Heath Formation— Cox Ranch Member

Region West, Northwest
States
Mineral systems
Deposit types
Commodities
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Black shales of the Mississippian Heath Formation, organic-rich black shale (Cox Ranch Member). Critical element potential based on Derkey and others (1985).
Identified resources The Heath Formation is recognized as a prospective tight oil play. Gypsum was produced from evaporite members of the Heath Formation.
Production Unknown.
Status Past mining for gypsum from carbonates in the Heath Formation.
Estimated resources Unknown.
Geologic maps Vuke and others (2007), scale 1:500,000.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Favorable rock types are thinly interbedded gray to black mudrock and carbonate strata capped by either coal or gypsum. Black mudrock has high contents of Zn, V, Mo, and other metals (Dumoulin and others, 2017).
Deposits Heath prospect (MRDS dep_id: 60000745).
Evidence from mineral occurrences MRDS.
Geochemical evidence Analyses of the Cox Ranch oil shale bed show ≤28% TOC, 5140 ppm Zn, 1910 ppm V, 1590 ppm Mo, and 509 ppm Ni (Dumoulin and others, 2017). See also Derkey and others (1985).
Geophysical evidence None.
Evidence from other sources None.
Comments Investigated as potential mineable oil shale in the 1970s and 1980s.
Cover thickness and description Outcrops along Big Snowy and Little Belt Mountains in central Montana.
Authors Jay A. Gunderson.
New data needs Geophysics, sampling and geochemical analyses of Heath Formation to identify extent of critical mineral occurrence. Detailed mapping of Cox Ranch Member of Heath Formation.
Geologic mapping and modeling needs More detailed geologic mapping of mineralized areas and related intrusions.
Geophysical survey and modeling needs High resolution aeromagnetic and radiometric coverage.
Digital elevation data needs Lidar adequate.