time scales of hybridisation of magmatic enclaves in regular and chaotic flow fields petrologic and volcanologic implications this paper describes numerical models of advection diffusion between enclaves and host magmas applied with the aim of estimating time scales during which enclaves can be homogenised in particular advection was simulated using a numerical system consisting of regular and chaotic regions results indicate that the homogenisation time of enclaves in chaotic regions is several orders of magnitude faster than in regular regions for instance an enclave with a diameter of 100 cm may be homogenised in the chaotic region in 380 years assuming an advection velocity of 10 cm year whereas in the regular region it would require 6 5 105 years for complete homogenisation this implies that in the same magmatic system large differences in the degree of homogenisation may co exist generating magmatic masses with large spatial and temporal inhomogeneities

timescales of mingling in shallow magmatic reservoirs arrival of magma from depth into shallow reservoirs has been documented as one of the possible processes leading to eruption magma intruding and rising to the surface interacts with the already emplaced degassed magmas residing at shallower depths leaving chemical signatures in the erupted products we performed two dimensional numerical simulations of the arrival of gas rich magmas into shallow reservoirs we solve the fluid dynamics for the two interacting magmas evaluating the space time evolution of the physical properties of the mixture convection and mingling develop quickly into the chamber and feeding conduit dyke leading on longer timescales to a density stratification with the lighter gas richer magma mixed with different proportions of the resident magma rising to the top of the chamber due to buoyancy over timescales of hours the magmas in the reservoir appear to have mingled throughout and convective patterns become harder to identify our simulations have been performed changing the geometry of the shallow reservoir and the gas content of the initial end member magmas horizontally elongated magma chambers as well as higher density contrasts between the two magmas cause faster ascent velocities and also increase the mixing efficiency

fractal analysis of mingled mixed magmas an example from the upper pollara eruption salina island southern tyrrhenian sea italy abstract upper pollara eruption products 13 ka salina island italy include both homogeneous and heterogeneous pumices resulting from mixing mingling processes between an hk andesite and a high sio2 rhyolite representative samples of heterogeneous pumices are collected and analyzed in order to check the correspondence between glass composition and morphological features of the mingling mixing structures image analysis techniques are applied and eight grey color ranges classes are extracted from high resolution scans of pumice class 1 lighter colors and class 8 darker colors show end member glass compositions i e hk andesite and high sio2 rhyolite respectively these two classes show spot to cluster like morphological structures intermediate classes show an hk dacitic to rhyolitic composition and a banding to fold like morphology fractal analysis by box counting of the boundary pattern of eight grey classified images is performed over a length scale of 0 028 1 8 cm fractal dimension d is between 1 01 and 1 84 coupled fractal analysis and geochemical data reveal that d increases as the degree of magma interaction homogenization increases this feature well fits the results from numerical models on the convective mixing of fluids driven by thermal convection we conclude that the increase of d observed in the upper pollara samples reflects the transition from fractal mixing to homogenization end member magmas hk andesite and high sio2 rhyolite represent isolated mixing regions while homogenized magmas represent active mixing regions in the analyzed pumices isolated and active mixing regions coexist at scales between 10 4 and 10 2 m morphological and compositional features of the upper pollara pumices result from turbulence

fractal structure of heterogeneous ejecta from the me akan volcano eastern hokkaido japan implications for mixing mechanism in a volcanic conduit abstract during the somma building activity about 13 ka of the me akan volcano eastern hokkaido simultaneous eruptions of basaltic andesite andesite and dacite magmas yielded a variety of heterogeneous juvenile ejecta these heterogeneous ejecta ranging from mafic scoria to dacite pumice can be divided into three types based on the morphological structure of the pumicescoria boundary type 1 is characterized by a spot pattern type 2 by a banded pattern containing streaky dense banded and vortical structures and type 3 by irregular lumps with fingering patterns these structures and the eruptive sequence suggest that the basaltic andesite magma was injected into or drawn up with the dacite magma within the volcanic conduit beneath the nakamachineshiri crater a fractal analysis of boundary patterns of the heterogeneous ejecta was performed by a counting method over a length scale of 0 2 mm to 17 mm in order to characterize the mixing mechanism in the conduit the morphological patterns of heterogeneous ejecta have a self similar structure with fractal dimensions of d 0 9 to 1 2 for type 1 d 1 2 to 1 6 for type 2 and of d 1 2 to 1 4 for type 3 the mean value of d 1 37 0 11 for types 2 and 3 ejecta is almost the same as the value measured for fluid turbulence structures such as clouds or jets thus we infer that formation of banded and irregular lump structures was probably produced by turbulent entrainment of dacite magma into basaltic andesite magma in the conduit the lower fractal dimension of type 1 d 1 11 0 08 is due to weakly turbulent or nearly laminar processes homogeneous andesite magma is inferred to result from complete vigorous turbulent mixing

kinematic significance of mingling rolling structures in lava flows a case study from porri volcano salina southern tyrrhenian sea a basaltic andesite lava flow from porri volcano salina southern tyrrhenian sea is composed of two different magmas magma a 51 vol of crystals has a dacitic glass composition and magma b 18 vol of crystals a basaltic glass composition magma b is hosted in a and consists of sub spherical enclaves and boudin like banding and rolling structures rs four types of rs have been recognized type type complex types and transitional structures between sub spherical enclaves and rolling structures an analysis of the rs has been performed in order to reconstruct the flow kinematics and the mechanism of flow emplacement rolling structures have been selected in three sites located at different distances from the vent in all sites most rs show the same sense of shear kinematic analysis of rs allows the degree of flow non coaxiality to be determined the non coaxiality is expressed by the kinematic vorticity number wk a measure of the ratio sr between pure shear strain rate and simple shear strain rate the values of wk calculated from the measured shapes of microscopic rs increase with increasing distance from the vent from approximately 0 5 to 0 9 results of the structural analysis reveal that the rs formed during the early intermediate stage of flow emplacement they represent originally sub spherical enclaves deformed at low shear strain at higher strain rs deformed to give boudin like and stretched banding structures results of the kinematic analysis suggest that high viscosity lava flows are heterogeneous non ideal shear flows in which the degree of non coaxiality increases with the distance from the vent in the vent area deformation is intermediate between simple shear and pure shear farther from the vent deformation approaches ideal simple shear lateral extension processes occur only in the near vent zone where they develop in response to the lateral push of magma extruded from the vent lateral shortening processes develop in the distal zone and record the gravity driven movement of the lava the lava flow advanced by two main mechanisms lateral translation and rolling motion lateral translation equals rolling near the vent while rolling motion prevailed in the distal zones

wavelet based correlation wbc of zoned crystal populations and magma mixing magma mixing is a common process and yet the rates kinematics and numbers of events are difficult to establish one expression of mixing is the major trace element and isotopic zoning in crystals which provides a sequential but non monotonic record of the creation and dissipation of volumes of distinct chemical potential we demonstrate a wavelet based correlation wbc technique that uses this zoning for the recognition of the minimum number of mixing or open system events and the criteria for identifying populations of crystals that have previously shared a mixing event when combined with field observations of the spatial distribution of crystal populations wbc provides a statistical link between the time varying thermodynamic and fluid dynamic history of the magmatic system wbc can also be used as a data mining utility to reveal open system events where outcrop is sparse an analysis of zoned plagioclase from the tuolumne intrusive suite provides a proof of principle for wbc 1 2002 elsevier science b v all rights reserved

development of a dynamics based statistical prediction model for the changma onset abstractthe timing of the changma onset has high impacts on the korean peninsula yet its seasonal prediction remains a great challenge because the changma undergoes various influences from the tropics subtropics and midlatitudes in this study a dynamics based statistical prediction model for the changma onset is proposed this model utilizes three predictors of slowly varying sea surface temperature anomalies sstas over the northern tropical central pacific the north atlantic and the north pacific occurring in the preceding spring season sstas associated with each predictor persist until june and have an effect on the changma onset by inducing an anticyclonic anomaly to the southeast of the korean peninsula earlier than the climatological changma onset date the persisting negative sstas over the northern tropical central pacific and accompanying anomalous trade winds induce enhanced convection over the far western tropical pacific in turn these induce a cyclonic anomaly over the south china s

role of magma mixing in the pre eruptive dynamics of the aeolian islands volcanoes southern tyrrhenian sea italy abstract we combined literature and experimental data to determine the role of magma mixing in the pre eruptive dynamics of the aeolian islands volcanoes as a first step we systematically reviewed the evidence supporting the hypothesis of mixing triggered eruptions in the aeolian archipelago providing textural chemical and rheological constraints the existing data highlighted the significant role of magma mixing in many eruptions within the aeolian archipelago examples include the upper pollara and porri volcano eruptions at salina monte guardia and the ad 1230 monte pilato eruption at lipari as well as the present day activity at stromboli then we focused on vulcano island chosen as a case study because it represents one of the volcanoes posing the highest risk in the aeolian archipelago at vulcano island we highlighted the role of magma mixing in the ad 1739 and 1888 90 eruptions finally we investigated mixing to eruption timescales for the ad 1739 eruption performing mixing experiments and evaluated the progressive decay of the chemical concentration variance with time results pointed to mixing to eruption timescales of the order of 29 9 h and magma ascent rates ranging between 3 10 2 and 5 10 2 m s 1 we finally emphasized that the presented results may have significant implications in the context of volcanic hazard mitigation and planning of emergency activities

thermal mechanical modeling of the role of thermal stresses and stoping in magma contamination mantle derived magmas emplaced in the upper crust depth 10 km are in thermal disequilibrium with the surrounding country rock as a consequence of the large temperature contrasts not only will the magma cool quite rapidly but the surrounding country rock will be heated and affected by large thermal stresses using coupled time dependent thermal mechanical models we find that a a single stage 3 km radius magma body has an eruptive life of on the order of 104 years b near the magma wall rock boundary large thermal stresses develop over short time spans 10 years and c material stoped into the chamber as a result of these thermal stresses will be assimilated either in the upper reaches of the chamber or at its base leaving a relatively uncontaminated central core these results indicate that contamination of a primary magma by stoped crustal blocks is an efficient mechanism for producing hybrid lava sequences

effects of chaotic advection on the timescales of cooling and crystallization of magma bodies at mid crustal levels we numerically define the thermochemical evolution of a subduction related crystal bearing magmatic mass at mid crustal levels 0 7 gpa 20 25 km two main dynamic mechanisms are considered 1 a pure buoyancy driven system where the convective flow is induced by density changes during magma cooling 2 a buoyancy driven convective system governed by chaotic advection the non newtonian rheology of natural magmas is taken into account linking the herschel bulkley formulation with the results of fractional crystallization experiments of magmas with the same composition and at the same conditions of temperature and pressure of the studied system the latent heat of crystallization is also considered in order to address the thermal release in the system induced by the crystallization results indicate that the development of chaotic advection generates a complex thermochemical evolution of the system speeding up the crystallization process and the timing required to reach the jamming condition relative to the pure buoyancy driven convective system nearly 2 times faster our results have important implications for both the rheological history of the magmatic body and the refilling of shallower magmatic systems in particular 1 a time dependent composition ranging from basalt to andesite can be extracted from an initial basaltic magmatic batch 2 at the attainment of the maximum packing fraction i e just before the jamming condition homogeneous andesitic melts can be potentially extracted from the system and 3 the development of chaotic advection within the system allows for the extraction of andesitic melt in shorter times compared to a buoyancy dominated system

evolutionary structures in double diffusive convection in magma chambers finite amplitude solutions to subcritical time dependent double diffusive convection d d c applicable for magma chambers are obtained by a two dimensional finite element method based on stream function temperature and compositional fields grid refinement is used for resolving the disparately scaled thermal and chemical boundary layers present for large ratios of the thermal to chemical diffusivity lewis number characteristic of magmas the occurrence of layered convection depends strongly on the initial conditions of the temperature and composition it is shown that in the infinite prandtl number limit a local transition from a diffusive to a finger like regime can take place for large enough lewis numbers this time dependent finding suggests that a strict categorization of d d c into the finger and diffusive regimes requires modification in geological applications

non destructive multi method internal analysis of multiple inclusions in a single diamond first occurrence of mackinawite fe ni 1 xs a single gem lithospheric diamond with five sulfide inclusions from the udachnaya kimberlite siberia russia has been analyzed non destructively to track the growth conditions of the diamond sulfides are the most abundant mineral inclusions in many lithospheric diamond crystals and are the most favorable minerals to date diamond crystals by re os isotope systematics our investigation used non destructive micro techniques combining x ray tomography x ray fluorescence x ray powder diffraction and raman spectroscopy this approach allowed us to determine the spatial distribution of the inclusions their chemical and mineralogical composition on the microscale and finally the paragenetic association leaving the diamond host completely unaffected the sample was also studied by x ray diffraction topography to characterize the structural defects of the diamond and to obtain genetic information about its growth history the x ray topographic images show that the sample investigated exhibits plastic deformation one set of 111 slip lamellae corresponding to polysynthetic twinning affects the entire sample chemical data on the inclusions still trapped within the diamond show they are monosulfide solid solutions of fe ni and indicate a peridotitic paragenesis micro x ray diffraction reveals that the inclusions mainly consist of a polycrystalline aggregate of pentlandite and pyrrothite a thorough analysis of the raman data suggests the presence of a further fe ni sulfide never reported so far in diamonds mackinawite the total absence of any oxides in the sulfide assemblage clearly indicates that mackinawite is not simply a late alteration of pyrrhotite and pentlandite due to secondary oxidizing fluids entering diamond fractures after the diamond transport to the surface instead it is likely formed as a low temperature phase that grew in a closed system within the diamond host it is possible that mackinawite is a more common phase in sulfide assemblages within diamond crystals than has previously been presumed and that the percentage of mackinawite within a given sulfide assemblage could vary from diamond to diamond and from locality to locality

non linear deformation and break up of enclaves in a rhyolitic magma a case study from lipari island southern italy 1 a dome from lipari island southern italy consists of 12 vol of circular elongated and folded latitic enclaves hosted in a rhyolitic matrix the dm to cm scale enclaves are more deformed than the mm scale blobs the critical value of the ratio between the viscous forces which allow deformation and eventually break up blobs of latitic magma and the interfacial tension forces is larger than 0 29 the reynolds number is 5 3 the equivalent radius and the axial ratio of the enclaves follow power law distributions this feature suggests that the break up and stretching of magmas are non linear scale invariant probably cyclic processes the coexistence of enclaves of different shape and the self similar size distributions suggest that chaotic advection plays a major role in the formation of mingled magmas caution must be used when measuring the finite strain from enclave shapes because they may break apart during the deformation

condensation heating of the asian summer monsoon and the subtropical anticyclone in the eastern hemisphere the effects of condensation heating on the formation of the subtropical anticyclone in the eastern hemisphere eh are studied by means of theoretical analysis and numerical simulation the complete vorticity equation is employed for the analysis it is found that due to the vertical gradient of strong condensation heating the distribution of cyclone and anticyclone in the upper troposphere is out of phase with that in the middle and lower troposphere this is confirmed by a series of numerical experiments the horizontal gradient of the condensation heating also affects the configuration of the subtropical anticyclone it is concluded that condensation heating is a key factor for the formation and location of the summer subtropical anticyclone in the eh the latent heating released by the asian monsoon rainfall contributes to the formation of the 200 hpa south asian anticyclone on the western side of the heating center and the 500 hpa western pacific subtropical anticyclone on the eastern side of the center such configurations are modified to some extent by surface sensible heating and orography the circulation in mid latitudes is also affected by the latent heating in the subtropical area through the propagation of rossby waves

time scales of recent phlegrean fields eruptions inferred from the application of a diffusive fractionation model of trace elements the variation of chemical element compositions in two pyroclastic sequences astroni 6 and averno 2 phlegrean fields italy is studied both sequences are compositionally zoned indicating a variability of melt compositions in the magma chamber prior to eruption a clear dichotomy between the behaviour of major vs trace elements is also observed in both sequences with major elements displaying nearly linear inter elemental trends and trace elements showing a variable scattered behaviour together with previous petrological investigations these observations are consistent with the hypothesis that magma mixing processes played a key role in the evolution of these two magmatic systems recently it has been suggested that mixing processes in igneous systems may strongly influence the mobility of trace elements inducing a diffusive fractionation phenomenon whose extent depends on the mixing time scale here we merge information from 1 numerical simulations of magma mixing and 2 magma mixing experiments using as end members natural compositions from phlegrean fields to derive a relationship relating the degree of diffusive fractionation to the mixing time scales application of the diffusive fractionation model to the two studied pyroclastic sequences allowed us to apply the relationship derived by numerical simulations and experiments to estimate the mixing time scales for these two magmatic systems results indicate that mixing processes in astroni 6 and averno 2 systems lasted for approximately 2 and 9 days respectively prior to eruption

testing the tracer ratio method for modeling active compositional fields in mantle convection simulations 1 tracer methods are attractive for modeling compositional fields because they offer the potential of zero numerical diffusion composition is typically taken to be proportional to the absolute local concentration of tracers but an increasingly popular method is to have dense and regular tracers with composition being equal to the local fraction of dense tracers this paper tests this ratio method using established benchmarks and by comparing the performance of the two tracer methods and grid based methods for simulating the long term evolution of a convecting mantle with a thick dense stable layer for this scenario the ratio method is found to have several advantages giving sharp stable long term layering with no tracer settling minimal statistical noise and low entrainment even with only 5 tracers per cell the method is equally applicable to finite volume and finite element treatments of the underlying flow entrainment in grid based advection methods is heavily dependent on resolution and numerical details and is reduced 1 order of magnitude by the filter proposed by a lenardic numerical determination of physically correct entrainment rates remains a challenging problem comparing tracer and grid based methods the spatial pattern of the thermal and chemical fields appear to be converging on the finest grids however the estimated entrainment differs significantly

formation of composite dykes by contact remelting and magma mingling the shaluta pluton transbaikalia russia abstract a unique opportunity to study the source areas from which composite dykes were injected occurs in the shaluta pluton transbaikalia russia the major quartz syenite pluton was intruded by several synplutonic gabbro bodies of various sizes investigations of the contact zones between gabbro and host syenite showed that liquid basalt magma intruded the incompletely crystallized coarse grained quartz syenite with t 700 720 c and caused contact remelting of the silicic rock at about 900 950 c mechanical interaction between newly formed silicic melt and partially crystallized mafic magma resulted in extensive magma mingling chemical interaction was exhibited by migration of mgo cao feo sr h2o and cl from the basalt magma whereas silica alkalis rb and ba migrated from the silicic refusion zone into the crystallized gabbro presence of melt inclusions with homogenization temperature ranging from 640 to 790 c in quartz and attaining 850 900 c in late clinopyroxene indicates that at least part of newly formed minerals crystallized from the hybrid melt mingled magmatic material was squeezed out inwards into the host solid quartz syenite pluton and formed dyke like apophyses that can be traced for a distance of 60 70 m from the contact zone apophyses have the same dimensions structure and composition as typical composite dykes that are common in the roof pendant over the gabbro bodies and nearby the gabbro exposures

strange attractors in plagioclase oscillatory zoning petrological implications oscillatory zoning in plagioclase crystals from different mixed lava flows cropping out on the island of capraia italy has been investigated an calibrated profiles from back scattered electron images are used as compositional time series of oscillatory zoning they are analyzed by a qualitative visual method that allows to appreciate at first sight the global structure of the time series and by a quantitative method to reconstruct the attractors associated to the oscillatory patterns and to calculate the fractal dimension of attractors results show that attractors have fractional dimensions indicating that series are chaotic in addition it is evidenced that there is a wide variation in oscillatory zoning in crystals from the same lava flow and that plagioclase populations from the different lava flows differ in the shape of frequency histograms of attractor dimension the development of oscillatory zoning is simulated by considering a chemically inhomogeneous magmatic mass governed by chaotic flow fields coupled with chemical diffusion in which plagioclase crystals grow according to the availability of nutrients in their neighborhoods results show that in such a dynamical system plagioclase crystals develop chaotic zoning patterns analogous to those observed in natural plagioclases this approach allows us to explain the differences observed in plagioclase crystals from the same lava flow and the differences in the shape of frequency histograms of attractor dimensions in the four lava flows

morphochemistry of patterns produced by mixing of rhyolitic and basaltic melts abstract in this work we present the results of time series experiments performed by mixing basaltic and rhyolitic melts at high temperature using a device recently developed to trigger chaotic dynamics in a mixing system the morphology of mixing patterns is quantified at different times by measuring their fractal dimension and a linear relationship is derived between mixing time and morphological complexity the complexity of mixing patterns is also compared to the degree of homogenization of chemical elements during mixing and empirical relationships are established between the fractal dimension and the temporal variation of concentration variance of elements new concepts and tools to study the magma mixing process unfold from the experimental results presented in this work the first one is that the mixing patterns are fractals and they can be quantified by measuring their fractal dimension this represents a further step in the quantification of the magma mixing process the second outcome is that the relationship between the fractal dimension of the mixing patterns and mixing time is linear this has important volcanological implications as the analyses of the morphology of mixing patterns in volcanic rocks can be complemented by experiments to build a new chronometer to estimate the mixing to eruption time a further result from this work is the relationship between the fractal dimension of mixing patterns and concentration variance of chemical elements this represents the first morphochemical study in igneous petrology bringing with it the potential to infer the relative mobility of chemical elements during the time progression of mixing by analyzing the morphology of mixing patterns in the rocks

the mixing of magmas in plutonic and volcanic environments analogies and differences abstract magma mixing processes have been widely recognized in both the plutonic and volcanic environments but the quality and quantity of information that can be extracted from the two environments are substantially different understanding the advantages and limits associated with the study of plutonic and volcanic rocks is essential to establish precise methodological approaches to build the most complete conceptual model by merging information from these two complementary igneous environments in this work we review magmatic interaction processes in the plutonic and volcanic environments by considering several aspects of these geological phenomena in particular we first briefly report on the structural and geochemical evidence for magma mixing in both plutonic and volcanic rocks with the aim to provide a general picture of this natural phenomenon successively we discuss some recent results about magma mixing achieved using the concepts from chaos theory and discuss their potential impact on magma differentiation finally we attempt to build a general picture of this igneous process by merging present day information from both the plutonic and volcanic environments it emerges from the general picture that the time spent by the magmatic system in the molten or partially molten state is the crucial factor for the preservation of the fingerprints of magma mixing in the two environments we propose a conceptual model that may be useful to understand what kind of information we can obtain from volcanic and plutonic rocks and ultimately to maximize our knowledge about magma mixing

interactions between rhyolitic and basaltic melts unraveled by chaotic mixing experiments abstract magma mixing may operate at any stage in the evolution of a magmatic system the development of mixing is strongly controlled by fluid dynamics and its understanding requires a comprehensive physico chemical approach in order to identify and interpret its occurrence in nature here we experimentally study the physical and chemical interplays during the mixing of basaltic and rhyolitic natural melts from the snake river plains usa in particular we present the results of the first high temperature mixing experiments performed under controlled chaotic dynamic conditions providing a new methodological approach to constrain the complexities of the mixing process between natural silicate melts the mixing process is initially governed by the dynamics of stretching and folding of the melts producing alternating flow bands these bands increase the contact area between the end members which subsequently enhance chemical exchanges and thus contribute to the generation of regions with variable degrees of hybridization we quantified the mobility of major and trace elements across contact areas and analyzed the concentration variance decay induced by chemical diffusion the analysis shows that elements diffuse with different efficiencies as the chemical gradient evolves and therefore the achievement of hybrid compositions contrasts between elements the approach introduced in this study can in principle be applied to mixing trends observed in nature in order to estimate the time scales and degree of magma mixing evidenced across volcanic rocks deposits

exponential decay of concentration variance during magma mixing robustness of a volcanic chronometer and implications for the homogenization of chemical heterogeneities in magmatic systems abstract the mixing of magmas is a fundamental process in the earth system causing extreme compositional variations in igneous rocks this process can develop with different intensities both in space and time making the interpretation of compositional patterns in igneous rocks a petrological challenge as a time dependent process magma mixing has been suggested to preserve information about the time elapsed between the injection of a new magma into sub volcanic magma chambers and eruptions this allowed the use of magma mixing as an additional volcanological tool to infer the mixing to eruption timescales in spite of the potential of magma mixing processes to provide information about the timing of volcanic eruptions its statistical robustness is not yet established this represents a prerequisite to apply reliably this conceptual model here new chaotic magma mixing experiments were performed at different times using natural melts the degree of reproducibility of experimental results was tested repeating one experiment at the same starting conditions and comparing the compositional variability we further tested the robustness of the statistical analysis by randomly removing from the analysed dataset a progressively increasing number of samples results highlight the robustness of the method to derive empirical relationships linking the efficiency of chemical exchanges and mixing time these empirical relationships remain valid by removing up to 80 of the analytical determinations experimental results were applied to constrain the homogenization time of chemical heterogeneities in natural magmatic system during mixing the calculations show that when the mixing dynamics generate millimetre thick filaments homogenization timescales of the order of a few minutes are to be expected

contribution of the phase transition of pacific decadal oscillation to the late 1990s shift in east china summer rainfall based on our previous study the interdecadal changes in summer rainfall over east china in the late 1990s are further explored here the increased local rising motion is implicated as the dominant factor of increased rainfall in the lower huang huai river valley lhr both the observation and numerical experiments using community atmosphere model version 4 suggest that the negative pacific decadal oscillation pdo mode can result in rising anomalies and thus more rainfall in the lhr the east asian westerly jet stream eawjs is suggested as a bridge to link the pacific sea surface temperature anomalies and east asian summer rainfall model results reveal that the negative pdo mode can lead to significant easterly anomalies over east asia as a result the eawjs is weakened and shifts poleward which coincides with observed changes in eawjs after the late 1990s in addition weakened and poleward shifted eawjs can result in an anomalous ascending motion to its south in the lhr by modulating the jet related secondary meridional vertical circulation consequently rainfall increased in the lhr after the late 1990s besides the positive atlantic meridional oscillation can only induce insignificant changes over east asia and partly counteract the negative pdo effect there

mixing and compositional stratification produced by natural convection 1 experiments and their application to earth s core and mantle an extensive series of laboratory experiments is used to quantify the circumstances under which fluids can be mixed by natural convection at high flux rayleigh number a compositionally buoyant fluid was injected at a fixed rate into an overlying layer of ambient fluid from a planar horizontally uniform source the nature of the resulting compositional convection was found to depend on two key dimensionless parameters a reynolds number re and the ratio u of the ambient fluid viscosity to the input fluid viscosity increasing the reynolds number corresponded to increasing the vigor of the convection while the viscosity ratio was found to determine the spacing between plumes and whether buoyant fluid rose as sheets u 1 from measurements of the final density profile in the fluid after the experiments we quantified the extent to which buoyant liquid was mixed in terms of a thermodynamic mixing efficiency e the mixing efficiency was found to be high e 0 9 when either the reynolds number was large re 100 or the viscosity ratio was small u 200 the amount of mixing was related to whether ascending plumes generated a large scale circulation in the ambient fluid when our results are applied to the differentiation of the earth s core we suggest that the convection resulting from the release of buoyant residual liquid into the liquid outer core due to crystallization at the boundary between the inner and the outer core will probably lead to nearly complete mixing in the dynamically very different context of the mantle mantle plumes are predicted to ascend through the mantle and pond beneath the lithosphere whereas convection driven by the subduction of oceanic lithosphere is expected to produce moderate to extensive mixing of the mantle when the competing plate and plume modes of mantle convection are considered together we find that owing to a larger driving buoyancy flux the plate scale flow will destroy any stratification at the top of the mantle produced by mantle plumes applying our results to the stagnant lid style of thermal convection predicted to occur in the mantles of the moon mercury mars venus and pre archean earth we expect the respective flows to produce minor thermal stratification at the respective core mantle boundaries in part 2 of this study jellinek and kerr this issue we apply our results to the differentiation of magma chambers and komatiite lava flows

time evolution of chemical exchanges during mixing of rhyolitic and basaltic melts we present the first set of chaotic mixing experiments performed using natural basaltic and rhyolitic melts the mixing process is triggered by a recently developed apparatus that generates chaotic streamlines in the melts mimicking the development of magma mixing in nature the study of the interplay of physical dynamics and chemical exchanges between melts is carried out performing time series mixing experiments under controlled chaotic dynamic conditions the variation of major and trace elements is studied in detail by electron microprobe and laser ablation icp ms the mobility of each element during mixing is estimated by calculating the decrease in the concentration variance in time both major and trace element variances decay exponentially with the value of exponent of the exponential function quantifying the element mobility our results confirm and quantify how different chemical elements homogenize in the melt at differing rates the differential mobility of elements in the mixing system is considered to be responsible for the highly variable degree of correlation linear nonlinear or scattered of chemical elements in many published inter elemental plots elements with similar mobility tend to be linearly correlated whereas as the difference in mobility increases the plots become progressively more nonlinear and or scattered the results from this study indicate that the decay of concentration variance is in fact a robust tool for obtaining new insights into chemical exchanges during mixing of silicate melts concentration variance is in a single measure an expression of the influence of all possible factors e g viscosity composition and fluid dynamic regime controlling the mobility of chemical elements and thus can be an additional petrologic tool to address the great complexity characterizing magma mixing processes

spiral growth of grossular under hydrothermal conditions grossular grs 99 adr 01 crystals were synthesized in hydrothermal experiments by the reaction wollastonite calcite anorthite grossular co 2 400 mpa 695 750 c x co 2 0 1 solid fluid 2 1 using natural minerals as starting materials growth spirals are visible due to silica decorations the crystals are bounded by 110 and 211 if crystallized at t 730 c they are birefringent and show sector twinning grown at t 730 c they are optically isotropic the crystal growth rates in the experiments ranged from about 1 to 100 m d the edges of the growth terraces moved by 5 200 nm s the morphology of the growth steps is interpreted against the background of supersaturation with respect to grossular in the fluid the highest supersaturation occurs during the initial stage of the reaction 1 h ultimately at the wollastonite surfaces in this initial stage grossular crystallizes with only 111 faces present covered by round growth spirals when a steady state with respect to dissolution and precipitation rates is reached after 24 h all grossular crystals show 110 and 211 with polygonal spirals on 110 and parallel growth steps on 211 all straight growth step edges parallel 111 when the solid phases assume equilibrium with the fluid after calcite in calcite deficient experiments is used up completely round growth spirals appear on 211 the spirals are elongated parallel to 111 and compete against parallel steps in that same direction the surface morphology of the crystals synthesized under steady state conditions mimicks that of natural grandite crystals and their growth rates equal the estimated growth rates of grandite crystals from natural hydrothermal systems

transition to chaos and implications for time scales of magma hybridization during mixing processes in magma chambers abstract in this contribution numerical simulations of magma mixing are carried out with the aim of understanding the physico chemical conditions that trigger the development of chaotic mixing dynamics in detail the mixing process is simulated in a magma chamber where a less evolved magma underplates a more evolved magma the chaoticity of this system is quantitatively estimated via computed finite time lyapunov exponents it is shown that magma chamber dynamics are strongly controlled by the rayleigh number ra whereas other parameters such as buoyancy ratio and viscosity ratio play a subordinate role results indicate that magma chambers with ra of the order of 10 6 are dominated by non chaotic behaviour increasing ra shifts the system towards an increasing chaotic state and in particular above ra 10 7 chaotic dynamics are fully developed in the magma chamber estimates of possible time scales of hybridization of magmas during chaotic mixing suggest for example that a blob of mafic magma with an initial diameter of 100 m within a magma chamber with a width of 1000 m is stretched to a filament like structure with a thickness of 15 m after 320 years and after 1900 years its thickness is reduced to 4 0 mm using typical chemical diffusion coefficients for magmas of the order of 10 14 m 2 s it can be calculated that a 4 0 mm thick filament would homogenize by diffusion in 10 years such homogenization time scales are orders of magnitude lower that typical life times estimated for magma chambers even in the volcanic environment indicating that fast hybridization of magmas can be rapidly achieved when chaotic dynamics govern the evolution of the magmatic system

diffusive fractionation of trace elements by chaotic mixing of magmas abstract recent research on magma mixing systems has shown that the mixing process is governed by chaotic dynamics and that this process is responsible for the generation of fractal structures that propagate within the magmatic mass from the meter to the micrometer length scale laser ablation icp ms trace element analyses have been performed on rock samples with evidence of chaotic mixing phenomena results indicate that trace elements with similar values of diffusion coefficient display good correlations in inter elemental plots whereas as the difference between diffusion coefficients increases the correlation is progressively lost in addition a large variability of ree patterns is observed with the remarkable feature of the presence of positive and negative eu anomalies occurring at short length scale of the order of few mm given the chaotic nature of magma mixing structures the mixing process has been simulated by coupling a chaotic advection and a chemical diffusion numerical scheme by considering several trace elements with variable diffusivities simulations indicate that such a model explains with good approximation the variable correlations among trace elements observed in natural samples in addition the same patterns of ree observed in natural samples including the occurrence of positive and negative eu anomalies at short length scale are observed indicating that a chaotic advection diffusion dynamic system is a suitable model to explain natural data results presented in this contribution indicate that at the micrometric length scale small volumes of magmas are strongly influenced by the coupled action of chemical diffusion and chaotic flow fields and hence they do not represent magmas de facto present in the magmatic system because their compositions may have experienced a diffusive fractionation process these results may have important petrogenetic implications for instance if such melts were trapped as melt inclusions they would provide misleading information about melt compositions it is suggested that the approach of studying the degree of correlation among trace elements may be a possible method to test if melt inclusion compositions commonly used as petrogenetic indicators display evidence of such a diffusive fractionation process

vanadio oxy chromium dravite nav3 cr4mg2 si6o18 bo3 3 oh 3o a new mineral species of the tourmaline supergroup vanadio oxy chromium dravite nav3 cr4mg2 si6o18 bo3 3 oh 3o a new mineral species of the tourmaline supergroup

mn tourmaline crystals from island of elba italy growth history and growth marks the growth history reconstruction of tourmaline macro crystals from pegmatite pockets in the aplite veins of grotta d oggi island of elba italy was carried out using a multi disciplinary and multi analytical approach x ray diffraction topography xrdt and electron microprobe analysis empa the work covered in this paper is closely related to the previous crystal chemical characterization of the same macro crystals bosi et al 2005 the tourmalines examined here are bi colored crystals exhibiting greenish yellow to colorless zoning perpendicular to and parallel to the c axis the transition from the inner yellow regions to the colorless ones occurs suddenly xrdt and empa studies show relationships between color and chemical zoning and crystal growth evolution thus identifying two main growth stages which developed under different conditions the first stage corresponds to greenish yellow mn tourmaline grown as a result of a 2d growth mechanism in a f rich pegmatitic environment the second one corresponds to colorless elbaitic tourmaline which developed chiefly by a spiral growth mechanism in an oh rich hydrothermal environment the structural defects found in greenish yellow mn tourmaline growth bands absence of dislocations near uniform chemical element concentrations are the same as those observed in beryl crystals from pegmatite pockets of the island of elba therefore these features are growth marks that characterize the pegmatitic crystallization stage and differentiate it from the hydrothermal stage in which the dislocations normal to the growing faces occurred hence the role of tourmaline as a petrogenetic indicator can be extended from chemical composition to crystal growth reflecting both chemical environment and growth mechanism and contributing to a better understanding of mineral genesis in pegmatitic crystallization

isotopic constraints on the production rates crystallisation histories and residence times of pre caldera silicic magmas long valley california pre caldera high silica rhyolites of glass mountain california erupted episodically from 2 1 ma until the catastrophic eruption of the bishop tuff at 0 74 ma the lavas are extremely evolved with rb sr ratios between 128 to 3640 the latter being the highest recorded from a volcanic rock glass separates from pre l 2 ma lavas define two geographically controlled rb sr isoehrons lavas adjacent to the current caldera rim define an isochron age of 2 047 0 013 ma with an initial ratio of 0 7063 2 and lavas more distant from the caldera define an isochron of 1 894 0 013 ma with the same initial ratio the isochrons are consistent with the magmas forming within 26 ka which implies a minimum magma production rate of 0 75 10 3 km3 yr over this period new 4 ar 39ar ages on sanidine and biotite have established that lavas defining each isochron were erupted over a long time interval the isochron ages being up to 360 ka older than the youngest eruption age rb sr isotope data are reported for minerals from three lavas with eruption ages of 1 990 0 012 1 866 0 014 and 1 686 0 011 ma petrographically early apatite inclusions in biotite and biotite inclusions in feldspar and quartz have glass mineral rb sr ages that are indistinguishable from the relevant regional isochron sr diffusion in feldspar is slow at the magmatie temperatures inferred for glass mountain rhyolites 700 c such that over 0 5 ma the cores of large feldspars 1 ram will retain 99 9 of their original sr the cores of sanidine and plagioclase yield glass mineral ages that are up to 300 ka older than eruption ages feldspar rim ages for two samples are indistinguishable from eruption ages the rims of sanidines and plagioclases from the third sample are 110 and 280 ka older than the eruption age and 180 and 20 ka younger than the cores these mineral age data probably reflect the combination of extended periods of mineral growth and partial isotopic exchange with the host liquid during protracted residence in a magma reservoir however the ar and sr isotopic data for biotite phenocrysts are consistent with the presence of a significant component that is recycled from earlier magmatic pulses due to the extreme rb sr ratios of the rocks and minerals it is possible to very precisely resolve the time difference between the formation of different phases assuming that they crystallised from the same host magmas

cooling of a magmatic system under thermal chaotic mixing the cooling of a basaltic melt undergoing chaotic advection is studied numerically for a magma with a temperature dependent viscosity in a two dimensional 2d cavity with moving boundary different statistical mixing and energy indicators are used to characterize the efficiency of cooling by thermal chaotic mixing we show that different cooling rates can be obtained during the thermal mixing of a single basaltic magmatic batch undergoing chaotic advection this process can induce complex temperature patterns inside the magma chamber the emergence of chaotic dynamics strongly modulates the temperature fields over time and greatly increases the cooling rates this mechanism has implications for the thermal lifetime of the magmatic body and may favor the appearance of chemical heterogeneities in the igneous system as a result of different crystallization rates results from this study also highlight that even a single magma batch can develop under chaotic thermal advection complex thermal and therefore compositional patterns resulting from different cooling rates which can account for some natural features that to date have received unsatisfactory explanations including the production of magmatic enclaves showing completely different cooling histories compared with the host magma compositional zoning in mineral phases and the generation of large scale compositional zoning observed in many plutons worldwide

dynamics and thermodynamics of magma mixing insights from a simple exploratory model the mixing of magmas of distinct temperature bulk composition mineralogy and physical properties plays a central role in explaining the diversity of magma types on earth and in explaining the growth of continental and oceanic crust magma mixing is also of practical importance for example the mixing of distinct magmas has been cited as an important process in creation of economically important horizons in layered intrusions as well as a triggering mechanism for initiation of volcanic eruptions the motivation for better quantifying the dynamics and thermodynamics of magma mixing and its attendant plutonic and volcanic products is clear the degree of magma mixing which spans a continuum from mingling to complete hybridization depends upon initial and boundary conditions magma properties driving forces and time available for mixing magma mingling produces a heterogeneous mixture of discrete clumps of the end member magmas whereas complete hybridization involves the thermodynamic equilibration of two distinct magmas to form a third qualitatively mixing occurs via reduction in the size of compositional heterogeneities i e clumps through stretching and folding by viscous flow followed by homogenization once shear has reduced the size of compositional anomalies to diffusive length scales quantification of this process relies on two statistical measures the linear scale of segregation defined as the spatial integral of the compositional correlation function related to the size distribution of the segregated clumps within the mixture and the intensity of segregation i a measure that quantifies how much the composition at each location differs from the average the mixing dynamics of a layered system are analyzed in terms of the parameters governing mixing rayleigh lewis and buoyancy numbers and viscosity ratio to estimate how the timescale for magma hybridization h compares to solidification recharge diffusive and assimilation timescales this analysis illustrates that hybridization times can be shorter than or comparable to thermal solidification and replenishment timescales thus formation of hybridized or nearly hybridized magmas is one anticipated outcome of mixing the machinery of thermodynamics can be used to compute the hybrid magma state an exploratory model for the thermochemistry of hybridization is developed based on binary eutectic phase relations and thermodynamics eight thermodynamic parameters define the phase diagram and associated energetics and six parameters initial temperatures compositions mass ratio of mixing magmas and an enthalpy parameter are necessary and sufficient to determine the state of hybrid magma uniquely while relevant combinations of 14 thermodynamic and mixing parameters might suggest that the number of mixing outcomes i e products is too high to systematize monte carlo simulations using the exploratory model document how millions of arbitrary initial states evolve into five possible final mixed states such an analysis implies that a magma mixing taxonomy that defines possible mixed product states can be developed and tied to petrologic indicators of mixing additional insights gained from this exploratory model that are supported by independent results from a multicomponent multiphase thermodynamic model of magma mixing magma chamber simulator include 1 the proclivity of invariant point hybrid states which may explain some instances of compositionally monotonous melts associated with mixed magma eruptions 2 a surprising thermal effect such that the temperature of hybridized magma can be significantly less than the initial temperature of either of the mixing magmas this type of magma mixing may result in crystal resorption thus invalidating an assumption that resorption textures in crystals are typically the result of a magma heating event 3 illustration of the differing effects of stoped block temperature and composition on hybrid magma temperature and phase state and 4 illustration of a cessation of crystallization effect that may pertain to the morb pyroxene paradox differences between adiabatic or r hybridization and diabatic or rfc hybridization are also explored the model can be used to elucidate the thermodynamic principles underlying magma mixing in the hybridization limit these principles are of general applicability and carry over to more compositionally complicated systems

enhancement of magma mixing efficiency by chaotic dynamics an experimental study magma mixing is common in the earth understanding the dynamics of the mixing process is necessary for dealing with the likely consequences of mixing events in the petrogenesis of igneous rocks and the physics of volcanic eruptive triggers here a new apparatus has been developed in order to perform chaotic mixing experiments in systems of melts with high viscosity contrast the apparatus consists of an outer and an inner cylinder which can be independently rotated at finite strains to generate chaotic streamlines the two cylinder axes are offset experiments have been performed for ca 2 h at 1 400 c under laminar fluid dynamic conditions re 10 7 two end member silicate melt compositions were synthesized 1 a peralkaline haplogranite and 2 a haplobasalt the viscosity ratio between these two melts was of the order of 103 optical analysis of post experimental samples reveals a complex pattern of mingled filaments forming a scale invariant i e fractal distribution down to the m scale as commonly observed in natural samples this is due to the development in space and time of stretching and folding of the two melts chemical analysis shows strong non linear correlations in inter elemental plots the original end member compositions have nearly entirely disappeared from the filaments the generation of thin layers of widely compositionally contrasting interfaces strongly enhances chemical diffusion producing a remarkable modulation of compositional fields over a short length scale notably diffusive fractionation generates highly heterogeneous pockets of melt in which depletion or enrichment of chemical elements occur depending on their potential to spread via chemical diffusion within the magma mixing system results presented in this work offer new insights into the complexity of processes expected to be operating during magma mixing and may have important petrological implications in particular 1 it is shown that in contrast with current thinking rheologically contrasting magmas can mix i e with large proportions of felsic magmas and high viscosity ratios thus extending significantly the spectrum of geological conditions under which magma mixing processes can occur efficiently 2 the mixing process cannot be modeled using the classical linear two end member mixing model and 3 the chemical compositions on short length scales represent snapshots within the process of mixing and therefore may not reflect the final composition of the magmatic system this study implies that microanalysis on short length scales may provide misleading information on the parental composition of magmas

replenishment of magma chambers comparison of fluid mechanic experiments with field relations magma chambers are commonly replenished at low reynold s number by liquids denser than that already resident in the chamber and nearly always the injected liquid is less viscous than the resident liquid in the magma chamber we report fluid mechanic experiments that are designed to investigate this case specifically treating the injection process itself before a multilayered convecting system develops the injected fluid is emplaced as a viscous gravity current with a nose slightly elevated above the floor trapping a thin layer of ambient fluid beneath it further these injections develop a flow front instability that takes the form of fingers that extend in the direction of the flow using scaling arguments we model the height and the length of the current as functions of time and we use dimensional analysis and our experimental data to model the wavelength of the fingers the fingers and other structures observed in the experiments correlate well with similar features found in silicic intrusions that have been replenished with basic liquid we argue that these and associated mafic pillows are formed by this finger instability our scaling can be combined with finger widths measured in the field to estimate magma reinjection rates we suggest that structures observed in similar environments composite lava flows sills and dikes also formed by a flow front instability when applied to basic replenishments of basic magma chambers the scaling arguments constrain the time required for emplacement the emplacement time scale is short relative to the cooling time scale indicating that even when traveling tens of kilometers such injections cool little during emplacement

interplay between geochemistry and magma dynamics during magma interaction an example from the sithonia plutonic complex ne greece orogenic granitoids often display mineralogical and geochemical features suggesting that open system magmatic processes played a key role in their evolution this is testified by the presence of enclaves of more mafic magmas dispersed into the granitoid mass the occurrence of strong disequilibrium textures in mineralogical phases and or extreme geochemical and isotopic variability in this contribution intrusive rocks constituting the sithonia plutonic complex northern greece are studied on the basis of mineral chemistry whole rock major trace element geochemistry and sr and nd isotopic composition sithonia rocks can be divided into a basic group bearing macroscopic mafic enclaves microscopic disequilibrium textures geochemical and isotopic evidence of magma interaction and an acid group in which most geochemical and isotopic features are consistent with a magma mixing process but macroscopic and microscopic features are lacking a two step mixing plus fractional crystallization mfc process is considered responsible for the evolution of the basic group the firststepexplainsthechemicalvariationinthemaficenclavegroup abasicmagma representedbytheleastevolvedenclaves interacted

tourmaline nodules from capo bianco aplite elba island italy an example of diffusion limited aggregation growth in a magmatic system the morphology of tourmaline nodules occurring in the capo bianco aplite elba island italy is studied outcrop features indicate that tourmaline nodules are the product of magmatic crystallization as they are aligned along flow fields developed within the magmatic hosting mass mesoscopic observations indicate that nodule morphologies are very variable from rounded to dendritic morphometric analyses show that tourmaline nodules are fractals and that fractal dimension quantifies their degree of irregularity numerical simulations of nodule growth are performed by using a diffusion limited aggregation process the presence in natural samples of nodules with different morphologies is explained by considering a chaotic magmatic system characterized by a complex interplay between growth rate in different dynamical regions latent heat of crystallization and local convection dynamics it is suggested that higher growth rates correspond to growth of tourmaline nodules in dynamical regions where the transfer of nutrients is very efficient in such conditions the latent heat released by the growing nodule is high inducing strong local convection dynamics destabilizing the nodule interface and promoting the formation of dendritic morphologies on the contrary the growth of nodules in dynamical regions characterized by weak transfer of nutrients is inhibited leading to weak local convection dynamics and consequently to the formation of rounded morphologies

kinematic significance of morphological structures generated by mixing of magmas a case study from salina island southern italy morphological features of mixing mingling structures of heterogeneous juveniles from the 13 ka old upper pollara eruption salina island southern italy are studied these heterogeneous rocks result from the mixing between an andesitic and a rhyolitic magma concentration patterns generated by magma mixing are analyzed on digital images and results have been compared with those obtained from numerical simulations of mixing processes coupling chaotic advection and chemical diffusion results show that the upper pollara rocks were produced by mixing 24 49 of andesite and 76 51 of rhyolite multifractal analysis of the mixing structures is performed and the mixing intensity i e the degree of interaction between the two end member magmas has been deduced from the analysis of the singularity spectrum results show that narrower is the multifractal spectrum the higher is the degree of homogenization of magmas reynolds number re during mixing has been estimated from the geometrical analysis of mixing structures by using experimentally defined relationships between shape parameters and re results show that re is between ca 500 and 7000 there is a positive correlation between the estimated initial percentage of mafic magma in the different analyzed samples and re in agreement with the observation that the higher is the percentage of the mafic lower viscosity magma the higher is the turbulence of the mixing system in addition our analysis reveals an unexpected inverse relationship between the calculated re and the degree of magma homogeneity suggesting that energy dissipation may have had a major role in the controlling mixing process because dissipation is inversely proportional to the mixing efficiency results suggest that mixing processes between the andesitic and rhyolitic magmas mainly developed in the conduit it is also suggested that mixing occurred in a shear layer type or pipe type flow

strange attractors in magmas evidence from lava flows abstract magma mixing structures from three different lava flows salina vulcano and lesbos are studied in order to assess the possible chaotic origin of magma mixing processes structures are analysed using a new technique based on image analysis procedures that extract time series that are representative of the relative change in composition through the structures these time series are then used to reconstruct the attractors underlying the magma mixing process and to calculate the fractal dimension of the attractors results show that attractors exist and possess fractional dimensions this evidence suggests that the mixing of magmas is a chaotic process governed by a low number of degrees of freedom in addition fractal dimension analyses allows us to discriminate between different regimes of mixing in the three lava flows in particular our analyses suggest that the lava flow of salina underwent more turbulent mixing than the lava flows of lesbos and vulcano

viscous fingering during replenishment of felsic magma chambers by continuous inputs of mafic magmas field evidence and fluid mechanics experiments vegetation island outcrops terra nova intrusive complex antarctica offer a unique example of the replenishment of a felsic magma chamber fossilized at the initial stages of intrusion of a mafic magma the morphology of interfaces between the mafic and the felsic magma ranges from rounded to finger like and their quantification by means of fractal dimension indicates a wide variability of morphological complexity fluid mechanics experiments of viscous fingering have been performed by injecting water glycerin solutions with different viscosity ratios into pure glycerin using the hele shaw cell the fact that interface morphologies between the injected and the host fluid are identical to those observed on outcrops indicates that the latter shows the development of viscous fingering processes during the initial stages of intrusion of the mafic magma into the felsic magma chamber the fractal dimension of the simulated structures was measured and a very good exponential empirical relationship between the logarithm of viscosity ratio and fractal dimension has been derived the empirical relationship is used to estimate viscosity ratios of natural structures by using measured values of fractal dimension results indicate that in the same magmatic system a wide range of viscosity ratio existed between the two magmas these results are used to reconstruct the mechanism of replenishment of the felsic magma chamber as characterized by continuous heating of the resident felsic magma by continuous inputs of the mafic magma

x ray topographic study of a diamond from udachnaya implications for the genetic nature of inclusions abstract in recent years several studies have focused on the growth conditions of the diamonds through the analysis of the mineral inclusions trapped in them in these studies it is crucial to distinguish between protogenetic syngenetic and epigenetic inclusions x ray topography xrdt can be a helpful tool to verify in a non destructive way the genetic nature of inclusions in diamond with this aim a diamond from the udachnaya kimberlite siberia was investigated the diamond previously studied by nestola et al 2011 has anomalous birefringence and the two largest olivines have typical diamond imposed shapes the study of the topographic images shows that the diamond exhibits significant deformation fields related to post growth plastic deformation the absence of dislocations starting from the olivine inclusions and the dark contrasts around them represent the main results obtained by xrdt contributing to the elucidation of the relationships between the diamond and the olivines at the micron meter scale the dark halo surrounding the inclusions was likely caused by the effect of different thermo elastic properties between the diamond and the inclusions the absence of dislocations indicates that the diamond imposed morphology did not produce the volume distortion commonly associated with the entrapment of the full grown inclusions and thus only based on such evidence a syngenetic origin could be proposed in addition stepped figures optically observed at the interface between diamond and one of the olivines suggest processes of selective partial dissolution that would contribute to a change in the final morphology of inclusions these results show that a diamond morphology may be imposed to a full grown protogenetic olivine during their encapsulation suggesting that the bulk of the inclusion is protogenetic whereas its more external regions close to the diamond inclusion interface could be syngenetic

horizontal structure and energetics of northern hemisphere wintertime teleconnection patterns abstract the horizontal structure and dynamical properties of the teleconnection patterns in the interannual variability of the northern hemisphere wintertime 500 mb height field are investigated regression maps based on indices for the eastern atlantic ea pacific north american pna western atlantic wa western pacific wp and eurasian eu patterns defined by wallace and gutzler are used to define the geographically fixed patterns space spectrum analysis including a spherical harmonic decomposition is applied to these maps anomalous geostrophic wind fields derived from these regression maps are used to estimate the kinetic energy conversion between the climatological mean state and the wave structures associated with the teleconnection patterns the teleconnection patterns comprise seesaw and or wavelike structures in general the kinetic energy of the teleconnection patterns is concentrated in total wavenumber n 5 and 6 components with zonal wavenumbers m 0 1 and 2 which correspond

chromo alumino povondraite nacr3 al4mg2 si6o18 bo3 3 oh 3o a new mineral species of the tourmaline supergroup chromo alumino povondraite nacr3 al4mg2 si6o18 bo3 3 oh 3o a new mineral species of the tourmaline supergroup

the grizzly lake complex yellowstone volcano usa mixing between basalt and rhyolite unraveled by microanalysis and x ray microtomography abstract magma mixing is a widespread petrogenetic process it has long been suspected to operate in concert with fractional crystallization and assimilation to produce chemical and temperature gradients in magmas in particular the injection of mafic magmas into felsic magma chambers is widely regarded as a key driver in the sudden triggering of what often become highly explosive volcanic eruptions understanding the mechanistic event chain leading to such hazardous events is a scientific goal of high priority here we investigate a mingling event via the evidence preserved in mingled lavas using a combination of x ray computed microtomographic and electron microprobe analyses to unravel the complex textures and attendant chemical heterogeneities of the mixed basaltic and rhyolitic eruption of grizzly lake in the norris mammoth corridor of the yellowstone plateau volcanic field yvf we observe evidence that both magmatic viscous inter fingering of magmas and disequilibrium crystallization dissolution processes occur furthermore these processes constrain the timescale of interaction between the two magmatic components prior to their eruption x ray microtomography images show variegated textural features involving vesicle and crystal distributions filament morphology the distribution of enclaves and further textural features otherwise obscured in conventional 2d observations and analyses although our central effort was applied to the determination of mixing end members analysis of the hybrid portion has led to the discovery that mixing in the grizzly lake system was also characterized by the disintegration and dissolution of mafic crystals in the rhyolitic magma the presence of mineral phases in both end member for example forsteritic olivine sanidine and quartz and their transport throughout the magmatic mass by a combination of both mixing dynamics and flow imposed by ascent of the magmatic mass and its eruption might have acted as a geometric perturbation of flow fields further fuelling mass exchange between magmas in terms of both chemical diffusion and crystal transfer these results illuminate the complexity of mixing in natural magmatic systems identifying several reaction related textural factors that must be understood more deeply in order to advance our understanding of this igneous process

an analytical and experimental study of zoning in plagioclase a detailed electron microprobe study has been conducted on natural and experimentally grown zoned plagioclase feldspars discontinuous sector and oscillatory chemical zoning are observed superimposed on continuous normal or reverse zoning trends the relative accuracy of 3 element na ca k microprobe traverses was found statistically to be 2 mole percent comparison of microprobe data on natural zoned plagioclase with zoned plagioclase grown in controlled experiments has shown that it may be possible to distinguish zonal development resulting from physio chemical changes to the bulk magma from zoning related to local kinetic control on the growth of individual crystals

relationship between the onset date of the meiyu and the south asian anticyclone in april and the related mechanisms the onset date of the meiyu has attracted extensive attention because it marks the beginning of the rainfall season in the yangtze huai river basin yhrb in this study the relationship between the onset dates of the meiyu and its precursors is investigated and the south asian anticyclone saa in april which is generated by atmospheric apparent sources over south asia is introduced the results show that years with stronger saa in april are concurrent with earlier onsets of the meiyu and increased precipitation in june over the yhrb and vice versa the mechanisms involved in this relationship are further investigated the saa emerges in early april and moves eastward to the western north pacific wnp in the late pentad of april due to the abrupt zonal energy transport leading to anomalous divergence in the upper troposphere over the wnp the divergence anomaly enhances ascending motion in situ due to ekman pumping leading to an anomalous cyclone at lower levels over this region due to the southward moving ascending motion and the presence of the lower tropospheric cyclone in the fourth pentad of may the precipitation moves southward to the philippine sea phs the associated stronger convection over the phs further triggers a meridional overturning pattern which develops into the pacific japan like pattern pj like pattern the pj like pattern persists from the end of may to the beginning of june which promotes the earlier onset of the meiyu in addition due to the increased heating associated with the abundant precipitation over the phs around the fourth pentad of may the western pacific subtropical high wpsh shifts northward earlier ultimately the earlier establishment of the pj like pattern and the earlier northward shift of the wpsh cause stronger than normal southwesterly flows and additional water vapor transport to the yhrb leading to the advanced onset of the meiyu and additional precipitation in june

chaotic advection fractals and diffusion during mixing of magmas evidence from lava flows structures of magma mixing from three different lava flows have been analyzed and the degree of mingling has been quantified by measuring the contact perimeter between magmas and the fractal dimension of structures in each lava flow the values of these parameters suggest that the magma mixing structures were produced by chaotic dynamics induced by stretching and folding processes between the interacting magmas the mingling of magmas has been simulated using a chaotic dynamical system consisting of repeated stretching and folding processes the simulation shows the same patterns of variation of contact perimeter and fractal dimension as those observed in natural structures and indicates that magma interaction processes acted with different intensities in the three lava flows in response to different magmatic interaction regimes since physical dispersion of one magma inside another through stretching and folding processes and chemical exchanges are closely related we performed coupled numerical simulations of chaotic advection and chemical diffusion the results show a good agreement between the computed and natural structures in particular the occurrence in the same system of well and poorly mixed regions it is shown that magma interaction processes are able to generate magmatic masses having wide spatial heterogenity at many length scales this occurrence can account for the presence of magmatic enclaves inside host rocks showing a variable degree of hybridization in both plutonic and volcanic environments

composite dikes in four successive granitoid suites from transbaikalia russia the effect of silicic and mafic magma interaction on the chemical features of granitoids abstract in the study area of 60 by 15 km located south of lake baikal coeval mafic rocks form small intrusive bodies synplutonic dikes and composite mafic felsic dikes in four successive late paleozoic and early mesozoic syenite and granite suites mafic rocks in all suites are monzogabbro with similar mineral and chemical composition this attests that mantle derived mafic magmas produced at post collisional and within plate tectonic settings were not noticeably distinguished in chemical composition within a time interval of about 60 65 m y detailed study of the interaction zones between synplutonic mafic magma and host syenite at two key localities allowed recognition of syenite remelting stage at about 900 950 c remelting was accompanied by sr and ba enrichment by diffusion from the adjacent mafic magma diffusive transport of ba also caused enhanced bao content 0 37 0 54 wt in alkali feldspars of the newly formed syenite remelting of the host syenite was followed by mingling chemical interaction and mixing of mafic and silicic magmas within the contact zone the results of petrographic and geochemical study of the composite and synplutonic dikes are used to interpret the chemical features of the large about 1000 km2 essentially syenitic ust khilok pluton two varieties of syenite are recognized in the pluton one with ba

regular vs chaotic mantle mixing abstract most quantitative models of mantle mixing have been based on simulations of tracer advection by 2 d flows the present work shows that the mixing properties of 3 d time independent flows cannot be understood or extrapolated from previous 2 d models steady convective flows appropriate to simulate a uniform fluid with large viscosity are restricted to poloidal components they seem to have regular streamlines however the existence of plates on the earth s surface imposes the existence of a strong toroidal field flows where both poloidal and toroidal components are present can yield chaotic pathlines which are very efficient in mixing the mantle within areas of turbulent mixing where the stretching increases exponentially with time regular islands of laminar stretching persist in which unmixed material can survive our findings indicate that the intrinsic three dimensionality of convection coupled with plates as much as its time dependence must be included in numerical models to understand the mixing properties of the mantle as the viscosity is significantly larger in the lower mantle than in the upper mantle the toroidal component of the flow is confined to the upper mantle where a more thorough mixing should take place

the space and time complexity of chaotic mixing of silicate melts implications for igneous petrology abstract we present new experimental results on the study of the space and time modulation of compositional fields during chaotic mixing between mafic and felsic silicate melts the experimental strategy was planned using numerical simulations performed using the experimental geometry these mixing experiments were performed using a recently developed experimental apparatus which is capable of mixing high viscosity silicate melts at high temperatures and under precisely controlled conditions of fluid dynamics and strain the compositional variability produced by the mixing process was investigated both along linear analytical transects and on high resolution 2d x ray maps covering the mixing patterns our results indicate that chaotic flow fields represent very powerful dynamics to blend silicate melts even under laminar fluid dynamic conditions reynolds number ca 10 7 and for dissimilar melts with high viscosity ratios on the order of 103 the repetition of stretching and folding processes between the two melts induced a strong increase of contact interfaces thus favoring efficient chemical exchanges as a result the initial mafic composition is no longer detectable in the mixing system after ca 2 h i e the duration of the experiment a further important result is the observation of highly non linear patterns in inter elemental plots produced by the onset of diffusive fractionation processes this is contrary to common thinking that magma mixing should always produce linear trends between pairs of chemical elements a new measure the concentration variance is proposed to quantify chemical element mobility during the mixing process this measure is statistically robust and can be quantitatively used to measure chemical element mobility independently of the geometry in which the compositional variation i e transects areas etc is embedded or the local strain history of the mingling our results highlight concentration variance as a robust probe of the as yet poorly understood processes involved in the common petrological process of magma mixing