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Granitic plutons of Late Cretaceous to middle Tertiary age comprise three major plutonic belts that occur in a large segment of the Coast Mountains Complex east of Juneau; they can be grouped, according to petrographic and chemical characteristics, into six northwest-trending subbelts. The Admiralty-Revillagigedo belt consist of two types of plutons; those of the Grand Island subbelt consist of magnetite-free, garnetand epidote-bearing tonalites and quartz diorites, whereas the two plutons of the Taku Harbor subbelt are magnetiteand epidote-bearing, hornblende quartz monzodiorites. The two plutons of the Great tonalite sill belt are foliated, equigranular, magnetite-rich biotite-hornblende tonalites that differ from plutons from this belt to the northeast which are more acidic and felsic in composition. The Coast Mountains belt contains two major suites of plutons; the western subbelt consist of large piutonic units of predominantly massive, magnetiteand titanite-bearing biotite-hornblende granodiorite, whereas the eastern subbelt consist of undivided, massive, porphyritic, coarse-grained allanite-bearing hornblende-biotite granite and a stock of fineto medium-grained seriate granite. Across the Coast Mountains Complex, the three major plutonic belts are distinguished by abrupt changes in age, structure, mineralogy, and composition, and the six subbelts are also distinguished by abrupt rather than gradual changes in chemical and modal composition, and magnetic susceptibilities. Plutons of the Admiralty-Revillagigedo belt are characterized by high FeO*/MgO ratios, high total alkalies and iron content, and high Sr abundances (700-1000 ppm). Rocks of the Great tonalite sill belt have restricted SiC>2 range (59-66 percent), high normative An content, and high ferromagnesian trace element (Sc, Cr, Co, and Zn) abundances, whereas rocks of the Coast Mountains belt are typically more acidic (64-74 percent SiC>2), less mafic, and contain higher abundances of K^O, Rb, Ur, and Th. Granites of the eastern part of the Coast Mountains belt are further distinguished by low Sr (<400 ppm) and high Rb (>100 ppm) contents, pronounced negative Eu anomalies, and high Hf and Ta concentrations. The Wright Glacier stock is also characterized by very low Sr (<250 ppm) abundance and high Zr (280-380 ppm) and Y (30-50 ppm) concentrations. The compositional differences between rocks of the various suites or subbelts reflect their differences in age and in the lithotectonic terranes and tectonic regimes into which they were emplaced. Plutons of the Admiralty-Revillagigedo belt represent an unrelated magmatic event from the plutonism of the mainland batholithic belts. Physical and chemical features support a common origin and magmatic evolution for most plutons of the Great tonalite sill and Coast Mountains belts, but some younger granites of the eastern part of the region may have been derived from a separate and unrelated magmatic event.

Geology, petrography, and geochemistry of granitic rocks from the Coast Mountains Complex near Juneau, southeastern Alaska