The McKinley sequence of granitic rocks consists of discrete plutons in the central Alaska Range. Most of these plutons crop out S of the Denali fault system (DFS) in the Talkeetna quadrangle. Plutons of the McKinley sequence largely intrude deformed upper Mesozoic flysch between the DFS and the N edges of Wrangellia and the Peninsular terrane, which jointly make up the Talkeetna superterrane. The average K-Ar age of biotite from 9 granites of the McKinley sequence is 57.3 Ma; Rb-Sr data for whole rock samples indicate that the McKinley sequence cannot be older than 60 Ma. The Sr isotopic ratios, peraluminous nature, REE patterns, and high delta 18O values suggest that granitic rocks of the McKinley sequence crystallized from hybrid magmas produced by assimilation of sedimentary rocks by a mantle-derived melt. Mesozoic flysch is the likely source of the crustal component of the hybrid magmas. Geologic evidence suggests that the Talkeetna superterrane collided with stable Alaska after Early Cretaceous time.-after Authors
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The McKinley sequence of granitic rocks: a key element in the accretionary history of southern Alaska ( USA).