Modeling the Barite Deposition Process in the Jbel Irhoud Deposit, Western Jebilet, Morocco: Implications for Barite Exploration and Insights Into Mineralization Mechanisms

Abstract

The barite of the Jbel Irhoud deposit in Western Jebilet, Morocco, is a Paleozoic massif known for its mineralization, which occurs mainly in shale, sandstone, and Middle Cambrian limestone. Three main types of barite deposits are known in the area: karst, vein fillings, and limestone replacement. The karst formations make up the majority of the reserves. Barite-quartz-galena and Fe-Cu-Zn- and Ag-sulfides, as well as hematite-carbonates, form the mineral paragenesis. Oxidation and mixing models are proposed for the deposition of barite. To check the effects of oxidation, numerical modeling of aqueous fluid composition for Irhoud barite deposition (at 150°C–250°C, Psat, and 1–6 m NaCl) was performed using a program developed by Professor Moine at the Paul Sabatier University in Toulouse, France. It shows that a large amount of barium can be transported as Ba²⁺ (barium chloride becomes more significant at relatively high temperatures) and that the decrease in solubility of barium under the given conditions can be caused by an increase in fO2, with or without a decrease in temperature, pressure, and/or salinity. Moreover, it is shown that the mixing of two fluids with different compositions leads to an oxidation (and a partial decrease in temperature) that causes a significant decrease in the solubility of barium (more than 130 ppm) and thus an efficient precipitation of barite in the Jbel Irhoud deposit. This modeling could be used to explain the manifestation of fluids with different compositions associated with the deposition of barite worldwide. The hydrothermal and structurally controlled Irhoud barite is the result of rapid decompression and Ba²⁺/BaCl⁺ transport under moderate to high P–T conditions, suggesting an epigenetic, postsedimentary system.