Marysvale-Pioche belt

Region West, Southwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area This focus area covers the belt stretching from the Marysvale volcanic area in the east to Dry Lake Valley (Nevada) in the west, covering the most well agreed upon portion of the Marysvale-Pioche (or Pioche-Marysvale, Wah Wah-Tushar) mineral/igneous/aeromagnetic belt/lineament and is based on belt outlines in Christiansen and others (1986) and Rowley (1998) and on mineral districts as defined in Krahulec (2018b) and Tingley (1998). This area includes the largest alunite deposit in the United States at Blawn Mountain, the undeveloped Pine Grove Mo porphyry, and the fifth and sixth largest Zn districts in the state at San Francisco and Mount Baldy-Ohio mining districts. Other moderate to minor mining districts in Utah include: Bradshaw, Gold Mountain, Fortuna, Kingston Canyon, Gold Springs, Mount Baldy-Ohio, Confidence, Stateline, Henry, White Mountain, Newton, Beaver Lake, Rocky, Indian Peak, Washington, Wah Wah Summit, Blue Mountain, Roosevelt Hot Springs, Monroe, Broken Ridge, Star-North Star, Lincoln, Jarloose, Sulphurdale, Antimony, Marysvale, Pink Knolls, Granite, Antelope Springs, and the Nevada mining districts Atlanta, Silverhorn, Bristol, Highland, Ely Springs, Comet, Pioche, and Eagle Valley. There are many mineral systems in the belt but the majority fall under Climax-type, though the significant San Francisco district is porphyry Cu-Mo-Au and the Antimony district is Carlin-type.
Identified resources Identified resources of aluminum (alunite), uranium, manganese, potash (K2SO4), and molybdenum. Historical production of aluminum (alunite), antimony, beryllium (gemstone beryl), bismuth, copper, fluorite, gold, iron, lead, manganese, mercury, silver, sulfur, tungsten, uranium, and zinc.
Production Antimony: 105,000 tons Sb (Mills and Rupke, 2020); Marysvale: 1330797 lbs U, 1669 lbs V, 446 long tons iron, 3643 lbs Mn, 13,100 tons alunite, minor fluorite; San Fransisco: 44,142,000 lbs Cu, 405,484,000 lbs Pb, 46,775,888 lbs Zn, 44,920 oz Au, 19,642,000 oz Ag, 892 lbs WO3; >350,000 lbs Mn from Henry and Monroe districts, 3500 to 8500 lbs Mn from Newton and Blue Mountain districts; 160,000 lbs WO3 from Granite district, 25,000 to 85,000 lbs WO3 from Rocky and North Star districts, 300 to 2800 lbs WO3 from Lincoln, Bradshaw, Antelope Springs districts.
Status Past mining. Current carbonate replacement exploration at Deer Trail in Mount Baldy district; Development drilling at Pine Grove and Blawn Mountain.
Estimated resources Blawn Mountain is the largest alunite resource in the U.S. (Hall, 1978) with a Measured + Indicated resource of 812 Mt ore, 153 Mt of alunite = 77 Mt Al2O3 and 32 Mt K2SO4 (Kerr and others, 2017). Pine Grove is a significant Mo resource with 125 Mt at 0.17% Mo (Keith and others 1993); Marysvale Total resources as of 2006: 3,750,000 metric tons at 0.039% U3O8; Hall (1978) estimated resources of 2.12 Mt of ore @ >80% alunite in veins and 40.62 Mt of ore @ >23% alunite in replacement deposits. Approximately 1000 metric tons at 5% Mn (Blackbird). Potential for a few thousand tons at 25 to 35% Mn associated with Dry Canyon Claims (Crittenden, 1951). A subeconomic Inferred antimony resource is based on the channel samples near the old mines of about 14 million tons at an average grade of 0.75% Sb (Krahulec, 2018b).
Geologic maps Majority of the belt is covered by 1:24,000 mapping.
Geophysical data Inadequate Rank 3 (Marysvale) and 4 aeromagnetic coverage.
Favorable rocks and structures The overall area underlain largely by calc-alkaline igneous rocks and formed under extension parallel to the subduction direction and were bounded by transverse structures (“lineaments”) of the same trend that separate areas of different amounts and types of extension. The intrusive rocks probably have a volume considerably greater than that of the overlying volcanic rocks. The Blue Ribbon Lineament within the belt is a major crustal structure. The middle Cenozoic calc-alkaline rocks are overlain by an upper Cenozoic, fundamentally bimodal (rhyolitic and basaltic) volcanic rocks. Miocene, bimodal rift-related magmatism of 2 ages: ~ 22-18 Ma at Pine Grove and Blawn Mountain and ~ 12 Ma at Broken Ridge. Virtually all the mineral deposits are localized by intrusive rocks, which are regarded as being sourced from batholiths that largely underlie the belt. Basement rock is mainly a thick sequence of Neoproterozoic and Early Cambrian quartzose clastic sedimentary rocks and Middle Cambrian carbonates. Marysvale area characterized by hydrothermally altered porphyritic flows and tuffs (argillic alteration), siliceous sinter knobs associated with hot spring centers, vein and fissure-filling fluorite, manganese associated with veins, often in volcanic rocks, along the Sevier fault.
Deposits Emma-Albion (MRDS dep_id: 10088231, antimony), Marysvale Peak (MRDS dep_id: 10088078, alunite), Fluorite mine (MRDS dep_id: 10108867, fluorite), Dry Creek Manganese, Blackbird, Georgia mine (MRDS dep_ids: 10010342, 10015215, 10103846, manganese), Pine Grove (MRDS dep_ids: 10178769, 10042325), Wah Wah mine (Tasso mine; MRDS dep_id: 10276097), Pine Grove Summit prospect (MRDS dep_id: 10042324), Earth Science Alunite deposit (MRDS dep_id: 10010707, 10227548), Staats mine (MRDS dep_id: 10020440), Blawn Mountain (also known as NG Alunite Area).
Evidence from mineral occurrences MRDS; UMOS (Utah Geological Survey, 2021).
Geochemical evidence Pine Grove/Blawn Mountain: Multiple topaz rhyolite volcanic centers enriched in F, Li, Be, Mo, Sn, Rb, and Nb above an inferred granite pluton. Lindsey and Osmonson (1978) report the occurrence of very low-level geochemical anomalies for Be, Mo, and Sn associated with the rhyolite stock. Marysvale: Numerous fluorite (associated with U) and Mn veins (post-volcanic) throughout study area. The primary U ore occurs as pitchblende and jordisite containing geochemically anomalous As, Mo, Sb, Tl, and W in steeply pitching shoots within the veins and as breccia pipes and stockworks (Krahulec, 2018b). Broken Ridge: Anomalous Be, F, Sn, Nb, Mo, Cu, Zn, W, and Ba in altered rocks [cassiterite in panned concentrates] (Duttweiler and Griffitts, 1989). Mount Baldy-Ohio: Trace elements in Deer Trail massive sulfide ores average roughly 1.5% F, 1000 ppm As, 1000 ppm Sb, 100 ppm Te, 100 ppm Se, 50 ppm Mo, 10 ppm Bi, and 3 ppm Hg. Bullion Canyon: Four U.S. Geological Survey National Geochemical Database rock samples report over 100 ppm Mo (150, 300, 300, and 500 ppm) with one sample also having strongly anomalous Sn at 150 ppm.
Geophysical evidence The overall east-northeast trend of the belt includes some strongly east-trending aeromagnetic anomalies especially in the easternmost part of the belt (Rowley, 1998).
Evidence from other sources See Rowley (1998), Mills and Rupke (2020), Krahulec (2018b), Rowley and others (1998), Kerr and others (2017).
Comments This focus area is a large regional area that covers other focus areas that are smaller and more specific to local geology and mineralization. The intention of this focus area is to show regional potential, whereas the more specific focus areas provide vectoring for known mineralization. This area covers a number of mining districts with past producing critical mineral districts, but also a number of areas with what may be shallow expressions of deeper Climax-type systems. The Marysvale and surrounding districts have large alunite lithocaps, and Blawn Mountain is the largest alunite resource in the U.S., and the deeper Climax system hypothesis bears out in Pine Grove where a deep porphyry Mo resource has been identified. Other districts such as Granite have produced W from skarns around Oligocene-Miocene intrusions, and have indications of Mo potential (Krahulec, 2018b). This belt also contains notable porphyry Cu-Mo-Au deposits and potential deposits (for example, San Francisco); the Carlin-type Antimony district, Utah's largest antimony producer, is also included.
Cover thickness and description Variable; a porphyry Mo deposit may be present below the lithocap alunite deposit at Blawn Mountain and possibly below White Mountain and Broken Ridge. Concealed lithocap alunite may be present below younger mafic volcanic rocks and valley fill between Blawn Mountain and White Mountain. Marysvale: Uranium-fluorine mineralization occurred during late stages of protracted period of magmatism and in close association to rhyolite dikes (Cunningham and others, 2007). Potential magmatic connection suggests more potential exists beneath current exposure level.
Authors Stephanie Mills.
New data needs Regional aeromagnetics survey to create a regional interpretation of major structural, igneous, geophysical, and mineral trend; modern geochronology to better identify magmatic evolution and overprinting mineral potential; airborne hyperspectral would be useful in this area given the lithocap signature.
Geologic mapping and modeling needs Digitization and synthesis of existing maps to identify gaps.
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and radiometric surveys.
Digital elevation data needs Lidar variable. High-resolution lidar to define mine waste and tailings under reclamation for examination of mining waste potential.