| Abstract: | The Kilbuck terrane in southwestern Alaska is a narrow, thin crustal sliver or flake of amphibolite facies orthogneiss. The igneous protolith of this gneiss was a suite of subduction-related plutonic rocks. U-Pb data on zircons from trondhjemitic and granitic samples yield upper-intercept (igneous) ages of 2070 ?? 16 and 2040 ?? 74 Ma, respectively. Nd isotope data from these rocks suggest that a diorite-tonalite-trondhjemite suite (??Nd[T] = +2.1 to +2.7; T is time of crystallization) evolved from partial melts of depleted mantle with no discernible contamination by older crust, whereas a coeval granitic pluton (??Nd[T] = -5.7) contains a significant component derived from Archean crust. Orthogneisses with similar age and Nd isotope characteristics are found in the Idono complex 250 km to the north. Early Proterozoic rocks are unknown elsewhere in Alaska. The possibility that the Kilbuck terrane was displaced from provinces of similar age in other cratons (e.g., Australian, Baltic, Guiana, and west African shields), or from the poorly dated Siberian craton, cannot be excluded. -from Authors |
| Genre: | Article |
| ProdID: | 70015913 |
| Citation Author: | Box, S. E.; Moll-Stalcup, E. J.; Wooden, J. L.; Bradshaw, J. Y. |
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| Citation End Page: | 1222 |
| Citation Issue: | 12 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geology |
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| Citation Number Of Pages: | 4 |
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| Citation Search Results Text: | Kilbuck terrane: oldest known rocks in Alaska; 1990; Article; Journal; Geology; Box, S. E.; Moll-Stalcup, E. J.; Wooden, J. L.; Bradshaw, J. Y. |
| Citation Start Page: | 1219 |
| Citation Volume: | 18 |
| Citation Year: | 1990 |
| Type: | citation/reference |
| Text: | Kilbuck terrane: oldest known rocks in Alaska; 1990; Article; Journal; Geology; Box, S. E.; Moll-Stalcup, E. J.; Wooden, J. L.; Bradshaw, J. Y. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Mon, 1 Jan 1990 00:00 -0600 |
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