Geochemical study of evaporite and clay mineral-oxyhydroxide samples from the Waste Isolation Pilot Plant site
- Univ. of New Mexico, Albuquerque, NM (US). Dept. of Geology
Samples of clay minerals, insoluble oxyhydroxides, and their host evaporites from the WIPP site have been studied for their major and minor elements abundances, x-ray diffraction characteristics, K-Ar ages, and Rb-Sr ages. This study was undertaken to determine their overall geochemical characteristics and to investigate possible interactions between evaporates and insoluble constituents. The evaporite host material is water-soluble, having Cl/Br ratios typical of marine evaporites, although the Br content is low. Insoluble material (usually a mixture of clay minerals and oxyhydroxide phases) yields very high Cl/Br ratios, possibly because of Cl from admixed halide minerals. This same material yields K/Rb and Th/U ratios in the normal range for shales; suggesting little, if any, effect of evaporite-induced remobilization of U, K, or Rb in the insoluble material. The rare-earth element (REE) data also show normal REE/chondrite (REE/CHON) distribution patterns, supporting the K/Rb and Th/U data. Clay minerals yield K-Ar dates in the range 365 to 390 Ma and a Rb-Sr isochron age of 428 {+-} 7 Ma. These ages are well in excess of the 220- to 230-Ma formational age of the evaporites, and confirm the detrital origin of the clays. The ages also show that any evaporite or clay mineral reactions that might have occurred at or near the time of sedimentation and diagenesis were not sufficient to reset the K-Ar and Rb-Sr systematics of the clay minerals. Further, x-ray data indicate a normal evaporitic assemblage of clay minerals and Fe-rich oxyhydroxide phases. The clay minerals and other insoluble material appear to be resistant to the destructive effects of their entrapment in the evaporites, which suggests that these insoluble materials would be good getters for any radionuclides (hypothetically) released from the storage of radioactive wastes in the area.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); New Mexico Univ., Albuquerque, NM (United States). Dept. of Geology
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 10177738
- Report Number(s):
- SAND-86-7168; ON: DE93018677; TRN: 93:002988
- Resource Relation:
- Other Information: PBD: Jun 1993
- Country of Publication:
- United States
- Language:
- English
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54 ENVIRONMENTAL SCIENCES
MINERALS
X-RAY DIFFRACTION
WIPP
GEOCHEMICAL SURVEYS
EVAPORITES
HALIDE MINERALS
SHALES
CLAYS
SEDIMENTATION
DIAGENESIS
RADIOACTIVE WASTE STORAGE
RADIOACTIVE WASTES
RADIONUCLIDE MIGRATION
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540250
WASTE DISPOSAL AND STORAGE
SITE RESOURCE AND USE STUDIES