Geology of the Tulk's Hill area, central Newfoundland

Cooper, Gordon Evans (1967) Geology of the Tulk's Hill area, central Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The thesis area, 3 miles south of the upper end of Red Indian Lake, lies in the Central Mobile Belt of Newfoundland. The rocks consist of schistose sericitic to chloritic acid volcanic flows and pyritic acid volcanics, with massive to schistose acid pyroclastic breccia, intermediate volcanics, minor sedimentary rocks and diabase dykes. All are metasomatized and metamorphosed to the greenschist facies. -- The rocks have been folded into a central, south-westerly trending anticline and a northern, south-westerly plunging syncline. A major fault, paralleling the fold axis of the syncline, lies just north of it. Small isoclinal folds parallel the major folds. Two types of drag folds are present. -- Four major pyritic horizons with base metal sulphide concentrations of economic interest occur in the area. Three mineralized zones occur within, and are a part of these mineralized horizons. The mineralized zones are principally massive pyrite and sphalerite, with lesser amounts of banded and disseminated sulphides. All three zones are steeply dipping and tabular in shape. The mineralized horizons, excluding the mineralized zones, are largely disseminated and banded sulphides with minor amounts of massive mineralization of the pyritic and sphaleritic types. -- Paragenetic studies show that pyrite was the first formed mineral, followed by a group comprising arsenopyrite, unknown "A" and some pyrrhotite. A subsequent group includes the remaining pyrrhotite, chalcopyrite, sphalerite, tetrahedrite and galena, followed by unknown "B". Secondary chalcocite, covellite and digenite were the last minerals to form. -- Gangue minerals in both the mineralized zones and horizons are quartz, albite, carbonate, sericite and chlorite. They appear to be later than the sulphides. -- Hydrothermal fluids appear to have deposited the sulphides in tabular porous tops of acid volcanic flows on the northwest limb of the central anticline,. The deposit may be described as exogenetic and epigenetic.

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