1. Mineral Resources
  2. Online Spatial Data
  3. Earth MRI focus areas

Chemical weathering (unsaturated zone, in situ )

Chemical weathering systems operate in stable areas of low to moderate relief with sufficient rainfall to chemically dissolve and concentrate elements present in various rock types and mineral occurrences by the downward percolation of surface water in the unsaturated zone. Chemical gradients cause different elements to be concentrated at different positions in the weathering profile and at the water table. Bauxite, Ni-laterite, and carbonatite laterite are restricted to tropical climatic zones, others form in temperate and arid climates.
Color on map:

Deposit types

Name Commodities Critical minerals
Nickel-cobalt laterite Ni, Co Co, Mn, Sc
Bauxite Al Al, Ga, REE
Clay Kaolin Ga, Li, REE
Carbonatite laterite Nb, REE Nb, REE
Regolith (Ion adsorption) REE REE REE
Surficial uranium U U
Lacustrine carbonaceous uranium U U
Coal uranium U U
Lacustrine manganese Mn Mn
Supergene (and laterite) gold Au not-applicable
Supergene silver Ag unknown
Supergene lead Pb unknown
Supergene zinc Zn Ge, Ga, In
Supergene (and exotic) copper Cu Te, Bi
Supergene cobalt Co Co
Supergene PGE PGE PGE
Supergene manganese Mn Mn, Co
Supergene iron Fe Mn

References

Source: Hofstra, A.H., and Kreiner, D.C., 2020, Systems-Deposits-Commodities-Critical Minerals Table for the Earth Mapping Resources Initiative: U.S. Geological Survey Open-File Report 2020-1042, 24 p., https://doi.org/10.3133/ofr20201042.

List of Earth MRI focus areas with mineral system = Chemical weathering

37 focus areas match these criteria.

Focus area Region States Mineral Systems Deposit types Commodities
Hawaii bauxite Hawaii Hawaii Chemical weathering Bauxite (none)
Cretaceous weathering of Archean and Paleoproterozoic rocks North Central Minnesota; South Dakota Chemical weathering Regolith (Ion adsorption) REE (none)
Paleoproterozoic weathering beneath mature quartzites North Central Iowa; Minnesota; South Dakota; Wisconsin Chemical weathering Regolith (Ion adsorption) REE (none)
Turtle Mountains manganese North Central North Dakota Chemical weathering Supergene manganese (none)
Mitchell ore bed Northeast Vermont Chemical weathering Supergene iron; Supergene manganese iron
Salisbury Mining District Northeast Connecticut; Massachusetts; New York Chemical weathering Supergene iron; Supergene manganese iron
California-Oregon laterites Northwest California; Oregon Chemical weathering Nickel-cobalt laterite (none)
Fall Creek uranium area Northwest Idaho Chemical weathering Coal uranium coal; uranium
SE Idaho manganese Northwest Idaho Chemical weathering Supergene manganese (none)
Southwest Washington bauxite Northwest Oregon; Washington Chemical weathering Bauxite (none)
Washington bauxite district Northwest Washington Chemical weathering Bauxite (none)
Washington-Idaho clay Northwest Idaho; Washington Chemical weathering Clay (none)
Climax-Sweet Home and Leadville Area Supergene System Rocky Mountains Colorado Chemical weathering Supergene iron; Supergene manganese; Supergene silver iron; silver
Coal REE deposits Rocky Mountains Colorado Chemical weathering Regolith (Ion adsorption) REE coal
Cretaceous-Paleocene coals, underclays, and interbeds Rocky Mountains Montana; North Dakota; South Dakota; Wyoming Chemical weathering Clay; Coal uranium, Regolith (Ion adsorption) REE; Surficial uranium aggregate (coal clinker); clay; coal; molybdenum; uranium; yttrium
Arkansas Bauxite Region South Central Arkansas Chemical weathering Bauxite (none)
Central Kentucky Phosphate District South Central Kentucky Chemical weathering Regolith (Ion adsorption) REE phosphate
Manganese in Sedimentary Rocks South Central Missouri Chemical weathering Supergene manganese iron
Midwest Permian Ultramafic Dike District South Central Illinois; Indiana; Kentucky Chemical weathering Regolith (Ion adsorption) REE phosphate
Missouri Cheltenham Fireclay District South Central Missouri Chemical weathering Clay silica; oxide; clay
Ouachita manganese-cobalt district South Central Arkansas; Oklahoma Chemical weathering Supergene manganese (none)
Pennsylvanian Phosphate, Black Shale, Underclay South Central Alabama; Arkansas; Georgia; Illinois; Indiana; Iowa; Kansas; Kentucky; Maryland; Michigan; Missouri; Nebraska; New York; Ohio; Oklahoma; Pennsylvania; Tennessee; Texas; Virginia; West Virginia Chemical weathering Clay (none)
Alabama bauxite Southeast Alabama Chemical weathering Bauxite (none)
Alleghanian-NeoAcadian regolith Southeast Alabama; Georgia; North Carolina; South Carolina; Virginia Chemical weathering Regolith (Ion adsorption) REE (none)
Georgia bauxite Southeast Georgia Chemical weathering Bauxite (none)
Jumping Branch manganese Southeast North Carolina; South Carolina Chemical weathering Supergene manganese (none)
Neoproterozoic granitoids Southeast North Carolina; Virginia Chemical weathering Regolith (Ion adsorption) REE (none)
Neoproterozoic regolith Southeast Maryland; North Carolina; Tennessee; Virginia; West Virginia Chemical weathering Regolith (Ion adsorption) REE (none)
North Carolina fireclays Southeast North Carolina; South Carolina Chemical weathering Clay ilmenite; iron; monazite
Puerto Rico Ni-Co laterite Southeast Puerto Rico Chemical weathering Nickel-cobalt laterite (none)
South Carolina/Georgia kaolin deposits Southeast Georgia; South Carolina Chemical weathering Clay ilmenite; iron; monazite
Virginia bauxite Southeast Virginia Chemical weathering Bauxite (none)
Valley and Ridge manganese Southeast; South Central Alabama; Georgia; North Carolina; Pennsylvania; Tennessee; Virginia; West Virginia Chemical weathering Supergene manganese (none)
Borderlands Carbonate Replacement Deposits Southwest Arizona; New Mexico; Texas Chemical weathering Supergene manganese copper; gold; lead; silver
Little Florida Mountains district Southwest New Mexico Chemical weathering Supergene manganese (none)
Luis Lopez district Southwest New Mexico Chemical weathering Supergene manganese (none)
Silver City (Chloride Flat) manganese deposits Southwest New Mexico Chemical weathering Supergene manganese copper; gold; iron; lead; silver