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

Abstract

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 (K1f) 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.

Keywords

• sandstone-type copper-rhenium deposits
• scattered metals rhenium
• organic matter
• bitumen
• extraordinary enrichment
• mishi basin