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Fluid circulation related to post-messinian extension, Thassos Island, North Aegean

Abstract : In the North Aegean Domain, Thassos Island contains a Plio-Pleistocene basin controlled by a large-scale flat-ramp extensional system with a potential décollement located at depth within a marble unit. Numerous mineralizations associated with normal faults of Plio-Pleistocene age are the sign of fluid circulation during extension. Two main generations of fluid flow are recognized, related to Plio-Pleistocene extension. A first circulation under high-temperature conditions (about 100­200°C) resulted in dolomitization of marbles near the base of the Plio-Pleistocene basin. The dolomites are characterized by low d18O values (down to 11 versus Standard Mean Ocean Water). Some cataclastic deformation affected the dolomites. Hydrothermal quartz that crystallized in extension veins above a blind ramp also has low d18O values (about 13). This shows that high-temperature fluids moved up from the décollement level toward the surface. A second downward circulation of continental waters at near-surface temperature is documented by calcite veins in fault zones and at the base of the Plio-Pleistocene basin. These veins have O isotope values relatively constant at about 23­25 and C isotope values intermediate between the high d13C value of the carbonate host rock (about 1­3 versus Peedee Belemnite) and the low d13C value of soil-derived carbon (-10). The calcites associated with the oxidative remobilization of primary sulphide Zn­Pb mineralization of Thassos carbonates have comparable O and C isotope compositions. Hot fluids, within the 100­200°C temperature range, have likely contributed to the weakening of the lower marble unit of Thassos and, thus, to the process of décollement.
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Contributor : Isabelle Dubigeon <>
Submitted on : Friday, June 15, 2007 - 3:20:15 PM
Last modification on : Sunday, August 18, 2019 - 8:30:03 PM

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Philippe Boulvais, Jean-Pierre Brun, D. Sokoutis. Fluid circulation related to post-messinian extension, Thassos Island, North Aegean. Geofluids, Wiley, 2007, 7 (2), pp.159-170. ⟨10.1111/j.1468-8123.2007.00171.x⟩. ⟨insu-00155152⟩

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