Abstract

The structure at Kirkland Lake, Ontario, Canada, has been influenced by faults of several ages. Rocks present in the area are Keewatin lavas and agglomerates, Temiskaming sediments, and Algoman intrusives. The ores occur in the sediments and later intrusives and are cut by quartz diabase dikes.

The north and south margins of the 2-mile-wide sedimentary belt are found highly sheared by faulting, and this belt of younger rocks appears to be in a fault trough or graben, the older Keewatin rocks being found outside the marginal fault zones.

The several Algoman intrusive stocks have their larger axes roughly paralleling the strike of the sediments, have a general westerly plunge, and a divergence in dips of the north and south contacts causes a widening with depth.

The vein structures are thrust faults and associated tension fractures. The main vein fault, the Kirkland Lake fault, occurs slightly to the north of the center of the sedimentary belt, strikes N. 67°E., dips steeply south, and, cutting through the sediments and intrusives, has a thrust of 1400 feet. Vein faults of smaller movements branch off this fault on the footwall side in the east half of the camp and on the hanging wall side in the west half with the tension fractures showing the same relationship.

Post-ore faulting of several ages is evident, the earliest being a horizontal movement along the Kirkland Lake fault followed by strike faulting and rotatory cross faulting, each of two ages.

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