John Jennings

B. Sc. Honours Thesis

A Geophysical Study of the Liscomb Satellite Pluton

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The Liscomb Satellite Pluton is located to the north of the Main Liscomb Complex in central Nova Scotia. Because of the limited amount of outcrop the boundaries of the pluton have yet to be accurately determined through geology. However due to the density contrast that exist between the granite and the surrounding metasedimentary rocks, the boundaries of the pluton can be determined using contoured Bouguer gravity values which show a 5.0 mgal low centered over the pluton.

Thirteen refraction lines were shot over the study area with two purposes in mind: 1. To determine the thickness and the variation of the till layer, which would then allow for the stripping of the till layer from the Bouguer gravity values. 2. To determine if bedrock differentiation is possible due to their differences in seismic velocity. The refraction profiling determined that the subsurface can be approximated by three layers; a till layer (velocity ~170 m/sec), a weathered layer (velocity ~3500 m/sec) and basement (velocity ~5000 m/sec). Determination of the basement type i.e. granite versus metasediments was not possible to the inaccuracy of the seismic profiling.

The gravitational attraction of the till layer is ~.2-.3 mgals, which is insignificant and can therefor be ignored when modeling. The pluton model constructed, using a 3D modeling program, show a elliptical cylinder, with a cross section of 7 km by 3 km with a minimum depth of 10 km. No contact is evident to the Main Liscomb Complex above 1.0 km. Depth to the surface closely approximates a plane.

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Pages: 85
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