how are diagenesis and reservoir quality linked to depositional facies a deltaic succession edgeoya svalbard abstract middle to late triassic strata exposed at edgeoya eastern svalbard represents an uplifted part of the northwestern corner of the barents sea this interval is characterized by a predominantly mud dominated deltaic depositional system where rocks with petroleum reservoir potential are expected both in delta front and channelized sandstone deposits recent drilling campaigns into time equivalent rocks in the barents sea have however been disappointing with porosity and permeability below expectation this study improves the current understanding of reservoir potential within depositional systems of this kind by examining the link between different depositional facies diagenesis and their impact on reservoir quality five depositional facies were mapped and correlated channel floodplain shallow marine prodelta and offshore our study suggests that diagenetic signatures that control the quality of reservoir rocks vary systematically with these depositional facies mechanical compaction was the main cause of porosity destruction in the channel shallow marine and floodplain samples while early carbonate cementation occludes the intergranular volume in the prodelta samples moreover quartz cement reduced the porosity in the shallow marine depositional facies the estimated maximum burial temperature of 124 c indicates burial to several km depths depositional settings within a deltaic to shallow marine system do not exert a strong control on the abundance of chlorite but it does impact whether the chlorite is pore filling or grain coating and porosity preserving efficient chlorite coating have aided in preserving porosities up to 32 in the very well well sorted medium to fine grained sandstones deposited by fluvial dominated channels

circulation about the mediterranean tongue an analysis of an eof based model ocean abstract absolute circulation about the mediterranean salt tongue is examined using a combined box spiral inverse model applied to a model ocean constructed from a limited number of degrees of freedom the region of analysis is inside a square box 12 on each side centered about 30 n 25 w the resulting flow field is consistent with other recent analyses of the region but demonstrates that no mixing is required to obtain a consistent picture the circulation consists of an anticyclonic flow order 1 cm s 1 above the thermocline and a cyclonic flow order 1 mm s 1 near the core of the mediterranean water these findings imply that an efficient description of the hydrographic structure of the ocean retains essential features of the ocean from which circulation can be determined

characterisation of archaeological mortars and plasters from kyme turkey abstract the present study focuses on the compositional characterisation of roman proto byzantine and medieval mortars sampled in the archaeological site of kyme turkey an aeolian city founded in the middle of the xi century bc by greek populations the mortars were studied through elemental sem eds xrf mineralogical xrpd de astis calcimeter and petrographic polarised optical microscopy analysis the comparison between the samples allowed us to emphasise compositional differences within mortars of the same historical period in particular we detected the prevalent use of cocciopesto which was used as a pozzolanic additive to create hydraulic mortars in the roman and byzantine period the cocciopesto was used to improve the technological properties of an initially slaked lime furthermore compositional similarities allowed us to attribute an unknown sample to the roman period our study also pointed out the fact that the lower quality mortars belonged to the medieval period as a matter of fact the most friable sample belonging to the middle ages turned out to be a mixture of clay lime and volcanic sand

the spatial distribution of grains and crystals in rocks characterisation and analysis of the spatial distribution pattern sdp of grains or crystals in rocks is potentially a powerful technique which can be used to constrain the processes which operate in the formation of rocks a method to quantify the sdp of grains in thin section is presented the distance betwen the centre of a grain and the centre of its nearest neighbour is calculated for all the grains in the sample area to produce a distribution of distances that characterises the spatial pattern of grains in the rock this distribution is then normalised to a random distribution of points with the same population density to give a descriptive value r values of r for rock samples are plotted against porosity modal abundance of other phases in igneous and metamorphic rocks to characterise the sdp the sdp of randomly packed distributions of equal size spheres varies systematically with porosity producing a line on a porosity versus r plot termed the random sphere distribution line rsdl rocks which plot above the rsdl have an ordered sdp and those that plot below a clustered sdp the effects of variation in grain packing order grain sorting compaction and random crystallisation overgrowth on determined r values were investigated using a combination of 3 d sphere models and 2 d texture models the maximum possible value of r is 2 148 corresponding to a perfect section through hexagonal cubic close packing of grains the minimum value of r is dependent on the proportion of grains in the sample volume and may be as low as 1 2 for a sample volume with 30 grains which are clustered variations in size sorting can cause r to vary by approximately 0 25 mechanical compaction of a loose framework of grains results in a higher packing order and an increase in r continued compaction creates a fabric in the texture and r decreases as cluster patterns are developed perpendicular to the principal stress the overgrowth of grains in a touching framework alters the location of the geometric grain centre as the crystal shape changes leading to an increase in r as porosity decreases results reveal that grain sorting compaction and grain overgrowth produce different r versus porosity relationships which can be identified in and therefore used to constrain the relative importance of these processes in rock samples

a simple model of the large scale circulation of mediterranean water and labrador sea water abstract a steady 2 1 2 layer planetary geostrophic model is used to study the circulation and mixing of mediterranean water mw and labrador sea water lsw the model includes parameterizions of salt fingering mesoscale variability and meddies a close relationship between the vertical density ratio and expected strength of salt fingering and the potential vorticity anomaly of the upper salt tongue is identified and used to parameterize salt fingering as a spatially nonhomogeneous diapycnal mass flux a balance between baroclinic rossby wave propagation and salt fingering produces an asymmetric tongue of potential vorticity extending into the interior from the eastern boundary consistent with the observed mediterranean salt tongue the resulting internal pressure gradients give rise to a large scale anticyclonic circulation in the upper layer of the salt tongue with northward flow at mid latitudes consistent with geostrophic flow estimates based on hydrographic data salt fingering that attains maximum strength at mid latitudes forces a large scale circulation in the lower mw lsw depth range that advects water from the western boundary into the eastern basin near 50 n where it then flows to the south under the upper mw and finally returns to the western boundary this pattern is generally consistent with a variety of estimates for the circulation of lsw and suggests that the eastward flow of lsw off the western boundary may be at least in part forced by salt fingering in the interior the addition of mixing due to mesoscale eddies modifies the details of the potential vorticity distribution but does not change the qualitative behavior representing meddies as a distributed source of mass to the upper layer results in a further westward extension of the salt tongue signature and enhances the strength of the deep recirculation

rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste the interaction of groundwater with cement in a geological disposal facility gdf for intermediate level radioactive waste will produce a high ph leachate plume such a plume may alter the physical and chemical properties of the gdf host rock however the geochemical and mineralogical processes which may occur in such systems over timescales relevant for geological disposal remain unclear this study has extended the timescale for laboratory experiments and shown that after 15 years two distinct phases of reaction may occur during alteration of a dolomite rich rock at high ph in these experiments the dissolution of primary silicate minerals and the formation of secondary calcium silicate hydrate c s h phases containing varying amounts of aluminium and potassium c a k s h during the early stages of reaction up to 15 months have been superseded as the systems have evolved after 15 years significant dedolomitisation mgca co3 2 2oh mg oh 2 caco3 co32 aq has led to the formation of magnesium silicates such as saponite and talc containing variable amounts of aluminium and potassium mg al k silicates and calcite at the expense of the early formed c a k s h phases this occured in high ph solutions representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a koh and naoh or a ca oh 2 dominated solution but a greater extent of alteration in the higher ph koh naoh leachate the high ph alteration of the rock over 15 years also increased the rock s sorption capacity for u vi the results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomite rich rock in the geosphere these processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geological disposal

the lower zone critical zone transition of the bushveld complex a quantitative textural study the lower zone critical zone boundary of the bushveld complex is an intrusion wide major stratigraphic transition from ultramafic harzburgite and pyroxenite in the lower zone to increasingly plagioclase richpyroxenitesandnoritesinthecriticalzone quantitative textural and compositional data for 29 samples through this transition show the following lower zone orthopyroxene grains are larger have higher aspect ratios are better foliated and have a lower trapped liquid component than those of the critical zone the larger grain size of the lower zone results in crystal size distribution plots that are rotated to lower slopes and intercepts relative to those in the critical zone although all rocks show differing amountsoffoliation mineral lineations are weak to absent these data are consistent with significant compaction driven recrystallization in the study section numerical modeling of concurrent compaction and crystallization provides a quantitative model of how the lower zone critical zone transition may have formed plagioclase is rare in the lower zone because compaction removes interstitial liquid before it reaches plagioclasesaturation however asthecrystalpilegrows plagioclase saturation is reached in the interstitial liquid before compaction is complete in more evolved pyroxenites producing more abundant but still modest amounts of plagioclase characteristic of the lower critical zone it is concluded that both the textures and the modal mineralogy are largely controlled by compaction and compactiondriven recrystallization primary magmatic textures are not preserved

interdecadal variability of the thermohaline circulation in box ocean models forced by fixed surface fluxes intrinsic modes of decadal variability are analyzed using box geometry ocean models forced by constant surface fluxes an extensive parameter sensitivity analysis of the oscillatory behavior is carried out with respect to the spherical cartesian geometry the b effect the coriolis parameter the parameterization of momentum dissipation and associated boundary conditions the vertical and horizontal diffusivities the convective adjustment algorithm the horizontal and vertical model resolution the forcing amplitude and the basin width the oscillations stand out as a robust geostrophic feature whose amplitude is mainly controlled by the horizontal diffusivity unsuccessful attempts to reproduce the variability in zonally averaged 2d models suggest that the 3d adjustment processes are necessary however the b effect is not necessary for decadal variability to occur and therefore classical rossby waves play no fundamental role in the mechanism various experiments with different geometry and forcing are conducted and do not support the necessity of viscous numerical boundary waves or any boundary in sustaining the oscillations the models show two types of oscillatory behavior 1 temperature anomalies propagating geostrophically westward in the eastward jet northern part of the basin and inducing an opposite anomaly in their wake and 2 stationary temperature anomalies in the northwest quarter that respond to the western boundary current transport changes and reinforce geostrophically this change until the opposite temperature anomaly built on the east finally reverses the meridional overturning anomaly the analysis of the transition from steady to oscillatory states using heat fluxes diagnosed at the equilibrium under restoring boundary conditions and the comparison of the variability under various forcing fields suggest that the oscillations are triggered in the regions of strongest surface cooling finally a simple box model analogy is proposed that captures the crucial phase shift between meridional overturning and north south density gradient anomalies on these decadal timescales

carbon oxygen and sulphur isotope variations in concretions from the upper lias of n e england carbon oxygen and sulphur isotope data for transects across two pyrite bearmg carbonate concretions and their host sediments from the upper lias of n e england show symmetrical zonation 13cpdb values of the calcite cement 12 9 to 15 4 indicate that most of it originated from organic matter by bacterial reduction of sulphate augmented with marine and to a lesser extent fermentation derived carbonate organic carbon 13cpdb 26 1 to 37 0 reflects the admixture of allochtho nous terrestrial organic matter with marine material and the selective preservation of isotopically light organic material through microbiological degradation two phases of pyrite are present in each concretion the earlier framboidal pyrite formed throughout the sediment prior to concretionary growth and has 34scd values of 22 to 26 indicating formation by open system sulphate reduction the later euhedral phase is more abundant and reaches values of 2 5 to 5 5 at concretion margins this phase of sulphate reduction provided the carbonate source for concretionary growth and occurred in a partially closed system the 13c and 34s data are consistent with mineralogical and chemical evidence which suggest that both concretions formed close to the sediment surface the 18o values of the calcite in one concretion 18opdb 2 3 to 4 8 indicate precipitation in pore waters whose temperature and isotopic composition was close to that of overlying seawater the other concretion is isotopically much lighter 18opdb 8 9 to 9 9 and large 18o differences between concretions in closely spaced horizons imply that local factors control the isotopic composition of pore waters

products and timing of diagenetic processes in upper rotliegend sandstones from bebertal north german basin parchim formation flechtingen high germany aeolian fluvial upper rotliegend sandstones from bebertal outcrops flechtingen high north germany are an analogue for deeply buried permian gas reservoir sandstones of the north german basin ngb we present a paragenetic sequence as well as thermochronological constraints to reconstruct the diagenetic evolution and to identify periods of enhanced mesodiagenetic fluid rock reactions in sandstones from the southern flank of the ngb bebertal sandstones show comparatively high concentrations of mesodiagenetically formed k feldspar but low concentrations of illite cements illite rich grain rims were found to occur preferentially directly below sedimentary bounding surfaces i e aeolian superimposition surfaces and indicate the lowest intergranular volume illite grain rims also indicate sandstone sections with low quartz and feldspar cement concentrations but high loss of intergranular volume due to compaction 40ar 39ar age determination of pronounced k feldspar grain overgrowths and replacements of detrital grains indicates two generations an early triassic and a late jurassic generation the latter age range is similar to published diagenetic illite ages from buried rotliegend reservoir sandstones the first generation suggests an early intense mesodiagenetic fluid flow with remarkably high k activity synchronous with fast burial of proximal initial graben sediments on the southern flank of the ngb accordingly zircon fission track data indicate that the strata already reached the zircon partial annealing zone of approximately 200 c during early mesodiagenesis zircon u th he ages 92 12 ma as well as apatite fission track ages 71 75 ma indicate the termination of mesodiagenetic processes caused by rapid exhumation of the flechtingen high during late cretaceous basin inversion

melt extraction from crystal mushes numerical model of texture evolution and calibration of crystallinity ordering relationships abstract mechanical crystal melt interactions in magmatic systems by separation or accumulation of crystals or by extraction of interstitial melt are expected to modify the spatial distribution of crystals observed as phenocrysts in igneous rocks textural analysis of porphyritic products can thus provide a quantitative means of interpreting the magnitude of crystal accumulation or melt loss and reconstructing the initial crystal percentage at which the process occurred we present a new three dimensional numerical model that evaluates the effects of crystal accumulation or interstitial melt removal on the spatial distribution of crystals both processes lead to increasing apparent crystallinity but also to increasing spatial ordering expressed by the clustering index r the trend of progressive crystal packing deviates from a random texture trend produced by static crystal nucleation and growth and it is universal for any texture with straight log linear crystal size distribution for sparse crystal suspensions 5 vol crystals r 1 03 up to 97 melt can be extracted corresponding to a new crystallinity of 65 vol and r 1 32 when the rheological threshold of crystal interlocking is reached for initially crystal rich suspensions the compaction path is shorter this is because the initial crystal population is more aggregated and it reaches the limit of interlocking sooner crystal suspensions with 35 vol crystals cannot be compacted without mechanical failure these results illustrate that the onset of the rheological threshold of magma immobility strongly depends on the spatial configuration of crystals in the mush the primary rigid percolation threshold 35 vol crystals corresponds to touching or interlocking crystal framework produced by in situ closed system crystallization whereas the secondary rigid percolation threshold 35 to 75 vol crystals can be reached by compaction which is particularly spatially efficient when acting on sparse crystal suspensions illustrative quantitative evaluation of the crystallinity clustering relationships to representative porphyritic granites from a single intrusive unit of the krkonose jizera pluton central europe reveals a single crystal accumulation path starting at low initial crystallinity 5 7 vol k feldspar phenocrysts with 24 84 melt extracted leading to the observed crystallinity of 9 26 vol by contrast a camptonite dyke from the ceske st edoho i volcanic province has experienced the onset of crystal accumulation later 18 vol amphibole crystals and lost 23 interstitial melt only the combination of modal and clustering analysis offers a sensitive tool for identifying differentiation processes in natural magma chambers and here it illustrates examples of mechanically dominated open system vs in situ nearly closed system crystallization from two contrasting magmatic settings

a statistical analysis of the distribution of cordierite and biotite in hornfels from the bugaboo contact aureole implications for the kinetics of porphyroblast crystallization

crystal rich mass flow deposits related to the eruption of a sublacustrine silicic cryptodome early permian collio basin italian alps abstract sedimentological granulometric and petrographic data are presented from a detailed study on a crystal rich mass flow deposit which is presumably related to the eruption of a sublacustrine cryptodome the deposit forms a prominent intercalation in the lower permian collio formation in the italian alps north of brescia outcrops of the 10 20 m thick volcaniclastic deposit dasdana i beds db can be traced over 12 km from east to west the db consists of a thick crystal rich sandy gravelly lower subunit representing a sequence of amalgamated bouma a b divisions overlain by a thin well bedded sandy muddy subunit that is rich in outsize porphyritic silicic fragments modal and computer aided image analyses reveal that the crystal rich lower subunit contains up to 80 of volcanogenic crystals some samples contain up to 60 of porphyritic fragments which have a phenocryst content of about 20 the wide textural range from cryptocrystalline poikilomosaic to rarer medium grained granophyric groundmass the irregular to lensoid shapes of the porphyritic fragments and the presence of basement and sedimentary clasts suggest that the db originated from a sublacustrine eruption of a partially extrusive cryptodome ca 1 6 km3 two other porphyritic felsic cryptodomes dosso dei lupi dosso del bue described briefly here emplaced into the collio formation sometime after the db event and expose flat bases and tilted sediments at their sides textures observed in these domes are comparable to those found in the db porphyritic fragments

feldspar dissolution authigenic clays and quartz cements in open and closed sandstone geochemical systems during diagenesis typical examples from two sags in bohai bay basin east china feldspar dissolution and precipitation of clays and quartz cements are important diagenetic reactions affecting reservoir quality evolution in sandstones with detrital feldspars we examined two sets of sandstone reservoirs to determine whether the sandstone diagenetic systems were open or closed to the mass transfer of products from feldspar dissolution and its impact on reservoir quality one of the reservoirs is the eocene fan delta sandstone buried 2 5 4 0 km 1 5 2 5 mi below sea level bsl in the gaoliu gl area of the nanpu sag and the other is the eocene subaqueous fan sandstone buried 1 5 4 5 km 1 2 8 mi bsl in the shengtuo st area of the dongying sag both sandstones consist mainly of lithic arkoses and feldspathic litharenites and have secondary porosity formed by dissolution of feldspars in the gl sandstones the absolute amounts of authigenic clays and quartz cements generally 125 c 257 f the low abundance of authigenic clays and quartz cements and low pore water salinity indicate that much of the and released from leached k feldspars were exported from the gl sandstone system and the extensive feldspar dissolution enhanced much porosity and permeability in contrast the st sandstones with secondary pores formed by feldspar dissolution generally contain authigenic clays kaolinite and illite and quartz cements with almost identical volume of secondary pores kaolinite dominates in the st sandstones at shallower depth 3 1 km 2 mi bsl where temperature exceeds 125 c 257 f the presence of abundant clays and quartz cements indicates that and released from leached feldspars were retained in the st sandstone system the dominance of authigenic illite at greater depth indicates that sufficient should have been retained within the sandstones for occurrence of illitization of kaolinite and feldspars secondary porosity in thin sections can be up to 3 but little porosity the diagenetic difference between the gl and the st sandstones can be interpreted by assessing pore water evolution in these two areas the current pore waters with low salinity and negative hydrogen isotopic compositions in the gl sandstone system indicate the significant impact of meteoric water whereas the current pore waters with high salinity and the paleofluids with positive oxygen isotopic compositions in the st sandstone system indicate little trace of meteoric water access of meteoric freshwater to the gl area probably occurred during the late oligocene to neogene through widely developed faults in the paleogene and neogene strata the low salinity water could have been responsible for flushing of solutes derived from feldspar dissolution as such diagenesis in the gl sandstones is considered to have occurred in an open geochemical system whereas with limited faults and high water salinity the st sandstones acted as a closed geochemical system where precipitation of kaolinite illite and quartz cements occurred following dissolution of feldspars

chromite in komatiites 3d morphologies with implications for crystallization mechanisms high resolution x ray computed tomography has been carried out on a suite of komatiite samples representing a range of volcanic facies chromite contents and degrees of alteration and metamorphism to reveal the wide range of sizes shapes and degrees of clustering that chromite grains display as a function of cooling history dendrites are spectacularly skeletal chromite grains formed during very rapid crystallization of supercooled melt in spinifex zones close to flow tops at slower cooling rates in the interiors of thick flows chromite forms predominantly euhedral grains large clusters up to a dozen of grains are characteristic of liquidus chromite whereas fine dustings of mostly individual 20 m grains form by in situ crystallization from trapped intercumulus liquid chromite in coarse grained olivine cumulates from komatiitic dunite bodies occurs in two forms as clusters or chains of euhedral crystals developing into chicken wire texture where chromite is present in supra cotectic proportions and as strongly dendritic semi poikilitic grains these dendritic grains are likely to have formed by rapid crescumulate growth from magma that was close to its liquidus temperature but supersaturated with chromite in some cases this process seems to have been favoured by nucleation of chromite on the margins of sulphide liquid blebs this texture is a good evidence for the predominantly cumulus origin of oikocrysts and in situ origin of heteradcumulate textures our 3d textural analysis confirms that the morphology of chromite crystals is a distinctive indicator of crystallization environment even in highly altered rocks

physical oceanography of the western iberia ecosystem latest views and challenges the present review is focused on the mesoscale physical processes recognized in the western iberia ecosystem complementing earlier reviews dedicated to larger scales recent studies support the idea that the mesoscale processes superimposed on the larger scale variability are the major factor controlling the ecosystem functioning in the region a complex structure of interleaved alongshore slope shelf and coastal currents that interact with eddies buoyant plumes upwelling filaments and fronts surface layer expressions of the subsurface circulation and internal waves is revealed by the latest research all of these contribute in different ways to have an effect on the ecosystem the supposedly less variable winter circulation also exhibits significant mesoscale activity in the form of eddy shedding from the poleward slope current intermittent upwelling events and transient nearshore poleward flows the present incomplete knowledge of this complex system presents a number of challenges and questions that must be addressed if we are to arrive at a satisfactory understanding and predictive capability for the system as a whole 2007 elsevier ltd all rights reserved

petrology and chemistry of mil 03346 and its significance in understanding the petrogenesis of nakhlites on mars antarctic meteorite miller range mil 03346 is a nakhlite composed of 79 clinopyroxene 1 olivine and 20 vitrophyric intercumulus material we have performed a petrological and geochemical study of mil 03346 demonstrating a petrogenetic history similar to previously discovered nakhlites quantitative textural study of mil 03346 indicates long 1 x 101 yr residence times for the cumulus augite whereas the skeletal fe ti oxide fayalite and sulfide in the vitrophyric intercumulus matrix suggest rapid cooling probably as a lava flow from the relatively high forsterite contents of olivine up to fo43 compared with other nakhlites and compositions of augite cores wo38 42en35 40fs22 28 and their hedenbergite rims we suggest that mil 03346 is part of the same or a similar martian cumulate rich lava flow as other nakhlites however mil 03346 has experienced less equilibration and faster cooling than other nakhlites discovered to date calculated trace element concentrations based upon modal abundances of mil 03346 and its constituent minerals are identical to whole rock trace element abundances parental melts for augite have ree patterns that are approximately parallel with whole rock and intercumulus melt using experimentally defined partition coefficients this parallelism reflects closed system crystallization for mil 03346 where the only significant petrogenetic process between formation of augite and eruption and emplacement of the nakhlite flow has been fractional crystallization a model for the petrogenesis of mil 03346 and the nakhlites nakhla governador valadares lafayette yamato 000593 northwest africa nwa 817 nwa 998 would include 1 partial melting and ascent of melt generated from a long term lree depleted mantle source 2 crystallization of cumulus augite olivine magnetite in a shallow level martian magma chamber 3 eruption of the crystal laden nakhlite magma onto the surface of mars 4 cooling crystal settling overgrowth and partial equilibration to different extents within the flow 5 secondary alteration through hydrothermal processes possibly immediately succeeding or during emplacement of the flow this model might apply to single or multiple flow models for the nakhlites ultimately mil 03346 and the other nakhlites preserve a record of magmatic processes in volcanic rocks on mars with analogous petrogenetic histories to pyroxene rich terrestrial lava flows and to komatiites

a new study of the mediterranean outflow air sea interactions and meddies using multisensor data previous studies of the mediterranean sea outflow and meddies o m were limited by the poor spatial and temporal resolution of conventional in situ observations as well as the confinement of satellite observations to the ocean s surface accordingly little is known about the formation and transport of meddies and the spatial and temporal variation of o m trajectories which are located on average at a depth of 1000 m however a new remote sensing method has been developed by the authors to observe and study the o m through unique approaches in satellite multisensor data integration analyses satellite altimeter scatterometer infrared satellite imagery and xbt data were used to detect and calculate the trajectories and the relative transport of the o m january 1993 december 2002 two experiments covering 1993 95 a mediterranean undercurrent seeding experiment amuse and structures des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore and xbt temperature measurements were used to directly validate the method presented herein the monthly mean features derived from floats and xbts for multiple meddies and the results of the presented method were significantly correlated based on a statistical chi square test in addition the complex singular value decomposition method was used to identify the propagating features and their phase speeds it was found that saltier water from the mediterranean sea was transported into the north atlantic ocean over the strait of gibraltar in boreal spring and summer relative to boreal autumn and winter streamfunctions using altimetry and time frequency energy distributions using the hilbert huang transform were computed to evaluate the meddy interactions with the sea surface variation since the o m play a significant role in carrying salty water from the mediterranean sea into the atlantic such new knowledge about their trajectories transport and life histories is important to the understanding of their mixing and interaction with north atlantic water this may lead to a better understanding of the global ocean circulation and global climate change

weak mixing in the eastern north atlantic an application of the tracer contour inverse method abstract the tracer contour inverse method is used to infer mixing and circulation in the eastern north atlantic solutions for the vertical mixing coefficient d the along isopycnal mixing coefficient k and a geostrophic streamfunction are all direct outputs of the method the method predicts a vertical mixing coefficient o 10 5 m2 s 1 in the upper 1000 m of the water column consistent with in situ observations the method predicts a depth dependent along isopycnal mixing coefficient that decreases from o 1000 m2 s 1 close to the mixed layer to o 100 m2 s 1 in the interior which is also consistent with observations and previous hypotheses the robustness of the result is tested with a rigorous sensitivity analysis including the use of two independently constructed datasets this study confirms the utility of the tracer contour inverse method the results presented support the hypothesis that vertical mixing is small in the thermocline of the subtropical atlantic ocean a strong depth dependence o

the peridotite plugs of rum crystal settling and fabric development in magma conduits the rum igneous complex contains numerous circular to elongate exposures of peridotite cumulates within the layered series and the country rock the extent of thermal effects on quartzo feldspathic country rock surrounding the mam tuath and west sgaorishal plugs demonstrates that these are pipe like bodies inclined at various angles to the vertical that remained at magmatic temperatures for periods of up to several months tabular olivine grains within the plugs preserve a weak sub horizontal fabric that is stronger in the plug centres than at their margins the olivine mode increases from 50 vol at the plug margins to 85 vol at the centre the spatial arrangement of the olivine grains is consistent with their being clustered with the increase in mode towards the plug centres achieved by a combination of overgrowth and mechanical re arrangement comparison of fabrics with those of the ard mheall peridotites of the rum western layered intrusion is consistent with porosity reduction in the ard mheall cumulates also having been primarily achieved by overgrowth and mechanical re arrangement compaction via intra crystalline deformation did not occur we suggest that the rum ultramafic plugs are deep level cross sections presenting the ultimate snap shots of volcanic conduits through which olivine rich magmas flowed for substantial periods probably giving rise to fire fountains of the kind associated with hawaiian eruptions the exposed parts of the plugs are now miniature cumulate bodies that developed in situ from the settling of olivine phenocrysts once flow had ceased within the conduit

global observations of horizontal mixing from argo float and surface drifter trajectories mixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers with important implications for physical and biochemical systems at local to global scales roach et al 2016 https doi org 10 1002 2015jc011440 demonstrated that a two particle analysis of argo trajectories produces robust estimates of horizontal mixing in the southern ocean here we extend this analysis to produce global 1 1 maps of eddy diffusivity at the nominal argo parking depth of 1 000 m we also applied this methodology to estimate surface eddy diffusivities from global drifter program gdp surface drifters the global mean eddy diffusivity was 543 155 m2 s at 1 000 m and 2637 311 m2 s at the surface with elevated diffusivities in regions of enhanced eddy kinetic energy such as western boundary currents and along the antarctic circumpolar current the eddy kinetic energy at the equator is high at both the surface and depth but the eddy diffusivity is only enhanced near the surface at depth the eddy diffusivity is strongly suppressed due to the presence of mean flow we used our observational estimates to test the validity of an eddy diffusivity parameterization that accounts for mixing suppression in the presence of zonal mean flows our results indicated that this parameterization generally agrees with the directly observed eddy diffusivities in the midlatitude and high latitude oceans

changes in the ventilation of the oxygen minimum zone of the tropical north atlantic changes in the ventilation of the oxygen minimum zone omz of the tropical north atlantic are studied using oceanographic data from 18 research cruises carried out between 28 5 and 23 w during 1999 2008 as well as historical data referring to the period 1972 85 in the core of the omz at about 400 m depth a highly significant oxygen decrease of about 15 mol kg 1 is found between the two periods during the same time interval the salinity at the oxygen minimum increased by about 0 1 above the core of the omz within the central water layer oxygen decreased too but salinity changed only slightly or even decreased the scatter in the local oxygen salinity relations decreased from the earlier to the later period suggesting a reduced filamentation due to mesoscale eddies and or zonal jets acting on the background gradients here it is suggested that latitudinally alternating zonal jets with observed amplitudes of a few centimeters per second in the depth range of the omz contribute to the ventilation of the omz a conceptual model of the ventilation of the omz is used to corroborate the hypothesis that changes in the strength of zonal jets affect mean oxygen levels in the omz according to the model a weakening of zonal jets which is in general agreement with observed hydrographic evidences is associated with a reduction of the mean oxygen levels that could significantly contribute to the observed deoxygenation of the north atlantic omz

dynamics of the mediterranean salinity tongue abstract a reduced gravity planetary geostrophic model of the north atlantic consisting of two active layers overlying a motionless abyss is developed to investigate the effect of the wind field in shaping the dynamics of the mediterranean salinity tongue the model is driven by climatological winds and eastern boundary ventilation in a basin of realistic geometry and includes a parameterization of meddies the upper layer depth from the model shows a clear similarity to observations both in terms of the location and intensity of the subtropical gyre and also the position of the outcropping line in the northern basin potential vorticity in layer two reproduces the sweep of potential vorticity contours southwestward from the eastern boundary and extending westward into the interior and provides the pathways along which mediterranean water spreads into the model interior the authors solve for the steady salinity field in the second layer including sources of upper labrador sea water and antarctic inter

seasonal evolution of upper ocean horizontal structure and the remnant mixed layer 1 we discuss the seasonal evolution of upper ocean thermohaline structure at small horizontal scales the upper 350 m of a 1000 km long section in the subtropical north pacific was observed in winter spring and summer with 3 14 km horizontal resolution four vertical regions had distinct density and salinity structure the mixed layer remnant mixed layer high stratification layer and permanent thermocline the remnant mixed layer consists of water from the winter mixed layer left over after restratification the remnant mixed layer was most similar to the mixed layer in winter and spring and most similar to the high stratification layer below in summer the high stratification layer had elevated stratification that varied seasonally the permanent thermocline varied little seasonally and was horizontally and vertically uniform in comparison in all seasons density ratios showed that mixed layer s differences tended to compensate in density with the strongest tendency toward compensation in winter density ratios were temperature dominated in the remnant mixed layer consistent with salt fingering salinity anomalies were largest at the surface and decayed with depth in all seasons spectra of isopycnal depth and s anomalies along isopycnals are compared between the three seasons and four vertical layers isopycnal depth variance at 30 46 km wavelengths decreased from winter to spring to summer by a factor of 2 10 in stratified regions by treating salinity anomalies as a tracer the effective isopycnal diffusivity in the remnant mixed layer was estimated to be 1 4 m2 s 1 over 30 46 km wavelengths

chemical evolution of intercumulus liquid as recorded in plagioclase overgrowth rims from the skaergaard intrusion the intercumulus liquid of a crystal mush fills pore spaces and typically solidifies to form overgrowths on cumulus grains and poikilitic post cumulus minerals if the liquid is immobile solidification produces zoned intercumulus minerals as a result of progressive fractionation of the residual liquid convection within the mush results in buffering of the liquid composition and thus limits mineral zonation for fully solidified cumulates fossil changes in liquid composition or porosity are difficult to identify however detailed study of immobile minor components of plagioclase overgrowth rims can provide information about the progressive solidification of intercumulus material ti contents of plagioclase overgrowths in samples from the lowermost parts of the skaergaard intrusion show strong variations with anorthite content with decreasing xan ti concentrations first rise and then fall consistent with changing tio2 contents of the intercumulus liquid during solidification tio2 in plagioclase decreases sharply at an55 reflecting local saturation of fe ti oxides ti in clinopyroxene oikocrysts also falls rimward but zoning in faster diffusing species fe mg is limited other than slight reverse zones that may occur on the plagioclase margins xan falls continuously during crystallization the reverse zoning is interpreted as the result of compaction driven dissolution and reprecipitation of plagioclase the continual decrease in xan is exploited together with back scattered electron images of the cumulates to produce calibrated images showing regions of progressive crystallization this allows the regions crystallizing at each stage of solidification to be visualized these images show that the final remnants of interstitial melt were present in triangular pockets and as thin grain boundary melt films this approach can provide information about the progressive reduction of porosity during cumulate solidification

ventilation of red sea water with respect to chlorofluorocarbons chlorofluorocarbon cfc measurements were made in the northwestern indian ocean in august september 1995 as part of the world ocean circulation experiment hydrographic program section i1 the data in the gulf of aden section from this expedition provide information on the mixing processes that affect red sea water rsw as it flows from its source into the open northwestern indian ocean combining measurements by rhein et al 1997 with the outcome from a two end member mixing model results in an estimate of 65 70 saturation for the cfcs in the rsw end member at bab el mandeb a boundary condition that may be more applicable to ocean models is given by the cfc content of rsw after its initial diapycnal descent along the continental slope in the western gulf of aden entrainment of water containing lower amounts of cfcs produces rsw that has cfc saturations of 20 50 once rsw has settled at its depth of neutral buoyancy apparent pcfc ages at bab el mandeb and after the separation of rsw from the bottom are 12 13 and 18 27 years respectively as rsw continues eastward through the gulf of aden as an isopycnal flow horizontal eddy diffusion plays an important role in further diluting rsw which is characterized by a maximum in salinity and a positive anomaly in cfc concentrations horizontal eddy diffusion parameters estimated from tracer conservation in a box model of the central and eastern gulf of aden range from 0 2 104 to 2 0 104 m2 s 1 as other observations show eddy diffusion is presumably enhanced in this part of the ocean

northwest africa 5790 a previously unsampled portion of the upper part of the nakhlite pile we present a geochemical study of recently discovered martian meteorite northwest africa nwa 5790 and use our results to constrain its origin and relationship with the other nakhlites this nakhlite is a clinopyroxene cumulate composed of phenocrysts of augite olivine and rare oxides surrounded by a mesostasis composed of vitrophyric glass feldspars oxides phosphates and fine grained olivines and augite petrography and major and trace element compositions of the phases present are consistent with derivation of nwa 5790 from a parental magma common to all the nakhlites olivine cores grew from a distinct incompatible element enriched magma and are surrounded by rims containing augite inclusions that grew from the nakhlite parental liquid supporting previous arguments for xenocrystic olivine cores in nakhlites rare earth element microdistributions suggest derivation of nwa 5790 augites from an evolved relatively oxidized magma produced by augite fractionation from the common nakhlite parental liquid augite grain shapes and csd patterns are consistent with rapid cooling and derivation near the top of the nakhlite cumulate pile but patterns are distinct from other nakhlites thought to have formed near the stratigraphic top the high mesostasis abundance 44 vol indicates solidification near the top of the nakhlite pile close to locations suggested for nakhlites nwa 817 and miller range mil 03346 however the geochemical and petrographic characteristics of these three samples do not permit their placement in a simple stratigraphic order as would occur in a single lava flow this lack of simple ordering suggests that the nakhlite lava flow split into multiple sections as would occur during breakouts from a single lava flow finally we note that nwa 5790 is unique among currently available nakhlites in having phenocryst abundances low enough to allow it to flow

material flux and porosity changes during sediment diagenesis understanding the changes in porosity that occur during burial of sediments is of importance both in modelling fluid flow in sedimentary basins and for prediction of petroleum reservoir quality when deposited up to 50 of the volume of sands is intergranular pore space porosity generally decreases with depth because of compaction and precipitation of diagenetic minerals but some sandstones retain an anomalously high porosity whether this is due to dissolution and removal of material or to its local redistribution is not clear we originally intended to quantify losses of major chemical components during burial of a complete sedimentary unit we have investigated ten reservoir sandstones of permian to tertiary age from oilfields worldwide these show consistent results and here we present detailed data from four of them we found that the silica content of these sandstones actually increased by 220 to 350 kg m 3 following compaction no statistically significant changes were observed for aluminium potassium or sodium the flux of silica cannot be modelled satisfactorily using currently accepted values of permeability silica solubility and flow rates posing a challenge for existing models of fluid flow and ore emplacement

currents fronts and eddy fluxes in the canary basin hydrographic data from two cruises in the canary basin meteor 57 july 1981 poseidon 86 april 1982 are analysed with respect to current distribution and lateral heat flux in the azores madeira region the first part of the data base consists of long transects of xbt and g e k measurements between cape finisterre north west spain and the northern canary basin where several year long current meter records exist further information is obtained by thermosalinograph surface data and by expendable current profilers xcp geostrophic currents are derived from xbt profiles using the tight temperature salinity relationship in the depth range of the warmwassersphare the results compare well with the g e k and xcp current observations the second part consists of ctd data from an eddy resolving box shaped ctd survey 500 500 km2 centered at the mooring location 33 n 22 w the observations are supplemented by satellite buoy trajectories horizontal parameter distribution is shown in terms of objectively contoured maps bands of spatially enhanced energetic structures seen in the long transects are further resolved by the box survey as a deep jet like current system cross the canary basin in a west east direction associated with this azores current is a frontal zone with near surface temperature and salinity steps of order 2 k and 0 3 practical salinity units the dynamic topography field can be decomposed into a linear background field a rossby wave and a mesoscale eddy field we find that major contributions to the meridional eddy heat flux are confined to the vicinity of the azores current frontal zone it is shown that the principal balance in the temperature equation is between heating by the mean horizontal advection terms and cooling by the eddy flux divergence

the inference of north atlantic circulation patterns from climatological hydrographic data we present a review of spiral techniques which have recently been developed for the determination of absolute velocity profiles from hydrographic observations a specific technique is then designed and applied to the north atlantic part of levitus 1982 climatological hydrographic atlas with the aim of estimating reference velocities and diffusivities for heat salt and potential vorticity these quantities are determined on a 1 grid from the local gradients of temperature and salinity under the constraints of the thermal wind relations and the conservation of the respective tracers including diapycnic and isopycnic mixing terms the estimation procedure includes the statistical framework of inverse modeling in the weighting of the constraints by the data noise variances and the determination of the covariances of the model parameters the resulting circulation pattern bears strong resemblance to the classical view of the north atlantic circulation as put foreward by wust 1935 and defant 1941 the upper layers are dominated by the gulf stream north atlantic current system with a broad subtropical gyre recirculation in the lower layer a western boundary current is fed from norwegian sea overflow penetrating the gibbs fracture zone and partly circulating around the labrador sea as a consequence of the climatological averaging the currents appear in broad shape with much reduced velocities in particular in the upper layer the vertical structure reveals an almost horizontal level of no motion pattern much along the concepts of defant 1941 diffusion coefficients were determined for an upper layer depth of mixed layer to 800 m depth and a lower layer 800 m to 2000 m the spatial pattern of these coefficients correlates with maps of eddy activity showing higher values in the strong current regimes and low values within the subtropical and subpolar gyre average values in the lower layer of the quiet regions are 10 5 m s and 10 m s for the diapycnal and isopycnal diffusivity respectively and 10 1 m s for the vertical diffusivity of vorticity which yields 10 m s for the lateral diffusivity of potential vorticity toward the regions of strong currents and in the upper layer these values roughly increase by an order of magnitude

the fry method applied to an augen orthogneiss problems and results the application of the fry method to measure strain in deformed porphyritic granites is discussed this method requires that the distribution of markers has to satisfy at least two conditions it has to be homogeneous and isotropic statistics on point distribution with the help of a morishita diagram can easily test homogeneity isotropy can be checked with a cumulative histogram of angles between points application of these tests to undeformed mte capanne granite elba and to deformed randa orthogneiss alps of switzerland porphyritic granite reveals that their k feldspars phenocrysts both satisfy these conditions and can be used as strain markers with the fry method other problems are also examined one is the possible distribution of deformation on discrete shear bands providing several tests are met we conclude that the fry method can be used to estimate strain in deformed porphyritic granites

textural character of gabbroic rocks from pito deep a record of magmatic processes and the genesis of the upper plutonic crust at fast spreading mid ocean ridges

four views of a portion of the north atlantic subtropical gyre abstract data from four cruises to the triangle centered at 27 n 32 30 w were smoothed by fitting second degree polynomials at each of about 30 different density surfaces the density intervals were p 0 3 corresponding to about 50 db intervals in pressure from the polynomials determination was made of central values horizontal derivatives and laplacians of the fields of pressure salt oxygen and dynamic height in addition maps of the fits and deviations of each nation from the smoothed fits were produced from the steady advective diffusive equation and the smoothed fits to the age oxygen and dynamic height fields the lateral isopycnal diffusivity as estimated to be kh 0 5 103 m2 s 1 although the salt field was reasonably stable from cruise to cruise the variability of the baroclinic velocity shear was found to be as large as the baroclinic shear itself the maps suggest a wobble of the gyre the standard deviation of the fluctuations at each nation from the smoothed fits when norma

a quasi synoptic survey of the thermocline circulation and water mass distribution within the canary basin shipboard hydrographic measurements and moored current meters are used to infer both the large scale and mesoscale water mass distribution and features of the general circulation in the canary basin we found a convoluted current system dominated by the time dependent meandering of the eastward flowing azores current and the formation of mesoscale eddies at middepths several distinctly different water masses are identified subpolar mode and labrador sea water are centered in the northwest subantarctic intermediate water is centered in the southeast and the saltier warmer mediterranean tongue lies between them mesoscale structures of these water masses suggest the presence of middepth meanders and detached eddies which may be caused by fluctuations of the azores current

quantitative textural analysis of packings of elongate crystals the spatial distribution of grains in a solidifying igneous rock controls the physical properties of the crystal mush and in turn is controlled by the rate of crystal growth and accumulation a predominant non spherical habit for igneous minerals brings into question the use of spherical particles in reference packings used for quantification of spatial distribution furthermore variations of crystal clustering ordering with length scale require spatial statistics which take into account the distribution of particles beyond nearest neighbours using random close packings of spherocylinders we demonstrate the importance of aspect ratio for the aggregation index usually known as r and show that packings of spherical particles have more structure than packings of rods the spatial distribution functions demonstrate that the plagioclase grains in the colonnade from the holyoke basalt are clustered on a length scale of 0 5 mm understanding the controls on grain spatial distribution in igneous rocks will depend on the application of these techniques to well understood environments

in situ interaction of cement paste and shotcrete with claystones in a deep disposal context in situ sampling was performed in the andra meuse haute marne france underground research laboratory url allowing the study of two cement based materials claystone interfaces that have undergone 4 to 5 years of interaction the first interface concerned a shotcrete that was sprayed on the wall of an access drift at the laboratory level and the second one a class g cement paste that was injected in a borehole filled from the surface and was intercepted during the excavation of a new gallery in the first case the hydrodynamic conditions were controlled by the ventilation of the drift while in the second the cement paste and claystone materials were considered saturated and far from any mechanical perturbation a multi scale investigation was carried out to identify any evidence of alkaline perturbation in the cement based materials and the claystone chemical mineralogical and textural measurements were thus performed on the different materials in contact at the nanometer to a centimeter scale results showed that all the perturbations resulting from the geochemical contrast between the cement materials and the claystone were limited to a m scale on each side of the interfaces carbonation was observed in the cement materials leading to an opening or a clogging of the porosity according to the hydrodynamic conditions and the formulation of the cement material the distribution of the cation exchange population was also modified in the claystone in contact with the cement paste where a potassium saturation of the exchangeable fraction was identified the originality of the present work is that realistic field controlled samples from the andra url were studied hereby allowing the evaluation of the impact of natural heterogeneities of the in situ experimental conditions that is hydrodynamic conditions engineered damage zone mineralogical variations on the perturbations at the cement paste claystone interfaces an important result is that the clogging of porosity was not homogenous along the interfaces

paired nakhlites mil 090030 090032 090136 and 03346 insights into the miller range parent meteorite abstract miller range mil 03346 is the most oxidized and least equilibrated nakhlite known and displays the highest amount of intercumulus phase the discovery of three new nakhlites mil 090030 mil 090032 and mil 090136 in the miller range antarctica geographically close to the location of mil 03346 suggests that they may come from the same parent meteorite in this study we investigate the mineralogy and texture of cumulus and intercumulus phases in situ major and trace element compositions for the cumulus phases as well as pyroxene crystal size distribution patterns and spatial distribution patterns of mil 090030 090032 and 090136 using these combined results we conclude that the three nakhlites studied here are paired with mil 03346 however modal mineral abundances of mil 090030 090032 090136 and 03346 exhibit variations indicating that a single sample of a miller range nakhlite is not modally representative of the parent meteorite and that analyses of multiple samples for a single nakhlite may be necessary to obtain representative modal data for placement in the cumulate pile our calculated parental melt composition based on all the paired samples confirms a previous study suggesting that the nakhlite parent melt crystallized as a closed system

spatial variability of subducting water in the north atlantic a pilot study hydrographic and tritium 3he data obtained on a small scale survey conducted in 1986 south of the azores show strong horizontal and isopycnic gradients across the azores front examination of small scale spatial variability reveals a dominant scale for salinity oxygen and tritium 3he age of the order of 160 km comparable to estimates of sea surface height correlation scales from geosat data this spatial variability correlates strongly with large scale horizontal gradients two mesoscale resolving surveys separated by 300 km reveal spatial scales and amplitudes of thickness variability that decrease rapidly with age becoming incoherent on scales greater than 18 km within 1 year and approaching internal wave background values there appears to be a substantial reduction in mode thickness between the two surveys which may be the result of non conservation of potential vorticity or the result of interannual changes in formation subduction rates computed from tritium 3he age gradients are comparable to or larger than ekman pumping estimates based on climatological data

chemical and mineralogical characterization of historic mortars from the santa eulalia de boveda temple nw spain bulk samples of mortars from the santa eulalia de boveda temple nw spain have been characterized from a chemical and mineralogical point of view with the aims of contributing technological and provenance inferences and evaluating possible correlations with the various identified stages along historical periods of construction mortar samples were analyzed by x ray diffraction and neutron activation analysis mineralogical associations found are similar quartz alkali feldspars calcite and mica for all samples only varying in their proportions mainly calcite statistical and geochemical studies allowed the differentiation of two main groups enhancing definition of the granite nature of the aggregate and of a significant variation in calcite proportion lime binder two outlying samples were identified one with higher calcite proportion and other corresponded to a plaster with a different raw material source a clear correlation between the chemical groups and the independently defined chronological stages could not be found in this work however mortar samples from the earlier stage were associated with a higher aggregate binder proportion

the use of volcanic materials for the manufacture of pozzolanic plasters in the maya lowlands a preliminary report this paper focuses on the description and characterization of the nature of isotropic and silicon rich particles observed in plaster samples from the maya archaeological sites of calakmul and lamanai based on the composition and morphology of these particles it is proposed that volcanic ash and glass were incorporated into some of the ancient maya plasters in order to produce hydraulic reactions from a technological point of view the intent on the part of the maya to produce such reactions is relevant because it would reflect resource planning and complex knowledge of materials results also confirm previous reports of the presence of volcanic ash layers at the site of calakmul and suggest that there were considerable ash falls in the maya lowlands during prehispanic times which may have made the material available in many areas of the central lowlands if as we propose here volcanic ash was employed in lowland maya plasters then the use of volcanic materials by the lowland maya was more intensive than has been recognized our paper also reviews the literature about the use of volcanic materials in lowland maya materials and suggests future lines of research

an origin for harrisitic and granular olivine in the rum layered suite nw scotland a crystal size distribution study dendritic crystal morphologies occur in a number of igneous rocks and are thought to originate from the rapid growth of crystals yet many examples of dendritic morphologies are found in plutonic igneous rocks where cooling rates should be low results from crystal size distribution csd measurements on harrisitic olivines from rum scotland combined with estimated olivine growth rates suggest that the characteristic skeletal hopper and branching olivines of harrisitic cumulates that are up to centimetres long may have exceptionally short crystal growth times several hours to several hundreds of days this together with very low calculated nucleation densities for harrisitic olivine supports the interpretation of harrisite being a disequilibrium texture developed in response to supersaturation of the magma in olivine we propose that this supersaturation arose through undercooling of thin picrite sheets emplaced along the rum magma chamber floor beneath cooler resident magma it is envisaged that the picrite sheets were largely free of suspended olivine crystals coupled with the olivine enriched composition of the melt and the increasing cooling rate this allowed homogeneous nucleation of olivine to set in at deeper undercooling and greater olivine supersaturation than if there had been plentiful suspended olivines to act as heterogeneous nuclei the enhanced supersaturation caused rapid growth of olivine once nucleation began with skeletal and dendritic shapes it is suggested that the observed interlayered sequences of harrisite and cumulus peridotite found throughout the rum layered suite are a result of multiple episodes of harrisite crystallization resulting from picrite emplacement that alternated with periods of crystal growth and accumulation in the main body of magma at lesser degrees of undercooling

a diagnostic study of the wind and buoyancy driven north atlantic circulation a two moving layer diagnostic model with a variable depth mixed layer on top is applied to the annual mean climatology of the north atlantic estimates of the annual mean mass flux from the mixed layer into the upper thermocline called mixed layer pumping and subsurface heating rates are obtained on the basin scale from hydrographic data alone no independent measures of wind stress or other surface forcings are required in addition it is shown that the nonlinear terms in the vorticity equation are critical to balance the subsurface heat flux in the gulf stream and over most of the subtropical gyre evidence is presented for the existence of interior southeastern northeastern and recirculation regimes in the north atlantic these regimes are distinguished by the behavior of the characteristic trajectories of the system and by whether the flow is a direct cell interfacial flux and vertical velocity have the same sign or indirect cell interfacial flux and vertical velocity have the opposite sign it is demonstrated here that one can make use of analytic approaches in the analysis of historical data sets to yield relatively simple solutions that give a direct link between theory and observations

meddy seamount interactions implications for the mediterranean salt tongue abstract a quasigeostrophic point vortex numerical model is used to explore interactions of eddies and seamounts the ultimate objective of this study is to assess the role of meddy seamount interaction as an input to mediterranean salt tongue maintenance secondary objectives are to clarify the dynamics of meddy seamount interaction the results suggest that meddies survive seamount collisions with 60 70 of their initial cores remaining intact as coherent vortices given observed formation rates it appears meddies in their interactions with seamounts inject between one quarter and one half of the salt anomaly necessary to sustain the mediterranean salt tongue other considerations suggest the anomalous mass flux by meddies is comparable to that due to the mean flow in summary meddies are important to the maintenance of the salt tongue although other mechanisms are needed coherent vortex transport of which meddies are one example is a mesoscale process not well described by the downgradient mix

diagenesis of the rotliegend sandstone the answer ain t blowin in the wind abstract aeolian rotliegend sandstones from the village fields area of the southern north sea were cemented by illite and kaolinite during the latter part of the jurassic coincident with a phase of active rifting in the basin the components for the formation of the clays could not have been supplied from the original detritus which was rich in quartz and poor in feldspar and lithic fragments instead large quantities of aluminium potassium and silicon must have been supplied to the sandstone from elsewhere the source for the potassium is likely to have been either the laterally equivalent silverpit claystone formation or the overlying zechstein evaporite sequences which were plumbed into the rotliegend during the late jurassic rifting the source of silica and alumina has not been uniquely identified

igneous microstructures from kinetic models of crystallization during crystallization a variety of competing kinetic processes determine the evolution of the igneous microstructure yet the relative contribution of each process remains elusive to this end a stochastic algorithm is developed to yield a detailed spatial representation of the igneous microstructure during progressive crystallization this algorithm is used to test a variety of kinetic models for nucleation and crystal growth that yield realistic igneous microstructures the algorithm itself relies on a theoretical model of crystallization the avrami method and can therefore be internally validated in addition to being verified against natural microstructures using crystal size distributions csds the most realistic simulated igneous microstructure in which the csds remain approximately log linear throughout the crystallization interval is produced using a kinetic model involving exponential nucleation rate and constant growth rate an extension of the algorithm is used to simulate multiply saturated mineral growth emulating basalt crystallization through simultaneous nucleation and growth of plagioclase and clinopyroxene a fundamentally important feature of this procedure is the numerical production of detailed 3d representations of the microstructure that can be interrogated to study many physical and chemical processes for example the critical crystallinity necessary for the onset of a finite yield strength and the interstitial melt flow within the igneous microstructure depend on the percolation of the solid and melt phases respectively bounds on the percolation thresholds the critical crystallinity at which the phase of interest is connected or contiguous such that it extends across the full microstructure from one face to the opposite face are determined for the simulated igneous microstructure and are comparable with previously published results for the percolation threshold of both the melt phase and solid network the simulated igneous microstructure can also be used as input into other physical models to ascertain the physical properties of partially molten magmas that are otherwise difficult to estimate by experiment in a real sense these computed microstructures are equivalent to 3d microtomographic images of partially molten basalt within a solidification front

15 years of in situ cement argillite interaction from tournemire url characterisation of the multi scale spatial heterogeneities of pore space evolution the solution selected by some countries to isolate radioactive wastes from the biosphere for up to one million years in deep geological repositories includes a multi barrier disposal design with steel canister bentonite and cement materials the geochemical contrast between such materials and the host rock formation creates perturbations potentially altering the confinement properties of the formation in this context the french institute for the radiological protection and nuclear safety irsn have developed an in situ experimental programme based on the study of cement argillaceous formation interfaces in their underground research laboratory at tournemire aveyron france an in situ engineered analogue of a cement clay rock interface which has undergone 15 years of interaction has been characterised such important interaction time for an in situ engineered analogue provides a bridge between laboratory derived data and the long time scale of safety assessment modelling as the mineralogical and petrological investigations have already been published this work presents for the first time a quantitative characterisation of the spatial distribution of the porosity in the cement and the clay rock in terms of time scale and design interfaces have been characterised using an autoradiography technique in addition to petrophysical measurements this technique enables visualisation and quantification of the spatial distribution of the porosity using 2d mapping of decimetric scale specimens thus autoradiographs allow highlighting the relationship between the field heterogeneities and the pore space evolution in each material in contact moreover the porosity measurements show a clogging of the porosity in the clay rock while the porosity increases in the cement the extension of the porosity evolution extends to a centimetre on both sides of the interface but is heterogeneously distributed in space as a function of the fissure network and interface geometries the connected fissure network visualised using autoradiography in the clogged area could permit solute e g radionuclide transport and may also be interpreted as an evolution of the mechanical properties of the clay rock formation upon alkaline perturbation this set of data with the spatial quantification of the porosity in both cement and clay materials will be useful to constrain reactive transport modelling and thus to predict long term evolution of an engineered barrier

the role of second phases for controlling microstructural evolution in polymineralic rocks a review abstract we present a state of the art review of the microstructural evolution in rocks under static and deformational conditions first the general concepts and processes are introduced using monomineralic aggregates then they are expanded into the more complex context of polymineralic rocks with a dominant matrix phase the first part of this contribution delivers information on sample strategies to quantify polymineralic microfabrics based on comparisons between microfabrics of monomineralic and polymineralic rocks we use the common knowledge collected over the past decades for monomineralic systems and discuss the differences to polymineralic ones in terms of microstructures modal compositions spatial distribution of phases crystallographic preferred orientations and associated processes the article puts particular emphasis on the effect of coupled grain growth mass transfer processes and deformation mechanisms we speculate on the effect of mineral reactions during the evolution of microstructures and rheology in polymineralic aggregates at different metamorphic conditions at the end of the article we demonstrate the great potential of grain size evolution maps as microstructural tool to unravel the geological history of polymineralic rocks that evolved under a variety of geodynamic situations

k feldspar megacryst accumulations formed by mechanical instabilities in magma chamber margins asha pluton nw argentina abstract the asha pluton the oldest unit of the san blas intrusive complex early carboniferous exhibits impressive examples of magmatic structures formed by accumulation of k feldspar megacrysts enclaves and schlieren almost all recognized structures are meter scale vertically elongate bodies of variable shapes defined as fingers trails drips and blobs they preferentially developed near the external margin of the asha pluton and generally are superimposed by chamber wide magmatic fabrics they mostly have circular or sub circular transverse sections with an internal fabric defined by margin parallel inward dipping concentric foliation and steeply plunging lineation at upper parts and flat foliation at lower parts the concentration of megacrysts usually grades from upper sections where they appear in a proportion similar to the host granite to highly packed accumulations of k feldspar along with grouped flattened enclaves at lower ends these features suggest an origin by downward localized multiphase magmatic flow narrowing and log jamming and gravitational sinking of grouped crystals and enclaves with compaction and filter pressing as main mechanisms of melt removal crystal size distribution analysis supports field observations arguing for a mechanical origin of accumulations the magmatic structures of the asha pluton represent mechanical instabilities generated by thermal and compositional convection probably owing to cooling and crystallization near the pluton margins during early stages of construction of the intrusive complex

isopycnal diffusivities in the antarctic circumpolar current inferred from lagrangian floats in an eddying model average 750 250 m 2 s 1 around the polar frontal zone the results imply that parameterizations that only use eddy kinetic energy to parameterize the diffusivities are incomplete we suggest that dominant correlations of lagrangian eddy diffusivities with eddy kinetic energy found in previous studies may have been due to the use of too short time lags in the integration of the velocity autocovariance used to infer the diffusivities we find evidence that strong mean flow inhibits cross stream mixing within the acc but there are also areas where cross stream diffusivities are large in spite of strong mean flows for example in regions close to topographic obstacles such as the kerguelen plateau

provenance of glass shards in archaeological lime plasters by la icp ms implications for the ancient routes from the gulf of mexico to teotihuacan in central mexico abstract we present the chemical characteristics of samples collected from the central courtyard of teopancazco a neighbourhood centre in teotihuacan mexico the most important classic mesoamerican city the rhyolitic glass shards used as aggregates have a composition comparable to the glass material sourced from the magmatic system of altotonga located along the route to the gulf coast people travelling from the gulf coast may have transported the glass shards to teotihuacan during the xolalpan phase 350 550 ad however the reasons for using glass shards as a construction material remain unknown these new data confirm the close relationship between inhabitants of teopancazco and the gulf coast already revealed by previous archaeological and archaeometric studies

heterogeneous nucleation as the predominant mode of crystallization in natural magmas numerical model and implications for crystal melt interaction crystallization of natural magmas is inherently a disequilibrium process which involves nucleation and growth kinetics melt crystal mechanical interactions and subsolidus modifications which are all recorded in the resulting rock texture we use a new high resolution three dimensional numerical model to address the significance and consequences of homogeneous versus heterogeneous crystal nucleation in silicate magmas with increasing amount of heterogeneous nuclei during crystallization initially equigranular textures evolve to porphyritic bimodal and spherulitic types the corresponding crystal size distributions csds become concave up curved the clustering index progressively decreases and the grain contact relationships record increased clustering concave up curved csds previously interpreted as resulting from multistage crystallization mixing of crystal populations grain agglomeration or size dependent growth are now predicted consistently with other size spatial and clustering parameters to form by heterogeneous crystal nucleation correlation relationships between various textural parameters and the fraction of heterogeneous nuclei are calibrated and used on representative volcanic and plutonic rocks including cumulate rocks to deduce the fraction of heterogeneous nuclei the results indicate that 60 to 99 of all nuclei are heterogeneous for plutonic and cumulate rocks the estimate of the heterogeneous nuclei fraction based on the clustering index is significantly lower than other estimates such discrepancies in general point to the occurrence of other processes and here the results imply that crystal mush compaction and interstitial melt extraction were involved during the magma solidification formation of crystals in clusters implicit for heterogeneous nucleation implies that greater efficiency of crystal melt separation is expected in these situations

mixing of a tracer in the pycnocline a patch of sulfur hexafluoride was released in may 1992 in the eastern north atlantic on an isopycnal surface near 300 m depth and was surveyed over a period of 30 months as it dispersed across and along isopycnal surfaces the diapycnal eddy diffusivity k estimated for the first 6 months was 0 12 0 02 cm2 s while for the subsequent 24 months it was 0 17 0 02 cm2 s the vertical tracer distribution remained very close to gaussian for the full 30 months as the root mean square rms dispersion grew from 5 to 50 m lateral dispersion was measured on several scales the growth of the rms width of the tracer streaks from less than 100 m to approximately 300 m within 2 weeks implies an isopycnal diffusivity of 0 07 m2 s at scales of 0 1 to 1 km larger than expected from the interaction between vertical shear of the internal waves and diapycnal mixing teasing of the overall patch initially about 25 km across into streaks with an overall length of 1800 km within 6 months supports predictions of exponential growth by the mesoscale strain field at a rate of 3 0 5 10 7 s 1 the rms width of these streaks estimated as 3 km and maintained in the face of the streak growth indicates an isopycnal diffusivity of 2 m2 s at scales of 1 to 10 km much greater than expected from internal wave shear dispersion the patch was painted in albeit streakily by 12 months confirming expectations from analytical and numerical models homogenization of the patch continued during the subsequent 18 months while the patch continued to spread with an effective isopycnal eddy diffusivity on the order of 1000 m2 s acting at scales of 30 to 300 km

characteristics of the near surface currents in the indian ocean as deduced from satellite tracked surface drifters part i pseudo eulerian statistics using the 1985 2013 record of near surface currents from satellite tracked drifters the pseudo eulerian statistics of the near surface circulation in the indian ocean io are analyzed it is found that the distributions of the current velocities and mean kinetic energy mke in the io are extremely inhomogeneous in space and nonstationary in time the most energetic regions with climatologic mean velocity over 50cms 21 and mke over 500cm 2 s 22 are found off the eastern coast of somalia with maxima of over 100cms 21 and 1500cm 2 s 22 and the equatorial io associated with the strong annually reversing somalia current and the twice a year eastward equatorial jets high eddy kinetic energy eke is found in regions of the equatorial io western boundary currents and agulhas return current with a maximum of over 3000cm 2 s 22 off the eastern coast of somalia the lowest eke 500cm 2 s 22 occurs in the south subtropical gyre between 308 and 408s and the central eastern arabian sea annual and semiannual variability is a significant fraction of the total eke off the eastern coast of somalia and in the central eastern equatorial io in general both the mke and eke estimated in the present study are qualitatively in agreement with but quantitatively larger than estimates from previous studies these pseudo eulerian mke and eke fields based on the most extensivedrifterdatasettodate arethemostpreciseinsituestimatestodateandcanbeusedtovalidatesatellite and numerical results

eddy stirring and horizontal diffusivity from argo float observations geographic and depth variability stirring along isopycnals is a significant factor in determining the distribution of tracers within the ocean salinity anomalies on density surfaces from argo float profiles are used to investigate horizontal stirring and estimate eddy mixing lengths eddy mixing length and velocity fluctuations from the ecco2 global state estimate are used to estimate horizontal diffusivity at a 300 km scale in the upper 2000 m with near global coverage diffusivity varies by over two orders of magnitude with latitude longitude and depth in all basins diffusivity is elevated in zonal bands corresponding to strong current regions including western boundary current extension regions the antarctic circumpolar current and equatorial current systems the estimated mixing lengths and diffusivities provide an observationally based data set that can be used to test and constrain predictions and parameterizations of eddy stirring

on the origin of the azores current the azores current south of the azores archipelago is part of the subtropical north atlantic gyre using an international hydrographic data set we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the azores current in the western basin and seasonal changes in the related flow geostrophic currents are obtained by using the method applied by stramma 1984 in the eastern basin the azores current is found to originate in the area of the southwest newfoundland rise figure 10 in winter an almost uniform current connects this region of origin with the azores current while a branching into two current bands is observed in summer with the southern band forming a marked cyclonic loop within the upper 800 m all of the transport in the northern band and about 70 of the transport in the southern band recirculates in the eastern basin additionally expendable bathythermograph data from the azores current region indicate an increase of eddy potential energy from winter to summer

dynamically consistent hydrography and absolute velocity in the eastern north atlantic ocean the problem of mapping a dynamically consistent hydrographic field and associated absolute geostrophic flow in the eastern north atlantic between 24 deg and 36 deg n is related directly to the solution of the so called thermocline equations a nonlinear optimization problem involving needler s p equation is solved to find the hydrography and resulting flow that minimizes the vertical mixing above about 1500 m in the ocean and is simultaneously consistent with the observations a sharp minimum at least in some dimensions is found apparently corresponding to a solution nearly conserving potential vorticity and with vertical eddy coefficient less than about 10 exp 5 sq m s estimates of residual quantities such as eddy coefficients are extremely sensitive to slight modifications to the observed fields boundary conditions vertical velocities etc are a product of the optimization and produce estimates differing quantitatively from prior ones relying directly upon observed hydrography the results are generally insensitive to particular elements of the solution methodology but many questions remain concerning the extent to which different synoptic sections can be asserted to represent the same ocean the method can be regarded as a practical generalization of the beta spiral and geostrophic balance inverses for the estimate of absolute geostrophic flows numerous improvements to the methodology used in this preliminary attempt are possible

quartz crystal size distribution of the ordovician millbrig k bentonite abstract crystal size distribution csd analysis has been applied to quartz crystals of the ordovician millbrig k bentonite which represents one of the largest known fallout ash deposits in the phanerozoic era to establish crystal growth histories and conditions in the magma chamber prior to eruption specific csds were examined for crystal growth conditions all millbrig samples exhibit lognormal concave down shapes in agreement with previously reported csds on large silicic systems but in contrast to more mafic systems characterized by linear csds concave down csds are possibly an intrinsic property of phenocryst growth in large volume silicic magmas as documented in the literature bindeman i n 2003 crystal sizes in evolving silicic magma chambers geology 31 367 370 quartz crystals of the millbrig must have been produced by surface controlled size dependent growth with a minor ostwald ripening component which could have easily changed to supply controlled growth due to a limited supply of nutrients as the crystals grew larger csds were also used to examine the possible origin of multiple ash beds in the millbrig these ash beds appear to be a product of a series of separate eruptions that represent separate magma layers or batches each with slightly different crystal growth conditions

influence of mixing on cfc uptake and cfc ages in the north pacific thermocline 1 a diagnostic isopycnal advection diffusion model based on a climatological geostrophic flow field is used to study the uptake of chlorofluorocarbons cfcs into the portion of the thermocline that outcrops in the open north pacific 26 6 kg m 3 in addition to advection isopycnal diffusion is required to match the cfc data collected during the world ocean circulation experiment woce in the early 1990s using reduced outcrop saturations of 80 95 for isopycnals outcropping in the northwestern north pacific 25 4 kg m 3 together with an isopcynal interior diffusivity of 2000 m2 s 1 and enhanced diffusion 5000 m2 s 1 in the kuroshio extension region further improves the model data agreement along isopycnal diffusion is particularly important for isopycnals with shadow zones pool regions in the western subtropical north pacific that are isolated from direct advective ventilation the isopycnal mixing causes an estimated increase in cfc 12 inventories on these isopycnals compared to advection only ranging from 10 20 25 6 kg m 3 to 50 130 26 6 kg m 3 over the subtropics in 1993 this contribution has important consequences for subduction rate estimates derived from cfc inventories and for the location of the subsurface cfc maxima when tracer ages are derived from the modeled cfc distributions time evolving mixing biases become apparent that reflect the nonlinearities in the atmospheric cfc time histories comparison with model calculated ideal ages suggests that during the time of woce 1993 ventilation ages based on cfc 12 were biased young by as much as 16 24 years for pcfc 12 ages of 25 years underestimating ideal ages by as much as 40 50

geological mineralogical and geochemical characteristics of zeolite deposits associated with borates in the bigadic emet and kirka neogene lacustrine basins western turkey the bigadic emet and kirka lacustrine basins of western turkey may be considered as tibet type graben structures that were developed during the miocene within the izmir ankara suture zone complex the volcanic sedimentary successions of these basins are made up of mudstone carbonate limestone and dolomite and detrital rocks and also of crystal or vitric tuffs about 135 to 200 m thick the degirmenli bigadic emirler bigadic kopenez emet and karaoren kirka tuffs constituting the zeolite deposits are situated beneath four borate deposits colemanite ulexite borax the most abundant diagenetic silicate minerals are k and ca clinoptilolites in the zeolite deposits and li rich trioctahedral smectites stevensite saponite and hectorite and k feldspar in the borate deposits in the degirmenli emirler kopenez and karaoren deposits the following diagenetic facies were developed from rhyolitic glasses rich in k and poor in na glass smectite k clinoptilolite opal ct caclinoptilolite k feldspar analcime quartz and k feldspar analcime quartz k feldspar which is also rarely associated with phillipsite karaoren and heulandite degirmenli and karaoren succeeds clinoptilolite and precedes analcime in these diagenetic facies where dioctahedral smectites opal ct and quartz are the latest minerals no diagenetic transformations exist between clinoptilolite k feldspar and analcime that were formed directly from glass the lateral facies distributions resulted from the differences in salinity and ph of pore water trapped during deposition of the tuffs but vertical distributions in vitric tuffs seem to have been controlled by the glass liquid ratio of the reacting system and the permeability or diffusion rate of alkali elements the bigadic emet and kirka zeolite deposits which were formed in saline basins rich in ca and mg ions show similar chemical changes i e loss of alkalis and gain in alkaline earth elements that have taken place during the diagenetic transformation of rhyolitic glasses to dioctahedral smectites or clinoptilolite the absence of sodic zeolites such as mordenite erionite chabazite and silica rich phillipsite is mainly due to the very high k na ratio of the starting materials rather than initial alkaline conditions or high na content in lake waters

observations and laboratory modeling of meddy generation at cape st vincent abstract the amuse canigo and ampor observations provided a large amount of subsurface float data showing evidence of several distinctly different flow behaviors within the mediterranean water layers in the vicinity of cape st vincent southwest portugal some of the floats followed the coastline and moved northward and some were trapped either in anticyclonic lenses of mediterranean water meddies generated at cape st vincent or in cyclonic structures these observations clearly indicated that the anticyclones were accompanied by cyclones at least during their early stages as the dipolar structure moves away from the cape the cyclone tends to shift slowly away from the anticyclone while decaying so that after some time only the meddy persists these in situ observations are compared with large scale laboratory experiments and the agreement between the two sets of observations is remarkably good near the cape and shortly after the generation the nondimensional radius relative vorticity and r

crystal size distributions derived from 3d datasets sample size versus uncertainties crystal size distributions csd are the most commonly studied character in quantitative textural investigations of igneous rocks the quality of csd depends fundamentally on the sample size i e total number of crystals here we use 3d x ray tomographic datasets of two early erupted bishop tuff pumice clasts comprising 849 and 446 quartz crystals to investigate the effect of sample size on the quality of the quartz size distributions because csd are obtained using a counting procedure uncertainties related to counting statistics can be used as minimum estimates of error given that most natural samples are characterized by a decreasing number of crystals with increasing crystal size uncertainties tend to increase markedly with crystal size and the number of small crystals to be counted grows very quickly with increasing sample size accordingly with as few as 100 crystals in total it is possible to properly estimate the population densities for small size bins 20 80mm however to obtain meaningful estimates across four bin sizes 20 320mm at least 250 crystals but preferably 400 crystals are needed to minimize the total number of crystals counted and keep the uncertainties on the larger size ranges within reasonable values it becomes necessary to study multiple volumes at variable spatial resolution

meddies and decadal changes at the azores front from 1980 to 2000 twenty years of time series observations from the deep sea mooring kiel276 are used to obtain information on the frequency and propagation of meddies mediterranean water eddies on long term changes in flow properties and on a possible relation to the north atlantic oscillation the mooring was set at the nominal position 33 n 22 w at a water depth of more than 5200 m in the northern canary basin it is located near the southern boundary of the azores current ac which is part of the north atlantic subtropical gyre and also in the large scale mediterranean water mw tongue originating from the strait of gibraltar the amplitudes of time varying vertical quasi geostrophic modes and the correlation of current and temperature changes at levels in the mw and the north atlantic central water above are used to identify meddies a total of 10 meddies passed the mooring during the period 1980 2000 half of the events can be related to earlier observations directional changes in meddy related velocities are used to estimate speeds and directions of meddy propagation directions of propagation are very homogeneous with all the 10 meddies observed propagating with a southward velocity component within a sector of 90 and typical speeds are 2 3 cm s meddy occurrence was uneven in time with six meddies found during the first four years and only four meddies during the remaining 16 years decadal changes show the annual mean and the fluctuating kinetic energy levels at the site changing from lower values in the 1980s to high values in the 1990s this change appears to be correlated with variations in the north atlantic oscillation nao index with a delay in oceanic response of about 3 years a conceptual model of ac meanders is used to identify meander signals in the upper layer time series the ac axis appears to be closer to the site during the 1990s than during the preceding decade and indicates a southward or southwestward displacement of the ac with increasingly positive values of the nao index meddy frequency is lower when the ac gets closer from the north a reduction in meddy occurrence in the region just south of the ac is possibly caused by the shear induced blocking of some meddies crossing the front from the north

thermochimie database developments in the framework of cement clay interactions we present here the global results of an eight year project where we attempted to complete the thermochimie database for cement minerals zeolites and clay minerals this work reports the methodology adopted to ensure the consistency between the three groups of minerals our first step concerns the relations between the three groups of minerals from field observations and experimental results gathered from the literature a summary of the selection process is then given for clay and cement minerals and a specific focus is proposed for zeolites with examples of analcime and mordenite the global consistency of the selection is investigated with respect to the main chemical tendencies found for cement clay interactions especially considering the alkalinity of the minerals consistency is checked by establishing predominance diagrams in the chemical sub systems of interest for the three groups of minerals then comparing the phase relations with respect to experimental results or field observations the methodology is illustrated using the case of gismondine and zeolite p ca

an introduction to the application of x ray microtomography to the three dimensional study of igneous rocks imaging rocks in three dimensions through x ray microtomography enables routine visualization of structures in samples which can be spatially resolved down to the sub micron scale although x ray tomography has been applied in biomedical research and clinical settings for decades it has only recently been applied to studies of rocks and few geoscientists realize its value and potential this contribution provides an introduction to the principles and techniques of x ray microtomography to the study of igneous rock textures as well as reviewing the current state of the art we hope that this short review will encourage more geoscientists to apply x ray microtomography in their research and that this will lead to new insights into the processes that occur in magmatic as well as other geological systems

wavelet transform a future of rock fabric analysis abstract although twenty years ago fabric was defined as the complete spatial and geometrical configuration of all those components that make up a deformed rock fabric was mainly synonymous with lattice preferred orientation very little attention has been paid to the multi scale geometrical and spatial relationships of the rock components fabric quantification in terms of size shape orientation and location at all scales is now performed in two dimensions using anisotropic wavelets as a first example the wavelets are applied to the famous colour plate of sander and the results compared to his axial distribution analysis applied to the k feldspars of a rock section from the sidobre granite pluton montagne noire france the wavelet analysis shows i alignment of grains resulting from mechanical interactions between grains and shows that shearing occurred within the crystalline frame ii preferred grain orientation the classical grain shape fabric parallel to the overall mineral lineation and iii small tensional domains elongate perpendicular to the lineation infilled by the residual melt just before total crystallisation attesting to the stretching nature of the mineral lineation the future of rock fabric analysis will come from new steps in understanding the processes acting during fabric development along with a further development of wavelet analysis using high resolution three dimensional fabric data

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

a microscale view of mixing and overturning across the antarctic circumpolar current abstractthe relative roles of isoneutral stirring by mesoscale eddies and dianeutral stirring by small scale turbulence in setting the large scale temperature salinity relation of the southern ocean against the action of the overturning circulation are assessed by analyzing a set of shear and temperature microstructure measurements across drake passage in a triple decomposition framework it is shown that a picture of mixing and overturning across a region of the antarctic circumpolar current acc may be constructed from a relatively modest number of microstructure profiles the rates of isoneutral and dianeutral stirring are found to exhibit distinct characteristic and abrupt variations most notably a one to two orders of magnitude suppression of isoneutral stirring in the upper kilometer of the acc frontal jets and an order of magnitude intensification of dianeutral stirring in the subpycnocline and deepest layers of the acc these variations balance an overturning circulation with meridional flo

understanding crystal populations and their significance through the magma plumbing system crystals are rarely composed of a single crystal population that have grown solely from the batch of magma in which they are resident on emplacement either by eruption or shallow intrusion close investigation of the majority of crystal populations reveal that they comprise up to four main components phenocrysts crystals co genetic with their magmatic host xenocrysts crystals wholly or in part foreign to the magmatic host and magma system antecrysts crystals which are recycled one or several times before inclusion in the host magma but have an origin within the magmatic system and microlites which represent small co genetic crystals which nucleate and grow rapidly on decompression and eruption textural analysis techniques are employed to quantify key aspects of the crystal population including crystal shape crystal size distributions spatial distribution patterns and textural modification using dihedral angles santorini provides a case study of an active volcanic system where a combined textural analysis study has been developed highlighting how the crystal population is being continuously modified by a series of replenishment and mixing events developing textural and microgeochemical techniques provides the next stage in the interrogation of crystal populations linking textures to isotopic heterogeneities and providing fingerprints of where crystals are sourced and re cycled

crystallization kinetics of olivine phyric shergottites crystal size distribution csd and spatial distribution pattern sdp analyses are applied to the early crystallizing phases olivine and pyroxene in olivine phyric shergottites elephant moraine eet 79001a dar al gani dag 476 and dhofar dho 019 from each sampling locality inferred from mars ejection ages trace element zonation patterns p and cr in olivine are also used to characterize the crystallization history of these martian basalts previously reported 2 d csds for these meteorites are re evaluated using a newer stereographically corrected methodology kinks in the olivine csd plots suggest several populations that crystallized under different conditions csds for pyroxene in dag 476 and eet 79001a reveal single populations that grew under steady state conditions pyroxenes in dho 019 were too intergrown for csd analysis magma chamber residence times of several days for small grains to several months for olivine megacrysts are calculated using the csd slopes and growth rates inferred from previous experimental data phosphorus imaging in olivines in dag 476 and dho 019 indicate rapid growth of skeletal sector zoned or patchy cores probably in response to delayed nucleation followed by slow growth and finally rapid dendritic growth with back filling to form oscillatory zoning in rims spd analyses indicate that olivine and pyroxene crystals grew or accumulated in clusters rather than as randomly distributed grains these data reveal complex solidification histories for martian basalts and are generally consistent with the formation at depth of olivine megacryst cores which were entrained in ascending magmas that crystallized pyroxenes small olivines and oscillatory rims on megacrysts