Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes

A Late Jurassic seafloor remnant of the Rocas Verdes basin in southern Chile, the Sarmiento Complex {ca. 52°S), bears lithological layers with bimodal meta-igneous rocks appropriate for a comprehensive investigation of magma genesis in part of a lateral lithological transition from continental rifti...

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Autores principales:	Calderón,Mauricio, Hervé,Francisco, Cordaní,Umberto, Massonne,Hans-Joachim
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2007
Materias:	Rocas Verdes basin Sarmiento Complex Bimodal magmatism Petrogenesis Patagonia Chile
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200005
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spelling	oai:scielo:S0716-020820070002000052007-09-07Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian AndesCalderón,MauricioHervé,FranciscoCordaní,UmbertoMassonne,Hans-Joachim Rocas Verdes basin Sarmiento Complex Bimodal magmatism Petrogenesis Patagonia Chile A Late Jurassic seafloor remnant of the Rocas Verdes basin in southern Chile, the Sarmiento Complex {ca. 52°S), bears lithological layers with bimodal meta-igneous rocks appropriate for a comprehensive investigation of magma genesis in part of a lateral lithological transition from continental rifting to initial seafloor spreading. Metamorphosed mafic rocks collected from different layers in the ophiolite pseudostratigraphy and a plagiogranite have positive sNd150 values (+ 1 and +2). Granophyres, which are crosscut by ophiolitic mafic dikes, have negative sNd150 values (-5). Dacitic dikes within thick successions of pillow basalt have the least negative sNd150 values (-3 and -4). Although mafic and felsic igneous rocks show contrasting isotopic signatures, thermochemical modeling (EC-AFC) suggests they can share a common origin. Models consider an arbitrary composition of the crustal assimilant (mostly metapelite with an average eNd150 value of-7) and evaluate the feasibility for generation of silicic melts through the interaction of mafic magmas and metasedimentary rocks. A quantitative evaluation of basaltic magma contaminated by crustal wall rocks requires a Ma7 Mc (mass of anatectic melt/ mass of cumulates) ratio of 0.04. Analyses using dikes of dacite (with MaVMc ratios ranging between 0.28-0.35) and granophyres (with MaVMc ratios of 0.63-0.89) require the silicic magmas to contain higher proportions of anatectic melts derived from metamorphic rocks. Isotopic differences among granophyres and dacites could be controlled by eruption dynamics, regional stress field and/or differences in thermal regimes in magma chambers. Bimodal magmatism in the earliest tectonic evolution of the Rocas Verdes basin could reflect regimes of slow extension of the continental crust along the Jurassic southwestern margin of Gondwanainfo:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Revista geológica de Chile v.34 n.2 20072007-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200005en10.4067/S0716-02082007000200005
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Rocas Verdes basin Sarmiento Complex Bimodal magmatism Petrogenesis Patagonia Chile
spellingShingle	Rocas Verdes basin Sarmiento Complex Bimodal magmatism Petrogenesis Patagonia Chile Calderón,Mauricio Hervé,Francisco Cordaní,Umberto Massonne,Hans-Joachim Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
description	A Late Jurassic seafloor remnant of the Rocas Verdes basin in southern Chile, the Sarmiento Complex {ca. 52°S), bears lithological layers with bimodal meta-igneous rocks appropriate for a comprehensive investigation of magma genesis in part of a lateral lithological transition from continental rifting to initial seafloor spreading. Metamorphosed mafic rocks collected from different layers in the ophiolite pseudostratigraphy and a plagiogranite have positive sNd150 values (+ 1 and +2). Granophyres, which are crosscut by ophiolitic mafic dikes, have negative sNd150 values (-5). Dacitic dikes within thick successions of pillow basalt have the least negative sNd150 values (-3 and -4). Although mafic and felsic igneous rocks show contrasting isotopic signatures, thermochemical modeling (EC-AFC) suggests they can share a common origin. Models consider an arbitrary composition of the crustal assimilant (mostly metapelite with an average eNd150 value of-7) and evaluate the feasibility for generation of silicic melts through the interaction of mafic magmas and metasedimentary rocks. A quantitative evaluation of basaltic magma contaminated by crustal wall rocks requires a Ma7 Mc (mass of anatectic melt/ mass of cumulates) ratio of 0.04. Analyses using dikes of dacite (with MaVMc ratios ranging between 0.28-0.35) and granophyres (with MaVMc ratios of 0.63-0.89) require the silicic magmas to contain higher proportions of anatectic melts derived from metamorphic rocks. Isotopic differences among granophyres and dacites could be controlled by eruption dynamics, regional stress field and/or differences in thermal regimes in magma chambers. Bimodal magmatism in the earliest tectonic evolution of the Rocas Verdes basin could reflect regimes of slow extension of the continental crust along the Jurassic southwestern margin of Gondwana
author	Calderón,Mauricio Hervé,Francisco Cordaní,Umberto Massonne,Hans-Joachim
author_facet	Calderón,Mauricio Hervé,Francisco Cordaní,Umberto Massonne,Hans-Joachim
author_sort	Calderón,Mauricio
title	Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
title_short	Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
title_full	Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
title_fullStr	Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
title_full_unstemmed	Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes
title_sort	crust-mantle interactions and generation of silicic melts: insights from the sarmiento complex, southern patagonian andes
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2007
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200005
work_keys_str_mv	AT calderonmauricio crustmantleinteractionsandgenerationofsilicicmeltsinsightsfromthesarmientocomplexsouthernpatagonianandes AT hervefrancisco crustmantleinteractionsandgenerationofsilicicmeltsinsightsfromthesarmientocomplexsouthernpatagonianandes AT cordaniumberto crustmantleinteractionsandgenerationofsilicicmeltsinsightsfromthesarmientocomplexsouthernpatagonianandes AT massonnehansjoachim crustmantleinteractionsandgenerationofsilicicmeltsinsightsfromthesarmientocomplexsouthernpatagonianandes
_version_	1718439440599220224

Crust-mantle interactions and generation of silicic melts: insights from the Sarmiento Complex, southern Patagonian Andes

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