GEOCHEMICAL INVESTIGATION AND MODELLING OF AN ACID PIT LAKE FROM A HIGH SULFIDATION ORE DEPOSIT: KIRKI, NE GREECE

Open pit mining of a high sulfidation epithermal type deposit at Kirki (Thrace, NE Greece) resulted in the formation of an acid pit lake by infilling of the open cast by rain and drainage waters after mine closure. The acidic and oxidative pit lake waters show high concentrations of trace metals largely due to the high toxic metals content of the ore, the limited buffering capacity of host rocks and the direct exposure of the ore zone to weathering. The floor of the pit lake is covered by a finegrained mineral precipitate that comprises mainly detrital minerals, originating from erosion of the rocks exposed on the walls of the open pit. Secondary anglesite, several species of the jarosite-group, rozenite, melanterite, gypsum, bukovskyite, beaverite, scorodite and minor goethite are also detected. The mineral precipitate presents significant heavy metal content indicating effective removal of metals from the acidic waters. The speciation/mass transfer computer code PHREEQC-2 and the MINTEQ database were employed for geochemical modelling of the equilibrium between the acidic pit lake waters and the secondary phases of the mineral precipitate

The context and nature of the evidence for metalworking from mid 4th Millennium Yali (Nissyros)

Two crucibles with copper adhering (and one lead rivet) have been found on Yali (Nissyros) dating to the Final Neolithic, mid-4th millennium BCE. This is important and rare evidence for the earliest phase of Aegean metallurgy, now recognized as emerging in circumstances of high mobility and variable technological preference and practice. The finds are presented here through a study of their context, typology and chemical and lead isotope analysis. The results show that the crucibles come from the main settlement on the island; they were locally made, using a clay recipe deliberately tailored to the needs of metalworking. The copper was pure, with low levels of naturally occurring arsenic. The copper and lead came from the same source which, on current evidence, appears to be to Kythnos. The community on Yali was in contact with a broader Aegean where multiple metallurgical technologies are known. The presence of tin ore, or its product, might be indicated. Though small in scale, there are some parallels with the nature and technology of metallurgical activities in the succeeding Early Bronze Age

Setting, sulfur isotope variations, and metamorphism of Jurassic massive Zn-Pb-Ag sulfide mineralization associated with arc-type volcanism (Skra, Vardar zone, Νorthern Greece)

Massive Zn-Pb-Ag sulfide mineralization appears conformable with felsic volcanism, developed in an Upper Jurassic volcanic arc to the Southwest (SW) of the Serbo-Macedonian continent in Northern Greece. The host volcanic sequence of the mineralization comprises mylonitized rhyolitic to rhyodacitic lavas, pyroclastics, quartz-feldspar porphyries, and cherty tuffs. A “white mica—quartz—pyrite” mineral assemblage characterizes the volcanic rocks in the footwall and hanging-wall of massive sulfide ore layers, formed as a result of greenschist-grade regional metamorphism on “clay-quartz-pyrite” hydrothermal alteration haloes. Massive ore lenses are usually underlain by deformed Cu-pyrite and quartz-pyrite stockworks. Most of the sulfide ore bodies have proximal-type features. Ductile deformation and regional metamorphism have transformed many of the stockwork structures. The mineralization is characterized by high Zn, Pb, and Ag contents, while Cu and critical metals are low. Primary depositional textures, for example, layering, clastic pyrite, colloform, and atoll textures were identified. The overall textural features of the mineralization indicate it has undergone mechanical deformation. The most prominent features of the effects of metamorphism, folding and shearing, are modification of the ore body morphology toward flattened and boudinage structures and transformation of the ore textures toward the dominance of planar fabrics. Sulfur isotope analyses of sulfides along with textural observations are consistent with a dual source of sulfide sulfur. Sulfur isotope values for sphalerite, non-colloform pyrite, galena, and chalcopyrite fall in a limited range from −1.6 to +4.8‰ (mean δ34S + 2‰), indicating a hydrothermal source derived from the reduction of coeval seawater sulfate in the convective system. Pyrites with colloform and atoll textures are characterized by a 34S depletion, indicating a bacterial reduction of coeval seawater sulfate. The morphology of ore beds, the mineralogy, sulfide textures, and ore chemistry along with the petrology and tectonic setting of the host rocks can be attributed to typical of a bimodal-felsic metallogenesis. Although similar in many respects to classic Kuroko-type volcanogenic massive sulfide mineralization, it has some atypical features, like the absence of barite ore, which is possibly a result of significant temporal depletion in sulfate due to bacterial reduction, a conclusion supported by the widespread occurrence of colloidal and atoll textures of pyrite. © 2020 The Society of Resource Geolog

Lateritization processes of ultramafic rocks in Cretaceous times: The fossil weathering crusts of mainland Greece

The lateritic weathering crusts exposed in mainland Greece were developed on ophiolitic ultramafic lithologies during lower Cretaceous times. The lateritic profile consists of four zones: Bedrock, saprolite clay (nontronite) and goethitic. The profiles show large variations in thickness, continuity, mineralogy and chemical characteristics. They are broadly similar to clay nickel laterite deposits. The uppermost gravelly ferruginous sector was eroded and the material reworked and redeposited partly on the lateritic crust. Silcrete layers, characteristic of groundwater silcretes, were formed into the clay and goethitic zones. Significant supergene nickel enrichments occur in the clay and saprolite zones, indicating that water moved downward to a very low water table. The structure and mineralogy of the weathering crusts indicates that environmental conditions were likely to have been dominated by alternating wet and dry periods. © 2005 Elsevier B.V. All rights reserved

The Lavrion deposit (SE Attica, Greece): Geology, mineralogy and minor elements chemistry

In southeastern Attica the Cycladic "Blueschist" and the "Basal" units are superposed and separated by a detachment fault. The widespread carbonate-hosted massive sulfide Pb-Zn-Ag ores of Lavrion are spatially related to the detachment fault, shear bands within marbles, and the shear contact between marbles and the intercalated metaclastics of the Basal Unit. The ores are both structurally and lithologically controlled. A low tonnage Ag-rich tension gash vein, hosted within hydrothermally altered hornfelses surrounding the Lavrion granodiorite, is structurally related to the regional stress field with roughly N-S direction. The ore mineral suite consists of base metal sulfides and a variety of sulfosalts and native elements. Galena and fahlore are the main silver carriers. There are no significant enrichments in minor elements other than Cd, Ag and Au. The sulfide mineral assemblages and the range of FeS compositions of sphalerite coexisting with pyrite, indicate an intermediate sulfidation state for the hydrothermal fluids generating the manto ores. Mineral assemblages characteristic of low or high sulfidation state are locally present. The ore geometry, structural and lithological control of the mineralization, textural features, carbonate alteration and silicification, and the mineralogic and chemical composition of the ores suggest a carbonate-replacement deposit affiliation. © by E. Schweizerbart'sche Verlagsbuchhandlung 2007

Environmental impact from supergene alteration and exploitation of a high sulphidation epithermal type mineralisation (Kirki, NE Greece)

The base-metal sector of the high-sulphidation epithermal deposit of Kirki (St Philippe) was occasionally mined during the period 1973-1998, without strict environmental management. The mineralisation shows a significant content of polluting elements. Mineralogical investigations indicate a very low degree of sulphide alteration. Sphalerite and galena concentrates were produced by conventional flotation techniques. Mine excavation wastes and flotation tailings were dumped and exposed to weathering. Waters draining downstream of the mine waste dump are near neutral. Acid mine waters forming a pit lake are highly polluted. Evapoconcentration of the pit lake waters leads to the generation of a toxic mineral precipitate on the open pit floor, comprising soluble secondary salts. The paper concludes with a consideration of the remedial measures required. © 2004 IoM Communications Ltd