Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará
Abstract The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, v...
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| Format: | Article |
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Sociedade Brasileira de Geologia
2023-08-01
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| Series: | Brazilian Journal of Geology |
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| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892023000200307&lng=en&tlng=en |
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| author | Hélio Junior Lima Monteiro Artur Corval Débora Grala Roldão Benevides Aires Filho Luighi Santos Rinaldi Letícia Martins Gustavo Diniz Oliveira |
| author_facet | Hélio Junior Lima Monteiro Artur Corval Débora Grala Roldão Benevides Aires Filho Luighi Santos Rinaldi Letícia Martins Gustavo Diniz Oliveira |
| author_sort | Hélio Junior Lima Monteiro |
| collection | DOAJ |
| description | Abstract The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, volcanoclastic rocks, and gabbro dikes/sills, thus being inserted in the Serra Sul district in the Mineral Province of Carajás, Pará. This study aimed to understand the igneous processes involved in the genesis of these basalts from both geological formations, supported by field, petrographic, and geochemical data. Inserted in the metavolcanosedimentary sequence of the Grão Pará Group (Carajás Domain), the basalts and basalt andesites, the most abundant types of the Parauapebas and Igarapé Cigarra Formations, occur as successions of massive and amygdaloidal lava flows. The study of core samples from nine stratigraphic holes that intersected basaltic rocks of the two geological formations in body S11D (Serra Sul) showed that these rocks reach thick layers with different characteristics, ranging from aphanitic to phaneritic. The basalts are dark green, aphanitic, phaneritic, thin to medium, and hypocrystalline. They show preserved igneous texture being commonly seriated as inequigranular, intersertal, ophitic, subophytic, intergranular, branching, and swallow tail. Its essential primary constituents are plagioclase, orthopyroxene, and clinopyroxene, and its accessory constituents are titanite and apatite. Chlorite, epidote, quartz, and calcite occur as secondary phases and are interpreted as the products of ocean-bottom hydrothermal alteration and/or incipient metamorphism. In general, the studied volcanic rocks stand out for SiO2 content between 47.00 and 56.04%, high alkali contents (4.70–7.50%), K2O contents between 0.40 and 3.97%, TiO2 (< 1.0%), and MgO between 4.90 and 8.16%. In the classification diagrams, the samples are situated in the fields of basalts, basalt andesites, trachyandesite, and trachybasalt basalts, in the transition of the toleitic and calc-alkaline series. The basalts of the Parauapebas and Igarapé Cigarra Formations were probably formed in an intraplate continental environment influenced by subduction zones. Therefore, the Grão-Pará Basin was probably formed in a convergent regime related to a subduction-type environment. The geochemical data indicate that the studied rocks of the Parauapebas Formation and the Igarapé Cigarra Formation correspond to basalts of calc-alkaline affinity. Two facies were identified in the Parauapebas Formation, namely, the Amendoim and Violão facies. In the Igarapé Cigarra Formation as well, the following facies were identified: Jacaré and Três Marias. Based on the geochemical interpretation, it is assumed that the rocks studied are arc-like continental basalts, which are formed in a subduction environment with influence from a possible asthenospheric source and modified by crustal contamination. |
| first_indexed | 2024-03-12T12:31:31Z |
| format | Article |
| id | doaj.art-3690e88f13d44728b303be79ce955fc0 |
| institution | Directory Open Access Journal |
| issn | 2317-4692 |
| language | English |
| last_indexed | 2024-03-12T12:31:31Z |
| publishDate | 2023-08-01 |
| publisher | Sociedade Brasileira de Geologia |
| record_format | Article |
| series | Brazilian Journal of Geology |
| spelling | doaj.art-3690e88f13d44728b303be79ce955fc02023-08-29T07:45:26ZengSociedade Brasileira de GeologiaBrazilian Journal of Geology2317-46922023-08-0153210.1590/2317-4889202320220053Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, ParáHélio Junior Lima Monteirohttps://orcid.org/0000-0003-2277-4464Artur Corvalhttps://orcid.org/0000-0002-5154-2737Débora Grala Roldãohttps://orcid.org/0009-0001-6317-7239Benevides Aires Filhohttps://orcid.org/0009-0002-4635-996XLuighi Santos Rinaldihttps://orcid.org/0009-0006-2770-8078Letícia Martinshttps://orcid.org/0009-0006-6428-9749Gustavo Diniz Oliveirahttps://orcid.org/0000-0002-2630-1165Abstract The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, volcanoclastic rocks, and gabbro dikes/sills, thus being inserted in the Serra Sul district in the Mineral Province of Carajás, Pará. This study aimed to understand the igneous processes involved in the genesis of these basalts from both geological formations, supported by field, petrographic, and geochemical data. Inserted in the metavolcanosedimentary sequence of the Grão Pará Group (Carajás Domain), the basalts and basalt andesites, the most abundant types of the Parauapebas and Igarapé Cigarra Formations, occur as successions of massive and amygdaloidal lava flows. The study of core samples from nine stratigraphic holes that intersected basaltic rocks of the two geological formations in body S11D (Serra Sul) showed that these rocks reach thick layers with different characteristics, ranging from aphanitic to phaneritic. The basalts are dark green, aphanitic, phaneritic, thin to medium, and hypocrystalline. They show preserved igneous texture being commonly seriated as inequigranular, intersertal, ophitic, subophytic, intergranular, branching, and swallow tail. Its essential primary constituents are plagioclase, orthopyroxene, and clinopyroxene, and its accessory constituents are titanite and apatite. Chlorite, epidote, quartz, and calcite occur as secondary phases and are interpreted as the products of ocean-bottom hydrothermal alteration and/or incipient metamorphism. In general, the studied volcanic rocks stand out for SiO2 content between 47.00 and 56.04%, high alkali contents (4.70–7.50%), K2O contents between 0.40 and 3.97%, TiO2 (< 1.0%), and MgO between 4.90 and 8.16%. In the classification diagrams, the samples are situated in the fields of basalts, basalt andesites, trachyandesite, and trachybasalt basalts, in the transition of the toleitic and calc-alkaline series. The basalts of the Parauapebas and Igarapé Cigarra Formations were probably formed in an intraplate continental environment influenced by subduction zones. Therefore, the Grão-Pará Basin was probably formed in a convergent regime related to a subduction-type environment. The geochemical data indicate that the studied rocks of the Parauapebas Formation and the Igarapé Cigarra Formation correspond to basalts of calc-alkaline affinity. Two facies were identified in the Parauapebas Formation, namely, the Amendoim and Violão facies. In the Igarapé Cigarra Formation as well, the following facies were identified: Jacaré and Três Marias. Based on the geochemical interpretation, it is assumed that the rocks studied are arc-like continental basalts, which are formed in a subduction environment with influence from a possible asthenospheric source and modified by crustal contamination.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892023000200307&lng=en&tlng=enSerra SulCarajásBrazilhigh-pressure meltingpetrologygeochemistry |
| spellingShingle | Hélio Junior Lima Monteiro Artur Corval Débora Grala Roldão Benevides Aires Filho Luighi Santos Rinaldi Letícia Martins Gustavo Diniz Oliveira Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará Brazilian Journal of Geology Serra Sul Carajás Brazil high-pressure melting petrology geochemistry |
| title | Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará |
| title_full | Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará |
| title_fullStr | Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará |
| title_full_unstemmed | Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará |
| title_short | Petrology of volcanic rocks of the Serra Sul mine, Carajás Province, Pará |
| title_sort | petrology of volcanic rocks of the serra sul mine carajas province para |
| topic | Serra Sul Carajás Brazil high-pressure melting petrology geochemistry |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892023000200307&lng=en&tlng=en |
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