| Abstract:In this paper, it is considered that the Baiyinchang ore field is formed in a struc-tural setting of paleorifting that cuts the sial on the basis of deep-seated structure, vol-canic foration and bimodal volcanism with basic and cala-alkalic, intermediate as well as acidic volcanic rocks, among them, two times of mineralization events in Xiaotieshan, Tongchanggou and so on ore deposits, togehter with Zheyaoshan, Hoyanshan ore de-posits are contemporaneous with the bimodal volcanic activity, that is to say, ore-forming process is spatiotemporally consitent with acidic volcanic rocks. Composition of CO2 fluid inclusion in ore consists with those of upper mantle, except that H2O is hight in con-tent. Ore is characterized by riched in large ion lithophile element and by bearng the assem-blage of mineralization alteration riched in Mg and K, S and Pb derives from lower crust or from upper antle. Sr isotope initial values of exhalation silicalite show that ore-forming meterals origined from an imhomogeneity mantle.S/Se, Co/Ni and Se/Te implay that ore-forming meterals come from deep-seated as well.
In this paper, it is set out that the ore deposit is formed in a strong extensional rifting, which made away with the volatite component, from deep-seated mantle to extending of rift. Mantle releaseda plenty of CO2, containing metallic element, togehter with basic magma of upper mantle, was intruded upwards crust, thus resulted in melting of lower crust to form acidic magma. In the meanwhile, hot brine riched in volatite component and metallic element, being hight in salinity, upswings along the rift, and then flows into sea floor to from ore deposit. |
