29 Undergraduate Research in the Geological Sciences II (Posters)

Tuesday, 26 March 2002
1:00 PM - 5:00 PM

FABRIC AND KINEMATIC INDICATORS IN THE CRETACEOUS KLINKIT BATHOLITH: IMPLICATIONS FOR THE ADJACENT KLINKIT FAULT IN NORTH-CENTRAL BRITISH COLUMBIA

Paper number: 29-5
Program: THEME
Time: 1:00 PM – 5:00 PM

Authors

Abstract

Fabric development in the Klinkit batholith, a foliated Cretaceous biotite-quartz monzonite in north-central British Columbia, was analyzed using the autocorrelation function (ACF) of the program NIH Image. The Klinkit batholith has fabric that ranges from isotropic, to weak and barely distinguishable, to weakly mylonitized. Where fabric is anisotropic, a consistent lineation occurs that is generally stronger than foliation. ACF analysis was based on grayscale images scanned from rock slabs cut perpendicular to foliation and parallel to lineation. The ACF program quantifies the average grain shape and the intensity of preferred orientation of grains by assessing how a point in the image correlates in gray tone with neighboring points along vectors in each of all possible directions. Comparing the shape and size of the ACF correlation value contour plots with analyses of conventional microstructures in thin section yielded a robust sense of shear for Klinkit batholith fabric.

Shear within the Klinkit batholith is correlated to displacement on the adjacent Klinkit Fault, which lies in a covered valley approximately five kilometers south of the study area. The Klinkit Fault and Klinkit batholith are situated near the western edge of the Omineca Crystalline Belt of the Canadian Cordillera, an orogen-parallel physiographic region composed primarily of metamorphic rocks and plutons produced from Cretaceous tectonic thickening associated with terrane accretion and affected by Mesozoic and Cenozoic transcurrent faulting. As a consequence, both thrust and strike-slip faults occur in the study area and the character of the Klinkit Fault has been open to question.