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| DOI | 10.5027/ANDGEOV42N1-A03 | ||||||
| Año | 2015 | ||||||
| Tipo | artículo de investigación |
Citas Totales
Autores Afiliación Chile
Instituciones Chile
% Participación
Internacional
Autores
Afiliación Extranjera
Instituciones
Extranjeras
Post-crystallization evolution of the metatroctolites of the (N) over tilde orquinco lake zone, Alumine Igneous-Metamorphic Complex, is analyzed. These mafic rocks show coronas around olivine, composed of Opx, Cpx, Spl and Amp (Hbl(1) and Hbl(2)). 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 degrees 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 Hbl(1)-Pl are 780 degrees 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-Hbl(2)-Spl-H2O. Equilibrium temperature and pressure for this stage are 780 degrees 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 degrees C) for the stable association Pl-Opx-Hbl(2)-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 (N) over tilde orquinco lake metatroctolites to Upper Paleozoic times.
| Ord. | Autor | Género | Institución - País |
|---|---|---|---|
| 1 | Urraza, Ivana | Mujer |
UNIV NACL SUR - Argentina
UNIV NACL COMAHUE - Argentina Universidad Nacional del Sur - Argentina Universidad Nacional del Comahue - Argentina |
| 2 | Delpino, Sergio | Hombre |
UNIV NACL SUR - Argentina
Universidad Nacional del Sur - Argentina |
| 3 | Grecco, Laura | Mujer |
UNIV NACL SUR - Argentina
Universidad Nacional del Sur - Argentina |
| Agradecimiento |
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| This work was financed by funds of the PICT2008 No. 1379 granted to Dra. L. Grecco. We thank Dr. M. Zentilli of Dalhousie University and Dr. L. Heamann of University of Alberta, Canada, where the laboratory works were carried out. We are grateful to Dr. Indares, Dr. Steenken and Dr. Cruciani for the constructive reviews. |