SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian-Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics

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Research Article| March 01, 2010 SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian–Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics K. Lund; K. Lund † 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA †E-mail: klund@usgs.gov Search for other works by this author on: GSW Google Scholar J.N. Aleinikoff; J.N. Aleinikoff 2U.S. Geological Survey, MS 963, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar K.V. Evans; K.V. Evans 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar E.A. duBray; E.A. duBray 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar E.H. Dewitt; E.H. Dewitt 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar D.M. Unruh D.M. Unruh 2U.S. Geological Survey, MS 963, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA Search for other works by this author on: GSW Google Scholar Author and Article Information K. Lund † 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA J.N. Aleinikoff 2U.S. Geological Survey, MS 963, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA K.V. Evans 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA E.A. duBray 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA E.H. Dewitt 1U.S. Geological Survey, MS 973, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA D.M. Unruh 2U.S. Geological Survey, MS 963, Denver Federal Center, Box 25046, Denver, Colorado 80225, USA †E-mail: klund@usgs.gov Publisher: Geological Society of America Received: 20 Oct 2008 Revision Received: 08 Apr 2009 Accepted: 10 May 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (3-4): 430–453. https://doi.org/10.1130/B26565.1 Article history Received: 20 Oct 2008 Revision Received: 08 Apr 2009 Accepted: 10 May 2009 First Online: 08 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 K. Lund, J.N. Aleinikoff, K.V. Evans, E.A. duBray, E.H. Dewitt, D.M. Unruh; SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian–Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics. GSA Bulletin 2010;; 122 (3-4): 430–453. doi: https://doi.org/10.1130/B26565.1 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 Composite alkalic plutonic suites and tuffaceous diamictite, although discontinuously exposed across central Idaho in roof pendants and inliers within the Idaho batholith and Challis volcanic-plutonic complex, define the >200-km-long northwest-aligned Big Creek-Beaverhead belt. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dates on these igneous rocks provide direct evidence for the orientation and location of the Neoproterozoic–Paleozoic western Laurentian rift margin in the northern U.S. Cordillera. Dating delimits two discrete magmatic pulses at ca. 665–650 Ma and 500–485 Ma at the western and eastern ends, respectively, of this belt. Together with the nearby 685 Ma volcanic rocks of the Edwardsburg Formation, there is a 200 Ma history of recurrent extensional magmatic pulses along the belt. A similar history of recurrent uplift is reflected in the stratigraphic record of the associated miogeoclinal and cratonal platform basins, suggesting that the Big Creek–Beaverhead belt originated as a border fault during continental rift events. The magmatic belt is paired with the recurrently emergent Lemhi Arch and narrow miogeoclinal facies belts and it lies inboard of a northwest-striking narrow zone of thinned continental crust. These features define a northeast-extending upper-plate extensional system between southeast Washington and southeast Idaho that formed a segment of the Neoproterozoic–Paleozoic miogeocline. This segment was flanked on the north by the St. Mary–Moyie transform zone (south of a narrow southern Canadian upper-plate margin) and on the south by the Snake River transfer zone (north of a broad Great Basin lower-plate margin). These are the central segments of a zigzag-shaped Cordilleran rift system of alternating northwest-striking extensional zones offset by northeast-striking transfers and transforms. The data substantiate polyphase rift and continental separation events that included (1) pre- and syn-Windermere rifting, (2) Windermere margin subsidence, (3) late Ediacaran-Cambrain rifting, and (4) well-developed late Ediacaran-Devonian passive margin subsidence and deposition. Timing and geometries support synchronous but opposing divergence along Cordilleran and Atlantic rifts with a junction in Southern California–Sonora. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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