Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source

A petrological and geochemical study of Lower Ordovician epidote-bearing granitoids of the Sierra de Chepes (Famatinian Orogen, Sierras Pampeanas, Argentina) indicates low-pressure emplacement of these extensive metaluminous suites. Textural relationships combined with major oxide and REE data suppo...

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Autor principal:	Dahlquist,Juan A
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2001
Materias:	Magmatic Epidote Metaluminous granitoids Lower Ordovician Low emplacement pressure Geothermobarometry Famatinian Orogen
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082001000200001
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spelling	oai:scielo:S0716-020820010002000012002-04-09Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma sourceDahlquist,Juan A Magmatic Epidote Metaluminous granitoids Lower Ordovician Low emplacement pressure Geothermobarometry Famatinian Orogen A petrological and geochemical study of Lower Ordovician epidote-bearing granitoids of the Sierra de Chepes (Famatinian Orogen, Sierras Pampeanas, Argentina) indicates low-pressure emplacement of these extensive metaluminous suites. Textural relationships combined with major oxide and REE data support a magmatic origin for the ubiquitous epidote in hornblende-biotite granodiorite and tonalite plutons. Geothermobarometry using mineral assemblages in igneous rocks indicates a temperature interval from 780 to 850°C, and low emplacement pressures in the range of 2.2 to 4.1 kbar, consistent with those estimated from the metasedimentary envelope of the plutons. The widespread occurrence of primary epidote is a distinctive characteristic of the Lower Ordovician granitoids as opposed to the Andean Carboniferous granitoids emplaced at middle pressures (e.g., Santo Domingo Complex, 7 kbar), where magmatic epidote-granitoids are scarce and secondary epidote is commonly present. On the other hand, the pistacite value (Ps=[Fe3+/(Fe3++Al)] x 100, in %) in magmatic epidote of the Ordovician granitoids (average Ps=28) sharply contrasts with that of magmatic epidote in the Carboniferous Andean granitoids (average Ps=24). This strongly suggests that the occurrence of magmatic epidote-bearing granitoids might be related to different sources, the Famatinian Orogen granitoids being mainly derived by melting of old continental lithosphere with probable partial contribution from subcontinental lithospheric mantle, and the Carboniferous Andean granitoids mainly resulting from mixing of crustal- and mantle- derived magmas. If the relationship of epidote-bearing granitoids to the characteristics of the source is confirmed in future studies, this will constrain the geotectonic environment in which the epidote-bearing magmas occurinfo:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Revista geológica de Chile v.28 n.2 20012001-12-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082001000200001en10.4067/S0716-02082001000200001
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Magmatic Epidote Metaluminous granitoids Lower Ordovician Low emplacement pressure Geothermobarometry Famatinian Orogen
spellingShingle	Magmatic Epidote Metaluminous granitoids Lower Ordovician Low emplacement pressure Geothermobarometry Famatinian Orogen Dahlquist,Juan A Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
description	A petrological and geochemical study of Lower Ordovician epidote-bearing granitoids of the Sierra de Chepes (Famatinian Orogen, Sierras Pampeanas, Argentina) indicates low-pressure emplacement of these extensive metaluminous suites. Textural relationships combined with major oxide and REE data support a magmatic origin for the ubiquitous epidote in hornblende-biotite granodiorite and tonalite plutons. Geothermobarometry using mineral assemblages in igneous rocks indicates a temperature interval from 780 to 850°C, and low emplacement pressures in the range of 2.2 to 4.1 kbar, consistent with those estimated from the metasedimentary envelope of the plutons. The widespread occurrence of primary epidote is a distinctive characteristic of the Lower Ordovician granitoids as opposed to the Andean Carboniferous granitoids emplaced at middle pressures (e.g., Santo Domingo Complex, 7 kbar), where magmatic epidote-granitoids are scarce and secondary epidote is commonly present. On the other hand, the pistacite value (Ps=[Fe3+/(Fe3++Al)] x 100, in %) in magmatic epidote of the Ordovician granitoids (average Ps=28) sharply contrasts with that of magmatic epidote in the Carboniferous Andean granitoids (average Ps=24). This strongly suggests that the occurrence of magmatic epidote-bearing granitoids might be related to different sources, the Famatinian Orogen granitoids being mainly derived by melting of old continental lithosphere with probable partial contribution from subcontinental lithospheric mantle, and the Carboniferous Andean granitoids mainly resulting from mixing of crustal- and mantle- derived magmas. If the relationship of epidote-bearing granitoids to the characteristics of the source is confirmed in future studies, this will constrain the geotectonic environment in which the epidote-bearing magmas occur
author	Dahlquist,Juan A
author_facet	Dahlquist,Juan A
author_sort	Dahlquist,Juan A
title	Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
title_short	Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
title_full	Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
title_fullStr	Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
title_full_unstemmed	Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source
title_sort	low-pressure emplacement of epidote-bearing metaluminous granitoids in the sierra de chepes (famatinian orogen, argentina) and relationships with the magma source
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2001
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082001000200001
work_keys_str_mv	AT dahlquistjuana lowpressureemplacementofepidotebearingmetaluminousgranitoidsinthesierradechepesfamatinianorogenargentinaandrelationshipswiththemagmasource
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Low-pressure emplacement of epidote-bearing metaluminous granitoids in the Sierra de Chepes (Famatinian Orogen, Argentina) and relationships with the magma source

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