Journal of Geophysical Research: Solid Earth最新文献

In this study, we demonstrate that it is possible to fit the resilience at the high temperature limit using only the atomic mean square displacement determined from cryogenic temperature single crystal diffraction data. Our method introduces the Debye phonon model, under which the atomic mean square displacement displays quantum behavior at cryogenic temperatures and deviates from a linear temperature dependence. From the resilience of Si extrapolated from cryogenic temperature X-ray diffraction data, one can calculate the Si isotope fractionation using our recently developed force constants approach. We applied our method to epidote and coesite, which are common minerals in ultra-high pressure metamorphic rocks, and our predicted Si isotope fractionation lnα_Si30/28 are consistent with mass spectroscopy observations of Δ³⁰Si in Dabie eclogite and Alps whiteschist. Our results indicate that the geofluid involved in the fluid-rock interaction in Dabie and Alps orogens doesn't significantly alter the Si-isotope composition of ultrahigh pressure metamorphism. Our manuscript presents a novel experimental methodology to determine the high-temperature resilience and equilibrium isotope fractionation factors of silicon in minerals, which can be applied to the metastable upper mantle silicates that are non-quenchable at high temperatures and room pressure.

Mantle convection causes the most important contribution to the geoid and dynamic topography. With mantle density inferred from high-resolution tomography models and numerical methods solving the governing equations of viscous mantle flow, the modeled geoid can fit the observations well. However, there is still a large discrepancy between present dynamic topography predicted by mantle flow and residual topography deduced from observations: Especially, large negative topography is predicted in cratons, contrary to observations. In order to improve the fit of model dynamic topography compared to observations, in this study, we include chemical density anomalies in Earth's lithosphere to model geoid and dynamic topography. We also combine these anomalies with lateral viscosity variations and study the effect on predicted dynamic topography and geoid and investigate which density models would yield a good fit. In the sublithospheric mantle, under the assumption that the density anomalies are induced from temperature variations, we use temperature-dependent viscosity. Our results show that by adding chemical density anomalies in the continental lithosphere, we can improve the correlation between dynamic topography and residual topography by 37%–59% for the three tomography models compared with one of the residual tomography models considered (RT1) and 1%–11% compared with the other (RT2). Similarly, correlation can also be improved and amplitude ratio brought closer to 1 by downscaling lithospheric density anomalies. Our results could provide a good reference for further studies of the Earth's mantle.

What happens when subduction stops is a key, but poorly understood, part of the tectonic cycle. Northern Borneo (Sabah) with a complex geological history of multiple episodes of subduction, magmatism, uplift, subsidence, and extension since the Mesozoic, is an ideal location for studying post-subduction processes. Major events in this region include subduction of the proto-South China Sea beneath Sabah, terminating ∼21 Ma; postulated subduction of the Celebes Sea plate, terminating ∼9 Ma; extension in central Sabah ∼9–10 Ma; rapid emplacement and exhumation of a granite intrusion ∼7 Ma; and the development of a fold-thrust belt offshore during the last 5 Myr. While these events have left imprints in the surface rock record, it has not been possible, until recently, to investigate deeper lithospheric processes. The installation of 46 broadband seismometers–the northern Borneo Orogeny Seismic Survey (nBOSS)–between 2018 and 2020 means we can now constrain the architecture of the crust and uppermost mantle beneath Sabah. We use two years of passive seismic data recorded by the nBOSS network, and 24 Malaysian Meteorological Service broadband seismometers to calculate P-wave receiver functions. We then jointly invert these with surface wave data to obtain shear velocity models of crustal structure. The thickest crust (60 km) occurs beneath the Crocker Range, while the thinnest crust (24 km) is found in central Sabah, potentially recording Miocene extension. The crust beneath Mt Kinabalu (4,095 m) is also comparatively thin. Distinct, low-velocity, dipping anomalies identified in models provide clear evidence for under thrusting of Dangerous Grounds continental crust following subduction and collision.

Ongoing climate change is leading to an increase in prolonged droughts and severe weather events, which are particularly pronounced in semi-arid regions, such as the western United States. These extremes could have lasting social and environmental impacts. Continuous monitoring of near-surface hydrological processes and groundwater resources provides helpful information for effective water resource management. The seismological signature of groundwater fluctuations is clear in the temporal variations in seismic velocities, dv/v. To this end, developing a proxy for groundwater level using dv/v represents an opportunity, but further understanding of the relation between dv/v and subsurface hydrology is required. In this study, we apply single-station cross-component correlation analysis to 28 broadband seismic stations in Utah between January 2006 and March 2023 and analyze the dv/v in the 2–4 Hz frequency band. To explain dv/v, we linearly superimpose thermoelastic stresses, soil moisture estimated from remote sensing data products, and a long-term deep water table pore pressure. We find that the relative contributions of each depend on the location. Still, adding a long-term water table decline, which is not systematically observed in soil moisture, better fits our data. We conclude that soil moisture alone does not explain the variations in total water storage when subsurface moisture is decoupled from the deep-water table. We also conclude that dv/v can be used as a proxy for water storage.

Basalt mineralization storage is widely recognized as a secure, permanent method for large-scale CO₂ sequestration. At present, the majority of research endeavors are centered around the investigation of reaction mechanisms and microscopic properties. However, research on standard basalt rock samples (before/after storage) and the quantification of CO₂ consumption during reactions remains limited. This study explored CO₂-water-rock interactions, focusing on how mineral carbonation alters rock physical/mechanical properties and how to characterize CO₂ consumption rate. Experiments were conducted using a self-designed rock reactor on standard cylindrical basalt samples (from Wenchang, Hainan) under 12 MPa and 70°C for 0, 10, 20, 30, and 60 d. A theoretical CO₂ consumption calculation method (based on pressure drop, accounting for gas-liquid-solid three-phase systems) was proposed. Validated against actual consumption data (from water and rock weigh changes in the reactor), it showed an average absolute deviation (AAD) <5%, confirming high reliability. CO₂ consumption data were fitted with a double exponential function to derive the reaction rate curve, which peaked initially, then decreased continuously, and finally flattened. Changes in uniaxial compressive strength, tensile strength, Poisson's ratio, elastic modulus, porosity, T₂ and mineral composition were observed at different reaction times. Though siderite and calcite precipitated on sample surfaces, rock dissolution dominated—increasing porosity, reducing mechanical properties and leaving yellowish-brown precipitates (more pronounced with longer reactions). These findings support safety evaluation of basalt reservoirs.

Myanmar is located on the eastern margin of the India-Eurasia collision zone, where the Indian sub-continent is subducting beneath the Burma microplate. Magmatic processes during subduction and collision in orogenic belts are significant and well-studied for oceanic subduction; however, the magmatism associated with continental subduction remains poorly understood. Seismic attenuation is highly sensitive to changes in lithospheric thermodynamics and fluid content. Understanding arc volcanism is vital for comprehending a key manifestation of subduction-related processes. However, there is still no high-resolution 3D attenuation model for this region. Here, we use the coda-normalized method to image the lithospheric-scale 3D attenuation structure in the Indo-Burma subduction zone. Our results reveal high attenuation in major sedimentary basins. The prominent high-attenuation anomalies in the mid-to-lower crust of the Indo-Burma Ranges (IBR) may represent thick, fluid-rich sediments scraped off from the subducting Indian Plate and accumulated beneath the IBR. Low-attenuation anomalies at depths of 30–50 km beneath the Monywa volcano are a clear signature of a cooled mantle wedge, which currently overlies strong attenuation anomalies deeper than 50 km, likely associated with the upwelling of hot asthenospheric material. Compared to oceanic subduction systems, the insufficient water content of the continental subduction plate, coupled with the compressional regime induced by oblique subduction, leads to weak attenuation within the mantle wedge.

We present elemental geochemistry and multiple isotopic systematics (Re-Os, Lu-Hf, Sm-Nd and Sr) for mantle peridotite xenoliths from Lashaine in northern Tanzania. We use the data to examine how the major Proterozoic tectono-thermal events that affected the crust of the western Tanzanian craton are imprinted on the lithospheric mantle in the Mozambique belt adjacent to the eastern margin of the Tanzanian craton. Whole-rock and mineral compositions together with ¹⁸⁷Os/¹⁸⁸Os ratios of Lashaine peridotites are consistent with Archean-aged cratonic mantle assembled to create the root beneath the Tanzanian cratonic nucleus. Highly radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.70411−0.83604), unradiogenic Nd (ɛNd = −14 − +2) and variable Hf isotope ratios (ɛHf = +4 − +2,912) of minerals combined with the other geochemical features in Lashaine peridotites reflect extensive melt extraction followed by metasomatic enrichment of the lithospheric mantle by subduction-related melts/fluids. Mineral Lu-Hf isotopic compositions define a 1.4 Ga isochron and, together with the distinctive, robust Lu-Hf model age (1.4 Ga) of one garnet with very high ¹⁷⁶Lu/¹⁷⁷Hf ratio (3.182), indicate that a major Mesoproterozoic subduction-related metasomatic event reset Lu-Hf isotope systematics of the Lashaine peridotites. This over-printing of the mantle lithosphere indicates a clear link to the Mesoproterozoic Kibaran event along the western margin of the Tanzanian craton. We invoke a flat-slab subduction model during the Kibaran event to introduce subduction-related components in a pervasive Mesoproterozoic metasomatic event beneath Lashaine.