GRANITE EMPLACEMENT MECHANISMS

The ca. 1.4 Ga Curecanti granite in the  SE corner of the Black Canyon of the Gunnison, CO.   The main body is a sub-horizontal dike (light orange) that truncates the steep foliation in the migmatitic host rock.  Image of cliff below Pioneer Point overlook where the contact is clearly visible. Photo: Donnie Hicks (M.S. 2013)


Hicks, G. & Jessup, M.J. in prep. Emplacement mechanisms and magma driving pressure of the Proterozoic Curecanti pluton; The Black Canyon of the Gunnison, Colorado


STRAIN PARTITIONING

Slide Lake shear zone is located along the continental divide near the summit of Homestake Peak, CO.   Splays of low-angle mylonites are exposed in the cirque above Slide Lake.  This low-angle shear zone system is rare in a region where the dominant high strain zones are subvertical.  Liz Lee (MS: 2010).




*Lee, P., Jessup, M.J., Shaw, C.A. *Hicks, G.L. & Allen, J.L. (2012) Strain partitioning in the mid-crust of a transpressional shear zone system:  Insights from the Homestake and Slide Lake shear zones, Central Colorado.  Journal of Structural Geology, 39, 237-252. Lee_et_al_JSG_12.pdf


GROWTH, STABILIZATION AND REACTIVATION OF CONTINENTAL CRUST

Proterozoic rocks in the Black Canyon of the Gunnison record Yavapai (1741-1689Ma), Mazatzal and intracratonic tectonism at 1.4 Ga.  Pitts Meadow granodiorite (1713 Ma) intruded into the Black Canyon succession (>1741 Ma) during high-temperature metamorphism (>650C) associated with the Yavapai orogeny between 1741-1690 Ma (in situ monazite).  The Vernal Mesa monzogranite (1434 Ma) was emplaced into a steep NE-striking shear zone.









Jessup, M.J., Jones, J.V., Karlstrom, K.E., Connelly, J.N., Williams, M.L., & Heizler, M.T. (2006) Three Proterozoic orogenic episodes and an intervening exhumation event in the Black Canyon of the Gunnison Region, Colorado. Journal of Geology, 114, 555-576. Jessup_et_al_JG_06.pdf

Jessup, M.J., Karlstrom, K.E., Connelly, J.N., Williams, M.L., Livaccari, R., Tyson, A., & Rogers, S.A. (2005) Complex Proterozoic crustal assembly of southwestern North America in an arcuate subduction system: The Black Canyon of the Gunnison, southwestern Colorado. In: Karlstrom, K.E. & Keller, R.G. (eds) The Rocky Mountain Region: An Evolving Lithosphere. American Geophysical Union monograph, 154, 21-38. Jessup.etal.2005.pdf

Karlstrom, K.E., Whitmeyer, S.J., Williams, M.L., Bowring, S.A. & Jessup, M.J. (2007) Does the arc-accretion model adequately explain the Paleoproterozoic evolution of southern Laurentia: An expanded interpretation--Comment. Geology, e143-144.  Karlstrom_et_al_GEO_Reply.pdf

 

TECTONIC EVOLUTION OF PROTEROZOIC ROCKS