T164 Using Geophysics to Evaluate and Explore for Mineral, Energy, and Groundwater Resources I

Wednesday, 28 October 2020
5:30 PM - 8:00 PM
Meeting Rooms

INTEGRATED FIELD GEOLOGY AND AIRBORNE GEOPHYSICAL STUDY OF THE ST. ALBAN’S AREA, NEWFOUNDLAND APPALACHIANS, CANADA: EXPLORATION POTENTIAL

Paper number: T164-8
Program: Technical Sessions
Time: 7:15 PM – 7:30 PM

Authors

  • Anne Westhues Presenting Author
    Geological Survey of NL, St. John's, NL
  • Gerry Kilfoil
    Govt of Newfoundland and Labrador Industry, Energy & Technology, St. John's, NL

Abstract

Results from a detailed airborne geophysical survey (gamma-ray spectrometric, and gradient magnetic airborne analyses) and a bedrock mapping project at a 1:50,000 scale refine and update the geology of the St. Alban's map area on the south coast of Newfoundland, Canada. The study area straddles the boundary between two major tectono-stratigraphic domains within the Newfoundland Appalachians, the Gander and Dunnage zones. Further, it has been a focus of exploration activity for several decades for its gold, arsenic and base-metal potential.

The Day Cove Thrust, an easily recognized magnetic low, separates the volcano-sedimentary sequences of the Ordovician Baie d'Espoir Group (Dunnage Zone) from the Little Passage Gneiss (Gander Zone). Alternating stratigraphic units in the Baie d’Espoir Group are expressed as banded patterns within both the residual magnetic field and the first vertical derivative of the magnetic field. Silurian and Devonian granitoids, which have intruded rocks of both Gander and Dunnage zones, are readily distinguished based upon their magnetic and radiometric expressions. Areas showing magnetic patterns not explained by previous geological mapping, were specifically targeted during bedrock mapping, and included in lithogeochemical and U-Pb geochronological studies as part of this project. New exploration targets from this study having high gold contents (with up to 7 ppm Au in a grab sample at Southeast Brook) are associated with local magnetic lows. These targets are underlain by sandstone and conglomerate, potentially more permeable to mineralizing fluids compared to surrounding shales with higher magnetic signatures.

The study demonstrates how the combination of a detailed airborne geophysical survey, along with bedrock mapping and rock sampling, can refine geological mapping and guide future exploration efforts. An additional airborne geophysical survey was recently completed to the north and northeast of the St. Alban’s map area to continue this work in those areas equally prospective for mineral exploration.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-354106

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