南アフリカ共和国ブッシュフェルト北リムにおけるウォーターバーグ白金族鉱床の発見

In October 2009, JOGMEC entered into a mineral exploration joint venture ("JV") agreement with Vancouver based Platinum Group Metals Ltd. ("PTM") and South Africa based Mnombo Weth Consultant CC to conduct a grass-rooted Waterberg PGE project at the north of the Bushveld Northern limb, South Africa. The project area is totally covered with Proterozoic Waterberg Group, a dense sedimentary package after Bushveld igneous complex intrusion, thus none has ever attempted PGE exploration due to lacking any mineral showings. The exploration target of the JV was deep-seated hidden PGE reefs suggested by high gravity and high magnetic features elongating NW to SE in the area.<br>After two-year detailed ground gravity and magnetic surveys and following two structural diamond drill holes ("DDH"), the third hole WB003 located southeast end of the area intersected significant PGE mineralization in Main Zone from 643.25m to 646.75m (3.50m) with an average grade of 3.47g/t [2PGE+Au], and 661.50m to 665.50m (5.00m) of 7.00g/t. Since following several holes surrounding to WB003 also intersected similar mineralization in the same igneous horizon, the JV confirmed that PGE mineralization occurs as a continuous "reef". Then, massive 250m-grid drilling campaign has been conducted up to September 2013. The JV completed 111 DDH of total 128,505 m length, and delineated 17.7million ounces (545t) of precious metals [Pt (163.3t), Pd (328.4t) and Au (53.3t)] under the inferred resource category. Further exploration room is still remaining in northward and in depth from the current resource area.<br>The JV concludes that Waterberg deposits consist of two new PGE reefs, shallower T zone and deeper F zone, both are dipping to west 34 to 38 degree, extending NNE-SSW which trend is different from JV's initial idea suggested by geophysics. Major ore minerals in both zones are mostly pentlandite and chalcopyrite. Pyrrohtite and pyrite are common in F zone but rare in T zone. The shallowest part of the T zone is 130m from surface which mostly consists of gabbronorite, anorthosite, troctolite and pyroxenite. Texture is coarse to pegmatoidal in part. Thickness of mineralization is 3.7m in average (T2 zone), swelling up to 25m. T zone is characterized by unusually high gold ratio of 20% in a metal split of Pt, Pd and Au, as a Bushveld PGE reef. Another deeper PGE reef, F-zone is an igneous horizon located 100m to 450m below the bottom of T-zone. F-zone mostly consists of troctolite and hurzburgite, rarely pyroxenite. Width and grade vary place by place, but its width tends to be greater than T-zone. F-zone occupies the lowest Bushveld igneous stratigraphy in the area contacting to meta-granite basement. Alteration minerals, talc and serpentine gradually increase with depth toward the basement boundary. On a metal split, F-zone ore shows high Pd contents of more than 60%, while Au contents are less than 5% that are common level in Bushveld PGE reefs.<br>Upon recently disclosed positive results of preliminary economic assessment of the Waterberg project, the JV is preparing the pre-feasibility study. Concurrently, JOGMEC plans to transfer its project interest to qualified Japanese company(s).