Mineral Geochemical Characteristics And Genesis Of VHMS-type Deposits

This essay contrast the Noranda Hongtoushan Cu-Zn massive sulfide depositsin Baiyinchang，Paleozoic polymetallic massive sulfide deposits which came from Arcand back arc basin tectonic environment with the tectonic environment mineralassemblage characteristics of modern seafloor black smoker in Okinawa Trough. Andthrough the test methods of ICP-MS，electron probe and laser ablation etc，the essayalso contrast the The Cu-Zn mine, Baiyin Cu polymetallic in Hongtoushan area withthe geochemical characteristics of ores and mineral elements in Different zonings ofOkinawa Trough. The Research suggests that the Hongtoushan deposit of Cu-Zn，Cu(Zn) deposits in Baiyinchang and Okinawa trough modern black smoker chimneyswere formed in island arc，arc and back-arc basin tectonic environment. And Themetallogenic epoch respectively Archean，Paleozoic and modern time. Although thereare great diffirences among them, the main characteristics of the ore deposit are verysimilar with some little differences. The Hongtoushan Cu-Zn deposit ore mineralassemblage are sphalerite+chalcopyrite+pyrite and pyrrhotite. The galena is notdevelopment. And Cu (Zn) deposits in Baiyinchang are with chalcopyrite, sphalerite,pyrite and a small amount of pyrrhotite and magnetite. But the galena and sphaleriteare develop in Xiaotieshan.and the chalcopyrite+galena+sphalerite are developedwell in Jade area of Okinawa Trough modern seafloor black smoker. In Yipingwu thatare chalcopyrite+sphalerite with little galena. Ore types are the same in essentialswhile differing in minor points because of the same geological environment and localsource rock， tectonic environment and conditions of temperature and pressuredifferences. And these may reflect the same hydrothermal metal concentrationdifference and metallogenic system of water rock reaction system differences. Test data of the ore ICP-MS show that The main elements of the massive sulfidedeposits are Fe，Cu，Zn，Pb and the contents of Fe，Cu are higher In each modernseafloor hydrothermal area. The content of Zn，Pb varie greatly because of the Theinfluence of various factors as Source material, elements geochemical behavior ofelements and properties of fluids. In the Baiyinchang and Hongtoushan deposit，Cuand Zn were positively related to and Pb come from different sources with Cu and Znbecause Pb is negative correlation with Cu，Zn. In Minor element of ore Co, Mncontent is high，affected by the geochemical behavior with low content of Ni in whichThe Hongtoushan deposit of Cu-Zn Co, Mn content was higher than that of Cu (Zn)deposits in Baiyinchang. In Cu (Zn) miners of the Okinawa trough chimneys andsilver factory As，Sb，Se，Tl，Ag，Au are higher than the Hongtoushan. this showsthat the ore material sources of acidic volcano rock from its heat and mass transfer.And the mineral sources of Cu-Zn deposits in Hongtoushan is more affinity to basicrock.Chalcopyrite and sphalerite are the miners that developed in the Hongtoushandeposit of Cu-Zn, Cu (Zn) deposits in Baiyinchang and Okinawa trough modern blacksmoker chimney. Maybe the differences in geochemical characteristics reflct theDifference of ore-forming material source and metallogenic water-rock reactionsystem. With the analysis of the main contents of trace test on mineral electron probe，laser ablation ICP-MS tests and ore，the contents of Co，Fe，Mn and Sn are higher ininner sphalerite zone with the higher contents for In、Sb、T1、Ge、Ag in central andouter sphalerite zone. Among them, the average content of Cd were0.23%，0.18%and0.15%respectively in inner，central and outter sphalerite zone. And these show thefeature that the content gradually reduced with the temperature reduced.The formation of the Okinawa trough modern black smoker chimney and Cu (Zn)deposits in Baiyinchang has to do with acidic volcanic rocks，whereas the Cu-Zndeposit Hongtoushan and mafic rocks are closely related. It is an importantsignificance to provide the basis for prospecting.