PAIRED ZIRCON U-PB-HF ISOTOPE ANALYSIS OF THE YAVAPAI-MAZATZAL BOUNDARY IN NEW MEXICO: EVIDENCE FOR A MAZATZAL CONTINENTAL ARC SYSTEM

Lithospheric growth along the southwestern margin of Laurentia during the Paleoproterozoic has been described as accretion of dominantly juvenile terranes to a long-lived convergent margin. Major crustal provinces likely resulted from accretion of distinct arc terranes, but sutures and province boundaries remain poorly constrained. The Jemez lineament is the southern limit of exposed >1.7 Ga crust and has been interpreted as the suture between the Yavapai and Mazatzal Provinces. To test this hypothesis, we report paired U-Pb-Hf analyses of zircon from 17 temporally and spatially associated intrusive and supracrustal rocks in northern and central New Mexico. Northern New Mexico igneous basement contains dominantly 1.75-1.70 Ga zircon with juvenile eHf signatures, but yield εHf(t) values ranging from +2.9 to +11.6 at 1.75-1.70 Ga and 1.9-1.8 Ga xenocrystic grains consistent with recycling of 1.85 Ga lower crust. Both the 1.72 Ga San Pedro quartzite and the 1.72 Ga Ortega quartzite are unimodal and derived from 1.72-1.68 Ga crust, consistent with derivation from local Yavapai basement. Igneous rocks of the Mazatzal province contain granites and rhyolites that yield juvenile εHf(t) values ranging from +6 to +12 at 1.65 Ga, as 2.0-1.7 Ga inherited zircon grains, suggesting a heterogeneous lower crust and/or differential assimilation of older crust. We interpret this as recycling of the recently assembled Yavapai province. The Manzano Group metasedimentary units are dominated by 1.65 Ga detrital zircon ages with εHf(t) values ranging from +3 to +10, but include older >1.8 Ga detritus interpreted to be of Laurentian origin. The 1.45 Ga Guadalupe Box, Sandia, and Priest plutons have εHf(t) values that range from +1.9 to +11.8, which is consistent with recycling of Yavapai/Mazatzal crust. The presence of >1.7 Ga crustal material indicated by Hf isotopes and detrital or inherited zircon in metasediments and multiple plutons from throughout the northern Mazatzal terrane coupled with frequent juvenile additions—In both supracrustal and intrusive rocks—support the notion that the Mazatzal province represents a 1.65-1.60 Ga continental arc built on older Yavapai age crust and that the Yavapai-Mazatzal province boundary is transitional rather than a discrete boundary at the Jemez lineament.