TY - THES

T1 - Fluid Inclusions in Magnesites of Brumado Deposit, Bahia, Brazil

AU - Hauzinger, Elisabeth

N1 - embargoed until 01-03-2026

PY - 2021

Y1 - 2021

N2 - Abstract Fluid inclusions in magnesites were investigated from two active mines as well as from two magnesite prospects from Brumado deposit, Bahia, Brazil. The deposit lies in the Serra das Éguas, a mountain range in an Archean greenstone belt within the Gaviao block, the oldest of four crustal segments which make up the Sao Francisco Craton in Eastern Brazil. Two different mineralizations could be distinguished. The first consists of red magnesite and light-coloured magnesite at Pedra Preta mine and at Pedra de Ferro prospect, while the second type is composed of white magnesite only currently produced at Pomba mine and prospected for at Pirajá prospect. Mineralogical characterisation included optical microscopy in transferred and reflected light, SEM, Raman spectroscopy, XRF and XRD. Microthermometry and Raman analysis of primary and pseudosecondary fluid inclusions in magnesite showed that these are strongly saline H2O-CO2 fluids. Two populations of fluid inclusions are distinguished. They show different styles of homogenisation (LH2OLCO2VCO2  LH2OVCO2; LH2OLCO2VCO2  LH2OLCO2) which reflect different total densities of the entrapped fluids and correspond to the first and the second mineralization stage, respectively. The fluids have low Na/Br (4.0 – 10.9) and Cl/Br (43.0 – 68.4) values and originated from highly differentiated evaporitic brines which were mobilized during orogenic metamorphism.

AB - Abstract Fluid inclusions in magnesites were investigated from two active mines as well as from two magnesite prospects from Brumado deposit, Bahia, Brazil. The deposit lies in the Serra das Éguas, a mountain range in an Archean greenstone belt within the Gaviao block, the oldest of four crustal segments which make up the Sao Francisco Craton in Eastern Brazil. Two different mineralizations could be distinguished. The first consists of red magnesite and light-coloured magnesite at Pedra Preta mine and at Pedra de Ferro prospect, while the second type is composed of white magnesite only currently produced at Pomba mine and prospected for at Pirajá prospect. Mineralogical characterisation included optical microscopy in transferred and reflected light, SEM, Raman spectroscopy, XRF and XRD. Microthermometry and Raman analysis of primary and pseudosecondary fluid inclusions in magnesite showed that these are strongly saline H2O-CO2 fluids. Two populations of fluid inclusions are distinguished. They show different styles of homogenisation (LH2OLCO2VCO2  LH2OVCO2; LH2OLCO2VCO2  LH2OLCO2) which reflect different total densities of the entrapped fluids and correspond to the first and the second mineralization stage, respectively. The fluids have low Na/Br (4.0 – 10.9) and Cl/Br (43.0 – 68.4) values and originated from highly differentiated evaporitic brines which were mobilized during orogenic metamorphism.

KW - Fluid Inklusionen

KW - Magnesit

KW - Sao Francisco Kraton

KW - Serra das Éguas

KW - Brumado

KW - Fluid inclusions

KW - magnesite

KW - Sao Francisco craton

KW - Serra das Éguas

KW - Brumado deposit

M3 - Master's Thesis

ER -