Geology topics
Research about Clark County, Nevada
Source-linked reports with geographic coverage including Clark County, Nevada.
Mineral resources of the South McCullough Mountains Wilderness Study Area, Clark County, Nevada
No abstract available.
Ground-water quality and geochemistry of Las Vegas Valley, Clark County, Nevada, 1981-83: Implementation of a monitoring network
As a result of rapid urban growth in Las Vegas Valley, rates of water use and wastewater disposal have grown rapidly during the last 25 years. Concern has developed over the potential water quality effects of this growth. The deep percolation of wastewater and irrigation return flow (much of which originates as imported water from Lake Mead), along with severe overdraft conditions in the principal aquifers of the valley, could combine to pose a long-term threat to groundwater quality. The quantitative investigations of groundwater quality and geochemical conditions in the valley necessary to address these concerns would include the establishment of data collection networks on a valley-wide scale that differ substantially from existing networks. The valley-wide networks would have a uniform areal distribution of sampling sites, would sample from all major depth zones, and would entail repeated sampling from each site. With these criteria in mind, 40 wells were chosen for inclusion in a demonstration monitoring network. Groundwater in the northern half of the valley generally contains 200 to 400 mg/L of dissolved solids, and is dominated by calcium, magnesium , and bicarbonate ions, reflecting a chemical equilibrium between the groundwater and the dominantly carbonate rocks in the aquifers of this area. The intermediate to deep groundwater in the southern half of the valley is of poorer quality (containing 700 to 1,500 mg/L of dissolved solids) and is dominated by calcium, magnesium, sulfate, and bicarbonate ions, reflecting the occurrence of other rock types including evaporite minerals among the still-dominant carbonate rocks in the aquifers of this part of the valley. The poorest quality groundwater in the valley is generally in the lowland parts of the valley in the first few feet beneath the water table, where dissolved solids concentrations range from 2,000 to > 7,000 mg/L , and probably reflects the effects of evaporite dissolution, secondary recharge, and evapotranspiration. The most common water quality constraint on potential groundwater use is the high salinity. No evidence of large-scale contamination of deep groundwater was found in this study.
Ground-water conditions in Las Vegas Valley, Clark County, Nevada; Part I, Hydrogeologic framework
No abstract available.
Mineral resource potential map of the Muddy Mountains Wilderness Study Area, Clark County, Nevada
The Muddy Mountains Wilderness Study Area (WSA 050-0229), Clark County, Nevada, has a high potential for mineral deposits of calcium borates and lithium. The known and potential mineral deposits are concentrated in the east-central and south-central parts of the study area (see map). Zeolites (in particular clinoptilolite) are present in some tuff beds throughout much of the study area, and this resource potential is probably moderate to high. Stream-sediment sampling suggests that the Muddy Mountains area has little potential for mineral deposits of metals (other than lithium). Clay minerals are mined at one locality in the (!rea (see map). Building stone and silica sand have moderate to low potential in some places. Oil and gas potential within the study area is low, but complete evaluation of its potential is not possible without drilling.
Preliminary report on the mineral resource potential of the Red Rocks Escarpment Instant Study area, Clark County, Nevada
The Red Rocks Escarpment Instant Study area in Clark County, Nevada, is 2 mi (32 km) west of Las Vegas and covers about 31,000 acres (12,500 ha) of the rugged Sandstone Bluffs area in the Spring Mountains (fig. 1). It includes the crest of the range, which is slightly higher than 7,200 ft (2,190 m), the Sandstone Bluffs east of the crest where steep cliffs as high as 2,500 ft (760 m) occur, and part of the gently sloping western range front. The Instant Study area (fig. 2) is within land administered by the U.S. Bureau of Land Management.
Leveling data; Eglington fault scarp, Las Vegas Valley, Nevada
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Lithium-bearing rocks of the Horse Spring Formation, Clark County, Nevada
The Horse Spring Formation of Miocene age in Clark County, Nevada, contains as much as 0.5% Li in individual samples. Rock sequences which average 0.1% Li range from 3 m thick near Gold Butte (south of Mesquite, Nev.) to as much as 40 m thick near Lava Butte (east of Las Vegas, Nev.) about 75 km to the west. The lithium-bearing beds are light colored to white and contain hectorite in a dolomite, magnesite, or calcite matrix. Varied amounts of gypsum, halite, celestite, clinoptilolite, quartz, feldspar, biolite and colemanite are also present locally. Hectorite is the only lithium mineral recognized to date. The lithium-rich rocks contain low concentrations of most other minor elements except that boron and strontium are enriched. Rarely, barium, arsenic, and zinc are present in anomalously large amounts. The lithium-enriched part of the Horse Spring Formation was formed from a series of volcanic ashes which were deposited in a playa. Relict volcanic ash is recognizable in thin sections as remnant glass shards and vitroclastic textures. Most of the original glass has been altered to clay minerals, carbonate minerals, or zeolites, presumably through interaction with highly saline pore waters. Abundant evidence of spring activity suggests that thermal waters played a part in releasing the lithium from volcanic materials.
Chemistry of Tertiary volcanic rocks in the Eldorado Mountains, Clark County, Nevada, and comparisons with rocks from some nearby areas
Chemical variations of 27 rocks that erupted from in and near the Eldorado Mountains, southern Nevada, show (1) fair to good correlation suggestive of a cogenetic suite, (2) a range of uncorrected silica values from about 48 to 74 weight percent with no strong tendency toward bimodality, (3) a calc-alkaline characteristic, and (4) a shift from early eruptions having an anomalously low level of iron enrichment to later eruptions having a more normal level of iron enrichment. Analyses of rocks not known to have been erupted from the Eldorado Mountains (for example, five analyses of the tuff of Bridge Spring and two analyses of the Fortification Basalt Member of the Muddy Creek Formation) are not anomalous when compared with the other rocks, except that iron concentration in the Fortification Basalt Member may be higher than normal. Extensive K-Ar age data provide a clear time framework for the chemical changes as well as for the structural history of the area. The inception of intense extensional tectonism about 15 million years ago was marked by an abrupt shift to more iron-rich and more typically calc-alkalic volcanic products (Mount Davis Volcanics) than those erupted earlier (Patsy Mine Volcanics), but no corresponding shift in K 2 O or total alkali contents or ratios is recognized nor is there any obvious shift toward bimodality in rocks younger than 15 million years. These data, together with data from the Oatman district of Arizona, 100 kilometers to the south-southeast, indicate that the northern part of the lower Colorado River area does not fit into the published Cenozoic patterns of volcanic and tectonic evolution of the western United States. A brief review of nearby areas indicates that they may not fit well either.