Origin of quartz and amphibole precipitates in omphacite in the ultrahigh-pressure metamorphosed eclogite from Xitieshan, North Qaidam

• Main Authors: Yi-Chi Tsau, 曹懿麒
• Other Authors: Yen-Hong Shau
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/10311974445258637166

碩士 === 國立中山大學 === 海洋生物科技暨資源學系研究所 === 99 === Oriented needle-shaped or rod-shaped quartz precipitates occur in clinopyroxenes have been commonly observed in eclogites or garnet peridotites from the high pressure or ultra-high pressure (HP/UHP) metamorphic belts, and their occurrence has been used as an indicator of UHP metamorphism. However, the origin of those quartz precipitates and their crystallographic orientation relationships with clinopyroxene hosts are still not clear. In order to understand the formation mechanisms and environments of the quartz precipitates, the present study has used electron backscattered diffraction (EBSD) analysis, petrographic and scanning electron microscopy, and electron microprobe analysis to study textural features, mineral assemblages, mineral compositions, and crystallographic orientation relationships of mineral precipitates in the omphacite from Xitieshan, North Qaidam UHP metamorphic belt. The results show that the oriented rod-like precipitates in the omphacite hosts are mainly composed of quartz + edenite, and the rods are 5~20