Minerals, exsolution features and geochemistry of Fe-Ti ores of the Suwa?ki district (North-East Poland)

The Fe-Ti deposits of the Suwalki District (North-East Poland) are magmatic in origin and were formed as a consequence of differentiation of magma melt that served as a parent for mineralization in the host and ore rocks. Ore mineralization in the host rocks is of accessory and segregational type and was formed in conditions characterized by low content of interprecipitable liquid, relatively high oxygen fugacity and slow, continuous cooling. Nearly all Ti was removed from titanomagnetite above the solvus; hence, the true exsolution of ulvospinel was of minor importance in the host. Ore mineralization is characterized there by low content of impurities and low Fe/Ti ratio. High content of admixtures, extreme mineralogical and compositional variations, lack of geochemical cyclicity patterns in particular sections are typical of ore rocks. Both an increased amount of interprecipitable liquid and higher temperatures, stimulated by intermediate fO2, controlled the formation of ore rocks. The fO2 here remained credibly intermediate from early to late stages of mineral evolution. The formation of magma and minerals enriched in Fe-Ti, settling in a bottom part of the magma chamber, governed the formation of large ore bodies. Some other mechanisms such as filterpressing or immiscible segregation may be responsible for the formation of some discordant and concordant smaller ore bodies in the host. The disclosed partitioning pattern of major and minor elements in ore minerals of host and ore rocks suggests that titanum-free magnetite concentrate should be not practicable.