Thoughts Regarding the Dimensions of Faults at Rainier and Aqueduct Mesas, Nye County, Nevada, Based on Surface and Underground Mapping

Abstract

The geologic setting and history, along with observations through 50 years of detailed geologic field work, show that large-displacement (i.e., greater than 30 meters of displacement) syn-to post-volcanic faults are rare in the Rainier Mesa area. Faults observed in tunnels and drill holes are mostly tight, with small displacements (most less than 1.5 meters) and small associated damage zones. Faults are much more abundant in the zeolitized tuffs than in the overlying vitric tuffs, and there is little evidence that faults extend downward from the tuff section through the argillic paleocolluvium into pre-Tertiary rocks. The differences in geomechanical characteristics of the various tuff lithologies at Rainier Mesa suggest that most faults on Rainer Mesa are limited to the zeolitic units sandwiched between the overlying vitric bedded tuffs and the underlying pre-Tertiary units (lower carbonate aquifer-3, lower clastic confining unit-1, and Mesozoic granite confining unit).iv This page intentionally left blank.

Development and Calibration of Dual‐Permeability Flow Models with Discontinuous Fault Networks

“…he three largest faults at the T-tunnel complex, which all have surface traces, were allowed to extend throughout the entire model domain regardless of rock type. Allowing these faults to penetrate the full model extent is consistent with the framework model of Drellack and Ortego (2007) and Drellack et al (2009) and adds conservatism to the simulations because these features provide continuous pathways for luid low and radionuclide migration. More information regarding the dimensions of the faults and fault networks in the Tertiary volcanic units can be found in the appendix.…”

“…Fault and fracture data consisted of 1:200-scale maps of the largest normal faults encountered in the T-tunnel complex (e.g., Fig. 4), 1:50-scale detailed fracture maps of speciied locations along the main T-tunnel drit and Drits 01 and 04, mechanical properties from the Brethauer et al (1980) database, fault studies and compilations conducted by the USGS (Sweetkind and Drake, 2007) and National Security Technologies (Drellack et al, 2009), fracture outcrop mapping and borehole fracture logging (Doyle, personal communication, 2003), and hydraulic testing of the LCA3 in ER-12-3 (Stoller-Navarro Joint Venture, 2006a) and ER-12-4 (Stoller-Navarro Joint Venture, 2006b) ( Fig. 1).…”

Heterogeneous multiphase flow properties of volcanic rocks and implications for noble gas transport from underground nuclear explosions

“…Recent fractures include damage associated with excavations (e.g., drifts, boreholes, and cavities) or UNEs (e.g., shock damage or chimney collapse). Aqueduct Mesa does not show evidence of large‐scale faulting (e.g., tens of meters of displacement) like the adjacent Rainier Mesa (Drellack et al., 2011; Prothro, 2018). No faults or fractures with >1.5 m displacement have been observed in any of the drifts of the P‐Tunnel complex in Aqueduct Mesa (Drellack et al., 2011).…”

“…Aqueduct Mesa does not show evidence of large‐scale faulting (e.g., tens of meters of displacement) like the adjacent Rainier Mesa (Drellack et al., 2011; Prothro, 2018). No faults or fractures with >1.5 m displacement have been observed in any of the drifts of the P‐Tunnel complex in Aqueduct Mesa (Drellack et al., 2011). The volcanic rocks at Aqueduct Mesa are, in general, a layer‐cake sequence of lithologies that have not been greatly deformed by basin and range extension (Prothro, 2018).…”

“…The zeolitized (i.e., altered) volcanic tuffs (GFM layer UZNT; ZN lithology; Figures 1b and 10) are more similar to the vitric tuffs from which they were derived than the uppermost welded layers, but are physically stronger, lower porosity, and lower permeability than the vitric tuffs (Prothro, 2018). They can possibly maintain open fractures from human activities, since they are mechanically stronger, but few open natural fractures are observed at the P‐Tunnel level (Drellack et al., 2011; Prothro, 2018). In general, the UZNT (i.e., ZN lithology) is described as being poorly to moderately fractured (Prothro, 2018).…”