evidence for fluoride melts in earth s mantle formed by liquid immiscibility comment and reply reply i welcome the opportunity to reply to dolejs s comments regarding the nature and the origin of fluoride melts found in mantle xenoliths klemme 2004 1 before discussing the comments in detail i would like to comment on the fact that the composition of the precursor melt was indeed

spatial distribution and budget for submarine groundwater discharge in eckernforde bay western baltic sea submarine groundwater discharge sgd from subseafloor aquifers through muddy sediments was studied in eckernforde bay western baltic sea the fluid discharge was clearly traced by 222 rn enrichment in the water column and by the chloride profiles in pore water at several sites a considerable decrease in chloride to levels less than 10 of bottom water concentrations was observed within the upper few centimeters of sediment studies at 196 sites revealed that 22 of the seafloor of the bay area was affected by freshwater admixture and active fluid venting a maximal discharge rate of 9lm 22 d 21 was computed by modeling pore water profiles based on pore water data the freshwater flow from subseafloor aquifers to eckernforde bay was estimated to range from 4 3 10 6 to 57 3 10 6 m 3 yr 21 therefore 0 3 4 1 of the water volume of the bay is replaced each year owing to negligible surface runoff by rivers sgd is a significant pathway within the hydrological cycle of this coastal zone high resolution bathymetric data and side scan sonar surveys of pockmarks depressions up to 300 m long were obtained by using an autonomous underwater vehicle steep edges with depths increasing by more than 2 m within 8 10 m in lateral directions equivalent to slopes with an angle of as much as 118 were observed the formation of pockmarks within muddy sediments is suggested to be caused by the interaction between sediment fluidization and bottom currents fluid discharge from glacial coastal sediments covered by mud deposits is probably a widespread but easily overlooked pathway affecting the cycle of methane and dissolved constituents to coastal waters of the baltic sea

phase equilibria in the silica undersaturated part of the kalsio 4 mg 2 sio 4 ca 2 sio 4 sio 2 f system at 1 atm and the larnite normative trend of melt evolution the evolution of nephelinitic melts in equilibrium with mica bearing liquidus assemblages and melting relations have been studied on two silica undersaturated joins of the kalsio4 mg2sio4 ca2sio4 sio2 f system at atmospheric pressure by quench runs in sealed platinum capsules fluorine has been added to the batch compositions by the direct exchange of fluorine for oxygen 2f o2 the first join is the pseudo ternary forsterite diopside kalsio3f2 system forsterite diopside f phlogopite and leucite crystallisation fields and a fluoride silicate liquid immiscibility solvus are present on the liquidus surface of the join sub liquidus and sub solidus phases include akermanite cuspidine spinel fluorite and some other minor fluorine phases the second system is the pseudo binary akermanite f phlogopite join that intersects the forsterite diopside kalsio3f2 join akermanite forsterite diopside f phlogopite leucite and cuspidine are found to crystallise on the join forsterite fo and leucite lc are related to f phlogopite phl by a reaction with the fluorine bearing liquid fo lc l phl and the reaction proceeds until forsterite or leucite are completely consumed the reaction temperature and resulting phase association depend on batch composition thus leucite is not stable in the sub solidus of the akermanite f phlogopite join but is preserved in a part of the forsterite diopside kalsio3f2 system where forsterite reacts out or does not crystallise at all the phlogopite in reaction has an important effect on the composition of the coexisting liquid the liquids initially saturated in forsterite evolve to extremely ca rich larnite normative residuals the experimental data show that larnite normative melilitolites can crystallise from evolved melilititic melts generated from normal melanephelinitic parental magmas with no normative larnite the evolution towards melilitites requires fractionation of phlogopite bearing assemblages under volatile pressure

evidence from seismites for glacio isostatically induced crustal faulting in front of an advancing land ice mass rugen island sw baltic sea abstract it is hitherto commonly thought that earthquakes triggered by geologically rapid changes in the pressure caused by the fluctuating extent of thick land ice masses occur exclusively during ice retreat our study of deformed sediment layers within an undeformed glaciolacustrine and glaciofluvial succession exposed in a coastal cliff on rugen island south western baltic sea challenges this widespread idea based on their structural and deformational features the layers under investigation are interpreted as seismites which formed as a result of seismically induced liquefaction the stratigraphic context aided by optically stimulated luminescence osl dating indicate that the documented seismites must have formed shortly before the front of the pleistocene scandinavian ice sheet reached the study area during the last glacial maximum thus during a stage of ice advance this implies that the flexural isostatic response of the earth s crust as a consequence of the ice load during ice advance was accompanied by earthquakes probably due to local re activation of pre existing faults the crustal response to an increasing ice load was consequently less gradual than previous studies about glaciation related tectonics suggest

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

liquid immiscibility in the caf2 granite system and trace element partitioning between the immiscible liquids abstract the recent discoveries of ca fluoride melt in magmatic systems especially in peralkaline granites with rare earth element enrichment has raised questions about the presence and nature of liquid immiscibility in caf2 granite systems as well as the partitioning behavior of trace elements between such immiscible liquids we have experimentally explored the immiscibility in this system using natural granite fluorite starting materials at fast and slow cooling rates temperatures from 500 c to 1200 c and 1 atmosphere pressure our experiments confirm the presence of a miscibility gap in the caf2 granite system over a wide range of temperatures the two immiscible liquids are a mafic fluorosilicate melt fm with high cao and f and a felsic oxysilicate melt sm with high sio2 and alkalis immiscibility is encountered when the bulk f content exceeds approximately 4 4 wt at 1200 c and then rapidly decreases to only 0 75 wt at low temperature below 900 c this indicates that calcic magmas are able to evolve to the liquid immiscibility domain by the residual enrichment of fluorine resulting from fractional crystallization and that liquid immiscibility should be common the peritectic reaction fm sm fluorite removes the fluorosilicate liquid around 600 c and could explain the absence of fluorosilicate observations in natural granites the compositions of the liquids in fast cooling experiments show a significantly larger miscibility gap which is characterized by compared to slow cooling runs similar sm compositions but higher ca and f content in fm this difference is caused by suppression of fluorite nucleation and is interpreted as a metastable extension of the high temperature liquid immiscibility immiscibility results in strong fractionation of trace elements which is primarily governed by melt structure and the ionic potential z r of the elements the behavior of trace elements can be categorized into three groups 1 network formers si al ga pb b partition into the oxysilicate melt 2 the partitioning of the alkalis and alkali earths is strongly dependent on the ionic potential with the partitioning coefficients d fm sm in the order dcs

the behavior of rare earth elements in seawater precise determination of variations in the north pacific water column abstract we present new highly precise and accurate data for ten rare earth elements rees in two water column profiles and in bottom waters from three additional localities in the north pacific our results presented here and in an earlier publication indicate that the water column in the western north pacific is stratified with respect to the isotopic composition of nd as well as nd la sm nd and er la both the nd isotopic and the ree data show that ree transport is strongly influenced by horizontal advection even in the sluggish circulation of the pacific in general rees increase in concentration with depth at mid latitude they reach a maximum concentration at about 3000 m and then decrease to the bottom at high latitude heavy rees reach a maximum concentration near 3000 m whereas light rees continue to increase in concentration with depth the deep water maximum and bottom water depletion is interpreted as an advective feature resulting from the flow of a lower concentration of rees in antarctic bottom water under a higher concentration of rees in the north pacific concentrations of rees do not show a linear relationship with those of si indicating that the ree cycle is not directly coupled to that of the si cycle ree element ratios i e nd la correlate with hydrographie properties which suggests that major features of the ree patterns may be conserved during lateral transport comparison of our ree data to those in previously published reports on pacific seawater shows that the identification of ree distributions affected by advection is only made possible by the high precision analysis we developed for this study the ce concentration we observe is relatively constant over 200 4500 m depth at both sites where we have complete profiles this unique constancy of ce is in contrast to the contiguous rees la and nd which show substantial concentration variations with depth

structure and quantification of processes controlling the evolution of the inverted ne german basin abstract a ne sw reflection seismic transect crossing the entire ne german basin negb was investigated in detail to study the interaction between tectonics and sedimentation during the multiphase evolution of the region by restoring a geological section across the post rotliegend the kinematic evolution was reconstructed and rates of important geological processes such as erosion or basin shortening were quantified the present day structural style of the negb is the result of several major deformation events 1 regional subsidence accompanied by local thin skinned e w extension during the permo triassic jurassic was followed by basin inversions at the 2 jurassic cretaceous and at the 3 cretaceous tertiary boundary zechstein salt played an important role since mobile zechstein evaporites decoupled the supra salt from the sub salt succession and allowed the transmission of deformation over a large distance of major significance to the late cretaceous structural development was the crustal scale upthrusting of the calfoerde block along the gardelegen fault at the southern basin margin the accompanying horizontal shortening has a minimum value of 9 km and led to the development of thrusts and folds within the post zechstein succession

chemical evolution of rare earth elements fractionation between colloidal and solution phases of filtered river water abstract within the dissolved fraction of connecticut river water there is large scale fractionation of rare earth elements between colloidal and solution phases colloidal particles carry a large part of the dissolved ree pool filtration through filters with progressively smaller pore size 0 45 0 22 and 0 025 m results in filtrates with lower absolute concentrations of ree and more fractionated compositions with decreasing pore size the filtrates have shale normalized abundances which become systematically more depleted in the lree relative to the hree hence both the solution and colloidal phases are significantly fractionated with respect to the dissolved fraction these conclusions are consistent with previous studies of ree in rivers estuaries and soils and with surface solution speciation models colloids play an important role in the aquatic geochemistry of rare earth elements they are responsible for the fractionation of ree during the estuarine removal of ree the removal of suspended and colloidal particles from river water leaves the solution phase of river water with compositions of ree as evolved as those of surface seawater hence the evolution of the composition of ree in river water and seawater is significantly influenced by colloid formation during chemical weathering on the continents

the temporal evolution of fluid flow through the tahiti barrier reef traced by sr isotopes and pore water chemistry abstract the internal fluid circulation of the tahiti barrier reef has been studied with sr isotopes and pore water chemistry the study is based on 15 sample series recovered over 2 years from a 150 m deep core drilled through the entire barrier reef down to the volcanic basement temperature data suggest that the interstitial fluids originate from seawater that penetrated the volcanic basement to at least 200 m depth on the ocean sided slope below the barrier reef subsequently the fluids migrated upward driven by buoyancy through the entire reef chemical evolution of the interstitial fluids is mainly controlled by basalt seawater interaction and by admixture of seawater from the open ocean during upward migration these processes are monitored with 87sr 86sr isotope ratios h4sio4 concentrations and alkalinity to give a picture of the evolution of interstitial fluid flow over 2 years the results indicate that the internal circulation patterns change through time the modifications concern mainly the residence time of the fluids within the volcanics and the intensity and localization of lateral seawater admixture within the karstified pleistocene reef

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

salty groundwater flow in the shallow and deep aquifer systems of the schleswig holstein area north german basin abstract in the schleswig holstein area salty groundwaters are not always spatially related to the presence of shallow sat structures furthermore hydrochemical data point to instable salinity profiles and to the occurrences of deep brines close to the surface therefore complex interaction between shallow and deep solute migration must occur numerical simulation of fluid flow mass and heat transport have been carried out in order to understand the role of shallow salt dissolution and young geological features on groundwater flow as well as to investigate the interrelationships between shallow and deep aquifer systems for these purposes a shallow 500 m and a deep profile model 5 km have been constructed the results indicate that different flow regimes coexist within the study area shallow brine migration is strongly controlled by the geological features of the basin such as salt flank glacial channels and sand layers furthermore shallow salt dissolution is the major cause for gravitational convection in the deeper aquifers this source of salinization from above leads to the formation of instable salinity profiles at 2 km depth further interactions between shallow and deep fluid flow exist in the eastern part of the basin where brine upconing is due to both topography driven flow and thermohaline convection the simulations also showed that the hydraulic conductivity of the stratigraphic units influences the brine regime on a regional scale gravitational convection is likely to occur in permeable units located near shallow salt structures while thermohaline convection persists within thick permeable areas in which salt dissolution is not the dominant process the presented study provides new insights into fluid basin processes the described flows could develop in any geothermal basin hosting salt diapirs which pierce shallow aquifer systems

late cretaceous to recent tectonic evolution of the north german basin and the transition zone to the baltic shield southwest baltic sea abstract in this study we investigate the late cretaceous to recent tectonic evolution of the southwestern baltic sea based on a dense grid of seismic reflection profiles this area covers the baltic sea sector of the salt influenced north german basin and its transition to the salt free baltic shield across the tornquist zone the upper cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high resolution time structure maps of the main horizons i e the upper cretaceous tertiary and pleistocene the upper cretaceous and tertiary layers reveal numerous significant faults throughout the study area several of these faults propagate upwards across the unconsolidated pleistocene sediments and occasionally penetrate the surface the salt influenced north german basin reveals three major fault trends nw se n s and nne ssw several of these faults are located directly above basement sub salt faults and salt pillows the majority of these faults are trending n s to nne ssw and parallel the direction of the gluckstadt graben faults in the salt free tornquist zone we identify two major shallow fault trends which are nw se and ne sw the majority of these faults are located above basement faults following the direction of the tornquist zone we conclude that generally basement tectonics controls activation and trends of shallow faults if salt is present the ductile salt layer causes a lateral shift between the sub and supra salt faults major plate reorganisation related to the africa iberia europe convergence and the subsequent alpine orogeny caused reactivation of pre existing faults and vertical salt movement in the late cretaceous the change of stress orientation from ne sw to a nw se during neogene caused another phase of fault and salt tectonic reactivation we explain that the ice sheet loading and or present day stress field may have acted in combination causing the recent tectonics and upward extension of the faults

subglacial hydrology in north western germany during the last glaciation groundwater flow tunnel valleys and hydrological cycles abstract numerical modelling of groundwater dynamics in an overpressured system of subglacial aquifers and aquitards under the marginal portion of the scandinavian ice sheet in northwestern germany has been coupled with calculations of basal meltwater production rates and with field evidence of meltwater erosional features largely fine grained subglacial sediments with relatively low hydraulic conductivities had a capacity to drain only about 25 of all basal meltwater produced in the relevant subglacial catchment area the rest of the meltwater was evacuated through tunnel valleys in spontaneous outburst events subglacial drainage cycles are proposed in which each cycle begins with meltwater drainage through the substratum groundwater flow followed by water ponding at the ice bed interface and ends in catastrophic meltwater releases through tunnel valleys

alteration of basaltic glasses from north central british columbia canada abstract evidence of palagonitization glass replacement by poorly crystallized clay like material is seen on all glasses studied from three pleistocene subglacial volcanoes in north central british columbia canada samples from foreset breccias of tuya butte are more highly palagonitized than those from the tephra cones of ash mountain and southern tuya extensive palagonitization is generally associated with authigenic mineralization clays zeolites palagonite composition varies widely relative to glass composition and palagonite can be broadly categorized as either high al or low al depending on whether al was retained or lost to aqueous solutions during palagonitization the lowest al palagonites are those from the foreset breccias of tuya butte loss of al during palagonitization is related to closed system alteration including precipitation of aluminosilicate authigenic cements low initial ph is suggested for al depletion consistent with the behavior of ni co and cr which are retained in high al and depleted in low al palagonite microenvironment appears to be more influential than macroenvironment in determining the composition of palagonite palagonite rinds are compositionally zoned generally becoming progressively higher in al and ca and lower in fe and mg towards the innermost later formed portions of the rinds this apparently reflects changing solution composition increasing ph with time compositional zoning does not change the overall stoichiometry of palagonite which resembles smectite clay mineral paragenesis is related to the ca content of the palagonite with partial replacement of palagonite by smectite fe saponite occurring when ca is retained in the rind this replacement phenomenon occurs prior to zeolitization no such replacement clay occurs with low ca palagonite but a late stage nontronite film overgrows zeolite phillipsite is the first zeolite formed followed by chabazite analcime and calcite occur in the most highly palagonitized samples mass balance considerations indicate higher mass loss where palagonitization has not proceeded to the point where zeolite solubility limits were attained in the local solution zeolites occur in closed system conditions low flow rates where little net system mass loss or gain has occurred the colloidal nature of palagonite allows the effective adsorption of rb cs sr ba and rees

impact of late cretaceous to neogene plate tectonics and quaternary ice loads on supra salt deposits at eastern gluckstadt graben north german basin

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

the mesozoic cenozoic structural framework of the bay of kiel area western baltic sea a dense grid of multichannel high resolution seismic sections from the bay of kiel in the western baltic sea has been interpreted in order to reveal the mesozoic and cenozoic geological evolution of the northern part of the north german basin the overall geological evolution of the study area can be separated into four distinct periods during the triassic and the early jurassic e w extension and the deposition of clastic sediments initiated the movement of the underlying zechstein evaporites the deposition ceased during the middle jurassic when the entire area was uplifted as a result of the mid north sea doming the uplift resulted in a pronounced erosion of upper triassic and lower jurassic strata this event is marked by a clear angular unconformity on all the seismic sections the region remained an area of non deposition until the end of the early cretaceous when the sedimentation resumed in the area throughout the late cretaceous the sedimentation took place under tectonic quiescence reactivated salt movement is observed at the cretaceous cenozoic transition as a result of the change from an extensional to compressional regional stress field the vertical salt movement influenced the cenozoic sedimentation and resulted in thin skinned faulting

introduction geological and geophysical studies in the trans european suture zone the trans european suture zone tesz is the boundary between ancient precambrian lithosphere of the east european craton eec and the younger lithosphere beneath the latest neoproterozoic palaeozoic mobile belts of western europe the former is characterized by a thick crust c 45 km low heat flow and a tectono thermal age of about 3000 to 800 ma the latter by a thinner crust c 30 km higher heat flow and a tectonothermal age of 560 to 290 ma these contrasting types of crust were juxtaposed during the caledonian and variscan orogenic episodes the crystalline basement of the tesz is largely concealed by sedimentary basins controlled by the reactivation of structures within the suture zone during permian mesozoic extension and cenozoic inversion the pre permian evolution of the craton and the mobile belts and the location of the sutures is inferred from isolated outcrops hundreds of boreholes and geophysical evidence existing seismic data demonstrates that the tesz is rather narrow and has an expression at all levels of the lithosphere and deep into the asthenosphere teleseismic studies have demonstrated that the differences in the velocity structure of the asthenospheric and lithospheric mantle across the tesz persist to depths of c 400 km zielhus nolet 1994

the margins of avalonia during cambrian and earliest ordovician times avalonia was an area forming an integral part of the huge gondwanan continent probably along the northern margin of amazonia until in early ordovician late arenig or llanvirn time it split off from gondwana leaving a widening rheic ocean to its south today its southern margin with gondwana extends northeast from east of cape cod massachusetts through nova scotia north of the meguma terrane and thence below sea level to the south of newfoundland on the eastern side of the present atlantic the southern margin may separate southwest portugal from the rest of the iberian peninsula it can be traced eastwards with more certainty from the south cornwall nappes to a line separating the northern phyllite belt on the southern margin of the rhenohercynian terrane and the mid german crystalline high there is no certain evidence of avalonian crust to the northeast of the elbe line the northern margin of avalonia extends westwards from south of denmark to the british isles where it merges with the iapetus ocean suture between scotland and england traced westwards it crosses ireland and reappears in northern newfoundland to the east of new world island where it may follow the trace of the dog bay line and the cape ray fault recent work suggests that the northern margin of avalonia may clip the northern tip of cape breton island in nova scotia and then enter the north american mainland at the bay of chaleur it may then be traced from north and west of the popelogan and bronson hill arcs to long island sound near newhaven connecticut the cambrian to devonian faunas reflect the history of avalonia initially they were purely gondwanan but as ordovician time proceeded more genera crossed firstly the tornquist ocean as it narrowed between avalonia and baltica to close in latest ordovician and early silurian times and secondly the iapetus ocean so that by the early silurian most of the benthic shelly faunas apart from the ostracods were the same round the adjacent margins of all three palaeocontinents

origin of the salt valleys in the canyonlands section of the colorado plateau evaporite dissolution collapse versus tectonic subsidence abstract the salt valleys over the axis of the salt cored anticlines in the paradox fold and fault belt canyonlands utah and colorado are created by subsidence of the anticline crests traditionally the collapse of the anticlinal crests was attributed to dissolution of the salt walls diapirs forming the anticline cores recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions this paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation the development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution induced subsidence explanation however these salt dissolution models do not reproduce the karstification of salt walls in a realistic way since their analog involves removal of salt from the base of the diapirs during the experiments additionally numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults field evidence against the regional extension model includes 1 a thick cap rock at the top of the salt walls 2 the concentration of subsidence deformation structures along the crest of the anticlines salt walls 3 deformational structures not consistent with the proposed nne extension like crestal synforms and ne sw grabens 4 dissolution induced subsidence structures controlled by ring faulting revealing deep seated dissolution 5 large blocks foundered several hundred meters into the salt wall 6 evidence of recent and active dissolution subsidence and 7 the aseismic nature of the recently active collapse faults although underground salt dissolution seems to be the main cause for the generation of the salt valleys this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution

an experimental investigation of high temperature interactions between seawater and rhyolite andesite basalt and peridotite natural seawater was allowed to react with rhyolite andesite basalt and peridotite at 200 500 c and 1 000 bars at water rock mass ratios of 5 and 50 in order to investigate the effects of rock type water rock ratio and temperature on solution chemistry and alteration mineralogy the results indicate that interactions of seawater with various igneous rocks are similar in the production of a hydrous mg silicate and anhydrite as major alteration products fluids involved in the interactions lose mg to alteration phases while leaching fe mn and si from the rocks the ph of the solutions is primarily controlled by mg oh silicate formation and therefore varies with mg and si concentration of the system other reactions which involve mg such as mg ca exchange or which produce free h cause major differences in fluid chemistry between different seawater rock systems high water rock ratio systems 50 1 are generally more acidic and more efficient in leaching than low ratio systems 5 1 due to relatively more seawater mg available for mgsilicate production the experiments show that large scale seawater rock interaction could exert considerable control on the chemistry of seawater as well as producing large bodies of altered rock with associated ore deposits

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

formation by silicate fluoride phosphate melt immiscibility of ree rich globular segregations within aplite dikes aplite dikes intruding the proterozoic 1 42 3 ga longs peak st vrain silver plume type peraluminous granite near jamestown colorado contain f p and rare earth element ree rich globular segregations with 40 46 ree 3 7 4 8 wt p2o5 and 5 8 wt f a combination of textural features and geochemical data suggest that the aplite and ree rich globular segregations co existed as two co genetic liquids prior to their crystallization and we propose that they are formed by silicate fluoride phosphate s co2 melt immiscibility following ascent cooling and decompression of what was initially a single homogeneous magma that intruded the granite the ree distribution coefficients between the silica rich aplites and ree rich segregations are in good agreement with experimentally determined distribution coefficients for immiscible silicate fluoride phosphate melts although monazite ce and uraninite u th pb microprobe ages for the segregations yield 1 420 25 and 1 442 8 ga respectively thus suggesting a co genetic relationship with their host granite end1 42ga values for the granites and related granitic pegmatites range from 3 3 to 4 7 average 3 9 and differ from the values for both the aplites and ree rich segregations which range from 1 0 to 2 2 average 1 6 furthermore the granites and pegmatites have la yb n 100 and absence of an eu anomaly in both the aplites and segregations these data are consistent with the aplite dikes and the ree rich segregations they contain being co genetic but derived from a source different from that of the granite the higher end1 42ga values for the aplites and ree rich segregations suggest that the magma from which they separated had a more mafic and deeper dryer and hotter source in the lower crust or upper mantle compared to the quartzo feldspathic upper crustal source proposed for the longs peak st vrain granite

hydrothermal alteration in oceanic ridge volcanics a detailed study at the galapagos fossil hydrothermal field abstract the galapagos fossil hydrothermal field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern galapagos rift between 85 49 w and 85 55 w the discharge zone of the hydrothermal system is revealed along scarps thus providing an opportunity to examine the uppermost mineralized and highly altered interior parts of the crust altered rocks collected in situ by the submersible alvin show complex concentric alteration zones microsamples of individual zones have been analysed for major minor trace elements and strontium isotopes in order to describe the complex compositional details of the hydrothermal alteration interlayered chlorite smectite and chlorite with disequilibrium compositions dominate the secondary mineralogy as replacement phases of primary glass and acicular pyroxene phenocrysts and matrix grains of plagioclase are unaffected during alteration using a modification of the gresens equation we demonstrate that the trivalent rare earth elements rees are relatively immobile and calculate degrees of enrichment and depletion in other elements strontium isotopic ratios increase as sr concentrations decrease from least altered cores to most altered rims and cross cutting veins in individual samples and can be modeled by open system behaviour under low fluid rock ratio

behavior of rare earth elements in groundwater during flow and mixing in fractured rock aquifers an example from the dandenong ranges southeast australia a previously defined flow system is used to investigate ree behavior at different stages along groundwater flow paths in fractured basalt and sedimentary aquifers results from this study indicate that ree concentrations and patterns predominantly reflect different types and rates of reactions taking place to those controlling major ion chemistry in areas where recharge is through sediments ree concentrations are high nd 8 62 31 61 ng l and localised processes such as source heterogeneity control ree patterns and concentrations increased concentrations of rees in these groundwaters where ph 6 1 is a result of early stage ree mobilisation in the flow system in contrast where groundwater recharges through basalt ree concentrations are low nd 2 40 4 75 ng l and ree concentrations are relatively constant along groundwater flow paths indicating steady state conditions groundwater from both the sediment and basalt aquifer systems flows into the local discharge area in contrast to tds contents and major ion ratios groundwater from the discharge area has ree concentrations nd 1 84 4 18 ng l and patterns that reflect a larger component of flow from the basalt aquifer lower ree concentrations of groundwater from the regional sedimentary aquifer may result from progressive ree sorption or co precipitation as indicated by an increase in y ho cl cn ratios and hree enrichment for groundwater with ph not vert similar 7 1 due to greater abundances of hree vs lree dicarbonato complexes

low temperature alteration of basalt by interstitial seawater mururoa french polynesia chemical and isotopic analysis of interstitial fluids and secondary phases in two drill cores from the volcanic pile of the mururoa atoll french polynesia permits documentation of the lowtemperature alteration by seawater of basalt and secondary minerals as a function of rock water ratio r w up to 110 g l as r w increases in this system up to 70 g l the interstitial waters exhibit an almost total removal of mg and k a net decrease of ph and eh a marked enrichment in ca sr and si and depletion of 18o and d with further increases in r w above 70 g l a reversal of mg ca exchange is observed mg accumulates in the fluid while ca is removed in addition the enrichment of 18o and d is also observed in the fluids at these high r w these chemical and isotopic reversals are shown to result from the transformation of early precipitated mg rich saponite into ca na saponite chemical and isotopic reactions take place at two separate solid solution interfaces 1 1 an interface at the surface of the fresh basalt that leads to the formation of a hydrated amorphous layer which progressively crystallizes into clay and 2 2 a second interface between the interstitial bulk fluid and the resultant clay layer consequently geochemical codes which fail to account for both aqueous diffusion in altered layers and the existence of multiple reaction interfaces cannot accurately describe alteration at high rock water ratios

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

the glueckstadt graben a sedimentary record between the north and baltic sea in north central europe abstract the glueckstadt graben is one of the deepest post permian structures within the central european basin system and is located right at its heart at the transition from the north sea to the baltic sea and from the lower saxony basin to the rynkoebing fyn high the mesozoic to recent evolution is investigated by use of selected seismic lines seismic flattening and a 3d structural model a major tectonic event in the latest middle late triassic keuper was accompanied by strong salt tectonics within the glueckstadt graben at that time a rapid subsidence took place within the central part which provides the core of the glueckstadt graben the post triassic tectonic evolution of the area does not follow the typical scheme of thermal subsidence in contrast it seems that there is a slow progressive activation of salt movements triggered by the initial triassic event starting with the jurassic the subsidence centre partitioned into two parts located adjacent to the triassic core in comparison with other areas of the central european basin system the glueckstadt graben was not strongly affected by additional jurassic and cretaceous events during the late jurassic to early cretaceous the area around the glueckstadt graben was affected by relative uplift with regional erosion of the elevated relief however subsidence was reactivated and accelerated during the cenozoic when a strong subsidence centre developed in the north sea during paleogene and quaternary neogene the two centres of sedimentation moved gradually towards the flanks of the basin the data indeed point toward a control of post permian evolution by gradual withdrawal of salt triggered by the initial exhaustion along the triassic subsidence centre in this sense the glueckstadt graben was formed at least partially as basin scale rim syncline during post permian times the present day hamburger east and westholstein troughs are the actual final state of this long term process which still may continue and may play a role in terms of young processes and e g for coastal protection

seismic evidence of caledonian deformed crust and uppermost mantle structures in the northern part of the trans european suture zone sw baltic sea abstract collisional structures from the closure of the tornquist ocean and subsequent amalgamation of avalonia and baltica during the caledonian orogeny in the northern part of the trans european suture zone tesz in the sw baltic sea are investigated a grid of marine reflection seismic lines was gathered in 1996 during the dekorp basin 96 campaign shooting with an airgun array of 52 l total volume and recording with a digital streamer of up to 2 1 km length the detailed reflection seismic analysis is mainly based on post stack migrated sections of this survey but one profile has also been processed by a pre stack depth migration algorithm the data provides well constrained images of upper crustal reflectivity and lower crustal uppermost mantle reflections in the area of the caledonian suture a reflection pattern is observed with opposing dips in the upper crust and the uppermost mantle detailed analysis of dipping reflections in the upper crust provides evidence for two different sets of reflections which are separated by the o horizon the main decollement of the caledonian deformation complex s dipping reflections beneath the sub permian discontinuity and above the o horizon are interpreted as caledonian thrust structures beneath the o horizon sw dipping reflections in the upper crust are interpreted as ductile shear zones and crustal deformation features that evolved during the sveconorwegian orogeny the caledonian deformation complex is subdivided into 1 s dipping foreland thrusts in the north 2 the s dipping suture itself that shows increased reflectivity and 3 apparently ne dipping downfaulted sedimentary horizons south of the avalonia baltica suture which may have been reactivated during mesozoic normal faulting the reflection moho at 28 35 km depth appears to truncate a n dipping mantle structure which may represent remnant structures from tornquist ocean closure or late collisional compressional shear planes in the upper mantle a contour map of these mantle reflections indicates a consistent northward dip which is steepest where there is strong bending of the caledonian deformation front the thin skinned character of the caledonian deformation complex and the fact that n dipping mantle reflections do not truncate the moho indicate that the baltica crust was not mechanically involved in the caledonian collision and therefore escaped deformation in this area

trace element mobility during sub seafloor alteration of basaltic glass from ocean drilling program site 953 off gran canaria trace element concentrations of altered basaltic glass shards layer silicates and zeolites in volcaniclastic sediments drilled in the volcanic apron northeast of gran canaria during ocean drilling program odp leg 157 document variable element mobilities during low temperature alteration processes in a marine environment clay minerals saponite montmorillonite smectite replacing volcanic glass particles are enriched in transition metals and rare earth elements ree the degree of retention of ree within the alteration products of the basaltic glass is correlated with the field strength of the cations the high field strength elements are preferentially retained or enriched in the alteration products by sorption through clay minerals most trace elements are enriched in a boundary layer close to the interface mineral altered glass this boundary layer has a key function for the physico chemical conditions of the subsequent alteration process by providing a large reactive surface and by lowering the fluid permeability the release of most elements is buffered by incorporation into secondary precipitates sodium rich zeolites phillipsite fe and mn oxides as shown by calculated distribution coefficients between altered glasses and authigenic minerals chemical fluxes change from an open to a closed system behavior during prograde low temperature alteration of volcaniclastic sediments with no significant trace metal flux from the sediment to the water column

structure and evolution of the northeastern german basin and its transition onto the baltic shield abstract the post permian sequence stratigraphical and structural evolution of the northeastern german basin and its transition onto the baltic shield has been studied in the bay of mecklenburg sw baltic sea by means of seismic interpretation five major sequences have been identified middle triassic upper triassic jurassic cretaceous and cenozoic time isochore maps allowed the identification of several phases of salt pillow growth the contemporaneity of active salt tectonics and the well studied tectonic evolution of the northeastern german basin suggest a causative correlation the e w directed extension during the triassic early jurassic marking the beginning break up of pangaea is seen as the trigger process for the first period of salt movement a fault system outside the limit of the zechstein evaporates is understood as the consequence of thin skinned faulting and brittle thick skinned deformation that accompanied this extension the observed pronounced erosion of upper triassic and lower jurassic strata is considered to result from the uplift due to the mid north sea doming event in middle jurassic times the seismic data show an undisturbed late cretaceous succession which reflects a period of rising sea level tectonic quiescence and no salt movement in contrast to the salt pillows which emerged above triassic fault systems in the westernmost baltic and western north german basin the cenozoic salt movement activity is the most pronounced this period of reactivated salt pillow growth started coevally with the onset of the alpine orogeny at the cretaceous cenozoic transition when the africa arabian plate collided with eurasia generally no significant faults were identified in the overburden of the salt floored southern bay of mecklenburg where ductile zechstein salt decouples deep rooted faulting from supra salt deformation

hydrothermal alteration at mururoa atoll french polynesia abstract petrological study of altered aerial basaltic flows submarine pillow lavas and oceanitic basalts of a rift zone sampled in two drill cores in the mururoa atoll viviane 1000 m depth fuchsia 550 m depth shows that during hydrothermal alteration processes the secondary clay minerals evolve the following three different trends controlled by permeability of the rocks and by rock fluid interaction mg saponite al saponite and al montmorillonite in the basaltic pillow lavas first celadonite saponite assemblage crystallizes in fresh glass rich rocks in altered and brecciated rocks the latter mineral assemblage is followed by fe saponite and mg saponite in breccias the glass is replaced by fe saponite the residual voids are sealed by zeolites mainly phillipsite apophyllite or gypsum indicating an upper temperature limit of 65 c in the aerial basaltic flows massive rocks are affected by celadonite and random mixed layer chlorite saponite crystallizations in the strongly altered rocks veined or brecciated the primary minerals and glass are partly replaced by al saponites and locally by chabazite the same al saponite fills up the veins and constitutes the major part of the cement as rock fluid interaction increases the si al and ca content in the solution increases inducing the late precipitation of aluminous smectite and chabazite in the oceanitic basalts sampled in the rift zone massive rocks are affected by crystallization of secondary clay minerals which is governed by local equilibrium femg clay minerals talc mg saponite celadonite partly replace the olivine phenocrysts and al saponite replaces the glass in veined and brecciated rocks the paragenesis is dioctahedral al smectite silica amorphous for a temperature range 2 content in the solution

alteration in the irdp drill hole compared with other drill holes in iceland the overall alteration pattern in the drill hole at reydarfjordur is very similar to alteration patterns observed in icelandic geothermal areas and in low grade metamorphosed basalts in deep crustal sections elsewhere in iceland however more detail is obtained by the study of the irdp drill core than by study of drill cuttings sampled in previous drill holes in iceland a comparatively high fossil thermal gradient is obtained at reydarfjordur by a combination of mineral stability data and the observed occurence of secondary minerals this high gradient is consistent with the measured dike dilation at the drill site and the location of the drill site adjacent to a central volcano

response of salt structures to ice sheet loading implications for ice marginal and subglacial processes abstract during the past decades the effect of glacioisostatic adjustment has received much attention however the response of salt structures to ice sheet loading and unloading is poorly understood our study aims to test conceptual models of the interaction between ice sheet loading and salt structures by finite element modelling the results are discussed with regard to their implications for ice marginal and subglacial processes our models consist of 2d plane strain cross sections which represent simplified geological cross sections from the central european basin system the model layers represent i sedimentary rocks of elastoplastic rheology ii a viscoelastic diapir and layer of salt and iii an elastoplastic basement on top of the model a temporarily variable pressure simulates the advance and retreat of an ice sheet the durations of the individual loading phases were defined to resemble the durations of the pleistocene ice advances in northern central europe the geometry and rheology of the model layers and the magnitude spatial distribution and timing of ice sheet loading were systematically varied to detect the controlling factors all simulations indicate that salt structures respond to ice sheet loading an ice advance towards the diapir causes salt flow from the source layer below the ice sheet towards the diapir resulting in an uplift of up to 4 m the diapir continues to rise as long as the load is applied to the source layer but not to the crest of the diapir when the diapir is transgressed by the ice sheet the diapir is pushed down up to 36 m as long as load is applied to the crest of the diapir during and after ice unloading large parts of the displacement are compensated by a reversal of the salt flow plastic deformation of the overburden is restricted to the area immediately above the salt diapir the displacements after unloading range between 3 1 and 2 7 m larger displacements are observed in models with deep rooted diapirs thicker ice sheets longer duration of the loading phase thicker salt source layers and lower viscosity of the salt the rise or fall of diapirs triggered or amplified by ice sheet loading are likely to affect glacigenic deformation erosion and deposition above the diapir and within the rim synclines ice load induced uplift in front of an ice sheet will provide favourable conditions for the formation of push moraines for example by creating a topographic obstacle and inclining potential detachments subglacial subsidence of salt structures will enhance erosion by providing a preferential drainage pathway and fracturing of the overburden of the salt structure and thereby contribute to the incision of tunnel valleys however the resulting displacements are probably too low to have a marked effect on the advance or retreat pattern of the ice sheets

subglacial conditions under the last ice sheet in northwest germany ice bed separation and enhanced basal sliding abstract theoretical reconstruction of ice thickness during the weichselian glaciation in a portion of northwest germany yields maximum thicknesses of about 280 m some 50 km into the ice sheet from the margin this corresponds to averaged driving stress at the glacier bed in the order of 17 kpa the increase in ice thickness away from the margin was non uniform caused by undulations in pre existing topography steady state subglacial water pressure heads were high up in the ice sheet reaching the flotation point in places hydraulic lifting of the ice sheet probably occurred causing non deforming bed conditions where transformation of basal shear stresses to soft subglacial sediments was prevented by a water film thin stringers of undeformed sorted sediments occurring in tills are attributed to basal meltwater washing during phases of ice bed separation the basal water film was over 5 mm thick using a quantitative approach coupled with field data we demonstrate that neither internal ice deformation nor bed deformation contributed much to the ice motion instead the rapid movement of the weichselian ice sheet was caused by basal sliding with ploughing the ice sheet was probably characterized by an unstable behaviour

behaviour of rare earth elements during seawater basalt interactions in the mururoa massif abstract the rare earth elements ree were analysed in the interstitial fluids in the basalts and in the alteration products clays and zeolites of mururoa atoll volcanic rocks french polynesia in order to investigate ree behaviour during seawater basalt interactions at low temperature the ree distribution coefficients between fluids and secondary products were calculated using the eq3 6 geochemical code the reversible irreversible character of the ree entrapment in secondary products was tested the ree concentrations in the clays are close to that of basalt the concentrations in zeolites are 10 times lower comparison of measured and modeled concentrations in solutions favours the irreversible incorporation assumption the affinity of the ree for the secondary products is shown to be high the calculated distribution coefficients range from 3 105 for lu and eu to 107 for ce in clays and from 104 to 7 105 in zeolites the distribution coefficients exhibit a progressive decrease from la to lu this behaviour is related to the greater stability of hree complexes relative to lree complexes in solution under reducing conditions in the interstitial fluids eh down to 500 mv eu undergoes reduction to the mobile eu ii this enhanced mobility is reflected by eu distribution coefficient being lower than those of adjacent ree the distribution coefficient of ce is higher as ce is trivalent in the fluids fractionation from the other trivalent ree was unexpected the calculated distribution coefficients of ree are lower in zeolites than in clays and this can be related to the spatial distribution and paragenesis of the secondary phases the dissolution of the basalt promotes the precipitation of clays at the basalt fluid interface and of zeolites in the bulk solution the ree released by dissolution are incorporated into the clays and further uptake occurs in zeolites for the ree left in solution

a consistent map of the postglacial uplift of fennoscandia a consistent map of the recent postglacial rebound of fennoscandia is constructed on the basis of sea level records lake level records and repeated high precision levellings the uplift rates calculated from the sea level series form a consistent framework of the map the sea level stations used are 56 reliable stations in the baltic sea and adjacent waters with series spanning 60 years or more many of them about 100 years using a reference station in the baltic sea and another one outside the baltic all results are reduced to a common time span the 100 year period 1892 1991 in order to eliminate oceanographic changes inland uplift differences are obtained from the repeated national levellings and in four of the large lakes from long water level series in pairs the levellings however yield less accurate land uplift values than the sea level and lake level data the resultant map shows a fairly smooth phenomenon with a maximum apparent uplift in the gulf of bothnia of 9 0 mm yr 1 the standard error is typically 0 2 mm yr i close to the sea level stations larger inland finally the pattern of the present uplift as determined here is observed to be very similar to that of the past uplift as determined from ancient shore lines of the litorina sea however the ratio between the past uplift and the present uplift rate tends to increase somewhat towards the uplift centre this might reflect a non uniform mantle viscosity also the uplift maximum seems to have migrated towards nne

revisiting the structural setting of the glueckstadt graben salt stock family north german basin abstract reprocessing of seismic data of a salt stock family from the north german basin provided new insights into the structural evolution of this area the common reflection surface crs stack technique was applied to reprocess the reflection data acquired by the hydrocarbon industry in the 1980s due to the low fold of these data and the complex geology in the study area severe imaging challenges were encountered when the data were initially processed using conventional cmp stack the crs stack technique is particularly suited for low fold data in complex areas since it builds physically correct super gathers even if dipping structures are present this leads to a considerably improved signal to noise ratio in the crs stack compared to cmp stack sections moreover the crs stack parameters obtained during the stack form the foundation for a robust reflection tomography used for velocity model building these models allowed the application of pre stack and post stack depth migration the obtained depth images provided structural details not seen before motivating an alternative view on the structural setting of the area the image of the jurassic salt plug indicates tectonics similar to observations in the allertal region where reverse faulting plays a major role in the evolution of the salt structures as a consequence shortening of the mesozoic strata was included into the revised interpretation of the glueckstadt graben area the new depth images also allowed an updated look on the petroleum system of this graben which indicates new possible exploration targets

differentiating marine vs hydrothermal processes in devonian carbonatemounds using rare earth elements kess kess mounds anti atlas morocco abstract petrological and geochemical analyses were carried out on early devonian kess kess mound limestones of the seheb el rhassel group exposed in the hamar laghdad ridge tafilalt platform eastern anti atlas morocco in order to evaluate marine vs hydrothermal processes for the origin of the mounds hydrothermal fluid circulation affected limestone deposition resulting in the formation of a plumbing system preserved in the mound facies and inter mound facies as cavities veins and dykes shale normalized rare earth element ree patterns for limestones display pronounced light ree depletion compared to middle ree average prsn dysn 0 46 and heavy ree average prsn ybsn 0 55 a super chondritic y ho ratio up to 87 and positive la anomaly consistent with precipitation from normal marine seawater within our data set the ce anomaly as well as u and other trace element concentrations vary with facies providing evidence for variable redox conditions the presence of positive ce anomaly in carbonates of the plumbing system is consistent with precipitation under anoxic condition samples from mound facies and quartz veinlets in the upper part of the group show ree patterns consistent with precipitation from hydrothermal fluids early devonian hypothetical seawater ree patterns were calculated from samples showing normal marine ree patterns i e inter mound facies and from samples with weaker marine signature i e fossiliferous mound limestones and plumbing system deposits hypothetical patterns are slightly enriched in ree compared to modern open ocean seawater this study reveals that ree analysis is a powerful tool for understanding polygenetic carbonate systems it sheds light into the genesis of the kess kess mounds by reconstructing fluid pathways and palaeo redox conditions

reflections of the geological characteristics of cyprus in soil rare earth element patterns abstract rare earth elements rees are used as indicators or proxies for a range of geological and mineralogical processes due to their unique geochemical characteristics total and aqua regia extractable concentrations of rees and 57 other elements have been determined for 5350 soil samples as part of the high sampling density geochemical atlas of cyprus the bedrock geology of cyprus is dominated by the sequence of ultramafic to mafic units formed at a spreading ridge and subsequently obducted to form the troodos ophiolite to and the surrounding carbonate rich circum troodos sedimentary sequence ctss deposited in environments ranging from deep marine to sub aerial total and aqua regia extractable ree patterns are similar for each element and are largely controlled by parent lithology soil to rock ree ratios are generally elevated in the to units 4 for lrees and 1 5 3 for hrees due to loss of more mobile elements during weathering but are close to 1 in the ctss units hrees are more elevated than lrees in soils derived from to units with upper continental crust normalised patterns indicating the main source to be pyroxenes and zircon trace element trends indicate rees in the ctss were largely derived from detrital material shedding off the to and deposited in progressively shallowing basins under largely anoxic conditions absence of ce4 anomalies with a minor contribution from seawater via adsorption onto secondary fe mn oxides or co precipitation with carbonates heavy mineral associated elements such as zr and th display a relative consistent ratio in the ctss soils peak hree concentrations occur in the mafic cumulates and intrusives where the median laucc ybucc is 0 12 whereas in ctss units the lrees are more elevated with a median laucc ybucc 0 7 due to the strong lithogeochemical controls soil ree spatial patterns reflect even subtle mineralogical variations within the various to units the location of major transform faults and other structures and areas that have been affected by hydrothermal alteration

ice load induced tectonics controlled tunnel valley evolution instances from the southwestern baltic sea abstract advancing ice sheets have a strong impact on the earth s topography for example they leave behind an erosional unconformity bulldozer the underlying strata and form tunnel valleys primarily by subglacial melt water erosion and secondarily by direct glacial erosion the conceptual models of the reactivation of faults within the upper crust due to the ice sheets load are also established however this phenomenon is also rather under explored here we propose a causal link between ice load induced tectonics the generation of near vertical faults in the upper crust above an inherited deep rooted fault and the evolution of tunnel valleys the kossau tunnel valley in the southeastern bay of kiel has been surveyed by means of high resolution multi channel seismic and echosounder data it strikes almost south to north and can be mapped over a distance of ca 50 km it is 1200 8000 m wide with a valley of up to 200 m deep quaternary deposits fill the valley and cover the adjacent glaciogenic unconformity a near vertical fault system with an apparent dip angle of 80 which reaches from the top zechstein upwards into the quaternary underlies the valley the fault partially pierces the seafloor and growth is observed within the uppermost quaternary strata only consequently the fault evolved in the late quaternary the fault is associated with an anticline that is between 700 and 3000 m wide and about 20 40 m high the fault anticline assemblage neither resembles any typical extensional compressional or strike slip deformation pattern nor is it related to salt tectonics based on the observed position and deformation pattern of the fault anticline assemblage we suggest that these structures formed as a consequence of the differential ice load induced tectonics above an inherited deep rooted sub salt fault related to the gluckstadt graben lateral variations in the ice load during the ice sheet s advance caused differential subsidence thus rejuvenating the deep rooted fault as a result the inherited fault propagated upwards across the zechstein and post permian overburden and further grew during the ice sheet s retreat the developing fault and anticline system under the ice sheet created a weakness zone that facilitated erosion by pressurized glacial and subglacial melt water as well as by the glaciers themselves near vertical faults cutting through the post permian are abundant in the southwestern baltic realm which implies that the ice load induced tectonic activity described above was not an isolated incident

triassic to recent tectonic evolution of a crestal collapse graben above a salt cored anticline in the gluckstadt graben north german basin abstract in this study we investigate faulting above a salt wall in the gluckstadt graben north german basin two supra salt faults are mapped from coast to coast over a distance of 6 9 km based on offshore and onshore seismic data these faults form a ca 2 km wide crestal collapse graben and pierce the seafloor salt wall evolution started in the early late triassic to early jurassic due to regional extension and resulting sub salt faulting the salt wall was eroded following exposure to costal and sub aerial erosion by the regional mid late jurassic to early cretaceous uplift late cretaceous to early paleogene compressional tectonics reactivated the vertical salt movement and shortened the salt wall creating a salt cored anticline with the crestal collapse graben above the supra salt faults were reactivated between the late eocene and middle miocene when the principal horizontal stress orientation changed from a ne sw to a nw se the present day orientation stratigraphic data indicate that these faults moved mainly in the cenozoic several observations strongly suggest that the faults continued developing during the pleistocene until today i the pleistocene unconformity is concave upwards and cut by faults ii growth strata within the marine holocene deposits above the graben imply recent tectonic movements iii onshore high resolution p wave vibroseis data of the south eastern eckernforde bay suggest about 10 m of faulted holocene strata and iv marine seismic data show the faults piercing the seafloor we suggest that the recent salt tectonics and upward propagation of supra salt faults resulted from differential ice sheet loading that effect on the salt wall stopped once ice grew over the whole structure at which time the wall subsided because of ice loading the salt wall and faults were reactivated again once the ice front retreated so that the ice loaded only one side of the structure

trace elements and ree geochemistry of middle devonian carbonate mounds maider basin eastern anti atlas morocco implications for early diagenetic processes abstract trace and rare earth elements rees have proven their utility as tools for assessing the genesis and early diagenesis of widespread geological bodies such as carbonate mounds whose genetic processes are not yet fully understood carbonates from the middle devonian conical mud mounds of the maider basin eastern anti atlas morocco have been analysed for their ree and trace element distribution collectively the carbonates from the maider basin mud mounds appear to display coherent ree patterns three different geochemical patterns possibly related with three different diagenetic events include i dyke fills with a normal marine ree pattern probably precipitated in equilibrium with seawater ii mound micrite with a particular enrichment of overall ree contents and variable ce anomaly probably related to variation of ph increase of alkalinity or dissolution remineralization of organic matter during early diagenesis and iii haematite rich vein fills precipitated from venting fluids of probable hydrothermal origin our results reinforce the hypothesis that these mounds were probably affected by an early diagenesis induced by microbial activity and triggered by abundance of dispersed organic matter whilst venting may have affected the mounds during a later diagenetic phase

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

major and trace element compositions of melt particles and associated phases from the yaxcopoil 1 drill core chicxulub impact structure mexico melt particles found at various depths in impactites from the yaxcopoil 1 borehole into the chicxulub impact structure yucatan have been analyzed for their major and trace element abundances a total of 176 electron microprobe and 45 la icp ms analyses from eight different melt particles were investigated the main purpose of this work was to constrain the compositions of precursor materials and secondary alteration characteristics of these melt particles individual melt particles are highly heterogeneous which makes compositional categorization extremely difficult melt particles from the uppermost part of the impactite sequence are ca and na depleted and show negative ce anomalies which is likely a result of seawater interaction various compositional groupings of melt particles are determined with ternary and binary element ratio plots involving major and trace elements this helps distinguish the degree of alteration versus primary heterogeneity of melt phases comparison of the trace element ratios sc zr y zr ba zr ba rb and sr rb with compositions of known target rocks provides some constraints on protolith compositions however the melt compositions analyzed exceed the known compositional diversity of possible target rocks normalized ree patterns are unique for each melt particle likely reflecting precursor mineral or rock compositions the various discrimination techniques indicate that the highly variable compositions are the products of melting of individual minerals or of mixtures of several minerals small angular shards that are particularly abundant in units 2 and 3 represent rapidly quenched melts whereas larger particles 0 5 mm that contain microlites and have fluidal schlieric textures cooled over a protracted period angular shard like particles with microlites in unit 5 likely crystallized below the glass transition temperature or underwent fragmentation during or after deposition

petrology of the volcanic bedrock of mururoa atoll tuamotu archipelago french polynesia abstract the south pacific atoll of mururoa is located in the southeastern part of the tuamotu archipelago it is about 28 km long and represents the emergent part of a 60 km long submarine plateau this atoll is composed of submarine volcanic rocks resting on oceanic crust then above subaerial volcanic rocks and finally a coral coating about 300 m thick the volcanic rocks are markedly alkaline and this alkaline magmatic trend evolved by fractional crystallization from nepheline normative 10 wt basalts to quartz normative 5 wt trachyte fractionation of phlogopite played a significant role in this evolution the basic lavas contain olivine spinel magnetite ilmenite clinopyroxene and plagioclase phenocrysts rare feldspathoids occur in the groundmass of the hawaiites two trends can be distinguished the first one characterized by the presence of mica plagioclase and ilmenite has evolved under high p h 2 o the second characterized by amphibole richterite and arfvedsonite aegirine alkali feldspar and magnetite has evolved under lower p h 2 o and silica activity but higher f o 2 thermodynamic conditions of crystallization at depth deduced from olivine liquid plagioclase liquid and magnetite ilmenite equilibria are high temperature 1100 to 1200 c medium water pressure 1 to 1 5 kbar and medium to low oxygen fugacity 10 10 bar the mururoa magmas may have issued from fissures along the australes fault it may not result from the activity of the hot spot situated east of pitcairn island considered as responsible for the volcanism of others islands of the tuamotu archipelago fangataufa gambier pitcairn

ferruginous and manganiferous haloes around massive sulphide deposits of the urals proximal brecciform ferruginous and manganiferous rocks related to vms deposits of the urals are subdivided into jasperites gossanites and umbers in addition to thin bedded jaspers and cherts the coherence of host rock composition and mn fe fertility of the sediments have been established fe poor pink hematitic and gray sulphidic chert are typical of the felsic class of vms deposits in contrast the contents of fe vary from high to moderate in ferruginous rocks enclosed in basaltic units associate with vms deposits fe and mn rich ferruginous rocks and umbers occur in association with limestones and calcareous sedimentary rocks in both types of volcanic sequences a common feature of jasperites and umbers is the abundance of replacement textures of hyaloclastites and carbonates by hematite and silica in addition replacement of clastic sulphides by hematite and magnetite is a characteristic genetic feature of gossanites all of these sedimentary rocks are accompanied by pseudomorphs of hematite and quartz formed after bacterial filaments the abundance of replacement textures are supportive of the halmyrolysis model in addition to hydrothermal sedimentary and sub seafloor hydrothermal replacement theories study of chemical zonation of altered hyaloclasts shows depletion of their rims not only in mobile na k mg but also in immobile al ti and ree whereas si and fe are concentrated in situ the halmyrolysis model presented here involving organic rich calcareous hyaloclastic sediments resolves the problem of subtraction of al ti ree and other elements which are commonly immobile under hydrothermal conditions the evolution of the halmyrolysis process from acidic reducing to alkaline oxidized conditions infers a possible range in transformation from fe ii mg smectites to fe silicates and fe si oxides as precursors of brecciform jasperite and thin bedded jasper the higher acidic initial stage of gossanite formation seems to be required for oxidation of organic matter and or pyrite the acidic condition facilitates the temporal preservation of immobile elements al ti ree in immature chlorite hematite gossanites another peculiarity of the gossanite forming processes is the likely sorption of p u and v by iron hydroxides displacing sulphides the general evolution of all ferruginous sediments results in complete fe 2 oxidation and silicification accompanied by subtraction of other elements the vertical diagenetic differentiation leads to concentration of mn carbonates silicates and oxyhydroxides into the tops of jasperite and gossanite layers mn oxyhydroxides scavenge positively charged hydrated cations like co and ni near vent bacterial communities may activate the processes of volcanic glass and sulphide degradation the proposed processes of halmyrolysis followed by silicification in situ may resolve the enigma of silica rich sediment formation in a silica undersaturated ocean the discrimination between gossanite and jasperite is useful for elaboration of new criteria for local exploration of vms and mn deposits halo dispersion of gossanites covering an area about two to three times that of the massive sulphide deposit is a good vector for ore body discovery proximal gossanites can be differentiated from jasperites by presence of relic sulphide clasts or elevated contents of chalcophile elements cu fe zn pb bi te as sb ba noble metals au ag and distinct ree patterns with la and eu positive anomalies the development of halmyrolysis and biomineralization models merit further elaboration and testing in on going research in order to add or revise theories of iron and manganese deposit formation 2012 elsevier b v

the ree content of some hydrothermal fluids ree concentrations were determined in solutions from submarine hydrothermal vents on the east pacific rise and for the first time from continental geothermal fields in tibet and bulgaria they indicate that in hydrothermal systems ree are immobile at temperatures below 350 c and for water rock ratios of 105 nd values of submarine solutions and anhydrites 4 7 to 6 2 suggests recharge on the sedimentcovered flanks of the ridge carbonate anions as measured by alkalinity appear to increase the solubility of heavy ree somewhat but not to the extent that substantial amounts of ree could be driven out from rocks by hydrothermal activity

geochemical and petrographic characteristics of impactites and cretaceous target rocks from the yaxcopoil 1 borehole chicxulub impact structure mexico implications for target composition we present major and trace element data as well as petrographic observations for impactites suevitic groundmass bulk suevite and melt rock particles and target lithologies including cretaceous anhydrite dolomite argillaceous limestone and oil shale from the yaxcopoil 1 borehole chixculub impact structure the suevitic groundmass and bulk suevite have similar compositions largely representing mixtures of carbonate and silicate components the latter are dominated by melt rock particles trace element data indicate that dolomitic rocks represented a significant target component that became incorporated into the suevites in contrast major elements indicate a strong calcitic component in the impactites the siliceous end member requires a mafic component in order to explain the low sio2 content multicomponent mixing of various target rocks the high alteration state and dilution by carbonate complicate the determination of primary melt particle compositions however two overlapping compositional groups can be discerned a high ba low ta group and a high fe high zn and high hf group cretaceous dolomitic rocks argillaceous limestone and shale are typically enriched in u as br and sb whereas anhydrite contains high sr contents the oil shale samples have abundances that are similar to the north american shale composite nasc but with a comparatively high u content clastic sedimentary rocks are characterized by relatively high th hf zr as and sb abundances petrographic observations indicate that the cretaceous rocks in the yaxcopoil 1 drill core likely register a multistage deformation history that spans the period from pre to post impact contrary to previous studies that claimed evidence for the presence of impact melt breccia injection veins we have found no evidence in our samples from a depth of 1347 1348 m for the presence of melt breccia we favor that clastic veinlets occur in a sheared and altered zone that underwent intense diagenetic overprint prior to the impact event

topography of the top chalk surface on and offshore denmark abstract a time structure map of the top of the upper cretaceous danian chalk group the top chalk surface in the entire danish sector is presented the present topography of the top chalk surface is a result of various erosional and tectonic events taking place during the cenozoic the analysis shows that the cenozoic is characterised by significant reactivation of the mesozoic structural elements of which the central graben the ringkobing fyn high and the sorgenfrei tornquist zone are the most important a tectonically controlled relief caused the generation of widespread sheet like erosion on the ringkobing fyn high and incisions along the margins of ringkobing fyn high during the mid paleocene incisions in the northern part of the danish sector formed valleys which probably transported sediment towards the west the present topography of top chalk in the eastern part of the danish sector is highly influenced by the late cenozoic erosion of the uplifted eastern margin of the north sea basin the topography of top chalk also reflects the distribution of mobile zechstein salt as collapse structures follow the pitch out line of mobile salt onto the ringkobing fyn high and numerous salt structures deformed the top chalk surface

geological history and petroleum system of the mittelplate oil field northern germany the geological history of germany s largest and most productive petroleum accumulation the mittelplate oil field in schleswig holstein northern germany is reconstructed by simulating the structural and thermal evolution along a 2d cross section the mittelplate field is located at the western flank of the busum salt dome at the transition from the schleswig holstein mainland to the german north sea sector organic geochemical data confirm the lower jurassic posidonia shale to be the predominant oil source rock in the schleswig holstein area the studied section is characterized by salt walls and salt domes built up by permian evaporites reconstruction of the structural and thermal evolution of the mittelplate field by means of basin modelling reveals the dominating influence of salt dynamics on the entire petroleum system the development of secondary rim synclines during salt rise provided accommodation space for the deposition of the posidonia shale as well as the deltaic middle jurassic reservoir sandstones the rise of the nearby oldenswort salt wall controlled the timing of maturation and petroleum generation during cenozoic times hydrocarbon migration from the posidonia shale into the reservoirs occurred up dip from the deeper subsiding rim syncline into the structural trap with the middle jurassic reservoir sandstones pinching out at the flank of the busum salt dome along the modelled 2d section the field s recent temperature field and its complex reservoir architecture are reconstructed