Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina

The ‘El Nihuil Mafic Unit’ is exposed at the Loma Alta region northwards of the El Nihuil dam. This igneous body consists mainly of mafic rocks assigned to the Precambrian and Lower Paleozoic according to different authors. The mafic unit shows an elongated shape with aNNE–SSWorientation on the west...

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Autores principales: Cingolani, Carlos Alberto, Llambías, Eduardo Jorge, Chemale Jr., Farid, Abre, Paulina, Uriz, Norberto Javier
Formato: Libro Capitulo de libro
Lenguaje:Inglés
Publicado: Springer 2017
Materias:
Geología
Lower Paleozoic
Extensional event
Mafic rocks
El Nihuil
Western Cuyania
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/156976
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-156976
record_format dspace
spelling I19-R120-10915-1569762023-08-28T20:08:00Z http://sedici.unlp.edu.ar/handle/10915/156976 Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina Cingolani, Carlos Alberto Llambías, Eduardo Jorge Chemale Jr., Farid Abre, Paulina Uriz, Norberto Javier 2017 2023-08-28T19:11:22Z Cingolani, Carlos Alberto Springer en Geología Lower Paleozoic Extensional event Mafic rocks El Nihuil Western Cuyania The ‘El Nihuil Mafic Unit’ is exposed at the Loma Alta region northwards of the El Nihuil dam. This igneous body consists mainly of mafic rocks assigned to the Precambrian and Lower Paleozoic according to different authors. The mafic unit shows an elongated shape with aNNE–SSWorientation on the western side of the San Rafael Block (SRB), developed for a length of 17.5 km and with a maximum width of 4.2 km and is composed of deformed gabbros, amphibolites, and tonalites that represent the Mesoproterozoic continental crust, and dykes and sills of undeformed Lower Paleozoic porphyritic dolerites. We present the petrology, geochemistry, isotope data, and determinations of emplacement conditions of the dolerites that could represent a sliver of Cuyania-Chilenia terranes suture. The dolerites show classical porphyritic texture, with elongated subhedral plagioclase (andesine) and clinopyroxene phenocrysts. Geochemical analyses of El Nihuil Dolerite samples indicate that the rocks are MORB-type basalts. In the P2O5 versus Zr diagram, the dolerites plot in the tholeiitic field similarly to western Cuyania basalts, and in the Th–Hf/3–Ta tectonic discrimination diagram the dolerite dykes plot mainly as E-MORB. Dolerite samples were dated byK–Ar (whole rock) systematic and the ages are 448.5 ± 10 and 434.2 ± 10 Ma (Upper Ordovician and close to the Lower Silurian boundary). The dolerites represent the unique Lower Paleozoic mafic rock outcrops within the SRB. Nd(TDM) ages are in between 0.51 and 0.80 Ga; εNd(0) record positive values ranging from +3.85 and +7.84; εNd(t) record +4.27 to +12.42. 87Sr/86Sr ratios are in between 0.7032 and 0.7050 in agreement with values for ocean ridge tholeiites. These mafic rocks are interpreted as a part of a dismembered ‘Famatinian ophiolite belt’ emplaced during the Lower Paleozoic extensional environment within a thinned Mesoproterozoic continental crust on western Cuyania terrane. Centro de Investigaciones Geológicas Libro Capitulo de libro http://creativecommons.org/licenses/by-nc-sa/4.0/ Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) application/pdf 105-125
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Geología
Lower Paleozoic
Extensional event
Mafic rocks
El Nihuil
Western Cuyania
spellingShingle Geología
Lower Paleozoic
Extensional event
Mafic rocks
El Nihuil
Western Cuyania
Cingolani, Carlos Alberto
Llambías, Eduardo Jorge
Chemale Jr., Farid
Abre, Paulina
Uriz, Norberto Javier
Cingolani, Carlos Alberto
Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
topic_facet Geología
Lower Paleozoic
Extensional event
Mafic rocks
El Nihuil
Western Cuyania
description The ‘El Nihuil Mafic Unit’ is exposed at the Loma Alta region northwards of the El Nihuil dam. This igneous body consists mainly of mafic rocks assigned to the Precambrian and Lower Paleozoic according to different authors. The mafic unit shows an elongated shape with aNNE–SSWorientation on the western side of the San Rafael Block (SRB), developed for a length of 17.5 km and with a maximum width of 4.2 km and is composed of deformed gabbros, amphibolites, and tonalites that represent the Mesoproterozoic continental crust, and dykes and sills of undeformed Lower Paleozoic porphyritic dolerites. We present the petrology, geochemistry, isotope data, and determinations of emplacement conditions of the dolerites that could represent a sliver of Cuyania-Chilenia terranes suture. The dolerites show classical porphyritic texture, with elongated subhedral plagioclase (andesine) and clinopyroxene phenocrysts. Geochemical analyses of El Nihuil Dolerite samples indicate that the rocks are MORB-type basalts. In the P2O5 versus Zr diagram, the dolerites plot in the tholeiitic field similarly to western Cuyania basalts, and in the Th–Hf/3–Ta tectonic discrimination diagram the dolerite dykes plot mainly as E-MORB. Dolerite samples were dated byK–Ar (whole rock) systematic and the ages are 448.5 ± 10 and 434.2 ± 10 Ma (Upper Ordovician and close to the Lower Silurian boundary). The dolerites represent the unique Lower Paleozoic mafic rock outcrops within the SRB. Nd(TDM) ages are in between 0.51 and 0.80 Ga; εNd(0) record positive values ranging from +3.85 and +7.84; εNd(t) record +4.27 to +12.42. 87Sr/86Sr ratios are in between 0.7032 and 0.7050 in agreement with values for ocean ridge tholeiites. These mafic rocks are interpreted as a part of a dismembered ‘Famatinian ophiolite belt’ emplaced during the Lower Paleozoic extensional environment within a thinned Mesoproterozoic continental crust on western Cuyania terrane.
format Libro
Capitulo de libro
author Cingolani, Carlos Alberto
Llambías, Eduardo Jorge
Chemale Jr., Farid
Abre, Paulina
Uriz, Norberto Javier
Cingolani, Carlos Alberto
author_facet Cingolani, Carlos Alberto
Llambías, Eduardo Jorge
Chemale Jr., Farid
Abre, Paulina
Uriz, Norberto Javier
Cingolani, Carlos Alberto
author_sort Cingolani, Carlos Alberto
title Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
title_short Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
title_full Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
title_fullStr Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
title_full_unstemmed Lower Paleozoic ‘El Nihuil Dolerites’: Geochemical and Isotopic Constraints of Mafic Magmatism in an Extensional Setting of the San Rafael Block, Mendoza, Argentina
title_sort lower paleozoic ‘el nihuil dolerites’: geochemical and isotopic constraints of mafic magmatism in an extensional setting of the san rafael block, mendoza, argentina
publisher Springer
publishDate 2017
url http://sedici.unlp.edu.ar/handle/10915/156976
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