Halogen Content Research Articles

Combining multivariate statistical analysis to shed light on distribution and interaction of halogens in two economic ports along Red Sea Coast in Egypt

Mabahiss Bay and Safaga Bay are two important ports along the Red Sea coast of Egypt. The present study is the first to monitor halogen concentrations in these two ports. Certain halogens (F, Cl, Br and I) in coastal waters and sediments exhibited different behaviors. Fluoride (1.92–8.31 mg/L and 0.34–1.24 mg/g), chloride (20.76–22.68 g/L and 0.38–8.31 mg/g), bromide (95.90–151.84 mg/l and 6.66–50.61 mg/g), and iodide (2.77–39.19 μg/L and 1.71–3.76 μg/g) appeared in the seawater and sediments of Mabahiss Bay, respectively. In Safaga Bay, F, Cl, Br and I yielded ranges of (1.80–10.15 mg/L and 0.14–0.74 mg/g), (21.47–22.57 g/L and 0.68–1.42 mg/g), (15.98–146.51 mg/L and 6.13–74.59 mg/g) in seawater and sediments, respectively. In Mabashis Bay exclusively, the bromide and iodide levels in seawater increased significantly, and the sediments were vice versa. The average fluoride value in the two ports' seawater was higher than that in the unpolluted Mediterranean Sea. In contrast, the average bromide content in Mabahiss Bay seawater exceeded the Mediterranean Sea level. The seawater chloride content of the two ports was within the Mediterranean seawater's value, but the iodide concentration was lower than that of the unpolluted seawater. The application of different multivariate statistical techniques showed that halogen's distribution and halogen's geochemical characteristics control interaction in each region, ground flux, and proximity to human sources.

Halogen Enrichment of Siberian Traps Magmas During Interaction With Evaporites

Volatile emissions to the atmosphere associated with the Siberian Traps eruptions at the Permian-Triassic boundary were sourced from the outgassing of primary magmas and the sedimentary host rocks into which they were intruded. Halogens in volcanic gases may have played an important role in environmental degradation and in stratospheric ozone destruction. Here we investigate how halogens behave during the interaction between salts and basalt magma emplaced as sills and erupted as lava. We present whole-rock, trace, and halogen concentrations for a suite of samples from three locations in the Siberian Traps Large Igneous Province, including basalt lavas erupted, and dolerites intruded into both organic-bearing shales and evaporites. Dolerites are enriched in Cl, Br, and I; their enrichment in Cl is similar to MORB and OIB that have been inferred to have assimilated seawater. The dolerites exhibit halogen compositional systematics, which extend towards both evaporites and crustal brines. Furthermore, all analyzed samples show enrichment in Rb/Nb; with the dolerites also showing enrichment in Cl/K similar to MORB and OIB that have been inferred to have assimilated seawater. We infer that samples from all three locations have assimilated fluids derived from evaporites, which are components of crustal sedimentary rocks. We show that up to 89% of the chlorine in the dolerites may have been assimilated as a consequence of the contact metamorphism of evaporites. We show, by thermal modeling, that halogen transfer may occur via assimilation of a brine phase derived from heating evaporites. Halogen assimilation from subcropping evaporites may be pervasive in the Siberian Traps Large Igneous Province and is expected to have enhanced emissions of Cl and Br into the atmosphere from both intrusive and extrusive magmatism.

Lead-free Cs2SnX6 (X = Cl, Br, I) nanocrystals in mesoporous SiO2 with more stable emission from VIS to NIR light

Lead-free double-perovskite Cs2SnX6 (X = Cl, Br, I) containing Sn4+ is a more stable lead-free photovoltaic material than its homologue CsSnX3. However, its stability in air still affects its application. In this Letter, lead-free inorganic Cs2SnX6 (X = Cl, Br, I) nanocrystals (NCs) were synthesized by a hot injection method and in-situ loaded into mesoporous SiO2. With the change of halogen content, the PL emission peak of pristine Cs2SnX6 NCs were tuned from 430 nm to 780 nm covering the visible and near infrared spectrum region. Taking Cs2SnI6/SiO2 NCs as an example, the optical property stability in solution is obviously improved, and it can be stored in air for over 2 h. Especially, the more stable NIR emission, non-toxicity and easy hydrolysis characteristics of Cs2SnX6/SiO2 composite nanoparticles will have potential medical applications like photothermal and photodynamic therapies for cancers.

Revealing phase evolution mechanism for stabilizing formamidinium-based lead halide perovskites by a key intermediate phase

Revealing phase evolution mechanism for stabilizing formamidinium-based lead halide perovskites by a key intermediate phase

Determination of halogens in geological reference materials using neutron irradiation noble gas mass spectrometry

We determined the heavy halogen (Cl, Br, and I) concentrations of fourteen powdered geological reference materials distributed by the Geological Survey of Japan (GSJ) and the US Geological Survey, and seven original blocks of GSJ geological reference materials, using neutron irradiation noble gas mass spectrometry (NI-NGMS). The halogen concentrations obtained from the powder and original blocks of geological reference materials are systematically lower than their reference values for low-concentration samples. This discrepancy can be explained by contamination on the sample surface during the preparation of the reference materials. Contaminated halogen-derived noble gases were, at least partially, removed before analysis during preheating of the samples under vacuum after sample loading. The presence of the contaminated component in the reference materials is not a matter for other analytical methods as long as the contaminated component is completely homogenized in the powder reference materials and not removed before analysis. However, the present results indicate that the standard materials used in NI-NGMS should be selected more carefully than those used in other methods. In addition, we propose an F-determination method using NI-NGMS based on Ne systematics of neutron-irradiated samples.

Ultrasound-enhanced coagulation for Microcystis aeruginosa removal and disinfection by-product control during subsequent chlorination

Ultrasound techniques have gained increased interest in environmental remediation because of their promising performance and reagent-free nature. This study investigated the effects of ultrasound-coagulation on Microcystis aeruginosa removal, disinfection by-product (DBP) formation during subsequent chlorination, and acute toxicity and DBP-associated toxicity variations in chlorinated effluents. Compared with coagulation using polymeric aluminum chloride (5 mg-Al/L) alone, ultrasound-coagulation showed significantly enhanced turbidity removal, with the removal ratio increasing from 51% to 87%–96%. Although the addition of ultrasound may not substantially improve and even deteriorate the coagulation removal of DOC following the leakage of intracellular organic matter, the significantly improved DBP control was achieved as the cells dominated DBP formation. With the addition of ultrasound, the chlorine demand, aggregate DBP concentration and total organic halogen concentration reductions in the chlorinated M. aeruginosa solution increased from 15%, 47% and 52% (coagulation alone), respectively, to 56%–78%, 56%–80% and 68%–89%. The enhanced DBP mitigation was mainly attributed to the enhanced algal removal. Similarly, the acute toxicity and DBP-associated toxicity of chlorinated effluents further decreased from 100% and 0.0092 (coagulation alone) to 30%–88% and 0.0029–0.0060. Therefore, ultrasound-enhanced coagulation is a promising strategy for urgent algal removal, DBP mitigation and toxicity abatement.

Halogen (F, Cl, Br, I) contents in silt and clay fractions of a Cambisol from a temperate forest

AbstractIn spite of considerable efforts to understand the role of halogens (F, Cl, Br, I) in soil, concentration data for different soil size fractions is still sparse and information on the sorption behavior of halogens in natural soils is limited. We determined total halogen concentrations in different soil horizons and particle size fractions (i.e., coarse silt with 20–63 µm, medium and fine silt with 2–20 µm, coarse clay with 0.2 to <2 µm and medium clay with 0.02–0.2 µm) of a Cambisol from a temperate forest ecosystem in SW Germany. Furthermore, we estimated the minimum proportions of sorbed halogens onto clay minerals and pedogenic oxides for different soil horizons and different particle size fractions.Vertical depth profiles of halogens in the individual soil particle size fractions matched with the bulk soil vertical patterns. The lack of vertical differences of total halogens concentrations (Ftot, Brtot, and Itot) in the mineral soil during soil development may be due to steady state or equilibrium conditions between weathering, sorption processes, and surface input. In contrast, the vertical depth pattern of Cltot tended to decrease, suggesting the process of Cl accumulation in the topsoil and nutrient uplift. While F was likely mainly incorporated into the crystal lattice of clay minerals and gibbsite occupying OH-sites, significant amounts of the halogens with larger ionic radii (Cl, Br, and I) were sorbed. The largest amounts (around 90% Cl and 70% Br and I, respectively) were sorbed on the smallest particle size fraction investigated (medium clay fraction; 0.02–0.2 µm), although this fraction only contributed about 1 wt% to the bulk soil. This is probably related to the highest sorption capacity of small particles due to their large surface area.Our study provides new data on sorption behavior of the various halogens in soils of forest ecosystems, which is different between F and the heavier halogens (Cl, Br, I) and further depends on soil particle sizes. The understanding of the chemical behavior of halogens in soils has implications for the retention processes of pollutants in landfills or radioactive waste disposal.

Petrological and geochemical constraints on the origin of apatite ores from Mesozoic alkaline intrusive complexes, Central High-Atlas, Morocco

Five main apatite deposits from the Moroccan Central High-Atlas —including Anemzi, Tirrhist-Inouzane, Tassent, Ait-Daoud-Toumliline and Tasraft— have been investigated through integrated field, petrographic, mineralogical, and geochemical studies. The apatite ore occurs as veins, few mm to several cm thick, spatially associated with syenite-quartz monzonite (dominant) to monzodiorite-gabbrodiorite bodies emplaced during the Atlas Jurassic-Cretaceous alkaline magmatic event. Gem-quality apatite crystals, up to 15 cm in size, are associated with albite, clinopyroxene (hedenbergite–augite–diopside), amphibole (hornblende–edenite–actinolite), K-feldspar, quartz, magnetite, titanite, epidote, prehnite, and calcite. Two types of apatite have been distinguished according to their halogen contents: F-rich and Cl-rich apatites. Both types are enriched in REE (up to 2 wt% ΣREE), and have major and trace element contents consistent with a magmatic origin, corroborated by the chemical similarity with accessory apatite in the host alkaline intrusions, as well as with other reference igneous apatites. However, hydrothermal fluids percolating through country sedimentary rocks were also involved, as indicated by the striking Na enrichment observed in the Cl-rich apatites, likely inherited from Triassic evaporites, showing close spatial relationships with the alkaline intrusions. These fluids would also account for pervasive Na-metasomatism of alkaline magmatic rocks, as observed in the wall rocks of the apatite veins.

Chemical Recycling of WEEE Plastics—Production of High Purity Monocyclic Aromatic Chemicals

More than 200 kg real waste electrical and electronic equipment (WEEE) shredder residues from a German dismantling plant were treated at 650 °C in a demonstration scale thermochemical conversion plant. The focus within this work was the generation, purification, and analysis of pyrolysis oil. Subsequent filtration and fractional distillation were combined to yield basic chemicals in high purity. By means of fractional distillation, pure monocyclic aromatic fractions containing benzene, toluene, ethylbenzene, and xylene (BTEX aromatics) as well as styrene and α-methyl styrene were isolated for chemical recycling. Mass balances were determined, and gas chromatography–mass spectrometry (GC-MS) as well as energy dispersive X-ray fluorescence (EDXRF) measurements provided data on the purity and halogen content of each fraction. This work shows that thermochemical conversion and the subsequent refining by fractional distillation is capable of recycling WEEE shredder residues, producing pure BTEX and other monocyclic aromatic fractions. A significant decrease of halogen content (up to 99%) was achieved with the applied methods.

Halogen (F, Cl) Concentrations and Sr‐Nd‐Pb‐B Isotopes of the Basaltic Andesites From the Southern Okinawa Trough: Implications for the Recycling of Subducted Serpentinites

AbstractSerpentinites are increasingly recognized as playing an important role in the global geochemical cycle. However, discriminating the contributions of serpentinites to arc magmas from those of other subduction components is challenging. The Okinawa Trough is a back‐arc basin developed behind the Ryukyu subduction zone, where magmas are extensively affected by sediment subduction. In this study, we reported the F‐Cl concentrations and Sr‐Nd‐Pb‐B isotopes of basaltic andesites from the Yaeyama Graben, Yonaguni Graben, and Irabu Knoll in the southern Okinawa Trough. The Irabu Knoll lavas show the most enrichment of fluid‐mobile elements and F ± Cl, and have the heaviest B isotopes (δ11B: +6.6 ± 1.5‰). They also have decoupled Sr‐Nd isotopes: higher 87Sr/86Sr (∼0.7049) but have no obvious decrease of 143Nd/144Nd (∼0.5128). Results from slab dehydration modeling and mixing calculations suggest that the heavy δ11B in the Irabu Knoll lavas is not consistent with fluids derived from altered oceanic crust (AOC), sediments, or wedge serpentinites (formed in the mantle wedge), but rather from slab serpentinites (formed within the subducting plate); sediments control the subduction input of Nd, whereas the decoupled Sr‐Nd isotopes are most likely due to the excess radiogenic Sr carried by AOC fluids. Our results imply that recycling of serpentinite fluids and AOC fluids are usually coupled in subduction zones, as the arc lavas influenced by subducted serpentinite generally show Sr‐Nd isotopes decoupling. The large variation of Sr‐Nd‐B isotopes observed in a relatively localized area is consistent with a focused migration through the mantle wedge of components from multiple sources.

Halogen Bearing Amphiboles, Aqueous Fluids, and Melts in Subduction Zones: Insights on Halogen Cycle From Electrical Conductivity

AbstractAmphiboles are hydrous minerals that are formed in the oceanic crust via hydrothermal alteration. The partial substitution of halogens for OH− makes amphibole one of the principal hosts of Cl and F in the subducting slab. In this study, we investigated the electrical conductivity of a suite of halogen bearing amphibole minerals at 1.5 GPa up to 1,400 K. The discontinuous electrical behavior indicates dehydration of amphibole at ∼915 K. This is followed by dehydration induced hydrous melting at temperatures above 1,070 K. We find that the released aqueous fluids have an electrical conductivity of ∼0.1 S/m. This high electrical conductivity is likely to explain anomalously high electrical conductivity observed in certain subduction zone settings. This high electrical conductivity of an order of magnitude greater than the electrical conductivity of pure aqueous fluids at similar conditions is likely due to the partitioning of the F and Cl into the aqueous fluids. We also noted that subsequent to the dehydration, secondary phases form due to the breakdown of the primary halogen bearing amphibole. Chemical analyses of these secondary phases indicate that they are repositories of F and Cl. Hence, we infer that upon dehydration of the primary halogen bearing amphibole, first the F and Cl are partitioned into the aqueous fluids and then the halogens are partitioned back to the secondary mineral phases. These secondary minerals are likely to transport the halogen to the deep Earth and may in part explain the halogen concentration observed in ocean island basalt.

Microwave-based strategies for sample preparation and halogen determination in blood using ICP-MS

In this work, two microwave-assisted sample preparation methods based on combustion and ultraviolet digestion for futher determination of Br, Cl, and I in blood by inductively coupled plasma mass spectrometry were proposed. For microwave-induced combustion (MIC), blood was spotted on square pieces of Munktell TFN paper, and water and diluted NH4OH were evaluated as absorbing solutions. The stability of the analytes in the spotted blood was also evaluated. During 90 days, no changes of halogen content were observed for samples (with and without anticoagulant) on paper stored in a desiccator at 20 ± 5 °C. Whole blood was also digested by microwave-assisted ultraviolet digestion (MAD-UV). Some parameters as the volume of HNO3 solution, the influence of H2O2, and the effect of UV radiation were investigated. The interferences caused by C and K on halogen determination were carefully investigated. The results for MIC and MAD-UV and Br, Cl and I determination by ICP-MS presented no difference. The accuracy of MIC and MAD-UV was also evaluated by analyte spike with reference solutions of Br, Cl and I using inorganic species and also organic I standard (T4-levothyroxine). For both methods, recoveries were 94 and 108% for Br, 96 and 103% for Cl, and 104 and 97% for I. In case of organic I, recoveries were 99 and 111% for MIC and MAD-UV, respectively. The limits of quantification for MIC and MAD-UV after ICP-MS determination were 0.06 and 0.04 μg g−1 for Br, 14 and 30 μg g−1 for Cl and 12 and 8 ng g−1 for I, respectively. The proposed methods provide a suitable digestion approach, assuring safety and high digestion efficiency for further halogen determination in blood, with the possibility to use in clinical analysis.

Halogen content relative to the chemical and biochemical composition of fifteen marine macro and micro algae: nutritional value, energy supply, antioxidant potency, and health risk assessment.

Marine algae have made a strong contribution to global food security in the future. This study is the first report describing the concentration, pathways, and interactions of halogens in 15 species of marine algae collected from the Eastern Harbor in Alexandria, Egypt, relative to 22 key variables. The relationship between halogen content and chemical and biochemical parameters was studied through multivariate analysis. Among all the tested algae, the iodine content was the lowest (2.53-3.00μg/g). The range of fluoride and chloride in macroalgae (1.12-1.70 and 0.10-0.46mg/g) was smaller than that of microalgae (0.10-0.46 and 1.48-3.17mg/g). The bromide content in macroalgae (0.36-5.45mg/g) was higher than that in microalgae (0.40-0.76mg/g). The halogen content in macroalgae was arranged in the order of Br > F > Cl > I. In addition, the biochemical parameters such as carbohydrates, proteins, lipids, and certain heavy metals (Fe, Zn, Cu, Mn, Pb, Ni, Co, Cd, and Cr) were determined. Calories, energy, total antioxidant activity (TAC), K/Na, and ion quotient amounts were estimated. The results showed that the green seaweed species had the highest TAC content. In most of the studied algal species, the calculated ion quotient referred to their likelihood of overcoming high blood pressure. The estimated daily intake (EDI) of algae showed no adverse effects on human health. Most of the research variables are below the acceptable WHO/FAO level. Generally, the calorie content of the selected algae is less than 2kcal, which makes the algae considered an alternative source of healthy food to reduce obesity.Graphical abstract.

Changes in Halogen (F, Cl, Br, and I) and S Ratios in Rock-Forming Minerals as Monitors for Magmatic Differentiation, Volatile-Loss, and Hydrothermal Overprint: The Case for Peralkaline Systems

We determined the halogen (F, Cl, Br, and I) and sulfur (S) concentrations in Cl-rich rock-forming minerals from five peralkaline complexes. We investigated sodalite (N = 42), eudialyte-group minerals (N = 84), and tugtupite (N = 8) from representative rock samples derived from Ilímaussaq (South Greenland), Norra Kärr (Sweden), Tamazeght (Morocco), Lovozero, and Khibina (Russian Federation). Taken together, sodalite and eudialyte-group minerals dominate the Cl and Br budget of the investigated rocks. For F, however, several other phases (e.g., amphibole, fluorite, villiaumite, and minerals of the rinkite group and the apatite supergroup) are additional sinks, and parts of the S may be scavenged in generally rare sulfides. The investigated minerals contain Cl at the wt.% level, F and S concentrations are in the hundreds to thousands of µg/g-range, Br is less common (0.2–200 µg/g) and I is rare (mostly well below 1 µg/g). Normalized to Cl, sodalite prefers Br relative to eudialyte-group minerals, while F is always enriched in the latter. Our data show that both F and S may represent important components in eudialyte-group minerals, sometimes at similar levels as Cl, which normally dominates. Sulfur reveals redox-dependent behavior: Under reduced crystallization conditions, S is more compatible in eudialyte-group minerals (EGM) than in sodalite, which flips to the opposite under water-rich and presumably more oxidized conditions. We investigate the applicability of F/Cl, Br/Cl, and S/Cl ratios in these minerals in peralkaline systems to better understand the interplay of magmatic differentiation, fluid loss and hydrothermal overprint. Similar to apatite in metaluminous systems, fractionation of sodalite, and eudialyte-group minerals in peralkaline magmas leads to decreasing Br/Cl ratios. The data presented in this study bear implications for the mineral chemistry and compositional variation of sodalite and especially EGM in general. Volatile components in EGM that are not normally considered, such as F and S, can reach concentrations of thousands of µg/g. Especially in the case of F, with its low atomic weight, the results obtained in this study indicate that it is very significant for formulae calculations, neutral charge-balance, and similar aspects at such concentration levels. This study demonstrates that halogen contents and ratios are sensitive monitors for a variety of processes in magmatic-hydrothermal systems, including magmatic fractionation, volatile loss, and fluid–rock interaction.

Influence of Halogen Ions on Electrical, Magnetic and Shielding Properties of Some B2O3- V2O5- Na2O Glasses

Some sodium boro-vanadate glasses containing various halogen ions (chlorine, bromine and iodine) were prepared. These glasses were characterized by measuring the experimental densities, dc conductivities and volume-magnetic susceptibilities. Then the empirical densities, experimental and empirical molar volume values, electrical activation energies, mass- and molar-magnetic susceptibilities as well as the total mass attenuation coefficients of all glasses were calculated. The gradual increase in halogen ions act to decrease experimental density from 2.45 to 2.13 g/cm3, while it acts to increase the molar volume. It was found that, the activation energy decreased around 0.3 eV as the halogen content was increased, it decreased also ongoing from chlorine to iodine that can be ascribed to the differences in ionic radii of halogen ions, and this was confirmed by the molar volume. It was supposed that the increase in the paramagnetic character of the studied glasses with the increase of halogen content may be due to the formation of VXO3 groups. Also, the magnetic properties were found to increase as the ionic radius of the introduced halogen ions increased, and this can be attributed to the increase in the internal vacancies through the network. Correlations were established between both the activation energy and molar susceptibility with molar volume. According to the results of the mass attenuation coefficients, it was found that, the sample contains 25 mol% NaI is the best one that can be used as -ray attenuator, but only at gamma-ray energies up to 356 keV.

Constraining the presence of amphibole and mica in metasomatized mantle sources through halogen partitioning experiments

We present experimentally determined partition coefficients (Dmin/melt) for F and Cl between pargasite (amphibole), phlogopite (mica), clinopyroxene and basanitic melts. All experiments were performed at 1.4 GPa and temperatures between 1015 °C and 1250 °C to simulate fractionation of halogens during melting of metasomatized mantle. The water content of all starting materials was 16 wt% to promote crystallization of amphibole and mica. The halogen content of all starting mixtures was 0.45 wt% for F and 0.61 wt% for Cl. Our data show that F is compatible (D > 1) in pargasite and phlogopite, while Cl is strongly incompatible (D < 0.1) in both phases.The experimentally derived partition coefficients allow to quantitatively constrain the amounts of mica- and amphibole in metasomatized spinel-lherzolite sources from the observed halogen and rare earth element contents in derivative melts. Calculated F/Cl and F/Nd values of melts from different mantle sources, ranging from depleted to fertile and metasomatized mantle, are compared to those of melt inclusions from basalts from mid ocean ridges, ocean islands, and arc and intra-plate continental settings. Our results suggest that, depending on the tectonic setting, F/Cl and F/Nd of melt inclusions can be used to determine the presence and the amount of amphibole and mica in different mantle sources, and thus allow distinguishing between melting of nominally anhydrous and volatile-rich mantle sources.

SYNTHESIS OF AZIDOCELLULOSE NITRATES

A synthesis method of azidocellulose nitrate by chemical interaction between cellulose nitrates or chlorocellulose nitrates with various degree of chlorination with sodium azide in a medium of dimethylsulfoxide and with heating in the temperature range 40–70 °C is proposed. The chemical composition, structure and properties of the obtained compounds are determined on the basis of combination of physico-chemical methods of analysis: IR, 1H NMR and 13C NMR spectroscopy; elemental analysis; gel permeation chromatography; viscometry; thermogravimetric analysis; differential scanning calorimetry; thermal polarization microscopy. The main directions of the chemical interaction between polymers and sodium azide were predicted by quantum-chemical methods using the Gaussian 09 software. The reaction mechanism was confirmed by a mathematical model of kinetics. The scheme of the preferred simultaneously going reaction directions has been composed, which includes substitution of nitrate groups by the azide fragment; rupture of polymer chains by β-glycosidic bond leading to depolymerization; opening of the glucopyranose cycle with addition of the azidogroup to the formed free bonds. Use of the chlorocellulose nitrate for the azidation allows to get products with a higher degree of substitution by azidogroups, and the rate of azidation of chlorocellulose nitrate depends on halogen content directly.

Late-stage fluid exsolution and fluid phase separation processes in granitic pegmatites: Insights from fluid inclusion studies of the Luumäki gem beryl pegmatite (SE Finland)

The fluid inclusion record of the miarolitic gem beryl-bearing Luumäki pegmatite (SE Finland) has been studied by petrography, microthermometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Four types of fluid inclusion assemblages could be distinguished, which record the nature and timing of fluids exsolved in the pegmatite. Type I and type II fluid inclusions are two-phase (LV) aqueous with intermediate salinities of 8.0 ± 2.7 and 8.1 ± 0.9 wt% NaCl, respectively. Type I fluids occur at the transition between the quartz core and euhedral smoky quartz crystals formed in miarolitic cavities. Type II inclusions are present throughout smoky quartz and gem beryl crystals in miarolitic cavities. Type III are three-phase (LLV), low-salinity (1.2 ± 1.1 wt% NaCl), aqueous‑carbonic inclusions, whereas type IV are three-phase (LVS) aqueous inclusions with halite daughter crystals and high salinity (39.6 ± 4.5 wt% NaCl equiv.). Both type III and type IV inclusions occur texturally late in the smoky quartz crystals and are closely related to each other, sometimes coexisting on the same inclusion trail. The chemical data show that type I, type III and type IV inclusions lie on linear trends in many elemental variation diagrams, where type I inclusions plot between the data for type III and type IV inclusions. The saline type IV inclusions are strongly enriched in many elements, such as alkalis, alkaline earths and transition metals, whereas the aqueous‑carbonic type III inclusions are depleted in these metals. The chemical data, in conjunction with petrographic features, demonstrate that type III and type IV inclusions were formed by phase separation of the type I intermediate-salinity fluid. The metal and halogen content of all four fluid types suggests that they are of magmatic-hydrothermal origin and supports the model that the Luumäki pegmatite reached fluid saturation at the transition between core quartz crystallization and formation of miarolitic cavities. Representative fluid inclusion isochores calculated for type II fluids preserved in gem beryl, in conjunction with the P-T slope constructed from the water content in beryl, yield a best P-T estimate for pocket formation of 380 ± 80 °C and 1.2 ± 0.7 kbar. This P-T estimate constrains the range of pressure-depth conditions proposed for the rapakivi granites that host the Luumäki pegmatite, and is consistent with recent estimates suggesting a maximum pressure of emplacement of 1.9 kbar.

The Cl isotope composition and halogen contents of Apollo-return samples

Lunar mare basalts are depleted in F and Cl by approximately an order of magnitude relative to mid-ocean ridge basalts and contain two Cl-bearing components with elevated isotopic compositions relative to the bulk-Earth value of ∼0‰. The first is a water-soluble chloride constituting 65 ± 10% of total Cl with δ37Cl values averaging 3.0 ± 4.3‰. The second is structurally bound chloride with δ37Cl values averaging 7.3 ± 3.5‰. These high and distinctly different isotopic values are inconsistent with equilibrium fractionation processes and instead suggest early and extensive degassing of an isotopically light vapor. No relationship is observed between F/Cl ratios and δ37Cl values, which suggests that lunar halogen depletion largely resulted from the Moon-forming Giant Impact. The δ37Cl values of apatite are generally higher than the structurally bound Cl, and ubiquitously higher than the calculated bulk δ37Cl values of 4.1 ± 4.0‰. The apatite grains are not representative of the bulk rock, and instead record localized degassing during the final stages of lunar magma ocean (LMO) or later melt crystallization. The large variability in the δ37Cl values of apatite within individual thin sections further supports this conclusion. While urKREEP (primeval KREEP [potassium/rare-earth elements/phosphorus]) has been proposed to be the source of the Moon's high Cl isotope values, the ferroan anorthosites (FANs) have the highest δ37Cl values and have a positive correlation with Cl content, and yet do not contain apatite, nor evidence of a KREEP component. The high δ37Cl values in this lithology are explained by the incorporation of a >30‰ HCl vapor from a highly evolved LMO.

Young and Old Granulites: A Volatile Connection

Granulite facies metamorphism of the lower crust has decreased in scale since the Late Archean, but many of its definitive features have persisted: (1) Punctuated, sometimes relatively short-lived, episodes of high-grade metamorphism. These are recorded, in favorably simple cases, by discrete growth rims on zircons. (2) A consistent age gap of a few to several tens of millions of years between juvenile magmatism (crustal accretion) and high-temperature metamorphism. The secondary thermal pulse is an event distinct from primary crustal accretion. (3) Involvement of mineralizing pore fluids of lowered H2O activity, that is, with high CO2 and saline concentrations. Very high oxidation states of some granulites implicate sulfur as an important fluid component. (4) Transcurrent faulting as a conspicuous feature of synmetamorphic deformation. This gives rise to characteristic transposed foliation and lineation. (5) Emplacement of coeval postorogenic K-rich granites at midcrust levels. These features can be rationalized by concepts of modern plate tectonics. High-angle plate collision is succeeded by orogen-parallel transport. This change of plate motion necessarily detaches the underthrust portion of the lithosphere, liberating asthenospheric melts and/or fluids in a postorogenic resurgence. A generation of volatile-rich mafic magmas invades the continental margin; high CO2 and halogen contents cause outgassing and freezing of the magmas at depth. Liberated volatiles effect granulite facies metamorphism by leaching H2O and lithophile elements, importantly K, and transporting these components and heat upward. Extensive melting of the lower crust is inhibited by the low H2O activity of saline-carbonic pore fluids at high pressure. Melting of orthogneiss and supracrustal rocks occurs at midcrust levels by increase of H2O activity as pressure on alkali chloride solutions falls below 0.6–0.5 GPa. The foregoing hypothesis is an alternative to the classical view that granite results from fluid-absent partial melting of, and extraction from, the lower crust, leaving granulites.