Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil
In the westernmost portion of the state of Paraná, in the city of Foz do Iguaçu, basic pegmatites occur within inflated pahoehoe basaltic flows of the Paraná Igneous Province. Both rock groups are composed of similar mineral assemblages which include labradorite, augite, ilmenite and titano-magneti...
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Universidade de São Paulo
2023-12-01
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| Series: | Geologia USP. Série Científica |
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| Online Access: | https://www.revistas.usp.br/guspsc/article/view/220578 |
| _version_ | 1797384272730914816 |
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| author | Bruno Titon Eleonora Maria Gouvêa Vasconcellos Otávio Augusto Boni Licht Andrea Marzoli |
| author_facet | Bruno Titon Eleonora Maria Gouvêa Vasconcellos Otávio Augusto Boni Licht Andrea Marzoli |
| author_sort | Bruno Titon |
| collection | DOAJ |
| description |
In the westernmost portion of the state of Paraná, in the city of Foz do Iguaçu, basic pegmatites occur within inflated pahoehoe basaltic flows of the Paraná Igneous Province. Both rock groups are composed of similar mineral assemblages which include labradorite, augite, ilmenite and titano-magnetite, but pegmatites are medium to coarse grained, whereas basalts are fine grained. Host rocks are geochemically classified as basalts (s.s.), while pegmatitic segregations are basaltic andesite and basaltic trachy-andesite, according to the TAS [(Na2O + K2O) x SiO2] diagram. Based on the AFM [(Na2O + K2O) – (FeOtot) – (MgO)] diagram, all rocks are included in the tholeiitic series, classified as high-Fe tholeiite basalts in the cation plot [Al x (Fetot + Ti) x Mg]. Variation diagrams indicate enrichment of SiO2, TiO2, FeO, Na2O, K2O e P2O5 coupled with depletion of Al2O3, MgO e CaO from basalts to pegmatites. La/LuN ratios range between 5.4 to 6.5 for basalts and 6.3 to 7.9 for pegmatites reflecting a greater degree of fractionation in the pegmatitic segregations and, therefore, their more evolved character. Plagioclase crystals in pegmatites have higher sodic contents when compared to those found in host basalts, while CaO content in basaltic pyroxenes is higher than those from pegmatitic segregations. Trace element geochemical modeling results show that it is possible to generate basic pegmatites from basalts comprised of 55 wt.% plagioclase, 35 wt.% clinopyroxene and 10 wt.% titanium and iron oxides. The process occurs as fractional crystallization with 50% residual melt.
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| id | doaj.art-49f97db69eb94562bdb16c23e58ae742 |
| institution | Directory Open Access Journal |
| issn | 2316-9095 |
| language | English |
| last_indexed | 2024-03-08T21:34:01Z |
| publishDate | 2023-12-01 |
| publisher | Universidade de São Paulo |
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| series | Geologia USP. Série Científica |
| spelling | doaj.art-49f97db69eb94562bdb16c23e58ae7422023-12-21T04:12:34ZengUniversidade de São PauloGeologia USP. Série Científica2316-90952023-12-01234Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, BrazilBruno Titon0Eleonora Maria Gouvêa Vasconcellos1Otávio Augusto Boni Licht2Andrea Marzoli3Universidade Federal do Paraná, Departamento de GeologiaUniversidade Federal do Paraná, Departamento de GeologiaUniversidade Federal do Paraná, Departamento de GeologiaUniversità degli Studi di Padova, Dipartimento TESAF In the westernmost portion of the state of Paraná, in the city of Foz do Iguaçu, basic pegmatites occur within inflated pahoehoe basaltic flows of the Paraná Igneous Province. Both rock groups are composed of similar mineral assemblages which include labradorite, augite, ilmenite and titano-magnetite, but pegmatites are medium to coarse grained, whereas basalts are fine grained. Host rocks are geochemically classified as basalts (s.s.), while pegmatitic segregations are basaltic andesite and basaltic trachy-andesite, according to the TAS [(Na2O + K2O) x SiO2] diagram. Based on the AFM [(Na2O + K2O) – (FeOtot) – (MgO)] diagram, all rocks are included in the tholeiitic series, classified as high-Fe tholeiite basalts in the cation plot [Al x (Fetot + Ti) x Mg]. Variation diagrams indicate enrichment of SiO2, TiO2, FeO, Na2O, K2O e P2O5 coupled with depletion of Al2O3, MgO e CaO from basalts to pegmatites. La/LuN ratios range between 5.4 to 6.5 for basalts and 6.3 to 7.9 for pegmatites reflecting a greater degree of fractionation in the pegmatitic segregations and, therefore, their more evolved character. Plagioclase crystals in pegmatites have higher sodic contents when compared to those found in host basalts, while CaO content in basaltic pyroxenes is higher than those from pegmatitic segregations. Trace element geochemical modeling results show that it is possible to generate basic pegmatites from basalts comprised of 55 wt.% plagioclase, 35 wt.% clinopyroxene and 10 wt.% titanium and iron oxides. The process occurs as fractional crystallization with 50% residual melt. https://www.revistas.usp.br/guspsc/article/view/220578Paraná Igneous ProvinceBasaltic flowsLithogeochemistryFractional crystallizationTrace elements |
| spellingShingle | Bruno Titon Eleonora Maria Gouvêa Vasconcellos Otávio Augusto Boni Licht Andrea Marzoli Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil Geologia USP. Série Científica Paraná Igneous Province Basaltic flows Lithogeochemistry Fractional crystallization Trace elements |
| title | Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil |
| title_full | Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil |
| title_fullStr | Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil |
| title_full_unstemmed | Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil |
| title_short | Geochemical modeling of basic pegmatites from Foz do Iguaçu in the Itaipu region, western Paraná, Brazil |
| title_sort | geochemical modeling of basic pegmatites from foz do iguacu in the itaipu region western parana brazil |
| topic | Paraná Igneous Province Basaltic flows Lithogeochemistry Fractional crystallization Trace elements |
| url | https://www.revistas.usp.br/guspsc/article/view/220578 |
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