cosmogenic nuclides in the kirin chondrite abstract radioactive and stable cosmogenic nuclides have been determined in the various fragments of the kirin chondrite h5 experimental results obtained from our samples are described and compared with similar data obtained in other laboratories cosmogenic 54 mn 22 na 60 co 26 al 53 mn 40 k in the metal phase and light noble gases were measured based on these data the irradiation history of this meteorite can be explained in terms of 1 a multi stage exposure which involves a first stage irradiation for 10 7 years and a second stage for about 4 10 5 years and 2 depth effects in the productions of the nuclides in 4 second stage and 2 first stage geometries these conclusions are consistent with those of our previous work which was based on a limited number of samples

the 1986 kalamata south peloponnesus earthquake detailed study of a normal fault evidences for east west extension in the hellenic arc tectonic and seismological data collected in the field following the september 13 1986 kalamata earthquake south peloponnesus are presented and analyzed to discuss the earthquake rupture process and the regional tectonics the event occurred on the kalamata normal fault whose trace was mapped with spot images and topographic and field observations this fault is part of an approximately nnw sse en echelon system cutting through the hellenic nappes the fault striking n15 e on the average with a dip of about 50 has a minimum cumulated quaternary throw of the order of 1 km the measured coseismic slip is 6 18 cm over a length of 6 km the main shock focal mechanism obtained from long period waveform modeling strike 201 10 20 dip 45 5 rake 283 10 25 represents almost pure east west extension and is in good agreement with tectonic observations the centroid depth is constrained to 5 3 km and the seismic moment to 7 0 2 5 1017 n m over 700 aftershocks located by a 16 station network installed after the earthquake for a period of 2 weeks define two clusters separated by a gap of aftershock activity from the surface to a depth of about 10 km the main cluster to the south defines a 45 west dipping plane which lies on the downward extension of the fault mapped at the surface focal mechanisms of aftershocks on this fault plane are homogeneous and represent e w extension as the main shock in contrast the majority of focal mechanisms in the uppermost part of the foot wall show more or less e w compression probably corresponding to postseismic stress release the northern cluster of aftershocks is very dense and located away from the surface rupture within a relay zone between the kalamata and the next en echelon faults to the nw the thouria faults there focal mechanisms represent extension from about n115 to n70 and n20 corresponding mostly to fault reactivation in an area where nonrigid deformations prevail the main shock probably initiated in this relay zone 3 4 s before the rupture front reached the main fault plane and released most of the energy there the rupture presumably propagating southward the focal mechanism of the kalamata earthquake and that of the april 27 1965 earthquake located to the northwest of crete as well as the regional active normal fault pattern imply that e w extension oblique to the hellenic arc is presently the dominant tectonic regime e w stretching occurs partly on reactivated nw se faults parallel to the hellenic structures but mostly on newly formed n s normal faults across those structures the latter faults are responsible for the apparent segmentation of the hellenic belt from southern peloponnesus to crete the existence of active e w extension in this region implies a recent change in the tectonic regime and consequently a change in boundary conditions at the subduction zone probably in response to the incoming margin of africa

hf w chronometry of core formation in planetesimals inferred from weakly irradiated iron meteorites abstract the application of hf w chronometry to determine the timescales of core formation in the parent bodies of magmatic iron meteorites is severely hampered by 182w burnout during cosmic ray exposure of the parent meteoroids currently no direct method exists to correct for the effects of 182w burnout making the hf w ages for iron meteorites uncertain here we present noble gas and hf w isotope systematics of iron meteorite samples whose w isotopic compositions remained essentially unaffected by cosmic ray interactions most selected samples have concentrations of cosmogenic noble gases at or near the lowermost level observed in iron meteorites and for iron meteorite standards have very low noble gas and radionuclide based cosmic ray exposure ages

new constraints on the active tectonic deformation of the aegean 1 site velocities from six separate global positioning system gps networks comprising 374 stations have been referred to a single common eurasia fixed reference frame to map the velocity distribution over the entire aegean we use the gps velocity field to identify deforming regions rigid elements and potential microplate boundaries and build upon previous work by others to initially specify rigid elements in central greece the south aegean anatolia and the sea of marmara we apply an iterative approach tentatively defining microplate boundaries determining best fit rigid rotations examining misfit patterns and revising the boundaries to achieve a better match between model and data short term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long term kinematics we find that present day aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them the rms misfit of model to data is about 2 sigma very good when compared to the typical match between coseismic fault models and gps data the simplicity of the microplate description of the deformation and its good fit to the gps data are surprising and were not anticipated by previous work which had suggested either many rigid elements or broad deforming zones that comprise much of the aegean region the isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain year nstrain year 10 9 year 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries lower strain rates may exist elsewhere within the microplates but are only resolved in anatolia where extension of 13 4 nstrain year is required by the data our results suggest that despite the detailed complexity of active continental deformation revealed by seismicity active faulting fault geomorphology and earthquake fault plane solutions continental tectonics at least in the aegean is to first order very similar to global plate tectonics and obeys the same simple kinematic rules although the widespread distribution of aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized

transformation of jarosite to hematite in simulated martian brines the presence of jarosite a hydrous iron sulfate at meridiani planum supports the past existence of water on mars surface thermodynamic calculations suggest that jarosite should transform to ferric oxyhydroxides in aqueous media here we show that jarosite can transform directly to hematite the iron oxide identified at meridiani planum in simulated martian brines our results are consistent with a short aqueous history but also indicate that jarosite can persist in highly saline martian brines the formation of goethite a common iron oxyhydroxide on earth is prevented by the low water activity and or high phosphate concentration of martian brines

composition of metal in aubrites constraints on core formation abstract aubrites are differentiated stone meteorites with small amounts of metal study of eight aubrites reveals that fe ni grains occur in a variety of textures from irregular m sized particles to rounded nodules of up to 1 5 cm in diameter the pattern of siderophile element abundances in the silicates is characteristic of igneous metal segregation the more siderophilic elements are more depleted despite large uncertainties in metal silicate distribution coefficients the calculated minimum metal content of the aubrite precursor is not unlike that of enstatite chondrites and suggests that metal segregation was an extensive process in the early magmatic evolution of the aubrite parent body however the lack of appreciable fractionation in the trace element signature of the metal suggests that the metal now observed in aubrites did not undergo fractional crystallization in a core we argue instead that the analyzed metal nodules represent a fraction of the iron nickel that during partial melting was not completely segregated from the silicates

chaotic obliquity and the nature of the martian climate recent calculations of the martian obliquity suggest that it varies chaotically on timescales longer than about 107 years and varies between about 0 and 60 we examine the seasonal water behavior at obliquities between 40 and 60 up to several tens of centimeters of water may sublime from the polar caps each year and possibly move to the equator where it is more stable co2 frost and co2 h2o clathrate hydrate are stable in the polar deposits below a few tens of meters depth so that the polar cap could contain a significant co2 reservoir if co2 is present it could be left over from the early history of mars also it could be released into the atmosphere during periods of high obliquity causing occasional periods of more clement climate

behavior of ni zn and cr during low temperature aqueous fe oxidation processes on mars abstract the behavior of ni ii zn ii and cr iii during the melanterite feso4 7h2o to hematite fe2o3 oxidative transformations involving evolution pathways via jarosite h3o k fe3 oh 6 so4 2 schwertmannite fe8o8 oh 6 so4 and goethite feooh were investigated in an acidic saturated mgso4 matrix results provide important clues about how elevated levels of trace elements are incorporated into the secondary fe mineralogy assemblages found on mars and the mechanism for formation of hematitic concretions at meridiani planum on mars our results demonstrate that starting at the same concentrations in the initial solution final amounts of ni zn and cr in hematite via different pathways are very different in path 1 melanterite jarosite hematite partitioning of ni zn and cr into jarosite and hematite formed through dissolution of jarosite is most likely in the order cr zn ni in path 2 melanterite schwertmannite goethite hematite schwertmannite and goethite exhibited strong affinities for divalent ni and zn during such a pathway ni should accumulate more than zn by at least a factor of two and partitioning of ni zn and cr to the hematite is most likely in the order cr ni zn therefore our results suggest that the high ni and moderate zn distribution pattern observed in meridiani hematitic spherule bearing samples can be explained best by the schwertmannite goethite to hematite pathway path 2 without need for an additional high ni source in this region although the lack of goethite at meridiani renders it uncertain if goethite ever served as a precursor to facilitate hematite formation dehydration of nano crystalline goethite is thermodynamically favored and cannot be ruled out on the other hand if hematitic concretions were formed by dissolution of jarosite path 1 then much higher initial ni zn ratios than 1 in initial diagenetic fluids may be necessary to explain the elevated levels of ni in the spherules cr iii when starting in equal amounts as ni and zn in the solution accumulated at least two orders of magnitude more than ni and zn in all fe iii phases given that cr concentrations are of the same order of magnitude as ni and zn in most rocks and soils measured by the rover opportunity cr concentrations should be much lower than ni and zn in the initial diagenetic fluids mobility of cr was greatly limited by precipitation of fe iii phases due to substitution for fe iii and sequestration in the solids

the 36cl 36ar 40k 41k records and cosmic ray production rates in iron meteorites this is the first contribution towards a reevaluation of exposure histories of iron meteorites and of the constancy of the cosmic ray flux over the last billion years as recorded in these fossil detectors we have performed new 36cl 26al 10be and noble gas measurements including determination of the shielding parameter s 4he 21ne in samples with published k data the k isotopic data coupled to 36ar and 36cl concentrations permit selection of meteorites which have only experienced simple constant geometry irradiation histories these objects can be used for the calibration of shielding dependent production rates within these metallic detectors in order to carry out production rate calibrations based on 40k 41k data we assume constancy of the cosmic flux during the interval 150 to 700 my ago we note that meteorites with very old potassium ages cannot be included in this calibration as these meteorites require distinct parameter sets a calibration data set representing a total of 13 meteorites was used to compute long term 0 5 gy average production rates these average production rates of 36cl from this particular calibration set are significantly 28 lower than those determined for the recent 10 my cosmic ray flux we also document here the quality of the resulting potassium production rate parameter m0 s with a calculated isochron for irons of group iva

crustal motion and strain accumulation in western bulgaria abstract global positioning system gps data acquired between 1996 and 2004 and fault plane solutions for four seismic zones are analyzed to obtain the velocity and strain rate fields for western bulgaria the gps derived velocities suggest that southwestern bulgaria moves to the s to sse at a rate of 1 mm year with respect to northern bulgaria and southern romania defining an approximately ese trending extensional boundary that marks the northernmost extent of the aegean extensional domain the boundary includes the e w trending sub balkan graben system of central bulgaria and its westward continuation into the sofia graben active faults within the boundary region trend ene to wnw and they have normal or oblique normal and strike slip displacements consistent with the velocity field within the western part of the boundary region extension is transferred to the north of the sofia graben across the westernmost part of the stara planina mountains and the ridges of the western sredna gora the geodetically derived n s extension is in agreement with the seismic data that show a variable pattern but with projections of the t axes mostly lying within the n s quadrant the predominant type of faulting is caused by sub horizontal extensional stresses in an approximate n s direction this is consistent with extension and oblique strike slip interpreted from geological studies that show numerous wnw ene to e w trending active normal faults in western bulgaria

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

26al and10be production in iron meteorites abstract we have measured by accelerator mass spectrometry the 26 al contents of 20 and the 10 be contents of 14 iron meteorites the 26 al contents are typically 30 or more lower than values obtained by counting techniques the 10 be contents are 10 15 lower the production rates p of these nuclides decrease by more than a factor of two as the 4 he 21 ne ratio increases with increasing shielding from 200 to 400 for the lighter shielding conditions expected in stony meteorites we estimate p 26 fe as 3 4 dpm kg and p 10 fe as 4 5 dpm kg the average p 10 p 26 activity ratio is close to 1 5 exposure ages calculated from 21 ne 26 al ratios cannot be calibrated so as to agree with both 40 kk ages and ages based on the shorter lived nuclides 39 ar and 36 cl if agreement with the latter is forced then the disagreement with 40 kk ages may signal a 35 increase in the cosmic ray intensity during the last 10 7 a

seismic coupling and structure of the hellenic subduction zone in the ionian islands region abstract the western hellenic arc has been commonly considered as a largely aseismic subduction zone from the comparison of a small rate of shortening derived from the seismic moment release with a large rate of convergence inferred from geology complete seismic coupling would instead be expected from models that consider a control by plate tectonic forces because of the trenchward velocity of the hellenic aegean upper plate now confirmed with gps measurements in the region of the ionian islands a subduction interplate boundary has been recently imaged and its seismogenic downdip width suggested to be moderate from reflection seismic profiling and local earthquake tomography in the appropriate model for such an earthquake source region which considers a single interplate fault and takes into account these features the moderate seismic moment release is found consistent with complete seismic coupling of this subduction the shallow downdip limit of the seismogenic zone can be interpreted as due to the interplate boundary being overlain there by the ductile deeper crust of the orogenically thickened hellenides

formation of jarosite bearing deposits through aqueous oxidation of pyrite at meridiani planum mars 1 the discovery of sulfate rich layered deposits with hematite spherules at the landing site of the opportunity rover is consistent with mineral deposition in an aqueous environment we evaluate conditions responsible for the formation of a jarosite goethite gypsum assemblage with speciation calculations the results show that the assemblage could have precipitated from acidic solutions formed through near surface aqueous oxidation of pyrite our hypothesis is that regional heating in the meridiani planum caused a release of sulfide rich hydrothermal waters leading to formation of pyrite rich regional deposits in a depression aqueous oxidation of these deposits by atmospheric o2 created an acidic environment that allowed formation of sulfates and goethite partial neutralization of the solution caused further goethite precipitation and conversion of jarosite to goethite leading to formation of goethite concretions subsequent dehydration of goethite to coarse grained hematite would also have been facilitated by regional heating

fe oxidation processes at meridiani planum and implications for secondary fe mineralogy on mars fe oxidation processes may have occurred during groundwater mediated diagenesis in meridiani planum sediments to address this question melanterite oxidation experiments were conducted at epsomite saturation as a function of ph results show that schwertmannite is initially formed from acidic fe oxidation and that its formation and aging to mixtures of jarosite and nanocrystalline goethite is strongly controlled by ph over the range b 2 0 4 0 the ph is controlled in turn by fe oxidation and fe3 hydrolysis in one 77 d oxidation experiment nanocrystalline hematite was tentatively identified by mc6ssbauer spectroscopy accordingly aging experiments with synthetic nanocrystalline goethite were conducted 1 to further resolve the formation mechanisms of fe phases identified from oxidation experiments and 2 to test whether low water activity aw controls the thermodynamically favored goethite to hematite transition at low temperature mc6ssbauer spectroscopy and total x ray scattering show no observable changes after 4 months of aging and instead these results point to a jarosite precursor for the tentatively identified hematite on the basis of these results we suggest that the oxidation and maturation of initially formed fe2 bearing saline minerals may account in large part for the distribution of secondary fe minerals at the martian surface contributing to the association of fe oxides and mg ca sulfates observed from orbital surface analyses we hypothesize that oxidation of fe2 sulfates at low temperature could account for sustained diagenetic acidity in addition to much of the observed fe mineralogy in meridiani planum outcrop rocks the origin of the gray crystalline hematite at meridiani however is deserving of further experimental work to test this mechanism copyright 2008 by the american geophysical union

hydrated minerals in the deposits of aureum chaos abstract hydrated minerals have been detected in many martian chaos regions and chasmata playing a major role in its past aqueous activity based on short wave infrared data from crism imagery and elevation data we identified and mapped hydrated minerals in aureum chaos to shed light on their stratigraphy and geological context the interior layered deposits ilds display three stratigraphic units the lowest unit shows massive and also layered high albedo monohydrated sulfate mhs best matching kieserite 20 650 m thick with intercalated hydroxylated ferric sulfates hfss best matching jarosite and ferric oxides the overlying polyhydrated sulfate phs is commonly layered 20 40 m thick smooth to heavily fractured of lower albedo and partially contains ferric oxides spectrally neutral distinctly layered and bumpy cap rock 40 300 m thick forms the top we found spectral and morphological similarities to aram chaos phs mhs ferric oxides texture of ild and cap rock and juventae chasma hfs besides the phyllosilicate nontronite was found attributed to chaotic terrain as light toned fractured exposure and within dark smooth mantling the coexistence of sulfates and phyllosilicates indicates changes in the geochemistry of the aqueous environment since sulfates and phyllosilicates could be alteration products the observed mineralogy presumably is not the original conversions between phs and mhs mhs or phs into jarosite jarosite into iron oxides are considered due to its occurrence along mantling edges and on flat surfaces of mhs without textural differences it appears that phs is an alteration product of mhs e g due to surface exposure the facies and relative timing of sulfate formation remains undefined however two different formation models are considered the first implies contemporaneous ild and phs deposition and diagenetic sulfate conversion into mhs iron oxides due to overburden later on this model is less conclusive than groundwater evaporation the second model due to the lack of a sharp phs mhs boundary that would indicate a diagenetic formation alternatively the second model suggests subsequent sulfate formation groundwater would have penetrated into pre existing sulfate free ild the permeability and porosity of ild material would have defined the rate of water absorption and sulfate precipitation low in cap rock resulting in cementation of probably aeolian deposited ilds we think this model is more consistent and could explain ild stratigraphy with the potential anhydrous cap rock on top the surface age of chaotic terrain late hesperian and mantling deposits mid to late amazonian limit the ild age and possibly the emplacement of sulfates phyllosilicates in the mantling are presumably allochthonous limiting the timing of in situ phyllosilicates is more complicated they could be noachian excavated material following the phyllosian era or instead syn or post chaotic a close spatial and temporal association of sulfates and phyllosilicates in which nontronite represents the deep facies and sulfates the evaporitic facies is known from earth and is also possible and would combine groundwater alteration with the observed mineralogy the preservation of nontronite hfs and mhs probably reflects a relatively dry environment with intermittent aqueous activity since their emplacement

establishment of a continuous gps network across the kephalonia fault zone ionian islands greece abstract we report on the establishment of a continuous gps network across the kephalonia fault zone kfz central ionian islands greece the kfz is an important segment of the boundary zone between the rapidly moving aegean microplate and the apulian platform italy repeated gps measurements carried out between the northern ionian islands and the island of crete have shown rates of crustal motion of the aegean reaching 35 mm a oriented sw relative to southern italy the kfz coincides with a maximum shear strain rate 180 nano strain a and a very high level of seismicity in order to monitor the ongoing deformation across the kfz and correlate the strain accumulation with earthquakes a continuous gps network has been installed operating at a sampling rate of 5 s this paper describes the instrumental set up the data logging strategy and first preliminary results

synthesis of akaganeite in the presence of sulfate implications for akaganeite formation in yellowknife bay gale crater mars abstract akaganeite a cl bearing fe iii hydr oxide has been recently discovered in yellowknife bay in gale crater on mars by the mars science laboratory msl curiosity rover akaganeite was associated with sulfate and sulfide minerals at yellowknife bay indicating that sulfate ions could be present in solution during akaganeite formation the mechanism and conditions of akaganeite formation in the yellowknife bay mudstone are unknown we investigated formation of akaganeite through hydrolysis of ferric chloride solution in the presence of 0 0 01 0 05 0 1 and 0 2 m sulfate and at initial ph of 1 5 2 and 4 at 90 c mineralogy of the precipitated fe iii phases was characterized by x ray diffraction and infrared spectroscopy the precipitates were also acid digested to determine total sulfate and chloride contents akaganeite and natrojarosite formed at initial solution ph of 1 5 akaganeite goethite and natrojarosite precipitated in initial ph 2 solutions and goethite hematite and 2 line ferrihydrite precipitated at initial solution ph of 4 sulfate addition did not inhibit akaganeite formation increasing initial solution sulfate concentrations resulted in increasing sulfate to chloride ratio in the precipitated akaganeite infrared spectroscopy revealed akaganeite bands at 2 m h 2 o combination band and at 2 46 m oh combination band the h 2 o combination band position linearly correlated with total chloride content in akaganeite overall laboratory studies demonstrated formation of akaganeite at initial sulfate concentration 0 2 m sulfate to chloride molar ratio 0 3 and ph 2 implying that those conditions might prevail perhaps as micro environments during akaganeite formation in yellowknife bay mudstone the occurrence of fe ii sulfides pyrite and pyrrhotite in yellowknife bay mudstone is a potential acidity source dissolution of sulfide minerals might occur under localized oxidizing water limiting cl rich conditions creating favorable environments for akaganeite formation

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

jarosite formation by an amd sulphide oxidizing environmental enrichment implications for biomarkers on mars abstract the formation of jarosite in acid mine drainage amd accompanies microbial oxidation of reduced sulphidic minerals such as pyrite fes 2 and pyrrhotite fe 1 x s found in mining waste materials the discovery of jarosite at meridiani planum mars has been used to interpret past hydrologic conditions as episodically wet acidic and evaporative based on evidence from jarosite formed abiotically or through microbial iron oxidation to date no study has specifically assessed jarosite formation via microbial sulphide oxidation the most likely pathway in amd or the mineral stability of any jarosite formed via this pathway here using both aerobic and anaerobic conditions to control iron and sulphide oxidation metabolisms we demonstrate that oxidation of pyrrhotite a putative mars mineral by a sulphur oxidizing environmental amd enrichment produces crystalline jarosite at a higher ph than previously described we further show that jarosite produced via microbial sulphide oxidation is stable under the drying heating and wet aging conditions shown to impact abiotic and microbial iron oxidation derived jarosite our results indicate that preservation of microbially produced jarosite via pyrrhotite associated sulphide oxidation does not require the evaporitic conditions that have been proposed to date if water is established to have persisted on mars then this new evidence signals that the occurrence of stable crystalline jarosite at meridiani planum may itself be a clear biomarker indicating that not only water occurred at some time s on mars but also life

the complex exposure histories of the pitts and horse creek iron meteorites implications for meteorite delivery models the concentrations of cosmogenic radionuclides and noble gases in pitts iab and horse creek ungrouped provide unambiguous evidence that both irons have a complex exposure history with a first stage irradiation of 100 600 myr under high shielding followed by a second stage exposure of 1 myr as small objects the first stage exposure ages of 100 myr for horse creek and 600 myr for pitts are similar to cosmic ray exposure ages of other iron meteorites and most likely represent the yarkovsky orbital drift times of irons from their parent bodies in the main asteroid belt to one of the nearby chaotic resonance zones the short second stage exposure ages indicate that collisional debris from recent impact events on their precursor objects was quickly delivered to earth the short delivery times suggests that the recent collision events occurred while the precursor objects of horse creek and pitts were either very close to the chaotic resonance zones or already in earthcrossing orbits since the cosmogenic noble gas records of horse creek and pitts indicate a minimum radius of a few meters for the precursor objects but do not exclude km sized objects we conclude that these irons may represent fragments of two near earth asteroids 3103 eger and 1986 da respectively finally we used the cosmogenic nuclide concentrations in horse creek which contains 2 5 wt si to test current model calculations for the production of cosmogenic 10be 26al and neonisotopes from iron nickel and silicon

new constraints on the rapid crustal motion of the aegean region recent results inferred from gps measurements 1993 1998 across the west hellenic arc greece abstract in this paper we present the most recent observations of crustal motion across the entire west hellenic arc wha these are based on repeated gps measurements carried out in the period from 1993 to 1998 the results are presented in terms of trajectories and rates relative to eurasia within these five years southwestern greece has moved to the southwest by an average rate of 30 mm a increasing from 10 mm a at the island of lefkada in the center of the ionian islands to nearly 40 mm a along the southwest part of the peloponnesus and to 35 mm a on the islands of crete and gavdhos the data provide strong evidence that distributed shear strain starts at the kephalonia fault zone kfz were an anomalously high earthquake activity is also observed a striking interruption of the motion is seen at the island of strofades at the southwest leading edge of the wha where a south oriented displacement of 12 cm was detected coincident with the m 6 4 strofades earthquake of nov 18 1997

how long was meridiani planum wet applying a jarosite stopwatch to determine the duration of aqueous diagenesis jarosite dissolution rates can be used to determine the duration of water at meridiani planum and other environments containing this ephemeral metastable ferric sulfate salt the maximum duration of aqueous fluids in the region is calculated based on the dissolution rate of jarosite under varying temperature and ionic strength conditions jarosite lifetimes predicted in this study range from 1 5 a in warm dilute environments to 100 ka in nacl saturated brines at 250 k the preservation of jarosite within rocks at meridiani planum requires that aqueous fluids were active over a small fraction of the billions of years since jarosite formed or was deposited in the region limiting the probability of life being established in such a temporally restricted system in addition water related features such as hematite spherules and crystal molds must have formed relatively quickly during this geologically short period of aqueous diagenesis

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

jarosite and hematite at meridiani planum from opportunity s mossbauer spectrometer mossbauer spectra measured by the opportunity rover revealed four mineralogical components in meridiani planum at eagle crater jarosite and hematite rich outcrop hematite rich soil olivine bearing basaltic soil and a pyroxene bearing basaltic rock bounce rock spherules interpreted to be concretions are hematite rich and dispersed throughout the outcrop hematitic soils both within and outside eagle crater are dominated by spherules and their fragments olivine bearing basaltic soil is present throughout the region bounce rock is probably an impact erratic because jarosite is a hydroxide sulfate mineral its presence at meridiani planum is mineralogical evidence for aqueous processes on mars probably under acid sulfate conditions

new gps constraints on the africa eurasia plate boundary zone in southern italy 1 southern italy is a key area for understanding the tectonic processes in the africa eurasia collision zone we analyze new gps measurements carried out between 1994 and 2001 the results are presented in terms of time series trajectories and velocities of crustal motion as well as a geodetic strain rate field while central italy corsica sardinia and the tyrrhenian sea move like the eurasian plate the overall motion of the sicily rift zone region matches african plate motion unexpected are the north northwest directed motions of northeastern sicily and the eolian islands most striking on the deformation field are a north south oriented compression along the northern sicilian coast compression between apulia and northwestern greece as well as extension in the sicily rift zone and the interior of sicily

geochemical and mineralogical indicators for aqueous processes in the columbia hills of gusev crater mars 1 water played a major role in the formation and alteration of rocks and soils in the columbia hills the extent of alteration ranges from moderate to extensive five distinct rock compositional classes were identified the order for degree of alteration is watchtower clovis wishstone peace backstay the rover s wheels uncovered one unusual soil paso robles that is the most s rich material encountered clovis class rocks have compositions similar to gusev plains soil but with higher mg cl and br and lower ca and zn watchtower and wishstone classes have high al ti and p and low cr and ni peace has high mg and s and low al na and k backstay basalts have high na and k compared to plains adirondack basalts and paso robles soil has high s and p some rocks are corundum normative indicating that their primary compositions were changed by loss and or gain of rock forming elements clovis materials consist of magnetite nanophase ferric oxides npox hematite goethite ca phosphates ca and mg sulfates pyroxene and secondary aluminosilicates wishstone and watchtower rocks consist of fe oxides oxyhydroxides ilmenite ca phosphate pyroxene feldspar mg sulfates and secondary aluminosilicates peace consists of magnetite npox mg and ca sulfates pyroxene olivine feldspar apatite halides and secondary aluminosilicates paso robles consists of fe3 mg ca and other sulfates ca phosphates hematite halite allophane and amorphous silica columbia hills outcrops and rocks may have formed by the aqueous alteration of basaltic rocks volcaniclastic materials and or impact ejecta by solutions that were rich in acid volatile elements

the gps strain rate field in the aegean sea and western anatolia the gps velocity field of the aegean sea and western anatolia is used to determine crustal deformation strain rates for the period 1988 to 1996 the zone from the marmara sea to the north aegean trough is associated with strong right lateral shear motion with maximum strain rates of 170 nstrain a in the northern aegean sea the extensional deviatoric axes are oriented nne ssw associated with strain rates reaching 150 nstrain a and in western anatolia varying around n s with rates of up to 95 nstrain a the extensional areas mostly coincide with active graben features the south western aegean sea is almost strain free in general the areas of high geodetic strain rates are accompanied by distinct seismic clusters whereas the strain free regions are nearly aseismic

ferric sulfates on mars evidence is presented for the possible formation and existence of ferric sulfato complexes and hydroxo ferric sulfate minerals in the permafrost on mars acidic groundwater derived from atmospheric oxidation of volcanogenic h2s to h2so4 aerosols promoted chemical weathering of fayalitic olivines iron rich pyroxenes plagioclase feldspar and pyrrhotite pentlandite mineral assemblages in crustal ultramafic and basic igneous rocks the acidic groundwater entered into electrochemical reactions with the iron sulfides yielding dissolved feso4 fe so4 2 and feoh2 complex ions and the precipitation of basic ferric sulfate minerals such as those belonging to the roemerite copiapite botryogen and jarosite alunite groups these phases are stabilized at low temperatures and ph in martian permafrost the occurrence of jarosites in terrestrial arid regions suggests that they could also survive on the surface of mars melting of the permafrost and raising of the ph may have initiated the hydrolysis of dissolved ferric sulfato complex ions and led to the precipitation of feooh which reacted with precipitated silica to form phyllosilicates alternatively degradation of the hydrolysate feooh to fe2o3 during sublimation of permafrost exposed on mars surface may account for the presence of eolian maghemite suspected to be the magnetic mineral observed on the viking landers

crustal motion and deformation in greece from a decade of gps measurements 1993 2003 abstract the hellenic plate boundary region located in the collision zone between the nubian arabian and eurasian lithospheric plates is one of the seismo tectonically most active areas of europe during the last 15 years gps measurements have been used to determine the crustal motion in the area of greece with the aim to better understand the geodynamical processes of this region an extended reoccupation network covering whole greece has been measured periodically in numerous gps campaigns since the late eighties and a continuous gps network has been operated in the region of the ionian sea since 1995 in this paper we present a new detailed high quality solution of continuous and campaign type measurements acquired between 1993 and 2003 during the gps processing a special effort was made to obtain consistent results with highest possible accuracies and reliabilities data of 54 mainly european igs and euref sites were included in the gps processing in order to obtain results which are internally consistent with the european kinematic field and order to allow for a regional interpretation after an overview of the results of the igs euref sites the results from more than 80 stations in greece are presented in terms of velocities time series trajectories and strain rates previous geodetic geological and seismological findings are generally confirmed and substantially refined new important results include the observation of deformation zones to the north and to the south of the north aegean trough and in the west hellenic arc region arc parallel extension of about 19 mm yr along the hellenic arc and compression between the ionian islands and the greek mainland due to continuous long term observations of 4 8 years it was possible to extract height changes from the gps time series in greece we observe a differential subsidence of the order of 2 mm yr between the northern and central ionian islands across the kefalonia fault zone the differential subsidence of the central ionian islands with respect to the northwestern greek mainland amounts to 4 mm yr

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

41ca in iron falls grant and estherville production rates and related exposure age calculations recent technical developments in accelerator mass spectrometry have enabled us to measure routinely and with a precision of 5 7 the41ca 1 2 104 ky contents of extraterrestrial samples weighing approximately 100 mg in essence these advances have elevated41ca to the role of a new and potent cosmogenic radioisotope with wide ranging applications we present here the results from the first phase of our41ca cosmogenic studies program aimed at establishing baseline concentrations and trends in selected meteorites and the use of41ca in estimating exposure ages and pre atmospheric meteorite radii the average41ca saturation activity recorded in four small iron falls is 24 1 dpm kg this result together with measurements at the center and surface of the large iron grant indicates that production of41ca from spallation on iron is weakly dependent on shielding to depths as large as 250 g cm2 we estimate the41k 41ca exposure age of grant to be 330 50 my and an upper limit to its terrestrial age of 43 15 ky a comparison of the41ca contents of stony and metallic material separated from the mesosiderite estherville identifies low energy neutron capture on native ca as a second important channel of production we find that the41ca signal in the stone phase from three meteorites correlates with their size and that the inferred low energy neutron fluxes vary by a factor of at least 20

the rio tinto basin spain mineralogy sedimentary geobiology and implications for interpretation of outcrop rocks at meridiani planum mars abstract exploration by the nasa rover opportunity has revealed sulfate and hematite rich sedimentary rocks exposed in craters and other surface features of meridiani planum mars modern holocene and plio pleistocene deposits of the rio tinto southwestern spain provide at least a partial environmental analog to meridiani planum rocks facilitating our understanding of meridiani mineral precipitation and diagenesis while informing considerations of martian astrobiology oxidation thought to be biologically mediated of pyritic ore bodies by groundwaters in the source area of the rio tinto generates headwaters enriched in sulfuric acid and ferric iron seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite while mg al fe3 copiapite coquimbite gypsum and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action during the wet season hydrolysis of sulfate salts results in the precipitation of nanophase goethite holocene and plio pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time hematite in meridiani spherules also formed during diagenesis although whether these replaced precursor goethite or precipitated directly from groundwaters is not known the retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of meridiani rocks diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry rio tinto environments organic matter does not persist in rio tinto sediments but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers surface blisters formed by biogenic gas and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of meridiani outcrops

complex exposure histories for meteorites with short exposure ages we report measurements of 26al and 10be activities in nine ordinary chondrites and of the light noble gas concentrations and 36cl and 41ca activities in subsets of those meteorites all but murray have low 21ne concentrations 1 0 10 8cm3stp g and have previously been used to estimate 21ne production rates ladder creek murchison sena and timochin have inventories of cosmogenic radionuclides that are compatible with a single stage of irradiation and give 21ne production rates that are consistent with the standard l chondrite value of 0 33 10 8cm3stp g ma in contrast cullison guenie shaw and tsarev experienced complex irradiation histories they and several other meteorites with low nominal exposure ages also have lower 3he 21ne ratios than expected based on their 22ne 21ne ratios a general association between low 21ne contents and 3he losses suggests that meteorites with short lifetimes often occupy orbits with small perihelia however meteorites with low 21ne contents one stage exposure histories and losses of cosmogenic 3he are rare possible explanations for the scarcity are 1 statistical 2 that it is harder for more deeply buried protometeoroids to lose gas in a liberating collision and 3 that it is harder to insert more deeply buried protometeoroids directly into orbits with small perihelia

global mapping functions for the atmosphere delay at radio wavelengths i have developed expressions for calculating the ratios mapping functions of the line of sight hydrostatic and wet atmospheric path delays to their corresponding zenith delays at radio wavelengths for elevation angles down to 3 the coefficients of the continued fraction representation of the hydrostatic mapping function depend on the latitude and height above sea level of the observing site and on the day of the year the dependence of the wet mapping function is only on the site latitude by comparing with mapping functions calculated from radiosonde profiles for sites at latitudes between 43 s and 75 n the hydrostatic mapping function is seen to be more accurate than and of comparable precision to mapping functions currently in use which are parameterized in terms of local surface meteorology when the new mapping functions are used in the analysis of geodetic very long baseline interferometry vlbi data the estimated lengths of baselines up to 10 400 km long change by less than 5 mm as the minimum elevation of included data is reduced from 12 to 3 the independence of the new mapping functions from surface meteorology while having comparable accuracy and precision to those that require such input makes them particularly valuable for those situations where surface meteorology data are not available

extension of the north anatolian fault into the north aegean trough evidence for transtension strain partitioning and analogues for sea of marmara basin models 1 the north aegean trough is tectonically controlled by the projection of the north anatolian fault from western turkey and the sea of marmara into the aegean where deformation is distributed in contrast to the simple strike slip fault model for central eastern turkey this region accommodates extensional and dextral displacement new side scan sonar data coupled with new subbottom profiler and published seismic data reveal evidence for dextral displacement within the eastern trough and gulf of saros in the form of oblique en echelon and riedel r r and p fractures and displaced geomorphic features strain partitioning in the shallow crust allows the following two styles of faulting to coexist supported by earthquake focal mechanisms 1 transtensional basin bounding faults controlling the significant vertical topography of the basin and 2 dextral faulting within the central basin these styles of faulting merge at greater depths into a single fault a possible sinistral nw striking fault separates two subbasins and may indicate crustal block rotation with deformation focused in block corners such evidence and models from the north aegean are similar to models of transtension and pull apart basins within the sea of marmara

cosmogenic nuclides in the brenham pallasite cosmic ray produced cosmogenic nuclides were studied in fragments of the brenham pallasite a large stony iron meteorite the contents of light noble gases he ne and ar and long lived radionuclides 10be 26al 36cl and 53mn produced by nuclear reactions with cosmic rays were measured in the separated metal and olivine phases from numerous samples representing a wide range of shielding conditions in the meteoroid the distribution of cosmogenic nuclide concentrations in the metal follows patterns similar to that observed in large iron meteorites shielding effects were estimated from the relative proportions of low and high energy reaction products the production rates varied from surface to interior by a factor of more than several hundred the 36cl 36ar cosmic ray exposure age of brenham is 156 8 myr this determination is based on a multiple nuclide approach that utilizes cosmogenic nuclide pairs this approach not only yields a shielding independent exposure age but also demonstrates that the production of cosmogenic nuclides occurred in a single stage the depth profiles of 10be in the stone phase and 53mn in the metal phase are shown superimposed on corresponding profiles from the apollo 15 long drill core surprisingly low abundances of lithophile elements such as k u and th provided a unique opportunity to examine the production systematics of those nuclides whose inventories typically have significant contributions from non cosmogenic sources particularly radiogenic contributions the u and th contents of the olivine samples are extremely low allowing detection of cosmogenic 4he production from oxygen magnesium silicon and iron

a continuum model of continental deformation above subduction zones application to the andes and the aegean large scale continental tectonics of back arc extensional and andean type compressional environments are investigated by using the thin viscous sheet model to calculate the deformation within continental lithosphere that is subjected to horizontal forces on its plate boundaries and to basal drag from the asthenospheric flow beneath the shear tractions acting on the base of a deformable lithosphere are derived from a corner flow model that assumes a rigid subducting plate and a deformable overlying plate because the calculated shear tractions and the deformation within the overlying plate are interdependent the corner flow and the thin viscous sheet models are solved simultaneously we use a perturbation method to obtain analytical solutions for the velocity and strain rate fields within the overlying continental lithosphere the solutions depend on the angle of subduction the dimensionless thickness of the lithosphere and the ratio of asthenospheric to lithospheric viscosities which governs the viscous coupling between the asthenosphere and the lithosphere calculations are compared with observations from the andes and the aegean our results explain some of the features of the deformation in these regions that have heretofore not been explained by other models our model predicts that in a compressional environment a broad region of uplifted topography will tend to develop above a more steeply dipping slab 30o rather than above a shallower slab 10o 15o this is in accord with observations in the various segments of the central andes for an extensional environment the model predicts that a zone of compression can develop near the trench and that extensional strain rate can increase with distance from the trench as is observed in the aegean we also estimate the effective viscosities of 102o pa s for the asthenosphere 2x 1021 pa s for the aegean lithosphere and 1022 pa s for the andean lithosphere

noble gases in the xinjiang armanty iron meteorite a big object with a short cosmic ray exposure age abstract we measured the concentrations and isotopic ratios of the cosmogenic noble gases he ne and ar in the very large iron meteorite xinjiang iiie the 3he and 4he data indicate that a significant portion of the cosmogenic produced helium has been lost via diffusion or in a recent impact event high 22ne 21ne ratios indicate that contributions to the cosmogenic 21ne from sulfur and or phosphorous are significant by combining the measured nuclide concentrations with model calculations for iron meteorites we were able to determine the preatmospheric diameter of xinjiang to 260 320 cm which corresponds to a total mass of about 70 135 tons the cosmic ray exposure age of xinjiang is 62 16 ma i e relatively short compared to most of the other iron meteorites with the current database we cannot firmly determine whether xinjiang experienced a complex irradiation history the finding of 3he and 4he losses might argue for a recent impact event and therefore for a complex exposure

diagenetic haematite and sulfate assemblages in valles marineris abstract previous orbital mapping of crystalline gray haematite ferric oxides and sulfates has shown an association of this mineralogy with light toned layered deposits on the floor of valles marineris in chaos terrains in the canyon s outflow channels and in meridiani planum the exact nature of the relationship between ferric oxides and sulfates within valles marineris is uncertain the observatoire pour la mineralogie l eau les glaces et l activite omega spectrometer initially identified sulfate and ferric oxides in the layered deposits of valles marineris the thermal emission spectrometer tes has also mapped coarse gray haematite in or at the base of these deposits we use compact reconnaissance imaging spectrometer for mars crism spectra and context camera ctx and high resolution imaging science experiment hirise imagery from the mars reconnaissance orbiter mro to explore the mineralogy and morphology of the large layered deposit in central capri chasma part of the valles marineris canyon system that has large clear exposures of sulfate and haematite we find kieserite mgso 4 h 2 o and ferric oxide often crystalline red haematite in the lower bedrock exposures and a polyhydrated sulfate without ferric oxides in the upper bedrock this stratigraphy is duplicated in many other basinal chasmata suggesting a common genesis we propose the haematite and monohydrated sulfate formed by diagenetic alteration of a sulfate rich sedimentary deposit where the upper polyhydrated sulfate rich haematite poor layers either were not buried sufficiently to convert to a monohydrated sulfate or were part of a later depositional phase based on the similarities between the valles marineris assemblages and the sulfate and haematite rich deposits of meridiani planum we hypothesize a common evaporite and diagenetic formation process for the meridiani planum sediments and the sulfate bearing basinal interior layered deposits

relationship of e type apollo asteroid 3103 1982 bb to the enstatite achondrite meteorites and the hungaria asteroids visible and near infrared observations confirm that apollo asteroid 3103 1982 bb has a reflectance spectrum consistent with its previous assignment to taxonomic type e it has been generally believed that the e type asteroids are analogous and perhaps even genetically related to the enstatite achondrite meteorites aubrites correlated variations of previously published visible and thermal infrared lightcurves and the lack of rotational color variations in the present data indicate that this is an elongated object with no substantial surface albedo variations apollo asteroid 3103 1982 bb is presently in an orbital resonance 3 5 with earth and appears to be a relatively long lived member of the earthapproaching population its orbit is consistent with both the fall dates and long cosmic ray exposure ages of the aubrites combined with the rarity of e type asteroids in the near earth asteroid population this indicates that 3103 1982 bb is probably either a major or the primary immediate source body of the aubrites the aphelion location and the mineralogy of 3103 1982 bb indicate that it was most probably derived from the hungaria region at the innermost edge 1 9 au of the asteroid belt although the exact dynamical mechanism for producing its present orbit is not clear these results represent the first plausible direct link of a set of meteorites aubrites or enstatite achondrites back to a particular source region in the asteroid belt this link allows the composition of the solar nebula to be constrained at that heliocentric distance during the time interval when the parent assemblage of the aubrites was isolated from contact with the nebular gas by accretion into its parent planetesimal 1992 academic press inc

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

the strain rate field in the eastern mediterranean region estimated by repeated gps measurements we use the combined gps velocity field of the eastern mediterranean for the period 1988 to 1996 to determine crustal deformation strain rates in a region comprising the hellenic arc the aegean sea and western anatolia we interpret the velocity field and determine the strain rate tensor by the spatial derivatives of the collocated motion vectors the region following the line marmara sea north aegean trough northern central greece and the central ionian islands is associated with strong right lateral shear motion with maximum shear strain rates of 180 nano strain a 180 10 9 a in the central aegean sea n s oriented extensional processes prevail reaching 100 nano strain a the southern aegean is characterized by relatively small strain rates maximum extensional components of the strain rate tensor reaching 150 nano strain a in a n s direction are found in central greece the hellenic arc is associated with moderate arc parallel extension and strong compression perpendicular to it projections of the strain rates parallel to the major fault zones reveal that the northern aegean is governed by the westward continuation of the north anatolian fault zone which is associated with strong dextral shearing maximum 220 nano strain a accompanied by numerous large earthquakes in this century

european mediterranean regional centroid moment tensor catalog solutions for years 2001 and 2002 abstract we present regional centroid moment tensor rcmt solutions for 168 moderate magnitude earthquakes that occurred in the european mediterranean region during 2001 and 2002 events with moment magnitudes as low as 4 0 were successfully analyzed although this low threshold is only achievable in regions with the best azimuthal coverage and with stations at a few hundred kilometers distance earthquakes with focal depths from 10 to more than 200 km were analyzed comparison with standard harvard cmts when available shows good agreement the solutions shown in this paper represent an addition to the european mediterranean rcmt catalog that we are maintaining the rcmt catalog now spans 6 years from 1997 to 2002 and contains 420 solutions we also outline the main seismic sequences that occurred in the european mediterranean region during 2001 2002

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

gps and geologic estimates of the tectonic activity in the marmara sea region nw anatolia a dense network of 52 global positioning system gps sites is used to determine the velocity field and strain rate pattern at the western end of the north anatolian fault zone nafz in the marmara sea region nw anatolia based on four gps campaigns carried out biannually between 1990 and 1996 the detailed kinematic field of crustal motion is calculated the southernmost station shows an average rate of 22 3 mm yr oriented westward relative to istanbul eurasia this value is indicative of the dextral strike slip motion of nw anatolia relative to the black sea the gps velocity field reveals that the sites located on the thrace black sea block show negligible motion relative to istanbul the gps based deformation pattern of three sections crossing the westward prolongation of the nafz is compared with neotectonic data both the gps and the neotectonic data give clear evidence that most of the deformation occurs along a relatively narrow e w oriented zone this belt extends from the single fault trace of the nafz through the gulf of izmit the marmara sea the arkoy region and the gulf of saros into the north aegean trough nat in addition the cross sections show the increasing influence of the n s oriented extension in the aegean sea region from the comparison of the directions and rates of shear and normal strain deduced from gps data with geologic and seismic observations we conclude that the most active zone of dextral shear follows a line along mudurnu valley the northern marmara sea and the saros trough where it joins the nat

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

noble gases and cosmogenic radionuclides in the gold basin l4 chondrite shower thermal history exposure history and pre atmospheric size we measured the concentrations of the cosmogenic radionuclides 10be 26al 36cl and 41ca in the stone and metal fractions of 15 fragments of the gold basin l4 chondrite shower as well as noble gases in 18 gold basin fragments a comparison of 10be 26al and 41ca concentrations with calculated production rates from two different models indicates that the gold basin samples came from depths of about 10 cm to more than 150 cm in an object with a radius of 3 5 m as was predicted by recent model calculations the noble gases show a reversal of the 22ne 21ne ratio at very high shielding the 21ne 10be and 21ne 26al ratios in most samples are constant and correspond to a 4 exposure age of 18 2 myr however three gold basin samples show a 30 120 excess of 21ne implying that they were previously exposed close to the surface of the parent body whereas the other samples were buried several meters deeper concentrations of neutron capture 36ar in most samples are consistent with measured concentrations of neutron capture 36cl and an exposure age of 18 myr large excesses of neutron capture 36ar were found in those samples with an excess of 21ne providing additional evidence of a first stage exposure on the parent body the excess of spallation produced 21ne and neutron capture produced 36ar in these samples indicate a first stage exposure of 35 150 myr on the parent body the radiogenic 4he and 40ar concentrations indicate a major impact on the parent body between 300 and 400 myr ago which must have preceded the impacts that brought the gold basin meteoroid to the surface of the parent body and then expelled it from the parent body 18 myr ago

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz

laboratory simulated acid sulfate weathering of basaltic materials implications for formation of sulfates at meridiani planum and gusev crater mars 1 acid sulfate weathering of basaltic materials is a candidate formation process for the sulfate rich outcrops and rocks at the mer rover opportunity and spirit landing sites to determine the style of acid sulfate weathering on mars we weathered basaltic materials olivine rich glassy basaltic sand and plagioclase feldspar rich basaltic tephra in the laboratory under different oxidative acid sulfate conditions and characterized the alteration products we investigated alteration by 1 sulfuric acid vapor acid fog 2 three step hydrothermal leaching treatment approximating an open system and 3 single step hydrothermal batch treatment approximating a closed system in acid fog experiments a1 fe and ca sulfates and amorphous silica formed from plagioclase rich tephra and mg and ca sulfates and amorphous silica formed from the olivine rich sands in three step leaching experiments only amorphous si formed from the plagioclase rich basaltic tephra and jarosite mg and ca sulfates and amorphous silica formed from olivine rich basaltic sand amorphous silica formed under single step experiments for both starting materials on the basis of our experiments jarosite formation in meridiani outcrop is potential evidence for an open system acid sulfate weathering regime waters rich in sulfuric acid percolated through basaltic sediment dissolving basaltic phases e g olivine and forming jarosite other sulfates and iron oxides aqueous alteration of outcrops and rocks on the west spur of the columbia hills may have occurred when vapors rich in so 2 from volcanic sources reacted with basaltic materials soluble ions from the host rock e g olivine reacted with s to form ca mg and other sulfates along with iron oxides and oxyhydroxides