remote sensing estimates of glacier mass balances in the himachal pradesh western himalaya india abstract although they correspond to an important fraction of the total area of mountain glaciers 33 000 km2 out of 546 000 km2 himalayan glaciers and their mass balance are poorly sampled for example between 1977 and 1999 the average area surveyed each year on the field was 6 8 km2 only no direct mass balance measurement is available after 1999 to contribute to fill this gap we use remote sensing data to monitor glacier elevation changes and mass balances in the spiti lahaul region 32 2 n 77 6 e himachal pradesh western himalaya india our measurements are obtained by comparing a 2004 digital elevation model dem to the 2000 srtm shuttle radar topographic mission topography the 2004 dem is derived from two spot5 satellite optical images without any ground control points this is achieved thanks to the good on board geolocation of spot5 scenes and using srtm elevations as a reference on the ice free zones before comparison on glaciers the two dems are analyzed on the stable areas surrounding the glaciers where no elevation change is expected two different biases are detected a long wavelength bias affects the spot5 dem and is correlated to an anomaly in the roll of the spot5 satellite a bias is also observed as a function of altitude and is attributed to the srtm dataset both biases are modeled and removed to permit unbiased comparison of the two dem on the 915 km2 ice covered area digitized from an aster image on most glaciers a clear thinning is measured at low elevations even on debris covered tongues between 1999 and 2004 we obtain an overall specific mass balance of 0 7 to 0 85 m a water equivalent depending on the density we use for the lost or gained material in the accumulation zone this rate of ice loss is twice higher than the long term 1977 to 1999 mass balance record for himalaya indicating an increase in the pace of glacier wastage to assess whether these ice losses are size dependant all glaciers were classified into three samples according to their areal extent all three samples show ice loss the loss being higher for glaciers larger than 30 km2 in the case of the benchmark chhota shigri glacier a good agreement is found between our satellite observations and the mass balances measured on the field during hydrological years 2002 2003 and 2003 2004 future studies using a similar methodology could determine whether similar ice losses have occurred in other parts of the himalaya and may allow evaluation of the contribution of this mountain range to ongoing sea level rise

examining geodetic glacier mass balance in the eastern pamir transition zone glaciers in the eastern pamir have reportedly been gaining mass during recent decades even though glaciers in most other regions in high mountain asia have been in recession questions still remain about whether the trend is strengthening or weakening and how far the positive balances extend into the eastern pamir to address these gaps we use three different digital elevation models to reconstruct glacier surface elevation changes over two periods 2000 09 and 2000 15 16 we characterize the eastern pamir as a zone of transition from positive to negative mass balance with the boundary lying at the northern end of kongur tagh and find that glaciers situated at higher elevations are those with the most positive balances most 67 of 55 glaciers displayed a net mass gain since the 21st century this led to an increasing regional geodetic glacier mass balance from 0 06 0 16 m w e a 1 in 2000 09 to 0 06 0 04 m w e a 1 in 2000 15 16 surge type glaciers which are prevalent in the eastern pamir showed fluctuations in mass balance on an individual scale during and after surges but no statistical difference compared to non surge type glaciers when aggregated across the region

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

metamorphism and granite genesis in the hidaka metamorphic belt hokkaido japan the main zone of the hidaka metamorphic belt is an uplifted crustal section of island arc type the crust was formed during early tertiary time as a result of collision between two arc trench systems of cretaceous age the crustal metamorphic sequence is divided into four metamorphic zones i iv in which zone iv is in the granulite facies a detailed study of the evolution of the hidaka belt based on a revised p t t analysis of the metamorphic rocks notably a newly found staurolite bearing granulite confirms a prograde isobaric heating path after a supposed event of tectonic thickening of accretionary sedimentary and oceanic crustal rocks during the peak metamorphic event c 53 ma the regional geothermal gradient attained 33 40 c km 1 and the highest p t condition obtained from the lowest part of the granulite unit is 830 c 7 kbar in this part xh2o of gt opx cd gneiss is about 0 15 and that of gt cd bt gneiss is 0 4 the p t xh2o condition of the granulite unit is well within a field where fluid present partial melting of pelitic and greywacke metamorphic rocks takes place this is in harmony with the restitic nature of the gt opx cd gneiss in the lowest part of the granulite unit the possibility that partial melting took place in the main zone is significant for the genesis of the peraluminous s type granitic rocks within it the s type granitic rocks in this zone are opx gt bt tonalite in the granulite zone gt cd bt tonalite in the amphibolite zone and cd bt mus tonalite in the bt mus gneiss zone the mineralogical and chemical nature of these strongly peraluminous tonalitic rocks permit them to be regarded as having been derived from s type granitic magma generated by crustal anatexis of pelitic metamorphic rocks in deeper crust

accelerated lake expansion on the tibetan plateau in the 2000s induced by glacial melting or other processes ccelerated lake expansion in the 2000s has been confirmed by both dramatic lake area increases for 312 lakes larger than 10 km2 derived from optical images and rapid water level rises for 117 lakes with water level data measured by satellite altimetry however the underlying climate causes remain unclear this paper analyzes the relationship between the water level changes of lakes on the plateau and the potential driving factors such as the glacier meltwater supply and a dependency on precipitation and runoff over the whole plateau and in each zone the results show that the rates of change of non glacier fed lakes in the 2000s were as high as those of glacier fed lakes across the whole plateau and the lake level changes were closely associated with the lake supply coefficients the basin lake area ratio the lake variations agreed well with the spatial pattern of precipitation changes however in different zones especially at around 33 n north of the plateau glacier fed lakes did exhibit faster lake level increases than no glacier fed lakes indicating that the presence of a glacier meltwater supply augmented the precipitation driven lake expansions in these areas despite the absence of quantitative modeling due to limited data availability this study provides qualitative support that the lake expansions on the tibetan plateau in the 2000s have been driven primarily by changes in precipitation and evapotranspiration and not solely by the effect of glacier wastage

lake volume and groundwater storage variations in tibetan plateau s endorheic basin the tibetan plateau tp the highest and largest plateau in the world with complex and competing cryospheric hydrologic geodynamic processes is particularly sensitive to anthropogenic warming the quantitative water mass budget in the tp is poorly known here we examine annual changes in lake area level and volume during 1970s 2015 we find that a complex pattern of lake volume changes during 1970s 2015 a slight decrease of 2 78 gt yr 1 during 1970s 1995 followed by a rapid increase of 12 53 gt yr 1 during 1996 2010 and then a recent deceleration 1 46 gt yr 1 during 2011 2015 we then estimated the recent water mass budget for the inner tp 2003 2009 including changes in terrestrial water storage lake volume glacier mass snow water equivalent swe soil moisture and permafrost the dominant components of water mass budget namely changes in lake volume 7 72 0 63 gt yr 1 and groundwater storage 5 01 1 59 gt yr 1 increased at similar rates we find that increased net precipitation contributes the majority of water supply 74 for the lake volume increase followed by glacier mass loss 13 and ground ice melt due to permafrost degradation 12 other term such as swe 1 makes a relatively small contribution these results suggest that the hydrologic cycle in the tp has intensified remarkably during recent decades

slight glacier mass loss in the karakoram region during the 1970s to 2000 revealed by kh 9 images and srtm dem an anomalously slight glacier mass gain during 2000 to the 2010s has recently been reported in the karakoram region however to date no investigations of the region wide glacier mass balance in the karakoram prior to 2000 have been reported leaving a knowledge gap for assessing glacier responses to climate change we calculated elevation and mass change using dems generated from kh 9 images acquired during 1973 1980 and the 1 arc second srtm dem we find a slight mass loss of 0 09 0 03 m w e a 1 12 366 km2 for 1973 2000 which is less negative than the global average rate for 1971 2009 0 31 0 19 m w e a 1 within the karakoram the glacier change patterns are spatially and temporally heterogeneous in particular a nearly stable state in the central karakoram 0 04 0 05 m w e a 1 during the period 1974 2000 implies that the karakoram anomaly dates back to the 1970s combined with the previous studies we conclude that the karakoram glaciers as a whole were in a nearly balanced state during the 1970s to the 2010s

lake seasonality across the tibetan plateau and their varying relationship with regional mass changes and local hydrology the recent growth and deepening of inland lakes in the tibetan plateau tp may be a salient indicator of the consequences of climate change the seasonal dynamics of these lakes is poorly understood despite this being potentially crucial for disentangling contributions from glacier melt and precipitation which are all sensitive to climate to lake water budget using in situ observations satellite altimetry and gravimetry data we identified two patterns of lake level seasonality in the central northern and northeastern tp lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons which is consistent with regional mass changes related to monsoon precipitation and evaporation in the northwestern tp however lake levels exhibit dramatic increases during both warm and cold seasons which deviate from regional mass changes this appears to be more connected with high spring snowfall and large summer glacier melt the variable lake level response to different drivers indicates heterogeneous sensitivity to climate change between the northwestern tp and other regions

karakoram geodetic glacier mass balances between 2008 and 2016 persistence of the anomaly and influence of a large rock avalanche on siachen glacier karakoram glaciers experienced balanced or slightly positive mass budgets since at least the 1970s here we provide an update on the state of balance of central and eastern karakoram glaciers 12 000 km2 between 2008 and 2016 by differencing dems derived from satellite optical images the mass budget of central karakoram glaciers was slightly positive 0 12 0 14 m w e a 1 while eastern karakoram glaciers lost mass 0 24 0 12 m w e a 1 the glacier wide mass balances of surge type and nonsurge type glaciers were not statistically different our elevation change data also depict the effect of a 100 mm3 rock avalanche on siachen glacier ablation area in september 2010 it covered a 4 km2 area with a thick debris layer that unexpectedly led to locally enhanced glacier mass loss during the following years enhanced melt opened a 100 m deep 2 km2 depression and contributed to 6 of the mass loss of siachen glacier from 2010 to 2016 0 39 m w e a 1 we hypothesize that sub or englacial melt may be responsible for this intriguing behaviour this study contributes to a better knowledge of the regional pattern of the karakoram anomaly and of the influence of rock avalanches on glacier mass changes

tertiary deep crustal ultrametamorphism in the hidaka metamorphic belt northern japan the main zone of the hidaka metamorphic belt is an imbricate stack of crustal material derived from an island arc in which a sequence of units with increasing metamorphic grade from low to high structural levels is exposed the basal part of the metamorphic sequence underwent granulite facies metamorphism with peak p t conditions of 7kbar 870 c in this zone pelitic granulite includes leucosomes which consist mainly of orthopyroxene plagioclase quartz to test whether the leucosome was derived by partial melting of the surrounding pelite melting experiments of the pelitic granulite were carried out for water saturated and dry systems at 7 kbar and 850 c the chemical composition of the leucosome produced during these runs shows a peraluminous s type tonalitic affinity and is located very close to the tie line between the average melts produced in water saturated systems and the average composition of the residual orthopyroxene plagioclase this therefore suggests that the lecosome in pelitic granulite was formed by incipient anatexis at close to the highest p t condition of the main zone the age of the crustal anatexis is determined by the rb sr whole rock isochron method for garnet cordierite biotite gneiss host rock garnet orthopyroxene cordierite gneiss restite and s type tonalite melt this gives an age of 56 0 ma with an initial 87sr 86sr ratio of 0 705711 the s type tonalite magmas that form large intrusive masses in the main zone were probably generated by crustal anatexis in deeper parts of the crust at the same time late palaeocene

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

penetration depth of interferometric synthetic aperture radar signals in snow and ice digital elevation models of glaciated terrain produced by the nasa jet propulsion laboratory jpl airborne interferometric synthetic aperture radar insar instrument in greenland and alaska at the c 5 6 cm wave length and l band 24 cm frequencies were compared with surface elevation measured from airborne laser altimetry to estimate the phase center of the interferometric depth or penetration depth p on cold polar firn at greenland summit p 9 2m at c and 14 4m at l band on the exposed ice surface of jakobshavn isbrae west greenland p 1 2 m at c and 3 3 m at l band except on smooth marginal ice where p 15 5 m on colder marginal ice of northeast greenland p reaches 60 to 120 m at l band on the temperate ice of brady glacier alaska p is 4 2 m at c and 12 6 m at l band with little dependence on snow ice conditions the implications of the results on the scientific use of insar data over snow ice terrain is discussed

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

changes in ice dynamics elevation and mass discharge of dinsmoor bombardier edgeworth glacier system antarctic peninsula abstract the northern antarctic peninsula is one of the fastest changing regions on earth the disintegration of the larsen a ice shelf in 1995 caused tributary glaciers to adjust by speeding up surface lowering and overall increased ice mass discharge in this study we investigate the temporal variation of these changes at the dinsmoor bombardier edgeworth glacier system by analyzing dense time series from various spaceborne and airborne earth observation missions precollapse ice shelf conditions and subsequent adjustments through 2014 were covered our results show a response of the glacier system some months after the breakup reaching maximum surface velocities at the glacier front of up to 8 8 m d in 1999 and a subsequent decrease to 1 5 m d in 2014 using a dense time series of interferometrically derived tandem x digital elevation models and photogrammetric data an exponential function was fitted for the decrease in surface elevation elevation changes in areas below 1000 m a s l amounted to at least 130 15 m between 1995 and 2014 with change rates of 3 15 m a between 2003 and 2008 current change rates 2010 2014 are in the range of 1 7 m a mass imbalances were computed with different scenarios of boundary conditions the most plausible results amount to 40 7 3 9 gt the contribution to sea level rise was estimated to be 18 8 1 8 gt corresponding to a 0 052 0 005 mm sea level equivalent for the period 1995 2014 our analysis and scenario considerations revealed that major uncertainties still exist due to insufficiently accurate ice thickness information the second largest uncertainty in the computations was the glacier surface mass balance which is still poorly known our time series analysis facilitates an improved comparison with grace data and as input to modeling of glacio isostatic uplift in this region the study contributed to a better understanding of how glacier systems adjust to ice shelf disintegration

a refined garnet biotite fe mg exchange geothermometer and its application in amphibolites and granulites a new formulation of garnet biotite fe mg exchange thermometer has been developed through statistical regression of the reversed experimental data of ferry and spear input parameters include available thermo chemical data for quaternary fe mg ca mn garnet solid solution and for excess free energy terms associated with mixing of al and ti in octahedral sites in biotite solid solution the regression indicates that fe mg mixing in biotite approximates a symmetrical regular solution model showing positive deviation from ideality withw femg bi 1073 490 cal mol h r and s r for the garnet biotite exchange equilibrium were derived to be 4301 cal and 1 85 cal respectively the resultant thermometer gives consistent results for rocks with a much wider compositional range than can be accommodated by earlier formulations

dehydration melting fluid buffering and decompressional p t path in a granulite complex from the eastern ghats india a suite of metapelites charnockites calc silicate rocks quartzo feldspathic gneisses and mafic granulites is exposed at garbham a part of the eastern ghats granulite belt of india reaction textures and mineral compositional data have been used to determine the p t x evolutionary history of the granulites in metapelites and charnockites dehydration melting reactions involving biotite produced quartzofeldspathic segregations during peak metamorphism however migration of melt from the site of generation was limited subsequent to peak metamorphism at c 860 c and 8 kbar the complex evolved through nearly isothermal decompression to 530 650 c and 4 5 kbar during this phase coronal garnet grew in the calc silicates while garnet in the presence of quartz broke down in charnockite and mafic granulite fluid activities during metamorphism were internally buffered in different lithologies in the presence of a melt phase the p t path of the granulites at garbham contrasts sharply with the other parts of the eastern ghats granulite belt where the rocks show dominantly near isobaric cooling subsequent to peak metamorphism

calculation of co 2 activities using scapolite equilibria constraints on the presence and composition of a fluid phase during high grade metamorphism thermodynamic and phase equilibrium data for scapolite have been used to calculate co2 activities aco2 and to evaluate the presence or absence of a fluid phase in high grade scapolite bearing meta anorthosite granulites calc silicates and mafix xenoliths the assemblage scapolite plagioclase garnet quartz may be used to calculate or limit aco2 by the reaction meionite quartz grossular anorthite co2 granulites from four high grade terranes grenville province canada sargut belt india furua complex tanzania bergen arcs norway yield aco2 0 4 1 with most 0 7 for scapolite bearing granulites from the furua complex in which aco2 0 9 calculated h2o activities ah2o based on phlogopite dehydration equilibria are uniformly low 0 1 0 2 the aco2 calculated for meta anorthosite from the grenville province ontario ranges from 0 2 to 0 8 for grenville meta anorthosite also containing epidote the ah2o calculated from clinozoisite dehydration ranges from 0 2 to 0 6 calc silicates from the grenville sargur and furua terranes mostly yield aco2 1 the calculated fluid activities are consistent with metamorphism 1 in the presence of a mixed co2 h2o fluid phase in which co2 is the dominant fluid species but other c o h s species are minor 2 in the absence of a bulk fluid phase fluid absent metamorphism or 3 in the presence of a fluid bearing melt phase the results for many granulites and grenville meta anorthosite are consistent with the presence of a co2 rich mixed co2 h2o fluid phase in contrast the relatively restricted and low values of aco2 for calc silicates require an h2o rich fluid or absence of a fluid phase during metamorphism the range of values for xenoliths are most consistent with absence of a fluid phase the primary implication of these results is that a co2 rich fluid accounts for the reduced ah2o in scapolite bearing granulites however scapolite may be stable with a wide range of fluid compositions or in the absence of a fluid phase and the presence of scapolite is not a priori evidence of a co2 rich fluid phase in addition close association of scapolite free mafic granulites with scapolite bearing granulites having identical mineral compositions in the furua complex and the absence of scapolite from most granulite terranes implies that a co2 rich fluid phase is not pervasive on an outcrop scale or common to all granulite terranes

elevation change of fedchenko glacier pamir mountains from gnss field measurements and tandem x elevation models with a focus on the upper glacier fedchenko glacier experienced a large thickness loss since the first scientific investigations in 1928 as the largest glacier in the pamir mountains this glacier plays an important role for the regional glacier mass budget we use a series of global navigation satellite systems observations from 2009 to 2016 and tandem x elevation models from 2011 to 2016 to investigate recent elevation changes accounting for radar wave penetration minimizes biases in elevation that can otherwise reach up to 6 m in dry snow on fedchenko glacier with mean values of 3 4 m in the high accumulation regions the seasonal elevation changes reach up to 5 m the glacier surface elevation decreased along its entire length over multi year periods thinning rates increased between 2000 and 2016 by a factor of 1 8 compared with 1928 2000 resulting in peak values of 1 5 m a 1 even the highest accumulation basins above 5000 m elevation have been affected by glacier thinning with change rates between 0 2 and 0 4 m a 1 from 2009 to 2016 the estimated glacier wide mass balance rates are 0 27 0 05 m w e a 1 for 2000 to 2011 and 0 51 0 04 m w e a 1 between 2011 and 2016

glacier mass balance in the qinghai tibet plateau and its surroundings from the mid 1970s to 2000 based on hexagon kh 9 and srtm dems abstract in the context of global warming glacier changes in the qinghai tibet plateau qtp and its surroundings have attracted a great amount of public attention to date there have been many studies of glacier mass balance across the qtp however given that most of the previous studies have focused on a short observation period 2000 2015 and that long term mass change measurements are available only for some local regions we utilized declassified kh 9 images and 1 arc second shuttle radar topography mission srtm digital elevation models dems to provide the region wide mass balance from the mid 1970s to 2000 for a larger scale including 11 sample regions across the qtp and its surroundings the final results indicate that the glaciers in the northwest of the qtp have shown a less negative or near zero mass balance ranging from 0 11 0 13 m w e a 1 to 0 02 0 10 m w e a 1 compared to those in the southeast part with a mass balance range of 0 30 0 12 m w e a 1 to 0 11 0 14 m w e a 1 the most serious mass loss has emerged in the central eastern himalaya integrating our results with the observations after 2000 suggests that over the past four decades mid 1970s to the mid 2010s the glaciers in the himalaya nyainqentanglha and tanggula mountains as a whole have exhibited accelerated mass loss and the most significant acceleration has occurred in the eastern nyainqentanglha moreover the hindu raj glaciers have shown a stable rate of continuous mass loss while a nearly stable or slight mass gain state in the western kunlun region can be dated back to at least as far as the mid 1970s

complete three dimensional coseismic deformation field of the 2016 central tottori earthquake by integrating left and right looking insar observations with the improved sm vce method

the timescale and mechanism of granulite formation at kurunegala sri lanka incipient charnockite formation at kurunegala in sri lanka is characterized by the growth of orthopyroxene at the expense of amphibole and biotite in an originally homogeneous gneiss mineral equilibria in the charnockite assemblage record pressure temperature p t conditions of 738 60 c and 6 9 1 2 kbar at 17 0 1 2 log fo2 and ah2o 0 18 0 16 wholerock trace element and isotopic measurements show that charnockite formation was accompanied by a systematic depletion of sm rb pb u sr nd with a fractionation of rb sr sm nd and th u ratios and crystallization of the charnockite assemblage at 535 5 ma major element fe mg ca and sm nd equilibration between minerals occurred at 524 9 ma whereas pb and rb sr underwent continued exchange to 501 5 ma and 486 1 ma respectively trace element data for both amphibolite and charnockite minerals show that depletion on a whole rock scale can be accounted for either by changes in mineral modes or trace element abundances within the immediate area of dehydration the fractionation of sm nd on a whole rock scale is controlled by the breakdown of amphibole without the growth of a major new host phase for sm in the charnockite rubidium and sr are dependent on the relative behaviour of biotite plagioclase and alkali feldspar modelling of dehydration melting involving the breakdown of amphibole biotite and alkali feldspar reproduces the observed sm nd and rb sr fractionation and indicates the loss of small melt fractions on a cm scale from the charnockite these observations suggest that partial melting is the most plausible means of effecting both the dehydration and depletion that accompanies charnockite formation

reversed determination of the reaction phlogopite quartz enstatite potassium feldspar h 2 o in the ranges 750 875 degrees c and 2 12 kbar at low h 2 o activity with concentrated kcl solutions the reaction of phlogopite plus quartz to enstatite potassium feldspar and aqueous fluid in the system kmash kcl was reversed at 2 12 kbar and 750 875 degrees c and at low h 2 o activities by reversal of the h 2 o content of concentrated kcl solutions equilibrated with product and reactant assemblages synthetic 1m phlogopite kmg 3 alsi 3 o 10 oh 2 and enstatite mgsio 3 maintained end member stoichiometry throughout and the potassium feldspar kalsi 3 o 8 was a high sanidine based on unit cell refinements the broad p t xh 2 o and narrow reversal ranges of this investigation were possible because of the low and well defined h 2 o activity yet powerful fluxing action of concentrated kcl solutions solubility experiments on quartz and potassium feldspar in our p t xh 2 o range showed that fluid phase solution of silicate constituents was too small to have affected the h 2 o activity in the experiments the new determinations are more definitive than previous work done at very low pressures with pure h 2 o or in co 2 h 2 o mixtures they establish the standard free energy of the reaction in the experimental range with an uncertainty of about 1 kj and indicate that the synthetic phlogopite has maximal al si disorder under our experimental conditions the standard enthalpy of reaction at 298 k is 106 54 or 2 0 kj 2sigma based on our reversals a value 6 kj less positive than that currently used by many workers in calculations of biotite stability and h 2 o activity in the petrogenesis of high grade metamorphic rocks the lower thermal stability that we find for phlogopite requires revision in estimates of h 2 o activity of granulite facies metamorphism typical values for the natural assemblage orthopyroxene biotite garnet potassium feldspar plagioclase quartz at deep crustal metamorphic conditions 750 850 degrees c 5 10 kbar are alpha h2o 0 4 0 6 compared with values of 0 15 0 30 which would have been estimated with previously available data on phlogopite stability an important consequence of the expanded h 2 o activity range of granulites is that alkali chloride solutions of only moderate concentration xh 2 o 0 5 0 7 which are the values observed in actual fluid inclusions in many kinds of igneous and metamorphic rocks are a feasible alternative to the vapor absent conditions considered necessary by many workers based on previous low estimates of h 2 o participation of concentrated brines in deep crust upper mantle metamorphic processes enables alkali metasomatism and other kinds of chemical transport in an aqueous fluid without large scale melting of the crust

quantifying the contribution of glacier meltwater in the expansion of the largest lake in tibet lake siling co is currently the largest endorheic lake in tibet and the lake surface area has expanded by about 40 since the 1970s with a remarkable acceleration after 1999 in this study a hydrologic modeling framework was established by linking the variable infiltration capacity vic land surface hydrologic model with the degree day glacier melt model over the lake siling co basin with an aim to quantify the contribution of each runoff component to changes in the lake storage we found that glacier melt contributed to less than 10 of the total water input to the lake during 1979 2013 while precipitation induced runoff in nonglacierized area was responsible for about 67 75 the mean annual water input to the lake increased by 2 15x10 9 m 3 yr 1 in 2000 2013 relative to that in 1979 1999 the amount of precipitation over the lake surface precipitation induced runoff and glacier melt runoff accounted for 13 82 and 5 of this total increase respectively suggesting that the substantial expansion of siling co in the 2000s was mostly due to the increase in precipitation induced runoff when modeling lake level changes during 1979 2013 we found that the water level rose by 14 1m when glacier melt was included and by only 10 5m a reduction of about one fourth when glacier melt was removed it is concluded that glacier melt played an important role in controlling the water level of siling co although it only contributed less than 10 of water input to the lake during 1979 2013

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

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

rheology of some continental lower crustal rocks abstract to gain insight into the rheology of selected feldspar bearing rocks from the continental lower crust clc three granulites from exposed lower crustal terrains and a microgabbro have been deformed to ca 10 strain at confining pressures of 0 8 1 0 gpa temperatures of 600 900 c and constant strain rates of 10 4 10 7 s 1 the most extensive work was done on the mafic pikwitonei and felsic adirondack granulites the pikwitonei mg hornblende plag an70 2 px has only a limited t range of apparent steady state behavior and strain softens at t 800 c at 10 5 10 6s 1 apparently associated with developing shear zones this strain softening is pressure insensitive from pc 0 8 1 0 gpa at t 850 c 10 6s 1 even though the dominant strain accommodation mechanisms change from semibrittle cataclastic to crystal plastic including dynamic recrystallization with increasing pressure plagioclase appears to bear more of the creep strain than amphibole at most experimental conditions except in those runs where both plagioclase and amphibole recrystallization occurs kapuskasing plag cpx gt granulite deformed at 800 c and at 850 c 10 6 s 1 has deformed in the steady state at stress levels only slightly greater than the pikwitonei the stillwater microgabbro and adirondack granulite are appreciably weaker and the latter exhibits homogeneous semibrittle steady state behavior over the entire range of conditions investigated for the adirondack 2 felds 2 px gt qtz granulite quartz 21 appears to control the creep rate at these low strains and steady state mechanical data fit well a creep power law with a 8 10 3 mpa ns 1 qc 243 kj mol and n 3 1 extrapolation of this flow law and of preliminary power law creep relations for the pikwitonei and microgabbro to a range of physical conditions assumed to encompass those at the continental moho supports geological and geophysical inferences that a mechanical discontinuity occurs at this transition zone with the lower crust generally being the weaker material in addition the stain softening exhibited by the pikwitonei may bear directly on the development of detachment zones at mid to lower crustal depths during prograde metamorphism

massive collapse of two glaciers in western tibet in 2016 after surge like instability surges and glacier avalanches are expressions of glacier instability and among the most dramatic phenomena in the mountain cryosphere until now the catastrophic collapse of a glacier combining the large volume of surges and mobility of ice avalanches has been reported only for the 2002 130 106 m3 detachment of kolka glacier caucasus mountains which has been considered a globally singular event here we report on the similar detachment of the entire lower parts of two adjacent glaciers in western tibet in july and september 2016 leading to an unprecedented pair of giant low angle ice avalanches with volumes of 68 2 106 m3 and 83 2 106 m3 on the basis of satellite remote sensing numerical modelling and field investigations we find that the twin collapses were caused by climate and weather driven external forcing acting on specific polythermal and soft bed glacier properties these factors converged to produce surge like enhancement of driving stresses and massively reduced basal friction connected to subglacial water and fine grained bed lithology to eventually exceed collapse thresholds in resisting forces of the tongues frozen to their bed our findings show that large catastrophic instabilities of low angle glaciers can happen under rare circumstances without historical precedent two catastrophic glacier collapse events in western tibet in 2016 were caused by a convergence of weather and glacier bed conditions according to an analysis of observations and modelling

texturally early fluid inclusions in garnets evidence of the prograde metamorphic path well formed texturally early fluid inclusions in garnets from the archean pikwitonei granulite domain manitoba canada have been analyzed using microthermometric methods the mean co2 homogenization temperature to liquid for inclusions in 12 of 13 samples from the cauchon lake nelson river area is 15 2 c n 125 2 8 2 c corresponding to a co2 density of 0 82 g cm3 inclusions in the remaining sample have somewhat lower co2 homogenization temperatures mean 5 4 c n 24 the studied inclusions contain an estimated 10 to 20 vol percent h2o with minor amounts of other fluid species such as ch4 n2 and or h2s the fluid inclusions were probably trapped during early garnet growth at relatively low pressures 5 kbar if at 750 c and appear to have undergone only limited or possibly no subsequent re equilibration this interpretation is consistent with the anti clock wise p t t path heating before loading determined for the pikwitonei region by other workers for such a prograde path inclusions entrapped early at high temperatures but at relatively low pressures would experience internal underpressures during most of the subsequent prograde and retrograde phases of metamorphism the texturally early fluid inclusions in garnets from the pikwitonei region therefore cannot be used to provide direct information about the highest metamorphic temperature and pressure conditions 750 c and 7 kbar however the results obtained in this study suggest that texturally early fluid inclusions in garnets may in some cases retain evidence of the prograde metamorphic path

garnet composition as a petrogenetic indicator an example from a marble calc silicate granulite interface at kondapalle eastern ghats belt india thep t fluid histories of aluminous garnet clinopyroxene bearing calc silicate granulites are commonly constrained through interpretation of sequential reaction textures based on activity corrected petrogenetic grids for model systems for example the widely used cas co2 h2o topologies application of these topologies to calc silicates of diverse bulk composition is limited by the fact that the role of clinopyroxene and hence of garnet composition in the garnet forming reactions is ignored or not adequately considered in this contribution the complexities that arise from the involvement of clinopyroxene in the garnet forming reactions are critically evaluated as an example the paragenetic relations and compositional features of clinopyroxene and coronitic garnet across paired scapolite and wollastonite dominated reaction zones scp cpx qtz cal qtz wo cal cpx scp developed between marble layers cal cpx wo scp and their host calc silicate granulite cpx pl qtz scp at an exposure in the high grade eastern ghats belt india are examined the microtextural features and systematic changes of modal and phase compositions across the profile indicate that clinopyroxene scapolite plagioclase quartz and calcite as well as wollastonite participated in the garnet forming reactions using the sub assemblage qtz cal cpx scp grt v in the system cao feo al2o3 sio2 co2 it is demonstrated that at the ambient p t xfluid conditions the reaction coefficients of the participating phases are uniquely defined by the garnet composition as a result the p t slope of a garnet forming reaction changes with the garnet composition with sharp changes at singular points across which one or more phases change their sides with respect to garnet in a given reaction to consider the consequences of these complexities on the reaction topology of calc silicate granulites a new petrogenetic grid for the system cao feo al2o3 sio2 co2 involving clinopyroxene has been constructed the effects of fluid composition co2 h2o o2 fluid pressure pfluid

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

the role of fluids in granulite facies metamorphism as deduced from oxygen and carbon isotopic compositions abstract based on stable isotope data of whole rock samples the main fluid rock exchange reactions in the high grade rocks of the crystalline basement of sri lanka is deduced to have occurred prior to granulite facies metamorphism the influx of external fluids during and after granulite facies conditions was only channellized and did not give rise to the formation of interconnected fluid films in rock volumes larger than several cm3 fluid present conditions were thus only manifest for relatively short periods of time much less than 106 y so that the conditions of granulite facies metamorphism of the sri lankan basement rocks in general can be characterized as fluid absent

early 21st century glacier thickness changes in the central tien shan abstract although studies based on satellite gravimetry 2003 2010 and laser altimetry 2003 2009 measurements have achieved region wide glacier mass change for the tien shan the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately in this study we investigated region wide glacier thickness change in the central tien shan cts during 2000 2012 by differencing the shuttle radar topographic mission srtm digital elevation model dem with a newly constructed dem from 27 tandem x images for a total glacier area of 7239 8 527 2 km 2 an average glacier thickness change rate of 0 24 0 22 m a was derived this result agrees well with the result based on satellite laser altimetry measurements reported earlier 0 31 0 41 m a with temporal synchronization a fine spatial resolution and wide coverage our measurements are able to reveal abundant glacier change features and dependencies in the cts firstly the lower mountains have seen a more severe glacier decline and the glaciers facing the prevailing wind westerlies have experienced a greater decline because of the stronger evaporation furthermore those glaciers lying along the extremely high meridian mountain range have obviously gained mass in their upper reaches because the air current from the west is blocked and lifted by the meridian mountain range secondly for the entire glacier body the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish some huge glaciers covered by heavy debris have still experienced a severe decline however even though the heavy debris did not prevent the ablation its attenuating effects were considerable thirdly for the glaciers that surged before 2000 the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones some large glaciers surged again during 2000 2012 however with much lower magnitudes than in previous surges in general the surge glaciers have experienced a greater decline than the non surge glaciers fourthly due to the ice front calving and subglacial thermal erosion glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land terminated glaciers overall the glaciers in the cts are more stable than those in other parts of the tien shan however the glacier state there is still alarming a moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones

the origins of granulites a metamorphic perspective although many recent reviews emphasize a uniformity in granulite pressure temperature p t conditions and paths granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation a thorough survey of over 90 granulite terranes or occurrences reveals that over 50 of them record p t conditions outside the 7 5 1 kbar and 800 50 c average granulite regime preferred by many authors in particular an increasing number of very high temperature 900 1000 c terranes are being recognized both on the basis of distinctive mineral assemblages and geothermobarometry petrogenetic grid and geothermobarometric approaches to the determination and interpretation of p t histories are both evaluated within the context of reaction textures to demonstrate that the large range in p t conditions is indeed real and that both near isothermal decompression itd and near isobaric cooling ibc p t paths are important amphibolite granulite transitions promoted by the passage of co 2 rich fluids as observed in southern india and sri lanka are exceptional and not representative of fluid related processes in the majority of terranes it is considered on the contrary that fluid absent conditions are typical of most granulites at or near the time of their recorded thermal maxima itd granulites are interpreted to have formed in crust thickened by collision with magmatic additions being an important extra heat source erosion alone is not however considered to be the dominant post collisional thinning process instead the itd paths are generated during more rapid thinning 1 2 mm yr exposure related to tectonic exhumation during moderate rate or waning extension ibc granulites may have formed in a variety of settings those which show anticlockwise p t histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion with or without additional crustal extension ibc granulites at shallow levels very rapid 5 mm yr extensional thinning subsequent to collision it is suggested that the preservation of ibc paths rather than itd paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust and that hybrid itd to ibc paths should also be observed most ibc granulites and probably many itd granulites have not been exposed at the earth s surface as a result of the tectonic episodes which produced them but have resided in the middle and lower crust for long periods of time 100 2000 ma following these events the eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation

numerical simulations of the atmospheric response to a sea surface temperature anomaly over the equatorial eastern pacific ocean abstract the atmospheric response to a sea surface temperature anomaly over the equatorial eastern pacific ocean ssta is investigated using the ucla general circulation model the ssta used is an idealization of that compiled by rasmusson and carpenter for the mature phase of el nino two simulations over seasons one without and the other with the ssta are performed and their results are compared for the northern hemisphere winter season in the tropics the ssta enhances precipitation over the central and eastern equatorial pacific while it decreases precipitation over the adjacent regions the anomalous precipitation is predominantly balanced by the anomalous moisture flux convergence which has comparable magnitude in the planetary boundary layer pbl and in the free atmosphere with quite different geographical distribution this suggests that the anomalous precipitation and hence the anomalous tropical cumulus heating cannot be related exclusively to either flow anomalies in the pbl or in the

raman spectroscopic characterization of h2o in co2 rich fluid inclusions in granulite facies metamorphic rocks abstract water h2o has been identified during raman analyses at 150 200 c of fluid inclusions from granulites that were previously thought to contain pure co2 at room temperature h2o in a co2 rich fluid inclusion forms an optically unresolvable liquid wetting the inclusion walls during heating the h2o phase evaporates into the co2 phase to produce a homogeneous h2o co2 fluid throughout the inclusion volume and the h2o raman peak at 3640 cm 1 is clearly resolvable at elevated temperatures to test and confirm the method synthetic h2o co2 fi of known composition 87 5 mol and 95 mol co2 were also analyzed previously studied granulite samples from the adirondack mountains usa and from the kerala khondalite belt sittampundi complex and sevitturangampatti india were tested for the presence of h2o in co2 rich fluid inclusions traces of h2o were found in co2 rich fluid inclusions in quartz crystals from the adirondacks and from the kerala khondalite belt h2o was not detected in co2 rich secondary fluid inclusions in garnet from the sittampundi complex and from sevitturangampatti rather hydrogarnet was detected along the walls of inclusions in garnet as evidenced by a peak at 3661 cm 1 the hydrogarnet is interpreted to be a step daughter phase that formed by reaction of the h2o in the fluid inclusion with the garnet host during retrogression these observations confirm the presence of an h2o bearing co2 rich fluid at some time during granulite petrogenesis but do not resolve the question of whether these co2 rich fluids were trapped at peak metamorphic conditions or during retrogression or whether the fluid inclusions have reequilibrated following entrapment

teleconnection mechanisms for tropical pacific descent anomalies during el nino abstract teleconnection mechanisms in relative descent zones are examined using the quasi equilibrium tropical circulation model qtcm the regions of anomalous descent neighboring the warm sea surface temperature sst anomalies in the eastern and central pacific ocean during the 1997 98 el nino are used as an example and results are verified for three other el nino warm events 1982 1987 and 1991 by analyzing the moisture and moist static energy budgets over these regions it is found that the physical processes responsible for the descent anomalies are different for each region anomalous dry advection is the dominant mechanism for the reduced precipitation to the north of the el nino warm region on the other hand the relative descent to the south of the el nino warm ssts is caused by reduced surface wind speed and reduced air sea contrast and resulting weaker than normal evaporation budget analysis based on the national aeronautics and space administration seasonal to interannual prediction p

post metamorphic co2 rich fluid inclusions in granulites in granulite facies samples from the adirondack mountains ny estimates of peak metamorphic co2 fugacities based on mineral equilibria are not consistent with estimates based on data for high density co2 rich fluid inclusions of the 21 adirondack samples investigated for this study all contain co2 rich inclusions inclusions occur in quartz apatite and garnet they range in size from 3 to 50 m and are without visible h2o in a few of the inclusions freezing point determinations and preliminary laser raman spectroscopy show the presence of small amounts 3 of other fluids n2 and h2s co2 liquid vapor homogenization temperatures are between 46 and 31 c corresponding to densities between 1 14 and 0 5 gm cc some of these densities are consistent with peak metamorphic entrapment 1 06 to 1 1 gm cc

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

enrichment of co2 in fluid inclusions in quartz by removal of h2o during crystal plastic deformation abstract ductile strain induced leakage of h 2 o from mixed co 2 h 2 o fluid inclusions in quartz is proposed as a mechanism for producing occurrences of pure co 2 fluid inclusions in metamorphic rocks the h 2 o needed for hydrolytic weakening of quartz under stress may be provided by the h 2 o in fluid inclusions with dislocation creep as dislocations nucleate on the walls of fluid inclusions or intersect them h 2 o can be transported with the dislocations from the inclusion to the grain boundaries the process should continue so long as there is stress on the host quartz and the inclusion contains h 2 o the h 2 o taken to the grain boundaries would due to its wetting properties be wicked out along the grain boundaries if the h 2 o is totally removed from an inclusion by a flux of dislocations through the quartz during the crystal plastic flow then a residual inclusion bearing components other than water should remain a mixed co 2 h 2 o inclusion would as a consequence of the process become a pure co 2 fluid inclusion during dynamic recrystallization the co 2 would collect at grain boundary triple junctions and following grain boundary migration would become incorporated into the recrystallized quartz as fluid inclusions this mechanism of generating pure co 2 inclusions could result in co 2 fluid inclusions having densities appropriate for the pressure temperature conditions during deformation using estimates of temperature of deformation the total confining pressure during deformation could be determined from the density of the co 2 fluid in these inclusions

titanium substitution in biotite an empirical model with applications to thermometry o2 and h2o barometries and consequences for biotite stability abstract an empirical model for solution of ti in biotite is developed and calibrated on the basis of various equilibria among biotite and ti saturating assemblages sources of data used for the calibration include both experimental products and published analyses of natural assemblages ti solution in biotite can be satisfactorily modelled by means of the exchange component tife 2 whose non ideal behavior can be approximated empirically by means of a linear function of the relative concentrations of ti and octahedral al in biotite within assemblages which fix the chemical potential of the exchange component tife 2 the concentration of this component in biotite is very sensitive to temperature and oxygen fugacity making it possible to use biotite oxide assemblages to obtain reliable t and f o 2 estimates in igneous and metamorphic rocks in assemblages which also contain alkali feldspar it is possible to use breakdown equilibria of ti additive components in biotite to estimate h 2 o fugacity such uses are likely to find important applications in rocks in which other assemblages sensitive to temperature f o 2 and or f h 2 o are absent in general rocks containing a single oxide phase plus biotite as the only mafic silicate phase alkali feldspar the empirical model for solution of ti in biotite also allows to calculate the loci of various terminal reactions for the assemblage titanian biotite quartz which by comparison with equivalent equilibria in ti free systems provide insight into the effect of ti on the stability of biotite solubility of ti in biotite increases with temperature in a strongly non linear fashion as a consequence calculations predict that the effect of ti on the stability of biotite is very small up to conditions typical of the beginning of the granulite facies of metamorphism but beyond those conditions ti concentration increases markedly and biotite is rendered very refractory at mid to deep crustal pressures 10 kbar the vapor absent solidus of biotite quartz in rocks containing ti saturating phases is likely to exceed 900 c even in bulk compositions with subequal concentrations of fe and mg

tropical teleconnection and local response to sst anomalies during the 1997 1998 el nino the quasi equilibrium tropical circulation model qtcm is used to examine the response to various sea surface temperature sst anomalies in the tropical oceans during the 1997 1998 el nino both local and remote responses are noted the negative precipitation anomalies to the north and south of the el nino southern oscillation enso enhanced precipitation region are largely a response to the warm sst anomalies in the central and eastern pacific however in the western pacific and maritime continent reduction of rainfall is mainly caused by local cold sst anomalies in the winter of the 1997 1998 el nino strong warm sst anomalies in the indian ocean contributed to the local enhanced rainfall they affect precipitation anomalies in central eastern and southern africa the drought in northern south america is clearly a remote response to enso warm sst anomalies in the pacific while the sst anomalies in the atlantic also impact the drought the tropical pacific cold sst anomalies surrounding the enso warm anomalies appear not to be caused by surface flux changes associated with atmospheric teleconnection in simulations with specified sst in the enso warm region and a mixed layer ocean model elsewhere atmospheric circulation tends to spread the warm anomalies but ocean dynamics appears also to be important for both cold and warm sst anomalies outside the equatorial upwelling region in both the regional specified sst experiments and mixed layer experiments relative subsidence tends to occur within convective zones and it is generally localized on the other hand tropospheric temperature and wind anomalies spread much farther the typical spatial scale of the remote response in temperature and wind fields tends to be larger than the dominant scale of the precipitation response the remote response in precipitation anomalies does not appear to be related to temperature and wind anomalies in a simple manner

upb geochronology of the sri lankan basement abstract u pb ages of zircons and monazites from ortho and paragneisses representing the major crystalline basement units of sri lanka establish a new geochronological framework which is consistent with previously published work on sm nd model ages rb sr whole rock ages and u pb mineral ages in the highland complex three newly dated orthogneisses one previously dated by baur et al 1991 and one dated by kroner and williams 1992 all intruded 1 85 to 1 9 ga ago this widespread intrusion event occurred soon after the end of sediment deposition which is estimated at 1 9 to 2 0 ga using upper intercept ages of zircons from metapelites in the highland complex within the boundaries of this complex established by sm nd model age mapping milisenda et al 1994 only one orthogneiss has been found which is substantially younger than 1 8 ga this is the metatonalite from polonnaruwa which intruded 670 ma ago baur et al 1991 three orthogneisses from the vijayan complex which lies to the east of the highland complex yield similarly consistent crystallization ages of 1023 8 1016 28 and 1033 121 ma in the wanni complex which lies to the west of the highland complex a sillimanite bearing gneiss which is apparently of metasedimentary origin but contains zircons of igneous appearance yields a primary crystallization age of 793 4 ma consistent with a previously dated orthogneiss from kurunegala of 770 ma baur et al 1991 in addition single zircon data by kroner et al 1994 indicate primary crystallization ages of 1 0 to 1 1 ga for orthogneisses from the vavuniya charnockite province which is considered to be part of the wanni complex these results confirm the age contrast between the highland complex on the one hand and the vijayan complex and wanni complex on the other as previously inferred from sm nd model ages milisenda et al 1988 1994 post tectonic granitoids and pegmatites intruded throughout all three complexes 550 ma ago the age of regional high grade metamorphism mostly granulite facies in the highland complex mostly amphibolite facies in the vijayan complex and both granulite and amphibolite facies in the wanni complex is constrained to be less than 670 ma the primary crystallization age of the polonnaruwa metatonalite it is more closely defined by lower intercept zircon ages which include one concordant age of 608 4 ma and one discordant but well defined age of 611 23 ma and by a nearly concordant monazite age of 592 2 ma this indicates that peak metamorphic conditions occurred 610 ma ago numerous other lower intercept ages between 590 and 550 ma and post tectonic intrusion ages of 550 ma set a lower age limit for high grade conditions and deformation the temperature history between 610 and 550 ma is not yet well resolved and it is not clear whether there was a separate thermal event 550 ma ago previously published whole rock rb sr and sm nd isochrons for gneisses from the highland complex yielding ages of 2 ga and greater and previously interpreted to date the time of granulite grade metamorphism must be reinterpreted in the light of the new data presented here as well as other recently published results e g burton and o nions 1990b baur et al 1991 and in view of the accumulated evidence for very limited element mobility during high grade metamorphism these whole rock ages are in fact identical or close to the ages of primary granitoid emplacement rather than the age of granulite facies metamorphism

fluid absent melting and the roles of fluids in the lithosphere a slanted summary abstract the presence or absence nature and compositions of lithospheric fluids are crucial factors in the evolution of igneous and metamorphic rocks despite this confusion still surrounds perceptions of the degrees of fluid involvement in many geological settings however experimental and field investigations constrain these roles and we are able to make some valid generalizations studies of prograde metamorphism have highlighted the spatial heterogeneity of fluid concentrations in many crustal environments this commonly indicates internal lithological control of volatile activities under fluid present conditions crustal fluids do not appear to mix readily fluid flow is generally structurally or lithologically controlled the transition from amphibolite to granulite facies is characterized by a decrease in ah2o as well as a temperature increase in many terranes these phenomena correlate with the appearance of migmatites some granulites are not migmatitic but have chemical and mineralogical characteristics of melt depleted restites this indicates efficient extraction of melts incongruent melting reactions involving the breakdown of crystalline hydrates in crustal rocks produce granitoid melts plus denser restites that are nearly or actually anhydrous experimental and theoretical treatments of fluid absent melting show that micas and amphiboles decompose at 700 to 900 c for mid to lower crustal pressures the melts resemble the compositions of s and i type granitoids pervasive aqueous fluids could not generally have been present during this melting since exposed granulite terranes are not characterized by high melt proportions and the magmas themselves are water undersaturated likewise the general presence of very h2o poor pervasive fluids is unlikely since this would allow only subsolidus dehydration at normally attainable crustal temperatures in this case the amphibolite granulite transition is possible at relatively low temperatures and the resultant rocks would not contain evidence of in situ melting the granulite granite connexion and effective crustal differentiation seem viable only during high temperature fluid absent metamorphism data on continental geotherms show that the lower crust is not entirely granulitic granulites are produced in regions of anomalously high heat flow the mantle connexion thus inferences on the nature of the lower crust should not be entirely based on studies of exposed granulite terranes mineral assemblages in eclogites also indicate widespread internal buffering of volatile activities and probable fluid absent conditions mantle derived basaltic magmas too are volatile bearing and it is plausible that volatile fixing phases also occur in the mantle volatiles may largely be introduced into the mantle through subduction processes and only released during the melting attending the breakdown of hydrous minerals as in the crust

interhemispheric teleconnections from tropical heat sources in intermediate and simple models themechanismsthatcontroltheinterhemisphericteleconnectionsfromtropicalheatsourcesareinvestigated using an intermediate complexity model a quasi equilibrium tropical circulation model qtcm and a simple linear two level model with dry dynamics illustrating the interhemispheric teleconnection process with an atlantic warm pool principal case the heat source directly excites a baroclinic response that spreads across the equator then threeprocesses involvingbaroclinic barotropicinteractions shearadvection surfacedrag and vertical advection forcea cross equatorial barotropicrossbywaveresponse ananalysis ofthese processes in qtcm simulations indicates that 1 shear advection has a pattern that roughly coincides with the baroclinic signal in the tropics and subtropics 2 surface drag has large amplitude and spatial extent and can be very effective in forcing barotropic motions around the globe and 3 vertical advection has a significantcontribution locally and remotely where large vertical motions and vertical shear occur the simple model is modified to perform experiments in which each of these three mechanisms may be included or omitted by adding surface drag and vertical advection and comparing each to shear advection the effects of the three mechanisms on the generationandpropagationofthebarotropicrossbywavesareshowntobequalitativelysimilartotheresultsin qtcm it is also found that the moist processes included in the qtcm can feed back on the teleconnection process and alter the teleconnection pattern by enlarging the prescribed tropical heating in both intensity and geographical extent and by inducing remote precipitation anomalies by interaction with the basic state

impacts of sst anomalies on the north atlantic atmospheric circulation a case study for the northern winter 1995 1996 the present paper selects the northern winter of december 1995 february 1996 for a case study on the impact of sea surface temperature sst anomalies on the atmospheric circulation over the north atlantic and western europe in the atlantic the selected winter was characterized by positive sst anomalies over the northern subtropics and east of newfoundland and negative anomalies along the us coast a weak la nina event developed in the pacific the north atlantic oscillation nao index was low precipitation over the iberian peninsula and northern africa was anomalously high and precipitation over northern europe was anomalously low the method of study consists of assessing the sensitivity of ensemble simulations by the ucla atmospheric general circulation model ucla agcm to sst anomalies from the observation which are prescribed either in the world oceans the atlantic ocean only or the subtropical north atlantic only the results obtained are compared with a control run that uses global time varying climatological sst the ensemble simulations with global and atlantic only sst anomalies both produce results that resemble the observations over the north atlantic and western europe it is suggested that the anomalous behavior of the atmosphere in the selected winter over those regions therefore was primarily determined by conditions within the atlantic basin the simulated fields in the tropical north atlantic show anomalous upward motion and lower upper level convergence divergence in the atmosphere overlying the positive sst anomalies consistently the subtropical jet intensifies and its core moves equatorward and precipitation increases over northern africa and southern europe the results also suggest that the sst anomalies in the tropical north atlantic only do not suffice to produce the atmospheric anomalies observed in the basin during the selected winter the extratropical sst anomalies would provide a key contribution through increased transient eddy activity which causes an extension of the subtropical jet eastward from the coast of north america

petrology of granulite facies metapelites of the highland complex sri lanka implications for the metamorphic zonation and the p t path in the pan african granulite facies highland complex of sri lanka the metamorphic grade increases from the central northwestern part towards boththe east and the southeast in metapelites the following prograde changes in metamorphic assemblage are recognized biotite ilmenite garnet or co cordierite sillimanite alkali feldspar quartz in the central northwestern part give way to garnet rutile sillimanite ilmenite or biotite alkali feldspar quartz in the e and se and are replaced by gar garnet cordierite biotite magnetite ilmenite alkali feldspar quartz bearing assemblages in the southwest cordierite coexisting with garnet is restricted to the western highland complex where metamorphic pressures of 5 7 kbar havebeen determined in the eastern highland complex where garnet clinopyroxene quartz is stable in metabasic rocks metamorphic pressures of 8 10 kbar have been obtained from barometers on metapelites phase relations of metapelites as well as geobarometry point to a continuous metamorphic transition between the eastern and the western part of the highland complex a clockwise p t path for the whole highland complex is indicated by the succession kyanite sillimanite andalusite an even earlier stage of the prograde metamorphism documented by sillimanite needles older than kyanite inclusions in garnet hhave been found in two samples of the eastern highland complex this points to a strong pressure increase at amphibolite facies conditions probably due to tectonic thickening of the crust during prograde metamorphism other inclusion assemblages in garnet and reaction textures indicate the breakdown of staurolite to kyanite spinel garnet and subsequent continued garnet growth in the sillimanite field at the expense of biotite sillimanite and quartz during further heating ternary feldspars in metapelites bear evidence of extreme metamorphic temperatures of about 900 c previously only indicated by coexisting pyroxenes in metabasic and charnockitic rocks within a few garnets inclusions of staurolite which are ti rich 1 34 wt tio2 and richer in fe xfe 0 745 than the enclosing garnet have survived the very high grade metamorphism the high grade stage of the prograde metamorphism was accompanied by strong flattening and a general n s stretching which is many metapelites ceased after peak temperatures but proceeded in others tectonic uplift of the whole highland complex occurred only after a phase of near isobaric cooling in the lower crust zircon 610 ma and biotite cooling ages 460 ma holzl et al 1991 as well as retrograde p t paths which passed the andalusite stability field are similar in the eastern and western part of the highland complex this suggests that the lower crustal cross section exposed in the highland complex was already tilted during cooling

anatexis and metamorphism in tectonically thickened continental crust exemplified by the sevier hinterland western north america the generation of granitoid magmas by partial melting of crustal rocks during continental thickening events is well documented in many geological provinces throughout the world including the late mesozoic sevier belt of western north america we present a thermal and petrologic model of anatexis and metamorphism in regions of crustal thickening where the only mantle contribution is the normal conductive supply of heat through the base of the lithosphere i e advection of mass and energy are excluded we distinguish between formation of migmatites and generation of mobile granitoid magmas and examine the temporal and spatial relationships between these two distinct anatectic processes between anatexis and regional deformation and between anatexis and metamorphism a fundamental conclusion is that if protoliths rich in hydrous minerals are present regional anatexis is the end product of classical barrovian metamorphism in thickened continental crust even in the absence of a free water rich fluid phase barrovian metamorphic facies series are predicted with thickening ratios maximum crustal thickness attained initial crustal thickness as low as 1 3 but mobile granitoid magmas are not formed if this ratio is less than approximately 1 5 above these lower bounds barrovian metamorphism and anatectic granitoid magmatism occur independently of the magnitude of thickening and of the way in which thickening is accomplished both processes are sensitive to a diminished heat supply lowering either moho heat flow or crustal radioactive heat production results in blueschist eclogite metamorphism and inhibits the formation of mobile granitoid magmas we model anatexis under fluid absent conditions and show that with such a constraint migmatization is always a syn kinematic process relative to the crustal thickening event whereas generation of mobile granitoid magmas is in most cases post kinematic relative to crustal thickening but can be syn kinematic if thickening takes more than approximately 50 myr the typical time intervals for melting are consistent with geological observations mobile granitoid magmas are predicted by most of our models within approximately 10 myr of the end of the crustal thickening event this incubation period results primarily from the temperature increase required for the dehydration melting reactions capable of producing large melt fractions to occur the energetic requirements of anatexis are relatively minor compared to conductive crustal thermal budgets as shown by the fact that once the necessary p t conditions are attained melting reactions are completed within time intervals on the order of 1 myr i e 1 2 orders of magnitude smaller than the characteristic time scales of the tectonic processes involved in crustal thickening

arrested charnockite formation in southern india and sri lanka arrested prograde charnockite formation in quartzofeldspathic gneisses is widespread in the high grade terrains of southern india and sri lanka two major kinds of orthopyroxene producing reactions are recognized breakdown of calcic amphibole by reaction with biotite and quartz in tonalitic granitic gray gneiss produced the regional orthopyroxene isograd manifest in charnockitic mottling and veining of mixed facies exposures as at kabbal karnataka and in the kurunegala district of the sri lanka central highlands chemical and modal analyses of carefully chosen immediately adjacent amphibole gneiss and charnockite pairs show that the orthopyroxene is produced by an open system reaction involving slight losses of cao mgo and feo and gains of sio2 and na2o rb and y are depleted in the charnockite another kind of charnockitization is found in paragneisses throughout the southern high grade area and involves the reaction of biotite and quartz garnet to produce orthopyroxene and k feldspar although charnockite formation along shears and other deformation zones at such localities as ponmudi kerala is highly reminiscent of kabbal close pair analyses are not as suggestive of open system behavior this type of charnockite formation is found in granulite facies areas where no prograde amphibole bearing gneisses exist and connotes a higher grade reaction than that of the orthopyroxene isograd metamorphic conditions of both kabbaltype and ponmudi type localities were 700 800 c and 5 6 kbar lower p h2o in the ponmudi type metamorphism was probably the definitive factor

glacier mass loss induced the rapid growth of linggo co on the central tibetan plateau remote sensing and gis techniques in conjunction with field investigations show how glacier mass loss has led to the rapid growth of linggo co a glacier fed lake on the central tibetan plateau which has expanded by 21 3 in area between 1974 and 2010 with a lake level rise of 11 2 m the lake volume of linggo co increased at a rate of 0 02 10 6 42 67 10 6 and 65 8 10 6 m 3 a 1 during the periods 1974 92 1992 99 and 1999 2010 respectively other non glacier fed lakes in the vicinity i e longwei co amur co and darngo co ngion shrank considerably from the early 1970s to 1992 and then expanded from 1992 to 2010 despite being in the same climate region linggo co and the non glacier fed lakes have differed in response to climate change the glaciers in the catchment of linggo co retreated by 2 4 in area between 1974 and 2007 and their mean thickness decreased by 6 19 1 91 m between 1974 and 2000 with an associated glacier meltwater runoff of 7 52 2 32 10 8 m 3 the results indicate that glacier mass loss had a significant impact on the growth of linggo co over the past 40 years

isotopic mapping of age provinces in precambrian high grade terrains sri lanka nd model ages of amphibolite and granulite grade rocks in sri lanka form a simple regional pattern that broadly correlates with mappable geological units and is in effect an isotopic map of the island s basement the granulite grade units of the highland group and southwest group have model ages of 2 2 3 0 ga indicating derivation mainly from late archean sources they are bounded to the east and west by late proterozoic gneisses of the vijayan complex with model ages of 1 1 2 0 ga the isotopic data identify three distinct crustal provinces and are not consistent with earlier suggestions that the vijayan gneisses are retrograde equivalents of the highland granulites sri lanka is not a direct continuation of the archean dharwar craton of southern india identification of vijayan type juvenile crustal terrains in other gondwana fragments may play a key role in determining the precise attachment of southern india sri lanka in eastern gondwana

coeval migmatites and granulites muskoka domain southwestern grenville province ontario we present new field observations and petrologic and geochronological data from the muskoka domain in the southwestern grenville province of ontario in an attempt to constrain the relationship between amphibolite facies and granulite facies gneisses in areas of transitional metamorphic grade and to examine their implication for tectonometamorphic models for the grenville province of ontario the predominant medium grained amphibolite facies migmatitic orthogneisses of the muskoka domain contain several generations of leucosome some of which are related to southeast directed extensional structures the amphibolite facies granitoid gneisses contain numerous mafic enclaves with granulite facies assemblages recrystallized from anhydrous precursors during grenvillian metamorphism other associated granulites are characterized by their patchy occurrence and gradational contacts similar to the charnockites in southern india patchy granulites leucocratic vein networks in mafic enclaves and crosscutting leuc

quasi stationary waves in the southern hemisphere part ii generation mechanisms abstract in this part ii the authors investigate the role that antarctic elevations the rest of the world orography thermal forcing from lower latitudes and the transient eddy component of the flow play on the generation of the quasi stationary wave field in the southern hemisphere an approach based on the ucla gcm is followed results from a control simulation with full orography and from experiments without the antarctic elevations and without the rest of the world orography suggest that the quasi stationary wave with zonal wavenumber 1 qs wave 1 around antarctica is primarily generated by mechanisms other than the antarctic elevations comparison of a three dimensional eliassen palm flux vector in the control simulation and those where the antarctic elevation and the rest of the world orography are removed suggests that wave activity propagates both from the subtropics and from polar latitudes although in qualitative agreement with results of part i the horizontal and vertical structure of t

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

variations in water level and glacier mass balance in nam co lake nyainqentanglha range tibetan plateau based on icesat data for 2003 09 water level fluctuations of inland lakes are related to regional scale climate changes and reflect variations in evaporation precipitation and glacier meltwater flowing into the lake area in its catchment in this paper ice cloud and land elevation satellite icesat altimeter data and landsat imagery 2002 09 are used to estimate nam co lake nyainqentanglha range tibetan plateau water elevation changes during 2002 09 in 2003 nam co lake covered an area of 1998 8 4 2 km 2 and was situated at 4723 m a s l over such inland water bodies icesat altimeter data offer both wide coverage and spatial and temporal accuracy we combine remote sensing and gis technology to map and reconstruct lake area and increased volume changes during a 7 year time series nam co lake water level increased by 2 4 0 12 m 0 33 m a 1 between 23 february 2003 and 1 october 2009 and lake volume increased by 4 9 0 5 km 3 in the past 7 years nam co lake area has increased from 1998 78 5 4 to 2023 8 3 4 km 2 the glacier covered area has decreased from 832 34 to 821 0 km 2 and the drainage basin area has decreased from 201 1 4 2 to 196 1 2 3 km 2 however the most spectacular feature is the continual water level rise from 2003 to 2009 without an obvious associated increase in precipitation based on digital elevation models dems from shuttle radar topography mission srtm dem data and corrected icesat elevation data significant changes to glacier mass balance in the western nyainqentanglha mountains are indicated nyainqentanglha mountain glacier surface elevations decreased by 8 39 0 45 m during 2003 09 over the same period at least 1 01 km 3 of glacial meltwater flowed into nam co lake assuming a glacial runoff coefficient of 0 6 the mean glacier mass balance value is 490 mm w e over the corresponding period indicating that glacier meltwater in the catchment contributes to lake level rise the contribution rate of glacial meltwater to lake water volume rise is 20 75 the temporal lake level fluctuation correlates with temperature variations over the same time span

smnd isotopes and ree geochemistry of madras granulites india an introductory statement abstract major and trace elements including ree as well as sm nd isotope analyses of eight granulite samples from the madras area are presented the data provide evidence for the origin of some of the granulites but in other cases demonstrate metasomatic changes in major and trace element contents including lree the data furthermore demonstrate that the analysed granulites are not cogenetic however when plotted in a sm nd isochron diagram the samples yield a linear array which corresponds to an age t 2555 140 ma and nd t 1 1 4 this age of 2555 140 ma could represent the time of granulite facies metamorphism immediately preceded by the formation of the protolith the nd t 1 value may be indicative of a near chondritic mantle source or alternatively of mixing between a depleted mantle and a crustal component

evidence for prograde metamorphic evolution of sri lankan pelitic granulites and implications for the development of continental crust petrological evidence for prograde metamorphic evolution is obtained for pelitic granulites of the newly defined highland complex in sri lanka it includes the occurrences of relict kyanite quartz staurolite corundum kyanite hercynite kyanite and sapphirine kyanite spinel within garnet in the sillimanite quartz rich rocks of special interest is the mineralogy of khondalites graphitic garnet sillimanite k feldspar quartz gneisses the matrix of which is free of hydrous minerals indicating that dehydration reactions have been completed in this kind of rocks however relict hydrous minerals such as al ti rich more than 58 wt al2o3 and more than 1 wt tio2 staurolite and extremely ti rich up to 9 8 wt tio2 biotine occur as inclusions within garnet the local relict mineral assemblages within garnet in khondalites indicate the following continuous staurolite breakdown reactions which may have progressed as temperature increased and pressure decreased staurolite quartz kyanite garnet h2o staurolite corundum kyanite garnet h2o staurolite kyanite hercynite garnet h2o staurolite sillimanite hercynite garnet h2o some of these dehydration reactions are inferred to have also taken place in other widespread pelitic granulites of the highland complex moreover garnet in the highland complex pelitic granulites occasionally preserves growth zoning though modified slightly to extensively by post growth volume diffusion based on the evidence a clockwise prograde p t path of evolution is inferredfor meta sedimentary granulites belonging to the highland complex on the other hand no evidence for prograde metamorphism has so far been obtained in lower grade rocks of the wanni complex to the northwest of the highland complex such a difference between these complexes may be the first petrological feature which supports the new geotectonic division of the sri lankan basement rocks based virtually on the distinctly different neodymium model ages it suggests that these two complexes were amalgamated during the very last part of prograde metamorphism of the highland complex rocks that is during decompression and heating probably by the lower crustal lateral flow after tectonic overthickening and delamination the clockwise prograde p t t path followed by the meta sedimentary granulites of the highland complex is in marked contrast with the near isobaric cooling path for meta igneous granulites suggested by some authors it is proposed that both types of p t t paths albeit for different rock types are possible and resulted from diverse deep crustal processes such as underplating of continental crust by sediments and magmas or near convergent plate boundaries

quantifying glacier mass change and its contribution to lake growths in central kunlun during 2000 2015 from multi source remote sensing data abstract joint monitoring of the variations of glaciers and lakes within a basin is essential for an accurate understanding of region wide climate change and the water cycle process the central kunlun kekexili region is an ideal experimental field due to the wide distribution of glaciers and lakes in this study we first investigated the glacier mass balance of 2000 2015 16 for seven major glacier clusters by utilizing high resolution spot 6 7 stereo imagery and the srtm dem the final results revealed an overall mass balance of 0 16 0 05 m w e a for the study region with a total glacier area of 967 km2 secondly icesat glas altimetry data were used to quantify the water level change of 2003 2008 09 for the two largest glacier fed closed lakes i e lexiewudan lake and kekexili lake in this region based on this we applied a strategy which establishes the statistical relationship between the lake area change and the lake water level change for 2003 2008 09 to estimate the specific water level using the corresponding lake area we then further calculated the variation in lake water storage between 2000 and 2015 the results showed that the water storage of lexiewudan lake and kekexili lake increased by 1 82 0 14 km3 and 1 90 0 38 km3 respectively for each lake basin meanwhile the glaciers lost 0 18 0 03 km3 and 0 21 0 04 km3 of water accounting for 9 9 and 11 1 of the increase in lake water storage for lexiewudan lake and kekexili lake respectively our results not only demonstrate that glacier meltwater has only a limited impact on the lake expansion in this region but they also provide new evidence for the warming and wetting process of the climate in the northern part of the qinghai tibet plateau

secondary siderite oxide sulphide and carbonate andalusite assemblages in cordierite granulites from sri lanka post granulite facies fluid evolution during uplift we report here that some of the pelitic rocks from the wanni and highland complexes of sri lanka reacted with co2 rich fluids to produce a wide range of unusual secondary carbonate silicate oxide sulphide assemblages these enable the depth temperature and fluid compositions of co2 reactions to be calculated more rigorously than is generally possible for the patches of arrested charnockite that have been described from sri lanka magnesite andalusite quartz has partially replaced primary cordierite and siderite rutile replaced ilmenite paragenetic sequences involving primary pyrrhotite ilmenite and magnetite and secondary pyrite siderite rutile magnetite hematite demonstrate the control which carbonate equilibria have upon evolving fluid compositions during cooling direct evidence for the role of graphite as a source of co2 is found in the highland complex where primary graphite partially reacted with silicates to form secondary siderite assemblages it is proposed that following peak metamorphism continued uplift along a clockwise p t t path was accompanied by a series of devolatilization reactions involving breakdown of graphite and the continuous production of secondary co2 rich fluids the limited extent of disseminated secondary carbonate reflects the small amount of graphite inferred to have been present in the source rocks these rocks demonstrate that co2 rich fluids as found in disseminated fluid inclusions need not form during peak granulite metamorphism but may be an inevitable consequence of continued uplift along a clockwise p t t path the arrested charnockite which overprinted some of the hornblende bearing felsic intermediate composition rocks in sri lanka most likely formed by the same process

u pb isotopic systematics of zircons from prograde and retrograde transition zones in high grade orthogneisses sri lanka we present u pb zircon isotopic data from locally restricted prograde arrested in situ charnockitization and retrograde metamorphic transition zones which are well exposed in proterozoic orthogneisses tectonically interbanded with granulite facies supracrustal rocks of the highland group in sri lanka these granitoid rocks yield apparent ages of 1942 pm 22 ma 770 ma 660 ma and 560 ma all samples show severe pb loss some 550 560 ma ago the main phase of granulite formation could not be dated unambiguously but is bracketed between 660 ma and 550 ma the pervasive pb loss event around 550 560 ma reflects the end of this period of high grade metamorphism and was associated with widespread igneous activity and retrogression this is constrained by the 550 pm 3 ma intrusion age for a post tectonic granite we relate this late phase of thermal activity to crustal uplift of the sri lankan granulites our data unambiguously prove the high grade history of the sri lanka gneisses to be a late

icesat measurements of sea ice freeboard and estimates of sea ice thickness in the weddell sea 1 sea ice freeboard heights in the weddell sea of antarctica are derived from the ice cloud and land elevation satellite icesat laser altimeter measurements which have a unique range precision to flat surfaces of 2 cm within 70 m footprints spaced at 172 m along track although elevations of flat surfaces can be obtained to an accuracy of 10 cm 1s per footprint direct determination of freeboard heights is precluded by errors in knowledge of the geoid and temporal variability of the ocean surface therefore freeboards are determined relative to an ocean reference level detected over areas of open water and very thin ice within the sea ice pack using an along track filtering method the open water thin ice selections show good agreement in the combined analysis of icesat segments and envisat synthetic aperture radar sar imagery the average residual between the icesat measured ocean level and the egm96 geoid is 1 4 m estimates of snow depth on the sea ice from amsr e passive microwave data along with nominal densities of snow water and sea ice are used to estimate sea ice thickness four periods of icesat data in may june fall and october november late winter of 2004 and 2005 between longitudes 298e and 360e are analyzed in the fall the mean freeboards are 0 28 m in 2004 and 0 29 m in 2005 and the mean thicknesses are 1 33 m in 2004 and 1 52 m in 2005 in late winter the freeboards grew to 0 37 m in 2004 and 0 35 in 2005 and the thicknesses grew to 2 23 m in 2004 and 2 31 m in 2005 the interannual differences in freeboard are small and the larger interannual change in estimated thickness mainly represents differences in the snow depth estimates seasonal changes in the spatial patterns of freeboard and thickness over the 4 months correlate with the expected circulation of sea ice in the weddell sea as indicated by sea ice velocity fields

arrested charnockite formation at kottavattam southern india at kottavattam southern kerala india late proterozoic homogeneous leptynitic garnet biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation charnockitization post dates the polyphase deformation regional high grade metamorphism and anatexis and evidently occurred at a late stage of the pan african tectonothermal history geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar p lith t conditions 650 700 degrees c 5 6kbar in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases x co2 0 7 0 6 x h2o 0 2 0 3 x n2 0 1 logf o2 l7 5 mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow outward migrating transition zones adjacent to the gneiss followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone compared to the host gneiss the charnockite shows higher concentrations of k na sr ba and zn and lower concentrations of mg fe ti v y zr and the hree with a complementary pattern in the narrow transition zones of biotite breakdown the p lith t x h2o data and chemical zonation patterns indicate charnockitization through subsolidus dehydration reaction in an open system subsequent residence of the carbonic fluids in the charnockite resulted in low grade alteration causing modification of the syn charnockitic elemental distribution patterns and the properties of entrapped fluids we favour an internally controlled process of arrested charnockitization in which during near isothermal uplift the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from fluid absent in the gneiss to fluid present in the fracture zones and to the development of an initial fluid pressure gradient triggering the dehydration reaction

palaeomagnetic and rock magnetic study of charnockites from tamil nadu india and the ur protocontinent in early palaeoproterozoic times abstract palaeomagnetic and magnetomineralogical results are reported from charnockites in basement terrane at the eastern sector of the wsw ene granulite belt of south india magnetite is the dominant ferromagnet identified by rock magnetic and optical study it is present in several phases including large homogeneous titanomagnetites and disseminated magnetite in microfractures linked to growth stages ranging from primary charnockite formation to uplift decompression and exhumation within the interval 2500 2100 ma several components of magnetization are resolved by thermal demagnetization and summarized by four pole positions in the northern pallavaram sector these are p1 33 n 99 e dp dm 8 9 and p2 79 n 170 e dp dm 3 6 and in the southern vandallur sector they are v1 23 n 116 e dp dm 8 9 and v2 26 s 136 e dp dm 5 10 these magnetizations are linked to uplift cooling of the basement and unblocking temperature spectra suggest acquisition sequences p1 p2 and v1 v2 in each case implying movement of the shield from higher to lower palaeolatitudes sometime between 2500 and 2100 ma palaeomagnetic poles from the cratonic nuclei of africa australia and india all identify motion from higher to lower palaeolatitudes in early palaeoproterozoic times and this is dated 2400 and 2200 ma in the former two shields the corresponding apparent polar wander apw segments match the magnetization record within the charnockite basement terranes of southern india to yield a preliminary reconstruction of the ur protocontinent the oldest surviving continental protolith with origins prior to 3000 ma although subject to later relative movements these nuclei seem to have remained in proximity until the mesozoic break up of gondwana