Basin and Range Laramide and Jurassic W veins and skarns

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

Information leading to the delineation of this focus area

Basis for focus area All tungsten occurrences from all sources were plotted and locations were compared with mapped distributions of Laramide and Jurassic intrusive rocks. Additional units were selected based on knowledge of the Reef mine and the area of mines around the Texas Canyon pluton, Arizona, and based on proximity and examination of records. Small clusters of relatively important past-producer mines were then enclosed into small district-sized groups, particularly if there was record of any ore left in place when mines closed. Three such small district-size groups were then selected to be parts of this focus area.
Identified resources Historical production of gold, silver, and tungsten.
Production Pinal County, Arizona: Pure Gold mine, near Oracle, produced "the equivalent of 11,815 stu of WO3 in 1943-44" (Dale, 1959, p. 52); Morning Star claim produced in excess of 6000 stu of WO3, operating sporadically between 1913 and 1953 (Dale, 1959, p. 61); Old Maudina mine produced at least 3000 stu WO3 between 1908 and 1916 (Dale, 1959, p. 52). Cochise County, Arizona: Reef (Exposed Reef, Tungsten Reef) mine, near Sierra Vista, produced a total of 11,345 stu of WO3 in three periods of mining: 1916-18, 1934-42, and 1955-56 (Dale and others, 1960, p. 29). The Primos group of claims, near Dragoon, are "estimated to have produced several thousand units of WO3" (Dale and others, 1960, p. 46) from quartz-wolframite veins; Tungsten King mine, located on the north flank of the same Texas Canyon pluton, produced at least 4000 lbs of scheelite-rich concentrates (somewhat less than 200 stu WO3 depending on concentrate grade). Several tens of additional mines in both states produced similar or smaller amounts, with production principally centered around the years of WWI and WWII.
Status Past mining.
Estimated resources Small resources at a variety of grades were left when mines closed. Some mines have obvious potential for additional undiscovered resources, but with no examples known with potential for truly large tonnages among Laramide and Jurassic examples.
Geologic maps Cooper and Silver (1964, plates 1 and 13), scale 1:31,680 and 1:600, respectively; Richter and Sharp (1984), scale: 1:250,000.
Geophysical data Adequate but unpublished aeromagnetic coverage; inadequate aeroradiometric coverage. The area is entirely covered by aeromagnetic and aeroradiometric coverage collected on a 1000-foot grid, so Rank 1, but the coverage is unpublished. USGS can study it, but can't publish the coverage, only a map derived from it, and cannot give coverage to the states. Other than that, inadequate coverage.
Favorable rocks and structures Clearly, the Laramide and Jurassic plutons of the region are more prone to produce economic porphyry Cu deposits than WO3 deposits, but a few areas are divisible that instead lean toward WO3 production. Included in the latter are (1) the Huachuca Mountains southwest of Sierra Vista, Arizona, the area of the Reef mine and several other very small ones arrayed around a Jurassic pluton, and (2) the west flank of the Baboquivari Mountains in the Tohono O'odam Indian Reservation, also an area of Jurassic intrusives but with associated small scheelite skarn shows. The Little Dragoon Mountains near Johnson Camp porphyry copper mine, and several additional areas have both porphyry Cu-related mineralization and WO3 mineralization in close proximity to one-another.
Deposits Reef mine (MRDS dep_id: 10109798), Pure Gold (MRDS dep_id: 10039523), Morning Star (MRDS dep_id: 10283583), Old Maudina (MRDS dep_id: 10138041), Tungsten King mine (MRDS dep_id: 10039394), Three Musketeers mine, Lucky Strike mine (MRDS dep_id: 10027019), Samsel mine (MRDS dep_id: 10026807).
Evidence from mineral occurrences MRDS.
Geochemical evidence Unknown.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments There are many example mineral occurrences of Laramide or Jurassic WO3 mineralization, but none appears to have potential for enough tonnage to make it a worthwhile exploration target. Minor scheelite also occurs in probably all of the mined copper skarns in Arizona and New Mexico. Private companies have investigated the possibility of secondary recovery of WO3 from deposits such as the Johnson Camp mine. Tailings were found to average around 0.1% WO3. Early tests using flotation recovered 80% of the WO3 and made a concentrate that graded 1.38% WO3, but a far more thorough 1957 test found that neither gravity, nor flotation methods, nor both used in sequence would make an economic recovery of the scheelite. It was too fine grained to gravity concentrate, and flotation could produce a concentrate that doubtfully would assay higher than 20% WO3 (Dale and others, 1960, p. 52-53).
Cover thickness and description Highly variable cover with basins having cover perhaps as great as 14,200 feet (in the Higley Basin east and south of Phoenix).
Authors Timothy S. Hayes, Lukas Zurcher.
New data needs Size of targets probably do not justify much additional data collection. It might be a more productive to make a new investigation of secondary recovery of scheelite from the copper skarn ore being processed in at least three operating copper mines after some [?70 years of progress on scheelite flotation technology] since the earlier tests.
Geologic mapping and modeling needs None requested at this time.
Geophysical survey and modeling needs None requested at this time.
Digital elevation data needs Lidar coverage available locally within the focus area.