Geochemistry of siliciclastic rocks in the Peninsular, Chugach, and Prince William terranes: Implications for the tectonic evolution of south central Alaska

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5588306

Gilbert, S A; Casey, J F ^[1]; Bradley, D ^[2]; Kusky, T ^[3]

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1. Univ. of Houston, TX (United States). Dept. of Geosciences
2. USGS, Anchorage, AK (United States). Branch of Alaskan Geology
3. Boston Univ., MA (United States). Dept. of Geology

According to some interpretations, south-central Alaska consists of a series of unrelated terranes juxtaposed by dominantly strike-slip motions some time after formation. Alternatively, these so-called terranes may be related components of a seaward-facing arc, forearc, and accretionary prism. To shed new light on the tectonic history of this area, 150 samples of siliciclastic rocks were analyzed for major, trace, and rare earth elements (REE). Shales were sampled from the Upper Cretaceous Matanuska and Paleogene Chickaloon Fms. of the Peninsular Terrane (forearc basin); argillaceous melange matrix from the Mesozoic McHugh Complex and slate from turbidites of the Upper Cretaceous Valdez Group of the Chugach Terrane (landward part of accretionary prism); and slate from turbidites of the Paleogene Orea Group of the Prince William Terrane (seaward part of accretionary prism). One tectonic model that may fit these geochemical data requires an early linkage between the Peninsular and Chugach-Prince William composite terranes. The geochemical signatures suggest that the McHugh Complex was derived from a mafic volcanic source and may represent an early accretionary stage of sediments derived from an oceanic arc. The progressive continental enrichment of the Valdez and Orca Groups may reflect later accretionary processes during and/or after the collision of the Talkectna arc with the North American continent. The similar increasingly continental source documented in the geochemistry of the forearc basin shales of the Matanuska and Chickaloon Fms. may suggest: that the presently defined Peninsular, Chugach, and Prince William terranes collectively represent one continuously evolving, seaward facing arc, forearc, and accretionary prism complex.

• OSTI ID: 5588306
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALASKA
GEOLOGIC FORMATIONS
GEOCHEMISTRY
TECTONICS
ALUMINIUM OXIDES
GEOLOGIC MODELS
RARE EARTHS
SAMPLING
TITANIUM OXIDES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
METALS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
USA
580000* - Geosciences