Summary:
The Sturec Gold Project is located in the Central Slovakia Volcanic Area in the Kremnica Mountains of the Western Carpathians. The Central Slovakia Volcanic Field hosts several Ag, Au epithermal vein-type deposits including Banská Štiavnica, Kremnica, Hodruša-Hámre, and Nová Bana, which were important sources of precious and base metals in the past. The area is characterised by Tertiary pyroxene-amphibole andesite flows and tuffs of the Zlata Studna Formation. The andesites are underlain by Mesozoic limestone. Deep-seated structures and faults within the pre-Tertiary basement interpreted to be extensional Horst and Graben in style, focused sub-volcanic intrusions of gabbrodiorite, diorite, diorite porphyry, and minor quartz-diorite porphyry at depth and associated mesothermal mineralising events, which were then overprinted by the epithermal precious metal mineralisation.
In the Kremnica area, the structure is controlled by a 6- 7km long, N-S trending horst, known as the Kremnica Horst Structure, which is interpreted to be the result of the subvolcanic intrusions of gabbro-diorite, diorite, diorite porphyry, and minor quartz-diorite porphyry at depth causing this zone to be uplifted relative to the two graben structures to either side.
The Sturec Gold Project mineralisation is classified as a low-sulphidation epithermal Ag-Au deposit type and is interpreted to have formed from low-salinity fluids composed of a mixture of meteoric and magmatic waters at temperatures mostly between ~270 to 190 °C. The mineralisation is hosted by quartz–dolomite veins also containing adularia, sericite, illite and chalcedony that cut through Neogene propyllitised (low pressure/low to medium temperature hydrothermal alteration) andesites of the Kremnica stratovolcano. The hydrothermal alteration from the veins outwards consists of silicification and potassic-metasomatism (adularia), propylitization and argillisation. Vein styles include large banded to massive quartz veins, smaller quartz veins and sheeted veins, quartz stockwork veining and silicified hydrothermal breccias.
The Sturec deposit occurs in the southern part of the central First Vein System. It is continuously mineralised for 1,600m along a north-south strike, is typically 100 to 150m wide, generally dips steeply to the east and extends to a known depth of at least 300m. The deposit is composed of massive to sheeted quartz veins and is classified as a low-sulphidation epithermal Ag-Au deposit and is open to extension both at depth and along strike to the north and the south.
In the northern part of the deposit, a northeast-striking quartz vein system joins with the main north-south striking vein system (Schramen Vein). This vein system projects southwestward away from the Schramen Vein where it outcrops approximately 100m to the west. It then bends to the south and strikes parallel to the Schramen Vein. This vein system dips 40° to 55° east, re-joining with the Schramen Vein at depth.
Zones of stockwork gold mineralisation occur between the two principal veins and appear to plunge to the south. This plunging zone contains some of the highest-grade mineralisation within the deposit and is still open towards the south.
Numerous targets have been identified in addition to the existing Mineral Resource, which has the potential to increase provide resource expansion opportunities. These include the Vratislav and Wolf targets, which are located 1 and 2km north, respectively, along the continuation of the Kremnica vein structure as well as a large area of strongly clay and silica altered rhyolite, referred to as South Ridge, located south of the deposit, and which is considered to be prospective for several styles of epithermal gold mineralisation.
The main zone of mineralisation of current economic interest is the Šturec zone, which is continuously mineralised for 1,200m along strike, is typically 100 to 150m wide and extends to a depth of at least 300m.
The most significant part of the Šturec zone is the Schramen Vein, which is a massive to sheeted quartz vein striking north and dipping to the east. Mineralisation occurs in large banded to massive quartz veins, smaller quartz veins and sheeted veins, quartz stockwork veining, and silicified hydrothermal breccias. Geological work completed by Tournigan in 2005 has demonstrated that gold and silver mineralisation within the sheeted veins and stockwork vein zones is primarily localised in areas immediately adjacent to the main vein zones.
Gold occurs freely and in non-refractory association (coatings, etc.) with sulfides and with silver as electrum. Besides electrum, silver occurs in the minerals polybasite, pyrargyrite, and argentite. Sulfide minerals consist predominately of pyrite and marcasite with much lesser amounts of chalcopyrite, arsenopyrite, stibnite, sphalerite and galena.
Sulfide contents rarely exceed 2% and average 0.5%. Average gold grades throughout the deposit are approximately 2 g/t Au but high-grade zones can exceed 30 g/t Au locally. Silver/gold ratios vary but average approximately 8:1.
Large, mineralised banded to massive quartz veins and associated silica, argillic and propylitic alteration zones are localised along a major, broad approximately north to northeast striking structural zone that is mineralised for a length of at least 6.5km. Some 80 veins are documented within the Kremnica vein system, with individual vein groups being up to 100m thick.
Dimensions
Drilling indicates that the mineralisation continues up to 1600m along strike and up to 500m wide. The limits of mineralisation have not been completely defined and are open at depth and along strike.