黔西南卡林型金矿床有机质特征及其与矿床形成关系  

The characteristics of organic matter and its relationship with the formation of Carlin-type gold deposits in Southwest Guizhou Province

作　　者：刘寅[1] 胡凯[1] 韩善楚[2] 孙泽航 

机构地区：[1]南京大学地球科学与工程学院内生金属矿床成矿机制研究国家重点实验室,江苏南京210023 [2]东华理工大学地球科学学院核资源与环境教育部重点实验室,江西南昌330013

出　　处：《地球化学》2016年第3期281-302,共22页Geochimica

基　　金：国家自然科学基金(41373044);教育部博士点基金(20130091130007);南京大学内生金属矿床成矿机制研究国家重点实验室自主课题(ZZKT-201308)

摘　　要：黔西南为我国重要的卡林型金矿产区,有机质丰富为该区矿床的重要特点之一。综合利用多种有机地球化学指标,选取六处典型的金矿床及四处古油藏进行了详细的有机地球化学分析。结果表明:矿床中有机质主要有分散型有机质和聚集型有机质两大类,可能来自于海相菌藻类与陆相植物的混合,并在强还原-还原环境下沉积;金矿床中有机碳的含量与样品为矿石或围岩无关,但与岩性有关;绝大多数样品中R^0均大于2%,表明有机质处于过成熟阶段;氯仿沥青"A"含量、有机转化率、Ts/(Ts+Tm)、C_(29)Ts/(C_(29)H+C_(29)Ts)、升藿烷指数、甾烷异构化指数等多个参数也反映有机质处于成熟-过成熟阶段,并且矿石中有机质的成熟度要高于围岩中,暗示成矿热液对于有机质成熟具有促进作用。综合分析认为大规模烃类运移携带金成矿可能并不存在,有机质对金矿床形成的作用主要体现在对金的预富集、金离子的还原、还原硫的供给及提供可容空间等方面。The Southwest Guizhou Province is an important enrichment area of the Carlin-type gold deposits, in which usually contain abundant organic matter. In this study, a detailed organic geochemistry investigation has been performed on six typical Carlin-type gold deposits and four paleo-oil reservoirs in Southwest Guizhou. The results indicate that organic matter in the gold deposits can be divided into two major types, i.e., dispersed and enriched organic matter, which are mainly sourced from the mixing of marine bacteria and algae and terrestrial plants, and deposited in a strong reducing environment. The content of organic matter in the deposits has no relationship with the sample types, i.e., ores or wall rocks, but is related to the lithology of samples. Most of the samples have R~ values larger than 2%, indicating that the organic matter is at the over mature stage. Chloroform bitumen ＂A＂ content, organic matter conversion rate, Ts/（Ts＋Tm）, C29Ts/（C29H＋C29Ts）, homohopane index, sterane isomerization index all reflect that the maturity of organic matter in the ores is higher than in the wall rocks, implying that the ore-forming hydrothermal fluids probably accelerate the maturation of organic matter. The results indicate that the migration of hydrocarbons may not be the main reason for the formation of gold deposit, and the roles of organic matter in the ore-forming process are mainly reflected in the preconcentration of Au, the reduction of Au ion, the supply of sulfur and accommodation space for Au sedimentation.

关 键 词：卡林型金矿 有机质 成矿过程 黔西南 

分 类 号：P593[天文地球—地球化学] P611[天文地球—地质学]