Mafic‐ultramafic complexes of the Greenvale area, North Queensland: Devonian intrusions or precambrian metamorphics?

Abstract

Abstract In the Greenvale area, mafic‐ultramafic complexes occur along the boundary between the Georgetown and Broken River Provinces, in a zone believed to have been a continental margin in the Precambrian and early Palaeozoic. This margin was the site of repeated metamorphism, deformation, and igneous activity until the Carboniferous; the resulting complication of the geology clearly exemplifies problems in the interpretation of the genesis of ultramafics and ophiolites in highly deformed regions. Following their emplacement, Precambrian layered mafic‐ultramafic complexes were interfolded and metamorphosed with schist and phyllite of the Georgetown Province. The Broken River Province was subsequently the site of lower Palaeozoic igneous activity contemporaneous with the initial deposition of quartz‐rich flysch intercalated with basaltic lavas. In the Gray Creek Complex this phase of igneous activity is represented by gabbro, tonalite, and trondhjemite, and basaltic and calcalkaline dykes which intruded ...