西昆仑奇台达坂北中新世石英二长岩侵入岩年代学、地球化学及其构造意义
Geochronology,Geochemistry and Tectonic Significance of Miocene Quartz Monzonite from the Northern of Qitai Mountain in Western Kunlun
代新宇 1周斌 2李新林 1杜彪 2范鹏 2赵江林 2杨文博 2武忠山2
作者信息
- 1. 陕西省地质调查院,陕西 西安 710054;陕西省地质调查规划研究中心,陕西 西安 710068
- 2. 陕西省地质调查院,陕西 西安 710054
- 折叠
摘要
奇台达坂位于新疆西昆仑新藏公路 540 km处,在其北侧分布有小规模的中酸性侵入岩,呈NE向展布,岩性主要为石英二长岩.笔者以西昆仑地区东段奇台达坂北石英二长岩侵入体为研究对象,进行岩石地球化学、锆石LA-ICP-MS U-Pb年代学分析.结果表明,石英二长岩锆石U-Pb年龄加权平均值为(10.4±0.2)Ma,形成时代为中新世;岩石具有高SiO2(63.16%～68.20%)、贫Al2O3(13.39%～15.47%)、高K2O(4.23%～5.24%)、低MgO(1.06%～1.49%)、低TiO2(0.60%～0.83%)、准铝质(A/CNK=0.83～0.90)的地球化学性质,具有A型花岗岩特征;富集K、Rb、Th、U而亏损Ba、Sr等大离子亲石元素,相对亏损Nb、Ta、Ti等高场强元素,δEu具明显的负异常特征.岩石的地球化学特征和构造环境判别图解均指示,石英二长岩可能形成于深部岩石圈强烈伸展的环境下,地壳深部形成高温低压环境,促使下地壳发生低程度部分熔融并沿深大断裂快速上升侵位,代表了板内伸展背景作用下的岩浆响应.
Abstract
Qitai Mountain is located in Xinjiang-Xizang Highway 540 km west of Xinjiang Kunlun area,there are small-scale medium acid intrusive rocks distributed around it,the lithology is mainly composed of the quartz monzonite.Here we present bulk-rock geochemistry,zircon U-Pb geochronology of the Miocene quartz mon-zonite in Qitai Mountain in Western Kunlun in order to shed light on this issue.Zircon U-Pb dating yielded Miocene ages of(10.4±0.3)Ma.Geochemically,this early Miocene quartz monzonite is A-type granites with high SiO2(63.16%～68.20%),K2O(4.23%～5.24%),and low Al2O3(13.39%～15.47%),MgO(1.06%～1.49%),TiO2(0.60%～0.83%).They are enriched in light rare earth elements(LREEs),large ion lithophile ele-ments(LILEs,including K,Rb,Th,U,Ba and Sr),but depleted in high-field strength elements(Nb,Ta and Ti)and heavy rare earth elements(HREEs),and have obvious negative Eu anomalies.The geochemical characteris-tics of the rocks and the tectonic setting diagram indicate that the quartz monzonites may have been formed in an environment where the deep lithosphere was strongly extended,and a high temperature and low pressure envi-ronment was formed in the deep crust,which prompted a low degree of partial melting of the lower crust and rapid along deep and large faults.The uplift emplacement represents the magmatic response to the intraplate ex-tensional background.We suggest that the Miocene magmas from the northern of Qita Mountain in Western Kunlun were likely sourced from low-degree partial melting of the lower crust with a high temperature and low pressure environment,there may have formed in the background of strong extension of the deep lithosphere,which promotes the magmas rapid uplift along deep and large faults.
关键词
奇台达坂北/锆石U-Pb年代学/地球化学/板内伸展Key words
the northern of Qitai Mountain/zircon LA-ICP-MS age/geochemistry/intraplate extension引用本文复制引用
基金项目
中国地质调查局项目(1212011220654)
陕西省地质勘查基金(61201908334)
出版年
2024
国家科技期刊平台
NSTL
万方数据