Age, provenance, and tectonic setting of Paleoproterozoic quartzite successions in the southwestern United States

Abstract

New fi eld studies combined with U-Pb zircon geochronology constrain the ages of deposition and sedimentary provenance of Paleoproterozoic quartzite successions exposed in the southwestern United States. Orthoquartzites were deposited in shortlived basins at two times (ca. 1.70 and 1.65 Ga) during crustal assembly of southern Laurentia. The more voluminous ca. 1.70 Ga successions occur in southern Colorado, northern New Mexico, and central Arizona and are interpreted here to be time correlative, though not necessarily deposited in the same basins. Detrital zircon from quartzites and metaconglomerates exposed in southern Colorado and northern New Mexico is characterized by a single population with a relatively narrow range of ages (1.80-1.70 Ga) and minimal Archean input (<5% of grains analyzed). Peak detrital zircon ages (1.76-1.70 Ga) vary slightly from location to location and mimic the age of underlying basement. Unimodal detrital populations suggest local sources and a fi rst-cycle origin of the orthoquartzites within a short time interval (1.70-1.68 Ga) during unroofi ng of local underlying basement. The maximum age of quartzite exposed at Blue Ridge, Colorado, is constrained by the 1705-1698 Ma coarse-grained granitoid basement on which quartzite was deposited unconformably. The minimum age of Ortega Formation quartzite (New Mexico) is constrained by ca. 1680-1670 Ma metamorphic monazite overgrowths. These dates agree with direct ages on the lower Mazatzal Group, Arizona, and suggest that orthoquartzite deposition occurred over a wide region during and soon after the ca. 1.70 Ga Yavapai orogeny. Regional structural arguments and the thrust style of quartzite deformation suggest that the metasedimentary successions were deformed during the ca. 1.66-1.60 Ga Mazatzal orogeny, thus making them important time markers separating the Yavapai and Mazatzal orogenic events. Our model for syntectonic deposition involves extensional basin development followed by thrust closure, possibly due to opening and closing of slab rollback basins related to outboard subduction. The fi rst-cycle origin of orthoquartzites near the end of the arc collisions of the Yavapai orogeny seems to contrast sharply with their extreme compositional maturity. This can be explained in terms of protracted, extreme diagenesis and/or special environmental infl uences that enhanced chemical weathering but were unique to the transitional atmosphere and ocean chemistry of the Proterozoic. Similarities among quartzites exposed throughout the southwestern United States and along the Laurentian margin suggest that they represent a widespread regional, and perhaps global, episode of sedimentation involving a distinctive syntectonic setting and unique climatic conditions, a combination that might make these units a signature lithology for Paleoproterozoic time.

Provenance of late Paleozoic strata in the Yili Basin: Implications for tectonic evolution of the South Tianshan orogenic belt

“…Han et al, 2015). Many different methods have been applied to determine the maximum depositional age of strata using U-Pb ages of detrital zircons (Dickinson and Gehrels, 2009;Jones et al, 2009). Dickinson and Gehrels (2009) concluded that the weighted mean ages of youngest cluster of two or more grain ages (n ≥ 2) overlapping in age at 1σ (YC1σ [2+]) are more consistently compatible with depositional ages, especially for strata derived from contemporaneous volcanic rocks.…”

Sr–Nd isotope and geochemical characterisation of the Paleoproterozoic Västervik formation (Baltic Shield, SE-Sweden): a southerly exposure of Svecofennian metasiliciclastic sediments

“…; thus, less mature sediments would have been expected. Such an apparent contradiction was already observed and described by Jones et al (2009) for the Paleoproterozoic orthoquartzitic Yavapai and Matzatal successions along the southern Laurentian margin. As stated earlier, these can be compared to the Västervik succession as all were deposited along the long-lived southern margin of the combined Laurentia-Baltica craton in similar geodynamic settings.…”

“…Buchan et al 2000) can be followed from SE-Sweden (Svecofennian metaarenites) via Greenland (Ketilidian metapsammites) to the SW-United States (Yavapai and Matzatal orthoquartzites) along a more than 9,000 km long continental margin (Beunk and Page 2001;Karlstrom et al 2001). Deposition ages of the sedimentary successions show a general trend with younging ages from Baltica (1.86-1.83 Ga; Bergman et al 2008) to Ga; Garde et al 2002) and finally Laurentia (1.70-1.65 Ga;Jones et al 2009). Deposition environments are generally described as being shallowwater fluvial with marine and tidal influences (Jones et al 2009;Sultan and Plink-Björklund 2006;Garde et al 2002).…”

“…Deposition ages of the sedimentary successions show a general trend with younging ages from Baltica (1.86-1.83 Ga; Bergman et al 2008) to Ga; Garde et al 2002) and finally Laurentia (1.70-1.65 Ga;Jones et al 2009). Deposition environments are generally described as being shallowwater fluvial with marine and tidal influences (Jones et al 2009;Sultan and Plink-Björklund 2006;Garde et al 2002). Metasediments further share relatively short deposition intervals of around *20 to 30 m.y.…”

“…Gavelin and Russell 1967). In addition, most of these sedimentary basins subsided shortly after the end of sedimentation and underwent HT/LP metamorphism with extensive migmatisation (Beunk and Page 2001;Bergman et al 2008;Jones et al 2009).…”