The formation of SiO2 phase in eucrite is closely related to the thermal transformation of the parent body,which can indicate the thermal metamorphic history of the parent body to a certain extent.Taking GRV 13001,a eucrite discovered by the 30th Chinese Antarctic expedition,as the research object.This research analy-zes the different occurrence SiO2 phases,and finds three types:irregular granular cristobalite and quartz with rela-tively pure composition,Al-and K-rich lath-shaped tridymite,and vermicular SiO2 phase contained in high-Ca pyroxene rim.The genesis of SiO2 phases with different occurrences and the thermal metamorphism history of the parent body of GRV 13001 are as follows:(1)the shallow surface magma of the parent body cooled rapidly and crystallized to form filling irregular granular cristobalite;(2)slow thermal metamorphism to form pyroxene with type 4 thermally metamorphosed degree,which also results in the transformation of some cristobalite in the me-sostasis to normal quartz;(3)during the slow thermal metamorphism,a relatively short and high-temperature re-heating event causes the formation of lath-shaped tridymite by partial melting of the mesostasis area,which also leads to the formation of high-Ca pyroxene accretive rims at the edges of the primitive pyroxene grains.The ver-micular SiO2 phase is included in the accretive rims during the growth process.The genesis of the SiO2 phases with different occurrences provides a basis for the thermal transformation process of the meteorite parent body.
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