Sedimentological and Mineralogical Analysis of Seabed Sediments of Afantou Bay, Rhodes Island, Ne Greece

Marine and Coastal Resources SEDIMENTOLOGICAL AND MINERALOGICAL ANALYSIS OF SEABED SEDIMENTS OF AFANTOU BAY, RHODES ISLAND, NE GREECE. Tsoutsia Antonia1, Anastasatou Marianthi1, Petrakis Stylianos1, Stamatakis Giorgos2, Poulos Serafim1, Stamatakis Michael1, Kapsimalis Vasilis3, Roussakis Grigoris3 1 National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironment, University Campus, Zografou, 15784, Athens, Greece 2 National and Kapodistrian University of Athens, Department of Chemistry, University Campus, Zografou, 15784, Athens, Greece 3 Hellenic Center for Marine Research, (HCMR), 46,7 km Athens Sounio ave., P.O. Box 712, P.C. 19013 Anavyssos, Attica, Greece Introduction The aim of the present research is the sedimentological and mineralogical study of the offshore deposits of Afantou Bay, Rhodes Island, Dodecanese, SE Aegean Sea, Greece, aspiring to the qualitative definition of a possible exploitable marine aggregates deposit, in the area bounded by the contours of ~15m (shallower boundary) and ~50m (deeper boundary). Methodology Twelve seabed sediments samples were collected from three profiles, running vertically to the coastline of Afantou [fig 1] by an HCMR scientific and technical group being onboard on the oceanographical ship ALKYON in late 2013. The samples were analyzed to identify their granulometry, density and mineralogy. Sedimentology The samples analyzed are granulometrically classified as: sand (S) (3 samples), gravelly sand ((g)S) (3 samples), slightly muddy sand ((g)mS) (5 samples), gravelly sand (gS) (1 sample), according to Folk 1973. In general, the samples trend to spatially distribute by the depth, specifically as the depth increases the grain-size of the sediment is finer. The granulometrical analysis shows that the sandy samples (S) occur at a depth between 10-20 meters, the gravelly sand samples at a depth between 20-30 meters, and the slightly muddy sandy samples between 30-40 meters depth. At depths between 40-50 meters, the gravelly sand and slightly muddy sand occur. Measurements on the density of the sample collected showed that it varies between 2,676 to 2,806 gr/cm3. Mineralogy X-Ray Diffraction analysis was used to identify the mineral components of the sediments, and to determine if their nature is siliceous and/or calcareous. As it was resulted, the main phases in all samples are calcite and dolomite quartz. The clay mineral clinochlore, clinochrysotile, actinolite and sodium feldspar (albite) were identified as medium to minor content minerals. Moreover a few samples contain aragonite and magnesian calcite (shells of bivalves, gastropods and other biogenic material), potassium feldspar (sanidine), pyroxenes and spinel as minor minerals. As a result, the 179 Marine and Coastal Resources samples studied can be characterized as mixed calcareous (predominate phase) – siliceous (significant silica content). Macroscopic observation and binocular microscopy revealed plurality of skeletal remains of marine organisms in the third sedimentary section’s samples. This fact can justify the aragonite trace content in these samples (AFA-3A, AFA-3B and AFA-3C). Specially, in AFA-3D sample aragonite performs as a medium component and furthermore magnesium calcite identified as major mineral. Moreover, the samples of the third sedimentary section, unlikely with the other two sedimentary sections, contain pyroxenes and spinel as minor minerals. This differentiation of the samples, at the SW part of Afantou Bay contrary to the samples of central and NE part of Afantou Bay, is maybe due to the lower discharge of terrigenous sediments derive from Pelemonis and Loutanis torrents and strong currents presence. Possible industrial uses The composition of the sediments studied is not proper for their exploitation as source of silica in applications in the construction industry, i.e. silica-raw materials for the production of clinker and insulation blocks, and siliceous mortars. In contract they can find application in beach replenishment/ nourishment in Rhodes and the surrounding islands. Acknowledgments The authors team is supported by the project MARE (MIS: 375655) which is co-finance by the European Union (European Social Fund - ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) - Research Funding Program: THALES (Investing in knowledge society through the European Social Fund). Literature Folk, R.L., 1974. The natural history of crystalline calcium carbonate: Effect of magnesium content and salinity. Journal of Sedimentary Petrology, 44, 40–53 180 .

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