Binchuan - Chenghai Permian High-mg Volcanic Rock Geochemistry And Ore

Emeishan basalts widely spread out in the west margin of the Yangzi block. Because of this, Geo-science circles are interested in this region. According to characteristics of petro-assemblage and petrography, Emeishan basalts can be divided into three-big rock regions- west, middle and east. These basalts are mainly formed in the course of mantle upwelling and widely continental extensionism through analyzing tectonic setting and pale-geographical setting. This extensional activity is similar to the basin-and-range province of western America, and can be thought as an intra-continental tectonic system.On the basis of formers' research results, the paper systemistically discuss some characteristics of Emeishan basalts' petro-geochemistry and magma activation. Emei-mantle plume's activity is very violent in Binchuan-Chenghai region,and a lot of its axis material is exposed in this region. According to the content of MgO, Emeishan basalt can de divided into high-Mg (MgO>12%) volcanic rock and lower- Mg (MgO<12%) basalt. Using the tracer ability of petro-geochemistry,the paper discusses on source characteristics and magma evolution of the high-Mg volcanic rocks. High-Mg volcanic rocks approach the primitive mantle compositions, and their magmatic source is close to the composition of BSE , derives from the lower mantle and formed by this type- mantle rocks' fractional melting highly (>25% ) .High-Mg volcanic magma , formed in the axis of the Emei mantle plume, underwent the crystallization differentiation of olivines and some pyroxenes; some olivines reflect fair cumulus crystallization. During the magma evolution, this primary magma suffered effects of the containing water fluid and a small extent contaminate of continental crust.According to all of features above,the paper analyzes the formatting mechanism of high-Mg volcanic rocks.Beginning with the minerogenetic theory of mantle plume, the basic geological conditions of this type deposit can be summarized through studying typical copper-nickel sulfide deposits which have close bearing on continental flood basalt .In contrast with high-Mg volcanic magmatic activity,it can be found that some intrusive rock bodies have Ni-minerogenetic geology condiction.Xilaping rocks in Binchuan-Chenghai region has some basic geological condiction and reflects some extent minerogenetic.All these testify this region has very larger potentiality of finding copper-nickel sulfide deposits.