Geology

Regional Geology

Red Mountain is located near the western margin of the Stikine terrain in the Intermontane Belt. There are three primary stratigraphic elements in Stikinia and all are present in the Stewart area: Middle and Upper Triassic clastic rocks of the Stuhini Group, Lower and Middle Jurassic volcanic and clastic rocks of the Hazelton Group, and Upper Jurassic sedimentary rocks of the Bowser Lake Group. Many primary textures are preserved in rocks from all of these groups, and mineralogy suggests that that the regional metamorphic grade is probably lower greenschist facies.

Intrusive rocks in the Red Mountain region range in age form Late Triassic to Eocene and form several suites. The Stikine plutonic suite is comprised of Late Triassic calc-alkaline intrusions that are coeval with the Stuhini Group rocks. Early to Middle Jurassic plutons are roughly coeval with the Hazelton Group rocks and have important economic implications for gold mineralization in the Stewart area, including the Red Mountain gold deposits. Intrusive rocks of this age are of variable composition. Eocene intrusions of the Coast Plutonic Complex occur to the west and south of Red Mountain and are associated with high-grade silver-lead-zinc occurrences.

Structurally, Red Mountain lies along the western edge of a complex, northwest-southeast trending, doubly-plunging structural culmination, which was formed during the Cretaceous. At this time rocks of the Stuhini, Hazelton and Bowser Lake groups were folded and/or faulted, with up to 40% shortening in a northeast-southwest direction. The Red Mountain deposits lie at the core of the Bitter Creek antiform, a northwest-southeast trending structure created during this deformation event.
 
Property Geology

The oldest rocks, Middle to Upper Triassic mudstone, siltstone and chert of the Stuhini Group outcrops over about two-thirds of the project’s mapped area. The Triassic rocks grade upward into Lower Jurassic Hazelton Group clastic and volcaniclastic rocks, which outcrop in the northeastern portion of the map area. Rocks of both groups are folded about axes that plunge towards 345° and dip steeply to the southwest. An approximate contact between rocks of the two groups also follows this trend and occurs along the projected trace of the Bitter Creek antiform, a structure that has been mapped. Hazelton Group volcaniclastic rocks on the southwest limb of this structure have been eroded away.

Three phases of the Early Jurassic Goldslide intrusions are exposed in the map area. The Hillside porphyry, a fine- to medium-grained hornblende and plagioclase porphyry, occurs near the summit of Red Mountain and along the ridge to the southeast of the summit. The medium- to coarse-grained hornblende, biotite ± quartz Goldslide porphyry, is distinguishable from the Hillside porphyry by mineralogy and phenocryst size. It is exposed along the Goldslide Creek valley, extending from the surface expression of the Marc Zone to the southwest for two kilometres. Finally, sills of the Biotite porphyry intrude Upper Triassic sediments on the west side of Red Mountain. It is distinguished from the Hillside porphyry by the presence of biotite phenocrysts and from the Goldslide porphyry by the small size of hornblende and plagioglase phenocrysts. Contact breccias and strongly disrupted bedding are common along the contacts of these intrusions, particularly in association with the Hillside porphyry. In addition, the Hillside porphyry contains rafts of the sedimentary rocks ranging in size from one or two metres to several tens of metres.

A Tertiary intrusion, the McAdam Point Stock, is exposed in the southern portion of the map area adjacent to the Bromley Glacier. It is a medium- to coarse-grained biotite quartz monzonite dated to 45 Ma.

Structural deformation at the property scale is consistent with the observations at the regional and tectonic scales. Folds have been mapped in the entire Triassic-Jurassic succession with north to northwest plunging axes and generally steeply dipping limbs. Fold traces can be complicated and difficult to trace, particularly near intrusive contacts. The timing suggests that the folds are a manifestation of the Cretaceous Skeena fold belt deformation. There is no evidence to suggest that the intrusive units were affected by this folding event.

Brittle faulting has affected all rock units at Red Mountain. Two phases of faulting have been recognized: northeast striking, steeply northwesterly dipping faults; and north to northwest trending faults. Faults of the former group are those that offset the mineralized zones, such as the Rick Fault. The latter group is noted to contain more gouge and have broader alteration envelopes than the former. Both of these sets of faults are believed to be the result of a Miocene extensional event.