Geological and 40Ar/39Ar geochronological constraints on the timing of quartz vein formation in Meguma Group lode-gold deposits, Nova Scotia

Authors

  • Daniel J. Kontak Nova Scotia Department of Mines and Energy, P.O. Box 1087, Halifax, Nova Scotia B3J 2X1, Canada
  • Paul K. Smith Nova Scotia Department of Mines and Energy, P.O. Box 1087, Halifax, Nova Scotia B3J 2X1, Canada
  • Peter Reynolds Department of Geology, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada
  • Keith Taylor Department of Geology, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada

DOI:

https://doi.org/10.4138/1704

Abstract

The results of geological and 40Ar/39Ar geochronological investigations of several gold districts hosted by the Meguma Group are presented. Observations at both the macro- (deposit to ore zone) and micro- (hand sample to thin section) scale indicate that quartz vein formation followed major Acadian folding and metamorphism (ca. 400 ±10 Ma) and was broadly coincident with mafic-felsic magmatism at ca. 370 Ma. 40Ar/39Ar analyses of vein-fill mica and amphibole from the Beaver Dam, Moose River, Fifteen Mile Stream, Upper Seal Harbour and Caribou deposits indicate ages of ca. 380 Ma to ca. 362 Ma. The age data are interpreted to reflect discrete hydrothermal events with rapid cooling following crystallization of vein constituents. The age data do not reflect either variable amounts of resetting by later granitic intrusions or diachronous cooling. Genetic models that interpret the generation of the auriferous quartz veins as either before or during major Acadian folding are considered to be inconsistent with the present results. Instead, a model is favored that interprets quartz vein formation in the context of continued transpression of the Meguma Terrane following regional folding and metamorphism. RÉSUMÉ On présente les résultats d'études géologiques et géochronologiques [40Ar/39Ar] effectuées dans plusieurs districts aurifères au sein du Groupe de Meguma. Des observations tant macroscopiques (du gite à la zone de minéral) que microscopiques (de l'échantillon à la lame mince) indiquent que la formation des veines de quartz suivit un métamorphisme et un plissement majeurs acadiens (env. 400 ± 10 Ma) et coiincida d'une facon générale avec unmagmatisme mafique à felsique vers 370 Ma. Des analyses 40Ar/39Ar effectuées sur des micas et des amphiboles de remplissages de veine provenant des gites de Beaver Dam, Moose River, Fifteen Mile Stream, Upper Seal Harbour et Caribou révèlent des âges aux environs de 380 à 362 Ma. On interprète ces données d 'âge comme le reflet d'épisodes hydrothèrmaux distincts avec un refroidissement rapide suite à la cristallisation des constituants filoniens. Ces données ne reflètent ni un degré variable de remise à ziro par des intrusions granitiques ultérieures, ni un refroidissement diachrone. On considere que les modèles genetiques interprétant la formation des veines de quartz auriferes comme precedent ou ayant eu lieu pendant le plissement majeur acadien, sont en contradiction avec les resultats actuels. En leur lieu, on favorise un modèle qui interprète la formation des veines de quartz dans le contexte d'une transpression continue de la Lanière de Méguma à la suite d'un plissement et d'un métamorphisme régionaux. [Traduit par le journal]

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Published

1990-11-01

How to Cite

Kontak, D. J., Smith, P. K., Reynolds, P., & Taylor, K. (1990). Geological and 40Ar/39Ar geochronological constraints on the timing of quartz vein formation in Meguma Group lode-gold deposits, Nova Scotia. Atlantic Geoscience, 26(3). https://doi.org/10.4138/1704

Issue

Vol. 26 No. 3 (1990)

Section

Articles

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