發(fā)布時(shí)間：2018-05-23 08:21

  本文選題：峨眉山玄武巖 + 巖石地球化學(xué)　； 參考：《東華理工大學(xué)》2017年碩士論文

【摘要】：峨眉山玄武巖主要分布于中國(guó)四川、云南、貴州等地,關(guān)于峨眉山玄武巖的研究一直是國(guó)內(nèi)外地質(zhì)學(xué)家熱點(diǎn)之一。云南會(huì)澤縣位于揚(yáng)子板塊西南緣,區(qū)內(nèi)峨眉山玄武巖廣泛發(fā)布,出露厚度1314m左右,本文結(jié)合野外實(shí)測(cè)剖面數(shù)據(jù),對(duì)該地區(qū)峨眉山玄武巖的巖相學(xué)及巖石地球化學(xué)等方面進(jìn)行了的研究,進(jìn)而分析了其巖漿源區(qū)、演化及其巖石成因。會(huì)澤峨眉山玄武巖系巖石主要以基性熔巖(溢流相)為主,含少量火山角礫巖(爆發(fā)相)、凝灰?guī)r(空落相)。韻律旋回性特征明顯,其中熔巖、火山碎屑類的噴發(fā)總體表現(xiàn)為:致密狀玄武巖→斑狀玄武巖→杏仁狀玄武巖組合→凝灰?guī)r,熔巖類(溢流相)巖石厚度比較巨大,熔巖類多具有少斑狀-斑狀結(jié)構(gòu)和微晶質(zhì)結(jié)構(gòu),部分具有隱晶結(jié)構(gòu),斑晶礦物以單斜輝石為主,局部為斜長(zhǎng)石,主要發(fā)生低溫蝕變�；鹕浇堑[巖局部出露,凝灰?guī)r分布較為廣泛,但厚度較薄。會(huì)澤峨眉山玄武巖SiO_2含量在46.02%~50.91%之間,含量變化較小,平均值48.5%;TiO2含量變化較大,變化于3.32%~4.84%之間;Na2O/K2O變化范圍為0.53-5.70;Mg#變化于37.01%~67.86%,均值為50.47%,其Mg#值均相對(duì)較低。稀土元素特征展現(xiàn)出輕稀土元素富集,重稀土相對(duì)虧損,輕重稀土分餾特征明顯(∑REE=170.16×10-6~286.02×10-6,LREE/HREE=7.23~9.56),稀土配分模式表現(xiàn)出一致的陡右傾型,Eu、Ce具弱的正異�；蛉醯呢�(fù)異常。相容及不相容元素特征顯示:高場(chǎng)強(qiáng)元素富集(Rb、Th、U、Nb、La、Ce、Ti、Sr、Zr、Sm等),而K、Ti、P明顯虧損,Mg#與Co、Cr、Ni、Nb呈明顯的負(fù)相關(guān)關(guān)系。不相容元素比值與EM-1板內(nèi)洋島玄武巖或EM-2板內(nèi)洋島玄武巖相當(dāng)。根據(jù)巖相學(xué)及主量、輕重稀土元素及分布特征分析,會(huì)澤峨眉山玄武巖形成的構(gòu)造環(huán)境為板內(nèi)拉張環(huán)境,研究區(qū)峨眉山玄武巖TiO2介于2.15%~4.84%之間,Ti/Y介于440~620,說明研究區(qū)的玄武巖中既有高鈦玄武巖,也有低鈦玄武巖,為地幔柱中帶的產(chǎn)物。研究區(qū)峨眉山玄武巖Nb/U平均值為27.71,處于地殼與大洋中脊玄武巖(MORB)之間,同時(shí)玄武巖Th、U、K、Ti、P明顯虧損,部分樣品還有明顯的Ta負(fù)異常,說明巖漿上升過程中受到了地殼混染作用。研究區(qū)的峨眉山玄武巖基本不顯示Eu異常,δEu=0.95~1.08,表明斜長(zhǎng)石結(jié)晶程度低,巖漿結(jié)晶分離作用很弱,末期巖漿上升過程中受到了地殼混染作用。
[Abstract]:Emeishan basalt is mainly distributed in Sichuan, Yunnan, Guizhou and other places in China. The study of Emei mountain basalt has always been one of the hot spots of geologists at home and abroad. Huize County in Yunnan Province is located in the southwest margin of Yangtze plate. The Emeishan basalt is widely released in this area, and the exposed thickness is about 1314m. The petrographic and petrogeochemical aspects of the Emeishan basalt in this area are studied, and the magmatic source, evolution and petrogenesis of the basalt are analyzed. The basalt rocks in Huize Emeishan are mainly composed of basic lava (overflow facies) and a small amount of volcanic breccia (explosive facies and tuff). The characteristics of rhythmic cyclicity are obvious, among which the eruptions of lava and pyroclastic are as follows: dense basalt, porphyry basalt and almond-like basalt assemblage tuff, and the thickness of lava (overflow phase) rock is very large. Most of the lava have less porphyry-porphyry structure and microcrystalline structure and some have cryptic structure. The porphyry minerals are mainly clinopyroxene and some are plagioclase. Volcanic breccia is localized, tuff is widely distributed, but its thickness is thin. The content of SiO_2 in the basalt of Huize Emeishan is between 46.02% and 50.91%, the average value of which is 48.5%, and the average value is 48.5%. The variation range of Na _ 2O / K _ 2O is between 3.32% and 4.84%, ranging from 0.53-5.70% to 37.01% and the mean value is 50.47.The Mg# value is relatively low. The REE features show light REE enrichment, relative depletion of heavy REE, and obvious fractionation characteristics of LREE / R (鈭，

本文編號(hào)：1923985