Sedimentary Ores


Basin Type

Relationship to mineralization

Role of mudstones

Process of mineral precipitation

Source of metals

Fluid temperature/ Receiving water type

Metals carried in hydrothermal fluids rising from below

Pb, Zn, Ba

Marine Rift

High heat flow, vertical pathways, sufficient accommodation for marine flooding; seawater provides source of S

Thick, organic-rich mudstones provide thermal blanket to allow high temperatures to develop

Pb and Zn precipitate where rapidly-rising fluids intersect permeable strata or exit to seafloor; Ba precipitates distal to metals

Organic-rich shales deeper in the sedimentary basin




Continental Rift

Arid climate forms red beds and evaporites;  vertical tectonics  provide high relief, high heat flow, and pathways for fluids

Hydraulic separation of oxidizing groundwater (high in Cu) from reducing groundwater (high in S)

Cu precipitates where fluids mix around paleo-highs

Mafic volcanic rock fragments in footwall aquifer




Peripheral Foreland

High water flux from accretionary prism caused by compression in subduction zone

Organic matter reduces sulfate to sulfide, which dissolves BaSO4 and releases Ba++ to solution

Ba precipitates where exiting fluids mix with SO4-rich seawater

Organic-rich shales deeper in the sedimentary basin



Metals carried in seawater at low temperature


Passive Margin or Strike-slip

Low sedimentation rates; basin geometry that restricts circulation

Reducing muds in deep water export Mn to redox boundary where Mn oxides precipitate

Mn accumulates where anoxic-oxic boundary intersects the seafloor; commercial grade if clastic/carbonate dilution is low

Clastic sediments deposited below the chemocline in H2S-rich water or volcanic vents in deep water



U, Mo

Retroarc Foreland or Passive Margin

Very slow sedimentation rates; restricted circulation

Slowly-deposited muds provide host for abundant organic matter

Metals from seawater absorb slowly onto organic matter

River water flux of metal ions in solution