ABSTRACT Prodelta sedimentary dynamics in open‐lacustrine depression basins remain poorly understood compared to marine models. To decipher the interplay between hyperpycnal and gravity flows, this study investigates the Upper Triassic Yanchang Formation, Ordos Basin. Integrating 888 well logs and over 2500 m of cores, a high‐resolution sequence stratigraphic framework was established. The results reveal a wedge‐shaped progradational geometry controlled by palaeogeomorphic slope breaks, challenging traditional ‘layer‐cake’ correlations. Five identified microfacies (gully fill, lobe/lobe fringe, plume fallout mud drape, slump and tuffaceous event beds) record fluid transformations driven by flood‐generated hyperpycnal flows and slump‐induced gravity flows. A sequence‐constrained depositional model demonstrates that the Highstand Systems Tract features a supply‐driven ‘channel‐lobe’ framework under confined progradation, whereas maximum flooding periods transition to fine‐grained suspension settling and unconfined slump deformation. These findings establish a generic paradigm for progradational wedges in terrestrial depression basins, providing a predictive template for unconventional hydrocarbon ‘sweet spot’ exploration globally.
ABSTRACT Cenozoic intraplate basalts in SE China provide a crucial window into deep mantle recycling and Palaeo‐Pacific plate subduction dynamics. However, the petrogenesis of the transitional ‘central belt’ remains poorly constrained compared to its coastal and inland counterparts, hindering a comprehensive understanding of the lithospheric mantle beneath South China. This study presents new high‐precision 40 Ar‒ 39 Ar geochronological, geochemical and Sr‒Nd‒Pb isotopic data for alkaline basalts from Minqing, Fujian. Dating yields a plateau age of 13.15 ± 0.92 Ma, establishing a distinct coastal‐to‐inland younging trend driven by slab rollback. Geochemically, these basalts exhibit ocean island basalt (OIB)‐like trace element patterns with pronounced negative Ti and K anomalies, alongside high Zr/Hf ratios. These geochemical fingerprints strongly indicate the involvement of recycled sedimentary carbonate components in the mantle source. Sr‒Nd‒Pb isotopic compositions reveal mixing between depleted mantle (DM) and enriched mantle II (EM2) end‐members. Quantitative trace element modelling demonstrates that these basalts originated from a hybrid source dominated by carbonated garnet pyroxenite with minor garnet peridotite. We propose that this mantle source was metasomatised by carbonate‐rich melts derived from the subducted Palaeo‐Pacific slab within the Big Mantle Wedge (BMW). This mechanism highlights the crucial role of deep carbon recycling in generating subcontinental mantle chemical heterogeneity.
The development of underground space can effectively mitigate pressure on urban land resources. An appropriate evaluation of underground space is essential for sustainable urban development. Most existing studies on the suitability evaluation of underground space focus primarily on geological conditions while neglecting socioeconomic factors, making it difficult for planning departments to directly adopt the evaluation results. Taking Qingdao as the study area, this study conducted a comprehensive quality evaluation considering geological and socioeconomic conditions based on a genetic algorithm and an improved technique for order preference by similarity to ideal solution (TOPSIS) evaluation framework. On the basis of the results, overall planning guidelines for different functional zones of underground space within 30 m were provided. The findings indicate that the sub-shallow layer has become a key layer for underground space development in the study area, with 60% of the region exhibiting favourable comprehensive quality. In addition, the evaluation framework proposed in the study has increased the safety of the results by 13%, ensuring high-quality planning of underground space. This study can provide a reference for the comprehensive quality evaluation and planning of underground spaces in other cities.
Brittle faults record tectonic deformations of the Earth's surface and interior.Constraining their active timing is crucial for reconstructing geotectonic evolution,constraining seismicity models,and assessing seismic hazards.However,the low temperature and pressure conditions of brittle fractures and the fast strain rate of rocks pose significant challenges for dating brittle faults.Recently,in situ U-Pb dating of calcite has emerged as an important method due to its high resolution,low detection limits and short detection periods.This method requires identifying calcite characteristics and determining its genetic types in the field.Here,we summarise the main methods for constraining the timing of brittle fracture activity,the basic principles of in situ U-Pb calcite dating,and the field types and petrographic characteristics of syntectonic calcite.We also present case studies of in situ U-Pb dating of calcite in major fault zones as reference points.This study provides a overview of in situ U-Pb calcite dating techniques,highlighting the critical role of field and petrographic characteristics in accurately dating brittle fault activity and demonstrating their application in constraining the timing of tectonic events,which offers valuable insights for understanding tectonic evolution and assessing seismic hazards.
ABSTRACT The Hendouabad Cu–Au deposit, located in the central Urumieh–Dokhtar Magmatic Arc, represents a newly explored example of an epithermal deposit hosted by Late Eocene volcanic rocks of basaltic andesite to andesite composition. Mineralization occurs in two zones: A Cu–Au zone in the east and a Cu‐only zone in the west hosted by andesite, basalt and associated dikes. Ore minerals include pyrite, chalcopyrite, chalcocite, galena and bornite, and enargite with supergene assemblages of malachite, haematite and chrysocolla. Hydrothermal alteration is dominated by propylitic and silicic assemblages. Fluid inclusions yielded homogenization temperatures of 109–280°C and low‐to‐moderate salinities (1.6–9.0 wt% NaCl equiv.), with petrographic evidence of boiling. Stable isotope analyses indicate mixed magmatic–meteoric signatures, with quartz‐ and epidote‐derived δ 18 O fluid values ranging from +2.2‰ to +14.2‰ and sulphide δ 34 S values from (−12.0‰ to −5.3‰, CDT). These results suggest that ore‐forming fluids were derived from a magmatic source but were strongly modified by meteoric water infiltration and evolving redox conditions. The combined geological, petrographic, geochemical, fluid inclusion and isotopic evidence supports classification of the Hendouabad deposit as a structurally controlled low‐to‐intermediate sulphidation epithermal Cu–Au system formed through boiling, mixing and cooling of magmatic–meteoric hydrothermal fluids.
The wood anatomy of corystosperms is fundamentally consistent with that of gymnosperms,yet their growth ring boundaries share anatomical features with extant angiosperms.This transitional morphology strongly supports the interpretation of corystosperms as an evolutionary intermediate between gymnosperms and angiosperms.The first application of X-Ray fluorescence(XRF)chemical analysis to fossil wood taxa of Fengweioxylon yielded the above conclusion.By using growth ring analysis and ecological reconstructions,we suggest that corystosperms were large evergreen trees with leaf retention periods of three to five years.They likely thrived in warm summer environments where prolonged foliage retention provided adaptive benefits.
The Guyuan-Hongshanzi uranium metallogenic belt (GHUMB) in North China, particularly the Hongshanzi area within the southern Great Xing'an Range (GXR), hosts uranium mineralization significantly impacted by post-mineralization uplift and exhumation. Field investigations, drill core analysis, electron probe microanalysis (EPMA) and apatite fission track (AFT) dating reveal that uranium orebodies occur within basement uplift zones hosted by the Upper Jurassic Manketou'ebo and Xinmin formations, Lower Permian Dashizhai Formation and Hercynian granodiorite. These orebodies are predominantly shallow and are structurally controlled, associated with hydrothermal alteration including carbonatization, silicification, hematitization, chloritization, fluoritization and sulfidization. Critically, deep-seated potash feldspathization and albitization features are now exposed at shallow depths or the surface. AFT analysis and thermal history modelling indicate rapid cooling during 70-50 Ma, signifying rapid uplift through the partial annealing zone to near-surface levels. This evidence, combined with the surface exposure of deep alteration, demonstrates that primary uranium mineralization initially formed at depths of similar to 2-4 km during the Cretaceous. Subsequent rapid uplift triggered intense erosion, preserving some orebodies shallowly while eroding others and transporting uranium into adjacent basins, potentially contributing to secondary sandstone-type mineralization.
The synrift basins of the West and Central African Rift System (WCARS) contain Lower Cretaceous lacustrine shale, which is considered to be the main source rock of hydrocarbons that accumulated in these basins. Recent studies of these lacustrine shales do not consider the diversity of organic-rich lithofacies within these basins. This study aims to investigate Lower Cretaceous organic-rich facies in the Babouri-Figuil Basin, part of the WCARS. The samples collected (n = 173) were subjected to bulk geochemical and elemental analyses and organic petrological observations. Oil shales exhibit a higher average total organic carbon (TOC) value of 17 wt%, whereas the associated facies contain less than 2 wt% TOC. The oil shales display an average hydrogen index (HI) value of 769 mg HC/g TOC. However, the associated facies generally exhibit HI values below 300 mg HC/g TOC. Oil shales and associated facies contain well-preserved kerogen, ranging from Types I to III, indicating good to very good potential for hydrocarbon generation. Rock-Eval pyrolysis reveals relatively similar thermal maturity across the studied organic-rich facies, with an average T max value of 430 degrees C, displaying an immature to early oil window stage of maturation. These results suggest that the WCARS basins generally hold promise for further petroleum exploration efforts.
Mesozoic exotic tectonic fragments in the Yarlung Zangbo suture zone (YZSZ) preserve key records for reconstructing Neo-Tethyan evolution. This study investigates basalts and limestones from the Buma area in the central segment through petrology, calcite U-Pb geochronology, and whole-rock geochemistry. Calcite U-Pb dating of two recrystallized limestone samples yields ages of ca. 244 Ma and ca. 246 Ma. The Buma basalts are subalkaline, with SiO2 contents of 37.95-53.61 wt.% and high TiO2 (1.63-3.43 wt.%). Their rare earth elements (REEs) and trace element patterns resemble Hawaiian ocean island basalts (OIBs), and they exhibit moderately depleted Nd isotopic compositions (epsilon Nd(t) = +4.20 to +4.93). The pronounced negative Ce anomalies in limestones and the absence of terrigenous clastic components in collapse conglomerates indicate deposition in an open-ocean setting. Integrated evidence indicates that the basalt-limestone association in the Buma area represents a Neo-Tethyan ocean island-seamount system. Combined with the 253 Ma continental rift basalts from the Zhongba area, this result suggests that the opening of the Neo-Tethys Ocean in the central segment of the YZSZ occurred no later than the Early Triassic, providing key empirical evidence for the spatiotemporal framework of the early evolution of the Neo-Tethys Ocean.
The W-Sn-Ag-Pb-Zn polymetallic deposit in the Bozhushan ore concentration area is closely related to Late Cretaceous magmatic activity, and the diagenetic age of the granite body is 88.8-87.1 Ma. The granites in the Bozhushan ore district are characterized by high silica and aluminium contents, high abundances of Rb, Sr, Sn and Th, and low contents of Ba, P and Ti. The granites are peraluminous S-type granites that underwent fractional crystallization during magmatic evolution. The epsilon Hf(t) values of the zircons from -17.92 to -1.77, with T DM2 age ranging from 1.1 to 2.0 Ga, indicate that they may be mainly derived from partial melting of the lower crust without the addition of mantle-derived materials. The Late Cretaceous magmatic activity in the Bozhushan area formed in a syn-collisional tectonic environment and transitioned to a post-collisional orogenic environment. In the later stage, it transforms into a post-collisional extensional environment. The upwelling of deep-seated asthenospheric melts has provided substantial fluxes of W, Sn, Pb, Zn and other ore-forming elements. The ore-forming fluid and materials carried by magma rise and migrate along favourable parts of the structure to precipitate and mineralize. Therefore, understanding the tungsten-tin metallogenic history in the Bozhushan ore district is important.
The Dahongshan Cu-Fe deposit is located within the central Yunnan uplift, bordered by the Honghe and L & uuml;zhijiang faults. It exemplifies a typical stratabound-hydrothermal reworked deposit within the Kangdian Cu-Fe metallogenic belt, situated on the western margin of the Yangtze Block. This study focused on the 60 m elevation above sea level. Using short-wave infrared (SWIR) spectroscopy, we analysed the spectral parameters of alteration minerals, primarily the chlorite group and muscovite. Spatial distribution models were developed through mineral spectral mapping to quantify the relationship between alteration minerals and copper grades. Key findings include: (1) Copper grades exceed the industrial cut-off grade of 0.2 wt% in zones corresponding to moderate to high relative spectral index values of chlorite-group minerals. (2) High chlorite spectral peak intensity zones are spatially coincident with high-grade Cu mineralization, reflecting the paragenetic association of chlorite and sulphides in hydrothermal fluid pathways. (3) Muscovite crystallinity is on average lower in ore-proximal zones than in surrounding wall rock. This distinct difference reflects Cu mineralization-related hydrothermal alteration, which induces muscovite lattice distortion and consequent crystallinity reduction in ore-bearing hydrothermal fluid zones. In conclusion, the spatial distribution of chlorite content, its spectral characteristics, and the pattern of muscovite crystallinity attenuation provide essential geological-spectral criteria for predicting concealed ore bodies within the Dahongshan Cu-Fe deposit.
This study addresses the origin and evolution of Early Pleistocene basanites from Harrat Dahrat Humayyan (HDH) in the northeastern Arabian Shield, part of the Hutaymah volcanic field. Integrated mineralogical, geochemical and thermobarometric data are used to constrain magma genesis and mantle source characteristics beneath the Arabian Plate. The HDH basanites display features typical of anorogenic alkaline volcanism associated with continental rifting. Thermobarometric estimates indicate crystallization temperatures of 1420-714 degrees C and pressures of 3.1-0.4 GPa, with early olivine crystallization followed by clinopyroxene and feldspar. Trace element modelling suggests that the magmas were derived from low degree partial melting (7%-12.5%) of a heterogeneous garnet-spinel peridotite mantle source. The rocks are enriched in incompatible elements and show rare-earth element (REE) patterns consistent with limited crustal contamination, implying rapid magma ascent. Their prevalent mantle (PREMA)-like geochemical signatures resemble those of other Cenozoic intraplate volcanic provinces in Arabia and elsewhere. These signatures are best explained by melting of a fusible mantle domain triggered by lithospheric extension associated with Red Sea rifting. Overall, the results support a model of passive mantle upwelling beneath an extending lithosphere and provide new insights into mantle heterogeneity and melting processes.
The Late Carboniferous-Permian magmatic and sedimentary records in the Alxa area are crucial to understanding the tectonic evolution of the Paleo-Asian Ocean.We present petrological,whole-rock geochemical,zircon U-Pb geochronological and Hf isotopic data for magmatic and siliciclastic rocks from northern Alxa.Rhyolite and granite porphyry related to the Amushan Formation crystallized at ca.309-304 Ma,derived from juvenile to moderately evolved lower crust reworked by oceanic subduction.Sandstones from the Quagan Qulu and Engger Us tectonic belts display contrasting detrital-zircon age spectra.Quagan Qulu samples,characterized by an early Paleozoic peak at ca.430 Ma,record mixed input from early Paleozoic arc rocks,Precambrian basement and recycled cover strata,whereas Engger Us samples are dominated by a Devonian peak at ca.381 Ma and were supplied by a nearby Devonian arc source.Together with published data,our results support a segmented Late Carboniferous-Permian forearc-arc-retroarc system along the northern margin of Alxa.Continued southward subduction of the Quagan Qulu oceanic lithosphere beneath the Nuru-Langshan continental arc is the preferred interpretation,whereas Late Carboniferous to early Permian slab rollback is a plausible mechanism for the ensuing magmatic flare-up,arc uplift and provenance shift.
The Wunugetushan (Wushan) porphyry Cu-Mo deposit is located in the southwestern segment of the Derbugan metallogenic belt. In this study, geochemical analyses of zircon and apatite from pre-mineralization biotite granite (BG) and inter-mineralization monzogranitic porphyry (MGP) were conducted, aiming to discuss petrogenesis and their constraints on mineralization. BG apatites have distinctly lower epsilon Nd(t) (-4.28 to -1.03) and higher two-stage Nd model ages (1063-1328 Ma) than MGP apatites, showing values of -0.23 to +1.31 and 860-984 Ma. MGP zircons have higher Ce/Nd, Ce4+/Ce3+, delta Eu, 10,000 & times; delta Eu/Y and (Ce/Nd)/Y values, and lower Yb/Gd values than those in BG zircon. These geochemical features suggest that the MGP has a higher oxidation state and higher water content of magma than BG. Trace element concentrations in zircon and apatite reveal that the MGP is less evolved and exhibits amphibole-dominated fractionation. In contrast, the BG is evolved and shows plagioclase- and apatite-dominated fractionation. We propose that the key factors making the MGP fertile for mineralization, including its high Cl, S and H2O contents, high oxidation state, significant fluid exsolution and multiple recharges of deep-seated mafic magma, were all critical for the Wushan porphyry Cu-Mo deposit.
As a rare marine carbonate reservoir developed after the Eocene in the world, the oil and gas source of Palaeogene carbonate reservoirs in Kekeya area and the evolution process and mechanism of hydrocarbon accumulation are not clear, restricting the reasonable and effective development of Kekeya area. By the use of drilling cores and experimental data, oil and gas source correlation, reservoir evaluation, accumulation period and reservoir formation process were studied. Results show that the source rocks in the study area are mainly Permian lacustrine mudstone and Jurassic coal-bearing source rocks. The Palaeogene carbonate reservoirs are generally low porosity and ultra-low permeability, with secondary dissolution pores as the main reservoir space. The oil-gas source correlation shows that the Palaeogene crude oil is derived from the Permian source rock, and the natural gas is derived from the Jurassic source rock. The ancient and present reservoirs have experienced two oil and gas filling stages. The first stage is the middle and late Pliocene and the second stage is the early Pleistocene. The hydrocarbon accumulation mode was built as 'source-reservoir separation, fracture dredging, multi-stage filling'. The research results guide exploration in Tarim Basin and similar basins.
The tectonic affinity of the quartzite unit is essential for reconstructing the Cenozoic evolution of the Eastern Himalaya Syntaxis. We presented new petrographic and zircon U-Pb geochronological data from the quartzite unit collected from the western boundary of the Namche Barwa syntaxis. The maximum depositional ages indicated multiple depositional stages at >1800, 1122-1136, 885, 451-493 and 54 Ma. Detrital zircon ages spanned from 50 to 3269 Ma with dominant populations at 500-900, 950-1400, 1550-1700 and 1750-2000 Ma. These age distributions suggested that the detritus were derived mainly from the Central Indian Tectonic Zone, Shillong Plateau and the Eastern Ghats Orogeny of the northeastern Indian subcontinent, and Western Australia. This provenance signature was distinct from the typical sequences of the Lesser Himalayan Sequence, Greater Himalayan Sequence and Tethyan Himalayan Sequence in the central-western Himalayas. Integrating our results with existing data from the Nyingchi Complex in the southern Lhasa terrane and Lesser Himalayan Sequence in the Eastern Himalayan Syntaxis, we proposed that the Namche Barwa syntaxis, Nyingchi Complex and Lesser Himalayan Sequence shared common source regions. Long-lived fluvial systems likely transported detrital material from northwestern Australia and the northeastern Indian subcontinent to these tectonic units.
Magmatic evolution involves oxygen fugacity () changes that affect tungsten (W) and tin (Sn) transport and enrichment, but how varies during magmatic fractionation and differentially impacts W-Sn enrichment remains unclear. We studied mineralogical and geochemical compositions of Dayishan (Sn) and Guidong (W) granites in Nanling Range to clarify difference during the magmatic fractionation of W- and Sn-bearing magmas. Both granites are divided into less-fractionated (DYS(Sn)-L and GD(W)-L) and highly fractionated (DYS(Sn)-H and GD(W)-H) groups. The apatites of Dayishan and Guidong granites have low S (4-10 and 4-49 ppm), and the S of apatite from DYS(Sn)-L are higher than those from DYS(Sn)-H, but the S of apatite from GD(W)-L are lower than those from GD(W)-H. The trace element of zircon shows a variation pattern similar to that of apatite: the of GD(W)-L (Delta FMQ = -0.42 to 0.33) is lower than that of GD(W)-H (Delta FMQ = -0.31 to 0.81), but the of DYS(Sn)-L (Delta FMQ = -1.08 to -0.41) is higher than that of DYS(Sn)-H (Delta FMQ = -0.37 to -0.67). Therefore, in a reductive condition, decrease in can help the enrichment of Sn, whereas increase in is favoured by the enrichment of W.
The Kangding geothermal area presents a promising potential for the development and exploitation of geothermal resources. However, the understanding of the hydrogeochemical genesis and geothermal scaling potential remains limited. In this study, water samples from 18 geothermal wells and 4 hot springs were collected within north (ZG) and south (YL) of Kangding geothermal area. The major ion concentrations, hydrogen-oxygen isotopes and strontium isotopes were analysed. The hydrochemistry of the geothermal water is predominantly of the Na-HCO3 (ZG) and Na-HCO3-Cl (YL) types. The delta D and delta 18O isotope signatures suggest that the recharge of the geothermal water originates from snow and ice meltwater and local meteoric precipitation, whereas YL also has magmatic water. The dissolution of siliciclastic and carbonatitic rocks and reverse cation exchange during the upwelling process contributes to the water-rock interactions of the geothermal water. There are two thermal reservoirs and a deep reservoir primarily composed of granite (YL), whereas a shallow reservoir is dominated by sand slate (ZG). The geothermal system in Kangding exhibits significant carbonate scaling, posing a substantial challenge to the development and utilization of geothermal resources. The investigation of hydrogeochemical genesis and scaling potential is crucial for guiding the efficient development and utilization of geothermal resources.
Young continental rift settings are premier sites for studying the dynamic interplay between sediment provenance and depositional setting. We integrated geochemical and detrital zircon U-Pb geochronology data of the Red Sea beach sediments to infer the weathering history and identify source terranes. Chemical composition with low Al2O3/TiO2 ratios suggests an apparent mafic-to-intermediate provenance. Although internal variability exists, the chemical index of weathering (CIW) and Th, Sr, U and Ba contents reveal moderate weathering intensity in the source region. This interpretation is contradicted by our zircon U-Pb data, which uniformly fingerprint the felsic-to-intermediate Neoproterozoic (550-990 Ma) Arabian-Nubian Shield (ANS) as the single primary source. We resolve this paradox by demonstrating that robust coastal processes fundamentally overprint the primary source signature. Intense hydrodynamic sorting in heavy mineral placers removes light, felsic minerals, creating a residual deposit with an artificial 'mafic' signature and an artificially high CIW signal. Elsewhere, the detrital signal is masked by biogenic carbonate dilution. Furthermore, a subordinate suite of recycled Archean to Cretaceous zircons reveals cryptic contributions from the regional Nubian Sandstone Formation, tracking long-term crustal inheritance. This work provides a case study of how depositional processes can mimic and mask source signatures in an active rift margin.
Crust-mantle architecture in large igneous provinces (LIPs) controls magma generation and crustal growth. The coeval gabbro and monzonite in the inner zone of the Emeishan Large Igneous Province (ELIP) provide a key opportunity. They display different whole-rock and mineral compositions, indicating different sources and melting conditions. The gabbro displays moderate TiO2 and MgO contents, with Ti/Y ratios of 408-413. Its elevated Nb/Ta and Zr/Hf ratios, evolved zircon Hf isotope, and apatite chemistry suggest a volatile-poor primitive melt, which was derived from the melting of sub-continental lithospheric mantle. The monzonite displays high Zr and Nb contents, TFeO/MgO and 10,000 & times; Ga/Al ratios, indicating high-temperature melting of mafic lower crust, the high Sr contents suggest plagioclase incorporation into the melts. Its relatively depleted isotopic compositions (epsilon Nd(t) = +3.2 to +3.7; epsilon Hf(t) = +0.87 to +0.88) reveal a juvenile crust source region. Apatite in the monzonite indicates a volatile-rich melt, supporting a high-temperature crustal melting origin. This geochemical dichotomy illuminates a two-stage crustal evolution model: (1) melting of plume-modified lithospheric mantle to generate the gabbro, followed by (2) thermal remelting of the juvenile mafic crust to form the monzonite. Such plume-induced crust-mantle interaction offers a window into understanding crust-mantle architecture in global LIPs.
