Pacific Palm Copper Polymetallic Deposit In Yunnan Province Volcanic Construction And Chronology Study

This paper takes Simao Dapingzhang copper-poly metallic deposit in volcanic rock formation as the research object. We have unfolded amply and further some studies which have containded the petrology, petrochemistry, trace elements and rare earth element geochemistry, isotope geochemistry(Sr、Nd and Pb) and zircon U-Pb chronology. On the basis this volcano rock of tectonic environment had been renewed, attribute of source and magma evolution had been discussed.Dawazi formation in Dapingzhang copper-polymetallic deposit in mining area are widely distributed, mainly is a set of marine and general alteration of volcanic rocks=And volcanic rocks of the Mining area is divided into four lithologic members and three volcanic activity subcycle.Main rock types of volcanic rocks in Dapingzhang mine:dacite, sodic rhyolite (quartz keratophyre), altered rhyolite, altered basalt (spilite), keratophyre (Na-rich andesite-dacite), volcanic breccia.Volcanic rocks of the mining area on the performance of SiO2focus on the basic and acidic two-side, the larger proportion of mafic volcanic rocks and acidic volcanic and intermediate volcanic rocks smaller proportion have "bimodal" volcanic rocks features. The spilite, angle porphyry, quartz keratophyre, dacite have the characteristics of high-sodium, low potassium, showing the mining area sodium volcanic rocks, volcanic rocks in general has spilite-the quartz keratophyre construction features; and alterationthe the spilite keratophyre quartz keratophyre, has the characteristics of hyponatremia, hypokalemia, never altered flow rhyolite rhyolite�'weakly altered rhyolite�'strong alteration of flow patterns rock SiO2gradually increase, Al2O3, K2O and Na2O in reducing.Volcanic rocks of the mining area series belong to the calc-alkaline series. The volcanic rocks formed in transitional zone which is between active continental margin Island arc environment and back-arc rifting basin.Different volcanic trace elements and REE composition shows that the distribution from the (altered) spilite�'(altered) keratophyre�'dacite�'rhyolite�'(alteration) quartz keratophyre, trace elements and rare earth elements curve is basically consistent with homology to the same period geochemical characteristics of volcanic rocks. The lead isotopic composition of volcanic rocks reflect the lead comes mainly from the orogenic belt, with crust-mantle mixing of lead characteristics. The volcanic87Sr/86Sr higher radiogenic87Sr relative enrichment, and also reflect the characteristics of the magma with crust-mantle mixing source.Chronological study of the mining area of volcanic rocks, the second paragraph of the Dawazi formation dacites of LA-ICP-MS zircon U-Pb age value of428.28±6Ma, combined with relying on the project in this article derived from plagioclase granite porphyrybody age (401.0±1.7Ma) and Liwenchang, Yinguanghou, the mine Au subgroups measured the first paragraph of rhyolite and tuff SHRIMP zircon U-Pb age of417.3±1.5Ma and420.8±1.6Ma,the combination of stratigraphic analysis, that the mining area of volcanic rocks in diagenetic age between410Ma-430Ma, equivalent to the-late Silurian. On this basis, retaining the name of the mining area volcanic rocks of the original stratigraphic units±Dawazi formation, but the volcanic rocks of the Dawazi formation time is redefined the medium-Late Silurian (S2+3). Therefore, volcanic rocks formed late Caledonian.The volcanic magma of the mining area derived from depleted mantle and has crust-mantle mixing characteristics, but to a certain extent by crustal magma source region of the crust-mantle mixing characteristics. Volcanic magma evolution of Dawazi formation has experienced partial melting, fractional crystallization of the assimilation of the role and magma mixing in the formation. So it is a complex process.The relationship between volcanism in the area and Dapingzhang copper polymetallic deposit is very consanguineous. Caledonean-volcanism in this area for Dapingzhang copper polymetallic deposits had offered the formation of material sources,the power of mine, and had restricted its mineralization in time and space.