本文選題：黑龍江省同江—撫遠(yuǎn)地區(qū)　切入點(diǎn)：花崗質(zhì)巖石　出處：《吉林大學(xué)》2015年碩士論文

【摘要】：本文以黑龍江省東北部同江—撫遠(yuǎn)地區(qū)的“晚印支期”花崗質(zhì)巖石作為研究對象，在詳細(xì)的野外地質(zhì)調(diào)查和室內(nèi)巖相學(xué)研究的基礎(chǔ)上，通過鋯石LA-ICP-MSU-Pb定年、全巖地球化學(xué)分析和鋯石Hf同位素測試結(jié)果，結(jié)合區(qū)域地質(zhì)資料對這些花崗質(zhì)巖石的形成時代、巖漿源區(qū)性質(zhì)及其構(gòu)造意義進(jìn)行了討論。 同江—撫遠(yuǎn)地區(qū)的花崗質(zhì)巖石主要出露在街津口、勤得利和撫遠(yuǎn)三個地區(qū)，在礦物組成上這些花崗質(zhì)巖石極為相近，主要巖石類型為含黑云母和/或角閃石的花崗閃長巖和花崗閃長斑巖，角閃石的普遍出現(xiàn)表明它們屬于I型花崗巖的成因類型。 在所選擇的8件鋯石LA-ICP-MS U-Pb定年樣品中，鋯石多呈自形-半自形晶，普遍發(fā)育振蕩環(huán)帶，Th/U比值較高（主要為0.31~0.83），指示其為巖漿成因，定年結(jié)果代表了巖石的形成時代。從定年結(jié)果來看，它們的形成時代基本一致，均為晚白堊世（89.5~94.8Ma）。 在主量元素特征上，研究區(qū)花崗質(zhì)巖石均屬于準(zhǔn)過鋁-弱過鋁質(zhì)的高鉀-中鉀鈣堿性系列，總體顯示出富SiO2, K2O和貧TFe2O3, MgO, CaO以及過渡族元素的地球化學(xué)特征。暗示其原始巖漿應(yīng)起源于陸殼基性-中基性火成巖的部分熔融。不同樣品中的主要氧化物與SiO2含量存在相同的變化趨勢，暗示它們具有同源巖漿特征。從稀土元素的組成以及稀土配分模式上看，研究區(qū)花崗質(zhì)巖石的總體特征相似，表現(xiàn)為富含輕稀土元素、虧損重稀土元素、銪異常較弱，重稀土分餾中等且相對含量較高。從微量元素組成與原始地幔標(biāo)準(zhǔn)化蛛網(wǎng)圖上來看，，這些花崗質(zhì)巖石均表現(xiàn)為Nb、Ta以及Ti的虧損，其Th/U比值為4.22~9.53，平均為6.10，顯示出明顯的殼源特征。結(jié)合鋯石Hf同位素特征（Hf（t）=+4.45~+9.01、二階段Hf模式年齡（TDM2）＝583~875Ma），認(rèn)為研究區(qū)花崗質(zhì)巖石的源區(qū)巖石應(yīng)為基性-中基性火成巖，原始巖漿起源于深部陸殼新增生的基性-中基性火成巖的部分熔融。 根據(jù)區(qū)域上存在的晚白堊世火成巖的組合特征及其分布規(guī)律，結(jié)合區(qū)域構(gòu)造演化歷史對研究區(qū)花崗質(zhì)巖石形成的構(gòu)造背景進(jìn)行了討論。認(rèn)為同江—撫遠(yuǎn)地區(qū)晚白堊世花崗質(zhì)巖石形成于大陸邊緣的構(gòu)造背景，其動力學(xué)機(jī)制與古太平洋板塊向東亞大陸之下的正向俯沖作用有關(guān)。
[Abstract]:In this paper, the granitic rocks of the late Indosinian period in Tongjiang-Fuyuan area, northeast of Heilongjiang Province, are taken as the research objects. On the basis of detailed field geological surveys and laboratory petrographic studies, zircon LA-ICP-MSU-Pb dating is used to determine the age of the granitic rocks. The geochemistry analysis and zircon HF isotopic measurements are combined with regional geological data to discuss the formation age, magmatic origin and tectonic significance of these granitic rocks. The granitic rocks in Tongjiang-Fuyuan area are mainly exposed in the three areas of Jiejinkou, Guanli and Fuyuan. The mineral composition of these granitic rocks is very similar. The main rock types are granodiorite with biotite and / or hornblende and granodiorite porphyry. The common occurrence of amphibole indicates that they belong to the genetic type of I-type granite. Among the 8 selected zircon LA-ICP-MS U-Pb dating samples, the zircons are mostly automorphic and semi-automorphic, and there is a high ratio of Th / U (mainly 0.31 ~ 0.83) in the oscillating ring zone, indicating that the zircon is of magmatic origin. The dating results represent the age of formation of rocks, and the age of their formation is basically the same as that of the late Cretaceous. The granitic rocks in the study area belong to the high and medium potassium calc-alkaline series of quasi-peraluminum-weak peraluminous elements. The geochemical characteristics of Sio _ 2, K _ 2O and poor TFE _ 2O _ 3, MgO, CaO and transition group elements are shown. It is suggested that the primitive magma originated from the partial melting of continental basic-mesogenic igneous rocks. The main oxides in different samples and SiO2 contents. There is the same trend of change in quantity, From the composition of rare earth elements and the REE distribution pattern, the general characteristics of granitic rocks in the study area are similar, showing that they are rich in light rare earth elements, depleted in heavy rare earth elements, and very weak in europium. The heavy rare earth fractionation is medium and the relative content is high. From the composition of trace elements and the standard spider web diagram of the primitive mantle, these granitic rocks are characterized by the depletion of NB, Ta and Ti. The Th/U ratio is 4.22 ~ 9.53, with an average of 6.10, which shows obvious crustal characteristics. Combined with zircon HF isotopic characteristics (HF) = 4.45 ~ 9.01, the two-stage HF model age of TDM _ 2N _ (583) (875 Ma) shows that the source rocks of the granitic rocks in the study area should be basic-mesogenic igneous rocks, and the source rocks of the granitic rocks in the study area should be basic-mesogenic igneous rocks. The primitive magma originated from the partial melting of the basic-mesogenic igneous rocks newly proliferated in the deep continental crust. According to the assemblage characteristics and distribution of late Cretaceous igneous rocks in the region, Based on the history of regional tectonic evolution, the tectonic background of granitic rock formation in the study area is discussed. It is considered that the late Cretaceous granitic rocks formed in the tectonic setting of continental margin in Tongjiang-Fuyuan area. Its dynamic mechanism is related to the forward subduction of the paleo-Pacific plate beneath the East Asian continent.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P588.121

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