A FINDING OF WEATHERING CRUST AT THE INTERFORMATIONAL CONTACT IN THE UPPER PECHORA AREA, NORTHERN URALS

Abstract

While carrying out prospecting work at the upper reaches of the Pechora River in 2002, V.S. Ozerov, a leading geologist at the Komigeologiya Joint-Stock Company, found a contact of ancient, presumably Riphean carbonate rocks with quartzitic sandstone of the Lower Ordovician Telpos Formation in a rocky outcrop. This outcrop extends along the azimuth 215° NW for more than 500 m along the left wall of the Sastumnel Creek valley, a large tributary of the Yelma River 3.75-4.30 km upstream of the creek mouth. Ozerov described the carbonate rocks as the Sastumnel Sequence. It is known from the experience of geological work in the near-Polar Urals that the interformational basement/cover contact is an ore-bearing zone. The finding of such a contact in the poorly exposed, forest-covered territory of the northern Urals is of great scientific and applied interest. Therefore, we examined the rocks in the contact zone in the summer of 2003. We sampled these rocks, examined 50 thin sections under a microscope, and analyzed the mineral composition in heavy mineral fractions (25 samples). In addition, 12 chemical analyses and 16 carbonate phase analyses were recalculated for the normative mineral compositions.