sims zircon u pb geochronology and sr nd isotopes of ni cu bearing mafic ultramafic intrusions in eastern tianshan and beishan in correlation with flood basalts in tarim basin nw china constraints on a ca 280 ma mantle plume zircon sims u pb dating of the poshi hongshishan bijiashan and huangshan ni cu bearing and xiangshan ni cu ti fe bearing mafic ultramafic intrusions in the eastern tianshan and beishan rift yields a relatively restricted range of 278 6 ma to 284 0 ma the histogram of compiled age data of basalts in the tarim basin and mafic ultramafic intrusions in the eastern tianshan and beishan rift has a peak of 280 ma which probably represents the time of mantle plume activity the basalts have lower end t values in the range of 9 2 1 7 and mg of 2 wt indicating that they were generated directly from a peripheral zone of the mantle plume by low degree of melting the mafic ultramafic intrusions have higher end t of 1 3 11 2 and mg of 33 90 and lower tio2

air sea interactions over terra nova bay during winter simulation with a coupled atmosphere polynya model a preliminary simulation of the terra nova bay polynya has been performed with a coupled atmosphere polynya model the atmospheric model is a hydrostatic primitive equations model that has been validated previously by a simulation of the strong katabatic winds observed in that area the polynya model includes a representation of the free drift of frazil ice and simple sea ice dynamics and thermodynamics two and three dimensional experiments have been performed under polar night conditions two dimensional experiments show that an open warm water area influences significantly the atmospheric circulation in the antarctic coastal zone an additional ice breeze effect is simulated and is responsible for the strenghthening of the katabatic winds near the coast because of the important temperature difference between the continental air and the ice free ocean up to 40 c strong surface heat fluxes are simulated over the polynya finally a three dimensional experiment has been performed the integration domain includes terra nova bay the polynya observed in that region is well simulated it is found that heat losses from the polynya surface are stronger than previously thought but are probably constrained by the idealized representation of frazil ice which is assumed to be uniform in each grid box this stresses the need for having a better knowledge of frazil ice evolution in large polynyas

measurements of katabatic winds between dome c and dumont d urville dumont d urville on the antarctic coast is an area well known for the presence of strong katabatic winds since the austral summer 1979 80 a us french joint experiment has been investigating the katabatic wind in this region in early 1980 three automatic weather stations aws were installed along a trajectory from dome charlie to dumont d urville measurements from these stations include air pressure temperature wind speed and direction at ground level only to supplement these data with information regarding the vertical structure and the advective changes in the katabatic flow two airborne missions were undertaken in november 1980 along a route from dome charlie dome c to dumont d urville

spatial and temporal variability of surface mass balance near talos dome east antarctica 1 predictions concerning antarctica s contribution to sea level change have been hampered by poor knowledge of surface mass balance snow accumulation is the most direct climate indicator and has important implications for paleoclimatic reconstruction from ice cores snow accumulation measurements stake core snow radar taken along a 500 km transect crossing talos dome east antarctica have been used to assess accumulation signals and the representativeness of ice core records stake readings show that accumulation hiatuses can occur at sites with accumulation rates below 120 kg m 2 yr 1 differences between cores and stakes can lead to statistical misidentification of annual layers determined from seasonal signals at sites with accumulation rates below 200 kg m 2 yr 1 because of nondetection of higher and lower values achieving 10 accuracy in the reconstruction of snow accumulation from single cores requires high accumulation 750 kg m 2 yr 1 low accumulation sites are representative if cumulative rates computed over several years are used to reach the 750 kg m 2 yr 1 threshold temporal variability of accumulation over the last two centuries shows no significant increase in accumulation wind driven processes are a fundamental component of surface mass balance spatial variations in accumulation are well correlated with surface slope changes along the wind direction and may exceed 200 kg m 2 yr 1 within 1 km wind driven sublimation rates are less than 50 kg m 2 yr 1 in plateau areas and up to 260 kg m 2 yr 1 in slope areas and account for 20 75 of precipitation whereas depositional features are negligible in surface mass balance

the lower atmosphere of the polar regions alfred wegener initiated the study of the free polar atmosphere with more than 100 kite and tether balloon soundings to above 3000 m at danmarkshavn north greenland during 1906 09 from this beginning polar aerology advanced through a series of similar point studies to the first full upper air network during the igy 1957 8 while its replacement by satellite remote sensing is gradually taking shape the accumulated polar information has been thoroughly analyzed a series of comprehensive accounts is referenced the aspects singled out for this review are themes that would have been of special interest to wegener the surface energy balance and the polar inversion the katabatic winds and snow drift and the aerosols of the polar atmosphere

simulation of the last glacial cycle by a coupled sectorially averaged climate ice sheet model 1 the climate model this paper describes a sectorially averaged seasonal model developed for simulating the long term response of the climate system to the astronomical forcing the model domain covers the northern hemisphere the atmospheric dynamics is represented by an improved zonally averaged quasi geostrophic model it includes a new parameterization of the meridional transport of quasi geostrophic potential vorticity and a parameterization of the hadley sensible heat transport the atmosphere interacts with the other components of the climate system ocean sea ice and land surface covered or not by snow and ice through vertical fluxes of momentum heat and water vapor the model explicity incorporates detailed radiative transfer surface energy balances and snow and sea ice budgets the vertical profile of the upper ocean temperature is computed by an integral mixed layer model which takes into account meridional convergence of heat sea ice is represented by a thermodynamic model including leads and a new parameterization for lateral accretion this paper presents the model climate for present conditions and results of sensitivity experiments obtained by modifying some internal parameters or by deactivating certain parameterizations in the model simulation of the present climate shows that the model is able to reproduce the main characteristics of the general circulation and in particular the surface wind field the seasonal cycles of oceanic mixed layer sea ice and snow cover are also well reproduced sensitivity experiments show the importance of the meridional sensible heat transport by the hadley circulation in the tropics the seasonal cycle of the oceanic mixed layer depth and sea ice formation in latitude bands where the average water temperature is above the freezing point in a forthcoming paper this model will be coupled to an ice sheet model and applied to the simulation of the last glacial cycle in the northern hemisphere

u pb ages and hf o isotopes of zircons from late paleozoic mafic ultramafic units in the southern central asian orogenic belt tectonic implications and evidence for an early permian mantle plume abstract u pb age and hf o isotope data of zircons from the mafic ultramafic complexes and their related rhyolites and granites in the eastern tianshan and beishan regions were obtained by sims and la icpms the hf o isotopic composition and hf model age of the zircons are closely related to their tectonic setting and formation age the zircons from the mafic ultramafic complexes in the bogeda haerlike and jueluotage belts have higher ehf t 8 17 and lower 18o 4 6 whereas most of the zircons in the gabbros granites and rhyolite from the middle tianshan massif and beishan rift display lower ehf t 0 8 and higher 18o 5 8 the positive ehf t and relatively lower 18o values suggest that these mafic ultramafic complexes were derived from depleted mantle which was subjected to subduction related modification processes the hf isotopic composition of zircons in the granites has revealed that the growth of juvenile crust was also very significant in the southern margin of the central asian orogenic belt during the paleozoic the hf model ages of the analyzed zircons together with the regional geology suggest that the beishan area had a northward subduction possibly from ca 900 ma to ca 400 ma whereas the eastern tianshan had a south directed subduction most likely from ca 600 ma to ca 310 ma additionally zircons with ca 280 ma u pb ages display wider and more scattered ehf t and 18o variations than the relatively older and younger ones which further support the early permian mantle plume model

on the sea ice regime of the ross sea antarctica variations spatiotemporelles de la glace de mer determinees a partir de donnees microondes passives et meteorologiques hydrologiques

rossby number similarity in the atmospheric boundary layer over a slightly inclined terrain abstract the structure of the steady state flow homogeneous along an inclined flat underlying surface is studied on the basis or the atmospheric boundary layer equations the resistance laws of geostrophic drag and heat transfer are obtained the general form of the resistance law universal functions is found the slope influence is shown in the figures which were obtained by numerical solution of the resistance laws

subduction induced mantle heterogeneity beneath eastern tianshan and beishan insights from nd sr hf o isotopic mapping of late paleozoic mafic ultramafic complexes abstract extensive late paleozoic mafic ultramafic complexes in the eastern tianshan and beishan regions in the southern central asian orogenic belt caob represent an ideal opportunity to assess the characteristics of the mantle in this area whole rock nd sr and zircon hf o isotopic data from the mafic ultramafic complexes of the jueluotage belt middle tianshan massif and beishan rift were compiled for isotopic mapping end t and 87sr 86sr i values range from 5 5 to 9 5 and 0 702 to 0 706 respectively in the jueluotage belt and from 2 to 11 and 0 703 to 0 710 respectively in the middle tianshan and beishan zircon ehf t and 18o values are in the range of 6 0 17 0 and 4 14 8 00 respectively in the jueluotage belt 1 8 and 5 17 6 30 respectively in the middle tianshan and show large variations of 1 17 and 4 12 respectively in the beishan spatially the 87sr 86sr i ratios of mafic ultramafic complexes increase from the jueluotage belt and beishan to the middle tianshan while the end t values show an opposite trend and reflect a mixing character between depleted mantle and em ii reservoirs zircon ehf t and 18o values exhibit an apparent southward decreasing and increasing trends respectively from the jueluotage belt through middle tianshan to beishan rift their corresponding hf model ages increase continuously from north to south these observations demonstrate that the mantle sources beneath the eastern tianshan and beishan are compositionally heterogeneous which presumably result from significant and variable degrees of subduction related modification we therefore suggest that the late paleozoic subcontinental lithospheric mantle beneath the jueluotage belt was modified by slab derived melts and fluids during the subduction of the junggar ocean whereas the mantle beneath the beishan rift was influenced mainly by slab derived fluids during the subduction of the south tianshan ocean the unique similarities of the middle tianshan mafic ultramafic complexes reflect a two stage modification of their mantle source namely the sequential subduction of the early south tianshan ocean followed by subduction of the junggar ocean thus the subduction induced mantle heterogeneity beneath the caob is probably regional in scope

a numerical study of strong katabatic winds over antarctica abstract certain coastal sections of antarctica most notably adelie land and terra nova bay experience anomalously intense persistent katabatic winds the forcing of such katabatic outflow is believed to originate several hundred kilometers upslope in the interior of the continent where cold air drainage currents from a large area converge into a relatively narrow zone focused on the steeply sloping ice terrain near the coastline numerical simulations with a three dimensional hydrostatic model incorporating terrain features representative of adelie land reveal a significant topographical channeling of the surface airflow katabatic wind speeds as depicted by the model are greatly enhanced downslope of the convergence channel these results emphasize the importance of topography in the continental interior in shaping the character of coastal katabatic flow

an analysis of strong wind events simulated in a gcm near casey in the antarctic abstract strong wind events occurring near casey antarctica in a long july gcm simulation have been studied to determine the relative roles played by the synoptic situation and the katabatic flow in producing these episodes it has been found that the events are associated with strong katabatic and strong gradient flow operating together both components are found to increase threefold on average for these strong winds and although the geostrophic flow is the stronger it rarely produces strong winds without katabatic flow becoming stronger than it is in the mean the two wind components do not flow in the same direction indeed there is some cancellation between them since katabatic flow acts in a predominant downslope direction while the geostrophic wind acts across slope the stronger geostrophic flow is associated with higher than average pressures over the continent and the approach of a strong cyclonic system toward the mast and a blocking system downstream the anomalous synoptic patterns lea

observations of blowing snow at the south pole 1 observations of blowing snow from visual observers records as well as ground based infrared and lidar measurements at south pole station are analyzed to obtain the first climatology of blowing snow over the antarctic plateau occurrence frequencies of blowing snow wind direction and speed during blowing snow events typical snow layer heights as well as optical depths are determined blowing snow is recorded in roughly one third of the visual observations and occurs under a narrow range of wind directions blowing snow layers are usually less than 400 m in thickness but can exceed 1000 m during blowing snow conditions these near surface layers are apparent in lidar backscatter profiles these layers emit radiances similar to those from optically thin clouds frequently seen over the antarctic plateau because the near surface blowing snow layers are frequently present they are a factor in space borne laser altimetry and other satellite remote sensing

interaction of katabatic flow with local thermal effects in a coastal region of adelie land east antarctica katabatic flows largely dominate the climate of the adelie land coastal region a detailed climatological data analysis of dumont d urville has been conducted results of this study support the idea that katabatic flow can be locally enhanced by the diurnal cycle of solar insolation and the temperature contrast between the continent and the ocean the interaction between katabatic wind and local thermal effects is expressed in terms of scale analysis except for surface stress all terms in the momentum equation for a katabatic flow in a coastal region of antarctica can reach the same order of magnitude the local circulation then is the result of a relatively tenuous force balance which can be disrupted even by a weak perturbation of any term to estimate the effect of the temperature contrast between the ocean and the continent on the katabatic flow two numerical experiments have been conducted the simulations consider an ocean free of sea ice representative of the summer months and another winter case with the ocean covered by thick sea ice these simulations show that with the ocean free of sea ice the katabatic flows extend only a limited distance over the open ocean during the day due to the local thermal effects with the ocean covered by sea ice the katabatic winds are not constrained and extend a considerable distance offshore

influence of coupling on atmosphere sea ice and ocean regional models in the ross sea sector antarctica air sea ice ocean interactions in the ross sea sector form dense waters that feed the global thermohaline circulation in this paper we develop the new limited area ocean sea ice atmosphere coupled model tango to simulate the ross sea sector tango is built up by coupling the atmospheric limited area model mar to a regional configuration of the ocean sea ice model nemo a method is then developed to identify the mechanisms by which local coupling affects the simulations tango is shown to simulate realistic sea ice properties and atmospheric surface temperatures these skills are mostly related to the skills of the stand alone atmospheric and oceanic models used to build tango nonetheless air temperatures over ocean and winter sea ice thickness are found to be slightly improved in coupled simulations as compared to standard stand alone ones local atmosphere ocean feedbacks over the open ocean are found to significantly influence ocean temperature and salinity in a stand alone ocean configuration the dry and cold air produces an ocean cooling through sensible and latent heat loss in a coupled configuration the atmosphere is in turn moistened and warmed by the ocean sensible and latent heat loss is therefore reduced as compared to the stand alone simulations the atmosphere is found to be less sensitive to local feedbacks than the ocean effects of local feedbacks are increased in the coastal area because of the presence of sea ice it is suggested that slow heat conduction within sea ice could amplify the feedbacks these local feedbacks result in less sea ice production in polynyas in coupled mode with a subsequent reduction in deep water formation

non pegmatitic deposits of beryllium mineralogy geology phase equilibria and origin non pegmatitic occurrences of be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest they currently provide the majority of the world s be ore and emeralds and they contain the greatest resource of these commodities of the approximately 100 be minerals known see chapter 1 by grew appendix a most occur in hydrothermal deposits or non pegmatitic igneous rocks where their distribution varies systematically with the setting and origin table 1 fig 1 view this table table 1 beryllium minerals in non pegmatitic deposits formulas use and occurrence 1 figure 1 chemography of the principal solid phases in the beo al2o3 sio2 h2o f2o 1 bash system with the projected positions of helvite group and alkali be silicates also shown are generalized fields for some of the major types natural of occurrences cf table 1 fig 4 see text for discussion beryllium minerals are best known from geologic systems associated with felsic magmatism they also occur in a variety of settings that lack evident igneous associations environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition genetically related igneous rocks are felsic and share low calcium and high f contents but are diverse in composition setting and origin compositions range from strongly peraluminous to peralkaline and can be silica undersaturated beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes table 2 summarizes the types and significance of major groups of occurrences by their lithologic associations figure 2 shows the global distribution of some important examples and regional belts for most types at least one example has been described in some detail and can be used to help evaluate general patterns however

influence of the orographic roughness of glacier valleys across the transantarctic mountains in an atmospheric regional model glacier valleys across the transantarctic mountains are not properly taken into account in climate models because of their coarse resolution nonetheless glacier valleys control katabatic winds in this region and the latter are thought to affect the climate of the ross sea sector frsater formation to snow mass balance the purpose of this paper is to investigate the role of the production of turbulent kinetic energy by the subgrid scale orography in the transantarctic mountains using a 20 km atmospheric regional model a classical orographic roughness length parametrization is modified to produce either smooth or rough valleys a one year simulation shows that katabatic winds in the transantarctic mountains are strongly improved using smooth valleys rather than rough valleys pressure and temperature fields are affected by the representation of the orographic roughness specifically in the transantarctic mountains and over the ross ice shelf a smooth representation of escarpment regions shows better agreement with automatic weather station observations than a rough representation this work stresses the need to improve the representation of subgrid scale orography to simulate realistic katabatic flows this paper also provides a way of improving surface winds in an atmospheric model without increasing its resolution

development of a three dimensional meso γ primitive equation model katabatic winds simulation in the area of terra nova bay antarctica the spatial evolution of antarctic katabatic winds in the area of terra nova bay is examined using the three dimensional version of the universite catholique de louvain modele atmospherique regional ucl mar mesoscale primitive equation models the ability of the model to replicate classical linear mountain wave simulations is verified then three dimensional experiments are performed for the terrain configuration of terra nova ross sea coastal zone using different horizontal resolutions 5 10 and 20 km the model converges for resolutions lower than 10 km results are in qualitative agreement with available observations and previous modeling work strong katabatic winds are simulated with a jet over terra nova bay the model seems able to initiate the mesocyclonic activity in the ross sea due to the katabatic circulation

simulation of the mesocyclonic activity in the ross sea antarctica the mesocyclonic activity in the southwestern ross sea is examined with emphasis on its forcing by katabatic winds the three dimensional version of the meso gamma scale primitive equation model modele atmospherique regional is used in which a representation of cloud microphysical processes has been introduced idealized boundary conditions are prescribed in particular the ocean is assumed to be completely ice free or partially ice covered the former case corresponds to a fall situation that coincides with the climatological maximum of estimated precipitation at mcmurdo station on ross island due to the propagation of katabatic winds over the ocean boundary layer fronts form clouds are generated in the fronts a surface pressure trough also forms and extends northeastward from terra nova bay mesocyclones are simulated in the trough when the ocean is ice free strong sensible heat fluxes toward the atmosphere amplify the strength of the trough up to typically observed values tn this case snow precipitation is associated with the boundary layer fronts and occurs in particular over mcmurdo sound it is also found that latent heat release due to precipitation formation in the fronts does not significantly affect the deepening of the trough

chasma boreale mars topographic characterization from mars orbiter laser altimeter data and implications for mechanisms of formation 1 chasma boreale a large reentrant in the north polar cap of mars is distinct in scale detailed topography and orientation from the spiraling troughs that characterize the majority of the polar cap we use new high resolution mars orbiter laser altimeter mola data and mars orbiter camera moc and viking images of the chasma region to assess hypotheses of origin of chasma boreale these hypotheses include formation by glacial flow and ablation by eolian processes such as katabatic winds and sublimation by outflow of meltwater or by a combination of two or more of these processes we find that these new data support initial formation by outflow of meltwater with later modification by katabatic winds and sublimation on the basis of our analysis we suggest a possible scenario in which outflow has occurred in several stages the outflow appears to have begun near an enclosed depression at the head of the chasma meltwater migrated within and below the ice down the regional slope and eventually broke out to the surface removal of material by melting caused subsidence and erosion of the polar deposits forming the chasma which has subsequently undergone modification by eolian and sublimation processes the outflow deposited most of its sediment in the form of a lobe that stratigraphically overlies the polygonal plains mapped at the mouth of the chasma and scoured some of the circumpolar sediment mantle in the surrounding region the lowest portions of the north polar basin received the rest of the sediment as a deposit a few meters thick mola data also reveal evidence for similar events of smaller magnitude elsewhere on the margins of the polar cap

late paleozoic mafic ultramafic intrusions in southern central asian orogenic belt nw china insight into magmatic ni cu sulfide mineralization in orogenic setting abstract the mafic ultramafic intrusions hosting magmatic ni cu sulfide ore deposits usually present within the precambrian cratons and on their margin have been extensively studied whereas those occurring within the phanerozoic orogenic belts have received little attention the southern margin of the central asian orogenic belt is a region of late paleozoic mafic ultramafic intrusions emplaced during post orogenic stage in order to recognize the mineralization features this study compares barren or weakly mineralized mafic ultramafic intrusions in the beishan with those hosting ni cu sulfide ore deposit in the altay and eastern tianshan in petrology mineralogy and geochemistry aspects several mineralization features can be recognized with respects to petrology mineralogy and geochemistry from comprehensive comparisons among the mineralization indicators we highlight strong alteration accompanying sulfide emplacement post erosion exposure of magma conduit abundant primary hydrous minerals and potential transportation mechanism of ore forming elements other indicators are the presence of orthopyroxene and pyroxenite for potential sulfide formation through crystal fractionation restricted fo and ni ranges in olivines for sulfide segregation and some other special geochemical characteristics related to crustal contamination the variation in mineralization could be ascribed to different degrees of partial melting crustal assimilation and subduction related modification of a mantle source we suggest that the ni cu sulfide mineralization of mafic ultramafic intrusions within orogenic belts is remarkably different from that of cratonic and continental marginal settings in respects of petrogenesis and mineralizing mechanism magmatic conduit type ni cu sulfide ore deposit is a target for future prospecting and exploration for mafic ultramafic intrusions in the orogenic belts

the effect of blowing snow on katabatic winds in antarctica an acceleration of the katabatic winds during periods of blowing snow was observed in adelie land antarctica data collected by automatic weather stations a ws showed a change in the relationship between the katabatic term of the surface geostrophic wind katabatic force and the wind speed for periods of blowing snow when measurements of the katabatic force were plotted against cube of the wind speed the slope was steeper for wind speeds at less than a threshold speed for blowing snow the difference between these two slopes was partly explained by the effect of blowing snow entrained into the atmospheric boundary layer

the formation of goethite jarosite and alunite during the weathering of sulfide bearing felsic rocks quantities of goethite and jarosite produced by weathering correlate with abundance and composition of sulfide minerals originally in rocks to characterize processes forming these minerals chemical weathering of sulfide bearing rocks was simulated using differential equations which describe mass transfer between aqueous solutions and minerals helgeson 1968 goethite begins precipitating during reaction between meteoric water f sub o 2 10 super 06 atm and sulfides after dissolution of 6 7 x 10 super 9 g pyrite or 6 0 x 10 super 9 g chalcopyrite per 1 000 g h 2 o reaction of the oxygen dissolved in 1 000 g water that is initially saturated with the atmospheric abundance of oxygen consumes 0 0085 g pyrite or 0 013 g chalcopyrite goethite is the only reaction product the calculations predict that weathering produces jarosite or alunite after goethite when 0 04 moles of oxygen have been consumed per 1 000 g h 2 o and where rates of oxygen replenishment approximately equal or exceed consumption simultaneous reactions between k feldspar an aqueous solution and pyrite or chalcopyrite produce alunite and goethite if the irreversible molar flux of fe al is less than 0 5 reactions with fluxes of fe al between 0 5 and 1 0 produce alunite goethite and jarosite those with fe al fluxes greater than 1 0 generate only jarosite after goethite following saturation of the solution with jarosite the mass ratio goethite goethite jarosite decreases smoothly from 1 0 to 0 0 accompanying continuous dissolution of pyrite and chalcopyrite the interval of reaction progress over which goethite and jarosite coexist increases relative to pyrite and k feldspar reactions when weathering involves muscovite or chalcopyrite in simulations whose sulfides have been totally oxidized this ratio varies antithetically with the volume percent sulfide and or ratio of pyrite pyrite chalcopyrite initially present a prediction consistent with geologic observations

surface pressure change through loewe s phenomena and katabatic flow jumps study of two cases in adelie land antarctica abstract preliminary results from the 1985 iago interaction atmosphere glace ocean field programme in adelie land antarctica allow for a detailed description of several katabatic events especially of their vertical structure and time and space variations several loewe s phenomena where a sudden transition from shooting to tranquil flow takes place have been observed two of them have been well documented and are shown here for both cases as observed at a downstream station close to the coast the mean wind speed suddenly decreased from about 20 m s 1 to almost zero while a large pressure increase was recorded 5 7 hpa on 3 december 1985 and 2 1 hpa on 18 december 1985 this paper aims at explaining such large surface pressure changes as more usual approaches cannot for both cases it is found that the flow is stratified upwards with a surface well mixed cold air layer a very stable capping inversion layer an overlying unstable layer thickening from upstream to downstream and a stable transi

surface airflow over east antarctica abstract surface winds over the antarctic interior occur mainly due to the strong radiational cooling of the ice slopes as a consequence such winds exhibit a high degree of persistence with a predominant direction closely related to the terrain orientation using detailed contour maps of the interior ice topography and representative values of the mean wintertime strength of the temperature inversion it is possible to infer the terrain induced accelerations a simple diagnostic equation system is formulated from which a time averaged surface airflow pattern of east antarctica is generated the results appear consistent with observations the occurrence of localized anomalously strong katabatic winds is explained as a result of typographically forced patterns of cold air convergence depicted in the airflow analysis

the role of eolian processes in forming surface features of the martian polar layered deposits abstract the major topographic features of the martian polar layered deposits include the conspicuous spiral troughs subtle undulations broad reentrants chasma steep arcuate scarps and dune fields a prominent role for eolian processes in the formation of all of these features is proposed strong katabatic winds occur on the north polar cap producing widespread frost streaks these cold drainage winds are analogous to those on the terrestrial antarctic cap in the chasmae convergent katabatic winds create yardangs and erode arcuate scarps in the layered deposits that are also the source for local dune fields migrating outward from the polar cap the chasmae are postulated to originate by long term erosion by katabatic wind wind plays a role in formation of the troughs and scarps primarily through removal of dust freed from exposed layered deposits by ablation of ice on defrosted equator facing slopes the undulations are created by interaction between surface erosion or deposition of perennial ice and standing waves in the shallow katabatic windflow the south polar layered deposits exhibit topographic features similar to those at the north polar cap but erosion and depositional processes creating these features may be inactive during the current epoch because of the lack of an extensive perennial ice cover and associated katabatic wind

surface winds over the antarctic continent a review surface winds over antarctica often classified as katabatic are intimately related to the orientation and steepness of the underlying ice terrain such flows result primarily from the strong radiational cooling of the sloping ice surface which creates a downslope directed horizontal pressure gradient force it is possible to diagnose the time averaged near surface streamline patterns of cold air drainage currents using recently compiled detailed antarctic ice topography maps and appropriate estimates of the strength of the surface temperature inversion the resulting streamlines agree with available observations and illustrate the high degree of nonuniformity of gravity driven flows off the ice sheets in certain interior sections negatively buoyant air from a large catchment area drains through a restricted section of coastline such confluence zones represent regions of enhanced supplies of cold air and are shown to be related to anomalously strong katabatic winds implications for sea ice formation are discussed

petrological characteristics and copper nickel ore forming processes of early permian mafic ultramafic intrusion belts in east tianshan mafic ultramafic intrusions in east tianshan area are reclassified into seven belts which are distributed as clusters and belts with the intrusions in the same belt controlled by a regional structure in the light of petrography the ore bearing intrusions must have been formed by multiple intrusion or a single intrusion indicating a perfect magmtic evolution and fractionation with high mg and low alkaline ca al and ti the ore bearing lithofacies show high mg value and high m f and m s ratios sulfide segregation and magmatic fractionation took place simultaneously with a tio2 10p2o5 10mno plot the transitional nature of the primary magma from tholeiite to calc alkaline can be identified with most intrusions assuming the calc alkaline trend the intrusions of this area mostly possess hydrous minerals such as hornblende and biotite generated from alteration of pyroxenes implying metasomatism of the mantle magma caused by the early subducting oceanic crust the mineralization can be classified into three processes and five stages the processes consisted of magmatic mieralization hydrothermal mineralizaion oxidation and eluviation the five stages were successive and constituted a whole process and in the middle magma chamber the sulfur reached saturation with the magma experiencing pulsating intrusion as well as ore rich magmatic intrusion at the final stage loaded with hydrothermal mineralization oxidation and eluviation magmatic mineralization occurred synchronously with hydrothermal mineralization the magmatic stage could offer hydrothermal sources and the hydrothermal process could be favorable to the sulfur saturation and sulfide segregation the hydrothermal alteration structures and ores formed at the magmatic stage were reformed at the hydrothermal stage during the uplift of the intrusions ore bodies were subjected to oxidation and eluviation resulting in a special kind of oxiding alteration which can serve as indicators for prospecting in depth

re os isotope and platinum group element geochemistry of the pobei ni cu sulfide bearing mafic ultramafic complex in the northeastern part of the tarim craton a number of mafic ultramafic intrusions that host ni cu sulfide mineralization occur in the northeastern tarim craton and the eastern tianshan orogenic belt nw china the sulfide mineralized pobei mafic ultramafic complex is located in the northeastern part of the tarim craton the complex is composed of gabbro and olivine gabbro cut by dunite wehrlite and melatroctolite of the poyi and poshi intrusions disseminated ni cu sulfide mineralization is present towards the base of the ultramafic bodies the sulfide mineralization is typically low grade 4 wt samples from the pobei complex have end at 280 ma values up to 8 1 consistent with the derivation of the magma from an asthenospheric mantle source fo 89 5 mol olivine from the ultramafic bodies is consistent with a primitive parental magma sulfide bearing dunite and wehrlite have high cu pd ratios ranging from 24 000 to 218 000 indicating a magma that evolved under conditions of sulfide saturation the grades of ni cu and pge in 100 sulfide show a strong positive correlation a model for these variations is proposed where the mantle source of the pobei magma retained 0 033 wt sulfide during the production of a pge depleted parental magma the parental magma migrated from the mantle to the crust and underwent further s saturation to generate the observed mineralization along with its high cu pd ratio at an r factor varying from 100 to 1 200 the mineralization at poshi and poyi has very high os at 280 ma values 30 to 292 that are negatively correlated with the abundance of os in 100 sulfide 5 81 271 ppb and positively correlated with the re os ratios this indicates that sulfide saturation was triggered by the assimilation of crustal sulfide with both high os and re os ratios when compared to other permian mafic ultramafic intrusions with sulfide mineralization in the east tianshan the poyi and poshi ultramafic bodies were formed from more primitive magmas and this helps to explain why the sulfide mineralization has high ni tenor

the surface windfield over the antarctic ice sheets the intense radiative cooling of air over the ice slopes of antarctica generates a surface wind regime that is strongly controlled by topography and plays a key role in determining the behaviour of the atmosphere and ocean in high southern latitudes1 7 resultant surface winds are intimately linked to the orientation of the ice terrain fig 1 and display the highest degree of persistence found on earth the close coupling between wind and topography allows estimation of the former if the latter is known with some precision here we report on time averaged near surface airflow over the antarctic continent during winter diagnosed from a recent accurate synthesis of terrain slopes and from estimates of the lower atmospheric temperature structure the simulated drainage pat tern exhibits strong spatial variability with the airflow concentrated into several zones near the coastal margin these confluence regions are responsible for strong persistent katabatic winds over downstream coastal stretches and are indicative of zones of greatest katabatic potential

mapping advanced argillic alteration at cuprite nevada using imaging spectroscopy mineral maps based on airborne visible infrared imaging spectrometer aviris data were used to study late miocene advanced argillic alteration at cuprite nevada distributions of fe bearing minerals clays micas sulfates and carbonates were mapped using the tetracorder spectral shape matching system the al content of white micas increases toward altered areas and near intrusive rocks alunite composition varies from pure k to intimate mixtures of na k endmembers with subpixel occurrences of huangite the ca analogue of alunite intimately mixed na k alunite marks areas of relatively lower alteration temperature whereas co occurring na alunite and dickite may delineate relict hydrothermal conduits the presence of dickite halloysite and well ordered kaolinite but absence of disordered kaolinite is consistent with acidic conditions during hydrothermal alteration partial lichen cover on opal spectrally mimics chalcedony limiting its detection to lichen free areas pods of buddingtonite are remnants of initial quartz adularia smectite alteration thus spectral maps provide a synoptic view of the surface mineralogy and define a previously unrecognized early steam heated hydrothermal event faulting and episodes of hydrothermal alteration at cuprite were intimately linked to upper plate movements above the silver peak lone mountain detachment and growth collapse and resurgence of the nearby stonewall mountain volcanic complex between 8 and 5 ma isotopic dating indicates that hydrothermal activity started at least by 7 61 ma and ended by about 6 2 ma spectral and stable isotope data suggest that cuprite is a late miocene low sulfidation adularia sericite type hot spring deposit overprinted by late stage steam heated advanced argillic alteration formed along the margin of the stonewall mountain caldera