Fluid inclusions and stable isotopes in non-ore minerals of the manganese ore deposits in the north of the Córdoba province

Abstract

In this paper the non-ore minerals of the southern sector of this deposit are studied. Microthermometric analysis on calcite, barite and fluorite show fluid salinities of 2.7 and 4% wt eq. NaCl, and temperatures below 100°C. Isotopes of ¹³C, ¹⁸O and ³⁴S allow to determine a meteoric source for the fluids associated to their precipitation. The d¹³C values obtained in calcite are considered the result of a fluid in equilibrium with atmospheric CO₂ plus the addition of carbon due to dissolution of organic compounds. On the other hand, the d³⁴S values of barites can be explained by another fluid with H₂S contents resulting from the dissolution of sulfides from the wall-rock. Finally, the presence of two different fluids is postulated here. An upward fluid was responsible for the barite precipitation where the H₂S was oxidized to SO₄⁼. This fluid could form fluorite and silica varieties as its temperature decreases. The existence of a downward fluid explains calcite generation as the descending fluid is heated.