Abstract

ARAGON, E. et al. The Escuela Piedra Parada Vitrophyric Dome, from the Rio Chubut Medio Volcanic-Pyroclastic Complex. Rev. Asoc. Geol. Argent. [online]. 2004, vol.59, n.4, pp.634-642. ISSN 0004-4822.

Geology and geochemistry of a 0.8 km² rhyolitic vitrophyric dome, related to other five domes that line up along the moat of a 25 km diameter cauldron of Paleocene age is studied. The dome belongs to the post-collapse intra calderas magmatism. Ring fractures controlled domes distribution along moat. Radial fractures controlled dome's local feeding conduits. The Dome shows intrusive and extrusive relations with tuffaceous stratified lacustrine sediments. A foliated rhyolite intruded the dome and extruded through the apex of it, while the dome was still at high temperature. Geochemistry shows that vitrophyres and foliated lavas are high potassium rhyolites of calcalkaline nature, comagmatic and probably related to a funnel like (etmolith) andesitic intrusive that is also restricted to the caldera's moat.

Keywords : Vitrophyric dome; Rhyolitic; Caldera; Chubut.

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