Chapinskii

About 50 small bodies of alkaline ultramafic rocks occur as pipes, dykes and small volcanic fields. The dykes vary from 0.3 to 30 m thick and up to 600 m in length; the pipes have diameters of 25 to 460 m. The volcanic fields extend over 1x2 and 1x3 km with the volcanics up to 70 m thick. Both flows and tuffs occur but all are much altered. The dominant rock type is low alkali basalt but micaceous picrites are also present. The latter rock consists of altered olivine, which comprises as much as 40% of some flows, altered clinopyroxene with relicts of titanaugite, biotite and phlogopite. Volcanic glass is replaced by carbonate, serpentine, chlorite and iron hydroxides. A suite of heavy minerals consists of ilmenite, perovskite, apatite, zircon and, from lavas, garnet, baddeleyite and chromite.