Geochemical Characteristics Of Wanbaogou Group-complex Volcanic Rocks From Gouli Area, Qinghai, And Their Significancee

This dissertation mainly studies the meso-proterozoic Wanbaogou Group-complex volcanic rocks from Gouli in the DuLan Area,Qinghai,in geochemistry combining with Stratigraphy, structure,tectonics,regional geology,and petrography etc,to discuss the characteristics of magma evolution and the formation of tectonic setting,A brief analysis of the relationship between Wanbaogou group-complex volcanic rocks and copper-cobalt mineralization,and summed up the genesis of ore deposits of Copper-Cobalt,pointed out that a favorable cobalt copper prospecting area.The following new progresses and knowledge have been procured by the studies of the meso-proterozoic Wanbaogou Group-complex volcanic rocks:1) On the basis of previous studies,the original Wanbaogou Croup is disintegrated,by using non-Smith strata.The disintegrated Wanbaogou Croup is only composed of the volcanic rock association and carbonate rock association,and renamed the Wanbaogou Croup-complex.the volcanic rock association are composed mainly of intermediate basic volcanics,pyroclastic rock and a spot of carbonate rock.carbonate rock association are composed mainly of limestone,dolomitic limestone and Dolostones.2) The major elements of volcanic rocks geochemistry are characterized by lower in SiO2, lower in K2O,lower in Mg#(0.50～0.58),and higher in Na2O,similar to TiO2 of MORB, Chondrite-normalized REE patterns show oblique to the HREE side with intensive enrichment in LREE,similar to the REE patterns of Hawaii ocean island basalts,which indicate that Wanbaogou Croup-complex formed in the oceanic island environment.The spider diagram of trace element shows trace element of this area is 10 to 100 times richer than Primitive mantle.3)The correlation diagram of different kinds of geochemical elements,ratio of incompatible elements,and comparison result of various mantle members indicate that the types of volcanic rocks combination is formed by the partial melting of balance magma;volcanic rocks magma may come from EM1.4) According to tectonic setting diagrams of various kinds of major element and trace element,we can know that the tectonics environment of Gouliwanbaogou group-complex volcanic rocks is ocean island.5)According to the summarization of former researchers' results about Cu-Co deposit in wanbaogou group-complex,and the result of our research,we made further analysis about the relationship between volcanic rocks and the formation of Cu-Co deposit.We think that the volcanic rocks provide material source for ore-forming,and the original tectonics environment provide favorable environment for ore-forming,and the later regional metamorphism transformation further helps the ore-forming material to concentrate. Metallogenesis of Dulenggou Cu-Co deposit can be divided into three stages:The first stage belongs to submarine sedimentary exhalation;the second stage belongs to dynamics -metamorphism hydrothermal mineralization;the last stage is weathering leaching mineralization.