衡阳盆地北缘盐田桥铜多金属矿床地质特征及成因分析

Geological characteristics and genesis analysis of Yantianqiao copper polymetallic deposit in the north margin of Hengyang Basin

盐田桥铜多金属矿床位于衡阳盆地北缘,属湘东金-银-铜-铅-锌成矿带茶恩寺铅锌多金属成矿区,受长寿—双牌断裂构造控制,该矿床发现和突破为深入探索衡阳盆地铜多金属成矿规律带来契机,扩大铜矿资源提供了找矿方向。在研究成矿地质背景、矿床地质特征基础上,矿体中石英、黄铜矿分别进行了包裹体、铅同位素和相关的电子探针测试,结果显示:成矿流体具中低温度、中低盐度、中等密度特征,矿石铅同位素绝大多数具有地壳和造山带特征,显示矿床成矿物质主要来源于地壳深部。由于构造多期次活动,地壳深部带来富硅质含矿热液,沿构造带渗透、运移,在物理化学条件变化的构造空间上沉淀富集,形成硫化物矿体,矿床类型属中低温热液充填交代型铜多金属矿床。

Yantianqiao copper polymetallic deposit is located in the north margin of Hengyang Basin. It belongs to Chaensi lead-zinc polymetallic metallogenic area of Au-Ag-Cu-Pb-Zn metallogenic belt in East Hunan. The deposit is controlled by Changshou-Shuangpai fault structure, the discovery and breakthrough of the deposit brings opportunities to further explore for the metallogenic regularity of polymetallic copper deposit in Hengyang Basin and provides a prospecting direction for expanding copper mineral resources. Based on the study of metallogenic and geological background and characteristics of the deposit, the inclusions, lead isotope and related electron microprobes of quartz and chalcopyrite in the orebody are tested respectively. The test result shows that the ore-forming fluid has the characteristics of medium and low temperature, medium and low salinity and medium density, and most of the ore lead isotopes have the characteristics of crust and orogenic belt. It indicates that the ore-forming materials of the deposit mainly come from the deep crust. Due to the multi-stage tectonic activities, siliceous ore-bearing hydrothermal fluid is brought up from the deep crust, which penetrates and migrates along the structural belt, precipitates and enriches in the structural space with changing physical and chemical conditions, and sulfide orebody forms. The deposit type belongs to medium-low temperature hydrothermal filling metasomatic copper polymetallic deposit.