【摘要】：赤峰南部樓子店地區(qū)位于華北克拉通北緣,中亞造山帶以南。研究區(qū)廣泛發(fā)育中生代中酸性侵入巖,巖性以二長花崗巖、正長花崗巖為主。本文在野外觀察、巖相學分析基礎上,針對研究區(qū)出露的中酸性侵入巖進行了主量元素、微量元素、同位素及U-Pb年代學研究,并結(jié)合區(qū)域地質(zhì)背景,對研究區(qū)中酸性侵入巖的巖石成因、巖漿源區(qū)、構(gòu)造環(huán)境以及動力學背景進行了討論。研究區(qū)獲得的花崗巖的鋯石U-Pb年齡分別為220.4±1.9Ma(MSWD=0.54),217.9±1.3Ma(MSWD=0.95),204.3±2.3Ma(MSWD=5.4)。主量元素特征顯示研究區(qū)中生代花崗巖富硅、富堿,堿度率AR在3.09~5.64之間,鋁飽和指數(shù)A/CNK變化于0.96~1.04之間,花崗巖屬于準鋁質(zhì)-弱過鋁質(zhì),高鉀鈣堿性系列。Na_2O含量與SiO_2含量的關(guān)系變化不明顯,K_2O、Al_2O_3、CaO、TiO_2、MgO、P_2O_5含量均隨著SiO_2含量增加而降低。微量元素特征顯示,花崗巖富集Rb、Th、K等大離子親石元素,虧損Ba、Ta、Nb、Sr、P、Ti等元素,表明出現(xiàn)了磷灰石、長石類的礦物分異,以及鈦鐵氧化物的分異。稀土元素總量∑REE為114.05~399.96×10~(-6),平均值為216.53×10~(-6),高于地殼∑REE值,輕稀土(LREE)含量在73.76~329.28×10~(-6)之間,重稀土(HREE)含量在11.71~70.68×10~(-6)之間。稀土元素球粒隕石標準化分布型式曲線呈右傾,輕稀土富集,輕重稀土分餾明顯,δEu為0.14~1.00,平均值為0.53,整體具有弱的負Eu異常。花崗巖的(87Sr/86Sr)ⅰ為0.704538~0.710634,平均值為0.706165,εNd(t)值較低,為-11.8~-5.7,二階段Nd模式年齡TDM2為1459~1712Ma。研究認為,赤峰南部樓子店地區(qū)中生代花崗巖屬于I型花崗巖,形成于俯沖碰撞—后碰撞構(gòu)造環(huán)境中,在造山后伸展垮塌過程中出露地表。花崗巖巖漿源區(qū)以古-中元古代地殼物質(zhì)重熔為主,有部分幔源物質(zhì)的加入。通過赤峰南部地區(qū)中生代花崗巖的地球化學與年代學研究,對赤峰南部地區(qū)的構(gòu)造演化進行約束,為華北克拉通中生代以來的構(gòu)造演化提供新的重要信息。
[Abstract]:Laozidian area in the south of Chifeng is located in the north margin of North China craton and south of the Central Asian orogenic belt. Mesozoic intermediate-acid intrusive rocks are widely developed in the study area, the lithology of which is monzogranite and syenite. On the basis of field observation and petrographic analysis, the main elements, trace elements, isotopes and U-Pb chronology of the intermediate-acid intrusive rocks exposed in the study area are studied in this paper, and combined with the regional geological background, The petrogenesis, magmatic source area, tectonic environment and dynamic background of acid intrusive rocks in the study area are discussed. The zircon U-Pb ages of the granite obtained in the study area are 220.4 鹵1.9Ma (MSWD=0.54), 217.91.3 Ma (MSWD=0.95) and 204.3 鹵2.3 Ma (MSWD=5.4), respectively. The characteristics of major elements show that the Mesozoic granites in the study area are rich in silicon and alkali, the alkalinity rate AR is between 3.09 and 5.64, and the aluminum saturation index A/CNK is between 0.96 and 1.04. The granites belong to quasi-aluminous-weak peraluminous type, and the granites belong to quasi-aluminous-weak peraluminous type. The relationship between Na _ 2O content and SiO_2 content is not obvious. The contents of K _ 2O, Al _ 2O _ 3, Cao, TIO _ 2, MgO and P _ 2O _ 5 decrease with the increase of SiO_2 content. The characteristics of trace elements show that the granite is rich in large ion lithophile elements such as Rb,Th,K and depleted in Ba,Ta,Nb,Sr,P,Ti, indicating the mineral differentiation of apatite, feldspar, and the differentiation of titanium and iron oxides. The total content of rare earth elements 鈭，

本文編號：2433274