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Research paper thumbnail of Mineralização de esmeralda durante a orogênese Brasiliana no Nordeste do Brasil : o caso do depósito da Fazenda Bonfim, estado do Rio Grande do Norte

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Gradua... more Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2017.A região da Fazenda Bonfim situa-se na Faixa de Dobramentos Seridó, um importante domínio metalognético da Província Borborena, no qual são registradas mineralizações de W-Mo-Bi ± Au, Be-Ta-Li, Sn-Ta e gemas associadas ao magmatismo Brasiliano. Apesar de inúmeros trabalhos, muito pouco se sabe sobre corpos graníticos mineralizados intrusivos no embasamento gnáissico migmatítico, sua origem, fontes, profundidades da intrusão e posicionamento na história evolutiva da Província Borborema. Contudo, recentes ocorrências de esmeraldas associadas a corpos félsicos intrusivos no embasamento caracterizam uma nova fronteira prospectiva no âmbito na riqueza mineral da Província Borborema. A gênese da esmeralda Fazenda Bonfim envolveu um clássico processo de metassomatismo decorrente da interação de corpos félsicos ricos em Be com rochas máfica-ultramáficas, porém fortemente in...

Research paper thumbnail of Novos dados U/Pb para as idades dos protólitos e da colisão entre os Blocos Jequié e Itabuna-Salvador-Curaçá, Cráton do São Francisco, no centro-leste do estado da Bahia, Brasil

Research paper thumbnail of Ediacaran emerald mineralization in Northeastern Brazil: the case of the Fazenda Bonfim Deposit

Brazilian Journal of Geology, 2019

The Fazenda Bonfim emerald deposit lies within the Seridó Belt. It is a classic example of deposi... more The Fazenda Bonfim emerald deposit lies within the Seridó Belt. It is a classic example of deposit formed through metasomatic interactions between Be-rich granite intrusions and Cr(± V)-rich mafic-ultramafic rocks. The setting of the emerald mineralization was built under strong strikeslip dynamics, which produced serpentinization and talcification of mafic-ultramafic host-rocks, and was followed by syn-kinematic emplacement of Be-rich albite granite, favoring hydrothermal/metasomatic processes. The structural control and lithological-contrast were fundamental to the fluid flow and the best ore-shoot geometry, developed in the S-foliation intra-plane at the contact zone (phlogopite hornfels) between mafic-ultramafic rocks and the albite granite. Subsequently, an albitization process, linked to the final-stage of magmatic crystallization, led to an overall mineralogical and chemical change of the albite granite. 207U-235Pb data revealed inheritance ages from Archean to Neoproterozoic and a crystallization age of 561 ± 4 Ma for albite granite. However, 40Ar/39Ar data revealed plateau age of 553 ± 4 Ma for phlogopite hornfels, interpreted as the closure time for the metasomatic event responsible for the nucleation and growth of emerald crystals. The short interval of time between U-Pb and Ar-Ar data indicates an intense, but not protracted, metasomatic history, probably due to low volume of intrusive magma.

Research paper thumbnail of Emerald from the Fazenda Bonfim Deposit, northeastern Brazil: chemical, fluid inclusions and oxygen isotope data

Brazilian Journal of Geology

The Fazenda Bonfim emerald deposit, State of Rio Grande do Norte, is within the regional geologic... more The Fazenda Bonfim emerald deposit, State of Rio Grande do Norte, is within the regional geological domain known as Seridó Mobile Belt, Borborema Tectonic Province. It was formed from metasomatic fluids interaction at along lithological contacts between Be-rich albite-granite intrusions and Cr (±V)-rich mafic-ultramafic host-rocks, enclosed in the lens-shaped "hornfels" phlogopite schist. Emerald crystals display relatively high contents of Mg and Na, as well as trace amounts of Ca,

Research paper thumbnail of Mineralização de esmeralda durante a orogênese Brasiliana no Nordeste do Brasil : o caso do depósito da Fazenda Bonfim, estado do Rio Grande do Norte

Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Gradua... more Dissertação (mestrado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2017.A região da Fazenda Bonfim situa-se na Faixa de Dobramentos Seridó, um importante domínio metalognético da Província Borborena, no qual são registradas mineralizações de W-Mo-Bi ± Au, Be-Ta-Li, Sn-Ta e gemas associadas ao magmatismo Brasiliano. Apesar de inúmeros trabalhos, muito pouco se sabe sobre corpos graníticos mineralizados intrusivos no embasamento gnáissico migmatítico, sua origem, fontes, profundidades da intrusão e posicionamento na história evolutiva da Província Borborema. Contudo, recentes ocorrências de esmeraldas associadas a corpos félsicos intrusivos no embasamento caracterizam uma nova fronteira prospectiva no âmbito na riqueza mineral da Província Borborema. A gênese da esmeralda Fazenda Bonfim envolveu um clássico processo de metassomatismo decorrente da interação de corpos félsicos ricos em Be com rochas máfica-ultramáficas, porém fortemente in...

Research paper thumbnail of Novos dados U/Pb para as idades dos protólitos e da colisão entre os Blocos Jequié e Itabuna-Salvador-Curaçá, Cráton do São Francisco, no centro-leste do estado da Bahia, Brasil

Research paper thumbnail of Ediacaran emerald mineralization in Northeastern Brazil: the case of the Fazenda Bonfim Deposit

Brazilian Journal of Geology, 2019

The Fazenda Bonfim emerald deposit lies within the Seridó Belt. It is a classic example of deposi... more The Fazenda Bonfim emerald deposit lies within the Seridó Belt. It is a classic example of deposit formed through metasomatic interactions between Be-rich granite intrusions and Cr(± V)-rich mafic-ultramafic rocks. The setting of the emerald mineralization was built under strong strikeslip dynamics, which produced serpentinization and talcification of mafic-ultramafic host-rocks, and was followed by syn-kinematic emplacement of Be-rich albite granite, favoring hydrothermal/metasomatic processes. The structural control and lithological-contrast were fundamental to the fluid flow and the best ore-shoot geometry, developed in the S-foliation intra-plane at the contact zone (phlogopite hornfels) between mafic-ultramafic rocks and the albite granite. Subsequently, an albitization process, linked to the final-stage of magmatic crystallization, led to an overall mineralogical and chemical change of the albite granite. 207U-235Pb data revealed inheritance ages from Archean to Neoproterozoic and a crystallization age of 561 ± 4 Ma for albite granite. However, 40Ar/39Ar data revealed plateau age of 553 ± 4 Ma for phlogopite hornfels, interpreted as the closure time for the metasomatic event responsible for the nucleation and growth of emerald crystals. The short interval of time between U-Pb and Ar-Ar data indicates an intense, but not protracted, metasomatic history, probably due to low volume of intrusive magma.

Research paper thumbnail of Emerald from the Fazenda Bonfim Deposit, northeastern Brazil: chemical, fluid inclusions and oxygen isotope data

Brazilian Journal of Geology

The Fazenda Bonfim emerald deposit, State of Rio Grande do Norte, is within the regional geologic... more The Fazenda Bonfim emerald deposit, State of Rio Grande do Norte, is within the regional geological domain known as Seridó Mobile Belt, Borborema Tectonic Province. It was formed from metasomatic fluids interaction at along lithological contacts between Be-rich albite-granite intrusions and Cr (±V)-rich mafic-ultramafic host-rocks, enclosed in the lens-shaped "hornfels" phlogopite schist. Emerald crystals display relatively high contents of Mg and Na, as well as trace amounts of Ca,