Mineralogy and spectroscopy of Owen Group sandstones, Australia: implications for the provenance, diagenesis, and origin of coloration

摘要

Mineralogical studies were conducted on sandstones of Late Cambrian-Early Ordovician Owen Group, southern West Coast Range, Tasmania, Australia. Several samples were analysed using conventional thin section and point counting techniques, while others were further analysed under a Scanning Electron Microscope with back scattering and Energy Dispersive X-ray Spectroscopy capabilities. The result of petrographic analyses includes provenance, possible sources and controls over coloration in sandstone samples. The sandstones are mainly comprised of quartz, mica, lithic grains (volcanic, metamorphic and sedimentary), clays, zircon, tourmaline, leucoxene, rutile, and chert grains. These were derived from a Proterozoic Tyennan metamorphic and a Middle Cambrian Mount Read Volcanic provenance. Following deposition, sediments underwent severe diagenesis including quartz overgrowth, iron coatings, haematite, chlorite and sericite alterations, linings and cements. Multi-phase haematite-related diagenesis is present and late stage hydrothermal fluid alterations assemblages have severely altered and colored the sediments.