Comparison of morphology of quartz crystals – “Marmarosh diamonds” – from Paleogene Flysch sequences of Krosno (Silesian) Zone, Dukla Zone in Ukrainian Carpathians, and Intra-Carpathian sequences of Western Carpathians

Abstract

Quartz crystals of “Marmarosh diamonds” type were goniometrically studied in Ukrainian Carpathians from the veins in flysch deposits of Krosno (Silesian) unit (137 crystals, locality 1 – New Beskydy Tunnel) and the Oligocene sediments of the Dukla Zone (77 crystals; loc. 2 – Pryslip pass). They were compared with quartz crystals from intra-Carpathian Paleogene sequences of the Western Carpathians in Slovakia (175 crystals; loc. 3 – Šoltysa stream). The analysis of the obtained results allows to state that the “Marmarosh diamonds” from the studied Ukrainian and Slovak localities are generally similar. The main simple forms represent the hexagonal prism m {101̅0} and the rhombohedra r {101̅1} and z {011̅1}. The following types of crystal habit have been identified: hexagonal-dipyramidal, pseudocubic, hexagonal-prismatic, trigonal-prismatic. For the polyhedra from the Ukrainian Carpathians, minor forms are less typical, such as the trigonal dipyramid s {112̅1} and the trapezoid x {516̅1}. Statistically, the shape of “Marmarosh diamond” crystals from the Ukrainian Carpathians is closer to isometric. For them, elongation along the main crystallographic axis is even less typical than for polyhedra from the Slovak localities. In addition, “Marmarosh diamonds” from the W. Carpathians in Slovakia are more often flattened at {101̅0}. In the process of crystal growth with decreasing temperature, the habit changes from hexa- gonal-dipyramidal to trigonal-prismatic. Quartz from Krosno (Silesian) zone of Ukrainian Carpathians was found in the association with calcite. There are numerous hydrocarbon inclusions in both minerals. The mineralogical crystallographic and geochemical investigations (especially of the migrating hydrocarbon fluids), are important for oil and gas geology of the Carpathian oil and gas-bearing province.