The Petrogeochemical Characreristics And The Metallogenic Analysis Of The Ore-bearing Basic-ultrabasic Rocks In Panxi,Sichuan

The basic-ultrabasic rocks in Panxi is a Emei igneous province. The basic-ultrabasic rocks’ petrogeochemical characreristics of Baima Orefield, Hongge Orefield, Panzhihua Orefield are analyzed, and some preliminary conclusions are drawn as follows:(1) According to the relationship between rock mass and structure,Panxi basic-ultrabasic rocks are divided into two main sub-types. One of which mainly distributed along the Anning River and it belongs to the Anning River basic-ultrabasic sub-type, beginning from Taihe ore body in the north, the basic-ultrabasic rocks are mainly occurred as layers; southwards through the Baima rock to Hongge rock. The other one is Panzhihua sub-type,and they mainly distributed at the eastside of the Panzhihua fracture, the basic-ultrabasic rocks are also mainly occurred as layers, and the vanadium bearing titanomagnetite in the rock body are occurred with a stable horizon.(2) Rhythmic layering and lithofacies cycles are developed in the rocks of Panxi region, the rhythmic layering result from the push of the solidification surface and the diffusion of the magma, while the lithofacies cycles show up as regularly repetition of lithofacies assemblages cycles. In general, the basicity is gradually increased from the bottom to the top. Rhythmic cycles indicate that the magma in this region have a mutli-phase characteristic. Metallogenic basic-ultrabasic rocks are located at the middle and lower segments of the cycle.(3) The alternating interbed layers are embodied in the alternation and superposition of color ratio, content and chemical composition of major rock-forming minerals. The whole rocks can be divided into several large rhythmic layers, and each of them can be further divided into several small rhythmic layers, and all of the rhythmic layers have a common characteristic that the top-down color ratio roughly change from light to dark.(4) The petrogeochemistry of the Hongge orefield, Baima orefield, Panzhihua orefield demonstrates that the basic-ultrabasic rocks of all three belong to high-K tholeiite series. Revelant plots of oxides show that oxides take part in the process of the magmatic crystallization-differentiation all the time. The standard curve of chondrite of rare earth element reveals that Panzhihua orefield and Baima orefield have a Eu positive anomaly, while the Hongge orefield has no Eu anomaly. The primitive mantle-normalized spider diagram of trace elements reveal that all three orefields deplete Zr, one of the elements of HFSE.(5) Based on the predecessor’s dating data, the formation age of the basic-ultrabasic rocks in Panxi is consistent with the age of the main eruption of Emeishan basalts, and the is approximate to 260±2Ma. And this evidence indicate that Emeishan basalts and the basic-ultrabasic rocks in Panxi are homologous but heterogeneous product formed during the process of the evolution of the same magma.