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Lihir Operation - Ladolam, Minifie, Lienitz, Kapitz |
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Papua New Guinea |
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Au
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Super Porphyry Cu and Au
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The Ladolam gold mine lies within the Luise Caldera, located on the eastern side of the north-south elongated, 20 x 12 km, Lihir, or Aniolam Island within the Tabar-Lihir-Feni-Tanga chain of islands northeast of New Ireland.
(Location: 3° 7' 42"S, 152° 38' 6"E).
Indications of gold mineralisation associated with hydrothermal alteration and thermal activity were first detected during geological mapping conducted by the Australian Bureau of Mineral Resources between 1969 and 1974. Based on these observations, Kennecott Exploration Australia in joint venture with Niugini Mining Limited in 1982 sampled the locations indicated, resulting in a rock chip sample in Luise Harbour averaging 1.7 g/t Au. This resulted in an application for an Exploration lisence being lodged and granted, also in 1982, and a drilling program commencing in 1983. By the end of 1984 the presence of a large gold resource had been confirmed. This work had concentrated on the Luise Harbour and adjacent Lienetz area. Further sampling between 1985 and 1987 identified gold in the neighbouring Ladolam Creek with follow-up drilling intersecting the Minifie deposit. Further drilling defined several other adjacent and partly overlapping deposits, known as the Camp and Kapit areas. In 1988, RTZ plc (now Rio Tinto) acquired Kennecott from BP Minerals America and took over as the joint venture partner with Niugini Mining Limited. In June 1995, Lihir Gold Limited (LGL) was incorporated in PNG for the purpose of acquiring formal ownership of the project from the Lihir Joint Venture. This entity was owned by Rio Tinto, Niugini Mining and the Lihir Islanders. Mining Leases were granted in 1995. Construction began in the same year, and by 1997 the processing plant at the Putput site was complete with the first gold pour on 25 May 1997. Rio Tinto sold their remaining interest in 2005. In 2010, Lihir Gold Limited was merged into Newcrest Mining. Production increased from 7.24 to over >20
tonnes of gold per annum between 1997 and 2008, and has varied between 18.7 and 29.7 t per annum over the period from then to 2020, for a total production of 504.2 tonnes of gold since mining commenced in 1997 to June 2020. Average recovery between 1997 and 2020 has been 83.4%
Lihir is a major bulk gold deposit with mineralisation represented by an earlier un-economic porphyry stage, and a later, overprinting low sulphidation advanced argillic phase that accompanied the introduction of the bulk of the gold mineralisation. The three main orebodies, from south to north, Minifie, Lienitz and Kapit (the latter two connected by the Link zone) are located within a generally north-south elongated area inside the breached 5.5 x 3.5 km Luise Caldera on the east coast of Lihir Island. All fall within a 1.5 to 2 km radius of the centre of the caldera.
Minifie has a mushroom shape with plan dimensions of the order of 700 x 400 m with mineralisation extending from 50 m above to 150 m below sea level. Shallow-level refractory sulphide ore is associated with pervasive adularia-sulphide alteration, and had a concave, blanket-like geometry. Beneath the refractory sulphide mineralisation is quartz-calcite vein stockwork material.
Lienitz is 600 x 300 m in plan and is mineralised from 140 m above to 250 m below sea level, although the bulk of the ore is from sea level to 200 m below. It is separated from Minifie by unmineralised, propylitically-altered igneous units and breccias.
Kapitz is located between Lienetz and Luise Harbour to the east, and is ~500 m due north of the western limit of
Lienetz. It is linked to Lienetz by a sub-horizontal zone of low-grade mineralisation, generally carrying <2.0 g/t Au, that is up to 100 m in thickness, and comprises a funnel-shaped zone associated with adularia-pyrite alteration and open-space breccias.
The smaller Coastal zone has a NW trend, and is moderately to steeply NE dipping. It is located immediately NE of Lienitz extending to the shore of Luise Harbour. Mineralisation is hosted within leached, vuggy breccias as well as more discrete calcite-quartz-pyrite-anhydrite vein/breccias. This deposit has remained poorly drilled due to its proximity to Luise Harbour and to the apparent relatively small and narrow nature of the mineralised zones.
Lihir Island is one of a series of four volcanic island groups which rise from a submarine platform and form a chain roughly parallel to and 50 km to the north-east of New Ireland in Papua New Guinea. This chain is also parallel to and 100 km south-west of the Kilinailau Trench where the Pacific plate subducted below the Melanesian Arc which is peripheral to the Australian Plate until the Mid Miocene. The magmatic arc of the Tabar-Lihir-Feni-Tanga chain of islands however, is apparently related to subduction below the New Britain Trench to the south, exploiting a pre-existing crustal weakness from the earlier subduction, and/or a transform fault associated with extension on the Manus Spreading Centre.
The 3 to 1 Ma Luise Caldera occupies the youngest of several Miocene to Holocene alkaline volcanoes developed on the island. The oldest rocks on the island comprise 350 m of Pliocene to Miocene mafic lavas and volcaniclastics of the Londolovit Block on the northern tip, while a NE-SW elongated, unconformably overlying and partly fault bounded block of Pliocene to Pleistocene mafic lavas, agglomerates and lahars around 500 m thick, the Wurtol Wedge adjoins, the Londolovit Block and stretches across the island to the west coast. The Londolovit Block and Wurtol Wedge probably represent portions of a deeply eroded Late Miocene to Pliocene volcano. Sub-economic gold with associated potassic, phyllic and argillic alteration is hosted by altered intermediate volcanics and intrusives. The southern part of the island is occupied by the Pliocene to Pleistocene Kinami Volcano lavas, pyroclastics, breccias and derivative epiclastics. This volcano has associated phyllic and argillic alteration, which grades into potassic zones at depth, which in turn pass out into propylitic zones. Low grade gold accompanies the phyllic alteration. The Pleistocene Huniho Volcano, which has a number of satellite cones and craters makes up the north-western segment of the island with tephras and lahars overlying mafic lavas. The late 5.5 x 3.5 km Luise Caldera is the remnants of a volcanic edifice on the central east coast, north of the Kinamo volcano and east of the Wurtol Wedge. The associated volcanics include trachy-basaltic lavas, pyroclastics and breccias. All three of the remnant volcanic centres have undergone some form of seaward collapse, particularly the most recent, the Luise volcano. Raised coral reefs fringe most of the island, but are absent in Luise Harbour, suggesting they predate the caldera flooding event.
Volcanic rocks predominate in the upper parts of the ore zones of the Luise Caldera, and the margins of the system, and are underlain by intrusives. The host volcanic sequence occupies most of the floor of the Luise Caldera and comprises intermediate (latitic, andesitic and trachytic) lavas, tuffs and volcanic breccias. These extrusives are intruded by a series of fine to medium grained, quartz poor but silica saturated monzonitic to monzodioritic porphyries ranging from pyroxene microdiorite to biotite syenite and some andesite porphyry.
Intrusion-related potassic alteration occurred in the period 0.917 to 0.342 Ma, while the epithermal gold mineralisation is dated at 0.336 Ma, possibly continuing to 0.1 Ma, although the geothermal system is presently active. While the Luise Caldera trends elongate NNE, it is cut by north-south structures associated with the deep fractures that are interpreted to localise the magmatism of Lihir Island. NW-trending fractures are also evident and host the NE-dipping Minifie mineralisation. The Luise volcano is interpreted to have collapsed sideways at about 0.34 Ma. NE-dipping listric-style faults are interpreted to have developed within the remaining underlying part of the edifice. This failure removed about 1 km from above an active porphyry Cu-Au deposit. In doing so, it is believed to have removed the confining pressure and allowed epithermal fluids to escape up the listric faults produced during the collapse, and as such initiated development of the epithermal mineralisation.
Mineralisation is coincident with a NNE trending zone of hydrothermally altered volcanics and breccias intruded at depth by porphyries. Three stages of alteration have been identified,
i). an early porphyry style accompanied by low grade Cu-Au-Mo mineralisation at depth, with a potassic core (mostly phlogopitic biotite-anhydrite with lesser orthoclase, magnetite with pyrite, chalcopyrite and molybdenite) and a peripheral propylitic phase (chlorite ±amphibole ±albite ±epidote ±calcite ±magnetite);
ii). A transitional zone, which forms the bulk of the ore at Minifie, characterised by pervasive adularia ±illite and fine grained, refractory auriferous pyrite within extensive shallow hydrothermal breccias located above biotite altered porphyritic stocks, and grading abruptly downward into sub-economic anhydrite-K feldspar ±pyrite alteration of the porphyry system; and
iii). a younger, overprinting and shallower low sulphidation epithermal style as in the Lienetz area, comprising advanced argillic (alunite ±opaline silica ±kaolinite ±sulphur), argillic (kaolinite ±smectite ±illite) and phyllic (illite ±K-feldspar ±silica). Alteration generally forms a horizontal layering, with porphyry style potassic and propylitic assemblages at depth, grading up through phyllic to epithermal argillic and advanced argillic phases nearer the surface.
Alunite and opal fill veins and stockworks near the surface, grade to quartz and adularia at intermediate depths, underlain by anhydrite and carbonate. Sulphides and gold mineralisation generally mimic the horizontal alteration pattern, although some follows steep 'feeder' fractures. The horizontal zonation represents a surface oxidation regime, related to mixing with ground water, passing down progressively into argillaceous altered and silica clay, through to a boiling layer and then the anhydrite sealed zone. Grades are best from the silica-clay to the boiling zones. Gold is predominantly fine grained and contained within pyrite and marcasite. The overall sulphide or reactive sulphur content averages 6%. Geothermal activity is still taking place.
Mineral Resources and Ore Reserves at Lihir as of January 2004 (Newcrest Annual Report, 2004) were:
Total Identified Mineral Resource at a 1.5 g/t Au cut-off - 442.5 Mt @ 3.14 g/t Au for 1390 tonnes of contained gold.
Proved + probable reserves were - 163.5 Mt @ 3.88 g/t Au for 635 tonnes of contained gold.
Mineral Resources and Ore Reserves at Lihir in August 2011 (Newcrest Mining website, 2012) were:
Measured + Indicated + Inferred Mineral Resource - 830 Mt @ 2.1 g/t Au for 1745 tonnes of contained gold.
Proved + Probable Reserves - 400 Mt @ 2.4 g/t Au for 960 tonnes of contained gold.
NOTE: Mineral Resources are inclusive of Ore Reserves.
Remaining Mineral Resources and Ore Reserves at 30 June 2022 (Newcrest Mining Annual Mineral Resources and Ore Reserves Statement, August 2022) were:
Mineral Resources
Open Pit Measured + Indicated Mineral Resource - 510 Mt @ 2.3 g/t Au;
Open Pit Inferred Mineral Resource - 67 Mt @ 2.3 g/t Au;
Stockpile Measured + Indicated Mineral Resource - 72 Mt @ 1.8 g/t Au;
TOTAL Mineral Resource - 649 Mt @ 2.25 g/t Au for 1456 tonnes of contained gold.
Ore Reserves
Open Pit Proved + Probable Ore Reserves - 230 Mt @ 2.4 g/t Au;
NOTE: Mineral Resources are inclusive of Ore Reserves.
As of July 2023, the Lihir operation was owned by Newcrest Mining Limited.
Some of the information above has been drawn from "Gleeson, K., Butt, S., O’Callaghan, J. and Jones, C., June 2020 - Lihir Operations, Aniolam Island, Papua New Guinea; an NI 43-101 Technical Report prepared by Newcrest Mining Limited, 197p."
The most recent source geological information used to prepare this decription was dated: 2020.
Record last updated: 21/7/2023
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Lihir
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Selected References:
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Blackwell J L, Cooke D R, McPhie J and Simpson K A, 2014 - Lithofacies Associations and Evolution of the Volcanic Host Succession to the Minifie Ore Zone: Ladolam Gold Deposit, Lihir Island, Papua New Guinea : in Econ. Geol. v.109 pp. 1137-1160
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Carman G D 2002 - Factors Contributing to the Formation of the Giant Ladolam Gold Deposit, Lihir Island, PNG: in Conference Proceedings, AusIMM Conference 2002, Auckland, New Zealand, 1-4 September AusIMM, Melbourne pp 185-189
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Davies R M, Ballantyne G H 1992 - Geology of the Ladolam gold deposit, Lihir Island, Papua New Guinea: in Epithermal Gold in Asia and the Pacific, Mineral Concentrations and Hydrocarbon Accumulations in the ESCAP Region UN Econ & Social Comm to Asia & the Pacific v6 pp 189-194
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Gemmell JB, Sharpe R, Jonasson IR, Herzig PM 2004 - Sulfur Isotope Evidence for Magmatic Contributions to Submarine and Subaerial Gold Mineralization: Conical Seamount and the Ladolam Gold Deposit, Papua New Guinea: in Econ. Geol. v99 pp 1711-1725
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Kidd R P and Robinson J R 2004 - A review of the Kapit orebody, Lihir Island Group, Papua New Guinea: in Pacrim 2004 Conference, Hi Tech and World Competitive Mineral Success Stories Around the Pacific Rim, Adelaide, 19-22 September, 2004, AusIMM, Melbourne, Proceedings volume, pp. 323-331
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Lihir Gold Limited 1995 - Description of the Lihir Project: in extract from the Lihir Gold Limited prospectus, 1995 pp 46-59
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Moyle A J, Doyle B J, Hoogvliet H and Ware A R, 1991 - The Geology and Mineralisation of the Ladolam Gold Deposit, Lihir Island, Papua New Guinea: in PNG Geology, Exploration and Mining Conference, Rabaul, June 1991 The AusIMM, Melbourne, pp. 101-111
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Moyle A J, Doyle B J, Hoogvliet H, Ware A R 1990 - Ladolam gold deposit, Lihir Island: in Hughes FE (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1793-1805
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Muller D and Groves D I 1993 - Direct and indirect associations between potassic igneous rocks, shoshonites and gold-copper deposits : in Ore Geology Reviews v8 pp 383-406
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Muller D, Kaminski K, Uhlig S, Graupner T, Herzig P M and Hunt S 2002 - The transition from porphyry- to epithermal-style gold mineralization at Ladolam, Lihir Island, Papua New Guinea: a reconnaissance study: in Mineralium Deposita v37 pp 61-74
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Orogen Minerals Ltd 1996 - Lihir gold project: in Extracts from Orogen Minerals Ltd Prospectus, 1996 pp 73-81, 170-186
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Petersen S, Herzig P M, Hannington M D, Jonasson I R, Arribas A 2002 - Submarine Gold mineralization near Lihir Island, New Ireland fore-arc, Papua New Guinea: in Econ. Geol. v97 pp 1795-1813
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Richards, J.P., 2009 - Postsubduction porphyry Cu-Au and epithermal Au deposits: Products of remelting of subduction-modified lithosphere: in Geology v.37, pp. 247-250.
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Rutter J, Blackwell J L, Carman G D, Cooke D R, Dala K, Javati N, Johnstone R, Kikiha D, Likia B, McPhie J and O’Sullivan T, 2008 - The Character and Spatial Distribution of Epithermal Gold Mineralisation at the Ladolam Gold Deposit, Lihir Island, Papua New Guinea: in Pacrim 2008 Conference, 24-26 November 2008, Gold Coast, Queensland, Australia, The AusIMM, Melbourne, Extended Abstracts Volume, pp. 433-438
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Sykora, S., Cooke, D.R., Meffre, S., Stephanov, A.S., Gardner, K., Scott, R., Selley, D. and Harris, A.C., 2018 - Evolution of Pyrite Trace Element Compositions from Porphyry-Style and Epithermal Conditions at the Lihir Gold Deposit: Implications for Ore Genesis and Mineral Processing: in Econ. Geol. v.113, pp. 193-208.
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Sykora, S., Selley, D., Cooke, D.R. and Harris, A.C., 2018 - The Structure and Significance of Anhydrite-Bearing Vein Arrays, Lienetz Orebody, Lihir Gold Deposit, Papua New Guinea: in Econ. Geol. v.113, pp. 237-270.
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White, N.C., Leake, M.J., McCaughey, S.N. andd Parris, B.W., 1995 - Epithermal gold deposits of the southwest Pacific: in J. of Geochemical Exploration v.54, pp. 87-136.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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