Acta Musei Moraviae

Minerals containing Cr, V, Ni and Co in basic and ultrabasic rocks from the Pohled quarry near Havličkův Brod (Moldanubian area of the Bohemian Massif, Czech Republic)

Granitic pegmatites and hydrothermal veins occurring in the Pohled quarry (Moldanubian area of the Bohemian Massif) contain elevated contents of Cr, V, Co, and Ni although they are hosted by granites and paragneisses with low concentrations of these elements. Therefore, it was hypothesized that these elements could have been sourced from basic and ultrabasic rocks forming small xenoliths (dunite, serpentinite, hornblendite, a garnetic metaultramafite) or up to 10 m thick lenticular bodies (“amphibolite”) enclosed in paragneisses of the Pohled quarry. We studied these rocks mineralogically with an emphasis to mineral phases containing the above-mentioned transitional metals. A wide suite of accessory minerals containing Cr, Co, and Ni as major constituents was identified: chromspinelides (spinel, chromite), aucherite, nickeline, pentlandite, violarite, polydymite, cobaltite, millerite, and westerveldite. In addition, these elements and/or V are minor constituents of silicate minerals (garnet, clinopyroxene, amphiboles, olivine, talc, phlogopite, chlorite, titanite), oxide minerals (magnetite, ilmenite), as well as common sulfides (monoclinic and hexagonal pyrrhotite). The results confirm that these ultramafic rocks really could act as a fertile source of Cr, Ni, and Co for pegmatite and hydrothermal processes in the area of the Pohled quarry. In contrast, the possible source of V remains questionable, because V is present in small concentrations in a small number of minerals only (up to 0.35 wt. % V₂O₃, mainly in titanite and chromspinelides) in the studied rocks.