Changes In Fluid Composition Research Articles

Tracing Carbonate Formation, Serpentinization, and Biological Materials With Micro-/Meso-Scale Infrared Imaging Spectroscopy in a Mars Analog System, Samail Ophiolite, Oman.

Visible‐shortwave infrared (VSWIR) imaging spectrometers map composition remotely with spatial context, typically at many meters‐scale from orbital and airborne data. Here, we evaluate VSWIR imaging spectroscopy capabilities at centimeters to sub‐millimeter scale at the Samail Ophiolite, Oman, where mafic and ultramafic lithologies and their alteration products, including serpentine and carbonates, are exposed in a semi‐arid environment, analogous to similar mineral associations observed from Mars orbit that will be explored by the Mars‐2020 rover. At outcrop and hand specimen scales, VSWIR spectroscopy (a) identifies cross‐cutting veins of calcite, dolomite, magnesite, serpentine, and chlorite that record pathways and time‐order of multiple alteration events of changing fluid composition; (b) detects small‐scale, partially altered remnant pyroxenes and localized epidote and prehnite that indicate protolith composition and temperatures and pressures of multiple generations of faulting and alteration, respectively; and (c) discriminates between spectrally similar carbonate and serpentine phases and carbonate solid solutions. In natural magnesite veins, minor amounts of ferrous iron can appear similar to olivine's strong 1‐μm absorption, though no olivine is present. We also find that mineral identification for carbonate and serpentine in mixtures with each other is strongly scale‐ and texture‐dependent; ∼40 area% dolomite in mm‐scale veins at one serpentinite outcrop and ∼18 area% serpentine in a calcite‐rich travertine outcrop are not discriminated until spatial scales of <∼1–2 cm/pixel. We found biological materials, for example bacterial mats versus vascular plants, are differentiated using wavelengths <1 μm while shortwave infrared wavelengths >1 μm are required to identify most organic materials and distinguish most mineral phases.

Mineralization processes involved in the formation of the Jinya Carlin-type Au deposit, northwestern Guangxi, China: Evidence from in situ trace element and S isotope geochemistry of Au-bearing zoned pyrite

The Jinya Au deposit is a representative example of the Carlin-type Au mineralization located within the “Golden Triangle” area of the Yunnan, Guizhou, and Guangxi provinces, China. The deposit is located within a fault zone at the contact between a carbonate platform and contains Au mineralization hosted by arsenopyrite and pyrite, with the latter providing evidence of changes in fluid composition during pyrite growth. Back-scattered electron (BSE) images indicate that this Au-bearing zoned pyrite can be divided into dark cores (Py1), lighter colored central sections (Py2), and dark rims (Py3). Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) and secondary ion mass spectrometry (SIMS) analyses provide information on compositional and S isotopic variations within this pyrite. These data indicate that each pyrite zone is compositionally homogeneous, showing Co/Ni ratios of <1. Pyrite has δ34S values ranging from –8.54‰ to –4.05‰, with Py1, Py2, and Py3 having average δ34S values of –6.89‰, –5.60‰, and –5.99‰, respectively. These values are indicative of thermochemical sulfate reduction (TSR) processes. Mineralizing fluids that formed the deposit derived from a sedimentary source mixed with variable amounts of meteoric water (Py1 = 3%; Py2 = 32%; Py3 = 23%). The ore-forming fluids within the sedimentary basin metasomatized the Fe-rich dolomitic rocks of the forming the early pyrite cores (Py1). This fluid flow focused along the main fault zone, which at this time was permeable, allowing with an influx of meteoric water. This mixing process lowered the temperature of the system, causing the precipitation of large volumes of Au and As. This caused the formation of the light-colored and As- and Au-enriched central parts of the pyrite within the deposit (i.e., Py2). A subsequent decrease in the amount of meteoric water in the system led the formation of the darker Py3 rims that contain low concentrations of As and Au.

Immediate and short-term effects of Gufoni and Appiani liberatory maneuver for treatment of ageotropic horizontal canal benign paroxysmal positional vertigo: A prospective randomized trial.

ObjectiveTo examine the treatment effects of repositioning maneuvers with the head turned 45° downwards (Gufoni maneuver) and 45° upwards (Appiani maneuver) in 25 patients with ageotropic horizontal semicircular canal (HSCC) benign paroxysmal positional vertigo (BPPV).MethodsPatients were randomly assigned to the Gufoni or Appiani maneuvers, and their immediate and short‐term efficacy was investigated.ResultsThe immediate treatment response was successful in four of 16 patients who were treated with the Appiani maneuver and were not successful in any of the nine patients treated with the Gufoni maneuver. The patients who showed spontaneous resolution during follow‐up outnumbered the patients who showed resolution of ageotropic HSCC BPPV immediately after the repositioning maneuvers.ConclusionThis study showed a very low immediate resolution rate of ageotropic HSCC BPPV after the Gufoni maneuver; this may be attributed to the less effectiveness of the Gufoni maneuver against debris that often exists in the canal side of the cupula. Another interesting finding was that the rate of spontaneous resolution during the follow‐up period was higher than that of immediate resolution after the repositioning maneuvers, which may support the recently proposed hypothesis that ageotropic positional nystagmus can also be evoked by causes other than the otolithic attachment on the cupula, such as a slight change in the biochemical composition of the inner ear fluids.Level of Evidence3.

Quantitative Assessment of Age and Gender Related Changes in Human Lacrimal Fluid Composition in Subjects

Purpose: The frequency of eyelids blink rate has effect on the integrity of the tear fluid and replacement of old of tears on the ocular surface. Comprehension of the effect of advancing age and gender on tears fluid stability and quality is contentious. Basal tears continuously bathe the ocular facet lubricating and providing protection from viral and bacterial infections, cooling the surface as warmth encourages pathogen. Basal tear dysfunction basically results in conjunctival and corneal conditions which exposes the ocular facet to dryness, ulceration, opacity and even blindness. This study determined the quantitative assessment of age and gender related changes in human lacrimal fluid composition in subjects&#x0D; Methods: The design involved 400 (192 males and 208 females) human subjects aged 6 years and above who do not wear contact lenses, not on topical medication and having healthy eyes grouped into twelve groups based on age and gender. Maximum blink interval (for tear break-up time) and phenol red thread procedure (for tear volume) were carried out monocularly for each subject.&#x0D; Results: Findings from this study have established that tear fluid stability among different age groups; are often higher for group 6-12years and lower for 60years and above; therefore, study established that tear fluid stability is age dependent. In addition, tear fluid stability (average MBI. Tear volume and flow rate) are gender independent.&#x0D; Conclusion: The present study revealed that tears fluid breakup time increases with decrease in tears fluid flow rate, volume and flow.

Basement aquifer evolution and the formation of unconformity-related hydrothermal vein deposits: LA-ICP-MS analyses of single fluid inclusions in fluorite from SW Germany

The main ore stage of three similar unconformity-related vein systems in the Schwarzwald, SW Germany spanning a period of activity of ~150 Ma, was investigated to understand the details of fluid penetration from overlying sediments/marine environment into the basement, their evolution as well as the processes involved in vein formation. To investigate temporal and spatial variations of the hydrothermal fluids responsible for mineralization, over 1650 fluid inclusions were analyzed by microthermometry. Of these, a total of 108 fluid inclusions (mainly in fluorite) were successfully analyzed by LA-ICP-MS. The fluid inclusions reveal a binary mixing trend between a CaCl2- and a NaCl-rich endmember. Independent of major element composition, the fluids are metal-bearing (e.g., up to ~100 mg/kg Ba, Pb, Zn, Ni and up to 10 mg/kg Ag), show high As (up to 1000 mg/kg) and low S (below the detection limit in most analyses). Over time, the mixed fluid shows a gradual decrease in CaCl2 and increase in NaCl with slightly decreasing total salinity.Based on earlier studies and geochemical arguments, the veins formed by anisothermal binary fluid mixing of two fluids, which both were originally derived from seawater and chemically modified through interaction with the basement and sedimentary rocks in different ways. This produced a gradual stratified basement fluid reservoir comprising a modified bittern/halite dissolution brine. The fluids involved in the vein formation are sourced from different depths of this modified bittern/halite dissolution basement brine reservoir: fluid A, a CaCl2-dominated, KCl-poor, deeper seated brine with a salinity of ~25 wt% CaCl2 + NaCl, and fluid B, an NaCl-dominated and KCl-richer brine situated at shallower depths in the crystalline basement with salinities of ~22 wt% NaCl+CaCl2. Based on the Na-Ca-K and NaK thermometers and on Rb/Cs systematics, fluid A records alteration of the Na-, K- and Ca-bearing feldspars of the host rocks; progressive alteration led to consumption of mainly Ca-rich plagioclase in contact with these basement brines. Accordingly, fluid B that subsequently entered the basement was only in equilibrium with alkali feldspars and clay minerals. This scenario produced a gradual change of fluid composition with depth that was pushed to greater depth over time.The source temperatures are estimated to ~250 °C while vein formation occurred at 100–170 °C, based on fluid inclusion homogenization temperatures. Thus, significant fluid cooling without abundant fluid mixing (and without major mineralization) must have occurred during fluid ascent (3–7 km, depending on the assumed geothermal gradient). Fluid mixing then resulted in the formation of the major gangue minerals fluorite, quartz, barite and calcite, while the locally confined sulfides must have formed due to an influx of sulfide into the binary mixed fluid. The process of fluid mixing is a rapid and turbulent process. This is recorded by a great diversity of fluid compositions (including ones close to the mixing endmembers) trapped within the same crystal. Compositional variations are even visible within individual fluid inclusion trails.

Features of biodegradation of sol-gel bioactive glass 60S doped with Ga, Ge

Samples of BG 60S (4% P2O5, 36% CaO, 60% SiO2) and doped with Ga2О3 (1%), GeО2 (1%) were synthesized by the sol-gel method. In the environment of model physiological fluid (Kokubo's SBF) in vitro biodegradation processes of synthesized BG samples were studied and in vivo studies of bone formation were performed. The methods of atomic absorption (for Ca2+, Mg2+) and photometric (for HPO4 2–) analysis were used to study the change in the ionic composition of the model physiological fluid, the pH changes of which were recorded potentiometrically. BG samples before and after in vitro bioresorption studies were tested by IR spectroscopy. The studied dependences of the activity of ion exchange processes and the rate of formation of hydroxy-carbonate apatite on the surface from doping additives confirm the bioactivity of the synthesized samples. The highest bioactivity according to the results of in vitro and in vivo studies shows BG 60S without alloying additives.

T2 relaxation time shortening in the cochlea of patients with sudden sensory neuronal hearing loss: a retrospective study using quantitative synthetic magnetic resonance imaging.

High cochlear signal intensity on three-dimensional (3D) T2 fluid-attenuated inversion recovery (FLAIR) sequences in patients with sudden sensorineural hearing loss (SSNHL) has been reported. Here, we evaluated the cochlear T2 relaxation time differences in patients with idiopathic SSNHL using quantitative synthetic MRI (SyMRI). Twenty-four patients with unilateral SSNHL who underwent precontrast conventional 3D FLAIR and SyMRI were retrospectively included. T1 and T2 relaxation times and the proton density (PD) of the bilateral ears were measured by manually drawn regions of interest. Wilcoxon signed-rank tests and intra- and interobserver correlation analyses were performed. Qualitative analysis was also performed to determine the presence and laterality of the asymmetric high signal intensity on synthetic FLAIR (SyFLAIR) images. The T2 relaxation time was significantly lower in the affected (basal and apico-middle turns) than in the unaffected cochlea (basal turn: 519 ± 181.3 vs. 608.8 ± 203.6, p = 0.042; apico-middle turn: 410.8 ± 163.8 vs. 514.5 ± 186.3, p = 0.037). There were no significant differences in the T1 relaxation time and PD between the affected and unaffected ears (p > 0.05). Additionally, three patients without asymmetric signal intensity on conventional MRI showed asymmetric increased signal intensity in the affected ear on SyFLAIR. The T2 relaxation time was significantly shorter in the affected than in the unaffected cochlea of patients with idiopathic SSNHL. The SyMRI-derived T2 relaxation time may be a promising imaging marker, suggesting that the changes in inner ear fluid composition are implicated in the idiopathic SSNHL development. • T2 relaxation time was significantly lower in the affected than in the unaffected cochlea. • SyFLAIR showed increased lesion conspicuity compared to conventional 3D-FLAIR in detecting asymmetric high signal intensity of the affected side. • SyMRI-derived T2 relaxation time may be a promising imaging marker of the affected ear in patients with idiopathic SSNHL.

Positional Nystagmus after Acute Vertiginous Attack in Meniere’s Disease

There have been no reports regarding nystagmus observed immediately after the end of an acute vertiginous attack in patients with Meniere’s disease. The aim of this study was to demonstrate positional direction-changing nystagmus in patients with Meniere’s disease, and to discuss the mechanism that underlies this nystagmus. Video-nystagmography was recorded in two patients with definite Meniere’s disease, who showed positional direction-changing nystagmus during the period immediately after a vertigo attack. In one patient, video-nystagmographic recording was conducted 5 h after an episode of vertigo attack, and it showed very weak, persistent positional geotropic direction-changing nystagmus. In the other patient, video-nystagmographic recording was conducted 23 h after an episode of vertigo attack, and it showed very weak, persistent positional apogeotropic direction-changing nystagmus. Our patients exhibited very weak, persistent positional direction-changing nystagmus, which was geotropic in one and apogeotropic in the other. This type of positional nystagmus has been reported in other inner ear disorders and it cannot be clearly explained by typical benign paroxysmal positional vertigo. The change in chemical composition and/or electrolyte concentration of the inner ear fluid, although still unclear, may underlie the production of this characteristic nystagmus in these patients.

Chorioamnionitis alters lung surfactant lipidome in newborns with respiratory distress syndrome.

Chorioamnionitis is associated with preterm delivery and morbidities; its role in lung disease is controversial. The aim of this study is to assess the effect of chorioamnionitis on metabolite and lipid profiles of epithelial lining fluid in preterm newborns with respiratory distress syndrome (RDS). The study involved 30 newborns with RDS, born from mothers with or without histological chorioamnionitis (HCA): HCA+, N = 10; HCA-, N = 20. Patients had a gestational age ≤30 weeks; the groups were matched for age and birth weights. Tracheal aspirates were collected within 24 h after birth and analyzed using liquid chromatography/mass spectrometry-based untargeted lipidomics. According to Mann-Whitney U tests, 570 metabolite features had statistically significantly higher or lower concentrations (p < 0.05) in tracheal aspirates of HCA+ compared to HCA-, and 241 metabolite features were putatively annotated and classified. The most relevant changes involved higher levels of glycerophospholipids (fold change 2.42-17.69) and sphingolipids, with lower concentration of all annotated sphingomyelins in HCA+ (fold change 0.01-0.50). Untargeted lipidomics of tracheal aspirates suggested the production of lipid mediators in the context of an ongoing inflammatory status in HCA+ babies. However, the effect of chorioamnionitis on epithelial lining fluid composition deserves further investigations on a larger group of infants. Our lipidomics investigation on tracheal aspirates of preterm newborns at birth suggested that exposure to maternal histological chorioamnionitis may cause changes in epithelial lining fluid composition. This is the first description of epithelial lining fluid lipidomic profiles in preterm infants with and without exposition to chorioamnionitis. These results could provide novel link between placental membrane inflammation and newborns' respiratory outcome.

Deformation-Induced and Reaction-Enhanced Permeability in Metabasic Gneisses, Iona, Scotland: Controls and Scales of Retrograde Fluid Movement

The spatial distribution of greenschist-facies retrograde reaction products in metabasic gneisses from Iona, western Scotland, has been investigated. The retrograde products may be broadly accounted for by a single reaction, but their different spatial and temporal development indicates that a series of reactions occur with significantly different scales of metasomatic transfer. After initial fluid influx linked to deformation-induced high permeability, reaction-enhanced permeability, coupled to cycling of fluid pressure during faulting, strongly controls the pervasive retrogression. Ca-plagioclase and pyroxene in the gneisses are replaced by albite and chlorite in pseudomorphic textures, and this is followed by localized epidotization of the albite. Two main generations of epidote are formed in the gneisses. Epidosite formation is associated with prominent zones of cataclasite indicating a strong link between faulting and fluid influx. In contrast, complete alteration of albite to epidote in the host metabasic gneisses is spatially complex, and areas of pervasive alteration may be constrained by both epidote-rich veins and cataclasites. In other instances, reaction fronts are unrelated to structural features. Volume changes associated with individual stages of the reaction history strongly control the localized distribution of epidote and the earlier more widespread development of chlorite and albite. Such behaviour contrasts with adjacent granitic gneisses where epidotization is restricted to local structural conduits. Many small-scale mineralized fractures with evidence of having previously contained fluids do not enhance the pervasive retrogression of the metabasic gneisses and represent conduits of fluid removal. Retrogression of these basement gneisses is dominated by a complex combination of reaction-enhanced and reaction-restricted permeability, kinetic controls on the nucleation of reaction products, changes in fluid composition buffered by the reactions, and periodic local migration of fluids associated with fault movements. This combination generates spatially complex patterns of epidotization that are limited by cation supply rather than fluid availability and alternations between focused and pervasive types of retrogression.

Fe and S-isotope compositions of hydrothermal deposits from Kings Triple Junction, Lau Basin, southwest Pacific Ocean

We analyzed iron and sulfur isotopic compositions of polymetallic sulfides from an extinct hydrothermal mound near the Kings Triple Junction of the northern Lau basin belonging to a back-arc basin for understanding the origin and mineral zoning processes in this study. Sulfides from the hydrothermal mound's pedestal slab consisting of chalcopyrite and pyrite show enrichment of heavy S-isotope (δ34SV-CDT = +8.3 to +9.6‰). Sphalerite-dominated chimney on the mound's slope also has variable δ34S values between +5.5 and + 8.3‰ from central orifice to outer wall. These isotopic ratios indicate the substantial contribution of heavy isotope rich sulfate-S in seawater circulating within the mound. Low Δ33S values in these sulfides also indicate that the sulfate reduction is of thermal origin, with minimal or no role for microbes. Circulating seawater induced changes in fluid composition and post-depositional zone refinement of certain minerals can explain the variation in δ34S in different layers within the chimney and pedestal slab. The Fe-isotopic compositions (δ56FeIRMM-014) show a range from −1.1 to −0.3‰ in the pedestal slab while they vary between −1.7 and − 0.6‰ at different parts of the peripheral chimney section. We explain such changes are mostly due to redox processes and mineral zoning development during these sulfide deposit formation. The tree-like FeMn oxide growth structures in the vicinity of the hydrothermal mound having a thin birnessite top layer and amorphous iron oxide bottom part show distinct δ56Fe values of −3.0 and − 0.8‰, respectively.

Dissolution-reprecipitation vs. solid-state diffusion in electrum: Examples from metamorphosed Au-bearing, volcanogenic massive sulfide (VMS) deposits

Abstract Native Au-Ag alloys (electrum) are the predominant precious metal host in Au-bearing volcanogenic massive sulfide (VMS) deposits. The chemical composition and distribution of electrum records crystal growth and post-crystallization processes. In this study, we present detailed textural and compositional data of electrum from the Ming (Canada) and Boliden (Sweden) Au-bearing VMS deposits. Electron probe micro-analyzer (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of electrum enable characterization of chemical zoning in heterogeneous electrum grains. Electrum from Ming exhibits Ag-rich cores, in gradational contact with an outer Au-rich transition zone also enriched in S, Fe, Cu, Zn, and Pb, which is in sharp contact with Ag-rich rims. The textural observations, coupled with in situ LA-ICP-MS data, highlight that the electrum zoning arises from a complex interaction between fluid facilitated solid-state diffusion (SSD) within the grain and coupled dissolution and reprecipitation (CDR) reactions at the grain interface, in response to changing fluid composition and extrinsic parameters, such as temperature, pH, and redox state at Ming. Electrum from Boliden, in contrast, shows an Au-rich core in contact with a gradually increasing Ag-rich rim enriched in Se, Bi, Sb, Te, Sn, S, and Zn, which indicates the formation by fluid facilitated SSD reactions. The different local re-equilibrium caused by SSD from two deposits are attributed to different transport ligands and effects of physicochemical parameters of fluids (e.g., pH and fO2), resulting in different compositional zoning patterns within the electrum. The long-lived metamorphic events that affected the occurrence and compositions of electrum at both VMS deposits, probably provided the elevated temperature and deformation to allow pervasive fluids to remobilize trace metals in electrum, which resulted in the complex chemical zoning in electrum. This study provides insights from in situ, textural and chemical analyses to understand the formation of complex chemical zoning in electrum in metamorphosed VMS deposits.

Thermodynamic modeling and elemental migration for the early stage of rodingitization: An example from the Xialu massif of the Xigaze ophiolite, southern Tibet

The analysis of early stage rodingite from the ultramafic rocks of the Xialu Massif in the Xigaze Ophiolite, Tibet, in China shows that the rodingitization involved continuous changes in fluid composition during different stages of subduction. The early stage prehnite-bearing rodingite was produced at low pressures and temperatures along extensional fractures. Samples of rodingite were collected along a profile from the center to the margin of a rodingitized intrusive igneous rock (~10 m × 30 m), and they record wide variations in bulk composition, mineralogy, and texture. The mineral assemblages, from center to margin, vary from (1) relics of primary clinopyroxene (Cpxr) and primary amphibole (Ampr) + newly formed late amphibole (Act) + primary plagioclase (Plr) + clinozoisite + prehnite + albite + chlorite + titanite + ilmenite (R1 rodingite), through (2) relics of primary clinopyroxene (Cpxr) + newly formed late clinopyroxene (Cpxn) + primary and late amphiboles (Ampr + Act) + clinozoisite + prehnite + albite + chlorite + titanite (R2 rodingite), to (3) newly formed late clinopyroxene (Cpxn) and amphibole (Act) + clinozoisite + prehnite + albite + chlorite + titanite (R3 rodingite). As a result of the metasomatic process of rodingitization, the content of CaO in the whole rock chemical composition from R1 to R3 increases, SiO2 decreases, and Na2O + K2O is almost completely removed. Mass-balance diagrams show enrichments in large ion lithophile elements such as Rb, Cs, Ba, and Pb as well as Ni during rodingitization. The central part of the rodingitized intrusion (R1 rodingite) was only slightly affected by metasomatism. On the other hand, the contents of the rare earth elements (REEs), high field strength elements (HFSEs; e.g. Zr, Nb, Ta, Hf, and Y), and some highly compatible elements such as Cr and Sc decreased slightly during rodingitization. Thermodynamic modeling based on equilibrium mineral assemblages indicates that the rodingite of the Xialu Massif formed in an H2O-saturated, CO2-rich environment. The estimated conditions of metamorphism were ~281–323 °C and 0.4–3.9 kbar, representing the subgreenschist facies. In this environment, REEs and HFSEs were soluble in the fluids and partly removed. Moreover, these prehnite rodingites formed in a progressively reducing and less alkaline environment, as indicated by decreases in f(O2) and bulk-rock Fe3+/Fe2+ ratios, and the records of fluid ΔpH from the center to the margin of the studied rodingitized intrusion.

Pyrite Textures and Trace Element Compositions from the Granodiorite-Hosted Gold Deposit at Jonnagiri, Eastern Dharwar Craton, India: Implications for Gold Mineralization Processes

Abstract The lone granodiorite-hosted gold deposit at Dona sector of Jonnagiri, eastern Dharwar craton, India, contains typical shear-hosted and vein-hosted alteration zones. Pyrite is the dominant sulfide mineral in these alteration zones. Texturally three varieties of pyrites were identified in these alteration zones: (1) early pyrite-I is coarse to medium grained and subhedral shaped and contains near margin-parallel silicate inclusions, (2) main (ore)-stage pyrite-II overgrows early pyrite-I and also occurs as discrete grains invariably associated with visible gold, and (3) late-stage pyrite-III is anhedral and coarse grained and contains randomly oriented inclusions of silicates, sulfides, and native gold grains. Electron microprobe analysis, coupled with X-ray element mapping and laser ablation-inductively coupled plasma-mass spectrometry, reveals that most early pyrites (pyrite-I) have higher concentrations of As and Au in both the zones. The shear-hosted main-stage pyrite-II can be divided into Ni-rich (median 211 ppm) pyrite-IIa and Co-rich (median 274 ppm) pyrite-IIb, respectively. While invisible gold content is higher in vein-hosted late-stage pyrite (pyrite-IIIa; ≤287 ppm) when compared to shear-hosted pyrites, native visible gold is associated with only vein-hosted main- and late-stage pyrites (pyrite-II and IIIa). Arsenic, Ni, Au, Se, Mo, and Te concentrations decrease from pyrite-I to pyrite-III, reflecting remobilization of trace elements during subsequent dissolution-reprecipitation of early formed pyrites. The oscillatory zoning of As, Co, and Ni and slight increase in Bi, Te, Se, Au, and Ag in pyrite-II and pyrite-IIIa represent pressure fluctuations and repeated local fluid phase separation in the ore-forming environment. A positive correlation of Au with Pb, Sb, Bi, and Te confirms the presence of nanoinclusions of mineral phases such as nagyagite, Pb-Sb-Bi tellurides, Au-Ag tellurides, tellurosulfides, and sulfosalts within pyrites, particularly in the vein-hosted zone. Based on several lines of evidence, the following paragenetic sequence is proposed for pyrite formation at Dona, Jonnagiri. Rapid crystallization of early (porous) pyrite-I was followed by its dissolution during ~E-W–trending Sh1 shearing. Crystallization of main-stage pyrite-II and the late-stage pyrite-IIIa is the product of dissolution-reprecipitation of early pyrite during ~N-S–trending Sh2 shearing. Changing fluid compositions caused by episodic fault-valve actions and associated boiling resulted in dissolution-reprecipitation of early formed pyrites and remobilization of trace elements. This further resulted in precipitation of the bulk of gold within the inner vein-hosted zone during the later Sh2 shearing event. At the culmination of shearing, late-stage pyrite-IIIb precipitation occurs with very low concentrations of all trace elements, including gold.

Ore-forming processes in the Khetri Copper Belt, western India: constraints from trace element chemistry of pyrite and C-O isotope composition of carbonates

The Khetri Copper Belt of the Aravalli-Delhi Fold Belt in western India hosts Cu (± Au ± Ag ± Co ± Fe ± REE ± U) mineralization that is likely of iron oxide-copper-gold (IOCG) type. The study on the Madan-Kudan deposit in this belt documents four vein types: Type-1 (pyrite ± chalcopyrite ± magnetite ± biotite ± scapolite ± amphibole ± chlorite), Type-2 (chalcopyrite-pyrrhotite-pyrite-magnetite-amphibole-chlorite), Type-3 (chalcopyrite-pyrrhotite-pyrite-dolomite-quartz), and Type-4 (chalcopyrite-pyrrhotite-biotite). Pyrite is grouped on texture and major and trace element chemistry into Pyrite-1A, Pyrite-1B, Pyrite-1C (Type-1 veins), Pyrite-2 (Type-2 veins), Pyrite-3A, and Pyrite-3B (Type-3 veins). This sequence documents changing fluid composition and suggests that sulfide mineralization was associated with Na-Ca-K alteration (Type-1 and Type-2 veins), carbonate alteration (Type-3 veins), and K-Fe-Mg alteration (Type-4 veins). The C and O isotope composition of dolomite from Type-3 veins suggests that the ore fluid contained mantle-derived carbon (possibly carbonatite-related) and mixed with an isotopically heavier fluid or exchanged isotopes with crustal rocks. A strong positive correlation between Au and Cu is interpreted to reflect their “coupling” in the pyrite structure. In contrast, Pb, Zn, Bi, and Ag are present in mineral inclusions. Intragrain Fe, Co, As, and Ni variability in pyrite suggests that replacement by coupled dissolution-precipitation and formation of overgrowths were important. Pyrite-1A has high Co (up to 3.3 wt%) and Co/Ni ratios (500 to 16,000) that have not been reported elsewhere. The Co/Ni ratios of KCB pyrite are similar to those from iron oxide-apatite and other IOCG deposits, although the latter do not have a characteristic Co/Ni ratio but consistently have high Co concentrations (up to 1 wt% or more).

Formation and evolution of multistage ore-forming fluids in the Miocene Bangpu porphyry–skarn deposit, Southern Tibet: Insights from LA–ICP–MS trace elements of quartz and fluid inclusions

Abstract The large Bangpu Mo–Cu–Pb–Zn deposit, is a Mo-rich (~0.089%), Cu-poor (~0.32%) porphyry–skarn deposit located in the northeastern Gangdese porphyry copper belt (GPCB), Southern Tibet. In this study, LA–ICP–MS data for fluid inclusions and quartz formed during different stages of the mineralization are used to (1) constrain changes in fluid composition during mineralization; (2) infer the origin, transport pathways, and conditions of ore precipitation; and (3) explore the influence of magma chamber on fluid exsolution and shallow mineralization. The Cu content of the vapor-rich (VL) inclusions is higher than that of the halite-bearing (LVH) inclusions, while the Mo, Pb, and Zn contents of the VL and LVH inclusions are similar, indicating that Mo, Cu, Pb, and Zn had a common source, which is inferred to be the intermediate-level magma chamber. The metal contents of fluid inclusions in the early stage potassic alteration-related vein (A vein) and later stage sericitic alteration-related vein (B vein) are similar but variable, implying the intermediate-level magma chamber was too small to form a large stable fluid system. The enrichment of Mo, Pb, and Zn in the Bangpu deposit relative to other porphyry deposits in the GPCB is related to the participation of ancient crustal material. A comparison of our results with those from super-large porphyry Cu deposits elsewhere indicates that metal-rich fluids are not the sole factor to form ore deposits, and the variability of metal contents in the early exsolved fluids is a better predictor of mineralization potential than absolute metal concentrations.

From Mantle Transition Zone with Microstructures: A New Paradigm in Ophiolite Studies

AbstractThe SE Ladakh (India) area displays one of the best ‐preserved ophiolite sections in this planet, in places up to 10 km thick, along the southern bank of the Indus River. Recently, in situ ultra‐high pressure (UHP) microstructural evidences from mantle transition zone (MTZ ∼ 410–660 km) with diamond and reduced fluids were discovered from two peridotite bodies in the basal mantle part of this Indus ophiolite (Das et al., 2015; 2017). Ultrahigh‐pressure phases were also found by early workers from podiform chromitites of another equivalent Neo–Tethyan ophiolite in southern Tibet (e.g., Yang et al., 2007; Yamamoto et al., 2009). However, the MTZ phases in the Indus ophiolite are found in silicate peridotites not metallic chromitites and the peridotitic UHP phases show systematic and contiguous phase transitions from the MTZ to shallower depth, unlike the discrete ultrahigh‐pressure inclusions, all in Tibetan chromitites. The gradual change in oxygen fugacity (fo2) and fluid composition from (C‐H + H2) to (CO2 + H2O) in the upwelling peridotitic mantle causing melting to produce MORB. At shallow depths (&lt; 100 km) the free water stabilizes into hydrous phases, such as amphiboles and serpentines, capable of storing water and prevent melting (Fig. 1). The results from Indus ophiolite provide unique insights into deep sub‐oceanic mantle processes, and link deep mantle upwelling and MORB genesis (Fig. 1).The tectonic setting of Neo‐Tethyan ophiolites has been a difficult problem since the birth of plate tectonics concept. This problem for the origin of ophiolites in mid‐ocean ridge versus supra subduction‐zone settings clearly confused the Geoscience community. However, Indian Ocean –type isotopic characteristics are present in Neo‐Tethyan ophiolites (Zhang et al., 2005). Recently, continental materials (quartz, k‐feldspar etc.) bearing old zircons (up to 2700 Ma) are also recovered from UHP chromitite of Tibetan ophiolite (Yamamoto et al., 2013). Eventually, the presence of older continental material can produce non‐MORB like basalts in Neo‐Tethyan ophiolites in mid‐oceanic‐ridge following the “historical contingency” model (Moores et al., 2000).

Cyclic zoning in authigenic saddle dolomite-ankerite: Indications of a complex interplay between fault-rupturing and diagenetic alteration

Zoned authigenic minerals reflect temporal changes in fluid composition and can shed light on the dynamic evolution of sedimentary systems. The chemistry of the zoned saddle dolomite-ankerite from the Bohai Bay Basin, China, changes in a cyclic way from core to rim, reflecting a dynamic system perturbated several times from thermodynamic steady-state. The distribution of the dolomite-ankerite close to faults suggests that the cyclic evolution may be related to the faulting. Oxygen isotope ratios, relatively high precipitation temperatures (80–160°C), and association with late-stage pyrite cementation, suggest that dolomite-ankerite formation may be connected to thermochemical sulphate reduction within the hydrocarbon reservoir. The chemical zones alternate between low and high Fe-content, and show evidence of corrosion before each growth stage. The complex relation between the silicate, carbonate, and sulphur/sulphide systems can be explained in terms of open-system diagenesis, where fault rupturing triggers an influx of CO2 and thermogenic H2S. Pyrite scavenges both H2S and Fe, until all H2S is exhausted, and the aqueous Fe then builds up again from slow silicate dissolution. The Fe-content of dolomite-ankerite growth after such a perturbation therefore depends on the rate of Fe-supply from the silicate dissolution, and the length of time between the chemical perturbations. If such a relation exists between time and the coupled mineral reactions, then the Fe-content of the carbonates may provide an indication of the length of time between the fault-triggered chemical perturbations of a system. This must be regarded as a working hypothesis for further detailed studies on the relation between faulting and the silicate-sulphur/sulphide‑carbonate system.

Prograde and retrograde metasomatic reactions in mineralised magnesium-silicate skarn in the Cu-Au Ertsberg East Skarn System, Ertsberg, Papua Province, Indonesia

The 2.7–2.9 Ma Ertsberg East Skarn System (EESS) is a world-class Cu-Au skarn that formed within and adjacent to an intrusion within a paleodepth of 0.5 km and >2.5 km. Its economic mineralisation developed by sustained reaction of magmatic fluid with contact metamorphosed siliciclastic and carbonate rocks at the margin of the adjacent Ertsberg quartz monzodiorite intrusion. Based on high-resolution mineral mapping, chemical analysis and thermodynamic calculations, the multistage formation processes of the exoskarn components of the EESS are examined in the context of changing pressure, temperature, fluid composition and fluid phase. We show that contact metamorphism of dolomitic sediments occurred at 51 ± 5 MPa, between 700 °C and 800 °C and in the presence of a H2O-CO2-fluid containing ~10 to ~70 mol% CO2. This prograde metamorphism formed a forsterite + diopside + calcite + phlogopite + spinel assemblage. Such forsterite-dominated skarns account for ~55 vol% of the EESS exoskarns. Rare pargasite (previously unrecognized in this deposit) formed locally in the metamorphosed carbonate sequence where the protolith was composed of supratidal evaporites with dolomitic carbonate and interlayered calc-silicate rocks. The subsequent flux of a lower pressure magmatic gas containing SO2(g) caused sulphate metasomatism. This high temperature gas alteration of the metamorphic assemblage also caused skarn Cu-Fe-sulphide mineralisation. The influx of a SO2 gas through fracture permeability occurred at a temperature between ~600 and 700 °C and caused calcite to be replaced by anhydrite, with the coupled release of H2S(g). This in-situ release of H2S(g) scavenged trace Cu from the gas phase to deposit Cu-Fe-sulphides, which make the economic value of the distinct. We demonstrate that the formation of metal sulphides within forsterite skarns of the Ertsberg East Skarn System required a minimum flux of ~1,050 Mt SO2(g) and show that volcanic degassing may have occurred over a time span of ~3,900 years. As the system waned, the ambient fluid resulted in partial retrograde serpentinization of olivine and diopside without carbonation, and at temperatures sufficiently high to preserve anhydrite.

Fluid Degradation Measurement Based on a Dual Coil Frequency Response Analysis.

Electrical industry uses oils for cooling and insulation of several machines, such as power transformers. In addition, it uses water for cooling some synchronous generators. To avoid malfunctions in these assets, fluid quality should be preserved. To contribute to this aim, a sensor that detects changes in fluid composition is presented. The designed sensor is like a single-phase transformer whose magnetic core is the fluid whose properties will be measured. The response of this device to a frequency sweep is recorded. Through a comparison between any measurement and a reference one corresponding to a healthy state, pollutants presence, such as water in oil or salt in water, can be measured. The performance of the sensor was analyzed through simulation. In addition, a prototype was built and tested measuring water concentration in oil and salt content in water. The correlation between pollutant concentration measured with the sensor and known pollutant concentrations is good.