Ultrahigh pressure (>7 GPa) gneissic K-feldspar (-bearing) garnet clinopyroxenite in the Altyn Tagh, NW China: Evi- dence from clinopyroxene exsolution in garnet

作     者：LIU Liang1,3, CHEN Danling1, ZHANG Anda1, SUN Yong1, WANG Yan1, YANG Jiaxi1,2 & LUO Jinhai1 1. Key Laboratory of Continental Dynamics of the Ministry of Education of China, Northwest University, Xi’an 710069, China 2. College of Earth Science and Land Resources, Chang’an University, Xi’an 710054, China 3. The Laboratory of Orogen and Basin of the Ministry of Education, Peking University, Beijing 100871, China 

作者机构：Key Laboratory of Continental Dynamics Ministry of Education of China Northwest University Xi'an 710069 China Laboratory of Orogen and Basin Ministry of Education Peking University Beijing 100871 China College of Earth Science and Land Resources Chang'an University Xi'an 710054 China 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2005年第48卷第7期

页      面：1000-1010页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 0708[理学-地球物理学] 0704[理学-天文学] 

基　　金：the National Key Basic Research Program of China(Grant No. 1999075508) the National Natural Science Foundation of China(Grant Nos.40372088,49972063 , 140032010-c) the Cadreman Teacher Foundation of the Ministry of Education of China (Grant No. 40133020) the Open Foundation of the Laboratory of Orogen and Basin of the Ministry of Education of Peking University 

主　　题：Altyn Tagh gneissic K-feldspar (-bearing) garnet clinopyroxenite clinopyroxene exsolution in garnet ultra-high pressure metamorphism. 

摘      要：The exsolution of clinopyroxene and rutile in coarse-grain garnet is found in the gneissic K-feldspar(-bearing) garnet clinopyroxenite from Yinggelisayi in the Altyn Tagh, NW China. The maximum content of the exsolved clinopyroxene in the garnet is up to 5% by volume. The reconstructed precursor garnet (Grt1) before exsolution has a maximum Si content of 3.061 per formula uint, being of supersilicic or majoritic garnet. The peak-stage metamorphic pressure of 7 GPa is estimated using the geobarometer for volume percentage of exsolved pyroxene in garnet and the Si-(Al+Cr) geobarometer for majoritic garnet, and the temperature of about 1000℃ using the ternary alkali-feldspar geothermometer and the experimental data of ilmen- ite-magnetite solid solution. The protoliths of the rocks are intra-plate basic and intermediate ig- neous rocks, of which the geochemical features indicate that they are probably the products of the evolution of basic magma deriving from the continental lithosphere mantle. The rocks are in outcrops associated with ultrahigh pressure garnet-bearing lherzolite and ultrahigh pressure garnet granitoid gneiss. All of these data suggest that the ultrahigh pressure metamorphic rocks in the Altyn Tagh are the products of deep-subduction of the continental crust, and such deep- subduction probably reaches to 200 km in depth. This may provide new evidence for further discussion of the dynamic mechanism of the formation and evolvement of the Altyn Tagh and the other collision orogenic belts in western China.