Geology of the alkaline Gifford Creek Complex, Gascoyne Complex, Western Australia

Abstract

The Mesoproterozoic Gifford Creek Complex is a recently recognised suite of high‐level alkaline intrusions located in the Gascoyne Complex of Western Australia. Two alkaline magmatic episodes are recognised: a swarm of ultrabasic intrusions accompanied by an extensive zone of metasomatism located along the Lyons River and emplaced prior to the deposition of the Bangemall Group sediments at 1679 ± 6 Ma; and a younger phase of high‐level dykes and sills of carbonatitic affinity that intrude Bangemall Group sedimentary rocks. Ultrabasic intrusions along the Lyons River occur in two forms: as a swarm of metasomatised sills exhibiting preserved primary igneous textures, and as intensely deformed and remobilised lenses. Interpretation of the pseudomorphed igneous textures in the Lyons River sills suggest that the original rock was composed of olivine macrocrysts or phenocrysts, with a groundmass comprising mica, perovskite, titanomagnetite and carbonate. Textures, such as centimetre‐scale layering and gravity s...