Geological Journal最新文献

The mafic magmatism during the Middle-late Early Neoproterozoic period (ca. 830–720 Ma) is frequently construed as indicative of plume magmatism, facilitating the breakup of the supercontinent Rodinia and establishing a climatic backdrop conducive to the onset of the Sturtian glaciation. Nevertheless, the tectonic models proposed to explain the formation of the latest Tonian magmatism in the Yangtze Block remain a subject of debate. In this study, four mafic dyke samples yielded weighted mean ²⁰⁶Pb/²³⁸U ages of 733 ± 14 Ma, 722 ± 8 Ma and 734 ± 6 Ma, 733 ± 5 Ma, respectively, indicating their crystallisation age in the Neoproterozoic era. These mafic dykes are characterised by a subalkaline tholeiitic composition, with relatively low concentrations of SiO₂ (43.04–46.75 wt%) and MgO (5.50–7.86 wt%), and Mg^# values ranging from 48 to 64. Furthermore, the mafic dykes are also marked by relatively high FeO^T (9.26–12.28 wt%), TiO₂ (1.20–1.62 wt%). They exhibit a slight enrichment in LREE with (La/Yb)_N ratios of 2.99–3.35 and demonstrate trace element patterns that are typical of continental tholeiite. Moreover, the mafic dykes display εNd (t) values ranging from −3.7 to +4.4, εHf(t) values ranging from −12.33 to 4.41, along with low ratios of (²⁰⁶Pb/²⁰⁴Pb)_i (16.70–17.46), (²⁰⁷Pb/²⁰⁴Pb)_i (15.37–15.70) and (²⁰⁸Pb/²⁰⁴Pb)_i (36.67–38.00). The combination of these characteristics and clinopyroxene compositions provides evidence that the source region of the mafic dykes was created through the partial melting of the depleted asthenosphere mantle mixed with subduction fluid metasomatic lithospheric mantle during the transition of the spinel-garnet facies peridotite within an extensional setting. The congruities in formation chronology, petrogenesis, source attributes and tectonic settings among the mafic rock samples within the Douling Complex, the Yaolinghe Group and the Wudang Block suggest that the South Qinling Belt was in an extension setting during the Middle-late Early Neoproterozoic, and presumably witnessed the rifting of the Rodinia supercontinent.

Potassic–ultrapotassic volcanic rocks are the products of post-collisional magmatism in the Tibetan Plateau and can reveal the deep lithospheric processes and subduction dynamics of the Tethys oceanic crust and Indian continent. To better understand the genesis and tectonic setting of potassic magmatic rocks, this study presents zircon U–Pb ages, Sr–Nd–Pb and Hf isotope data, and whole-rock major and trace element data for the Konglong potassic–ultrapotassic volcanic rocks in the central Lhasa terrane. The Konglong volcanic rocks mainly consist of low-silica trachyte and high-silica rhyolite. Zircon U–Pb dating reveals that the trachyte formed at 21.0 ± 0.1 Ma, while the rhyolite formed at 20.6 ± 0.1 Ma. Both rock types are characterised by relatively high potassium contents and are K-rich (K₂O = 5.81%–8.52%; K₂O/Na₂O > 1). These rocks are strongly enriched in large-ion lithophile elements (e.g., Rb, Th, U, and K) and light rare earth elements (LREEs), with noticeable depletions in high-field-strength elements (e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs) can be observed in these samples. The rhyolite contains comparatively low concentrations of Ba, Sr, and δEu, and the trachyte features glomeroporphyritic aggregates. The isotopic signature shows relatively high radiogenic ⁸⁷Sr/⁸⁶Sr_(t) ratios (0.71–0.72), low εNd_(t) values (−11.1 to −9.8) and zircon εHf_(t) values (−12.2 to −10.0) and more uniform radiogenic Pb isotope ratios (²⁰⁶Pb/²⁰⁴Pb_(t) = 18.79–18.95, ²⁰⁷Pb/²⁰⁴Pb_(t) = 15.76–15.81, ²⁰⁸Pb/²⁰⁴Pb_(t) = 39.51–40.00). These findings suggest that the enriched lithospheric mantle source region in the Konglong area has experienced two episodes of metasomatism. During the oceanic slab subduction stage, the enrichment was primarily derived from oceanic crustal sediments, whereas during the Indian continental crust subduction, it was dominated by melts and fluids produced by metamorphism of the Indian crust. During the Miocene, delamination of the lithospheric mantle slab led to asthenospheric mantle flow upwelling, with high heat flow triggering partial melting of the enriched lithospheric mantle and mixing with magma of Lhasa crustal origin. The mixed magma underwent differentiation through crystal-melt separation, with the trachyte representing a crystal-enriched and melt-depleted cumulate and the rhyolite representing the resultant high-silica, crystal-poor melt.

This paper aims to provide an overview of the geochemistry and mineralogical characterisation of coal within the Sohagpur coalfield, located in the Burhar–Amlai Sub Basin of Madhya Pradesh, India. The study involves the determination of proximate and ultimate analysis components, major elements, and trace elements by using various techniques, including x-ray diffraction (XRD), x-ray fluorescence (XRF), oranic petrography, Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM-EDS). Petrological studies identify the types of macerals and minerals associated in coals, assess their concentration, and examine their association with elements found in the coal samples. Our research also delves into the environmental implications of these elements, particularly those considered environmentally sensitive, such as As, Cd, Co, Cr, Mn, Ni, Pb, Th and U. These findings are crucial for understanding the potential environmental impact associated with the utilisation of coal. This study identified several major sources of these elements within the coal, including silicate minerals (Quartz and Feldspar), oxides (Haematite, Rutile and Anatase), sulphides (Pyrite and Marcasite), sulphates (Gypsum) and carbonates (Calcite). Recognising these sensitive components is vital as they require mitigation or elimination before coal utilisation to minimise environmental risks. Our study delivers a valuable understanding of the geochemical composition and mineralogical characteristics of coal in the Sohagpur coalfield, highlighting the importance of environmental considerations in the utilisation of these resources.

Systematic investigations into the deep diagenetic fluid environment, diagenetic evolution and their effects on reservoir properties in the deep layers of the Pinghu Formation within the N structural belt of the Xihu Sag in the East China Sea Shelf Basin remain scarce. Drawing upon petrographic thin sections, scanning electron microscopy (SEM), whole-rock and clay mineral X-ray diffraction (XRD), fluid inclusion analyses, well logging and other analytical data—integrated with burial and thermal history modelling—this study elucidates the alternating acidic and alkaline fluid conditions, their diagenetic evolutionary pathways and their consequent influence on reservoir performance. The results indicate that the deep Pinghu Formation reservoirs experienced multiple episodes of acid-alkaline diagenetic environments during their geological evolution. Presently, they are at the mid-diagenetic stage A₂, characterised by a transition from weakly alkaline to acidic and then to alkaline conditions. Acidic environments are primarily marked by the dissolution of feldspar and lithic fragments, precipitation of authigenic kaolinite, development of secondary quartz overgrowths and minor calcite dissolution. Alkaline environments are recognised by quartz dissolution, illite and chlorite cementation, carbonate precipitation and replacement, as well as albite precipitation. We establish a pore evolution model featuring ‘early compaction, intermediate dissolution and late cementation’. Four fluid environment types can be identified: weakly alkaline–weakly acidic, weakly acidic–moderately to strongly acidic, acidic–weakly alkaline and weakly alkaline–alkaline. Acidic fluids derive mainly from organic acids, complemented by humic acids, whereas alkaline conditions arise when acidic fluids are extensively consumed and metal cation enrichment elevates the pH of formation waters. Repeated cycles of acidic and alkaline diagenesis foster multi-phase carbonate cementation and clay mineral transformations. Overall, acidic fluids enhance reservoir quality, while alkaline fluids exert both constructive and destructive influences. Compaction-related porosity loss is largely depth-dependent, cementation-related porosity loss correlates with alkaline diagenesis and dissolution-related porosity gain hinges upon the intensity of acidic fluid supply.

To investigate the evaluation performance of different models across various evaluation units, 174 landslide samples were selected from Xide County, Sichuan Province, China, as the study area, considering 12 conditioning factors such as aspect, slope and elevation. Using software tools such as ArcGIS and SPSS, the landslide susceptibility in the study area was assessed across different units (12.5 and 30 m grid units and slope units). Four models were employed for this evaluation: the information value model (IV), the logistic regression model (LR), the information value–logistic regression coupled model (IV-LR) and the decision tree model (DT). The evaluation accuracy of various models across different evaluation units was analysed using rationality testing and ROC curves. The results indicate that, within the same evaluation model, the landslide susceptibility assessment accuracy for the 12.5 m grid unit surpasses that of the other two evaluation units, with an average AUC value of 0.849. Under the same evaluation unit, the IV-LR coupled model consistently demonstrated strong performance across all units, achieving the highest AUC value of 0.881 with the 12.5 m grid unit.

The final closure time and tectonic evolution of the middle segment of the Paleo-Asian Ocean (PAO) remain poorly constrained. The northern part of the Zhusileng-Hangwula arc, located in the middle segment of the Central Asian Orogenic Belt, is crucial for understanding its tectonic evolution and for constraining the closure time of the middle segment of the PAO. Field structural, microstructural, and fabric analyses reveal that the NE-trending ductile shear zone within the Baishan Formation has undergone sinistral shearing. Zircon U–Pb and ³⁹Ar/⁴⁰Ar dating indicate that the shear zones formed at 216 Ma. In addition, the northern part of the Zhusileng-Hangwula arc experienced superimposed folding deformation. Kinematic studies show that the second phase of folding refolded the tightly upright NE-trending F1 folds into NE-trending asymmetric steeply plunging F2 folds under a sinistral transpression regime. ⁴⁰Ar/³⁹Ar geochronology data indicate that the first phase of folding deformation occurred at 215 Ma, while the second phase of folding deformation occurred slightly later than 215 Ma. Geochemical characteristics indicate that the Baishan Formation formed in an active magmatic arc setting during the Late Permian. Combined with published data, the final closure time of the northern part of the Yagan and Zhusileng-Hangwula arcs in the middle segment of the PAO can be constrained to the Late Permian–Early Triassic. The formation of the shear zones and the superimposed folding deformation can be attributed to the oblique convergence orogenic process between the South Gobi Zone and the Yagan and Zhusileng-Hangwula arcs during the Late Triassic.

In carbon capture and storage system (CCS), the task of the CO₂ source–sink matching involves optimising source–sink cluster deployment, transportation path, and pipe network layouts. This task is an integral aspect of the CCS commercialization process and constitutes a combinatorial optimization problem aimed at achieving low cost and maximum storage capacity within the system. Here, a novel mathematical model of source–sink matching combinatorial optimization is established. (1) The model can account for various factors, including the lifespan of the source–sink, the capture (injection) rate of CO₂ sources (sinks), and the duration of the CCS system. The objective aimed to maximise CO₂ storage capacity while minimising transportation costs over the entire operational period. Additionally, based on genetic algorithm, a rapid solution approach was introduced to address the objective. (2) A comparative study was conducted through existing cases. The results show that, compared to the Pinch analysis method, the newly constructed optimization model in Case 1 can increase the total storage of the system by 4.6%. Similarly, the results of Case 2 demonstrate that the matching results of the new model can increase the total storage by 13.3%. (3) Through Case 3, the model provides a preferred but not unique matching scheme, which meets the criteria of maximising storage while minimising transportation costs at any given time. Finally, the practicability and reliability of the novel model were verified through the cases. The model can provide a framework for the development of source–sink matching decision system and CCS planning.

The Bocaranga area belongs to the northern part of the Adamawa-Yadé Domain (AYD) in the Central African Republic (CAR) where the occurrence and petrogenesis of mafic rocks still remain a subject of debate. New field observations, petrographic, mineralogical, and geochemical data of mafic rocks from Bocaranga show palaeo-oceanic crust character within the Adamawa-Yadé domain on the northern margin of the Congo Craton. These mafic rocks consist of amphibolites (biotite-amphibolites, garnet-amphibolites, epidote-amphibolites and actinolite-amphibolites) and amphibole-pyroxenites associated with gneisses of trondhjemite, tonalite, and granodiorite compositions (TTG). These mafic rocks display basalts, dioritic basalts, and diorites geochemical character, sub-alkaline to tholeiitic N-MORB and E-MORB affinities, with Th (0.03–1.60 ppm) and U (0.01–0.49 ppm) contents very close to the average values for oceanic crust (Th = 0.40 ppm, U = 0.12 ppm). Amphibolites derived from 5% to 15% degrees of partial melting of a mantle source are enriched in LREE relative to HREE ([La/Sm] _N  = 1.53–2.04; [Gd/Yb] _N  = 0.98–1.54; [La/Yb] _N  = 1.60–3.80), show slight Nb, Zr, Hf, and Ti negative anomalies, as well as low ratios of (Dy/Yb)_N (1.1–1.3) < 1.6 and of Nb/Y (0.1–0.2) which are compatible with the contribution of subduction components. These data are different from those from the Ngaye amphibolites (Cameroon) and those in the Adamawa-Yadé domain, which are almost similar to those of the Banda tholeiites in south-eastern CAR on the Congo Craton edges, in terms of petrography and geochemistry. Amphibole-pyroxenites show a relatively low REE fractionation ([La/Sm] _N  = 0.53; [Gd/Yb]N = 1.04; [La/Yb]_N = 1.0), derived from a relatively high degree of partial melting (35%) which is compatible with their low HFSE levels and low ratios in (La/Yb) _N  = 0.58. Similar results are described in neighbouring regions (Sudan, Chad and Cameroon) for the Bayuda Desert amphibolites, the South Ouaddaï amphibolites, the Ngaye amphibolites, Banda, and Mbomou amphibolites (Congo Craton). The petrographic and mineralogical data indicate that mafic rock from Bocaranga underwent prograde-(peak?)-retrograde metamorphism whose prograde-peak phase was attained in the upper amphibolites– to low granulite facies, coeval to the continent–continent collision between the Saharan Metacraton and the Congo Craton. The retrograde phase followed peak metamorphism in amphibolite facies for P–T conditions of 1.4–5.2 kbar and 742°C–876°C related to decompression coeval to the post–collisional history of Western Gondwana.

The Pleistocene reef terraces of the Red Sea serve as a valuable geological archive, reflecting past marine conditions and environmental fluctuations. Among these, the Farasan Islands, located in the southern Red Sea off the Saudi Arabian coast, host a remarkable diversity of coral families, including Acroporidae, Agariciidae, Euphylliidae, Fungiidae, Lobophylliidae, Merulinidae, Pocilloporidae, and Poritidae, underscoring the region's ecological significance during the Pleistocene epoch. This study focuses on the taxonomy, biogeography, and evolutionary trends of three previously unreported scleractinian coral families Diploastraeidae, Pachyseridae, and Rhizangiidae from the Pleistocene reef units at the Seir Peninsula, Farasan Islands. We document, for the first time, the occurrence of Diploastrea heliopora and Pachyseris inattesa in the Pleistocene of the Red Sea, with P. inattesa representing the first known fossil record of this species globally. A comparison between Pleistocene and extant populations reveals a significant decline in D. heliopora abundance, reflecting substantial environmental and ecological shifts over time. P. inattesa, historically misidentified under different taxonomic names, is an endemic Red Sea species with a cryptic nature, whose first fossil occurrence in this study provides new insights into its evolutionary history and biogeographic distribution. This study advances our understanding of coral diversity and environmental changes in the Red Sea's Pleistocene reefs. It highlights the importance of fossil records in tracking biodiversity shifts and underscores the need for further research on the geographic distribution and conservation of these coral genera.