magnetism and transmission electron microscopy of fe ti oxides and pyroxenes in a granulite from lofoten norway granulites from southwest lofoten norway often carry intense and stable components of natural remanent magnetization nrm coercivities in excess of 100 mt and blocking temperatures up to 580 645 c are common several phases in these rocks can carry stable components of nrm clinopyroxenes augite with exsolved pigeonite and orthopyroxene usually contain abundant fe ti oxides the majority of which are too small to be studied conclusively with visible light additionally these rocks typically contain coarse grained 100 1000 m exsolution intergrowths of rhombohedral fe ti oxides and coarse grained magnetite we have studied the magnetism and mineralogy of the titanohematite and the inclusion bearing augites in one granulite sample using transmission electron microscopy tem and magnetic experiments to understand better the remanence properties of naturally occurring fe ti oxides and their relationships to silicate minerals the coarse grained titanohematite has a coercivity of 350 mt and a laboratory saturation remanence that unblocks at 570 600 c the hysteresis characteristics of this titanohematite are typical of much smaller 10 m sized single domains which apparently reflects the presence of exsolved ilmenite lamellae as small as 10 nm in thickness these lamellae presumably inhibit 1 domain wall nucleation and 2 movement of walls that manage to nucleate the inclusions in the augites serve as carriers of lower coercivity remanence with blocking temperatures less than about 560 c magnetite hematite and ilmenite are present in the augite and intergrowth of the rhombohedral phases revealed by tem persists down to the 20 nm scale the distribution of the magnetite inclusions in the augite appears to be unrelated to any silicate microstructure while that of the rhombohedral fe ti oxides is strongly controlled by silicate microstructure with intergrowths of these oxides commonly decorating lamellae of pigeonite orthopyroxene and clinoamphibole within the augite the nrm of this sample possibly dates from the amphibolite facies metamorphism that the region experienced about 1000 m y ago paleomagnetic studies of these rocks could readily recover virtual geomagnetic poles dating from this event in addition to the included oxides the augites display a number of unusual features that probably result from the protracted polymetamorphic history of these granulites pigeonite lamellae are not parallel to the b crystallographic axis pigeonite lamellae cut across those of orthopyroxene and numerous included minerals occur rare earth elements are concentrated within inclusions that reside in the augite

revisiting tectonic corrections applied to pleistocene sea level highstands tectonic displacement contaminates estimates of peak eustatic sea level and equivalently minimum continental ice volumes determined from the elevation of quaternary interglacial highstand markers for sites at which a stratigraphic or geomorphic marker of peak marine isotope stage mis 5e sea level exists the standard approach for estimating local tectonic uplift or subsidence rates takes the difference between the elevation of the local highstand marker and a reference mis 5e eustatic value commonly chosen as 6 m and divides by the age of the marker the resulting rate is then applied to correct the elevation of all other local observed sea level markers for tectonic displacement including peak highstands of different ages e g mis 5a mis 5c and mis 11 under the assumption that the tectonic rate remained constant over those periods this approach introduces two potentially significant errors first the peak eustatic value adopted for mis 5e in most previous studies i e 6 m is likely incorrect second local peak sea level during mis 5e is characterized by significant departures from eustasy due to glacial isostatic adjustment in response to both successive glacial interglacial cycles and excess polar ice sheet melt relative to present day values we use numerical models of glacial isostatic adjustment that incorporate both of these effects to quantify the plausible range of the combined error and show that even at sites far from melting ice sheets local peak sea level during mis 5e may depart from eustasy by 2 4 m or more we also demonstrate that the associated error in the estimated tectonic rates can significantly alter previous estimates of peak eustatic sea level during quaternary highstands notably those associated with earlier interglacials e g mis 11

drivers of holocene sea level change in the caribbean abstract we present a holocene relative sea level rsl database for the caribbean region 5 n to 25 n and 55 w to 90 w that consists of 499 sea level index points and 238 limiting dates the database was compiled from multiple sea level indicators mangrove peat microbial mats beach rock and acroporid and massive corals we subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on rsl we account for the local scale processes of sediment compaction and tidal range change using the stratigraphic position overburden thickness of index points and paleotidal modeling respectively we use a spatio temporal empirical hierarchical model to estimate rsl position and its rates of change in the caribbean over 1 ka time slices because of meltwater input the rates of rsl change were highest during the early holocene with a maximum of 10 9 0 6 m ka in suriname and guyana and minimum of 7 4 0 7 m ka in south florida from 12 to 8 ka following complete deglaciation of the laurentide ice sheet lis by 7 ka mid to late holocene rates slowed to

40ar39ar dating of combustion metamorphism mottled zone israel tertiary surface combustion of cretaceous bituminous sediments in israel produced high t low p metamorphic assemblages which were dated by conventional k ar and 40ar39ar techniques meaningful ages were obtained from samples of high metamorphic grade and k content higher than 0 8 containing sanidine anorthite gehlenite and zeolites in these minerals the k ar system has been reset and equilibrated with atmospheric ar yielding a mean age of 3 1 ma 40ar39ar plateau and isochron ages for four whole rock samples range between 2 3 and 4 0 ma one gehlenite rock yielded an 40ar39ar age of 16 0 2 ma 1 these results indicate a major combustion metamorphic event around 3 ma probably preceded by an event around 16 ma the early event took place upon initial exposure of the protolith in the miocene whereas the second followed the removal of neogene sediments and re exposure of the bituminous rocks

rock magnetic and remanence properties of synthetic fe rich basalts implications for mars crustal anomalies abstract we characterized the magnetic mineral assemblage and remanence properties of a set of synthetic samples patterned on the meteorite derived basalt composition a which contains 18 9 total feo basalts were synthesized at conditions that track 4 oxygen fugacity f o 2 buffer curves from 3 4 log units below the quartz fayalite magnetite qfm buffer to 5 log units above qfm and 6 cooling rates from 10 5 to 3 c h the resulting array of samples was characterized using magnetic hysteresis loops temperature dependence of saturation magnetization and saturation remanence 10 to 1000 k and the acquisition and demagnetization of anhysteretic remanent magnetization arm and thermoremanent magnetization trm the magnetic mineral assemblage characteristics are strongly dependent on f o 2 samples synthesized at the iron wustite iw buffer have a very low concentration of remanence carrying grains which are likely near the superparamagnetic stable single domain boundary samples synthesized at the qfm and nickel nickel oxide nno buffers contain a slightly higher concentration of remanence carrying grains which are stable single domain to fine pseudo single domain particles respectively samples synthesized at the manganese oxide mno buffer contain the highest concentration of magnetic grains which are up to 100 m in diameter the dominant fe ti oxide produced is an mg and al bearing titanomagnetite with 2 4 2 7 fe cations per formula unit the curie temperatures of the qfm samples are consistent with their electron microprobe derived compositions those of the nno sample set are very slightly elevated with respect to their electron microprobe derived compositions the curie temperatures of the mno samples are elevated up to 200 c above what they should be for their composition we attribute the curie temperature elevation to high temperature nonstoichiometry of the titanomagnetite the iw sample set acquired very weak trms with intensities of 0 02 to 0 5 a m this intensity of remanence is a factor of 50 500 too low to generate the observed 1000 nt anomalies detected on mars by the mars global surveyor mag er experiment the qfm nno and mno samples acquired trms up to 40 a m in a 10 t applied field and up to 200 a m in a 50 t field with little or no dependence on cooling rate our results suggest that fe rich melts that crystallize extensive titanomagnetite can generate an intensely magnetized layer in the martian crust even if the remanence was acquired in a weak field the qfm sample set can easily account for the observed 1000 nt mars magnetic anomalies even in a magnetized layer as thin as 15 30 km

tracing interactions between natural argillites and hyper alkaline fluids from engineered cement paste and concrete chemical and isotopic monitoring of a 15 years old deep disposal analogue abstract samples of toarcian argillite were collected both next to and far from a cem ii cement paste and a cem ii concrete within the specific context of a 15 a old borehole located in the tournemire experimental platform aveyron france the objectives were evaluation of the mineralogical and geochemical changes of the claystone at the contact with the cementitious materials and determination of the spatial extent of the interactions the approach includes the examination of the mineralogical xrd sem tem chemical major trace rare earth elements and isotopic sr c o compositions of argillite whole rocks and of various soluble phases at two scales in the rock matrix p1 scale and along micro cracks p2 scale the two study scales outline nearly similar mineralogical modifications shown by the presence of ca silicate hydrates c s h and newly formed caco 3 within 10 15 mm of the cement paste and concrete chemical data from whole rock argillites indicate few changes in a slightly thicker zone 18 20 mm mainly consisting of an increase in the cao wt and a decrease in sr contents the other elementary contents remained quite constant except for mgo which suggests redistribution with precipitation of a mg rich mineral phase at 20 mm from cement paste concrete interface acetic acid leachates had more pronounced variations including a decrease of the total elementary content in the same geochemical disturbed zone gdz together with a significant increase of the sr isotopic ratios a combination of sr and c o isotopic patterns was used to distinguish the behavior of secondary cementitious phases in the clay rich rock i calcite dissolution and re precipitation is supported by c o isotopic data and ii c s h neoformation is evidenced by the 87 sr 86 sr ratios this tool also contributes to determine the origin of the fluids the proportion of newly formed c s h in the matrix and in the micro cracks of the argillite is modeled

the origin and growth of a recently active fissure ridge travertine over a seismic fault tivoli italy abstract an enigmatic c 2 km long and 15 m high travertine ridge the colle fiorito ridge occurs in the northwestern sector of the tivoli travertine plateau central italy the main questions addressed in this paper concern the origin and mode of growth of this prominent ridge the presence of active structures beneath the studied ridge is inferred by recent and past earthquakes located at shallow depths immediately beneath colle fiorito to understand the surficial structure of the colle fiorito ridge and the travertine depositional environment we constructed a 10 m resolution dem analyzed recent and past aerial photographs and conducted field surveys and meso to micro scale sedimentological analyses to understand the ridge subsurface structure we studied a set of 32 stratigraphic well logs available from previous works and from the local decorative stone industry and realized a 2d electrical resistivity tomography ert across the ridge results show a gentle antiformal structure affected by subvertical zones of strata discontinuity the colle fiorito structure is interpreted as a previously unknown fissure ridge travertine grown at the edge of the tivoli travertine plateau perhaps when the volumetric deposition rate reached its climax in the plateau for the abundance of fluid discharge and the rise of the water table such a fluid pressure may have activated the faults and fractures beneath colle fiorito thus opening new pathways for the ascension of geothermal fluids toward the surface

intermediate members of the lime monteponite solid solutions ca1 xcdxo x 0 36 0 55 discovery in natural occurrence lime monteponite solid solutions ca cd o ss with 58 5 73 3 wt cdo were discovered as an accessory phase in medium temperature combustion metamorphic cm spurrite fluorellestadite fluorapatite marbles from central jordan the type locality is situated in the northern part of the siwaqa complex tulul al hammam area the largest area of the mottled zone formation in the dead sea region the marbles were derived from bitumen rich calcareous marine sediments of the muwaqqar chalk marl formation which have high cd zn u and ni enrichments and contain cd rich wurtzite and sphalerite oxidative sintering of these sediments at 800 850 c gave rise to unusual oxide accessories lime monteponite solid solutions cd bearing ca and zn aluminate tululite zincite and zn ni and cu rich periclase cadmium incorporation into different oxides was controlled by steric factors while cd 6 ca 6 was the principal isomorphic substitution the intermediate members ca 0 645 cd 0 355 o ca 0 453 cd 0 547 o with a halite type structure have a cadmium incorporation ratio k cd cd mineral cd rock of about 843 and are the main sites for cadmium in cm marbles in supergene environments at low water rock ratios ca 1 x cd x oh 2 ss x 0 5 constitute the main secondary phase after ca cd o ss at higher water rock ratios and in the presence of cl and f in the solutions calcium and cadmium precipitated as separate phases fluorite caf 2 and basic cadmium chloride cd oh 2 x cl x a part of cadmium becomes retained in calcium silicate hydrates the common occurrence of anhydrous ca cd o grains in natural rocks only partly altered to ca cd hydroxide after at least 100 ka exposure to weather and climate proves that both phases are effective long term cd immobilizers

sedimentology palaeoenvironments and biostratigraphy of the pliocene pleistocene carbonate platform of grande terre guadeloupe lesser antilles forearc pliocene and pleistocene deposits from grande terre guadeloupe archipelago french lesser antilles provide a remarkable example of an isolated carbonate system built in an active margin setting with sedimentation both controlled by rapid sea level changes and tectonic movements based on new field sedimentological and palaeontological analyses these deposits have been organized into four sedimentary sequences s1 to s4 separated by three subaerial erosion surfaces sb0 sb1 and sb2 sequences s1 and s2 calcaires inferieurs a rhodolithes deposited during the late zanclean to early gelasian planktonic foraminiferal zones pl2 to pl5 in low subsidence conditions on a distally steepened ramp dipping eastward red algal rich deposits which dominate the western part of grande terre change to planktonic foraminifer rich deposits eastward vertical movements of tens of metres were responsible for the formation of sb0 and sb1 sequence s3 formation volcano sedimentaire calcaires superieurs a rhodolithes and calcaires a agaricia was deposited during the late piacenzian to early calabrian zones pl5 to pt1a on a distally steepened red algal dominated ramp that changes upward into a homoclinal coral dominated ramp deposition of sequence s3 occurred during a eustatic cycle in quiet tectonic conditions its uppermost boundary the major erosion surface sb2 is related to the cala1 eustatic sea level fall finally sequence s4 calcaires a acropora probably formed during the calabrian developing as a coral dominated platform during a eustatic cycle in quiet tectonic conditions the final emergence of the island could then have occurred in late calabrian times

morphologic and geologic effects of the subduction of bathymetric highs morphologic and geologic observations suggest that subduction of bathymetric highs such as aseismic ridges chains of seamounts and fracture zones are important in the development of many forearc features and that those features form during relatively brief episodes of intense tectonism a bathymetric high obliquely entering a subduction zone tends to compress sediments along its leading edge resulting in arcward compression of the accretionary wedge a landward deflection of the trench axis and a steepened inner wall result from this deformation if a significant component of oblique slip occurs along the subduction zone then along strike movement of the accretionary wedge may also occur stresses resulting from subduction of bathymetric features with sufficient buoyancy or high relief extend farther landward than in the case of smaller less buoyant features inducing uplift of the leading edge of the overriding plate tectonic erosion of the base of the overriding plate and along strike transport of are material may also occur the accelerated tectonism observed along several convergent margins can be attributed to the consumption of bathymetric irregularities on the seafloor rather than temporally abrupt changes in rates and directions of plate motions or other episodic events in the accretionary prism

veins in the combusted metamorphic rocks israel weathering or a retrograde event abstract for about four decades the hatrurim formation israel the palestinian authority and its equivalent in jordan were considered to have formed between 16 and 3 ma ago by combustion of bituminous chalks dehydration and decarbonation resulting in two stages a prograde country rock of high t low p portland cement like assemblages and a retrograde closely time related stage of concrete like vein fillings of rehydration and recarbonation we now dated carbonate calcite aragonite vaterite containing veins in both spurrite marbles and gehlenite metamorphic rocks by 230th 234u dating the ages of most veins range between 250 ka and 30 ka with only a minority being older than 450 ka the method limit 18o of the vein carbonates indicates water 18o as low as 14 smow much lighter than present day rain in the area these values are in accord with previous information on the area s paleo rain derived from speleothem analysis and from fossil aquifers both 13c 18 to 5 and 87sr 86sr 0 70786 0 70811 ratios indicate interaction between rain derived circulating solutions and country metamorphic rock affected water thus vein formation is closer to a weathering process rather than to retrograde metamorphism textural relationships between vein filling minerals suggest the possibility that they represent reactivation and replacement of a pre existing phase by younger minerals the veins some of them enriched in cr and fe bearing minerals indicate short distance metal mobilization in the weathering process as opposed to a large scale nearly closed system behavior in the prograde stage the occurrence of high ph waters in the hatrurim outcrop of north jordan suggests vein formation in an alkaline environment

lodestone natures only permanent magnet what it is and how it gets charged magnetite and titanomagnetite exhibit magnetic properties which are attributable to the micro structures developed during oxidation and exsolution all magnetite iron ores which are lodestones contain maghemite these lodestones have hc between 10 and 30 mt sirm between 8 and 18 am kg and ri between 0 10 and 0 26 magnetite titanomagnetite and metals have rem values ratio of nrm to sirm 0 05 samples called fulgarites obtained from the smithsonian institution have rem values ranging from 0 45 to 0 92 the rem value serves as a witness parameter to the magnetic fields associated with the lightning bolt if a high rem value say 0 1 can be verified as not to be due to contamination by man and does not contain md hematite then the rock has lrm lightning remanent magnetization the magnetic field associated with lightning can be revealed from an isothermal remanent acquisition ra curve

thermoremanent magnetization of the martian lithosphere 1 this paper investigates the thermoremanent magnetization trm of the martian lithosphere assuming that the upper part of the lithosphere acquired trm in the early history of the planet and in the presence of the core field the primary magnetization whereas the lower part has been gradually magnetized by the magnetic field of the upper part as it has cooled below the curie temperature secondary magnetization the secondary magnetization is relatively weak if the magnetic properties of the lower lithosphere are taken to be similar to that of the extrusive basalt near the oceanic ridge axes on earth however if the martian lower lithosphere is more magnetic e g by an order of magnitude the secondary magnetization can be significant although still weaker than the primary magnetization of the upper part such a highly magnetic lower lithosphere does not seem plausible by terrestrial standards and it remains to be confirmed whether it is geologically plausible for mars i also examine a lithospheric model with a strongly magnetic layer beneath the crust 25 times more magnetic than the extrusive basalt representing a possible ilmenite rich layer with a considerable amount of hematite ilmenite lamellae i assume that the layer was not magnetized by the core field because it was hotter than the curie temperature of the lamellae when the core dynamo was active it acquired secondary magnetization later in the presence of the magnetic field of the crust despite adopting an extraordinarily high magnetic layer which seems implausible by terrestrial standards the secondary magnetization of the layer has minor contributions to the observed magnetic anomalies in all models considered the primary magnetization is 20 30 a m and has the dominant contribution to the observed magnetic anomalies it is worth noting that the radial components of the primary and secondary magnetization are parallel whereas the tangential components are in opposite directions because the strong magnetic anomalies in the south likely arise from the tangential magnetization considering the secondary magnetization requires even stronger primary magnetization

the chemical composition of martian soil and rocks returned by the mobile alpha proton x ray spectrometer preliminary results from the x ray mode the alpha proton x ray spectrometer apxs on board the rover of the mars pathfinder mission measured the chemical composition of six soils and five rocks at the ares vallis landing site the soil analyses show similarity to those determined by the viking missions the analyzed rocks were partially covered by dust but otherwise compositionally similar to each other they are unexpectedly high in silica and potassium but low in magnesium compared to martian soils and martian meteorites the analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of earth s crust addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition

mercury the enigmatic innermost planet abstract the planet mercury a difficult object for study by astronomical observation and spacecraft exploration alike poses multiple challenges to our general understanding of the inner planets mercury s anomalously high uncompressed density implies a metal fraction of 60 or more by mass an extreme outcome of planetary formational processes common to the inner solar system whether that outcome was the result of chemical gradients in the early solar nebula or removal by impact or vaporization of most of the silicate shell from a differentiated protoplanet can potentially be distinguished on the basis of the chemical composition of the present crust our understanding of the geological evolution of mercury and how it fits within the known histories of the other terrestrial planets is restricted by the limited coverage and resolution of imaging by the only spacecraft to have visited the planet the role of volcanism in mercury s geological history remains uncertain and the dominant tectonic structures are lobate scarps interpreted as recording an extended episode of planetary contraction issues that require global imaging to be fully examined that mercury has retained a global magnetic field when larger terrestrial planets have not stretches the limits of standard hydromagnetic dynamo theory and has led to proposals for a fossil field or for exotic dynamo scenarios hypotheses for field generation can be distinguished on the basis of the geometry of mercury s internal field and the existence and size of a fluid outer core on mercury can be ascertained from measurements of the planet s spin axis orientation and gravity field and the amplitude of mercury s forced librations the nature of mercury s polar deposits suggested to consist of volatile material cold trapped on the permanently shadowed floors of high latitude impact craters can be tested by remote sensing of the composition of mercury s surface and polar atmosphere the extremely dynamic exosphere which includes a number of species derived from mercury s surface offers a novel laboratory for exploring the nature of the complex and changing interactions among the solar wind a small magnetosphere and a solid planet recent ground based astronomical measurements and several new theoretical developments set the stage for the in depth exploration of mercury by two spacecraft missions within the coming decade

ph control on oxygen isotopic composition of symbiotic corals abstract boron carbon and oxygen isotopic compositions were determined at the micrometre scale by high resolution ion microprobe in a sample of modern coral massive hermatypic coral porites lutea the ion probe data show for b and o much larger isotopic variations at the micrometre scale than those measured at the millimetre scale by conventional techniques 18opdb values range from 10 6 0 9 to 0 2 0 5 and 11b values range from 18 6 1 5 to 30 6 1 6 by contrast 13c values show the same range of variations from 4 6 0 65 to 2 2 0 67 at the micrometre and millimetre scales the range of 11b values indicates that significant ph variations from 7 1 to 9 0 are present at the sites of calcification the largest 18o variations correspond to the highest 11b values i e to the highest phs this measurement of ph allows modelling the oxygen isotopic fractionation occurring during aragonite precipitation taking into account the rate of o isotopic equilibrium between dissolved carbonate species h2co3 hco3 and co32 and water via the two reactions of hydration and hydroxylation the full range of 18o values measured at the micrometre scale can be modelled for residence times of dissolved carbonates in the calcifying fluid ranging between 1 h and at maximum 12 h the ph controls the 18o of the growing carbonate through the relative fractions of dissolved carbonate species and through the kinetics of their isotopic equilibration with water via hydration and hydroxylation the so called vital effect systematically observed for 18o in corals can thus be understood as representing an average of rapid ph variations due to coral biology during coral growth selectively measuring 18o values in the zones of coral skeletons that have low 11b values i e formed at low ph should significantly improve the quality of palaeoclimatic reconstructions based on 18o values

thickness of the magnetic crust of mars 1 to estimate the thickness of the magnetic crust of mars six observational magnetic spectra are fitted with the theoretical spectrum expected from a novel bimodal distribution of magnetic sources observational spectra differ for each comes from a different map or model of variously selected and analyzed mars global surveyor magnetometer electron reflectometer measurements of the vector magnetic field around mars the new theoretical spectrum represents fields from both compact sources and extended laterally correlated sources on a spherical shell so the estimated shell depth can now be doubled to obtain layer thickness this typical magnetic crustal thickness is put at 47 8 8 4 km the extensive sources are enormous typically 650 km across and account for over half the magnetic energy at low degrees there is some indication that these sources are relatively shallow but the typical area remains about 330 000 km2 granted such extended sources represent magnetization of mars ancient crust in a core source field dominated by a reversing areocentric paleodipole each one arguably formed during a single polarity chron how did such vast regions of magnetic crust form a survey of many eligible mechanisms suggests magnetization of cooling igneous rock at minimal rates of about 1 to 0 1 km3 a during superchrons of order 15 to 150 ma long

reactive transport modeling of the interaction between a high ph plume and a fractured marl the case of wellenberg abstract in the context of the proposed low and intermediate level radioactive waste repository at wellenberg switzerland calculations simulating the interaction between hyperalkaline solutions and a fractured marl at 25 c have been performed the aim of these calculations is to evaluate the possible effects of mineral dissolution and precipitation on porosity and permeability changes in such a fractured marl and their impact on repository performance solute transport and chemical reaction are considered in both a high permeability zone fracture where advection is important and the wall rock where diffusion is the dominant transport mechanism the mineral reactions are promoted by the interaction between hyperalkaline solutions derived from the degradation of cement a major component of the engineered barrier system in the repository and the host rock both diffusive dispersive and advective solute transport are taken into account in the calculations mineral reactions are described by kinetic rate laws the fluid flow system under consideration is a two dimensional porous medium marl 1 porosity with a high permeability zone simulating a fracture 10 porosity crossing the domain the dimensions of the domain are 6 m per 1 m and the fracture width is 10 cm the fluid flow field is updated during the course of the simulations permeabilities are updated according to kozeny s equation the composition of the solutions entering the domain is derived from modeling studies of the degradation of cement under the conditions at the proposed underground repository at wellenberg two different cases have been considered in the calculations these 2 cases are representative of 2 different stages in the process of degradation of cement ph 13 5 and ph 12 5 in both cases the flow velocity in the fracture diminishes with time due to a decrease in porosity this decrease in porosity is caused by the precipitation of calcite replacement of dolomite by calcite and other secondary minerals brucite sepiolite analcime natrolite tobermorite however the decrease in porosity and flow velocity is much more pronounced in the lower ph case the extent of the zone of mineral alteration along the fracture is also much more limited in the lower ph case the reduction of porosity in the fractures would be highly beneficial for repository performance since it would mean that the solutions coming from the repository and potentially carrying radionuclides in solution would have to flow through low conductive rock before they would be able to get to higher conductive features the biggest uncertainty in the reaction rates used in the calculations arises from the surface areas of the primary minerals additional calculations making use of smaller surface areas have also been performed the results show that the smaller surface areas and therefore smaller reaction rates result in a smaller reactivity of the system and smaller porosity changes

low temperature reflectivity spectra of red hematite and the color of mars reflectivity spectra visible and near ir were measured near 141 210 and 300 k for four red and well crystalline powders of hematite red hematite used as commercial pigments two samples of volcanic tephra from mauna kea volcano that contain red hematite as their dominant pigment three samples of palagonitic tephra from the same location that contain nanophase ferric oxide as their dominant pigment and two mixtures of the two types of pigmenting phases relative proportions of red hematite and nanophase ferric oxide were determined by mossbauer spectroscopy for samples containing red hematite as the dominant pigment the positions of the ferric electronic transitions near 430 500 630 and 860 nm are essentially independent of temperature but their widths decrease with decreasing temperature this decrease results in a well defined minimum for the band at 630 nm at low temperatures and in significant increases in reflectivity in spectral regions near 1050 and 600 nm for example the reflectivity ratios r 600 r 530 and r 600 r 860 both increase by a factor as large as l 4 between 300 and 140 k the spectral features from nanophase ferric oxide in samples of palagonitic tephra are nearly independent of temperature spectral data of martian bright regions that are characterized by a shallow band minimum near 860 nm a reflectivity maximum near 740 nm a distinct bend near 600 nm and a shallow absorption edge from 400 to 740 nm are attributed to the presence of nanophase ferric oxide plus subordinate amounts of red hematite the 600 740 and 860 nm features are associated with red hematite because the reflectivity of red hematite at 600 nm is strongly dependent on temperature and because this wavelength is in the red part of the visible spectrum the color of the martian surface may vary as a function of its temperature a conservative upper limit for the red hematite content of the optical surface of mars is 5

paired stable isotopes o c and clumped isotope thermometry of magnesite and silica veins in the new caledonia peridotite nappe abstract the stable isotope compositions of veins provide information on the conditions of fluid rock interaction and on the origin of fluids and temperatures in new caledonia magnesite and silica veins occur throughout the peridotite nappe in this work we present stable isotope and clumped isotope data in order to constrain the conditions of fluid circulation and the relationship between fluid circulation and nickel ore forming laterization focusing on the koniambo massif for magnesite veins occurring at the base of the nappe the high 18 o values between 27 8 and 29 5 attest to a low temperature formation clumped isotope analyses on magnesite give temperatures between 26 c and 42 c that are consistent with amorphous silica magnesite oxygen isotope equilibrium the meteoric origin of the fluid is indicated by calculated 18 o water values between 3 4 to 1 5 amorphous silica associated with magnesite or occurring in the coarse saprolite level displays a narrow range of 18 o values between 29 7 and 35 3 for quartz veins occurring at the top of the bedrock and at the saprolite level commonly in association with ni talc like minerals the 18 o values are lower between 21 8 and 29 0 and suggest low temperature hydrothermal conditions 40 95 c thermal equilibration of the fluid along the geothermic gradient before upward flow through the nappe and or influence of exothermic reactions of serpentinization could be the source s of heat needed to form quartz veins under such conditions

uranium mineralization in the judean desert and in the northern negev israel abstract secondary yellow uranium minerals formed by weathering soil formation or sedimentation processes are widespread in arid areas of the northern negev and the judean desert israel they occur in scattered exposures as much as several hundreds of square meters in extent over an area of 700 square kilometers the uranium content in hand specimens ranges from 200 to 3900 ppm in most samples uranium is in disequilibrium with respect to its daughters geologic considerations suggest that the uranium is leached out of the senonian phosphorites which are exposed over much of the area and from the metamorphosed phosphorites of the hatrurim formation senonian to palaeocene and migrate towards the local base levels mainly towards the dead sea rift valley the uranyl ion together with ions of vanadate phosphate and carbonate form various uranium minerals mainly meta autunite meta tyuyamunite and carnotite the secondary uranium minerals are associated with gypsum which forms thin veins and is found also as matrix in pedogenic layers that range from 0 2 to 1 5 meters in thickness this gypsum rich pedogenic layer like calcrete might be a lithological marker and trap especially under reducing conditions

the magnetic properties of metaperidotitic rocks as a function of metamorphic grade implications for crustal magnetic anomalies seventeen samples from the malenco serpentinite in the swiss alps representing systematic prograde metamorphic conditions from prehnite pumpellyite to upper amphibolite are moderately to strongly magnetic average susceptibility of 6 61 10 2 si units due predominantly to the presence of a magnetite rich spinel some greenschist facies samples contain the metal alloy awaruite ni3fe these contain in addition much greater amounts of magnetite small amounts of pyrrhotite in about half the samples complete the contributions to the total magnetization susceptibilities generally decrease with increasing metamorphic grade because of the production of increasing amounts of chromerich spinel which dilutes the magnetite component these results indicate that significant magnetic anomalies should be generated in suture zones containing metamorphosed serpentinite and in areas where serpentinite is being actively subducted

paleoweathering and depositional conditions in the inter flow sediment units bole beds of deccan volcanic province india a mineral magnetic approach abstract a total of 54 samples from thirteen different profiles of interflow sediment units occurring in the deccan volcanic province dvp india are studied using an integrated mineral magnetic and field documentation approach the occurrence and distribution of ferri and antiferromagnetic oxides associated with these sediments infer depositional conditions dominated by various detrital modes and recycling of baked sediments under limited authigenic environments the baking of underlying sediments is conditioned by aqueous or dry nature of the substrate vis a vis the viscosity of the overlying lava flow that can be identified by a combination of brown red boles and compact pahoehoe type flows the presence of antiferromagnetic superparamagnetic sp fraction in the red bole capped brown boles indicates the depth of baking to 20 cm while the sp fraction also marks infilling recycling and pigmentation in other occurrences of the red boles studied here overall the mixed magnetic mineralogy and sediment characters depict frequent recycling and re deposition by surface run off infiltration and ponding as the most common processes of bole bed formation in dvp governed by shallow streams or laterally migrating channels infiltration of the baked or unbaked sediments into fragmentary topped basalts is frequently shown by the red and brown boles while infilling into the interstices and cavities is common with green boles the red boles are also characteristic of detrital mixing of oxidized partially oxidized ferrimagnets many times coated with pigmentary hematites the present results envisage a great scope for the routine mineral magnetic studies integrated with field observations for rapid characterization of the extensively occurring bole bed horizons in the dvp and their study as analogs of martian soils and sediments

mineralogy and origin of surficial uranium deposits hosted in travertine and calcrete from central jordan abstract secondary uranium encrustations are hosted in thick travertine and calcrete deposits of pleistocene recent age in central jordan the central jordan varicolored marble and travertine are equivalent to the active metamorphic area in maqarin north jordan more than 100 samples were collected from the outcrops of the varicolored marble travertine calcrete and the yellow uranium encrustations the secondary yellow encrustations are mainly composed of uranyl vanadate complexes tyuyamunite ca uo 2 2 v 2 5 o 8 3 h 2 o strelkinite na2 uo2 2v2o8 6 h2o solid solution series are the major components and their composition reflects changes in the ca na ratio in solution potentially new vanadium free calcium uranate phases restricted to the varicolored marble were identified with cao uo3 ratios different from the known mineral vorlanite cau6 o4 carbon and oxygen isotope data from calcite in the varicolored marble are characterized by rayleigh type enrichment in light isotopes associated with release of 13c and 18o enriched co2 by high temperature decarbonation during combustion of the bituminous marl stable isotope results from uranium hosted travertine and calcrete varieties exhibit a wide range in isotopic values between decarbonated and normal sedimentary carbonate rocks the depleted 13c and 18o values in the travertine are related to the kinetic reaction of atmospheric co2 with hyperalkaline ca oh 2 water the gradual enrichment of 13c and 18o values in the calcrete towards equilibrium with the surrounding environment is related to continuous evaporation during seasonal dry periods uranium mineralization in central jordan resulted from the interplay of tectonic climatic hydrologic and depositional events the large distribution of surficial uranium occurrences hosted in travertine and calcrete deposits is related to the artesian ascending groundwater that formed extensive lakes along nnw sse trending depressions fresh groundwater moved upward through the highly fractured phosphate bituminous marl and varicolored marble to form unusual highly alkaline water hydroxide sulfate type enriched with sensitive redox elements among which were u and v

grain size dependent potential for self generation of magnetic anomalies on mars via thermoremanent magnetic acquisition and magnetic interaction of hematite and magnetite abstract early in the history of planetary evolution portions of martian crust became magnetized by dynamo generated magnetic field a lateral distribution of the secondary magnetic field generated by crustal remanent sources containing magnetic carriers of certain grain size and mineralogy is able to produce an ambient magnetic field of larger intensity than preexisting dynamo this ambient field is capable of magnetizing portions of deeper crust that cools through its blocking temperatures in an absence of dynamo we consider both magnetite fe3o4 and hematite fe2o3 as minerals contributing to the overall magnetization analysis of magnetization of magnetic minerals of various grain size and concentration reveals that magnetite grains less than 0 01 mm in size and hematite grains larger than 0 01 mm in size can become effective magnetic source capable of magnetizing magnetic minerals contained in surrounding volume preexisting crustal remanence for example 250 a m relates to 25 of multi domain hematite can trigger a self magnetizing process that can continue in the absence of magnetic dynamo and continue strengthening and or weakening magnetic anomalies on mars thickness of the primary magnetic layer and concentration of magnetic carriers allow specification of the temperature gradient required to trigger a self magnetization process

cementation of kerogen rich marls by alkaline fluids released during weathering of thermally metamorphosed marly sediments part i isotopic c o study of the khushaym matruk natural analogue central jordan abstract the khushaym matruk site in central jordan may represent a natural analogue depicting the interaction of alkaline solutions with a clayey sedimentary formation or with clay rich confining barriers at the interface with concrete structures in waste disposal sites in this locality past spontaneous combustion of organic matter in a clayey biomicritic formation produced a ca 60 m thick layer of cement marble containing some of the high temperature phases usually found in industrial cements e g spurrite brucite and ca aluminate a vertical cross section of the underlying sediments was used in order to study the interaction between cement marbles and neighbouring clayey limestones under weathering conditions a thermodynamic approach of the alteration parageneses calcite jennite afwillite brucite and csh phases in the cement marbles constrains the interacting solutions to have had ph values between 10 5 and 12 over 3 m the sediments located beneath the metamorphic unit were compacted and underwent carbonation they display large c and o isotopic variations with respect to pristine sediments from the bottom of the section low 13c values down to 31 4 pdb show the contribution of co2 derived from the oxidization of organic matter and from the atmosphere to the intense carbonation process affecting that particular sedimentary level the size of the c isotopic anomalies their geometrical extent and their coincidence with the variations of other markers like the zn content the structure of organic matter the mineralogical composition all argue that the carbonation process was induced by the percolation of high ph solutions which derived from the alteration of cement marbles the temperature of the carbonation process remains conjectural and some post formation o isotopic reequilibration likely affected the newly formed carbonate carbonation induced a considerable porosity reduction both in fractures and matrixes the khushaym matruk site may have some bearing to the early life of a repository site when water saturation of the geological formations hosting the concrete structures is incomplete enabling simultaneous diffusion of alkaline waters and gaseous co2 in the near field

origin of the extreme polymetallic enrichment cd cr mo ni u v zn of the late cretaceous early tertiary belqa group central jordan abstract the sedimentary formations of the late cretaceous to early tertiary belqa group correspond to pure to slightly clayey limestones and minor black shales characterized by a remarkable enrichment in phosphorous and various redox sensitive elements cd cr mo ni u v zn phosphorous enrichment is related to the great phosphorite deposition event that has occurred at the southern margin of the tethys ocean during this period the very low organic matter contents in the limestones despite their strong enrichment in redox sensitive elements is attributed to a deposition in anoxic water but under shallow water conditions permitting the bacterial degradation of a large part of the organic matter most of the elements constituting the belqa group sediments have been deposited from the sea water either directly by chemical precipitation most ca and redox sensitive elements or indirectly through biogenic activity p part of ca and u except for the minor detritial contribution presents in some limestones and more significantly in the shales such an origin is also supported by the ree patterns of the limestones which are similar to that of the present sea water the anomalously high concentrations of some redox sensitive trace metals cr ni and probably cd compared to worldwide black shales is explained by an exogenic metal flux corresponding to the leaching of the huge amounts of ophiolites obducted during the collision between the african arabian and eurasian plates at the same time as the deposition of the belqa group sediments uranium is substituted for calcium in biogenic apatite in the limestones but was also directly precipitated from sea water in the black shales in relation with the suboxic environment with the periodic anoxia developed during their deposition in restricted deeper basins the pyrometamorphism resulting from the burning of organic rich levels in clayey limestones has created a further enrichment of redox sensitive elements in the resulting marbles by a volume loss resulting from decarbonatation reactions and the combustion of the organic matter

the physical isolation and identification of carriers of geologically stable remanent magnetization paleomagnetic and rock magnetic microanalysis and electron microscopy paleomagnetic and rock magnetic microanalysis of fully oriented microspecimens provides a more direct understanding of the source and origin of geologically stable remanent magnetizations scanning transmission electron microscopy allows direct observation and characterization of magnetic phases we provide a brief history of micromagnetic research describe a functional microspecimen preparation method evaluate instrumentation and present results of three combined micromagnetic stem studies

magnetization of martian lower crust revisited 1 this paper examines the magnetization that can be acquired by the lower crust of mars in the absence of a core field but in the presence of the magnetic field of the upper crust that is magnetized by the core field a uniformly magnetized vertical prism of a square horizontal cross section is considered to be a magnetic source in the upper crust for simplicity three thicknesses of 40 60 and 80 km and six horizontal dimensions of 180 300 600 900 1200 and 1500 km are considered for the prism to estimate the upper limit for the contribution of the lower crust to the observed magnetic anomalies a potentially magnetic layer of 100 km thickness is adopted coarse grain hematite is uniformly distributed in the lower crust with 4 10 20 or 30 concentration of hematite the first is equivalent to the oceanic extrusive basalt as far as its thermo remanent magnetization trm is concerned it is shown that the magnetization of the lower crust has minor effects on the strong magnetic anomalies of mars over the southern hemisphere however if the lower crust has 20 to 30 coarse grain hematite which is highly unlikely it may have appreciable contributions to small magnetic anomalies of mars with horizontal dimensions smaller than 200 km

mossbauer spectroscopy on the surface of mars constraints and expectations abstract mossbauer spectrometers will be included on the upcoming mer athena and mars express beagle rovers these instruments have the exciting potential to characterize the surface mineralogy of mars but there are several complicating factors it is difficult to differentiate minerals with similar structures particularly if the rock or soil is multimineralic and the peaks overlap mineral modes cannot be determined from mossbauer spectra alone the temperature dependence of mossbauer parameters for common rock forming minerals and glasses is known for only a few minerals but it is strong no database of mars surface temperature mossbauer spectra of minerals or glasses currently exists with which martian data can be compared peak areas in mossbauer spectroscopy do not directly correspond to the abundances of the minerals that give rise to them and the calibration correction factors to compensate for this problem are currently known for only a few minerals we assess here the advantages and disadvantages of mossbauer spectroscopy for remote data acquisition and describe work currently under way in our laboratory to address these potential complications

geochemical assessment of hydrocarbon migration phenomena case studies from the south western margin of the dead sea basin abstract calcite veins with fluid and solid bitumen inclusions have been discovered in the south western shoulder of the dead sea rift within the masada zohar block where hydrocarbons exist in small commercial gas fields and non commercial fields of heavy and light oils the gas liquid inclusions in calcite are dominated either by methane or co2 and aqueous inclusions sometimes bear minor dissolved hydrocarbons the enclosed flake like solid bitumen matter is a residue of degraded oil which may be interpreted as dead carbon about 2 3 of this matter is soot like amorphous carbon and 1 3 consists of n c8 c18 carboxylic acids and traces of n alkanes light dicarboxylic acids and higher molecular weight c20 branched and or cyclic carboxylic acids both bitumen and the host calcites show genetic relationship with mature maastrichtian chalky source rocks mcsrs evident in isotopic compositions 13c 34s and 18o and in ree y patterns the bitumen precursor may have been heavy sulfur rich oil which was generated during the burial compaction of the mcsr strata within the subsided blocks of the dead sea graben the 18o and 13c values and ree y signatures in calcites indicate mixing of deep buried fluids equilibrated with post mature sediments and meteoric waters the temperatures of fluid generation according to mg li geothermometer data range from 55 to 90 corresponding to the 2 5 4 0 km depths and largely overlap with the oil window range 60 90 in the dead sea rift hunt 1996 gvirtzman and stanislavsky 2000 buryakovsky et al 2005 the bitumen rich vein calcites originated in the course of late cenozoic rifting and related deformation when tectonic stress triggers damaged small hydrocarbon reservoirs in the area produced pathways and caused hydrocarbon bearing fluids to rise to the subsurface the fluids filled open fractures and crystallized to calcite with entrapped bitumen the reported results are in good agreement with the existing views of maturation migration and accumulation of hydrocarbons as well as basin fluid transport processes in the dead sea area

magnetic studies on shergotty and other snc meteorites abstract hysteresis measurements on three shergottite and two nakhlite meteorites indicate single domain grain size behavior for the highly shocked shergotty zagami and eeta 79001 meteorites with more multidomain like behavior for the unshocked nakhla and governador valadares meteorites high viscosity and initial susceptibility for antarctic shergottite alha 77005 indicate the presence of superparamagnetic grains in this specimen thermomagnetic curves likewise reveal a range of oxidation states for the high ulvospinel titanomagnetite grains which dominate the magnetic properties of these first five meteorites thermomagnetic analysis indicate shergotty and zagami as the least initially oxidized while eeta 79001 appears to be the most oxidized cooling of the meteorite samples from high temperature in air results in a substantial increase in magnetization due to the production of magnetite through oxidation exsolution of titanomagnetite however vacuum heating substantially suppresses this process and in the case of eeta 79001 and nakhla results in a rehomogenization of the titanomagnetite grains remanence measurements on several subsamples of shergotty and zagami meteorites reveal a large variation in intensity that does not seem related to the abundance of remanence carriers the other meteorites carry only weak remanence suggesting weak magnetizing fields as the source of their magnetic signal a paleointensity experiment on a weakly magnetized subsample of shergotty reveals a low temperature component of magnetization acquired in a field of 2 000 gammas also present was a high temperature component reflecting a paleo field strength of between 250 and 1 000 gammas depending on the nature and degree of alteration that the sample may have undergone with heating this is consistent with an earlier paleointensity estimate of 1 000 gammas for alha 77005 the weak field environment that these meteorites seem to reflect is consistent with either a martian or asteroidal body origin but inconsistent with a terrestrial origin

geochemical evolution of st kitts and montserrat lesser antilles the volcanic rocks of st kitts have uniform 87 sr 86 sr ratios c 0 7037 and high 143 nd 144 nd ratios c 0 5130 in a suite which ranges from basalt to rhyolite trace element abundances and the flat chondrite normalized ree patterns resemble those of island arc tholeiitic suites in comparison the montserrat lavas have higher concentrations of alkaline elements and are lree enriched geochemical differences may be related to partial displacement of the axis of the volcanic arc about 9 ma this would have led to the development of the st kitts suite in an essentially new and immature island arc environment being closer to the junction with the former arc axis the composition of the montserrat lavas may reflect previous subduction related mantle enrichment and or the influence of a sedimentary component isotopic ratios and most trace elements in the redonda basalt indicate island arc tholeiite or in some respects morb affinities but it has a high sr content and is lree enriched despite its distinctive composition redonda is situated on the main axis of the volcanic arc and its lavas were evidently contemporaneous with the younger eruptions of st kitts and montserrat

matching martian crustal magnetization and magnetic properties of martian meteorites magnetic properties of 26 of 32 unpaired martian meteorites sncs are synthesized to further constrain the lithology carrying martian magnetic crustal sources magnetic properties of ultramafic cumulates i e chassigny allan hills alh 84001 and lherzolitic shergottites alh 77005 lewis cliff lew 88516 are one or two orders of magnitude too weak to account for the crustal magnetizations assuming magnetization in an earth like field nakhlites and some basaltic shergottites which are the most magnetic sncs show the right intensity titanomagnetite is the magnetic carrier in the nakhlites 7 meteorites whereas in most basaltic shergottites 11 meteorites it is pyrrhotite dhofar dho 378 los angeles and nwa 480 1460 and 2046 are anomalous basaltic shergottites as their magnetism is mainly due to titanomagnetite pyrrhotite should be among the candidate minerals for the magnetized noachian crust

magnetic lineations in the ancient crust of mars the mars global surveyor spacecraft in a highly elliptical polar orbit obtained vector magnetic field measurements above the surface of mars altitudes 100 kilometers crustal magnetization mainly confined to the most ancient heavily cratered martian highlands is frequently organized in east west trending linear features the longest extending over 2000 kilometers crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude groups of quasi parallel linear features of alternating magnetic polarity were found they are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on earth but with a much larger spatial scale they may be a relic of an era of plate tectonics on mars

chemical and 13c 12c and 18o 16o isotope evolution of alkaline drainage waters and the precipitation of calcite carbon and o isotope ratios demonstrate that calcite precipitating from alkaline tunnel drainage waters has formed by two distinct chemical mechanisms calcium carbonate sulfate ground water dissolves portlandite preferentially this leads to an increase of ca2 ph and the co32 hco3 ratio so that calcite is precipitated the c content of this calcite is a mixture of c from soil co2 and the dissolved limestone resulting in 13c 13 pdb the o isotope composition 18o 24 smow corresponds to thequilibrium fractionation between calcite and water the precipitation continues as atmospheric co2 is absorbed by the alkaline solutions in this type of calcite the c isotope composition 13c 25 pdb is controlled by the individual reaction rate constants for the hydroxylation of 13co2 and 12co2 the o isotope composition 18o 11 smow is a mixture of the compositions of atmospheric co2 and oh the isotope compositions may be used in order to evaluate the proportions of the two different mechanisms of calcite precipitation other mechanisms which cause chemical changes of the ground water are the formation of ettringite from initially unhydrated c3a phases and the formation of brucite precipitation and dissolution rates for the various solids range from 10 3 to 10 4 kg d m2

post late glacial calcareous tufas from the kurai fault zone southeastern gorny altai russia abstract calcareous tufa deposits have been discovered in the chibitka river valley near lake cheybek kohl at the junction of the kurai and teletsk kurai large active faults in the southeastern gorny altai russia at an altitude of 1800 2000 m fossil tufa is composed of calcite and cements holocene grey colluvium and glacial till deposited by the late glacial chibitka glacier current tufa precipitation has been observed from a low flow spring with cold 10 c hco 3 so 4 ca mg water 6 86 the stable isotope composition of spring water is 5 8 vpdb 13 c of dissolved inorganic carbon and 14 5 vsmow 18 o modern tufa consists of thin laminated mg calcite and sr aragonite crusts with abundant algae and biofilms on their surfaces both modern and fossil tufas are depleted in ree a total of 0 40 16 4 ppm and 0 40 3 80 ppm respectively and share similar paas normalised ree y spectra with hree enrichment and slight progressive lree depletion the modern tufas show positive 13 c values of 0 1 to 0 9 vpdb while the fossil ones have an isotopically lighter composition of 13 c 4 1 to 1 9 vpdb the 18 o range is very narrow 13 0 to 13 8 vpdb both stable isotope and trace element signatures including ree patterns of the tufas indicate precipitation from cold groundwaters subjected to prolonged interaction with a carbonate aquifer the baratal group of limestone and dolostone in a cold continental climate similar to the present conditions tufa deposition in the lake cheybek kohl area began with the onset of post late glacial global warming and permafrost degradation unlike the fossil tufa formation current precipitation of freshwater carbonates has been microbially mediated the discovered tufa deposits provide new palaeoclimatic and active tectonic proxies in the southeastern gorny altai

in situ investigations and reactive transport modelling of cement paste argillite interactions in a saturated context and outside an excavated disturbed zone abstract the interactions between cementitious materials and a clayey deep formation were investigated by studying the specific in situ context of the tournemire underground research laboratory url of the french institute for radioprotection and nuclear safety and by reactive transport modelling using the hytec code the study forms part of the safety assessment framework for the deep geological disposal of high to intermediate level long lived radioactive waste the in situ context investigated in the tournemire url corresponds to an engineered cemented borehole crosscutting the toarcian argillite formation the argillite cem ii cement paste contacts have been in place over 18 a and were sampled in a saturated context outside the excavated disturbed zone edz studies of the mineralogy xrd carbonatometry sem and tem petrophysical properties bet and geochemistry toc sr contents c o and sr isotopes eds analyses were carried out both on the argillite and on the cement paste in contact alteration of the cement paste is clearly expressed by decalcification and the opening of macroporosity these modifications are mainly due to the dissolution of portlandite the neoformation of c s h phases was identified in the first few micrometre next to the argillite interface along with secondary carbonates at the outermost contact geochemical measurements argue for the introduction of a sedimentary fluid into the macroporosity of the cement paste to explain the formation of part of these secondary phases this hypothesis is considered and tested using the hytec code which indicates that such transport could have occurred near the argillite cement paste contact at a very early stage after this stage the transport was reversed and cementitious fluids flowed from the cement paste to the argillite the changes brought about by these fluids are observed over a thickness of 11 13 mm in a so called black rim in which carbonates and c s h secondary phases are identified in the matrix of the sediment an illitization process may also be observed in this altered rim reaching its maximum development towards the inner part geochemical analyses show that the argillite disturbances are strictly confined to the black rim theoretical mineralogical profiles based on thermodynamic equilibria defined by the hytec code are in good agreement with the observations and are used to achieve a better understanding of transport processes

snc meteorites clues to martian petrologic evolution the shergottites nakhlites and chassigny snc meteorites are apparently cumulate mafic and ultramafic rocks that crystallized at shallow levels in the crust of their parent body the mineralogy and chemistry of these meteorites are remarkably like equivalent terrestrial rocks although their ratios of fe fe mg and certain incompatible elements and their oxygen isotopic compositions are distinctive all have crystallization ages of 1 3 b y or younger and formed from magmas produced by partial melting of previously fractionated source regions isotope systematics suggest that the snc parent body had a complex and protracted thermal history spanning most of geologic time some meteorites have been severely shock metamorphosed and all were ejected from their parent body at relatively recent times possibly in several impact events late crystallization ages complex petrogenesis and possible evidence for a large gravitational field suggest that these meteorites are derived from a large planet trapped gases in shergottite shock melts have compositions similar to the composition measured in the martian atmosphere ejection of martian meteorites may have been accomplished by acceleration of near surface spalls or other mechanisms not fully understood if snc meteorites are of martian origin they provide important information on planetary composition and evolution the bulk composition and redox state of the martian mantle as constrained by shergottite phase equilibria must be more earthlike than most current models planetary thermal models should benefit from data on the abundances of radioactive heat sources the melting behavior of the mantle and the timing of planetary differentiation calculated depletion of chalcophile elements in source regions indicates a core dominated by sulfides and paleomagnetic measurements suggest the presence of a weak magnetic field within the last several hundred thousand years concentrations of volatile elements indicate that the snc parent body was not volatile depleted and trapped atmospheric components measured in shock melts may be useful in understanding planetary degassing by providing comparisons for spectral reflectance data and viking soil analyses these meteorites may also constrain surface mineralogy and weathering mechanisms

shock experiments up to 30 gpa and their consequences on microstructures and magnetic properties in pyrrhotite 1 shock experiments with pressures ranging from 3 to 30 gpa have been conducted on a mixed assemblage of hexagonal and monoclinic pyrrhotite all samples were studied with respect to their particular shock induced microstructures and magnetic properties at high and low temperatures up to 8 gpa microstructures in shocked pyrrhotite are characterized by mechanical deformation producing a damage of the crystal structure at pressures of 20 gpa and upward amorphization and mechanical twinning are the dominant structural features induced by shock within the lower pressure range coercivity saturation isothermal remanent magnetization and coercivity of remanence increase with shock pressures in agreement with more single domain sd like behavior simultaneously the peak of hexagonal pyrrhotite decreases and the 34 k transition of monoclinic pyrrhotite broadens and is depressed magnetic hardening is triggered by grain size reduction but also by the formation of sd within discrete multidomain grains planar deformation features subdivide such multidomain grains into lath shaped domains with average sizes lying in the sd range the planar deformation features disappear at 20 gpa and irregular nanometer sized amorphous domains occur instead pressure release from 30 gpa finally triggers partial melting of pyrrhotite the sharp interfaces between molten and crystalline pyrrhotite document a rapid change of thermal conditions within molten pyrrhotite quenched iron crystals occur the presence of native iron strongly influences the magnetic properties depending on the particular amount in the studied sample and likely affects the magnetic properties of impact lithologies on earth and extraterrestrial material

evidence for weak ferromagnetic moment within the basal plane of hematite natural crystals at low temperature 1 low temperature magnetization of hematite within the basal plane has been studied in a collection of natural crystals by means of torque magnetometry comparison between the torque curves at room temperature and at 77 k allows identification of a weak ferromagnetic moment constrained within the basal plane at temperatures well below the morin transition annealing the samples produces the expected reduction of the weak ferromagnetic moment but there is also a relationship between the ferromagnetic moment before and after annealing low temperature measurements after the annealing experiment reveal the presence of a weak ferromagnetic moment that survives the annealing this observation suggests the magnetic structure of natural hematite crystals below the morin transition can still be a carrier of magnetization

on the possibility of single domain pseudo single domain magnetic particles existing in the lower crust of mars source of the strong magnetic anomalies 1 this paper shows that single domain or pseudo single domain sd psd magnetite grains can exist in the upper 30 45 km of the martian crust the upper 50 km of the martian crust have likely formed by volcanic eruptions on a stagnant lithosphere a given lava flow cools very rapidly at the surface but is then gradually heated up through burial heating as it is overlain by other successive flows the thermal evolution models of a lava flow show that its temperature remains below the magnetic blocking temperatures of magnetite 480 580 c until it reaches 30 45 km depth the highly magnetic sd psd magnetite grains can easily explain the strong magnetic anomalies of mars less than 1 by volume of magnetite particles is sufficient

rockmagnetic properties of fine grained natural low temperature haematite with reference to remanence acquisition mechanisms in red beds summary grain size dependence of some remanent magnetic properties of a natural low temperature haematite is reported the haematite was obtained from a gossan in montarnu france and upgraded by magnetic separation seven grain size fractions were prepared ranging from 10 down to 0 25 m by means of microprecision sieving and centrifuging the haematite has an average crystallite size of 60 nm and contains minor contents of si al and h2o its unit cell dimensions are very close to those of ideal haematite the magnetic properties of the haematite are strongly dependent on its thermal history for the original unheated haematite fractions the isothermal saturation remanence jrs decreases with grain size the remanent coercive force hcr remanent acquisition coercive force hcr and median destructive field of the saturation remanence h1 2i are maximal in the 1 0 0 5 m fraction this grain size range can be understood as the sd threshold size in analogy with ferrimagnetic minerals jrs hcr x xin is a useful grain size indicator lowtemperature cycling of jrs shows identical behaviour for all fractions the remanence decreases slightly and shows no sharp morin transition after annealing the haematite fractions at 700 c jrs is considerably reduced relative to the original haematite predominantly due to removal of the defect moment both hcr and hcr have increased and their maximal values are shifted to the 2 1 1 0 m fraction all fractions show a much sharper morin transition during low temperature cycling of jrs due to crystallite enlargement trm decreases with grain size the different rock magnetic properties before and after annealing might provide a basis for the discrimination in sediments between a haematite drm with a high temperature origin and a haematite crm which has a low temperature origin two natural red beds one with a crm and one with a drm associated with high temperature haematite broadly show the expected differences in coercivity and in annealing behaviour although a full account of all aspects of the observed behaviour can not yet be given

unique thermoremanent magnetization of multidomain sized hematite implications for magnetic anomalies intense magnetic remanence 100 1000 a m associated with md hematite and or titanohematite and associated with high koenigsberger ratios 40 1000 indicate that magnetic remanence may dominate the total magnetization if these minerals are volumetrically significant titanohematite behaves similarly to hematite and thus the grain size dependence of trm acquisition in hematite is considered as a generalization the transition between truly md behavior and tendency towards sd behavior in hematite has been established to be between grain sizes of 0 1 and 0 05 mm in contrast to magnetite and titanomagnetite hematite exhibits inverse grain size dependence with md hematite acquiring a relatively intense trm in the geomagnetic field comparable to sub micrometer sized magnetite and only an order of magnitude less than sd magnetite consequently md hematite and by analogy titanohematite remanence may be of significance as a source of magnetic anomalies at all scales md hematite exhibits trm weak field acquisition behavior that is different from all other magnetic minerals being the only magnetic mineral having an rem trm sirm value e0 1 for trm acquisition in the geomagnetic field the very different trm behavior of md hematite in contrast to magnetite is due to two factors the first is the lesser influence of demagnetizing energy with respect to wall pinning energy at temperatures almost up to the curie temperature for hematite the second is the greater importance of the magnetostatic energy in the applied field which for hematite dominates the total energy at high temperatures fl 2000 published by elsevier science b v all rights reserved

sapphirine bearing paragneiss from the northern grenville province in labrador canada protolith composition and metamorphic p t conditions sapphirine has recently been found to be abundant throughout proterozoic 1 7 1 6 ga granulite facies quartzofeldspathic paragneiss in central labrador the pressure temperature p t trajectory of metamorphism culminated at 900 c and 9 kbar and was succeeded by nearly isobaric cooling the paragneiss has 18 o enrichment and chemical compositions which suggest that the protolith was probably highly oxidized shale chemical constraints render the involvement of partial melting during the formation of the paragneiss unlikely

characteristics of an unusual highly alkaline water from the maqarin area northern jordan abstract an unusual highly alkaline natural water ph 12 5 is recorded in adits and wells from the maqarin area northern jordan it is a calcium hydroxide sulfate type of water rich in base metals concentration the hydration of lime is responsible for the high ph value of this water the high calcium and base metals concentration is related to the effect of spontaneous combustion of organic matter in the bituminous marl formation a low temperature transformation process is still active as a result of reaction of these waters with the rocks

magnetic field and plasma observations at mars initial results of the mars global surveyor mission the magnetometer and electron reflectometer investigation mag er on the mars global surveyor spacecraft has obtained magnetic field and plasma observations throughout the near mars environment from beyond the influence of mars to just above the surface at an altitude of 100 kilometers the solar wind interaction with mars is in many ways similar to that at venus and at an active comet that is primarily an ionospheric atmospheric interaction no significant planetary magnetic field of global scale has been detected to date 2 1021 gauss cubic centimeter but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of mars is reported

magnetic properties of martian meteorites implications for an ancient martian magnetic field the magnetic properties of samples of seven martian meteorites eet 79001 zagami nakhla lafayette governador valadares chassigny and alh 84001 have been investigated all possess a weak very stable primary natural remanent magnetization nrm and some have less stable secondary components in some cases the latter are associated with magnetic contamination of the samples imparted since their recovery and with viscous magnetization acquired during exposure of the meteorites to the geomagnetic field since they fell the magnetic properties are carried by a small content 1 of titanomagnetite and in alh 84001 possibly by magnetite as well the most likely source of the primary nrm is a thermoremanent magnetization acquired when the meteorite material last cooled from a high temperature in the presence of a magnetic field current evidence is that this was 1 3 ga ago for the nakhlites and chassigny and 180 ma for shergottites the time of the last relevant cooling of alh 84001 is not presently known preliminary estimates of the strength of the magnetizing field are in the range 0 5 5 ut which is at least an order of magnitude greater than the present field it is tentatively concluded that the magnetic field was generated by a dynamo process in a martian core with appropriate structure and properties

transmission electron microscopy of minerals in the martian meteorite allan hills 84001 we have studied carbonate and associated oxides and glasses in a demountable section of allan hills 84001 alh 84001 using optical scanning and transmission electron microscopy tem to elucidate their origins and the shock history of the rock massive fracture zone and fracture filling carbonates in typical locations were characterized by tem x ray microanalysis and electron diffraction in a comprehensive study that preserved textural and spatial relationships orthopyroxene is highly deformed fractured partially comminuted and essentially unrecovered lamellae of diaplectic glass and other features indicate shock pressures 30 gpa bridging acicular crystals and foamy glass at contacts of orthopyroxene fragments indicate localized melting and vaporization of orthopyroxene carbonate crystals are 5 m in size untwinned and very largely exhibit the r3c calcite structure evidence of plastic deformation is generally found mildly only in fracture zone and fracture filling carbonates even adjacent to highly deformed orthopyroxene and appears to have been caused by low stress effects including differential shrinkage high dislocation densities like those observed in moderately shocked calcite are absent carbonate contains impact derived glasses of plagioclase silica and orthopyroxene composition indicating brief localized impact heating stringers and lenses of orthopyroxene glass in fracture filling carbonate imply flow of carbonates and crystallization during an impact periclase mgo occurs in magnesite as 30 50 nm crystals adjacent to voids and negative crystals and as 1 m patches of 3 nm crystals showing weak preferred orientation consistent with 111 mgo 0001 carb as observed in the thermal decomposition of caco3 to cao magnetite crystals that are epitaxially oriented at voids negative crystals and microfractures clearly formed in situ fully embedded faceted magnetites are topotactically oriented in general with 111 mag 0001 carb so that their oxygen layers are aligned in optically opaque rims magnetites are more irregularly shaped and except for the smallest crystals poorly aligned all magnetite and periclase crystals probably formed by exsolution from slightly non stoichiometric co2 poor carbonate following impact induced thermal decomposition any magnetites that existed in the rock before shock heating could not have preserved evidence for biogenic activity

magnetic zones of mars deformation controlled origin of magnetic anomalies intense magnetic anomalies over martian surface suggest preservation of large volumes of very old crust 3 gyr that formed in the presence of a global magnetic field the global distribution of the magnetic intensities observed above the martian crust suggests a division into three zones zone 1 is where the magnetic signature is negligible or of relatively low intensity at mars global surveyor mgs satellite mapping altitude 400 km zone 2 is the region of intermediate crustal magnetic amplitudes and zone 3 is where the highest magnetic intensities are measured crater demagnetization near zone 3 reveals the presence of rocks with both high magnetic intensity and coercivity magnetic analyses of terrestrial rocks show that compositional banding in orogenic zones significantly enhances both magnetic coercivity and thermal remanent magnetization trm efficiency such enhancement offers a novel explanation for the anomalously large intensities inferred of magnetic sources on mars we propose that both large magnetic coercivity and intensity near the south pole is indicative of the presence of a large degree of deformation associated compositional zoning creates conditions for large scale magnetic anisotropy allowing magnetic minerals to acquire magnetization more efficiently thereby causing the distinct magnetic signatures in zone 3 expressed by intense magnetic anomalies we use a simple model to verify the magnetic enhancement we hypothesize that magnetically enhanced zone would reside over the down welling plume at the time of magnetization acquisition

subduction of aseismic ridges beneath the caribbean plate implications for the tectonics and seismic potential of the northeastern caribbean normal seafloor entering the puerto rico and northern lesser antillean trenches in the northeastern caribbean is interrupted by a series of aseismic ridges on the north and south american plates these topographic features lie close to the expected trend of fracture zones created about 80 110 m y ago when this seafloor was formed at the mid atlantic ridge the northernmost of the ridges that interact with the lesser antillean subduction zone the barracuda ridge intersects the arc in a region of high seismic activity some of this seismicity including a large shock in 1974 occurs within the overthrust plate and may be related to the deformation of the caribbean plate as it overrides the ridge a large bathymetric high the main ridge is oriented obliquely to the puerto rico trench and intersects the subduction zone north of the virgin islands in another cluster of seismic activity along the inner wall of the trench data from a seismic network in the northeastern caribbean indicate that this intersection is also characterized by both interpolate and intraplate seismic activity magnetic anomalies bathymetric trends and the pattern of deformed sediments on the inner wall of the trench strongly suggest that the main and barracuda ridges are parts of a formerly continuous aseismic ridge a segment of which has recently been overridden by the caribbean plate reconstruction of mid miocene to recent plate motions also suggest that at least two aseismic ridges and possibly fragments of the bahama platform have interacted with the subduction zone in the northeastern caribbean the introduction of these narrow segments of anomalous seafloor into the subduction zone has segmented the arc into elements about 200 km long these ridges may act as tectonic barriers or asperities during the rupture processes involved in large earthquakes they also leave a geologic imprint on segments of the arc with which they have interacted a 50 km landward jump of the locus of island arc volcanism occurred in late miocene time along the northern half of the lesser antilles we postulate that the subduction of a segment of seafloor of anomolously thick crust being more buoyant than adjacent seafloor resulted in a marked shoaling in the dip of the descending slab and therefore a shift of the locus of volcanism in the region near western puerto rico and eastern hispanolia plio pleistocene interaction with a similar feature in this case a part of the bahama platform about 3 4 m y ago led to a jump in the locus of subduction as evidenced by a gap in the downgoing seismic zone that segment of the bahama platform interferred with the subduction process and was subsequently sutured onto the caribbean plate when the boundary jumped about 60 km to the northeast the maximum size of historic shallow earthquakes along the lesser antillean arc varies from about 7 0 7 5 in the center of the arc where the dip of the shallow part of the plate boundary is steep to 8 0 8 5 along the northern part of the arc where the dip is shallow the interaction of anomalous seafloor as along the northern lesser antilles can lead to the development of a wider than normal zone of interplate contact and hence to earthquakes that are larger than those associated with more typical seafloor entering subduction zones major seismic gaps and regions of high seismic potential currently exist along the northern lesser antilles and to the north of puerto rico both gaps are bounded by anomalous features on the downgoing plate the intersection of these features with the plate boundary created large asperities that may be good places to search for precursors to future large earthquakes a great shock in 1787 may have ruptured an existing seismic gap north of puerto rico between 65 and 67 w thus that gap can be expected to eventually rupture again in a great shock and not to accommodate plate motion by totally aseismic processes

vorlanite cau6 o4 a new mineral from the upper chegem caldera kabardino balkaria northern caucasus russia the new mineral vorlanite cau 6 o 4 d calc 7 29 g cm 3 h 4 5 vhn 10 360 kg mm 2 was found near the top of mt vorlan in a calcareous skarn xenolith in ignimbrite of the upper chegem caldera in the northern caucasus kabardino balkaria russia vorlanite occurs as aggregates of black platy crystals up to 0 3 mm long with external symmetry 3 m the strongest powder diffraction lines are d a hkl 3 107 111 2 691 200 1 903 220 1 623 311 1 235 331 1 203 420 1 098 422 0 910 531 single crystal x ray study gives isometric symmetry space group fm 3 m a 5 3813 2 a v 155 834 10 a 3 and z 2 x ray photoelectron spectroscopy indicate that all u in vorlanite is hexavalent the mineral is isostructural with fluorite and uraninite u 4 o 2 in contrast to synthetic rhombohedral cauo 4 and most u 6 minerals the u 6 cations in vorlanite are present as disordered uranyl ions 8 ca 2 and 8 u 6 are disordered over a single site with average m o 2 33 a vorlanite is believed to be a pseudomorphic replacement of originally rhombohedral cauo 4 we assume that this rhombohedral phase transformed by radiation damage to cubic cauo 4 vorlanite the new mineral is associated with larnite chegemite reinhardbraunsite lakargiite rondorfite and wadalite which are indicative of high temperature formation 800 c at shallow depth

coastal morphology and late quaternary history cayman islands west indies abstract instrumental surveys of coastal profiles in the cayman islands western caribbean reveal the presence of a horizontal erosional bench at 1 9 m on grand cayman and a deep horizontal notch at 6 4 m on cayman brac but no raised erosional features on little cayman each island is surrounded by a horizontal constructional raised reef usually below 2 m here dated by u series methods as 124 000 8000 yr old and hence broadly contemporary with other western atlantic raised reefs of similar elevations the different raised erosional features indicate independent vertical tectonic movement of the three islands predating the formation of the raised reef the accordance and horizontality of the raised reef indicates stability of the islands since the last interglacial times an erosional notch at present sea level has formed since the sea reached its present level less than 2100 b p and algal benches on exposed coasts are also in equilibrium with present conditions

fe ti oxides in metamorphic basites from the eastern alps austria a contribution to the formation of solid solutions of natural fe ti oxide assemblages the development of fe ti oxide assemblages in basic rocks from the penninic series of the southern venediger rea austria during polyphase alpine metamorphism has been studied textural and compositional relations indicate thorough reequilibration of the opaque mineral assemblages during late barrovian metamorphism at essentially static conditions of lower amphibolite to greenschist facies in contrast silicate mineralogy of the preceeding blueschist to eclogite facies metamorphism might still be preserved to a large extent

the origin of magnetic anomalies in lower crustal rocks labrador mid to lower crustal granulites near wilson lake in central labrador exhibit pronounced aeromagnetic anomalies areas characterized by high and low field strength correlate with the wilson lake allochthon and the surrounding autochthon respectively the induced magnetization in both units has mean values of 0 34 a m allochthon and 0 33 a m autochthon however the mean values of remanent magnetizations are 9 2 a m allochthon and 3 3 a m autochthon in directions contributing to the present geomagnetic field therefore the remanent magnetization plays the main role in generating the observed magnetic anomaly thermal demagnetizations indicate that titanhematite is stable to 585 600 c the absence of significant verwey transitions indicates that titanhematite is the predominant carrier in some rocks and a significant carrier along with magnetite in others any interpretation of the magnetic anomalies above these rocks must consider magnetic remanence as the principle anomaly source

barbuda an emerging reef and lagoon complex on the edge of the lesser antilles island are the pliocene to holocene limestones of barbuda have formed on a wide shallow outlying bank of the lesser antilles island arc some 50 km east of the older axis of the limestone caribbees and 100 km east of the newer axis of the active volcanic caribbees contrasts with neighbouring islands of similar size include the lack of exposed igneous basement or mid tertiary sediments the dominance of younger flat lying carbonates and the greater frequency of earthquake shocks the history of emergence of the island has been studied through aerial reconnaissance mapping logging hand coring facies and microfacies analysis these show a pattern of progressively falling high sea level stands from more than 50 m down to the present level on which are superimposed at least three major phases of subaerial exposure when sea levels were close to or below their present level this sequence can be summarized as follows 1 bank edge facies early pliocene highlands formation deposited at not more than c 50 100 m above the present sea level 2 emergence with moderate upwarping in the north associated with the bat hole subaerial phase forming widespread karst 3 older pleistocene transgression with fringing reefs and protected bays formed at l0 to l5 m high sea level stands beazer formation 4 marl pits subaerial phase with widespread karst and soil formation 5 late pleistocene transgression up to 6 m high stand with fringing and barrier reefs protected backreefs and bays codrington formation phase i 6 gradual regression resulting in emergence of reefs enclosure of lagoons and progradation of beach ridges at heights falling from c 5 m to below present sea level codrington phase ii 7 castle bay subaerial phase produced karst caliche and coastal dunes that built eastwards to below present sea level and 8 holocene transgression producing the present mosaic with reefs lagoons and prograding beach ridge complexes with the present sea level reached before c 4085 years bp the evidence suggests that slight uplift took place in the north of the island after early pliocene times subsequent shoreline fluctuations are consistent with glacio eustatic changes in sea level indicating that the island has not experienced significant uplift during the quaternary

long term analog of carbonation in travertine from uleimat quarries central jordan quaternary travertine capping the metamorphic cement zones in uleimat quarries central jordan has been precipitated from hyperalkaline paleogroundwaters such waters are similar to the cement pore water and to the present day hyperalkaline seepages ph 12 5 in maqarin north jordan the isotopic depletions observed in uleimat travertine with 13c values as low as 25 45 suggest that they have been precipitated during co2 uptake by highly alkaline calcium hydroxide waters the travertine in uleimat quarries indicates a long term analog of carbonation and remobilization of silica in cementitious barriers for radioactive waste repositories the presence of cr rich smectites and relatively high levels of cr 4 1 v 657 ppm ni 163 ppm zn 634 ppm and u 34 ppm in the green travertine and the associated opaline silica phases suggests the use of the uleimat travertines as analogs with the repository disturbed zone smectites and silica phases are expected to be a sink for alteration products in the late stage evolution of a high ph plume co precipitation of these elements in mineral phases is of great importance to control the concentration of these elements in groundwater

search for magnetic minerals in martian rocks overview of the rock abrasion tool rat magnet investigation on spirit and opportunity 1 the rock abrasion tool rat on board the mars exploration rovers mer is a grinding tool designed to remove dust coatings and or weathering rinds from rocks and expose fresh rock material four magnets of different strengths that are built into the structure of the rat have been attracting substantial amounts of magnetic material during rat activities from rocks throughout both rover missions the rat magnet experiment as performed on spirit demonstrates the presence of a strongly ferrimagnetic phase in gusev crater rocks which based on mossbauer and visible near infrared reflectance spectra is interpreted as magnetite the amount of abraded rock material adhering to the magnets varied strongly during the mission and is correlated in a consistent way to the amount of magnetite inferred from mossbauer spectra for the corresponding rock the rat magnet experiment as performed on opportunity also indicates the presence of a strongly ferrimagnetic phase in outcrops such as magnetite or an altered version of magnetite however the evidence is weaker than in the case of spirit according to data from the particle x ray spectrometer apxs and the mossbauer spectrometer mb the eagle crater outcrops should not contain magnetite and their magnetization should not exceed 0 03 a m2 kg 1 however this assertion seems to be in contradiction with the results of the rat magnet experiment the evidence for a strongly ferrimagnetic phase at low abundance in the meridiani outcrops is discussed

13c 12c partitioning and kinetics of co2 absorption by hydroxide buffer solutions abstract absorption of co2 gas into a borate buffer solution is a linear function of time the measured absorption rate logr 10 33 mol cm 2 s 1 compares well to a value calculated from the diffusion constant of co2 aq and the rate constant for the reaction of co2 aq with oh the stable carbon isotope composition of the dissolved carbonate is constant as function of time and is depleted in13c by 19 5 with respect to the gas phase the kinetic fractionation due to diffusion is 13d 12d 0 5 1 103 0 7 while that caused by the chemical reaction is 13k 12k 0 5 1 103 18 8 these values have to be taken into account if a borate buffer is used for sample concentration techniques in order to deduce the carbon isotope composition of co2 g absorption of co2 into a ba oh 2 solution is a linear function of time too but the absorption rate varies with the experimental boundary conditions the precipitated baco3 is depleted in13c with respect to the gas phase however 13c values are not constant and decrease as a function of time

natural analogs of belite sulfoaluminate cement clinkers from negev desert israel ye elimite larnite rocks in the hatrurim formation of the negev desert israel are natural analogs of belite sulfoaluminate bsa cement clinkers they have been produced by ultrahigh temperature combustion metamorphism at ambient pressure of a calcareous sedimentary precursor their mineralogy consists of 35 50 vol ca2sio4 15 20 vol ye elimite 7 15 vol ferrites and 15 20 vol fluorapatite and or fluorellestadite a few grains of hatrurite ca3sio5 and ca2sio4 have been observed as well the composition of and ca2sio4 polymorphs by epma are near ca1 96 1 98na0 01 0 02 si0 96p0 03al0 01o4 whereas ye elimite has an approximate composition by epma of ca3 99mg0 02ba0 01na0 02k0 02al5 73fe3 0 16si0 10s0 97p0 02o16 the al content of brownmillerite ca2 fe1 x al x 2o5 ranges from x 0 20 0 27 fe analog of shulamitite ca3fe2tio8 contains up to 15 1 wt tio2 ye elimite larnite rocks were derived from chalky sediments by burning of combustible gas with a t max at 1200 1350 c the mineral content microstructure and texture fabric of the ye elimite larnite rocks imply that chalky and or marly sediments with randomly distributed clay phosphorite and gypsum may be utilized as cheap naturally homogenized and pulverized mixtures for industrial production of bsa cement clinker as an environment friendly alternative to ordinary portland cement opc

late cenozoic marine deposition in the united states atlantic coastal plain related to tectonism and global climate abstract major hiatuses in upper cenozoic marine deposits in the united states atlantic coastal plain are recognized on the basis of molluscan faunal changes at erosional unconformities these hiatuses generally coincided with periods of global cooling and ice sheet formation such hiatuses provide information to supplement global climatic data major hiatuses are recognized within the early miocene 23 20 m y ago at the end of the middle miocene 11 10 m y ago at the end of the late miocene 6 5 5 m y ago at the end of the early pliocene 4 0 2 5 m y ago at the end of the late pliocene 1 9 or 1 8 m y ago within the pleistocene 1 1 0 5 m y ago and several times within the last 0 4 m y estimates of the amount of water contained in ice sheets at different times in the pliocene and pleistocene facilitate calculation of probable minimum sea levels on the coastal plain during different high stands of the sea the altitudes of dated shoreline deposits in the atlantic coastal plain show that the amount of uplift in the cape fear area has averaged at least 1 3 cm per 1000 years since the beginning of pliocene time the coastal plain of georgia has apparently experienced relatively little vertical deformation during this same time

stable isotope evidence for near surface low temperature formation of mg hydro carbonates in highly altered greek mesozoic serpentinites authigenic magnesite hydromagnesite and huntite associated with intensely altered and serpentinized ophiolitic rocks in attica mainland greece occur predominantly as veinlets and nodules within a totally weathered former serpentinite groundmass carbonate 18 o values are consistent with post geothermal fluid temperatures between 25 and 70 c but mostly between 25 and 30 c from a dominantly meteoric sourced groundwater indicating near surface low temperature conditions despite the proximity of a volcanic centre with strong co 2 flux 75 of the carbon isotope data imply little or no incorporation of this co 2 into the authigenic mg hydro carbonates indeed many 13 c values are more negative than soil zone calcrete values and in this setting mg hydro carbonate 13 c values below 6 vpdb probably indicate disequilibrium effects in alkaline groundwaters geothermal fluids and groundwaters were mainly routed through structural conduits some of the low temperature hydromagnesite subsequently dehydrated to magnesite under near surface conditions and huntite is probably a diagenetic transformation of hydromagnesite forming close to the volcanic centre where fluid mg ca ratios were low the isotopic signatures are distinct from previously published balkan east mediterranean magnesite data arrays but are consistent with many other ultramafic associated magnesium carbonates worldwide their association with likely fluid compositions provides important context for mg hydro carbonate formation as geothermal conditions cool to near surface temperatures

a sediment based reconstruction of caribbean effective precipitation during the little ice age from freshwater pond barbuda contemporary climate dynamics of the circum caribbean region are characterised by significant precipitation variability on interannual and interdecadal timescales controlled primarily by el nino southern oscillation enso and the atlantic multidecadal oscillation amo however our understanding of pre industrial climate variability in the region is hampered by the sparse geographic distribution of palaeoclimate archives here we present a high resolution reconstruction of effective precipitation for barbuda since the mid 16th century based on biostratigraphic and stable isotope analyses of fossil ostracods and gastropods recovered from lake sediment cores from freshwater pond the only freshwater lake on the island we interpret episodic fluctuations in shell accumulation in the sediment record to represent changes in the balance between precipitation and evaporation during the little ice age lia 1400 1850 ce and industrial 1850 present periods comparisons between indices of reconstructed enso and amo variability the abundance of the freshwater gastropod pyrgophorus parvulus and the 18o records from ostracod calcite suggest that the relative influence of enso and amo on long term rainfall patterns in barbuda has changed over the last 400 years our findings are in agreement with other high resolution palaeoclimate studies that suggest that long term changes in effective precipitation during the lia were much more variable temporally and spatially than previously suggested

mineralogy of the sources for magnetic anomalies on mars abstract recent discovery of intense magnetic anomalies on mars which are due to remanent magnetization requires some explanation for the possible minerals responsible for the anomalous signature thermoremanent magnetization trm in single domain sd and multidomain md sized magnetite hematite and pyrrhotite all potential minerals are considered the intensity of trm in 0 05 mt is in descending order sd sized magnetite sd sized pyrrhotite md sized hematite md sized pyrrhotite md sized magnetite sd sized hematite the trm intensity is 50 of the sirm each of these minerals and estimated concentrations of magnetic remanence carriers assumed to be titanomagnetite in the shergotty nakhlaxhassigny martian meteorites are used in a thin sheet approximation model to reveal the concentration of each mineral required for the generation of an observed magnetic anomaly 1 500 nt at 100 km altitude assuming trm acquisition in a 0 05 mt magnetic field