Thermal pressurization driven by frictional heating is a potentially important dynamic weakening mechanism in low-permeability clay-rich fault gouge, producing reduced frictional resistance with limited temperature rise. However, geological evidence of high-temperature coseismic processes recorded in such fault rocks suggests that mechanisms capable of reducing the effectiveness of thermal pressurization have also operated. Here, we report coseismic dilatancy in foliated gouge from the Yangsan fault, a large strike-slip fault in southeastern Korea, and discuss its implications for thermal pressurization efficiency and fluid redistribution. Our observations include gouge injection structures (IV type) penetrating into the surrounding rock, foliation opening structures (F type) within the gouge, and calcite aggregates precipitated within these structures. The IV type is interpreted to record coseismic extension fracturing of the surrounding rock under fault-parallel dynamic tension, whereas the F type is inferred to reflect the opening of foliation driven by thermal pressurization. The formation of these structures may have caused a rapid drop in fluid pressure, potentially diminishing the effectiveness of thermal pressurization and promoting fluid redistribution. Our findings suggest that gouge foliation, while acting as a fluid flow barrier that promotes thermal pressurization, may simultaneously serve as a mechanically weak plane that, once opened during seismic slip, reduces its efficiency by providing a pathway for fluid flow. Notably, the postseismically precipitated calcite aggregates within these coseismic opening structures may represent promising targets for directly constraining the timing of past seismic slip using U-Pb or U-series dating.
The mantle sources of carbonatite and alkaline magmatic systems that host rare earth element (REE) deposits are difficult to constrain because whole-rock compositions are commonly altered. Alteration-resistant zircon trace-element compositions are used to fingerprint mantle sources at Mountain Pass, California, the largest REE deposit in the United States, and extend this approach to a global carbonatite−alkaline rock dataset. Autocrystic zircon samples from the Mountain Pass intrusive suite record subduction-like U-Sc-Nb-Yb compositions, oxidized fO2 (0.8−2.4 relative to fayalite-magnetite-quartz buffer [ΔFMQ]), and Ti-in-zircon temperatures up to ∼970 °C, indicating a lithospheric mantle source enriched and oxidized by Paleoproterozoic subduction and subsequently tapped during Mesoproterozoic postcollisional lithospheric thinning. This contrasts with the ocean island basalt−like enriched mantle recorded by Mesoproterozoic zircon from the Bayan Obo carbonatite complex, China, demonstrating that world-class REE deposits of comparable age can reflect fundamentally different mantle sources. New classifiers separate subduction-metasomatized from non-subduction-enriched mantle domains with ∼90% accuracy, providing a zircon-based tool for fingerprinting the mantle source regions of magmatic REE deposits.
Arctic Alaska’s eastern Brooks Range and coastal plain host large earthquakes and active folds, but the rates and drivers of deformation in this setting—over 1000 km north of the Yakutat−North American plate boundary—have been elusive. We show that 101−105-yr-averaged deformation rates decay northward across Alaska from near-plate-rates above the Yakutat microplate flat-subduction zone to the eastern Brooks Range, where GPS velocities accord with ≤1 mm/yr of distributed NNE-trending seismic left shear. On the adjacent coastal plain, we estimate ∼0.4−1.6 mm/yr late Quaternary shortening across the kinematically compatible Marsh Creek anticline. Moho depth and lower-lithosphere temperature models imply that the crust may transfer Yakutat microplate strain >1000 km north along compatible stress directions via faulting, lower crustal detachment, and distributed seismic deformation to drive active folding of the Arctic coastal plain. Oppositional Chersky−Gakkel−Atlantic plate boundary forces may buttress and/or amplify the Yakutat-driven deformation.
The Grand Canyon encompasses two billion years of Earth history, but more than half this record is absent across a regionally extensive erosional surface known as the Great Unconformity. This enigmatic surface has been linked to multi-phase regional tectonics accompanying supercontinent assembly and breakup and to Cryogenian glacial erosion. Although rift-related uplift during the breakup of Rodinia has long been implicated in erosion associated with the Great Unconformity, we argue that exhumation in the Grand Canyon region was focused along a continent-scale rift-flank escarpment. This “Great Escarpment of Laurentia,” initiated ca. 800−750 Ma, occupied a position analogous to major escarpments generated during Mesozoic Gondwana breakup and experienced similar magnitudes of exhumation. Our landscape evolution models simulating rift-driven topography suggest that rocks within several hundred kilometers of this feature endured substantial erosion, reaching 8 km near the escarpment and decreasing to ≤2 km at lateral distances of ∼200 km from its peak. Such differential erosion, evidenced in prior thermochronology models, necessitates exhumation of mid-crustal basement lithologies including along reactivated crustal fault blocks. This model helps explain the variable magnitude of erosion associated with the Great Unconformity in the southwestern United States.
Carbon cycling into Earth's interior regulates long-term climate and habitability, yet the fate of subducted sedimentary carbon remains widely debated. Competing models predict either efficient carbon release from the subducting slab and surface return or massive deep sequestration into the mantle. Here, we present coupled Mg and Zn isotope systematics of Oligocene adakite-like granites derived from partially melted metasediments previously relaminated into the lower continental crust. The granites display variable delta 26Mg (-0.41%0 to +0.02%0) and delta 66Zn (0.27%0 to 0.46%0) values that define a negative correlation, trending from silicate sediment signatures toward isotopically lighter Mg and heavier Zn characteristic of carbonates. These signatures indicate recycled contribution from carbonate-bearing sediments to the magma source. We propose that diapiric relamination of carbonate-bearing sediments during subduction represents an efficient mechanism for storing carbon in the deep crust, thereby helping to resolve the imbalance between subducted and released carbon at convergent margins. Partial melting of such relaminated carbonate during the postcollision stage may subsequently act as a potential driver of atmospheric CO2.
Abstract Mississippi Valley-type (MVT) deposits are important sources of Pb, Zn, and critical metals such as Ag, Ga, and Ge. However, their metal sources and the mechanisms behind the formation of giant deposits remain contentious. Here, we address these questions by studying Hg-Pb isotope signatures of MVT sulfides and potential source rocks in the southeastern Yangtze block. These data reveal that the ore metals come from at least two upper-crustal sources: shallower sedimentary rocks and deeper metamorphic basement. The giant deposits show isotopic signatures compatible with increased metal input from the deeper basement. Together with higher ore-fluid temperatures and salinities, as well as preferential localization of larger deposits along major fault intersections, this suggests that large MVT deposits form where specific geological factors coincide during regional orogeny, driving high fluid fluxes and deep fluid circulation. These can efficiently mobilize metals from basement rocks and concentrate them in shallow carbonate traps.
We present a new, comprehensive carbon isotope (δ13C) compilation for the Triassic that demonstrates a strong coupling between volcanic forcing, carbon cycle stability, and the evolution of ecosystems. The first ∼25 m.y. of the Triassic were characterized by profound δ13C volatility, initiated by the Siberian Traps eruptions and concluding with perturbation linked to the Wrangellia large igneous province. Such volatility is manifested by major negative δ13C excursions as large as ∼8‰−10‰, followed by positive shifts largely reflecting enhanced carbon burial during ecosystem recovery. During the final ∼25 m.y. of the Triassic (Norian−Rhaetian), δ13C variability declined to ∼2‰, indicating a transition to long-term carbon-cycle stability. This stabilization coincided with a reduction in major environmental crises as resilient, modern-style ecosystems became firmly established.
Abstract Ice sheets and atmospheric circulation are tightly coupled, yet gaps remain in defining glacial anticyclonic wind patterns in both models and proxy data. Using high-resolution digital elevation models, we discovered >3000 relict iceberg scour marks on Late Pleistocene proglacial lake beds spanning >1000 km in the eastern Great Lakes, USA. We propose that iceberg scour marks spanning the last deglaciation (ca. 17–12 calibrated k.y. B.P.) act as paleowind proxies that record the anticyclonic wind system fronting the Laurentide Ice Sheet. Easterly winds steered iceberg drift, producing scour marks oriented WSW (258° ± 19°), the same general orientation as regional dune fields and longshore drift. Relict thermokarst lakes discovered in our study area are found to be impacted by the same wind system. Our discoveries provide the most extensive record of relict iceberg scour marks in the Great Lakes and offer evidence for sustained easterly winds driven by the Laurentide Ice Sheet glacial anticyclone fronting ~5000 years of ice sheet recession.
Abstract Rare-metal granites and pegmatites are commonly interpreted to form either by extreme fractionation of granitic magmas or by low-degree crustal melting. Despite renewed interest in the anatectic model, the mechanisms governing Li release into melts and whether crustal melting alone can concentrate Li to ore-grade levels remain debated. Here, we present the first comprehensive database of Li concentrations in anatectic melt inclusions, providing direct constraints on the Li budget of primary melts formed under typical mid- to lower-crustal pressure-temperature (P-T) conditions and compositions. The dataset shows that Li release into anatectic melts is optimized during early, fluid-absent equilibrium melting of biotite at 750–800 °C in cordierite-free rocks, reaching up to ~600 μg/g Li. Although these concentrations exceed those of S-type granites, they overlap the range of barren pegmatites, indicating that extreme fractionation is required to produce hard-rock Li ores. Integration of natural constraints with petrological modeling suggests that direct generation of ore-forming Li enrichments (3000–20,000 μg/g Li) requires strongly pre-enriched sources (600–2000 μg/g Li, i.e., >20 times ordinary crustal abundances). Given the lack of compelling evidence that such sedimentary sources retain Li anomalies up to anatectic conditions, the formation of hard-rock Li ores of anatectic origin likely reflects the convergence in space and time of favorable melting mechanisms, P-T conditions, and tectonic controls enabling rapid melt extraction and extensive fractionation—a convergence that, although rare, is preferentially achieved during the waning stages of orogenic cycles.
Abstract Modern lake triple oxygen isotopes (17O-excess [Δ′17O], δ18O) can be used to distinguish flow-through from closed-basin systems and to quantitatively model precipitation composition and evaporative loss. Extending this framework to paleolake carbonates enables new hydrologic and climate reconstructions. For example, regional hydrologic models suggest that cold temperatures and reduced evaporation, not increased precipitation, sustained large Last Glacial Maximum (LGM) lakes. But this has not been tested with proxies sensitive to lake hydrology. We quantitatively assessed changing evaporation and temperature conditions at Pleistocene Lake Bonneville (Utah, USA), the LGM counterpart of the Great Salt Lake, using Δ′17O and clumped isotope (Δ47) analyses of modern lake water and lacustrine carbonates. We measured the Δʹ17O, δ18O, and Δ47 of 26–18 ka Lake Bonneville gastropods, tufa, and deep-lake carbonate. Δ47 values consistently indicate paleolake waters 6–12 °C below modern. Δ′17O–δ18O data place Lake Bonneville with modern flow-through lakes and clearly separate it from evaporative systems like the Great Salt Lake. Combined Δ′17O and Δ47 analyses robustly characterize paleolake hydrology and provide new proxy-based support for the lower-temperature, lower-evaporation hypothesis. We find via Δ′17O–based reconstruction of meteoric δ18O that LGM precipitation had higher Δ′17O values than modern. One explanation is that regional LGM moisture was sourced from higher latitudes, as a southward westerlies shift would drive ice-adjacent air masses toward the lake.
Abstract Determining the timing of mineralization in orogenic gold systems is a major challenge, given the difficulty of constraining fluid flow events and linking them to gold enrichment. However, it is critical for assessing whether world-class gold deposits result from a single mineralizing event or a multi-stage Au mobilization. In Paleoproterozoic settings, minerals suitable for precise dating of fluid flow are rare, and relying solely on intrusion-related geochronology may prove insufficient. In this context, combining detailed microstructural analysis with petrochronological data provides valuable insights into the tectonic and metallogenic evolution of deposits. In situ U–Pb dating was conducted on both zircon and apatite to investigate the timing of magmatism, deformation, and gold mineralization at Oko West, Guyana. Zircon and apatite ages from intrusive bodies indicate a magmatic event at ca. 2125 Ma, with apatite yielding the same age as that of zircon. Interpretation of the apatite U–Pb data set from mineralized volcano-sedimentary rocks was integrated with microstructural constraints on deformation and fluid flow. Apatite associated with metamorphic fluids and gold-bearing sulfidation records two successive stages at ca. 2100 Ma and ca. 2065 Ma, respectively. The clear temporal gap between the intrusion and the second mineralization stage supports the interpretation of at least two distinct geological events, the latter associated with post-magmatic gold mobilization. These results highlight the suitability of apatite U–Pb geochronology for resolving multi-stage gold deposition during the Rhyacian.
Mud volcanism is a widespread geological phenomenon characterized by spectacular mud flow deposits extending for kilometers. However, only a few eruptive events have been reported to be long-lasting and voluminous enough to create such extensive flows. We report findings from a multidisciplinary investigation conducted after three eruptions occurring since August 2022 at the Lokbatan mud volcano in Azerbaijan. During these three short-lived events, only a moderate volume of mud breccia was expelled around the crater site. However, field observations show that these events promoted the downslope motion of the >1-km-long older mud flow. Electrical tomography reveals a conductive unit at similar to 25 m depth below the volcano, which lubricates the detachment upon which sediments slide. Cross-checking legacy satellite imagery (from 2009) combined with InSAR data (from 2014) reveals that this type of movement was already occurring as early as 2009, indicating a long-lasting process. Our findings suggest that kilometer-sized mud flows observed at other mud volcanoes may not stem from single, voluminous eruptions, as previously thought, but from gradual sliding processes initiated by new loads of erupted material. This mechanism is essential for understanding the dynamics of mud volcanoes on Earth.
Whether Earth's continents developed continent-scale highlands comparable to the Tibetan Plateau and Cordilleran systems in the past, and what governed their formation, remains a fundamental question. Here, we present the first globally consistent reconstruction of continental paleoelevation over the past 4 b.y., integrating a global igneous geochemical dataset (>100,000 samples) with machine-learning-derived crustal thickness and time-varying isostatic modeling. Continents remained largely underwater through most of the Archean, progressively emerging in the Neoarchean. Since ca. 2.1 Ga, extreme elevations recurrently exceeded Tibetan-level thresholds (similar to 4.5 km; 95th percentile), forming laterally coherent, continent-scale orogenic systems. These super-highland intervals broadly coincide with major supercontinent assembly phases, including Columbia (Nuna), Rodinia, Gondwana, and Pangea. Spatial clustering further shows that these extreme elevations formed organized orogenic belts rather than isolated topographic highs. In contrast, the Mesoproterozoic exhibits persistently subdued topography and weak orogenic clustering, reflecting sluggish plate convergence and inefficient crustal thickening, favoring distributed, low-relief deformation. Renewed orogenesis in the Stenian to Tonian (ca. 1.1-0.9 Ga) briefly restored high elevations before Rodinia breakup. After Rodinia's breakup, extreme elevations became more sustained, consistent with a cooler and mechanically stronger lithosphere under a more efficient convergent regime. These results show that laterally extensive orogenic super highlands have recurred since the Paleoproterozoic and were controlled by the coupled evolution of plate kinematics and lithospheric strength. The Mesoproterozoic marks a pivotal transition toward the colder, stronger-lithosphere configuration that governs modern orogeny.
Abstract Oceanic transform faults (OTFs) accommodate a substantial proportion of tectonic plate motion aseismically. Systematic along-strike coupling patterns have been observed at both fast and slow OTFs. Patches of high-coupling rupture regularly, generating earthquakes of magnitude (M) greater than 5.5. These zones are separated by regions of low coupling that act as barriers to rupture propagation. The mechanisms controlling these persistent barrier zones remain poorly understood. We used magnetotelluric (MT) methods to image a rupture barrier on the westernmost Gofar oceanic transform fault, a left-lateral fault offsetting the East Pacific Rise near 5° S. Our results reveal heterogeneity within the barrier zone: a high-conductivity western section and a low-conductivity eastern section, which also exhibit distinct patterns in seismicity and surface structure. The electrical resistivity model derived from the MT data suggests porosity on the order of 3% through much of the crust in the western section, which likely results from seawater infiltration facilitated by a highly damaged fault zone. Fluid infiltration would promote alteration and low coupling, and could explain the long-term seismic deficit of the barrier. Under such conditions, dilatancy-induced pore-pressure fluctuation could exert control on seismicity and slip mode, including arresting adjacent M 6 ruptures. Seismic behavior in the eastern barrier zone differs from the western barrier zone, possibly due to differences in fluid content. Taking the Gofar barrier as an analog, aseismic OTFs around the world may have fluid-rich fault zones with rupture behavior regulated by hydromechanical processes.
Squids (Orders Oegopsida and Myopsida) are an essential component of the modern marine ecosystem, having high biodiversity and a huge biomass. Their global distribution, owing to their elaborate locomotor systems, is a key feature that has made them a very successful group of nektonic organisms. They originated at the Early-Late Cretaceous boundary (100 Ma), but records of early squids are extremely scarce due to the low fossilization potential of their shell-less body. Squids of Cretaceous age are so far only known from the northwest Pacific Ocean; therefore, to understand their early radiation, paleobiogeographic investigations are required. Here, we discovered new oegopsid squid fossils from late Maastrichtian sediments (ca. 67 Ma) in South Dakota. These sediments were deposited in the Western Interior Seaway, a vast inland sea that existed in North America. This is the first documentation of Cretaceous squids outside the Pacific. Based on beak morphology, these fossils are assigned to two new species, Scuthoteuthis concavus sp. nov. and Fringillorostrus simplex gen. et sp. nov. The morphological similarity between the new species and contemporaneous squid taxa from the northwest Pacific Ocean suggests that they emerged from the same ancestors. Since the Western Interior Seaway is a region most distant from the northwest Pacific, our results indicate that squids had already radiated globally before the Cretaceous−Paleogene mass extinction (66 Ma).
Reduced phosphorus (P), in particular phosphite [P(III)] has been identified as a potentially key ingredient for prebiotic chemistry that may have facilitated the phosphorylation of organic compounds. One possible source of reduced P is asteroid impacts. To test this hypothesis, we investigated P redox speciation across an impact deposit that formed at 3.26 Ga in the Barberton Greenstone Belt in South Africa and that has previously been linked to extraterrestrial delivery of phosphate [P(V)]. Our results show that at least 0.1% of the total P that was delivered by the impactor was indeed in reduced form. In addition, we found a persistent background of 10-200 ppb P(III) in all samples, independent from the impact layer. This background may be explained by post-depositional silicifying fluids that mobilized P(III) from underlying oceanic crust. We conclude that asteroid impacts and hydrothermal fluids could have provided reduced P to the early oceans and supported the origin and early evolution of life.
The prograde breakdown of hydrous minerals like lawsonite is energy-intensive and releases fluids at depths coincident with extensive slow earthquake phenomena for many subduction geotherms. However, there remains inconsistency between the spatial occurrence and inferred temporal rates of these dehydration reactions relative to the episodic character of slow earthquakes. The example of lawsonite breakdown shows that dehydration reactions will dictate heat consumption, thus buffering the rate of temperature increase for a rock undergoing intervals of metamorphism (<30 °C) and delaying each small increment (∼1 °C) of fluid release. A nonlinear behavior is predicted involving periods of fast fluid release paused by periods of slower heat absorption. Such stepped reaction progress is consistent with natural rock textures of lawsonite breakdown indicating intermittent fluid-present crack propagation and associated step changes in mineral growth. Pulsed fluid flow into rocks of heterogeneous permeability may result in stress build-up enabling crack propagation and slip at different scales. Energetics of punctuated dehydration and resultant fluid flow match temporal and spatial characteristics of slow slip behavior. Consequently, episodic dehydration is suggested as a viable trigger for slow slip.
Abstract Cryogenian (717–635 Ma) Snowball Earth glaciations are the most extreme episodes of climate change in the geological record, but their impact on landscapes and environmental change remain uncertain. Some climate models predict thin, cold-based, stable ice sheets, with low sliding velocity and minimal erosion, whereas others predict thick, warm-based ice sheets that were sensitive to orbital forcing and highly erosive. These models make predictions for the stratigraphy, sedimentation rates, and provenance of deep-water deposits. The Zerrissene fan in Namibia is a Cryogenian–Ediacaran turbidite succession that records the deep-sea sedimentary response to the Marinoan (639–635 Ma) glaciation. We report the stratigraphically lowest traceable horizon of dropstones in the upper Brak River Formation of the Zerrissene Group, which we interpret to record Marinoan Snowball glacial onset in a deep-water setting. The youngest zircon grain in a preglacial detrital sample 153 m below this horizon yields a concordant chemical abrasion–isotope dilution–thermal ionization mass spectrometry date of ca. 642 Ma, which is consistent with Marinoan onset at ca. 639 Ma. In contrast with glacially influenced Pleistocene deep-sea fans, for which intensifying glaciation has driven accelerated sedimentation, provenance variability, and sea-level–mediated progradation, the Brak River Formation exhibits none of these responses to glaciation. The insensitivity of deep-sea sedimentary dynamics to Snowball Earth glaciation conflicts with the hypothesis of expansive syn-Snowball continental denudation. Instead, the continuity of deep-sea sediment routing is consistent with a cold-based, stable Snowball ice sheet with low sliding velocity and minimal erosion.
