Deep sandstone/mudstone interbedded reservoirs have become a key area of interest in the study of petroleum geology. Unlike the conventional fracture development model of interbedded sand/mudstone fractures, within the context of rapid compression, fractures develop in mudstone but not in sandstone, resulting in a reverse fracture development pattern. The traditional rock fracture theory has limitations for explaining the formation mechanism of such fractures, resulting in an unclear understanding of fracture distribution patterns in sand/mudstone interbedded reservoirs. In this study, data from deep (>4500 m) cores and geophysical data from the Tarim Basin in northwestern China were employed to elucidate the rupture patterns of sandstone–mudstone interbeds. The results indicated that the rate of structural deformation is a key factor controlling the location of fracture development. On the basis of core and imaging logging data, the development characteristics of tectonic fractures in sandstone and mudstone were assessed, and the lithological layers where tectonic movement-driven fracturing occurred were clarified. Tight sandstone and mudstone samples were collected from blocks with different tectonic deformation rates, and rock mechanics experiments with variable loading rates were conducted to reveal the effects of the tectonic deformation rate on the mechanical properties and fracture strength of rock, thereby establishing a relationship between the tectonic deformation rates and locations of formation fractures in sand–mud interbeds. Finally, by combining X-ray diffraction experiments and diagenesis strength analyses, the genetic mechanisms of various rock fractures with different tectonic deformation rates were revealed. The results provide reference value for the development of rupture depth prediction models for sand–mud interbeds, the quantitative prediction of reservoir fractures, deep-ultradeep energy exploration and development, and the refinement of fracture theory for composite rock masses, which can promote the understanding and development of the theory of fractured composite rock masses.
The East Kunlun Orogen (EKO) is a compound orogenic belt and a Proto-Tethyan tectonic collage. Its constituent blocks document long-term accretionary and collision processes, with episodic, arc-related magmatism and dispersal of several eclogite-hosting units along the orogenic strike. To shed new light on the controversial Early Paleozoic accretion of the EKO to adjoining Gondwana-derived terranes to the south, we present the first investigation of eclogite blocks in banded orthogneisses from the upper Hatu Valley, southern EKO. The Hatu eclogites exhibit varying modal abundances of green amphibole, garnet, omphacite, phengite pseudomorphs, plagioclase, and quartz. Most omphacite and all phengite in the matrix have been replaced by calcic clinopyroxene–plagioclase and biotite–plagioclase symplectites, respectively. The inferred peak assemblage is garnet + omphacite (with 20–28 mol% jadeite) + calcic amphibole + phengite. Pseudosection modeling and conventional thermobarometry reveal a clockwise, four-stage P-T path with peak conditions of 620–700 °C and 14–16 kbar, typical of warm continental subduction. The protoliths of the Hatu eclogites were derived from metasomatized mantle, most likely in a rifted continental-margin setting rather than a mid-ocean ridge environment. Differences in mineralogy, whole-rock geochemistry, and P-T paths during exhumation between the Hatu eclogites and their central EKO equivalents may reflect two distinct tectonic regimes within the Proto-Tethyan subduction system. The concordant, ∼1.10-Ga U–Pb ages of magmatic zircon cores in orthogneisses link the eclogite–gneiss association to the Bayanhar terrane that rifted away from the Gondwana supercontinent. The ∼450-Ma U–Pb ages of high-pressure metamorphic overgrowths on zircon from eclogites and the host granitic gneisses suggest an in situ eclogite origin, supporting the Ordovician collision between the Proto- and Paleo-Tethyan terranes. This is consistent with the first occurrence of A-type granites in the southern EKO at ∼440 Ma, which typically form in post-orogenic extensional settings.
Acid mine drainage (AMD), a serious global environmental problem that degrades water quality, causes severe ecological damage, and poses significant health hazards. In this study, AMD water samples from a high sulphur coalmine area were assessed and evaluated for human health and toxicological risks associated with contamination by potential heavy metals (HMs). The integrated study using correlation, principal component, and cluster analyses indicated that anthropogenic activities such as mining along with natural weathering processes, are the primary sources of HMs in the AMD water. Heavy metal toxicity load (HMTL) indicated significant removal ofheavy metalsfrom AMD mine water and discharge water, achieving compliance with potable water standards. The non-carcinogenic health hazard assessment indicates, adults are more vulnerable compared to children, with both carcinogenic and non-carcinogenic risks potentially present due to exposure to heavy metals. Cytotoxicity and in vitro assays using normal fibroblast L929 cells demonstrated nuclear morphological alterations and elevated intracellular reactive oxygen species (ROS) levels, indicating oxidative stress and cellular damage. The result highlights the urgent need for effective remediation strategies and continuous monitoring of AMD-impacted areas associated with high-sulfur coal mining, to protect both environmental and public health.
Tungsten (W) and tin (Sn) deposits associated with highly fractionated granites are commonly separated in both space and time. Although magmatic differentiation and hydrothermal fluid evolution have long been invoked to explain this decoupling, the coupled chemical behavior of W and Sn in magmatic-hydrothermal systems, and its role in governing the segregation of wolframite and cassiterite, remains poorly constrained. Here, we synthesize whole-rock geochemical data for W-Sn-related granites from major global metallogenic belts and apply t-distributed stochastic neighbor embedding (t-SNE)-based unsupervised machine learning to identify a robust association between iron (Fe) content and barren, Sn-related, and W-related granites. This data-driven pattern suggests that granite-related W-Sn mineralization is fundamentally governed by Fe abundance. We further use total Fe content as an input to a Rayleigh distillation model simulating Fe behavior in the multiphase equilibrium system FeWO4–SnO2–NaCl–HCl–H2O–CO2. Our results show that, in addition to Fe availability, the thermodynamic properties of W and Sn exert a first-order control on the decoupling of wolframite and cassiterite during hydrothermal mineralization. At 200–300 °C, wolframite precipitation is favored, whereas cassiterite predominates at 340–400 °C. Low-Fe conditions (0.080–0.214 mol/kg) promote wolframite as the dominant phase but are insufficient for economically significant cassiterite formation. In contrast, higher Fe contents (0.226–0.420 mol/kg) substantially enhance cassiterite precipitation relative to wolframite, facilitating W-Sn co-enrichment. Economically significant cassiterite-dominated deposits require both elevated Fe contents (0.226–0.420 mol/kg) and higher initial Sn concentrations (W = 0.013 mol/kg, Sn = 0.020 mol/kg). Pressure exerts contrasting effects on W and Sn solubility: W solubility increases with pressure, whereas Sn solubility decreases with pressure below 300 °C, producing asynchronous responses that amplify their differential precipitation. CO2 modifies mineral solubility by regulating fluid pH; increased CO2 enhances the solubility of both wolframite and cassiterite, with the magnitude of this effect depending on the initial pH of the hydrothermal fluid. Oxygen fugacity (fO2) controls mineral solubility through its influence on the Fe3+/Fe2+ ratio: increasing fO2 lowers cassiterite solubility, whereas wolframite remains comparatively insensitive. Across all modeled conditions, Fe variations have a greater effect on wolframite solubility than on cassiterite. Collectively, these results clarify the geochemical controls on W-Sn mineralization and establish Fe as a key parameter governing the formation and decoupling of wolframite- and cassiterite-bearing systems in highly evolved granitic environments.
The role of post-diagenetic hydrothermal processes in cobalt (Co) enrichment in sediment-hosted stratiform Cu-Co (SSC) deposits remains controversial, particularly regarding whether high-grade Co mineralization is primarily diagenetic or requires later tectonic overprinting. The Shizishan deposit, SW China, exhibits a well-defined vertical Co zoning and coexisting disseminated and veinlet sulfide assemblages, making it an ideal example to address this issue. Here we integrate in-situ sulfide trace element geochemistry, Fe–S isotopes, and rutile U–Pb dating to distinguish two mineralization events. Early disseminated chalcopyrite, cobaltite, and pyrite formed during diagenesis, with Co distribution controlled by organic matter in the host rocks. The later post-diagenetic stage formed veinlet chalcopyrite, bornite, cobaltite and cobaltian pyrite cross-cutting early-stage mineralization. Veinlet chalcopyrite shows systematic depletion of Co, Ni and As relative to disseminated chalcopyrite, while cobaltite and pyrite show opposite trends, indicating remobilization and recrystallization of pre-existing sulfides. Chalcopyrite from Co-rich layers exhibits lower δ56Fe values (−0.53‰ to −0.17‰) than Co-depleted layers (−0.31‰ to −0.02‰), suggesting more reduced fluids. Hydrothermal rutile associated with veinlet ores yields a U–Pb lower intercept age of 1449 ± 33 Ma, defining a post-diagenetic tectonic-hydrothermal event. This overprinting event significantly upgraded Co grades, particularly in dolostone enriched in organic matter. Our results demonstrate that while the diagenetic stage provided primary metals and traps, it is the later orogenic-related hydrothermal modification that was essential for the formation of economic Co concentrations, and a reduced setting is a key factor controlling Co precipitation.
