Metallogeny in the Capricorn Orogen, Western Australia, the result of multiple ore-forming processes

Abstract

The Capricorn Orogen includes metamorphosed tectonic units, intrusive igneous rocks, volcano-sedimentary and sedimentary basins situated between the Pilbara and Yilgarn cratons. These include the Gascoyne Complex, Ashburton, Blair, Bresnahan, Yerrida, Bryah, Padbury, and Earaheedy basins, and Edmund and Collier (former Bangemall) basins. Mineral deposits and occurrences in these units comprise stratabound base metals, including the giant Abra Pb–Cu–Ba (Edmund Basin) and Magellan Pb (Earaheedy Basin), and numerous hydrothermal veins and precious and/or base metal lodes. Some of the more important orogenic precious metal lodes are those of the Peak Hill group in the Bryah-Padbury basins and the Egerton field in the Gascoyne Complex. The metallogeny of the Capricorn Orogen reflects syn- to post-Capricorn orogenic events, linked to either protracted convergence tectonics between the Pilbara and Yilgarn cratons, or to a two-stage convergence history, one during the Capricorn Orogeny (ca. 1.83 Ga; Pilbara–Yilgarn convergence), the other during the Yapungku orogeny (ca. 1.79; North Australian–West Australian convergence). The metallogeny of the Capricorn Orogen was further sustained by continental mafic magmatism at about 1.45 and 1.07 Ga, during which heat advection may have caused widespread hydrothermal circulation, particularly in the Edmund, Collier, Earaheedy basins and adjacent tectonic units. An interesting, but as yet unexplained, aspect of the Capricorn metallogeny is the regional Pb–Ba enrichment. A conceptual model that attempts to explain the billion-year-long history of the metallogeny in the Capricorn Orogen is proposed. Mineral exploration in the Capricorn Orogen is somewhat limited and not as intensive as is in the brown-fields of the Archaean terranes of Western Australia.