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The Frieda River Prospect is located within the New Guinea mobile belt, between the Frieda and Lagaip fault systems. Mineralization is associated with an andesitic volcanic complex, interstratified in the mid-Miocene Wogamush formation.
The volcanic edifice of the Frieda Igneous Complex was built up by two cycles of pyroclastic and flow deposition, and has been intruded by five phases of co-magmatic and post-volcanic porphyritic diorite, andesite, and trachyandesite intrusions.
Extensive hydrothermal alteration has given rise to a widespread assemblage, consisting of quartz, alunite, kaolinite, pyrite, and locally, native sulfur. Superimposed on this, and localized around centers of porphyry copper mineralization, is an assemblage which progresses from a central potassic core through a transitional zone into sericite-quartz-chlorite; sericite-quartz-andalusite; and eventually propylitic zones.
The known deposits are related to the same series of igneous events and represent a spectrum of physical and chemical conditions in a large hydrothermal system, ranging from deep level porphyry copper mineralization, to near surface, pyrite, luzonite/enargite, chalcocite, and barite mineralization. A halo of quartz-sericite-chalcopyrite-tetrahedrite-sphalerite-galena veins, peripheral to the porphyry copper deposits, appears to be an intermediate style in the system.
The porphyry copper reserves consist of a probable 760 million tonnes of mineralization, made up of 500 million tonnes at Horse and Ivaal, with an average grade of 0.5% Cu and 0.3% Au, and 260 million tonnes at Koki, averaging 0.41% Cu and 0.28 g/t Au.
Initial feasibility studies indicate that the high capital and operating costs of a project in this remote region, combined with current depressed copper prices, make the project uneconomic at this stage.
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