Geology of the Mount Costigan lead-zinc deposit, west-central New Brunswick.

Abstract

The Mount Costigan Pb-Zn deposit is located about 40km east of Plaster Rock, New Brunswick within the Early Devonian Costigan Mountain Formation, in the Matapedia Cover Sequence (formerly the Cialeur Bay Synclinorium). It occurs about 250m east of the summit of Mount Costigan within a series of brecciated and unbrecciated crystal and lapilli tuff, rhyolite and minor siltstone which are exposed in six trenches (North, South, East, West, Southwest and Central). To the west the Costigan Mountain Formation is overlain by the Wapske Formation. The most significant feature of the deposit is the large amount of brecciation, which, in the Central Trench, also serves as the main sulphide host. Petrographic studies indicate that the breccia consists of angular to subangular blocks of massive and banded crystal tuff, massive to spherulitic to flow-banded rhyolite and minor lapilli tuff. The Mount Costigan deposit is interpreted to represent a base metal variety of epithermal deposit. (Abstract shortened by UMI.)