Petrology, geochemistry and Ar-Ar geochronology of eclogites in Jinshajiang orogenic belt, Gonjo area, eastern Tibet and restriction on Paleo-Tethyan evolution  

作　　者：Yuan Tang Ya-dong Qin Xiao-dong Gong Yong Li Dong-bing Wang Bao-di Wang 

机构地区：[1]Chengdu Center,China Geological Survey(Geosciences Innovation Center of Southwest China),Ministry of Natural Resources,Chengdu 610081,China [2]China Aero Geophysical Survey and Remote Sensing Center for Natural Resources,Beijing 100083,China

出　　处：《China Geology》2023年第2期285-302,共18页中国地质（英文）

基　　金：funded by two Second Tibetan Plateau Comprehensive Scientific Investigation and Research Projects(2019QZKK0702,2019QZKK0706);a project of National Natural Science Foundation of China(42230311);two geological survey projects of China Geological Survey(DD20221635,DD20221811).

摘　　要：As one of the important Paleo-Tethys suture zones in eastern Tibet,the Jinshajiang orogenic belt is of great significance to study the tectonic evolution of the main suture zone of Paleo-Tethys.In this paper,eclogites developed in the Jinshajiang suture zone in Gonjo area,eastern Tibet,are selected as specific research objects,and petrological,geochemical and Ar-Ar geochronological analyses are carried out.The major element data of the whole rock reveals that the eclogite samples have the characteristics of picritic basalt-basalt and belong to the oceanic low potassium tholeiites.The results of rare earth elements and trace elements of the samples show that the protoliths of eclogites have characteristics similar to oceanic island basalt(OIB)or normal mid ocean ridge basalt(N-MORB).Muscovite(phengite)from two eclogite samples yield the Ar-Ar plateau ages of 247±2 Ma and 248±2 Ma respectively,representing the peak metamorphic age of eclogite facies and the timing of complete closure of the Jinshajiang Paleo-Tethys Ocean.Muscovite and biotite selected from the hosting rocks of eclogite yield the Ar-Ar plateau ages are 238±2 Ma and 225±2 Ma respectively,reflecting the exhumation age of eclogites and their hosting rocks.Combined with the zircon U-Pb dating data(244 Ma)of eclogites obtained in previous work,it can be concluded that the Jinshajiang Paleo-Tethys ocean was completely closed and arc-continent collision was initiated at about 248-244 Ma(T21).Subsequently,due to the large-scale arc(continent)-collision orogeney between Deqin-Weixi continental margin arc and Zhongza block(T31-T32),the eclogites were rapidly uplifted to the shallow crust.

关 键 词：ECLOGITE Ar-Ar geochronology Closure of Paleo-Tethys ocean Arc-continent collision Geological survey engineering Jinshajiang orogenic belt Eastern Tibet 

分 类 号：P542.2[天文地球—构造地质学] P588.34[天文地球—地质学]