Advanced search
Start date
Betweenand
(Reference retrieved automatically from SciELO through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Oxygen fugacity of Alto Paranaíba kimberlites and diamond instability: Três Ranchos IV and Limeira I intrusions

Full text
Author(s):
Bruna Coldebella [1] ; Rogério Guitarrari Azzone [2] ; Luanna Chmyz [3] ; Excelso Ruberti [4] ; Darcy P. Svisero [5]
Total Authors: 5
Affiliation:
[1] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação Geociências (Mineralogia e Petrologia) - Brasil
[2] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação Geociências (Mineralogia e Petrologia) - Brasil
[3] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação Geociências (Mineralogia e Petrologia) - Brasil
[4] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação Geociências (Mineralogia e Petrologia) - Brasil
[5] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação Geociências (Mineralogia e Petrologia) - Brasil
Total Affiliations: 5
Document type: Journal article
Source: BRAZILIAN JOURNAL OF GEOLOGY; v. 50, n. 1 2020-03-09.
Abstract

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. (AU)

FAPESP's process: 16/12627-6 - Intensive parameters of crystallization (P-T-fO2) for kimberlites from the alto Paranaíba alkaline province and the diamond instability: the Três Ranchos IV e Limeira I intrusions
Grantee:Bruna Coldebella
Support type: Scholarships in Brazil - Master
FAPESP's process: 17/03768-8 - Xenocryst and Antecryst compositional influence in basic to ultrabasic alkaline magmas
Grantee:Rogério Guitarrari Azzone
Support type: Regular Research Grants
FAPESP's process: 18/15731-4 - Elements mobility during fenitization processes: the carbonatite metasomatism in the Alto Paranaíba and Ponta Grossa Arch alkaline provinces
Grantee:Luanna Chmyz
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 12/06082-6 - The Paraná-Etendeka magmatic province in Brazil: temporal and petrologic relationships between the tholeiitic and alkaline magmatism and geodynamic implications
Grantee:Excelso Ruberti
Support type: Research Projects - Thematic Grants