The volcanism of the Jurassic Chon Aike Silicic LIP influenced by Paleozoic inherited crustal structures in the northeastern Deseado Massif, Patagonia

CÉSAR NAVARRETE

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 112

0895-9811

An area of ~40 km2 located in the northeastern sector of the Deseado Massif is detailed studied, in whichPaleozoic metamorphic and Jurassic volcanic rocks crop out. Two genetically linked and compositionallydifferent Jurassic volcanic events of the Chon Aike Silicic LIP are documented by geological mapping andlithofacies and petrographic analyses. The first event was only represented by andesitic lava flows assignable tothe intermediate portion of the Bahía Laura Volcanic Complex (Bajo Pobre Formation). The second was representedby the acidic rocks of the Bahía Laura Volcanic Complex (Chon Aike and La Matilde formations) and it wasconstituted by low-grade and moderate grade ignimbrites, pyroclastic fall deposits (ash tuffs) and several lavabodies (rhyolitic lava domes and lava flows). Firstly, the effusive eruptions dominated during the intermediatemagmatic eruptions, whereas the explosives mechanisms dominated during the first stage of the acidic magmaextrusion, to end with effusive eruptions of previously degassed magma. According to the morphology of theNNW-elongated lava domes (feeder conduits plugs) and internal measurements carried out on these rhyoliticbodies, fissure conduits are interpreted, which were directly controlled by the Paleozoic inherited structuresduring the Jurassic extensional tectonic reactivation ascribed to the initial stages of the Gondwana breakup.