本文關鍵詞： 浦北花崗巖 花崗巖體 包體 地球化學特征 巖石成因　出處：《成都理工大學》2016年碩士論文　論文類型：學位論文

【摘要】：本文以大容山花崗巖(南)東亞帶中的浦北巖體為研究對象,通過對花崗巖、包體及地球化學特征三個方面的詳細研究,分析了花崗巖的特征、包體的特征及與寄主花崗巖的相互關系、花崗巖地球化學特征,并探討了巖石成因類型。浦北花崗巖位于大容山花崗巖(南)東亞帶,巖體主要由黑云母花崗巖構成,根據(jù)結構可分為中心相、過渡相和邊緣相帶。中心相帶由中粗粒花崗巖組成;過渡相帶由細中�；◢弾r組成;邊緣相帶有細粒或中細�；◢弾r組成,其中以過渡相較發(fā)育,各巖相之間均為過渡關系。基質(zhì)的形成溫度明顯的低于斑晶,說明雖然巖石具有似斑狀結構,但斑晶和基質(zhì)并非同時形成,斑晶形成較早,基質(zhì)是在巖漿進一步冷卻結晶過程中所形成的。浦北花崗巖中所含包體均為變質(zhì)巖包體,礦物組合為石英+斜長石+鉀長石+黑云母±堇青石±石榴石±矽線石,屬于角閃巖相。形成溫度為中溫,最高500℃,低于寄主花崗巖的形成溫度,表明包體是先形成的,花崗巖是變質(zhì)巖重熔形成的。包體具有富鋁質(zhì)特征,變質(zhì)巖包體的原巖為泥質(zhì)巖。浦北花崗巖中Si O2含量高,為鈣堿性巖,屬高鉀鈣堿性系列。巖石中鋁飽和指數(shù)ASI1.1,巖石表現(xiàn)出鋁過飽和,屬于過鋁質(zhì)花崗巖。K相對富集,Na含量較低,Na2O/K2O1。K2O-Na2O圖解中投射區(qū)落在S型花崗巖范圍內(nèi)。浦北花崗巖為殼源花崗巖,其形成巖漿由上部陸殼物質(zhì)熔融產(chǎn)生。花崗巖中稀土元素特征與上部陸殼的稀土元素特征相似,稀土總量均較大,LREE較HREE分異程度好。稀土元素分配模式圖中曲線均呈右傾,LREE曲線呈中等斜率,HREE曲線近于平緩,具有明顯的負Eu異常。浦北花崗巖中Rb、Th、La、U相對富集,而Ba、Nb、Sr虧損,與S型花崗巖微量元素分配模式相似。根據(jù)浦北花崗巖巖石學及地球化學的特征,與I型、S型花崗巖對比后確定浦北花崗巖屬于S型花崗巖。浦北花崗巖的形成與欽防殘留洋盆的關閉密切相關,它形成于欽防殘留洋盆向南俯沖碰撞過程中的島弧背景。
[Abstract]:Based on the study of the Pubei rock body in the Darongshan granite (south) East Asian belt, this paper analyzes the characteristics of the granite in detail from three aspects: granite, inclusion and geochemistry. The characteristics of the xenoliths and their relationship with host granites, the geochemical characteristics of the granites, and the petrogenetic types of the granites are discussed. The Pubei granites are located in the Darongshan granite (south) East Asian belt. The rock mass is mainly composed of biotite granites, which can be divided into central facies, transitional facies and marginal facies belt according to the structure. The central facies belt is composed of medium-coarse granites. The transitional facies zone is composed of fine-grained granites; The marginal facies are composed of fine-grained or medium-fine-grained granites, in which the transitional facies is relatively developed, and the transition relationship is between each lithofacies. The formation temperature of the matrix is obviously lower than that of the porphyry, which indicates that the rocks have a porphyry like structure. However, the porphyry and matrix did not form at the same time, and the porphyry formed earlier, and the matrix was formed during the further cooling and crystallization of magma. The inclusions contained in Pubei granite are metamorphic inclusions. The mineral assemblage is quartz plagioclase potassium feldspar biotite 鹵cordierite 鹵garnet 鹵sillimanite, which belongs to amphibolite facies. The results show that the inclusions are formed first and the granites are formed by the remelting of metamorphic rocks. The xenoliths are aluminum-rich, and the primary rocks of the xenoliths are argillaceous rocks. In Pubei granite, the content of Sio _ 2 is high, which is calc-alkaline. It belongs to the high-potassium calc-alkaline series. The aluminum saturation index (ASI1.1) in the rocks shows aluminum supersaturation, which belongs to the peraluminous granite. K is relatively rich in Na content. The projection area in the Na2O/K2O1.K2O-Na2O diagram falls within the range of S-type granite. Pubei granite is a crust-derived granite. The magma is formed by the melting of the upper continental crust. The characteristics of rare earth elements in the granite are similar to those in the upper continental crust, and the total amount of rare earth elements is large. LREE is better than HREE. The curve of REE distribution pattern is right tilted and LREE curve is medium slope and hree curve is close to flat. There is an obvious negative EU anomaly in Pubei granite, where the RbPU is relatively enriched and the Ba-NbPU Sr is depleted. The distribution pattern of trace elements is similar to that of S-type granite. According to the petrological and geochemical characteristics of Pubei granite, it is similar to that of type I. Compared with S-type granite, Pubei granite belongs to S-type granite. The formation of Pubei granite is closely related to the closure of Qinphang residual ocean basin. It was formed in the island arc background during the southward subduction and collision of the residual ocean basin.
【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：P588.121

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