Date(s) - Thursday, 08/08/2019
UWA 2019 School of Earth Sciences Seminar Series
The role of variable magma oxidation state on the grade and size of porphyry Cu-Mo-Au deposits
Presented by: Prof. Steven Rowins, CET Director
Thursday, 8 August 2019
Time: 4.00 – 4:45pm
Although a high magmatic oxidation state in I-type arc magmas is advantageous to the development of large porphyry Cu-Mo-Au systems by promoting both S and Cu enrichment in evolving parental silicate melts, the wide range of magmatic oxidation states observed in porphyry magmas (?FMQ +3/-2) suggests that it is not a limiting factor in their formation – possibly only their size. A high magmatic oxygen fugacity will supress crystallization of magmatic sulphide phases/immiscible sulphide liquids, which extract Cu and Au from the magma and prevents their partitioning into a magmatic volatile phase (MVP) upon fluid saturation. However, early-formed magmatic sulphides may be viewed an efficient Cu, Au and S pre-concentration mechanism in relatively reduced and S-poor I-type porphyry magmas. Subsequent release of a more oxidizing MVP allows for the dissolution of the early magmatic sulphides and incorporation of their metal load for later ore forming processes.
Steve Rowins is the Director of the Centre for Exploration Targeting (CET) and Professor of Mineral Geoscience at UWA. He was previously the Chief Geologist and Executive Director of the British Columbia Geological Survey and has held academic appointments at the University of British Columbia and the University of Victoria. He has worked for major, mid-tier, and junior resource companies and has a special interest in identifying the fundamental factors that the control the development of precious and base metal mineral systems, and developing practical exploration tools for their discovery.