kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern mediterranean region since the late cretaceous the relationship between subduction dynamics and crustal deformation in the mediterranean region has been recently studied using three dimensional 3d numerical models such models require however a detailed information concerning the past geological evolution we use stratigraphic petrologic metamorphic structural paleomagnetic and magmatic data to build new kinematic reconstructions of the eastern mediterranean region since the late cretaceous using the principle of non rigid domains the motions of the 56 deforming domains defined in this work are calculated based on published paleomagnetic rotations the directions and amounts of displacement on crustal scale shear zones and the burial and exhumation histories of the main metamorphic units extracted from these reconstructions paleotectonic maps and lithospheric scale cross sections illustrate that the present day subduction zone has been continuously retreating southward since the late cretaceous and has accreted several small continental domains in the process we find evidence for two back arc related extensional events 1 slow extension along the balkans and the pontides in the late cretaceous while the trench was long and linear and 2 faster extension in the rhodope aegean west anatolian region since the eocene oligocene rapid rotation of the hellenides between 15 and 8 ma probably indicates a slab tearing event below western anatolia that could have further accelerated this extensional kinematics spatial distribution and the geochemical signature of magmatic centers integrated in these reconstructions allow us to trace mantle related processes revealing the deep dynamics that controls both the magma genesis and the crustal deformation

imaging crustal discontinuities and the downgoing slab beneath western crete the migration of teleseismic receiver functions yields high resolution images of the crustal structure of western crete data were collected during two field campaigns in 1996 and 1997 by networks of six and 47 short period three component seismic stations respectively a total of 1288 seismograms from 97 teleseismic events were restituted to true ground displacement within a period range from 0 5 to 7 s the application of a noise adaptive deconvolution filter and a new polarization analysis technique helped to overcome problems with local coda and noise conditions the computation and migration of receiver functions results in images of local crustal structures with unprecedented spatial resolution for this region the crust under crete consists of a continental top layer of 15 20 km thickness above a 20 30 km thick subducted fossil accretionary wedge with a characteristic en echelon fault sequence the downgoing oceanic moho lies at a depth of 40 60 km and shows a topography or undulation with an amplitude of several kilometres as a consequence of slab depth and distribution of local seismicity the mediterranean ridge is interpreted as the recent accretionary wedge

deformation of western greece during neogene clockwise rotation and collision with apulia following an early miocene phase of n s extension affecting the entire hellenides 50 clockwise rotation affected western greece modern gps analyses show rapid southwestward motion in southwestern greece over subducting oceanic lithosphere and no motion in the northwest where greece collided with apulia we aim to identify the deformation history of western greece associated with the rotation and the collision with apulia the timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures the results show that accompanying the onset of rotation compression was re established in western greece in the early langhian around 15 ma subsequently western greece collided with the apulian platform leading in the late miocene to a right lateral strike slip system running from the aliakmon fault zone in northern greece via the kastaniotikos fault and the thesprotiko shear zone to the kefallonia fault zone offshore western greece ne sw compression and uplift of the ionian islands was accompanied by ne sw extension in southwestern greece associated with faster southwestward motion in the south than in the north this led in the middle pliocene around 3 5 ma to collision without further shortening in northwestern greece from then onward nw se to n s extension east of apulia and gradually increasing influence of e w extension in the south accommodated motion of the hellenides around the apulian platform as a result curved extensional basin systems evolved including the gulf of amvrakikos sperchios basin gulf of evia system and the gulf of corinth saronic gulf system

the geochemistry of carbonate replacement pb zn ag mineralization in the lavrion district attica greece fluid inclusion stable isotope and rare earth element studies strata bound carbonate replacement pb zn ag deposits in the lavrion district greece are spatially related to a late miocene granodiorite intrusion 7 10 ma and various sills and dikes of mafic to felsic composition the plaka granodiorite contains porphyry molybdenum mineralization and is locally associated with a ca fe skarn carbonate replacement deposits occur predominantly in marbles upper and lower marble of the basal unit kaesariani schists and along a major detachment fault that separates the basal unit from the upper unit orebodies are mainly strata bound carbonate replacement although sulfides also occur in veins the mineralogy of carbonate replacement deposits is dominated by base metal sulfides and sulfosalts of ag bi sn sb as and pb particularly at plaka and kamariza carbonates are intergrown with earlier formed sulfides and sulfosalts but are more abundant late in the paragenetic sequence with fluorite and barite fluid inclusion studies of sphalerite fluorite calcite and quartz in carbonate replacement deposits suggest that they were deposited from 132 to 365 c from co2 poor low to high salinity fluids 1 20 wt nacl equiv carbon and oxygen isotope compositions of calcite 13c 15 6 to 1 5 and 18o 9 2 to 17 3 intergrown with sulfides reflect variable exchange of the ore bearing fluid with the upper and lower marbles and proximity to the plaka granodiorite post archean australian shale paas normalized rare earth and yttrium patterns of the upper and lower marbles and calcite intergrown with sulfides show positive eu and negative ce anomalies as well as y ho ratios between 40 and 80 normalized rare earth and yttrium patterns of fluorite also have positive eu and negative ce anomalies such anomalies for both the carbonates and fluorite reflect the high ph or high f o2 conditions of the late stage hydrothermal fluids and the likely derivation of calcium from marine carbonates precursors of the upper and lower marbles the range of sulfur isotope compositions for sulfides 34s 4 9 to 5 3 with one outlier of 9 4 in carbonate replacement and vein deposits is due likely to a magmatic sulfur source with a contribution of reduced seawater sulfate sulfur isotope compositions of barite from carbonate replacement range from 34s 17 2 to 23 7 per mil and reflect miocene seawater sulfate values if a magmatic source of sulfur is assumed along with an average temperature of 250 c for the ore forming fluids as based on fluid inclusion studies sulfides in carbonate replacement deposits were deposited at values of log f o2 41 to 36 and a ph 5 8 to 9 1 however the range of sulfur isotope values does not rule out the possibility that sulfur in sulfides could have been produced by the reduction of seawater sulfate with no contribution from a magmatic source the carbonate replacement deposits resemble manto type sulfide deposits in mexico central colorado south korea nevada and northern greece

tectonostratigraphic models of the alpine terranes and subduction history of the hellenides abstract the tectonostratigraphy of the hellenic terranes is related to their paleogeodynamic and paleogeographic evolution which comprises three major stages i continental rifting in the northern margin of gondwana characterised by volcanosedimentary complexes of late paleozoic triassic ii continental drifting and contemporaneous oceanic opening of tethyan basins in between the continental terranes during triassic paleogene with shallow water carbonate platforms on the continental terranes and ophiolite suites interlayered with pelagic sediments within the tethyan basins iii accretion of the tectonostratigraphic terranes with docking along the active european margin characterised by flysch melange sedimentation along the trenches from early jurassic to neogene two tectonostratigraphic models can be distinguished one for the continental terranes carbonate platforms and another for the oceanic basins the duration of each geodynamic stage for each terrane is obtained from the chronology of the tectonostratigraphic facies change the general trend is younger ages observed in the southern terranes and older ages towards the northern terranes the two alternative tectonostratigraphic models are applied in the two groups of terranes and the chronology of the geodynamic paleogeographic stages is estimated the hellenic subducted slab as shown in the seismic tomographic images is correlated to the terrane paleogeography using the estimated widths and the average subduction rates the upper 1700 km of the slab correspond to the three southern more external terranes whereas the remainingpart of the slab may represent the other more internal terranes a palinspastic model of the hellenides is presented taking into account the chronology of each stage for every terrane obduction of ophiolites over the southern platforms is observed in all four oceanic basins blueschist exhumation formation of core complexes and tectonic windows through extensional detachments occur after micro collision of continental terranes platforms and their isostatic uplift within the upper plate after their detachment from the subducting slab

vorticity analysis in calcite tectonites an example from the attico cycladic massif attica greece abstract although calcite tectonites are widespread in nature their use to quantify flow vorticity is limited we use new micro structural petrofabric and vorticity data to analyse the kinematics of flow in outcrop scale calcite mylonite zones these zones are genetically related to a crustal scale ne directed ductile thrust basal thrust that emplaced the blueschist over the basal unit during the exhumation of the attico cycladic massif calcite microstructures reveal that the last stage of deformation occurred at temperatures 200 300 c achieved by mild heating which is possibly related with the reburial of the basal thrust s footwall vorticity analyses were based on the degree of asymmetry of calcite c axis fabrics as well as on the assumption that the orientation of the long axes of calcite neoblasts within an oblique foliation delineates the direction of instantaneous stretching axis both methodological approaches provide consistent estimates with a simple shear component between 55 and 82 w n 0 76 0 96 the use of the stress axis 1 orientation recorded by twin c axis pairs to quantify vorticity generally gives significantly lower simple shear component comparison of our vorticity estimates with previous estimates inferred from quartz fabrics and rigid porphyroclasts reveals that exhumation related deformation in the nappe pile was steady state

mass wasting and uplift on crete and karpathos during the early pliocene related to initiation of south aegean left lateral strike slip tectonics reconstruction of the vertical motion history of crete and karpathos southeastern aegean region greece from the messinian to recent revealed a previously poorly documented late messinian phase of strong subsidence with rates of 50 100 cm k y followed by stasis during the fi rst 250 k y of the pliocene and then by uplift of 500 700 m during the late early to early middle pliocene uplift continued up to recent albeit at a slower pace and at different rates in different areas the lower pliocene in crete and karpathos is characterized by widespread occurrences of mass wasting deposits which were emplaced over a period of time spanning the fi rst 1 35 m y of the pliocene the origin of these masswasting deposits has long been enigmatic but is here related to uplift which started in crete as early as ca 5 ma it is suggested that the beginning uplift following strong subsidence of various fault blocks until late in the messinian is related to the onset of south aegean strike slip faulting we postulate that small scale tilting of fault blocks by transtensional strike slip faulting and increased seismic activity generated slope failures and subsequent sliding of poorly cemented lower pliocene and uppermost messinian lago mare sediments overlying the terminal miocene erosional unconformity the absence of mass wasting deposits after 3 98 ma while uplift continued is most likely the result of progressive compaction and cementation of the increasingly deeper buried lago mare and lower pliocene sediments thereby preventing slope failure to a depth of the terminal miocene unconformity hiatuses in some places in crete and on karpathos however indicate that slope failures continued to occur although on a smaller scale and less frequent than before connecting the change from subsidence to uplift in the earliest pliocene with the onset of left lateral strike slip tectonics in the southeastern aegean arc would make this major strike slip system much older by 2 m y than the generally accepted age of middle to late pliocene a recently postulated scenario of subduction transform edge propagator step faulting to explain the south aegean strike slip system predicts rates distribution and amount of uplift as rebound to southwestward retreat of the subducted slab along a transform fault zone that is in line with our fi ndings on crete and karpathos and explains the absence of compressional structures associated with the uplift as well as the ongoing southwestward motion of crete

tectono sedimentary evolution of lower to middle miocene half graben basins related to an extensional detachment fault western crete greece crustal extension in the overriding plate at the aegean subduction zone related to the rollback of the subducting african slab in the miocene resulted in a detachment fault separating high pressure low temperature hp lt metamorphic lower from non metamorphic upper tectonic units on crete in western crete detachment faulting at deeper crustal levels was accompanied by structural disintegration of the hangingwall leading to the formation of half graben type sedimentary basins filled by alluvial fan and fan delta deposits the coarse grained clastic sediments in these half grabens are exclusively derived from the non metamorphic units atop the detachment fault being in direct tectonic contact with hp lt metamorphic rocks of the lower tectonic units today the basins must have formed in the period between c 20 and 15 ma prior to the exposure of the hp lt metamorphic rocks at the surface and juxtaposed with the latter during ongoing deformation

how to resist subduction evidence for large scale out of sequence thrusting during eocene collision in western turkey significant along strike variations have locked large parts of the alpine subduction complex in the eastern mediterranean in the eocene and defined the end of high pressure accretion in western turkey structural analysis reveals that the anatolide belt in western turkey formed under greenschist facies metamorphic conditions in the eocene when a high pressure metamorphic fragment of the adriatic plate the cycladic blueschist unit was thrust onto the imbricated mid crustal units of the anatolian microcontinent the menderes nappes the contact between the cycladic blueschist unit and the menderes nappes the cyclades menderes thrust represents an out of sequence ramp which cuts up section towards the south the lack of alpine high pressure fabrics below the cyclades menderes thrust implies c 35 km of exhumation of the cycladic blueschist prior to its eocene emplacement on top of the menderes nappes structure and geodynamic evolution of the anatolide belt are in striking contrast to the neighbouring aegean and contradict the model of a laterally continuous orogenic zone in which the anatolide microcontinent is interpreted as an eastern extension of the adriatic plate

fission track analysis unravels the denudation history of the bonar range in the footwall of the alpine fault south island new zealand we apply fission track thermochronology to shed new light on the tectonic history of zealandia during late cretaceous continental extension and the onset of late tertiary mountain building in the southern alps of new zealand the southern alps are one of the fastest erosionally exhuming mountain belts on earth exhumation of the bonar range in westland just to the northwest of the alpine fault is orders of magnitude slower we report apatite and zircon fission track ages from samples that were collected along an ene wsw profile across the central bonar range parallel to the tectonic transport direction of a prominent ductile fabric in the basement gneiss zircon fission track zft ages show a large spread from 121 9 12 1 ma to 74 9 7 2 ma 1 errors the youngest zft ages of 78 to 75 ma occur at low elevations on either side of the bonar range and become older towards the top of the range thereby showing a symmetric pattern parallel to the ene trending profile across the range age elevation relationships suggest an exhumation rate of 50 100 m ma 1 we relate the zft ages to slow erosion of a tectonically inactive spot in the late cretaceous magmatic arc of zealandia therefore the first main significance of the paper is that it demonstrates that not all of 110 90 ma zealandia was necessarily participating in extreme core complex related extension but that there were enclaves of lithosphere that underwent slow erosion the apatite fission track aft ages range from 11 1 1 9 ma to 5 3 1 0 ma and age elevation relationships suggest an exhumation rate of c 200 m ma 1 we relate the aft ages to the inception of transpressive motion across the alpine fault and modest exhumation in its footwall in late miocene times if so the second significant point of this paper is that transpressive motion across the alpine fault was already under way by c 11 ma

vertical ductile thinning and its contribution to the exhumation of high pressure rocks the cycladic blueschist unit in the aegean the contribution of vertical ductile thinning to the exhumation of high pressure rocks is evaluated by estimating finite strain in 75 exhumed high pressure rocks of the cycladic blueschist unit in the aegean sea greece and western turkey strain data indicate heterogeneous deformation principal stretches are 1 24 5 03 for s x 0 63 2 53 for s y and 0 10 0 81 for s z with a tensor average of s x s y s z 1 52 1 28 0 51 a 1d numerical model which integrates velocity gradients along a vertical flow path with a steady state orogen is used to estimate the contribution of ductile thinning of the overburden of the high pressure rocks to exhumation using a strain rate law that is proportional to depth averaged results show that ductile flow contributed c 20 to exhumation a major implication is that the vertical strain in the exhumed rocks is an overestimate of the contribution that ductile flow makes to the total exhumation a proportional strain rate law that scales linearly with depth implies that material points rising towards the surface move quickly out of the more rapidly deforming part of the orogen therefore very large vertical strains 90 in deeply exhumed rocks are needed for vertical ductile thinning to be a major exhumation process

thrust faults and extensional detachment faults in cretan tectono stratigraphy implications for middle miocene extension abstract the revised tectono stratigraphy of crete and especially of the phyllites quartzites complex demonstrated the distinction of the probable paleozoic low medium grade metamorphic rocks of the arna unit from the underlying permo triassic phyllites and associated carbonate sediments trypali facies of western crete unit as well as the overlying permo triassic phyllites and associated sediments of the tyros ravdoucha beds at the base of the tripolis unit the pre existing mixture of the above tectono stratigaphic units in a single complex created a number of misinterpretations as far as stratigraphy metamorphism and interpretation of low angle faults as thrusts or detachments especially in cases where the inferred tectonic contact concerns the transition between the tyros beds and the base of the tripolis carbonate platform there is no structural omission and therefore the contact represents a minor disharmonic sliding surface and not a detachment based on the revised tectono stratigraphic analysis the determination of the structural omission for each tectonic contact was possible and several detachments were described for the first time footwall rocks of the detachments comprised several tectonic units usually from the lower nappes and hanging wall rocks comprised several tectonic units usually from the upper nappes the detachment may separate not only metamorphosed units in the footwall mani western crete arna from non metamorphosed units in the hanging wall tripolis pindos and higher nappes but also all other possible combinations from the cretan nappe pile extension in crete started in the middle late miocene with the formation of extensional detachment faults the reported extensional structures of oligocene to early miocene age do not correspond to crustal extension of crete but to localized shear zones related to nappe stacking and the exhumation of metamorphic rocks extensional detachments in crete form a tectonic horst through two oppositely dipping e w trending zones one dipping north related to the opening of the cretan basin and the other dipping south related to the formation of the messara supra detachment basin the deformation history of units within crete can be summarized as i compressional deformation producing arc parallel east west trending south directed thrust faults in oligocene to early miocene time ii extensional deformation along arc parallel east west trending detachment faults in middle miocene time with hanging wall motion to the north and south and iii late miocene quaternary transtensional deformation along high angle normal and oblique normal faults that disrupt the older arc parallel structures

u pb sims dating of synkinematic granites timing of core complex formation in the northern anatolide belt of western turkey secondary ion mass spectrometry sims u th pb dating of magmatic zircon from the synkinematic egrigoz and koyunoba granites and a leucogranite dyke dates core complex formation in the northern anatolide belt of western turkey at 24 19 ma the granites intrude into the footwall of the simav detachment and are strongly elongated in the nne direction parallel to tectonic transport on the detachment although large parts of the granites are undeformed localized mylonitic to ultramylonitic deformation occurs directly beneath the simav detachment and preserves evidence of progressive deformation from ductile to brittle conditions oscillatory zoned rims of long prismatic zircon from the egrigoz and koyunoba granites yield identical and well constrained intrusion ages of 20 7 0 6 ma and 21 0 0 2 ma whereas inherited grains range from palaeoproterozoic 2972 13 ma to neoproterozoic 653 6 ma to 500 5 ma in age a leucogranite dyke yields an intrusion age of 24 4 0 3 ma with inherited neoproterozoic 640 7 ma to 511 6 ma grains our data in conjunction with published 40 ar 39 ar biotite ages indicate very rapid cooling greater than c 200 c ma 1 for the granites during and after synkinematic emplacement

an oligocene extrusion wedge of blueschist facies nappes on evia aegean sea greece implications for the early exhumation of high pressure rocks we show that the styra nappe of the cycladic blueschist unit on evia constitutes a wedge of high pressure rocks extruded during early stages of orogeny the nappe pile on evia was assembled during d 2 top to the ssw directed thrusting in restored oligocene coordinates which emplaced the styra and ochi nappes of the cycladic blueschist unit above the almyropotamos nappe between c 33 and 21 ma peak metamorphism of the almyropotamos nappe at c 23 ma occurred at lower metamorphic pressure showing exhumation of the styra nappe during underthrusting and burial of the almyropotamos nappe this exhumation was largely accomplished by the d 2 top to the nne displacing mt ochi normal sense shear zone normal shearing commenced at c 33 ma under peak high pressure metamorphism in the styra and ochi nappes fission track dating indicates slow cooling after d 2 in the styra nappe subsequently the former thrust contact between the almyropotamos nappe and the styra nappe was reactivated as a d 3 top to the ese extensional shear zone and this extensional phase led to the formation of a number of middle to late miocene graben our main conclusion is that there is strong evidence for an oligocene extrusion wedge accomplishing the early exhumation of the styra nappe which demonstrates the importance of extrusion wedges for the initial exhumation of the cycladic blueschist unit

structural analysis of a complex nappe sequence and late orogenic basins from the aegean island of samos greece the island of samos in the aegean sea exposes high pressure metamorphic rocks of the cycladic blueschist unit which are sandwiched between the mildly blueschist facies kerketas nappe below and the overlying non metamorphic kallithea nappe structural and metamorphic analysis shows that deformation can generally be divided into four main stages 1 eocene and earliest oligocene 0ese wnw oriented nappe stacking d1 and d2 associated with blueschist and transitional blueschist greenschist facies metamorphism m1 and m2 d2 caused emplacement of the blueschist unit onto the kerketas nappe indicating that thrusting occurred during decompression 2 a subsequent history of oligocene and miocene horizontal crustal extension d3 before and after greenschist facies metamorphism m3 ductile flow during d3 was characterized by a high degree of coaxial deformation but in general caused displacement of upper units towards the ene nonetheless the late stage d3 emplacement of the kallithea nappe between 9 and 10 ma had a top to the nw nnw sense of shear 3 a short period of brittle e w crustal contraction d4 occurred between 8 6 and 09 ma 4 a phase of n s directed normal faulting d5 8 6 ma to recent ese wnw directed tectonic transport during d1 through d3 is in contrast to uniform nne sswdirected tectonic transport in the adjacent cyclades greece as well as in the neighbouring menderes massif of western turkey published paleomagnetic data reveal sinistral rotation between the cyclades and western turkey we interpret this rotation as a consequence of diaerential extension between the severely extended aegean and the moderately extended menderes massif during d3 the onset of d3 crustal extension is coeval with a marked change in the thermal structure we propose that the thermal reorganization was associated with the retreat of the subduction zone towards the external hellenides in the early oligocene and a subsequent increase in magmatic activity 1999 elsevier science ltd all rights reserved

the north cycladic detachment system low angle normal faults accommodate a large part of continental post orogenic extension besides the intrinsic rheological characteristics of the continental crust that may lead to the formation of shallow dipping shear zones at the brittle ductile transition the role of pre existing low angle structures such as large thrusts has been proposed by several authors we explore this question with the example of the north cycladic detachment system ncds that is composed of a series of distinct detachments cropping out on the islands of andros tinos and mykonos separating the cycladic blueschists in the footwall from the upper cycladic nappe in the hanging wall we show that these extensional structures are part of a single large scale structure more than 200 km along strike that reactivates the vardar suture zone it extends eastward on ikaria and westward offshore evia and thessalia where it probably connects to recent shallow dipping normal faults evidenced on published seismic reflection profiles the ncds started its activity in the oligocene concommitantly with the aegean extension and was still active in the late miocene it has exhumed a series of metamorphic domes from southern evia to mykonos below low angle detachment systems made of low angle normal faults and low angle ductile shear zones the ductile shear zones and the faults were created with a low dip and they kept the same attitude throughout their exhumation we identify three main detachments that are part of a continuum of extension on the ncds tinos detachment livada detachment and mykonos detachment a fourth detachment vari detachment is the reactivation of an eocene exhumation related structure deformation in the footwall is characterized by intense stretching and flattening using the spatial evolution observed along strike from andros to mykonos we construct a history of formation of the ncds starting with the reactivation of former thrusts leading to the exhumation of high temperature metamorphic domes the aegean example shows that reactivation of earlier shallow dipping discontinuities can play a fundamental role in continental post orogenic extension

sequential development of interfering metamorphic core complexes numerical experiments and comparison with the cyclades greece the mechanics of metamorphic core complex mcc development and the associated process of lower crustal flow have been the topic of several modelling studies the model setup usually includes a local heterogeneity forcing deformation to localize at a given site enabling only one mcc to develop this paper presents numerical lithospheric scale experiments in whichdeformationis not a priorilocalizedinaspecificplace inordertoexaminewhethermultiple mccs could develop during extension at which conditions and how configurations with either a singlemccorseveralfar distantmccsalignedinthesectionparalleltoextensionare obtainedfor arelativelywiderangeofinitialconditions theonlyfirmrequirementbeingthatthelowercrustand the sub moho mantle both have very low strengths in contrast only a narrow range of conditions leads to the development of closely spaced mccs in this case the mccs interfere with one another the domes are partly superimposed or and share a shear zone in common and develop in sequence this configuration is compared with the cyclades archipelago where closely spaced chains of mccs have been described in the literature a review of available data on the islandsdocumentsa goodagreement with the experiments intermsoffinal depthofthe moho geo metry and kinematic pattern of the mccs and timing of exhumation of the metamorphic rocks based on this agreement we tentatively deduce from the numerical results some of the conditions that prevailed at the initiation of and during post orogenic mcc type extension in the cyclades themostlikely initial thicknessofthecrust is between40 and44 km a thermallithospheric thick ness of only c 60 km is also likely which might be a condition at the onset of extension or may have been obtained during early stages of extension while the lithosphere was warmed up either a backarc subduction setting or a process of mantle delamination may account for this situ ation the numerical results also suggest a boundary velocity of 2 0 2 3 cm a which should basi cally reflect the rate at which the south hellenic subduction zone retreated considering c 500 km as an upper bound for the amount of retreat balanced by aegean extension and assuming that this retreat mostly occurred during mcc type extension in the cyclades we find that the boundary velocity could have been as high as 2 1 cm a if mcc type extension lasted 24 ma starting at c 30 ma and finishing at c 6 ma as suggested by available geochronological data a velocity of 2 1 cm a agrees well with the numerical results

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

hydrocarbon prospectivity in the hellenic trench system organic geochemistry and source rock potential of upper miocene lower pliocene successions in the eastern crete island greece results of the current and already published studies suggest that the tortonian in age deposits could serve a major source rocks for both oil and gas beneath the messinian evaporites in the hellenic trench system additionally the strong terrestrial input in pliocene deposits could lead to the production of biogenic gas similar to the po basin in adriatic sea italy in the current study fourteen samples from late miocene faneromeni section and twelve samples from the early pliocene makrilia section in eastern crete were collected in order to evaluate their hydrocarbon generation potential for this purpose rock eval analysis and characterization of the organic matter were performed the results document a clear distinction between the two sections faneromeni section contains organic matter of kerogen type iii whereas the makrilia section contains organic matter of kerogen type iv the hi toc plot diagram in both sections indicates poor oil generating potential with the exception of several samples showing fair to good gas and oil potential although thermal maturities of the samples from the two successions are similar according to the t max values samples from faneromeni succession exhibit higher hydrogen index values indicating a better quality of organic matter in terms of hydrocarbon generation very low obtained concentrations of bitumen mg g of rock as well as the predominance of nso compounds compared to the saturates and aromatics indicate low maturation level the n alkanes profiles exhibit a bimodal distribution indicating a mixed origin marine and terrestrial of the organic matter in both areas terrestrial organic matter input is more pronounced in makrilia section the analysis of saturated biomarkers indicates that faneromeni deposits were accumulated under constant organic matter input in an environment influenced by cyclic changes from marine to lagoon origin and vice versa faneromeni section corresponds to a restricted basin during tortonian with quick and often sea level fluctuations just before the messinian crisis while makrilia section represents a very restricted intramontane basin with strong terrestrial influence

low angle faults above and below a blueschist belt tinos island cyclades greece new observations from the island of tinos greece allow a better definition of the structural position of the alpine eocene blueschist belt exposed in the islands of the aegean sea these blueschists over a significant part of the aegean sea are delimited from below by a low angle thrust fault while from above they are delimited by a low angle normal type fault which omits a substantial crustal interval both underlying and overlying rocks were not affected by the high metamorphism the rapid uplift and exhumation of the high rocks was therefore mainly the result of fault movements rather than erosion and whole crust uplifting the low angle normal fault apparently had a major role in the uplift of the blueschists

low effective viscosity during high pressure metamorphism due to dissolution precipitation creep the record of hp lt metamorphic carbonates and siliciclastic rocks from crete the micro structural record of high pressure low temperature hp lt metamorphic rocks t 400 50 c p 10 2 kbar of the phyllite quartzite unit in western crete greece is interpreted in terms of deformation mechanisms and flow stress phyllites were deformed at low stress by dissolution precipitation creep governed by strongly enhanced dissolution along quartz mica 001 phase boundaries quartzites and quartz veins were deformed by dislocation creep at higher flow stress the contrasting effective viscosities caused stress concentration in the quartzites and quartz veins also microstructures from aragonite marbles indicate that dissolution precipitation creep was the dominant deformation mechanism and that dislocation creep has not been activated in these rocks pervasive ductile deformation was restricted to hp lt metamorphic conditions and the microstructural record of deformation at maximum depth has been preserved with all subsequent deformation localized and confined to the brittle field constraints on the timing of deformation allow an estimation of strain rates experimentally determined flow laws for dislocation creep are used to pose upper bounds on flow stress and bulk viscosities of rocks deformed by dissolution precipitation creep for the phyllites a conservative estimate is about 1019 pa s or below in contrast to 1020 pa s derived for the quartzites this compares well to the viscosity contrast of 1 2 orders of magnitude reflected by the mesoscopic structures since phyllites and carbonate rocks form large portions of the subducted sedimentary pile the low flow stress during rapid deformation of these rocks at hp lt metamorphic conditions and the lack of deformation along the burial and exhumation path imply very low strength of the plate boundary shear zones and negligible shear heating

timing slip rate displacement and cooling history of the mykonos detachment footwall cyclades greece and implications for the opening of the aegean sea basin we constrain the slip and cooling history of the mykonos detachment footwall using thermochronometry a u pb zircon age of 13 5 0 3 ma dates intrusion of the mykonos monzogranite 40 ar 39 ar hornblende and biotite ages from the monzogranite are 12 7 0 6 ma and 10 9 0 6 ma whereas zircon and apatite fission track ages range from 13 0 8 ma to 10 7 0 8 ma and 12 5 2 2 ma to 10 5 1 8 ma u th he ages range from 13 6 0 6 ma to 9 0 0 7 ma for zircon and 11 1 0 5 ma to 8 9 0 4 ma for apatite the ages in part overlap within 2 errors and together with the long apatite fission track lengths 14 m support rapid cooling at rates 100 c ma 1 the low temperature thermochronometric ages decrease east northeastwards in the direction of hanging wall transport on the mykonos detachment age distance relationships show that the mykonos detachment slipped at an average rate of 6 0 9 2 2 4 km ma 1 causing c 30 km of offset and c 12 km of exhumation this result indicates that miocene low angle normal faulting was not important for the exhumation of the cycladic blueschist unit the opening of the aegean sea basin in the miocene was controlled by a few large magnitude low angle normal faults

a review of tectonics and sedimentation in a forearc setting hellenic thrace basin north aegean sea and northern greece abstract exposure of the forearc region of the north aegean sea greece offers insight into evolving convergent margins the sedimentary fill of the thrace basin during the late eocene to oligocene time provides a record of subduction driven processes such as growth of magmatic arcs and construction of accretionary complexes this large sediment repository received sediment from two sources the southern outboard basin margin reflects the active influence of the exhumed accretionary prism e g pindic cordillera or biga peninsula while the northern inboard margin records the effect of the magmatic arc in the rhodope region the forearc basin sedimentary fills shoal upward into shallow marine strata but are dominated mainly by deep marine facies the depositional trend and stacking pattern are dominated by progradational patterns this trend which is observed in both basin margins is related to tectonic deformation rather than sea level fluctuations additional evidence for this tectonic uplift comes from the backstripping analysis the accretionary complex provided material into the forearc basin this material was transported northeast and formed a sand rich turbidity system that evolved upslope into shallow marine deposits stratigraphic data indicate that this turbidity system exhibits a successive landward inboard migration of the depocenter provenance data utilizing sandstone petrography conglomerate clast composition and bulk rock geochemistry suggest that this system reflects an increased influx of mafic material into the basin volcanic arc derived material was transported south and east and accumulated in deep marine settings both stratigraphic and provenance data indicate a seaward outboard migration of the basin depocenter and a significant increase in felsic detritus into the forearc

single grain argon laser probe dating of phengites from the blueschist to greenschist transition on sifnos cyclades greece measurements of 40ar 39ar age spectra on single white mica crystals of tertiary age is a new means of obtaining detailed geochronological information of alpine blueschists internal consistency of the data set as well as excellent agreement with previous conventional k ar results demonstrates that this new technique can be used with confidence to obtain information on the thermal evolution of young metamorphic belts

the lavrion pb zn ag rich vein and breccia detachment related deposits greece involvement of evaporated seawater and meteoric fluids during postorogenic exhumation

slab fragmentation beneath the aegean anatolia transition zone insights from the tectonic and metamorphic evolution of the eastern aegean region abstract slab tearing below western turkey had first order tectonic and magmatic consequences by inducing a lateral gradient of extension in the upper plate and toroidal flow of asthenosphere that affected the typology and distribution of melts at the surface but the coupling mechanisms between the 3d mantle flow at depth and deformation in the upper plate above a slab tear have received little attention so far this paper is focused on the description of the distribution and kinematics of deformation in the eastern part of the aegean sea within the transition zone between the cyclades and the menderes massif which have been little studied by investigating the dodecanese and eastern aegean islands we thus complete the description of the extensional strain field in the overriding plate around the slab tear there extension related to slab retreat and tearing keeps a constant nne ssw direction accommodating the difference in finite rates of extension without localized crustal scale strike slip faults and block rotations above the tear in addition despite the complexity involved in the aegean anatolian orogenic wedge a similar structural position is recognized through the entire region from top to bottom we found that i the lycian units which were exhumed earlier in the late cretaceous ii the higher pressure and higher temperature units i e the upper cycladic blueschist nappe with exception of the vourliotes nappe in samos and finally iii the colder units such as amorgos unit the menderes and its cover before the main menderes metamorphism overprint and the lower cycladic blueschist nappe e g milos folegandros a part of the dodecanese and fourni islands

the extensional messaria shear zone and associated brittle detachment faults aegean sea greece structural thermochronological and metamorphic data are used to elucidate the tectonic nature and evolution of the ductile extensional messaria shear zone and the associated brittle messaria and fanari detachment faults which exhumed their footwall from mid crustal depths on the island of ikaria in the aegean thermobarometric data indicate that the messaria shear zone formed at 350 400 c and 3 4 kbar i e at a depth of c 15 km normal faulting was accompanied by the intrusion of two granites which together with the thermobarometric data indicate a relatively high thermal field gradient of 25 35 c km 1 zircon and apatite fission track and apatite u th he ages demonstrate rapid cooling in the footwall of the messaria detachment from c 400 c to c 40 c between 11 and 3 ma age distance relationships of the data suggest that the messaria shear zone and the messaria detachment slipped at apparent rates of c 6 9 km ma 1 kinematic indicators show a consistent top to the nne shear sense for the extensional faults however at the southern part of the messaria detachment some late stage shear sense indicators are top to the ssw and are assumed to be associated with updoming of the footwall numerous deformed pegmatite veins in the messaria shear zone allow the reconstruction of deformation and flow parameters the mean kinematic vorticity number ranges from 0 13 to 0 80 indicating that shearing deviated significantly from simple shear that is extensional shearing was associated with vertical ductile thinning which contributed to tectonic exhumation finite strain shows oblate geometries and axial ratios of the finite strain ellipse in sections parallel to tectonic transport and normal to the mylonitic foliation range from 1 8 to 19 9 we calculate using a 1d numerical model that vertical ductile thinning contributed c 20 to exhumation during extensional shearing normal faulting was the major agent exhuming the footwall from c 15 km depth

kinematics of a twisted core complex oblique axis rotation in an extended terrane betic cordillera southern spain 1 the sierra de las estancias is a metamorphic core complex that developed during the late oligocene to early miocene extensional collapse of the betic cordillera structural and paleomagnetic analysis shows that the northern half of the complex has been strongly modified by rotation about an inclined axis requiring reassessment of the kinematics of the extensional phase of deformation the extensional tectonic event produced two major detachment faults associated mylonitic foliation and lineation and pervasive sets of shear bands and brittle normal faults with a top to ne shear sense an older foliation was largely transposed and reoriented during this event the regional foliation now defines a broad antiform with a steep north dipping limb and the trend of shear related lineations swings from nne to ene from the southern gently dipping limb into the north dipping limb the remanent magnetization in a suite of near vertical early miocene mafic dikes intruded into the north dipping limb has a declination of 243 and an inclination of 27 assuming that the dikes were originally vertical a rotation of approximately 50 about an inclined ssw plunging axis preserves the near vertical orientation of the dikes and brings the remanence into agreement with the expected orientation for an early miocene age correction for this rotation brings the foliation and lineation in the surrounding schists into orientations subparallel to those on the present southern limb of the antiform and the dikes into a vertical e w orientation the corrected orientation of the shear related lineation nne normal faults and dikes suggests that the original direction of extension during the late orogenic extensional event in the internal betic cordillera may therefore have been around nne ssw rather than e w as currently accepted the observed net tectonic rotation can be decomposed into a series of geologically plausible rotations involving domino style rotation due to slip on the late brittle normal faults tilting about the regional fold axis related to thrust ramping onto the iberian margin during miocene collision and a 30 clockwise rotation about a vertical axis related to oblique convergence with the iberian margin

constraining the long term evolution of the slip rate for a major extensional fault system in the central aegean greece using thermochronology the brittle ductile transition is a major rheologic boundary in the crust yet little is known about how or if rates of tectonic processes are influenced by this boundary in this study we examine the slip history of the large scale naxos paros extensional fault system npefs cyclades greece by comparing published slip rates for the ductile crust with new thermochronological constraints on slip rates in the brittle regime based on apatite and zircon fission track aft and zft and u th he dating we observe variable slip rates across the brittle ductile transition on naxos zft and aft ages range from 11 8 0 8 to 9 7 0 8 ma and 11 2 1 6 to 8 2 1 2 ma and u th he zircon and apatite ages are between 10 4 0 4 to 9 2 0 3 ma and 10 7 1 0 to 8 9 0 6 ma respectively on paros zft and aft ages range from 13 1 1 4 ma to 11 1 1 0 ma and 12 7 2 8 ma to 10 5 2 0 ma while the u th he zircon ages are slightly younger between 8 3 0 4 ma and 9 8 0 3 ma all ages consistently decrease northwards in the direction of hanging wall transport most of our new thermochronological results and associated thermal modeling more strongly support the scenario of an identical fault dip and a constant or slightly accelerating slip rate of 6 8 km myr 1 on the npefs across the brittle ductile transition even the intrusion of a large granodiorite body into the narrowing fault zone at 12 ma on naxos does not seem to have affected the thermal structure of the area in a way that would significantly disturb the slip rate the data also show that the npefs accomplished a minimum total offset of 50 km between 16 and 8 ma

kinematic finite strain and vorticity analysis of the sisters shear zone stewart island new zealand abstract the sisters shear zone ssz on stewart island new zealand is a greenschist facies extensional shear zone active prior to and possibly during the development of the pacific antarctica spreading ridge at 76 ma we report quantitative kinematic and rotation data as well as apatite fission track aft ages from the ssz early kinematic indicators associated with the nne trending stretching lineation formed under upper greenschist facies metamorphism and show alternating top to the nnw and top to the sse senses of shear during progressive exhumation lowermost greenschist facies and brittle ductile kinematic indicators depict a more uniform top to the sse sense of shear in the topmost ssz just below the detachment plane deformed metagranites in the ssz allow the reconstruction of deformation and flow parameters the mean kinematic vorticity number w m ranges from 0 10 to 0 89 smaller numbers prevail in the deeper parts of the shear zone with a higher degree of simple shear deformation in the upper parts of the shear zone deeper and upper parts relate to present geometry high finite strain intensity correlates with low w m and high w m numbers near the detachment correlate with relatively weak strain intensity finite strain shows oblate geometries overall our data indicate vertical and possibly temporal variations in deformation of the ssz most aft ages cluster around 85 75 ma we interpret the aft ages to reflect the final stages of continental break up just before and possibly during the initiation of sea floor spreading between new zealand and antarctica

postnappe stacking extension and exhumation of high pressure low temperature rocks in the island of crete greece the island of crete consists largely of nappes of contrasting lithologies and metamorphism that were stacked southward during an oligocene early miocene n s compression with the lower nappes undergoing a high pressure low temperature hp lt metamorphism this was followed by a n s miocene crustal extension that caused thinning of the nappes and uplift of the hp lt metamorphic rocks ductile conditions took place in the lower nappes associated with a retrograde greenschist metamorphism while semiductile to brittle conditions took place in the upper nappes a major normal detachment fault separates the lower and the upper nappes the quartz texture analyses and the symmetry of structures indicate bulk coaxial deformation while the results of strain analysis suggest both constrictional and flattening strains a younger ne sw compression affected both the thinned nappe pile and the late miocene pliocene sedimentary basins finally a pliocene ne sw extension led to further uplift and exhumation of the hp lt metamorphic rocks this cyclic tectonometamorphic process of alternate compression and extension took place during the migration of the hellenic orogenic belt toward the most external units including successive tectonic events

miocene high pressure metamorphism in the cyclades and crete aegean sea greece evidence for large magnitude displacement on the cretan detachment the cyclades in the backarc region of the present hellenic subduction zone are known for widespread late cretaceous to eocene high pressure metamorphism in the cycladic blueschist unit we report 40 ar 39 ar and rb sr phengite ages of 24 21 ma for high pressure metamorphism 8 10 kbar 350 400 c in the lowest tectonic unit in the cyclades the basal unit which structurally underlies the cycladic blueschist unit the basal unit is correlated with the tripolitza unit of the external hellenides in the forearc region of the hellenic subduction zone the tripolitza unit is unmetamorphosed on crete where it is separated from the underlying high pressure 8 10 kbar 300 400 c plattenkalk and phyllite quartzite units by the extensional cretan detachment the age for high pressure metamorphism in the latter units is similar to our age for the basal unit in the cyclades because pressure temperature conditions in the plattenkalk and phyllite quartzite units on crete and the basal unit in the cyclades are also similar they must have been in close proximity in the early miocene hellenic subduction zone a palinspastic reconstruction suggests a subsequent displacement of 100 km on the cretan detachment this is one of the greatest displacement magnitudes ever reported from detachment faults because of this large offset the cretan detachment was an efficient agent for exhuming high pressure rocks

the shelf to basin iron shuttle in the black sea revisited continental shelf sediments are a major source of iron fe for phytoplankton in surface waters in this study we investigate the mechanisms that control release of fe from shelf sediments and its lateral transport shuttling in oxic and hypoxic waters on the northwestern black sea shelf we find that at two coastal stations near the outflow of the danube river high input of organic matter drives strong reductive dissolution of fe oxyhydr oxides henceforth termed fe oxides in surface sediments supporting high rates of fe release to oxygenated bottom waters 0 36 mmol m 2 d 1 we suggest that bioirrigation plays a key role in the release of fe from these sediments at four stations further offshore organic matter deposition is lower resulting in limited mobilization of fe2 in the sediment and low benthic fluxes of fe 0 2 m in the lower part of the water column likely through repeated deposition and resuspension of fe oxides from surface sediments using synchrotron based x ray spectroscopy and sequential chemical extractions we demonstrate that the suspended matter and surface sediments are enriched in easily reducible fe oxides mostly ferrihydrite and fe associated with clay the mobilization of fe in the coastal zone and subsequent lateral transport of these fe bearing particles results in higher ratios of fe al in surface sediments at outer shelf stations ca 1 2 to 2 wt wt 1 than at coastal stations ca 0 5 to 0 9 wt wt 1 however below the sediment surface layer fe al ratios are similar at all stations indicating limited burial of the laterally transported fe our results highlight the critical role of organic matter input associated biological activity and riverine fe input as drivers of fe shuttling on continental shelves we also show that in shelf areas where sediments receive low inputs of organic matter physical transport controls the ultimate fate of the shuttled fe

normal faulting at convergent plate boundaries mylonitic extensional fabrics in the franciscan subduction complex in del puerto canyon california revisited 1 using a strain and rotation analysis we tested the hypotheses that top east mylonitic extensional structures in the uppermost franciscan subduction complex in del puerto canyon california accomplished exhumation of the franciscan blueschists we found no evidence of strongly noncoaxial deformation instead our data indicate overall coaxial deformation in the proposed zone of mylonitic extensional deformation there are no extensional strains moderate vertical shortening occurred without horizontal extension and was compensated by modest deformation related volume loss there is also no strain gradient toward and within the proposed shear zone therefore the results of our work indicate that mylonitic extensional structures in del puerto canyon do not exist overall we conclude that there is no currently identifiable structure adjacent to or within the franciscan in california that could have accommodated large scale horizontal extension exhumation of the franciscan blueschists was mainly achieved by erosion of an emergent forearc high our strain results and published data are also inconsistent with the development of a supercritically tapered franciscan wedge that ultimately should have triggered normal faulting strain magnitudes are low despite the relatively long residence time of the rocks in the accretionary wedge from this we infer that strain rates were low and that the wedge material flowed with a relatively high viscosity therefore ductile flow probably was not fast enough to form a supercritically tapered franciscan wedge

along strike variations of p t conditions in accretionary wedges and syn orogenic extension the hp lt phyllite quartzite nappe in crete and the peloponnese syn orogenic detachments in accretionary wedges make the exhumation of high pressure and low temperature metamorphic rocks possible with little erosion the velocity of exhumation within the subduction channel or the accretionary complex and thus the shape of p t paths depend upon the kinematic boundary conditions a component of slab retreat tends to open the channel and facilitates the exhumation we document the effect of slab retreat on the shape of p t paths using the example of the phyllite quartzite nappe that has been exhumed below the cretan syn orogenic detachment during the miocene in crete and the peloponnese data show a clear tendency toward colder conditions at peak pressure and during exhumation where the intensity of slab retreat is larger this spatial evolution of p t gradient is accompanied with an evolution from a partly coaxial regime below the peloponnese section of the detachment toward a clearly non coaxial regime in crete

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

core complex related extension of the aegean lithosphere initiated at the eocene oligocene transition 1 core complex related stretching of the aegean lithosphere was accommodated in part by the south cyclades shear zone scsz which outcrops on the islands of ios and thera aegean sea greece this paper reports new microstructurally focused 40ar 39ar geochronology that suggests the scsz initiated just before the time of the eocene oligocene transition at 35 ma therefore it is not only miocene extension that led to the tethyan metamorphic core complexes exposed in the cycladic archipelago it is shown here that pervasive top to the south directed ductile shear took place in the scsz for 5 ma during the early oligocene followed by initiation of overprinting north sense shear zones at the time of the oligocene miocene transition at 25 ma this means that modern core complex related extension in the aegean started much earlier than has been previously recognized and that stretching of the aegean lithosphere took place in a distinctly episodic fashion not in a manner that can be described as continuous or progressive the data also mean that the complementary shear sense geometry of the scsz and the north cyclades shear zone ncsz cannot be interpreted as crustal scale boudinage initiated during crustal extension in miocene time since the opposing sense shear zones operated at distinctly different times the paper illustrates the difficulties involved in systematically determining the age of deformation fabrics using 40ar 39ar geochronology and provides a case study that shows the value of carefully designed step heating experiments on microstructurally controlled samples in samples such as these from complex metamorphic tectonites laser fusion or step heating experiments with relatively few steps would have led to erroneous conclusions

rb sr isotope studies on tinos island cyclades greece additional time constraints for metamorphism extent of infiltration controlled overprinting and deformational activity this study presents new rb sr age data concerning the metamorphic evolution of the attic cycladic crystalline belt which represents a complex polymetamorphic terrane within the alpidic orogenic belt of the hellenides two major groups of tectonic units can be distinguished metamorphism in parts of the upper units is commonly considered as a cretaceous event in contrast the group of lower units experi enced tertiary high pressure metamorphism which was followed by a medium pressure overprint we focus on the island of tinos where a representative spectrum of the rock units found in the cyclades is exposed in three tectonic units the upper unit the intermediate unit and the basal unit the complete range of tectono metamorphic and magmatic events affecting the attic cycladic crystalline belt is documented by numerous petrological and tectonic studies phyllites and phyllonites from the ophiolitic upper unit yielded rb sr apparent ages phengite whole rock between c 92 and 21 ma the older age differs from the cretaceous dates reported for upper unit rocks elsewhere in the cyclades it is suggested that the sequence studied belongs to the jurassic ophiolites of the hellenides rather than to cretaceous occurrences the spread to younger ages is related to non pervasive rejuvenation and resetting of the rb sr system during tectonic juxtaposition of the upper unit over the intermediate unit the youngest age obtained so far for a sample from the upper unit 21 ma is believed to approximate the timing of tectonic juxtaposition which probably occurred during a regional greenschist facies episode producing a pervasive overprint in the struc turally lower tectonic unit the major phyllite meta gabbro serpentinite sequence of the upper unit is inter preted as an emplacement related ductile shear zone which experienced reworking under brittle conditions in the intermediate unit a gradient in rb sr ages from top c 40 ma to the bottom c 22 ma was recog nized which is interpreted to represent greater effects of fluid infiltration and overprinting in the lower parts of this unit possibly controlled by variable intensity of deformation which might be related to tectonic jux taposition onto the basal unit we suggest that synmetamorphic stacking of all three tectonic units took place during an oligocene miocene greenschist event extensional deformation continued after tectonic stacking and after intrusion of the main granite as is indicated by a rb sr whole rock isochron 15 1 0 6 ma for a ductilely deformed garnet bearing leucogranite from the marginal parts of the main undeformed pluton application of the rb sr dating technique provided no unequivocal evidence that previously pub lished eocene k ar and 40 ar 39 ar dates for high pressure phengites from the lower units are significantly contaminated with excess argon

granite intrusion in a metamorphic core complex the example of the mykonos laccolith cyclades greece abstract the aegean domain is a well suited place to study the formation of metamorphic core complex mcc and to investigate the role of syn tectonic granites on their development in the northern cyclades the mykonos delos rhenia mcc is characterized by the intrusion of a kilometer scale late miocene pluton of i type granitoids within a migmatitic gneiss dome new combined ams anisotropy of magnetic susceptibility and microstructural studies on the mykonos granitoids together with recently published thermochronological data allow us to use the granitoids as strain markers the mykonos granitoids form a laccolith like intrusion with a n70 e long axis the laccolith is strongly asymmetric with an outlying root zone to the sw and a major body mainly developed to the ne the laccolith construction is due to successive pulses of more or less differentiated magma that intruded the cycladic blueschist unit the attitude of stretching markers suggests an important about 60 vertical axis local rotation phenomenon in the cycladic upper crust during the exhumation of the mykonos mcc structural data suggest a four stage evolution of the mykonos mcc i a first stage characterized by flat shearing toward the n ne and by the formation of a domal structure in migmatitic paragneisses with multi scale generation of folds with axes either perpendicular or parallel to the regional stretching as a result of the interplay between regional n20 e directed extension and ew shortening ii a second stage marked by the emplacement of the mykonos laccolith at 13 5 0 3 ma at the top of the migmatitic paragneisses iii the third stage corresponding to the development of protomylonitic foliations and lineations in the whole laccolith in high to medium temperature conditions and iv the late stage marked by an acceleration of the exhumation of the mykonos mcc this exhumation was accommodated by important rotations of upper crustal blocks during the end of the exhumation processes around 10 ma deformation localized at the top of the laccolith in semi ductile conditions and then in brittle conditions in the major detachment plane our study shows that the cycladic plutonism event had no role on the initiation of the mcc however the geometry of the mykonos intrusion supports that the magmas are sucked into the direction of regional extension and that the intrusion of magmas has caused an acceleration of the last stages of the mcc development this acceleration was marked by a very fast exhumation of the laccolith after its emplacement

alpine high pressure metamorphism at the almyropotamos window southern evia greece the alpine orogenic belt of the hellenides has been strongly reworked by ductile and brittle extensional tectonics extensional structures have affected the central aegean region and obliterated much of the original orogenic architecture since at least early miocene times in the area of almyropotamos on the island of evia flanking the western part of the aegean a unique remnant compressional nappe stack involving tertiary metamorphic rocks has been preserved this nappe sequence comprises a high pressure rock unit on top of a lower grade unit the upper unit south evia blueschist belt is thought to be the westward continuation of the cycladic blueschist belt metamor phosed at high pressure conditions during late cretaceous eocene times the underlying unit the almyropotamos unit is a continental margin sequence covered by a flysch and containing lutetian nummulites indicating that this unit accumulated sediments until at least late eocene times in the present study we analyse the petrology of the almyropotamos nappe stack and define the p t conditions of each of the different rock units exposed there the presence of glaucophane law sonite rimmed by epidote and jadeite 70 mol suggest that peak p t conditions in the south evia blueschist belt reached approximately 10 12 kbar and 350 450 c unlike previous studies which estimated that the underlying almyropotamos unit reached only greenschist facies conditions glau cophane relics and si rich phengites were found by us in this unit these indicate that high pressure metamorphism and crustal thickening in this part of the aegean lasted until at least the late eocene or early oligocene we note that in this respect the architecture of southern evia resembles that of north ern greece olympos ossa our structural data indicate that rock units in the almyropotamos area record different folding phases with the south evia blueschist belt having a more complex fold his tory than the underlying almyropotamos unit the entire nappe stack shares large scale folds which are e w trending and locally overturned to the south and which may represent at present coordi nates n s contraction and nappe transport

a numerical model of the hellenic subduction zone active stress field and sea level changes a 2 d viscoelastic finite element model for subduction in the southern aegean sea allows us to study the distribution of stress and surface velocities in a vertical cross section through the island of crete recent tomographic results constrain the geometry of the slab and the structure of the crust lithosphere and mantle two models are considered the first for passive subduction driven solely by slab pull and the second one where active convergence between the african and aegean plates is also included both models predict subsidence of the hellenic trench and of cretan trough uplift of crete and of the aegean volcanic arc the island of crete is subject to differential uplift highest in the southern part with maximum rates of 1 5 and of 3 2 mm yr for the two models respectively these results agree with the tectonic uplift inferred from holocene sea level changes in the island the style of stress within the modeled african and aegean plates is in general agreement with the focal mechanisms of the largest earthquakes along the subduction zone

the lavrion pb zn fe cu ag detachment related district attica greece structural control on hydrothermal flow and element transfer deposition abstract the impact of lithological heterogeneities on deformation fluid flow and ore deposition is discussed based on the example of the lavrion low angle detachment partly accommodating gravitational collapse of the hellenides orogenic belt in greece the lavrion peninsula is characterised by a multiphase pb zn fe cu ag ore system with a probable pre concentration before subduction followed by progressive remobilisation and deposition coeval with the development of a low angle ductile to brittle shear zone the mylonitic marble below the detachment shear zone is composed of white layers of pure marble alternating with blue layers containing impurities sio2 al2o3 carbonaceous material ductile mylonitic deformation is more pervasive in the less competent impure blue marble we propose that localised deformation in the impure marble is associated with fluid circulation and dolomitisation which in turn causes an increase in competence of these layers mineralised cataclastic zones crosscutting the mylonitic fabric are preferentially localised in the more competent dolomitic layers oxygen and carbon isotopic signatures of marble invaded by carbonate replacement deposits during ductile to ductile brittle deformation are consistent with decarbonation coeval with the invasion of magmatic fluids mineralised cataclastic zones reflecting brittle deformation evolve from low 13c to low 18o signatures interpreted as local interaction with carbonaceous material that trends toward the contribution of a surface derived fluid these features indicate that the lavrion area records a complex deposition history influenced by the evolution of fluid reservoirs induced by the thermal and mechanical evolution of the marble nappe stack ore remobilisation and deposition associated with the activity of the low angle detachment is i firstly related to the intrusion of the plaka granodiorite leading to porphyry type and carbonate replacement mineralisation during ductile brittle deformation and ii then marked by progressive penetration of surface derived fluids guided by strain localisation in the more competent levels leading to epithermal mineralisation associated with brittle deformation

late permian early triassic igneous activity in the attic cycladic belt attica new geochronological data and geodynamic implications article i nfo article history igneous rocks of the attic cycladic belt acb formed prior to the alpine orogeny have received relatively little attention especially regarding their crystallisation age new u pb shrimp zircon data from mylonitised metagranitoid rocks within metapelites and metabasites of the pentelikon mountain lower tectonic unit ltu of attica in combination with internal zircon characteristics reveal the following the metagranitoid precursor was very likely an i type pluton crystallising in two successive stages at 255 3 ma and 246 2 ma weighted mean 206 pb 238 u ages error at 95 c l these age results are respectively marginally older than and within un certainty of the 240 4 ma protolith age reported for metagranitoids of the same unit in the area of lavrion at tica they are in line with the protolith ages of several meta igneous rocks within the cycladic blueschist unit of aegean islands one core zircon domain and one single zircon grain yielded

raman spectroscopic carbonaceous material thermometry of low grade metamorphic rocks calibration and application to tectonic exhumation in crete greece we present new raman spectra data of carbonaceous material cm to extend the range of the raman spectra of cm thermometer rscm to temperatures as low as 100 8c previous work has demonstrated that raman spectroscopy is an excellent tool to describe the degree of graphitization of cm a process that is independent of pressure but strongly dependent on metamorphic temperature a linear relationship between temperature and the raman parameter r2 derived from the area of the defect band relative to the ordered graphite band forms the basis of a previous thermometer because r2 shows little variability in low temperature samples 330 8c serves as a lower limit on the existing thermometer herein we present raman spectra from a suite of low temperature 100 to 300 8c samples from the olympics mountains and describe other aspects of the raman spectra of cm that vary over this range in particular the raman parameter r1 the ratio of heights of the disordered peak to ordered peak varies regularly between 100 and 350 8c these data together with published results from higher temperature rocks are used to calibrate a modified rscm thermometer applicable from 100 to 700 8c application to low grade metasediments in the otago region in the south island of new zealand gives temperatures consistent with previous estimates demonstrating the reliability of the modified rscm thermometer we apply the modified rscm thermometer to 53 samples from crete to evaluate the role of the cretan detachment fault in exhuming miocene high pressure low temperature metamorphic rocks exposed there the metamorphic rocks below the detachment the plattenkalk and phyllite quartzite units give metamorphic temperatures that range from 250 to 400 8c consistent with previous petrologic estimates we also demonstrate that the tripolitza unit which lies directly above the detachment gives an average metamorphic temperature of about 260 8c the modest break in metamorphic temperature in central crete indicates that the cretan detachment accounts for only 5 to 7 km of exhumation of the underlying hp lt metamorphic rocks which were initially accreted at 35 km we argue that the bulk of the exhumation 28 km out of 35 km total occurred by pervasive brittle stretching and erosion of structural units above the detachment d 2005 elsevier b v all rights reserved

extension and exhumation of the hp lt rocks in the hellenic forearc ridge localized intensive ductile and ductile brittle extension of along the arc orientation is prominent in phyllite quartzite unit pqu rocks in kythera and the adjacent southeastern peloponnese but declines in prominence to the north and to the south along the cretan peloponnese ridge using zircon and apatite fission track dating we find that this structural characteristic is correlated with the youngest zircon fission track cooling ages of 14 to 9 ma and with the highest pressure temperature condition recorded in the metamorphic rocks below the structural detachment the cooling ages of the high pressure phyllite quartzite unit pqu rocks along the hellenic forearc ridge show that exhumation migrated from both crete and from the peloponnese to the area with the youngest ages in kythera and the southeastern peloponnese starting in the early miocene and continuing to the present trench rollback and slab retreat expanded the hellenic arc and this bending of the arc from an initial more rectilinear geometry increased areas of oblique convergence and we suggest this localized the subsequent arc parallel extension and local enhanced exhumation of hp rocks the zircon fit exhumation ages from the arc parallel stretching episode restrict the ductile part of this episode in exposed rocks to between about 14 and 9 ma apatite ft ages suggest brittle along arc extension continued to about 7 ma this episode is proposed to be the result of a temporary higher rate of rollback and slab retreat younger normal faults including those which define the margins of the present hellenic arc show return to arc normal extension

high pressure metamorphism in the aegean eastern mediterranean underplating and exhumation from the late cretaceous until the miocene to recent above the retreating hellenic subduction zone 1 we report 40ar 39ar ages from various tectonic units in the aegean and westernmost turkey on the basis of published geochronologic data and our 40ar 39ar ages we propose that the aegean is made up of several high pressure units which were successively underplated from the late cretaceous until the miocene ages for high pressure metamorphism range from 80 83 ma in parts of the vardar izmir ankara suture zone in the north to 21 24 ma for the basal unit in the cyclades and the external high pressure belt on crete in the south published seismic data suggest that high pressure metamorphism is currently occurring underneath crete younging of high pressure metamorphism in a southerly direction mimics the southward retreat of the hellenic subduction zone we propose that distinct stages of high pressure metamorphism were controlled by the underthrusting of fragments of mainly thinned continental crust and that these punctuated events were superposed on progressive slab retreat by far most of the exhumation of the high pressure units occurred early during the orogenic history in a forearc position

eocene tectonometamorphism on serifos western cyclades deduced from zircon depth profiling geochronology and mica thermochronology abstract phengite bearing metasedimentary sequences preserving relict glaucophane from serifos western aegean are indicative of high pressure conditions during cycladic blueschist metamorphism depth profiling and conventional sims u pb geochronology and o isotope analysis on zircon from highly strained orthogneisses at the base of the sequence reveal xenocrystic zircon with varying degrees of recrystallization one end member population has needle like or prismatic morphologies is internally oscillatory zoned with little to no rim material created during recrystallization these zircons yield triassic to carboniferous ages elevated th u and 18 o mostly ranging between 4 and 11 in marked contrast a separate zircon population has a spongy structure created by complete recrystallization of the pre existing crystal these zircons possess low th u and flat hree patterns and yield eocene ages with 18 o 7 chondrite normalized ree profiles are extremely depleted within this spectrum other zircons show variable states of recrystallization and mixed ages regression of u pb data from three mylonitic orthogneiss samples that exhibit near complete recrystallization and similar age depth profiles yields c 40 ma ages these new data are the first geochronological constraints that successfully demonstrate an eocene metamorphic event in the western cyclades and new 40 ar 39 ar phengitic mica ages of 38 32 ma presented here suggest the metamorphic wedge was exhumed into the shallow crust shortly thereafter

low grade retrogression of a high temperature metamorphic core complex naxos cyclades greece retrogressive deformation and metamorphism are often reported from the main low angle shear zones and detachments of metamorphic core complexes but their importance is not sufficiently emphasized for the footwall interior in order to contribute to a better understanding of exhumation related retrogression processes within and at the top of metamorphic core complexes an integrated detailed microstructural textural 40 ar 39 ar geochronological and thermobarometric study on the naxos metamorphic core complex within the aegean sea is presented that provides a new perspective on low grade retrogression during exhumation through shallow ductile levels we found variable retrogressive deformation within the naxos metamorphic core complex which even pervasively affected significant portions of the migmatite grade metamorphic core and remnant high pressure areas of the metamorphic core complex where retrogression led to pervasive formation of new fabrics within greenschist facies metamorphic conditions during brittle ductile transition within a continuum of retrogression 40 ar 39 ar white mica dating allowed us to deduce three retrogressive ages at 16 52 0 39 ma within the naxos metamorphic core complex 12 6 0 28 ma moutsounas detachment shear zone on the eastern boundary of the metamorphic core complex and 10 43 0 44 ma to 8 40 0 76 ma last ductile activity along the naxos paros shear zone to the north of the metamorphic core complex a further stage of retrogression at 12 11 ma occurred along distinct low angle normal faults within the middle miocene naxos granite retrogressive microstructures low temperature calcite fabrics in marbles and chloritization in metapelites at temperatures of 350 130 c in the metamorphic core complex core resulted mainly from late stage e w shortening and folding late stage flow of hydrous fluids resulted in resetting of fabrics and enhancement of ductile deformation the middle late miocene retrogression events are also reflected by a similarly aged tectonic collapse basin in the hanging wall unit above the detachment the wide temporal range of retrogression within the naxos metamorphic core complex coincides in age with retrogressive deformation within other metamorphic core complexes of the aegean sea we interpret the long temporal range of retrogression to reflect outward southwestward retreat of the subduction and sequential activation of major detachment zones

tectono stratigraphy of the neogene basins in western turkey implications for tectonic evolution of the aegean extended region abstract the western part of the aegean region includes several neogene basins containing volcano sedimentary successions the neogene basins located along the northern menderes extensional metamorphic complex memc were developed during the miocene as supra detachment basins they contain two distinct volcano sedimentary successions separated by a regional unconformity the basins located to the west of the memc were developed as strike slip basins and contain volcanic and sedimentary units getting younger from ne to sw with no remarkable unconformity available paleomagnetic studies in the aegean region suggest to us that the basins to the west of the memc were developed in response to southward clockwise rotational roll back of the aegean subduction zone the eastern margin of this rotational deformation is characterized on the surface by a large strike slip zone which is known as izmir balikesir transfer zone ibtz the sedimentary successions in the basins along the northern memc do not show southward younging and are interpreted to be developed in response to exhumation of the memc during the pliocene to quaternary e w trending grabens such as the gediz alasehir buyuk and kucuk menderes grabens were developed in response to tectonic escape accompanying the slab roll back process these grabens truncate the memc basins during this time strike slip deformation and associated sedimentation continued along the ibtz

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

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

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

dynamics of orogenic wedges and the uplift of high pressure metamorphic rocks subduction accretion complexes can be approximated as wedge shaped continua with a rigid buttress behind and a subducting litho spheric slab beneath thick wedges undergoing prograde metamorphism have a negligible long term yield strength and are likely to exhibit a complex nonlinear viscous rheology such a wedge will tend to deform internally until it reaches a stable configuration in which the gravitational forces generated by the wedge geometry balance the traction exerted on its underside by the subducting slab accretion of material at the wedge front will lengthen the wedge and cause it to shorten internally to regain the stable geometry this shortening will be expressed as late out of sequence thrusting backthrusting and folding conversely underplating of sediment or crustal slices will thicken the wedge which may need to extend internally to regain stability extension will cause listric normal faults that may merge downward into zones of ductile extension continued underplating at depth and compensating extension above provides a mechanism for bringing high p low t metamorphic rocks to upper levels in the rear of the wedge where they are commonly observed many major tectonic boundaries in convergent orogens such as the coast range thrust in the franciscan complex major nappe contacts in the alps and the contact between the nevado filabride and higher betic nappe complexes in the betic cordillera show abrupt increases in metamorphic grade downward across them this is consistent with their origin or reactivation as uplift related extensional structures

the 3d geometry of the naxos detachment fault and the three dimensional tectonic architecture of the naxos metamorphic core complex aegean sea greece we reconstruct the three dimensional 3d geometry of the naxos detachment fault and quantify e w shortening associated with strong n s extensional deformation in addition 3d reconstruction of the detachment indicates how it interacted with the underlying metamorphic sequence as well as a set of concentric metamorphic isograds that formed during extensional deformation for doing so we used the software move midland valley ltd to develop a 3d model of the naxos metamorphic core complex ncc and the naxos detachment fault the model is constrained by structural data metamorphic isograds and fission track ages from the footwall of the ncc our analysis shows that greater minimum amounts of e w shortening correlate with higher metamorphic grade ranging from 6 to 10 outside the migmatite dome and up to 17 within the migmatite dome the metamorphic isograds around the migmatite dome are less intensely folded by e w shortening than the lithologic layering we conclude that this is because the isograd surfaces froze in after folding had already started our model indicates that the isograds are cut by the brittle detachment demonstrating that the final stages of top to the nne extension outlasted the formation of the metamorphic dome and the isograds despite some limitations of the 3d model the outlined geometric reconstruction of a major extensional fault system in the central aegean highlights 1 the interplay between large scale extension and temperature dependant shortening perpendicular to the extension direction 2 the evolution of metamorphism and migmatization 3 the formation of metamorphic isograds and 4 granitoid intrusions during extension and exhumation

no significant post eocene rotation of the moesian platform and rhodope bulgaria implications for the kinematic evolution of the carpathian and aegean arcs abstract the region located between the carpathian balkan and aegean arcs the moesian platform and bulgarian rhodope is generally assumed to have been stably attached to the east european craton during the cenozoic evolution of these arcs the kinematic evolution of this region is however poorly constrained by paleomagnetic analysis in this paper we provide new paleomagnetic data 800 volcanic and sedimentary samples from 12 localities showing no significant post eocene rotation of the moesian platform and rhodope with respect to eurasia therefore confirming the stability of this region we compare this result to a provided review of paleomagnetic data from the south carpathians tisza block and the aegean region the tisza block underwent 68 4 16 7 of middle miocene 15 10 ma clockwise rotation with respect to the moesian platform in line with previous rotation estimates based on structural geology the stability of the moesian platform during middle miocene eastward emplacement of the tisza block into the carpathian back arc supports dextral shear along the southern carpathians recorded by 13 6 ma clockwise strike slip related rotations in foreland deposits the new reference direction for the moesian platform and rhodope allows accurate quantification of the rotation difference with the west aegean domain at 38 0 7 2 occurring between 15 and 8 ma to accommodate this rotation we propose that the pivot point of the west aegean rotation was located approximately in the middle of the rotating domain rather than at the northern tip as previously proposed this new scenario predicts less extension southeast of the pivot point in good agreement with estimates from aegean structural geology northwest of the pivot point the model requires contraction or extrusion that can be accommodated by the coeval motion of the tisza block around the northwestern edge of the moesian platform

peri equatorial paleolatitudes for jurassic radiolarian cherts of greece abstract radiolarian rich sediments dominated pelagic deposition over large portions of the tethys ocean during middle to late jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the mediterranean region which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the jurassic and the nature of a tethys wide change from biosiliceous to biocalcareous mainly nannofossil deposition at the beginning of cretaceous time have remained open questions previous paleomagnetic analyses of jurassic red radiolarian cherts in the italian apennines indicate that radiolarian deposition occurred at low peri equatorial latitudes similar to modern day deposition of radiolarian rich sediments within equatorial zones of high biologic productivity to test this result for other sectors of the mediterranean region we undertook paleomagnetic study of mesozoic mostly middle to upper jurassic red radiolarian cherts within the aegean region on the peloponnesus and in continental greece sampled units are from the sub pelagonian zone on the argolis peninsula the pindos olonos zone on the koroni peninsula near karpenissi in central greece and the ionian zone in the varathi area of northwestern greece thermal demagnetization of samples from all sections removed low temperature viscous and moderate temperature overprint magnetizations that fail the available fold tests at argolis and koroni however the cherts carry a third high temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests we interpret the high temperature component to be the primary magnetization acquired during chert deposition and early diagenesis at kandhia and koliaky argolis the primary declinations and previous results indicate clockwise vertical axis rotations of 40 relative to stable europe due to ambiguities in hemispheric origin n or s and thus paleomagnetic polarity the observed declinations could indicate either clockwise cw or counterclockwise ccw vertical axis rotations thus at adriani koroni the primary declinations indicate either cw or ccw rotations of 95 or 84 depending on paleomagnetic polarity and age the primary inclinations for all peloponnesus sites indicate peri equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other mediterranean orogenic belts our new paleomagnetic data support the interpretation that mesozoic radiolarites within the tethys ocean were originally deposited along peri equatorial belts of divergence and high biologic productivity

thermochronologic evaluation of postcollision extension in the anatolide orogen western turkey 1 to better understand the driving mechanisms behind the transition from collision to extension in a convergent orogen data from multiple low temperature thermochronometers were obtained from the simav detachment fault sdf the earliest developed major extensional structure recognized in the western anatolide orogen of western turkey twenty two zircon fission track ft 26 apatite ft 12 apatite u th he ages and 26 apatite ft track length analyses are presented the data establish that the sdf was a major extensional fault active between 25 and 19 ma the coincidence in timing of magmatism with cessation of sdf activity implies the detachment became locked owing to doming induced by magma emplacement zircon ft ages away from the influence of miocene magmatism record rapid footwall cooling between 25 and 21 ma at a slip rate of up to 15 km myr and demonstrate that active ductile deformation along the sdf migrated northward with time apatite ft ages from the footwall of the sdf are spatially invariant over 100 km and consistently 2 3 myr younger than the zircon fission track ages from the same samples these data are consistent with a regional but relatively rapid erosion linked cooling phase that removed 2 3 km of overburden following cessation of sdf activity but before deposition of sedimentary rocks on the detachment surface at 16 4 ma postcollision extension of the anatolide orogen with development of the sdf can be best explained as the result of postcollision magmatism and thermal weakening of the crust inducing the extensional reactivation of an earlier major out of sequence thrust

back arc extension and denudation of mediterranean eclogites eclogite facies rocks exposed in mediterranean back arcs are delimited from above by low angle normal faults and detachments nevertheless our work demonstrates that these extensional structures associated with back arc extension played only a limited role in removing the overburden from above the eclogites extension in mediterranean back arcs began in the late oligocene or early miocene but the pressure temperature time p t t paths of eclogite facies rocks exposed in these areas indicate that a major part of the overburden several tens of kilometers has been removed from above these rocks prior to the oligo miocene we show that the time period bracketed between the peak of eclogite metamorphism eocene in the central aegean probably upper cretaceous in corsica and the betics and the onset of back arc extension in the oligo miocene was characterized by thrust faulting in the central aegean corsica and the betics eclogite bearing units were partly unroofed and then overthrusted lower pressure units we emphasize that with one exception tinos island greece the entire inventory of extensional contacts operated subsequently to the overthrusting of the eclogites above the lower grade sequences thus mediterranean back arc extension lags behind a major part of the denudation process and is superposed on orogenic wedges that contain eclogite facies rocks at relatively shallow structural levels we emphasize that the mode of occurrence of eclogites in mediterranean back arc regions involves a continuum of in situ crustal accretion below the eclogites widespread p t paths that show cooling or isothermal decompression and lower grade rocks at the bottom of the structural pile thus instead of reflecting whole crust back arc extension the tectonic style associated with the denudation of mediterranean eclogites better fits an active accretionary wedge setting this is similar to the mode of occurrence of eclogite facies rocks in mountain belts such as the western alps where decompression was synorogenic and back arc extension played no role

u pb zircon geochronology of unusual eclogite facies rocks from syros and tinos cyclades greece low temperature eclogite facies rocks from syros and tinos cyclades greece include meta igneous blocks of unclear origin meta olistostrome or tectonic melange with very high trace element concentrations e g zr up to 4850 ppm y up to 475 ppm the unusual geochemistry is considered to be the result of metasomatic alteration in a subduction zone environment locally metasomatic exchange with an ultramafic matrix further enhanced compositional anomalies a concordant u pb zircon age of 78 1 ma recorded for an omphacitite from syros is interpreted as the time of pre eocene high pressure metamorphism in the cyclades zircon dates of 61 and 63 ma for a jadeitite from tinos possibly indicate an additional discrete event deformation these results are a first geochronological indication that high pressure metamorphism in the cyclades commenced signif icantly earlier than indicated by previous white mica chronology which provided ages between c 50 and 40 ma

the genesis of epithermal au ag te mineralization panormos bay tinos island cyclades greece the panormos bay au ag te vein system tinos island greece which is hosted in mesozoic marbles comprises 30 subparallel steeply dipping quartz veins that extend for at least 500 m in places gold telluride mineralization occurs in hydraulic breccias and alteration halos which are the products of co 2 effervescence of the ore fluid and wall rock interaction respectively seventy ore and gangue minerals have been identified zones of chlorite talc and muscovite albite tourmaline alteration up to 50 cm wide are associated with precious metal bearing milky and clear quartz veins the au ag te mineralization is developed in stage v of eight hydrothermal stages stage v consists of three substages early middle and late that are characterized by ag cu and au bearing tellurides respectively hessite sylvanite altaite native tellurium stutzite cuprian cervelleite and an unnamed cu bearing precious metal sulfotelluride ag au cu 9 te 2 s 3 characterize the early substage whereas melonite rickardite vulcanite weissite and native tellurium are present in the middle substage the late substage contains rickardite kostovite krennerite petzite and calaverite unexploited au ag te mineralization at panormos bay is though to be genetically related to a fluorine and boron bearing per aluminous leucogranite tinos leucogranite a combination of fluid inclusion microthermometry and sylvanite geothermometry suggests that the hydrothermal mineralization was deposited under hydrostatic pressures at a minimum depth of 1 km from moderate temperature 155 320 c low to moderate salinity 0 2 13 2 wt nacl equiv effervescing co 2 bearing fluids that contained appreciable amounts of cacl 2 and mgcl 2 calculated isotope compositions of 18 o 3 3 to 5 1 per mil and d of 73 to 62 per mil for waters in equilibrium with muscovite quartz and talc are consistent with the ore fluids being derived from the tinos leucogranite 18 o 4 2 and d 71 and their subsequent mixing with a more dilute low temperature miocenic meteoric hydrothermal fluid calculated 13 c fluid 2 0 to 0 3 and 34 s h 2 s 10 5 to 0 8 compositions of the ore fluids indicate an igneous source of carbon and sulfur which were highly exchanged with a metasedimentary source physicochemical conditions of the ore fluids were t 300 to 200 c ph 4 6 to 6 5 f s 2 10 10 9 to 10 15 f o 2 10 31 5 to 10 41 f te 2 10 7 7 to 10 10 7 f co 2 10 0 2 to 10 0 8 and f h 2 s 10 1 7 to 10 1 8

forced return flow deep in the subduction channel syros greece we present the results of a detailed structural study in the cycladic blueschist unit at fabrika on syros island greece and discuss their significance for tectonic processes at the subduction int

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin

age resetting of hanging wall rocks above a low angle detachment fault tinos island aegean sea the central aegean region has been affected by extensional tectonics since at least the oligo miocene on tinos island cyclades greece a low angle normal fault places low grade metamorphic rocks the upper unit above high pressure rocks the cycladic blueschist unit k ar and 40ar 39ar ages were obtained by us on white micas amphiboles and whole rock samples separated from various metamorphic rocks representing different structural levels of the hanging wall the hanging wall upper unit is commonly thought to have resided at shallow crustal levels since late cretaceous times but our geochronological data supported by previously published rb sr dating brocker m franz l 1998 rb sr isotope studies on tinos island cyclades greece additional time constraints for metamorphism extent of infiltration controlled overprinting and deformational activity geol mag 135 3 369 382 indicate severe age resetting of the base of the hanging wall during tertiary times amphiboles from the top of the hanging wall section yielded late cretaceous ages which correlate well with other cretaceous upper unit rocks in the cyclades their preservation implies that tertiary age resetting was mainly confined to the lower part of the upper unit while upper parts retained older ages the base of the hanging wall section where age resetting and ductile deformation are most pronounced is taken to represent a part of a thick extensional shear zone that operated in low greenschist facies conditions during tertiary time the results of one dimensional thermal modeling suggest that warm footwall rocks emerging from great depth subsequently to hp lt metamorphism may have supplied the heat required for the metamorphism and ductile deformation at the base of the hanging wall the model also indicates that only minor cooling of the footwall during decompression is allowed if the footwall is to warm up the hanging wall this is a priori consistent with the isothermal decompression path of footwall blueschists and eclogites deduced from previous petrological studies on tinos