application of magnetic amplitude inversion in exploration for volcanic units in a basin environment abstractwe have performed a case study on the use of magnetic amplitude inversion in imaging volcanic rocks that are buried in a sedimentary basin and have strong remanent magnetization the application arises in exploration for natural gas hosted in volcanic rocks in basin environments the weak anomaly associated with the volcanic units and the presence of remanent magnetization therein pose major challenges in the magnetic interpretation we first use a wiener filter based on an ensemble analysis to examine the depth characteristics of the anomalies and then we use an inversion based signal separation to extract the anomaly for final interpretation we apply an amplitude inversion method to recover the distribution of effective susceptibility in the absence of the knowledge about the total magnetization direction the result effectively identifies the volcanic rock units at large depths and the imaged distribution of these units is consistent with information from drillholes and local geology

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

timing and origin of recent regional ice mass loss in greenland within the last decade the greenland ice sheet gris and its surroundings have experienced record high surface temperatures mote 2007 box et al 2010 ice sheet melt extent fettweis et al 2011 and record low summer sea ice extent nghiem et al 2007 using three independent data sets we derive for the first time consistent ice mass trends and temporal variations within seven major drainage basins from gravity fields from the gravity recovery and climate experiment grace tapley et al 2004 surface ice velocities from inteferometric synthetic aperture radar insar rignot and kanagaratnam 2006 together with output of the regional atmospheric climate modelling racmo2 gr ettema et al 2009 and surface elevation changes from the ice cloud and land elevation satellite icesat sorensen et al 2011 we show that changing ice discharge d surface melting and subsequent run off m r and precipitation p all contribute in a complex and regionally variable interplay to the increasingly negative mass balance of the gris observed within the last decade interannual variability in p along the northwest and west coasts of the gris largely explains the apparent regional mass loss increase during 2002 2010 and obscures increasing m r and d since the 1990s in winter 2002 2003 and 2008 2009 accumulation anomalies in the east and southeast temporarily outweighed the losses by m r and d that prevailed during 2003 2008 and after summer 2010 overall for all basins of the gris the decadal variability of anomalies in p m r and d between 1958 and 2010 w r t 1961 1990 was significantly exceeded by the regional trends observed during the grace period 2002 2011 2012 elsevier b v

elevation changes of ice caps in the canadian arctic archipelago 1 precise repeat airborne laser surveys were conducted over the major ice caps in the canadian arctic archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region our measurements reveal thinning at lower elevations below 1600 m on most of the ice caps and glaciers but either very little change or thickening at higher elevations in the ice cap accumulation zones recent increases in precipitation in the area can account for the slight thickening where it was observed but not for the thinning at lower elevations for the northern ice caps on the queen elizabeth islands thinning was generally 0 5 m yr 1 which is consistent with what would be expected from the warm temperature anomalies in the region for the 5 year period between surveys and appears to be a continuation of a trend that began in the mid 1980s farther south however on the barnes and penny ice caps on baffin island this thinning was much more pronounced at over 1 m yr 1 in the lower elevations here temperature anomalies were very small and the thinning at low elevations far exceeds any associated enhanced ablation the observations on barnes and perhaps penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation as has been previously suggested for barnes ice cap on the basis of the regional relationships between elevation and elevation change in our data the 1995 2000 mass balance for the archipelago is estimated to be 25 km3 yr 1 of ice which corresponds to a sea level increase of 0 064 mm yr 1 this places it among the more significant sources of eustatic sea level rise though not as substantial as the greenland ice sheet alaskan glaciers or the patagonian ice fields

accelerated ice mass depletion revealed by low degree gravity field from satellite laser ranging greenland 1991 2011 1 we detect the acceleration of ice mass depletion in greenland for the period 1991 2011 from the low degree gravity field up to degree and order 4 derived from the satellite laser ranging slr data between 2003 and 2011 during the era when the grace gravity recovery and climate experiment satellite data are available our slr results of gravity changes agree well with grace showing significant negative patterns in greenland prior to that the slr linear trend maps show a near balance in greenland ice mass during 1991 2002 after the glacial isostatic adjustment is accounted for using model values we further confirm the consistency of our slr results with the vertical crustal uplift of the region observed by the global positining system gps which manifests ice mass loading unloading thus the slr data series constitute a continuous benchmark for the time history of the greenland ice mass changes for over two decades

changes in mass balance velocity and surface profile along a flow line on barnes ice cap 1970 1984 on a number of occasions between 1970 and 1984 measurements of mass balance surface velocity and surface elevation were made along a 10 2 km flow line extending from the divide to the margin on barnes ice cap baffin island canada the average mass balance rate on this arctic ice cap appears to be controlled principally by summer temperature years of negative mass balance dominated during the 14 year period of the study according to our measurements this should have resulted in a thinning of an average of 2 65 m along the flow line surface elevation measurements however suggest that the glacier thinned only 1 7 m during this time period the slightly compressive mean transverse strain can account for 0 20 m of the discrepancy between these two figures the rest is attributed to errors in mass balance in particular increases in density of old firn and freezing of water in crevasses could not be evaluated adequately from our measurements the thinning was not uniform near the margin the glacier thinned 5 m and near the divide 2 5 m but between 3 5 and 5 5 km from the divide there seems to have been no substantial change in thickness thus along the down glacier half of the flow line the decrease in thickness was accompanied by an increase in slope within 4 km of the margin the decrease in thickness resulted in a decrease in horizontal velocity of up to 15 despite the increase in slope higher on the glacier however the horizontal velocity increased 5 these changes are broadly consistent with those estimated from the changes in shear stress calculated using the hydrostatic approximation

mass balance of white glacier axel heiberg island n w t canada 1960 91 white glacier is a valley glacier at 79 5 n with an area of 38 7 km 2 its mass balance has been measured over 32 years with a 3 year gap by standard techniques using the stratigraphic system with a stake density of the order of one stake per km 2 errors in stake mass balance are about 200 250 mm due largely to the local unrepresentativeness of measurements errors in the whole glacier mass balance b are of the same order as single slake errors however the lag 1 autocorrelation in the time series of b is effectively zero so it consists of independent random samples and the error in the long term balance normal b is noticeably less b is 100 48 mm the equilibrium line altitude ela averages 970 m with a range of 470 1400 m mass balance is well correlated with ela but detailed modelling shows that the equilibrium line is undetectable on visible band satellite images a reduced network of a few stakes could give acceptable but less accurate estimates of the mass balance as could estimates based on data from a weather station 120 km away there is no evidence of a trend in the mass balance of white glacier to detect a climatologically plausible trend will require a ten fold reduction of measurement error a conclusion which may well apply to most estimates of mass balance based on similar stake densities

metamorphism of pelites in nkfmash a new petrogenetic grid with implications for the preservation of high pressure mineral assemblages during exhumation a petrogenetic grid for metapelites in the system nkfmash is presented the p t range is investigated in three sections 1 the high and ultrahigh pressure range is discussed in the system nfmash because phengite is the only stable potassic phase 2 the transition region is characterised by four nkfmash invariant points that separate high pressure glaucophane bearing from medium pressure biotite bearing metapelites 3 the medium pressure range contains the fifth nkfmash invariant point the univariant reactions of this point terminate the stability range of paragonite which breaks down to form staurolite or kyanite and plagioclase during decompression and or heating as the growth of albitic plagioclase by decomposition of paragonite via continuous reactions may be conspicuous already before these staurolite or kyanite producing reactions are reached such albite porphyroblast schists are typical indicators of a former high pressure metamorphic history considering the preservation of high pressure metapelitic assemblages those crossing the nkfmash transition region during exhumation commonly dehydrate and preservation is unlikely three types of metapelites have a fairly good survival potential 1 low temperature metapelites up to c 540 c with an exhumation path back into the chlorite albite stability field 2 assemblages with chloritoid glaucophane and 3 the relatively high temperature glaucophane kyanite and jadeite kyanite bearing parageneses that are relatively dry at the onset of exhumation a comparison with data from the literature shows that these rock types are the most abundant in nature

tracing high pressure metamorphism in marbles phase relations in high grade aluminous calcite dolomite marbles from the greek rhodope massif in the system cao mgo al2o3 sio2 co2 and indications of prior aragonite abstract four different types of parageneses of the minerals calcite dolomite diopside forsterite spinel amphibole pargasite ti clinohumite and phlogopite were observed in calcite dolomite marbles collected in the kimi complex of the rhodope metamorphic province rmp the presence of former aragonite can be inferred from carbonate inclusions which in combination with an analysis of phase relations in the simplified system cao mgo al 2 o 3 sio 2 co 2 cmas co 2 show that the mineral assemblages preserved in these marbles most likely equilibrated at the aragonite calcite transition slightly below the coesite stability field at ca 720 c 25 kbar and a co 2 0 01 the thermodynamic model predicts that no matter what activity of co 2 garnet has to be present in aluminous calcite dolomite marble at uhp conditions

metalliferous mining geophysics state of the art after a decade in the new millennium mining exploration was very active during the first decade of the twenty first century because there were numerous advances in the science and technology that geophysicists were using for mineral exploration development came from different sources instrumentation improvements new numerical algorithms and cross fertilization with the seismic industry in gravity gradiometry kept its promise and is on the cusp of becoming a key technology for mining exploration in potential field methods in general numerous techniques have been developed for automatic interpretation and 3d inversion schemes came into frequent use these inversions will have even greater use when geologic constraints can be applied easily in airborne electromagnetic em methods the development of time domain helicopter em systems changed the industry in parallel improvements in em modeling and interpretation occurred in particular the strengths and weaknesses of the various algorithms became better understood simpler imaging schemes came into standard use whereas layered inversion seldom is used in the mining industry today improvements in ground em methods were associated with the development of squid technology and distributed acquisition systems the latter also impacted ground induced polarization ip methods developments in borehole geophysics for mining and exploration were numerous borehole logging to measure physical properties received significant interest perhaps one reason for that interest was the desire to develop links between geophysical and geologic results which also is a topic of great importance to mining geologists and geophysicists

recent glacier mass changes in the gulf of alaska region from grace mascon solutions the mass changes of the gulf of alaska goa glaciers are computed from the gravity recovery and climate experiment grace inter satellite range rate data for the period april 2003 september 2007 through the application of unique processing techniques and a surface mass concentration mascon parameterization the mass variations in the goa glacier regions have been estimated at high temporal 10 day and spatial 2 2 arc degrees resolution the mascon solutions are directly estimated from a reduction of the grace k band inter satellite range rate data and unlike previous grace solutions for the goa glaciers do not exhibit contamination by leakage from mass change occurring outside the region of interest the mascon solutions reveal considerable temporal and spatial variation within the goa glacier region with the largest negative mass balances observed in the st elias mountains including the yakutat and glacier bay regions the most rapid losses occurred during the 2004 melt season due to record temperatures in alaska during that year the total mass balance of the goa glacier region was 84 5 gt a 1 contributing 0 23 0 01 mm a 1 to global sea level rise from april 2003 through march 2007 highlighting the large seasonal and interannual variability of the goa glaciers the rate determined over the period april 2003 march 2006 is 102 5 gt a 1 which includes the anomalously high temperatures of 2004 and does not include the large 2007 winter balance year snowfall the mascon solutions agree well with regional patterns of glacier mass loss determined from aircraft altimetry and in situ measurements

positive degree day factors for ablation on the greenland ice sheet studied by energy balance modelling ice ablation is related to air temperature by the positive degree day factor variations of the positive degree day factor in west greenland are studied using an energy balance model to simulate ablation under different conditions degree day factors for simulated and measured ice ablation at nordbogletscher and qaman rssup sermia agree well with values around 8 mm d 1 c 1 degree day factors for snow are less than half those for ice energy balance modelling shows that degree day factors vary with summer mean temperature surface albedo and turbulence but there is only evidence of large positive degree day factors at lower temperatures and with low albedo 0 3 the greatest effect of albedo variations 0 3 0 7 is at lower temperatures while variations in turbulence have greater effect at higher temperatures current models may underestimate runoff from the greenland ice sheet by several tenths because they use a degree day factor for melting ice that is too small for the colder parts of the ice sheet i e the upper ablation area and the northerly margin

syn metamorphic nappe complex in the rhodope massif structure and kinematics mylonitic gneisses of the bulgarian and greek rhodope were deformed under medium pressure type metamorphism the kinematic information contained in these gneisses shows that shear deformation occurred during development of a nappe complex lithologies and metamorphic histories allow a lower footwall and an upper hanging wall terrane to be distinguished that define a crustal scale duplex as oceanic crust is involved collision between two continental units with subsequent crustal thickening is inferred the blocks would be moesia to the north and the lower rhodope promontory to the south which collided in the mesozoic to early cenozoic the nappe complex is characterized by south to southwestward foreland directed piling up and is associated with both coeval and subsequent extension the late extension is associated with the establishment of a high temperature low pressure metamorphic gradient and plutonism that predates but makes a transition to the lithospheric extension of the aegean arc

accumulation storage and release of atmospheric mercury in a glaciated arctic catchment baffin island canada abstract part of the mercury hg entering arctic ecosystems is believed to be delivered from the atmosphere in snow but this source is difficult to quantify due to limited spatial coverage of hg data in snow here we evaluate the atmospheric deposition storage and release of total hg thg and monomethyl mercury mehg on penny ice cap baffin island this is the first such study in the baffin region thg levels in snow and firn mean 0 61 ng l 1 are comparable to those on high arctic glaciers but mehg levels are noticeably higher mean 0 11 ng l 1 we find little evidence of springtime enhancement of hg deposition in snow attributable to atmospheric mercury depletion events estimated accumulation rates of thg and mehg in firn are 0 33 and 0 03 g m 2 a 1 higher than on high arctic glaciers possibly due to higher precipitation on southern baffin island the estimated net annual release of thg by glacial snow and ice melt is small thg 1 86 kg mehg 0 18 kg in the study area geogenic hg contributions from sediment loaded glacial meltwater could be as large or larger than those from melting ice mehg levels are very low in meltwater fed streams and lakes 0 01 ng l 1 suggesting that mehg is released early in the snowmelt season and or quickly removed from meltwater by various processes summer melt and percolation on penny ice cap remobilise hg in firn after deposition and this imposes resolution limits of at least 3 years on depositional trends inferred from ice cores

a 3d model of crustal magnetization at the pinacate volcanic field nw sonora mexico abstract the pinacate volcanic field pvf is located near the western border of the southern basin and range province in the state of sonora nw mexico and within the gulf of california extensional province this volcanic field contains the shield volcano santa clara which mainly consists of basaltic to trachytic volcanic rocks and reaches an altitude of 1200 m the pvf disrupts a series of discontinuous ranges of low topographic relief aligned in a nw direction which consist mainly of proterozoic metamorphic rocks and proterozoic through paleogene granitoids the pvf covers an area of approximately 60 by 55 km and includes more than 400 well preserved cinder cones and vents and eight maar craters it was active from about 1 7 ma until about 13 ka we have used the ages and magnetic polarities of the volcanic rocks along with mapped magnetic anomalies and their inverse modeling to determine that the pinacate volcanic field was formed during two volcanic episodes the oldest one built the santa clara shield volcano of basaltic and trachytic composition and occurred during the geomagnetic matuyama chron of reverse polarity which also includes the normal polarity jaramillo and olduvai subchrons thus imprinting both normal and reverse magnetization in the volcanic products the younger pinacate series of basaltic composition represents monogenetic volcanic activity that extends all around the pvf and occurred during the subsequent geomagnetic brunhes chron of normal polarity magnetic anomalies toward the north of the santa clara volcano are the most intense in the pvf and their inverse modeling indicates the presence of a large subsurface body magnetized in the present direction of the geomagnetic field this suggests that the magma chambers at depth cooled below the curie temperature during the brunhes chron

application of 3d magnetic amplitude inversion to iron oxide copper gold deposits at low magnetic latitudes a case study from carajas mineral province brazil abstractstrong hydrothermal alteration modifies rock physical properties in iron oxide copper gold deposits iocgs and may result in characteristic signatures detectable in geophysical surveys magnetic data are commonly used in characterizing orebodies and 3d inversions are often used to assist in interpretations in areas with strong remanence and self demagnetization the total magnetization can have directions different from the inducing field direction this deviation precludes the use of traditional inversion methods magnetic amplitude inversion offers one solution to this challenge because the amplitude data are weakly dependent on the magnetization direction in addition the low magnetic latitude also imposes difficulty in amplitude data calculation due to the instability in the component conversion in the wavenumber domain to formulate a practical approach we present a case study on applying the magnetic amplitude inversion to the furnas southeast iocg deposit at the low magnetic latitude i

nappe stacking resulting from subduction of oceanic and continental lithosphere below greece we quantitatively investigate the relation between nappe stacking and subduction in the aegean region if nappe stacking is the result of the decoupling of upper crustal parts 5 10 km thick from subducting lithosphere then the amount of convergence estimated from balancing the nappe stack provides a lower limit to the amount of convergence accommodated by subduction the balanced nappe stack combined with the estimated amount of completely subducted lithosphere indicates 700 km of jurassic and 2400 km of post jurassic convergence from seismic tomographic images of the underlying mantle we estimate 2100 2500 km of post jurassic convergence we conclude that 1 the imaged slab represents the subducted lithosphere that originally underlay the nappes 2 since the early cretaceous subduction in the aegean has occurred in one single subduction zone and 3 the composition of the original basement of the nappes indicates that at least 900 km of sub upper crust continental lithosphere subducted in the aegean

late cenozoic extension in northeastern greece strymon valley detachment system and rhodope metamorphic core complex the strymon valley detachment system accommodated at least 25 km of extension at the northern margin of the aegean extensional province from middle miocene through early pliocene time the primary detachment surface is exposed as a gently southwest dipping low angle normal fault similar to those widely known in core complex settings of the u s basin and range province for more than 150 km along strike from the aegean sea coast in northeastern greece northward into the struma valley of southern bulgaria hanging wall rocks in the strymon valley detachment system moved in a s53 w direction relative to the footwall resulting ultimately in the tectonic unroofing of the rhodope metamorphic core complex several segments of the strymon valley detachment have previously been interpreted as thrust faults formed during a miocene compressional event our results negate the principal evidence for this event and imply instead that extensional deformation has characterized the northern aegean region since at least middle miocene time displacement ceased on the strymon valley detachment with the late pliocene development of the strymon and drama basins we propose that those basins together with the other principal basins of the northern aegean region are subsiding above an active northeast dipping extensional detachment zone that forms a unified kinematic system with the western offshore continuation of the dextral north anatolian strike slip fault the north aegean trough if this hypothesis is correct then the north aegean trough the western strands of the north anatolian fault and the principal modern depocenters of the northern aegean region may all have originated no earlier than late pliocene time

inverse modelling of the reversely magnetized shallow plumbing system hosting oil reservoirs of the auca mahuida volcano payeina retroarc neuquen basin argentina

geikielite mg al spinel titanoclinohumite association from a marble quarry near rajapalaiyam area part of the 550 ma old southern granulite terrain southern india abstract geikielite and titanoclinohumite in association with fo mg al spl ap phl an fassaitic cpx chu cal dol assemblage are being reported for the first time from a marble quarry in the vicinity of rajapalaiyam town this locality forms part of the madurai block of the 550 ma southern granulite terrain and exhibits metamorphic p t conditions ranging from 7 9 kbars at 800 1000 c as deduced from the sil opx grt crd bt bearing pelitic assemblages the role of co 2 in the formation of the granulites has been dealt with most of the papers but only recently attention is being paid to the role of f rich halogenated fluids in the formation of humite bearing minerals and in the migration of elements like ti zr and ree the metamorphic fluid activity which led to the formation of the above unique fo spl ap chu assemblage including the geikielite and titanoclinohumite minerals can be associated with intrusive granites the charnockitic pods in the deformed calcitic marble zone may also have helped in providing ti p and zr k rich halogenated fluid activity seems to be common to the 550 ma eastern gondwana segments

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

reconstruction of geologic bodies in depth associated with a sedimentary basin using gravity and magnetic data summary we present a comprehensive review of the most comm on gravity and magnetic interpretation methods to in depth retrieval of the geometry of two types of geologic bodies associated with a sedimentary basin 1 sedimentary basement relief and 2 salt bodies in reconstructing a basement topography we identify three groups of methods the automatic the spectral and the nonspectral methods the reconstruction of salt bodies geometries from gravity data usually uses the interactive forward modeling but recently gravity inversion methods have been developed to interpret this kind of geological environment

potential field signatures along the zagros collision zone in iran abstract the zagros orogenic belt known as an active fold thrust belt was formed in southwestern iran due to the convergence of the arabian and eurasian plates in this study potential field data are inverted in 3d to image the variations of magnetic susceptibility and density contrast along the collision zone resulting in better tectonic understanding of the studied region geophysical data measured by airborne magnetic and ground based gravity systems are used to construct an integrated model that facilitates the interpretations of various tectonic zones across a 450 km line this line intersects the main structural units from the sw portion of the zagros belt the constructed model reveals a contrast that indicates the transition between the two continental plates coinciding with the western boundaries of the sanandaj sirjan zone ssz at the main zagros thrust mzt fault the subduction of the arabian continental crust below the iranian one is evident because of its lower susceptibility property and alternating sequence of high and low density regions higher susceptibility magnetic remanence and density are the mainstays of the urumieh dokhtar magmatic assemblage udma zone at the ne of the studied route whereas lower values of these properties correspond to 1 the thin massive tertiary neogene and quaternary sediments of the central domain cd zone and 2 the thick sedimentary and salt intrusion cover over the zagros fold and thrust belt zftb higher density of regions in the arabian crust below the zftb implies that fault activities have caused significant vertical displacement of the basement finally a simplified geological model is presented based upon the inversions of the geophysical data in which the main geological units are divided along the studied route

static mass balance sensitivity of arctic glaciers and ice caps using a degree day approach the purpose of this study is to enhance our understanding of the response of glaciers to climate change global sea level is affected by changes in glacier ice volume and melt water from glaciers is a principal water source in many regions this study applies glacier mass balance modelling with varying complexity and spatial resolution ranging from individual glaciers to regional and global assessments of glacier mass losses glaciers located in maritime environments generally show considerably higher mass balance sensitivities than those in continental settings on average an assumed increase in annual precipitation of 10 tends to offset the effect of an annual temperature change of 1 k by roughly 20 two case studies at storglaciaren sweden and hofsjokull iceland involve model results of future mass balance change and glacier melt induced changes in runoff applying a temperature and precipitation scenario for iceland in 2050 results in increased total runoff from hofsjokull by roughly one third and results emphasize the role of the firn layer in delaying water flow through glaciers yielding a redistribution of discharge within the year based on a global gridded data set of glacierized area the sea level equivalent from all mountain glaciers and ice caps outside the ice sheets in greenland and antarctica during 1961 2004 caused by changes in temperature and precipitation is estimated to be 0 58 0 34 mm a 1 the mountain glaciers and ice caps around antarctica alone contribute almost 40 of the global estimate and hence their contribution is considerably larger than previously assumed

multiple generations of extensional detachments in the rhodope mountains northern greece evidence of episodic exhumation of high pressure rocks abstract an integrated structural and petrological study shows that exhumation of high rocks of the rhodope occurred in several pulses the structurally uppermost kimi complex recording an early cretaceous high p metamorphism was exhumed between about 65 and 42 ma the sidironero kardamos and kechros complexes that record early tertiary high metamorphism at least 19 kbar at 700 c were exhumed at 42 30 ma exhumation occurred with isothermal decompression strain episodes depict thrusting of medium high grade above lower grade high p rocks syn thrusting extension and post thrusting extension polyphase extension created several generations of detachment zones which in sum excise about 20 km of material within the crustal profile this reduction in crustal thickness is consistent with a reduction of the present crustal thickness from more than 40 km to less than 30 km in the eastern rhodope we mapped the post thrusting xanthi low angle detachment system over 100km from its break up zone above the sidironero complex central rhodope into the eastern rhodope this detachment shows an overall ese dip with a ramp and flat geometry cutting across the earlier thrust structures the kimi complex is the hanging wall of all synand post thrusting extensional systems on top of the kimi complex marine basins were formed from the lutetian c 48 43 ma through the oligocene during extension successively at c 26 to 8 ma the thasos pangeon metamorphic core complexes were exhumed in these times representing the early stages of aegean back arc extension the strymon and thasos detachment systems caused crustal thinning in the western rhodope renewed heating of the lithosphere associated with magmatism and exhumation of hot middle crust from beneath the sidironero complex occurred we focusoxn the geometry timing and kinematics of extension and contraction structures related to the 42 30 ma interval and how these exhumed high p rocks we interpret high rocks exhumed in this interval as a window of the apulian plate beneath the earlier in the cretaceous accreted kimi complex

sea level rise from glaciers and ice caps a lower bound 1 one of the most easily measured dimensions of a glacier the accumulation area is linked to future changes in glacier volume and consequent changes in sea level currently observed accumulation areas are too small forcing glaciers to lose 27 of their volume to attain equilibrium with current climate as a result at least 184 33 mm of sea level rise are necessitated by mass wastage of the world s mountain glaciers and ice caps even if the climate does not continue to warm if the climate continues to warm along current trends a minimum of 373 21 mm of sea level rise over the next 100 years is expected from glaciers and ice caps when compared to recent estimates from all other sources melt water from glaciers must be considered as a particularly important fraction of the total sea level rise expected this century

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

greenland freshwater pathways in the sub arctic seas from model experiments with passive tracers accelerating since the early 1990s the greenland ice sheet mass loss exerts a significant impact on thermohaline processes in the sub arctic seas surplus freshwater discharge from greenland since the 1990s comparable in volume to the amount of freshwater present during the great salinity anomaly events could spread and accumulate in the sub arctic seas influencing convective processes there however hydrographic observations in the labrador sea and the nordic seas where the greenland freshening signal might be expected to propagate do not show a persistent freshening in the upper ocean during last two decades this raises the question of where the surplus greenland freshwater has propagated in order to investigate the fate pathways and propagation rate of greenland meltwater in the sub arctic seas several numerical experiments using a passive tracer to track the spreading of greenland freshwater have been conducted as a part of the forum for arctic ocean modeling and observational synthesis effort the models show that greenland freshwater propagates and accumulates in the sub arctic seas although the models disagree on the amount of tracer propagation into the convective regions results highlight the differences in simulated physical mechanisms at play in different models and underscore the continued importance of intercomparison studies it is estimated that surplus greenland freshwater flux should have caused a salinity decrease by 0 06 0 08 in the sub arctic seas in contradiction with the recently observed salinification by 0 15 0 2 in the region it is surmised that the increasing salinity of atlantic water has obscured the freshening signal

implications of shear sense criteria for the tectonic evolution of the central rhodope massif southern bulgaria a systematic record of sense of shear criteria associated with peak conditions of amphibolite facies metamorphism from the central rhodope massif bulgaria gives evidence for superposition of two distinct terranes the lower terrane is characterized by south vergent flat lying thrusting that involved eclogites the upper terrane is characterized by east vergent flat lying shearing possibly associated with crustal extension we suggest that both regional metamorphism and deformation may be cretaceous in age there was erosion prior to emplacement of several crystalline sheets at shallow depths during the early cenozoic this was followed by oligocene extension and rhyolitic volcanism the rhodope massif can no longer be regarded as a stable paleozoic or older microcontinent

influence of the arctic circumpolar vortex on the mass balance of canadian high arctic glaciers abstract variability in july mean surface air temperatures from 1963 to 2003 accounted for 62 of the variance in the regional annual glacier mass balance signal for the canadian high arctic a regime shift to more negative regional glacier mass balance occurred between 1986 and 1987 and is linked to a coincident shift from lower to higher mean july air temperatures both the interannual changes and the regime shifts in regional glacier mass balance and july air temperatures are related to variations in the position and strength of the july circumpolar vortex in years when the july vortex is strong and its center is located in the western hemisphere positive mass balance anomalies prevail in contrast highly negative mass balance anomalies occur when the july circumpolar vortex is either weak or strong without elongation over the canadian high arctic and its center is located in the eastern hemisphere the occurrence of westerly positioned july vortices has decreased by 40 since 1987 the associat

separation of magnetic anomalies into induced and remanent magnetization contributions abstract inversion of magnetic data is complicated by the presence of remanent magnetization and it provides limited information about the magnetic source because of the insufficiency of data and constraint information we propose a fourier domain transformation allowing the separation of magnetic anomalies into the components caused by induced and remanent magnetizations the approach is based on the hypothesis that each isolated source is homogeneous with a uniform and specific koenigsberger ratio the distributions of susceptibility and remanent magnetization are subsequently recovered from the separated anomalies anomaly components susceptibility distribution and distribution of the remanent and total magnetization vectors direction and intensity can be achieved through the processing of the anomaly components the proposed method therefore provides a procedure to test the hypotheses about target source and magnetic field by verifying these models based on available information or a priori information from geology we test our methods using synthetic and real data acquired over the zhangfushan iron ore deposit and the yeshan polymetallic deposit in eastern china all the tests yield favourable results and the obtained models are helpful for the geological interpretation

modeling the microwave emission of bubbly ice applications to blue ice and superimposed ice in the antarctic and arctic passive microwave remote sensing is extensively used in polar regions to study the cryosphere to better understand the measured signal above continental ice covered areas our objective is to estimate the microwave emission of bubbly ice surfaces using a physically based multilayer electromagnetic model i e the dense media radiative transfer multilayer model dmrt ml this model accounts for ice layers with variable amounts of bubbles each layer is fully described by its temperature density thickness and air bubble radius simulations are performed using in situ data from two distinct sites one in antarctica on a coastal blue ice area near the cap prud homme cph station in adelie land and the other on the barnes ice cap bic located on baffin island in the arctic on this ice cap superimposed ice with seasonal snow cover about 1 m thick was observed in both cases several ice parameters were measured or estimated and the others were optimized results of the dmrt ml simulations are compared with in situ surface based radiometer sbr measurements at 11 19 and 37 ghz at both horizontal and vertical polarizations results show that dmrt ml is able to reproduce the microwave emission of different ice types with good accuracy when accounting for ice bubbles final hbox rmse 7 37 hbox k and 8 42 k for cph and bic respectively compared with rmse ranging from 15 k to 40 k without bubbles comparisons between sbr measurements and satellite data for the bic also show good agreement hbox rmse 4 1 hbox k for 19 and 37 ghz both polarizations

fluid rock history of granulite facies humite marbles from ambasamudram southern india an extensive humite bearing marble horizon within a supracrustal sequence at ambasamudram southern india was studied using petrological and stable isotopic techniques to define its metamorphic history and fluid characteristics at peak metamorphic temperatures of 775 73 c based on calcite graphite carbon isotope thermometry the mineral assemblages suggest layer by layer control of fluid compositions clinohumite calcite bearing assemblages suggest xco2 0 9 at 790 c and local wollastonite scapolite grossular bearing zones formed at xco2 of c 0 3 retrograde reaction textures such as scapolite quartz symplectites after feldspar and calcite and replacement of dolomite diopside or tremolite dolomite after calcite forsterite or calcite clinohumite are indicative of retrogression under high xco2 conditions calcite preserves late proterozoic carbon and oxygen isotopic signatures and the marble lacks evidence for extensive retrograde fluid infiltration while during prograde metamorphism the possible infiltration of aqueous fluids did not produce significant isotopic resetting isotopic zonation of calcite and graphite grains was likely produced by localized co2 fluid infiltration during retrogression contrary to the widespread occurrence of humite marbles related to retrograde aqueous fluid infiltration the ambasamudram humite marbles record a prograde to peak metamorphic humite formation and retrogression under conditions of low xh2o

well productivity in the ponta grossa dike swarm brazil an integrated study with magnetic data inversion and clustering analysis of model solutions abstract dike swarms are mega structures observed in different geological contexts which may affect groundwater flow systems these structures are well recognizable from airborne magnetic however it is difficult to obtain quantitative information about distribution and mean properties of dikes that generate the observed magnetic anomalies this work presents a procedure to perform magnetic data inversion along profiles transecting the ponta grossa dike swarm pgds and determine its mean properties with application of cluster analysis to obtained solutions next the mean model solutions are correlated with a regional database of borehole productivity suggesting that more productive wells are found close to a group of shallow dikes of the pdgs in southeastern brazil for the area mainly composed by sedimentary rocks the wells situated over shallow dikes show higher values of specific capacity by a factor of 14 5 than those not close to a dike in the same domain for the area mainly composed by granitic rocks the productivity of wells over dikes is still higher a factor of 4 3 higher than those with no dikes a conceptual model is presented to explain the higher productivity of wells close to the dikes as resulting from fracturing on host rock caused by dikes emplacement only a group of shallow dikes seems to be associated with more productive wells

inversion of magnetic anomaly on rugged observation surface in the presence of strong remanent magnetization abstractwe study the inversion of magnetic data acquired over a rugged observation surface and where the buried source bodies have strong remanent magnetization that leads to unknown total magnetization directions these factors pose significant challenges for processing and inversion of such data to tackle the challenges from both a rugged observation surface and an unknown magnetization direction we propose a strategy through the joint use of the equivalent source technique and 3d amplitude inversion to obtain 3d magnetization strength we use equivalent source processing to calculate the amplitude data in the space domain because the use of the wavenumber domain method is invalid due to large variations in the data elevation we then carried out an amplitude inversion to generate a 3d subsurface distribution of the magnitude of the total magnetization vector the results from a synthetic example and aeromagnetic data in daye mine in china showed that this approach is effective and images the magnetic

grace observes small scale mass loss in greenland using satellite gravity data between february 2003 and january 2008 we examine changes in greenland s mass distribution on a regional scale during this period greenland lost mass at a mean rate of 179 25 gt yr equivalent to a global mean sea level change of 0 5 0 1 mm yr rates increase over time suggesting an acceleration of the mass loss driven by mass loss during summer the largest mass losses occurred along the southeastern and northwestern coast in the summers of 2005 and 2007 when the ice sheet lost 279 gt and 328 gt of ice respectively within 2 months in 2007 a strong mass loss is observed during summer at elevations above 2000 m for the first time since the start of the observations

diamond former coesite and supersilicic garnet in metasedimentary rocks from the greek rhodope a new ultrahigh pressure metamorphic province established abstract we report here the first discovery of ultrahigh pressure uhp indicator minerals and textures from the rhodope metamorphic province rmp northern greece in particular we document the exsolution of quartz rutile and apatite in sodic garnet from metapelites garnet biotite kyanite gneisses which attests to the presence of a si ti na p rich precursor garnet phase similar textures in garnet have been reported in the literature only once before for eclogites from the su lu uhp metamorphic province china we also document the presence of microdiamonds and multicrystalline quartz pseudomorphs after coesite included in garnet from both eclogites and metapelites we then argue that these rocks had once been transported to depths exceeding 220 km well into the upper mantle thus establishing the rmp as another important uhp metamorphic belt in the world

mass balance of glaciers and ice caps consensus estimates for 1961 2004 1 working with comprehensive collections of directly measured data on the annual mass balance of glaciers other than the two ice sheets we combine independent analyses to show that there is broad agreement on the evolution of global mass balance since 1960 mass balance was slightly below zero around 1970 and has been growing more negative since then excluding peripheral ice bodies in greenland and antarctica global average specific balance for 1961 1990 was 219 112 kg m 2 a 1 representing 0 33 0 17 mm sle sea level equivalent a 1 for 2001 2004 the figures are 510 101 kg m 2 a 1 and 0 77 0 15 mm sle a 1 including the smaller greenland and antarctic glaciers global total balance becomes 0 38 0 19 mm sle a 1 for 1961 1990 and 0 98 0 19 mm sle a 1 for 2001 2004 for 1991 2004 the glacier contribution 0 77 0 26 mm sle a 1 is 20 30 of a recent estimate of 3 2 0 4 mm a 1 of total sea level rise for 1993 2005 while our error estimates are not rigorous we believe them to be liberal as far as they go but we also discuss several unquantified biases of which any may prove to be significant

recent changes in glacier velocities and thinning at novaya zemlya abstract ice loss from the glaciers of novaya zemlya nvz is the dominant contributor to sea level for the russian arctic here we present maps of glacier elevation change rates dh dt and velocities at novaya zemlya that reveal evidence of the impact of both calving flux and surface melt on ice mass loss dh dt are calculated by applying a weighted linear regression to stacked digital elevation models dems from a 1952 map and dems created from stereo pairs of worldview images acquired between 2012 and 2014 the 60 year average mass change rate is 0 23 0 04 m w e yr 1 the recent short term 2012 2013 2014 average mass change rate is 0 40 0 09 m w e yr 1 we apply the same weighted linear regression to stacked worldview dems and icesat elevations from 2003 to 2009 as well as stacked worldview dems and aster dems from 2000 to 2013 the dh dt from both datasets confirm that thinning has been more rapid than the 60 year average since 2000 average mass loss has accelerated at the lower elevations of land terminating glaciers suggesting that recent near surface warming and increased melt have led to greater thinning marine terminating glaciers along the barents sea coast have substantially higher thinning rates near their termini in recent years than adjacent land terminating glaciers suggesting that calving flux is an important contributor to overall ice mass loss in the region flow velocities are generated by feature tracking on optical and radar image pairs marine terminating glaciers along the barents sea coast have the highest frontal velocities of any glaciers on nvz our surface velocity measurements constrain the calving flux at the two fastest retreating glaciers inostrantseva ino and vil kitskogo vis which are both on the barents sea coast we find that the calving flux is high enough to drive frontal thinning and retreat at those two glaciers summer terminus speeds at inostrantseva glacier have accelerated from a 2006 maximum of 3 m day 1 to a 2012 maximum of 9 to 10 m day 1 and the front has retreated by more than 3 km between 2006 06 27 and 2013 08 17

the ice cloud and land elevation satellite 2 icesat 2 science requirements concept and implementation abstract the ice cloud and land elevation satellite icesat mission used laser altimetry measurements to determine changes in elevations of glaciers and ice sheets as well as sea ice thickness distribution these measurements have provided important information on the response of the cryopshere earth s frozen surfaces to changes in atmosphere and ocean condition icesat operated from 2003 to 2009 and provided repeat altimetry measurements not only to the cryosphere scientific community but also to the ocean terrestrial and atmospheric scientific communities the conclusive assessment of significant ongoing rapid changes in the earth s ice cover in part supported by icesat observations has strengthened the need for sustained high accuracy repeat observations similar to what was provided by the icesat mission following recommendations from the national research council for an icesat follow on mission the icesat 2 mission is now under development for planned launch in 2018 the primary scientific aims of the icesat 2 mission are to continue measurements of sea ice freeboard and ice sheet elevation to determine their changes at scales from outlet glaciers to the entire ice sheet and from 10s of meters to the entire polar oceans for sea ice freeboard icesat carried a single beam profiling laser altimeter that produced 70 m diameter footprints on the surface of the earth at 150 m along track intervals in contrast icesat 2 will operate with three pairs of beams each pair separated by about 3 km cross track with a pair spacing of 90 m each of the beams will have a nominal 17 m diameter footprint with an along track sampling interval of 0 7 m the differences in the icesat 2 measurement concept are a result of overcoming some limitations associated with the approach used in the icesat mission the beam pair configuration of icesat 2 allows for the determination of local cross track slope a significant factor in measuring elevation change for the outlet glaciers surrounding the greenland and antarctica coasts the multiple beam pairs also provide improved spatial coverage the dense spatial sampling eliminates along track measurement gaps and the small footprint diameter is especially useful for sea surface height measurements in the often narrow leads needed for sea ice freeboard and ice thickness retrievals the icesat 2 instrumentation concept uses a low energy 532 nm green laser in conjunction with single photon sensitive detectors to measure range combining icesat 2 data with altimetry data collected since the start of the icesat mission in 2003 such as operation icebridge and esa s cryosat 2 will yield a 15 year record of changes in ice sheet elevation and sea ice thickness icesat 2 will also provide information of mountain glacier and ice cap elevations changes land and vegetation heights inland water elevations sea surface heights and cloud layering and optical thickness

reconstructing hydrographic change in petersen bay ellesmere island canada inferred from sar imagery abstract synthetic aperture radar sar satellite imagery was used to reconstruct the change in limnological conditions adjacent to an arctic ice shelf by examining the backscatter values of coastal ice in mid winter scenes high sar backscatter values 6 db suggest that an ice dammed lake was present adjacent to the south coast of petersen bay from 1992 until 2005 following a large calving event of the adjacent petersen ice shelf 8 07 km2 in august 2005 the lake drained through a region where the ice shelf had separated from the coastline this loss of freshwater and replacement of lake ice with sea ice along the southern coast of petersen bay were confirmed from analyses of ice core samples and conductivity temperature depth ctd profiles the exception to this pattern was one distinct area where terrestrial streams entered the edge of petersen bay and freshwater continued to collect from 2006 to 2008 however this ephemeral area of freshwater has not reformed since 2009 due to the persistence of open water events in petersen bay observed in optical satellite imagery which likely facilitated mixing of freshwater with sea water based on the continued break ups of petersen ice shelf and the frequency of open water events it is unlikely that this ice dammed lake will reform the results of this study underscore the utility of sar for reconstructing past hydrographic conditions in the water column below

metamorphic evolution and geochemistry of kyanite eclogites in central rhodope northern greece in central rhodope of northern greece kyanite eclogites were discovered in the area of thermes they are strongly overprinted and exhibit a multi stage development of minerals and mineral assemblages formed during successive stages of the exhumation the initial high pressure assemblage was garnet omphacite kyanite zoisite phengite rutile quartz corundum fe mg spinel sapphirine and hogbomite occur as products of a first high temperature overprint still at high pressures whereas various symplectites corundum plagioclase pl spinel pl sapphirine pl clinopyroxene pl biotite pl amphibole pl grew during subsequent stages of the exhumation diablastic amphibole plagioclase formed as end products of the amphibolitization according to geochemical data the protoliths of the kyanite eclogites were basalts to basaltic andesites with volcanic arc affinities for the high pressure stage of metamorphism minimum pt conditions were around 19 kbar 700 c while for the initial stages of the overprint high pressure granulite facies conditions prevailed t 800 c at p 15 kbar the pt conditions of the amphibolite facies were 8 11 kbar 580 690 c the kyanite eclogites of thermes record the highest temperatures of metamorphism within the whole of rhodope

mountain glaciers and ice caps around antarctica make a large sea level rise contribution the intergovernmental panel on climate change ipcc estimates that the sum of all contributions to sea level rise for the period 1961 2004 was 1 1 0 5 mm a 1 leaving 0 7

kyanite eclogite to amphibolite fades evolution of hydrous mafic and pelitic rocks adula nappe central alps in the southern adula nappe central alps two stages of regional metamorphism have affected mafic and pelitic rocks earlier eclogite facies with a regional zonation from glaucophane eclogites to kyanite hornblende eclogites was followed by a tertiary overprint which varied from greenschist to high grade amphibolite facies despite a common metamorphic history contrasting equilibration conditions are often recorded by high pressure mafic eclogite and adjacent predominantly lower pressure pelite assemblages this pressure contrast may be explained by different overprinting rates of the two bulk compositions during unloading the rates are controlled by a mechanism in which dehydrating metapelites provide the h2o required for simultaneous overprinting of enclosed mafic eclogites by hydration

calcite inclusions in forsterite forsterite in metamorphosed siliceous dolomites commonly contains calcite inclusions that are significantly more magnesian than even the most magnesian calcite grains in the matrix of the same rock calcite inclusions in forsterite from dolomite bearing rocks therefore have an unexploited potential for providing more accurate estimates of the peak t of metamorphism than do matrix calcite grains some consequences for estimating fluid pressure and for the development of models of heat and fluid transport during contact metamorphism are reviewed measured compositions of calcite inclusions in forsterite from five contact aureoles indicate that significant growth of forsterite grains continues over a 50 200 c range in t after the initial nucleation and growth of the mineral during heterogeneous mineral fluid reaction the continued growth may occur by an annealing mechanism driven by reduction in interfacial free energy

ice velocity changes on penny ice cap baffin island since the 1950s predicting the velocity response of glaciers to increased surface melt is a major topic of ongoing research with significant implications for accurate sea level rise forecasting in this study we u

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

k2o prograde zoning pattern in clinopyroxene from the kokchetav diamond grade metamorphic rocks missing part of metamorphic history and location of second critical end point for calc silicate system abstract despite extensive studies of calc silicate rocks of the kokchetav massif there is no satisfactory explanation of the origin of potassium bearing clinopyroxene in alkali poor metamorphic rocks in this paper we report the finding of potassium bearing clinopyroxene with prograde zonation k 2 o increases from core to rim from diamond grade but diamond free uhp calc silicate rocks of the kokchetav massif we believe that the crystallization of potassium bearing clinopyroxene started on the prograde stage and slightly prior to the peak of uhp metamorphism thus prograde metamorphic history is only traceable in diamond free uhp calc silicate rocks while in diamond bearing uhpm rocks it is completely reset fluid and polyphase solid inclusions originally representing melt inclusions occur in the core of potassium bearing clinopyroxene and imply that melt and fluid may coexist in calc silicate rocks even at 1000 1100 c and 6 7 gpa

comprehensive approaches to 3d inversion of magnetic data affected by remanent magnetization three dimensional 3d inversion of magnetic data to recover a distribution of magnetic susceptibility has been successfullyusedformineralexplorationduringthelastdecade however the unknown direction of magnetization has limited the use of this technique when significant remanence is present we have developed a comprehensive methodology for solving this problem by examining two classes of approaches and have formulated a suite of methods of practical utility the first class focuses on estimating total magnetization direction and then incorporating the resultant direction into an inversion algorithm that assumes a known direction thesecondclassfocusesondirectinversionoftheamplitude of the magnetic anomaly vector amplitude data depend weaklyuponmagnetizationdirectionandareamenabletodirect inversion for the magnitude of magnetization vector in 3d subsurface two sets of high resolution aeromagnetic dataacquiredfordiamondexplorationinthecanadianarctic areusedtoillustratethemethods usefulness

three dimensional inversion of magnetic data in the simultaneous presence of significant remanent magnetization and self demagnetization example from daye iron ore deposit hubei province china

raman micro spectroscopy on diamond graphite and other carbon polymorphs from the ultrahigh pressure metamorphic kimi complex of the rhodope metamorphic province ne greece raman micro spectroscopy was applied on carbon inclusions in garnet porphyroblasts from kyanite biotite garnet schists of the rhodope metamorphic province rmp ne greece diamond and cuboids of poorly to highly ordered graphite were identified either as single phase inclusions or as polyphase inclusions along with co2 and or carbonates calcite magnesian calcite questionable raman bands that may be assigned to other c phases nanodiamond lonsdaleite a different c polymorph have been observed the presence of diamond confirms beyond any doubt the ultrahigh pressure uhp metamorphism reported by mposkos and kostopoulos 1 e mposkos d kostopoulos diamond former coesite and supersilisic garnet in metasedimentary rocks from the greek rhodope a new ultrahigh pressure metamorphic province established earth planet sci lett 192 2001 497 506 in the rmp cuboid graphite showing variable degree of disordering most probably formed after diamond the possible involvement of co2 and or c o h fluids in the formation of diamond is discussed

titanian clinohumite and geikielite in marbles from the bergell contact aureole the assemblage titanian clinohumite forsterite spinel calcite is widespread in marbles from the eastern bergell contact aureole switzerland italy the bergell titanian clinohumites vary considerably in composition tio2 0 19 to 2 05 wt f 2 2 to 3 4 wt electron microprobe analyses show that the titanian clinohumites contain less than detectable amounts of co cu ni zn al cr and cl no trace of ferric iron could be detected by moessbauer spectroscopy moreover the moessbauer spectra indicate that fe2 occurs only in one of the five octahedral positions in the crystal structure of the studied titanian clinohumite under the conditions of the contact metamorphism 600 650 c 3 kb total pressure the compositional variation along the exchange vector tio2m 1 oh f 2 takes place at constantxoh which is fixed by the pore fluid titanian clinohumite sometimes contains geikielite inclusions which strongly fractionate fe and mn relative to titanian clinohumite the geikielites from the bergell marbles are poor in cr2o3 fe2o3 and mno and thus different from those found in carbonatites kimberlites and serpentinized ultramafic rocks

updated estimates of glacier volume changes in the western chugach mountains alaska and a comparison of regional extrapolation methods and 2001 2004 average net balance rates ranged between 3 1 to 0 16 m yr 1 for the tidewater and 1 5 to 0 02 m yr 1 for the nontidewater glaciers we tested several methods for extrapolating these measurements to all the glaciers of the western chugach mountains using a process similar to cross validation predictions of individual glacier changes appear to be difficult probably because of the effects of glacier dynamics which on long multidecadal timescales complicates the response of glaciers to climate in contrast estimates of regional contributions to rising sea level were similar for different methods mainly because the large glaciers whose changes dominated the regional total were among those measured for instance the above sea level net balance rate of columbia glacier 3 1 0 08 km 3 yr 1 water equivalent weq or an equivalent rise in sea level sle of 0 0090 0 0002 mm yr 1 was nearly half of the total regional net balance rate of the western chugach mountain glaciers 7 4 1 1 km 3 yr 1 weq or 0 020 0 003 mm yr 1 sle between 1950 1957 and 2001 2004 columbia glacier is a rapidly retreating tidewater glacier that has lost mass through processes largely independent of climate tidewater glaciers should therefore be treated separately when performing regional extrapolations

integrated geophysical imaging of a concealed mineral deposit a case study of the world class pebble porphyry deposit in southwestern alaska abstractwe combined aeromagnetic induced polarization magnetotelluric and gravity surveys as well as drillhole geologic alteration magnetic susceptibility and density data for exploration and characterization of the cu au mo pebble porphyry deposit this undeveloped deposit is almost completely concealed by postmineralization sedimentary and volcanic rocks presenting an exploration challenge individual geophysical methods primarily assist regional characterization positive chargeability and conductivity anomalies are observed over a broad region surrounding the deposit likely representing sulfide minerals that accumulated during multiple stages of hydrothermal alteration the mineralized area occupies only a small part of the chargeability anomaly because sulfide precipitation was not unique to the deposit and mafic rocks also exhibit strong chargeability conductivity anomalies similarly reflect widespread sulfides as well as water saturated glacial sediments mineralogical and magnetic suscep

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

geophysical inversions applied to 3d geology characterization of an iron oxide copper gold deposit in brazil abstract mineral exploration dynamics often requires an efficient and objective means of evaluating a prospect in early exploration stages when few holes have been drilled in the case of deep prospects or prospects under cover this evaluation will mostly be based on geophysical data to develop an objective interpretation method capable of combining all the information available we have developed an integrated interpretation scheme of geophysical models and sparse geologic data our method is based on the relationship between recovered physical properties obtained from 2d and 3d inversions aiming to find patterns associated with geologic units such as iron formation copper ore and host rock the interpretation is guided by theoretical relations of the minerals of interest chalcopyrite and magnetite and the sparse geologic information available it is suitable for prospects in the initial stages of exploration when only limited mineralogical information is available from say one drillhole we h

recrystallization of high pressure marble sivrihisar turkey abstract in the sivrihisar massif turkey the southern margin of a blueschist facies terrane was affected by heating and deformation associated with later regional barrovian metamorphism creating a recrystallization front that can be observed in calcite microstructures calcite marble records a progression from high pressure h p textures in a northern domain to completely recrystallized greenschist to amphibolite facies textures in a southern domain with intermediate stages of partial recrystallization of the h p textures h p marble is characterized by rod shaped calcite aragonite pseudomorphs arranged in series with the long axis of each grain oblique to compositional layering obliquity varies from 50 to nearly parallel but high angles are most common in a narrow 200 m thick transition zone that contains partially retrogressed blueschist and eclogite the h p texture is partially overprinted by chains of small equant recrystallized grains that preserve the crystallographic orientation of the pre existing rod shaped calcite as revealed by electron backscatter diffraction analysis rod shaped crystals occur locally in a 100 m thick zone south of the transition zone all calcite grains are equant but have a crystallographic preferred orientation further south in the barrovian sequence recrystallized marble contains equant calcite that is randomly oriented the similarity in fabric elements foliation lineation of the two domains further shows the effect of barrovian related processes on the h p domain including the rotation of the calcite rods during shearing along foliation planes white mica 40 ar 39 ar ages for phengite in h p marble are 88 ma and for muscovite in barrovian marble are 59 ma indicating 30 ma time interval between initial exhumation and cooling of the h p rocks and final cooling of the rocks that were deformed and heated during the later metamorphic event

automatic boundary extraction from magnetic field data using triangular meshes boundary extraction is a collective term that we use for the process of extracting the locations of faults lineaments and lateral boundaries between geologic units using geophysical observations such as measurements of the magnetic field the process typically begins with a preprocessing stage where the data are transformed to enhance the visual clarity of pertinent features and hence improve the interpretability of the data the majority of the existing methods are based on raster grid enhancement techniques and the boundaries are extracted as a series of points or line segments in contrast we set out a methodology for boundary extraction from magnetic data in which we represent the transformed data as a surface in 3d using a mesh of triangular facets after initializing the mesh we modify the node locations such that the mesh smoothly represents the transformed data and that facet edges are aligned with features in the data that approximate the horizontal locations of subsurface boundaries to illustrate our boundary extraction algorithm we first apply it to a synthetic data set we then apply it to identify boundaries in a magnetic data set from the mcfaulds lake area in ontario canada the extracted boundaries are in agreement with known boundaries and several of the regions that are completely enclosed by extracted boundaries coincide with regions of known mineralization

patagonia icefield melting observed by gravity recovery and climate experiment grace 1 using recently released reprocessed gravity solutions from the gravity recovery and climate experiment grace we estimate the ice loss rate for the patagonia icefield pif of south america for the period april 2002 through december 2006 after postglacial rebound and hydrological effects are corrected the estimated rate is 27 9 11 km 3 year equivalent to an average loss of 1 6 m year ice thickness change if evenly distributed over the entire pif area the estimated contribution to global sea level rise is 0 078 0 031 mm year this is an independent confirmation of relatively large melting rate estimates from earlier studies employing topographic and cartographic data

estimating the contribution of arctic glaciers to sea level change in the next 100 years in this paper we report on an approach to estimate the contribution of arctic glaciers to sea level change in our calculation we assume that a static approach is feasible we only calculate changes in the surface balance from modelled sensitivities these sensitivities summarized in the seasonal sensitivity characteristic can be used to calculate the change in the surface mass budget for given anomalies of monthly temperature and precipitation we have based our calculations on a subdivision of all arctic ice into 13 regions four sectors of the greenland ice sheet the canadian arctic 74 n the canadian arctic 60 n as forcing for the calculations we have used the output from five climate models for the period 2000 2100 these models were forced by the same greenhouse gas scenario ipcc b2 the calculated contributions to sea level rise in the year 2100 vary from almost zero to about 6 cm the differences among the models stem first of all from differences in the precipitation the largest contribution to sea level change comes from the greenland ice sheet the glaciers in alaska also make a large contribution not because of the area they cover but because they are more sensitive than other glaciers in the arctic the climate models do not agree on regional patterns the runoff from svalbard glaciers for instance increases for two models and decreases for the three other models we conclude that the uncertainty due to a simple representation of the glaciological processes is probably smaller than the uncertainty induced by the differences in the climate change scenarios produced by the models

rock magnetic investigation and its geological significance for vein type uranium deposits in southern china to characterize the metallogenic environment of a typical vein type uranium deposit samples from diabase dykes alteration zones including metamorphic diabase and uranium ore and granites were systematically investigated for six boreholes from southeastern china rock magnetic results indicate that coarse grained magnetites pseudosingle domain psd and multidomain md are dominant magnetic carriers in diabase in contrast the uranium ore is dominated by fine grained magnetites superparamagnetic sp and single domain sd the concentration of magnetic particles in fresh granites is low magnetic properties of metamorphic diabases exhibit much greater variability of magnetic properties and higher degrees of sulfuration than unaltered diabase and granite due to contact metasomatism and reduction effects close to the vein compared with diabase magnetic remanence of the uranium ore is much lower but displays much higher stability the koenigsberger ratio q peaks in the uranium ore with a value of 1 00 using the systematic rock magnetic results to constrain the interpretation the contribution of the intersection zone of diabase dyke and silicified fault to magnetic anomalies was further modeled and the effects of the ore body are significant for magnetic exploration overall rock magnetic investigations of vein type uranium deposit provide a better understanding of the interactions between different rock types and further facilitate regional magnetic surveys on the ground

glaciers dominate eustatic sea level rise in the 21st century ice loss to the sea currently accounts for virtually all of the sea level rise that is not attributable to ocean warming and about 60 of the ice loss is from glaciers and ice caps rather than from the two ice sheets the contribution of these smaller glaciers has accelerated over the past decade in part due to marked thinning and retreat of marine terminating glaciers associated with a dynamic instability that is generally not considered in mass balance and climate modeling this acceleration of glacier melt may cause 0 1 to 0 25 meter of additional sea level rise by 2100