Fluid-rock Interaction Research Articles

Ultramafic Rocks from the Sanbagawa Belt: Records of Mantle Wedge Processes

Mantle wedge domains beneath the forearc Moho are unique regions of Earth’s interior where mantle encounters subducting oceanic plates. Crystal-plastic deformation and fluid-induced reactions in the supra-subduction mantle control global material circulation, arc volcanism, and seismicity within subduction zones. The Sanbagawa metamorphic belt contains numerous ultramafic blocks in its higher-grade zones, some of which likely originated as lower crustal arc cumulates that were subsequently incorporated into the mantle wedge and transported to the slab–mantle interface by mantle flow. Properties of these ultramafic rocks provide a valuable opportunity to understand the dynamic processes of the mantle wedge up to 80 km depth, including mantle flow, hydration/dehydration, and fluid–rock interactions near the slab–mantle interface of a warm subduction zone.

Metasomatism is a source of methane on Mars

The abundance of inactive Martian volcanic centres suggests that early Mars was more volcanically active than today. On Earth, volcanic degassing releases climate-forcing gases such as H2O, SO2, and CO2 into the atmosphere. On Mars, the volcanic carbon is likely to be more methane-rich than on Earth because the interior is, and was, more reducing than the present-day Terrestrial upper mantle. The reports of reduced carbon associated with high-temperature minerals in Martian igneous meteorites back up this assertion. Here, we undertake irreversible reaction path models of the fluid-rock interaction to predict carbon speciation in magmatic fluids at the Martian crust-mantle boundary. We find methane is a major carbon species between 300 and 800 °C where logfO2 is set at the Fayalite = Magnetite + Quartz redox buffer reaction (FMQ). When logfO2 is below FMQ, methane is dominant across all temperatures investigated (300–800 °C). Moreover, ultramafic rocks produce more methane than mafic lithologies. The cooling of magmatic bodies leads to the release of a fluid phase, which serves as a medium within which methane is formed at high temperatures and transported. Metasomatic methane is, therefore, a source of reduced carbonaceous gases to the early Martian atmosphere and, fundamentally, for all telluric planets, moons, and exoplanets with Mars-like low logfO2 interiors.

Mechanism of Opal-CT deposit from the Lam Narai Volcanics in Lop Buri, Thailand by using Petrography

Common opals were discovered in the rhyolite host rock, where various structural features such as cavities, fractures, and veins are observed. These voids served as pathways for the infiltration of silica-rich fluids originating from meteoric water, establishing a hydrothermal connection. The aqueous solution derived from meteoric water actively dissolves silica from the rhyolite host rock, thereby increasing the silica saturation within the fluid. Subsequently, the silica-saturated hydrothermal fluid fills the cavities and veins within the host rock. The margin of the host rock underwent alteration as it interacted with infiltrating hydrothermal fluid in a phenomenon known as hydrothermal fluid-rock interaction. At the periphery of the cavities, quartz crystals begin to form, effectively reducing the concentration of dissolved silica in the solution. As a result, the subsequent precipitation of amorphous opals occurs, predominantly within the inner part or central region of the vein or cavity. The formation of opals associated with Lam Narai volcanic activity occurred at a relatively high temperature of about 105-170 °C through a hydrothermal process.

Unraveling the Impact of Ethylenediaminetetraacetic Acid Chelating Agents on the Oil Recovery Processes: An Insight into Its Role in Fluid-Fluid and Rock-Fluid Interactions.

In recent years, chelating agents have garnered increasing attention due to their unique capabilities in addressing challenges associated with chemically enhanced oil recovery materials. Most previous studies have primarily focused on examining the influence of chelating agents on rock-fluid interactions. However, their effects on fluid-fluid interactions, specifically on interfacial tension (IFT) characteristics under various conditions, remain relatively unknown. This study investigates the effect of crucial reservoir parameters on the performance of ethylenediaminetetraacetic acid (EDTA) chelating agents in the IFT between crude oil and brine. Furthermore, the study evaluated the impact of varying concentrations of this agent on rock wettability alteration, zeta potential, and spontaneous imbibition. The results illustrated that introducing EDTA at high concentration into seawater (SW) solution reduced the IFT by 85%. Additionally, while higher pH levels contributed to IFT reduction due to increased hydroxyl ions, excessive salinity levels resulted in elevated IFT. Raising the temperature from 30 to 75 °C further decreased the IFT, changing the IFT for optimal EDTA concentration from 20.43 to 2.56 mN/m (∼88% reduction). The changes in zeta potential and contact angle measurements indicated that solutions of 5 and 7 wt % EDTA shifted rock wettability from oil-wet to strongly water-wet, resulting in the wettability alteration index of 1.01 and 1.02, respectively. Inductively coupled plasma analysis, on the other hand, revealed substantial chelation of metal ions from both the solution and rock when EDTA was added to the rock/SW system. This resulted in a significant increase in Ca2+ ions and a decrease in Mg2+ ions, attributed to the multi-ion exchange phenomenon.

Gold source and deposition in the Sanakham gold deposit, SW Laos: Constrains from textures, trace element geochemistry and in-situ sulfur isotopes of pyrite

The Luang Prabang (Laos) – Loei (Thailand) metallogenetic belt is endowed with major porphyry-skarn, and epithermal gold deposits. The Sanakham gold deposit is a newly discovered hydrothermal vein-type orogenic gold deposits (10.6 t Au @ 3.05 g/t) in the belt, and consist of a series of quartz-sulfide veins that are controlled by secondary structures of the regional NNE-trending brittle-ductile shear zone. Its mineralization can be divided into four stages: (I) quartz–pyrite–arsenopyrite, (II) quartz–pyrite–pyrrhotite–chalcopyrite, (III) quartz–pyrite–base-metal sulfide, and (IV) quartz–carbonate. Three pyrite generations were identified: py1 (stage I) as disseminated euhedral to subhedral coarse grains; py2 (stage II) as subhedral to anhedral fine grains occur around the cataclastic and corrosion textures in py1; py3 (stage III) as subhedral to anhedral fine grains occurred in sulfide veins or veinlets that overprint the existing quartz-sulfides. All three generations of pyrite have low trace-element contents including very low lattice-bound gold (py1: 0.040 ppm; py2: 0.098 ppm; py3: 0.028 ppm) and arsenic (py1: 227 ppm; py2: 133 ppm; py3: 13.3 ppm) contents. Visible gold grains are sited in textures of pyrite grains that relate to brittle cataclastic deformation. Considering the relatively low contents of pyrite in the ores of Sanakham, it is impossible to derive the high-gold grade orebodies through local remobilization of originally lattice-bound gold in pyrite. The py2 might be formed during hydrothermal overprinting and dissolution of py1 led by continuous supply of ore fluids with relatively higher contents of Au, Ag, Cu, Sb, Te, Pb, and Bi. A reduction reaction related to reduced carbon species in wallrock is an assignable cause for gold deposition, even though the fluid-rock interaction and fluid immiscibility processes might be important. The Au- and As-poor pyrites have similar δ34S values (py1: –2.58 to –0.83 ‰; py2: –2.17 ‰ to + 0.25 ‰; py3: –1.24 to –0.60 ‰ ppm) that close to 0 ‰, indicating the sulfur may have been originated from magmatic or mantle sources. Therefore, we propose that the Sankham gold deposit is a member of the orogenic deposit class, but notably characterized by the low concentrations of invisible gold in the relatively As-poor pyrite lattice.

Genesis of the Haidewula volcanic rock-hosted uranium deposit in the East Kunlun Orogen, northwestern China

The Haidewula deposit in Northwest China is a recently discovered volcanic-related uranium deposit. To determine the origin of this deposit, whole-rock geochemical, stable isotope, U–Pb isotope and trace element compositions of the pitchblende were obtained, and microthermometric analyses of the fluid inclusions were performed. The Haidewula deposit is located within the Phanerozoic volcanic basin and contains Silurian trachyte, rhyolite, rhyolitic tuff, and Triassic basalt. These Silurian volcanic rocks are characterized by high-K calc-alkaline properties and were intruded by Triassic dolerite, which served as a source for mineralization. The mineralized zones were primarily influenced by NE-NNE-trending and SE-dipping faults. Vein-like pitchblende is commonly associated with calcite, illite, quartz, pyrite, and fluorite. Geochronology indicated that uranium mineralization occurred during 235–230 Ma. The ore-forming fluids contained meteoric water with limited magmatic water and exhibited moderate to low temperatures (246–133 °C), moderate to low salinities (17.3–1.06 wt% NaCleqv) and Cl-bearing rocks. U precipitation was attributed to changes in physicochemical conditions resulting from fluid–rock interactions and fluid boiling. The uranium mineralization at Haidewula coincided with the evolution of the Tethys Ocean. During late Wenlock, an extensional environment, triggered by the closure of the Proto-Tethys Ocean, led to the extrusion of Haidewula rhyolite and trachyte. During the crustal extensional environment resulting from the subduction of the A’nyemaqen Ocean in the Middle Triassic, ore-forming fluids circulated and remobilized uranium from the Haidewula volcanic rocks. As a result of fluid–rock interactions and fluid boiling within brittle structures, the U-complexes destabilized and formed pitchblende at Haidewula.

Fluid-metasomatized rocks with extremely low δ26Mg values in subducted oceanic lithosphere: Implications for mantle Mg isotope heterogeneity and the origin of low-δ26Mg magmas

The subduction of oceanic slabs with diverse lithologies greatly contributes to the geochemical heterogeneity of the mantle. Oceanic metasomatism leads to the formation of rocks with heterogeneous geochemical characteristics, which can be further modified by fluid–rock interactions during subduction zone processing. Investigations of exhumed high-pressure oceanic rocks not only shed light on the compositional variations that occur during oceanic metasomatism and subduction processes but also help in understanding mantle heterogeneity and magma genesis. Here, we present a comprehensive Mg–O–Sr–Nd isotope study on eclogite-facies Mg- and Ca-metasomatized rocks (Ti-clinohumite dikelets and metarodingites, respectively) and their host meta-serpentinites from the Voltri Massif (Ligurian Western Alps). Compared to their Fe–Ti gabbroic protoliths, the Ti-clinohumite (Ticl) dikelet and metarodingite are characterized by high MgO contents (∼32–38 wt%) and CaO contents (∼17–25 wt%), respectively. These Mg- and Ca-enriched rocks both display low δ26Mg values of −0.54 ‰ to −0.43 ‰ and −1.49 ‰ to −0.82 ‰, respectively, while the serpentinite hosts have mantle-like δ26Mg values of −0.26 ‰ to −0.20 ‰. The Ticl-chlorite rind rimming the metarodingite has a low δ26Mg value of −1.00 ‰. No carbonate minerals were found for metasomatized rocks that have low δ18O values ranging from +2.0 ‰ to +3.4 ‰, demonstrating that their low δ26Mg signature cannot be attributed to metasomatism by fluids involved with carbonate components. The increase in MgO content and decrease in δ26Mg in the Ticl dikelets are ascribed to fluid-induced mass transfer through low-δ26Mg fluids buffered by serpentinization of the host ultramafic rocks. The metarodingite has comparable MgO but extremely low δ26Mg values compared to those of the gabbroic protolith. By integrating reported Mg isotope data for low-grade rodingites, we propose that the low δ26Mg values of metarodingites are ascribed to isotopic exchange with serpentinizing fluids during progressive rodingitization reactions at the seafloor. However, the extremely low δ26Mg value of the Voltri metarodingite (as low as −1.49 ‰) may be attributed to further metasomatic modification in the subduction zone. High pressure metamorphic recrystallization of these metasomatized rocks play a limited role in their Mg isotope compositions. Therefore, our results show that the oceanic metasomatized metarodingite and Ticl-bearing dikes hosted in serpentinite display systematically low-δ26Mg features. Such isotopically light Mg compositions can be preserved during subduction to eclogite-facies conditions. Hence, subduction of these metasomatized rocks may lead to the transfer of a low-δ26Mg component into the deep mantle, which was overlooked thus far and may further contribute to the origin of low-δ26Mg magmas.

Dehydration‐driven deformation of eclogite: Interplay between fluid discharge and rheology

AbstractAqueous fluids released during dehydration of a subducting slab have a large effect on the rheology of the subduction interface. While high‐pressure experiments and natural‐case studies link deformation with critical dehydration reactions during eclogitization, the exact interplay between these processes remains ambiguous. To investigate fluid–rock interaction and associated deformation at high‐pressure, we studied a suite of eclogites from the Tsäkkok Lens of the Scandinavian Caledonides that record prograde metamorphism within an Early Palaeozoic cold subduction zone. Our results show that in‐situ dehydration during the blueschist to eclogite facies transition produces fluid fluxes leading to rheological weakening and densification, consequently promoting ductile‐brittle deformation. Petrographic evidence, supported by thermodynamic modelling and thermobarometry, attest to a prograde passage from lawsonite‐blueschist to peak eclogite facies of ~2.5 GPa and ~620°C. Phengite‐bearing eclogites imply interaction with an externally‐derived fluid, whereas rare phengite‐free, kyanite‐eclogites only record internally‐derived fluid production. Models predict that prograde breakdown of chlorite, lawsonite and amphibole between 500 and 610°C lead to progressive dehydration and release of up to 4.6 wt.% of aqueous fluid. Microstructural data reveal elongated shapes of highly strained omphacite porphyroblasts, displaying minor yet gradual changes in misorientation towards the grain boundaries. Occasionally, these intragranular structures form subgrain cells that have similar sizes to those of neoblasts in the rock matrix. These observations point to the potential onset of dynamic recrystallization processes via dislocation creep. Moreover, the omphacite neoblasts and rutile show non‐random crystallographic preferred orientations (CPOs), which are characterized by the subparallel alignment of point‐like maxima in rutile [001] and [100] axes to those of [001] and (010) of omphacite neoblasts, respectively. Additionally, the [001] axes of these minerals are also subparallel to the weak stretching mineral lineation, and the (100) of rutile and the (010) of omphacite neoblasts are distributed in the plane of the foliation. This suggests that the development of their CPOs was coeval and structurally controlled. Garnet microfractures normal to the foliation are dilated and sealed predominantly by omphacite. The lack of obliquity between CPO and foliation plane, as well as the systematic orientation of garnet microfracture orientations, are consistent with coaxial deformation at peak‐pressure conditions. Unlike other studies, we show that neither an external fluid source nor channelized fluid flow is needed to facilitate a ductile‐brittle deformation of eclogite in a subduction setting.

Geology and geochronology of the Yingqian granite-type uranium deposit in the Taoshan-Zhuguang Belt, South China

The Yingqian uranium deposit in the Taoshan-Zhuguang belt, South China is a typical granite-type uranium deposit. The geological characteristics and timing of mineralization are not clear, which hinders the understanding of the ore genesis of the Yingqian deposit as well as regional uranium metallogeny in the Taoshan-Zhuguang belt. These scientific problems are examined in this study through detailed field work and petrographic study, as well as geochemical and geochronological analyses on apatite, rutile and zircon. The orebodies of the Yingqian uranium deposit are mostly present in the medium–coarse grained biotite granite and fine grained two-mica granite, and controlled by the NE-trending faults. The principle U-bearing minerals are pitchblende and brannerite, with the presence of metal minerals like pyrite, hematite and minor galena and sphalerite. The predominant hydrothermal alterations are hematitization, fluoritization, illitization, silicification, chloritization and carbonatization. Gangue minerals are mainly quartz, fluorite, illite and calcite. Moreover, four hydrothermal stages can be recognized in the Yingqian deposit, and the second and third stages are the uraniferous ones. The alterations and mineral assemblages indicate ore fluids are acidic, oxidized, and rich in F, P, CO2, which is favorable for dissolving uranium. Abundant apatite and rutile are discovered in the uraniferous third-stage veins. Geochemical analyses indicate that rutile is plotted in the hydrothermal area in the Ti-100 (Fe + Cr + V)-1000 (W) ternary diagram, and apatite is classified as fluorapatite. In-situ LA-ICP-MS dating indicates that the ore-hosting medium–coarse grained biotite granite and fine grained two-mica granite obtain the zircon U-Pb ages of 160.0 ± 0.3 Ma and 164.1 ± 0.6 Ma, which are consistent with many Jurassic granites in the South China Block. The hydrothermal apatite and rutile yield the U-Pb ages of 96.4 ± 11.6 Ma and 85.6 ± 10.8 Ma, respectively, indicating that uranium mineralization is significantly younger than the ore-hosting granites and generally coeval with the regional mafic magmatism. Consequently, the uraniferous fluids in the Yingqian deposit are independent from the magmatic system. Combined with previous research, it is concluded that fluid convection promoted by mantle–crust interaction would leach uranium from various lithologies, and fluid-rock interactions, fluid boiling and cooling are the causes for uranium precipitation.

Rock structural changes monitored by fibre Bragg Grating sensors and Nuclear magnetic Resonance during static and dynamic carbonated brine core flooding experiments

One proposed solution to reduce greenhouse gas emissions is the capture and storage of carbon dioxide (CCS) in geological formations such as depleted oil and gas reservoirs. Injected carbon dioxide (CO2) forms carbonic acid once dissolved in the formation water, which can lead to dissolution of certain types of rock minerals. This may weaken rock geomechanical properties that can jeopardize the safety of long-term storage. In this work, the use of Fibre Bragg Grating (FBG) sensors associated with Nuclear Magnetic Resonance (NMR) was investigated to measure the change in rock strain during core flooding experiments. Optical fibres were glued onto two synthetically calcite cemented sandstone rock samples (called CIPS). The samples were saturated with dead brine followed by live brine.The FBG sensors accurately monitored a change of approximately −30 µstrain during dead brine migration at a fast rate within 10–20 min, and then the FBG strain became constant when the sample reached 100% saturation. Exposing the CIPS to live brine induced up to −1000 µstrain in a dynamic injection exercise and – 250 µstrain in the static condition, these changes occurred after 5 h exposure, which was interpreted as the result of fluid-rock interactions occurred within the sample. Those changes continued to increase over the next 35 h, albeit at lower rate. The NMR T2, spatial T2 and FBG data confirmed structural changes within the rock samples. X-ray Computer Tomography (CT) imaging also supported the structural change at certain locations in the sample while featuring good agreement with FBG results.Overall, FBG sensing technology associated with NMR can accurately measure the changes in rock strain during core flooding experiments, while allowing it to monitor the reservoir’s geo-mechanical strength which is a key factor to ensure the long-term safety of CO2 storage.

Evaluation of drying shrinkage effects on the elastic properties of porous sandstones using a modified micromechanical model

SUMMARY The effects of pore fluids on the elastic properties of sedimentary rocks can be broadly categorized into two mechanisms: variations in pore compressibility due to the physical properties of the fluids and alterations in the stiffness of the rock frame resulting from rock–fluid interactions. Particularly, as rock–fluid interactions alter the stiffness of contacts between mineral grains, changes in the fluid properties around grain contacts can induce volumetric deformation of the rock as well as in variations of the associated elastic coefficients. Even though many previous studies have explored the influence of swelling of clay minerals, the relationships between changes in elastic moduli and deformation in rocks, which hardly contain swellable minerals, remain to date enigmatic. In this paper, to evaluate quantitatively these effects, drying rates, strains and ultrasonic velocities of small cylindrical Berea sandstone samples were measured as their water saturation was decreased by evaporative drying. The measurements clearly showed drying shrinkage and drastic increases in shear and compressional moduli for all the samples under an almost fully dried condition. Previous studies considered that the alteration in surface energy of grain minerals between wet and dry states affected the contact stiffness between them. Some of them used micromechanical model, uniting the Digby grain contact model with the effective medium theory, to interpret the changes in elastic moduli observed in the non-swellable sandstones during water adsorption on the grain surface. The conventional micromechanical model assumes that a mineral grain is a pure sphere and that the number of contacts between the grains is one. However, grains in a sedimentary rock are generally not purely spherical, and the contact surface is composed of several adhesive asperities. We therefore modified the conventional model by introducing the curvature radius and the number of asperities per contact surface. The modified model well reproduced the shear moduli under wet conditions using the strain and moduli measured under dry conditions. On the other hand, the predictions of the compressional moduli using the model were partially in agreement with the experimental results. Therefore, we attempted to qualitatively interpret the relationship by combining the model with the viscoelastic effect associated with wave-induced fluid flow. The deformation and changes in the elastic moduli of rocks resulting from multiple pore fluids within them can be better understood by the present combined model.

The source and ore-forming processes of post-collisional Qulong porphyry Cu-Mo deposit in Tibet constrained by Mo isotopes

Porphyry deposits supply most of the world's Cu and Mo resources. Most porphyry deposits are developed in magmatic arcs above subduction zones. However, abundant Miocene porphyry Cu-Mo deposits have been found in the post-collision stage in Tibet, more than ∼30 Myr after the Indian-Eurasian continental collision. The magma source and the enrichment process of ore-forming elements for these post-collision porphyry deposits remain controversial. Here, we present Sr-Nd-Mo isotope compositions of a suite of mineralized and barren igneous rocks from the Rongmucuola pluton in the Miocene post-collisional Qulong porphyry Cu-Mo deposit in Tibet to reveal their magma sources and ore-forming processes. Our results indicate that the mineralized and barren igneous rocks in the Qulong deposit were derived from a cogenetic source with similar Sr-Nd isotope compositions (87Sr/86Sr(i) = 0.7049–0.7050 and εNd(t) = −0.24 to 0.20). However, the mineralized igneous rocks have large variations in δ98/95Mo values (−0.30‰ to 0.74‰; relative to NIST SRM 3134) and Mo/Ce ratios (0.01 to 4.84) compared to those of the barren igenous rocks (δ98/95Mo = −0.74‰ to −0.02‰; Mo/Ce = 0.01 to 0.04). In combination with the higher LOI values, Mo/Ce and Cs/Ta ratios and Cu concentrations and lower Ce/Pb ratios of the mineralized igneous rocks relative to the barren igneous rocks, we propose the mineralized igneous rocks were affected by ore-forming hydrothermal fluids originated from the exsolution of later co-genetic magmas, which significantly changed the isotopic and elemental compositions of intrusions and resulted in Mo mineralization. The fluid-rock interaction modeling supports this interpretation and successfully reproduce the observed δ98/95Mo and Mo/Ce compositions of mineralized igneous rocks. Our study indicates that the exsolved magmatic-hydrothermal fluids have heavy Mo isotopes, and the fluids with a slightly heavier Mo isotope composition have the greatest potential for mineralization. As the water-rock reaction progresses, leading to the precipitation of Mo-rich minerals, ore-forming fluids with a heavier Mo isotope composition may not have significant mineralization potential. This highlights that Mo isotope system is an effective tool to study the ore-forming processes of porphyry deposits.

Reactive transport modeling constraints on the complex genesis of a lacustrine dolomite reservoir: A case from the Eocene Qaidam Basin, China

Reactive transport modeling (RTM) is an emerging method used to address geological issues in diagenesis research. However, the extrapolation of RTM results to practical reservoir prediction is not sufficiently understood. This paper presents a case study of the Eocene Qaidam Basin that combines RTM results with petrological and mineralogical evidence. The results show that the Eocene Xiaganchaigou Formation is characterized by mixed siliciclastic-carbonate-evaporite sedimentation in a semiclosed saline lacustrine environment. Periodic evaporation and salinization processes during the syngenetic-penecontemporaneous stage gave rise to the replacive genesis of dolomites and the cyclic enrichment of dolomite in the middle-upper parts of the meter-scale depositional sequences. The successive change in mineral paragenesis from terrigenous clastics to carbonates to evaporites was reconstructed using RTM simulations. Parametric uncertainty analyses further suggest that the evaporation intensity (brine salinity) and particle size of sediments (reactive surface area) were important rate-determining factors in the dolomitization, as shown by the relatively higher reaction rates under conditions of higher brine salinity and fine-grained sediments. Combining the simulation results with measured mineralogical and reservoir physical property data indicates that the preservation of original intergranular pores and the generation of porosity via replacive dolomitization were the major formation mechanisms of the distinctive lacustrine dolomite reservoirs (widespread submicron intercrystalline micropores) in the Eocene Qaidam Basin. The results confirm that RTM can be effectively used in geological studies, can provide a better general understanding of the dolomitizing fluid-rock interactions, and can shed light on the spatiotemporal evolution of mineralogy and porosity during dolomitization and the formation of lacustrine dolomite reservoirs.

Mineralization processes of the Mount Garnet Zinc deposit, NE Queensland (Australia): Insights from garnet geochemistry and U-Pb geochronology

The Mount Garnet Zinc deposit in NE Queensland, Australia, is located in the region of voluminous magmatism associated with the formation of Palaeozoic continental arcs of Gondwana. Ore-forming events of this deposit are related to the intrusion of the Kennedy Igneous Association (KIA) – a large suite of igneous rocks spanning Late Carboniferous to Early Permian in age – into the Silurian limestone (Chillagoe Formation) in the Hodgkinson Province (Mossman Orogen). Petrographic observations and in situ major and trace element analysis reveal the sequence of garnet growth and fluid-rock interaction during skarn formation. Three types of garnets are identified, Grt I (including IA and IB) and Grt II. Grt IB is related to Zn-Pb mineralization. All garnets have elevated Sn and W and the highest levels of W and Sn are observed in Grt II. Garnet U-Pb ages of Grt IB provide the first direct geochronological result of hydrothermal minerals in the Mount Garnet region. New data argues that the base metal mineralization may take place during early Permian period and be sourced from the Claret Creek Supersuite. Sn-W mineralization may be associated with the O’Briens Creek Supersuite.

Characterization of deep ore-forming fluid in the Zhaoxian gold deposit within the Jiaodong gold province: insights from quartz vein fluid inclusion, in-situ trace element analysis, and S isotopic composition in pyrite

The Jiaodong gold province, situated in the southeastern margin of the North China Craton, is globally renowned for its substantial gold reserves exceeding 5,000 tonnes. The Zhaoxian gold deposit is part of the significant Jiaojia gold belt within the Jiaodong gold province. Fieldwork has identified four distinct stages of ore formation in this study: an early barren quartz vein stage (Stage 1) containing fine-grained pyrite; a gold-bearing stage (Stage 2) consisting of quartz, pyrite, and native gold; a polymetallic sulfide-rich stage (Stage 3) comprising quartz, polymetallic sulfides, and native gold; and a late-stage (Stage 4) primarily composed of quartz and calcite with minimal pyrite content. We conducted fluid inclusion analysis using microthermometry and Raman spectroscopy techniques to examine the fluid characteristics. In-situ analysis of trace elements in pyrite was performed to investigate the fluid composition and evolution. Additionally, we determined the sulfur isotope composition in pyrite to analyze the source of sulfur. Our findings indicate that the ore-forming fluid in the Zhaoxian gold deposit belongs to a medium-to-low-salinity H₂O-NaCl-CO₂-CH₄ system. Fluctuations in Au and As concentrations observed along with oscillating zones and sulfide inclusions during Stage 2 suggest potential fluid boiling processes occurring during mineralization. High concentrations of Ag, Cu, Zn, Cd, In, Pb, and Bi without oscillating zones during Stage 3 imply precipitation of polymetallic sulfides under stable fluid conditions. The δ34S values observed in the Zhaoxian gold deposit are slightly higher than those found in granitoids from other areas within Jiaodong but similar to those seen in other deposits within the Jiaojia gold belt region. In conclusion, magmatic-hydrothermal ore-forming fluids were involved along with significant fluid-rock interaction during metallogenic processes of the Zhaoxian gold deposit.

Fluid-induced dissolution–reprecipitation of tungsten minerals in the Hongling deposit, South China

Tungsten is a critical metal that is predominantly found in magmatic-hydrothermal W-Sn deposits. However, the behavior and controlling factors of tungsten in highly evolved granitic systems are not yet well-known. In this study, we examined the integrated mineral textures and geochemistry of wolframite and scheelite from the Hongling tungsten deposit in the word-class Nanling W-Sn metallogenic belt, South China. Our results reveal that wolframite and scheelite from the muscovite granite of the highly evolved Reshui granite pluton can be classified into three generations formed through a process of coupled dissolution-reprecipitation. Wolframite with altered relict textures was formed during the early magmatic stage, while the two generations of scheelite (Sch-I and Sch-II) were formed during the magmatic-hydrothermal transitional stage. The formation of Sch-I, which exhibits a notable positive Eu anomaly, required the participation of external Ca-rich reduced fluids within the magmatic exsolved fluids from the highly evolved peraluminous pluton. The porous Sch-II occurs as marginal overgrowth or fracture-filling textures and exhibits a similar negative Eu anomaly as the dissolved wolframite. These three generations of tungsten minerals exhibit distinguishable REE contents and distribution patterns, with increasing LREE and decreasing HREE trends. The fluctuation of oxygen fugacity and the compositional evolution of tungsten minerals from wolframite through Sch-I to Sch-II indicate the involvement of external Ca-rich reduced fluids within the magmatic exsolved fluids from the highly evolved peraluminous pluton. The coupled dissolution of wolframite and the reprecipitation of scheelite were likely induced by intensive fluid-rock interactions, which are critical for the remobilization and enrichment of tungsten in magmatic-hydrothermal deposits. We inferred that such fluid-induced dissolution-reprecipitation of tungsten minerals provides new insights into the formation of the world-class Nanling W-Sn metallogenic belt in South China.

Interpretation of low-frequency distributed acoustic sensing data based on geomechanical models

Distributed acoustic sensing (DAS) is a technology that enables continuous, real-time measurements along the entire length of a fiber-optic cable. The low-frequency band of DAS can be used to analyze hydraulic fracture geometry and growth. In this study, the low-frequency strain waterfall plots with their corresponding pumping curves were analyzed to obtain information on fracture azimuth, propagation speed, number of fractures created in each stage, and restimulation of preexisting fractures. We also use a simple geomechanical model to predict fracture growth rates while accounting for changes in treatment parameters. As expected, the hydraulic fractures principally propagate perpendicular to the treated well, that is, parallel to the direction of maximum horizontal stress. During many stages, multiple frac hits are visible, indicating that multiple parallel fractures are created and/or reopened. Secondary fractures deviate toward the heel of the well, likely due to the cumulative stress shadow caused by previous and current stages. The presence of heart-shaped tips reveals that some stress and/or material barrier is overcome by the hydraulic fracture. The lobes of the heart are best explained by the shear stresses at 45° angles from the fracture tip instead of the tensile stresses directly ahead of the tip. Antennas ahead of the fracture hits indicate the reopening of preexisting fractures. Tails in the waterfall plots provide information on the continued opening, closing, and interaction of the hydraulic fractures within the fracture domain and stage domain corridors. The analysis of the low-frequency DAS plots thus provides in-depth insights into the rock deformation and rock-fluid interaction processes occurring close to the observation well.

Cold deep subduction of Indian continental crust and release of ultrahigh‐pressure fluid during initial exhumation: Insights from coesite‐bearing eclogite‐vein systems in Kaghan Valley, Pakistan

AbstractThe ultrahigh‐pressure (UHP) eclogites from the Kaghan Valley in Pakistan, which formed by the deep subduction of the Indian plate beneath the Asian plate in the Eocene, contain complex metamorphic vein systems (including both isolated veins and vein networks), with mineral assemblages of epidote + quartz + kyanite + phengite ± omphacite ± garnet. The investigations on the Kaghan UHP eclogite‐vein systems provide important insights into the mechanism and timing of metamorphic dehydration, fluid flow, and fluid–rock interaction in the deeply subducted Indian continental slab as well as the chemical characteristics of slab‐derived, aqueous fluids. Abundant lawsonite pseudomorphs, characterized by prismatic aggregates of epidote, kyanite, and quartz porphyroblasts, are first recognized in the Kaghan eclogites. This observation, in combination with the occurrence of coesite pseudomorphs in epidote porphyroblasts as well as the coexistence of epidote and coesite in the eclogite zircon, indicates the previous existence of UHP lawsonite in these eclogites. Petrological studies and phase equilibrium modelling reveal clockwise P–T trajectories for the Kaghan eclogites that are featured by prograde vectors in lawsonite‐stability regions with peak conditions of 3.0–3.4 GPa/650–690°C, followed by isothermal decompression and lawsonite breakdown under UHP conditions during the initial exhumation stage. The results of metamorphic evolution, together with in situ epidote and bulk Sr isotopic analyses, indicate that the fluids responsible for vein systems are most likely derived from the breakdown of UHP lawsonite in the eclogites. SIMS U–Pb dating of metamorphic zircons from the eclogites, integrated with the Raman analysis of inclusions in zircons, indicates that the UHP dehydration of eclogites occurred at 46.4 ± 1.2 and 46.8 ± 0.9 Ma. Analyses of hydrothermal zircons from the veins yielded slightly younger ages of 44.7 ± 1.0 and 44.9 ± 1.4 Ma, which represent the timing of fluid flow and/or vein crystallization during exhumation of the UHP rocks. Mass‐balance calculation results, in combination with the vein compositions, show that the fluid flow and fluid‐eclogite interaction led to the transfer of Si, Al, Ca, K, and incompatible trace elements from the eclogites into the fluids, from which the vein systems crystallized. This study indicates cold deep subduction of Indian continental crust along low geothermal gradients (6–7°C/km). The UHP fluid liberation and channelized fluid flow occurred during the initial exhumation of the cold Indian slab and are expected to induce the transfer of H2O and incompatible trace elements from the Indian slab to the Asian lithosphere, which potentially contributes to the formation of post‐collisional magmas. Moreover, we suggest that metamorphic vein systems in UHP lawsonite eclogites offer important constraints on the occurrence and timing of fast slab exhumation in continental subduction‐collision zones.

Fluid metasomatism of subducted continental crust: Insights from Si isotope compositions of metasomatic rocks from the Western and Eastern Alps

Serpentinite-derived fluids play a crucial role in mass exchange between the Earth's crust and mantle. However, there is currently a limited understanding of how serpentinite-derived fluids influence the Si isotope composition of mantle and subducted crustal materials. Whiteschists in the Dora-Maira Massif of the Western Alps and leucophyllites in Austria of the Eastern Alps were formed through serpentinite-derived fluid metasomatism of metagranite protoliths. Thus, they can provide valuable insights into the geochemical diversity of such rocks resulting from fluid–rock interactions. A special focus is on Si isotope compositions, which were analyzed in whiteschists, leucophyllites, and their corresponding country rocks. The aim of this paper is to investigate the impact of serpentinite-derived metasomatic fluids on the Si isotope compositions of subducted continental crust. With the exception of one whiteschist sample, which contains high amounts of pyrope, and one pyrope megablast, all other whiteschists and leucophyllites exhibit Si isotope compositions similar to those of their country rocks. This observation suggests that the Si isotopes of whiteschists and leucophyllites were inherited from their respective country rocks; fluid metasomatism did not significantly modify the Si isotope compositions of whiteschists and leucophyllites. Because pyrope has much lower δ30Si values than quartz and phengite as further major mineral constituents of the studied whiteschists, the samples with high pyrope contents reveal lighter Si isotopes than those containing lower amounts of pyrope. Interestingly, the metagranites and the majority of whiteschists and leucophyllites exhibit Si isotope compositions below the igneous array, implying that their protoliths are S-type granites. These granites commonly contain sedimentary components derived from their sources. Our results document that Si behaves immobile during serpentinite-derived fluid metasomatism of the subducted continental crust. Combined with previous results, we were able to show that slab derived fluids, including serpentinite-derived fluids, produce only a minimal influence on the Si isotope composition of the overlying mantle wedge and its derived magmas. Thus, the Si isotope compositions of rocks, even if highly affected by metasomatizing fluids, can be used as significant fingerprints that refer to their unaltered precursors.

Increasing Oil Recovery by Varying Surfactant Concentrations and Expanding the Well Drainage Area

Surfactant flooding plays a crucial role in advanced techniques for boosting oil recovery. There remains a significant volume of unrecovered oil in reservoirs, particularly in carbonate reservoirs. These reservoirs often face challenges with low primary and water-flood recovery due to inadequate sweep efficiency, resulting in the presence of bypassed or trapped oil. Chemical flooding approaches, including surfactant flooding, have demonstrated their effectiveness in the retrieval of this trapped oil. The fundamental concept of surfactant flooding involves injecting a surface-active agent, known as a surfactant, to reduce the interfacial tension and mobilize the residual oil saturation. Surfactants have been widely utilized for various purposes in the petroleum industry since its early years, owing to their capacity to modify interfacial interactions between two immiscible fluids in contact with one another. Interfacial phenomena play a significant role in rock-fluid interactions and the interactions between fluids from the reservoir to distribution pipelines. Consequently, surfactants find application in a variety of activities within the petroleum industry. Laboratory experiments, pilot-scale projects, and field-scale initiatives worldwide have yielded diverse outcomes regarding the use of surfactants for enhancing oil recovery. Multiple types of surfactants have been investigated to determine highly effective chemical formulations for enhanced oil recovery, with anionic and non-ionic surfactants being commonly employed in sandstone reservoirs.