摘要: The Jinchuan Cu-Ni Sulfide Deposit is the biggest magmatic Cu-Ni sulfide deposit in China. It occurs in the Jinchuan Ultramafic Massif which is located in central Gansu Province. The massif was formed through the intrusion of thre... 展开 The Jinchuan Cu-Ni Sulfide Deposit is the biggest magmatic Cu-Ni sulfide deposit in China. It occurs in the Jinchuan Ultramafic Massif which is located in central Gansu Province. The massif was formed through the intrusion of three stages. The lherzolite, plagioclase-lherzolite, olivine-websterite etc. were formed in the first and the second stages; and the sulfide dunite was formed in the third stage. The Cu-Ni orebodies of the Jinchuan Deposit mainly occur in the lherzolite and sulfide-dunite. The original magma of this massif is komatiitic. The main minerals of the massif and the orebodies are chrysolite, bronzite, endiopside, pargasite, plagioclase, Ti-bearing phlogopite, phlogopitc, clinochlore, pyrrhotite, pentlandite, chalcopyrite, cubanite, mackinawite, magnetite, chromite, etc. The chrysolite, pyroxenes was often replaced by serpentine, magnesiocummingtonite and tromolitc. The fabrics of the Tocks in the massif and ores in the orebodies are similar. Based on the mineral intergrowth relationships the authors get to the conclusion that the evolution history of each intrusive can be divided into two stages: The first stage is the main solidifying stage. During this stage, about 70-80% of the volume of the intrusive was solidified, and chrysolite, pyroxenes, plagioclase, euhedral pargasite, etc. formed. The second stage is the ore forming and autometamorphism stage. In this stage, pyrrhotite, pentlandite, chalcopyrite, chromite(Chr2), magnetite, etc. and some hydrosillcates such as Ti-bearing phlogopite, phlogopite, fibrous pargasite, tromolite, clinochlore, serpentine, etc. formed. There was a late stage liquation of Fe-Ni-Cu-Cr-S-O melt from silicate melt which was rich in water and alkalis in the residual magma after the main solidifying stage. The mineralization process of the Jinchuan Deposit is recognized as " crystallization differentiation + late stage liquation". The ore minerals of the Jinchuan deposit had a very special crystallization process. Simply, the process can be described as: chromite(Chri)→pyrrhotite→"pentlandite +magnetite solid solution (PMSS)"+iss; when PMSS exsolved, pentlandite and magnetite(Mt2) formed; and chalcopyrite and cubanite formed when iss exsolved. 收起