• High spatial resolution laser ablation U-Pb zircon dating afforded by depth profiling indicates >50 Myr duration of batholith crystallization. • This duration, deduced from zircons from single samples, implies a history of mush crystallization followed by re-melting. • Preservation of zircons suggest mush temperatures remained below zircon saturation for long periods. • Long-lived mushes were sustained by a regional flare-up providing heat and H 2 O to the system. • Batholith intrusion also triggered the anatexis of its host rock that also lasted tens of million years. Accurate constraints on magma crystallization timescales at convergent margins are critical for understanding arc thermal evolution and crustal differentiation. Prolonged zircon crystallization beyond single magmatic pulse timescales challenge rapid magma cooling models, yet how the durations of crystallization are recorded by zircons remains unclear. To clarify this, we dated zircons from the lower crustal Gangdese arc including the Cretaceous Lilong batholith and its Jurassic tonalite host rocks, both remelted into migmatites. High-resolution depth-profile dating via laser ablation-inductively coupled plasma-mass spectrometry resolved multiple date domains within individual zircons from rims towards the core, with an average width of 12 μm, providing precise reconstruction of magmatic timescales. Combining dates with chemistry of different date domains, we found that the younger Lilong batholith experienced ∼40 Myr of mush crystallization and subsequent re-melting for ∼30 Myr, with a 10 Myr overlap. The older host Jurassic tonalite records ∼50 Myr long crystallization and ∼40 Myr of re-melting triggered by the Lilong batholith intrusion, with a 10 Myr hiatus. These findings record a repetitive process of intrusion and re-melting over 100 Myr, indicating deep arc roots can remain near solidus conditions in a mushy state for tens of millions of years, causing prolonged zircon crystallization recorded in individual rock samples. These mushy magma reservoirs may either crystallize or be re-melted by heat and aqueous fluids flow into the crust during regional magmatic flare-ups. Long-lived lower crustal mushes allow extraction of evolved melts from increasingly residual cumulates, and may occur throughout the lifespan of an arc driving crustal differentiation.

Breakup of strong cratonic lithosphere causes extensive magmatism at continental margins.

ABSTRACT Recent geological surveys and drilling of scientific exploration well QK‐1 in the Qiangtang Basin have confirmed that the Middle Jurassic Xiali Formation comprised a thick evaporite sedimentary sequence with regional continuous distribution crucial for sealing hydrocarbon resources. However, the formation of these evaporites is still debated, with some attributing their development solely to climate while others emphasise the control of basin tectonics. Here, field outcrop investigations combined with sedimentological, geochemical and clay mineral content analyses of the evaporite‐bearing sediments from well QK‐1 were conducted. Geochemical paleoclimate indicators, including clay mineral content, Sr/Cu, Sr/Ba and other proxy data derived from fine‐grained interlayers in evaporite sedimentary sequences, suggest a climatic shift from semi‐humid to prevalent arid conditions, associated with a progressive increase in paleosalinity during deposition of the Xiali Formation. Provenance analysis of the Xiali Formation is interpreted based on bivariate diagrams (K 2 O/Na 2 O‐SiO 2 , TiO 2 ‐Al 2 O 3 , TiO 2 ‐Zr), along with elevated REE signatures and (La/Yb) n , which reveal that the detrital material was primarily derived from felsic and intermediate igneous rocks within active continental margin and continental island‐arc tectonic settings. Increased tectonic subduction during the Middle Jurassic led to the development of a semi‐enclosed, tidal flat‐lagoon depositional environment in the northern Qiangtang Depression. This indicates that the coupled interplay between enhanced arid paleoclimate and a semi‐enclosed basin configuration jointly controlled the formation of the thick evaporite succession in the Xiali Formation. These findings provide new geological evidence for elucidating evaporite depositional mechanisms and their crucial role in sealing and preservation of hydrocarbon resources in the Qiangtang Basin.

In recent years, an ion-adsorption type REE deposit has been discovered for the first time in the weathering crust of epimetamorphic rocks in Ningdu County, Jiangxi Province, which provides a new idea for the exploration of ion-adsorption-type REE deposits. However, most previous studies on the ore-forming parent rocks of ion-adsorption-type REE deposits have focused on granites and volcanic rocks, while studies on epimetamorphic rocks remain extremely scarce. In this paper, petrographic analysis of epimetamorphic rocks, LA-ICP-MS U–Pb dating and trace element analysis of zircon and apatite were conducted on the metamorphic tuff from the Kuli Formation in Ningdu County, Jiangxi Province, so as to constrain the formation age and tectonic dynamic setting of the rock mass, investigate the petrogenesis and material source of the rock mass, and reveal the metallogenic potential of the rock mass. The results of zircon and apatite U–Pb dating show that the protolith of the metamorphic tuff from the Kuli Formation formed at ca. 700 Ma, representing a product of mid-Neoproterozoic magmatic activity. The protolith restoration of metamorphic rocks suggests that the protolith of the metamorphic tuff from the Kuli Formation is magmatic rock. The estimated results of zircon Ti thermometry indicate that the magmatic crystallization temperature ranges from 623 to 723 °C, with an average value of approximately 696 °C, and the calculated zircon oxygen fugacity values vary from −18.7 to −9.4, with an average of −13.8, implying that the rock formed under conditions of relatively low temperature and high oxygen fugacity. The correlation diagrams of trace elements and element ratios in zircon and apatite reveal that the magmatic evolution involved extensive fractional crystallization of minerals such as zircon, monazite, apatite, titanite, rutile, and plagioclase during the formation of the rock mass. The discrimination diagrams of trace elements in zircon and apatite demonstrate that the metamorphic tuff from the Kuli Formation was formed in a continental margin arc or arc-related orogenic belt, and the magmatic source is characterized by crust–mantle mixing. Combined with previous research findings on regional tectonic-magmatic activities, it can be concluded that the metamorphic tuff from the Kuli Formation was formed in a tectonic setting of back-arc extension and intra-arc rifting caused by the rollback of the subducting oceanic slab. The upwelling of the asthenospheric mantle induced the partial melting of arc-derived sediments in the continental crust, which was subsequently mixed with mantle-derived magma, ultimately generating the parent magma of the metamorphic tuff. The metamorphic tuff from the Kuli Formation in Ningdu County, Jiangxi Province, has high REE abundance and relatively easily weathered REE mineral assemblages, which can provide sufficient material sources for ion-adsorption REE mineralization and have a great metallogenic potential for ion-adsorption REE deposits.

Bayesian tectonic subsidence modeling supports polyphase extension of the western continental margin of Laurentia

This study investigates the rare-earth element (REE) geochemistry of twenty-nine clastic rock samples from the Paleogene Liushagang Formation in the Weixi’nan Sag. The primary objectives were to quantitatively evaluate the depositional paleoenvironment, determine the provenance lithology, and constrain the tectonic setting of the source area. Results reveal distinct chondrite-normalized REE distribution patterns characterized by light REE (LREE) enrichment, relatively flat heavy REE (HREE) segments, and pronounced negative Eu anomalies. The cerium anomaly index (Ceanom, normalized to the North American Shale Composite) ranges from −0.06 to 0.00, implying broadly suboxic to anoxic-reducing conditions in the water column during deposition. The chondrite-normalized (La/Yb)N ratio, utilized as a proxy for relative depositional residence time, decreases stratigraphically from member 3 to member 1, reflecting a transition to shorter residence times and higher relative sedimentation rates. Laterally, (La/Yb)N increases toward the basin center, accurately recording progressively lower sedimentation rates basinward. Provenance analysis indicates that the sediments were predominantly derived from felsic igneous rocks of the upper continental crust. Spatially, the northern steep-slope belt reflects a uniform source, whereas the southern gentle-slope belt and the Weixi’nan low-uplift periphery record multisource mixed inputs. Finally, tectonic discrimination reveals an “active continental margin” affinity. This geochemical signature represents the inherited tectonic environment of the Mesozoic parent rocks in the surrounding source uplifts, rather than the Cenozoic extensional rift setting of the Weixi’nan Sag itself.

Understanding species range dynamics is central to ecology and biogeography, particularly as global environmental change accelerates range shifts, expansions, and biological invasions. Carnivores are notable for their capacity to exploit human-modified landscapes, yet most research has focused on temperate regions where apex predator extirpation often facilitates expansion. By contrast, carnivore range expansions in tropical landscapes remain poorly documented. Here we assess the recent southward expansion of coyotes (Canis latrans) into the human-modified tropics of Mesoamerica, where they now overlap with apex predator assemblages. We compiled 278 coyote records from areas lacking previous evidence of their presence by integrating data from 44 camera-trap surveys (1125 cameras deployed, totaling 203,682 camera-trap/days between 2012 and 2025) and citizen-science platforms (iNaturalist and the Global Biodiversity Information Facility). To investigate drivers of coyote occurrence, we fitted a generalized linear model (GLM) using the Global Human Modification Index (GHMI), the Normalized Difference Vegetation Index (NDVI), and spatiotemporal factors as predictors. Model results indicated higher probabilities of coyote occurrence in more human-modified landscapes (higher GHMI) and areas with lower vegetation greenness (lower NDVI). Furthermore, a significant positive temporal trend indicated that the probability of occurrence increased annually. This case highlights how land-use change facilitates range expansions at continental margins and underscores the conceptual blurring between native range expansion and invasion processes. The ability of coyotes to thrive in both natural and human-dominated environments suggests continued spatial expansion, reinforcing the need for proactive management strategies grounded in both ecological science and local sociocultural contexts.

Microplastics and POPs on the Southwestern Atlantic deep-sea floor: a study of megafauna and sediments.

Abstract The shoaling of high-amplitude internal solitary waves (ISWs) of depression in the South China Sea (SCS) is examined through large-scale parallel turbulence-resolving high-accuracy/resolution simulations. A select, near-isobath-normal, bathymetric transect of the gentle SCS continental slope is employed together with stratification and current profiles obtained by in situ measurements. Three simulations of separate ISWs with initial deep-water amplitudes in the range [136, 150 m] leverage a novel wave-tracking capability for a propagation distance of 80 km and accurately reproduce key features of in situ–observed phenomena with significantly higher spatiotemporal resolution. The interplay between convective and shear instability and the associated turbulence formation and evolution as a function of deep-water ISW amplitude are further studied in part revealing processes previously not observed in the field. Across all three waves, the convective instability develops in a similar fashion. Heavier water entrained from the wave rear plunges into its interior, giving rise to transient, yet distinct, subsurface vortical structures. Ultimately, a gravity current is triggered which horizontally advances through the wave interior and mixes it down to pycnocline’s base. Although the waveform remains distinctly symmetric, Kelvin–Helmholtz billows emerge near the well-mixed ISW trough, disturb the wave’s trailing edge, and give rise to an active wake. The evolution of the kinetic energy associated with fine-scale perturbations to the ISW-induced velocity field shows two different growth regimes, each dominated by either convective or shear instability. The wake’s perturbation kinetic energy is nonlinearly dependent on deep-water wave amplitude and can become a sizable fraction of the kinetic energy of the deep-water ISW.

ABSTRACT Terrigenous sediments are transported from coastal areas and shelves to deeper continental margins by multiple processes. Understanding these processes is critical for evaluating the ecological impacts of fine‐grained sediment deposition and predicting future changes in sediment dispersal under rapid climate change. This study investigated sediment transport and hydrodynamic controls on the eastern Korean continental margin, characterised by a wave‐dominated coast and a slope shaped by contour currents and complex morphology. Surface sediment granulometry and grain‐size end‐member (EM) analysis distinguished three regimes: a wave‐dominated shelf and upper slope, a middle to lower slope influenced by bottom currents and a deeper slope marked by hemipelagic settling. Seaward‐fining trends subparallel to isobaths reflected sorting by declining wave energy, while deviations in the sand–mud transition to greater depths occurred near transgressive lags and stream mouths. A shift from wave‐induced erosion to bottom‐current‐driven deposition coincided with clay enrichment (>10%), which enhanced cohesion and produced distinct linear trends between sortable silt (SS) mean size and proportion. Variations in SS mean size across steeper and protruding slopes highlighted the topographic modulation of the southward‐flowing North Korean Cold Current. Five grain‐size end members were identified, corresponding to relict deposits, riverine bedload sands, suspended coarse and fine silts, and aeolian dust. Their abundance ratios quantitatively capture sediment fractionation effects induced by waves and bottom currents across the shelf and slope. This study demonstrates that integrating granulometric parameters with EM analysis provides a robust framework for identifying dominant sedimentary processes and assessing how seafloor morphology and oceanographic conditions regulate sediment dynamics along continental margins.

Mass-transport complexes (MTCs) are common features on all continental margins, with stacked MTCs indicating repeated slope failure. This suggests that MTC generation and emplacement may precondition a slope to fail again, although direct evidence for this is currently lacking. Determining the relationship between MTC development and slope stability is important, given its implications for understanding long-term basin evolution and geohazard assessment. Here, we use 3-D seismic reflection data from the Kangaroo Syncline, offshore Northwest Australia, to investigate how preexisting MTCs can prime subsequent failure events. We interpreted 11 MTCs that constitute ∼80% of the total stratigraphy of the post-Miocene interval, with individual MTCs spanning areas ≤2500 km2. We show that (1) lithological heterogeneity present within a sedimentary succession due to MTC emplacement can impact the location of subsequent slope failures; (2) topography formed by a buried MTC can enhance the erosive ability and affect the transport pathway of subsequent slope failures; (3) differential compaction between debrite matrix and blocks can produce a rugose MTC top surface that can influence the distribution and stratigraphy of subsequent slope failures; (4) the thickness pattern of buried MTCs can provide a mechanism for predicting the depocenter of future slope failures; and (5) the nature of the sedimentary succession, the aseismic setting, the presence of fluid venting systems, and slope oversteepening can collectively contribute to the preconditioning of recurrent MTCs in the Kangaroo Syncline. Our results show that buried MTCs have profound effects on the location, nature, geometry, and hazard potential of future slope failures. Therefore, investigating the interaction between stacked MTCs is a crucial component of future geohazard impact assessments.

Abstract The dispersal of meltwater discharged from the Laurentian Channel (LC) is investigated from numerical experiments with an eddy-resolving model representing the western North Atlantic during the last ice age. Meltwater dispersal is simulated over a full summer, when glacial ablation rates were presumably the highest. In our experiments, meltwater forms a buoyant plume which flows to the southwest along the continental slope owing to the Coriolis force. Four mechanisms of offshore export are identified. (1) Meltwater is carried seaward by Ekman currents driven by upwelling-favorable winds along the slope. (2) Part of it is entrained away from the slope by meander crests and warm-core rings of the Gulf Stream (GS) between the LC and Cape Hatteras. (3) The other part is generally diverted offshore by the GS near Cape Hatteras, where the GS leaves the slope. (4) Meltwater can be trapped in a GS meander trough that pinches off and produces a cold-core ring, leading to its penetration into the subtropical gyre. In turn, the buoyant plume has relatively small but noticeable effects on the GS. In the western, weakly-meandering segment of the GS, the vertical velocity shear is generally reduced due to the presence of melt (light) water along the inshore flank of the GS. Our results are discussed in the light of (i) a two-layer theory of a surface density front subjected to background flow and wind stress and (ii) sediment records from the Laurentian Fan and the Sargasso Sea.

Fifty new Nd isotope analyses are presented for a 230 km north-south suite along the eastern Labrador coast of the Grenville Province. Depleted mantle model T(DM) ages for foliated pre-Grenvillian orthogneisses display an overall decrease in age from ca. 2 Ga in the north to ca. 1.8 Ga in the south, but with considerable variability. The noise is attributed to variable mixing of Nd from Makkovik and Labradorian-aged sources, with an increasing Labradorian component to the south. The variability of T(DM) ages decreases markedly in the Pinware terrane south of Red Bay, suggesting that this represents the approximate limit of reworked Makkovikian crust. To the southwest, the total area of juvenile Labradorian crust in Eastern Quebec is substantial (>100,000 km2), suggesting the accretion of a juvenile Labradorian arc. However, the suture between heavily reworked Makkovik crust to the north and juvenile Labradorian crust to the south is unclear. Meanwhile, it is likely that back arc rifting in the hinterland of the orogen led to a second collisional suture ≈ 250 km to the north, in the vicinity of the Trans-Labrador Batholith. The occurrence of ensialic arc magmatism on the Makkovik continental margin prior to these collisional events can explain the intensity of the Labradorian magmatic event. Conversely, a model involving two opposite-dipping subduction zones can explain the relatively sudden cessation of Labradorian magmatism and rapid transition to a post-Labradorian passive margin.

Deep geodynamic processes are critical for controlling surface environments and shaping the evolution of Earth’s habitable conditions. However, the mechanisms by which deep geodynamic processes interact with surface processes to influence climate changes remain unclear. Here, we present geochemical and paleontological data from early Mesozoic strata in the northeastern North China Craton to track paleoclimatic fluctuations and variations in sedimentary processes. By integrating tectonic evolution, we reveal the mechanism of tectonic evolution driving climatic fluctuations. Tectonically driven uplift accelerates weathering-erosion, thereby modulating climate change, which explains the temporal consistency between climate and tectonics in the northeastern North China Craton. The Early Triassic was characterized by arid-to-semiarid and warm-to-cool climate conditions, with poorly sorted and minimally weathered sediments resulting from the southward subduction of the Paleo-Asian plate and the collision of the North China and Yangtze cratons. The Middle Triassic climate is inferred to have been characterized by persistent cooling, accompanied by extensive stratigraphic denudation, driven by the final closure of the Paleo-Asian Ocean. The Late Triassic transitional climate, with high sediment maturity and recycling in a passive continental margin, reflects the tectonic shift from the Paleo-Asian Ocean to the Paleo-Pacific tectonic regime. The Early Jurassic humid and warm-to-hot climate conditions, with sediments displaying low maturity and rapid deposition in an active continental margin, are potentially linked to the global greenhouse and the initial subduction of the Paleo-Pacific plate beneath Eurasia.

ABSTRACT Continental margins are reservoirs of materials of terrestrial and marine origin, and they play a crucial role in understanding the spatial and temporal variability of biogeochemical cycles. This, in turn, provides insights into the development and intensity of oxygen minimum zones (OMZs). In the present investigation, a series of geochemical variables was evaluated, including grain size, organic carbon and nitrogen contents, calcium carbonate, biogenic opal, stable isotopes of carbon and nitrogen, and dissolved oxygen concentration. In order to facilitate comprehension of the interactions and relative importance of the source and the state of organic matter degradation, hydrodynamic processes and dissolved oxygen availability, we analysed samples from the northern border of the Mexican Pacific OMZ. Seven perpendicular transects were sampled from the shallow shelf to the continental slope, where surface sediments were collected at 37 stations. Grain size exhibited a monotonic trend, with very fine sands and organic carbon low on the inner shelf and high clay content and organic carbon on the continental slope. The accumulation and enhanced preservation of organic carbon can be attributed to the high clay content and its characteristically large surface area, which reduces exposure time to dissolved oxygen. This organic carbon was derived mainly from marine siliceous plankton, with a minor contribution from terrestrial organic matter. Cluster and principal component analyses defined two biogeochemical provinces on the south‐western margin of the Baja California Peninsula: (1) a coastal province with high dissolved oxygen concentrations, fine sands and low clay and organic carbon contents, and (2) an oceanic province with low dissolved oxygen concentrations, high fine clay and organic carbon contents, located within the northeastern Pacific OMZ. Both provinces have high inputs of marine organic matter derived mainly from siliceous plankton, that is, diatoms and silicoflagellates.

Many global cratons contain lithospheric nuclei composed of ancient continental materials (pre−3.0 Ga), whereas the geodynamic processes and pathways responsible for their growth into mature cratons remain subjects of significant debate. Pervasive Neoarchean mantle-derived magmatism along the margins of ancient continental nuclei serves as critical geological archives for deciphering these issues. Here, we focus on the late Neoarchean mantle-derived volcanic rocks of the Northern Liaoning terrane (NLT), which is located between the Anshan-Benxi continental nucleus (ABCN) and Baishan continental nucleus (BSCN) in the northeastern North China Craton (NCC). Regional investigations in structural geology, lithological assemblages, chronology, geochemistry, and isotopic characteristics suggest that the Archean crystalline basement of the NLT can be divided into three independent tectonic domains: Waitoushan−Weiziyu−Jiubing domain in the southwest, Fushun−Tangtu−Xinbin (FTX) domain in the central, and Hongtoushan−Qingyuan−Xiajiabao (HQX) domain in the northeast. The HQX domain was likely separated from the adjacent Southern Jilin terrane (SJT) through the sinistral displacement of the Mishan-Dunhua fault zone. Detailed studies of geochemical classification and petrogenesis of mantle-derived volcanic rocks, and their tectonic implications, indicate that the NLT and SJT preserve a continuous record of a ca. 2.58−2.50 Ga continental margin arc system along the ABCN, involving processes ranging from subduction initiation to deep subduction, a ca. 2.60−2.50 Ga intra-oceanic arc system, together with a ca. 2.58−2.51 Ga continental margin arc system proximal to the BSCN. The lateral plate motions induced by multiple subduction systems would lead to convergence of the ABCN and BSCN, and subsequent ca. 2.53−2.47 Ga arc-arc and/or arc-continent collisions, finally forming a unified continental block of the northeastern NCC. Our results provide direct evidence for the operation of plate tectonics during the late Neoarchean, offering new insights into the transformation from ancient continental nuclei to mature Archean cratons.

The continental margin of SE New Zealand is strongly influenced by the Southland Current and associated water masses. This new seismic stratigraphic study of the margin has revealed a range of depositional mounds and erosional channels that document the close interaction of turbidity and bottom currents in shaping the margin from the Mid‐Eocene onward. Bottom‐current influence was initiated with the onset of the Antarctic Circumpolar Current, following the opening of the Tasmanian Gateway. Following this event, four stages of evolution are identified: (1) the Mid‐Eocene saw the onset of the first mixed depositional system with a series of levee‐drifts adjacent to downslope channels, alongslope‐oriented contourite‐dominated drifts, and an alongslope contourite moat; (2) the Early to Late Oligocene saw the continued vertical growth and incision of these mixed depositional and erosional elements; (3) the Late Oligocene to Mid‐Miocene saw a significant change to a more turbidite‐dominated mixed system, with a weakened bottom‐current influence; and (4) the Mid‐Miocene to Recent saw a resumption in bottom‐current activity, and development of a more contourite‐dominated system. The changes observed in margin evolution reflect variations in tectonic activity and source area uplift, variation in continental slope topography, and evolving bottom‐current systems.

Planktonic foraminifera assemblages have been extensively used to reconstruct paleotemperatures along the Quaternary. Most of reconstructions focused on surface temperature or in a specific water depth. However, assemblages preserved in sediments represent a pluriannual deposition of species inhabiting the upper 1,000 m. Based on those assumptions, fossil assemblages should reflect better the thermal structure of the water column than a determined water depth. Considering this, we applied transfer functions based on planktonic foraminifera and the Hill sigmoidal function on two sediment cores of the Western South Atlantic in order to simulate and reconstruct past upper ocean thermal structure. These sediment cores were retrieved from the equatorial and subtropical continental slope and cover the last 185 kiloyears (kyr), which allowed us to make inferences about the glacial and interglacial heat storage and release. Eleven paleotemperature reconstructions along the upper 1,000 m were calculated by modern analog technique (MAT) followed by Hill’s sigmoidal function fitting to simulate the past thermal structures. Hill’s coefficients were used to estimate physical parameters in order to improve the paleoceanographic diagnostic. The double-stepped Hill function performed the best simulations of thermal structures. MAT-derived paleotemperatures for 11 depths and their respective errors were within the range of best analogs, indicating that those results are reliable to be applied in reconstructions. The reconstructions indicated that key depths to investigate the glacial–interglacial thermal variation were different in our two study sites. Important variations of the heat storage occurred in the upper 80–120 m in the equatorial margin and the lower thermocline layer in the subtropical margin. Based on this, four main scenarios of heat distribution were suggested for the western border of the tropical South Atlantic, which were associated with events linked to variations of the Earth’s orbit, trade wind intensity, and the South Atlantic large-scale circulation.

Mud volcanism is widespread along the Sunda–Banda Arc in eastern Indonesia extending from Rote, Timor, Babar, Tanimbar islands and the Kai Archipelago to Ceram Island. Extensive mud volcanic ejecta distributed on the western side of Tanimbar Island and nearby areas provides evidence of the frequent occurrences of mud volcanism. A magnitude 7.5 earthquake that struck Tanimbar on 10 January 2023 was responsible for the formation of two new islands including Batu Arang Besar Island. Fieldwork by a small team from the Marine Geological Institute on the newly created Batu Arang Besar Island, 10 km west of northern Tanimbar Island, found expelled ejecta consisting of boulders and gravels from subsurface Mesozoic strata in a matrix of mud showing lamination, oxidation, red clay, chert and bioturbation. Mud volcanism occurs in the tectonically most active part of non-volcanic Banda Outer Arc and is always accompanied by methane emissions, which indicate that there is a relationship between mud volcano characteristics and the hydrocarbon potential. The event itself is commonly associated with seismic activity that influences mud volcano systems through static and dynamic stress changes that activate liquefaction and open conduits. No hydrocarbon deposits have been found in this most deformed non-volcanic arc region, while on the less deformed Australian continental plate passive margin toward the south and southeast, giant natural gas fields of Babar Selaru and Masela occur on the Indonesian side of the border, and numerous fields are present in the Australian part. Ongoing orogeny is responsible for mud volcanism as well as the formation of these giant gas fields. The field structures were formed during the Pliocene to Pleistocene by plate bending and faulting associated with the Banda Arc and Australian continent collision. Migration and accumulation of oil and gas into these fields mainly occurred during the Pleistocene to Recent. This very young migration provides evidence of the influence of neo-tectonics on the accumulation of hydrocarbons and is manifested by the common occurrence of big earthquakes and mud volcanism.

This study explores weathering and tectonic settings of sediments, source area, maturity, metal enrichment and distribution using geochemical data from elemental analysis of major oxides and trace metals in sediments within parts of the Oban Massif, southeastern Nigeria. Stream sediment samples were collected and taken to the Department of Pure and Applied Chemistry laboratory, University of Calabar for analysis using Atomic Absorption Spectrophotometer (AAS). The major oxides are SiO2, Al2O3, Na2O, FeO, MgO, K2O, CaO, and TiO2, while trace metals analyzed include Fe, Cr, Co, Cu, Pb, Ni, and Zn. Result showed variation in the concentration of major oxides is in the order; SiO2 > Al2O3 > Na2O > Fe2O3 > K2O > CaO > FeO > MgO > TiO2., while that of trace metals is in the order; Fe > Co > Pb > Cr > Ni > Cu > Zr. Bivariate plots revealed relatively high amount of silica (SiO2) content which is typical of a matured sediment. Indexical approach revealed that values obtained for pollution load index (PLI) and geo-accumulation index (Igeo) indicates there are no pollution, suggesting that the sediments are geochemically pristine. There is also low contamination of all the trace metals analyzed, the only exception is Co which revealed considerable contamination owing to the computed values obtained. However, localized enrichment of trace metals obtained may possibly be due to natural mineralization or lithological variations other than anthropogenic inputs, since the study area consists predominantly of uninhabited farmlands and forest where human activities are minimal. The A-CN-K (Al2O3-CaO+Na2O-K2O) ternary plot indicates that the dominant crust from whence these sediments are derived consists of felsic to intermediate igneous rocks. The diagram of chemical index of weathering (CIW) versus chemical index of alteration (CIA) showed that the samples plotted between the low silicate weathering to no silicate weathering fields, and this indicates that there was low to moderate chemical alteration of primary silicates. The plot of K2O/Na2O versus SiO2 indicates a mixed tectono-provenance, where majority of the samples (75 %) come from the passive margin (PM), while the remaining (25 %) are source from active continental margin (ACM).