Geoscience Map 1993-9: Geology of the Noaxe Creek and Southwestern Big Bar Creek Map Areas
(NTS 92O/1, 2)
View Geoscience Map (PDF, 4.93MB)
Geoscience Map 1993-9 presents the geology of the Noaxe Creek and southwest Big Bar Creek area (92O/1, 2). The publication consists of a 1:50 000 scale geology map with legend and reference list.
The area is underlain by strata of the Intermontane Belt and Methow terrane, Ophiolitic assemblages, strata of the Cadwallader, Bridge River and Relay Mountain terranes, and overlap assemblages. Intermontane Belt strata may be of Cretaceous age. They are represented by the Dash-Churn succession that consists of units dominated by volcanic conglomerate; andesitic volcanic breccia and lapilli tuff; and volcanic conglomerate and breccia. Methow Terrane is represented by the Churn Creek facies and the Yalakom Mountain facies. Churn Creek facies consists of Middle Jurassic siltstone and fine sandstone, and rocks of the Lower Cretaceous Jackass Mountain Group with a lower unit of lithic sandstone to pebble conglomerate, and an upper unit of pebble to boulder conglomerate. Yalakom Mountain facies contains a Lower (?) to Middle Jurassic unit dominated by lithic-arkosic sandstone, a Middle (?) Jurassic unit of mainly volcanic breccia and andesitic flows, and Lower Cretaceous Jackass mountain Group strata with a lower unit dominated by lithic sandstone, granule conglomerate and conglomeratic sandstone, and an upper unit of arkosic sandstone, conglomeratic sandstone, siltstone, shale and conglomerate. The Ophiolitic assemblages include an assemblage of serpentinite, serpentinized ultramafite, and listwanite altered rocks; the Permian and younger Shulaps Ultramafic Complex with a harzburgite unit and a serpentinite melange unit; and the Bralorne-East Liza Complex of serpentinite, gabbro, diabase, and pillowed and massive greenstones. Cadwallader Terrane strata include the Upper Triassic Cadwallader and Tyaughton Groups, and the Lower to Middle Jurassic Last Creek Formation. The Cadwallader Group is represented by the Hurley Formation, which consists of a volcanic greenstone-tuff unit, and a unit comprised mainly of sandstone, calcarenite and siltstone. Tyaughton Group strata consist of a lower unit dominated by conglomerate and conglomeratic sandstone intercalated with sandstone, and an upper unit of mainly limestone conglomerate that is overlain by sandstone and conglomerate. Bridge River Terrane is represented by the Bridge River Complex. The Bridge River Complex consists of Mississippian to Middle Jurassic strata consisting mainly of ribbon chert, argillite and pillowed to massive greenstone. The Relay Mountain Terrane of the Lower Tyaughton Basin contains Middle Jurassic to Lower Cretaceous strata. The lower unit is mainly siliceous shale intercalated with sandstone and siltstone; the middle unit is dominantly sandstone and siltstone; and the upper unit is mostly shale and siltstone.
The Relay Mountain-Bridge River overlap assemblage comprises the Upper Tyaughton Basin consists of the Lower and perhaps Upper Cretaceous Taylor Creek Group, the Lower and/or Upper Cretaceous Silverquick Formation, and the Upper Cretaceous Powell Creek Formation. The Taylor Creek Group has the lower, Elbow Pass Formation sandstone, shale and conglomerate; the Paradise Formation of shale and sandstone; the Dash Formation of mainly chert pebble conglomerate, chert-rich sandstone, shale and siltstone; the Lizard Formation with micaceous sandstone and shale; a unit of volcanic breccia; and the Beece Creek succession of sandstone, siltstone and shale. The Silverquick Formation comprises mainly pebble to cobble conglomerate, and the Powell Creek Formation is mainly volcanic breccia and lapilli tuff. Tertiary rocks include the Miocene and possibly Pliocene Red Mountain volcanics, with a lower sedimentary unit overlain by andesite flows and rhyolite that is partly intrusive, the Big Sheep Mountain rhyolites, and olivine basalt flows of the Chilcotin Group.
Intrusive rocks in the area include Late Cretaceous and/or Early Tertiary hornblende-bearing porphyries, and quartz diorite to granodiorite, and Tertiary hornblende-biotite-quartz feldspar porphyries, quartz diorite and granodiorite, and Miocene or Pliocene mafic plugs.
The map area is cut by a northwest-trending system of dextral strike-slip faults that was active in Late Cretaceous time. Northerly trending splays of the Relay Creek-Marshall Creek fault system connect with the Yalakom fault system to define a large-scale extensional duplex structure. This fault system steps across and bounds the northwestern margin of the Shulaps ultramafic complex at its southeastern end. In contrast to the extensional zone to the northwest, the Shulaps complex may have been deformed and uplifted during Late Cretaceous movement on the bounding strike-slip fault systems.
The map area includes strata similar to those that host the Bridge River mining camp, British Columbia’s foremost historical gold producer from low sulphide mesothermal quartz veins. Other known and potential deposit types in the area are copper-molybdenum porphyries, pluton-associated high sulphide auriferous veins, skarns, scheelite-stibnite or stibnite-only veins, gold-silver polymetallic veins, epithermal gold-silver veins and cinnabar veins and disseminations.
Metallic mineral concentrations within or adjacent to strike-slip faults or associated structures have a close spatial relationship with plutons or dykes. The age of mineralization seems closely tied to igneous activity between Late Cretaceous and Early Tertiary time. The protracted history of mineralization and plutonism combined with differential uplift across faults has led to the juxtaposition of deposits of contrasting structural level. In addition, the ultramafic rocks have small chromite concentrations, and potential for jade, magnesite and chrysotile.
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