Physicochemical conditions of deposition and origin of carbonate-hosted base metal sulfide mineralization, Thermes ore-field, Rhodope Massif, northeastern Greece |
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| Authors: | S I Kalogeropoulos S P Kilias N D Arvanitidis |
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| Institution: | (1) Rusvar Holdings BV, 4 Nikis St., 105 62 Athens, Greece;(2) Institute of Geology and Mineral Exploration (IGME), 1 Fragon St., 546 26 Thessaloniki, Greece |
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| Abstract: | Vein and stratabound base metal sulfide mineralization of the Thermes ore-field, Rhodope Massif, NE Greece, is hosted in marbles.
The Thermes area is a structurally complex, E-W-trending zone consisting of felsic gneisses alternating with amphibolites,
amphibole-biotite, and biotite gneisses, and marbles. These rocks have undergone amphibolite facies metamorphism (5–7 kbar,
580°–620°C), in Upper Cretaceous to Eocene times, and were subsequently retrograded to greenschist facies metamorphism of
Miocene age. Granitoids of Oligocene age, and volcanic rocks of Eocene-Oligocene age, crosscut the metamorphic rocks. Two
major base metal sulfide ore varieties occur in the Thermes ore-field. The first comprises brecciated vein Pb-Zn mineralization,
related to NNWand NNE-trending faults. The second comprises stratabound (manto) polymetallic, and Pb-Zn replacement ores with
associated veins. On the basis of ore geochemistry, as well as field and textural evidence, these two ore varieties form part
of a vein associated skarnreplacement base metal sulfide ore system. Based on fluid inclusion data in quartz, together with
the iron content of sphalerites and existing lead and sulfur isotope data, it is suggested that after the cessation of the
regional amphibolite facies metamorphism circulating evolved meteoric waters, probably with magmatic fluid contributions,
deposited sulfide ores at temperatures of 200°2-400°C, and pressures of less than 300 bar. Ore was deposited as a result of
increase in pH of the mineralizing fluids due to fluid-rock interaction, and adiabatic cooling and/or simple cooling accompanying
fluid boiling. Thermochemical considerations indicate a pH increase from about 4 to 7 and a decrease in
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