Origin and Evolution of Miocene Basanite to Comendite Lavas at the Mount Overlord Volcanic Field, Northern Victoria Land, Antarctica.

This article focuses on the geological, geochronological, petrographic, and geochemical study of the Mount Overlord Volcanic Field (MOVF), a continental alkaline volcanic province in northern Victoria Land, Antarctica. The MOVF records volcanic activity spanning approximately 21 million years (from about 21.2 to 6.9 million years ago), making it the longest volcanic record in northern Victoria Land, with eruptions ranging from basanite to highly evolved comendite compositions. The magmatic evolution involved polybaric fractional crystallization primarily at lower crustal depths, coupled with about 10% assimilation of Granite Harbor Intrusive Complex granitoids, and shallow crustal evolution of felsic magmas (<8 km depth). Isotopic and trace element data indicate that the mantle source was a metasomatized lithospheric mantle near the base of the continental lithospheric mantle (CLM), dominated by amphibole-bearing metasomes with limited interaction between parental melts and juvenile CLM, resulting in diverse alkaline magma compositions within this continental rift system.