The Gangdese magmatic belt is ideal for studying crustal growth/reworking and crust-mantle interaction processes. In this study, we report a newly identified late Early Eocene granitic pluton and mafic microgranular enclaves (MMEs) in the Middle Gangdese magmatic belt. The MMEs hosted within the granitic pluton display fine-grained textures and contain more mafic minerals (amphibole and clinopyroxene) than the host pluton. The sharp contacts and fine-grained textures of the MMEs as well as acicular apatite crystals indicate a rapid quenching process. Zircon U-Pb dating results indicate that the host pluton formed ca. 48.41 ± 0.29 Ma (MSWD = 0.58), and MMEs crystallized at 48.94 ± 0.56 Ma (MSWD = 2.9), potentially suggesting a crust-mantle interaction process during the late Early Eocene. Geochemically, the host pluton has variable silica contents (SiO₂) of 58.67 wt.%–64.65 wt.%, Mg^# values of 42–58, and low aluminum saturation ratios (A/CNK = 0.81–0.91) that show an Ⅰ-type granitic affinity. Additionally, the host pluton is characterized by enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs), and depletion of high field strength elements (HFSEs) that show arc-type geochemical features. Like the host pluton, the MMEs also show arc-type geochemical features characterized by enrichment of LREEs and LILEs but depletion of HFSEs. Isotopically, the host pluton and associated MMEs both have depleted Hf isotopic compositions Additionally, the host pluton and MMEs have low Ce⁴⁺/Ce³⁺ ratios of 18.48–114.29 and 2.59–36.45, resembling Chilean ore-barren granitoid rocks. Integrated with petrological and whole-rock geochemical and zircon Hf isotopic features, we argue that the host pluton originated from partial melting of juvenile mafic lower crust with the contribution of mantle-derived materials. The MMEs were derived from partial melting of depleted mantle and was a product of two end-member magmas mixing. Based on the previous studies, we argue that the late Early Eocene magmatism and crust-mantle interaction were related to the breakoff the Neo-Tethyan oceanic slab, and further propose that crustal large-scale thickening might begin during the Middle–Late Eocene in the Gangdese magmatic belt rather than the Early Eocene.

The Cambrian and Lower Ordovician strata of the Bachu area in central Tarim Basin are characterized by extensively dolomitized, which have significant potential for favourable hydrocarbon reservoirs. The study herein combined petrographic, mineralogical and geochemical analyses to investigate the formation environments of these dolomite units and utilized Mg isotopic profiles to constrain the changes in the fluid flow trajectory. Positive excursions of δ¹⁸O and upward-increasing δ²⁶Mg profiles were observed in samples of the Wusonger formation (Є₁w), which may result from evaporation. Moreover, based on high ⁸⁷Sr/⁸⁶Sr ratios, high total REE concentrations and the occurrence of specific minerals, including quartz, barite, gypsum and pyrite, we interpret an evaporitic near-surface origin for the Є₁w dolomites. Samples of the Xiaoerblak Formation (Є₁x) are the product of seepage-reflux dolomitization, suggested by upward-decreasing δ²⁶Mg profiles and relatively lower ⁸⁷Sr/⁸⁶Sr ratios than the Є₁w samples. The overlapping isotope (δ¹⁸O, δ¹³C and ⁸⁷Sr/⁸⁶Sr) values between samples of the Shayilik (Є₂s) and Awatagh (Є₂a) Formation, in addition to the petrography evidence and Mg isotope variations, suggest that the formation of these dolomites were due to the shallow-burial dolomitization. The occurrence of the Xiaqiulitagh (Є₃ql) and Penglaiba (O₁p) dolomites along stylolites, together with their large crystals with opaque cores and clear rims and vertically constant δ²⁶Mg profiles, indicate that their formation may be related to pressure dissolution by mechanical compaction during deep-burial dolomitization. Therefore, the assembling of multiple petrographic, mineralogical and geochemical methods can shed light on the complicated generation processes of regional-scale dolomite within Tarim Basin or elsewhere.

Carbonate, present in the marine sediments, oceanic crust and seamounts, can be transported into the mantle via subduction, playing a crucial role in deep carbon cycling. However, the characteristics and origin of carbonate in seamounts are rarely studied. Here we focus on the carbonates from the Louisville Seamount chain in the southwestern Pacific Ocean, which were drilled by the IODP Expedition 330. These carbonates are predominantly composed of calcite, and can be divided into vesicle-type, vein-type, cement-type, and cap-type. The vein-type carbonates show high Eu/Eu*, indicating the possible influence of high-temperature hydrothermal fluid. In contrast, the rare earth elemental (with high Y/Ho) and carbon-oxygen isotopic signatures of other types of carbonates are generally similar to those of carbonates found within the oceanic crust, indicating that they are also precipitated from the seawater driven by water-rock interaction. A low-temperature water-rock interaction is suggested since these carbonates are precipitated at a temperature of 4.1–14.5 ℃. Due to the high δ¹³C_VPDB and δ¹⁸O_VPDB for these carbonates in the seamount, the recycling of seamount is thus suggested to be a potential candidate for contributing the mantle source of intraplate alkaline basalts in certain regions, such as the Cenozoic basalts in eastern China.

Sulfur is closely associated with various types of ore deposits, particularly orogenic gold (Au) systems, where sulfur-bearing melts and fluids play a critical role in transporting ore-forming elements essential for ore formation. The widely accepted metamorphic devolatilization model suggests that compositionally fertile sedimentary rocks serve as potential gold sources. Therefore, understanding sulfur behavior during prograde metamorphism is essential for elucidating the mechanisms underlying metal activation and mobility. In this study, we conducted in-situ sulfur isotope (δ³⁴S) analyses using secondary ion mass spectrometry (SIMS) on samples from the Hongshankou area, a representative Barrovian-type metamorphic sequence characterized by intermediate pressure-temperature (P-T) conditions. This sequence comprises the biotite, garnet, staurolite, and kyanite zones. Our results show a systematic increase in δ³⁴S values (from 3.1‰ to 5.5‰) coupled with a progressive decrease in total sulfur content (from 320 ppm to 165 ppm) as metamorphic grade increases. The most pronounced sulfur mobilization occurs between the garnet and staurolite zones. In all analyzed samples, Au or Au-bearing minerals predominantly occur along the edges or within pyrite grains, highlighting the critical role of pyrite breakdown in controlling gold mobility. Thus, sulfur isotope fractionation provides robust constraints for quantitatively assessing sulfur mobility during metamorphism. These findings reinforce the concept that metasedimentary rocks and their metamorphic fluids represent fertile sources of Au and other metals enriched in orogenic gold deposits.

The role of ore metals in magmatic fluids during the magmatic-hydrothermal transition in porphyry systems remains unclear, and their contributions to porphyry ore genesis are unclear. This study offers fresh perspectives on the ore-forming process during this critical transition, focusing on the Hongyuan porphyry Mo (Cu) deposit (PMCD) in West Junggar, China. We find that sulfide-quartz-rich miarolitic cavities (MCs), characterized by micrographic quartz and feldspar, indicate the formation of initial mineralizing fluids from magmatic fluids. This conclusion is supported by three key observations: the simultaneous formation of feldspar and sulfides in the micrographic zones of MCs, the high formation temperatures (approaching 750 ℃) suggested by the sector-zoned bright CL cores of quartz phenocrysts, and the magmatic sulfur source indicated by the narrow sulfur isotopic composition ranges (+0.18‰ to +4.63‰). LA-ICP-MS analyses reveal distinct trace element distribution patterns between the early magmatic and transition stages and the later hydrothermal stage. Chalcopyrite from the early stages has higher Cd and lower Zn contents, while molybdenite has higher Re contents, and pyrite has higher Co and Ni contents than its counterparts in the hydrothermal stage. The decrease in sulfur concentrations at sulfide saturation from granite porphyry to micrographic quartz-feldspar melts (from 200 ppm to 100 ppm) suggests that nearly half of the sulfur was exsolved during the formation of feldspar and quartz intergrowths from fractionated granitic magma. These findings indicate that the initial mineralizing fluids of the porphyry deposit were high-temperature, melt-bearing, and ore-rich and originated from magma. The transition from initial melt-bearing, metal-rich fluids to hydrothermal ore-forming fluids is marked by decreasing temperatures and logf_S2 values, underscoring the critical role of sulfide formation during the magmatic-hydrothermal transition in the development of porphyry deposits.

Carbonaceous debris (CD) is widely disseminated within sandstones in the Shuanglong uranium deposit, southern Ordos Basin, and is the dominant enrichment agent for uranium precipitation. The occurrence and chemical composition of uranium minerals within CD were investigated by using scanning electron microscope and electron microprobe analyses. The results show that uranium minerals mostly occur in cell pores in the forms of fructus aurantia and concentric band structure. Pitchblende and coffinite are the main uranium minerals, and the former is dominant. According to the crystal morphology and composition of trace elements of uranium minerals, uranium precipitation on the pores is grouped into two periods, orderly Ⅰ, Ⅱ. Moreover, the Ⅰ period is further divided into two sub-period, orderly I₁, I₂. Moreover, askew sphere uranium minerals could indicate fluid migration. Under certain geological environment condition, uranium is unevenly adsorbed on the surface of the pore by the Van der Waals (i.e., I₁ period), and then is precipitated towards to the center of the pore until the whole pore is filled up with uranium minerals by complicated process such as microorganism activities (i.e., I₂, Ⅱ period). It will provide some guidance for studying the metallogenic environment and genesis of sandstone-type uranium deposit.

The formation of Caosiyao giant porphyry Mo deposit is related to three granitic porphyries: coarse-grained granite porphyry (CG), fine-grained granite porphyry (FG), and giant plagioclase phenocryst bearing granite porphyry (PG). To investigate the mineralization significance of three porphyries, Microthermometry, Laser micro-Raman Spectra, and H-O-He-Ar isotope analyses of fluid inclusions were conducted. Intermediate density with high temperatures (> 550 ℃) and moderate-low salinities (~10 wt.%) characterizes CG-related initial exsolved fluids. Vapor-rich and brine phases separated from the initial fluid following a continuous decrease in pressure and temperature, inducing molybdenite precipitation. FG-related initial fluids are characterized by high temperatures (> 550 ℃) and salinities (> 65 wt.%). The mixing of low-salinity fluids led to a rapid decrease in the salinity of FG-related fluid, promoting the deposit of the Mo element. The lead-zinc mineralization is closely related to the FG-related fluid, and the addition of meteoric fluid induced the formation of galena and sphalerite. The ore-forming fluid related to the PG is CO₂-rich and accompanied by the addition of mantle-derived He-Ar. The presence of CO₂ did not contribute to the solubility of Mo, resulting in the absence of a considerable amount of molybdenite.

The paleo-geothermal gradient is a crucial parameter for converting the thermal history to the exhumation history. However, the precise estimation of this parameter has been a challenge. This paper presents a simple two-step method to model the paleo-geothermal gradient using low-temperature thermochronology. (1) It uses the Monte Carlo approach to generate thermal histories in a vertical section randomly and calculates the entire thermal history within the goodness-of-fit thresholds based on different paleo-geothermal gradients. (2) It selects the optimum paleo-geothermal gradient by comparing the entire thermal history within different goodness-of-fit thresholds. We validated the method with apatite (U-Th)/He and fission track data collected from two drill cores in the Haiyuan-Liupanshan region. The result revealed that the best-fit paleo-geothermal gradient was ~42 ℃/km during the Early Cretaceous–Miocene and has decreased rapidly to 20 ℃/km since ~10 Ma. The crust thickening in the study area may explain the rapid reduction in the paleo-geothermal gradient since ~10 Ma. Our results are consistent with earlier studies in the region, suggesting that our simple and more intuitive approach provides an alternative method for paleo-geothermal gradient modeling.

Dissolution trapping is one of the most promising mechanisms for safe geological carbon storage. Density-driven convection substantially accelerates the conversion of free-phase CO₂ to the dissolved state, enhancing the sequestration safety. Since this process occurs on time scales of hundreds to thousands of years, reproducing it through conventional laboratory physical model tests is challenging. The hypergravity experiment reduces the model size and shortens the experimental time, enabling the modeling of gravity-driven flow processes at the field scale. However, it is uncertain whether the preferential flow effect caused by fractures can be reproduced in a hypergravity experiment. In this study, a three-dimensional discrete fracture-matrix model (3D-DFM) was used to evaluate the feasibility of hypergravity experiment of the transport of dissolved CO₂ in fractured reservoirs. Numerical hypergravity tests were performed to examine the feasibility of modeling density-driven convection in homogeneous and heterogeneous media at different centrifuge accelerations. The hypergravity experiment can be used to study density-driven convection of dissolved CO₂ at the field scale in homogeneous system. The numerical results show that the hypergravity experiment enables a faster breakthrough of plume and overestimates CO₂ migration in the matrix surrounding the fractures.

The India-Asia collision resulted in the formation of Qinghai-Tibet Plateau. Lower crustal flow model was proposed to explain the mechanism of Cenozoic tectonic deformation of Qinghai-Tibet Plateau. In this study, we propose a new approach by combining centrifugal analog modeling with numerical simulation to simulate the tectonic uplift history of the plateau based on the lower crustal flow model, and to investigate the material migration characteristics and the influence of crustal motion velocity and ductile layer viscosity on the plateau tectonic geomorphology. The models reproduce steep-sided flat-topped geomorphic features and clockwise rotation of the material at eastern Himalayan Syntaxis, verifying the rationality of the models. The results show that the greater the crustal motion velocity and the greater the ductile layer viscosity, the steeper the terrain change; and conversely, the smaller the crustal motion velocity and the smaller the ductile layer viscosity, the gentler the terrain change. This study further indicates that the weak lower crust plays an important role in the formation of geomorphic features and material migration characteristics of Qinghai-Tibet Plateau, and provides a new insight for the study of the uplift mechanism of the Tibetan Plateau.

Chlorite coats are believed to inhibit quartz cementation and preserve deeply-buried sandstone porosity. However, geologists face numerous challenges in evaluating the influences of chlorite coats in real cases. To tackle these challenges, this work reviewed a large number of case studies to discuss the proper way to evaluate their role using petrography. The following five main conclusions were drawn: (1) Compared to other coat parameters, coat coverage is more reliable in evaluating the influence of chlorite coats on quartz cements. (2) In addition to chlorite coats, quartz growth is influenced by multiple factors such as temperature, while sandstone porosity is affected by various factors including mechanical compaction; therefore, when evaluating the influence of chlorite coats, geologists should take these factors into account. (3) Even if no negative correlation exists between chlorite coats and quartz cements, and no positive correlation is observed between chlorite coats and sandstone porosity, one cannot simply conclude that chlorite coats do not inhibit quartz cements and protect sandstone porosity. (4) Chlorite coats can significantly occupy pore space, leading to a net porosity decrease. (5) Chlorite coats can undergo significantly dissolution, while whether this phenomenon is ubiquitous remains underexplored.

The pore structure of shale oil reservoir significantly affects the occurrence and mobility of hydrocarbons. The potential of a new type of alkaline lake shale oil has been demonstrated, but there are few reports on the pore system of alkaline lake shale, which restricts the efficient exploration and development of shale oil. This study investigates the Fengcheng Formation shale in the Mahu sag of the Junggar Basin, employing methods such as low-temperature nitrogecn adsorption (LTNA), mercury intrusion capillary pressure (MICP), and nuclear magnetic resonance (NMR) to quantitatively characterize the multi-scale pore structure and fractal characteristics of shale, while evaluating the applicability of these methods. Based on a comprehensive analysis of material composition, different pore types, and fractal dimensions, the controlling factors for the development of different pore types and their seepage capacity are discussed. The results indicate that inorganic mineral pores are the main development in alkaline lake shale, with the pore morphology being characterized by slit-like and ink-bottle shapes. The multi-scale pore size distribution (PSD) shows that Ⅱ-micropores (10–100 nm) and mesopores (100–1 000 nm) are the main contributors to the pore system. The development of Ⅱ-micropores is associated with feldspar and calcareous minerals, the development of Ⅰ-micropores (< 10 nm) and mesopores is related to quartz content, while large pores are mainly found in interlayer fissures of clay minerals. The development of Ⅰ-micropores increases the roughness of pore surface and enhances the adsorption capacity of the pores, while the development of Ⅱ-micropores associated with calcareous minerals hinders pore seepage capacity. Mesopores and macropores (> 1 000 nm) exhibit good flowability. The high content of siliceous minerals plays a positive role in the pore system of alkaline lake shale. The shale with higher fractal dimension D_min exhibits greater adsorption capacity, which hinders the accumulation of free-state shale oil. Different types of pore space play different roles in the occurrence of shale oil, with free-state shale oil primarily occurring in micro-fractures and inorganic mineral pores, and the pore size is exceeding 10 nm.

To clarify the thermal evolution characteristics of organic matter in the Zizhong-Weiyuan area in Sichuan Basin, solid bitumen reflectance of the Lower Cambrian Qiongzhusi Formation (QFm) shale was measured by Raman Spectroscopy (RS) method. Constrained by vitrinite reflectance (Ro) data, burial and thermal evolution histories of QFm shale were reconstructed through basin numerical simulation technology. The evolution model of and critical period of organic matter was determined, and its dominant drivers were analyzed. The results show that the asphalt Raman vitrinite reflectance (_RmcRo) ranges from 3.21% to 4.15%. Thermal maturity within the trough follows a southern part > central part > northern part trend. Thermal maturity is moderate within the paleo-uplift, whereas organic matter outside the paleo-uplift has undergone graphitization. Two types of thermal evolution imprints were established: a continuous heating type and a stop heating type of Silurian–Permian. Sedimentary burial, paleogeomorphology, tectonic movement and Emeishan mantle plume are the dominant drivers of multi-stage thermal imprints of the QFm shale. The three factors are coupled with each other. The Late Caledonian and Late Indosinian are the key periods of organic matter thermal evolution. The Leshan-Longnüsi paleo-uplift weakens the thermal effect of the Permian Emeishan mantle plume. The current thermal evolution pattern of the QFm is mainly determined by the continuous subsidence of the Triassic–Cretaceous. Stop heating model of Silurian–Permian locks the maturity of organic matter in the gold window, thus controlling the enrichment of QFm shale gas. It provides new insights for shale gas migration, enrichment and effective exploration and development of shale gas in the Lower Paleozoic QFm.