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The Maronia Cu-Mo ± Re ± Au deposit is spatially related to a microgranite porphyry that intruded an Oligocene monzonite along the Mesozoic Circum-Rhodope belt in Thrace, NE Greece. The magmatic rocks and associated metallic mineralization show plastic and cataclastic features at the south-eastern margin of the deposit that implies emplacement at the ductile-brittle transition, adjacent to a shear zone at the footwall of the Maronia detachment fault. The conversion from ductile to brittle deformation caused a rapid upward magmatic fluid flow and increased the volume of water that interacted with the host rocks through high permeable zones, which produced extensive zones of potassic and sodic-calcic alteration. Potassic alteration is characterized by secondary biotite + K-feldspar (orthoclase) + magnetite + rutile + quartz ± apatite and commonly contains sulfides (pyrite, chalcopyrite, pyrrhotite). Sodic-calcic alteration consists of actinolite + sodic-calcic plagioclase (albite/oligoclase/andesine) + titanite + magnetite + chlorite + quartz ± calcite ± epidote-allanite. The high-oxidation state of the magmas and the hydrothermal fluid circulation were responsible for the metal and sulfur enrichments of the aqueous fluid phase, an increase in O2 gas content, the breakdown of the magmatic silicates and the production of the extensive potassic and sodic-calcic alterations. Brittle deformation also promoted the rapid upward fluid flow and caused interactions with the surrounding host rocks along the high temperature M-, EB-, A-and B-type veins. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. |
