The Diabase Characteristics And Tectonic Background Analysis Of Shangri-la Area, Northwest Yunnan, China

Shangri-La is located in Jinsha Northwest region tectonic belt east of thecontinental blocks in Zhongdian micro Ganzi-Litang suture zone, Yidun island arcand the southern tip of the western margin of the Yangtze block combined with strongregional tectonic activities, outputs a large number of NW-SE of diabase dikes, Thispaper compares the discussion of petrographic and geochemical diabase dikes in threedifferent tectonic units of indicating three diabase at both similarities and differencesdifferences. In Ganzi-Litang combined with a low silicon LuoJi diabase, hightitanium, potassium, are alkaline magma series, LREE fractionation obvious, obviousLREE enrichment, HREE, almost no Eu anomaly, loss P element with similaroceanic island basalt geochemistry of magmatic apatite containing garnet phasethrough to clinopyroxene dominated fractional crystallization products, mainlybelonging to the enrichment of type I-oceanic island basalts (EMI-OIB) with a smallamount of enriched II-oceanic island basalts (EMII-OIB) feature is enriched mantlegarnet phase after0.5%enriched mantle partial melting and spinel phase occurred1%to2%partial melting magma formed by mixing action.La Ba diabase of Yidun arc with high potassium, low-titanium, the alkalicontent, belong to sub-alkaline magma series, the overall geochemical characteristicsof trace rare earth close to OIB-type, obvious loss Sr, Ti, Eu, magma experience thecrystalline clinopyroxene and plagioclase differentiation is enriched mantle spinelphase occurred1%to2%partial melting.La Jia diabase of Zhongdian micro-continental blocks has high titanium, lowpotassium, rich P2O5, belongs to the alkaline magma series, iron is more apparent, K,Ce strong losses, positive Sr anomaly, overall has the geochemical characteristics ofOIB type with similar and Luo Ji diabase, magmatic crystallization differentiation inclinopyroxene, at the same time by fluid metasomatism or deep sea sedimentcontamination, melting degree from low to high evolution, through alkaline basalt,basalt and tholeiite transition process of evolution, and the enrichment of II typeocean island basalt (EMII OIB) is similar, enriched mantle garnet phase after1%partial melting of enriched mantle and spinel phase occurred2%~mixed the5%part of molten magma formed by the interaction of.Three diabase are produced in within plate tectonic environment, may be formedin the asthenosphere upwelling of mantle lithosphere transformation background,cause not mantle plumes, upwelling asthenospheric mantle in the lithospheric mantlestrongly modified, are formed extensional tectonic background, suggests that differenttectonic units the stretching rate and stretching degree are not the same, speculatedthat the residual magma may belong to the late Mesozoic Triassic early Jurassic three.