Origin of magnetic anomalies associated with the Yallalie impact structure, Perth Basin,Western Australia

Abstract

The Yallalie impact structure is located within the Mesozoic sedimentary rocks of the Perth Basin, Western Australia. A high-resolution aeromagnetic survey across the structure at a 200 metre line spacing and 60 metre flying height has defined a series of concentric anomalies centred on the structure. The causes of magnetic anomalies associated with meteorite impacts in sedimentary basins are poorly understood in comparison with those into crystalline basement rocks. Modelling suggests the most likely source of the magnetic anomalies at Yallalie is either an injected melt sheet or new magnetic species created by hydrothermal alteration of pyrite or glauconite within the Cretaceous marine sediments of the Leederville Formation or Parmelia Formations.