本文選題：岡底斯 + 永珠地區(qū)　； 參考：《吉林大學》2015年碩士論文

【摘要】：岡底斯地塊中北部出露大面積中生代巖漿巖，其巖石成因與地球動力學意義一直存在爭議。本文以岡底斯中北部永珠地區(qū)花崗巖類為研究對象，對其進行詳細的巖石學、地球化學和鋯石U-Pb年代學研究，試圖為解決這問題提供資料。 根據巖石野外地質特征和鋯石U-Pb定年，永珠花崗巖類可以分為三期：早侏羅世（176.4Ma）、早白堊世（120~110Ma）和晚白堊世（~75Ma）。早侏羅世花崗巖巖石類型為花崗閃長巖，具弱片麻狀；全巖地球化學特征顯示過鋁質、鈣堿性特征；輕稀土富集、重稀土虧損，具明顯負Eu異常；富集大離子親石元素，虧損高場強元素。早白堊世花崗巖巖石類型為花崗閃長巖、似斑狀二長花崗巖，含有暗色包體，與碳酸巖圍巖接觸處發(fā)生矽卡巖化、大理巖化；花崗巖與包體顯示出準鋁質、鈣堿性-高鉀鈣堿性特征；輕稀土富集、重稀土虧損；富集大離子親石元素，虧損高場強元素。晚白堊世花崗巖巖石類型為二長花崗巖、似斑狀二長花崗巖，含有暗色包體，與碳酸巖圍巖接觸處發(fā)生矽卡巖化；花崗巖與包體顯示出準鋁質、鈣堿性-高鉀鈣堿性特征；輕稀土富集、重稀土虧損；富集大離子親石元素，虧損高場強元素。早侏羅世花崗巖為未分異S型花崗巖，早、晚白堊世花崗巖為未分異I型花崗巖；三期花崗巖均具有較高的鋯石飽和溫度、Mg#、Cr和Ni數值，反映形成與幔源巖漿有密切關系，其中早、晚白堊世花崗巖形成可能與巖漿混合有關；早侏羅世花崗巖巖漿源區(qū)可能為中、上地殼（變）沉積巖，早、晚白堊世花崗巖巖漿源區(qū)可能為中、上地殼角閃巖相變質基性火成巖。 永珠早侏羅世過鋁質、未分異S型花崗巖可能形成于班公湖-怒江和雅魯藏布江特提斯洋雙向俯沖作用影響下，中岡底斯內部發(fā)生擠壓、碰撞（幔源巖漿影響?），中、上地殼（變）沉積巖熔融形成；早白堊世未分異I型花崗巖可能形成于班公湖-怒江特提斯洋南向俯沖的背景下，俯沖板片斷離引起軟流圈物質上涌，導致巖石圈地幔和中、上地殼發(fā)生熔融，產生基性和酸性巖性巖漿，兩者發(fā)生巖漿混合作用形成；晚白堊世未分異I型花崗巖可能形成于岡底斯-羌塘地塊發(fā)生碰撞進入后碰撞構造環(huán)境背景下，增厚巖石圈地幔局部發(fā)生拆沉，引起軟流圈物質上涌，產生底侵幔源巖漿、促使中、上地殼熔融產生酸性巖漿，，兩者發(fā)生巖漿混合作用形成。中生代岡底斯中北部動力學背景主要表現為班公湖-怒江特提斯洋的俯沖消減、岡底斯與羌塘地塊碰撞以及造山后的垮塌。 永珠地區(qū)與成礦作用有關的花崗巖為早白堊世和晚白堊世兩期，成礦作用類型主要為矽卡巖型（銅）成礦作用。
[Abstract]:A large area of Mesozoic magmatic rocks emerged from the central and northern parts of the Gangdis block, and its petrogenesis and geodynamic significance have always been controversial.In this paper, granitic species in Yongzhu area, central and northern Gangdis, are studied in detail in petrology, geochemistry and zircon U-Pb chronology, in order to provide data for solving this problem.According to the field geological characteristics of rocks and zircon U-Pb dating, the Yongzhu granites can be divided into three stages: early Jurassic (176.4 Mai), early Cretaceous (120,110 Ma) and late Cretaceous (75 Ma).The early Jurassic granitic rocks are granodiorite with weak granodiorite, the geochemical characteristics of the whole rock show the characteristics of peraluminous, calc-alkaline, LREE enrichment, heavy REE depletion, obvious negative EU anomaly, enrichment of large ion lithophile elements,Loss of high field strength elements.The early Cretaceous granitic rocks are granodiorite, porphyry monzonitic granites, containing dark inclusion, skarn and marble in contact with the surrounding rock of carbonatite, granites and inclusions showing quasi-aluminite,The characteristics of calcium alkalinity and high potassium calcium alkalinity; light rare earth enrichment, heavy rare earth deficiency; enrichment of large ion lithophile elements, depletion of high field strength elements.The late Cretaceous granite rock type is monzogranite, similar to porphyry monzogranite, contains dark color inclusion, occurs skarn in contact with the surrounding rock of carbonatite, the granite and enclave show quasi-aluminite, calc-high-potassium calc-alkaline characteristic, granitoids and xenoliths show the characteristics of quasi-aluminite, calc-alkaline and high-potassium calc-alkaline.Light rare earth enrichment, heavy rare earth deficiency, enrichment of large ion lithophile elements, depletion of high field strength elements.The early Jurassic granites are undifferentiated S-type granites, and the early and late Cretaceous granites are undifferentiated I-type granites, and the third stage granites have higher zircon saturation temperatures, Mg#cr and Ni values, indicating that the formation of the granites is closely related to the mantle magma.The early and late Cretaceous granitic formation may be related to magmatic mixing, the early Jurassic granitoid magma source region may be middle, upper crust (metamorphic) sedimentary rocks, early and late Cretaceous granitic magmatic source region may be middle,Metamorphic basic igneous rocks of amphibolite facies in upper crust.Yongzhu early Jurassic peraluminous, undifferentiated S-type granites may have formed under the influence of bidirectional subduction of the Tethys ocean in Bangong Lake, Nujiang River and Yarlung Zangbo River.In the early Cretaceous undifferentiated I-type granite may have been formed under the background of the southern subduction of Bangong Lake and the Nu River Tethys, and the partial detachment of the subduction plate caused the upwelling of the asthenospheric material, which resulted in the lithospheric mantle and the middle lithosphere.The melting of the upper crust, the formation of basic and acidic magma, and the formation of magmatic mixing, the late Cretaceous undifferentiated I-type granites may have formed in the background of the collision of Gangdish-Qiangtang block and the post-collision tectonic environment.The partial delamination of thickened lithospheric mantle results in the upwelling of asthenosphere material and the formation of submersible mantle derived magma, resulting in the formation of acidic magma in the melting of the middle and upper crust, and the formation of magma mixing between the two.The dynamic background of the central and northern Gangdes in Mesozoic is mainly reflected by the subduction of the Bangong Lake-Tethys of the Nujiang River, the collision between the Gangdes and the Qiangtang landmass and the collapse after orogeny.The granites related to mineralization in Yongzhu area are of early Cretaceous and late Cretaceous, and the types of mineralization are skarn type (copper) mineralization.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P588.121

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