Abstract

Although faults, as a rule, integrate themselves quite neatly within a network of lineaments, there is a basic difference between faults and lineaments. Hidden and often elusive, the lineaments are the deeper, wider and more significant planes of weakness in the earth’s crust. Frequently affected by recurring movements, they are by far the more important structures, with a regional and even continental connotation, while faults are only side-effects of the interplay and interaction of lineaments. Be if in Arizona, in British Columbia or in the Yukon, lineaments are more likely to be represented by the axes of major valleys than by an interpolation of fault zones.

The larger and more important the lineaments, the broader the zones of weakness at their intersections. For instance, wherever the “Continental Lineament” (combining the Tintina and the Rocky Mountain trenches) changes. in direction, affected by the encounter with secondary lineaments, the zone of intersection results in what one may call a broad, relatively smooth “plain”, irregular in shape, like the one occurring to the southwest of Prince George in British Columbia for instance.

Lineament intersections are of special importance: (1) Demographically, this type of intersection may correspond to a confluence of rivers or to o lake where the flat plains of aggradation surrounding it have become ideal emplacements for so many towns and cities and, the larger the plain, the more room is allowed for expansion of rural and farming communities; (2) Economically, in terms of hydrothermal ore deposits, an important lineament intersection could well coincide with a basic, very deep and important plumbing system, but mine occurrences do not appear within the immediate vicinity. On the contrary, they will show up at a distance of ten to fifty or more miles from this primary intersection, being connected instead with intersections of faults (assimilated to lineaments of a third or fourth order) within a distance of less than a mile.