本文選題：峨眉山玄武巖 + 地質(zhì)特征��； 參考：《成都理工大學(xué)》2016年碩士論文

【摘要】：分布在云、貴、川3省的二疊紀(jì)至三疊紀(jì)的玄武巖,一直備受眾多學(xué)者關(guān)注。峨眉山大火成巖省總體分布在揚(yáng)子地塊西緣,目前來說它是我國為數(shù)不多被國際地學(xué)界認(rèn)可的大火成巖省。而在我國礦產(chǎn)分布方面,峨眉大火成巖省是西南地區(qū)典型的集礦區(qū)域。由于其成因主要與地幔柱活動有關(guān),所以它顯著特點(diǎn)為產(chǎn)出大量火山巖漿巖系的時間很短。由此看出峨眉山玄武巖的研究對我們探討地幔柱演化、形成及其地質(zhì)效應(yīng)都有指示意義,峨眉大火成巖省便成為開展地幔柱研究非常理想的地區(qū)。通過野外實(shí)測剖面分析發(fā)現(xiàn)區(qū)內(nèi)峨眉山玄武巖組厚度約為1571.25m。與上覆須家河組地層呈平行不整合接觸,與下伏陽新組為噴發(fā)不整合接觸關(guān)系。結(jié)合野外觀察和前人的資料將其分為三段。越西峨眉山玄武巖組是以溢流相為主,爆發(fā)相次之。論文通過對越西地區(qū)峨眉山玄武巖鏡下巖相學(xué)研究、巖石地球化學(xué)實(shí)驗分析,通過實(shí)驗數(shù)據(jù)界定主量元素的含量變化范圍。對數(shù)據(jù)進(jìn)行細(xì)致分析,同時對超出合理范圍的樣品進(jìn)行相應(yīng)解釋。通過哈克圖解、TAS圖解、硅-鉀圖等分析主量元素性質(zhì)。稀土元素分餾情況靈敏地反映出巖石的成因和源區(qū)特征。越西地區(qū)峨眉山玄武巖稀土配分模式圖呈明顯的右傾型,而大陸堿性玄武巖是富集輕稀土的右傾斜線。微量元素中大離子親石元素K、Sr、Ba強(qiáng)烈虧損,而Rb、LREE相對富集。同時高場強(qiáng)元素Nb、P、Ce強(qiáng)烈虧損,Th、Zr、HREE相對富集。但是大離子親石元素中K、Sr、Ba及重稀土元素中的Yb波動范圍較大,相應(yīng)樣品結(jié)合鏡下觀察分析基本排除了蝕變的可能,所以初步判斷應(yīng)該是巖漿的同化混染作用造成的。在巖漿源區(qū)方面,分析結(jié)果表明越西峨眉山玄武巖來源于高壓高熔融的條件下的石榴石相,結(jié)晶溫度較高,隨著深度的變化,壓力降低,溫度降低,熔融程度減小,形成了玄武巖。同時初步判定越西地區(qū)峨眉山玄武巖是源自地幔柱不是巖石圈地幔。
[Abstract]:The Permian to Triassic basalt distributed in Yunnan, Guizhou and Sichuan provinces has been concerned by many scholars. Emeishan great igneous province is distributed in the western margin of Yangtze block and is one of the few major igneous provinces recognized by the international geosciences in China. In the distribution of mineral resources in China, Emei great igneous province is a typical ore gathering area in southwest China. Because its genesis is mainly related to mantle plume activity, it is characterized by a short time to produce a large number of volcanic magmatic rocks. It can be seen that the study of Emeishan basalt is instructive for us to study the evolution of mantle plume and its formation and geological effects. Emei igneous province is an ideal region for the study of mantle plume. It is found that the thickness of Emeishan basalt formation is about 1571.25m. There is a parallel unconformable contact with the Xujiahe formation and an eruption unconformity with the Xiafuyangxin formation. Combined with field observation and previous data, it is divided into three sections. The Emeishan basalt formation in Yuexi is dominated by overflow facies, followed by explosive phase. In this paper, the lithofacies of Emeishan basalt in Yuexi area is studied under the microscope, and the range of main elements content is defined by the experimental data. Analyze the data carefully and interpret the samples beyond the reasonable range. The properties of principal elements were analyzed by means of Huck diagram, TAS diagram and Si-K diagram. The fractionation of rare earth elements sensitively reflects the origin and source characteristics of rocks. The REE distribution pattern of Emeishan basalt in Yuexi area shows an obvious right-dip pattern, while continental alkaline basalt is the right-dip inclined line for the enrichment of LREE. The large ion lithophile element K ~ (2 +) Sr ~ (2 +) Ba in trace elements is strongly depleted, while the RbBX LREE is relatively enriched. At the same time, the high field strength element NbPX ce is strongly depleted and the HREE is relatively enriched. However, the fluctuation range of K ~ (2 +) Sr ~ (2 +) Ba in large ion lithophile elements and Yb in heavy rare earth elements is large, and the possibility of alteration is basically excluded from the corresponding sample observation and analysis under microscope, so the preliminary judgement should be caused by the assimilation and contamination of magma. In the magmatic source area, the results show that the basalts of Emei Mountain in Yuexi are derived from the garnet phase under high pressure and high melting, and the crystallization temperature is higher. With the change of depth, the pressure decreases, the temperature decreases and the melting degree decreases. Basalt was formed. At the same time, it is preliminarily determined that the Emeishan basalt originates from mantle plume and not lithospheric mantle in Yuexi area.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P588.145

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