Three‐Dimensional Evolution of the Early Paleozoic Western Laurentian Margin: New Insights From Detrital Zircon U‐Pb Geochronology and Hf Isotope Geochemistry of the Harmony Formation of Nevada

Abstract

Uranium‐lead (U‐Pb) geochronology and Hafnium (Hf) isotope geochemistry of detrital zircons of the Harmony Formation of north central Nevada provide new insights into the tectonic evolution of the Late Paleozoic western Laurentian margin. Using laser‐ablation inductively coupled plasma mass spectrometry, 10 arenite samples were analyzed for U‐Pb ages, and 8 of these samples were further analyzed for Hf isotope ratios. Three of the sampled units have similar U‐Pb age peaks and Hf isotope ratios, including a 1.0–1.4 Ga peak with εHf values of +12 to −3 and a 2.5–2.7 Ga peak with εHf values of +7 to −5. The remaining seven samples differ significantly from these three, but are similar to one another; having age peaks of 1.7–1.9 Ga with εHf of +10 to −20 and age peaks of 2.3–2.7 Ga with εHf of +6 to −8. The data confirm the subdivision of the Harmony Formation into two petrofacies: quartzose (Harmony A) and feldspathic (Harmony B). The three samples with 1.0–1.4 and 2.5–2.7 Ga peaks are the Harmony A, which originated in the central Laurentian craton. The other seven samples are the Harmony B, which originated in eastern Alberta‐western Saskatchewan, north of the Harmony A source. We propose that all Harmony Formation strata were deposited near eastern Alberta and subsequently tectonically interleaved with Roberts Mountains allochthon strata. We interpret that the entire package was tectonically transported south along the western Laurentian margin and then emplaced eastward onto the craton during the Late Devonian‐Early Mississippian Antler orogeny.

Neoproterozoic Windermere Supergroup Near Bayhorse, Idaho: Late‐Stage Rodinian Rifting Was Deflected West Around the Belt Basin

“…1,860 Ma and a scattering of older Neoarchean ages. This is consistent with provenance from the Peace River Arch and surrounding Trans-Hudson basement of the northern Canadian Shield (Gehrels & Pecha, 2014;Linde et al, 2017).…”

Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

“…Secondary sources for Precambrian detrital zircons may include reworked detrital zircons from the Yukon-Tanana terrane in southeastern Alaska (Pecha et al, 2016), as well as from primary magmatic sources in western Canada and sources on the Canadian Shield (Gehrels et al, 1995;Linde et al, 2017). Recycled zircons from the Grenville orogen may also have served as a secondary source, as previous studies have noted Grenville-aged (1350-950 Ma) detritus in the Northern Cordillera (Rainbird et al, 1997).…”

Tectonic Analysis of the Pennsylvanian Ely‐Bird Spring Basin: Late Paleozoic Tectonism on the Southwestern Laurentia Margin and the Distal Limit of the Ancestral Rocky Mountains

“…Parts of this orogenic belt experienced head-on collision, whereas others had oblique collision or transform motion (e.g., Blakey, 2007). In contrast, western Laurentia was a complex margin with evidence of subduction with back-arc spreading (Colpron & Nelson, 2009;Miller et al, 1984Miller et al, , 1992 and sinistral translation and convergence (Colpron & Nelson, 2009;Dickinson, 2013;Lawton et al, 2017;Linde et al, 2016Linde et al, , 2017Trexler et al, 2004). Younger tectonism has obscured much of the tectonic setting evidence of Late Paleozoic western Laurentia.…”