Borderlands Carbonate Replacement Deposits

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

Information leading to the delineation of this focus area

Basis for focus area Paleozoic carbonates.
Identified resources Indicated resources and historical production for copper, gold, lead, manganese, and silver from the Patagonia Mountains, New Mexico and the Tombstone mining district area, Arizona (Keith, 1973; Chatman, 1994).
Production New Mexico: the Chloride Flat district (Silver City) produced 1.6 million long tons of Mn (11.7-16%). The Little Florida Mountains district produced 19,526 longs tons of ore with Mn grades from 19-21%, resulting in 21,393 long tons of Mn concentrates. Arizona: between 1879 and 1970 the Tombstone mining district produced 15,000 tons Cu, 22,500 tons Pb, 9,000 tons Mn, 590 tons Zn, 240,000 oz Au, and 30,000,000 oz Ag (Keith, 1973).
Status Past mining, active exploration.
Estimated resources The Hermosa project east of Sunnyside has >12 billion lbs Mn at grades >9% (Methven and others, 2018). Resources remain in New Mexico deposits.
Geologic maps Cetinay (1967), scale 1:12,000; Denney (1968), scale 1:24,000; Ferguson and others (2006), scale 1:24,000; Gilluly and others (1956), scale 1:62,500; Graybeal and others (2015), scale 1:48,000; Kluth (1982), scale 1:24,000; Moore (1993), scale 1:50,000; Pearthree and others (2006), scale 1:24,000; Rabasso Vidal (1971), scale 1:12,000; Nutt and others (1998, plate 1), scale 1:24,000.
Geophysical data Adequate Rank 2 aeromagnetic coverage and inadequate aeroradiometric coverage.
Favorable rocks and structures Carbonates for in situ oxidation of manganese; post-mineral basin deposits for exotic mineralization.
Deposits Arizona: Hardshell mine (MRDS dep_id: 10103551), Hermosa mine (MRDS dep_id: 10037094), Mowry mine (MRDS dep_id: 10109889); New Mexico: Chloride Flat, Little Florida Mountains, Lake Valley (MRDS dep_id: 10105528).
Evidence from mineral occurrences MRDS.
Geochemical evidence Psilomelane and braunite in the Hardshell mine occur with pyrolusite, manganite, and wad, with a gangue of Ag-bearing Pb minerals. McLemore and Nutt (2002) have samples >20% Mn with additional trace element chemistry for Lake Valley district.
Geophysical evidence Unknown.
Evidence from other sources Exotic manganese horizons have been documented east of Hermosa (Methven and others, 2018) towards San Rafael Valley. Manganese occurrences have been noted in the Canelo Hills (Chatman, 1994).
Comments Many more individual deposits and districts could fall into this category, but a focus on the Patagonia Mountains, Canelo Hills, and Tombstone due to known potential is suggested.
Cover thickness and description Variable, and in many cases unknown at present.
Authors Carson A. Richardson, Virginia T. McLemore.
New data needs Detailed geologic mapping of the eastern flanks of the Patagonia Mountains, Canelo Hills, San Rafael Valley, Tombstone area, and Courtland-Gleeson area.
Geologic mapping and modeling needs Detailed geologic mapping of the eastern flanks to the Patagonia Mountains, Canelo Hills, San Rafael Valley, Tombstone area, and Courtland-Gleeson area.
Geophysical survey and modeling needs High resolution, Rank 1 aeromagnetic and aeroradiometric coverage (proposal submitted).
Digital elevation data needs Lidar variable across a large area, with some complete, in progress, and inadequate.