KINEMATIC INTERPRETATION OF PLANAR AND LINEAR FABRICS IN THE KLINKIT BATHOLITH, BRITISH COLUMBIA

Field observations, stereographic projection, and oriented thin section analysis of rocks sampled from the Klinkit Batholith, a biotite quartz monzonite, indicate the presence of two generations of planar and linear fabric. Cross-cutting relationships observed locally in the field establish the relative ages of the fabrics but in general they are spatially distinct. The older fabric is characterized by uniformly northeast striking, steeply northwest dipping foliation and a weakly developed lineation that plunges steeply in most places. The younger fabric generation is characterized by a strongly aligned, shallowly plunging, west-northwest trending lineation, and foliation that strikes parallel to lineation but dips variably from horizontal to vertical. These relationships, aided by microscopic fabric analyses, allow for kinematic interpretations about regional faulting that may have accompanied fabric development.

The Cretaceous Klinkit Batholith sits among a framework of tectonically accreted and laterally offset terranes in the Canadian Cordillera, within the Omineca Crystalline Belt, west of the Cordilleran fold and thrust belt. The valley of the northwesterly flowing Jennings River, less than five kilometers south of the study area, is thought to conceal a thrust fault that juxtaposes Quesnellia (a Mesozoic arc terrane) to the southwest and Paleozoic sedimentary and volcanic rocks of uncertain origin to the northeast. Other nearby and parallel valleys are underlain by dextral transcurrent faults. Kinematic analysis of fabric in the Klinkit Batholith helps constrain the post Cretaceous history of faulting in the study area.