US EPA

6889107 

Journal Article 

Metamorphism and tectonic evolution of the sedimentary-matrix mélange in the central Yarlung Zangbo Suture Zone, southern Tibet 

Wang, X; Li, X; Kong, F; Zhang, Y; Sun, G; Wang, X; Liu, H; Willner, A 

2020 

0 

Shandong Keji Daxue Xuebao (Ziran Kexue Ban)
ISSN: 1672-3767 

2 

12 

Chinese 

In this paper,petrographic and mineral chemical analysis and pseudosection computation were adopted to investigate the metamorphic characteristics of the phengite schist and stilpnomelane schist from the central Yarlung Zangbo Suture Zone(YZSZ). The study reveals that the phengite schist has a mineral assemblage of phengite, chlorite, albite, quartz and sphene, and a peak condition of 366 ℃/6.4 kbar, while the stilpnomelane schist,as a product of post-peak temperature and pressure reduction, has a mineral assemblage of actinolite, chlorite, epidote, albite, quartz, sphene and ilmenite, and a peak condition of 363 ℃/6.1 kbar. The peak metamorphic temperature and pressure conditions of these sedimentary-matrixmélange have reached the high-pressure greenschist facies with a subduction depth of 21～23 km and a geothermal gradient of 15～18 ℃/km. The metamorphic characteristics are very similar to those of low-grade metamorphic rocks formed when the subducted ocean crust scraped into the accretion wedge system by the upper mantle wedge.Combined with previous geochronology studies, this study further proposes that the sedimentary-matrix mélange in the central part of YZSZ experienced high-pressure greenschist facies metamorphism as a response to a northward subduction of the Neo-Tethyan oceanic lithosphere during the initial India-Asia collision stage. 

Mines And Mining Industry; Metamorphic rocks; Chemical analysis; Ilmenite; Metamorphism; Upper mantle; Deposition; Metamorphism (geology); Temperature; Sutures; Pressure reduction; Geochronology; Accretion; Pressure; Tectonics; Ocean crust; Mountains; Lithosphere; Subduction (geology)