spatially integrated geodetic glacier mass balance and its uncertainty based on geostatistical analysis application to the western svartisen ice cap norway estimates of glacier mass balance using geodetic methods can differ significantly from estimates using direct glaciological field based measurements to determine if such differences are real or methodological there is a need to improve uncertainty estimates in both methods in this paper we focus on the uncertainty of geodetic methods and describe a geostatistical technique that takes into account the spatial correlation of the elevation differences when calculating spatially averaged elevation changes we apply this method to the western svartisen ice cap norway using elevation differences from the surrounding bedrock derived from stereophotogrammetry we show that the uncertainty is not only dependent on the standard error of the individual elevation differences but is also dependent on the size of the averaging area and the scale of the spatial correlation to assess if the geostatistical analysis made over bedrock is applicable to glacier surfaces we use concurrent photogrammetrical and laser scanning data from bedrock and a range of glacier surfaces to evaluate the dependency of the geostatistical analysis on the surface type the estimated geodetic mass balance and its uncertainty is 2 6 0 9 m w e for the period 1968 85 and 2 0 2 2 m w e for 1985 2002

ultrahigh temperature metamorphism under isobaric heating new evidence from the north china craton abstract the khondalite belt within inner mongolia suture zone imsz in the north china craton ncc preserves evidence for extreme crustal metamorphism under ultra high temperature uht conditions at ca 1 92 ga associated with the subduction collision tectonics between the yinshan and ordos blocks here we report a new locality in hongsigou where cordierite and spinel bearing granulites record uht metamorphism the prograde peak and retrograde mineral assemblages in these pelitic granulites have been identified based on petrography and mineral chemistry as bt1 grt1 sil1 kfs1 pl1 ilm qtz1 grt1 sil2 kfs2 pl2 spl ilm qtz2 liq and crd grt2 sil3 kfs2 pl2 ilm qtz2 respectively the peak metamorphic conditions of the pelitic granulite were estimated as 930 1050 c and 6 5 7 5 kbar based on pseudosection analysis in the system nckfmashto suggesting extreme thermal metamorphism we report la icpms zircon u pb data from the granulite which show weighted mean 207pb 206pb age of 1881 6 6 ma marking the timing of uht metamorphism lu hf analyses of the zircons show ehf t values within a restricted range of 4 2 to 0 3 and together with hf model ages a paleoproterozoic arc magmatic source is inferred for the detrital zircons the estimated p t path for the uht granulite suggests isobaric heating followed by cooling and decompression along a clockwise trajectory different from the anti clockwise p t paths defined in earlier studies for the 1 92 ga uht rocks from the imsz the younger age and the isobaric heating trajectory suggest that the hongsigou uht rocks are related to heat input from underplated mafic magmas following continental collision

flow laws for rocks containing two non linear viscous phases a phenomenological approach abstract mylonitic rocks and rock analogue materials reveal two basic types of structure 1 a load bearing framework lbf of strong phase contains isolated pockets of weak phase 2 interconnected layers of weak phase iwl separate boudins and clasts of strong phase aggregates with the lbf microstructure are characterized by nearly uniform strain rate stress is concentrated in the load bearing framework in aggregates with an iwl microstructure strain rate and sometimes also stress are higher in the interconnected weak phase than in the boudins and clasts of strong phase the degree of stress and strain partitioning depends strongly on the viscous strength contrast and on the relative amounts of the constituent mineral phases based on these observations the rheology of two phase rock is modelled with separate functions for lbf and iwl microstructures a new flow law is derived for rock with iwl structure in which two phases undergo dislocation creep the flow law expresses composite creep strength in terms of temperature bulk strain rate and the volume proportions and creep parameters of the minerals in the rock strain rate and stress are averaged in the constituent phases and slip along phase boundaries maintains strain compatibility within the aggregate composite strengths predicted with the iwl flow law fall well within the uniform stress and uniform strain rate bounds and are generally consistent with the viscous strengths of experimentally deformed bimineralic aggregates a hypothesis of viscous strain energy minimization is used to determine the relative stability of the lbf and iwl microstructures during steady state creep the iwl microstructure is predicted to be stable over a broad range of two phase compositions and mineral strength contrasts whereas the lbf microstructure is stable only in rocks with low volume proportions of weak phase and low to moderate mineral strength contrasts the iwl flow law indicates that rheological stratification in the lithosphere depends strongly on rock composition especially in rocks with low volume proportions of a weak phase and high mineral strength contrasts

global open access dem performances in earth s most rugged region high mountain asia a multi level assessment abstract over the past decades climate change has exerted pronounced influences on the cryo hydrologic environments in high mountain asia hma digital elevation models dems are one of the critical datasets required in many hydrology and cryosphere related studies in hma which include estimations of glacier mass balances and lake water storage changes and hydrological runoff modelling several global or near global coverage dems e g srtm and aster missions have been widely utilized for such studies however a comprehensive assessment of the quality of these dems particularly over the high relief hma area is still lacking this study investigated the performances of seven public freely accessed dem datasets aster gdem v2 srtm 3 v4 1 dem srtm 1 dem aw3d30 dem vfp dem merit dem seamless srtm 1 dem over the hma region by referring to high accuracy elevation data from icesat altimetry we also provided an additional detailed assessment for typical lake basins and extremely rugged areas in the himalayas by using available global positioning system gps measurements and gridded setsm dem raster data results show that aw3d30 exhibits the highest accuracy in hma land areas among these datasets the accuracy of all studied dems demonstrates high spatial variation which shows the strongest relationship with slope among several topographical factors such as elevation and aspect over these rugged terrains with a large slope such as the hengduan mountains and himalayas the vertical accuracy is relatively low in all investigated dems we established empirical models for fitting the relationship between dem vertical error and mean slope which can be used to estimate the average elevation errors for any given local or basin scale dem grids in addition this study identified regions with anomalous elevation data in each dataset caused by the imperfect void filling processing scheme in sum the 3 arc second merit dem is judged to be relatively dependable for hma which not only achieves good performances in statistical error values but also retains few void filling anomalies the 1 arc second aw3d30 could be the most promising product over hma with its high spatial resolution and accuracy although some void filling anomalies need to be noted in some regions

rheological behavior of high temperature garnet bearing migmatites the khondalite belt example north china craton the contribution presents microstructural and petrological results obtained on garnet bearing felsic migmatites from the khondalite belt north china craton the study focused on low melt fraction felsic migmatites in which peritectic garnet are strongly elongated and show plastic deformation these peritectic garnet grains show different typology depending on their petrographic location within the layered migmatite an elongated shaped garnet with sillimanite and biotite inclusion lies within al rich layer whereas poecilithic garnets are located within s rich layers forming a garnet quartz aggregate the study presents petrological microstructural observation and ebsd analyses of the garnet grains and garnet quartz aggregates phase diagram sections modeling allows to constrain the p t conditions of the deformation at 850 1000 c and 0 6 1 1 gpa at such high to ultra high temperature conditions a low melt fraction was produced between 1 and 12 generally under 7 forescattered diffraction and misorientation maps with orientation pole figure argue for dislocation creep with development of subgrains in garnets our results suggest that at high to ultra high temperature the quartz feldspar garnet solid framework of felsic migmatites strongly accommodate the deformation and contribute to weakening of migmatite even at low melt fraction

glacier elevation and mass changes over the central karakoram region estimated from tandem x and srtm x sar digital elevation models snow cover and glaciers in the karakoram region are important freshwater resources for many down river communities as they provide water for irrigation and hydropower a better understanding of current glacier changes is hence an important informational baseline we present glacier elevation changes in the central karakoram region using tandem x and srtm x sar dem differences between 2000 and 2012 we calculated elevation differences for glaciers with advancing and stable termini or surge type glaciers separately using an inventory from a previous study glaciers with stable and advancing termini since the 1970s showed nearly balanced elevation changes of 0 09 0 12 m a 1 on average or mass budgets of 0 01 0 02gt a 1 using a density of 850 kg m 3 our findings are in accordance with previous studies indicating stable or only slightly negative glacier mass balances during recent years in the karakoram the high resolution elevation changes revealed distinct patterns of mass relocation at glacier surfaces during active surge cycles the formation of kinematic waves at quiescent surge type glaciers could be observed and points towards future active surge behaviour our study reveals the potential of the tandem x mission to estimate geodetic glacier mass balances but also points to still existing uncertainties induced by the geodetic method

garnet plasticity in the lower continental crust implications for deformation mechanisms based on microstructures and sem electron channeling pattern analysis abstract elongated garnets which preserved deformational microstructures boudinage pinch and swell structures occur in granulite facies quartzites in the highland complex of sri lanka in spite of these microstructures and in contrast with previous reports on garnet plasticity there are no or only few signs of intracrystalline deformation like subgrains or lattice distortion this can be explained by annealing and slow static cooling from high temperatures sem electron channeling pattern analysis reveals that the garnets have a significant crystallographic preferred orientation aspect ratio grain size analysis shows that the deformation mechanism is grain size sensitive these features indicate a diffusion assisted dislocation glide mechanism with dominant 1 2 110 slip system a comparison of the deformation behavior between garnet quartz and feldspar shows that differences in flow strength are low under the high grade conditions 850 50 c garnet is still the phase with the highest flow strength but dry quartz is slightly stronger than feldspar

climatic and geometric controls on the global distribution of surge type glaciers implications for a unifying model of surging financial support was provided by the conocophillips lundin northern area program project crios

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

review of the status and mass changes of himalayan karakoram glaciers we present a comprehensive review of the status and changes in glacier length since the 1850s area and mass since the 1960s along the himalayan karakoram hk region and their climate change context a quantitative reliability classification of the field based mass balance series is developed glaciological mass balances agree better with remotely sensed balances when we make an objective systematic exclusion of likely flawed mass balance series the himalayan mean glaciological mass budget was similar to the global average until 2000 and likely less negative after 2000 mass wastage in the himalaya resulted in increasing debris cover the growth of glacial lakes and possibly decreasing ice velocities geodetic measurements indicate nearly balanced mass budgets for karakoram glaciers since the 1970s consistent with the unchanged extent of supraglacial debris cover himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short wave radiation balance melt contributions from hk glaciers should increase until 2050 and then decrease though a wide range of present day area and volume estimates propagates large uncertainties in the future runoff this review reflects an increasing understanding of hk glaciers and highlights the remaining challenges

spatial distribution of 1950 1800 ma metamorphic events in the north china craton implications for tectonic subdivision of the craton abstract great progress has been made in the last twenty years in understanding the unification of the north china craton according to a prevailing model it developed by amalgamation of four sub blocks by three spatially and temporally separate orogenic belts the first at 1950 ma formed the western block the second at 1900 ma created the eastern block and the third at 1850 ma unified the eastern and western blocks however new data show that the 1950 ma orogen was affected by granulite facies reequilibration at 1800 ma and parts of the 1850 ma orogen have evidence of metamorphism at 1950 1900 ma new zircon u pb ages enable the paleoproterozoic metamorphic events to be statistically sub divided into four at 1955 ma m 1 1920 ma m 2 1885 ma m 3 and 1850 ma m 4 the m 1 2 events always appear together mainly in two belt areas including the helanshan qianlishan northern ordos yinshan liangcheng huai an lushan jiaobei and liaodong regions whereas the m 3 4 events are distributed over larger areas and were superimposed on the m 1 2 activities this age distribution is inconsistent with previous models of three separate orogens it should also be noted that the igneous rocks contemporary with the regional ultra high temperature high pressure granulite facies metamorphisms m 1 2 were previously described as arc related series i e the gabbro norites i s type granites and trimodal volcanics based on the spatial distribution of the paleoproterozoic metamorphic events m 1 4 and of the coeval igneous rocks we speculate that the assembly of the ncc was created by one orogen which formed between the eastern and western cratons in two tectonic stages two marginal arcs the korean and xuwujia developed against both eastern sides of the two sub cratons and were both accreted and deformed at 1965 1900 ma m 1 2 subsequently the amalgamation of the two sub cratons resulted in metamorphism on the western side of the eastern craton and in metamorphism that was superimposed on both accreted arcs at 1900 1790 ma m 3 4

plastic deformation and recrystallization of garnet a mechanism to facilitate diffusion creep elongate and deformed garnets from glenelg nw scotland occur within a thin shear zone transecting an eclogite body that has undergone partial retrogression to amphibolite facies at circa 700 c optical microscopy back scattered electron imaging electron probe microanalysis and electron back scatter diffraction reveal garnet sub structures that are developed as a function of strain subgrains with low angle misorientation boundaries occur at low strain and garnet orientations are dispersed around rational crystallographic axes across these boundaries towards high strain areas boundary misorientations increase and there is a loss of crystallographic control on misorientations which tend towards random in high strain areas a polygonal garnet microstructure is developed the garnet orientations are randomly dispersed around the original single crystal orientation some garnet grains are elongate and ca rich garnet occurs on the faces of elongate grains oriented normal to the foliation commonly the garnet grains are admixed with matrix minerals and where in contact with other phases garnet is well faceted we suggest that individual garnet porphyroclasts record an evolution from low strain conditions where dislocation creep and recovery accommodated deformation through increasing strain where dynamic recrystallization occurred by subgrain rotation to highest strains where recrystallized grains were able to deform by diffusion creep assisted grain boundary sliding with associated rotations

calculation of partial melting equilibria in the system na2o cao k2o feo mgo al2o3 sio2 h2o nckfmash a thermodynamic model for haplogranitic melts in the system na2o cao k2o al2o3 sio2 h2o nckash is extended by the addition of feo and mgo with the data for the additional end members of the liquid incorporated in the holland powell 1998 internally consistent thermodynamic dataset the resulting dataset with the software thermocalc is then used to calculate melting relationships for metapelitic rock compositions the main forms for this are p t and t x pseudosections calculated for particular rock compositions and composition ranges the relationships in these full system pseudosections are controlled by the low variance equilibria in subsystems of nckfmash in particular the solidus relationships are controlled by the solidus relationships in nkash and the ferromagnesian mineral relationships are controlled by those in kfmash however calculations in nckfmash allow the relationships between the common metapelitic minerals and silicate melt to be determined in particular the production of silicate melt and melt loss from such rocks allow observations to be made about the processes involved in producing granulite facies rocks particularly relating to open system behaviour of rocks under high grade conditions

hydrology of debris covered glaciers in high mountain asia abstract the hydrological characteristics of debris covered glaciers are known to be fundamentally different from those of clean ice glaciers even within the same climatological geological and geomorphological setting understanding how these characteristics influence the timing and magnitude of meltwater discharge is particularly important for regions where downstream communities rely on this resource for sanitation irrigation and hydropower such as high mountain asia the hydrology of debris covered glaciers is complex rugged surface topographies typically route meltwater through compound supraglacial englacial systems involving both channels and ponds as well as pathways that remain unknown low gradient tongues that extend several kilometres retard water conveyance and promote englacial storage englacial conduits are frequently abandoned and reactivated as water supply changes new lines of permeability are exploited and drainage is captured due to high rates of surface and subsurface change seasonal influences such as the monsoon are superimposed on these distinctive characteristics reorganising surface and subsurface drainage rapidly from one season to the next recent advances in understanding have mostly come from studies aimed at quantifying and describing supraglacial processes little is known about the subsurface hydrology particularly the nature or even existence of subglacial drainage in this review we consider in turn the supraglacial englacial subglacial and proglacial hydrological domains of debris covered glaciers in high mountain asia we summarise different lines of evidence to establish the current state of knowledge and in doing so identify major knowledge gaps finally we use this information to suggest six themes for future hydrological research at high mountain asian debris covered glaciers in order to make timely long term predictions of changes in the water they supply

diffusion creep of fine grained garnetite implications for the flow strength of subducting slabs creep experiments were performed on synthetic fine grained garnetite to investigate the flow strength of the earth s subducting slabs experiments were conducted at temperatures t of 1373 1543 k and total pressure p of 0 1 mpa in controlled atmospheres of f 02 10 17 10 8 mpa the mechanical data indicate a grain size sensitive diffusion flow and the creep behavior can be described by an equation of the form e 5 32 3 10 10 6 td 2 5 0 3 f 0 o2 1 1 0 2 exp 347 46 kj mol rt where t in kelvin d in meter and f o2 in mpa based on the diffusivities d calculated from creep and diffusion experiments we proposed that grain boundary diffusion is the dominant mechanism for high temperature creep of the fine grained garnetite normalized creep strength of the garnetite is found to be comparable to those of feldspar and olivine in diffusion creep regime suggesting that garnetite may not form a strong layer in the subducted oceanic lithosphere if it deforms by grain boundary diffusion creep

discovery of sapphirine bearing mg al granulites in the north china craton implications for paleoproterozoic ultrahigh temperature metamorphism abstract we report here for the first time the occurrence of mg al granulites within the khondalite belt of the north china craton and provide robust evidence for extreme crustal metamorphism at ultrahigh temperature uht conditions in this region the uht indicator assemblages in these rocks include equilibrium sapphirine quartz high alumina orthopyroxene sillimanite quartz and high temperature perthites the surrounding khondalites also carry spinel quartz equilibrium assemblage the sapphirines occurring in various microstructural associations are markedly magnesian x mg 0 69 0 77 with a composition varying from 7 9 3 to 2 2 1 end members spinel is a solid solution of mg spinel and hercynite x mg 0 41 0 54 with zno content varying from 0 48 to 1 79 wt garnet shows a compositional range between pyrope and almandine x mg 0 39 0 48 with minor grossular 2 6 3 8 mol and spessartine 0 5 1 8 mol the orthopyroxenes display marked compositional variations in terms of al 2 o 3 content with the core of the medium grained orthopyroxene adjacent to sillimanite in the matrix showing the highest al 2 o 3 content 8 4 wt the history of prograde to peak metamorphism of these rocks is indicated by inclusions of sapphirine spinel quartz and sillimanite within garnet sapphirine formed during the peak stage through the reaction spl qtz sil spr occurrence of sapphirine and quartz inclusions trapped in sillimanite suggests the reaction spr qtz grt opx sil a series of retrograde reactions are observed in these rocks as corona and symplectite textures around early coarse grained minerals such as opx sil qtz crd grt sil qtz crd grt qtz crd opx grt o 2 crd qtz fe 2 o 3 in mag or ilm and finally opx kfs h 2 o bt qtz whereas the stability of sapphirine quartz and orthopyroxene sillimanite quartz in the matrix assemblage suggests t 1000 c and p 10 kbar peak metamorphism conventional geothermobarometric estimates confirm the ultrahigh temperature nature and also trace the retrograde conditions 930 970 c at p 10 kbar al in opx 900 1000 c perthite 930 990 c grt opx and 910 940 c sapphirine spinel electron microprobe dating of monazites in textural association with the uht assemblages yield a sharply defined isochron age of 1917 48 ma which correlates with the 1927 11 ma obtained in a previous study from monazites in the surrounding khondalites carrying spinel quartz assemblage an evaluation of the assemblages and textures using appropriate petrogenetic grids indicate that following peak ultrahigh temperature conditions the rocks underwent initial isobaric cooling and subsequent isothermal decompression and we interpret these trajectories to be part of an overall anti clockwise p t evolution the study area located within the northern margin of the north china craton defines a collisional orogenic belt where continental collision and deep subduction was possibly followed by extensional collapse of the orogen evidence for the extensional phase is provided by the several mafic magmatic intrusives of paleoproterozoic age occurring in the region which suggest a possible link between the thermal anomaly associated with extreme crustal metamorphism in this region with mantle derived magmas the uht metamorphism in north china craton coincided with the assembly of the paleoproterozoic supercontinent columbia

crystal plasticity of natural garnet new microstructural evidence scanning electron microscope sem orientation contrast images of mantle nodules show that garnets contain cellular domains of different crystallographic orientation electron backscatter diffraction shows small crystallographic mismatches

migmatites granites and orogeny flow modes of partially molten rocks and magmas associated with melt solid segregation in orogenic belts abstract this paper presents a model for the genesis of migmatites and granites during orogenic evolution based on the analysis of several phanerozoic crustal segments and a review of the physical properties of partially molten rocks and magmas this model inventories the modes of bulk flow of partially molten rocks and magmas and the mechanisms of melt solid segregation for each mode partial melting of rocks is associated with a strength decrease of two to three orders of magnitude leading to strain partitioning expressed by channel flow driven either by forces related to plate tectonics vertical channel flow or by the gravity force associated with lateral variations of crustal thicknesses horizontal channel flow although the structural characteristics of migmatites indicate that deformation plays a role in melt migration the emplacement of laccoliths of leucogranites above migmatites attests to the efficiency of the buoyancy force another decrease in apparent strength of about ten orders of magnitude is associated with the loss of continuity of the solid framework marking the transition from partially molten rocks to magmas the breakdown of the solid framework also allows for settling of the solid in suspension increasing the buoyancy of the remaining magma accordingly domes cored by diatexites former heterogeneous magmas and mantled by metatexites former partially molten rocks are interpreted as gravitational instabilities driven by the relative buoyancy of the magma and permitted by the weakness of the partially molten rocks this model provides a first order framework to elucidate the development of a crustal scale horizontal layering during the evolution of orogenic belts that are affected by partial melting in this case the middle crust is dominated by migmatites with domes cored by diatexites and mantled by metatexites that correspond to a partially molten and magmatic zone respectively the granitic dikes and sills and the associated laccoliths of leucogranites correspond to an intrusive zone overlying the partially molten zone the refractory lower crust is potentially in part formed by accumulation of solids segregated from the overlying heterogeneous magmas

modeling deformation induced by seasonal variations of continental water in the himalaya region sensitivity to earth elastic structure strong seasonal variations of horizontal and vertical positions are observed on gps time series from stations located in nepal india and tibet china we show that this geodetic deformation can be explained by seasonal variations of continental water storage driven by the monsoon for this purpose we use satellite data from the gravity recovery and climate experiment to determine the time evolution of surface loading we compute the expected geodetic deformation assuming a perfectly elastic earth model we consider green s functions describing the surface deformation response to a point load for an elastic homogeneous half space model and for a layered nonrotating spherical earth model based on the preliminary reference earth model and a local seismic velocity model the amplitude and phase of the seasonal variation of the vertical and horizontal geodetic positions can be jointly adjusted only with the layered earth model while an elastic half space model fails emphasizing the importance of using a realistic earth elastic structure to model surface displacements induced by surface loading we demonstrate based on a formal inversion that the fit to the geodetic data can be improved by adjusting the layered earth model therefore the study also shows that the modeling of geodetic seasonal variations provides a way to probe the elastic structure of the earth even in the absence of direct measurements of surface load variations

feldspar thermometry in ultrahigh temperature metamorphic rocks evidence of crustal metamorphism attaining 1100 c in the archean napier complex east antarctica ultrahigh metamorphic temperatures attained in the mid to lower crust have been assessed by examining the mineral chemistry of ternary feldspars with relatively coarse exsolution lamellae from the archean napier complex east antarctica chemical compositions of re integrated perthitic mesoperthitic and antiperthitic feldspars are calculated from the modal proportions and the chemical analyses of host and lamellar domains formed through exsolution based on ternary feldspar solvus models re integrated compositions of feldspars from a variety of rock types yield the minimum equilibrium temperatures ranging from 1000 to 1110 c 0 8 gpa these data confirm the suggestion that the regional thermal conditions of the napier complex reached or exceeded 1100 c as feldspar is one of the common constituents of the crustal rocks this approach could be applicable to a wide variety of rocks in which feldspar represents exsolution textures

on the pseudomorphing of melt filled pores during the crystallization of migmatites pseudomorphs of melt filled pores recognized by their generally cuspate shape are used as diagnostic for the former presence of partial melt they are commonly observed in migmatites from the mid to deep crust although they occur in the smaller pores in migmatites from shallower levels 1 2 kbar the pseudomorphing of meltfilled pores is controlled by the kinetics of nucleation and is a consequence of the greater supersaturation required for nucleation in a small pore compared with a larger one we examine three migmatites in detail a contact metamorphosed cherty band from an iron formation an archaean regional granulite from an accretionary prism and an amphibolite facies sample from the roots of an archaean mountain chain the greater undercooling required for nucleation in progressively smaller pores is recorded by the composition of plagioclase pseudomorphs a study of dihedral angles at the corners of pseudomorphed pores demonstrates that melt solid textural equilibrium was probably attained only in the contact aureole the regional granulite preserves an almost unmodified reaction controlled melt distribution with little evidence for either melt solid textural equilibration or solid solid re equilibration whereas the reactioncontrolled melt distribution in the regional amphibolite facies example has been modified by a partial approach to solid solid textural equilibrium it is not clear whether the differences in dihedral angle population are due to differences in uplift and exhumation rates or due to the presence of h2o on grain boundaries

ductility of garnet as an indicator of extremely high temperature deformation discoidal shaped garnets alm63 prp33 grs3 sps1 occur in the foliation plane of lineated quartzofeldspathic mylonites of the morin shear zone located along the eastern boundary of the morin anorthosite complex grenville province quebec the flattened shape of garnets records a component of coaxial strain x y z different from the dominant rotational shear strain x y z in this mylonite tem observations indicate dislocation slip and recovery to be the main mechanism for the deformation of garnet extrapolation of available experimentally determined flow laws to natural strain rates shows an inversion of flow strength between quartz feldspar and garnet garnet much stronger than quartz and feldspar at temperatures below 700 c becomes weaker than quartz and feldspar above 900 c the coaxial ductile strain recorded by the garnets could be produced by a local uncharacterized deformation under extremely high temperature conditions at the roof of the rising anorthositic diapir 1155 ma subsequent lower temperature rotational deformation is related to strike slip movement along the morin shear zone 1020 ma

geodetic and direct mass balance measurements comparison and joint analysis this paper describes a new compilation of both direct and geodetic mass balance measurements develops a procedure to reduce diverse balance measurements over different time spans to common time spans and presents updated estimates of global average balance of small glaciers based on the enlarged compilation although geodetic measurements are fewer than direct measurements they cover four times as many balance years direct and geodetic measurements are unbiased with respect to one another but differences are often substantial the statistical procedure can be understood by imagining that an n year balance measurement is an average of a series of 1 year measurements the series is hypothetical but we can calculate the uncertainty of each of its elements if in addition to its measured average we can also estimate its standard deviation for this claim to be valid the annual series must be stationary and normally distributed with independent roughly uncorrelated elements for which there is reasonable evidence the need to know the standard deviation means that annual direct measurements from a nearby glacier or equally reliable information about variability are indispensable given this information the new methodology results in moderately more negative balances this is probably because tidewater glaciers are better represented in the geodetic data in any case the most recent published estimate of global average balance 0 8 1 0 mm a 1 of sea level equivalent for 2001 04 is now increased substantially to 1 1 1 4 mm a 1 for 2001 05

mass balance and a glacier surge of guliya ice cap in the western kunlun shan between 2005 and 2015 abstract contemporary estimates of glacier changes are necessary to assess the impact of climate change associated hazards and water resources management glaciers in high mountain asia hma are mostly retreating except the karakoram and western kunlun shan confirmed by remote sensing measurements however ground validation with precise measurements of these mass balance estimates are scarce this study selected guliya ice cap in the western kunlun shan to observe its recent changes regarding surface dynamics and mass balance using aster dem of 2005 and 2015 our findings indicate that one of the north facing glaciers surged with no previous surging history during july and early november 2015 advancing at about 8 m per day on average the mass balance shows a balance condition 0 01 0 02 m w e a 1 the icesat data 2004 2008 at selected locations compared to dgps data collected in the field during 2015 indicating a minute difference of 0 03 0 05 m a 1 with aster data in the same area our findings suggest that guliya ice cap in the western kunlun shan is in equilibrium state following a similar pattern mass gain or stable conditions as observed previously

a spatially resolved estimate of high mountain asia glacier mass balances from 2000 to 2016 glacier mass balances in high mountain asia are uncertain satellite stereo imagery allows a spatially resolved estimate for about 92 of the glacierized area and yields a region wide average of about 16 gt yr 1 for 2000 to 2016

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

heterogeneous mass loss of glaciers in the aksu tarim catchment central tien shan revealed by 1976 kh 9 hexagon and 2009 spot 5 stereo imagery the meltwater released by the glaciers in the aksu tarim catchment south of tomur peak central tien shan feeds the tarim river which is the main artery for the oases at the northern margin of the taklamakan desert the correct modeling of the contribution of the glaciers meltwater to the total runoff of the tarim river is hampered by the lack of mass balance data multi temporal digital terrain models dtms allow the determination of volume changes for large samples of glacier here we present the mass changes for 12 glaciers using 1976 kh 9 hexagon 2000 srtm3 and 2009 spot 5 datasets the results show that most of the glaciers have been losing mass since 1976 the largest glaciers koxkar and west qongterang lost 0 27 0 15 m w e a 1 and 0 43 0 15 m w e a 1 between 1976 and 2009 despite thick debris cover however some smaller glaciers show mass gain at their tongues indicating glacier surges using srtm3 data the volume gain of qinbingtan glacier no 74 could be dated to the time period 1999 2009 the overall mass budget of 0 33 0 15 m w e a 1 for 1976 2009 of the investigated glaciers is within the variability range of the global average however in the recent years 1999 2009 a slightly decelerated mass loss of 0 23 0 19 m w e a 1 could be observed c 2012 elsevier inc all rights reserved

impact of gneissic layering and localized incipient melting upon melt flow during experimental deformation of migmatites in this study we test experimentally the role of compositional layering as a key parameter for controlling melt flow in a natural migmatite during coaxial deformation we performed in situ pure shear experiments on two natural gneisses the first gneiss is weakly foliated with minerals homogenously distributed the second gneiss shows a pronounced compositional layering of alternating quartz feldspar rich and biotite muscovite rich layers experimental conditions were selected to obtain homogeneous melt distribution in the homogeneous gneiss and heterogeneous melt distribution in the layered gneiss initial melt distribution is not modified by deformation in experiments on the homogeneous gneiss implying that melting products did not migrate from their initiation sites in contrast melt flowed in shear zones or in inter boudin positions during experimental deformation of the heterogeneous gneiss these experiments attest to the strong influence of initial gneissic layering on melting pattern melt segregation and flow during deformation of partially molten rocks

evaluation of glacier changes in high mountain asia based on 10 year grace rl05 models in this paper 10 years of time variable gravity data from the gravity recovery and climate experiment release 05 have been used to evaluate the glacier melting rate in high mountain asia hma using a new computing scheme i e the space domain inverse method we find that in hma area there are three different kinds of signal sources that should be treated together the two generally accepted sources glacier melting and india underground water depletion are estimated to change at the rate of 35 0 5 8 gt yr 0 09 mm yr sea level rising and 30 6 5 0 gt yr respectively the third source is the remarkable positive signal 30 gt yr in the inner tibetan plateau which is challenging to explain further we have found that there is a 5 year undulation in pamir and karakoram which can explain the controversies of the previous studies on the glacier melting rate here this 5 year signal can be explained by the influence of arctic oscillation and el nino southern oscillation

melt enhanced deformation a major tectonic process convergent tectonics between continental crustal blocks result in deep burial and anatexis of supracrustal rocks anatectic and or mantle derived melts combine to form a melt weakened zone in the thickened lower crust the accumulation of melt eventually leads to crustal failure along melt lubricated shear zones rapid 1 mm yr vertical component movements of large crustal blocks result we refer to these crustal displacements as tectonic surges the melt lubricated shears are characterized by the close association of sheared country rocks with foliated or massive igneous sills and plutons rocks that formed at different crustal levels are juxtaposed across these shear zones one result of surges with large lateral component of movement is metamorphic inversion with high pressure and high temperature metamorphic rocks structurally over lower pressure and temperature assemblages large and rapid vertical surges may displace crust containing abundant melt and may result in high t p including granulite facies metamorphism and preservation of metamorphic textures caused by rapid decompression

frictional viscous flow in mylonite with varied bimineralic composition and its effect on lithospheric strength abstract a theoretical composite flow law is presented for mylonite containing interconnected layers of a weak mineral undergoing power law creep and porphyroclasts of a stronger mineral undergoing fracture and frictional sliding such mylonite termed clastomylonite is said to undergo frictional viscous fv mylonitic flow its bulk strength is expressed as a function of bimineralic composition temperature effective pressure and shear strain rate as well as the material parameters for the constituent minerals the fv flow law predicts that the rheology of clastomylonite is predominantly non linear viscous and only slightly pressure sensitive for most bimineralic compositions fv mylonitic flow is shown to occupy a depth interval between cataclastic flow involving adhesive wear in the upper crust and fully viscous mylonitic flow at greater depths the transition from adhesive wear to fv mylonitic flow is related to the onset of dislocation creep glide plus climb in the weakest phase and is inferred to coincide with a crustal strength maximum a peak strength of about 80 mpa is calculated with a combination of byerlee s constants for frictional sliding of granite and the fv flow law for granitic clastomylonite 30 vol quartz at elevated fluid pressures this value falls within the range of flow stresses independently obtained from quartz palaeopiezometry in many greenschist facies granitic mylonite zones

an automated strategy for calculation of phase diagram sections and retrieval of rock properties as a function of physical conditions we formulate an algorithm for the calculation of stable phase relations of a system with constrained bulk composition as a function of its environmental variables the basis of this algorithm is the approximate representation of the free energy composition surfaces of solution phases by inscribed polyhedra this representation leads to discretization of high variance phase fields into a continuous mesh of smaller polygonal fields within which the composition and physical properties of the phases are uniquely determined the resulting phase diagram sections are useful for understanding the phase relations of complex metamorphic systems and for applications in which it is necessary to establish the variations in rock properties such as density seismic velocities and volatile content through a metamorphic cycle the algorithm has been implemented within a computer program that is general with respect to both the choice of variables and the number of components and phases possible in a system and is independent of the structure of the equations of state used to describe the phases of the system

the role of sedimentary and tectonic brines in the damara orogen namibia abstract along the southern margin of the upper proterozoic damara orogen namibia an accumulation of extraordinarily large megacrystalline quartz dolomite bodies occur they were emplaced in tectonically controlled positions during an early deformational phase of the damara orogeny where hot nappes were thrust over a fluvial lacustrine and evaporitic metaplaya sequence kamtsas and duruchaus formations which was deposited on the faulted ew trending continental margin of the kalahari craton individual occurrences of the quartz dolomite bodies often cover several hundred square meters characteristic for the quartz dolomite bodies is zoning with an outer shell of giant milky quartz crystals some more than 15 m long along the c axis tightly intergrown or twinned brazilian twins with a perfect cleavage parallel to the positive rhombohedral faces 1011 there is an inner shell of crystalline dolomite and a central pipe of dolomitic breccia based on fluid inclusions studies the formation fluids of quartz dolomite bodies can be related to the mobilization of interstitial fluids and to dehydration and leaching of evaporitic hydrate minerals of the metaplaya sequence the fluids are characterized by extremely high salinities of up to 68 wt total salt content minimum temperatures of formation as determined in fluid inclusion studies ranged from 150 to 250 c at a later stage co 2 derived from decarbonatization reactions was dissolved in the fluids changes in pressure and temperature led to effervescence and the formation of a quartz stockwork in the surrounding country rock during the main phase of the progressive damara orogeny the southward advancing accretionary nappe pile of the khomas trough drove ahead large amounts of tectonometamorphic fluids characterized by intermediate salinity and high co 2 contents when these fluids met with the previously established hypersaline fluid system large amounts of co 2 were released due to the mixing of the two fluids if there is no mixing each fluid then maintains its salinity and there is no co 2 degassing the co 2 from this mixing is now present as secondary high density inclusions not only in the quartz dolomite bodies but also in the surrounding country rock pressure estimations indicate at least 100 600 mpa as a minimum pressure of formation for these inclusions the remaining aqueous fluid phase has produced local alterations and cu pb and au mineralization

elevation changes of glaciers revealed by multitemporal digital elevation models calibrated by gps survey in the khumbu region nepal himalaya 1992 2008 due to remoteness and high altitude only a few ground based glacier change studies are available in high mountain areas in the himalaya however digital elevation models based on remotely sensed data rs dems provide feasible opportunities to evaluate how fast himalayan glaciers are changing here we compute elevation changes in glacier surface total area 183 3 km in the khumbu region nepal himalaya for the period 1992 2008 using multitemporal rs dems and a map derived dem calibrated with differential gps survey data in 2007 elevation change is calculated by generating a weighted least squares linear regression model our method enables us to provide the distribution of uncertainty of the elevation change debris covered areas show large lowering rates the spatial distribution of elevation change shows that the different wastage features of the debris covered glaciers depend on their scale slope and the existence of glacial lakes the elevation changes of glaciers in the eastern khumbu region are in line with previous studies the regional average mass balance of 0 40 0 25mw e a for the period 1992 2008 is consistent with a global value of about 0 55mw e a for the period 1996 2005

contrasted surface mass balances of debris free glaciers observed between the southern and the inner parts of the everest region 2007 15 three debris free glaciers with strongly differing annual glaciological glacier wide mass balances mbs are monitored in the everest region central himalaya nepal the mass budget of mera glacier 5 1 km 2 in 2012 located in the southern part of this region was balanced during 2007 15 whereas pokalde 0 1 km 2 in 2011 and west changri nup glaciers 0 9 km 2 in 2013 30 km further north have been losing mass rapidly with annual glacier wide mbs of 0 69 0 28 m w e a 1 2009 15 and 1 24 0 27 m w e a 1 2010 15 respectively an analysis of high elevation meteorological variables reveals that these glaciers are sensitive to precipitation and to occasional severe cyclonic storms originating from the bay of bengal we observe a negative horizontal gradient of annual precipitation in south to north direction across the range 21 mm km 1 i e 2 km 1 this contrasted mass balance pattern over rather short distances is related i to the low maximum elevation of pokalde and west changri nup glaciers resulting in years where their accumulation area ratio is reduced to zero and ii to a steeper vertical gradient of mb for glaciers located in the inner arid part of the range

detecting himalayan glacial lake outburst floods from landsat time series abstract several thousands of moraine dammed and supraglacial lakes spread over the hindu kush himalayan hkh region and some have grown rapidly in past decades due to glacier retreat the sudden emptying of these lakes releases large volumes of water and sediment in destructive glacial lake outburst floods glofs one of the most publicised natural hazards to the rapidly growing himalayan population despite the growing number and size of glacial lakes the frequency of documented glofs is remarkably constant we explore this possible reporting bias and offer a new processing chain for establishing a more complete himalayan glof inventory we make use of the full seasonal archive of landsat images between 1988 and 2016 and track automatically where glofs left shrinking water bodies and tails of sediment at high elevations we trained a random forest classifier to generate fuzzy land cover maps for 2491 images achieving overall accuracies of 91 we developed a likelihood based change point technique to estimate the timing of glofs at the pixel scale our method objectively detected ten out of eleven documented glofs and another ten lakes that gave rise to previously unreported glofs we thus nearly doubled the existing glof record for a study area covering 10 of the hkh region remaining challenges for automatically detecting glofs include image insufficiently accurate co registration misclassifications in the land cover maps and image noise from clouds shadows or ice yet our processing chain is robust and has the potential for being applied on the greater hkh and mountain ranges elsewhere opening the door for objectively expanding the knowledge base on glof activity over the past three decades

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

overall recession and mass budget of gangotri glacier garhwal himalayas from 1965 to 2015 using remote sensing data thinning rates for the debris covered gangotri glacier and its tributary glaciers during the period 1968 2014 length variation and area vacated at the snout from 1965 to 2015 and seasonal variation of ice surface velocity for the last two decades have been investigated in this study it was found that the mass loss of gangotri and its tributary glaciers was slightly less than those reported for other debris covered glaciers in the himalayan regions the average velocity during 2006 14 decreased by 6 7 as compared with that during 1993 2006 the debris covered area of the main trunk of gangotri glacier increased significantly from 1965 until 2015 with the maximum rate of increase 0 8 0 2 km2 a 1 during 2006 15 the retreat 9 0 3 5 m a 1 was less in recent years 2006 2015 but the down wasting 0 34 0 2 m a 1 in the same period 2006 2014 was higher than that 0 20 0 1 m a 1 during 1968 2006 the study reinforced the established fact that the glacier length change is a delayed response to climate change and in addition is affected by debris cover whereas glacier mass balance is a more direct and immediate response therefore it is recommended to study the glacier mass balance and not only the glacier extent to conclude about a glacier s response to climate change

plastic deformation of silicate garnets ii deformation microstructures in natural samples abstract we have used transmission electron microscopy to characterize the deformation microstructures in natural garnets from several localities eclogites from sesia lanzo alps eclogites and garnet amphibolite from braganca portugal garnet pyroxenite from lherz france and eclogites from yakutia pipe siberia two characteristic microstructures have been identified the first found in eclogites from the alps consists of microplasticity associated with microcracking that suggests brittle behavior the remaining samples show a microstructure characteristic of dislocation creep with recovery sub grain boundaries the transition between these deformation regimes occurs at 600 c i e at the boundary between group c and group b eclogites the deformation microstructures suggest that the dislocations experience strong lattice friction below 600 c whereas at high temperature diffusion assists dislocation glide and climb recovery we observed the following glide systems in the whole temperature range 1 2 111 110 1 2 111 112 1 2 111 123 100 010 and 100 011 no correlation could be established between the dislocation microstructure and the hydrous component or the chemistry of the garnets among the pyralspites comparison of the natural deformation microstructures and those generated in high pressure experiments voegele et al 1998 part i validates the extrapolation of experimental data to nature

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

slight mass gain of karakoram glaciers in the early twenty first century the mass balance of hindu kush karakoram himalaya glaciers has been debated partly because of a severe lack of observations from the region an analysis of the regional mass balance of karakoram glaciers by comparison of digital elevation models from 1999 to 2008 reveals a small glacier mass gain in the area

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

deformation history of the qianlishan complex khondalite belt north china structures ages and tectonic implications abstract the qianlishan complex is a multiply deformed granulite terrane of the khondalite belt that represents a paleoproterozoic continent continent collisional orogen in the western block of the north china craton two major stages of deformation d1 and d2 were identified in the qianlishan complex d1 mainly produced nww trending overturned to recumbent intrafolial isoclinal folds f1 sub horizontal penetrative foliations s1 nne ssw mineral lineations l1 associated with top to the ssw thrust shear reflecting crustal thickening due to the nne ssw compression d1 was developed with the prograde m1 and peak m2 granulite facies metamorphism d2 successively superposed the d1 structures and was characterized by nww see trending doubly plunging open to tight upright folds f2 and minor sub vertical axial planar foliations cleavages s2 d2 was accompanied by post peak near isothermal decompression m3 probably related to exhumation following the crustal thickening sims u pb zircon ages of deformation related leucocratic dykes demonstrate that d1 broadly occurred at 1976 1936 ma and d2 subsequently happened at 1936 1854 ma these results indicate that the khondalite belt underwent long term 100 myr polyphase deformation and high grade metamorphism associated with magmatism timing constraints and kinematic compatibility suggest that the deformation sequence resulted from the nne ssw collision between the yinshan and ordos blocks to form the western block at 1 95 ga

crystal preferred orientations of garnet comparison between numerical simulations and electron back scattered diffraction ebsd measurements in naturally deformed eclogites observations of dislocations sub grains and elongated crystal shapes support plastic deformation of garnet in laboratory experiments and naturally deformed eclogites to evaluate the crystal preferred orientations cpo of garnet formed in axial shortening pure shear and simple shear we performed numerical simulations of cpo development during plastic flow using the visco plastic self consistent model as input for the models we use the slip systems determined by transmission electron microscopy using experimentally deformed specimens although in garnet 66 slip systems are available slip on the k111l 110 system provides over 86 of the total strain in the simulations characteristic cpo distributions are produced for the three deformation paths with the cpo being strongest for axial shortening and weakest for simple shear compared with low symmetry minerals the pole figure densities of garnet which has cubic symmetry are weak k100l axes tend to align with the shortening direction in all three deformation modes the simulations are compared with cpo of naturally deformed garnet from nine eclogite samples from the alps norway and mali which contain 20 40 garnet all samples show weak garnet cpo only two samples have a cpo pattern similar to the simulations for simple shear no samples are similar to simulations for axial strain or pure shear the presence of other weaker minerals such as omphacite and quartz with volume fractions higher than garnet probably prevented garnet from becoming highly strained and developing characteristic cpos in these eclogites higher volume fractions of garnet and higher temperature conditions may however allow the development of garnet cpo in the mantle transition zone particularly within subducted oceanic material morb q 2004 published by elsevier ltd

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

dislocation creep regimes in quartz aggregates abstract using optical and tem microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates depending on the relative rates of grain boundary migration dislocation climb and dislocation production within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization at lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion controlled dislocation climb to be an effective recovery mechanism in this regime recovery is accommodated by strain induced grain boundary migration recrystallization with an increase in temperature or decrease in strain rate the rate of dislocation climb becomes sufficiently rapid to accommodate recovery in this regime dynamic recrystallization occurs by progressive subgrain rotation with a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery however in this regime grain boundary migration is rapid thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation the identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers in addition the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred

accelerated glacier mass loss 2011 2016 over the puruogangri ice field in the inner tibetan plateau revealed by bistatic insar measurements abstract the temporal variation of glacier mass balance during recent years remains poorly known for the mountain glaciers in the inner tibetan plateau itp due to the lack of field measurements in this study we retrieved the annual glacier mass balance of the puruogangri ice field which is the largest modern ice mass in the itp by differencing multi temporal digital elevation models dems generated with five pairs of tandem x bistatic interferometric synthetic aperture radar insar images acquired between april 2011 and january 2016 we compared the tandem x dems in january and april 2012 to estimate the x band radar penetration depth difference 0 61 0 06 m which enabled systematic bias correction in the estimation of annual glacier mass balance the observed mass balance reveals a glacier mass gain of 0 44 0 10 m w e yr 1 in 2011 12 which was followed by accelerated glacier mass loss in 2012 16 glacier mass balances of 0 13 0 03 0 34 0 06 and 0 52 0 10 m w e yr 1 were estimated for the periods of 2012 13 2013 14 and 2014 16 respectively this accelerating trend of glacier mass loss is likely caused by the continuous decrease in annual precipitation according to the climate data recorded by adjacent meteorological stations this study demonstrates that repeated bistatic insar measurement is a promising method for monitoring glacier elevation change and mass balance at regular intervals