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Weidong He，Yunpeng Dong，Jiaopeng Sun，Junxiang Zhang
2026,100(3):511-538, DOI: 10.1111/1755-6724.70064
Abstract:
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.
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Youpeng Zhang，Chao Wang，Haoxuan Li，Zhenbang Liu，Xiaodong Wang
2026,100(3):539-555, DOI: 10.1111/1755-6724.70062
Abstract:
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 (εNd(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.
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2026,100(3):556-575, DOI: /10.1111/1755-6724.70046
Abstract:
The Changchengian System represents one of the earliest sedimentary covers deposited on the Archean–Paleoproterozoic basement of the North China Craton. We report zircon U-Pb-Hf isotope data for Changzhougou Formation sandstones in the Chaiguan area, central–southern Taihang Mountains. The youngest detrital zircon ages (~1782 Ma) constrain the maximum depositional age to ~1.78 Ga. Combined with regional constraints, deposition is bracketed between ~1.76 and ~1.64 Ga. Detrital zircon age spectra exhibit a dominant peak at ~2.5 Ga, with secondary peaks at 2.8–2.6, 2.2–2.0 and 1.9–1.8 Ga, alongside rare ~3.25 and ~3.70 Ga grains. Coupled with Hf isotopic signatures, these diverse populations suggest derivation primarily from the basement of the Trans-North China Orogen. Although the age spectra are broadly similar to the Archean-dominated Yanliao Rift, the presence of subordinate Paleoproterozoic and minor Paleoarchean grains, coupled with a predominant southeast-to-northwest paleocurrent, implies a closer affinity with the Xiong’er Group. These results suggest deposition in an extensional setting—likely associated with the breakup of the Columbia supercontinent—and record a northward marine transgression from the Xiong’er Rift Basin. Consequently, the central–southern Taihang Mountains served as a critical transition zone connecting the Xiong’er Basin with the Yanliao Basin.
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2026,100(3):576-599, DOI: /10.1111/1755-6724.70060
Abstract:
The Beishan Fold-Thrust Belt (BFTB), located in the southern part of the Central Asian Orogenic Belt (CAOB), underwent complex intracontinental deformation during the late Mesozoic and is a key tectonic unit for deciphering the remote effects of plate margin orogenesis. In this study, we selected the Yemaquan region in southern Beishan and conducted remote sensing interpretation, field mapping, seismic profile interpretation and low-temperature thermochronological analyses. The Permian pluton and Carboniferous strata thrust over the Jurassic strata and developed a series of SEE-trending thrusts, NE-striking left strike-slip faults, and several SEE- and NE-trending folds. This area experienced two directions (NE and NW) of compression deformation. Under the joint influence of compression stress and pluton blocking, fold structures related to strike-slip faults also developed (the Big Ear syncline). The above constituted the Yemaquan Fold-Thrust system (YFTS). Zircon (U-Th)/He (ZHe) data reveal cooling events at ~175–165 Ma; combining the regional deformation, it may indicate the compression time. We concluded that the intracontinental deformation of the BFTB in the southern CAOB was driven by the far-field effects. NE compression is related to the closure of the Mongol–Okhotsk Ocean and the collision of the Lhasa–Qiangtang block; NW compression is related to westward subduction of the Paleo-Pacific plate.
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Huiju Shi，Lin Wu，Shuwei Guan，Peng Xia，Yuyang Liu，Zhuliang Qian
2026,100(3):600-615, DOI: 10.1111/1755-6724.70049
Abstract:
The Sichuan Basin, adjacent to the Himalayas in China, exhibits complex structural deformation and stress regimes, necessitating systematic structural and stress analysis. The Luzhou region in the southern Sichuan Basin is cut by three sets of faults, which trend NNE (NE)–SSW (SW), E (NEE)–W (SWW), and N (NNW)–S (SSE). Late Ordovician to early Silurian strata lie between the basement and cover sequences, and the faults are mainly extrusion thrust faults. Integrated geophysical data and finite element numerical modelling reveal that the maximum horizontal principal stress (SH) is 76–131 MPa, the minimum horizontal principal stress (Sh) is 64–113 MPa, and the vertical stress (Sv) is 69–125 MPa, consistent with a strike-slip regime (SH >Sv >Sh). Consequently, the present-day stress regime differs from that of existing thrust-fault models. The NNE (NE)–SSW (SW) trending faults have the greatest impact on the magnitude and orientation of the stress, and the E (NEE)–W (SWW) faults have the greatest impact on the horizontal stress differences (ΔS). ΔS is negatively correlated with the total gas content and negatively correlated with borehole deformation in seven wells in the Luzhou region; therefore, E (NEE)–W (SWW) trending faults should be avoided during petroleum exploration in the Luzhou region.
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Joyjeet Sen，Shamik Sarkar，Nibir Mandal
2026,100(3):616-636, DOI: 10.1111/1755-6724.70050
Abstract:
Using a novel thermo-mechanical model, this study explores the role of multi-ordered 3D convective dynamics of the mushy region in modulating the strongly heterogeneous stress fields in mid-ocean ridge (MOR) systems. This model couples the subridge mushy (fluid) regions with the elastic (solid) crustal layer within a mathematical framework of fluid–structure interaction (FSI) mechanics. Model-based calculations of the total stress tensor provide quantitative estimates of the across- and along-axis horizontal tension/compression (σ丄 and σ聂) and across-axis horizontal shear stress (σ#) that dominantly control the ridge-axis morphologies. The stress analysis forms an alternative explanation for the off-axis ridge-parallel second-order hill topography, located at a distance of 20–50 km. This study also shows how along-axis compressional σ聂 can localise a row of ridge-normal narrow, 10–30 km wide stripes on a wavelength of 40–150 km. Their overall patterns conform to the second-order magmatic segmentation structures of MORs. The σ# mapping suggests that ridge-transverse discontinuities, including transform offsets, transpression and transtension zones, originate spontaneously from FSI interactions during MOR evolution. The article finally presents a set of MOR examples from modern plate tectonic settings to support model interpretations.
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Hui Qian，James Mechie，Haibing Li，Xiaosan Zhu，Dongliang Liu
2026,100(3):637-650, DOI: 10.1111/1755-6724.70057
Abstract:
A dense seismological profile with 45 stations at a spacing of 5–10 km across the Longmenshan fault zone was deployed from 2018 to 2020. It complemented an array of 80 stations deployed in the region from 2012 to 2013. Using data from both deployments, dispersion curves were obtained from ambient noise Green’s functions. Subsequently, a 3D shear (S) velocity model was derived using tomographic methods. Combining this S-wave velocity model with an existing 3D compressional velocity model, a 3D Poisson’s ratio model was derived. These models show that the Precambrian Pengguan complex, which cores this part of the Longmenshan, is approximately 20-km thick and displays high velocities and low Poisson’s ratios. The result of this study is that, along the dense profile, the complex is underlain between 20 and 40 km depth by low S velocities, which likely extend out beneath the Sichuan Basin in a 10-km thick basal crustal layer. These low S velocity zones have high Poisson’s ratios and are best explained as a result of the compressive forces and push exerted by the Tibetan Plateau, causing processes such as ductile shearing and fluid/melt infiltration to occur.
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Yantong Wang，Xuanlong Shan，Guoqiang An，Ang Li，Yuhui Feng，Jian Yi，Yu Bai
2026,100(3):651-672, DOI: 10.1111/1755-6724.70068
Abstract:
The Central Asian Orogenic Belt (CAOB) is Earth’s largest Phanerozoic accretionary orogen, yet the tempo and mechanisms of arc magmatism remain incompletely constrained. Carboniferous island-arc volcanism in the Zhongguai Uplift, northwestern Junggar Basin, is investigated to establish magmatic cyclicity during closure of the Paleo-Asian Ocean. Integrated 3D seismic interpretation and well-log correlation, together with zircon U-Pb geochronology, whole-rock major–trace element geochemistry and Sr-Nd-Pb isotopes, subdivide the Carboniferous volcanic succession into three volcanic cycles. Cycle I (ca. 335–322 Ma; Early Carboniferous) is dominated by intermediate to mafic lavas and volcanic breccias and exhibits typical subduction-arc characteristics. Cycle II (ca. 321–317 Ma; Late Carboniferous) comprises a felsic-dominated interval (dacite–tonalite) and is interpreted to relate to slabwindow processes. Cycle III (ca. 313–303 Ma; latest Carboniferous–earliest Permian) forms a thick bimodal assemblage from andesite to rhyolite, consistent with arc–continent collision and subsequent tectonic reworking. Geochemical–isotopic signatures evolve from a fluid-modified depleted mantle source in Cycle I, to highly fractionated and slab-influenced melts in Cycle II, and to mixed mantle–crust magmas with locally developed A-type affinities in Cycle III. The cycle-based stratigraphic and geochemical framework documents a transition from oceanic subduction to collision along the West Junggar margin, refines the timing of PaleoAsian Ocean closure and highlights that Carboniferous arc magmatism occurred in discrete pulses linked to tectonic events. This integrated approach provides constraints on episodic arc magmatism and associated continental crustal growth in accretionary orogens.
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2026,100(3):673-687, DOI: 10.1111/1755-6724.70055
Abstract:
The mid-Neoproterozoic tectonic evolution of the western Jiangnan Orogen in the context of the Rodinia supercontinent remains unresolved due to debates regarding the interpretation of the petrogenesis of igneous rocks. In this study, we present an integrated dataset of petrology, whole-rock geochemistry, zircon U-Pb ages, and Hf isotopes for granitic samples from the Fanjingshan area in the western Jiangnan Orogen. LA-ICP-MS zircon U-Pb dating indicates that they crystallised ca. 810 Ma. Whole-rock geochemical data demonstrate that they exhibit typical features of S-type granites and were derived from dehydration melting of a metasedimentary protolith. Zircon εHf(t) values range from _7.9 to 1.6, with a main peak value of _3.5. Two-stage Hf model ages of 1.5–1.9 Ga suggest that these granites were derived from ancient crustal materials. Extensive fractional crystallisation and magmatic–hydrothermal interactions are inferred from low rare earth element (REE) contents, low Nb/Ta and Zr/Hf ratios, and a distinct REE tetrad effect. Combined with coeval arc-related magmatism and rift basins, the Fanjingshan granites were most likely emplaced in a back-arc setting. Available data indicate that rift basins occurred extensively at the periphery of the Yangtze Block ca. 810 Ga, implying their involvement in the breakup of the Rodinia supercontinent.
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Seyed Ali Mazhari，Santosh Kumar
2026,100(3):688-707, DOI: 10.1111/1755-6724.70056
Abstract:
The Zouzan pluton in the Lut Block (eastern Iran) comprises coeval gabbro–diorite and felsic intrusions that contain abundant mafic enclaves (MEs). Integrated zircon U-Pb dating, whole-rock Sr-Nd isotopes and amphibole-apatite chemistry are used to investigate ME formation. Zircon ages indicate synchronous emplacement of the gabbro–diorite, MEs, and granodiorite ca. 40 Ma. The MEs plot along a Sr-Nd isotopic mixing line between mantle-derived gabbro–diorite and more crustally contaminated granodiorite, supporting a magma-mixing origin. Mineral chemistry, however, reveals more complex interactions. Apatite in MEs is acicular with trace element compositions intermediate between those of mafic and felsic magmas, indicating rapid crystallisation from a hybrid melt. Amphiboles display two distinct compositional groups: one matching gabbro–diorite amphiboles and the other resembling those in the granodiorite. This bimodality suggests that ME formation involved incomplete mixing, crystal transfer between magmas and variable re-equilibration rather than simple hybridisation. A dynamic model is proposed in which mafic magma globules were injected into a partly crystallised felsic chamber, producing mingling, quenching and crystal exchange that ultimately shaped the petrographic and geochemical features of the Zouzan pluton.
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Vartan Simmonds，Mohssen Moazzen，Gültekin Topuz，Ali Mohammadi，Thomas Zack，Marcel Guillong
2026,100(3):708-730, DOI: 10.1111/1755-6724.70059
Abstract:
The Qaradagh Batholith in northwestern Iran, adjacent to the Meghri–Ordubad pluton (MOP) within the South Armenian Block, is dominated by granodiorite, which represents its earliest intrusive phase. Both the Qaradagh Batholith and the MOP formed in a subduction-to-post collisional setting linked to the closure of Neo-Tethys Ocean between middle Eocene and early Miocene. U–Pb zircon dating of the granodiorite was conducted to constrain its emplacement age, yielding a 206Pb/238U weighted mean age of 43.81 ± 0.18 Ma and a U–Pb concordia age of 44.04 ± 1.00 Ma, placing intrusion in the middle Eocene, earlier than previously suggested Oligocene ages. In situ zircon Lu–Hf isotope analyses, conducted to determine magma source characteristics, yielded εHf(t) values between +8.7 and +11.1, indicating derivation from a depleted, juvenile mantle source with minimal crustal contamination. This is supported by low initial 87Sr/86Sr (0.7037–0.7041), positive εNd(i) (+2.69) and low zircon U and Th contents relative to Miocene intrusions in NW Iran, which have higher crustal contribution. Model TDM ages of zircons (256–354 Ma) indicate a Carboniferous–Permian source material, consistent with late Paleozoic subduction. These results place the Qaradagh granodiorite among the earliest manifestations of Paleogene magmatism in the region.
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Bowen Zhou，Lin Ding，Jinxiang Li，Chao Wang，Zheng Yin，Guanglong Deng，Yahui Yue，Fulong Cai
2026,100(3):731-744, DOI: 10.1111/1755-6724.70070
Abstract:
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.
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Tongzhi Lu，Junsheng Luo，Zhifeng Wan，Juncheng Hu，Xuewan Wu，Bing Zou，Qiqi Chen，Leyao Ran
2026,100(3):745-763, DOI: 10.1111/1755-6724.70045
Abstract:
As products of deep fluid-tectonic-sedimentary coupling, mud volcanoes have scientific value for oil–gas exploration, indicate neotectonic activity and aid global climate change studies. This study focuses on mud volcanoes in China’s offshore areas (northern South China Sea, Okinawa Trough of the East China Sea), investigating tectonic control on their development and fluid activity’s impact on shallow gas and gas hydrate accumulation. Through numerical simulation, stress field analysis and comparative geological background analysis, key findings include: (1) Tectonically controlled distribution: strike-slip extensional basins host large mud diapirs, extensional basins small–medium ones and compressional back-arc basins show zonal clustering; intensified tectonic activity exacerbates fluid seepage. (2) Formation relies on coupling of ‘material basis-dynamic conditions-triggering mechanisms’: Early Cenozoic mud-rich strata (material), overpressure (driven by undercompaction/hydrocarbon generation, dynamics), and tectonic/seismic activity (triggers). (3) Fluid seepage correlates with parameters: overpressure coefficient positively correlates with eruption intensity; shallower source layers and increased compressive stress enhance seepage efficiency. (4) Mud volcanoes influence accumulation via ‘gas supply-channel transport-temperature-pressure regulation’, acting as a ‘source-channeltrap’ system to promote enrichment, though deep thermal fluid upwelling may cause hydrate dissociation and hazards. This study elucidates their formation mechanisms and resource-environmental effects, providing theoretical support for deep-water oil–gas exploration and geohazard early warning
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2026,100(3):764-780, DOI: 10.1111/1755-6724.70051
Abstract:
The structural evolution and deformation conditions of ore-controlling shear zones in the large-scale Jinshan orogenic gold deposit were studied through structural mapping, petrographic analysis and electron backscatter diffraction (EBSD) observation. Four distinct deformation events are identified, including pre-mineralisation ductile deformation (D1 and D2), syn-mineralisation brittle?ductile shearing (D3) and post-mineralisation brittle faulting (D4). Gold-bearing quartz veins are confined to D3-stage NE–SW-trending shear zones characterised by thrust plus sinistral slip movement under NW–SE-oriented compression. The mineral assemblage includes pyrite, arsenopyrite, chalcopyrite, galena, and native gold associated with quartz-sericite alteration. The quartz can be divided into two groups: pre-mineralisation coarse (>100 μm) grains and gold-related fine (<50 μm) grains. The coarse-grained quartz displays dominant prism and rhomb slip with intermediate- to high-temperature deformation fabrics (400?C–600?C) and has undergone sub-grain rotation recrystallisation after its formation. In contrast, the gold-related quartz distributed along the margins of coarse-grained quartz displays bulging recrystallisation with dominant basal slip, indicating intermediate- to low-temperature conditions (300?C–400?C). The intermediate- to low-temperature gold mineralisation event overprinted earlier intermediate- to high-temperature fabrics. This study highlights that the reactivation of the pre-mineralisation shear zones provided fluid pathways for subsequent auriferous fluid flow and gold deposition.
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2026,100(3):781-794, DOI: 10.1111/1755-6724.70047
Abstract:
The Jinqingding gold deposit in eastern Jiaodong is a significant gold mineralization within the Muping–Rushan metallogenic belt. This study integrates structural analysis and trace element geochemistry of sulphides to elucidate ore-controlling mechanisms and metallogenic models. The deposit occurs as pyrite-quartz veins and polymetallic sulphide veins/disseminations hosted in biotite monzonitic granite, controlled by the NNE-striking Jiangjunshi–Quhezhuang fault. Structural analysis reveals that mineralization was controlled by conjugate shear joints, tension fractures, and en échelon faults formed under a tectonic stress field with σ1 oriented NE–SW. LA-ICP-MS trace element analysis of pyrite reveals dual geochemical affinities—high-temperature magmatic signatures (elevated Co, Ni, Ti) and medium-low temperature hydrothermal signals (enriched As, Pb, Bi)—suggesting episodic fluid inputs from magmatic-hydrothermal and meteoric sources. Rare earth elements (REEs) are low in pyrite and show slight LREE enrichment. The results suggest that the main ore-controlling structures formed under a stress field with σ1 oriented NE–SW during the Early Cretaceous, and the mineralization may be related to episodic fluid pulses, as reflected by the changes in trace elements during the crystallization of pyrite. Furthermore, this study reveals an NEE-trending set of potential ore-controlling structures for epizonal gold mineralization, which is of great significance for regional gold exploration in Jiaodong.
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Genyuan JI，Sihong Jiang，Yang Cheng，Hongyan Bao，Huachuan Zhang
2026,100(3):795-813, DOI: 10.1111/1755-6724.70067
Abstract:
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 εNd(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+, δEu, 10,000 × δEu/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 apatitedominated 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.
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2026,100(3):814-833, DOI: 10.1111/1755-6724.70071
Abstract:
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 εHf(t) values of the zircons from _17.92 to _1.77, with TDM2 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.
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Xiuqi Shang，Weidong Sun，Xing Ding，Ruifang Huang，Shuai Yuan，Guozhi Xie，Kun Wang
2026,100(3):834-845, DOI: 10.1111/1755-6724.70058
Abstract:
Hydration of the lithospheric mantle is a critical part of deep water cycling and is essential in shaping Earth’s habitable environments. At low water/rock ratios, water is stored in nominally anhydrous minerals or hydrous minerals; however, at high water/rock ratios, the leaching effect of water on mantle minerals remains poorly understood. Here, we present hydrothermal experiments of the ‘phlogopite + H2O’ system at 500?C–950?C and 0.9–1.8 GPa, showing that incongruent dissolution of phlogopite in water produces corundum (Al2O3) as an insoluble residual phase at pressures above~1.5 GPa. Water leaches soluble components (K, Mg and Si) from phlogopite, leaving corundum as the residue under lithospheric mantle P?T conditions. This provides a mechanistic explanation for sapphire formation in the lithospheric mantle, consistent with natural sapphire gemstones occurring as mantle xenoliths and xenocrysts within alkaline basalts. Sapphires form through hydrous leaching of phlogopite at depths greater than ~50 km and are subsequently transported to the surface by alkaline basaltic magmas originating from at least ~70 km depth. The widespread sapphire deposits associated with alkaline basalts in East China indicate extensive hydrous leaching of the lithospheric mantle, with water ultimately sourced from the subducted slab, mantle transition zone or mantle plumes.
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2026,100(3):846-869, DOI: 10.1111/1755-6724.70069
Abstract:
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 Tmax value of 430?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.
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2026,100(3):870-893, DOI: 10.1111/1755-6724.70048
Abstract:
Investigation of the dynamic transformation characteristics of hydrocarbon generation and evaluation of hydrocarbon potential and expulsion are of guiding significance for the evaluation of lacustrine shale oil and gas resources. A total of 1977 pyrolysis dataset points were collected from lacustrine shale samples selected from 202 wells across eight regions within five basins in China. The kinetic parameters were derived, and the original hydrogen index was obtained to identify the kerogen types. Subsequently, the original total organic carbon was estimated to analyse organic matter enrichment. Finally, the hydrocarbon generation, retention and expulsion characteristics of the lacustrine shales were compared. The results demonstrate that lacustrine shales in China exhibit different hydrocarbon generation, retention and expulsion characteristics, which are controlled by both basin lake type and primary productivity. Type I kerogens exhibit the largest hydrocarbon generation and retention amounts and the highest hydrocarbon expulsion efficiency. These kerogens also exhibit the narrowest hydrocarbon generation window and the earliest hydrocarbon expulsion. However, when the source rocks have a high sulphur content, hydrocarbon generation and expulsion occur earlier. Furthermore, when the source rock contains large amounts of terrestrial organic matter input, the hydrocarbon generation and expulsion windows broaden.
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2026,100(3):894-909, DOI: 10.1111/1755-6724.70061
Abstract:
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.
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2026,100(3):910-933, DOI: 10.1111/1755-6724.70052
Abstract:
Submarine canyons critically control reservoir heterogeneity in deep-water settings, yet their erosional surfaces often evade seismic detection. This study integrates the instantaneous phase, variance coherence, spectral whitening and acoustic impedance inversion of advanced seismic attributes to resolve the morphology of the Cretaceous Matruh Canyon (Egypt’s Western Desert) and quantify its impact on the Alam El Bueib IIIG reservoir. Conventional 2D seismic data initially obscured the canyon’s basal erosional surface due to velocity push-down artefacts and sparse line spacing. Our workflow successfully delineated a U-shaped, faultcontrolled incision system, revealing stark thickness variations (> 440 ft locally) where canyon infill replaced reservoir sands with sealing Matruh Shale. Paradoxically, while this erosion disrupted continuity evidenced by shale-plugged wells (e.g., Emry Deep_04), it concurrently created stratigraphic traps through lateral sand-shale juxtaposition and shale-drape seals. Note that shale gouge ratio analysis confirmed robust lateral seals (> 80%) along bounding faults, notably where shale thickness exceeded 200 ft. We initially struggled to reconcile the abrupt transition from productive sands (Emry Deep_01X) to non-reservoir intervals until spectral whitening resolved thin (< 138 ft) SII sand remnants. Global analogues (Brazil Pre-salt, Niger Delta) highlight Matruh’s uniqueness: its syn-rift tectonic setting and > 400-m incision depth create traps distinct from post-rift carbonates or shale diapirs.
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2026,100(3):934-955, DOI: 10.1111/1755-6724.70054
Abstract:
Several sandstone-type uranium deposits were identified within the Upper Cretaceous red-variegated strata in the Qianjiadian area of the Songliao Basin, NE China. However, a consensus regarding the genesis of multilayer tabular ore bodies within a sandstone reservoir remains elusive. This paper investigates the provenance, palaeoenvironment, and unique mineralisation characteristics of the Qingshankou Formation within the newly discovered Dalin deposit on the basis of lithofacies, element–environment– organic geochemistry and stable isotopes. The results indicate that the fragment provenance of the ore-bearing strata is primarily composed of intermediate–felsic rocks, and the source areas are characterised by a complex tectonic background that encompasses both passive and active continental margins, as well as continental arcs. Its sedimentary environment shows a general (semi-) arid and hot palaeoclimate, with ancient lacustrine water exhibiting both fresh and brackish properties. Pure grey mudstone (PGM) features low Fe2O3 T but exhibits elevated levels of ferrous iron, uranium, molybdenum, Fe2+/Fe3+ ratio and reduction capacity; pure red mudstone (PRM) displays contrasting characteristics; and certain geochemical indicators of mottled mudstone (MD) are intermediate between those of the above-mentioned mudstones. Green alteration within the MD is identified as having a synsedimentary origin, as opposed to the previously assumed secondary reduction of foreign hydrocarbons. The associated organic matter is classified as Type-III kerogen, initially derived from aquatic plankton and herbaceous plants. Finally, a sedimentary model is proposed for the red-variegated Qingshankou Formation in the study area, where the original interbedded architecture with varying geochemical properties is influenced by alternations in palaeoclimate and associated redox stratification of ancient lacustrine water. Some lenticular native grey beds, which were deposited in local low-lying lands during semi-arid and pluvial interphases, exhibit pronounced uranium pre-concentration due to phreatic oxidation during the sedimentary stage. Subsequently, differential redox activities in the Cenozoic era led to the development of multilayer geochemical zoning and tabular ore bodies in a reservoir. This research offers valuable insights into the uranium mineralisation of oxidative red-variegated strata within global basins and contributes to the development of uranium exploration strategies.
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Xiaowei Gao，Kejun Hou，Shunda Yuan，Jiaxin Zhang，Mengqi Zhang，Ziwei Liu
2026,100(3):956-964, DOI: 10.1111/1755-6724.70053
Abstract:
Alunite is a common sulphur-rich mineral in high-sulphidation epithermal deposits and can occasionally form independent alunite deposits, demonstrating a close spatial relationship with epithermal mineralization. In situ sulphur isotope analysis of alunite offers valuable insights into detailed mineralization processes. In this study, using LA-MC-ICP-MS, we evaluated matrix effects, spectral interferences and instrumental parameters that influence measurement accuracy, leading to the development of a high-precision microanalytical method for sulphur isotopes in alunite. In order to verify the results of the in situ method, LA-MCICP-MS measurements were compared with GS-IRMS analyses on two natural alunite samples: MT-1 and MTS-1. The internal precision of the in situ δ34S measurement was better than 0.22‰ when the 32S signal exceeded 5 V. The long-term reproducibility for these two samples was better than 0.33‰ (2SD). These results suggest that either of the two materials can serve as an in situ sulphur isotope standard. Based on GS-IRMS results, recommended δ34S values for MT-1 and MTS-1 are 9.37‰ ± 0.13‰ and 3.42‰ ± 0.31‰, respectively.
2026年第100卷第3期
2026年第100卷第3期
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青藏高原东北缘祁连–海原断裂带中段金强河断裂晚第四纪滑动行为
梁淑敏, 郑文俊, 陈干, 张培震, 张冬丽, 毕海芸, 杨雪, 张逸鹏, 段磊, 卢本添
Abstract:
祁连–海原断裂带控制着青藏高原东北缘地区的强震活动。在其中段的金强河断裂是天祝地震空区一条关键的活动断裂，但目前对该断裂的滑动行为认识不足。本文针对沿金强河断裂的水平位移分布，利用WorldView-2立体像对和无人机摄影测量数据，提取断裂沿线高精度的DEM数据，并进行精细的构造地貌解译和水平位错测量。通过断错地貌标志的测量，得到135个位错量和8个位错丛集。同时，利用放射性碳测年方法构建4个典型点断错河流阶地的地貌单元年龄序列，从而通过位错与年龄的关系将位错丛集和地貌单元年龄序列关联起来，并获得金强河断裂全新世的滑动速率在 ~4–12 ka期间为4.8–5.6 mm/a ，在 ~4 ka以来为2.9–4.7 mm/a。最近的三次地震事件的复发间隔约为1000年，形成了一个地震活跃期，揭示着近1500年来缺乏破裂记录的金强河断裂可能具有较高的地震危险性。
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南阿尔金早古生代构造演化：来自茫崖花岗质岩石地球化学、锆石U-Pb和Lu-Hf同位素的证据
徐楠, 吴才来, 刘和武, 宋帅兵, 张贵生, 郑坤, 高栋
Abstract:
南阿尔金造山带是中国西南典型的俯冲造山带，由南阿尔金蛇绿混杂岩带和南阿尔金陆块组成，位于柴达木板块北侧。造山带出露大量早古生代花岗质岩石，但是这些岩石的成因及构造环境尚未查明。本文对茫崖花岗质岩石进行岩石学和地球化学研究，确定岩浆活动的期次，并深入了解南阿尔金造山带的构造演化过程。茫崖花岗质岩浆活动可以划分为三期：494-458Ma，450-436Ma和416-404Ma。根据这些岩石的成岩构造环境，我们认为第一期岩浆活动与南阿尔金洋的北向俯冲有关，形成了大量高价钙碱性、I型花岗质岩石。南阿尔金洋闭合后，柴达木板块开始向南阿尔金陆块碰撞，行了了一系列高价钙碱性、I型花岗岩。第三期岩浆活动形成了大量的造山后A-型花岗岩。
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超微量（80nanomole）硫化物硫酸盐硫同位素的EA-IRMS测试
Abstract:
常规EA-IRMS进行硫同位素测试时需硫量大于2 μmol，这限制了该技术在测试含硫量低的样品时的使用。如此大的需硫量是因为He载气携带样品气体在经过元素分析仪（EA）时的流速为~100 mL/min，而气体同位素质谱仪仅允许气体以低流速进入，所以99.7%的混合气体会通过连续流接口排出，以保证混合气体以~0.3 mL/min的流速通过连续流接口。因此，大部分的样品气体会被浪费，样品的利用率仅有0.3%。在本研究中，我们将自主研发的冷冻富集、分离与纯化系统与EA-IRMS联用测试了六种标准物质的硫同位素，并检测该系统的表现。实验结果表明，使用本研究中改进的方法进行硫化物和硫酸盐标准物质的硫同位素测试，得到的硫同位素结果与常规方法一致，即需硫量仅80 nmol即可得到硫同位素测试结果精度 ±0.24‰–±0.76‰ (1σ)，与使用吸附柱进行硫同位素测试的方法获得的精度相似。所以，改进后的EA-IRMS可以实现超微量硫化物、硫酸盐的硫同位素测试。此外，本方法也可应用至需样量低至100 nmol的碳、氮和氧同位素分析测试工作中。
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粤北早古生代强过铝质花岗岩及其共生岩石的岩石成因及对广西运动的指示意义：来自元素和Sr-Nd-Hf同位素的制约
Abstract:
本文系统报道了粤北地区早古生代强过铝质花岗岩及其共生岩石的锆石U-Pb年代学、主、微量元素及Sr-Nd-Hf同位素组成，探讨其源区特征、岩石成因及构造意义。青州花岗闪长岩为弱-强过铝质，A/CNK= 1.05–1.96。它们具有相对高的初始Sr同位素组成ISr= 0.7087– 0.7148和低的εNd(t)值(-11.2 – -10.1)，以及变化的εHf(t)值-13.4– +4.81。与之不同，大帽山花岗闪长岩为准铝质（A/CNK= 0.79– 0.94），ISr= 0.7083– 0.7110, εNd(t)= -7.92– -5.28和εHf(t)= -8.69– -2.06。高寿石英闪长岩为准铝-强过铝质（0.87– 1.24），ISr值和εNd(t)值分别为0.7104– 0.7111和-9.64– -8.63。元素和Sr-Nd-Hf同位素组成结果显示，青州、大帽山和高寿花岗质侵入岩主要分别源自变杂砂岩、英安质岩和角闪石岩的部分熔融。结合前人的研究成果，这些强过铝质花岗岩形成于同造山环境。本文尝试提出一种关于华南早古生代花岗岩的岩石成因及区域地壳重组的新思路。而广西运动动力机制的揭示需要更加广阔的视野和更加丰富的地质证据。
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Birendra P. Singh, Kapesa Lokho, Naval Kishore, Nancy Virmani
2014,88(2):380-393, DOI:
Abstract:
A new locality bearing ichnofossils of the Cruziana Assemblage Zone-III from the Mussoorie syncline, Lesser Himalaya, is located in rocks of Member-B of the Dhaulagiri Formation, Tal Group, exposed along the Maldewta-Chhimoli fresh road cut section. The site yielded ichnofossils Bergaueria perata, Cochlichnus anguineus, ?Diplocraterion isp., Dimorphichnus obliquus, diplichnitiform Cruziana bonariensis, Diplichnites gouldi, Glockeria isp., Helminthopsis isp., Monomorphichnus lineatus, Phycodes palmatum, Palaeophycus striatus, Planolites beverleyensis, Planolites montanus, Treptichnus cf. T. pedum, scratch marks and an undetermined worm impression. An Early Cambrian age (Cambrian Series 2) is assigned to the ichnofossil-bearing strata based on the stratigraphic position between the Drepanuroides and Palaeoolenus trilobite zones. A revised Cambrian ichnofossil zonation is presented for the Tal Group of the Mussoorie syncline. Together with their occurrence on rippled surfaces, and the lateral displacement of some trackways (due to current action), a sub-aqueous shallow-marine depositional setting is proposed for the rocks of Member-B.
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ZHU Song, WU Zhenhan, ZHAO Xitao, LI Jianping, WANG Hua
2012,86(1):266-283, DOI:
Abstract:
Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691~505 kaBP middle Pleistocene ice age, 75–40 kaBP the early stage of last glacier, 27–8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn’t erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn’t form stable lake.
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WANG Runfu, XU Shichao, WU Xiaochun, LI Chun, WANG Suozhu
2013,87(5):1185-1197, DOI:
Abstract:
Shansisuchus shansisuchus Young, 1964 was restudied on the basis of a new specimen. Some anatomical features that were either briefly or not described at all in the original study were detailed. The new specimen not only provides further information on the skull anatomy and the vertebral column but also expands the range of the geographical distribution of the taxon. With new information, the diagnosis of S. shansisuchus was emended and its phylogenetic relationships were further analyzed. S. shansisuchus differs from other archosauriforms primarily in the presence of a large subnarial fenestra anterior to the antorbital fenestra, tongue-in-groove articulations between the ascending process of the premaxilla and nasal and between the premaxilla and maxilla, a tall and posterodorsally directed ascending process of the maxilla, a knee-shaped process of the postorbital projecting into the orbit, a broad descending process of squamosal distally well forked and a large, deeply bow-shaped intercentrum tightly anchoring/capping the sharp ventral edges of two neighboring centra together in cervical and at least first eight dorsal vertebrae. With additional information derived from the new specimen, the phylogenetic relationships of S. shansisuchus were reanalyzed; it is closely related to Erythrosuchus-Vjushkovia clade.
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CHEN Lan1, 2, 3, * , YI Haisheng4, 5, TSAI Louis Loung-Yie2, XU Guiwen1, DA Xuejuan1, LIN Andrew Tien-Shun3
2013,87(2):540-554, DOI:
Abstract:
The Biluo Co and Amdo 114 station, northern Tibet, cropping out the Early Toarcian and Middle-Late Tithonian (Jurassic) organic-rich black shales, have been a focus to petroleum geologists in discussing their oil-producing potential. This paper first reports the trace elements and rare earth elements to discuss the paleoenvironments, redox conditions and sedimentary mechanisms of those black shales. Both sections exhibit variation in trace element abundances with concentrations <0.1 ppm to 760 ppm, mostly enriched in V, Cr, Ni, Cu, Zn, Mo, Ba and U. Element ratios of Ni/Co, V/Cr, U/Th and V/(V+Ni) plus U were used to identify redox conditions. The shale-normalized rare earth element (REE) patterns are characterized by the flat-shale type with instable Ce anomalies and very weekly positive Eu anomalies. Positive Ceanom values are significant with values varying between –0.064 and 0.029 in Biluo Co, which may be interpreted as release of REE and input of riverine terrestrial matter with rich Ce (resulting in pH change) during the anoxic conditions. In the middle parts of Amdo 114 station, distinct negative Ceanom values are observed (?0.238 to ?0.111) and associated surface water warming were interpreted as being related to a major sea level rise. In contrast, the formation of the black shales in the lower and upper part of the studied succession took place during a cooler (Ceanom values >–0.10), lower surface water productivity, and lower sea-level stage. Thus, we emphasize the role of different factors that control the formation of local and regional black shales. The most important factors are sea-level fluctuations and increasing productivity.
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SHEN Caizhi, Lü Junchang, LIU Sizhao, Martin KUNDRáT, Stephen L. BRUSATTE, GAO Hailong
2017,91(3):763-780, DOI:
Abstract:
A new troodontid dinosaur, Daliansaurus liaoningensis gen. et sp. nov., is erected based on a nearly complete specimen from the Lower Cretaceous Yixian Formation of Beipiao City, Liaoning Province, China. This well preserved skeleton provides important new details of the anatomy for Liaoning troodontids, and gives new insight into their phylogenetic relationships and evolution. Daliansaurus is distinguished from other troodontids by an enlarged ungual on pedal digit IV, which is approximately the same size as the sickle-shaped second ungual, and is differentiated from other Liaoning troodontids by a number of characters of the skull, manus, pelvis, and hindlimb. A phylogenetic analysis recovers Daliansaurus within a subclade of Liaoning troodontids that also includes Sinovenator, Sinusonasus, and Mei. We erect a name for this group—Sinovenatorinae—and argue that it reflects a localized radiation of small-bodied troodontids in the Early Cretaceous of eastern Asia, similar to previously recognized radiations of Liaoning dromaeosaurids and avialans. As more Liaoning theropods are discovered, it is becoming apparent that small, feathered paravians were particularly diverse during the Early Cretaceous, and future work is needed to clarify how this diversity arose, which species coexisted, and how these numerous species partitioned niches.
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2014,88(1):260-275, DOI:
Abstract:
This paper reviews the current progress and problems in the study of microbialites and microbial carbonates. Microbialites and microbial carbonates, formed during growth of microbes by their calcification and binding of detrital sediment, have recently become one of the most popular geological topics. They occur throughout the entire geological history, and bear important theoretical and economic significances due to their complex structures and formative processes. Microbialites are in place benthic microbial buildups, whereas microbial carbonates can be classified into two categories: stabilized microbial carbonates (i.e., carbonate microbialites, such as stromatolites and thrombolites) and mobilized microbial carbonates (i.e., microbial carbonate grains, such as oncoids and microbial lumps). Various texture, structures, and morphologies of microbialites and microbial carbonates hamper the systematic description and classification. Moreover, complex calcification pathways and diagenetic modifications further obscure the origin of some microbialites and microbial carbonates. Recent findings of abundant sponge spicules in previously identified “microbialites” challenge the traditional views about the origins of these “microbialites” and their implications to reef evolution. Microbialites and microbial carbonates did not always flourish in the aftermath of extinction events, which, together with other evidences, suggests that they are affected not only by metazoans but also by other geological factors. Their growth, development, and demise are also closely related to sea-level changes, due to their dependence on water depth, clarity, nutrient, and sunlight. Detailed studies on microbialites and microbial carbonates throughout geological history would certainly help understand causes and effects of major geological events as well as the co-evolution of life and environment.
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2014,88(z2):597-598, DOI:
Abstract:
Please refer to the attachment(s) for more details
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DU Chunguo, WANG Jianjun, ZHANG Jun, WANG Ping, XUE Mei, ZHOU Huayao
2014,88(3):865-877, DOI:
Abstract:
On the basis of field observations, microscopic thin-sections and laboratory data analysis of ten faults in Xuanhan County area, northeastern Sichuan Basin, central China, the internal and megascopic structures and tectonite development characteristics are mainly controlled by the geomechanical quality in brittle formation of the Changxing-Feixianguan Formation. The fluid transportation performance difference between the faults formed by different geomechanics or different structural parts of the same fault are controlled by the megascopic structure and tectonite development characteristics. For instance, the extension fault structure consists of a tectonite breccia zone and an extension fracture zone. Good fluid transportation performance zones are the extension fracture zone adjacent to the tectonite breccia zone and the breccia zone formed at the early evolutionary stage. The typical compression fault structure consists of a boulder-clay zone or zones of grinding gravel rock, compression foliation, tectonite lens, and dense fracture development. The dense fracture development zone is the best fluid transporting area at a certain scale of the compression fault, and then the lens, grinding gravel rock zone and compression foliation zones are the worst areas for hydrocarbon migration. The typical tensor-shear fault with a certain scale can be divided into boulder-clay or grinding gravel rock zones of the fault, as well as a pinnate fractures zone and a derivative fractures zone. The grinding gravel rock zone is the worst one for fluid transportation. Because of the fracture mesh connectivity and better penetration ability, the pinnate fractures zone provides the dominant pathway for hydrocarbon vertical migration along the tensor-shear fault.
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MA Shengming, ZHU Lixin, LIU Chongmin, XI Mingjie, TANG Shixin
2013,87(3):843-857, DOI:
Abstract:
This paper discusses the enrichment and depletion regularities for porphyry copper-molybdenum ore deposits in different regions and varied deposit genetic types in the same area, taking three porphyry copper-molybdenum ore deposits (i.e., the Chengmenshan in Jiangxi, Wunugetushan in Inner Mongolia, Baishantang in Gansu) and two copper deposits in Gansu Province (the Huitongshan skarn deposit and Gongpoquan composite deposit) as case studies. The results show that porphyry Cu-Mo deposits or skarn copper deposits include both enrichment of the ore-forming elements and associated elements, and depletion of some lithophile dispersed elements, rare earth elements (REE) and some major elements. And the depleted elements vary with deposits, having generality and their own features. On a deposit scale, the positive anomalies of enriched elements and negative anomalies of depleted elements follow in a sequence to comprise regular anomaly models of spatial structures. The exploration in the Tongchang deposit in Jiangxi and Huitongshan deposit in Gansu suggests that anomaly models play a key role in the identification of mineral occurrences and deposits compared to one single enriched element anomaly. And the anomaly models exert a critical effect on the optimization of prospecting targets and their potential evaluation.
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2010,84(2):241-246, DOI:
Abstract:
A new boreopterid pterosaur: Zhenyuanopterus longirostris gen. et sp. nov. from the Yixian Formation of western Liaoning is erected, based on the complete skeleton with a skull and lower jaws preserved. It is characterized by: a large boreopterid pterosaur with a high number of teeth, where the anterior teeth are much larger than posterior ones; the length of the dorsal + sacral vertebrae is nearly half the length of the skull; ratio of the length of the humerus to metacarpal IV is approximately 91% and the, humerus, femur and third wing phalanx are all equal in length and the feet are specially small. It represents the largest boroepterid pterosaur discovered from western Liaoning and its surrounding areas so far
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WANG Sufen, ZHANG Tingshan, ZHOU Jixian, HU Yu
2017,91(1):320-340, DOI:
Abstract:
The distribution characteristics of the oil-water contact are the basis for the reservoir exploration and development and reserves evaluation. The reservoir with a tilted oil-water contact has a unique formation mechanism, and the understanding of its distribution and formation mechanism will directly affect the evaluations for the reservoir type, well deployment, selection of well pattern and type, determination of test section, and reserves evaluation. Based on the analysis of reservoir characteristics, petrophysical properties and geological structure in 40 reservoirs worldwide with tilted oil-water contacts, the progress of the research on the formation mechanisms of titled oil-water contacts is summarized in terms of the hydrodynamic conditions, reservoir heterogeneity, neotectonic movement and oil-gas exploitation. According to the formation mechanism of tilted oil-water contacts and the needs of exploration research, different aspects of research methods are summarized and classified, such as the calculation of equipotential surfaces for oil and water in the formation, analysis of formation pressure and analysis of reservoir physical properties and so on. Based upon statistical analysis, it is suggested that the degree of the inclination of the oil-water contact be divided based on the dip of oil-water contact (DipTOWC). The tilted oil-water contact is divided into three categories: large dip (DipTOWC≥55 m/km), medium dip (4 m/km≤DipTOWC<55 m/km), and small dip (DipTOWC<4 m/km). The classification and evaluation method can be combined with structure amplitude and reservoir property. The formation mechanism of domestic and international reservoirs with tilted oil-water contacts are summarized in this paper, which have important significance in guiding the exploration and development of the oilfield with tilted oil-water contacts, reserves evaluation, and well deployment.
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Mahboobeh JAMSHIDI BADR, Fariborz MASOUDI, Alan S. COLLINS, Ali SORBI
2012,86(1):48-64, DOI:
Abstract:
The Soursat metamorphic complex (SMC) in northwestern Iran is part of the Sanandaj–Sirjan metamorphic belt. The complex is composed of different metamorphic and plutonic rocks, but is dominated by metapelites composed of garnet, staurolite, kyanite, fibrolite, cordierite, and andalusite. Porphyroblasts in schists have the same fabric, and three stages of schistosity are present. The internal schistosity (Sn) inclusion trails are also offset by conjugate sets of extensional schistosity (Sn+1) and a second (Sn+2) that crenulates (Sn+1). Polyphase metamorphisms are present in the complex. Garnet, staurolite, kyanite, and fibrolite assemblage preserves conditions during the M1 metamorphic event. This assemblage yields a P–t estimate of 645±11°C and 6.5±0.5 kbar. Other samples of the central part of SMC contain cordierite and andalusite (M2) overgrowth that yields a P–t estimate of 532±33°C and 2.1±1.1 kbar.
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ZHENG Yadong, ZHANG Qing, HOU Quanlin
2015,89(4):1133-1152, DOI:
Abstract:
The essential difference in the formation of conjugate shear zones in brittle and ductile deformation is that the intersection angle between brittle conjugate faults in the contractional quadrants is acute (usually ~60°) whereas the angle between conjugate ductile shear zones is obtuse (usually 110°). The Mohr-Coulomb failure criterion, an experimentally validated empirical relationship, is commonly applied for interpreting the stress directions based on the orientation of the brittle shear fractures. However, the Mohr-Coulomb failure criterion fails to explain the formation of the low-angle normal fault, high-angle reverse fault, and the conjugate strike-slip fault with an obtuse angle in the σ1 direction. Although it is ten years since the Maximum-Effective-Moment (MEM) criterion was first proposed, and increasingly solid evidence in support of it has been obtained from both observed examples in nature and laboratory experiments, it is not yet a commonly accepted model to use to interpret these anti-Mohr-Coulomb features that are widely observed in the natural world. The deformational behavior of rock depends on its intrinsic mechanical properties and external factors such as applied stresses, strain rates, and temperature conditions related to crustal depths. The occurrence of conjugate shear features with obtuse angles of ~110° in the contractional direction on different scales and at different crustal levels are consistent with the prediction of the MEM criterion, therefore ~110° is a reliable indicator for deformation localization that occurred at medium-low strain rates at any crustal levels. Since the strain–rate is variable through time in nature, brittle, ductile, and plastic features may appear within the same rock.
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CHI Guoxiang1, *, CHU Haixia1, Ryan SCOTT1, CHOU I-Ming2
2014,88(4):1169-1182, DOI:
Abstract:
Raman peaks of various hydrates in the H2O-NaCl-CaCl2 system have been previously identified, but a quantitative relationship between the Raman peaks and XNaCl (i.e., NaCl/(NaCl+CaCl2)) has not been established, mainly due to the difficulty to freeze the solutions. This problem was solved by adding alumina powder to the solutions to facilitate nucleation of crystals. Cryogenic (-185oC) Raman spectroscopic studies of alumina-spiced solutions indicate that XNaCl is linearly correlated with the total peak area fraction of hydrohalite. Capsules of solutions made from silica capillary were prepared to simulate fluid inclusions. Most of these artificial fluid inclusions could not be totally frozen even at temperatures as low as -185oC, and the total peak area fraction of hydrohalite is not correlated linearly with XNaCl. However, the degree of deviation (DXNaCl) from the linear correlation established earlier is related to the amount of residual solution, which is reflected by the ratio (r) of the baseline “bump” area, resulting from the interstitial unfrozen brine near 3435 cm-1, and the total hydrate peak area between 3350 and 3600 cm-1. A linear correlation between DXNaCl and r is established to estimate XNaCl from cryogenic Raman spectroscopic analysis for fluid inclusions.
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LI Jianjun, Martin G. LOCKLEY, ZHANG Yuguang, HU Songmei, MATSUKAWA Masaki, BAI Zhiqiang
2012,86(1):1-10, DOI:
Abstract:
A large track site with multiple, well-preserved trackways of an Early Jurassic quadrupedal ornithischian dinosaur is the first report of Moyenisauripus-like trackways from Asia, herein named Shenmuichnus youngteilhardorum. The tracks occur in a clastic fluvial sequence in the Fuxian Formation in Shenmu County, Shaanxi Province, which is in the same general region as the discovery site of Sinoichnites，the first dinosaur track reported from China. Based on size and morphology, it is likely that Sinoichnites, which is now lost, also represents an ornithischian. The Shenmuichnus youngteilhardorum trackways show two modes of preservation: the first representing deeper tracks, with sediment rims, results in Deltapodus-like tracks, with indistinct pes digit traces and sub-circular manus traces, the second produces Moyenosauripus-like tracks, with clear tridactyl and pentadactyl digit traces in the pes and manus respectively. Thus the Shenmu trackways play a key role in resolving globally significant ichnotaxonomic problems surrounding the nomenclature of Sinoichnites, Moyenosauripus, Deltapodus and other named (Ravatichnus) and unnamed trackways from Asia, Africa and Europe. In addition they shed important light on the paleogeographical and paleoecological distribution of quadrupedal ornithischians in the Early Mesozoic. The track site has been the focus of a major excavation to transfer the trackways from their original remote location to the new Shenmu Museum, in Shenmu City. Other tracksites in the area which reveal Anomoepus, Grallator and the Deltapodus morphotype, together with Shenmuichnus and plant fossil evidence, suggest an Early Jurassic age for the tracksite.
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DU Jianjun, LI Dunpeng, WANG Yufang, MA Yinsheng
2017,91(1):76-92, DOI:
Abstract:
The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.
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2015,89(3):715-725, DOI:
Abstract:
Re-equilibration of fluid inclusions in crystals takes place by loss or gain of solvents and solutes from fluid inclusions and by changes in their volumes. Volume change of fluid inclusions are primarily dictated by elastic properties and available slip planes of host crystals. In the present study, the phase-behavior of fluids entrapped in co-precipitated calcite and barite is studied. While calcite contains only biphase fluid inclusions, barite has predominantly monophase fluid inclusions. Fluid inclusion petrography, microthermometry and leachate analysis are used to establish the nature of entrapped fluids and entrapment temperature is substantiated through independent sulfur isotope geothermometry using coexisting barite and pyrite. Phase transitions in the monophase fluid inclusions in barite are explained in terms of over-pressuring of fluids in these fluid inclusions relative to fluids entrapped in calcite owing to the low bulk modulus of barite.
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2021,95(3):1056-1056, DOI: 10.1111/1755-6724.14310
Abstract:
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ZHANG Gang, WANG Xuben, FANG Hui, GUO Ziming, ZHANG Zhaobin, LUO Wei, CAI Xuelin, LI Jun, LI Zhong, WU Xing
2015,89(2):531-541, DOI:
Abstract:
The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate. The long-period magnetotelluric (LMT) and broadband magnetotelluric (MT) techniques are both used to study the deep electrical conductivity structure in this region; magnetic and gravity surveys are also performed along the profile. According to the 2-D resistivity model along the Yanyuan-Yongshan profile, a high-conductivity layer (HCL) exists widely in the crust, and a high-resistivity block (HRB) exists widely in the upper mantle in general, as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust, while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone. In addition, the gravity and magnetic field anomalies are of high value. Combined with geological data, the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region, which indicates that fracture activity once occurred in the lithosphere. As a result, we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock. The seismic sources along the profile are counted according to seismic record data. The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL, where the tectonic activity zone is generally acknowledged to be; however, the earthquakes occurring in the HCL are not so violent, which reflects the fact that the HCL is a plastic layer, and the fracture threshold of a plastic layer is low generally, making high stress difficult to accumulate but easy to release in the layer. As a result, a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone, and violent earthquakes occurred at the binding site of high- and low-resistivity blocks at the Panxi tectonic zone.
