Characterization, classification, and mechanisms for mineralization of critical metal-bearing occurrences in southwestern Meguma Terrane, Canadian Appalachians

Abstract

Multiple polymetallic vein-type occurrences with a suspected but unconfirmed genetic relationship and polymetallic critical metal-bearing assemblages occur in the Meguma Terrane metasediments in southwestern Nova Scotia. A multi-analytical approach integrating results from detailed petrography, scanning electron microscopy (SEM), Re-Os geochronology of arsenopyrite, U-Pb geochronology of apatite, Al-in-chlorite thermometry via electron probe micro-analyzer (EPMA), in-situ secondary ion mass spectrometry (SIMS) of sulfur isotopes in sulfides, and fluid inclusion systematics has allowed for the characterization and interpretation of mineralization at the Lansdowne (Sb-Pb-Zn-Co-Ag) and Cape St. Mary’s (Sb-Pb-As-Co-Ni-Bi-Au-REE) occurrences, and comparisons with the Nictaux Falls Dam occurrence (Co-Ni-As-Bi-Au). These results suggest a complex multi-stage mineralizing history for both occurrences due to reactivation of Neoacadian structures. Critical metal mineralization of the Lansdowne occurrence represents a newly classified occurrence type in Nova Scotia related to extensional tectonics from the breakup of Pangea in the Late-Triassic.