Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Giorgis, S. Articles by McClelland, W. Search for Related Content GeoRef GeoRef Citation

Missing Idaho arc: Transpressional modification of the ⁸⁷Sr/⁸⁶Sr transition on the western edge of the Idaho batholith

Scott Giorgis^*,,1, Basil Tikoff^*,1 and William McClelland^*,2

¹ Department of Geology and Geophysics, University of Wisconsin, 1215 West Dayton Street, Madison, Wisconsin 53706, USA
² Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA

The North American Cordillera is characterized by subduction-related Mesozoic batholiths with voluminous middle Cretaceous plutonism. In the Cordillera, the Idaho batholith is anomalous, containing only a narrow (<10 km) band of middle Cretaceous plutons on its extreme western margin. These plutons are spatially coincident with the Late Cretaceous, crustal-scale, dextral transpressional western Idaho shear zone. Finite strain analysis indicates that there is significant east-west shortening in the western Idaho shear zone. A reconstruction using isotopic variations as strain markers, and comparing them to the undeformed middle Cretaceous Sierra Nevada batholith, results in a middle Cretaceous magmatic arc in western Idaho similar in width (85– 100 km) to other sections of the Cordilleran magmatic arc. The tectonic implications include: (1) a full magmatic arc existed in Idaho in the middle Cretaceous prior to Late Cretaceous deformation; (2) the currently sharp ⁸⁷Sr/⁸⁶Sr transition in western Idaho represents structural modification of the batholith after emplacement (i.e., the steep isotopic gradient results from deformation); and (3) as a result of Late Cretaceous shortening in the western Idaho shear zone, the main part of the Idaho batholith (i.e., post–ca. 90 Ma) intruded farther eastward into thick North American lithosphere. Consequently, the main part of the Idaho batholith has a stronger continental signature than the other coastal batholiths.

Key Words: western Idaho shear zone • Idaho batholith • transpression • Sr 0.706 line • magmatic arc

This article has been cited by other articles:

				S. Giorgis, W. McClelland, A. Fayon, B. S. Singer, and B. Tikoff Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho Geological Society of America Bulletin, September 1, 2008; 120(9-10): 1119 - 1133. [Abstract] [Full Text] [PDF]

				R. J. Dorsey and T. A. LaMaskin Stratigraphic record of Triassic-Jurassic collisional tectonics in the Blue Mountains province, northeastern Oregon Am J Sci, December 1, 2007; 307(10): 1167 - 1193. [Abstract] [Full Text] [PDF]

				W.C. McClelland and J.S. Oldow Late Cretaceous truncation of the western Idaho shear zone in the central North American Cordillera Geology, August 1, 2007; 35(8): 723 - 726. [Abstract] [Full Text] [PDF]

				R. J. Dorsey and R. J. Lenegan Structural controls on middle Cretaceous sedimentation in the Toney Butte area of the Mitchell inlier, Ochoco basin, central Oregon Geological Society of America Special Papers, January 1, 2007; 419(0): 97 - 115. [Abstract] [Full Text] [PDF]

				P. R. Hooper, V. E. Camp, S. P. Reidel, and M. E. Ross The origin of the Columbia River flood basalt province: Plume versus nonplume models Geological Society of America Special Papers, January 1, 2007; 430(0): 635 - 668. [Abstract] [Full Text] [PDF]