DETRITAL ZIRCONS FROM MIDDLE PROTEROZOIC QUARTZITES OF CENTRAL ARIZONA: IMPLICATIONS FOR REGIONAL CORRELATIONS, BASIN EVOLUTION, AND CRUSTAL RECYCLING

Paleoproterozoic quartzites exposed across Arizona’s Transition Zone record a complex period of regional exhumation, basin development, and volcanism during growth and stabilization of the Yavapai and Mazatzal provinces. New detrital zircon data were collected from quartzites of the Tonto Basin Supergroup including the Houdon Quartzite of the Alder Group, Pine Creek Conglomerate of the Mazatzal Group, and formations of the Hess Canyon Group, and quartzites exposed in Chino Valley. Samples were also collected from the Pinal Schist in the Pinaleño Mountains of southeast Arizona. Detrital zircons in most of the samples showed unimodal peaks with variable age range from ca. 1780 to 1610 Ma that reflect the age of local underlying basement. A general decrease in peak ages from northwest to southeast generally matches with the age of basement assemblages across the Transition Zone. Dated ashflows within the upper Alder Group indicate that basin development occurred beginning at ca. 1705 Ma. Similarities in detrital zircon age spectra from the Alder Group and lower Mazatzal Group at the Slate Creek movement zone suggest that >6 km of sediment was locally derived from Yavapai-age sources. The timing of deposition of the Mazatzal Group is not well understood and could be significantly younger than ca. 1700 Ma since proposed correlative rocks of the Hess Canyon Group exposed to the southeast overlie the ca. 1660 Ma Redmond Rhyolite. Orthoquartzites of the White Ledges Formation of the Hess Canyon Group contain 1778–1728 Ma and 2716–2443 Ma peaks, suggesting subdued topography with linkage to relatively old source regions or extensive recycling of older metasedimentary successions. In contrast, the Yankee Joe and Black Jack Formations of the Hess Canyon Group, together with quartzites of the Pinal Schist, contain some of the youngest detrital zircons in the region with peak ages of 1666–1610 Ma. These ages indicate derivation from younger sources most likely from the south, perhaps recording a transition from extensional basins to a foreland setting during onset of the Mazatzal Orogeny. Final basin closure and inversion occurred after 1610 Ma. Our results provide a new means of testing regional correlations and lead to a better understanding of the nature, timing, and setting of sedimentation within an evolving margin setting.