Both islands of Viti Levu (South Island) and Vanua Levu (North Island) are on the prolific Pacific “Ring of Fire” in the Republic of Fiji.
The Ring of Fire is a trend that has produced numerous large epithermal gold deposits, including Porgera, Lihir and Grasberg and on Viti Levu, the exceptional Vatukoula Gold Mine (or Emperor Mine) and the Tuvatu Project with recently announced exceptional results.
The Vatu Aurum Gold Project sits within a 300 km long northeast trending extensional fault zone which contains multiple Eocene age calderas, two of which host the Vatukoula and Tuvatu Gold Deposits.
The Vatukoula Gold Mine has produced in excess of 7 million ounces since 1937 and is still in production today.
The Tuvatu Project has a reported Indicated Resources of 1.00 million tonnes at 8.48 g/t Au (274,600 ounces Au), and Inferred Resources of 1.33 million tonnes at 9.0 g/t Au (384,000 ounces Au) at a 3.0 g/t Au lower cut-off.
The island of Viti Levu also hosts Namosi, with a published Proven and Probable Reserves of 1.3 billion tonnes at 0.37% Cu and 0.12 g/t Au (5.2M ounces Au and 4.9M tonnes Cu).
Geology of the Republic of Fiji
Tectonic reconstruction of the Fiji, New Hebrides – Tonga region at (a) about 10 Ma, (b) about 5.5 Ma and © present. The Indo-Australian Plate is fixed. The Fiji Platform rotated about 135 degrees anticlockwise during the opening of the North Fiji Basin. It is during this episode of rapid rotation of the Fiji Platform that magmatism occurred (ca 5.5 – 3 Ma). The Tonga Arc has rotated about 20 degrees during opening of the Lau Basin. Ridges outlined by the 4000 m bathymetric contour. NHT, New Hebrides Trench; TT, Tonga Trench; HFZ, Hunter Fracture Zone. Arrows indicate direction and relative magnitude of arc migration.
The deep-sea trench, volcanic line, accretionary prism, backarc basin, and third arc generally associated with island arcs are shown here and in the case of Fiji the trench forms an arc in plan view, and islands with explosive volcanoes developed on the overriding plate creating the gold and copper and other mineral deposits on the islands.
The formation of ore deposits is closely associated with plate tectonic processes. Label B1 refers to the location of the location of the formation of porphyry copper (Mo and Au) deposits and Label B2 refers to the location of the formation of epithermal Au, Ag (Hg) deposits such as those of the Tuvatu and Vatukoula Gold Mines.
Kalo Gold holds a 100% interest in the 367 km2 Vatu Aurum Gold Project that hosts a minimum of seven volcanic arc related calderas ranging between 1 km to 10 km in diameter in a geological setting directly analogous to the alkaline related low sulphidation epithermal gold deposits of both the Vatukoula and Tuvatu Gold Deposits. The giant Vatukoula Gold Deposit, or Emperor Mine, is associated with the 5 km wide Tavua caldera and the Tuvatu Gold Deposit is associated with the 7 km wide Navilawa caldera.
Exploration on the Project has identified extensive areas of hydrothermal alteration, including silicification, argillic and propylitic alteration and several areas of intense clay-sulphate alteration interpreted to represent steam heated alteration associated with several low sulphidation epithermal gold systems.
Large gold and epithermal pathfinder element soil anomalies have been identified along with a significant number of gold in rock and trench sample results have identified fourteen named prospects including two known gold deposits which are open along strike and at depth.
The Qiriyaga Hill Prospect sits on the boundary of the interpreted Qiriyaga Caldera in an analogous geological setting as the alkaline related low sulphidation epithermal Vatukoula Gold Deposit which has produced over 7 million ounces of gold since 1937.
Modelling of the Qiriyaga Hill Gold Deposit indicates there are a minimum of five high grade (see Table 1) parallel veins that have been modelled within a large argillic alteration zone. The Qiriyaga Hill Prospect has excellent potential for the discovery of additional gold mineralization and expansion of the existing Qiriyaga Hill and Vuinubu Ridge Gold Deposits, both of which are open along strike and down dip, and the discovery of new gold deposits within the defined and expanded argillic alteration zone.
Diamond drill holes KGD-06 and KGD-07, drilled to test geophysical anomalies at the Qiriyaga Hill Prospect, both intersected pervasive argillic alteration. Argillic alteration can be found associated with epithermal gold veins. KGD-06 and KGD-07 have been presented in a geological model and are interpreted to have been drilled within the alteration envelope surrounding the Vuinubu Ridge Gold Deposit and high-grade epithermal gold mineralization of the Qiriyaga Hill Gold Deposit.
Both KGD-06 and KGD-07 have outlined a large 3km by 1.5km argillic alteration zone that indicates the presence of a low sulphidation epithermal gold system.
The Qiriyaga Hill and Vuinubu Ridge Gold Deposits sit within this argillic alteration zone and both gold deposits are open along strike and down dip.
Geological features of the Vatukoula Mine (Emperor) with over 7 million oz Au produced to date:
- Within an Eocene aged collapsed caldera (4.5km*5km)
- Associated with volcanic arcs
- Low sulphidation epithermal gold system (low temp)
- Alkaline type – like Grasberg, Porgera, Lihir
- Post caldera collapse – a critical genetic feature (NW trending shear transects caldera)
- Gold deposit is located within a 2 sq km fractured block with gold in arsenopyrite and in tellurides
- Epithermal alteration up to 4 km from deposit
- Steep dipping dykes, shears intersecting flat structures
- Veins 1cm to 1.2m and shallow depths – 50 to 700m
- Gold in soil anomalies associated with a 3.3 km by 2.5 km silica and silica clay alteration zone
- A 2.49 g/t gold outcrop sample and 12 m trench sample averaged 1.0 g/t gold
- A 24 m trench sample averaged 1.0 g/t gold, including 2 m @ 3.41 g/t gold
- The Daloga Mine, which produced manganese and copper between 1956 and 1960
- Situated in an analogous geological setting as Vatukoula (Emperor) Mine being a prominent caldera with significant structural complexity
- Gold in soil anomalies associated with a 3.0 km by 0.5 km mapped silica clay alteration zone
- Grab rock samples of up to 9.05 g/t, 2.22 g/t, 2.16 g/t and 2.01g/t gold
- A 330 m long NE-trending soil anomaly characterized by coincident Au-Ag-As-Sb-Hg-Cu-Pb-Zn
- 6.2 g/t gold, 645 g/t silver and 3.12% copper from rock grab sampling
- 3.06 g/t gold, 819 g/t silver and 1.63% copper from historical stockpile grab samples
- A 47-tonne historical bulk sample with average of 14% copper
- Defined by a 3.3 km by 1.2 km gold in soil anomaly
- Exploration has concentrated on the Qiriyaga Hill Gold Deposit and is limited to a 250 m by 150 m area to an average hole depth of 129 m
- The Qiriyaga Hill Gold Deposit contains a near surface historical Inferred Mineral Resource (see new release dated 12.1.2022) of gold and is open along strike and at depth.
Vuinubu Ridge Zone
- Defined by a 1 km by 0.4 km gold in soil anomaly
- The Vuinubu Ridge Gold Deposit is defined by 13 drill holes drilled to a maximum vertical depth of 100 m and contains a near surface historical Inferred Mineral Resource (see new release dated 12.1.2022) and is open along strike and at depth.
The Company intends to continue its methodical exploration approach to advance the Project with next steps to include ongoing field exploration and importantly a remote spectral geology and structural studies to integrate remote sensing data with the current exploration database to define and prioritize possible alkaline related, epithermal gold targets and with subsequent drill testing to discover an economic gold deposit.