t ne Dew GENERAL GEOLOGY The mercury belt lies along a major fault zone striking approximately northwest and extending from near Fort St. James 90 miles northwestward to Kwanika Creek, A thick succession of steeply folded Permian limestones and other interbedded sedimentary rocks out- crop on the southwest side of the fault zone. Upper Triassic sedi- mentary strata and durassic tuffs and lavas predominate on the north- east side of the fault zone. All the formations trend northwesterly. Bodies of intrusive rocks ranging in composition from granodiorite to pyroxenite cut the Permian and Upper Triassic rocks and probably also those of Jurassic:.Ag@en icc imme see Permian Permian strata comprise not less than 10,000 feet of interbedded limestone, quartzite, chert, argillite, slate, greywacke, and derived schists; Limestone is the most characteristic and com- petent rock type. It occurs chiefly in three northwesterly trending bands. The .southwesterly-and middle bands are from 1 to 4 miles wide and more than:60 miles long, and the northeasterly band is about a mile wide and more than 20 miles long. The three bands probably represent the same limestone strata repeated by folding. hey range in thickness frow:3,000 to. 8,000 feet and include lenses of chert.,. argillite, quartzite, and.schist up to.60. feet thick. Smaller bands and lens-like bodies of limestone as much as 600 feet thick occur throughout the Permian section. — “ih et The normal limestone’ is blue-grey, grey weathering, médium-grained to dense, and massively bedded. In places the beds -prade.from blue«grey-to white and cream.across widths of from 15 to 20 feet. Stylolitic structures occur along some of the bedding planes. In many parts of the area the lime stones are completely: “reerystallized so that all 6videhéds of bedding are lost except — in some of the more thinly bedded sections where preferential. :.. -“ghertification has*taken place. The chert. occurs along original “pedding planes and weathers out -in ridges @ inch: to. 2 inches wide separated by béds’ of. limestone + inch to 6 inches thick. In the. more massively bedded limestones chert occurs in white weathering bodies, averaging 2:to 6 inches in diameter. ‘The limestones out~-. cropping from: Ichentsut Mountain to Tsayta Lake contain much red and “brown, hematitic: and limonitic iron occurring as’ minute stringers, specks, and stain. Most of the grey limestones are criss-crossed with calcite stringers a fraction of an inch wide. In the vicinity of the principal faults the grey limestone has been altered to buff weathering dolomite. The Permian non=-caleareous rocks also form three long northwesterly trending bands and are conformably interbedded with the limestones. They are relatively incompetent rocks and are much more closely folded and more generally sheared and faulted than the lime- stone. As a result it is difficult to estimate their total thickness, but they make up at least 6,000 feet of the Permian section, partly underlying and partly overlying the limestone bands. j The most characteristic of the non-calcareous Permian rocks are thinly bedded, argillaceous quartzites, ribbon cherts, and argillites. The argillaceous guartzites and ribbon cherts are generally blue-grey, but vary from cream-grey to black, and in places are pale ' green.: They consist of beds of quartzite or of chert, # inch to 6 inches thick, commonly minutely crumpled, and separated by partings