Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Tectonics. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]Deformation in western Guatemala associated with the NAFCA (North America-Forearc-Caribbean) triple junction: Neotectonic strain localization into the Guatemala City grabenAuthorsBridgetGarnieriDBasilTikoffOmarFloresBrian R.JichaCharlesDemetsBeatrizCosenza MurallesiDWalterHernándezDavid C.GreeneiDSee all authors Bridget GarnieriDCorresponding Author• Submitting AuthorUniversity of Wisconsin-MadisoniDhttps://orcid.org/0000-0001-9622-8269view email addressThe email was not providedcopy email addressBasil TikoffUniversity of Wisconsin-Madisonview email addressThe email was not providedcopy email addressOmar FloresUSACview email addressThe email was not providedcopy email addressBrian R. JichaDepartment of Geoscience, University of Wisconsin-Madisonview email addressThe email was not providedcopy email addressCharles DemetsUniversity of Wisconsin-Madisonview email addressThe email was not providedcopy email addressBeatriz Cosenza MurallesiDUniversity of Wisconsin-MadisonInstituto de Investigación en Ciencias Físicas y Matemáticas, Universidad de San Carlos de GuatemalaiDhttps://orcid.org/0000-0002-4626-2757view email addressThe email was not providedcopy email addressWalter HernándezObservatorio Ambiental, Ministerio de Medio Ambiente y Recursos Naturales (MARN)view email addressThe email was not providedcopy email addressDavid C. GreeneiDDenison UniversityiDhttps://orcid.org/0000-0002-6384-9752view email addressThe email was not providedcopy email address
Research Article| September 01, 2008 Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho Scott Giorgis; Scott Giorgis † 1Department of Geological Sciences, State University of New York–Geneseo, 1 College Circle, Geneseo, New York 14454, USA †E-mail: giorgis@geneseo.edu Search for other works by this author on: GSW Google Scholar William McClelland; William McClelland 2Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA Search for other works by this author on: GSW Google Scholar Annia Fayon; Annia Fayon 3Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455-0219, USA Search for other works by this author on: GSW Google Scholar Brad S. Singer; Brad S. Singer 4Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA Search for other works by this author on: GSW Google Scholar Basil Tikoff Basil Tikoff 4Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2008) 120 (9-10): 1119–1133. https://doi.org/10.1130/B26291.1 Article history received: 25 May 2007 rev-recd: 21 Feb 2008 accepted: 14 Mar 2008 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Scott Giorgis, William McClelland, Annia Fayon, Brad S. Singer, Basil Tikoff; Timing of deformation and exhumation in the western Idaho shear zone, McCall, Idaho. GSA Bulletin 2008;; 120 (9-10): 1119–1133. doi: https://doi.org/10.1130/B26291.1 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 SocietyGSA Bulletin Search Advanced Search Abstract The western Idaho shear zone is one of several Cretaceous high-strain zones in the Cordillera that are thought to have been associated with the northward translation and/or docking of terranes presently in British Columbia. Located in west-central Idaho, this zone of intense deformation consists of a mid-crustal exposure of a lithospheric-scale, intra-arc dextral shear zone that overprints the Salmon River suture zone along the western edge of the Idaho batholith. U/Pb zircon geochronology constrains the main phase of deformation to between ca. 105 and 90 Ma. Cessation of movement on the shear zone occurred by 90 Ma, as determined by dating of the syntectonic Payette River tonalite and a crosscutting pegmatite dike in the Little Goose Creek complex. The 40Ar/39Ar thermochronology indicates that the shear zone passed through both the hornblende (~550 °C) and biotite (~325 °C) closure temperatures between 85 and 70 Ma. The 40Ar/39Ar biotite dates from an outcrop-scale, crosscutting shear zone are indistinguishable from that of the host rock, indicating that deformation occurred above the closure temperature of biotite. Apatite fission-track analysis suggests that exhumation to shallow crustal levels occurred ca. 40 Ma during mid-Tertiary regional exhumation or renewed tectonic activity along the Salmon River suture zone. Taken together, the 40Ar/39Ar results and apatite fission-track analyses indicate a two-stage uplift history for the western Idaho shear zone. Overall, the geochronology indicates that dextral transpressional movement on the western Idaho shear zone was temporally distinct from the Early Cretaceous suturing event. Additionally, the first stage of exhumation recorded by the western Idaho shear zone immediately followed transpressional deformation. Cessation of displacement on the western Idaho shear zone by ca. 90 Ma indicates that the exhumation did not solely occur as a result of ductile deformation on the shear zone itself. Moreover, dextral strike-slip movement on the western Idaho shear zone had also ceased by 90 Ma, indicating that terrane translation models for the Cordillera can only use the western Idaho shear zone to accommodate northward translation up to ca. 90 Ma. Lastly, the timing of movement on the western Idaho shear zone and contractional deformation recorded in the Insular terrane suggests a correlation between these events. This hypothesis implies that the deformation recorded in the western Idaho shear zone may have been linked to the oblique collision of the Insular superterrane with North America. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
The western Idaho shear zone is a major, lithospheric-scale structure separating accreted terranes of the Blue Mountains from continental North America. We document the occurrence of the western Idaho shear zone in West Mountain, west-central Idaho. Rocks deformed by the western Idaho shear zone at West Mountain are dominantly orthogneisses, although exposures on West Mountain containing screens of metamorphosed sedimentary rocks are also present. Steeply E-dipping, N-NNE–oriented foliations and downdip lineations characterize the fabric in the orthogneisses, consistent with dextral transpressional kinematics. The foliation orientation changes from 005° to 024° from the northern to the southern part of the field area, and this is interpreted to reflect a primary along-strike variation in the orientation of the western Idaho shear zone. The westernmost unit in West Mountain (Four Bit Creek tonalite) has a U-Pb zircon age of 101 ± 3.0 Ma, yet it is only weakly deformed. We interpret this unit to have been emplaced pretectonically, thus constraining the initiation of the western Idaho shear zone. The youngest unit at West Mountain is the undeformed Rat Creek granite (88.2 ± 3.3 Ma). U-Pb analyses of zircons from orthogneisses at West Mountain span ages of 111–91 Ma, indicating both precursory and continuous magmatism coeval with western Idaho shear zone deformation. Two Lu-Hf garnet isochron ages, 97.3 ± 0.7 Ma and 99.5 ± 1.4 Ma, are interpreted to indicate peak metamorphism during western Idaho shear zone deformation. Geochemical analyses suggest that the westernmost exposed orthogneiss units are dominantly derived from continental material in West Mountain, and yet there is also evidence for a component of accreted terrane rocks at depth east of the western Idaho shear zone.
