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    Gold ore characterisation, mercury use & value chains analysis of the artisanal & small-scale gold mining sector of Wau, Morobe Province, Papua New Guinea : thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Earth Science, Massey University, Palmerston North, New Zealand. EMBARGO PENDING.
    (Massey University, 2018) Lucas Ponyalou, Olive Kimale
    Wau, in the Morobe Province of Papua New Guinea (PNG), is a rural township with a growing artisanal and small-scale gold mining (ASGM) sector working with mercury (Hg). It was once the centre of gold mining activities for European prospectors and companies between the 1930s and the late 1980s. Mercury amalgamation is used globally for gold extraction in the ASGM industry but was banned by the Minamata Convention in 2013 due to its toxicity to human beings. Miners and their families in Wau are exposed to Hg contamination during the amalgamation and retorting of the Au-Hg amalgam. The Mineral Resources Authority (MRA) regulates the PNG mining industry using the Mining Act 1992 and the Mining Safety Act 1997. Gravity concentration and mercury amalgamation are gold recovery techniques used in the ASGM sector of Wau. Cyanidation, a common technique for processing free-milling Au and AuAg grains less than 0.2 mm in size, is largely used in the corporate mining sector but has not been used within the ASGM sector of PNG. The purpose of this research is to halt the use of mercury in Wau through an improved understanding of its gold ore characteristics. Hence, a study into the economic value chains system, gold grade distribution and ore characterisation was conducted on nine selected ASGM sites located throughout the Namie and Kaindi prospects in Wau. Although modestly profitable, all sites excluded the fundamental practices of grade control and ore characterisation, which are vital to the mining value chain. Comminution, also an important step for liberating gold, was only practised at one mine site. The average gold grades of the nine sites ranged from 0.06 to 5.45 mg/kg Au with the primary mineralization of Kaindi containing higher gold grades than the secondary deposits of Namie. The main gold minerals observed in the scanning electron microscope (SEM) include native Au and electrum AuAg with a predominant grain size of less than 0.07 mm. Mercury amalgamation is only useful on gold crystals with a grain size of 0.07-1.5 mm. Hylander et al. (2007) discovered that mercury will not efficiently amalgamate gold particles less than 0.07 mm. In addition, mercury amalgamation is only useful on free-milling, liberated native gold but will not recover gold that is attached to or encapsulated within other minerals. This suggests that the Wau miners are losing fine-grained gold less than 0.07 mm or any gold that is insufficiently liberated as waste or tailings. This was confirmed in the tailings sample from Site 1 which had numerous fine-grained Au measuring less than 0.07 mm. Thus, cyanidation would be the appropriate technique to process the gold mineral type (Au and AuAg) and gold grain size observed in most sites in Wau. Cyanidation after comminution are steps that must be included in the Wau ASGM value chain in order to optimize the recovery of the dominantly fine-grained Au.
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    Deposits, character and timing of recent eruptions and gravitational collapses in Tatun Volcanic Group, Northern Taiwan: Hazard-related issues
    (ELSEVIER SCIENCE BV, 2010) Belousov A; Belousova M; Chen C-H; Zellmer GF
    Taipei City, with a population of around 8 million, as well as two nuclear power plants is located in close proximity to the Quaternary, dominantly andesitic Tatun Volcanic Group (TVG) of Northern Taiwan. We have investigated the stratigraphy of the youngest volcaniclastic deposits, as well as the morphology of lava flows and domes of the TVG in order to reconstruct the character and timing of the most recent eruptions and related hazardous events in the area. Our data indicate that recent eruptions of the group were dominated by long-term, voluminous extrusions of crystal-rich, very viscous lavas. These eruptions formed closely spaced monogenetic domes and lava flows. Based on morphological parameters of the lava flows (thicknesses 80–150 m, lengths up to 5.6 km, and volumes up to 0.6 km3), average rates of magma effusion ranged from 1 to 10 m3/s, eruption durations from 500 to 1800 days, and lava front speeds from 0.5 to 6 m/h. Explosive activity of TVG was diverse, ranging from weak phreatic to highly explosive (VEI 4) Plinian eruptions; vulcanian activity with deposition of lithic ashes was most common. Interaction of rising magma with ground water frequently occurred during the eruptions. This study presents the first radiocarbon dates of various volcaniclastic deposits of the TVG, which indicate that Cising, Siaoguanyin, and possibly Huangzuei volcanoes had magmatic eruptions in the period 13,000–23,000 years ago. In addition, Mt. Cising had a phreatic eruption 6000 years ago, and possibly an effusive eruption just before that. Gravitational collapses of volcanic edifices with volumes 0.01–0.1 km3 and H/L 0.16–0.25 were also common. They occurred on intersections with tectonic faults and may have been triggered by seismic activity. The youngest collapses occurred at Mt. Siaoguanyin (23,000 BP) and Mt. Cising (6000 BP). It is concluded that the TVG should be considered volcanically active. The results of this study provide a basis for volcanic hazard assessment and mitigation in the area.