Review on Petrology of Eclogites in Central Qiangtang of Qinghai-Tibet Plateau(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2017年第05期
- Page:
- 620-632
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Review on Petrology of Eclogites in Central Qiangtang of Qinghai-Tibet Plateau
- Author(s):
- WANG Xiao-sai; DU Jin-xue; WANG Gen-hou
- School of Earth Sciences and Resources,China University of Geosciences, Beijing 100083, China
- Keywords:
- petrology; eclogite; high-pressure metamorphism; geothermobarometer; P-T path; Longmu Co-Shuanghu suture zone; central Qiangtang; Qinghai-Tibet Plateau
- PACS:
- P588.3
- DOI:
- -
- Abstract:
- The low-temperature high-pressure (LT-HP) metamorphic belt in central Qiangtang is the largest high-pressure metamorphic belt occurring in Qinghai-Tibet Plateau, and is an important window for understanding the early formation and evolution of Qinghai-Tibet Plateau. The high-pressure metamorphic belt is mainly exposed along Longmu Co-Shuanghu suture zone, and is composed of phengite schists, blueschists, eclogites and so on. Among these high-pressure rocks, the eclogites in central Qiangtang are found in Pianshishan, Guoganjianian Mt., Gemu and Gangma Co, and occur as lenses, blocks and layers in phengite schists or metasediments. Based on the available data, the mineral assemblage of the peak eclogite-facies stage of eclogites in central Qiangtang is garnet+omphacite+phengite+rutil±glaucophane±quartz.The pseudomorphs of box-shape epidote+paragonite found in garnet and P-T results from traditional geothermobarometers indicate that they have reached the lawsonite eclogite-facies metamorphism. Although some eclogites preserve the evidence of suspected ultra-high pressure metamorphism, such as the quartz lamellae exsolves from omphacite, the rutile, quartz or amphibole exsolve from garnet, and the rutile exsolves from apatite, there is no typical ultra-high pressure indicator mineral (such as coesite, diamond, etc.) in the eclogites. “The ultra-high pressure indicator” from garnet compositions and P-T recalculation using traditional geothemobarometers indicate that the eclogites in central Qiangtang do not undergo the ultrahigh-pressure metamorphism. The eclogites in central Qiangtang have a retrograde P-T path characterized by the isothermal decompression, and experience several stages of retrograde metamorphism.
Last Update: 2017-10-19