Geoscience Map 2010-4: Geology of the Area South and West of Princeton, British Columbia (parts of NTS 092H/01; 02; 07; 08 and 10), 1:50 000 scale
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The map covers an area centred about 15 km to the southwest of Princeton. The map area stretches from the Copper Mountain and Wolfe Creek area southwest to East Gate and the boundary of Manning Park and northwest to the Tulameen River.
The map area lies at the western edge of Quesnellia and includes some of the southernmost exposures of the late Triassic Nicola Group. To the east of the Boundary Fault, rocks of the Nicola group are assigned to the “Eastern Belt” (Preto 1979; Mortimer 1987). Interbedded black argillites, grey siltstones and sandstones are overlain by volcanic and volcaniclastic rocks of the Wolfe Creek Formation, which display an alkalic affinity. They host the important porphyry and skarn deposits of the Copper Mountain area (Preto, 1972).
To the west, rocks of the Nicola Group were included in the calc-alkaline “western belt” by Mortimer (1987). They are lithologically similar to those in the east, though differing in details of stratigraphic succession. Clastic sedimentary rocks, dominated by black argillites, are intercalated with feldspathic tuffs and tuffaceous sediments. These pass westwards, and probably upwards, into typical Nicola pyroxene-feldspar tuffs, lapilli tuffs and breccias. A sequence of massive feldspar basalt and greenstone flows occurs in the area southeast of the Granite Creek campsite. The volcanic rocks become more deformed to the west, the change from massive to schistose rocks being transitional and gradual from east to west as foliation becomes progressively more penetrative and steeper. Both schistose metasediments and metavolcanic rocks occur in the aureole of the Jurassic to Cretaceous Eagle Plutonic Complex along the western margin of the map area.
The Late Triassic Tulameen Ultramafic-Gabbro Complex is structurally emplaced into, though probably coeval with, the Nicola Group. Several smaller bodies of diorite-gabbro or pyroxenite also occur in the map area. The Tulameen Complex is host to chromite±Pt, magnetite, and copper deposits and an important source of platinum and gold-platinum placers of the area.
In the west of the map area, rocks of the Eastgate-Whipsaw metamorphic belt have been correlated with the Nicola by Rice (1947) and Monger (1989). The belt is bound by the syntectonic Eagle Plutonic Complex to the west and the Similkameen fault to the east. The belt shows significant lithological differences to the immediately adjacent Nicola volcanic rocks. It can be divided it into three northwest trending lithological assemblages that show increasing metamorphic grade from greenschist in the east to amphibolite in the west. The belt is host to VMS mineralization (e.g. Red Star and S&M group), as well as porphyry-Cu style mineralization associated with the Whipsaw porphyry. The belt may, in part, be equivalent to the Late Permian to Early Triassic Sitlika-Kutcho sequences, although preliminary zircon geochronometry suggests an Early Permian age (Oliver, work in progress).
Volcanic and sedimentary rocks of the Eocene Princeton Group occur in the northern (Tulameen coal basin), central (Princeton basin) and eastern parts of the map area. They lie unconformably on the Nicola Group and all older intrusive rocks. Comagmatic minor intrusions occur throughout the map area, particularly to the east of the Boundary fault.
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