topographic meandering of antarctic circumpolar current and antarctic circumpolar wave in the ice ocean atmosphere system 1 topographic meandering of antarctic circumpolar current acc is found to be an impediment in the propagation of antarctic circumpolar wave acw in the indian ocean sector of antarctica reasons for this are attributed to the southward advection of the acw anomalies associated with the topographic meandering of the acc the southward meandering of acc facilitates warming up of the region east of 20 e by about 1 c during winter thereby reducing the sea ice these processes interfere with the eastward propagating positive sea ice anomalies and reduce its strength warming of ocean induced by topographic meandering leads to upward vertical velocities between 40 60 e where the ocean surface velocities are weak and southward and the vertical meridional advection of temperature dominates the zonal advection in the atmosphere this results in the decoupling of the acw in the region east of 40 e in regions out side the indian ocean sector vertical advection is minimum and zonal velocity of acc becomes positive which facilitates the acw propagation in the central pacific ross and weddell seas citation nuncio m a j luis and x yuan 2011 topographic meandering of antarctic circumpolar current and antarctic circumpolar wave in the ice ocean atmosphere system geophys res lett 38 l13708

sulfur isotopic variations among minerals and aqueous species in the salton sea geothermal system a shrimp ion microprobe and conventional study of active ore genesis in a sediment hosted environment

mineralogical and stable isotope studies of gold arsenic mineralisation in the sams creek peralkaline porphyritic granite south island new zealand at sams creek a gold bearing peralkaline granite porphyry dyke which has a 7 km strike length and is up to 60 m in thickness intrudes camptonite lamprophyre dykes and lower greenschist facies metapelites and quartzites of the late ordovician wangapeka formation the lamprophyre dykes occur as thin 3 m slivers along the contacts of the granite dyke 18omagma values 5 to 8 vsmow of the a type granite suggest derivation from a primitive source with an insignificant mature crustal contribution hydrothermal gold sulphide mineralisation is confined to the granite and adjacent lamprophyre metapelite country rocks have only weak hydrothermal alteration three stages of hydrothermal alteration have been identified in the granite stage i alteration high fo2 consisting of magnetite siderite biotite stage ii consisting of thin quartz pyrite veinlets and stage iii low fo2 consisting of sulphides quartz and siderite veins and pervasive silicification the lamprophyre is altered to an ankerite chlorite sericite assemblage stage iii sulphide veins are composed of arsenopyrite pyrite galena sphalerite gold chalcopyrite pyrrhotite rutile graphite three phases of deformation have affected the area and the mineralised veins and the granite and lamprophyre dykes have been deformed by two phases of folding the youngest of which is early cretaceous locally preserved early formed fluid inclusions are either carbonic showing two or three phases at room temperature liquid co2 ch4 liquid h2o co2 vapour or two phase liquid rich aqueous inclusions some of which contain clathrates salinities of the aqueous inclusions are in the range of 1 4 to 7 6 wt nacl equiv final homogenisation temperatures th of the carbonic inclusions indicate minimum trapping temperatures of 320 to 355 c which are not too different from vein formation temperatures of 340 380 c estimated from quartz albite stable isotope thermometry 18o values of stage ii and iii vein quartz range from 12 and 17 and have a bimodal distribution 14 5 and 16 with stage ii vein quartz accounting for the lower values siderite in stage iii veins have 18o 12 to 16 and 13c values 5 relative to vpdb unlike those from wangapeka formation metasediments 13cbulk carbon values of 24 to 19 and underlying arthur marble marine carbonates 18o 25 and 13c 0 calculated 18owater 8 to 11 at 340 c and delta 13 text c rm co 2 5 values from vein quartz and siderite are consistent with a magmatic hydrothermal source but a metamorphic hydrothermal origin cannot be excluded 34s values of sulphides range from 5 to 10 relative to cdt and also have a bimodal distribution modes at 6 and 9 correlated with stage ii and stage iii mineralisation respectively the 34s values of pyrite from the arthur marble marine carbonates range from 3 to 13 and wangapeka formation range from 4 to 9 5 indicate that they are potential sources of sulphur for sulphides in the sams creek veins another possible source of the sulphur is the lithospheric mantle which has positive values up to 14 ages of the granite lamprophyre alteration mineralisation and deformation in the region are not well constrained which makes it difficult to identify sources of mineralisation with respect to timing our mineralogical and stable isotope data does not exclude a metamorphic source but we consider that the source of the mineralisation can best be explained by a magmatic hydrothermal source assuming that the hydrothermal fluids were sourced from crystallisation of the sams creek granite or an underlying magma chamber then the sams creek gold deposit appears to be a hybrid between those described as reduced granite au bi deposits and alkaline intrusive hosted au mo cu deposits

the arctic and subarctic ocean flux of potential vorticity and the arctic ocean circulation according to observations the arctic ocean circulation beneath a shallow thermocline can be schematized by cyclonic rim currents along shelves and over ridges in each deep basin the circulation is also believed to be cyclonic this circulation pattern has been used as an important benchmark for validating arctic ocean models however modeling this grand circulation pattern with some of the most sophisticated ocean ice models has been often difficult the most puzzling and thus perhaps the most interesting finding from the arctic ocean model intercomparison project aomip an international consortium that runs 14 arctic ocean models by using the identical forcing fields is that its model results can be grouped into two nearly exact opposite patterns while some models produce cyclonic circulation patterns similar to observations others do the opposite this study examines what could be possibly responsible for such strange inconsistency it is found here that the flux of potential vorticity pv from the subarctic oceans strongly controls the circulation directions for a semienclosed basin like the arctic the pv integral over the whole basin yields a balance between the net lateral pv inflow and the pv dissipation along the boundary when an isopycnal layer receives a net positive pv through inflow outflow the circulation becomes cyclonic so that friction can generate a flux of negative pv to satisfy the integral balance for simplicity a barotropic ocean model is used in this paper but its application to the 3d models will be discussed in the first set of experiments the model with a realistic arctic bathymetry is forced by observed inflows and outflows in this case there is a net positive pv inflow to the basin due to the fact that inflow layer is thinner than that of outflow the model produces a circulation field that is remarkably similar to the one from observations in the second experiment the model bathymetry at fram strait is modified so that the same inflows and outflows of water masses lead to a net negative pv flux into the arctic the circulation is reversed and becomes nearly the opposite of the first experiment in the third experime nt the net pv flux is made to be zero by modifying again the sill depth at fram strait the circulation becomes two gyres a cyclonic one in the eurasian basin and an anticyclonic one in the canada basin to elucidate the control of the pv integral a second set of model experiments is conducted by using an idealized arctic bathymetry so that the pv dynamics can be better explained without the complication of rough topography the results from five additional experiments that used the idealized topography will be discussed while the model used in this study is one layer the same pv integral constraint can be applied to any isopycnal layer in a threedimensional model variables that affect the pv fluxes to this density layer at any inflow outflow channel such as layer thickness and water volume flux can affect the circulation pattern the relevance to 3d models is discussed in this paper

scaling wind stirring effects in an oceanic bulk mixed layer model with application to an ogcm of the tropical pacific the mixed layer depth mld plays an important role in the climate system through its influences on sea surface temperature sst the kraus turner niiler hereafter referred to as ktn bulk mixed layer ml model is designed for describing the mld and has been adopted widely by many ocean modeling however large biases exist in the mld simulation using the original ktn model in the tropical pacific this is partly due to the uncertainties in representing wind stirring effect in the model which is scaled by a parameter m 0 traditionally m 0 is taken as a constant uniformly in space in this study the m 0 is estimated as spatially and seasonally varying through its inverse calculation from a balance equation describing the turbulent kinetic energy tke budget of the ml it is illustrated that the m 0 is spatially varying over the tropical pacific the derived m 0 fields are then embedded into an ocean general circulation model ogcm compared with the observations and the global ocean data assimilation system godas analyses the mld simulations in the ogcm with varying m 0 are substantially improved in the tropical pacific ocean on seasonal and interannual time scales additionally the pacific subtropical cells stcs become intensified accompanied with the strengthening of upwelling in the eastern equatorial pacific thus more realistic simulations are obtained in spatially and seasonally varying m 0 case compared with the constant m 0 case as the related cooling effect from the upwelling is enhanced the simulated sst is slightly cooled down in the eastern equatorial pacific further applications and implications are also discussed

ages and geodynamic settings of xilamulun mo cu metallogenic belt in the northern part of the north china craton abstract the xilamulun belt along the northern part of the north china craton is located in eastern segment of the central asian orogenic belt and has great economic potential for mo cu mineralization more than ten medium to large ore deposits have been discovered in this region in the recent years the major types of mineralization type include porphyry chehugou mo cu kulitou mo cu xiaodonggou mo and jiguanshan mo quartz vein nianzigou mo xinjing mo epithermal hongshanzi mo u and alteration assemblage liulingou mo the timing of mineralization was previously thought to be yanshanian 208 290 ma however indosinian 260 208 ma ages for intrusions and mineralization have been recognized in recent years based on geochronologic data and regional geological evidence it is suggested that the mineralization in the xilamulun belt was formed during multiple events the mineralization processes are related to a post collisional extension stage 258 210 ma with the generation of the porphyry molybdenum copper deposit a tectonic stress transformation from ns to ew 185 150 ma that gave rise to vein or porphyry molybdenum deposit and a lithospheric thinning stage 140 110 ma with porphyry molybdenum deposit

on the boundary conditions applied to the sea ice coupled model 1 the formulation of suitable boundary conditions at the water ice interface during ice formation melting is an important aspect of the sea ice coupled model the transfer of water and salt through the water ice can be posed as different boundary conditions behavior of the model under these boundary conditions is illustrated through simple analytical models and a numerical model based on pressure coordinate it is emphasized that the correct handling of the boundary conditions associated with sea ice formation requires an accurate treatment of the equivalent pressure on the top of water column and the total volume mass of the water column in the ice formation regime improper treatment of these boundary conditions may lead to an artificial loop current near the edge of ice in numerical simulations of oceanic circulation in the arctic ocean or near the antarctica

end permian to mid triassic termination of the accretionary processes of the southern altaids implications for the geodynamic evolution phanerozoic continental growth and metallogeny of central asia the altaids is one of the largest accretionary orogenic collages in the world with the highest rate of phanerozoic continental growth and significant metallogenic importance it is widely accepted that subduction related orogenesis of the altaids started in the late precambrian and gradually migrated southward present coordinates however it is uncertain when and how the building of the altaids was finally completed based on structural geology geochemical geochronological and paleomagnetic data this paper presents late paleozoic to early mesozoic accretionary tectonics of two key areas north xinjiang in the west and inner mongolia in the east together with neighboring mongolia the late paleozoic tectonics of north xinjiang and adjacent areas were characterized by continuous southward accretion along the wide southern active margin of siberia and its final amalgamation with the passive margin of tarim which may have lasted to the end permian to early mid triassic in contrast in inner mongolia and adjacent areas two wide accretionary wedges developed along the southern active margin of siberia and the northern active margin of the north china craton which may have lasted to the mid triassic the final products of the long lived accretionary processes in the southern altaids include late paleozoic to permian arcs late paleozoic to mid triassic accretionary wedges composed of radiolarian cherts pillow lavas and ophiolitic fragments and high pressure ultrahigh pressure metamorphic rocks permian alaskan type zoned mafic ultramafic complexes intruded along some major faults of the tien shan we define a new tarim suture zone immediately north of the tarim craton that is probably now buried below the tien shan as a result of northward subduction of the tarim block in the cenozoic the docking of the tarim and north china cratons against the southern active margin of siberia in the end permian to mid triassic resulted in the final closure of the paleoasian ocean and terminated the accretionary orogenesis of the southern altaids in this part of central asia this complex geodynamic evolution led to formation of giant metal deposits in central asia and to substantial continental growth

uncertainty of the 20th century sea level rise due to vertical land motion errors assessing the vertical land motion vlm at tide gauges tg is crucial to understanding global and regional mean sea level changes slc over the last century however estimating vlm with accuracy better than a few tenths of a millimeter per year is not a trivial undertaking and many factors including the reference frame uncertainty must be considered using a novel reconstruction approach and updated geodetic vlm corrections we found the terrestrial reference frame and the estimated vlm uncertainty may contribute to the global slc rate error by 0 2 mmyr 1 in addition a spurious global slc acceleration may be introduced up to 4 8 x 10 3 mmyr 2 regional slc rate and acceleration errors may be inflated by a factor 3 compared to the global the difference of vlm from two independent glacio isostatic adjustment models introduces global slc rate and acceleration biases at the level of 0 1 mmyr 1and 2 8 x 10 3 mmyr 2 increasing up to 0 5 mm yr 1 and 9 x 10 3 mmyr 2 for the regional slc errors in vlm corrections need to be budgeted when considering past and future slc scenarios

spatial and temporal antarctic ice sheet mass trends glacio isostatic adjustment and surface processes from a joint inversion of satellite altimeter gravity and gps data we present spatiotemporal mass balance trends for the antarctic ice sheet from a statistical inversion of satellite altimetry gravimetry and elastic corrected gps data for the period 2003 2013 our method simultaneously determines annual trends in ice dynamics surface mass balance anomalies and a time invariant solution for glacio isostatic adjustment while remaining largely independent of forward models we establish that over the period 2003 2013 antarctica has been losing mass at a rate of 84 22 gt yr 1 with a sustained negative mean trend of dynamic imbalance of 111 13 gt yr 1 west antarctica is the largest contributor with 112 10 gt yr 1 mainly triggered by high thinning rates of glaciers draining into the amundsen sea embayment the antarctic peninsula has experienced a dramatic increase in mass loss in the last decade with a mean rate of 28 7 gt yr 1 and significantly higher values for the most recent years following the destabilization of the southern antarctic peninsula around 2010 the total mass loss is partly compensated by a significant mass gain of 56 18 gt yr 1 in east antarctica due to a positive trend of surface mass balance anomalies

preface to special section on arctic ocean model intercomparison project aomip studies and results more than 130years ago theaustrian arctic explorer carl weyprecht weyprecht and ihne 1913 who discov ered franz josef land an archipelago north of russia andwho advanced a successful scheme for international coop eration in polar science the international polar year con cept postulated that a number of fundamental problems ofmeteorology and geophysics could be solved near theearth spoles thishypothesisisstillvalidinthe21stcenturybecause the arctic is recognized as a region where globalclimate change signals are amplified the model basedconclusion of manabe and stouffer 1994 that the firstsigns of climate change could be detected in the arctic hasbeen corroborated by numerous other model results e g holland and bitz 2003 symon et al 2005 on the otherhand it has been demonstrated that model conclusions maybe highly uncertain and that model estimates of futureclimate change differ significantly from model to model in order to reduce these uncertainties it is important tovalidate and to improve models the latter is the first majorgoal of the arctic ocean model intercomparison project aomip the second major aomip goal is to investigatevariability of the arctic ocean and sea ice at seasonal todecadal timescales and identify mechanisms responsible forthe observed changes some of the latest aomip activitiesassociated with these project goals arereflected inthe papersof this special section

growth history of hydrothermal black smoker chimneys hollow mineral spires known as black smoker chimneys precipitate around 350 c jets of hydrothermal fluid spouting from the sea floor on the east pacific rise epr at 21 n refs 1 2 i describe and discuss here the formation of mineral zoning across the walls of these structures throughout two major growth phases a sulphate dominated stage and a sulphide replacement stage during the sulphide replacement stage at least four distinct sulphide mineral zonation sequences develop across chimney walls from interior to exterior the apparently successive formation of these sulphide zonation sequences is attributed to evolution of radial thermal and chemical gradients accompanying the gradual thickening and sealing of black smoker chimney walls

the goldsbrough stommel circulation of the world oceans abstract goldsbrough first showed how the mass flux at the ocean surface due to the difference between evaporation and precipitation could induce barotropic flow in the ocean interior through the requirement of vorticity conservation stommel proposed to close this circulation by adding the western boundary currents here a first otder description of the goldsbrough stommel circulation for the world oceans is presented using available climatologies while such flows are an order of magnitude smaller than the wind driven circulation the interaction between the goldsbrough stommel gyres and the wind driven and thermally driven circulation determines the salinity distribution of the world oceans therefore it is important to study the goldsbrough stommel circulation and its interaction with motions driven by other forcings in addition the western boundary currents required to close the goldsbrough interior and to satisfy interbasin mass transport can be substantial in the atlantic the southward wester

vertical land motion from present day deglaciation in the wider arctic vertical land motion vlm from past and ongoing glacial changes can amplify or mitigate ongoing relative sea level change we present a high resolution vlm model for the wider arctic that include

assessing the precision in loading estimates by geodetic techniques in southern europe summary this paper investigates the precision of the estimation of geophysical fluid load deformation computed from grace space gravity gps vertical displacement and geophysical fluids models global circulation models gcms for ocean atmosphere and hydrology using the three cornered hat method this method allows the estimation of the variance of the errors of each technique when the same quantity is monitored by three instruments with independent errors appliedonanetworkofstations severalpointsofviewcanbeconsidered thetechnique level inordertodeterminetheerrorofeachtechnique grace gpsandgcms thesolution level allowingtocomparetheprecisionofthesametechniquewhendifferentstrategies models are used and the station level in order to emphasize local anomalies and geographical patterns in particular our results show a precision of the loading vertical displacement at the level of 1 mm when using grace or the fluid models and of 2 mm using gps we do not find significant differences between the precision of different solutions of the same techniques even when there are strong differences in the data processing

atmospheric effects and spurious signals in gps analyses improvements in the analyses of global positioning system gps obser vations yield resolvable mm to sub mm di erences in coordinate estimates thus provid ing su cient resolution to distinguish subtle di erences in analysis methodologies here we investigate the e ects on site coordinates of using di erent approaches to modelling atmospheric loading deformation atml and handling of tropospheric delays the rig orous approach of using the time varying vmf1 mapping function yields solutions with lower noise at a range of frequencies compared with solutions generated using empiri cal mapping functions this is particularly evident when atml is accounted for some improvement also arises from using improved a priori zenith hydrostatic delays zhd with the combined e ect being site speci c importantly inadequacies in both mapping functions and a priori zhds not only introduce time correlated noise but signi cant pe riodic terms at solar annual and semi annual periods we nd no signi cant di erence between solutions where non tidal atml is applied at the observation level rather than as a daily averaged value but failing to model diurnal and semi diurnal tidal atml at the observation level can introduce anomalous propagated signals with periods that closely match the gps draconitic annual 351 4 d and semi annual period 175 7 d ex acerbated by not xing ambiguities these signals are evident in both stacked and sin gle site power spectra with each tide contributing roughly equally to the dominant semi annual peak the amplitude of the propagated signal reaches a maximum of 0 8 mm with a clear latitudinal dependence that is not correlated directly with locations of maximum tidal amplitude this is the first evidence of aliased signals being produced from tidal atml deformations

sulphur isotopic fractionation between sulphate and sulphide in hydrothermal ore deposits disequilibrium vs equilibrium processes correlative fractionation relationships of sulphur isotope data for coexisting sulphate and sulphide pairs from hydrothermal ore deposits on 38s versus 34s diagrams are deciphered theoretically taking into account dissolved h2s and so42 in hydrothermal fluids during precipitation of both sulphate and sulphide minerals a 4 species closed system is suggested for describing the conservation of mass among all sulphur bearing species on the diagrams the covariation in the 34s values of both sulphate and sulphide is ascribed to isotopic exchange between oxidized and reduced sulphur species during mineral precipitation the isotopic exchange could be a thermodynamic process due to simple cooling of high temperature fluids which results in an equilibrium fractionation or a kinetic process due to mixing of two sulphur reservoirs which leads to a disequilibrium fractionation the 34s value of total sulphur in a hydrothermal system could change due to the precipitation of minerals or due to the escape of h2s and or so42 sulphur isotope data for anhydrite and pyrite pairs from the luohe porphyrite iron deposit in the yangtze river valley is used to illustrate the mixing responsible for the disequilibrium fractionation

geology re os ages sulfur and lead isotopes of the diyanqinamu porphyry mo deposit inner mongolia ne china the diyanqinamu porphyry mo deposit in the southern greater khingan range of the central asian orogenic belt contains 800 million metric tons mt of ore with an average grade of 0 097 molybdenum the deposit is hosted in late jurassic volcanic rocks of tuff andesite and volcanic breccia multiple stage hydrothermal activities have resulted in propylitic phyllic and argillic alteration in this deposit five stages i v of hydrothermal activity are identified stage i is represented by a mineral assemblage of epidote chlorite and magnetite with some discontinuous barren veinlets of quartz k feldspar fluorite magnetite epidote chlorite stage ii is marked by occurrence of quartz fluorite molybdenite magnetite pyrite sericite siderite veinlets veins with phyllic halos stage iii consists of fluorite siderite quartz molybdenite pyrite ankerite calcite chalcopyrite veins that are commonly related to phyllic alteration and dissemination of fluorite in the altered rocks stage iv has an assemblage of fluorite quartz pyrite ankerite calcite molybdenite chalcopyrite sphalerite galena in coarse veins 10 20 mm wide stage v consists of narrow 5 mm wide veinlets of calcite fluorite pyrite quartz molybdenite mainly occurs in stages ii and iii re os dating results for molybdenite samples from these two stages yielded an isochron age of 156 2 4 2 ma 2 mswd 0 96 n 10 most molybdenite samples have high 34s values 8 4 relative to other sulfide minerals i e galena sphalerite pyrite and chalcopyrite of stages ii to v 34s 2 5 8 3 n 22 molybdenite also has low 207pb 204pb and 208pb 204pb ratios relative to other sulfide minerals although there are minor overlaps in a diagram of 206pb 204pb versus 207pb 204pb these pb isotope data display a positive trend transecting the growth curves of crustal lead which could be invoked by mixing of crustal and mantle sources with distinct pb isotopes in combination with the s isotope data and mineral paragenesis we suggest that magmas were the main source of molybdenum whereas other metals i e pb zn and cu were possibly sourced from the country rocks

copper isotopic zonation in the northparkes porphyry cu au deposit se australia abstract significant systematic cu isotopic variations have been found in the northparkes porphyry cu au deposit nsw australia which is an orthomagmatic porphyry cu deposit copper isotope ratios have been measured in sulfide minerals chalcopyrite and bornite by both solution and laser ablation multi collector inductively coupled plasma mass spectrometry mc icp ms the results from both methods show a variation in 65cu of hypogene sulfide minerals of greater than 1 relative to nist976 significantly the results from four drill holes through two separate ore bodies show strikingly similar patterns of cu isotope variation the patterns are characterized by a sharp down hole decrease from up to 0 8 0 29 0 56 1 n 20 in the low grade peripheral alteration zones phyllic propylitic alteration zone to a low of 0 4 0 25 0 36 1 n 30 at the margins of the most mineralized zones cu grade 1 wt in the high grade cores of the systems the compositions are more consistent at around 0 2 0 19 0 14 1 n 40 the cu isotopic zonation may be explained by isotope fractionation of cu between vapor solution and sulfides at high temperature during boiling and sulfide precipitation processes sulfur isotopes also show an isotopically light shell at the margins of the high grade ore zones but these are displaced from the low 65cu shells such that there is no correlation between the cu and s isotope signatures fe isotope data do not show any discernable variation along the drill core this work demonstrates that cu isotopes show a large response to high temperature porphyry mineralizing processes and that they may act as a vector to buried mineralization

stable isotope studies of sulfates and sulfides in the mineral park porphyry cu mo system arizona sulfide minerals from five vein stages in and near mineral park have a shared delta 34 s range of 0 to 5 per mil 47 values anhydrites from anhydrite molybdenite and anhydrite chalcopyrite vein stages have nearly identical delta 34 s ranges of 12 6 to 22 7 per mil no spatial isotopic zonation is evident in the anhydrite molybdenite vein stage a delta 34 s versus delta 34 s plot for anhydrite pyrite pairs suggests an h 2 s dominated fluid and a bulk fluid delta 34 s value near 1 per mil but general isotopic disequilibrium is suspected in the anhydrite chalcopyrite vein stage mineral relationships indicate a sulfate dominated hydrothermal fluid isotopic temperatures from anhydrite pyrite pairs of this stage generally match fluid inclusion data in veins from felsic hosts but are more dispersed in veins from mafic hosts this may reflect local isotopic disequilibrium resulting from reduction of sulfate by ferrous silicates in the mafic hosts use of the delta 34 s versus delta 34 s plot which indicated different values for the sulfate sulfide ratio and bulk fluid delta 34 s for mafic and felsic hosted data subsets is thus compromised the fluid that deposited late polymetallic quartz veins appears to have been h 2 s dominated with a bulk fluid delta 34 s value of 2 to 4 per mil the isotopic data are not sufficient to discriminate among potential sources for the hydrothermal sulfur oxygen isotope data on anhydrites indicate that two distinct generations were deposited the data are compatible with a mixed magmatic meteoric origin for waters calculated delta 18 o water range 6 5 9 2ppm that deposited anhydrite molybdenite veins and with either a magmatic or an evaporitic origin for the waters calculated delta 18 o water range 11 8 17 1ppm that deposited anhydrite chalcopyrite veins magmatic sources for the fluids that deposited anhydrite are the most compatible with geologic and fluid inclusion data

geochronology and isotopic geochemistry of the a type granites from the huanggang sn fe deposit southern great hinggan range ne china implication for their origin and tectonic setting abstract the huanggang sn fe deposit inner mongolia is located in southern great hinggan range metallogenic belt la icp ms zircon u pb dating show that the k feldspar granite and granite porphyry in the huanggang mine were formed at 136 7 1 1 ma and 136 8 0 57 ma respectively sr nd pb isotope of the rocks and in situ zircon hf isotopic systematics show that 87 sr 86 sr i values range from 0 70211 to 0 70729 close to the 87 sr 86 sr i of oceanic basalts and lower than those of continental crust the e nd t values and nd model ages t dm vary from 0 8 to 0 9 and 855 to 993 ma respectively the pb isotopic compositions are also variable with 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of 18 974 26 107 15 554 15 914 and 38 894 39 890 respectively suggesting that the lead is derived from a mixed source the 176 hf 177 hf values range from 0 282744 to 0 282922 with corresponding e hf t values ranging from 1 9 to 18 3 and two stage hf model ages t dm2 of between 561 and 888 ma the isotope composition shows that huanggang granites were derived from partial melting of juvenile lower crust that originated from depleted mantle perhaps contaminated by small amounts of ancient continental crust younger nd hf isotope model ages imply that an important crustal growth event took place in this area during the neoproterozoic integrating our data with previously published results and the late mesozoic regional tectonic setting we conclude that the huanggang granites were generated in an intraplate tectonic magmatic setting asthenospheric mantle upwelling due to lithospheric delamination and magma underplating caused the partial melting of a mantle wedge metasomatized by the fluids released from subducted oceanic crust or by decompression of depleted mantle this resulted in remelting differentiation and a continued evolution of the mafic juvenile crust producing a large quantity of granitic magma the tectonic setting for these processes may be linked to the nnw subduction of the pacific plate izanagi in the mesozoic which affected most of eastern china

the sea level budget along the northwest atlantic coast gia mass changes and large scale ocean dynamics sea level rise and decadal variability along the northwestern coast of the north atlantic ocean are studied in a self consistent framework that takes into account the effects of solid earth deformation and geoid changes due to large scale mass redistribution processes observations of sea and land level changes from tide gauges and gps are compared to the cumulative effect of gia present day mass redistribution and ocean dynamics over a 50 year period 1965 2014 gia explains the majority of the observed sea level and land motion trends as well as almost all interstation variability present day mass redistribution resulting from ice melt and land hydrology causes both land uplift and sea level rise in the region we find a strong correlation between decadal steric variability in the subpolar gyre and coastal sea level which is likely caused by variability in the labrador sea that is propagated southward the steric signal explains the majority of the observed decadal sea level variability and shows an upward trend and a significant acceleration which are also found along the coast the sum of all contributors explains the observed trends in both sea level rise and vertical land motion in the region as well as the decadal variability the sum of contributors also explains the observed acceleration within confidence intervals the sea level acceleration coincides with an accelerating density decrease at high latitudes

lower satellite gravimetry estimates of antarctic sea level contribution a new model of glacial isostatic adjustment used in conjunction with grace satellite data suggests that ice loss from antarctica is contributing 0 19 millimetres per year to global mean sea level which is substantially less than previous grace based estimates estimates for recent mass loss from antarctica vary widely making it difficult to calculate any subsequent contributions to sea level rise one prominent approach uses the grace gravity recovery and climate experiment satellites to detect changes in gravity but the final estimates are dependent on the modelled response of the continent to changes in ice loading over time and to changes in lithospheric elastic rebound matt king and colleagues apply a new model of this glacial isostatic adjustment to the grace data and estimate antarctic mass loss between 2002 and 2010 to be about 69 gigatonnes per year much lower than previous estimates and equivalent to an annual sea level rise of about 0 2 millimetres recent estimates of antarctica s present day rate of ice mass contribution to changes in sea level range from 31 gigatonnes a year gt yr 1 ref 1 to 246 gt yr 1 ref 2 a range that cannot be reconciled within formal errors3 time varying rates of mass loss2 4 5 6 contribute to this but substantial technique specific systematic errors also exist3 in particular estimates of secular ice mass change derived from gravity recovery and climate experiment grace satellite data are dominated by significant uncertainty in the accuracy of models of mass change due to glacial isostatic adjustment7 8 gia here we adopt a new model of gia developed from geological constraints which produces gia rates systematically lower than those of previous models and an improved fit to independent uplift data9 after applying the model to 99 months from august 2002 to december 2010 of grace data we estimate a continent wide ice mass change of 69 18 gt yr 1 0 19 0 05 mm yr 1 sea level equivalent this is about a third to a half of the most recently published grace estimates2 5 which cover a similar time period but are based on older gia models plausible gia model uncertainties and errors relating to removing longitudinal grace artefacts destriping confine our estimate to the range 126 gt yr 1 to 29 gt yr 1 0 08 0 35 mm yr 1 sea level equivalent we resolve 26 independent drainage basins and find that antarctic mass loss and its acceleration is concentrated in basins along the amundsen sea coast outside this region we find that west antarctica is nearly in balance and that east antarctica is gaining substantial mass

common mode error in antarctic gps coordinate time series on its effect on bedrock uplift estimates spatially correlated common mode error cme always exists in regional or larger global positioning system gps networks we applied independent component analysis ica to gps vertical coordinate time series in antarctica from 2010 to 2014 and made a comparison with the principal component analysis pca using pca ica the time series can be decomposed into a set of temporal components and their spatial responses we assume the components with common spatial responses are cme an average reduction of 40 per cent about the root mean square rms values was achieved in both pca and ica filtering however the common mode components obtained from the two approaches have different spatial and temporal features ica time series present interesting correlations with modelled atmospheric and non tidal ocean loading displacements a white noise plus power law pl noise model was adopted in the gps velocity estimation using maximum likelihood estimation analysis with 55 per cent reduction of the velocity uncertainties after filtering using ica meanwhile spatiotemporal filtering reduces the amplitude of pl and periodic terms in the gps time series finally we compare the gps uplift velocities after correction for elastic effects with recent models of glacial isostatic adjustment gia the agreements of the gps observed velocities and four gia models are generally improved after the spatiotemporal filtering with a mean reduction of 0 9 mm yr 1 of the weighted rms values possibly allowing for more confident separation of various gia model predictions

sulfur isotopes and pyrite anhydrite equilibria in a volcanic basin hydrothermal system of the middle to lower yangtze river valley anhydrite pyrite mineral pairs from a paleohydrothermal system of the volcanic area of the middle to lower yangtze river valley have been quantitatively interpreted within the constraints of sulfur isotope and thermochemical data on relevant mineral assemblages the delta 34 s values of pyrite in this deposit range from 11 to 9 per mil and those of anhydrite from 14 to 20 per mil the fractionation between coexisting pyrite and anhydrite delta 34 s anhydrite pyrite ranges from 9 to 25 per mil if sulfur isotopes equilibrated between pyrite and anhydrite then these fractionations imply mineralization temperatures of 550 degrees to 310 degrees c these temperatures are roughly 100 degrees c higher than fluid inclusion homogenization temperatures for the same anhydrites suggesting probable sulfur isotope disequilibrium between coexisting pyrite and anhydrite the chemistry of the ore forming fluid is constrained by thermodynamic data and observed mineralization for example early stage ph ranged from 6 4 to 5 0 sigma m s was roughly 0 02 and m sub ca super 2 0 17 whereas late stage values of the same variables were 6 0 to 3 0 0 02 to 0 01 and 0 17 to 0 1 respectively the sulfur isotope composition of the ore forming fluid remained relatively constant with delta 34 s 15 5 to 16 0 per mil from early to late stage deposition the heavy sulfur isotope signature of the ore fluid was presumably acquired by interaction of isotopically lighter more magmatic fluids with basal sediments including anhydrite the delta 34 s values of pyrite decrease from roughly 10 per mil in the early ore stages to roughly 10 per mil in the late stages this is attributed primarily to increasing oxygen fugacity and decreasing temperature throughout ore deposition at the same time the delta 34 s values of coexisting anhydrites increase from roughly 15 to 20 per mil apparently in response to continuing fractionation of heavier sulfur into later stage sulfates which would also decrease the delta 34 s value of coprecipitated sulfides

mineralogic and stable isotope zonation at the surface over the el salvador porphyry copper deposit chile we examined in detail the mineralogic and stable isotope characteristics of alteration minerals exposed at the surface of the el salvador porphyry copper deposit a total of 276 samples was collected from 203 localities over an area of 5 km 2 at elevations between 2 900 and 3 300 m the alteration assemblages can be separated into two groups broadly corresponding to the stages previously identified from underground studies although the early stage k silicate alteration identified underground is not evident at the surface a transitional to late stage is characterized at the surface by assemblages of 1 muscovite andalusite with trace diaspore including some areas rich in andalusite and 2 muscovite with trace diaspore there is a sharp contact outward with a marginal propylitic assemblage chlorite calcite epidote pyrophyllite occurs as a retrograde overprint of muscovite in both of the transitional to late stage assemblages these assemblages are concentrically zoned and centered on a core of least altered granodiorite porphyry a late intramineral intrusion the muscovite andalusite assemblage occurs up to 500 m away from the granodiorite porphyry and andalusite rich zones are located near the brecciated margin of the porphyry further outward is the muscovite zone from 500 to 1 500 m wide the pyrophyllite overprint overlaps the contact of the muscovite andalusite and muscovite zones and occurs mainly above 3 000 m elevation such that its present distribution is controlled largely by topography very late alteration minerals occur in radial pebble dikes of hydrothermal breccia and their extensions and they are dominated by an advanced argillic assemblage of alunite aluminum phosphate sulfate minerals diaspore zunyite pyrophyllite dickite with residual muscovite in one case a breccia extends upward and appears to be the root of a 300 500 m outcrop 80 m thick of massive quartz alunite replacement of rhyolite pure mineral separates were prepared from these samples for o h and s isotope analysis including 48 samples of silicate minerals muscovite pyrophyllite dickite and supergene kaolinite and 20 samples of alunite some supergene in origin information on mineral assemblage was used to estimate temperatures of formation which then allowed calculation of the isotopic composition of associated hydrothermal fluids the fluid responsible for forming the muscovite had a relatively narrow range of isotopic composition 6 5 1 5 per mil 18 o and 40 10 per mil d the heaviest 18 o and d values about 8 and 35 per mil respectively were obtained from the samples with andalusite muscovite diaspore assemblage this composition is close to that expected for a magmatic fluid with 10 to 20 percent meteoric water component responsible for forming the other muscovite samples the fluid compositions calculated for the very late stage alunite range from 5 and 30 per mil to 1 and 40 per mil 18 o and d respectively this range in composition agrees with the trend predicted for magmatic vapor absorbed by local groundwater the latter similar in composition to that responsible for forming the supergene kaolinite there is no systematic spatial zonation of the alunite samples in terms of isotopic composition or paleotemperature the temperature estimates from s isotope geothermometry are higher than those based on mineral assemblage possibly caused by partial supergene replacement of some hypogene alunites there is no strong isotopic zonation of hydrothermal minerals from surface alteration assemblages at el salvador that can be applied to generate clear exploration guidelines by contrast mapping of alteration mineralogy in the field backed up by laboratory checking of mineralogy and examination of relict minerals and replacement textures in thin section clearly indicates the center of the late intramineral intrusion

a new global gps data set for testing and improving modelled gia uplift rates glacial isostatic adjustment gia is the response of the solid earth to past ice loading primarily since the last glacial maximum about 20 k yr bp modelling gia is challenging because of large uncertainties in ice loading history and also the viscosity of the upper and lower mantle gps data contain the signature of gia in their uplift rates but these also contain other sources of vertical land motion vlm such as tectonics human and natural influences on water storage that can mask the underlying gia signal in this study we use about 4000 gps vertical velocities as observational estimates of global gia uplift rates after correcting for major elastic deformation effects a novel fully automatic strategy is developed to postprocess the gps time series and to correct for non gia artefacts before estimating vertical velocities and uncertainties we detect outliers and jumps and correct for atmospheric mass loading displacements we correct the resulting velocities for the elastic response of the solid earth to global changes in ice sheets glaciers and ocean loading as well as for changes in the earth s rotational pole relative to the 20th century average we then apply a spatial median filter to remove sites where local effects are dominant to leave approximately 4000 gps sites the resulting novel global gps data set shows a clean gia signal at all post processed stations and is therefore suitable to investigate the behavior of global gia forward models the results are transformed from a frame with its origin in the centre of mass of the total earth s system cm into a frame with its origin in the centre of mass of the solid earth ce before comparison with 13 global gia forward model solutions with best fits with pur 6 vm5 and ice 6g predictions the largest discrepancies for all models were identified for antarctica and greenland which may be due to either uncertain mantle rheology ice loading history magnitude and or gps errors

displacements of the earth s surface due to atmospheric loading effects on gravity and baseline measurements atmospheric mass loads and deforms the earth s crust by performing a convolution sum between daily global barometric pressure data and mass loading green s functions we estimate the time dependent effects of atmospheric loading including those associated with short term synoptic storms on surface point positioning measurements and surface gravity observations we calculate the response for both an oceanless earth and an earth with an inverted barometer ocean load responses for near coastal stations are significantly affected by the inclusion of an inverted barometer ocean peak to peak vertical displacements are frequently 15 20 mm with accompanying gravity perturbations of 3 6 gal baseline changes can be as large as 20 mm or more the perturbations are largest at higher latitudes and during winter months these amplitudes are consistent with the results of rabbel and zschau 1985 who modeled synoptic pressure disturbances as gaussian functions of radius around a central point deformation can be adequately computed using real pressure data from points within about 1000 km of the station knowledge of local pressure alone is not sufficient rabbel and zschau s hypothesized corrections for these displacements which use local pressure and the regionally averaged pressure prove accurate at points well inland but are in general inadequate within a few hundred kilometers of the coast

tourmaline boron and strontium isotope systematics reveal magmatic fluid pulses and external fluid influx in a giant iron oxide apatite ioa deposit abstract tourmaline is a common boron bearing mineral in hydrothermal system and has been widely used as a mineral probe to reconstruct geological processes because of its broad range in composition and resistance to metasomatic alteration the origin of kiruna type iron oxide apatite ioa deposits commonly linked to andesitic subvolcanic or volcanic rocks is highly controversial constraints on the evolution of these mineralizing systems are needed to advance understanding of the ore forming process in this study we apply in situ elemental and combined b sr isotopic analyses of tourmaline to elucidate the nature and evolution of the subsurface hydrothermal system associated with ioa mineralization in the giant taocun deposit eastern china taocun is hosted at the top of a diorite intrusion and exhibits three stages of hydrothermal alteration that contain tourmaline pre ore na alteration tur i syn ore magnetite formation and associated ca fe alteration tur ii and post ore ca mg alteration with sulfide veins tur iii compositional data for each stage of tourmaline plot along the oxy dravite povondraite join which is indicative of precipitation from relatively oxidizing fluids ranges of sr isotopic compositions in tur i 0 7065 0 7078 and tur ii 0 7068 0 7076 are identical to those of the igneous host rocks indicating precipitation from magmatic hydrothermal fluids the range of b isotopic compositions in tur i 11b values of 6 3 to 1 2 is also consistent with a magmatic source higher 11b values 2 4 to 5 4 obtained from tur ii are mainly ascribed to rayleigh fractionation in the magmatic hydrothermal system as tourmaline precipitated post ore tur iii has a wide range of mostly lower b isotopic compositions 8 5 to 0 8 that record another pulse of magmatic fluid input this interpretation is supported by the enrichment of na li be w sn v and ti in tur iii relative to tur i and ii however the higher sr isotope composition 0 7076 0 7086 of tur iii and available o isotope composition 7 to 3 5 of fluids of this stage record the infiltration of meteoric ground water from adjacent sedimentary country rocks the results suggest that the taocun ioa deposit formed in a magmatic hydrothermal system characterized by two or more pulses of magmatic fluid discharge from subvolcanic diorite intrusions followed by the influx of external ground water as the system waned this study highlights the utility of tourmaline as a robust geochemical and isotopic monitor of ore forming processes in such systems

hydrological deformation induced by the west african monsoon comparison of gps grace and loading models three dimensional ground deformation measured with permanent gps stations in west africa was used for investigating the hydrological loading deformation associated with monsoon precipitation the gps data were processed within a global network for the 2003 2008 period weekly station positions were retrieved with a repeatability including unmodeled loading effects of 1 2 mm in the horizontal components and between 2 5 and 6 mm in the vertical component the annual signal in the vertical component for sites located between 9 6n and 16 7n is in the range 10 15 mm it is consistent at the 3 mm level with the annual regional scale loading deformations estimated from grace satellite products and modeled with a combination of hydrological atmospheric and nontidal oceanic models an additional 6 month transient signal was detected in the vertical component of gps estimates at most of the west african sites it takes the form of an oscillation occurring between september and march and reaching a maximum amplitude of 12 16 mm at ouagadougou 12 5n the analysis of in situ hydro geological data revealed a strong coincidence between this transient signal and peak river discharge at three sites located along the niger river timbuktu gao and niamey at ouagadougou a similar coincidence was found with the seasonal variations of the water table depth we propose a mechanism to account for this signal that involves a sequence of swelling shrinking of clays combined with local loading effects associated with flooding of the niger river

reduced ice mass loss and three dimensional viscoelastic deformation in northern antarctic peninsula inferred from gps we consider the viscoelastic rheology of the solid earth under the antarctic peninsula due to ice mass loss that commenced after the breakup of the larsen b ice shelf we extend the previous analysis of nearby continuous gps time series to include five additional years and the additional consideration of the horizontal components of deformation they show strong uplift from 2002 to 2011 followed by reduced uplift rates to 2018 modelling the gps derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper mantle viscosities of 0 3 3 1018 pa s in this region but allows a wide range of elastic lithosphere thickness the observed and modelled north coordinate component shows little nonlinear variation due to the location of ice mass change to the east of the gps sites however comparison of the observed and modelled east coordinate component constrains the upper mantle viscosity to be less than 9 1018 pa s consistent with the viscosity range suggested by the uplift rates alone and providing important largely independent confirmation of that result our horizontal analysis showed only marginal sensitivity to modelled lithospheric thickness the results for the horizontal components are sensitive to the adopted plate rotation model with the estimate based on itrf2014 suggesting that the sum of residual plate motion and pre 2002 glacial isostatic adjustment is likely less than 0 5 mm yr 1 in the east component

contents and sulphur isotope composition of trace sulphate and sulphide in various rock types abstract the in vacuo kiba extraction technique for trace sulphate and sulphide has been extended to a variety of rocks including some altered granites provided by the canadian nuclear fuel waste management programme although the technique requires considerable development it shows promise for determining the redox conditions temperature and the sulphur isotope composition of dissolved species in fluids involved in initial mineralization and subsequent alteration processes this may in turn be used to identify sources of sulphur in fluids and provide information about long term weathering of resistant rocks preliminary concentration and sulphur isotope data for altered granite samples from the underground research laboratory whiteshell manitoba suggest that sulphur of other than igneous origin is minor or absent

study of the atmospheric pressure loading signal in very long baseline interferometry observations 1 redistribution of air masses due to atmospheric circulation causes loading deformation of the earth s crust which can be as large as 20 mm for the vertical component and 3 mm for horizontal components rigorous computation of site displacements caused by pressure loading requires knowledge of the surface pressure field over the entire earth surface a procedure for computing three dimensional displacements of geodetic sites of interest using a 6 hourly pressure field from the national centers for environmental prediction numerical weather models and the ponte and ray 2002 model of atmospheric tides is presented we investigated possible error sources and found that the errors of our pressure loading time series are below the 15 level we validated our model by estimating the admittance factors of the pressure loading time series using a data set of 3 5 million very long baseline interferometry observations from 1980 to 2002 the admittance factors averaged over all sites are 0 95 0 02 for the vertical displacement and 1 00 0 07 for the horizontal displacements for the first time horizontal displacements caused by atmospheric pressure loading have been detected the closeness of these admittance factors to unity allows us to conclude that on average our model quantitatively agrees with the observations within the error budget of the model at the same time we found that the model is not accurate for several stations that are near a coast or in mountain regions we conclude that our model is suitable for routine data reduction of space geodesy observations

chronology geochemistry and sr nd isotope studies of jurassic intrusions in the diyanqinamu porphyry mo mine central inner mongolia china abstract available cores of porphyritic granite and aplitic granite from the diyanqinamu porphyry mo deposit in the north central great xing an range presented an opportunity to examine and analyze mesozoic igneous rocks far from the paleo pacific subduction zone the diyanqinamu granites are highly fractionated i type distinguished from the m a or s type granite by high sio 2 and rb low zr nb y and ce low fe 2 o 3 total mgo and k 2 o na 2 o cao ratios low alumina saturation index sr ratios 0 70137 0 70451 positive e nd t values 2 37 3 77 and negative correlation between p 2 o 5 and sio 2 the aplitic granites were generated by fractional crystallization of the porphyritic granite as evidenced by spatial proximity consistent zircon u pb ages 156 ma within error correlations between other oxides and sio 2 in haker diagrams low ba sr nb p ti eu linear relationship in both la yb n vs la and sr vs ba diagrams and decreasing lree and ree with increasing sio 2 the diyanqinamu granites have young depleted mantle two stage model ages avg t dm2 660 ma similar to those of most mesozoic voluminous felsic magmas in northeastern china and were likely sourced from pre existent crustal components both old and juvenile that had been juxtaposed during the tectonic evolution of the paleo asian ocean these granites project in the transitional field from syn collision to post collision tectonic settings on tectonic discrimination diagrams implying emplacement in an extensional environment extensional volcanism and basin formation in the great xing an range region in late jurassic is coeval with the diyanqinamu granites demonstrating that post orogenic lithospheric extension related to the closure of the mongol okhotsk ocean was the main driving force for late jurassic magmatism in this region

separating climate induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements we estimate the signature of the climate induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the gravity recovery and climate experiment grace mission we show results at the globe scale and compare them with repeated absolute gravity ag time behavior in three zones where ag surveys have been published northwestern europe canada and tibet for 10 yearly campaigns the uncertainties affecting the determination of a linear gravity rate of change range 3 4 nm s 2 a in most cases in the absence of instrumental artifacts the results are consistent with what is observed for long term repeated campaigns we also discuss the possible artifact that can result from using short ag survey to determine the tectonic effects in a zone of high hydrological variability we call into question the tectonic interpretation of several gravity changes reported from stations in tibet in particular the variation observed prior to the 2015 gorkha earthquake

nonlinear subsidence at fremantle a long recording tide gauge in the southern hemisphere a combination of independent evidence continuous gps repeat geodetic leveling groundwater abstraction satellite altimetry and tide gauge tg records shows that the long recording fremantle tg has been subsiding in a nonlinear way since the mid 1970s due to time variable groundwater abstraction the vertical land motion vlm rates vary from approximately 2 to 4 mm yr i e subsidence thus producing a small apparent acceleration in mean sea level computed from the fremantle tg records we exemplify that gps derived vlm must be geodetically connected to the tg to eliminate the commonly used assumption that there is no differential vlm when the gps is not colocated with the tg in the perth basin we show that groundwater abstraction can be used as a diagnostic tool for identifying nonlinear vlm that is not evident in gps time series alone

a time varying 3 d displacement model of the 5 9 year westward motion and its applications for the global navigation satellite system positions and velocities

annual variations in gps measured vertical displacements near upernavik isstrom greenland and contributions from surface mass loading in response to present day ice mass loss on and near the greenland ice sheet steady crustal uplifts have been observed from the network of global positioning system gps stations mounted on bedrock in addition to the secular uplift trends the gps time series also show prominent annual variability here we examine the annual changes of the vertical displacements measured at two gps stations srmp and upvk near upernavik isstrom in western greenland we model elastic loading displacements due to various surface mass loading including three non ice components atmospheric pressure ocean bottom pressure continental water storage and one ice component i e surface mass balance smb we find that the contribution from atmospheric pressure changes can explain 46 and 78 of the annual amplitude observed in the gps verticals at srmp and upvk respectively we also show that removing the predicted loading displacements due to smb adversely increases the annual variance of the gps residuals however using the gps data alone we cannot identify the exact cause s of this discrepancy because the annual loading displacements are sensitive to the smb changes from over 85 of the ice sheet area alternatively by differencing vertical displacements between the two stations we find a good agreement between the modeled differential smb loading displacements and the gps residuals after removing non ice components our study highlights the necessity of correcting for non ice loading contributions in the gps measurements of crustal deformation to infer ice mass changes in greenland at annual periods

gravitational potential energy balance for the thermal circulation in a model ocean abstract the gravitational potential energy balance of the thermal circulation in a simple rectangular model basin is diagnosed from numerical experiments based on a mass conserving oceanic general circulation model the vertical mixing coefficient is assumed to be a given constant the model ocean is heated cooled from the upper surface or bottom and the equation of state is linear or nonlinear although the circulation patterns obtained from these cases look rather similar the energetics of the circulation may be very different for cases of differential heating from the bottom with a nonlinear equation of state the circulation is driven by mechanical energy generated by heating from the bottom on the other hand circulation for three other cases is driven by external mechanical energy which is implicitly provided by tidal dissipation and wind stress the major balance of gravitational energy in this model ocean is between the source of energy due to vertical mixing and the conversion from kinetic

length scales of eddy generation and nonlinear evolution of the seasonally modulated south pacific subtropical countercurrent the dynamical processes behind the seasonal modulation of the two dimensional eddy kinetic energy eke wavenumber spectrum in the subtropical countercurrent region of the south pacific are investigated with 14 yr of satellite altimeter data and climatological hydrographic data the authors find a seasonally modulated generation of eke via baroclinic instability in modes with larger meridional length scales subsequent nonlinear eddy eddy interactions redistribute the eke to larger total horizontal length scales and larger zonal scales in particular this is confirmed by diagnosing the spectral transfer of eke in the surface geostrophic flow which is found to drive an anisotropic inverse cascade being redirected in the sense consistent with the effect as predicted by geostrophic turbulence theory on the plane because of the seasonal renewal of meridionally elongated anomalies by baroclinic instability and possibly because of the barotropization process however the net outcome for the formation of surface zonal flows is observed to be limited

geodetic secular velocity errors due to interannual surface loading deformation geodetic vertical velocities derived from data as short as 3 yr are often assumed to be representative of linear deformation over past decades to millennia we use two decades of surface loading deformation predictions due to variations of atmospheric oceanic and continental water mass to assess the effect on secular velocities estimated from short time series the interannual deformation is time correlated at most locations over the globe with the level of correlation depending mostly on the chosen continental water model using the most conservative loading model and 5 yr long time series we found median vertical velocity errors of 0 5 mm yr 1 over the continents 0 3 mm yr 1 globally exceeding 1 mm yr 1 in regions around the southern tropic horizontal velocity errors were seven times smaller unless an accurate loading model is available a decade of continuous data is required in these regions to mitigate the impact of the interannual loading deformation on secular velocities

present day vertical land motion of australia from gps observations and geophysical models the secular rate of australia s vertical surface deformation due to past ice ocean loading changes is not consistent with present vertical velocities observed by a previously sparse network of global positioning system gps sites current understanding of the earth s rheology suggests that the expected vertical motion of the crust should be close to zero given that australia is located in the far field of past ice sheet loading recent gps measurements suggest that the vertical motion of the australian continent at permanent sites is between 0 and 2 mm year here we investigate if vertical deformation due to previous ice sheet loading can be recovered in the time series of australian gps sites through enlarging the number of sites compared to previous studies from 20 to more than 100 and through the application of improved data filtering we apply forward geophysical models of elastic surface displacement induced by atmospheric hydrologic nontidal ocean and ice loading and use independent component analysis as a spatiotemporal filter that includes multivariate regression to consider temporally correlated noise in gps using this approach the common mode error is identified and subsequent multivariate regression leads to an average reduction in trend uncertainty of 35 the average vertical subsidence of the australian continent is substantially different to vertical motion predicted by glacial isostatic adjustment and surface mass transport models

decadal geodetic variations in ny alesund svalbard role of past and present ice mass changes the geodetic rates for the gravity variation and vertical uplift in polar regions subject to past and present day ice mass changes pdimcs provide important insight into the rheological structure of the earth we provide an update of the rates observed at ny alesund svalbard to do so we extract and remove the significant seasonal content from the observations the rate of gravity variations derived from absolute and relative gravity measurements is 1 39 0 11 gal yr 1 the rate of vertical displacements is estimated using gps and tide gauge measurements we obtain 7 94 0 21 and 8 29 1 60 mm yr 1 respectively we compare the extracted signal with that predicted by gldas noah and era interim hydrology models we find that the seasonal gravity variations are well represented by local hydrology changes contained in the era interim model the phase of seasonal vertical displacements are due to non local continental hydrology and non tidal ocean loading however a large part of the amplitude of the seasonal vertical displacements remains unexplained the geodetic rates are used to investigate the asthenosphere viscosity and lithosphere asthenosphere thicknesses we first correct the updated geodetic rates for those induced by pdimcs in svalbard using published results and the sea level change due to the melting of the major ice reservoirs we show that the latter are at the level of the geodetic rate uncertainties and are responsible for rates of gravity variations and vertical displacements of 0 29 0 03 gal yr 1 and 1 11 0 10 mm yr 1 respectively to account for the late pleistocene deglaciation we use the global ice evolution model ice 3g the little ice age lia deglaciation in svalbard is modelled using a disc load model with a simple linear temporal evolution the geodetic rates at ny alesund induced by the past deglaciations depend on the viscosity structure of the earth we find that viscous relaxation time due to the lia deglaciation in svalbard is more than 60 times shorter than that due to the pleistocene deglaciation we also find that the response to past and pdimcs of an earth model with asthenosphere viscosities ranging between 1 0 and 5 5 10 18 pa s and lithosphere resp asthenosphere thicknesses ranging between 50 and 100 km resp 120 and 170 km can explain the rates derived from geodetic observations

is land subsidence increasing the exposure to sea level rise in alexandria egypt delta margins are subject to relatively high rates of land subsidence and have the potential to significantly exacerbate future changes in sea levels predicted by global warming models used in impact studies through a combined analysis of gps and persistent scatterer interferometry data we determine that most of the coastline of alexandria has been subject to moderate land subsidence over the past decade 0 4 mm yr on average and up to 2 mm yr locally this contrasts to previous studies that suggested subsidence in excess of 3 mm yr based on our findings we infer that on multi century to millennia timescales land subsidence in the area of alexandria is dominated by tectonic setting and earthquakes or gravitational collapse episodes of a growth fault whereas on shorter interseismic decadal to century timescales subsidence rates are likely steady and moderate in agreement with natural compaction and dewatering of the observed holocene sediment layer

a decade of horizontal deformation from great earthquakes 1 the 21st century has seen the occurrence of 17 great earthquakes mw 8 including some of the largest earthquakes ever recorded numerical modeling of the earthquakes shows that nearly half of the earth s surface has undergone horizontal coseismic deformation 1 mm with the 2004 sumatra andaman earthquake dominating the global deformation field this has important implications for both the realization of a terrestrial reference frame and in the interpretation of regional tectonic studies based on gps velocities we show that far field coseismic deformations from great earthquakes will if unaccounted for introduce errors in estimates of linear site velocities of at least 0 1 0 3 mm yr across most of the surface of the earth the accumulated global deformation field shows that two regions australia and the north atlantic arctic ocean have been largely undeformed by these great earthquakes with accumulated deformations generally 0 5 mm using gps estimates of surface deformation we show that the majority of the australian continent is deforming at 0 2 mm yr the northern part of new zealand is rotating clockwise relative to the australian plate with relative horizontal velocities of 2 mm yr while the southeastern coast of australia is undergoing post seismic relaxation caused by the 2004 mw 8 1 macquarie ridge earthquake the presence of ongoing post seismic relaxation thousands of kilometers from plate margins violates the secular linear assumption made in current terrestrial reference frame definitions these effects have significant ramifications for regional tectonic interpretations and global studies such as sea level rise that require reference frame accuracy greater than this level

the role of evaporites in the formation of magnetite apatite deposits along the middle and lower yangtze river china evidence from la icp ms analysis of fluid inclusions abstract numerous magnetite apatite deposits occur in the ningwu and luzong sedimentary basins along the middle and lower yangtze river china these deposits are located in the contact zone of gabbro dioritic porphyries with surrounding volcanic or sedimentary rocks and are characterized by massive vein and disseminated magnetite apatite anhydrite mineralization associated with voluminous sodic calcic alteration petrologic and microthermometric studies on multiphase inclusions in pre to syn mineralization pyroxene and garnet from the deposits at meishan ningwu basin luohe and nihe both in luzong basin demonstrate that they represent extremely saline brines 90 wt nacl equiv that were trapped at temperatures of about 780 c laser ablation icp ms analyses and raman spectroscopic studies on the natural fluid inclusions and synthetic fluid inclusions manufactured at similar p t conditions reveal that the brines are composed mainly of na 13 24 wt k 7 11 wt ca 7 wt fe 2 wt cl 19 47 wt and variable amounts of so 4 3 39 wt their cl br na k and na b ratios are markedly different from those of seawater evaporation brines and lie between those of magmatic fluids and sedimentary halite suggesting a significant contribution from halite bearing evaporites high s b and ca na ratios in the fluid inclusions and heavy sulfur isotopic signatures of syn to post mineralization anhydrite 34 s anh 15 2 to 16 9 and pyrite 34 s py 4 6 to 12 1 further suggest a significant contribution from sedimentary anhydrite these interpretations are in line with the presence of evaporite sequences in the lower parts of the sedimentary basins the combined evidence thus suggests that the magnetite apatite deposits along the middle and lower yangtze river formed by fluids that exsolved from magmas that assimilated substantial amounts of triassic evaporites during their ascent due to their fe oxide dominated mineralogy their association with large scale sodic calcic alteration and their spatial and temporal associations with subvolcanic intrusions we interpret them as a special type of iocg deposits that is characterized by unusually high contents of na ca cl and so 4 in the ore forming fluids evaporite assimilation apparently led to the production of large amounts of high salinity brine and thus to an enhanced capacity to extract iron from the gabbro dioritic intrusions and to concentrate it in the form of ore bodies hence we believe that evaporite bearing sedimentary basins are more prospective for magnetite apatite deposits than evaporite free basins

ongoing deformation of antarctica following recent great earthquakes antarctica s secular motion is thought to be almost everywhere governed by horizontal rigid plate rotation plus three dimensional deformations due to past and present changes in ice ocean loading known as glacial isostatic adjustment gia we use geodetic data to investigate deformation following the 1998 m 8 2 antarctic intraplate earthquake and show sustained three dimensional deformation along east antarctica s coastline 600 km from the rupture location using a model of viscoelastic deformation we are able to match observed northward velocity changes and either east or height but not all three directions simultaneously apparently partly due to lateral variations in mantle rheology our modeling predicts that much of antarctica may still be deforming with further deformation possible from the 2004 m 8 macquarie ridge earthquake this previously unconsidered mode of antarctic deformation affects geodetic estimates of plate motion and gia its viscous nature raises the prospect of further present day deformation due to earlier great earthquakes

decoding the origins of vertical land motions observed today at coasts in recent decades geodetic techniques have allowed detecting vertical land motions and sea level changes of a few millimetres per year based on measurements taken at the coast tide gauges on board of satellite platforms satellite altimetry or both global navigation satellite system here contemporary vertical land motions are analysed from january 1993 to july 2013 at 849 globally distributed coastal sites the vertical displacement of the coastal platform due to surface mass changes is modelled using elastic and viscoelastic green s functions special attention is paid to the effects of glacial isostatic adjustment induced by past and present day ice melting various rheological and loading parameters are explored to provide a set of scenarios that could explain the coastal observations of vertical land motions globally in well instrumented regions predicted vertical land motions explain more than 80 per cent of the variance observed at scales larger than a few hundred kilometres residual vertical land motions show a strong local variability especially in the vicinity of plate boundaries due to the earthquake cycle significant residual signals are also observed at scales of a few hundred kilometres over nine well instrumented regions forming observation windows on unmodelled geophysical processes this study highlights the potential of our multitechnique database to detect geodynamical processes driven by anthropogenic influence surface mass changes surface loading and glacial isostatic adjustment and tectonic activity including the earthquake cycle sediment and volcanic loading as well as regional tectonic constraints future improvements should be aimed at densifying the instrumental network and at investigating more thoroughly the uncertainties associated with glacial isostatic adjustment models

the anatomy of a pyroclastic density current the 10 july 2015 event at volcan de colima mexico pyroclastic density currents pdcs represent one of the most dangerous phenomena occurring in explosive volcanic eruptions and any advance in the physical understanding of their transport and sedimentation processes can contribute to improving their hazard assessment the 10 11 july 2015 eruption at volcan de colima provided a unique opportunity to better understand the internal behaviour of pdcs based on seismic monitoring data on 10 july 2015 the summit dome collapsed producing concentrated pdcs that filled the main channel of the montegrande ravine a lahar monitoring station installed 6 km from the volcano summit recorded a pdc before being completely destroyed real time data acquisition from a camcorder and a geophone that were part of the station along with field observations and grain size data of the pyroclastic deposits are used here to interpret the internal flow structure and time variant transport dynamics of low volume valley confined concentrated pdcs the pdc that reached the monitoring station moved at a velocity of 7 m s and filled a 12 m deep channel the outcrops show massive block and ash flow deposits with trains of coarse clasts in the middle and towards the top of the depositional units the seismic record gathered with the geophone was analysed for the time window when the flow travelled past the sensor the geophone record was also compared with the recordings of a broadband seismic station located nearby two main frequency ranges were recognised which could be correlated with the basal frictional forces exerted by the flow on the channel bed 10 20 hz and a collisional regime 20 40 hz interpreted to be associated with a clast segregation process i e kinematic squeezing this latter regime promoted the upward migration of large blocks which subsequently deviated towards the margin of the flow where they interacted with the sidewall of the main channel the energy calculated for both seismic components shows that the collisional regime represents 30 of the total energy including an important sidewall stress component these results gathered directly from a moving flow contribute to unravelling the internal behaviour of concentrated pdcs providing information on energy partitioning and particle particle interactions this confirms previous assumptions inferred from field observations and tested by analogue or numerical modelling the nature of the contact between grains is still poorly documented in natural pdcs and there is still much uncertainty and discussion about dominant forces in such currents data reported here may thus be useful to better constrain the physics of low volume valley confined concentrated pdcs and our findings need to be considered in theoretical models in parallel this study shows how geophones can provide a cheap alternative for pdc detection

regional biases in absolute sea level estimates from tide gauge data due to residual unmodeled vertical land movement the only vertical land movement signal routinely corrected for when estimating absolute sea level change from tide gauge data is that due to glacial isostatic adjustment gia we compare modeled gia uplift ice 5g vm2 with vertical land movement at 300 gps stations located near to a global set of tide gauges and find regionally coherent differences of commonly 0 5 2 mm yr reference frame differences and signal due to present day mass trends cannot reconcile these differences we examine sensitivity to the gia earth model by fitting to a subset of the gps velocities and find substantial regional sensitivity but no single earth model is able to reduce the disagreement in all regions we suggest errors in ice history and neglected lateral earth structure dominate model data differences and urge caution in the use of modeled gia uplift alone when interpreting regional and global scale absolute geocentric sea level from tide gauge data

geodynamic setting of gold deposits in eastern and central trans baikal chita region russia abstract it is proposed that there are three types of gold deposits in eastern and central transbaikalia trans baikal province namely i high sulphide intrusion related deposits with some signs of porphyry deposits ii low sulphide intrusion related deposits and iii low sulphide epithermal au ag deposits most of the gold deposits belong to the first two types and their ages are middle late jurassic deposits of the third type are not numerous and their age is early cretaceous the majority of the gold mineralization is spatially related to the two branches of the mongolia okhotsk suture along which siberia collided at the early middle jurassic boundary with the mongolia north china continent and the onon island arc terrane located between the two continents collision related thrusting folding and magmatism lasted until the latest jurassic when they gave way to post collisional rifting that continued until the end of early cretaceous according to their age relation to magmatism and tectonic framework the intrusion related deposits high and low sulphide were formed in a regional collisional setting extensional environments at that time existed only in local areas in the roofs of great magmatic chambers low sulphide epithermal deposits were formed during early cretaceous post collisional rifting

metallogenic province derived from mantle sources nd sr s and pb isotope evidence from the central asian orogenic belt abstract the central asian orogenic belt caob is one of the most important regions for cu au and polymetallic and rare metallic li be nb ta mineralization over the world most of the ore deposits in the caob are closely associated with granitoids available sr nd s and pb isotopic data indicate that the metallogenic epoch and sources of the mineral deposits in the caob are consistent with that of the regional granites available data suggest that mantle sources could have played an important role in the paleozoic to mesozoic mineralization in the caob

effect of annual signals on geodetic velocity 1 our analysis of global positioning system gps site coordinates in a global reference frame shows annual variation with typical amplitudes of 2 mm for horizontal and 4 mm for vertical with some sites at twice these amplitudes power spectrum analysis confirms that gps time series also contain significant power at annual harmonic frequencies with spectral indices 1 2 which indicates the presence of repeating signals van dam et al 2001 showed that a major annual component is induced by hydrological and atmospheric loading unless accounted for we show that annual signals can significantly bias estimation of site velocities intended for high accuracy purposes such as plate tectonics and reference frames for such applications annual and semiannual sinusoidal signals should be estimated simultaneously with site velocity and initial position we have developed a model to calculate the level of bias in published velocities that do not account for annual signals simultaneous estimation might not be necessary beyond 4 5 years as the velocity bias rapidly becomes negligible minimum velocity bias is theoretically predicted at integer plus half years as confirmed by tests with real data below 2 5 years the velocity bias can become unacceptably large and simultaneous estimation does not necessarily improve velocity estimates which rapidly become unstable due to correlated parameters we recommend that 2 5 years be adopted as a standard minimum data span for velocity solutions intended for tectonic interpretation or reference frame production and that we be skeptical of geophysical interpretations of velocities derived using shorter data spans

characteristics and genesis of gangdese porphyry copper deposits in the southern tibetan plateau preliminary geochemical and geochronological results porphyry type cu mo au deposits have been discovered along the gangdese magmatic arc in the southern tibetan plateau extensive field investigations and systematic studies of geochemistry s pb isotopic tracing together with re os and 40ar 39ar isotopic dating indicate that the mineralisation of the copper belt is genetically related to emplacement of late orogenic granitic porphyries during the post collisional crustal relaxation period of the late himalayan epoch these porphyries are petrochemically k enriched and belong to shoshonitic to high k calc alkaline series they display enrichment of large ion lithophile elements lile rb k u th sr pb and depletion of high field strength elements hfse nb ta ti and the heavy rare earth elements hree and y without eu anomalies these characteristics demonstrate that subduction played a dominant role in their petrogenesis and residual garnet was left in the magma sources pb isotope data show a linear correlation in the plumbotectonic framework diagram ranging from orogenic pb in the eastern segment of the copper belt to mantle pb in the western segment these constitute a mixing line of the indian oceanic morb with indian oceanic sediments and suggest that the porphyry magmas were dominantly derived from partial melting of subducted oceanic crusts mixed with a minor quantity of sediments and mantle wedge components the gangdese porphyry copper polymetallic belt has alteration characteristics and zonation typical of porphyry type copper deposits which include potassic alteration k feldspathisation and biotitisation silicification sericitisation and propylitisation mineralisation mainly occurs in strongly altered granitic cataclasite at the exo contact with veinlet disseminated textures the porphyries themselves are weakly mineralised with disseminated pyrite and chalcopyrite the copper deposits contain simple ore mineral associations consisting of chalcopyrite pyrite bornite molybdenite sphalerite and oxidised minerals of malachite covellite and molybdite during supergene oxidation primary ores underwent secondary enrichment to form economic orebodies with cu grade ranging from 1 to 5 ore sulphides of the copper belt display s and pb isotopic compositions identical to the ore bearing porphyries their 34s values vary between 3 8 and 2 4 and are typical of mantle sulphur the 206pb 204pb 207pb 204pb and 208pb 204pb ratios vary in the ranges 18 106 to 18 752 15 501 to 15 638 and 37 394 to 39 058 respectively and yielded radiogenetic lead enriched signatures twelve molybdenite samples from the copper belt yielded isochron ages of 14 76 0 22 ma and 13 99 0 16 ma for the nanmu and chongjiang deposits and model ages of 13 5 to 13 6 ma for the lakang e deposit meanwhile 40ar 39ar isotopic dating of two biotite phenocrysts from the chongjiang and lakang e deposits give plateau ages of 13 5 1 0 ma and 13 42 0 10 ma respectively during the geodynamic evolution of the gangdese collision orogenic belt intrusion of the ore bearing porphyries took place just before the rapid uplift and e w extension of the southern plateau and the ore forming process may have occurred simultaneously with the uplift and extension 14 0 1 ma

rapid ice unloading in the fleming glacier region southern antarctic peninsula and its effect on bedrock uplift rates rapid regional warming in the antarctic peninsula has led to the significant retreat and eventual collapse of several major ice shelves since the 1970s triggering the subsequent acceleration and thinning of their feeding glaciers the wordie ice shelf lying off the west coast of the antarctic peninsula has undergone long term disintegration since the 1960s with a substantial calving event occurring around 1989 followed by continuous steady retreat and its almost complete disappearance the dynamic response of the upstream glaciers to the ice shelf collapse and the response of the solid earth to the associated mass loss are not fully understood to quantify the mass loss from the system we generated a digital elevation model dem using airborne vertical and oblique imagery from 1966 and compared it to a dem derived from 2008 spot data this analysis reveals lowering over that time of approximately 60 m at the front of fleming glacier using icebridge and icesat 2 glas data spanning 2002 2014 we show an increased rate of mean ice surface lowering with rates post 2008 more than twice those of 2002 2008 we use these load change data as a basis for the simulation of viscoelastic solid earth deformation we subtract modeled elastic deformation rates and a suite of modeled viscous rates from gps derived three dimensional bedrock velocities at sites to the south of fleming glacier to infer properties of earth rheology assuming the pre breakup bedrock uplift was positive due to post last glacial maximum lgm ice retreat our viscoelastic corrected gps uplift rates suggest upper mantle viscosities are 2 1019pas and likely 1 1020pas in this region 1 2 orders of magnitude greater than previously found for the northern antarctic peninsula horizontal velocities at the gps site nearest the fleming glacier after the application of elastic and plate tectonic corrections point away from marguerite bay rather than the present glacier front this suggests that horizontal motion in the region reflects the earlier retreat of the glacier system following the lgm compatible with a relatively strong mantle in this region these findings highlight the need for improved understanding of ice load changes in this region through the late holocene in order to accurately model glacial isostatic adjustment

palladium platinum and gold distribution in porphyry cu mo deposits of russia and mongolia the porphyry cu mo deposits in the southern siberian craton and northern mongolia including subduction collision and rift related igneous series of early paleozoic to mesozoic age are all characterized by varying crustal contribution to their parent magmas and the presence of explosive breccias precious metal and associated element contents are reported for mineralized samples sulphide concentrates and chalcopyrite molybdenite flotation concentrates from porphyry cu mo intrusions of russia sora aksug and zhireken and mongolia erdenetiun obo average pge contents in rocks are 17 ppb pd and 22 ppb pt in the aksug deposit 13 ppb pd and 10 ppb detection limit pt in the sora 14 ppb pd and 21 ppb pt in the erdenetuin obo and 18 ppb pd and 28 ppb pt in the zhireken deposit average gold content in rocks is 61 ppb in the aksug deposit 17 ppb in the sora 21 ppb in the erdenetuin obo and 30 ppb in the zhireken deposit the highest average 2 3 ppm ag was recorded in the rocks of the sora deposit in general the precious metal distribution in the studied deposits has no apparent relationship with the alteration types the molybdenum content in rocks ranges between 1 and 128 ppm mo in the aksug deposit from 1 to 5400 ppm mo in the sora deposit from 2 to 755 ppm mo in the erdenetuin obo deposit and from 3 to 1530 ppm mo in the zhireken deposit the average copper content in rocks is 1540 ppm in the aksug deposit 460 ppm in the sora deposit 1460 ppm in the erdenetuin obo deposit and 220 ppm in the zhireken deposit the cu mo ratios are highest in the aksug and erdenetuin obo deposits and lowest in the sora and zhireken deposits the correlation matrix for selected major and trace element data on mineralized samples and sulphide concentrates 34 samples indicates that precious metals are associated with either chalcopyrite or molybdenite copper shows a strong positive correlation with au and pd r 0 91 while mo shows a strong positive correlation with pt r 0 98 in addition mo exhibits a strong positive correlation with w r 0 94 an interelement positive correlation between precious metals is 0 57 ag au the pd and pt contents of both chalcopyrite and molybdenite in flotation concentrates are low varying from 9 to 83 ppb pd and from 10 to 110 ppb pt the highest values recorded are 924 ppb pd in sulphide concentrates from the aksug deposit and 684 ppb pd and 299 ppb pt in sulphide concentrate from breccia of the zhireken deposit the highest gold content 5450 ppb au is in chalcopyrite flotation concentrate from the aksug deposit whereas in the majority of concentrates the gold content is in the order of a few hundreds parts per billion the relatively low contents and limited variation of the precious metal contents in the individual deposits of russia and mongolia point to the essential role of the composition of the source and composition of parent magmas

origin of spatial variation in us east coast sea level trends during 1900 2017 identifying the causes of historical trends in relative sea level the height of the sea surface relative to earth s crust is a prerequisite for predicting future changes rates of change along the eastern coast of the usa the us east coast during the past century were spatially variable and relative sea level rose faster along the mid atlantic bight than along the south atlantic bight and the gulf of maine past studies suggest that earth s ongoing response to the last deglaciation1 5 surface redistribution of ice and water5 9 and changes in ocean circulation9 13 contributed considerably to this large scale spatial pattern here we analyse instrumental data14 15 and proxy reconstructions4 12 using probabilistic methods16 18 to show that vertical motions of earth s crust exerted the dominant control on regional spatial differences in relative sea level trends along the us east coast during 1900 2017 explaining most of the large scale spatial variance rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near north carolina maryland and virginia such structure indicates that earth s elastic lithosphere is thicker than has been assumed in other models19 22 we also find a substantial coastal gradient in relative sea level trends over this period that is unrelated to deglaciation and suggests contributions from twentieth century redistribution of ice and water our results indicate that the majority of large scale spatial variation in long term rates of relative sea level rise on the us east coast is due to geological processes that will persist at similar rates for centuries vertical motions of earth s crust had the greatest effect on regional spatial differences in relative sea level trends along the eastern coast of the usa during 1900 2017 explaining most of the large scale spatial variance in regional rates of sea level rise

rapid bedrock uplift in the antarctic peninsula explained by viscoelastic response to recent ice unloading abstract since 1995 several ice shelves in the northern antarctic peninsula have collapsed and triggered ice mass unloading invoking a solid earth response that has been recorded at continuous gps cgps stations a previous attempt to model the observation of rapid uplift following the 2002 breakup of larsen b ice shelf was limited by incomplete knowledge of the pattern of ice unloading and possibly the assumption of an elastic only mechanism we make use of a new high resolution dataset of ice elevation change that captures ice mass loss north of 66 s to first show that non linear uplift of the palmer cgps station since 2002 cannot be explained by elastic deformation alone we apply a viscoelastic model with linear maxwell rheology to predict uplift since 1995 and test the fit to the palmer cgps time series finding a well constrained upper mantle viscosity but less sensitivity to lithospheric thickness we further constrain the best fitting earth model by including six cgps stations deployed after 2009 the larissa network with vertical velocities in the range 1 7 to 14 9 mm yr this results in a best fitting earth model with lithospheric thickness of 100 140 km and upper mantle viscosity of 6 10 17 2 10 18 pa s much lower than previously suggested for this region combining the larissa time series with the palmer cgps time series offers a rare opportunity to study the time evolution of the low viscosity solid earth response to a well captured ice unloading event

nature origin and evolution of the granitoid hosted early proterozoic copper molybdenum mineralization at malanjkhand central india at malanjkhand central india lode type copper molybdenum mineralization occurs within calcalkaline tonalite granodiorite plutonic rocks of early proterozoic age the bulk of the mineralization occurs in sheeted quartz sulfide veins and k silicate alteration assemblages defined by alkali feldspar k feldspar albite dusty hematite in feldspar biotite muscovite are prominent within the ore zone and the adjacent host rock weak propylitic alteration defined by albite biotite epidote zoisite surrounds the k silicate alteration zone the mineralized zone is approximately 2 km in strike length has a maximum thickness of 200 m and dips 65 75 along which low grade mineralization has been traced up to a depth of about 1 km the ore reserve has been conservatively estimated to be 92 million tonnes with an average cu content of 1 30 supergene oxidation accompanied by limited copper enrichment is observed down to a depth of 100m or more from the surface primary ores consist essentially of chalcopyrite and pyrite with minor magnetite and molybdenite 34s values in pyrite and chalcopyrite 0 38 to 2 90 fall within the range characteristic of granitoid hosted copper deposits 18o values for vein quartz 6 99 to 8 80 suggest exclusive involvement of juvenile water annealed fabrics are common in the ore the sequence of events that led to the present state of hypogene mineralization is suggested to be as follows fracturing of the host rock emplacement of barren vein quartz pronounced wall rock alteration accompanied by disseminated mineralization and the ultimate stage of intense silicification accompanied by copper mineralization fragments of vein quartz and altered wall rocks and striae in the ore suggest post mineralization deformation the recrystallization fabric particularly in chalcopyrite and sphalerite is a product of dynamic recrystallization associated with the post mineralization shearing the petrology of the host rocks hydrothermal alteration assemblages ore mineral associations fluid inclusions and the sulfur and oxygen isotopes of ores are comparable to those in phanerozoic and reported precambrian porphyry copper systems and the malanjkhand deposit has important implications for both metallogenic models for and mineral exploration in precambrian terrains

estimating network effect in geocenter motion applications the network effect is the error associated with the sub sampling of the earth surface by space geodetic networks it is an obstacle towards the precise measurement of geocenter motion that is the relative motion between the center of mass of the earth system and the center of figure of the earth surface in a complementary paper we proposed a theoretical approach to estimate the magnitude of this effect from the displacement fields predicted by geophysical models here we evaluate the effectiveness of our estimate for two illustrative physical processes co seismic displacements inducing instantaneous changes in the helmert parameters and elastic deformation due to surface water movements causing secular drifts in those parameters for the first we consider simplified models of the 2004 sumatra andaman and the 2011 t hoku oki earthquakes and for the second we use the observations of the gravity recovery and climate experiment grace complemented by an ocean model in both case studies it is found that the magnitude of the network effect even for a large global network is often as large as the magnitude of the changes in the helmert parameters themselves however we also show that our proposed modification to the definition of the center of network frame to include weights proportional to the area of the earth surface that the stations represent can significantly reduce the network effect in most cases

sea surface elevation and bottom pressure anomalies due to thermohaline forcing part i isolated perturbations sea surface elevation and bottom pressure anomalies due to thermohaline forcing are examined through analytical and numerical models including boussinesq and non boussinesq models it is shown that boussinesq approximations can introduce noticeable errors depending on the spatial and temporal scales of the perturbations according to the theory of geostrophic adjustment when the initial perturbations have horizontal scales comparable to the barotropic radius of deformation the initial pressure perturbations will be basically retained through the adjustment on the other hand if the initial perturbations have horizontal scales much smaller than the barotropic radius of deformation the initial pressure perturbations will be largely lost precipitation has horizontal scales on the order of 10 100 km much smaller than the barotropic radius of deformation thus for timescales longer than days the contribution from individual precipitation events to the local free surface elevation and bottom pressure is small and is difficult to identify from satellite data on the other hand thermal forcing has horizontal scales comparable to the barotropic radius of deformation so its long term contribution to sea surface height anomaly is noticeable and is easily identified from satellite data because boussinesq models induce faulty sea surface height and bottom pressure signals the errors introduced by these models are noticeable for anomalies in large scale o 1000 km thermohaline forcing