Airborne hyperspectral characterisation of hydrothermal alteration in a regolith-dominated terrain, southern Gawler Ranges, South Australia

Abstract

Key alteration minerals associated with epithermal and porphyry Cu–Au mineralisation have been successfully identified using HyMap airborne hyperspectral imagery in a regolith-dominated terrain in the southern Gawler Ranges, South Australia. Alteration assemblages were mapped using Spectral Feature Fitting, a spectral matching algorithm, identifying the spatial distribution of localised advanced argillic and broader argillic alteration. X-ray diffraction (XRD) analysis was undertaken to independently identify the mineralogy of 57 surface soil and rock samples collected from the study area. This analysis confirmed the presence of key alteration minerals including alunite, pyrophyllite and dickite. The integration of spectral and XRD analytical techniques allowed interpretation of mineralogical patterns across the landscape. This study demonstrates that it is possible to identify surface alteration related to potential mineralisation using airborne hyperspectral imagery and semi-quantitative XRD even in a weathered regolith-dominated terrain.

KEY POINTS

1. Advanced argillic and argillic alteration identified through hyperspectral image analysis in a regolith-dominated terrain

2. X-ray diffraction used to validate the presence of advanced argillic alteration minerals alunite, pyrophyllite and dickite in the landscape

3. Relationship of advanced argillic and argillic alteration interpreted in two key landscape features in the context of a porphyry mineral system

4. Demonstrates potential for detection of alteration signatures with airborne hyperspectral imagery in regolith-dominated terrains elsewhere

Keywords:

• mineral exploration
• regolith-dominated terrain
• hyperspectral imagery
• HyMap
• Spectral Feature Fitting
• X-ray diffraction
• hydrothermal alteration
• Gawler Ranges

Acknowledgements

The support received for this research through the provision of an Australian Government Research Training Program Scholarship is kindly acknowledged. The Minerals Council of Australia ‘Australian Minerals Industry Research Scholarship’ contributed in part to this research. Dr Tony Hall is gratefully acknowledged for assistance with XRD data collection and analysis. A special thank you to the land and tenement holders for allowing access to conduct fieldwork used in this study. Thank you to Dr Jon Huntington, an anonymous reviewer and an examiner for their valuable comments that greatly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article or its supplementary materials. The data that support the findings of this study are openly available in The University of Newcastle’s institutional repository at http://dx.doi.org/10.25817/5f5047e001412, reference number uon:37184.