DEPOSITIONAL AGE CONSTRAINTS AND DETRITAL ZIRCON AGE POPULATIONS WITHIN THE PALEOPROTEROZOIC MANZANO GROUP, CENTRAL NEW MEXICO: WHAT IS THE PROVENANCE OF “YAVAPAI” AGE (CA. 1.70-1.78) DETRITUS IN THE MAZATZAL CRUSTAL PROVINCE?

Paleoproterozic metasedimentary rocks from the Manzano and Los Piños mountains in the Mazatzal crustal province (ca. 1.68-1.60 Ga) preserve significant populations of Yavapai age (ca. 1.70-1.78 Ga) detrital zircon intermixed with younger, Mazatzal age detrital zircon. LA-ICPMS ages for igneous and detrital zircon constrain the age of rhyolitic magmatism and provenance of the metasedimentary succession. The Sevilleta and Blue Springs metarhyolite units yield U-Pb zircon crystallization ages of ca. 1660 Ma and ca. 1601 Ma, respectively, and bracket the depositional age of the intercalated metasedimentary layers. Detrital zircon age distributions for metasedimentary rocks broaden and shift to older age populations up section, suggesting a shift from local to distal source regions through time. Detrital zircon from the oldest metasedimentary unit, a lithic arenite, shows narrow unimodal age distribution ranging from 2750 Ma to 1690 Ma with a peak age of 1695 Ma. Two samples of the White Ridge quartzite yielded similar unimodal age distributions ranging from 1600 Ma to 1875 with peak ages of 1680 and 1650 Ma. Sais formation quartzite in the Manzanos yielded a narrow bimodal age distribution ranging from 2810 Ma to 1645 Ma with peak ages of 1720 Ma and 1670 Ma. The same formation in the Los Piños yielded a unimodal age distribution with ages from 2638 Ma to 1617 Ma and a peak age of 1688 Ma. The Blue Springs quartzite shows bimodal age distribution that ranges from 3108 Ma to 1700 Ma with peak ages of 1785 Ma and 2695 Ma. The youngest unit of the Blue Springs quartzite yielded a unimodal age distribution ranging from 3200 Ma to 1660 Ma with a peak age of 1735 Ma.

Detrital zircon with Mazatzal ages (1.68-1.60 Ga) are inferred to be locally derived from surrounding exposures of the Mazatzal crustal province. There are at least two possible sources for the older, Yavapai age (1.70-1.78 Ga) detritus - the Yavapai crustal province just over 100 km to the north or Yavapai-aged basement exposures about 650 km to the south in northern Mexico. The older age peaks within the Blue Springs quartzite were likely derived from the north where Archean aged sediments were reworked into the Manzano and Los Piños Mts. Our new ages also indicate that regional deformation and metamorphism must have postdated ca. 1601 Ma, the age of the Blue Springs metarhyolite.