Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina

Post-crystallization evolution of the metatroctolites of the Norquinco lake zone, Aluminé Igneous-Metamorphic Complex, is analyzed. These mafic rocks show coronas around olivine, composed of Opx, Cpx, Spl and Amp (Hbl1 and Hbl2). The temporal evolution of these rocks was evaluated via petrographic a...

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Autores principales:	Urraza,Ivana, Delpino,Sergio, Grecco,Laura
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2015
Materias:	Metatroctolites Aluminé Igneous-Metamorphic Complex Reaction coronas Geothermobarometry, P-T path
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000100003
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spelling	oai:scielo:S0718-710620150001000032015-03-12Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, ArgentinaUrraza,IvanaDelpino,SergioGrecco,Laura Metatroctolites Aluminé Igneous-Metamorphic Complex Reaction coronas Geothermobarometry, P-T path Post-crystallization evolution of the metatroctolites of the Norquinco lake zone, Aluminé Igneous-Metamorphic Complex, is analyzed. These mafic rocks show coronas around olivine, composed of Opx, Cpx, Spl and Amp (Hbl1 and Hbl2). The temporal evolution of these rocks was evaluated via petrographic analysis and the construction of a suitable pseudosection based on the whole-rock chemical composition. This analysis was complemented with classic geothermobarometry, from which four stages on the P-T path were established: A. Starting point lies in the stability field of the Pl-Ol-Opx-Cpx-H2O, with P-T of 936 °C and 2.7 kbar, respectively, indicative of granulite facies conditions; B. Another point in the trajectory is represented by first appearance of amphibole. P-T conditions for Hbl1-Pl are 780 °C and 5.9 Kbar, respectively.; C. The third point is characterized by the presence of Hbl2 and Spl and the disappearance of Ol, leading to the association Pl-Opx-Cpx-Hbl2-Spl-H2O. Equilibrium temperature and pressure for this stage are 780 °C and 5.69 Kbar, respectively; and D. The last point in the path implies the disappearance of Cpx and the retrogression of the phases to Chl with, a concomitant consumption of excess water. Both the equilibrium temperature (694.2 °C) for the stable association Pl-Opx-Hbl2-Spl-Chl, and the narrow stability pressure range (4.5-5.2 Kbar), are constrained by the absence of olivine and garnet. The defined portion of the P-T path indicates cooling from granulite to amphibolite facies with a concomitant pressure increment, defining a counter-clockwise P-T path. U-Pb zircon ages determined for basement xenoliths in metatroctolites and gabbroic inclusions in granodiorites, allows constraining the emplacement of Norquinco lake metatroctolites to Upper Paleozoic times.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.42 n.1 20152015-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000100003en10.5027/andgeoV42n1-a03
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Metatroctolites Aluminé Igneous-Metamorphic Complex Reaction coronas Geothermobarometry, P-T path
spellingShingle	Metatroctolites Aluminé Igneous-Metamorphic Complex Reaction coronas Geothermobarometry, P-T path Urraza,Ivana Delpino,Sergio Grecco,Laura Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
description	Post-crystallization evolution of the metatroctolites of the Norquinco lake zone, Aluminé Igneous-Metamorphic Complex, is analyzed. These mafic rocks show coronas around olivine, composed of Opx, Cpx, Spl and Amp (Hbl1 and Hbl2). The temporal evolution of these rocks was evaluated via petrographic analysis and the construction of a suitable pseudosection based on the whole-rock chemical composition. This analysis was complemented with classic geothermobarometry, from which four stages on the P-T path were established: A. Starting point lies in the stability field of the Pl-Ol-Opx-Cpx-H2O, with P-T of 936 °C and 2.7 kbar, respectively, indicative of granulite facies conditions; B. Another point in the trajectory is represented by first appearance of amphibole. P-T conditions for Hbl1-Pl are 780 °C and 5.9 Kbar, respectively.; C. The third point is characterized by the presence of Hbl2 and Spl and the disappearance of Ol, leading to the association Pl-Opx-Cpx-Hbl2-Spl-H2O. Equilibrium temperature and pressure for this stage are 780 °C and 5.69 Kbar, respectively; and D. The last point in the path implies the disappearance of Cpx and the retrogression of the phases to Chl with, a concomitant consumption of excess water. Both the equilibrium temperature (694.2 °C) for the stable association Pl-Opx-Hbl2-Spl-Chl, and the narrow stability pressure range (4.5-5.2 Kbar), are constrained by the absence of olivine and garnet. The defined portion of the P-T path indicates cooling from granulite to amphibolite facies with a concomitant pressure increment, defining a counter-clockwise P-T path. U-Pb zircon ages determined for basement xenoliths in metatroctolites and gabbroic inclusions in granodiorites, allows constraining the emplacement of Norquinco lake metatroctolites to Upper Paleozoic times.
author	Urraza,Ivana Delpino,Sergio Grecco,Laura
author_facet	Urraza,Ivana Delpino,Sergio Grecco,Laura
author_sort	Urraza,Ivana
title	Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
title_short	Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
title_full	Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
title_fullStr	Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
title_full_unstemmed	Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina
title_sort	counterclockwise post-emplacement evolution of metatroctolites from aluminé igneous-metamorphic complex, neuquén, argentina
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2015
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062015000100003
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Counterclockwise post-emplacement evolution of metatroctolites from Aluminé Igneous-Metamorphic Complex, Neuquén, Argentina

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