本文選題：花崗巖 + 輝長巖��； 參考：《中國科學院研究生院(廣州地球化學研究所)》2015年碩士論文

【摘要】：華南三疊紀花崗巖分布廣泛,尤其是武夷山到湘中雪峰山的華南內(nèi)陸地區(qū)。本文選擇江西與福建交界的資溪-光澤雜巖體,通過系統(tǒng)的LA-ICP-MS鋯石U-Pb定年分析,獲得資溪花崗巖體的年齡為231.7-238.0Ma;而光澤中-基性巖體的SHRIMP鋯石U-Pb年齡為220.1-231.7 Ma。資溪花崗巖地球化學特征顯示出:(1)具有高Si O2,高K2O,弱過鋁質(zhì)(ACNK=1.00-1.11)的特征,屬于高鉀鈣堿性系列;(2)微量元素和稀土元素上,虧損Ba,Sr,Nb,Ta,Ce,和Ti,并出現(xiàn)Eu(δEu=0.35-0.47)的負異常;Th,U,Nd,La,Pb的富集,輕重稀土分異明顯(La/Yb)N=28.8,(Sm/Yb)N=4.4;(3)初始Sr比值高(Isr=0.7068-0.711 3),εNd(t)低(εNd(t)= 11.94~ 7.66)反映它們來自于地殼源區(qū),并有少量基性巖/年輕物質(zhì)的加入。光澤輝長巖地球化學特征顯示出:(1)Si O2=51~59%,具有比資溪花崗巖低的K2O,Na2O和Al2O3含量,較高的Mg O,Mn O,Ti O2,Fe2O3和P2O5含量,屬于高鉀鈣堿性-鉀玄巖系列;(2)微量元素和稀土元素上表現(xiàn)出與資溪花崗巖相似的特征,但是比資溪花崗巖具有更高的大離子親石元素和高場強元素(Ba,Ti,Sr)和更弱的Eu負異常(δEu=0.50~0.69);(3)具有比資溪花崗巖高的初始Sr比值(ISr=0.71096~0.71169),低的εNd(t)(εNd(t)=-10.08~-9.16),表明光澤輝長巖來自于富集巖石圈地幔源區(qū)。光澤輝長巖微量元素特征上顯示出經(jīng)歷過俯沖流體交代作用的島弧特征(如虧損Nb-Ta,高Th,富集LILEs),很可能與古太平洋板塊向華南板塊水平俯沖有關。此外,結合收集的華南內(nèi)陸地區(qū)已有的印支期巖漿巖的年齡資料,觀察其年齡在SE-NW和SW-NE向的時空變化情況,發(fā)現(xiàn)華南內(nèi)陸印支期巖漿巖年齡分布具有從東南沿海到北西內(nèi)陸地區(qū)呈逐漸變年輕的趨勢,而在大致沿武夷山走向的南西到北東方向上呈寬闊的近水平的線性分布趨勢。我們的研究認為,大約260Ma的印支期沿海巖漿弧消失約20Ma之后,~240Ma在距離海溝大約400~500km的整個武夷山地區(qū)幾乎同時出現(xiàn),是水平俯沖造成的華南內(nèi)陸新生巖漿弧形成,類似于新生代北美拉拉米造山和墨西哥中部的水平俯沖情況。由于加厚的中下地殼溫度較高,少量水平俯沖前端脫水形成的地幔巖漿侵入中、下地殼,帶來的熱很容易造成中、下地殼物質(zhì)發(fā)生部分熔融,形成北武夷,乃至整個武夷山地區(qū)大量的印支期花崗質(zhì)巖漿巖。
[Abstract]:The Triassic granites in South China are widely distributed, especially in the inland areas of South China from Wuyi Mountain to Xuefeng Mountain in Central Hunan. In this paper, the Zixi lustre complex at the junction of Jiangxi and Fujian is selected. By systematic LA-ICP-MS zircon U-Pb dating, the age of Zixi granitic body is 231.7-238.0 Ma, while the SHRIMP zircon U-Pb age of lustrous meso-basic rock body is 220.1-231.7 Ma. The geochemical characteristics of Zixi granites show that they have the characteristics of high Sio _ 2, high K _ 2O and weak peraluminous ACNK _ (1.00-1.11). They belong to the high-potassium calc-alkaline series (~ (2) trace elements and rare earth elements. The difference between light and heavy rare earth elements is obvious (La / Yb ~ (28. 8) / Sm- / Yb ~ (4 / 4) N ~ (3) the initial Sr ratio is high (Isr = 0.7068-0.711 ~ (3), 蔚 Ndt _ (t) is low (蔚 Ndndt ~ (?) = ~ (11.94) ~ (7.66), which indicates that they are from the crustal source region and have a small amount of basic rock / young material added. The geochemical characteristics of lustrous gabbro show that the content of K _ 2O-Na _ 2O and Al2O3 is lower than that of Zixi granite, and the content of Fe _ 2O _ 3 and P2O5 is higher than that of Zixi granite. The trace elements and rare earth elements are similar to those of Zixi granite. However, compared with Zixi granites, they have higher large ion lithophile elements and high field strength elements, such as Baan Tiao Sr) and weaker EU negative anomalies (未 EU ~ (0.50) ~ (0.69) with a higher initial Sr ratio than the Zixi granites, and a lower 蔚 -Ndtt ~ (-10.08) ~ (-9.16), which indicates that the lustrous gabbro originated from the enriched lithospheric mantle source area. The trace element characteristics of the lustrous gabbro show that the island arc features experienced subduction fluid metasomatism (such as depleted Nb-Ta, high Thh, enriched Lile Esn), which may be related to the paleo-Pacific plate subduction to the South China plate level. In addition, based on the collected age data of Indosinian magmatic rocks in inland South China, the temporal and spatial variations of their ages in the direction of SE-NW and SW-NE are observed. It is found that the age distribution of the Indosinian magmatic rocks in South China shows a trend of gradually becoming younger from the southeast coast to the north west inland area, and a broad near level linear distribution trend in the direction of the south west to the north east roughly along the Wuyi Mountain strike. Our study suggests that about 240 Ma after the disappearance of the Indosinian coastal magmatic arc about 260Ma occurred almost simultaneously in the entire Wuyishan area, about 400~500km from the trench, resulting from horizontal subduction of the inland Cenozoic magma in southern China. Similar to the Cenozoic Lalami orogenic and central Mexico horizontal subduction. Due to the thickening of the middle and lower crust temperature, a small amount of horizontal subduction front end dehydration of the mantle magma intrusion, the lower crust, the heat is easy to cause partial melting of the lower crust material, resulting in the north Wuyi. The Indosinian granitic magma in Wuyishan area.
【學位授予單位】：中國科學院研究生院(廣州地球化學研究所)
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P597.3;P542

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