Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin

The metamorphic P-T conditions of low-grade units from the Famatina belt, Central Andes of Argentina, were estimated through petrography, X-ray diffraction, and electron microscopy. For the Middle-Upper Cambrian Negro Peinado Formation a tectono-metamorphic event associated with intense intrafoliar...

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Autores principales: Collo, G., do Campo, M., Nieto, F.
Formato: JOUR
Materias:
Famatina belt
Low-grade metamorphism
Ocloyic orogeny
Western gondwana margin
Cambrian
electron microscopy
Gondwana
low grade metamorphism
Ordovician
orogeny
P-T conditions
parameterization
petrography
phyllosilicate
pressure effect
tectonic evolution
tectonic setting
X-ray diffraction
Argentina
La Rioja [Argentina]
Sierra de Famatina
Sierras Pampeanas
Micas
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_07187092_v38_n2_p284_Collo
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_07187092_v38_n2_p284_Collo
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spelling todo:paper_07187092_v38_n2_p284_Collo2023-10-03T15:36:37Z Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin Collo, G. do Campo, M. Nieto, F. Famatina belt Low-grade metamorphism Ocloyic orogeny Western gondwana margin Cambrian electron microscopy Gondwana low grade metamorphism Ordovician orogeny P-T conditions parameterization petrography phyllosilicate pressure effect tectonic evolution tectonic setting X-ray diffraction Argentina La Rioja [Argentina] Sierra de Famatina Sierras Pampeanas Micas The metamorphic P-T conditions of low-grade units from the Famatina belt, Central Andes of Argentina, were estimated through petrography, X-ray diffraction, and electron microscopy. For the Middle-Upper Cambrian Negro Peinado Formation a tectono-metamorphic event associated with intense intrafoliar folding, with estimated temperatures between 290 and 400°C (KICIS: 0.16-0.27Δ°2θ, biotite blastesis and compositional homogeneity in dioctahedral micas) and intermediate pressure conditions (white mica b parameter: 9.010Å-9.035Å), was recognized. The Achavil Formation (Middle-Upper Cambrian) presents a main metamorphic event associated with temperatures between 200 and 290°C (KICIS: 0.26-0.41Δ°2θ) and intermediate- to low-pressure conditions (white mica b parameter values: 8.972Å-9.017Å). Some illitic infstitution in dioctahedral micas also indicates lower metamorphic grade than the Negro Peinado Formation. For Upper Cambrian to Middle Ordovician sequences a burial metamorphic pattern, with a progressive decrease in metamorphic grade from Volcancito Formation to Cerro Morado Group (ca. 490-465 Ma; KICIS: 0.31-0.69Δ°2θ) and absence of tendency changes linked to stratigraphic discontinuities was proposed. Mica and chlorite are the main phyllosilicates in the oldest units, while Ilt/Sme (R3) mixed-layer is almost the only one in the youngest. White mica b parameter indicates intermediate- to low-pressure conditions for all these sequences. This burial metamorphic pattern presents a marked break as the youngest Ordovician unit (La Aguadita Formation, after ca. 452 Ma) records higher metamorphic conditions (IKCIS: 0.28-0.19Δ°2θ) than units from the Ordovician arc, with estimated temperatures between 270 and 330°C and intermediate-pressure conditions. Our results indicate that basin contraction and inversion processes related to the Ordovician Ocloyic Orogeny involved at least two well-discriminated and not superposed metamorphic episodes in this region. Fil:do Campo, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_07187092_v38_n2_p284_Collo
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Famatina belt
Low-grade metamorphism
Ocloyic orogeny
Western gondwana margin
Cambrian
electron microscopy
Gondwana
low grade metamorphism
Ordovician
orogeny
P-T conditions
parameterization
petrography
phyllosilicate
pressure effect
tectonic evolution
tectonic setting
X-ray diffraction
Argentina
La Rioja [Argentina]
Sierra de Famatina
Sierras Pampeanas
Micas
spellingShingle Famatina belt
Low-grade metamorphism
Ocloyic orogeny
Western gondwana margin
Cambrian
electron microscopy
Gondwana
low grade metamorphism
Ordovician
orogeny
P-T conditions
parameterization
petrography
phyllosilicate
pressure effect
tectonic evolution
tectonic setting
X-ray diffraction
Argentina
La Rioja [Argentina]
Sierra de Famatina
Sierras Pampeanas
Micas
Collo, G.
do Campo, M.
Nieto, F.
Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
topic_facet Famatina belt
Low-grade metamorphism
Ocloyic orogeny
Western gondwana margin
Cambrian
electron microscopy
Gondwana
low grade metamorphism
Ordovician
orogeny
P-T conditions
parameterization
petrography
phyllosilicate
pressure effect
tectonic evolution
tectonic setting
X-ray diffraction
Argentina
La Rioja [Argentina]
Sierra de Famatina
Sierras Pampeanas
Micas
description The metamorphic P-T conditions of low-grade units from the Famatina belt, Central Andes of Argentina, were estimated through petrography, X-ray diffraction, and electron microscopy. For the Middle-Upper Cambrian Negro Peinado Formation a tectono-metamorphic event associated with intense intrafoliar folding, with estimated temperatures between 290 and 400°C (KICIS: 0.16-0.27Δ°2θ, biotite blastesis and compositional homogeneity in dioctahedral micas) and intermediate pressure conditions (white mica b parameter: 9.010Å-9.035Å), was recognized. The Achavil Formation (Middle-Upper Cambrian) presents a main metamorphic event associated with temperatures between 200 and 290°C (KICIS: 0.26-0.41Δ°2θ) and intermediate- to low-pressure conditions (white mica b parameter values: 8.972Å-9.017Å). Some illitic infstitution in dioctahedral micas also indicates lower metamorphic grade than the Negro Peinado Formation. For Upper Cambrian to Middle Ordovician sequences a burial metamorphic pattern, with a progressive decrease in metamorphic grade from Volcancito Formation to Cerro Morado Group (ca. 490-465 Ma; KICIS: 0.31-0.69Δ°2θ) and absence of tendency changes linked to stratigraphic discontinuities was proposed. Mica and chlorite are the main phyllosilicates in the oldest units, while Ilt/Sme (R3) mixed-layer is almost the only one in the youngest. White mica b parameter indicates intermediate- to low-pressure conditions for all these sequences. This burial metamorphic pattern presents a marked break as the youngest Ordovician unit (La Aguadita Formation, after ca. 452 Ma) records higher metamorphic conditions (IKCIS: 0.28-0.19Δ°2θ) than units from the Ordovician arc, with estimated temperatures between 270 and 330°C and intermediate-pressure conditions. Our results indicate that basin contraction and inversion processes related to the Ordovician Ocloyic Orogeny involved at least two well-discriminated and not superposed metamorphic episodes in this region.
format JOUR
author Collo, G.
do Campo, M.
Nieto, F.
author_facet Collo, G.
do Campo, M.
Nieto, F.
author_sort Collo, G.
title Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
title_short Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
title_full Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
title_fullStr Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
title_full_unstemmed Low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: Burial-inversion history linked to the evolution of the proto-andean gondwana margin
title_sort low-grade metamorphism of cambro-ordovician successions in the famatina belt, southern-central andes: burial-inversion history linked to the evolution of the proto-andean gondwana margin
url http://hdl.handle.net/20.500.12110/paper_07187092_v38_n2_p284_Collo
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