Classification, Distribution and Uses of Ores and Ore Deposits - Metals and Society: An Introduction to Economic Geology - page 25

Table 2.5 Tectonic classification of ore deposits
I. Deposits at oceanic ridges (divergent plate margins)
Volcanogenic massive sulfide deposits (Cu, Zn)
Exhalative deposits (Zn, Cu, Pb, Au and Ag). e.g. Red Sea
Mn nodules (Mn, Ni, Cu, Co)
Cr, PGE, asbestos in ultramafic rocks
II. Deposits at convergent plate margins
Porphyry Cu-Mo deposits
Other base metal deposits (Cu, Pb, Zn, Mo).
Precious metals (Pt, Au, Ag).
Pb-Zn-Ag veins and contact metasomatic deposits
Other metals (Sn, W, Sb, Hg).
III. Deposits in cratonic rift systems
Deposits of Sn, fluorite, barite in granites
Evaporites in rift basins
Carbonatites containing Nb, P, REE, U, Th and other rare elements
IV. Deposits in intracontinental settings
Ni and PGE in layered intrusions
Ti in anorthosites
Iron-oxide Cu-Au deposits
Pb-Zn-Ag deposits in limestones and clastic sediments
Sedimentary Cu deposits
Ni, Al laterites
Diamonds in kimberlites
particularly when discussing the broad-scale distribution of ore deposits, as we do
in the following section. However, newer schemes in which the basic criterion is the
ore-forming process have largely replaced this type of classification (Table 2.6 ).
Although it might be argued that a rigorous classification should be based on
objective parameters that can be measured and quantified, and not on properties
that must be inferred, this is the classification we will use in this topic.
The scheme we have chosen has some disadvantages, and, as will be seen in
following chapters, it is sometimes not at all clear whether a certain deposit should
be placed in one box and not another, but it also has the great advantage that it
emphasizes that an ore deposit results from a normal geological process like those
that form common igneous or sedimentary rocks. It provides an incentive to move
the discipline from “gitologie” - a French term that can the translated as
“depositology”, a descriptive catalogue of ore deposits - to a modern interpretative
science. Finally, the approach provides a means of applying knowledge of geologi-
cal processes including concepts such as the partitioning of major and trace
elements between melt and crystal, the sorting of light from heavy minerals during
fluvial transport, or the stability of mineral phases in aqueous solutions, to develop
an understanding of how an ore deposit is created.