miocene nne directed extensional unroofing in the menderes massif southwestern turkey structural investigations in the central part of the menderes massif odemio kiraz submas sif reveal the presence of a large scale low angle extensional shear zone with a top to the n ne shear sense regional ductile deformation was accompanied by the intrusion of two syntectonic granodiorites that have been dated with the 40 ar 39 ar method one hornblende isochron age of 19 5 1 4 ma and two biotite plateau ages of 13 1 0 2 and 12 2 0 4 ma respectively constrain that extension was already active in the early miocene successive tectonic denudation of the odemio kiraz submassif resulted in the formation of a n dipping detachment fault in which ductile fabrics were severely reworked by cataclasis under decreasing temperature syntectonic neogene sediments currently exposed along the southern margin of the gediz graben were deposited in the hanging wall of the extensional fault system and were tectonically emplaced onto the cataclasites during progressive exhumation minor rotation c 15 caused southward tilting of the sediments ongoing nne directed extension created a steep normal fault that truncates the detachment fault and constitutes the southern boundary fault of the gediz graben

tectonic evolution of the gediz graben field evidence for an episodic two stage extension in western turkey western turkey is one of the most spectacular regions of widespread active continental extension in the world the most prominent structures of this region are e w trending grabens e g gediz and buyuk menderes grabens and intervening horsts exposing the menderes massif this paper documents the result of a recent field campaign field geological mapping and structural analysis along the southern margin of the modern gediz graben of pliocene 5 ma age this work provides field evidence that the presently low angle ductile brittle detachment fault is cut and displaced by the high angle graben bounding normal faults with total displacement exceeding 2 0 km the evolution of the n s extension along the gediz graben occurred during two episodes each characterized by a distinct structural styles 1 rapid exhumation of menderes massif in the footwall of low angle normal fault core complex mode during the miocene 2 late stretching of crust producing e w grabens along high angle normal faults rift mode during pliocene quaternary times separated by a short time gap the later phase is characterized by the deposition of now nearly horizontal sediments of pliocene age in the hanging walls of the high angle normal faults and present day graben floor sediments the evolution of extension is at variance with orogenic collapse and or back arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the aegean cyprean subduction zone consequently it is misleading to describe the miocene sediments exhumed on shoulders of the gediz graben as simple graben fill

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

an active bivergent rolling hinge detachment system central menderes metamorphic core complex in western turkey two symmetrically arranged detachment systems delimit the central menderes metamorphic core complex and define a bivergent continental breakaway zone in the anatolide belt of western turkey structural analysis and apatite fission track thermochronology show that a large east trending syncline within the alpine nappe stack in the central part of the orogen is related to late miocene early pliocene to recent core complex formation the syncline formed as a result of two opposite facing rolling hinges in the footwalls of each of the two detachments back rotation of the syncline limbs suggests that the detachments rotated from an initial dip of 408 608 to a currently shallow orientation of 08 208

water geochemistry of the seferihisar geothermal area izmir turkey abstract the na cl thermal waters of seferihisar have measured temperatures of 30 153 c and conductivities of 7400 55200 s cm they issue from upper cretaceous to paleocene bornova melange rocks which are made up of sandstone shale intercalations conglomerate mafic submarine volcanics limestone lenses serpentinite and limestone bodies and their complexes through the intersection of faults the clay rich zones of the overlying neogene terrestrial sediments cap the system the heat source is the high geothermal gradient caused by graben tectonics of the area na and cl ions mainly dominate the chemistry of thermal waters thus thermal waters of the seferihisar area appear to be mixtures of groundwaters and seawater the seawater contribution in thermal waters varies from 10 to 80 assessments from empirical chemical geothermometers mineral equilibria and silica mixing model applied on the thermal waters of the seferihisar geothermal area suggest that the temperatures of the reservoir systems vary between 60 and 180 c the seferihisar geothermal area has been physically divided into five main groups and estimated reservoir temperatures provided by the entire methods give the increase as doganbey burnu karakoc spa doganbey tuzla and cumali spa areas in ascending order of reservoir temperature hydrogeochemical assessments indicate that thermal waters were mixed with cold waters before and or after heating at depth in different proportions the results of mineral equilibrium modeling indicate that the thermal waters of seferihisar are undersaturated with respect to gypsum and amorphous silica oversaturated with respect to calcite dolomite and aragonite and undersaturated or oversaturated with respect to quartz chalcedony and anhydrite

the role of the flexural rotation rolling hinge model in the tectonic evolution of the alasehir graben western turkey the alasehir graben is a well defined prominent extensional structure in western turkey generally trending e w and containing four sedimentary units at the beginning of graben formation during early middle miocene times the first fault system was active and responsible for the accumulation of the first and second sedimentary units in pliocene times a second fault system developed in the hanging wall of the first system and a third sedimentary unit was deposited the recently active third fault system separates older graben fill and a fourth sedimentary unit activity on each fault system caused the rotation and uplift of previous systems similar to the flexural rotation rolling hinge model but our field observations indicate that the rotated first fault system is also active allowing exhumation of larger amounts of rock units this paper documents that graben formation in western turkey is a sequential process its different periods are represented by three fault systems and associated sedimentation consequently recent claims using age data from only the second and or third sedimentary units to determine the timing of graben formation are misleading

aegean tectonics strain localisation slab tearing and trench retreat abstract we review the geodynamic evolution of the aegean anatolia region and discuss strain localisation there over geological times from late eocene to present crustal deformation in the aegean backarc has localised progressively during slab retreat extension started with the formation of the rhodope metamorphic core complex eocene and migrated to the cyclades and the northern menderes massif oligocene and miocene accommodated by crustal scale detachments and a first series of core complexes mccs extension then localised in western turkey the corinth rift and the external hellenic arc after messinian times while the north anatolian fault penetrated the aegean sea through time the direction and style of extension have not changed significantly except in terms of localisation the contributions of progressive slab retreat and tearing basal drag extrusion tectonics and tectonic inheritance are discussed and we favour a model 1 where slab retreat is the main driving engine 2 successive slab tearing episodes are the main causes of this stepwise strain localisation and 3 the inherited heterogeneity of the crust is a major factor for localising detachments the continental crust has an inherited strong heterogeneity and crustal scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation the dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate successive slab ruptures from the middle miocene to the late miocene have isolated a narrow strip of lithosphere still attached to the african lithosphere below crete the formation of the north anatolian fault is partly a consequence of this evolution the extrusion of anatolia and the aegean extension are partly driven from below asthenospheric flow and from above extrusion of a lid of rigid crust

magnetization of lower crust and interpretation of regional magnetic anomalies example from lofoten and vesteralen norway the interpretation of regional magnetic anomalies commonly observed over continental crust in both satellite and near surface magnetic data has remained enigmatic in its requirement for laterally extensive thick highly magnetic and deep seated sources presented here are the results of a detailed field analytical and experimental study of the magnetic mineralogy and magnetic properties of rocks from lofoten and vesteralen norway a province of deep seated origin with associated regional magnetic and gravity anomalies these rocks have a bulk magnetic character of surprising uniformity with susceptibilities hysteresis and curie temperatures defined solely by coarse grained magnetite stable remanence is observed in samples from sw lofoten but is not of significant magnitude the thermal enhancement of magnetic susceptibility the hopkinson effect is not important rocks from the deepest part of the section have the largest average susceptibilities 6 10 2 si and magnitudes of natural remanent magnetization nrm 5 10 4 a m2 kg these values of susceptibility together with the oft observed viscous character of the nrm suggest that these granulite facies lithologies particularly those of sw lofoten are perfect examples of lower crustal sources of typical regional magnetic anomalies furthermore these intermediate pressure granulites define a unique magnetic petrology especially for mafic compositions at higher grades of metamorphism high pressure granulites and eclogites or lower grades greenschist and amphibolite facies such magnetite bearing assemblages will be unstable and their high or low grade equivalents will be only weakly magnetic this evidence and these conclusions may be used to constrain models of lower crustal sources of regional magnetic anomalies over stable cratons it portrays the lower crust as a highly magnetic unit defined by metamorphic grade with a curie isotherm of 575 c magnetite and magnetization parallel to the ambient geomagnetic field induced and viscous components

ion probe and fluid inclusion evidence for co seismic fluid infiltration in a crustal detachment we have investigated the geochemical pattern of fluid infiltration in the extensional detachment of tinos island cyclades greece ion microprobe o isotope analyses and fluid inclusion studies have been conducted in strain fringes developing around pyrite blasts in the mylonite of the shear zone micro scale traverses in quartz and calcite fibres show that 18o increases from 17 18 to 20 21 in 1 mm towards the blast drops of 3 in 200 m then rises again in the direction of growth 18o variations are interpreted as transient influxes of exotic fluids into the shear zone between periods of closed system buffering by the host rock fluid inclusions trapped in the fibres show fluctuating salinities 0 4 wt nacl eq and densities that reflect drops of the pore pressure from lithostatic 1 to hydrostatic 0 4 values during fringe growth isotopic and microthermometric data are consistent with models of seismic pumping developed for compressive shear zones we therefore suggest that co seismic pore pressure variations developed suction forces sufficient to drive large scale fluid migration in the tinos detachment as in convergent tectonic settings

long wavelength undulations of the seismic moho beneath the strongly stretched western anatolia summary western turkey provides spectacular examples of the two end member models of deformation of the continental lithosphere with strain localization along the north anatolian fault and distributed north south extension along the aegean coast to provide constraints on the mechanisms of continental deformation we present a new high resolution image of lithospheric structurealonga 650kmtransectcrossingwesternanatoliaat28 elongitudefromtheblack sea to the mediterranean more than 2600 receiver functions are computed from records of teleseismic earthquakes at 40 broadband seismic stations with an average spacing of 15km lateral variations of crustal thickness and vp vs ratio are inferred from both h k and common conversion point stacks we observe long wavelength variations of moho depth from 31km in the thrace basin to 25km beneath the marmara sea 32km beneath the izmir ankara suture 25km beneath the menderes massif and 20km on the coast of the mediterranean no mid or lower crustal interface is visible in the migrated depth section and seismic discontinuities are confined to the shallow crust the small amplitude and long wavelength lateral variations of the moho topography suggest that viscous flow in a hot lower crust has smoothed out the lateral variations of crustal thickness induced by cenozoic continent continent collision thecrust mantleboundaryisflatbeneaththecentralandsouthernmenderesmassif the rougher moho topography and more heterogeneous crust of the marmara region likely result from transtension in the north anatolian fault zone superimposed onto aegean extension the moho of the subducted african lithosphere is observed dipping northward between 40 and 60km depth at the southern end of the profile the abrupt termination of the subducted slab only 50km to the north of the mediterranean coast confirms the slab tear inferred from previous tomographic studies

the menderes massif of western turkey and the cycladic massif in the aegean do they really correlate based on lithostratigraphic comparisons the menderes massif has been correlated with the cycladic massif thereby implying that the eastern mediterranean consists of a narrow pre alpine basement belt which is laterally continuous over a long distance and which experienced a similar alpine orogenic history our work indicates that the architecture the age of basement and the pre alpine and alpine tectonometamorphic history of both massifs differ fundamentally from each other the menderes massif consists of remnants of the cycladic massif which overly an exotic unit the menderes nappes both massifs do not represent lateral continuations which has implications for palaeogeographic reconstructions

geochemical and temporal evolution of cenozoic magmatism in western turkey mantle response to collision slab break off and lithospheric tearing in an orogenic belt post collisional magmatism in western anatolia began in the eocene and has occurred in discrete pulses throughout the cenozoic as it propagated from north to south producing volcano plutonic associations with varying chemical compositions this apparent sw migration of magma tism and accompanying extension through time was a result of the thermally induced collapse of the western anatolian orogenic belt which formed during the collision of the sakarya and tauride anatolide continental blocks in the late paleocene the thermal input and melt sources for this prolonged magmatism were provided first by slab break off generated aesthenospheric flow then by lithospheric delamination related aesthenospheric flow followed by tectonic extension driven upward aesthenospheric flow the first magmatic episode is represented by eocene granitoid plutons and their extrusive carapace that are linearly distributed along the izmir ankara suture zone south of the marmara sea these suites show moderately evolved com positions enriched in incompatible elements similar to subduction zone influenced subalkaline magmas widespread oligo miocene volcanic and plutonic rocks with medium to high k calc alkaline compositions represent the next magmatic episode partial melting and assimilation fractional crystallization of enriched subcontinental lithospheric mantle derived magmas were important processes in the genesis and evolution of the parental magmas which experienced decreasing subduction influence and increasing crustal contamination during the evolution of the eocene and oligo miocene volcano plutonic rocks collision induced lithospheric slab break off provided an influx of aesthenospheric heat and melts that resulted in partial melting of the previously subduction metasomatized mantle lithosphere beneath the suture zone producing the eocene and oligo miocene igneous suites the following magmatic phase during the middle miocene 16 14 ma developed mildly alkaline bimodal volcanic rocks that show a decreasing amount of crustal contamination and subduction influence in time both melting of a subduc tion modified lithospheric mantle and aesthenospheric mantle derived melt contribution played a significant role in the generation of the magmas of these rocks this magmatic episode was attended by region wide extension that led to the formation of metamorphic core complexes and graben systems aesthenospheric upwelling caused by partial delamination of the lithospheric root beneath the western anatolian orogenic belt was likely responsible for the melt evolution of these mildly alkaline volcanics lithospheric delamination may have been caused by peeling off during slab rollback the last major phase of magmatism in the region starting c 12 ma is represented by late miocene to quaternary alkaline to super alkaline volcanic rocks that show oib like geochemical features with progressively more potassic compositions increasing toward south in time these rocks are spatially associated with major extensional fault systems that acted as natural conduits for the transport of uncontaminated alkaline magmas to the surface the melt source for this magmatic phase carried little or no subduction component and was pro duced by the decompressional melting of aesthenospheric mantle which flowed in beneath the atte nuated continental lithosphere in the aegean extensional province this time progressive evolution of cenozoic magmatism and extension in western anatolia has been strongly controlled by the interplay between regional plate tectonic events and the mantle dynamics and provides a realistic template for post collisional magmatism and crustal extension in many orogenic belts

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

dynamic cyrstallization of chondrule melts of porphyritic olivine composition textures experimental and natural abstract melts of the same composition as has been defined for porphyritic olivine chondrules have been crystallized under controlled cooling conditions dynamic crystallization the full range of textures observed in such chondrules has been duplicated in the experimentally produced analogs the primary controlling factor in producing this range of textuures is the heterogeneous nucleation behavior in general if nuclei are present when cooling begins growth starts immediately at low degrees of supercooling and porphyritic textures result the shapes of the phenocyrsts depend on the growth rate which in turn depends on the cooling rate with high nucleation densities and modest to low cooling rates the textures are microporphyritic with generally equant euhedral phenocrysts as the nucleatio density decreases the phenocrysts become larger and as the cooling rate increases they become increasingly skeletal if nuclei are not present when cooling begins growth is delayed until subcritical sized embryos graduate to supercritical nuclei growth usually begins at some significant degree of supercooling depending on the cooling rate and how long it takes the embryos to become nuclei the shapes of the crystals depend on the degree of supercooling when growth is initiated and on the subsequent cooling rate the resulting textures vary from plate dendrites barred olivine chondrules to randomly oriented elongated skeletal crystals as the degree of supercooling and cooling rates decreases the results of a matrix of experiments set limits on the maximum melting temperatures of chondrule forming materials and the subsequent cooling rates based primarily on crystal shape the porphyritic textures develop best for this composition at melting temperatures less than 1590 c and cooling rates near 100 c hr and definitely less than 1000 c hr at cooling rates significantly less than 100 c hr the phenocrysts are generally larger than observed in chondrules and as cooling rates approach 1000 c hr they become more skeletal barred olivine chondrule textures form best from materials melted at higher temperatures and cooling rates in the range 1000 to 3000 c hr

menderes massif western turkey structural metamorphic and magmatic evolution a synthesis the menderes massif covers large areas in western turkey the better understanding of its tectono metamorphic history would provide insight for the alpine evolution of western turkey and the entire eastern mediterranean region this paper summarizes the available literature on the metamorphic rocks of western turkey and that of the menderes massif with special reference and emphasis to the papers presented in the special issue

tectonic significance of mafic volcanic rocks in a mesozoic sequence of the menderes massif west turkey the mesozoic platform sequence of the menderes massif consists of thick succession of detrital and carbonate rocks in this sequence there are mafic metavolcanic rocks at two different levels the first level of mafic metavolcanic intercalations is in the late triassic detrital rich series located in the caltasi formation which is the lowermost unit of the mesozoic platform the second level of the mafic metavolcanic rocks is located in the late cretaceous paleocene selcuk formation laying on top of the platform sequence the caltasi formation which is composed of mica schists thinly bedded cherts calc schist and mafic volcanic intercalations unconformably overlie the bayindir formation which consists of mica schists phyllites and white quartzites of palaeozoic or probably older age the mafic volcanic rocks in the caltasi formation are alkaline basalts with within plate characteristics and are formed during an intraplate extension the caltasi formation is conformably overlain by the kayaalti formation represented by calc schists dolomitic marbles and rudist and emery bearing massive marbles in ascending order the selcuk formation overlies the kayaalti formation and consists of a mica schist matrix with allochthonous blocks of mafic volcanic rocks metaperidotites metagabbros and massive marbles the mafic volcanic rocks in the selcuk formation are tholeiitic basalts and are petrologically similar to mid oceanic basalts the geological and geochemical characteristics of the mafic metavolcanic rocks in the caltasi formation indicate that during the late triassic the menderes platform was segmented probably by the opening of a branch of the neotethyan ocean between the late triassic and the late cretaceous the menderes carbonate platform was built up during the latest cretaceous early paleocene a slab of oceanic crust obducted on this platform and provided slices of mafic metavolcanic rocks into the selcuk formation

the determination of fault movement history from the interaction of local drainage with volcanic episodes the kula volcanic province lies in an area of active normal faulting in western turkey in this study we show that the interaction of the basalts with the local drainage and in particular the gediz river can be used to determine the history of fault movements downstream the lava flows have been studied previously and some of them dated we use these results and combine them with new field observations of lavas that flowed into the river valley to measure the rate of down cutting of the river and hence the rate of uplift of the footwall block due to movement of the graben bounding fault we show that there has been in general an acceleration of fault movement with time during the last 2 ma this increased activity of the graben bounding fault is matched by an intensification of volcanic activity an inferred four fold increase in fault movement rate over the last 0 2 ma has been matched by a similar increase in volume of volcanic activity

late alpine evolution of the central menderes massif western turkey the central menderes massif western turkey is characterized by an overall dome shaped alpine foliation pattern and a n nne trending stretching lineation a section through the southern flank of the central submassif along the northern margin of buyuk menderes graben has been studied there asymmetric non coaxial fabrics indicate that the submassif has experienced two distinct phases of alpine deformation a top to the n nne contractional phase and a top to the s ssw extensional event the former fabrics are coeval with a regional prograde barrovian type metamorphism at greenschist to upper amphibolite facies conditions this event known as the main menderes metamorphism is thought to be the result of internal imbrication of the menderes massif rocks along south verging thrust sheets during the collision of the sakarya continent in the north and the anatolide tauride platform in the south across the izmir ankara suture during the palaeocene eocene top to the s ssw fabrics represented by a well developed ductile shear band foliation associated with inclined and or curved foliation asymmetric boudins and cataclasites were clearly superimposed on earlier contractional fabrics these fabrics are interpreted to be related to a low grade greenschist retrogressive metamorphism and a continuum of deformation from ductile to brittle in the footwall rocks of a south dipping presently low angle normal fault that accompanied early miocene orogenic collapse and continental extension in western turkey a similar tectono metamorphic history has been documented for the northern flank of the dome along the southern margin of the gediz graben with top to the n nne extensional fabrics the exhumation of the central menderes massif can therefore be attributed to a model of symmetric gravity collapse of the previously thickened crust in the submassif area the central submassif is thus interpreted as a piece of ductile lower middle crust that was exhumed along two normal sense shear zones with opposing vergence and may be regarded as a typical symmetrical metamorphic core complex these relationships are consistent with previous models that the miocene exhumation of the menderes massif and cycladic massif in the aegean sea was a result of bivergent extension

the 40ar 39ar age of extensional ductile deformation and granitoid intrusion in the northern menderes core complex implications for the initiation of extensional tectonics in western turkey the simav detachment fault in the northern part of menderes core complex in western turkey separates cover sequence rocks with brittle deformation from high grade metamorphic core rocks and young granitoid intrusions the timing of shear zone formation and the intrusion of syn tectonic granitoids is constrained by 40ar 39ar geochronology on muscovite from mylonitic gneiss and biotite from the egrigoz granitoid 40ar 39ar data indicate that mylonitic deformation occurred at 22 86 0 47 ma whilst the cooling age of the granitoid is 20 19 0 28 ma the intrusion and cooling of the egrigoz granitoid occurred between 23 20 ma these data demonstrate that extensional deformation in the northern menderes core complex began before early miocene times and represents an early stage in the tertiary extensional tectonics of western turkey

hydrogeochemistry of the simav geothermal field western anatolia turkey thermal waters hosted by menderes metamorphic rocks emerge along fault lineaments in the simav geothermal area thermal springs and drilled wells are located in the eynal citgol and nasa locations which are part of the simav geothermal field studies were carried out to obtain the main chemical and physical characteristics of thermal waters these waters are used for heating of residences and greenhouses and for balneological purposes bottom temperatures of the drilled wells reach 163 c with total dissolved solids around 2225 mg kg surface temperatures of thermal springs vary between 51 c and 90 c all the thermal waters belong to na hco3 so4 facies the cold groundwaters are ca mg hco3 type dissolution of host rock and ion exchange reactions in the reservoir of the geothermal system shift the ca mg hco3 type cold groundwaters to the na hco3 so4 type thermal waters thermal waters are oversaturated at discharge temperatures for aragonite calcite quartz chalcedony magnesite and dolomite minerals giving rise to a carbonate rich scale gypsum and anhydrite minerals are undersaturated with all of the thermal waters boiling during ascent of the thermal fluids produces steam and liquid waters resulting in an increase of the concentrations of the constituents in discharge waters steam fraction y of the thermal waters of which temperatures are above 100 c is between 0 075 and 0 119 reservoir ph is much lower than ph measured in the liquid phase separated at atmospheric conditions since the latter experienced heavy loss of acid gases mainly co2 assessment of the various empirical chemical geothermometers and geochemical modelling suggest that reservoir temperatures vary between 175 c and 200 c

pattern of normal faulting in the gediz graben sw turkey hanging wall deformation of the fault systems controlling the southern margin of the gediz graben were investigated separately within the plio quaternary and neogene predominantly miocene deposits of the graben fill fault styles observed in both packages share many similarities in terms of geometry and comprise conjugate fault sets that show clustering of strike orientations predominantly around wnw ese but also sw ne and nw se directions the main difference between the two units is observable in terms of fault dips and rake of the slickenside lineations measured on the exposed fault planes both measurements show a uni modal distribution for the plio quaternary deposits but a tri modal distribution for the neogene deposits this variation is probably related to the geometrical modification of the older faults by the process of domino style back rotation in the hanging wall of higher order faults similarities among the two units are not limited to geometrical aspects of the fault systems but also counts for the orientation of the principal stress axes that controlled the deformation during the deposition of each sedimentary package inversion of the fault slip data showed that approximately n s oriented extension which varies in the range of nnw sse and nne ssw controlled the faulting during the accumulation of the entire graben fill with almost no evidence of change in the state of stress during the graben evolution however some heterogeneity in terms of stress field is observable among the fault systems formed within the same time frame this heterogeneity is probably related to poorly defined direction of extension in the graben indeed low ratio in the order of 0 25 suggests that 2 and 3 are close in magnitudes and the direction of extension is not well constraint with a potential of 2 3 axes permutations local stress field anomalies related to fault segment interaction could also contribute to the observed heterogeneity

the kula volcanic field western turkey the development of a holocene alkali basalt province and the adjacent normal faulting graben the kula province of western turkey provides an excellent example of an alkali basalt province in an area of active rifting this paper establishes the relationship between the generation of the basalts and the extension of the region the wide shallow terrestrial basin formed by early extension was subsequently cut through by narrow fault bounded grabens the genesis of alkali basalt magmas began soon after the concentration of the extension into two grabens 2 ma the basalts in the form of some 80 small cinder cones and associated lava flows and fields have a total volume of 2 3 km 3 this small volume reflects the small amount of extension in the region

miocene detachment in crete and exhumation p t t paths of high pressure metamorphic rocks a major problem posed by the geology of crete is the horizontal contact of an upper unit without miocene metamorphism onto a metamorphosed lower one with early miocene high pressure low temperature hp lt parageneses this very sharp contact is roughly parallel to the major oligo miocene thrust planes which were reactivated as a large scale detachment which allowed exhumation of high pressure units we describe the extensional deformation and the metamorphic evolution of the lower plate most first order deformation features relate to the retrogression from high pressure to low pressure conditions a n s pervasive stretching is observed everywhere often associated with a top to the north sense of shear the extreme variation of thickness of the phyllite quartzite nappe upper part of the lower plate is probably the result of large scale boudinage similar to the one seen in large outcrops the most important observation is the systematic occurrence of fresh carpholite immediately below the base of the tripolitza nappe except in northwestern crete where a late extensional shear zone is present deeper in the nappe pile carpholite is systematically retrograded this observation reveals a drastically different pt history for the upper part of the phyllite quartzite nappe it also suggests that the late extensional shear zone found along the northern side of crete cuts inside the metamorphic structure and brings the nonmetamorphosed tripolitza nappe directly in contact with the deeper parts of the phyllite quartzite nappe pt t paths suggest a fast temperature decrease in the top of the phyllite quartzite during retrogression and hence during the top to the north shear the deeper part of the phyllite quartzite nappe shows a low temperature regime throughout but its pt path includes an isothermal decompression in the first stage we produce a tentative map of domains having experienced similar pt trajectories during decompression the overall cool regime is related to the continuous underthrusting of cola continental units during exhumation isothermal decompression observed in the core of the phyllite quartzite nappe implies fast exhumation during extension and the faster cooling of the upper part is related to a continuous displacement toward the north of a cooler unit during exhumation single grain 39ar 40ar ages obtained on phengites 15 25 ma in various structural sites are in good agreement with these conclusions and with the geological context suggesting that underthrusting of cold units at the front the accretionnary complex occurred contemporaneously with unroofing below a north dipping detachment near the top of the wedge the age of this detachment is bracketed between the end of the high pressure event 20 ma and the deposition of the breccia early to middle miocene in the neogene basins

structural lithological and geodynamic controls on geothermal activity in the menderes geothermal province western anatolia turkey western turkey belongs to the regions with the highest geothermal potential in the world resulting in significant electricity production from geothermal resources located predominantly in the menderes massif although geothermal exploitation is increasingly ongoing geological and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood several studies on the menderes massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin this paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs on the basis of field studies we suggest that crustal scale low angle normal faults convey hot fluids to the surface and represent the first order control on geothermal systems at the basin scale connected on low angle normal faults kilometric high angle transfer faults are characterized by dilational jogs where fluids may be strongly focused in addition favourable lithologies in the basement e g karstic marble could play a critical role in the localization of geothermal reservoirs finally a compilation of geochemical data at the scale of the menderes massif suggests an important role of the large mantle thermal anomaly which is related to the hellenic subduction heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low angle faults hence geothermal activity in the menderes massif is not of magmatic origin but rather associated with active extensional tectonics related to the aegean slab dynamics i e slab retreat and tearing

flow of mantle fluids through the ductile lower crust helium isotope trends heat and mass are injected into the shallow crust when mantle fluids are able to flow through the ductile lower crust minimum 3he 4he ratios in surface fluids from the northern basin and range province western north america increase systematically from low crustal values in the east to high mantle values in the west a regional trend that correlates with the rates of active crustal deformation the highest ratios occur where the extension and shear strain rates are greatest the correspondence of helium isotope ratios and active transtensional deformation indicates a deformation enhanced permeability and that mantle fluids can penetrate the ductile lithosphere even in regions where there is no substantial magmatism superimposed on the regional trend are local high 3he 4he anomalies indicating hidden magmatic activity and or deep fluid production with locally enhanced permeability identifying zones with high resource potential particularly for geothermal energy development

tectonic significance of deformation patterns in granitoid rocks of the menderes nappes anatolide belt southwest turkey deformation fabrics in proterozoic cambrian granitic rocks of the cine nappe and mid triassic granites of the bozdag nappe constrain aspects of the tectonometamorphic evolution of the menderes nappes of southwest turkey based on intrusive contacts and structural criteria the proterozoic cambrian granitic rocks of the cine nappe are subdivided into older orthogneisses and younger metagranites the deformation history of the granitic rocks documents two major deformation events an early pre alpine deformation event dpa during amphibolite facies metamorphism affected only the orthogneisses and produced predominantly top to ne shear sense indicators associated with a ne trending stretching lineation the younger metagranites are deformed both by isolated shear zones and by a major shear zone along the southern boundary of the cine submassif we refer to this alpine deformation event as da3 da3 shear zones are associated with a n trending stretching lineation which formed during greenschist facies metamorphism kinematic indicators associated with this stretching lineation reveal a top to south sense of shear the greenschist facies shear zones cut the amphibolite facies structures in the orthogneisses 207pb 206pb dating of magmatic zircons from a metagranite which crosscuts orthogneiss containing amphibolite facies top to ne shear sense indicators shows that dpa occurred before 547 2 1 0 ma such an age is corroborated by the observation that mid triassic granites of the cine and bozdag nappes lack dpa structures the younger top to south fabrics formed most likely as a result of top to south alpine nappe stacking during the collision of the sakarya continent with anatolia in the eocene

evolution of hydrothermal regime along a crustal shear zone tinos island greece 1 structural cathodoluminescence and sims 18o analyses of quartz calcite veins are combined to constrain the evolution in space and time of fluid infiltration in an exhuming detachment shear zone tinos island cyclades greece careful description of vein arrays shows that the plumbing system evolved into an interconnected network just beneath the ductile to brittle transition microtextures of quartz and calcite infilling veins display deformed relics and newly precipitated grains high resolution 18o mapping in relics yields a steady quartz calcite fractionation of 2 at 400 c whereas fractionation increases in neograins from 2 to 5 in 190 m toward the fault or a 150 c temperature fall cooling is associated with a shift of fluid stable isotope signature from 15 to 0 beneath the detachment results are interpreted as advective removal of heat by massive infiltration of surface derived fluids over depths of 10 15 km fluid penetration was promoted by the coalescence of late ductile early brittle veins as the exhuming footwall crossed the ductile brittle transition only small amounts of fluids penetrated the ductile crust beneath the transitional rheology

helium isotopic signature of modern and fossil fluids associated with the corinth rift fault zone greece implication for fault connectivity in the lower crust abstract helium isotopic ratios of modern groundwaters and of fossil fluids trapped in secondary calcites from fault planes have been measured along the southern corinth rift in order to investigate the nature of fluids circulating in these fault zones and to set constraints on tectonic processes responsible for this extension the observed isotopic ratios of modern fluids range from the air composition to moderately radiogenic compositions 0 15 0 4 ra with ra being the atmospheric 3 he 4 he ratio whereas fossil fluids display more radiogenic compositions 0 04 to 0 15 ra suggesting that they have been trapped deeper in the fault zone in the absence of significant atmospheric contamination these compositions result from mixing of a deep radiogenic and hot fluid with cold and shallow air saturated aquifer waters the absence of a mantle he signal in the corinth rift fluids is remarkable and evidences the lack of active volcanic fluids in the basin it further suggests that the fault system is not connected at depth with zones where mantle he might have been trapped at the scale of the corinth rift this observation suggests that faults are rooted in the upper crust if extension results from displacement of the crust above a north dipping shear zone then this shear zone should be relayed at depth through the lower crust by impermeable ductile deformation at a larger scale it appears that basins in the western side of the aegean host crustal helium whereas basins in the anatolian side present systematically mantle he this he isotope distribution is difficult to explain by symmetrical tectonic evolution of the aegean domain and could instead be related to the recent propagation of the north anatolian fault naf propagation of the naf may have recently disturbed hydrothermal circulations established after miocene extension by progressively reactivating the western basins with a different style of tectonic deformation re localising most of the fault controlled flow pathway in shallower basins and as a consequence displacing the fluids mixture toward a crustal origin

helium isotopes in alpine regions abstract the isotopic composition of helium has been determined for a variety of groundwaters from springs and boreholes in the alps and adjacent regions the main alpine block in france italy switzerland and austria is characterized by a virtual absence of mantle derived 3he in near surface groundwaters in contrast adjacent areas where crust has been thinned by extension to the west in the rhone valley and ardeche to the north in the rhine valley and to the east in the vienna and pannonian basins mantle derived helium is clearly identified helium and undoubtedly other gases are introduced by melts whose generation is associated with crustal thinning however the surface distribution of mantle helium covers a much larger than that of associated surface volcanics this probably results from the dispersion of helium following its solution in groundwaters the po and the molasse neogene sedimentary basins developing by loading on the south and the north sides of the alps respectively have helium with typical crustal composition and a mantle component cannot be resolved these results clearly indicate the control of tectonics on the distribution of helium isotopes in the alpine regions

3 d imaging of the upper crust beneath the denizli geothermal region by local earthquake tomography western turkey abstract the denizli basin and its surroundings are one of the regions that have high seismic activity and rich geothermal fields in western anatolia in the first half of year 2000 an increasing seismic activity was observed around the denizli basin without a large mainshock occurrence a temporary seismic network consisting of 28 stations were deployed to observe the seismic activity in the region by the scientific and technological research council of turkey marmara research center earth and marine science institute tubitak mam emsi in this study one and three dimensional vp and vp vs structure of the denizli basin have been determined by using the travel times of the 635 recorded earthquake data firstly one dimensional inversion schema was performed to stabilize initial velocity model and to have more reliable hypocentral locations then an iterative and simultaneous three dimensional inversion procedure was carried out to obtain 3 d high resolution seismic velocity models furthermore to assess the solution quality of our inversion we conducted a series of resolution tests we concluded high resolution 3 d vp and vp vs seismic velocity models for the upper 20 km of the crust beneath the denizli basin and surroundings and interpreted the results in the context of known geologic and tectonic units the resulting 3 d vp models define the geometry of the basin sediment thickness and intrusive magmatic bodies as well as regions of anomalous velocity the vp vs models help to constrain the location and geometry of the faults zones of weakness and gas or fluid saturated formations with high pore pressure zones all tomographic results show that there is a strong correlation between local seismicity and the high vp and vp vs anomalies consequently this relationship indicates that the reason of the high seismicity in the denizli basin depends on activity of hydrothermal system as well as tectonic regime

processes of late cretaceous to late miocene episodic thrust sheet translation in the lycian taurides sw turkey the lycian taurides of sw turkey consist of an allochthonous mesozoic passive margin succession that was episodically detached from its autochthon and translated southeastwards between latest cretaceous to late miocene times a combination of structural analysis sedimentology palaeontology and geochemistry allows subdivision of this orogenic event into 1 latest cretaceous trench passive margin collision causing ophiolite obduction and detachment of the koycegyiz thrust sheet 2 mid late eocene continent continent collision renewing southeastwards thrusting and causing detachment of the teke dere thrust sheet and yavus thrust sheets 3 miocene extensional collapse of the orogen with southeastwards translation of the allochthon coeval with rift basin formation in the hinterland

complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis the main exhumation of the menderes massif western turkey occurred along an originally n dipping datca kale main breakaway fault that controlled depositions in the kale and the gokova basins during the oligocene early miocene interval the isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface in the early miocene e w trending n and s dipping graben bounding faults fragmented the exhumed dome shaped massif the development of half grabens by rolling master fault hinges has allowed further exhumation of the central menderes massif after the pliocene high angle normal faults cut all of the previous structures this model suggests that the menderes massif is a single large metamorphic core complex that has experienced a two stage exhumation process

lithosphere tearing at step faults response to edges of subduction zones abstract slab edges are a relatively common feature in plate tectonics two prominent examples are the northern end of the tonga subduction zone and the southern end of the new hebrides subduction zone near such horizontal terminations of subduction trenches ongoing tearing of oceanic lithosphere is a geometric consequence we refer to such kinks in the plate boundary as a subduction transform edge propagator or step other steps are the north and south ends of the lesser antilles trench the north end of the south sandwich trench the south end of the vrancea trench and both ends of the calabria trench volcanism near steps is distinct from typical arc volcanism in some cases slab edges appear to coincide with mantle plumes using 3d mechanical models we establish that step faults are stable plate tectonic features in most circumstances in the probably rare cases that the resistance to fault propagation is high slab break off will occur relative motion along the transform segment of the plate boundary often is non uniform and the step is not a transform plate boundary in the rigid plate tectonics sense of the phrase step propagation may result in substantial deformation rotation topography and sedimentary basins with a very specific time space evolution surface velocities are substantially affected by nearby steps

two dimensional resistivity imaging in the kizildere geothermal field by mt and dc methods abstract magnetotelluric mt and schlumberger dc surveys were conducted to identify conductive zones inside metamorphic complex in the easternmost part of b menderes graben in this study using these surveying data creation of some two dimensional images of the shallow and deeper parts of the area was aimed broadband 200 0 002 hz mt and schlumberger data were acquired along four profiles crossing the b menderes graben with a total of 18 mt and 19 dc stations these data were modeled using two dimensional inverse techniques the main findings are 1 presence of wide conductive regions with very low resistivity

late orogenic crustal extension in the northern menderes massif western turkey evidence for metamorphic core complex formation the simav metamorphic core complex of the northern menderes massif western turkey consists of a plutonic tertiary and metamorphic precambrian core footwall separated from an allochthonous cover sequence hanging wall by a low angle ductile to brittle extensional fault zone i e detachment fault the core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres two main deformation events have affected the core rocks the first deformational event d1 was developed within the precambrian metamorphic rocks the second event d2 associated with the tertiary crustal extension includes two distinct stages stage one is the formation of a variably developed ductile mylonitic deformation d2d in metamorphic and granitic core rocks under greenschist facies conditions the majority of the mylonites in the study area have foliations that strike nnw to nne and dip sw to se stretched quartz and feldspar grains define the mineral lineation trending sw ne direction and plunging gently to sw the kinematic indicators indicate a top to ne sense of shear stage two formation of brittle deformation d2b that affected all core and cover rocks d2b involves the development of cataclasites and high angle normal faults an overall top towards the north sense of shear for the ductile mylonitic fabrics in the core rocks is consistent with the n s regional extension in western turkey

quantifying rates of detachment faulting and erosion in the central menderes massif western turkey by thermochronology and cosmogenic 10be exhumation of rocks in extensional tectonic settings results from a combination of normal faulting and erosion but the relative contribution of these processes has rarely been quantified here we present new low temperature thermochronological data and the first 10 be based catchment wide erosion rates from the boz dag region in the central menderes massif which has experienced nne ssw extension since the miocene the slip rate of the shallow dipping gediz detachment fault which defines the northern flank of the boz dag block is 4 3 3 0 1 2 mm a 1 as constrained by zircon u th he ages of c 4 2 ma in the footwall apatite and zircon u th he and fission track ages from the northern flank of the boz dag block yield exhumation rates of 0 6 2 km ma 1 beneath the gediz detachment whereas those on the southern flank are only 0 2 0 6 km ma 1 erosion of catchments on the northern and southern flanks proceeds at rates of 80 180 and 330 460 mm ka 1 respectively this marked contrast is a combined effect of the topographic asymmetry of the boz dag block and differences in rock erodibility if these erosion rates persisted in the past rock exhumation on the northern flank occurred predominantly by tectonic denudation whereas rocks on the southern flank were mainly exhumed by erosion

helium isotope variations in turkey relationship to tectonics volcanism and recent seismic activities the distribution of helium isotope ratios in the various tectonic provinces of turkey is examined through a synthesis of previously published data and the results of a recent survey along the north anatolian fault zone nafz following the catastrophic 1999 earthquakes the r ra values where r sample 3he 4he and ra air 3he 4he cover a wide range from 0 05 to 7 87 and the mantle derived helium is clearly identified in most locations the mantle derived component is high 50 of total he in a regions of central and eastern anatolia both of which are associated with historically active volcanoes and b the seismically active west to central segment of nafz while the mantle contribution reaches a maximum at nemrut volcano in eastern anatolia a region of dominantly compressional tectonics and with moderate enthalpy geothermal fields it is relatively low 50 in the western anatolian extensional province even though this region has the highest geothermal potential the average 3he enthalpy ratios estimated for the different provinces suggest lithospheric stretching and rise of the geotherm as the major mechanism of high heat flow yet limited intrusive activity in western anatolia is suggested as the reason for the comparatively low he additions and consequently low 1 7 106 atoms j 3he enthalpy ratios a more extensive magmatic activity appears to be responsible for the greater input of both heat and helium in eastern and central anatolia with intra province 3he enthalpy variations from 3 1 106 atoms j in eastern to 0 25 106 atoms j in central anatolia reflecting the ageing of hydro magmatic systems the relatively high 3he concentrations in low enthalpy waters of northern anatolia 2 8 106 atoms j are particularly significant since there is no evidence of volcanic activity associated with the strike slip motion along the seismically active segment of nafz continuous monitoring of he isotope compositions along nafz should lead to a better understanding of this apparent anomaly as well as the relationship if any between he isotope variations and seismic activities in this region

the geological signature of a slab tear below the aegean in this paper we explore the geology of the aegean region in the miocene to identify the geological signature of a first order slab tear observed in all tomographic models from 15 to 8 ma the tear is associated spatially and timely with a fast clockwise rotation of the external hellenides alkaline volcanism high temperature metamorphic domes with a predominance of north dipping detachments and south westward migration of granitoid intrusions these features suggest a warmer geodynamic environment during the rotation and the impact of a hot mantle flow associated with the tear the 8 ma duration between the first high temperature metamorphic domes in the centre of the archipelago and the beginning of the fast rotation may correspond to the time needed for the slab to bend stretch and finally tear

complex layered deformation within the aegean crust and mantle revealed by seismic anisotropy continental lithosphere can undergo pervasive internal deformation often distributed over broad zones near plate boundaries however because of the paucity of observational constraints on three dimensional movement at depth patterns of flow within the lithosphere remain uncertain endmember models for lithospheric flow invoke deformation localized on faults or deep shear zones or alternatively diffuse viscous fluid like flow here we determine seismic rayleigh wave anisotropy in the crust and mantle of the aegean region an archetypal example of continental deformation our data reveal a complex depth dependent flow pattern within the extending lithosphere beneath the northern aegean sea fast shear wave propagation is in a north south direction within the mantle lithosphere parallel to the extensional component of the current strain rate field in the south central aegean where deformation is weak at present anisotropic fabric in the lower crust runs parallel to the direction of palaeo extension in the miocene the close match of orientations of regional scale anisotropic fabric and the directions of extension during the last significant episodes of deformation implies that at least a large part of the extension in the aegean has been taken up by distributed viscous flow in the lower crust and lithospheric mantle

the geoelectrical structure of northwestern anatolia turkey the magnetotelluric method has been employed to generate a geoelectrical model that will reveal the rich geological pattern and dynamic character of western and northwestern anatolia turkey magnetotelluric data were collected from 53 sites along a profile of 290 km from the dardanelles to the alasehir graben magnetotelluric data were in the range of 0 00055 hz to 320 hz the models were obtained through 2 d joint inversion of transverse electric and transverse magnetic modes lateral changes in geoelectrical models are verified by using gravity and magnetic data in addition some of the seismological data presented here agree with proposed models that suggest a brittle ductile structure boundary at a depth of 20 km generally speaking a regional extensional regime caused reduction in the thickness of the crust and consequent uplift towards the south the constructed model delineates the western part of the north anatolian fault zone along the biga peninsula the current patterns of volcanic activity on the biga peninsula and at kula are related to conductive spots presented in the models the border of the gordes basin located between the izmir ankara suture zone and the menderes massif is also well delineated the north anatolian fault zone presents a pattern in which density and susceptibility anomalies attain relatively high values fillings covering most of the surface have lower density and susceptibility values than those of underlying structures

reservoir and hydrogeochemical characterizations of geothermal fields in salihli turkey abstract geothermal and hydrochemical characteristics of thermal waters in the salihli geothermal area are described in this study this geothermal area is geographically divided into five main groups kursunlu caferbey greenhouse ufuruk and sart geothermal fields in the study area the outlet temperatures of the thermal waters are between 30 and 90 c their discharges are between 2 and 80 l s in springs and the depths of wells vary between 200 and 1189 m hydrochemical analysis results suggest four different water types of na hco 3 ca mg hco 3 ca na hco 3 and ca mg so 4 in kursunlu caferbey greenhouse sart and ufuruk respectively cold waters are mainly dominated by the hco 3 and so 4 anions and na ca and mg cations results of environmental isotope and chemical analysis show that the thermal waters are of meteoric origin and the major hydrogeochemical processes show that the thermal waters may be mixing of their end members and or water rock interaction at high temperature conditions the mixed thermal waters are replenished by rainwater and or groundwater at various depths ec tritium and ec chloride plots indicated shallow and deep circulating groundwater types in the study area assessment of the various empirical chemical geothermometers and geochemical modelling suggests that the aquifer temperature in the study area is about 160 c the thermal waters are mostly supersaturated with respect to carbonate minerals calcite aragonite and dolomite at all temperatures these are likely to cause scaling problems during production and utilization of thermal water

what caused the denudation of the menderes massif review of crustal evolution lithosphere structure and dynamic topography in southwest turkey the deformation of earth s lithosphere in orogenic belts is largely forced externally by the sinking slab but can also be driven by internal delamination processes caused by mechanical instabiliti

variation in noble gas isotopic composition of gas samples from the aegean arc greece abstract in contrast to most other arcs with oceanic plate subduction the aegean arc is characterized by continent continent subduction noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc 2 islands in the back arc region and 7 sites in the surrounding areas the 3he 4he ratios of the samples ranged from 0 027ra to 6 2ra ra denotes the atmospheric 3he 4he ratio of 1 4 10 6 demonstrating that even the maximum 3he 4he ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems which are equal to the morb value of 8 1 ra regional variations in the 3he 4he ratio were observed both along and across the arc the maximum 3he 4he ratio was obtained from nisyros volcano located in the eastern end of the arc and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano across the volcanic arc the 3he 4he ratio decreased with an increasing distance from the arc front reaching a low ratio of 0 063ra in macedonia which suggested a major contribution of radiogenic helium derived from the continental crust at nisyros a temporal increase in 3he 4he ratio due to ascending subsurface magma was observed after the seismic crisis of 1995 1998 and mantle neon was possibly detected the maximum 3he 4he ratio 6 2ra in the aegean region which is significantly lower than the morb value is not probably due to crustal assimilation at shallow depth or addition of slab derived helium to morb like mantle wedge but inherent characteristics of the subcontinental lithospheric mantle sclm beneath the aegean arc

fault kinematics in supradetachment basin formation menderes core complex of western turkey abstract the neogene alasehir supradetachment basin in western turkey occurs in the footwall of the modern alasehir gediz graben and is a major component of the aegean extensional province in anatolia that developed during the late cenozoic exhumation of the menderes core complex the size geometry accommodation space and internal structure stratigraphy of this basin were strongly controlled by the kinematics and interplay of four different fault generations throughout its early miocene pleistocene evolution the e w striking nne dipping 10 30 alasehir detachment fault separates the high grade crystalline rocks of the core complex below from the neogene deposits of the basin in the hanging wall above the basin parallel synthetic and antithetic high angle normal faults represent a block faulting stage of the continued horizontal extension that terminated the northerly slip along the detachment surface and produced horst graben structures in and across the basin these faults were also responsible for the back tilting of the basinal strata into steeper dips and the rotation of the previously formed faults into gently dipping planes the mutually crosscutting relationships between the intra basinal low angle and basement involved high angle and normal faults indicate their contemporaneous development and operation the nne striking basin perpendicular oblique slip hinge faults are reminiscent of transfer cross faults in both continental and oceanic extension and divide the supradetachment basin into a series of fault blocks with their own internal structure and stratigraphy differential uplift and exhumation of the core complex rocks along these hinge faults and the varied displacement and slip along and across them within the basinal strata caused differential extension and block uplift leading to the formation of local unconformities in the supradetachment basin significant changes in the dip directions and strike orientations of the sedimentary beds and the observed deviations from the inferred direction of maximum extension in the adjacent fault blocks resulted from rotational deformation due to hinge faulting fault segmentation of the alasehir basin as a result of extension parallel hinge faulting is a characteristic feature of its supradetachment basin evolution

ductile brittle transition along the alasehir detachment fault and its structural relationship with the simav detachment fault menderes massif western turkey abstract western turkey has experienced extensional deformation since the tertiary an early phase of extensional deformation resulted in the formation of detachment faults in the northern part of the menderes massif the alasehir and simav detachment faults the footwalls of these two detachment faults are mid crustal level rocks the alasehir detachment fault developed in metamorphic rocks and in a syn extensional intrusion the salihli granodiorite the salihli granodiorite shows a gradual change from undeformed isotropic granodiorite to protomylonite mylonite and ultramylonite towards its upper structural levels the deformed granodiorite in turn grades into a cataclastic zone whose uppermost part is the alasehir detachment surface this gradual upward change from the undeformed granodiorite to a brittlely deformed detachment surface suggests that tertiary extension resulted in a ductile deformation at depth and the ductilely deformed granitoids were brought to shallower depths where they were brittlely deformed the metamorphic wall rocks of the intrusion are also mylonitized structurally upward a similar transition has also been found in the footwall of the simav detachment fault the upper part of which is also a cataclastic zone leading to the simav detachment fault separating the low grade metamorphic rocks and or non metamorphic rocks in its hanging wall from mainly high grade metamorphic rocks and syn tectonic granitoids in its footwall during ductile extension greenschist facies grade mylonitic deformation developed in the metamorphic rocks and the granitoids shear sense indicators along the two shear zones show top to n ne sense shear consistent with the regional cenozoic extension direction in western turkey available radiometric age data from the granitoids in the footwall of the two detachment faults suggest that the cenozoic extension in western turkey was initiated in oligocene to early miocene and the simav detachment fault is older than the alasehir detachment fault extensional features of these detachment faults suggest that the simav detachment fault characterise the earlier stage of the tertiary extensional tectonics of the menderes massif and later stage of this deformation resulted in the development of the alasehir detachment fault

sedimentation of the neogene recent alasehir gediz continental graben system used to test alternative tectonic models for western aegean turkey abstract the alasehir gediz graben exemplifies clastic sedimentation in a long lived continental half graben in a semi arid setting developed within relatively incompetent metamorphic rocks early miocene to recent rift related sediments are exhumed on both flanks of the graben allowing detailed three dimensional study during the early miocene small fan delta lobes were shed northwards from the rugged menderes metamorphic massif into a bordering lacustrine basin during early to mid miocene time large alluvial fans prograded northwards into this basin through drainage to the aegean sea was established as the basin widened and filled discrete lobes of coarse alluvial fan sediments of latest miocene pliocene age also shedding northwards are likely to have been climatically influenced quaternary alluvium party infills the modern alasehir rift basin the sedimentary information can be used to test two alternative tectonic models for the alasehir graben in the first model an e w graben bounded by high angle faults was active during latest miocene recent time whereas earlier miocene sedimentation was controlled by n s faulting related to a n s compressional stress regime in the second hypothesis the alasehir graben was initiated much earlier in the early miocene and was then either continuously or episodically active until recent our results especially facies and palaeocurrent data from alluvial sediments indicate that clastic sedimentation was controlled by mainly e w faulting in a n s stress regime assuming the early miocene clastic sediments are correctly dated this supports the second long lived extension model however rather than steady state extension for ca 15 ma the sedimentary evidence and regional context are consistent with a pulsed extension model whereby initial early to mid miocene extension and related clastic sedimentation was followed by a second phase of extension in latest miocene pliocene time the driving force of initial early miocene extension was probably gravity spreading towards a south aegean subduction zone whereas the inferred second extension pulse is seen as being triggered by westward tectonic escape of anatolia towards the extending aegean back arc region

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

shear heating in extensional detachments implications for the thermal history of the devonian basins of w norway article i nfo the supra detachment basins in western norway were formed during lower to middle devonian in the hangingwall of the extensional system of detachments known as the nordfjord sogn detachment zone nsdz the basins experienced elevated peak temperatures up to 345 c adjacent to the main detachment fault during the terminal stages of the extension in this study we show that the heat generated by the de formation of the rocks within the shear zone of the detachment also known as shear heating played a role in the thermal evolution of the entire region during the extension and could have induced the elevated peak temperatures of the supra detachment basins we numerically analyse the influence of the rheology and the deformation style within the shear zone the rate of exhumation of the footwall and the thickness of the sedimentary accumulation on the top of the system the model reproduces the elevated temperatures recorded in the supra detachment basins where locally 100 c and 25 of the total heat budget can be attrib uted to shear heating we show that this additional heat source may increase the peak temperatures of the hangingwall as far as 5 km away from the detachment

detection of lineaments in denizli basin of western anatolia region using bouguer gravity data the aim of this study is to investigate the geostructural boundaries of the eastern part of western anatolia to achieve this three methods horizontal gradient analytic signal and tilt angle were used with the application of each method to the bouguer gravity data the common lineaments were determined using maximum values of the horizontal gradient analytic signal maps and zero contours of the tilt angle maps the basement topography was also produced using the parker oldenburg algorithm then the produced lineaments were compared with the active fault map of the region the results suggested that although a good agreement between the current work and earlier work exists the new four lineament regions were also detected we concluded that this work will lead to better understanding of anatolian geostructural and its impact on the larger scale geological processes

the stress regime in a rotliegend reservoir of the northeast german basin in situ stresses have significant impact either positive or negative on the short and long term behaviour of fractured reservoirs the knowledge of the stress conditions are therefore important for planning and utilization of man made geothermal reservoirs the geothermal field gros schonebeck 40 km north of berlin germany belongs to the key sites in the northeastern german basin we present a stress state determination for this lower permian rotliegend reservoir by an integrated approach of 3d structural modelling 3d fault mapping stress ratio definition based on frictional constraints and slip tendency analysis the results indicate stress ratios of the minimum horizontal stress s hmin being equal or increasing 0 55 times the amount of the vertical stress s v s hmin 0 55s v and of the maximum horizontal stress s hmax 0 78 1 00s v in stress regimes from normal to strike slip faulting thus acting stresses in the 4 100 m deep reservoir are s v 100 mpa s hmin 55 mpa and s hmax 78 100 mpa values from hydraulic fracturing support these results various fault sets of the reservoir are characterized in terms of their potential to conduct geothermal fluids based on their slip and dilatation tendency this combined approach can be adopted to any other geothermal site investigation

bivergent extension in orogenic belts the menderes massif southwestern turkey the central menderes massif is characterized by an overall dome shaped foliation pattern and a north northeast trending stretching lineation the asymmetry of shear bands and quartz c axis fabrics on either side of the structural dome demonstrate a top to thenorth northeastshearsenseinthenorthernpartandatoptothesouth southwestshear sense in the southern part of the submassif i e a bivergent downdip movement this suggests a symmetric collapse of the alpine menderes orogenic belt along two extensional shearzones conjugateshearbandsandsymmetricquartzc axisfabricsintheeast trendingtransitionzonedemonstrateacoaxialdeformationbetweenthetwoextensiondomains bivergent extension in the menderes massif is in contrast to asymmetric extension in the aegeansea here thestill activehellenicsubductionzoneevolvedfromanadvancingplate boundary associated with crustal thickening into a retreating plate boundary in oligocene miocene time southward rollback of the subducting plate during continuous northward subduction allowed asymmetric top to the north northeast extension in the back arc region during the exhumation of the cycladic core complexes in western turkey the arrival of the thick continental crust of the menderes massif halted subduction and probably caused the symmetric collapse of the massif because the high potential energy of the thickened crust was no longer supported by subduction

helium carbon relationships in geothermal fluids of western anatolia turkey abstract we investigate the helium carbon and oxygen hydrogen isotopic systematics and co2 3he ratios of 8 water and 6 gas samples collected from 12 geothermal fields in western anatolia turkey 3he 4he ratios of the samples r normalized to the atmospheric 3he 4he ratio ra 1 39 10 6 range from 0 27 to 1 67 and are significantly higher than the crustal production value of 0 05 fluids with relatively high r ra values are generally found in areas of significant heat potential kizildere and tuzla fields co2 3he ratios of the samples ranging from 1 6 109 to 2 3 1014 display significant variation and are mostly higher than values typical of an upper mantle source 2 109 the 13c co2 and 13c ch4 values of all fluids vary from 8 04 to 0 35 and 25 80 to 23 92 vs pdb respectively stable isotope values 18o d of the geothermal waters are conformable with the mediterranean meteoric water line and indicate a meteoric origin the temperatures calculated by gas geothermometry are significantly higher than estimates from chemical geothermometers implying that either equilibrium has not been attained for the isotope exchange reaction or that isotopic equilibration was disturbed due to gas additions en route to the surface evaluation of he co2 abundances indicates that hydrothermal degassing and calcite precipitation controlled probably by adiabatic cooling due to degassing significantly fractionate the elemental ratio co2 3he in geothermal waters such processes do not affect gas phase samples to anywhere near the same extent for the gas samples mixing between mantle and various crustal sources appears to be the main control on the observed he c systematics however crustal inputs dominate the co2 inventory considering that limestone is the main source of carbon 70 to 97 of the total carbon inventory the carbon flux from the crust is found to be at least 20 times that from the mantle as to the he inventory the mantle derived component is found to vary up to 21 of the total he content and is probably transferred to the crust by fluids degassed from deep mantle melts generated in association with the elevated geotherm and adiabatic melting accompanying current extension the range of 3he enthalpy ratios 0 000032 to 0 19 10 12 cm3 stp j of fluids in western anatolia is consistent with the release of both helium and heat from contemporary additions of mantle derived magmas to the crust the deep faults appear to have facilitated the deep circulation of the fluids and the transport of mantle volatiles and heat to the surface