(U-Th)/He Ages from the Fluorite Mineralization of the Tanguá Alkaline Intrusion

Autores

  • Daniel Adelino da Silva Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Programa de Pós-Graduação de Análise de Bacias e Faixas Móveis, Rua São Francisco Xavier 524 - Bairro Maracanã - 20559-900. Rio de Janeiro, RJ - Brasil.
  • Mauro César Geraldes Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Departamento de Mineralogia e Petrologia, Rua São Francisco Xavier 524 - Bairro Maracanã - 20559-900. Rio de Janeiro, RJ - Brasil.
  • Sérgio Wilians de Oliveira Rodrigues Universidade Federal de Goiás, Faculdade de Ciências e Tecnologia, Rua Mucuri, s/n - Setor Conde dos Arcos - 74968755 - Aparecida de Goiânia, Goiás - Brasil.
  • Michael McMaster Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Programa de Pós-Graduação de Análise de Bacias e Faixas Móveis, Rua São Francisco Xavier 524 - Bairro Maracanã - 20559-900. Rio de Janeiro, RJ - Brasil.
  • Noreen Evans CSIRO Exploration and Mining, ARRC, 26 Dick Perry Ave. Kensington Western Australia. John De Laeter Centre of Mass Spectrometry, Curtin University for Technology, Western Australia.
  • Alexis Rosas Nummer Universidade Federal Rural do Rio de Janeiro, Instituto de Agronomia, Departamento de Geociências. Antiga Estrada Rio São Paulo Km 47, 23851-970 - Seropédica, RJ - Brasil.
  • Thais Vargas Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Departamento de Mineralogia e Petrologia, Rua São Francisco Xavier 524 - Bairro Maracanã - 20559-900. Rio de Janeiro, RJ - Brasil.

DOI:

https://doi.org/10.11137/2018_2_14_21

Palavras-chave:

Tanguá Alkaline Intrusion, Fluorite mineralization, (U-Th)/He Ages, Mesozoic to Cenozoic magmatism

Resumo

The Tanguá Alkaline Suite formed as a result of Mesozoic to Cenozoic magmatic events that affected the part of the South American Platform in Brazil’s southeast. The alkaline intrusion is composed of alkali-feldspar syenite with nepheline (pulaskites and umptekites), syenite (with or without the presence of pseudo-leucite), varied nepheline syenites (foyaites, micro-foyaites etc.) and alkaline magmatic breccias. The intrusion contains important fluorite mineralization, in the form of NE-SW oriented veins, which were economically extracted in recent decades at the Emitang Mine. This paper focuses on the analysis of these centimetric crystals of fluorite which vary in color from (yellow, to white and purple.) associated with mineralization of Tanguá Body. Geochronological dating by (U-Th)/He of fluorite mineralization showed a wide range of ages, with the oldest age of 74 ± 3 Ma (Late Cretaceous) and the youngest of 0.11 ± 0.02 Ma (Late Pleistocene). Most ages are concentrated between 25 and 8 Ma (Miocene). The oldest age (74.0 ± 3 Ma) is associated with hydrothermal fluids percolating at the time of intrusion of the Tanguá Body. The other ages represent episodes of percolation of hydrothermal fluids and consequent growth of fluorite crystals. Of note is a set of Miocene ages that can be associated with regional tectonic events. This phase of flurite growth may be associated with the reactivation of basement faults and structures in the Tanguá region and the circulation of hydrothermal fluids associated with intrusion of younger dikes. The youngest ages may be associated with neotectonic reactivation of faults during neotectonic events.

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2019-09-09

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