Development of a fully constrained structural model in a volcano caldera and its influence on open pit slope design

Authors: Stoch, B; Darakjian, T; Zorzi, L; Luck, S; Luck, D; Moffitt, K; Nicoll, S; Tennant, D; Pothitos, F

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DOI https://doi.org/10.36487/ACG_repo/2335_30

Cite As:
Stoch, B, Darakjian, T, Zorzi, L, Luck, S, Luck, D, Moffitt, K, Nicoll, S, Tennant, D & Pothitos, F 2023, 'Development of a fully constrained structural model in a volcano caldera and its influence on open pit slope design', in PM Dight (ed.), SSIM 2023: Third International Slope Stability in Mining Conference, Australian Centre for Geomechanics, Perth, pp. 467-476, https://doi.org/10.36487/ACG_repo/2335_30

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Abstract:
The Ladolam gold deposit, is located on Lihir Island, part of the Tabar-Lihir-Tanga-Feni island chain, New Ireland Province, Papua New Guinea. The Luise volcano hosts the deposit, presenting a 4 × 3.5 km-wide amphitheatre, elongated and breached to the northeast. A detailed structural model of the site is required in order to incorporate the influence of structure on slope stability for pit design and optimisation. Complex tectonic evolution, late diatreme intrusion, significant metasomatic overprint, ongoing hydrothermal activity and weathering of the country rock present challenges to developing a comprehensive, fully constrained structural model across the deposit. Given this geological complexity, structural model development and structural characterisation has utilised an evidence-based approach, with inputs from numerous disparate datasets ranging from high-resolution photogrammetry to field mapping data, core logs and downhole photographs. Photogrammetry data proved highly effective in delineating deposit scale structural trends, particularly in areas that are no longer accessible or that have historically been omitted from study. Geological structures and geotechnical variations have implications for slope design and operational risk management. Strain shadows of major north–south trending structures present zones of rheological weakness and preferential fluid ingress at Lihir, further highlighting the potential influence of geological structure on slope stability. Ongoing structural characterisation has important safety and economic benefits. As the structural model is further developed, it supports the identification of potentially higher-risk areas in current slope design. This, in turn, justifies more detailed analysis or monitoring controls to ensure safe and efficient mining and/or mine design adjustments to mitigate hazards. The following work is presented in this paper: 1) the methodology used to identify and delineate key structures, 2) characterisation methodologies employed, and 3) how identification and characterisation of structural systems have successfully informed decision-making at Lihir gold mine.

Keywords: structural geology, structural characterisation, caldera, stability analysis, geotechnical characterisation, slope optimisation, slope stability

References:
Blackwell, JL 2010, Characteristics and Origins of Breccias in a Volcanichosted Alkalic Epithermal Gold Deposit, Ladolam, Lihir Island, Papua New Guinea, PhD thesis, University of Tasmania, Hobart.
Blackwell, JL, Cooke, DR, McPhie, J & Simpson, KA 2014, ‘Lithofacies associations and evolution of the volcanic host succession to the Minifie ore zone, Ladolam gold deposit, Lihir Island, Papua New Guinea’, Economic Geology, vol. 109, no. 4, pp. 1137–1190,
Carman, GD 1994, Genesis of the Ladolam Gold Deposit, Lihir Island, Papua New Guinea, PhD thesis, Monash University, Melbourne.
Cole, JW, Milner, DM & Spinks, KD 2005, ‘Calderas and caldera structures: a review’, Earth-Science Reviews, vol. 69, no. 1–2,
pp. 1–26,
Cooke, D & Sykora, S 2020, ‘Lihir Alkalic epithermal gold deposit, Papua New Guinea’, in E Lawlis, J Blackwell, M Ageneau, N Jansen, A Harris & D Selley (eds), Geology of the Yukon-Tanana Terrane and Adjacent Regions, Society of Economic Geologists, Littleton, pp. 491–512.
Corbett, GJ 2012, ‘Structural controls to, and exploration for, epithermal Au-Ag deposits’, Australian Institute of Geosciences Bulletin, vol. 56, pp. 43–47.
Davies, RH & Ballantyne, GH 1987, ‘Geology of the Ladolam gold deposit Lihir Island, Papua New Guinea’, paper presented at Pacific Rim Congress 87, Gold Coast.
Gordon, RG, Cox, A & Harter, CE 1978, ‘Absolute motion of an individual plate estimated from its ridge and trench boundaries’, Nature, vol. 274, no. 5673, pp. 752–755,
Hall, R 2002, ‘Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations’, Journal of Asian Earth Sciences, vol. 20, no. 4, pp. 353–431,
Holt, RM 1990, ‘Permeability reduction induced by a nonhydrostatic stress field’, SPE Formation Evaluation, vol. 5 no. 04,
pp. 444–448,
Lawlis, E 2020, Geology of the Kapit NE and coastal ore zones, Lihir gold deposit, Papua New Guinea, BSc Hons thesis, University Of Tasmania.
Lawlis, E, Cooke, DR & Harris, AC 2015, ‘Volcanic-hydrothermal breccias at the Lihir alkalic gold deposits, Papua New Guinea’, paper presented at 13th Biennial Society for Geology Applied to Mineral Deposits Meeting, Nancy.
Moyle, AJ, Doyle, BJ, Hoogvliet, H & Ware, AR 1990, ‘Ladolam gold deposit, Lihir Island’, Australasian Institute of Mining and Metallurgy, vol. 14, pp. 1793–1805.
Pichler, T, Giggenbach, WF, McInnes, BIA, Buhl, D & Duck, B 1999, ‘Fe sulfide formation due to the seawater-gas-sediment interaction in a shallow-water hydrothermal system at Lihir Island, Papua New Guinea’, Economic Geology, vol. 94, pp. 281–288,
Seequent 2020, Leapfrog Geo, computer software, Seequent, Christchurch, https://www.seequent.com
Sharp, WD & Clague, DA 2006, ‘50-Ma Initiation of Hawaiian-Emperor bend records major change in Pacific plate motion’, Science, vol. 313, no. 5791, pp. 1281–1284,
Simmons, SF & Brown, KL 2006, ‘Gold in magmatic hydrothermal solutions and the rapid formation of a giant ore deposit’, Science, vol. 314, no. 5797, pp. 288–291,
Sykora, S 2016, Origin, Evolution and Significance of Anhydrite-Bearing Vein Arrays and Breccias, Lienetz Orebody, Lihir Gold Deposit, Papua New Guinea, PhD thesis, University of Tasmania, Hobart.
Sykora, S, Selley, D, Cooke, DR & Harris, AC 2018, ‘The structure and significance of anhydrite-bearing vein arrays, Lienetz orebody, Lihir Gold Deposit, Papua New Guinea’, Economic Geology, vol. 113, no. 1, pp. 237–270,
10.5382/econgeo.2018.4550
Tregoning, P 2002, ‘Plate kinematics in the western Pacific derived from geodetic observations’, Journal of Geophysical Research, Solid Earth, vol. 107, no. B1, pp. 71–78,
Wallace, DA, Johnson, RW, Chappell, BW, Arculus, RJ, Perfit, MR & Crick, IM 1983, ‘Cainozoic volcanism of the Tabar, Lihir, Tanga, and Feni Islands, Papua New Guinea: Geology whole-rock analyses and rock-forming mineral compositions’, Australian Bureau of Mineral Resources, Geology and Geophysics, vol. 243, no. MF197, pp. 1–140,
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