Tuesday, 28 August 2007
2.PS-43

Evidence for magma mixing/mingling in lavas from Minna Bluff, South Victoria Land

Mary K. Scanlan1, Kurt S. Panter1, and Nelia W. Dunbar2. (1) Department of Geology, Bowling Green State University, 190 Overman Hall, Bowling Green, OH 43403, (2) Department of Earth and Environmental Sciences, New Mexico Tech, 801 Leroy Pl, Socorro, NM 87801

This work consists of a detailed petrologic study of inclusion-rich lavas that are found near the southeastern tip of Minna Bluff; a ~50 km-long volcanic peninsula located in the southern Ross Sea.  This newly discovered deposit, informally named Xeno-Ridge, forms a narrow 0.5 km-long ridge located stratigraphically on top of a thick interbedded sequence (~1000 m) of lavas and volcaniclastic deposits.  The lavas at Xeno-Ridge are gray in color, strongly flow banded, and contain abundant inclusions of light-colored feldspathoid-rich plutonic rocks, reddish cognate xenoliths of anorthoclase-bearing lavas, black amphibole megacrysts and dark-gray, highly vesiculated, amphibole-rich inclusions that display fluidal and irregular boundaries with the host-lava.  Phenocrysts in the dark-gray inclusions and the host-lava show abundant disequilibrium textures, including complex zoning and reaction coronas of clinopyroxene after amphibole, skeletal olivine, and embayed and sieved feldspars.  The textures indicate that the lavas experienced multiple episodes of magma mixing/mingling prior to eruption.  

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