F/OH ratio in a rare fluorine-poor blue topaz from Padre Paraiso (Minas Gerais, Brazil) to unravel topaz's ambient of formation.

ABSTRACT: Topaz [Al₂SiO₄(F,OH)₂] is one of the main fluorine-bearing silicates occurring in environments where variably acidic (F)/aqueous (OH) fluids saturate the silicate system. In this work we fully characterized blue topaz from Padre Paraíso (Minas Gerais, Brazil) by means of in situ synchrotron X-Ray and neutron powder diffraction measurements (temperature range 298-1273 K) combined with EDS microanalyses. Understanding the role of OH/F substitution in topaz is important in order to determine the hydrophilicity and the exchange reactions of fluorine by hydroxyl groups, and ultimately to characterize the environmental redox conditions (H₂O/F) required for mineral formation. The fluorine content estimated from neutron diffraction data is ~ 1.03 a.f.u (

SUBMITTER: Precisvalle N 

PROVIDER: S-EPMC7846733 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature