| 滇西“三江”地区临沧花岗岩基早-中奥陶世花岗质片麻岩的发现及其意义 |
| |
| 引用本文： | 彭智敏,张辑,关俊雷,张璋,韩文文,付于真.滇西“三江”地区临沧花岗岩基早-中奥陶世花岗质片麻岩的发现及其意义[J].地球科学,2018,43(8):2571-2585. |
| |
| 作者姓名： | 彭智敏 张辑 关俊雷 张璋 韩文文 付于真 |
| |
| 作者单位： | 1.中国地质调查局成都地质调查中心, 四川成都 610081 |
| |
| 基金项目： | 中国地质调查局项目DD20160016国家自然科学基金项目41273047国家自然科学基金项目41303043 |
| |
| 摘 要： | 前人对"三江"地区临沧花岗岩基早古生代的岩浆事件研究极少.在双江地区临沧花岗岩基中首次识别出早古生代花岗质片麻岩.采用LA-ICP-MS锆石U-Pb定年、微区原位Hf同位素分析，结合全岩地球化学特征，对2件花岗质片麻岩样品进行了系统的研究.获得锆石U-Pb年龄分别为476.9±1.9 Ma、465.7±1.9 Ma，表明这些花岗质片麻岩形成于早-中奥陶世.花岗质片麻岩SiO2含量为70.67%~74.03%，K2O/Na2O值皆大于1，为1.04~1.55，属过铝质S型花岗岩.岩石微量元素特征显示其富集大离子亲石元素Rb、Th、U，亏损高场强元素Nb、Ta、Ti和Zr等，轻重稀土分异明显，轻稀土相对富集、重稀土亏损，具有明显的负Eu异常.2件样品锆石εHf（t）均为负值（-7.2~-0.7，均值-3.0），Hf同位素地壳模式年龄（tDMC）均值基本一致（1 639 Ma、1 630 Ma），说明花岗质片麻岩可能来源于古老地壳物质的部分熔融.综合分析表明，花岗质片麻岩是由原特提斯洋向东俯冲消减而引起的古老地壳物质部分熔融形成，是原特提斯俯冲消减的岩浆事件响应；说明在早奥陶世昌宁-孟连洋就存在俯冲消减，昌宁-孟连特提斯演化历史最早可以追溯到早奥陶世.
|
| 关 键 词： | 花岗质片麻岩 锆石U-Pb定年 原-古特提斯洋 昌宁-孟连结合带 滇西 三江 地球化学 地质年代学 |
| 收稿时间： | 2018-05-08 |
The Discovery of Early-Middle Ordovician Granitic Gneiss from the Giant Lincang Batholith in Sanjiang Area of Western Yunnan and Its Geological Implications |
| |
| Abstract: | There are little research on the Early Paleozoic magma events of the giant Lingcang batholith in Sangjiang area.Early Paleozoic granitic gneiss was recognized for the first time from the Lincang batholith in Shuangjiang area of western Yunnan.LA-ICP-MS U-Pb dating and Hf isotopic analysis of zircons, combined with geochemical characteristics of two granitic gneiss samples are applied in this paper.The zircon U-Pb ages of 476.9±1.9 Ma and 465.7±1.9 Ma are obtained from two samples, which indicates that two granitic gneisses were formed in Middle-Late Ordovician.SiO2 content of the granitic gneisses ranges from 70.67% to 74.03%.The K2O/Na2O ratio is greater than 1, ranging from 1.04 to 1.55, and belonging to peraluminous S-type granitoids.They also enriched in LILEs (Rb, Th and U), but strongly depleted in HFSEs (Nb, Ta, Ti and Zr), showing strongly fractionated REE pattern, with apparently negative Eu anomalies.Their zircons have negative εHf(t) values (-7.2 to -0.7, average -3.0), and Hf isotope crust model ages (tDMC) are basically the same (average 1 639 Ma, 1 630 Ma).It is suggested that granitic gneiss may have originated from partial melting of ancient crustal materials.Based on the above analyses, granitic gneiss is formed by partial melting of ancient crustal materials that was caused by the eastward subduction of the Paleo-Tethys, and is the response of the magmatic events during subduction of the Paleo-Tethys.It shows that there was subduction in the Changning-Menglian ocean in the Early Ordovician, and the evolution history of the Tethys in the Changning-Menglian combination can be traced back to the Early Ordovician. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
| 点击此处可从《地球科学》下载免费的PDF全文 |
|
