Geology and petrology of the basalts of Crater Flat: applications to volcanic risk assessment for the Nevada Nuclear Waste Storage investigations

Technical Report · Mon Jun 01 04:00:00 EDT 1981

OSTI ID:59123

Vaniman, D; Crowe, B

Volcanic hazard studies of the south-central Great Basin, Nevada, are being conducted for the Nevada Nuclear Waste Storage Investigations. This report presents the results of field and petrologic studies of the basalts of Crater Flat, a sequence of Pliocene to Quaternary-age volcanic centers located near the southwestern part of the Nevada Test Site. Crater Flat is one of several basaltic fields constituting a north-northeast-trending volcanic belt of Late Cenozoic age extending from southern Death Valley, California, through the Nevada Test Site region to central Nevada. The basalts of Crater Flat are divided into three distinct volcanic cycles. The cycles are characterized by eruption of basalt magma of hawaiite composition that formed cinder cone clusters and associated lava flows. Total volume of erupted magma for respective cycles is given. The basalts of Crater Flat are sparsely to moderately porphyritic; the major phenocryst phase is olivine, with lesser amounts of plagioclase, clinopyroxene, and rare amphibole. The consistent recurrence of evolved hawaiite magmas in all three cycles points to crystal fractionation from more primitive magmas at depth. A possible major transition in mantle source regions through time may be indicated by a transition from normal to Rb-depleted, Sr-enriched hawaiites in the younger basaltic cycles. The recurrence of small volumes of hawaiite magma at Crater Flat supports assumptions required for probability modeling of future volcanic activity and provides a basis for estimating the effects of volcanic disruption of a repository site in the southwestern Nevada Test Site region. Preliminary data suggest that successive basalt cycles at Crater Flat may be of decreasing volume but recurring more frequently.

• Research Organization: Los Alamos National Lab., NM (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 59123
• Report Number(s): LA--8845-MS; ON: DE81026682
• Country of Publication: United States
• Language: English

Related Subjects

05 NUCLEAR FUELS
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
BASALT
FORECASTING
GEOLOGY
GREAT BASIN
HIGH-LEVEL RADIOACTIVE WASTES
MINERALOGY
MULTI-ELEMENT ANALYSIS
NEVADA
NEVADA TEST SITE
PETROLOGY
RADIOACTIVE WASTE DISPOSAL
RISK ASSESSMENT
TECTONICS
UNDERGROUND DISPOSAL
VOLCANIC REGIONS
VOLCANOES
Yucca Mountain Project