Analysis Of Sedimentary Environments And Geochemical Features For The Cretaceous Sandstone-hosted Copper Mine Of Liuju In Yunnan Province

In the present paper the sedimentary environments and geochemical features of the Cretaceous Matoushan Formation, main ore-bearing deposits, are studied in north-central part of the Mesozoic basin of Chuxiong, Yunnan Province, and the following condition are drawn.1.Two types of sedimentary facies, the fluvial facies and lake facies, are recognized in the Matoushan Formation and the top part of the underlying Puchanghe formation. From below upwards, the sequence of sedimentary environments is shallow-shore-lake →river → fluvial-crevasse fan → the overbank lakes→the alluvial fan →dry shallow-lake.2.According the contents of Fe²⁺, Fe³⁺ and copper, the relation between Fe²⁺/Fe³⁺ and contents of copper is analyzed. According the ratios of Fe²⁺/Fe³⁺ and the mineral assemblages in rocks and ores, 5 types of redox environments, strong oxidation facies, weak oxidation facies, redox transition facies, weak deoxidation and strong deoxidation facies are recognized in the study area.3.It is suggested that the tectonic background of the source rock areas of Chuxiong Mesozoic basin are both passive continental margin and active continental margin according to the characteristics of invariable and trace elements of clastic rocks in Liuju sandstone-hosted copper mine.