| Summary: | 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.
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