PALEOZOIC AND MESOZOIC ROCKS OF STIKINIA EXPOSED IN NORTHWESTERN BRITISH-COLUMBIA - IMPLICATIONS FOR CORRELATIONS IN THE NORTHERN CORDILLERA

Stikinia is a tectonostratigraphic terrane in the Canadian Cordillera that formed in a volcanic are environment during Paleozoic and Mesozoi c time, Until now the Paleozoic rocks that form a semicontinuous belt along its western margin (Stikine assemblage) were only recognized in a restricted area in northern British Columbia, between the Stikine an d Taku river areas, In contrast, Mesozoic Stikinia rocks form an almos t continuous belt that extends much farther to the north, leading some authors to question the nature of the unexposed Paleozoic basement no rth of the Taku River area, The following correlations have significan t implications for tectonic reconstructions of the northern Cordillera because they suggest that Stikinia's Paleozoic volcanic-sedimentary b asement is more widespread than previously thought, On the basis of si milar rock types and lithologic associations, six new U-Pb zircon date s, and the common intrusive relationship with 184-195 Ma plutons, the Stikine assemblage is correlated with the Boundary Ranges suite, a met amorphosed Paleozoic volcanic assemblage exposed in the Tagish Lake ar ea, north of the Taku River and south of the Yukon-British Columbia bo rder, The recognition of the Boundary Ranges suite and the Jurassic pl utons that intruded it (Tagish Lake suite) as part of Stikinia has imp lications for the age and character of the Stikinia-Tracy Arm terrane boundary because the Boundary Ranges and Tagish Lake suites form the f ootwall of a major Middle Jurassic shear zone that carried the contine ntal margin-like rocks of the Tracy Arm terrane in its hanging wall, T his correlation also implies that the late Paleozoic basement to the M esozoic Stikinia are is not a continental margin assemblage, at least as far north as the British Columbia-Yukon border, and possibly farthe r, The Boundary Ranges suite, and therefore the Stikine assemblage, ar e also tentatively correlated with parts of the Yukon-Tanana terrane i n Yukon (Aishihik Lake area), parts of the Taku terrane in southeast A laska, and undivided metamorphic rocks in west-central British Columbi a. Differences in the isotopic signatures of these rocks may reflect a long-strike changes in the character of the basement rocks of the late Paleozoic Stikinia volcanic arc.