The Formation of Barite and Celestite through the Replacement of Gypsum

Abstract

Barite (BaSO4) and celestite (SrSO4) are the end-members of a nearly ideal solid solution. Most of the exploitable deposits of celestite occur associated with evaporitic sediments which consist of gypsum (CaSO4·2H2O) or anhydrite (CaSO4). Barite, despite having a broader geological distribution is rarely present in these deposits. In this work, we present an experimental study of the interaction between gypsum crystals and aqueous solutions that bear Sr or Ba. This interaction leads to the development of dissolution-crystallization reactions that result in the pseudomorphic replacement of the gypsum crystals by aggregates of celestite or barite, respectively. The monitoring of both replacement reactions shows that they take place at very different rates. Millimeter-sized gypsum crystals in contact with a 0.5 M SrCl2 solution are completely replaced by celestite aggregates in less than 1 day. In contrast, only a thin barite rim replaces gypsum after seven days of interaction of the latter with a 0.5 M BaCl2 solution. We interpret that this marked difference in the kinetics of the two replacement reactions relates the different orientational relationship that exists between the crystals of the two replacing phases and the gypsum substrate. This influence is further modulated by the specific crystal habit of each secondary phase. Thus, the formation of a thin oriented layer of platy barite crystals effectively armors the gypsum surface and prevents its interaction with the Ba-bearing solution, thereby strongly hindering the progress of the replacement reaction. In contrast, the random orientation of celestite crystals with respect to gypsum guarantees that a significant volume of porosity contained in the celestite layer is interconnected, facilitating the continuous communication between the gypsum surface and the fluid phase and guaranteeing the progress of the gypsum-by-celestite replacement.

Sedimentological and mineralogical-petrographic characteristics of Miocene evaporitic deposits (SW Erzincan)

“…Diagenetic solutions rich in strontium (waters released during gypsum anhydrite transformation) or hydrothermal related waters mix with groundwater, allowing the reaction of Sr and Ca in the late diagenetic stage. Thus, the mineral of celestin rich in SrSO4 is formed instead of gypsum [71][72]. At the same time, high amounts of iron-rich hematite or magnetite type Fe oxide minerals, very high amounts of manganese and Fe-rich Ca, Mg, Al silicate minerals (smectite, saponite type) were detected in these gypsum (Fig.…”

Barite Scaling Potential Modelled for Fractured-Porous Geothermal Reservoirs

“…One example is the aforementioned solidsolution barite-celestite, which may lead to an increased precipitation potential compared to the sum of the endmembers. Another example would be the dissolution of anhydrite within the reservoir due to cool water injection, which could facilitate further barite and celestite precipitation due to the release of sulfate into solution [61]. A comprehensive assessment of the chemical system and possible interaction effects may be needed for specific sites, and is subject to future work.…”

Long-term experimental diagenesis of aragonitic biocarbonates: from organic matter loss to abiogenic calcite formation

“…This secondary porosity network adds to the primary one and provides new pathways for the infiltration and circulation of the hydrothermal fluid within the biomaterial (Jonas et al, 2017;Casella et al, 2018). The tortuosity and permeability of this network, which depends on the shape, size and interconnectivity of its constituting pores (Forjanes et al, 2020a) define the extent of hydrothermal fluid infiltration through the hard tissue (Casella et al, 2018).…”