Geological Characteristics And Genesis Of The Beizhan Iron Deposit In Hejing,Xinjiang

Beizhan iron deposit is a large-scale magnetite deposit which located in Hejing,Xinjiang. The proved iron reserves of it has been almost reached to 500 million tons. The formation of the iron deposit has a close relationship with the basic- intermediate volcanic wall rocks which around it both in spatio-temporal and genesis. Though predecessors have carried out many research works of the two through various research methods in different aspects and at different levels,they failed to reach an agreement on the issues of the tectonic environment,the metallogenic mechanism and genetic type of this iron deposit.Based on the research achievements of the predecessors firstly and we use many methods to study it further in this paper. The research methods which we used in this course mainly including field geology, petrography and mineralography of trace geochemistry, Sr-Nd isotopic geochemistry, zircon U-Pb isotope chronology, typomorphic characteristics/ O isotopes characteristics/ in-situ analysis of the magnetite and so on.Research results suggest that the wall rocks formed in the tectonic setting of continental island-arc,which have a close correlation with the subduction of the North Tianshan Oceanic basin towards south beneath the Yili plate during the Late of Early Carboniferous. The forming of mother magma of basic- intermediate volcanic wall rocks was controlled by partial melting of the lithosphere mantle which had been metasomatited by fluid. The parent magma has experienced fractional crystallization and crustal contamination in the process of evolution. Fe is from basaltic magmatism. And metallogenetic ways of this iron deposit mainly including liquation of oxide, cryptoexplosion and hydrothermal metasomatism. According to the study of ore fabric and some other aspects, the metallogenic phases of Beizhan iron deposit can be devided into two periods, namely cryptoexplosive-pulp metallogenic period and cryptoexplosive-hydrothermal period. Lithosphere extension, volcanic mechanism, evaporation and many other important factors do a joint control to the form of Beizhan iron deposit.The genesis of this iron ore deposit belongs to volcanogenic deposit which was the product of synthetic action of ore pulp and volcanic hydrotherm.