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[Display omitted] • Fluid overpressure plays a key important role in the formation of skarn iron deposit. Skarn iron deposits are important resources for iron-rich ores and their genesis has been a topic of debate. The Nanminghe iron deposit is a typical skarn iron deposit in Wu'an, Hebei Province, China which provides a good example to investigate the metallogenic mechanism. In this paper, we present a detailed study of the geology, petrography, and geochemical characteristics of magnetite in the Nanminghe iron deposit. Two types of magnetite can be identified in the massive ores: Mag1 is euhedral with radial cracks developed in the margin. It is a low-Si magnetite, with SiO 2 content ranging from 0.07% to 0.92%, with an average value of 0.49%. The SiO 2 content of Mag2 is from 0.90% to 3.29%, and an average value of 2.03%. The Mag2 is associated with quartz, goethite, and apatite. Geochemical characteristics of Mag1, together with the ore textures suggest its crystallization from an iron magma. There are significant differences in the geochemical characteristics between Mag1 and Mag2. Mag2 is rich in Nb, Ta, high field strength elements, large ion lithophile elements and has higher silica content. The Nb/Ta of Mag2 is higher than that of the original mantle. These characteristics as well as La/Ta vs Th/La, Th/U vs Sm/Nd and Nb/Ta vs Nb features show that Mag2 is formed in the environment of supercritical fluids. The δ56Fe of Mag1 is 0.157‰-0.172‰, with an average value of 0.166‰, and the δ56Fe of Mag2 is 0.119‰-0.160‰, with an average value of 0.139‰. The Fe isotope of Mag2 is lighter than Mag1. There is a negative correlation between δ56Fe and SiO 2 of Mag1 and Mag2, suggesting that the lighter δ56Fe of Mag2 was caused by injection of Si-rich fluids. We propose a genetic model where we envisage that the iron-rich melt formed in the deep magma chamber by reaction of dioritic rocks and carbonates. Mag1 formed by cooling of the iron-rich magma, following which Si-rich supercritical fluid were injected into the deep chamber resulting in fluid overpressure. The iron-bearing melt-fluid migrated upward along the magmatic conduit, when Mag2 formed. Our study provides insights into the formation mechanism of skarn iron deposits. [ABSTRACT FROM AUTHOR]

After the initial impoundment of the Baihetan Reservoir in April 2021, the water level in front of the dam rose about 200 m. The mechanical properties and effects of the bank slopes in the reservoir area changed significantly, resulting in many bank collapses. This study systematically analyzed the bank slope of the head section of the reservoir, spanning 30 km from the dam to Baihetan Bridge, through a comprehensive investigation conducted after the initial impoundment. The analysis utilized UAV flights and ground surveys to interpret the bank slope's distribution characteristics and failure patterns. A total of 276 bank collapses were recorded, with a geohazard development density of 4.6/km. The slope gradient of 26% of the collapsed banks experienced an increase ranging from 5 to 20° after impoundment, whereas the remaining sites' inclines remained unchanged. According to the combination of lithology and movement mode, the bank failure mode is divided into six types, which are the surface erosion type, surface collapse type, surface slide type, bedding slip type of clastic rock, toppling type of clastic rock, and cavity corrosion type of carbonate rock. It was found that the collapsed banks in the reservoir area of 85% developed in the reactivation of old landslide deposits, while 15% in the clastic and carbonate rock. This study offers guidance for the next phase of bank collapse regulations and future geohazards prevention strategies in the Baihetan Reservoir area. [ABSTRACT FROM AUTHOR]

CO2 is being considered as an effective alternative working fluid for geothermal applications due to its superior fluid dynamics and heat transfer properties compared to water. Utilizing sedimentary rocks for geothermal energy recovery through a CO2-plume geothermal system, especially in carbonate reservoirs, has been shown to be a practical approach that eliminates the need for hydraulic fracturing. However, uncertainties remain regarding the thermal and hydraulic behavior, particularly the chemical interactions between CO2 and carbonate rocks. This study develops a comprehensive wellbore–reservoir coupling reactive transport model based on specific information obtained from the Ordovician limestone geothermal reservoir in Shandong, China. The model aims to assess the feasibility of heat extraction in carbonate reservoirs by evaluating the heat extraction performance and fluid–rock interaction. The results indicate a rapid temperature drop after CO2 breakthrough due to the Joule–Thomson effect. Simultaneously, the fluid transitions into and maintains a two-phase state throughout the operation. Chemical reactions within the reservoir are not aggressive since complete mixing between unsaturated water and CO2 only occurs in the vicinity of the production well, highlighting the potential of utilizing carbonate reservoirs for efficient heat extraction in geothermal systems. Further research is needed to optimize the performance of CO2-based geothermal systems in carbonate reservoirs. [ABSTRACT FROM AUTHOR]

South China Karst faces the challenge of balancing ecological conservation and regional development, a task made more intricate by the geological limitations of carbonate formations. Large‐scale conservation and restoration initiatives have mitigated rocky desertification and positioned South China Karst as a global hotspot for vegetation regrowth over the past two decades. However, challenges stemming from geological constraints and oversights in recognizing the synergies within social‐ecological systems remain. Here, we propose a social‐ecological framework that integrates the extended timescale of both historical and recent human impacts with the corresponding processes of forest evolution. The framework elucidates the enduring and continuous progression of "forest‐deforestation‐reforestation," offering applicability for optimizing ecological space across diverse social‐ecological contexts. Moreover, it serves to enhance the sustainability of reforestation efforts when faced with geological constraints. Plain Language Summary: South China is one of the most remarkable greening regions in the world in the last 20 years, but it is unknown whether the greening trend is sustainable. The soil is thin in South China Karst and carbonate rocks under the vegetation will affect water storage, thus affecting growth of vegetation. Moreover, the region is facing serious conflicts between people and land. We summarize the effectiveness of ecological restoration in the South China as well as the present social and natural challenges. Subsequently, we propose a research framework to get a comprehensive view of the vegetation changes in the past, present and future. It helps enhance the reforestation sustainability in the Karst critical zone. Key Points: Both the natural and social dimensions of rocky desertification controls in South China Karst are reviewedChallenges of a sustainable reforestation under geological constraints are revealedA social‐ecological framework designed to enhance sustainability of reforestation is proposed [ABSTRACT FROM AUTHOR]

The reservoir of the M oilfield in Tarim Basin is an unconventional fracture-cave carbonate rock, encompassing various reservoir types like fractured, fracture-cave, and cave, exhibiting significant spatial heterogeneity. Despite the limited pore space in fractures, they can serve as seepage pathways, complicating the connectivity between reservoirs. High-precision fracture prediction is critical for the effective development of these reservoirs. The conventional post-stack seismic attribute-based approach, however, is limited in its ability to detect small-scale fractures. To address this limitation, a novel pre-stack fracture prediction method based on azimuthal Young's modulus ellipse fitting is introduced. Offset Vector Tile (OVT) gather is utilized, providing comprehensive information on azimuth and offset. Through analyzing azimuthal anisotropies, such as travel time, amplitude, and elastic parameters, smaller-scale fractures can be detected. First, the original OVT gather data are preprocessed to enhance the signal-to-noise ratio. Subsequently, these data are partially stacked based on different azimuths and offsets. On this basis, pre-stack inversion is carried out for each azimuth to obtain the Young's modulus in each direction, and, finally, the ellipse fitting algorithm is used to obtain the orientation of the long axis of the ellipse and the ellipticity, indicating the fracture orientation and density, respectively. The fracture prediction results are consistent with the geological structural features and fault development patterns of the block, demonstrating good agreement with the imaging logging interpretations. Furthermore, the results align with the production dynamics observed in the production wells within the block. This alignment confirms the high accuracy of the method and underscores its significance in providing a robust foundation for reservoir connectivity studies and well deployment decisions in this region. [ABSTRACT FROM AUTHOR]

The Youjiang Basin in China is the world's second-largest concentrated area of Carlin-type Au deposits after Nevada, USA, boasting cumulative Au reserves nearing 1000 t. This study examined the recently unearthed Lintan Carlin-type Au deposit within the Youjiang Basin. Factor analysis and association rule algorithms were used to identify exploration vectors and indicators essential for navigating this promising geological territory. In the Lintan mining area, the geological strata encompass the Triassic Bianyang, Niluo, and Xuman formations comprised clastic rocks, followed by the deeper Permian Wujiaping Formation with massive carbonate rocks. The orebodies are restricted to the F14 inverse fault, cutting through the Xuman Formation, with an additional F7 fault between the Wujiaping and Xuman formations. A total of 125 rock samples from the F14 fault and a representative cross-section were analyzed for 15 elements (Au, Ag, As, Bi, Cd, Co, Cu, Hg, Mo, Ni, Pb, Sb, Tl, W, and Zn). The elements were divided into four groups based on cluster and factor analysis. Group 1 (Co, Cu, Zn, Ni, Tl, W, and Bi) was mainly enriched in the Xuman, Niluo, and Bianyang formations controlled by sedimentary diagenesis. Group 2 (Au, As, Hg, and Sb) was concentrated in the F14 and F7 faults, representing Au mineralization. Group 3 (Pb, Ag, and Mo) was mostly enriched near the F14 and F7 faults, displaying a peripheral halo of Au mineralization, and was probability controlled by ore-forming hydrothermal activities. Group 4 (Cd and Mo) exhibited extreme enrichment along the periphery of the F7 fault. This pattern indicates the presence of a substantial hydrothermal alteration zone surrounding the fault, likely influenced by ore-forming hydrothermal processes. Additionally, Pb, Ag, Cd, Mo, and W are considered essential indicators for ore formation besides Au, As, Sb, Hg, and Tl. Twelve effective association rules were derived using the association rule algorithm, which can aid in discriminating Au mineralization. The spatial distributions of the 15 elements indicated that the F14 fault is the main ore-bearing fracture zone, while the F7 fault serves as the ore-conducting structure, channeling ore-forming fluids into the F14 fault. Faults between the Wujiaping and Xuman formations, along with their associated reverse faults, present potential prospecting targets both within and outside the Lintan Au deposit in the Youjiang Basin. Exploration geochemical data can be fully utilized by combining factor analysis and association rule algorithms, offering key guidance for prospecting Carlin-type gold and similar deposits. [ABSTRACT FROM AUTHOR]

Scheelite (CaWO4) is an economically important W mineral in skarns that form when magmatic fluids exsolved from a granitic intrusion react with carbonate wall rocks. In the Fujiashan W skarn deposit, scheelite formed during four stages of the hydrothermal skarn development. We present cathodoluminescence (CL) images and in situ trace element and Sr-O isotope data of scheelite from these four stages, i.e., scheelite in prograde and retrograde skarn, quartz-sulfide veins, and late calcite replacements. Scheelite from prograde skarn and quartz sulfide veins are homogeneous and show oscillatory zoning textures in CL images, whereas scheelite from retrograde skarn and late carbonate stages display dissolution-reprecipitation and patchy textures. The brightness of CL textures decreases with a higher substitution of Mo. Molybdenum-rich scheelite (up to 2.1 wt%) is characterized by relatively high contents of Nb and Ta (up to 156 and 0.9 ppm, respectively), positive Eu anomalies, high-δ18O values (5.2 to 5.9‰), and relatively low-87Sr/86Sr values (0.70661 to 0.70727), and has grown in a system with a continuous supply of magmatic fluid. Molybdenum-poor scheelite (0.2 wt%) has low contents of Nb and Ta, negative Eu anomalies, low-δ18O values (4.2 to 4.3‰), and relatively high-87Sr/86Sr ratios (0.70748 to 0.70804). This type of scheelite formed in a system with a restricted flow of magmatic fluid during scheelite precipitation became increasingly depleted in elements that substitute into scheelite. The continued reaction of the magmatic fluid with the wall rocks and the precipitation of minerals from the fluid resulted in a systematic change of the δ18O and 87Sr/86Sr ratios. Chemical and isotopic variations in scheelite may reflect the pulsed flow of a magmatic fluid and do not require the involvement of different fluids or contrasting redox conditions. [ABSTRACT FROM AUTHOR]

Although carbonate rocks are important for carbonate-hosted Pb Zn deposits, there is no effective constraint on the role of carbonate rocks during the Pb Zn mineralization process. This paper uses the giant Huize Pb Zn deposit (>7 Mt. metals @ 25–35 % Pb + Zn) as a case study and employs zinc isotopes to gain new insights into such issue. The Huize deposit, located in the Sichuan-Yunnan-Guizhou (SYG) Pb Zn metallogenic province, is the largest carbonate-hosted deposit in the western Yangtze Block, SW China. Zinc isotope compositions of sphalerite, altered carbonate rocks and fresh carbonate rocks from the Huize deposit are of +0.39 ‰ to +0.68 ‰ (mean + 0.52 ‰, n = 20), −0.25 ‰ to +0.34 ‰ (mean + 0.07 ‰, n = 11) and + 0.35 ‰ to +0.71 ‰ (mean + 0.51 ‰, n = 6), respectively. The initial δ66Zn value of hydrothermal fluids calculated by the Rayleigh fractionation simulation is +0.4 ‰. Such zinc isotope signatures are significantly different from those of potential source rocks, such as the basement Proterozoic metamorphic rocks (δ66Zn = +0.10 ‰ to +0.34 ‰, mean + 0.22 ‰), the host Upper Ediacaran to Middle Permian sedimentary rocks (δ66Zn = −0.24 ‰ to +0.35 ‰, mean + 0.1 ‰) and the cover Upper Permian Emeishan basalts (δ66Zn = +0.30 ‰ to +0.44 ‰, mean + 0.35 ‰). Hence, it is likely that the carbonate rocks acted zinc source and provided heavy zinc isotopes for the Pb Zn mineralization. The ore-forming fluids extracted the heavy zinc isotopes of the ore-hosting carbonate rocks, resulting in the zinc isotopes of the altered carbonate rocks being far lighter than those of the marine carbonate rocks (δ66Zn = +0.24 ‰ to +1.32 ‰). The sulfur isotope compositions (+12.9 ‰ to +15.6 ‰, mean + 14.3 ‰, n = 20) of sphalerite from the Huize deposit also suggested that the source of reduced sulfur is the marine sulfate minerals within the ore-hosting carbonate rocks. Therefore, carbonate rocks play key roles in the formation of carbonate-hosted Pb Zn deposits: 1) provide ore-forming elements and ore-hosting space through dissolution; 2) cause isotope variation (e.g., zinc isotopes) by isotope exchange; 3) act as a carbonate buffer to adjust physicochemical conditions (e.g., pH) via cyclical carbonate dissolution, CO 2 degassing and recrystallization. On the other hand, the zinc isotope mapping shows that the western part of the SYG Pb Zn metallogenic province has lighter zinc isotopes than those of the eastern part. This suggests that the migration pathway of hydrothermal fluids is likely west to east, which provides a new clue for regional Pb Zn ore prospecting. The outcomes have important benefits for understanding the genesis of Pb Zn deposits, the role of carbonate rocks and the application of zinc isotopes. [Display omitted] • Zinc isotope fractionation was jointly controlled by fluid mixing and Rayleigh fractionation. • Heavy zinc isotopes were extracted from carbonate rocks through water/rock interaction. • Carbonate rocks played a key role in the formation of carbonate-hosted Pb Zn deposits. • Zinc isotope mapping provides a new clue for regional Pb Zn ore prospecting. [ABSTRACT FROM AUTHOR]

The Laojunshan ore cluster region is situated at the north Song Chay dome, which is the junction of the Yangtze, the Cathaysia, and the Indo-China Blocks. The north Song Chay dome characterized by the Laojunshan metamorphic core complex is an important ore-forming region for W-Sn-Pb-Zn-In elements related to the Late Cretaceous granitic magmatism. In this paper, the Bi-dimensional empirical mode decomposition (BEMD) is applied to separate gravity components from the original gravity data, combined with the known geological and mineralized information, to explore the relationships between the gravity components and various ore-controlling factors at different depths. Four intrinsic mode functions (IMFs) and a residue are obtained. They may imply the spatial distribution of the geological bodies with featured gravity components at different depths. The results are shown as follows: (1) The low-pass filtering gravity component (BIMF4) implies the deeply buried geological units in the study region. The Cretaceous Laojunshan granitic complex and the Nanwenhe gneissic granite display negative gravity components and weak positive gravity components, respectively. The former is closely related to Sn-Zn-In mineralization, the latter is closely related to W polymetallic deposits. Therefore, the negative gravity components showing the Laojunshan granitic complex are the prospecting targets for deeply buried Sn-Zn-In deposits. The weak positive gravity components displaying the Nanwenhe gneissic granite are the prospecting targets for deeply buried W polymetallic deposits. (2) The band-pass filtering gravity component (BIMF3) implies the geological units at middle depth. The skarn-type Sn-W polymetallic deposits are observed in the transition zones from the positive to the negative gravity components, which coincide with the contact metasomatic zones between the Cretaceous granite and the Cambrian-Devonian carbonate rocks. Some small quartz vein W deposits occur within the Cretaceous Laojunshan granite with negative gravity components, and some layered W deposits occur in the Silurian gneissic granite with a weak positive gravity component. (3) High-pass filtering gravity component (BIMF2) implies geological units at the shallow crust, which shows that most of the deposits (occurrences) are located within the positive gravity component zones. These positive gravity component zones should be ore-finding targets for further prospecting for the undiscovered Sn and W polymetallic deposits. (4) The gravity components separated by BEMD coincide with the spatial distribution of the granites associated with various types of mineralization and alteration zones at different depths, which will give insights for further prospecting for concealed ore bodies in this study region. [Display omitted] • The mineralized characteristics of both the Sn-Zn-In and the W polymetallic deposits are recognized. • The gravity components implying ore-controlling factors at different depths are separated using BEMD. • The ore-finding targets of both the Sn-Zn-In and the W polymetallic deposits are identified using the gravity components. [ABSTRACT FROM AUTHOR]

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions. [ABSTRACT FROM AUTHOR]

To understand the cause of the high content of phosphorus in the North Chaohu Lake Catchment of China, the distribution of the total phosphorus in groundwater and the dissolution of rock phosphorus near Chaohu Lake were investigated, and a few interesting findings have been revealed. Firstly, four main processes affecting the groundwater quality in North Chaohu Lake Catchment were identified with the results of factor analysis, including anthropogenic activities and the dissolution of carbonate rocks, phosphorus, and fluorine-bearing minerals. Secondly, the dissolution of rock phosphorus can be well described using the one-dimensional diffusion equation, with a semi-infinite boundary condition, and the Langmuir kinetic equation. A relatively low ambient temperature (less than 25 °C) was probably responsible for the small diffusion coefficient compared to that of the previous studies. Thirdly, the high-potential maximum dissolution of rock phosphorus (Cmax) indicated that the dissolution of rock phosphorus could pose a risk to the ambient water body, and Cmax was found to be independent of the total rock phosphorus content. [ABSTRACT FROM AUTHOR]