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GEOCHEMICAL INVESTIGATIONS OF HYDROTHERMAL PROCESSES IN RELATION TO THE FORMATION OF MARINE MINERAL DEPOSITS IN A CONVERGENT PLATE ENVIRONMENT: THE HELLENIC VOLCANIC ARC REGION

Objective

The main aim of the research is to study the hydrothermal processes taking place in a convergent-plate environment in the Southern Aegean Sea.
The geochemical analysis of surface sediments, sediment cores and hydrothermal waters from near shore and deep sea areas along the Hellenic Volcanic Arc demonstrated that significant hydrothermal fluxes of iron, manganese, copper, zinc and arsenic to the seafloor take place. On the basis of the geochemical behaviour of the elements studied it is implied that seawater and rock interaction processes similar to those described from mid ocean ridges are responsible for the above fluxes. The composition of the hydrothermal solutions formed show significant variations both with time and from one locality to another in the Hellenic Volcanic Arc. These variations could be assigned to variations: in the chemical composition of the rocks leached by seawater; in the temperature and pressure of the seawater and rock interaction; in the volumes of rocks being leached; in the degree of mixing of hydrothermal solutions with seawater.

The geochemical analysis of sediment cores from the fore arc basins led to the location of manganese rich horizons at a number of stations located along the lines of faults and/or above volcanic intrusions. The similarities between the geochemical features of these deposits (such as the iron to manganese ratios and the concentrations of nickel, cobalt and copper) and those of known recent and ancient hydrothermal manganiferous sediments, coupled with their association with volcanic intrusions suggest their hydrothermal origin.
The research will include detailed geochemical analyses of hydrothermal waters from offshore submarine vents, their time series analyses, analyses of bottom waters, surface sediments and sediment cores from deep waters along the Hellenic Volcanic Arc and from the fore-arc basins along the lines of normal faults and above intrusive volcanic bodies, in order i) to clearly define the areas where submarine hydrothermal activity and associated mineral deposition is occurring or has occurred in the past and to assess the efficiency of removal of hydrothermally derived elements from seawater; ii) to identify the hydrothermally derived elements and determine the rate of their fractionation in the seawater, iii) to evaluate the hydrothermal deposits in comparison with the much better known hydrothermal metalliferous sediments and polymetallic sulphides in deep water on mid-ocean ridges; and iv) to study the variability and evolution of hydrothermal activity during the recent past.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

University of Patras
Address
University Campus
26110 Patras
Greece

Participants (3)

IMPERIAL COLLEGE OF SCIENCE, TECHNOLOGY AND MEDICINE
United Kingdom
Address
South Kensington Campus
London
Institute of Geology and Mineral Exploration
Greece
Address
70,Messogeion Street
11527 Athens
NATIONAL CENTRE FOR MARINE RESEARCH
Greece
Address
Aghios Kosmas, Hellinikon
16604 Eliniko, Athens