mesoscale structure of the midlatitude ionosphere during high geomagnetic activity airglow and gps observations on the night of november 22 1997 the cornell all sky imager recorded a spectacular display of structure in the 630 0 nm emission over arecibo puerto rico this event is an example of a phenomenon we have termed intense midlatitude spread f in this paper we describe the stormtime geophysical conditions for the period and detail the evolution of the event the daytime midlatitude ionosphere was disturbed for four consecutive days the initial daytime doubling of the total electron content tec was associated with equatorward propagation of a high tec patch that seemed to have associated composition changes the following days had distinct diurnal double maxima ddm the tec in the caribbean was very high during the first night of the storm and was extremely structured airglow depletions and enhancements surged poleward bifurcating numerous times in the process the airglow depletions were collocated with tec minima along similar lines of sight to global positioning system satellites eventually four parallel and very similar airglow wave packets were visible and oriented at an angle similar to the less violent structures reported in the companion paper garcia et al this issue and moving slowly toward the southwest we explore a number of possible explanations for these features we are most confident that secondary instabilities of the generalized exb process can explain the evolution of the structures once they are formed the initial process itself remains controversial

organic metamorphism as a key for reconstructing tectonic processes a case study from the austroalpine unit eastern alps at the northwestern margin of the gurktal alps eastern alps eoalpine cretaceous thrusting of carbonaceous material cm bearing metasediments formed a very low to low grade metamorphic nappe stack above higher grade metamorphic basement nappes sedimentary burial as well as progressive metamorphism transformed the enclosed cm to anthracite metaanthracite and semigraphite in a kinematically well constrained section at the northwestern frontal margin of the nappe stack this transformation has been investigated by vitrinite reflectance measurements and raman spectroscopy of carbonaceous materials rscm automated interactive fitting of raman spectra estimates the metamorphic peak temperatures in a complete section through the upper part of the upper austroalpine unit a rscm trend indicates a temperature profile of ca 250 600 c the top part of the gradient is reconstructed by one dimensional thermal modeling the certainty of ca 25 c at a confidence level of 0 9 resembles the data variability within a sample location due to the large calibration range the method is able to reconstruct a thermal crustal profile in space and time the study highlights the versatility of rscm which characterizes almost 250 ma of a complex and polyphase tectonic history rscm data characterize the variscan metamorphic grade in nappes now imbricated in the eoalpine nappe stack they additionally constrain a numerical model which emphasizes the significance of an increased thermal gradient in a continental margin towards the western neotethyan ocean during permo triassic lithospheric extension it finally characterizes the eoalpine metamorphic gradient during nappe stacking and a significant metamorphic jump related to exhumation and normal faulting

caribbean ionosphere campaign year one airglow and plasma observations during two intense mid latitude spread f events a series of campaigns has been carried out in the caribbean over a one year period to study intense mid latitude spread f events using a cluster of diversified instrumentation these events are relatively rare but a number of them have now been captured and will be discussed in this and several companion papers this paper focuses on 630 nm airglow images obtained by the cornell all sky imager for two of the more spectacular cases that began on february 17 1998 and february 17 1999 in the latter case and for the first time a poleward surge of depletion enhancement airglow zones was captured by radar as well as an airglow imager in the former case structures grew in place overhead and produced strong vhf f region backscatter as observed by the cupri and university of illinois radars the other event exactly one year later did not result in detectable 3 m backscatter the two data sets show quantitatively that the low airglow region is elevated in height and depleted in plasma density and pedersen conductivity we suggest an enhanced eastward electric field inside the low conductivity zone may be responsible for the surge the data also suggest small scale turbulence can only be observed in developing structures

a quaternary solution model for white micas based on natural coexisting phengite paragonite pairs a thermodynamic model for the quaternary white mica solid solution with end members muscovite mg celadonite paragonite feceladonite ms mgcel pg fecel is presented the interaction energies for the mgcel pg join the fecel pg join and the ternary interactions were obtained from natural coexisting phengite paragonite pairs phengite paragonite pairs were selected based on the criteria that their chemical compositions may be represented as a linear combination of the model end member compositions and that the respective formation conditions 350 650 c 4 21kbar are accurately known previously published excess free energy expressions were used for the ms pg ms mgcel and ms fecel binaries the suggested mixing model was tested by calculating multicomponent equilibrium phase diagrams this proved to be particularly well suited to reproduce compositional variations of white micas from amphibolite facies metapelites

mixing properties of phengitic micas and revised garnet phengite thermobarometers mixing properties for muscovite celadonite ferroceladonite solid solutions are derived from combining available experimental phase equilibrium data with tabulated thermodynamic data for mineral end members when a partially ordered solution model is assumed the enthalpy of mixing among the end members muscovite celadonite ferroceladonite is nearly ideal although the gibbs energies of muscovite celadonite and muscovite ferroceladonite solutions are asymmetric due to an asymmetry in the entropy of mixing thermodynamic consistency is achieved for data on phengite compositions inassemblages with a pyrope kyanite quartz coesite b almandine kyanite quartz coesite c talc kyanite quartz coesite and d garnet phengite pairs equilibrated both experimentally at high temperatures and natural pairs from low grade schists the muscovite paragonite solvus has been reanalysed using the asymmetric van laar model and the effects of the phengite substitution into muscovite have been quantitatively addressed in order to complete the simple thermodynamic mixing model for the solid solution among the mica end members results are applied to a natural pyrope coesite phengite talc rock from the western alps and to investigate the conditions under which biotite bearing mica schists transform to whiteschist like biotite absent assemblages for average pelite bulk compositions

advection of the equatorial anomaly over arecibo by small storm related disturbance dynamo electric fields during highly disturbed geomagnetic periods both the arecibo radar and the ramey ionosonde have recorded impressive nighttime ionospheric enhancements in which the peak electron density exceeded 1 1012 m 3 and the f2 peak height went above 400 km in the past it has been suggested that these events could be caused by either a downward plasmaspheric flux that increases the density in the f region or by an eastward electric field that pushes the equatorial anomaly poleward to the caribbean sector on february 17 18 1999 the arecibo radar made observations during an event in which the electron density again rose to daytime values near midnight for this event the peaks in density were observed predominantly southeast of arecibo while the ions sustained a northward eastward motion due to an eastward southward storm dynamo electric field tec maps from gps for this night confirmed that the density enhancements were due to a poleward expansion of the equatorial anomaly

variations in stalagmite luminescence laminae structure at poole s cavern england ad 1910 1996 calibration of a palaeoprecipitation proxy duplicate records of variations in the structure of stalagmite annual luminescence laminae are investi gated for the period ad 1910 to 1996 for poole s cavern buxton central england for the two stalagmites 88 of the years have luminescence laminae that exhibit a near sinusoidal shape with no structural variations however 10 laminae 12 of total exhibit a double band structure these are demonstrated to occur in years with high monthly or daily mean precipitation it is suggested that high intensity 60 mm d 1 and high quantity 250 mm per month of precipitation may flush luminescent organic material onto the stalagmites from either the soil or groundwater zones and generate a double lamina however not all precipitation events generated double laminae high intensity events in summer were ineffective due to a soil moisture deficit and or interception by the woodland canopy high rainfall months 250 mm failed to generate double laminae when preceded by two or more months of greater than 150

a thousand year speleothem proxy record of north atlantic climate from scotland luminescent organic matter in stalagmites may form annual bands allowing growth rate to be precisely determined stalagmite growth rate is controlled by precipitation so annual bands can be used to derive long precipitation records a continuously banded stalagmite from a cave in nw scotland was used to provide a 1100 year high resolution record of precipitation the location of the cave means that precipitation is closely linked to the north atlantic oscillation for which a record is also derived this suggests that changes in the north atlantic oscillation state was an important control on european climate over the past millennium

p t d histories from quartz a case study of the application of the titaniq thermobarometer to progressive fabric development in metapelites 1 this study investigates the ability of quartz to record segments of the pressure temperature deformation p t d path in poly deformed metamorphic terranes and the associated application of the ti in quartz thermobarometer titaniq metapelites from the strafford dome eastern vermont were selected for this study because they record progressive fabric development during prograde metamorphism and have well constrained p t d histories from previous work results of this investigation are in agreement with previous studies and demonstrate that quartz in these samples records additional distinct intervals of the p t d path six preserved quartz equilibration events include 1 early prograde growth during burial 2 kyanite in quartz producing reactions 3 prenappe emplacement equilibration during isobaric heating 4 precipitation of quartz in quartz feldspar domains during crenulation cleavage development due to solution transfer 5 quartz producing chlorite out reactions during heating postnappe emplacement and 6 retrograde quartz overgrowths from an influx of siliceous fluids modeling quartz volume allows for the identification of quartz producing reactions in p t space the same may be done for ti phases to better constrain activities during reequilibration events an integration of cathodoluminescence imaging microstructural and petrographic investigation isochemical forward stability modeling and thermobarometry allows identification and interpretation of zoning patterns in quartz to unravel histories that would otherwise not be obtainable

quantification of electron microprobe compositional maps of rock thin sections an optimized method and examples quantification of discrete pressure temperature domains in deformed chlorite white mica bearing metapelites was undertaken on mineral compositions derived by two dimensional microprobe compositional mapping of selected areas of rock thin sections in order to achieve compositional information at sufficient analytical precision spatial resolution and sample coverage within a typical analysis time of 1 day an optimization of measurement methods was necessary the method presented here allows collection of raw counts for eight different element concentrations at an analytical precision of 1 2 wt x ray intensity multiplane maps one map per measured chemical element are translated into concentration multiplane maps utilizing selected conventionally measured spot analyses combined with the castaing approximation for each mineral as this step requires identification of the different minerals present in the mapped area a statistical clustering technique to identify different groups of composition was developed guided by simple petrographic inspection of the thin section to delineate the important minerals in the mapped area finally the compositions of each pixel are translated into a mineral structural formula thus yielding a new kind of image with a high content of petrological information the reliability of the mineral composition images was emphasized by carrying out precision tests on the analytical data the possible use of chemical maps to infer the p t deformation history of metamorphic rocks is illustrated with two samples from the spitzbergen and the sambagawa blueschist facies belts in both samples a strong correlation between structures and chemistry is observed qualitative estimates of p t conditions from the si content of mica and chlorite are in good agreement with their location in microstructures that formed at different times therefore the combination of chemical maps with microstructural observations is a very powerful approach to understand both the evolution of complex metamorphic rocks and the control by deformation of mineral reactivity

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

satellite traces an ionogram signature for large scale wave structure and a precursor for equatorial spread f 1 although the source that controls day to day variability in the occurrence of equatorial plasma structure i e equatorial spread f or esf remains to be identified progress is being made there is evidence that the appearance of large scale wave structure lsws in the bottomside f layer around the time of its post sunset rise pssr is a more direct precursor of esf than the pssr itself the bulk of the evidence however is in the form of satellite f traces in ionograms which may be viewed as less than convincing because these signatures have not been shown to be causally related to lsws in this paper incoherent scatter radar and ionosonde data both collected on 24 july 1979 from the kwajalein atoll marshall islands are used to show that this is indeed the case

annual trace element variations in a holocene speleothem high resolution secondary ionization mass spectrometry sims analysis along the growth axis of a holocene speleothem from northern scotland reveals high frequency oscillations and longer term trends in mg ca sr ca and ba ca at the scale of the high frequency oscillations mg ca and sr ca display a well defined anticorrelation while sr ca and ba ca are positively correlated imaging of elemental ratios in two dimensions reveals that the high frequency signal is well preserved and laterally continuous across the sample tims 230th ages and annual ultraviolet luminescence banding provide chronological control and demonstrate that the high frequency cyclicity is annual trace element variations in speleothem calcite are a reflection of hydrochemical processes in the unsaturated zone overlying the cave supply effects and partitioning at the water calcite interface mg partitioning between water and calcite is temperature dependent calculations suggest that the annual mg ca oscillations may be caused by seasonal temperature changes however the longer timescale variations in mg ca are too great to be explained by this mechanism seasonal variations in water residence time in the unsaturated zone which reflect effective precipitation provide a more probable explanation for the observed annual oscillations and also explain the inverse relationship between mg ca and sr ca this record suggests that trace elements in speleothems have the potential to provide the high resolution insights into interannual palaeoclimatic variability required for assessment of general circulation models

exhumation of the high pressure tsakkok lens swedish caledonides insights from the structural and white mica 40ar 39ar geochronological record

holocene climate variability in europe evidence from δ18o textural and extension rate variations in three speleothems time series o isotope profiles for three u th dated stalagmites have revealed that for much of the holocene a site on the atlantic seaboard sw ireland exhibits first order 18o trends that are almost exactly out of phase with coupled 18o curves from two southern european sites se france and nw italy in the irish stalagmite cc3 from crag cave sw ireland low 18o at 10 000 cal yr bp reflects cool conditions by the early to mid holocene 9000 6000 cal yr bp 18o had increased reflecting the onset of warmer conditions on the atlantic seaboard this shift to higher 18o was accompanied by a marked increase in the stalagmite extension rate reinforcing our interpretation that this was a period of relative warmth except for an episode of increased extension rate about 5500 yr ago 18o in the crag stalagmite exhibits a gradual decrease accompanied by declining extension rates between 7800 and 3500 cal yr bp interpreted as a cooling trend there is evidence for increases in both 18o and stalagmite extension rate in the period from 3500 cal yr bp to the present day suggesting a return to warmer conditions on the atlantic seaboard in the stalagmite from nw italy er76 grotta di ernesto trentino province the early holocene c 9200 7800 cal yr bp is characterised by high 18o probably indicative of warm and or dry conditions exceptionally low 18o from 7800 to 6900 cal yr bp at this site reflects a well defined wet phase cerin wet phase in the last three millennia this stalagmite exhibits a shift to lower 18o interpreted as some combination of cooler and or wetter conditions unlike the irish stalagmite the italian sample does not show a correlation between 18o and extension rate instead its extension rate correlates roughly with 13c presumably reflecting a climate driven vegetation change in the early holocene 18o in the french stalagmite cl26 grotte de clamouse herault province se france was low relative to its holocene average for much of the period since c 3500 cal yr bp this stalagmite exhibits higher 18o than in the early holocene suggesting warmer conditions like the irish stalagmite the french sample exhibits a well defined correlation between 18o and extension rate had drip water availability been the dominant control on 18o at this semi arid site then higher 18o would have been accompanied by lower not higher extension rates this suggests strongly that temperature rather than rainfall amount was the dominant control at this site while conclusions regarding the patterns of climate variability on a continent scale must remain tentative because of the limited number of stalagmites studied we argue that early holocene warm conditions on the atlantic seaboard irish site coincided with relatively cool conditions at the clamouse site by c 3500 yr ago the pattern appears to have been reversed

testing theoretically predicted stalagmite growth rate with recent annually laminated samples implications for past stalagmite deposition annually laminated stalagmites deposited over the last 30 160 years are analysed to determine their growth rate three natural and artificial cave sites in england france and belgium were chosen for their wide range of variability in growth rate determining variables and multiple samples were taken from each site the annual nature of laminae deposition within the stalagmite calcite was confirmed by comparison to the date of cave void opening 14c analyses or by using dated event horizons measured stalagmite growth rate was determined from annual laminae thickness measurements and compared to that theoretically predicted from the chemical kinetics of the calcite precipitation reaction a good agreement is observed between empirical observations and theoretical predictions although two complicating factors variations in calcite porosity and seasonal cessation of the water supply to the samples both affect the growth rate implications for the extraction of palaeoclimate information from stalagmite growth rate are discussed

interaction between a southwestward propagating mstid and a poleward moving wsa like plasma patch on a magnetically quiet night at midlatitude china region

fluorine mobility during early diagenesis of carbonate sediment an indicator of mineral transformations abstract the abundant occurrence of calcium carbonate minerals in marine sediment their well documented dissolution or precipitation during diagenesis and their high f content suggest that carbonate mineral diagenesis may be an important influence on f behavior in marine sediment to test this hypothesis we have examined the geochemistry of f in shallow carbonate mud bank sediment of florida bay usa the f content of biogenic calcium carbonate in florida bay varies with mineralogy positively correlates with the mg content of calcite and occurs in similar abundance to sr high mg calcite f sr 2 4 mol mol aragonite 0 53 0 79 mol mol low mg calcite 0 22 mol mol models of porewater distributions direct solute flux measurements and reaction rate estimates over the upper 0 16 cm of sediment from bob allen key bank predict net fluxes out of the sediment of 170 mol f m2 d 230 mol sr m2 d and 5 6 mmol ca m2 d the net solute flux ratio of f sr 0 71 mol mol is consistent with dissolution of aragonite or high mg calcite but f ca and sr ca ratios 28 mmol mol and 40 mmol mol respectively are 3 10 that of biogenic carbonate sources selective dissolution of a high f and sr content phase or more likely based on dissolution experiments concurrent dissolution and reprecipitation of phases with different f and sr contents account for this discrepancy the loss of f sr and ca to fluorapatite precipitation as predicted from a stoichiometric model of phosphate release can be added to the transport reaction model predicted net fluxes a resulting more complete mass balance model incorporating both carbonate mineral reactions and fluorapatite formation yields total release estimates of f sr and ca of 770 mol 332 mol and 53 mmol m2 d respectively calcium carbonate minerals apparently undergo transformation whereby 34 mmol high mg calcite m2 d and 19 mmol aragonite m2 d dissolve and 46 mmol low mg calcite m2 d precipitates ignoring other cations besides ca if no fluorapatite formation occurs the required fluxes are that 23 mmol aragonite m2 d dissolves and 3 4 mmol high mg calcite m2 d and 14 mmol low mg calcite m2 d precipitate net loss of caco3 from the deposit by dissolution is 6 7 mmol m2 d 3 of the accumulation flux the magnitude of these fluxes could cause significant mineralogical and chemical changes on rapid time scales in nearshore carbonate sediment fluorine is probably mobile in other carbonate deposits undergoing diagenetic alteration on short and longer time scales and is a powerful additional constraint on the rates and nature of carbonate mineral diagenesis

metamorphic evolution and 40ar 39ar geochronology of the wuguan complex eastern qinling area china implications for the late paleozoic tectonic evolution of the qinling orogen abstract the late paleozoic tectonic evolution of the qinling orogen is poorly constrained the wuguan complex which lies between the north qinling and south qinling tectonic belts represents a late paleozoic metamorphic belt of the qinling orogen in this contribution we report new metamorphic pressure temperature p t constraints and 40ar 39ar ages of garnet amphibolites and garnet bearing metapelites from the wuguan complex textural observations and mineral compositions especially garnets with two stages of growth indicate the wuguan complex experienced two distinct metamorphic events conventional geothermobarometry and phase equilibria modelling indicate that the earlier metamorphism had peak p t conditions of 660 725 c and 8 0 12 0 kbar with a clockwise p t path whereas the later metamorphic overprint records p t conditions of 560 610 c and 7 5 9 0 kbar hornblendes from amphibolites yield 40ar 39ar ages of 306 299 ma whereas muscovites from garnet bearing metapelites yield 40ar 39ar ages of 252 251 ma the two groups of 40ar 39ar ages correspond to the cooling time of the two distinct metamorphic events respectively combining with previously published zircon u pb ages from the wuguan complex and two groups of metamorphic ages from the guishan complex and the xiongdian eclogite belt we infer that the earlier metamorphism probably occurred at the hangingwall of a subduction zone during carboniferous subduction of oceanic crust the later metamorphic overprint might have been related to the initial collision between the sino korean and yangtze cratons during the late permain

aeolian contribution to strontium and strontium isotope variations in a tasmanian speleothem abstract a speleothem from south central tasmania shows marked secular variations in its strontium content the element exhibits a striking bimodal distribution pattern with abrupt changes between two modal groups that is believed to be due to rapid changes in the direction of the dominant strong winds strontium isotope compositions in the speleothem range from 0 70865 to 0 70898 indicating derivation of sr from at least two distinct sources the first a persistent one from the overlying limestone the second a higher 87 sr 86 sr component probably representing input from terrestrial dust the speleothem record is unusual because it indicates a greater input of radiogenic sr dust flux during interstadial times than under full glacial conditions if an aeolian origin of some of the strontium contained in speleothems at other inland cave sites around the world can be confirmed variations in strontium isotope composition will provide high resolution records of how terrestrial dust flux has varied during the quaternary in near coastal sites significant amounts of strontium may be derived from seasalt and in those areas temporal variation of the element in speleothems may reflect at least in part changing distance from the coast due to changes in sealevel

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

petrology of hp metamorphic veins in coesite bearing eclogite from western tianshan china fluid processes and elemental mobility during exhumation in a cold subduction zone abstract a petrological study was carried out for high pressure hp veins which cut through the host coesite bearing eclogites at habutengsu kebuerte in western tianshan china the results place constraints on the origin and property of metamorphic fluids during subduction zone metamorphism omphacite clinozoisite and quartz dominated veins occur on centimeter to meter scales within lens shaped and layered eclogites or cutting into the country rocks of garnet phengite schists coesite bearing eclogites mainly consist of fibrous fine grained omphacite and porphyroblastic garnet with minor amounts of amphibole mainly barroisite clinozoisite white mica mainly paragonite and rutile the veins are pronouncedly coarse grained compared to the host eclogites and commonly consist of quartz clinozosite rutile white mica phengite and paragonite and garnet with or without omphacite titanite apatite carbonate mainly dolomite and glaucophane fluid inclusions are abundant in vein omphacite titanite and apatite but are rare in the equivalent minerals of host eclogites rounded vein garnets usually occur close to the sharp interface of vein and host eclogite omphacite in the veins is characterized by its euhedral form surrounded by quartz or coarse bladed aggregates in contrast to the fibrous or patchy one suggesting dynamic recrystallization in the host rocks omphacite in both veins and host eclogites has similar jadeite contents jd 40 50 indicating formation at eclogite facies metamorphic conditions vein phengite uniformly contains certain amounts of ba with maximum bao content of 3 16 4 25 wt suggesting that ba was mobilized during the exhumation of uhp rocks specific textures of vein minerals such as the enclosure of magnesite or calcite in dolomite rutile in titanite and the occurrence of zoned ba rich phengite indicate the chemical variability of channelized fluids over time based on zr content in rutile and the presence of paragonite omphacite phengite glaucophane as well as the little deformed textures of hp veins it is estimated that the vein forming fluids would flow at about 1 3 2 1 gpa and 540 580 c corresponding to the stage of retrograde eclogite facies recrystallization during exhumation of the uhp eclogites that formed at peak p t conditions of 2 7 gpa and 460 520 c the hp veins occur as a consequence of a regional tectonothermal event triggering breakdown of lawsonite within the uhp eclogites based on the petrology of vein minerals it is inferred that the hp fluids were enriched in si ca na al and ba this suggests that these elements could be mobilized during the retrograde metamorphism of uhp eclogites in a cold subduction zone coeval pervasive flow of hp metamorphic fluids through the uhp eclogites at this stage may be an important process to eliminate most mineralogical evidence of the uhp metamorphism

recalibration of the garnet muscovite gm geothermometer and the garnet muscovite plagioclase quartz gmpq geobarometer for metapelitic assemblages the garnet muscovite gm geothermometer and the garnet muscovite plagioclase quartz gmpq geobarometer have been simultaneously calibrated under conditions of t 1 4 450 760 c and p 1 4 0 8 11 1 kbar using a large number of metapelitic samples in the compositional ranges x grt fe 1 4 0 53 0 81 x grt mg 1 4 0 05 0 24 x grt ca 1 4 0 03 0 23 in garnet x pl ca 1 4 0 17 0 74 in plagioclase and fe 1 4 0 04 0 16 mg 1 4 0 04 0 13 al 1 4 1 74 1 96 in muscovite on the basis of 11 oxygens the resulting gm thermometer yielded similar temperature estimates mostly within 50 c to that of the garnet biotite thermometer and successfully discerned the expected systematic temperature change of prograde sequences thermal contact zones and an inverted metamorphic zone the resulting gmpq barometer yielded similar pressure estimates mostly within 1 0 kbar to the garnet aluminum silicate plagioclase quartz gasp barometer and placed the aluminosilicate bearing samples in the appropriate aluminosilicate stability fields application of the gmpq barometer to thermal contact aureoles or rocks within limited geographical areas confirmed the expected constant pressures that should exist in these settings the random errors of the gm thermometer and the gmpq barometer are estimated to be 16 c and 1 5 kbar respectively when biotite or aluminosilicate is absent in metapelites metamorphic p t conditions may be determined by simultaneously applying the gm thermometer and the gmpq barometer

calibration of the speleothem delta function an absolute temperature record for the holocene in northern norway the speleothem delta function sdf provides a new transfer function between the d18o signal of speleothem calcite and surface ground temperature the function is based on physical principles relating d18o of the calcite to thermodynamic fractionation and to the dripwater function which in turn relates d18o of dripwaters to that of the local precipitation and thus to the modification of source water in relationship to the geographical position of the site the sdf must be calibrated against at least two reliable and well dated palaeotemperature points the end product is a reconstruction of absolute cave and surface temperatures the technique is tested using a holocene speleothem from north norway sg93 dated by 12 tims u th dates the reconstructed temperature curve is presented and compared with the gisp2 ice core record and with the historic record in both cases the correlation with sg93 is impressive indicating the validity of the technique

microdiamond on areskutan confirms regional uhp metamorphism in the seve nappe complex of the scandinavian caledonides metamorphic diamond in crustal rocks provides important information on the deep subduction of continental crust here we present a new occurrence of diamond within the seve nappe complex snc of the scandinavian caledonides on areskutan in jamtland county sweden microdiamond is found in situ as single and composite diamond carbonate inclusions within garnet in kyanite bearing paragneisses the rocks preserve the primary peak pressure assemblage of ca mg rich garnet phengite kyanite rutile with polycrystalline quartz surrounded by radial cracks indicating breakdown of coesite calculated p t conditions for this stage are 830 840 c and 4 1 4 2 gpa in the diamond stability field the ultrahigh pressure uhp assemblage has been variably overprinted under granulite facies conditions of 850 860 c and 1 0 1 1 gpa leading to formation of ca mg poor garnet biotite plagioclase k feldspar sillimanite ilmenite quartz this overprint was the result of nearly isothermal decompression which is corroborated by ti in quartz thermometry chemical th u pb dating of monazite yields ages between 445 and 435 ma which are interpreted to record post uhp exhumation of the diamond bearing rocks the new discovery of microdiamond on areskutan together with other evidence of ultrahigh pressure metamorphism uhpm within gneisses eclogites and peridotites elsewhere in the snc provide compelling arguments for regional at least 200 km along strike of the unit uhpm of substantial parts of this far travelled allochthon the occurrence of uhpm in both rheologically weak gneisses and strong lithologies eclogites peridotites speaks against the presence of large tectonic overpressure during metamorphism

low pressure temperature stability of pyrope quartz relative to orthopyroxene kyanite a new model for aluminous orthopyroxene with vacancies determination of the stability of pyrope with quartz could provide theoretical pressure temperature p t constraints on silica saturated eclogites as well as near end member pyrope bearing terrains the lower p t stability of pyrope in the presence of quartz in the system mgo al2o3 sio2 can be modeled by the reaction 3 enstatite 2 kyanite 2 pyrope 2 quartz reaction reversals were experimentally obtained using a in diameter piston cylinder press and a 1000 t multi anvil press besides natural quartz all other starting materials including orthopyroxene pyrope and kyanite were synthesized the reaction has been bracketed at 1 50 gpa at 1040 1080 c 1 69 1 79 gpa at 1000 c 2 26 gpa at 920 940 c 2 90 gpa at 840 860 c the bracketed boundary is higher in temperature and pressure than that calculated using the newest dataset of holland et al j petrol 59 881 900 https doi org 10 1093 petrology egy048 2018 particularly at higher pressures aluminum is usually thought to be taken into orthopyroxene in the form of mg tschermak s pyroxene mgts mgal2sio6 under these experimental p t conditions in contrast the observed orthopyroxene composition indicated the involvement of a non stoichiometric component mg eskola pyroxene mges mg0 5 0 5alsi2o6 an aluminous orthopyroxene with octahedral vacancies end member thermodynamic properties for mges as well as a mixing model for the ternary enstatite mgts mges solid solution have been derived the thermodynamic calculations employing the mixing model are in good agreement with the experimental brackets the new model has potential applications to constrain p t conditions of tectonic settings such as ultrahigh pressure and ultrahigh temperature metamorphisms

ionospheric plasma blobs observed by oi 630 nm all sky imaging in the brazilian tropical sector during the major geomagnetic storm of april 6 7 2000 1 this paper presents first observations of plasma blobs localized plasma density enhancements associated with large scale plasma density depletions plasma bubbles in the nighttime low latitude f region during a major geomagnetic disturbance ground based observations of the oi 630 nm all sky images obtained at cachoeira paulista 22 7 s 45 0 w brazil in the appleton anomaly region showed the presence of plasma blobs during the major geomagnetic storm of april 6 7 2000 kp 38 40 dst max 288 nt the oi 630 nm emission images were used to map the spatial and temporal locations of plasma blobs and bubbles in the bottomside of the f region the f region parameters presented in this work were obtained from ionosondes operating near the same site and also at sao luis 2 6 s 44 4 w brazil ionospheric plasma blobs and bubbles zonal drift velocities measured by the all sky imaging system showed that both the plasma blobs and the bubbles moved westward normally the plasma drift is eastward during nighttime on this magnetically disturbed night furthermore the plasma blobs showed typically east west and north south extensions in the range of 110 160 km and 200 450 km respectively it appears that the dmsp 15 satellite orbiting at about 850 km altitude passed through one of the blobs detected by the ground based observations on this night while crossing the brazilian sector this indicates the enormous altitude extent from about 275 km oi 630 0 nm emission to 850 km dmsp satellite altitude of the localized plasma density enhanced regions in this work we present and discuss several features related to the dynamics of the localized plasma density enhancements and large scale plasma density depletions during this major geomagnetic disturbance

inverted oligo miocene metamorphism in the lesser himalaya sequence arunachal pradesh india age and grade relationships the lesser himalaya sequence in the siyom valley eastern arunachal pradesh exposes a telescoped and inverted greenschist upper amphibolite facies sequence over 20 km tectonically overlain by an upright grade decreasing upward granulite to lower amphibolite facies sequence over 30 km such grade relationships would normally attribute the boundary to a main central thrust mct structure and predict a change from underlying lesser himalaya sequence lhs to greater himalaya sequence rocks across the boundary however all pelitic and psammitic samples have similar detrital zircon age spectra involving c 2500 1750 1500 1200 and 1000 ma gondwanan populations correlated with the lhs isograds are broadly parallel to a penetrative nw dipping s2 foliation developed contemporaneously with the inversion garnet growth in garnet staurolite and kyanite zone schists beneath the thrust commenced at 8 kbar and 550 c before syn to post s2 heating of staurolite and kyanite zone rocks to 640 c at 8 5 kbar most probably at c 18 5 ma kyanite rutile garnet migmatite immediately above the thrust records peak conditions of 10 kbar and 750 c and c 21 5 ma monazite ages slip on a se propagating thrust was likely contemporaneous with early miocene metamorphism based on the distribution of structure metamorphic textures and overlap of age relationships it is inferred to have initially controlled the uplift of granulite to mid crustal levels between 22 and 19 ma thermal relaxation within a disrupted lhs metamorphic profile inducing a post s2 thermal peak in lower grade footwall rocks

airglow observations of nighttime medium scale traveling ionospheric disturbances from yonaguni statistical characteristics and low latitude limit the characteristics of nighttime medium scale traveling ionospheric disturbance mstid features observed over yonaguni 24 5 n 123 0 e 19 3 n dip latitude japan are studied using all sky imaging of oi 630 0 nm airglow emission the uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere typical low latitude limit of midlatitude type nighttime mstids possessing phase front alignments along the northwest to the southeast occurs in this region these mstid features are rarely sighted at dip latitudes below 15 we selected 2 year period for analysis in which 1 year corresponded to the solar minimum conditions and another year to the solar maximum conditions the mstids were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods their observed range of wavelengths phase velocities phase front alignment and propagation directions are similar to those observed at typical midlatitude sites however on many occasions the phase fronts of the observed mstids did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes detailed investigation suggests that the poleward propagating enhancement of airglow intensity probably associated with the midnight pressure bulge causes the mstid features to disappear when they reach lower latitudes later in the night when the mstids reach lower latitudes well before midnight they are found to be inhibited by the equatorial ionization anomaly crest region

shrinking equatorial plasma bubbles the formation of equatorial plasma bubbles epbs associated with spread f irregularities are fairly common phenomenon in the postsunset equatorial ionosphere these bubbles grow as a result of eastward polarization electric field resulting in upward e b drift over the dip equator as they grow they are also mapped to low latitudes along magnetic field lines the epbs are often observed as airglow depletions in the images of oi 630 nm emission on occasions the growth of the features over the dip equator is observed as poleward extensions of the depletions in all sky images obtained from low latitudes herein we present interesting observations of decrease in the latitudinal extent of the epbs corresponding to a reduction in their apex altitudes over the dip equator such observations indicate that these bubbles not only grow but also shrink on occasions these are the first observations of shrinking epbs the observations discussed in this work are based on all sky airglow imaging observations of oi 630 0 nm emission made from panhala 11 1 n dip latitude in addition ionosonde observations made from dip equatorial site tirunelveli 1 1 n dip latitude are used to understand the phenomenon better the analysis indicates that the speed of shrinking occurring in the topside is different from the bottomside vertical drifts when the epbs shrink they might decay before sunrise hours

mesoscale field aligned irregularity structures fais of airglow associated with medium scale traveling ionospheric disturbances mstids in this paper we report the evolution generation amplification and dissipation of optically observed mesoscale field aligned irregularity structures fais similar to 150 km associated with a medium scale traveling ionospheric disturbance mstid event there have not been observations of mesoscale fais of airglow before the mesoscale fais were generated in an airglow depleted front of southwestward propagating mstids that were simultaneously observed by an all sky imager a gps monitor and a digisonde around xinglong 40 4 degrees n 30 5 degrees magnetic latitude china on 17 18 february 2012 a normalized cross correlation method has been used to obtain the velocities of mesoscale fais and mstids the mesoscale fais had an obvious northwestward relative velocity to main body mstids about 87 0 m s on average the direction of this relative velocity was roughly parallel to the depleted fronts furthermore the evolution of the mesoscale fais was mostly controlled by the intensity of the depleted fronts occurred in a highly elevated ionosphere that had a total electron content depletion associated with large negative airglow perturbations 25 the mesoscale fais grew rapidly when they experienced southeastward wind which had a speed of about 100 m s and were measured by a fabry perot interferometer a northeastward polarization electric field within a depleted airglow front can play a controlling role in the development of the mesoscale fais the electric field can significantly elevate the ionosphere and move the mesoscale fais northwestward by the e x b drift the processes for the generation and development of the polarization electric field and the mesoscale fais however need further study

annual growth banding in a cave stalagmite the presence of microscopic luminescence banding in cave calcite deposits speleothems has recently been reported1 3 the luminescence seems to be caused by excitation of humic and fulvic acids derived from the overlying soil and subsequently incorporated into the calcite3 4 we have tested whether such luminescence corresponds to annual growth layers using high precision thermal ionization mass spectrometric 238u 234u 230 th ages from banded sections of a holocene stalagmite we report here that the timespans yielded by counting bands on the assumption that they are annual agree within error limits with those obtained by our uranium thorium dating this demonstration that the banding is annual should make banded speleothems valuable resources for providing high resolution records of past climate in which precipitation can be estimated from growth rates5 6 and temperatures from stable isotope measurements7 and solar terrestrial correlations as the luminescence intensity can be related to the solar sunspot cycle1 3

mg sr and sr isotope geochemistry of a belgian holocene speleothem implications for paleoclimate reconstructions in this study variations in mg ca sr ca and 87sr 86sr ratios in a holocene belgian speleothem cave secondary carbonate deposit are interpreted in terms of changes in water residence time and changes in weathering processes possibly induced by changes in west european climate a stalagmite from the pere noel cave belgium was dated with the tims u th method and was deposited between 13 and 2 ka bp the 1000 mg ca ratio varies between 4 9 and 26 and displays short term changes but no significant long term trend the 1000 sr ca ratio varies between 0 09 and 0 31 and displays both short term changes and a long term decreasing trend from 12 9 to 3 5 ka in parallel the sr isotopic composition of the speleothem decreases from 0 7090 at 12 9 ka to 0 7088 at 3 5 ka the sr isotope ratio is higher than expected from the overlying limestone 87sr 86sr 0 7081 which implies an external source of radiogenic sr most probably from a silicate phase short term and long term changes in mg ca sr ca as well as long term changes of 87sr 86sr ratios can be explained by changes in the dissolution and precipitation processes of the host limestone these processes are controlled by changes in water residence times linked to changes in the water excess precipitation minus evapo transpiration c 2000 elsevier science b v all rights reserved

midlatitudinal special airglow structures generated by the interaction between propagating medium scale traveling ionospheric disturbance and nighttime plasma density enhancement at magnetically quiet time

calculated phase relations in high pressure metapelites in the system nkfmash na2o k2o feo mgo al2o3 sio2 h2o using an internally consistent thermodynamic dataset and updated models of activity composition relation for solid solutions petrogenetic grids in the system nkfmash na2o k2o feo mgo al2o3 sio2 h2o and the subsystems nkmash and nkfash have been calculated with the software thermocalc 3 1 in the p t range 5 36 kbar and 400 810 c involving garnet chloritoid biotite carpholite talc chlorite kyanite sillimanite staurolite phengite paragonite albite glaucophane jadeite with quartz coesite and h2o in excess these grids together with calculated afm compatibility diagrams and p t pseudosections are shown to be powerful tools for delineating the phase equilibria and p t conditions of na bearing pelitic assemblages for a variety of bulk compositions from high p terranes around the world these calculated equilibria are in good agreement with petrological studies moreover contours of the calculated phengite si isopleths in p t pseudosections for different bulk compositions confirm that phengite barometry is highly dependent on mineral assemblage

spatial relationship of nighttime medium scale traveling ionospheric disturbances and f region field aligned irregularities observed with two spaced all sky airglow imagers and the middle and upper atmosphere radar 1 we report simultaneous observations of medium scale traveling ionospheric disturbances mstids and field aligned irregularities fais in the f region using two all sky airglow imagers and the middle and upper atmosphere mu radar mstids propagating southwestward were observed simultaneously in 630 nm airglow images over sakata 39 0 n 139 9 e and shigaraki 34 9 n 136 1 e japan on the night of 16 june 2004 by using all sky images over both sites we estimated the altitude of the airglow layer to be 260 km by the triangulation method during the mstid event fais in the f region were observed by making multibeam measurements with the mu radar at shigaraki in order to investigate the spatial relationship between the mstids and fais the fais were mapped onto the 630 nm airglow layer altitude 260 km along the geomagnetic field lines we found that fais with an intense weak signal to noise ratio coincided with the airglow depletion enhancement caused by the mstids fai velocity obtained from a combination of the doppler velocities on the three radar beams oscillated in the northwest southeast direction with an amplitude of approximately 82 m s the fai velocity was northwestward southeastward at the airglow depletion enhancement the directions of the fai velocity were consistent with those of the e b drifts caused by the polarized electric fields associated with the mstids the northeastward polarized electric field at the airglow depletion region strengthened the background eastward effective electric field and drove the gradient drift instability generating fais this might be the reason why the fais preferred to occur at the airglow depletion region

on the importance of wave like structures in the occurrence of equatorial plasma bubbles a case study 1 coordinated observations of equatorial plasma bubbles epbs have been made with an all sky airglow imager narrow bandwidth photometer vhf radar and ionosonde over the indian sector on the night of 23 march 2009 the prereversal enhancement pre in the vertical plasma drift during the postsunset hours on this day was moderate range type spread f was found to occur immediately after the satellite traces were noted in the ionograms this was well recorded in measurements made by all sky imager narrow band photometer and vhf radar the airglow emission intensities also revealed the presence of a large scale wave like structure lsws together with the plasma bubbles that coincided with plume structures observed in the vhf radar echoes the periodicity of the occurrence of bubbles and plumes and their interdepletion distances suggest the presence of small scale wave like structures ssws on this night the results are compared with the ionosonde observations made on the night of 21 february 2008 the pre and the maximum height attained by the f layer were very similar to that of 23 march 2009 in addition the ionograms showed the presence of satellite traces however no subsequent evolution of spread f was noticed considering the satellite traces to have their origin in lsws these observations imply that though the presence of lsws is important for the triggering of epbs they alone are not sufficient however the coexistence of both lsws and ssws may have the potential to trigger epbs

coordinated measurements of f region dynamics related to the thermospheric midnight temperature maximum abstract as part of the nsf cedar program coupling energetics and dynamics of atmospheric regions in multi instrumented studies of equatorial thermospheric aeronomy miseta an all sky ccd airglow imaging system has been in operation in arequipa peru since october 1993 here we report on the first such use of a wide field imager to document the optical signature and variability of a brightness feature associated with the so called midnight temperature maximum mtm while the observational driver of this study is a rightness wave bw seen in 6300 a and 5577 airglow images detailed case studies are conducted during two campaign periods when fabry perot interferometer fpi and digital ionosonde data were also available during the passage of a bw the fpi observed enhancements in thermospheric temperatures reversals from equatorward to poleward of the meridional neutral winds and local minima in the zonal neutral winds the ionosonde recorded decreases in the height of the f layer during bw events this lends support to the concept that the poleward winds generated by the mtm pressure bulge cause the lowering of the f layer to regions of enhanced loss h 300 km and corresponding airglow production the two dimensional field of view of the imager allows identification of the geographical orientation of the bw pattern we use the orientation angle of the bw as an indicator of the geographical orientation of the mtm significant day to day variability in these patterns suggest a complex mix of tidal mode interactions that lead to the overall mtm phenomena

empirical garnet muscovite plagioclase quartz geobarometry in medium to high grade metapelites abstract based on the net transfer reactions among garnet muscovite plagioclase and quartz for both mg and fe end member models the garnet muscovite plagioclase quartz gmpq geobarometry was empirically calibrated under the physical conditions of p 1 0 11 4 kbar and t 505 745 c for 128 natural metapelitic rock samples collected from the literature the input temperatures and pressures were simultaneously determined by the garnet biotite thermometer and the garnet aluminosilicate plagioclase quartz gasp barometer the gmpq calibrations adopted the same asymmetric quaternary solid solution model of garnet and the same al avoidance asymmetric ternary model of plagioclase as the calibrations of the garnet biotite geothermometer and the gasp geobarometer a symmetric fe mg al vi ternary solid solution model of muscovite was adopted and the margules parameters of muscovite were obtained through regression the mg and fe model reactions along with the assumption of whether the ferric iron content in muscovite is 0 or 50 resulted in four gmpq barometry formulae the gmpq barometry formulae reproduce the input gasp pressures well within 1 0 kbar mostly within 0 5 kbar for both aluminosilicate bearing and aluminosilicate absent samples the gmpq barometry formulae yield identical pressures for every sample whether the sample was included or not in calibrating the barometers for each of the mg or fe model reaction the formulae gave identical pressures within 40 bars the random error of the gmpq barometry may be expected as 1 4 kbar the d p d t slopes of these gmpq formulae are close to that of the gasp barometer in the p t space applications of the gmpq barometry to aluminosilicate absent metapelites within a limited geographic area without postmetamorphic structural discontinuity generally show no pressure difference it may be concluded that the gmpq barometry formulae derived in this work may be used as practical tools for metamorphic pelites under the conditions of 505 745 c and 1 11 4 kbar in the composition range of x gros 3 in garnet and x an 17 in plagioclase

trace element variation in speleothem aragonite potential for palaeoenvironmental reconstruction trace element variation in annually laminated stalagmites has the potential to record long term high resolution palaeoclimatic data provided both 1 the relationship between trace element content in the carbonate and the climate and 2 the mechanism of stalagmite growth are understood here we report a secondary ion mass spectrometry sims study of an aragonitic speleothem t7 from cold air cave southern africa which achieves small m spatial resolution and ppm precision t7 has a series of fine visible laminae believed to be annual to subannual this article establishes 1 the usefulness of sims in analyzing speleothem aragonite at the spatial resolution and precision relevant to climatic studies 2 the distribution of trace elements in aragonite on micron scales and their relationship to models for speleothem growth and 3 the potential of aragonite speleothems to encode climatic data at subannual resolution complex reproducible oscillations in sr ca and ba ca are observed parallel to the growth direction of the speleothem however in addition to this variability we observe trace element oscillations perpendicular to the growth direction and infer that aragonite crystallites in the speleothem are laterally as well as vertically zoned stepscans parallel to the growth direction demonstrate complex zoning patterns from which simple climatic data are difficult to extract due to small scale lateral heterogeneity in the aragonite however time series analysis of the whole data set reveals regular cycles in sr ca and ba ca at a scale that matches the magnitude of the visible laminae on this basis it appears that within the complex geochemical variability there resides a regular environmental control possibly variation in water throughput hence rainfall

a large scale traveling ionospheric disturbance during the magnetic storm of 15 september 1999 enhancement of gps total electron content 1 0 10 16 m 2 multipoint and imaging observations of these parameters show that the lstid moved equatorward over japan with a velocity of 400 450 m s from a comparison with the sheffield university plasmasphere ionosphere model supim we conclude that an enhancement 250 300 m s of poleward neutral wind that is propagating equatorward caused these observational features of the lstid at midlatitudes to investigate generation of the lstid by auroral energy input we have used auroral images obtained by the polar uvi instrument magnetic field variations obtained at multipoint ground stations and the empirical joule heating rate calculated by the assimilative mapping of ionospheric electrodynamics amie technique intense auroral energy input was observed at 0800 1100 ut 4 6 hours before the lstid probably causing equatorward neutral wind at lower latitudes it is likely that the poleward wind pulse that caused the observed lstid was generated associated with the cessation of this equatorward wind the effect of lorentz force is also discussed index terms 0310 atmospheric composition and structure airglow and aurora 2427 ionosphere ionosphere atmosphere interactions 0335 2435 ionosphere ionospheric disturbances 2437 ionosphere ionospheric dynamics 2788 magnetospheric physics storms and substorms keywords large scale traveling ionospheric disturbance thermosphere ionosphere coupling magnetic storm airglow imaging gps network ionosonde

high resolution temporal record of holocene ground water chemistry tracing links between climate and hydrology strontium isotope analysis of precisely dated calcite growth layers in holocene speleothems from barbados west indies reveals high resolution temporal variations in ground water composition and may provide a new approach to documenting the links between climate variability andfluctuations in the hydrologic cycle such as recharge rates andflow paths the speleothems grew in a cave that developed in a fresh water aquifer in upliftedpleistocenereeflimestones threeperiodsofground watersrisotopeevolutionare observed 87 sr 86 srvaluesdecreasedfrom6to4ka increasedfrom4to1ka anddecreased again after 1 ka the sr isotope oscillations appear to record periodic variations in the relative sr fluxes to ground water from exchangeable soil sites vs carbonate mineral reactions asreflectedin 87 sr 86 srvaluesofmodernbarbadosgroundwaters ahydrologic model that explains changes in ground waterflow routes in karst aquifers as a function of amountofrainfallrechargecanaccountforthespeleothemsrisotoperecord independent holoceneclimaterecordsthatindicateamajorperiodofaridityataround1 3 1 1kainthe american tropics correspond with periodic variations in rainfall on barbados that are predicted by this hydrologic model

application of mineral equilibria modeling to constrain t and x co2 conditions during the evolution of the magdala gold deposit stawell victoria australia mineral equilibria modeling involving solid solution calculations has been combined with mineral assemblage information from the alteration zones associated with gold mineralization to determine the t and xco2 conditions for the formation of the magdala gold deposit at stawell victoria australia economic gold mineralization is primarily hosted within the stilpnomelane alteration zone of the stawell facies that is adjacent to the magdala basalt evolution of the magdala gold deposit involved at least three fluid infiltration events 1 a co2 bearing fluid during the d2 deformation event produced carbonate spots throughout the chlorite zone 2 a co2 s k bearing fluid accompanied the d3 4ab deformation and produced a muscovite zone and siderite rims on ankerite and 3 a co2 k s au bearing fluid during the d4c deformation event produced the stilpnomelane zone of the stawell facies the proximal and distal alteration zones within the magdala basalt and the main economic gold mineralization mineral equilibria modeling constrains the temperature of formation of the magdala deposit to t 345 390 c at 3kbar substantially lower than indicated by other previous classical thermobarometry methods furthermore this method has allowed the characterization of the mineralizing fluid and constrained its composition to xco2 0 08 at 3kbar the timing and composition of the mineralizing fluids are similar to that of metamorphic fluid generated from devolatilization of a greenstone pile with peak of metamorphism occurring earlier and at deeper levels in the crust

dehydration of dioctahedral aluminous phyllosilicates thermodynamic modelling and implications for thermobarometric estimates we propose a solid solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations including hydration observed in natural smectites interlayered illite smectite illites and phengites from diagenetic to high grade metamorphic conditions the suggested formalism involves dehydrated micas and hydrated pyrophyllite like thermodynamic end members with these end members the equilibrium conditions of quartz water k bearing mica like phyllosilicates of fixed 2 1 composition are represented by a line in p t space along which the interlayer water content varies the relevant thermodynamic properties required for the calculation of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions which covers a range between 25 c and few mpa to 800 c and 5 gpa the temperatures calculated at fixed pressure with our model are in fair agreement with those reported in the literature for the 250 natural data at low temperature and pressure the amount of interlayer water in k deficient phengite and illite is predicted to reach 100 of the apparent vacancies which is consistent with previous values reported in the literature although the amount of interlayer water is predicted to decrease with pressure and temperature it is calculated to be significant in k deficient phengite from lt hp pelites metamorphosed at about 350 c 10 kbar the presence of molecular water in the interlayer site of such phengites has been confirmed by ftir mapping its implications for p t estimates are discussed

petrography strontium barium and uranium concentrations and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies soreq cave israel the reconstruction of the palaeoclimate of the eastern mediterranean region for the last 60 ka bp is based on the 18o and 13c variations of speleothems from soreq cave israel climatic conditions during most of the time interval between 60 and 17 ka bp the period equivalent to the last glacial were relatively cold and dry while they were warmer and wetter from 17 ka bp to the present at 17 ka bp there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8 5 and 7 0 ka bp during the colder and drier period large detritus free preferentially oriented calcite crystals were deposited from slow moving water as a result of a sharp change in the hydrological regime at 17 ka bp fast moving water started entrainment of the soil and carrying detrital material into the cave and the calcite crystals deposited became small and anhedral coinciding with the petrographic and isotopic changes a sharp drop occurred in the concentration

spectral analysis of a 1000 year stalagmite lamina thickness record from shihua cavern beijing china and its climatic significance stalagmite laminae provide a high resolution geological record of climate change in this paper moving spectral analysis is used to analyse a stalagmite lamina thickness record to study climatic v

the eastern mediterranean paleoclimate as a reflection of regional events soreq cave israel the climate of the eastern mediterranean region of the last 60 ky was determined by a high resolution study of the oxygen and carbon isotopic composition 1500 measurement pairs of speleothems from the soreq cave israel with chronology provided by 53 precise 230 th 234 u tims ages the high precision of the speleothem tims ages permits us to determine the timing of regional climatic events in the eastern mediterranean region and to see if they correlate with global events during the period from 60 to 17 ky the 18 o and 13 c values were generally 2 2 5 higher than during the period from 17 ky to present this is consistent with the climatic transition from glacial to interglacial within the 60 to 17 ky period the soreq cave stable isotope profile includes four cold peaks at 46 35 25 and 19 ky and 2 warm peaks at 54 and 36 ky in addition the period 17 ky has two more cold peaks at 16 5 and from 13 2 to 11 4 ky the ages of four of the six cold peaks correlate well with the ages of three heinrich events h1 h2 h5 and with the age of the younger dryas however the other two heinrich events are not reflected in the soreq cave record several other isotope peaks which appear during the last 7 ky are contemporaneous with regional climatic events in the middle east and north africa in addition to the drop in 18 o and 13 c observed between the last glacial and the holocene sharp simultaneous drops in 234 u 238 u 0 ratios sr concentrations and in 87 sr 86 sr are also observed suggesting that the latter are climate related these variations are interpreted in terms of major changes in the temperature the mean annual rainfall and its isotopic composition the isotopic composition of the mediterranean vapor source the soil moisture conditions and in the mixing proportions of sources with different 87 sr 86 sr ratios sea spray dust particles and dolomitic host rock

structural controls of fluid flow and gold mineralization in the easternmost parts of the karagwe ankole belt of north western tanzania abstract gold mineralization in the biharamulo region of western tanzania is confined to the sheared low angle basement cover contact between archaean basement gneisses of the tanzania craton and the structurally overlying low grade metamorphic metasediments of the mesoproterozoic karagwe ankole belt regional scale fluid flow along this detachment is indicated by the pervasive silicification and retrogression of wall rocks to pervasively foliated phyllonites and pyritization of particularly metasediments commonly graphite rich in the hanging wall of the shear zone gold mining centres on specific structural sites along the detachment but also in stratigraphically higher sections in the structurally overlying metasediments zones of gold mineralization along the detachment correlate with ne trending ramp structures dip angles 20 35 that are most ideally orientated for slip and reactivation within the low angle phyllonitic detachment repeatedly overprinted auriferous quartz vein stockworks in quartzofeldspathic gneisses immediately below the detachment indicate brittle fracturing of the competent footwall lithotypes during slip along the weaker detachment in cases of massive silicification up to 50 m thick quartz blows are formed along the contacts between detachment phyllonites and footwall gneisses the multiple overprinting relationships of successive quartz vein generations in these zones of massive silicification suggests that the quartz blows acted as competent blocks in the weak detachment causing the repeated overprint of earlier silicification by later fracturing and quartz veining events gold mineralization above the detachment and in stratigraphically higher metasediments is closely associated with fold structures that form part of the low grade metamorphic fold and thrust belt veining is particularly abundant in competent lithotypes such as quartzite and chemically reactive ferruginous mafic sills overprinting relationships between quartz vein sets illustrate fluid flow during fold amplification and importantly the final lock up stage of folds during which much of the mineralization was introduced oxygen isotope values for quartz veins indicate fluids were likely derived from clastic mainly metapelitic sedimentary sequences of the karagwe ankole fold belt the data also implies that the partially reworked archaean granitoid greenstone basement of the tanzania craton has not contributed to the fluid evolution and possibly gold mineralization the extent 100 km of the basement cover detachment and associated alteration is indicative for a regional scale fluid system gold mineralization is however controlled by local structures and lithological contrasts that require the detailed mapping and sampling of the regional structure

annual to sub annual resolution of multiple trace element trends in speleothems this study aims to establish evidence for the widespread existence of preserved high resolution trace element variations in speleothems that may have climatic significance ion microprobe analysis of speleothems reveals that annual to sub annual variations in element chemistry exist at five shallow western european cave sites crag cave county kerry and ballynamintra county waterford ireland uamh an tartair sutherland scotland grotte pere noel belgium grotta di ernesto ne italy with widely varying climatic geomorphic and geological settings the variations are not restricted to species mg sr and ba known to substitute directly for ca in the calcite lattice but include h f na and p phosphorus as phosphate displays the greatest variability and may have the most significance as a proxy for the seasonal temperature cycle because of its role as a nutrient element the technique allows estimation of growth rate of speleothems at any interval of interest which is one of several possible uses in palaeoclimatology

inverse ductile thinning via lower crustal flow and fold induced doming in the west carpathian eo alpine collisional wedge 1 continental core complexes are generally interpreted to result from extensional doming due to gravity driven upflow of lower crust in contrast the vepor dome is characterized by the lack of inverted density profile and relatively cold metamorphic field gradient which precludes an activation of rayleigh taylor instability instead the crustal structure of the vepor unit is marked by dense and weak metapelitic lower crust and light and strong granitoid upper crust inherited from variscan nappe stacking it is shown that the cretaceous eo alpine tectonic evolution of the vepor dome is controlled by the dynamics of two neighboring mechanically strong continental blocks i e the overthrusting of the suprastructural gemer unit from the south and the underthrusting of the fatric basement from the north structural metamorphic and geochronological data from the vepor unit imply two main phases of the convergent process 1 lower cretaceous crustal thickening due to overthrusting and internal deformation of the gemer unit together with upper crustal folding in the vepor unit led to the progressive development of the orogenic front parallel pressure gradient the instantaneous response of the lower crustal and low viscosity metapelites led to an along strike lower crustal flow accompanied by prograde barrovian type metamorphism 2 as the south vergent underthrusting of the fatric basement propagated to greater depths during the upper cretaceous the convergent process switched from top driven to bottom driven and the exhumation of the lower crust occurred via polyharmonic folding overall doming of the vepor unit induced upper crustal detachment faulting and eastward unroofing of the dome

refining the timing of eclogite metamorphism a geochemical petrological sm nd and u pb case study from the pohorje mountains slovenia eastern alps high pressure metamorphism in the pohorje mountains of slovenia austroalpine unit eastern alps affected n morb type metabasic and metapelitic lithologies thermodynamic calculations and equilibrium phase diagrams of kyanite phengite bearing eclogites reveal pt conditions of 2 1 gpa at t 750 c but within the stability field of quartz metapelitic eclogite country rocks contain the assemblage garnet phengite kyanite quartz for which calculated peak pressure conditions are in good agreement with results obtained from eclogite samples the eclogites contain a single population of spherical zircon with a low th u ratio combined constraints on the age of metamorphism come from u pb zircon as well as garnet whole rock and mineral mineral sm nd analyses from eclogites a coherent cluster of single zircon analyses yields a 206pb 238u age of 90 7 1 0 ma that is in good agreement with results from sm nd garnet whole rock regression of 90 7 3 9 and 90 1 2 0 ma end 8 for two eclogite samples the agreement between u pb and sm nd age data strongly suggests an age of approximately 90 ma for the pressure peak of the eclogites in the pohorje mountains the presence of garnet omphacite and quartz inclusions in unfractured zircon indicates high pressure rather than ultrahigh pressure conditions the analysed metapelite sample yields a sm nd garnet whole rock scatterchron age of 97 15 ma these data probably support a single p t loop for mafic and pelitic lithologies of the pohorje area and a late cretaceous high pressure event that affected the entire easternmost austroalpine basement including the koralpe and saualpe eclogite type locality in the course of the complex collision of the apulian microplate and europe