Gravity and Magnetic Investigations of the Deep Cove Intrusive, Cape Breton County, Nova Scotia

Abstract

Gravity and magnetic surveys were conducted on the Deep Cove quartz monzonite intrusive to ascertain its subsurface configuration and, in particular, the attitude of its west contact with the surrounding Fourchu volcanic rocks.

Laboratory measurements of both intrusive and volcanic rock samples from Deep Cove indicate a density contrast of 0.10-0.15 g cm-3 and a magnetic susceptibility contrast of 1.5 x 10-3 measured in cgs units. The Koenigsberger Q-ratios of the samples are, in general, considerably less than unity. The expected anomalies caused by these contrasting properties are observed in the survey data.

Using a two-dimensional modelling computer program, models were developed which result in calculated gravity and magnetic anomalies that approximate the observed data. Gravity models suggest that the west contact of the intrusive is almost vertical, perhaps dipping steeply to the west. The calculated anomalies of magnetic models are less sensitive to the attitude of contacts.

Magnetic models require: (1) a great susceptibility contrast than that measured in the laboratory and (2) a depth to the top of the "magnetic body" of approximately 30 metres. These requirements possibly indicate weathering of ferrimagnetic minerals in the uppermost volcanic rocks.

Keywords: Pages: 69 Supervisor: John Pierce