Geology topics

Research about Wasatch Mountains

Source-linked reports with geographic coverage including Wasatch Mountains.

4 recordsLinked to original sources

USGS1997

Geologic setting and characteristic of mineral deposits in the central Wasatch Mountains, Utah

Base- and precious-metal deposits in the central Wasatch Mountains southeast of Salt Lake City were mined for more than 100 years beginning in 1868. Deposits present in the Park City, Little Cottonwood, and Big Cottonwood mining districts include Ag-Pb-Zn ± Cu ± Au replacements and veins, a low-grade porphyry Cu-Au deposit, Cu-bearing skarns, a quartz monzonite-type (low F) porphyry Mo deposit, and high sulfidation (quartz-alunite) Au deposits. Most production came from polymetallic replacement and vein deposits in the Park City mining district, which has a recorded production of more than 1.4 million oz Au, 253 million oz Ag, 2.7 billion lbs Pb, 1.5 billion lbs Zn, and 129 million lbs Cu from 1872 to 1978. Production in the Little and Big Cottonwood districts, mostly from Pb-Ag replacement deposits, was much smaller. Most mineral deposits in the central Wasatch Mountains are genetically related to the Wasatch igneous belt, a series of high-K calc-alkaline stocks and cogenetic volcanic rocks that formed about 41(?) to 30 Ma. The mineral deposits mostly formed near the end of magmatic activity between about 36 to 31.4 Ma. A subeconomic porphyry Mo deposit in the Little Cottonwood stock is notably younger having formed about 26 to 23.5 Ma. The intrusive rocks were emplaced mostly along the westward extension of the west-trending Uinta arch during a period of NW-SE-directed extension, and much of the mineralization in the Park City district was controlled by ENE-striking normal faults. About 15 degrees of eastward tilting of the central Wasatch Mountains during Late Cenozoic Basin and Range extension has resulted in progressively deeper levels of exposure from <1 km on the east to about 11 km on the west and in profound variations in the types of mineral deposits exposed in different parts of the range. Most deposits formed at paleodepths ≤5 km, and the most productive deposits in the Park City district formed at depths of 1 to 2 km. The porphyry Mo deposit in the Little Cottonwood stock formed at greater depths of about 6 km.

Utah↗

USGS1997

New K-Ar and 40Ar/39Ar ages of plutonism, hydrothermal alteration, and mineralization in the central Wasatch Mountains, Utah

Twenty-one new K-Ar and 10 new 40 Ar/ 39 Ar ages are reported for igneous and hydrothermal minerals from intrusive rocks of the Wasatch igneous belt in the central Wasatch Mountains. Interpretation of our new data combined with previously published K-Ar ages and with new 40 Ar/ 39 Ar and U-Pb ages reported by Vogel et al. (1997) suggests that the Clayton Peak stock was emplaced at about 36 to 35 Ma, the Alta stock at about 35 to 33 Ma, and the Little Cottonwood stock at about 31 to 30 Ma. Biotite K-Ar ages progressively increase from west to east in the Little Cottonwood stock, which is consistent with more rapid cooling of the eastern part of the stock and with other evidence suggesting about 15 degrees of eastward tilting of the central Wasatch Mountains following emplacement of the Wasatch igneous belt. Most porphyry stocks in the Park City mining district were emplaced at about 41 to 40 Ma; the Ontario stock was emplaced at about 36 Ma. Vein deposits in the Park City mining district formed at about 36 to 33 Ma. The Park Premier stock was emplaced in several pulses between about 35 to 32 Ma. Alteration related to porphyry copper mineralization in the Park Premier stock formed at 33.5 Ma and advanced argillic alteration and gold mineralization formed at 31.4 Ma. Molybdenum mineralization in the eastern part of the Little Cottonwood stock formed between 26 to 23.5 Ma.

Utah↗

USGS1997

Day one road log: Mid-Tertiary igneous rocks and mineral deposits in the central Wasatch Mountains, Utah

Today's field trip examines late Eocene and Oligocene granitoid intrusions, cogenetic volcanic rocks (Keetley Volcanics), and associated hydrothermally altered and mineralized rocks in the central Wasatch Mountains. Because of late Cenozoic tilting related to Basin and Range extension, a continuum of mid-Tertiary paleodepths is exposed that ranges from about 11 km on the west side of the Little Cottonwood stock to the actual paleosurface on the east side of the range (Fig. 1; John, 1989a). Consequently, we will see a wide variety of textures and styles of emplacement in the intrusive rocks, and a correspondingly wide variety of hydrothermal alteration types and mineral deposits (Lawton et al., 1980; John, 1989a). Mid-Tertiary igneous rocks in the central Wasatch Mountains consist of three phaneritic stocks exposed in the western and central parts of the range (Little Cottonwood, Alta, and Clayton Peak stocks); six porphyry to fine-grained phaneritic stocks exposed in the middle and eastern parts of the range, primarily in the Park City mining district (Flagstaff, Glencoe, Mayflower, Ontario, Pine Creek, and Valeo stocks); a subvolcanic porphyry complex (Park Premier stock) exposed near the Park Premier mine which is now partly covered by water filling the Jordanelle Reservoir; and coeval volcanic rocks (Keetley Volcanics), subvolcanic intrusions, and a volcanic neck (Indian Hollow plug) are exposed on the east side of the range (Figs. 2 and 3). The intrusive rocks range from coarse-grained, coarsely porphyritic on the west to fine-grained, porphyroaphanitic on the east (John, 1989a). They form a high-K, calc-alkaline series (Vogel

Utah↗

USGS1956

The physical behavior and geologic control of radon in mountain streams

Radon measurement were made in several small, turbulent mountain streams in the Wasatch Mountains near Salt Lake City and Ogden, Utah, to determine the relationship between the distribution of radon and its geologic environment. In this area, the distribution of radon in streams can be sued to locate points where relatively large amounts of radon-bearing ground water enter the stream, although other evidence of spring activity may be lacking. These points of influence ground water are marked by abrupt increases (as much as two orders of magnitude within a distance of 50 feet) in the radon content of the stream waters. The excess radon in the stream water is then rapidly lost to the atmosphere through stream turbulence. The rate of radon dissipation is an exponential function, of different slopes, with respect to distance of streamflow, and depend upon the rate and volume of streamflow, and the gradient and nature of the stream channel. The higher radon concentration can be generally related to specific stratigraphic horizons in several different drainage area. Thus, lithologic units which act as the primary aquifers can be identifies. In one area, thrust faults were found to control he influx of ground water into the stream. Estimates, based on radon concentration in stream and related spring waters, can also be made of the major increments of addition of ground water to streamflow where conventional methods such as stream gaging are not practical. The radon in the waters studied was found to be almost completely unsupported by radium in solution.

Utah↗