Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil
Abstract The Paraná emerald deposit is one of the few occurrences of emerald, a rare beryl variety, in Borborema Province, northeastern Brazil. We characterized the Paraná deposit by combining field geology, petrography, whole-rock geochemistry, mineral chemistry, and reflectance spectroscopy. The m...
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Academia Brasileira de Ciências
2021-03-01
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| Series: | Anais da Academia Brasileira de Ciências |
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| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000101218&tlng=en |
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| author | JOSÉ F. ARAÚJO NETO SANDRA B. BARRETO THAIS A. CARRINO IGOR M.B.A. SOUZA GLENDA L. SANTOS |
| author_facet | JOSÉ F. ARAÚJO NETO SANDRA B. BARRETO THAIS A. CARRINO IGOR M.B.A. SOUZA GLENDA L. SANTOS |
| author_sort | JOSÉ F. ARAÚJO NETO |
| collection | DOAJ |
| description | Abstract The Paraná emerald deposit is one of the few occurrences of emerald, a rare beryl variety, in Borborema Province, northeastern Brazil. We characterized the Paraná deposit by combining field geology, petrography, whole-rock geochemistry, mineral chemistry, and reflectance spectroscopy. The mineralization is associated with phlogopite-, actinolite-phlogopite-, and phlogopite-phengite schists, mylonitic gneisses, and several acidic rocks (e.g. granitic pegmatites/aplites, quartz ± feldspar veins) along the Portalegre Shear Zone. Emerald can be found in quartz-feldspar and aplite veins and veinlets interleaved with phlogopite- or actinolite-phlogopite schists, or within the foliation of the schists. The presence of albitites and the compositional variation of the schists suggest a metasomatic origin for emerald with variations of the metasomatic process. All these different lithotypes can be readily identified through reflectance spectroscopy especially in the range of 2,150-2,450 nm, where the main mafic minerals show absorption features related to Al-OH (phengite), and Fe-OH and Mg-OH bonds (phlogopite/actinolite). Our study shows that possible mineralized phlogopite schists can be distinguished from other sterile rocks, although point spectral analysis does not separate emerald-bearing phlogopite schists from schists without emerald due to the dominance of major phlogopite absorption features rather than emerald features. |
| first_indexed | 2024-04-11T16:44:58Z |
| format | Article |
| id | doaj.art-57872f2223a04cf0921f6bca0d3b9d3f |
| institution | Directory Open Access Journal |
| issn | 1678-2690 |
| language | English |
| last_indexed | 2024-04-11T16:44:58Z |
| publishDate | 2021-03-01 |
| publisher | Academia Brasileira de Ciências |
| record_format | Article |
| series | Anais da Academia Brasileira de Ciências |
| spelling | doaj.art-57872f2223a04cf0921f6bca0d3b9d3f2022-12-22T04:13:36ZengAcademia Brasileira de CiênciasAnais da Academia Brasileira de Ciências1678-26902021-03-0193110.1590/0001-3765202120200236Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, BrazilJOSÉ F. ARAÚJO NETOhttps://orcid.org/0000-0002-1780-9469SANDRA B. BARRETOhttps://orcid.org/0000-0001-8464-7087THAIS A. CARRINOhttps://orcid.org/0000-0001-8528-5225IGOR M.B.A. SOUZAhttps://orcid.org/0000-0002-2235-5668GLENDA L. SANTOShttps://orcid.org/0000-0002-6271-950XAbstract The Paraná emerald deposit is one of the few occurrences of emerald, a rare beryl variety, in Borborema Province, northeastern Brazil. We characterized the Paraná deposit by combining field geology, petrography, whole-rock geochemistry, mineral chemistry, and reflectance spectroscopy. The mineralization is associated with phlogopite-, actinolite-phlogopite-, and phlogopite-phengite schists, mylonitic gneisses, and several acidic rocks (e.g. granitic pegmatites/aplites, quartz ± feldspar veins) along the Portalegre Shear Zone. Emerald can be found in quartz-feldspar and aplite veins and veinlets interleaved with phlogopite- or actinolite-phlogopite schists, or within the foliation of the schists. The presence of albitites and the compositional variation of the schists suggest a metasomatic origin for emerald with variations of the metasomatic process. All these different lithotypes can be readily identified through reflectance spectroscopy especially in the range of 2,150-2,450 nm, where the main mafic minerals show absorption features related to Al-OH (phengite), and Fe-OH and Mg-OH bonds (phlogopite/actinolite). Our study shows that possible mineralized phlogopite schists can be distinguished from other sterile rocks, although point spectral analysis does not separate emerald-bearing phlogopite schists from schists without emerald due to the dominance of major phlogopite absorption features rather than emerald features.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000101218&tlng=enGeochemistrymineral chemistryParaná emerald depositpetrographyreflectance spectroscopy |
| spellingShingle | JOSÉ F. ARAÚJO NETO SANDRA B. BARRETO THAIS A. CARRINO IGOR M.B.A. SOUZA GLENDA L. SANTOS Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil Anais da Academia Brasileira de Ciências Geochemistry mineral chemistry Paraná emerald deposit petrography reflectance spectroscopy |
| title | Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil |
| title_full | Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil |
| title_fullStr | Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil |
| title_full_unstemmed | Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil |
| title_short | Geochemical and reflectance spectroscopy data integration to characterize emerald deposits: the case of the Paraná deposit, Brazil |
| title_sort | geochemical and reflectance spectroscopy data integration to characterize emerald deposits the case of the parana deposit brazil |
| topic | Geochemistry mineral chemistry Paraná emerald deposit petrography reflectance spectroscopy |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652021000101218&tlng=en |
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