Blackwell, JL and Cooke, DR and McPhie, J and Simpson, KA, Lithofacies associations and evolution of the volcanic host succession to the Minifie ore zone: Ladolam gold deposit, Lihir Island, Papua New Guinea, Economic Geology, 109, (4) pp. 1137-1160. ISSN 0361-0128 (2014) [Refereed Article]
Copyright 2014 Society of Economic Geologists, Inc.
The 46-million-ounce Ladolam gold deposit, the largest alkalic epithermal gold deposit in the world in terms of contained gold, is composed of four ore zones: Minifie, Lienetz, Kapit, and Coastal. This detailed lithofacies study of the Minifie ore zone recognized three evolutionary stages: (1) volcanosedimentary strata (part of an alkalic composite volcanic island), (2) a porphyry-style breccia dike, and (3) epithermal-style breccias. The Plio-Pleistocene volcanosedimentary stratigraphy reflects the transition from subaerial deposition of pyroclastic surge deposits close to vent to a subaqueous, quiet depositional environment into which a cryptodome was emplaced. The stratigraphy is predominantly composed of polymictic, matrix-supported breccia and sandstone interbedded with lavas and shallow intrusions. The Minifie strata have a shallow southward dip as a result of Quaternary uplift. Overprinting the volcanosedimentary stratigraphy are three hydrothermally cemented breccia facies—one deposited in the porphyry environment and two deposited in the epithermal environment.
Porphyry-style alteration assemblages and a 3- to 5-m-wide biotite-K-feldspar-calcite-anhydrite–cemented breccia dike are focused around the central "Minifie shear" fault. The porphyry alteration assemblages are overprinted by shallow-level and deeper-level epithermal-style features. The deeper-level (below the present mining surface; >140 m below sea level) epithermal vein stockwork is composed of quartz-calcite-adularia-anhydrite–cemented breccias and shallowly northward to near-horizontal dipping veins that have gold grades of 1 to >60 g/t Au. Shallow-level epithermal facies (adularia-quartz-pyrite–cemented breccias, veins, and associated alteration) host the bulk mineable gold ore, and typically yield >4 g/t Au over 12-m blast hole samples.
|Item Type:||Refereed Article|
|Keywords:||hydrothermal, breccia epithermal, Lihir|
|Research Division:||Earth Sciences|
|Objective Division:||Expanding Knowledge|
|Objective Group:||Expanding Knowledge|
|Objective Field:||Expanding Knowledge in the Earth Sciences|
|Author:||Blackwell, JL (Ms Jacqueline Blackwell)|
|Author:||Cooke, DR (Professor David Cooke)|
|Author:||McPhie, J (Professor Jocelyn McPhie)|
|Author:||Simpson, KA (Dr Kirstie Simpson)|
|Funding Support:||Australian Research Council (CE0561595)|
|Web of Science® Times Cited:||11|
|Deposited By:||Earth Sciences|
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