Estudo da precipitação de silicatos magnesianos a partir da coluna de água visando a compreensão da diagênese do pré-sal

Abstract

The evaporation and precipitation process in alkaline lake systems can be a key element to explain the mineralogy found in the pre-salt reservoirs. However, simulating the precipitation conditions of these minerals in the laboratory, mostly stevensite / kerolite, calcite and dolomite, is a challenge. In this sense, geochemical modeling assists to carry out geochemical experiments through software that allows the simulation of the evaporation and precipitation processes of magnesian phyllosilicates and carbonates. In the present work, in order to study the precipitation of stevensite / kerolite and calcite, from the water column, experiments of controlled evaporation were performed, on a laboratory scale, using glass slides arranged in a Becker glass at different levels containing a synthesized solution equivalent to the composition Mono Lake (USA), an analogue of the precursor precursor lakes. Allied to the experiments, the geochemical modeling indicated that the evaporation is capable of creating a supersaturation allowed the precipitation of the carbonate in the first days and of the stevensite from the 14th day. In the liquid phase, there is a reduction in alkalinity, calcium, magnesium and silicon in solution during the evaporation process, in addition to the formation of minerals such as silicates, carbonates and common salts in evaporative systems like hydrated sodium bicarbonate (Na3H(CO3)2·2H2O), anhydrous sodium sulfate (Na₂SO₄), sodium carbonate / sulfate (Na6(CO3)(SO4)2) and sodium chloride (NaCl).