From Geoscience Australia
JSON format icon JSON RDF format icon RDF ISO19115-3 XML

Petrology and platinum-group-element geochemistry of Archaean layered mafic-ultramafic intrusions, west Pilbara Block, Western Australia

Created 17/10/2025

Updated 17/10/2025

JSON format icon JSON RDF format icon RDF ISO19115-3 XML

In a group of Archaean, layered, mafic-ultramafic intrusions in the west Pilbara Block, Western Australia, the Munni Munni Complex (2925 Ma) contains a substantial resource of PGEs (20-30 Mt @ 2.9 ppm Pt + Pd + Au) and other intrusions contain subeconomic resources of Ni and Cu. Contrasting PGE distribution patterns within the group indicate that the timing and mechanism of S-saturation were critical for the formation of PGE-enriched sulphide units. Generally, overlying mafic units are thicker than the rhythmically layered ultramafic components. Olivine and clinopyroxene were usually the first minerals to crystallise and cumulus orthopyroxene is restricted to the upper parts of the ultramafic zones. Chromium partitioned into early crystallising clinopyroxene, thus downgrading the potential for PGE-chromite associations. The parent magmas were probably siliceous, high-Mg basalts of Aldepleted komatiitic affinity. In this study, the variations of PGEs and incompatible trace elements were documented up the entire stratigraphic successions. In the Munni Munni Complex (the intrusion studied in most detail) the PGEsulphide mineralisation is directly below the ultramafic/gabbroic contact and is thought to have resulted from crystal fractionation and mixing of S-undersaturated and S-saturated magmas; as in the Great Dyke of Zimbabwe, it does not occur at or near the base of clearly defined cyclic units. The other (smaller,mainly sheet-like) intrusions studied typically contain basal segregations of PGE-poor Ni-Cu sulphides; the magmas were generally S-saturated early in their evolution and there was no PGE enrichment at higher levels. In exploration, variations in the ratios of precious metals and the trends of the incompatible lithophile and chalcophile elements should be used in association with field and mineralogical evidence to indicate potential PGE-enrichment processes, such as S-saturation, crustal contamination, crystal fractionation, magma mixing, and/or hydrothermal remobilisation.

Files and APIs

Tags

Additional Info

Field Value
Title Petrology and platinum-group-element geochemistry of Archaean layered mafic-ultramafic intrusions, west Pilbara Block, Western Australia
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/b86f16e0-ef99-4267-9bae-cb4f607741b8
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        116.0,
        -22.25
      ],
      [
        121.5,
        -22.25
      ],
      [
        121.5,
        -20.25
      ],
      [
        116.0,
        -20.25
      ],
      [
        116.0,
        -22.25
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Petrology and platinum-group-element geochemistry of Archaean layered mafic-ultramafic intrusions, west Pilbara Block, Western Australia". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/petrology-and-platinum-group-element-geochemistry-of-archaean-layered-mafic-ultramafic-intrusio