Fracture-Lining Minerals in the Lower Topopah Spring Tuff at Yucca Mountain

by Barbara A. Carlos, Los Alamos Natl Lab, Los Alamos, United States,
David L. Bish, Los Alamos Natl Lab, Los Alamos, United States,
Steve J. Chipera, Los Alamos Natl Lab, Los Alamos, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1991


Fracture-lining minerals in the lower Topopah Spring Member of the Paintbrush Tuff at Yucca Mountain, Nevada, are being examined to characterize potential flow paths within and away from the candidate repository horizon. Fracture coatings within this interval can be divided into five categories based on rock matrix and type of fracture. Fracture coatings in the densely welded tuff above the basal vitrophyre, near the candidate repository horizon, include (1) those related to lithophysal cavities; (2) mordenite and manganese oxides on nearly planar fractures; (3) later fracture coatings consisting of zeolites, smectite, and calcite. Fracture-coating minerals in the vitrophyre are fine-grained and consist of smectite and a variety of zeolites. The non- to partially-welded vitric and/or zeolitic tuff below the vitrophyre contains fractures mostly lined by cristobalite and clinoptilolite.

Subject Headings: Cracking | Minerals | Radioactive wastes | Coating | Waste storage | Underground storage | Welding | Nevada | United States

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