Geologic characteristics and ore-controls of the Fenghuoshan copper ore deposit, Qinghai province, China

Abstract

The Fenghuoshan copper ore depositis hosted by the lower to middle part of a continental red rock senes of the Upper Cretaceous Fenghuoshan Group in the Hoh Xil Basin in the northern Qinghai-Tibet Plateau. Host rocks consist mainly of dust coloured celadon medium to fine grained lithic quartzose sandstone. Copper-stained layers have lower clay contents and high contents of siliceous or calcareous cement, which formed as a hypabyssal lake depost or delta-front deposit. The ore deposit is composed of 42 copper ore bodies and five silver ore bodies. Ore bodies are shaped as beds or lenses and wallrock alteration isn’t obvious. The ore minerals are composed of chalcocite, digenite and a few of bornite, chalcopyrite, pyrite, galena, sphalerite and argentite. The_δ³⁴S of ore minerals range from_−16.77 to 10.92‰ relative to CDT. Sulfur in the ore was probably derived from a mixture of sedimentogenic sulfate and biogenic H₂S in different proportions, but the sulfur of ore remains close to biogenic sulfur in composition. The man controls of the ore deposit include the comparatively steady continental sedimentary basin, the land source denudation area with high copper content and iron-copper ores, periodic changes of climate and sedimentary environment, the reducing conditions resulting from abundant carbon in moderate-sized sandstone bodies. The genetic type of the Fenghuoshan copper ore deposit belongs to the sandstone type copper deposit in Mesozoic fault basin on the stable block.