發(fā)布時(shí)間：2018-01-31 19:56

  本文關(guān)鍵詞： I-A型復(fù)合花崗巖 年代學(xué) 地球化學(xué) 巖石成因 福州復(fù)式巖體　出處：《中國(guó)地質(zhì)大學(xué)(北京)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：華南沿海地區(qū)發(fā)育有大量的中生代花崗巖,雖然這是我國(guó)花崗巖研究程度較高的地區(qū)之一,但是對(duì)于該時(shí)期復(fù)式巖體的研究并不是很多,其巖石成因和構(gòu)造背景一直存在較大爭(zhēng)議。本文報(bào)道了福州復(fù)式巖體花崗巖的巖石學(xué)、鋯石U-Pb年代學(xué)、鋯石微量元素、Hf同位素和全巖主、微量地球化學(xué)的研究結(jié)果,試圖為深入探討該時(shí)期的巖石成因提供新資料。福州復(fù)式巖體的花崗巖主要分為鈣堿性和堿性?xún)纱箢?lèi),分別采自于福州巖體、丹陽(yáng)巖體和魁岐巖體,巖石類(lèi)型主要為:黑云母鉀長(zhǎng)花崗巖,二長(zhǎng)花崗巖和堿性花崗巖。LA-ICP-MS鋯石U-Pb定年結(jié)果表明:福州巖體和丹陽(yáng)巖體形成的年齡約為:106 Ma和111 Ma、101Ma,是早白堊世多期次巖漿活動(dòng)作用的產(chǎn)物;魁岐巖體形成的年齡為:93Ma、95Ma,是晚白堊世巖漿活動(dòng)的產(chǎn)物。鋯石微量的差異可以推斷早白堊世鈣堿性花崗巖為I型花崗巖,晚白堊世堿性花崗巖為A型花崗巖,構(gòu)成了I-A型巖石系列。研究區(qū)內(nèi)的巖石樣品均具有Eu負(fù)異常、LREE富集和HREE虧損的特征,均顯示Rb、Th、U、K、Pb等大離子親石元素相對(duì)富集,Ba、Sr以及高場(chǎng)強(qiáng)元素Nb、Ta、P、Ti相對(duì)虧損。本文I型花崗巖的輕重稀土分餾程度較之A型花崗巖明顯,LREE/HREE比值較大,A型花崗巖的負(fù)銪異常比I型花崗巖明顯,同時(shí)也佐證了前面I-A型巖石系列的推測(cè)。鋯石Hf同位素的結(jié)果表明,I型花崗巖的εHf(t)值由負(fù)到正,地殼模式年齡表明花崗質(zhì)巖漿源巖來(lái)自于新元古代古老地殼的部分熔融,并有少量的地幔組分卷入。A型花崗巖樣品εHf(t)值為正,地殼模式年齡指示花崗質(zhì)巖漿源巖來(lái)自于新元古代古老地殼的部分熔融,并有大量幔源組分的混入。福州復(fù)式巖體中I-A型花崗巖具有相同的源區(qū),其形成的差異主要是構(gòu)造環(huán)境的變遷、幔源巖漿的加入以及巖漿分異演化多種因素綜合作用的結(jié)果。
[Abstract]:There are a large number of Mesozoic granites developed in the coastal areas of South China. Although this is one of the areas with a high degree of granite research in China, there are not many studies on the composite rock mass in this period. The petrology, zircon U-Pb geochronology, zircon trace element HF isotope and the whole rock host of the complex granites in Fuzhou are reported in this paper. The results of trace geochemistry try to provide new data for the further study of the petrogenesis of this period. The granites of Fuzhou complex rock body are mainly divided into two types: calc-alkaline and alkaline, which were collected from Fuzhou rock body respectively. Danyang and Qui-qi rock bodies, the main rock types are: biotite potassium feldspar granite. The zircon U-Pb dating results of the monzogranites and alkaline granites show that the ages of formation of Fuzhou and Danyang pluton are about 10 ~ 106 Ma and 111 Ma. 101 Ma was the product of multistage magmatism in early Cretaceous; The age of formation of Kui-qi rock body is: 93 Ma-95 Ma, which is the product of late Cretaceous magmatic activity. The difference of trace zircon can be inferred that the early Cretaceous calc-alkaline granite is I-type granite. The late Cretaceous alkaline granites are A-type granites, forming I-A type rock series. The samples in the study area are characterized by negative EU anomaly LREE enrichment and HREE depletion, indicating RB. The large ion lithophile elements such as Th _ (+) U _ (U) K _ (+) Pb are relatively enriched in Ba-Ba _ (Sr) and the high field strength element (NB ~ (+) Ta _ (P)). The REE / hree ratio of the I-type granite is larger than that of the A-type granite, and the negative europium anomaly of the A-type granite is more obvious than that of the I-type granite. The results of zircon HF isotopes indicate that the 蔚 Hft values of the I-A type granites vary from negative to positive. The crustal model age indicates that the granitic magmatic source rocks originated from the partial melting of the Neoproterozoic ancient crust, and a small amount of mantle components are involved in the sample of .A-type granite. The crustal model age indicates that the granitic magmatic source rocks are derived from the partial melting of the Neoproterozoic ancient crust and are mixed with a large number of mantle-derived components. The I-A type granites in the Fuzhou complex have the same source area. The difference of formation is mainly caused by the changes of tectonic environment, the addition of mantle magma and the comprehensive action of many factors of magmatic differentiation and evolution.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P588.121

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