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<jats:title>Abstract</jats:title> <jats:p> Phanerozoic reactivations of basement fault zones are documented in 5000 m of basement core recovered from beneath the updip Atlantic Coastal Plain underlying the US Department of Energy Savannah River Site (SRS) in South Carolina. These basement fault zones are adjacent to the excised Rheic Ocean suture. Meta-intrusive rocks from <jats:italic>c.</jats:italic> 620 and 625 Ma contain a mylonitic fabric and intrude foliated mafic metavolcanic rocks. At <jats:italic>c.</jats:italic> 305 Ma, granulite facies orthogneisses were thrust over amphibolite facies meta-igneous rocks in the transpressive Tinker Creek Nappe. The overturned limb of the nappe localizes the Triassic Dunbarton Basin Border Fault. The border fault acted as a conduit for fluids in the Mesozoic and Cenozoic. At <jats:italic>c.</jats:italic> 220 ± 5 Ma, a potassium and silica metasomatic event affected the SRS basement. A propylitic event flushed reducing fluids through rocks as young as the Santonian. The remains of a Triassic sub-basin were identified in the northwesten part of the site. A Cretaceous and younger vein paragenesis overprints the previous events. More than 30 pseudotachylytes are found in the SRS basement and are preferentially localized on metasomatized Alleghanian chloritic fractures. Pseudotachylyte post-dates mineralized fractures. The Pen Branch Fault offsets the basement–Cretaceous unconformity and is present in <jats:italic>c.</jats:italic> 242 m of core between PBF-7-419 m and PBF-7-660.8 m. The Pen Branch Fault cross-cuts mineralized fractures and must post-date strike-normal zeolites. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The recent discovery of Ediacaran ophiolites in the SW Iberian Massif has made it possible to pinpoint the evolution of the Cadomian basement of Europe. The Calzadilla and Mérida ophiolites (gabbroic protoliths dated at <jats:italic>c.</jats:italic> 600 and 594 Ma, respectively) have geochemical characteristics typical of supra-subduction zone ophiolites. They are interpreted as originating during the initial opening of a forearc basin with boninitic magmatism (Calzadilla), followed by the formation of a back-arc basin with arc-tholeiites (Mérida). Widening of the back-arc led to the rifting and drifting of a section of the active continental margin (Cadomia). Closure of these oceanic domains initiated rapid contraction, culminating in the collision of Cadomia with Gondwana ( <jats:italic>c.</jats:italic> 590–540 Ma). The application of a PANALESIS model to this palaeogeographic setting confirms the plausibility of Cadomian rifting and the likely opening of broad oceanic domains. It also confirms the final collision of Cadomia with Gondwana, although the synthetic and regional data disagree in the precise chronology of the convergence and collision of Cadomia with the West Africa Craton. This work shows that the evolution of the Cadomian basement is much more complex than traditionally considered. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The North German Basin is part of a Central European-wide sedimentary recycling system that has existed since at least the Neoproterozoic. Understanding the evolution of such a system is crucial for further studies, as the North German Basin inherits vast natural gas resources and may act as an intermediate sink for younger strata. This study presents new detrital zircon morphology, trace element and U–Pb age data obtained from Upper Rotliegend II strata (Upper Permian). Detrital zircon dating revealed Cambrian, Carboniferous and Permian main age clusters. There are also several minor Paleo-, Meso- and Neoproterozoic age clusters. Zircon grain morphologies show completely unrounded to completely rounded grains throughout each age range. The heterogeneity of the data is key to deciphering the sedimentary history of the Central German Basin, as the basin fill is most likely a mixture of (repeatedly) recycled material and also directly derived from bedrock sources. These results are supported by trace element data, which show a wide range of values indicating different magma sources. This study further explores the dispersal patterns of detrital zircon over time and demonstrates their complexity.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Detrital zircon morphometrics, trace element data and U–Pb isotopic data are available at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6664773">https://doi.org/10.6084/m9.figshare.c.6664773</jats:ext-link> </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Laurentia, core of the North American continent, is surrounded by Neoproterozoic to Cambrian rifted margins. This led to early suggestions that it was located within a Neoproterozoic supercontinent, Rodinia. Recent models of Precambrian palaeogeographical development also point to a ‘Laurentia-centric’ Rodinian supercontinent. Before plate tectonics, the geometry of continental margins, comparison of cratonic interiors and sedimentary covers, and orogenic piercing points were employed to postulate the geography of Phanerozoic Pangaea. Marine studies have subsequently demonstrated that the results were remarkably accurate. Absent <jats:italic>in situ</jats:italic> Precambrian oceanic crust, the same lines of evidence are employed here to reconstruct Rodinia, together with others unavailable at that time. A strong case can be made for the former juxtaposition of the Pacific margins of Laurentia and East Antarctica–Australia approximately as proposed in the 1990s, even though the precise match remains elusive. The Atlantic margin is likely to have rifted from Baltica, Amazonia and other South American cratons along the Grenvillian orogenic suture in the early Paleozoic, although the suture itself makes accurate reconstruction difficult. A piercing point and ‘tectonic tracer’ can be used to position the Kalahari craton and Coats Land crustal block of Antarctica off the present southern margin of Laurentia and contemporaneous large igneous provinces point to Siberia being located off the Arctic margin. Hence Laurentia does appear to be the ‘Key’ to Rodinian palaeogeography even though the exact geometric fit to its surrounding cratons remains to be refined. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> We present a new structural study of a D <jats:sub>2</jats:sub> –M <jats:sub>2</jats:sub> tectono-thermal structure in SW Iberia (Ponte de Sor–Seda gneiss dome) characterized by a spatial distribution of telescoping isograds providing a record of Buchan-type metamorphic conditions. The gneiss dome comprises an infrastructure made up of a lower gneiss unit (LGU) and an intermediate schist unit (ISU), separated by early D <jats:sub>2</jats:sub> ductile extensional shear zones. The LGU and the ISU are composed of Ediacaran–Cambrian rocks that experienced the highest-grade M <jats:sub>2</jats:sub> metamorphic conditions (amphibolite facies). Late Ediacaran–Early Terreneuvian and Late Miaolingian–Early Furongian protolith ages for LGU (496 ± 3 Ma) and ISU (539 ± 2 Ma) orthogneisses are reported. A superstructure made of Cambrian–Devonian rocks (Upper Slate Unit, USU) deformed under M <jats:sub>2</jats:sub> greenschist facies conditions, tectonically overlies the ISU across a D <jats:sub>2</jats:sub> extensional shear zone. Kinematic criteria associated with D <jats:sub>2</jats:sub> –M <jats:sub>2</jats:sub> fabrics indicate top-to-ESE–SE sense of shear. A late-D <jats:sub>2</jats:sub> brittle-ductile high-angle extensional shear zone (Seda shear zone) crosscuts the gneiss dome. D <jats:sub>3</jats:sub> upright folds, thrusts and transpressive shear zones caused the steepening of D <jats:sub>2</jats:sub> structures and the local crenulation of S <jats:sub>2</jats:sub> foliation. The Mississippian D <jats:sub>2</jats:sub> –M <jats:sub>2</jats:sub> event recorded in the Ossa–Morena Zone may be regarded as a regional-scale phenomenon that markedly influenced the crustal architecture of North Gondwana during the assembly of Pangaea. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> U–Pb ages of detrital ( <jats:italic>n</jats:italic> = 2391) and magmatic ( <jats:italic>n</jats:italic> = 170) zircon grains from the Harz Mountains were obtained by LA-ICP-MS for provenance studies and absolute age dating. Results point to a complete closure of the Rheic Ocean at <jats:italic>c.</jats:italic> 419 Ma. A narrow Rhenish Seaway then re-opened in Emsian to mid-Devonian time ( <jats:italic>c.</jats:italic> 390–400 Ma). Devonian sedimentary rocks of the Harz Mountains were deposited on the northwestern (Rheno-Hercynian) and on the southeastern (Saxo-Thuringian) margins of the Rhenish Seaway. A new U–Pb zircon age from a plagiogranite (329 ± 2 Ma) within a harzburgite makes the existence of oceanic lithosphere in the Rhenish Seaway probable. The Rhenish Seaway was completely closed by Serpukhovian time ( <jats:italic>c.</jats:italic> 328 Ma). Existence of a terrane in the seaway is not supported by the new data. Provenance studies and spatial arrangement allow reconstruction of the thin- to thick-skinned obduction style of the Harz Mountains onto the southeastern margin of East Avalonia (Rheno-Hercynian Zone) during the Variscan orogeny. Detrital zircon populations define Rheno-Hercynian and Saxo-Thuringian nappes. Intrusion of the granitoid plutons of the Harz Mountains occurred in a time window of <jats:italic>c.</jats:italic> 300 to 295 Myr and constrained the termination of Variscan deformation. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>New geochronological (U–Pb isotope dilution thermal ionization mass spectrometry), geochemical and isotopic data from Upper Ordovician felsic volcanic rocks recorded in the Pyrenees and Mouthoumet massifs, SW Europe, suggest that this volcanic activity is more widely represented than previously accepted, and allows a better refinement of the age span involved in the Sardic Unconformity. This Sandbian volcanism represents the final pulse of the Sardic tectonothermal event, starting with the Floian–Darriwilian emplacement of voluminous plutonic rocks and the contemporaneous erosion of the uplifted pre–Upper Ordovician basement, and followed by a tholeiitic volcanism contemporaneous with extensional features and the opening of (half-)grabens finally sealed by Hirnantian glaciomarine deposits. The Sardic-related lithospheric extension may be linked to thermal doming originated by a superplume activity that caused, in turn, an extensive crustal melting responsible for the onset of the felsic (calc-alkaline-dominated), Floian–Darriwilian intrusive and Sandbian extrusive magmatism along the northern margin of Gondwana.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The Early Cambrian palaeogeographical enigma arises when tectonic reconstructions are made using palaeoclimatic v. palaeomagnetic data that result in possibly contradictory tropical, mid-latitude, and south polar locations for major continents. For example, NW Africa and Cadomia may have lain in a tropical zone (0° to ±30° latitude) based on the presence of archaeocyath reefs, minor evaporites, and carbonate platforms at <jats:italic>c.</jats:italic> 520 Ma ± 5 Ma or, alternatively, NW Africa and Cadomia may have lain in a south polar zone (90° to 60° south latitude) based on palaeomagnetic constraints. Greater Avalonia may have evolved independently from NW Africa if a dropstone constraint implying polar latitudes at <jats:italic>c.</jats:italic> 530 Ma and a palaeomagnetic constraint implying <jats:italic>c.</jats:italic> 50° latitude at <jats:italic>c.</jats:italic> 505 Ma are accommodated. We show here how counterclockwise rotation of Gondwana during the Cambrian about an interior axis may solve the enigma. Gondwanan apparent polar wander becomes consistent with tropical conditions inferred for NW Africa when adjusted to accommodate constraints placing the south pole near Peru for <jats:italic>c.</jats:italic> 540–520 Ma. Concurrent counterclockwise rotation of Baltica and Gondwana during the Middle Cambrian may have facilitated separation of Greater Avalonia from Baltica across dextral shear zones. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Large igneous provinces (LIPs) have been linked to both surface and deep mantle processes. During the formation, tenure and break-up of the supercontinent Pangaea, there is an increase in emplacement events for both continental and oceanic LIPs. There is currently no clear consensus on the origin of LIPs, but a hypothesis relates their formation to crustal emplacement of hot plume material originating in the deep mantle. The interaction of subducted slabs with the lowermost mantle thermal boundary and subsequent return flow is a key control on such plume generation. This mechanism has been explored for LIPs below the interior of a supercontinent (i.e. continental LIPs). However, a number of LIPs formed exterior to Pangaea (e.g. Ontong Java Plateau), with no consensus on their formation mechanism. Here, we consider the dynamics of supercontinent processes as predicted by numerical models of mantle convection and analyse whether circum-supercontinent subduction could generate both interior (continental) and exterior (oceanic) deep mantle plumes. Our numerical models show that subduction related to the supercontinent cycle can reproduce the location and timing of the Ontong Java Plateau, Caribbean LIP and potentially the Shatsky Rise by linking the origin of these LIPs to the return flow that generated deep mantle exterior plumes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> This study re-examines a reported mylonitic ‘metabasic granulite’ block in a megabreccia that is the most outboard igneous rock outcrop in the Avalon terrane, near the Meguma–Avalon terrane boundary in the northern Appalachians. The block of foliated gabbro is one of several igneous rock blocks in a largely dissolved salt wall and in style of deformation, mineralogy, lithogeochemistry and Sm/Nd isotopes resembles foliated and locally mylonitized late Devonian–early Carboniferous gabbro plutons along the Cobequid Shear Zone to the north. Garnet porphyroclasts in the foliated gabbro are exceptional, with a distinctive composition of Alm <jats:sub>55</jats:sub> Pyr <jats:sub>25</jats:sub> Grs <jats:sub>13</jats:sub> And <jats:sub>4</jats:sub> Sps <jats:sub>3</jats:sub> . Inclusions of pyroxene, andesine and ilmenite, lack of zoning and corroded rims suggest the garnets are antecrysts. Elsewhere in the world, garnets of similar composition in arc-related andesites are interpreted to be from disintegration of comagmatic cumulate material at 0.8–1.0 GPa under hydrous conditions. The Clarke Head foliated gabbro has two mafic components, one resembling arc-related hydrous magma and the other with tholeiitic back-arc character, similar to coeval rocks in the Cobequid Highlands. The gabbro is a product of complex mixing in crustal magma chambers and rapid rise of magma containing lower crustal antecrysts along strike-slip faults. </jats:p>