Mineralogical, petrological, stable isotope, and fluid inclusion studies of the Palea Kavala reduced intrusion-related and the transitional Fakos porphyry Cu-Mo to epithermal Au-Te ore systems

Abstract

Reduced intrusion-related gold systems are generally characterized by a Au-BiTe -W metal assemblage genetically linked to the emplacement of granitoids. The Palea Kavala ore system, Greece, consists of ~150 minor Fe-Mn (Pb±Zn±Ag), Fe-Mn-Au, Fe-As-Au, Fe-Cu-Au, and BiTe -Au ore occurrences that occur primarily in quartz-calcite-sulfide veins (hypogene mineralization), or as supergene bodies, in overlapping zones centered on the ~21-22 Ma granodioritic Kavala pluton, which intrudes metamorphic rocks of the Paleozoic Rhodope metamorphic core complex. The pluton consists mostly of granodiorite with lesser amounts of diorite, tonalite and monzodiorite, which was emplaced along the regional E-W trending Kavala-Komotini fault. The recently discovered, ~4 km long, E-W trending so-called Kavala vein is a sheeted quartz vein system of BiTe -Pb-Sb±Au mineralization that crosscuts the Kavala pluton and the schists and gneisses of the Rhodope Massif. The Kavala vein system is comprised of quartz with lesser amounts of K-feldspar, plagioclase, and muscovite. Quartz-sericite-pyrite alteration is pervasive but minor kaolinite is also present. Pyrite (~5% of vein volume) contains inclusions of tetradymite (some gold-bearing), bismuthinite, and cosalite. Sulfur isotope values (n = 27) of pyrite from the Kavala and Chalkero veins, as well as pyrite and 5 galena from Garizo Hill Fe-Mn-Pb vein range from-1.9 to 1.0 per mil (with one outlier of-4.6 per mil) and suggest a magmatic sulfur source. Homogenization temperatures (T h) of type I (two-phase aqueous liquid-vapor) and type II (three-phase, H 2 O-CO 2-rich) fluid inclusions that homogenize into the liquid phase in quartz from the Kavala and Chalkero veins range from 216.0º to 420.0ºC (n = 216) and 255.7 º to 414.0 ºC (n = 112), respectively. The T h of type III (two-phase aqueous liquid-vapor), which homogenize into the vapor phase, ranges from 210.4 o to 323.4 o C (n = 28). The salinities of type I and type II inclusions range from 15.9 to 22.6 wt. % NaCl equiv. and 5.5 to 11.2 wt. % NaCl equiv., respectively. Eutectic temperatures of-58.5 o to-44.3 o C for type I inclusions suggest the presence of appreciable CaCl 2 in addition to NaCl. Clathrate melting temperatures for type II inclusions of ~-56.7 o C indicate that CO 2 is the major component of the gaseous phase. The presence of a zoned metallogenetic district centered on BiTe -Pb-Sb±Au mineralization within the Kavala pluton and the two high-temperature, high-salinity, immiscible carbonic and aqueous fluids associated with the Kavala and Chalkero veins are consistent with them being part of a reduced intrusion-related gold system.

“Geo-Archaeo-Routes” on the Island of Lemnos: The “Nalture” Experience as a Holistic Geotouristic Approach within the Geoethical Perspective

“…The first is located in the southern part, in the quartz veins within the sandstones and quartz monzonite. The second zone is located in the western part, while the third and largest is located in the eastern part, displaying a length of 1 km and a thickness of 10 m and is characterized by a high concentration of gold as an indication of a magmatic-hydrothermal contribution to the vein system [117].…”

Hydrothermal Alteration Zones Detection in Limnos Island, Through the Application of Remote Sensing

“…Limnos Island is located in the area of Aegean Sea that is characterized by a moderate positive heat flow anomaly. This anomaly, in conjunction with active hot springs found on the island, indicate that a steepened thermal gradient has persisted even after the end of observable igneous activity on the island (Skarpelis and Voudouris, 1998;Fornadel, 2010). The presence of hot springs on the island implies that brittle structures on the island play a role in conducting fluids (Fornadel, 2010).…”

“…Remote sensing can assist and provide valuable information in bedrock mapping, detection, identification and estimating affluence of specific minerals at a specific scale (Ahmed and Beiranvand Pour, 2014;Sabins, 1999;Hunt, 1977). In Limnos Island, field geological studies have referred the detection of hydrothermal alteration zones in several sites like Sardes, Roussopouli and Fakos peninsula (Papoulis et al, 2014;Fornadel, 2010;Papoulis et al, 2009;Skarpelis and Voudouris, 1998). Positive results can be obtained using band rationing and false colour using these ratios.…”