Forming Conditions Researching Of "Black-type" And "Cyprus-type" Massive Sulfide Deposits In The North Qilian Mountains

North Qilian Orogenic Belt is one of the most important copper mineralized belts in China. Besides the sedimentary-hosted deposits of exhalation (SEDEX)-Jingtieshan iron deposit, volcano-associated massive sulfide (VMS) deposition is the main type in the area. Based on the mineralized tectonics, Petrography and ore geochemistry divide the deposits into two types: one is Cu (Pb, Zn) type mineralization which formed in the felsic lava of continent rift and IA setting; the other is Cu(Zn) type which formed in the ocean crust. The former have been studing for a long time since the exploration of Baiyinchang deposits, in contrary, the later is discussed only for the founding of ShiJuLi (XueQuan) deposits in these years, then shows immense exploitation potential.In North Qilian Orogenic Belt, the Cu (Pb, Zn) type mineralization which formed in the felsic lava of continent margin rift and IA setting has characters of "Black-type" massive sulfide deposit; the Cu (Zn) type which formed in the ocean crust has characters of "Cyprus-type" massive sulfide deposit. Through analyze the mineralizing geological characters, rocks geochemistry, zircon U—Pb LAICPMS dating, tectonic setting, hydro-fluid, regional mineralization potential, we know that both the two kinds deposits formed in the Caledonian time of Ordovician. The "Black-type" massive sulfide deposit formed in the island arc rift setting in North Qilian Mountains, hosted in quartz keratophyre. Magma hydrotherm, seawater and subducting plate liquid composed the mineralizing liquid system together. Different types of mineralizing model formed with the convective circulation system, which limited the margin of the back-arc basin and centered the cove. The "Cyprus-type" massive sulfide deposit formed in the back-arc basin setting during North Qilian ocean-basin subduction within ocean, with the eruption of basic lavas. Magma hydrothermal blended with ocean water, and produced hydrothermal circulation system. The mineralization was controled under seafloor volcano framework and the earth's surface part valley. And altered by the orogenic action later to enrich copper deposit. The acid volcanic rocks in continental rift and IA, basic lava back-arc basin ophiolites developing Ordovician are the very important place to exploration "Black-type" and "Cyprus-type" deposits separately.This paper systemically studies on main elements, trace elements , rare element and Sr,Nd,Pd isotopes of the ore-hosting volcanic rocks represents of Baiyinchang and Shijuli areas. The two kinds of volcanic rocks have clear characters of subduction zone magmas. The difference is the ore-hosting volcanic rocks of Baiyingchang "Black-type" massive sulfide deposit forming in continental margin arc of acting continental margin; and the ore-hosting volcanic rocks of Shijuli "Cyprus-type" sulfide copper deposit forming in ocean arc of within ocean plate. Correspondingly, the quartz keratophyre of Baiyinchang comes from original mantle partly melting with liquid of subduction plate, mixed with some continental crust during the magma rising and invading. Same as Baiyinchang, the source of the rich natrium basalts of Shijuli is partly melting of the original mantle with liquid of subduction plate, but no intermingle of continental materials. The volcanic magma liquid offered abundance of metallic elements Cu, Pb, Zn and so on. Different magma liquid from magma lost gas contains different metallic elements, and formed different types of mineralization elements combination. Researching show that the mineralizing liquid formed the Qilian Mountains Baiyingchang "Black-type" massive sulfide deposit is mixed of magma and marine water, and marine water is primary. The sulfur is mainly from mantal magma, and mixed with continental crust sulfur. The mineralizing hydrothermal system infected by continental crust mostly, and produced with calcium- alkali acid volcanic rocks, so has mineralized characters of "Black-type" massive sulfide deposit, and the mineralizing elements compounding is Zn-Cu-Pb-Au. In the mineralizing liquid formed back-arc "Cyprus-type" massive sulfide deposit, magma increase and marine water decrease. The mineralizing sulfur mainly is sulfate deoxidized sulfur of marine water. The deposit coexists with basalt, and the mineralizing elements compounding is Cu-Zn, showing mineralizing characters of "Cyprus-type" massive sulfide deposit.