| 西藏打加错晚三叠世安山质岩浆作用的锆石U-Pb年代学和Hf同位素 |
| |
| 引用本文： | 宋绍玮,刘泽,朱弟成,王青,张立雪,张亮亮,赵志丹.西藏打加错晚三叠世安山质岩浆作用的锆石U-Pb年代学和Hf同位素[J].岩石学报,2014,30(10):3100-3112. |
| |
| 作者姓名： | 宋绍玮 刘泽 朱弟成 王青 张立雪 张亮亮 赵志丹 |
| |
| 作者单位： | 中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083;中国地质大学地质过程与矿产资源国家重点实验室, 中国地质大学地球科学与资源学院, 北京 100083 |
| |
| 基金项目： | 本文受中国科学院青藏高原专项（B类）（XDB03010301）、国家973项目（2011CB403102）和国家自然科学杰出青年基金项目（41225006）联合资助。 |
| |
| 摘 要： | 青藏高原南部拉萨地体晚三叠世-早侏罗世时期岩浆活动的地球动力学背景仍是尚待解决的一个重要科学问题。本文报道了南部拉萨地体西部打加错地区新发现的安山玢岩的锆石U-Pb年代学、Hf同位素和全岩地球化学数据。打加错安山玢岩主要由蚀变细粒斜长石、辉石和角闪石组成。2件样品的LA-ICP-MS锆石U-Pb定年结果分别为204±4Ma和203±2Ma,表明打加错地区在晚三叠世发生了安山质岩浆活动。结合近期报道的打加错地区辉石角闪二长闪长岩的年龄(207.3±3.6Ma)记录,表明南部拉萨地体西部打加错地区发生了晚三叠世岩浆活动。2件安山玢岩的锆石εHf(t)值多为正值(分别为-2.2~+8.8和-2.0~+10.7),可比于南部拉萨地体中东部其它地区同期岩浆记录的Hf同位素成分(如:工布江达南部203Ma正长花岗岩的锆石εHf(t)为-4.9~+2.7;日喀则东部约205Ma二长花岗岩的锆石εHf(t)为+11.9~+15.8),这表明南部拉萨地体晚三叠世岩浆活动从东工布江达向西延伸到打加错一带,东西延伸约800km。打加错地区2件安山玢岩样品(SiO2=56.1%~59.0%)以较低Mg#(45.8~48.7)和Al2O3含量(16.4%~17.0%)为特征,属于偏铝质钾玄质-高钾钙碱性火山岩。本文获得的新数据,结合最近报道的早侏罗世桑日群岩浆活动记录以及打加错地区上三叠统地层研究新进展,本文更赞成打加错地区和南部拉萨地体其它地区的晚三叠世岩浆活动形成于与班公湖-怒江洋壳南向俯冲有关的弧后环境。
|
| 关 键 词： | 锆石U-Pb年代学 晚三叠世岩浆活动 弧后背景 打加错 南部拉萨地体 |
| 收稿时间： | 2014/5/10 0:00:00 |
| 修稿时间： | 9/1/2014 12:00:00 AM |
Zircon U-Pb chronology and Hf isotope of the Late Triassic andesitic magmatism in Dajiacuo, Tibet |
| |
| SONG ShaoWei,LIU Ze,ZHU DiCheng,WANG Qing,ZHANG LiXue,ZHANG LiangLiang and ZHAO ZhiDan.Zircon U-Pb chronology and Hf isotope of the Late Triassic andesitic magmatism in Dajiacuo, Tibet[J].Acta Petrologica Sinica,2014,30(10):3100-3112. |
| |
| Authors: | SONG ShaoWei LIU Ze ZHU DiCheng WANG Qing ZHANG LiXue ZHANG LiangLiang and ZHAO ZhiDan |
| |
| Institution: | State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China |
| |
| Abstract: | The geodynamic setting of the Late Triassic-Early Jurassic magmatic activities in the Lhasa Terrane remains hotly debated. This paper reports zircon LA-ICP-MS U-Pb dating, Hf isotopic, and whole-rock geochemical data of the andesite porphyrites from Dajiacuo in the western segment of the southern Lhasa subterrane. The Dajiacuo andesite porphyrites consist mainly of hornblende, pyroxene, and altered fine-grained plagioclase. Two andesitic porphyrite samples have been dated at 204±4Ma and 203±2Ma, respectively, indicating the present of the Late Triassic andesitic magmatism in this region. In combination with the presence of pyroxene-bearing amphibole monzodiorite of 207.3±3.6Ma recently reported from Dajiacuo, it is suggesting that the Late Triassic magmatism was active in the western segment of the southern Lhasa subterrane. These two andesitic porphyrite samples mainly show positive zircon εHf(t) values (-2.2~+8.8 and -2.0~+10.7, respectively), comparable to those of the coeval magmatic records reported from the middle and eastern segments of the southern Lhasa subterrane (e.g., ca.203Ma syenogranite to the south of Gongbogyamda display zircon εHf(t) of -4.9~+2.7, and ca.205Ma monzogranite to the east of Xigaze exhibit zircon εHf(t) of +11.9~+15.8). Such similarity indicates that the Late Triassic magmatic activity extended from Gongbogyamda in the east to Dajiacuo in the west, covering over 800km along the length of the southern Lhasa subterrane. Two andesitic porphyrite samples (SiO2=56.1%~59.0%) are characterized by low Mg# (45.8~48.7) and Al2O3 (16.4%~17.0%) contents and are shoshonitic or high-K calc-alkaline. These new data, together with the data of volcanic rocks recently reported from the Lower Jurassic Sangri Group and the new identification of the Upper Triassic strata around the Dajiacuo, enable us to favor that the Late Triassic magmatic activity documented from Dajiacuo and other segments of the southern Lhasa subterrane is most likely associated with a back-arc setting in response to the southward subduction of the Bangong-Nujiang oceanic lithosphere. |
| |
| Keywords: | Zircon U-Pb chronology Late Triassic magmatism Back-arc setting Dajiacuo southern Lhasa Terrane |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《岩石学报》浏览原始摘要信息 |
| 点击此处可从《岩石学报》下载免费的PDF全文 |
|
