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 Web of Science (19) Citing Articles via Google Scholar Google Scholar Articles by Mueller, P. A. Articles by Mogk, D. W. Search for Related Content GeoRef GeoRef Citation

Paleoproterozoic crust within the Great Falls tectonic zone: Implications for the assembly of southern Laurentia

¹ Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA
² U.S. Geological Survey, Menlo Park, California 94050, USA
³ Department of Earth Science, Montana State University, Bozeman, Montana 59717, USA

The Great Falls tectonic zone and the Vulcan structure both have been proposed as the site of a Paleoproterozoic suture between the Archean Hearne and Wyoming provinces. Both hypotheses remain viable because all Precambrian rocks composing the Vulcan structure and much of the Great Falls tectonic zone are buried beneath Phanerozoic cover. The primary exceptions to this are the mafic to felsic igneous and metamorphic rocks of the Little Belt Mountains (Montana), previously considered the northernmost exposures of the Wyoming province. New U-Pb zircon ages from the late kinematic Pinto diorite (²⁰⁷Pb/²⁰⁶Pb age: 1864 ± 5 Ma) and a gneissic unit intruded by the Pinto (²⁰⁷Pb/²⁰⁶Pb age: 1867 ± 6 Ma), however, confirm their Paleoproterozoic age. These rocks exhibit an overall calc-alkaline affinity and the depletion in high field strength elements typical of convergent margin environments. Whole-rock Sm-Nd data (initial epsilon of –1 to +4) and a lack of premagmatic zircons indicate that the magmas were principally derived from a depleted mantle source, not from older crust. These data suggest that at least some rocks within the Great Falls tectonic zone originated at a convergent margin that developed during the closure of an ocean basin along the northwestern margin of the Wyoming craton ca. 1.9 Ga.

Key Words: Precambrian orogeny • Wyoming province • Laurentia • geochronology • isotopes • tectonics

This article has been cited by other articles:

				J. L. Payne, M. Hand, K. M. Barovich, A. Reid, and D. A. D. Evans Correlations and reconstruction models for the 2500-1500 Ma evolution of the Mawson Continent Geological Society, London, Special Publications, January 1, 2009; 323(1): 319 - 355. [Abstract] [Full Text] [PDF]

				H. Mirnejad and K. Bell GEOCHEMISTRY OF CRUSTAL XENOLITHS FROM THE HATCHER MESA LAMPROITE, WYOMING, USA: INSIGHTS INTO THE COMPOSITION OF THE DEEP CRUST AND UPPER MANTLE BENEATH THE WYOMING CRATON Can Mineral, June 1, 2008; 46(3): 583 - 596. [Abstract] [Full Text] [PDF]

				S. J. Whitmeyer and K. E. Karlstrom Tectonic model for the Proterozoic growth of North America Geosphere, August 1, 2007; 3(4): 220 - 259. [Abstract] [Full Text] [PDF]

				J.W. Sears Belt-Purcell Basin: Keystone of the Rocky Mountain fold-and-thrust belt, United States and Canada Geological Society of America Special Papers, January 1, 2007; 433(0): 147 - 166. [Abstract] [Full Text] [PDF]

				G. M. Ross and M. Villeneuve Provenance of the Mesoproterozoic (1.45 Ga) Belt basin (western North America): Another piece in the pre-Rodinia paleogeographic puzzle Geological Society of America Bulletin, October 1, 2003; 115(10): 1191 - 1217. [Abstract] [Full Text] [PDF]

				J. W. Sears and R. A. Price Tightening the Siberian connection to western Laurentia Geological Society of America Bulletin, August 1, 2003; 115(8): 943 - 953. [Abstract] [Full Text] [PDF]