More than 90 percent of the titanium minerals currently produced come from magmatic ilmenite deposits and from young shoreline placer deposits. This means that the two geologic processes most directly responsible for economic titanium-mineral deposits are (1) the accumulation of dense oxide-rich liquids immiscible in cooling magmas of ferrodioritic to gabbroic composition, and (2) the interference between deposition and entrainment in the enrichment of dense minerals on the upper swash zones of beaches (and removal of some concentrates to eolian environments). Both processes are essentially mechanical; i.e., chemical remobilization of titanium does not form its major ore deposits.
Both processes also require precursor conditions that ensure that titanium is present predominantly in the form of oxide minerals. In magmatic deposits, these are physical and chemical conditions that favor titanium-oxide over titanium-silicate minerals. In sedimentary deposits, these conditions are a combination of proper source rocks, weathering history, and sedimentary conduits, all necessary to permit the supply of favorable minerals and prevent their dilution with unfavorable ones.
Some titanium-mineral production currently comes from fluvial placer deposits (Gbangbama, Sierra Leone) and from deeply weathered alkalic pyroxenites (Tapira, Brazil). In addition, several other deposit types could well become economic in the near future: (1) rutile from eclogites, (2) rutile from contact-metasomatic zones of alkalic anorthosites, (3) perovskite from alkalic pyroxenites, and (4) rutile byproduct from porphyry Cu-Mo deposits; detrital titanium-mineral deposits could be exploited (5) on continental shelves, (6) in Pleistocene glaciolacustrine deltas, or (7) in older, semiindurated beach deposits. If young shoreline placers are depleted, these other deposit types may become important.