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<title lang=en>Bimodal back-arc alkaline magmatism after ridge subduction: Pliocene felsic rocks from Central Patagonia (47 degrees S)</title>
<creator>Espinoza, F.</creator>
<creator>Morata, D.</creator>
<creator>Polve, M.</creator>
<creator>Lagabrielle, Yves</creator>
<creator>Maury, René, </creator>
<creator>Guivel, C.</creator>
<creator>Cotten, Joseph</creator>
<creator>Bellon, H.</creator>
<creator>Suarez, M.</creator>
<contributor>Departemento de Geologia [Santiago] ; Universidad de Santiago de Chile [Santiago] (USACH)</contributor>
<contributor>Laboratoire des Mécanismes et Transfert en Géologie (LMTG) ; Université Paul Sabatier - Toulouse 3 (UPS) - Observatoire Midi-Pyrénées (OMP) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Domaines Océaniques (LDO) ; Institut national des sciences de l'Univers (INSU - CNRS) - Université de Brest (UBO) - Observatoire des Sciences de l'Univers - Institut d'écologie et environnement - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Laboratoire de Planétologie et Géodynamique de Nantes (LPGN) ; Université de Nantes (UN) - Institut national des sciences de l'Univers (INSU - CNRS) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Servicio Nacional de Geología y Minería, Santiago ; Université du Québec</contributor>
<description>International audience</description>
<source>ISSN: 0024-4937</source>
<source>Lithos</source>
<publisher>Elsevier</publisher>
<identifier>hal-00412030</identifier>
<identifier>https://hal.archives-ouvertes.fr/hal-00412030</identifier>
<source>https://hal.archives-ouvertes.fr/hal-00412030</source>
<source>Lithos, Elsevier, 2008, 101 (3-4), pp.191-217. 〈10.1016/j.lithos.2007.07.002〉</source>
<identifier>DOI : 10.1016/j.lithos.2007.07.002</identifier>
<relation>info:eu-repo/semantics/altIdentifier/doi/10.1016/j.lithos.2007.07.002</relation>
<language>en</language>
<subject lang=it>mafc-felsic alkaline magmatism</subject>
<subject lang=it>syenites</subject>
<subject lang=it>central Patagonia back-arc</subject>
<subject lang=it>pliocene</subject>
<subject lang=it>chemical modeling</subject>
<subject>[SDU.STU.PE] Sciences of the Universe [physics]/Earth Sciences/Petrography</subject>
<type>info:eu-repo/semantics/article</type>
<type>Journal articles</type>
<description lang=en>Volumetrically minor microsyenites, alkali microgranite and related trachytic dykes intrude early Pliocene OIB-like alkali basaltic and basanitic flows of the Meseta del Lago Buenos Aires in Central Patagonia (47 degrees S-71 degrees 30'W), and occur together with scarce trachytic lava flows. Whole-rock K-Ar ages between 3.98 and 3.08 Ma indicate that the emplacement of these felsic rocks occurred more or less synchronously with that of the post-plateau basaltic sequence that they intrude, during a bimodal mafic-felsic magmatic episode devoid of intermediate compositions. Chemically, these rocks have A(1)-type granitoid affinities and are characterized by high silica and alkali contents (60-68 wt.% SiO2; 8.7-10.8 wt.% Na2O+K2O), major and trace elements patterns evidencing evolution by low-pressure fractional crystallization, and Sr and Nd isotopic signatures similar to those of coeval basalts ((Sr-87/Sr-86)o=0.70488-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512645). Nevertheless, some of them have the most radiogenic Sr values ever reported for a magmatic rock in the Meseta and even in the whole Neogene Patagonian Plateau Lavas province ((Sr-17/Sr-86)(o)= 0.70556-0.70571; (Nd-143/Nd-144)(o)=0.512603-0.512608). In addition, very high contents of strongly incompatible elements in the most evolved rocks, together with Sr isotopic ratios higher than those of coeval basalts, suggest the occurrence of open-system magmatic processes. Continuous fractional crystallization from a primitive basaltic source, similar to post-plateau coeval basalts, towards alkali granites combined with small rates of assimilation of host Jurassic tuffs (AFC) in a shallow magmatic reservoir, best explains the geochemical and petrographic features of the felsic rocks. Therefore, A(1)-type magmatic rocks can be generated by open-system crystallization of deep asthenospheric melts in back-are tectonic settings. In Central Patagonia, these similar to 3-4 Ma old alkaline intrusions occur aligned along a similar to N160-170 trending lineament, the Zeballos Fault Zone, stacking the morphotectonic front of one segment of the Patagonian Cordillera. Intrusion along this fault zone</description>
<date>2008</date>
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