Research Of Characteristics And Petrogenesis Of Emeishan Basalt In Huize Area Of Yunnan

Permian Emeishan basalt,which is widely distributed in Sichuan,Yunnan and Guizhou andother place,has been one of hot spots both at home and abroad.Huize area,in Yunnan county?is located at the southwest margin of Yangtze landmass,Eruption with thickness of 1314 m of late Permian emeishan basalt(southern district is located in the emeishan large igneous province).In this paper,based on the measured profile,emeishan basalt in the area are the petrography and the study of the geochemical characteristics of rocks,and analysis of the cause of magma source area,evolution and rock analysis.The rock types of Emeishan basalt in Huize area are mainly lava rocks(overflow)and containing a small amount of volcanic breccia(explosive phase),tuff(rock of pyroclastic fallout facies).with obvious rhythm and cycle characteristics.The generally eruption of the lava rocks is: compact basalt?porphyritic olivine?amygdaloidal basalt?tuff,With great thickness,the main texture of the lava rocks is less-porphyritic texture and adiagnostic texture,some part of its texture is adiagnostic texture?Most of the phenocryst mineral is monoclinic pyroxene while part of it is anorthose,and low temperature alteration is the main alteration..The volcanic breccia Local exposed.The tuff is relatively concentrated,but the thickness is thinner.Analysis of major elements shows:the content of SiO2 is from 46.02% to 50.91% with average value of 48.5%,have characters of centralized distribution,he content of TiO2 show a great difference,it is from 3.32% to 4.84%,the content of Na2O/K2 O is from 0.53 to 5.70,the content of Mg# is from 37.01% to 67.86% with average value of 50.47%,the content of Mg# at a relative low compared with the other.Rare earth elements embraces characteristics of relatively enrichment of the light ones,relatively depletion of the heavy ones and obvious fractionation between the light and the heavy ones(?REE =170.16×10-6~ 286.02×10-6,LREE/HREE=7.23 ~ 9.56),TheSamples show that curve is right dip type,andEu and Ce have weak positive or negative anomaly.anomaly or weak negative anomaly.Compatible and incompatible element characteristics show that the high field strength elements enrichment(Rb,Th,U,Nb,La,Ce,Ti,Sr,Zr,Sm,etc.),and K,Ti,P loss obviously,Mg# and Co,Cr,Ni,Nb was significantly negative correlation relationship.Incompatible element ratios and oceanic island basalt in the plate or EM EM-1-2 oceanic island basalt in the plate.According to the lithology and the main content,light and heavy rare earth elements and distribution analysis,huize emeishan basalt formation of the tectonic environment of intraplate extensional environment,the content of TiO2 witch Emeishan basalt in the study areais from 2.15% to4.84%,the content of Ti/Y is from 440 to 620.Basalt has both high titanium in the basalt in the study area,also have low titanium basalt,so Huize emeishan basalt are the products of Mantle PlumeTectonics.the content of Nb/U with average value of 27.71.this value in between MORB and the earth's crust.And meantime relatively Th and U is depleted in K?Ti and P,Some samples have obvious negative anomaly of Ta,Instructions in the process of magma rising under the effect of crust.Basalt basic does not display the europium anomalies,the content of Euis from 0.95 to 1.08,Suggests that low degree of plagioclase crystallization,magma crystallization separation effect is very weak,in the process of rising afterthe formation of magma,low-degree fractional crystallization has occurred withbeing contaminated by continental crust materials.