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USGS Publications Warehouse

Neutron scattering reveals fractionation of natural gas mixtures in unconventional petroleum reservoir pores: Perspectives on energy resource recovery and storage Summaries of goals, actions, and information needs by management entity Spawning habitat suitability models for Lake Erie cisco (Coregonus artedi) during the historical period of pre- and post-population declines 1877–1957 Inland recreational fisheries harvest far exceeds reported inland harvest in the United States Abundance and movement patterns of fish accessing a reconnected Lake Erie coastal wetland: Insights from high-resolution sonar data Ecology of Lake Erie – Wetlands and lake-wide planktonic communities: A synthesis The WOAH global wildlife health collaborating centre network (WOAH-WildNet): A coordinated and transformative approach to global wildlife health challenges Tsunami hazards posed by sublacustrine landslides in Lake Quinault, Washington State Detecting bumble bees in the wild using environmental DNA: Development and validation of a qPCR assay for the endangered Franklin’s bumble bee (Bombus franklini) Critical minerals in zinc ore—An update on Earth Mapping Resources Initiative Research in the Boulder Batholith region, Montana Computation of regional groundwater budgets for the Virginia Coastal Plain aquifer system Historical ice jams and associated environmental conditions on Osoyoos Lake A roadmap for implementing the Emergency Recovery Plan for freshwater biodiversity Arsenic and isotope concentrations in the lower Platte River valley of eastern Nebraska, early 1970s to 2023 Geochemical disequilibrium at the brittle-ductile transition Seabed maps showing topography, ruggedness, backscatter intensity, sediment mobility, and the distribution of geologic substrates in quadrangle 3 of the Stellwagen Bank National Marine Sanctuary region offshore of Boston, Massachusetts Co-occurrence of pesticides and pharmaceuticals and personal care products (PPCPs) across Zostera marina (common eelgrass) communities Range-wide relative abundance of the Appalachian grizzled skipper (<i>Pyrgus centaureae wyandot</i>) in the Eastern United States Geochemical, mineralogical, and isotopic evidence for multi-stage genesis of the Hicks Dome REE + Y-HFSE-fluorite deposit, Illinois, USA Status and trends of pelagic and benthic prey fish populations in Lake Michigan, 2025 Continuous and high-resolution longitudinal profiles of the water surface and riverbed elevation for 282 miles of the Colorado River from Lees Ferry to Pearce Ferry, Arizona, 2021 Biochar modulates the dynamics of legacy nutrients in enhancing soil health and crop productivity Tracking toxins: A pilot investigation of cyanotoxins in north-central Tennessee’s surface waters and wells Waves, watersheds, and sediment in a coral reef embayment: Towards parsimonious models of accumulation and composition High-resolution transboundary vegetation community maps of the Sonoran and Mojave Desert ecoregion to support critical landscape conservation planning and habitat management needs Rearing method has limited effect on post-release movement of reintroduced age-0 Lake Sturgeon Critical minerals memory match game Indicators of mercury concentration in Lake Trout: Can fish location and appearance provide information to anglers to reduce their exposure? Ecology of reintroduced Rocky Mountain bighorn sheep in Dinosaur National Monument Modeling the seasonality of wind-driven hydrocarbon waves in Titan’s polar lakes
Unraveling protracted modification of Archean and Paleopr...
Ian William Hillenbrand · 2026-06-11 · via USGS Publications Warehouse

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Abstract

Proterozoic metamorphism and deformation of the southern margin of the Superior craton in the Lake Superior region is attributed to the Penokean orogeny (1890−1830 Ma). This model includes a period of crustal inversion in which Archean basement blocks were exhumed through overlying Paleoproterozoic strata, producing the corridor of gneiss domes that parallels the trend of the Penokean orogen across the northern Midcontinent, USA. However, recent geologic mapping and 40Ar/39Ar geochronology challenge this interpretation, suggesting instead that the gneiss dome structures reflect younger episodes of tectonic activity along the southern margin of Laurentia. In absence of integrated pressure-temperature-time-deformation constraints for these rocks, interpretations are largely limited to their final cooling history, making it difficult to both identify the tectonic forces that shaped the architecture of the Penokean orogenic belt and assess the extent to which later Proterozoic tectonism modified the southern Superior craton. We address this problem with an approach joining thermodynamic modeling, garnet and accessory mineral geochronology, and microstructural analysis for several metamorphic rocks across the gneiss dome corridor. The U-Pb ages of titanite reveal that the Proterozoic geometries of exhumed basement gneiss domes are governed by preexisting Archean structures. Garnet Lu-Hf geochronology constrains the timing of prograde-to-peak metamorphism in the Penokean orogenic belt. Granulite facies metamorphism is related to the final stages of the Penokean orogeny at 1837 Ma and localized in a belt of high-grade rocks near a major Penokean suture. Garnet Lu-Hf ages of samples adjacent to gneiss domes reflect regional metamorphism following the accretionary phase of the Penokean orogeny, between 1825 Ma and 1782 Ma, which we suggest reflects continued crustal thickening related to convergence farther south during this time interval. Combination of garnet microstructures and Sm-Nd ages reflects later exhumation of gneiss domes and buried metasedimentary rocks by ca. 1750 Ma, consistent with previously published 40Ar/39Ar cooling ages across the region. Reset Lu-Hf and Sm-Nd garnet ages and U-Pb ages of syn-kinematic titanite reflect reactivation of primary Penokean structures during this period of basement uplift. These data document significant modification of the Penokean orogen and the Archean crust of the southern Superior province between 1800 Ma and 1700 Ma. Tectonic activity during this interval coincides with collisional events recognized in western Laurentia, suggesting that the period immediately following the Penokean orogeny may be a broadly important time for crustal growth and modification in proto-North America.

Suggested Citation

Salerno, R., Cannon, W.F., Thompson, J.M., Souders, A., Vervoort, J.D., and Hillenbrand, I.W., 2026, Unraveling protracted modification of Archean and Paleoproterozoic crust in central Laurentia, Penokean orogen, with garnet and accessory mineral geochronology and microstructural analysis: GSA Bulletin, https://doi.org/10.1130/B38894.1.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Unraveling protracted modification of Archean and Paleoproterozoic crust in central Laurentia, Penokean orogen, with garnet and accessory mineral geochronology and microstructural analysis
Series title GSA Bulletin
DOI 10.1130/B38894.1
Edition Online First
Publication Date May 15, 2026
Year Published 2026
Language English
Publisher Geological Society of America
Contributing office(s) Geology, Energy & Minerals Science Center
Country United States
State Michigan, Wisconsin
Additional publication details