Granitoids of northern Victoria Land, Antarctica: implications of chemical and isotopic variations to regional crustal structure and tectonics.

Abstract

Two different groups of granitic rocks are distiguished, comprising various lithologies whose compositional variations in both major- and trace-element contents and their spatial distribution have been studied to determine relationships with the three geological terrains identified in the pre-Devonian basement. The data indicate that one group, the Cambro-Ordovician Granite Harbour intrusives, represents a plutonic belt on the margin of the East Antarctic craton. The Devonian Admiralty intrusives exhibit increasing involvement of old crustal material from south to north, as distinct from the east to west trend of the Granite Harbour intrusives. The compositional polarity of the Admiralty intrusives is interpreted as evidence that the two terrains with which they are associated are allochthonous and whose emplacement is inferred to have occurred after the Admiralty plutonism, probably before deposition of the Beacon supergroup whose basal units are presumed to be Permian.-M.S.