Southwestern Australia Acid-Saline Mineralogy: Observations From Reflectance Spectroscopy

Acid-saline sediments in shallow-lake environments in southwestern Australia host complex mineralogical suites representing long-term weathering and modern extreme acid-saline chemistry. It is not known whether large-scale reflectance spectroscopy datasets from watersheds across the Yilgarn Craton show regional mineralogical variability. This study assesses over 2500 spectra from datasets of shallow subsurface sediments by using automatic minima detections for spectral features of interest. Integrating microscopic and spectral observations show that proportionally similar mineral assemblages exist in a variety of recognizable textures. Spectral results indicate that iron oxide and phyllosilicates are the most detected mineral types, alongside less common alunite, jarosite, and gypsum. The difference in detection abundance by percentage for mineral groups, particularly iron oxides, accounts for the largest regional variation observed in spectra. Spectral feature characteristics show significant regional variation for iron oxide, alunite, and hydrated mineral absorptions. The spectral observations align with previous mineralogical observations of these landscapes and the expected weathering evolution for granitoids, where Al-phyllosilicates and iron oxides are most prevalent. Observations of these mineral suites enhance understanding of regional differences and similarities in chemical precipitates and products of water-rock interaction in extreme acid-saline environments and have implications for studying sediments and rocks on Mars.

Automated summary

This study evaluates over 2500 spectra of shallow subsurface sediments in acid-saline environments in southwestern Australia. The results show that iron oxide and phyllosilicates are the most frequently detected mineral types, along with less common alunite, jarosite, and gypsum. The differences in detection abundance for different mineral groups account for the observed regional variation in spectra.