Drift prospecting and glacial geology in the Sheffield Lake-Indian Pond Area, north central Newfoundland

Alley, Douglas Wayne (1975) Drift prospecting and glacial geology in the Sheffield Lake-Indian Pond Area, north central Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Drift prospecting is defined as the application of glacial geologic, geochemical, geophysical and sedimentological techniques to the problem of mineral exploration in areas mantled by glacial overburden. Glacial drift in the Sheffield Lake - Indian Pond area of north central Newfoundland contains local accumulations of massive sulphide float, grading up to 8.2% Cu. Previous investigations by industry have failed to locate the source of the float. -- The objects of this research were to locate the source of the float by means of drift prospecting, to evaluate the applicability of combined exploration techniques to the glaciated terrain of Newfoundland and to resolve the glacial history of the study area. -- Glacial drift thickness in the area, determined by hammer seismic profiling, varies from 5 to 60 feet. An extensive trenching program revealed the presence of two till units. Till fabric analyses indicated local ice flow directions toward 020 for the Lower Red Till, and either 020-045 (low) or 000-315 (high) for the Upper Grey Till. The sulphide float occurs as first-cycle clasts only in the Lower Red Till and, sparsely, as second-cycle clasts in the Upper Grey Till. The two lodgement tills have been differentiated on the basis of colour, stratigraphy, fabric, texture, pebble lithology, clay mineralogy and geochemistry. The two tills provide the first conclusive evidence of multiple glaciation in north central Newfoundland. -- The sulphide float, which generally weighs 1-5 lbs., ranges in composition from weakly pyritized and chloritized (host) andesite to massive phyrite-chalcopyrite. Clasts are concentrated in the Lower Red Till where they form a well-defined dispersion fan with the apex pointing toward the southwest. Anomalous concentrations of Cu, Fe, S, Co, and Zn in the Lower Red Till likewise indicate a southwesterly bedrock source of the micro-float dispersion fan. A target area for further detailed exploration of the bedrock source of the float has been delineated on this basis. -- It was determined that the combination of methods employed was essential for delineating the probable source area and it is recommended that they be employed in any future investigations with similar objectives. Of the methods employed, trenching with a backhoe and geochemical analysis of only a restricted size fraction of till samples were found to be particularly valuable. Cu, Fe, and S were found to be the best geochemical tracer elements, particularly when they were mutually associated.

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