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<jats:p>To understand breakup styles and syn-rifting magmatism in the northern South China Sea (SCS), we analyze how the continent-ocean transition zone (COT) varies along strike in its potential field and deep structures. High free-air gravity anomaly and accompanied basement structures evidence significant mantle upwelling and serpentinization in the northeastern COT. The top basement of the COT is uplifted and rough, but gradually retrogrades into a relatively flat and low relief towards the mid-northern margin, where reduced gravity anomaly reflects subdued mantle upwelling but perhaps stronger syn-rifting magmatism. In the northwestern margin, low gravity anomaly suggests fairly limited mantle upwelling, but more syn-rifting magmatic intrusions in the crust, and the top basement of the COT is smooth and slightly deepened. The COT widths are mostly less than 30 km, and within the COT the oldest legible magnetic anomaly C11r is related to the final continental breakup. The seaward limit of the COT should be relocated further south beyond anomaly C11r, pointing to a very narrow zone of true oceanic lithosphere in the Northwest Subbasin. The coexistence of mantle upwelling/serpentinization, magmatic underplating, and volcanisms atop the COT during continental breakup characterizes a typical intermediate rifted margin that shows, nonetheless, significant along-strike variations.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Emerging knowledge on the tectonics of the South China Sea 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/south-china-sea">https://www.lyellcollection.org/topic/collections/south-china-sea</jats:ext-link> </jats:p>

<jats:p>Previous work has proposed climatic cooling and atmosphere-ocean oxygenation as potential triggers for the Great Ordovician Biodiversification Event, with the suggestion of better oxygenated oceans during the Middle to Late Ordovician. However, recent studies have argued for spatial and temporal heterogeneity in marine redox state on several continents. Here we investigated a black-shale succession accumulated within the Tarim Platform via a combination of geochemical proxies to address these debates. Negative shifts in bulk nitrogen isotopes and synchronous increases in excess P suggest moderate-high marine primary production coinciding with the development of bottom-water anoxia, as indicated by enrichments in highly reactive iron and modest concentrations of redox-sensitive trace metals (Mo, U). Moreover, the occurrence of black shale correlates well with equivalent successions formed in deep-water marginal basins along several continents, including South China, North China, Laurentia and Baltica. This may suggest an expansion of marine anoxia in low-latitude zones of the late Darriwilian to early Sandbian oceans, probably as a result of enhanced upwelling in sync with climatic cooling. The extent and ultimate cause of marine anoxia requires further quantifying constraints at a global scale, which will enable potential links between global oceanic redox conditions and concurrent biotic changes to be evaluated in more detail.</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 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.7036552">https://doi.org/10.6084/m9.figshare.c.7036552</jats:ext-link> </jats:p>

<jats:p>Whether the North China Block (NCB) remained extension from its cratonization to mid-Paleozoic is questionable. Here, we conducted a synthesis of zircon U-Pb data of Statherian–Ordovician sandstones to make a historical review of provenance changes in the western NCB through time. In contrast to typical NCB basement sources characterized by ca. 2.7–1.8 Ga ages with spectral peaks at ca. 2.5 and 1.9 Ga during much of ca. 1.8–0.45 Ga, Ediacaran to Cambrian Stage 3 succussions contain abundant zircons with Meso- to Neoproterozoic ages. The exotic provenance, further verified by southeastward paleo-flow, implies sources from the western Bainaimiao arc terrane (BAT), where basement rocks with suitable ages exist. Hence, the BAT should evolve at the NCB margin before ca. 0.56 Ga, but after rifting of the NCB (until ca. 773 Ma). This event led to a craton-wide stratigraphic break intervening Mesoproterozoic–Ediacaran. Presence of 521–515 Ma detrital zircons in the Cambrian Stage 3 strata indicates subduction onset of the Paleo-Asian Ocean before ca. 515 Ma, coincident with the Precambrian-Cambrian boundary paraconformity. A sequence of depositional shifts triggered by tectonic activities of the BAT unveil a complicated plate re-organization history of the northern NCB, contesting the NCB remained passive from Statherian.</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.7040743">https://doi.org/10.6084/m9.figshare.c.7040743</jats:ext-link> </jats:p>

<jats:p>The Palu Formation, previously known as the Celebes Molasse in the Palu area, is understudied and was previously considered to be associated with the Pliocene collision between an Australian-derived micro-continent – Banggai Sula– and the eastern margin of Sundaland (West Sulawesi). Here, we present sedimentological, heavy mineral, and zircon geochronological data to provide insights into sediment provenance and to elucidate Neogene tectonic activity in Sulawesi. These analyses suggest that the Pleistocene Palu Formation comprises syn-orogenic alluvial fan to braided river deposits that record the rapid uplift of metamorphic and granitoid rocks in the Neck and west Central Sulawesi. The Palu Formation is characterised by predominant granitoid and metamorphic clasts and heavy mineral assemblages dominated by pyroxene, amphibole, and garnet. Detrital zircons record youngest grain ages of ca. 2.5 and 3.0 Ma with a significant Pliocene age population and subsidiary Eocene, Cretaceous, Jurassic, and Late Triassic age peaks. Rapid uplift and erosion associated with mountain building shaped the topography and influenced the evolution of Palu River networks.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change 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/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change">https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change</jats:ext-link> </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.7033388">https://doi.org/10.6084/m9.figshare.c.7033388</jats:ext-link> </jats:p>

<jats:p>The appearance of hydrous magmas and the following separation of volatile-rich fluids through hydrothermal alteration are intricately linked to forming granitic rare-metal deposits, the principal source of worldwide Li, Be, Nb, Ta, and Cs production. The lack of mineralogical information from the developing magmatic-hydrothermal system has, however, prevented a thorough comprehension of these processes. Apatite occurs as an accessory mineral in the metasedimentary (schist)–magmatic (muscovite monzogranite)–pegmatite (ore-free/ore-bearing pegmatite) rocks in Mufushan Complex (MFSC) rare-metal ore field of the northeastern Hunan, South China, potentially providing insights into Nb-Ta-(Li-Be-Cs) mineralization. To demonstrate that apatite can potentially record the magmatic-hydrothermal evolution of metasedimentary-magmatic-pegmatite systems, this study presents a combined textural and geochemical study of apatite from the MFSC granitic pegmatite-type rare-metal mineralization. The MFSC apatite textures and compositions have changed (i.e., post-crystallization alteration) since it first crystallized. Apatite from the schist shows homogeneous rim or homogeneous textures with crack or inclusion (S-ap1) and patch core (S-ap2), indicative of a magmatic-hydrothermal origin. Apatite from the muscovite monzogranite (G-ap) displays altered and distinctive core-rim textures, with visible voids, mineral inclusions, and cracks, suggestive of overprinting of early-magmatism texture by hydrothermal fluid. However, compared to the S-ap1, S-ap2, and G-ap, the pegmatite apatite shows more complicated textures, i.e., P-ap1: homogeneous bright and dark areas, and P-ap2: replacement texture involving alteration rim, growth zonation, patchy, and complex zoning patterns. P-ap1 underwent early magmatism and weaker post-hydrothermal overprinting, P-ap2 reflects a magmatic-hydrothermal product. S-ap1 and S-ap2 yield lower intercept ages of 130.6 ± 1.8 Ma and 128.4 ± 3.8 Ma, respectively, which are consistent with the transitional age of magmatic-hydrothermal metallogenic environment in northeastern Hunan. The G-ap and P-ap1 yield older ages of 136.3 ± 2.8 Ma and 141.3 ± 6.7 Ma, respectively, which are corresponding to the age of magmatic early-stage (Nb-Ta)-mineralization within their uncertainty in the northeastern Hunan. The Sr isotopic composition of apatite provide evidence for the provenance of the MFSC batholith in the rare-metal metallogenesis of the Lengjiaxi Group. Therefore, we hypothesize that apatite in granitic rare-metal deposits within metasedimentary-magmatic-pegmatite systems might be employed as a viable proxy to explore fluid exsolution and hydrothermal alteration signature concerning its textures and geochemical fingerprints.</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.7038699">https://doi.org/10.6084/m9.figshare.c.7038699</jats:ext-link> </jats:p>

<jats:p>Subduction processes of the Eastern Tianshan are crucial to understand the mechanism of the orogenic evolution of the southern Altaids. To identify whether the tectonic setting of the Late Carboniferous or later was continuous subduction, we present a systematic study on Late Carboniferous volcanic and intrusive rocks exposed continuously in time and space in the Weiya area, which were mainly derived from crustal materials with involvement of mantle-derived materials in a subduction-related setting. Our newly discovered 319 Ma A-type granites imply an extensional environment; 306 Ma diorites were derived from thickened crust. Combined with published data, we propose that rollback of the southward subducted North Tianshan oceanic plate induced subduction retreating and tectonic extension in the Yamansu-Central Tianshan arc from 324 Ma to 318 Ma. It was followed by advancing subduction from 315 Ma to 301 Ma, during which the crust of the arc was thickened, and much more crustal materials were involved in subduction-related magmatism. In the Early Permian, the arc was in an extensional environment followed by a change in the movement direction of the subducting plate, rather than in a post-orogenic setting. The final closure of the North Tianshan Ocean was likely completed in the Middle Triassic.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Processes of Pangea construction 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/processes-of-pangea-construction">https://www.lyellcollection.org/topic/collections/processes-of-pangea-construction</jats:ext-link> </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.7038686">https://doi.org/10.6084/m9.figshare.c.7038686</jats:ext-link> </jats:p>

<jats:p>Regional variations in the evolution of the Tibetan plateau has important implications for our understanding of crustal deformation processes. The evolution of the NW margin of the plateau and its transition to the Pamir to the west is one under-studied region. We focus on this region with a multi-technique detrital study of two sedimentary sections in the Tarim Basin. Our provenance data show that an appreciable component of the detrital material in the sedimentary sections was derived from the Songpan-Ganzi – Tianshuihai composite terrane, with some contribution from the Karakoram and/or the West Qiangtang. Given the proximity of the West Kunlun to the sedimentary sections under study, and its long history of exhumation, this terrane in all likelihood also contributed to the studied successions. Our thermochronological data record phases of exhumation in the hinterland in the Triassic, Early Cretaceous and Oligo-Miocene. Similar to the Pamir, the Triassic and Oligo-Miocene periods of exhumation are attributed to the Cimmerian and Himalayan orogenies respectively. The Early Cretaceous signal may reflect the distal effects of the Lhasa–Qiangtang collision. Coevality with deformation in Pamir suggests a coupled geodynamic system, with retroarc deformation associated with NeoTethyan subduction in the west, and terrane accretion in the east.</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.7040686">https://doi.org/10.6084/m9.figshare.c.7040686</jats:ext-link> </jats:p>

<jats:p>The lack of data on the complex tectonics of the Qiongdongnan Basin has thus far restricted the understanding of overpressure, deep hydrocarbon, and shallow gas hydrate distribution. In this study, integrated seismic, well, and borehole-test data were combined with basin models to clarify the relationship between tectonic activity and overpressure evolution, as well as potential effects of sub-surface pressure on gas hydrate accumulation. The results show differences in tectonic activity and pressure characteristics between the eastern and western basins. Since the Late Miocene (∼10.5 Ma), large amounts of faults and magmatic intrusions developed in the post-rift layer of the eastern basin (Baodao to Changchang sub-basins), while they seldom formed in the western basin (Lengdong to Lingshui sub-basins). Correspondingly, the eastern basin was characterized by lower overpressures (up to 40 MPa) and the western basin displayed higher overpressures (up to 110 MPa). The results indicated that the tectonic activity since ∼10.5 Ma caused the overpressure relief in the eastern basin. In stark contrast, the overpressure in the western basin increased significantly due to the lack of structural conduits and rapid sedimentation of the thick Pliocene and Quaternary. Numerical models reveal that faults and gas chimneys associated with intrusions constituted shallow plumbing systems through which deep natural gas was able to migrate upward. The formation of gas hydrates relied on the migration of deep gas to the hydrate stability zone below the seafloor. Therefore, the relatively lower overpressured zones due to pressure relief in the eastern basin are considered the next areas potentially favorable to the formation of gas hydrates.</jats:p> <jats:p content-type="thematic-collection"> <jats:bold>Thematic collection:</jats:bold> This article is part of the Emerging knowledge on the tectonics of the South China Sea 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/south-china-sea">https://www.lyellcollection.org/topic/collections/south-china-sea</jats:ext-link> </jats:p>

<jats:p>The Devonian to early Carboniferous western margin of Patagonia (South America) includes a NW-SE-trending magmatic arc associated with a palaeo NE-dipping subduction zone. Along the Andean region of southern Patagonia, the Eastern Andean Metamorphic Complex (EAMC) developed in a forearc position, consisting of a succession of very low- to low-grade metaturbidite-metabasic rocks emplaced from the Devonian to Carboniferous periods. There are significant uncertainties surrounding this metamorphic complex, mainly related to the tectonosedimentary setting of the basin and subsequent conditions of deformation and metamorphism, which hinder our understanding of the orogenic architecture. To reveal the link between tectonics and metamorphism, we conducted a structural analysis and sampled metapelites to measure illite crystallinity along a regional structural cross-section in the EAMC. Our analysis reveals broadly Lower to Upper Anchizonal metamorphism which is roughly synchronous with deformation along northward-verging thrusts. These findings support the development of a forearc hyperextended basin that was subsequently closed during the Gondwanide orogeny (late Paleozoic), a model that reconciles previous proposals suggesting passive margin vs. back-arc basin models. This closure led to the emplacement of suprasubduction zone ophiolites and turbidites over the continent through landward migration of brittle-ductile reverse shear zones.</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 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.7160849">https://doi.org/10.6084/m9.figshare.c.7160849</jats:ext-link> </jats:p>

<jats:p> The Bajgan Complex in the North Makran Domain (Makran Accretionary Prism) comprises disrupted meta-ophiolitic sequences originating from oceanic crust protoliths. They include ultramafic and mafic cumulates, isotropic gabbros, plagiogranites, and basalts. Ultramafic-mafic cumulates and plagiogranites exhibit compositions akin to rocks formed in mid-ocean ridge settings. Isotropic gabbro and basalt protoliths can be subdivided in three distinct geochemical types. Type-1 rocks is sub-alkaline (Nb/Y &lt; 0.1) with low Th, Nb, and Ta contents and La <jats:sub>N</jats:sub> /Yb <jats:sub>N</jats:sub> ratios &lt;1, resembling those of normal-type (N-) mid-ocean ridge basalts (MORB). Type-2 rocks display slight enrichment in Th, Ta, Nb (Nb/Y = 0.36 – 0.45), and La <jats:sub>N</jats:sub> /Yb <jats:sub>N</jats:sub> = 2.12 – 3.20, resembling the chemistry of enriched-type (E-) MORB. Type-3 basalts show an alkaline nature (Nb/Y=0.88-1.82), significant Th, Ta, Nb enrichment, and high La <jats:sub>N</jats:sub> /Yb <jats:sub>N</jats:sub> ratios (7.01 – 20.08), resembling the chemistry of alkaline basalts (OIB). Petrogenetic modeling indicates that N-MORB protoliths originated from a depleted MORB mantle source, while E-MORB and OIB protoliths were generated from partial melting of sub-oceanic depleted sources that underwent varying degrees of OIB-type enrichment. The Bajgan meta-ophiolitic protoliths were formed within a Late Jurassic to Cretaceous oceanic basin influenced by mantle plume activity and plume-ridge interaction. </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 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.7193937">https://doi.org/10.6084/m9.figshare.c.7193937</jats:ext-link> </jats:p>