a melt inclusion study of the toba tuffs sumatra indonesia the toba caldera in northern sumatra indonesia is the site of earth s largest quaternary volcanic eruption this eruption dated at 74 ka produced the 2800 km3 youngest toba tuff ytt and ash fall quartz bearing silicic pumices ranging from 68 to 77 wt sio2 indicate that the ytt magma was zoned compositionally and mineralogically prior to the ytt eruption two other silicic quartz bearing tuffs known as the middle toba tuff mtt and the oldest toba tuff ott were erupted from toba at 0 501 ma and 0 840 ma respectively although the volatile contents of the toba magmas are poorly constrained aerosols generated by the ytt eruption are generally thought to have caused a global volcanic winter an evaluation of the pre eruptive dissolved gas contents of the ytt magma is fundamental to understanding the global effects of this eruption we used melt inclusions in quartz crystals to determine the dissolved h2o co2 s cl and f contents of the ytt mtt and ott magmas quartz crystals selected from pumice blocks and welded tuffs that spanned the compositional ranges of the three units were chosen for study major and trace element analyses of melt inclusions were also conducted to characterize melt evolution and provide context to the volatile data melt inclusions from the ytt mtt and ott are rhyolitic in composition 73 77 wt sio2 and have overlapping indistinguishable major element trends inclusions from the large eruptions ytt and ott have similar geochemical relationships where the most evolved melt inclusions occur in the least silicic bulk rock samples and are more evolved than their matrix glasses in contrast the least evolved melt inclusions occur in the most silicic samples and either overlap with or are less evolved than their matrix glasses these patterns can be explained if quartz crystals in the least silicic magmas were inherited from more evolved melt while those in the most silicic melt formed in situ several lines of evidence suggest that crystal settling of early formed quartz crystals in long lived magma bodies was an important process in the ytt and ott magmas trace element data from the ytt melt inclusions have wide ranges rb 250 830 ppm ba 10 485 ppm and mostly support these models however incompatible trace elements are enriched 2 3 over their matrix glass compositions in all samples in the smaller mtt melt inclusions overlapped with the compositional range of the bulk rock samples and are consistent with in situ crystallization ftir analyses indicate that the ytt mtt and ott melts contained about 4 0 5 5 2 0 5 5 and 2 0 5 5 wt h2o respectively co2 contents in all units are generally 100 ppm and cl is 2000 ppm water gradients occur in all 3 tuffs cl gradients are evident only in the ytt and the least silicic samples from all units had no detectable co2 sulfur contents in melt inclusions are low in all samples 32 ppm and overlap with matrix glass s contents applying broad degassing constraints about 1014 g of h2so4 aerosols were likely loaded into the atmosphere during the ytt eruption 2 orders of magnitude less than previous petrologic estimates considerably more cl and f about 1015 g of each may have been part of the ytt aerosol cloud

chemical differentiation of the bishop tuff and other high silica magmas through crystallization processes re examination of petrochemical data for high silica ash flow tuffs suggests that crystal liquid fractionation plays a major role in the differentiation of high silica magmas for the high silica bishop tuff the enrichment and depletion of 27 major and trace elements correlates with the bulk crystal liquid partition coefficients calculated from the data of hildreth in ways that are consistent with crystal fractionation comparison of the bishop tuff with other high silica tuffs and rhyolites with different compositional variations and different phenocryst assemblages shows the correspondence of chemical gradients with mineralogy crystal zoning studies in the cordillera paine granite in southern chile suggest that the evolution of differentiated liquids similar to those in the bishop tuff results from crystal fractionation the physical mechanisms of separation of liquid and crystals for the paine granite and bishop tuff were quite different however differentiation of the high silica ash flows might result from advection of a less dense liquid from a crystallizing boundary into the top of the magma chamber

diffusional gradients at the crystal melt interface and their effect on the compositions of melt inclusions melt inclusions are widely believed to represent melts from which host crystals grew melt inclusions represent melt adjacent to growing crystals where compositional gradients exist due to preferential incorporation or exclusion of components by the crystallizing mineral the possibility arises therefore that melt in inclusions may differ significantly from melt which was more remote from growing crystals at the time the crystals grew we have tested this possibility by analyzing 45 major minor and trace components in 50 to 400 m diameter melt inclusions in phenocrysts from the rhyolitic bishop tuff california the following observations indicate that the effects of compositional gradients on chemical compositions of melt inclusions are negligible 1 melt inclusions in quartz and sanidine phenocrysts have indistinguishable compositions 2 no correlation is observed between sizes of melt inclusions and their chemical compositions 3 ten melt inclusions in four quartz phenocrysts from a single

cathodoluminescence of quartz from sandstones interpretation of the uv range by determination of trace element distributions and fluid inclusion p t x properties in authigenic quartz quartz overgrowths from keuper sandstones of the paris basin were examined using cathodoluminescence cl microscopy and spectroscopy coupled with a scanning electron microscope sem with the use of standard cold cl equipment it was observed that the emission of authigenic quartz is much less intense than that of detrital quartz grains but a reversal of intensity was observed with scanned cl in the 200 800 nm range the main cl emission band of diagenetic quartz is at 330 340 nm in the uv range with other bands in the visible range the determination of trace element distributions in authigenic quartz by in situ analyses and by sims imagery reveals the correlation of the 330 340 nm emission band with the highest al and li contents the cathodoluminescence emission of diagenetic quartz in the uv range appears to be influenced by the coupled substitution of al and li into the crystal two explanations are suggested 1 ai li or both serve as activators and 2 the incorporation of al and li causes lattice defects that lead to an enhancement of the intrinsic luminescence trace element analyses and fluid inclusion studies revealed that quartz overgrowths precipitated from a fluid that partially originated from an li enriched primary brine derived from eastern triassic evaporites of the paris basin the specific cl emission band in the uv range can be linked to the diagenetic environment the chemistry of the fluids appears to be the essential parameter whereas precipitation temperatures do not influence the occurrence of such emissions

quartz and feldspar zoning in the eastern erzgebirge volcano plutonic complex germany czech republic evidence of multiple magma mixing abstract zoned quartz and feldspar phenocrysts of the upper carboniferous eastern erzgebirge volcano plutonic complex were studied by cathodoluminescence and minor and trace element profiling the results verify the suitability of quartz and feldspar phenocrysts as recorders of differentiation trends magma mixing and recharge events and suggest that much heterogeneity in plutonic systems may be overlooked on a whole rock scale multiple resorption surfaces and zones element concentration steps in zoned quartz ti and feldspar phenocrysts anorthite content ba sr and plagioclase mantled k feldspars etc indicate mixing of silicic magma with a more mafic magma for several magmatic phases of the eastern erzgebirge volcano plutonic complex generally feldspar appears to be sensitive to the physicochemical changes of the melt whereas quartz phenocrysts are more stable and can survive a longer period of evolution and final effusion of silicic magmas the regional distribution of mixing compatible textures suggests that magma mingling and mixing was a major process in the evolution of these late variscan granites and associated volcanic rocks quartz phenocrysts from 14 magmatic phases of the eastern erzgebirge volcano plutonic complex provide information on the relative timing of different mixing processes storage and recharge allowing a model for the distribution of magma reservoirs in space and time at least two levels of magma storage are envisioned deep reservoirs between 24 and 17 km the crystallisation level of quartz phenocrysts and subvolcanic reservoirs between 13 and 6 km deflation of the shallow reservoirs during the extrusion of the teplice rhyolites triggered the formation of the altenberg teplice caldera above the eastern erzgebirge volcano plutonic complex the deep magma reservoir of the teplice rhyolite also has a genetic relationship to the younger mineralised a type granites as indicated by quartz phenocryst populations the pre caldera biotite granites and the rhyodacitic schonfeld volcanic rocks represent temporally and spatially separate magma sources however the deep magma reservoir of both is assumed to have been at a depth of 24 17 km the drastic chemical contrast between the pre caldera schonfeld westfalian b c and the syn caldera teplice westfalian c d volcanic rocks is related to the change from late orogenic geotectonic environment to post orogenic faulting and is considered an important chronostratigraphic marker

thermal tides in the dusty martian atmosphere a verification of theory major features of the daily surface pressure oscillations observed by the viking landers during the two great dust storms on mars in 1977 can be explained in terms of the classical atmospheric tidal theory developed for the earth s atmosphere the most dramatic exception is the virtual disappearance of only the diurnal tide at viking lander 1 just before the second storm this disappearance is attributed to destructive interference between the usually westward traveling tide and an eastward traveling diurnal kelvin mode generated by orographically induced differential heating the continuing viking lander 1 pressure measurements can be used with the model to monitor future great dust storms

radio occultation measurements of forced atmospheric waves on mars mars global surveyor performed a series of radio occultation experiments in december 1998 resulting in 36 profiles of the neutral atmosphere in late northern spring ls 74 1 77 3 the measurements are confined in latitude 64 6 67 2 n and local time 0321 0418 but their distribution in longitude is fairly uniform we used least squares spectral analysis to characterize the zonal structure of the atmosphere and constructed longitude height cross sections of both temperature and geopotential zonal variations of temperature exceed 12 k near the surface but are much smaller 2 3 k at higher altitudes zonal variations of geopotential are 200 m throughout the vertical range of the measurements these patterns of temperature and geopotential appear to be stationary relative to the surface with little day to day variation within the 7 sol span of the measurements we relied heavily on mars general circulation models gcms for guidance in understanding these data stationary planetary waves are responsible for some aspects of the temperature and geopotential fields particularly at pressures exceeding 100 200 pa on the basis of strong similarities between a gcm simulation and the observations we conclude that the disturbance takes the form of a planetary wave train excited by alba patera the data also include the signature of non sun synchronous thermal tides which produce a pattern that appears to be stationary when sampled at fixed local time comparison between a gcm simulation and the measured geopotential field provides evidence for the presence of the resonantly enhanced diurnal wave 1 kelvin mode

thermal history of the bandelier magmatic system evidence for magmatic injection and recharge at 1 61 ma as revealed by cathodoluminescence and titanium geothermometry abstract the rhyolitic valles caldera complex new mexico is one of the type examples of resurgent calderas and has experienced two well studied caldera forming eruptions the first formed the lower bandelier tuff lbt at 1 61 ma and the second emplaced the upper bandelier tuff ubt at 1 22 1 26 ma during the time between the lbt and the ubt the much smaller scale cerro toledo rhyolite ctr was sporadically erupted quartz crystals from these stages of activity were imaged with cathodoluminescence microscopy and growth zones in certain quartzes due to varying ti content were revealed crystallization temperatures were obtained with a titanium in quartz geothermometer the lbt quartzes are unzoned with temperatures clustering between 660 and 715 c when a calculated documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsm

observations of planetary waves and nonmigrating tides by the mars climate sounder 1 temperature profiles from the mars reconnaissance orbiter s mro mars climate sounder mcs indicate the presence of several types of stationary planetary waves and nonmigrating thermal tides in the martian atmosphere we analyze 35 months of mcs data to identify the dominant waves with the contribution of the zonal mean and migrating tides removed the temperature perturbations remaining are due to planetary waves nonmigrating tides and topographic and surface albedo thermal inertia effects we characterize waves with satellite relative wave numbers 1 through 4 in the martian middle atmosphere 40 80 km in tropical latitudes eastward propagating diurnal kelvin waves are the dominant component observed in the satellite relative wave number 2 through 4 fields we identify these as diurnal kelvin waves 1 through 3 respectively the kelvin waves have very long vertical wavelengths and amplitudes of 1 3 k this is the first unambiguous detection of diurnal kelvin wave 3 we also identify the zonally symmetric diurnal tide and an eastward propagating semidiurnal wave 1 tide possibly the semidiurnal kelvin wave 1 stationary planetary waves with wave numbers 1 and 2 produce 5 10 k amplitudes in the middle and high latitudes of both hemispheres

silicate melt inclusion evidence for extreme pre eruptive enrichment and post eruptive depletion of lithium in silicic volcanic rocks of the western united states implications for the origin of lithium rich brines to evaluate whether anatectic and or highly fractionated lithophile element enriched rhyolite tuffs deposited in arid lacustrine basins lose enough lithium during eruption lithification and weathering to generate significant li brine resources pre eruptive melt compositions preserved in inclusions and the magnitude of post eruptive li depletions evident in host rhyolites were documented at six sites in the western united states each rhyolite is a member of the bimodal basalt rhyolite assemblage associated with extensional tectonics that produced the basin and range province and rio grande rift an evolving pattern of closed drainage basins and geothermal energy or mineral resources results from the 0 8 ma bishop tuff geothermal in california 1 3 to 1 6 ma cerro toledo and upper bandelier tephra geothermal and 27 9 ma taylor creek rhyolite sn in new mexico 21 7 ma spor mountain tuff be u f and 24 6 ma pine grove tuff mo in utah and 27 6 ma hideaway park tuff mo in colorado support the following conclusions melt inclusions in quartz phenocrysts from rhyolite tuffs associated with hydrothermal deposits of sn mo and be are extremely enriched in li 1 000s of ppm those from spor mountain have the highest li abundance yet recorded max 5 200 ppm median 3 750 ppm forty five to 98 of the li present in pre eruptive magma was lost to the environment from these rhyolite tuffs the amount of li lost from the small volumes 1 10 km3 of li enriched rhyolite deposited in closed basins is sufficient to produce world class li brine resources after each eruption meteoric water leaches li from tuff which drains into playas where it is concentrated by evaporation the localized occurrence of li enriched rhyolites may explain why brines in arid lacustrine basins seldom have economic concentrations of li considering that hydrothermal deposits of sn mo be u and f may indicate potential for li brines in nearby basins we surmise that the world s largest li brine resource in the salar de uyuni 10 mt received li from nearby rhyolite tuffs in the bolivian tin belt

evolution of crystal sizes in the series of dissolution and precipitation events in open magma systems article i nfo we propose a model that describes the evolution of crystal sizes and crystal size distributions csd of igneous phenocrysts in a sequence of dissolution and crystallization events this model is based on the assumption that crystal dissolution is rate limited by diffusion in melt while crystal growth is controlled by the slower kinetic of new nucleation and growth as a result the dissolution rate is inversely proportional to crystal size coming into effect through the curvature of the crystal s surface but the growth rate does not depend on the crystal size closed form analytical solution of equation for csd is obtained we apply results of modeling to quartz and zircon two prime minerals in silicic igneous systems that are widely used in geochemical and isotopic investigations the time series of multiple solution reprecipitation episodes generate concave downward csds and this result fits well with experimental and natural observations on the abundant concave down csd in silicic igneous rocks we suggest that maturation of crystal populations with sizes above several micrometers can not be caused by a size effect on the solubility of the crystals ostwald ripening but is rather driven by thermal oscillations in experiments and in nature the model predicts that mean crystal size increases with time proportionally to t 0 20 which is very close to the published experimental results for quartz maturation with the exponent of 0 19 0 22 our proposed model gives an opportunity to use natural csds for interpretation of pre eruptive magma history when solubilities and diffusion data are available for constituent elements of the dissolving mineral in particular we present time estimates for maturing zircon populations in large volume ignimbrites and estimate that it takes 100 1000 yrs to mature an initially exponential csd to a lognormal csd

the magmatic hydrothermal transition evidence from quartz phenocryst textures and endoskarn abundance in cu zn skarns at the empire mine idaho usa information about the magmatic to hydrothermal transition is preserved in late stage features of quartz phenocrysts and endoskarn alteration in some cu zn skarn deposits such as the empire mine in idaho important features include 1 quartz phenocrysts with strong resorption textures such as vermicular zones of igneous groundmass cutting primary quartz cathodoluminescence banding 2 anomalous amounts of endoskarn more than 50 of mineralized rock 3 high f activities as evidenced by fluorite as an accessory mineral in igneous rocks in alteration assemblages and in fluid inclusions and by high f in hydroxyl sites in igneous biotite and amphibole and 4 direct association of zn which normally is deposited distally at low temperature with cu in proximal locations and in endoskarn these features are explained by the following model 1 f lowers the solidus temperature of the magma thus changing the timing temperature and duration of hydrothermal fluid exsolution 2 upon magmatic vapor saturation the f rich hydrothermal fluids form bubbles that adhere to quartz phenocrysts and chemically corrode tunnel into the quartz forming vermicular resorption textures 3 f rich hydrothermal fluids also promote the formation of endoskarn silicic rocks are attacked by f rich fluids in the same sense that carbonate wall rocks are dissolved by weakly to moderately acidic hydrothermal fluids 4 low fluid exsolution temperature facilitated by high f activity promotes high zn cu ratios in proximal locations due to the solubility of zn relative to cu at lower temperatures this model may be applicable at other localities such as the world class cu zn skarn antamina mine as well as some tin and rapakivi granites

fragmentation phenomena in populations of magmatic crystals fragmentation of crystals is an important mechanism and a component of particle dynamics in igneous and metamorphic rocks that has received surprisingly little attention recent advances in textural analysis extraction techniques digital imaging and computer assisted measurements enable rapid accumulation of 3d data on particle shapes and size distributions this paper reviews fragment size distributions fsd that result from fragmentation lognormal fractal loggamma and weibull discusses their genesis mechanisms and presents relevant examples of fragmentation from experimental physics next the paper considers fsds of feldspars on digitized images of thin sections and on published images and quartz extracted from vesicular pumice by acid from eight well known large volume eruptive units the acid solution of pumice enables examination of volume abundance 3d shapes proportions of fragmented crystals and measurements of their csds and fsds fsds were also measured in samples of welded tuff and a granite disaggregated by electric pulse products of syneruptive shock wave fragmentation and fragmentation by an electric pulse are found to be fractal with large breakage probabilities branching ratios and fractal dimensions of 2 to 3 in contrast most quartz fragments in pumice obey a lognormal distribution and fragmentation is driven by a melt inclusion decrepitation mechanism which results in low breakage probability and small number 2 3 of fragments per breakage cycle these results are consistent with one atmosphere heating experiments of quartz phenocrysts that led to melt inclusion decrepitation and caused quartz to break up into several smaller pieces collectively having lognormal fsd measured melt inclusion size distributions suggest decrepitation of outermost melt inclusions and low survival rate for large inclusions and inclusions with large radius crystal size ratio the modeling of periodic fragmentation of crystals with melt inclusions due to overheating and or decompression which may occur many times during the lifetime of a long lived magma body may explain concave down lognormal csds abundant in igneous rocks the genesis of lognormality can be explained by the fragmentation algorithm of kolmogorov 1941 other algorithms may generate lognormal like loggamma distributions fragmentation serves as an important size limiting factor a nucleation aid and it facilitates isotopic and trace elemental exchange

radio occultation measurements and mgcm simulations of kelvin waves on mars we have derived new results concerning thermal tides on mars from a combination of radio occultation measurements and numerical simulations by a mars general circulation model mgcm this investigation exploits a set of concurrent observations by mars express mex and mars global surveyor mgs in mid 2004 when the season on mars was midspring in the northern hemisphere the mex occultations sampled the atmosphere near the evening terminator at latitudes ranging from 54 n to 15 s the mgs occultations provided complementary coverage near the morning terminator at latitudes of 35 n and 71 s the geopotential field derived from these measurements contains distinctive modulation caused by solar asynchronous thermal tides through careful analysis of the combined observations we characterized two prominent wave modes obtaining direct solutions for some properties such as the amplitude and phase as well as constraints on others such as the period zonal wave number and meridional structure we supplemented these observations with mgcm simulations after evaluating the performance of the mgcm against the measurements we used the validated simulation to deduce the identity of the two tidal modes and to explore their behavior one mode is a semidiurnal kelvin wave with a zonal wave number of 2 sk2 while the other is a diurnal kelvin wave with a zonal wave number of 1 dk1 both modes are known to be close to resonance in the martian atmosphere our observations of the sk2 are more complete and less ambiguous than any previous measurement the well known dk1 is the dominant solar asynchronous tide in the martian atmosphere and our results confirm and extend previous observations by diverse instruments

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

origin of ti rich rims in quartz phenocrysts from the upper bandelier tuff and the tunnel spring tuff southwestern usa four compositionally zoned melt inclusion bearing quartz phenocrysts from the upper bandelier tuff new mexico and the tunnel spring tuff utah were examined in detail by cathodoluminescence laser ablation icp ms and titanium in quartz titaniq thermobarometry in order to reconstruct the conditions of quartz crystallization temperature and tio2 activity atio2 in the magma were estimated from melt inclusion compositions by means of zircon saturation thermometry and an experimentally calibrated tio2 solubility model whereas pressure was estimated with the most recent calibration of the titaniq thermobarometer on the host quartz next to the analyzed melt inclusions all four investigated quartz phenocrysts display a low luminescent ti poor core overgrown by a high luminescent ti rich rim reconstructed p t atio2 conditions suggest that the rimward increase in the ti content of the two quartz crystals from the upper bandelier tuff is due to a combination of increasing temperature increasing atio2 and decreasing pressure with the temperature effect being dominant in one crystal and the atio2 effect being dominant in the other crystal in the two crystals from the tunnel spring tuff the rimward increase in ti content is mostly due to increasing temperature but in one of them a negative pressure change played an equally important role this study demonstrates that in rapidly cooled peraluminous or metaluminous rhyolites the crystallization conditions of quartz phenocrysts can be reconstructed at the scale of individual growth zones which allows to investigate the origin and evolution of such magmas in great detail

timescales of mixing and mobilisation in the bishop tuff magma body perspectives from diffusion chronometry we present two feldspar thermometry and diffusion chronometry from sanidine orthopyroxene and quartz from multiple samples of the bishop tuff california to constrain the temperature stratification within the pre eruptive magma body and the timescales of magma mixing prior to its evacuation two feldspar thermometry yields estimates that agree well with previous fe ti oxide thermometry and gives a 80 c temperature difference between the earlier and later erupted regions of the magma chamber using the thermometry results we model diffusion of ti in quartz and ba and sr in sanidine as well as fe mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on these crystal phases diffusion profiles of ti in quartz and fe mg in orthopyroxene both yield timescales of 150 years for the formation of overgrowth rims in contrast both ba and sr diffusion in sanidine yield nominal timescales 1 2 orders of magnitude longer than these two methods the main cause for this discrepancy is inferred to be an incorrect assumption for the initial profile shape for ba and sr diffusion modelling i e growth zoning exists utilising the divergent diffusion behaviour of ba and sr we place constraints on the initial width of the interface and can refine our initial conditions considerably bringing ba and sr data into alignment and yielding timescales closer to 500 years the majority of which are then within uncertainty of timescales modelled from ti diffusion in quartz care must be thus taken when using ba in sanidine geospeedometry in evolved magmatic systems where no other phases or elements are available for comparative diffusion profiling our diffusion modelling reveals piecemeal rejuvenation of the lower parts of the bishop tuff magma chamber at least 500 years prior to eruption timescales from our mineral profiling imply either that diffusion coefficients currently used are uncertain by 1 2 orders of magnitude or that the minerals concerned did not experience a common history despite being extracted from the same single pumice clasts introduction of the magma initiating crystallisation of the contrasting rims on sanidine quartz orthopyroxene and zircon was prolonged and may be a marker of other processes that initiated the bishop tuff eruption rather than the trigger itself

prolonged ascent and episodic venting of discrete magma batches at the onset of the huckleberry ridge supereruption yellowstone abstract how exceedingly large volcanic supereruptions begin provides crucial information on the storage ascent and release of silica rich magma in catastrophic events initial fall deposits of the 2 08 ma 2500 km 3 huckleberry ridge eruption are multiply bedded and in several places contain reworked intervals indicating time breaks in the opening phases of the eruption a 2 5 m section of these fall deposits was sampled at nine levels below the earliest ignimbrite member a at mount everts mammoth wyoming we analyzed major and trace elements and volatiles in quartz hosted melt inclusions mis reentrants res unsealed melt inclusions and associated obsidian pyroclasts thick walled shards to establish quartz crystallization and storage depths and melt compositional groupings systematic relationships between rb and other incompatible elements u cl b indicate 55 fractional crystallization between the least and most evolved glass compositions in contrast h 2 o concentrations in mis show scattered relationships with trace elements and are interpreted to reflect variable loss of h 2 o by diffusion through the quartz host during magma ascent the wide h 2 o variations 1 0 4 7 wt in mis from individual fall horizons imply as much as 14 days of diffusive loss reflecting highly variable and surprisingly slow decompression conditions water and co 2 gradients in reentrants however are consistent with final ascent times of 0 3 1 5 m s similar to those represented by mis that we infer to have experienced little to no diffusive h 2 o loss the wide range of ascent rates for co erupted crystals mirrors that of intermittent explosive activity at mount st helens in summer 1980 and implies that the huckleberry ridge magma body was not strongly overpressured at eruption onset restored entrapment pressures and geochemical data for mis provide evidence for six distinct populations of quartz that originally crystallized in geochemically distinct magma domains the compositions of res and obsidian pyroclasts by comparison show that by the onset of eruption the quartz had been brought together into three discrete magma bodies which we interpret to have been cupolas on the roof of the main magma body these cupolas were erupted sequentially and episodically from separate vents to generate the fall deposits before escalating activity led to generation of voluminous pyroclastic flows and this pattern of activity suggests that tectonic triggering may have destabilized multiple magma bodies supereruptions as large as the huckleberry ridge event may start hesitatingly if the parental magma bodies are not strongly overpressured with small scale episodic activity that is modulated by external controls that may leave no other geological evidence for their presence

a comment on titaniq under pressure the effect of pressure and temperature on the solubility of ti in quartz by jay b thomas e bruce watson frank s spear philip t shemella saroj k nayak and antonio lanzirotti trace concentrations of ti in quartz are used to indicate the pressure and temperature conditions of crystallization in the titaniq geothermobarometer of thomas et al contrib miner petrol 160 743 759 2010 it utilises the partitioning of ti into quartz as an indicator of the pressures and or temperatures of crystal growth for a given value of tio2 activity in the system if temperatures are inferred to 20 c pressure is constrained to 1 kbar and vice versa there are significant contrasts however between the conclusions from titaniq and those for natural quartz as well as other mineral phases in volcanic rocks application of the titaniq model to quartz from the 27 ka oruanui and 760 ka bishop high silica rhyolites where the values of t p and tio2 activity are constrained by other means fe ti oxide equilibria melt inclusion entrapment pressures in gas saturated melts melt and amphibole compositions yields inconsistent results if realistic values are given to any two of these three parameters then the value of the third is wholly unrealistic the model yields growth temperatures at or below the granite solidus pressures in the lower crust or upper mantle or tio2 activities inconsistent with the mineralogical and chemical compositions of the magmas cl imagery and measurements of ti and other elements in quartz are of great value in showing the growth histories and changes in conditions experienced by crystals but direct linkages to p t conditions during crystal growth cannot be achieved

rutile solubility in hydrous rhyolite melts at 750 900 c and 2 kbar with application to titanium in quartz titaniq thermobarometry abstract the solubility of rutile in water saturated haplogranite melts with molar al na k ratios ranging from 0 84 to 1 25 was determined at 750 900 c and 2 kbar in cold seal pressure vessel experiments due to the low diffusivity of ti at these conditions a new method was developed to determine tio2 solubility in this method glasses with tio2 gradients were used as starting material and after the experiments the tio2 content was measured at the contact between rutile bearing and rutile free glass the glasses were either directly equilibrated at the desired p t conditions i e crystallization experiments or first treated at 50 150 c lower temperatures and then subjected to the desired conditions i e dissolution experiments the results obtained in crystallization and dissolution experiments agree well with each other suggesting that equilibrium was attained rutile solubility in peralkaline melts strongly increases with temperature and the amount of excess alkalies according to the relation log tio 2 wt 1 8 ank 0 53 10 000 t 12 8 ank 4 3 in which ank is the deviation of the molar al na k ratio from unity and t is given in kelvin excess alumina does not seem to promote tio2 solubility for natural melt compositions it was found that if ca mg and fe are assumed to be 10 times less effective in promoting tio2 solubility than excess na and k good fits to previous solubility data in silicic 70 wt sio2 melts at upper crustal pressures 10 kbar are obtained application of this extended tio2 solubility model to natural melt inclusions in quartz phenocrysts from five silicic volcanic systems returns tio2 activities that are similar to those calculated with a previous experiment based model and to those calculated from pairs of coexisting fe ti oxides but are up to 2 9 times higher than those calculated with melts and rhyolite melts pressures calculated from ti concentrations in the host quartz using the most recent calibration of the titaniq thermobarometer are in good agreement with independent pressure estimates suggesting that at upper crustal conditions this calibration is valid

thermal tides during the 2001 martian global scale dust storm the 2001 mars year 25 global dust storm radically altered the dynamics of the martian atmosphere using observations from the thermal emission spectrometer onboard the mars global surveyor spacecraft and marswrf general circulation model simulations we examine the changes to thermal tides and planetary waves caused by the storm we find that the extratropical diurnal migrating tide is dramatically enhanced during the storm particularly in the southern hemisphere reaching amplitudes of more than 20 k the tropical diurnal migrating tide is weakened to almost undetectable levels the diurnal kelvin waves are also significantly weakened particularly during the period of global expansion at ls 200 210 in contrast the westward propagating diurnal wavenumber 2 tide strengthens to 4 8 k at altitudes above 30 km the wavenumber 1 stationary wave reaches amplitudes of 10 12 k at 50 70 n far larger than is typically seen during this time of year the phase of this stationary wave and the enhancement of the diurnal wavenumber 2 tide appear to be responses to the high altitude westward propagating equatorial wavenumber 1 structure in dust mixing ratio observed during the storm in previous works this work provides a global picture of dust storm wave dynamics that reveals the coupling between the tropics and high latitude wave responses we conclude that the zonal distribution of thermotidal forcing from atmospheric aerosol concentration is as important to understanding the atmospheric wave response as the total global mean aerosol optical depth

application of cathodoluminescence to magmatic quartz in a tin granite case study from the schellerhau granite complex eastern erzgebirge germany a model of the cooling history of tin bearing granitic magma forming the schellerhau granites eastern erzgebirge germany is shown on the basis of quartz textures similar grain size similar grain habit and correlatable growth textures of phenocrysts in different granite varieties give proof of a common crystallization history before the melts of the schellerhau granite varieties were intruded four nucleation events occurred during crystallization in different crustal levels between about 20 and 1 km depth the parental melt of the schellerhau granites is interpreted to have contained 2 5 wt h2o originally the water content of the melt during the subvolcanic intrusion stage amounted to more than 5 wt and characterizes highly evolved residual melts that enable the formation of tin deposits this study contributes to a better understanding of the development and behaviour of fractionated tin bearing granitic melts and links quartz cathodoluminescence cl with microanalytical studies

the bishop tuff new insights from eruptive stratigraphy the 0 76 ma bishop tuff from long valley caldera in eastern california consists of a widespread fall deposit and voluminous partly welded ignimbrite the fall deposit f exposed over an easterly sector below and adjacent to the ignimbrite is divided into nine units f1 f9 with no significant time breaks except possibly between f8 and f9 maximum clast sizes are compared with other deposits where accumulation rates are known or inferred to estimate an accumulation time for f1 f8 as ca 90 hrs the ignimbrite ig is divided into chronologically and or geographically distinct packages of material earlier packages ig1 were emplaced mostly eastward are wholly intraplinian coeval with fall units f2 f8 lack phenocrystic pyroxenes and contain few or no glass mountain derived rhyolite lithic fragments earlier packages ig2 were erupted mostly to the north and east are at least partly intraplinian interbedded with fall unit f9 to the east contain pyroxenes and have lithic fractions rich in g

a multi year survey of dynamics near the surface in the northern hemisphere of mars short period baroclinic waves and dust storms abstract baroclinic waves figure prominently in the dynamics of the northern hemisphere of mars and extensive observations by the viking landers and two atmospheric sounders on mars global surveyor have revealed many of their basic properties however previous investigations considered these data sets individually so that their cumulative value is not fully appreciated we have re examined these data to extract new information about the dynamics near the surface at mid to high northern latitudes by applying the same method of spectral analysis to each type of observation we derive a uniform multi year characterization of basic elements of martian weather this survey documents the time evolution of baroclinic waves among modes with different periods and zonal wave numbers we devote particular attention to a recurring wave 3 mode which is distinguished by its capacity to initiate regional dust storms in the topographic basins of the northern hemisphere our results include a detailed case study that shows how the intermittence of this mode and the strong zonal modulation of its amplitude influence the timing and location of these distinctive flushing dust storms more generally we find that the properties of the wave 3 mode are largely the same whenever it appears and that its intermittence plays an important role in the annual dust cycle

melt generation and fluid flow in the thermal aureole of the bushveld complex granite sheets emplaced into the migmatite zone of the eastern contact aureole of the bushveld complex resulted from fluid enhanced incongruent biotite melting of the underlying silverton formation shales during prograde metamorphism ba concentrations are extreme in both the sheets 1000 ppm and the hornfels 800 ppm into which they have been emplaced we conclude that a ba rich hydrothermal fluid induced melting in the aureole and that fluid transport of ba2 and to a lesser extent sr2 and eu2 persisted in the melt zones under subsolidus conditions sr isotope systematics from high ba localities define an errorchron of 2161 106 ma with an initial 87sr 86sr ratio of 0 705 0 001 metasedimentary rocks unaffected by fluid infiltration were homogenized at the same time but with an increased initial ratio suggesting that whereas isotope homogenization was achieved between outcrops permeated by fluids there is no evidence of regional homogenization oxygen isotope compositions of psammitic metasediments in the aureole are uncorrelated with distance from the contact suggesting the infiltrating fluid equilibrated isotopically with the metasediments their elevated 18o values 11 3 12 1 are consistent with a fluid source from devolatilization of the sedimentary lithologies textural analysis at both outcrop and thin section scale of arkose and psammites in the aureole lakenvalei and magaliesberg formations shows that the extent of melting was highly heterogeneous even on the grain scale and resulted from heterogeneously distributed infiltration of aqueous fluid on dilatant cracks and grain boundaries cathodoluminescence imaging of quartz shows a marked difference in the amount of fine structure with that in the melted rocks having uniform luminescence in contrast to that in rocks containing little or no melt which preserve textures inherited from the regionally metamorphosed protolith simple finite difference thermal modelling of the aureole suggests that the width of the melt zone 500 m is inconsistent with conductive heat transfer and hence that the thermal structure has been modified by fluid advection

cathodoluminescence and trace element zoning in quartz phenocrysts and xenocrysts quartz phenocrysts and xenocrysts are a common component of volcanic rocks but rarely contribute to our understanding of magmatic or eruptive processes due to an apparent internal chemical and structural homogeneity scanning electron microscopy cathodoluminescence imaging sem cl and secondary ion mass spectroscopy ion microprobe analysis sims are used here to demonstrate that quartz crystals in volcanic rocks show hitherto unrecognised internal structural and chemical zoning two contrasting crystal morphologies have been studied porphyritic euhedral bipyramidal quartz crystals in dacite from bonne nuit bay jersey uk show fine scale growth zoning in sem cl zones are narrow 1 40 m wide planar parallel to crystal faces and overgrow more broadly zoned rounded cores these crystals are interpreted to have formed at small degrees of undercooling by diffusion controlled growth quiescent magma conditions are indicated by the preservation of an al rich diffusive boundary layer which has not been removed by melt shearing during convection in contrast rounded and embayed porphyritic quartz grains in a quartz dacite from the esperanza mine e1 salvador northern chile show broad internal sem cl zones with irregular boundaries some of which are truncated by grain margins indicating dissolution crystal rounding may occur by dissolution or melting due to thermal or thermal chemical disequilibrium with surrounding melt and embayments by gas bubble enhanced convective dissolution are consistent with the development of incipient ocelli textures strings of amphibole inclusions adjacent to quartz rims several episodes of rounding can be recognised in some xenocrysts ion microprobe sims analysis of quartz from both samples shows that a1 contents are higher in areas of bright cl emission previous studies of cl in quartz have suggested that several factors control luminescence although a1 substitution for si in sio4 tetrahedra may be partly responsible for sem cl zoning recorded in volcanic quartz additional mechanisms including the effect of growth rate on defect density probably also play a major role

second reply to comment of r s j sparks h e huppert and c j n wilson on evidence for long residence times of rhyolitic magma in the long valley magmatic system the isotopic record in the precaldera lavas of glass mountain

cordilleran slab windows the geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics as a consequence of subduction of the kula farallon and east pacific rises slab windows formed and migrated beneath the north american cordillera the probable shape and extent of these windows which represent the asthenosphere filled gaps between two separating subducting oceanic plates are depicted from the late cretaceous to the present possible effects of the existence and migration of slab windows on the cordillera at various times include cessation of arc volcanism and replacement by rift or plate edge volcanism lithospheric uplift attenuation and extension and increased intensity of compressional tectonism eocene extensional tectonism and alkaline magmatism in southern british columbia and the northwestern united states were facilitated by slab window development

moc observations of the 2001 mars planet encircling dust storm abstract from 15 september 1997 through 21 january 2006 only a single planet encircling martian dust storm was observed by mgs moc the onset of the storm occurred on 26 june 2001 l s 184 7 earliest recorded to date it was initiated in the southern mid to low latitudes by a series of local dust storm pulses that developed along the seasonal cap edge in malea and in hellas basin l s 176 2 184 4 the initial expansion of the storm though asymmetric was very rapid in all directions 3 32 m s 1 the main direction of propagation however was to the east with the storm becoming planet encircling in the southern hemisphere on l s 192 3 several distinct centers of active dust lifting were associated with the storm with the longest persisting for 86 sols syria claritas these regional storms helped generate and sustain a dust cloud haze which reached an altitude of about 60 km and a peak opacity of dust 5 0 by l s 197 0 the cloud had encircled the entire planet between 59 0 s and 60 0 n obscuring all but the largest volcanoes the decay phase began around l s 200 4 with atmospheric dust concentrations returning to nominal seasonal low levels at l s 304 0 exponential decay time constants ranged from 30 117 sols the storm caused substantial regional albedo changes darkening and brightening as a result of the redistribution removal and deposition of a thin veneer of surface dust at least 0 1 11 1 m thick it also caused changes in meteorological phenomena i e dust storms dust devils clouds recession of the polar caps and possibly surface temperatures that persisted for just a few weeks to more than a single mars year the redistribution of dust by large annual regional storms might help explain the long period 30 years between the largest planet encircling dust storms events

band pass filtering of one year of daily mean pressures on mars the sol mean atmospheric pressures measured at the two viking landers exhibit fluctuations ranging in period from seasonal to a few days the time series are highly nonstationary which severely limits standard methods such as power spectrum analysis we take advantage of the rather precise annual periodicity of these data to design sharp numerical filters and use them to split the series at each lander into six time series each containing oscillations associated with a discrete frequency band this analysis reveals 2 to 4 sol waves during the cold seasons at both landers and 8 sol waves during the spring at lander 2 confirming previous results from spectral analysis as previously predicted high frequency waves appear suppressed during the second dust storm certain low frequency signals probably associated with the global dust storms are detected and demonstrated to be significant for the first time

oxygen isotope study of the long valley magma system california isotope thermometry and convection in large silicic magma bodies products of voluminous pyroclastic eruptions with eruptive draw down of several kilometers provide a snap shot view of batholith scale magma chambers and quench pre eruptive isotopic fractionations i e temperatures between minerals we report analyses of oxygen isotope ratio in individual quartz phenocrysts and concentrates of magnetite pyroxene and zircon from individual pumice clasts of ignimbrite and fall units of caldera forming 0 76 ma bishop tuff bt pre caldera glass mountain 2 1 0 78 ma and post caldera rhyolites 0 65 0 04 ma to characterize the long lived batholith scale magma chamber beneath long valley caldera in california values of 18o show a subtle 1 decrease from the oldest glass mountain lavas to the youngest post caldera rhyolites older glass mountain lavas exhibit larger 1 variability of 18o quartz the youngest domes of glass mountain are similar to bt in 18o quartz values and reflect convective homogenization during formation of bt magma chamber surrounded by extremely heterogeneous country rocks ranging from 2 to 29 oxygen isotope thermometry of bt confirms a temperature gradient between late 815 c and early 715 c bt the 18o quartz values of early and late bt are 8 33 and 8 21 consistent with a constant 18o melt 7 8 0 1 and 100 c temperature difference zircon melt saturation equilibria gives a similar temperature range values of 18o quartz for different stratigraphic units of bt and in pumice clasts ranging in pre eruptive depths from 6 to 11 km based on melt inclusions and document vertical and lateral homogeneity of 18o melt worldwide five other large volume rhyolites lava creek lower bandelier fish canyon cerro galan and toba exhibit equal 18o melt values of earlier and later erupted portions in each of the these climactic caldera forming eruptions we interpret the large scale 18o homogeneity of bt and other large magma chambers as evidence of their longevity 105 years and convection however remaining isotopic zoning in some quartz phenocrysts trace element gradients in feldspars and quartz and zircon crystal size distributions are more consistent with far shorter timescales 102 104 years we propose a sidewall crystallization model that promotes convective homogenization roofward accumulation of more evolved and stagnant volatile rich liquid and develops compositional and temperature gradients in pre climactic magma chamber crystal melt gas bubbles mush near chamber walls of variable 18o gets periodically remobilized in response to chamber refill by new hotter magmas one such episode of chamber refill by high ti sr ba zr and volatile richer magma happened 103 104 years prior to the 0 76 ma caldera collapse that caused magma mixing at the base mush thawing near the roof and walls and downward settling of phenocrysts into this hybrid melt

cathodoluminescence properties of quartz eyes from porphyry type deposits implications for the origin of quartz hyperspectral cathodoluminescence cl mapping combined with electron probe microanalysis epma and fourier transform infrared spectroscopy was used for the reconstruction ofcrystallization conditions of quartz from porphyry environments quartz eyes from the two porphyry deposits rio blanco chile and climax u s a were studied three peaks are found to be responsible for the total cl emission 1 93 2 05 and 2 72 ev the first two peaks are assigned to o m with m being an alkali ion and oxygen vacancies respectively the 2 72 ev peak shows a linear correlation with the ti concentration determined by epma point measurements in addition a negative correlation between the 1 93 ev emission and the al concentration was observed quartz grains often form clusters in which adjacent grains show identical cl patterns indicating that they crystallized attached to each other and were not disturbed later quartz cores display sector zoning and enrichment in li oh and sometimes al which points to rapid crystallization from an extremely evolved melt quartz rims show high ti and low li and oh contents indicating crystallization from a less evolved melt either at higher temperatures or at higher titanium activities the al and ti distribution patterns are frequently not correlated and both show uneven distribution indicating fast growth from inhomogeneous melts only ti displays sharp transitions and fine oscillatory zoning which can be explained by the higher mobility of al in the quartz lattice the quartz eyes crystallized after magma emplacement under non equilibrium conditions it is likely that the crystallization occurred from the melt enriched in al li and oh and probably other metals and or volatiles on the brink of fluid exsolution subsequent fluid exsolution brought about disequilibrium to the system resulting in dissolution of quartz and redistribution of elements between the melt and the fluid the oh li and other alkali metals and volatiles partitioned into the fluid whereas ti and al remained in the melt resorption of quartz caused by the fluid exsolution continued until equilibrium was reached again after which crystallization of quartz rims began from the water alkali and volatile poor melt with higher ti activity furthermore accumulation of al and ti in the residual melt led to crystallization of extremely al and ti rich quartz

a trace element geochemical model for imperfect fractional crystallization associated with the development of crystal zoning abstract although many petrological studies of volcanic rocks have suggested that crystallization proceeds within magma bodies highly compatible trace elements do not display the marked variations and extreme depletions predicted to result from perfect fractional crystallization imperfect crystal liquid separation is a key process in explaining this paradox the presence of suspended crystals greatly affects variations in highly compatible elements and has been quantitatively modeled by assuming perfect equilibrium between the suspended crystals and the liquid equilibrium crystallization and imperfect separation ecis however volcanic rocks generally contain zoned phenocrysts that reflect the absence of solid state equilibration the present study develops a mass balance model for zoned crystallization and imperfect separation zcis the zcis process is more efficient than the conventional ecis process in generating depleted compatible elements these two end member models are able to explain the compositional range of igneous rocks that experienced imperfect fractional crystallization under natural conditions the predicted compositional regions in bivariate trace element diagrams successfully account for the sizes and shapes of the regions defined by whole rock and melt inclusion data from the bishop tuff ca usa

nonmigrating tides inferred from the mars odyssey and mars global surveyor aerobraking data 1 we analyzed mars odyssey ody and mars global surveyor mgs accelerometer density retrievals in narrow local time lt bands during their respective aerobraking phases to study the large scale longitudinal density variations in the martian upper atmosphere the ody data and three seasons of mgs data fall winter and spring all displayed large zonal variations in density especially wave 2 and 3 with little vertical phase variation consistent with previous studies using mgs aerobraking data the large scale density structures were most likely nonmigrating tides sampled at specific lts the wave 2 modes observed in the ody and mgs data were approximately out of phase and their respective lt samplings were approximately 12 hours apart this reinforces the conclusion from previous studies that this mode is most likely an eastward propagating diurnal kelvin wave of zonal wave 1 which is produced by the interaction of the diurnal thermal forcing and the wave 2 component of the martian topography we also note a close association of enhanced gravity wave variances with the strong longitudinal variations in the large scale densities suggesting the possibility of tidal filtering of the gravity wave gw field

observations of martian tides over two annual cycles abstract the first four diurnal surface pressure harmonics have been analysed over major portions of two martian annual cycles mars years at the two viking lander sites the diurnal harmonies of surface wind have also been analysed at one of the sites since the atmospheric tides have previously been shown to provide a good indication of martian global dust storms these results provide a basis for comparing dust storm activity in the two years two global dust storms occurred during the first year during the second year there was only one major storm and it closely followed the pattern of the first storm of the first year a significant feature of the results is the brief but nearly complete vanishing of the diurnal pressure tide at the onset of one of the global dust storms it is proposed that this may have been due to interference between the normal westward propagating diurnal tide and a topographically forced eastward propagating tide and that the latter may have helped initiate the global s

mars global atmospheric oscillations annually synchronized transient normal mode oscillations and the triggering of global dust storms observation and analyses of the atmospheric pressure at the surface on mars for several martian years has led to the discovery of transient events in the daily pressure variations of an unusual nature these events last only a few sols mars days appear to repeat on an annual basis to within a few sols appear to cover a large portion of the hemisphere on the same sol or at least within a few sols occur in pairs with separations of 20 sols in some instances are coincident with the annual pressure minimum i e the maximum concentration of carbon dioxide in the southern hemisphere and consist of spectral components near to and sometimes identical in frequency to the diurnal and semidiurnal harmonics it is suggested that these events are kelvin normal mode transient global oscillations examination of the initiation of the 1977a 1977b and 1982a global dust storms indicate that pseudo diurnal and some times pseudo semidiurnal oscillations exist during the initiation phase and might be involved in triggering the global dust storms possibly in conjunction with winds due to longer period circulations the diurnal harmonic disappears prior to the 1977b global dust storm and is replaced by an oscillation at 1 1 cycles sol if the lack of a classical diurnal tide indicates the suppression of convection this might partially explain the slow growth of the 1977b storm the daily average pressure during the transient season which precedes the global dust storm season by almost one fourth of a year exhibits a different behavior during the global dust storm years than during the nonglobal dust storm years this implies that the global circulation must differ significantly in these cases and may be related to the presence or absence of global dust storms later in a given year these analyses suggest that an almost diurnal and an almost semidiurnal high frequency global oscillation different from the classical solar driven tides may be quite common on mars

wetting behavior of partial melts during crustal anatexis the distribution of hydrous silicic melts in polycrystalline aggregates of quartz the equilibrium distribution of hydrous silicic melts in polycrystalline aggregates of quartz was characterized in a series of partial melting and melt distribution experiments in the systems quartz albite orthoclase h2o and quartz anorthite h2o at 650 to 1000 mpa and 800 to 900 c near equilibrium textures in these experiments are characterized by very low quartz quartz melt wetting angles and by a substantial number of thin melt films along grain boundaries wetting angles in the h2o saturated experiments are as follows 18 at 800 c 1000 mpa and 12 at 900 c 1000 mpa in the granitic system 18 at 850 c 650 mpa 15 at 900 c 650 mpa and 15 at 900 c 1000 mpa in the quartzanorthite system in the granitic system at 900 c 1000 mpa a decrease of h2o content in melt from 17 wt at saturation to 6 wt results in a slight increase of wetting angle from 12 to 16 these low wetting angles and the observation that many grain boundaries are wetted by melt films indicate that the ratio of quartz quartz to quartz melt interfacial energies ss s1 is high 2 secondary electron imaging of fracture surfaces of melt poor samples provided a three dimensional insight into the geometry of melt at low melt fraction melt forms an interconnected network of channels along grain edges as predicted for isotropic systems with wetting angles below 60 this high permeability geometry suggests that the segregation of granitic melts is not as sluggish as previously anticipated simple compaction calculations for a permeability range of 10 12 to 10 9 m2 indicate that segregation may operate at low to moderate melt fractions below 30 vol within relatively short time scales i e 105 to 106 years quartzmelt textures show significant deviations from the equilibrium geometries predicted for isotropic partially molten systems the most consistent deviation is the pervasive development of crystallographically controlled planar faces of quartz these faces provide definitive evidence for non isotropic quartz melt surface energy for most silicates other than quartz the grain scale distribution of partial melts deviates even more significantly from equilibrium distributions in isotropic systems accordingly in order to describe adequately melt distributions in most natural source regions the equilibrium model should be modified to account for anisotropy of solid liquid interfacial energy

zoned quartz phenocrysts from the rhyolitic bishop tuff cathodoluminescence cl reveals growth zones in quartz phenocrysts from the rhyolitic bishop tuff melt inclusions occur in various zones and record the evolving melt composition during zonal growth the zones form an oscillatory pattern between bright and dark cl quartz there are three recognizable patterns of cl zoning in these crystals 1 weakly zoned cores and bright cl rims 2 weakly zoned cores and dark cl rims and 3 no cl intensity difference from core to rim dark cl quartz generally occurs at crystal edges contains most of the melt inclusions and is interpreted as fast growing zones that occur along recognizable crystal edges edge zones are thicker than the same zone on adjacent faces consistent with relatively fast growth of these zones in each successive zone these edge zones decrease in size toward the rim while the zones along the crystal faces increase some of the melt inclusions have bright cl quartz locally associated with them this is interpreted as the postentrapment crystallization of slow growing quartz in the melt inclusions many crystals display zone discordance from the weakly zoned interiors to the rims most of the discordant surfaces are rational and probably are primary growth features pumice clasts from the southern vents are largely compositionally and texturally distinct from those from the northern vents and this distinction is also evident in the quartz cl the crystals that have bright cl rims are all associated with the late erupted northern part of the bishop tuff melt inclusion compositions and cl zoning patterns suggest a common origin for early and middle erupted quartz and the interior zones of late erupted quartz however the bright cl rim on the late erupted quartz indicates an additional stage of crystallization in late erupted magma melt inclusions in individual early erupted crystals have small variations in ba whereas inclusions in late erupted crystals markedly increase in ba toward the rim which is opposite to the normal zoning of sequentially trapped melts expected during closed system crystallization differentiation the quartz zoning features are consistent with the hypothesis of crystal settling in evolving magma that erupted late from northern vents

40ar 39ar laser probe ages of bishop tuff quartz phenocrysts substantiate long lived silicic magma chamber at long valley united states laser probe ar 40 ar 39 dating of quartz phenocrysts with rhyolite glass inclusions from the bishop tuff air fall and ignimbrite deposits reveals that the long valley magma system existed as a long lived silicic magma chamber throughout most of the pleistocene sanidine phenocryst and matrix glass analyses show that the bishop tuff eruption occurred at 759 1 to 761 1 ha initial and radiogenic ar isotope ratios indicate isotopic equilibrium between the sanidine phenocrysts and their host melt at the time of eruption the quartz phenocrysts in contrast the most abundant phenocryst phase of the bishop rhyolite crystallized trapped their glass inclusions and became a closed system with respect to ar at 1 89 0 03 to 2 3 0 3 ma consequently the bishop rhyolite magma already resided in the long valley basement and had formed most of its quartz phenocrysts similar to 1 1 m y before its principal eruption providing important constraints on the longevity of large silicic magma chambers

micro analytical perspectives on the bishop tuff and its magma chamber new in situ major and trace element analytical data are presented for crystals sanidine plagioclase biotite orthopyroxene clinopyroxene and matrix glasses from juvenile materials representing the full bishop tuff sequence from the earliest fall unit f1 to the latest ignimbrite package ig2nc these data are combined with published information to investigate the nature and zonation of the pre eruptive bishop magma chamber our data confirm that this magma chamber was a single unitary body that was thermally and compositionally zoned the zonation was largely established prior to the growth of crystals and also prior to mixing in the lower parts of the chamber induced by late stage intrusion of a magma of contrasting composition and slightly higher temperature the bright rim magma sparse mixed swirly and dacitic pumices show enrichments in ba sr and ti that identify these pumices as possible representatives of the bright rim magma a model revised from previously published work for the pre eruptive magma chamber comprises three main parts 1 an upper volumetrically dominant 2 3 relatively unzoned region that was the source of the earlier eastern erupted ignimbrite units and their coeval fall units 2 a volumetrically minor transition zone that shows evidence for minor degrees of mixing and was the dominant source for the latest eastern erupted part of ig1eb sherwin subunit and the earlier part of the northern erupted ignimbrite ig 2na 3 a lower volumetrically subordinate 1 3 region that was affected by mixing with the bright rim invasive magma in the lead up to the eruption and fed later northern erupted units ingress of the bright rim magma introduced orthopyroxene and bright rimmed zircon crystals and induced partial resorption then overgrowth of rims enriched in ti sr and ba on sanidine and quartz and development of zoning in clinopyroxene based on pumice proportions and associated crystal and glass chemistries through the eruptive sequence we infer that the roof and floor of the magma chamber were stepped down to the north such that the transition zone magma formed the floor of the southern part of the melt dominant chamber and the roof of the northern part our data reinforce the previous concept of a single compositionally and thermally zoned bishop magma chamber and additionally support a temporally constrained role for pre eruptive magma mixing and the introduction of melts and minerals with contrasting compositions to the resident bishop magma

microstructures and composition of melt inclusions in a crustal anatectic environment represented by metapelitic enclaves within el hoyazo dacites se spain abstract this article reports microstructures and compositions of melt inclusions in anatectic metapelites found as enclaves within el hoyazo dacites in the neogene volcanic province of southeastern spain the enclaves represent fragments of continental crust partially melted at 800 850 c and 5 7 kbar and brought to surface rapidly within the host volcanics while they still were in a molten state rapid cooling produced the solidification of silicate melt to glass in the rock matrix and in inclusions within minerals melt inclusions mi are present within nearly all mineral phases in the enclaves and their associated microstructures indicate a primary or pseudo secondary origin the entrapment mechanisms of mi within plagioclase were associated with 1 the presence of micron sized solids mostly graphite on the surface of growing crystals 2 partial resorption of crystals generation of embayments and later growth in the presence of melt and 3 entrapment of melt during crystal growth within crystallographic controlled planar structures e g on crystal faces melt inclusions in garnet are commonly associated with regularly oriented planar discontinuities filled with glass interpreted either as spaces left between adjacent mineral growth spirals or as crystallographic controlled cracks generated in between stages of mineral growth melt was trapped or percolated along these microstructures and later on necking down phenomena individualized inclusions with negative crystal shape melt inclusions in biotite are abundant show negative crystal shape and parallel cleavage planes melt inclusions in cordierite alkali feldspar and ilmenite are isolated sparse and sometimes rather large the composition of glass from all mi is leucogranitic and peraluminous with small differences among glasses in each mineral host there is some variation in glass composition within each textural location as well compositional heterogeneity can be partially explained by a combination of processes such as generation of boundary layers during mineral growth crystallization of daughter phases and hydrogen loss via diffusion through the host mean glass compositions in the several textural locations however can be tentatively interpreted as reflecting the evolution of melt chemistry during the prograde low to medium pressure anatexis of quartz poor metapelites

martian south polar cap boundary 1971 and 1973 data abstract international planetary patrol photographs of mars obtained during the 1971 and 1973 apparitions have been used to produce regression curves for the martian south polar cap for those years useful data span the range in areocentric longitude l s 186 261 in 1971 and l s 255 301 in 1973 these regression curves are compared to the 1977 regression curve obtained from viking observations and to the results of 1956 observations there is remarkable consistency between the 1971 ipp and 1977 viking data points and the 1973 regression does not appear to have differed significantly from those of 1971 or 1977

the martian dust storm of sol 1742 after nearly five earth years on mars the mutch memorial station viking lander 1 finally witnessed a local dust storm that eroded trenches conical piles and other disturbed surfaces in the sample field and near the lander the event called the dust storm of sol 1742 occurred late in the third winter of lander observations between sols 1728 and 1757 analyses of tiny new wind tails and movement of materials indicate that the eroding winds were variable but more northeasterly than those that had previously shaped the surface pebbly residues and movement of 4 5 mm clods suggest drag velocities or friction speeds of the winds were about 2 2 4 0 m s wind speeds at the height of the meteorology boom 1 6 m were probably about 40 50 m s much of the observed erosion could have occurred in a few to several tens of seconds but somewhat longer times are suggested by analogy with the erosion of terrestrial soils most of the erosion occurred where preexisting equilibrium conditions of surface configurations and surface material properties had been altered by the lander during landing and during surface sampler activities but thin layers of bright fine grained dust were also removed and redistributed surfaces where preexisting equilibrium conditions were unaltered appeared to be uneroded

mars surface pressure tides and their behavior during global dust storms simulations of mars atmospheric tides with the nasa ames mars general circulation model are presented and analyzed in an annual simulation diurnal and semidiurnal tides in the model s surface pressure field are shown to compare well with tides observed by the viking landers throughout the mars year focused simulations of global dust storms during the northern winter season show a semidiurnal tide that responds very strongly to the increased dust load during the storms again matching well with observations analysis of the structure and behavior of this tide during global storms verifies that it is dominated by the gravest symmetric hough mode h22 as has been noted previously however it is shown here that additional symmetric and asymmetric modes play an important role in accounting for the structure of the tide and its variation during the dust storms the phase advance observed between the viking lander sites earlier semidiurnal phase at the higher latitude site is explained by the presence of these higher order modes finally decomposition of the semidiurnal tide during a global dust storm into its component hough modes shows that the amplitude of the h22 mode mirrors changes in the observed overhead visible dust opacity while variations in higher order modes are indicative of the zonal and possibly longitudinal distribution of airborne dust

observations of martian surface winds at the viking lander 1 site partial failure of the wind instrumentation on the viking lander 1 vl1 in the martian sub tropics 22 5 n has limited previous analyses of meteorological data for this site we describe a method for reconstructing surface winds using data from the partially failed sensor and present and analyze a time series of wind pressure and temperature at the site covering 350 mars days sols at the beginning of the mission during early summer winds were controlled by regional topography but they soon underwent a transition to a regime controlled by the hadley circulation diurnal and semidiurnal wind oscillations and synoptic variations have been analyzed and compared with the corresponding variations at the viking lander 2 middle latitude site 48 n diurnal wind oscillations were controlled primarily by regional topography and boundary layer forcing although a global mode may have been influencing them during two brief episodes semidiurnal wind oscillations were controlled by the westward propagating semidiurnal tide from sol 210 onward comparison of the synoptic variations at the two sites suggests that the same eastward propagating wave trains were present at both sites at least following the first 1977 great dust storm but discordant inferred zonal wave numbers and phase speeds at the two sites cast doubt on the zonal wave numbers deduced from analyses of combined wind and pressure data particularly at the vl1 site where the signal to noise ratio of the dominant synoptic waves is relatively small

inference of dust opacities for the 1977 martian great dust storms from viking lander 1 pressure data abstract a eddington radiative transfer algorithm is used to compute the thermal tidal heating of a dusty martian atmosphere for a given set of dust optical depth effective single scattering albedo and phase function asymmetry parameter the resulting thermal tidal forcing is used in a classical atmospheric tidal model to compute the amplitudes of the surface pressure oscillations at the viking lander 1 site for the two 1977 martian great dust storms parametric studies show that the dust opacities and optical parameters derived from the viking lander imaging data are roughly representative of the global dust haze needed to reproduce the tidal surface pressure amplitudes also observed at lander 1 except that the model inferred asymmetry parameter is smaller during the onset of a great storm the observed preferential enhancement during dust storm onset of the semidiurnal tide at viking lander 1 relative to its diurnal counterpart is shown to be due primarily to the elevation of the tidal heating source in a very dusty atmosphere although resonant enhancement of the main semidiurnal tidal mode makes an important secondary contribution

refractory inclusions in the prototypical cm chondrite mighei abstract refractory inclusions in the mighei cm2 meteorite are very abundant 35 being found in three thin sections of the meteorite the most common are pyroxene rimmed spinel rich inclusions that occur in a range of structural and textural types some inclusions are simple aggregates of crystals or rimmed crystals ranging from loose clusters of spinel grains to distended chains of pyroxene rimmed spinel knots others are more compact and may have experienced recrystallization or melting these include nodular spinel inclusions with polygonal granular textured spinel interiors and pyroxene rims ribbons of spinel in some cases with hibonite and or perovskite that are again rimmed by pyroxene and refractory spherules four inclusions are complex aggregates of several texturally distinct objects each collectively mighei inclusions are similar to those in murchison but appear to be somewhat more altered volatility fractionated and unfractionated trace element patterns similar to those found in refractory inclusions in other carbonaceous chondrites are represented in mighei inclusions and in addition some mighei inclusions have volatility fractionated pattern types not previously found in refractory inclusions in three of the complex aggregates fundamentally different trace element patterns are present within different portions of each inclusion meaning that these objects accreted from genetically different components that never equilibrated with one another subsequent to accretion bulk inclusion magnesium isotopic compositions show minor mass fractionation effects fmg values range from 2 3 to 7 5 but the average fmg value is indistinguishable from normal 1 8 1 2 there are no correlations between magnesium isotopic composition and textural type or trace element pattern type the diverse inclusion types in mighei represent a variety of origins and histories textures suggest that the nodular and banded inclusions may have experienced solid state recrystallization whereas the porous and chain like varieties and complex aggregates have not magnesium isotopic compositions and trace element abundances suggest that the mighei inclusions are unlikely to be evaporation residues and are more likely to be the products of condensation or recondensation processes

two major dust storms one mars year apart comparison from viking data the viking mars landers have been on the mars surface for over two mars years during the first year two major probably global dust storms occurred the first was unusually early compared to most previous earth based observations a major storm occurred during the second year almost precisely one year after the first storm of the first year meteorological data show roughly similar atmospheric behavior for the two early storms of particular note is the increase in amplitude of pressure oscillations probably of baroclinic origin and concurrent increases in wind speed during the build up phase of all three storms the generation of these waves appears to be a natural consequence of seasonal effects not associated with the dust storms it is suggested that baroclinic waves should they exist in the southern hemisphere during the time of dust storm generation could be an important factor in growth and development of the dust storms

initial results from radio occultation measurements with mars global surveyor a series of radio occultation experiments conducted with mars global surveyor in early 1998 has yielded 88 vertical profiles of the neutral atmosphere the measurements cover latitudes of 29 n to 64 s and local times from 0600 through midnight to 1800 during early summer in the southern hemisphere ls 264 308 retrieved profiles of pressure and temperature versus radius and geopotential extend from the surface to the 10 pa pressure level near surface uncertainties in temperature and pressure are about 1 k and 2 pa respectively far smaller than in previous radio occultation measurements at mars the profiles resolve the radiative convective boundary layer adjacent to the surface and also reveal gravity waves particularly at northern and equatorial latitudes which appear to be breaking in some cases distinctive meridional gradients of pressure and temperature indicate the presence of a low altitude westerly jet at latitudes of 15 30 s at southern summer solstice this jet appears in predictions of general circulation models in connection with the strong seasonal cross equatorial hadley circulation the pressure gradient at 2 km altitude implies a wind speed of 33 m s 1 stronger than predicted which may help explain the occurrence of numerous local dust storms within this latitude band in late southern spring these measurements also characterize the response of the atmosphere to stationary thermal forcing at midsouthern latitudes where high terrain south of tharsis and low terrain in hellas planitia produce large zonal temperature variations in the lowest scale height above the surface pressure measured at constant geopotential decreases at an average rate of 0 13 per degree ls due primarily to condensation of co2 at the north pole

comagmatic granophyric granite in the fish canyon tuff colorado implications for magma chamber processes during a large ash flow eruption the 27 8 ma fish canyon tuff a vast ash flow sheet 5000 km 3 of uniform phenocryst rich dacite is representative of monotonous intermediate eruptions from a magma chamber that lacked compositional gradients sparse small fragments of comagmatic granophyre in late erupted tuff and postcaldera lava having mineral compositions indistinguishable from phenocrysts in the tuff and precaldera lava like rocks record complex events in the fish canyon chamber just prior to eruption sanidine phenocrysts in the granophyre preserve zoning evidence of mingling with andesitic magma then shattering by decompression and volatile loss accompanying early fish canyon eruptions before overgrowth by granophyre the textural and chemical disequilibria indicate that the eruption resulted from batholith scale remobilization of a shallow subvolcanic chamber contrary to previous interpretations of magma storage and phenocryst growth in the lower crust

atmospheric tides on venus iii the planetary boundary layer abstract diurnal solar heating of venus surface produces variable temperatures winds and pressure gradients within a shallow layer at the botton of the atmosphere the corresponding asymmetric mass distribution experiences a tidal torque tending to maintain venus slow retrograde rotation it is shown that including viscosity in the boundary layer does not materially affect the balance of torques on the other hand friction between the air and ground can reduce the predicted wind speeds from 5 to 1 m sec in the lower atmosphere more consistent with the observations from venus landers and descent probes implications for aeolian activity on venus surface and for future missions are discussed

further observations of regional dust storms and baroclinic eddies in the northern hemisphere of mars abstract we have investigated the near surface meteorology in the northern hemisphere of mars through detailed analysis of data obtained with mars global surveyor in january august 2005 the season in the northern hemisphere ranged from midsummer through winter solstice of mars year my 27 we examined composite wide angle images from the mars orbiter camera and compiled a catalog of the dust storms that occurred in this interval as in previous martian years activity in the northern hemisphere was dominated by regional flushing dust storms that sweep southward through the major topographic basins most frequently in acidalia planitia we also used atmospheric profiles retrieved from radio occultation experiments to characterize eddy activity near the surface at high northern latitudes there are strong correlations between the two sets of observations which allowed us to identify three factors that influence the timing and location of the regional dust storms 1 transitions among baroclinic wave modes which strongly modulate the intensity of meridional winds near the surface 2 storms zones which impose strong zonal variations on the amplitude of some baroclinic eddies and 3 stationary waves which further modulate the wind field near the surface the flushing dust storms ceased abruptly in midautumn possibly in response to source depletion co 2 condensation a shift in the period of the baroclinic eddies and changes in the tidal wind field near the surface our results extend the meteorological record of the northern hemisphere substantiate the findings of previous investigations and further illuminate the climatic impact of baroclinic eddies