Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America

The magmatic arc of the Fuegian Andes is composed mostly of Upper Mesozoic to Cenozoic calc-alkaline plutons and subordinated lavas. To the rear arc, however, isolated mid-Cretaceous monzonitic plutons and small calc-alkaline dykes and sills crop out. This calc-alkaline unit (the Ushuaia Peninsula A...

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Autores principales: Guillot, M.G., Escayola, M., Acevedo, R.
Formato: JOUR
Materias:
Fuegian Andes
Rear-arc magmatism
Slab flattening
Source enrichment
calc alkaline rock
Cretaceous
crustal deformation
geochemistry
geochronology
magmatism
mineralogy
pluton
subduction
tectonic evolution
Andes
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08959811_v31_n1_p1_Guillot
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_08959811_v31_n1_p1_Guillot2023-10-03T15:42:57Z Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America Guillot, M.G. Escayola, M. Acevedo, R. Fuegian Andes Rear-arc magmatism Slab flattening Source enrichment calc alkaline rock Cretaceous crustal deformation geochemistry geochronology magmatism mineralogy pluton subduction tectonic evolution Andes The magmatic arc of the Fuegian Andes is composed mostly of Upper Mesozoic to Cenozoic calc-alkaline plutons and subordinated lavas. To the rear arc, however, isolated mid-Cretaceous monzonitic plutons and small calc-alkaline dykes and sills crop out. This calc-alkaline unit (the Ushuaia Peninsula Andesites, UPA) includes hornblende-rich, porphyritic quartz meladiorites, granodiorites, andesites, dacites and lamprophyres. Radiometric dating and cross-cutting relationships indicate that UPA is younger than the monzonitic suite. The geochemistry of UPA is medium to high K, with high LILE (Ba 500-2000 ppm, Sr 800-1400 ppm), HFSE (Th 7-23 ppm, Nb 7-13 ppm, Ta 0.5-1.1 ppm) and LREE (La 16-51 ppm) contents, along with relatively low HREE (Yb 1.7-1.3 ppm) and Y (9-19 ppm). The similar mineralogy and geochemistry of all UPA rocks suggest they evolved from a common parental magma, by low pressure crystal fractionation, without significant crustal assimilation. A pure Rayleigh fractionation model indicates that 60-65% of crystal fractionation of 60% hornblende + 34% plagioclase + 4% clinopyroxene + 1% Fe-Ti oxide, apatite and sphene (a paragenesis similar of UPA mafic rocks) can explain evolution from lamprophyres to dacites. The UPA has higher LILE, HFSE and LREE, and lower HREE and Y than the calc-alkaline plutons and lavas of the volcanic front. The HREE and Y are lower than in the potassic plutons as well. High concentrations of Th, Nb, Ta, Zr, Hf, LREE and Ce/Pb, and low U/Th, Ba/Th ratios in UPA, even in the least differentiated samples, suggest contributions from subducted sediments to the mantle source. On the other hand, relatively low HREE and Y, high LREE/HREE (La/Yb 11-38) ratios and Nb-Ta contents can be interpreted as mantle metasomatism by partial melts of either subducted garnetiferous oceanic sediment or basalt as well. Additionally, high LILE content in UPA, similar to the potassic plutons, suggests also a mantle wedge previously metasomatized by potassic parental magmas in their route to crustal levels. Therefore, UPA represents a unique suite in the Fuegian arc generated in a multiple hybridized source. UPA generation is related to a transition from normal to flat subduction which additionally caused the widening and landward migration of the magmatic arc, as well as crustal deformation. Rear-arc magmatism endured ca. 22 m.y.; afterwards, calc-alkaline magmatism remained at the volcanic front. © 2010 Elsevier Ltd. Fil:Escayola, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Acevedo, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08959811_v31_n1_p1_Guillot
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Fuegian Andes
Rear-arc magmatism
Slab flattening
Source enrichment
calc alkaline rock
Cretaceous
crustal deformation
geochemistry
geochronology
magmatism
mineralogy
pluton
subduction
tectonic evolution
Andes
spellingShingle Fuegian Andes
Rear-arc magmatism
Slab flattening
Source enrichment
calc alkaline rock
Cretaceous
crustal deformation
geochemistry
geochronology
magmatism
mineralogy
pluton
subduction
tectonic evolution
Andes
Guillot, M.G.
Escayola, M.
Acevedo, R.
Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
topic_facet Fuegian Andes
Rear-arc magmatism
Slab flattening
Source enrichment
calc alkaline rock
Cretaceous
crustal deformation
geochemistry
geochronology
magmatism
mineralogy
pluton
subduction
tectonic evolution
Andes
description The magmatic arc of the Fuegian Andes is composed mostly of Upper Mesozoic to Cenozoic calc-alkaline plutons and subordinated lavas. To the rear arc, however, isolated mid-Cretaceous monzonitic plutons and small calc-alkaline dykes and sills crop out. This calc-alkaline unit (the Ushuaia Peninsula Andesites, UPA) includes hornblende-rich, porphyritic quartz meladiorites, granodiorites, andesites, dacites and lamprophyres. Radiometric dating and cross-cutting relationships indicate that UPA is younger than the monzonitic suite. The geochemistry of UPA is medium to high K, with high LILE (Ba 500-2000 ppm, Sr 800-1400 ppm), HFSE (Th 7-23 ppm, Nb 7-13 ppm, Ta 0.5-1.1 ppm) and LREE (La 16-51 ppm) contents, along with relatively low HREE (Yb 1.7-1.3 ppm) and Y (9-19 ppm). The similar mineralogy and geochemistry of all UPA rocks suggest they evolved from a common parental magma, by low pressure crystal fractionation, without significant crustal assimilation. A pure Rayleigh fractionation model indicates that 60-65% of crystal fractionation of 60% hornblende + 34% plagioclase + 4% clinopyroxene + 1% Fe-Ti oxide, apatite and sphene (a paragenesis similar of UPA mafic rocks) can explain evolution from lamprophyres to dacites. The UPA has higher LILE, HFSE and LREE, and lower HREE and Y than the calc-alkaline plutons and lavas of the volcanic front. The HREE and Y are lower than in the potassic plutons as well. High concentrations of Th, Nb, Ta, Zr, Hf, LREE and Ce/Pb, and low U/Th, Ba/Th ratios in UPA, even in the least differentiated samples, suggest contributions from subducted sediments to the mantle source. On the other hand, relatively low HREE and Y, high LREE/HREE (La/Yb 11-38) ratios and Nb-Ta contents can be interpreted as mantle metasomatism by partial melts of either subducted garnetiferous oceanic sediment or basalt as well. Additionally, high LILE content in UPA, similar to the potassic plutons, suggests also a mantle wedge previously metasomatized by potassic parental magmas in their route to crustal levels. Therefore, UPA represents a unique suite in the Fuegian arc generated in a multiple hybridized source. UPA generation is related to a transition from normal to flat subduction which additionally caused the widening and landward migration of the magmatic arc, as well as crustal deformation. Rear-arc magmatism endured ca. 22 m.y.; afterwards, calc-alkaline magmatism remained at the volcanic front. © 2010 Elsevier Ltd.
format JOUR
author Guillot, M.G.
Escayola, M.
Acevedo, R.
author_facet Guillot, M.G.
Escayola, M.
Acevedo, R.
author_sort Guillot, M.G.
title Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
title_short Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
title_full Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
title_fullStr Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
title_full_unstemmed Calc-alkaline rear-arc magmatism in the Fuegian Andes: Implications for the mid-cretaceous tectonomagmatic evolution of southernmost South America
title_sort calc-alkaline rear-arc magmatism in the fuegian andes: implications for the mid-cretaceous tectonomagmatic evolution of southernmost south america
url http://hdl.handle.net/20.500.12110/paper_08959811_v31_n1_p1_Guillot
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AT escayolam calcalkalinereararcmagmatisminthefuegianandesimplicationsforthemidcretaceoustectonomagmaticevolutionofsouthernmostsouthamerica
AT acevedor calcalkalinereararcmagmatisminthefuegianandesimplicationsforthemidcretaceoustectonomagmaticevolutionofsouthernmostsouthamerica
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