Intrusive and depositional constraints on the Cretaceous tectonic history of the southern Blue Mountains, eastern Oregon
MetadataShow full item record
© 2016 Geological Society of America. We present an integrated study of the postcollisional (post-Late Jurassic) history of the Blue Mountains province (Oregon and Idaho, USA) using constraints from Cretaceous igneous and sedimentary rocks. The Blue Mountains province consists of the Wallowa and Olds Ferry arcs, separated by forearc accretionary material of the Baker terrane. Four plutons (Lookout Mountain, Pedro Mountain, Amelia, Tureman Ranch) intrude along or near the Connor Creek fault, which separates the Izee and Baker terranes. High-precision U-Pb zircon ages indicate 129.4-123.8 Ma crystallization ages and exhibit a north-northeast-younging trend of the magmatism. The40Ar/39Ar analyses on biotite and hornblende indicate very rapid ( < 1 m.y.) cooling below biotite closure temperature (~350 °C) for the plutons. The (U-Th)/He zircon analyses were done on a series of regional plutons, including the Lookout Mountain and Tureman Ranch plutons, and indicate a middle Cretaceous age of cooling through ~200 °C. Sr, Nd, and Pb isotope geochemistry on the four studied plutons confirms that the Izee terrane is on Olds Ferry terrane basement. We also present data from detrital zircons from Late Cretaceous sedimentary rocks at Dixie Butte, Oregon. These detrital zircons record only Paleozoic-Mesozoic ages with only juvenile Hf isotopic compositions, indicating derivation from juvenile accreted terrane lithosphere. Although the Blue Mountains province is juxtaposed against cratonic North America along the western Idaho shear zone, it shows trends in magmatism, cooling, and sediment deposition that differ from the adjacent part of North America and are consistent with a more southern position for terranes of this province at the time of their accretion. We therefore propose a tectonic history involving moderate northward translation of the Blue Mountains province along the western Idaho shear zone in the middle Cretaceous.
Showing items related by title, author, creator and subject.
Post-accretionary exhumation of the Meguma terrane relative to the Avalon terrane in the Canadian AppalachiansArchibald, D.; Murphy, J.; Reddy, Steven; Jourdan, Fred; Gillespie, J.; Glorie, S. (2018)The accretion of the Avalon and Meguma terranes to the Laurentian margin was a major event in the development of the Appalachian orogen. The Minas Fault Zone delineates the boundary between these terranes. A strongly ...
Petrogenesis of Cretaceous shoshonitic rocks in the northern Wuyi Mountains, South China: A result of the roll-back of a flat-slab?Li, W.; Li, X.; Wang, Xuan-Ce; Yang, D. (2017)© 2017 Elsevier B.V. Potassic magmatism is commonly linked to post-/late-orogenic environments, such as foundering or convection thinning of continental lithosphere. Their petrogenesis is crucial for constraining the ...
Piotraschke, R.; Cashman, S.; Furlong, K.; Kamp, P.; Danisik, Martin; Xu, G. (2015)The Klamath Mountains province of northwestern California–southwestern Oregon is an anomalous element in the Cascadia margin; these mountains have the highest average topography, the oldest rocks, and the only identified ...