The Basic Characteristics Of The Zhuopan Alkaline Complex In West Yunnan, SW China, And Its Significances On Tectonics And Resuorces

Although the distribution of alkaline rocks on Earth is less, it brings the deep material and ore-bearing fluid, which have important significance for the study of deep material composition and associated mineralization. Zhuopan alkaline intrusive complex is located in the west of Lanping basin,next to the Jinshajiang-Ailaoshan fault zone. This paper made a further study about its petrography, petrogeochemistry and isotopic chronology. Meanwhile, we discussed its formation and evolution, and significances on resuorces reference to previous research results.This alkaline complex composed mainly of alkaline gabbronite and some pyroxenite. The light-colored mineral, alkali feldspar, and more have been mudding, with poor euhedral degree. The dark minerals, mainly consisting of pyroxene and biotite, have fine euhedral degree and most of the pyroxene is augite. The accessory minerals include apatite, sphene, magnetite, zeolite, kaliophilite and other minerals. MLA scan showed the most important REE-riched mineral is（cerium） apatite.SiO₂ content of all the rock samples range from basic rock to intermediate rock. Total alkali content and Rittman index confirmed the complex is characterized by high alkaline. Geochemical illustration shows it belongs to high-K shoshonite series. Chatracteristics of REE show high ∑REE and LREE enrichment type, with weak Ce and Eu anomaly. Trace elements are characterized by enrichments in LILE, relatively depletion of HFSE. Characteristics of trace element indicate that the source region is enriched mantle or metasomatic mantle, and subjected to intense crustal assimilation and contamination.The result of zircon U-Pb dating is 37.4Ma, representing the emplacement age of the complex. The K-Ar ages of orthoclase ranging from 19.8Ma to 30.3Ma, is likely to show that the rock has undergone multiperiodic and longstanding hydrothermal activity after emplacement. Reference to previous research results, we believe that the original enriched mantle magma and mantle derived fluid is in a state of immiscibility. After the end of the regional main-collision stage, they rised along regional deep strike-slip faults in the beginning of local stress adjustment. On the way up to shallow crust, they contaminated lots of crustal components and ore-forming elements, and eventually emplaced along the main pull-apart fault and buried fault. Then the complex gradually formed the current petrographical zonations and geochemical characteristics, and caused the loss and dispersion of ore-forming elements, on account of the later tectonic movement, weathering denudation and multiple hydrothermal activities which began around 30 Ma.In the vicinity of the complex, clay minerals and iron ores have been mining, and gold placer-mining has a long history. Local rare earth content is also very high. Thus the further investigation for surrounding Au and REE is very necessary. At the same time, Zhuopan complex, as the only "deep phase" alkaline rock in West Yunnan, the further study of it can help to explore the deep material composition of other Cenozoic alkaline rocks.