Classification, Distribution and Uses of Ores and Ore Deposits - Metals and Society: An Introduction to Economic Geology - page 26

2.2.1 A Classification Based on the Ore-Forming Process
The list of headings in Table 2.6 overlaps the list of geological processes that would
be found in any introductory geology text. We see for example that magmatic
processes form some deposits, and sedimentation or surface weathering form
Table 2.6 Genetic classification of ore deposits
1. Magmatic: ores that form by the accumulation of minerals that crystallize directly from magma.
(a) In mafic and ultramafic rocks
• Chromite and platinum-group elements (PGE) in large layered intrusions (Bushveld in
South Africa, Great Dyke in Zimbabwe)
• Chromite in ophiolites (Turkey)
• Cu-Ni-Fe sulfide in the layered intrusions (Sudbury, Noril'sk)
• Sulfide Ni-Cu-Fe in komatiitic lavas (Kambalda)
• Diamonds in kimberlites
(b) Associated with felsic intrusions
• Cu ore in carbonatites (Phalabora)
• REE, P, Nb, Li, Be etc in pegmatites
2. Deposits associated with hydrothermal fluids: metals are mobilized within and precipitated
from hot aqueous fluids or various origins
(a) Cu-Mo-W deposits in granitic intrusions
• Deposits of the type “porphyry” (porphyry copper) (USA, Chile, Philippines)
(b) Epigenetic deposits - minerals in veins or replacing host rocks
• Cu, Zn, Pb, Mo, Ag, Au ores related to granitic rocks (Butte, Potosi)
• “orogenic” gold deposits (Abitibi, Canada, Yilgarn, Australia)
• Ag-Ni-Co-As-S deposits (Potosi, Bolivia; Cobalt, Canada)
(c) Volcanogenic massive sulfide (VMS) deposits
• Precambrian deposits (Noranda, Canada)
• Modern (Kuroko, Japan)
(d) Deposits unrelated to magmatic activity
• Pb-Zn ore in limestone (Mississippi Valley Type, USA)
• Uranium deposits (Athabasca, Canada; Colorado, USA)
3. Sedimentary deposits: concentrations of detrital minerals or precipitates
(a) SEDEX - Pb-Zn sulfides in shales (Mt Isa, Australia; Sullivan, Canada)
(b) Cu ores in sandstones (Copperbelt of Central Africa; Kupferschiefer, Poland)
(c) BIF (banded iron formations) (Australia, Brazil, Canada)
(d) Evaporites, phosphatites, Li-rich brines, limestone
(e) Placer deposits
• Placer gold in rivers (California, Australia, Brazil)
• Ti, Zr in beach sands (Australia)
• Diamonds in sand and gravel (South Africa)
4. Deposits related to weathering
(a) Al laterites - bauxite (Jamaica, France, Australia)
(b) Ni laterite (New Caledonia)
(c)“Supergene” ore enrichment
5. Metamorphic deposits
(a) Deposits in skarn (China, Scandinavia, USA)