Geology & Mineralization
The Atlin region is located in the northwestern corner of the northern Cache Creek (Atlin) Terrane. It contains a fault-bounded package of late Paleozoic and early Mesozoic dismembered oceanic lithosphere, intruded by post-collisional Middle Jurassic, Cretaceous and Tertiary felsic plutonic rocks. Mixed graphitic argillite and pelagic sedimentary rocks that contain minor pods and slivers of metabasalt and limestone dominate the terrane. Remnants of oceanic crust and upper mantle lithologies are concentrated along the western margin. Dismembered ophiolitic assemblages have been described at three localities along this margin: from north to south they are the Atlin, Nahlin and King Mountain assemblages. Each area contains imbricated mantle harzburgite, crustal plutonic ultramafic cumulates, gabbros and diorite, together with hypabyssal and extrusive basaltic volcanic rocks. Thick sections of late Paleozoic shallow-water limestone dominate the western margin of the terrane and are associated with alkali basalts. These are interpreted to be carbonate banks constructed on ancient ocean islands within the former Cache Creek ocean basin.
-- (reproduced from Ash, 2001)