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K-Ar ages from the Near Islands, western Aleutian Islands, Alaska: Indication of a mid-Oligocene thermal event

1975; Geological Society of America; Volume: 3; Issue: 12 Linguagem: Inglês

10.1130/0091-7613(1975)3 2.0.co;2

1943-2682

Stephen E. DeLong, Fred W. McDowell,

Geological Studies and Exploration

Research Article| December 01, 1975 K-Ar ages from the Near Islands, western Aleutian Islands, Alaska: Indication of a mid-Oligocene thermal event Stephen E. DeLong; Stephen E. DeLong 1Department of Geological Sciences, State University of New York at Albany, Albany, New York 12222 Search for other works by this author on: GSW Google Scholar Fred W. McDowell Fred W. McDowell 2Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712 Search for other works by this author on: GSW Google Scholar Geology (1975) 3 (12): 691–694. https://doi.org/10.1130/0091-7613(1975)3 2.0.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Stephen E. DeLong, Fred W. McDowell; K-Ar ages from the Near Islands, western Aleutian Islands, Alaska: Indication of a mid-Oligocene thermal event. Geology 1975;; 3 (12): 691–694. doi: https://doi.org/10.1130/0091-7613(1975)3 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Deformed and metamorphosed basaltic volcanic rocks (one pillow lava, one amphibolite) from the basement on Attu Island have yielded whole-rock K-Ar ages of about 30 m.y. The greenschist (or higher grade) assemblage of these rocks and their presumed correlation with late Eocene or older early-series rocks elsewhere in the Aleutian arc suggest that these dates indicate a time of metamorphism. Similar ages (≅30 m.y.) for two mafic intrusions into the basement may also signify a time of metamorphism. These four ages place an older limit on, and may coincide with, the mid-Tertiary tectonism that deformed rocks of the early series along the length of the Aleutian arc. One post-early-series intrusion on Agattu is 14 m.y. old, in agreement with previous results from Shemya on a similar rock and in accord with the observation of a relatively abrupt start of late Tertiary magmatism throughout the arc about 15 m.y. ago. The youngest recognized igneous activity in the Near Islands is represented by hornblende-bearing rocks (one andesite lava, one dacite dike) on Attu that have yielded ages of 6 to 8 m.y. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.