The geology of the Stirling copper property, Springdale, Newfoundland

McArthur, J. G. (1973) The geology of the Stirling copper property, Springdale, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Stirling property at Springdale in north-central Newfoundland is one of many pyritic copper prospects found in the dominantly pillowed Lower Ordovician. Lush's Bight Group. The nearby Whalesback and Little Bay mines within the Group are recent past-producers of copper. -- The map-area is underlain by a 3800-foot thick sequence of Lush's Bight Group volcanics which has been divided into four mappable units: tuffaceous schists and siliceous tiffaceous schists; chloritic metabasalts; volcanic breccia; and epidote basalt and isolated pillow basalt. Numerous mafic intrusives are considered to be feeder dykes and sills to the volcanic pile. Ten whole rock analyses support the interpretation that the Lush's Bight Group is a low-potash tholeiite that formed in the upper part of layer two of ancient oceanic crust. -- The volcanic units and the related intrusives have been metamorphosed to the greenschist facies and have one good penetrative, steeply dipping S₁ fabric produced by the main regional deformation - D₁. This deformation produced very large-scale folds such that the entire map-area is underlain by part of one limb of a major F₁ fold. Small-scale kink bands and crenulations are evidence for a locally developed D₂ deformation. Two sets of faults trending 030ﾟ and 060ﾟ have been recognized in the subsurface drilling and they correspond to strong topographic linears. -- Two separate zones of pyrite and chalcopyrite mineralization with minor pyrrhotite and sphalerite have been designated "A" and "B". The sulphides occur as massive or nearly massive lenses, pods and as a stock-work of stringers. Disseminated sulphides are common throughout the zones. In the "A" zone, the sulphides occur in the chloritic metabasalts similar to many of the pyritic copper deposits in the Group. In the "B" zone, the sulphides occur in the siliceous tuffaceous schists and to a lesser extent in the chloritic metabasalts. The mineralized zones are steeply dipping and generally conformable with the stratigraphy and structure. Primary sulphide textures are absent due to recrystallization and remobilization during the D₁ deformation. The present distribution of sulphides resembles the disseminated stockwork zone in the 'Cyprus type' ophiolite mineralization.

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