毕家山铅锌矿床有机地球化学研究(Ⅱ):整体有机质特征与成矿物质来源探讨

ORGANIC GEOCHEMISTRY OF THE BIJIASHAN LEAD-ZINC DEPOSIT (Ⅱ) - FEATURES OF BULK ORGANIC MATTER AND SOURCES OF ORE-FORMING MATERIALS

本文应用有机地球化学方法，对毕家山铅锌矿床各类围岩和矿石样品进行了分析，研究了有机质丰度与成矿金属元素含量、有机质演化与矿化之间的关系，进而探讨了成矿物质的来源，为毕家山铅锌矿床的形成提供了一些有机成矿的证据。

The Bijiashan lead-zinc deposit is one of the largest deposits in the Xicheng lead-zinc orefield. ore host rocks are silicolites. The orebodies occur in the contact zone between phyllite andbiological carbonates as well as in cracks of their neighboring rocks. Homogenization temperaturesof fluid inclusions range from 140℃to 290℃, averaging 219℃. The ore-forming solutions have asalinity of 17. 2 equiv. wt% NaCl. Ores and country rocks apparently contain large amounts of organic matter. Possible roles of organic matter in the minerogenesis of ore deposits are discussed.Moreover, the relationship between organic carbon contents and Pb-Zn contents, and between organic matter pyrolysis and Pb-Zn mineralization, and the sources of ore-forming materials arestudied. Pyrolysis data indicate that organic matter in ore deposits is derived from country rbeks,particularly organic-rich carbonates, and the evolution of organic matter in ores and adjacent rockshas reached the over-mature stage. Based on the geological and geochemital data, it is believed thatmetallic elements involved in mineralization come from ore source layers of organic-rich carbonatesand their formation is due to adsorption and enrichment of dissolved metals in seawater by organicmatter, and that sulfur resulted from reaction between the mechanically reduced sulfate and organicsulfur.