Red Mountain, Arizona

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

Information leading to the delineation of this focus area

Basis for focus area Lithocap alunite at the surface, porphyry Cu mineralization intersected by drilling. Modified outline of the Patagonia Mountains was used for the focus area. This area includes both the Red Mountain and Sunnyside porphyry Cu systems, with large exposed advanced argillic lithocaps at the surface. Additional mineralization in the vicinity includes carbonate replacement deposits (for example, Hermosa) with significant, economic Mn. Numerous small historical mines in the area.
Identified resources Identified resources of silver, manganese, and zinc. Historical production of copper, gold, lead, silver, and zinc.
Production Historical production from Three R, Flux, Washington Camp, Trench, Mowry, and World's Fair mines with total production of 1.87 Mt with 0.9% Cu, 3% Pb, 3.5% Zn, 3.5 oz Ag/t, and <0.001 oz Au/t (Vikre and others, 2014).
Status Active exploration and project advancement. South32 is working on the Hermosa project; other active companies in the area include Bronco Creek Exploration (EMX Royalty), Barksdale Capital Corporation/Regal Resources.
Estimated resources The advanced argillic lithocaps at Red Mountain and Sunnyside have approximate volumes of 0.9 and 2.7 km3. Bodnar and Beane (1980) reported 10 to 15% alunite and 10 to 20% kaolinite for the advanced argillic alteration in one drill hole. This would correspond to 200 to 400 billion lbs Al at Red Mountain and 600 billion to >1 trillion lbs Al at Sunnyside. The Hermosa project east of Sunnyside currently being advanced by South32 has a combined Measured, Indicated, and Inferred mineral resource of 65.3 Mt @ 2.2% Zn, 2.3 oz/t Ag, and 9.5% Mn; there is an estimated >12 billion lbs Mn at grades >9% Mn (Methven and others, 2018).
Geologic maps Graybeal and others (2015), scale 1:48,000.
Geophysical data Adequate Rank 2 aeromagnetic and inadequate aeroradiometric coverage.
Favorable rocks and structures Late Cretaceous to early Paleogene ("Laramide") plutonic rocks.
Deposits Red Mountain mine (MRDS dep_id: 10048337), Sunnyside Mine Group (MRDS dep_id: 10048335), Ventura Mine Group (MRDS dep_id: 10037098), Four Metals mine (MRDS dep_id: 10037102), Hardshell mine (MRDS dep_id: 10103551), Three R Group (MRDS dep_id: 10046338), Flux mines (MRDS dep_id: 10048344), Trench and Josephine Mine Group (MRDS dep_id: 10048334), Mowry mine (MRDS dep_id: 10109889), World's Fair mine (MRDS dep_id: 10109888), Hermosa mine (MRDS dep_id: 10037094).
Evidence from mineral occurrences MRDS; Vikre and others (2014); Methven and others (2018).
Geochemical evidence NURE geochemistry.
Geophysical evidence Unknown.
Evidence from other sources None.
Comments The Patagonia Mountains contain diverse mineralization and represent a relative rarity in Arizona in that the area is largely upright and the structural deformation is apparently relatively minor. Although the area has been and continues to be subject to minerals exploration, a systematic mapping of the area could yield new perspectives for potential exploration targets as the full extent of the structural deformation could be documented and assessed.
Cover thickness and description Cover rocks include Triassic-Jurassic volcanic and sedimentary rocks, Cretaceous volcanic and sedimentary rocks, and Paleozoic sedimentary rocks, which can also all serve as host rocks.
Authors Albert H. Hofstra, Laurel G. Woodruff, David A. Ponce, Carson A. Richardson.
New data needs Detailed geologic mapping, aeroradiometric survey.
Geologic mapping and modeling needs Geologic mapping of the plutonic rocks and adjacent wall-rocks with alteration overlay, with particular emphasis on structural geology.
Geophysical survey and modeling needs Has Rank 2 aeromagnetic coverage, needs high resolution Rank 1 aeroradiometric coverage.
Digital elevation data needs Lidar in progress.