An analysis of geochemistry and metallogenesis of Bengge alkaline igneous complex in northwestern Yunnan Province

Abstract：The metallogenic theory of trans-magmatic fluid and mechanism of the interaction between mantle fluid and crustal hydrothermal fluid provides a credible explanation for the idea “little intrusion could form large deposit”. The geochemical characteristics suggest that the Bengge alkaline complex had been strongly affected by deep fluid and the ore-forming elements were not provided by the magma or melt which formed the Bengge complex. The ore-forming fluid system and the magma were independent of each other. It is believed that the mineralizing process was controlled by the trans-magmatic fluid and the mechanism of interaction between mantle fluid and crustal hydrothermal fluid. The ore-forming mantle fluid was not mixed with the alkaline magma but they could move together. During the crystallization of the alkaline magma, on the one hand, the mantle fluid could alter the alkaline body; on the other hand, the mantle fluid might escape from the magma and move to the physical-chemical boundary layer which was favorable for the enrichment of the ore-forming elements. During this process, the mantle fluid could react and extract the ore-forming elements in the crust, which was helpful to the formation of a large ore deposit. Based on the above analysis, the authors hold that Bengge alkaline complex has attractive ore potential.