The Dingqing ophiolite in the eastern segment of the Bangong-Nujiang suture zone records multiple episodes of magmatic events, providing crucial constraints on the tectonic evolution of the Meso-Tethyan Ocean. We focus on sheet dikes recently discovered during the geological survey of 1 : 50 000 scale mapping the Dingqing East ophiolite. The studied samples are categorized into two types of high-Ca boninite and high-Mg andesite. Two high-Mg andesite samples yield in-situ zircon U-Pb ages of 161.59 ± 0.59 and 162.85 ± 0.76 Ma, respectively. All samples show high contents of SiO₂ (55.00 wt.%–59.76 wt.%), large range of MgO (4.32 wt.%–17.12 wt.%) and low TiO₂ (0.17 wt.%–0.25 wt.%). In primitive mantle-normalized trace-element diagrams, they are characterized by enrichment in large ion lithophile elements (LILEs) such as Rb and Ba, and depletion in high field strength elements (HFSEs) such as Nb, Ta and Th. The absence of an obvious Zr-Hf spike is distinct from those of Izu-Bonin forearc boninites, but analogues for those of the Tonga boninites. We propose that the boninitic sheeted dikes formed in an ocean-continent subduction zone during the northward subduction of the Meso-Tethyan oceanic slab to the southern Qiangtang continental lithospheric mantle, which was probably influenced by an Early Permian mantle plume.

The initial timing of uplift at the southeastern margin of the Tibetan Plateau (SMTP) remains under debate, with estimates ranging from the Eocene, to the Oligocene. The Jinsha River was formed before the Miocene, therefore, it is likely to record the uplift information of the Tibetan Plateau, which is important for understanding the tectonic uplift of the SMTP. Here, we collected granite samples from the Yangla area in the middle part of the Jinsha River, and analyzed the uplift characteristics of the Cenozoic in the middle part of the Jinsha River by using the apatite fission tracks and the river longitudinal profiles. We show that the uplift time of the first phase is about 25–20 Ma, and the uplift time of the second phase is about 5 Ma. From the channel profile, seven tributaries of the Jinsha Rivers also have developed two phases of knickpoints. The tributaries consist of three sections with distinct geomorphological parameters, each separated by knickpoints. We argue that large-scale uplift occurred in the Late Cenozoic on the SMTP, with different locations having different uplift times, and the interior may have undergone significant uplift in the early Oligocene, but significant uplift of the SMTP occurred by the Late Oligocene to Early Miocene. The Jinsha River flowing from the interior of the plateau has developed multiple knick points during the uplift process, recording information about the uplift of the Tibetan Plateau.

The ash aggregates occur in the pyroclastic rocks of Early Cretaceous Yingcheng Formation, which are outcropped in the southeastern margin of the Songliao Basin, China. We focus on the types and genesis of the ash aggregates. Five types of ash aggregates are identified, including ash pellets (Ap), layered accretionary lapilli (Lacc), ultrafine rim-type accretionary lapilli (Ufacc), coated lava particle (Clp), and coated breccia (Cb), and there are six types of lithofacies related to ash aggregate accumulation: (1) Ap and Lacc bearing fine tuff with hummocky-parallel bedding, (2) Ufacc bearing fine tuff with hummocky-parallel bedding, (3) Lacc and Ufacc bearing fine tuff with hummocky-parallel bedding, (4) Ap, Clp, Lacc, and Ufacc bearing medium-fine tuff with graded and parallel bedding, (5) Lacc and Cb bearing lapilli-ash tuff with massive-graded bedding, and (6) Cb bearing lapilli tuff with massive-welded structure. Base surges, pyroclastic flows, and ash falls contribute to the ash aggregation, especially ash falls. Our study of the ash aggregate accumulation relative to the lithofacies and their spatial distribution is helpful to reconstruct the paleo-volcano edifice, distinguish the ash fall deposits from the pyroclastic flow/surge deposits and infer wind direction during the time of volcanic activity in the research area.

The Tibetan Plateau is one of the regions with the most active neotectonic movement and frequent seismic activity in the world. The Bayan Har Block, located in the Northern Tibetan Plateau, has been the main area for clusters of major earthquakes with M ≥ 7 on the Chinese mainland in the past 28 years. The Kunzhong fault (KZF) is an important branch of the East Kunlun fault zone (EKF), which forms the northern boundary of the Bayan Har Block. The KZF is crucial for understanding regional tectonic evolution and seismic activity, but research on its Late Quaternary tectonic activity remains limited. On the basis of satellite image interpretation, field investigations, and high-resolution unmanned aerial vehicle photogrammetry, this study identifies an ~40 km-long seismic surface rupture zone well preserved in the eastern segment of the KZF. The rupture zone is characterized by left-lateral dislocated small gullies, cracks and scarps, with a maximum co-seismic horizontal displacement of ~2.9 ± 0.1 m. This earthquake's magnitude is estimated to be M7.2 ± 0.2 according to the statistical relationships between parameters of strike-slip seismic surface rupture zone and magnitude. Based on the surface rupture characteristics, seismogenic faults, and historical seismic records, this earthquake may have been a clustered event occurring shortly before or after the 1937 Tuosuo Lake M_S7.5 earthquake. Alternatively, it may also have been a joint earthquake involving the KZF and EKF that occurred simultaneously with the Tuosuo Lake earthquake. Combined with deep crustal magnetotelluric profiles, these findings suggest that the region between the KZF and EKF forms a diffuse transition boundary zone in the northern Bayan Har Block. In seismic risk assessments of active faults, greater attention should be given to clustered or joint rupture earthquakes occurring along both main block boundary faults and their branch faults.

The cause resulting in alkaline rocks with superchondritic Nb/Ta ratios remains a geochemical enigma. This paper presents zircon and apatite geochronology, mineralogy, geochemistry, and Nd-Hf-Zn isotope investigation on the Ejinao nepheline syenite from South China to constrain the petrogenesis of alkaline rocks. The occurrence of alkaline minerals, including alkaline feldspar, arfvedsonite, and nepheline, indicate an alkaline feature of the Ejinao nepheline syenite. Zircon and apatite from the rock show U-Pb concordia age of 135.4 ± 0.9 and 137.5 ± 5.8 Ma, respectively, suggesting generation in the Early Cretaceous. The rock is characterized by low MgO (0.17 wt.%–0.26 wt.%) contents, but high Fe₂O₃^T (4.66 wt.%–6.16 wt.%) and total alkalis (Na₂O + K₂O = 12.1 wt.%–13.1 wt.%) contents, consistent with the melts from subducting oceanic crust rather than mantle peridotite. The rock has low TiO₂ (0.13 wt.%–0.21 wt.%) contents and superchondritic Nb/Ta and Zr/Hf ratios, resulting from rutile residue in the source area. The ε_Nd(t) (-1.35 to -1.09), ε_Hf(t) (-3.03 to -1.52), and δ⁶⁶Zn (0.32‰ to 0.34‰) values of the nepheline syenite manifest the involvement of 15%–20% carbonate-bearing sediments in the altered oceanic crust. Geochemical modeling further reveals that the nepheline syenite was sourced from 10%–20% melting of such a source. This superchondritic Nb/Ta nepheline syenite was generated during the steep subduction of the Paleo-Pacific Ocean, which is needed to bring oceanic slab to a hot mantle and resulted in the altered oceanic crust melting. Our study highlights that the altered oceanic crust represents a novel source for superchondritic Nb/Ta alkaline rocks.

Oxygen fugacity of magmas and hydrothermal fluids is an important factor affecting element migration and mineralization. Zircon is an excellent monitor for oxygen fugacity of melts and fluids due to its exceptionally stable nature. However, zircon oxybarometers involve many complex algorithms leading to difficulties in use. Therefore, there is an urgent need to realize automatic calculation of various zircon oxybarometers. This study developed a Visual Basic for Applications (VBA) program, ZirconfO2, built in an Excel^TM workbook, for calculating the oxygen fugacity of magmatic and hydrothermal fluids through the trace element characteristics of zircons. The program covers almost all the algorithms of zircon oxybarometers commonly-used so far. Through the user-friendly interface, users may input data expediently, obtain multiple results of various algorithms and find the most reliable oxygen fugacity range, effectively avoiding the possible misdirection of a single algorithm.

The Edanggang area is characterized by small-scale Li-Be-bearing granitic pegmatites in the Quanji Massif, northwest China. The genesis of these Li-Be-bearing pegmatites remains unresolved. In this study, we use tourmalines as an indicator to constrain the genesis of them. In-situ major and trace elements and boron isotopic compositions of tourmaline are analyzed. Two types of tourmalines are recognized, i.e., coarse-grained tourmaline (Tur 1) and fine tourmaline (Tur 2). Both types of tourmalines share similar geochemical characteristics and are enriched in Fe, Na, and Al, but relatively depleted in Ca and Mg, with compositions close to alkali-group tourmaline and schorl. Petrography, chemical discrimination diagrams, and Al occupations in the Y-site suggest that the tourmalines are magmatic origin formed in the late stage of granitic pegmatite crystallization. Low V and Sr contents, and relatively high Co/Ni ratios of tourmalines are also in agreement with the above origin. The δ¹¹B values of all tourmalines vary from -14.13‰ to -10.40‰, indicating the boron in the pegmatites was mainly derived from parental granitic pegmatite magma. The last-formed magmatic mineral assemblages of magmatic crystallizations in the Early Triassic might contribute to predominant Li and Be reserves rather than the late external hydrothermal metasomatism.

Despite extensive studies on Nb deposits associated with alkaline rocks, the key factors controlling Nb enrichment remain uncertain, with conditions varying across distinct alkaline intrusions. To better understand Nb mineralization in alkaline rocks, we conducted an integrated investigation of samples from an Nb-bearing peralkaline-alkaline intrusion in the Yilan-like region of the northern Tarim Basin. The Yilan-like intrusion is predominatly composed of granitic pegmatite, alkali pegmatite, syenite, and sodalite syenite. Zircon dating results reveal that this intrusion was emplaced at about 276 Ma. The Yilan-like intrusion is characterized by high SiO₂ and total alkali contents and prominent enrichment of HFSE and LREE, with obvious depletions of Ba, K, P, and Ti. The peralkaline-alkaline rocks have high initial ⁸⁷Sr/⁸⁶Sr ratios (0.715 8 to 0.853 3) and negative ε_Nd(t) values (-7.8 to -8.5). We propose that the Yilan-like peralkaline-alkaline intrusion was generated via remelting of deep crustal materials enriched in alkali, F, and HFSE. With Nb concentrations reaching up to 252 ppm and Nb primarily hosted in titanite, ilmenite, rutile, pyrochlore, and columbite, the intrusion shows significant potential for Nb mineralization. Based on the chemical compositions of Nb minerals, we suggest that both magmatic and hydrothermal processes played key roles in Nb enrichment.

The metallogenic age of sandstone-type uranium deposits has always been a scientific problem to be solved in uranium exploration. This paper proposes a method combining the homogenization temperature of secondary fluid inclusions with the apatite (U-Th)/He dating method to determine the metallogenic age related to fluid trapping. The dates of apatite (U-Th)/He can be used as the lower limit of the metallogenic age when the closure temperature of apatite (U-Th)/He is less than the homogenization temperature of the secondary fluid. The samples of the uranium deposits in the Qianjiadian sag show that the homogenization temperatures of secondary fluid inclusions in the ore-bearing horizon are about 83–204 ℃ with a peak of 110–115 ℃, and the apatite (U-Th)/He dates in the same horizon vary between 29.0 ± 1.5–41.8 ± 2.7 Ma. Because the homogenization temperatures of secondary fluid are greater than the closure temperature of apatite (U-Th)/He (75 ± 5 ℃), the dates of apatite (U-Th)/He (29.0 ± 1.5–41.8 ± 2.7 Ma) are considered as the lower limit of the metallogenic age.

The Miguel Burnier manganese (Mn)-ore deposit, located in the Quadrilátero Ferrífero of Minas Gerais, Brazil, has enrichments in the rare-earth elements (REE). Here, this finding is reported. Three types of REE enrichments have been identified in: (1) Cenozoic wad-like diamictite; (2) hydrothermally altered manganiferous mudstone of Cenozoic age; (3) lithiophorite-rich veinlets and pockets within Precambrian itabirite. In the latter, churchite-(Y) [Y(PO₄)·2H₂O] and rhabdophane-(La) [La(PO₄)·H₂O] are the main REE-bearing minerals. Other metals, in particular mercury (Hg), are also enriched, indicating that metalliferous overprint took place during the Cenozoic in a tectonically stable, cratonic terrane.

This research has investigated the oil content of lacustrine shale-oil systems from the Junggar Basin. Twenty-eight samples are used for different pyrolysis experiments to study the characteristics of shale oil occurrence and the difference between various evaluation methods. Additionally, the factors affecting the physical states of shale oil are discussed. Compared with the standard Rock-Eval, the two-step pyrolysis and multi-step pyrolysis can eliminate the influence of the carryover effect. Therefore, these two types of pyrolysis are used to obtain the total, free, and adsorbed oil yield of the shale. The results demonstrate that the total oil yield acquired by multi-step pyrolysis is quite similar to that obtained by two-step pyrolysis. Both of them can prevent the retained oil yield from being underestimated by more than 50%. However, the free oil yield obtained by multi-step pyrolysis is significantly higher than that obtained by two-step pyrolysis. The multi-step pyrolysis can easily exaggerate the real free oil yield in resource evaluation. Therefore, this article suggests using the two-step pyrolysis to eva-luate the characteristics of petroleum in shales. Furthermore, the amount of hydrocarbons within shales is related to organic matter properties. The higher the organic matter richness, the higher the total/adsorbed oil yield within the shale before reaching the adsorption saturation. The better the kerogen type, the higher the amount of liquid hydrocarbons within shales. As the thermal evolution of shales increases, the free oil proportion and the mobility of petroleum increase. This study compared different pyrolysis methods, which provided new insight for obtaining the oil content of shales, a key parameter of shale oil resource evaluation.

The reservoir's physical properties control the seepage capacity of the shale oil. Developing a method to classify and identify high-quality reservoirs is important to commercial shale oil production. In this study, the Qingshankou Formation shale oil reservoir in the southern Songliao Basin in China was selected. A series of reservoir characterization experiments were conducted to investigate the characteristics of the micropore structure of the reservoir and its influencing factors. A shale reservoir classification evaluation standard was established using fractal theory. It is based on the reservoir micro- and macrocharacteristics. The research results show that the reservoir qualities are controlled by mineral composition, sedimentation, and diagenesis. The larger the pore-throat ratio of the reservoir, the more significant the permeability decrease under compaction. A pore size classification standard based on the shale pore characteristics can be established using fractal theory. There is a coupling relationship between pore size and macroscopic physical properties, which can be used to establish the evaluation standard of the reservoir. Based on the division of hydraulic flow units, the standard can be applied to predict favorable reservoirs.

The practice of shale oil exploration and development all over the world has shown that reservoir quality is a key factor restricting oil and gas production, the study of ultra-deep (4 500 m) reservoirs in petroliferous basins is a hot spot for oil and gas exploration in the world today. In this paper, taking the Fengcheng Formation (P₁f) in Mahu sag of Junggar Basin as an example, through experiments such as geochemistry, whole rock analysis, FE-SEM, N₂ adsorption, and CO₂ adsorption, the lithofacies are separated, and the pore structure properties of the various lithofacies are compared. Discuss the primary influencing elements that lead to pore structure differences. The results reveal that the shale of the P₁f can be separated into four lithofacies (namely felsic shale, mixed shale, lime shale and dolomitic shale), according to the mineral composition. The shale pores of P₁f develop intergranular pores, intragranular pores, organic pores and micro-fractures. Among them, intergranular pores, intragranular pores and micro-fractures are the most developed, and the pore size is larger, which is a favorable storage space. Different lithofacies have different pore development characteristics. With the change of lithofacies (mixed shale-dolomitic shale-lime shale-felsic shale), the size of the developed pores changes from small to large, and the pore structure changes from "mainly microporous" to "mainly macropores". The felsic shale has developed laminae, mainly mesopores and macropores, with the largest pore diameter and the highest content of brittle minerals, which is the dominant lithofacies in the shale oil reservoir of the P₁f. TOC, felsic and clay minerals all affect the pore development of shale in the P₁f, but the influence of organic matter and inorganic minerals on pore volume varies with pore size. The purpose of this article is to characterize the pore structures and regulators of various lithofacies in lacustrine shale and to provide new ideas for ultra-deep shale oil exploration.

The shale gas exploration of marine-continental transitional facies has gained great attention in China, which is viewed as another breakthrough following the marine shale gas prior to continental shale gas. The Upper Paleozoic marine-continental transitional shales have high TOC abundance with large total thickness in the eastern Ordos Basin, progressively becoming a favorable area for exploration of transitional shale gas. Nevertheless, compared with the relatively homogeneous marine shales, the marine-continental transitional shales demonstrated strong anisotropy in the aspects of thickness, lithology and organic matter (OM). Thus, in this paper, based on the trace element and rock-eval data, we investigated the sedimentary facies, provenance, paleoclimate, paleobathymetry, and redox condition, as well as their controls on the enrichment of organic matter in the Shenfu Block, eastern Ordos Basin. The results of trace element experiments indicate that the paleoenvironment of the Ordos Basin underwent a transition from a marine to a continental environment, evolving from the Benxi Formation of the Carboniferous system to the Upper Shihezi Formation of the Permian system. The provenance area is characterised by the presence of high iron and high magnesium feldspar, with a medium degree of weathering. The paleoclimate experienced alternating periods of dry heat, relatively warm wet conditions, and dry heat. The paleowater depth decreased along the sedimentary profile. With regard to the redox environment index, the Taiyuan Formation is the stratum exhibiting the highest degree of reduction. The detection criteria for biomarkers were found to be consistent with the inorganic geochemical characteristics. The relationship between various trace elements and TOC indicates that redox conditions are the primary factors influencing the accumulation of organic matter in transitional shale. Organic matter is more abundant in warm and humid marine and terrestrial environments than in deep water and anoxic conditions. The characteristics of trace elements can be inferred to suggest that the Benxi Formation and Taiyuan Formation have greater potential for exploration and development.

The Lishu depression, located in the southeastern region of the Songliao Basin, exhibits diverse fault types and complex tectonic evolution characteristics. However, the slipping direction and activity duration of strike-slip faults, as well as the overall tectonic evolution process remain unknown. This study applied a method for determining the slipping direction and activity duration of strike-slip faults, and reconstructed the tectonic evolution process of the Lishu depression using balanced cross sections. The determination of the slipping direction of strike-slip faults was based on the analysis of the dislocation distance of a specific set of strata on two fault walls within the anticline zone, and the activity duration of strike-slip faults was defined by the sedimentary period of the strata cut by faults, and the variation characteristics of formation thickness. The slipping direction and activity duration of the strike-slip faults in the study area suggest that the depression experienced a left-lateral strike regime during the sedimentary periods of 135–131.8 and 124.5–112 Ma. However, during the sedimentary periods of the Yingcheng Formation (131.8–124.5 Ma), the region was influenced by a right-lateral strike background. The study area experienced a continuous process of extension from 145.6 to 124.5 Ma, and compression commenced from the depositional period of the Nenjiang Formation (88.5 Ma), as shown by negative values of the extension rate. The findings of this study hold significant theoretical implications for the identification of the slipping direction and distance of strike-slip faults within comparable depressions. Moreover, these results have practical implications for further hydrocarbon exploration in the Lishu depression.

The Wushi sag is located in the central part of the Beibuwan Basin, northern South China Sea. Above the thick oily shale unit in the Wushi East subsag, a suite of terrace-like extensional décollement fault systems exists, which, in conjunction with the No. 7 boundary fault, control a complex fault system. This study integrates the high-resolution 3D seismic data and quantitative analysis of fault displacement to analyze the growth history of the complex fault system and to establish a model of fault system evolution in the Wushi East subsag. The findings reveal two phases of fault growth northward migration during the rifting process. The first phase occurred between the rift Ⅰ phase and the décollement Ⅰ phase, witnessing fault activity migrating northward from the No. 7 boundary fault to the décollement faults (Fd and Fe) in the hangingwall. The second phase occurred between the décollement Ⅰ phase and the décollement Ⅱ phase, with fault activity migrating further northward from Fd and Fe to Fa, Fb and Fd. By the end of the Oligocene, basin inversion controlled the syn- to post-rift transition of the Wushi East subsag. This study bears significant implications for hydrocarbon exploration and for understanding the mechanism underlying the syn- to post-rift process in the north continental marginal basins of the South China Sea.

Currently, significant hurdles lie ahead in China's lacustrine shale oil exploration and exploitation, particularly due to the high clay mineral content, which severely impacts pore development in organic-rich shales. In this study, we take the medium- to high-maturity shale of the Qingshankou Formation (K₂qn) in the Gulong sag, Songliao Basin, China, as an example and analyze the dynamic evolution of the clay minerals and their effects on pore development by core observations, scanning electron microscopy, X-ray diffraction, physical property and nitrogen adsorption to provide a valuable reference for the effective evaluation of lacustrine clay-rich shale oil reservoirs. Our findings reveal that the dynamic transformation of clay minerals in the Qingshankou Formation is classified into three stages based on diagenesis, thermal maturity, and mineral characteristics: the initial stage (vitrinite reflectivity (R_o) < 0.7%), the rapid transformation stage (R_o = 0.7%–1.3%), and the late diagenesis stage (R_o > 1.3%). Clay minerals play crucial roles in controlling shale reservoirs during the rapid transformation process, which is evidenced by the formation of shrinkage fractures, enhanced pore connectivity, increased porosity, and expanded space for shale oil adsorption and storage. In addition, authigenic quartz can form during the transformation of clay minerals, contributing to increased reservoir brittleness and improving the potential for reservoir fracturing.

This study investigates the factors controlling organic matter accumulation in organic-bearing shales around the Bolu area of Western Pontides and their implications for hydrocarbon potential through elemental and organic geochemical analyses. The organic-bearing shales in this area contain both organic matter and various critical trace elements and also attract interest as a hydrocarbon resource. In the end, the paleoceanographic model of the depositional environment was established. The findings indicate that the studied shales were deposited in a shallow-marine shelf environment with a brackish to saline marine setting, under semi-humid to semi-arid paleoclimate conditions, and subject to low to moderate chemical weathering. However, paleoclimate and variability in water column productivity did not significantly influence organic matter enrichment. Redox indicators suggest deposition occurred under oxic to suboxic conditions, with minor oxygen deficiency aiding organic matter preservation. Fluctuations in sedimentation rate likely influenced organic matter by either promoting its degradation in an oxidizing environment or diluting its concentration. While detrital input contributed to organic matter enrichment, clay minerals did not appear to play a significant role in its preservation. These shales exhibit fair organic matter content and are characterized by Type Ⅳ kerogen, indicating limited or no gas generation potential, thereby classifying them as spent hydrocarbon sources. Furthermore, prolonged atmospheric exposure of outcrop samples may have led to organic matter degradation, resulting in residual carbon at high thermal maturity. By integrating multiple geochemical proxies, this study presents the first comprehensive assessment of these shales, offering new insights into their hydrocarbon potential.