sulfur isotope compositions. The specific differences are: the intrusion-related deposits have large amounts of tellurides and a high temperature H₂O–NaCl–CO₂ hydrothermal system, and mineral deposition was trigged by boiling and gas transport of Te (Wang et al., 2019), while the metamorphic rock related deposits have relatively less tellurides and a moderate temperature H₂O–NaCl hydrothermal system, and the main deposition mechanisms were fluid mixing and water-rock reaction (Shen et al., 2020). The common features of these two types of deposits may have resulted from the same sources of metals, and the Shuiquangou syenite was the main provider (Bao et al., 2016). The differences may relate to the origins of ore-forming fluids. Ore-forming fluids of the intrusion-related deposits were derived mainly from magmatic water (Mao et al., 2003) and had high temperature and metal contents. Because of the syenite wallrock, hydrothermal fluid cooling and water-rock reaction were slow, and boiling and gas transport during fracturing became the main mechanisms of mineral deposition. In contrast, ore-forming fluids of the metamorphic rock related deposit were derived from mixing of magmatic and meteoric waters or heated meteoric water, and temperature and metals contents were relatively low. When the hydrothermal fluid flowed through the cooler metamorphic rocks, temperature decreased and water-rock interaction occurred, leading to the precipitation of minerals.

碲,金矿,华北克拉通北缘