Structural controls on uranium mineralization at the Kiggavik Project (NE Thelon area, Canada)

This paper deciphers the complex multiphase fracture network associated with uranium mineralization of the unconformity-related uranium deposits in the Kiggavik area. It combines field work, drill-core logging and sampling, and macro- to micro- petro-structural analyses. Key results from this study show that uranium bearing ENE-WSW and NE-SW fracture systems formed early during the Thelon and Trans-Hudsonian orogenies and were mineralized in three stages with distinctive fracture patterns, alteration and mineralization types. The first stage mineralization, inferred from a magmatic source, is related to micro-brecciation and is crosscut by intense quartz brecciation and veining (silica breccia) that predates formation of the Thelon basin. The second stage of mineralization (fluids of unconstrained origin) is coeval with the formation and reactivation of the E-W trending faults in the area, locally reusing the previously formed quartz veins of the silica breccia event. The third stage of uranium enrichment and reconcentration occurred with post-Thelon NE-SW compression and reactivation of the NE-SW and E-W trending faults, and is inferred to form from oxidizing basinal brines circulating on trans-tensional fault zones. Later sinistral offset by NNW-SSE faults and uranium remobilization by meteoric fluids gave uranium ore bodies their final architecture.