Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions
Abstract Oxygen fugacity (ƒO2) conditions were established for Três Ranchos IV (TR-IV, diamond-bearing) and Limeira I (LM-I, barren) kimberlite intrusions, in Alto Paranaíba Alkaline Province, to constrain a possible correlation between fO2 and diamond instability. Temperature and pressure estimates...
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| Language: | English |
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Sociedade Brasileira de Geologia
2020-03-01
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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=S2317-48892020000100300&tlng=en |
| _version_ | 1798019655916322816 |
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| author | Bruna Coldebella Rogério Guitarrari Azzone Luanna Chmyz Excelso Ruberti Darcy P. Svisero |
| author_facet | Bruna Coldebella Rogério Guitarrari Azzone Luanna Chmyz Excelso Ruberti Darcy P. Svisero |
| author_sort | Bruna Coldebella |
| collection | DOAJ |
| description | Abstract Oxygen fugacity (ƒO2) conditions were established for Três Ranchos IV (TR-IV, diamond-bearing) and Limeira I (LM-I, barren) kimberlite intrusions, in Alto Paranaíba Alkaline Province, to constrain a possible correlation between fO2 and diamond instability. Temperature and pressure estimates obtained from the xenocryst assemblage composition are compatible up to garnet lherzolite levels. It suggests that both intrusions could cross the diamond-stability field. The ƒO2 of the TR-IV constrained by perovskite oxygen barometry presents an average value of -2.4 for ΔNNO, with standard deviation of 1.30 (n = 120), whereas those calculations for LM-I have an average value of -1.31 for ΔNNO, with standard deviation of 1.38 (n = 81). Considering these uncertainties, there is an important superposition of fO2 values for both intrusions, in which there is higher tendency of more reduced conditions for TR-IV. For the LM-I, an oxybarometer based on the composition of monticellite yielded a similar ΔNNO range: -4.2 and +2.5. Some crystals and samples present trends towards more reduced conditions, while others display more oxidized conditions for each intrusion. Due to the superposition of ranges and absence of a preferential trend, the influence of fO2 for the possible instability of diamonds in the study area remains uncertain. |
| first_indexed | 2024-04-11T16:44:16Z |
| format | Article |
| id | doaj.art-c9b92f7c91d54111a0ca83b953196675 |
| institution | Directory Open Access Journal |
| issn | 2317-4692 |
| language | English |
| last_indexed | 2024-04-11T16:44:16Z |
| publishDate | 2020-03-01 |
| publisher | Sociedade Brasileira de Geologia |
| record_format | Article |
| series | Brazilian Journal of Geology |
| spelling | doaj.art-c9b92f7c91d54111a0ca83b9531966752022-12-22T04:13:36ZengSociedade Brasileira de GeologiaBrazilian Journal of Geology2317-46922020-03-0150110.1590/2317-4889202020190087Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusionsBruna Coldebellahttps://orcid.org/0000-0002-5016-3401Rogério Guitarrari Azzonehttps://orcid.org/0000-0002-6362-7340Luanna Chmyzhttps://orcid.org/0000-0002-4881-0489Excelso Rubertihttps://orcid.org/0000-0003-2375-9004Darcy P. SviseroAbstract Oxygen fugacity (ƒO2) conditions were established for Três Ranchos IV (TR-IV, diamond-bearing) and Limeira I (LM-I, barren) kimberlite intrusions, in Alto Paranaíba Alkaline Province, to constrain a possible correlation between fO2 and diamond instability. Temperature and pressure estimates obtained from the xenocryst assemblage composition are compatible up to garnet lherzolite levels. It suggests that both intrusions could cross the diamond-stability field. The ƒO2 of the TR-IV constrained by perovskite oxygen barometry presents an average value of -2.4 for ΔNNO, with standard deviation of 1.30 (n = 120), whereas those calculations for LM-I have an average value of -1.31 for ΔNNO, with standard deviation of 1.38 (n = 81). Considering these uncertainties, there is an important superposition of fO2 values for both intrusions, in which there is higher tendency of more reduced conditions for TR-IV. For the LM-I, an oxybarometer based on the composition of monticellite yielded a similar ΔNNO range: -4.2 and +2.5. Some crystals and samples present trends towards more reduced conditions, while others display more oxidized conditions for each intrusion. Due to the superposition of ranges and absence of a preferential trend, the influence of fO2 for the possible instability of diamonds in the study area remains uncertain.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892020000100300&tlng=enkimberlitesAlto Paranaíba Provinceintensive parameters of crystallizationoxygen fugacity |
| spellingShingle | Bruna Coldebella Rogério Guitarrari Azzone Luanna Chmyz Excelso Ruberti Darcy P. Svisero Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions Brazilian Journal of Geology kimberlites Alto Paranaíba Province intensive parameters of crystallization oxygen fugacity |
| title | Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions |
| title_full | Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions |
| title_fullStr | Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions |
| title_full_unstemmed | Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions |
| title_short | Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions |
| title_sort | oxygen fugacity of alto paranaiba kimberlites and diamond instability tres ranchos iv and limeira i intrusions |
| topic | kimberlites Alto Paranaíba Province intensive parameters of crystallization oxygen fugacity |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892020000100300&tlng=en |
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