regionally differentiated contribution of mountain glaciers and ice caps to future sea level rise the contribution to sea level rise from mountain glaciers and ice caps has grown over the past decades a projection of their melting during the twenty first century based on temperature and precipitation projections from ten climate models suggests that by 2100 these glaciers will lose about 21 of their total global volume

mantle phase changes and deep earthquake faulting in subducting lithosphere inclined zones of earthquakes are the primary expression of lithosphere subduction a distinct deep population of subduction zone earthquakes occurs at depths of 350 to 690 kilometers at those depths ordinary brittle fracture and frictional sliding the faulting processes of shallow earthquakes are not expected a fresh understanding of these deep earthquakes comes from developments in several areas of experimental and theoretical geophysics including the discovery and characterization of transformational faulting a shear instability connected with localized phase transformations under nonhydrostatic stress these developments support the hypothesis that deep earthquakes represent transformational faulting in a wedge of olivine rich peridotite that is likely to persist metastably in coldest plate interiors to depths as great as 690 km predictions based on this deep structure of mantle phase changes are consistent with the global depth distribution of deep earthquakes the maximum depths of earthquakes in individual subductions zones and key source characteristics of deep events

retrograde methane dominated fluid inclusions from high temperature granulites of rogaland southwestern norway non aqueous inclusions in the high grade 800 1 000c 4kbar metamorphic rogaland region southwestern norway consist of mixtures of co sub 2 ch sub 4 n sub 2 in particular the fluid inclusions in quartz veins in migmatites are characterized by high ch sub 4 concentrations and they were re equilibrated at temperatures below 500c during isobaric cooling observations by microthermometry demonstrated several complicated sequences of phase transitions including partial and metastable homogenization at lower temperature than melting and s l or s v transitions the phase behavior reflects a wide variation in composition and molar volume fluid compositions were measured by raman microspectrometry by this method also small amounts of graphite have been detected in co sub 2 ch sub 4 inclusions the instantaneous formation of graphite in a co sub 2 ch sub 4 inclusion by induction of the argon laser beam has been observed which points to the metastability of the co sub 2 ch sub 4 mixture the calculated densities of the observed fluid mixtures are relatively low necessitating a revision of the earlier interpretation of these inclusions as containing pure high density fluids inclusions in quartz trapped after the peak of metamorphism record fluid heterogeneity which may present evidence for fluid deficient metamorphism during the retrograde m2 m3 metamorphism

fluid inclusion evidence for immiscibility in magmatic differentiation abstract after a brief review of recent work on melt inclusions in diamond and in normal magmatic environments the nature of the fluid inclusion evidence for various stages of magmatic immiscibility is summarized during magmatic differentiation by crystal fractionation from originally low volatile content silicate melts yielding normal plutonic rocks through hydrous silicate melts yielding pegmatites to late stage water rich fluids yielding quartz veins and ore deposits the composition of the residual liquid changes drastically in some geologic environments this change in composition of the residual liquid may be continuous with no phase change in the fluid part of the system under most natural conditions however it is far more likely to have one or more stages in the evolution during which globules of a separate new immiscible fluid phase exsolve the term immiscibility is used here in its more general sense to refer to the existence at equilibrium of two or more non crystalline polycomponent solutions fluids differing in properties and generally in composition i believe that the great bulk of the magmatic inclusions that are being studied today have come about through the intervention of one or more such stages of immiscible fluid separation i e magmatic differentiation by fluid immiscibility examples include silicate melt dense co2 fluid silicate melt sulfide melt silicate melt silicate melt silicate melt low density vapor i e vesiculation and as presented in more detail in this paper various stages of silicate melt hydrous saline melt aqueous fluid co2 fluid immiscibility generally only parts of these stages are recorded by the trapping of fluid inclusions and the interpretation of the inclusion record is commonly ambiguous and difficult particularly that stage between hydrous silicate melts and the hydrous saline melts and aqueous solutions responsible for many ore deposits the ambiguity results mainly from problems of inclusion origin and nonrepresentative trapping within any given individual inclusion thus the probability of trapping of only one vs various amounts of two immiscible fluids or of trapping solid phases along with the fluid present severe difficulties in addition there is the almost universal superposition of various stages of trapping of fluids within any given sample these problems can only be approached by very careful petrography and analysis of optimum material combined with field data and experimental p v t x studies of pertinent systems completely unequivocal statements of the course of evolution of the fluids in such natural systems may never be possible

a new self organizing mechanism for deep focus earthquakes the mechanism of deep focus earthquakes has been a puzzle since their discovery almost 70 years ago1 2 because brittle fracture and frictional sliding at depths in excess of 100 200 km would require unrealistic rock strengths3 4 rock strength does increase with pressure but a few hundred mpa equivalent to 10 20 km depth suffices to inhibit most fracture and elevated temperature activates ductile mechanisms that operate at stresses less than the fracture stength a range of mechanisms has been proposed for deep earthquakes including plastic instabilities5 7 shear induced melting8 11 and instabilities accompanying recrystallization12 13 or polymorphic phase transformation14 23 each of these proposed mechanisms has exhibited certain inherent weaknesses see kirby22 for review and discussion here we report experimental observations of high pressure faulting of metastable mg2geo4 olivine as it undergoes incipient transformation to a spinel 24 25 structure we present a model in which this faulting arises from the generation propagation and linking up of spinel filled anticracks26 when applied to the olivine spinel transformation in the earth s mantle the anticrack model27 satisfactorily accounts for the similarities and differences between shallow and deep earthquakes and removes the problems associated with frictional sliding

ammonium partitioning and nitrogen isotope fractionation among coexisting micas during high temperature fluid rock interactions examples from the new england appalachians abstract despite recent advances in the field of n isotope geochemistry our understanding of the behavior of this element in the solid earth remains limited by a lack of fundamental information regarding the partitioning of ammonium and isotopic fractionation of n among coexisting mineral and fluid phases study of n behavior in regionally metamorphosed rocks provides the opportunity to assess intermineral nh 4 partitioning and n isotope fractionation among coexisting micas during metamorphism and affords an application of the n system as a tracer of high t fluid rock interactions analyzed mica samples range in 15 n air from 3 3 to 11 9 and contain 9 to 1820 ppm n the outcrop at townshend dam vermont allows examination of n behavior across strike on a relatively small scale and samples from western maine demonstrate the effect of varying metamorphic conditions on n behavior in metapelites 15 n bt w mica 15 n biotite 15 n white mica ranges from 0 9 to 2 7 for all samples from both suites mean 0 36 with 1 0 79 with samples containing a separate paragonite white mica phase showing the greatest range 0 12 to 1 02 mean 0 58 1 1 03 thirteen samples containing only na poor muscovite six from townshend dam seven from western maine have mean 15 n bt w mica of 0 07 1 0 41 in both suites biotite nearly always contains more n than coexisting white mica but n w mica n bt also shows some significant scatter mean n w mica n bt 0 46 with 1 0 34 the thirteen samples containing only a na poor muscovitic white mica phase have mean n w mica n bt 0 39 with 1 0 26 similar to that reported by others for other metamorphic suites containing only muscovite as the white mica phase there is no obvious suggestion of equilibrium n isotopic fractionation among coexisting micas at epidote amphibolite to amphibolite facies metamorphic conditions although nh 4 appears to partition systematically among coexisting biotite and white mica significant scatter in both 15 n bt w mica and nh 4 partitioning conceivably the result of differential closure to exchange during cooling or of retrograde replacements could however obscure observation of small equilibrium intermica fractionations related to the characteristics of the interlayer sites in which nh 4 resides samples most unlike the mean in both 15 n bt w mica and n w mica n bt contain abundant chlorite some of which is likely retrograde based on petrographic observations chl chl bt 0 3 thus retrograde replacement of biotite by chlorite may have been accompanied by fluid mineral n isotope exchange perhaps involving the production of fine grained retrograde n bearing white mica observed petrographically for some samples it is also possible that sampling at scales greater than those of n isotope equilibrium domains e g across fine interlayers results in some scatter because of varying relative modal proportions of the two micas in adjacent fine interlayers although further investigation of the extent of retrograde reequilibration of mica n systematics is warranted the observed lack of systematic n isotope fractionation among coexisting micas and the reasonably systematic nh 4 partitioning data for these phases provide important preliminary constraints for attempts to model n isotope behavior in fluid rock systems these results and other attempts to calibrate n isotope fractionation through field studies point to the conspicuous lack of experimentally determined mica fluid n isotope fractionation factors

topographic context of glaciers and perennial snowfields glacier national park montana abstract equilibrium line altitudes elas of modem glaciers in the northern rocky mountains are known to correspond with regional climate but strong subregional gradients such as across the continental divide in glacier national park montana also exert topoclimatic influences on the ela this study analyzed the relationships between glacier and snowfield morphology ela and surrounding topography glaciers and perennial snowfields were mapped using multitemporal satellite data from the landsat thematic mapper and aerial photography within an integrated geographic information system gis relationships between glacier morphology and ela were investigated using discriminant analysis four morphological categories of perennial snow and ice patches were identified cirque glacier niche glacier ice cap and snowfield ela was derived from overlaid glacier boundaries and digital elevation models dems within the gis dems provided topographic variables and models of solar radiation and wind exposure shelteredness regression analysis showed the effects of exposure on snow accumulation the strong influence of local topography through upslope zone morphology such as cirque backwalls and the tendency for glaciers with high elas to exhibit compactness in morphology results highlight the relatively compact shape and larger area of glaciers adjacent to the continental divide discriminant analysis correctly predicted the type of glacier morphology in more than half the observations using factored variables of glacier shape elevation range and upslope area

a new satellite derived glacier inventory for western alaska glacier inventories provide the baseline data to perform climate change impact assessment on a regional scale in a consistent and spatially representative manner in particular a more accurate calculation of the current and future contribution to global sea level rise from heavily glacierized regions such as alaska is much needed we present a new glacier inventory for a large part of western alaska including kenai peninsula and the tordrillo chigmit and chugach mountains derived from nine landsat thematic mapper scenes acquired between 2005 and 2009 using well established automated glacier mapping techniques band ratio because many glaciers are covered by optically thick debris or volcanic ash and partly calve into water outlines were manually edited in these wrongly classified regions during post processing in total we mapped 8830 glaciers 0 02 km2 with a total area of 16 250 km2 large parts of the area 47 are covered by a few 31 large 100 km2 glaciers while glaciers less than 1 km2 constitute only 7 5 of the total area but 86 of the total number we found a strong dependence of mean glacier elevation on distance from the ocean and only a weak one on aspect glacier area changes were calculated for a subset of 347 selected glaciers by comparison with the digital line graph outlines from the us geological survey the overall shrinkage was 23 between 1948 57 and 2005 09

challenges and recommendations in mapping of glacier parameters from space results of the 2008 global land ice measurements from space glims workshop boulder colorado usa on 16 18 june 2008 the us national snow and ice data center held a glims workshop in boulder co usa focusing on formulating procedures and best practices for operational glacier mapping using satellite imagery despite the progress made in recent years there still remain many cases where automatic delineation of glacier boundaries in satellite imagery is difficult error prone or time consuming this workshop identified six themes for consideration by focus groups 1 mapping clean ice and lakes 2 mapping ice divides 3 mapping debris covered glaciers 4 assessing changes in glacier area and elevation through comparisons with older data 5 digital elevation model dem generation from satellite stereo pairs and 6 accuracy and error analysis talks presented examples and work in progress for each of these topics and focus groups worked on compiling a summary of available algorithms and procedures to address and avoid identified hurdles special emphasis was given to establishing standard protocols for glacier delineation and analysis creating illustrated tutorials and providing source code for available methods this paper summarizes the major results of the 2008 glims workshop with an emphasis on definitions methods and recommendations for satellite data processing while the list of proposed methods and recommendations is not comprehensive and is still a work in progress our goal here is to provide a starting point for the glims regional centers as well as for the wider glaciological community in terms of documentation on possible pitfalls along with potential solutions

hasty retreat of glaciers in northern patagonia from 1985 to 2011 mapping changes in glacier extent from repeat optical satellite data has revealed widespread glacier decline in nearly all regions of the world over the past few decades while numerous studies have documented the changes of the outlet glaciers of the northern and southern patagonia icefields npi spi information about glacier changes in the patagonian andes to the north of the npi is much scarcer here we present an assessment of area changes for glaciers mainly located in the palena district of chile based on glacier inventories for 1985 2000 and 2011 that were derived from two consecutive landsat scenes and a digital elevation model the analysis revealed a dramatic area decline for the largest glaciers and total area loss of 25 from 1985 to 2011 the lower parts of several larger glaciers 10 km 2 melted completely area loss below 1000 m elevation was 50 100 in both periods and 374 glaciers out of 1664 disappeared the number of proglacial lakes increased from 223 to 327 and their area expanded by 11 6 km 2 59 between 1985 and 2011 seasonal snow persisting at high elevations in the 2011 scene was a major obstacle to glacier delineation so the obtained area change rate of 1 a 1 over the entire period is a lower bound estimate the observed climate trends e g cooling in puerto montt are in contrast to the observed shrinkage

compilation of a glacier inventory for the western himalayas from satellite data methods challenges and results abstract due to their sensitive reaction to changes in climatic conditions glaciers have been selected as an essential climate variable ecv although a large amount of ice is located in the himalayas this region is yet only sparsely represented in global glacier databases accordingly a sound and comprehensive change assessment or determination of water resources was not yet possible in this study we present a new glacier inventory for the western himalayas compiled from landsat etm scenes acquired between 2000 and 2002 coherence images from alos palsar image pairs the srtm digital elevation model dem and the aster global dem gdem several specific challenges for glacier mapping were found in this region and addressed they are related to debris cover orographic clouds locally variable snow conditions and creeping permafrost features in cold dry regions additional to seven topographic parameters that are obtained from the aster gdem for each glacier we also determined the relative amount of debris cover on the glacier surface the inventory contains 11 400 glaciers larger than 0 02 km2 which cover a total area of 9 310 km2 analysis of the inventory data revealed characteristic patterns of mean glacier elevation and relative debris cover amounts that might be related to the governing climatic conditions the full dataset will be freely available in the glims glacier database to foster further analyses and modeling of the glaciers in this region

improved estimates of glacier change rates at nevado coropuna ice cap peru accurate quantification of rates of glacier mass loss is critical for managing water resources and for assessing hazards at ice clad volcanoes especially in arid regions like southern peru in these regions glacier and snow melt are crucial dry season water resources in order to verify previously reported rates of ice area decline at nevado coropuna in peru which are anomalously rapid for tropical glaciers we measured changes in ice cap area using 259 landsat images acquired from 1980 to 2014 we find that coropuna ice cap is presently the most extensive ice mass in the tropics with an area of 44 1 km 2 and has been shrinking at an average area loss rate of 0 409 km 2 a 1 0 71 a 1 since 1980 our estimated rate of change is considerably lower than previous studies 1 4 km 2 a 1 or 2 43 a 1 but is consistent with other tropical regions such as the cordillera blanca located 850 km to the nw 0 68 a 1 thus if glacier recession continues at its present rate our results suggest that coropuna ice cap will likely continue to contribute to water supply for agricultural and domestic uses until 2120 which is nearly 100 years longer than previously predicted

grain size evolution in subducted oceanic lithosphere associated with the olivine spinel transformation and its effects on rheology we investigate the role of grain size reduction during the olivine spinel transformation on rheological properties of subducting slabs on the basis of a scaling model for microstructural development during nucleation and growth in this model the size of spinel grains nucleating at olivine grain boundaries is controlled by the relative rates of nucleation and growth taking into account the impingement through the collision of grains due to growth when the volume fraction of spinel reaches a certain threshold value critical volume fraction 1 10 depending on the p t conditions in the slab the new phase will form a continuous film and will significantly reduce the strength of the two phase aggregate if spinel grain size is small the size of spinel grains d at this stage is calculated and is shown to be highly sensitive to 0 size and 2 a subducting slab has a complicated rheological structure containing a weak region below the tip of a metastable olivine bearing wedge in a cold slab possible implications of these anomalous rheological structures of slabs on the dynamics of subduction are discussed including the mechanisms of deep earthquakes

mechanisms of transformation and deformation in mg1 8fe0 2sio4 olivine and wadsleyite under non hydrostatic stress abstract we have studied the effect of non hydrostatic stress on the mechanisms of the olivine wadsleyite ringwoodite phase transformations and deformation mechanisms of olivine and wadsleyite at high pressure experiments were performed at 900 c in the stability field 15 gpa for 0 5 h and in the stability field 16 gpa for 11 h using a multianvil apparatus with san carlos olivine as the starting material a sample assembly designed to produce non hydrostatic stress was used the deformed samples have been characterised using optical and transmission electron microscopy remnant olivine contains high densities of mostly c dislocations and deformation occurs by dislocation glide involving the slip systems 010 001 and 100 001 in wadsleyite dislocations are in a climb configuration which suggests that self diffusion of si and or o is much faster in wadsleyite than in olivine at 900 c wadsleyite also contains 010 stacking faults which are interpreted to be growth defects that anneal out with time during the olivine wadsleyite transformation non hydrostatic stress results in anisotropic reaction textures wadsleyite nucleates preferentially on olivine grain boundaries that are oriented at a high angle to the direction of principal compressive stress and or the growth of wadsleyite occurs preferentially in this direction wadsleyite transforms to ringwoodite by two competing mechanisms i coherent intracrystalline nucleation on a dislocations probably where they intersect 010 stacking faults and ii partially coherent nucleation at wadsleyite grain boundaries non hydrostatic stress enhances transformation rates by increasing the density of dislocations which act as nucleation sites for ringwoodite although the samples were partially reacted under non hydrostatic stress there is no evidence for transformational faulting

fluid inclusions in granulite facies metapelites of the hercynian ancient lower crust of the serre calabria southern italy investigations of fluid inclusions in granulitefacies metapelites of southern calabria enable characterization of the fluid composition of these lower crustal rocks and constrain the petrologically deduced retrograde p t path characterized by isothermal uplift prior to isobaric cooling in middle crustal levels fluid inclusions in cordierite garnet and sillimanite have a co2 rich composition inclusions in cordierite rarely contain minor amounts of n2 and h2o and in garnets some co2 ch4 n2 inclusions have been analyzed by raman microprobe quartz reveals the most complex fluid melusion compositions 1 co2 rich 2 co2 ch4 n2 3 ch4 n2 4 h2o mgcl2 cacl2 nacl 5 h2o nacl and 6 h2o co2 the earliest fluid inclusions after peak metamorphism are rich in co2 with minor amounts of n2 and h2o an early co2 h2o n2 fluid composition has been confirmed by detection of co2 h2o and n2 in the channels of the cordierite structure most of the early co2 rich fluid inclusions were modified during the uplift from the lower to the middle crustal level resulting in a density decrease with co2 still dominant the subsequent isobaric cooling led to further modifications of the fluid inclusions high density inclusions around implosion textures or scattered amongst lower density ones must have formed during this cooling episode aqueous inclusions in quartz are mostly formed late and are consistent with trapping during retrograde rehydration

package fluids 1 computer programs for analysis of fluid inclusion data and for modelling bulk fluid properties the computer package fluids contains five sets of computer programs written in c for the calculation of fluid properties both model fluids and data from fluid inclusions can be analysed in the programs bulk density molar volume and composition of fluid inclusions are calculated with the program bulk which uses microthermometric data micro raman spectroscopic data cation ratios and volume fraction estimations as input the program offers a broad variety of equations of state which are selected according to the fluid system or the temperature and pressure conditions of interest the isochores that correspond to the output or test v x properties of fluid inclusions are calculated by the program isoc in calculating the isochores this program takes account of the compressibility and expansion of selected host minerals the program test allows different equations of state to be compared directly with experimental data thereby facilitating selection of the most adequate model in the programs bulk and isoc loner is a group of programs that handle individual equations of state eos for all fluid systems presented in the programs bulk and isoc aqso is a group of programs that allows purely empirical modelling of electrolyte bearing aqueous solutions henry s law for dilute gas bearing aqueous solutions and osmotic coefficients for dilute electrolyte bearing aqueous solutions the programs are available on the university of leoben web site at http www unileoben ac at buero62 minpet ronald

mobility and h2o loss from fluid inclusions in natural quartz crystals petrographic observations on quartz crystals from the mole granite australia and other localities shed new light on the mechanisms of post entrapment modification of fluid inclusions these modifications include migration away from pseudosecondary trails changes in fluid salinity and density shape distortion and the formation of sweat haloes around strongly deformed inclusions increases in fluid salinity which usually are associated with inclusion migration indicate water losses of up to 50 however la icp ms analysis of unmobilized and mobilized inclusions of the same trail reveals basically unchanged ratios of major and trace element cations with the exception of li which seems to be incorporated into the crystal lattice during migration despite the fact that all these modifications are closely related to deformation processes they occur not only in mechanically deformed quartz but also in free standing crystals in the latter samples stress has been generated internally as a result of brazil twinned growth and compositional zonation these observations and their interpretation leads to a list of practical criteria that should help in differentiating between reliable and suspect fluid inclusions in other samples

two types of deep seismicity in subducting slabs the relation between variation of seismic activity with depth and temperature structure in the subducting slabs in five subduction zones kuril ne japan izu bonin mariana and tonga is investigated when the temperature of the core of the slab at depths of 300 350 km is higher than the kinetic cut off temperature of the olivine spinel phase transformation there is no seismicity maximum in the slab below that depth range when the temperature of the core of the slab at 300 350 km depths is lower than the kinetic cut off temperature there is a depth range of relatively high seismic activity in the slabs moreover estimated temperature in the depth range of relatively high seismicity is near the kinetic cut off temperature it is inferred that the phase transformation of meta stable olivine triggers deep earthquakes and causes high seismic activity below the depths of 300 350 km in relatively low temperature slabs when the phase transformation is the cause of deep earthquakes in relatively high temperature slabs however it is considered that the phase transformation occurs in nearly equilibrium conditions and meta stable olivine does not exist other mechanisms in addition to the phase transformation are required to explain observed deep seismicity especially in relatively high temperature slabs

modeling glacier thickness distribution and bed topography over entire mountain ranges with glabtop application of a fast and robust approach 1 the combination of glacier outlines with digital elevation models dems opens new dimensions for research on climate change impacts over entire mountain chains of particular interest is the modeling of glacier thickness distribution where several new approaches were proposed recently the tool applied herein glabtop glacier bed topography is a fast and robust approach to model thickness distribution and bed topography for large glacier samples using a geographic information system gis the method is based on an empirical relation between average basal shear stress and elevation range of individual glaciers calibrated with geometric information from paleoglaciers and validated with radio echo soundings on contemporary glaciers it represents an alternative and independent test possibility for approaches based on mass conservation and flow as an example for using glabtop in entire mountain ranges we here present the modeled ice thickness distribution and bed topography for all swiss glaciers along with a geomorphometric analysis of glacier characteristics and the overdeepenings found in the modeled glacier bed these overdeepenings can be seen as potential sites for future lake formation and are thus highly relevant in connection with hydropower production and natural hazards the thickest ice of the largest glaciers rests on weakly inclined bedrock at comparably low elevations resulting in a limited potential for a terminus retreat to higher elevations the calculated total glacier volume for all swiss glaciers is 75 22 km3 for 1973 and 65 20 km3 in 1999 considering an uncertainty range of 30 these results are in good agreement with estimates from other approaches

localized polymorphic phase transformations in high pressure faults and applications to the physical mechanism of deep earthquakes earthquake mechanisms based on frictional instabilities are widely accepted for relatively shallow earthquakes such mechanisms in unmodified form are highly unlikely for deep earthquakes because of the expected high frictional shear stresses at depths of 300 700 km several alternative mechanisms have been proposed here i discuss a new type of shear instability observed in experiments on ordinary polycrystalline ice and polycrystalline tremolite by my colleagues and me these shear instabilities lead to rapid stress drops and sound emissions and have the following characteristics 1 a single sharp shear zone forms in the maximum shear stress orientation 2 confining pressure does not suppress the instability and under some conditions raising confining pressure pc lowers the differential stress at which it occurs 3 stress drops can occur repeatedly after reloading at about the same differential stress 4 the mean stress vs temperature conditions at which the instabilities occur in ice and tremolite place them in the fields of thermodynamic stability of ice ii and diopside talc respectively although i have not as yet confirmed the existence of these high pressure phases in the shear zones transformation in the shear zone is implicated because such shear instabilities do not occur in similar materials in which polymorphic phase changes do not occur reconstructive polymorphic phase changes localized along shear zones may be a general phenomenon in crystalline materials stressed non hydrostatically near transition boundaries moreover by analogy the reconstructive phase transformations that are thought to occur in deeply subducted lithosphere may lead to localized shear instabilities manifested by deep earthquakes and produce the observed double couple first motion distribution finally if this is the earthquake source mechanism in deeply subducted lithosphere then earthquakes should shut off when all of the polymorphic phase changes have occurred this may explain the maximum depth of earthquakes at about 680 km

subsurface iceberg melt key to greenland fjord freshwater budget liquid freshwater fluxes from the greenland ice sheet affect ocean water properties and circulation on local regional and basin wide scales with associated biosphere effects the exact impact however depends on the volume timing and location of freshwater releases which are poorly known in particular the transformation of icebergs which make up roughly 30 50 of the loss of the ice sheet mass to liquid freshwater is not well understood here we estimate the spatial and temporal distribution of the freshwater flux for the helheim sermilik glacier fjord system in southeast greenland using an iceberg melt model that resolves the subsurface iceberg melt by estimating seasonal variations in all the freshwater sources we confirm quantitatively that iceberg melt is the largest annual freshwater source in this system type we also show that 68 78 of the iceberg melt is released below a depth of 20 m and seasonally about 40 100 of that melt is likely to remain at depth in contrast with the usual model assumptions iceberg melt also peaks two months after all the other freshwater sources peak our methods provide a framework to assess individual freshwater sources in any tidewater system and our results are particularly applicable to coastal regions with a high solid ice discharge in greenland iceberg melt is the largest annual freshwater source in a south greenland fjord with release largely below 20 m depth according to iceberg model simulations furthermore iceberg melt peaks later in the year than other sources of freshwater

kinetics of the olivine spinel transformation in subducting lithosphere experimental constraints and implications for deep slab processes abstract the persistence of metastable olivine to depths greater than 400 km in subducting slabs has implications for the generation of deep focus earthquakes the magnitude of buoyancy forces driving plate motion and the state of stress in the slab the depth to which metastable olivine can survive in a subduction zone and the depth interval over which transformation to or mg fe 2sio4 occurs have been evaluated from experimental kinetic data for the mg2geo4 and ni2sio4 transformations and the mg2sio4 transformation the data were extrapolated using a kinetic model for grain boundary nucleation and interface controlled growth under non isothermal and non isobaric conditions the results predict that metastable mg1 8fe0 2sio4 olivine survives to depths greater than 500 km in the cold interior of rapidly subducting slabs of old lithosphere the onset of transformation to mg fe 2sio4 spinel depends only on growth kinetics and coincides with the 550 50 c isotherm including the effects of latent heat production causes the transformation to occur by a runaway process over a very narrow depth interval at the onset of transformation high nucleation rates and low growth rates are consistent with the formation of very fine grained reaction products which are required for the transformational faulting mechanism of deep focus earthquakes when olivine crosses the equilibrium boundaries at higher temperatures e g higher than 700 c at 400 km depth transformation to or occurs much closer to equilibrium at a depth controlled by nucleation kinetics in this case the effect of latent heat production on the transformation kinetics is small and microstructural evolution is unlikely to result in transformational faulting below the depth of olivine breakdown cold slabs are likely to have a complex rheological structure owing to temperature dependent microstructural evolution during the phase transformation

the effect of strain energy on growth rates during the olivine spinel transformation and implications for olivine metastability in subducting slabs we have studied growth kinetics during the transformation of mg1 8fe0 2sio4 san carlos olivine to its high pressure polymorphs wadsleyite phase and ringwoodite phase at 800 1200 c and nominal pressures of 16 20 gpa in experiments in which a large 500 600 m olivine single crystal contained in a matrix of either fine grained olivine or nacl was transformed reaction rims of wadsleyite ringwoodite form on the margins of the single crystal by incoherent grain boundary nucleation and interface controlled growth contrary to theoretical expectations the growth rate of these reaction rims decreases sharply as a function of time for instance at 1100 c and 18 gpa growth ceases on an experimental timescale after the rim width reaches 20 25 m in order to explain this observation we develop an elastic model based on the theory of a misfitting inclusion comparing the results of this model with the experimental data suggests that elastic strain energy which develops because of the large volume decrease associated with the transformation is responsible for the decreasing growth rates on the other hand experimental and theoretical results suggest that elastic strain energy is relatively unimportant when grains of the product phase are randomly dispersed and distinct reaction rims do not form this is the case when the nucleation rate is low the growth rate is fast and the reactant olivine is fine grained on a geological timescale in subducting lithosphere where the grain size of the olivine is large the growth rates of grain boundary nucleated reaction rims are likely to be controlled by viscoelastic relaxation therefore current kinetic models of olivine metastability in subducting slabs which are based on simple extrapolations of experimental data and on the assumption that the growth rate is constant at fixed temperature and pressure need to be reevaluated

regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data 1 very few global scale ice volume estimates are available for mountain glaciers and ice caps although such estimates are crucial for any attempts to project their contribution to sea level rise in the future we present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from 123 000 glaciers from a recently extended world glacier inventory we compute glacier volumes and their sea level equivalent sle for 19 glacierized regions containing all mountain glaciers and ice caps on earth on the basis of total glacierized area of 741 103 68 103 km2 we estimate a total ice volume of 241 103 29 103 km3 corresponding to 0 60 0 07 m sle of which 32 is due to glaciers in greenland and antarctica apart from the ice sheets however our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried i e antarctica north america greenland and patagonia this emphasizes the need for more volume observations especially of large glaciers and a more complete world glacier inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps

isotopic evidence for involvement of c0 2 bearing magmas in granulite formation it has been suggested1 2 that co2 bearing magmas play an important part in the formation of granulites these magmas crystallize directly into granulites and also expel fluids which promote the development of granulite facies mineral assemblages in adjacent country rocks direct evidence for carbonic fluids remains elusive however as granulite facies aureoles adjacent to charnockitic intrusives1 may result either from the influx of carbonic fluids derived from the intrusives or simply from extraction of water into a vapour absent melt here we report results of a detailed study of carbon isotope compositions of graphite associated with a charnockite dyke from the ponmudi quarry of south india higher graphite abundances and an anomalously heavy carbon isotopic composition 13cgr 8 1 0 at the dyke margins indicate that externally derived co2 rich fluids were transported into the ponmudi paragneisses by the intrusive and precipitated nearly quantitatively as graphite on encountering reducing country rocks the occurrence of large orthopyroxene crystals along the dyke margins suggests that these fluids also served to dehydrate the country rocks this dyke may thus be representative of the widespread transport of carbonic fluids in this terrain by felsic magmas

fluid inclusions as microchemical systems evidence and modelling of fluid host interactions in plagioclase dense co2 rich fluid inclusions hosted by plagioclases an45 to an54 of the o v gruber anorthosite body central dronning maud land east antarctica contain varying amounts of small calcite paragonite and pyrophyllite crystals detected by raman microspectroscopy these crystals are reaction products that have formed during cooling of the host and the original co2 rich h2o bearing enclosed fluid variable amounts of these reaction products illustrates that the reaction did not take place uniformly in all fluid inclusions possibly due to differences in kinetics as caused by differences in shape and size or due to compositional variation in the originally trapped fluid the reaction albite 2anorthite 2h2o 2co2 pyrophyllite paragonite 2calcite was thermodynamically modelled with consideration of different original fluid compositions although free h2o is not detectable in most fluid inclusions the occurrence of oh bearing sheet silicates indicates that the original fluid was not pure co2 but contained significant amounts of h2o compared to an actual fluid inclusion it is obvious that volume estimations of solid phases can be used as a starting point to reverse the retrograde reaction and recalculate the compositional and volumetrical properties of the original fluid isochores for an unmodified inclusion can thus be reconstructed leading to a more realistic estimation of p t conditions during earlier metamorphic stages or fluid capturing

experimental constraints on the depth of olivine metastability in subducting lithosphere the hypothesis that metastable olivine persists in some subducting slabs into the transition zone has wide implications for mantle dynamics and rheology in order to evaluate this possibility we derive new thermo kinetic subduction zone models to predict the extent of olivine metastability within the stability fields of its high pressure polymorphs wadsleyite and ringwoodite our updated models improve on previous work by incorporating experimental kinetic data on realistic mantle compositions mg fe 2sio4 rather than analogue systems furthermore latent heat due to the transformation is fed back into both the kinetics and the thermal model we also consider the effects of transformation stress on growth kinetics and the possibility of an intracrystalline transformation mechanism previously thought to be important only at high shear stresses our models predict significantly smaller wedges of metastable olivine than previous work in the case of tonga for example where high values of lithospheric age 100 140 million years and convergence rate 14 cm per year are most favorable for metastability models considering only grain boundary nucleation and interface controlled growth predict olivine metastability to 600 km depth in contrast to 660 km predicted previously by kirby et al rev geophys 34 1996 261 when intracrystalline transformation is considered the depth of metastability is further reduced by as much as 100 km due to the large increase in the density of nucleation sites inhibition of growth by transformation stress can increase the depth interval over which the transformation takes place but is unlikely to be a dominant factor especially if the intracrystalline mechanism operates these results indicate that the existence of metastable olivine at depths corresponding to those of the deepest earthquakes 680 km requires subduction of old lithosphere 100 million years and a high vertical subduction velocity 15 cm per year such conditions currently may only be achieved in the very northern part of the tonga subduction zone yet earthquakes occur at depths down to 680 km in other subduction zones in which lithospheric age and or subduction velocity are relatively low e g indonesia and the marianas therefore mechanisms other than transformational faulting in metastable olivine must operate to cause the deepest earthquakes

dynamic phase boundaries of olivine wadsleyite in subduction zones in the western pacific 1 a modified coupling scheme is proposed to calculate the thermal structures and the kinetics of olivine to wadsleyite phase transformation in subduction zones which assures a high computational precision the phase and thermal structures of some subduction zones in the western pacific region are calculated computational results show that most subduction zones don t have large wedges of metastable olivine which lets the mechanisms of transformational faulting have difficulty explaining deep seismicity

the high mountain asia glacier contribution to sea level rise from 2000 to 2050 we estimate all the individual glacier area and volume changes in high mountain asia hma by 2050 based on randolph glacier inventory rgi version 4 0 using different methods of assessing sensitivity to summer temperatures driven by a regional climate model and the ipcc a1b radiative forcing scenario a large range of sea level rise variation comes from varying equilibrium line altitude ela sensitivity to summer temperatures this sensitivity and also the glacier mass balance gradients with elevation have the largest coefficients of variability amounting to 50 among factors examined prescribing ela sensitivities from energy balance models produces the highest sea level rise 9 2 mm or 0 76 of glacier volume a 1 while the ela sensitivities estimated from summer temperatures at chinese meteorological stations and also from 1 x1 gridded temperatures in the berkeley earth database produce 3 6 and 3 8 mm respectively different choices of the initial ela or summer precipitation lead to 15 uncertainties in modelled glacier volume loss rgi version 4 0 produces 20 lower sea level rise than version 2 0 more surface mass balance observations meteorological data from the glaciated areas and detailed satellite altimetry data can provide better estimates of sea level rise in the future

derivation and analysis of a complete modern date glacier inventory for alaska and northwest canada we present a detailed complete glacier inventory for alaska and neighboring canada using multi sensor satellite data from 2000 to 2011 for each glacier we derive outlines and 51 variables including center line lengths outline types and debris cover we find 86 723 km 2 of glacier area 27 109 glaciers 0 025 km 2 similar to 12 of the global glacierized area outside ice sheets of this area 12 0 is drained by 39 marine terminating glaciers 74 km of tidewater margin and 19 3 by 148 lake and river terminating glaciers 420 km of lake river margin the overall debris cover is 11 with considerable differences among regions ranging from 1 4 in the kenai mountains to 28 in the central alaska range comparison of outlines from different sources on 2500 km 2 of glacierized area yields a total area difference of similar to 10 emphasizing the difficulties in accurately delineating debris covered glaciers assuming fully correlated systematic errors uncertainties in area reach 6 for all alaska glaciers but further analysis is needed to explore adequate error correlation scales preliminary analysis of the glacier database yields a new set of well constrained area length scaling parameters and shows good agreement between our area altitude distributions and previously established synthetic hypsometries the new glacier database will be valuable to further explore relations between glacier variables and glacier behavior

a satellite derived glacier inventory for north asia this study outlines a consistent methodology for identifying glacier surfaces from landsat 5 7 and 8 imagery that is applied to map all mainland north asian glaciers providing the first methodologically consistent and complete glacier inventory for the region 2010 we identify 5065 glaciers covering a planimetric area of 2326 186 km 2 most of which is located in the altai mountain subregion the total glacier count is 15 higher but the total glacier area is 32 11 6 lower than the estimated glacier coverage provided in version 4 0 of the randolph glacier inventory we investigate the distribution of glacier size within north asia and find that the majority of glaciers 82 are smaller than 0 5 km 2 but only account for a third of the total glacier area with the largest 1 60 glaciers 5 km 2 accounting for 28 of the total area we present hypsometric characterizations of north asian glaciers largely substantiating existing findings that glaciers in this region are dominated by cold relatively dry conditions we provide a detailed assessment of errors and determine the uncertainty in our area estimate to be 8 0 with snow cover uncertainty the largest contributing factor based on this assessment the new glacier inventory presented here is more complete and of higher quality than other currently available data sources

multispectral imaging contributions to global land ice measurements from space global land ice measurements from space glims is an international consortium established to acquire satellite images of the world s glaciers analyse them for glacier extent and changes and assess change data for causes and implications for people and the environment although glims is making use of multiple remote sensing systems aster advanced spaceborne thermal emission and reflection radiometer is optimized for many needed observations including mapping of glacier boundaries and material facies and tracking of surface dynamics such as flow vector fields and supraglacial lake development software development by glims is geared toward mapping clean ice and debris covered glaciers terrain classification emphasizing snow ice water and admixtures of ice with rock debris multitemporal change analysis visualization of images and derived data and interpretation and archiving of derived data a global glacier database has been designed at the national snow and ice data center nsidc boulder colorado parameters are compatible with and expanded from those of the world glacier inventory wgi these technology efforts are summarized here but will be presented in detail elsewhere our presentation here pertains to one broad question how can aster and other satellite multispectral data be used to map monitor and characterize the state and dynamics of glaciers and to understand their responses to 20th and 21st century climate change our sampled results are not yet glaciologically or climatically representative our early results while indicating complexity are generally consistent with the glaciology community s conclusion that climate change is spurring glacier responses around the world mainly retreat whether individual glaciers are advancing or retreating the aggregate average of glacier change must be climatic in origin as nonclimatic variations average out we have discerned regional spatial patterns in glaciological response behavior these patterns are best attributed to climate change variability and to regional differences in glacier size and response times in many cases glacier length changes under represent the magnitude of glacier ablation because thinning sometimes without immediate length changes is also important an expanded systematic uniform analysis of many more glaciers is needed to isolate the glacier response components due to climatic and nonclimatic perturbations to produce quantitative measures of regional variation in glacier changes and to predict future regional glacier trends relevant to water resources glaciological hazards and global sea level this comprehensive assessment to be completed in stages is expected to lend a critically needed filter to identify successful climate models that explain recent glacier changes and change patterns and hence are apt to describe future changes and to eliminate unsuccessful models

landsat based inventory of glaciers in western canada 1985 2005 abstract we report on a glacier inventory for the canadian cordillera south of 60 n across the two western provinces of british columbia and alberta containing 30 000 km2 of glacierized terrain our semi automated method extracted glacier extents from landsat thematic mapper tm scenes for 2005 and 2000 using a band ratio tm3 tm5 we compared these extents with glacier cover for the mid 1980s from high altitude aerial photography for british columbia and from landsat tm imagery for alberta a 25 m digital elevation model dem helped to identify debris covered ice and to split the glaciers into their respective drainage basins the estimated mapping errors are 3 4 and arise primarily from seasonal snow cover glaciers in british columbia and alberta respectively lost 10 8 3 8 and 25 4 4 1 of their area over the period 1985 2005 the region wide annual shrinkage rate of 0 55 a 1 is comparable to rates reported for other mountain ranges in the late twentieth century least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover the highest relative ice loss in british columbia 24 0 4 6 occurred in the northern interior ranges while glaciers in the northern coast mountains declined least 7 7 3 4

strength of mg fe 2sio4 wadsleyite determined by relaxation of transformation stress abstract the growth of a reaction rim around a crystal undergoing a polymorphic phase transformation generates elastic strain energy as a consequence of the reaction volume change the strain energy inhibits the transformation by counteracting the chemical free energy driving force for growth stress relaxation enables growth to continue at a rate controlled primarily by the mechanical properties of the rim we studied this process in high pressure experiments in order to constrain the rheology of wadsleyite one of the high pressure polymorphs of olivine single crystal spheres of san carlos olivine surrounded by a quasi hydrostatic pressure medium of nacl or au were partially transformed to wadsleyite at 1100 c and 16 17 gpa to determine the rate of growth as a function of time microstructural observations indicate that the relict olivine remains largely undeformed while the wadsleyite rims deform by dislocation creep application of an elastoplastic model to fit the observed decrease in growth rates with time constrains the yield strength of wadsleyite at these conditions to between 4 and 6 gpa a decrease in growth rates was also observed in another study in which varying amounts of water were added to the samples kubo t ohtani e kato t shinmei t fujino k 1998a experimental investigation of the transformation of san carlos olivine single crystal phys chem miner 26 1 6 kubo t ohtani e shinmei t fujino k 1998b effects of water on the transformation kinetics in san carlos olivine science 281 85 87 modeling these results gives values for the yield strength of wadsleyite between 2 and 5 gpa under various conditions a strength difference of 1 gpa is indicated by experiments at 1030 c conducted under nominally dry 200 ppm h2o and water added 500 ppm h2o conditions supporting the hypothesis that hydrolytic weakening is an important process in wadsleyite the calculated yield strengths for wadsleyite indicate that it is three to six times stronger than olivine at the same conditions based on an extrapolation of the low temperature plasticity flow law for olivine these results imply a strong increase in the strength of subducting slabs in the mantle transition zone provided that the deformation mechanism is the same as in the experiments furthermore inhibition of growth by transformation stress may be an important factor in extending the depth range over which metastable olivine transforms to its high pressure polymorphs in subducting slabs

mass changes of alpine glaciers at the eastern margin of the northern and southern patagonian icefields between 2000 and 2012 fil falaschi daniel consejo nacional de investigaciones cientificas y tecnicas centro cientifico tecnologico conicet mendoza instituto argentino de nivologia glaciologia y ciencias ambientales provincia de mendoza instituto argentino de nivologia glaciologia y ciencias ambientales universidad nacional de cuyo instituto argentino de nivologia glaciologia y ciencias ambientales argentina

implications of slab mineralogy for subduction dynamics phase relations among mantle minerals are perturbed by the thermal environment of subducting slabs both under equilibrium and disequilibrium metastable conditions such perturbations yield anomalies not only in seismic velocities but also in density the buoyancy forces arising from these density anomalies may exert several important effects they contribute to the stress field within the slab in a fashion consistent with observed patterns of seismicity they may affect subduction rates both by inducing time dependent velocity changes under equilibrium conditions and by imposing velocity limits through a thermal feedback loop under disequilibrium conditions they may affect slab morphology possibly inhibiting penetration of slabs into the lower mantle and allowing temporary stagnation of deflected or detached slabs latent heat release from phase transitions under disequilibrium conditions in slabs can yield isobaric superheating which may generate adiabatic shear instabilities capable of triggering deep seismicity 2001 elsevier science b v all rights reserved

multiple discontinuities near 660 km beneath tonga area 1 we study the discontinuities beneath tonga subduction zone using the deep earthquakes recorded by the pacific northwest seismic network pnsn the multiple discontinuities around 660 km beneath tonga subduction zone are found using converted phase sdp the amplitude ratios of the converted phase with the direct p wave ac ap are also determined the largest number of robust converted phases with large ac ap comes from the depth range of 660 690 km its peak is at 680 km the second one appears in the depth range of 700 745 km its peak is at 740 km the two discontinuities are obviously depressed by the subduction slab according to experimental and numerical studies a possible explanation of the observation is that the first discontinuity is formed by the transition of spinel to perovskite and magnesiowustite and the second is formed by the transition of ilmenite to perovskite

formation of elliptical garnet in a metapelitic enclave by melt assisted dissolution and reprecipitation metapelitic residual enclaves in the neogene volcanic province of se spain are residues left after melt extraction glass quenched melt of granitic composition occurs as inclusions in most minerals and as intergranular pockets the most common enclave types show one stage of garnet growth that is interpreted to have occurred at the same time as glass production some of these show a well developed foliation outlined by fibrolite biotite graphite and glass which wraps around elongate garnet crystals that have aspect ratios up to 10 1 based on microstructures and chemistry the garnet within these rocks shows clear core and mantle structure the core has an average composition of alm76 prp08 sps14 grs03 and contains primary inclusions of biotite and melt trapped during garnet growth a thin c 100 lm irregular mantle overgrows the garnet core enclosing oriented fibrolite inclusions in strain caps and biotite in strain shadows in places the overgrowths form skeletal elongated arms which extend parallel to the foliation the garnet mantle contains less mn and higher xmg but both core and mantle display flat mn profiles the contact being a sharp break ternary feldspar and grt bt thermometry yield temperatures in the range 800 900 c with no systematic differences among the different microstructural domains of elliptical garnet based on the observed intracrystalline microstructures the high amount of melt extraction in the rock by flattening component strain and the chemical zoning of garnet the formation of elliptical garnet is modelled by a multistage sequence this involves pressure solution and reprecipitation of the core followed by post kinematic partly mimetic growth of the garnet mantle

experimental diffusion of hydrogen into synthetic fluid inclusions in quartz quartz hosted synthetic co2 h2o fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory simulated metamorphic re equilibration at 650 750 and 825 c and 1 5 kbar total pressure with fo2 defined by the c ch4 buffer microthermometry and raman spectroscopy show that the initial co2 h2o inclusions become co2 ch4 h2 h2o inclusions after diffusive influx of hydrogen from the reducing confining medium measurable changes are observed in inclusion compositions after only 15 days of re equilibration implying significant hydrogen mobility at still lower temperatures over geological time spans results of synthetic inclusion re equilibrium experiments have profound implications for the interpretation of natural fluid inclusion data failure to account for potential hydrogen migration in inclusions from high temperature geological environments may lead to erroneous estimates of p t and or the compositions of metamorphic fluids

solubility of excess alumina in hydrous granitic melts in equilibrium with peraluminous minerals at 700 800 c and 200 mpa and applications of the aluminum saturation index we have studied the controls on the alumi num saturation index asi molec al2o3 cao na2o k2o and the concentration of normative corundum of granitic liquids saturated in alumina by equilibrating peraluminous minerals with initially meta luminous haplogranitic minimum composition liquids at 700 800 c and 200 mpa at and below h2o saturation the asi and normative corundum increase with increasing h2o concentration in the melt 0 04 to 0 10 moles excess al2o3 per mole of h2o temperature and with addition of the non haplogranitic components fe mg and b the asi parameter and concentration of normative corundum cannot be used to monitor aal2o3 between different mineral assemblages and melt because other components that affect the solubility of alumina including h2o fe mg and b do not appear in their formulations asi and normative corundum however provide petrogenetic information about magmas gener ated by partial melting of strongly peraluminous proto liths by virtue of their regular and predictable variation with melt composition e g h2o concentration and temperature for the application of these data to natural rocks it is necessary to choose as an analogue system the asi solubility or normative corundum solubility relations of the most chemically complex peraluminous mineral present in the rock comparison of asi values of anatectic leucosomes and allochthonous leucogranites with experimentally predicted values suggests low h2o concentrations in melt during crustal partial melting rapid melt segregation before equilibration with restitic peraluminous phases is also suggested in some cases

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

raman microspectrometry of fluid inclusions abstract for many kinds of fluid inclusions the coupling of microthermometry and raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions a review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation analytical conditions and methodology of the application of raman microspectrometry to gaseous aqueous and hydrocarbon inclusions and their daughter minerals

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

fluid present anatexis of metapelites at el joyazo se spain constraints from raman spectroscopy of graphite the garnet biotite sillimanite anatectic xenoliths in the neogene dacite dome of el joyazo also called cerro de hoyazo se spain contain four types of graphite i to iv distinguished on the basis of grain size and texture structural characterization of graphite by laser raman spectroscopy lrs shows systematic differences in the degree of ordering among the four types only type iii is fully consistent with the granulite facies conditions reached by the xenoliths during partial melting the others indicate metamorphic temperatures covering amphibolite facies conditions with only a few examples of granulite grade crystallinity all graphite crystallized before or during the anatectic event indicating that a large fraction of the graphite did not equilibrate at peak temperatures the mm scale coexistence of different types and degrees of ordering in the graphite suggests different origins i e of biogenic derivation and fluid deposited and is explained in terms of fluid melt graphite interaction during the anatectic event disequilibrium behaviour during high temperature metamorphism and anatexis is typical of types i ii and particularly of iv and is attributed to sluggish kinetics of solid state graphitization mainly owing to the limited time of the process and carbon saturation of the intergranular fluid the coexisting well ordered type iii graphite is the product of melting in the presence of a graphite saturated fluid a process that would account for the deposition of new graphite the lrs results together with petrologic observations suggest that it is possible that high melt fractions can be generated by fluid present melting of a metasedimentary protolith also in a closed system although this contradicts the commonly accepted hypothesis that due to limited rock porosities extensive fluid present melting is precluded unless infiltration occurs it is a possible end member model in anatectic settings characterized by rapid heating rates and low grade source rocks

isotopic variations of the fixed nitrogen in metamorphic rocks the content and isotopic composition of fixed nitrogen nh 4 n in metasedimentary rocks phyllites mica schists and gneisses from prograde metamorphic zones in the erzgebirge saxon ore mountains g d r were measured and show that the nitrogen content decreases and 15n increases with increasing metamorphic grade the geochemical and isotopic behaviour of nitrogen during contact metamorphism was investigated in a mica schist profile through the contact aureole of a granitic pluton the nitrogen concentrations of the wall rocks decrease towards the contact whereas the 15n values become higher various model experiments were carried out in the laboratory to explain the changes observed in the rock samples the nitrogen isotope fractionation factor was determined for the isotopic exchange in the system ammonium sulphate ammonia at 250 c 1 0143 0 0012 and 350 c 1 0128 0 0006 in accordance with the model experiments the conclusion seems warranted that the change in nitrogen content and its isotopic composition in rocks during metamorphic processes depend mainly on the metamorphic temperature

relationship of deep seismicity to the thermal structure of subducted lithosphere recent experimental work on silicate olivine polymorphs1 has confirmed earlier observations of mechanical failure in analogous compounds2 3 as a result of phase transformations when non hydrostatic stresses were applied to a metastable phase this transformational faulting 4 mechanism is considered to be a leading candidate5 among others involving olivine transformation6 7 for the cause of deep earthquakes evidence consistent with this mechanism comes from the observation2 4 that worldwide earthquakes become more numerous with increasing depth after a seismicity minimum at about 350 km depth8 this depth lies within the range anticipated for mineralogical transformations in the subducted lithosphere9 but individual subduction zones differ in their thermal structures so if transformational faulting indeed contributes to deep seismicity this should be reflected in the location of the seismicity minimum for each zone the depth at which the minimum occurs should depend on temperature in the same way as do the polymorphic transformations of olivine and should always lie deeper than the depth at which the equilibrium transformation takes place here we test these predictions for eight subduction zones worldwide we find that with one exception the north japan zone the depth of the seismicity minimum decreases linearly with increasing thermal age of the slab a measure of its temperature profile these results support the proposal that deep earthquakes are a consequence of phase transformations in olivine

stress fields associated with metastable phase transitions in descending slabs and deep focus earthquakes inside subducting slabs the interaction of different metastable phase transformations olivine spinel spinel spinel spinel perovskite magnesiowustite associated with the latent heat release and absorption for these transitions can result in a complex thermal slab structure thermokinetic coupling processes cause thermal anomalies and buoyancy contrasts between slab and mantle that strongly influence the stress field within subducting plates we have described the thermal field within the downgoing slab in a lagrangian framework by a self consistent high resolution two dimensional thermokinetic coupling model which also incorporates the effects of nucleation site saturation using an adaptive method the threshold for the nucleation site saturation is found to be less than 0 1 transformation degree in the cold slab interior this can significantly shift the metastable wedge of olivine deeper as suggested from previous thermokinetic slab models however this effect is compensated by the latent heat release during the olivine spinel and spinel spinel phase transitions latent heat release produce very sharp phase boundaries in the slab for fast slabs the phase boundaries reveal significant metastable perturbations from the equilibrium state in the cold interior however the strong thermal interaction between both ongoing phase transitions results in sharp overlapping phase boundaries with dramatic consequences for the slab stress field we have investigated the detailed physical properties and the state of stress in the deeper portion of a subducting plate by using up to date temperature field and physical properties determined from recent high p t experiments we find that the slab is denser up to 100 kg m 3 than the surrounding mantle remarkable denser portions up to 260 kg m 3 are located just below the uplifted and equilibrium phase transitions while lighter portions up to 210 kg m 3 can be found just above the depressed spinel to perovskite magnesiowustite transition and for the metastable wedge of olivine these density differences effectively act as a body force and produce a significant stress field which we calculated with a two dimensional finite element code the results show that the buoyancy induced forces produce maximum shear stress up to 23 mpa along the metastable wedge and deeper portion just above the depressed last phase transition involving spinel for the latter the dominant state of stress is down dip compression the calculated p t dependent state of stress is very similar to the depth distribution of deep focus

variable conductivity effects on the thermal structure of subducting slabs understanding the thermal structure of the lithosphere in subduction zone environments is a key element in the realization of the source of deep focus earthquakes and other geodynamic processes model predictions of the thermal structure of subducting slabs are dependent upon a priori knowledge of how thermal conductivity varies within the slab using recent results for the variation of thermal conductivity as a function of temperature pressure and gross mineralogy we investigate how models that utilize a realistic model for variable conductivity compare with canonical models for constant conductivity results suggest that jumps in thermal conductivity across the phase boundaries that arise due to transformations to and spinel phases lead to old fast steeply dipping slabs being considerably warmer than previously thought although these results do not rule out the possibility of a metastable wedge source of deep focus earthquakes they do imply the likelihood of metastable olivine being found at depth is less than once thought

beginning of melting and composition of first melts in the system qz ab or h 2 o co 2 solidus temperatures have been determined for minimum melt compositions in the system qz sio2 ab naalsi3o8 or kalsi3o8 at p fluid 2 5 and 10 kbar and at various water activities the dry solidus was investigated in a dry argon environment water activities ah2o between 0 0 and 1 0 were obtained by using h2o co2 mixtures the or ab or ratio of first melts increases considerably with decreasing water activity at 10 kbar it is 0 28 in the water saturated system and 0 56 at water activity 0 1 the qz content does not change with changing water activities the ab content of minimum melts formed at high pressures and low ah2o may remain almost constant in ascending magmas that are cooling and crystallizing qz content increases at the expense of the or component solidus temperatures decrease considerably when ah2o increases slightly from zero at 10 kbar the temperature difference between dry melting and the solidus for ah2o 0 1 is 120 c the influence of pure co2 on the solidus is very limited in the investigated p t range the solidus is approximatively 760 c at ah2o 0 5 between 2 and 10 kbar and approximatively 830 c at ah2o 0 3 this means that melting of quartz feldspar assemblages may induce dehydration reactions at p t conditions of the granulite facies

combining satellite multispectral image data and a digital elevation model for mapping debris covered glaciers automated glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces supraglacial debris exhibits the same spectral properties as lateral and terminal moraines fluvioglacial deposits and bedrock outside the glacier margin and is thus not detectable by means of multispectral classification alone based on the observation of low slope angles for debris covered glacier tongues we developed a multisource method for mapping supraglacial debris the method combines the advantages of automated multispectral classification for clean glacier ice and vegetation with slope information derived from a digital elevation model dem neighbourhood analysis and change detection is applied for further improvement of the resulting glacier debris map a significant percentage of the processing can be done automatically in order to test the sensitivity of our method against different dem qualities it was also applied to a dem obtained from aster stereo data additionally we compared our multisource approach to an artificial neural network ann classification of debris using only multispectral data while the combination with an aster derived dem revealed promising results the ann classification without dem data does not

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

rheological structure and deformation of subducted slabs in the mantle transition zone implications for mantle circulation and deep earthquakes abstract rheological structure of subducted slabs of oceanic lithosphere in the mantle transition zone is investigated based on mineral physics observations incorporating grain size stress temperature and pressure dependence of rheology it is shown that the rheological structure of slabs depends strongly on subduction parameters through temperature that controls the grain size of spinel ringwoodite and the magnitude of forces acting on a slab we use a theoretical model of grain size evolution associated with the olivine spinel transformation plastic flow laws of olivine and spinel combined with a thermal model of subducting slab in which the effect of latent heat release is incorporated three deformation mechanisms for olivine and spinel diffusional creep power law dislocation creep and the peierls mechanism are considered due to the large variation in temperature stress and grain size a subducting slab is shown to have a complicated rheological structure which varies both laterally and with depth a cold slab in the deep transition zone is characterized by a weak fine grained spinel region surrounded by narrow but strong regions the flexural rigidity and the curvature of a slab are calculated using a new formulation in which the effects of stress dependent rheology is incorporated in a self consistent fashion although uncertainties in both the transformation kinetics and the rheology of high pressure phases are still large the general trend of dependence of slab flexural rigidity and the curvature on the subduction parameters is well constrained slabs with very low thermal parameters warm slabs are weak but slabs with large thermal parameters cold slabs are also weak due to small spinel grain size and large external force bending moment slabs with intermediate thermal parameters will have a relatively large flexural rigidity and could penetrate into the lower mantle without much deformation thus the 660 km discontinuity may work as a rheological filter for mantle convection this prediction provides a natural explanation for a paradoxical observation that significant deformation of slabs is observed exclusively in the western pacific where temperatures of the slabs are considered to be low our slab rheology models also have important implications for deep earthquakes overall rheological weakening of slabs in the deep transition zone results in high rates of deformation under relatively low temperatures providing a favorable environment for thermal runaway instability adiabatic shear instability our model predicts heterogeneous energy dissipation as a result of heterogeneous rheology energy dissipation in deep cold slabs is concentrated in high strength regions surrounding a weak fine grained spinel core the regions of high energy dissipation are prone to thermal runaway instability and are likely to be seismogenic the width of this seismogenic region is well constrained by our model and is predicted to be 40 60 km which is in excellent agreement with seismological observations other features of deep earthquakes including low seismic efficiency and low aftershock activities can also be explained by the thermal instability model

fe 3 reduction during biotite melting in graphitic metapelites another origin of co 2 in granulites the fe 3 fetot of all fe bearing minerals has been analysed by mossbauer spectroscopy in a suite of biotite rich to biotite free graphitic metapelite xenoliths proxies of an amphibolite granulite transition through progressive biotite melting biotite contains 9 to 16 fe 3 fetot whereas garnet cordierite and ilmenite are virtually fe 3 free 0 1 fe 3 fetot in all samples regardless of biotite presence under relatively reducing conditions graphite bearing assemblages biotite is the only carrier of fe 3 during high temperature metamor phism therefore its disappearance by melting represents an important event of iron reduction during granulite formation because haplogranitic melts usually incorpo rate small amounts of ferric iron iron reduction is accompanied by the oxidation of carbon and the production of co2 according to the redox reaction 2fe2o bt 3 c gr 4feo crd grt ilm opx co fluid melt crd 2 depending on the nature of the peritectic fe mg mineral produced garnet cordierite orthopyroxene the co2 can either be present as a free fluid component or be completely stored within melt and cordierite the oxi dation of graphite by iron reduction can account for the in situ generation of co2 implying a consequential ra ther than causal role of co2 in some granulites and migmatites this genetic model is relevant to graphitic rocks more generally and may explain why co2 is present in some granulites although it is not required for their formation

distributed ice thickness and volume of all glaciers around the globe 1 a new physically based approach for calculating glacier ice thickness distribution and volume is presented and applied to all glaciers and ice caps worldwide combining glacier outlines of the globally complete randolph glacier inventory with terrain elevation models shuttle radar topography mission advanced spaceborne thermal emission and reflection radiometer we use a simple dynamic model to obtain spatially distributed thickness of individual glaciers by inverting their surface topography results are validated against a comprehensive set of thickness observations for 300 glaciers from most glacierized regions of the world for all mountain glaciers and ice caps outside of the antarctic and greenland ice sheets we find a total ice volume of 170 103 21 103 km3 or 0 43 0 06 m of potential sea level rise

a new glacier inventory on southern baffin island canada from aster data i applied methods challenges and solutions the quantitative assessment of glacier changes as well as improved modeling of climatechange impacts on glaciers requires digital vector outlines of individual glacier entities unfortunately such a glacier inventory is still lacking in many remote but extensively glacierized regions such as the canadian arctic multispectral satellite data in combination with digital elevation models dems are particularly useful for creating detailed glacier inventory data including topographic information for each entity in this study we extracted glacier outlines and a dem using two adjacent terra aster scenes acquired in august 2000 for a remote region on southern baffin island canada additionally little ice age lia extents were digitized from trimlines and moraines visible on the aster scenes and landsat mss and tm scenes from the years 1975 and 1990 were used to assess changes in glacier length and area because automated delineation of glaciers is based on a band in the shortwave infrared we have developed a new semi automated glacier mapping approach for the mss sensor wrongly classified debris covered glaciers water bodies and attached snowfields were corrected manually for both aster and mss glacier drainage divides were manually digitized by combining visual interpretation with dem information in this first paper we describe the applied methods for glacier mapping and the glaciological challenges encountered e g data voids snow cover ice caps tributaries while the second paper reports the data analyses and the derived changes

deep focus earthquakes and recycling of water into the earth s mantle for more than 50 years observations of earthquakes to depths of 100 to 650 kilometers inside earth have been enigmatic at these depths rocks are expected to deform by ductile flow rather than brittle fracturing or frictional sliding on fault surfaces laboratory experiments and detailed calculations of the pressures and temperatures in seismically active subduction zones indicate that this deep focus seismicity could originate from dehydration and high pressure structural instabilities occurring in the hydrated part of the lithosphere that sinks into the upper mantle thus seismologists may be mapping the recirculation of water from the oceans back into the deep interior of our planet

fluid infiltration into fault zones chemical isotopic and mechanical effects fluid infiltration into fault zones and their deeper level counterparts brittle ductile shear zones is examined in diverse tectonic environments in the 2 7 ga abitibi greenstone belt major tectonic discontinuities with lateral extents of hundreds of kilometres initiated as listric normal faults accommodating rift extension and acted as sites for komatiite extrusion and locally intense metasomatism during reverse motion on the structures accommodating shortening of the belt these transcrustal faults were utilised as a conduit for the ascent of trondhjemitic magmas from the base of the crust and of alkaline magmas from the asthenosphere and for the discharge of thousands of cubic kilometres of hydrothermal fluids such fluids were characterised by 18o 6 2 d 50 20 13c 4 4 and temperatures of 270 to 450 c probably derived from devolatilisation of crustal rocks undergoing prograde metamorphism hydrothermal fluids were more radiogenic 87sr 86sr 0 7010 to 0 7040 and possessed higher than did contemporaneous mantle komatiites or tholeiites and thus carried a contribution from older sialic basement a provinciality of87sr 86sr and 13c is evident signifying that fault plumbing sampled lower crust which was heterogeneous at the scale of tens of kilometres mineralised faults possess enrichments of large ion lithophile lil lil elements including k rb ba cs b and co2 and rare elements such as au ag as sb se te bi and w fluids were characterised by xco2 0 1 neutral to slightly acidic ph low salinity 3 wt k na 0 1 they carried minor ch4 co and n2 and they underwent transient effervescence of co2 during decompression clastic sediments occupy graben developed at fault flexures the40ar 39ar release spectra indicate that fault rocks experienced episodic disturbance on time scales of hundreds of millions of years

incongruent melting of biotite to spinel in a quartz free restite at el joyazo se spain textures and reaction characterization in the grt bt sil restitic xenoliths of el joyazo cerro de hoyazo hercynitic spinel is a minor phase commonly associated with biotite the possible reaction relationships among biotite and spinel are studied in reaction textures developed around biotites at their contact with patches of fibrolitic sillimanite and rhyolitic melt in these textures resorbed biotite crystals about 1 mm long are rimmed by a layer of glass 5 mm away from the reaction texture biotite is chemically zoned cores bt 1 have xmg 0 35 0 02 and ti 0 58 0 01 atoms whereas the outer rims bt 2 have xmg 0 45 0 01 and ti up to 0 68 atoms the hercynite rich spinel spl has low zno content 0 80 wt and xmg 0 26 0 04 the chemical compositions of the mix aggregate represent linear combinations between sillimanite and a silica rich melt this melt melt 1 is different from that of the layer around biotite melt 2 which is also richer in ca and alkalis garnet rims grt have low ca and mn and xmg 0 14 plagioclase is characterized by large homogeneous cores pl 1 an31 2 and more calcic rims pl 2 an49 6 matrix analysis in the 9 component al ca fe k mg mn na si ti 9 phase bt1 bt2 grt spl ilm melt2 mix pl1 pl2 system provides the mass balance in mole units

a new semi automatic approach for dividing glacier complexes into individual glaciers many glaciological and hydrological studies require outlines of individual glaciers rather than total ice cover here we develop a new semi automatic algorithm that uses a digital elevation model dem and outlines of glacier complexes to calculate the extents of individual glaciers the algorithm first applies hydrological modeling tools to a modified dem to calculate flowsheds it then merges flowsheds that belong to individual glaciers using a distance based approach whose required empirical parameters are derived from the juneau icefield area in alaska in this region 2 of similar to 1300 glaciers were misclassified the algorithm was validated on 25 000 km 2 of ice in other regions in alaska and on 40 000 km 2 of ice in arctic canada resulting in similar to 2 and similar to 3 misclassified glaciers respectively results indicate that the algorithm is robust provided the dem and the outlines are of good quality

time dependent interaction between subduction dynamics and phase transition kinetics summary numerical subduction models are presented that account for the kinetics of the olivine spinel transformation and the equilibrium transformation of spinel into perovskite and magnesiowustite temperature depth and stress dependent rheology is used buoyancy due to temperature and the olivine spinel and magnesiowustite perovskite phases leads to free subduction into the transition zone and retarded penetration into the lower mantle a dynamic feed back mechanism is found between the different buoyancy forces the kinetics of the phase transition and the release of latent heat this mechanism modulates the parachute effect of the metastable olivine mo in a subducting slab and leads to characteristic temporal variations of the depth of mo and with a time delay variations of the subduction velocity time periods are of the order of 3 4 myr this mechanism allows to explain variations of the depths of the deepest earthquakes in otherwise similar subduction zones further conclusions are as follows the maximum depth of mo increases roughly linearly with lithospheric thickness and the maximum depth may reach as deep as 720 750 km different subduction zones may represent different stages of velocity depth phase loops of mo

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

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

immiscibility between carbonic fluids and granitic melts during crustal anatexis a fluid and melt inclusion study in the enclaves of the neogene volcanic province of se spain in the restitic crustal enclaves in the neogene volcanics of el hoyazo and mazarron se spain associations of fluid and silicate melt inclusions indicative of immiscibility are frequently observed in the bt poor crd rich graphitic metapelites these occurrences extremely rare for anatectic crustal rocks have been studied by microthermometry micro raman spectroscopy and emp analysis both at el hoyazo and mazarron the immiscible fi and mi are hosted in plagioclase and cordierite with microstructures that suggest primary trapping the fi hosted in cordierite are monophase whereas they may contain crystals of calcite when hosted in plagioclase indicating fluid host reaction during cooling decrepitation microstructures have not been observed the mi contain fresh glass of peraluminous felsic rhyolitic composition typical of anatectic s type melts in all samples the fluids are co2 dominated n85 mol with minor amounts of n2 and ch4 and traces of co and h2 the nucleation of graphite induced by the laser beam in some inclusions demonstrates that the fluids are graphite saturated large scatter in microthermometric behaviour of fi indicates significant density variations only in one sample from el hoyazo are fluid densities compatible with the estimated p tconditions of trapping 5 7 kbar 850 50 c whereas in the remaining samples the extremely low densities suggesting trapping pressures b1 kbar are in contrast with the microstructural indications of primary entrapment and little evidence of decrepitation in addition although some measured compositions are compatible with c o h n fluid speciation at the estimated p t conditions of anatexis the lack of h2o in all fi is inconsistent with the slightly hydrated character of coexisting glasses the possible mechanisms accounting for departure of densities and compositions of fi from expected values are discussed and leakage of h2o suggested as the most plausible

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

the second chinese glacier inventory data methods and results the second chinese glacier inventory was compiled based on 218 landsat tm etm scenes acquired mainly during 2006 10 the widely used band ratio segmentation method was applied as the first step in delineating glacier outlines and then intensive manual improvements were performed the shuttle radar topography mission digital elevation model was used to derive altitudinal attributes of glaciers the boundaries of some glaciers measured by real time kinematic differential gps or digitized from high resolution images were used as references to validate the accuracy of the methods used to delineate glaciers which resulted in positioning errors of 10 m for manually improved clean ice outlines and 30 m for manually digitized outlines of debris covered parts the glacier area error of the compiled inventory evaluated using these two positioning accuracies was 3 2 the compiled parts of the new inventory have a total area of 43 087 km 2 in which 1723 glaciers were covered by debris with a total debris covered area of 1494 km 2 the area of uncompiled glaciers from the digitized first chinese glacier inventory is similar to 8753 km 2 mainly distributed in the southeastern tibetan plateau where no images of acceptable quality for glacier outline delineation can be found during 2006 10

the effects of phase transition kinetics on subducting slabs the effects of kinetics on the non equilibrium aspects of the olivine to spinel transition in a descending slab have been studied numerically a one dimensional model consisting of the kinetic equations and the heat diffusion equation with latent heat release has been constructed numerical results show that the position and sharpness of the kinetic phase boundary is determined by the surface tension and the activation volume for slow slab velocities less than 6 cm yr near equilibrium conditions are found finger like structures emanating from the phase boundaries are obtained in this regime these phase boundary prolusions may cause earthquakes for slab velocities of around 10 cm yr the metastable olivine region may be pushed down to a depth of about 600 km with a sharp phase boundary a direct transition from olivine to perovskite may be feasible

c o h s fluid composition and oxygen fugacity in graphitic metapelites c 0 h fluid produced by the equilibration of hzo and excess graphite must maintain the atomic h o ratio of water 2 1 this constraint implies that all thermodynamic properties of the fluid are uniquely determined at isobaric isothermal conditions the o h20 and co fugacities j fhto and fc of such fluids have been estimated from equations of state and fit as a function of pressure and temperature these fugacities can be taken as characteristic for graphitic metamorphic systems in which the dominant fluid source is dehydration e g pelitic lithologies because there are no compositional degrees of freedom for graphite saturated fluids produced entirely by dehydration the variance of the dehydration process is not increased in comparison with that in non graphitic systems thus compositional buffering of c 0 h fluids by dehydration equilibria a common petrological model requires that redox reactions decarbonation reactions or external h o 2 fluid sources perturb the evolution of the metamorphic system such perturbations are not likely to be significant in metapelitic environments but their tendency will be to increase the fo of the fluid phase at high metamorphic grades pyrite desulphidation reactions may cause a substantial reduction of fhz0 and slight increases info and fcs relative to sulphur free fluid at low metamorphic grade sulphur solubility in h o s 2 fluids is so low that pyrite decomposition must occur by sulphurconserving reactions that cause iron depletion in silicates a common feature of sulphidic pelites with increasing temperature and sulphur solubility pyrite desulphidation may be driven by dehydration reactions or infiltration of h o rich fluids the absence of magnetite and the assemblages carbonate aluminosilicate or pyrite pyrrhotite ilmenite from most graphitic metapelites is consistent with an h o 2 model for gcoh s fluid for graphitic rocks in which such a model is inapplicable a phase diagram variable that defines the h o ratio of gcoh s fluid is more useful than the conventional

textural evolution of synthetic fluid inclusions in quartz during reequilibration with applications to tectonic reconstruction experimental reequilibration of synthetic 10 wt nacl h2o inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the p t path followed by the inclusion after formation these differences combined with other geological information may be used to determine whether the sample rock followed a dominantly isothermal or isobaricp t path following entrapment the intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of thep t path from the original isochore for the inclusion thus fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradep t path but also the magnitude of departure of this path from one that is isochoric

contrasts in the response of adjacent fjords and glaciers to ice sheet surface melt in west greenland neighboring tidewater glaciers often exhibit asynchronous dynamic behavior despite relatively uniform regional atmospheric and oceanic forcings this variability may be controlled by a combination of local factors including glacier and fjord geometry fjord heat content and circulation and glacier surface melt in order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics we made coincident ice ocean atmosphere observations at high temporal resolution minutes to weeks within a 10 000 km 2 area near uummannaq greenland water column velocity temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns the observed ocean velocity and hydrography combined with numerical modeling suggest that subglacial discharge plays a major role in setting fjord conditions in addition satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow down in response to melt as well as differences in calving style among the neighboring glaciers glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior for the studied region individual glacier and fjord geometry modulate subglacial discharge which leads to contrasts in both fjord and glacier dynamics

primary melt inclusions in andalusite from anatectic graphitic metapelites implications for the position of the al2sio5 triple point anatectic crustal xenoliths in the miocene volcanic rocks of mazarron southeast spain contain andalusite with melt inclu sions an unprecedented finding microstructures indicate that the melt inclusions were trapped during andalusite growth the vola tile content of the peraluminous inclusions is too low cl 0 4 wt f 0 3 wt p 1500 ppm b 850 ppm to have caused a significant reduction of the wet solidus temperature moreover the presence of graphite as observed during partial melting is expected to have raised the temperature of the wet solidus melting temperatures for the inclusions obtained from quartz albite or thoclase haplogranite system 680 790 8c zr 620 705 8c and light rare earth element 615 725 8c thermometry indicate that the stability of andalusite 1 melt is incompatible with the position of the most commonly used andalusite 5 sillimanite equilibrium and that the al2sio5 triple point must be placed at higher tem peratures and pressures

shear instability in a viscoelastic material as the cause of deep focus earthquakes the mechanism of deep focus earthquakes has been examined by numerical and linear analysis of shear instability in subducting slabs we assume subducting slabs deform such that the spatially averaged strain rate becomes time independent furthermore we assume that rheology depends on temperature in the manner of an activation process using this model we investigate quantitatively the conditions under which shear instability takes place i e the deformation in the material concentrates in a thin layer whose temperature increases explosively until melting occurs first we study instability in a material whose rheological properties are spatially homogeneous shear instability takes place in a homogeneous material when exceeds a certain critical level e c which depends strongly on the stress in the slabs but does not depend on the detail of the creep law the value of the activation energy next we study instability in a material that contains shear zones similar to those often observed by field geologists i e a thin layer made of material with lower vicosity than the surrounding region we find that shear zones trigger shear instability even for the case of provided that g the ratio of characteristic time of thermal diffusion to that of shear heating in shear zones exceeds 1 and that f the ratio of stiffness of elastic deformation in the surrounding region to that of ductile deformation in shear zones becomes lower than 1 applying this condition to subducting slabs with shear zones we find that shear zones trigger shear instability even when the average strain rate is lower than by an order of magnitude from these results and from an estimate of in subducting slabs we conclude that shear instability is a mechanism likely to induce deep focus earthquakes

metastable mantle phase transformations and deep earthquakes in subducting oceanic lithosphere earth s deepest earthquakes occur as a population in subducting or previously subducted lithosphere at depths ranging from about 325 to 690 km this depth interval closely brackets the mantle transition zone characterized by rapid seismic velocity increases resulting from the transformation of upper mantle minerals to higher pressure phases deep earthquakes thus provide the primary direct evidence for subduction of the lithosphere to these depths and allow us to investigate the deep thermal thermodynamic and mechanical ferment inside slabs numerical simulations of reaction rates show that the olivine spinel transformation should be kinetically hindered in old cold slabs descending into the transition zone thus wedge shaped zones of metastable peridotite probably persist to depths of more than 600 km laboratory deformation experiments on some metastable minerals display a shear instability called transformational faulting this instability involves sudden failure by localized superplasticity in thin shear zones where the metastable host mineral transforms to a denser finer grained phase hence in cold slabs such faulting is expected for the polymorphic reactions in which olivine transforms to the spinel structure and clinoenstatite transforms to ilmenite it is thus natural to hypothesize that deep earthquakes result from transformational faulting in metastable peridotite wedges within cold slabs this consideration of the mineralogical states of slabs augments the traditional largely thermal view of slab processes and explains some previously enigmatic slab features it explains why deep seismicity occurs only in the approximate depth range of the mantle transition zone where minerals in downgoing slabs should transform to spinel and ilmenite structures the onset of deep shocks at about 325 km is consistent with the onset of metastability near the equilibrium phase boundary in the slab even if a slab penetrates into the lower mantle earthquakes should cease at depths near 700 km because the seismogenic phase transformations in the slab are completed or can no longer occur substantial metastability is expected only in old cold slabs consistent with the observed restriction of deep earthquakes to those settings earthquakes should be restricted to the cold cores of slabs as in any model in which the seismicity is temperature controlled via the distribution of metastability however the geometries of recent large deep earthquakes pose a challenge for any such models transformational faulting may give insight into why deep shocks lack appreciable aftershocks and why their source characteristics including focal mechanisms indicating localized shear failure rather than implosive deformation are so similar to those of shallow earthquakes finally metastable phase changes in slabs would produce an internal source of stress in addition to those due to the weight of the sinking slab such internal stresses may explain the occurrence of earthquakes in portions of lithosphere which have foundered to the bottom of the transition zone and or are detached from subducting slabs metastability in downgoing slabs could have considerable geodynamic significance metastable wedges would reduce the negative buoyancy of slabs decrease the driving force for subduction and influence the state of stress in slabs heat released by metastable phase changes would raise temperatures within slabs and facilitate the transformation of spinel to the lower mantle mineral assemblage causing slabs to equilibrate more rapidly with the ambient mantle and thus contribute to the cessation of deep seismicity because wedge formation should occur only for fast subducting slabs it may act as a parachute and contribute to regulating plate speeds wedge formation would also have consequences for mantle evolution because the density of a slab stagnated near the bottom of the transition zone would increase as it heats up and the wedge transforms to denser spinel favoring the subsequent sinking of the slab into the lower mantle

plastic instabilities implications for the origin of intermediate and deep focus earthquakes adiabatic or catastrophic plastic shear has been reported in metals polymers and metallic glasses the phenomenon is associated with rapid stress drops and audible pings or clicks as the material deforms in a plastic manner the driving force for the plastic instability is the stored elastic strain energy of the loading system and in many respects the behavior is reminiscent of the shear stress response arising from stick slip events during unstable frictional sliding although the precise mechanism is different it is shown here that adiabatic plastic shear is capable of explaining the detailed distribution of intermediate and deep focus earthquakes within subduction zones the earthquake events being the result of instabilities in material undergoing plastic flow it is argued that for a particular strain rate there exists a critical temperature tc which is depth dependent for temperatures below tc the material is strain rate softening and for a soft enough loading system may undergo catastrophic plastic shear for temperatures above tc the material is strain rate hardening and is always stable during plastic shear the cutoff depth for deep focus earthquakes then corresponds to the transition from strain rate softening to strain rate hardening material and for commonly accepted geothermal gradients within the slab corresponds to approximately 800 km the precise distribution of earthquakes within the slab is a function of the subtle interplay between the geothermal gradient and the tc gradient in particular a decrease in seismic activity is to be expected below about 300 km in the slab with total stress drops decreasing from a maximum of 700 mpa above 300 km to a maximum of 50 mpa below 300 km the differences in foci distribution between subduction zones such as tonga new hebrides and peru result from minor differences in the geothermal gradients within the slabs the model predicts the development of triple seismic zones high in the slab double seismic zones down to approximately 300 km and single seismic zones down to 800 km such a distribution is to be expected of relatively young cool slabs as the slab heats up the seismic activity retreats up the slab the paper only proposes a deformation mechanism for earthquake generation it does not address the stress field within the slab but only the distribution of strength thus the distribution of focal plane mechanisms is not considered only the locations where earthquakes due to plastic instabilities are possible the absence of earthquakes does not necessarily mean that the slab does not exist it only means that the slab is too hot to undergo plastic instability this means that aseismic subduction is a distinct possibility in many regions of high geothermal gradient within the slab i e circa 3 c km 1

an inventory and morphometric analysis of british columbia glaciers canada we describe an automated method to generate an inventory of glaciers and glacier morphometry from a digital topographic database containing glacier boundaries and a digital elevation model for british columbia canada the inventory contains over 12 000 glaciers with a total cumulative area that exceeds 25 000 km 2 based on mapping from aerial photographs circa the mid 1980s we use the inventory to examine dimensional characteristics among glaciers namely the scaling relations between glacier length width and area glacier length is a good predictor of glacier area and its predictive ability improves when glaciers are stratified by the number of up valley accumulation basins the spatial pattern of glacier mid range altitude parallels glaciation limits previously mapped for british columbia and similarly reflects large scale controls of orographic precipitation and continentality the inventory is also used to refine models that relate glacier mid range and terminus altitudes to regional position aspect and in the case of terminus altitudes an index of glacier shape relations between glacier altitude limits and controlling spatial and topographic factors are used to make further climatic and mass balance inferences from the glacier inventory

melt producing versus melt consuming reactions in pelitic xenoliths and migmatites abstract melt producing reactions have operated both in pelitic xenoliths and in pelitic migmatites but melt consuming reactions related to in situ melt crystallization are largely restricted to migmatites hence xenolith reaction textures may provide clues on the relative roles of both reaction types in migmatites a comparison of xenoliths and migmatites results in a catalogue of textural and chemical features some of which are argued to be diagnostic the results have implications for the identification of restite in igneous rocks and for the relative importance of prograde and retrograde processes in different domains of layered migmatites