271-1 Assessing the CO2 Reactivity of Serpentinites from Puerto Rico: An Experimental Study

Session: Geologic Energy Resources and Storage for Now and the Future (Posters)

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Abstract:

Mineral carbonation of ultramafic rocks offers a suitable alternative for offsetting the rampant carbon dioxide (CO₂) emissions to the atmosphere via carbon capture and storage. However, it requires collaborative efforts to identify the availability and suitability of global ultramafic rock reserves to be effective. Serpentinite rocks are the product of hydrothermal alteration (serpentinization) of ultramafic rocks such as peridotites. Puerto Rico is known for having serpentinite rocks that are part of an ophiolite sequence resulting from an oceanic convergent zone and are scattered throughout the southwestern part as three separate, elongated serpentinite belts. These rocks, however, have not been evaluated yet as potential rock formations for carbon capture and storage. Therefore, it is imperative to fill the existing gap in knowledge to contribute to these collaborative efforts at a global scale. The objective is to experimentally evaluate the suitability and capabilities of serpentinite rocks from Puerto Rico for carbon mineralization via their interaction with CO₂ fluids. Several serpentinite rock samples were collected, prepared into fragments of approximately 10 to 20 mm, and cleaned using a sonic bath with deionized water (DI). A total of four experiments were conducted. The experimental setup consisted of placing approximately 2 to 3 rock fragments at the bottom of a Teflon-lined stainless steel autoclave reactor with a brine solution (0.5 M NaCl and 0.25 M CaCl₂). In addition, ammonium carbonate (NH₄)₂CO₃ was placed into a Teflon tube exposed above the fluid level to ensure the supply of CO₂ to the system as a function of ammonium carbonate decomposition. Analysis of experimental solids encompassed X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Experimental fluids were analyzed using an inductively coupled plasma optical emission spectroscopy (ICP-OES). Out of the 3 main serpentinite minerals (antigorite, chrysotile, and lizardite), the predominant one in the samples is lizardite. The presence of critical minerals, including nickel, titanium, cobalt, and chromium, was detected within the samples via SEM-EDS analysis. Nucleation of crystals was observed via optical microscopy and took place on the surface of the fragments. Overall, results from this study will shed light on and assess the potential of serpentinites in Puerto Rico and thus potentially join the global contributions.  

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10973

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