NITROGEN DISTRIBUTION IN LOWER PALAEOZOIC SLATES OF THE MEGUMA SUPERGROUP, NOVA SCOTIA, CANADA: IMPLICATIONS FOR AU AND ZN-PB METALLOGENY AND EXPLORATION

Major and trace elements and nitrogen were analyzed in 59 Cambrian and Ordovician slates of various litho-stratigraphic levels within the Meguma Supergroup, 14 Ordovician slates of The Ovens gold district, and 16 Ordovician slates of the Eastville Pb-Zn-Cu deposit. The fixed nitrogen content and the normative N_fix/K2O ratio of muscovite were also determined in muscovite separates from greywacke and slate from the Goldenville and Halifax Groups, respectively. In general, nitrogen concentration is inversely related to manganese content, and can be used to distinguish and correlate different stratigraphic members of the Goldenville-Halifax transition zone. Black slates of the saddle-reef type gold mineralization in The Ovens are characterized by high fixed nitrogen and high N_fix/K2O ratios in muscovite. The nitrogen is interpreted to have been contributed by hydrothermal fluids responsible for epigenetic gold mineralization. Therefore nitrogen can be used as an exploration guide in these districts. Conversely, Pb-Zn mineralized slates from Eastville cannot be distinguished from unmineralized equivalent units neither on the basis of fixed nitrogen nor N_fix/K2O ratio of muscovite. This fact suggests Pb-Zn mineralization in Eastville is not related to gold and may be syngenetic rather than epigenetic.