Mineral Concentrations in the Recent Sediments Off Eastern Macedonia, Northern Greece: Geological and Geochemical Considerations

Abstract

An extensive marine geological and geochemical research program has been carried out on the Strymonikos Plateau off eastern Macedonia, northern Greece. During the program the surface sediments were examined in order to locate possible placer deposits in the area. The plateau is covered mainly by fine-grained sediments such as silty clays and clayey silts, while sands are present along the shoreline, at the outer parts of the gulfs and landward of the shelf break. The fine-grained sediments were deposited by the rivers after the latest transgression, while the coarse sediments are the result of modern coastal erosion or represent relict and palimpsest sediments. The heavy minerals are represented mainly by amphiboles, pyroxenes, garnet, epidote and opaques (mainly pyrite), which occur along the coastal area, in the sandy sectors off the gulfs and near the shelf break. These occurrences are related either to present-day erosional products of the igneous and metamorphic formations on land, or to earlier fluvial action during lower sea level stages.

The geochemical data show that the major elements Si and Ca are related to the content of quartz and biogenic material in the sediments, while the distribution of Al and Fe show the influence of the river load in supplying aluminosilicate material to the area. The minor element distributions (Ti,Cr), however, do not always correlate with the heavy mineral content in the coarse fraction, probably because the latter is sometimes in the fine fraction of the sediment or is diluted by other phases in the sediments.

The evaluation of the data shows that there are no present-day, economically important heavy mineral occurrences in the surface sediments in this study area.