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The geology of Hawkesbury Island, Skeena mining division, British Columbia Money, Peter Lawrence

Abstract

Hawkesbury Island is in the Skeena Mining Division of British Columbia. It is underlain by Coast Intrusions, younger lamprophyre dykes and older metamorphic rocks. The latter form part of the Ecstall septum or roof pendant. The metamorphic rocks are mainly amphibolites and quartz-feldspar gneisses. A few bands of quartzite, crystalline limestone, kyanite-staurolite-almandine mica schist and other rock types are present. These rocks have been formed by dynamothermal metamorphism of the regional type. They generally have assemblages indicative of the staurolite-quartz and kyanite-muscovite-quartz subfacies of the almandine amphibolite facies. Shear zones are strongly sericitized. Small percentages of sericite and chlorite are common throughout the metamorphic rocks. These minerals have been formed during retrogressive metamorphism. Apart from a few small metamorphosed igneous bodies, these rocks were originally a thick eugeosynclinal sequence consisting mainly of tuffaceous sediments and semi-pelitic or arkosic sediments. The metamorphic rocks have probably undergone at least two periods of deformation, so that their structure is complex. However, the foliation has a general trend of north 50° west to north 70° west in the northern part of the septum and of north 20° east to north 55° east in the southern part. The Coast Intrusions have reached their present positions by The Coast Intrusions have reached their present positions by intrusion. They have not been formed by granitization in situ. Some assimilation of the country rock has occurred but this is a marginal feature. The Coast Intrusions have had little affect on the grade of metamorphism of the metamorphic rocks.

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