skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Pyritic ash-flow tuff, Yucca Mountain, Nevada

Abstract

The Yucca Mountain site is underlain by a 1,500-m-thick Miocene volcanic sequence that comprises part of the southwestern Nevada volcanic field. Rocks of this sequence, which consists mainly of ash-flow tuff sheets with minor flows and bedded tuff, host precious metal mineralization in several areas as near as 10 km from the site. In two such areas, the Bullfrog and Bare Mountain mining districts, production and reserves total over 60 t gold and 150 t silver. Evidence of similar precious metal mineralization at the Yucca Mountain site may lead to mining or exploratory drilling in the future, compromising the security of the repository. The authors believe that most of the pyrite encountered by drilling at Yucca Mountain was introduced as pyroclastic ejecta, rather than by in situ hydrothermal activity. Pyritic ejecta in ash-flow tuff are not reported in the literature, but there is no reason to believe that the Yucca Mountain occurrence is unique. The pyritic ejecta are considered by us to be part of a preexisting hydrothermal system that was partially or wholly destroyed during eruption of the tuff units. Because it was introduced as ejecta in tuff units that occur at depths of about 1,000 m, such pyritemore » does not constitute evidence of shallow mineralization at the proposed repository site; however, the pyrite may be evidence for mineralization deep beneath Yucca Mountain or as much as tens of kilometers from it.« less

Authors:
; ;  [1]
  1. Univ. of Nevada, Reno NV (United States). Nevada Bureau of Mines and Geology
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
145221
Resource Type:
Journal Article
Journal Name:
Economic Geology
Additional Journal Information:
Journal Volume: 89; Journal Issue: 2; Other Information: PBD: Mar-Apr 1994
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; 58 GEOSCIENCES; YUCCA MOUNTAIN; SITE CHARACTERIZATION; GEOLOGY; GEOLOGIC DEPOSITS; MINERALIZATION; NEVADA; RADIOACTIVE WASTE DISPOSAL; HIGH-LEVEL RADIOACTIVE WASTES; Yucca Mountain Project

Citation Formats

Castor, S.B., Tingley, J.V., and Bonham, H.F. Jr. Pyritic ash-flow tuff, Yucca Mountain, Nevada. United States: N. p., 1994. Web. doi:10.2113/gsecongeo.89.2.401.
Castor, S.B., Tingley, J.V., & Bonham, H.F. Jr. Pyritic ash-flow tuff, Yucca Mountain, Nevada. United States. doi:10.2113/gsecongeo.89.2.401.
Castor, S.B., Tingley, J.V., and Bonham, H.F. Jr. Tue . "Pyritic ash-flow tuff, Yucca Mountain, Nevada". United States. doi:10.2113/gsecongeo.89.2.401.
@article{osti_145221,
title = {Pyritic ash-flow tuff, Yucca Mountain, Nevada},
author = {Castor, S.B. and Tingley, J.V. and Bonham, H.F. Jr.},
abstractNote = {The Yucca Mountain site is underlain by a 1,500-m-thick Miocene volcanic sequence that comprises part of the southwestern Nevada volcanic field. Rocks of this sequence, which consists mainly of ash-flow tuff sheets with minor flows and bedded tuff, host precious metal mineralization in several areas as near as 10 km from the site. In two such areas, the Bullfrog and Bare Mountain mining districts, production and reserves total over 60 t gold and 150 t silver. Evidence of similar precious metal mineralization at the Yucca Mountain site may lead to mining or exploratory drilling in the future, compromising the security of the repository. The authors believe that most of the pyrite encountered by drilling at Yucca Mountain was introduced as pyroclastic ejecta, rather than by in situ hydrothermal activity. Pyritic ejecta in ash-flow tuff are not reported in the literature, but there is no reason to believe that the Yucca Mountain occurrence is unique. The pyritic ejecta are considered by us to be part of a preexisting hydrothermal system that was partially or wholly destroyed during eruption of the tuff units. Because it was introduced as ejecta in tuff units that occur at depths of about 1,000 m, such pyrite does not constitute evidence of shallow mineralization at the proposed repository site; however, the pyrite may be evidence for mineralization deep beneath Yucca Mountain or as much as tens of kilometers from it.},
doi = {10.2113/gsecongeo.89.2.401},
journal = {Economic Geology},
number = 2,
volume = 89,
place = {United States},
year = {1994},
month = {3}
}