Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks

Autores
Grosse, Pablo; Toselli, Alejandro Jose; Rossi, Juana Norma
Año de publicación
2010
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
The Velasco orbicular granitoid is a small (65 × 15 m), irregularly-shaped body that cropsout within the Huaco granite, central Sierra de Velasco, NW Argentina. It consists of ellipsoid-shapedorbicules of 3 to 15 cm length immersed in an aplitic to pegmatitic matrix. The orbicules are formedby a core made up of a K-feldspar megacryst, partially to totally replaced by plagioclase, an inner shellof radial and equant plagioclase crystals, a layer of tangentially oriented biotite laths, and an outer shellof plumose plagioclase crystals, containing diffuse rings of tangentially oriented biotite. The orbiculargranitoid formed in situ in a pocket of evolved and volatile-rich melt segregated from the surroundingpartially crystallized Huaco granite, possibly via a filter pressing mechanism. The segregated meltentrained relatively few K-feldspar megacrysts into the pocket, leaving behind a concentration ofmegacrysts around the pocket. High water concentration caused effective superheating of the meltand destruction of nuclei, with only the large megacrysts surviving as solids. Sudden water-pressureloss and exsolution of the volatile phase, perhaps related to a volcanic eruption or fracturing of thesurrounding granite, caused rapid undercooling of the melt. The orbicules grewin the undercooled meltby heterogeneous nucleation on the megacrysts, which acted as nucleation seeds, and crystallizationof reversely zoned radial plagioclase and sporadic crystallization of tangential biotite rings accordingto fluctuations in its saturation. Orbicular growth gave way to crystallization of the equiaxial interorbicularmatrix in two stages, when sufficient polymerization of the melt was attained. The time scaleof formation of the orbicular granitoid was fast, possibly a matter of a few weeks or months.
Fil: Grosse, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina
Fil: Toselli, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina
Fil: Rossi, Juana Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina
Materia
Orbicular Granitoids
Plumose Plagioclase
Reverse Zoning
Huaco Granite
Nivel de accesibilidad
acceso abierto
Condiciones de uso
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repositorio
CONICET Digital (CONICET)
Institución
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identificador
oai:ri.conicet.gov.ar:11336/90748
Acceder
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oai_identifier_str oai:ri.conicet.gov.ar:11336/90748
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network_name_str CONICET Digital (CONICET)
spelling Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocksGrosse, PabloToselli, Alejandro JoseRossi, Juana NormaOrbicular GranitoidsPlumose PlagioclaseReverse ZoningHuaco Granitehttps://purl.org/becyt/ford/1.5https://purl.org/becyt/ford/1The Velasco orbicular granitoid is a small (65 × 15 m), irregularly-shaped body that cropsout within the Huaco granite, central Sierra de Velasco, NW Argentina. It consists of ellipsoid-shapedorbicules of 3 to 15 cm length immersed in an aplitic to pegmatitic matrix. The orbicules are formedby a core made up of a K-feldspar megacryst, partially to totally replaced by plagioclase, an inner shellof radial and equant plagioclase crystals, a layer of tangentially oriented biotite laths, and an outer shellof plumose plagioclase crystals, containing diffuse rings of tangentially oriented biotite. The orbiculargranitoid formed in situ in a pocket of evolved and volatile-rich melt segregated from the surroundingpartially crystallized Huaco granite, possibly via a filter pressing mechanism. The segregated meltentrained relatively few K-feldspar megacrysts into the pocket, leaving behind a concentration ofmegacrysts around the pocket. High water concentration caused effective superheating of the meltand destruction of nuclei, with only the large megacrysts surviving as solids. Sudden water-pressureloss and exsolution of the volatile phase, perhaps related to a volcanic eruption or fracturing of thesurrounding granite, caused rapid undercooling of the melt. The orbicules grewin the undercooled meltby heterogeneous nucleation on the megacrysts, which acted as nucleation seeds, and crystallizationof reversely zoned radial plagioclase and sporadic crystallization of tangential biotite rings accordingto fluctuations in its saturation. Orbicular growth gave way to crystallization of the equiaxial interorbicularmatrix in two stages, when sufficient polymerization of the melt was attained. The time scaleof formation of the orbicular granitoid was fast, possibly a matter of a few weeks or months.Fil: Grosse, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Toselli, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaFil: Rossi, Juana Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaCambridge University Press2010-02info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfapplication/pdfapplication/pdfhttp://hdl.handle.net/11336/90748Grosse, Pablo; Toselli, Alejandro Jose; Rossi, Juana Norma; Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks; Cambridge University Press; Geological Magazine; 147; 3; 2-2010; 451-4680016-7568CONICET DigitalCONICETenginfo:eu-repo/semantics/altIdentifier/doi/10.1017/S0016756809990707info:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-sa/2.5/ar/reponame:CONICET Digital (CONICET)instname:Consejo Nacional de Investigaciones Científicas y Técnicas2025-09-03T09:56:38Zoai:ri.conicet.gov.ar:11336/90748instacron:CONICETInstitucionalhttp://ri.conicet.gov.ar/Organismo científico-tecnológicoNo correspondehttp://ri.conicet.gov.ar/oai/requestdasensio@conicet.gov.ar; lcarlino@conicet.gov.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:34982025-09-03 09:56:38.63CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicasfalse
dc.title.none.fl_str_mv Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
title Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
spellingShingle Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
Grosse, Pablo
Orbicular Granitoids
Plumose Plagioclase
Reverse Zoning
Huaco Granite
title_short Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
title_full Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
title_fullStr Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
title_full_unstemmed Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
title_sort Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks
dc.creator.none.fl_str_mv Grosse, Pablo
Toselli, Alejandro Jose
Rossi, Juana Norma
author Grosse, Pablo
author_facet Grosse, Pablo
Toselli, Alejandro Jose
Rossi, Juana Norma
author_role author
author2 Toselli, Alejandro Jose
Rossi, Juana Norma
author2_role author
author
dc.subject.none.fl_str_mv Orbicular Granitoids
Plumose Plagioclase
Reverse Zoning
Huaco Granite
topic Orbicular Granitoids
Plumose Plagioclase
Reverse Zoning
Huaco Granite
purl_subject.fl_str_mv https://purl.org/becyt/ford/1.5
https://purl.org/becyt/ford/1
dc.description.none.fl_txt_mv The Velasco orbicular granitoid is a small (65 × 15 m), irregularly-shaped body that cropsout within the Huaco granite, central Sierra de Velasco, NW Argentina. It consists of ellipsoid-shapedorbicules of 3 to 15 cm length immersed in an aplitic to pegmatitic matrix. The orbicules are formedby a core made up of a K-feldspar megacryst, partially to totally replaced by plagioclase, an inner shellof radial and equant plagioclase crystals, a layer of tangentially oriented biotite laths, and an outer shellof plumose plagioclase crystals, containing diffuse rings of tangentially oriented biotite. The orbiculargranitoid formed in situ in a pocket of evolved and volatile-rich melt segregated from the surroundingpartially crystallized Huaco granite, possibly via a filter pressing mechanism. The segregated meltentrained relatively few K-feldspar megacrysts into the pocket, leaving behind a concentration ofmegacrysts around the pocket. High water concentration caused effective superheating of the meltand destruction of nuclei, with only the large megacrysts surviving as solids. Sudden water-pressureloss and exsolution of the volatile phase, perhaps related to a volcanic eruption or fracturing of thesurrounding granite, caused rapid undercooling of the melt. The orbicules grewin the undercooled meltby heterogeneous nucleation on the megacrysts, which acted as nucleation seeds, and crystallizationof reversely zoned radial plagioclase and sporadic crystallization of tangential biotite rings accordingto fluctuations in its saturation. Orbicular growth gave way to crystallization of the equiaxial interorbicularmatrix in two stages, when sufficient polymerization of the melt was attained. The time scaleof formation of the orbicular granitoid was fast, possibly a matter of a few weeks or months.
Fil: Grosse, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina
Fil: Toselli, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina
Fil: Rossi, Juana Norma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentina
description The Velasco orbicular granitoid is a small (65 × 15 m), irregularly-shaped body that cropsout within the Huaco granite, central Sierra de Velasco, NW Argentina. It consists of ellipsoid-shapedorbicules of 3 to 15 cm length immersed in an aplitic to pegmatitic matrix. The orbicules are formedby a core made up of a K-feldspar megacryst, partially to totally replaced by plagioclase, an inner shellof radial and equant plagioclase crystals, a layer of tangentially oriented biotite laths, and an outer shellof plumose plagioclase crystals, containing diffuse rings of tangentially oriented biotite. The orbiculargranitoid formed in situ in a pocket of evolved and volatile-rich melt segregated from the surroundingpartially crystallized Huaco granite, possibly via a filter pressing mechanism. The segregated meltentrained relatively few K-feldspar megacrysts into the pocket, leaving behind a concentration ofmegacrysts around the pocket. High water concentration caused effective superheating of the meltand destruction of nuclei, with only the large megacrysts surviving as solids. Sudden water-pressureloss and exsolution of the volatile phase, perhaps related to a volcanic eruption or fracturing of thesurrounding granite, caused rapid undercooling of the melt. The orbicules grewin the undercooled meltby heterogeneous nucleation on the megacrysts, which acted as nucleation seeds, and crystallizationof reversely zoned radial plagioclase and sporadic crystallization of tangential biotite rings accordingto fluctuations in its saturation. Orbicular growth gave way to crystallization of the equiaxial interorbicularmatrix in two stages, when sufficient polymerization of the melt was attained. The time scaleof formation of the orbicular granitoid was fast, possibly a matter of a few weeks or months.
publishDate 2010
dc.date.none.fl_str_mv 2010-02
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/11336/90748
Grosse, Pablo; Toselli, Alejandro Jose; Rossi, Juana Norma; Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks; Cambridge University Press; Geological Magazine; 147; 3; 2-2010; 451-468
0016-7568
CONICET Digital
CONICET
url http://hdl.handle.net/11336/90748
identifier_str_mv Grosse, Pablo; Toselli, Alejandro Jose; Rossi, Juana Norma; Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks; Cambridge University Press; Geological Magazine; 147; 3; 2-2010; 451-468
0016-7568
CONICET Digital
CONICET
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/doi/10.1017/S0016756809990707
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
eu_rights_str_mv openAccess
rights_invalid_str_mv https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.format.none.fl_str_mv application/pdf
application/pdf
application/pdf
dc.publisher.none.fl_str_mv Cambridge University Press
publisher.none.fl_str_mv Cambridge University Press
dc.source.none.fl_str_mv reponame:CONICET Digital (CONICET)
instname:Consejo Nacional de Investigaciones Científicas y Técnicas
reponame_str CONICET Digital (CONICET)
collection CONICET Digital (CONICET)
instname_str Consejo Nacional de Investigaciones Científicas y Técnicas
repository.name.fl_str_mv CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicas
repository.mail.fl_str_mv dasensio@conicet.gov.ar; lcarlino@conicet.gov.ar
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score 13.13397

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