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Department of Mines, Industry Regulation and Safety

MnO/Al2O3 content for all sample media included in the GSWA near-surface geochemistry datasets. This statewide dataset includes information from WACHEM, OZCHEM (the WA subset), CRCLEME-laterite and WAMEX (surface rock chip, stream, soil and shallow drillhole).

The MnO/Al2O3 index demonstrates areas where MnO has been enriched relative to a less mobile element oxide, such as Al2O3.

A unique legend and colour scheme has been chosen for this geochemical layer to best highlight geochemical trends, via a 3 × 3 cell mean neighbourhood statistics raster. Cell resolution is 0.05º (~5 km). Areas in red indicate a higher value.

The use of this ratio ‘normalizes’ disparate primary data sets obtained from different sample media, using a variety of laboratory methods, allowing their combination and comparison. Even so, all these indices will be sensitive to precursor rock chemistry and to the effects of overprinting events, such as weathering. These factors need to be taken into consideration when interpreting alteration indices.

Legend Range Classification
MnO/Al2O3 index TRAP 10.01 – 91.00 Manual breaks
  3.01 – 10.00 Manual breaks
  1.01 – 3.00 Manual breaks
  0.40 – 1.00 Manual breaks
  0.01 – 0.39 Manual breaks


GSWA near-surface geochemistry (Accelerated Geoscience Program data release)

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