Subduction Research Articles

Serpentinization as a Tape Recorder of (Dis)Continuous Mantle Exhumation along the Alpine Tethys Ocean-Continent-Transition

Abstract Serpentinization has been widely documented and investigated at mid-ocean ridges (MOR) and subduction zones. In contrast, at magma-poor rifted margins serpentinization has received much less attention, despite its importance in controlling rheology and mass fluxes during breakup and establishing of a steady-state MOR. In this study, we present new petrological and geochemical data on subcontinental exhumed serpentinized peridotites from the spectacularly exposed Platta, Tasna and Totalp nappes in the Eastern Central Alps in SE Switzerland, belonging to the Alpine Tethys Ocean Continent Transition (OCT). The results testify of a complex history of fluid–rock interactions recorded by several serpentinization events starting with lizardite mesh and bastite textures (S1), subsequently followed by a succession of serpentine-filling veins with distinct textures and serpentine polysomes that include spherical polyhedral serpentine (S2); chrysotile ± polygonal ± lizardite banded veins (S3); lamellar antigorite veins and patches (S4) and chrysotile crack-seal (S5). The serpentinization sequence differs at proximal (i.e. continentwards) and distal (i.e. oceanwards) domains of the OCT. At proximal domains of the OCT (Upper Platta, Tasna) serpentinites record the complete serpentinization sequence (S1 to S5), whereas at distal domains (Lower Platta) serpentinization is restricted to pseudomorphic mesh and bastite (S1) and chrysotile crack-seal (S5). We attribute this discrepancy to contrasted mechanisms of mantle exhumation along the OCT. While at proximal domains mantle is unroofed along continuous and single large offset detachment faults allowing for the formation of all serpentine generations, mantle exhumation at distal domains is a more discontinuous process, controlled by sequential out-of-sequence detachment and flip-flop faults preventing the full development of all serpentine generations. In this frame, the nature and order of formation of the serpentine polysomes are directly controlled by the conditions of serpentinization (i.e. temperature, mantle composition and fluid/rock ratio). We propose that this new conceptual model can be extrapolated to serpentinization at slow to ultra-slow MORs, where close similarities in the serpentinization sequences have been recently reported.

Slab buckling as a driver for rapid oscillations in Indian plate motion and subduction rate

Plate tectonics is primarily driven by the constant gravitational pull of slabs where oceanic lithosphere sinks into the mantle at subduction zones. Under stable plate boundary configurations, changes in plate motion are then thought to occur gradually. Surprisingly, recent high-resolution Indian plate reconstructions revealed rapid (2–3 Million-year) plate velocity oscillations of ±50 %. We show, through numerical experiments, that the buckling of slabs in the mantle transition zone causes such oscillations. This buckling results from the deceleration of slabs as they sink into the lower mantle. The amplitude and period of buckling-associated oscillations depend on average subduction velocity and the available space in the mantle transition zone. The oscillations also affect the upper plate which may explain enigmatic observations of episodic deformation and fluid flow in subduction-related orogens. We infer that the slab pull that drives plate tectonics is generated in just the top few hundred kilometers of the mantle.

Continental crust recycling in collisional zones: insights from Li isotope compositions of the syn-exhumation and post-collisional mafic magmatic rocks

Syn-exhumation and post-collisional mafic magmatism in continental collision orogenic belts may provide insights into the nature of orogenic lithospheric mantle and recycled continental components in continental subduction zones. Lithium and its isotopes have emerged as potentially valuable tools for shedding light on the origin of these magmas, given the contrast Li contents and isotopic compositions between the subducting continental crust and the mantle. Here, we present high-precision Li isotopes data for representative orthogneiss, continental eclogite, syn-exhumation and post-collisional mafic magmatic rocks from the North Qaidam orogen. The syn-exhumation mafic magmatic rocks have relatively higher Li contents (26.5–50.0 ppm) and lower δ7Li values (−1.01‰–1.48‰) than those of the post-collisional mafic magmatic rocks (Li = 11.1–22.7 ppm, δ7Li = 1.20‰–3.38‰), which are comparable to those of orthogneiss and continental eclogite, respectively. Dehydration and melting modelling results show that these mafic magmatic rocks have similar Li contents and δ7Li values to the continental eclogite- and orthogneiss-derived melts but are different from their derived fluids. Monte Carlo simulation for Li-Nd isotopes suggests the syn-exhumation and post-collisional mafic rocks could be derived from an enriched mantle source that contains ∼3–8% continental crustal components dominated by the orthogneiss and continental eclogite. The calculated results are consistent with the results from the previous study simulated by trace elements. Therefore, our results highlight Li isotopes as a potential tool to trace the nature of the continental crustal components recycling in continental subduction zones.

Microdroplets initiate organic-inorganic interactions and mass transfer in thermal hydrous geosystems

Organic-inorganic interactions regulate the dynamics of hydrocarbons, water, minerals, CO2, and H2 in thermal rocks, yet their initiation remains debated. To address this, we conducted isotope-tagged and in-situ visual thermal experiments. Isotope-tagged studies revealed extensive H/O transfers in hydrous n-C20H42-H2O-feldspar systems. Visual experiments observed water microdroplets forming at 150–165 °C in oil phases near the water-oil interface without surfactants, persisting until complete miscibility above 350 °C. Electron paramagnetic resonance (EPR) detected hydroxyl free radicals concurrent with microdroplet formation. Here we propose a two-fold mechanism: water-derived and n-C20H42-derived free radicals drive interactions with organic species, while water-derived and mineral-derived ions trigger mineral interactions. These processes, facilitated by microdroplets and bulk water, blur boundaries between organic and inorganic species, enabling extensive interactions and mass transfer. Our findings redefine microscopic interplays between organic and inorganic components, offering insights into diagenetic and hydrous-metamorphic processes, and mass transfer cycles in deep basins and subduction zones.

Geology and genesis of the Aqishan Pb-Zn deposit, NW China: Insights from mineralogy, geochemistry, and in situ U-Pb geochronology

The unique ore-forming processes and the key factors responsible for formation of skarn deposits are still obscure, and challenges exist in the determination of timing of Pb-Zn skarns owing to lacking suitable mineral chronometers. Here we present detailed paragenesis, bulk geochemistry, in situ U-Pb dating of zircon and garnet, and garnet oxygen isotopes together with in situ zircon Hf-O isotopes from the newly discovered Aqishan Pb-Zn deposit in the southern Central Asian Orogenic Belt (CAOB), northwest China. This comprehensive data set revealed a Late Carboniferous subduction-related distal Pb-Zn skarn system associated with the granitic magmatism. Pre-ore stage garnets are generally subhedral to euhedral with oscillatory zoning and show slightly fractionated rare earth element patterns with positive Eu anomalies that point to an infiltration metasomatism origin under high water/rock ratios. The syn-ore stage sphalerite is typically enriched in Mn and Cd and has moderate Zn/Cd ratios (337–482), with a formation temperature of 265 °C to 383 °C, which indicate magmatic-hydrothermal signatures. The isocons defined by P2O5 decipher that the principal factors for skarn formation were elevated activities of Fe, Ca, and Si species, where remobilization of Pb metals, meanwhile, contributed to ore-forming budgets to mineralizing fluids. SIMS U-Pb dating of zircons from granite porphyry that occurs distal to the skarns and Pb-Zn orebodies shows that these intrusions emplaced at ca. 311.3–310.6 Ma, recording the subduction of the Paleo-Tianshan oceanic plate. Hydrothermal garnets in close textural association with Pb-Zn sulfides yield indistinguishable in situ LA-ICP-MS U-Pb ages of 310.5 ± 4.1 Ma. Whole-rock geochemistry and in situ zircon Hf-O isotopes (δ18O = 4.6‰–6.0‰) indicate that the granite porphyry was derived from partial melting of juvenile crust and influenced by subducted oceanic crust. Oxygen isotope compositions of garnets (δ18O = 8.0‰–9.0‰) demonstrate that the equilibrated ore fluids were inherited from fluid-rock interactions between a primary magmatic water and host tuff rocks. Our study highlights the application of garnets as a potential robust U-Pb geochronometer and isotopic tracer of ore fluids in skarn mineralizing systems in subduction-related arc environments.

Detection of slow slip events along the southern Peru - northern Chile subduction zone

Detections of slow slip events (SSEs) are now common along most plate boundary fault systems at the global scale. However, no such event has been described in the south Peru - north Chile subduction zone so far, except for the early preparatory phase of the 2014 Iquique earthquake. We use geodetic template matching on GNSS-derived time series of surface motion in Northern Chile to extract SSEs hidden within the geodetic noise. We detect 33 events with durations ranging from 9 to 40 days and magnitudes from Mw 5.6 to 6.2. The moment released by these aseismic events seems to scale with the cube of their duration, suggesting a dynamic comparable to that of earthquakes. We compare the distribution of SSEs with the distribution of coupling along the megathrust derived using Bayesian inference on GNSS- and InSAR-derived interseismic velocities. From this comparison, we obtain that most SSEs occur in regions of intermediate coupling where the megathrust transitions from locked to creeping or where geometrical complexities of the interplate region have been proposed. We finally discuss the potential role of fluids as a triggering mechanism for SSEs in the area.

Meta-Ultramafic Rocks of the Maksyutov Complex, Southern Urals: High-Pressure Si-Al Metasomatism and Carbonatization at the Crust-Mantle Interface in the Subduction Zone

The eclogite-blueschists Maksyutov Complex is characterized by a complex fold-and-thrust structure that was developed during the Late Devonian collision between Baltica (East European Plate) and the Magnitogorsk Arc, that was formed during the Early Devonian intraoceanic subduction. Eclogites are the most studied rocks of the complex; their formation and exhumation are usually associated with the collisional stage of orogen development. At the same time, the origin of meta-ultramafic rocks, which together with eclogites form sheeted and lenses within metasedimentary rocks (shales and quartzites), still remains unknown. This paper presents the results of the first detailed petrological study of meta-ultramafic rocks, represented by antigorite-chlorite and magnesite-antigorite metaharzburgites, chlorite-antigorite metaorthopyroxenite. Mineral compositions and textural relationships between minerals in metaharzburgites indicate at least two stages of rock transformations. Minerals of the early mineral paragenesis (first stage) – olivine, accessory chromite and low-fluorine Ti-clinohumite – have a metamorphic genesis; ultrahigh-pressure (UHP) conditions of their formation are discussed. At the second stage, there was a partial replacement of olivine by orthopyroxene-bearing parageneses with Cr-Al antigorite and/or high-chromium chlorite. Based on the phase equilibria modeling using the Perple_X software package, it was found that the formation of antigorite-orthopyroxene paragenesis was associated with Si-Al metasomatism at: T ~ 630°С, P ~ 2 GPa, logaSiO₂~ –0.6, logaAl₂O₃~ – 2.5. It is important to note that the mineral paragenesis are highly sensitive to aSiO₂: a slight decrease in lgaSiO2 relative to the above value would lead to the growth of olivine with antigorite, and an increase would lead to the growth of orthopyroxene. The latter may explain the formation of meta-orthopyroxenites, which are widely distributed among the meta-ultramafic rocks of the Maksyutov Complex. Similar calculations performed for the range of XCO₂= 0.01–0.05 in H₂O-CO₂fluid showed replacing silicate minerals by magnesite under the established thermodynamic conditions. Carbonation and Si-Al metasomatism are specific features of high-pressure transformations of meta-ultramafic rocks, which have not been established in the associated eclogites, quartzites, and shales. Such selectivity of fluid influence on different rock types is interpreted as a result their different tectono-metamorphic evolution: meta-ultramafic rocks are fragments of the suprasubduction mantle, which were tectonically combined with the rocks of the subducting plate (eclogites and metasedimentary rocks).

A note on the seismicity of Sumatra, western Sunda Arc, Indonesia, in relation to the potential for back-arc thrusting

The existence of back-arc thrust faults along the eastern part of the Sunda Arc, ranging westwards from Flores to the western tip of Java, has been recognised for decades. In contrast, it is still unknown whether such back-arc thrust faults exist in Sumatra, which is located in the western part of the Sunda Arc. To investigate the possible existence of back-arc thrusts in Sumatra, we examine regional earthquake data reported by the Agency for Meteorology, Climatology and Geophysics of Indonesia, as well as global earthquake data reported by the International Seismological Centre and the United States Geological Survey. It appears that back-arc thrusts in the study area are not extensively developed, unlike in the eastern Sunda Arc, which may be caused by oblique subduction beneath the Sumatran forearc. The stress associated with the trench-parallel component of subduction is largely accommodated by the ~ 1650-km-long dextral strike-slip fault zone of the Great Sumatran Fault. The seismicity data from various sources do, however, show that there is a dipping seismogenic zone in several parts of the back-arc region of Sumatra, in the opposite direction to the NNE subduction of the Indo-Australian plate. This new observation may be related to the presence of spatially intermittent back-arc thrust faults in the study area, which may need to be taken into account when improving Indonesia's national earthquake hazard maps.

Deep learning for deep earthquakes: insights from OBS observations of the Tonga subduction zone

SUMMARY Applications of machine learning in seismology have greatly improved our capability of detecting earthquakes in large seismic data archives. Most of these efforts have been focused on continental shallow earthquakes, but here we introduce an integrated deep-learning-based workflow to detect deep earthquakes recorded by a temporary array of ocean-bottom seismographs (OBSs) and land-based stations in the Tonga subduction zone. We develop a new phase picker, PhaseNet-TF, to detect and pick P- and S-wave arrivals in the time–frequency domain. The frequency-domain information is critical for analysing OBS data, particularly the horizontal components, because they are contaminated by signals of ocean-bottom currents and other noise sources in certain frequency bands. PhaseNet-TF shows a much better performance in picking S waves at OBSs and land stations compared to its predecessor PhaseNet. The predicted phases are associated using an improved Gaussian Mixture Model Associator GaMMA-1D and then relocated with a double-difference package teletomoDD. We further enhance the model performance with a semi-supervised learning approach by iteratively refining labelled data and retraining PhaseNet-TF. This approach effectively suppresses false picks and significantly improves the detection of small earthquakes. The new catalogue of Tonga deep earthquakes contains more than 10 times more events compared to the reference catalogue that was analysed manually. This deep-learning-enhanced catalogue reveals Tonga seismicity in unprecedented detail, and better defines the lateral extent of the double-seismic zone at intermediate depths and the location of four large deep-focus earthquakes relative to background seismicity. It also offers new potential for deciphering deep earthquake mechanisms, refining tomographic models, and understanding of subduction processes.

Heavy magnesium isotopic signatures in arc lavas may be attributed to dehydration of subducting hydrated mantle

Fluids released from subducting slabs profoundly affect mantle composition, rock melting points, and arc magma generation. However, identifying fluid sources (sediments, crust, or mantle) and their ascent paths remains challenging. Magnesium isotopes are potential tracers for subduction-related fluids, though their behavior during hydrous peridotite dehydration remains unclear. Here we determined the equilibrium magnesium isotope fractionation factors between aqueous fluids and hydrous peridotitic minerals using first-principles calculations. Aqueous fluids prefer heavy magnesium isotopes relative to mantle silicate minerals, indicating that fluids released during hydrous peridotite dehydration are enriched in heavy magnesium isotopes relative to the residual minerals. Our simulations proposed that magnesium isotope variations in arc lavas from different subduction zones could be attributed to different dehydration reactions influenced by subduction zone thermal structures. This study highlights the potential of magnesium isotopes for tracing fluids originating from subducting hydrated mantle, providing insights into the thermal structure of various subduction zones.

Petrogenesis and Geodynamic Evolution of the Archean Shawmere Anorthosite Complex and Associated Gneisses, Kapuskasing Uplift, Superior Province, Canada

Abstract In this study, we integrated extensive field, petrographic, whole-rock major and trace element, and Nd–Pb–Sr–O isotope, and zircon U–Pb ages, trace element and Lu–Hf isotope data from the Neoarchean Shawmere Anorthosite Complex and surrounding gneisses to unravel their petrogenetic origin and tectonic history. The ~2765 Ma Shawmere Anorthosite Complex is interpreted to have been emplaced into a sequence of interlayered greywacke and basalt deposited in an intra-continental arc rift system above a north-dipping subduction zone. The complex consists mainly of anorthosite, leucogabbro, gabbro, and hornblendite that were emplaced as several batches of magmas and crystal mushes originating from sub-arc mantle sources. In contrast to the previous studies, our field and petrographic data suggest an igneous origin for the most hornblende in the complex, implying hydrous parental magmas. A hydrous magma origin is also consistent with the high-anorthite content (mostly 70–90%) of the plagioclase in the complex. Percolation of hydrous basaltic melts through gabbroic cumulates in crustal magma chambers led to extensive (>50%) replacement of igneous clinopyroxene by igneous hornblende. Continued subduction resulted in the closure of the intra-arc rift system and the intrusion of the complex by tonalite, granodiorite and diorite between 2765 and 2680 Ma in an Andean-type margin. The complex and surrounding gneisses underwent hornblende granulite-facies metamorphism mainly between 2680 and 2620 Ma, overlapping with mid-crustal east-west extension between 2660 and 2640 Ma. The granulite-facies metamorphism is recorded by the replacement of hornblende, plagioclase and clinopyroxene by garnet and the development of a garnet-orthopyroxene-plagioclase metamorphic assemblage with a granoblastic texture. Tectonic rebounding of mid-crustal rocks to upper crustal levels after 2620 Ma led to the formation of an extensive network of extensional fractures and retrograde metamorphism. Migration of CO2-rich hydrous fluids along the extensional fractures and grain boundaries resulted in the precipitation of many metasomatic minerals mainly at the expense of hornblende and plagioclase, including epidote, clinozoisite, tremolite, actinolite, paragonite, margarite, titanite, quartz, calcite, sillimanite, dolomite, and chlorite. Prevalent replacement of hornblende by garnet during prograde metamorphism and metasomatic replacement of hornblende and plagioclase by retrograde mineral assemblages disturbed the Sm–Nd, U–Th–Pb, and Rb–Sr isotope systems.

Deep-seated crustal faults and their role in the thermo-tectonic evolution of an active mountain belt: New evidence from the Northern Andes

Deep-seated structures can exhume deep crustal rocks (>20 km), transmitting the signal of geodynamic processes from the subduction zone to the interiors of the continents. The role of deep-seated structures can be analyzed with low-temperature thermochronological dating techniques. However, studies coupling low-temperature thermochronology with structural geological analyses of the deformational style are not common in the Northern Andes. In this contribution, we present new apatite (AFT) and zircon (ZFT) fission-track data coupled with meso- and microstructural analyses to reveal the deformational and exhumation history of the Santander Massif (SM; Northern Andes) and the related cortical Bucaramanga strike-slip fault (BF). Samples for thermochronological analyses were collected along an elevation profile with a significant elevation difference of 2.4 km across the western flank of the SM, crossing the BF. The time-temperature history modeling of ZFT data reveals phases of prolonged residence in the zircon partial annealing zone from ∼125 to 94 Ma and a cooling phase related to an exhumation episode at around 25 Ma based on samples collected near the BF. Inverse modeling of AFT data reveals structurally-controlled Pliocene exhumation rates of 0.6–0.7 km/Myr mediated by the action of secondary faults. A shift in the deformation style resulting from the oblique interaction of the SM and Mérida Andes domain is interpreted as the main driver of the Pliocene exhumation. This deformation phase is observed in the fault damage zone, where evidence of brittle-ductile deformation was exhumed. Finally, we discuss the geodynamic implications of our thermochronological and structural analyses, contrasting local and more regional competing hypotheses (Pamplona Indenter vs. slab break-off of the Caribbean plate), which may explain the tectonic evolution of the northern part of the Eastern Cordillera and the SM in the Colombian Northern Andes.

Review: Andesitic aquifers—hydrogeological conceptual models and insights relevant to applied hydrogeology

Research on the hydrogeology of andesitic volcanic aquifers in subduction areas is reviewed. Andesitic aquifers are of high interest in volcanic arc islands and subduction zones, where they constitute a strategic water resource. This review gathers a compilation of worldwide results and case studies to propose a generic hydrogeological conceptual model (GHCM). It is based on the geological conceptual model splitting the volcanic edifice, from upstream to downstream, into central, proximal, medial and distal zones. In this geological structure, the GHCM identifies where the main aquifer types (fractured lava, pyroclastic flows, and the volcano-sedimentary basins downstream) and the typical aquitards (lahars, fine pyroclastic falls and surges, indurated pyroclastic flow, and weathered rocks) are structured and organized. To integrate the evolution of volcanoes and some specific volcanic activities, a specific GHCM for old andesitic volcanoes or andesitic shield volcanoes is detailed. The paper also describes how the GHCM results are of use to hydrogeologists in terms of scale (from the lithological units to the regional scale), to effectively site water wells, and to sustainably manage groundwater resources in such aquifers. Among these various scales, the volcanic “flank continuum” is presented as the most adapted to support groundwater resources management. Several ways to improve this GHCM are suggested, notably to better consider the geological complexity of these aquifers.

Coastal Hazards in the Sunda Strait: Mitigation Strategy and Coastal Management

Abstract Sunda strait is one of the strategic waters in Indonesia situated at the Indonesian archipelagic sea lane passage. The water is also known as one of the national strategic regions as governed in the Presidential Decree of 32/2019 about marine spatial planning. The coasts of the region have been developed as industrial areas, marine tourism and associated facilities, fisheries, agriculture, mining, etc. Despite the huge economic potency, Sunda Strait has high coastal hazards due to volcanic and tectonic activities. The Krakatau volcanic eruption in 1883 generated a tsunami run-up to ∼35 m high causing catastrophic damage along the coasts of Banten and Lampung and more than 36.000 people were reported killed. More recently, the eruption and flank collapse of the Anak Krakatau volcano generated a tsunami in the Sunda Strait causing severe damage, extensive inundation, and more than 430 deaths. Likewise, the Sunda Strait has a high potency of tsunami impacts generated by the earthquake sourced from the subduction zone known as megathrust. These conditions must become a valued lesson learned to all of us to raise awareness and preparedness through mitigation-based disaster management. Thus, we can reduce the impacts of the disaster and the high investment for post-disaster rehabilitation and reconstruction.

Shaken and Stirred: A Comparative Study of Earthquake‐Triggered Soft‐Sediment Deformation Structures in Lake Sediments

AbstractSubaqueous paleoseismic studies used soft sediment deformation structures (SSDS) to discern the shaking strength of past earthquakes, as the deformation degree of SSDS related to Kelvin Helmholtz Instability evolves from disturbed lamination and folds to intraclast breccia with higher peak ground accelerations (PGA). We lack comparative studies of different sediment types with SSDS related to earthquakes from different seismogenic sources to comprehend how these factors modulate earthquake‐induced deformation. Here, we compile sediment records with seven earthquake‐triggered SSDS from 10 lakes with organic‐, carbonate‐, siliciclastic‐, and diatom‐rich sediment from three subduction zones and one collisional setting. We target basin sequences with slope angles <0.65° to reduce the influence of gravitational downslope stress. We find that even minimal increases in slope angle, maximal 1°, lead to higher deformation degrees and, for some earthquakes, SSDS are only present at >0.65°. Fine‐grained clastics enhance sediment susceptibility to deformation, whereas abundant diatoms reduce it, demonstrating the influence of composition. Deformation correlates best with PGA and the vicinity of the earthquakes, suggesting that high frequency shaking promotes deformation. In addition, deformation only occurs above a minimum magnitude dependent on sediment composition, and higher deformation degrees in our studied basin sedimentary sequences only above Mw 4.9 for all sediment types, suggesting that sufficient duration of shaking—magnitude correlates with duration—is essential for SSDS development. We advise taking multiple cores on gentle slopes to study SSDS—additional to basin cores—to resolve small magnitude local earthquakes and relative differences in frequency content of past events.

Attenuation characteristics of coda wave in Northern Aceh, Sumatra, Indonesia

Abstract Sumatra Island is located in the subduction zone between Indo-Australian and Eurasian Plates. The tectonic activity has resulted in an active region. Hence, it may cause more heterogeneous crust in the region. To understand the relationship between the attenuation factor and the tectonic setting, we apply coda wave attenuation study Sumatra Island. This preliminary result focuses at the northern Aceh from observation at LHMI station. A total of about 123 earthquake waveforms of local distance (less than 3°) with depth less than 40 km is analyzed in this study. We employ a back-scattering model assumption to determine the attenuation of coda waves. Our coda wave quality factor (Qc ) estimation covers frequencies from 1 to 8 Hz. Onset of the coda window is determined by considering twice the arrival time of shear wave, with varying window lengths between 20 and 120 s. The Q0 (Qc at frequency 1 Hz) varies from 65.84 ± 5.50 to 183.09 ± 7.17. We observe a decrease in the factor of frequency dependence (η) between 1.14 ± 0.06 and 1.04 ± 0.03. Depth dependent of coda wave attenuation can be seen from the increase of Q0 (which is Qc at 1 Hz) with window length. We suggest that the Low Q0 (< 200) and high η (> 1) may be associated with high tectonic activity in this region.

Disparate Far‐Field Responses of Deep Pacific‐Plate Subduction Beneath Northeastern Asia: Implication for the North–South Segmented Crustal Modification of the Great Khingan Range

AbstractThe far limit of a plate subduction process and its related far‐field dynamic process are fundamental topics for plate tectonics. The Great Khingan Range (GKAR) in the western flank of NE China is currently under the far‐field influence of the Pacific plate subduction. Benefiting from the newly deployed seismic arrays in the northern GKAR, we take full advantage of seismic data from both temporary and permanent networks and employ an improved scheme of the H‐κ stacking method by introducing surface wave dispersion to obtain the integrated maps of Moho depth and crustal bulk Vp/Vs ratio in this region. Our results show that the Moho depth has a giant step near the North–South Gravity Lineament (NSGL). Meanwhile, the distribution of bulk Vp/Vs ratio presents a north–south difference roughly by 50°N, where the south subregion consists of a collage of high and low Vp/Vs ratio; by contrast, the north subregion is characterized by unified high values. The east‐west structural discrepancies across the NSGL from the Earth's surface to the mantle transition zone indicate the difference in the strength of modifications between the near and far‐fields from the Pacific plate subduction. The complicated distribution of the Vp/Vs ratio in the south subregion supports that secondary small‐scale upwellings underneath the Cenozoic volcanic groups dominate the tectonic reworking in this area. The lack of Cenozoic volcanism and a more straightforward distribution of the Vp/Vs ratio in the north subregion might allude to a tectonically inactive part of NE China.

Risk assessment of cardiovascular adverse events with BTK inhibitors in hematological malignancies: Insights from FAERS.

12145 Background: Burton tyrosine Kinase inhibitors (BTKi) have revolutionized the care of chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphomas (NHL) – including relapsed/refractory mantle cell, ABC diffuse large B cell lymphoma and and lymphoplasmacytic lymphoma. Ibrutinib was the first BTKi to be approved. The newer covalent BTKi include acalabrutinib and zanubrutinib, both of which are approved for frontline and relapsed CLL as well as relapsed NHL. All these agents have cardiovascular adverse events. We aimed to assess the pharmacovigilance (PV), reporting rate, severity, and reaction outcomes of different approved BTKi in the CLL as cancer reported to the United States Food and Drug Administration Adverse Event Reporting System (FAERS). Methods: We analyzed cardiovascular events in 86,370 patients on BTKi. Cardiovascular event reports were submitted to FAERS between 2004-2023 and analyzed using the AERS Mine framework. We compared these incidences within different BTKI. We divided cardiovascular events to three categories: cardiac arrythmia, major coronary or vascular event (MACE) and pericardial complication including effusion or hemorrhage. Our primary composite endpoint was the PV of cardiovascular events caused by BTKI. To mitigate confounding, BTKI were analyzed as mutually exclusive cohorts: Ibrutinib (n = 79,278), acalabrutinib (5200), and zanubrutinib (1354). Two-way ANOVA testing was done to evaluate for statistical significance across the different groups. Results: Across the 86,370 patients on BTKI, we identified 8500 reports of cardiovascular events – ibrutinib (10.15%), acalabrutinib (5.73%), and Zanubrutinib (4.72%). Arrythmia risk was higher with ibrutinib (6.6%) compared to acalabrutinib (3.12%) and zanubrutinib (2.29%). The major difference in the groups was driven by atrial fibrillation (5.1% vs 2.1% vs 1.8%). The MACE rate was 2.79% vs. 2.4% vs. 2%, and pericardial events were 0.72% vs. 0.21% vs. 0.44% in the ibrutinib, acalabrutinib, and zanubrutinib groups, respectively. All the AEs were to have statistical significance (p = 0.011) across all the BTKI as mentioned in table 1. Conclusions: We report the prevalence rate of BTKI-related cardiovascular events in a large cohort of patients. Ibrutinib has demonstrated a higher incidence of toxicity, especially in cardiac arrythmias, while smaller but significant differences exist in other toxicities, including major cardiovascular events and pericardial effusion or hemorrhage. Patient selection and toxicity monitoring are important aspects of the care of these patients, who stay on these therapies for indefinite periods. [Table: see text]

Immunohistochemical markers in the prognostic model for survival of patients with diffuse large B-cell lymphoma.

e19055 Background: Currently, relevant issues include the study of the role of immunohistochemical markers in patients with diffuse large B-cell lymphoma (DLBCL) with extranodal involvement to predict the outcomes of the conducted therapy. Methods: A retrospective study included 81 patients with diffuse large B-cell lymphoma (DLBCL) involving the liver and spleen with extranodal manifestations, who underwent treatment and were under outpatient monitoring in a hospital setting. The average age of the patients was 60.7±7.5 years. The expression of pan-B-cell antigens CD20, CD79A, PAX 5 (monomorphic intense nuclear expression), CD5, CD45, CD30, BCL-2, BCL-6, Ki-67, MUM1, GCET1, FOXP1 was examined in the patients. To exclude the polymorphic blastoid variant of lymphoma with CD5 expression in mantle cells, the study of cyclin D1 expression was conducted. Results: All patients began treatment with R-CHOP chemotherapy. In 37 cases, this regimen had to be replaced with DHAP in 23 (62.2%) patients due to the low effectiveness of the 1st-line chemotherapy, and in 14 (37.8%) after completing the full course (6 cycles) of treatment. Over the 6-year observation period, despite identical treatment, the 5-year survival rate was 60.5%. Among 32 (39.5%) patients, there was a fatal outcome due to the progression of the pathological process during treatment. Moderate expression was characteristic for the markers CD5, CD30, PAX-5, FOXP1, and GCET1, while high expression was observed for CD10, CD45, CD79A, Bcl-6, MUM1, and Ki-67. High expression of Bcl-2, Bcl-6, GCET1, and Ki-67 exceeding 60% is a prognostically unfavorable factor significantly impacting the survival of patients. The most unfavorable outcomes were observed with the combination of Bcl-2 and Ki-67 expression exceeding 60% along with CD-45. The combination of Ki-67 expression exceeding 60%, CD-79, and MUM1 also resulted in an unfavorable outcome in all cases. The prognostic scale, using Cox's proportional hazard, allows predicting the prognosis of diffuse large B-cell lymphoma with extranodal involvement with a probability of 87.2%. Conclusions: In our studies, it has been demonstrated that adverse immunohistochemical characteristics of diffuse large B-cell lymphoma with extranodal involvement include high expression of Bcl-2, Bcl-6, GCET1, and a Ki-67 proliferation index exceeding 60% (p<0.025).

Apatite Fission‐Track Thermochronology in the Tamusu Area, Bayingobi Basin, NW China, and its Geological Significance

AbstractThe Bayingobi basin is located in the middle of Central Asia Orogenic Belt, at the intersection of Paleo‐Asian Ocean and Tethys Ocean, as well as the junction of multiple tectonic plates. This unique tectonic setting underpins the basin's intricate history of tectonic activity. To unravel the multifaceted tectono‐thermal evolution within the southwestern region of the basin and to elucidate the implications of sandstone‐hosted uranium mineralization, granitic and clastic rock samples were collected from the Zongnai Mts. uplift and Yingejing depression, and apatite fission track (AFT) dating and thermal history simulation analysis were performed. AFT dating findings reveal that the apparent ages of all samples fall within the range of 244 Ma to 112 Ma. In particular, the bedrock of the Zongnai Mts. and Jurassic detrital apatite fission tracks have undergone complete annealing, capturing the uplift‐cooling age. Meanwhile, the AFT ages of Cretaceous detrital rocks are either equivalent to or notably exceed the age of sedimentary strata, signifying the cooling age of the provenance. A comprehensive examination of AFT ages and palaeocurrent direction analyses suggests that the Cretaceous source in the Tamusu area predominantly originated from the central and southern sectors of the Zongnai Mts. uplift. However, at a certain juncture during the Late Early Cretaceous, the Cretaceous provenance expanded to include the northern part of the Zongnai Mts. uplift. Based on the results of thermal history simulations and previous studies, it is considered that the Tamusu area has undergone four distinct tectonic uplift events since the Late Paleozoic. The first is the Late Permian to Early Triassic (260–240 Ma), which is associated with the closure of the Paleo‐Asian Ocean and the accretionary orogeny within the Alxa region. The second uplift event took place in the Early Jurassic (190–175 Ma) and corresponded to intraplate orogeny following the closure of the Paleo‐Asian Ocean. The third uplift event is the Late Jurassic to Early Cretaceous (160–120 Ma), which is linked to the East Asia's position as the convergence center of multiple tectonic plates during this period. The fourth uplift event is linked to the Late Early Cretaceous (112–100 Ma), driven either by the westward subduction of the eastern Pacific plate or the mantle upwelling resulting from the Bangong–Nujiang oceanic lithosphere subduction and slab break‐off. The primary stress orientation for the first three tectonic uplift phases approximated a nearly SN direction, while the fourth stage featured a principal stress direction of NW. The fourth tectonic uplift event of the Late Early Cretaceous and basaltic eruption thermal event during this period likely exerted a significant influence on the formation of the Tamusu sandstone‐hosted uranium deposit.