Abstract:

The Luchun massive sulfide deposit is located in the LuchunHongponiuchang rift basin. The Luchun copper deposit occurs in a series of bimodal volcanic rocks which are dominated by acidic volcanics. There are upper and lower orebodies in the ore district: the upper is black and lower is yellow. The assemblage of minerals, with higher contents of sphalerite, galena and chalcopyrite, is simple. Trace elements and REEs geochemical data on the minerals are similar to the volcanics. The result of sulfur isotopic analyses shows that the 34S values vary from 115‰ to 178‰. Ore lead isotopic compositions are rather uniform, as evidenced by the Pb isotopic ratios: 206Pb/204Pb=18498 to 18626；207Pb/204Pb=15588 to 15760；208Pb/204Pb=38430 to 38974. It is clear that the evolution history of the rift basin. And the bimodal volcanics in the basin are typical of oceanic ridges or intraplate extensional settings and island arc, it suggests that the tectonic setting in this area is extensional and rifting. The deposit was associated with the bimodal volcanic rocks in the extensional setting, which was favoured to the formation of the hydrothermal fluids circulatory system. The hydrothermal fluids exhaled and precipitated to form the Luchun VMS deposit.

Key words: basin evolution, geological characteristic, geochemical characteristic, Luchun copper deposit, Yunnan