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Undeformed rhyolite and granophyre in the Coats Land crustal block of East Antarctica, dated as 1112 ± 4 Ma, are identical in age to both the Umkondo large igneous province (LIP) of the Kalahari craton (southern Africa) and the early Keweenawan LIP of Laurentia (North America). Although marine and satellite data demonstrate that Coats Land was close to Kalahari within the Gondwana supercontinent, the Coats Land rocks yield Pb isotope compositions strikingly distinct from those of the Umkondo province, yet indistinguishable from rocks of the Keweenawan province. The anorogenic Red Bluff granitic suite, along the present-day southern Laurentian margin in the Franklin Mountains (Texas, USA), is of comparable age, general rock type, and Pb isotope composition to rocks of Coats Land and may provide a piercing point for a Coats Land-Laurentia link. Paleomagnetic poles permit the Coats Land block to be close to this part of Laurentia ca. 1100 Ma and allow juxtaposition of Kalahari and southern Laurentia ca. 1000 Ma. The Coats Land crustal block may therefore be a critical tectonic tracer for placing Laurentia within late Mesoproterozoic and Neoproterozoic paleogeographic reconstructions. If this hypothesis is correct, Laurentia collided with the Kalahari craton along Antarctica's Maud orogen, which would represent a continuation of the ca. 1000 Ma Grenville orogen of eastern and southern Laurentia.

Resolving the timing of crustal processes and meteorite impact events is central to understanding the formation, evolution and habitability of planetary bodies. However, identifying multi-stage events from complex planetary materials is highly challenging at the length scales of current isotopic techniques. Here we show that accurate U-Pb isotopic analysis of nanoscale domains of baddeleyite can be achieved by atom probe tomography. Within individual crystals of highly shocked baddeleyite from the Sudbury impact structure, three discrete nanostructural domains have been isolated yielding average 206Pb/238U ages of 2,436±94 Ma (protolith crystallization) from homogenous-Fe domains, 1,852±45 Ma (impact) from clustered-Fe domains and 1,412±56 Ma (tectonic metamorphism) from planar and subgrain boundary structures. Baddeleyite is a common phase in terrestrial, Martian, Lunar and asteroidal materials, meaning this atomic-scale approach holds great potential in establishing a more accurate chronology of the formation and evolution of planetary crusts.

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U-Pb zircon ages obtained from the late-to post-tectonic 'Newer Granite' suite in Shetland, northernmost Scottish Caledonides, indicate a significantly more protracted intrusion history than was inferred previously from K-Ar data. Emplacement of the Brae Complex (c. 465 Ma), Graven Complex (c. 440 Ma) and the Muckle Roe Granophyre (c. 438 Ma) followed regional deformation and metamorphism of metasedimentary successions during the Grampian orogenic event, and is attributed to NW-directed subduction beneath Laurentia. The almost complete absence of plutons of this age along strike in mainland Scotland suggests a change in subduction angle and/or the distance between the subduction zone and the Laurentian margin. Intrusion of the Ronas Hill Granite (c. 427 Ma) was approximately coeval with displacement on the Moine Thrust in mainland Scotland, and so was likely emplaced during Baltica-Laurentia collision. A gap of c. 35 myr followed before emplacement of the Mangaster Voe intrusion and Eastern Granophyre (c. 390 Ma), and a further gap of c. 20 myr before emplacement of the Sandsting Complex (c. 370 Ma). Both periods of magmatism are attributed to pulses of localised lithospheric melting in the Article text vicinity of the Walls Boundary Fault during Devonian sinistral relative displacements between Laurentia and Baltica.

Granite stocks across southwest England have played a significant role in the genesis of world-class polymetallic mineralisation. This study presents the first geochemical and geochronological dataset for the composite Crownhill stock, placing it into the newly emerging geochronological framework for the Cornubian Batholith. The Crownhill stock comprises kaolinised two-mica granite in the north and variably-grained biotite granite in the south that encloses pods of tourmaline granite. All granites are peraluminous (A/CNK>1) and the biotite (BG) and tourmaline granites (TG) are related by the replacement of biotite by tourmaline and secondary muscovitization. Integrated LA-ICP-MS and CA-ID-TIMS geochronology indicate two-phase magmatism, where zircon cores yield 288.9 ± 5 Ma and 286.4 ± 5 Ma and rims yield 277.74 ± 0.33 Ma and 278.35 ± 0.35 Ma, for BG and TG respectively. The zircon cores crystallised during initial magmatism, that formed the two-mica and muscovite granites (e.g., Carnmenellis, Bodmin, and Hemerdon) exposed in the north of the Crownhill stock. The zircon rims crystallised from the second phase of magmatism the formed the biotite and tourmaline granites (e.g., Dartmoor and St. Austell). This indicates that zircon crystals were assimilated from older twomica and muscovite granites and entrained in the second phase of magmatism. Trace element compositions of zircon grains suggest that the rims crystallised from a more evolved magma, where zircon grains hosted in tourmaline granites are broadly more evolved than those from biotite granites. This is likely a result of elevated volatile concentrations delaying zircon fractionation. Trace cassiterite has been observed within interstitial tourmaline in the tourmaline granites, where crystallisation was likely induced by the removal of boron through tourmaline fractionation, coupled with the addition of Sn sourced from the alteration of biotite. The assimilation and over-printing of older granites by second-stage magmatism suggests that the initial phase of magmatism could be more widespread than initially thought and that tourmalinisation may have been responsible for leaching and remobilising Sn from the biotite-rich granites.

The tectonic significance of the Muness Phyllite which overlies the Unst-Fetlar ophiolite in Shetland, Scottish Caledonides is poorly understood. U-Pb analyses of detrital zircons show that it was deposited after c. 469 Ma. Lower Palaeozoic grains have εHf values of -0.3 to +12.3 and were likely derived from the extension of the Midland Valley arc. Psammite clasts and the matrix of the Muness Phyllite contain Proterozoic and Archaean detrital zircons with age peaks of c. 1 Ga, 1.4 - 1.5 Ga, 1.6 - 1.7 Ga, 1.8 - 1.9 Ga and 2.7 Ga. These are consistent with ultimate derivation from NE Laurentia sources and were probably recycled from the Neoproterozoic East Mainland Succession that underlies the Mesozoic East Shetland Basin. The Muness Phyllite is interpreted to have been deposited soon after the Grampian I orogeny in a successor basin that overstepped, and received detritus from, the Midland Valley arc, the East Mainland Succession and the Unst-Fetlar ophiolite. It was then deformed and metamorphosed, probably at c. 450 Ma during the Grampian II orogenic event. The Muness Phyllite therefore provides a record of middle to late Ordovician tectonic events along the Scottish sector of the Laurentian margin following ophiolite obduction.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5324986