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Title: Origins of secondary silica within Yucca Mountain, Nye County, southwestern Nevada

Abstract

The accuracy of predictions of the hydrologic response of Yucca Mountain to future climate depends largely on how well relations between past climate and hydrology can be resolved. To advance this reconstruction, secondary minerals in and near Yucca Mountain, deposited by ground waters that originated both as surficial recharge at Yucca Mountain and from regional aquifers, are being studied to determine past ground-water sources and chemistries. Preliminary data on stable oxygen isotopes indicate that, although silica (opal, quartz, and chalcedony) and calcite and have formed in similar settings and from somewhat similar fluids, the authors have found no compelling evidence of coprecipitation or formation from identical fluids. If verified by further analyses, this precludes the use of silica-calcite mineral pairs for precise geothermometry. The preliminary data also indicate that opal and calcite occurrences in pedogenic and unsaturated-zone settings are invariably compatible with formation under modern ambient surface or subsurface temperatures. Silica and calcite stable-isotope studies are being integrated with soil geochemical modeling. This modeling will define the soil geochemical condition (climate) leading to opal or calcite deposition and to the transfer functions that may apply at the meteorologic soil unsaturated-zone interfaces. Additional study of pedogenic and unsaturated-zone silica is neededmore » to support these models. The hypothesis that the transformation of vapor-phase tridymite to quartz requires saturated conditions is being tested through stable oxygen-isotope studies of lithophysal tridymite/quartz mixtures. Should this hypothesis be verified, mineralogic analysis by X-ray diffraction theoretically would permit reconstruction of past maximum water-table elevations.« less

Authors:
;
Publication Date:
Research Org.:
Geological Survey, Denver, CO (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States); Department of the Interior, Washington, DC (United States)
OSTI Identifier:
373821
Report Number(s):
USGS-OFR-95-289
ON: DE96014511; TRN: 96:024905
DOE Contract Number:  
AI08-92NV10874
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1996
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; YUCCA MOUNTAIN; RADIOACTIVE WASTE FACILITIES; SITE CHARACTERIZATION; HYDROLOGY; PALEOCLIMATOLOGY; SILICON OXIDES; ORIGIN; MINERALOGY; CALCITE; RESERVOIR TEMPERATURE; GEOCHEMISTRY; GEOLOGIC MODELS; PETROLOGY; EXPERIMENTAL DATA

Citation Formats

Moscati, R J, and Whelan, J F. Origins of secondary silica within Yucca Mountain, Nye County, southwestern Nevada. United States: N. p., 1996. Web. doi:10.2172/373821.
Moscati, R J, & Whelan, J F. Origins of secondary silica within Yucca Mountain, Nye County, southwestern Nevada. United States. https://doi.org/10.2172/373821
Moscati, R J, and Whelan, J F. Sun . "Origins of secondary silica within Yucca Mountain, Nye County, southwestern Nevada". United States. https://doi.org/10.2172/373821. https://www.osti.gov/servlets/purl/373821.
@article{osti_373821,
title = {Origins of secondary silica within Yucca Mountain, Nye County, southwestern Nevada},
author = {Moscati, R J and Whelan, J F},
abstractNote = {The accuracy of predictions of the hydrologic response of Yucca Mountain to future climate depends largely on how well relations between past climate and hydrology can be resolved. To advance this reconstruction, secondary minerals in and near Yucca Mountain, deposited by ground waters that originated both as surficial recharge at Yucca Mountain and from regional aquifers, are being studied to determine past ground-water sources and chemistries. Preliminary data on stable oxygen isotopes indicate that, although silica (opal, quartz, and chalcedony) and calcite and have formed in similar settings and from somewhat similar fluids, the authors have found no compelling evidence of coprecipitation or formation from identical fluids. If verified by further analyses, this precludes the use of silica-calcite mineral pairs for precise geothermometry. The preliminary data also indicate that opal and calcite occurrences in pedogenic and unsaturated-zone settings are invariably compatible with formation under modern ambient surface or subsurface temperatures. Silica and calcite stable-isotope studies are being integrated with soil geochemical modeling. This modeling will define the soil geochemical condition (climate) leading to opal or calcite deposition and to the transfer functions that may apply at the meteorologic soil unsaturated-zone interfaces. Additional study of pedogenic and unsaturated-zone silica is needed to support these models. The hypothesis that the transformation of vapor-phase tridymite to quartz requires saturated conditions is being tested through stable oxygen-isotope studies of lithophysal tridymite/quartz mixtures. Should this hypothesis be verified, mineralogic analysis by X-ray diffraction theoretically would permit reconstruction of past maximum water-table elevations.},
doi = {10.2172/373821},
url = {https://www.osti.gov/biblio/373821}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1996},
month = {9}
}