Fluid-induced breakdown of white mica controls nitrogen transfer during fluid–rock interaction in subduction zones     

Ralf Halama  Gray E. Bebout  Horst R. Marschall  Timm John 《International Geology Review》2017,59(5-6):702-720

ABSTRACT

In order to determine the effects of fluid–rock interaction on nitrogen elemental and isotopic systematics in high-pressure metamorphic rocks, we investigated three different profiles representing three distinct scenarios of metasomatic overprinting. A profile from the Chinese Tianshan (ultra)high-pressure–low-temperature metamorphic belt represents a prograde, fluid-induced blueschist–eclogite transformation. This profile shows a systematic decrease in N concentrations from the host blueschist (~26 μg/g) via a blueschist–eclogite transition zone (19–23 μg/g) and an eclogitic selvage (12–16 μg/g) towards the former fluid pathway. Eclogites and blueschists show only a small variation in δ¹⁵N_air (+2.1 ± 0.3‰), but the systematic trend with distance is consistent with a batch devolatilization process. A second profile from the Tianshan represents a retrograde eclogite–blueschist transition. It shows increasing, but more scattered, N concentrations from the eclogite towards the blueschist and an unsystematic variation in δ¹⁵N values (δ¹⁵N = + 1.0 to +5.4‰). A third profile from the high-P/T metamorphic basement complex of the Southern Armorican Massif (Vendée, France) comprises a sequence from an eclogite lens via retrogressed eclogite and amphibolite into metasedimentary country rock gneisses. Metasedimentary gneisses have high N contents (14–52 μg/g) and positive δ¹⁵N values (+2.9 to +5.8‰), and N concentrations become lower away from the contact with 11–24 μg/g for the amphibolites, 10–14 μg/g for the retrogressed eclogite, and 2.1–3.6 μg/g for the pristine eclogite, which also has the lightest N isotopic compositions (δ¹⁵N = + 2.1 to +3.6‰).

Overall, geochemical correlations demonstrate that phengitic white mica is the major host of N in metamorphosed mafic rocks. During fluid-induced metamorphic overprint, both abundances and isotopic composition of N are controlled by the stability and presence of white mica. Phengite breakdown in high-P/T metamorphic rocks can liberate significant amounts of N into the fluid. Due to the sensitivity of the N isotope system to a sedimentary signature, it can be used to trace the extent of N transport during metasomatic processes. The Vendée profile demonstrates that this process occurs over several tens of metres and affects both N concentrations and N isotopic compositions.  相似文献   

The great sulfur depletion of Earth’s mantle is not a signature of mantle–core equilibration     

Chris?BallhausEmail author  Raúl?O.?C.?Fonseca  Carsten?Münker  Arno?Rohrbach  Thorsten?Nagel  Iris?M.?Speelmanns  Hassan?M.?Helmy  Aurelia?Zirner  Antje?K.?Vogel  Alexander?Heuser 《Contributions to Mineralogy and Petrology》2017,172(8):68

The extreme depletion of the Earth’s mantle in sulfur is commonly seen as a signature of metal segregation from Earth’s mantle to Earth’s core. However, in addition to S, the mantle contains other elements as volatile as S that are hardly depleted relative to the lithophile volatility trend although they are potentially as siderophile as sulfur. We report experiments in metal-sulfide–silicate systems to show that the CI normalized abundances of S, Pb, and Sn in Earth’s mantle cannot be reproduced by element partitioning in Fe ± S–silicate systems, neither at low nor at high pressure. Much of the volatile inventory of the Earth’s mantle must have been added late in the accretion history, when metal melt segregation to the core had become largely inactive. The great depletion in S is attributed to the selective segregation of a late sulfide matte from an oxidized and largely crystalline mantle. Apparently, the volatile abundances of Earth’s mantle are not in redox equilibrium with Earth’s core.  相似文献   

Physical characteristics of Acidic Mining Lake 111     

G?kay?KarakasEmail author  Iris?Brookland  Bertram?Boehrer 《Aquatic Sciences - Research Across Boundaries》2003,65(3):297-307

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Bioassay‐directed fractionation for analyzing estrogens in surface waters of the German Baltic Sea     

Iris‐Constanze Beck  Regina Bruhn  Juergen Gandrass 《洁净——土壤、空气、水》2006,34(6):560-567

A reversed‐phase fractionation method with subsequent biological and chemical analysis has been developed to estimate the contributions of the most potent estrogens to observed estrogenic effect potentials. Surface water samples were taken in the German Baltic Sea (Inner Wismar Bay and Darss Peninsula, sampling campaign July 2003) and were separated into seven individual fractions. Three fractions showed significant estrogenic activities and clear dose‐dependant responses were obtained in the yeast estrogen screen (YES). In the 2nd fractions liquid chromatographic‐electrospray‐tandem mass spectrometric (LC‐ESI‐MS‐MS) analyses showed the presence of bisphenol A (Inner Wismar Bay: 4.8 ng L^–1 and 6 ng L^–1; Darss Peninsula: 0.91 ng L^–1 and 1.7 ng L^–1) and ethinylestradiol (Inner Wismar Bay: 2.0 ng L^–1 and 6.0 ng L^–1; Darss Peninsula: < MDL and 1.7 ng L^–1), whereas estrogenic activities in the YES were only around 10% of the positive control E2. Although not identified prior in the total extract the natural hormones estradiol (Inner Wismar Bay: 0.13 ng L^–1 and 0.19 ng L^–1; Darss Peninsula: 0.12 ng L^–1 and 0.16 ng L^–1) and estriol (Inner Wismar Bay: < MDL and 0.33 ng L^–1; Darss Peninsula: < MDL) could be detected in the 3rd fractions, where high estrogenic potentials could be observed. The 4th fractions showed high responses as well and estrone were herein quantified with concentrations of 0.16 ng L^–1 and 0.18 ng L^–1 (Darss Peninsula) up to 0.37 ng L^–1 (Inner Wismar Bay). Measured and calculated estradiol equivalents for individual fractions correlated very well (R² = 0.78), when disregarding results of the 2nd fraction, where high deviations occurred.  相似文献   

Tourmaline Reference Materials for the In Situ Analysis of Oxygen and Lithium Isotope Ratio Compositions     

Michael Wiedenbeck  Robert B. Trumbull  Martin Rosner  Adrian Boyce  John H. Fournelle  Ian A. Franchi  Ralf Halama  Chris Harris  Jack H. Lacey  Horst Marschall  Anette Meixner  Andreas Pack  Philip A.E. Pogge von Strandmann  Michael J. Spicuzza  John W. Valley  Franziska D.H. Wilke 《Geostandards and Geoanalytical Research》2021,45(1):97-119

Three tourmaline reference materials sourced from the Harvard Mineralogical and Geological Museum (schorl 112566, dravite 108796 and elbaite 98144), which are already widely used for the calibration of in situ boron isotope measurements, are characterised here for their oxygen and lithium isotope compositions. Homogeneity tests by secondary ion mass spectrometry (SIMS) showed that at sub‐nanogram test portion masses, their ¹⁸O/¹⁶O and ⁷Li/⁶Li isotope ratios are constant within ± 0.27‰ and ± 2.2‰ (1s), respectively. The lithium mass fractions of the three materials vary over three orders of magnitude. SIMS homogeneity tests showed variations in ⁷Li/²⁸Si between 8% and 14% (1s), which provides a measure of the heterogeneity of the Li contents in these three materials. Here, we provide recommended values for δ¹⁸O, Δ’¹⁷O and δ⁷Li for the three Harvard tourmaline reference materials based on results from bulk mineral analyses from multiple, independent laboratories using laser‐ and stepwise fluorination gas mass spectrometry (for O), and solution multi‐collector inductively coupled plasma‐mass spectroscopy (for Li). These bulk data also allow us to assess the degree of inter‐laboratory bias that might be present in such data sets. This work also re‐evaluates the major element chemical composition of the materials by electron probe microanalysis and investigates these presence of a chemical matrix effect on SIMS instrumental mass fractionation with regard to δ¹⁸O determinations, which was found to be < 1.6‰ between these three materials. The final table presented here provides a summary of the isotope ratio values that we have determined for these three materials. Depending on their starting mass, either 128 or 512 splits have been produced of each material, assuring their availability for many years into the future.  相似文献   

What is the Meaning of ‘Social Mix’? Shifting perspectives in planning and implementing public housing estate redevelopment     

Kathy Arthurson  Iris Levin  Anna Ziersch 《The Australian geographer》2015,46(4):491-505

This paper unravels a variety of perspectives about the concept of social mix, drawing on a case study of the implementation of a redevelopment project in Melbourne. The first part provides a theoretical overview of two internationally predominant academic debates around policy interpretations of this concept, namely social mix as a means for promotion of social inclusion; and as a state-led form of gentrification. These two arguments are usually presented as one, with social inclusion and reductions of concentrations of disadvantage one side of the ‘social mix policy’ coin, and state-led gentrification the other. This paper contributes to the national and international literature on public housing estate regeneration and social mix policies through exploring the question of whether these two ideas about social mix were shared by different stakeholders as the ‘messy’ process of redevelopment unfurled. Interviews were conducted with public tenants, homeowners and homebuyers, private renters and local service providers at the Carlton Housing Estate to explore the diverse perspectives of various stakeholder groups as estate design and implementation shifted. The study identified that as a result of the global financial crisis and the developers exerting pressure on government there was a gradual move away from perceiving social mix as a policy tool for encouraging social inclusion at Carlton, between public housing tenants and private residents, towards a different form of social mix and inclusion. Contrary to intentions, the revised form of social mix at Carlton was perceived as a means to harness market capital and attract higher income residents to the inner city.  相似文献   

3D Direct Simulation Monte Carlo Modelling of the Inner Gas Coma of Comet 67P/Churyumov–Gerasimenko: A Parameter Study     

Y. Liao  C. C. Su  R. Marschall  J. S. Wu  M. Rubin  I. L. Lai  W. H. Ip  H. U. Keller  J. Knollenberg  E. Kührt  Y. V. Skorov  N. Thomas 《Earth, Moon, and Planets》2016,117(1):41-64

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Evolution of a tourmaline-bearing lawsonite eclogite from the Elekdağ area (Central Pontides,N Turkey): evidence for infiltration of slab-derived B-rich fluids during exhumation   总被引：3，自引：0，他引：3  

Rainer?AltherrEmail author  Gültekin?Topuz  Horst?Marschall  Thomas?Zack  Thomas?Ludwig 《Contributions to Mineralogy and Petrology》2004,148(4):409-425

An undated high-pressure low-temperature tectonic mélange in the Elekda area (central Pontides, N Turkey) comprises blocks of MORB-derived lawsonite eclogite within a sheared serpentinite matrix. In their outer shells, some of the eclogite blocks contain large (up to 6 cm) tourmaline crystals. Prograde inclusions in poikiloblastic garnet from a well-preserved eclogite block are lawsonite, epidote/clinozoisite, omphacite, rutile, glaucophane, chlorite, Ba-bearing phengite, minor actinolite, winchite and quartz. In addition, glaucophane, lawsonite and rutile occur as inclusions in omphacite. These inclusion assemblages document the transition from a garnet-lawsonite-epidote-bearing blueschist to a lawsonite eclogite with the peak assemblage garnet + omphacite I + lawsonite + rutile. Peak metamorphic conditions are not well-constrained but are estimated approximately 400–430°C and >1.35 GPa, based on Fe–Mg exchange between garnet and omphacite and the coexistence of lawsonite + omphacite + rutile. During exhumation of the eclogite–serpentinite mélange in the hanging wall of a subduction system, infiltration of B-rich aqueous fluids into the rims of eclogite blocks caused retrogressive formation of abundant chlorite, titanite and albite, followed by growth of tourmaline at the expense of chlorite. At the same time, omphacite I (X_Jd=0.24–0.44) became unstable and partially replaced by omphacite II characterized by higher X_Jd (0.35–0.48), suggesting a relatively low silica activity in the infiltrating fluid. Apart from Fe-rich rims developed at the contact to chlorite, tourmaline crystals are nearly homogeneous. Their compositions correspond to Na-rich dravite, perhaps with a small amount of excess (tetrahedral) boron (~5.90 Si and 3.10 B cations per 31 anions). ¹¹ B values range from –2.2 to +1.7. The infiltrating fluids were most probably derived from subducting altered oceanic crust and sediments.  相似文献   

Use of suppressive subtractive hybridization and cDNA arrays to discover patterns of altered gene expression in the liver of dihydrotestosterone and 11-ketotestosterone exposed adult male largemouth bass (Micropterus salmoides)     

Jason L. Blum  Iris Knoebl  Patrick Larkin  Kevin J. Kroll  Nancy D. Denslow   《Marine environmental research》2004,58(2-5):565

In this study male largemouth bass (LMB) were exposed to the naturally occurring androgens, dihydrotestosterone (DHT) or 11-ketotestosterone (11-KT) in order to identify genes that are differentially regulated by these steroid hormones. Using subtractive hybridization on livers of fish treated with DHT against vehicle control, many novel LMB genes were cloned. These genes were added to our gene library and arrayed. Six genes were up-regulated and five were down-regulated by both androgens. But, each androgen also regulated specific genes. One gene that was identified as a potential androgen marker was spermidine-spermine-N¹-acetyltransferase that was up-regulated by both androgens. Determining which genes are responsive to natural androgens will help to identify biochemical pathways that are impacted.  相似文献   

Assessing the sustainability factors of traditional olive groves on Lesvos Island,Greece (Sustainability and traditional cultivation)     

Christina Giourga  Angeliki Loumou  Iris Tsevreni  Assimina Vergou 《GeoJournal》2008,73(2):149-159

In Europe the process of agricultural engagement or disengagement is attributed to the economic factor and mainly on the level of alternative employment source development. It is the relational quality of economic, social and environmental factors that determine sustainability of agricultural holdings and, hence, households. In regions of poor agricultural structures and of many employment opportunities as well as in regions suffering from agricultural depression, households exhibit stronger tendencies towards agricultural disengagement. Remarkably in southern Europe a stable agricultural engagement and not disengagement is observed, even though in recent years there are limited possibilities of alternative income sources and prevailing agricultural depression. This article highlights the factors which lead households to stable engagement with agriculture in a region of southern Europe, the island of Lesvos. The island is characterised by traditional olive grove mono-culture, poor agricultural structures and limited employment opportunities. The investigation of the economic, social and environmental farm household characteristics concluded that in regions where poor agricultural infrastructure and lack of employment prevail, all three factors of sustainability contribute to stability and/or low agricultural disengagement. Among these, the economic factor is the most sensitive and hence highly influential. The social factor is highlighted as a quality and consistent factor due to the respect for tradition. The environmental factor, finally, is characterised by mild cultivation practices, contributing to environment conservation.  相似文献