Geochemistry and Geochronology of A-Type Granite from Northern Humboldt Mountain, East Antarctica: Vestige of Pan-African Event

A-type granite and gabbro-norite-anorthosite (GNA) suite in the Nordvestoya and Hjornehorna Hills of Northern Hurnboldt Mountains, Central Dronning Maud Land, East Antarctica, intrude the multi-deformed basement rocks that show intermediate pressure, granulite facies metamorphism. The granite consists of perthitic K-feldspar, strain free quartz and sodic plagioclase as the main minerals, with minor biotite and hornblende and accessory phases of zircon, apatite and apaques. The granite is metaluminous and shows A-type geochemical signatures - high silica (69.26 to 78.09%), high alkalis, high FeO/MgO ratio and significant HFSE and LREE enrichment with prominent negative Eu anomaly. The granite has yielded whole rock Rb - Sr isochron age of 514±59 Ma with an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.7071±0.0013. This age is synchronous with the Pan-African tectono-thermal event, recorded elsewhere in the Eastern Gondwanaland. The A-type granite has resulted from crustal melting initiated by mantle uprise. The ascent and emplacement of granite was facilitated by crustal thinning and fracturing under extensional tectonic regime.