Correlating Proterozoic synorogenic metasedimentary successions in southwestern Laurentia: New insights from detrital zircon U-Pb geochronology of Paleoproterozoic quartzite and metaconglomerate in central and northern Colorado, U.S.A.

摘要

Detrital zircon ages from quartzite and metaconglomerate exposed in the Park Range, Front Range, and Sawatch Range of northern and central Colorado reveal new information about age and provenance trends within the Yavapai province of southwestern Laurentia and provide a critical test of regional correlations. Six samples from the three exposure areas-the Lester Mountain area in the Park Range, Coal Creek area in the Front Range, and Collegiate Peaks area in the Sawatch Range-are dominated by Paleoproterozoic detrital zircon that define a relatively narrow range of peak ages between 1772 and 1701 Ma. The unimodal character of most age spectra and the age of the dominant age-probability peaks indicate that the metasedimentary successions were derived largely from local sources within the ca. 1.78-1.70-Ga Yavapai province. Age-probability peaks between 1830 Ma and 2716 Ma are attributed to older source regions to the north and northeast such as the Trans-Hudson orogen, Black Hills, or Wyoming province. However, the percentage of older grains is relatively minor and decreases to almost zero from north to south. Maximum depositional ages constrained by the youngest age populations are 1763 Ma, 1717 Ma, and 1701 Ma for the respective localities from north to south. All of the metasedimentary successions were deformed and metamorphosed after deposition, and quartzite at one locality is intruded by ca. 1672-Ma plutons. On the basis of similarities between outcrop characteristics, structural style, and comparison of detrital zircon age spectra, we correlate the two southern localities with a regional suite of quartzite successions deposited ca. 1.70 Ga following the culmination of the Yavapai orogeny. The northern succession represents an earlier cycle of sedimentation predating ca. 1750-Ma deformation in the northern Yavapai province. The southward progression of ages is consistent with regional tectonic models for the evolution of the Paleoproterozoic accretionary provinces in southern Laurentia, and the multiple cycles of sedimentation suggest that basin formation and collapse were important processes in the tectonic evolution of the continent.