Subduction zone forearcs represent the first major devolatilization window of the downgoing slab and play a critical, yet poorly constrained, role in regulating volatile recycling between Earth’s surface and interior. Here we present the first coupled dataset of dissolved noble gases (He–Ne–Ar–Kr–Xe), halogens (Cl–Br–I), and iodine isotopes from Mariana forearc borehole fluids to better constrain the sources, transport, and modification of slab-derived volatiles. The fluids reflect mixing between seawater and deep mantle and slab-derived components. Halogen systematics identify altered oceanic crust containing carbonates and iron oxyhydroxides as the dominant slab fluid source, with volatile release linked to decarbonation and mineral breakdown. Iodine isotopes indicate that these fluids tap ancient reservoirs isolated within the slab for tens to hundreds of millions of years prior to subduction. Ultra-high-precision (sub-permil) xenon isotope measurements provide the first identification of resolvable Xe isotope anomalies in forearc fluids, with heavy Xe excesses uniquely fingerprinting contributions from both mantle and U-rich slab lithologies. In contrast, elemental noble gas systematics reveal strong fractionation during slab processing, with preferential loss of light noble gases relative to heavier species. This is expressed as systematic neon depletion and decoupling of helium from heavier noble gases, consistent with diffusive loss during progressive burial and heating of the slab. Together, these results demonstrate that the Mariana forearc system acts as an efficient filter of slab-derived volatiles, selectively removing light noble gases and limiting their recycling to the deeper mantle.
Thermal ionization mass spectrometry measurements of non-mass-dependent calcium isotope effects in calcium-aluminum-rich refractory inclusions show resolvable anomalies, both 48Ca isotope excesses and deficits, when compared to measured reference materials used to define the normal terrestrial planet composition (ε48Ca = 0±3.52SD ε-unit, part in 10,000, for the 48Ca/44Ca ratio). For two of the studied inclusions resolvable intra ε48Ca heterogeneity also exists. The measured range and heterogeneity of calcium isotope effects represent a vestige of presolar stellar nucleosynthetically distinct carriers contributed to the Solar protoplanetary disk at the time refractory inclusions were forming, representing the earliest record of infall events since molecular cloud collapse. When directly compared to mass-dependent calcium isotope fractionation effects, as well as mass-dependent and non-mass-dependent titanium isotope effects, and moderately refractory element isotopic signatures, a more complete view of how inclusions, and through their compositions, the early Solar System formed. Additionally, the long-debated nature of several common inclusion types, e.g., melilite-mantled coarse-grained Type B’s, can be more clearly understood when evidence from both refractory elements, for a primordial record, and the moderately refractory elements, for late nebular formation events are considered. Collectively, cosmochemical and chronological records contained in refractory inclusions are important because they formed during the early period of Solar System evolution in which the protoplanetary disk began to dissect into distinct radial reservoirs, likely caused by the formation of giant gaseous planets, directly recording reservoirs, processes, and timescales from which building blocks of terrestrial planets emerged.
The chemical composition of siliciclastic rocks provided key insights into the chemical composition of the upper continental crust and was suggested to record the onset of modern-style plate tectonics by ∼3.0 Ga. Recent studies aiming to establish the crustal µ182W and µ142Nd isotope compositions, which record processes within the first 60 and 500 million years after Earth’s formation, yielded contradictory results. Previously reported µ182W and µ142Nd data for sedimentary rocks yielded deficits, excesses, and Bulk Silicate Earth-like compositions. This complicates interpretations of the formation of Earth’s crust and the homogenisation history of Hadean mantle components. To constrain these processes and obtain a first-order estimate of the evolution of µ182W and µ142Nd in the upper crust, we provide new µ182W and µ142Nd data for Archean to Proterozoic siliciclastic rocks from the Kaapvaal and Yangtze cratons, including complementary trace-element, 176Lu-176Hf, and 147Sm-143Nd data. The absence of µ182W and µ142Nd anomalies in the investigated siliciclastic rocks indicates that crustal units with anomalous µ182W and µ142Nd compositions were only minor contributors. To reconcile these findings with previous studies, we suggest a model where crustal and mantle domains with anomalous short-lived isotope compositions were relatively small and isolated. Efficient pooling of detrital material during sediment transport can explain the striking absence of anomalous µ182W and µ142Nd values in the investigated sedimentary rocks. The available data for sedimentary rocks can be reproduced by simple geochemical modelling assuming silicate differentiation and subsequent homogenization of Earth’s mantle, which reduced the size of anomalous domains over time.
The 29 July 2025 Mw 8.8 Kamchatka megathrust earthquake was the largest global earthquake since the 2011 Mw 9.0 Tohoku earthquake and provides an important opportunity to investigate the rupture process of giant subduction events. Here, we combine low-frequency W-phase inversions with high-frequency image deconvolution back-projection (IDBP) to resolve jointly the spatial distributions of coseismic slip and radiated seismic energy. Point-source and finite-fault W-phase inversions show that low-frequency slip is concentrated in the shallow, trenchward portion of the megathrust. In contrast, multi-array IDBP imaging indicates that high-frequency radiation is primarily emitted from the deeper, downdip part of the seismogenic zone.This pronounced high-frequency–low-frequency partitioning closely resembles that observed in other giant megathrust earthquakes, particularly the 2011 Mw 9.0 Tohoku earthquake. The depth-dependent frequency segregation likely reflects mechanical heterogeneity along the plate interface, controlled by along-dip variations in interplate coupling, effective normal stress, and frictional properties. To quantitatively characterize this separation, we combine W-phase waveform modeling with IDBP constraints and calculate the Frequency Dependence Index (FD Index). For the Kamchatka earthquake, the FD Index is 55%, and the centroids of the high- and low-frequency source regions are separated by approximately 70 km. These results provide quantitative constraints on the along-dip mechanical structure of the megathrust and offer new insight into the generation of strong ground motion and tsunami hazards during giant subduction earthquakes.
The rise of the Tibetan Plateau and the Himalayan Orogen is subject to long-standing, unresolved discussion of possible geodynamic models. Although difficult to assess, the strength of the lithosphere and the depth variation of rheology are key parameters for discriminating between these models. The depth distribution of earthquakes defines the extent of the brittle seismogenic zones and provides first-order constraints on lithospheric rheology. Earthquake catalogues and recent seismological studies suggest that earthquakes occur at all depths in the crust and uppermost mantle of both the Tibetan Plateau and the Himalayas, but hypocentre location is highly uncertain due to poor station coverage. We demonstrate that seismicity is shallower than 25 km depth in the Tibetan Plateau whereas it covers the whole crust and uppermost mantle below the Himalayas, based on our relocation of local earthquakes recorded on a dense network, together with our compilation of earlier relocations in the region. We further interpret a 300–350 km long section of localized steep subduction of the Indian plate below the Himalayas between ∼85°E and ∼88.5°E with implications for regional deformation and seismicity. Our observations of relocated seismicity depth require completely different lithospheric strength profiles in Tibet and the Himalayas. Weak rheology of the mid-lower crust and mantle in the whole Tibetan Plateau facilitates deformation by ductile flow and buoyancy below a 25 km thick brittle upper crust, while strong crust and uppermost mantle support tectonic deformation in the Himalayas. This fundamental contrast explains the difference in deformation processes responsible for the uplift, compression and extension of the Tibetan Plateau and the Himalayas..
Nonstationary extensions of the Epidemic Type Aftershock Sequence (ETAS) model, in which the background rate and triggering productivity vary in time, are increasingly used to infer transient post-seismic processes from earthquake catalogs. Their flexible parameterization, however, raises an identifiability problem: an improved statistical fit may stem from parameter trade-offs rather than from a genuine change in the seismic regime. We present a diagnostic that pairs penalized nonstationary ETAS inference with an independent, model-agnostic anomaly-detection analysis, and ask whether inferred parameter transients are accompanied by observable changes in catalog properties. We apply it to the aftershock sequence of the 2025 Mw 7.1 Dingri earthquake in southern Tibet, for which independent geodetic and mechanical constraints are available. An empirical-Bayes nonstationary ETAS inversion, with smoothing weights selected by ABIC, yields time-varying background rate and triggering productivity, with the strongest variations about 8–10 days after the mainshock. Using an Isolation Forest applied to temporal, magnitude, depth, and spatial features, we find no coherent anomaly during this interval. Semi-synthetic experiments that perturb only the temporal occurrence rate, consistent with the temporal ETAS formulation, together with feature-ablation tests, show that the detector responds primarily to temporal-rate changes and recovers the injected transient when present. The absence of a corresponding anomaly in the real catalog indicates that the inferred parameter variations should be interpreted with caution. More broadly, the results show the value of validating nonstationary ETAS inferences against independent, model-agnostic diagnostics.
Archean cratons represent the oldest preserved cores of continental crust, assembled through over two billion years of magmatism and crustal reworking. This protracted history obscures the nature of the progenitor materials that sourced the Neo- to Mesoarchean felsic rocks dominating most cratons. Although long-lived radiogenic isotopic systems provide insights into crustal evolution, they can be affected by post-magmatic processes, potentially leading to ambiguous interpretations, particularly when characterizing early crustal components absent in the geological record. The coupling of long-lived systems with short-lived isotopic tracers offers a more robust approach to resolving early crustal evolution.Here, we combine 147–146Sm-143–142Nd isotopic systematics with whole-rock major and trace element geochemistry for ca. 3.2 Ga orthogneisses from the Assean Lake Complex (Manitoba, Canada) to constrain the age and origin of their crustal precursors. The 146Sm-142Nd data indicate these Mesoarchean granitoids were derived from multiple crustal sources with distinct formation ages and composition. Sodic tonalite-trondhjemite-granodiorite (TTG) gneisses likely formed by partially melting a hydrated mafic crustal precursor (weighted mean µ142Nd ∼ -3.2) extracted from the mantle near the Hadean-Eoarchean transition. Conversely, coeval granitic gneisses were produced by reworking older TTG-like crust ultimately derived from a Hadean mafic reservoir (weighted mean µ142Nd ∼ -7.1). Together, these results provide direct evidence that the Assean Lake high-K granitoids inherited Hadean isotopic signatures through reworking of older crustal precursors ultimately derived from a Hadean mafic reservoir. They demonstrate that compositionally and temporally distinct crustal reservoirs, including ancient Hadean components, were mobilized and reworked contemporaneously during Mesoarchean magmatism, highlighting the dynamic, multi-source nature of early continental crust formation.
The Moon is currently airless, but intense impact bombardments in its history may have resulted in transient atmospheres on the early Moon. However, the existence and scale of the impact-induced atmosphere have remained speculative. Here, we identified pervasive Na and K in-gassing profiles in Chang’e 6 impact glass beads that were produced from formation of craters with diameters larger than 10 m. These profiles were generated in the impact plumes where both Na and K partial pressures were larger than 10–6 to 10–4 bar. Using mass balance calculations, the total vapor pressures in the impact plumes containing H, N, S, C, Cl, and F could have been larger than 10–5 to 10–3 bar. Combined with lunar impact-flux models, our results imply that impact bombardments could have provided an important mechanism capable of generating a global transient atmosphere on the Moon with high impact flux at ≥4.4 Ga, and younger impacts alone likely only sustained local transient atmospheres as impact flux decreased after 4.4 Ga.
Inferring fault locking depth from interseismic geodetic observations is important to assessing seismic hazard. Interseismic deformation changes with time due to Earth’s viscoelastic rheology, but elastic models commonly employed for estimating locking depths assume time-invariant deformation. Consequently, the apparent locking depth depends on the time when the deformation is observed. In this study, with a focus on large strike-slip faults, we propose replacing the elastic models with an existing analytical viscoelastic model that incorporates time-dependent deformation while maintaining operational simplicity. Using InSAR observations around the Altyn Tagh Fault as illustrative examples, we explain the application of this approach and discuss how to address practical complications of real faults: (1) The use of this model requires knowledge of the earthquake recurrence interval and the time since the last earthquake in terms of the viscoelastic relaxation time. We show a trade-off relation between these two parameters that can be used to assess the ambiguity of inferred locking depth due to their uncertainties. (2) A stiffness contrast across the fault causes asymmetric deformation. We provide an empirical scaling relationship to allow the application of the laterally homogeneous viscoelastic model. (3) Shallow creep of the fault causes discontinuity of surface deformation. We explain that the rate of steady shallow creep without afterslip and slow slip events is controlled by the ratio of the widths (i.e., depth ranges) of the creep zone and locked zone, and we accordingly design a procedure to incorporate shallow creep. (4) Postseismic transients from nearby earthquakes can cause underestimation of locking depth. We demonstrate that modelling the postseismic effect using the same viscoelastic model can enable an effective correction.
Understanding how earthquake energy budgets scale from laboratory to natural faults remains a fundamental challenge in earthquake physics. Laboratory experiments report fracture energies consistent with classical friction, yet seismological observations show that breakdown work scales strongly with slip, and the relationship between these two quantities remains unclear. Here we show that this discrepancy reflects two genuinely different physical quantities: the near-front dissipation governed by rupture-tip processes, which we use as a proxy for fracture energy because these small ruptures sustain no K-dominant field, and the system-scale breakdown work dominated by nonlocal elastic unloading which includes the loading column in our experiments. We conducted stick-slip experiments on 15-cm long granite faults under normal stresses of 1–20 MPa in a double-direct-shear configuration. A dense strain-gauge array tracked rupture propagation, enabling near-front dissipation estimates via cohesive zone modeling, while finite element simulations quantified energy partitioning between the fault and loading system. The near-front dissipation remains low ( < 10 J/m2) and scales roughly linearly with normal stress, consistent with classical friction. In contrast, total breakdown work scales quadratically with slip, exceeding the near-front dissipation by over an order of magnitude. Finite element simulations confirm that elastic unloading of the compliant loading column dominates this energy release. Normal stress heterogeneity on the lab fault produces additional weakening, after the rupture has reached maximum size, without additional dissipative mechanisms. These results demonstrate that apparent breakdown work scaling in laboratory earthquakes can arise from nonlocal elastic effects rather than intrinsic fault weakening. Our work provides a framework for distinguishing local near-front dissipation from system-scale energy release and breakdown work when extrapolating laboratory results to natural faults.
To investigate whether the presence of helium in apatite slows fission track (FT) annealing, we performed isothermal annealing experiments on large Durango apatite crystals in which we had created He-depleted rims and He-retaining cores. Single crystals were annealed at 310 °C under vacuum for 30–270 min to stimulate helium diffusion and damage annealing, after which spontaneous FT lengths were measured separately in rim and core regions. An unannealed control sample showed no rim–core length difference, indicating negligible geometric or etching bias. With increasing annealing duration, rim tracks shorten more than core tracks, and rim–core length distributions and means diverge significantly after ∼90 min. We interpret this rim–core contrast as evidence that helium impedes FT annealing, consistent with helium stabilization of defect structures known to occur in irradiated solids. These results imply that FT annealing kinetics is affected by helium content, with potential consequences for both apatite FT and (U–Th)/He thermochronometry.
