Volatile Enrichment Research Articles

Dielectric properties of Asteroid Vesta’s surface as constrained by Dawn VIR observations

Earth and orbital-based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid’s surfaces are defined, one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith—employing an analogy to the dielectric properties of lunar soil, and adjusted for the surface densities and temperatures deduced from Dawn’s Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the real part of the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.3 to 2.5 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diurnal temperature, ranging from 6×10−3 to 8×10−3. We estimate the surface porosity to be ∼55% in the upper meter of the regolith, as derived from VIR observations. This is ∼12% higher than previous estimation of porosity derived from previous Earth-based X- and S-band radar observation. We suggest that the radar backscattering properties of asteroid Vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the X- and S-band.

Basalt volatile fluctuations during continental rifting: An example from the Rio Grande Rift, USA

AbstractHydration and metasomatism of the lithospheric mantle potentially influences both the magmatic and tectonic evolution of southwestern North America. Prior studies have suggested that volatile enrichments to the mantle underlying western North America resulted from shallow subduction of the Farallon Plate during the Laramide (∼74–40 Ma). This study examines temporal and spatial variations in volatile elements (H2O, Cl, F, and S) determined from olivine and orthopyroxene‐hosted melt inclusions along and across the Rio Grande Rift, the easternmost extent of Laramide shallow subduction. Maximum chlorine enrichments are observed in the southern rift with a Cl/Nb of ∼210 and reduce with time to MORB‐OIB levels (∼5–17). Measured water abundances are <0.8 wt % in rehomogenized inclusions; however, calculated H2O, based on Cl/Nb systematics, primarily varies from 0.5 to 2 wt % H2O. Sulfur abundances (<0.61 wt %), and calculated sulfide saturation, indicate magmas with high Cl/Nb also contain oxidized sulfur. The abundance of fluorine in melt inclusions (up to 0.2 wt %) is not correlated to other volatile elements. Temporal variations in melt inclusion volatile abundances coupled with varying isotopic (Sr‐Nd‐Pb) whole‐rock systematics suggest a transition from lithospheric to asthenospheric melt generation in the southern RGR and potential lithosphere‐asthenosphere melt mixing in the central RGR. East to west decrease in volatile enrichment likely reflects a combination of varying mantle sources and early removal of metasomatized lithospheric mantle underlying regional extension. Results indicate, from multiple causes, subduction‐related volatile enrichment to the lithospheric mantle is ephemeral, and strong enrichments in volatiles are not preserved in active magmatic‐tectonic provenances.

Organic building block based microporous network SNW-1 coating fabricated by multilayer interbridging strategy for efficient enrichment of trace volatiles.

Microporous organic polymers (MOPs) are an emerging class of functional porous materials for diverse potential applications. Typically, tailored microporous structures of MOPs are generated by linkages of organic polymerizable monomer building blocks, providing high permanent porosity and excellent stability. Herein, we reported the first example of the application of organic building block based MOPs (OBB-MOPs) as efficient enrichment media for sample preparation. A novel multilayer interbridging strategy was proposed to fabricate OBB-MOP coatings, and hereby SNW-1 (a kind of OBB-MOPs) was coated on silica substrate with well-controlled thickness. Strong covalent bonds throughout the network and interlayer bridging improved the durability of the coating significantly. Outstanding chemical stability was observed in diverse solvents as well as solutions with a wide range of pH or high ionic strength and even under extremely harsh conditions like boiling water. The SNW-1 coating possessed a microporous network structure constructed of conjugated and nitrogen-rich building blocks. Thus, the coating exhibited a superior enrichment performance of polycyclic aromatic hydrocarbons and volatile fatty acids (VFAs) over commercial coatings based on interactions including π-π affinity and acid-base interaction. For further application, this coating was combined with gas chromatography/mass spectrometry for the noninvasive analysis of VFAs from tea leaf and tobacco shred samples. The low detection limits of 0.014-0.026 μg/L were achieved with the relative standard deviations (RSDs) between 4.3 and 9.0%. Consequently, trace original VFAs from the samples were detected. Good recoveries were obtained in the range of 90-129% and 77-118% with the corresponding RSDs (n = 3) of 2.6-9.3% and 1.9-10%, respectively.

Geochemical features of the quaternary lamproitic lavas of Gaussberg Volcano, East Antarctica: Result of the impact of the Kerguelen plume

Petrological-geochemical data were obtained on the lamproites of the Gaussberg Volcano located at the eastern Antarctic coast and compared with data on the magmatic rocks developed in the East Antarctica and Indian Ocean in relation with the Kerguelen plume. It was shown that the lamproites were derived from the ancient Gondwana lithosphere repeatedly modified at the early stages of its evolution, including significant enrichment in volatiles, lithophile elements, and radiogenic Sr and Pb isotopes.

Contrasting behaviours of CO2, S, H2O and halogens (F, Cl, Br, and I) in enriched-mantle melts from Pitcairn and Society seamounts

In order to improve characterisation of volatiles in the EM1 and EM2 mantle sources, which are interpreted to contain subducted sedimentary or lithospheric components, we report electron microprobe, FTIR and SIMS CO2, H2O, S, F and Cl concentrations of variably enriched glasses from Pitcairn and Society seamounts in Polynesia. The analyses complement previously published Cl, Br and I data for some of the same glasses and all the techniques show reasonable agreement of better than 5–9% for S, Cl and H2O. The concentrations of H2O and all the halogens increase as a function of melt evolution with the highest values of 1.6wt.% H2O, 2100ppm F, 1500ppm Cl, 3.7ppm Br and 80ppb I in melts with <2wt.% MgO. In contrast, CO2 and S are strongly influenced by degassing and it is the least evolved melts that preserve the highest CO2 concentrations, that indicate CO2 oversaturation of some lavas. Comparison of volatile and non-volatile elements of similar compatibility (e.g. H2O/Ce, Cl/K) as a function of equilibration depth and 87Sr/86Sr, suggests H2O and halogens were not significantly degassed from melts equilibrated at >100bars and most of the variation in H2O/Ce reflects source composition. Despite their overall enrichment in volatiles, both the Pitcairn and Society EM1 and EM2 sources are depleted in H2O as well as Cl, Br, and I relative to Ce and K. Slightly different behaviour is suggested for F and a correlation between F/Cl and K/Cl in Pitcairn melts, could be explained by preferential subduction of F relative to Cl into the EM sources. The relative abundances of H2O, halogens and lithophile elements in melts from different tectonic settings indicate subduction-related H2O and Cl loss efficiencies are similar at ~90–96%; F is suggested to have a lower loss efficiency; whereas Br and I are lost more efficiently. Nonetheless, dehydrated lithosphere containing 5–10% of its original volatile content is interpreted as the most likely source of volatile enrichment in the Pitcairn and Society mantle sources.

Determination of volatile components of saffron by optimised ultrasound-assisted extraction in tandem with dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

In the present research, a combined extraction method of ultrasound-assisted extraction (UAE) in conjunction with dispersive liquid–liquid microextraction (DLLME) was applied to isolation and enrichment of saffron volatiles. The extracted components of the saffron were separated and determined by gas chromatography–mass spectrometry (GC–MS) technique. The mixture of methanol/acetonitrile was chosen for the extraction of the compounds and chloroform was used at the preconcentration stage. The important parameters, such as composition of extraction solvent, volume of preconcentration solvent, ultrasonic applying time, and salt concentration were optimised by using a half-fraction factorial central composite design (CCD). Under the optimal conditions, the linear dynamic ranges (LDRs) were 10–10,000mgL−1. The determination coefficients (R2) were from 0.9990 to 0.9997. The limits of detection (LODs) and limits of quantification (LOQs) for the extracted compounds were 6–123mgL−1 and 20–406mgL−1, respectively. The relative standard deviations (RSDs) were 2.48–9.82% (n=3). The enhancement factors (EFs) were 3.6–41.3.

Convection in a volcanic conduit recorded by bubbles

Microtextures of juvenile pyroclasts from Kīlauea’s (Hawai‘i) early A.D. 2008 explosive activity record the velocity and depth of convection within the basaltic magma-filled conduit. We use X-ray microtomography (μXRT) to document the spatial distribution of bubbles. We find small bubbles (radii from 5 μm to 70 μm) in a halo surrounding larger millimeter-size bubbles. This suggests that dissolved water was enriched around the larger bubbles—the opposite of what is expected if bubbles grow as water diffuses into the bubble. Such volatile enrichment implies that the volatiles within the large bubbles were redissolving into the melt as they descended into the conduit by the downward motion of convecting magma within the lava lake. The thickness of the small bubble halo is ∼100–150 μm, consistent with water diffusing into the melt on time scales on the order of 103 s. Eruptions, triggered by rockfall, rapidly exposed this magma to lower pressures, and the haloes of melt with re-dissolved water became sufficiently supersaturated to cause nucleation of the population of smaller bubbles. The required supersaturation pressures are consistent with a depth of a few hundred meters and convection velocities of the order of 0.1 m s−1, similar to the circulation velocity observed on the surface of the Halema‘uma‘u lava lake.

Infiltration of Martian outflow channel floodwaters into lowland cavernous systems

The hydrosphere of Mars has remained mostly concealed within the subsurface for the past ∼3.5 Gyr. Localized rupturing of the permafrost‐capped crust led to voluminous groundwater discharges that carved some of the largest known channels in the solar system. However, our knowledge of the nature of the flows and their ultimate fate remains incomplete, partly because diagnostic landforms at outflow channel termini have been largely destroyed or buried. The Hebrus Valles outflow channels were excavated by fluid discharges that emanated from two point sources, and they mostly terminate in systems of fractures and depressions within the northern plains. Our investigation indicates that outflow channel floodwaters were captured and reabsorbed into the subsurface in zones where caverns developed within the northern plains. These findings imply that the study region comprises the only known location in the Martian northern lowlands where the fate of outflow channel discharges can be assessed with confidence. We propose that evacuation of subsurface materials via mud volcanism was an important process in cavern formation. Our conceptual model provides a hypothesis to account for the fate of sediments and fluids from some of the Martian outflow channels. It also reveals a mechanism for lowland cavern formation and upper crustal volatile enrichment after the development of the Martian global cryosphere.

PLANETESIMAL COMPOSITIONS IN EXOPLANET SYSTEMS

We have used recent surveys of the composition of exoplanet host stars to investigate the expected composition of condensed material in planetesimals formed beyond the snow line in the circumstellar nebulae of these systems. Of the major solid forming elements, we find that, as for the Sun, the C and O abundances (and particularly the C/O abundance ratio) have the most significant effect on the composition of icy planetesimals formed in these systems. The calculations use a self-consistent model for the condensation sequence of volatile ices from the nebula gas after refractory (silicate and metal) phases have condensed. The resultant proportions of refractory phases and ices were calculated for a range of nebular temperature structure and redox conditions. Planetesimals in systems with sub-solar C/O should be water ice-rich, with lower than solar mass fractions of refractory materials, while in super-solar C/O systems planetesimals should have significantly higher fractions of refractories, in some cases having little or no water ice. C-bearing volatile ices and clathrates also become increasingly important with increasing C/O depending on the assumed nebular temperatures. These compositional variations in early condensates in the outer portions of the nebula will be significant for the equivalent of the Kuiper Belt in these systems, icy satellites of giant planets and the enrichment (over stellar values) of volatiles and heavy elements in giant planet atmospheres.

Os diques latíticos portadores de ouro e sulfetos da Associação Shoshonítica de Lavras do Sul – RS: petrogênese e geoquímica

A Associação Shoshonítica de Lavras do Sul (ASLS), situada no extremo sul do Brasil, tem idade neoproterozóica e hospeda ocorrências importantes de Au-Cu-sulfetos, relacionadas por alguns autores a depósitos do tipo Cu-Au pórfiro. Dados de campo, petrográficos, mineralógicos e geoquímicos permitiram identificar e classificar os diques que ocorrem na ASLS cortando os monzonitos hipabissais, andesitos e lamprófiros, em três tipos principais: diques compostos autoclásticos, diques latíticos e diques latíticos com anfibólio. Sua grande variedade litológica e textural é resultado da diferenciação magmática, segregação mineral e processos de mistura de magmas. Os diques mostram afinidade shoshonítica, com teores de K2O &gt; (Na2O –2), acompanhados de conteúdos elevados de Rb, Ba e Sr e baixos a moderados de Nb, Zr e ETRP, assinatura típica da Associação Shoshonítica de Lavras do Sul. Os dados obtidos permitiram identificar dois trends composicionais: um alto-Ti, enriquecido em Fe2O3t, P2O5, HFS, LILE e ETR, com razões K2O/Na2O &lt; 0,8; outro baixo-Ti, que predomina na ASLS, com menores teores dos elementos anteriormente citados e razão K2O/Na2O &gt; 1,4. Os diques alto-Ti, com menores razões K2O/Na2O indicam uma evolução das fontes e processos no sentido da produção de magmas alcalinos saturados em sílica mais sódicos, como é comum na evolução do magmatismo pós-colisional. A cristalização dos magmas e o progressivo enriquecimento dos voláteis e de complexos de Au-S-Cl geraram uma supersaturação do sistema, causando o segundo ponto de ebulição e a vesiculação de porções dos diques. Admite-se que o magma lamprofírico pode ser a fonte principal do ouro e enxofre do sistema. A mistura dos magmas latíticos ou traquíticos com os lamprofíricos, pode ser responsável por um aumento do potencial de oxidação e dos voláteis no sistema, desencadeando assim a separação da fase volátil, a desestabilização dos complexos e a precipitação dos sulfetos magmáticos portadores de Au, além da própria formação das soluções hidrotermais.

Alkaline basalt from the Central Iran, a mark of previously subducted Paleo-Tethys oceanic crust

In western part of the CEIM (Central-East Iranian Microcontinent) (Bayazeh area, Isfahan province, Iran), a series of Paleozoic basaltic rocks, occur. Major minerals of these basalts are olivine, clinopyroxene (diopside, augite), plagioclase (albite), sanidine, amphibole (kaersutite), phlogopite, ilmenite and magnetite. Secondary minerals include epidote, pumpellyite, albite, calcite and chlorite. Olivine and clinopyroxene are as phenocryst, while feldspars are restricted to groundmass. Chemical composition of clinopyroxenes indicates crystallization during ascending of magma. Geochemical analysis of whole rock samples shows that these rocks are characterized by low SiO2 (43.21–48.45 wt %), high TiO2 (1.81–3.00 wt %) and P2O5 (0.18–0.34 wt %). Petrography, chemistry of clinopyroxenes and whole rock analyses reveal an alkaline nature of these basalts. They are enriched in alkalis (Na2O + K2O = 4.1–7.7 wt %), LILE, HFSE and LREE. The Bayazeh alkali-basalts present strong enrichment in LREE relative to HREE (La/Lu ratio = 77.6–119.6) and were dominantly derived from partial melting of a metasomatized asthenospheric garnet-amphibole lherzolite. Field relationships reveal that junction of faults in west of the Bayazeh prepared a suitable path for ascending of magma from deep regions to surface and intra-plate continental magmatism. The Paleo-Tethys subduction from lower to upper Paleozoic is too enough for mantle enrichment in volatiles and basaltic alkaline magmatisrn in upper Paleozoic of Bayazeh area.

Middle Eocene volcanic shoshonites from western margin of Central-East Iranian Microcontinent (CEIM), a mark of previously subducted CEIM-confining oceanic crust

In western margin of the CEIM (Ashin area), Middle Eocene volcanic shoshonites present very good exposures. This shoshonitic association comprises of all shoshonite group members from basic to acidic. Major minerals of basic members (absarokite and shoshonite) are olivine, clinopyroxene (augite), plagioclase (labradorite), K-feldspar (sanidine and anorthoclase), analcime, calcite, apatite, ilmenite and magnetite. Secondary minerals include chlorite, calcite, epidote and zeolite (mesolite). The Ashin shoshonitic rocks consist of SiO2 undersaturated (absarokite or phonotephrite) to SiO2 oversaturated (toscanite or rhyolite) units. The studied rocks are characterized by wide range of SiO2 (48 to 70 wt %), low content of TiO2 (0.35 to 1.17 wt %), and high values of Alkalis [(Na2O + K2O) = 7.03 to 11.4 wt %]. Other main geochemical characteristics of Ashin shoshonites are potassic to ultra-potassic nature (K2O/Na2O = 1.04 to 5.06), high ratios of LREE/HREE (e.g. La/Yb up to 19.16), and enrichment in LILEs. Primitive mantle normalized spidergram of the studied rocks shows positive anomalies of Cs, U, K, Pb, Hf and negative spikes of Nb, Ta, Sm, Ti and Y. All analyzed samples display markedly negative Nb, Ta, and Ti anomalies, typical features of orogenic magmas. These geochemical signatures point out to the subduction—related nature of Ashin shoshonites and their similarity to potassic volcanic rocks of continental arcs or convergent margins. The parental magma of these shoshonites is an alkalibasalt (absarokite) which produced by low-degree of partial melting of a metasomatized enriched mantle source. Petrographical evidences together with geochemical characteristics (e.g., high values of Pb and U) of the studied rocks conclude crustal contamination of magma during ascending throughout the continental crust. The former subduction of CEIM confining ocean from Triassic to Eocene is too enough for volatile enrichment of the mantle and shoshonitic magmatism in middle Eocene of Ashin area.

The composition of the incipient partial melt of garnet peridotite at 3 GPa and the origin of OIB

We determined experimentally the composition of an incipient partial melt of a garnet lherzolite similar to KLB-1 peridotite at 3 GPa using modified iterative sandwich experiments (MISE). The MISE method enables microbeam analyses of quenched liquids that are in equilibrium at the onset of melting (nominally, 0% melt fraction) with a specified peridotite bulk composition. The equilibrium incipient partial melt is a TiO 2-enriched (2.5 ± 0.2 wt.%) alkali olivine basalt with 44.8 ± 0.2 wt.% SiO 2 and 15.8 ± 0.1 wt.% MgO. Therefore, it has some compositional characteristics similar to a plausible parent to many alkalic oceanic island basalts. But in detail, several key components of this melt are different from parental liquids of typical primitive alkalic OIB, including lower FeO* (9.7 ± 0.1 wt.%) and higher Al 2O 3 (12.7 ± 0.2 wt.%). It is also distinct from basalts derived from the EM and HIMU mantle end-members. We conclude that the vast majority of alkalic OIB cannot originate from volatile-poor partial melting of garnet peridotite at the base of the oceanic lithosphere unless there are contributions from non-peridotitic lithologies and/or enrichment in volatiles, iron, or other metasomatic components, and that such lithologic heterogeneities are intrinsic features of the HIMU and EM mantle reservoirs.

Low temperature wort flavour evaporation: A new dimension in evaporation efficiencies

It is shown that the vapour liquid equilibrium of wort flavour components in wort and thus the efficiency of evaporation processes during the production of beer can be influenced by means of changing the evaporation temperature. Here, the enrichment of unwanted volatiles in the vapour is increasing with decreasing temperature. Thus, an evaporation in the cold parts of the brewery brings advantages concerning the needed over-all evaporation and thus the needed energy amount of the brewing process. In combination with a countercurrent guidance of wort and vapour during the evaporation process, a maximum evaporation efficiency can be reached. In order to prove the theory, test trials were performed in a 10 hl scale. In addition, a new procedure was researched, wherein wort is only heated up to moderate temperatures providing an onward evaporation in the cold part of a brewery. Here, additional savings can be reached. Using an evaporation of unwanted flavours in the cold parts of the brewery leads to enormous advantages for each brewery and thus for the whole brewing sector.

Diamonds through Time

Diamonds form in the upper mantle during episodic events and have been transported to the Earth’s surface from at least the Archean to the Phanerozoic. Small diamonds occur as inclusions in robust minerals in tectonically activated, ultrahigh-pressure metamorphosed crustal rock, establishing an association with subduction processes and recycled carbon, but providing no economic deposits. Diamonds in economic deposits are estimated to be mainly (99%) derived from subcontinental lithospheric mantle and rarely (approx. 1%) from the asthenosphere. Harzburgite and eclogite are of roughly equal importance as source rocks, followed by lherzolite and websterite. Diamonds which provide evidence of extensive residence time in the mantle are, with minimal exceptions, smooth-surfaced crystalline diamonds (SCD) with potential commercial value. The oldest prolific SCD formation event documented on the world’s major diamond producing cratons occurs in Archean lithospheric mantle harzburgite, metasomatized by likely subduction-related potassic carbonatitic fluids. Disaggregation of the diamondiferous carbonated peridotite on decompression during volcanic transit gives rise to the association between diamonds, G10 garnets, and diamond inclusion-type chromites, well used in diamond exploration. Within the mantle domains of diamond stability, there have been repeated episodes of further diamond crystallization and/or growth. These are associated with old, often Proterozoic, subduction-related melt generation, metasomatic fluid migration, and reaction with preexisting mantle eclogite, websterite, and peridotite. Using improved methods of isotope analysis, diamond formation ages can be correlated with specific major processes such as craton accretion, craton edge subduction, and magmatic mantle refertilization. Fibrous cuboid diamond and fibrous coats on SCD are rough-surfaced diamonds with abundant fluid inclusions. They have low mantle residence time, forming rapidly from late stage metasomatic fluids in diamond stable domains that may already contain SCD. The symbiotic relationship between formation of fibrous diamond and magmatic sampling and transport of diamonds into the crust suggest that the associated fluids contribute diamond-friendly volatile loading of the deep lithospheric mantle shortly before the triggering of a volcanic eruption, continuing a process of volatile enrichment in the lithospheric mantle already identified in the Archean harzburgite diamond event. Mantle-derived SCD commonly shows evidence of resorption, illustrating that diamond-unfriendly processes, including lamproite and kimberlite generation, are also active and may have a substantial negative effect in extreme cases on SCD crystal size. Exposure of SCD to a long period of changing conditions during mantle residence contributes to the difficulty of assigning specific parageneses and ages to individual inclusion-free diamonds with our current state of knowledge.

Magmatic fluids of Tatun volcanic group, Taiwan

Two distinctive magmatic fluids were recognized in the Tatun volcanic group (TVG), Taiwan. One is a relatively reduced fluid represented by the fumarolic gases at Hsiao-you-ken (HYK) geothermal field. Another is an oxidized fluid containing high concentrations of HCl represented by the fumarolic gases at Da-you-ken (DYK). An intermediate gas was recognized at Gung-tze-ping (GTP) and She-hung-ping (SHP). The fumarolic gases at HYK and GTP possess the features of so-called primary steam generated on mixing of magmatic gas and meteoric groundwater. The fumarolic gases at DYK are a simple mixture between magmatic gas and water vapor of meteoric origin. The CO2/H2O molar ratio of the magmatic component in the fumarolic gases at DYK was estimated to be 0.018, meanwhile it was estimated to be 0.027 for the fumarolic gases at HYK and GTP, suggesting the magma beneath DYK is depleted in volatiles relative to the magma beneath HYK and GTP. The estimated CO2/H2O ratio for the magmatic component is comparable to that of some active volcanoes in Japan, suggesting the enrichment of volatiles in the magmas beneath TVG.

Influence of water on the generation of Strecker aldehydes from dry processed foods

Completeness of extraction, losses during isolation and, in particular, the formation of new constituents are challenges during the enrichment of volatiles for GC analysis. Especially the isolation of volatiles by simultaneous steam distillation/extraction has long been known to generate artifacts due to the hot water treatment. However, even a simple treatment of dry foods with cold water may already lead to the release of odour-active volatiles. After treatment of chocolate or cocoa beans with water, the concentrations of the four Strecker aldehydes 2- and 3-methylbutanal, 3-(methylthio)propanal and phenylacetaldehyde were increased by factors between 10 and 100. Also in other dry processed foods, such as malt or crackers, the concentrations of the Strecker aldehydes were substantially increased upon water addition. Although a physical release of the aldehydes weakly bound to, e.g. proteins or starch is possible, in a further experiment, it could be shown that a yet unknown precursor of 3-(methylthio)propanal and phenylacetaldehyde could be isolated by solvent extraction from caramalt and Munich malt. As a consequence, the presence or absence of water during the work-up procedure might either lead to an over- or underestimation of the relevance of the respective aroma compounds, which might also effect aroma formation and perception during the process of eating.

Late Permian lamprophyric magmatism in North-East of Isfahan Province, Iran: A mark of rifting in the Gondwanaland

Lamprophyric stocks and pillow lavas are situated in Pal-e-Havand area (South-East of Anarak, North-East of Isfahan Province, Iran) along the Turkmeni–Ordib fault. The predominant minerals of these rocks are amphibole (kaersutite), plagioclase (albite), K-feldspar (sanidine), Cr–Ti spinel, ilmenite, and apatite, with minor amounts of magnetite, chlorite, pumpellyite, epidote, sphene, leucoxene and calcite. Textures are porphyritic, microlitic and variolitic, with calcite amygdals. Combined petrological and geochemical studies classify these rocks as alkaline lamprophyre, in general, and camptonites in particular. The rocks studied are enriched in alkalis, TiO 2 and LREE, with SiO 2 content between 40 to 52 weight percent (wt.%). Similar geochemical characteristics of pillow lavas and stocks and parallel chondrite REE patterns of all samples reveal that they were all derived from a similar mantle source region and underwent similar melt extraction. These rocks are intracontinental alkaline lamprophyres, produced by low degree of partial melting of upper mantle garnet lherzolites. The Paleo-Tethys subduction from Lower Paleozoic is the cause of mantle enrichment in volatiles and lamprophyric magmatism in Upper Paleozoic along the Turkmeni–Ordib fault.

Fracture-related hydrothermal alteration of metagranitic rock and associated changes in mineralogy, geochemistry and degree of oxidation: a case study at Forsmark, central Sweden

Red-staining of rocks due to fluid–rock interaction during hydrothermal circulation in fractures is a common feature in crystalline sequences. In this study, red-stained metagranitic rock adjacent to fractures in Forsmark, central Sweden, has been studied with emphasis on the mineral reactions and associated element mobility occurring during the alteration. The main mineral reactions associated with the hydrothermal alteration are an almost complete saussuritization of plagioclase accompanied by total chloritization of biotite. Magnetite has been partly replaced by hematite whereas quartz and K-feldspar were relatively unaffected by the hydrothermal alteration. We show that redistribution of elements on the whole rock scale was very limited and is mainly manifested by enrichment of Na2O and volatiles and depletion of CaO, FeO and SiO2 in the red-stained rock. However, on the microscale, element redistribution was more extensive, with both intragranular and intergranular migration of e.g. Ca, K, Na, Al, Si, Fe, Ba, Cs, Rb, Sr, Ti and REEs. The altered rock shows a shift towards higher total oxidation factors, but the change is smaller than 1σ and the red-staining of the rock is due to hematite dissemination rather than a significant oxidation of the rock. An increase in the connected porosity is also observed in the altered rock.

Evidence for a compositional boundary within the lithospheric mantle beneath the Kalahari craton from S receiver functions

S and P receiver functions from the Southern African Seismic Experiment are analyzed for lithospheric discontinuities beneath the Kalahari craton. Besides the Moho, the most prominent feature is a discontinuous reduction in seismic velocity of about 4.5% at approximately 150 km depth. The discontinuity appears to have a width of about 10 km. Termed the K-discontinuity, this feature is restricted to the northern half of the array, extending from the Zimbabwe craton south to the TML (Thabazimbi–Murchison lineament), and in the west from Botswana to the edge of the Kalahari craton in the east. It spans several Archean sutures and is thus unlikely related to Archean tectonics. It does, however, appear to be related to subsequent magmatic episodes. The strongest anomaly is coincident with the most intense Karoo volcanism, and it extends to the northern edge of the Bushveld intrusion. From mantle xenoliths and xenocrysts, the entire lithosphere in this region appears to have experienced a long-term infiltration of basaltic melt and metasomatic fluids. We propose that the K-discontinuity reflects the influence of this melt/metasomatic infiltration, which has, over time, intruded and refertilized the lithosphere. Based on kimberlites pipes that show obvious signs of melt metasomatism and likely Karoo influence, the observed reduction in seismic velocity is plausibly consistent with the observed major-element and volatile enrichment at 150 km depth in such kimberlites. If this interpretation is correct, then the high-temperature kimberlite nodules that most clearly reflect this perturbation likely represent the general state of the lower lithosphere, rather than only reflecting local mantle properties in the immediate vicinity of the kimberlite eruption.