Constraining High Temperature Deformation and Metamorphism in the Southern Wet Mountains, Colorado, USA: Implications for the Regional Extent of the Picuris Orogeny.

Sarah Morse, Greg Dumond, Barry Shaulis

University of Arkansas Master's Thesis

ProQuest Link

The Wet Mountains of Colorado are underlain by exhumed Proterozoic metamorphic rock that lies north of the recently identified 1.46 to 1.40 Ga Picuris orogen in northern New Mexico.  The Picuris orogen is inferred to have formed in response to a Mesoproterozoic (ca. 1.49-1.40 Ga) contractional to transpressional event extrapolated to be regional in extent.  It has been proposed that the Picuris orogen composes the westernmost tectonic segment of the Pinware-Baraboo-Picuris orogen that formed along an evolving convergent margin that becomes younger from northeast to southwest.  This study is focused on the record of high temperature deformation, metamorphism, and plutonism in the southern Wet Mountains interpreted as a consequence of Mesoproterozoic tectonism related to the Picuris orogeny.  Geochronology results yielded two populations:  ~ 1.45 Ga age of crystallization for granitic intrusions and ~ 1.7 Ga date for a metasedimentary rock.  P-T thermobarometric results for a Grt + Sil + Crd + Bt + Kfs + Pl + Qtz migmatite yielded inferred peak conditions of > 0.6 GPa and > 700^oC.  These results suggest that the Picuris Orogeny was the deformative and metamorphic event that displaced sediments to > 0.6 GPa and caused a regional overprinting of foliation throughout the Wet Mountains.