Surface Microtextures of Heavy Minerals from the Mediterranean Coast of Israel

Abstract

ABSTRACT Results are reported of SEM examination of grains of magnetite, tourmaline, hornblende, zircon, calcite and quartz from the Mediterranean coast between Tel-Aviv and Acre, including the littoral (swash) zone (in which the sediments are in permanent contact with the sea water), beach sands 7-10 m from the water line (in which contact is occasional), and dunes. The surface microtextures are the result of mechanical and chemical processes (the former shown by comminution studies to modify the grain surfaces in ways that render them more susceptible to chemical attack), and influenced by the physical and chemical properties of the minerals and by the energy and chemistry of the environment. In the swash zone and beach sands, the marks of mechanical and chemical action depend on the crystal structure of the mineral and its resulting cleavage (or parting). In the dunes, this dependence is obviated and a rolling topography (as defined by Krinsley and Doornkamp, 1973) tends to develop, especially in less stable minerals which could thus be used for differentiation of beach and dune sand. The rolling topography or quartz grains from calcareous sandstones of the Late Quaternary, believed to be ancient dunes, exhibits changes due to chemical attack on the calcareous cement. The chemically modified microtextures correlate well with published stability series (Pettijohn, 1957)--the one exception being calcite, which shows crystal growth in the swash zone.