Marine chemocline (bathtub rim)

Marine chemocline systems operate where basin brines disharge into the ocean. Consequent increases in bioproductiviy produce metalliferous black shales. Changes in ocean chemistry (oceanic anoxic events) and development of chemoclines result in chemical sedimentation of phosphate and Mn and Fe carbonates and oxides.
Color on map:

Deposit types

Name Commodities Critical minerals
Black shale Stone coal, petroleum, V, Ni, Mo, Au, PGE V, Re, PGE, Cr, U
Phosphate Phosphate fertilizer F, REE, Cr, U
Iron-manganese Fe, Mn, Co Mn, Co
Superior iron Fe not-applicable

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 = Marine chemocline

25 focus areas match these criteria.

Focus area Region States Mineral Systems Deposit types Commodities
Triassic Phosphate REE Alaska Alaska Marine chemocline Phosphate phosphate fertilizer; uranium
Upper Mississippian (Visean) Phosphate REE Alaska Alaska Marine chemocline Phosphate phosphate fertilizer; uranium
Chamberlain district North Central South Dakota Marine chemocline Iron-manganese iron
Manganese (Mn) in iron-formations North Central Michigan; Minnesota; Wisconsin Marine chemocline Iron-manganese iron
Mesoproterozoic Phosphate North Central Michigan; Wisconsin Marine chemocline Phosphate phosphate fertilizer; uranium
Upper Ordovician Phosphate (Rawtheyan and Richmondian) North Central Alabama; Iowa; Illinois; Indiana; Kentucky; Michigan; Minnesota; Missouri; Ohio; Oklahoma; Tennessee; Wisconsin Marine chemocline Black shale; Iron-manganese; Phosphate copper; gold; iron; molybdenum; petroleum; phosphate fertilizer; stone coal; uranium
Aroostook County manganese Northeast Maine Marine chemocline Iron-manganese iron
Blue Hill manganese prospects Northeast Maine Marine chemocline Iron-manganese iron
Bowers Mountain black shale Northeast Maine Marine chemocline Black shale copper; gold; molybdenum; petroleum; stone coal; uranium
Devonian Marcellus black shale Northeast Kentucky; Maryland; New York; Ohio; Pennsylvania; Virginia; West Virginia Marine chemocline Black shale copper; gold; molybdenum; petroleum; stone coal; uranium
Dover-Foxcroft manganese prospect Northeast Maine Marine chemocline Iron-manganese iron
Greenfield manganese prospects Northeast Maine Marine chemocline Iron-manganese iron
Penobscot black shale Northeast Maine Marine chemocline Black shale copper; gold; molybdenum; petroleum; stone coal; uranium
Heath Formation— Cox Ranch Member Northwest Montana Marine chemocline Black shale copper; molybdenum; petroleum; stone coal; uranium
Phosphoria Formation Rocky Mountains Colorado; Idaho; Montana; Nevada; Utah; Wyoming Marine chemocline Black shale; Phosphate copper; gold; molybdenum; petroleum; phosphate fertilizer; stone coal; uranium
Batesville cobalt-manganese District South Central Arkansas Marine chemocline Iron-manganese iron
Fayetteville Shale; Upper Mississippian (Serpukhovian) Phosphate South Central Arkansas; Missouri; Oklahoma Marine chemocline Phosphate phosphate fertilizer; uranium
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 Marine chemocline Black shale; Phosphate copper; gold; molybdenum; petroleum; phosphate fertilizer; stone coal; uranium
Upper Devonian Phosphate South Central Alabama; Arkansas; Georgia; Illinois; Indiana; Iowa; Kentucky; Maryland; Michigan; Mississippi; Missouri; Ohio; Oklahoma; Pennsylvania; Tennessee; Virginia; West Virginia Marine chemocline Black shale; Iron-manganese; Phosphate copper; gold; iron; molybdenum; petroleum; phosphate fertilizer; stone coal; uranium
Middle Devonian REE phosphates Southeast West Virginia Marine chemocline Phosphate phosphate; uranium
Miocene-Pliocene phosphate strata Southeast Florida; Georgia; Maryland; North Carolina; South Carolina; Virginia Marine chemocline Phosphate phosphate; uranium
Gibellini and Carlin Vanadium Southwest Nevada Marine chemocline Black shale copper; gold; molybdenum; petroleum; stone coal; uranium
Lower Mississippian (Osagean-Meramecian) Phosphate Southwest Utah Marine chemocline Phosphate phosphate fertilizer; uranium
Middle-Late Miocene Phosphate Southwest California Marine chemocline Phosphate phosphate; uranium
Three Kids district Southwest Nevada Marine chemocline Iron-manganese iron