Separation and characterization of pedogenic barite crystals from petrocalcic horizon materials for future isotopic and geochronological applications

Abstract Although extensive work has been conducted on pedogenic barite in the petrocalcic soil horizons at Mormon Mesa, NV, further investigations are required to understand the mode and timing of its precipitation. Isolation of barite crystals from petrocalcic soil materials is an important first step, after which, crystal morphology can be examined. We sought a method to isolate barite and other heavy minerals to examine their feasibility for future isotopic and geochronological techniques. Using XRD, SEM with EDS and microprobe analyses, barite was analyzed for evidence of chemical or physical alteration after chemical separation procedures with HCl to remove carbonate and methylene iodide to separate minerals with specific gravities greater than and less than 3.3 g/mL. After separation, barite clusters were observed within the heavy mineral separates. Barite showed no remarkable signs of physical or chemical alteration after separation and small (< 1 mm) clusters of barite were large enough to be hand-picked from the heavy separates. The isolation of barite from other petrocalcic soil materials is the critical first step in applying isotopic and geochronological techniques that will contribute to a better understanding of the timing and development of this unique soil system.