2013

Compositional peculiarities of ilmenite from different types of magmatic rocks

Alymova N.V., Vladykin N.V.

Ilmenite widely occurs in the rocks of different genesis (alkaline rocks, kimberlites, granites, etc.). Its composition, structure and features are well studied. At the same time, the researchers studying alkaline rocks provide scarce information on morphology, compositional features and contents of the given mineral in studied rocks (Ivanyuk et.al., Yakovenchuk et al., 1999; Arzamastsev et al., 1988). Ilmenite has not been thoroughly studied yet in the alkaline rocks of the Northern Baikal area.

In the alkaline rocks studied by us the mineral includes ilmenite of isomorphous series of solid solutions FeTiO3-MgTiO3-MnTiO3  and demonstrates the increased content of TiO2 (41,14-59,3 wt.%), FeO total (26,06-52,35 wt.%), MnO (5,19-28,68 wt.%), Nb2O5 (0,32-4,74 wt.%). Ilmenite contains insignificant amount of hematite component (1,08-13,62 wt.% Fe2O3) as opposed to ilmenites from kimberlites (Fe2O3 to 40 wt.%) and granites (Fe2O3 to 22,21 wt.%). Ilmenites from the Burpala massif (Northern Baikal Area) are specific in terms of contents of elements-impurities, Al2O3 content is not more than 0,8 wt.% and  Cr2O3- 0,1 wt.%, that significantly differs it from ilmenites of other rocks. Low magnesium content is a characteristic feature of ilmenites from alkaline rocks and granites (MgO up to 1 wt.%) that differs it from ilmenite of kimberlites in which MgO content reaches 15 wt.% (Alymova et al., 2006). Another specific features of the Burpala ilmenite is high MnO content ( to 28.69%). However, the pegmatites of the Burpala massif contain the end member of the isomorphous series- pirophanite (MnTiO3). It shows the increased TiO2 (46,94-62,41 wt.%), MnO (36,07-42,92 wt.%), Nb2O5 (0,74-5,53 wt.%) contents. The chemical composition of ilmenites is a typormophic feature of magmatic rocks of different composition (from ultra-basic to granites).