Abstract:

The Hongliugou mafic-ultramafic rock in Beishan of Gansu is located in the Beishan rift belt on the northern margin of the Tarim Plate, rock mass was emplaced in the Dunhuang rock Group. The main rock types include gabbro, olive gabbro, olive norite-gabbro, olive hornblende norite, olive gabbro-norite, lherzolite, olive pyroxenite and pyroxenite. The olivine belongs to chrysolite, and its Fo is between 66.97% and 82.92%; meanwhile, the orthopyroxene and clinopyxene are bronzitite and oblique/diopside, their composition of En ranged from 68.49 to 77.65 and 45.85 to 48.81; the plagioclase is labradorite, and its An is between 58.70 and 72.69; amphibole is hornblende. The Mg# of parental magma ranged from 0.59 to 0.62, indicating that the parental magma belongs to high magnesium tholeiitic magma. The process of magmatic evolution experienced fractional crystallization, such as olivine, orthopyroxene, clinopyroxene and plagioclase, which controlled by clinopyroxene and orthopyroxene.The process of magma emplacement has suffered contamination of the lower crust. By the research of the tectonic environment, parent magma, rock type, degree of magmatic differentiation, contamination, we consider that the Hongliugou intrution has a potential to form a sulphide deposit.

Key words: petrogenesis, mineralization, Hongliugou rock, Beishan,Gansu