Abstract

The author postulates the existence of a significant north-south trending geofracture in the Canadian Shield, the trace of which has been displaced at several places along other fractures (Figs. 1, 3). The name "Hudson Bay Paleolineament" is proposed, expressing its character over a considerable distance.A part of the geofracture is represented by a long linear element that was recognized by Canadian geologists and geophysicists in the Precambrian basement beneath Hudson Bay. This structure has restricted early Paleozoic sedimentation to the west side of the basin. The author deduces that it was present on the Precambrian and early Paleozoic surfaces as a prominent, roughly north-south trending lineament and is referring to it as to the "Hudson Bay Paleolineament" sensu stricto.Study of the drainage pattern and the distribution of aeromagnetic anomalies revealed that one of the north-south trending lineaments extends southward from James Bay more than 200 miles and represents the southern extension of the Hudson Bay Paleolineament.It is suggested that the Hudson Bay Paleolineament extends northward into the Arctic Archipelago. The northern extension may be represented by the 150 mile long Phanerozoic-Precambrian boundary trending north-south through the Ellesmere Island and/or the Nares submarine rift valley between the Ellesmere Island and north Greenland.Structurally favorable areas for the emplacement of endogenous ore deposits occur in the vicinity of intersections of the Hudson Bay Paleolineament with fractures of other sets. Two significant ore concentrations are located along the Hudson Bay Paleolineament in the area south of Hudson Bay and James Bay. One of them is the Noranda ore knot of the Val d'Or-Noranda-Kirkland Lake-Timmins ore field and another is the Cobalt ore knot. Comparable accumulations of metals along another parallel north-south trending lineament west of the Hudson Bay Paleolineament is the Timmins-Porcupine ore knot and possibly some of the ore bodies of the Sudbury district.In the area of the Hudson Bay itself, the copper occurrences on Belcher Islands lie near the paleolineament.It is suggested that the Hudson Bay Paleolineament and associated structures are of fundamental importance in controlling the location of ore fields in the Precambrian of Canada and could be of major economic importance.

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