A radiometric renaissance: making better use of an under-utilised geophysical-geochemical dataset
Exploring for new mineral responses using natural radioactivity from the rocks
There is evidence that with better understanding of the variations in radioelement (K, Th,U) content in mineralised environments and a better capability to model these responses, radiometric data could play a much greater role in exploration.
Opportunities exist to work with geochemical and radiometric datasets from a wide range of deposit types to understand their radiometric signatures. The proposed research will comprise two basic approaches both of which will be tested using a new modelling method:
(i) A radioelement (K, Th, U) based classification of rocks will be created. Radioelement concentrations are known to be correlated with concentrations of some major elements (Dickson and Scott, 1997), but no systematic study has been described. Establishing the relationships between ‘radiometric-based’ geology and geochemical rock classifications is key to better utilisation of radiometrics in a mapping role during exploration.
(ii) There are periodic reports of detectable radiometric responses from hydrothermal alteration from various individual deposits of various types, e.g. VMS, orogenic gold and epithermal precious metals (Shrive et al., 1997). However, responses are inconsistent and often examples do not unequivocally demonstrate that alteration zones are the dominant causes of responses.
We propose to use a compilation of published descriptions of geochemical variations within alteration zones establish systematic relationships to better understand enhancement/depletion of the radioelements in alteration zones.
Key to understanding radiometric responses from both alteration and different rock types is modelling of expected responses. Radiometric data are the only kind of geophysical data that are not routinely ‘modelled’. A unique radiometric forward modelling software package has been created by Dr Brian Minty and is available for this project. This software can be used to model radiometric responses of mineral system components, systematically exploring the effects of varying radioelement contents (for example in alteration zones), accounting for variable exposure, size and shape of the components and also topography.
The integration of these different lines of research has the potential to improve greatly our ability to extract geological information from radiometric datasets for exploration purposes.
For more background information, see the suggested readings below.