Search Results (334)

Pressurized seepage alters the water-accessible pore system of clay-mineral-rich slate, but its scale-dependent response remains unclear. Argillaceous calcareous slate from the Lower Cambrian Qiongzhusi Formation (Є₁q) was investigated using paired low-field NMR measurements on two specimen batches before and after 72 h treatments at nominal 0 MPa (low-head seepage), 1, 3, and 5 MPa. Total pore volume, pore-size composition, characteristic radii, and pore-size non-uniformity were evaluated. The total pore-volume increment increased from 0.98% to 1.43% in Batch I and from 0.88% to 1.56% in Batch II between 0 and 5 MPa. The dominant peak remained near 1.2 × 10⁻² μm, whereas its amplitude and large-pore spectral tail increased. The combined nanopore and micropore proportion decreased from 90.16–95.28% before treatment to 83.13–89.69% after treatment. The macropore increment increased from 0.15%/0.16% to 0.52%/0.52% in Batches I/II, while r₅₀, r₆₀, and C_u increased and r₁₀ changed only slightly. Sensitivity analysis over ρ₂ = 5–50 μm/s preserved the larger-pore enhancement. These results indicate pressure-enhanced opening, water accessibility, and local redistribution of pre-existing pores rather than extensive pore-system reconstruction, providing a pore-scale reference for seepage-related deterioration assessment. Full article

Oil–source relationships in the Tarim Basin remain controversial because Paleozoic oils may record contributions from multiple marine source rock systems. We compiled 207 source rock trace element, 184 source rock rare earth element (REE), 44 crude oil trace element, and 33 crude oil REE records to evaluate elemental proxies in an overmature marine carbonate petroleum system. Lower Cambrian source rocks generally record more reducing conditions than the Saergan Formation, although both groups are compositionally variable. PERMANOVA shows significant separation in V/Ni–Ni/Co and Ni/Mo–Mo/Co spaces (R² = 0.4675 and 0.6381; p < 0.001), but PERMDISP indicates unequal dispersion only for V/Ni–Ni/Co. Thus, Ni/Mo–Mo/Co provides the more robust source rock separation. Some Ordovician reservoir oils are compositionally compatible with the Lower Cambrian field, whereas others occupy intermediate or outlying positions. However, whole-rock and ashed oil analyses represent different elemental pools, precluding unique genetic assignment. REE parameters have limited discriminatory capacity because source rock fields overlap and oil data are incomplete and strongly study dependent. V–Ni–Mo–Co relationships should therefore be used as complementary evidence together with biomarkers, stable isotopes, and regional petroleum geology. Full article

The Tazhong No. 2 fault zone is a major fault zone in the Tazhong area, and studying its structural characteristics is of great significance for hydrocarbon exploration. Based on detailed structural interpretation of 2D and 3D seismic data, this study suggests that the Tazhong No. 2 fault zone exhibits distinct segmented deformation characteristics and can be divided into four segments along strike, with the individual structural segments bounded by NE-trending strike-slip faults. The eastern and western parts of the Tazhong No. 2 fault zone differ in their evolutionary characteristics: during the early stage, deformation was intense in the east and relatively weak in the west, whereas during the late stage, the central segment was more active while the eastern and western segments were essentially inactive. Vertically, the fault zone displays stratified deformation: taking the Middle–Lower Cambrian evaporites as the boundary, the suprasalt strata are more strongly deformed than the subsalt strata. The segmented and layered deformation characteristics of the Tazhong No. 2 fault zone are mainly controlled by factors such as the basement structure, the Middle–Lower Cambrian evaporites, and regional tectonic events. Based on the segment-specific accumulation–evolution model, the shallow fault–lithologic traps and volcanic-rock-related traps in the west, the subsalt structural traps, and the buried-hill interior and drape traps are all favorable exploration targets. Full article

This study takes the Ankang area in the Qinling–Dabashan Mountains on the northern margin of the Yangtze Block as an example to investigate whether effective shale gas preservation conditions can exist in large-scale thrust nappe belts at convergent plate margins—a critical scientific question. The aim is to provide new concepts and models for shale gas exploration in tectonically complex regions. An integrated approach combining surface geological mapping, geophysical surveying (2D seismic and wide-field electromagnetic method), calibration of a key borehole (ZBDR01), and geochemical analysis was employed to reconstruct the deep geological structure and evaluate the hydrocarbon generation potential and reservoir characteristics of the target shale interval. The results reveal a relatively gentle, weakly deformed “structural stability window” beneath the Zhongbao Fault, a major thrust nappe surface. Within this window, strata dip at low angles and faults are sparse, exhibiting a significant stress-shielding effect. The Lower Cambrian Niutitang Formation shale within this window is well preserved, characterized by high total organic carbon (average TOC: 4.26%) and moderate thermal maturity (average R_o = 3.02%), falling within the effective shale gas generation window. In contrast, the Lujiaping Formation shale in the hanging wall of the fault, though widely distributed, shows excessive thermal maturity and poor reservoir properties. The study demonstrates that the “stress-shielding” effect is the core mechanism controlling the formation of this stability window and proposes a new “tectonic shielding” accumulation model. This model elucidates how the thrust nappe body itself acts as a thick regional caprock, which together with lateral sealing by the fault zone forms a composite seal-cap system, ensuring in situ preservation of shale gas under a strongly tectonic background. It is concluded that local preservation units can form in the footwalls of thrust nappe belts at convergent plate margins due to stress shielding, challenging the conventional view that intensely deformed zones are unfavorable for shale gas preservation. This research not only provides a new direction and model for shale gas exploration in the tectonically complex Qinling–Dabashan region but also offers important theoretical and technical insights for unconventional hydrocarbon exploration in similar tectonic settings globally. Full article

Chitons, ancient polyplacophoran mollusks, are ideal models for studying biomineralization evolution due to their conserved morphology since the Cambrian. This study investigates the matrix proteins in shell plates and spicules of Acanthochitona rubrolineata using liquid chromatography–tandem mass spectrometry. By extracting proteins from 30 individuals and using proteomic method, we identified 26 soluble proteins and 22 insoluble proteins in the shell plates and 25 insoluble proteins, and found domains such as von Willebrand factor type A, chitin-binding, ferritin, and cadherin. These domains, prevalent in molluscan biominerals, suggest conserved roles in organic matrix formation. Despite genomic dynamism, the conservation of key domains across species highlights a core biomineralization mechanism. Notably, eight of the shell proteins and eight of the spicule proteins were homologous between A. rubrolineata and chiton Acanthopleura loochooana, indicating functional conservation. Phylogenetic analysis further supported the evolutionary significance of these domains in chitons. The study advances understanding of biomineralization in Polyplacophora, emphasizing the interplay between morphological stasis and molecular evolution. Full article

Organic matter (OM) enrichment is a fundamental control on source-rock quality and shale-gas potential, yet the relative roles of organic matter supply, preservation, and mineralogical dilution remain poorly constrained in the Lower Cambrian Niutitang Formation at the northwestern margin of the Upper Yangtze Platform. Nineteen shale samples from Well ZHD1 in the Zhenba area, on the northwestern Upper Yangtze Platform, were analyzed for total organic carbon (TOC), mineral composition, and major and trace elements. TOC contents range from 0.98% to 9.09%, with an average of 3.82%, while quartz and clay minerals range from 25% to 44% and from 27% to 53%, respectively. Among the sampled intervals, the middle interval (1694.00~1709.75 m) is characterized by the highest TOC contents (4.48~9.09%), accompanied by elevated Si_excess (10.95~11.67), U/Th (2.60~6.84), Mo_EF (16.83~34.38), and U_EF (9.74~23.85). In contrast, Ti/Al and CIA show relatively limited variations across the sampled section. Quartz is positively related to TOC, whereas clay and carbonate minerals show negative relationships with TOC. Paleoproductivity increased from the lower interval to a maximum during the middle interval and then declined during the upper interval. Redox conditions evolved from moderately reducing to persistently anoxic during the middle interval before becoming less reducing. The middle interval records the highest TOC contents, greatest paleoproductivity, and most favorable preservation conditions. The combined Si_excess, mineralogical, and detrital-input evidence is consistent with a significant biogenic contribution to the non-detrital silica, although subordinate hydrothermal or authigenic contributions cannot be completely excluded. The negative relationships of clay and carbonate minerals with TOC are consistent with a net dilution effect at the bulk-rock scale, although potential clay-surface protection of OM cannot be excluded. These results emphasize the coupled effects of productivity and preservation rather than a single dominant control and provide region-specific constraints on OM enrichment in the northwestern Upper Yangtze Platform. Full article

Drying is widely used to stabilize foods, but long processing times and thermal exposure increase energy demand and can impair color, texture, nutrients, and flavor. Cold plasma (CP) pretreatment has attracted interest as a nonthermal strategy for accelerating moisture removal while maintaining product quality. This critical review examines CP pretreatment-assisted drying across food materials by linking structural remodeling with redox regulation and metabolic responses. Current evidence shows that changes in surface wettability, cuticular barriers, cell-wall and membrane integrity, and pore connectivity can facilitate water migration and shorten drying. CP-associated modulation of browning enzymes, oxidative status, and bioactive or flavor-related metabolites may also influence color, antioxidant capacity, nutrient retention, and flavor. However, these effects vary with discharge mode, treatment intensity, gas composition, pressure, temperature, and food-matrix properties. Excessive exposure can instead aggravate oxidation and diminish product quality. Current mechanistic evidence is strongest for plant foods and edible fungi and remains limited for animal-source foods. Together, these findings link plasma-generated chemical and physical agents to structural, biochemical, and drying responses. They provide a basis for defining material-specific operating windows and developing reproducible, safe, and scalable CP pretreatment-assisted drying of foods. Full article

An accurate prediction of gypsum-salt cap rocks is crucial for safe drilling and efficient development of subsalt hydrocarbons in the Tarim Basin. However, due to the complex lithological assemblages within the Middle Cambrian sequences, the P-impedance of gypsum severely overlaps with that of the background carbonate rocks, making conventional seismic prediction based on a single impedance threshold inadequate. To address this issue, this paper proposes a multi-parameter coupling while-drilling prediction method that integrates seismic data, drilling parameters and geochemical logging. First, pre-stack P-impedance inversion is performed on amplitude-preserved seismic data to macroscopically delineate the depth interval of gypsum-salt development. Second, a weighted synthetic change-rate model incorporating drilling time (DT), weight on bit (WOB), and outlet conductivity is constructed to dynamically calibrate the top interface of the gypsum-salt layer while drilling. Finally, within the constrained depth interval, X-ray fluorescence (XRF) elemental inversion of cuttings is used to quantitatively calculate the contents of clay, dolomite, gypsum and calcite, achieving fine-scale lithofacies identification at the sublayer level. An empirical application to Well XSC1 in the Keping fault-uplift, Tarim Basin, demonstrates that compared with the conventional single P-impedance threshold method, the proposed approach effectively distinguishes gypsum, salt and carbonate wall rocks, and significantly reduces the prediction errors of individual salt beds and gypsum sublayers. Specifically, the mean absolute error (MAE) of total gypsum-salt content decreases from 24.56% to 13.73% (a reduction of 44.1%), the bias drops from 2.45% to 0.31%, and the root mean square error (RMSE) decreases from 33.63% to 21.55%. At a 1% content threshold, the F1 score for gypsum-salt identification increases from 0.63 to 0.82; the absolute depth error of the top and bottom interfaces is reduced by approximately 70%, and the relative thickness error shrinks from $\pm$40% to within $\pm$10%. Transferability of this multi-parameter coupling strategy to other salt-bearing basins in central-western China remains unvalidated and requires future validation and testing. Full article

Located 30 km south–southeast of Kabul in Logar province, Aynak is the largest and best-known copper orebody in Afghanistan. The deposit is hosted by the Loy Khwar Formation, a Neoproterozoic–Cambrian metasedimentary sequence of dolomite marble, carbonaceous quartz schist and quartz–biotite–dolomite schist. The primary ore minerals are chalcopyrite and bornite, with less abundant pyrite and minor cobaltite, chalcocite, pyrrhotite, sphalerite and molybdenite. Sulphides occur as bedded laminae and disseminations, in metamorphic segregations, and in syn- to post-metamorphic cross-cutting veins. Building on the mineralogical, lithogeochemical and sulphur isotope framework established by Waizy et al. (2020), ICP-MS analyses of sulphide-rich separates from Central and Western Aynak (n = 31) were undertaken to characterise trace-element distributions, evaluate possible metal sources, and further constrain the genetic model of the deposit. Co and As enrichment in chalcopyrite-dominant samples is consistent with cobaltite, whereas Co enrichment in the absence of arsenic suggests the possible presence of carrollite. Fluid inclusion analyses of secondary quartz-hosted inclusions indicate interaction between the Aynak deposits and saline aqueous fluids (32 to 47 equivalent wt% NaCl) at minimum P-T conditions of ~100–200 MPa and 300 °C. It is uncertain whether these fluid parameters relate to primary copper transport and deposition, or to remobilisation during metamorphism. Nevertheless, comparison with analogous sediment-hosted copper deposits suggests that highly saline basinal brines played an important role in the formation and evolution of the deposit. Occurrences of scapolite provide additional evidence for a model of brine-related mineralisation. Together with previously published mineralogical, lithogeochemical and sulphur isotope evidence, these findings support a sedimentary–diagenetic origin for the Aynak copper deposit that is broadly comparable with sediment-hosted stratiform copper systems of the Central African Copperbelt. Full article

The southern Zhuguangshan complex is one of the most important sources of granite-hosted uranium deposits in the Nanling region and consists predominantly of Caledonian (Cambrian–Silurian), Indosinian (Late Permian–Triassic), and Yanshanian (Jurassic–Cretaceous) granitoids. However, the Caledonian plutonic rocks have not yet been systematically investigated. In this study, we present new LA-ICP-MS zircon U–Pb ages and Hf isotopes, together with whole-rock elemental and Sr–Nd isotope data, for the Guantian and Shangbao granodiorites from the southern Zhuguangshan complex, in order to constrain their petrogenesis and tectonic setting. Zircon U–Pb dating yields emplacement ages of ca. 431.5 and 442.3 Ma for the Guantian and Shangbao plutons, respectively. Both plutons are characterized by high Al₂O₃ (14.35–14.77 wt.% and 13.55–14.38 wt.%) and total alkali (Na₂O + K₂O = 6.22–6.82 wt.% and 6.46–6.85 wt.%) contents, with A/CNK ratios <1.0, and are classified as metaluminous I-type granites. They show enrichment in light rare earth elements (LREE), K, Th, and U, coupled with marked depletion in Ba, Sr, Nb, Ta, P, and Ti, and exhibit pronounced negative Eu anomalies. These geochemical signatures indicate fractional crystallization of Ti-bearing minerals (e.g., rutile and ilmenite) and plagioclase. The granodiorites have initial ⁸⁷Sr/⁸⁶Sr ratios of 0.70595–0.71227, negative εNd(t) values (−7.8 to −4.1), and negative εHf(t) values (−8.7 to −0.4), pointing to a dominantly continental crustal source. Their average Nb/Ta (11.42) and Th/U (5.07) ratios are also consistent with typical continental crust. Based on the lithological assemblage and geochemical characteristics, we propose that the Guantian and Shangbao granodiorites were formed in a post-collisional extensional setting. Full article

Despite recent Cambrian subsalt gas discoveries in the Keping fault-uplift, northwestern Tarim Basin, organic abundance, type, maturity, and depositional setting of Lower Cambrian source rocks remain poorly documented. We evaluated the Yuertusi and Lower Xiaoerbulake Formations using total organic carbon (TOC) analysis, Rock-Eval pyrolysis, kerogen microscopy, solid bitumen reflectance, X-ray diffraction, and ICP-MS trace-element analysis of samples from 11 wells and 6 outcrops. The Yuertusi Formation is organic-rich in northern Keping (TOC = 0.13–28.20%) but thins and deteriorates southward. The Lower Xiaoerbulake Formation (TOC = 0.10–9.68%; 70–160 m thick) is a widespread, moderate-to-good source rock, challenging the view that the Yuertusi Formation is the only Cambrian source rock. Sapropelinite-dominated kerogen (>80%) indicates Type I–II organic matter; equivalent vitrinite reflectance (2.28–3.50%) confirms overmature, gas-prone rocks. The Yuertusi Formation reflects upwelling-fed high productivity and anoxic–euxinic waters; the Lower Xiaoerbulake Formation, moderately high productivity and dysoxic waters. The subsalt gas is oil-cracked gas from marine sapropelic source rocks of either formation. Chloroform bitumen “A” estimates give in-place gas resources of 1121.4 × 10⁹ m³; the static share for southern Keping (20.1 × 10⁹ m³) understates its dynamic potential. A lower-generation/upper-reservoir, fault-controlled, near-source model favors Trap 1-1 for future drilling. Full article

Inverted swimming behavior has been documented in marine arthropods from the Cambrian to modern oceans. It was previously theorized that this behavior contributed to bringing the center of gravity to a lower position, thereby enhancing balance and stability, and preventing clogging of the mouth in deposit and suspension feeders. In this study, by using the computational fluid dynamics analysis method and wave impact experiments, we evaluate the hydrodynamics of inverted swimming behavior in the early Cambrian Ercaicunia multinodosa when it was at the water surface. The results show that when Ercaicunia multinodosa swam at the water surface, the inverted swimming was more stable than the normal posture regardless of the direction from which the waves came. Moreover, as the wave amplitude increased (within the tested and validated range of 0.33 to 1.0 times the body height), the rate at which the flipping occurred in the normal posture was accelerated and then remained stable in the inverted posture. Finally, we used a stereolithography apparatus to create a physical model of Ercaicunia multinodosa and performed wave impact experiments to verify the research results. Our findings support the hypothesis that the inverted swimming behavior of Ercaicunia multinodosa helps increase balance and stability. Full article

The Lower Cambrian Yurtus Formation along the northwestern margin of the Tarim Basin has commonly been regarded as a regionally developed marine source-rock interval. However, the formation features strong internal source-rock heterogeneity, and the paleogeographic mechanism governing its thin organic-poor intervals remains to be further clarified, which constrains a more comprehensive understanding and evaluation of the Yurtus Formation. This study integrated whole-well source-rock geochemical data with major- and trace-element records from Well K1 in the Keping area to evaluate the geochemical background of the Yurtus Formation, its contrast with adjacent strata, and the internal differentiation of a thin and organic-poor interval at 5269–5274 m. The whole-well dataset of analytical results shows that the deep Yurtus-related section occurs within an overall low-TOC and low-S2 background. The 5269–5274 m interval is represented by only approximately 5 m of source-rock-bearing strata and is compositionally distinct from the adjacent carbonate-dominated strata. Compared with the adjacent intervals, the target interval has higher mean Al, Si, K, Ti, Fe, V, Cr, Zr, Rb, Sr, and U values, but lower Ca and Mg values. Elemental profiles and ratio data further define three first-order meter-scale geochemical subunits: an upper carbonate-rich subunit with high Ca and Ca/Al values, a middle aluminosilicate-rich subunit with higher Al, Si, K, Ti, and Fe values, and a lower chemically enriched subunit marked by elevated V, Cr, U, Sr, P/Ti, Sr/Ca, V/Cr, and S/Fe values. Mo enrichment is weak, and the available Mo–U and Mo/Al evidence does not support a definitive interpretation of persistent euxinic conditions. Therefore, the lower subunit is interpreted as recording relatively stronger reducing and chemically reactive conditions rather than a stable euxinic water column. Elevated P/Ti in the lower subunit is treated as phosphorus enrichment associated with redox-sensitive chemical fixation and/or early diagenetic redistribution, rather than as direct evidence for increased primary productivity alone. Regional comparison with published Yurtus sections and wells indicates that the thin, low-TOC, and compositionally differentiated interval in Well K1 represents a local expression of source-rock heterogeneity. The results suggest that slope-break-related paleogeographic differentiation controlled accommodation, sediment supply, hydrodynamic disturbance, preservation efficiency, and early diagenetic modification, thereby governing the heterogeneous development of the Yurtus Formation along the northwestern Tarim margin. Full article

Ultra-deep dolomite formations exhibit pronounced mechanical heterogeneity governed by mineral composition, inter-particle cementation, and observation scale, complicating their mechanical characterization. Because intact downhole cores are difficult to obtain, a mesoscopic numerical framework that reproduces and classifies such behavior is needed. A two-dimensional mesoscopic model of Cambrian ultra-deep dolomite from the Tarim Basin was developed using the combined finite–discrete element method, incorporating mineral composition from X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy. A Weibull-distribution discretization scheme was introduced to represent matrix and cementation heterogeneity separately. Sensitivity analyses examined three factor groups: mineral composition and spatial distribution, matrix and cementation shape parameters, and mesh size as the observation scale. Accordingly, a three-level graded characterization framework was proposed, in which the compositional level governs strength magnitude; the structural level governs the elastic modulus, pre-peak nonlinearity and failure mode; and the scale level governs response representativeness and convergence. Quantitative grading indicators and threshold ranges were extracted for each level. Triaxial validation against laboratory experiments at confining pressures of 0 to 220 MPa confirmed strength and stress–strain response consistent with the proposed grading. The model and framework offer a transferable methodological reference for the mesoscopic mechanical evaluation of ultra-deep heterogeneous dolomite. Full article