Mafic-ultramafic intrusions form a 32-km-long NE-SW-trending array within Paleoproterozoic arc-related calc-alkaline plutonic rocks of the Rio Piranhas terrane in the Borborema Province, Northeast Brazil. The mafic-ultramafic intrusions consist of wehrlite, clinopyroxenite, and troctolite. They outcrop as small elongated bodies hosted by orthogneiss and migmatites associated with minor amphibolite and supracrustal rocks. Primary magmatic features predominate in the core of the intrusions, whereas metamorphic minerals and textures characterize their outer zones. The composition of cumulus olivine from different intrusions ranges from Fo80.6 to Fo67.6 (forsterite), indicating moderately primitive parental magmas. The compositional range of cumulus plagioclase coexisting with cumulus olivine in troctolites is characterized by high anorthite content (An79.9–An89.0). This feature, together with interstitial magmatic amphibole in troctolites, is characteristic of gabbroic intrusions in subduction-related magmatic arcs. U-Pb zircon ages indicate that mafic-ultramafic intrusions crystallized at ca. 2190 ± 5 Ma. U-Pb zircon ages of host orthogneiss indicate that they crystallized from calc-alkaline felsic magmas at ca. 2220–2223 Ma, thus providing only ∼30 My for the reported events of felsic and mafic plutonism. U-Pb zircon ages of host rocks include older ages (2.47 and 2.69 Ga) indicating that older crustal components are associated with the 2.23 Ga calc-alkaline magmatism. The presence of older crustal components is consistent with arc-related features, indicated by geochemical data and variable εNd(t) values in the mafic-ultramafic intrusions. The tholeiitic and calc-alkaline magmatism is correlated with the ca. 2.15–2.25 Ga magmatic arc reported in previous studies of the Rio Piranhas terrane. The mafic-ultramafic magmatism is interpreted as having originated in a magmatic arc, possibly resulting from partial melting of a mantle wedge above the subduction zone in late stages of the orogeny and suggests a new window of opportunity for exploration of Ni-Cu–platinum group element deposits.
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September 01, 2019
Paleoproterozoic Mafic-Ultramafic Magmatism in the Northern Borborema Province, Northeast Brazil: Tectonic Setting and Potential for Deposits
Alanielson da C. D. Ferreira;
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
*
Author for correspondence; email: [email protected].
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Cesar F. Ferreira Filho;
Cesar F. Ferreira Filho
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
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Elton Luiz Dantas;
Elton Luiz Dantas
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
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Valmir da Silva Souza
Valmir da Silva Souza
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
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Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
Cesar F. Ferreira Filho
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
Elton Luiz Dantas
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
Valmir da Silva Souza
Instituto de Geociências, Universidade de Brasília, 70910-900 Brasília, Distrito Federal, Brazil
*
Author for correspondence; email: [email protected].
Publisher: The University of Chicago Press
Received:
19 Oct 2018
Accepted:
26 Mar 2019
First Online:
03 Nov 2023
Online ISSN: 1537-5269
Print ISSN: 0022-1376
© 2019 by The University of Chicago. All rights reserved.
The University of Chicago
The Journal of Geology (2019) 127 (5): 483–504.
Article history
Received:
19 Oct 2018
Accepted:
26 Mar 2019
First Online:
03 Nov 2023
Citation
Alanielson da C. D. Ferreira, Cesar F. Ferreira Filho, Elton Luiz Dantas, Valmir da Silva Souza; Paleoproterozoic Mafic-Ultramafic Magmatism in the Northern Borborema Province, Northeast Brazil: Tectonic Setting and Potential for Deposits. The Journal of Geology 2019;; 127 (5): 483–504. doi: https://doi.org/10.1086/704256
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Index Terms/Descriptors
- absolute age
- alkalic composition
- amphibolites
- Borborema Province
- Brasiliano Orogeny
- Brazil
- calc-alkalic composition
- cathodoluminescence
- copper ores
- crystal chemistry
- crystallization
- dates
- felsic composition
- gabbros
- geochemistry
- geodynamics
- gneisses
- host rocks
- ICP mass spectra
- igneous rocks
- intrusions
- isotope ratios
- isotopes
- lithogeochemistry
- mafic composition
- magmas
- magmatism
- mantle
- mantle wedges
- mapping
- mass spectra
- metal ores
- metals
- metamorphic rocks
- migmatites
- mineral composition
- mineral exploration
- models
- Nd-144/Nd-143
- neodymium
- nesosilicates
- nickel ores
- orogeny
- orthogneiss
- orthosilicates
- Paleoproterozoic
- Pan-African Orogeny
- partial melting
- petrography
- plate tectonics
- platinum group
- platinum ores
- plutonic rocks
- plutons
- Precambrian
- Proterozoic
- rare earths
- Rhyacian
- Rio Grande do Norte Brazil
- silicates
- Sm/Nd
- South America
- spectra
- stable isotopes
- subduction
- supracrustals
- textures
- tholeiitic composition
- trace elements
- troctolite
- U/Pb
- ultramafic composition
- upper Precambrian
- zircon
- zircon group
- zoning
- northeastern Brazil
- Rio Piranhas Terrane
Latitude & Longitude
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