The Geochemical Characteristics And Deposit Genesis Analysis Of Liu Mao Graphite Deposit In Ji Xi County Of Hei Long Jiang Province

This paper aims to explore deposit geological characteristics, metallogenic types and patterns of liumao graphite in Jixi,Heilongjiang province through rocks geochemistry test, light thin section identification, SHRIMP zircon U- Pb dating and carbon isotope analysis.Liumao graphite deposit is located in the southern section of the Jiamusi uplift in Jixi Heilongjiang province. It’s ores are hosted in Ximashan formation of Mashan group of the lower Proterozoic. Granites in mining area are rich in K and have high Si contents, which belong to peraluminous rock. The rock is I type granite. The Rb/Sr ratio is greater than 1 and the Sr/Ba ratio is less than 1, which shows that magma derived from the continental crust. Rb/Sr ratio is small and Ba has loss indicate that the original rocks may derived from marine sediments. 206Pb/238 U age distribution of graphite ore is in 478.3±3.9~2 308±16Ma and has wide age range. But most are concentrated in 478.3±3.9~746±16 Ma and 1 870±13Ma~1 958±14Ma. According to the related geochemical diagrams, speculate the original rocks of the graphite ore metamorphic rock series are sedimentary rocks, and almost are sedimentary rocks with calcium, calcareous sandstone, graywackes, mud shale and clay rocks. δ13C of ores samples value is about-20.8 ‰. Comparing the graphite samples in other regions, founded that δ13C values are very close to organic carbon while different to inorganic carbon. It can be concluded that the carbon of graphite ore deposit mainly comes from organic carbon, partly from inorganic carbon deposition.Metallogenic mechanism of Liumao graphite mine is the original rock mining area is a set of shallow Marine- littoral facies sand shale and calcium deposition. Mineralized rocks are mainly sand argillaceous clastic rocks which turned into graphite ore after a series of metamorphism, carbonate which formed marble. Conditions such as temperature, pressure and metamorphic solution changes in the process of regional metamorphism carbon formation, which make the original organic carbon gradually change to graphite. With the augmentation of the late metamorphism, the temperature and pressure increasing, and the superposition of later granite intrusion, the graphite become further rich and recrystallized. Therefore,CO2 carried in carbonate rocks and granite decomposited, which provides more carbon materials for graphite. The organic carbon and inorganic carbon finally formed large crystalline flake graphite after migration, enrichment and recrystallization. Through these analysis and research,it can be summed up that Liumao graphite deposit is predominantly sedimentary metamorphic with superposition of late granite intrusion.