The Porgera gold deposit, Papua New Guinea : geology, geochemistry and geochronology
type: CreativeWork
description: The Porgera gold deposit, located in the highlands of Papua New Guinea (PNG), contains ~410 tonnes Au and ~890 tonnes Ag, distributed between a large lower-grade ore zone (78.6 million tonnes, 3.5 g/tonne Au, 9.9 g/tonne Ag), and a smaller highgrade zone (5.0 million tonnes, 26.5 g/tonne Au, 22.1 g/tonne Ag). Lower-grade mineralization occurs as stockworks and disseminations of auriferous arsenical pyrite associated with strong sericite-carbonate alteration, which cross-cut and overprint a suite of epizonal mafic stocks and dykes of the Porgera Intrusive Complex (PIC) and their sedimentary host rocks (Jurassic-Cretaceous shelf sediments). Minor free gold also occurs in base metal-sulphide veins associated with these alteration zones. Later, high-grade mineralization (locally up to 3000 g/tonne Au) occurs in quartz-oscoelite veins associated with the Roamane Fault (an extensional structure which cross-cuts the intrusive complex and the earlier dissemiriated ore). Abundant visible gold occurs with Au-Ag-Ag-tellurides in these epithermal-style, vuggy, banded veins. Deposition of both types of ore is shown by K-Ar dating of sericite (illite) and roscoelite to have occurred within 1 Ma of the time of emplacement of the PIC at 6.0 ± 0.3 Ma (2a; K-Ar dating of igneous biotite, and 40Ar/39 Ar dating of hornblende). Geochemical, isotopic, and petrographic studies of the PIC indicate that the intrusions represent a comagmatic, volatile-rich alkali basalt/gabbro - hawaiite (trachybasalt) -mugearite (basaltic trachyandesite) fractionation suite, derived from a larger fractionating magma chamber located deeper in the upper crust (aeromagnetic evidence). The intrusions are medium- to coarse-grained, and textures vary from porphyritic to ophitic. Mafic rocks contain olivine (pseudomorphs) and Cr-rich diopside phenocrysts, whereas hornblende (titanian magnesio-hastingsite), Ti-rich salite, and plagioclase phenocrysts occur in hawaiites and mugearites. Fluor-apatite and magnetite (C…
abstract: The Porgera gold deposit, located in the highlands of Papua New Guinea (PNG), contains ~410 tonnes Au and ~890 tonnes Ag, distributed between a large lower-grade ore zone (78.6 million tonnes, 3.5 g/tonne Au, 9.9 g/tonne Ag), and a smaller highgrade zone (5.0 million tonnes, 26.5 g/tonne Au, 22.1 g/tonne Ag). Lower-grade mineralization occurs as stockworks and disseminations of auriferous arsenical pyrite associated with strong sericite-carbonate alteration, which cross-cut and overprint a suite of epizonal mafic stocks and dykes of the Porgera Intrusive Complex (PIC) and their sedimentary host rocks (Jurassic-Cretaceous shelf sediments). Minor free gold also occurs in base metal-sulphide veins associated with these alteration zones. Later, high-grade mineralization (locally up to 3000 g/tonne Au) occurs in quartz-oscoelite veins associated with the Roamane Fault (an extensional structure which cross-cuts the intrusive complex and the earlier dissemiriated ore). Abundant visible gold occurs with Au-Ag-Ag-tellurides in these epithermal-style, vuggy, banded veins. Deposition of both types of ore is shown by K-Ar dating of sericite (illite) and roscoelite to have occurred within 1 Ma of the time of emplacement of the PIC at 6.0 ± 0.3 Ma (2a; K-Ar dating of igneous biotite, and 40Ar/39 Ar dating of hornblende). Geochemical, isotopic, and petrographic studies of the PIC indicate that the intrusions represent a comagmatic, volatile-rich alkali basalt/gabbro - hawaiite (trachybasalt) -mugearite (basaltic trachyandesite) fractionation suite, derived from a larger fractionating magma chamber located deeper in the upper crust (aeromagnetic evidence). The intrusions are medium- to coarse-grained, and textures vary from porphyritic to ophitic. Mafic rocks contain olivine (pseudomorphs) and Cr-rich diopside phenocrysts, whereas hornblende (titanian magnesio-hastingsite), Ti-rich salite, and plagioclase phenocrysts occur in hawaiites and mugearites. Fluor-apatite and magnetite (C…
author: Richards, Jeremy Peter
language: en_AU
keywords: gold ore, Papua New Guinea, Porgera area, Mt Kaijende, tectonics of Papua New Guinea, mineralization, noble metal analyses, Memorial University of Newfoundland, University of Saskatchewan in Saskatoon, X-ray diffraction analyses
date published: 1990
date modified: 2026-07-24T00:54:54Z
provider: Australian National University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Australian National University

PropertyValue
property ID: Handle
value: http://hdl.handle.net/1885/12535