Xu Maichao geological and geochemical characteristics of mafic rock

Title: Xu Maichao geological and geochemical characteristics of mafic rock
　　Author: Li Jiaqing
　　Degree-granting units: Chengdu University of Technology
　　Keywords: ultramafic rocks;; geochemistry;; structural environment;; Xu Mai rock;; Jinsha River ophiolite belt
　　Summary:
　　Jinsha River ophiolite zone exposed in northwest Yunnan in southwest Sichuan was Rongxian Deqin County to the territory from north to south through the multi-turn located in the east bamboo, book loose, white Mang Snow Mountain, Xu Mai, Kim Magnetic lifter Ga mountains and down angle area, longer than 300 km wide and usually a few kilometers. North-south plane lenticular discontinuous distribution, constitute the main body of the Jinsha suture. Mai Xu Jinsha suture zone rock is several of the larger, ore-bearing surface of one of the better rock, intruded into the Jinsha River suture zone in the mountain group in the Permian Ga gold.
　　Xu Mai rock by geological, petrological, geochemical analysis of systems integration, and the rocks were supporting major and trace element geochemical data analysis and the formation of environmental studies, primarily to obtain an initial understanding of the following:
　　(1) Jimmy Xu shape of irregular rock surface strip, on section was asymmetrical yoke-shaped. Rock and rock is often exposed at the inside and outside the alteration zone, and the rock was intrusive contact, was the fault of local contacts. Xu Mai rock rocks are subjected to a certain degree of serpentinization and carbonation.
　　(2) XU Mai rock major element analysis results show that, SiO2 content in the range between 35.27% ~ 42.25%, TFeO the content in the range between 5.072% - 9.083%, MgO content in the range of 34.85% ~ 38.16 %, and the overall content features similar to the Troodos harzburgite composed of major element geochemistry, and low TiO2 (with TiO2 <2.5% for the standard) and the characteristics of low-P2O5. Rock Mg # 80.00 ~ 87.95, consolidation index (SI) for the 79.52 - 87.92, Rittmann index δ less than 0.001, Na2O + K2O is between 0.0022% ~ 0.0373%, alkalinity ratio AR of 1.03 to 1.12 , the calc-alkaline rocks. (K2O + Na2O)-SiO2 (TAS) diagram, SiO2-Nb / Y diagram and Zr/TiO2-Nb/Y map, SiO2-AR (alkalinity ratio) diagram, most of the performance of rock Xu wheat calc-alkaline series. Rock m / f ratio of 7.06 to 13.4, is a magnesium ultramafic rocks. In the FMC map, Xu Mai rock samples are calcium-poor mafic falls area.
　　(3) Xu Mai rock transition elements Ti and V were significantly lower than the corresponding values ​​of primitive mantle, and Cr, Co and Ni content is similar with the primitive mantle, primitive mantle-normalized element distribution patterns for the asymmetry of the "W" shape, Ti and Cu at the formation of two distinct negative anomaly, "Valley", the performance characteristics of the residual mantle of the partition. Large from the lithophile elements (LILE) Rb, Sr, Ba, U was enriched, high field strength elements (HFSE) Nb, Ta, Zr relative loss. There Sr, Rb and other elements of enrichment, in particular, the loss of Nb, with a typical N-MORB-ocean ridge is somewhat different, which reflects the geochemical characteristics of island-arc environment figure.
　　(4) Xu Mai rock REE content is low, compared with the mantle of serious losses. In the chondrite-normalized distribution patterns of the map, http://www.999magnet.com/products/131-magnetic-lifter showing LREE enrichment, heavy rare earth heavy losses, and slightly right-wing type. LREE fractionation was internal, HREE fractionation is relatively weak internal possessed significant positive Eu anomalies. Xu Mai rock LREE enrichment is likely to be mantle peridotite metasomatism and who have been late alteration (serpentinization).
　　(5) through the use of trace element abundance ratios and major elements, trace elements and multi-pattern synthesis method, Xu Mai rock island arc calc-alkaline magma as the magma, resulting in the closure plate to bring the edge of the cut.
　　Degree Year: 2010