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dc.contributor.author
Verma, Sanjeet K.
dc.contributor.author
Oliveira, Elson P.
dc.contributor.author
Silva, Paola M.
dc.contributor.author
Moreno Moreno, Juan Antonio
dc.contributor.author
Amaral, Wagner S.
dc.date.available
2018-05-11T12:20:23Z
dc.date.issued
2017-07
dc.identifier.citation
Verma, Sanjeet K.; Oliveira, Elson P.; Silva, Paola M.; Moreno Moreno, Juan Antonio; Amaral, Wagner S.; Geochemistry of komatiites and basalts from the Rio das Velhas and Pitangui greenstone belts, São Francisco Craton, Brazil: Implications for the origin, evolution, and tectonic setting; Elsevier Science; Lithos; 284; 7-2017; 560-577
dc.identifier.issn
0024-4937
dc.identifier.uri
http://hdl.handle.net/11336/44865
dc.description.abstract
The Neoarchean Rio das Velhas and Pitangui greenstone belts are situated in the southern São Francisco Craton, Minas Gerais, Brazil. These greenstone belts were formed between ca. 2.79?2.73 Ga, and consist mostly of mafic to ultramafic volcanics and clastic sediments, with minor chemical sediments and felsic volcanics that were metamorphosed under greenschist facies. Komatiites are found only in the Rio das Velhas greenstone belt, which is composed of high-MgO volcanic rocks that have been identified as komatiites and high-Mg basalts, based on their distinctive geochemical characteristics. The Rio das Velhas komatiites are composed of tremolite + actinolite+serpentine+albitewith a relict spinifex-texture. The Rio das Velhas komatiites have a highmagnesium content ((MgO)adj ≥ 28 wt.%), an Al-undepleted Munro-type [(Al2O3/TiO2)adj and (CaO/Al2O3)adj] ratioranging from 27 to 47 and 0.48 to 0.89, relatively low abundances of incompatible elements, a depletion of light rare earth elements<br />(LREE), a pattern of non-fractionated heavy rare- earth elements (HREE), and a low (Gd/Yb)PM ratio (≤1.0). Negative Ce anomalies suggest that alteration occurred during greenschist facies metamorphism for the komatiites and high-Mg basalts. The low [(Gd/Yb)PM b 1.0] and [(CaO/Al2O3)adj b 0.9)], high [(Al2O3/TiO2)adj N 18]<br />and high HREE, Y, and Zr content suggest that the Rio das Velhas komatiites were derived from the shallow upper mantle without garnet involvement in the residue. The chemical compositions [(Al2O3/TiO2)adj, (FeO)adj, (MgO)adj, (CaO/Al2O3)adj, Na, Th, Ta, Ni, Cr, Zr, Y, Hf, and REE] indicate that the formation of the komatiites, high- Mg basalts and basalts occurred at different depths and temperatures in a heterogeneous mantle. The komatiites<br />and high-Mg basalts melted at liquidus temperatures of ~1450?1550 °C. The Pitangui basalts are enriched in the highly incompatible LILE (large-ion lithophile elements) relative to the moderately incompatible HFS (high field strength) elements. The Zr/Th ratio ranging from 76 to 213 and the relationship between the Nb/Th and Th/Yb ratios indicate that there is no crustal contamination in the Pitangui greenstone basalts. New multi-dimensional discrimination<br />diagrams and conventional normalized multi-element diagrams indicate an island arc (IA) setting for the komatiites and high-Mg basalts from the Rio das Velhas and a mid ocean-ridge (MOR) to IA setting for the basalts from the Pitangui greenstone belts.
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
Elsevier Science
dc.rights
info:eu-repo/semantics/restrictedAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
Komatiites
dc.subject
High-Mg Basalts
dc.subject
Geochemistry
dc.subject
Greenstone Belt
dc.subject.classification
Meteorología y Ciencias Atmosféricas
dc.subject.classification
Ciencias de la Tierra y relacionadas con el Medio Ambiente
dc.subject.classification
CIENCIAS NATURALES Y EXACTAS
dc.title
Geochemistry of komatiites and basalts from the Rio das Velhas and Pitangui greenstone belts, São Francisco Craton, Brazil: Implications for the origin, evolution, and tectonic setting
dc.type
info:eu-repo/semantics/article
dc.type
info:ar-repo/semantics/artículo
dc.type
info:eu-repo/semantics/publishedVersion
dc.date.updated
2018-05-09T16:15:13Z
dc.journal.volume
284
dc.journal.pagination
560-577
dc.journal.pais
Países Bajos
dc.journal.ciudad
Amsterdam
dc.description.fil
Fil: Verma, Sanjeet K.. Instituto Potosino de Investigación Científica y Tecnológica; México
dc.description.fil
Fil: Oliveira, Elson P.. Universidade Estadual Do Campinas. Instituto de Geociencias; Brasil
dc.description.fil
Fil: Silva, Paola M.. Universidade Estadual Do Campinas. Instituto de Geociencias; Brasil
dc.description.fil
Fil: Moreno Moreno, Juan Antonio. Universidade Estadual Do Campinas. Instituto de Geociencias; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina
dc.description.fil
Fil: Amaral, Wagner S.. Universidade Estadual Do Campinas. Instituto de Geociencias; Brasil
dc.journal.title
Lithos
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/doi/http://dx.doi.org/10.1016/j.lithos.2017.04.024
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/https://www.sciencedirect.com/science/article/pii/S0024493717301755
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