Fe Isotopic Characteristics of V-Ti Magnetite Deposit in Panzhihua Area of Sichuan Province and Their Genetic Implications

The whole rock and ore mineral magnetite Fe isotope compositions of layered rocks and ores in the Panzhihua vanadium-titanium magnetite deposit of Sichuan Province were analyzed in this paper.The distribution range of δ 57 Fe in the whole rock is about 0.02‰ to 0.25‰,with the average of 0.17‰,and that in magnetite is about 0.05‰ to 0.61‰,with the average of 0.36‰.Fe isotope composition of magnetite is higher than that of whole rock in every sample,and there exists a negative correlation between the heavy degree and the magnetite content.The negative correlation between Fe isotope composition of magnetite and environmental oxygen fugacity suggests that the magnetite in the whole rock was in-situ crystallized,and no gravitational differentiation of magnetite happened.The characteristics of magnetite Fe isotope composition demonstrats that the process of magma complement and fractional crystallization resulted in the formation of the Panzhihua vanadium-titanium magnetite deposit.During the creation of bottom petrofacies,frequent basaltic magma complement formed bulk magmetite with insignificant variation of δ57Fe.During the creation of middle petrofacies,infrequent magma complement formed many alternations of magnet gabbro and gabbro.The ore-forming oxygen fugacity of the initial magma in Panzhihua was relatively high,and the oxygen fugacity gradually decresed with the magma evolution.The conclusion also reveals the ore-forming mechanism of the Panzhihua vanadium-titanium magnetite deposit in Sichuan.