MINERALOGICAL STUDY OF SEDIMENTS IN CHROMIUM-CONTAMINATED PLUME: IMPLICATION FOR NATURAL ATTENUATION
LANL is located on the Pajarito Plateau at the western edge of the Española basin. The older unit comprising the aquifer is the Miocene Pumiceous. This series of reworked, buff pumice beds have sub-units which correlate to the Peralta Rhyolite (6.9 Ma). The younger unit is the Plio-Pliestocene Puye formation, a heterogeneous volcanoclastic fanglomerate sourced predominantly from dacitic flows on the western side of the Pajarito Plateau. Preliminary mineralogical assessment of the Puye formation based on outcrop and borehole samples show the following: combined SiO₂ phases 1.3-25.2 wt. %, feldspars 31.5-54.3 wt. %, magnetite 1.03-1.98 wt. %, amorphous 9.1-43.9 wt. % and smectite 0-33.7 wt. %. Ongoing mineralogy from sonic cores is consistent with these findings, with the addition of muscovite. Continued study of sediment constituents with potential to attenuate will help inform the optimal procedure for remediation of the Cr6+ plume.