Interpretation of the aeromagnetic anomalies of southern Vancouver Island

Abstract

A low-pass filtered aeromagnetic map of southern Vancouver Island is inverted into a magnetization-contrast map that illustrates the lateral variations in the magnetization of the crust. The Island Intrusions and the West Coast Crystalline Complex are characterized by high magnetization relative to the other lithologic groups. The Island Intrusions form an almost continuous pluton in the deeper part of the crust. The low-magnetic Leech River Formation thickens northward. The almost uniform magnetic signature of the Leech River Formation in the east–west direction indicates that the crustal structure revealed from the Lithoprobe seismic results is typical throughout the formation west of the Survey Mountain fault. A low-magnetic zone, elongated in the northwest–southeast direction, cuts through the high-magnetic Metchosin basalts from the southern tip of the island to the Leech River fault. It coincides with the Sooke gabbros exposed in the southern tip of the island, implying that the gabbros probably cut the entire Metchosin basalts at depth.