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<jats:p> Ophiolitic peridotites in Burma (Myanmar) occur along three major tectonic zones, the Kaleymyo–Nagaland suture, Indo-Burman ranges, the Jade Mines belt, and the Tagaung–Mytkyina belt. These belts all show harzburgite–lherzolite–dunite peridotites, but the Hpakan-Taw Maw region (Jade Mines belt) hosts jadeitites including pure jadeite, mawsitsit (chromium-rich jadeite) kosmochlore (chromium-rich clinopyroxene), and albitite. High Na and Al contents of jadeitites require either very unusual Al-rich, Si-poor protoliths, or extensive fluid metasomatism, or both. The Hpakan jadeitites formed by Na-, Al-, (and Si) metasomatic alteration of pyroxenite–wehrlite intrusions into harzburgite–dunite, from widespread fluid alteration. Fluids could have been derived from a mid-Jurassic intermediate pressure subduction event during ophiolite formation and emplacement. In the Indawgyi Lake area, normal ophiolitic peridotites, including harzburgite and dunite with pyroxenite veins, have not been jadeitised. Gabbros related to the Jade Mines ophiolite gave a U-Pb zircon age of 169.71±1.3 Ma (MSWD 2.2), similar timing to the Myitkyina ophiolite (173 Ma) to the east, suggesting that the ophiolite belts were originally continuous. The jade ‘boulders’ in the Uru conglomerate beds at Hpakan have also resulted from normal <jats:italic>in-situ</jats:italic> serpentinisation weathering processes, followed by limited fluvial mass transport processes along the Uru river. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.6655269">https://doi.org/10.6084/m9.figshare.c.6655269</jats:ext-link> </jats:p>

<jats:p>An integrated petrological-petrophysical model for the Ediacaran crust of S Britain is based on a review of the c. 570 – 550 Ma Charnian volcano-sedimentary complex. The latter was emplaced in a magmatic rift wedge within juvenile continental crust of the c. 720 – 600 Ma Marches Terrane, a subduction magmatic domain formed at the margin of the Gondwana palaeocontinent. Primitive island arc tholeiite to more evolved calc-alkaline compositions characterize the Charnian magmatic arc. Inversion of aeromagnetic potential-field data and petrophysical modelling, reveal details of the internal structure of the Charnian Domain, including a median rift, superimposed annular structures and partitioning lineaments. The modelling suggests that the arc foundation could incorporate magnetite-rich cumulates, which may explain the anomalous geophysical properties, including crustal thickness, rigidity and buoyancy. There is no evidence for significant tectonic displacement between the Charnian Domain and its Marches Terrane host. Instead, the domain likely occupies a wedge-shaped arc/marginal rift-basin complex, propagated from a neighbouring ocean into the Gondwana margin. Contemporaneous volcanic rift successions in the Welsh Borderland and Wales of the 570 – 550 Ma Charnian magmatic phase developed in coeval ensialic rifts within less strongly extended Marches Terrane lithosphere. Comparable diversity of subduction-related magmatism is found in the Neogene–recent Hikurangi destructive margin of New Zealand, providing a plausible analogue for Charnian magmatism.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.6805248">https://doi.org/10.6084/m9.figshare.c.6805248</jats:ext-link> </jats:p>

<jats:p>The seismotectonic setting of external Marche Apennines (Central Italy) was defined integrating geomorphological, structural, and seismological data. Strong historical earthquakes characterized the area, but geometries and kinematics of the seismogenic sources are not well defined. Plio-Quaternary Apennine compressional NW-SE structures are segmented by NE-SW oriented transversal faults, whose origin and role are still debated. We characterize the geometry, kinematics, and activity of four main transversal faults to better define their seismogenic potential. These high-angle and deeply rooted transversal fault systems have been mapped; they separate the external Apennine sector into blocks and sub-blocks with different structural and evolutionary features. The integrated dataset revealed that some inherited fault segments have recently been reactivated displacing Quaternary deposits. Spatial distribution of seismicity indicates that some clusters of hypocentres are located within the basement. Stress field analysis using available focal mechanism solutions confirms the prevalence of left-lateral kinematics on roughly SW–NE oriented structures. The transversal structures thus contribute to the longitudinal segmentation of the Apennine structures and, more in general, they are involved in the northern part of Adria plate kinematics toward N and NNW. Assessing seismic hazard and planning to mitigate risk in populated areas close to the Adriatic coast should consider these potentially active faults evidenced by the instrumental seismicity and important historical earthquakes.</jats:p>

<jats:p> The Late Triassic Carnian pluvial event (CPE) was an interval marked by global climatic and environmental changes that occurred simultaneously with enhancement of the hydrologic cycle. This event is characterized by multiple negative carbon isotope excursions (NCIEs). However, the driving mechanism behind these multiple NCIEs remains elusive because each of the NCIEs had different magnitudes in different geological settings. In this study, we present a high-resolution record of carbonate carbon isotope (δ <jats:sup>13</jats:sup> C <jats:sub>carb)</jats:sub> and major-trace element data from Well QZ-8 in the Qiangtang Basin, eastern Tethys. The carbon-isotope profile from Well QZ-8 in the Qiangtang Basin, eastern Tethys displays a similar trend to contemporaneous strata in the NW Tethys and South China. This trend is characterized by a distinct negative excursion during the CPE, supporting a global event. Interestingly, our results reveal five NCIEs for the first time in the marine sedimentary succession. Furthermore, each of these NCIEs corresponds well to changes in Ti/Al, Sr/Al, and Sr/Ba, suggesting a regional effect of the hydrologic cycle on carbon isotope excursions. This study emphasizes that each of the NCIEs was influenced by regional hydrological cycles although long carbon-isotope excursion during the CPE was driven by global carbon cycle. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.6805266">https://doi.org/10.6084/m9.figshare.c.6805266</jats:ext-link> </jats:p>

<jats:p> Intramountain late Carboniferous–Permian basins of western Europe developed during the latest orogenic stages of the Variscan Mountain Belt in eastern Pangaea, at equatorial palaeolatitudes. Their stratigraphic framework is mainly based on continental subdivisions (e.g. Stephanian and Autunian continental stages), which can be contentious due to biostratigraphic biases, resulting in long-distance diachronous subdivisions. To provide precise inter-basinal and global correlations to the internationally recognized chronostratigraphic marine stages, this study reports new U–Pb geochronology from the Aumance and Decize–La Machine basins, located in the northern French Massif Central. Zircon grains extracted from three volcanic ash-fall layers give weighted mean <jats:sup>206</jats:sup> Pb/ <jats:sup>238</jats:sup> U ages of 299.11 ± 0.35 Ma; 298.73 ± 0.36 Ma and 298.59 ± 0.35 Ma (2σ total propagated uncertainty) by the chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) method, coinciding with the Carboniferous–Permian transition (Gzhelian and Asselian stages). These ages imply that the northern Massif Central basins developed synchronously in relatively short periods of time (&lt;10 Myr), reflecting substantial sedimentation rates. Finally, the new chronology of infilling of these basins confirms that they were connected during the late Carboniferous and early Permian periods, improving the knowledge on the late-orogenic Variscan geodynamic setting in this area. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> <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.6805228">https://doi.org/10.6084/m9.figshare.c.6805228</jats:ext-link> </jats:p>

<jats:p>The end-Triassic mass extinction (ETME) is one of the five catastrophic extinction events. However, the driving mechanisms of biodiversity loss during this interval remain controversial. In this study, we investigate the marine sediment geochemistry and fauna across the Triassic–Jurassic boundary in the Wenquan section of Qiangtang Basin, and the triggering mechanism of the Late Triassic extinction in the eastern Tethys Ocean. Our study shows that the main pulse of the ETME occurred in Bed 8, manifesting as the disappearance of four brachiopod species, a significant decrease of other faunas, and the ‘Lilliput effect’ on bivalves. Analyses of pyrite framboids and redox-sensitive trace elements suggest the development of photic zone anoxia near the T/J boundary and coincident with the Late Triassic extinction. Thus, the development of abrupt and intense photic-zone anoxia could play an important role in the end-Triassic extinction.</jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Supplementary tables giving element contents and palaeontological 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.6771606">https://doi.org/10.6084/m9.figshare.c.6771606</jats:ext-link> </jats:p>

<jats:p> Alteration of serpentinized peridotites of the Highland Border Complex in Scotland took place in two steps. Listvenite-like dolomite–quartz rocks formed by addition of CaO, Sr and CO <jats:sub>2</jats:sub> at constant MgO and SiO <jats:sub>2</jats:sub> involving a mass increase of <jats:italic>c.</jats:italic> 140%. Stage two involved the dissolution of dolomite, evinced by the abundant pores and rhombohedral grains of quartz, to form Cr- and Ni-rich jasper and quartzites. Formation of the jasper–quartzites involves a mass reduction of <jats:italic>c.</jats:italic> 80%. The listvenite-like and jasper–quartzite rocks show enrichment in the fluid-mobile elements Ba, Sr, Cs, As and Sb. The As is present in the Aluminium–Phosphate–Sulfate group of minerals formed during alteration of Cr-spinel. Cr-spinel also alters to porous hematite and ferrihydrite with patches containing up to 5.5 wt% As <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> . Enrichment of As, related to alteration of chromite, is previously unknown from natural rocks, but strongly resembles efficient methods used for remediation of this toxic element. Formation of quartzite and jasper from peridotite and their common presence as pebbles in the Devonian Old Red conglomerates, the Highland Border Complex and Devonian basins in the Scandinavian Caledonides highlight their importance and potential for provenance and tectonostratigraphic correlations. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Supplementary data tables 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.6764598">https://doi.org/10.6084/m9.figshare.c.6764598</jats:ext-link> </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Ophiolites, melanges and blueschists collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists">https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists</jats:ext-link> </jats:p>

<jats:p> Early to mid-Paleozoic tectonothermal events in the Qilian Orogen developed during the closure of the Proto-Tethys Ocean and the convergence of microcontinents in the periphery of East Gondwana. In this paper, we present geochronological, geochemical and Sr–Nd-Hf isotopic data for the granitoid rocks and mafic dykes in southeastern Qilian Orogen. The Liwan (440 Ma), Shixia (434 Ma) and Huchuan (429 Ma) granitoid rocks have metaluminous to weakly peraluminous features, with whole-rock <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> </jats:inline-formula> <jats:sub>Nd</jats:sub> ( <jats:italic>t</jats:italic> ) values of 1.1 to 1.6, −4.2 to −4.4 and −2.6 to 1.1, and zircon <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> </jats:inline-formula> <jats:sub>Hf</jats:sub> ( <jats:italic>t</jats:italic> ) values of 0 to 8.9, −6.6 to 1.6 and −4.6 to 2.2, respectively. Geochemical data suggest that the Liwan, Shixia and Huchuan granitoids are derived from partial melting of the Proterozoic basement with addition of juvenile material, felsic crustal basement and mafic crustal material, respectively. The Zhangjiayuan mafic dykes (403 Ma) are high-K to shoshonitic with whole-rock <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> </jats:inline-formula> <jats:sub>Nd</jats:sub> ( <jats:italic>t</jats:italic> ) (−1.1 to −0.9) and zircon <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> </mml:math> </jats:inline-formula> <jats:sub>Hf</jats:sub> ( <jats:italic>t</jats:italic> ) values (−0.9 to 13.3), derived from an enriched lithospheric mantle. We suggest that these Silurian–Early Devonian intrusive rocks were formed via complex events involving arc-related subduction followed by slab-tearing to post-collisional processes during the Silurian and subsequent lithospheric extension in the Early Devonian. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> Tables giving zircon U–Pb isotopic data, whole-rock major and trace element results, whole-rock Sr–Nd isotopic data and zircon <jats:italic>in situ</jats:italic> Lu–Hf 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.6693575">https://doi.org/10.6084/m9.figshare.c.6693575</jats:ext-link> </jats:p>

<jats:p> The Sommerodde positive organic carbon isotope excursion (SOCIE) within the <jats:italic>Oktavites spiralis</jats:italic> graptolite Biozone (Telychian, Silurian) was first identified in the Sommerodde-1 core, Bornholm, Denmark, where it is the largest positive excursion within the Upper Ordovician–lower Silurian part of the core. Other published occurrences of the SOCIE are discussed here, including new <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>δ</mml:mi> </mml:math> </jats:inline-formula> <jats:sup>13</jats:sup> C <jats:sub>org</jats:sub> data from the Jabalón River section, Corral de Calatrava, central Spain, where the SOCIE is only a very minor positive excursion. Very unusually, the SOCIE is best developed in deeper water settings, contrary to the typical pattern of declining excursion magnitude offshore. In the Sommerodde-1 core (Bornholm), and where it has been tentatively identified in the Vežaičiai-2 core (Lithuania), the SOCIE is developed in pale, organic-poor mudstones. It is considered likely that the magnitude of the SOCIE has been enhanced in the Sommerodde-1 core record by a change in organic matter composition in the deep-marine environment that did not have such a significant effect in shallower marine environments. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary material:</jats:bold> A table of organic carbon isotope data from the Jabalón River section, Corral de Calatrava, central Spain is 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.6769514">https://doi.org/10.6084/m9.figshare.c.6769514</jats:ext-link> </jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at: <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system">https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system</jats:ext-link> </jats:p>

<jats:p> Like many rift basins worldwide, the Inner Moray Firth Basin (IMFB) is bounded by major reactivated fault zones, including the Helmsdale Fault and the Great Glen Fault (GGF). The Jurassic successions exposed onshore close to these faults at Helmsdale and Shandwick preserve folding, calcite veining and minor faulting consistent with sinistral (Helmsdale Fault) and dextral (GGF) transtensional movements. This deformation has been widely attributed to Cenozoic post-rift fault reactivation. Onshore fieldwork and U–Pb calcite geochronology of five vein samples associated with transtensional movements along the Helmsdale Fault and a splay of the GGF show that faulting occurred during the Early Cretaceous ( <jats:italic>c.</jats:italic> 128–115 Ma, Barremian–Aptian), while the Helmsdale Fault preserves evidence for earlier Late Jurassic sinistral movements ( <jats:italic>c.</jats:italic> 159 Ma, Oxfordian). This demonstrates that both basin-bounding faults were substantially reactivated during the episodic NW–SE-directed Mesozoic rifting that formed the IMFB. Although there is good evidence for Cenozoic reactivation of the GGF offshore, the extent of such deformation along the north coast of the IMFB remains uncertain. Our findings illustrate the importance of oblique-slip reactivation processes in shaping the evolution of continental rift basins given that this deformation style may not be immediately obvious in interpretations of offshore seismic reflection data. </jats:p> <jats:p content-type="supplementary-material"> <jats:bold>Supplementary Material:</jats:bold> Appendix A – orthomosaic model obtained from unmanned aerial vehicle (UAV) photography of the Helmsdale locality (GeoTiff format); Appendix B – orthomosaic model obtained from UAV photography of the Shandwick locality (GeoTiff format); Appendix C – geochronology data; and Appendix D – additional thin section microphotographs of sample HD1 showing repeated cycles of syntaxial grain growth 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.6708518">https://doi.org/10.6084/m9.figshare.c.6708518</jats:ext-link> </jats:p>