Orbicular structure at Taylor Valley occurs in a hornblende-rich zone of the Larsen Granodiorite. The orbicule horizon is parallel to the contact between the granodiorite and metasedimentary rocks of the Skelton Group. The gradational relationship between xenoliths and orbicules, the breakage of some orbicules, and the parallelism of gneissosity, schlieren, and xenolith lineation indicate that the orbicules were formed by a diffusion reaction between xenoliths and granodiorite magma.

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