Mineral Occurrence Maps of Australia - MOMAs

The following MOMAs are available at the moment:

Alteration Minerals:  Pyrophyllite, Dickite and Apatite

Aluminosilicate Minerals : Andalusite, Kyanite, and Sillimanite

Metamorphic Minerals:  Axinite, Cordierite, Datolite, Wollastonite, Garnet, Serpentine 

REE Occurrences: Detection based on the Nd lines in the VNIR

Assemblages: Talc/Carbonate, 

Properties: The layers in this this MOMA reflect information about the hole that can provide an indication of the reliability of the TSA+ and jCLST interpretations. The current layers are:

  • SWIR Aspectral Fractional Occurrance: Shows the fraction of the unmasked samples that were found to be aspectral by TSA+
  • CVS-A Interval Maximum: CVS-A is a scalar computed from the TIR data to detect Type A Carbonate Volume Scattering which invalidates the linear mixing models used by jCLST and can sometimes cause carbonates to be interpreted as garnets.

Explaining MOMAs

Because CorStruth has easy access to all the NVCL HyLogger-3 data sets it is possible to search all the holes and extract information that might be useful for research or economic purposes. This can then be displayed using Google Maps.The production of these maps is a three stage process

  1.  A scalar corresponding to some property of interest is generated for every unmasked sample in every hole. Often these scalars display the relative abundance of selected minerals as determined by TSA+ or jCLST hence the name MOMA (Mineral Occurrence Map of Australia). 

But it is also possible to display any other property that can be generated from the raw hyperspectral data. Instrumental measurements like the Signal-to-Noise Ratio or some measure of the core condition based on the laser profilometer are possible. Alternatively scalars based on spectral features such as the wavelength or depth of selected absorption features are possible.

  1. This scalar must be summarized in some way to be presented as a single property of the hole. There are currently three ways this is done.

Occurrences: This is a simple measure of the number samples in the hole that have the property. It is useful for less-common minerals that generally occur infrequently. The Aluminosilicate MOMA is a good example.

Average Abundance: This is a rough guide to proportion of the property in the hole. For example the Average Abundance of quartz would be the fraction of quartz seen by jCLST averaged over every unmasked sample in the hole.

Interval Maximum: Here a moving window average abundance of the scalar is computed for every unmasked sample and the maximum of this moving average is reported. The window width is adjustable but is typically 5 m. This measure is designed to detect small occurrences of less common (and perhaps economically important) minerals.

  1. Thirdly the summary results for each hole must be uploaded to Google Maps (GM). Multiple scalar summaries can be uploaded as separate layers which can then be selected for display in GM. 

NOTE: There is currently a problem for display on mobile devices with the Google Maps App installed. In this case, although the maps display properly, the links in the sidebar that come up when a hole is selected are no longer active. I’m still looking for a solution to this problem.