A REVIEW OF THE MESOTHERMAL GOLD DEPOSITS OF THE MEGUMA GROUP, NOVA-SCOTIA, CANADA

The gold province of the Meguma Terrane in Nova Scotia contains severa l classic examples of turbidite-hosted mesothermal gold deposits. Ther e are over 300 gold occurrences and deposits hosted by the Cambro-Ordo vician Meguma group rocks in southern Nova Scotia, Canada. The Meguma Group consists of two formations: (1) a lower, sand-dominated flysch ( Goldenville Formation) and (2) an upper shaley flysch (Halifax Formati on). Subdivision of the Goldenville Formation into several map units i s leading to a better understanding of the stratigraphic constraints o n the gold mineralization. Although detailed stratigraphic investigati ons in all of the major gold-producing areas is still ongoing, it is e vident that the Steve's Road-Beaverbank and the Mt. Uniacke stratigrap hic intervals contain most of the major past gold producers in the pro vince. The Meguma Group rocks are variably deformed into upright gentl y to moderately doubly-plunging folds with multiple cleavages. The str ata are metamorphosed from greenschist to amphibolite facies and are s ubsequently intruded by ca. 370 Ma peraluminous granites and minor maf ic intrusions. The gold deposits can be divided into three main types: (1) high grade (approximately 15 g/t Au) narrow gold-bearing quartz v eins; (2) low-grade (0.5-4 g/t Au) slate/argillite hosted; and (3) low -grade meta-sandstone hosted. A combination of two or more of the abov e can also occur. Almost all of the historic production (47 million g Au) has come from the high-grade veins within 200 m of surface. A vari ety of vein types occur although most of the gold produced came from b edding concordant, stockwork and fissure veins. Isotopic investigation s and dating of the vein minerals indicate that the mineralization was related to migration of metamorphic fluids from multiple reservoirs i n the waning stages of the Acadian Orogeny. Disseminated low-grade gol d, with minor electrum and associated intermetallic compounds and meta l alloys have recently been recognized in host rocks at several of the former gold mining areas in Nova Scotia. The presence of disseminated gold in combination with high-grade vein mineralization greatly enhan ces the economic viability of gold deposits in the Meguma Group. The a ssociation of disseminated gold and narrow vein-hosted deposits has im portant exploration implications for similar mesothermal gold district s elsewhere. (C) 1998 Elsevier Science B.V. All rights reserved.