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<jats:p>Prehistoric records of subduction earthquakes are often distinguished by evidence of synchronous widespread coastal deformation, the extent of which negates the plausibility of alternative source faults. At the Hikurangi subduction margin in New Zealand, untangling the record of subduction interface ruptures is complicated. Large earthquake age uncertainties inhibit unique solutions of along-strike correlations, and complex patterns of coastal deformation caused by upper-plate faulting prevent reliable indication of source faults. In this work, we improved paleoearthquake reconstructions on the central Hikurangi margin with a new, well-constrained 5000 yr earthquake record from Pakuratahi Valley near Napier, North Island, New Zealand. Evidence of laterally extensive paleoenvironmental changes is consistent with coseismic subsidence and coseismic uplift in large earthquakes. Radiocarbon dates on fragile terrestrial macrofossils and tephra isochrons were used to construct robust age models that yielded earthquake ages of 4839−4601 calibrated (cal.) yr B.P., 3630−3564 cal. yr B.P., 2687−2439 cal. yr B.P., and 1228−823 cal. yr B.P. Integration of these ages with refined earthquake chronology from nearby Ahuriri Lagoon indicated that the next large earthquake impacting the Napier area is more likely to cause coastal subsidence than uplift. Drawing on correlations with cotemporal evidence elsewhere on the central margin, we infer that the overall patterns of coseismic deformation could be generated by either rupture of the subduction interface or upper-plate faults, or both. This inability to separate source faults for past earthquakes limits the efficiency of forecasting future earthquakes. Similar problems of intertwined paleoearthquake signatures likely apply to other plate boundaries, where we recommend cautious interpretation of coastal deformation to accurately address the hazard from both types of source faults.</jats:p>

<jats:p>The Cretaceous paleocommunities of North America preserve a rich record of biodiversity that suggests many species occupied narrow biogeographic ranges in comparison to their ecological equivalents in extant systems. How taxa in these systems partitioned their niches and structured their communities can be difficult to determine from fossils alone, which has led to a variety of hypotheses concerning diets and habitat use. Here, we examine element ratios (Sr/Ca, Ba/Ca) in the enamel of a suite of co-occurring vertebrate taxa sampled from a spatiotemporally constrained interval in the Oldman Formation of Alberta, Canada, to reconstruct trophic structure, and use δ13C, δ18O, and 87Sr/86Sr compositions to test for niche partitioning and habitat use among hadrosaurids, ceratopsids, and ankylosaurs. We also test previously proposed dietary hypotheses of troodontid theropods.</jats:p> <jats:p>In large ornithischians, we find Ba/Ca and Sr/Ca ratios that are consistent with herbivory, with hadrosaurs distinct from ceratopsids and ankylosaurids in their 87Sr/86Sr ranges, a pattern that is indicative of differences in habitat use/breadth, dietary plant sources, and feeding height. The sampled mammals, varanoid lizards, dromaeosaurids, and tyrannosaurids preserve a gradient of lower Sr/Ca and Ba/Ca ratios that is consistent with animal-dominant omnivorous to faunivorous diets. Troodontids, which have been variably hypothesized as either faunivorous, omnivorous, or herbivorous due to their distinct and unusual dentition, preserve Sr/Ca and Ba/Ca ratios that fall between those of the ornithischians and the dromaeosaurids. From these multi-proxy data, we interpret troodontids as mixed-feeding to plant-dominant omnivores. These proxies represent a valuable tool for understanding the trophic and community ecology of Cretaceous ecosystems and hold enormous potential for future research in paleobiology.</jats:p>

<jats:p>The northern margin of the North China Craton experienced prolonged tectono-magmatic evolution during the late Paleozoic−early Mesozoic in response to the southward subduction and closure of the Paleo-Asian Ocean. However, details about the subduction process and the timing of the tectonic transition from subduction to post-collision are still poorly constrained. Here, we identify two-stage crust-mantle interactions in the Wulashan area and report new geochronology, geochemistry, and Sr-Nd-Pb-Hf isotopic data for magmatic rocks that record such processes following the subduction and closure of the Paleo-Asian Ocean. The early Carboniferous Xiguanjing pluton features a bimodal suite of gabbro (ca. 333 Ma) and syenogranite (ca. 331 Ma). The gabbros have arc-like geochemical affinities, with low Nb/La (0.31−0.40) and La/Ba (0.04−0.09) ratios, and variable Rb/Y (1.22−2.94) ratios, as well as enriched, mantle-like Sr-Nd-Pb (87Sr/86Sri = 0.7046−0.7047; εNd(t) = −3.8 to −3.5; 206Pb/204Pbi = 17.078−17.141) and enriched to depleted Hf (εHf(t) = −4.5 to +6.2) isotopic values. Such geochemical signatures indicate that they were derived from partial melting of the subcontinental lithospheric mantle that was metasomatized by slab-derived fluids, with minor involvement of asthenospheric components. In contrast, the contemporaneous syenogranites are characterized by lower negative εNd(t) (−13.5 to −12.1) and εHf(t) values (−16.3 to −8.2), which suggests that they were formed by partial melting of the lower crust. Late Triassic Shadegai and Xishadegai plutons are mainly composed of enclave-bearing syenogranite, and both mafic microgranular enclaves and syenogranites crystallized at ca. 233−231 Ma. The mafic microgranular enclaves have geochemical features similar to those of the early Carboniferous gabbros, and also have moderately enriched isotopic compositions (εNd(t) = −9.7 to −8.4; εHf(t) = −9.2 to −0.3), which suggests that they originated from interaction between mantle-derived magma and overlying crust-derived magma, with minor additions of asthenospheric melts in their sources. Field and petrological observations, coupled with the similar ages of the host granites and mafic microgranular enclaves, suggest a magmatic mingling process. Isotopic mixing models suggest that minor amounts (∼10%−20%) of lower crustal materials were mixed during the formation of the mafic microgranular enclaves. The host syenogranites display calc-alkaline to alkalic and metaluminous to weakly peraluminous compositions, and negative εNd(t) (−15.0 to −12.1) and εHf(t) values (−16.4 to −9.8), which indicates that they were mainly derived from partial melting of the lower crust and experienced the injection of deep mantle-derived magmas. Our new data, along with previously published data for magmatic rocks in the northern margin of the North China Craton, suggest that the early Carboniferous bimodal intrusive rocks formed in a localized back-arc extensional regime that was probably triggered by slab rollback of the Paleo-Asian Ocean. However, the Late Triassic plutons formed in a post-collisional extensional regime in response to slab breakoff or lithospheric delamination. Temporal variations of Nd-Hf isotopes for the magmatism in the northern margin of the North China Craton suggest that tectonic switching from advancing to retreating subduction to post-collisional extension occurred during the late Paleozoic to early Mesozoic. We propose that a tectonic transition from subduction to post-collisional extension may have occurred during the Early−Middle Triassic, marking the final closure of the Paleo-Asian Ocean, which most likely took place at ca. 250−235 Ma.</jats:p>

<jats:p>Deformation along strike-slip plate margins often accumulates within structurally partitioned and rheologically heterogeneous crustal blocks within the plate boundary. In these cases, contrasts in the physical properties and state of juxtaposed crustal blocks may play an important role in accommodation of deformation. Near the San Francisco Bay Area, California, USA, the Pacific−North American plate-bounding San Andreas fault bisects the Santa Cruz Mountains (SCM), which host numerous distinct, fault-bounded lithotectonic blocks that surround the San Andreas fault zone. In the SCM, a restraining bend in the San Andreas fault (the SCM bend) caused recent uplift of the mountain range since ca. 4 Ma. To understand how rheologic heterogeneity within a complex fault zone might influence deformation, we quantified plausible bounds on deformation and uplift across two adjacent SCM lithotectonic blocks on the Pacific Plate whose stratigraphic and tectonic histories differ. This was accomplished by combining 31 new apatite (U-Th)/He ages with existing thermochronological datasets to constrain exhumation of these two blocks. Additionally, surface exposures of the latest Miocene to late Pliocene Purisima Formation interpreted in 18 structural cross sections spanning the SCM allowed construction and restoration of Pliocene deformation in a three-dimensional geologic model. We found that rock uplift and deformation concentrated within individual Pacific Plate lithotectonic blocks in the SCM. Since 4 Ma, maximum principal strain computed for the more deformed block adjacent to the fault exceeded that computed for the less deformed block by at least 375%, and cumulative uplift has been more spatially extensive and higher in magnitude. We attribute the difference in uplift and deformation between the two blocks primarily to contrasts in lithotectonic structure, which resulted from diverging geologic histories along the evolving plate boundary.</jats:p>

<jats:p>Fluid flow in sedimentary basins not only impacts redistribution of the geothermal cycle and precipitation of ore deposits, but also exerts control on hydrocarbon migration and accumulation. However, reconstructing the history of fluid flow in basins that have experienced multiple tectonic deformation events is exceedingly difficult. Here, we examined petrography, in situ U-Pb geochronology, and rare earth element (REE) and C-O isotope geochemistry, as well as fluid inclusion microthermometry of fracture fillings within the Cambrian Niutitang Formation shales at the southeastern margin of the Upper Yangtze platform, southwestern China. The results show that four main fluid flow pulses are identified based on cathodoluminescence images, U-Pb ages, and geochemical data, namely, 446−428 Ma (fibrous calcite and barytocalcite), 343−329 Ma (calcite I), 113 Ma (calcite II), and 63 Ma (calcite III). The fibrous calcite (ca. 446 Ma) and barytocalcite (ca. 428 Ma) veins, corresponding to the late Caledonian Orogeny, show significantly positive Eu-Y anomalies, negative Ce anomalies, and enrichment in heavy REE, similar to their host rocks, suggesting that the mineral-forming fluids were derived mainly from dissolution of the host rocks. An abundance of bitumen inclusions with homogenization temperatures (Th) of 93.1−137.4 °C and high salinities (5−8 wt%) indicate that the first fluid flow pulse occurred during the oil generation stage in a closed fluid system. Calcite I (ca. 343−329 Ma) exhibits REE depletion and high Y/Ho ratios, a low fluid inclusion salinity (2−10 wt%) with Th = 78.4−125.8 °C, and C-O isotopic compositions similar to the underlying marine carbonates. This suggests that calcite I formed in an open fluid system, which was related to the transition from compression to extension during the Hercynian Orogeny. The pre-existing faults were reactivated and opened, resulting in the leakage and reconstruction of hydrocarbon reservoirs. Calcite II (ca. 113.4 Ma) has similar REE+Y patterns and C-O isotopic compositions to the host rocks. It contains abundant single-phase hydrocarbon gas (CH4) inclusions with high Th (164.1−211.1 °C) and salinity (6−14 wt%) values, indicating that the third phase fluid was derived largely from the host rocks and migrated during the early Yanshanian Orogeny. Lastly, calcite III (ca. 62.7 Ma) exhibits extremely low REE concentrations, low δ13CPDB [Peedee belemnite] values (−6.74‰), and low fluid inclusion salinities (0.3−7.0 wt%) with Th = 61.9−97.1 °C, suggesting that the fourth fluid flow pulse was affected by meteoric water to some extent. This can be interpreted to represent an open fluid system, which caused gas dispersion in the Niutitang Formation shales. Our findings provide important references for reconstructing the history of fluid flow in tectonically complex basins worldwide.</jats:p>

<jats:p>Germanium (Ge) is a critical raw material used in high-technology industry (i.e., optical industry) applications, and it is predominantly concentrated in coals and Zn-rich deposits. Previous studies on Zn-rich deposits have documented a correlation between Ge enrichment and the Cu, Ag, and/or Pb-Mn contents in the sphalerite crystal lattice. In this study, we observed Ge-rich nanoparticles hosted in Cu-poor sphalerite from the Banbianjie Zn-Ge deposit (&amp;gt;800 t graded at ∼100 ppm Ge), located in southwest China. Laser-ablation−inductively coupled plasma−mass spectroscopy (LA-ICP-MS) analyses revealed that sphalerite contains very heterogeneous Ge contents (172−1553 ppm). Germanium contents showed positive correlations with Fe, Mn, and Pb contents and negative correlations with Cd contents. Higher Ge contents were detected in the darker zones, whereas the lighter zones showed systematically low Ge contents and were enriched in Cd. Using transmission electron microscopy (TEM), Zn-Ge-Pb-S nanoparticles were identified in the darker zones of sphalerite. These nanoparticles exhibited Ge/Pb ratios (0.48−1.96) very similar to those measured in sphalerite (0.36−2.04), suggesting that Ge could be essentially hosted within the nanoparticles. We propose that the amounts of Zn-Ge-Pb-S nanoparticles are related to a self-organization model induced by rapid crystal growth. This self-organization processes may control the fluctuations of element concentrations in the boundary layer. This study highlights the importance of studying the nanoscale expression of critical elements to understand their incorporation mechanisms into natural materials.</jats:p>

<jats:p>The mechanisms by which complex intracontinental deformation in the northern Tibetan Plateau was accommodated since the India-Asia collision remain debated. Characterization of the formation of arcuate structures in northern Tibet provides important constraints on this debate. We conducted a new paleomagnetic study on the mid- to late Miocene strata along the curved Lenghu-Nanbaxian and Eboliang-Hulushan belts of the Qaidam Basin, northern Tibet. Our results revealed that there is nonsignificant relative rotation within localities along these arcuate belts, which yielded a common mean direction of declination (D) = 3.6°, inclination (I) = 35.7° (α95 = 2.4°) after tilt correction, suggesting negligible Neogene vertical-axis rotation along the arcuate belts in the Qaidam Basin. Outcropped fault striations and the positive flower structures indicate dextral strike-slip−dominated motion along the faults since the mid- to late Miocene. By integrating the paleomagnetic results with the kinematics of these associated faults, we ruled out the possibility that these curved belts formed due to the frictional drag of the Altyn Tagh fault or due to differential shortening across the Qaidam Basin. Instead, we attribute the formation of these nonrotational arcuate belts to dextral transpressional deformation occurring within the basin since the mid- to late Miocene. Different from the orogenic belts in the northern Tibetan Plateau that absorbed postcollisional convergence through block rotation, crustal shortening, and lateral extrusion, the Qaidam Basin has also accommodated significant intracontinental deformation in the northern Tibetan Plateau through transpressional deformation within the basin. This inference underscores the importance of recognizing crustal extrusion within rigid blocks as a record of intracontinental deformation in the northern Tibetan Plateau.</jats:p>

<jats:p>Late Cenozoic gneiss domes cover ∼30% of the surface of the Pamir salient in the northwestern end of the India−Asia collision zone. The highest peaks of the Pamir are in the east, where the ∼250-km-long, ∼N−S-trending Kongur Shan extensional system controls the topography. We combined 115 new apatite (U-Th-Sm)/He and zircon (U-Th)/He single-grain dates from 18 samples and previous thermochronologic data with three-dimensional thermokinematic models to constrain the thermo-tectonic history of the southern portion of the Muztaghata dome, one of the largest gneiss domes in the eastern Pamir. The new cooling dates from the western boundary of the southern Muztaghata dome generally increase with distance from the southern Kongur Shan fault and are related to normal faulting along the fault at near-surface levels over the last 6.5 m.y. The new dates across the central−eastern portion of the dome outline the previously recorded U-shaped date pattern at a higher spatial resolution. The modeling indicates that this pattern is most likely the result of uplift and erosion above a flat-ramp-flat thrust fault at depth over the last 7 m.y. Modeling does not resolve how topographic changes may have affected the observed distribution of cooling dates, but it indicates a faster thrust-slip rate associated with an increase in relief and a slower one associated with steady-state topography. Our results suggest that the modern topography along the southern Muztaghata dome, similar to the rest of the eastern Pamir salient, is shaped by normal faulting at shallow depth, but its growth may still be governed by contraction and crustal thickening at depth.</jats:p>

<jats:p>For sedimentary archives to be used as a record of hinterland evolution, the factors affecting the archive must be known. In addition to tectonics, a number of factors, such as changes in climate and paleodrainage, as well as the degree of diagenesis, influence basin sediments. The Indus River delta-fan system of South-Central Asia records a history of Himalayan evolution, and both the onshore and offshore sedimentary repositories have been studied extensively to research orogenesis. However, a number of unknowns remain regarding this system. This paper seeks to elucidate the paleodrainage of the Indus River, in particular when it took on its modern drainage configuration with respect to conjoinment of the main Himalayan (Punjabi) tributary system with the Indus trunk river. We leverage the fact that the Punjabi tributary system has a significantly different provenance signature than the main trunk Indus River, draining mainly the Indian plate. Therefore, after the Punjabi tributary system joined the Indus River, the proportion of Indian plate material in the repositories downstream of the confluence should have been higher than in the upstream repository. We compared bulk Sr-Nd data and detrital zircon U-Pb data from the Cenozoic upstream peripheral foreland basin and downstream Indus delta and Indus Fan repositories. We determined that throughout Neogene times, repositories below the confluence had a higher proportion of material from the Indian plate than those above the confluence. Therefore, we conclude that the Indus River took on its current configuration, with the Punjabi tributary system draining into the Indus trunk river in the Paleogene, early in the history of the orogen. The exact time when the tributary system joined the Indus should correlate with a shift to more Indian plate input in the downstream repositories only. While the upstream repository records no change in Indian plate input from Eocene to Neogene times, a shift to increased material from the Indian plate occurs at the Eocene−Oligocene boundary in the delta, but sometime between 50 Ma and 40 Ma in the fan. Though further work is required to understand the discrepancy between the two downstream repositories, we can conclude that the tributary system joined the Indus trunk river at or before the start of the Oligocene.</jats:p>

<jats:p>The generation and modification of silicic magma systems are essential processes in resolving the differentiation of continental crust. This understanding motivated the geochronological and geochemical study of the early Permian Hongliujing granite complex, consisting of quartz monzonite, granite, and leucogranite in the Central Tianshan microcontinent of the southern Central Asian Orogenic Belt. Laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) zircon U-Pb dating of the Hongliujing complex rock units revealed almost identical ages (279 ± 2 Ma to 270 ± 2 Ma). The high-silica leucogranite and granite are characterized by positive Rb and negative Eu anomalies and Ba, Sr, P, and Ti depletions. The zircon trace elements are characterized by relatively low Ti and Th/U and high Yb/Gd. In contrast, the quartz monzonite and its mafic microgranular enclaves display minor negative Ba, Sr, P, Ti, and Eu anomalies, while the zircon trace elements are characterized by relatively high Ti and Th/U and low Yb/Gd. The complex has similar zircon Hf and whole-rock Nd isotopic compositions, with Hf and Nd model ages younger than 1.4 Ga, suggesting that their magmas were derived from an isotopically depleted mantle, with some contributions from crustal melts. The leucogranites further showed relatively large variations of εHf(t) and lower εNd(t) values, implying that their magma was affected by higher amounts of crustal contamination. We suggest that crystal-melt segregation was the major mechanism responsible for the evolution of the magmatic system, and that the early Permian magmatism represents a crust-forming episode triggered by slab rollback of the subducting South Tianshan oceanic plate beneath the eastern Central Tianshan microcontinent. Thus, our study reveals that microcontinents with Precambrian crustal basement were major sites of juvenile continental growth during the accretionary evolution of the Central Asian Orogenic Belt.</jats:p>