Ancient Pacific Margin Part II: A Preliminary Comparison of Potential VMS-hosting Successions of the Yukon Tanana Terrane, from Finlayson Lake District to Northern British Columbia*

The Yukon-Tanana Terrane of Yukon, Alaska and northern British Columbia consists of poorly understood, lithologically diverse successions of metasedimentary and metavolcanic rocks and voluminous midand late Paleozoic granitic metaplutonic bodies (Mortensen and J i l s o n , 1 9 8 5 ; M o r t e n s e n , 1 9 9 2 ) . S i g n i f i c a n t volcanogenic massive sulphide deposits occur in the terrane in the Delta and Bonnifield districts in Alaska and in the Finlayson Lake belt in southeastern Yukon, and the potential for further discoveries is considered to be high. However, exploration for new deposits has been hindered by the paucity of stratigraphic information from the terrane as a whole. One of the goals of the Ancient Pacific Margin NATMAP project is to address the deficiencies in stratigraphic information from the Yukon-Tanana Terrane. The Central Component of the Ancient Pacific Margin Project, which spans both Yukon and British Columbia, includes bedrock geological mapping of the Finlayson Lake belt (Murphy and Piercey 1999, 2000; location 1 on Figure 1), the Glenlyon area in central Yukon (Colpron, 1999; Colpron and Reinecke, 2000; locations 2, 3 on Figure 1), the Wolf Lake/Jennings River map area straddling the Yukon/B.C. border (Roots et al., 2000; location 4 on Figure 1), the Big Salmon Complex in northern Jennings River map area (Mihalynuk et al. this volume; location 5 on Figure 1), and the southeastern Dorsey Terrane in south-central Jennings River map area (Nelson, this volume; location 6 on Figure 1). The Finlayson Lake belt is currently separated from the other areas by the Tintina Fault. Restoration of about 425 kilometres of displacement on the fault (Roddick, 1967; Murphy,Mortensen and Abbott, in prep.) aligns all of these areas in a continuous belt from the Finlayson Lake area to the southern Jennings River (Figure 1). The Yukon-Tanana Terrane along this belt represents a target for volcanogenic massive sulphide deposits that extends over 500 kilometres of strike length.