Search Results (110)

The Dehbid region, located in the southern part of the Sanandaj–Sirjan Zone (SSZ), is a significant iron oxide mining district with over 20 iron oxide deposits (IODs) and reserves of up to 50 million tons of iron oxide ores. The region features a NW–SE oriented ductile shear zone, parallel to the Zagros thrust zone, experienced significant deformation. Detailed structural studies indicate that the iron mineralization is primarily stratiform to stratabound and hosted in late Triassic to early Jurassic silicified dolomites and schists. These ore deposits consist of lenticular iron oxide orebodies and exhibit various structures and textures, including banded, laminated, folded, disseminated, and massive forms of magnetite and hematite. The Fe₂O₃ content in the mineralized layers varies from 30 to 91 wt%, whereas MnO has an average of 3.9 wt%. The trace elements are generally low, except for elevated concentrations of Cu (up to 4350 ppm) and Zn (up to 3270 ppm). Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis of magnetite reveals high concentrations of Mg, Al, Si, Mn, Ti, Cu, and Zn, with significant depletion of elements such as Ga, Ge, As, and Nb. This study refutes the hypothesis of vein-like or hydrothermal genesis, providing evidence for a sedimentary origin based on the trace element geochemistry of magnetite and LA-ICP-MS geochemical data. The Dehbid banded iron ores (BIOs) are thought to have formed under geodynamic conditions similar to those of BIOs in back-arc tectonic settings. The combination of anoxic conditions, submarine hydrothermal iron fluxes, and redox fluctuations is essential for the formation of these deposits, suggesting that similar iron–manganese deposits can form during the Phanerozoic under specific geodynamic and oceanographic conditions, particularly in tectonically active back-arc environments. Full article

The Aït Abdellah copper deposit in the Bou Azzer-El Graara inlier of the Moroccan Anti-Atlas provides key insights into structurally and lithologically controlled mineralization in Precambrian terranes. The deposit is hosted in feldspathic sandstones of the Tiddiline Group, which unconformably overlie the Bou Azzer ophiolite, and is spatially associated with a NE–SW-trending shear zone. This zone is characterized by mylonitic fabrics, calcite veining, and an extensive network of fractures, reflecting a two-stage deformation history involving early ductile shearing followed by brittle faulting and brecciation. These structural features enhanced rock permeability, enabling fluid flow and metal precipitation. Copper mineralization includes primary sulfides such as chalcopyrite, bornite, pyrite, chalcocite, digenite, and covellite, as well as supergene minerals like malachite, azurite, and chrysocolla. Sulfur isotope values (δ³⁴S = +5.9% to +22.8%) indicate a mixed sulfur source, likely derived from both ophiolitic rocks and volcano-sedimentary sequences. Carbon and oxygen isotope data suggest fluid interaction with marine carbonates and meteoric waters, potentially linked to post-Snowball Earth deglaciation processes. Fluid inclusion studies reveal homogenization temperatures ranging from 195 °C to 310 °C and salinities between 5.7 and 23.2 wt.% NaCl equivalent, supporting a model of fluid mixing between magmatic-hydrothermal and volcano-sedimentary sources. The paragenetic evolution of the deposit comprises three stages: (1) early hydrothermal precipitation of quartz, dolomite, sericite, pyrite, and early chalcopyrite and bornite; (2) a main mineralizing stage characterized by fracturing and deposition of bornite, chalcopyrite, and Ag-bearing sulfosalts; and (3) a late supergene phase with oxidation and secondary enrichment. The Aït Abdellah deposit is best classified as a shear zone-hosted copper system with a complex, multistage mineralization history. The integrated analysis of structural features, mineral assemblages, isotopic signatures, and fluid inclusion data reveals a dynamic interplay between deformation processes, hydrothermal alteration, and evolving fluid sources. Full article

The Silvermines Pb-Zn-Ag-Ba orebodies comprise vein, replacement, cross-cutting and stratiform mineralization mostly hosted in Lower Carboniferous limestones in the vicinity of a major ENE and E-W trending normal fault array and represent a classic example of Irish-Type Zn-Pb mineralization. Historically the deposits have been exploited at various times, but the major limestone-hosted Zn-Pb-Ba mineralization was not discovered until the 1960s. Structurally controlled crosscutting vein and breccia mineralization represent pathways of hydrothermal fluids escaping from the Silvermines fault at depth that exhaled and replaced shallowly buried Waulsortian limestones creating the larger stratiform orebodies such as the Upper G and B-Zones. The B-Zone, comprising a pre-mining resource of 4.64 Mt of 4.53% Zn, 3.58% Pb, 30 g/t Ag has a locally highly variable host mineralogy dominated by pyrite, barite, siderite, within dolomitic and limestone breccias with local silica-haematite alteration. A small, highly unusual pod of very high-grade Ag-rich mineralization in the B-Zone, the 4611 Pod, discovered in 1978, has not been previously documented. Unpublished records, field notes, and mineralogical and chemical data from consultant reports have been assimilated to document this interesting and unusual occurrence. The pod, representing an irregular lens of mineralization ca 2 m thick and representing 500 t, occurs within the B-Zone orebody and comprises high grade Zn and Pb sulfides with significant patches of proustite-pyrargyrite (ruby silvers) and a host of associated Pb, Ag, Sb, As, Cu, Ge sulfide minerals, including significant argyrodite. Although evidence of any distinct feeder below the pod is lacking, the nature of the pod, its unusual mineralogy and its paragenesis suggests that it represents a small, possibly late source of exotic hydrothermal fluid where it entered the B-Zone stratiform mineralizing system. Full article

Carbonatites, which are rare mantle-derived igneous rocks that are mainly enriched in carbonate minerals and host relatively higher amounts of rare earth element (REE)-bearing phases, remain subjects of extensive geological research due to their enigmatic origin and potential economic importance. This study aims to describe the petrographic, mineralogical, and some rare-earth element (REE) abundances of four carbonatite bodies (known as Sillai Patti, Loe Shilman, Warsak, and Jambil) exposed in the Peshawar Plain Alkaline Igneous Province (PPAIP), northwestern Himalaya, Pakistan, to identify their economic potential. The observed petrographic, textural features, and chemical compositions of the constituent minerals of the carbonatites were utilized to elucidate the evolutionary processes through which the rocks evolved. The results indicate distinct mineralogical assemblages dominated by calcite, dolomite, apatite, pyroxene, biotite, and feldspar, with accessory opaque and REE-bearing phases, such as pyrochlore, monazite, and britholite. The apatite grains display compositional zoning reflecting their growth under magmatic conditions. The petrographic features of apatite in some carbonatite samples, exhibiting preferred orientation in a particular direction and spongy or murky textures, indicate that the studied rocks underwent post-magmatic deformation or hydrothermal alteration. Calcite and dolomite, coexisting in some carbonatite samples, exhibit significant Mg-Fe variation, which is possibly related to magmatic differentiation. The pyroxene compositions vary from a low-calcium enstatite–ferrosilite series to high-calcium diopside, suggesting variable crystallization environments among the carbonatite bodies studied. The abundance of REE-bearing phases in the studied carbonatites emphasizes their high economic potential. These findings indicate that the PPAIP carbonatites originated from mantle-derived magmas and subsequently experienced metamorphic/metasomatic overprinting during their tectonic evolution. The abundance of REE-rich phases such as apatite, pyrochlore, monazite, and britholite underscores their high economic potential. Full article

The complex interaction of hydrothermal fluids and carbonate rocks is recognized to promote significant impacts on petroleum systems, reservoir porosity, and potential. The objective of this study is to investigate the fluid phases entrapped in the mineral phases of the Barra Velha Formation (Santos Basin), including their petrographic paragenetic relationships, relative timing, temperatures of migration events, and maximum temperature reached by the sedimentary section. The petrographic descriptions (387), Rock-Eval pyrolysis (107), fluid inclusion petrography (14), and microthermometry (428) were performed on core and sidewall samples from two wells from one field of the Santos Basin. Hydrocarbon source intervals were primarily identified in lithologies with high argillaceous content. Chert samples still retain some organic remnants indicative of their original composition prior to extensive silicification. Redeposited intraclastic rocks exhibit the lowest organic content and oil potential. A hydrothermal petroleum system is identified by fluids consisting in gas condensate, light to heavy undersaturated oil, occasionally accompanied by aqueous fluids influenced by juvenile and evaporitic sources, and localized flash vaporization events. These hydrothermal fluids promoted silicification and dolomitization, intense brecciation, and lead to enhanced porosity in different compartments of the reservoir. The relative ordering of paleo-hydrothermal oils and the main oil migration and accumulation events has improved our understanding of the petroleum systems in the basin. This contribution is significant for future regional research on the evolution of fluid systems and their implications for carbonate reservoirs. Full article

The Zaghouan Fluorite Province (ZFP) encloses F-Ba(Pb-Zn) ores hosted within Jurassic carbonate series, in northeastern Tunisia. Critical breakthroughs on the Jebel Stah fluorite deposits, an MVT-style F-mineralization, have been made within the Lower Jurassic limestones along the Zaghouan Fault, which is a major target for mineralization. This study presents the first REE-Y analyses conducted by LA-ICP-MS on fluorites in Tunisia, and specifically on the fluorites of Jebel Stah deposit. This analytical technique provides highly accurate insights into the geochemical regime of mineralizing fluids and the related scavenging sources. Distinct geochemical characteristics between two fluorite generations (G1 and G2) were revealed. Fluorites (Fl2) from the early generation (G1) showed low ΣREE + Y (36.3 and 39.73 ppm, respectively). When normalized to chondrites, early fluorite G1 displayed a bell-shaped REE + Y pattern with a depletion in LREE relative to HREE and a slight MREE hump. Late fluorite (Fl3) generation (G2) displayed higher ΣREE + Y concentrations (77.43 ppm), but an almost similar REE pattern. Ce/Ce* ratios demonstrated strong negative Ce anomalies in all fluorites, while Eu/Eu* ratios indicated weak negative Eu anomalies. The positive Y anomaly observed in the REE + Y patterns of fluorites G1 and G2 suggests Y-Ho fractionation in the fluid system. Moreover, significant degrees of differentiation between terbium (Tb) and lanthanum (La) have been observed in all fluorite samples. The plot of fluorites from both fluorite generations on the Tb/La–Tb/Ca diagram gives evidence of the sedimentary hydrothermal origin of the ore-forming fluids in the Jebel Stah F-deposit. Sr isotopes show that the mineralizing fluids are radiogenic and deeply sourced basinal brines, whereas the small variation in ⁸⁷Sr/⁸⁶Sr ratios suggests a similar source for Sr in fluorites G1 and G2. These results allow us to conclude that the economic fluorite (G1) ore of Jebel Stah was deposited due to the interaction of the deeply sourced hydrothermal fluid with the carbonated host rocks (dolomitization, an increase in pH, and Ca activity), whereas the late fluorite (G2) is an accessory and could have resulted from the mixing of the hydrothermal fluid with shallow meteoric waters. Full article

The Ordovician/Silurian boundary (Wufeng/Longmaxi formations) in the Shizhu region, eastern Sichuan Basin, China hosts organic-rich black shales which are frequently interbedded with bentonite and hydrothermal minerals (e.g., pyrite). This study investigated the mineralogical, total organic carbon (TOC), total sulfur (TS), and major and trace element compositions of organic-rich samples. Non-visible volcanic input is identified to influence organic matter accumulation, as shown by the correlations between TOC and proxies, including Zr and Hf contents and the Cr/Al₂O₃, V/Al₂O₃, Ni/Al₂O₃, and SiO₂/Al₂O₃ ratios. Redox indicators (V/Cr, v/v + Ni, degree of pyritization (DOP), U/Th, and Mo contents) display positive correlations with TOC values, suggesting that an oxygen-depleted environment is necessary for organic matter (OM) preservation. The TOC values exhibit better regression coefficients (R²) against redox indicators, including DOP (0.43), U/Th (0.70), and Mo contents (0.62), than V/Cr (0.16) and v/v + Ni (0.21). This may because some V, Cr, and Ni is hosted in non-volcanic ashes within shales but not inherited from contemporaneous water columns. The greater scatter in TOC-DOP and TOC-Mo relative to TOC-U/Th relations may result from hydrothermal venting in shales, evidenced by the coexistence of framboid and euhedral pyrite and the previous finding of hydrothermally altered dolomites in the studied sections. There is no systematic relation between TOC and Ni/Co ratios, and this means that portions of Ni are contributed by non-visible volcanic ashes and Ni and Co are redistributed during the precipitation of hydrothermal pyrites due to their strong chalcophile affinities. Such a feature may further suggest that most pyrites are precipitated during hydrothermal venting. The DOP displays broad correlations with non-visible volcanic indicators, supporting that hydrothermal venting may be triggered by volcanic activities. The outcomes of this study highlight that caution is necessary when evaluating the sedimentary facies features of volcanism-affected organic-rich black shales with the used metallic proxies. Full article

The ocean is a significant global reservoir of uranium (U) and thorium (Th). These elements can be incorporated into marine sediments through processes involving organic matter (OM), redox conditions, terrigenous inputs, and mineral interactions. Helium generated through the radioactive decay of U and Th within geological formations represents a critical potential resource. Marine black shales, which are rich in U and Th, are widespread in the Ediacaran Doushantuo Formation of the Upper Yangtze Platform, making them a key target for helium exploration. However, there is limited research on the mechanisms behind U and Th accumulation in these shales. This study focuses on shales from the Doushantuo Formation in Chongqing, China, aiming to explore the mechanisms of U and Th accumulation and assess the potential for helium generation, and argillaceous dolomites are included for comparative analysis. The results show that the average U and Th content in the black shales (17.58 and 9.78 ppm, respectively) is higher than that of argillaceous dolomites (3.52 and 2.75 ppm, respectively). Uranium mainly comes from authigenic precipitation and hydrothermal inputs, while thorium is primarily sourced from terrigenous and hydrothermal inputs. The semi-humid climate in the provenance area facilitated parent rock weathering, with atmospheric precipitation and river systems transporting U and Th to the ocean. However, excessive terrigenous input can dilute the U and Th content in the sediments. In the shales, uranium is primarily adsorbed and/or complexed by organic matter (OM), with the anoxic–euxinic sedimentary environment and high OM content (TOC = 0.06–34.58 wt.%, r = 0.95) promoting U accumulation. Thorium accumulation is largely controlled by adsorption onto clay minerals. The total amount of helium generated from the Doushantuo shales is estimated to be 7.20 × 10¹⁰ m³. Full article

The Drake Goldfield, also known as Mount Carrington, is located in north-eastern New South Wales, Australia. It contains a number of low–intermediate-sulfidation epithermal precious metal deposits with a current total resource of 724.51 metric tons of Ag and 10.95 metric tons of Au. These deposits occur exclusively within the Drake Volcanics, a 60 × 20 km NW-SE trending sequence of Late Permian volcanics and related epiclastics. Drilling of the Copper Deeps geochemical anomaly suggests that the volcanics are over 600 m thick. The Drake Volcanics are centered upon a geophysical anomaly called “the Drake Quiet Zone” (DQZ), interpreted to be a collapsed volcanic caldera structure. A total of 105 fresh carbonate samples were micro-drilled from diamond drillcores from across the field and at various depths. A pXRD analysis of these carbonates identified five types as follows: ankerite, calcite, dolomite, magnesite, and siderite. Except for three outlier values (i.e., −21.32, −19.48, and 1.42‰), the δ¹³C_VPDB generally ranges from−15.06 to −5.00‰, which is less variable compared to the δ¹⁸O_VSMOW, which varies from −0.92 to 17.94‰. μ-XRF was used to analyze the elemental distribution, which indicated both syngenetic/epigenetic relationships between calcite and magnesite. In addition, a total of 53 sulfide samples (primarily sphalerite and pyrite) from diamond drillcores from across the Drake Goldfield were micro-drilled for S isotope analysis. Overall, these have a wide range in δ³⁴S_CDT values from −16.54 to 2.10‰. The carbon and oxygen isotope results indicate that the fluids responsible for the precipitation of carbonates from across the Drake Goldfield had complex origins, involving extensive mixing of hydrothermal fluids from several sources including those of magmatic origin, meteoric fluids and fluids associated with low-temperature alteration processes. Sulfur isotope ratios of sulfide minerals indicate that although the sulfur was most likely derived from at least two different sources; magmatic sulfur was the dominant source while sedimentary-derived sulfur was more significant for the deposits distal from the DQZ, with the relative importance of each varying from one deposit to another. Our findings contribute to a greater understanding of Au-Ag formation in epithermal environments, particularly in collapsed calderas, enhancing exploration strategies and models for ore deposition. Full article

Dolomitization is a critical diagenetic alteration that impacts the formation of carbonate hydrocarbon reservoirs. In the offshore Bohai Bay Basin, the Lower Paleozoic carbonate reservoirs in buried hill traps, and the basement highs unconformably overlain by younger rock units, are emerging as a prospective target and predominantly occur in dolomite layers. Meanwhile, the formation mechanisms of the dolomite are not clear, which affects the understanding of the occurrence of deep dolomite reservoirs and hinders oil and gas exploration. Based on comprehensive observations of the thin sections of the carbonate samples, the dolomite types were meticulously categorized into micritic dolostone, fine-crystalline dolostone, and saddle dolomite. Then, carbon, oxygen, and strontium isotope and trace elements were examined to elucidate the dolomitization fluids and propose diagenetic models for the three kinds of dolomite formation. The mineralogical and geochemical evidence reveals that there were two kinds of dolomitization fluids, including penecontemporaneous seawater, and hydrothermal fluid. The diagenetic fluid of the micritic dolostone and fine-crystalline dolostone both involved penecontemporaneous seawater, but fine-crystalline dolostone is also affected by later burial dolomitization processes. The saddle dolomite, filling in pre-existing fractures or dissolution pore cavities, is attributed to a hydrothermal fluid associated with magmatic activities. Notably, the extensive layered fine-crystalline dolostone was the predominant reservoir rock. The initial mechanism for its formation involves penecontemporaneous seepage reflux dolomitization, which is superimposed by later burial dolomitization. The burial dolomitization enhanced porosity, subsequently facilitating the formation of a fracture-related dissolution pore cavity system, and partly filled by saddle dolomite during the Cenozoic hydrothermal events. The findings highlight that the layered fine-crystalline dolostone that underwent multiphase dolomitization is the most potential target for hydrocarbon exploration. Full article

The large-scale vein-type Zn-Pb-Ag deposit in the Eastern Qinling Orogen (EQO) has sparked a long-standing debate over whether magmatism or metamorphism was the primary control or factor in its formation. Among the region’s vein-type deposits, the large-sized Bailugou deposit offers a unique opportunity to study this style of mineralization. Similar to other deposits in the area, the vein-type orebodies of the Bailugou deposit are hosted in dolomitic marbles (carbonate–shale–chert association, CSC) of the Mesoproterozoic Guandaokou Group. Faults control the distribution of the Bailugou deposit but do not show apparent spatial links to the regional Yanshanian granitic porphyry. This study conducted comprehensive H–O–C–S–Pb isotopic analyses to constrain the sources of the ore-forming metals and metal endowments of the Bailugou deposit. The δ³⁴S_CDT values of sulfides range from 1.1‰ to 9.1‰ with an average of 4.0‰, indicating that the sulfur generated from homogenization during the high-temperature source acted on host sediments. The Pb isotopic compositions obtained from 31 sulfide samples reveal that the lead originated from the host sediments rather than from the Mesozoic granitic intrusions. The results indicate that the metals for the Bailugou deposit were jointly sourced from host sediments of the Mid-Late Proterozoic Meiyaogou Fm. and the Nannihu Fm. of the Luanchuan Group and Guandaokou Group, as well as lower crust and mantle materials. The isotopic composition of carbon, hydrogen, and oxygen collectively indicate that the metallogenic constituents of the Bailugou deposit were contributed by ore-bearing surrounding rocks, lower crust, and mantle materials. In summary, the study presents a composite geologic-metallogenic model suggesting that the Bailugou mineral system, along with other lead-zinc-silver deposits, porphyry-skarn molybdenum-tungsten deposits, and the small granitic intrusions in the Luanchuan area, are all products of contemporaneous hydrothermal diagenetic mineralization. This mineralization event transpired during a continental collision regime between the Yangtze and the North China Block (including syn- to post-collisional settings), particularly during the transition from collisional compression to extension around 140 Ma. The Bailugou lead-zinc-silver mineralization resembles an orogenic-type deposit formed by metamorphic fluid during the Yanshanian Orogeny. Full article

The Ordovician dolomite in the Ordos Basin is an important natural gas reservoir. Exploring dolomite genesis and the factors influencing reservoir characteristics is essential for deep carbonate rock exploration. This study offers a comprehensive analysis of dolomite evolution using methods such as thin-section petrography, isotope analysis, and trace and rare earth elements. The analysis shows that: Based on petrographic observations of the Majiagou Formation in the study area, the dolomite in the study area can be divided into residual oolitic dolomite of synsedimentary or metasomatic origin, micritic dolomite of secondary metasomatism or recrystallization origin, powder crystal dolomite, and fine crystal dolomite. Reservoir pores mainly develop intergranular pores, mold pores, dissolved pores, and fractures. Combined with the characteristics of major elements, trace elements, carbon and oxygen isotopes, rare earth elements, and inclusions in the study area, it can be concluded that the fifth member dolomite of the Majiagou Formation is of shallow–medium burial origin. The diagenetic evolution sequence from the penecontemporaneous period to the middle–deep burial period in the study area is penecontemporaneous dolomite, anhydrite dissolution → seepage silt filling, freshwater dolomite, calcite, and gypsum filling, pressure solution compaction, calcite partial dissolution → gypsum filling, karst cave, buried hydrothermal dolomite, dolomite partial dissolution → calcite complete dissolution, pore dissolution expansion, and quartz pyrite filling. In the early stage of compaction and pressure solution, the primary pores are rapidly reduced, and in the later stage, sutures are generated to provide channels for reservoir fluid migration. The recrystallization reduces the porosity during the middle–deep burial period. Full article

The Kavokta deposit of the dolomite type nephrite is located in the Middle Vitim mountain country, Russia (Russian Federation). The deposit area is composed of granite of the Late Paleozoic Vitimkan complex. The granite contains complex shape blocks of Lower Proterozoic rocks. They are represented by metasandstone, crystalline schist, amphibolite, and dolomite marble. The calcite–tremolite and epidote–tremolite skarns were formed on the contact of dolomite and amphibolite. Calcite–tremolite skarn contains nephrite bodies. The mineral composition of 16 core samples obtained during the geological exploration conducted by JSC “Transbaikal Mining Enterprise” within Vein 1 of Prozrachny site has been studied in thin sections using a petrographic microscope, and in polished sections using a scanning electron microscope, with an energy-dispersive microanalysis system. Twenty-five minerals have been identified. They have been attributed to relict, metasomatic associations of the pre-nephrite and nephrite stages and hydrothermal and secondary associations. The intensity of the nephrite’s green color is explained by the Fe admixture in tremolite, and the black color is explained by its transition to actinolite in the areas of contact with epidote–tremolite skarn after amphibolite. In the formation and alteration of nephrite, dolomite is replaced by diopside, diopside by tremolite, prismatic tremolite by tangled fibrous tremolite, and tremolite by chlorite. Granite provides heat for metasomatism. Participation of amphibolite in the nephrite formation determines the variety of nephrite colors. The role of metamorphism is reduced to tectonic fragmentation facilitating fluid penetration; stress provides a tangled fibrous cryptocrystalline texture. Full article

Serpentine (Mg₃Si₂O₅(OH)₄), like quartz, dolomite and magnesite minerals, is a versatile mineral group characterized by silica and magnesium silicate contents with multiple polymorphic phases. Among the phases composed of antigorite, lizardite, and chrysotile, lizardite and chrysotile are the most prevalent phases in the serpentinites studied here. The formation process of serpentinites, which arise from the hydrothermal alteration of peridotites, influences the ratio of light rare earth elements (LREE) to heavy rare earth elements (HREE). In serpentinites, the ratio of light rare earth elements (LREE)/heavy rare earth elements (HREE) provides insights into formation conditions, geochemical evolution, and magmatic processes. The depletion of REE compositions in serpentinites indicates high melting extraction for fore-arc/mantle wedge serpentinites. The studied serpentinites show a depletion in REE concentrations compared to chondrite values, with HREE exhibiting a lesser degree of depletion compared to LREE. The high ΣLREE/ΣHREE ratios of the samples are between 0.16 and 4 ppm. While Ce shows a strong negative anomaly (0.1–12), Eu shows a weak positive anomaly (0.1–0.3). This indicates that fluid interacts significantly with rock during serpentinization, and highly incompatible elements (HIEs) gradually become involved in the serpentinization process. While high REE concentrations indicate mantle wedge serpentinites, REE levels are lower in mid-ocean ridge serpentinites. The enrichment of LREE in the analyzed samples reflects melt/rock interaction with depleted mantle and is consistent with rock–water interaction during serpentinization. The gradual increase in highly incompatible elements (HIEs) suggests that they result from fluid integration into the system and a subduction process. The large differential thermal analysis (DTA) peak at 810–830 °C is an important sign of dehydration, transformation reactions and thermal decomposition, and is compatible with H₂O phyllosilicates in the mineral structure losing water at this temperature. In SEM images, chrysotile, which has a fibrous structure, and lizardite, which has a flat appearance, transform into talc as a result of dehydration with increasing temperature. Therefore, the sudden temperature drop observed in DTA graphs is an indicator of crystal form transformation and CO₂ loss. In this study, the mineralogical and structural properties and the formation of serpentinites were examined for the first time using thermo-gravimetric analysis methods. In addition, the mineralogical and physical properties of serpentinites can be recommended for industrial use as additives in polymers or in the adsorption of organic pollutants. As a result, the high refractory nature of examined serpentine suggests that it is well-suited for applications involving high temperatures. This includes industries such as metallurgy and steel production, glass manufacturing, ceramic production, and the chemical industry. Full article

The Bailugou vein-type zinc-lead-silver deposit is located in the Eastern Qinling Orogen, China. There has been a long-standing debate about whether its formation is related to magmatism or metamorphism. To determine the origin of ore-forming materials and fluids, we conducted a geological and fluid inclusion investigation of the Bailugou. Field surveys show that the vein-type orebodies are controlled by faults in the dolomitic marbles of the Mesoproterozoic Guandaokou Group, and they are distal to the regional Yanshanian intrusions. Four ore stages, i.e., quartz–pyrite ± sphalerite (Stage 1), quartz–polymetallic sulfides (Stage 2), dolomite–polymetallic sulfides (Stage 3), and calcite (Stage 4), are identified through microscopic observation. The homogenization temperatures of measured fluid inclusions vary in the range of 100 °C to 400 °C, with the dominating concentration at 350 °C to 400 °C, displaying a descending trend from early to late stages. The estimated formation depth of the Bailugou deposit varies from 2 km to 12 km, which is deeper than the metallogenic limit of the epithermal hydrothermal deposit but conforms to the typical characteristics of a fault-controlled deposit. The ore-forming fluid in Stage 1 originates from a fluid mixture and experiences a phase separation (or fluid immiscibility) between the metamorphic-sourced fluid and the fluids associated with ore-bearing carbonate-shale-chert association (CSC) strata. This process results in the transition to metamorphic hydrothermal fluid due to water–rock interactions in Stage 2, culminating in gradual weakening and potential fluid boiling during the mineralization of Stage 3. Collectively, the Bailugou lead-zinc-silver mineralization resembles an orogenic-type deposit formed by metamorphic fluids in the Qinling Yanshanian intracontinental orogeny. Full article