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The Tulameen intrusion (Late Triassic), an 18 by 6 km ultramafic-mafic body...
The Tulameen intrusion (Late Triassic), an 18 by 6 km ultramafic-mafic body in the Quesnel terrane of southern British Columbia, is hosted by metavolcanic and metasedimentary rocks of the Nicola Group (Upper Triassic). The intrusion is zoned, with a dunite core passing outwards through olivine clinopyroxenite and clinopyroxenite, to hornblende clinopyroxenite and hornblendite at the margin. It contains widespread gabbroic rocks and a dioritic-syenodioritic phase along the southeastern margin. Detailed mapping along a >4 km transect of near-continuous exposure in the Tulameen River during a period of low water level was assisted by a remotely piloted aircraft system (RPAS). Overlapping, highresolution digital imagery acquired by the RPAS was used to create 3-dimensional (3D) models, digital elevation models, and orthomosaics using Structure-from-Motion (SfM) photogrammetry. The transect along the Tulameen River includes dunite, chromitite, olivine clinopyroxenite, hornblende clinopyroxenite, gabbro, and minor olivine wehrlite. These rocks are cut by layered gabbro-diorite tabular bodies and fine-grained mafic to intermediate dikes. Contacts between the major map units are predominantly north-trending shear zones. Primary intrusive contacts are rarely exposed, and are typically limited to olivine clinopyroxenite, hornblende clinopyroxenite, and gabbro. Zones of intermingled ultramafic cumulates defi ned by entrained and variably deformed enclaves of dunite and olivine wehrlite in olivine clinopyroxenite are typical of the section. These zones are interpreted to record magma recharge and remobilization of crystal-rich magma mushes across a range of physical and rheological conditions.
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