INVESTIGADORES
GONZALEZ Pablo Diego
artículos
Título:
Thermal divide andesites - trachytes, petrologic evidence and implications from Jurassic North Patagonian Massif alkaline volcanism
Autor/es:
ARAGÓN, EUGENIO; GONZÁLEZ, PABLO D.; AGUILERA, YOLANDA; CAVAROZZI, CLAUDIA; LLAMBÍAS EDUARDO; RIVALENTI, GIORGIO
Revista:
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Editorial:
Elsevier
Referencias:
Lugar: Oxford; Año: 2003 vol. 16 p. 91 - 103
ISSN:
0895-9811
Resumen:
The Andesitas Alvar Formation is part of the large Jurassic volcanic province of Patagonia (southern South America) that, in Jurassic time,
participated in the disassembling of Gondwana in a tensionaltranstensional regime with large-scale half-grabens. This large igneous
province contains alkaline and calc-alkaline series of andesitetrachyte, trachyterhyolite, and andesitedacite trends. Four-phase
experimental diagrams of QzOrAbAn and AbAnOlDi correlate with the TAS diagram and explain the Andesitas Alvar
Formations sodium-rich andesitetrachyte, which evolved through a thermal divide edge. This alkaline set initially included the paragenesis
olivineplagioclasediopsidic augite, which was later replaced by hornblendeplagioclasediopsidic augite. The andesitetrachyte trend
is saturated in silica and rich in sodium and alumina. Diopsidic augite, plagioclase, and hornblende crystals are reverse zoned in magnesium,
iron, calcium, and sodium, so the sodium-rich cores of plagioclase are not due to contamination, and the magmas mix several batches of
partial melts of basic rock. Crystallization temperatures and pressures show that magma chamber emplacement and thermal reversal took
place mainly at 4 kb. This is interpreted as the emplacement of collecting chambers at the brittleductile transition in the crust, where mixing
and crystallization took place, followed by rapid extrusion in a transtensional tectonic environment.
q 2003 Elsevier Ltd. All rights reserved.2003 Elsevier Ltd. All rights reserved.