Wpływ procesów fizycznych i chemicznych na ukształtowanie powierzchni ziarn kwarcu w oparciu o analizę w mikroskopie elektronowym

Abstract

Przeprowadzono obserwacje morfologii powierzchni ziarn osadów piaszczystych z różnych środowisk sedymentacyjnych w elektronowych mikroskopach: transmisyjnym i skanującym. Omówiono wpływ różnych procesów fizycznych i chemicznych na rodzaj urzeźbienia powierzchni ziarn, kwarcu w powiązaniu z krystalograficznymi własnościami tego minerału.INFLUENCE OF PHYSICAL AND CHEMICAL PROCESSES ON MORPHOLOGY OF QUARTZ GBAIN SURFACE AS REVEALED BY ELECTRON MICROSCOPYThe paper presents an attempt to evaluate the influence of various physical and chemical processes on the type of quartz grains textures with the reference to crystalographic properties of this mineral. Morphology of quartz grain surface was studied with the use of scanning electron microscope JEOL P-15 and Zeiss D 2. The studies covered samples of quartz grains from various environments.Single sand grains have rarely euhedral habit but they are rather well-rounded or angular, with traces of mechanical impacts (Table I, Figs. 1-2). The surface of fracture is often large, dish-shaped or, rarely, ideally smooth (Table III, Fig. 3). It often displays cracks, ripple marks, grooves and straight to somewhat arcuate step-like forms or arc ridges (Table II, Fig. 4). In the glacial environment characterized by a high variability in size of transported material the morphology of quartz grains is especially diverse.Mechanical processes which are very intense in deserts contribute to the origin ,of characteristic pitted surface (Table III, Fig. 5). Grains from littoral and especially beach environments are characterized by small irregular random or somewhat oriented V-shaped depressions (Table III, Fig. 6; Table IV, Fig. 7). Textural elements of quartz grain surface ,reflect trends in .growth of crystals (Table IV, Fig. 8; Table V, Fig. 9). Quartz orvergrowths differ in shape depending on crystallographic section (Table V, Fig. 10; Table VI, Fig. 11), being usually step-like, pyramidal or conical in shape (Table VI, Fig. 112; Table VII, Fig. 13, 14). The processes of chemical etching result in origin of various morphological forms; these, are triangular, pyramidal, crystallographicalIy oriented forms (Table VIII, Fig. 15). The wealth of the textural forms on surface of grains facilitates origin of nuclei initiating growth of quartz crystals (Table VIII, Fig. 16.). Rapid crystallization results in growth of needle-like or rhombohedral projections with apparently euhedral habitus (Table IX, Figs. 17, 18).