psinsar as a new tool to monitor pre eruptive volcano ground deformation validation using gps measurements on piton de la fournaise 1 the permanent scatterers synthetic aperture radar interferometry psinsar is a technique which aims at ground deformation mapping with millimetric precision in the framework of the globvolcano esa project we evaluated a psinsar derived approach to monitor ground deformation in highly active volcanic areas based on the example of piton de la fournaise the permanent scatterer ps velocities show two main areas of deformation 1 the eastern flank displaying old lava flow subsidence 0 05 0 13 m y 1 and 2 the summit cone highly disturbed by eruptions the ps time series for the summit area agree with the cgps trends with small long term weeks months ground displacements preceding eruptions 0 05 0 35 m y 1 and large rapid ground displacements linked to eruptions despite some limitations such as the loss of coherence during the most rapid ground displacements and lava flow emplacement psinsar and its derived approach provide a reliable inference of the volcano ground deformation over large areas

the influence of fluid type on elastic wave velocity and attenuation in volcanic rocks abstract volcano seismic signatures are the convolution of source and path effects the source signature provides important information about the dynamic rock deformation and fluid resonance processes within the volcano but path effects are the result of the volcanic plumbing the edifice physical conditions and the complex geological structure complicating the inversion of seismic data further is the influence of fluid properties here we use ultrasonic experiments to understand the effect of variable fluid viscosity and bulk modulus on p wave attenuation and velocity for volcanic rocks from white island volcano whakaari new zealand our experimental conditions for high porosity ash tuff and low porosity lava resemble shallow and deep volcano facies respectively p wave velocity vp and quality factor qp increase with the viscosity and bulk modulus of the saturating fluid and decrease with porosity and fracture volume tuffs are highly sensitive to saturating fluid with variations in vp of up to 67 and qp of 383 vp and qp in fractured lavas are slightly less sensitive to fluids 24 and 296 respectively but vp can be used to identify lithology for these tuff vs lavas comparison of the experimental data with rock physics models suggests that squirt flow is the dominant attenuation mechanism for viscosities greater than that of water while scattering losses may be important in gas saturated rocks our results have significant implications for the interpretation of seismic tomography studies and for volcano hazard monitoring based on the characteristics of detected seismicity

chromium vanadium and titanium valence systematics in solar system pyroxene as a recorder of oxygen fugacity planetary provenance and processes pyroxene is arguably the most powerful single phase geochemical and petrologic recorder of solar system processes from nebular condensation through planetary evolution over a wide range of temperatures pressures and f o 2 it is an important mineral phase in the crusts and mantles of evolved planets in undifferentiated and differentiated asteroids and in refractory inclusions the earliest solar system materials here we review the valence state partitioning behavior of cr cr 2 cr 3 ti ti 3 ti 4 and v v 2 v 3 v 4 v 5 among crystallographic sites in pyroxene over a range of f o 2 from approximately fayalite magnetite quartz fmq to 7 log units below iron wustite iw 7 and decipher how pyroxene can be used as a recorder of conditions of planetary and nebular environments and planetary parentage the most important crystallographic site in pyroxene with respect to its influence on mineral melt partitioning is m2 its ca content has a huge effect on partitioning behavior because the large ca cation expands the structure as a result distribution coefficients d s for cr and v increase with increasing ca content from orthopyroxene to pigeonite to augite in addition it is noted that v 3 is favored over v 4 in olivine and pyroxene in pyroxene in refractory inclusions ti 3 is favored over ti 4 and incorporation of ti is facilitated by the high availability of al for coupled substitution the most important results from analysis of pyroxene in martian meteorites e g que 94201 are the oxygen fugacity estimates of iw 0 2 and iw 0 9 derived from partitioning and valence data for cr and v respectively obtained from experiments using appropriate temperatures and melt compositions in angrites changes in v valence state may translate to changes in f o 2 from iw 0 7 during early pyroxene crystallization to iw 0 5 during later episodes of pyroxene crystallization in addition to f o 2 the partitioning behavior of cr v and ti between pyroxene and melt is also dependent upon availability of other cations especially al for charge balancing coupled substitutions

in situ oxygen isotope trace element and fluid inclusion evidence for a primary magmatic fluid origin for the shell shaped pegmatoid zone within the giant dahutang tungsten deposit jiangxi province south china abstract the world class dahutang tungsten deposit is located within the jiuling mining district of the central jiangnan orogenic belt jiangxi province china the deposit consists of a massive and gently dipping scheelite orebody that contains disseminated and veinlet hosted mineralization located within a medium to coarse grained biotite granodiorite the no 1 ore block of the deposit also contains a 1 50 1 75 m thick shell shaped pegmatoid zone that defines an inner contact zone between the mineralization related porphyritic like biotite granite and strongly mineralized biotite granodiorite that hosts the tungsten deposit this pegmatoid zone contains very low concentrations of tungsten but records the processes involved in the migration and enrichment of this element within the deposit the pegmatoid contrasts with typical hydrothermal pegmatite type ore in that it often contains megacrystic to giant alkali feldspar quartz and muscovite and is spatially zoned in terms of unique texture and composition the pegmatoid is zoned from a felsic aplite zone with a layered texture proximal to the intrusion through quartz feldspar pegmatoid and feldspar quartz pegmatoid zones to a final distal quartz dominated zone the quartz feldspar pegmatoid is striped and contains megacrystic feldspars that have grown nearly perpendicular to the edge of the pegmatoid indicating the direction of movement of early exsolved magmatic fluids cathodoluminescence imaging indicates that there are five types of quartz within the feldspar quartz pegmatoid megacrystic large phenocrystic small phenocrystic matrix and vein hosted quartz each of these generations of quartz crystallized early with the disseminated metasomatic quartz that crystallized during the middle stages of pegmatoid generation being followed by the uniform crystallization of late stage space filling quartz in situ oxygen isotopic and trace element analysis indicates that all of the quartz within the pegmatoid records accelerated growth with the middle stage disseminated metasomatic quartz associated with an increase in 18oquartz values and the late stage space filling quartz associated with a decrease in 18oquartz values all of this quartz contains elevated concentrations of alkali metals and has low li al ratios generally 10 reflecting the fact that the fluids that formed these minerals were of the peraluminous granite water pgw the trace element compositions of the samples analyzed during this study also indicate a drop in the ph of the pegmatoid forming fluids over time the quartz within the feldspar quartz pegmatoid also contains melt and gas liquid fluid inclusions with the latter containing significant amounts of gas phase ch4 indicating that the pegmatoid formed from low oxygen fugacity fluids our data indicate that the shell shaped pegmatoid zone within the dahutang no 1 ore block formed from primary pgw exsolved from the hosting intrusion with the pegmatoid recording the transition from magmatic to hydrothermal processes during the continuous but multi stage evolution of the dahutang deposit the late stage high temperature water rich high 18o alkali metal rich low oxygen fugacity and acidic nature of the hydrothermal fluids that formed the deposit promoted the transportation and further deposition of tungsten

origin of rhythmic layering in the calamity peak satellite pluton of the harney peak granite south dakota the role of boron abstract the calamity peak satellite granite pluton on the flanks of the harney peak granite south dakota displays prominent mineral and textural layering the latter defined by alternating fine grained and pegmatitic granite superimposed on the fine grained granite layers is a fine scale 0 1 5 cm rhythmic layering defined by modal differences in tourmaline microcline albite and muscovite there is very little variation in the major element mineral compositions in the whole complex analyses by prompt gamma neutron activation gave a b2o3 content of 0 07 in the light layers albite quartz and muscovite and 0 65 in the dark layers tourmaline microcline quartz and albite these contents are essentially proportional to tourmaline abundance in each layer the textural and mineralogic layering is the result of the interplay of tourmaline crystallization and shifts in phase equilibria due to changes in b concentration in the melt initial cotectic crystallization of albite quartz and muscovite increased the activity of fe and mg in the adjacent melt to levels sufficient for tourmaline to form tourmaline crystallization depleted b and decreased the solubility of h2o in the melt causing exsolution of h2o from the melt and further removal of b due to high fluid melt partition coefficient this process also resulted in the precipitation of k feldspar partly at the expense of muscovite and partly due to a slight increase in the solidus temperature once the crystallization front moved to an fe and mg poor region of the melt tourmaline precipitation ceased and the equilibrium shifted back toward quartz muscovite and albite the pegmatitic layers some of which cut across previously formed rhythmic layers and commonly have tourmaline along their borders appear to have crystallized from melt enriched in the exsolved fluid phase

maskelynite hosted apatite in the chassigny meteorite insights into late stage magmatic volatile evolution in martian magmas apatite hosting maskelynite and alkali maskelynite within regions interstitial to cumulus olivine differ compositionally from that found within melt inclusions in the chassigny martian meteorite feldspar glass compositions within the interstitial regions evolve along a high temperature crystallization path within the melt inclusions feldspar glass shows evolution to low temperatures extending into the subsolidus regime coupled with these differences in maskelynite compositions are differences in volatile abundance in apatite included within the maskelynite apatite found within the large olivine hosted polyphase melt inclusions is uniformly fluorapatite whereas that interstitial to cumulus olivine is chlor fluorapatite we propose that the differences in maskelynite and apatite compositions within the melt inclusion and interstitial regions arose primarily from different crystallization conditions melt inclusion maskelynite and apatite are consistent with nearly closed system buildup of magmatic volatiles during crystallization within the melt inclusions exsolution of a cl bearing fluid phase and retention of this fluid phase within the melt inclusions into the hydrothermal regime for the interstitial regions however the higher solidus temperatures of the interstitial melts the early crystallization of feldspar with significant ternary component and the cl rich nature of the apatite all suggest open system fluid migration through the cumulus pile ingress of cl rich h2o poor brine from a hotter less evolved portion of the magma plumbing system and interaction of this cl rich fluid with melt prior to the crystallization of feldspar such processes of fluid migration through a cumulus pile have been suggested on earth in layered intrusions and apatite is the primary recorder of this process

the role of h 2 o in rapid emplacement and crystallization of granite pegmatites resolving the paradox of large crystals in highly undercooled melts granite pegmatite sheets in the continental crust are characterized by very large crystals there has been a shift in viewing pegmatites as products of very slow cooling of granite melts to viewing them as products of crystal growth in undercooled liquids with this shift there has been a renewed debate about the role of h2o in the petrogenesis of pegmatites based on data on nucleation of minerals and new viscosity models for hydrous granite melts it is argued that h2o is the essential component in the petrogenesis of granite pegmatites h2o is key to reducing the viscosity of granite melts which enhances their transport within the crust it also dramatically reduces the glass transition temperature which permits crystallization of melts at hundreds of degrees below the thermodynamic solidus which has been demonstrated by fluid inclusion studies and other geothermometers published experimental data show that because h2o drastically reduces the nucleation rates of silicate minerals the minerals may not be able to nucleate until melt is substantially undercooled in a rapidly cooling intrusion nucleation starts at its highly undercooled margins followed by inward crystal growth towards its slower cooling hotter core delay in nucleation may be caused by competition for crystallization by several minerals in the near eutectic melts and by the very different structures of minerals and the highly hydrated melts once a mineral nucleates however it may grow rapidly to a size that is determined by the distance between the site of nucleation and the point in the magma at which the temperature is approximately that of the mineral s liquidus assuming components necessary for mineral growth are available along the growth path granite pegmatites are apparently able to retain h2o during most of their crystallization histories within the confinement of their wall rocks pegmatitic texture is a consequence of delayed nucleation and rapid growth at large undercooling both of which are facilitated by high h2o li b f and p contents in granite pegmatite melts without retention of h2o the conditions for pegmatitic textural growth may be difficult to achieve loss of h2o due to decompression and venting leads to microcrystalline texture and potentially glass during rapid cooling as seen in rhyolites in contrast slow cooling within a large magma chamber promotes continuous exsolution of h2o from crystallizing magma growth of equant crystals and final solidification at the thermodynamic solidus these are the characteristics of normal granites that distinguish them from pegmatites

a monazite oxygen isotope thermometer a quartz monazite oxygen isotope thermometer was calibrated based on 18 o measurements of mineral separates from monazite bearing rocks and on piston cylinder calcite monazite oxygen exchange experiments the oxygen isotope composition of monazite was measured using secondary ion mass spectrometry sims and multiple fluorination techniques the results of these measurements suggest that 1 differences in th content of monazite can cause the instrumental mass fractionation in an ion microprobe to vary by at least 4 o 2 the oxygen isotope compositions of chemically distinct zones in the monazite grains analyzed are probably similar and 3 18 mnz is most accurately determined by extracting oxygen via fluorination in nickel vessels comparing the oxygen isotope fractionation between quartz and monazite with independently derived temperature estimates suggests that 1 the coefficient of fractionation between quartz and monazite a qtz mnz equals 2 2 0 6 and 2 100 m monazite grains in a multiply metamorphosed granulite facies orthogneiss from the wind river range record the high temperature history of this rock whereas other isotopic thermometers suffered retrograde oxygen exchange this evidence indicates that monazite might be used to constrain peak metamorphic temperatures which may correlate with the ages recorded by the same mineral

monitoring of phreatic eruptions using interferometry on retrieved cross correlation function from ambient seismic noise results from mt ruapehu new zealand abstract since the last major eruption in 1995 96 mt ruapehu has erupted twice on 4 october 2006 and on 25 september 2007 these events occurred without any clear precursors and were mostly phreatic explosions the technique of interferometry on retrieved cross correlation function from ambient seismic noise irccasn is used to monitor subtle temporal changes of mt ruapehu s elastic properties the computation of cross correlation functions of seismic noise recorded at several stations around the volcano allowed us to observe variations during the 2006 eruption period the comparison between a reference cross correlation function and a current cross correlation function allows us to infer relative seismic velocity variations a 0 8 decrease of relative seismic velocity in the edifice starting two days before the 2006 eruption was observed this drop is due to a reversible and ephemeral effect which can be attributed to a pressurization of a magma pocket beneath the east flank of ruapehu due to new magma entering a small reservoir this pressure increase produced an inflation of the east flank of ruapehu and opened fractures in this area leading to a localised drop of seismic velocity we conducted the same analysis for the 2007 eruption but no significant seismic velocity variation was observed this difference is possibly due to the varying time scales of pressurization for the two events and also the irccasn time resolution an analysis of the seismicity before these two eruptions allows us to propose a conceptual model which explains the velocity drop for the 2006 eruption and the lack of velocity variations for the 2007 eruption since there was no surface deformation recorded by the geonet gps network we modelled the maximum radius and pressure change for a simple mogi point source at 5 km depth that produced no deformation we inferred the maximum fresh magma volume of 0 0017 km 3 entering the reservoir as a detectability threshold for gps ground deformation measurements

crystallization of the little three layered pegmatite aplite dike ramona district california subhorizontally layered pegmatite aplite bodies are characterized by fine grained sodic to granitic aplite that is usually juxtaposed abruptly above by much coarser grained commonly graphic potassic pegmatite although well studied there currently is little concensus as to how such dikes form the little three dike near ramona california is representative of such zoned bodies in this and other regions and contains discontinuous miarolitic pockets near the base of the graphic pegmatite zone tourmaline garnet biotite and muscovite show no changes in major or minor element compositions indicative of progressive magmatic fractionation until the immediate vicinity of the main miarolitic zone where they record abrupt and extreme enrichments in li f and mn there is no correlation of chemical changes in the dike with the appearance of small miarolitic vugs well below the main miarolitic zone nor is there any indication that the aplite graphic pegmatite or miarolitic pockets represent separate magma injections the chemistries of tourmaline garnet and micas however preclude conventional models of rayleigh fractionation or traditional zone refining textural features and modeled cooling histories indicate that the dike cooled quickly and might have solidified partially or totally to glass before crystallization commenced geothermometry based on the compositions of coexisting plagioclase and homogeneous nonperthitic k feldspar indicates inward crystallization of the dike from 400 435 c at the margins to 350 390 c within 20 30 cm of the pocket horizon then a sharp decrease to 240 275 c in the pockets where k feldspar is perthitic we interpret the feldspar geothermometry except perhaps in the miarolitic cavities to reflect the temperatures at crystallization fronts that advanced into the pegmatite first from the foot wall and eventually joined by a similar front downward from the hanging wall crystallization down from the hanging wall may have commenced after 70 80 of the foot wall aplite had crystallized the very abrupt increases of li mn and f in tourmaline and garnet near the miarolitic zone appear to be explained best by the process of constitutional zone refining in which a fluxed crystallization front sweeps an incompatible element enriched boundary layer through a solid or semi solid after these two highly fluxed boundary layers merged near the main miarolitic zone compositional evolution could have proceeded by crystal melt fractionation

a petrologic assessment of internal zonation in granitic pegmatites abstract cameron et al 1949 devised the nomenclature and delineated the patterns of internal zonation within granitic pegmatites that are in use today zonation in pegmatites is manifested both in mineralogy and in fabric mineral habits and rock texture although internal zonation is a conspicuous and distinctive attribute of pegmatites there has been no thorough effort to explain that mineralogical and textural evolution in relation to the zoning sequence presented by cameron et al 1949 or in terms of the comprehensive petrogenesis of pegmatite bodies pressure temperature and whole rock composition this overview of internal zonation within granitic pegmatites consists of four principal parts 1 a historic review of the subject 2 a summary of the current understanding of the pegmatite forming environment 3 the processes that determine mineralogical and textural zonation in pegmatites and 4 the applications of those processes to each of the major zones of pegmatites based on the concepts presented in london 2008 the fundamental determinates of the internal evolution of pegmatite zones are 1 the bulk composition of melt 2 the magnitude of liquidus undercooling prior to the onset of crystallization 3 subsolidus isothermal fractional crystallization by which eutectic or minimum melts fractionate by sequential non eutectic crystallization 4 constitutional zone refining via the creation of a boundary layer liquid chemically distinct from but continuous with the bulk melt at the crystallization front and 5 far field chemical diffusion the long range and coordinated diffusion of ions particularly of alkalis and alkaline earths through melt

u pb systematics of the unique achondrite ibitira precise age determination and petrogenetic implications abstract ibitira is an unbrecciated equilibrated vesicular basaltic achondrite that is considered to have originated on a parent body distinct from all other known meteorites we present the first combined high precision u and pb isotopic data for this unique meteorite the 238 u 235 u value of 137 777 0 013 determined for the whole rock is comparable to values determined for bulk chondrites and other basaltic achondrites this value results in corrections of 1 1 ma for pb pb dates calculated using the previously assumed invariant 238 u 235 u value of 137 88 using the determined 238 u 235 u value the 7 most radiogenic pb isotopic analyses for acid leached pyroxene rich and whole rock fractions yield an isochron pb pb age of 4556 75 0 57 ma in excellent agreement with the results of mn cr chronology which give the ages of 4557 4 2 5 ma and 4555 9 3 2 ma using the u corrected pb pb age of d orbigny as a time anchor along with the previously proposed thermal history of ibitira and our closure temperature estimates for pb diffusion the pb pb age is interpreted as the timing of the last chemical equilibration and coarse pyroxene exsolution that occurred during high temperature metamorphism the metamorphism may have been caused by burial of ibitira lava under successive lava flows and if so the pb pb age should post date the crystallization by a short time interval the pb isotopic data for acid leachates suggest partial re equilibration of pb between plagioclase and phosphate perhaps during an impact event at 4 49 ga as recorded by k ar systematics the whole rock 238 u 204 pb indicates that compared to ci chondrites ibitira is less depleted in pb than in some alkali elements despite a lower condensation temperature of pb than the alkali elements the restricted pb depletion may reflect preferential concentration of metals with high fluid melt partition coefficients including pb and zn as a result of fluid exsolution and migration within the parent magma we discuss the implications of the u pb systematics for the origin and differentiation of the parent body

timing of the magmatic activity and upper crustal cooling of differentiated asteroid 4 vesta abstract eucrites are extraterrestrial basalts and cumulate gabbros formed and subsequently more or less metamorphosed at the crustal level of the hed howardite eucrite diogenite parent body thought to be the asteroid 4 vesta unbrecciated eucrites offer the best way to understand the igneous metamorphic and cooling processes occurring in the crust of vesta following accretion since they were not substantially affected altered by secondary impact processes the 40ar 39ar system of unbrecciated eucrites should be in a relatively pristine state and thus can inform us on the early volcanic and thermal history of the hed parent body and in particular the cooling history of various crustal parts below the 300 c isotherm which represents the average closure temperature of the ar diffusion in plagioclase we analysed plagioclase and pyroxene groundmass separates of two cumulate moore county and moama and five caldera btn 00300 eet 90020 gra 98098 que 97053 equilibrated basaltic eucrites with the 40ar 39ar technique using a thermo argus vi multi collection mass spectrometer the two cumulate unequilibrated gabbros also gave cooling ages of 4531 11 ma and 4533 12 ma and combined with a fast cooling rate estimated from lamella thicknesses suggest that magmatic activity persisted up to 4533 11 and 4535 12 ma and that the plutons were intruded in a relatively shallow part of the crust above the metamorphosed regions four equilibrated eucrites yielded a well defined cluster of ages between 4523 8 ma to 4514 6 ma those ages indicate when the part of the upper crust where those eucrites probably resided 10 15 km deep cooled below 300 c at a rate of 17 3 3 6 c ma 2 such a slow cooling rate combined with available global thermal models supports the hypothesis of a global crustal metamorphism by burial and reheating of lava flows finally an age of 4531 5 ma was obtained for metamorphosed eucrite eet 90020 and combined with petrographic observations indicates the age of a major crustal excavation event by impact 40ar diffusion models suggest that it is possible to differentiate impact vs crustal cooling provided that a sufficient quantity of pyroxene is measured by 40ar 39ar

granulite facies amphibole and biotite equilibria and calculated peak metamorphic water activities samples located near the oregon dome anorthosite massif in the south central adirondack mountains new york contain the fluid buffering mineral assemblages amphibole clinopyroxene orthopyroxene quartz or biotite quartz orthopyroxene k feldspar these rocks were metamorphosed under granulite facies conditions t 725 750 c p 7 5 kbar during the grenville orogeny the mg rich nature of amphiboles micas and pyroxenes allow accurate calculation of water activities because corrections for the effects of solid solution are relatively small the activity of water was low during the peak of granulite facies metamorphism with h2o 0 15 0 14 wollastonite occurrences indicate that the co2 was low 0 3 in nearby rocks demonstrating that large quantities of co2 did not infiltrate in a pervasive manner the combination of low h2o with low co2 is consistent with the hypothesis that magmatic processes were dominant generating dry fluid absent conditions

oxygen isotope evidence for rapid mixing of the hed meteorite parent body abstract the 16 o 17 o and 18 o abundances of howardites eucrites and diogenites have been used to assign them to a single hed parent body thought to be asteroid 4 vesta we report the first evidence of oxygen isotopic heterogeneity among hed meteorites indicating incompletely mixed sources new high precision oxygen isotope measurements of 34 hed meteorites reveal that most have the same 17 o consistent with a very rapid early history of large scale mixing on vesta however howardites are on average very slightly enriched in 16 o whereas ibitira caldera pasamonte and alha78132 are 16 o depleted compared to other investigated eucrites the 17 o of ibitira is completely different from all other heds measured some of the results for eucrites and diogenites can be explained by partial melting and rapid mixing of the interior of vesta others require a separate parent body or indicate that parts of the outer layer of vesta retained some primary isotopic heterogeneity the oxygen isotopic composition of howardites provides an upper limit for the amount of admixed carbonaceous chondritic material into the hed parent body regolith

location and mechanism of very long period tremor during the 2008 eruption of okmok volcano from interstation arrival times 1 we describe continuous very long period vlp tremor that occurred during the 2008 eruption of okmok volcano alaska due to its low frequency content in band from the 0 2 0 4 hz the wave field of the vlp tremor is relatively free of path effects from continuous recordings of the vlp tremor on 2 three component broadband and 3 single component short period instruments we devise a method to locate the epicenter of the tremor based on interstation arrival times computed with cross correlation we find the epicenter since the vertical and radial components of the vlp tremor wave field are dominated by rayleigh waves and the time shifts are related to lateral propagation over the 4 h period studied this procedure yields a location nnw of cone d close to the new cone built over the course of the eruption similar analysis using the transverse horizontal components from the 2 three component broadband instruments yields strong constraints on the source mechanism of the vlp tremor we observe an anomalous interstation arrival time due to the existence of a nodal plane in the love wave radiation pattern the orientation of a compensated linear vector dipole clvd source estimated from the transverse components closely aligns with the regional maximum horizontal stress direction the depth of the clvd source is constrained by matching the vertical components to the rayleigh wave radiation pattern at all five stations we find the vlp tremor source depth to be 2 km bsl positioned between the magma chamber at okmok 3 km bsl and the surface

explosive volcanic eruptions ix the transition between hawaiian style lava fountaining and strombolian explosive activity the commonest eruption styles of basaltic volcanoes involve hawaiian lava fountaining or intermittent strombolian explosions we investigate the ways in which magma rise speed at depth magma volatile content and magma viscosity control which of these eruption styles takes place we develop a model of the degree of coalescence between gas bubbles in the magma which allows us to simulate the transition between the two extreme styles of activity we find that magma rise speed is the most important factor causing the transition with gas content and viscosity also influencing the rise speed at which the transition occurs counter to intuitive expectations a decrease in gas content does not cause a transition from hawaiian to strombolian activity but instead causes a transition to passive effusion of vesicular lava rather a change from hawaiian to strombolian style requires a significant reduction in magma rise speed

petrology of the unbrecciated eucrites abstract twenty nine unbrecciated eucrites have been thoroughly characterized in terms of the petrologic factors that affect their spectra such as mineral chemistry modal adundances grain sizes and textures we have conducted a combined petrologic and spectral study designed to provide insight into the petrogenesis of the basaltic crust of vesta and the variety of rock types that exist within it as well as aid in the petrologic interpretation of spectra to be collected by the dawn orbiting spacecraft this paper details the petrology part of the study unbrecciated eucrite samples were selected to avoid the complications of lithologic mixing in the accompanying spectral study a wide variety of textural types are seen within the basaltic eucrites encompassing quenched coarse grained and granoblastic samples zoned pyroxenes in eucrites and those that preserve a history of initial rapid cooling are rare nearly all eucrite samples have been thermally metamorphosed and would commonly be classified as equilibrated however this term reflects only the quadrilateral mg fe and ca compositions of pyroxenes and considerable variations are seen within the minor elements al ti and cr in pyroxenes as well as plagioclase compositions determination of both pyroxene and plagioclase compositions together with pyroxene geothermometry provides a better estimate for the relative degree of thermal metamorphism a eucrite has experienced the petrologic differences observed here might allow different eucrites to be distinguished spectrally this is especially true for the varying pyroxene compositions as the spectra of eucrites are dominated by absorption features attributed to pyroxene

fluids on differentiated asteroids evidence from phosphates in differentiated meteorites gra 06128 and gra 06129 abstract paired meteorites graves nunatak 06128 and 06129 gra represent an ancient cumulate lithology 4565 9 ma 0 3 containing high abundances of sodic plagioclase textures and stable isotope compositions of gra indicate that superimposed on the igneous lithology is a complex history of subsolidus reequilibration and low temperature alteration that may have extended over a period of 150 myr in gra apatite is halogen rich with cl between 4 5 and 5 5 wt and f between 0 3 and 0 9 wt the cl cl f oh ratio of the apatite is between 0 65 and 0 82 the cl and f are negatively correlated and are heterogeneously distributed in the apatite merrillite is low in halogens with substantial na in the 6 fold coordinated na site 2 5 and mg in the smaller octahedral site the merrillite has a negative eu anomaly whereas the apatite has a positive eu anomaly the chlorine isotope composition of the bulk gra leachate is 1 2 relative to standard mean ocean chloride smoc ion microprobe chlorine isotope analyses of the apatite range between 0 5 and 1 2 textural relationships between the merrillite and apatite and the high cl content of the apatite suggest that the merrillite is magmatic in origin whereas the apatite is a product of the interaction between merrillite and a cl rich fluid if the replacement of merrillite by apatite occurred at approximately 800 c the fluid composition is f hcl f h2o 0 0383 and a hcl molality of 2 13 and f hcl f hf 50 100 it is anticipated that the calculated f hcl f h2o and a hcl molality are minimum values due to assumptions made on the oh component in apatite and basing the calculations on the apatite with the lowest xcl the bulk 37cl of gra is a 2 outlier from chondritic meteorites and suggests that parent body processes resulted in fractionation of the cl isotopes

questions about myrmekite in deformed rocks abstract several questions about the development of myrmekite in deformed felsic and metapelitic rocks remain unanswered although a general relationship between deformation and myrmekite appears to be well established the fact that myrmekite grows into relatively non deformed k feldspar while being simultaneously deformed and recrystallized at the rear of the growing lobes suggests that strain energy may not be a major contributor to the advance of the growth interface of the myrmekite colony furthermore because myrmekite typically nucleates on existing plagioclase rather than in k feldspar strain energy may not contribute directly to nucleation of myrmekite either at least in many instances however strain energy probably contributes indirectly by facilitating access of fluids to growth sites thereby altering the local chemical environment and so promoting development of myrmekite because myrmekite recrystallizes readily in deformed felsic rocks it is one of the main contributors to the development of folia

earthquake volcano interaction imaged by coda wave interferometry 1 large earthquakes are often assumed to influence the eruptive activity of volcanoes a major challenge to better understand the causal relationship between these phenomena is to detect and image in detail all induced changes including subtle non eruptive responses we show that coda wave interferometry can be used to image such earthquake induced responses as recorded at yasur volcano vanuatu following a magnitude 7 3 earthquake which occurred 80 km from its summit we use repeating long period events to show that the earthquake caused a sudden seismic velocity drop followed by a slow partial recovery process the spatial distribution of the response amplitude indicates an effect centered on the volcano our result demonstrates that even if no major change in eruptive activity is observed volcanoes will be affected by the propagation of large amplitude seismic waves through their structure suggesting that earthquake volcano interaction is likely a more common phenomenon than previously believed

calculated relationships between activity of alumina and phase assemblages of silica saturated igneous rocks petrogenetic implications of magmatic cordierite garnet and aluminosilicate abstract many peraluminous igneous rocks are characterized by the presence of al rich minerals such as cordierite garnet and aluminosilicate polymorphs clearly one of the important thermodynamic intensive variables controlling the stability of these minerals relative to al poor phases such as ortho and clinopyroxene must be the activity of al 2 o 3 a al 2 o 3 in the melt calculated phase relationships of anhydrous mineral assemblages in equilibrium with quartz saturated liquids show that at crustal pressures less than about 10 kbar garnet cordierite and aluminosilicate are only likely to crystallize from melts in which a al 2 o 3 is up to one order of magnitude higher than that required for orthopyroxene clinopyroxene crystallization in spite of this peraluminous granitoid liquids saturated with orthopyroxene garnet or orthopyroxene cordierite do not ordinarily contain significantly larger amounts of excess al al in excess of that required to form feldspars than peraluminous liquids saturated with orthopyroxene clinopyroxene these observations indicate that there must be profound compositional controls on the activity coefficient of al in silicic melts and the strongest of such controls appears to be the total alkali content of the melt the activity coefficient of al in silicic melts varies directly with total alkali oxide content so that alkali poor melts can become markedly peraluminous without ever becoming saturated in aluminous phases whereas alkali rich melts of similar normative corundum content can crystallize garnet cordierite or even aluminosilicate because activity of alumina in a silicic melt is not a simple function of excess al content classification schemes for silicic igneous rocks based on model mineralogical assemblages which reflect the value of the thermodynamic effective concentration of al during crystallization convey more petrologic information than those based on chemical parameters such as normative corundum content or alumina saturation index

the role of magmatic and hydrothermal processes in the evolution of be bearing pegmatites evidence from beryl and its breakdown products beryl and euclase crystals from the mina do santino and the jacu pegmatites in the borborema pegmatite province in northeastern brazil contain several generations of melt and fluid inclusions which allow interpretation of p t x conditions responsible for beryl crystallization and for alteration of a primary pegmatitic mineral assemblage to a mixture of hydrothermal minerals euclase bertrandite kaolinite and quartz primary melt and fluid inclusions hosted by beryl were trapped simultaneously however their homogenization temperatures are significantly higher 870 900 c than the values previously reported for pegmatitic systems 712 c and should be treated with caution an isobaric drop of temperature resulted in the exsolution of a fluid a low salinity co2 enriched phase and a saline water rich phase were trapped in pseudosecondary inclusions in beryl at a pressure of 2 1 2 7 kbar and temperature of 390 480 c cooling of the country rocks below 400 c caused a ductile to brittle transition and allowed infiltration of cold groundwater which further decreased the temperature in the system to 190 240 c at the same time the pressure dropped from a lithostatic 2 1 2 7 kbar to a hydrostatic value 0 57 0 73 kbar consequently minerals deposited under magmatic conditions feldspars and beryl became unstable and a newly formed hydrothermal mineral paragenesis euclase bertrandite kaolinite and quartz overprinted the earlier one the hydrothermal fluids responsible for the alteration differ from the earlier exsolved fluids in having a lower salinity lower homogenization temperature the absence of co2 and the presence of ch4

emplacement of sills into wet sediments at grunehogna western dronning maud land antarctica the mid proterozoic ritscherflya supergroup antarctica is intruded by numerous mafic to intermediate sills and small layered bodies contact relations are well exposed where the grunehogna and kullen sills intruded argillaceous and arenaceous sedimentary rocks of the schumacherfjellet and hogfonna formations of the ahlmannryggen group a 3 m thick peripheral zone above the upper contact of the grunehogna sill consists of reconstituted sedimentary rocks which have been fluidized and recrystallized due to the intrusion local melting and crystallization of the sediments under hydrous conditions and pressures below 312 bars have produced zones of granite and granophyre which grade into arenites where primary sedimentary structures are preserved the sedimentary rocks have been deformed into large disharmonic folds where the sill transgresses the schumacherfjellet formation the contact relations suggest that emplacement of the mafic sills and sheets at grunehogna occurred when the sediments were still water saturated and only partially lithified

the miocene pliocene macusani volcanics se peru i mineralogy and magmatic evolution of a two mica aluminosilicate bearing ignimbrite suite

long term dynamics of piton de la fournaise volcano from 13 years of seismic velocity change measurements and gps observations we study the piton de la fournaise pdf volcano dynamics through the observation of continuous seismic velocity changes from 2000 to 2013 we compute the cross correlations of ambient seismic noise recorded at more than 30 short period and broadband stations of the undervolc temporary seismic experiment and of the pdf volcano observatory network the velocity changes are estimated from the travel time delay measured on the cross correlations computed between pairs of stations we average the relative velocity changes for all pairs of stations and obtain a time series of the velocity change of piton de la fournaise volcano over 13 years from the period 0 5 to 4 s the depth sensitivity of the velocity change is ranging from approximately 100 m to 2500 m a slow decrease of velocity is measured from 2000 and ends with a major eruption that occurred in april 2007 this eruptive episode is followed by an increase of the velocity these long term changes are compared to the deformation of the piton de la fournaise edifice estimated from geodetic measurements an analysis of baseline change between gps stations indicates an inflation of the volcanic edifice prior to april 2007 followed by a deflation since then this deflation predominantly affects the terminal cone seismic velocity changes and deformation have similar long term trends with velocity decrease observed during inflation and velocity increase during deflation however the velocity change magnitude is about 2 orders of magnitude greater than the deformation this suggests nonlinear relation between velocity changes and deformation

seismic evidence of nonlinear crustal deformation during a large slow slip event in mexico repeated cross correlations of ambient seismic noise indicate a long term seismic velocity change associated with the 2006 m7 5 slow slip event sse in the guerrero region mexico because the sse does not radiate seismic waves the measured velocity change cannot be associated with the response of superficial soil layers to strong shaking as observed for regular earthquakes the perturbation observed maximized at periods between 7 s and 17 s which correspond to surface waves with sensitivity to the upper and middle crust the amplitude of the relative velocity change 10 3 was much larger than the volumetric deformation 10 6 at the depths probed 5 20 km moreover the time dependence of the velocity perturbation indicated that it was related to the strain rate rather than the strain itself this suggests that during strong slow slip events the deformation of the overlying crust shows significant nonlinear elastic behavior

mineralogical constraints on the magmatic hydrothermal evolution of rare elements deposits in the bailongshan granitic pegmatites xinjiang nw china abstract the bailongshan pegmatite district in south xinjiang province nw china is a newly discovered area of rare element pegmatites it is a superlarge li rb reserve that includes an estimated 3 45 million tons of li2o and 176 000 tons of rb2o on the basis of a detailed characterization of textures and minerals in the bailongshan 2 and 5 pegmatites six zones are identified a saccharoidal albite zone zone i a graphic pegmatite zone zone ii a blocky microcline zone zone iii a muscovite quartz zone zone iv a cleavelandite spodumene zone zone v and a quartz spodumene zone zone vi the detailed mineralogical characteristic is performed by epma for illustrating both the existent state of rare elements and the magmatic hydrothermal evolution of the bailongshan pegmatite lithium be rb nb ta and sn are major economic rare elements which are concentrated in zones v and vi the rare elements are hosted by minerals including spodumene montebrasite eucryptite lepidolite beryl rb enriched k feldspar columbite group minerals cassiterite and tourmaline which formed from the fractional crystallization of pegmatitic magma the bailongshan pegmatites show lower degrees of fractional crystallization than many other li cs ta lct family pegmatites worldwide as evidenced by the relatively low nb ta zr hf and k rb fractional degree in the carrier minerals in zones v and vi the primary minerals record intense interaction with hydrothermal fluids which caused the alteration of spodumene and mica the development of cs or na enriched veinlets in beryl and the formation of mn and ta enriched veinlets coupled with micropores within columbite group minerals the hydrothermal fluids were composed predominantly of li f cs and ta which conformed to the evolved trend of pegmatitic melt these late hydrothermal fluids exsolved from the magma as it differentiated and may have the benefit with rare elements metallogeny

bunburra rockhole exploring the geology of a new differentiated asteroid bunburra rockhole is the first recovered meteorite of the desert fireball network we expanded a bulk chemical study of the bunburra rockhole meteorite to include major minor and trace element analyses as well as oxygen and chromium isotopes in several different pieces of the meteorite this was to determine the extent of chemical heterogeneity and constrain the origin of the meteorite minor and trace element analyses in all pieces are exactly on the basaltic eucrite trend major element analyses show a slight deviation from basaltic eucrite compositions but not in any systematic pattern new oxygen isotope analyses on 23 pieces of bunburra rockhole shows large variation in both 17o and 18o and both are well outside the hed parent body fractionation line we present the first cr isotope results of this rock which are also distinct from heds detailed computed tomographic scanning and back scattered electron mapping do not indicate the presence of any other meteoritic contaminant contamination is also unlikely based on trace element chemistry we therefore conclude that bunburra rockhole represents a sample of a new differentiated asteroid one that may have more variable oxygen isotopic compositions than 4 vesta the fact that bunburra rockhole chemistry falls on the eucrite trend perhaps suggests that multiple objects with basaltic crusts accreted in a similar region of the solar system

petrology of biotite cordierite garnet gneiss of the mccullough range nevada i evidence for proterozoic low pressure fluid absent granulite grade metamorphism in the southern cordillera proterozoic migmatitic paragneisses exposed in the mccullough range southern nevada consist of cordierite almanditic garnet biotite sillimanite plagioclase k feldspar quartz ilmenite hercynite this assemblage is indicative of a low pressure facies series at hornblende gr anulite grade textures record a single metamorphic event involving crystallization of cordierite at the expense of biotite and sillimanite thermobarometry utilizing cation exchange between garnet biotite cordierite hercynite and plagioclase yields a preferred temperature range of 590 750 c and a pressure range of 3 4 kb equilibrium among biotite sillimanite quartz garnet and k feldspar records ahlo between 0 03 and 0 26 the low ah o together with low fol qfm and optical properties of cordierite indicate metamorphism under fluid absent conditions preserved mineral compositions are not consistent with equilibrium with a melt phase earlier limited partial melting was apparently extensive enough to cause desiccation of the pelitic assemblage the relatively low pressures attending high grade metamorphism of the mccullough range paragneisses allies this terrane with biotite cordierite garnet granulites in other orogenic belts closure pressures and temperatures require a transient apparent thermal gradient of at least 50 c km during part of this proterozoic event in the southern cordillera

successive zoning of amphiboles during progressive oxidation in the daito yokota granitic complex san in belt southwest japan abstract clinoamphibole present in shallow intrusive masses of quartz diorite in the daito yokota area of the san in belt southwest japan is strongly zoned successively from a magnesio homblende core to an actinolite rim systematically decreasing in fe 2 fe 2 mg towards the rim the features of compositional variation and cation substitution are similar to those of amphiboles which have been altered by fluid separated during secondary boiling in porphyry copper bearing granitoids mineralogie data and textural relations of amphibole and the accompanying minerals indicate that the zoned amphibole has crystallized or recrystallized from a subsolidus fluid phase under progressively oxidizing conditions truly magmatic amphibole is restricted to small patches in the core of strongly zoned amphibole grains progressive oxidation is responsible for reequilibration of early formed fe ti oxide to yield extensive development of secondary magnetite and sphene the decreasing fe trend of amphibole has resulted from progressive fe depletion of the fluid phase by abundant magnetite precipitation the amphibole grains usually show an alternation of chemically distinct zones with unconformable boundaries indicating repeated growth and corrosion by multiple circulation of fluids

the structure of basaltic scoria and reticulite and inferences for vesiculation foam formation and fragmentation in lava fountains in this investigation pyroclast structures are used to constrain degassing in basaltic lava fountains vesicle size shape number density interconnectedness and packing character are quantified and related to 1 the kinetics of bubble nucleation and growth 2 the structural evolution of magmatic foams and 3 the influence of vesiculation rate on magma fragmentation measurements made on a diverse suite of pyroclasts from kilauea volcano indicate that basaltic foams evolve through an initially disordered closed celled spherical state to a well ordered open celled polyhedral state as the vesicularity rises from 75 to 98 the structural changes occur rapidly 10 s in the conduit and fountain in response to an intense vesiculation burst vesicle size distribution systematics indicate bubble nucleation rates 2 104 events cm 3s 1 that are approximately three orders of magnitude greater than those found for effusive eruptive activity bubble growth rates 9 10 4 cm s exceed effusive estimates by a factor of 3 the observed runaway rate of bubble production indicates strong supersaturations at the onset of nucleation we speculate that the rise speed of the magma as it reaches the level where significant volatile exsolution begins determines the intensity of the vesiculation burst and hence the vigor of the eruption rapid expansion and acceleration of the magma under these conditions may provide the impetus for fragmentation

archaean ttgs as sources of younger granitic magmas melting of sodic metatonalites at 0 6 1 2 gpa two natural low k2o na2o ttg tonalitic gneisses one hornblende bearing and the other biotite bearing were partially melted at 0 8 1 2 gpa fluid absent the chief melting reactions involve the breakdown of the biotite and hornblende the hornblende tonalite is slightly less fertile than the biotite tonalite but melt volumes reach around 30 at 1 000 c this contrasts with results of most previous work on more potassic ttgs which generally showed much lower fertility though commonly producing more potassic melts garnet is formed in biotite bearing tonalitic protoliths at p 0 8 gpa and at 1 0 gpa in hornblende bearing tonalitic protoliths all fluid absent experiments produced peraluminous granitic to granodioritic melts typically with sio2 70 wt for the biotite tonalite increasing t formed progressively more melt with progressively lower k2o na2o however the compositions of melts from the hornblende tonalite do not vary significantly with t with increasing p melts from the biotite tonalite become less potassic due to the increasing thermal stability of biotite for the hornblende tonalite again there is no consistent trend fluid absent melting of sodic ttgs produces melts with insufficient k2o to model the magmas that formed the voluminous late potassic granites that are common in archaean terranes reconnaissance fluid present experiments at 0 6 gpa imply that h2o saturated partial melting of ttgs is also not a viable process for producing magmas that formed these granites the protoliths for these must have been more potassic and less silicic nevertheless at granulite facies conditions sodic ttgs will produce significant quantities of broadly leucogranodioritic melt that will be more potassic than the protoliths upward abstraction of this melt would result in some lile depletion of the terrane younger k rich magmatism is unlikely to represent recycling of ttg crust on its own and it seems most likely that evolved crustal rocks and or highly enriched mantle must be involved

temporal change of phase velocity beneath mt asama japan inferred from coda wave interferometry 1 we estimated the temporal changes of phase velocity of rayleigh waves extracted from cross correlations of s coda waves recorded at 12 stations around mt asama japan first we extracted a rayleigh wave by taking cross correlations of s coda waves for 315 regional earthquakes between october 2005 and february 2009 the dispersion curve of the rayleigh wave was measured and compared with the one extracted from 18 days of ambient seismic noise we found that both dispersion curves are consistent with each other demonstrating the dominance of the fundamental rayleigh waves we then divided the entire time period into sub periods each of which consists of 80 earthquakes to measure the temporal changes at frequencies between 0 3 and 0 6 hz the result shows the reduction of phase velocity by 1 5 and the subsequent recovery before the eruption of mt asama in 2008

fractional crystallization and zoning in igneous feldspars ideal water buffered liquid fractionation lines and feldspar zoning paths diagrams giving plagioclase and sanidine fractionation paths and liquid fractionation lines under conditions of ideal water buffered fractional crystallization in the ternary feldspar system were constructed graphically using topological reasoning and experimental data and calculated phase relationships from the literature the liquidus lines and solidus or solvus paths are unique at constant p and ah2o the composition of a liquid evolves with time and moves along a fractionation line by removal of successive crystal fractions whereas the compositions of each of the crystal fractions lie on and define a solidus or solvus path most but not all such water buffered lines and paths differ only slightly from those in which water is free to build up during crystallization and ah2o to increase as in many rocks liquid compositions lying along liquidus fractionation lines are not normally preserved unless erupted as aphyric lavas the solidus or solvus paths may be preserved either as overgrowth zones in crystals zoning paths or as a series of crystal fractions in layered intrusions the topologies of the lines and paths depend mainly on the nature of the two feldspar boundary line separating the plagioclase and sanidine fields which is a function of ph2o or ah2o at constant p increases in either progressively lower the liquidi and solidi and cause larger intersections of the solidi with the solvus one feldspar solidus paths at high p and ah2o are simple whereas they are complex and may bend back on themselves at low ph2o or low ah2o at high p two feldspar paths may be simultaneous cotectic or sequential peritectic the former are simple and do not meet at high p and ah2o the critical solution line lying in the gap they are complex and may bend back or overlap at low ph2o or low ah2o at high p the position of the critical solution line being hard to determine liquids which have simultaneously fractionated two feldspars may fractionate only one towards the end crystallization changing from subsolvus to hypersolvus sequential paths may involve overgrowth of an early feldspar by a later one usually sanidine overgrowths on plagioclase but plagioclase overgrowths on sanidine occur these complexities explain in part the difficulties of unravelling the textural and compositional relationships of ternary feldspars in water poor felsic igneous rocks even in the absence of alteration or complex magma dynamics and of trying to deduce phase relationships from natural occurrences of feldspars

imaging preeruptive and coeruptive structural and mechanical changes of a volcano with ambient seismic noise 1 forecasting the location of an eruption is of primary importance for risk management in volcanic regions locating the underground structural changes associated with a potential eruption is also a key issue to better understand the dynamics at work in a volcano using recent results in wave physics we develop an imaging procedure that is based on the sensitivity of multiply scattered waves to weak changes in heterogeneous media this procedure allows to locate changes in both mechanical and scattering properties of the studied medium we study ambient seismic noise from 19 broadband stations at the active volcano piton de la fournaise on reunion island recorded from june to december 2010 during this period two volcanic eruptions occurred at two different locations we calculate the noise cross correlations and study two types of changes in the coda apparent velocity variations related to changes in the elastic properties of the medium and waveform decoherence associated with variations in the scattering and thus the geological structures we observe that the temporal variations of both of these parameters provide potential precursors of volcanic eruptions at piton de la fournaise the locations determined from the preeruptive and coeruptive changes in both parameters are in good agreement with the actual eruptive activities these data demonstrate that the coda of ambient noise correlations contains deterministic information on the locations of the eruptive processes in an active volcano our analysis offers an original and significant constraint for the localization of forthcoming volcanic eruptions

formation of vesicles in asteroidal basaltic meteorites rare asteroidal vesicular basalts have previously been thought to form in surficial lava flows with co as the vesicle forming gas however vesicular lava flows are unlikely on small airless bodies such as asteroids to unravel the origin of these rocks we analyzed vesicle sizes and abundances for two angrites and two eucrites using high resolution x ray computed tomography and conducted numerical modeling of bubble formation in a dike of ascending magma modeling results indicate that thin 30 cm wide dikes are trapped at 5 km depth where 75 ppm of co and co2 contribute equally to vesicle formation vesicular eucrites were metamorphosed in this deep seated environment the gas was lost and they were excavated by impacts

seismic envelope based detection and location of ground coupled airwaves from volcanoes in alaska abstract volcanic explosions and other infrasonic sources frequently produce acoustic waves that are recorded by seismometers here we explore multiple techniques to detect locate and characterize ground coupled airwaves gca on volcano seismic networks in alaska gca waveforms are typically incoherent between stations thus we use envelope based techniques in our analyses for distant sources and planar waves we use f k beamforming to estimate back azimuth and trace velocity parameters for spherical waves originating within the network we use two related time difference of arrival tdoa methods to detect and localize the source we investigate a modified envelope function to enhance the signal to noise ratio and emphasize both high energies and energy contrasts within a spectrogram we apply these methods to recent eruptions from cleveland veniaminof and pavlof volcanoes alaska array processing of gca from cleveland volcano on 4 may 2013 produces robust detection and wave characterization our modified envelopes substantially improve the short term average long term average ratios enhancing explosion detection we detect gca within both the veniaminof and pavlof networks from the 2007 and 2013 2014 activity indicating repeated volcanic explosions event clustering and forward modeling suggests that high resolution localization is possible for gca on typical volcano seismic networks these results indicate that gca can be used to help detect locate characterize and monitor volcanic eruptions particularly in difficult to monitor regions we have implemented these gca detection algorithms into our operational volcano monitoring algorithms at the alaska volcano observatory

distribution of seismic wave speed changes associated with the 12 may 2008 mw 7 9 wenchuan earthquake 1 we used continuous recordings in sichuan china to track the temporal change of the seismic wave speed at a regional scale for 2 years including the wenchuan mw 7 9 earthquake the data are recorded by a temporary network of 156 broad band seismographs in a region that covers the southern 2 3 of the fault activated during the earthquake a doublet analysis applied on the codas of seismic noise cross correlation functions is used to detect temporal velocity changes we found clear evidence that the seismic velocity drops by up to 0 08 in the fault region just after the earthquake with fluctuations within 0 02 before the earthquake we compared the measurements in different sub arrays to get a spatial distribution of the velocity changes this distribution is consistent with the volumetric strain change during the wenchuan earthquake and shows that the co seismic velocity change is not controlled by the response of sediments

the effect of melt composition on metal silicate partitioning of siderophile elements and constraints on core formation in the angrite parent body we present 275 new metal silicate partition coefficients for p s v cr mn co ni ge mo and w obtained at moderate p 1 5 gpa and high t 1683 1883 k we investigate the effect of silicate melt composition using four end member silicate melt compositions we identify possible silicate melt dependencies of the metal silicate partitioning of lower valence elements ni ge and v elements that are usually assumed to remain unaffected by changes in silicate melt composition results for the other elements are consistent with the dependence of their metal silicate partition coefficients on the individual major oxide components of the silicate melt composition suggested by recently reported parameterizations and theoretical considerations using multiple linear regression we parameterize compiled metal silicate partitioning results including our new data and report revised expressions that predict their metal silicate partitioning behavior as a function of p t x fo2 we apply these results to constrain the conditions that prevailed during core formation in the angrite parent body apb our results suggest the siderophile element depletions in angrite meteorites are consistent with a cv bulk composition and constrain apb core formation to have occurred at mildly reducing conditions of 1 4 0 5 log units below the iron wustite buffer iw corresponding to a apb core mass of 18 11 the core mass range is constrained to 21 8 mass if light elements s and or c are assumed to reside in the apb core incorporation of light elements in the apb core does not yield significantly different redox states for apb core mantle differentiation the inferred redox state is in excellent agreement with independent fo2 estimates recorded by pyroxene and olivine in angrites

the formation and chronology of the pat 91501 impact melt l chondrite with vesicle metal sulfide assemblages the l chondrite patuxent range pat 91501 is an 8 5 kg unshocked homogeneous igneous textured impact melt that cooled slowly compared to other meteoritic impact melts in a crater floor melt sheet or sub crater dike mittlefehldt d w and lindstrom m m 2001 petrology and geochemistry of patuxent range 91501 and lewis cliff 88663 meteoritics planet sci 36 439 457 we conducted mineralogical and tomographic studies of previously unstudied mm to cm sized metal sulfide vesicle assemblages and chronologic studies of the silicate host metal sulfide clasts constitute about 1 vol comprise zoned taenite troilite and pentlandite and exhibit a consistent orientation between metal and sulfide and of metal sulfide contacts vesicles make up 2 vol and exhibit a similar orientation of long axes 39ar 40ar measurements probably date the time of impact at 4 461 0 008 gyr b p cosmogenic noble gases and 10be and 26al activities suggest a pre atmospheric radius of 40 60 cm and a cosmic ray exposure age of 25 29 myr similar to ages of a cluster of l chondrites pat 91501 dates the oldest known impact on the l chondrite parent body the dominant vesicle forming gas was s2 15 20 ppm which formed in equilibrium with impact melted sulfides the meteorite formed in an impact melt dike beneath a crater as did other impact melted l chondrites such as chico cooling and solidification occurred over 2 h during this time 90 of metal and sulfide segregated from the local melt remaining metal and sulfide grains oriented themselves in the local gravitational field a feature nearly unique among meteorites many of these metal sulfide grains adhered to vesicles to form aggregates that may have been close to neutrally buoyant these aggregates would have been carried upward with the residual melt inhibiting further buoyancy driven segregation although similar processes operated individually in other chondritic impact melts their interaction produced the unique assemblage observed in pat 91501

observation and modeling of source effects in coda wave interferometry at pavlof volcano sorting out source and path effects for seismic waves at volcanoes is critical for the proper interpretation of underlying volcanic processes source or path effects imply that seismic waves interact strongly with the volcanic subsurface either through partial resonance in a conduit garces et al 2000 sturton and neuberg 2006 or by random scattering in the heterogeneous volcanic edifice wegler and luhr 2001 as a result both source and path effects can cause seismic waves to repeatedly sample parts of the volcano leading to enhanced sensitivity to small changes in material properties at those locations the challenge for volcano seismologists is to detect and reliably interpret these subtle changes for the purpose of monitoring eruptions

a comparison of methods to estimate seismic phase delays numerical examples for coda wave interferometry time shift estimation between arrivals in two seismic traces before and after a velocity perturbation is a crucial step in many seismic methods the accuracy of the estimated velocity perturbation location and amplitude depend on this time shift windowed cross correlation and trace stretching are two techniques commonly used to estimate local time shifts in seismic signals in the work presented here we implement dynamic time warping dtw to estimate the warping function a vector of local time shifts that globally minimizes the misfit between two seismic traces we compare all three methods using acoustic numerical experiments we show that dtw is comparable to or better than the other two methods when the velocity perturbation is homogeneous and the signal to noise ratio is high when the signal to noise ratio is low we find that dtw and windowed cross correlation are more accurate than the stretching method finally we show that the dtw algorithm has good time resolution when identifying small differences in the seismic traces for a model with an isolated velocity perturbation these results impact current methods that utilize not only time shifts between multiply scattered waves but also amplitude and decoherence measurements

the generation and crystallization conditions of the proterozoic harney peak leucogranite black hills south dakota usa petrologic and geochemical constraints the mineralogy petrology and geochemistry of the proterozoic harney peak granite black hills south dakota were examined in view of experimentally determined phase equilibria applicable to granitic systems in order to place constraints on the progenesis of peraluminous leucogranites and commonly associated rare element pegmatites the granite was emplaced at 3 4 kbar as multiple sills and dikes into quartz mica schists at the culmination of a regional high temperature low pressure metamorphic event principally along the periphery of the main pluton and in satellite intrusions the sills segregated into granite pegmatite couplets the major minerals include quartz k feldspar sodic plagioclase and muscovite biotite mg no molar mgo mgo feo 0 32 0 38 is the predominant ferromagnesian mineral in the granite s core whereas at the periphery of the main pluton and in the satellite intrusions tourmaline mg no 0 18 0 48 is the dominant ferromagnesian phase almandine spessartine garnet is also found in the outer intrusions there is virtually a complete overlap in the wide concentration ranges of sio2 cao mgo feo sr zr w of the biotite and tourmaline bearing granite suites with no discernable differentiation trends on harker diagrams precluding the derivation of one suite from the other by differentiation following emplacement this is consistent with the oxygen isotope compositions which are 11 5 0 6 for the biotite granites and 13 2 0 8 for the tourmaline granites suggesting derivation from different sources the concentrations of tio2 and possibly ba are higher and of mno and b are lower in the biotite granites the normative orthoclase albite ratio is extremely variable ranging from 0 26 to 1 65 in the biotite granites to 0 01 1 75 in the tourmaline granites very few sample compositions fall near the high pressure watersaturated haplogranite minima eutectic trend indicating that the granites for the most part are not minimum melts generated under conditions with a text h text 2 text o 1 instead most biotite granites are more potassic than the water saturated minima and eutectics and in analogy with experimentally produced granitic melts they are best explained by melting at 6 kbar a text h text 2 text o 1 and temperatures 800 c such high temperatures are also indicated by oxygen isotope equilibration among the constituent minerals nabelek et al 1992 several of the tourmaline granite samples contain virtually no k feldspar and have oxygen isotope equilibration temperatures 716 775 c therefore they must represent high temperature accumulations of liquidus minerals crystallized under equilibrium conditions from melts more sodic than the water saturated haplogranite minima or during fractionation of intruded melts into granite pegmatite couplets accompanied by volatile aided differentiation of the alkali elements the indicated high temperatures a text h text 2 text o 1 the relatively high tio2 and ba concentrations and the relatively low partial 18 text o values of the biotite granites suggest that they were generated by high extent biotite dehydration melting of an immature archean metasedimentary source the ascent of the hot melts may have triggered low extent muscovite dehydration melting of schists higher in the crust producing the high b low ti melts comprising the periphery of the main pluton and the satellite intrusions alternatively the different granite types may be the result of melting of a vertical section of the crust in response to the ascent of a thermal pulse with the low partial 18 text o biotite granites generated at a deeper hotter region and the high partial 18 text o tourmaline granites at a higher cooler region of the crust the low ti and high b concentrations in the high partial 18 text o melts resulted in the crystallization of tourmaline rather than biotite which promoted the observed differentiation of the melts into the granitic and pegmatitic layers found along the periphery of the main pluton and the satellite intrusions

constraints on melting and magma production in the crust major intrusions of granitic rocks are found in several tectonic settings and in all cases crustal melts may contribute to the volumes of granitic magma high grade metamorphism and partial melting of the crust take place predominantly under fluid absent conditions we present a model for calculating the amounts of melt that may be formed by fluid absent breakdown of micas and amphiboles in common crustal rock types pelitic quartzofeldspathic intermediate and mafic melt proportions depend mainly on the kind of source rock the pressure at which melting takes place the temperature and the hydrous mineral h2o content of the source as a consequence of the pressure dependence of water solubility in silicate melts any given source rock will produce more melt by a given fluid absent reaction at lower pressure at a given pressure higher temperature reactions can produce more melt from a given source rock based on a survey of the compositions of common rock types we show that the amounts of melt can vary from 50vol thus crustal rocks vary widely in their fertility as magma sources depending on the types and amounts of hydrous phases they contain in general muscovite breakdown in pelites will yield only small quantities of melt and lead to migmatite formation biotite breakdown in pelites occurs at higher temperature and because most high grade pelites below granulite grade are biotite rich can yield up to about 50 vol of granitoid melt rocks of intermediate composition and hornblende rich mafic rocks are potentially highly fertile magma sources also provided that the high temperatures necessary for biotite and hornblende breakdown are realized pyroxene rich mafic rocks and quartzofeldspathic rocks are much less potentially fertile data suggest that mechanisms exist for the efficient segregation of melt and restite in systems with 30and probably 20vol melt the pressure temperature history of a region can greatly influence crustal source fertility through its control over the occurrence of subsolidus dehydration and melting equilibria

the fate of pyroclasts produced in explosive eruptions on the asteroid 4 vesta we evaluate the consequences of explosive activity having taken place during volcanic eruptions on the differentiated asteroid 4 vesta which is the likely parent body of the howardite eucrite diogenite hed meteorites for a wide range of magma volatile contents we calculate the eruption speeds and subsequent trajectories of the pyroclastic magma droplets produced by considering the size distribution and eruption speeds of the droplets and the mass fluxes at which they are ejected we show that under all realistic circumstances the droplets will have formed lava fountains that were extremely optically dense as a result virtually all of the droplets will have reached the surface having suffered a negligible amount of radiative cooling and will have coalesced into lava ponds feeding lava flows typically 1 of the pyroclasts will have undergone enough cooling to allow them to accumulate into a recognizable fall deposit consisting of unwelded or partly welded volcanic glass beads this result is consistent with the apparent absence of identifiable pyroclastic material in the hed and other types of differentiated meteorites

quantitative models linking igneous amphibole composition with magma cl and oh content minerals of the amphibole group are found in igneous rocks on earth and other rocky bodies since the o 3 site of amphibole can contain oh o 2 f and cl amphibole composition provides important information about water and halogen contents oxidation state and other features of its formation and alteration environments however the complexity of amphibole crystal chemistry means this information is difficult to extract furthermore it has been regular practice in the era of the electron microprobe to neglect h and fe 3 analyses for amphibole critically reducing the amount of information available in amphibole analyses in the literature we have assembled models and insights from previous work to create a methodology that allows the estimation of magmatic h 2 o and cl contents from existing amphibole analyses since the methodology requires use of a cation norm we begin with a deeper investigation of the consequences of different cation normalization schemes for amphibole analyses and provide grounds for deciding which scheme best fits a given amphibole analysis we then show how the existing model of popp and coworkers can be reversed to estimate the oh and o 3 o 2 contents of amphiboles in synthesis experiments using a synthetic data set collected from the literature 39 amphibole analyses we calibrate a partitioning model for the oh cl competition on the o 3 site of igneous amphiboles k cl x cl x oh amphibole cl oh melt ln k cl 6 59 k na a 0 679 mg 0 487 f 6 e where x signifies a mole fraction of an anion on the o 3 site cl and oh signify melt mole fractions of the anion in question on a one oxygen stolper zhang basis k na a mg and 6 fe signify the amount of each component in the amphibole in atoms per amphibole formula unit with a denoting vacancies on the amphibole a site we then combine the popp et al model with our new model to link the occupancy of the amphibole o 3 site and other crystal chemical parameters to the cl and h 2 o content of melts crystallizing amphibole the competition between oh and cl for this site can be used to calculate the melt and amphibole oh h 2 o contents as well as the speciation of fe in amphibole provided that the cl content of both the amphibole and its coexisting melt is known without analyzing either phase for h or fe 3 fe 2 while the models in this paper should be recalibrated using future experimental data this work shows that considerably more information about the volatile contents of magmas can be gleaned from amphibole than previously shown and provides additional information about the crystal chemistry of amphibole and how it affects cl partitioning into minerals of this group

depth extent of damage zones around the central calaveras fault from waveform analysis of repeating earthquakes summary we systematically investigate spatial variations of temporal changes and depth extent of damage zones along the calaveras fault that ruptured during the 1984 morgan hill earthquake by the waveform analysis of 333 sets of repeating earthquakes we use a sliding window waveform cross correlation technique to measure traveltime changes in waveforms generated by each repeating cluster we find clear traveltime delays in the s and early s coda waves for events immediately after the morgan hill main shock the amplitudes of the time delays decrease logarithmically with time since the main shock indicating a time dependent recovery healing process following the abrupt coseismic temporal changes the largest temporal changes are observed at station cco that is the closest to the rupture zone of the morgan hill main shock the time delays at this station are larger for clusters in the top 6 km and decrease systematically at larger depth in comparison the time delays observed at other five stations are much smaller and do not show clear relationship with hypocentral depth we suggest that the temporal changes at these five stations mostly occur in the top few hundred metres of the near surface layers while the temporal changes at station cco are likely associated with the damage zone around the calaveras fault that is well developed in the top few kilometres of the upper crust our results are consistent with the inference of a widespread damage and non linearity in the near surface layers associated with strong ground motions of nearby large earthquakes and localized damages and flower type structures around active faults based on previous studies of fault zone structures and recent 3 d numerical simulations

ground coupled airwaves at pavlof volcano alaska and their potential for eruption monitoring an abnormally high number of explosion quakes were noted during the monitoring effort for the 2007 eruption of pavlof volcano on the alaska peninsula in this study we manually cataloged the explosion quakes from their characteristic ground coupled airwaves this study investigates how the ground coupled airwaves might be used in a monitoring or analysis effort by estimating energy release and gas mass release over 3 104 quakes were recorded the energy release from the explosions is approximated to be 3 1011 j and the total gas mass assuming 100 water released was 450 t the tracking of explosion quakes has the potential to estimate relative eruption intensity as a function of time and is thus a useful component of a seismic monitoring program

global crustal metamorphism of the eucrite parent body abstract we conducted a petrologic study of 18 equilibrated eucrites with the goal of understanding the formation and evolution of the crust of asteroid 4 vesta the likely source of eucrite meteorites their textures indicate that eucrites were basaltic igneous rocks but modified by postcrystallization brecciation recrystallization and impact melting recrystallized rocks are the most common among clasts in the eucrites impact melt breccias are rare equilibration temperatures of the metamorphic clasts range from 700 to 1000 c with most in the 800 900 c range complex exsolution and recrystallization textures in pyroxenes suggest that eucrites cooled very slowly from high peak temperatures after reheating this extended period of thermal metamorphism requires a high interior temperature in a vesta sized body this metamorphism could have taken place during and shortly after crust formation we suggest the crust of vesta evolved through the eruption rapid cooling and subsequent burial and reheating of lava flows as the crust grew in thickness the depth of burial increased causing temperatures to rise and leading to global metamorphism this resulted in only a small percentage of unequilibrated eucrites only the last few percent of basalts erupted would not be metamorphosed and a wide range of metamorphic temperatures and durations for the equilibrated eucrites

april 2007 collapse of piton de la fournaise a new example of caldera formation collapse calderas are frequent in the evolution of volcanic systems but very few have formed during historical times piton de la fournaise is one of the world s most active basaltic shield volcanoes the caldera collapse which occurred during the april 2007 lateral eruption is one of the few large documented collapse events on this volcano it helps to understand the mode and origin of caldera collapses in basaltic volcanoes field observations gps and seismic data show that the collapse occurred at an early stage of the eruption the cyclic seismic signal suggests a step by step collapse that directly influenced the lateral eruption rate likely the caldera results from the combined effect of i the progressive collapse of the plumbing system above the magma chamber since 2000 and ii the large amount of magma withdrawal during the early stage of the eruption by both a significant intrusion within the edifice and an important emission rate

fluid inclusion microthermometry in be ta li sn bearing pegmatites from the borborema province northeast brazil abstract fluid inclusions in be ta li sn bearing pegmatites have been reported in the literature as hypersaline aqueous brines or low salinity aqueous or aqueous carbonic fluids the evolution paths of volatile fluids in equilibrium with the different crystallizing phases of rare element pegmatites do not seem to be unique the aim of this work is to contribute to this discussion on the basis of fluid inclusion information from the borborema pegmatite province bpp in northeast brazil some well known heterogeneous be ta li sn mineralized pegmatites of this province were systematically sampled along cross sections with the purpose of studying the fluid inclusions in the different pegmatite zones i muscovite rich contact zone ii homogeneous or graphic pegmatite iii blocky feldspar zone and iv quartz core the observed fluid inclusions mainly in quartz were almost always secondary or pseudosecondary grouped along healed fractures with random orientation even some trails paralleling quartz grain limits were not undoubtedly primary almost all these fluid inclusions were filled with low salinity aqueous or aqueous carbonic fluids primary inclusions were recognized only in some well formed crystals from druses with erratic distribution in the pegmatites microthermometric data from these samples confirm that the various crystallizing phases of the pegmatites were in equilibrium with low salinity aqueous or aqueous carbonic fluids with insignificant n 2 or ch 4 contents with frequent accidentally trapped solids the various types of primary inclusions found in these crystals compare well with the types of secondary inclusions of the samples from the systematic cross sections the relative age of the crystals hosting primary fluid inclusions the relative age of primary inclusion types in successive crystal growth zones the relative age of secondary fluid inclusion trails and the corresponding microthermometric data allowed to establish the most probable evolution of the fluid characteristics during pegmatite crystallization an early low salinity aqueous carbonic fluid with co 2 contents of 20 mol was present during the crystallization of early minerals such as garnet and tourmaline of the border zone and graphic quartz beryl manganotantalite and blue tourmaline of zones ii and iii the end of zone iii crystallization occurred in the presence of a low salinity aqueous fluid with very low co 2 contents as indicated by inclusions in the smoky core of quartz crystals at the limit between zones iii and iv later aqueous fluids barren in co 2 and with salinities increasing from 5 to 20 coexisted with the formation of the pegmatite nucleus and replacement bodies as indicated by inclusions in the border of these crystals and in euclase the estimated trapping conditions of 3 5 kbar and 580 c for the earliest inclusion types agree with the regional metamorphic conditions and with the known liquidus conditions of rare element bearing pegmatite crystallization the trapping conditions of inclusions in euclase and coexisting quartz crystal rims in the pegmatitic core at 3 5 kbar and 400 c are slightly below the conditions admitted for the solidus of rare element pegmatites and indicate an isobaric cooling during pegmatite crystallization

survey and evaluation of eucrite bulk compositions the purpose of this survey is to establish reference bulk elemental abundances for the eucrites and thereby provide the basis to test core formation models as well as partial melting fractional crystallization and magma ocean theories for the eucrite parent body in order to evaluate bulk elemental abundances for the eucrites 296 peer reviewed articles monographs theses or books and 143 abstracts dating from 1938 to 1997 were surveyed of the 101 eucrites having at least one set of elemental abundance analyses reported in the literature 20 were selected for in depth examination the selection criteria of our sample were based on the total number of analyses available for a given eucrite and the total number of elements for which data exist the mean bulk elemental abundance 1 standard deviation and the percent deviation were calculated for each element in a given eucrite in order to evaluate the quality of the mean abundances the elements were then grouped according to availability of data and percent deviations possible reasons for the different deviations in the different groups are briefly discussed from the major element abundances the normative cipw composition the molar compositions of pyroxene olivine and plagioclase and the bulk densities were calculated and compared to petrographic observations the calculated norms for the noncumulates agree well with the observations while the norms for the cumulates do not possible reasons for this are discussed unfortunately analyses of many elements are poorly represented in the literature and many bulk analyses suffer from unacceptable levels of uncertainty therefore future work requires bulk elemental analyses for some of the more poorly characterized elements in eucrites especially those of key elements used for planetary modeling

subsolidus isothermal fractional crystallization in theory multicomponent silicate liquids of minimum or eutectic composition should crystallize their solidus phases simultaneously and in their invariant proportions in reality the crystallization of those liquids of granitic composition produces sequential assemblages and normal fractional crystallization of solid solutions when crystallization commences at or along an isotherm well below the solidus of the system the sequence of mineral assemblages derives principally from their relative stabilities as measured by the gibbs free energy change for the reaction of melt to crystals in the metastable region below the liquidus surface rather than chemical concentration alone whereas crystallization close to the solidus t 50 c promotes the simultaneous eutectic crystallization of quartz and feldspars that leads to the formation of granite large liquidus undercooling t 200 c produces sequential assemblages from the margins to centers of melt bodies the liquidus undercooling that drives subsolidus isothermal fractional crystallization is the single most important process for the generation of zoned granitic pegmatites

geochemical criteria for distinguishing magmatic and metasomatic albite enrichment in granitoids examples from the ta li granite yichun china and the sn w deposit tikus indonesia two examples of albite rich granitoids of different genesis are discussed the ta li granite at yichun china exhibits dominantly igneous textures and the sodium enrichment zone in biotite granite of the sn w deposit at tikus is characterized by metasomatic textures the yichun stock shows a magmatic evolution from biotite muscovite granite to lepidolite granite with an increase of na2o and f concentrations and a decrease of cao and sr concentrations the composition of the different granite phases is close to pseudoternary minima in the haplogranite h2o li f system the composition of the f rich albitization zone at tikus deviates strongly from the pseudoternary minima and shows a tendency to become monomineralic nearly pure albitite cao and sr concentrations are increased or remain unchanged with respect to the unaltered biotite granite at tikus albitization produced by fluid rock interaction in f rich systems is characterized by that cao or sr released by the breakdown of plagioclase in the granite protolith are fixed in newly formed fluorite or albite respectively

assessment of resolution and accuracy of the moving window cross spectral technique for monitoring crustal temporal variations using ambient seismic noise summary temporal variations in the elastic behaviour of the earth s crust can be monitored through the analysis of the earth s seismic response and its evolution with time this kind of analysis is particularly interesting when combined with the reconstruction of seismic green s functions from the cross correlation of ambient seismic noise which circumvents the limitations imposed by a dependence on the occurrence of seismic events in fact because seismic noise is recorded continuously and does not depend on earthquake sources these cross correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station and can be used to extract observations of variations in seismic velocities these variations however are typically very small of the order of 0 1 per cent such accuracy can be only achieved through the analysis of the full reconstructed waveforms including later scattered arrivals we focus on the method known as moving window cross spectral analysis that has the advantage of operating in the frequency domain where the bandwidth of coherent signal in the correlation function can be clearly defined we investigate the sensitivity of this method by applying it to microseismic noise cross correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated we propose threshold signal to noise ratios above which these perturbations can be reliably observed such values are a proxy for cross correlation convergence and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving window cross spectral technique

feldspar thermometry in pegmatites truth and consequences temperatures of crystallization for all or portions of three thin granitic pegmatite dikes in southern california are derived from feldspar solvus thermometry with supporting data from the k cs ratio of k feldspar the extent of al si order in k feldspar and the texture of granophyre found along the margins of dikes although k feldspars become perthitic and increasingly ordered toward the centers of dikes their ratio of k cs falls from margin to core along trajectories that reflect fractional crystallization from silicate melt without subsequent interaction with an aqueous solution in an open system a few sporadic samples that record loss of cs and consequent rise in k cs validate the test of fidelity that the perthites generally retain their igneous compositions feldspar solvus thermometry from these three dikes indicates that their pegmatite forming melts crystallized at 375 475 c those low temperatures are consistent with the occurrence of granophyric plagioclase quartz intergrowths along the borders of pegmatites thick and thin that arise from thermal quenching of their melts against much cooler host rocks and hence at much shallower depths than the igneous sources of the pegmatite forming melts the temperature profiles are nearly isothermal across the pegmatites but where variation exists apparent temperatures are highest along their margins or in their central domains cores plagioclase shows normal fractionation of decreasing an content from margins to center which mimics the line of descent with cooling down the solidus and solvus surfaces however the fractionation trends in the feldspars are attributable to their isothermal crystallization far from the equilibrium of the liquidus at a highly undercooled state not to crystallization upon cooling on the solidus surface

characterization of seismic events during the 2009 eruption of redoubt volcano alaska abstract seismic events were automatically detected and characterized throughout the 2009 eruption of redoubt volcano alaska on a single short period station located 3 km from the volcanic crater a total of 126 789 individual events were identified from continuous recording of seismic data from january 1 to june 30 average 29 events per hour using a short term average long term average detection algorithm nine metrics were computed for this suite of events including event duration inter event time event rate peak amplitude peak to peak amplitude root mean square rms amplitude peak frequency center frequency and frequency index eight swarms were identified with event rates exceeding 100 events per hour the first two occurred in late january and are attributed to high amplitude spasmodic tremor five additional swarms were manually repicked including swarms on february 26 27 march 20 23 march 27 march 29 and april 2 4 three of these swarms immediately preceded major explosions including march 20 23 march 27 and april 2 4 a final swarm on may 2 9 was re picked using a correlation detection scheme we identified 146 event families that occurred within this suite of selected events using a cross correlation technique seven explosions were each immediately preceded by one or more event families events from the dominant family during each of these periods was additionally re picked using correlation detection the procession of event metrics and occurrence of event families formed a complex distribution throughout the eruption a single station approach was used to gain a fine scale view of variations in seismic behavior at redoubt with a focus on potential indicators of impending explosions these techniques may serve an important role in future real time eruption monitoring efforts

an experimental assessment of the potential of sulfide saturation of the source regions of eucrites and angrites implications for asteroidal models of core formation late accretion and volatile element depletions abstract the geochemistry of asteroidal magmas provides fundamental clues to the processes involved in the origin and early evolution of planetary bodies although sulfides are important reservoirs for a diverse suite of major and trace elements it is currently unclear whether the interiors of asteroid vesta and the angrite parent body were sulfide liquid saturated during petrogenesis of non cumulate eucrites and volcanic angrites to assess the potential of sulfide liquid saturation in the interiors of these bodies high pressure p temperature t experiments were used to quantify the sulfur concentrations at sulfide saturation scss for volcanic angrites and non cumulate eucrites the sulfide silicate partitioning behavior of various trace elements was simultaneously quantified to study their geochemical behavior at sulfide liquid saturation it was found that the measured scss values agree well with the scss values predicted from a previous thermodynamic model for high feo melts to assess the possibility of sulfide liquid saturation of the source regions of non cumulate eucrites and angrites their s abundances were compared with the calculated scss values for their source regions results show that if eucritic and angritic source regions were saturated with fes liquid significant degassing 50 80 of s must have occurred during or following their magmatic emplacement such loss is inconsistent with the s cl zn and rb isotopic compositions of non cumulate eucrites sulfide liquid saturation of eucrite and angrite source regions is also excluded from the strongly incompatible behavior of cu and hse in non cumulate eucrites and angrites riches et al 2012 additional calculations were performed to further explore the timing and extent of s loss during crystallization of the vestan magma ocean the assumption of chondritic bulk s abundances of bulk vesta would correspond with extremely high s contents of the eucrite source region s even after consideration of depletion of s due to core formation in light of the s cl zn and rb stable isotopic compositions of eucrites the s abundances in eucrites are most consistent with the hypothesis that the vestan mantle was already strongly depleted in s 70 80 by the time of vestan magma ocean crystallization resulting in more realistic s contents of the eucrite source region s the depletion of s could have been established during initial accretion of vesta or it could simply reflect accretion of volatile depleted components that experienced incomplete condensation wu et al 2018 modeling of the new experimentally determined sulfide silicate partition coefficients and previously reported vestan mantle depletions of the various chalcophile and siderophile elements suggests that sulfide liquid segregation during early vestan magma ocean crystallization is also unlikely the lack of sulfide liquid saturation in the source regions of non cumulate eucrites and angrites as well as during early vestan magma ocean solidification shows that current geochemical models of core formation and late accretion remain valid for these bodies

oxygen isotopic constraints on the origin and parent bodies of eucrites diogenites and howardites abstract a few eucrites have anomalous oxygen isotopic compositions to help understand their origin and identify additional samples we have analyzed the oxygen isotopic compositions of 18 eucrites and four diogenites except for five eucrites these meteorites have 17o values that lie within 2 of their mean value viz 0 242 0 016 consistent with igneous isotopic homogenization of vesta the five exceptional eucrites nwa 1240 pasamonte both clast and matrix samples pca 91007 a 881394 and ibitira have 17o values that lie respectively 4 5 5 15 and 21 away from this mean value nwa 1240 has a 18o value that is 5 below the mean eucrite value four of the five outliers are unbrecciated and unshocked basaltic eucrites like nwa 011 the first eucrite found to have an anomalous oxygen isotopic composition the fifth outlier pasamonte is composed almost entirely of unequilibrated basaltic clasts published chemical data for the six eucrites with anomalous oxygen isotopic compositions including nwa 011 exclude contamination by chondritic projectiles as a source of the oxygen anomalies only nwa 011 has an anomalous fe mn ratio but several anomalous eucrites have exceptional na ti or cr concentrations we infer that the six anomalous eucrites are probably derived from five distinct vesta like parent bodies pasamonte and pca 91007 could come from one body these anomalous eucrites like the isotopically normal unbrecciated eucrites with 4 48 gyr ar ar ages are probably deficient in brecciation and shock effects because they were sequestered in small asteroids 10 km diameter during the late heavy bombardment following ejection from vesta like bodies the preservation of vesta s crust and the lack of deeply buried samples from the hypothesized vesta like bodies are consistent with the removal of these bodies from the asteroid belt by gravitational perturbations from planets and protoplanets rather than by collisional grinding

maximum and minimum water contents of granitic melts generated in the crust a reevaluation and implications abstract recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure temperature melt composition and water activity it is concluded that melts generated in the crust at high temperature and low water activities such as a type granites contain higher water contents than previously assumed up to 20 at 800 900 c and 3 7 kbar as a consequence the melt fraction produced at a given amount of available water can be up to 20 lower the minimum water content of melts generated by partial melting of crustal protoliths especially quartzofeldspathic rocks can be predicted adequately from the liquidus curves in granitic systems this water content can be higher if the melt composition departs from a minimum or eutectic quartzofeldspathic composition melts generated from quartzofeldspathic rocks at low temperature 750 c and below are necessarily water rich 5 wt h 2 o and have approximately the same viscosity or even slightly lower viscosities than melts generated at higher temperatures viscosities in the range 10 4 3 10 5 4 pa s recent experimental data also show that the value of the positive d p d t slope of the liquidus curves for fixed water contents above 800 c is lower than predicted by previous models thus adiabatic decompression produces a higher amount of melt than previously assumed at high temperature the formation of melt by adiabatic decompression can be up to 50 higher than assumed

high calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites our analyses of high quality spectra of several s type asteroids 17 thetis 847 agnia 808 merxia and members of the agnia and merxia families reveal that they include both low and highcalcium pyroxene with minor amounts of olivine 0 4 high calcium pyroxene is a spectrally detectable and petrologically important indicator of igneous history and may prove critical in future studies aimed at understanding the history of asteroidal bodies the silicate mineralogy inferred for thetis and the merxia and agnia family members requires that these asteroids experienced igneous differentiation producing broadly basaltic surface lithologies together with 4 vesta and its smaller vestoid family members and the main belt asteroid 1489 magnya these new asteroids provide strong evidence for igneous differentiation of at least five asteroid parent bodies based on this analysis of a small subset of the near infrared asteroid spectra taken to date with spex at the nasa irtf we expect that the number of known differentiated asteroids will increase consistent with the large number of parent bodies inferred from studies of iron meteorites

structural environment around th4 in silicate glasses implications for the geochemistry of incompatible me4 elements the structural environment around th4 in several silicate glasses containing 1 3 wt th4 was investigated as a function of melt composition and polymerization using extended x ray absorption fine structure exafs spectroscopy one set of glasses had the bulk chemical composition of monticellite mo diopside di anorthite an albite al olivine basalt o bas tholeiitic basalt t bas calc alkaline dacite dac and calc alkaline rhyolite rhy a second set of th bearing glasses had the bulk al composition but also contained either 5 5 wt f or 2000 ppm cl in glasses containing 3 wt th th coordination varies from 8 d viiith o 2 41 0 02 a in mo and di to a mixture of 8 and 6 coordinations d vi viiith o 2 35 2 36 0 02 a in all other compositions the presence of viiith is related to the thorianite tho2 saturation in the glass in al glasses containing 1 wt th 6 fold coordinated th dominates d vith o 2 32 0 02 a no clear evidence for f or cl complexes around th is observed in any of the halogen containing glasses weak but significant interactions of th with tetrahedral si al network and or alkali elements are observed especially in highly polymerized compositions rhy in which th si ai na k contributions are detected between 3 25 and 3 50 0 05 a these results suggest that in this set of glasses th does not form complexes but rather acts as a weak network modifier the presence of vith in silicate glasses an unusual low coordination for th suggests that the ionic radius of th in magmatic systems is lower than previously reported rth 0 94 a the resulting high th o bond strength 0 7 vu unknown in minerals may explain the observed low crystal melt partition coefficients of th4 i e its incompatible character during magmatic differentiation increasing polymerization is predicted to favor higher coordination around th viii ix as a result of a shortage of nbo to which th preferentially bonds hence dramatic changes in the crystal chemistry of th are predicted i e the incorporation of th in minerals comparison with u4 suggests that vith is less abundant in similar glass melt systems compared with viu this may explain the u th fractionation often observed in zircon as well as the preferential incorporation of th in accessory minerals containing large sites in which th4 can be substituted e g the ca2 site in titanite apatite or zirkelite

experimental evidence against co2 promoted deep crustal melting there has been considerable controversy regarding the role of carbon dioxide in the metamorphism and melting of the earth s crust fuelled principally by reports of experimental evidence for co2 enhanced partial melting of the assemblage phlogopite mica quartz in the model system kalo2 mgo sio2h2o co21 2 the analogous process in the crust would lead to the formation of granulite facies rocks at temperatures characteristic of amphibolite facies metamorphism the granulite fades3 5 would thus be indicative not of unusually high temperatures but of the influx of carbonic fluids4 6 moreover the similarity of their low temperature melts to the compositions of some calc alkaline lamprophyres led peterson and newton2 to suggest that such magmas might be generated by the introduction of co2 rich fluids providing a means of large scale mass transfer in the deep crust these ideas have been highly influential6 but there are aspects of peterson and newton s results that are hard to reconcile with other available data i have accordingly tried to replicate the results of refs 1 and 2 but as i report here have been unable to do so the present results thus cast doubt on the general idea of melt fluxing by co2 and the formation of magnesium and co2 rich magmas at crustal pressures

igneous and shock processes affecting chassignite amphibole evaluated using chlorine water partitioning and hydrogen isotopes amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma but also shock and postshock processes we have analyzed amphibole and other phases from nwa 2737 melt inclusions and we evaluate these data along with published values to constrain the crystallization cl and h2o content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains using a model for the cl oh exchange between amphibole and melt we estimate primary crystallization oh contents of chassignite amphiboles sims analysis shows that amphibole from nwa 2737 currently has 0 15 wt h2o it has lost 0 6 wt h2o from an initial 0 7 0 8 wt h2o due to intense shock chassigny amphibole had on average 0 3 0 4 wt h2o and suffered little net loss of h2o due to shock nwa 2737 amphibole has d 3700 it absorbed martian atmosphere derived heavy h in the aftermath of shock chassigny amphibole with d 1900 incorporated less heavy h low h2o cl ratios are inferred for the primitive chassignite magma which had significant effects on melting and crystallization volatiles released by the degassing of martian magma were more cl rich than on earth resulting in the high cl content of martian surface materials

long period seismicity and very long period infrasound driven by shallow magmatic degassing at mount pagan mariana islands long period lp seismicity and very long period infrasound ivlp were recorded during continuous degassing from mount pagan mariana islands in july 2013 to january 2014 the frequency content of the lp and ivlp events and delay times between the two arrivals were remarkably stable and indicate nearly co located sources using phase weighted stacking over similar events to dampen noise we find that the lp source centroid is located 60 m below and 180 m west of the summit vent the moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike we model the seismoacoustic wavefields with a coupled earth air 3 d finite difference code the ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios so the ivlp is not the result of lp energy transmitting into the atmosphere at its epicenter based on crater shape and dimensions determined by structure from motion we model the ivlp as acoustic resonance of an exponential horn the source of the continuous plume from gas analysis is shallow magmatic degassing which repeatedly pressurized the dike sill portion of the conduit over the 7 months of observation periodic gas release caused the geologically controlled sill to partially collapse and resonate while venting of gas at the surface triggered resonance in the crater lp degassing only accounts for 12 of total degassing indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent

experimental study of a biotite bearing granitic system under water saturated and water undersaturated conditions phase relationships in haplogranitic melts con taining ferromagnesian minerals were investigated in the temperature range 760 850 c at ptotal 2 kbar ah2o 0 25 1 00 and at nno buffer conditions the composi tions of coexisting biotite orthopyroxene magnetite and granitic melt were determined by electron microprobe bio tite was the only fe mg mineral in the starting material it disappeared in water undersaturated melts at tempera tures above 830 c and in melts saturated with water above 810 c magnetite was present in all runs orthopyroxene became stable between 780 and 800 c the mg mg fe ratios of biotite 0 63 0 72 and orthopyroxene 0 63 0 71 are similar in water saturated and undersaturated melts at comparable temperatures and increase slightly with increas ing temperature the solubility of mg in haplogranitic melts is very low 0 07 0 24 wt mgo it increases slightly with temperature and is independent of the prevailing water ac tivity the solubility of fe is low 0 91 1 37 wt feo it also increases with increasing temperature and it is higher in water saturated than in water undersaturated melts

a thermal model for the differentiation of asteroid 4 vesta based on radiogenic heating a finite element code has been developed to model the thermal history of asteroid 4 vesta this is the first attempt to model the thermal history of a differentiated asteroid through core and crust formation and subsequent cooling until geochemical closure is attained the results of the simulation are consistent with chronological measurements and other constraints provided by cumulate and noncumulate eucrites believed to have been derived from vesta the work solves two major problems with the hypothesis of heating by decay of26al an extinct radionuclide postulated to be a plausible heat source in the early solar system first the model demonstrates that it is possible to keep the mantle of vesta hot for 100 ma thereby explaining the observed difference in ages between cumulate and noncumulate eucrites second the simulation offers a possible explanation of why detectable excesses of26mg the decay product of26al are not observed in noncumulate eucrites the simulation draws a model chronology of vesta and predicts times relative to cai formation for accretion at 2 85 myr core formation at 4 58 myr crust formation at 6 58 myr and geochemical closure at 100 myr for a h chondrite asteroidal bulk composition decay of60fe is found to cause no perceptible difference in the thermal history of vesta even when sequestered into a central core although chondritic xenoliths have not been described in hed igneous lithologies the thermal model suggests the possibility that a veneer of unmelted near surface material should remain

implications of prehistoric glassy biomass slag from east central botswana glassy biomass slag occurs in midden piles of prehistoric settlements of east central botswana the slag forms decimetre thick concordant layers in stratified ashy soil and lacks associations with domestic ceramic and iron melting activities petrographic evaluation of the slag suggests maximum temperatures in the order of 1155 1290 c during burning of the midden these values exceed reasonable estimates for combustion temperature of plant remnants and cattle manure in open fire it is suggested as alternatives that the glassy slag formed either from surface melting caused by strokes of lightning in an accumulation of partially decomposed organic soil or from subsurface combustion of organic soil strata ignited by grass fires glassy biomass slag of prehistoric settlements therefore may not result from human activities such as intentional burning of excess midden piles and may not be contemporaneous with human occupation of the sites 1995 academic press limited

crustal melts below 400 c we propose that the internally zoned li bearing tin mountain pegmatite in the harney peak granite pegmatite system of the black hills south dakota crystallized from fluid rich compositionally complex melts at 400 350 c the low crystallization temperatures resulted from the combined fluxing effects of li b p h 2 o and carbonate anions the presence of hydrous silicate melts at temperatures of 350 c is revealed by microthermometric data on primary fluid inclusions cogenetic with crystallized melt inclusions mineral assemblages of the crystallized melt inclusions and chemistry of bulk fluid leachates indicate that the melts and fluids contained significant amounts of li and na as carbonates and or borates that acted as powerful fluxes the low temperatures give a new perspective on the stability of silicate melts in the crust

coseismic and postseismic elastic wave velocity variations caused by the 2008 iwate miyagi nairiku earthquake japan 1 we analyze coseismic and postseismic velocity variations caused by the june 13 2008 iwate miyagi nairiku earthquake mw 6 9 using passive image interferometry pii seismic noise is correlated in order to reconstruct the green s function between two sensors shear wave velocity changes are determined by relating the coda parts of the daily green s functions to a long term reference green s function our study extends from january 2008 to august 2010 and includes the correlations for 190 station pairs in three different frequency ranges from 0 125 to 1 0 hz we show that combining the 9 different component cross correlation functions stabilizes the velocity change estimation and increases analysis resolution the observed velocity change curves can be fitted by model time series consisting of a coseismic velocity drop followed by logarithmic postseismic recovery and seasonal velocity variations the coseismic velocity drops are stronger at higher frequencies and are concentrated in the southern part of the fault zone a tomography algorithm was developed to reproject the observed velocity variations of the different sensor pairs onto the single sensors the depth distribution of coseismic changes was modeled for the three stations with the largest velocity drops at two stations the coseismic velocity changes are located in the upper several hundred meters the third station shows indications for deeper changes in the order of kilometers postseismic recovery takes significantly longer than the analyzed two year period seasonal velocity variations with periods of one year are observed at all analyzed frequencies for most station pairs

petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites

real time monitoring of relative velocity changes using ambient seismic noise at the piton de la fournaise volcano la reunion from january 2006 to june 2007 we present the results of a real time method based on coda wave interferometry from seismic noise cross correlation functions for relative seismic velocity variations monitoring on a volcanic edifice the ambient seismic noise at the piton de la fournaise volcano on la reunion island is analyzed from january 2006 to june 2007 during this period five eruptions occurred showing a great diversity in eruption duration intensity and eruptive fissure location two different methods are used to compute the velocity variations in order to compare their stability in quasi real time routine we compare the obtained velocity variations with the surface deformation observed by gps and extensometers networks this allows us to identify and quantify three major processes at the origin of seismic wave velocity variations in the edifice firstly the observed pre eruptive summit inflation is accompanied by a decrease in seismic velocity secondly the edifice deflation following the opening of an eruptive fissure is characterized by an increase of the velocity finally the summit caldera collapse generates a strong velocity drop coda wave interferometry from seismic noise cross correlation functions in quasi real time may allow us to forecast eruption and constrain the processes taking place in the volcanic plumbing system

ibitira a basaltic achondrite from a distinct parent asteroid and implications for the dawn mission i have done a detailed petrologic study of ibitira a meteorite that has been classified as a basaltic eucrite since 1957 the mean fe mn ratio of pyroxenes in ibitira with 10 mole wollastonite component is 36 4 0 4 this value is well resolved from those of similar pyroxenes in five basaltic eucrites studied for comparison which range from 31 2 to 32 2 data for the latter five eucrites completely overlap ibitira pyroxenes have lower fe mg than the basaltic eucrite pyroxenes thus the higher fe mn ratio does not reflect a simple difference in oxidation state ibitira also has an oxygen isotopic composition alkali element contents and a ti hf ratio that distinguish it from basaltic eucrites these differences support derivation from a distinct parent asteroid thus ibitira is the first recognized representative of the fifth known asteroidal basaltic crust the others being the hed mesosiderite angrite and nwa 011 parent asteroids 4 vesta is generally assumed to be the hed parent asteroid the dawn mission will orbit 4 vesta and will perform detailed mapping and mineralogical compositional and geophysical studies of the asteroid ibitira is only subtly different from eucritic basalts a challenge for the dawn mission will be to distinguish different basalt types on the surface and to attempt to determine whether 4 vesta is indeed the hed parent asteroid

vapor undersaturated experiments with macusani glass h 2 o at 200 mpa and the internal differentiation of granitic pegmatites vapor undersaturated fractional crystallization experiments with macusani glass macusanite a peraluminous rhyolite obsidian at 200 mpa yield mineralogical fabrics and zonation and melt fractionation trends that closely resemble those found in zoned granitic pegmatites and other granitoids of comparable composition typically peraluminous li be ta rich deposits the zonation from the edge of charges inward is characterized by 1 fine grained sodic feldspar quartz border zones 2 a fringe of very coarse grained graphic quartz feldspar intergrowths that flair radially toward melt and terminate with nearly monophase k feldspar 3 cores of very coarse grained nearly monominerallic quartz or virgilite lialsi5o12 mica and 4 late stage fine grained albite mica intergrowths that are deposited from alkaline na rich interstitial melt at vapor saturation similar experimental products have been observed in compositionally simpler less evolved systems liquid lines of descent from initially h2o undersaturated runs are marked by a decrease in sio2 and increases in na k b p f h2o and a variety of trace lithophile cations these trends are believed to be governed by three factors 1 disequilibrium growth of feldspars quartz via metastable supersaturation 2 fractionation of melt toward sio2 depleted na rich compositions due to increases in b p and f and 3 changes in nucleation and growth rates mostly as a function of the h2o content of melt x w m in contrast experiments that are cooled below the liquidus from the field of melt aqueous vapor london et al 1988 fail to replicate pegmatitic characteristics in most respects on the basis of these and other experiments we suggest that the formation of pegmatite fabrics stems primarily from fractional crystallization in volatile rich melts and that enrichments in normally trace lithophile elements result from melt differentiation trends toward increasingly alkaline silica depleted compositions although vapor saturation at near solidus and subsolidus conditions may promote extensive recrystallization an aqueous vapor phase does not appear to be necessary for the generation of most of the salient characteristics of pegmatites