赤峰南部楼子店地区中生代花岗岩地球化学特征及U-Pb年龄
发布时间：2019-03-02 17:14
【摘要】：赤峰南部楼子店地区位于华北克拉通北缘,中亚造山带以南。研究区广泛发育中生代中酸性侵入岩,岩性以二长花岗岩、正长花岗岩为主。本文在野外观察、岩相学分析基础上,针对研究区出露的中酸性侵入岩进行了主量元素、微量元素、同位素及U-Pb年代学研究,并结合区域地质背景,对研究区中酸性侵入岩的岩石成因、岩浆源区、构造环境以及动力学背景进行了讨论。研究区获得的花岗岩的锆石U-Pb年龄分别为220.4±1.9Ma(MSWD=0.54),217.9±1.3Ma(MSWD=0.95),204.3±2.3Ma(MSWD=5.4)。主量元素特征显示研究区中生代花岗岩富硅、富碱,碱度率AR在3.09~5.64之间,铝饱和指数A/CNK变化于0.96~1.04之间,花岗岩属于准铝质-弱过铝质,高钾钙碱性系列。Na_2O含量与SiO_2含量的关系变化不明显,K_2O、Al_2O_3、CaO、TiO_2、MgO、P_2O_5含量均随着SiO_2含量增加而降低。微量元素特征显示,花岗岩富集Rb、Th、K等大离子亲石元素,亏损Ba、Ta、Nb、Sr、P、Ti等元素,表明出现了磷灰石、长石类的矿物分异,以及钛铁氧化物的分异。稀土元素总量∑REE为114.05~399.96×10~(-6),平均值为216.53×10~(-6),高于地壳∑REE值,轻稀土(LREE)含量在73.76~329.28×10~(-6)之间,重稀土(HREE)含量在11.71~70.68×10~(-6)之间。稀土元素球粒陨石标准化分布型式曲线呈右倾,轻稀土富集,轻重稀土分馏明显,δEu为0.14~1.00,平均值为0.53,整体具有弱的负Eu异常。花岗岩的(87Sr/86Sr)ⅰ为0.704538~0.710634,平均值为0.706165,εNd(t)值较低,为-11.8~-5.7,二阶段Nd模式年龄TDM2为1459~1712Ma。研究认为,赤峰南部楼子店地区中生代花岗岩属于I型花岗岩,形成于俯冲碰撞—后碰撞构造环境中,在造山后伸展垮塌过程中出露地表。花岗岩岩浆源区以古-中元古代地壳物质重熔为主,有部分幔源物质的加入。通过赤峰南部地区中生代花岗岩的地球化学与年代学研究,对赤峰南部地区的构造演化进行约束,为华北克拉通中生代以来的构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 卤1.9Ma (MSWD=0.54), 217.91.3 Ma (MSWD=0.95) and 204.3 卤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，
本文编号：2433274
[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 卤1.9Ma (MSWD=0.54), 217.91.3 Ma (MSWD=0.95) and 204.3 卤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，
本文编号：2433274
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