Three barite samples of different provenance were studied using several characterization methods. The samples were initially examined as grain mounts by X-ray diffraction (XRD) to determine bulk mineralogy and grain sizes. Only barite (BaSO4) was observed in XRD patterns. Elemental abundance mapping by electron microprobe and x-ray microprobe were used to determine whether discrete phases contributed to the trace-metal composition of the bulk sediments. The samples included minute, broadly dispersed grains of lead sulfide, and an unidentified Pb phase that did not include sulfur or phosphorous. Hg was found within a subset of the Pb sulfide grains, along with Cu. A Sr sulfide was observed. Fe was present in all samples, as an oxide and a sulfide. The Fe sulfides were much less abundant in two of the samples. Cu was alos observed as a sulfide without associated Pb. Finally, Cr was observed as sub-µm oxide particles and as a chromium oxide component of Fe-rich, >10 µm lithic fragments. The detected trace metals in the barite samples were components of very minor discrete mineral phases within the more abundant barite grains. Abundant inclusions of Fe oxides, sulfides, and quartz were also observed.
Revised: November 10, 2006 |
Published: October 1, 2006
Citation
McKinley J.P. 2006.Mineralogic and compositional studies of barite samples. In Proceedings: Twenty-Third Gulf of Mexico Information Transfer Meeting, January 2005. OCS Study, MMS2005-066, edited by Melanie McKay and Judith Nides, 3-4. New Orleans, Louisiana:U.S. Dept. of the Interior, Minerals Management Service. PNWD-SA-7577.