Abstract

Phosphate deposits of igneous origin contributed some 19 million metric tons to the total world marketable output of phosphate rock of nearly 116 million metric tons in 1977. Most of this was produced in the USSR from the Khibiny Complex, Kola Peninsula. There was production at the neighboring Kovdor Complex and, in northern Europe, at Graengesberg in central Sweden. In Europe and the USSR, four other igneous complexes are known to be at various stages of development as commercial sources of phosphate.Most of the igneous complexes reviewed are characterized by assemblages of alkali-rich intermediate and ultrabasic rocks and carbonatite, the intrusions being generally of Siluro-Devonian or Carbo-Permian age, with the notable exception of the Precambrian Siilinjaervi carbonatite in central Finland. The complexes are also invariably located close to or within regional linear fracture zones.Associated with the igneous complexes in Europe and the USSR is an interesting variety of apatite-bearing rocks. In addition to the remarkable nepheline-apatite orebodies of the Khibiny Complex, there are other deposits, including apatite-forsterite and apatite-forsterite-magnetite rocks, as well as apatite-bearing carbonatites and, particularly, their weathering derivatives, which have their commercially important counterparts in other parts of the world. The phosphate mineral is invariably fluorapatite, with francolite occurring prominently in weathered zones. Other minerals of value or potential economic importance include magnetite, vermiculite, baddeleyite, bastnaesite, pyrochlore, chalcopyrite, fluorite, and barite.

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