The Tectonic Evolution Of The Dongchuan, Yunnan Copper And Gabbro Geochemical Characteristics

Dongchuan Copper deposit in Yunnan is a Large and Super-large copper deposit which occurs in the stratum of Mesoproterozoic Kunyang Group. The thesis sponsored by the national special prospecting of the resources crisis mines which named"Mineral resources survey of the Dongchuan Copper deposit in Yunnan"(Nunber:200553026).The rock-control and ore-control fuction of tectonic is obvious, meanwhile the magmatic and hydrothermal activity occurs frequently. Based on previous research, the thesis analysis emphasisly the mechanical property of tectonic structural plane and the impact on the ore body. Combined with the evolution history of Central Yunnan province and Kunyang rift valley,the history of tectonic deformation in Mining is restored. And applying the principles and methods of magmaticrock geochemistry, the thesis establishs the discrimination mode of the basic gabbro type and the tectonic environment. Through field investigation and indoor synthesized analysis, obtain the conclusions as below:(1) The orefield fractures highly developed, the construction types are various and the characteristics appear significantly. Combined with the tectonic development and the mechanical property of tectonic structural plane,the thesis divide the mine construction into at least three periods and six groups. Through the the division of the structural stage and the tectonic epochs, and meanwhile combined with the construction analysis and structural analysis, the paper reconstruct the mining history of structural system. The ESR dating data of quartz and calcite show that the post-transformation in mining still accurs intensely, the activities late age of the shallow brittle faults concentrated in the 22.4～32.8Ma.(2) The basic intrusive rock related to mineralization in Dongchuan copper deposit is the alkaline gabbro which shows the characteristics of higher Ti and richer alkali. All samples fall into the scope of alkali basalt. Total alkali vs silica diagram.The gabbro is characterized by "humped" in MORB normalized trace element sider diagram for gabbro, and is highly enriched K,Rb,Th, and Sr,Ta,Nb,Ta,Sm,Y are relatively deficit, Nb/Ta<1,(0.42～0.83),similar to the intea-contineral rift basalts and show the character of WPB.The REE pattern of gabbro is right dipped and the fractionation of LREE-HREE is obvious. The sample is characterized by obviously Eu positive anomaly, which maybe caused by the deep magma upwells and then occurs differentiation and evolution in the high oxidation state. Tectonic discrimination diagrams drop-in intraplate basalt region. Combined with regional geological features and prior research results, the gabbro in this district probably formed in the stretch stage or initial rift phase of the continental rift.(3)The thesis establish the orefield prospecting signs of the tectonic and magma, and according to geological conditions, combined with geochemical and geophysical prospecting signs, delineate 3 prospecting targets,and meanwhile forecast that the deep target extends deep well and conceales the existence possibility of the ore body. The researching results provide a new idea and method which can be useful in the structural control character, searching copper and iron ore deposit in magmatite region and the concealed orebody forecasting, which provides the theoretical basis for the mineing prospecting and the feature work.