扬子地块西北缘及西南缘卡林型金矿的有机质地质地球化学

扬子地块西北缘，西南缘卡林型金矿床的有机碳含量为０．０５％－８．７３％。含金建造形成的环境不同，其改造成的金矿床的有机碳含量不同；矿化主岩的岩性不同，基有机碳的含量不同。由浊积岩型含金建筑改造成的卡林型金矿床，其干酪根属Ⅱ型酪根，原始有机母质属还原环境沉积的海相菌藻类生物演化成的腐泥型有机质。

Geological and geochemical characteristics of organic matter in the carlin-type gold deposits in the northwest and southwest margins of Yangtze Plate

The organic matter of the Carlin type gold deposits in the northwest and southwest margins of Yangtze plate can be divided into three types based on their modes of occurrence: original sedimentary type, hydrothermal transformation type and structural migration type. The organic carbon content of the Carlin type gold deposits on the northwest and southwest margins of Yangtze plate is 0.05%~8.73%, averaging 0.95%. Organic carbon content is fairly high in gold deposits where thermal spring activity took part in the forming process of their auriferous formations, whereas organic carbon content is relatively low in gold deposits where auriferous formations were formed in abyssal and bathyal turbidite sedimentation environment. Clay rock and siltstone have somewhat high organic carbon content, while organic carbon content of limestone is comparatively low. There exists positive correlation between organic carbon content and gold content in turbidite type auriferous formations and also in mineralized altered shatter zones. Nevertheless, organic carbon content and gold content in ores or host rocks show negative correlation. In Carlin type deposits transformed from the turbidite type auriferous formations, the kerogen is of Type lI. and its original organic matter is sapropelic organic matter from evolution of bacteria and algae formed in a reducing environment. The maturity of kerogen is high, belonging to catagcncsis. The element composition of kerogen is an important criterion in judging metamorphic grade and ore potential of the auriferous formation. Element composition of kerogen in large Carlin type gold deposits on the northwest and southwest margins of Yangtze plate shows that decarbonization and endogenic oxidation of ore-forming fluids must have taken place in the metallogenic process. The gold content of kerogen is higher than that of ore, so that the kerogen must have been an important gold carrier in the Carlin Type gold deposits.