Tectonic-Magma-Mineralization Dynamic Evolution Pattern Of Baiyinchang Orefield

Marine volcanic massive sulfide deposit is one of the major commercial types of copper deposit in china. The Baiyinchang orefield is a typical bigger massive sulfide polymetallic orefield, which located on the eastern part of the Qilian mountain chains. Predecessors have done a great deal of work on structure, metallogenetic volcanic character, volcanic framework, genetic models of deposits, and metallogenetic laws, and all of these have been made a substantial contribution. Whereas there was not system cognition in coupling connection of tectonic-magma-mineralization. A great deal of dada show marine volcanic massive sulfide deposit was closely associated with tectonic settings in temporal aspect and spatial aspect. Therefore, solved the problem was propitious to deeply apprehend mechanism of rock and ore formation and metallogenic deposit regularity, and deeply know tectonic evolvement and metallogenic deposit regularity of Qilian mountain region, also to exploration appraise expansion of Qilian mountain region and search new the style of Baiyinchang marine volcanic massive sulfide deposit.Volcanic rock system in Baiyinchang orefield was formed in marine environment with multiple metamorphism, which explains high and general alteration, and radioactive parent and daughter could not keep relative stability closing system in the process, leaded stratum epoch of the ore bearing volcanic and outer volcanic sediment metamorphic rock was a difficult problem pendent, so geological events of tectogenesis, magmatic activity, metallogenesis lacked dating materials, and effected study coupling connection of tectonic-magma-mineralization.Wherefore, the first work was study area geology setting and character of type deposit of Baiyinchang orefield, and expatiate applicability and localization of diversified isotopes dating, then fixed on dating method first was U-Pb isotope and assisted Rb-Sr and Pb-Pb. Zircon typomorphic peculiarities, genetic classification, occurrence environment, metamict degree were researched using Pupin(1980) the population typology of zircon and Infra-red Spectra Analysis, and main methods of isotopic dating were confirmed by taking zircon as a principal research object. Age of main geological events and space variation regularity were determined, and Dynamic evolvement process on occurring, developing, continuing was taken to recognize the structure, magma activity and metallogenesis in the region. Lastly, found tectonic-magma-mineralization dynamic evolution pattern of Baiyinchang orefield. was that: Structure magma activity in the region had begun before 574.2 Ma. Because of frequent cracking and tensile tectogenesis and very flourish magma activity, magma in deep crust up intruded along tectonic fault, then there was appeared a strong thermal metamorphism process near the earth's surface. With continuing structure magma activity and energy accumulating, magma squirted the earth's surface and initiated volcanic activity event in the region in 458.99 Ma. It was floruit of volcanic activity in middle Caledonian between 446 Ma and 440 Ma. Mass volcanic rock was squirted, and ore bearing magma was risen by tectonic fissure, then formed a large-scale valuable polymetallic sulfide orefield. Then volcanic activity decreased, and mass magma activity went to end, there existed feebleness intension magma activity only in part area. Afterward, global large-scale massive volcanic activity in Permian Period generally brought about metamorphism whole middle Cambrian Period volcanic sediment rock in research area.