Geology, geochemistry, and geochronology of an A-type granite in the mulock glacier area, southern Victoria Land, Antarctica

Abstract

On the north side of the Mulock Glacier and at Cape Teall in southern Victoria Land, Antarctica, deformed greenschist facies Skelton Group metasediments are intruded by the post-kinematic A-type Mulock Granite. Geochemical data indicate that this intrusive complex is similar to A-type granitoids previously described both to the north (Glee In-trusives and Penny Hill Granite), where they form part of the Koettlitz Glacier Alkaline Province, and to the south (Foggy-dog Granite Suite). A U-Pb zircon date of 546 ± 3 Ma on the Mulock Granite places a minimum constraint on the age, and timing of deformation of the Skelton Group rocks in this area, and indicates that the Mulock Granite was emplaced during the initial stages of the Ross Orogeny. This age also confirms that crystallisation of this granite body was synchronous with that of A-type granitoids from the Royal Society Range to Skelton Glacier area immediately to the north. During the late Neoproterozoic, extension or transtension along this part of the paleo-Pacific margin of Gondwana allowed crustal-scale thinning to occur. This, coupled with the addition of an external heat supply through mafic underplat-ing and/or asthenospheric upwelling, caused lower crustal anatexis and the production of small volumes of A-type granitoid melt. Although the exact nature of this anatectic process remains unclear, it seems probable that melting did not occur under strictly anhydrous conditions, and an external water supply played a crucial role in melt generation. © 2006 Taylor & Francis Group, LLC.