OCGC Seminar - Porphyry and epithermal ore formation in post-subduction tectonic settings


Dr. Jeremy Richards 
University of Alberta,
Society of Economic Geologists: Thayer Lindsley Visiting Lecturer

Thursday, November 24th
11:30 a.m.

123 Marion Hall
University of Ottawa



Re-melting of the deep-crustal residues of arc magmatism (amphibole gabbro cumulates) during tectonic events that occur after subduction has ceased or migrated to a new location, such as collision or back-arc extension, may generate a suite of ore deposits that are only indirectly related to subduction. Such remobilization events may occur soon after arc activity has ceased, or millions to billions of years later in response to unrelated tectonic events, such as continental rifting. Because of the potential involvement of various crustal sources during these remobilization events, the type of magma can range from mafic and alkaline to highly silicic, and associated ore deposits can range from alkalic-type Au, though normal-looking porphyry Cu±Mo±Au, to felsic porphyry Mo. Some types of sulfur-poor iron oxide-copper-gold (IOCG) deposit may also form in rifted arc settings.