Mineralogical characterization of weathered and less weathered strata of the Meade Peak phosphatic shale member of the Permian Phosphoria Formation; measured sections E and F, Rasmussen Ridge, and measured sections G and H, Sage Creek area of the Webster

[摘要] The Permian Phosphoria Formation of the western U.S. includes one of the largestphosphate deposits in the world. Despite the economic significance of this formation, itsfine-grained nature has discouraged detailed mineralogical characterization andquantitative studies. Recently, selenium and other potentially hazardous trace elementsin mine wastes have drawn increased attention to these rocks and motivated moreextensive study. Part of this effort has focused on a more detailed geological andmineralogical characterization of the rocks. This study uses powder X-ray diffraction(XRD) with Rietveld quantification software to characterize the mineralogy of channelsamples from stratigraphic sections measured by the U.S. Geological Survey in theMeade Peak Phosphatic Shale Member of the Permian Phosphoria Formation. Measuredsections are at the Rasmussen Ridge mine and at the Smoky Canyon mine approximately15 and 25 miles, respectively, northeast of Soda Springs, Idaho.The dominant minerals present in these samples are carbonate-fluorapatite, whichis the most common phosphatic ore mineral in this and other marine phosphorites, quartz,muscovite, albite, orthoclase, the ammonium feldspar buddingtonite (NH4AlSi3O8),dolomite, and calcite. Because of their potential for hosting trace elements such as Se,the presence of minor pyrite and sphalerite is also noteworthy. Analysis of the carbonatecontent in the carbonate-fluorapatite by Rietveld refinement shows relatively lowcarbonate contents, generally between 2 ? 3% (wt.) CO32- in the apatite structure,compared to other marine phosphorites.

[发布机构] U.S. Geological Survey

[学科分类] 地球科学(综合)