發(fā)布時間：2018-05-11 23:18

  本文選題：花崗斑巖 + 鋯石U-Pb年代學(xué)　； 參考：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文

【摘要】：本文以青海省格爾木拉陵高里河上游地區(qū)出露的花崗斑巖為研究對象,對花崗斑巖的地質(zhì)學(xué)、巖相學(xué)、年代學(xué)和地球化學(xué)進行了研究,主要對上游地區(qū)花崗斑巖形成的時代和地球化學(xué)特征進行了測試分析,討論了花崗斑巖的巖漿源區(qū)性質(zhì)、巖石成因、巖石類型及其形成的大地構(gòu)造背景,其結(jié)果對于揭示東昆侖拉陵高里河上游地區(qū)的大地構(gòu)造演化具有一定意義。花崗斑巖的鋯石LA-ICP-MS U-Pb年齡跨度較大(215Ma-230Ma),主要集中在227.2±1.7Ma和218.7±1.2Ma兩個年齡群,其中218.7±1.2 Ma代表了拉陵高里河地區(qū)花崗斑巖巖漿最后固結(jié)的年齡。表明拉陵高里河上游地區(qū)花崗斑巖主要形成于印支晚期。拉陵高里河上游地區(qū)花崗斑巖具有較高的SiO2、K2O含量和分異指數(shù),顯示高鉀鈣堿性的弱過鋁質(zhì)特征,為高分異的S型花崗巖。微量元素分析結(jié)果顯示,拉陵高里河上游花崗斑巖顯示中等的稀土元素總量(∑REE=121.52×10-6~145.23×10-6),重稀土元素(HREE)虧損,輕稀土元素(LREE)富集,LREE/HREE為11.08~12.72,輕重稀土分餾現(xiàn)象相對明顯,σEu介于0.48~0.63之間,均小于1,具有中等Eu負(fù)異常。σCe介于0.82~0.90之間,為輕微的負(fù)異�；驘o異常。樣品中普遍表現(xiàn)出富集K、Rb、Th、U等元素,虧損Nb、Ta、P、Ti等元素,表現(xiàn)出與殼源相一致的特征。巖石的Al_2O_3/TiO_2比值為37~53,Rb/Sr介于0.87~1.20之間,巖漿源區(qū)表現(xiàn)為下地殼變質(zhì)雜砂巖特征。在花崗巖主量元素和微量元素顯示有后碰撞S型花崗巖特征。同時代東昆侖地區(qū)花崗巖特征、區(qū)域構(gòu)造背景和構(gòu)造環(huán)境判別圖解均表明研究區(qū)中花崗斑巖的形成主要與東昆侖造山帶的造山作用以及造山晚期的伸展作用有關(guān)。印支早期區(qū)域上古特提斯洋發(fā)生閉合,從而進入到陸陸碰撞階段,由于持續(xù)的擠壓作用使得上覆巖石圈增厚,到印支晚期由擠壓作用轉(zhuǎn)化為伸展作用,使得增厚的下地殼發(fā)生拆沉,因此可造成地幔巖漿上涌從而發(fā)生底侵作用,形成流體運移的通道,由于高溫流體的進入,提供相對較高的溫度,使下地殼雜砂巖發(fā)生重熔形成了本區(qū)花崗斑巖。
[Abstract]:In this paper, the granitic porphyry in the upper reaches of Gali River in Golmud Laling, Qinghai Province is taken as the research object, and the geology, petrography, geochronology and geochemistry of the granitic porphyry are studied. The age and geochemical characteristics of granitic porphyry formation in the upper reaches are analyzed, and the magmatic origin, petrogenesis, rock types and tectonic setting of the granitic porphyry are discussed. The results are of significance for revealing the tectonic evolution of the upper reaches of the Gali River in Laling, East Kunlun. The zircon LA-ICP-MS U-Pb age span of granitic porphyry is larger than 215Ma-230 Ma, mainly in two age groups of 227.2 鹵1.7Ma and 218.7 鹵1.2Ma, of which 218.7 鹵1.2Ma represents the final consolidation age of granitic porphyry magma in Laling Golihe area. This indicates that granitic porphyry was mainly formed in the upper reaches of the Laling Golihe River during the late Indosinian period. The granitic porphyry in the upper reaches of Laling Gaolihe has high SiO2K2O content and differentiation index, which shows the weak peraluminous character of high potassium calc-alkaline, and it is a S-type granite with high differentiation. The results of trace element analysis show that the granitic porphyry in the upper reaches of Lalinggaoli River shows that the total amount of rare earth elements (鈭，

本文編號：1876078