Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-05T11:12:15.306Z Has data issue: false hasContentIssue false

The Great Tonalite Sill of southeastern Alaska and British Columbia: emplacement into an active contractional high angle reverse shear zone (extended abstract)

Published online by Cambridge University Press:  03 November 2011

Donald H. W. Hutton
Affiliation:
D. H. W. Hutton, Department of Geological Sciences, Durham University, Durham DH1 3LE, U.K.
Gary M. Ingram
Affiliation:
G. M. Ingram, Department of Geological Sciences, Durham University, Durham DH1 3LE, U.K.

Extract

The Great Tonalite Sill (GTS) of southeastern Alaska and British Columbia (Brew & Ford 1981; Himmelberg et al. 1991) is one of the most remarkable intrusive bodies in the world: it extends for more than 800 km along strike and yet is only some 25 km or less in width. It consists of a belt of broadly tonalitic sheet-like plutons striking NW–SE and dipping steeply NE, and has been dated between 55 Ma and 81 Ma (J. L. Wooden, written communication to D. A. Brew, April 1990) (late Cretaceous to early Tertiary). The sill (it is steeply inclined and rather more like a “dyke”) is emplaced along the extreme western margin of the Coast Plutonic and Metamorphic Complex (CPMC), the high grade core of the Western Cordillera. The CPMC forms the western part of a group of tectonostratigraphic terranes including Stikine and Cache Creek, collectively known as the Intermontane Superterrane (Rubin et al. 1990). To the W of the GTS, rocks of the Insular Superterrane, including the Alexander and Wrangellia terranes and the Gravina belt, form generally lower metamorphic grade assemblages. The boundary between these two superterranes is obscure but it may lie close to, or be coincident with, the trace of the GTS.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1992

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Brew, D. A. & Ford, A. B. 1981. The Coast Plutonic Complex Sill, Southeastern Alaska. In Albert, N. R. D. & Hudson, T. (eds) The United States Geological Survey in Alaska—Accomplishments during 1979. U.S.G.S. CIRCULAR 823–B, 96–9.Google Scholar
Crawford, M. L. & Hollister, L. S. 1982. Contrasts of metamorphic and structural histories across the Work Channel Lineament, Coast Plutonic Complex, British Columbia. J GEOPHYS RES 87, 3849–60.Google Scholar
Himmelberg, G. R., Brew, D. A. & Ford, A. B. 1991. Development of inverted metamorphic isograds in the western metamorphic belt, Juneau, Alaska. J METAMORPHIC GEOL 9, 165–80.CrossRefGoogle Scholar
Hutton, D. H. W. 1982. A tectonic model for the emplacement of the Main Donegal Granite, NW Ireland. J GEOL SOC LONDON 139, 615–31.CrossRefGoogle Scholar
Hutton, D. H. W. 1988. Granite emplacement mechanisms and tectonic controls: inferences from deformation studies. TRANS R SOC EDINBURGH EARTH SCI 79, 245–55.Google Scholar
Hutton, D. H. W., Dempster, T. J., Brown, P. E. & Becker, S. M. 1990. A new mechanism of granite emplacement: intrusion in active extensional shear zones. NATURE 343, 452–5.CrossRefGoogle Scholar
Rubin, C. M., Saleeby, J. B., Cowan, D. S., Brandon, M. T. & McGroder, M. F. 1990. Regionally extensive mid-Cretaceous west-vergent thrust system in the northwestern Cordillera: implications for continent-margin tectonism. GEOLOGY 18, 276–80.2.3.CO;2>CrossRefGoogle Scholar