Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics

We present a chronological (K-Ar), petrologic and geochemical study (major and trace elements, Sr-Nd isotopes) of Middle Miocene (ca. 16-14 Ma) calc-alkaline rocks (basalts to andesites) extruded in the present-day back-arc region of Central Patagonia (Zeballos Volcanic Sequence (ZVS), 47°S). This m...

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Autores principales:	Espinoza,Felipe, Morata,Diego, Polvé,Mireille, Lagabrielle,Yves, Maury,René C, de la Rupelle,Aude, Guivel,Christèle, Cotten,Joseph, Bellon,Hervé, Suárez,Manuel
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2010
Materias:	Central Patagonia back-arc Calc-alkaline magmatism Low-angle subduction Miocene
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000200003
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spelling	oai:scielo:S0718-710620100002000032010-10-06Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamicsEspinoza,FelipeMorata,DiegoPolvé,MireilleLagabrielle,YvesMaury,René Cde la Rupelle,AudeGuivel,ChristèleCotten,JosephBellon,HervéSuárez,Manuel Central Patagonia back-arc Calc-alkaline magmatism Low-angle subduction Miocene We present a chronological (K-Ar), petrologic and geochemical study (major and trace elements, Sr-Nd isotopes) of Middle Miocene (ca. 16-14 Ma) calc-alkaline rocks (basalts to andesites) extruded in the present-day back-arc region of Central Patagonia (Zeballos Volcanic Sequence (ZVS), 47°S). This magmatism started shortly after mafic plutonism ceased in the are region (ca. 16 Ma, 200 km west), and ended ca. 2 My before the onset of volumi-nous slab tear-related back-arc alkaline basaltic magmatism (ca. 12 to Pliocene). The studied calc-alkaline rocks have a typical subduction-related signature (high LILE/HFSE ratios, depletion in Nb, Ta and Ti; Ba/La >20; Ta/Hf <1.5; (87Sr/86Sr)o=0.70366-0.70402, εNd=+0,1±3,8). Major and trace elements contents are consistent with their evolution by closed system fractional crystallization of a presumed parental liquid similar in composition to the most basic rock of the suite. Moreover, a strong subducted sediment imprint is recognized (increasing Th/HFSE and decreasing Ce/Pb during differentiation). However, these rocks show striking similarities with volcanic complexes emplaced above areas where a gently dipping slab oceurs (high K contents; similar LREE/HREE, Nb/Zr, Ba/Nb; Th/Hf; Th/Ta, Ta/Hf<0.3), particularly the present-day Andean flat-slab region and the Neuquén Basin during the Late Miocene. A comprehensive tectono-magmatic model is here presented to explain the generation and extrusion of these calc-alkaline magmas during the Middle Miocene. The development of a transient low-angle subduction and the resulting eastward migration of the volcanic front are then proposed. Mixing between stored remnants of calc-alkaline magmatism and later primitive alkaline melts is envisioned as the most likely process accounting for the transitional signature (Le., intermediate between calc-alkaline and alkaline, La/Nb >1; TiO2 <2 wt%) of some basalts extruded synchronously with genuine alkaline lavas in the Neogene Patagonian Plateau Lavas province.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.37 n.2 20102010-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000200003en
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Central Patagonia back-arc Calc-alkaline magmatism Low-angle subduction Miocene
spellingShingle	Central Patagonia back-arc Calc-alkaline magmatism Low-angle subduction Miocene Espinoza,Felipe Morata,Diego Polvé,Mireille Lagabrielle,Yves Maury,René C de la Rupelle,Aude Guivel,Christèle Cotten,Joseph Bellon,Hervé Suárez,Manuel Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
description	We present a chronological (K-Ar), petrologic and geochemical study (major and trace elements, Sr-Nd isotopes) of Middle Miocene (ca. 16-14 Ma) calc-alkaline rocks (basalts to andesites) extruded in the present-day back-arc region of Central Patagonia (Zeballos Volcanic Sequence (ZVS), 47°S). This magmatism started shortly after mafic plutonism ceased in the are region (ca. 16 Ma, 200 km west), and ended ca. 2 My before the onset of volumi-nous slab tear-related back-arc alkaline basaltic magmatism (ca. 12 to Pliocene). The studied calc-alkaline rocks have a typical subduction-related signature (high LILE/HFSE ratios, depletion in Nb, Ta and Ti; Ba/La >20; Ta/Hf <1.5; (87Sr/86Sr)o=0.70366-0.70402, εNd=+0,1±3,8). Major and trace elements contents are consistent with their evolution by closed system fractional crystallization of a presumed parental liquid similar in composition to the most basic rock of the suite. Moreover, a strong subducted sediment imprint is recognized (increasing Th/HFSE and decreasing Ce/Pb during differentiation). However, these rocks show striking similarities with volcanic complexes emplaced above areas where a gently dipping slab oceurs (high K contents; similar LREE/HREE, Nb/Zr, Ba/Nb; Th/Hf; Th/Ta, Ta/Hf<0.3), particularly the present-day Andean flat-slab region and the Neuquén Basin during the Late Miocene. A comprehensive tectono-magmatic model is here presented to explain the generation and extrusion of these calc-alkaline magmas during the Middle Miocene. The development of a transient low-angle subduction and the resulting eastward migration of the volcanic front are then proposed. Mixing between stored remnants of calc-alkaline magmatism and later primitive alkaline melts is envisioned as the most likely process accounting for the transitional signature (Le., intermediate between calc-alkaline and alkaline, La/Nb >1; TiO2 <2 wt%) of some basalts extruded synchronously with genuine alkaline lavas in the Neogene Patagonian Plateau Lavas province.
author	Espinoza,Felipe Morata,Diego Polvé,Mireille Lagabrielle,Yves Maury,René C de la Rupelle,Aude Guivel,Christèle Cotten,Joseph Bellon,Hervé Suárez,Manuel
author_facet	Espinoza,Felipe Morata,Diego Polvé,Mireille Lagabrielle,Yves Maury,René C de la Rupelle,Aude Guivel,Christèle Cotten,Joseph Bellon,Hervé Suárez,Manuel
author_sort	Espinoza,Felipe
title	Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
title_short	Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
title_full	Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
title_fullStr	Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
title_full_unstemmed	Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics
title_sort	middle miocene calc-alkaline volcanism in central patagonia (47°s): petrogenesis and implications for slab dynamics
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2010
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000200003
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Middle Miocene calc-alkaline volcanism in Central Patagonia (47°S): petrogenesis and implications for slab dynamics

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