velocity contrast across the 1944 rupture zone of the north anatolian fault east of ismetpasa from analysis of teleseismic arrivals 1 we use differences between arrival times of teleseismic events at sets of stations crossing the north anatolian fault east of ismetpasa where shallow creep has been observed to detect and quantify a contrast of seismic velocities across the fault waveform cross correlations are utilized to calculate phase delays of p waves with respect to expected teleseismic arrivals with incident angles corresponding to the generating events compiled delay times associated with 121 teleseismic events indicate about 4 3 average p wave velocity contrast across the fault over the top 36 km with faster velocity on the north side the estimated contrast is about 8 3 if the velocity contrast is limited to the top 18 km the sense of velocity contrast is consistent with the overall tectonic setting and inference made for the examined fault section based on theoretical expectations for bimaterial ruptures and observed asymmetry of rock damage across the fault our data indicate lack of significant microseismicity near the fault suggesting that creep in the area is limited to the depth section above the seismogenic zone

microearthquake activity in the dead sea region summary small earthquakes in the dead sea depression part of the jordan valley dead sea rift were recorded and analysed with 117 identified events of 0 5 ml 4 2 the microseismicity recorded by a local portable network during a period of about 20 months shows a normal rate of seismicity for the region with b values around 0 8 the recorded seismicity is mainly confined to the basin and its boundaries in the southern part of the dead sea basin we found a tendency to clustering which is clearly demonstrated in very similar seismograms of several events recorded at the same station two clusters on the eastern fault are separated by an area with no seismicity for at least 5 yr relative location of events in one of the clusters exhibits a clear north south lineament two active north south left lateral strike slip faults along the east and west boundaries of the southern section of the dead sea basin are distinguished and confirmed by using composite focal mechanism solutions in four out of more than 60 events we found normal faulting where one has a ml 4 1 for 34 events with 1 6 ml 4 2 we found seismic moment estimates m0 of 1 2 1019 m0 2 3 times 1022 dyne cm and brune stress drop estimates s between 0 6 and 92 bars for earthquakes of m0 smaller than about 5 times 1021 dyne cm we found only small variations in corner frequency f0 resulting in decreasing s with decreasing m0 this breakdown of the scaling relation for small earthquakes suggests an fmax slightly lower than 10 hz for the dead sea region the fmax is confirmed by available accelerometer data

petrophysical constraints on gravity magnetic interpretation in israel whether exploring for hydrocarbons and minerals or simply studying structural geology gravity and magnetic interpreters prefer to use density and magnetic susceptibility values that are determined for their area of investigation in exploration it is fairly common to have rock properties information from outcrops but it is rare to have real measured values for the subsurface the interpreter extrapolates from the surface bases assumptions on lithologies or uses approximate values from the literature this approach although unavoidable in many instances may lead to errors

a seismic refraction study of the north basin of the dead sea israel a seismic refraction experiment involving the use of 9 obs and 11 portable seismic land stations was conducted along a profile in the north basin of the dead sea the seismometers were deployed along a north south profile in the lake and the adjacent land area the interpretation of the recorded seismograms indicates the presence of two large pliocene salt diapirs in the young basin fill the basement lies at a relatively shallow depth 6 8 km under the north basin further south along the profile a major fault affecting the basement was detected the apparent sense of the faulting is down to the southeast representing the boundary of the south basin this major faulting with a downthrow of some 4 5 km has depressed the crystalline basement and the overlying cretaceous and pre cretaceous sediments the faulting was followed by the deposition of over 8 km of recent and tertiary sediments resulting in a 14 km thick sedimentary sequence in the south basin of the dead sea

lower crustal strength under the dead sea basin from local earthquake data and rheological modeling we studied the local seismicity of the dead sea basin for the period 1984 1997 sixty percent of well constrained microearthquakes ml 3 2 nucleated at depths of 20 32 km and more than 40 occurred below the depth of peak seismicity situated at 20 km with the moho at 32 km the upper mantle appeared to be aseismic during the 14 year data period a relocation procedure involving the simultaneous use of three regional velocity models reveals that the distribution of focal depths in the dead sea basin is stable lower crustal seismicity is not an artifact created by strong lateral velocity variations or data related problems an upper bound depth uncertainty of 5 km is estimated below 20 km but for most earthquakes depth mislocations should not exceed 2 km a lithospheric strength profile has been calculated based on a surface heat flow of 40 mw m 2 and a quartz depleted lower crust a narrow brittle to ductile transition might occur in the crust around 380 c at a depth of 31 km for the upper mantle the brittle to ductile transition occurs in the model at 490 c and at 44 km depth the absence of micro seismicity in the upper mantle remains difficult to explain

the structure of the dead sea basin abstract the dead sea basin is located along the left lateral transform boundary between the arabian and sinai plates its structure and history are known from surface geology drilling seismic reflection and other geophysical data the basin comprises a large pull apart almost 150 km long and mostly 8 10 km wide which is flanked by a few kilometres wide zones of normal faulting the basin formed at about 15 ma or earlier close to the beginning of the transform motion and it reached about half its present length before the end of the miocene a strong negative gravity anomaly records a thick sediment basin fill 5 km under half its length reaching a maximum of 10 km the fill includes a few km of salt ca 6 4 ma which forms several diapirs at any one time large parts of the basin subsided simultaneously but the site of fastest subsidence seems to have shifted northward sedimentation rates reached at least hundreds of metres per million years or more in the miocene and 1 km myr in later periods the basin structure is dominated by longitudinal faults intrabasinal faults which delimit the pull apart and which are the extensions of the major strike slip faults north and south of the basin and normal faults which extend along the basin margins the latter faults express a small component of extension across the basin whereas the pull apart resulted from the much larger lateral motion along the basin in addition transverse faults divide the pull apart into several segments with somewhat different histories the pull apart grew by becoming longer parallel to the transform motion at shallow levels this was probably achieved by normal slip on transverse listric faults while the fill between them was little deformed the crust under the basin was stretched and thinned during basin lengthening which caused its subsidence basin formation was accompanied by uplifting of its flanks by 1 km sparse igneous activity occurred along the basin and its flanks its presence suggests a thermal anomaly in the lower lithosphere beneath the basin and adjacent parts of the transform

seismic reflection profiles across the southern dead sea basin abstract the main structural and stratigraphic elements that form the southern dead sea basin sdsb which is part of the dead sea transform fault system have been broadly delineated with various degrees of certainty by a number of researchers the recent exchange of seismic data between israel and jordan enable us to fill in some of the dashed lines and eliminate some of the question marks that appear on the previously published geological cross sections two east west seismic time sections one from each side of the international border that dissect the basin have been selected composed and interpreted a remarkable correlation of the three major sedimentary sequences that form the basin fill miocene clastics pliocene salt and pleistocene holocene clastics and evaporites has been established between the lines and hence across the entire width of the sdsb the miocene and pliocene series are cut off in the east by the ghor safi fault that is the equivalent of the western sedom fault thus indicating that all three major structural steps known to exist in the west 1 rim block 2 intermediate block and 3 deep block occurs also in the east and that the sdsb is indeed a full graben the ghor safi fault is the northern extension of the major arava strike slip fault the very thin miocene if at all and lack of pliocene salt in the eastern intermediate block unlike the western one suggests that the ghor safi fault was initiated earlier then the sedom fault salt is present over the entire width of the basin but does not exceed the 900 m that were penetrated by the sedom deep 1 borehole the salt is conformable with the overlying thick pleistocene and except for the sedom diapir no halokinesis phenomena have been recognized to be associated with both units

biodegradation of oil in uplifted basins prevented by deep burial sterilization biodegradation of crude oil by bacterial activity which has occurred in the majority of the earth s oil reserves is known to reduce greatly the quality of petroleum in reservoirs for economically successful prospecting for oil it is therefore important to understand the processes and conditions in geological formations that lead to oil biodegradation although recent studies speculate that bacterial activity can potentially occur up to temperatures as high as 150 degrees c refs 3 4 it is generally accepted that effective petroleum biodegradation over geological timescales generally occurs in reservoirs with temperatures below 80 degrees c ref 2 this appears however to be at odds with the observation that non degraded oils can still be found in reservoirs below this temperature here we compile data regarding the extent of oil biodegradation in several oil reservoirs and find that the extensive occurrence of non biodegraded oil in shallow cool basins is restricted to those that have been uplifted from deeper hotter regions of the earth we suggest that these petroleum reservoirs were sterilized by heating to a temperature around 80 90 degrees c during deep burial inactivating hydrocarbon degrading organisms that occur in the deep biosphere even when such reservoirs are subsequently uplifted to much cooler regions and filled with oil degradation does not occur implying that the sterilized sediments are not recolonized by hydrocarbon degrading bacteria

investigation of seismic anisotropy beneath the dead sea fault using dense networks of broadband stations 1 shear waveforms from core refracted sks phases recorded at 105 portable stations belonging to the desert and desire campaigns and nine permanent broadband stations of the israel seismological network are analyzed to study polarization seismic anisotropy beneath the region of the dead sea transform fault in the middle east shear wave splitting parameters exhibit variations with back azimuth initial polarization of the incoming sks waves the pattern of this variation is nearly constant along the strike of the fault suggesting a laterally uniform anisotropic structure beneath the dead sea region the modeling of the azimuthal variations of the shear wave splitting parameters and split waveforms yields two layered anisotropic models consisting of an upper layer with nearly n s symmetry axis and a deeper layer with around n25 e symmetry axis the split time is almost equally partitioned between the upper and lower layers allotting a value of 0 6 0 8 s to each layer 2 d finite difference modeling across the southern segment of the dead sea transform fault demonstrates that anisotropic structure in the strike normal direction is relatively uniform the dead sea transform fault appears not to have a significant role in the development of the regional anisotropic fabric the upper anisotropic layer is possibly related to a fossil fabric in the lithosphere inherited from the precambrian pan african orogeny the lower layer may be related to the mantle deformation due to the relative motion between the lithospheric plates and the asthenosphere and possibly affected by the local flow field due to mantle plumes as inferred by other studies

microscopic sulfur isotope variations in ore minerals from the viburnum trend southeast missouri a shrimp study mississippi valley type ore samples from two mines in the viburnum trend of southeast missouri have been examined with the shrimp ion microprobe to determine the extent of their microscopic sulfur isotope variations approximately 140 shrimp delta 34 s values were obtained microscopic delta 34 s variations within and among the intergrown fe cu pb zn sulfides are very large 10 to 25 and indicate an extremely complex history of mineral deposition textures record the general paragenesis fe sulfide galena and sphalerite chalcopyrite and bornite and covellite early fes 2 delta 34 s 10 to 10 is generally much more depleted in 34 s than later galena or chalcopyrite delta 34 s 0 25 both early fes 2 and late chalcopyrite growth sequences exhibit large zonations in delta 34 s typically from light to heavy values over a 15 per mil range isotopic zoning in galena crystals is comparatively negligible but variations among different galena crystals encompass a large total range in delta 34 s values 0 25 that is similar in magnitude to the total ranges observed in early fes 2 and late chalcopyrite where later sulifides crosscut and replace earlier sulfides the shrimp data indicate that there has been negligible local recycling of s from earlier sulfides in the ore forming zone each generation of metal appears to have brought in its own isotopically distinct and evolving batch of sulfur during successive deposition of each metal generation the observed delta 34 s variations require mixing among two or more isotopically distinct distal source fluids feeding already reduced sulfur to the ore forming zone and or the existence of in situ sulfur isotope fractionation mechanisms producing reduced sulfur whose isotopic composition varied progressively with time in the ore forming zone

high resolution local earthquake tomography of the southern dead sea area summary local earthquake data from a dense temporary seismological network in the southern dead sea area have been analysed within the project desire dead sea integrated research project local earthquakes are used for the first precise image of the distribution of the p wave velocity and the vp vs ratios 65 stations registered 655 local events within 18 months of observation time a subset of 530 well locatable events with 26 730 p and s arrival times was used to calculate a tomographic model for the vp and vp vs distribution since the study area is at first order 2 d a gradual approach was chosen which compromised a 2 d inversion followed by a 3 d inversion the sedimentary basin fill is clearly imaged through high vp vs ratios and low vp the basin fill shows an asymmetric structure with average depth of 7 km at the western boundary and depth between 10 and 14 km at the eastern boundary this asymmetry is reflected by the vertical strike slip eastern border fault and the normal faulting at the western boundary caused by the transtensional deformation within the last 5 myr within the basin fill the lisan salt diapir is imaged through low vp vs ratios reflecting its low fluid content the extensions were determined to 12 km in e w and 17 km in n s direction while its depth is 5 6 km the thickness of the pre basin sediments below the basin fill cannot be derived from the tomography data it is estimated to less than 3 km from former investigations below the basin down to 18 km depth very low p wave velocities and low vp vs ratios are observed most likely caused by fluids from the surrounding crust or the upper mantle

biogenic and petroleum related ore forming processes in dongsheng uranium deposit nw china abstract sandstone hosted roll type u deposits has recently been found in the middle jurassic zhiluo formation in the dongsheng area north of the ordos basin in order to assess the origin of the uranium mineralization the host sandstone has been investigated with emphasis on 34s values of ore stage pyrite 13c of calcite fluid inclusion oil biomarkers x ray diffraction icp ms as well as studies by electron microprobe and scanning electron microscope the mineralization consists mainly of coffinite some of the coffinite is intimately intergrown with ore stage pyrite indicating co precipitation ore stage pyrite has 34s values from 34 to 17 suggesting the pyrite sulfur originated from bacterial sulfate reduction in the host sandstone calcite cement exhibits 13c values from 27 6 to 2 1 and fluid inclusion oils show evidence of biodegradation these lines of evidence indicate petroleum was likely oxidized by sulfate reducing bacteria srb and thus supplied a source of some of the carbon in the calcite microbial degradation of petroleum is partially supported by the low temperature diagenetic environment

on the growth of colloform textures a case study of sphalerite from the galmoy ore body ireland abstract colloform textures have been described from many of the world9s sulphide ore deposits and involve formation of distinct microcrystalline layers these textures provide information related to sequential stages of ore formation yet their mechanism of growth is poorly understood this study has analysed a series of colloform samples from the galmoy zn pb mine ireland results indicate that the growth sequence is not always intuitive and layers that appear stratigraphic upon cursory observation may not be the crystal preferred orientation cpo of discrete colloform layers abruptly switches between different orientation axes examination of the same layers using in situ laser sulphur isotope analysis reveals equally striking changes in 34 s signature between end member bacteriogenic 25 and hydrothermal 10 sources although these results combined with petrographic observation allow the determination of a probable growth history there is no correlation between shifting cpo and 34 s signature trace element analysis reveals changes in trace element sequestration between colloform layers cadmium and chlorine rich layers correspond to a hydrothermal sulphur source whereas iron rich layers correspond to a bacteriogenic sulphur source in the absence of alternative mechanisms we suggest that the most likely factors influencing cpo changes are temperature and degree of supersaturation during two fluid mixing

evidence of uranium biomineralization in sandstone hosted roll front uranium deposits northwestern china we show evidence that the primary uranium minerals uraninite and coffinite from high grade ore samples u3o8 0 3 in the wuyiyi wuyier and wuyisan sandstone hosted roll front uranium deposits xinjiang northwestern china were biogenically precipitated and psuedomorphically replace fungi and bacteria uranium vi which was the sole electron acceptor was likely to have been enzymically reduced post mortem accumulation of uranium may have also occurred through physio chemical interaction between uranium and negatively charged cellular sites and inorganic adsorption or precipitation reactions these results suggest that microorganisms may have played a key role in formation of the sandstone or roll type uranium deposits which are among the most economically significant uranium deposits in the world

a two dimensional coupled ice ocean model of the bering sea marginal ice zone a two dimensional coupled ice ocean model has been formulated and applied to the wintertime bering sea marginal ice zone the oceanic component is a multilevel model that incorporates second moment closure for turbulent mixing in the water column the ice cover is modeled as a viscous plastic continuum melting at the ice ocean interface is computed using well known lawof the wall concepts in a turbulent boundary layer with particular attention to the disparate momentum and scalar transfer resistance coefficients over rough walls the thermodynamic and dynamical interactions between the ocean and the ice cover and the energy balances at the air ice and air sea interfaces are modeled according to the companion paper mellor and kantha this issue the model incorporates barotropic tides both diurnal and semidiurnal for application to the bering shelf double diffusive fluxes across the interface between the colder fresher layer beneath the melting ice and the warmer more saline water underneath are prescribed from laboratory data on double diffusive convection during winter sea ice in the central bering sea is transported toward the shelf break by off ice winds where it encounters northward flowing warmer north pacific waters and melts it is this situation to which the two dimensional model has been applied by neglecting all variations in the along ice edge direction the water conditions downstream of the ice edge the ice conditions upstream and the wind stress are the primary inputs to the model the model simulates transition from ice covered to open ocean conditions and the associated ice edge front and the two layer circulation underneath the ice cover sensitivity studies indicate that the density structure and the circulation beneath the ice and the position of the ice edge are rather sensitive to the parameters affecting the dynamics and the thermodynamics of the coupled ice ocean system even small changes in the relevant parameters can cause a substantial retreat or advance of the ice edge which may help explain why marginal ice zones are such dynamically active regions

the structure of the crust and upper mantle in the dead sea rift abstract the previously published results of a deep seismic refraction study of the dead sea gulf of elat rift show crustal thinning underneath the rift and the presence of a 5 km thick velocity transition zone in the lower crust along the rift the structural interpretation of the first arrival data was revised using the detailed velocity depth distribution the revised crustal thicknesses are 35 km near elat and 27 km 160 km south of elat the crustal thinning and the presence of the velocity transition zone are interpreted as being the result of intrusion of upper mantle material into the lower crust possibly representing the initial shape of the processes which have been active further south in the red sea since earlier times

teleseismic traveltimes residuals across the dead sea basin new findings of the structure of the dead sea sedimentary basin and its eastern and western bordering regions are obtained by p and pkp wave relative traveltime residuals of 644 teleseisms as recorded by the dead sea integrated research portable seismic network in the dead sea basin and its neighboring regions the lisan peninsula is characterized by relatively small teleseismic traveltime residuals of about 0 14 s in the latitude range of 31 22 31 37 and at the longitude of 35 50 slowly decreasing toward the west the largest teleseismic traveltime residuals are in the southern dead sea basin south of the lisan peninsula in the latitude range of 31 05 31 15 and along longitude 35 45 and continuing southward toward the amaziahu fault reaching values of 0 4 0 5 s there is a small positive residual at the amaziahu fault and a small negative residual south of it probably marking the southern end of the dead sea basin east and west of the dead sea basin the mean teleseismic traveltime residuals are negative with overall averages of 0 35 s and 0 45 s respectively using the teleseismic residuals we estimate the horizontal dimensions of the lisan salt diapir to be 23 km 13 km at its widest and a maximal thickness of about 7 2 km the thickness of the mount sodom salt diapir is estimated as 6 2 km

organic geochemistry of the san vicente zinc lead district eastern pucara basin peru abstract isotopic and chemical studies of organic matter of the san vicente mississippi valley type zn pb district hosted in the dolomitic units of the eastern pucara basin peru provide insight into the source of organic matter and of the organic matter ore relationship a large scatter exists in the 13c and 15n values of the highly mature kerogens these bulk data were combined with 13c covariations of the saturated and aromatic fractions of the rock extracts to indicate a contribution of continental higher plant lipids to the marine algal source of the organic matter disseminated in the host carbonate rocks an enrichment in 15n of the kerogens of mineralized samples compared to barren samples suggests that isotopically heavy nitrogen compounds were introduced to the ore fluid the fluid likely leached these compounds from the underlying clastic rocks and other detrital units of the pucara the extracts from mineralized samples are enriched in 13c compared to the associated kerogens this suggests that the rocks in the mineralized areas were stained by a mixture of extrinsic and indigenous bitumens by the use of novel instrumentation such as a gas chromatograph gc coupled to a stable isotope ratio mass spectrometer irms through a combustion c interface gc c irms stable carbon isotope analyses of individual hydrocarbons were also obtained both the molecular and isotopic signatures of the individual hydrocarbons are related to mineralization the variability in the organic molecular parameters and the 13c values of the individual n alkanes and isoprenoids indicate mixing of indigenous hydrocarbons with extrinsic 13c depleted microbially derived hydrocarbons the extrinsic source hydrocarbons were introduced to the mineralization site by the ore fluid or later fluids using the same porosity network oxidative alteration of the migrating hydrocarbons was involved in the thermochemical reduction of sulfate to h2s and precipitation of pyrobitumen large differences 12 in the carbon isotope compositions of long chain c20 n alkanes can be utilized in distinguishing sources of organics in the barren and mineralized samples

moho depth and three dimensional p and s structure of the crust and uppermost mantle in the eastern mediterranean and middle east derived from tomographic inversion of local isc data summary 82 000 p and s arrival times from 3000 sources recorded by 250 seismic stations from the revised isc catalogue are employed to study a circular area of 6 radius centred on the dead sea we use the linearized tomographic approach based on the rays constructed in a 1 d spherical velocity model and corrected for the moho depth variation and relief all the sources were relocated as the result of simultaneous iterative inversion we get 3 d p and s velocity anomalies in the crust and uppermost mantle moho depth and corrected source parameters the resulting images fit well with the existing tectonic elements in the study area in the crust a narrow p and s low velocity anomaly marks the position of the dead sea transform dst that is interpreted as sediments in the shallower layer and a zone of fractured and deformed rocks in the middle and lower crust there is a narrow 50 km wide band of thickening of the crust along the dst in the arava valley between the red sea and dead sea and some 100 km north of the dead sea this zone may be associated with the minimum of the lithospheric strength and therefore explain the location of the dst in the arava valley the velocity anomalies under the crust and the map of the moho depth clearly distinguish the oceanic levant basin and continental types of crust asia minor zagros cyprus and eratosthenes mount verification of the results takes an important part in this study inversions of different starting models and independent processing of data subsets show high robustness of the results synthetic tests clearly show the limits of the resolving power of the inversion with the existing data set

the northern end of the dead sea basin geometry from reflection seismic evidence abstract recently released reflection seismic lines from the eastern side of the jordan river north of the dead sea were interpreted by using borehole data and incorporated with the previously published seismic lines of the eastern side of the jordan river for the first time the lines from the eastern side of the jordan river were combined with the published reflection seismic lines from the western side of the jordan river in the complete cross sections the inner deep basin is strongly asymmetric toward the jericho fault supporting the interpretation of this segment of the fault as the long lived and presently active part of the dead sea transform there is no indication for a shift of the depocenter toward a hypothetical eastern major fault with time as recently suggested rather the north eastern margin of the deep basin takes the form of a large flexure modestly faulted in the n s section along its depocenter the floor of the basin at its northern end appears to deepen continuously by roughly 0 5 km over 10 km distance without evidence of a transverse fault the asymmetric and gently dipping shape of the basin can be explained by models in which the basin is located outside the area of overlap between en echelon strike slip faults

active compressional tectonics in the jericho area dead sea rift abstract the results of several seismic reflection surveys in the jericho area north of the dead sea are described and the data are used to analyze the structure of this part of the dead sea rift in particular we describe the structure of the dead sea transform which in this area is a zone of intense deformation rather than a distinct fault plane the transform has a westerly dip away from the rift suggesting that it may have a reverse faulting component associated with the transform are several folds of which the best documented is the kalia monocline immediately north of the dead sea the kalia monocline lies along the transform and appears to be a young structure associated with it indicating that this part of the plate boundary is characterized by local compression the southerly extent of the kalia monocline is not clear presently but the available data suggest that the compressional field also characterize the northwestern part of the dead sea basin the other folds appear north of the kalia monocline and seem to be similar to it they are most probably also the result of recent compression along the transform a number of mechanisms of small earthquakes in this area are computed and several of them show thrusting suggesting that the local compression is still active

lower crustal flow and the role of shear in basin subsidence an example from the dead sea basin abstract we interpret large scale subsidence 5 6 km depth with little attendant brittle deformation in the southern dead sea basin a large pull apart basin along the dead sea transform plate boundary to indicate lower crustal thinning due to lower crustal flow along axis flow within the lower crust could be induced by the reduction of overburden pressure in the central dead sea basin where brittle extensional deformation is observed using a channel flow approximation we estimate that lower crustal flow would occur within the time frame of basin subsidence if the viscosity is 7 1019 1 1021 pa s a value compatible with the normal heat flow in the region lower crustal viscosity due to the strain rate associated with basin extension is estimated to be similar to or smaller than the viscosity required for a channel flow however the viscosity under the basin may be reduced to 5 1017 5 1019 pa s by the enhanced strain rate due to lateral shear along the transform plate boundary thus lower crustal flow facilitated by shear may be a viable mechanism to enlarge basins and modify other topographic features even in the absence of underlying thermal anomalies

isotopic evidence for microbial activity during supergene oxidation of a high sulfidation epithermal au ag deposit the light stable isotope chemistry of barite and acanthite in the pierina au ag deposit peru provides strong support for microbial involvement at the economically critical supergene oxidation stage early hypogene barite yields 34s values of 23 6 to 28 5 and 18o values of 5 8 to 10 9 and was precipitated with the original precious metal enriched sulfide assemblage in contrast late barite deposited during formation of supergene goethite and hematite the main ore hosts yields 34s and 18o values of 1 4 to 14 2 and 2 8 to 4 7 correlated mutually and with the 34s values of coprecipitated acanthite 34s 0 4 to 3 9 low 34s values of barite and acanthite record sulfide mineral oxidation by meteoric waters increasing 34s and 18o values of barite and 34s values of acanthite indicate enrichment of the sulfate reservoir in 34s and 18o reflecting the preferential utilization of light isotopes by microbes during aqueous sulfate reduction continued sulfate reduction locally reduced supergene fluids remobilizing iron and locally destroying the goethite hematite assemblage precious metals were released but reacted with sulfide in the reduced waters to form au rich acanthite

microbial structures and possible bacterial sulfide fossils in the giant jinding zn pb deposit yunnan sw china insights into the genesis of zn pb sulfide mineralization abstract the jinding zn pb sulfide deposit lanping yunnan china is one of the youngest sediment hosted giant zn pb deposit in the world it is also a well known deposit in china the large scale of the mineralization and especially the huge volume of h 2 s that was required to precipitate the zn pb sulfide are of great interest to ore geologists ore microscopy shows microbial structures such as framboidal sphalerite spherical aggregates of galena sphalerite oolite sphalerite dendritic colloidal sphalerite pyrite metacolloidal sphalerite pyrite multinuclear metacolloidalring like sphalerite pyrite botryoidal sphalerite pyrite framboidal pyrite and bacterial plate like of galena sphalerite detailed observations and analyses of the microbial structures at micron to nanometer scales by field emission scanning electron microscopy fesem and energy dispersive spectrometry eds reveal that the bacteria fossils are composed of sphalerite galena or pyrite or of multiple sulfide minerals with calcite and that they are distributed in bacterial colonies in the ore the individual bacteria fossils are spherical botryoidal or ring like with a diameter of 200 500 nm filamentous mucoid and tubular extracellular polymeric substances eps are commonly observed that are closely associated with and have the same composition as the bacteria fossils secondary ion microprobe analysis sims by in situ sulfur micro isotopic analysis of the microbial sulfide structures and bacteria fossils yield 34 s v cdt values varying from 48 6 to 9 5 per mil indicating that there was a high percentage of sulfate reducing bacteria in the zn pb sulfide mineralization process previous analyses have shown that the zn pb mineralization was formed at a shallow depth and low temperature with barely visible hydrothermal alteration the presence of evaporitic sulfate layers and paleo oil reservoir characteristics the authors believe that bacterial sulfate reduction might be the key h 2 s production mechanism in the jinding dome that was required to form this giant pb zn sulfide ore body

fault geometry and spatial clustering of microearthquakes along the dead sea jordan rift fault zone abstract earthquakes 1 0 m l 5 3 in the region around the dead sea jordan rift fault zone recorded by the israel scismograph station network issn from 1982 until the beginning of 1989 have been analyzed and interpreted the scismicity pattern clearly reveals activity along three fault zones the dead sea jordan rift fault zone the carmel faraa fault zone and the central sinai negev shear zone microearthquake occurrence tends to cluster in or near tensional features rhomb shaped grabens such as the hula sea of gallilee and dead sea depressions further eight representative focal mechanisms of individual earthquakes or earthquake clusters have been derived the seismicity and focal mechanism solutions near the branching of the carmel faraa and the dead sea jordan rift fault zones suggest a complicated tectonic breakup in this region microearthquakes in the arava may indicate a more complex pattern of active faults than was previously assumed

crustal and upper mantle structure across the dead sea rift and israel from teleseismic p wave tomography and gravity data abstract new findings of the structure of the crust and the upper mantle across the dead sea rift and israel were obtained by applying p and pkp wave relative travel time residuals inversion of 612 teleseisms recorded by the seismic networks in israel and jordan independently of the relative teleseismic travel time residuals the bouguer gravity anomalies were used as an additional aid to examine the structure of the crust and upper mantle an examination of the teleseismic travel time residuals in israel suggests the existence of two prominent provinces of distinct crustal structure the northward increase of the teleseismic travel time residuals is in good agreement with a gradual thickening of the sedimentary sequence and a simultaneous thinning of the crust examination of the inverted velocity anomalies indicates that the upper and lower crusts are sub divided into a number of structures we identify several velocity anomalies that are associated with prominent geological structures the southern dead sea basin is characterized with the largest decrease of velocity in both upper and lower crustal layers due to the infilling of light material relative to the surrounding material the velocity anomaly in the carmel structure is probably associated with variations in the upper part of the upper mantle examination of a cross section that traverses the dead sea transform supports the existence of lighter mass density material on the eastern side relative to that on the western side

crustal structure of the dead sea basin from local earthquake tomography summary new findings of the velocity structure of the crust across the dead sea basin are obtained by applying tomography based method to local earthquakes we use p wave traveltime of 614 earthquakes that occurred in the dead sea basin in 1983 2009 at all depths the dead sea basin is characterized by lower velocities relative to both the eastern and western sides of the basin there is significant seismic activity at a depth of about 20 km mainly in the centre and the northern part of the basin at shallow depths 15 km there is more seismic activity on the eastern side of the basin than on the western side and the northern basin is generally more active than the southern basin asymmetry is also observed in the faults that border the dead sea basin the arava fault on the eastern side with nearly vertical dip faulting appears to be a clear boundary at all depths down to about 20 km the depth extension of the jericho fault on the western side of the basin is definitely limited to less than 15 km at greater depths of 20 km or more the western side is only partially bounded by a fault the concentration of earthquakes in the central part of the basin at depths larger than 15 km suggests that the dead sea fault at those depths acts as one single fault that is located in or near the central axis of the basin the existence of a number of clusters of earthquakes that spread from shallow depths of a few kilometres up to a depth of about 22 km points to several defined faults that traverse the dead sea basin one such example is the aftershock sequence of the 2004 earthquake that occurred in the northern dead sea basin seismic activity near mt sodom is relatively low and occurs at shallow depths down to 10 km whereas at larger depths 15 km it ceases this implies that the whole structure is relatively shallow with no wide and deeper extension seismic activity near and within the lisan peninsula extends to somewhat larger depths 15 km and then it ceases the occurrence of earthquakes at large depths suggests that the upper and the lower crust are relatively cool as was also suggested by earlier studies pointing to the fact that the heat flow is significantly below the global average value

localized versus distributed shear in transform plate boundary zones the case of the dead sea transform in the jericho valley 1 continental transform plate boundaries are typically either localized along a single usually segmented major fault or distributed over a broad deformation zone in the latter shear is partitioned between major strike slip faults and intervening often rotating fault systems analog and numerical simulations suggest that such internal fault systems evolve and may be localized or delocalized depending on strain and fault zone strength this paper examines the degree and evolution of shear localization in the jericho valley section of the dead sea transform dst which is part of the africa arabia plate boundary in this section the current breadth of the transform valley and its penetrative strain field are difficult to reconcile with localized shear we integrate newly acquired high resolution reflection data reprocessed exploration reflection data both focused to 2 5 3 5 km depth relatively relocated earthquake epicenters and fault plane solutions based on p wave first arrivals and suggest reinterpretations for previously published structural and seismic data in the jericho valley and the northern dead sea basin it is found that shear in this section of the dst evolved from an early probably miocene pliocene stage of localized strike slip motion primarily along the jericho fault to a late stage pliocene recent when shear has been distributed over internal fault sets that apparently lean against a major eastern dst segment in the early stage the jericho fault formed the western boundary of a deep narrow probably pull apart basin filled by fluvial clastics and evaporites this is overlain by the late stage broad basin characterized by low energy deposition of lacustrine and fluvial sediments pliocene rock salt has apparently utilized the jericho fault zone as a conduit for diapirism causing the uplift normal faulting and surface deformation of late pleistocene and holocene sediments currently observed along the 15 km long jericho lineament on the basis of the currently observed dextral normal motion across the internal nne ne trending fault system counterclockwise rotation is expected to have occurred within the transform zone these tectonic and depositional changes were probably associated with onset of transtension across the dst related to the previously postulated shift of the africa arabia euler pole of rotation in the pliocene

crustal structure of israel constraints from teleseismic and gravity data summary the structure of the crust in israel was studied using p wave traveltime residuals of 169 teleseisms recorded by a seismic network throughout the country independently of the teleseismic residuals the bouguer gravity anomalies were used as an additional aid to examine the structure of the crust the average time difference between the traveltime residuals in the north and in the south of israel is up to 0 2s three distinct provinces are observed in the teleseismic residuals with distinct boundareis at 31 5 n and 30 25 n similar differences of traveltime residuals were derived for each of the four principal azimuth quadrants most of the difference in traveltime residuals between northern and southern israel can be explained by changes in the sedimentary thickness we suggest that the structure of the northern province is significantly different from the central or the southern provinces if the moho shallows by about 13 15 km along the profile as was previously suggested by seismic refraction data a thickening of the sedimentary sequence to about 15 km in the northern province is needed to satisfy the traveltime residuals similar results are obtained if the bouguer gravity anomalies due to the thickening sediments and the rise of the moho depth are modelled in the eilat region the sedimentary sequence thins in the sse direction from the negev to the gulf of eilat implying a decrease of the moho in the southward direction by about 10 km in agreement with the crustal refraction studies

teleseismic tomography reveals no signature of the dead sea transform in the upper mantle structure abstract we present results of a tomographic inversion of teleseismic data recorded at 48 stations of a temporary network which was installed in the area of the dead sea transform dst and operated for 1 yr in the framework of the multidisciplinary desert project the 3366 teleseismic p and pkp phases from 135 events were hand picked and corrected for surface topography and crustal thickness the inversion shows pronounced low velocity anomalies in the crust beneath the dst which are consistent with recent results from local source tomography these anomalies are likely related to the young sediments and fractured rocks in the fault zone the deeper the retrieved anomalies are quite weak most prominent is the high velocity strip like anomaly striking se nw we attribute this anomaly to the inherited heterogeneity of lithospheric structure with a possible contribution by the shallow precambrian basement east of the dst and to lower crustal heterogeneity reported in this region by other seismic studies we do not observe reliable signature of the dst in the upper mantle structure some weak indications of low velocity anomalies in the upper mantle beneath the dst may well result from the down smearing of the strong upper crustal anomalies we also see very little topography of the lithosphere asthenosphere boundary beneath the dst which would generate significant horizontal velocity variations these results are consistent with predictions from a recent thermo mechanical model of the dst our tomographic model provides some indication of hot mantle flow from the deeper upper mantle rooted in the region of the red sea however resolution tests show that this anomaly may well be beyond resolution of the model

structural geometry and evolution of the dead sea jordan rift system as deduced from new subsurface data abstract analysis of deep drilling data and seismic reflection surveys obtained in recent years permit establishment of a tectonic model of the dead sea jordan rift system that is in part conformable with some of the many often controversial theories on this subject but which also introduces new information negating some concepts that are widely accepted in the literature the dead sea jordan rift system is not a tensional graben between two parallel sets of faults but instead can be best defined as a sinistral transform connecting an incipient oceanic ridge the red sea with an upthrusted collision zone the taurus range the shear is caused by the opening of the red sea and the motion of the arabian sub plate away from the african plate the shearing occurs along a largely south north trending slightly arcuate une consisting of a series of en echelon left stepping left lateral strike slip master faults of varying lengths these faults characteristically die out to the north by bending outward northeast and the movement is taken up by the strike slip faults to the left i e to the west where overlap of the two faults occurs very narrow and very deep grabens have evolved in places the width being equal to the depth the narrowness of these grabens is dictated by the closeness of the overlapping segments of the successive strike slip faults this feature points to the probability that the en echelon strike slip faults have a common root zone at great depth these grabens are not typical leaky pull aparts in that they have no gravimetric magnetic or heat flow anomalies nor are they closed on all four sides by large faults their northern ends are characterized by gradually rising graben floors without major diagonal cross faults the dead sea jordan rift system sensu stricto extends over a distance of 420 km from the northern shore of the gulf of elat to the northern margin of the hula valley southward it is connected with the red sea along the gulf of elat transition zone which has elements of strike slip as well as tensional opening a northern transition zone exists between the hula valley and the taurus arc where diminishing strike slip movement is compensated by several underthrust belts the time of the beginning of the movement along the rift can be established as pre middle miocene because mid miocene sediments overlie an upper cretaceous graben floor rifting has continued intermittently to the present volcanism in the northern fifth of the rift is genetically associated with the seismically active tensional golan hauran jebel drouz wadi sirhan tectonic trend which has a north west southeast orientation and not with the north south trending dead sea jordan rift

displaced terranes and crustal evolution of the levant and the eastern mediterranean geophysical data from the levant and the eastern mediterranean suggest that this area can be divided into distinct crustal units of different origins for example a marked difference in crustal structure and structural style exists in the levant between samaria and judea south of the carmel structure and the galilee and lebanon north of it on the other hand several microcontinental fragments such as cyprus and the eratosthenes and anaximander seamounts are embedded within the oceanic crust of the eastern mediterranean the present location of these units has resulted from complex tectonic processes which were active during the mid paleozoic mesozoic evolution of this area during this period several crustal units were accreted to the northern margin of africa while others were detached away from it the crustal evolution of the eastern mediterranean and the levant is intimately linked with the closure of the paleo tethys the formation of the neo tethys and its subsequent closure

a first principles approach to supergene enrichment of a porphyry copper protore i cu fe s subsystem abstract a unified description of supergene enrichment of a porphyry copper protore is presented based on the principles of metasomatic zoning mathematically this formulation represents the supergene weathering process as a moving boundary problem a first principles approach is used to describe quantitatively the transport of oxygenated water through a porous host rock consisting of a cu bearing protore mineral reaction rates are represented by kinetic rate expressions for both precipitation and dissolution reaction zones containing mineral alteration products making up a leached zone oxide zone and enrichment blanket propagate downward in the direction of fluid transport the time evolution of the system is completely determined by the governing transport equations once initial and boundary conditions are specified giving the composition of the unaltered host rock and infiltrating fluid entering at the surface of the weathering column the description provides for both fully saturated conditions and undersaturated conditions in the presence of a water table at depth an order of magnitude estimate of the velocity of propagation of a redox front demonstrates that metasomatic effects become increasingly important as the o content of the infiltrating water increases regions of higher permeability resulting in higher fluid flow velocities lead to increased enrichment compared to regions of lower permeability with reduced flow velocities in agreement with field observations results of numerical calculations suggest that the enrichment blanket may be subdivided into three distinct zones 1 1 an enriched zone at the top of the blanket 2 2 the middle blanket in which chemical reactions of cu bearing minerals are absent and 3 3 the nascent blanket forming the interface between the protore and middle blanket both the nascent and middle blanket contain the same cu grade as the protore these results are in agreement with field observations of a high cu grade within a relatively narrow zone in the upper portion of the blanket results of numerical calculations for three different scenarios are presented the first example considers a simplified representation of the enrichment process with chalcopyrite covellite and chalcocite as the major cu minerals in this case chalcocite forms an enriched zone at the top of the blanket which migrates downward increasing in width the second and third examples differ by the presence of a water table at depth and include brochantite tenorite native cu and cuprite as secondary cu minerals in addition to the minerals used in the first example surprisingly in these two examples the enriched blanket zone does not grow indefinitely with time but reaches a steady state profile that is displaced rigidly in the direction of fluid transport without changing shape in the presence of a water table at depth the major enrichment occurs in the oxide zone lying above the blanket

lithospheric structure of the jordan dead sea transform from earthquake data abstract p wave travel times from 89 shallow earthquakes m 6 recorded at the jordan university seismological station unj from epicentral distances in the range 140 km x 1308 km are utilized in the derivation of a lithospheric model for the jordan dead sea transform region the selected events are of high signal noise ratio for most events the standard deviation of the origin time is in the range 0 1 1 2 s one dimensional ray tracing is used to model the p wave travel times results indicate that an average crustal thickness of about 35 km beneath the station as derived from explosion data is confirmed by the earthquake data the pn velocity for the uppermost mantle is 8 07 0 02 km s the first upper mantle refractor below the moho occurs at a depth of about 54 km with an apparent velocity at this discontinuity of 8 4 0 06 km s being measured the thickness of the layer below this discontinuity appears to be of the order of only 2 3 km below this the data are interpreted to represent a low velocity zone where the velocity gradually decreases to a minimum of about 8 1 km s at a depth of 80 km and increases thereafter at a constant rate of 0 02 s 1 down to a depth of 105 km at this depth the next refractor occurs producing a constant velocity of 8 6 0 04 km s the layer below this refractor seems to extend to a depth of not less than 150 km

late pleistocene extension and strike slip in the dead sea basin a newly discovered active small scale pull apart mor structure located in the western part of the dead sea basin shows recent basin parallel extension and strike slip faulting and offers a rare view of pull apart internal structure the mor structure is bounded by n s trending strike slip faults and cross cut by low angle e w trending normal faults the geometry of this pull apart suggests that displacement between the two stepped n s strike slip faults of the mor structure is transferred by the extension associated with the normal faults the continuing deformation in this structure is evident by the observation of at least three deformation episodes between 50 ka and present the calculated sinistral slip rate is 3 5 mm yr over the last 30 000 years this slip rate indicates that the mor structure overlies the currently most active strike slip fault within the western border of the dead sea pull apart the mor structure is an example of a small pull apart basin developed within a larger pull apart this type of hierarchy in pull apart structures is an indication for their ongoing evolution

origin of 3 45 ga coniform stromatolites in warrawoona group western australia a new occurrence of conical and branched pseudocolumnar stromatolites in archean dolostones in the pilbara region australia contributes significant new morphologic information on such structures these remains are interpreted as probably representing in part microbially mediated accretionary growth surfaces in an archean hypersaline depositional basin the structures comprise laterally linked pseudocolumns of centimeter width and decimeter height with first order conical laminae of as much as 15 cm of synoptic relief and apical angles of 30 80 the conical laminae are modified by a second order centimeter scale low amplitude primary corrugate lamination with crests and troughs occasionally stacked to form satellitic obliquely directed pseudocolumns bedding surfaces exhibit a preferred direction of elongation of the cones an orientation that is orthogonal and unrelated to the trend of younger folding the microstructure is secondary the stromatolites are better preserved than those previously known from chert in the warrawoona succession the remains exhibit certain distinct morphologic attributes corresponding to those in younger stromatolites such as displayed by thyssagetes and jacutophyton whose biogenicity is generally accepted although difficult to demonstrate conclusively the conical warrawoona forms may represent the oldest known precursor of these taxa

3 d density modelling of underground structures and spatial distribution of salt diapirism in the dead sea basin a new compilation of bouguer gravity data stemming from airborne shipborne and terrestrial data set in the entire dead sea basin dsb was reinterpreted by applying 3 d density modelling that incorporated independent information on other geophysical researches allowing for regional and residual filtering in the gravity field carrying out curvature analysis and euler deconvolution of the combined gravity field 3 d density modelling enables us to detailed resolution of upper crustal structures from the southern to the northern subbasin below the saline dead sea 3 d gravity modelling led to the identification of three salt structures which are found beneath the sedom area the lisan peninsula and the dead sea in the vicinity of the western margin of the dead sea a salt diapir segment with a thickness of about 4 km has been identified at a top depth of about 2 km which has not been recognised by any other geophysical interpretations the thickness of the sedimentary infill overlying the basement in the dsb decreases from 14 km in the vicinity of the lisan peninsula to 8 km in the northern and the southern subbasins large negative gravity anomalies lower than 100 x 10 5 m s 2 observed in the dsb correspond with the spatial distribution of salt diapirism with an average density of 2 100 kg m 3 the shallower microearthquakes registered in the dsb are related to the movement of salt diapir in the dsb

seismic tomography and deformation modeling of the junction of the san andreas and calaveras faults local earthquake p traveltime data is inverted to obtain a three dimensional tomographic image of the region centered on the junction of the san andreas and calaveras faults the resulting velocity model is then used to relocate more than 17 000 earthquakes and to produce a model of fault structure in the region these faults serve as the basis for modeling the topography using elastic dislocation methods the region is of interest because active faults join it marks the transition zone from creeping to locked fault behavior on the san andreas fault it exhibits young topography and it has a good spatial distribution of seismicity the tomographic data set is extensive consisting of 1445 events 96 stations and nearly 95 000 travel time readings tomographic images are resolvable to depths of 12 km and show significant velocity contrasts across the san andreas and calaveras faulls a low velocity zone associated with the creeping section of the san andreas fault and shallow low velocity sediments in the southern santa clara valley and nonhem salinas valley relocated earthquakes only occur where vp s kmls and indicate that portions of the san andreas and calaveras faults are non vertical although we cannot complctcly cxclude the possibility hat all or parr of this rcsults from ray uacing problems the new dips are more consistent with geological observations that dipping faults intcrscct thc surfacc where surface traces have been mapped the topographic modeling predicts extensive subsidence in regions characterized by shallow low velocity material presumably the result of recent sedimentation some details of the topography at the junction of the san andreas and calaveras faults are not consisknl with lhe modeling results suggesting that the current position or this triple junction has changed with time the model also predicts those parts of the fault subject to contraction or extension perpendicular to the fault strike and hence the sense of any dip slip component in each locality the relative vertical motion accross the fault is consistent with the fault dips found with the new hypocentral locations

formation of sequential basins along a strike slip fault geophysical observations from the dead sea basin abstract the dead sea basin is often cited as one of the classic examples for the evolution of pull apart basins along strike slip faults despite its significance the internal structure of the northern dead sea basin has never been addressed conclusively in order to produce the first comprehensive high resolution analysis of this area all available seismic data from the northern dead sea lake lower jordan valley land were combined results show that the northern dead sea basin is comprised of a system of tectonically controlled sub basins delimited by the converging western and eastern boundary faults of the dead sea fault valley these sub basins grow shallower and smaller to the north and are separated by structural saddles marking the location of active transverse faults the sedimentary fill within the sub basins was found to be relatively thicker than previously interpreted as a result of the findings of this study the classic model for the development of pull aparts based on the dead sea is revised the new comprehensive compilation of data produced here for the first time was used to improve upon existing conceptual models and may advance the understanding of similar basinal systems elsewhere

drop down formation of deep basins along the dead sea and other strike slip fault systems summary we address the mechanism of sedimentary basin formation along strike slip fault systems with 3 d numerical simulations based on a continuum damage rheology model the formation of these basins is usually explained by a pull apart mechanism that predicts a rhomb shaped basin geometry bounded by two longitudinal strike slip faults and two transverse listric faults significant ductile deformation of the lower crust and upper mantle associated with basin growth requires normal or elevated heat flux the dead sea continental transform is associated with some of the larger and unusually deep basins among which the southern dead sea is the deepest the heat flow in the dead sea basin is anomalously low and it is associated with deep seismicity moreover the basin is bounded by deep transverse normal faults rather than the listric faults required by the pull apart model hence the formation of the basin cannot be explained by the existing pull apart model ben avraham and schubert proposed an alternative conceptual model for the formation of the deepest basin at the southern dead sea they suggested that an isolated block of lithosphere has dropped into the mantle we simulate the formation of this and other deep basins along the dead sea fault and demonstrate that the drop down mechanism of the dead sea basin formation suggested by ben avraham schubert is possible density heterogeneities formed in the crust or upper mantle during a previous stage of regional magmatism drop into the upper mantle when strike slip faults are created and detach them from the surrounding lithosphere the simulations indicate that the resulting basin is rhomb shaped and that with time it grows by the addition of distinct segments to its edges the proposed mechanism could account for the formation and evolution of large sedimentary basins along other strike slip fault systems such as the san andreas fault and other continental transform faults

a teleseismic delay time study across the central african shear zone in the adamawa region of cameroon west africa summary p wave relative teleseismic residuals were measured for a network of seismological stations along a 300 km profile across the adamawa plateau and the central african shear zone of central cameroon to determine the variation in crust and upper mantle velocity associated with these structures a plot of the mean relative residuals for the stations shows a long wavelength 300 km variation of amplitude 0 45 s the slowest arrivals are located over and just to the north of the faulted northern margin of the adamawa plateau the residuals do not correlate with topography surface geology or the previously determined crustal structure in any simple way the aki inversion technique has been used to invert the relative residuals into a 3 d model of velocity perturbations from a mean earth model the results show the region is divided roughly into three blocks by two subvertical boundaries striking ene and traversing both the crust and upper mantle down to depths greater than 190km the central block which is 2 per cent slower than the adjacent blocks roughly corresponds to the central african shear zone the adamawa plateau as an individual uplifted area is explained by the interaction of a regional anomalous upper mantle associated with the west african rift system and the central african shear zone which provided a conduit for heat flow to the surface

extreme 34s depletions in zns at the mike gold deposit carlin trend nevada evidence for bacteriogenic supergene sphalerite we identified submicrometer sized framboidal sphalerite zns below the base of supergene oxidation in a carlin type gold deposit of eocene age in nevada united states where the framboidal sphalerite forms a blanket like body containing 400 000 metric tons of zinc framboidal sphalerite 0 1 mum in diameter formed in the early miocene ranges from 0 1 to 0 35 mol fes the delta 34 s values range from 25 to w 70 the lowest values measured in a marine or terrestrial environment these s isotope data demonstrate the involvement of sulfate reducing bacteria and provide the first documentation that sphalerite can form significant supergene sulfide enrichment blankets

salt diapirs in the dead sea basin and their relationship to quaternary extensional tectonics abstract regional extension of a brittle overburden and underlying salt causes differential loading that is thought to initiate the rise of reactive diapirs below and through regions of thin overburden we present a modern example of a large salt diapir in the dead sea pull apart basin the lisan diapir which we believe was formed during the quaternary due to basin transtension and subsidence using newly released seismic data that are correlated to several deep wells we determine the size of the diapir to be 13 10 km its maximum depth 7 2 km and its roof 125 m below the surface from seismic stratigraphy we infer that the diapir started rising during the early to middle pleistocene as this section of the basin underwent rapid subsidence and significant extension of the overburden during the middle to late pleistocene the diapir pierced through the extensionally thinned overburden as indicated by rim synclines which attest to rapid salt withdrawal from the surrounding regions slight positive topography above the diapir and shallow folded horizons indicate that it is still rising intermittently the smaller sedom diapir exposed along the western bounding fault of the basin is presently rising and forms a 200 m high ridge its initiation is explained by localized e w extension due monoclinal draping over the edge of a rapidly subsiding basin during the early to middle pleistocene and its continued rise by lateral squeezing due to continued rotation of the amazyahu diagonal fault

structure of the dead sea pull apart basin from gravity analyses analyses and modeling of gravity data in the dead sea pull apart basin reveal the geometry of the basin and constrain models for its evolution the basin is located within a valley which defines the dead sea transform plate boundary between africa and arabia three hundred kilometers of continuous marine gravity data collected in a lake occupying the northern part of the basin were integrated with land gravity data from israel and jordan to provide coverage to 30 km either side of the basin free air and variable density bouguer anomaly maps a horizontal first derivative map of the bouguer anomaly and gravity models of profiles across and along the basin were used with existing geological and geophysical information to infer the structure of the basin the basin is a long 132 km narrow 7 10 km and deep 10 km full graben which is bounded by subvertical faults along its long sides the bouguer anomaly along the axis of the basin decreases gradually from both the northern and southern ends suggesting that the basin sags toward the center and is not bounded by faults at its narrow ends the surface expression of the basin is wider at its center 16 km and covers the entire width of the transform valley due to the presence of shallower blocks that dip toward the basin these blocks are interpreted to represent the widening of the basin by a passive collapse of the valley floor as the full graben deepened the collapse was probably facilitated by movement along the normal faults that bound the transform valley we present a model in which the geometry of the dead sea basin i e full graben with relative along axis symmetry may be controlled by stretching of the entire brittle and ductile crust along its long axis there is no evidence for the participation of the upper mantle in the deformation of the basin and the moho is not significantly elevated the basin is probably close to being isostatically uncompensated and thermal effects related to stretching are expected to be minimal the amount of crustal stretching calculated from this model is 21 km and the stretching factor is 1 19 if the rate of crustal stretching is similar to the rate of relative plate motion 6 mm yr the basin should be 3 5 m y old in accord with geological evidence

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

crustal structure of the southern dead sea basin derived from project desire wide angle seismic data summary as part of the dead sea integrated research project desire a 235 km long seismic wideangle reflection refraction wrr profile was completed in spring 2006 across the dead sea transform dst in the region of the southern dead sea basin dsb the dst with a total of about 107 km multi stage left lateral shear since about 18 ma ago accommodates the movement between the arabian and african plates it connects the spreading centre in the red sea with the taurus collision zone in turkey over a length of about 1 100 km with a sedimentary infill of about 10 km in places the southern dsb is the largest pull apart basin along the dst and one of the largest pull apart basins on earth the wrr measurements comprised 11 shots recorded by 200 three component and 400 one component instruments spaced 300 m to 1 2 km apart along the whole length of the e w trending profile models of the p wave velocity structure derived from the wrr data show that the sedimentary infill associated with the formation of the southern dsb is about 8 5 km thick beneath the profile with around an additional 2 km of older sediments the depth to the seismic basement beneath the southern dsb is about 11 km below sea level beneath the profile seismic refraction data from an earlier experiment suggest that the seismic basement continues to deepen to a maximum depth of about 14 km about 10 km south of the desire profile in contrast the interfaces below about 20 km depth including the top of the lower crust and the moho probably show less than 3 km variation in depth beneath the profile as it crosses the southern dsb thus the dead sea pull apart basin may be essentially an upper crustal feature with upper crustal extension associated with the left lateral motion along the dst the boundary between the upper and lower crust at about 20 km depth might act as a decoupling zone below this boundary the two plates move past each other in what is essentially a shearing motion thermo mechanical modelling of the dsb supports such a scenario as the desire seismic profile crosses the dst about 100 km north of where the desert seismic profile crosses the dst it has been possible to construct a crustal cross section of the region before the 107 km left lateral shear on the dst occurred

crustal shear velocity structure across the dead sea transform from two dimensional modelling of desert project explosion seismic data an analysis of the shear s waves recorded during the wide angle reflection refraction wrr experiment as part of the desert project crossing the dead sea transform dst reveals average crustal s wave velocities of 3 3 3 5 km s 1 beneath the wrr profile together with average crustal p wave velocities of 5 8 6 1 km s 1 from an already published study this provides average crustal poisson s ratios of 0 26 0 27 v p v s 1 76 1 78 below the profile the top two layers consisting predominantly of sedimentary rocks have s wave velocities of 1 8 2 7kms 1 and poisson s ratios of 0 25 0 31 v p v s 1 73 1 91 beneath these two layers the seismic basement has average s wave velocities of around 3 6 km s 1 east of the dst and about 3 7 km s 1 west of the dst and poisson s ratios of 0 24 0 25 v p v s 1 71 1 73 the lower crust has an average s wave velocity of about 3 75 km s 1 and an average poisson s ratio of around 0 27 v p v s 1 78 no sn phase refracted through the uppermost mantle was observed the results provide for the first time information from controlled source data on the crustal s wave velocity structure for the region west of the dst in israel and palestine and agree with earlier results for the region east of the dst in the jordanian highlands a shear wave splitting study using sks waves has found evidence for crustal anisotropy beneath the wrr profile while a receiver function study has found evidence for a lower crustal high s wave velocity layer east of the dst below the profile although no evidence was found in the s wave data for either feature the s wave data are not incompatible with crustal anisotropy being present as the wrr profile only lies 30 degrees off the proposed symmetry axis of the anisotropy where the difference in the two s wave velocities is still very small in the case of the lower crustal high s wave velocity layer if the velocity change at the top of this layer comprises a small first order discontinuity underlain by a 2 km thick transition zone instead of just a large first order discontinuity then both the receiver function data and the wrr data presented here can be satisfied finally the s wave velocities and poisson s ratios which have been derived in this study are typical of continental crust and do not require extensional processes to explain them

sand injection and liquefaction structures in the jinding zn pb deposit yunnan china indicators of an overpressured fluid system and implications for mineralization the jinding deposit is a large zn pb deposit hosted in coarse siliciclastic strata of early cretaceous and paleocene ages in the lanping simao basin western yunnan china the deposit characterized by fine grained sphalerite and galena disseminated in sandstones of the cretaceous jingxing formation k 1j and sandstones and limestone breccias of the paleocene yunlong formation e 1y was generally considered as one formed from basinal fluids passively controlled by sedimentary lithofacies and structures this paper reports sand injection and liquefaction structures occurring as millimeter to centimeter wide mineralized sand veins and irregular bodies of light colored sandstones cutting red colored sedimentary rocks and relates them to episodic release of overpressured fluids the proposed model for the flow of ore forming fluids differs from previous models in that the fluid flow did not passively follow preexisting pore space and was actively creating new porosity and permeability in the conduits this implies that the development and distribution of fluid over pressures in the basin may have exerted a control on mineralization in addition to lithofacies and structures and the sand injection and liquefaction structures as described in this paper may be used as indicators of favorable conditions for mineralization

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

genesis and evolution of framboidal pyrite and its implications for the ore forming process of carlin style gold deposits southwestern china abstract southwestern guizhou an indispensable component of the golden triangle area of southwestern china is famous for its numerous carlin style gold deposits unlike other sulfides in the deposits that have been well studied the genesis of framboidal pyrite is still controversial because of its tiny size here we first determined the chemical and in situ sulfur isotopic compositions of framboidal pyrites from three typical carlin style gold deposits namely shuiyindong taipingdong and nibao using secondary electron image sei back scattered electron bse electron probe micro analysis epma and nanometer scale secondary ion mass spectroscopy nano sims methods our epma data show that the framboidal pyrites contain a minor amount of trace elements ni

peloids in stratabound zn pb deposits and their genetic importance peloids from sediment hosted zn pb deposits in belgium ireland and poland are composed of zn calcite siderite smithsonite silica pyrite melnikovite sphalerite galena thiosulphates and zn as bearing limonite the size of peloids is between 7 and 60 m the core and the shell of peloids are composed of different minerals and the shell is usually coarsely crystalline peloids are present in collapse breccias of karst cavities stromatactis cavities debris flow breccias and fractures cross cutting carbonates hosting the mineralization in places peloids form a major microtexture of the sulfide mineralization peloids are cemented and replaced by sulfides organic acids extracted from sulfide peloids are composed of amido acids considered to be characteristic of bacterial origin the size and specific texture of peloids are independent of mineralogy location and age of the mineralization therefore the peloids disussed are considered as forms induced by bacterial activity rather than forms precipitated inorganically

fault and salt tectonics in the southern dead sea basin abstract the sedimentary fill of the southern dead sea basin contains large amounts of salt and halokinetic features in this study the relationship between these halokinetic features and major faults was investigated the basis for the interpretation was seismic reflection profiles from the southern dead sea basin the seismic profiles were used to construct a series of two way time structural maps and two way time isochore maps for the various reflectors and sedimentary sequences in the area such maps are published for the first time in the dead sea basin electrical and geophysical logs from wells in the area were used to relate the mapped reflectors and sequences with geological units the seismic profiles give evidence to the largest subsidence that had occurred during the late pliocene and that the amount of subsidence was much larger in the deeper part of the basin than in the median block this difference in subsidence is partly a result of salt withdrawal there are two ways to explain the present day structures of the southern dead sea basin either 1 basement faulting took place before salt deposition or 2 basement faulting took place during or after salt deposition in this research a combination of the two is favored in particular the influence of the movement on the longitudinal fault separating the deeper part of the basin from the median block sedom fault on salt flow is outlined the much larger offset on the sedom fault in the northern part of the area is thought to be the reason for salt piercing only in this part of the area it is also suggested that the sedom fault has experienced strike slip movements and not only vertical movements a ridge the neot hakikar ridge is shown to divide the southern basin into two sub basins the presence of this ridge and the salt tectonics triggered motion on a listric fault amazyahu fault in the early pleistocene the listric curvature of the amazyahu fault induced antithetic faulting recognized in the pleistocene sediments earlier studies have suggested that the depocenter migrated to the north the isochore maps however show that locally the depocenter shifted to the southeast this shift is probably caused by the movement along the amazyahu fault and the withdrawal of salt a much larger amount of salt than previously thought is identified and it is suggested that salt reaches as far south as the iddan fault

what controls thickness of sediments and lithospheric deformation at a pull apart basin we present a simplified three dimensional thermomechanical model of a pull apart basin formed at an overstepping of an active continental transform fault the modeling shows that for a given strike slip displacement and friction on the faults the major parameter that controls basin length thickness of sediments and deformation pattern beneath the basin is the thickness of the brittle layer the unusually large length and sediment thickness of the dead sea basin the classical pull apart basin associated with the dead sea transform can be explained by 100 km of strike slip motion and a thick 20 22 km up to 27 km locally brittle part of the cold lithosphere beneath the basin the thinner sedimentary cover in the gulf of aqaba basin located at the southernmost part of the dead sea transform close to the red sea rift is probably due to a thinner brittle part 15 km of the warmer lithosphere the modeling also suggests no more than 3 km of moho uplift beneath narrow 10 15 km pull apart basins formed in cold lithosphere such as the dead sea basin we also infer that a pull apart basin may only form if a several kilometer thick ductile detachment zone exists between the brittle crust and upper mantle modeling shows that this would not be the case for the dead sea basin if the surface heat flow there were indeed as low as 40 mw m 2 as previously reported we consider this result as an indication that the surface heat flow at the dead sea might have been underestimated

pyrite discs in coal evidence for fossilized bacterial colonies discs of pyrite from 1 to 3 mm in diameter and 100 m thick were observed within fracture planes in coal from the black mesa coal deposit in northeastern arizona the pyrite discs were composed of aggregates of crystals which suggested that sulfide mineral diagenesis had initiated at multiple nucleation sites and occurred prior to the compaction forces occurring during coal formation stable sulfur isotope analysis of the discs 34s 31 7 supports a bacterial origin resulting from dissimilatory sulfate reduction fossilized bacteria on the disc surfaces average 27 100 m2 appeared as halos when viewed using reflected light microscopy but were lenticular by scanning electron microscopy each microfossil being 2 3 m in length a fossilized bacterial colony pyrite disc 1 mm in diameter would contain 2 1 107 microfossils these microfossils were not observed on hydrothermal pyrite coating and in filling of sulfate reducing bacteria with iron disulfide during in vitro sulfide mineral diagenesis provide mechanisms to explain the preservation of the three dimensional lenticular microfossils observed on the pyrite discs

crustal structure of the dead sea basin dsb from a receiver function analysis summary the dead sea transform dst is a major left lateral strike slip fault that accommodates the relative motion between the african and arabian plates connecting a region of extension in the red sea to the taurus collision zone in turkey over a length of about 1100 km the dead sea basin dsb is one of the largest basins along the dst the dsb is a morphotectonic depression along the dst divided into a northern and a southern sub basin separated by the lisan salt diapir we report on a receiver function study of the crust within the multidisciplinary geophysical project dead sea integrated research desire to study the crustal structure of the dsb a temporary seismic network was operated on both sides of the dsb between 2006 october and 2008 april the aperture of the network is approximately 60 km in the e w direction crossing the dsb on the lisan peninsula and about 100 km in the n s direction analysis of receiver functions from the desire temporary network indicates that moho depths vary between 30 and 38 km beneath the area these moho depth estimates are consistent with results of near vertical incidence and wide angle controlled source techniques receiver functions reveal an additional discontinuity in the lower crust but only in the dsb and west of it this leads to the conclusion that the internal crustal structure east and west of the dsb is different at the present day however if the 107 km left lateral movement along the dst is taken into account then the region beneath the desire array where no lower crustal discontinuity is observed would have lain about 18 ma ago immediately adjacent to the region under the previous desert array west of the dst where no lower crustal discontinuity is recognized

new progress in study of superlarge jinding pb zn deposit discovery of intrusive breccia and its geological implications there are many breccia type orebodies in the jinding lead zinc ore district in which the authors found for the first time intrusive breccia type orebodies studies show that the original rock of the limestone breccia type orebody is a kind of intrusive breccia instead of a kind of paleocene continental sedimentary breccia it is a half fluid mixture of oil lead zinc carbonate and gypsum solution rubbles and its origin is similar to that of modern mud volcano the longitudinal axial fracture zone of lanping basin is a mud volcano conduit and the intrusive breccia type lead zinc orebody with concrete characteristics was formed in the upright fractural zone of jinding district

extending the upper temperature limit for life the upper temperature limit for life is a key parameter for delimiting when and where life might have evolved on a hot early earth the depth to which life exists in the earth s subsurface and the potential for life in hot extraterrestrial environments a combination of geological and

localised and distributed deformation in the lithosphere modelling the dead sea region in 3 dimensions article i nfo the earth s lithosphere behaves as a strain softening elasto plastic material in the laboratory such materials are known to deform in a brittle or a ductile manner depending on the applied geometric boundary conditions in the lithosphere however the importance of boundary conditions in controlling the deformation style has been largely ignored under general boundary conditions both laboratory and field scale observations show that only part of the deformation can localise on through going faults while the rest must remain distributed in process zones where spatially varying shear directions inhibit localisation conventional modelling methods finite difference finite or discrete elements use rheologies deduced from laboratory experiments that are not constrained as a function of the geometry of the applied boundary conditions in this paper we propose an alternative modelling method that is based on the use of an appropriate distribution of dislocation sources to create the deformation field this approach because it does not rely on integrating differential equations from more or less well constrained boundary conditions does not require making assumptions on the parameters controlling the level and distribution of stresses within the lithosphere it only supposes that strain accumulates linearly away from the dislocation singularities satisfying the compatibility equations we verify that this model explains important and hitherto unexplained features of the topography of the dead sea region following the idea that strain can only localise under specific conditions as inferred from laboratory and field scale observations we use our model of deformation to predict where deformation can localise and where it has to remain distributed we find that 65 of the deformation in the dead sea region can localise on kinematically stable through going strike slip faults while the remaining 35 has to remain distributed observations suggest that distributed deformation occurs at stress levels that can be ten times greater than that associated with motion on well localised faults thus although only representing a minor part of the total deformation distributed deformation should provide the greatest source of resistance to motion along this part of the levant plate these results can change dramatically our view of the behaviour of this and other plate boundaries if the lithosphere can be regarded as a strain softening elasto plastic material then similar behaviour should occur throughout with important implications not only for its mechanical behaviour but also for heat generation and related issues like metamorphism or magma genesis

seismic imaging of deep low velocity zone beneath the dead sea basin and transform fault implications for strain localization and crustal rigidity 1 new seismic observations from the dead sea basin dsb a large pull apart basin along the dead sea transform dst plate boundary show a low velocity zoneextending to a depth of 18 km under the basin the lower crust and moho are not perturbed these observations are incompatible with the current view of mid crustal strength at low temperatures andwith support ofthebasin snegative load byarigid elastic plate strain softening in the middle crust is invoked to explain the isostatic compensation and the rapid subsidence of the basin during the pleistocene whether the deformation isinfluencedbythepresenceoffluidsandbyalonghistoryof seismic activity on the dst and what the exact softening mechanism is remain openquestions the uplift surrounding the dstalso appears to be an upper crustal phenomenon but its relationship to a mid crustal strength minimum is less clear the shear deformation associated with the transform plate boundary motion appears on the other hand to cut

fossil sulphate reducing bacteria in the bleiberg lead zinc deposit austria polished ore samples from the world class bleiberg lead zinc deposit in austria were studied by field emission scanning electron microscopy fesem at magnifications in the range of 105 106 the zinc ore shows nano sized sphalerite filaments and spherules which are morphologically similar to recent biofilms of sulphate reducing bacteria the activity of sulphate reducing bacteria is suggested by a large 34s difference of 40 between coeval seawater sulphate 16 and sulphide sulphur 25 in the bleiberg ores and by variable sulphur valences peloids of sphalerite zn bearing calcite and pyrite have features typical of bacterial colonies combined with geological and mineralogical evidence a significant role of bacteria during ore deposition at bleiberg is likely

intrabasin paleoearthquake and quiescence correlation of the late holocene dead sea 1 a comprehensive multisite paleoseismic archive of the late holocene dead sea basin past 2500 years is established by constructing two age depth chronological models of two sedimentary sections exposed at the retreating shores of the modern dead sea two new paleoseismic study sites studied are the ein feshkha nature reserve outcrop located at the northern part of the basin and close to an active underwater transverse fault and the east ze elim gully outcrop at the southern part of the basin age depth regression models are calculated for these sections based on atmospheric radiocarbon ages of short lived organic debris calibrated with a bayesian model the uncertainties on individual model ages are smaller than 100 years the new chronological records are compared to a laminae counting study of the ein gedi core migowski et al 2004 located at the central dead sea basin the ein feshkha outcrop yielded the largest number of seismites in the studied time interval n 52 while lower numbers of seismites are recovered from the ze elim outcrop and ein gedi core n 15 and 36 respectively the seismites show no strong dependence on the limnological sedimentological conditions in the particular sampling sites they coappear in both shallow and deep water environments and in different sedimentary facies during time intervals when the chronologies are comparable it appears that the number of seismites is significantly larger in the northern part of the basin ein gedi and ein feshkha seismic quiescence intervals are apparent at all three sites from 2nd 4th century a d and at 500 150 b c at ze elim and ein gedi several synchronous seismites appear in all sections termed here the intrabasin seismites ibs among them 1927 1293 1202 1212 749 551 419 and 33 a d and 31 and mid 2nd century b c the recurrence time of the ibs from the 2nd century b c to the 14th century a d is 200 years compared with 100 years for all earthquakes on a diagram of epicentral distance versus magnitude historic earthquakes that are correlated with ibs plot in a field of high local intensity the farther and stronger ibs earthquakes require lower local intensities to be recorded this study demonstrates that a painstaking effort is still needed for unraveling the seismic history of the dead sea basin the results also indicate that such a study will likely be highly rewarding

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

deep drop down basin in the southern dead sea abstract the large dead sea graben is located within the dead sea fault a plate boundary of the transform type the graben is composed of two basins the northern one is occupied by a lake about 300 m deep and has a sedimentary fill of about 6 km the southern dead sea basin however is unusually deep with about 14 km of sedimentary fill the geometry of the southern dead sea basin is anomalous along the entire dead sea fault we suggest that the southern dead sea basin was formed during the first stage of the formation of the dead sea fault when the tips of propagating faults one from the collision front in the north and one from the red sea in the south met in this area the fault tips overlapped and curved towards each other isolating a block of crust and lithosphere that dropped into the mantle geophysical data indicate that the basin is probably bordered on all sides by vertical faults that cut deep into basement the deep part of the southern dead sea basin is not a pull apart but instead a drop down basin the salton trough in california is probably another example of such a basin

geochemical modeling of zns in biofilms an example of ore depositional processes the precipitation of nearly pure nanocrystalline zinc sulfides primarily sphalerite and wurtzite within a biofilm dominated by sulfate reducing bacteria of the family desulfobacteriaceae has been observed in the flooded tunnels of an abandoned mine in southwestern wisconsin zns accumulations are limited to biofilms growing on old mine timbers zns deposits which comprise about 20 percent of the volume of the biofilm formed in less than 30 yr from solutions containing only a few milligrams per liter mg l zn 2 a model is proposed wherein sulfate reduction is followed by the formation of aqueous metal sulfide clusters that aggregate to form 1 to 3 nm diameter crystals that are transported and agglomerate to form micron scale aggregates geochemical modeling shows how reduction of sulfate leads to exclusive precipitation of zns until most of the zn 2 is consumed the model also predicts a series of discrete metal sulfide precipitation events that may be used to interpret sulfide mineral paragenesis of low temperature cu pb zn ore deposits for example the paragenesis of essentially monomineralic and mixed sulfide layers in mississippi valley type strataform and strata bound pb zn cu and sedex deposits can be predicted thermodynamically if the rate of aqueous sulfide generation does not outstrip the flux of metals into the system based on the characteristics of zns produced by sulfate reducing bacteria features of ore deposit minerals consistent with a biogenic origin can be identified these include microstructures formed by coarsening of nanophase materials the presence of micron scale spherical aggregates in organic rich microenvironments and spatially heterogeneous patterns of sulfide mineral distribution consistent with local variations in redox potential and activity of sulfate reducing bacteria

microseismicity distribution in the southern dead sea basin and its implications on the structure of the basin summary while the dead sea basin has been studied for a long time the available knowledge about the detailed seismicity distribution in the area as well as the deeper structure of the basin is limited therefore within the framework of the international project desire dead sea integrated research project a dense temporary local seismological network was operated in the southern dead sea area we use 530 local earthquakes having all together 26 730 p and s arrival times for a simultaneous inversion of 1 d velocity models station corrections and precise earthquake locations jackknife tests suggest an accuracy of the derived hypocentre locations of about 1 km thus the result is the first clear image of the absolute distribution of the microseismicity of the area especially in depth the seismicity is concentrated in the upper crust down to 20 km depth while the lower limit of the seismicity is reached at 31 km depth the seismic events at the eastern boundary fault ebf in the southern part of the study area represent the northward transform motion of the arabian plate along the dead sea transform north of the boqeq fault the seismic activity represents the transfer of the motion in the pull apart basin from the eastern to the western boundary we find that from the surface downward the seismic events are tracing the boundary faults of the basin the western boundary is mapped down to 12 km depth while the ebf reaches about 17 km depth forming an asymmetric basin one fifth of the data set is related to a specific cluster in time and space which occurred in 2007 february at the western border fault this cluster is aligned vertically that is it is perpendicular to the direction of the dominating left lateral strike slip movement at the main transform fault

formation of a giant zn pb deposit from hot brines injecting into a shallow oil gas reservoir in sandstones jinding southwestern china the association between mineralization and hydrocarbons in sedimentary basins is widely recognized but the nature and significance of their relationships are not fully understood this paper provides an example of metalliferous brines injecting into a palaeo oil gas reservoir to form a world class zn pb deposit jinding china petrographic and microthermometric studies of oil inclusions and pvt simulations suggest that oil and gas were charged in a shallow 1300 m environment before mineralization this environment favoured bacterial sulfate reduction bsr which produced large amounts of h2s that accumulated in the gas cap forceful injection of hot brines penetrated the oil zone to reach the h2s rich gas cap and precipitated sulfide ores individual fluid injection events were short lived and the reservoir was only partly and briefly heated to beyond the bacterial survival temperature episodic injection of metalliferous brines and sustained supply of h2s through bsr resulted in the formation of a large zn pb deposit this article is protected by copyright all rights reserved

geometry and subsidence history of the dead sea basin a case for fluid induced mid crustal shear zone 1 pull apart basins are narrow zones of crustal extension bounded by strike slip faults that can serve as analogs to the early stages of crustal rifting we use seismic tomography 2 d ray tracing gravity modeling and subsidence analysis to study crustal extension of the dead sea basin dsb a large and long lived pull apart basin along the dead sea transform dst the basin gradually shallows southward for 50 km from the only significant transverse normal fault stratigraphic relationships there indicate basin elongation with time the basin is deepest 8 8 5 km and widest 15 km under the lisan about 40 km north of the transverse fault farther north basin depth is ambiguous but is 3 km deep immediately north of the lake the underlying pre basin sedimentary layer thickens gradually from 2 to 3 km under the southern edge of the dsb to 3 4 km under the northern end of the lake and 5 6 km farther north crystalline basement is 11 km deep under the deepest part of the basin the upper crust under the basin has lowerpwave velocity than in the surrounding regions which is interpreted to reflect elevated pore fluids there within data resolution the lower crust below 18 km and the moho are not affected by basin development the subsidence rate was several hundreds of m m y since the development of the dst 17 ma similar to other basins along the dst but subsidence rate has accelerated by an order of magnitude during the pleistocene which allowed the accumulation of 4 km of sediment we propose that the rapid subsidence and perhaps elongation of the dsb are due to the development of inter connected mid crustal ductile shear zones caused by alteration of feldspar to muscovite in the presence of pore fluids this alteration resulted in a significant strength decrease and viscous creep we propose a similar cause to the enigmatic rapid subsidence of the north sea at the onset the north atlantic mantle plume thus we propose that aqueous fluid flux into a slowly extending continental crust can cause rapid basin subsidence that may be erroneously interpreted as an increased rate of tectonic activity

microbial sphalerite formation in carbonate hosted zn pb ores bleiberg austria micro to nanotextural and sulfur isotope evidence microglobular sphalerite 90 180 m is a major form of sphalerite in the abandoned triassic carbonate hosted zn pb deposit at bleiberg austria it is common in ores from the crest horizon and the first cardita horizon which contain about 0 5 to 3 mm thick and up to 5 cm long wavy discontinuous sphalerite rich bands composed of agglomerations of microglobular sphalerite based on comparisons with modern environments these textures are interpreted as peloids and probably represent fossil microbial mats these are inter layered with carbonate and marcasite rich as well as finely banded sphalerite layers fibrous galena and relics of oxysulfides resulting in the characteristic rhythmically banded macrotexture of these zn dominated ores microbial nanotextures made visible by field emission scanning electron microscopy fesem after etching include sphalerite nanospheres 10 90 nm and bacterial filaments the sphalerite nanospheres are identical to those previously reported for mixed calcite sphalerite peloids from bleiberg and are very similar to nanotextures observed in recent bacterial biofilms made by desulfobacteriaceae the observed sphalerite nanospheres are interpreted as in situ metabolic products of sulfate reducing bacteria micro and nanotextures suggest that the larger m sized sphalerite globules formed by agglomeration of sphalerite nanospheres as well as by replacement of peloids representing former bacterial colonies the latter are now composed of zn calcite cores surounded by serrated sphalerite rims most samples studied evidence recrystallization of sphalerite that is broadly coeval with formation of fluorite involvement of sulfate reducing bacteria in the formation of this early sphalerite mineralization is supported by sulfur isotope data sphalerite is generally characterized by isotopic light sulfur with 34 s per mil values ranging from 30 5 to 20 3 per mil the most negative sulfur isotope values are recorded from sphalerite 30 5 30 2 and galena with unusual fibrous to dendritic morphology 31 9 31 8 both are associated with oxysulfides microglobular sphalerite with well preserved sphalerite globules has a 34 s value of 28 8 to 28 2 per mil colloform sphalerite schalenblende ranges from 29 0 to 25 0 per mil microglobular sphalerite associated with fine grained fluorite and euhedral sphalerite formed through recrystallization processes show a trend to less negative values i e 26 3 to 22 2 per mil and 22 9 to 20 3 per mil respectively we suggest that the combined biogenic nano to macrotextures and sulfur isotope data are evidence that microbes played a key role in formation of alpine carbonate hosted zn pb deposits results of this study contradict the mvt model suggested for alpine pb zn deposits which calls for formation of pb zn mineralization during late diagenetic burial in the late triassic early jurassic

trace and minor elements in sphalerite from base metal deposits in south china a la icpms study laser ablation icp mass spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine zn pb deposits in south china the deposits which are of different ages and belong to different metallogenic provinces have been assigned to the following genetic types skarn hetaoping luziyuan syngenetic massive sulphide dabaoshan laochang and bainiuchang and mississippi valley type huize mengxing niujiaotang based on the features of the ore even though their origin is heavily debated based on other criteria the giant jinding deposit is considered separately sphalerite from each genetic class of deposit shows a distinct chemical signature sphalerite from the skarn deposits is characterised by elevated lattice bound concentrations of co and mn the distal character of these skarn systems is reflected by the low in content of sphalerite the three syngenetic massive sulphide deposits feature sphalerite strongly enriched in in sn and ga whereas the deposits of mvt type are typically enriched in ge cd tl and as these divergent characters are reflected in absolute element abundances as well as in element ratios time resolved depth profiles for sphalerite from the chinese deposits confirm the presence of elements such as co in ge ga and cd in solid solution but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements whose ability to enter the crystal structure of sphalerite has been previously debated ag sn tl sb may also be in solid solution sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as south china and help resolve the mechanism by which many of the debated ore deposits were formed

stress tensor and focal mechanisms along the dead sea fault and related structural elements based on seismological data the dead sea fault is among the largest active strike slip fault of the world this study is focused on the southern part of this fault from the sea of galilee to the gulf of aqaba as monitored mainly by the jordanian and israeli seismic networks the data of arrival times and polarities allowed relocation of earthquakes with a better azimuthal coverage and computation of focal mechanisms this last step has been realized by inverting the polarities to determine a unique stress tensor for the region and the compatible focal mechanisms inversion with different subsets of the data set based on tectonic regionalization has also been performed to evaluate the impact of each cluster of earthquakes on the global solution the population of focal mechanisms is clearly dominated by strike slip events with the notable exception of a cluster of earthquakes south of the dead sea which displays several normal focal mechanisms this last cluster forces 1 to be vertical and 2 to be horizontal a large number of fault planes however are close to the vertical inhibiting the action of the vertical component of the stress tensor and acting like under strike slip stress regime we observed a good agreement between the location of the earthquakes and the active faults based on geological data in addition there is a good agreement between the fault plane solutions and the orientation of the active faults

hierarchic three dimensional structure and slip partitioning in the western dead sea pull apart 1 rifted basins are bounded by marginal belts with fault networks and flexures we analyze the internal structure of such a belt the western margins of the dead sea basin this basin is 150 km long 15 20 km wide with more than 10 km of sediment fill and it is currently subsiding due to slip of the dead sea pull apart the western margin of the dead sea basin is an elongated n s belt with an intricate three dimensional 3 d pattern of zigzag faults flexures and joints the dominant structures are four sets of oblique normal faults arranged in orthorhombic symmetry the faults are steep with prevalent strike directions of nnw and nne large flexures developed along and above these faults forming tilted blocks and localized asymmetric folds two sets of subvertical joints that dominate the area trend nne and nnw subparallel to the strikes of the dominant fault sets the parallel relations between these structures at all scales suggest that they formed during a single tectonic phase three dimensional fault modeling reveals a 3 d strain field with a large vertical shortening a minor horizontal shortening in n s direction belt parallel and a large horizontal e w extension basinward the calculated stress fields associated with the zigzag fault segments are compatible with the observed fault parallel flexures further the calculations predict the formation of local tensile belts above the faults and these tensile belts could explain the penecontemporaneous development of the two joint sets architecture similar to the western margins of the dead sea basin is likely to develop on rifted margins wherever 3 d deformation is required by the rifting kinematics

a combined chemical isotopic and microstructural study of pyrite from roll front uranium deposits lake eyre basin south australia abstract the common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at pepegoona pepegoona west and pannikan lake eyre basin south australia combined chemical isotopic and microstructural analysis of pyrite indicates variation in fluid composition sulfur source and precipitation conditions during a protracted mineralization event the results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low temperature hydrothermal systems in situ micrometer scale sulfur isotope analyses of pyrite demonstrated broad scale isotopic heterogeneity 34 s 43 9 to 32 4 vcdt indicative of complex multi faceted pyrite evolution and sulfur derived from more than a single source preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation authigenic pyrite underwent prolonged evolution and recrystallization evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra secondary hydrothermal pyrite commonly displays hyper enrichment of several trace elements mn co ni as se mo sb w and tl in ore bearing horizons hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types irregular variation in 34 s coupled with oscillatory trace element zonation in secondary pyrite is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization a late stage oxidizing fluid may have mobilized selenium from pre existing pyrite subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re crystallization and precipitation of selenium as native selenium these results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at beverley north insights into depositional conditions and sources of both sulfide and uranium mineralization and an improved understanding of pyrite geochemistry can also underpin an effective vector for uranium exploration at beverley north and other sedimentary systems of the lake eyre basin as well as in comparable geological environments elsewhere

sedimentary basins investigation using teleseismic p wave time delays abstract passive seismic methods have been proven successful in recent years at retrieving information about the large scale structure of a sedimentary basin these methods are based on ambient noise recordings and local and distant teleseismic earthquake data in particular it has been previously observed that the arrival time of teleseismic p waves recorded inside a sedimentary basin shows time delays and polarization that both strongly depend on the basin properties and structure in this paper we present a new methodology for determining seismic p wave velocity in a sedimentary basin based on the time delay of a teleseismic p wave travelling through the low velocity basin infill with respect to a teleseismic wave recorded outside the basin the new methodology is developed in a bayesian framework and thus it includes estimates of the uncertainties of the p wave velocities for this study we exploit synchronous recordings of teleseismic p wave arrivals at a dense linear array of broadband seismic stations using data from two teleseismic events coming from two different incoming angles the results obtained by the new proposed methodology are successfully compared to classical cross correlation measurements and are used to infer properties of a sedimentary basin such as the basin bounding fault s geometry and the average p wave velocity of the sedimentary basin fill

geology and evolution of the southern dead sea fault with emphasis on subsurface structure the dead sea fault is an active transform fault linking opening in the red sea with collision in the taurus zagros mountains motion is left lateral and estimated at approximately 5 7 mm year 1 the fault is seismically active and can be divided into two distinct structural segments this study focuses on the southern segment based mainly on the wealth of geophysical data owing to transtention caused by oblique slip and the overlapping of en echelon fault strands a series of pull apart basins were formed along the fault s length these basins are long and deep reaching in places more than 10 km deep they are characterized by extensional compressional and asymmetrical structures varying in size from large scale defining the general structure of the dead sea fault valley to small scale defining the internal structure this study examines the internal structure of these basins from south to north and summarizes the state of knowledge to date

micro textures and in situ sulfur isotopic analysis of spheroidal and zonal sulfides in the giant jinding zn pb deposit yunnan china implications for biogenic processes abstract the jinding deposit in yunnan southwest china is the largest sandstone and conglomerate hosted zn pb deposit in the world in this paper we report various micro textures of spheroidal and zonal sulfides such as pellet shaped and colloform aggregates of pyrite and sphalerite from the deposit and interpret them to be possibly related to micro colonies of sulfate reducing bacteria probably supporting an in situ bsr hypothesis micro scale sulfur isotope analysis in different parts of the spheroidal and zonal sulfide aggregates using secondary ion mass spectrometry sims revealed 34s vcdt values as low as 48 4 for sulfides formed in the early main stage disseminated ores in the western part of the deposit possibly suggesting maximum sulfur isotopic fractionation through bsr relatively elevated 34s vcdt values 7 7 to 34 8 mainly from 10 to 20 for the late stage cavity filling ores in the eastern part of the deposit are interpreted to be possibly related to elevated temperatures close to the hydrothermal conduit and elevated 34s values of the remaining sulfates resulting from the preceding bsr processes the apparent discrepancy between the low temperatures required for bsr and the high temperatures indicated by fluid inclusions 120 c may be reconciled through invoking episodic influx of ore forming hydrothermal fluids into a shallow relatively cool environment it is proposed that the host rocks of the jinding deposit have not been buried to great depths 1 km which combined with the availability of hydrocarbons in the jinding dome a paleo oil and gas reservoir provides an ideal environment for bsr episodic influx of metal carrying hydrothermal fluids temporarily and locally suppressed bsr and promoted thermo chemical sulfate reduction tsr resulting in deposit and micro scale variations of 34s

a crustal structure study of jordan derived from seismic refraction data abstract the interpretation of a deep seismic refraction study in jordan performed in may 1984 shows that much of the country is underlain by continental crust 32 35 km thick and normal mantle with a velocity of 8 0 8 2 km s in the aqaba region southwest and central jordan east of wadi araba the crustal thickness is of the order of 32 35 km while in the amman region it is not less than 35 km in southeast jordan the crust thickens to at least 37 km in what is probably the transition to the arabian shield type of crust the boundaries between the upper and lower crust at about 20 km depth and the lower crust and uppermost mantle are probably transition zones the upper crystalline crust has velocities of 5 8 6 5 km s while the lower crust has velocities greater than or around 6 65 km s while the crystalline basement is exposed in southwest jordan and is at a depth of 2 2 5 km north of amman it is at a depth of not less than 5 km in central jordan a comparison of the crustal type and structure of jordan and the adjacent dead sea rift with that of the black forest and the rhine valley yields a striking resemblance the situation of the jordan dead sea rift is explained in terms of the continental crust of arabia rifting in preference to the thin oceanic crust of the mediterranean sea

three dimensional numerical models of the evolution of pull apart basins abstract pull apart basins are depressions that form as the result of crustal extension along strike slip systems where the sense of fault stepping or bending coincides with that of fault slip they are common features of strike slip systems we perform a number of numerical thermomechanical experiments to explore how the rheology of the lithosphere influences basin evolution and lithospheric structure beneath the basin our modeling shows that basin subsidence results from the competition of extension of the brittle part of the lithosphere which leads to its subsidence and of the compensating flow of the deeper ductile part of the lithosphere which pushes the extended brittle block upwards the result of this competition is the subsidence rate strain partitioning beneath the basin and crustal structures is controlled by i the thickness of the brittle layer and basin width ii the magnitude of strike slip displacement iii the rate of frictional softening of the crust and iv the viscosity of the ductile part of the lithosphere the thickness of the brittle layer and the viscosity of the underlying ductile part of the lithosphere in turn depend on temperature composition and material softening we interpret the modeling results deducing simple analytical expressions based on the brittle brick stretching bbs approach which despite its simplicity describes the structure and evolution of pull apart basins reasonably well we also demonstrate that the structure and evolution of the dead sea basin located at a left step of the dead sea transform in the middle east is consistent with a bbs type of deformation with only a minor contribution from compensational flow in the ductile part of the lithosphere finally we show that the formation of a deep narrow pull apart basin in relatively cold lithosphere as in the dead sea basin requires very low friction at major faults lower than 0 1 0 2 if this condition is not satisfied strike slip deformation does not localise and deep basins do not form