Host-rock origin of magnetite in pyroxene skarn and gneiss and its relation to alaskite and hornblende granite

If pyroxene skarns were formed from iron carbonates less siliceous than but otherwise similar to those of Lake Superior, an outside source for iron and other elements of the skarns and associated magnetite deposits is unnecessary. 'Volume losses created by the formation of dense minerals and by subtraction of some elements in released fluids provide openings in which magnetite can be concentrated.' Biotite and hornblende in gneiss are a potential source of fluids for catalysis and migration of elements. 'Fluids squeezed out of tight areas and into more open, crushed, and sheared rocks may cause melting and formation of hornblende granite and alaskite.'

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