molybdenum and tungsten in volcanic rocks and in surface and 100 c ground waters in iceland abstract the concentrations of mo and w in tholeiite series basaltic to silicic volcanics in iceland increase with the concentrations of incompatible magmatic elements in normal mid ocean ridge basalt morb mo and w levels are as low as 0 03 and 0 01 ppm but in rhyolites they are up to 4 and 1 3 ppm respectively in the slightly evolved tertiary tholeiites of the main study area of skagafjordur northern iceland mo and w concentrations are 1 01 and 0 32 ppm respectively on average surface waters in this area typically contain 10 000 years waters in river and ground waters the average mo w ratio is the same as that of the basalt host rock on the other hand in peat soil waters the average mo w ratio is higher due to adsorption processes involving w in river and ground waters both mo and w display conservative behavior progressive water rock interaction leads to successively lower aquatic b mo and b w ratios however the b mo and b w ratios of the most reacted waters are considerably higher than those of the basalt due to non stoichiometric rock dissolution b is dissolved preferentially to both mo and w because b is largely present in a soluble form but mo and w are concentrated in the fe ti oxides these minerals are stable under both surface and sub surface conditions i e the waters are over saturated with respect to these minerals the main supply of mo and w to surface waters is from dissolution of plagioclase and pyroxene as well as volcanic glass olivine is not an important source due to its scarcity in the basalts in

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

new gas geothermometers for geothermal exploration calibration and application calibration of five gas geothermometers is presented three of which used co2 h2s and h2 concentrations in fumarole steam respectively the remaining two use co2h2 and h2sh2 ratios the calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures after establishing the gas content in the aquifer gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions it is shown that the concentrations of co2 h2s and h2 in geothermal reservoir waters are fixed through equilibria with mineral buffers at temperatures above 230 c epidote prehnite calcite quartz are considered to buffer co2 two buffers are involved for h2s and h2 and two functions are therefore presented for the geothermometers involving these gases for waters containing less than about 500 ppm chloride and in the range 230 300 c pyrite pyrrholite epidote prehnite seem to be involved but pyrite epidote prehnite magnetite or chlorite for waters above 300 c and waters in the range 230 300 c if containing over about 500 ppm the gas geothermometers are useful for predicting subsurface temperatures in high temperature geothermal systems they are applicable to systems in basaltic to acidic rocks and in sediments with similar composition but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones the geothermometry results may be used to obtain information on steam condensation in upflow zones or phase separation at elevated pressures measured aquifer temperatures in drillholes and gas geothermometry temperatures based on data from nearby fumaroles compare well in the five fields in iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected the results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled icelandic fields

the chemistry of geothermal waters in iceland ii mineral equilibria and independent variables controlling water compositions abstract the major element chemistry of icelandic geothermal waters is predictable provided two parameters are known this follows from an attainment of or a close approach to an overall chemical equilibrium in the geothermal systems at temperatures as low as 50 c it is considered that the geothermal system composition temperature and kinetic factors determine which alteration minerals form the system composition is not so much fixed by rock composition as by the rate of leaching of the various constituents from the fresh rock and the composition of inflowing water the water chemistry is determined by the system composition and the external variables acting on the system they include temperature and the mobility of chloride pressure which theoretically should be regarded as an external variable has insignificant effect on water compositions in the range 1 200 bars occurring in the geothermal systems

the geochemistry of trace elements in geothermal fluids iceland abstract trace element geochemistry was studied in geothermal fluids in iceland the major and trace element compositions of hot springs sub boiling and two phase liquid and vapor wells from 10 geothermal areas were used to reconstruct the fluid composition in the aquifers at depth aquifer fluid temperatures ranged from 4 to 300 c ph values between 4 5 and 9 3 and fluids typically contained total dissolved solids

the use of mixing models and chemical geothermometers for estimating underground temperatures in geothermal systems abstract application of various chemical geothermometers and mixing models indicate underground temperatures of 260 c 280 c and 265 c in the geysir hveravellir and landmannalaugar geothermal fields in iceland respectively mixing of the hot water with cold water occurs in the upflow zones of all these geothermal systems linear relations between chloride boron and 18o constitute the main evidence for mixing which is further substantiated by chloride silica and sulphate relations in the geysir and hveravellir fields a new carbonate silica mixing model is proposed which is useful in distinguishing boiled and non boiled geothermal waters this model can also be used to estimate underground temperatures using data from warm springs this model as well as the chloride enthalpy model and the na li and co2 gas geothermometers invariably yield similar results as the quartz geothermometer sometimes also does by contrast the na k and the na k ca geothermometers yield low values in the case of boiling hot springs largely due to loss of potassium from solution in the upflow the results of these geothermometers are unreliable for mixed waters due to leaching subsequent to mixing

molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems iceland abstract molybdenum mo isotopes have proved useful in the reconstruction of paleoredox conditions their application generally relies upon a simplified model of ocean inputs in which rivers dominate mo fluxes to the oceans and hydrothermal fluids are considered to be a minor contribution to date however little attention has been paid to the extent of mo isotope variation of hydrothermal waters or to the potential effect of direct groundwater discharge to the oceans here we present mo isotope data for two icelandic groundwater systems m vatn and eistareykir that are both influenced by hydrothermal processes relative to nist 3134 0 25 the cold n 13 show little if any fractionation from the host basalt 98 95 mobasalt 0 16 to 0 12 and are on average lighter than both global and icelandic rivers in contrast waters that are hydrothermally influenced 10 c possess isotopically heavy 98 95mohydrothermal values of 0 25 to 2 06 n 18 with the possibility that the high temperature endmembers are even heavier although the mechanisms driving this fractionation remain unresolved the incongruent dissolution of the host basalt and both the dissolution and precipitation of sulfides are considered regardless of the processes driving these variations the 98mo data presented in this study indicate that groundwater and hydrothermal waters have the potential to modify ocean budget calculations

migration of activity within normal fault systems examples from the quaternary of mainland greece abstract we examine five areas of mainland greece where active extension occurs on sub parallel systems of normal faults and where geomorphological and stratigraphic evidence indicates that the faulting has migrated basinwards into the original hanging walls in several cases within the late quaternary by comparing fault slip rates estimated from geomorphological data with current extension rates known from geodetic measurements it appears that the newest faults can account for effectively all the present day motions fault migration of this sort is easy to recognize in young systems close to sea level because vertical movements of footwalls and hanging walls are obvious and reveal which faults are currently most active but is less easy to confirm away from reliable reference levels or in older terrains with poorer time resolution it is probably more common than is appreciated and has a profound effect on syn rift sedimentation and erosion patterns fault migration is probably an inevitable consequence of the interplay between stresses generated by the fault related topography and the ultimate strength of major faults it is likely to be further encouraged in places where lower crustal flow or rotations about a vertical axis are important however it is not clear why migration should preferentially occur into the hanging walls as observed in central greece

source and fate of inorganic solutes in the gibbon river yellowstone national park wyoming usa ii trace element chemistry the gibbon river in yellowstone national park receives inflows from several geothermal areas and consequently the concentrations of many trace elements are elevated compared to rivers in non geothermal watersheds water samples and discharge measurements were obtained from the gibbon river and its major tributaries near norris geyser basin under the low flow conditions of september 2006 allowing for the identification of solute sources and their downstream fate norris geyser basin and in particular tantalus creek is the largest source of many trace elements al as b ba br cs hg li sb tl w and rees to the gibbon river the chocolate pots area is a major source of fe and mn and the lower gibbon river near terrace spring is the major source of be and mo some of the elevated trace elements are aquatic health concerns as sb and hg and knowing their fate is important most solutes in the gibbon river including as and sb behave conservatively or are minimally attenuated over 29 km of fluvial transport some small attenuation of al fe hg and rees occurs but primarily there is a transformation from the dissolved state to suspended particles with most of these elements still being transported to the madison river dissolved hg and rees loads decrease where the particulate fe increases suggesting sorption onto suspended particulate material attenuation from the water column is substantial for mn with little formation of mn as suspended particulates

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

strike slip kinematics in central and eastern iran estimating fault slip rates averaged over the holocene 1 according to gps measurements the right lateral shear between central iran and afghan blocks amounts to 16 mm yr a model based on very long term estimates of fault rates suggests the current shear originated about 5 ma ago and has been accommodated by strike slip faulting limited to the western 2 mm yr gowk nayband fault and eastern 14 mm yr sistan system fault edges of the lut block we have used high resolution spot5 pixel size 2 5 m images to measure recent cumulative offsets and estimate slip rates over shorter time periods that average several seismic cycles only recent offsets a few tens of meters have been found along the anar fault inside the central iran plateau and along the sistan faults east of the lut the offset morphologies postdate the last incision of the network and are most probably of holocene age 12 2 ka the corresponding slip rates range between 0 5 0 75 mm yr 1 75 2 5 mm yr 1 5 mm yr 1 2 5 mm yr for the anar east neh west neh and asagie fault respectively these estimates suggest the gps shear rate across the lut may not extrapolate over the holocene they also indicate strike slip faulting is not confined to the lut edges but also occurs in central iran suggesting the ongoing strike slip tectonics might have originated between 8 and 22 ma ago earlier than considered previously and consistent with observations in ne iran

molybdenum in icelandic geothermal waters molybdenum concentrations in icelandic geothermal waters lie in the range 1 70 ppb warm waters and dilute high temperature waters which contain high concentrations of sulphide are lowest in molybdenum no correlation is otherwise observed between molybdenum concentrations and temperature surface waters and cold ground waters do not contain detectable molybdenum 1 ppb it seems likely that leaching rate is the prime factor in limiting molybdenum levels in these waters within individual geothermal fields molybdenum concentrations are either approximately constant or they vary regularly across the field this regular variation may often be correlated with variations in other solute concentrations and subsurface temperatures and is taken to indicate a control of molybdenum mobility by a temperature dependent equilibrium the evidence suggests that the solubility of molybdenite is responsible molybdenite has not been found in active geothermal systems in iceland but is known to occur in some new zealand geothermal systems and it has been identified in hydrothermally altered tertiary basalt formations at reydarartindur in southeast iceland boiling and mixing with cold water leads to molybdenite undersaturation and thus these processes favour leaching of molybdenum from the rock on the other hand conductive cooling leads to supersaturation which favours removal of molybdenum from solution

the continuity of active fault systems in greece summary evidence from geomorphology the distribution of large earthquakes and geodetic measurements suggests that the active faulting in mainland greece and the north aegean sea is concentrated into a small number of discrete linear zones that bound relatively rigid blocks on land the zones are most clearly identified where the faulting is associated with large escarpments particularly in hard footwall rocks the zones can become indistinct and diffuse near their ends sometimes because they enter high unstable topography where landsliding obscures the fault morphology but mostly because the extension rates decrease along strike as a consequence of the relative rotation of the blocks they bound the main graben systems of chalkidiki southern thessaly and the north gulf of evia all seem to connect with the strike slip faulting in the offshore aegean and to die out in the west a configuration related to clockwise rotations in east central greece by contrast the gulf of corinth which is the fastest opening graben system in greece opens more rapidly in the west than the east both these features of the gulf of corinth are consequences of the motion of the south aegean and peloponnese as a single block late pliocene and quaternary geology and geomorphology indicate that the boundaries of the rigid blocks in central greece have changed over that time with faulting migrating into the hanging walls sometimes changing in orientation these changes are probably related to the way faulting in the seismogenic layer adapts to block rotation so as to maintain the general features of a velocity field that is controlled by larger scale effects such as buoyancy forces and the seaward migration of the subducting slab beneath crete the image of greece as a mosaic of rigid blocks whose boundaries change with time is a useful framework for seismic hazard evaluation but we emphasize that some moderate sized earthquakes do occur away from the main fault zones within the relatively rigid blocks and especially near their diffuse ends

the chemistry of trace elements in surface geothermal waters and steam iceland abstract the geochemistry of trace elements in surface geothermal fluids in iceland was studied the sampled fluids included hot springs mud pots steam vents and soil solutions with temperatures ranging from 4 to 100 c ph between 2 01 and 9 10 and total dissolved solids between 86 and 4375 ppm the surface geothermal waters may be categorized into three groups based on their chemical composition namely nacl waters steam heated acid sulfate waters and mixed waters nacl waters with ph 8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow they contained only low concentrations of most metals

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

description and interpretation of the composition of fluid and alteration mineralogy in the geothermal system at svartsengi iceland abstract the bulk composition and mineralogy of hydrothermally altered tholeiite along with the composition and speciation of fluid have been determined for a well defined alteration zone at 240 c and 110 bars at svartsengi iceland mass balances between the geothermal fluid and altered tholeiite relative to a seawater fresh water mixture and unaltered tholeiite indicate the overall reaction per 1000 cm 3 is 1325 gm plagioclase 1228 gm pyroxene 215 gm oxide minerals break down to form 685 gm chlorite 636 gm albite 441 gm quartz 249 gm epidote 266 gm calcite 201 gm oxide minerals 15 gm pyrite requiring an influx of 123 gm co 2 10 gm h 2 s and 4 gm na 2 o and a release of 57 gm sio 2 35 gm feo 21 gm cao 8 gm mgo and 4 gm k 2 o principal reactions deduced from textural evidence include na ca exchange in plagioclase precipitation of quartz calcite and anhydrite and formation of chlorite and epidote by reactions between groundmass minerals and fluid thermodynamic analyses of authigenic minerals and downhole fluid indicate that the fluid maintains a state close to equilibrium with the secondary mineral phases chlorite epidote albite quartz calcite prehnite anhydrite pyrite and magnetite whereas remnant primary labradorite and augite are out of equilibrium with the fluid water rock ratios for the system are determined under a variety of assumptions however the open nature of the system makes comparisons with experimental and theoretical closed system studies ambiguous

stress orientation evaluated from strain localisation analysis in aigion fault abstract within the frame of the crl corinth rift laboratory project cornet f bernard p moretti i 2004a the corinth rift laboratory comptes rendus geosciences 336 4 5 235 242 centered on the south western sector of the gulf of corinth http www corinth rift lab org fault zone cores from the active aigion fault have been collected continuously from depths between 708 and 782 m inside this clayey core a clear shearing surface with marked slip lines is visible on a plane that makes a 68 angle with respect to the core axis this failure surface was not induced by the decompression process but is indeed a slip plane as clear striation is observed at the interface on the basis of an elasto plastic constitutive model calibrated on triaxial tests on the clayey gouge it is shown that shear band formation inside the clayey core is possible the solution for the orientation of the shear band is compared to the orientation of an existing slip surface inside the clayey gouge and this result is used to deduce the orientation of the principal stresses it is shown that as commonly observed in weak fault zones the orientation of the principal stresses is locally almost parallel and perpendicular to the fault axis

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

nw iran eastern turkey present day kinematics results from the iranian permanent gps network abstract a network of continuous gps stations has been installed in nw iran since 2005 to complement the survey gps network already existing in the region we present the 1999 2009 gps derived velocity field for this region based on the continuous and survey mode observations the results confirm a right lateral slip of 7 1 mm yr for the north tabriz fault in agreement with previous studies this rate is consistent with earthquakes of magnitude 7 7 3 and recurrence times of 250 300 yr the higher spatial coverage of the new network shows that deformation is localized in the vicinity of the chalderan south gailatu siah cheshmeh khoy fault and the north tabriz fault however the eastern end of the north tabriz fault appears to cross mount bozgush rather than following its southern foothills this new velocity field does not indicate the 8 mm yr of nne ssw extension suggested earlier for the region but rather shows lower extension of 1 2 1 mm yr across the eastern segment of the north tabriz fault and the talesh to the west the chalderan and the western north tabriz fault segment act like pure strike slip faults without significant extension or compression the denser network in the rudbar earthquake region ms 7 3 1992 shows no significant motion across the fault suggesting that the recurrence time of earthquakes like the rudbar event must be very long the lack of substantial compressive strain and the sharp azimuth change of the velocity vectors in the transition zone from arabia to lesser caucasus motion imply that processes other than extrusion possibly related to old subduction or delamination contribute to active deformation

the 2012 august 11 ahar earthquakes consequences for tectonics and earthquake hazard in the turkish iranian plateau we have examined the faulting in the 2012 august 11 mw 6 4 and 6 3 ahar nw iran earthquakes using a combination of field mapping remote sensing observations of tectonic geomorphology the cross correlation of optical satellite images and the inversion of seismic waveforms the first event was close to pure strike slip and the second was an oblique combination of thrust and strike slip motion mapped surface ruptures indicate at least one of these events accommodated mostly right lateral strike slip motion on an e w striking plane the occurrence of these earthquakes highlights the spatially distributed deformation in nw iran which has implications for both hazard assessment the ahar events killed over 300 people and injured over 3000 and also tectonic models of the region furthermore these earthquakes demonstrate that the tectonics of the ahar area is characterized by strike slip faulting and a component of shortening and not the previously suggested extension

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

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

active tectonics of the turkish iranian plateau 1 this paper examines how active faulting in the turkey iran caucasus region accommodates the arabia eurasia collision and the velocity field observed by gps the overall shortening across the zone is in general spatially separated partitioned into right lateral strike slip in the turkish iranian plateau and thrusting in the greater caucasus a band of counterclockwise rotating nw se right lateral strike slip faults accommodates a nw se gradient in ne directed velocity relative to eurasia between the black and caspian seas a nnw sse band of previously unrecognized oblique normal faults is present on the turkey iran border we estimate the offsets on faults from geomorphological features and show that these offsets can be achieved in 5 2 ma at present rates this implies a reorganization of deformation in the collision zone at that time after the initial collision at 12 ma probably in response to mantle induced dynamic uplift

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