Niektoré špecifické príklady chemického zvetrávania karbonátových hornín Belianskych Tatier

Abstract

The Belianske Tatry Mts. represent one of the typical and valuable karst regions in the Western Carpathians. In the present climatic conditions, the karst relief is under intensive modeling and denudation by erosion factors in which karst processes hold an important place. Karst creation is in principle chemical erosion in which oxidation, hydrolysis, hydration, and other chemical reactions cause partial or total weathering and erosion of rocks depending on rock structure under certain physical conditions. In the Belianske Tatry Mts., not only Mesozoic rocks from the Triassic, Jurassic, and early Cretaceous periods but also mid Triassic Ramsaus dolomites are affected by weathering and erosion processes. Chemical weathering of Mesozoic carbonates is supported by reaction of sulfuric acid with pyrite and markasite in the zone of hypergenesis. This process leads to developmerit of several types of secondary chemoge-nous minerals. The newly detected minerals belong to the group of sulfates, oxides, and phosphates according to the Belechtin's classification. Limonite (α-FeOOH) represents the group of oxides. Limonite has been found in kar-sted holes opened by mining in quarry in the Tatranska Kotlina. Geothite was proved by the rontgenodiffractive method. The mineral was precipitated in the cavity karst soils in the cavities of carbonate-dolomite complex in the Buja-ci Mt Similar fragments of aggregates were detected on the mountain ridge in the area of the Predne Jatky Mt. From the secondary sulfates, gypsum (CaSO₄ . 6H₂0) is the most common. It is found in the two different geological positions. On the first place, it creates crystalline forms of water white or white color in the high mountain Alabastrova cave. Hypotheses regarding its origin are still unclear. On the second place, quantitatively greatest amount of secondary gypsum was detected around the Stary Mt. Hexahydrate (MgSO₄ . 6H₂0) was found in the quarry in the southern edge of the Palenica Mt It occurs in the thin layers of white and pale grey color, opaque lustre, covering weathered rocks. Sulfates in origin are directly and closely tied to chemical processes in the acidic rock base. Secondary phosphates are represented the most probably by carbonatehydroxil apatite -dahllite [Ca₅(PO₄,CO₃)3(OH)]. It was determined by the analogous occurrence in the cave V Zaskoci in the Nizke Tatry Mts. published by Cilek and Komasko (1984). Firstly, it was detected in the cave Novy č. 2 in the massif of the Novy Mt, where it occurs in pale-dark brown very thin opaque coats covering dark grey early Cretaceous limestone. Secondary phosphates originate from the mineralized solutions containing ammoniate phosphates and sulfates originating from the bat excrements.