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

semi brittle deformation of anhydrite halite shear zones simulating mylonite formation abstract a series of new shear experiments on similar volume mixes of anhydrite and halite have been run at 100 and 400 c at the same constant loading rate and constant confining pressure of 200 mpa increasing temperature is found to decrease the viscosity contrast between anhydrite and halite the hard and soft phases respectively the mechanical response is similar at all temperatures regardless of volume proportions of mix an initial high stress steady state portion of the stress strain curve is followed by a stress drop and then by a second steady state stress interval at a much lower value that is nearly equal to the strength of the softer phase halite individual mineral behaviours and deformation mechanisms appear to correlate with specific portions of the stress strain curve as the fabric s evolve with increasing strain mechanism s of strain accomodation at all temperatures is semi brittle deformation mechanisms change gradually with conditions with shear dominated by stable sliding along r 1 and r 2 shear fracures especially in mixes of high anhydrite content at 100 c while homogeneous ductile flow along s and c surfaces is observed at 400 c in all variations of composition these features are very similar to those observed in natural shear zones

tectonics and magmatism in turkey and the surrounding area this volume contains 23 papers from a range of international contributors describing recent research into the tectonics and magmatism of turkey and its surroundings this region is sited at the collision zone between eurasia and afro arabia and as such provides an extraordinarily complete and well exposed record of the staged tectonic evolution of this sector of the alpine himalayan orogen the geological history of this area involves separation of continental fragments from the margin of gondwana their migration across the tethyan oceans the subsequent closure of these oceans and finally the development of the neotectonic regime which continues to evolve to the present day such a comprehensive record is relevant to the understanding of collisional zones worldwide the volume is divided into five sections tethyan evolution neotethyan ophiolites post tethyan basin evolution neotectonics and igneous activity the first two sections deal with tethyan oceans whose growth and subsequent closure dominated the geodynamic framework in the mesozoic and cenozoic the subsequent sections deal with more recent geological developments from the balkan peninsula in the west to the transcaucasus in the east that followed consumption of the tethyan oceans there is a broad mix of papers throughout the volume wide ranging review papers on ocean development and extensional tectonics are followed by detailed descriptions of petrology and geochemistry and geographically focused studies on basin evolution specific aspects of extensional and strike slip tectonics and discussions of the relationship of magmatic activity to the tectonic development of the area tectonics and magmatism in turkey and the surrounding area presents up to date results and ideas from a large number of international contributors on a wide range of current research activity in this region it is essential reading for all geoscientists with an interest in both academic and applied aspects of eastern mediterranean geology

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

effects of temperature and co2 on the frictional behavior of simulated anhydrite fault rock the frictional behavior of anhydrite bearing faults is of interest to a the safety and effectiveness of co2 storage in anhydrite capped reservoirs b seismicity induced by hydrocarbon production and c natural seismicity nucleated in evaporite formations we performed direct shear experiments on simulated anhydrite fault gouges at a range of temperatures 80 150 c and sliding velocities 0 2 10 ms 1 under a fixed effective normal stress of 25 mpa four types of experiments were conducted 1 dry experiments 2 experiments pressurized with water 3 dry experiments pressurized with co2 and 4 wet experiments pressurized with co2 fluid pressures of 15 mpa were used when applied over the temperature range investigated water saturated samples were found to be up to 15 frictionally weaker than dry equivalents wet samples containing co2 were also up to 15 weaker than co2 free equivalents dry sample strength without co2 was independent of temperature whereas wet samples without co2 strengthened 10 from 80 to 150 c samples containing co2 weakened by 4 dry and 10 wet from 80 to 150 c under the p t conditions investigated only dry anhydrite fault gouge showed velocity weakening behavior above 120 c required for faults to potentially generate earthquakes assuming natural fault gouges are wet in situ seismicity is unlikely to nucleate in anhydrite rich faults though the presence of dolomite or reaction produced calcite may change seismic potential co2 penetration into wet anhydrite rich faults may trigger slip on critically stressed faults due to the observed short term co2 weakening effects excluding possible formation of secondary minerals but is not expected to influence slip stability

exhumation with a twist paleomagnetic constraints on the evolution of the menderes metamorphic core complex western turkey 1 much remains to be understood about the links between regional vertical axis rotations continental extension and shortening in western turkey miocene vertical axis rotations have been reported that occur simultaneously with the extensional exhumation of the menderes metamorphic core complex which has been related to back arc extension in the eastern part of the aegean back arc in this paper we explore the spatial and temporal relationships between vertical axis rotations in southwestern turkey and extensional unroofing of the menderes massif to this end we provide a large set of new paleomagnetic data from western turkey and integrate these with the regional structural evolution to test the causes and consequences of oroclinal bending in the aegean region the lycian nappes and bey daglari are shown to rotate 20 between 16 and 5 ma defining the eastern limb of the aegean orocline this occurred contemporaneously with the exhumation of the central menderes massif along extensional detachments and after the latest oligocene to early miocene exhumation of the northern and southern menderes massifs exhumation of the latter two was not associated with vertical axis rotations the lower miocene volcanics in the region from lesbos to usak to the north of the central menderes massif underwent a small clockwise rotation insignificant with respect to eurasia this shows that exhumation of the central menderes massif was associated with a vertical axis rotation difference between the northern and southern menderes massifs of 25 30 this result is in excellent agreement with the angle defined by the trends of buyuk menderes and alasehir detachments as well as the angle defined by the regionally curving stretching lineation pattern across the central menderes massif these structures define a pivot point rotation pole for the west anatolian rotations the rotation of the southern domain including the southern menderes massif the lycian nappes and bey daglari must have led to n s contraction east of this pole the eastern limit of the rotating domain is formed by the transpressional couple of the aksu thrust and kirkkavak fault in the center of the isparta angle previously reported clockwise rotations in the volcanic fields near afyon may be the result of distributed n s shortening east of the pivot point the precise accommodation of this shortening history remains open for investigation late oligocene to early miocene extension in the eastern part of the aegean back arc was ne sw oriented and likely bounded by a discrete transform this transform may be associated with an early evolution of the eastern aegean subduction transform edge propagator fault oroclinal bending in the west anatolian region is likely related to a reconnection of the eastern part of the aegean orocline with the african northward moving plate in tandem with roll back in the aegean back arc comparable to a recently postulated scenario for western greece

strain pattern within and around denser blocks sinking within newtonian salt structures abstract blocks of dense material such as anhydrite entrained in salt structures have been proposed to sink through their host material here we present the results of numerical models that analyse strain patterns within and around initially horizontal anhydrite blocks viscosity 1021 pa s sinking through newtonian salt with a viscosity of 1017 pa s in addition the influence of the block aspect ratio thickness to width ratio ar is analysed the model results show that the blocks are folded and marginally sheared to approach streamlined shapes the effectiveness of this process is a function of the block ar and influences the sinking velocity of the blocks significantly final sinking velocities are in the range of ca 1 7 3 1 mm a around the block in the salt an array of folds and shear zones develops during block descent the structure of which is principally the same independent of the block ar however the size and development of the structures is a function of the block size monitoring of strain magnitudes demonstrates that the salt is subject to extremely high strains with successively changing stress regimes resulting in closely spaced zones of high adjacent to low strain in comparison to the anhydrite blocks strain magnitudes in the salt are up to one order of magnitude higher

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

fault zone architecture and deformation processes within evaporitic rocks in the upper crust 1 recently in the northern apennines geophysical data have identified the triassic evaporites te anhydrites and dolomites as the source region of the major extensional earthquakes of the area m 6 in order to characterize fault zone architecture and deformation processes within the te we have studied exhumed evaporite bearing normal faults within the upper crust the structure of large displacement 100 m normal faults is given by 1 a zoned fault core with a wider portion of fault parallel foliated ca sulphates ductile deformation overprinted by an inner fault core ifc of localized brittle deformation and 2 wide dolostones to absent ca sulphates damage zones of fault fracture patterns fault rock assemblage within the ifc is characterized by fault breccia gouge and cataclasites of different grain size most of the deformation within the ifc is localized along thin and fault parallel principal slip surfaces pss made of dolomite rich fine grained cataclasite sem analyses show an evolution from ca to st to gypsum rich mineralization due to episodic fluid flow events channeled along the fault zones during different stages of fault exhumation the development of the observed fault geometry can be explained by a mechanical fault evolution model where initial faulting occurs along broad and ductile shear zones within the anhydrites and causes fracturing within the dolostones progressive deformation within the fault core leads to the development of fault parallel dolomite rich cataclastic layers their reactivation coupled with transient fluid overpressures can produce embrittlement and localization of brittle deformation within the ifc

deformation experiments on anhydrite rocks of different grain sizes rheology and microfabric miiller w h schmid s m and briegel u 1981 deformation experiments on anhydrite rocks of different grain sizes rheology and microfabric in g s lister h j behr k weber and h zwart editors the effect of deformation on rocks tectonophysics 78 527 543 three anhydrite rocks of different grain size were experimentally deformed in the 20 to 45o c temperature range the strength of the finegrained varieties becomes strongly temperature and strain rate dependent above 3oo c and a flow law of the form 6 a exp h rt sinh o a with an activation energy h of 27 36 kcal mole and a very low value for the exponent n of 1 5 2 was found the course grained rock remains relatively insensitive to strain rate and temperature even at 45o c microstructural and x ray texture analyses suggest that intracrystalline glide and twinning are the major deformation mechanisms the transition from strong work hardening observed at high stresses into steady state flow at low stresses was found to correlate with the onset of dynamic recrystallization by grain boundary migration

frictional properties of simulated anhydrite dolomite fault gouge and implications for seismogenic potential the frictional properties of anhydrite dolomite fault gouges and the effects of co2 upon them are of key importance in assessing the risks associated with co2 storage in reservoir formations capped by anhydrite dolomite sequences and in understanding seismicity occurring in such formations such as the italian apennines therefore we performed velocity stepping direct shear experiments on simulated dolomite anhydrite and 50 50 anhydrite dolomite gouges at representative in situ conditions 120 c and ne 25 mpa they were conducted under vacuum or else using water or co2 saturated water as pore fluid pf 15 mpa friction coefficients varied between 0 55 and 0 7 all dry samples exhibited velocity weakening behavior whereas all wet samples exhibited velocity strengthening behavior without or with co2 this is consistent with trends previously reported for such gouges a compilation of literature data shows that the transition from velocity strengthening to velocity weakening occurs in these materials between 80 and 120 c when dry and between 100 and 150 c when wet this implies little seismogenic potential for wet dolomite anhydrite and mixed gouges under co2 storage conditions at 2 4 km depth seismic slip in the italian apennines at depths of 6 km and beyond may be explained by the velocity weakening behavior expected in anhydrite and especially dolomite at temperatures above 150 c

the effect of the salt viscosity on future evolution of the gorleben salt diapir germany abstract the gorleben diapir which has been targeted for radioactive waste disposal contains large blocks of anhydrite numerical models that depict the geometrical configuration of the gorleben diapir are used to understand internal structure of diapir caused by movement of the anhydrite blocks for various salt rheologies it is shown that the rheology of the salt plays a significant role in how and at which rate the anhydrite blocks sink within the diapir the mobility of anhydrite blocks depends on the effective viscosity of salt which has to be lower than threshold value of around 1018 1019 pa s decreasing salt viscosity allows the previously stationary anhydrite blocks to sink if the effective viscosity of salt in post depositional stage of the gorleben diapir falls below this threshold value induced internal flow due to the present anhydrite layer might disturb any repository within the diapir

the influence of viscosity contrast on the strain pattern and magnitude within and around dense blocks sinking through newtonian rock salt abstract dense inclusions in salt cover a wide range of materials and therefore material properties depending on their origin we have modelled the deformation associated with gravity driven sinking of horizontal initially rectangular blocks of dense material through newtonian salt our two dimensional finite differences models analyse the influence and interaction of two parameters 1 the size i e the aspect ratio ar of the block and 2 the viscosity contrast between the salt and the more viscous block over four orders of magnitude the results demonstrate that during gravity driven sinking the blocks are folded and sheared the strain magnitude within the block increases with increasing block ar and decreases with increasing viscosity contrast sinking velocities of the blocks are in the range of 6 mm a 1 and are a function of block and salt deformation that depend on the block mass and ar as well as on the viscosity contrast salt deformation is characterised by the development of an array of characteristic structures that include folds and shear zones as well as a zone characterised by extreme vertical stretching above the block termed entrainment channel strain in the salt is locally more than two orders of magnitude higher than in the block and increases with increasing block ar and viscosity contrast salt deformation is distributed in closely spaced high and low strain zones concentrated in the block vicinity and the entrainment channel

initiation and growth of gypsum piercement structures in the zechstein basin abstract the importance of tectonic processes in initiating halite diapirs has become much better understood in recent years less well understood is the development of diapiric structures involving rocks composed predominantly of gypsum below about 1000 m gypsum dehydrates to anhydrite which often obscures primary sedimentary textures if the strain associated with diapiric rise in the rock induces the transition to anhydrite obliteration of primary features in the gypsum can be expected in our study we infer that the diapiric movement in the werra anhydrite member of cycle 1 of the zechstein formation of europe occurred before the initial transition of gypsum to anhydrite based on the presence of pseudomorphs of bedded primary gypsum crystals the overburden lithologies and depositional environment and the mechanical properties of gypsum anhydrite and carbonate rocks faulting and differential loading of a shallow overburden were the key components in initiating the gypsum diapirism the transition to anhydrite occurred after burial and after cessation of diapirism in comparison the diapirism of calcium sulfate of the leine anhydrite into the leine halite members of cycle 3 of the zechstein formation probably occurred much later after burial and appears to have been triggered by halite diapirism which in turn triggered the dehydration reaction causing the calcium sulfate to become the incompetent phase relative to the halite

quantitative texture analysis of naturally deformed anhydrite by neutron diffraction texture goniometry abstract the crystallographic texture of coarse grained 1 mm foliated anhydrite from an evaporite diapir in the canadian arctic islands was analysed by neutron diffraction texture goniometry the orientation distribution function odf which quantatively defines the texture was calculated from eight pole figures the odf was used to calculate the pole figures for slip systems and twin planes a strong concentration of 020 was found parallel to the lineation x with 002 forming a girdle normal to the lineation with a strong maximum near the foliation normal z the maxima are slightly asymmetric with respect to the structural framework x y z which is typical of non coaxial deformation the orientation of 020 and 002 are consistent with 010 001 glide in a non coaxial flow regime the axial symmetry about the lineation x of the pole figures and the tubular structure of the odf are thought to have been caused by an important component of extension parallel to x the calculated 100 pole figure has a submaximum parallel to z presumably a direction of high compressive stress the 101 maxima at about 45 to z are then indicative of twinning on 101 approximately 30 of the odf is in a twinned orientation 100 subparallel to z and it is suggested that twinning contributed to the axial symmetry of the fabric few grains show undulary extinction their boundaries are generally straight and rarely serrated this points to extensive migration recrystallization and associated twin gliding at 300 c previous studies seem to have underestimated the contribution of twinning to texture development which is dominated by 010 001 slip

tablet boudinage of an anhydrite layer in rock salt matrix results from thermomechanical experiments abstract a single competent layer of anhydrite embedded in a matrix of incompetent rock salt was deformed in a flattening type of bulk deformation at temperature t 345 c strain rate 10 7 s 1 to a maximum finite strain e z 30 as the anhydrite layer was oriented perpendicular to the main shortening direction z the layer underwent equal layer parallel extension in all directions resulting in tablet shaped boudins boudinage results from tensile fracture of anhydrite the rock salt matrix on the other hand behaved viscously crystal plastic deformation of halite was accommodated by slip on 110 which led to formation and rotation of subgrains and a 001 maximum parallel to the principal shortening axis z an axisymmetric texture of halite however is present only in high strain domains at the contact to the anhydrite layer where the differential stress obtained from subgrain size of halite reaches maximum values of ca 6 mpa subgrains remote from the anhydrite layer yielded 2 3 mpa which is consistent with the flow stress recorded by the load cell of the machine the non isometric shape of the tablet boudins in plan view is indicated by the ratio between long and short axis r 1 2 1 9 and can be explained by the interaction of concentric and radial tensile fractures both the mean diameter of the tablet boudins in plan view w a and the number of boudins n show a linear relation to the layer thickness progressive finite strain results in a higher number and a smaller mean diameter of the boudins the thickness of the boudins h f is almost the same like the initial layer thickness h i while the aspect ratio w d w a h f decreases with finite strain the mean w d values obtained from all runs are ranging from ca 0 8 to ca 1 5 this range is much lower than the aspect ratio of boudins in viscous or brittle viscous layers but is similar to the aspect ratio expected from fracture saturation models the aspect ratio of the tablet shaped anhydrite boudins is further consistent with aspect ratios published so far for tensile fracture boudins which developed in a plane or constrictional type of bulk deformation

disruption of the hellenic arc late miocene extensional detachment faults and steep pliocene quaternary normal faults or what happened at corinth 1 extensional faults exposed in the peloponnesus and mainland greece most of which are described here for the first time record a transition from regional extension of the aegean domain to the modern tectonic system the east peloponnesus detachment system trends north northwest from the southern peloponnesus to 30 km north of the gulf of corinth dips gently northeast and is late miocene early pliocene in age it has a minimum displacement of 25 30 km and appears to be the youngest of the regional scale extensional systems with significant displacement that formed parallel to the hellenic arc the partially coeval east sterea extensional system which extends from the gulf of corinth to the aegean sea contains low angle normal faults that both crosscut and trend parallel to older structures of the hellenic arc late miocene to early pliocene displacement within this zone disrupted the arc parallel structures of the hellenides upper pliocene quaternary normal faults which trend approximately east west and generally dip steeply at the surface continue the disruption of the hellenic arc much of the subsidence within the gulf of corinth appears to be unrelated to the younger faults and is instead related to the motion on the east peloponnesus detachment which crosscuts the modern graben

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 2 deformation mechanisms and the role of fluids abstract composite natural samples consisting of a single layer of anhydrite embedded in matrix of rock salt were experimentally deformed at temperature t 345 c and strain rate 10 7 s 1 the geometry and kinematics of folds and boudins which affect the stiff anhydrite layers were described in part 1 of the present study zulauf et al 2009 the microfabrics deformation mechanisms and the role of fluids are treated in the present paper anhydrite was deformed under brittle viscous conditions as is indicated by fracturing twinning and local recrystallization the latter based on strain induced grain boundary migration viscous deformation of halite was accommodated by slip on 110 110 which led to formation and rotation of subgrains and a striking 001 maximum parallel to the long axis x of the strain ellipsoid differential stress obtained from subgrain size of halite is largely consistent with stresses recorded by the load cells of the machine despite of the high deformation temperature and the low water content of the starting samples nacl brine and hydrocarbons expelled from fluid inclusions of both halite and anhydrite led to hydraulic fracturing and redistribution of matter the fluids migrated along newly formed microfractures in anhydrite and along halite anhydrite boundaries released hydrocarbons and nacl brine were redeposited in open space of neck domains in the form of black organic coatings condensate and fine grained halite respectively as these fluid controlled phenomena are common in salt domes of northern germany and released fluids may led to contamination of bed rock and biosphere the results of the present study should be important for workers who are dealing with radioactive waste deposits in rock salt

numerical analysis of x ray texture data an implementation in fortran allowing triclinic or axial specimen symmetry and most crystal symmetries abstract the use of complete descriptions of preferred orientation for studies of experimentally and naturally deformed rocks is discussed diagrammatic representations of preferred orientations are defined and conventions for coordinate systems are given methods of extracting information from the orientation distribution function are described a system of fortran programs which enables the orientation distribution function to be calculated for most suitable minerals is described

bridging onshore and offshore present day kinematics of central and eastern mediterranean implications for crustal dynamics and mantle flow we present a new kinematic and strain model of an area encompassing the calabrian and hellenic subduction zones western anatolia and the balkans using haines and holt s 1993 method we derive continuous velocity and strain rate fields by interpolating geodetic velocities including recent gps data in the balkans relative motion between stable eurasia and the western aegean sea is gradually accommodated by distributed n s extension from southern balkans to the eastern corinth gulf so that the westward propagation of the north anatolian fault naf throughout continental greece or peloponnesus is not required we thus propose that the naf terminates in north aegean and that n s extension localized in the corinth gulf and distributed in southern balkans is due to the retreat of the hellenic slab the motion of the hyblean plateau apulia peninsula south adriatic sea ionian basin and sirte plain can be minimized by a single rigid rotation around a pole located in the sirte plain compatible with the opening the pelagian rifts 2 2 5 mm yr and seismotectonics in libya we interpret the trenchward ultraslow motion of the calabrian arc 2 2 5 mm yr as pure collapse the calabrian subduction being now inactive in the absolute plate motion reference frame our modeled velocity field depicts two toroidal crustal patterns located at both ends of the hellenic subduction zone clockwise in nw greece and counter clockwise in western anatolia we suggest the nw greece toroidal pattern is the surface expression of a slab tear and consequent toroidal asthenospheric flow

recent stress field and neotectonics in the eastern jura mountains switzerland the regional stress field and its local variation were determined for the northern part of central switzerland fig 1 by using overcoring techniques doorstopper triaxial strain cell and observations of breakouts in deep boreholes the results are compared with fault plane solutions of earthquakes and with the orientation of horizontal stylolites in the northern part of central switzerland the nw se orientation of the maximum horizontal stress sh which is characteristic for central europe was observed only in the crystalline basement in the folded jura and south of it in one well the greatest principal horizontal stress above the triassic decollement horizon is oriented approximately in a n s to nne ssw direction this direction persists into the western tabular jura and the southernmost rhine graben only in the eastern part of the tabular jura the greatest principal horizontal stress shows a nnw sse to nw se orientation comparison of the near surface stress field as determined by in situ stress measurements and borehole breakouts with the directions of horizontal stylolites generated during the evolution of the folded jura indicates that the orientation of the recent stress field near the earth s surface is the same as that which prevailed during the upper miocene to lower pliocene the central part of northern switzerland is therefore the first area in central europe where it is possible to demonstrate that the near surface stress field is decoupled from that in the crystalline basement the difference in the orientation of the greatest principal horizontal stress is about 50

geometry and kinematics of compressional growth structures and diapirs in the la popa basin of northeast mexico insights from sequential restoration of a regional cross section and three dimensional analysis 1 diapirism in the la popa basin ne mexico was triggered and sustained by compressional decollement tectonics coeval development of contractional structures and diapirs was recorded by growth strata of late cretaceous tertiary age a palinspastic reconstruction of a regional cross section based on the restoration of growth strata related to both diapirs and detachment folds was carried out on the basis of this reconstruction and field data a three dimensional geometrical study was done to quantify the movement of evaporites within the detachment horizon and two diapirs the latter allowed determining the tectonodiapiric potential of a structure or set of structures i e the amount of ductile rocks forced to flow in association with the growth of a tectonic structure which is not accommodated by thickening of the ductile horizon nor by the tectonic structure itself and is capable of producing diapiric phenomena this study demonstrates that there is a direct coupling between tectonodiapiric potential and diapiric activity geometrical results show that the main factors that controlled the amount of ductile material moved as a consequence of compressional tectonics were shortening the depth to detachment the folding style and the style of deformation process i e pure shear simple shear in response to folding the overburden experienced a downward movement that was the major cause of diapiric phenomena in addition to field and geometrical data mechanical data indicate that forceful intrusion was the prevailing emplacement mechanism temperatures 150 197 c and strain rates in the order of 10 16 10 17 s 1 calculated for top of the evaporite layer were adequate for the flow of these rocks from the initiation of compression onward however an inferred overpressure in the ductile layer should be considered the key factor for the emplacement mechanism

the timing of partial melting barrovian metamorphism and granite intrusion in the naxos metamorphic core complex cyclades aegean sea greece abstract the relationship between partial melting and granite intrusion in a classic barrovian metamorphic terrane has been assessed thirteen samples were dated by shrimp u pb zircon geochronology from the island of naxos greece one of the aegean metamorphic core complexes the effect of partial melting during peak barrovian metamorphism on naxos is recorded by fine

healing and sliding stability of simulated anhydrite fault gouge effects of water temperature and co2 abstract anhydrite bearing faults are currently of interest to 1 co2 storage sites capped by anhydrite caprocks such as those found in the north sea and 2 seismically active faults in evaporite formations such as the italian apennines in order to assess the likelihood of fault reactivation the mode of fault slip and or fault leakage it is important to understand the evolution of frictional strength during periods of no slip and upon reloading healing and relaxation behavior and of the velocity dependence of friction of anhydrite fault gouge therefore we performed slide hold slide experiments combined with a velocity stepping sequence using simulated anhydrite fault gouge 95 wt caso4 vacuum dry and water wet experiments were performed at temperatures ranging from 20 to 150 c and at an effective normal stress of 25 mpa we also performed tests using dry co2 water wetted co2 and co2 saturated water as pore fluid but only at 120 c if pore fluid was present a fluid pressure of 15 mpa was present vacuum dry samples exhibit similar frictional healing to samples containing lab air but healing is significantly enhanced in wet samples dry samples exhibit velocity weakening behavior at t 120 c and wet samples exhibit velocity strengthening behavior over the full temperature range the presence of co2 does not influence the healing behavior or the velocity dependence of friction samples containing water wetted co2 exhibit behavior similar to wet samples we infer that the healing in dry samples is controlled by plastic asperity creep dieterich type possibly through dislocation creep and or twinning in wet samples healing is inferred to be controlled by increases in contact area and cohesion by pressure solution using a pressure solution rate model to extrapolate healing by contact area growth indicates that the maximum re strengthening through such a mechanism will only take days to tens of days

microstructural analysis of anhydrite rocks from the triassic evaporites umbria marche apennines central italy an insight into deformation mechanisms and possible slip systems abstract anhydrite rich layers within foreland fold and thrust belts are frequently the weakest horizon of the sequence characterizing the microstructural textures of anhydrite is therefore important for interpreting the larger scale deformation history of these rocks the microstructure of naturally deformed anhydrite from the triassic evaporites of the umbria marche apennines italy has been analyzed using electron backscatter diffraction ebsd this technique has been used to measure the misorientation across distorted grains and the crystallographic preferred orientation cpo of the samples the reference frame of the standard space group cmcm was used to represent the structure of anhydrite during this analysis which is different to that used in previous studies some grains show significant intracrystalline distortions 4 18 misorientation lines of measurements across distortions showed a dispersion of crystallographic data around a clear misorientation axis 010 these data are combined with the trace orientations of distortions to confirm that the 100 001 slip systems previously recognized also best explains grain distortions these interpretations are based on and consistent with a tilt boundary model containing edge dislocations cpo data are also interpreted as a likely 100 001 slip system as has previously been recognized a high degree of twinning within many of the anhydrite grains apparently has little effect on the crystallographic textures observed

folding in regions of extension summary many extension zones have been subjected to folding and shortening in a direction perpendicular to the stretching such deformation can be accounted for by the extension of a thin superficial elastic layer overlying a substrate that has small elastic moduli or that deforms in a viscous regime laboratory experiments are used to document the wavelength and amplitude of the folds for a range of geometrical configurations folding is observed even for very small amounts of extension less than 1 per cent with characteristics that are consistent with finite amplitude scaling laws because of the intrinsically 3 d nature of the deformation field the size of the region affected by folding and the direction of the fold axes depend on the orientation of the extension with respect to the rigid blocks that bound the deforming region for regions of extension where the elastic thickness is about 10 km as in the basin and range province for example it is predicted that folding occurs with wavelengths in a 20 40 km range such that it induces little deformation in the lower crust and maintains a flat moho discontinuity these predictions are consistent with the observations the characteristics of faulting that is associated with such deformation are discussed

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

texture development in experimentally deformed two phase aggregates of calcite and anhydrite abstract fully quantitative textures have been measured from experimentally deformed two phase aggregates of calcite and anhydrite two sets of deformation experiments were performed firstly to investigate the development of microstructure and texture with composition samples with varying volume proportions of calcite and anhydrite were deformed to 20 strain at identical conditions secondly to study the texture development of the two materials with strain and explore the possible use of texture index as a strain gauge in polyphase materials pure calcite and pure anhydrite were deformed at the same conditions as the two phase rocks to strains of 6 12 and 20 the textures in both calcite and anhydrite were found to be similar but not identical to those reported in previous studies for pure samples our experimental investigations and measured textures show that the textures both of the pure materials and of the two phase rocks depend not only on strain but also on stress and grain size through their influence on the deformation mechanisms the dependence of texture index with change in deformation mechanism is particularly pronounced in the anhydrite component where the texture index decreases with grain size which decreases with anhydrite content the texture in the pure calcite and in the calcite component of the two phase rocks was influenced by a preexisting fabric the intensity of the texture in the deformed samples seems to correlate with the stress in the calcite rather than with strain

intrusion age of pan african augen gneisses in the southern menderes massif and the age of cooling after alpine ductile extensional deformation

mechanisms for the formation of domal and basinal detachment faults a three dimensional analysis detachment faults i e regional low angle normal faults in metamorphic core complexes of the north american cordillera commonly exhibit doubly plunging antiformal domal and synformal basinal geometries these geometries have been previously attributed to the superposition of two processes 1 the antiforms and synforms with axes parallel to the extension direction originated as primary fault undulations or corrugations developed coevally with fault slip and 2 the antiforms and synforms with axes perpendicular to the extension direction were produced by isostatic uplift due to tectonic denudation however the coaxial relationship between undulations of detachment faults and the sedimentary beds and metamorphic foliations in both the upper and lower plates of some detachment fault systems in the u s cordillera suggests that the synforms and antiforms with axes parallel to the extension direction may have formed as folds and that the domal and basinal geometry of detachment faults may have formed synchronously by a single process a three dimensional elastic thin plate model is developed to investigate possible mechanisms for the formation of domal and basinal detachment faults this model explores the interactions among the vertical horizontal and basal shearing forces during the formation of warped detachment faults the model considers the role of compression perpendicular to the extension direction and stress reduction parallel to the extension direction the results of the model suggest that the stress reduction itself in the extension direction is insufficient to cause buckling of a thin elastic crust two mechanisms are most likely to explain the formation of domal and basinal geometries of detachment faults 1 an upward pushing by undulatory crustal roots or buoyant synextensional plutons beneath the extensional belt and 2 buckling caused by a compression perpendicular to the extension direction both mechanisms are consistent with the geologic constraints during the development of cordilleran core complexes in addition to isostatic uplift due to tectonic denudation upward warping of detachment faults can also be caused by buckling basal shearing and buoyant forces

rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock mechanics based yield criteria for the inelastic deformations at the top and base at mid plate depths stresses are likely to be supported elastically because bending strains and elastic stresses are low the collisional tectonic regime however is far more complex because very large permanent strains are sustained at mid plate depths and this requires us to include the broad transition between brittle and ductile flow moreover important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid plate depths two specific contributions of laboratory rock rheology research are considered in this paper first the high temperature steady state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere the thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm tc above which at geologic strain rates the high temperature ductile strength falls below some arbitrary strength isobar e g 100 mpa for olivine tc is about 700 800 c but for other crustal silicates tc may be as low as 400 600 c suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the moho as suggested by a number of workers on independent grounds put another way the moho is a rheological discontinuity a second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant strain rate tests or as an accelerating creep rate stage at constant differential stress a number of physical mechanisms have been identified that may be responsible for ductile faulting including the onset of dynamic recrystallization phase changes hydrothermal alteration and hydrolytic weakening microscopic evidence for these processes as well as larger scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere

sulfate minerals in evaporite deposits evaporite deposits preserve a wealth of information on earth s past surface conditions the deposits are sensitive indicators of depositional environment and climate recorded in a wide variety of mechanically and chemically produced sedimentary structures and fabrics unique to evaporite deposits is the record they carry of the hydrochemistry of surface waters including seawater sulfate minerals are important components in understanding the hydrochemistry of ancient surface waters sedimentological aspects of evaporite deposits were compiled by melvin 1991 in the compilation sedimentology specific to ca bearing sulfates was described by warren 1991 lowenstein and hardie 1985 handford 1991 and smoot and lowenstein 1991 discussed the sedimentology of evaporites in general these general principles can be applied specifically to the sulfate minerals in evaporite deposits sedimentological aspects of sulfate minerals in evaporite deposits are not discussed here for this information the reader is referred to the above references hardie et al 1985 and spencer and lowenstein 1988 discussed the petrography of evaporites and the interpretation of fabrics of evaporite minerals examples of petrographic aspects of sulfate minerals in evaporites are presented here along with references specific to the sulfate minerals for a more complete understanding of these aspects the reader is referred to the above references the major focus of this chapter is on the chemical aspects of the common sulfate minerals that occur in evaporite deposits the discussion begins with an explanation of the concept of chemical divides and the determination of evaporation paths and the evolution of brines in accordance with mineral solubility and the composition of dilute inflow waters determination of the precipitation pathways of the more soluble salts is more complex examples of sulfate mineral assemblages in evaporation systems calculated via thermochemical modelling are given for both marine and non marine systems the mineralogy of evaporite deposits is

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

experimental deformation of a single layer anhydrite in halite matrix under bulk constriction part 1 geometric and kinematic aspects a new deformation apparatus has been used to model the internal kinematics of salt diapirs composite natural samples consisting of a single layer of anhydrite embedded in halite matrix were constrictionally deformed at temperature t 345 c strain rate 10 7 s 1 maximum viscosity 2 1013 pa s and maximum finite strain ex 122 the anhydrite layer oriented parallel to the major stretching axis x was deformed by fracturing whereas halite behaved viscously at advanced state of constriction ex 90 a strong increase in strain hardening of halite led to a transient tension fracture that healed up and was shortened by folding during the final phase of viscous deformation tiny prismatic anhydrite inclusions disseminated inside the halite matrix were reoriented during constriction resulting in a linear grain shape fabric 3d images of the anhydrite layer based on computer tomography revealed rare kink folds with axes subparallel to x and boudins which result from tension fracture with increasing layer thickness hi the width of boudins wa increases linearly wa 0 3 1 3 hi the normalized width of boudins wd wa hi is almost constant at 1 5 1 0 these geometrical parameters can be used to reveal fracture boudinage under bulk constriction the oblique orientation of most of the boudins with respect to the principal strain axes results from folding of the boudins by a second generation of folds the latter with axes subperpendicular to the layer

comment on borgia a mazzoldi a brunori c a allocca c delcroix c micheli l vercellino a grieco g 2014 volcanic spreading forcing and feedback in geothermal reservoir development amiata volcano italia j volc geoth res 284 16 31 abstract borgia et al 2014 illustrated an active volcanic spreading model for the amiata volcanic area southern tuscany italy although at first glance the model may appear appealing this is not fully supported by the available data and the paper does not take into account their discussion accordingly the supposed negative consequences of the borgia et al 2014 model on both contamination of shallow water and geothermal exploitation can likely be regarded as speculative

influence of trench width on subduction hinge retreat rates in 3 d models of slab rollback subduction of tectonic plates limited in lateral extent and with a free trailing tail i e free subduction is modeled in a three dimensional 3 d geometry the models use a nonlinear viscoplastic rheology for the subducting plate and exhibit a wide range of behaviors depending on such plate characteristics as strength width and thickness we investigate the time evolution of this progressive rollback subduction measure the accompanying return flow in the upper mantle and quantify the plate kinematics due to the 3 d geometry flow is allowed to accompany slab rollback around the lateral edges of the slab the toroidal component as opposed to 2 d geometry where material is forced to flow underneath the slab tip the poloidal component a simple force balance is provided which relates the speed of backward trench migration to the resistive forces of generating flow and weakening the plate our results indicate most of the gravitational energy of the system i e the negative buoyancy of the subducting slab is converted into a toroidal flow 69 a much smaller amount goes into weakening the plate 18 and the remaining amount goes into driving flow parallel to displacement of the slab 13 for the trench widths w we investigate 1500 km a maximum trench retreat rate occurs for trenches 600 km wide which is attributed to the interaction between a plate of finite width and the induced flow which has a lengthscale in the horizontal direction these numerical results quantitatively agree with comparable 3 d laboratory experiments using analogue models with a purely viscous plate material schellart 2004a 2004b including correlations between increasing retreat rate with increasing plate thickness trench width for maximum retreat rate 500 km and estimated amount of slab buoyancy used to drive rollback induced flow 70 several implications for plate tectonics on earth result from these models such as rollback subduction providing a physical mechanism for ephemeral slab graveyards situated above the more viscous lower mantle and endothermic phase transition prior to a flushing event into the lower mantle mantle avalanche

high pressure metasediments in central turkey constraints on the neotethyan closure history 1 the distribution of oceanic domains and continental blocks in central anatolia remains a challenge in understanding the alpine geodynamic evolution of the tethys realm the consumption of a neotethys oceanic branch at the mesozoic cenozoic boundary welded the central anatolian crystalline complex in central turkey and the anatolide tauride block in western turkey with the northerly eurasian margin whether those two regions constituted a single or two distinct continental masses is still matter of debate high pressure metamorphism has been locally evidenced in the afyon zone which was however defined as a greenschist facies metamorphic zone of the anatolide tauride block since the afyon zone composes a metamorphic equivalent of a continental margin exposed far south of the izmir ankara suture zone this encouraged us to reevaluate its metamorphic evolution in order to better understand the relation between western and central turkey our investigations reveal that the high pressure minerals fe mg carpholite and glaucophane are present in the entire afyon zone which we reconsider as a blueschist facies zone we additionally present a tectonic reconstruction stripping off the postcollisional tectonics it reveals that today s bending of the high pressure belt is consistent with an eocene collision of the anatolide tauride block around the southern edge of the central anatolian crystalline complex we argue that the central anatolian crystalline complex and the anatolide tauride block were two distinct continental masses separated by a neotethyan oceanic stripe the closure of which engendered subduction related metamorphism in the latter and arc volcanism and high grade metamorphism in the former by late cretaceous to early cenozoic

textural evolution of synthetic anhydrite halite mylonites the rheology and textural evolution of mylonites for both crustal and mantle rocks are generally poorly understood stress and strain partitioning between shear zones and wall rock foliation development flow mechanisms and constitutive relations are little known to address these problems we have begun an experimental study in which anhydrite and halite aggregates are deformed in simple shear homogeneous mixes at intervals of 10 vol of anhydrite and halite powders of 90 to 180 m grain size comprise the 1 mm thick zone between the 35 precut surfaces in 2 by 4 cm right circular cylinders of anhydrite all specimens are confined under 200 mpa pc and tested at 300 c t producing an aggregate of near zero porosity all specimens are shortened at an axial displacement rate of 5 l0 6 cm s to shear strains of about 2 0 most stress strain curves have a similar form they are characterized by an initial linear response that is followed by a work hardening region that leads to a plateau of constant stress whilst strain continues to accumulate this apparent steady state behavior is followed by a drop in stress to a second apparent steady state stress the strain at this stress drop and the magnitude of the drop increase with increasing anhydrite content the second lower steady state stress for all mixes approaches that of sheared pure halite optical examination of the fabrics shows that straining under the initial apparent steady state is accommodated by both mineral phases a foliation evolves as defined by mineral segregation and grain elongation of halite at 15 to 30 to the shear zone walls anhydrite grains rotate until their 001 010 slip system parallels the foliation the anhydrite also exhibits twin lamellae kinks and microfractures following the stress drop rheologic behavior is dominated by dynamic recovery in halite the recrystallized grain size increasing consistent with the lower stress level

preferred orientation of anorthite deformed experimentally in newtonian creep abstract synthetic anorthite aggregates were deformed in a paterson gas deformation apparatus at confining pressures up to 400 mpa in torsion and axial compression at temperatures between 950 c and 1200 c samples deformed in torsion under newtonian creep display development of texture or crystallographic preferred orientation as documented with synchrotron x ray diffraction measurements complex diffraction patterns were deconvoluted with the rietveld method to obtain quantitative texture information torsion samples deformed up to shear strains of 4 and samples deformed in compression at higher stresses to total strains of 0 3 develop clear textures texture and shape preferred orientation spo of torsion samples display a monoclinic pattern with an asymmetry inclined against the sense of shear consistent with polycrystal plasticity simulations that assume the deformation is accomplished by dislocation glide these results show that a material deforming in linear viscous creep can develop a strong texture in striking contrast to the paradigm that the presence of a texture precludes low stress newtonian behavior our observations show that the presence or absence of crystallographic preferred orientation is not sufficient to uniquely infer the dominant rheological mechanical regime as sometimes applied for interpretation of seismic anisotropy in the earth

the deformational behaviour of bimineralic limestone halite aggregates abstract a compositional foliation banding develops within synthetic limestone halite aggregates experimentally deformed in axially symmetric compression and in simple shear the strength of the bulk aggregate decreases as the foliation becomes stronger foliation weakening in calcite rich specimens the development of foliation starts with the formation of cataclastic shear systems in calcite domains between isolated halite domains with increasing deformation halite is sheared into these systems the halite domains coalesce into halite rich shear systems and accommodate an increasing amount of the bulk deformation the bulk strength of bimineralic aggregates at a given amount of strain increases with decreasing halite content the influence of halite on the bulk strength is much greater than would be expected from its volume fraction and becomes dominant with increasing deformation due to the development of the foliation it is postulated that such processes also occur during natural deformation of polyphase rocks competent clasts within a weaker ductile matrix showing no recrystallization differ in shape and rotational behaviour from recrystallizing clasts such as feldspar augen these competent clasts denoted as type clasts may cause problems in deducing the sense and direction of shear when formed as almost exact mirror images of type recrystallizing clasts

saline lake carbonates within an upper jurassic lower cretaceous continental red bed sequence in the atacama region of northern chile the codocedo limestone member is a thin but laterally persistent lacustrine sequence within the red beds of the upper jurassic lower cretaceous quebrada monardes formation in the atacama region of northern chile the thick succession of clastic terrigenous sediments of the quebrada monardes formation was deposited in an arid to semi arid environment sedimentary facies are indicative of deposition of aeolian dunes alluvial fans and braided streams playa lake mudflats and saline lakes and coastal lagoons the strata accumulated in a n s elongated extensional back arc basin on the landward side of an active volcanic arc the 3 m thick codocedo limestone member marks striking facies changes within the quebrada monardes formation it is underlain by a thick sequence of conglomerates and sandstones deposited on alluvial fans the limestone itself is characterized by evaporite minerals and laterally continuous laminations indicative of deposition by vertical accretion in a perennial saline lake the overlying siltstones and fine sandstones contain geodes and gypsum pseudomorphs and were deposited on playa lake mudflats the limestone therefore represents a relatively short period of lacustrine deposition within an essentially terrigenous succession the lake was possibly formed quite suddenly for example by damming of the basin by a lava flow sedimentation in the perennial lake was predominantly cyclical seasonal planktonic algal blooms produced millimetre scale laminations interbedded with these laminites are centimetre scale beds of evaporitic gypsum anhydrite and minor halite the evaporite minerals have been largely replaced by calcite chalcedony and quartz the centimetre scale cycles may have resulted from periodic freshwater input into the lake after a period of about 3000 yr the lake dried up to be replaced by extensive playa lake mudflats the codocedo limestone member possibly formed a plane of detachment during an early tertiary phase of e w directed regional compression the limestones and evaporites were folded and extensively brecciated this deformation probably resulted from simple shear along the bedding plane of the relatively weak evaporite minerals prior to their replacement by calcite and quartz

from carbonate sulphate interbeds to carbonate breccias the role of tectonic deformation and diagenetic processes cameros basin lower cretaceous n spain interpreting the origin of carbonate breccias requires a detailed analysis because they may be the result of a wide variety of processes that produce similar features this is the case of the lower cretaceous carbonate breccias of the cameros basin previously interpreted as slump or collapse breccias whose origin is interpreted after performing a detailed sedimentary petrographic and tectonic study the studied carbonate breccias consist of angular carbonate mudstone fragments floating in a matrix of calcite and quartz crystals the breccias are interbedded with and laterally associated to alternating layers of carbonate mudstone and calcite and quartz pseudomorphs after gypsum which show strong similirities to the breccia fragments and matrix respectively suggesting that the brecciated beds were originally composed of identical alternating carbonate mudstone and gypsum layers as the unbrecciated layers the breccias are associated with frequently polyharmonic deformation structures which are similarly oriented as the regional tectonic structures indicating that they are related with the alpine contractional deformation of this area of the cameros basin all these features suggest that the carbonate breccias were formed by tectonic deformation of alternating layers of carbonate mudstone and calcium sulphate which have very different rheological behaviours as a result during tectonic deformation sulphate flowed and carbonate layers were broken and displaced producing a breccia of carbonate fragments within a sulphate groundmass afterwards the sulphate groundmass was replaced by quartz and calcite and the breccia acquired its final composition

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

numerical study of tectonic structure evolution in a multi layer evaporite sequence abstract field studies carried out in the klodawa salt structure kss poland reveal that within a carnallite halite kieserite sequence finger like structures developed during an early pre diapiric stage of the kss evolution we used 99 numerical simulations to model finger development and investigate mechanical properties of carnallite halite and kieserite during deformation models used inverse density stratification of a three layer set with varying 1 layer viscosities 2 thicknesses and 3 density difference ratios finger shapes in the models were categorized into single and multiwavelength structures among the single wavelength shapes bulb mushroom thumb and bloated i e without a regular shape structures were distinguished we show two transitions between the single and multiwavelength structures which correspond to the cases of either the lower or upper layer having viscosity more than an order of magnitude larger than the two other layers through comparison of finger shapes developed in the models and in the natural structures we estimate viscosities of 1017 pa s for halite

criteria for distinguishing primary evaporite features from deformation features in sulfate evaporites abstract in many tectonized regions evaporites which served as decollement zones are brought to the surface where they are studied as part of the normal sedimentary succession and their internal structures are commonly treated as the primary products of deposition and synsedimentary deformation evaporites however respond to tectonism in a manner that is vastly different from other rocks in the succession associated limestone dolostone and siliciclastic beds may remain virtually unaffected by the same degree of deformation that significantly alters evaporites even modest differential stresses with geologically reasonable strain rates applied at low temperatures 20 200 c result in significant recrystallization foliation and flow in evaporites whereas other rocks non evaporites in the same succession may show little apparent change the large differences in physical properties between evaporites and both carbonate and siliciclastic lithologies in such tectonized sections result in evaporites that no longer reflect their original sedimentary environment because of recrystallization and plastic deformation yet because their structures and fabrics may not be recognized as secondary they can be misinterpreted as original features indicative of primary depositional environments

modeling deformation and salt tectonics in the eastern mediterranean ridge accretionary wedge this study addresses some aspects of the kinematics and structural setting of the mediterranean ridge accretionary complex particularly those aspects related to the occurrence and distribution of messinian evaporites the approach is by 1 identification of the geometry of deformation through reprocessing of existing multichannel seismic reflection data from the levantine basin aimed at the definition of the velocity field and depth imaging 2 physical modeling in the laboratory aimed at the study of the kinematics of shortening of sedimentary sequences detaching on viscous decollements and 3 comparison between the results of the two approaches we conclude that the thick messinian sequence of the levantine basin is composed primarily of salt so that the entire evaporitic sequence can be expected to behave as a viscous material it follows that the main detachment of the post messinian wedge is located at the base of the messinian salt layer a viscous salt decollement would produce thrusting trending normal to the shortening direction but boundary conditions affect structural trends even more than stress and or movement direction both strain partitioning and the formation of major strike slip faults within the post messinian wedge are prevented by the high angle of convergence between the african and aegean plates as well as by the low intraplate friction in addition we show that curved and anastomosing thrust fronts are reflected in the cobblestone topography of the mediterranean ridge we finally postulate that extension may occur in the central mediterranean ridge as a result of the geometry of the plate boundaries this extension is considered as a possible cause of mud volcanism and mud diapirism

the role of pre impact topography in impact melt emplacement on terrestrial planets abstract on terrestrial planets flow like deposits of impact melt are commonly found exterior to fresh impact craters often these deposits are asymmetric about the crater rim and the direction of flow may relate to either the pre impact topography or the impact azimuth in this work we seek to determine the primary mechanism responsible for impact melt emplacement on two very different terrestrial worlds the moon and venus newly derived stereo topography data allows us to investigate the role of pre impact topography in melt emplacement on venus for the first time we determine that pre impact topography plays an important role in melt emplacement around complex craters on the moon but not on venus this difference may relate to the differences in gravity and hence crater depth and melt volume on the two worlds melt trapped in the relatively deep lunar craters may require additional momentum to be pushed over the crater rim and therefore emerges preferentially from the region of rim crest low this added momentum might come from uplift during the crater modification stage for the shallower craters on venus the downrange momentum imparted in oblique impacts may be sufficient to push the melt up and over the crater rim explaining the correlation between melt direction and impact azimuth understanding the emplacement of impact melt on terrestrial planets of different sizes and geologic histories provides added insight into the impact cratering process

nature origin and evolution of the granitoid hosted early proterozoic copper molybdenum mineralization at malanjkhand central india at malanjkhand central india lode type copper molybdenum mineralization occurs within calcalkaline tonalite granodiorite plutonic rocks of early proterozoic age the bulk of the mineralization occurs in sheeted quartz sulfide veins and k silicate alteration assemblages defined by alkali feldspar k feldspar albite dusty hematite in feldspar biotite muscovite are prominent within the ore zone and the adjacent host rock weak propylitic alteration defined by albite biotite epidote zoisite surrounds the k silicate alteration zone the mineralized zone is approximately 2 km in strike length has a maximum thickness of 200 m and dips 65 75 along which low grade mineralization has been traced up to a depth of about 1 km the ore reserve has been conservatively estimated to be 92 million tonnes with an average cu content of 1 30 supergene oxidation accompanied by limited copper enrichment is observed down to a depth of 100m or more from the surface primary ores consist essentially of chalcopyrite and pyrite with minor magnetite and molybdenite 34s values in pyrite and chalcopyrite 0 38 to 2 90 fall within the range characteristic of granitoid hosted copper deposits 18o values for vein quartz 6 99 to 8 80 suggest exclusive involvement of juvenile water annealed fabrics are common in the ore the sequence of events that led to the present state of hypogene mineralization is suggested to be as follows fracturing of the host rock emplacement of barren vein quartz pronounced wall rock alteration accompanied by disseminated mineralization and the ultimate stage of intense silicification accompanied by copper mineralization fragments of vein quartz and altered wall rocks and striae in the ore suggest post mineralization deformation the recrystallization fabric particularly in chalcopyrite and sphalerite is a product of dynamic recrystallization associated with the post mineralization shearing the petrology of the host rocks hydrothermal alteration assemblages ore mineral associations fluid inclusions and the sulfur and oxygen isotopes of ores are comparable to those in phanerozoic and reported precambrian porphyry copper systems and the malanjkhand deposit has important implications for both metallogenic models for and mineral exploration in precambrian terrains

deformational behavior of shale interlayers in evaporite detachment horizons jura overthrust switzerland shale deformation was studied in a series of naturally strained evaporites and shales deformed at low temperatures 70 high strain rates 10 14s 1 and low pressures overburden 2 km as well as in rock samples and sintered specimens experimentally deformed in coaxial and simple shear configurations at temperatures of 20 350 c strain rates of 10 4 10 6s 1 and confining pressures of 0 1 400 mpa within naturally strained shale sulfate multilayers three deformation regimes can be recognized that are separated by the inversion of relative competence of shale and anhydrite and the onset of gypsification respectively in deeper domains strain is focused on slickensides which are often coated with sulfate that acts as a lubricant in shallower domains and especially in domains with significant access to syntectonic water strain becomes pervasive and very low strength ductile shale gypsum tectonites form experiments reveal that confining pressure and water content have a significant influence on style of deformation pervasive or focused on discrete surfaces whereas temperature and strain rate have virtually no influence on either strength or deformation style except at temperatures 200 c that cause dehydration and embrittlement

sinking of anhydrite blocks within a newtonian salt diapir modelling the influence of block aspect ratio and salt stratification summary 2 d finite differences models are used to analyse the strain produced by gravity driven sinking of dense rectangular inclusions through homogeneous and vertically stratified newtonian salt we systematically modelled the descent of dense blocks of different sizes and initial orientations aspect ratios representing the main anhydrite fragments documented within for example the gorleben salt diapir model results demonstrate that size of the blocks is a governing parameter which dictates the amount of strain produced within the block and in the surrounding host salt initial block orientation aspect ratio on the other hand causes fundamental differences in block deformation while the resulting structures produced in the salt are principally the same in all models with homogeneous salt covering shear zones and folding of passive markers in models with vertically stratified salt with different viscosities block descent takes place along complex paths this results from greater strain accommodation by the salt formation with the lowest viscosity and an asymmetrical distribution of initial vertical shear stresses around the block consequently in these models block strain is lower compared with the models with homogeneous salt for the same viscosity as the high viscosity salt and sinking is accompanied by block rotation the latter causes diapir scale disturbance of the pre sinking salt stratigraphy and complex sinking paths of the blocks in particular vertically oriented blocks sink into high viscosity salt and drag with them some low viscosity salt while horizontal blocks sink in the low viscosity salt the resultant sinking velocities vary strongly depending on the sinking path of the block based on model results and observed structural configuration within the gorleben salt diapir we conclude that the internal complexity of a salt diapir governs its post ascent deformation salt structure and its interaction with dense blocks should hence be considered in the assessment of the long term stability of storage sites for hazardous waste