New Mexico Geological Society Annual Spring Meeting — Abstracts

The preferred model for growth of continental lithosphere along the southwest margin of Laurentia from 1.80 Ga to 1.60 Ga involves accretion of juvenile arc terranes in a continental arc or back arc environment. Addition of continental lithosphere during this time is interpreted to have occurred during two major orogenic events, the Yavapai and Mazatzal orogenies. The former affecting 1.80-1.70 Ga juvenile crust between 1.71 and 1.68 Ga, and the latter influencing 1.68-1.60 Ga juvenile crust from 1.66-1.60 Ga. Each event resulted in crustal provinces that, in addition to delineation based on structural and geophysical properties, have distinct zircon Hf isotopic domains reminiscent of the age of their respective terrane. Recent studies have shifted previous interpretations of the discreet boundary between the Yavapai and Mazatzal provinces, but did not fully address the transition zone between each province or offer a more concrete interpretation of where geochronologic data would indicated this zone to lie. Comparisons of paired U-Pb/Hf isotopic data from both igneous and detrital zircon collected from the Nacimiento, Zuni, Sandia, and Manzano Mountains indicate the presence of purely Yavapai-derived crust present in the southern Nacimiento Mountains, zones of mixed Yavapai and Mazatzal-derived crust in the Zuni and Sandia Mountains, with the central Manzano Mountains representing the first appearance of solely Mazatzal-derived crust in the region of study. This data indicates that there is an geochronologically distinct Yavapai-Mazatzal transition zone that approximately coincides with the transition zone described by Whitmeyer and Karlstrom in 2007. Additionally, this data adds temportal support for the notion that assembly of Yavapai-age crust ceased at approximately 1.7 Ga and resumption of accretion occured at approximately 1.68 Ga, with evidence of recycling portions of Yavapai-age crust into juvenile Mazatzal blocks during the early stages of the Mazatzal orogeny and cessation of this Yavapai influence on Mazatzal terrane by 1.65 Ga. This allows for more detailed intrepretation of the timing of, and subduction regimes dominant during, Paleoproterozoic growth of the North American continent.

References:

1. Grambling, T.A., Holland, M.E., Karlstrom, K.E., Gehrels, G.E., and Pecha, M., 2015, Revised location for the Yavapai-Mazatzal crustal province boundary in New Mexico: Hf isotopic data from Proterozoic rocks of the Nacimiento Mountains, in Lindline, J., Petroinis, M., Zebrowski, J., New Mexico Geological Society 66th Annual Fall Field Conference Guidebook, p. 175-184.
2. Whitmeyer, S.J., and Karlstrom, K.E., 2007, Tectonic model for the Proterozoic growth of North America, Geological Society of America Geosphere, vol. 3, no. 4, p. 220-259.