how mercury can be the most reduced terrestrial planet and still store iron in its mantle mercury is notorious as the most reduced planet with the highest metal silicate ratio yet paradoxically data from the messenger spacecraft show that its iron poor crust is high in sulfur up to 6 wt 80 earth crust abundance present mainly as ca rich sulfides on its surface these particularities are simply impossible on the other terrestrial planets in order to understand the role played by sulfur during the formation of mercury we investigated the phase relationships in mercurian analogs of enstatite chondrite like composition experimentally under conditions relevant to differentiation of mercury 1 gpa and 1300 2000 c our results show that mg rich and ca rich sulfides which both contain fe crystallize successively from reduced silicate melts upon cooling below 1550 c as the iron concentration in the reduced silicates stays very low 1 wt these sulfides represent new host phases for both iron and sulfur in the run products extrapolated to mercury these results show that mg rich sulfide crystallization provides the first viable and fundamental means for retaining iron as well as sulfur in the mantle during differentiation while sulfides richer in ca would crystallize at shallower levels the distribution of iron in the differentiating mantle of mercury was mainly determined by its partitioning between metal or troilite and mg fe ca rich sulfides rather than by its partitioning between metal or troilite and silicates moreover the primitive mantle might also be boosted in fe by a reaction at the core mantle boundary cmb between mg rich sulfides of the mantle and fes rich outer core materials to produce fe mg s the stability of mg fe ca rich sulfides over a large range of depths up to the surface of mercury would be consistent with sulfur calcium and iron abundances measured by messenger

crystallization experiments on a gusev adirondack basalt composition until recently the snc meteorites represented the only source of information about the chemistry and petrology of the martian surface and mantle the mars exploration rovers have now analyzed rocks on the martian surface giving additional insight into the petrology and geochemistry of the planet the adirondack basalts analyzed by the mer spirit in gusev crater are olivine phyric basaltic rocks which have been suggested to represent liquids and might therefore provide new insights into the chemistry of the martian mantle experiments have been conducted on a synthetic humphrey composition at upper mantle and crustal conditions to investigate whether this composition might represent a primary mantle derived melt the humphrey composition is multiply saturated at 12 5 kbar and 1375 c with olivine and pigeonite a primary anhydrous melt derived from a chondritic mantle would be expected to be saturated in orthopyroxene not pigeonite in addition the olivine and pigeonite present at the multiple saturation are too ferroan to have been from a martian mantle as is understood now therefore it seems likely that the humphrey composition does not represent a primary anhydrous melt from the martian mantle but was affected by mineral melt fractionations at lower crustal pressures

unexpected peak near 15 c in cloudsat echo top climatology 1 we examine a radar derived climatology of earth s cloudiness focusing on the vertical distribution echo tops between the two main peaks at 2 km and 14 km associated with low and high clouds respectively lie two distinct midlevel peaks in the tropics one is in the 5 6 km layer the other between 7 and 8 km both are seen day and night over land and sea over each tropical ocean basin and in published ground radar climatology in the extratropics the vertical echo top distribution by temperature reveals a strikingly sharp peak in the 15 to 20 c layer corresponding to the 7 8 km peak in the tropics again the signal is robust night day land sea summer winter we consider interpretations of the 15 c peak ranging from data artifacts unlikely to mere radar brightening to possible true microphysical or dynamical cloudiness enhancement mechanisms

permo carboniferous magmatism of the northeast german basin abstract variscan continent continent collision in central europe was followed by a period of syn to late tectonic magmatism involving the extrusion of large volumes of permosilesian age volcanic rocks particularly in the northeast german basin the volcanic suite up to ca 2000 m thick comprises rhyolites acid and basic andesites and tholeiitic and alkali basalts tectono geochemical analysis in conjunction with volume calculations and petrography reveals changes in volcanic activity over time a total of five eruptive stages are recognised beginning in the stephanian and extending up into the upper rotliegend permian these include the stephanian late carboniferous andesite pre ignimbrite stage i lower rotliegend permian age explosive ignimbrite stage ii post ignimbrite stage iii late rhyolite stage iv and upper rotliegend permian age late basalt stage v in addition several volcanic centres including at least two large caldera like structures are recognised the total calculated volume for the northeast german basin volcanics is ca 48 000 km3 comprising rhyolitic rocks and ignimbrites ca 70 andesitic rocks ca 26 and basalts with cogenetic dolerites ca 4 regional variations in composition and geochemistry are related to diverse crust mantle regimes which correlate with differing positions relative to the heterogeneous basement of the variscan foredeep or within the rhenohercynian orogenic zone the crustal thickening and increasing generation depth of the mafic magmas from north to south may reflect the presence of a pre existing subduction influenced basaltic magma source

3d structural model of the polish basin abstract a 3d structural modelling of the permian mesozoic polish basin was performed in order to understand its structural and sedimentary evolution which led to basin maturation permian cretaceous and its tectonic inversion late cretaceous paleogene the model is built on the present day structure of the basin and comprises 13 horizons within the permian to quaternary rocks the analysis is based on 3d depth views and thickness maps the results image the basin scale symmetry the perennial localization of the nw se oriented basin axis the salt movements due to tectonics and or burial and the transverse segmentation of the polish basin from these observations we deduce that salt structures are correlated to the main faults and tectonic events from the model analysis we interpret the stress conditions the timing and the geometry of the tectonic inversion of the polish basin into a nw se oriented central horst mid polish swell bordered by two lateral troughs emphasis is placed on the zechstein salt considering its movements during the mesozoic sedimentation and its decoupling effect during the tectonic inversion moreover we point to the structural control of the paleozoic basement and the crustal architecture teisseyre tornquist zone on the geometry of the polish basin and the mid polish swell

variation of the present day stress field within the north german basin insights from thin shell fe modeling based on residual gps velocities abstract we present a finite element based dynamic modeling study of the recent stress conditions within the north german basin which is part of the central european basin system based on geological geophysical and geomorphological data after compilation and evaluation of existing data thin shell modeling is applied to understand the recent structural evolution of the central european basin system cebs and its transition towards the baltic shield in contrast to previous modeling approaches we include a complex pattern of major faults from the alpine front to the sorgenfrei tornquist zone stz and gps measured residual velocities to define the boundary conditions of the model major deviations of the stresses occur along strong contrasts in the lithospheric structure and influence the stress pattern significantly high intraplate compression is a responsible large scale reactivation of the faults associated with the pre existing basin framework in northern central europe with an important record on vertical motions the modeled slip subsidence rates of the faults in the north german basin are in the order of 0 01 and 0 2 mm year 1 which are in accordance with field observations because no fault exhibits large quaternary displacement rates in the study area

crustal memory and basin evolution in the central european basin system new insights from a 3d structural model abstract the central european basin system cebs is composed of a series of subbasins the largest of which are 1 the norwegian danish basin 2 the north german basin extending westward into the southern north sea and 3 the polish basin a 3d structural model of the cebs is presented which integrates the thickness of the crust below the permian and five layers representing the permian cenozoic sediments structural interpretations derived from the 3d model and from backstripping are discussed with respect to published seismic data the analysis of structural relationships across the cebs suggests that basin evolution was controlled to a large degree by the presence of major zones of crustal weakness the nw se striking tornquist zone the ringkobing fyn high rfh and the elbe fault system efs provided the borders for the large permo mesozoic basins which developed along axes parallel to these fault systems the tornquist zone as the most prominent of these zones limited the area affected by permian cenozoic subsidence to the north movements along the tornquist zone the margins of the ringkobing fyn high and the elbe fault system could have influenced basin initiation thermal destabilization of the crust between the major nw se striking fault systems however was a second factor controlling the initiation and subsidence in the permo mesozoic basins in the triassic a change of the regional stress field caused the formation of large grabens central graben horn graben gluckstadt graben perpendicular to the tornquist zone the ringkobing fyn high and the elbe fault system the resulting subsidence pattern can be explained by a superposition of declining thermal subsidence and regional extension this led to a dissection of the ringkobing fyn high resulting in offsets of the older nw se elements by the younger n s elements in the late cretaceous the nw se elements were reactivated during compression the direction of which was such that it did not favour inversion of n s elements a distinct change in subsidence controlling factors led to a shift of the main depocentre to the central north sea in the cenozoic in this last phase n s striking structures in the north sea and nw se striking structures in the netherlands are reactivated as subsidence areas which are in line with the direction of present maximum compression the moho topography below the cebs varies over a wide range below the n s trending cenozoic depocentre in the north sea the crust is only 20 km thick compared to about 30 km below the largest part of the cebs the crust is up to 40 km thick below the ringkobing fyn high and up to 45 km along the teisseyre tornquist zone crustal thickness gradients are present across the tornquist zone and across the borders of the ringkobing fyn high but not across the elbe fault system the n s striking structural elements are generally underlain by a thinner crust than the other parts of the cebs the main fault systems in the permian to cenozoic sediment fill of the cebs are located above zones in the deeper crust across which a change in geophysical properties as p wave velocities or gravimetric response is observed this indicates that these structures served as templates in the crustal memory and that the prerift configuration of the continental crust is a major controlling factor for the subsequent basin evolution

phase equilibria of ultramafic compositions on mercury and the origin of the compositional dichotomy measurements of major element ratios obtained by the messenger spacecraft using x ray fluorescence spectra are used to calculate absolute element abundances of lavas at the surface of mercury we discuss calculation methods and assumptions that take into account the distribution of major elements between silicate metal and sulfide components and the potential occurrence of sulfide minerals under reduced conditions these first compositional data which represent large areas of mixed highreflectance volcanic plains and low reflectance materials and do not include the northern volcanic plains share common silica and magnesium rich characteristics they are most similar to terrestrial volcanic rocks known as basaltic komatiites two compositional groups are distinguished by the presence or absence of a clinopyroxene component melting experiments at one atmosphere on the average compositions of each of the two groups constrain the potential mineralogy at mercury s surface which should be dominated by orthopyroxene protoenstatite and orthoenstatite plagioclase minor olivine if any clinopyroxene augite and tridymite the two compositional groups cannot be related to each other by any fractional crystallization process suggesting differentiated source compositions for the two components and implying multi stage differentiation and remelting processes for mercury comparison with high pressure phase equilibria supports partial melting at pressure o10 kbar in agreement with last equilibration of the melts close to the crust mantle boundary with two different mantle lithologies harzburgite and lherzolite magma ocean crystallization followed by adiabatic decompression of mantle layers during cumulate overturn and or convection would have produced adequate conditions to explain surface compositions the surface of mercury is not an unmodified quenched crust of primordial bulk planetary composition ultramafic lavas from mercury have high liquidus temperatures 1450 1350 1c and very low viscosities in accordance with the eruption style characterized by flooding of pre existing impact craters by lava and absence of central volcanoes

classification of lithology from seismic tomography a case study from the messum igneous complex namibia 1 combined analysis of seismic p and s velocity information provides a reasonable and efficient basis for the petrologic interpretation of seismic cross sections in this paper a methodology is presented which allows extraction of prominent features related to well defined p velocities and poisson s ratios from a tomographic velocity model using a classification approach we used first arrival travel time data from a near vertical seismic experiment and independently determined p and s velocities by forward and inverse modeling resolution and uncertainties were estimated from inverting synthetic data the classification procedure was carried out in two subsequent steps first prominent classes were identified in the parameter space spanned by poisson s ratios and p wave velocities for this purpose a probability density function was calculated from the tomograms a function measuring the topography of the probability density was then determined and a histogram analysis was carried out to detect significant classes in the second step the results from principal component analysis for the identified classes were used to map their distribution along the seismic profile we applied the method to the messum intrusive complex of namibia and identified three prominent classes on the basis of the integration of petrophysical data and comparison with surface geology we conclude that quartz syenite composition dominates the upper 800 m of the crust under the complex outside of the intrusion the upper crust has properties corresponding to felsic metasediments and granites which are abundant in the local basement this material shows strong depth dependent changes of seismic properties which are ascribed to decreasing porosity and fluid saturation with depth

basin evolution of the northern part of the northeast german basin insights from a 3d structural model abstract a 3d structural model for the entire southwestern baltic sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area the model was compiled with information from several geological time isochore maps and digital depth maps from the area and consists of six post rotliegend successions the upper permian zechstein lower triassic middle triassic upper triassic jurassic cretaceous and cenozoic this structural model was the basis for a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region this method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement in general the successions above the highly deformed zechstein evaporites reveal a thickening trend towards the gluckstadt graben which also experienced the highest amount of tectonic subsidence during the mesozoic and cenozoic two periods of accelerating salt movement in the area has been correlated with the e w directed extension during the late triassic early jurassic and later by the late cretaceous early cenozoic inversion suggesting that the regional stress field plays a key role in halokinesis the final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium the result reveals that many of the salt structures in the region are still active and that future coastline will run with a wnw ese trend arguing that the compressional stresses related to the alpine collision are the prime factor for the present day landscape evolution

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

core formation in the earth and moon new experimental constraints from v cr and mn abstract the mantles of the earth and moon are similarly depleted in v cr and mn relative to the concentrations of these elements in chondritic meteorites the similar depletions have been used as evidence that the moon inherited its mantle from the earth after a giant impact event we have conducted liquid metal liquid silicate partitioning experiments for v cr and mn from 3 to 14 gpa and 1723 to 2573 k to understand the behavior of these elements during planetary core formation our experiments have included systematic studies of the effects of temperature silicate composition metallic s content metallic c content and pressure temperature has a significant effect on the partitioning of v cr mn with all three elements increasing their partitioning into the metallic liquid with increasing temperature in contrast pressure is not observed to affect the partitioning behavior the experimental results show the partitioning of cr and mn are hardly dependent on the silicate composition whereas v partitions more strongly into depolymerized silicate melts the addition of either s or c to the metallic liquid causes increased metal silicate partition coefficients for all three elements parameterizing and applying the experimental data we find that the earth s mantle depletions of v cr and possibly mn can be explained by core formation in a high temperature magma ocean under oxygen fugacity conditions about two log units below the iron wustite buffer though the depletion of mn may be due entirely to its volatility however more oxidizing conditions proposed in recent core formation models for the earth cannot account for any of the depletions additionally because we observe no pressure effect on the partitioning behavior the data do not require the mantle of the moon to be derived from the earth s mantle although this is not ruled out all that is required to create depletions of v cr and mn in a mantle is a planetary body that is hot enough and reducing enough during its core formation such conditions could have existed on the moon forming impactor

tomographic p wave velocity and vertical velocity gradient structure across the geothermal site gros schonebeck ne german basin relationship to lithology salt tectonics and thermal regime 1 seismic wide angle data were collected along a 40 km long profile centered at the geothermal research well grsk 3 90 in the northeast german basin tomographic inversion of travel time data provided a velocity and a vertical velocity gradient model indicative of cenozoic to pre permian sediments wide angle reflections are modeled and interpreted as top zechstein and top pre permian changes in velocity gradients are interpreted as the transition from mechanical to chemical compaction at 2 3 km depth and localized salt structures are imaged suggesting a previously unknown salt pillow in the southern part of the seismic profile the zechstein salt shows decreased velocities in the adjacent salt pillows compared to the salt lows which is confirmed by sonic log data this decrease in velocity could be explained by the mobilization of less dense salt which moved and formed the salt pillows whereas the denser salt remained in place at the salt lows we interpret a narrow subvertical low velocity zone under the salt pillow at grsk 3 90 as a fault in the deep permian to pre permian this wnw ese trending fault influenced the location of the salt tectonics and led to the formation of a fault bounded graben in the rotliegend sandstones with optimal mechanical conditions for geothermal production thermal modeling showed that salt pillows are related to chimney effects a decrease in temperature and increasing velocity the assumed variations in salt lithology density and strain must thus be even higher to compensate for the temperature effect

aubrite basalt vitrophyres the missing basaltic component and high sulfur silicate melts aubrite basalt vitrophyres abvs are clastic inclusions found in enstatite chondrites and aubrites three have been discovered so far pai from the parsa eh3 chondrite kti from the khor temiki aubrite and l87i from the lew 87007 aubrite their significance stems from the fact that their parental melts were formed from source materials similar to e chondrites therefore they provide an opportunity to study the process of aubrite formation from an e chondrite like protolith kti pai and l87i contain the feo poor highly reduced assemblage forsterite enstatite silicate glass kamacite troilite additionally kti and pai contain alabandite while l87i contains diopside abv glass contents are 51 vol for kti 30 vol for pai and 13 vol for l87i the abvs are thus representative of the different stages of crystallization of a reduced precursor basalt similar to that which gave rise to the aubrites the chemistry of all three abvs can be projected onto the system forsterite albite silica this system is where the bulk compositions of e chondrites fall the melting relations in this system outline the melting of aubrite parental liquids abv bulk compositions lie along the enstatite forsterite reaction boundary and are generally distinct from e chondrite bulk compositions analysis of the forsterite albite silica system and the loci of abv bulk compositions relative to that of the enstatite chondrites shows that the abvs can be derived by partial melting of an e chondrite protolith the l87i vitrophyre is more oxidizing than kti and pai this was determined by its higher enstatite and forsterite feo content lack of alabandite low kamacite si content and low ti in troilite forsterites enclosed in enstatite display a solid trend of anticorrelated mno and feo contrary to the positive correlation found for olivines in most gecochemical settings this anticorrelation can be explained by an oxidizing or reducing event that occurred to the l87i parental melt l87i olivine also displays an anticorrelation of cao with feo the event was determined to be an oxidizing one based upon the mno cao feo systematics of the olivine and an analysis of the effects of increasing oxygen fugacity on the chemistry of forsterite abv glasses contain high amounts of dissolved s that range up to 2 5 wt in pai these dissolved s contents are greater by over an order of magnitude than those determined by experiment under oxidizing conditions the high s contents are the result of the s solubility mechanisms under reducing conditions where cas and mgs complexes occur in the silicate melt both igneous and impact melt origins were considered for the abvs an igneous origin appears to be most consistent with a abv chemistry petrology and texture b phase equilibrium analysis of the melting and crystallization of abv melts and c theoretical considerations of the melting of an e chondrite like protolith abv formation can be modeled by the partial melting of an e chondrite like protolith the model provides a good explanation for the chemistry of abv bulk compositions and their positions along the enstatite forsterite reaction boundary a partial melt origin however is highly inconsistent with an impact origin since impact melting in a asteroidal setting cannot produce partial melts abvs are good candidate materials for the missing basaltic component that links aubrites with their protolith material

on the origin of the southern permian basin central europe abstract a detailed study of the structural and stratigraphic evolution of the southern permian basin during latest carboniferous to early jurassic times supported by quantitative subsidence analyses and forward basin modelling for 25 wells leads us to modify the conventional model for the rotliegend zechstein development of this basin the late permian early jurassic tectonic subsidence curves are typical for a permian to early triassic extensional stage that is followed by thermal subsidence however a purely extensional model is extremely problematic because active faulting during this time is minor and generally hard to document using inverse techniques to model the subsidence curves we quantitatively show that a significant component of late permian and triassic tectonic subsidence can be explained by thermal relaxation of early permian lithospheric thinning and by delayed infilling of paleo topographic depressions that developed during the early permian in this interpretation stephanian autunian wrenching resulted in thermal destabilisation of the lithosphere deep fracturing of the crust disruption and erosion of its sedimentary cover and regional uplift of the area of the future southern permian basin upon termination of wrench tectonics and associated volcanism towards the end of the autunian the southern permian basin began to subside in response to thermal contraction of the lithosphere the evolving basin was isolated from the world oceans and had subsided possibly up to some 700 m below their level at the beginning of upper rotliegend sedimentation after catastrophic flooding of this paleo topographic depression at the beginning of the zechstein changing sea level sedimentation and subsidence rates remained essentially in balance although the effects of triassic rifting overprinted parts of the southern permian basin its overall subsidence pattern persisted well into the jurassic in contrast to the remainder of the southern permian basin permian and triassic crustal extension contributed significantly to the subsidence of the polish trough

structure and evolution of the glueckstadt graben due to salt movements the salt tectonics of the glueckstadt graben has been investigated in relation to major tectonic events within the basin the lithologic features of salt sections from rotliegend zechstein and keuper show that almost pure salt is prominent in the zechstein dominating diapiric movements that have influenced the regional evolution of the glueckstadt graben three main phases of growth of the salt structures have been identified from the analysis of the seismic pattern the strongest salt movements occurred at the beginning of the keuper when the area was affected by extension this activation of salt tectonics was followed by a jurassic extensional event in the pompeckj block and lower saxony basin and possibly in the glueckstadt graben the paleogene neogene tectonic event caused significant growth and amplification of the salt structures mainly at the margins of the basin this event was extensional with a possible horizontal component of the tectonic movements 3d modelling shows that the distribution of the initial thickness of the permian salt controls the structural style of the basin regionally where salt was thick salt diapirs and walls formed and where salt was relatively thin simple salt pillows and shallow anticlines developed

heterogeneous tectonic inversion of the mid polish trough related to crustal architecture sedimentary patterns and structural inheritance abstract using a 3 d structural model we performed a basin scale analysis of the tectonically inverted mid polish swell which developed above the nw se oriented teisseyre tornquist zone the later separates the paleozoic west european platform from the precambrian east european craton the model permits a comparison between the present depths and sedimentary thicknesses of five layers within the permian mesozoic and cenozoic successions the inversion of the nw se trending mid polish trough during the late cretaceous paleogene resulted in uplift of a central horst the mid polish swell bounded by two lateral troughs these structural features are induced by squeezing of a weak crust along the teisseyre tornquist zone the swell is characterized by an inherited segmentation which is due to ne sw transversal faults having crustal roots from nw to se we distinguish the pomeranian kujavian and malopolska segments that are separated by two transversal faults during the inversion the zechstein salt occurring in the pomeranian and kujavian segments in the nw acted as decoupling level between the basement and the post salt cover leading to disharmonic deformation conversely because no salt occurs in the se both basement and cover were jointly deformed the vertical tectonic uplift at the surface is estimated to amount to 3 km in the malopolska segment the structural inheritance of the basement is expressed by the heterogeneous geometry of the swell and tectonic instability during mesozoic sedimentation the reasons for the inheritance are seen in the mosaic type paleozoic basement sw of the teisseyre tornquist zone contrasting the precambrian east european craton which acted as a stable buttress in the ne the horst and trough geometry of cenozoic sediments blanketing the mid polish swell reveals the ongoing intracontinental compressional stress in poland

mercury s thermal evolution controlled by an insulating liquid outermost core abstract the weak intrinsic magnetic field of mercury is intimately tied to the structure and cooling history of its metallic core recent constraints about the planet s internal structure suggest the presence of a fes layer overlying a silicon bearing core we performed 4 electrode resistivity experiments on core analogues up to 10 gpa and over wide temperature ranges in order to investigate the insulating properties of core materials our results show that the fes layer is liquid and insulating and that the electrical resistivity of a miscible fe si s core is comparable to the one of an immiscible fe s fe si core the difference in electrical resistivity between the fes rich layer and the underlying fe si s core is at least 1 log unit at pressure and temperature conditions relevant to mercury s interior estimates of the lower bound of thermal conductivity for fes and fe si s materials are calculated using the wiedemann franz law a thick 40 km fes rich shell is expected to maintain high temperatures across the core and if temperature in this layer departs from an adiabat then this might affect the core cooling rate the presence of a liquid and insulating shell is not inconsistent with a thermally stratified core in mercury and is likely to impact the generation and sustainability of a magnetic field

electrical investigation of metal olivine systems and application to the deep interior of mercury we report electrical conductivity measurements on metal olivine systems at about 5 and 6 gpa and up to 1 675 c in order to investigate the electrical properties of core mantle boundary cmb systems electrical experiments were conducted in the multianvil apparatus using the impedance spectroscopy technique the samples are composed of one metal layer fe fes fesi2 or fe ni s si and one polycrystalline olivine layer with the metal olivine ratio ranging from 1 0 7 to 1 9 2 for all samples we observe that the bulk electrical conductivity increases with temperature from 10 2 5 to 101 8 s m which is higher than the conductivity of polycrystalline olivine but lower than the conductivity of the pure metal phase at similar conditions in some experiments a conductivity jump is observed at the temperature corresponding to the melting temperature of the metallic phase both the metal olivine ratio and the metal phase geometry control the electrical conductivity of the two layer samples by combining electrical results textural analyses of the samples and previous studies of the structure and composition of mercury s interior we propose an electrical profile of the deep interior of the planet that accounts for a layered cmb outer core structure the electrical model agrees with existing conductivity estimates of mercury s lower mantle and cmb using magnetic observations and thermodynamic calculations and thus supports the hypothesis of a layered cmb outermost core structure in the present day interior of mercury we propose that the layered cmb outer core structure is possibly electrically insulating which may influence the planet s structure and cooling history

seismological studies at parkfield i simultaneous inversion for velocity structure and hypocenters using cubic b splines parameterization a model for the 3d p and s wave velocity structure at parkfield has been developed by the systematic inversion of arrival times for microearthquakes and surface vibroseis sources recorded by nearby calnet stations and by the local borehole installed 10 station high resolution seismic network there a modification of the linear b splines model parameterization method of thurber 1983 to a cubic b splines formulation through tests inverting synthetic data sets for the parkfield configuration is found to produce smooth velocity distributions that still retain some small scale features application of the method to 953 p wave and 288 s wave arrivals from 111 microearthquakes and 8 vibroseis locations throughout the study area yields a velocity structure having variable resolution a low velocity zone appears to coincide with the creeping segment of the san andreas fault zone northwest of the 1966 parkfield earthquake epicenter an increase of about 15 per cent in seismic velocities is seen from the northeast to southwest across this segment of the fault zone the higher velocities to the southwest apparently correspond to the granitic basement the contrast across the fault is subdued to the southeast along the 1966 rupture zone a high vp vs ratio of 1 9 is seen in a 2 km wide volume near the location of the 1966 main shock hypocenter presumably the nucleation zone for the expected m 6 parkfield earthquake

salt redistribution during extension and inversion inferred from 3d backstripping abstract a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step is used to reconstruct the subsidence history in the northeast german basin the method allows to determine basin subsidence and the salt related deformation during late cretaceous early cenozoic inversion and during late triassic jurassic extension in the northeast german basin the deformation is thin skinned in the basinal part but thick skinned at the basin margins the salt cover is deformed due to late triassic jurassic extension and late cretaceous early cenozoic inversion whereas the salt basement remained largely stable in the basin area in contrast the basin margins suffered strong deformation especially during late cretaceous early cenozoic inversion as a main question we address the role of salt during the thin skinned extension and inversion of the basin in our modelling approach we assume that the salt behaves like a viscous fluid on the geological time scale that salt and overburden are in hydrostatical near equilibrium at all times and that the volume of salt is constant because the basement of the salt is not deformed due to decoupling in the basin area we consider the base of the salt as a reference surface where the load pressure must be equilibrated our results indicate that major salt movements took place during late triassic to jurassic e w directed extension and during late cretaceous early cenozoic nne ssw directed compression moreover the study outcome suggests that horizontal strain propagation in the salt cover could have triggered passive salt movements which balanced the cover deformation by viscous flow in the late triassic strain transfer from the large graben systems in west central europe to the east could have caused the subsidence of the rheinsberg trough above the salt layer in this context the effective regional stress did not exceed the yield strength of the basement below the rheinsberg trough but was high enough to provoke deformation of the viscous salt layer and its cover during the late cretaceous early cenozoic phase of inversion horizontal strain propagation from the southern basin margin into the basin can explain the intensive thin skinned compressive deformation of the salt cover in the basin the thick skinned compressive deformation along the southern basin margin may have propagated into the salt cover of the basin where the resulting folding again was balanced by viscous salt flow into the anticlines of folds the huge vertical offset of the pre zechstein basement along the southern basin margin and the amount of shortening in the folded salt cover of the basin indicate that the tectonic forces responsible for this inversion event have been of a considerable magnitude

the redox state feo content and origin of sulfur rich magmas on mercury 1 mercury surface space environment geochemistry and ranging messenger orbital observations of mercury have revealed elevated s abundances ca s and mg s correlations and a low upper limit for ferrous iron in surface silicates these data indicate the presence of ca and or mg sulfides in volcanic rocks and a low oxygen fugacity fo2 in their parental magmas we have evaluated coupled fo2 and fs2 values and feo contents in mercury s magmas from silicate sulfide equilibria and empirical models for silicate melts and metallurgical slags the evaluated fo2 at 1700 1800 k is 4 5 to 7 3 log10 units below the iron wustite buffer these values correspond to 0 028 0 79 wt feo implying that fe must be also present in sulfides and metal and are also consistent with the composition of the partial melt of an enstatite chondrite this derived upper limit for feo is substantially lower than the limits obtained from reflectance measurements of mercury s surface materials the low fo2 and feo values provide new constraints for igneous processes on mercury as well as the formation evolution and internal structure of the innermost planet

compositions of mercury s earliest crust from magma ocean models article i nfo article history the size of the mercurian core and the low ferrous iron bearing silicate content of its crust offer constraints on formation models for the planet here we consider a bulk composition that allows endogenous formation of the planet s large core and by processing the mantle through a magma ocean would produce a low iron oxide crust consistent with observations more earth like bulk compositions require silicate removal perhaps by a giant impact to create the planet s large core fraction we find that the endogenous model can produce a large core with either a plagioclase flotation crust or a low iron oxide magmatic crust because a magma ocean creates a gradient in iron oxide content in the resulting planetary mantle the parts of the mantle removed by a putative giant impact could result in either a high iron oxide mantle in contradiction to current crustal measurements or a low iron oxide mantle consistent with the current understanding of mercury if a giant impact cannot preferentially remove shallow mantle material then the proto mercury must have had a bulk low iron oxide composition thus a specific bulk composition is required to make mercury endogenously and either a specific process or a specific composition is required to make it exogenously through giant impact measurements taken by the messenger mission when compared to predictions given here may help resolve mercury s formation process

partial melting of the indarch eh4 meteorite a textural chemical and phase relations view of melting and melt migration to test whether aubrites can be formed by melting of enstatite chondrites and to understand igneous processes at very low o fugacities we have conducted partial melting experiments on the indarch eh4 chondrite at 1000 1500 c silicate melting begins at 1000 c and indarch is completely melted by 1500 c the metal sulfide component melts completely at 1000 c substantial melt migration occurs at 1300 1400 c and metal migrates out of the silicate charge at 1450 c and 50 silicate partial melting as a group our experiments contain three immiscible metallic melts si p and c rich two immiscible sulfide melts fe and femgmnca rich and silicate melt our partial melting experiments on the indarch eh4 enstatite chondrite suggest that igneous processes at low fo2 exhibit several unique features the complete melting of sulfides at 1000 c suggests that aubritic sulfides are not relics aubritic oldhamite may have crystallized from ca and s complexed in the silicate melt significant metal sulfide melt migration might occur at relatively low degrees of silicate partial melting substantial elemental exchange occurred between different melts e g s between sulfide and silicate si between silicate and metal a feature not observed during experiments at higher fo2 this exchange may help explain the formation of aubrites from known enstatite chondrites

sulfur solubility in reduced mafic silicate melts implications for the speciation and distribution of sulfur on mercury abstract chemical data from the messenger spacecraft revealed that surface rocks on mercury are unusually enriched in sulfur compared to samples from other terrestrial planets in order to understand the speciation and distribution of sulfur on mercury we performed high temperature 1200 1750 c low to high pressure 1 bar to 4 gpa experiments on compositions representative of mercurian lavas and on the silicate composition of an enstatite chondrite we equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions iw 1 5 to iw 9 4 iw iron wustite oxygen fugacity buffer under these oxygen fugacity conditions sulfur dissolves in the silicate melt as s 2 and forms complexes with fe 2 mg 2 and ca 2 the sulfur concentration in silicate melts at sulfide saturation scss increases with increasing reducing conditions from 10 wt s at iw 8 and with increasing temperature metallic melts have a low sulfur content which decreases from 3 wt at iw 2 to 0 wt at iw 9 we developed an empirical parameterization to predict scss in mercurian magmas as a function of oxygen fugacity f o 2 temperature pressure and silicate melt composition scss being not strictly a redox reaction our expression is fully valid for magmatic systems containing a metal phase using physical constraints of the mercurian mantle and magmas as well as our experimental results we suggest that basalts on mercury were free of sulfide globules when they erupted the high sulfur contents revealed by messenger result from the high sulfur solubility in silicate melt at reducing conditions we make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and or that the mantle contains a minor metal phase and combine our parameterization of scss with chemical data from messenger to constrain the oxygen fugacity of mercury s interior to iw 5 4 0 4 we also calculate that the mantle of mercury contains 7 11 wt s and that the metallic core of the planet has little sulfur

heat flow and lithospheric thermal regime in the northeast german basin abstract new values of surface heat flow are reported for 13 deep borehole locations in the northeast german basin negb ranging from 68 to 91 mw m 2 with a mean of 77 3 mw m 2 the values are derived from continuous temperature logs measured thermal conductivity and log derived radiogenic heat production the heat flow values are supposed free of effects from surface palaeoclimatic temperature variations from regional as well as local fluid flow and from thermal refraction in the vicinity of salt structures and thus represent unperturbed crustal heat flow two d numerical lithospheric thermal models are developed for a 500 km section along the dekorp basin 9601 deep seismic line across the basin with a north eastward extension across the tornquist zone a detailed conceptual model of crustal structure and composition thermal conductivity and heat production distribution is developed different boundary conditions for the thickness of thermal lithosphere were used to fit surface heat flow the best fit is achieved with a thickness of thermal lithosphere of about 75 km beneath the negb this estimate is corroborated by seismological studies and somewhat less than typical for stabilized phanerozoic lithosphere modelled moho temperatures in the basin are about 800 c heat flow from the mantle is about 35 to 40 mw m 2 in the southernmost part of the section beneath the harz mountains higher moho temperatures up to 900 to 1000 c are shown while the relatively high level of surface heat flow in the negb obviously is of longer wave length and related to lithosphere thickness changes in crustal structure and composition are responsible for short wave length anomalies

modeling of the 3d thermal field in the northeast german basin the regional thermal field of the ne german basin is modeled by a three dimensional finite element approach and is compared to classical one dimensional extrapolations two alternative boundary conditions are assumed at the approximate depth of the moho a constant temperature distribution and a constant heat flow surprisingly both results are almost identical down to approximately 10 km depth based on the models presented the results are due to a complex interaction of different strata and the related regional variability of conductivities in addition the available temperature maps for different depths hurtig et al 1992 indicate a relative high heat flow at the basin margins especially at the southern and eastern boundary the models are able to reproduce the generalized pattern by regarding only a conductive heat flow however because both models are successful at shallow depth we conclude that the current techniques of thermal modeling require improvement even on the theoretical aspects of depth continuation and inversion

crustal structure along the central segment of the egt from seismic refraction studies abstract the seismic refraction line between the gulf of genova and the baltic sea was carried out in 1986 as part of the european geotraverse egt 86 the central segment of the egt also known as eugemi european geotraverse middle part has a total length of 825 km and runs from the northern margin of the alps to the baltic sea traversing mainly the variscan mountain area of western germany the p wave data of nine shotpoints were interpreted in detail and a two dimensional p velocity model of the crust was developed between the molasse basin and the southern end of the north german basin for the north german basin the data quality justifies only the construction of a simplified model the internal crustal structure is quite complex in the upper crust of the moldanubian and saxothuringian zones of the variscan orogen the velocities are lower than in the rhenohercynian area the velocity of 6 0 km s representing consolidated seismic basement is reached at depths of as much as 10 12 km northern margin of alps and north german basin and of only 3 km under the mid german crystalline rise mid crustal velocities range from 5 8 to 6 1 km s forming weak velocity reversals in some parts in the lower crust velocities as low as 6 2 km s are seen near the alps in contrast to velocities between 6 8 and 7 2 km s in the exposed variscan orogen north of shotpoint e between hannover and the river elbe the velocity of the lower crust is about 6 4 km s north of the elbe line it increases abruptly to 6 9 km s the crust mantle boundary rises from 34 km depth under the northern margin of the alps to 29 km under the swabian jura under the variscan orogen to the north the crustal thickness varies only slightly around an average depth of about 29 1 k but drops to about 30 km under the north german basin between the elbe line and the ringkobing fyn high the moho rises to a depth of about 26 km and the data indicate at least one fault like step of 1 km before the crust thickens toward the basement high the velocities in the uppermost mantle show considerable variation the highest velocity of 8 4 km s is observed beneath the saxothuringian zone and the lowest values of 7 8 7 9 km s are recorded under the hessen depression

melting processes and mantle sources of lavas on mercury abstract the messenger spacecraft provided geochemical data for surface rocks on mercury in this study we use the major element composition of these lavas to constrain melting conditions and residual mantle sources on mercury we combine modelling and high temperature 1320 1580 c low to high pressure 0 1 to 3 gpa experiments on average compositions for the northern volcanic plains nvp and the high mg region of the intercrater plains and heavily cratered terrains high mg icp hct near liquidus phase relations show that the s free nvp and high mg icp hct compositions are multiply saturated with forsterite and enstatite at 1450 c 1 3 gpa and 1570 c 1 7 gpa respectively for s saturated melts 1 5 3 wt s the multiple saturation point msp is shifted to 1380 c 0 75 gpa for nvp and 1480 c 0 8 gpa for high mg icp hct to expand our experimental results to the range of surface compositions we used and calibrated the pmelts thermodynamic calculator and estimated phase equilibria of 5800 compositions from the mercurian surface and determined the p t conditions of liquid forsterite enstatite msp 1300 1600 c 0 25 1 25 gpa surface basalts were produced by 10 to 50 partial melting of variably enriched lherzolitic mantle sources the relatively low pressure of the olivine enstatite liquid msp seems most consistent with decompression batch melting and melts being segregated from their residues near the base of mercury s ancient lithosphere the average melting degree is lower for the young nvp 0 27 0 04 than for the older icp hct 0 46 0 02 indicating that melt productivity decreased with time the mantle potential temperature required to form mercurian lavas and the initial depth of melting also decreased from the older high mg icp hct terrane 1650 c and 360 km to the younger lavas covering the nvp regions 1410 c and 160 km this evolution supports strong secular cooling of mercury s mantle between 4 2 and 3 7 ga and explains why very little magmatic activity occurred after 3 7 ga

the origin of boninites on mercury an experimental study of the northern volcanic plains lavas abstract phase equilibrium experiments were conducted on a synthetic rock composition matching that of the northern volcanic plains of mercury as measured by the mercury surface space environment geochemistry and ranging spacecraft messenger the northern volcanic plains are smooth plains of suspected volcanic origin that cover more than 6 of the surface area of mercury the northern volcanic plains are less cratered than their surroundings and reported to be the product of flood volcanism making them a prime candidate for experimental study the bulk composition of the northern volcanic plains is that of an alkali rich boninite and represents the first silica enriched crustal terrane identified on an extraterrestrial planet from orbital data phase equilibrium experiments were conducted over the pressure range of the mercurian mantle 0 5 5 gpa at very low oxygen fugacity iw0 to 7 using a piston cylinder apparatus p 0 5 1 7 gpa and a walker style multi anvil device p 2 5 gpa our results indicate the origin of the northern volcanic plains lavas boninites are best explained by high degrees of partial melting of an olivine dominant pyroxene and plagioclase bearing mantle source at low pressure 1 4 gpa and does not require hydrous melting to achieve the silica enriched melt composition the formation mechanism for boninites on mercury contrasts substantially with terrestrial boninites which typically occur in oxidized and hydrous arc environments associated with subduction zones instead mercurian boninites form at exceptionally low oxygen fugacity and do not require melting of hydrated source materials the nvp lavas represent a novel mechanism by which planetary bodies can form silica enriched secondary crusts without the aid of water

some results of deep seismic investigations in east germany abstract in recent years several deep seismic investigations have been carried out in the central and southern part of east germany in the present paper the results for p wave velocity distributions are shown and discussed some typical crustal features such as low velocity layers were found in some cases the moho was found to ascend from the se towards the nw with some interruptions for several profiles the s wave arrivals also were interpreted the simultaneous evaluation of p and s wave velocities were used to obtain information on the behaviour of the elastic parameters and respectively the seismic models discussed in the present paper have been confirmed by modelling the gravity field and the results have been published elsewhere

chemical heterogeneity on mercury s surface revealed by the messenger x ray spectrometer 1 we present the analysis of 205 spatially resolved measurements of the surface composition of mercury from messenger s x ray spectrometer the surface footprints of these measurements are categorized according to geological terrain northern smooth plains deposits and the plains interior to the caloris basin differ compositionally from older terrain on mercury the older terrain generally has higher mg si s si and ca si ratios and a lower al si ratio than the smooth plains mercury s surface mineralogy is likely dominated by high mg mafic minerals e g enstatite plagioclase feldspar and lesser amounts of ca mg and or fe sulfides e g oldhamite the compositional difference between the volcanic smooth plains and the older terrain reflects different abundances of these minerals and points to the crystallization of the smooth plains from a more chemically evolved magma source high degree partial melts of enstatite chondrite material provide a generally good compositional and mineralogical match for much of the surface of mercury an exception is fe for which the low surface abundance on mercury is still higher than that of melts from enstatite chondrites and may indicate an exogenous contribution from meteoroid impacts

magnesium rich crustal compositions on mercury implications for magmatism from petrologic modeling 1 we have conducted petrologic modeling of messenger derived compositions and analog compositions to gain a better understanding of the petrogenesis of the crust of mercury analog compositions included a 1425c partial melt of the indarch eh4 meteorite and a range of mg rich terrestrial rocks magnesian basalt basaltic komatiite and peridotitic komatiite all models were held at the iron wustite buffer to simulate the reducing conditions that likely existed during mercury s formation we then compared modeled mineral compositions and abundances liquidus temperatures and viscosities to better constrain the characteristics of the lavas that erupted on mercury s surface our results show that the surface composition of mercury is most similar to that of a terrestrial magnesian basalt with lowered feo composed mainly of mg rich orthopyroxene and plagioclase because the model magmas are mg rich their counterparts on mercury would have erupted at high temperatures and displayed low viscosities producing melts of these compositions would have required high temperatures at the mantle source regions on mercury the inferred low viscosity lavas would have erupted as thin laterally extensive flows depending upon their effusion rate and would be expected to display surficial flow features that might be preserved to the present

no fes layer in mercury evidence from ti al measured by messenger abstract in this study we investigate the likeliness of the existence of an iron sulfide layer fes matte at the core mantle boundary cmb of mercury by comparing new chemical surface data obtained by the x ray spectrometer onboard the messenger spacecraft with geochemical models supported by high pressure experiments under reducing conditions we present a new data set consisting of 233 ti si measurements which combined with al si data show that mercury s surface has a slightly subchondritic ti al ratio of 0 035 0 008 multiphase equilibria experiments show that at the conditions of mercury s core formation ti is chalcophile but not siderophile making ti a useful tracer of sulfide melt formation we parameterize and use our partitioning data in a model to calculate the relative depletion of ti in the bulk silicate fraction of mercury as a function of a putative fes layer thickness by comparing the model results and surface elemental data we show that mercury most likely does not have a fes layer and in case it would have one it would only be a few kilometers thick 13 km we also show that mercury s metallic fe si core cannot contain more than 1 5 wt sulfur and that the formation of this core under reducing conditions is responsible for the slightly subchondritic ti al ratio of mercury s surface

gravity field and internal structure of mercury from messenger radio tracking of the messenger spacecraft has provided a model of mercury s gravity field in the northern hemisphere several large gravity anomalies including candidate mass concentrations mascons exceed 100 milli galileos mgal mercury s northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for thinning beneath some impact basins the low degree gravity field combined with planetary spin parameters yields the moment of inertia c mr2 0 353 0 017 where m and r are mercury s mass and radius and a ratio of the moment of inertia of mercury s solid outer shell to that of the planet of cm c 0 452 0 035 a model for mercury s radial density distribution consistent with these results includes a solid silicate crust and mantle overlying a solid iron sulfide layer and an iron rich liquid outer core and perhaps a solid inner core

the formation of nuggets of highly siderophile elements in quenched silicate melts at high temperatures before or during the silicate quench the highly siderophile elements hse are powerful tracers of planetary differentiation despite the importance of their partitioning between silicate and metal for the understanding of planetary core formation especially for the earth and mars there is still a huge discrepancy between conclusions based on different high temperature ht experimental studies these disagreements may be due to the presence of hse micro and nanonuggets in ht experiments the formation of these nuggets is still interpreted in different ways one hypothesis is that these hse nuggets formed during the quench of the silicate melt while another hypothesis supposes that these nuggets formed before the quench and represented artefacts of ht experiments the goal of this work is to clarify whether the presence of hse nuggets in silicate melts is linked to a quench effect or not understanding the formation of these hse nuggets represents thus a necessary step towards the resolution of the earth s core formation scenarios we performed new ht experiments 1275 2000 c at different oxygen fugacities fo 2 between ambient air up to 5 log units below the iron wustite buffer iw 5 for two different silicate compositions synthetic martian and terrestrial basalts mixed with a metallic mixture of pt au pd ru our 1275 1600 c experiments were contained in either olivine diopside or graphite crucible experiments at 2000 c were performed using a levitation method so no capsule was necessary our samples contained quenched silicate melts minerals olivine pyroxene spinel depending on the run a two phase metallic bead and nano and micro nuggets of hse our samples underwent fine textural structural and analytical characterizations the distribution of the nuggets was not homogeneous throughout the quenched silicate melt hse nuggets were present within crystals dendritic textures from the quenched silicate melt formed around hse nuggets which could be crystallized showing that the nuggets acted as nucleation sites during the quench thus they predated the quench finally these nuggets also had strong heterogeneities suggesting at least a two stage formation process under reducing conditions consequently our observations clearly show that these hse nuggets formed before the quench in the silicate melt our results agreed with previous studies which concluded that hse abundances in the earth s mantle require the late accretion of chondritic material subsequent to core formation however the effects of metallic si o h or the effect of pressure on the hse partitioning are still not fully understood further work to constrain these effects is to be encouraged to understand the earth s core formation

the elbe fault system in north central europe a basement controlled zone of crustal weakness abstract the elbe fault system efs is a wnw striking zone extending from the southeastern north sea to southwestern poland along the present southern margin of the north german basin and the northern margin of the sudetes mountains although details are still under debate geological and geophysical data reveal that upper crustal deformation along the elbe fault system has taken place repeatedly since late carboniferous times with changing kinematic activity in response to variation in the stress regime in late carboniferous to early permian times the elbe fault system was part of a post variscan wrench fault system and acted as the southern boundary fault during the formation of the permian basins along the trans european suture zone sensu geol mag 134 5 1997 585 the teisseyre tornquist zone ttz most probably provided the northern counterpart in a pull apart scenario at that time further strain localisation took place during late mesozoic transtension when local shear within the elbe fault system caused subsidence and basin formation along and parallel to the fault system the most intense deformation took place along the system during late cretaceous early cenozoic time when the elbe fault system responded to regional compression with up to 4 km of uplift and formation of internal flexural highs compressional deformation continued during early cenozoic time and actually may be ongoing the upper crust of the elbe fault system which itself reacted in a more or less ductile fashion is underlain by a lower crust characterised by low p wave velocities low densities and a weak rheology structural seismic and gravimetric data as well as rheology models support the assumption that a weak stress sensitive zone in the lower crust is the reason for the high mobility of the area and repeated strain localisation along the elbe fault system

stress orientations found in north east germany differ from the west european trend knowledge about the acting stresses is of crucial importance for understanding the tectonics of a region data about the stress field in north eastern germany used to be very rare in general it was assumed that the orientation of the larger horizontal principal stress sh is similar to that found for western germany and central west europe i e nw se to check this several borehole logs of the late 1980s were analysed for information on the principal horizontal stress orientations they include four arm dipmeter and borehole televiewer data from 15 boreholes the depth range of our stress results reaches from 1500 to 6700 m they were compared to a few other data especially from hydraulic fracturing and to recent findings on the stresses in the northwest german basin in contrast to expectation sh derived from breakout orientations below the salt layers displayed n to ne orientation the latter was found at 10 locations spread over the ne german basin from berlin to the baltic sea from the polish border to the former border between east and west germany moreover this stress rotation in the subsaline formations seems to be the continuation of a trend found in the nw german basin

3d seismic refraction traveltime tomography at a groundwater contamination site we have applied traveltime tomography to 3d seismic refraction data collected at hillair force base utah in an approximately 95 40 m area over a shallow 20 m groundwater contamination site the purpose of this study is to test the ability of 3d first arrival time data to characterize the shallow environment and aid remediation efforts the aquifer is bounded below by a clay aquiclude into which a paleochannel has been incised and acts as a trap for dense nonaqueous phase liquiddnaplcontaminants aregularizednonlineartomographicapproachwasappliedto187 877 first arrival traveltimes to obtain the smoothest minimumstructure 3d velocity model the resulting velocity model contains a velocity increase from less than 300 to 1500 m s in the upper 15 m the model also contains a north southtrendinglow velocityfeatureinterpretedtobethepaleochannel based on more than 100 wells in the area checkerboard testsshow7 5 10 mlateralresolutionthroughoutmostofthe model the preferred final model was chosen after a systematic test of the free parameters involved in the tomographic approach includingthestartingmodel thefinalvelocitymodel compares favorably with a 3d poststack depth migration and 2d waveform inversion of coincident reflection data while the long wavelength features of the model reveal the primary target of the survey the paleochannel the velocity model is likely a very smooth characterization of the true velocity structure particularly in the vertical direction given thesizeofthefirstfresnelzoneforthesedata

porosity depth trends in reservoir sandstones theoretical models related to jurassic sandstones offshore norway abstract theoretical models of compaction and porosity modification in sandstones during burial are discussed theory predicts that mechanical compaction is the dominant porosity reducing mechanism during burial from 0 to 2 5 3 km porosity depth trends are at this stage mainly controlled by the stability of the grain framework and the effective stress time and temperature also influence the porosity depth gradients at shallow to moderate depths but are probably less important than effective stress and framework grain composition at greater burial depths below 2 5 3 km chemical compaction including pressure solution can explain most of the porosity reduction in well sorted clean arenites theoretical modelling of the intergranular pressure solution suggests that sandstones may lose porosity rapidly by this mechanism below 2 5 3 km and that factors capable of retarding pressure solution and quartz cementation are required to maintain prospective porosities below 4 km this theory and comparisons with empirical data from jurassic sandstones from offshore norway indicate that high porosity is favoured by 1 overpressures approaching the lithostatic pressure gradient 2 a short residence time below 3 km burial 3 coatings on grains of clay or microcrystalline quartz which prevent quartz dissolution and precipitation and 4 a high content of feldspar and early diagenetic secondary pores early hydrocarbon emplacement may retard quartz cementation and preserve porosity but chemical compaction probably continues after oil emplacement except at very high hydrocarbon saturations

a seismic velocity model for the sw baltic sea derived from basin 96 refraction seismic data abstract within the basin 96 project basin analysis and seismic investigation in north germany 1996 a marine survey gathered seismic data in the southwest baltic sea to study the caledonian collisional zone between baltica to the north and avalonia to the south additionally the airgun pulses have been observed by several land stations special attention was paid to record good quality data on rugen island aiming at linking offshore and land seismic wide angle observations therefore a complex geophone array the star of rugen was designed to enhance the signal quality the star of rugen data and other onshore observations in ne germany and on bornholm an island in the baltic sea have been used for p wave velocity modelling important structures of the transition zone from palaeozoic western europe to the precambrian baltic shield are imaged in the resulting three dimensional velocity model a pronounced basement high north of rugen island indicates the location of the caledonian deformation front cdf velocities also reflect other prominent features such as the ronne graben a pull apart structure of the tornquist zone and the basement outcrops around bornholm island in the investigated area the moho depth varies between 27 and 33 km a high velocity layer in the lower crust below the ne german mainland may indicate genetic relations to baltica the structural continuity however is disturbed by a velocity decrease in an area north of the cdf sporadic but strong reflections from the upper mantle below the cdf seem to be consistent with the reflection seismic data dekorp basin research group 1999 geology 27 1 55 58