Geochronology of Proterozoic rocks of the Sandia-Manzano-Los Pinos Uplift: implications for the timing of crustal assembly of the southwestern United States

New U-Pb zircon geochronologic data from plutons in the Sandia-Manzano-Los Pinos uplift are in agreement with older data that there were two major plutonic episodes, one at 1.66-1.65 Ga and the other at 1.46-1.45 Ga. These plutons are manifestations of a regional polyphase tectonic evolution for New Mexico during the Mazatzal and Picuris orogenies, respectively. Paleoproterozoic magmatism involved a bimodal rhyolite-basalt section of the basal Manzano Group; a new U-Pb zircon ICPMS age of 1665±16 Ma on the Sevilleta Metarhyolite Ma agrees with published ID-TIMS ages of 1662±1 Ma for the Sevietta Metarhyolite and 1662±2 Ma for interlayered mafic volcanic rocks. New ICPMS ages of 1655±14 Ma for the Manzanita, 1661±17 Ma for the Ojito, and 1662±14 Ma for the Los Pinos plutons, combined with older U-Pb dates, suggest these plutons overlap in age across the entire uplift. The 1.65-1.66 Ga plutons are interpreted to represent a magmatic arc system where plutons were intruding their own volcanic edifice and also intruding developing syn-contractional, arc-related sedimentary basins. New ICPMS U-Pb zircon ages from Mesoproterozoic plutons yield 1453±12 Ma for the Sandia and 1456±13 Ma for the Priest pluton. These plutons overlap in age, are about 20 Ma older than previously thought, and were emplaced syntectonically during the Picuris orogeny. 40Ar/39Ar data from coarse-grained muscovite crystals associated with these plutons yield complementary geochronologic information. In some cases, the muscovite ages are more precise than those obtained from zircon. Paired with our refined zircon ages, cooling ages obtained from muscovite provide insight into the secular thermal architecture of the Sandia-Manzano-Los Pinos uplift. 161