A Study on the Early Proterzoic Metamorphic Rocks from East Qilian

• Main Authors: Hang, San Feng, 黃三豐
• Other Authors: Ching-long Tsai
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/70779812927940752013

碩士 === 國立成功大學 === 地球科學系 === 84 === Qilian Mountain is a narrow long Caledonian accretion fold belt to the south-western margin of China-Korea Craton ,it is a suture zone between China -Korea craton and Qaidam massive. Three sections,Datung,Huagnyuan,and Huangzon were selected for study of metamorphism in aspect of reconstruction of original rock type, metamorphic facies. The reconstruction of original rock type is based on the whole rock chemisty,and mineral chemistry.In the Datung section, the main rock type are hornblende schist, biotite schist, two-mica schist and granulite.their original rocks are basic igneous rock and pelitic rock, the metamorphic facies ranges from low amphibolite facies to granulite facies. In the Huangyuan section,the main rock type are staurolite-mica schist, andalusite-mica schist, garnet -hornblende-biotite schist, hornblende schist, two-mica schist, garnet-mica schist, actinolite schist,their original rocks are basic igneous rock or pelitic rock, the pelitic metamorphic rocks are outcropped in the eastern and western part of the section, while the basic metamorphic rocks are in the central and western part of the section. In the section most garnet are subjected to chloritization, or retrogressive metamorphism to biotite, and andalusite is retrograded to sericite. three metamorphic zones are recongnized, garnet zone, staurolite zone and andalusite zone, and indicates a progressive matamorphism from west toward east, the metamorphic facies ranges from green schist facies to middle amphibolite facies.In the Huangzon section ,the main rock type are epidote amphibolite, meta-igneous rock, garnet-mica schist, plagioclase amphibolite, their original rocks are basic igneous rock, the metamorphic facies is low amphibolite to middle amphibolite facies. Based on the mineral assemblage and temperature and pressure revealed in the three sections, the metamorphic grade increase from Huanzon toward north gradually.