Rozsypiska minerałów ciężkich jako źródła pierwiastków rzadkich

Abstract

HEAVY MINERAL PLACERS AS A SOURCE OF RARE ELEMENTSSummaryHeavy mineral placers are one of the varieties of exogenic concentrations of rare elements. Here, the concentration of chemical elements takes place directly during the selective enrichment of the sedimentary formations in heavy minerals. Subdivisions of placer deposits are made according to various principles, e.g. according to origin, kind of minerals, cementation degree, exploitation technique, a.o. An interesting subdivision of placer deposits bas been presented by N. P. Hereskov, K. W. Potemkin, and A. N. Spicyn, who subdivide placers into contemporaneous, old, and old metamorphosed. These authors broadly discuss the contemporaneous placers, among which they distinguish three paragenetical complexes: placers of short transportation, placers of water streams, and placers of water basins. Each of these complexes consists of several genetical groups. As a rule, marine and river placers are thought to be most payable. However, at present old placers, usually covered with younger deposits, are more and more taken into account. According to numerous scientists, the development of placers depends upon the existence of regional weathering mantles. A development of such mantles is strongly affected by climatic factors, the best conditions being in both tropical and subtropical climates. The problem of distance of placers formed in water basins from the alimentation area seems to be very interesting, too. Ample data obtained by numerous authors allow us to assume that the distance of such basins from the direct alimentation source may not be greater than approximately hundred fifty – two hundred kilometers. Placer deposits are susceptible to destructive factors and can rarely be preserved, if not covered with a protective mantle. The search for buried placer deposits is one of the most difficult tasks requiring a detailed palaeogeographical and facial analyses. To the most interesting in Poland belong placer deposits formed on the Baltic Sea beach. These placers are first of all supplied with material from the destructed sea shores. Being not persistent, they are continuously regenerated and formed at sea shore intervals where is a considerable deficit in mineral materials. Lacustrine placers are not so rich as marine ones. Probable use of both types of placers depends mainly upon the profitableness of concentration technique, and upon the complex recovering of all valuable minerals. No doubt, alluvial placers of flood plains and of mountain torrents are promising ones. Prospections of old placers present considerable difficulties, but works of this kind should be conducted on a large scale. All the old sea shore formations like conglomerates, sandstones and sand are everywhere potential source of heavy minerals.