first evidence of high pressure metamorphism in the cover series of the southern menderes massif tectonic and metamorphic implications for the evolution of sw turkey abstract the menderes massif occupies a large part of western turkey it is tectonically overlain by nappes of the izmir ankara suture zone including the bornova flysch zone on its northern flank the afyon zone on its eastern border and the lycian nappes on its southern flank the discovery of magnesiocarpholite kyanite assemblages in the mesozoic cover sequence of the southern menderes massif leads to the very first consideration that a major high pressure hp metamorphic event affected the massif during its alpine evolution estimations of minimum pressure temperature conditions about 10 12 kbar and 440 c suggest a minimum burial of 30 km for the metasedimentary rocks of the menderes massif similar to that for the eocene dilek blueschists which belong to the cycladic complex this finding of high pressure rocks within the menderes cover series as well as the recent description of low grade high pressure parageneses in the basal thrust sheets of the overlying lycian nappe complex has strong implications for the tectono metamorphic evolution of these units the characteristics of this high pressure metamorphism and the deformation features observed in the southern menderes massif allow consideration of a fast burial during alpine subduction and nappe stacking three high pressure units were piled up during the eocene collision of the sakarya continent and the tauride menderes block the lowermost unit consists of the imbricated core and cover of the menderes massif the intermediate unit is the cycladic blueschist complex dilek and samos regions and the uppermost unit is made of the lycian nappes the retrogression of high pressure parageneses from the menderes massif follows an isothermal decompression path and the associated deformation is characterized by a severe stretching oriented n s to ne sw during the high pressure event and its exhumation we propose a tectono metamorphic model in three main stages 1 the southward translation of the high pressure lycian nappes and the burial of the menderes and cycladic metasediments to a depth of at least 30 km to allow their eocene high pressure metamorphism 2 a northward continuum of deformation responsible for top to the north fabrics associated with the main menderes metamorphism peak paleocene eocene and its progressive cooling late eocene north verging folding thrusting imbrication of core and cover series and n s to ne sw intense stretching associated with the menderes high pressure metamorphism and its exhumation these top to the north to top to the northeast movements are probably related to the northward backthrusting of the lycian nappes reactivating the contact between the menderes massif and the lycian nappes as a top to the ne shear zone that allowed exhumation of the lycian high pressure rocks 3 oligo miocene n s extension during which the final exhumation of the metamorphic rocks along kilometre scale low angle detachments occurred

deformation history of the high pressure lycian nappes and implications for tectonic evolution of sw turkey 1 in southwestern turkey the lycian nappe complex which overlies the autochthonous menderes massif and bey dag platform consists from base to top of metasediments a melange unit and an ophiolitic sequence fresh fe mg carpholite occurrence in the metasediments attests to a high pressure low temperature metamorphic event we report the distribution of fe mg carpholite and its breakdown products e g pyrophyllite and chloritoid on the bodrum peninsula south of the menderes crystalline massif the distribution of fe mg carpholite and its relics shows that the low grade high pressure metamorphism affected a widespread area in the lower units of the lycian nappes analysis of the ductile deformation in hp lt metasediments indicates shear senses top to the northeast to top to the east most of this deformation is contemporaneous with the retrogression of high pressure low temperature parageneses and is therefore coeval with exhumation from a depth of about 30 km at the top of the menderes massif cover series close to the contact with the lycian nappes similar eastward displacements are observed and trajectories of the stretching lineations are continuous from the lycian nappes to the menderes massif across the contact these observed movements are incompatible with the southward transport of the lycian nappes over the menderes massif we discuss the regional tectonic implications and conclude that the lycian nappes and the southernmost part of the menderes massif were exhumed in two stages 1 eocene top to the ne shear syn orogenic extension 2 miocene deformation contemporaneous with the aegean extension

development of single crystal σ shaped quartz porphyroclasts by dissolution precipitation creep in a calcite marble shear zone abstract within a greenschist facies calcite marble shear zone isolated quartz grains change shape across the shear zone profile whereas quartz grains have a spherical to elongated shape in the coarse grained marble protolith and protomylonite they are asymmetric shaped porphyroclasts with wedge shaped appendages wings in ultramylonites in all cases quartz grains are single crystals they are sometimes twinned but never recrystallized stress induced dissolution precipitation creep is the favourable shape controlling process during deformation providing a relatively undeformed core truncation of pre existing cathodoluminescence cl patterns and syntaxial precipitation of wings the necessary fluids may have been released from fluid inclusions during dynamic recrystallization of the calcite matrix the development of shape is not related to the crystallographic orientation of the quartz porphyroclasts crystallographic orientation analysis by electron backscatter diffraction ebsd and cl analyses exclude crystal plasticity as a shape controlling mechanism of quartz grains during mylonitisation however in ultramylonites quartz clasts have a strong crystallographic preferred orientation cpo with c axes sub parallel to the shear direction this fabric is uncommon for quartz under greenschist facies conditions it might be explained by a strengthening of a pre existing weak cpo during mylonitisation by rigid particle rotation of elongated quartz grains

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

constraints on the kinematics of post orogenic extension imposed by stretching lineations in the aegean region abstract new kinematic data from shear zones of tertiary age in the metamorphosed basement of the aegean region in combination with published kinematic lithological and palaeomagnetic data have enabled us to determine a detailed kinematic evolution of the region during post orogenic extension in the aegean three distinct stages are recognised firstly extension of both the western and eastern aegean started in the late oligocene early miocene 36 25 ma ago initially in an 023 direction stage two started shortly after this with the division of the aegean crust into the west aegean block a coupled assemblage of small blocks bound on its northwestern and southeastern margins by the scutari pec line and mid cycladic lineament fracture zones respectively between 25 ma and 3 ma the west aegean block underwent 30 clockwise rotation whilst the eastern aegean underwent on average 19 anticlockwise rotation rotation of the west aegean block as a semi coherent block was aided by the relative coolness of the block compared to the warmer eastern aegean region as the crust thinned and rotated the nw se trending faults which characterise the west aegean block were cross cut by e w trending faults in the latest miocene pliocene the thermal front migrated westwards into the west aegean block and the mid cycladic lineament ceased activity the final kinematic stage marked the start of the subdivision of the west aegean block into two portions in the pliocene the southeastern portion nw cycladic area coupled with the sw cycladic area to form a central aegean block that started to translate southwest the northern and western portion rotated a further 10 15 clockwise whilst the southeastern rim rotated anticlockwise these data demonstrate that aegean post orogenic extension is not dominated by a single block rotation or radial spreading event but is characterised by the sequential formation and reformation of lithospheric scale blocks that have developed in response to large scale partitioning of rotational strain

microstructures of deformed grains in the augen gneisses of southern menderes massif western turkey and their tectonic significance a detailed fabric and microstructural analysis of the granitic mylonites was carried out on the southern side of bes parmak mountain north of selimiye milas the mylonitic augen gneisses have a blastomylonitic texture characterized by large retort shape porphyroclasts or augen of feldspars around which a more ductile medium to fine grained matrix of muscovite biotite quartz and feldspar is deflected feldspars behave in both plastic and brittle fashion because size reduction occurs through grain boundary migration and or subgrain rotation and also through fracturing typical core and mantle structure characterized by a large feldspar core surrounded by a mantle of fine recrystallized grains is very characteristic the majority of plagioclase twins obey the albite twin law however the association with pericline law twinning suggests that many of the twins are mechanical evidence of strain such as deformation twins bent or curved twins undulatory extinction deformation bands and kink bands occur characteristically in plagioclase myrmekite is ubiquitous at k feldspar grain boundaries most notably on the long sides of inequant grains parallel to the s foliation direction which invariably face the maximum finite shortening direction deformation of quartz in mylonitic augen gneisses commonly results in the development of core and mantle structure and type 4 quartz ribbons of elongated preferably oriented newly recrystallized quartz aggregates suggesting a primary dynamic recrystallization undulatory extinction deformation bands and lamellae are the strain related features associated with quartz porphyroclasts micas especially biotite undergo internal deformation by bend gliding and kinking most of the micas are completely attenuated and aligned such that their 001 planes are subparallel or parallel to the margins of quartz ribbons and define the foliation in the rock these microstructures of feldspars quartz and mica in the mylonitic augen gneisses in this part of the southern menderes massif are broadly consistent with fabric development under upper greenschist to lower amphibolite facies conditions rather than almandine amphibolite facies as was previously believed this supports the previous contention of the authors that the protoliths of augen gneisses are younger granitoids and do not represent an exposed precambrian pan african basement in the menderes massif

aegean crustal thickness inferred from gravity inversion geodynamical implications since oligo miocene times the aegean domain has undergone regional extension due to the southward retreat of the hellenic subduction zone boundary conditions have been more recently modified by the westward extrusion of anatolia a new map of the aegean crustal thickness inferred from gravity inversion is proposed here to better constrain the variations in space and time of crustal thinning that has accumulated since oligo miocene times moho topography is obtained by inversion of satellite marine gravity data data are first corrected for terrain anomalies and deep mantle effects african subducting slab they are then filtered between 50 and 300 km to avoid short wavelength intracrustal effects results are consistent with previous 2d geophysical studies seismic refraction receiver functions and show that an overall regional isostatic compensation of the crust holds for the aegean area with a mean crustal thickness of 25 km three different provinces north aegean cyclades and cretan sea can be identified thinner crust is observed both in the north aegean region ne sw trending of thinning with crustal thickness lower than 24 km and in the cretan sea crustal thickness of 22 23 km between these two regions the cyclades are marked by a rather flat moho at 25 km a two stage model of the aegean extension could well explain the observed crustal thickness variation from oligocene to middle miocene gravitational collapse of the hellenides due to the southward retreat of the african slab reduced the aegean continental crust from 50 km by reference to continental greece and anatolia to a mean value of 25 km at the scale of the whole aegean from upper miocene to present the westward extrusion of anatolia modified the extension and the associated crustal thinning in the north aegean domain during this second episode crustal thinning related to the southward retreat of the african slab tends to localize in the cretan sea the cyclades likely behave as a rigid block translated toward the south west without significant deformation in agreement with the gps velocity field and the lack of major earthquakes d 2004 elsevier b v all rights reserved

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

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

geology and ore forming fluid evolution of the aktogai giant porphyry cu deposit kazakhstan abstract the aktogai group more than 12 5mt of cu and 80t of au is located in the western part of the central asian orogenic belt caob the mineralization of the aktogai deposit is associated with the early carboniferous tonalite porphyry which intruded into the koldar complex the ore forming tonalite porphyry has higher oxygen fugacity and sulfur contents than those of wall rocks based on results of mineralogical chemistry analyses hydrothermal fluid activities result in the potassic sericite chlorite and propylitic alteration and are associated with disseminated and or vein mineralization the alteration and mineralization include three stages potassic stage is characterized by hydrothermal k feldspar biotite magnetite a veins and disseminated mineralization sericite chlorite stage that partly overprinted on potassic stage is characterized by sericite chlorite c veins and disseminated mineralization propylitic stage is characterized by chlorite epidote and c veins and develops in the tonalite porphyry and wall rocks five types of fluid inclusions have been recognized in the aktogai deposit including liquid rich l type vapor rich v type daughter mineral bearing s type co2 bearing c type and minor so2 bearing fluid inclusions in the potassic stage ore forming fluid belongs to h2o nacl co2 system with four types fluid inclusions homogeneous temperatures and salinities of fluid inclusions are 320 c to 448 c and 0 35 wt to 51 08 wt respectively in the sericite chlorite stage the fluid belongs to h2o nacl co2 system with l type v type and c type fluid inclusions homogeneous temperatures and salinities of fluid inclusions are 243 c to 315 c and 1 22 wt to 13 27 wt respectively in the propylitic stage the fluid belongs to h2o nacl system with l type and v type fluid inclusions homogeneous temperatures and salinities of fluid inclusions are 211 c to 328 c and 0 35 wt to 11 46 wt respectively a relatively negative 34s values 4 61 to 3 18 indicate that the sulfur derived from a high oxygen fugacity magma decreases of the temperature pressure and oxygen fugacity of the ore forming fluid result in metal precipitation in the aktogai deposit

geology of the bozdag area central menderes massif sw turkey pan african basement and alpine deformation the menderes massif consists of a precambrian core series that preserves evidence for a polymetamorphic history and a paleozoic mesozoic cover series that experienced only the alpine tectonometamorphic evolution structural petrographic and geochronologic investigations in the central menderes massif demonstrate that a part of the metamorphic and structural evolution of the precambrian basement is older than the undeformed 551 1 4 ma old birgi metagranite and b inferred alpine fabrics overprinting the cover series largely have the same attitudes as the old structures in the much older core series the inferred alpine fabrics include both contractional and extensional structures contraction under greenschist to amphibolite facies conditions resulted in the imbrication of the core and cover series and generated an inverted metamorphic sequence by north directed thrusting during alpine extension most of the south dipping thrust faults were reactivated as extensional shear zones under decreasing greenschist facies conditions

relations between surface faulting and granite intrusions in analogue models of strike slip deformation analogue models investigating the emplacement of granitic magmas at upper crustal levels during strike slip deformation are presented in this paper variations in parameters such as ratio between horizontal displacement dv and vertical magma upraising iv and the number of feeding points were considered during the experiments model results show that a strong interaction between surface faulting and granite intrusions develops during deformation on one side magma intrusion influences the sequence of structures development and the final fault pattern on the other side magma emplacement is strongly influenced by the syn intrusion lateral displacement dt which in turn reflects variations in dv and iv for high dt values i e high displacement velocity or low injection rate the importance of the horizontal displacement with respect to the vertical magma upraising results in asymmetric and drop shaped plutons with a sheared tail elongating in the sense of the strike slip displacement in this case the intrusion long axis tracks the long axis of the strain ellipsoid for low dt values i e low displacement velocity or high injection rate the strike slip displacement is strongly subordinated to the vertical magma upraising and pluton emplacement is controlled by development of tensional shears at the surface in these conditions the long axis of the magmatic bodies lies in the quadrants of compression of the strike slip deformation and intrusions are apparently dragged in an opposite sense to that imposed by the transcurrent deformation

olivine basalt and trachyandesite peperites formed at the subsurface surface interface of a semi arid lake an example from the early miocene bigadic basin western turkey abstract miocene successions in western turkey are dominated by lacustrine fluvial and evaporitic sedimentary deposits these deposits include considerable amounts of volcaniclastic detritus derived from numerous ne trending volcanic centres in western turkey as well as in the bigadic region early miocene syn depositional ne trending olivine basalt and trachyandesite bodies that formed as intrusions and lava flows occur within the bigadic borate basin olivine basalts occur as partly emergent intrusions and trachyandesite dykes fed extensive lava flows emplaced in a semi arid lacustrine environment peperites associated with the olivine basalt and trachyandesites appear to display contrasting textural features although all the localities include a large variety of clast morphologies from blocky to fluidal fluidal clasts mainly globular ameboidal and pillow like varieties are widespread in the peperite domains associated with olivine basalts apparently due to large volume sediment fluidisation in contrast fluidal clasts related to trachyandesites are restricted to narrow zones near the margins of the intrusions and have commonly elongate and polyhedral shapes with digitate margins rather than globular and equant varieties blocky and fluidal clasts in the olivine basalt peperite display progressive disintegration suggesting decreasing temperature and increasing viscosity during fragmentation abundance of blocky clasts with respect to fluidal clasts in the trachyandesite peperite indicates that the fluidal emplacement and low volume sediment fluidisation in the early stages were immediately followed by quench fragmentation due to the high viscosity of the magma size texture and abundance of the blocky and fluidal clasts in the olivine basalt and trachyandesite peperites were mainly controlled by sediment fluidisation pulsatory magma injection and magma properties such as composition viscosity vesicularity and size abundance and orientation of phenocrysts variously combining these contrasting features to varying degrees may form diverse juvenile clast shapes in peperitic domains

paleostress reconstructions and geodynamics of the baikal region central asia part 2 cenozoic rifting abstract investigations on the kinematics of rift opening and the associated stress field present a renewed interest since it has recently been shown that the control of the origin and evolution of sedimentary basins depends to a large extent on the interplay between lithospheric strength and applied stresses it appears that changes of stress field with time are an important factor that either controls or results from the rifting process the object of this paper is to study the changes of fault kinematics and paleostress field with time in the baikal rift system during the cenozoic reduced paleostress tensors were determined by inversion from fault slip data measured in the central part of the rift and its southwestern termination between 1991 and 1995 results show that the stress field varies as well in time as in space two major paleostress stages are determined corresponding broadly to the classical stages of rift evolution late oligocene early pliocene and late pliocene quaternary the first paleostress stage is related to the rift initiation and the second to the major stage of rift development similarities between the recent paleostress field and the present day stress field inverted from focal mechanisms indicate that the second paleostress stage is still active therefore we propose to use proto rift for the late oligocene early pliocene stage and active rift for the late pliocene quaternary stage of rift development during the proto rift stage the stress field was characterized by a compressional to strike slip regime a progressive change from transpression to transtension is suspected for the central part of the rift baikal and barguzin basins during this period in the western termination of the rift sayan massif tunka depression a strongly compressional stress field with oblique thrusting kinematics is well constrained in the late miocene early pliocene interval the active rift stage was initiated by a marked change in fault kinematics and stress regime in the late pliocene in the central part of the rift the stress regime changed into pure extension while in the southwestern extremity it changed into pure strike slip fault kinematics suggests that rifting was initiated by an extrusion mechanism due to the interaction of far field compressional stress on a mechanically heterogeneous crust with the southwards pointing wedge of the siberian craton acting as a passive indentor the cenozoic time space evolution of the stress field is believed to reflect the increasing influence of locally generated buoyancy extensional stresses associated with density anomalies of the lithosphere on intraplate stresses generated by the india eurasia convergence and the west pacific subduction

southern menderes massif an incipient metamorphic core complex in western anatolia turkey in the southern sector of the menderes massif north of selimiye milas augen gneisses interpreted as a deformed peraluminous granite have been dynamothermally metamorphosed and are surrounded by and intrude a regionally metamorphosed palaeozoic envelope the granitic rocks exhibit a moderately dipping mylonitic foliation and nne ssw trending mineral elongation lineation the progressive deformation of the granitic rocks produces a structural sequence typical of an extensional shear zone marked from bottom to top by a very thick extensive zone of mylonites followed in turn by brecciated mylonite and cataclasite the kinematic indicators exhibit a top to the south down dip sense of shear these structures are attributed to exhumation of the granitic rocks of the massif along a major south dipping normal sense shear zone that accommodated crustal extension during late oligocene collapse of the orogen in western turkey thus the southern menderes massif may be interpreted as the exhumed footwall of a major extensional shear zone and possibly as an incipient core complex

i type plutonism in a continental back arc setting miocene granitoids and monzonites from the central aegean sea greece miocene extension in the aegean sea was accompanied by the intrusion of granitoid and monzonitic magmas at upper crustal levels with increasing distance from the trench the metaluminous to slightly peraluminous i type intrusives show a systematic regional variation in their compositions medium to high k granodiorites in the wsw high k low silica granites in the central region and high k high silica granites monzonites monzogranites and composite lamprophyric monzonitic dikes in the ene the granodioritic and low silica granitic plutons comprise similar ranges of sio2 63 5 71 6 wt and initial nd sr and o isotopic values end i 7 0 to 9 8 87sr 86sr i 0 7092 0 7115 18o 9 7 11 5 but display significant differences in their chemical compositions compared with the granodiorites the low silica granites have higher abundances of large ion lithophile light rare earth and some high field strength elements initial isotopic signatures of the high silica granites in the ene end i 9 0 to 9 6 87sr 86sr i 0 7128 0 7144 18o 10 8 12 0 are slightly more crust like than those of the low silica granites in chemical variation diagrams samples from the high silica granites continue the trends defined by those from the low silica granites it is suggested that all granitoid magmas originated by dehydration melting of metaluminous older crustal sources most probably metagreywackes u pb systematics of zircon populations in conjunction with zr sio2 systematics and zircon saturation temperatures suggest a high proportion of restitic or assimilated crustal material in these magmas monzonitic to monzogranitic rocks show chemical and isotopic characteristics end i 0 8 to 3 6 87sr 86sr i 0 7059 0 7071 18o 9 4 10 6 that are significantly different from those of the granitoids a small portion of an older crustal component in these magmas is indicated by u pb systematics of zircon populations lamprophyric dikes display chemical and isotopic signatures end i 0 5 87sr 86sr i 0 7044 18o 8 9 that are compatible with an origin from either a mantle source previously enriched by slab derived hydrous fluids melts as suggested by negative nb ta anomalies or a new k rich basaltic underplate abundant composite dikes indicate the coexistence of and mingling mixing between lamprophyric melts and monzonitic magmas

a new geodynamic interpretation for the south portuguese zone sw iberia and the iberian pyrite belt genesis 1 the south portuguese zone spz constitutes the southernmost segment of the variscan iberian massif it is bounded to the north by the beja acebuches ophiolitic complex and related accretionary wedge to the south lie the iberian pyrite belt ipb and flysch deposits forming the southern extent of the zone structural analysis within the spanish side of the spz supports continuous south propagating deformation evolving from early synmetamorphic thrusting in the internal zone to thin skinned tectonics in the southern external domain the accretion of the spz to the ossa morena zone is also witnessed by the presence of various melanges observed throughout the investigated area part of the melanges observed in the ipb are related to the volcanics and mineralizations setting a key point to understand the ipb mineralizations genesis is to constrain the volcanogenic model one underestimated feature is the large amount of submarine calc alkaline ignimbritic facies implying the presence of caldera structures within the province such correlation between caldera environment and ore deposits strongly suggests that the ipb developed in a continental arc our geodynamic model proposes an early north directed subduction associated with the obduction of the oceanic crust toward the south southward this episode is immediately followed by the development of the accretionary prism while farther south a second subduction zone responsible for the arc setting of the ipb initiates subsequent visean continental collision is associated with the deposit of the south propagating flysch and the present geometry of the spz

regional implications of geochemistry and style of emplacement of miocene i type diorite and granite delos cyclades greece abstract the miocene plutons of the cyclades were emplaced in a subduction setting during regional back arc extension of continental crust that led to flat lying mid crustal detachment faulting mapping of the island of delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction mafic magmas were followed by numerous small batches of felsic magma with magmatic and ductile deformation synchronous with magma emplacement late granite dykes occupy brittle fractures in the more deformed rocks mafic and intermediate rocks show a bimodal distribution of incompatible trace elements with one group of broadly tholeiitic character and the other with substantial enrichment in sr nb and hfse but low th and ba these differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern cyclades voluminous granodiorite results from these mafic magmas fractionating and or mixing with felsic crustal material some of which was derived by anatexis of a sedimentary protolith indicated by high b and mn some late granites appear derived from partial melting of hercynian paragneiss regionally the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones the shear zones parallel the mid cycladic lineament a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the hellenic subduction zone distinctive geochemical features in miocene igneous rocks suggests that these two blocks had quite different geological histories the localisation of plutonism and core complexes near the mid cycladic lineament suggests that this crustal scale shear played a role in bringing subduction derived magmas to mid crustal levels the heat supplied by the mafic magmas promoted ductile deformation high in the crust where extension was concentrated leading to the formation of core complexes the regional extension resulted in progressive shallowing of the position of the granite solidus within the crust leading to welding of the mid cycladic lineament which is no longer seismically active

pluton emplacement by wall rock thrusting hanging wall translation and extensional collapse latest devonian plutons of the cobequid fault zone nova scotia canada

fault rotation and core complex formation significant processes in seafloor formation at slow spreading mid ocean ridges mid atlantic ridge 13 15 n 1 the region of the mid atlantic ridge mar between the fifteen twenty and marathon fracture zones displays the topographic characteristics of prevalent and vigorous tectonic extension normal faults show large amounts of rotation dome shaped corrugated detachment surfaces core complexes intersect the seafloor at the edge of the inner valley floor and extinct core complexes cover the seafloor off axis we have identified 45 potential core complexes in this region whose locations are scattered everywhere along two segments 13 and 15 n segments steep outward facing slopes suggest that the footwalls of many of the normal faults in these two segments have rotated by more than 30 the rotation occurs very close to the ridge axis as much as 20 within 5 km of the volcanic axis and is complete by 1 my producing distinctive linear ridges with roughly symmetrical slopes this morphology is very different from linear abyssal hill faults formed at the 14 n magmatic segment which display a smaller amount of rotation typically 15 we suggest that the severe rotation of faults is diagnostic of a region undergoing large amounts of tectonic extension on single faults if faults are long lived a dome shaped corrugated surface develops in front of the ridges and lower crustal and upper mantle rocks are exposed to form a core complex a single ridge segment can have several active core complexes some less than 25 km apart that are separated by swales we present two models for multiple core complex formation a continuous model in which a single detachment surface extends along axis to include all of the core complexes and swales and a discontinuous model in which local detachment faults form the core complexes and magmatic spreading forms the intervening swales either model can explain the observed morphology

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

the mount kozak magmatic complex western anatolia abstract the mount kozak igneous complex is located close to the towns of ayvalik bergama and burhaniye in the western anatolia turkey magmatic activity occurred during the late oligocene early miocene beginning with the emplacement of the kozak pluton sheet intrusive rocks formed around it coevally they are surrounded by the volcanic rocks partly contemporaneously with the emplacement of the granitic rocks during the early miocene the upper oligocene lower miocene magmatic rocks of the kozak region are represented by a high k calc alkaline suite of predominantly intermediate and acidic composition their geochemical characteristics suggest that the magmas are hybrid and were formed from a similar source representing mantle derived magmas contaminated by crustal materials the cogenetic plutonic rocks the hypabyssal rocks and the overlying volcanic associations are related to one another in space and time and appear to have been connected to a shallow level granitic intrusion in a caldera collapse setting the calc alkaline magmatic activity waned during the middle miocene when the volcanism was rejuvenated during the late miocene pliocene alkaline basalt lavas were formed as fissure eruptions

a comparison of geodetic and finite strain pattern in the aegean geodynamic implications abstract a comparison of the active strain pattern of the aegean constrained by global positioning system measurements and the oligo miocene finite strain field shows some striking similarities in terms of direction and rates of extension the geometry of extension at crustal scale is also very similar with north dipping normal faults connecting near the brittle ductile transition to shallow north dipping shear zones this pattern of extension is not significantly modified by the recent extrusion of the motion of anatolia and aegea the persistence over more than 25 myr of the same pattern of extension suggests that the cause for extension resides within the aegean lithosphere gravitational collapse allowed by extensional boundary conditions after 30 ma slab retreat is the primary cause for post orogenic extension in the aegean and western anatolia

post plutonic unroofing and morphogenesis of the attic cycladic complex aegea greece abstract the attic cycladic complex of greece comprises an eocene high p unit with blueschist occurrences unroofing of this unit took place in oligocene miocene times and was accompanied by a regional low p medium t overprint and miocene granitic plutonism apatite fission track ages of 14 crystalline samples from the islands of tinos mikonos and serifos range between 13 1 and 5 3 ma corresponding to the middle and late miocene the frequency distributions of confined track lengths are characterised by high arithmetic means of 14 2 15 1 m and by standard deviations from 0 9 to 1 6 m thermochronological modelling of the data indicates rapid cooling between 10 and 6 ma and subsequent deceleration of the cooling rates for a short time the miocene plutons of tinos mikonos and serifos experienced maximum cooling rates above 50 c ma these exceptionally high cooling rates cannot be explained by strong vertical uplift and fast regional erosion such a process is disproved by preserved remnants of a former peneplain including inselbergs and kaolinized tropical subsoil on mikonos fast post plutonic cooling of the lower plate was apparently accompanied by simultaneous sedimentation on the upper plate we propose a post plutonic cooling model which assumes strong periplutonic heat flow into much cooler host rocks and fast extensional unroofing

pluton emplacement within an extensional transfer zone during dextral strike slip faulting an example from the late archaean abitibi greenstone belt abstract the lake abitibi area within the late archaean abitibi greenstone belt exhibits an interlinked plutonic structural and metamorphic evolution that may characterize segmented strike slip faults at upper to mid crustal levels along the major southeastward propagating macamic d 2 dextral strike slip fault theological and preexisting d 1 structural heterogeneities induced the development of nnw trending dextral oblique splays which evolved into an extensional trailing fan and created an extensional nnw dipping stepover magma flowing upwards from deeper parts of the macamic fault spread towards the southeast at upper crustal levels along both the oblique slip and extensional d 2 splays and built several plutons in a pull apart domain between 2696 and 2690 ma different emplacement and material transfer mechanisms operated simultaneously in different parts of the system including fault dilation and wedging lateral expansion wall rock ductile flow and stoping transfer of movement between d 2 splays occurred under ductile conditions during syn emplacement amphibolite grade metamorphism 500 700 c during cooling d 2 faults appear to have been closely linked during the superior province wide late transpressional event

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

an outline of shear sense analysis in high grade rocks ductile shear zones are important in tectonic reconstructions as a source of information on the relative motion of large crustal blocks or plates in the geological past methods to interpret fabric in ductile shear zones were mostly developed for low grade rocks where overprinting relations are usually well preserved however high grade shear zones are common and dominate in many precambrian terrains high grade shear zones should be analysed in a different way from low grade zones the plane on which shear sense markers should be observed the vorticity profile plane is more difficult to find than in low grade shear zones the most reliable shear sense markers in high grade shear zones are shear bands mineral fish mantled porphyroclasts sigmoids and asymmetric boudins 2006 published by elsevier b v on behalf of international association for gondwana research

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

microstructures in feldspars from a major crustal thrust zone the grenville front ontario canada abstract samples collected across the nw grenville front in ontario canada have been used to document the change in feldspar microstructures produced during shearing under metamorphic conditions that range from upper amphibolite to lower greenschist grade the differential displacement across this 5 km thick section of the grenville front tectonic zone is at least 10 km at upper to mid amphibolite conditions both plagioclase and potassium feldspars behave plastically grainsize reduction occurs through grain boundary migration and or subgrain rotation and produces a core and mantle structure at middle to lower amphibolite grade grain size reduction is accomplished through grain boundary migration at lower amphibolite to upper greenschist grade grain size reduction occurs by the nucleation and growth of new grains with a different composition the abundance of intracrystalline deformation at this grade is inversely proportional to the amount of fine grained matrix in ultramylonite with a high matrix to porphyroclast ratio few intracrystalline strain features occur other than ubiquitous undulatory extinction myrmekite is well developed on the high stress boundaries in k feldspar at upper to mid greenshist conditions feldspars deform mainly by slip on synthetic shear fractures deformation twins undulatory extinction deformation bands and kink bands occur in plagioclase and perthite flames and myrmekite occur principally on high stress boundaries in k feldspar grain size reduction in feldspar is accomplished through cataclasis at middle to lower greenschist facies deformation in feldspars is dominated by antithetic fractures the transition from the dominance of synthetic to antithetic fractures is gradational below lower greenschist grade rocks deform by pervasive cataclasis of all minerals

plutonism and the origin of metamorphic core complexes the formation of metamorphic core complexes may be triggered by plutonic activity during episodes of continental extension pulses of ductile deformation have taken place during short lived thermal events initiated by the heat input from intruded plutons sills or dikes such intrusions may be the underlying cause for differential uplift of the footwall during tectonic denudation of metamorphic core complexes fast cooling inferred from 40 ar 39 ar apparent ages may have taken place after periods of magma arrival and need not be the result of rapid erosional or tectonic denudation heterogeneity of 40 ar 39 ar apparent ages can be explained by rapid cooling of deforming mylonites formed at shallow crustal levels in the thermal aureoles of intruded sills or sill swarms under such circumstances apparently isothermal decompression paths may actually link pressure temperature points set during periods of transient mineral growth during and after periods of igneous activity

rapid early middle miocene exhumation of the kazdag massif western anatolia apatite fission track analyses indicate that the kazdag massif in northwestern anatolia was exhumed above the apatite partial annealing zone between 20 and 10 ma i e early middle miocene with a cluster of ages at 17 14 ma the structural analysis of low angle shear zones high angle normal faults and strike slip faults as well as stratigraphic analysis of upper plate sedimentary successions and previous radiometric ages point to a two stage structural evolution of the massif the first stage encompassing much of the rapid thermal evolution of the massif comprised late oligocene early miocene low angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic volcaniclastic and volcanic rocks kucukkuyu fm the second stage plio quaternary has been dominated by i strike slip faulting related to the westward propagation of the north anatolian fault system and ii normal faulting associated with present day extension this later stage affected the distribution of fission track ages but did not have a component of vertical normal movement large enough to exhume a new partial annealing zone the thermochronological data presented here support the notion that neogene extensional tectonism in the northern aegean region has been episodic with accelerated pulses in the early middle miocene and plio quaternary

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

miocene sedimentary evolution of the ne sw trending selendi and gordes basins w turkey implications for extensional processes abstract western turkey is one of the classic regions for the study of extensional processes in a recent interpretation the regional metamorphic basement the menderes massif was exhumed related to large scale extensional processes possibly during latest oligocene time regional scale ne sw trending basins including the gordes and selendi basins were created associated with this exhumation the ne sw trending basins are seen as regional scale corrugations 10 15 km across in the surface of an extensional detachment orientated parallel to the direction of extension the detached upper plate is represented by erosional remnants of unmetamorphosed tethyan ophiolitic melange we describe and interpret the gordes and selendi basins separately and then show that their sedimentary facies and evolution are very similar basal coarse alluvial fan deposits accumulated after extensional removal of the upper plate these basal sediments rarely exposed were rotated by up to 50 probably as a result of local extension or transtension later during the early miocene the gordes and selendi basins were infilled by a generally fining upward succession derived from the south based on palaeocurrent evidence coarse alluvial fan deposition was followed by the deposition of finer grained alluvial deposits from braided streams flowing northwards over a topographically subdued flood plain later deposition was within shallow ephemeral lakes after a possible change to a moister climate calc alkaline magmatism was initiated with the fall out of fine grained silicic ash followed by coarser grained tuff derived from local magmatic centres during early pliocene time the basins were dissected by e w extensional faults associated with the establishment of the modern pattern of westward drainage to the aegean sea we use the assembled sedimentary evidence to test alternative tectonic models for miocene basin formation in western turkey our preferred tectonic model emphasises the importance of deposition in regional basins created by exhumation of metamorphic basement that was previously assembled during early tertiary closure of the tethys ocean

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

transtensional origin of the ne sw simitli basin along the strouma strymon lineament sw bulgaria several depocentres have developed along the nnw sse striking strouma strymon lineament since the miocene forming the strouma strymon graben system some of these basins including the dzherman and simitli strike at high angles to the lineament the rhomboid shaped simitli basin is limited in the south by the ne sw striking seismically active kroupnik fault and contains terrestrial clastic sediments which have been deposited since the sarmatian its formation is attributed to wrench dominated transtension d b event which activated the basin9s ne sw striking boundary faults as left lateral strike slip structures during the early middle miocene this deformation was associated with nne ssw contraction and wnw ese extension and succeeded the nne ssw contraction caused by pure shear dominated transpression d a event which governed the region in late oligocene early miocene times during the middle late miocene the d b event was followed by wnw ese pure shear dominated extension d 1 event which caused further widening of the basin the transtensional origin of the simitli basin is explained by lateral extrusion of the crustal mass squeezed between the apulian adriatic microplate and the european foreland towards the north aegean sea the subduction retreat of the hellenic orogen possibly enhanced this lateral extrusion and from the late miocene onwards the ne sw oriented back arc extension balanced the continuing retreat

ductile and brittle shortening extension parallel folds and maintenance of crustal thickness in the central aegean cyclades greece in contrast to previous studies that concentrated on the two dimensional crustal strain in the central aegean region cyclades it is shown that nne ssw extension via ductile and brittle stretching and low angle detachments was accompanied and or alternated with horizontal shortening perpendicular to the stretching direction since at least the early miocene roughly e w directed ductile shortening produced large scale overturned and upright folds having axes parallel or slightly oblique to the stretching lineation upright folding and arching of low angle normal faults occurred above the brittle ductile transition and brittle e w compression culminated with vertical axis block rotations strike slip faults and minor thrusts since at least the early miocene the structure of the cycladic massif evolved through alternating and or coeval increments of horizontal shortening and vertical thinning associated with an approximately constant nne ssw stretching exact magnitudes of the vertical and horizontal deformational components are difficult to assess nevertheless we note that extensional tectonics that affected the cyclades during the last 15 20 m y have produced no net crustal thinning we suggest that crustal thickness was maintained by extension parallel folds which represent true contractional structures and that crust was fed into the extended region from its margins

effusive eruptions from a large silicic magma chamber the bearhead rhyolite jemez volcanic field nm abstract large continental silicic magma systems commonly produce voluminous ignimbrites and associated caldera collapse events less conspicuous and relatively poorly documented are cases in which silicic magma chambers of similar size to those associated with caldera forming events produce dominantly effusive eruptions of small volume rhyolite domes and flows the bearhead rhyolite and associated peralta tuff member in the jemez volcanic field new mexico represent small volume eruptions from a large silicic magma system in which no caldera forming event occurred and thus may have implications for the genesis and eruption of large volumes of silicic magma and the long term evolution of continental silicic magma systems 40ar 39ar dating reveals that most units mapped as bearhead rhyolite and peralta tuff the main group were erupted during an 540 ka interval between 7 06 and 6 52 ma these rocks define a chemically coherent group of high silica rhyolites that can be related by simple fractional crystallization models preceding the main group minor amounts of unrelated trachydacite and low silica rhyolite were erupted at 11 9 and 8 ma respectively whereas subsequent to the main group minor amounts of unrelated rhyolites were erupted at 6 1 and 1 5 ma the chemical coherency apparent fractional crystallization derived geochemical trends large areal distribution of rhyolite domes 200 km2 and presence of a major hydrothermal system support the hypothesis that main group magmas were derived from a single large shallow magma chamber the 540 ka eruptive interval demands input of heat into the system by replenishment with silicic melts or basaltic underplating to maintain the bearhead rhyolite magma chamber although the volatile content of main group magmas was within the range of rhyolites from major caldera forming eruptions such as the bandelier and bishop tuffs eruptions were smaller volume and dominantly effusive bearhead rhyolite domes occur at the intersection of faults and are cut by faults suggesting that the magma chamber was structurally vented preventing volatiles from accumulating to levels high enough to trigger a caldera forming eruption

grain growth kinetics of quartz and calcite aggregates grain growth rates for novaculite flint and jasper have been determined between 1000 and 800 c and 15 to 2 kb water pressure a pre treatment established an equilibrium microstructure and a nearly uniform mean grain diameter bar d 0 at 1000 c and 15 kb the grain growth data are linear on a log bar d bar d 0 vs log time plot and there is no significant difference between the three samples although the jasper contained 5 10 vol iron oxide at lower pressures and temperatures the growth curves are approximately parallel to the 1000 c and 15 kb data but growth is slower and that for jasper is slower than for the other two the growth rate is strongly dependent on the solubility of quartz in the intergranular fluid and the activation energy is about 11 kcal mole the data are used to estimate the growth rate of quartz at metamorphic conditions and to help evaluate the conditions where growth of dynamically recrystallized grains may be significant the growth rate of calcite grains s

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

biostratigraphic data from the cetmi melange northwest turkey palaeogeographic and tectonic implications abstract the cetmi accretionary melange is cropping out in the biga peninsula of northwest turkey it is characterised by an isolated position relatively far from the accretion complexes of the nearest suture zones which raises the question of its lateral correlations a detailed biostratigraphic investigation of the limestone and radiolarite blocks and the matrix of the cetmi melange allowed to propose a solution for this palaeogeographic problem scarce red nodular limestones in the han bulog facies represent the oldest lithology in the melange their late scythian ladinian age is based on chiosella gondolleloides the co occurrence of gladigondolella sp and nicoraella cf kockeli and paragondolella fuelopi light grey limestone blocks are a characteristic feature of the cetmi melange they occur in two distinct facies facies a consists of packstone to grainstone and is characterised by unsorted and poorly washed pelbiosparites facies b consists of wackestone to packstone and is characterised by poorly washed biopelmicrites to biopelsparites the foraminiferal assemblage of facies a containing triasina hantkeni is of late norian to rhaetian age the foraminiferal assemblage of facies b never contains t hantkeni and is characteristic of a late triassic carnian to norian rhaetian age radiolarian cherts are widely distributed in the cetmi melange they record fully pelagic sedimentation from the upper bajocian to the aptian the matrix of the cetmi melange consists of brown to black shales sometimes silty or siliceous intercalated with dark grey greywackes palynomorphs of one sample of brownish silty shale yielded an early to middle albian age based on the co occurrence of several dinoflagellate cysts the age of the matrix representing the youngest lithology within the melange and of the unconformable overlaying section latest albian cenomanian indicate that the melange forming process stopped between the early albian and the latest albian cenomanian at a regional scale the cetmi melange has little in common with the melanges from the izmir ankara and intra pontide sutures of northwestern turkey precluding a direct correlation on the other hand the cetmi melange shares several characteristics with the melange like units of the eastern rhodope zone bulgaria and greece like a major cenomanian transgression the reworking of triassic limestones and middle jurassic lower cretaceous radiolarians and the absence of jurassic cretaceous passive margin lithologies the occurrence of rhodopian units on the biga peninsula suggests that the studied units represent an isolated fragment of the rhodope zone in nw turkey

transtensional faulting patterns ranging from pull apart basins to transform continental margins an experimental investigation abstract seventeen small scale experiments were performed to study the deformation induced in brittle ductile models by a releasing stepover between two transform faults and by intersection between transform and divergent plate boundaries in both cases faulting depends on the rheological layering presence and strength of a ductile layer at depth and the width of the basal stepover successive types of pull apart basins are observed in the first set of experiments which are compared with natural examples firstly a lazy z shaped basin appears which is bounded by y faults above transform boundaries and r faults propagating from each corner of the stepover then r faults replace r faults leading to a rhomb shaped graben at every stage the basin length to width ratio remains between 2 2 and 3 8 suggesting that scale independence of pull apart basins is related to the geometrical shape of bounding faults in a second set of experiments deformation at the end of a transform boundary is characterized by a horsetail splay bounding a divergent basin within the horsetail splay block tilting and block rotation about vertical axes lead to a surface slope perpendicular to the slope of the divergent basin a feature that can be compared with marginal ridges at transform margins

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

dynamic recrystallization of feldspar a mechanism for ductile shear zone formation feldspar aggregates experimentally deformed in the dislocation creep regime undergo dynamic recrystallization because recovery is difficult due to the limited climb of dislocations recrystallizing aggregates have a lower strength because of the cyclic production of small strain free grains and they develop a strong preferred orientation consistent with that observed in mylonites thus recrystallization accommodated dislocation creep may be responsible for the grain size reduction and strain softening that lead to the formation of many mylonites and ductile shear zones

the mediterranean ridge backstop and the hellenic nappes the core of the mediterranean ridge backstop consists of a pile of hellenic nappes that migrated outward from the aegean continent within the adjacent mediterranean basins during late middle miocene about 15 ma and the present mediterranean ridge has developed since that time by accretion of a new wedge the arguments we use are 1 a similarity in thickness seismic velocity and structure between the backstop and the hellenic nappes in southern peloponnesus 2 the geometry of the westward limit of the backstop that is the one expected from the amount of relative displacement of the nappes on land 3 an agreement between the estimated ages of the present accretionary wedge and the period of activity of two major faults connecting the backstop to the adjacent aegean continent the seaward limit of the backstop is situated about 170 km southwest of western crete where the displacement of the nappes is maximal and it is close to the margin near the ionian islands where their displacement is small we assume that the hellenic subduction zone migrated southwestward relative to eurasia during middle miocene and that the corresponding gravity collapse of the aegean continent was maximum at this time because the westward extrusion of anatolia had not yet started

are turtleback fault surfaces common structural elements of highly extended terranes abstract the death valley region of the u s a contains three topographic surfaces resembling the carapace of a turtle these three surfaces are well exposed along the black mountain front and are named the badwater copper canyon and mormon point turtlebacks it is widely accepted that the turtlebacks are also detachment surfaces that separate brittlely deformed cenozoic volcanic and sedimentary rocks of the hanging wall from the strongly mylonitic ductilely deformed pre cenozoic rocks of the footwall we have found a turtleback like detachment surface along the southern margin of the alasehir gediz graben in western anatolia turkey this surface qualifies as a turtleback fault surface because it a is overall convex upward and b separates brittlely deformed hanging wall cenozoic sedimentary rocks from the ductilely to brittlely deformed strongly mylonitic pre cenozoic footwall rocks the surface named here horzum turtleback contains striations that overprint mylonitic stretching lineations indicating top to the ne sense of shear this suggests that the northeasterly directed cenozoic extension in the region resulted in a ductile deformation at depth and as the crust isostatically adjusted to the removal of the rocks in the hanging wall of the detachment fault the ductilely deformed mylonitic rocks of the footwall were brought to shallower depths where they were brittlely deformed the turtleback surfaces have been considered unique to the death valley region although detachment surfaces rollover folds and other extensional structures have been well observed in other extended terranes of the world the presence of a turtleback fault surface in western anatolia turkey suggests that the turtleback faults may be common structural features of highly extended terranes

tectonic significance of synextensional ductile shear zones within the early miocene alacamdag granites northwestern turkey synextensional granitoids may have significant structural features leading to the understanding of the evolution of extended orogenic belts one of the highly extended regions the aegean region includes a number of metamorphic core complexes and synextensional granitoids that developed following the alpine collisional events the alacamdag area in northwestern turkey is one of the key areas where miocene granites crop out along the boundary of various tectonic units structural data from the early miocene alacamdag granites demonstrated two different deformation patterns that may provide insights into the development of granitic intrusions and metamorphic core complexes 1 steeply dipping ductile shear zones caused emplacement of syn tectonic granite stocks they include kinematic indicators of a sinistral top to the sw displacement this zone has also juxtaposed the izmir ankara zone and the menderes massif in the west and east respectively 2 gently dipping ductile shear zones have developed within the granitic stocks that intruded the schists of the menderes massif on the structurally lower parts kinematic data from the foliated granites indicate a top to the ne displacement which can be correlated with the direction of the hanging wall movement documented from the simav and kazdag metamorphic core complexes the gently dipping shear zones indicate the presence of a detachment fault between the menderes massif and the structurally overlying izmir ankara zone mesoscopic to map scale folds in the shallow dipping shear zones of the alacamdag area were interpreted to have been caused by coupling between ne sw stretching and the accompanying nw se shortening of ductilely deformed crust during early miocene times one of the ne trending shear zones fed by granitic magmas was interpreted to form the northeastern part of a sinistral wrench corridor which caused differential stretching between the cycladic and the menderes massifs this crustal scale wrench corridor the izmir balikesir transfer zone may have controlled the asymmetrical and symmetrical extensions in the orogenic domains the combination of the retreat of the aegean subduction zone and the lateral slab segmentation leading to the sinistral oblique slip tearing within the eurasian upper plate appears to be a plausible mechanism for the development of such extensive ne trending shear zones in the aegean region

formation of the maturin foreland basin eastern venezuela thrust sheet loading or subduction dynamic topography 1 the maturin basin in eastern venezuela is considered a good example of a peripheral foreland basin earthquake and tomographic data indicate that eastern venezuela is affected by the oblique subduction of the south american plate underneath the caribbean plate new forward flexural isostatic modeling of eastern venezuela has been carried out in order to determine whether the maturin basin was generated purely by thrust sheet loading from the serrania and monagas foreland thrust belts a sequence of forward models from middle miocene to present was generated for 3 profiles across the serrania del interior thrust belt the monagas foreland thrust belt and the maturin foreland basin the predictions of these models are constrained using seismic reflection and well data the flexural isostatic modeling shows that thrust sheet loading associated with the serrania del interior and monagas foreland thrust belts is insufficient to generate the observed subsidence within the maturin basin dynamic fluid flow modeling of subduction related dynamic topography of eastern venezuela has been used to investigate the influence of south american plate subduction on the generation of the accommodation space observed in the maturin basin fluid flow modeling of subduction related dynamic topography suggests that the subduction of the south american lithospheric mantle caused downward deflection of the south american crust affecting the maturin basin and the serrania thrust belt this modeling suggests that the maturin basin subsidence has two components 55 related to thrust sheet loading and 45 driven by continental subduction

late miocene ductile extension and detachment faulting mykonos greece the geometry and style of structural relations at map to microscopic scale on mykonos cyclades aegean sea greece suggests ductile extension and detachment faulting during the late miocene this island is dominated by granitic rocks that have a well developed shallowly dipping mylonitic foliation and a northeast southwest trending mineral elongation lineation kinematic indicators in these rocks exhibit a top to the northeast down dip sense of shear textural relations suggest that conditions during mylonitic deformation were greenschist to amphibolite facies and published k ar geochronology suggests a late miocene age for this deformation event mylonitic rocks lie in the footwall of a low angle fault and fault striae parallel to the elongation lineation suggest kinematic coordination between mylonitic deformation and movement along the fault translation along the fault juxtaposes younger tilted sedimentary rocks of low metamorphic grade upon the once deeper mylonitic rocks the style and geometry of deformational fabrics and map relations on this island are strikingly similar to those observed in metamorphic core complexes of the western united states

geology of the ignimbrites and the associated volcano plutonic complex of the ezine area northwestern anatolia abstract the ezine region is located in the northwestern part of anatolia where young granitic and volcanic rocks are widespread and show close spatial and temporal association in this region magmatism began with the kestanbol granite which intruded into metamorphic basement rocks and formed contact metamorphic aureole to the east and southeast the pluton is surrounded by hypabyssal rocks which in turn are surrounded by volcanic associations the volcanic rocks may be divided into two main groups on the basis of their lithological properties lavas and lahar deposits dominate the northern sector while ignimbrites dominate the southern sector the ignimbrite eruptions were formed partly coevally with the plutonic and the associated volcanic rocks during the early miocene they appear to have been associated in a caldera collapse environment geochemical properties of the plutonic and the associated volcanic assemblages indicate that the magmas are hybrid and co genetic and were formed from a similar mantle source under a compressional regime prior to the opening of the present e w trending graben of the aegean western anatolian region