Volatiles in Basaltic Glasses from Loihi Seamount, Hawaii: Evidence for a Relatively Dry Plume Component

New H₂O, CO₂ and S concentration data for basaltic glasses fromLoihi seamount, Hawaii, allow us to model degassing, assimilation,and the distribution of major volatiles within and around theHawaiian plume. Degassing and assimilation have affected CO₂and Cl but not H₂O concentrations in most Loihi glasses. Waterconcentrations relative to similarly incompatible elements inHawaiian submarine magmas are depleted (Loihi), equivalent (Kilauea,North Arch, Kauai–Oahu), or enriched (South Arch). H₂O/Ceratios are uncorrelated with major element composition or extentor depth of melting, but are related to position relative tothe Hawaiian plume and mantle source region composition, consistentwith a zoned plume model. In front of the plume core, overlyingmantle is metasomatized by hydrous partial melts derived fromthe Hawaiian plume. Downstream from the plume core, lavas tapa depleted source region with H₂O/Ce similar to enriched Pacificmid-ocean ridge basalt. Within the plume core, mantle components,thought to represent subducted oceanic lithosphere, have waterenrichments equivalent to (KEA) or less than (KOO) that of Ce.Lower H₂O/Ce in the KOO component may reflect efficient dehydrationof the subducting oceanic crust and sediments during recyclinginto the deep mantle. KEY WORDS: basalt; Hawaii; mantle; plumes; volatiles     

CHARACTERIZATION OF THE EFFECT OF PEAK SHIFTS ON THE PERFORMANCE OF THE KALMAN FILTER IN MULTICOMPONENT ANALYSES

The effect of peak shifts on the performance of a Kalman filter multicomponent analysis algorithm hasbeen investigated.A series of Gaussian test systems were employed to characterize the concentrationestimation errors and the morphology of the on-line residuals(the innovations sequence).Both forwardand reverse filters were used in the generation of the innovations sequences.It was found that thedifference between the forward and reverse innovations sequences gave an accurate indication of thedirection and magnitude of the peak shift.A series of overlapped two-component systems were alsoinvestigated.Again,a correlation between the difference innovations and the degree of the responseshift was observed.The behavior of the Katman filter in fitting the shifted fluorescence emissionspectrum of benzo[a]pyrene was also examined.The response for henzo[a]pyrene in cyclohexanesolution was compared to that obtained on the surface of a reversed phase thin layer chromatographyplate.A red shift of 4 nm was detected for the surface spectrum by observing the difference innovationssequence.This approach holds promise for correction of response shifts in multicomponent systems.     

Phase Equilibria of the Lyngdal Granodiorite (Norway): Implications for the Origin of Metaluminous Ferroan Granitoids

The Proterozoic (950 Ma) Lyngdal granodiorite of southern Norwaybelongs to a series of hornblende–biotite metaluminousferroan granitoids (HBG suite) coeval with the post-collisionalRogaland Anorthosite–Mangerite–Charnockite (AMC)suite. This granitoid massif shares many geochemical characteristicswith rapakivi granitoids, yet granodiorites dominate over granites.To constrain both crystallization (P, T, fO₂, H₂O in melt) andmagma generation conditions, we performed crystallization experimentson two samples of the Lyngdal granodiorite (with 60 and 65 wt% SiO₂) at 4–2 kbar, mainly at fO₂ of NNO (nickel–nickeloxide) to NNO + 1, and under fluid-saturated conditions withvarious H₂O–CO₂ ratios for each temperature. Comparisonbetween experimental phase equilibria and the mineral assemblagein the Lyngdal granodiorite indicates that it crystallized between4 and 2 kbar, from a magma with 5–6 wt % H₂O at an fO₂of NNO to NNO + 1. These oxidized and wet conditions sharplycontrast with the dry and reduced conditions inferred for thepetrogenesis of the AMC suite and many other rapakivi granitesworldwide. The high liquidus temperature and H₂O content ofthe Lyngdal granodiorite imply that it is not a primary magmaproduced by the partial melting of the crust but is derivedby the fractionation of a mafic magma. Lyngdal-type magmas appearto have volcanic equivalents in the geological record. In particular,our results show that oxidized high-silica rhyolites, such asthe Bishop Tuff, could be derived via fractionation of oxidizedintermediate magmas and do not necessarily represent primarycrustal melts. This study underlines the great variability ofcrystallization conditions (from anhydrous to hydrous and reducedto oxidized) and petrogenetic processes among the metaluminousferroan magmas of intermediate compositions (granodiorites,quartz mangerites, quartz latites), suggesting that there isnot a single model to explain these rocks. KEY WORDS: ferroan granitoids; crystallization conditions; experiments; Norway; Sveconorwegian; Bishop Tuff     

游客原真性感知与世界遗产资源原真性内涵集合式关系研究(英文)

游客原真性感知对于世界遗产资源的未来发展具有重要价值。本文基于原真性学说针对游客感知与世界遗产资源旅游发展内涵之间的关系进行了探讨。通过对世界遗产故宫博物院实证研究的结果表明:数学集合理论模型能够很好地模拟游客原真性感知与遗产资源发展内涵之间的内在联系,继而5种集合式关系被建立起来,即"相离关系"、"相交关系"、"包含关系I"、"包含关系II"和"重合关系"。根据调查样本的分配规律5种集合式关系可以被进一步分为主要集合式关系和次要集合式关系。使用双因素方差分析法从被调研游客的人口统计学特征(性别、年龄、受教育程度、游览频率和已有感知程度)出发,针对集合式关系进行研究的结果进一步显示:游客对于5种集合式关系类别的感知具有差异性。本论文研究成果对于基于原真性视角下的世界遗产资源发展成效评判以及从游客原真性感知出发提出世界遗产资源发展未来策略均具有实际意义。     

Devensian Lateglacial palaeoecological changes in Shetland

Diatoms and plant macrofossils in Devensian Lateglacial lacustrine sediments in Shetland suggest that the earliest response to interstadial warming was from benthic aquatic communities that could develop under lake ice. Further warming permitted longer ice-free summers and plankton growth. The terrestrial vegetation communities responded more slowly. Pollen of land plants was then partly derived from long distance input. Macrofossils support a reconstruction of terrestrial vegetation of sparse Salix herbacea and mosses in the early interstadial, increasing to grass tundra with tall herbs and Empetrum locally present, and with patches of disturbed ground. The occurrence of Betula and Juniperus remains questionable because of a lack of macrofossils, despite the presence of their pollen. Rumex pollen peaks suggest significant local presence at the stadial/interstadial transitions. Overall, the palaeoenvironmental reconstruction at this isolated oceanic site depends on several proxy indicators, of which pollen is less reliable than diatoms and plant macrofossils.     

Kriging: a method of interpolation for geographical information systems

Geographical information systems could be improved by adding procedures for geostatistical spatial analysis to existing facilities. Most traditional methods of interpolation are based on mathematical as distinct from stochastic models of spatial variation. Spatially distributed data behave more like random variables, however, and regionalized variable theory provides a set of stochastic methods for analysing them. Kriging is the method of interpolation deriving from regionalized variable theory. It depends on expressing spatial variation of the property in terms of the variogram, and it minimizes the prediction errors which are themselves estimated. We describe the procedures and the way we link them using standard operating systems. We illustrate them using examples from case studies, one involving the mapping and control of soil salinity in the Jordan Valley of Israel, the other in semi-arid Botswana where the herbaceous cover was estimated and mapped from aerial photographic survey.     

Reaction Between Ultramafic Rock and Fractionating Basaltic Magma II. Experimental Investigation of Reaction Between Olivine Tholeiite and Harzburgite at 1150-1050?C and 5 kb

We present results of experiments on mixtures of olivine tholeiiteand mantle harzburgite, at 5 kb and 1050–1150?C, underconditions of controlled hydrogen fugacity. The basalt end-memberwas Kilauea 1921 olivine tholeiite+3 wt.% H₂O, and the harzburgiteend-member was a mixture of olivine and orthopyroxene mineralseparates made from a mantle-derived lherzolite xenolith. Theexperiments on mixtures of basalt and harzburgite difl not reachequilibrium in runs ranging from 12 to 200 h duration. Relativelylarge concentration gradients persisted in both liquid and solidphases in mixed samples, whereas ‘control’ samplescontaining only basalt were reasonably homogeneous and wereprobably close to equilibrium. Compositions of solid phases produced, measured by electronmicroprobe, show a regular increase in Mg/(Mg+Fe) with increasingproportion of harzburgite at constant temperature, but olivineand clinopyroxene in mixed samples were not in Fe-Mg exchangeequilibrium. Modes measured for each sample show that the fractionof liquid relative to the amount of basalt in the sample wasconstant at constant temperature, and independent of bulk composition:reaction between 1921 basalt and harzburgite does not changethe mass of liquid in the system. Average experimental liquidcompositions for each sample were obtained by mass balance.Using Kds defined by the ‘control’ sample for eachtemperature, and mass balance constraints, phase assemblages(solid- and liquid-phase compositions and proportions) werecalculated for all mixtures. Whether samples included harzburgite or not, all average experimentalliquid compositions, and all predicted liquid compositions,for samples run at 1050?C, are high-alumina basalts by the definitionof Kuno (1960). By the criteria of Irvine & Baragar (1971),all but two average experimental liquid compositions in basalt-harzburgitemixtures, and all predicted liquid compositions in basalt-harzburgitemixtures, are calc-alkaline basalts and basaltic andesites,whereas liquids in samples containing only basalt are tholeiiticbasalts. Combined crystallization and reaction with harzburgitein the upper mantle will produce calc-alkaline derivative liquidsfrom an olivine tholeiite liquid under conditions of temperature,pressure, water and oxygen fugacity, and initial bulk compositionwhich would produce a tholeiitic liquid line of descent by crystallizationin a closed system. ^*Present address: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543Present address: Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK     

An Experimental Study of Water and Carbon Dioxide Solubilities in Mid-Ocean Ridge Basaltic Liquids. Part I: Calibration and Solubility Models

Experiments were conducted to determine the solubilities ofH₂O and CO₂ and the nature of their mixing behavior in basalticliquid at pressures and temperature relevant to seqfloor eruption.Mid-ocean ridge basaltic (MORB) liquid was equilibrated at 1200°Cwith pure H₂O at pressures of 176–717 bar and H₂O—CO₂vapor at pressures up to 980 bar. Concentrations and speciationof H₂O and CO₂ dissolved in the quenched glasses were measuredusing IR spectroscopy. Molar absorptivities for the 4500 cm^–1band of hydroxyl groups and the 5200 and 1630 cm^–1 bandsof molecular water are 0•67±0•03, 0•62±0•07,and 25±3 l/mol-cm, respectively. These and previouslydetermined molar absorptivities for a range of silicate meltcompositions correlate positively and linearly with the concentrationof tetrahedral cations (Si+Al). The speciation of water in glass quenched from vapor-saturatedbasaltic melt is similar to that determined by Silver &Stolper (Journal of Petrology 30, 667–709, 1989) in albiticglass and can be fitted by their regular ternary solution modelusing the coefficients for albitic glasses. Concentrations ofmolecular water measured in the quenched basaltic glasses areproportional to f H₂O in all samples regardless of the compositionof the vapor, demonstrating that the activity of molecular waterin basaltic melts follows Henry's law at these pressures. Abest fit to our data and existing higher-pressure water solubilitydata (Khitarov et al., Geochemistry 5, 479–492, 1959;Hamilton et al., Journal of Petrology 5, 21–39, 1964),assuming Henrian behavior for molecular water and that the dependenceof molecular water content on total water content can be describedby the regular solution model, gives estimates for the V^{o, m}_H2Oof 12±1 cm³/mol and for the 1-bar water solubility of0•11 wt%. Concentrations of CO² dissolved as carbonate in the melt forpure CO₂-saturated and mixed H₂O-CO₂-saturated experiments area simple function of f_CO2 These results suggest Henrian behaviorfor the activity of carbonate in basaltic melt and do not supportthe widely held view that water significantly enhances the solutionof carbon dioxide in basaltic melts. Using a V^{o, m}_r of 23 cm³/mol(Pan et al., Geochimica et Cosmochimica Acta 55, 1587–1595,1991), the solubility of carbonate in the melt at 1 bar and1200°C is 0•5 p.p.m. Our revised determination of CO₂solubility is 20% higher than that reported by Stolper &Holloway (Earth and Planetary Science Letters 87, 397–408,1988). KEY WORDS: mid-ocean ridge basalts; water and carbon dioxide solubility; experimental petrology