Summary:
The Rovina, Colnic, and Ciresata porphyry deposits are the principal targets for exploration and mining within the Rovina Valley Project (RVP), with their locations defining a north-northeast trend. The Rovina porphyry is the northern-most deposit, with the Colnic porphyry lying approximately 2.5 km south of the Rovina porphyry, and the Ciresata porphyry approximately 4.5 km south of the Colnic porphyry.
Geometry of the mineralisation and host porphyries is different for each of the deposits. At Rovina, the host porphyries are generally cylindrical and vertical. At Colnic, the porphyries are lobate, with mineralisation decreasing with depth and a phyllic-altered cap locally preserved. Both Rovina and Colnic porphyries intrude extensive igneous-magmatic breccia carapaces, whereas Ciresata mineralisation is centred on a relatively narrow subvolcanic “neck” with a significant amount of mineralisation hosted in adjacent hornfelsed sediments.
Rovina Mineralisation Descriptions
Gold-copper mineralisation is associated with pyrite-chalcopyrite-magnetite occurring in veinlet stockworks and as finely disseminated grains. Oxidation is restricted to the uppermost few metres, except for a small area in Baroc Valley at the Rovina porphyry where weathering oxidation is 15 m to 25 m deep within the copper-gold mineralisation. In this area, secondary copper minerals malachite and chrysocolla are observed in the weathering zone, and minor occurrences of supergene copper minerals (chalcocite) occur below the weathering zone, typically associated with short drillhole intervals of elevated copper grades.
Deposit-scale controls to mineralisation are the localisation of the principal hornblende- plagioclase porphyry intrusion (Rovina porphyry POC), which is elongated in a north-westerly direction, measuring approximately 600 m northwest × 350 m northeast. This porphyry has vertical contacts over at least 600 m in depth, and apparently terminates northward in the northeast trending Baroc Valley zone. Lower-grade copper-gold mineralisation extends down the Baroc Valley zone to the southwest, to include the Baroc Valley porphyry as a satellite to the main Rovina porphyry. This intrusive geometry suggests possible northwest structural control for emplacement of the Rovina porphyry intersecting a northeast structural zone controlling emplacement of the Baroc Valley porphyry. A similarly oriented structural intersection is interpreted for the Colnic deposit.
At Rovina, two early-stage magmatic-fluid alteration events are recognised (PT, MACE, and a locally occurring magnetite-only alteration). Higher grades of gold-copper mineralisation are best developed and associated with broad zones of intense quartz-sulphide stockwork veining (up to 70 % of rock mass). Stockwork veining intensity typically correlates with alteration intensity, and in higher-grade zones, such as in the Baroc Valley area, intense stockwork veining with overprinting MACE alteration obscures all primary rock textures. The earliest copper-bearing assemblage is observed in both early magnetite-bearing veinlets/stringers and disseminated in the rock mass and consists of magnetite + chalcopyrite + bornite + minor pyrite. Cross-cutting veinlets indicated multiple fracturing and hydrothermal pulses. Seventeen vein types have been recognised, with five types most common with gold-copper mineralisation. These five vein types are hairline magnetite stringers, quartz veins, quartz-magnetite-sulphide veins, quartz-sulphide veins, and banded quartz- sulphide veins.
Molybdenum mineralisation is rarely observed in the drill core within quartz-molybdenite veinlets. Worldwide, other gold and gold-copper porphyries tend to be deficient in molybdenum; however, when present, it tends to concentrate as a halo to the copper-gold core (Sillitoe, 2000). Euro Sun Mining Inc. (ESM) has assayed on a limited basis for molybdenum at Rovina, with assay results to date being insignificant (averaging < 5 ppm to 20 ppm Mo); however, a localised enrichment of molybdenum cannot be ruled out pending further assay checks. Silver has been regularly assayed, and grades to date are generally exceptionally low throughout (averaging < 1 ppm to 2 ppm) and do not constitute economic mineralisation.
Colnic Mineralisation Descriptions
Deposit-scale controls to mineralisation consist of the localisation of two hornblende-plagioclase porphyry centres: the Colnic porphyry and the F-2 Hill porphyry. The Colnic porphyry occurs in the Rovina Valley, elongated parallel to the northeast-trending valley over an area approximately 400 m long × 200 m wide. This is interpreted as the older porphyry, and its upper part contains the highest grades at Colnic. The centre of the F-2 Hill porphyry complex occurs approximately 150 m southeast of the Colnic porphyry. Interpreted structural controls on the emplacement of these porphyries are the northeast-trending Rovina Valley (as suggested by an inter-mineral dyke and breccia swarm in the upper part of the Colnic porphyry) and the northwest-striking Chubby’s Fault/fracture zone (a brittle, post-mineral structure; however, may be a re-activated older structure, as evidenced by a spatial mineralisation association at depth).
At Colnic, the gold-copper mineralisation contains anomalous zinc ranging from 150 ppm to 600 ppm, with an approximate average of 300 ppm. A zone of elevated zinc + gold mineralisation has developed predominantly in or proximal to the transitional phyllic alteration zone (TRPH). Grades in this zone range from approximately 0.1 g/t Au to 3 g/t Au and 300 ppm Zn to 5,000 ppm Zn. The zinc-gold zone is interpreted to represent deposition of remobilised zinc and gold from a collapsing phyllic– potassic alteration front.
Molybdenum mineralisation is rarely observed in the drill core within quartz-molybdenite veinlets, typically in the deeper zones of K3 alteration. Molybdenum assay results to date at Colnic have been insignificant (averaging < 5 ppm to 20 ppm Mo); however, a localised enrichment of molybdenum cannot be ruled out pending further molybdenum assay checks. Silver has been regularly assayed, and grades to date are typical of porphyries worldwide; values are generally very low throughout (averaging <1 ppm to 2 ppm), and do not constitute economic mineralisation.
Ciresata Mineralisation Descriptions
Gold-copper mineralisation at Ciresata is associated with magnetite-pyrite-chalcopyrite occurring in veinlet stockworks and as finely disseminated grains over a wide area of approximately 450 m (NW-SE) by 300 m (NE-SW) and narrowing with depth. Deep drilling has intersected mineralisation 500 m below previous drilling, suggesting approximately 1,000 vertical metres of mineralisation. This mineralisation is centred on the early mineral porphyry (EM-P), with approximately 65 % hosted in the hornfels sediments (SED) and 35 % in the EM-P.
Gold correlates positively with copper grade and the gold:copper ratio is relatively constant throughout the deposit. Chalcopyrite is the only copper mineral present. Petrography and gold deportment studies show that gold is fine-grained, and associated with grains of chalcopyrite, pyrite, quartz, and rarely with magnetite (Damian, 2011; Wang and Prout, 2008; Sliwinski, 2012). In addition, scanning electron microscope (SEM) analysis of gold grains from Ciresata indicates they are native gold, with an average composition of 94.7 % Au and 5.2 % Ag. On a deposit scale, marginal to the gold-copper mineralisation, anomalous zinc (up to 400 ppm) and lead (up to 40 ppm) occur and appear to be associated with the phyllic alteration halo. Within the mineralisation, zinc is anomalous, with an approximate average value of 170 ppm. Limited analysis for molybdenum (670 samples) showed assays ranging from 2.5 ppm to 121 ppm, with an average of 20 ppm.