Abstract

Quartz pseudomorphs after possible retrogression of coesite were recognized petrographically within garnets of mafic eclogites from the Lanterman Range (Antarctica). In one of the quartz pseudomorphs the presence of a pristine coesite is indicated by in situ Raman microprobe spectroscopy. The results of the Raman analyses show that the quartz inclusion in addition to the typical quartz vibrations has a weak band at 521 cm-1, which corresponds to the most intense fundamental vibration in coesite. This finding represents a first piece of evidence for ultrahigh-pressure metamorphism in Antarctica which was part of the Gondwana supercontinent affected by the Cambro-Ordovician orogenic cycle.

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