The magmatic record of the mesozoic arc in northern Millerand Island. Margarite Bay. Antartic Peninsula

CERREDO, M. E.; REMESAL, M. B.; TASSONE A.; DEL VALLE, R.

Montevideo, Uruguay

Congreso; X Congreso Latinoamericano de Geología; 2001

Asociaci-on Geológica de Uruguay

The northern Millerand Island preserves part of the magmatic record of the Antarctic Península Mesozoic are. It is composed of two stratigraphically distinct plutonic units separated by an areally profuse volcanic episode. The oldest magmatic event of the surveyed área is represented by a group of heterogeneous plutonic rocks displaying a suite of meso-and microscopic magma mixing features. This group of probable Early-Jurassic age, comprises banded acidic and intermedíate rocks which generally bear mafic microgranular enclaves of different sizes. Rocks are variably foliated and partially recrystallized. A volcanic pile of pyroclastic rocks and lava flows of probable Middle-Late Jurassic age rest unconformably upon the plutonic rocks. The widespread volcanic unit is mainly composed of rhyolithic/ rhyodacitic crystalline and lithic tuffs and andesitic lava flows, which belong to the Antarctic Península Volcanic Group. A compositionally homogeneous unit of monzo- and syenogranites intrudes the volcanics. A set of rhyolite dikes predates granite emplacement. A compositionally diverse group of mafic dykes represents the final magmatic activity in this área