Study On The Geological Characteristics And Genesis Of The Bainaimiao Cu Deposit In The Siziwangqi Inner Mongolia

The Bainaimiao Cu deposit, Inner Mongolia, is located in the Ondor Sum Caledonian accretionary belt of eastern Central Asian Orogenic Belt. Its genesis and tectonic evolution have been debated for a long time. By taking Bainaimiao Cu deposit as research object, this paper is aimed to find out its mineral sources and sure metallogenic types, and provide theoretical basis for its development. Based on collecting and collating the data available, with the geological survey inBainaimiao Cu deposit and the observation of the samples of rocks and minerals from the mining area, this paper summarizes the geological background, geological and geochemical characteristics. It analyzes mineralization and prospecting on the exploration of Cu deposit. The main results are as follows:(1) The ore bodies and mineralization mainly distributed in of the 3 and 5 section of Bainaimiao Group ( mainly middle and low grade metamorphic greenschist ), and its original rock was a submarine eruption of the basic and intermediate-acidic volcanic lava and tuff. The ore bodies are strata-bound.(2) Lead isotope ratios are very stable and in a very small range. (206P)~Pb /(204)~ Pb=17.929~18.486,(207)~Pb/(204)_Pb=15.482~15.581,(208)~Pb/(204)~Pb=37.813~38.343。The lead isotopes of greenschist-type ore in southern belt, granodiorite porphyry-type ore in northern belt and Bainaimiao Group layer appear good linear relationship, which displays that ore-forming materials and stratum of Bainaimiao Cu deposit is formed in the same geological events(3) The range ofδ34S in metal sulfides of Bainaimiao mining area is -5.3‰~+1.9‰, and the average is -2.7‰. Theδ34S composition of southern and northern belts is similar, which explains that sulfur source was the same--mantle sulfur. Sulfur isotopic composition has obvious tower distribution characteristics, which displays volcanic sedimentary origin sulfur by later hot effect modification features.(4) Theδ18O‰average of northern belt in Bainaimiao Cu deposit is +9.72‰,δD‰average is -102.52‰,δ18OH2O average is +2.41‰. Theδ18O‰average of southern belt is +10.02‰,δD‰average is -114.41‰,δ18OH2O average is +2.69‰. The southern and northern belts have very similar hydrogen and oxygen isotopic compositions, which displays that ore-forming fluid was from the same source fluid, mainly mixed water of seawater and magma water.(5) The Bainaimiao Cu deposit has the characteristics of strata-bound, and its ore-forming material had various sources and multiphase. It is marine volcanic gush excessive-metamorphic hydrothermal superimposed copper deposit.