A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina

Two orthogneisses have been recognized in the sierras of Espinal and Maz (Western Sierras Pampeanas, NW Argentina) that were emplaced within a Grenvillian metasedimentary sequence. Microcline, plagioclase and quartz are the main rock-forming minerals, with accessory zircon, apatite-(CaF), magnetite,...

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Autores principales: Colombo, Fernando, Baldo, Edgardo Gaspar Agustín, Casquet, César, Pankhurst, Robert J., Galindo, Carmen, Rapela, Carlos Washington, Dahlquist, Juan Andrés, Fanning, C. Mark
Formato: Articulo Preprint
Lenguaje:Inglés
Publicado: 2009
Materias:
Ciencias Naturales
Anorogenic magmatism
Argentina
Mesoproterozoic
Rodinia
U-pb shrimp dating
Western sierras pampeanas
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/101698
https://ri.conicet.gov.ar/11336/55871
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-101698
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Naturales
Anorogenic magmatism
Argentina
Mesoproterozoic
Rodinia
U-pb shrimp dating
Western sierras pampeanas
spellingShingle Ciencias Naturales
Anorogenic magmatism
Argentina
Mesoproterozoic
Rodinia
U-pb shrimp dating
Western sierras pampeanas
Colombo, Fernando
Baldo, Edgardo Gaspar Agustín
Casquet, César
Pankhurst, Robert J.
Galindo, Carmen
Rapela, Carlos Washington
Dahlquist, Juan Andrés
Fanning, C. Mark
A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
topic_facet Ciencias Naturales
Anorogenic magmatism
Argentina
Mesoproterozoic
Rodinia
U-pb shrimp dating
Western sierras pampeanas
description Two orthogneisses have been recognized in the sierras of Espinal and Maz (Western Sierras Pampeanas, NW Argentina) that were emplaced within a Grenvillian metasedimentary sequence. Microcline, plagioclase and quartz are the main rock-forming minerals, with accessory zircon, apatite-(CaF), magnetite, biotite (Fe/(Fe + Mg) = 0.88-0.91), ferropargasite (Fetotal/(Fetotal + Mg) = 0.88-0.89), titanite (with up to 1.61 wt% Y2O3) and an REE-rich epidote. REE-poor epidote and zoned garnet (Ca and Fe3+-rich) are metamorphic minerals, while muscovite, carbonates and chlorite are secondary phases. Texture is mylonitic. Two representative samples are classified as granite (from Sierra de Espinal) and granodiorite/tonalite (from Sierra de Maz) on the grounds of immobile trace elements. Some trace element contents are rather high (Zr: 603 and 891 ppm, Y: 44 and 76 ppm, 10,000 × Ga/Al: 2.39-3.89) and indicate an affiliation with A-type granites (more specifically, the A2 group). Both samples plot in the field of within-plate granites according to their Y and Nb contents. Concordant crystallization ages (zircon U-Pb SHRIMP) are 842 ± 5 and 846 ± 6 Ma, respectively. 87Sr/86Sri (845) ratios are 0.70681 and 0.70666; εNdi (845) values are -1.5 and +0.3 and depleted-mantle Nd model ages (2TDM*) are 1.59 and 1.45 Ga, respectively. These values indicate the involvement of an isotopically evolved source. 2TDM* values are compatible with the presence of inherited zircon crystals of up to 1480 Ma in one of the rocks, thus implying that magmas incorporated material from Mesoproterozoic continental source. This is also indicated by the relatively high contents of Y, Ga, Nb and Ce compared to magmas derived from sources similar to those of oceanic-island basalts. These orthogneisses represent a period of extension at ca. 845 Ma affecting the Western Sierras Pampeanas continental crust that was already consolidated after the Grenvillian orogeny (1.2-1.0 Ga). They are thus a record of the early stages of Rodinia break-up. Metamorphic conditions during the subsequent Famatinian orogenic cycle (ca. 420 Ma, SHRIMP U-Pb on zircon) attained 7.7 ± 1.2 kbar and 664 ± 70 °C.
format Articulo
Preprint
author Colombo, Fernando
Baldo, Edgardo Gaspar Agustín
Casquet, César
Pankhurst, Robert J.
Galindo, Carmen
Rapela, Carlos Washington
Dahlquist, Juan Andrés
Fanning, C. Mark
author_facet Colombo, Fernando
Baldo, Edgardo Gaspar Agustín
Casquet, César
Pankhurst, Robert J.
Galindo, Carmen
Rapela, Carlos Washington
Dahlquist, Juan Andrés
Fanning, C. Mark
author_sort Colombo, Fernando
title A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
title_short A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
title_full A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
title_fullStr A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
title_full_unstemmed A-type magmatism in the sierras of Maz and Espinal: A new record of Rodinia break-up in the Western Sierras Pampeanas of Argentina
title_sort a-type magmatism in the sierras of maz and espinal: a new record of rodinia break-up in the western sierras pampeanas of argentina
publishDate 2009
url http://sedici.unlp.edu.ar/handle/10915/101698
https://ri.conicet.gov.ar/11336/55871
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