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

rare earth element patterns a tool for identifying trace metal sources during wetland soil reduction abstract in wetland soils several soil phases such as fe iii oxyhydroxides organic matter om or mixed fe om particles can host trace metals which can be subsequently released during soil reduction anoxic and oxic wetland soil incubation experiments combined with analyses of soil solutions sampled from a natural wetland during a reduction event are used to test the possibility that rare earth elements ree could be used as a tool to identify the soil phases contributing to trace metal solubilization significant amounts of trace metals cu cr co ni and pb and ree are released during anoxic incubation of the wetland soil concomitantly with the build up of high concentrations of fe ii and dissolved organic matter dom rare earth element patterns obtained in the soil solution exhibit a middle rare earth elements mree downward concavity the ree pattern obtained from field samples yields the same feature as developed in the soil solution from an oxic incubation experiment at ph 7 designed to promote soil om desorption by contrast significantly different ree patterns are obtained in incubation experiments designed to promote chemical reduction of fe oxyhydroxides in soils the ree pattern displays a continuous ree enrichment from la to lu these distinct and recognizable ree signatures allow us to conclude that i soil organic matter is the main source of ree and trace metals during wetland soil reduction ii fe ii is provided by the reduction of amorphous fe iii nanoparticles embedded within the organic matter which do not bind ree or other trace metals in significant proportions ree and trace elements being preferentially complexed to organic matter and finally iii ree provide a reliable and powerful tool suitable for identifying trace metal sources during wetland soil reduction

a laboratory investigation of assimilation at the top of a basaltic magma chamber the fluid dynamic processes affecting the mechanism and amount of assimilation of the roof of a magma chamber have been studied in a series of analogue laboratory experiments an aqueous solution of na 2 co 3 was first cooled and crystallized at the top of a laboratory tank to form a solid roof layer of prescribed composition the tank was then drained and refilled with warmer solution either na 2 co 3 of the same or different composition or in two experiments kno 3 the metal top in all cases was held below the eutectic temperature for the system na 2 co 3 h 2 o the experiments were continued until substantial crystallization and in some cases complete solidification were achieved starting with a dense solid roof layer of na 2 co 3 10h 2 o and ice on the na 2 co 3 side of the eutectic and a warmer eutectic na 2 co 3 solution below there was rapid convective cooling of the liquid layer accompanied by melting of the roof producing a compositional

some effects of viscosity on the dynamics of replenished magma chambers some aspects of the dynamical behavior of magma chambers replenished from below with hotter but denser magma have been modeled in a series of laboratory experiments in previously reported work the fluids used were aqueous solutions of comparable viscosity and thus the results should be applicable to basaltic magma chambers in which the magmas do not vary greatly in viscosity in that case the lower layer cools by convective heat transfer to the fluid above and crystallization causes the density of the residual liquid in the lower layer to decrease when the density becomes equal to that in the upper layer sudden overturning and intimate mixing take place the present paper reports experimental results that allow us to extend the application to systems in which there is a large viscosity ratio between the resident and the injected fluid for example to calcalkaline magmas where magma viscosity can vary by as much as 5 orders of magnitude the largest viscosity ratio in our experiments about 3000 was achieved using cold glycerine for the upper layer above a hot denser kno3 solution the most striking new feature with the very viscous upper layer is that now less dense fluid is released immediately and continuously from the interface and rises as plumes through the upper layer further crystallization occurs in the plumes and the crystals fall out but there is little mixing and a layer of depleted kno3 solution is eventually deposited at the top the transfer process between the layers is dominated by interfacial effects with the high viscosity upper layer acting as a nearly rigid lid that allows buoyant fluid to accumulate just below the interface and then rise in localized plumes across the interface into the viscous layer this physical picture is supported by a series of experiments in which the viscosity ratio is varied systematically the mixing behavior changes gradually between that described above for a large viscosity ratio and the sudden over turning characteristic of layers with comparable viscosity the importance of the viscosity ratio rather than just an increase in viscosity is confirmed by experiments in which both viscosities are increased by the same factor the overturning process is then slower but symmetrical other variations suggested by previous experiments are also described the release of gas by a chemical reaction to model the release of volatiles following an overturning event in a magma chamber the effect of a cold immiscible layer above the cooling crystallizing fluid the influence of two viscous layers with a density step between them and the constraining effects of a density with corresponding viscosity gradient in the upper region the experiments indicate that whatever the stratification whether it be in layers or continuous the form of the initial motion in the upper fluid is determined by the viscosity ratio between the two fluids immediately adjacent to the interface geological applications are not examined in detail in this paper but the experiments suggest that both sudden overturning characteristic of magmas of nearly equal viscosity and continuous release when the upper layer is much more viscous are viable mechanisms for magma mixing in the appropriate circumstances

granite emplacement at the termination of a major variscan transcurrent shear zone the late collisional viseu batholith abstract a major event of plutonic activity occurred all across the central iberian zone of the iberian variscan belt at the end of late paleozoic variscan collisional tectonism the present study focuses on the western sector of the viseu late post tectonic batholith central portugal a large composite intrusion comprising three main plutonic units a small bodies of mafic to intermediate composition preferentially concentrated along the northern border b a wide ring of coarse porphyritic biotite monzogranite cota viseu granite and c a more evolved medium porphyritic biotite muscovite monzogranite occupying the central part of the intrusion alcafache granite the compositional zonation pattern of the whole batholith and the complex mixing mingling relationships between the voluminous cota viseu porphyritic granite and the mafic intermediate rocks suggest that these melts were withdrawn from a lower crustal source region undergoing partial melting invasion by mantle derived mafic magmas mixing and fractional crystallization new ca id tims u pb zircon ages indicate that pluton assembly via multipulse injection of successive magma batches took place between 299 4 0 4 ma and 296 0 0 6 ma a detailed anisotropy of magnetic susceptibility ams survey suggests that pluton emplacement occurred at the extensional termination of a regional scale ene wsw trending sinistral d3 shear zone the juzbado penalva shear zone jpsz a dilational opening model involving the development of en echelon tensional gashes at the extensional termination of the fault followed by progressive opening and widening of north south trending fractures provided the space into which the successive magma batches arriving from below were emplaced vertical inflation was accommodated by depression of the pluton floor the proposed model is consistent with the asymmetric wedge shaped geometry of the intrusion steep root zone on the northern side discordant subvertical walls and a shallowing pluton floor towards the south

geochemical and b sr nd isotopic evidence for mingling and mixing processes in the magmatic system that fed the astroni volcano 4 1 3 8 ka within the campi flegrei caldera southern italy abstract the astroni volcano was built through seven eruptions that generated pyroclastic deposits and lava domes within the campi flegrei caldera southern italy 4 1 3 8 ka bp whole rock geochemical and b sr nd isotopic investigations were carried out on representative samples of all seven eruptions the products vary from tephriphonolites to phonolites and from latites to trachytes they show textural mineralogical and isotopic evidence of disequilibrium including distinct clinopyroxene populations rounded and or resorbed plagioclase and alkali feldspar and reverse zoned phenocrysts of all these mineral phases the sr nd and b isotopic composition of whole rocks is variable and correlated with the degree of chemical evolution suggesting open system processes in addition to fractional crystallisation moreover significant sr isotopic disequilibrium between the phenocrysts and glass has been documented for one sample the chemostratigraphy of the products indicates that astroni eruptions 1 through 5 were fed by magmas of trachytic to phonolitic composition that were less enriched in radiogenic sr and 11b up section this variability has been interpreted as the result of mingling between at least two distinct magmatic end members one more evolved and the other less evolved another heterogeneous batch of magma resulting from almost complete mixing between the same two end members was drained during eruptions 6 and 7 the more evolved end member characterised by 87sr 86sr 0 7075 143nd 144nd 0 51247 and 11b 8 was very similar to the magma that fed the final phases of the agnano monte spina eruption which occurred a few centuries earlier in the astroni vent area the less evolved end member had 87sr 86sr 0 70726 143nd 144nd 0 51251 and 11b 10 and was likely derived by fractional crystallisation of a mantle derived magma an abrupt decrease in both the sr isotope ratio and the th content detected at the transition between unit 4 and 5 suggests that another magma with a 87sr 86sr ratio intermediate between those of the two identified end members may have been involved in astroni activity the more evolved end member is interpreted as a residue of the agnano monte spina eruption that was invaded by either the intermediate or the less evolved magmatic end member promoting mingling and triggering astroni activity this study of astroni provides insights for both short and long term volcanic hazard assessment as the astroni volcano is the best example of a very close sequence of eruptions from the same vent area in the campi flegrei caldera

buoyant replenishment in silicic magma reservoirs experimental approach and implications for magma dynamics crystal mush remobilization and eruption 1 we present new experiments on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup water solutions we emphasize small density contrasts and show that buoyancy is the key controlling factor for whether injections will rise to the top if buoyant or pond at the base if denser during emplacement we observe little or no mixing of the injected liquid with the reservoir liquid as predicted by the fact that our injections have low reynolds numbers 10 typically at later stages the low buoyancy 1 kg m 3 injected liquid which has accumulated at the top of the reservoir undergoes mixing with the reservoir liquid which may originate by the gravitational destabilization of a thin layer of denser resident liquid trapped above the injected liquid layer the presence of a basal crystal mush modeled by acrylic beads in a corn syrup water solution matrix is also considered slightly buoyant injections entrain a small fraction of mush particles to the top of the overlying liquid layer entrainment efficiency increases dramatically for high buoyancy injections we hypothesize that the injected liquid can entrain a maximum quantity of mush particles which corresponds to the amount required for the injected liquid mush particle suspension to attain neutral buoyancy in the resident liquid hence for silicic systems a replenishing melt can entrain up to 12 5 crystals during its ascent through the mush our results have implications for rhyolites bearing crystals with disequilibrium features as they may represent mush crystals remobilized by a replenishing silicic magma

fractional crystallization and magma mixing in the tigalak layered intrusion the nain anorthosite complex labrador the tigalak intrusion is a dominantly dioritic layered body about 80 km2 in area which ranges in composition from norite to granodiorite local areas of the layered rocks display upward fractionation from norite to ferrodiorite periodic reversals of mineral composition trends record the emplacement of less fractionated dioritic magma heterogeneous mixtures of dioritic and granodioritic rocks occur widely in mappable lenses and layers that alternate up section and along the strike with more uniformly layered rocks in these mixtures chilled dioritic pillows occur abundantly in a hybrid cumulate matrix of granodiorite to diorite composition cross cutting granodioritic dikes grade upward into stratigraphically bound lensoid masses of the hybrid cumulates it appears that the hybrid rocks formed as a result of the emplacement of the granodioritic magma through lower cumulates into the dioritic magma chamber and that the dioritic pillows represent chilled bodies of ferich dioritic magma that commingled with cooler granodioritic magma and settled to the floor of the tigalak magma chamber

analog experiments on melting and contamination at the roof and walls of magma chambers abstract a series of analogue laboratory experiments were carried out to model melting and mixing processes occurring at the roof and sides of a magma chamber when hot dense mantle derived magmas are emplaced in the deep crust the experiments investigated the influence of a viscosity contrast between crustal melts and input magma the presence of crystals in the input magma and roof geometry the crust was modelled by aqueous ice or a cold low melting point wax arranged as a flat roof or in an upside down u the input magma was modelled by a hot dense aqueous solution of nano3 or feso4 which was injected into the cavity between the walls the experiments revealed the potentially important role that side wall processes may have in crustal melting and mantle magma contamination in this environment the walls melted back much faster than the roof and the melts from the opposite walls ponded next to each other under the roof and mixed with each other only in the central region when the input solution was able to crystallise it did so preferentially in the active side wall boundary layers the tiny dense crystals which were dragged up in the melt boundary layer and then dropped into the interior fluid enhanced hybridisation of the melt and contamination of the input fluid and through their influence on the boundary layer structure reduced the melting rate

the monte guardia eruption lipari aeolian islands an example of a reversely zoned magma mixing sequence the monte guardia rhyolitic eruption 22 ka lipari aeolian islands italy produced a sequence of pyroclastic deposits followed by the emplacement of lava domes the total volume of dense magma erupted was nearly 0 5 km3 the juvenile clasts in the pyroclastic deposits display a variety of magma mixing evidence mafic magmatic enclaves streaky pumices mineral disequilibria and heterogeneous glass composition petrographic mineralogical and geochemical investigations and melt inclusion studies were carried out on the juvenile clasts in order to reconstruct the mixing process and to assess the pre eruptive chemico physical magmatic conditions the results suggest that the different mingling and mixing textures were generated during a single mixing event between a latitic and a rhyolitic end member a denser mixed magma was first erupted followed by a larger volume of an unmixed lighter rhyolitic one this compositional sequence is the reverse of what would be expected from the tapping of a zoned magma chamber the monte guardia rhyolitic magma stored below 200 mpa was volatile rich and fluid saturated or very close to this despite its relatively low explosivity in contrast to previous interpretations there exists the possibility that the rhyolite could rise and erupt without the trigger of a mafic input the entire data collected are compatible with two possible mechanisms that would generate a reversely zoned sequence 1 the occurrence of thermal instabilities in a density stratified salic to mafic magma chamber and 2 the intrusion of rising rhyolite into a shallower mafic sill dike

the disruption of a diorite magma pool by intruding granite the sobu body ladakh batholith indian himalayas most examples of magma mingling described in the literature result from the intrusion of hot mafic magma into colder felsic magma this paper describes a small body 100 x 30 m in the ladakhi himalayas northwest india where mingling occurred when granite magma intruded and disrupted a pool of partially molten quartz diorite that formed fine grained pillow like enclaves the mingled body is surrounded by coarse grained quartz diorite that was effectively solid during granite emplacement and within a short distance from the body was brecciated by the granite because the enclaves are virtually in situ their shapes retain details related to their disruption and to the relative motion between the two magmas whereas this seems to be a rare description of mingling and formation of mafic enclaves by intrusion of felsic into mafic magma this paper argues that because many batholiths evolve from mafic to felsic this may be more common in nature than generally realized and not simply an extraordinary feat

analysis and numerical simulation of chaotic advection and chemical diffusion during magma mixing petrological implications abstract structures generated by magma mixing in a lava flow are studied with the aim to understand the interplay between chemical diffusion and the dynamics of the mixing process mesoscopic analysis of mixing structures indicates that magmas mixed intimately generating the contemporaneous occurrence of filament like and globular regions within the same system the extent of chemical exchange between interacting magmas has been measured by epma and lam icp ms analysis on a transect crossing filaments results indicate that elements with similar values of diffusion coefficients display linear correlations in interelemental plots whereas elements with different diffusion coefficients do not show any correlation the mixing process has been simulated by coupling a chaotic advection and a chemical diffusion numerical scheme for several elements simulations show that the occurrence of chaotic flow fields is essential to explain the decoupling of the correlation at a short length scale between elements with similar and different diffusion coefficients as observed in natural samples in particular the sensitivity to initial conditions of chaotic systems induces elements having similar values of diffusion coefficients to be linearly correlated in interelemental plots whereas at the same time the correlation between elements having different diffusion coefficients is lost the degree of correlation of the different elements in the simulations and natural data has been utilized to estimate the intensity of mixing and results indicate intermediate mixing intensities for the natural samples according to field evidence it is shown that chemical diffusion processes coupled with chaotic mixing dynamics can generate strongly dishomogeneous batches of magmas coexisting at a very short length scale of the order of a few microns in which elements display very different degrees of correlation depending on the magnitude of their diffusion coefficients these results open a key question about the suitability of using melt inclusions for petrogenetic purposes in magma mixing systems because they may be affected by the small scale dishomogeneity of the magmatic system on the contrary it is shown that whole rock analysis is a more suitable technique to understand rock petrogenesis because it is poorly influenced by this dishomogeneity

the architecture of intrusions in magmatic mush abstract magmatic reservoirs located in the upper crust have been shown to result from the repeated intrusions of new magmas and spend much of the time as a crystal rich mush the geometry of the intrusion of new magmas may greatly affect the thermal and compositional evolution of the reservoir despite advances in our understanding of the physical processes that may occur in a magmatic reservoir the resulting architecture of the composite system remains poorly constrained here we performed numerical simulations coupling a computational fluid dynamics and a discrete element method in order to illuminate the geometry and emplacement dynamics of a new intrusion into mush and the relevant physical parameters controlling it our results show that the geometry of the intrusion is to first order controlled by the density contrast that exists between the melt phases of the intrusion and resident mush rather than the bulk density contrast as is usually assumed when the intruded melt is denser than the host melt the intrusion pounds at the base of the mush and emplaced as a horizontal layer the occurrence of rayleigh taylor instability leading to the rapid ascent of the intruded material through the mush was observed when the intruded melt was lighter than the host one and was also unrelated to the bulk density contrast in the absence of density contrasts between the two melt phases the intrusion may fluidize the host crystal network and slowly ascend through the mush the effect of the viscosity contrast between the intruded and host materials was found to have a lesser importance on the architecture of intrusions in a mush analyzing the eruptive sequence of well documented eruptions involving an intrusion as the trigger shows a good agreement with our modeling results highlighting the importance of specifically considering granular dynamics when evaluating magmas and mush physical processes

petrology and geochemistry of the late eocene harrison pass pluton ruby mountains core complex northeastern nevada which suggest a single mixing event before emplacement in the upper the late eocene harrison pass pluton was emplaced in the crust late stage activity consisted of three pulses of monzogranitic transition zone between the infrastructure and suprastructure of the magma plus sparse mafic dikes the largest and youngest of these ruby mountains core complex emplacement was at 3 kbar pulses the two mica monzogranite of green mountain creek is pressure and was in two stages early stage tonalitic to monzogranitic distinct from all other units in the presence of restitic enclaves low magmas followed by late stage monzogranites and mafic dikes nd and high initial sr sr pod like bodies of leucocratic biotite the early stage began with emplacement of biotite hornblende amphibole monzogranite and sheets and dikes of leucocratic granodiorite of toyn creek followed by the biotite monzogranite of two mica monzogranite make up the other late stage granites these corral creek quenched equivalents of these units are preserved as rocks display deep negative eu anomalies and show wide nonporphyritic dikes in the roof leucocratic monzogranite that forms systematic concentrations of high field strength elements however cupolas in the roof zone represents the product of fractional crystheir isotopic compositions are identical to those of the early stage tallization of the early magmas al in hornblende barometry and rocks they are thought to be small melt fractions of the lower to the presence of magmatic epidote suggest that early stage magmas middle crust their elemental compositions are thought to result resided at a pressure of 5 6 kbar before emplacement in the from the effects of residual plagioclase and accessory minerals the upper crust compositional variation in the toyn creek and corral variable and non systematic isotopic compositions of all granitic creek units is essentially linear and can be explained by mixing units in the pluton suggest a heterogeneous source region such as of a tonalitic end member with a monzogranitic end member such the proterozoic mojave province as evolved samples of the monzogranite of corral creek the tonalitic end member was itself a hybrid that formed by interaction

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

mechanisms of iron photoreduction in a metal rich acidic stream st kevin gulch colorado u s a abstract iron photoreduction in metal rich acidic streams affected by mine drainage accounts for some of the variability in metal chemistry of such streams producing diel variations in fe ii differentiation of the mechanisms of the fe photoreduction reaction by a series of in stream experiments at st kevin gulch colorado indicates that a homogeneous solution phase reaction can occur in the absence of suspended particulate fe and bacteria and the rate of reaction is increased by the presence of fe colloids in the stream water in stream fe photoreduction is limited during the diel cycle by the available fe iii in the water column and streambed the quantum yield of fe ii was reproducible in diel measurements the quantum yield in mol e 1 from 300 to 400 nm was 1 4 10 3 in 1986 0 8 10 3 in 1988 and 1 2 10 3 in 1989 at the same location and under similar streamflow and stream chemistry conditions in a photolysis control experiment there was no detectable production of fe ii above background concentrations in stream water samples that were experimentally excluded from sunlight

replenishment of magma chambers by light inputs magma chambers particularly those of basaltic composition are often replenished by an influx of magma whose density is less than that of the resident magma this paper describes the fundamental fluid mechanics involved in the replenishment by light inputs if denotes the uniform density of the resident magma and that of the input the situation is described by the reduced gravity g g the volume flux q and the viscosities of the resident and input magmas e and i respectively the nondimensional reynolds numbers ree g q3 1 5 e and rei g q3 1 5 i and chamber geometry then completely specify the system for sufficiently low values of the two reynolds numbers each less than approximately 10 the input rises as a laminar conduit for larger values of the reynolds numbers the conduit may break down and exhibit either a varicose or a meander instability and entrain some resident magma at still larger reynolds numbers the flow will become quite unsteady and finally turbulent the values of the reynolds numbers at which these transitions occur have been documented by a series of experiments with water glycerine and corn syrup if the input rises as a turbulent plume significant entrainment of the resident magma can take place the final spatial distribution of the mixed magma depends on the geometry of the chamber if the chamber is much wider than it is high the mixed magma forms a compositionally stratified region between the roof and a sharp front above uncontaminated magma in the other geometrical extreme the input magma is mixed with almost all of the resident magma if the density of the resident magma is already stratified the input plume may penetrate only part way into the chamber even though its initial density is less than that of the lowest density resident magma the plume will then intrude horizontally and form a hybrid layer at an intermediate depth this provides a mechanism for preventing even primitive basaltic magmas of minimum density from erupting at the surface by conducting an experiment using aqueous solutions we show that entrainment can lead to crystallization of the magma in the input plume by making it locally supersaturated all these effects are discussed and illustrated by photographs of laboratory experiments

study of diel hydrochemical variation in a volcanic watershed using principal component analysis tatun volcano group north taiwan heavy metal contamination commonly appears in mining areas and volcanic watersheds due to the acidic drainage water under the hydrochemical condition the solar photocycle would result in changes of the water temperature in photosynthesis and in iron photoreduction which leads to substantial hydrochemical fluctuations especially for heavy metals it is important to consider the daily variations in water quality when developing a hydrochemical monitoring plan for an area with highly developed agriculture such as the tatun volcano group watershed area in this study the results show that the water chemistry is highly complicated by both solar photocycles and hydrochemical fluctuations in the upstream area using principal component analysis the contributions from the two factors can be successfully separated during the daytime the photocycle results in the formation of aluminum hydroxide which can remove heavy metals from water consequently the content of heavy metals including as cu ni co and ba increases after sunset and can reach a maximum before sunrise while fe behaves inversely due to the photoreduction the variation of as during a diel cycle can reach 97 however the content of most of the heavy metals during diel cycle is incomparable with those in the earlier studies due to the formation of aluminum hydroxide instead of iron hydroxide the other significant factor hydrochemical fluctuation can explain the variation of major components in water including cl so4 rare earth elements rees were also analyzed and can be an excellent natural tracer in this study the distribution of rees shows a depletion of light rees and an even normalized concentration of middle and heavy rees it is theorized that the rees in the water in this study derive mainly from the reservoir rock of geothermal water in a hydrochemical monitoring plan rees can be an indicator for identifying an anthropogenic source

relationship between plagioclase crystallization and cooling rate in basaltic melts rock textures commonly preserve a record of the near surface crystallization history of volcanic rocks under conditions of simple cooling without convection or mixing textures will reflect sample cooling rate the temperature at which crystallization was initiated and the distribution of mineral phase precipitation across the crystallization interval compilation of plagioclase size and number density data on natural dike sill and lava lake and experimental samples suggests that 1 growth and nucleation rates of plagioclase in natural basaltic samples are a predictable function of cooling rate and 2 the observed crystallization rate dependence on cooling rate is similar to that observed in experiments initiated at subliquidus temperatures comparison of natural and experimental samples thus suggests that most basalts crystallize under conditions of heterogeneous nucleation with the number density of preexisting nucleii partially controlling textural responses to cooling rate changes time scales of crystallization and cooling in magmatic systems are intimately linked through a balance between heat removal from the system and heat evolved through crystallization evaluation of textural data in the context of recent numerical models of crystallization in simple one and two component systems provides new insight into regularities in the crystallization behavior of basaltic magmas for example the rate of change in crystal size and number density as dictated by mass balance has been used as a measure of the relative importance of time scales of crystallization and cooling in numerical models of crystallizing systems in natural samples plagioclase size scales with the length scale of cooling such that a logarithmic plot of grain size as a function of normalized distance across the dike has a slope that appears approximately independent of dike width solidification time comparison with available textural data for other phenocryst phases suggests that the same may be true for pyroxene and magnetite crystallization with each phase having a characteristic slope probably controlled by the thermodynamic properties of the crystallizing phase measured crystal size distributions are unimodal and show maximum frequencies in the smaller size classes distributions broaden and the grain size at peak frequency increases with increasing crystallization times decreasing cooling rates in contrast partially crystallized makaopuhi lava lake samples have crystal size distributions that decrease exponentially with increasing crystal size measured size distributions in dikes can be explained by late stage modification of makaopuhi type distributions through loss of small crystals possibly the consequence of growth without nucleation finally this compilation of the textural response of basaltic magmas to changes in cooling rate suggests that empirical calibrations of crystallization rate dependence on cooling rate from natural samples provide a reasonable model for plagioclase crystallization in near surface basaltic systems predicted growth rates will be slow and relatively constant 10 10 10 11 cm s for crystallization times expected in most shallow volcanic systems 1000 years

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

anisotropy of magnetic susceptibility of silicic rocks from quarries in the vicinity of sao marcos rio grande do sul south brazil implications for emplacement mechanisms abstract the parana etendeka large igneous province includes acid volcanic rocks that can be found throughout its extension several aspects concerning those rocks remain controversial including their mechanism of emplacement and location of their eruptive sources opening of several quarries of dimension stone near the city of sao marcos rio grande do sul brazil offers a unique opportunity to study in detail the acid products here we present the results of a study of the anisotropy of magnetic susceptibility ams completed in some rocks that had been interpreted as the roots of volcanic conduits our results and reexamination of the textural features of the rocks lead to a reinterpretation that suggests that these rocks were emplaced subaerially and involved assimilation and remelting of clastic components of previous products due to the inferred conditions of emplacement it is unlikely that the eruptive vents are located far from the area of study therefore ruling out the long travelled nature of these products

rupture and inflation of a basic magma chamber by silicic liquid the prevailing view among volcanic geologists is that the introduction of basic magma into a silicic magma chamber may trigger explosive silicic volcanism1 and lead to the eruption of mixed magmas2 although the patterns of basic and silicic eruptions in some areas may support an input of basic magma1 just before silicic eruption evidence from the study of the erupted rocks is generally equivocal many occurrences are as readily explained by injection of silicic into basic magma although this latter sequence is a more efficient way to produce contemporaneous magma mixing and explosive silicic volcanism it appears to have been largely overlooked this report describes evidence in the newark island layered intrusion for the rapid emplacement of large volumes of silicic magma into a basic magma chamber and suggests that such events in the uppermost crust may also be important in triggering explosive silicic volcanism and commingling of magmas just before eruption

study on liquefaction mechanism of saturated sand considering stress redistribution abstract most of the saturated soil in actual condition is anisotropically consolidated and can liquefy during minor earthquake based on the analysis of stress state in actual soil the present paper considers that the stress redistributed during loading process which result in the liquefaction however in present conventional element tests the liquefaction in anisotropically consolidated saturated sands acs cannot be induced under dynamic cyclic loading without stress reversal it contributes to the uncertainty about the liquefaction resistance of soil and the development model of excess pore water pressure pwp a brief theoretical interpretation within the theory of limit state of soils is given to explain why the liquefaction in acs could not be induced using the conventional element test under dynamic cyclic load with low or moderate amplitude and the validity of the theoretical analysis is verified by experiments the stress redistribution is realized by confining the lateral deformation based on the conventional test and the liquefaction in acs under minor cyclic load is realized furthermore a new concept called continued liquefaction is proposed apart from transient liquefaction the pwp the total confining pressure and the total vertical stress are always at the same level and the mean effective stress of sands is always zero in the continued liquefaction stage finally a suggestion that the development model of pwp should be established on the basis of the ratio of the pwp to the initial vertical stress is recommended

petrogenesis and metallogenesis of the xinjie layered mafic ultramafic intrusion china modeling of recharge assimilation and fractional crystallization abstract the xinjie layered mafic ultramafic intrusion in the central emeishan large igneous province elip sw china hosts fe ti v oxide ore in the upper part and ni cu platinum group element pge sulfide deposits in the lower part in this study we use published sr nd isotopic data to simulate and evaluate the energy constrained recharge assimilation and fractional crystallization ec rafc model with a view to track the petrogenesis and mineralization in contrast to the energy constrained assimilation fractional crystallization ec afc model the ec rafc modeling shows that the xinjie intrusion may represent a shallow crustal magma chamber system where it experienced the rafc processes in the early stage of the magmatic process tm 1460 c a pulse of magma was injected into an actively evolving magma chamber minor melting ma 0 257 and assimilation of the wallrock underlying emeishan basalts occurred when the temperature of magma tm 1245 c decreased close to the equilibration temperature teq 1165 c the mass temperature plots indicate that fractional crystallization was significantly affected by the recharge and assimilation processes whereas the contaminated magma recharge favored the early crystallization of fe ti oxides as well as the formation of the pge bearing immiscible melt in the lower part of the intrusion in contrast the formation of the fe ti oxides ores in the upper part occurred probably through fractional crystallization and or immiscibility of the evolved fe ti rich magma resulting in the paragenesis of fe ti v oxides and ni cu pge sulfides in the xinjie layered intrusion

field chemical and physical constraints on mafic felsic magma interaction in the lamarck granodiorite sierra nevada california evidence of magma interactions resulting in both hybridization and mingling are preserved in a diverse suite of gabbroic to intermediate rocks associated with the compositionally zoned hornblende biotite lamarck granodiorite of the eastern sierra nevada california ellipsoidal mafic enclaves were formed by quenching of small amounts of high alumina basaltic magma upon injection into and dispersal through granodiorite magma early in its crystallization synplutonic intrusions of hornblende gabbro through hybridized mafic granodiorite represent injection of mafic magma at a later stage of crystallization of the granodiorite as they crosscut regional trends in foliation and compositional zoning in the host pluton where compositional contrasts between intrusion and host granodiorite are large contacts are sharp and abundant enclaves derived from the mafic intrusion are present in the granodiorite where the host is relatively mafic or where the local scale proportion of mafic magma is large contacts are zones of extensive hybridization that contain both enclaves and hybrid schlieren uncontaminated mafic intrusions have high alumina basaltic compositions whereas hybridized intrusions have silica contents as high as 63 5 mafic intrusions locally contain coarse grained cumulus gabbro inclusions mafic schlieren in granodiorite far from mafic intrusions represent localized accumulations of hornblende fe ti oxides and biotite from the granodiorite intrusion of late mafic dikes mobilized and entrained granitic residue from the granodiorite and formed composite dikes of aplite and pillowed diorite whether interacting magmas mix or mingle is a function of the heat contents and mass fractions of the end members calculations that account for compositions heats of fusion heat capacities of liquids and crystals and a range of initial temperatures crystallinities crystal sizes and magma water contents indicate that in most circumstances the basalt end member quenches the resulting large viscosity contrast between the end members prevents hybridization homogenization is likely only if the compositional difference between host and injected mafic magma is less than 10 sio2 or if the mass fraction of mafic magma is greater than 0 5 resulting mixtures have the composition of tonalite or mafic granodiorite thus the more silicic rocks of the granodiorite pluton must represent differentiation products rather than direct hybrids of mafic or intermediate magma and felsic magma

hydrogeochemistry of volcanic hydrogeology based on cluster analysis of mount ciremai west java indonesia summary hydrogeochemical analysis has been conducted on 119 spring locations to portray volcanic hydrogeological system of mount ciremai west java indonesia cluster analysis on 14 parameters has extracted three clusters cluster 1 112 springs is distinguished by normal temperatures low tds ec and high bicarbonate concentrations cluster 2 five springs has moderately high temperature tds ec and high concentration of chloride cluster 3 two springs exhibits high temperature anomalous high tds ec and chloride concentration three hydrogeological systems have been pictured based on the 3 clusters consecutively the 1st system is developed in shallow unconfined aquifer with domination of high bicarbonate 4 2 me l meteoric water the 2nd system is predominated with mixing processes between groundwater in unconfined aquifer and hot groundwater from deeper aquifers the 3rd system is primarily dominated by groundwater flow from deep formation the hot deep seated groundwater flow also carries mud particles it has anomalous high tds 1000 mg l ec 515 s cm and chloride 99 me l from interaction between groundwater with clay formations interpreted as kaliwangu formation

mingling in mafic magma chambers replenished by light felsic inputs fluid dynamical experiments abstract we investigate by means of laboratory analogues the fluid dynamics of magma hybridisation caused by the intrusion of felsic magma into a mafic magma chamber the input felsic magma is modelled by a cold low density fluid and the resident mafic magma by a layer of fluid wax close to its solidification point the cold rising input drives convection and solidification in the resident fluid and the solidification causes significant perturbations to an otherwise simple input flow greatly enhancing mixing and mingling between the two model magmas the dimensionless parameters controlling the evolution of the system are determined and different morphologies of the solid mass fit into clearly defined fields in the parameter space the most important implication of the experiments is that the freezing of mafic chambers due to felsic intrusion may give rise to intense hybridization of large volumes of magma this potentially important mechanism for hybridization has to date received little attention in the literature

on the deformation and freezing of enclaves during magma mixing abstract mixing of an enclave of hot mafic magma into cooler silicic magma involves the competing effects of heat transfer acting to rigidify the enclave and viscous shearing imposed by a flowing host magma acting to deform and disperse the enclave we model the time required to grow a rigid chilled margin and compare this with the time required to deform the initially hot enclave whether an enclave will deform before it freezes depends on the ratio of the thermal and deformation timescales pe app 3 a 2 s r 2 and the dimensionless rigidification temperature t r t s t m t s where app is the applied shear stress a is the enclave radius is the thermal diffusivity s is the viscosity of the host r is the strength of the chilled rind t r is the temperature at which the enclave attains strength r and t m and t s are the initial temperatures of the mafic enclave and silicic host according to the model small values of pe and large values of promote rapid rigidification the model is verified by laboratory experiments on the flow and freezing of polyglycol wax droplets in cold water geological observations show that correlations between enclave size degree of deformation and local shear stress match the model s predictions studies of enclave size and shape as functions of eruption rate and position within lava flows and minor intrusions offer a new technique for studying magma flow processes during eruptions

effects of volatiles on mixing in calc alkaline magma systems the intimate mixing between different magmas of disparate densities characteristic of some calc alkaline magma systems is explained by a new mechanism involving the emplacement of a layer of wet undersaturated mafic magma at the base of a magma chamber containing more differentiated magma turbulent transfer of heat between the mafic magma and the overlying magma leads to crystallization and exsolution of volatiles in the lower layer for an initial water content of a few per cent the bulk density of the mafic magma can become equal to that of the overlying magma causing overturning and intimate mixing of the magmas the mechanism is most probable in the low pressure environment of a high level magma chamber

the interplay between crystallization replenishment and hybridization in large felsic magma chambers abstract while hybridized granitoid magmas are readily identifiable the mechanisms of hybridization in large crustal magma chambers are so not clearly understood characteristic features of hybrid granitoids are 1 both the granitoid and included enclaves are commonly hybrids as shown by mineralogy geochemistry and isotopes 2 mixing seen in zoned plutons and synplutonic dykes and enclaves occurred early 3 zoned plagioclase phenocrysts commonly show very complex life histories of growth and dissolution 4 mafic end members in hybrids are commonly fractionated magmas and 5 stratification in subvolcanic granitoid magma chambers is not uncommon and stratification has been identified in some deeper level plutons hybridization must overcome the tendency to form a stable stratification of dense mafic magma underlying less dense felsic magma experimental work with magma analogues and theoretical considerations reveal very severe thermal rheological and dynamical limitations on mixing only very similar composition temperature magmas are likely to mix to homogeneity and only moderately silicic hybrids are likely to be produced however impossibly silicic hybrids do exist synchronous interactive fractional crystallization and hybridization may provide a mechanism for hybridization of magmas in the following manner a mafic magma intrudes into the base of a stratified felsic magma and is cooled against it crystallization of the upper boundary layer of the mafic magma yields an eventually buoyant residual melt that overturns and mixes with an adjacent stratum of the felsic magma chamber subsequently melt released by crystallization pf this now hybrid zone mixes with adjacent more felsic zones thus a suite of hybrid magmas are progressively formed density inhibitions are overcome by the generation of relatively low density residual melts as crystallization proceeds later injections are preserved as dykes and enclaves composed of hybrid magma in this process only physically adjacent and dynamically thermally similar magmas directly interact and so may mix to homogeneity finally not simply felsic and mafic endmembers mix but a whole suite of intermediate endmembers participate ranging from relatively mafic through to felsic pairs of magmas direct mixing between the primary magmas only occurs at the beginning

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

san jacinto intrusive complex 1 geology and mineral chemistry and a model for intermittent recharge of tonalitic magma chambers geological mapping within the san jacinto mountains of southern california has delineated three major and numerous minor plutons of the cretaceous peninsular ranges batholith early minor intrusives emplaced into quartz rich metasedimentary sequences span the compositional range olivine gabbro to granite the three large to 250 km2 plutons span a limited compositional range between mafic tonalite color index ci 15 and k feldspar poor granodiorite ci 10 all units are composed of plagioclase an30 40 50 55 quartz 20 30 k feldspar 1 8 biotite 10 15 hornblende 0 5 titanite 0 2 and accessory zircon apatite allanite and ilmenite variations in mineral abundances are geographically systematic only within the youngest major mass unit iii which grades from marginal mafic tonalite to central k feldsparpoor granodiorite mineral foliations and banding schlieren and inclusion orientation within each unit usually parallel the nearest contact alignment of foliations and apparent flow sorting and scour features are interpreted as reflecting flow patterns within each chamber mafic synplutonic dykes of quartz diorite and tonalite intruded the tonalites and were broken up to form extensive inclusion trains dyke tonalite relations are interpreted as showing that 1 magma adjacent to the pluton wall had considerable yield strength 2 magmatic flow adjacent to pluton walls was capable of moving material some distance up to kilometers to form the inclusion trains and 3 the dykes represent conduits through which a considerable amount of liquid was added to the inflating magma chambers mineral compositions throughout the major plutons are relatively uniform mean plagioclase composition ranges from an40 in the most mafic tonalites to an30 in the most felsic granodiorites the total microprobe observed range is an44 to an25 and to an47 in a mafic inclusion mg mg fe mn of biotite and hornblende drop similarly from 0 44 to 0 36 reflecting changes in rock mg mg fe the sole oxide mineral is almost pure ilmenite the limited ranges of mineral compositions imply considerable stability of physico chemical conditions during the crystallization of each pluton the field petrographic and mineral chemical data are interpreted in terms of an intermittently recharged continuously solidifying magma chamber

dike transport of granitoid magmas thermal and fluid dynamical analyses suggest that for viscosities and density contrasts spanning the range considered typical for many calc alkalic granitoids dike ascent is a viable mechanism for the transport of large volumes of granitoid melt through the continental crust we present calculations showing that a granitoid melt with calculated viscosity of the order of 10 6 pa s and a density contrast between magma and crust of 200 kg m 3 can be transported 30 km through the crust in 1 month corresponding to a mean ascent velocity of 1 cm s using analysis modified from numerical studies of the flow of basaltic magmas in dikes we also present an expression that allows the calculation of the critical minimum dike or fault width required for granitic magma to ascend without freezing for all reasonable estimates of cordilleran granitoid viscosity and density contrast the critical dike width is determined to be between 2 and 7 m calculated peak batholith filling rates are orders of magnitude greater than mean cavity opening rates based on estimated fault slippage which is consistent with chemical evidence for intermittent supply of magma pulses