Lower Colorado River IOCG

Region West, Southwest
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Outline of known areas of IOCG related mineralization, occurrences, and related alteration from Barton and others (2011).
Identified resources Historical production of iron at Eagle Mountain mine (California), with up to 3% Co in pyrite (Force, 2001).
Production Eagle Mountain mine produced 21,600,000 tons with average grades of 45.2% Fe, 0.072% P, 15.3% Si, 0.629% S (DuBois and Brummett, 1968; Force, 2001).
Status Past mining in California; exploration in Arizona.
Estimated resources Sugarloaf Butte has 256,000 st with 55% natroalunite (Sawyer and others, 1992).
Geologic maps Horton and others (2017), scale 1:500,000.
Geophysical data Partly adequate (25%) aeromagnetic coverage and inadequate aeroradiometric coverage.
Favorable rocks and structures Carbonate-bearing rocks near Jurassic igneous centers with associated calc-silicate alteration (i.e., iron skarns, cf., Einaudi and others, 1981) and magnetite(-apatite-actinolite) veins and breccia hosted in Jurassic igneous rocks.
Deposits Eagle Mountain mine (MRDS dep_id: 10064461).
Evidence from mineral occurrences Unknown.
Geochemical evidence Sodic-calcic alteration, presence of evaporites, known iron-rich mineralization in California.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments This iron-rich mineralization is much better documented in southern California due to past production, whereas the Arizona occurrences are more poorly studied and understood. Basic geologic mapping of much of western Arizona is needed.
Cover thickness and description Variable from place to place.
Authors Lisa L. Stillings, Albert H. Hofstra, David A. Ponce, Carson A. Richardson, Erica Key.
New data needs Detailed geologic mapping of ranges in western Arizona/eastern California, geochemical analyses to examine gains and losses and fluids.
Geologic mapping and modeling needs Many of these locales are poorly documented with historical production/exploration in the 1940s-1950s (dominantly California).
Geophysical survey and modeling needs High-resolution, Rank 1 aeromagnetic and radiometric surveys.
Digital elevation data needs Lidar inadequate.