The Magmatic Record of the Mesozoic Arc in Northern Millerand Island.Marguerita Bay. Antarctic Peninsula

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

Montevideo

Congreso; XI Congreso Latinoamericano de Geología y III Congreso Uruguayo de Geología; 2001

Congreso Uruguayo de Geología

The northern Millerand Island preserves part of the magmatic record of the Antarctic Peninsula Mesozoic arc. It is composed of two stratigraphically distinct plutonic units separated by an areally profuse volcanic episode. The oldest magmatic event of the surveyed area is represented by a group of heterogeneous plutonic rocks displaying a suite of mesoand microscopic magma mixing features. This group of probable Early-Jurassic age, comprises banded acidic and intermediate rocks which generally bear rnafic 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 rlyolithc/ rhyodacitic crystalline and lithic tuffs and andesitic lava flows, whch belong to the Antarctic Peninsula Volcanic Group. A compositionally homogeneous unit of monzo- and syenogranites intrudes the volcanics. A set of rhyolite dkes predates granite emplacement. A compositionally diverse group of mafic dykes represents the final magmatic activity in th~asr ea.