ABSTRACT
Infrared spectroscopic data collected using HyloggerTM technology is being used to assess the mineral
composition of Archean iron ore bedrock and Cenozoic detrital units in Western Australia’s Pilbara region.
Analysis of infrared spectra enables quantification of: (1) composite iron mineralogy, (2) composite clay
mineralogy, (3) hydrous silicates and (4) carbonate mineral abundances. Stratigraphic and rock mass unit
logging of core has identified several detrital and bedrock units recognisable across the Pilbara. However, due to
alteration related to mineralisation, weathering and later stage precipitate overprinting, it can often be difficult to
assess the detrital-bedrock boundary and the occurrences of specific geotechnical units in the detritals and
bedrock, particularly when using non-core drilling techniques and traditional geochemical assays. Infrared
spectroscopic data collected concurrently on core from several sites has shown distinct correlation against
existing unit subdivisions and associated geochemical parameters. Where infrared spectroscopic data have also
been collected on rock chips recovered from reverse circulation infill drilling, these correlations allow robust
geological and geotechnical models to be developed based on the typical mineralogical-geochemical signatures.
The geotechnical sub-units identified in core can be readily distinguished using the various iron and clay
minerals captured by the HyloggerTM technology as opposed to total iron, potassium, and alumina captured by
geochemical assays. Further, some of the minerals targeted by infrared spectroscopic analysis (eg gibbsite, white
mica, vitreous goethite) and their ubiquitous presence as the products of weathering, assist in recognition of
various ancient weathering surfaces and help to define the origin of the material, whether bedrock or detrital.
Overall, HyLogging of core and chips allows important mineralogy focussed data to be captured at minimal
additional financial outlay. Correlations against geochemical unit identifiers are robust both within deposits and
between deposits. Significant improvements in the confidence of geological and geotechnical models are
attained.