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The Early Jurassic Butcher Ridge Igneous Complex (BRIC) in the Transantarctic Mountains contains abundant and variably hydrated silicic glass which has the potential to preserve a rich paleoclimate record. Here we present Fourier Transform Infrared Spectroscopic data that indicates BRIC glasses contain up to ~8 wt.% molecular water (H2Om), and low (

The ca. 1.83 Ga Trans-Hudson orogeny resulted from collision of an upper plate consisting of the Hearne, Rae, and Slave provinces with a lower plate consisting of the Superior province. While the geologic record of ca. 1.83 Ga peak metamorphism within the orogen suggests that these provinces were a single amalgamated craton from this time onward, a lack of paleomagnetic poles from the Superior province following Trans-Hudson orogenesis has made this coherency difficult to test. We develop a high-quality paleomagnetic pole for northeast-trending diabase dikes of the post-Penokean orogen East-Central Minnesota Batholith (pole longitude: 265.8°; pole latitude: 20.4°; A95: 4.5°; K: 45.6 N: 23) whose age we constrain to be 1,779.1 ± 2.3 Ma (95% CI) with new U-Pb dates. Demagnetization and low-temperature magnetometry experiments establish dike remanence be held by low-Ti titanomagnetite. Thermochronology data constrain the intrusions to have cooled below magnetite blocking temperatures upon initial emplacement with a mild subsequent thermal history within the stable craton. The similarity of this new Superior province pole with poles from the Slave and Rae provinces establishes the coherency of Laurentia following Trans-Hudson orogenesis. This consistency supports interpretations that older discrepant 2.22–1.87 Ga pole positions between the provinces are the result of differential motion through mobile-lid plate tectonics. The new pole supports the northern Europe and North America connection between the Laurentia and Fennoscandia cratons. The pole can be used to jointly reconstruct these cratons ca. 1,780 Ma strengthening the paleogeographic position of these major constituents of the hypothesized late Paleoproterozoic supercontinent Nuna.

Lavas erupted at hotspot volcanoes provide evidence of mantle heterogeneity. Samoan Island lavas with high 87Sr/86Sr (>0.706) typify a mantle source incorporating ancient subducted sediments. To further characterize this source, we target a single high 87Sr/86Sr lava from Savai'i Island, Samoa for detailed analyses of 87Sr/86Sr and 143Nd/144Nd isotopes and major and trace elements on individual magmatic clinopyroxenes. We show the clinopyroxenes exhibit a remarkable range of 87Sr/86Sr-including the highest observed in an oceanic hotspot lava-encompassing ~30% of the oceanic mantle's total variability. These new isotopic data, data from other Samoan lavas, and magma mixing calculations are consistent with clinopyroxene 87Sr/86Sr variability resulting from magma mixing between a high silica, high 87Sr/86Sr (up to 0.7316) magma, and a low silica, low 87Sr/86Sr magma. Results provide insight into the composition of magmas derived from a sediment-infiltrated mantle source and document the fate of sediment recycled into Earth's mantle.

The Wager shear zone is an ~450-km long zone of high strain hosted within Proterozoic and Archean rocks of the Rae domain in northwestern Hudson Bay, Nunavut. New field mapping and microstructural analyzes, combined with titanite and apatite geochronology, define the style, kinematics, and timing of Proterozoic ductile deformation. The results indicate that the Wager shear zone accommodated high-temperature deformation between ca. 1.75 and 1.74 Ga with post-kinematic cooling through apatite U-Pb closure (425-530 [degrees]C) at ca. 1705 Ma. These new data show that the Wager shear zone was last active later than inferred in previous work, at a time when the western Churchill Province was undergoing lithospheric delamination and exhumation following the terminal collisional events in the western portion of the Trans-Hudson Orogen. Key words: shear zone, titanite, apatite, U-Pb geochronology, Zr-in-titanite geothermometry, Trans-Hudson Orogen, 1. Introduction The Trans-Hudson Orogen is a large and foundational orogen of the North American plate that formed during the amalgamation of the Nuna (Columbia) supercontinent, which subsequently broke up [...]

Intermontane basins are illuminating stratigraphic archives of uplift, denudation and environmental conditions within the heart of actively growing mountain ranges. Commonly, however, it is difficult to determine from the sedimentary record of an individual basin whether basin formation, aggradation and dissection were controlled primarily by climatic, tectonic or lithological changes and whether these drivers were local or regional in nature. By comparing the onset of deposition, sediment-accumulation rates, incision, deformation, changes in fluvial connectivity and sediment provenance in two interrelated intermontane basins, we can identify diverse controls on basin evolution. Here, we focus on the Casa Grande basin and the adjacent Humahuaca basin along the eastern margin of the Puna Plateau in northwest Argentina. Underpinning this analysis is the robust temporal framework provided by U-Pb geochronology of multiple volcanic ashes and our new magnetostratigraphical record in the Humahuaca basin. Between 3.8 and 0.8 Ma, ~120 m of fluvial and lacustrine sediments accumulated in the Casa Grande basin as the rate of uplift of the Sierra Alta, the bounding range to its east, outpaced fluvial incision by the Río Yacoraite, which presently flows eastward across the range into the Humahuaca basin. Detrital zircon provenance analysis indicates a progressive loss of fluvial connectivity from the Casa Grande basin to the downstream Humahuaca basin between 3 and 2.1 Ma, resulting in the isolation of the Casa Grande basin from 2.1 Ma to

The meta-sedimentary rocks from the North Shahrekord metamorphic Complex (NSMC) comprise micaschists, paragneisses, quartz-feldspathic schists, and marbles. Detrital zircons from the paragneisses yield ages of ca. 2811–507 Ma with most of the dated grains belonging to the Late Neoproterozoic to Cambrian, suggesting a maximum depositional age of the sedimentary protolith during the Late Ediacaran to the Early Cambrian times (543 ± 12 Ma). In contrast, detrital zircons from the quartz-feldspathic schists are mostly dominantly 692–577 Ma and a few at ca. 2369–703 Ma, suggesting that the maximum depositional age of 577 ± 9 Ma, Late Neoproterozoic. The age distribution of detrital zircons suggests that their main provenance was located within the Arabian-Nubian Shield and adjacent terranes. Rutiles from a paragneiss give a U-Pb lower-intercept age of 181 ± 3 Ma, indicating the occurrence of a high-pressure metamorphic event during the Early Jurassic. The trace element contents of the two rock units show enrichment in LREE relative to HREE and negative Eu anomalies, indicating upper continental crustal sources. The geochemical evidence (e.g. low to moderate Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration, high Index of Compositional Variability (PIA), and low Th/U) suggests that the quartz-feldspathic schists and paragneisses originated from an immature, and immature to less mature, respectively, intermediate-felsic igneous source and their protolith experienced a simple sedimentary recycling history with relatively weak to moderate chemical weathering. Geochemical and petrographic data also suggest that the precursor to the quartz-feldspathic schists and paragneisses were deposited in a continental island arc and a back-arc basin setting, respectively. Our new data, including depositional age, provenance, and geochemical evidence, provide perspectives on palaeogeographic affinities (provenance of sediments with different weathering and recycling materials), and paleotectonic reconstructions (from arc to back-arc) of the Iranian basement, exposed in the Sanandaj-Sirjan Zone, during Ediacaran. [ABSTRACT FROM AUTHOR]