Detrital zircon U–Pb and Hf signatures of Paleo-Mesoproterozoic strata in the Priest River region, northwestern USA: A record of Laurentia assembly and Nuna tenure

Abstract

Rocks of the Gold Cup Quartzite, Belt Supergroup and Deer Trail Group crop out in the Priest River region of northeastern Washington and northern Idaho (USA). As these sequences represent the westernmost exposures of Paleoproterozoic–Mesoproterozoic strata between New Mexico (USA) and the northern Yukon (Canada), they are key to understanding the assembly of Laurentia and evaluating the duration and configuration of the supercontinent Nuna/Columbia. Here, we present detrital zircon U–Pb and Lu–Hf isotope data from these sequences. The results indicate that the <1.73 Ga Gold Cup Quartzite contains similar detrital zircon components to other widespread late Paleoproterozoic units that record final assembly of the main Archean blocks of western Laurentia; as such, they do not require any non-Laurentian source. Prominent ca. 1.7–1.5 Ga, isotopically juvenile zircon grains form the main component of the overlying ca. 1.47 Ga Lower Belt Supergroup. Some of these detrital zircon components lack a Laurentian source and are instead consistent with derivation from the Gawler Craton in southeastern Australia. The >1.38 Ga upper Belt Supergroup strata are structurally overlain by <1.3 Ga Deer Trail Group rocks that contain detrital zircon components consistent with mixed Laurentian sources. The paucity of any syndepositional volcanic detrital zircon in Deer Trail Group strata along with its fine siliciclastic and carbonate nature suggest deposition within a tectonically-quiescent basin coeval with breakup of Nuna.