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The western region of the southern Pantanal is characterised by soils with high phosphorus (P) contents, derived from materials from the surrounding lithostratigraphic units, accumulated by fluvial transport. However, studies on forms and availability of P in these soils are scarce. The objective of this study was to evaluate the different forms of inorganic P and their relationship with some attributes of carbonatic soils in the Pantanal of Mato Grosso do Sul, Brazil. Hedley's sequential fractionation scheme was used to evaluate the forms of P in soil profiles: Kastanozems (profiles PI and P3) and Gleysol (profile P2). Total P contents were similar in the three profiles, 3782-5637 mg [kg.sup.-1], with mean values of 22% for organic P and 46% for inorganic P (P.i). The P.i results indicated that in the profiles there was a predominance of inorganic forms of P in the following order: P-NaOH 0.5 mol [L.sup.-1] > P-NaHC[O.sub.3] > P-NaOH 0.1 mol [L.sup.-1] > P-HC1, that is, adsorbed to microaggregates, labile, adsorbed to oxides and precipitated with calcium (Ca), respectively. The highest values of total organic P were verified in the surface horizons, with high correlation with total P contents. Residual P contents were high in all profiles, representing 29.0-33.3% of the total P, being correlated with CaC[O.sub.3] contents. The studied profiles had high contents of labile P, with the highest values in the fraction P.i-NaHC[O.sub.3], possibly associated with the processes of reduction of iron during the periods of floods, making the adsorbed P available. The contents of P.i-NaOH 0.1 mol [L.sup.-1], a moderately labile fraction adsorbed to oxides, showed few differences compared to the non-labile fractions associated with Ca (P.i-HCl). Possibly, organic matter was bound to Ca, inhibiting the formation of precipitates of Ca with P and making P available for the more labile fractions. Keywords: Secondary carbonate, Flood cycle, Phosphorus fractionation, Organic matter, Iron reduction., Introduction The Pantanal, with an area of ~ 150 988 [km.sup.2] (IBGE 2019), is the largest humid complex in the world (Por 2012) and has 11 distinct sub-regions. The sub-regions [...]

Abstract: Pseudo-first-order rate constants ([k.sub.obsd]) were measured for nucleophilic substitution reactions of O-Y-substituted-phenyl O-phenyl thionocarbonates (4a-4h) with alkali metal ethoxides (EtOM, M = Li, Na, or K) in anhydrous ethanol [...]

Despite intensive commercial agriculture in the rift zone of Tanzania, mineralogical studies on the soils influenced by volcanic parent materials are scarce. A mineralogical investigation of the soils and two buried ash layers from an irrigated sugar estate was undertaken using X-ray diffraction, transmission electron microscopy and measurements of extractable iron, aluminium and silicon and the specific surface arca (SSA) of the clay fraction. The dominant mineral in the sand and silt fractions was sanidine. The clay fractions contained mainly high-defect kaolin, illitc and K-feldspar, with small amounts of calcite, talc and gibbsitc in some samples. Electron microscopy revealed the presence of tubular and spheroidal halloysitc and Additional keywords: allophane, halloysite, high-defect kaolinite, sanidine, specific surface area. Received 9 October 2014, accepted 11 April 2016, published online 22 August 2016, Introduction Soils in areas associated with volcanic activity often have a unique assembly of clay minerals comprising both nanocrystalline and layered silicate minerals (Shoji et al. 1993; Harsh et al. [...]

The islands of the Azores archipelago emerge from an oceanic plateau built on lithosphere increasing in age with distance from the Mid-Atlantic Ridge from 10 to 45 Ma. Here, we present the first comprehensive major and trace element and Sr-Nd-Pb isotope data from Santa Maria, the easternmost island of the archipelago, along with published data from the other Azores islands situated much closer to the Mid-Atlantic Ridge axis. We can show that the distinctively more variable and more enriched trace element ratios at Santa Maria combined with a relatively small range in Sr-Nd-Pb isotope ratios are the result of low degrees of partial melting of a common Azores mantle plume source underneath thicker lithosphere. This implies that melt extraction processes and melting dynamics may be able to better preserve the trace element mantle source variability underneath thicker lithosphere. These conclusions may apply widely for oceanic melts erupted on relatively thick lithosphere. In addition, lower Ti/Sm and K/La ratios and Si[O.sub.2] contents of Santa Maria lavas imply melting of a carbonated peridotite source. Mixing of variable portions of deep small-degree carbonated peridotite melts and shallow volatile-free garnet peridotite could explain the geochemical variability underneath Santa Maria in agreement with the volatile-rich nature of the Azores mantle source. However, Santa Maria is the Azores island where the C[O.sub.2]-rich nature of the mantle source is more evident, reflecting a combination of a smaller extent of partial melting and the positioning at the edge of the tilted Azores mantle plume. Keywords Ocean Island Basalts * Azores * Lithosphere thickness * Melting dynamics * Carbonated peridotite, Introduction Basalts erupted at Ocean Islands (OIB) display a larger trace element and isotopic variability compared to those erupted along mid-ocean ridges (MOR) (e.g., Dupre and Allegre 1983; Hofmann 1997; [...]

Byline: G. Rosatelli (1), F. Wall (2), F. Stoppa (1), M. Brilli (3) Keywords: Extrusive carbonatite; Limestone; LAICPMS; Polino; Italy Abstract: Petrography-controlled laser ablation inductively coupled plasma mass spectrometry (LAICPMS) analyses of carbonate in fresh shallow level sub-volcanic Polino monticellite calcio-carbonatite tuffisite have been performed to assess the geochemical differences between fresh igneous, epigenetic carbonates and sedimentary accidental fragments. Igneous calcite has consistently high LREE/HREE ratios (La/Yb.sub.N, 15--130) due to high LREE ([summation over (term)]LREE, 425--1,269 ppm). Secondary calcite cements are characterized by progressively lower and more variable trace element contents, with lower LREE/HREE ratios. A distinguishing geochemical feature is progressively increasing negative Ce anomalies observed through coarse secondary calcite that can be related to the surface environment processes. The limestone accidental fragments in the tuffisite have trace element contents almost two orders of magnitude lower than igneous carbonate and low LREE ([summation over (term)]LREE < 9.5 ppm) with low LREE/HREE fractionation (La/Yb.sub.N ratios < 18). The stable isotope composition of different carbonate types is consistent with their formation in different environments. The tuffisitization processes during diatreme formation under high CO.sub.2-OH fugacity conditions may account for the differences noted in the igneous carbonates. Author Affiliation: (1) Dipartimento di Scienze della Terra, Universita G. d'Annunzio, Via dei Vestini, 30, 66013, Chieti, Italy (2) Camborne School of Mines, University of Exeter, Cornwall Campus, Penryn, TR10 9EZ, UK (3) CNR, Piazzale Aldo Moro, 00185, Rome, Italy Article History: Registration Date: 01/02/2010 Received Date: 12/05/2009 Accepted Date: 01/02/2010 Online Date: 19/03/2010 Article note: Communicated by J. Blundy. G. Rosatelli and F. Wall were formerly with the Natural History Museum, Cromwell Road, London, SW7 5BD, UK.

Carbon dioxide and carbonates are widely distributed in nature, are constituents of inorganic and organic matter, and are essential in vegetable and animal organisms. C[O.sub.2] is the principal greenhouse gas in the atmosphere. In human blood, C[O.sub.2]/HC[O.sub.3.sup.-] is an important buffering system. Quantification of bicarbonate and 'carbonate in inorganic and organic matter and in biological fluids such as blood or blood plasma by means of the GC-MS technology has been impossible so far, presumably because of the lack of suitable derivatization reactions to produce volatile and thermally stable derivatives. Here, a novel derivatization reaction is described for carbonate that allows for its quantification in aqueous alkaline solutions and alkalinized plasma and urine. Carbonate in acetonic solutions of these matrices (1:4 v/v) and added [sup.13]C-labeled carbonate for use as the internal standard were heated in the presence of the derivatization agent pentafluorobenzyl (PFB) bromide for 60 min and 50[degrees]C. Investigations with [sup.12]C[O.sub.3.sup.2-], [sup.13]C[O.sub.3.sup.2-], [(C[H.sub.3]).sub.2]CO, and [([CD.sub.3]).sub.2]CO in alkaline solutions and GC-MS and GC-MS/MS analyses under negative-inn chemical ionization (NICI) or electron ionization (EI) conditions of toluene extracts of the reactants revealed formation of two minor [i.e., PFB-OCOOH and O=C[O.sub.2]-[(PFB).sub.2]] and two major [i.e., C[H.sub.3]COC[H.sub.2]-C(OH)[(OPFB).sub.2] and C[H.sub.3]COCH=C[(OPFB).sub.2]] carbonate derivatives. The latter have different retention times (7.9 and 7.5 min, respectively) but virtually identical EI and NICI mass spectra. It is assumed that C[H.sub.3]COC[H.sub.2]-C(OH)[(OPFB).sub.2] is formed from the reaction of the carbonate dianion with two molecules of PFB bromide to form the diPFB ester of carbonic acid, which further reacts with one molecule of acetone. Subsequent loss of water finally generates the major derivative C[H.sub.3]COCH=C[(OPFB).sub.2]. This derivatization reaction was utilized to quantify total C[O.sub.2]/HC[O.sub.3.sup.-]/C[O.sub.3.sup.2-] (tC[O.sub.2]) in human plasma and urine by GC-MS in the NICI mode by selected ion monitoring of the anions [[M - H].sup.-] of C[H.sub.3]COCH=C[(OPFB).sub.2] at m/z 461 for the endogenous species and m/z 462 for the internal standard [sup.13]C[O.sub.3.sup.2-]. Oral intake of the carboanhydrase inhibitor drug acetazolamide by two healthy volunteers resulted in temporary increased excretion of tC[O.sub.2] in the urine. The method is specific for carbonate, accurate, sensitive and should be applicable to various matrices including human fluids and environmental samples. 10.1021/ac1007688

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2010.05.002 Byline: Jose Antonio de Almeida Keywords: carbonate reservoir; lithoclasses; geostatistics; multi-phase variable; sequential indicator simulation; truncated gaussian simulation; simulated annealing; probability field simulation Abstract: The construction of a reservoir model begins with the geology, specifically a geological conceptual model, sub-division into layers, top and bottom limits/surfaces, and characterization of rock types or facies within the layers. To model the geology in heterogeneous case studies, of which carbonate reservoirs are a good example, conceptual and deterministic models are unable to adequately represent the internal geometry and, for this reason, stochastic models are most, particularly used mainly for the spatial characterization of rock types. This paper presents a comparison of bi-point geostatistical simulation methods for characterization of lithoclasses, making use of a carbonated reservoir as a case study. To cope with the geological complexity, and to assist in understanding the internal distribution of properties, the lithoclasses were derived from cores based on their lithology, petrophysical properties and capillary pressure, and subsequently extended to log data. Five simulation methodologies, able to deal with categorical variables, are compared in a multi-phase framework: (1) truncated gaussian simulation, posterior conditioning and classification of simulated probabilities based on local and global proportions (TGSPC); (2) truncated gaussian simulation, posterior conditioning and classification using simulated annealing (TGSPC+SA); (3) sequential indicator simulation with correction for local probabilities (SIS); (4) simulated annealing post-processing of sequential indicator simulation images (SIS+SA); and (5) probability field simulation (PFS). Matched to experimental data, theoretical multi-phase variogram models, and proportions are observed, as well as the presence of artefacts. To evaluate the range of uncertainty of the simulated images, 30 realizations are generated, and entropy and average geobody volumes (connected blocks belonging to the same lithoclass) are computed and compared. Author Affiliation: CICEGe, Departamento de CiA*ncias da Terra, Faculdade de CiA*ncias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal Article History: Received 17 March 2009; Accepted 20 May 2010

Molecular beam scattering experiments are used to investigate reactions of S[O.sub.2] at the surface of a molten alkali carbonate eutectic at 683 K. We find that two-thirds of the S[O.sub.2] molecules that thermalize at the surface of the melt are converted to gaseous C[O.sub.2] via the reaction S[O.sub.2](g) + C[O.sup.2-.sub.3] [right arrow] C[O.sub.2](g) + S[O.sup.2-.sub.3]. The C[O.sub.2] product is formed from S[O.sub.2] in less than [10.sup.-6]s, implying that the reaction takes place in a shallow liquid region less than 100 [Angstrom] deep. The reaction probability does not vary between 683 and 883 K, further' implying a compensation between decreasing S[O.sub.2] residence time in the near-interfacial region and increasing reactivity at higher temperatures. These results demonstrate the remarkable efficiency of S[O.sub.2] [right arrow], C[O.sub.2] conversion by molten carbonates, which appear to be much more reactive than dry calcium carbonate or wet slurries commonly used for flue gas desulfurization in coal-burning power plants. flue gas desulfurization | gas scrubbing | gas-liquid reactions | liquid surface | molecular beam scattering doi/ 10.1073/pnas.0910993107

Byline: M. Santosh (1,2), Toshiaki Tsunogae (3), Hisako Shimizu (3), Jean Dubessy (4) Keywords: Eclogite; High pressure granulite; Mineral phase equilibria; Fluid inclusions; CO.sub.2; Southern India; Gondwana Abstract: Eclogite-facies rocks and high-pressure granulites provide windows to the deeper parts of subduction zones and the root of mountain chains, carrying potential records of fluids associated with subduction-accretion-collision tectonics. Here, we report petrological and fluid inclusion data on retrogressed eclogite and high-pressure granulite samples from Sittampundi, Kanji Malai and Perundarai in southern India. These rocks occur within the trace of the Cambrian collisional suture which marks the final phase of amalgamation of the Gondwana supercontinent. The garnet--clinopyroxene assemblage in the eclogites preserves relict omphacite, whereas the high-pressure granulites are characterized by an assemblage of garnet and clinopyroxene in the absence of omphacite and with minor plagioclase, orthopyroxene, and quartz. Phase relations computed for the eclogite assemblage yield peak P--T conditions of 19 kbar and 1,010degC. The mafic granulites also preserve the memory of high to ultrahigh-temperature metamorphism followed by an isothermal decompression. Systematic fluid inclusion optical, microthermometric and laser Raman spectroscopic studies were conducted in garnet and plagioclase from the eclogite--high pressure granulite suite. The results suggest that the early fluids were a mixture of CO.sub.2, CH.sub.4 and N.sub.2 probably derived from decarbonation and devolatilization reactions in a subduction setting during the prograde stage. The later generation inclusions, which constitute the dominant category in all the samples studied, are characterized by a near-pure CO.sub.2 composition with moderate to high densities (up to 1.154 g/cm.sup.3). The highest density fluid inclusions recorded in this study occur within the mafic granulites from Sittampundi (0.968--1.154 g/cm.sup.3) and Kanji Malai (1.092--1.116 g/cm.sup.3). In some cases, carbonate minerals such as dolomite and calcite are associated with the CO.sub.2-rich fluid inclusions. The composition and densities of the later generation fluids closely match with those of the CO.sub.2-bearing fluid inclusions reported from ultrahigh-temperature granulites occurring proximal to the eclogite--high pressure granulite suite within this suture zone, and suggest a common tectonic link for the fluid regime. We evaluate the fluid characteristics associated with convergent plate margin processes and propose that the early aqueous fluids probably associated with the eclogites were consumed during the formation of the retrograde hydrous mineral assemblages, whereas the fluid regime of the high-pressure and ultrahigh-temperature granulites was mostly CO.sub.2-dominated. The tectonic setting of the rocks along a collisional suture marking the trace along which crustal blocks were welded through subduction--collision process is in favor of a model involving the derivation of CO.sub.2 from sub-lithospheric sources such as a carbonated tectosphere invaded by hot asthenosphere, or underplated mafic magmas. Author Affiliation: (1) Faculty of Science, Kochi University, Akebono-cho, Kochi, 780-8520, Japan (2) Department of Earth and Atmospheric Sciences, Center for Environmental Sciences, Saint Louis University, St. Louis, MO, 63108, USA (3) Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan (4) G2R(UMR 7566), Nancy Universite and CNRS, BP70239, 54506, Vandoeuvre-les-Nancy Cedex, France Article History: Registration Date: 16/07/2009 Received Date: 22/10/2008 Accepted Date: 16/07/2009 Online Date: 30/07/2009 Article note: Communicated by J.L.R. Touret. Electronic supplementary material The online version of this article (doi: 10.1007/s00410-009-0431-4) contains supplementary material, which is available to authorized users.

Detailed mapping of a portion of the North Spirit Lake greenstone belt reveals a basal basaltic volcanic unit (ca. 3 Ga) with a komatiitic component and strong major and trace element geochemical affinity with typical mid-ocean ridge basalts (e.g., N-MORB). The overlying transitional unit includes basaltic tufts, which have close geochemical affinity to the underlying basalts, and to N-MORB. Interbedded with and overlying the tufts is a thin, laterally continuous sulfide-rich unit with chert interbeds, which is in turn over-lain by interbedded carbonate, chert, and iron-rich sedimentary rocks. The chemical sedimentary rocks of the transitional unit display rare-earth element (REE) patterns and positive Eu anomalies consistent with derivation from fluids associated with submarine hydrothermai vent fields. The sulfide unit is interpreted to represent proximal hydrothermal vent deposits derived from black smoker activity near a spreading center. The overlying carbonate and chert mounds and beds are interpreted as hydrothermal deposits formed at lower temperatures in a more distal setting relative to the spreading center. The carbonate deposits may have formed in an environment analogous to that of the Lost City hydrothermai field (Kelley et al., 2001), where abundant chimneys, dendrites, and beds of carbonate are produced ~15 km from the mid-Atlantic rift axis. The basal volcanic unit consequently is interpreted as ocean-floor basalts formed at an Archean spreading center, with the basaltic tufts representing the last volcanic emanations, and with the chemical sediments representing hydrothermalvents deposits both proximal and distal to the spreading center. The capping siliciclastic unit likely is part of an accretionary wedge, possibly representing ocean closure after a protracted seafloor speading episode. The sedimentary rocks were derived in part, from a weathered tonalite-trondhjemite-granodiorite source. The supracrustal rocks of the North Spirit Lake greenstone belt provide an unusually clear window into some tectonic activity on the primitive Earth, including evidence for the existence of ocean-floor basalts, proximal and distal hydrothermal activity, and possibly a protracted cycle of ocean opening and destruction.

We hypothesized that CaC[O.sub.3] dissolution, coupled to sulfide oxidation, is an important mechanism by which solid-phase inorganic P (iP) becomes available to seagrass in tropical carbonate sediments. To examine this supposition, we measured field sulfate reduction rates and simulated the acidity (10-50 [micro]mol [H.sub.2]S[O.sub.4] [cm.sup.-3] sediment) generated by subsequent sulfide oxidation from high (western) and low (eastern) total P (TP) sediments in Florida Bay. Dissolution experiments were conducted using sediment slurries at field pH (pore-water pH ~6.5-7.5). While CaC[O.sub.3] dissolution (maximum 1.3% of sediment dry weight) was evidenced at all sites by leaching of [Ca.sup.2+] into slurries, at three of the four sites P[O.sup.3-.sub.4] was primarily recovered in the sediment exchangeable pools and at a lower P:Ca ratio than observed in source sediments. In contrast, no P[O.sup.3-.sub.4] was recovered from an eastern bay site with the lowest TP and finest-grained sediments, suggesting that P[O.sup.3-.sub.4] was either tightly adsorbed or incorporated into the carbonate matrix post-acidification. The potential for tight P[O.sup.3-.sub.4] resorption by sediment from the low-TP site was also supported by the rapid rate of isotopic exchange of [sup.33] P[O.sup.3-.sub.4] into the sediment matrix. These adsorptive and incorporation processes may explain the low P[O.sup.3-.sub.4] in pore waters in the eastern vs. western regions of Florida Bay, even upon dissolution of carbonates. Carbonate dissolution coupled to sulfide oxidation could potentially provide 1.8 and 23.5 [micro]mol iP [m.sup.-2] [d.sup.-1] at eastern and western bay sites, respectively, meeting 5% of eastern and 29% of western bay seagrass (Thalassia testudinum) P requirements.

Byline: Steven Creighton (1), Thomas Stachel (1), Sergei Matveev (1), Heidi Hofer (2), Catherine McCammon (3), Robert W. Luth (1) Keywords: Mantle oxidation state; Mantle metasomatism; MARID; Kaapvaal craton; Kimberley kimberlite Abstract: The oxidation state, reflected in the oxygen fugacity (fO.sub.2), of the subcratonic lithospheric mantle is laterally and vertically heterogeneous. In the garnet stability field, the Kaapvaal lithospheric mantle becomes progressively more reducing with increasing depth from Ilog fO.sub.2 FMQ-2 at 110 km to FMQ-4 at 210 km. Oxidation accompanying metasomatism has obscured this crystal-chemical controlled depth-fO.sub.2 trend in the mantle beneath Kimberley, South Africa. Chondrite normalized REE patterns for garnets, preserve evidence of a range in metasomatic enrichment from mild metasomatism in harzburgites to extensive metasomatism by LREE-enriched fluids and melts with fairly unfractionated LREE/HREE ratios in phlogopite-bearing lherzolites. The metasomatized xenoliths record redox conditions extending up to Ilog fO.sub.2 = FMQ, sufficiently oxidized that magnesite would be the stable host of carbon in the most metasomatized samples. The most oxidized lherzolites, those in or near the carbonate stability field, have the greatest modal abundance of phlogopite and clinopyroxene. Clinopyroxene is modally less abundant or absent in the most reduced peridotite samples. The infiltration of metasomatic fluids/melts into diamondiferous lithospheric mantle beneath the Kaapvaal craton converted reduced, anhydrous harzburgite into variably oxidized phlogopite-bearing lherzolite. Locally, portions of the lithospheric mantle were metasomatized and oxidized to an extent that conversion of diamond into carbonate should have occurred. Author Affiliation: (1) Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Canada (2) Institut fur Geowissenschaften, Johann Wolfgang Goethe-Universitat, Frankfurt am Main, Germany (3) Bayrisches Geoinstitut, Universitat Bayreuth, Bayreuth, Germany Article History: Registration Date: 19/09/2008 Received Date: 29/04/2008 Accepted Date: 19/09/2008 Online Date: 19/10/2008 Article note: Communicated by J. Hoefs. Electronic supplementary material The online version of this article (doi: 10.1007/s00410-008-0348-3) contains supplementary material, which is available to authorized users.

Byline: Lili Xu (1), Jorg Renner (2), Marco Herwegh (3), Brian Evans (1) Keywords: Rheology; Carbonates; Constitutive laws; Solute strengthening; Normal grain growth Abstract: We extended a previous study on the influence of Mg solute impurity on diffusion creep in calcite to include deformation under a broader range of stress conditions and over a wider range of Mg contents. Synthetic marbles were produced by hot isostatic pressing (HIP) mixtures of calcite and dolomite powders for different intervals (2--30 h) at 850degC and 300 MPa confining pressure. The HIP treatment resulted in high-magnesian calcite aggregates with Mg content ranging from 0.5 to 17 mol%. Both back-scattered electron images and chemical analysis suggested that the dolomite phase was completely dissolved, and that Mg distribution was homogeneous throughout the samples at the scale of about two micrometers. The grain size after HIP varied from 8 to 31 um, increased with time at temperature, and decreased with increasing Mg content (>3.0 mol%). Grain size and time were consistent with a normal grain growth equation, with exponents from 2.4 to 4.7, for samples containing 0.5--17.0 mol% Mg, respectively. We deformed samples after HIP at the same confining pressure with differential stresses between 20 and 200 MPa using either constant strain rate or stepping intervals of loading at constant stresses in a Paterson gas-medium deformation apparatus. The deformation tests took place at between 700 and 800degC and at strain rates between 10.sup.-6 and 10.sup.-3 s.sup.-1. After deformation to strains of about 25%, a bimodal distribution of large protoblasts and small recrystallized neoblasts coexisted in some samples loaded at higher stresses. The deformation data indicated a transition in mechanism from diffusion creep to dislocation creep. At stresses below 40 MPa, the strength was directly proportional to grain size and decreased with increasing Mg content due to the reductions in grain size. At about 40 MPa, the sensitivity of log strain rate to log stress, (n), became greater than 1 and eventually exceeded 3 for stresses above 80 MPa. At a given strain rate and temperature, the stress at which that transition occurred was larger for samples with higher Mg content and smaller grain size. At given strain rates, constant temperature, and fixed grain size, the strength of calcite in the dislocation creep regime increased with solute content, while the strength in the diffusion creep regime was independent of Mg content. The results suggest that chemical composition will be an important element to consider when solid substitution can occur during natural deformation. Author Affiliation: (1) Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Mass. Avenue, Cambridge, MA, 02139, USA (2) Ruhr-University Bochum, 44780, Bochum, Germany (3) Institute for Geology, University Bern, 3012, Bern, Switzerland Article History: Registration Date: 15/08/2008 Received Date: 18/10/2007 Accepted Date: 15/08/2008 Online Date: 07/09/2008 Article note: Communicated by J. Blundy.

Byline: John R. Bowman (1), John W. Valley (2), Noriko T. Kita (2) Abstract: Oxygen isotope ratios have been measured by ion microprobe and millimeter-scale dental drill along detailed sampling traverses across the boundary between periclase-bearing ([delt[a].sup.18]O = 11.8[per thousand]) and periclase-free ([delt[a].sup.18]O = 17.2[per thousand]) marble layers in the periclase (Per) zone of the Alta Stock aureole, Utah. These data define a steep, coherent gradient in [delt[a].sup.18]O that is displaced a short distance (~4 cm) into the periclase-free (Cal + Fo) layer. SEM and ion microprobe analyses show two isotopically and texturally distinct types of calcite at the grain scale. Clear (well polished) calcite grains are isotopically homogeneous (within analytical uncertainty +-0.27[per thousand], 2SD). More poorly polished (pitted), texturally retrograde 'turbid'-looking calcite has lower and more variable [delt[a].sup.18]O values, and replaces clear calcite along fractures, cleavage traces or grain boundaries. Despite significant lowering of the [delt[a].sup.18]O values in calcite throughout both layers during prograde metamorphism, ion microprobe analyses indicate that individual clear calcite grains are now isotopically homogeneous across the entire gradient in [delt[a].sup.18]O. Diffusion calculations indicate that conservative time scales required for isotopic homogenization of calcite grains by volume diffusion, 30,000--62,000 years at 575--600degC, exceed significantly the timescale (~1,250 years) estimated for the prograde development of the [delt[a].sup.18]O gradient at the boundary between these two marble layers. The ion microprobe data and these diffusion calculations suggest instead that surface reaction mechanisms accompanying recrystallization are responsible for the observed oxygen isotope homogeneity of these calcite grains. Thus, the ion microprobe data are consistent with the formation of calcite in oxygen isotope exchange equilibrium with infiltrating fluid during prograde reaction and recrystallization. Author Affiliation: (1) Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, 84112, USA (2) Department of Geology and Geophysics, University of Wisconsin-Madison, Madison, WI, 53706, USA Article History: Registration Date: 20/06/2008 Received Date: 26/01/2008 Accepted Date: 20/06/2008 Online Date: 20/08/2008 Article note: Communicated by J. Hoefs. Electronic supplementary material The online version of this article (doi: 10.1007/s00410-008-0321-1) contains supplementary material, which is available to authorized users.

The ability of mudrock seals to prevent C[O.sub.2] leakage is a major concern for geological storage of anthropogenic C[O.sub.2]. The long-term performance of a mudrock seal, which provides a natural analogue, in the North Sea Miller oil field has been evaluated. This mudrock seal is immediately above a natural C[O.sub.2]-rich reservoir. The paper reports the stable isotopes of carbon from carbonate minerals in the mudrock that have precipitated in contact with COg during 4 km of burial. A well-defined linear trend of upward-decreasing [[delta].sup.13]C traces the progressive penetration of free-phase C[O.sub.2] causing dissolution and reprecipitation of carbonate minerals. The C[O.sub.2] was emplaced ca. 70-80 Ma, and has only penetrated 12 m vertically in this case. The infiltration rate is estimated as ~9.8 x [10.sup.-7]g [cm.sup.-2] [yr.sup.-1]. Engineered C[O.sub.2] storage under this type of mudrock seal will have a considerable safety margin.

The Triassic-Jurassic boundary is associated with widespread marine and terrestrial extinctions, but there is disagreement regarding the existence and extent of climatic changes that may have driven the biotic crisis. Here, we apply quantitative isotopic climate proxies in order to construct two age-equivalent, relatively continuous temperature and pC[O.sub.2] records that span the eight million years preceding the Triassic-Jurassic boundary and that supersede previous terrestrial records in temporal resolution. The [[delta].sup.18]O data suggest that mean annual temperatures (MAT) increased by 7-9[degrees]C from the late Norian to the Rhaetian in association with the peak increases in pC[O.sub.2] levels. The [[delta].sup.13]C data suggest relatively low late Norian pC[O.sub.2] levels (1500 ppmV), and at least two periods of extreme pC[O.sub.2] levels (~3000 ppmV) preceding the Triassic-Jurassic boundary. These estimates are consistent with a recent Late Triassic climate model that suggests the effects of increased pC[O.sub.2] levels on Pangea would cause severe climatic consequences, including a global MAT increase of 6[degrees]C (>10[degrees]C in some regions). While it is possible that periods of increased aridity could have resulted in erroneously high estimates of both temperature and pC[O.sub.2] levels, it is likely that climate was still fluctuating during the end of the Triassic. Although our data precede the Triassic-Jurassic boundary, many studies conclude that the mass extinction took place over a more prolonged period beginning in the Late Triassic. Thus, climate may have been a significant driving mechanism of the Late Triassic extinctions. Keywords: Late Triassic, paleoclimate, stable isotopes, pedogenic carbonates, extinction.

Byline: Alexis K. Ault (1,2), Jane Selverstone (1) Keywords: Alps; Fluid--rock reaction; Graphite; Titanite; Carbonic fluid; Embrittlement Abstract: Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees of embrittlement during exhumation, depending on the extent to which fluid--rock reactions proceeded. At one site, graphitic schists preserve textural evidence for two metamorphic reactions that modified X.sub. CO.sub.2 and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased X.sub. CO.sub.2 without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction involved net consumption of increasingly CO.sub.2-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I microcracks. Fluid inclusion arrays within the microcracks show that X.sub. CO.sub.2 increased from [proportional to]0.1 to 0.6 during decompression from 4.75 to 2 kbar at a reference temperature of 500degC. Titanite consumption is most pronounced within transgranular Mode I microcracks, but microcracks do not crosscut products of this reaction fluid consumption during reaction was coeval with the end of microcracking, at least on a local scale. At the other site, graphitic schists lack small-scale Mode I cracks as well as evidence for graphite consumption during decompression. SEM imaging shows that graphite is anhedral and pitted at the first site, but occurs in clusters of euhedral grains at the second site. Mass balance calculations demonstrate that rocks with partially consumed graphite were infiltrated by an externally derived, [H.sub.2]O-rich fluid that drove subsequent graphite-fluid reaction. Evidence for similar fluid infiltration is absent at the second site. Variations in the degree of reaction progress indicate that fluid pathways and deformation style were heterogeneous on the scale of millimeters to kilometers during exhumation from mid-crustal depths. Author Affiliation: (1) Department of Earth and Planetary Sciences, University of New Mexico, MSC03 2040, Albuquerque, NM, 87131-0001, Mexico (2) Department of Geological Sciences, University of Colorado at Boulder, 2200 Colorado Ave, Boulder, CO, 80309, USA Article History: Registration Date: 17/03/2008 Received Date: 31/08/2007 Accepted Date: 17/03/2008 Online Date: 29/03/2008 Article note: Communicated by T.L. Grove.

Beachrocks are hard coastal sedimentary formations consisting of various beach sediments, lithified through the precipitation of carbonate cements. The objectives of this contribution are to (a) collate and review information on the reported occurrences, characteristics and formation mechanisms of beachrocks and (b) consider their impacts on the coastal zone. The analysis of the available information has shown that (a) beachrock formation is a global and diachronic phenomenon and (b) the great majority of beachrocks are found in tropical/subtropical and low temperate latitude, microtidal coasts. The cementing agents of beachrocks are composed predominantly of the metastable carbonate phases High Magnesian Calcite (HMC) and Aragonite (Ar), appearing in a diverse crystalline morphology. It has been suggested that cement precipitation in the coastal environment is controlled by: (i) the physicochemical conditions; (ii) the presence of organic compounds and microbes; (iii) the magnitude and distribution of the wave energy along the coast; and (iv) the textural characteristics of the constituent sediments. Various theories have been proposed to explain beachrock formation itself, linking the phenomenon to either physicochemical or biological processes. These theories, however, do not seem to be of universal validity and acceptance, as each is able to explain only some of the reported occurrences. The presence of beachrocks appears to affect beach morphodynamics by: (i) 'locking' the beach profile; (ii) modifying the nearshore hydrodynamics; (iii) changing the porous character of the beach and, thus, its response to wave forcing; and (iv) differential bed erosion at the margins of the beachrock outcrops that can alter significantly the long- and, particularly, the cross-shore sediment transport. Therefore, although relict submerged beachrock outcrops may provide some coastal protection by reducing the wave energy impinging onto the coastline, modern beachrocks may promote offshore loss of unconsolidated beach sediments and buried beachrock outcropping. Finally, the presence of beachrocks may have also significant ecological impacts, as the indigenous (mobile substrate) fauna and flora of the beach is replaced by hard substrate benthic assemblages, which are commonly arranged in hydrodynamically-controlled zones. Keywords: beachrock; carbonate cements: coastal morphodynamics; beach erosion; sediment transport; beach profiles

The reactions of hydrated electron with various radicals are studied in pulse radiolysis experiments. The rate constants of hydrated electron reactions with various reactive radicals are measured over a temperature range of 5-75 degree C, which helps in understanding the hydrated electron radical reaction rates.

The mechanism of carbonate formation from boron hydrides plus allene ([B.sub.4][H.sub.10]{C.sub.3][H.sub.4]) was studied computationally. A new basketlike compound is less stable than the observed basket and the production of arachno carboranes was less favorable due to free energy of activation barrier for loss of [H.sub.2] from [B.sub.4][H.sub.10].

One-step solid-phase transformation from high-quality cadmium carbonate microcrystal into highly nanoporous cadmium oxide is demonstrated. The new approach is found to have good potential to prepare nanoporous material at a large scale by using perfect monolithic carbonate crystals, and is also useful to synthesize different nanoporous materials on metal-oxide-coated substrates.

Synthetic, X-ray structural and reactivity studies of Cp*[Ru.sup.IV] complexes containing bidentate dithiocarbonate, xanthate, carbonate, and phosphinate ligands (Cp*=[eta.sup.5]-[C.sub.5][Me.sub.5] was carried out. The observed reversible one step four-electron redox reactions in the [Ru.sup.II] complex [[Ru(DTC)(CO)(PP[h.sub.3])([mu]-SPh)].sub.2] indicates that electron-rich Ru(DTC) complexes are potential candidates as multielectron catalysis.

Neutron diffraction with isotopic substitution (NDIS) experiments and molecular dynamics (MD) simulations are applied to characterize the structure of aqueous guanidinium carbonate solutions. The presence of clustering on the nanometer length scale is confirmed by using small-angle neutron scattering experiments, which suggests a molecular-level explanation for the contrasting denaturant properties of guanidinium salts in solution.

Chemiluminescence energy transfer reaction is investigated for the on-line preparation of peroxymonocarbonate and Eu(II) - dipicolinate complex. The peroxymonocarbonate system is a simple, inexpensive and relatively nontoxic alternative to other oxidants and hence can be used in a mild, neutral-pH environment.

Results from Car-Parrinello molecular dynamics simulations are reported for three uranyl complexes such as [UO2[(OH2)5.sup.2+], UO2(NO3)2(OH2)2, and UO2(NO3)2([eta.sup.2]-tmma) in the gas phase and in aqueous solution. The distances between uranyl and neutral ligands such as water and tmma are decreased by up to 0.2 angstrom upon hydration, whereas those between uranyl and the nitrate ion are increased by up to 0.08 angstrom.

The redox behavior and complexation equilibria of Mn(super 2+) are investigated in aqueous solutions of bicarbonate by voltammetry and electron paramagnetic resonance (EPR) spectroscopy and the implications for the uptake of Mn(super 2+) by mangano-cluster enzymes such as photosystem II (PSII) are discussed. The derived molecular structures include Mn(super 2+)(HCO(sub 3)(super -))(OH2)(sub 4-5) for the 1 is to 1complex and Mn(super 2+=)(CO(sub 3)(super 2-))(HCO(sub 3)(super -))(OH2)(sub 3) for the 1 is to 2 complex.

Diastereoselective palladium-catalyzed formate reduction of allylic carbonates presents unique opportunities for application in organic synthesis provided that stereoselectivity in the course of this metal-catalyzed reaction can be controlled. Developments on efficient metal-catalyzed process exploiting resident stereocenters on the substrates as a means to control stereoselectivity en route to preparing propionate units containing an array of stereochemical patterns are presented.

Moller-Plesset perturbation theory and density functional theory calculations are used to study decomposition mechanisms of polymerization initiators, such as diethyl peroxydicarbonate, trifluoroacetyl peroxide, and acetyl peroxide, which posses a general structure of RC(O)OO(O)CR. Geometrical and energetic analyses indicate that despite the similar structures of the peroxydicarbonates, quite different decomposition energy barriers are determined by the nature of the R groups.

The melting relationships in the system CaMg[Si.sub.2][O.sub.6] (Di)--C[O.sub.2] have been studied in the 3-8 GPa pressure range to determine if there is an abrupt decrease in the temperature of the solidus accompanying the stabilization of carbonate as a subsolidus phase. Such a decrease has been observed previously in peridotitic and some eclogitic systems. In contrast, the solidus in the Di--C[O.sub.2] system was found to decrease in a gradual fashion from 3 to 8 GPa. This decrease accompanies an evolution in the composition of the melt at the solidus from silicate-rich with minor C[O.sub.2] at 3 GPa to carbonatitic at 5.5 GPa, where the carbonation reaction Diopside + C[O.sub.2] = Dolomite (Dol) + Coesite (Cst) intersects the solidus. The near-solidus melt remains carbonatitic at higher pressure, consistent with carbonate being the dominant contributor to the melt. Based on previous studies in both eclogitic and peridotitic systems, this conclusion can be extended to more complicated systems: once carbonate is a stable subsolidus phase, it plays a major role in controlling both the temperature of melting and the composition of the melt produced.

A novel tetranuclear mu4(super -)eta(super 2):eta(super 2-)O,O carbonate nickel cluster with an S = 4 ground state is constructed by dinuclear building blocks of a predefined S = 2 pair state and a suitable cross-link ligand. The dinucleating Schiff base induces a ferromagnetic coupling per se between the metal centers allocated in each one of its N(sub 2)O(sub 2) pockets and these dinuclear units act as initial building blocks in construction of transition metal clusters of large S ground states using linking donors.

Alkylation of metal carbonate in various ionic liquids with 1-bromo-3-phenylpropone as a model reactant was investigated. A new phosgene-free method for the synthesis of symmetrical organic carbonates through alkylation of metal carbonate with various alkyl halides and sulfonates in 1-n-butyl-3-methyl-imidazolium hexafluorophosphate, as an ecofriendly reaction media was reported.

A demonstration showing that the bis(triphenylphosphine)immium (PPN) manganese carbonyls and more interestingly the off-the-shelf reagent PPN(super +)Cl(super -) are good catalysts for the coupling reactions of CO2 with epoxides to yield cyclic carbonates is presented. The reactions are clean with no polycarbonate contamination and are performed in neat substrates with no need of organic solvents.

Cell extraction with cold nonionic detergents or alkaline carbonate prepares an insoluble membrane fraction whose buoyant density permits its flotation in discontinuous sucrose gradients. The lipid rafts are implicated in protein sorting and are attractive candidates as platforms that coordinate signal transduction pathways with intracellular substrates.

The reactions of anilines with 4-nitrophenyl, 4-methylphenyl, and 4-chlorophenyl 4-nitrophenyl carbonates are studied in the aqueous ethanol, to clarify the mechanisms of the aminolysis of diaryl carbonates. The main goal is to evaluate the influence of the amine nature and that of the leaving and nonleaving groups of the carbonate on the kinetics and mechanisms.

The reaction of CO2 with a variety of epoxides is examined in the presence of ionic liquids (ILs) wherein tetrahaloindate(III)-based ILs are found to exhibit interactions in the [Q][InX3Y]-catalyzed coupling reactions. The effects of various parameters such as temperature, pressure, and molar ratio of propylene oxide to catalyst are investigated, and the plausible reaction mechanism based on the (super 1)H and (super 13)C NMR studies is presented for the formation of propylene carbonate.

Benzotriazole reagents for thioacylation, thiocarbamoylation, aryl/alkoxy-thioacylation, and aryl/alkythiothiocylation are synthesized. Their utility is assessed of representative hetroaryl thioureas, thioamides, thionoesters, thiocarbamates, thuiocarbamates, thiocarbonates, and bithiocarbonates.

A demonstration that Gibbs ensemble Monte Carlo simulations could be employed to accurately predict the phase equilibria of a carbonate ether copolymer with CO2 is presented. The simulations indicate that the greater accessibility of the carbonyl oxygen plays a major role for the CO2-philicity to this copolymer surfactant.

Phenyl 4,6-di-O-benzyl-2,3-O-carbonyl-beta-D-glucothiopyranoside and the regiosiomeric phenyl 2,6-di-O-benzyl-3,4-O-carbonyl-beta-D-glucothiopyranoside are prepared and studied as glucosyl donors at -60 degrees Celsius in dichloromethane with preactivation by 1-benzenesulfinyl piperidine before addition of the acceptor alcohol. The 2,3-O-carbonate protected donor showed moderate to excellent beta-selectivity under these conditions depending on the acceptor employed.