Abstract

Apatite iron ores of the Kiruna type have been described from Painirova and Mertainen in northern Sweden. It is considered important that the ores are associated with volcanic rocks of a particular composition, i.e., iron-rich trachytes, which do not form part of a magmatic differentiation series. It is suggested that such a trachyte has been formed from the assimilation of iron-rich material during its formation. The ore, mostly in the form of magnetite, occurs in the host trachytes as disseminations, coarse aggregates, globular and spherical concentrations, and as a fracture infilling component. It is thought possible that the iron ores are the result of immiscibility aided by a high volatile content. The associated widespread brecciation in Painirova and Mertainen may have been caused by the mechanical effect of the iron-rich fluids in a differential stress field during consolidation of the trachyte.

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