發(fā)布時間：2018-01-11 01:17

  本文關(guān)鍵詞：巴基斯坦信德地區(qū)納格爾巴格爾雜巖學元素地球化學特征與鋯石U-Pb年齡　出處：《中國科學技術(shù)大學》2017年博士論文　論文類型：學位論文

  更多相關(guān)文章： 鋯石鈾-鉛年齡 元素地球化學 納格爾巴格爾雜巖體 巴基斯坦信德地區(qū) 印度地盾

【摘要】：納格爾巴格爾雜巖體位于巴基斯坦南部與印度交接的巴格爾沙漠地區(qū),靠近信德省大卡奇沼澤地,由變質(zhì)巖、侵入巖和火山巖組成,這些巖石以深成巖體的形式出露于沙漠平原中,其中花崗巖是主要巖石類型。本研究的主要目的是測定納格爾巴格爾雜巖體巖石的年齡和元素組成,以期對其成因、演化過程和大地構(gòu)造背景進行制約。為此,本文對采自納格爾巴格爾地區(qū)9個侵入體的28塊代表性巖石樣品進行了詳細的鋯石235U-207Pb年齡分析和主量元素及微量元素測定。為獲得U-Pb年齡數(shù)據(jù),巖石樣品被機械破碎以篩選出鋯石晶體,隨后這些鋯石被固定在環(huán)氧樹脂靶上并拋光。表面噴碳后,這些鋯石靶用裝配于Tescan掃描電子顯微鏡上的Gatan Chroma CL陰極光譜儀獲得鋯石的CL圖像,測定235U-207pb年齡的目標點被標注于鋯石的CL圖像上。235U-207Pb年齡采用LA-ICP-MS進行分析,在中國科學技術(shù)大學-中科院殼幔物質(zhì)導環(huán)境重點實驗室完成。235U-207Pb年齡測定結(jié)果在經(jīng)過普通鉛校正后由計算機軟件得到其諧和年齡圖解與加權(quán)平均年齡圖解。所有樣品的全巖主微量元素組成使用XRF、ICP-MS和ICP-AES在廣州澳實實驗室測定。結(jié)果在構(gòu)造環(huán)境判別圖解中投點以區(qū)別各巖石的分類、對應的構(gòu)造環(huán)境關(guān)系以及物質(zhì)來源。巖石微量元素組成在球粒隕石和原始地幔標準化圖解中的富集和虧損異常被用來推斷巖漿的原始源區(qū)。結(jié)果表明,雜巖體中深成巖是大陸下地殼部分熔融的產(chǎn)物,這些巖漿受到前存大陸下地殼圍巖的同化混染�？ㄆ娴貐^(qū)隨后因納格爾巴格爾斷裂的再次活躍和拉賈斯坦與卡奇附近地區(qū)的相關(guān)裂谷活動而被抬升。該地區(qū)具有富集地幔來源特征的火山巖證明該區(qū)域在抬升后又經(jīng)歷了火山活動。根據(jù)出露巖石的地球化學組成判斷,本區(qū)域在構(gòu)造環(huán)境判別圖解被歸為板內(nèi)花崗巖成因環(huán)境,雜巖體花崗巖具有中等到高的鉀-鈣含量特征,是典型的A型花崗巖。樣品的鋯石235U-207Pb年齡結(jié)果表明有三期主要的巖漿活動存在:(a)變質(zhì)作用階段:片麻巖具有884±6Ma的變質(zhì)年齡,角閃巖具有818±7 Ma的變質(zhì)年齡;(b)深成作用階段:深成巖漿活動從815 Ma持續(xù)到730 Ma,期間發(fā)生數(shù)次間斷性活動,產(chǎn)生了長英質(zhì)、中性和鎂鐵質(zhì)巖漿;(c)火山活動階段:形成283.2±2 Ma的粗面巖。結(jié)合地球化學特征來看,納格爾巴格爾雜巖體形成于岡瓦納大陸裂谷擴張階段,具有兩種不同的物質(zhì)來源,并且與印度地盾的拉賈斯坦克拉通地區(qū)在后德里巖漿事件中的馬拉尼火成巖套在地域上具有關(guān)聯(lián)性。
[Abstract]:The Nagar Bagger complex is located in the Bagger desert area, near the Grand Kachi Everglades in Sindh Province. It is composed of metamorphic rocks, intrusive rocks and volcanic rocks. These rocks are exposed to desert plains in the form of deep rock masses, among which granite is the main rock type. The main purpose of this study is to determine the age and elemental composition of the rocks in the Nagel Bagger complex. In order to restrict its origin, evolution process and tectonic background. In this paper, 28 representative rock samples collected from 9 intrusions in the Nagel Bagger area were analyzed in detail for zircon 235U-207Pb age and determination of principal elements and trace elements. B Age data. Rock samples are mechanically broken to screen out zircon crystals, which are then fixed on epoxy targets and polished. The surface is sprayed with carbon. The CL images of zircon were obtained by Gatan Chroma CL cathodic spectrometer assembled on Tescan scanning electron microscope. The target point for the determination of 235U-207pb age was labeled on the CL image of zircon. The age of 235U-207Pb was analyzed by LA-ICP-MS. The results of age determination of .235U-207Pb in the key laboratory of crust-mantle material conduction environment of the University of Science and Technology of China and the Chinese Academy of Sciences have been obtained by computer software after the correction of common lead. Weighted mean age diagram. All samples of the main and trace elements of the whole rock composition using XRF. ICP-MS and ICP-AES were measured in Guangzhou Australian laboratory. Results the input points were used to distinguish the classification of rocks in the tectonic environment discriminant diagram. The enrichment and depletion anomalies of trace element composition in chondrites and primitive mantle are used to infer the original source of magma. The deep diagenetic rock in the complex is the product of partial melting of the lower continental crust. The magma was assimilated by the surrounding rocks of the lower crust of the pre-existing continent. The Karch area was subsequently uplifted by the reactivation of the Nagel Bagger fault and the associated rift activities in the vicinity of Rajasthan and Kachi. The volcanic rocks enriched in mantle origin show that the region experienced volcanic activity after uplift. The geochemical composition of exposed rocks is judged. In this area, the tectonic environment discriminant diagram is classified as the genetic environment of intraplate granite, and the complex granite has the characteristics of medium to high potassium and calcium content. The zircon 235U-207Pb age of the sample indicates that there are three major magmatic activities in the three stages. Metamorphic stage: gneiss has a metamorphic age of 884 鹵6 Ma. Amphibolite has a metamorphic age of 818 鹵7 Ma. (B) the deep magmatic activity lasted from 815 Ma to 730 Ma, during which several intermittent activities occurred, resulting in felsic, neutral and magnesite magma; (C) volcanic activity stage: the coarse rock formed at 283.2 鹵2 Ma. In combination with geochemical characteristics, the Nagel Bagger complex was formed in the Gondwana continental rift extension stage. There are two different sources of material, and they are geographically related to the Malani igneous rocks in the Rajasthan craton of the Indian Shield in the post-Delhi magma event.
【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：P597.3;P584

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