A meteorite impact crater in the Eastern Goldfields of Western Australia—Shock metamorphism and projectile signature at the Ora Banda structure

Abstract The Ora Banda structure in Western Australia is situated within an Archean greenstone terrane known for orogenic gold deposits. It is defined by concentric gravity anomalies up to 4 km in diameter, and gravity and passive seismic data indicate the presence of a central uplift and annular trough. Shatter cones were found in surface samples and drill core during gold exploration. Breccia samples from drill core in the annular trough contain shocked quartz and glass with a projectile component. Planar deformation features (PDFs) were found in 17 quartz grains from suevite, and are oriented along crystallographic orientations typical for shock metamorphism, including and , recording shock pressures from 15 to 20 GPa. Analysis of glass in suevite by EMPA and LA‐ICP‐MS shows the composition is basaltic andesite (avg = 54 wt% SiO 2 ), with major oxide compositions reflecting mixing of local Archean greenstone target rocks. Average abundances of Ni (2640 ppm), Co (205 ppm), Ir (290 ppb), and other PGEs (Rh, Pd, Pt) in the glass are significantly higher than mafic and ultramafic target rock lithologies and are interpreted to be meteoritic in origin, with Cr‐Ir abundances indicating an iron projectile. Previous palynological analysis of crater fill sediments overlying the breccias indicates the impact event was likely Early Cretaceous or older. The Ora Banda structure offers insights into the cratering process near the simple‐to‐complex size transition, including the first documented occurrence of well‐preserved “Ries‐type” suevite described from Australia. In addition, Ora Banda represents one of the oldest known sites with strong geochemical evidence for an iron meteorite projectile and is one of few confirmed impact structures formed in an Archean greenstone terrane.