Structural and stratigraphic setting of sulphide deposits in Ordovician volcanics south of King's Point, Newfoundland

DeGrace, John R. (1971) Structural and stratigraphic setting of sulphide deposits in Ordovician volcanics south of King's Point, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The study area, located north of Springdale, Newfoundland, is underlain by basic volcanic rocks of the Ordovician Little Bay Head section of the Lush's Bight Group. From the base of the section to the top a general lithologic gradation (with considerable interdigitation of units) is present as follows: close-packed pillowed lavas, isolated pillow breccia, broken pillow breccia, coarse aquagene tuff, fine aquagene tuff. -- The section comprises the south limb of an anticline whose axial plane dips steeply northward and whose horizontal axis strikes east-northeast. Within the section discontinuous schist zones are approximately parallel to the volcanic layering. These are the result of inhomogeneous strain and are characterized by the presence of a strain-slip fabric, so that there are two fabrics in the zones and only one, an S or LS tectonite fabric outside. The schist zones are apparently pretectonic to the major anticline. Subsequent to the development of these structures, the rocks were disturbed by block-faulting and thrust-faulting from the north, and were finally folded again into an open flexure whose axial plane strikes north-south and whose axis plunges steeply northward. -- Sulphide mineralization is economically significant only in the schist zones, and chalcopyrite seems to be enriched in the hinges of the latest folds. It is postulated that the suplhides are stratabound by the volcanics, are pretectonic to the development of the schist zones, and were later remobilized in the schist zones during the folding episode(s).

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