Basement-hosted sandstone injectites of Colorado: A vestige of the Neoproterozoic revealed through detrital zircon provenance analysis

Abstract

Detrital zircon provenance analysis is used to resolve the age of sandstone injectites together with source sandstones that form faultbounded, tabular bodies within Mesoproterozoic crystalline rocks of the Colorado Front Range. Named Tava sandstone (informal), the unit is a product of liquefaction and remobilization of mature quartz sediment within source bodies having volumes ≥1 × 106 m3 into dikes up to 6 m in width. To surmount the indeterminate age of emplacement, we obtained new U-Pb detrital zircon age data for two source sandstones, three dikes and one sill, for comparison to four Paleozoic arenites. Tava age distributions feature a dominant 1.33-0.97 Ga broad age group and narrow ca. 1.11, 1.44, and 1.70 Ga groups, with several smaller age groups >1.5 Ga. The Tava detrital zircon results are dissimilar to Paleozoic sandstones but closely resemble published detrital zircon reference data for Grenville orogen-derived siliciclastic units of the western United States. The similarity in age distributions is borne out by statistical comparisons among Tava sandstone, Paleozoic samples, and Neoproterozoic strata that reveal a high probability of correlation of Tava sandstone to ca. 800-680 Ma strata deposited during intracontinental extension. We conclude that Tava sandstone is Neoproterozoic in age and provides a new avenue to investigation of Rodinia's terrestrial paleoenvironment.