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Title: Mineralogical and Chemical Analysis of Fracture and Matrix Minerals in Selected Samples of the Culebra Dolomite

Abstract

Contaminant release scenarios proposed for the Waste Isolation Pilot Plant (WIPP) repository suggest that the Culebra Dolomite member of the Rustler Formation could be an important radionuclide release path. This thin, vuggy, highly fractured unit is the most transmissive geologic unit overlying the WIPP. Many of the samples obtained from drill cores in the Culebra exhibit fractures that are lined with iron-oxyhydroxide-rich and clay-rich mineral coatings. The coatings are mineralogically distinct from the rock matrix, and may have sorptive characteristics that are different from a clay-poor dolomite matrix. Where locally abundant, such coatings could affect advective/diffusive exchange between matrix blocks and fractures and the accessible mineral surface area available for radionuclide adsorption. Clay minerals are present in the matrix and as fracture coatings in the samples from all the drill core locations examined in this study. Visual examination of rock sample surfaces in the H -19b7 core suggests that at least 7% of the total fracture surface area is coated with iron oxhydroxides or clays. In the samples from H-19b7, the amount of clay disseminated in the matrix varies from <1% to {approx}12 % by weight, and generally increases with stratigraphic height within the unit. In a suite of samplesmore » obtained from 12 other locations in the vicinity of the WIPP site, matrix samples from the Culebra contain 0.6--7% clay. These samples were taken from the more transmissive lower two-thirds of the unit (Culebra Units 2-4) which was considered to be the accessible portion of the unit in the WIPP Compliance Certification Application (CCA). Clay minerals also occur as clay-rich laminae and partings with the geometries of primary sedimentary structures and dissolution residues. Such partings are the loci of bedding plane fractures, and have the heaviest clay coatings found in the unit. Crosscutting fractures also commonly exhibit clay mineral coatings, but these are generally discontinuous and much thinner.« less

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
776347
Report Number(s):
SAND99-1512
TRN: US0300473
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Mar 2001; PBD: 1 Mar 2001
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ADSORPTION; CHEMICAL ANALYSIS; COATINGS; COMPLIANCE; DISSOLUTION; DOLOMITE; DRILL CORES; FRACTURES; IRON; RADIOISOTOPES; RESIDUES; SURFACE AREA; WIPP

Citation Formats

Bryan, C R, Siegel, M D, and Krumhansl, J L. Mineralogical and Chemical Analysis of Fracture and Matrix Minerals in Selected Samples of the Culebra Dolomite. United States: N. p., 2001. Web. doi:10.2172/776347.
Bryan, C R, Siegel, M D, & Krumhansl, J L. Mineralogical and Chemical Analysis of Fracture and Matrix Minerals in Selected Samples of the Culebra Dolomite. United States. https://doi.org/10.2172/776347
Bryan, C R, Siegel, M D, and Krumhansl, J L. 2001. "Mineralogical and Chemical Analysis of Fracture and Matrix Minerals in Selected Samples of the Culebra Dolomite". United States. https://doi.org/10.2172/776347. https://www.osti.gov/servlets/purl/776347.
@article{osti_776347,
title = {Mineralogical and Chemical Analysis of Fracture and Matrix Minerals in Selected Samples of the Culebra Dolomite},
author = {Bryan, C R and Siegel, M D and Krumhansl, J L},
abstractNote = {Contaminant release scenarios proposed for the Waste Isolation Pilot Plant (WIPP) repository suggest that the Culebra Dolomite member of the Rustler Formation could be an important radionuclide release path. This thin, vuggy, highly fractured unit is the most transmissive geologic unit overlying the WIPP. Many of the samples obtained from drill cores in the Culebra exhibit fractures that are lined with iron-oxyhydroxide-rich and clay-rich mineral coatings. The coatings are mineralogically distinct from the rock matrix, and may have sorptive characteristics that are different from a clay-poor dolomite matrix. Where locally abundant, such coatings could affect advective/diffusive exchange between matrix blocks and fractures and the accessible mineral surface area available for radionuclide adsorption. Clay minerals are present in the matrix and as fracture coatings in the samples from all the drill core locations examined in this study. Visual examination of rock sample surfaces in the H -19b7 core suggests that at least 7% of the total fracture surface area is coated with iron oxhydroxides or clays. In the samples from H-19b7, the amount of clay disseminated in the matrix varies from <1% to {approx}12 % by weight, and generally increases with stratigraphic height within the unit. In a suite of samples obtained from 12 other locations in the vicinity of the WIPP site, matrix samples from the Culebra contain 0.6--7% clay. These samples were taken from the more transmissive lower two-thirds of the unit (Culebra Units 2-4) which was considered to be the accessible portion of the unit in the WIPP Compliance Certification Application (CCA). Clay minerals also occur as clay-rich laminae and partings with the geometries of primary sedimentary structures and dissolution residues. Such partings are the loci of bedding plane fractures, and have the heaviest clay coatings found in the unit. Crosscutting fractures also commonly exhibit clay mineral coatings, but these are generally discontinuous and much thinner.},
doi = {10.2172/776347},
url = {https://www.osti.gov/biblio/776347}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2001},
month = {Thu Mar 01 00:00:00 EST 2001}
}