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The Mt Suckling project is situated at the eastern end of New Guinea’s Central Range, one of the world’s premier porphyry copper belts. This belt includes several giant porphyries including Grasberg, Ok Tedi, Frieda, Porgera and Wafi/Golpu. The Mt Suckling region has been by-passed by modern porphyry exploration. However, PPM has identified three prospective porphyry prospects in a linear belt some 19 km long and localised within the wide trace of the Keveri Fault Zone, part of the once active plate boundary between the Australian and Pacific plates (Fig 1). The Doriri Creek hydrothermal Ni-PGE prospect is also located in the trace of this structure, about 8 km west of the Urua Creek prospect.
Flagship prospect is the Urua Creek Au-Cu prospect, hosted in a very young likely Early Pliocene diatreme, a breccia filled volcanic vent containing carbonised wood fragments indicative of a direct connection to the surface (Fig 2). The breccia has dimensions in excess of 1,700 m x 900 m and comprises a series of nested igneous events. Soil gold-copper-molybdenum anomalism is coincident with the breccia, suggestive of a porphyry copper system (Fig 3). The breccia contains areas of both low-grade propylitic zone and high-grade phyllic zone gold-copper mineralisation. Gold-copper mineralisation in the propylitic zone in surface trenches ranges up to 33 m @ 0.17 % Cu, 0.27 g/t Au and in the phyllic zone up to 36 m @ 0.72 % Cu, 0.97 g/t Au (incl. 12 m @ 1.13 % Cu, 2.03 g/t Au). Obvious drill targets are available. (Table 1)
Ioleu Creek Cu-Au prospect is located 19 km east of Urua Creek prospect. The prospect is localised within the Keveri Fault Zone and is noteworthy for a float train of large 50-60 cm diameter boulders of basalt containing thick (up to 10 cm) veins of chalcopyrite-bornite (Fig 4). Their angularity indicates that they are sourced locally. A widespread area of pannable gold is coincident with the train of copper boulders. Detrital gold is fine-grained (<0.5 mm size) and angular, again suggestive of limited transport and a local source. The chalcopyrite-bornite boulders and detrital gold are coincident with two stocks of intensely pervasively argillised gabbro, suggesting a genetic link. The mafic rocks have a distinctive haematite stockwork and are associated with localised platinum-palladium and copper soil anomaly. (Table 2)
The recently identified Araboro Creek prospect is distinctive for its cluster of nested circular features. It is located in the linear belt that includes the Urua Creek and Ioleu Creek porphyry prospects and is another breccia-related intrusive centre localised along the Keveri Fault Zone (Fig 5). Sampling at Araboro Creek has located float of quartz-sulphide rock containing 1.3 % Cu, 0.14 g/t Au, and chalcopyrite-pyrite-covellite rock containing 1.16% Cu (Fig.6).
The Doriri Creek hydrothermal Ni-PGE prospect contains the highest platinum metals grades known in PNG (Figs 7 & 8). Mineralisation is confined to massive magnetite-mica rock hosted in Jurassic-Cretaceous gabbro. Sulphides are rare or absent. Bismuth, antimony and tellurides are associated with the nickel-palladium-platinum mineralised zones, but mineral species have yet to be identified. The Doriri Creek lode has a strike length in excess of 520 m and the mineralised zone an average width of 10-15 m. High nickel-palladium-platinum grades are contained in the zone of massive magnetite-mica rock and surface grades average 10-15 m @ 1.3 % Ni, 1-2 g/t 2PGE (Figs 9 & 10). Narrow intervals (0.46 cm) contain up to 2.58 % Ni, 14.7 g/t Pd, 3.4 g/t Pt. Nickel-palladium-platinum concentrations decrease at higher levels in the deposit as the lode splinters and inter-fingers with stockworked argillised gabbro. Patchy gold mineralisation is present in the stockwork zone overlying the main mica-magnetite mineralised zone. A ground magnetics survey across the mineralised zone is shown in Fig 11.
The Dimidi Creek prospects are located in a northern tributary of the Ada’u River (Fig 11). Dimidi Creek is noteworthy for both a persistent train of pannable gold and platinum well into its middle reaches, as well as the apparently unique occurrence of float boulders of chromitite (Fig 12). Three prospects have been identified within the area, viz. Muruk Pt-Ni-Cr prospect, Duna Creek Pt-Cr prospect and Dimidi Creek prospect. All three prospects are located in the Awariobo Range ultramafic complex.
The Muruk Pt-Ni-Cr prospect is a hydrothermal deposit noteworthy for its prominent exposure in the bed of Dimidi Creek (photo). The prospect has many similarities with the Doriri Creek Pd-Pt-Ni prospect and contains several mineralised magnetic lenses hosted in a + 25 m wide NE-SW trending zone of talc alteration. Reconnaissance surface samples have returned grades of 18 m @ 30 ppb Pt, 0.41 % Ni and 1 m @ 65 ppb 2PGE+Au, 0.14 % Ni, 0.32 % Cr.
The Duna Creek Pt-Cr prospect is located in a western tributary of Dimidi Creek, and is centred on a pegmatoid anorthosite dyke that contains an anomalous 88.2 ppb Pt and 0.54 % Cr. Ultramafic wall-rock to this dyke is also PGE-enriched, with an anomalous 30.3 ppb Pt. The extent of dyking is unknown at this early stage. Both lithologies are the first ultramafic rocks of the Papuan Ultramafic Belt to return anomalous PGE values and, given the reconnaissance nature of sampling to date, is considered to be extremely encouraging. Sampling has indicated the Awariobo Range complex to be PGE fertile. An average PGE content of 21 ppb Pt+Pd in unmineralized rocks compares with a global average of around 10 ppb.
The Dimidi Creek prospect consists of a 75 m interval of variably hydrothermally altered ultramafic, mafic and felsic rocks located along the western bank of the middle reaches of Dimidi Creek. Rock types within the prospect range from peridotite to pyroxenite, leucogabbro to felsite. Textures include equigranular fine- to coarse-grained porphyritic, pegmatitic and heterolithic gabbro breccia. To-date, no significant PGE results have been obtained from detailed sampling of these lithologies.