Summary:
The Project lies within the north to south trending Neoproterozoic Araguaia Fold Belt.
The belt comprises metamorphosed and deformed marine-clastic sediments of the Tocantins Group and is split into two formations based on the degree of metamorphism present. The prospective areas of HZM are located in the western Couto de Magalhães Formation which contains weakly metamorphosed, marine pelites with local carbonate, iron-rich, and mafic to ultramafic bodies.
The local geology has largely been interpreted from airborne geophysical survey data, soil sampling data, mapping and core drilling by HZM and previous owners of the tenements. Various types of metasediments cover the vast majority of the licence area. Large plateau areas, varying in size from a few hundred square metres to several square kilometres, and generally capped with a hard iron-rich duricrust that is occasionally silicified are frequently developed over mafic and ultramafic bodies. These bodies and numerous northwest-southeast to north-south trending lineaments have been identified from magnetic data and outcrop. These bodies are often bounded by a siliceous breccia. Bodies of pillow lava and other volcanic material also exist. The area is cut by numerous mafic dykes.
A distinctive lateritic sequence is developed over ultramafic and mafic rocks within the Project area and the same sequence can be recognised at each of the target sites though the thickness and extent of each facies varies from location to location. The sequence can be split into six main facies types: soil, ferricrete, limonite, transition, saprolite and fresh rock, as well as numerous sub-facies.
The Project can be divided into Araguaia Nickel North (ANN) and Araguaia Nickel South (ANS). The ANN section comprises the Vale dos Sonhos (VDS) deposit. ANS comprises the following deposits:
- Jacutinga (JAC);
- Vila Oito West (VOW);
- Vila Oito (VOI);
- Vila Oito East (VOE);
- Pequizeiro (PQZ);
- Pequizeiro West (PQW);
- Baião (BAI).
The target mineralisation of the Project area is characteristic of typical nickel laterite deposits formed in a seasonally wet tropical climate, on weathered and partially erpentinised ultramafic rocks. Features of nickel laterites include:
- The nickel is derived from altered olivine, pyroxene and serpentine that constitute the bulk of tectonically emplaced ultramafic oceanic crust and upper mantle rocks.
- Lateritisation of serpentinised peridotite bodies occurred during the Tertiary period and the residual products have been preserved as laterite profiles over plateaus/amphitheatres, elevated terraces and ridges/spurs.
- The process of formation starts with hydration, oxidation, and hydrolysis, within the zone of oxidation, of the minerals comprising the ultramafic protore.
- The warm/hot climate and the circulation of meteoric water (the pH being neutral to acid and the Eh being neutral to oxidant) are essential to this process. Silicates are in part dissolved, and the soluble substances are carried out of the system.
- This process results in the concentration of nickel in the regolith in hydrated silicate minerals and hydrated iron oxides; nickel and cobalt also concentrate in manganese oxides. The regolith hosting nickel laterite deposits is typically 10 m to 50 m thick, but can exceed 100 m.
- Concentration of the nickel by leaching from the limonite zone and enrichment in the underlying saprolite zones is also common. Leaching of magnesium +/- silicon causes nickel and iron to become relatively concentrated in the limonite zone. Nickel is released by recrystallisation and dehydration of iron oxy-hydrides and is slowly leached downwards through the profile, both vertically and laterally, re-precipitating at the base with silicon and magnesium to form an absolute concentration within the saprolite.
- The degree of the nickel concentration and the detailed type of regolith profile developed is determined by several factors including climate, geomorphology, drainage, lithology composition, and structures in the parent rock, acting over time.
- A typical laterite profile contains three distinct horizons (limonite, transition and saprolite).