Fluid evolution in Tertiary magmatic-hydrothermal ore systems at the Rhodope metallogenic province, NE Greece. A review

Abstract

Characterization of various fluid parameters in magmatic-hydrothermal ore mineralizationsis potentially essential for interpretation of the conditions of formation and therefore formineral exploration. Fluid inclusions can provide a useful and promising tool in the researchof the ore forming processes in these systems. This review focuses on the nature,composition and origin of magmatic-hydrothermal ore forming fluids involved in the formationof representative Tertiary ore deposits at the Rhodope metallogenic province in NEGreece. These deposits are spatially related to Tertiary magmatism in NE Greece. Casestudies are presented here and include an intrusion-hosted sheeted vein system (Kavala), aAu-rich carbonate replacement and quartz-vein mineralization (Asimotrypes), mineralizedveins in Eptadendro-Rachi and Thasos island (Kapsalina and Panagia), porphyry Cu-Mo-Re-Au deposits in Pagoni Rachi and Maronia and epithermal Au-Ag mineralizations inPerama and Loutros. Hydrothermal fluids rich in CO2 together with elevated Au and Tecontent are common and occur at the Kavala intrusion hosted sheeted vein system, at theAsimotrypes Au-rich carbonate replacement mineralization and at the Panagia (Thasos)vein system. We classify all these ore mineralizations as intrusion-related gold systems(IRGS)v. Transport and precipitation of metals including Au and Te is favoured when CO2is present. Precipitation of the ore mineralization takes place due to the immiscibility of thecarbonic and the aqueous fluids which have a magmatic origin with the contribution ofmeteoric water. Cooling of magmatic hydrothermal fluids and dilution with meteoric wateris a common cause for ore mineral formation in the vein mineralizations of Eptadendro/Rachi and Kapsalina Thasos. At the Pagoni Rachi and Maronia porphyry deposits, boilingand the high proportion of the vapour phase are the most essential fluid processes whichaffected ore formation. The epithermal veins overprinting the Pagoni Rachi and the Maroniaporphyry systems and the HS-IS epithermal system in Perama Hill and the IS epithermalmineralization in Loutros are characterized by low to moderate temperatures and lowto moderate salinities. Cooling and dilution of the ore fluids are the main process for goldprecipitation. We conclude that the different fluid parameters and microthermometric dataindicate a variety of fluid origin conditions and sources which can affect the strategy forexploration and prospecting for gold, rare and critical metals.