field measurements of wet deposition in an extended region of complex topography a model designed to predict the enhancement of rainfall and the wet deposition of aerosol in complex terrain has been extended and compared with field data the results of five separate field studies performed over an extensive region of complex terrain in northern england are presented and compared with the model predictions it is found that the main features of the data are predicted by the model in widely varying conditions but the full details of a particular case study cannot be reproduced quantitatively owing to the complexities of the meteorology over the extended distances and collection periods the main physical processes controlling the deposition pattern have been established and it is concluded that a simple model of the seeder feeder process is able to give reasonable descriptions of deposition patterns in complex terrain both for individual episodes and for longer period averages

the compositions of coexisting pyroxenes and garnet in the system cao mgo al2o3 sio2 at 900 1 100 c and high pressures the compositions of coexisting orthopyroxene clinopyroxene and garnet in the cao mgo al2o3 sio2 system are fixed at any givenp andt reversed hydrothermal experiments over thep t range 15 40 kb 900 l 100 c indicate that the garnet composition is nearly constant at py86gr14 the alcontent and ca ca mg values of the pyroxenes vary significantly however t p wt al2o3 frac ca ca mg times 100 c kbar in opx in cpx in opx in cpx 900 15 3 55 2 92 0 72 47 05 900 30 1 62 0 92 0 81 47 30 1 100 20 1 11 0 92 1 22 45 20 1 100 40 1 26 0 88 0 81 45 64 the significant variation of a12o3 content with pressure supports its use as a geobarometer the ca ca mg values of coexisting orthoand clino pyroxene have been used as a geothermometer however the present results show that the presence of a12o3 in the pyroxenes decreases significantly the mutual solubility of the pyroxenes which may cause errors of up to 200 c if the a12o3 effect is ignored

facies distribution and textural variation in faro drift contourites velocity fluctuation and drift growth abstract detailed study of seismic profiles piston cores and bottom photographs from the faro drift on the southern margin of portugal has led to a better understanding of drift development and its relationship to bottom current circulation data on the contourite facies characteristics and the surface microphysiography have been published elsewhere here we concentrate on sediment distribution and geometry longitudinal trends in facies types mean grain size sedimentary structures and composition can be interpreted in terms of relative intensity of currents over different parts of the drift these are generally more intense in the marginal channels and at the upstream or eastern end of the drift three different scales of vertical variation of facies can be identified at the large scale 300 500 m of sediment has accumulated over 4 6 ma in a regular vertical succession due to the northward progradation of the drift at the medium scale the upper 20 30 m of sediment shows alternating phases of active lateral progradation and uniform vertical accumulation that may correlate with episodes of more and less current activity related to high and low sea level stands respectively over the past 0 3 ma at the small scale the topmost 2 3 m of sediment deposited in approximately 0 03 ma shows three zones of coarser grained sediments separated by finer grained contourites this sequence can also be interpreted in terms of long term fluctuation in bottom current activity although the signal is clearly complex this kind of analysis of sedimentary drifts can lead to more accurate reconstruction of paleocirculation patterns

rain shadow hydrology influences on river flows and flood magnitudes across the central massif divide of la grande terre island new caledonia summary within the tropical south pacific islands meaningful examination of how mountain barriers influence river flow characteristics has not previously been attempted owing principally to the lack of reliable long term data from an adequate number of basins that are geographically spread across opposing sides of a major topographic divide the island of la grande terre in new caledonia provides an exception since robust flow records with effective durations between 15 and 52 years are available for 22 monitored rivers draining both sides of a massif dividing range cross island differences in several fundamental hydrological parameters were statistically analysed including runoff coefficients median daily discharges and specific flood flows results identify that significant flow contrasts exist between windward versus leeward basins which are not necessarily revealed by observing patterns of rainfall distribution over the island power relationships are derived using both empirical and theoretically based models for maximum decadal q 10y and centennial q 100y flood size against catchment area with basins grouped according to windward or leeward location on la grande terre a key finding is that the rain shadow influence ri is essentially constant and therefore quantifiable across the central massif divide flood magnitudes for both q 10y and q 100y events are between 35 and 80 greater for windward versus leeward basins of equivalent size depending on whether empirical or accepted theoretical models are applied the term rain shadow hydrology is proposed for the generalised concept of windward vs leeward divergence in hydrological patterns in spite of being developed for the la grande terre situation the theme has relevance for neighbouring high islands in the tropical south pacific and therefore contributes to understanding tropical island hydrological characteristics in the trade wind belt however the transferability of estimated ratios of the rain shadow influence ri ratios requires validation with flow data from other islands especially to establish windward vs leeward differences in flood magnitude basin area relationships

high resolution studies of rainfall on norfolk island part iii a model for rainfall redistribution abstract a dense network of high resolution rain gauges has provided data on spatial scales of about 1 5 km and time scales of 15 sec on norfolk island where the topography is dominated by a 300 m hill that is found to modify the spatial distribution of rainfall depending on wind direction a correlation method is used to track coherent storm motion so as to identify the dominant wind direction and speed transects are selected across the island in the wind direction and the rainfall interpolated along each transect it is found that there is often a decrease in rainfall upwind of the hill followed by an increase downwind of the peak the ratio of downwind to upwind catches increases linearly with wind speed these observations do not accord with the often accepted explanation using a seeder feeder mechanism a simple wind drift model is proposed in which raindrops follow trajectories modified by the perturbed wind flow over the hill the transects are approximated by bell shaped hill profiles analytic solutions for potential flow over a cylinder are then used to find a streamline with a bell shape similar to a topography transect through the hill and aligned with the wind direction this streamline is used as the solid surface boundary thereby giving a direct analytic flow field for the bell shaped hill a streamfunction is found for drop motion allowing rainfall variations to be predicted a parameterisation is developed that explains the shape and magnitude of the observed rainfall variations along a transect agreement between the rudimentary model and observations is found possible to within a few percent this indicates that the wind drift process is viable as the dominating mechanism for determining rainfall distribution in the presence of low hills when low level moisture is absent

diffusion gradients in an eclogite xenolith from the roberts victor kimberlite pipe 1 mechanism and evolution of garnet exsolution in al2o3 rich clinopyroxene

oriented precipitates of quartz and amphibole in clinopyroxene of metabasites from the greek rhodope a product of open system precipitation during eclogite granulite amphibolite transition in metabasites from the high grade metamorphic kimi complex of the greek rhodope lamellae of quartz and amphibole were observed together with either rutile or titanite precipitates in the cores of clinopyroxene that underwent a prolonged exhumation history from eclogite via granulite and amphibolite facies conditions lamellae are crystallographically oriented along clinopyroxene cleavage planes 010 and interpreted as the result of precipitation during a two step intracrystalline compositional adjustment from an omphacite to a ca tschermak rich clinopyroxene and finally to diopside even though retrograde diffusion profiles develop in clinopyroxene the diffusion rates of highly charged ions like si4 al3 and ti4 are too slow so precipitates rich in si4 quartz al3 amphibole and ti4 rutile or titanite form as viable kinetic alternatives these precipitation reactions are not possible isochemically and additional exchange of ions with the matrix is required for precipitation to occur this exchange of mainly rapidly diffusing low charge ions is postulated to proceed by bulk diffusion self diffusion and does not require special pathways or fluid even though these may play an additional role during metamorphism this hitherto undescribed process of precipitation made possible by diffusional exchange with the matrix through an intact host crystal lattice is termed here as open system precipitation osp no prior ca eskola rich ultrahigh pressure uhp composition of omphacite is required to explain the observed precipitates it is proposed that many precipitation phenomena that were hard to explain in a closed system scenario can now be explained more readily by osp calculation of an original solid solution composition as in an uhp phase from precipitate and host mineral analyses becomes imprecise to the degree that bulk diffusion and hence osp have been important

an investigation of the influence of latent heat release on cold frontal motion abstract the effects of condensational heating on cold frontal translation speed are explored through the use of potential vorticity pv diagnostics and model sensitivity experiments it is hypothesized that condensational heating can lead to faster frontal translation speeds in the presence of vertical shear because of the horizontal propagation of the positive pv anomaly associated with the front a case study of a cold front with an evolving precipitation structure is presented a positive correlation existed between the position of condensational heating relative to the frontal zone and frontal translation speed with faster frontal movement occurring when condensational heating was present in the prefrontal zone this front was numerically simulated to see if the hypothesized mechanism for frontal movement was active through the use of a pv budget it was confirmed that condensational heating did contribute to the forward propagation of the cold frontal pv band numerical experiments were performed

paleomagnetic dating of postglacial sediment offshore lake superior minnesota wisconsin u s a abstract four gravity cores and two piston cores obtained from offshore regions of lake superior were analyzed for variations in geomagnetic declination and inclination in natural remanent magnetization nrm sedimentation rates in offshore lake superior 20 cm 1000 yr are much slower than in great lakes environments where paleomagnetic dating has been applied before typically 1 m 1000 yr five of the six cores could be correlated on the basis of declination and four of the six could be correlated on the basis of inclination absolute age assignment to declination events by correlation to a radiocarbon dated core from lake st croix minnesota tentatively shows that sedimentation rates in lake superior have changed from relatively fast to relatively slow to intermediate values in postglacial times

mineralogy petrology u pb geochronology and geologic evolution of the dabie sulu classic ultrahigh pressure metamorphic terrane east central china the dabie sulu triassic collisional orogen in eastern asia was created by northward subduction of the yangtze continental crust capped plate beneath the sino korean craton eclogites garnet peridotites and surrounding country rock gneisses and marbles were all subjected to in situ uhp metamorphism as indicated by the presence of rare but widespread coesite inclusions in eclogitic minerals and in zircon crystals in the country rocks as well as by virtually identical metamorphic ages of various uhp rock types metamorphic p t estimates combined with investigations of mineral exsolution textures and high p polymorphs indicate that recovered depths of continental subduction may have exceeded 200 km parageneses of mineral inclusions in zoned zircon domains combined with u pb ages delineate a well constrained p t time path suggesting exhumation rates of 5 10 km myr a similar p t time trajectory has been established for the microdiamond bearing kokchetav massif thus far however diamond inclusions have not been confirmed from coesite bearing zircon domains of dabie sulu uhp rocks despite numerous detailed studies oxygen isotopes of minerals from many outcrop samples and the chinese continental scientific drilling ccsd project main hole cores indicate that delta 18 o depletion took place in a volume of proterozoic protoliths exceeding 100 000 km 3 along the northern edge of the yangtze craton evidently passive margin sediments and bimodal igneous rocks that had formed during rifting and breakup of the supercontinent rodinia were subjected to extensive meteoric water rock interactions attending terminal neoproterozoic snowball earth conditions such hydrothermal alteration volatilized and depleted c from the relatively oxidized protoliths accounting for the rare occurrences of graphite and apparent lack of microdiamond in dabie sulu uhp rocks

crystallographic orientation relationships in host inclusion systems new insights from large ebsd data sets crystallographic orientation relationships cors between mineral inclusions and their hosts could potentially deliver information about inclusion formation processes and conditions most previous studies are based on small numbers of analyses this paper uses ebsd to study host inclusion cors in an inclusion rich permian metapegmatite garnet koralpe region eastern alps austria demonstrating the importance of large data sets and of ebsd in particular for the analysis of cors the distribution of measured orientations reflects host garnet point group symmetry for 89 of inclusions analyzed total n 530 each inclusion phase rutile corundum and ilmenite shows at least three different cors to host garnet statistical cors are introduced to describe distributions of inclusion orientations that have one or two degrees of freedom with respect to the host but still reflect host crystal symmetry two end member characteristics of statistical cors are distinguished rotation and dispersion most statistical cors observed show a mixture of both each inclusion phase shows at least one statistical cor multiple coexisting cors and statistical cors are not restricted to rutile re examination of previous garnet rutile cor studies in light of the new results indicates that cor information may have been overlooked when using small data sets variation in cor parameters correlates with broad differences in assumed metamorphic conditions for new and literature samples suggesting that petrogenetic information may be available if cor formation can be understood the favorability of the detected cors cannot be explained by a simple model involving minimization of misfit between lattice planes implying that other interface properties or the inclusion formation mechanism are important controls on cor development

on the origin of oriented rutile needles in garnet from uhp eclogites although oriented rutile needles in garnet have been reported from several ultrahigh pressure uhp rocks and considered to be important uhp indicators their crystallographic features including growth habit and lattice correspondences with garnet host have never been properly characterized this paper presents a detailed analytical electron microscopic aem study on evenly distributed oriented rutile needles in garnet of two eclogitic rocks from sulu some garnet in one uhp diamondiferous quartzofeldspathic rock from the saxonian erzgebirge and in one high pressure hp felsic granulite from bohemia also contain a few unevenly distributed oriented rutile needles they have also been studied for the purpose of comparison despite different distribution patterns aem revealed that all rutile needles are oriented along the 111 directions of garnet with their lateral sides surrounded by the 110 planes of garnet and that the growth directions of most needles are close to the normal of the 101 planes of rutile no other specific crystallographic orientation relationships between rutile and garnet host were observed and there is no pyroxene associated with rutile as necessitated by the precipitation reaction of rutile in garnet as previously proposed a simple solid state precipitation scenario for the formation of the rutile needles in garnet in these two eclogitic rocks is not justified three alternative mechanisms are considered for the formation of oriented rutile needles i the rutile needles may be inherited from precursor minerals ii the rutile needles may be formed by a dissolution reprecipitation mechanism and iii the rutile needles may be formed by cleaving and healing of garnet with rutile deposition none of these mechanisms can fully explain the observations although the first one is less likely and the third one is preferred this study presents an example where the presence of oriented aligned inclusions in minerals does not necessarily imply a precipitation origin

a tem study of the oriented orthopyroxene and forsterite inclusions in garnet from otroy garnet peridotite wgr norway new insights on crystallographic characteristics and growth energetics of exsolved pyroxene in relict majoritic garnet regularly oriented orthopyroxene opx and forsterite fo inclusions occur as opx rutile rt or fo rt inclusion domains in garnet grt from otroy peridotite electron diffraction characterization shows that forsterite inclusions do not have any specific crystallographic orientation relationships cor with the garnet host in contrast orthopyroxene inclusions have two sets of cor that is cor i grt opx and 110 grt 100 opx 13 off and cor ii grt opx and 110 grt 100 opx 14 off in four garnet grains analysed both variants of orthopyroxene have a blade like habit with one pair of broad crystal faces parallel sub parallel to 110 grt plane and the long axis of the crystal opx for cor i and opx for cor ii along grt direction whereas the lack of specific cor between forsterite and garnet along with the presence of abundant infiltrating trails veinlets decorated by fo rt at garnet edges provide compelling evidence for the formation of forsterite inclusions in garnet through the sequential cleaving infiltrating precipitating healing process at low temperatures the origin of the epitaxial orthopyroxene inclusions in garnet is not so obvious in this connection the reported cor the crystal habit and the crystal growth energetics of the exsolved orthopyroxene in relict majoritic garnet were reviewed clarified the exsolved ortho pyroxene in a relict majoritic garnet follows cor iii 112 grt 100 opx and grt opx based on the detailed trace analysis on published sem images these exsolved orthopyroxene inclusions are shown to have the crystal habit with one pair of broad crystal faces parallel to 112 grt 100 opx and the long crystal axis along grt opx such a crystal habit can be rationalized by the differences in oxygen sub lattices of both structures and represents the energetically favoured crystal shape of orthopyroxene inclusions in garnet formed by solid state exsolution mechanism considering the very different cor crystal habit as well as crystal growth direction the orthopyroxene inclusions in garnet of the present sample most likely had been formed by mechanism s other than solid state exsolution regardless of their regularly oriented appearance in garnet and the cor specification between orthopyroxene and garnet in fact the crystallographic characteristics of orthopyroxene and the similar chemical compositions of garnet at opx rt inclusion domains fo rt inclusion domains trails and garnet rim suggest that the orthopyroxene inclusions in the garnet are most likely formed by similar cleaving infiltration process as forsterite inclusions though probably at an earlier stage of metamorphism this work demonstrates that the oriented inclusions in host minerals with or without specific cor can arise from mechanism s other than solid state exsolution caution is thus needed in the interpretation of such cor so that an erroneous identification of exhumation from uhp depths would not be made

geochronology and isotopic character of ultrahigh pressure metamorphism with implications for collision of the sino korean and yangtze cratons central china the collision zone between the sino korean and yangtze cratons in central china is marked by subduction related metamorphic rocks composed of crustal protoliths these range in metamorphic grade from ultrahigh pressure eclogite to low greenschist facies the paragenesis of the ultrahigh pressure rocks coesite and diamond bearing indicates subduction to depths greater than 120 km as a result of continental collision despite extreme metamorphic conditions zircons have not undergone pb loss but rather illustrate two periods of growth crystallization between 700 and 800 ma and ultrahigh pressure metamorphism at 218 2 5 ma previous studies have predicted a time transgressive collision but age data presented in this study indicate that the collision was approximately coeval along the length of the suture u pb zircon ages of these ultrahigh pressure metamorphic rocks are 218 4 2 5 ma and 217 1 8 7 ma for the dabie mountains and shandong peninsula respectively the similar ages imply that the tan lu fault which offsets the ultrahigh pressure metamorphic rocks is a secondary feature not related to collision or subduction whole rock isotopic data show that both rb sr and u pb were open systems during metamorphism but that sm nd probably remained closed nd initial isotopes display crustal signatures indicating that the crust subducted as a coherent slab rather than becoming intercalated with mantle material at depth sm nd data in conjunction with u pb zircon dating indicate that the ultrahigh pressure rocks are not typical yangtze craton basement 2 9 ga but that they originally crystallized in a rift environment between 700 and 800 ma discrepancies between 40ar 39ar plateaus sm nd isochrons and u pb zircon ages render calculation of a p t t path unrealistic

a three dimensional model of airflow and orographic rainfall enhancement a three dimensional model of airflow over hills has been used in conjunction with a two dimensional model of orographic rainfall enhancement this development has allowed the accurate production of rainfall contour maps in areas of complex terrain a comparison has been made using a variety of atmospheric stability profiles between the wind fields and rainfall distributions over a bell shaped hill and those over a two dimensional ridge of similar height the results show that in conditions of either stably stratified air or with an inversion layer aloft three dimensional airflow effects can lead to much reduced rainfall over a bell shaped hill it is shown that in such situations the use of a two dimensional approximation can introduce significant errors an example is presented of the rainfall distribution in complex hill terrain over south kintyre on the western coast of scotland

multiply exsolved clinopyroxene megacrysts from the frank smith mine cape province south africa abstract two clinopyroxene megacrysts from the frank smith kimberlite show multiple exsolution of garnet orthopyroxene and oxide phases in one of the megacrysts the lamellar texture has partly recrystallized to a granular one the chemical compositions of the exsolved phases are similar to those of discrete nodules and of granular pyroxenites found in the same kimberlite conditions of formation of the original homogeneous clinopyroxene solid solution are estimated to be 1500 c and 37 kb whereas the re equilibration conditions are closer to 900 c and 35 kb the megacrysts may have belonged to the karroo age magnetism which predated kimberlite activity and have been brought to the surface as accidental xenocrysts by the frank smith kimberlite

modification of garnet by fluid infiltration during regional metamorphism in garnet through sillimanite zone rocks dutchess county new york metapelitic rocks from a progressive metamorphic sequence in dutchess county new york record evidence for reaction between garnet and fluids associated with quartz plagioclase veins and for net transfer among garnet interiors mineral inclusions and fluid garnet fluid reaction resulted in modification of preexisting garnet textures compositions and growth zoning patterns the textural and compositional record of garnet fluid interaction varies with grade and with proximity of garnet to quartz veins garnet zone rocks do not contain evidence for extensive reaction with vein forming fluids in upper stauroliteand kyanite zone rocks garnet that is crosscut by quartz veins contains a fluid inclusion filled region near the garnet vein interface this region truncates growth zoning patterns and quartz inclusions fluid inclusions in garnet decrease in abundance away from quartz veins in some rocks lacking quartz veins fluid inclusions are concentrated in garnet interiors and in particular near fractures and are notably lacking around mineral inclusions in garnet inferences from textural and compositional features combined with thermobarometric results indicate that preexisting garnet grains were modified at t 525 550 c and 4 kbar by one or more reactions involving fluids the fluid pathways included foliationparallel channels in the rock as well as microcracks in mineral grains

timing of bottom water scour recorded by sedimentological parameters in the south australian basin abstract the south australian basin has been the site of extensive antarctic bottom water aabw scour during the late cenozoic the combination of detailed stratigraphy and sedimentological analyses of three piston cores allowed the identification of the major episodes of high bottom current paleovelocity the chronology of the cores was determined by magnetostratigraphy and biostratigraphy five parameters mean mode skewness coarsest 1 and sorting of the carbonate free silt particle size distribution were used to infer periods of high paleovelocity sorting was found to be an insensitive parameter within the inferred paleovelocity regimes the two major high velocity episodes during the last 3 3 m y occurred during the gauss chron and the upper matuyama chron several short episodes of high bottom water velocity occurred during the matuyama chron only one minor pulse was identified during the brunhes chron 0 0 73 m y b p the high velocity episode during the gauss chron produced a disconformity separating miocene and middle pliocene sediments while the upper matuyama episode may be responsible for the widespread disconformity at or near the seafloor which has been identified in many cores in the region

stably stratified shear flow over low hills summary an analysis is presented for the mean flow over hills with low slopes for various kinds of stable stratification in the approach flow the froude number f based on the height is always greater than unity the analysis is based on dividing up the flow into different regions with different dynamics we concentrate on the flow in the inviscid outer region of the flow it is shown that in the lower part of the outer region the middle layer where the shear is large the upwind velocity profile and the shape of the hill rather than the upwind density profile largely determine the vertical perturbation velocity in the upper layer the structure of the flow depends largely on the form of the upwind density profile for example this largely determines the location of maximum surface wind new solutions for stable conditions are obtained when there is a constant density gradient when n ub 0 z2 and when there is an elevated inversion layer in the first and third of these cases we compare the results with the hydrostatic approximation and also obtain new general formulae for the near surface winds an approximate formula is developed for surface winds at arbitrary values of f 1 for uniform stable stratification

chlorite stability in mantle peridotite the reaction clinochlore enstatite forsterite pyrope h2o chlorite crystallising in hydrated mantle peridotite is a potential source of water for subduction zone volcanism the reaction clinochlore enstatite forsterite pyrope h2o is the important reaction for defining the stability of chlorite in these rocks it has been investigated in phase equilibrium experiments in piston cylinder and multi anvil apparatus between 2 and 5 gpa the reaction has a steep negative p t slope at low pressures with brackets at 860 880 c at 2 5 gpa 840 860 c at 3 0 gpa and 820 840 c at 3 5 gpa the reaction flattens out with increasing pressure to 5 0 gpa at 650 c chlorite compositions close to the reaction were determined from unit cell parameters measured using high resolution synchrotron powder diffraction these showed a decrease in al content with increasing pressure along the reaction consistent with calculations using a previously published thermodynamic data set the experimental results are consistent with the results of earlier studies on the reaction defining the maximum thermal stability of clinochlore clinochlore forsterite pyrope spinel h2o they have been used in the derivation of revised thermodynamic data for clinochlore in the latest version of the previously published data set the new results show that chlorite in subducting slab or overlying mantle wedge could dehydrate below subduction zone volcanoes and be a major source of the water required for melting however the dehydration reaction is not sufficiently pressure dependent to be responsible for the narrow range in depth from the volcanoes to the slab and chlorite will not be the only hydrous mineral involved

exsolved silicate and oxide phases from clinopyroxenes in a single hawaiian xenolith implications for oxidation state of the hawaiian upper mantle a single garnet bearing clinopyroxenite xenolith from the salt lake crater on oahu hawaii contains two distinct types of clinopyroxene one contains exsolved garnet ilmenite and magnetite and the other contains exsolved hercynite pleonaste spinel orthopyroxene and ilmenite application of mineral geothermometers barometers and oxygen barometers to this unusual combination of exsolved phases defines the following conditions of last mantle equilibration of this xenolith p 19 kbar t 1153 c and log 10 f o 2 9 7

origin of rutile needles in star garnet and implications for interpretation of inclusion textures in ultrahigh pressure metamorphic rocks the asterism effect of star garnet has been attributed to the oriented distribution of needle like rutile inclusions rutile needles occur in garnet from a wide range of metamorphic settings and rock bulk compositions and their origin has been ascribed to different mechanisms such as exsolution and used to interpret petrological and tectonic processes results from an optical and transmission electron microscopy of idaho star garnet indicate a co precipitation origin it was found that rutile needles are predominantly oriented along the rt grt and rt grt directions following multiple crystallographic orientation relationships cors i e cor 1 2 2 3 4 and 5 in 6 ray star garnet and are oriented solely along the rt grt directions following exclusively cor 2 in 4 ray star garnet the sole presence of cor 2 grt needles in the common 4 ray star garnet in contrast to the presence of both grt and grt needles with multiple cors in the rare 6 ray star garnet suggests that the cor 2 grt needle probably is the energetically most favoured variant as is also supported by the coincidence site lattice considerations the unique crystallography controlled microstructures of 4 ray star garnet including the cloudy domains behind the 111 grt or 100 grt fronts with abundant inclusions of rutile needle rutile compound needle and multiple phase inclusion as well as the clear domains behind the 110 grt fronts with only a few above inclusions concentrated exclusively within the linear grt oriented continuous tube like domains further suggest that the cor 2 grt needles in 4 ray star garnet most likely have a growth in origin co precipitating with garnet at its growth fronts close to thermodynamic equilibrium conditions the 6 ray star garnet on the other hand most likely formed under far from equilibrium conditions thereby yielding a maximum of 99 crystallographic variants of rutile needles with multiple cors in a single crystal in the light of these findings along with the common occurrences of the sole cor in many inclusion host systems owing to the requirement to minimize the energy barrier in an exsolution process the presence of both rt grt and rt grt needles with multiple cors in garnet of sulu eclogite and erzegebirge quartzofeldspathic rock would therefore cast doubt on the assertion of an exsolution origin of rutile needles in garnet from these ultrahigh pressure rocks

the al 2 o 3 contents of enstatite in equilibrium with garnet in the system mgo al 2 o 3 sio 2 at 15 40 kbar and 900 1 600 c forty six reversed determinations of the al2o3content of enstatite in equilibrium with garnet were made in the p t range 15 40 kbar 900 1 600 c in the mgo al2o3 sio2 system starting materials were mixtures of synthetic pyrope al free enstatite and pyrope enstatite 5 12 al2o3 al2o3 contents in reversal run pairs closely approached common values from both the high and low al sides most experiments were done in a piston cylinder device using a nacl medium some runs at very high temperatures were made in pyrex nacl or pyrex talc assemblies the measured enstatite compositions expressed as mole fractions of mg2 mgal alsi3 o12 x opy en were fitted by a monte carlo method to the equilibrium condition begin gathered delta h 970 0 970 delta s 970 0 hfill mathop smallint limits 1 p delta v 970 0 dp mathop smallint limits 970 t delta s t 0 dt rt ln x opy en 0 hfill end gathered where the best fit parameters of h s and v 1 bar 970 k for the reaction pyrope opy are 2 040 cal mol 2 12 eu and 9 55 cc mol in addition to the determination of al2o3 contents of enstatite the univariant reaction pyrope forsterite enstatite spinel was reversibly located in the range 1 100 1 400 c a best fit line passes through 22 22 5 and 25 kbar at 1 040 1 255 and 1 415 c respectively our results for the univariant reaction are in agreement with previous studies of macgregor 1974 and haselton 1979 however comparison of the experimentally determined curve with thermochemical calculations suggests that there may be a small error in the tabulated h f 970 1 0 value for enstatite a value of 8 32 rather than 8 81 kcal mole charlu et al 1975 is consistent with the present data application of garnet enstatite spinel forsterite equilibria to natural materials is fraught with difficulties the effects of nonternary components are poorly understood and the low solubilities of al2o3 in enstatite under most geologically reasonable conditions make barometric or thermometric calculations highly sensitive more detailed studies including reversed determinations in low friction assemblies are sorely needed before the effects of important diluents such as fe ca and cr can be fully understood

clinopyroxenite from the sulu ultrahigh pressure terrane eastern china origin and evolution of garnet exsolution in clinopyroxene the rizhao garnet clinopyroxenite occurs as small mantle slices faulted into subducted continental crust in the sulu ultrahigh pressure uhp terrane china two representative garnet clinopyroxenites with exsolution microstructures were studied 1 a massive ilmenite rich specimen composed of coarse grained clinopyroxene containing abundant exsolution rods of grossular rich garnet 20 vol ilmenite 3 4 vol in a fine grained matrix of clinopyroxene garnet ilmenite and 2 megacrystic garnet bearing sample characterized by garnet containing inclusions of clinopyroxene and ilmenite the clinopyroxene inclusions show exsolution rods and blebs with variable amounts of garnet 1 15 vol and minor ilmenite both exsolved and matrix garnets have similar grossular rich compositions the aggregate composition of clinopyroxene garnet ilmenite intergrowth is similar to the whole rock composition we propose that the parental phase of exsolved garnet ilmenite lamellae and clinopyroxene host was either a homogeneous clinopyroxene hypothesis a or a majoritic garnet hypothesis b that experienced three discrete evolution stages if the parental phase was clinopyroxene abo3 with an si deficiency in the b site the rizhao garnet clinopyroxenite could have an initial assemblage clinopyroxene grt ilm formed at near solidus conditions 1400 c at 5 gpa in the upper mantle the second stage is defined by garnet exsolution from the primary clinopyroxene involving decreasing temperature and or increasing pressure related to continental subduction coexisting clinopyroxene host and garnet exsolution grtexs recrystallized at temperatures of 900 c at an assumed minimum p of 5 gpa the third stage is represented by recrystallization of exsolution phases to form the fine grained matrix of cpx grt ilm at 700 c and 3 gpa during the early exhumation of the uhp terrane the speculative hypothesis b implies that the proposed majoritic garnet was from the mantle transition zone 450 km depth this suggestion remains to be tested

rainfall redistribution over low hills due to flow perturbation abstract a simple potential flow model is developed for airflow over low hills the model readily allows incorporation of simple rain microphysics so that drop trajectories can be traced in the region of a hill complex rainfall intensity variations are found in the horizontal and in the vertical and a straightforward modification to the model allows for time dependence to be studied the model is shown to serve as a useful diagnostic tool to describe rain drop redistribution due to perturbed airflow in particular increased rainfall is predicted in the lee of hill peaks and depleted rainfall is predicted on ridges the redistribution effects dominate at low levels in contrast to predictions based on seeder feeder enhancement comparison with field measurements shows good qualitative agreement over low hills and in some cases close quantitative agreement redistribution of rain appears to be a significant process that should be considered in rainfall interpolation and prediction schemes involving hilly terrain

lamellar pyroxenes and their petrogenetic significance three examples from the czech massif the first event in the crystallization of pyroxenite in nodules from bory was the growth of clinopyroxene at an uncertain 1 190 30 c and 2 5 2 gpa lamellae of garnet and orthopyroxene in cpx nucleated slightly above 1 000 c and equilibrated at 940 20 c and 3 9 6 gpa the growth of lamellae was followed by crystallization of groundmass that corroded lamellar clinopyroxene phenocrysts of clinopyroxene and orthopyroxene in olivine pyroxenite from t i studn crystallized at 1 290 100 c and 2 3 1 4 gpa the lamellae in both phases nucleated between 1 400 and 1 200 c and equilibrated at 860 40 c and 0 2 3 gpa before regional metamorphism the temperatures of nucleation mentioned rest on uncertain assumptions in the phase boundary theory and should be viewed with caution the serpentinized peridotite pyroxenite from destna contains clinopyroxene relics the only primary phase with lamellae of a 1 42 nm sheet silicate topotactically pseudomorphing enstatite possibly a chlorite or vermiculite all phases in lamellae are crystallographically oriented in the hosts the present cases suggest that when applying the theory of phase boundaries a modified procedure of robinson et al should also be considered in which identity of adjacent areas rather than just vectors is the basis of calculation spinel lamellae in cpx are bounded not only by faces parallel to coherent interfaces but also by faces formed by accumulation of incoherent edges of growth ledges

impact of wind on the spatial distribution of rain over micro scale topography numerical modelling and experimental verification the wind driven rain effect refers to the redistribution of rainfall over micro scale topography due to the existence of local perturbed wind flow patterns rainfall measurements reported in the literature point to the fact that the wind driven rain distribution can show large variations over micro scale topography these variations should be taken into account in hillslope hydrology in runoff and erosion studies and in the design of rainfall monitoring networks in practice measurements are often not suitable for determining the wind driven rain distribution therefore a few researchers have employed numerical modelling in order to provide confidence in using numerical models experimental verification for a range of different topographic features is imperative the objective of this study is to investigate the adequacy of a two dimensional computational fluid dynamics cfd model to predict the wind driven rain distribution over small scale topography the numerical model is applied to a number of topographic features including a succession of cliffs a small isolated hill a small valley and a field with ridges and furrows the numerical results are compared with the corresponding measurement results reported in the literature it is shown that two dimensional numerical modelling can provide a good indication of the wind driven rain distribution over each type of micro scale topography that is considered in this study it is concluded that more detailed verification procedures are currently inhibited due to the lack of available and detailed spatial and temporal rainfall data from field measurements copyright 2005 john wiley sons ltd

apatite monazite relations in the kiirunavaara magnetite apatite ore northern sweden the magnetite apatite ores in the kiruna area northern sweden are generally considered to be of magmatic origin formed in a subvolcanic volcanic environment during the early proterozoic they are thought to have crystallised from volatile rich iron oxide magmas derived by immiscibility in calc alkaline to slightly alkaline parental magmas three major morphological types of the magnetite apatite ore primary brecciated and banded have been investigated for textural relations and mineral chemistry using transmitted light back scattered electron imaging bse electron microprobe analysis empa and laser ablation inductively coupled plasma mass spectrometry la icpms in all three types th and u poor monazite is present as small inclusions in the apatite larger up to 150 m recrystallised monazite grains both along apatite grain boundaries and intergrown with magnetite and silicate minerals are present in the brecciated and banded samples primary apatite grains without monazite inclusions are generally enriched in light rare earth elements lrees together with na and si petrological and mineralogical evidence suggest that the kiruna magnetite apatite ore experienced successive stages of fluid rock interaction the first stage occurred under high temperature conditions 700 800 c shortly after emplacement and crystallisation of the ore magmas and involved concentrated probably cl dominated brines expelled from the magma this fluid is held to be responsible for the nucleation of the numerous small monazite inclusions within the apatite due to high temperature leaching of na and si while the lrees were concentrated in the monazite the large monazite grains in the brecciated and banded samples are proposed to be the product of recrystallisation from the much smaller monazite inclusions during greenschist facies metamorphism t 300 400 c fluids from the surrounding country rock caused strong lree na si depletion along apatite grain boundaries and cracks in the apatite lrees were either redeposited as monazite grains along apatite grain boundaries or were flushed out of the ore this fluid interaction also introduced the silicate components responsible for the interstitial formation of allanite talc tremolite chlorite serpentine muscovite quartz and carbonates along apatite grain boundaries

airflow over hills of moderate slope a three layer model is presented this describes the flow on an inversion capped boundary layer over hills of moderate size and slope the linearized vorticity equation is solved using non linear boundary conditions the pressure field developed in the boundary layer is used to calculate a modified inner region velocity field jackson and hunt 1975 a low level inversion with height i 2h is found to decrease the speed up near the ground when i 2h the flow of the inversion layer shows an increasing tendency to be subcritical this leads to a much increased speed up increasing the stability of air above the inversion increases the asymmetry of the flow this causes an upwind lull and a subsequent rapid increase in the flow speed with very high wind speeds at the summit and downwind comparison of the theory with simple observations made on great dun fell cumbria shows encouraging agreement

mesoscale dynamics of cold fronts structures described by dropsoundings in fronts 87 the fronts 87 project was a european experiment to make mesoscale observations to deduce the dynamics of active cold fronts approaching north west europe with a minimum of orographic influences in this paper data from dropsoundings made by the meteorological office s c 130 research aircraft are analysed the aircraft flew a pattern with 4 or 5 runs oriented approximately at right angles to the front but with each run displaced in the along front direction by about 100 km the dropsondes gave soundings to a height of approximately 7 km with a cross frontal spacing of 20 km at best and 60 km on average between 30 and 50 soundings were made in each event over an area of 500 500 km2 these data are unique in their mesoscale resolution over a synoptic scale region this was made possible by the ability to track up to 5 sondes in the air at any time several new aspects of cold front dynamics have been identified from these data the approach here is to treat each run as an instantaneous cross frontal section the discussion is centred on the hypotheses postulated before the experiment these were intended to allow verification or refutation of aspects of models of frontal dynamics such as those embodied in semi geostrophic theory a minimal and purely objective analysis has been performed on the data presented here but the high resolution of the dropsonde observations permits evaluation of differentiated quantities such as potential vorticity pv with some confidence issues raised here include the degree of thermal wind balance the structure of conserved variables such as equivalent potential temperature and absolute momentum the cross frontal circulation and the role of diabatic processes such as the evaporation of snow and the potential vorticity structure on the mesoscale and its interpretation the intention is to present an integrated view of the dynamical structure of fronts in the light of theoretical rather than conceptual or airflow models

on the mechanism of resorption zoning in metamorphic garnet an analytical electron microscope study of almandine garnet from a metamorphosed al fe rich rock revealed detailed composition profiles and defect microstructures of resorption zoning along fluid infiltrated veins and even into the garnet ilmenite inclusion interface this indicates a limited volume diffusion for the cations in substitution mainly ca and fe and an interface controlled partition for the extension of a composition invariant margin a corrugated interface between the ca rich margin zone and the almandine garnet core is characterized by dislocation arrays and recovery texture further suggesting a resorption process facilitated by diffusion induced recrystallization diffusion induced dislocation migration and diffusion induced grain boundary migration integrated microstructural and chemical studies are essential for understanding the underlying mechanisms of processes such as garnet zoning and its modification without this understanding it will not be possible to reliably use garnet compositions for thermobarometry and other applications that rely on garnet chemical information

tio2 exsolution from garnet by open system precipitation evidence from crystallographic and shape preferred orientation of rutile inclusions we investigated rutile needles with a clear shape preferred orientation in garnet from ultra high pressure metapelites from the kimi complex of the greek rhodope by electron microprobe electron backscatter diffraction and tem techniques a definite though complex crystallographic orientation relationship between the garnet host and rutile was identified in that rt 001 is either parallel to grt or describes cones with opening angle 27 6 around grt each rt 001 small circle representing a cone on the pole figure displays six maxima in the density plots this evidence together with microchemical observations in tem when compared to various possible mechanisms of formation corroborates a precipitate origin a review of exchange vectors for ti substitution in garnet indicates that rutile formation from garnet cannot occur in a closed system it requires that components are exchanged between the garnet interior and the rock matrix by solid state diffusion a process we refer to as open system precipitation osp the kinetically most feasible reaction of this type will dominate the overall process the perhaps most efficient reaction involves internal oxidation of fe2 to fe3 and transfer from the dodecahedral to the octahedral site just vacated by text ti 4 6 text m 2 3 text tial left text alsi 2 right text o 1 2 6 text m 2 2 5 text tialsi 3 text o 1 2 10 text m 2 3 0 text al 1 8 text fe 0 2 text si 3 text o 1 2 text m 2 2 text e 1 2 text tio 2 osp is likely to occur at conditions where the transition of natural systems to open system behaviour becomes apparent as in the granulite and high temperature eclogite facies

titanium solubility in coexisting garnet and clinopyroxene at very high pressure the significance of exsolved rutile in garnet exsolution microstructures including ilmenite garnet in clinopyroxene and rutile in garnet are common in clinopyroxenite and eclogite from the sulu ultrahigh pressure uhp terrane in order to understand the phase relations and ti solubility in both garnet and clinopyroxene in a natural tio2 bearing system several experiments at 5 15 gpa 1000 1400 c were carried out using the multianvil high pressure apparatus the hujianlin ilmenite rich garnet clinopyroxenite showing exsolution microstructure was selected as starting material because it closely approaches a composition lying in the tio2 cao mgo feo al2o3 sio2 system except for minor melt in one experiment at 1400 c and 5 gpa other run products contain majoritic garnet clinopyroxene ilmenite or rutile and exhibit neoblastic texture with increasing pressure ti and ca mg and si contents of neoblastic garnet increase with decreasing al the principal coupled substitutions are ca2 ti4 2al3 and si4 mg2 2al3 responding to majorite component increase titanium solubility 0 8 4 5 wt as tio2 in garnet and grtti cpxti ratio have a pronounced positive correlation with pressure between 5 and 15 gpa on the other hand the coexisting clinopyroxene contains low ti 0 17 0 53 wt as tio2 and shows no significant pressure effect rutile exsolution in garnet is coupled to that of pyroxene exsolution both are exsolved from majoritic garnet on decompression therefore the amount of such exsolved lamellae is a potential indicator of high pressure metamorphism in exhumed rocks whereas the tio2 content of clinopyroxene coexisting with garnet is not sensitive to pressure change

sedimentation in large lakes processes associated with sedimentation in these lakes is in its infancy the large lakes of the world are precious resources that provide their nearby inhabitants with abundant fresh water food economical transpor tation and recreation they also provide additional benefits to the geologist unique paleoclimatic records and useful basins in which to test models of aquatic sedimentary processes this paper summarizes the global distribution oflarge lakes and focuses upon their geological attributes

aerial observations of hawaii s wake abstract under the influence of the east northeasterly trade winds the island of hawaii generates a wake that extends about 200 km to the west southwest during the harp project in july and august 1990 five wake surveys were carried out by the ncar electra the patterns of wind and aerosol concentration revealed by these flights suggest that hawaii s wake consists of two large quasi steady counterrotating eddies the southern clockwise rotating eddy carries a heavy aerosol load due to input from the k volcano at the eastern end of the wake the eddies are potentially warmer and more humid than the surrounding trade wind air several other features are discussed sharp shear lines near the northern and southern tips of the island dry and warm air bands along the shear lines a small embedded wake behind the kohala peninsula wake centerline clouds hydraulic jumps to the north and south of the island a descending inversion connected with accelerating trade winds and evidence for side to side wake mo

synoptic reconstruction of a major ancient lake system eocene green river formation western united states numerous 40ar 39ar experiments on sanidine and biotite from 22 ash beds and 3 volcaniclastic sand beds from the greater green river piceance creek and uinta basins of wyoming colorado and utah constrain 8 m y of the eocene epoch multiple analyses were conducted per sample using laser fusion and incremental heating techniques to differentiate inheritance 40ar loss and 39ar recoil when considered in conjunction with existing radioisotopic ages and lithostratigraphy biostratigraphy and magnetostratigraphy these new age determinations facilitate temporal correlation of linked eocene lake basins in the laramide rocky mountain region at a significantly increased level of precision to compare our results to the geomagnetic polarity time scale and the regional volcanic record the ages of eocene magnetic anomalies c24 through c20 were recalibrated using seven 40ar 39ar ages overall the ages obtained for this study are consistent with the isochroneity of north american land mammal ages throughout the study area and provide precise radioisotopic constraints on several important biostratigraphic boundaries applying these new ages average sediment accumulation rates in the greater green river basin wyoming were approximately three times faster at the center of the basin versus its ramp like northern margin during deposition of the underfilled wilkins peak member in contrast sediment accumulation occurred faster at the edge of the basin during deposition of the balanced filled to overfilled tipton and laney members sediment accumulation patterns thus reflect basin center focused accumulation rates when the basin was underfilled and supply limited accumulation when the basin was balanced filled to overfilled sediment accumulation in the uinta basin at indian canyon utah was relatively constant at 150 mm k y during deposition of over 5 m y of both evaporative and fluctuating profundal facies which likely reflects the basin margin position of the measured section the most rapid sediment accumulation for the entire system 1 m k y occurred between 49 0 and 47 5 ma when volcaniclastic materials from the absaroka and or challis volcanic fields entered the green river formation lakes from the north our new ages combined with existing paleomagnetic and biostratigraphic control permit the first detailed synoptic comparison of lacustrine depositional environments in all the green river formation basins coupled with previously published paleocurrent observations our detailed correlations show that relatively freshwater lakes commonly drained into more saline downstream lakes the overall character of eocene lake deposits was therefore governed in part by the geomorphic evolution of drainage patterns in the surrounding laramide landscape freshwater overfilled lakes were initially dominant 53 5 52 0 ma possibly related to high erosion rates of remnant cretaceous strata on adjacent uplifts expansion of balanced fill lakes first occurred in all green river formation basins at 52 0 51 3 ma and again between 49 6 and 48 5 ma evaporative underfilled lakes occurred in various basins between 51 3 and 45 1 ma coincident with the end of the early eocene climatic optima and subsequent onset of global cooling defined from marine record however evaporite intervals in the different depocenters were deposited at different times rather than being confined to a single episode of arid climate evaporative terminal sinks were initially located in the greater green river and piceance creek basins 51 3 48 9 ma then gradually migrated southward to the uinta basin 47 1 45 2 ma this history is likely related to progressive southward construction of the absaroka volcanic province which constituted a major topographic and thermal anomaly that contributed to a regional north to south hydrologic gradient the greater green river and piceance creek basins were eventually filled from north to south with absarokaderived detritus at sedimentation rates 1 2 orders of magnitude greater than the underlying lake deposits

wind profiles in the stable boundary layer and the effect of low relief wind profiles through the stable boundary layer are presented the data were collected at a site located in a shallow river valley and show evidence of upstream effects near the edge of the valley the wind speed profiles are consistent with a non dimensional shear om 1 3z l for z l 0 5 changes in wind speed and direction are found to occur over a greater depth than the depth of the turbulent nocturnal boundary layer estimated from various diagnostic formulae

airflow over a two dimensional escarpment ii hydrostatic flow hydrostatically dominated forced flow over the asymmetric topography of the darling scarp western australia is modelled using a hydrostatic numerical mesoscale model and compared with observations simulations reproduce the essential features of wave overturning and the development of a shooting hydraulic flow this response is dependent on the wind profile but not on the existence of a critical level the high backsheared environment leads to a high ratio of the brunt vaisala frequency to wind speed throughout the profile resulting in short wavelengths high nonlinearity and overturning with the ratio of the halfwidth of the topography to the boundary layer depth being small the flow fields are shown to be sensitive to the boundary layer

effects of bottom currents and fish on sedimentation in a deep water lacustrine environment sands and muds accumulating under the influence of apparently strong bottom currents in a deep water environment of lake superior were studied in detail using 3 5 khz echo sounding side scan sonar piston gravity and box coring and lake floor photography the study area includes a well defined slope and basin environment bottom currents maintain a scoured trough 20 m deep and 2 km wide at the base of the slope and modify the shapes of large ringlike depressions that are common in many regions of lake superior side scan sonar records reveal lineations subparallel to the direction of bottom current flow that are interpreted in different areas to be sand ribbons slight depressions or depositional furrows the sediments range from silty sand in the scoured trough to sandy clays farther offshore radiocarbon dating and 210 pb dating show the sediments to be postglacial rather than relic glacial lacustrine sediments grain size distributions are affected by bottom currents and a nearby source of sand some sedimentary structures including plane laminations and interbedded sands and muds are due to bottom currents fish create dish laminations however that often obscure the effects of the bottom currents fish and fish scour depressions are common in lake floor photographs whereas evidence for bottom currents is not biological activity therefore appears to erase traces of intermittent currents

orographic effects during a severe wintertime rainstorm in the appalachian mountains abstract the evolution of precipitation features during a severe wintertime rainfall and flooding event associated with a cold front that crossed the central appalachians on 19 january 1996 is illustrated through the analysis of radiosonde rainfall and streamflow gauge data and wsr 88d images striking evidence of the linkage between heavy precipitation cells and orography was obtained by tracking the movement of the center of mass of storm precipitation which closely followed the contours of regional orographic features higher intensity precipitation cells were consistently located windward of the orographic crest and the trajectory described by the center of mass of precipitation was also consistent with the spatial arrangement of the river basins where hazardous flooding occurred persistent low intensity 5 mm h 1 rainfall was registered in these basins during the 12 h period that preceded the arrival of frontal storm activity it is argued that this prefrontal precipitation had a critical im

deep sea bottom currents differentiated from texture of underlying sediment abstract forty five core top samples taken in the vema channel southwest atlantic within the deduced boundaries of two important bottom currents have been analyzed for the particle size distribution of the noncarbonate silt size fraction this was done in order to characterize the sediment beneath each water mass using statistical and graphical methods it was found that sediment beneath the high velocity antarctic bottom water in the bottom of the channel exhibits the coarsest mean size poor sorting and a large percent of coarse silt left as a lag deposit sediment beneath the overlying low velocity north atlantic deep water is marked by fine mean size good sorting no coarse silt and a large percent of fine silt sediment beneath the intervening transition zone is characterized by fine t mean size moderate sorting largest percent fine silt and a small lag component of coarse silt the methods developed for delineating bottom currents in the vema channel may be applied to a wide range of benthic oceanographic settings as well as the geologic record in order to examine relative paleovelocity fluctuations of major bottom currents

an aem study of garnet clinopyroxenite from the sulu ultrahigh pressure terrane formation mechanisms of oriented ilmenite spinel magnetite amphibole and garnet inclusions in clinopyroxene optical microscopy secondary electron microscopy and analytical electron microscopy were used to characterize crystallographic orientation relationships between oriented mineral inclusions and clinopyroxene cpx host from the hujialing garnet clinopyroxenite within the sulu ultrahigh pressure uhp terrane eastern china one garnet clinopyroxenite sample 2hj 2c and one megacrystic garnet bearing garnet clinopyroxenite rz 11d were studied porphyroblastic clinopyroxene from sample 2hj 2c contains oriented inclusions of ilmenite ilm spinel spl magnetite and garnet whereas clinopyroxene inclusions within megacrystic garnet from sample rz 11d contain oriented inclusions of ilmenite and amphibole specific crystallographic relationships were observed between ilmenite spinel plates and host clinopyroxene in sample 2hj 2c and between ilmenite plates and host clinopyroxene in sample rz 11d i e 1 bar 1 00 ilm 0 bar 1 0 cpx 0001 ilm 100 cpx and 110 spl 0 bar 1 0 cpx bar 1 11 spl 100 cpx these inclusions are suggested to be primary precipitates via solid state exsolutions most of the needle like magnetite spinel inclusions generally occur at the rims or along fractures of clinopyroxene within sample 2hj 2c despite the epitaxial relation with host clinopyroxene these magnetite spinel needles would have resulted from fluid melt infiltrations non epitaxial garnet lamellae in clinopyroxene of sample 2hj 2c were formed via fluid infiltration deposition primarily along 010 and subordinately along 100 partings epitaxial amphibole plates with a thickness 1 m and lamellae with a thickness 1 10 m in host clinopyroxene of sample rz 11d were probably results of hydration processes although amphibole plates could otherwise be interpreted as exsolution products temporal relations between mineral inclusions in each sample can be established and a semi quantitative p t path for this garnet clinopyroxenite body was derived accordingly the present results show that the hujialing garnet clinopyroxenite may not have subducted to mantle depths as deep as 250 km during uhp metamorphism as suggested by previous studies this study demonstrates that the crystallographic and temporal spatial relationships between aligned inclusions and host minerals are essential to a correct genetic interpretation of metamorphic rocks

thermodynamics of water solubility and partitioning when it was realized that nominally anhydrous minerals could be a major storage site of water in the mantle smyth 1987 bell and rossman 1992 it also became rather obvious that many mantle samples probably have lost most of their water during ascent e g ingrin and skogby 2000 while analyses of natural samples therefore in many circumstances only provide a lower limit of the actual water content in the mantle measurements of water solubility give an upper limit of the amount of water that might be stored in a mineral experimental measurements of water solubility have therefore naturally evolved in the last decades as a major tool for understanding the water storage capacity of the mantle closely related to studies of water solubility are studies of water partitioning among minerals if the water solubility in two minerals is known under given conditions the partition coefficient is just the ratio of the water solubilities under the same conditions provided that the composition of the fluid coexisting with the two minerals is the same since the pioneering work of bai and kohlstedt 1992 and of kohlstedt et al 1996 the water solubility in all major upper mantle minerals has been studied as well as the partitioning of water between the minerals of the lower mantle and the transition zone solubility studies by themselves do not directly give the water content in the mantle they constrain the storage capacity of the mantle i e the maximum amount of water that may be stored if the mantle were water saturated however as most of the mantle is very likely water undersaturated the actual water content is probably far below the storage capacity estimates of the actual abundance and distribution of water in the mantle may be obtained by combining solubility and partitioning data with direct

spatial rainfall distribution at a storm event in mountainous regions estimated by orography and wind direction in this paper the orographical effect for rainfall distribution at a storm event is discussed the main effect is represented by the ground forced ascending current of air a three dimensional numerical model of the hydrostatic atmosphere including basin orography is used to estimate the ascending current area for any wind direction the authors also propose a new concept named directional probability of storm event dipose a severe storm is more likely to occur when the wind blows from a high dipose direction rather than from a low dipose direction the wind direction at a storm event is determined from a dipose analysis and is used in the numerical model the calculated ascending air region is regarded as a severe rainfall area in mountainous river basins the results are examined and compared with observations

regionalization of extreme precipitation distribution using the principal components of the topographical environment this paper deals with the regionalization of the extreme rainfall intensities in the volcanic island of tahiti french polynesia and focuses how the method automatically takes into account the topographical relief features principal component analysis of a digital elevation model supplies a limited set of variables describing the topographical environment these synthetic descriptors are linked to the parameters of the rainfall intensity gumbel distribution by using a stepwise regression adjusted on 20 point rainfall records the model is then applied on a regular 300 points grid node and interpolated using a spline function to provide an approximation of the pluviometric risk all over the island in the case of the island of tahiti the relationship between the rainfall parameter distributions and the topographical descriptors is very strong and the method supplies a direct estimation in space of the rainfall statistics through the regression model validation of the results and comparison with simple kriging interpolation show the relevance of the approach however more data are needed for a better confidence in the parameter estimation in some areas of the island this automatic and objective method could be applied in any mountainous area where topography has a major influence on the precipitation features to characterize the non stationarity of point rainfall statistics in space

petrology of ultrahigh pressure rocks from the southern su lu region eastern china abstract in the su lu ultrahigh p terrane eastern china many coesite bearing eclogite pods and layers within biotite gneiss occur together with interlayered metasediments now represented by garnet quartz jadeite rock and kyanite quartzite in addition to garnet omphacite rutile coesite other peak stage minerals in some eclogites include kyanite phengite epidote zoisite talc nyboite and high al titanite the garnet quartz jadeite rock and kyanite quartzite contain jadeite quartz garnet rutile zoisite apatite and quartz kyanite garnet epidote phengite rutile omphacite assemblages respectively coesite and quartz pseudomorphs after coesite occur as inclusions in garnet omphacite jadeite kyanite and epidote from both eclogites and metasediments study of major elements indicates that the protolith of the garnet quartz jadeite rock and the kyanite quartzite was supracrustal sediments most eclogites have basaltic composition some have experienced variable crustal contamination or metasomatism and others may have had a basaltic tuff or pyroclastic rock protolith the su lu ultrahigh p rocks have been subjected to multi stage recrystallization and exhibit a clockwise p t path inclusion assemblages within garnet record a pre eclogite epidote amphibolite facies metamorphic event ultrahigh p peak metamorphism took place at 700 890 c and p 28 kbar at c 210 230 ma the symplectitic assemblage plagioclase hornblende epidote biotite titanite implies amphibolite facies retrogressive metamorphism during exhumation at c 180 200 ma metasedimentary and metamafic lithologies have similar p t paths several lines of evidence indicate that the supracrustal rocks were subducted to mantle depths and experienced in situ ultrahigh p metamorphism during the triassic collision between the sino korean and yangtze cratons

crystallographic orientations of magnesiochromite inclusions in diamonds what do they tell us we have studied by x ray diffractometry the crystallographic orientation relationships cors between magnesiochromite mchr inclusions and their diamond hosts in gem quality stones from the mines udachnaya siberian russia damtshaa botswana and panda canada in total 36 inclusions in 23 diamonds in nearly half of the cases n 17 111 mchr is parallel within error to 111 diamond but the angular misorientation for other crystallographic directions is generally significant this relationship can be described as a case of rotational statistical cor in which inclusion and host share a single axis 1 df the remaining mchr diamond pairs n 19 have a random cor 2 df the presence of a rotational statistical cor indicates that the inclusions have physically interacted with the diamond before their final incorporation of all possible physical processes that may have influenced mchr orientation those driven by surface interactions are not considered likely because of the presence of fluid films around the inclusions mechanical interaction between euhedral crystals in a fluid rich environment is therefore proposed as the most likely mechanism to produce the observed rotational cor in this scenario neither a rotational nor a random cor can provide information on the relative timing of growth of mchr and diamond some multiple iso oriented inclusions within single diamonds however indicate that mchr was partially dissolved during diamond growth suggesting a protogenetic origin of these inclusions