Zircon U-Pb Dating of Early Paleozoic Adakites from Nantinghe Ophiolitic Mélange in Changning-Menglian Suture Zone and Its Geological Implications

被引：0
|
作者：
Wu Z. [1 ,2 ]
Wang B. [2 ,3 ]
Wang D. [2 ,3 ]
Liu H. [2 ,3 ]
Zhou F. [2 ,3 ]
机构：
[1] Chinese Academy of Geological Sciences, Beijing
[2] Chengdu Center of China Geological Survey, Chengdu
[3] Research Center for Tibetan Plateau Geology, China Geological Survey, Chengdu
来源：
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2020年 / 45卷 / 08期
关键词：
Adakite; Changning-Menglian suture zone; Early Paleozoic; Geochemistry; Geochronology; Longmuco-Shuanghu suture zone; Tethyan;
D O I：
10.3799/dqkx.2020.141
中图分类号：
学科分类号：
摘要：
A large number of records of magmatic activities and sedimentary strata in the Late Paleozoic have been obtained in the Changning-Menglian suture zone, but the records of Early Paleozoic are very rare, which greatly limits understanding of the Early Paleozoic evolution process in this area. In this paper, the zircon U-Pb age and geochemical characteristics of the Early Paleozoic tonalite are reported in the Nantinghe area, and its petrogenesis is discussed to reveal the evolution process of the Early Paleozoic Tethys. LA-ICPMS zircon U-Pb dating shows that the weighted mean 206Pb/238U ages are 454.1±2.7 Ma and 443.2±2.4 Ma for tonalite, representing the crystallization age of magmatic rocks. Geochemical analyses of the tonalite show that its SiO2 content is 63.41%-68.57% and the K2O content is 1.31%-2.17%, and it is rich in Na (Na2O=4.11%-5.07%) and poor in Mg (MgO=0.98%-1.39%). The REE distribution curve shows the enrichment of LREE and the depletion of HREE, large ion lithophile elements Sr, Ba enrichment, high field strength elements Nb, Ta, Ti depletion, which is consistent with the characteristics of island arc magma, indicating that they were derived from the partial melting of subduction oceanic slab and was contaminated by subduction sediments in the magma rising process, and formed in the arc volcanic environment related to the subduction of the original Tethys ocean, further indicating that the subduction of the proto-Tethys Ocean occurred in 454-443 Ma. The chronology and geochemsitry characteristics of the Nantinghe ophiolite in Changning-Menglian suture zone can be well correlated with the Taoxing Lake ophiolite in the Longmuco-Shuanghu suture zone of Qiangtang area. Thus, it is suggested that both the Changning-Menglian and Longmuco-Shuanghu sutures probably represent the original of a unified paleo-Tethys oceanic crust. © 2020, Editorial Department of Earth Science. All right reserved.
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页码：3003 / 3013
页数：10
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