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Abstract

The isotopic-traeer data that are currently available on the igneous rocks of Alaska are inadequate to fully characterize the enormous areas of magmatic rock that are exposed on this subcontinent. Nevertheless, the existing data are quite useful for interpreting the origin and evolution of individual magmatic suites and their related ore deposits, the details of crustal growth in island arcs, the genesis of major continental-margin batholiths, and the nature of basement underlying vast areas of the remote interior.

This chapter is a summary of isotopic-tracer data on Mesozoic and Cenozoic igneous rocks of Alaska. Data published prior to the manuscript deadline of December 1986 are included, as are new data collected by the author from 1977 to 1986 in the course of collaborative studies with U.S. Geological Survey colleagues (references are provided if published prior to printing of this volume). The magmatic rocks are discussed in four sections: Mesozoic volcanic provinces, major Mesozoic to Cenozoic batholiths, magmatic suites of economic interest, and igneous rocks in Alaskan tectonostratigraphic terranes. Some of the longer subsections are followed by a one-paragraph summary that attempts a brief, generalized interpretation of the various isotopic results. The final section summarizes the Sr isotope data on a map of Alaska, and discusses the inferred nature of the deep continental crust.

Throughout the text, acronyms are used in place of the more cumbersome isotopic ratios, as follows:

Locations of geologic, geographic/physiographic, and tectonostratigraphic features referred to in this chapter are shown respectively on Plate 1 (Beikman), Plate 2

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