TECTONIC LINKS BETWEEN THE CLACHNACUDAINN TERRANE AND SELKIRK ALLOCHTHON, SOUTHERN OMINECA BELT, CANADIAN CORDILLERA

The Clachnacudainn terrane in the southern Omineca Belt is interpreted as an integral part of the overlying Selkirk allochthon based on stratigraphic, igneous, metamorphic, and deformational links across the boundary between them, the Standfast Creek fault. An inverted homocline correlated with lower Paleozoic Lardeau Group metasedimentary and metavolcanic rocks is continuous across the fault. The fault is transected by post-ductile-strain granitoids of inferred and known mid-Cretaceous age (such as the 104 +/- 1 Ma Albert stock), as well as by peak regional metamorphic (M2) isograds and contact metamorphic (M3) isograds associated with the Albert stock. Three phases of regional ductile deformation (including major west verging second-phase (F2) folds) are correlated across the fault. These tectonic links strongly suggest that the Clachnacudainn terrane and Selkirk allochthon share a similar tectonic history and thereby require that the Standfast Creek fault has minor tectonic significance compared with other faults in the southern Omineca Belt. M2 and coeval F2 folds are interpreted as resulting from Middle Jurassic tectonism documented elsewhere in the Selkirk allochthon. The main aspect that differentiates the Clachnacudainn terrane from the rest of the Selkirk allochthon east of the Monashee complex is the Clachnacudainn igneous complex, which dominates the northern part of the terrane and is the product of prolonged igneous activity.