四川西昌米市盆地砂岩型铜铼矿中沥青特征及与铜、铼富集成矿的关系

Characteristics of bitumen in sandstone-type copper-rhenium deposits in the Mishi Basin,Xichang,Sichuan Province,and its relationship with copper and rhenium enrichment mineralization

四川西昌地区的米市中生代陆相盆地位于扬子地台西缘。最近在盆地内下白垩统飞天山组(K_(1)f)中发现了与砂岩型铜矿伴生的铼。铜铼矿体赋存于飞天山组碎裂状、透镜状砂岩中,矿石中见有大量细脉状沥青分布。为探讨米市盆地砂岩型铜铼矿床(点)中有机质(沥青)对铜铼成矿的作用,对矿床(点)中矿石及沥青进行了矿相学、显微结构、红外光谱及有机碳同位素组成的研究。结果表明:铜矿物呈它形粒状分布于沥青之中,与之形成交代结构;沥青具有较高的Cu、Re含量;沥青是由下伏三叠系白果湾组中的古油藏发生热裂解形成的,证实了铜铼矿床的形成与古油藏有机质具有密切的空间和成因关系。该类型矿床的发现,为铼等分散元素超常富集成矿研究提供了新的对象。

The Mesozoic Mishi continental basin in the Xichang District,Sichuan Province,is located on the western margin of the Yangtze Craton.Rhenium associated with sandstone-type copper ore has recently been discovered in the Lower Cretaceous Feitianshan Formation(K_(1)f)in the basin.Copper-rhenium ore bodies are found in fragmented,lenticular sandstones of the Feitianshan Formation.Numerous fine-veined bitumen could be found in the ore.To explore the effect of organic matter(bitumen)on copper-rhenium mineralization in sandstone copper-rhenium deposits(spots)in the Mishi Basin,the ore and bitumen in the deposits(spots)were studied on mineralography,microstructure,infrared spectroscopy and isotope composition of organic carbon.The results show that the copper minerals occur in the bitumen as anhedral grains and display athel metasomatic structure.The bitumen has high Cu and Re contents and is formed by thermal cracking in the ancient oil reservoir in the Lower Triassic Baiguowan Formation.The formation of the copper-rhenium deposit has a close spatial and genetic relationship with the organic matter of the ancient oil reservoir.This type of deposit provides a new object for the study of super-enrichment of rhenium and other dispersed elements.