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Green beryl and the yellow beryl variety heliodor are well known from the Volyn pegmatite field in Ukraine, and this study presents details of their morphological characteristics. Visible etch pits are characteristic of beryl from this locality. In addition, they may contain an organic matter called kerite. Formation of the etch pits is asso ciated with a fluorine-rich, late-stage fluid phase. Etch pits on the pinacoidal face have a hexagonal outline and a pointed bottom (originating at linear defects) transitioning to etch pits with very steep walls, and they occur in three different orders of magnitude: =500 µm, =50 µm, and 1-3 µm. On the first-order prismatic faces, etch pits with a flat bottom (originating from point defects) or pointed bottom are square to rectangular, the latter oriented parallel or perpendicular to the beryl's c-axis. Flat bottom etch pits are more abundant than pointed bottom and also occur in three different orders of magnitude. In addition, small etch pits with a canoe shape and porosity on the nanometer scale were observed. Scanning electron microscopy of these etch pits was used to distinguish uncut stones from other pegmatitic beryls, but these phenomena are also visible with an optical microscope or even with a loupe. [ABSTRACT FROM AUTHOR]

We investigated emerald, the bright-green gem variety of beryl, from a new locality at Kruta Balka, Ukraine, and compare its chemical characteristics with those of emeralds from selected occurrences worldwide (Austria, Australia, Colombia, South Africa, Russia) to clarify the types and amounts of substitutions as well as the factors controlling such substitutions. For selected crystals, Be and Li were determined by secondary ion mass spectrometry, which showed that the generally assumed value of 3 Be atoms per formula unit (apfu) is valid; only some samples such as the emerald from Kruta Balka deviate from this value (2.944 Be apfu). An important substitution in emerald (expressed as an exchange vector with the additive component Al2Be3Si6O18) is (Mg,Fe2+)NaAl–1□–1, leading to a hypothetical end-member NaAl(Mg,Fe2+)[Be3Si6O18] called femag-beryl with Na occupying a vacancy position (□) in the structural channels of beryl. Based on both our results and data from the literature, emeralds worldwide can be characterized based on the amount of femag-substitution. Other minor substitutions in Li-bearing emerald include the exchange vectors LiNa2Al–1□–2 and LiNaBe–1□–1, where the former is unique to the Kruta Balka emeralds. Rarely, some Li can also be situated at a channel site, based on stoichiometric considerations. Both Cr- and V-distribution can be very heterogeneous in individual crystals, as shown in the samples from Kruta Balka, Madagascar, and Zimbabwe. Nevertheless, taking average values available for emerald occurrences, the Cr/(Cr+V) ratio (Cr#) in combination with the Mg/(Mg+Fe) ratio (Mg#) and the amount of femag-substitution allows emerald occurrences to be characterized. The "ultramafic" schist-type emeralds with high Cr# and Mg# come from occurrences where the Fe-Mg-Cr-V component is controlled by the presence of ultramafic meta-igneous rocks. Emeralds with highly variable Mg# come from "sedimentary" localities, where the Fe-Mg-Cr-V component is controlled by metamorphosed sediments such as black shales and carbonates. A "transitional" group has both metasediments and ultramafic rocks as country rocks. Most "ultramafic" schist type occurrences are characterized by a high amount of femag-component, whereas those from the "sedimentary" and "transitional" groups have low femag contents. Growth conditions derived from the zoning pattern—combined replacement, sector, and oscillatory zoning—in the Kruta Balka emeralds indicate disequilibrium growth from a fluid along with late-stage Na-infiltration. Inclusions in Kruta Balka emeralds (zircon with up to 11 wt% Hf, tourmaline, albite, Sc-bearing apatite) point to a pegmatitic origin. [ABSTRACT FROM AUTHOR]

Metal contacts on semiconductors devices are normally defined by lift-off process, because no well-defined etch processes exist for some rare metals. In this work, an RIE process for gold contacts is introduced which requires a high-density plasma, generated by electron cyclotron resonance. The proof is given by the residual-free etching without fence-generation and micromasking in the vicinity of the mask. [ABSTRACT FROM AUTHOR]

The Volyn pegmatites from Volodarsk-Volynskyi in the Zhytomyr Oblast, NW Ukraine, are associated with granites genetically related to the Paleoproterozoic Korosten pluton. Their late-stage evolution is characterized by the formation of opal-cemented breccia. A polymineralic pseudomorph after beryl within the breccia includes bertrandite (±euclase) + F-muscovite (with tobelite component) + buddingtonite + organic matter (OM) + opal (+ traces of K-feldspar, albite, columbite, FeS2, barite, REE-minerals). Sector-zoned and platy to fibrous buddingtonite has variable (K[sup +]Na)- vs. NH4-contents (electron microprobe analyses) and some H2O or H3O[sup +], as indicated by microscope infrared spectroscopy. We suggest that ammonium was produced by decay of OM, which is partly preserved in the pseudomorph. Energy-dispersive electron microprobe data of the OM show with increasing O-decreasing C-N-content due to degassing; the OM contains the high field strength elements Zr (≤7 at%), Y (≤3 at%), Sc (≤0.8 at%), REE (≤0.3 at%), Th (≤0.2 at%), and U (≤1.25 at%), which increase with increasing O-content. Transmission electron microscopy of the OM confirms the presence of N; Zr, Si, and O (with other HFSE) are concentrated in nanometer-sized areas and at the transition from OM to opal in nanometer-sized platy Zr-Si-O crystals. C-rich areas are amorphous but show poorly developed lattice fringes. OM is present in the pseudomorph also as brown pigmentation of opal and in pegmatitic beryl from Volyn as a component in late stage fluid inclusions, identified by C-H vibrational bands in infrared spectra. Stable isotope investigations of C and N of buddingtonite, black opal and kerite (fibrous OM known from the literature to occur in the Volyn pegmatites and interpreted as microfossils) indicate a biogenic origin of the OM. We propose that OM in the pseudomorph is condensed kerite, which achieved the high concentrations of high field strength elements via fluid-pegmatite interaction. Although no age determination of minerals in the pseudomorph is available, textural arguments and phase equilibria indicate its formation in a late stage of the pegmatite evolution, at P-T conditions below ~100 MPa/150 °C. We favor a conceptual model for the formation of the Volyn buddingtonite in analogy to Phanerozoic occurrences of buddingtonite, where over and around the shallow anorthositegranite Korosten pluton hydrothermal convection cells introduced N-bearing hydrocarbons and its precursors into the cooling igneous rocks. Due to the elevated temperature, the OM disintegrated into degassing volatile and non-volatile residual components analogous to petroleum maturation. Organic N, released as NH4, was then incorporated into buddingtonite. [ABSTRACT FROM AUTHOR]

The occurrence of a trioctahedral analog of illite, the dioctahedral interlayer-deficient K-mica, has long been debated. Due to the inherent difficulties of determining structure and chemical composition of the extremely fine-grained material, earlier descriptions based on separated material are equivocal. Here we describe low-temperature (diagenetic) formation of fluorophlogopite, which is interlayer-deficient and therefore analogous to illite, using high-resolution in situ methods (transmission electron microscopy, TEM, with preparation by focused ion beam milling, combined with wavelength-dispersive analysis by field-emission gun electron microprobe). The average composition is K0.5Mg2.8V0.01Fe0.005 [Si3.15Al0.85O10 (OH) 0.65F1.35], including minor amounts of NH4 for charge compensation as determined by electron energy loss spectroscopy. The K-deficient Mg-mica occurs in layer packages of ~10 layers, and no indications for interlayering with other sheet silicate layers such as chlorite or vermiculite could be identified with TEM. X-ray powder diffraction patterns of separated material confirm the absence of smectite components. The mineral was identified in phosphorites from the lowermost Cambrian Tal Group, Mussoori Syncline, Lesser Himalayas, India. The rocks are alternating phosphatic mudstones and phosphatic dolostones, at times interbedded with phosphate-poor carbonate layers, which are rich in organic matter. Sedimentary fluorophlogopite occurs in both rock types and in two textural associations; one in vesicles filled with amorphic organic matter, the other as reaction rims around illite, which contains up to 5 wt% V2O3 in its rims. Textural arguments favor an early diagenetic formation of both, V-bearing illite and fluorophlogopite, closely associated with organic matter and linked to dolomitization. The high-F content stabilizes phlogopite to low temperatures. Our findings confirm that the stability field of fluorophlogopite extends from magmatic to metamorphic and sedimentary conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Secondary minerals preferentially accumulate on corroding surfaces. [•] Pore space of porous filter materials only partly filled with precipitates. [•] Complete conversion of ferric minerals to magnetite. [ABSTRACT FROM AUTHOR]

Trace element distribution in titanite overgrowths on rutile has been investigated experimentally at 600 °C, 400 MPa and f near NiNiO buffer. Compositionally homogenous Cr- or Nb-doped synthetic rutile single crystals or Nb-containing natural rutile crystals were the source of Cr, Nb and Ti to synthesize titanite using the double-capsule technique. All element exchange with the source of Si, Ca and Al occurred via a NaCl-HO fluid. Titanite forms quickly and exclusively around the rutile crystals. The titanite overgrowth separates rutile from the bulk fluid, and all elements from rutile dissolution have to pass through the titanite rim. Trace element concentrations in titanite show a considerable scatter in experiments with and without Al, although the average concentrations of Cr or Nb of titanite around compositionally homogeneous synthetic rutile approach the expected values for closed system conditions. Variability of Al with Cr or Nb in the titanite is not correlated. The Al zoning is irregular and patchy, and also the distribution of trace elements does not show systematic trends in the spatial distribution. In experiments using zoned natural rutile, the concentrations of Nb in titanite are related to the Nb zoning in rutile, but the contents also vary unsystematically. Under the controlled conditions of the experiment, the explanation for the strongly irregular spatial distribution is most likely due to variations in elemental concentrations during transport from the rutile along the titanite grain boundaries. The transport pathway is complex because grain boundary migration is important during titanite growth. Such irregular element distribution is also found in a natural sample of titanite overgrowth on rutile from an eclogite with retrograde overprint in the amphibolite facies. Transport of Ti and trace elements was focused on grain boundaries and shielded from the rutile as a source of these elements. We conclude that this type of zoning is not related to changes in P-T or composition in an open system, but solely controlled by transport in and through the titanite rim. [ABSTRACT FROM AUTHOR]

Fluid-assisted mass transport reactions by dissolution-precipitation, where a precursor mineral reacts with a fluid, play an important role in metamorphism and metasomatism. We investigated titanite growth on rutile in time series experiments between one and 107 days at constant P-T conditions of 600 °C and 400 MPa in the system TiO2-CaO-SiO2-Na2O-HCl-H2O. A two-capsule assemblage allows for transport of Ca and Si from dissolving wollastonite to dissolving rutile, the Ti-source, in a NaCl-bearing aqueous fluid, according to the general reaction CaSiO3 + TiO2 = CaTiSiO5. Complete overgrowth of rutile by titanite occurred after just one day of experiment. Fine-grained lozenge-shaped titanite crystals of short-time runs (up to 14 days) reorganize to larger predominantly prismatic crystals after >14 days. After investigation by scanning electron microscopy, the titanite overgrowth was removed from the rutile by hydrofluoric acid, to provide a three-dimensional view of the dissolution-reaction front on the rutile surface. The morphology of the rutile surface is dominated by humps or ridges beneath the central region of a titanite crystal and valleys at the grain boundaries between adjacent titanite crystals. The dissolution pattern on the rutile surface mimics the titanite overgrowth and changes with changing grain size and shape of the titanite with longer run times. The preferred dissolution of rutile in the valleys is clearly linked to the position of the titanite grain boundaries, which served as pathways for fluid-assisted element transport. Rutile-titanite and titanite-titanite boundaries show a significant porosity in transmission electron microscopy images of foils prepared by focused ion beam milling. The large-scale dissolution pattern on the rutile surface is independent of the crystallographic orientation of the rutile and entirely dominated by the arrangement of titanite crystals in the overgrowth. Dissolution features on a scale smaller than ~1 µm are dominated by stepwise dissolution and etch-pits following the crystallographic orientation of the rutile. Similar observations were made in experiments with an additional Al-source, although these experiments result in a different overgrowth pattern; i.e., an exposed rutile surface is always present and solitary titanite crystals are accompanied by partial overgrowths. Quantitative characterization of the surface morphology by white-light interference microscopy demonstrates that, with increasing grain size of titanite, dissolution of rutile is strongly enhanced at the titanite grain boundaries. Natural examples of titanite overgrowths on rutile show the same relations between element pathways, arrangement of titanite crystals and 3D dissolution pattern on rutile as in the experimental systems. We conclude that the transport of Ti away from the rutile and of Ca + Si into the reaction rim occurred in a grain boundary fluid, the composition of which must have been strongly different from the composition of the bulk fluid in the experiment, as well as in the natural system. The reaction progress depends on the availability of a fluid, and relicts of rutile in titanite indicate restricted availability of fluid in the natural system (e.g., a fluid pulse that was consumed by the reactions). The reaction examined here can serve as a proxy for other reactions of the conversion of oxide minerals (e.g., spinel or corundum) into silicates. [ABSTRACT FROM AUTHOR]

The isotopic composition of mafic small-volume intra-plate magmatism constrains the compositions of the sub-continental mantle sources. The Nd, Pb, and Sr isotope signatures of widespread late Mesozoic to Quaternary intra-plate magmatism in NE Africa (Sudan, South Egypt) are surprisingly uniform and indicate the presence of a high-μ (μ = 238U/204Pb) source in the mantle. The rocks are characterized by small ranges in the initial isotopic composition of Nd, Pb, and Sr and most samples fall within ε Nd ca. 3–6, 206Pb/204Pb ca. 19.5–20.5, 207Pb/204Pb ca. 15.63–15.73, 208Pb/204Pb ca. 39–40 and 87Sr/86Sr ca. 0.7028–0.7034. We interpret this reservoir as lithospheric mantle that formed beneath the Pan-African orogens and magmatic arcs from asthenospheric mantle, which was enriched in trace elements (U, Th, and light REE). Combining our new data set with published data of intra-plate magmatic rocks from the Arabian plate indicates two compositionally different domains of lithospheric mantle in NE-Africa–Arabia. The two domains are spatially related to the subdivision of the Pan-African orogen into a western section dominated by reworked cratonic basement (NE-Africa; high-μ lithospheric mantle) and an eastern section dominated by juvenile Pan-African basement (easternmost NE-Africa and Arabia; moderate μ lithospheric mantle). The compositions of the Pan-African lithospheric mantle and the MORB-type mantle of the Red Sea and Gulf of Aden spreading centers could explain the Nd–Pb-Sr isotopic compositions of the most pristine Afar flood basalts in Yemen and Ethiopia by mixtures of the isotopic composition of regional lithospheric and asthenospheric sources. [ABSTRACT FROM AUTHOR]

The XeCI* excimer laser is a well-established system tool for many applications. During operation, highly volatile chlorides are often formed, which leads to enhanced electrode erosion and reduced lifetime. Therefore, special attention should be paid to the rate of erosion of all electrode materials that are used in chlorine based excimer lasers. In our work, we came to the result that the chemical behavior of the electrode material is much more important than the classical electrode parameters erosion rate and work function. To separate the erosion rate into a chemical and physical part, we used a nickel electrode as anode (almost no wear) and cathode (low wear compared to tungsten). We concluded that nickel as an electrode material is still the best material in our laser design. [ABSTRACT FROM AUTHOR]

Presents a study which measured enthalpies of drop solution in molten lead borate for zoisite and clinozoisite samples spanning epidote solid solutions. Experimental procedure; Results; Discussion.

We report an experimental study of an electron cyclotron wave resonance (ECWR) plasma source. The dimensions of the source are considerably larger than in similar experiments. The excitation frequency is 27.12 MHz, the working gas is argon at very low pressures below 0.13 Pa. Spectroscopic data connected with a global model yield electron temperature $T_{\mathrm{ e}}$ , electron number density $n_{\mathrm{ e}}$ , population of the metastable state $n_{\mathrm{ m}}$. The pressure dependencies of these quantities are discussed. Starting from $T_{\mathrm{ e}}\sim 5$ eV at pressure $p=0.13$ Pa the temperature grows as the pressure goes down until the discharge extinguishes at ${\sim }0.6\times 10^{-2}$ Pa. It becomes in the meantime so high that the emission spectra feature strong Ar(II) lines in the region 400–500 nm. At $p=0.13$ Pa and power 300 W the electron density on the axis is about $4\times 10^{10}~{\mathrm{ cm}}^{-3}$ and falls down due to the increase in $T_{\mathrm{ e}}$ as the pressure drops. The discharge was also electrically characterized to determine the plasma impedance $Z$. The impedance and the plasma resistance ${\mathrm{ Re}}(Z)$ are presented as functions of the static magnetic field $B_{\mathrm{ 0}}$. The distribution of power losses are also shown as $B_{\mathrm{ 0}}$ -dependencies. [ABSTRACT FROM AUTHOR]

Chemical zoning according to the substitution Al + (OH,F) = Ti + O is a common phenomenon in natural titanite and can be used to reconstruct its growth conditions. We synthesized titanite, which has a zoning pattern similar to that found in natural titanite that grew at the expense of rutile, visible in element distribution maps as a patchy irregular pattern. Run conditions in the system CaO-Al2O3-TiO2-SiO2-NaCl-H2O(-CaF2) were 600 °C, 0.4 GPa, 1 to 107 days duration. Natural rutile crystals were placed in a perforated Pt-tube within an outer Au-capsule containing wollastonite, γ-Al2O3, optionally powdered CaF2, and a NaCl brine, to simulate conditions, where rutile is transformed into titanite by a hydrous Ca-Si-Al(-F) fluid, driven by a chemical potential gradient between inner and outer capsule. Spontaneous nucleation of titanite is restricted to a small number of crystals on the rutile surface in the inner capsule. Growth proceeds from sparse isolated titanite crystals after 1 day to assemblages of several 100 µm large crystals in a reaction rim in the long-time runs. Titanite is strongly zoned in Al-Ti and shows up to ~0.5 Al per formula unit (pfu) in experiments containing F; without F, substitution is limited to ~0.25 Al pfu. The range of the Ti-Al exchange is already large in short run times and the same heterogeneity is observed in long-time runs. The Al-Ti distribution (with and without F) in compositional domains (up to several tens of micrometers) is patchy and irregular. No relation of the zoning with time (core-rim) or preferred growth directions was observed. In the case of fluid-mediated growth, mineral growth zoning represents a disequilibrium at supersaturated conditions. The concentration of Ti in the fluid is likely the limiting factor for titanite growth considering the low solubility compared to that of Al, Ca, and Si. Titanium is not transported in significant amounts into the outer capsule, indicating low mobility, in contrast to Al, Ca, and Si, which are transported into the inner capsule. Assuming buffered Al concentration from dissolution of the Al-source, we speculate that the Ti/Al of the fluid at the precipitation site was controlled by the local Ti concentration, which varies over the distance from the rutile surface to the growing titanite crystal and produces the irregular patchy zoning. [ABSTRACT FROM AUTHOR]

The Ca-Sr fractionation between zoisite and, respectively, lawsonite and an aqueous fluid has been determined by synthesis experiments in the presence of a 1 M (Ca,Sr)Cl2 aqueous fluid at 2.0 GPa/550, 600, and 700 °C and 4.0 GPa/800 °C for zoisite and 2.0 GPa/400 °C and 4.0 GPa/600 °C for lawsonite. Solid run products were characterized by EMP, SEM, and XRD with Rietveld refinement and fluids were analyzed by ICP-OES. Zoisite exhibits notable intracrystalline Ca-Sr fractionation between the A1 and A2 sites and calculated intracrystalline exchange coefficients KD(Sr-Ca)A1-A2 = 1.5 to 26 show strong preference of Sr over Ca for the slightly larger A2 site. Calculated individual site-dependent zoisite/aqueous fluid (af, in superscripts)-exchange coefficients for the studied 1 M (Ca,Sr)Cl2 aqueous fluids are K(Sr-Ca)zo A1-af = 3.38 to 41.08 for the A1 site and K(Sr-Ca)zo A1-af = 0.45 to 6.51 for the A2 site. Assuming γCaaf = γSraf and a symmetric mixing model, the thermodynamic evaluation of the site-dependent exchange reactions Ca2+(af) + SrA1(M2+)A2 Al3[Si3O11(O/OH)] = Sr2+(af) + CaA1 (M2+)A2Al3[Si3O11(O/OH)] and Ca2+(af) + (M2+)A1 SrA2 Al3[Si3O11(O/OH)] = Sr2+(af) + (M2+)A1 CaA2 Al3[Si3O11(O/OH)] yields Δµ0 = --29 kJ/mol and WSr-Cazo A1 = 5.5 kJ/mol for the A1 site and Δµ0 = -1.1 kJ/mol and WSr-Cazo A2 = 0 kJ/mol for the A2 site at P and T of the experiments. The data indicates ideal Ca-Sr substitution on the A2 site. Lawsonite formed in both the orthorhombic Cmcm and the monoclinic P21/m form. Calculated lawsonite-aqueous fluid-exchange coefficients indicate overall preference of Ca over Sr in the solid and are KD(Sr-Ca)law Cm -cm-af = 1.12 to 11.32 for orthorhombic and KDD(Sr-Ca)law Cm -cm-af = 1.67 to 4.34 for monoclinic lawsonite. Thermodynamic evaluation of the exchange reaction Ca2+(af) + SrAl2Si2O7(OH)2·H2O = Sr2+(af) + CaAl2Si2O7(OH)2·H2O assuming γCaaf = γSraf and a symmetric mixing model yields similar values of Δµ0 = --9 kJ/mol and WSr-Calaw Cmcm-af = 10 kJ/mol for orthorhombic and Δµ0 = -10 kJ/mol and WWSr-Calaw P21/m = 11 kJ/mol for monoclinic lawsonite. Calculated Nernst distribution coefficients for the studied 1 M (Ca,Sr)Cl2 aqueous fluids are DSrzo-af = 2.8 ± 0.7 for zoisite at 2 GPa/600 °C and DSrlaw Cmcm-af = 0.6 ± 0.2 for orthorhombic lawsonite at 4 GPa/600 °C and show Sr to be compatible in zoisite but incompatible in lawsonite. This opposite mineral-aqueous fluid-fractionation behavior of Sr with respect to zoisite and lawsonite on the one hand and the ideal Ca-Sr substitution on the zoisite A2 site in combination with the strong intracrystalline Ca-Sr fractionation in zoisite on the other hand, make Sr a potential tracer for fluid-rock interactions in zoisite- and lawsonite-bearing rocks. For low Sr-concentrations, xSrzo directly reflects xSraf and allows us to calculate Sr-concentrations in a metamorphic aqueous fluid. During high-pressure aqueous fluid-rock interactions in subduction zone settings the opposite mineral-aqueous fluid-fractionation behavior of Sr results in different aqueous fluid characteristics for lawsonite- vs. zoisite-bearing rocks. Ultimately, subduction zone magmas may trace these different aqueous fluid characteristics and allow distinguishing between cold, lawsonite-bearing vs. warm, zoisite-bearing thermal regimes of the underlying subduction zone. [ABSTRACT FROM AUTHOR]

Aerial parts of Daphne pontica were collected from Ilgaz-Çankırı, and D. oleoides subsp. oleoides was collected from 2 different localities (Ayrancı-Karaman and Ilgaz-Çankırı) in Turkey. The samples were subjected to hydrodistillation and microdistillation. The resulting volatile samples were analyzed both by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. The main components for D. pontica were identified as hexahydrofarnesyl acetone (8.6%), carvacrol (8.5%), dihydroedulane II (4.7%), (E)-geranyl acetone (4.6%), and thymol (4.5%), while nonacosane (42.5% and 27.2%), hexadecanoic acid (24.4% and 20.0%), phytol (12.3%), and carvacrol (5.0%) were identified as the main components of D. oleoides subsp. oleoides obtained by hydrodistillation. Carvacrol (12.0%), thymol (7.7%), dihydroactinidiolide (7.2%), bicyclosesquiphellandrene (5.5%), and (Z)-3-hexenal (4.1%) were the major components in D. pontica, while carvacrol (27.2% and 25.4%), nonacosane (24.6%), (Z)-3-hexenal (18.5% and 2.5%), decane (7.4%), hexahydrofarnesyl acetone (7.4% and 2.2%), hexanal (6.6% and 1.5%), heptacosane (6.1%), nonanal (5.6% and 1.9%), thymol (5.1% and 2.3%), and phytol (5.0%) were identified in the D. oleoides subsp. oleoides isolated by microdistillation, respectively. In addition, the volatile components were evaluated for their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals using a bioautographic thin layer chromatography (TLC) method, and the samples showed activity comparable with that of the tested standards, vitamins C and E. [ABSTRACT FROM AUTHOR]

New isotopic ages constrain the onset of the Andean Orogeny in central Chile (34°-37°S). They define three pulses of Early Mesozoic magmatism in the Cordillera de la Costa: granitic magmatism at 225-220 Ma, bimodal magmatism at 210-197 Ma, and mafic magmatism at 170-150 Ma. Each pulse has distinct field, petrographic, geochemical, and Sr-Nd-Pb isotopic characteristics and crystallization conditions. Major magmatic sources are the regional Mesozoic subarc-subcontinental mantle and the Paleozoic Chilean continental crust, with the importance of juvenile contributions increasing with time. All three Early Mesozoic magmatic pulses display geochemical signatures that are characteristic of subduction-related magmas of magmatic arcs, such as a Nb-Ta trough and a positive Pb anomaly. The 210-197-Ma magmatism is peculiar for its bimodal nature, the occurrence of transitional A-type granitoids, the presence of fayalite granites, and its association with an episode of crustal extension. A contemporaneous accretionary wedge nevertheless indicates ongoing subduction at that time. The 210-197-Ma magmatic pulse thus was formed in an extensional suprasubduction zone environment. It marks the transition from the Gondwana Orogeny to Andean- style subduction magmatism. We argue that the onset of the Andean Orogeny was related to a reconfiguration of the tectonic conditions of plate convergence during overall near-continuous subduction and arc magmatism since the Paleozoic. [ABSTRACT FROM AUTHOR]

We determined experimentally the Nernst distribution coefficient $$ D_{i}^{{{\text{opx}} - {\text{melt}}}} = \frac{{c_{i}^{\text{orthopyroxene}} }}{{c_{i}^{\text{melt}} }} $$ between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230°C up to 3.2 GPa/1,535°C in a piston cylinder apparatus. Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18–20 mol%. The rare earth elements show a continuous, significant increase in compatibility with decreasing ionic radius from D ∼ 0.0008 to D ∼ 0.15. For the high-field-strength elements compatibility increases from D ∼ 0.001 through D ∼ 0.0015, D ∼ 0.002, D ∼ 0.005, D ∼ 0.02 and D ∼ 0.04 to D ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D, D, r, r, E, and E for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene; for the divalent cations D varies by three orders of magnitude between D = 0.00098–0.00919 and D = 2.3–28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on M2; D reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our new comprehensive data set can be used for polybaric-polythermal melting models along the Earth’s mantle solidus. [ABSTRACT FROM AUTHOR]

Presents the first systematic study of synthetic iron-free and iron-bearing zoisite using X-ray powder diffraction and infrared spectroscopy. Electrone microprobe analysis; Fourier-transform infrared analysis; Lattice parameters and atom coordinates of all of the samples.

Focuses on a study which documented the mineral chemistry and boron-isotope composition of tourmaline in a suite of Palaeozoic to Mesozoic rock samples from the central Andes of Northwest Argentina. Geological setting and sample description; Techniques in analyzing boron isotopes; Chemical composition of whole-rocks and tourmalines.

Carbonates are excellent carriers for divalent cations such as Ca, Mg, and Sr, and knowledge about their stability and solid solutions is important to understanding the global strontium cycle. To shed light on the topology of the two-phase field between calcite-type and aragonite-type (Ca,Sr)CO3 solid solutions as a function of temperature and pressure, and to learn more about the distribution of Sr and Ca between carbonates and fluid, we studied the system CaCO3-SrCO3-H2O at 600 °C in the pressure range 0.5-5 kbar. Conventional and rapid-quench hydrothermal syntheses were performed using a range of different starting materials. All bulk compositions were within the assumed/postulated two-phase field of calcite-type and aragonite-type (Ca,Sr)CO3 solid solutions. The run products were analyzed by scanning electron microscopy, electron microprobe analysis, and powder X-ray diffraction with Rietveld refinement. The results show that the heterotype solid solution is more extensive than previously assumed, with calcite incorporating up to 20 mol% SrCO3, which is twice as much as previously predicted. The compositional range of the aragonite-type solid solution was identical to that found in the literature. Using the data from this study, an updated version of the phase diagram P-X (Sr) at 600 °C for the CaCO3-SrCO3 system was calculated. The phase diagram does not support a phase transition within the trigonal (Ca,Sr)CO3 solid solution associated with rotational disorder of the CO3-groups. This order-disorder phase transition was previously postulated to explain some observed compositional trends in this system. Our new data are in line with other more recent studies. The distribution of Sr and Ca between the fluid and solid phases D = XsolidSr/XfluidSr is near to 1.0 for calcite-type and on average around 2.0 for aragonite-type solid solutions. This contrasts with silicate-fluid systems in which Sr typically shows a strong preference for the fluid phase compared with Ca. [ABSTRACT FROM AUTHOR]

The metastable paragenesis of corundum and quartz is rare in nature but common in laboratory experiments where according to thermodynamic predictions aluminum–silicate polymorphs should form. We demonstrate here that the existence of a hydrous, silicon-bearing, nanometer-thick layer (called "HSNL") on the corundum surface can explain this metastability in experimental studies without invoking unspecific kinetic inhibition. We investigated experimentally formed corundum reaction products synthesized during hydrothermal and piston–cylinder experiments at 500–800 °C and 0.25–1.8 GPa and found that this HSNL formed inside and on the corundum crystals, thereby controlling the growth behavior of its host. The HSNL represents a substitution of Al with Si and H along the basal plane of corundum. Along the interface of corundum and quartz, the HSNL effectively isolates the bulk phases corundum and quartz from each other, thus apparently preventing their reaction to the stable aluminum silicate. High temperatures and prolonged experimental duration lead to recrystallization of corundum including the HSNL and to the formation of quartz + fluid inclusions inside the host crystal. This process reduces the phase boundary area between the bulk phases, thereby providing further opportunity to expand their coexistence. In addition to its small size, its transient nature makes it difficult to detect the HSNL in experiments and even more so in natural samples. Our findings emphasize the potential impact of nanometer-sized phases on geochemical reaction pathways and kinetics under metamorphic conditions in one of the most important chemical systems of the Earth's crust. [ABSTRACT FROM AUTHOR]

Depositing a film via chemical vapor deposition results in superior conformity compared with other deposition techniques, primarily due to the unique chemical interactions between the surface and the reactive compounds. This technique requires a readily accessible surface and so, if the transport of the reactive species is impeded, irrespective of whether this depletion is caused by diffusion or convective flow, a homogeneous layer thickness cannot be achieved. This is often the case when applying films to the interiors of tubes, especially tubes with a dead-end, such that the inevitable loss of film-building components leads to a drop in thickness along the deposition length. The present work examined the deposition of the organic polymer poly-p-xylylene, using a reactor with dimensions that were large compared with the mean free path and tubes in which this factor (the Knudsen number) becomes unity, such that the deposition can be approximately described with the continuum model. A so-called temperature seesaw was employed to mitigate variations in layer thickness by generating an opposing temperature gradient. It was found that, under a vacuum of several tens of mTorr, the polymer could be deposited on the interior wall of a tube with an aspect ratio of at least 100 with an accuracy of ±7.5 %. The true ceiling temperature for the N derivate of this polymer was also determined to be 70 ± 2 °C. [ABSTRACT FROM AUTHOR]

Ca-Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO-NaO-BO-AlO-MgO-SiO-HO-Cl between 0.2-4.0 GPa and 500-700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMgAlSiO(BO)(OH)(OH)], 'oxy-uvite' (i.e. 'Ca-Mg-O root name') [CaMgAlSiO(BO)(OH)O], and magnesio-foitite [☐(MgAl)AlSiO(BO)(OH)(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca-Na exchange at the X site via the exchange vector CaO[Na(OH)], with the exchange vector (Ca☐)[Na] serving as a secondary Ca-incorporation mechanism. Tourmaline's X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca-Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally. [ABSTRACT FROM AUTHOR]

Olenitic tourmaline with high amounts of tetrahedral B (up to 2.53 [4]B pfu) has been synthesized in a piston-cylinder press at 4.0 GPa, 700 °C, and a run duration of 9 days. Crystals are large enough (up to 30 × 150 μm) to allow for reliable and spatially resolved quantification of B by electron microprobe analysis (EMPA), single-crystal X‑ray diffraction, and polarized single-crystal Raman spectroscopy. Tourmalines with radial acicular habit are zoned in [4]B-concentration [core: 2.53(25) [4]B pfu; rim: 1.43(15) [4]B pfu], whereas columnar crystals are chemically homogeneous [1.18(15) [4]B pfu]. An amount of 1.4(1) [4]B pfu was found in the columnar tourmaline by single-crystal structure refinement (SREF) (R = 1.94%). The EMPA identify [T]Si–1 [V,W]O–1 [T]B1 [V,W](OH)1 as the main and [X]...–1 [T]Si–1 [X]Na1 [T]B1 as minor exchange vectors for [4]B-incorporation, which is supported by the SREF. Due to the restricted and well-defined variations in chemistry, Raman bands in the OH-stretching region (3000–3800 cm–1) are unambiguously assigned to a specific cation arrangement. We found the sum of the relative integrated intensity (Irel) of two low-frequency bands at 3284–3301 cm–1 (ν1) and 3367–3390 cm–1 (ν2) to positively correlate with the [4]B concentrations: [4]B [pfu] = 0.03(1) × [Irel (ν1) + Irel (ν2)]. Hence, those bands correspond to configurations with mixed Si/B occupancy at the T site. Our semi-quantitative correlation also holds for well-characterized natural [4]B-bearing tourmaline from the Koralpe, Austria. This work shows the potential for Raman spectroscopy as a non-destructive method for the chemical classification of (precious) natural tourmaline, and as a tool to rapidly characterize chemical zonation of tourmalines in thin section. [ABSTRACT FROM AUTHOR]

We performed hydration experiments of pure and Nb-, Cr-, and V-doped synthetic dry (H2O < 3 ppm) single rutile crystals. They were equilibrated with pure H2O in hydrothermal experiments at constant conditions of 600 °C, 400 MPa, and fO2 near the Ni-NiO buffer, run time between ~25 min and 14 days. Slabs cut parallel to (110) of the reacted single crystals (1 to 2 mm³) were analyzed for H+ by FTIR. Hydration occurs almost spontaneously and the H2O-equivalent is uniformly distributed in the samples, but depends extremely on trace element contents. In pure rutile, the average H2O-content is 314 ± 50 ppm, the saturation level at these conditions. Rutile doped with 500 ppm Nb has a lower average H2O content of ~235 ppm, rutile with 2000 ppm Cr has ~900 ppm H2O, and rutile with 2000 ppm V does not incorporate H2O. During stepwise heating at atmospheric pressure of a reacted Nb-doped rutile, H+ is quickly released between 450 and 550 °C. UV-VIS spectra of unreacted colorless and reacted deep blue pure rutile show the rutile-characteristic sharp absorption edge in the UV spectra. The reacted rutile has a broad absorption band at 6500 cm-1 wavenumber attributed to intervalence charge transfer transition Ti3++Ti4+ → Ti4++Ti3+. The reduction of Ti4+ to Ti3+ is charge balanced by the incorporation of H+. The Nb-doped rutile changed its color from light greenish-blue (untreated) to deep blue. In the untreated Nb rutile, the UV-VIS absorption band at 6500 cm-1 indicates that Nb5+ is charge balanced by Ti3+. In the reacted Nb-rutile the absorption band is more intense, but compared with the pure rutile, H+ incorporation is lower by the equivalent of Ti3+ reduced in the untreated rutile. Reacted Cr-rutile almost retains its brownish-orange color, but the spectrum shows a prominent Ti3+/Ti4+ IVCT band at ~6400 cm-1 with moderate intensity considering the high-H2O contents of ~900 ppm. The high-H+ contents are best explained by the reduction of Cr4+ to Cr2+. The UV-VIS spectra of the dark-blue to opaque V-doped rutile show a very strong absorption toward low energies, which is likely caused by reduction of Ti4+ to Ti3+ for charge balance of V5+. This forms a deep narrow window of transmittance in the range 25 000--20 000 cm-1, which causes the dark-blue color. To explore the possible use of H-in-rutile as a geohygrometer, geothermobarometer, and oxybarometer, we measured the H+ content in a natural rutile crystal from a retrograded eclogite with a zoned trace element (Fe, Nb, and Zr) content. The crystal reveals a slight correlation between the variable H2O (~200 to 900 ppm) and its trace element concentrations. The observations indicate that the preservation of H+ contents in this natural rutile is a complicated interplay of diffusive reequlibration of fast H+, slower Fe and very slow other trace elements. An interpretation of the H2O contents of the natural crystal in terms of fO2 or aH2O is not possible. [ABSTRACT FROM AUTHOR]

Interfacial tension between immiscible liquids is an important thermodynamic parameter of silicate melt unmixing and a property that determines the kinetics of phase separation. In this study, we present experimental measurements of interfacial tension between immiscible Fe-rich and silica-rich melts in the system K2O-FeO-Fe2O3-Al2O3-SiO2. We have also measured densities and surface tensions of the individual immiscible liquid phases. The measurements were carried out in air at 1500-1550 °C by the maximum detachment force method employing vertical cylinder geometry and using a gravimetric balance system. We have chosen the most oxidized and contrasting liquid compositions containing 73 and 17 wt% SiO2 and 14 and 80 wt% FeOt, respectively, that have been shown to coexist in air at and above 1465 °C. Interfacial tension between the synthetic immiscible liquids decreases with increasing temperature from 16.4 ± 3.1 mN/m at 1500 °C to 7.8 ± 1.1 mN/m at 1550 °C. Interfacial tension between natural, less compositionally contrasting ferrobasaltic and rhyolitic melts should be even lower by a factor of 2 or 3. Very low interfacial tension implies easy nucleation of immiscible liquid droplets and very slow coarsening of resulting silicate emulsions. [ABSTRACT FROM AUTHOR]

Titanite growth at the expense of rutile during retrograde hydration of eclogite into amphibolite is a common phenomenon. We investigated an amphibolite sample from the Tromsø eclogite facies terrain in Northern Norway to gain insight into the trace element distribution between rutile and titanite during incomplete resorption of the rutile by titanite. Patchy compositional zoning of Al, Ti, and F in titanite relates to the presence of a fluid with variable Ti/Al and/or F during its growth. Laser ablation ICP–MS and electron microprobe data for high field strength elements (HFSE: Nb, Zr, Ta, and Hf) of rutile resorbed by titanite indicate a pronounced enrichment of these elements in the rim of a large single rutile crystal (~8 mm) and a systematic decrease towards uniform HFSE contents in the large core. HFSE contents of smaller rutile grains (~0.5 mm) and rutile inclusions (<100 μm) in the titanite overgrowth are similar or higher than in the rims of large rutile crystals. Element profiles from the rim inward demonstrate that HFSE enrichment in rutile is controlled by diffusion. HFSE ratios in diffusion-altered rutile show systematic variations compared with the uniform core composition of the large rutile. Modelling of Zr and Nb diffusion in rutile indicates that diffusion coefficients in rutile in fluid-dominated natural systems must be considerably higher than those determined experimentally at 1 bar in dry systems. Variations of HFSE contents in the newly formed titanite show no systematic spatial distribution. HFSE ratios in titanite and the rims of rutile are different, indicating different solid/fluid distribution coefficients in these minerals. Element fractionation by diffusion into the relict rutile and during fluid-mediated growth of new titanite could substantially change the HFSE budget of these minerals and could affect their use for geochemical tracing and other applications, such as Zr-based geothermobarometry. [ABSTRACT FROM AUTHOR]

Although orthopyroxene (Opx) is present during a wide range of magmatic differentiation processes in the terrestrial and lunar mantle, its effect on melt trace element contents is not well quantified. We present results of a combined experimental and computational study of trace element partitioning between Opx and anhydrous silicate melts. Experiments were performed in air at atmospheric pressure and temperatures ranging from 1,326 to 1,420°C in the system CaO–MgO–Al2O3–SiO2 and subsystem CaO–MgO–SiO2. We provide experimental partition coefficients for a wide range of trace elements (large ion lithophile: Li, Be, B, K, Rb, Sr, Cs, Ba, Th, U; rare earth elements, REE: La, Ce, Nd, Sm, Y, Yb, Lu; high field strength: Zr, Nb, Hf, Ta, Ti; transition metals: Sc, V, Cr, Co) for use in petrogenetic modelling. REE partition coefficients increase from $$ D_{\text{La}}^{{\text{Opx}} {\hbox{-}} {\text{melt}}} \sim 0.0005 $$ to $$ D_{\text{Lu}}^{{{\text{Opx}} {\hbox{-}} {\text{melt}}}} \sim 0.109 $$, D values for highly charged elements vary from $$ D_{\text{Th}}^{{{\text{Opx}} {\hbox{-}} {\text{melt}}}} \sim 0.0026 $$ through $$ D_{\text{Nb}}^{{{\text{Opx}} {\hbox{-}} {\text{melt}}}} \sim 0.0033 $$ and $$ D_{\text{U}}^{{{\text{Opx}} {\hbox{-}} {\text{melt}}}} \sim 0.0066 $$ to $$ D_{\text{Ti}}^{{\text{Opx}} {\hbox{-}} {\text{melt}}} \sim 0.058 $$, and are all virtually independent of temperature. Cr and Co are the only compatible trace elements at the studied conditions. To elucidate charge-balancing mechanisms for incorporation of REE into Opx and to assess the possible influence of Fe on Opx-melt partitioning, we compare our experimental results with computer simulations. In these simulations, we examine major and minor trace element incorporation into the end-members enstatite (Mg2Si2O6) and ferrosilite (Fe2Si2O6). Calculated solution energies show that R2+ cations are more soluble in Opx than R3+ cations of similar size, consistent with experimental partitioning data. In addition, simulations show charge balancing of R3+ cations by coupled substitution with Li+ on the M1 site that is energetically favoured over coupled substitution involving Al–Si exchange on the tetrahedrally coordinated site. We derived best-fit values for ideal ionic radii r0, maximum partition coefficients D0, and apparent Young’s moduli E for substitutions onto the Opx M1 and M2 sites. Experimental r0 values for R3+ substitutions are 0.66–0.67 Å for M1 and 0.82–0.87 Å for M2. Simulations for enstatite result in r0 = 0.71–0.73 Å for M1 and ~0.79–0.87 Å for M2. Ferrosilite r0 values are systematically larger by ~0.05 Å for both M1 and M2. The latter is opposite to experimental literature data, which appear to show a slight decrease in $$ r_{0}^{{{\text{M}}2}} $$ in the presence of Fe. Additional systematic studies in Fe-bearing systems are required to resolve this inconsistency and to develop predictive Opx-melt partitioning models for use in terrestrial and lunar magmatic differentiation models. [ABSTRACT FROM AUTHOR]

The Jurassic to Early Cretaceous magmatic arc of the Andes in northern Chile was a site of major additions of juvenile magmas from the subarc mantle to the continental crust. The combined effect of extension and a near stationary position of the Jurassic to lower Cretaceous arc favoured the emplacement and preservation of juvenile magmatic rocks on a large vertical and horizontal scale. Chemical and Sr, Nd, and Pb isotopic compositions of mainly mafic to intermediate volcanic and intrusive rock units coherently indicate the generation of the magmas in a subduction regime and the dominance of a depleted subarc mantle source over contributions of the ambient Palaeozoic crust. The isotopic composition of the Jurassic (206Pb/204Pb: ∼ 18.2; 207Pb/204Pb: ∼ 15.55; 143Nd/144Nd: ∼ 0.51277; 87Sr/86Sr: ∼ 0.703–0.704) and Present (206Pb/204Pb: ∼ 18.5; 207Pb/204Pb: ∼ 15.57; 143Nd/144Nd: ∼ 0.51288; 87Sr/86Sr: ∼ 0.703–0.704) depleted subarc mantle beneath the Central and Southern Andes (18°–40°S) was likely uniform over the entire region. Small differences of isotope ratios between Jurassic and Cenozoic to Recent of subarc mantle-derived could be explained by radiogenic growth in a still uniform mantle source. [ABSTRACT FROM AUTHOR]

Multimineral Rb/Sr internal isochrons from eclogite facies rocks of the Eclogite Zone (Tauern Window, Eastern Alps) consistently yield an Early Oligocene age of 31.5±0.7 Ma. This age has been obtained both for late-prograde, dehydration-related eclogitic veins, and for rocks variably deformed and recrystallized under eclogite facies conditions (2.0–2.5 GPa, 600°C). Initial Sr-isotopic equilibria among all phases indicate absence of significant post-eclogitic isotope redistribution processes, therefore the ages date eclogite facies assemblage crystallization. Equilibria also prove that no prolonged pre-eclogite facies history is recorded in the rocks. Instead, subduction, prograde mineral reactions, and eclogitization proceeded rapidly. Fast exhumation immediately after eclogitization, with minimum rates >36 mm/a is inferred from a 31.5±0.5 Ma internal mineral isochron age of a post-eclogitic greenschist facies vein assemblage. Such rates equal typical subduction rates. Late Eocene to Early Oligocene subduction of the European continental margin, with subsequent rapid exhumation of high-pressure nappe complexes has previously been recognized only in the Western Alps. The new data signify synchronous continental collision all along the Alpine belt. Our results demonstrate the unique potential of Rb/Sr assemblage ‘system analysis’ for precise dating of both eclogite facies and post-eclogitic events, thus for precisely constraining exhumation rates of deep-seated rocks, and for straightforward linkage of petrologic evidence with isotopic ages. [ABSTRACT FROM AUTHOR]

Sulfate substituents naturally occurring in biomolecules, such as oligosaccharides and polysaccharides, can play a critical role in major physiological functions in plants and animals. We show that laminarin, a β-1,3 glucan with elicitor activity in tobacco (Nicotiana tabacum), becomes, after chemical sulfation, an inducer of the salicylic acid (SA) signaling pathway in tobacco and Arabidopsis thaliana. In tobacco cell suspensions, the oxidative burst induced by the laminarin sulfate PS3 was Ca2+ dependent but partially kinase independent, whereas laminarin triggered a strickly kinase- dependent oxidative burst. Cells treated with PS3 or laminarin remained fully responsive to a second application of laminarin or PS3, respectively, suggesting two distinct perception systems. In tobacco leaves, PS3, but not laminarin, caused electrolyte leakage and triggered scopoletin and SA accumulation. Expression of different families of Pathogenesis-Related (PR) proteins was analyzed in wild-type and mutant tobacco as well as in Arabidopsis. Laminarin induced expression of ethylene- dependent PR proteins, whereas PS3 triggered expression of ethylene- and SA-dependent PR proteins. In Arabidopsis, PS3- induced PR1 expression was also NPR1 (for nonexpressor of PR genes1) dependent. Structure-activity analysis revealed that (1) a minimum chain length is essential for biological activity of unsulfated as well as sulfated laminarin, (2) the sulfate residues are essential and cannot be replaced by other anionic groups, and (3) moderately sulfated β-1,3 glucans are active. In tobacco, PS3 and curdlan sulfate induced immunity against Tobacco mosaic virus infection, whereas laminarin induced only a weak resistance. The results open new routes to work out new molecules suitable for crop protection. [ABSTRACT FROM AUTHOR]

Mesozoic mantle-derived magmatic rocks from the Jurassic-Early Cretaceous active continental margin of N Chile near 24°S, and from the Cretaceous rift system of NW Argentina near 26°S (central rift) and 32°S (southern rift) are used to constrain the isotopic composition of mantle reservoirs before the onset of the Cenozoic Andean orogeny. They are largely uncontaminated by assimilation of the local Palaeozoic basement as seen in the major and trace element patterns and Sr and Nd isotopic composition of most samples, but small amounts of crustal contamination are detected in the Pb isotope composition. Two different types of mantle sources have been identified. (1) For rocks from the Jurassic arc, now at the continental margin at 24°S, and for rocks from the central rift at 26°S, a depleted mantle source with [sup 143]Nd/[sup 144]Nd[sub (t)] 0.5127-0.5128, [sup 87]Sr/ [sup 86]Sr[sub (t)] ca. 0.7033 may be inferred. Pb isotopic ratios of most samples from the magmatic arc are overall less radiogenic than those from the rift ([sup 206]Pb/[sup 204]Pb[sub (t)] ca. 18.0-18.4 vs. 18.1-19.1, [sup 207]Pb/[sup 204]Pb[sub (t)] 15.55-15.59 vs. 15.58-15.64 and [sup 208]Pb/[sup 204]Pb[sub (t)] 37.8-38.6 vs. 38.4-38.9). (2) In the southern rift at ca. 30-32°S [Sierras Los Cóndores region (LC) and Sierras Chaján region (Ch)], an enriched mantle source has been identified, which is similar to the composition of the mantle lithosphere beneath the Brazilian Shield. Samples from LC and Ch show some isotopic differences because of varying degrees of crustal contamination in the LC samples. The LC samples have a higher Th/U ratio than the Ch samples and different Pb isotopic ratios [sup 206]Pb/[sup 204]Pb[sub (t)] 18.0-18.6 (LC) vs. 17.7 and 17.8 (Ch), [sup 2]7]Pb/[sup 204]Pb[sub (t)] 15.50-15.66 (LC) vs. 15.50 (Ch) and [sup 208]Pb/[sup 204]Pb[sub (t)] 38.6-39.2 (LC) vs. ca. 37.5 (Ch). The Nd isotopic ratios of LC and Ch samples are similar [sup... [ABSTRACT FROM AUTHOR]

Studies the experimental sodium (Na) and potassium (K) distribution between amphiboles and aqueous chloride solutions. Equilibrium distribution coefficients for Na and K between Na- and K-richterite and aqueous liquids; Review of past studies; Conduction of a synthesis experiment; Usefulness of the richterite compositions.

A new type of sector zoning, with an hourglass shape, has been identified in metamorphic tourmalines that formed under a wide variety of physical and chemical conditions. The two sectors in the c-direction are not equivalent due to asymmetry in the crystal structure of tourmaline along the c-axis. The c+ sector is characterized by low concentrations of Ti, Ca, Mg, and Na, although Al is high, and has a pale (commonly blue or pale-green) color. Conversely, the c- sector is low in Mg and Al, and high in Ca, Fe, and Ti (the latter two causing the dark-brown color of this sector). The a-sector has intermediate characteristics and probably approximates a sector-free tourmaline. Thin sectioning of these sector-zoned tourmalines perpendicular to the c-axis can produce three types of apparent radial zoning patterns: blue-green cores, dark-brown cores, or no distinct cores. These apparent cores will further vary in relative diameter depending on the sectioning level. Furthermore, "core" boundaries can be straight or ragged depending on whether the relative growth speeds for the different faces was constant or variable. These textures have been used to argue for a prograde or detrital origin of tourmaline cores. However, sector zoning is a more appealing explanation for most of these textures, and can further explain the textural resemblance among metamorphic tourmalines from highly variable bulk-rock composition, metamorphic history, and mineral paragenesis. The sector zoning that is described here develops by preferential uptake of elements on the r growth plane, resulting from a combined effect of differences in surface charge and morphology of this plane in the c+ and c- directions. This leads to the preferential incorporation of more positively charged elements in the c- direction, and a preference for a vacant X-site in the c+ direction. Because the compositional differences among the sectors are pronounced in both major and trace elements and in the same order of magnitude as growth zoning variability, the presence of sector zoning must be established and taken into account when making inferences from tourmaline chemistry. [ABSTRACT FROM AUTHOR]