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Studies during the past decade have revealed that much of Alaska consists of a collection of generally far-traveled tectonostratigraphic terranes, most of which were transported to their present locations and accreted to North America in late Mesozoic to early Tertiary time (Jones and others, 1984; Silberling and others, this volume). This collage results in the exceedingly complex geologic and tectonic framework that constitutes much of present-day Alaska.

Magmatic activity in Alaska was influenced by a host of factors, including many involving plate interactions, such as the rate of subduction, the angle of dip, the motion of individual plates, and the composition, thickness, and age of material that was subducted beneath or collided with Alaska. The identification and interpretation of magmatic patterns as reflected by time of intrusion, areal distribution, and composition can therefore contribute to an understanding of the tectonic history of Alaska.

The following overview focuses on plutonic rocks in mainland (excludes southeastern) Alaska emplaced from the Proterozoic into the earliest Tertiary. Plutonic rocks and belts emplaced during a specific time frame (e.g., the Early Cretaceous) are not necessarily everywhere related in terms of genesis or tectonic setting, and some related rocks may be shown in different temporal episodes. Postplutonic terrane movement and Cenozoic strike-slip faulting with large displacements have further complicated the identification and interpretation of plutonic events and patterns. Rocks assigned to specific plutonic belts are assumed to be cogenetic regardless of the mechanism of formation. The informal name given to a temporal episode of intrusive activity

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