Τίτλος:
Submarine hydrothermal mineralization processes and insular mineralization in the Hellenic Volcanic Arc system: A review
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
Hydrothermal mineralization processes are investigated along the Hellenic Volcanic Arc (HVA) and associated environments in order to describe the factors that control the spatial and time variability in the hydrothermal intensity and the composition of the mineral deposits formed. Santorini is the most active hydrothermal center of the HVA. Two Fe-rich submarine hydrothermal deposits were formed. One in the Palaea Kameni (PK) embayment and the other in the Nea Kameni (NK) embayment. Hydrothermally introduced elements such as Fe, Mn, As and Si are more enriched in these metalliferous sediments than in any other similar deposit of the arc. Over a hundred volcanic events occurred in Santorini and this volcano is considered as one of the most violent and most famous in the world. The detailed study of these two deposits in combination with the tectonic regime provided an excellent opportunity to understand the hydrothermal mineralization processes in a convergent plate environment. The Santorini magma below the thinner continental crust and nearest to the greatest lithospheric extension prevents the early crystallization of Fe-Ti oxides, leading to extreme Fe oxide enrichments in the final hydrothermal fluids. The physicochemical conditions of formation of the two deposits are deduced on the basis of their mineralogical and geochemical features. The greater average values of Zn compared to those of Cu in PK deposit, suggest higher temperature of formation than that of NK deposit, where Cu concentrations are higher than those of Zn. This is in consistence with the abundance of pyrite in PK. The greater Mo and V values found in NK compared to those of PK Fe-rich sediments are indicative of the less oxygenated environment, favoring the biological activity of bacteria, known to be involved in the diagenetic transformation of Fe-oxyhydroxides to nontronite. This is in accordance with the plotting of the NK deposits in the nontronite field on the Fe2O3- Al2O3- MgO diagram. The high Si and low Al levels and the stagnant conditions are also in favor of the nontronite formation. Similar deposits were described from the Aeolean Arc and from EPR 18 °N. Applying the Dill et al. (1994) model on the PK and NK mineralogical, lithological and geochemical data, all processes involved during the formation of the final deposits and their fate are deduced. An examination of sediment geochemical data from the HVA fore-arc areas in relation to their tectonic setting, the seismic activity and geophysical data led to the production of a map showing the areas of potential presence of metal sulfides on the rock basement. Maleas basin is one of these areas which is characterized by high seismic activity and high heat flow measurements, associated with major fault planes along which magmatic material was injected. The sediment thickness there is very small. Other sites are the crossing points of the faulting lines with volcanic intrusive bodies and/or with a volcanic ridge of a NW-SE direction, near sites of high rates of lithospheric extension. A southward movement of the arc front is deduced. © 2020
Συγγραφείς:
Varnavas, S.P.
Papavasiliou, C.
Περιοδικό:
Ore Geology Reviews
Λέξεις-κλειδιά:
Alumina; Aluminum oxide; Binary alloys; Bioactivity; Copper; Deposits; Earthquakes; Faulting; Field plotting; Geochemistry; Hematite; Lithology; Magnesia; Mineralogy; Ore deposits; Pyrites; Sediments; Submarines; Sulfur compounds; Titanium alloys; Titanium oxides; Volcanoes, Diagenetic transformation; Geochemical features; Hydrothermal deposits; Hydrothermal fluids; Hydrothermal mineralization; Lithospheric extension; Oxygenated environments; Physicochemical conditions, Silicon, hydrothermal alteration; hydrothermal deposit; literature review; mineral deposit; mineralization; ore deposit; spatiotemporal analysis; underwater environment; volcanic arc, Hellenic Arc; Mediterranean Sea, Calluna vulgaris
DOI:
10.1016/j.oregeorev.2020.103541
