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

Geochemistry of Precambrian metapelites from East Antarctica: secular and metamorphic variations

Created 17/10/2025

Updated 17/10/2025

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

Early Archaean ( >3 b.y. old) metapelites from the Napier Complex of East Antarctica are enriched in MgO and depleted in K2O and Rb compared with late Archaean and Proterozoic metapelites, probably reflecting a higher proportion of mafic to ultramafic material and sodic (tonalitic to granodioritic) felsic igneous rocks in the source. A number of the more magnesian are strongly depleted in Cr, Ni, Cu, and V, and may have been formed by metamorphism of sediments derived from hydrothermally altered mafic or ultramafic igneous rocks. There is evidence for metamorphic depletion of Rb relative to K in these high-temperature granulite facies metapelites, many of which have high K/Rb ratios, and for depletion of U relative to Th in granulite-facies metapelites compared with those of amphibolite facies. The unique occurrence, on a regional scale, of assemblages containing sapphirine + quartz, and osumilite in metapelites of the Napier Complex may be due to their unusual chemical compositions, as well as to exceptionally high temperatures of metamorphism (900-950°C). Such assemblages are found only in the more magnesian rocks (mostly with mg > 0.6) in the Napier Complex, whereas younger metapelites are, with few exceptions, relatively iron-rich. Nevertheless, regional high-grade metamorphism with geothermal gradients sufficiently steep to allow formation of these rare assemblages is likely to have been confined to the Archaean.

Files and APIs

Tags

Additional Info

Field Value
Title Geochemistry of Precambrian metapelites from East Antarctica: secular and metamorphic variations
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/a729078d-f025-4298-82b1-f6667279fe17
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        45.0,
        -80.0
      ],
      [
        75.0,
        -80.0
      ],
      [
        75.0,
        -60.0
      ],
      [
        45.0,
        -60.0
      ],
      [
        45.0,
        -80.0
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Geochemistry of Precambrian metapelites from East Antarctica: secular and metamorphic variations". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/geochemistry-of-precambrian-metapelites-from-east-antarctica-secular-and-metamorphic-variations