ПИРОКСЕНЫ МЕСТОРОЖДЕНИЙ ПОЛОСЧАТОЙ ЖЕЛЕЗОРУДНОЙ ФОРМАЦИИ КОЛЬСКОГО ПОЛУОСТРОВА

Abstract

Pyroxenes are among the most widespread minerals in rocks of banded iron formation (B1F) of Kola Peninsula, at the same time their compositions are strictly related to compositions of rocks. Pyroxenes arc not typical for hematite-magnetite quartzites; magnetite quartzitcs are characterized by wide presence of diopside-hedcnbcr-gitc (and ferrosilitc in zones of granulitc metamorphism and in apoquartzite contact hornfels); sulfide-magnetite quartzites and hydromermal veins contain hcdcnbergitc; magnetite-pyroxene, magnctite-calcite-dolomite and other metasomatic rocks, as well as hydrothcrmal veins in gneisses, include diopsidc. The pair of diopsidc and ens-tatite is characteristic for gneisses and apoamphibolitc schists metamorphosed in condition of the granulitc fades. Both these minerals arc typical for various gabbroids, where augite occurs also but more rarely. The distinct zoning of ore bodies: with hematite-magnetite quartzites in core, intermediate zone of magnetite quartzitcs and sulfide-magnetite quartzites in outer zone and at deep levels, was provided, probably, by some buffer reactions between iron minerals during alteration of hematite-magnetite quartzitcs by the reduced endogen fluid. At the regressive stage of iron ore-forming processes, there was developed the secondary acgirinc (aegirinc-augitc) due to the inverse buffer reactions.