Permian Basalt In Northeastern Yunnan Copper Deposit

The northeast of Yunnan province laid on the west part of Yangtze Platform. This region cropped out very large areas of Emeishan continental flood basalt (CFB). Previous study contained much information about this region such as magma action, section, structure background, mineral geochemistry and deposit geochemistry related to the continental flood basalt, but there is little study about deposits types, metallogenetic material, metallogenetic process and metallogenetic time. Our research region's Emeishan Basalt has divided into four part of mineral, Most of the copper mineral occurred in the fourth layer of Emeishan Basalt and bottom of Permian Xuanwei formation which on the top of sedimentary discontinuity. According to the host rock controlled mineral, it can be classified to three types, the first one is basalt-type copper deposits, the second one is carbonaceous sedimentary interlayers-type, and the last one is bauxitic mudstone-type on the sedimentary discontinuity. Themineralization has significant related to the basalt in the deviate of mineral material and space distribution. At the same time, geological structure had affected mineralization in various degrees; metallogenetic function is later than the form of Permian basalt conspicuously.This article has selected several deposits of the three types of Cu deposits in the Ludian-Huize region. Based on the previous study, this article discusses host-rock, trace-elements, REE, stable isotopic, organic geochemistry and fluid inclusions of copper deposits systemically, and the metallogenetic process was discussed simply. The main conclusions are as follows:1. Base on the recent system study of Daheishan copper deposits, we built a new type of copper deposits- bauxitic mudstone-type. This type of copper deposits appeared in the gray, celadon bauxitic mudstone or purple and maroon bauxitic mudstone which laid in bottom of Permian Xuanwei formation. The ore body is stratiform or stratoid structure. Ore mineral is bornite and chalcocite, some part contain higher pyrite, secondary ore mineral is malachite, melaconis and covellite, gangue mineral is kaolinite, ascanite and so on..2.According to the research of Pb isotopic, the metallogenetic material mainly originated from the Permian basalts; the study of sulfur isotopic find that the sulfur of the basalt-type copper deposits and carbonaceous sedimentary interlayers-type copper deposits originated from both Permian basalts and evaporate of sedimentary section, S in bauxitic mudstone-type copper deposits originated from evaporate of sedimentary layers.3.The ore body of the copper deposits mainly occurred in the interlayer sliding belt/fracture belt, so the time of metallogenet is not before the structure of Yanshanian, in the stage caused the sliding of the sections.4.The copper value of bauxitic mudstone-type deposits on the sedimentary discontinuity is 0.022～2.71×10^-2, the value of Ga is 60～87×10^-6 and Co is 134～ 197×10^-6, both reach the standard of industrial utilization grade.