40Ar/39Ar thermochronology constraints on the timing of Proterozoic basement exhumation and fault ancestry, southern Sangre de Cristo Range, New Mexico

Research Article| November 01, 2006 40Ar/39Ar thermochronology constraints on the timing of Proterozoic basement exhumation and fault ancestry, southern Sangre de Cristo Range, New Mexico Robert E. Sanders; Robert E. Sanders 1Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar Matthew T. Heizler; Matthew T. Heizler 2Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA, and New Mexico Bureau of Geology, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar Laurel B. Goodwin Laurel B. Goodwin 3Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2006) 118 (11-12): 1489–1506. https://doi.org/10.1130/B25857.1 Article history received: 15 Jun 2005 rev-recd: 01 May 2006 accepted: 06 May 2006 first online: 03 Oct 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert E. Sanders, Matthew T. Heizler, Laurel B. Goodwin; 40Ar/39Ar thermochronology constraints on the timing of Proterozoic basement exhumation and fault ancestry, southern Sangre de Cristo Range, New Mexico. GSA Bulletin 2006;; 118 (11-12): 1489–1506. doi: https://doi.org/10.1130/B25857.1 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 Proterozoic ancestry is increasingly being proposed for both Ancestral Rocky Mountain (Pennsylvanian-Permian) and Laramide-age (Late Cretaceous–early Tertiary) faults in the southwestern United States. We test this hypothesis by using 40Ar/39Ar thermochronology on Proterozoic basement rocks in the southern Sangre de Cristo Range, New Mexico. Hornblende and mica yield ages consistent with basement rocks cooling below ∼500 °C after ca. 1.4 Ga regional metamorphism, followed by protracted basement residence at temperatures between 300 and 400 °C until the Neoproterozoic. K-feldspar age spectra are dominated by Neoproterozoic apparent ages and constrain basement exhumation from mid-crustal depths (∼10 km) to within a few kilometers of the surface during the Neoproterozoic. Samples were also collected across the north-striking, steeply west-dipping Montezuma fault, which bounds the eastern Rocky Mountain range front and has known Ancestral Rocky Mountain and Laramide-age movement. Contrasting 40Ar/39Ar K-feldspar–derived thermal histories from opposing sides of the fault require two episodes of Neoproterozoic fault movement. Overall, rocks to the west record multiple diffusion domain (MDD) thermal histories, which indicate that cooling was caused by 5–7 km of basement exhumation between 1000 and 800 Ma, whereas rocks to the east were exhumed later, between 750 and 600 Ma. Assuming that the present-day fault geometry was established in the Proterozoic, west-side-up throw late in the Grenville orogeny (ca. 1000 Ma) accommodated east-west shortening. West-side-down extensional movement at ca. 750 Ma is inferred to be associated with the incipient rifting of the supercontinent Rodinia. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.