本文關鍵詞： 北秦嶺 太白花崗巖體 鋯石U-Pb年齡 地球化學 Sr-Nd-Hf同位素　出處：《中國地質大學(北京)》2015年碩士論文　論文類型：學位論文

【摘要】：太白花崗巖體位于秦嶺造山帶商丹斷裂帶北側,野外侵入關系和鋯石U-Pb定年表明,該巖體由早志留世的五里峽巖體、晚三疊世的紅崖河巖體與早白堊世的下板寺巖體組成。五里峽巖體的主要巖石類型為片麻狀似斑狀黑云母二長花崗巖和片麻狀黑云母二長花崗巖,其中片麻狀似斑狀黑云母二長花崗巖鋯石U-Pb年齡為431±2Ma;紅崖河巖體的主要巖石類型為黑云母二長花崗巖和細粒黑云母花崗閃長巖,其鋯石U-Pb年齡分別為214±2Ma和212±3Ma;下板寺巖體巖性比較簡單,為粗粒黑云母花崗巖,鋯石U-Pb年齡為130±1Ma。五里峽片麻狀似斑狀黑云母二長花崗巖和片麻狀黑云母二長花崗巖具富硅、堿、高鋁的特點,屬高鉀鈣堿性系列,弱過鋁質I-A過渡型花崗巖;紅崖河黑云母二長花崗巖具富硅、堿、高鋁的特點,屬高鉀鈣堿性系列,弱過鋁質I-A過渡型花崗巖,細粒黑云母花崗閃長巖Si O2含量相對較低,富堿、高鋁,屬于高鉀鈣堿性系列,準鋁質I-A過渡型花崗巖;下板寺粗粒黑云母花崗巖具有富硅、堿、高鋁的特點,屬于鉀玄巖系列,弱過鋁質I型花崗巖,具有高分異的特點。太白花崗巖體的花崗質巖石屬于準鋁質-弱過鋁質和高鉀鈣堿性/鉀玄巖系列;球粒隕石標準化曲線表現(xiàn)為輕稀土相對富集的右傾特征,輕、重稀土元素分餾明顯[(La/Yb)N=9.05~107.33],具有較弱的銪異常(δEu=0.38~1.21);原始地幔標準化微量元素蛛網圖顯示,各巖石具有相似的微量元素配分模式,富集K、Rb、Ba、Sr、Pb等大離子親石元素,虧損Nb、Ta、P等高場強元素。在同位素組成上,五里峽巖體全巖ISr=0.701935,εNd(t)=-4.98,tDM2=1.58Ga,鋯石的εHf(t)=2.93~8.18,平均值為4.83,兩階段模式年齡tDM2=0.90~1.23Ga,平均年齡為1.11Ga;紅崖河巖體全巖ISr=0.702754,εNd(t)=-8.02,tDM2=1.65Ga,鋯石的εHf(t)=-7.10~-0.74,平均值為-3.52,兩階段模式年齡tDM2=1.29~1.70Ga,平均值年齡為1.47Ga;下板寺巖體全巖ISr=0.705506,εNd(t)=-6.00,tDM2=1.41Ga,鋯石的εHf(t)=-10.21~-1.11,平均值為-5.54,兩階段模式年齡tDM2=1.26~1.84Ga,平均年齡為1.54Ga。元素地球化學與Sr-Nd-Hf同位素組成特征顯示,組成太白花崗巖體的五里峽巖體、紅崖河巖體和下板寺巖體的成巖物質以元古界地殼物質(寬坪群和秦嶺群)為主,同時還有較多年輕組分的加入,并且從早到晚(五里峽巖體→紅崖河巖體→下板寺巖體),年輕組分參與程度減小。結合區(qū)域構造和巖漿演化特征分析,五里峽巖體形成于秦嶺古生代造山作用中的碰撞階段,形成于塊體碰撞擠出過程及略后的抬升環(huán)境;紅崖河巖體可能是揚子地塊與華北地塊后碰撞階段巖漿作用的產物;下板寺巖體形成于擠壓向伸展轉換的構造環(huán)境,是板內巖漿作用的產物,可能和太平洋板塊向歐亞板塊俯沖導致巖石圈伸展減薄有關。
[Abstract]:The Taibai granite body is located on the northern side of the Shangdan fault zone of the Qinling orogenic belt. The field intrusive relationship and zircon U-Pb dating indicate that the body is from the early Silurian Wuli Gorge rock body. The late Triassic Hongyahe rock body and the early Cretaceous Xiabansi rock body are composed of the main rock types of the Wuli Gorge body: the granitic porphyritic biotite monzogranite and the granitic biotite monzomorphic granite. The zircon U-Pb age of porphyritic biotite monzonitic granites is 431 鹵2Ma. The main rock types of Hongyahe pluton are biotite monzonitic granite and fine-grained biotite granodiorite with U-Pb zircon ages of 214 鹵2Ma and 212 鹵3Marespectively. The lithology of the Xiabansi rock mass is relatively simple, and it is a coarse biotite granite. The zircon U-Pb age is 130 鹵1 Ma.Wulixia granitic porphyritic biotite monzonitic granite and granitic biotite monzomorphic granite are characterized by rich in silicon, alkali and aluminum, and belong to high potassium calc-alkaline series. Weakly peraluminous I-A transitional granite; Hongyahe biotite monzogranite is characterized by rich in silicon, alkali and high aluminum. It belongs to high potassium calc-alkaline series, weakly peraluminous I-A transitional granite and relatively low Sio _ 2 content in fine-grained biotite granodiorite. Alkali rich, high aluminum, belongs to high-potassium calc-alkaline series, quasi-aluminous I-A transitional granite; Xiabansi coarse-grained biotite granite has the characteristics of rich in silicon, alkali and high aluminum. It belongs to the series of potash rocks and weakly peraluminous I-type granite. The granitic rocks of the Taibai granite body belong to the series of quasi-aluminite-weakly peraluminous and high-potassium calc-alkaline / kaliacite; The normalized curve of chondrites shows a right-dip characteristic of relative enrichment of light rare earth elements, and the fractionation of light and heavy rare earth elements is obvious. [La / YbN 9.05 (107.33), with weak europium anomaly (未 EU ~ (2 +) 0.38 ~ (1.21) ~ (-1) ~ (-1) ~ (-1) ~ (-1) ~ (-1)); The primitive mantle standardized trace element cobweb shows that the rocks have similar microelement distribution patterns, enriched in large ion lithophile elements, such as K _ (Rb) _ (B _ (B) _ (B) _ (B) _ (B) _ (Ba) _ S _ (Sr) _ (Pb), etc. The isotopic composition of the Wulixia body is 0.701935 for the whole rock, and 1.58 Ga for the 蔚 Ndndltzhui-4.98 TDM2Ga, and the isotopic composition of the isophoric field strength element of P is 0.701935 and 4.98 TDM2Ga, respectively. For zircon, the average value is 4.83, and the mean value is 4.83. The two-stage model age (tDM2 + 0.90) is 1.23Ga, with an average age of 1.11Ga. The whole rock of Hongyahe pluton is 0.702754, 蔚 -8.02tDM2Ga-1.65Ga. 蔚 Hf(t)=-7.10~-0.74 of zircon. The average value is -3.52, the two-stage model age is 1.291.70Ga, and the average age is 1.47Ga. The whole rock of Xiabansi rock is 0.705506, 蔚 Ndndltzhu-6.00 tDM2O1.41 Ga, 蔚 Hf(t)=-10.21~-1.11 of zircon. The mean value was -5.54, and the age of two-stage model was tDM2=1.26~1.84Ga. The average age is 1.54Ga.Elemental geochemistry and Sr-Nd-Hf isotopic composition show that the Wuli Gorge body is composed of Taibai granite. The diagenetic materials of Hongyahe and Xiabansi rock bodies are mainly Proterozoic crustal materials (Kuanping Group and Qinling Group), with the addition of many young components, and from morning to night (Wuli Gorge rock mass). 鈫扝ongyahe rock body. 鈫扐ccording to the analysis of regional tectonics and magmatic evolution, the Wulixia rock body was formed in the collision stage of the Qinling Paleozoic orogeny. It was formed in the extrusion process of block collision and the uplift environment. The Hongyahe pluton may be the product of magmatism in the post-collision stage of the Yangtze block and the North China block. The Xiabansi rock body was formed in the tectonic environment of compression-to-extensional transformation, which is the product of intraplate magmatism, and may be related to the extensional thinning of lithosphere caused by the subduction of the Pacific plate to the Eurasian plate.
【學位授予單位】：中國地質大學(北京)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P588.121;P597.3

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