地质界面对桂中凹陷区铅锌矿床的控制意义

Control Significance of Geological Surface for Pb-Zn Ore Deposits in Guizhong Depression

桂中凹陷大地构造条件特殊,其北为桂北台隆,与扬子地台接壤,其西与右江再生地槽连接,其东和南与大瑶山隆起相连.在区域性范围内,广西大部分铅锌矿床分布于桂中凹陷的边缘.其中,河池-南丹成矿带几十个大-中型和特大型铅锌铜矿床位于凹陷的西部及西北部边缘,在凹陷的东南部和东部边缘有武宣-象州成矿带的几十个大-中型和特大型铅锌铜矿床,在凹陷的南、北和东南、东北部边缘地带则连续分布着宾阳、贵县、锡基坑、北山、泗顶等若干个大-中型铅锌铜矿床.在矿区范围内,铅锌矿体主要产于不整合面附近、多组断裂的交汇部位、岩体的周围、沉积岩相变带、不同岩性接触面等.不论在宏观的区域范围内,还是在微观的矿区范围内,矿床的成矿作用和分布明显受到地质界面的控制,其主要特征与美国MVT铅锌矿床相似.地质界面是地球内部能量集中、汇集、传递、转化和释放的地带,是地球物质变化、活化、迁移和沉淀富集的部位,也是成矿作用发生的场所.桂中凹陷与周边地质构造单元接合处的地质界面是“MVT型”铅锌矿床形成的有利地段.

The Guizhong depression with special geotectology conditions is bounded on the north by the Guibei antiklise and the Yangtze platform, on the west by the Youjiang regenerated geosyncline, and on the east and the south by the Dayaoshan rise. In the region, most of the Pb-Zn deposits in Guangxi Zhuang Autonomous Region are distributed around the Guizhong depression. The ultra-large scale and large-moderate scale Pb-Zn ore deposits of the Hechi-Nandan metallogenetic belt lie on the boundary of the west and the northwest of the depression, the deposits of the Wuxuan-Xiangzhou metallogenetic belt lie on the boundary of the east and the southeast of the depression, and many deposits such as Binyang, Guixian, Xijikeng, Beishan and Siding lie on the boundary of the south, the north, and the northeast. In the ore district, the occurrences of the orebodies are controlled principally by different geological surfaces like the plane of unconformity, the contact of some faults, the periphery of magmatic rock, the site of sedimentary facies change, and the contact areas of diverse lithofacies. Whether within the region or within the ore district, the mineralization and distribution of Pb-Zn deposits are evidently controlled by the geological surfaces. The characteristics demonstrate that Pb-Zn deposits around the Guizhong depression are very similar to the MVT Pb-Zn deposits in the Mississippi Valley, USA (MVT). The various geological surfaces are the district of the transmission, concentration, conversion and release of energy within the earth, and are the place of the change, the activation, the transportation and the precipitation of the materials of the earth, and are the locale of the mineralization. The geological surfaces in the joint of the Guizhong depression with the peripheral geological structure units are the favorable districts of the mineralization of the MVT type lead-zinc deposits.