Overview of granitic rocks in the Bradfield Canal area, southeastern Alaska
- Geological Survey, Menlo Park, CA (United States)
Granitic rocks in the Bradfield Canal area of southeastern Alaska are part of the Coast plutonic-metamorphic complex and include rocks representing several different periods of magmatic activity. Units belonging to the previously named Admiralty-Revillagigedo, great tonalite sill, Coast Mountains, and Groundhog Basin-Cone Mountain belts are present. The Texas Creek Granodiorite is located in the southeastern part of the area and is probably 212 Ma or somewhat older. It consists mainly of locally deformed and altered calc-alkalic biotite-hornblende granodiorite and is closely associated with important mineral deposits. Distinguishing features include primary epidote, accessory garnet, and locally a distinctive plagioclase-porphyritic texture. Northeast of the Admiralty-Revillagigedo belt lies the northwest-trending great tonalite sill belt. These rocks are 58--55 Ma and consist of calc-alkalic, generally well-foliated and locally lineated biotite-hornblende and hornblende tonalite, quartz diorite, and granodiorite. The Coast Mountains belt granitic rocks are the most extensive in the area. The granite has been explored for U, Th, and REE deposits. The Coast plutonic-metamorphic complex records dynamothermal and regional contact metamorphic events related to the regional plutonism. Most of the lengthy and complicated magmatic and metamorphic history of the complex is related to Late Cretaceous collision of the Alexander and Wrangellia terranes and juxtaposition of the Gravina overlap assemblage to the west (Superterrane II) against the Yukon prong and Stikine terrane to the east (Superterrane I). An exception is the Texas Creek Granodiorite, which is related to a pre-accretionary Jurassic arc in the Stikine terrane.
- OSTI ID:
- 5098593
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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