teleseismic evidence for a break off subducting slab under eastern turkey abstract we present seismic images of the upper mantle beneath eastern turkey determined by teleseismic tomography the data are measured precisely from seismograms recoded by the eastern turkey seismic experiment network consisting of 29 portable stations and 2 permanent stations our results show that obvious high velocity high v anomalies of up to 2 are interrupted beneath eastern turkey and subcrustal earthquakes occurred along these high v anomalies pronounced low velocity low v anomalies are visible from the arabian foreland basin in the southwest to the caucasus region in the northeast which extend down to about 400 km depth these low v anomalies are consistent with the existence of late cenozoic volcanism in the region these results provide new constraints on the geodynamic processes in the east anatolian plateau suggesting that the break off of the arabian slab may play an important role in the formation of the anatolian plateau and the volcanism in the region these processes might be related to the collision of the arabian plate with the eurasian plate

the neogene recent hatay graben south central turkey graben formation in a setting of oblique extension transtension related to post collisional tectonic escape structural data and a regional tectonic interpretation are given for the ne sw trending hatay graben southern turkey within the collision zone of the african arabian and eurasian anatolian plates regional gps and seismicity data are used to shed light on the recent tectonic development of the hatay graben faults within upper cretaceous to quaternary sediments are categorized as of first second and third order type depending on their scale location and character normal oblique and strike slip faults predominate throughout the area the flanks of the graben are dominated by normal faults mainly striking parallel to the graben that is 045 225 in contrast the graben axis exhibits strike slip faults trending 100 200 together with normal faults striking 040 060 and 150 190 a subset strikes 110 130 similarly orientated normal faults occur throughout upper cretaceous to pliocene sediments whereas strike slip faults are mostly within pliocene sediments near the graben axis stress inversion of slickenline data from mostly pliocene sediments at ten suitable locations all near the graben axis show that 3 directions minimum stress axis extension direction are uniform in the northeast of the graben but orientated at a high angle to the graben margins more variable 3 directions in the southwest may reflect local block rotations during miocene times the arabian and anatolian plates collided forming a foreland basin associated with flexurally controlled normal faulting during the late miocene there was a transition from extension to transtension oblique extension the neotectonic hatay graben formed during the plio quaternary in a transtensional setting in the light of modern and ancient comparisons it is suggested that contemporaneous strain was compartmentalized into large scale normal faults on the graben margins and mainly small scale strike slip faults near the graben axis overall the graben reflects plio quaternary westward tectonic escape from a collision zone towards the east to a pre or syn collisional zone to the west in the mediterranean sea

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

a numerical method for determining the state of stress using focal mechanisms of earthquake populations application to tibetan teleseisms and microseismicity of southern peru the numerical method described in this paper enables the study in terms of stress of the kinematics of seismic faults provided by focal mechanisms this method assumes a mean state of stress in the source region and is based on the simple mechanical model used for fault population analysis which supposes slip in the direction of the resolved shear stress acting on the fault plane the proposed algorithm first defines compressional and tensional zones resulting from superimposition of the compressional and tensional quadrants limited by the nodal planes this enables one to test the data homogeneity furthermore this restricts the space where the principal stress axes have to be searched then for each principal stress reference whose location is constrained by above confined zones the r value chosen equal to 2 1 3 1 is computed which fits the slip vector on each nodal plane this permits one to select a set of preferred seismic fault planes from a set of auxiliary planes finally a state of stress is computed from the preferred seismic fault plane set using the non linear simplex method already applied to fault populations this algorithm is constructed so as to avoid two major difficulties misleading estimation of the deviatoric stress tensor which may result from excessive emphasis by minimizing the residuals by a least squares method if some of the data are wrong and a lengthy prospection of the stress references over all the space of directions this calculation does not take into account possible changes of the strike and dip of the nodal planes however we use rotations of nodal planes in agreement with the first arrival data to test the compatibility of these data with the computed state of stress tibetan teleseisms and southern peruvian microseisms are analyzed and results are compared with kinematics of superficial recent and active faults measured in field in the same regions this suggests that major seismic events may give a good evaluation of the regional mean state of stress focal mechanisms of the small events are also modelled by a mean stress deviator but this differs significantly from the regional state of stress in southern peru deduced from quaternary faulting this may be due to imprecise location of the small events however some movements are strongly different from those predicted by the computed mean stress deviator this suggests that small fault kinematics surely depend on the regional state of stress but that local effects may control the small deformations

a review of te and se systematics in hydrothermal pyrite from precious metal deposits insights into ore forming processes abstract pyrite is one of the most common minerals in many precious and base metal hydrothermal ore deposits and is an important host to a range of trace elements including au and co and the semi metals as se sb te and bi as such in many hydrothermal ore deposits where pyrite is the dominant sulphide phase it can represent a major repository for these elements furthermore the concentrations and ratios of au as and co in pyrite have been used to infer key ore forming processes however the mechanisms controlling the distribution of te and se in pyrite are less well understood here we compare the te and se contents of pyrite from a global dataset of carlin type orogenic au and porphyry epithermal deposits to investigate 1 the potential of pyrite to be a major repository for these elements and 2 whether te and se provide insights into key ore forming processes pyrite from carlin type low sulphidation and alkaline igneous rock hosted epithermal systems is enriched in te and se compared to pyrite from high sulphidation epithermal and porphyry cu deposits orogenic au pyrite is characterised by intermediate te and se contents there is an upper solubility limit for te as a function of as in pyrite similar to that established for au by reich et al 2005 and this can be used to identify te present as telluride inclusions which are common in some epithermal porphyry and orogenic au deposits physicochemical fluid parameters such as ph redox and temperature as well as crystal chemistry control the incorporation and concentration of se and te in pyrite neutral to alkaline fluids have the ability to effectively mobilise and transport te fluid boiling in porphyry epithermal systems as well as wall rock sulphidation and oxidation in carlin type and orogenic au deposits can effectively precipitate te in association with pyrite and au in contrast se concentrations in pyrite apparently vary systematically in response to changes in fluid temperature irrespective of ph and f o 2 hence we propose that the se contents of pyrite may be used as a new geo thermometer for hydrothermal ore deposits furthermore the comparison of bulk ore and pyrite chemistry indicates that pyrite represents the major host for te and se in carlin type and some epithermal systems and thus pyrite can be considered to be of economic interest as a potential source for these elements

evaluation of prehistoric land use intensity in the rhenish loessboerde by canonical correspondence analysis a contribution to lucifs abstract almost every agricultural activity has an effect on vegetation in fact human impact is the most important and continuous factor in the vegetational development of landscapes that have been settled since prehistoric times hence vegetational changes are the key to the evaluation of past human impact human impact in the pollen record can be assessed in two ways positively by so called cultural indicators pollen of cultivated plants such as cereals and of plants that tolerate human impact and negatively by the disappearance of pollen from plants that do not tolerate human impact the percentage values of cultural indicator pollen can serve as measure for the intensity of human impact this approach however neglects negative indicators of human impact which provide information on the response of the natural vegetation to anthropogenic influences here we introduce first results obtained by applying a multivariate statistical technique to extract a proxy for human impact from pollen data we use canonical correspondence analysis which has been applied successfully for the connection and spatial analysis of pollen data from the rhenish loessboerde the long term objective is to develop land use models derived from pollen data which allow diachronic comparison of the intensity and character of human impact for different landscapes of the rhine catchment as a result maps of land use intensity can be evaluated by maps of archaeological settlement density which are developed by an archaeological working group in cologne in the lucifs program

relation of alkaline volcanism and active tectonism within the evolution of the isparta angle sw turkey the isparta angle ia is formed along the boundary of the african and eurasian plates by ne and nw striking faults north of the antalya gulf in sw turkey the ne striking strike slip burdur fault bounds the ia to the west and is probably the continuation of the pliny system of the hellenic arc the nw striking aksehir fault bounds it to the east platform type parautochthonous mesozoic carbonate sequences such as the beydag and anamas akseki occur in the western and eastern parts of the ia respectively whereas allochthonous ophiolite nappes include the antalya beysehir hoyran and lycian nappes the ia and adjacent areas are divided into three areas the teke the antalya and the akseki fragments by ne nw and n striking active strike slip faults with normal components ia region volcanics are alkaline and hyperkaline in character potassic ultrapotassic and locally occur as subvolcanic stocks and dikes they can be traced between the afyon and isparta regions these volcanics consist mainly of

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

palaeostress determinations from fault kinematics application to the neotectonics of the himalayas tibet and the central andes this paper concerns the determination of the stress deviator from a set of striated faults or of focal mechanisms of earthquakes southern tibet and the cuzco region of the high andes illustrate the applied methodology then the spatial and temporal changes in the tectonic regimes of tibet and central andes are briefly examined the quaternary present day stress patterns in these two high plateaus favour models explaining the spatial changes in the state of stress at a large wavelength as a result of a compensated elevated topography major temporal changes in the tectonic regimes are attributed tentatively to uplift for the tibetan plateau and for the already elevated andean plateau to changes in the magnitude of the boundary forces due to subduction processes

plio quaternary stress state in the burdur basin sw turkey abstract this study defines the plio quaternary to present day stress regime in the burdur basin located at the northeastern end of the fethiye burdur fault zone in sw turkey this fault length which is considered the landward continuation of the pliny strabo trench is an important feature in sw turkey the inversion slip vectors measured on fault planes indicate a consistent normal faulting stress regime during plio quaternary time continuing into recent times as indicated by earthquake focal mechanism inversions both states have consistent nw se trending horizontal minimum stress axes 3 the orientation of fault sets is predominantly around the ne sw direction in the major fethiye burdur fault zone making the extension nw se the mean stress ratio is 0 74 indicating a triaxial stress state which is clearly different from radial extension the nw se extension is probably responsible for the formation of the burdur basin during plio quaternary time this extension which is probably caused by slab pull force due to the subduction process along the cyprus arc produces a dominant normal motion along the fbfz

strain and rotation rate from gps in tibet anatolia and the altiplano 1 deformation measured by regional gps networks in continental plateaus reflects the geologic and tectonic variability of the plateaus for two collisional plateaus tibet and anatolia and one noncollisional the altiplano we analyze the regional strain and rotation rate by inverting gps velocities to calculate the full two dimensional velocity gradient tensor to test the method we use gridded velocities determined from an elastic block model for the eastern mediterranean middle east region and show that to a first order the deformation calculated directly from the gps vectors provides an accurate description of regional deformation patterns principal shortening and extension rate axes vertical axis rotation and two dimensional 2 d volume strain dilatation are very consistent with long term geological features over large areas indicating that the gps velocity fields reflect processes responsible for the recent geologic evolution of the plateaus differences between geological and gps descriptions of deformation can be attributed either to gps networks that are too sparse to capture local interseismic deformation or to permanent deformation that accrues during strong earthquakes the altiplano has higher internal shortening magnitudes than the other two plateaus and negative 2 d dilatation everywhere vertical axis rotation changes sign across the topographic symmetry axis and is due to distributed deformation throughout the plateau in contrast the collisional plateaus have large regions of quasi rigid body rotation bounded by strike slip faults with the opposite rotation sense from the rotating blocks tibet and anatolia are the mirror images of each other both have regions of positive dilatation on the outboard sides of the rotating blocks positive dilatation in the aegean correlates with a region of crustal thinning whereas that in eastern tibet and yunnan province in china is associated with an area of vertical uplift rollback of the hellenic trench clearly facilitates the rotation of anatolia rollback of the sumatra burma trench probably also enables rotation about the eastern syntaxis of tibet

comment on miocene to quaternary tectonostratigraphic evolution of the middle section of the burdur fethiye shear zone south western turkey implications for the wide inter plate shear zones tectonophysics 690 336 354

variations in the crustal structure beneath western turkey summary we use teleseismic receiver functions to investigate the crustal structure at two locations in westernturkey using seismic data recorded on small arrays of temporary broad band seismographs the results from these analyses are compared with receiver function results from the gdsn station anto on the anatolian plateau in central turkey the crust is 30 km thick in the region of western turkey where active normal faulting reveals present day extension in the upper crust and alkali basaltic volcanism reveals recent extension within the subcrustal lithosphere the crust is 34 km thick further east where crustal extension is still evident but less pronounced in the anatolian plateau which is not currently extending the crust is 38 km thick the level of extension estimated from these measurements of crustal thickness implies a b factor of 1 2 this value agrees with the amount of extension estimated in the upper crust from the integrated seismic strain rate b factor of 1 3 from surface faulting b factor of 1 25 and from the amount of extension in the subcrustal lithosphere estimated from the volcanism b factor 2 all indicating that the extension is approximately uniformly distributed vertically throughout the lithosphere the moho transition in this region appears to thin slightly as the degree of extension increases westwards

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range

slab detachment beneath eastern anatolia a possible cause for the formation of the north anatolian fault in this paper we discuss the possibility that the north anatolian fault naf results from the deep deformation of the slab beneath the bitlis hellenic subduction zone we described the tectonic evolution of the anatolia aegean area in three main steps before during and after the formation of the naf we remark that the tectonic conditions that are assumed to have triggered the formation of the naf i e collision to the east and extension to the west was already achieved before the onset of that strike slip fault system we also highlight that the formation of the naf was accompanied by the uplift of the turkish iranian plateau and by a surge of volcanism in the eastern anatolia collisional area and probably by the acceleration of the aegean trench retreat we show tomographic images from global p wave model of piromallo and morelli c piromallo a morelli p wave tomography of the mantle under the alpine mediterranean area j geophys res 108 2003 doi 10 1029 2002jb001757 showing that the slab beneath the bitlis collisional belt is not continuous and that its possible rupture pursues to the west at least up to cyprus and possibly up to the eastern end of the hellenic trench all these observations suggest that the plate tectonic re organization occurred in the late miocene early pliocene in the region results from slab break off in the bitlis area and from its lateral propagation to the west this idea is tested in analogue laboratory experiments which confirm that the break of the slab under the collisional belt may trigger 1 the acceleration of slab retreat to the west due to the increase in slab pull force 2 the indentation of the continent in the collisional area and 3 produce the conditions that permit the lateral escape of material towards the west and the formation of the naf

slab temperature and thickness from seismic tomography 2 izu bonin japan and kuril subduction zones delay times from teleseismic and local p wave arrivals are used to invert for a high resolution three dimensional velocity model beneath the northwest pacific the model shows high velocity slabs with average velocity anomalies of the order of 3 4 assuming the positive velocity deviations in the subducting lithosphere are to first order due to a temperature anomaly the results of a theoretical slab temperature profile based on the diffusion equation are converted to a synthetic slab velocity model temperature variations between the ambient mantle and the interior of the slab are converted to p wave velocity perturbations using dvp dt 4 8 10 4 km s 1 c 1 a nonlinear optimization scheme compares the tomograms obtained via tomography to the theoretically predicted models in order to determine the optimal values for slab thickness and mantle potential temperature using 1180 100 c as the potential temperature thickness estimates of 88 8 km 85 8 km and 84 8 km are obtained for the izu bonin japan and kuril slabs respectively a correlation exists between slab thickness and age which is strong if mantle temperature variations along the slab strike can be ruled out in the process of estimating slab thickness the predicted slab velocity model is used as a filter to enhance the initial minimum norm tomographic result the initial tomogram is modified to closely resemble the synthetic slab tomogram by using only null space components the use of the null space components guarantees that the enhanced solution will satisfy the original seismic delay times the enhanced slab images show very continuous and narrow slabs compared to the initial tomographic results

lead isotope systematics and pyrite trace element geochemistry of two granitoid associated mesothermal gold deposits in the southeastern lachlan fold belt

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

the mechanical interaction between the propagating north anatolian fault and the back arc extension in the aegean we use fracture mechanics concepts to analyse the large scale deformation of anatolia and the aegean our purpose is to characterize the process of propagation of the north anatolian fault naf our approach incorporates long term geological constraints in dislocation modelling of present day gps velocities that allows for internal deformation in regions between major structures unravelling the superposition of two deformation fields now interacting in the aegean propagating naf and back arc extension permits us to characterise the large scale damage zone at the western end of the naf and to determine slip rates for the main structures the contemporary slip rate profile of the naf shows that it apparently behaves like a transform fault for 75 of its length the process zone corresponds to a rapid southwestward tapering of the naf slip rate modelling slip rate distributions for the naf under stress free conditions shows that the development of the process zone depends on the boundary conditions imposed at the hellenic arc our stress free modelling suggests a scenario for the evolution of the naf 1 at an earlier stage before the naf had reached the aegean it was not under the influence of hellenic arc pull its slip rate profile is modelled to have a half elliptical shape corresponding to a crack in elastic solid and an elastically strained anatolian lithosphere 2 the present day naf penetrates the aegean and a large process zone has developed due to interaction with the aegean extension and the hellenic arc pull elastic strains in the anatolian lithosphere are relaxed and the naf resembles a transform fault the models that we present suggest that changes in subduction zone behaviour should influence all of the boundaries associated with anatolian extrusion

laminated sediments human impact and a multivariate approach a case study in linking palynology and archaeology steisslingen southwest germany abstract situated in the alpine foreland lake steisslingen provides sediments covering the last 16 000 sidereal years the exceptional value as an environmental archive is due to large laminated sections found in several long cores counting of organic varves allowed the establishment of a detailed varve based age model a high resolution pollen analysis for the period 5457 bc to 813 ad was carried out and compared with an archaeological mapping of a 5 km radius around lake steisslingen the combined interpretation of the palynological and archaeological evidence facilitates a reconstruction of the settlement history and the evolution of the landscape over the last eight millenia several important aspects of vegetational and settlement history are illuminated the mathematical ordination method of correspondence analysis is used to extract the main dimension of explanation from the pollen data a single curve is generated and thought to reflect human impact the validity of this assumed proxy is tested against the vegetational and archaeological evidence of the micro scale area since neolithic times from the steisslingen example we conclude that human impact is the most important and in a mathematical sense continuous factor in vegetational development of those landscapes which are settled since prehistoric times

extensional compressional tectonics associated with the aegean arc comparison with the andean cordillera of south peru north bolivia extensional compressional tectonics are analysed along the convergent boundaries of the aegean arc and of the andean cordillera of south peru and north bolivia this paper deals only with deformations of miocene pliocene and pleistocene ages the prevailing regime in the aegean basin is extensional yet two compressional tectonic phases of u miocene l pliocene and of l pleistocene age have been recorded they are also known in many places all around the mediterranean thus forces that induce compressional tectonics in the aegean seem to have their origin outside the region they seem to be linked with changes in the conditions of convergence change in rate between the arabo african and eurasian plates beneath the andean cordillera of south peru north bolivia the subduction zone plunges at an angle of 25 30 as it does under the aegean arc there as in the aegean sea tectonics are predominantly extensional and several short lived compressional phases break up this extensional regime the latter may also be induced by changes of the conditions of convergence here between the nazca and south american plates beneath central peru north of the nazca ridge the subduction zone plunges at a small angle about 10 there neotectonic deformations are different in the recent they are essentially compressional or expressed by strike slip faulting geological data from the aegean and andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries

on the geodynamics of the aegean rift abstract the aegean rift is considered to be either a classic backarc basin or the result of the westward escape of anatolia or the effect of a gravitational collapse of an over thickened lithosphere here these models are questioned we alternatively present a number of geodynamic and magmatic constraints suggesting a simple model for the genesis of the extension as being related to the differential advancement of the upper lithosphere over a heterogeneous lower african plate the greek microplate overrides the ionian oceanic segment of the african plate faster than the anatolian microplate over the thicker levantine more continental segment this setting is evidenced by gps velocity gradient in the hangingwall of the hellenic cyprus subduction system and requires a zone of rifting splitting the hangingwall into two microplates this mechanism is unrelated to the replacement of retreated slab by the asthenosphere as typically occurs in the backarc of west directed subduction zones the supposed greater dehydration of the ionian segment of the slab is providing a larger amount of fluids into the low velocity channel at the top of the asthenosphere allowing a faster decoupling between the greek microplate and the underlying mantle with respect to the anatolian microplate slab ruptures associated with the differential retreat controlled by the inherited lithospheric heterogeneities in the lower plate and the proposed upwelling of the mantle suggested by global circulation models would explain the occurrence and coexistence of slab related and slab unrelated magmatism

isotopic geochemistry of the sawayaerdun orogenic type gold deposit tianshan northwest china implications for ore genesis and mineral exploration the sawayaerdun gold deposit is hosted by carbonaceous metasediments and is considered to be the largest muruntau type gold deposit in the chinese tianshan metallogenic belt gold mineralization at sawayaerdun occurs in quartz veins associated with three major hydrothermal events an early barren quartz vein stage middle stage mineralized quartz veins with pyrite and late carbonate quartz veins the isotopic compositions of quartz and sulfides from the sawayaerdun gold deposit show some variation but are generally comparable to those of other orogenic type gold deposits fluids trapped in early stage quartz have a 18o range of 13 6 to 15 4 d of 48 to 75 13c of 0 5 to 4 2 and 30si of 0 2 to 0 in contrast isotopic compositions of fluids trapped in middle stage quartz have 18o values of 6 7 to 14 7 d of 56 to 110 13c of 0 4 to 10 1 and 30si of 0 3 to 0 diagenetic and hydrothermal pyrite have similar sulfur 1 8 to 0 9 and pb isotopic values that are associated with host rock compositions the early stage 18o and 13c rich fluids are probably derived from metamorphic decarbonation of the sedimentary host rock at depth leading to the precipitation of early barren quartz veins in the middle stage a decrease in the regional pressure and temperature regime could have resulted in the incorporation of external fluids into the ore forming system these external fluids with isotopic signatures similar to that of the host rock and generally rich in 34s and radiogenic pb mixed with original ore forming fluids to generate extensive metal precipitation late stage fluids trapped by calcite veins show isotopic compositions similar to meteoric water indicating the cessation of hydrothermal fluid circulation at sawayaerdun occurred at this time the metallogenetic model illustrated by stable and pb isotopes is also consistent with fluid inclusion studies in sawayaerdun the development of mineralization at sawayaerdun is strongly linked to fluid mixing as witnessed by the isotopic signatures of fluids from identified ore bearing zones the isotopic compositions of other anomalous zones at sawayaerdun are similar to those of the mineralized zones suggesting a high potential for further exploration 2012 elsevier b v

the dynamics of the eastern mediterranean and eastern turkey summary in this study we investigate the dynamics of the region that includes greece the aegean sea and asia minor in a least squares inversion we solve for a continuous strain rate field and corresponding velocity field that satisfies 872 gps data the estimate of the geodetic strain rate field provides constraints for our dynamic analysis next we separately solve the depth integrated 3 d force balance equations for depth integrated deviatoric stresses within the lithosphere in which body force input comes from differences in vertically integrated vertical stress or differences in gravitational potential energy per unit area gpe these gpe estimates calibrate the absolute magnitudes of deviatoric stresses that are acting within the lithosphere further we investigate the sensitivity of our stress field solutions by using two different crustal structure models one from compiled crustal structure estimates obtained primarily from relatively recent seismic observations and the other from the crust 2 0 model in an iterative least squares inversion we then solve for stress field boundary conditions that when added to the contribution of deviatoric stresses associated with gpe differences provides a best fit to the directions of principal axes and relative magnitudes of the principal axes of the rates of strain obtained in the kinematic analysis robust features that arise from the boundary condition solution are nne forcing along the southern boundary east of about 33 e 0 5 1 2 1012 n m 1 with a rapid anticlockwise rotation of forces to the west of this along with an outward pulling force 0 4 1012 n m 1 directed ssw along the entire hellenic arc segment this force system along the hellenic arc can be interpreted as a result of slab rollback the total depth integrated 3 d deviatoric stresses in the final dynamic solution provides an excellent match to the deformation indicators throughout the region with vertically integrated stress magnitudes of order 0 5 2 5 1012 n m 1 we use constraints from derived stress magnitudes together with gps defined scalar values of strain rate magnitude to define bulk effective viscosities of the lithosphere depth averaged effective viscosities for the entire lithosphere are high within the black sea of order 0 7 3 1023 pa s relative to surrounding continental lithosphere north anatolian shear zone northern aegean sea and gulf of corinth are characterized by low depth averaged viscosities of order 1 5 1021 pa s deviatoric stresses from gpe differences and boundary condition effects combine in surprising ways in some regions resulting in near total stress cancellation in areas such as the southern aegean sea and portions of the central anatolian block gpe differences combine with boundary condition effects along the eastern segment of the north anatolian fault naf in a way that is compatible with the hypothesis that motion on the naf was facilitated by slab detachment beneath east anatolia and dynamic uplift of east anatolian plateau in general gpe differences play a nearly equal role as boundary condition influences in their contribution to the total deviatoric stress field the low depth integrated deviatoric stress magnitudes throughout the region suggest that zones of active deformation are facilitated by dramatic weakening mechanisms throughout the lithosphere

quaternary stress regime change in the hatay region se turkey in this study we determine the plio quaternary to present day stress regime acting in the hatay region located at the northeastern corner of the east mediterranean region the modern state of stress is obtained from inversion of focal mechanism solutions of shallow earthquakes this inversion identifies a dominantly extensional stress regime with a ne trending h m i n 3 axis at the present day the stress regime determined from inversion of slip vectors measured on fault planes confirms that this regime is extensional in the studied area both the kinematics and chronologies of fault slip vectors show that the stress state changed from an earlier strike slip regime to a younger extensional stress regime with a consistent ne trending h m i n 3 axis the change from strike slip to extensional stress regimes probably occurred during the quaternary regionally both stress regimes induce sinistral displacement on the east anatolian fault and dead sea fault systems the north anatolian fault naf is a dextral strike slip fault which runs about 1400 km from east to west and has been active since collision between the eurasian and arabian plates together with the sinistral east anatolian fault the naf intracontinental deformation zone contributes to the westward extrusion of anatolia as a consequence of northward drift of arabia consequently the late cenozoic stress regimes acting in the hatay region result from the coeval influence of forces due to 1 the subduction processes in the west and southwest 2 the continental collision in the east and 3 the westward escape of the anatolian block however the timing of the temporal stress transition suggests that the quaternary stress regime change resulted from subduction processes with the extensional stress regime in the hatay region being mainly attributable to roll back of the mediterranean subducted slab along the cyprus arc

responses of the upriver valley sediment to holocene environmental changes in the paju area of korea abstract multidisciplinary paleoproxy data from five sedimentary cores uj 03 06 07 10 and 12 recovered from the broad flat upriver valley in the paju area of korea are presented twelve ams radiocarbon dates from cores uj 03 and 12 provided a high resolution holocene record for the sedimentary sequence ranging from about 8000 ybp to the present from 6400 to 4400 14 c ybp 7100 5000 cal ybp the sediments were dominantly poorly sorted medium to coarse sands containing angular to subangular pebbles suggesting that the materials were locally derived the increased abundance of coarse grained sediment was attributed to intensified rainfall during the mid holocene despite the dense regional vegetational cover this period probably corresponded to the holocene climate optimum in the korean peninsula total organic carbon toc values showed a marked increase from 4400 to 2100 14 c ybp 5000 2200 cal ybp which coincided with an observed decrease in particle size i e a decrease in sand content these changes indicated the onset of paludification on the silty or sandy valley bottom contemporaneously relative abundances of pinus and herbaceous pollen increased and the east asian summer monsoon became weakened several intermittent depositional layers were observed ranging from 2100 14 c ybp 2200 cal ybp to the present which contained a high concentration of rootlets sand or clay particles these types of recurring sedimentation events are attributable to climatic shifts and or human impacts such as timber harvest and land clearing the upriver valley catchment was probably sensitive to flash floods due to poorly vegetated slopes accelerating rates of erosion as a consequence of land use change this research indicates that the response of a valley system such as that in paju to climate or human induced environmental changes can vary greatly on local and regional scales

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

geology geochemistry and ore genesis of the wenyu gold deposit xiaoqinling gold field qinling orogen southern margin of north china craton abstract the wenyu giant gold deposit is hosted in the precambrian taihua supergroup metamorphic rocks within the xiaoqinling terrane qinling orogen on the southern margin of the north china craton the mineralization can be divided into three stages quartz pyrite veins early quartz sulfide veins middle main and carbonate quartz veinlets late with gold being mainly introduced in main stage quartz formed in two earlier stages contains three compositional types of fluid inclusions i e pure co2 co2 h2o and nacl h2o but the late stage minerals only contain the nacl h2o inclusions the inclusions in quartz formed in the early main and late stages yield total homogenization temperatures of 262 417 c 236 407 c and 114 239 c respectively with salinities no higher than 13 wt nacl equiv trapping pressures estimated from co2 h2o inclusions are 139 399 mpa and 111 316 mpa in the early and main stages corresponding to mineralization depths of 14 km and 11 km respectively fluid boiling and mixing caused rapid precipitation of sulfides and native au through boiling and inflow of meteoric water the ore forming fluid system evolved from co2 rich to co2 poor in composition and from metamorphic to meteoric as indicated by decreasing 18owater values from early to late the carbon sulfur and lead isotope compositions suggest the hostrocks within the taihua supergroup to be a significant source of ore metals integrating the data obtained from the studies including regional geology ore geology fluid inclusion and c h o s pb isotope geochemistry we conclude that the wenyu gold deposit was an orogenic type system formed in the tectonic transition from compression to extension during the jurassic early cretaceous continental collision between the north china and yangtze cratons

active crustal deformation in the marmara sea region nw anatolia inferred from gps measurements deformation in the boundary zone between the anatolian and eurasian plates has been determined by means of repeated global positioning system gps measurements three campaigns 1990 1992 1994 were carried out around the marmara sea the network lies within the active earthquake belt of nw anatolia extending from the western part of the north anatolian fault zone nafz to the aegean extensional province results of the dense network consisting of 52 sites clearly reveal the westward motion of anatolia the rates amount to 17 mm a 3 mm a on average relative to istanbul located at the northeastern edge of the sea of marmara based on the trajectories for the displacements of the observation sites it is concluded that the marmara sea forms a transition zone between the europe fixed region of thrace black sea eurasia and nw anatolia at the western extremity of nw anatolia the motion bends from w to wsw 247 the strain field calculated yields an e w oriented right lateral strike slip movement average 0 12 ppm a maximum 0 41 ppm a accompanied by ne sw extension average 0 12 ppm a maximum 0 52 ppm a at the eastern end of the marmara sea and n s extension at the aegean shore line comparisons with the directions of t axes derived from 65 fault plane solutions of earthquakes show remarkable agreement

lithospheric structure of northern california from teleseismic images of the upper mantle teleseismic p wave travel time residuals from 120 earthquakes recorded across the u s geological survey california seismic network were used to determine the lithosphere p wave velocity structure beneath northern california a region characterized by complex interactions between the pacific north american and gorda plates lateral p wave velocity variations beneath the array were determined by inversion of 9383 travel time residuals inversion results for the crust show strong correlations to volcanic features the active volcanic fields shasta medicine lake lassen and clear lake are characterized by crustal low velocity anomalies that average approximately 6 possibly identifying partially molten magma bodies cooled solidified magma bodies beneath the extinct volcanic fields sonoma southern clear lake and sutler buttes are denoted by relative velocity highs averaging 3 the largest upper mantle velocity variations occur in the depth range 30 110 km where velocities vary from 5 5 to 9 5 these velocity variations reflect changes in the thickness and geometry of the pacific north american and gorda plates where they interact at the mendocino triple junction north of the mendocino triple junction the steep 70 east dipping portion of the gorda plate is imaged as a 5 velocity high to depths near 270 km a presumed segment of the gorda plate observed beneath the northern great valley and south of the inferred edge of the plate is characterized by a 9 velocity high in the depth range 30 70 km beneath the northern coast ranges shallow asthenosphere is imaged in the depth range 30 100 km as a pronounced southward tapering 4 low velocity zone which we interpret as the slab window results from this study provide improved constraints on gorda plate subduction evolution of the san andreas fault system and development of the lithosphere beneath western north america

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

sensitivity of floodplain geoecology to human impact a holocene perspective for the headwaters of the dijle catchment central belgium floodplain deposition rates have increased markedly under influence of human impact throughout the late holocene in many western and central european catchments consequently the geomorphology and ecology of many floodplains changed in this study we discuss this human impact and its influence on the floodplain geoecology during the middle and late holocene for the headwaters of the dijle catchment located in the belgian loess belt the floodplain geoecology and the regional vegetation was reconstructed from sedimentological and palynological analyses an age depth model for the studied sequences was obtained using 17 radiocarbon dates statistical analyses of the pollen data cluster analysis and canonical correspondence analysis were used to detect changes in the pollen record our data show that until c 2500 cal bp human impact was nearly absent or localized with no discernible influence on the floodplain geoecology the floodplain was in a stable phase and consisted of a marshy environment where organic material could accumulate which is interpreted as the natural state of the floodplain from c 2500 cal bp onwards human impact gradually increased however only when human impact in the catchment crossed a threshold around 500 cal bp the floodplain geoecology changed with clearing of the alder carr forest the establishment of a single channel river and the dominance of minerogenic overbank sedimentation spatial variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differences in hillslope floodplain connectivity and local differences in human impact

constraints on the evolution and vertical coherency of deformation in the northern aegean from a comparison of geodetic geologic and seismologic data abstract we study the 3 d strain evolution of the northern aegean and the vertical coherency of deformation we observe that finite strain orientations in the mantle inferred from published shear wave sks fast polarization orientations mid to upper crustal stretching lineations in metamorphic core complexes of mainly miocene age and the gradient in regional crustal thickness variations are subparallel to one another this correlation suggests that the miocene phase of extension is imprinted in the anisotropic fabric i e lattice preferred orientation lpo of the lithospheric mantle and that the orientation of finite strain due to extension is nearly constant with depth the lateral variation of published seismic delay times shows a correlation with laterally varying finite strain in the crust inferred from topography and crustal thickness estimates this correlation suggests that lateral variations in finite crustal and mantle strain are correlated and may point at a pure shear extension mechanism involving the entire lithosphere we also present a new strain rate model for the northern aegean based on global positioning system gps velocities and additional geological constraints no length change orientations calculated from the model near the north anatolian fault naf and north aegean trough are not consistent with anisotropy orientations at depth present day extension orientations are systematically and significantly more n s oriented than the stretching lineations and sks splitting orientations we conclude that the current shear dominated surface deformation pattern is not yet reflected by significant anisotropy in the lithosphere based on some simple calculations we postulate that the present day deformation pattern cannot be older than 4 ma which is consistent with independent arguments on the timing of the propagation of the north anatolian fault into the aegean domain

intrusion hosted mineralization in the charters towers goldfield north queensland new isotopic and fluid inclusion constraints on the timing and origin of the auriferous veins auriferous quartz sulfide veins of the charters towers goldfield are mainly hosted in oxidized i type granitoids of the ravenswood batholith k ar and ar ar isotope age data of hydrothermal muscovite from alteration envelopes of veins at charters towers and the hadleigh castle mine 40 km east of charters towers are indistinguishable within error suggesting broadly synchronous gold deposition between 410 and 404 ma and across a significant segment of the ravenswood batholith published geochronological data indicate that several granitoid bodies were emplaced into the ravenswood batholith at the time of gold mineralization despite their association in space and time with igneous rocks the gold deposits lack an obvious causative intrusion moreover published lead isotope studies indicate that the lead in the ore was not acquired from any of the exposed intrusions a distal origin of the ore forming fluids also may be inferred from nitrogen isotope values of hydrothermal sericite suggesting wall rock interaction with metamorphic fluids or fluids that were in equilibrium with metamorphic rocks during the paragenetic stage of pyrite and arsenopyrite deposition stage ii veins of the charters towers goldfield contain three different types of fluid inclusions which are distinguishable by petrography and microthermometry this study is the first to report saline fluid inclusions in sphalerite 18 9 28 3 wt nacl equiv and vein quartz 20 9 24 7 wt nacl equiv trapped during the stage of gold deposition stage iii the range of temperatures and salinities particularly of the saline inclusions in sphalerite could indicate mixing between hotter more saline fluids e g deep seated magmatic and cooler more dilute solutions e g modified meteoric as the cause of gold deposition the geological and geochemical data are not compatible with derivation of fluids metals and ligands from individual plutons similarity of host rocks ore element associations alteration assemblages structural controls and tectonic settings strongly suggest that the auriferous veins of the charters towers goldfield belong to a group of granitoid hosted lode gold deposits that are generally classified as orogenic

subduction hinge migration abstract it has been argued that back arc tectonics is controlled principally by the absolute motion of the overriding plate and the migration of the hinge of the downgoing plate thus hinge migration rollback is fundamentally important to understanding the geodynamics of back arc regions but even rates of hinge migration are unknown the rate of hinge migration can be estimated if the rate of back arc extension and the motion of the overriding plate are known rates of rollback in a hotspot reference frame range from near zero in the case of the new hebrides arc to 50 70 mm a at the south sandwich arc and may be as high as 100 mm a at the tonga trench but the hinge is actually advancing along the izu bonin trench as evidenced by the fact that there is no significant active extension behind the izu bonin arc the rate of hinge advance increases from north to south along the izu bonin trench and correlates well with the dip of the subducted slab active spreading in the mariana trough may be attributed to a rate of hinge advance which is lower than the rate of retreat of the philippine plate all of the possible motions of overriding plates and subduction hinges which might give rise to back arc opening are represented among the examples considered thus there is no unique circumstance in which back arc extension occurs finally there appears to be no clear correlation between hinge motion and the age of the subducted lithosphere

seismotectonics of the cyprian arc summary the cyprian arc forms the plate boundary between the anatolian plate in the north and the nubian and sinai plates in the south we examine the tectonic setting and seismic activity along the arc in light of new geodetic studies indicating relative ne sw plate motions across the arc the first order tectonic variations are determined by the arc s geometry the eastern arc oriented subparallel to relative motion is dominated by transcurrent tectonism the western arc is oriented almost normal to relative plate motion and is subjected to convergent processes variations in the level and depth of seismic activity along the western arc suggest that the northwestern section of the arc represents a subduction boundary whereas the southeastern section represents a collision boundary the two tectonic domains of the western arc are separated by a ne sw trending tear fault which produces large earthquakes such as the mw 6 8 1996 paphos earthquake we compare the geometrically similar cyprian and hellenic arcs and find significant differences in the rate direction and type of convergence across the two arcs the hellenic arc is subjected mainly to subduction whereas the shorter cyprian arc is subjected to subduction collision and transcurrent tectonic processes

late miocene recent evolution of the finike basin and its linkages with the beydaglari complex and the anaximander mountains eastern mediterranean abstract interpretation of 2500 km of high resolution multi channel seismic reflection profiles shows that the finike basin evolved during the pliocene quaternary as the result of dramatic subsidence associated with loading of large imbricate thrust panels that carry the western tauride mountains in the north in the late miocene the stacked seaward prograded quaternary deltas presently resting at 1000 1500 m water depths corroborate the rapid subsidence of the region the ubiquitous presence of evaporites in the 2000 2400 m deep antalya basin and their absence in the 3000 3200 m deep finike basin suggest that the morphology of the finike basin and environs must have been considerably different during the messinian and that this region must have remained above the depositional base of evaporites during this time the transition from the messinian to the pliocene quaternary is marked by partitioning of stress into several discrete spatial domains a dextral strike slip fault zone developed along the western antalya basin extending from the apex of the isparta angle southward into the anaximander mountains this fault zone referred to as the antalya fault zone transected the anaximander mountains sensu lato separating the anaxagoras mountain from the anaximander and anaximenes mountains hence the finike basin sirri erinc plateau and the anaximander and anaximenes mountains remained part of the onland beydaglari block and experienced 20 counterclockwise rotation during the late miocene we envisage the boundaries of the beydaglari block as the burdur fethiye fault zone in the west the newly delineated antalya fault zone in the east and the east west trending sector of the sirri erinc plateau in the southwest kinematic evaluation of the structural elements mapped across the finike basin and the sirri erinc plateau suggest that two additional strike slip zones developed during the pliocene quaternary relaying the stress between the antalya fault zone in the east and the pliny strabo fault zone in the west

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

mineralogy mineral chemistry fluid inclusion and stable isotope investigations of the kabaduz ore veins ordu ne turkey abstract hydrothermal vein type deposits of the kabaduz region ordu ne turkey are located in upper cretaceous andesitic basaltic rocks and were formed in fault zones along nw se direction lines with thicknesses varying between a few centimetres up to 2 m the primary mineral paragenesis of the many different ore veins consists of pyrite chalcopyrite sphalerite galena and tetrahedrite tennantite with quartz and lesser amounts of calcite and barite as gangue minerals electron microprobe analyses indicate that the sphalerite and tetrahedrite tennantite have low fe contents with values less than 3 37 wt and 1 56 wt respectively the very low ni and co contents of the pyrites h and the salinity data suggests that meteoric water was involved in the hydrothermal solutions based on the measured first melting temperatures cacl 2 mgcl 2 nacl and kcl were dominant in the fluid inclusions the 34 s compositions of the pyrite chalcopyrite sphalerite and galena mineral separates of the investigated ore veins were measured at between 2 14 and 1 47 and the oxygen and hydrogen isotope compositions varied between 7 8 8 5 and 40 57 respectively based on the sulphur oxygen and hydrogen isotope compositions magmatic sources were confirmed for the hydrothermal solutions taking into account all of the above data and the granitic intrusions around the area we concluded that younger granitic intrusions were responsible for the ore mineralisation around the kabaduz region

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

late cenozoic stress state distributions at the intersection of the hellenic and cyprus arcs sw turkey abstract the history of the late cenozoic stress regime was determined for an area between the gulfs of fethiye and antalya fault kinematic analysis and inversion of focal mechanisms of shallow earthquakes reveal significant evolution of the regional stress regime in sw anatolia i e the area of interaction between the hellenic and cyprus arcs from the mio pliocene to the present time fault kinematic analysis yields two different normal faulting stress regimes along the southwestern part of fethiye burdur fault zone e g in and around cameli basin zone a1 and two different strike slip to normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes between fethiye and demre zone b with an older nw se 3 axis for mio pliocene and a younger ne sw 3 axis for plio quaternary time inversion of focal mechanisms of the earthquakes occurring in zone a1 provides an extensional stress state with approximately n s 3 axis inversion of those occurring in zone b south of zone a1 yields a dominantly strike slip stress state with a ne sw 3 axis and a nw se 1 axis respectively the inversion slip vectors from fault planes yield a consistent normal faulting stress regime in burdur basin and its surroundings i e along the northeastern part of fethiye burdur fault zone zone a2 during plio quaternary continuing into recent time as indicated by earthquake focal mechanism inversions both states have a consistent nw se 3 axis fault kinematic analysis indicates nw se extension acting in zone c subarea between demre and antalya south of zone a2 during mio pliocene time the inversion of focal mechanisms yields normal faulting also characterized by a consistent nw se 3 axis the nearly orthogonal extensional stress regimes nw se and ne sw obtained by inversion of both measured and seismic faults seem to have been acting contemporaneously with each other at different intensities from the mio pliocene onwards in sw turkey this may be attributed to the geodynamic effects related to the subduction of the african plate beneath anatolia diffusing along the hellenic and cyprus arcs and in the west southwestward extrusion of anatolia the cause of the early nw se extension is the slab pull force due to the subduction process along the cyprus arc considered to be dominant until the plio quaternary in the western part of the study area in zones a1 and b the dominant status of the cyprus arc continues today in the eastern part of study area in zones a2 and c the later ne sw to present day approximately n s extension dominant since the plio quaternary is related to the combined forces of the anatolian extrusion and the subduction process along the hellenic arc

geodetic constraints on the tectonic evolution of the aegean region and strain accumulation along the hellenic subduction zone article i nfo we present evidence that gps velocity estimates of plate motions and fault slip rates agree to within uncertainties with geologic estimates during the most recent phase of the geologic evolution of the e mediterranean region post late miocene on this basis we use the gps differential velocities to estimate the timing of initiation of the principal structures in nw turkey the n aegean sea and central greece including the marmara sea the gulfs of evia goe and corinth goc and the kephalonia transform fault ktf we interpret these ages to indicate that the north anatolian fault propagated across the n aegean opening the goe and goc and initiating the ktf during the past 1 4 ma we further suggest that aegean extension that was earlier more distributed across the aegean basin became focused on this new fault system allowing the southern aegean and peloponnisos to translate sw with little internal deformation as observed today with gps this change in tectonic configuration may account for the clear geologic evidence for crustal thinning throughout the s aegean in apparent contradiction with low present day strain rates we further show that the low present day strain rate along the southern edge of the aegean micro plate requires substantial aseismic slip along the plate interface below crete consistent with the low level of historic subduction type earthquakes along this segment of the subduction zone

45 m y of aegean crust and mantle flow driven by trench retreat the available seismic anisotropy data in the aegean shallow mantle and their relationship with crustal deformation are used for deciphering the lithosphere scale flow pattern driven by rollback of the hellenic subduction slab in the north and central aegean the directions of mantle seismic anisotropy trend parallel to stretching lineations in core complexes of the overlying crust suggesting that crust and mantle have undergone the same direction of flow at the scale of the entire aegean crustal extension is controlled by dextral rotation around a pole located at scutary pec albania that is related to the hellenic trench retreat the intensity of mantle anisotropy increases as a function of distance from the pole and of amount of rotation surface geology reveals that this rotating flow pattern resulted in strains accumulated since 45 ma a slab tear model is suggested to integrate the observed variations of geological events in time and space to subduction dynamics

tectonic implications of the 2017 ayvacik canakkale earthquakes biga peninsula nw turkey abstract the west to southwestward motion of the anatolian block results from the relative motions between the eurasian arabian and african plates along the right lateral north anatolian fault zone in the north and left lateral east anatolian fault zone in the east the biga peninsula is tectonically influenced by the anatolian motion originating along the north anatolian fault zone which splits into two main northern and southern branches in the east of marmara region the southern branch extends towards the biga peninsula which is characterized by strike slip to oblique normal faulting stress regime in the central to northern part the southernmost part of peninsula is characterized by a normal to oblique faulting stress regime the analysis of both seismological and structural field data confirms the change of stress regime from strike slip character in the center and north to normal faulting character in the south of peninsula where the earthquake swarm recently occurred the earthquakes began on 14 january 2017 mw 4 4 on tuzla fault and migrated southward along the kocakoy and babakale s stepped normal faults of over three months the inversion of focal mechanisms yields a normal faulting stress regime with an approximately n s n4 e 3 axis the inversion of earthquakes occurring in central and northern biga peninsula and the north aegean region gives a strike slip stress regime with approximately wnw ese n85 w 1 and nne ssw n17 e 3 axis the strike slip stress regime is attributed to westward anatolian motion while the normal faulting stress regime is attributed to both the extrusion of anatolian block and the slab pull force of the subducting african plate along the hellenic arc

linear elastic fracture mechanics explains the past and present evolution of the aegean abstract geologically the deformation in the anatolian aegean region has been dominated by two processes the propagation of the north anatolian fault associated with the extrusion of the anatolian plateau and the north south stretching of the aegean we model gps data in the context of this understanding localised deformation zones are represented by dislocation elements which extend from the base of the lithosphere to the locking depth at the base of the seismogenic layer unlike other gps interpretations our models incorporate geological and seismological constraints to provide a robust description of the present day deformation of the anatolian aegean region we then show that the present day deformation observed by gps today is consistent with the continuation of the geological processes that started in the tertiary our approach is also consistent with the lithosphere preserving long term elastic strength and with the concepts of linear elastic fracture mechanics applying at a large scale

late and post glacial evolution of lake steisslingen i abstract piston cores from lake steisslingen a small hard water lake situated 20 km west of lake constance and mainly supplied by submerged springs reveal a record of the environmental history going back to 15 600 cal yr bp from the bolling to ca 9800 cal yr bp the sediments are partly seasonally laminated from then on up to the middle ages the lamination is mostly undisturbed providing a high resolution time scale by varve counting a detailed pollen profile and 13 ams 14c analyses all investigated sediment sections show evidence of exceptionally high sulphate concentrations in the lake water which lead to the fixation of all reactive iron as pyrite the high sulphur content can only be attributed to s rich water supplied by the submerged springs thus indicating the miocene obere meeres molasse as the dominant aquifer since soil erosion is strongly reduced due to increased forest density in the preboreal boreal the submerged springs are the main nutrient source for the lake mixing or stable stratification of the waterbody mostly depends on nutrient availability and bioproductivity in the epilimnion the controlling external factors are wind and changes in water level and or temperature at the end of the younger dryas and during the preboreal low water levels and precipitation rates are assumed the water column mixing was regular bioproductivity high and high degradation activity of organic matter led to a redissolution of calcite the hydrological separation of a northern shallow lake seeried probably fell into the period of this low lake level around 10 450 10 300 cal yr bp the lake level rose but never again reached the former level between 10 000 and 7200 cal yr bp non glacial varves are even found in shallower parts of the lake indicating a stable anoxic monimolimnion with a rising chemocline bioproductivity was low wind protection provided by the now dense forestation and favourable climatic conditions e g high summer temperatures and low winter temperatures seem to be the responsible factors fluctuating human impact is identified from about 7400 cal yr bp until permanent settlement by the alemanni about 1500 cal yr bp strong human influence is observed from 2000 cal yr bp onwards when agricultural activity and clearing of the shoreline vegetation by man caused high soil erosion rates and thus eutrophication at about 800 cal yr bp the recent hydrological conditions were established by implementing an artificial drain thus lowering the lake level

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

late cenozoic stress field in the cameli basin sw turkey a history of deformation has been determined for the cameli basin located in the western part of the major fethiye burdur fault zone interpreted as the on land continuation of pliny strabo fault system e g eastern boundary of the hellenic arc inversion of fault slip vectors affecting mio pliocene to quaternary formations in the cameli basin in the southwestern segment of the transtensional fethiye burdur fault zone yields two different normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes a nw se n129 19 e 3 axis and a ne sw n50 16 e 3 axis the orientation of fault sets is predominantly around the ne sw direction in the major fethiye burdur fault zone making the extension nw se the mean r values are 0 74 and 0 69 for both extensions indicating a triaxial stress state which is clearly different from radial extension and from transitional to strike slip stress state the nw se extension is probably responsible for the formation of the cameli basin during mio pliocene time in contrast the inversion of focal mechanism solutions of shallow earthquakes occurring within the cameli basin identifies a present day predominantly extensional stress regime characterized by an approximately n s n184 e 3 axis which has an r value of 0 637 indicating a triaxial stress state the nearly orthogonal extensional stress regimes seem to have been acting contemporaneously with each other at different intensities from the mio pliocene onwards in sw turkey this may be attributed to the geodynamic effects related to the subduction of the african plate beneath anatolia diffusing along hellenic and cyprus arcs and in the west southwestward extrusion of anatolia our hypothesis is that the cause of the early nw se extension is the slab pull force due to the subduction process along the cyprus arc considered to be dominant up to plio quaternary the later ne sw to present day n s extension dominant since the plio quaternary is related to the combined forces of the anatolian extrusion and the subduction process along the hellenic arc

a first deep seismic survey in the sea of marmara deep basins and whole crust architecture and evolution abstract increased source strength streamer length and dense spatial coverage of seismic reflection profiles of the seismarmara leg 1 allow to image the deep structure of the marine north marmara trough nmt on the strike slip north anatolian fault naf west of the destructive izmit 1999 earthquake a reflective lower crust and the moho boundary are detected they appear upwarped on an e w profile from the southern central basin eastwards towards more internal parts of the deformed region thinning of the upper crust could use a detachment suggested from an imaged dipping intracrustal reflector that would allow upper crustal material to be dragged from beneath it and above the lower crust accounting for the extensional component but also southwest motion of the southern margin of the nmt sections across the eastern half of the nmt crossing the cinarcik and imrali basins reveal several faults that are active reaching into the basement and have varying strike and proportions of normal and strike slip displacement they might be viewed as petals of a large scale negative flower structure that spreads over a width of 30 km at surface and is rooted deeper in the lithosphere under the central basin a very thick sediment infill is revealed and its extensional bounding faults are active and imaged as much as 8 km apart down to 6 km depth we interpret them as two deep rooted faults encompassing a foundering basement block rather than being merely pulled apart from a jog in a strike slip above a decollement the deep basin lengthening would account for only a modest part of the proposed 60 km finite motion since 4 myr along the same direction oblique to the nmt that sidesteps the shear motion from its two ends thus differential motion occurred much beyond the deep basins like subsidence involving the nmt bounding faults and the intracrustal detachments the complex partitioned motion localized on active faults with diverse natures and orientations is suggested to represent the overburden deformation induced from horizontal plane simple shear occurring in depth at lithospheric scale and in front of the north anatolian fault when it propagated through the region

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

seismic heterogeneity and small scale convection in the southern california upper mantle we invert traveltime residuals of teleseismic p and s phases for 3 d perturbations in vp vs and vp vs structures in the southern california upper mantle the tomographic inversion uses frequency dependent 3 d sensitivity kernels to interpret traveltime residuals measured in multiple frequency bands and recent advances in regional crustal thickness and velocity models to better isolate the mantle component of traveltime residuals in addition to separate vp and vs tomography we jointly invert the p and s data sets for vp vs perturbations by imposing a smoothness constraint on the lnvs lnvp field the regional upper mantle is very heterogeneous with the greatest amplitude of velocity and vp vs perturbations in the upper 200 km and mantle structures that correlate spatially with the major physiographic provinces of southern california our imaging improves the resolution of the geometry and amplitude of these features in addition to the major structures imaged and discussed in previous papers we find a large high velocity anomaly at depths between 340 and 500 km beneath the borderland transverse ranges and northern peninsular ranges this anomaly is separate from the well known uppermost mantle transverse ranges anomaly which extends no deeper than 175 200 km the strongest low velocity high vp vs anomaly is found beneath and west of the salton trough and is attributed to relatively high partial melt in the asthenosphere as a result of lithospheric thinning the magnitudes of vp vs and vp vs perturbations and knowledge of regional 1 d velocity and attenuation lead us to conclude that the asthenosphere contains up to 1 partial melt extending to depths as great as 150 200 km

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

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

reconstruction of postglacial to early holocene vegetation history in terrestrial central europe via cuticular lipid biomarkers and pollen records from lake sediments high resolution environmental reconstruction for central european terrestrial settings is commonly based on sediment records that provide the pollen spectra used for reconstruction of vegetation development alternatively complementary algal insect or zooplankton assemblages and or carbonate 18 o isotope profiles are investigated in this study vegetation development and inferred climate evolution were documented on a decadal to centennial scale by analysis of land plant cuticular lipids accumulated in lake sediments wax lipids derived from land plant leaves and blades are source diagnostic and highly resistant to degradation their aerodynamic properties favor short distance eolian transport but they are less affected by possible long distance transportation that complicates pollen analysis the late glacial to holocene sedimentary record of lake steisslingen southwestern germany was investigated by palynological and geochemical means tundra type pioneer vegetation consisting predominantly of grasses and herbs is dominated by nc31 alkanes whereas pioneer birch forest yields preferentially nc27 alkanes establishment of a pine assemblage is recognizable by elevated nc29 and nc31 leaf wax alkanes and the diversification of deciduous forests in the holocene is marked by nc29 dominance lipid geochemistry and palynology resolve decadal excursions such as the mid younger dryas event centennial climate trends with pronounced and rapid changes at the oldest dryas bolling allerod younger dryas and younger dryas preboreal transitions are consistently reflected by molecular and palynological proxy data the demonstrated suitability of an independent molecular proxy in paleoenvironmental studies provides new perspectives in high resolution climate reconstruction

a 15 000 year stable isotope record from sediments of lake steisslingen southwest germany abstract stable isotope records for carbon and oxygen in bulk carbonates carbon in bulk organic matter and for total and chromium reducible sulfur in a lacustrine sediment core from lake steisslingen southwest germany show several distinct and abrupt shifts during the last 15 000 years variations in the isotopic composition of authigenic carbonates indicate two major phases in the lake history in the pre holocene the hydrological budget of the lake was apparently stable variations of 18 o values of authigenic carbonates were therefore dominantly controlled by temperature changes a decrease in the 18 o carb values of about 2 at the allerod younger dryas transition is interpreted as a drop in mean annual air temperatures of approximately 5 c an abrupt temperature increase of a similar magnitude is inferred at the younger dryas preboreal boundary throughout most of the holocene the isotopic composition of authigenic carbonates was influenced by marked changes in the hydrological budget of the lake a major positive excursion in the 13 c carb and 18 o carb values at the beginning of the atlantic and a smaller one in the preboreal were related to evaporation effects which indicate that dry climatic conditions must have prevailed at that time a simultaneous increase in 13 c values of bulk organic matter at the beginning of the atlantic suggests a high level of productivity in the lake as a consequence aqueous sulfate became limited as indicated by variations in the 34 s values of total and chromium reducible sedimentary sulfur therefore we conclude that the beginning of the atlantic was characterized not only by dry but also by warm climatic conditions which triggered a higher productivity in the lake in the subatlantic sediments large variations in carbon oxygen and sulfur isotope ratios were observed as a result of human activities causing considerable perturbations in the biogeochemical element cycling of lake steisslingen results obtained by the study of the continuous 15 ka record of lake steisslingen document clearly that isotopic proxy data from lacustrine sediments can provide useful information on environmental and climatic changes of local regional and in the case of the younger dryas event of even hemispherical significance

palaeomagnetism of east siberian traps and kimberlites two new poles and palaeogeographic reconstructions at about 360 and 250 ma summary we studied basalt sills and dykes and kimberlite pipes from the eastern part of the siberian platform these are spread out over a few hundred kilometres and are divided into two age groups late permian early triassic mir aikhal and olenyek regions and late devonian early carboniferous viluy and markha basins aikhal region the palaeomagnetic poles determined for each sill or dyke are statistically different from each other but averaging all corresponding directions from these sills and dykes with those from kimberlites of different generations yields results with acceptable statistics this is probably due to the averaging out of secular variation and or changes in magnetic polarity the resulting palaeomagnetic poles allow one to reconstruct the palaeopositions of siberia during the two large flood basalt events at about 360 and 250 ma a significant rotation of the siberian platform during the devonian and carboniferous is suggested the new data are in general agreement with some earlier palaeomagnetic poles for the late permian early triassic traps of the tungusska basin and significantly reduce uncertainties for previous late devonian early carboniferous siberian poles which were very scattered together with geological and absolute age data the palaeomagnetic data support the hypothesis that kimberlite magmatism and trap intrusions were both rapid and relatively close in time the 360 ma event is emerging as a magmatic event with considerable extent over the russian and siberian platforms related to incipient continental break up and triple junction formation possibly at or near the time of the frasnian famennian mass extinction

upper mantle discontinuity structure beneath east anatolian plateau turkey from receiver functions abstract imaging of seismic velocity discontinuities with receiver functions suggests a complex mantle structure beneath the east anatolian plateau by stacking all the receiver functions as a function of ray parameter we examined the moveout characteristics of the data set and tested different velocity models to fit the arrival times of converted phases from the moho and the lithosphere asthenosphere boundary and their multiples the best fitting model shows anomalously thin crust 40 km and lithosphere 65 km and low uppermost mantle velocities causing systematic delays on later discontinuity arrivals these findings are consistent with the high plateau supported by partially molten and buoyant asthenosphere the upper mantle discontinuities are all visible in different frequencies 0 15 and 0 4 hz especially the 410 km discontinuity does not show frequency dependence in amplitude and suggests a sharpness of 10 km or less spatial variations of the 410 and 660 km discontinuities reveal anticorrelated topography and distinct zones of diminished amplitude associated with a detached slab and delaminated fragments of lithospheric mantle in the south the slab becomes deeper and horizontally deflected towards the east suggesting westward migration of slab detachment and resistance to slab penetration at the 660 km discontinuity in the north the mantle transition zone is characterized by two spatially limited lithospheric fragments with complex geometry at the center of the study area the transition zone is thin 230 km suggesting excess temperature of 120 c this warm mantle anomaly most likely is due to hot material trapped within the upper mantle between slab in the south and delaminated fragments in the north

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

recent temporal change in the stress state and modern stress field along the north anatolian fault zone turkey summary the north anatolian fault naf is a dextral strike slip fault which runs about 1400 km from east to west from the karliova triple junction to the aegean domain it was active during the plio quaternary as a consequence of the collision between the eurasian and arabian plates the naf intracontinental deformation zone contributes with the sinistral east anatolian fault to the westward extrusion of anatolia as a consequence of the northward drift of arabia the central naf zone forms a northward convex bend where the eastern naf n110 e trending segment extending from karliova is connected to the western naf n75 e trending segment running to aegea analysing the slip occurring in major earthquakes around the naf we show that the present day stress pattern along the naf agrees with stress magnitude and strike variations from east to west the stress regime along the naf is nnw trending hmax 1 transpression in eastern naf this progressively changes westwards to nw trending 1 transtension in central anatolia this lateral variation means a relative decrease of the hmax magnitude which evolves progressively to an extensional regime 1 vertical around the westernmost naf characterized by a nne trending hmin 3 the drastic change in the tendency of the regional stress state in the north anatolian block from compressional to extensional is effective within the central naf bend the stress regime determined by inversion of slip vectors measured on fault planes of various scales confirms the present day transtensional regime in the central part of the naf bend however the fault kinematic analysis of quaternary stress states within the central naf indicates that this stress state was not continuous throughout the quaternary indeed chronologies of fault slip vectors provide evidence for two distinct quaternary regional strike slip stress states within this zone both states have consistent ne and nw trending 3 and 1 axes respectively but have significantly different r values the change in the strike slip stress regime probably occurred in the middle pleistocene the older mean stress state is characterized by a n142 8 e trending 1 a n52 13 e trending 3 and a mean arithmetic rm value of 0 75 which indicates that the regional stress regime is transpressional the younger strike slip regime is characterized by a n142 14 e 1 axis a n52 10 e 3 axis and a mean rm of 0 24 which indicates the transtensional character for this regime the low r values of the stress deviators related to the recent stress state reflect normal component slips these temporal and spatial stress changes along the naf result from the coeval influence of forces due to the aegean subduction in the west and to the northward drift of arabia in the east over these boundary forces shear is superimposed along the naf which accommodates the anatolia extrusion however the timing of the temporal stress change permits the suggestion that the quaternary stress regime variation in north anatolia is mainly due to the influence of the aegean domain

recent state of stress change in the walker lane zone western basin and range province united states the nw to north trending walker lane zone wlz is located along the western boundary of the northern basin and range province with the sierra nevada this zone is distinguished from the surrounding basin and range province on the basis of irregular topography and evidence for both normal and strike slip holocene faulting inversion of slip vectors from active faults historic fault offsets and earthquake focal mechanisms indicate two distinct quaternary stress regimes within the wlz both of which are characterized by a consistent wnw 3 axis these are a normal faulting regime with a mean 3 axis of n85 9 w and a mean stress ratio r value r 2 1 3 1 of 0 63 0 74 and a younger strike slip faulting regime with a similar mean 3 axis n65 70 w and r values ranging between 0 1 and 0 2 this younger regime is compatible with historic fault offsets and earthquake focal mechanisms both the extensional and strike slip stress regimes reactivated inherited mesozoic and cenozoic structures and also produced new faults the present day strike slip stress regime has produced strike slip normal oblique slip and normal dip slip historic faulting previous workers have explained the complex interaction of active strike slip oblique and normal faulting in the wlz as a simple consequence of a single stress state with a consistent wnw 3 axis and transitional between strike slip and normal faulting maximum horizontal stress approximately equal to vertical stress or r 0 in both regimes with minor local fluctuations the slip data reported here support previous results from owens valley that suggest deformation within temporally distinct normal and strike slip faulting stress regimes with a roughly constant wnw trending 3 axis zoback 1989 a recent change from a normal faulting to a strike slip faulting stress regime is indicated by the crosscutting striae on faults in basalts 300 000 years old and is consistent with the dominantly strike slip earthquake focal mechanisms and the youngest striae observed on faults in plio quaternary deposits geologic control on the timing of the change is poor it is impossible to determine if there has been a single recent absolute change or if there is rather an alternating or cyclical variation in stress magnitudes our slip data in particular the cross cutting normal and strike slip striae on the same fault plane are inconsistent with postulated simple strain partitioning of deformation within a single regional stress field suggested for the wlz by wesnousky and jones 1994 the location of the wlz between the deep seated regional extension of the basin and range and the right lateral strike slip regional tectonics of the san andreas fault zone is probably responsible for the complex interaction of tectonic regimes in this transition zone in early to mid tertiary time the wlz appears to have had a similarly complex deformational history in this case as a back arc or intra arc region accommodating at least part of the right lateral component of oblique convergence as well as a component of extension

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge