surface circulation in the gulf of cadiz 2 inflow outflow coupling and the gulf of cadiz slope current 1 a study of the upper slope circulation in the gulf of cadiz is presented observations both original and revisited and realistic numerical modeling are used together to describe the structure and variability of the slope current system above the mediterranean outflow it is shown that the mediterranean inflow outflow coupling plays a stronger role than that of the atmospheric forcing in driving the upper slope currents the mediteranean outflow forces a surface open ocean current toward the strait of gibraltar part of it is entrained into the outflow and the remaining flows into the mediterranean this latter component does not suffice for the observed transport of the atlantic inflow into the mediterranean a secondary contribution to the inflow is therefore needed to complement the transport this contribution comes from a persistent equatorward current along the upper slope between cape st vincent and the strait of gibraltar the jet is 20 30 km wide and significant in the upper 200 m attaining subinertial maxima as much as 0 3 0 4 m s and monthly means in the order of 0 1 0 15 m s this current shows a strong variability at time scales in the order of 2 8 days and displays a significant vertical shear the response of the upper slope current to synoptic and seasonal atmospheric variability is analyzed very low correlation was detected at synoptic scales and the response of the system to seasonal forcing is unclear a cycle of intensification in june july and a decrease in winter is apparent in the measurements but is weak in the model results it is speculated that the cycle in the observed currents is associated with variability in the inflow outflow coupling system rather than driven by seasonally changing wind forcing

the miocene pakhna formation southern cyprus and its relationship to the neogene tectonic evolution of the eastern mediterranean abstract the miocene pakhna formation is interpreted as relating to onset of the present northward subduction of the african plate beneath cyprus and is thus critical to understanding of the neogene evolution of the eastern mediterranean basin following a perios of deep water pelagic chalk deposition in the late eocene and oligocene upper lefkara fm the pakhna formation records heterogeneous mainly carbonate sedimentation the pakhna formation is bounded by the limassol forest block an uplifted ophiolitic terrain to the north and by the akrotiri high a ridge of exotic mesozoic lithologies to the south two sub basins maroni in the e and khalassa in the w within the pakhna formation were separated by the wnw ese trending yerasa lineament located near the s margin of the ophiolite in most areas the pakhna formation overlies the lefkara formation disconformably the succession begins with deep water pelagic carbonates and shows increased input of shallow water bioclastic and terrigenous sediment upward during the early to mid miocene the ophiolitic terrain to the n was uplifted deformed and eroded followed by marine transgression and patch reef development in the tortonian late miocene ophiolite derived clastics were mixed with shallow water bioclastic sediment reworked in a high energy coastal setting and transported downslope within channels into the basin accumulating as massive sands debris flows and calciturbidites in the maroni sub basin localised debris aprons prograded into a pelagic carbonate environment to the se further west in the khalassa sub basin little uplift occurred along the basin margins and redeposited sediment was mainly bioclastic contrasting sediment including chert was derived from the allochthonous mamonia complex exposed on the akrotiri high to the s and its possible offshore extension bioclastic sediment including reef talus was also derived from an intrabasinal high in the khalassa sub basin eventually normal marine deposition was ended by the messinian salinity crisis

deep mantle diamonds from south australia a record of pacific subduction at the gondwanan margin diamonds from jurassic kimberlites at eurelia south australia contain coexisting inclusions of ferropericlase and mgsi perovskite that provide evidence for their deep 670 km lower mantle origin eurelia diamonds formed from mixed carbon sources likely including subducted carbonate as indicated by a trend toward isotopically heavy carbon compositions 13 c 0 and low nitrogen concentrations

the uplift of the troodos massif cyprus we constrain the fault pattern and the kinematics of faulting that facilitated the uplift of the troodos massif in cyprus in the eastern mediterranean the fault pattern consists of e w striking re

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

model for the origin of the troodos massif cyprus and other mideast ophiolites any comprehensive model for the origin of the troodos complex and other mideast ophiolite complexes must explain the geochemical evidence for subduction zone involvement the thin inferred oceanic crust the extensional environment indicated by sheeted dikes the existence of fault zones perpendicular to the inferred spreading axes and the discontinuous nature of ophiolite exposures around the arabian block the andaman sea region of the indian ocean may provide an actualistic model for the origin of these ophiolites there spreading takes place in short segments above a subduction zone in the region of active spreading the andaman sea model substantially accounts for the known geologic and geophysical data from the circum arabian ophiolite belt and it leads to some predictions about the structural and geophysical relationships to be expected in this important belt the model also predicts that andaman sea spreading center magmas may be similar in composition to those found in the mideast ophiolites

cretaceous seawater and hydrothermal fluid compositions recorded in abiogenic carbonates from the troodos ophiolite cyprus abstract we evaluate the potential of ophiolites as archives of paleoseawater and hydrothermal fluid compositions by analysing the chemical and isotopic composition of abiogenic carbonates precipitated from fluids within the oceanic crust of the 91 ma troodos ophiolite cyprus calculated variations in fluid mg ca sr ca and 87sr 86sr with temperature within the upper sections of the ophiolite are similar to those from drilled oceanic crust and yield literature values for late cretaceous seawater mg ca sr ca and 87sr 86sr this indicates that carbonates from ophiolites could be used to estimate the composition of ancient seawater at times before the age of the oldest preserved in situ oceanic crust whereas most carbonates recovered from in situ oceanic crust were precipitated at temperatures 44 c gradually transform cretaceous seawater into a troodos hydrothermal fluid comparison of the troodos data with a global dataset of abiogenic carbonates from in situ oceanic crust shows that the chemical pathways of low temperature fluid evolution are similar for all cretaceous sites these different sites represent varied geotectonic settings mid ocean ridge vs suprasubduction zone with different basement composition basalt basaltic andesite boninite and situated in different ocean basins atlantic pacific mediterranean tethys the similarity in the carbonate record indicates that these differences do not significantly influence seafloor weathering and hydrothermal alteration at low temperatures however abiogenic carbonates from younger oceanic crust differ from the cretaceous trends and follow different fluid evolution pathways this indicates that temporal variations in the composition of seawater may control the nature and the extent of seafloor weathering and hydrothermal alteration at low temperatures a thermodynamic model of fluid crust interaction in which modern and cretaceous seawater are heated to 200 c while an average troodos basaltic andesite is successively added under otherwise identical conditions predicts that fluid evolution and alteration of the oceanic crust were different in the cretaceous than they are today and that initial seawater chemistry affects the nature and the extent of seafloor alteration up to moderate fluid temperatures for example twice the amount of carbonate formed during alteration of the oceanic crust in the cretaceous compared to modern times indicating that the flux of co2 from the hydrosphere atmosphere system into the oceanic crust was greater in the cretaceous than it is nowadays and that it probably varied throughout geologic time

focused ion beam fib combined with sem and tem advanced analytical tools for studies of chemical composition microstructure and crystal structure in geomaterials on a nanometre scale abstract in order to make meaningful interpretations of trace element and isotopic information from geomaterials prior characterization of the material of interest with respect to structural and chemical homogeneity radiation damage and microstructure is often required transmission electron microscopy tem is a powerful analytical tool that may be used to fully characterise a wide range of synthetic and natural materials the focused ion beam technique fib is an ideal tool for tem sample preparation that allows for the fabrication of electron transparent foils with typical dimensions of 15 10 0 150 m from any region of interest i e site specific and in virtually any material fib sample preparation consumes only a small volume of material approximately 2300 m 3 for a standard foil with the dimensions 15 10 0 150 m leaving most of the material essentially unaffected by the sampling process modern tem facilitates the measurement of chemical composition with unsurpassed spatial resolution e g nanometer scale high resolution imaging and electron diffraction provide important complimentary structural information it is the combination of crystal structure information and chemical composition that allows for the complete characterization of the volume of interest high resolution elemental mapping or line scans may be used to acquire complete energy dispersive x ray analysis edx spectra of a material pixel by pixel subsequent evaluation of the data allows for the correlation of the edx spectrum with the respective elemental map or line scan with an image thus illustrating spatially resolved chemical composition variations at the 0 5 1 0 wt level frequently minerals enclose sub micrometer or even nanometre sized inclusions of minerals fluids or silicate melt which are of great interest to geoscientists nanoinclusions e g in diamond or olivine are of particular interest because they may have preserved their original crystal structure thus providing a geobarometer recording the pressure conditions at the time of formation of the inclusion fib tem are appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the nanometre scale the combination of fib with an sem allows for 3d information to be obtained from samples including 3d imaging e g phase distribution and volume of the individual phases in symplectites 3d distribution of elements in a specific volume 3d elemental maps and three dimensional texture analysis using electron backscatter diffraction ebsd

mediterranean outflow water dynamics during the past 570 kyr regional and global implications the gulf of cadiz constitutes a prime area to study teleconnections between the north atlantic ocean and climate change in the mediterranean realm in particular the highly saline mediterranean outflow water mow is an important modulator of the north atlantic salt budget on intermediate water levels however our understanding of its paleoceanographic evolution is poorly constrained due to the lack of high resolution proxy records that predate the last glacial cycle here we present the first continuous and high resolution 1 kyr benthic 18o and 13c as well as grain size records from integrated ocean drilling program site u1386 representing the last 570 kyr we find three distinct phases of mow variability throughout the late to middle pleistocene at site u1386 associated with prominent shifts in its composition and flow strength we attribute this long term variability to changes in water mass sourcing of the mow superimposed on the long term change in water mass sourcing is the occurrence of distinct and precession paced 18o enrichment events which contrast the pattern of global ice volume change as inferred from the global mean 18o signal i e lr04 but mimics that of the adjacent mediterranean sea we attribute these enrichment events to a profound temperature reduction and salinity increases of the mow aligning with similar changes in the mediterranean source region these events might further signify ice volume increases as inferred from significant sea level drops recorded in the red sea and or increased influence of north atlantic intermediate water masses when mow influence was absent at site u1386

quantifying differential rock uplift rates via stream profile analysis despite intensive research into the coupling between tectonics and surface processes our ability to obtain quantitative information on the rates of tectonic processes from topography remains limited due primarily to a dearth of data with which to test and calibrate process rate laws here we develop a simple theory for the impact of spatially variable rock uplift rate on the concavity of bedrock river profiles application of the analysis to the siwalik hills of central nepal demonstrates that systematic differences in the concavity of channels in this region match the predictions of a stream power incision model and depend on the position and direction of the channel relative to gradients in the vertical component of deformation rate across an active fault bend fold furthermore calibration of model parameters from channel profiles argued to be in steady state with the current climatic and tectonic regime indicates that 1 the ratio of exponents on channel drainage area and slope m n is 0 46 consistent with theoretical predictions 2 the slope exponent is consistent with incision either linearly proportional to shear stress or unit stream power n 0 66 or n 1 respectively and 3 the coefficient of erosion is within the range of previously published estimates mean k 4 3 10 4 m 0 2 yr application of these model parameters to other channels in the siwalik hills yields estimates of spatially variable erosion rates that mimic expected variations in rock uplift rate across a fault bend fold thus the sensitivity of channel gradient to rock uplift rate in this landscape allows us to derive quantitative estimates of spatial variations in erosion rate directly from topographic data

re os and 40ar 39ar isotope measurements of inclusions in alluvial diamonds from the ural mountains constraints on diamond genesis and eruption ages the re os isotope data for 20 syngenetic sulphide inclusions recovered from 15 diamonds and the 40ar 39ar laser probe eruption ages of 7 syngenetic clinopyroxenes recovered from 5 diamonds all from alluvial placer deposits in the ural mountains have been determined six eclogitic sulphide inclusions two of which coexist in the same diamond yield an isochron age of 1280 310 ma 2 with an unusually high initial 187os 188os ratio of 2 10 0 58 2 the age is interpreted to date remobilisation of carbon and sulphur and homogenisation of os during rift related thermal magmatic events that affected the east european craton eec at ca 1 3 ga the high initial os ratio suggests re os evolution over a 100 to 500 ma period within previously metasomatised lithosphere most likely the eec five eclogitic clinopyroxenes recovered from four diamonds yielded similar 40ar 39ar ages averaging 472 28 ma which likely approximate the time of source kimberlite lamproite eruption this age suggests that the ural diamonds are not likely to have derived either from the well known diamond bearing kimberlites of the siberian craton nor from presently known russian and finnish kimberlite provinces on the eec the urals placer deposits are mainly confined to 397 407 ma sedimentary rocks along the western side of these mountains with sediment transportation at that time generally from the north west present evidence suggests the existence of an undiscovered kimberlite lamproite source probably on the volgo uralia crustal segment of the eec which gave rise to the urals diamond deposits

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

methane derived hydrocarbons produced under upper mantle conditions there is widespread evidence that petroleum originates from biological processes 1 3 whether hydrocarbons can also be produced from abiogenic precursor molecules under the high pressure high tem

relations among subduction parameters clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones based on a critical appraisal of the geophysical and geological literature 26 parameters are estimated for each of 39 modern subduction zones to isolate causal relationships among these parameters multivariate analysis is applied to this data set this analysis yields empirical quantitative relations that predict strain regime and strike slip faulting in the overriding plate maximum earthquake magnitude benioff zone length slab dip arc trench gap and maximum trench depth excellent correlation is found between length of the benioff zone and the product of convergence rate and age of the downgoing slab this relationship is consistent with the conductive heating model of molnar et al 1979 if the model is modified in one respect the rate of heating of the slab is not constant it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate the structural style in the overriding plate is determined by its stress state though the stress state of overriding plates cannot be quantified one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional class 1 back arc spreading to strongly compressional class 7 active folding and thrusting this analysis indicates that strain class is probably determined by a linear combination of convergence rate slab age and shallow slab dip interplate coupling controlled by convergence rate and slab age is an important control on strain regime and the primary control on earthquake magnitude arc parallel strike slip faulting is a common feature of convergent margins forming a forearc sliver between the strike slip fault and trench optimum conditions for the development of forearc slivers are oblique convergence a compressional environment and a continental overriding plate the primary factor controlling presence of strike slip faulting is coupling strongly oblique convergence is not required the rate of strike slip faulting is affected by both convergence obliquity and convergence rate maximum trench depth is a response to flexure of the underthrusting plate the amount of flexural deflection at the trench depends on the vertical component of slab pull force which is very sensitive to slab age and shallow slab dip shallow slab dip conforms to the cross sectional shape of the overriding plate which is controlled by width of the accretionary prism and duration of subduction deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike slip faulting and strain regime empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones

neogene supra subduction zone extension in the polis graben system west cyprus the neotectonic polis graben and adjacent pegia half graben in west cyprus are extensional basins developed within the convergent tectonic regime of the eastern mediterranean both basins contain an early fill of miocene carbonates including reef limestones messinian extension oriented ene wsw produced the asymmetrically faulted polis graben structure evaporites were deposited in the south of the area while unconformity surfaces developed in the north pliocene mark and chalks were then deposited in a relatively quiescent phase in the north of the graben while faulting continued into the early pliocene in the south plio pleistocene to recent sediments record regional uplift of cyprus contemporaneous nne ssw oriented extension formed the pegia half graben and renewed minor faulting in the polis graben the extensional structures of the polis graben system are thought to result from extension above a subduction zone located south of cyprus driven by subduction 9roll back9 and trench migration accelerated convergence and rapid roll back during late miocene times caused the first stage of extension whilst the plio pleistocene faulting was driven by differential extension in the overriding plate as the eratosthenes seamount collided with the trench and locally impeded subduction the polis graben system may provide a model for the early stages of development of major suprasubduction zone extensional areas such as the aegean region

three new ways to calculate average u th he ages traditionally the average age of multiple u th he analyses has been calculated as the arithmetic mean age this paper presents three alternative methods a in analogy with the fission track method the pooled age is calculated by adding the respective u th and he abundances of several grains together thereby generating one synthetic multi grain measurement b the isochron age is the slope of helium concentration versus present day helium production c the central age is computed from the geometric mean u th he composition each of these methods is more appropriate than the arithmetic mean age in certain applications the pooled age is useful for comparing single grain with multi grain analyses while the isochron age can be used to detect parentless helium the central age is the most accurate and statistically robust way to calculate a sample average of several single grain analyses because u th and he form a ternary system and only the central age adequately captures the statistics of this compositional data space fortunately the expected difference between the arithmetic mean age and the central age is relatively small less than 1 if the external age reproducibility is better than 15 1 finally the u th he age equation is visualized on a ternary diagram to illustrate that the ejection correction should be applied before and not after age calculation in order to avoid a partial linearization of the age equation including sm as a fourth parent element precludes a straightforward visualization of the age equation on a two dimensional plot nevertheless the pooled isochron and central age methods can be easily generalized to the case of u th sm he dating to facilitate the calculation of the central age a web based calculator is provided at http pvermees andropov org central

spreading structure of the troodos ophiolite cyprus orientations of dikes within the sheeted dike complex of the troodos ophiolite reveal primary spreading structure produced at a complex ridge transform intersection three structural grabens are defined by listric and planar normal faults and rotated dikes that dip symmetrically toward graben axes faults flatten at depth into a detachment within the upper parts of the plutonic complex large exhalative massive sulfide deposits occur within the pillow sections of two of the grabens and appear to be associated with underlying altered and mineralized normal fault zones that channeled hydrothermal fluids we suggest that the grabens are fossil axial valleys produced by successive eastward jumps of an approximately north trending present coordinates slow spreading ridge crest a simple model for ridge migration indicates eastward jumps of 8 13 km changes in ridge orientation are suggested by changes in trends of dikes and graben axes comparison of the pattern of dikes near the arakapas fault zone with the structure of active ridge transform intersections suggests that the fault is a right offset sinistral transform in contrast to earlier models in which a ridge to the west of the exposed troodos complex was proposed

late quaternary uplift of the troodos ophiolite cyprus uranium series dating of pleistocene coral in an attempt to constrain the timing and mode of tectonic uplift of the classic troodos ophiolite colonial corals were collected from quaternary littoral raised terraces in coastal southern cyprus and dated using the uranium series disequilibrium method a total of 28 samples of cladocora caespitosa were collected at five localities from the 8 11 m high and 3 m high marine terraces the corals yield systematic ages of 185 192 ka ka 103 yr and 116 130 ka for the 8 11 m and 3 m terraces respectively when correlated with the global oxygen isotope stages the results suggest that southern cyprus was uplifted by 18 m during the past 185 192 ka as a single tectonic entity of this uplift 13 m took place between 130 and 185 ka at 24 cm ka and a maximum of 6 m of uplift at 5 cm ka took place over the past 116 ka but with some evidence of coastal subsidence in more recent time an exception the extreme southeast of cyprus cape greco was perhaps uplifted faster during the past 141 ka at a rate of 12 cm ka

crystalline inclusions and c isotope ratios in diamonds from the snap lake king lake kimberlite dyke system evidence of ultradeep and enriched lithospheric mantle abstract u type paragenesis inclusions predominate 94 7 among the crystalline inclusion suite of 115 diamonds 4 2 mm obtained from the recently discovered snap lake king lake skl kimberlite dyke system southern slave canada the most common inclusions are olivine 90 and enstatite 22 sulfide cr pyrope chromite and cr diopside inclusion are less abundant 15 10 5 and 1 respectively results of the inclusion composition study demonstrate the following a the relatively enriched character of the mantle parent rocks of the u type diamonds the average mg of olivine inclusions is 92 1 and of enstatite inclusions average 93 3 cao content in cr pyrope inclusions is relatively high 3 73 5 75 wt b four of ten u type cr rich pyrope inclusions contain a majoritic component up to 16 8 mol which requires pressures of 110 kbar carbon isotopes compositions for 34 diamonds with u type inclusions have a 13c range from 3 2 to 9 with a strong peak around 3 5 this is much heavier than the ratios of u type diamonds from siberia and south africa 4 5 diamonds with olivine inclusions can be divided into two groups based on their 13c values as well as the mg and ni fe ratio in the olivines most show a narrow range of 13c values from 3 2 to 4 8 average 3 72 and have olivine inclusions with mg less than 92 3 and relatively high fe ni ratios a second group is characterized by a much wider variation of c isotope composition 13c varies from 3 8 to 9 0 average 5 97 and the olivine inclusions having a higher mg up to 93 6 and relatively low fe ni ratios this difference in the c isotope composition may have several explanations a peculiarities of asthenosphere degassing coupled with an abnormal thickness of lithosphere b the abnormal thickness and enriched character of lithospheric mantle c involvement of subducted c of crustal origin in the processes of the diamond formation the presence of subcalcic cr rich majorite up to 17 mol pyropes of low ca harzburgite paragenesis among the crystalline inclusion suite of skl diamonds is strong evidence for the existence of diamondiferous depleted peridotite in lithospheric mantle at depth near 300 km beneath southern slave area and is postulated to be one of the main reasons for the much heavier c isotope composition of skl u type diamonds in comparison with those from siberian and south african kimberlites

multi stage metasomatism of diamondiferous eclogite xenoliths from the udachnaya kimberlite pipe yakutia siberia the primary garnet pyrope almandine omphacite cpx 1 6 5 7 wt na2o sulfide fe ni co mss assemblage of the two diamondiferous eclogite xenoliths studied u33 1 and ux 1 experienced two mantle metasomatic events the metasomatic event i is recorded by the formation of platy phlogopite 10 wt k2o prior to incorporation of the xenoliths in the kimberlite the bulk of the metasomatic alteration consisting of spongy textured clinopyroxene cpx 2a 1 3 wt na2o coarser grained clinopyroxene cpx 2b 2 5 wt na2o pargasitic amphibole 0 8 wt k2o 3 3 5 wt na2o kelyphite cpx 3 mostly 1 wt na2o and zoned mg fe al spinel sodalite calcite k feldspar djerfisherite k5 95na0 02fe18 72ni2 36co0 01cu4 08s26cl and a small amount of k ca fe mg glass is ascribed to the metasomatic event ii that occurred also in the upper mantle but after the xenoliths were incorporated in the kimberlite a pervasive chloritic alteration mainly clinochlore magnetite that overprints earlier assemblages probably took place in the upper crustal environment the diamonds are invariably associated with secondary clinopyroxene and chlorite but the diamonds formed before the entrainment of the xenoliths in the udachnaya kimberlite

high resolution neogene and quaternary estimates of nubia eurasia north america plate motion summary reconstructions of the history of convergence between the nubia and eurasia plates constitute an important part of a broader framework for understanding deformation in the mediterranean region and the closing of the mediterranean basin herein we combine high resolution reconstructions of eurasia north america and nubia north america plate motions to determine rotations that describe nubia eurasia plate motion at 1 myr intervals for the past 20 myr we apply trans dimensional hierarchical bayesian inference to the eurasia north america and nubia north america rotation sequences in order to reduce noise in the newly estimated nubia eurasia rotations the noise reduced rotation sequences for the eurasia north america and nubia north america plate pairs describe remarkably similar kinematic histories since 20ma consisting of relatively steady seafloor spreading from 20 to 8ma 20 percent opening rate slowdowns at 8 6 5ma and steady plate motion from 7ma to the present our newly estimated nubia eurasia rotations predict that convergence across the central mediterranean sea slowed by 50 percent and rotated anticlockwise after 25ma until 13ma motion since 13ma has remained relatively steady an absence of evidence for a significant change in motion immediately before or during the messinian salinity crisis at 6 3 5 6ma argues against a change in plate motion as its causative factor the detachment of the arabian peninsula from africa at 30 24ma may have triggered the convergence rate slowdown before 13ma however published reconstructions of nubia eurasia motion for times before 20ma are too widely spaced to determine with confidence whether the two are correlated a significant discrepancy between our new estimates of nubia eurasia motion during the past few myr and geodetic estimates calls for further investigation

local variations of carbon isotope composition in diamonds from sao luis brazil evidence for heterogenous carbon reservoir in sublithospheric mantle abstract taking advantage of the common occurrence of superdeep mineral inclusion assemblages we examined core to rim primary zonation in 69 diamonds from the alluvial deposits of the sao luis river juina brazil syngenetic inclusions were represented by phases of superdeep paragenesis the dominant inclusions are majoritic garnets ferropericlases and casi and casiti perovskites rare inclusions of mgsi perovskites olivines clinopyroxenes tapp phases of sio2 kyanites alsi phases kfsp k hollandite cf nal grossular merwinite native iron fe sulphides magnesite and caco3 camgsi2o6 composite inclusions were also found the diamonds from sao luis display wide variations in carbon isotopic compositions 13c from 2 7 to 25 3 the diamonds with inclusions of ferropericlase have a very narrow range of 13c values from 2 1 to 7 7 which are close to the normal mantle values in many cases diamonds with inclusions of calcic majoritic garnet and casi and casiti perovskites display marked differences from this range low 13c values 10 to 25 were observed exclusively in a series of diamonds with majorite garnets ca silicates aluminous silicates and sio2 the 13c values from the cores to rims in certain individual crystals varied substantially indicating multiple stages of growth the highly negative 13c values in the cores 20 to 25 potentially represent organic matter in metasediments of altered oceanic crust and the lower 13c values may represent mixing trends towards normal mantle compositions in this study we also found a set of diamonds that display an opposite trend of change of the carbon source from primordial mantle to subducted crust either biotic or abiotic carbon

geodynamic models of continental subduction and obduction of overriding plate forearc oceanic lithosphere on top of continental crust continental subduction takes place in the final stage of subduction when all oceanic lithosphere is consumed and continental passive margin is pulled into the mantle when the overriding plate is oceanic dense forearc oceanic lithosphere might be obducted onto light continental crust forming an ophiolite tethyan style ophiolite obduction four dimensional dynamic analog subduction models have been constructed to evaluate the mechanical feasibility of continental subduction and forearc oceanic lithosphere obduction on top of continental crust the roles of continental crust thickness passive margin length subducting lithosphere thickness and overriding plate thickness were investigated to determine the maximum continental subduction depth maximum forearc obduction distance and forearc deformation during continental subduction our buoyancy driven experiments indicate that deep continental subduction occurs in most circumstances down to 560 km and that obduction of dense oceanic forearc lithosphere on top of light continental crust is mechanically feasible maximum obduction distances are relatively small 26 37 km but are sufficient to explain obduction of short ophiolite sheets such as observed in new caledonia when including the thin 5 10 km thick accretionary wedge of off scraped deep sea sediments oceanic crust and mantle then maximum obduction distances are much larger 60 160 km sufficient to account for the obducted northland allochthon in new zealand results indicate that increasing continental crust thickness decreases continental subduction depth whereas increasing passive margin length and subducting lithosphere thickness increases continental subduction depth notably during continental subduction backarc extension continues while forearc deformation shortening increases moderately compared to the preceding phase of normal oceanic subduction

extension along the australian pacific transpressional transform plate boundary near macquarie island the australian pacific transform plate boundary fault zone along the macquarie and mcdougall segments of the macquarie ridge complex mrc south of new zealand is characterized by dominantly normal faults and pull apart basins in apparent conflict with the regional transpressional tectonic setting we propose that present day curvature of the transform is inherited from a preexisting divergent plate boundary and that the overall extensional kinematics shown by faults along the main plate boundary trace and exposed on macquarie island result from local stresses related to right lateral right stepping en echelon plate boundary faults and not to the current transpressional setting transpression along the australian pacific transform plate boundary has resulted in uplift along the 1500 km long macquarie ridge complex macquarie island the only subaerial exposure of the complex sits atop a 5 km high 50 km wide submarine ridge of oceanic crust and lies 4 5 km east of the major active plate boundary fault zone thus macquarie island and the surrounding seafloor provide a unique opportunity to study an active oceanic transform fault using complementary marine geophysical and land based geological data mapping of recent faults affecting the topography of macquarie island shows that the island is extensively cut by high angle normal faults forming pull apart basins furthermore evidence for reverse motion is rare using marine geophysical data including swath bathymetry reflectivity and seismic reflection data collected along the australian pacific plate boundary north and south of the island we have defined a 5 15 km wide plate boundary zone a series of right stepping en echelon faults within this zone lies along the main plate boundary trace at the right stepping fault terminations elongate depressions 10 km wide and 1 2 km deep parallel the plate boundary which we interpret as extensional relay zones or pull apart basins we propose that transpression is partitioned into en echelon strike slip faults at the plate boundary and a convergent component that flexes the crust causing the anomalous bathymetric ridge and trough morphology of the mcdougall and macquarie segments of the mrc

new insights into upper mow variability over the last 150kyr from iodp 339 site u1386 in the gulf of cadiz the upper mediterranean outflow water mow paleo oceanographic history in the gulf of cadiz is poorly constrained due to the lack of high resolution records that pre date the last glaciation existing proxy records concentrate on mow variability along the middle slope of the gulf of cadiz here we present a continuous high resolution benthic foraminifera 18o record from the upper mow core at iodp expedition 339 site u1386 in the gulf of cadiz of the past 150 000 years based on 18o grain size and zr al variability comparison of our results with existing mediterranean sea md01 2472 md95 2043 open ocean lr04 and gulf of cadiz md99 2339 records we have gathered new insights into the evolution of the upper mow core on glacial interglacial timescales the influence of the upper mow at site u1386 was strongest during mis 5 and mis 1 similar 18o variability can be seen in the levantine intermediate water liw originating from the levantine basin of the eastern mediterranean sea we found clear indication for a vertical shift of the mow from the upper to the middle slope of the gulf of cadiz during sea level lowstands coinciding with mis 4 and mis 2 but also during mis 3 additionally our results indicate an increased upper mow flow correlated with heinrich events 7 to 10 and the younger dryas and also inversely relate to precession forced monsoonal freshwater inputs into the eastern mediterranean in the context of sapropel formation we could not find conclusive evidence of the proposed mow shutdown in our data

late miocene surface uplift of the southern margin of the central anatolian plateau central taurides turkey the timing and pattern of surface uplift of miocene marine sediments capping the southern margin of the central anatolian plateau in southern turkey provide a first order constraint on possible mechanisms of regional uplift nannofossil ostracod and planktic foraminifera biostratigraphy of the basyayla section mut ermenek basin within the mut and koselerli formations suggests a tortonian age for marine sediments unconformably capping basement rocks at 2 km elevation the identification of biozone mmi 12a 7 81 8 35 ma from planktic foraminifera in the upper part of the section provides the tightest constraint on the age which is further limited to 8 35 8 108 ma as a result of the reverse polarity of the collected samples chron 4r 1r or 4r 2r this provides a limiting age for the onset of surface uplift at the margin of one of the world s major orogenic plateaus from which an average uplift rate of 0 24 0 25 mm yr can be calculated subhorizontal beds of the uppermost marine sediments exposed throughout the mut ermenek basin suggest minimal localized deformation with just minor faulting at the basin margin and broad antiformal deformation across the basin this implies that the post 8 ma uplift mechanism must be rooted deep within the crust or in the upper mantle published pn wave velocity data for the region are compatible with topography compensated by asthenosphere across the southern margin of the plateau showing a close match to the highest topography when elevations are filtered with a 100 km wide smoothing window uplift along the southern margin of the central anatolian plateau is also reflected by the pattern of miocene marine sediments capping the margin which form an asymmetric drape fold over the topography these observations together with tomographic evidence for slab steepening and break off beneath the eastern anatolian plateau suggest that at least some of the 2 km of post 8 ma uplift of the southern central anatolian plateau margin is compensated by low density asthenospheric mantle that upwelled following slab break off

metasomatic diamond growth a multi isotope study 13c 15n 33s 34s of sulphide inclusions and their host diamonds from jwaneng botswana abstract the formation of diamond through metasomatic events from volatiles enriched fluids melts brought into pre existing mantle rocks has been suggested from a series of independent studies however the link between these hypothetical volatile rich fluids and deep seated mineral inclusions mostly silicate and sulphides entrapped in diamonds remains unclear yet the relationship between these two species may provide the key to our understanding of diamond crystallization in order to address the relationship between the origin and formation of diamonds and their mineral inclusions we carried out the first coupled stable isotopic study 13 c 15 n and multiple s isotopes as 34 s 33 s 33 s of diamonds containing sulphide inclusions using samples from the jwaneng kimberlite as our model system sulphides extracted from the present collection of 55 diamonds belong to either eclogitic e type 52 diamonds or peridotitic p type 3 diamonds paragenetic suites as attested by their cr and ni content cr 0 18 wt and ni 14 wt for p types sulphur isotopic compositions have been measured in situ by multicollector secondary ion mass spectrometry and reveal that peridotitic sulphide inclusions in diamonds n 4 lie on the terrestrial fractionation line whereas mass independent sulphur isotope fractionations mif are preserved inside eclogitic sulphides inclusions 0 5 33 s n 33 such large mif values extended here to the negative values recorded in archean sediments are thought to be produced through photochemical reactions in the archean atmosphere which implies that sulphides inclusions contain an archean sedimentary sulphur component that was transferred to the earth s mantle in contrast to this isotopic dichotomy between e type and p type sulphides the geochemical characteristics of their host diamonds 13 c 15 n n content n speciation are largely homogeneous throughout the population and differ from silicate bearing diamonds previously studied in the same locality sulphide bearing diamonds appear to define a distinct population which might reflect a different crystallization process characterized by carbon and nitrogen isotopic compositions falling within the range of unfractionated mantle values the lack of a distinct isotopic signature of recycled sedimentary nitrogen and carbon in sulphide bearing diamonds leads us to infer that sulphide bearing jwaneng diamonds were not derived from the same chemical reservoir as their inclusions one possible formation mechanism that is compatible with our observations is diamond crystallization from a mantle derived carbon bearing fluid associated with pre existing sedimentary sulphide minerals this model has important implications for the interpretation of diamond ages obtained from sulphide inclusions using re os systematics here we suggest that the incorporation of a significant amount of mantle related sulphur during a diamond growth event into the original sulphide could lead to a re equilibration of the re os isotope composition in any inclusion and accordingly account for some scatter on re os isochrons

oxygen and hydrogen isotope signatures of northeast atlantic water masses abstract only a few studies have examined the variation of oxygen and hydrogen isotopes of seawater in ne atlantic water masses and data are especially sparse for intermediate and deep water masses the current study greatly expands this record with 527 18o values from 47 stations located throughout the mid to low latitude ne atlantic in addition d was analyzed in the 192 samples collected along the geotraces north atlantic transect ga03 ga03 e kn199 4 and the 115 iberia forams cruise samples from the western and southern iberian margin an intercomparison study between the two stable isotope measurement techniques cavity ring down laser spectroscopy and magnetic sector isotope ratio mass spectrometry used to analyze ga03 e samples reveals relatively good agreement for both hydrogen and oxygen isotope ratios the surface 0 100 m and central 100 500 m water isotope data show the typical evaporation related trend of increasing values equatorward with the exception for the zonal transect off cape blanc nw africa off cape blanc surface water isotope signatures are modified by the upwelling of fresher antarctic intermediate water aaiw that generally has isotopic values of 0 0 to 0 5 for 18o and 0 to 2 for d along the iberian margin the mediterranean outflow water mow is clearly distinguished by its high 18o 0 5 1 1 and d 3 6 values that can be traced into the open atlantic isotopic values in the ne atlantic deep water neadw are relatively low 18o 0 1 to 0 5 d 1 to 4 and show a broader range than observed previously in the northern and southern convection areas the neadw is best observed at ga03 e stations 5 and 7 in the central ne atlantic basin antarctic bottom water isotope values are relatively high indicating modification of the original antarctic source water along the flow path the reconstructed 18o salinity relationship for the complete data set has a slope of 0 51 i e slightly steeper than the 0 46 described previously by pierre et al 1994 j mar syst 5 2 159 170 for the tropical to subtropical northeast atlantic this slope decreases to 0 46 for the subtropical north atlantic central water nacw and the mow and to 0 32 for the surface waters of the upper 50 m the d salinity mixing lines have estimated slopes of 3 01 for the complete data 1 26 for the mow 3 47 for the nacw and 2 63 for the surface waters the slopes of the 18o d relationship are significantly lower than the one for the global meteoric water line with 5 6 for the complete data set 2 30 for the mow 4 79 for the nacw and 3 99 for the surface waters the lower slopes in all the relationships clearly reflect the impact of the evaporation surplus in the subtropics

the pissouri basin fan delta complex southwestern cyprus abstract the pliocene pleistocene sedimentary fill of a small 70 km 2 sub basin in southwestern cyprus is interpreted as representing a fan delta complex with braid channels which shows a broadly progradational sequence influenced by both sea level fluctuation and tectonic activity basin differentiation began in middle late miocene with the tectonic break up of uniform carbonate deposition along southern cyprus during the latest miocene messinian salinity crisis the pissouri basin was a shallow silled depression in which thick gypsum deposits accumulated renewed basin margin faulting led to the local development of slope fan deltas followed by extensive deeper marine micrites and marlstones upwards these are intercalated with terrigenous siltstone sandstone turbidites that represent the bottomsets and foresets of a large fan delta continued uplift and erosion of troodos resulted in the southward progradation of stacked micro gilbert type deltas with interbedded terra rossa palaeosols that form the fan delta topset unit a distinctive bioclastic calcarenite sandstone body appears to represent a local channelised unit within the fan delta complex

a reassessment of models for hydrocarbon generation in the khibiny nepheline syenite complex kola peninsula russia although hydrocarbon bearing fluids have been known from the alkaline igneous rocks of the khibiny intrusion for many years their origin remains enigmatic a recently proposed model of post magmatic hc generation through fischer tropsch type reactions suggests a primary co2 fluid this hypothesis is based upon textural data gas bulk and isotopic composition and low entrapment temperature of fluid inclusions that indicate an abiogenic origin for the hc gases however new petrographic microthermometric laser raman bulk gas and isotope data are presented and discussed in the context of previously published work in order to reassess models of hc generation the gas phase is dominated by ch4 with only minor proportions of higher hydrocarbons no remnants of the proposed primary co2 rich fluid are found anywhere in the complex primary and secondary fluid inclusions show similar compositions and entrapment conditions the majority of the fluid inclusions are of secondary nature and trapped in healed microfractures this indicates a high fluid flux after magma crystallisation entrapment condtions for primary fluid inclusions are 450 550 c at 2 8 4 5 kbar these temperatures are too high for hc gas generation through the ft reaction chemical analyses of rims of fe rich phases suggest that they are not the result of alteration but instead represent changes in magma composition during crystallisation furthermore there is no clear relationship between the presence of fe rich minerals and fluid inclusion abundance as reported elsewhere fluid inclusion planes generally start and terminate at mineral boundaries 13c values for methane range from 22 4 to 5 4 confirming also an abiogenic origin for the gas these data support an abiogenic hc origin but are not consistent with a post magmatic ft type reaction the presence of primary ch4 dominated fluid and melt inclusions which contain a methane rich gas phase indicate that a magmatic origin is more likely an increase in methane content together with a decrease in 13c isotope values towards the intrusion margin suggest that magmatically derived abiogenic hydrocarbons may have mixed with biogenic hydrocarbons derived from the surrounding country rocks

systematic change of foraminiferal mg ca ratios across a strong salinity gradient abstract the mg ca ratio of foraminiferal calcite is an important proxy for estimating past ocean temperatures used in conjunction with 18 o of foraminiferal calcite it allows deconvolution of temperature and ice volume signals to infer past ocean temperatures and salinities assuming the relationship between seawater 18 o and salinity is known such work assumes that temperature is the only or at least the dominant environmental controller of foraminiferal mg ca the semi enclosed mediterranean sea where salinity varies from 36 to 40 psu over a seasonal temperature range of between only 5 c to 8 c provides a relevant setting to test this assumption outside the laboratory in this study planktonic foraminifera o universa g siphonifera g bulloides and g ruber white and pink were picked from 11 box core tops spanning the mediterranean salinity gradient and analysed for their trace element concentrations mg ca ratios are higher for the associated calcification temperatures than in other regions where calibrations have been conducted and correlate poorly with calcification temperature mg ca ratios are particularly high for samples from the eastern mediterranean where salinity is unusually high correlations of mg ca with the calcification salinity are statistically significant with mg ca changing by 15 59 per psu suggesting that salinity may act as a control on mg ca ratios in addition to the dominant temperature control we show that contamination by non carbonate material and diagenetic high mg carbonate overgrowths cannot account for the observed trend of increasing mg ca with salinity a relationship between mg ca and salinity is also suggested by re analysis of calibrations from open ocean settings these new mediterranean results are from a region with unusually high salinity but suggest that the effects of salinity on the mg ca palaeothermometer should be considered even in open ocean settings particularly where large salinity changes occurred in the past

provenance and magmatic tectonic setting of campanian aged volcaniclastic sandstones of the kannaviou formation in western cyprus evidence for a south neotethyan continental margin volcanic arc abstract regionally developed late cretaceous subduction related magmatism in the eastern mediterranean records progressive closure of the southern neotethys in western cyprus the late cretaceous c 90 ma troodos ophiolite is depositionally overlain by volcaniclastic sandstones up to 750 m thick that are dominated by redeposited pyroclastic fallout interbedded with both non calcareous and calcareous radiolarian bearing mudstones the sands were mainly deposited by channelised mass flow processes and to a lesser extent by turbidity currents in a deep water forearc basin the succession was folded and locally thrust deformed related to latest cretaceous emplacement of adjacent mesozoic continental margin and oceanic units mamonia complex sims u pb analysis of euhedral to subhedral magmatic zircon crystals yielded a weighted mean 206pb 238u age of 80 1 1 1 ma campanian sandstone petrography including compositional framework q12f21l67 suggests sediment supply from a volcanic arc subordinate continentally derived detritus suggests a continental margin arc setting for the mafic to felsic fallout ash sims analysis of little altered volcanic glass indicates high th nb and th la ratios that suggest the involvement of continental crust and or subducted terrigenous sediments in magma genesis whole rock chondrite normalised ree patterns have comparable trends to modern and ancient forearc basin volcaniclastic sands and sandstones e g northwest pacific region trace element chemistry although scattered towards the continental island arc fields on some geochemical diagrams e g th sc zr mainly suggests an oceanic island arc source for the kannaviou formation sandstones with variable enrichments in v cr ni sc depletion in nb ta and relatively low trace element ratios e g la co th co la sc th sc an explanation for this apparent discrepancy is that the volcaniclastic sandstones were derived from a relatively primitive arc constructed on previously depleted rifted thinned neotethyan continental crust the inferred continental margin arc developed during early stage northward subduction of the southern neotethys beneath a tauride microcontinent to the north large volumes of volcanic ash were derived from continental margin arc volcanism probably in the vicinity of the kyrenia range in northern cyprus

nitrogen nanoinclusions in milky diamonds from juina area mato grosso state brazil abstract a unique set of diamonds with a milky optical appearance from the rio soriso placer deposit in the juina area mato grosso brazil was studied by combined transmission electron microscopy tem and fourier transform infrared ftir spectroscopy the main characteristics of the studied samples are large numbers of randomly distributed 111 faceted octahedral defect nanostructures the dislocation densities of the focused ion beam fib foils are generally low dislocation loops are observed only around larger inclusions the inclusion size shows a bimodal distribution and spreads around values of 20 and 200 nm electron energy loss spectroscopy eels and energy dispersive x ray edx spectroscopy mapping of both subsets yield high nitrogen contents for all sealed inclusions in cases where the nanoinclusions touch the surface of the fib section no nitrogen signal could be detected indicating the loss of a fluid or gas phase as the carrier of nitrogen ftir mapping of the same regions showed a strong correlation between structurally bound nitrogen hydrogen and the abundance of nanoinclusions we propose that the most likely phase included in these nanoinclusions is nh 3 these nanoinclusions could be the result of a high temperature episode or of long residence times at shallower depths and lower temperatures thus they might represent the last stage of the nitrogen aggregation or they may be syngenetic trapped nh bearing source fluids

from ocean depths to mountain tops uplift of the troodos ophiolite cyprus constrained by low temperature thermochronology and geomorphic analysis the timing and mode of uplift of the troodos ophiolite are constrained by low temperature thermochronology combined with geomorphic analysis zircon u th he and apatite fission track cooling ages in the troodos plutonic sequence are all cretaceous 83 106 ma and within error of published zircon u pb crystallization ages this indicates early cooling of the oceanic crust and termination of spreading axis magmatism at 90 ma apatite u th he ages decrease with reconstructed crustal depths from 40 ma near the top of the sheeted dike complex to 4 ma within the mantle sequence a prominent inflection point in the age versus depth curve defines the bottom of the exhumed helium partial retention zone and records the onset of rapid exhumation of the main troodos massif at 6 2 ma inverse thermal modeling supports this conclusion indicating that the timing of uplift is earlier than previously estimated the boundaries of the mantle sequence exposed in the core of the troodos structure closely overlap the boundaries of a concentric zone delineated by high local relief and higher channel steepness indices indicating differential exhumation and uplift of this area relative to its surroundings this zone also overlaps with a prominent negative bouguer gravity anomaly the timing and pattern of the troodos ophiolite uplift suggest that it is driven by serpentinite diapirism possibly triggered by miocene reactivation of subduction along the cyprean arc the worldwide ubiquity of suprasubduction zone ophiolites may thus reflect the importance of extensive serpentinization at the overthrusting mantle wedge in obduction processes

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

metasomatic origin of diamonds in the world s largest diamondiferous eclogite article i nfo the world s largest diamondiferous eclogite 8 8 kg ud 111 02 from the udachnaya kimberlite siberia is the subject of this investigation high resolution x ray computed tomography hrxct chemistry of host minerals and diamond inclusions stratigraphy of the diamonds cathodoluminescence zoning and carbon isotopes have been obtained hrxct images 3 d models and subsequent detailed dissection of this group b eclogite revealed linear distributions of diamonds along alteration zones both unusual multiple diamond clusters with dodecahedral morphologies and distinctive internal zoning recorded by cathodoluminescence analyses are indicative of multiple stages of diamond growth and resorption in ud 111 02 carbon isotope ratios 13 c of 16 diamonds have a total range of 7 2 0 to 9 2 with the majority at 5 4

fault related oceanic serpentinization in the troodos ophiolite cyprus implications for a fossil oceanic core complex article ultramafic rocks are exposed at the core of a domal structure near a fossil ridge transform intersection rti in the troodos ophiolite a sequence of heavily serpentinized rocks occurs adjacent to a major axis parallel fault the amiandos fault af which juxtaposes them against gabbro previously serpentinization and faulting were not considered to be related to the cretaceous ocean spreading history of the troodos ophiolite but instead were interpreted as associated with late emplacement related tectonics and diapirism unusually high 18 o values previously measured in troodos serpentine srp supported this view here petrographic and isotope tracers d 18 o of water rock interaction are examined in three profiles across the af to determine the spatial distribution temperature and the type of water involved in serpentinization in the troodos rti complete serpentinization widespread chrysotile veining and very high

tectonic significance of the eratosthenes seamount a continental fragment in the process of collision with a subduction zone in the eastern mediterranean ocean drilling program leg 160 abstract one of the objectives of odp leg 160 in the eastern mediterranean sea april may 1995 was concerned with the study of processes of genesis and incipient collision of an inferred crustal fragment the eratosthenes seamount with the active margin of the eurasian plate to the north represented by southern cyprus the upper part of the eratosthenes seamount i e upper several hundred metres was found to include both shallow and deep water carbonates dating back to early cretaceous time shallow water platform carbonate deposition similar to that of the onshore levant continental margin to the east i e part of the north african plate was followed by submergence to bathyal depths 1000 m in the late cretaceous to middle eocene punctuated by depositional and tectonic hiatuses tectonic uplift approximately 1 km was followed by shallow water carbonate deposition in the early miocene the platform was exposed during the messinian desiccation crisis during the early pliocene the platform subsided to bathyal depths associated with localised accumulation of limestone debris flows subsidence accelerated in the late pliocene early pleistocene reaching a present day maximum depth of ca 2500 m deformation of the eratosthenes seamount i e subsidence and high angle faulting resulted from crustal flexure induced by southward overthrusting of the cyprus active margin tectonic subsidence of the eratosthenes seamount was approximately synchronous with rapid surface uplift of the over riding plate the troodos ophiolite of southern cyprus this uplift is explained in terms of incipient collision of an eratosthenes continental fragment with a subduction trench coupled with the effects of diapiric protrusion of serpentinite located within the core of the troodos ophiolite the eratosthenes drilling thus documented a modern analogue of subduction collisional processes leading to accretion of continental fragments and carbonate platforms in orogenic belts

patterns of reef sedimentation and diagenesis in the miocene of cyprus abstract an early tertiary regressive sedimentary succession developed along an active plate margin in cyprus a varied clastic and carbonate succession of the miocene pakhna formation and then messinian evaporites culminate the regression within the pakhna formation two phases of reef growth were developed the aquitanian burdigalian terra member and the tortonian koronia member the terra member is exposed only in west and southeast cyprus mainly between pelagic carbonates the koronia member is exposed around the margins of the troodos massif in north south and west cyprus and on the akamas peninsula in northwest cyprus there was little tectonic influence on the growth pattern of the terra member reefs the koronia member reefs however are developed on up faulted blocks most of the koronia member fore reef facies and associated clastic input was shed into downfaulted basinal depocentres there are differences between the first and second miocene reef phases in cyprus in primary reef construction and in the level of background carbonate pelagic sedimentation the terra member reefs are dominantly framestones comprising faviids and domal poritids with several types of secondary reef dwelling corals there is no indication of a connection with the indo pacific coral faunal province benthonic foraminifera and fragments of crustose coralline algae are abundant in the off reef by contrast the koronia member is a bindstone comprising virtually monospecific laminar poritid corals but with coralline algae also playing a role in encrustation the koronia member off reef facies comprises decimetre thick beds of bioclastic reef detritus in north cyprus however beds of similar detritus centimetres in thickness are overlain by progressively thicker up to several metres debris flow sheets the terra member reefs have limited acicular fringe cement probably aragonitic this is overlain by an abundant marine bladed formerly high mg calcite cement later cements present in the reef facies include micritised calcite spars perhaps indicating microboring in cements during their precipitation neomorphism was extensive converting most cements to low mg calcite stable isotopic data for all the cyprus calcites exhibit depletion in the heavier isotopes 18 o and 13 c indicative of meteoric alteration the koronia member limestones show abundant indication of early lithification with fringing acicular aragonite and micrite cements stable isotopic data of the botryoidal aragonite cements indicate a marine origin the dolomite is thought to result from marine freshwater mixing and to be of pliocene age on the basis of stratigraphical solution replacement fabric and stable isotopic data sr isotopic data do not contradict a pliocene age dolomite characteristically replaces the pliocene fissure fill contents in southeast cyprus and off reef horizons in the terra member of west cyprus and koronia member of north cyprus the growth and burial history of miocene reefs contribute to the understanding of the tectonic history and palaeogeographical evolution of cyprus

modeling of the temperature sensitivity of the apatite u th he thermochronometer apatite u th he apparent ages will generally reflect residence for extended periods at temperatures where helium is neither quantitatively retained nor lost by diffusion to characterize the response of apatite he ages to thermal histories involving partial he retention we explored solutions to the he production diffusion equation under thermally static conditions the analytical solution to this equation coupled with published diffusivity data demonstrates that the zone of partial he retention extends from about 40 c to 85 c this zone lies at temperatures 35 c cooler than the analogous fission track partial annealing zone he ages within the partial retention zone ultimately achieve a balance between he production and loss yielding a steady state age both the ultimate age and the time it takes to achieve this age are temperature dependent for example an apatite held at 75 c equilibrates to an age of 2 ma after 17 myr regardless of whether equilibrium is approached from a higher or a lower initial he age for representative dynamic thermal histories we evaluated apatite he ages using a numerical solution to the ingrowth diffusion equation the results illustrate the sensitivity of he ages to various geologic histories and are useful for understanding he age elevation relationships and for testing time temperature paths derived from apatite fission track length distributions in addition although he diffuses rapidly from apatite at shallow crustal temperatures modeling of ambient temperature fluctuations indicates that he ages are nearly unaffected by surficial processes

structure of a fossil ridge transform intersection in the troodos ophiolite recent palaeomagnetic studies of sheeted dykes adjacent to the east west trending southern troodos transform fault of cyprus have demonstrated significant clockwise block rotations which are most easily interpreted as being due to drag induced by dextral strike slip faulting along the transform1 6 we show here that such rotations have not occurred along the entire length of the transform instead to the west of the areas previously studied the sheeted dykes have been subjected to simple tilting only indicating normal faulting but no strike slip the changeover between these two domains of differing structural styles near the village of mandria is approximately in line with the centre of the solea graben a north south trending structure within the troodos massif which has previously been interpreted as a fossil ridge axis7 we suggest that the mandria area represents a fossilized ridge transform intersection and present the results of a detailed field investigation of the area together with preliminary palaeomagnetic data to determine the relationship between tectonism and magmatism at such plate boundary zones we use our findings to test a recent theoretical model8 of deformation processes at ridge transform intersections and show that distributed deformation due to block rotation is largely confined to the ridge transform corner itself

mineral and fluid inclusions in diamonds from the urals placers russia evidence for solid molecular n2 and hydrocarbons in fluid inclusions abstract the compositions of mineral inclusions from a representative collection more than 140 samples of diamonds from the placer deposits in the ural mountains were studied to examine their compositional diversity the overwhelming majority of rounded octahedral and dodecahedral stones typical of placers contain eclogitic e type mineral inclusions up to 80 represented by garnets with mg 40 75 and ca 10 56 including the unique high calcic grospydite composition omphacitic pyroxenes containing up to 65 of jadeite as well as kyanite coesite sulfides and rutile peridotitic p type inclusions are represented by olivine subcalcic cr pyrope chrome diopside enstatite and magnesiochromite that are typical for diamonds worldwide comparing the chemical composition of olivine pyrope and magnesiochromite in diamonds of the urals north east of the siberian platform placers and arkhangelsk province kimberlites show striking similarity there are significant differences only in the variations of carbon isotopic composition of the diamonds from the placers of the urals and north east of the siberian platform one typical rounded dodecahedral diamond was found to contain abundant primary oriented submicrometer sized

high resolution stratigraphy of the mediterranean outflow contourite system in the gulf of cadiz during the late pleistocene the impact of heinrich events abstract a detailed high resolution stratigraphic analysis of the mediterranean outflow contourite system at the continental slope of the gulf of cadiz has been carried out through the correlation between a dense network of seismic reflection profiles sparker airgun 3 75 khz and parametric echosounder topas calypso giant piston and standard gravity cores from such correlation we determine a stacking pattern constituted by four main seismic units a d that are internally structured into ten subunits each subunit shows a single sequence formed by transparent seismic facies at the base to smooth parallel reflectors of moderate to high amplitude facies at the top being well correlated in the cores with a coarsening upward sequence the latest pleistocene holocene deposits form glacial interglacial depositional sequences related to cycles with a frequency range below the milankovitch band that corresponds to millennial timescale climatic changes such as dansgaard oeschger 1 5 ka and bond cycles 10 15 ka oxygen isotope records of planktonic foraminifera and the occurrence of ice rafted debris ird in the most recent contourite subunits show clear evidence of the influence of the north atlantic climatic conditions especially the climatic heinrich events h in the slope sedimentation of the gulf of cadiz and then in the circulation of the mediterranean outflow water mow the coarser contourite deposits are mostly associated with the last glacial maximum younger dryas and heinrich events on the central area of the middle slope during globally cooler conditions the mow was denser so that it was more active in deeper areas than today on the other hand during warm periods the mow became less dense favoring an increased intensity of the mow on the distal area of the upper slope therefore spatial and vertical fluctuations of the mow contourite system are strongly affected by global climate and oceanographic changes being clearly influenced by iceberg discharges and probably also by the resumption of thermohaline circulation in the north atlantic ocean during ice melting periods

depositional processes and basin analysis of messinian evaporites in cyprus messinian evaporites in cyprus resulted from the interplay of mediterranean wide and eustatic sea level changes and local tectonics in an inferred above subduction zone setting distinctive tortonian early messinian pre evaporitic facies include diatomaceous marls and microbial carbonates overlain by a variety of gypsum facies and then by lagoonal lacustrine deposits and local palaeosols facies analysis and comparisons allow construction of a simple model in which evaporites formed in semi isolated small basins not far below global eustatic sea level coarsely crystalline gypsum formedin situ along the margins of small basins and within shallow water lagoons 10 m deep this comprised common banded stacked i e layered selenite swallowtail selenite botryoidal selenite and sugary bedded selenite fine grained gypsum precipitated widely and was reworked into basinal areas 70 m deep by weak traction currents and low density turbidity currents shallow water derived selenite was also reworked basinwards by high density turbidity currents and debris flows slumps indicate tectonic instability more detailed basin analysis can be achieved by study of individual sub basins in the polemi sub basin in the west a lower unit up to 60 m thick comprises basinal gypsum interbedded with gypsum turbidites and mass flow deposits with slumps this is overlain by an extensive mega rudite up to 20 m thick including up to metre sized clasts of marginal gypsum facies above the upper unit up to 70 m thick includes shallow water gypsum e g swallowtails marl and minor microbial carbonates the pissouri sub basin in the south west exposes marginal facies of the upper unit including deltaic elastics and palaeosols the maroni sub basin in the south exhibits a basinal lower gypsum unit with laterally equivalent marginal facies up to 50 m thick overlain by an extensive mega rudite up to 20 m thick finally the mesaoria subbasin in the north exposes relatively marginal gypsum facies in an unstable tectonic setting formation of the polemi pissouri and mesaoria gypsum sub basins relates to coeval extensional faulting and graben development evaporites in south cyprus maroni sub basin formed in elongate basins between former compressional lineaments created by localized early miocene thrusting in the sub basins of west south west and south cyprus large scale slumping of marginal gypsum facies took place towards depocentres to form megarudite debris flows triggered by one or several phases of extensional faulting

hydrographic conditions along the western iberian margin during marine isotope stage 2 the surface water hydrography along the western iberian margin as part of the north atlantic s eastern boundary upwelling system consists of a complex seasonally variable system of equatorward and poleward surface and subsurface currents and seasonal upwelling not much information exists to ascertain if the modern current and productivity patterns subsisted under glacial climate conditions such as during marine isotope stage mis 2 and how north atlantic meltwater events especially heinrich events affected them to help answer these questions we are combining stable isotope records of surface to subsurface dwelling planktonic foraminifer species with sea surface temperature and export productivity data for four cores distributed along the western and southwestern iberian margin md95 2040 md95 2041 md99 2336 and md99 2339 the records reveals that with the exception of the heinrich events and greenland stadial gs 4 hydrographic conditions along the western iberian margin were not much different from the present during the last glacial maximum lgm subtropical surface and subsurface waters penetrated poleward to at least 40 6 n site md95 2040 export productivity was in general high on the western margin during the lgm and low in the central gulf of cadiz in agreement with the modern situation during the heinrich events and gs 4 on the other hand productivity was high in the gulf of cadiz and suppressed in the upwelling regions along the western margin where a strong halocline inhibited upwelling heinrich event 1 had the strongest impact on the hydrography and productivity off iberia and was the only period when subarctic surface waters were recorded in the central gulf of cadiz south of lisbon 39 n the impact of the other heinrich events was diminished and not all of them led to a significant cooling in the surface waters thus climatic impacts of heinrich events highly varied with latitude and the prevailing hydrographic conditions in this region

eclogitic inclusions in diamonds evidence of complex mantle processes over time the first ion probe trace element analyses of clinopyroxene garnet pairs both included within diamonds and from the eclogite host xenoliths are reported these diamondiferous eclogites are from the udachnaya and mir kimberlite pipes yakutia russia the major and trace element analyses of these diamond inclusion and host rock pairs are compared in order to determine the relative ages of the diamonds confirm or deny genetic relationships between the diamonds and the eclogites evaluate models of eclogite petrogenesis and model igneous processes in the mantle before during and after diamond formation the most striking aspect of the chemical compositions of the diamond inclusions is the diversity of relationships with their eclogite hosts no single distinct pattern of variation from diamond inclusion minerals to host minerals is found for all four samples garnet and clinopyroxene inclusions in the diamonds from two samples u 65 3 and u 66 3 have lower mg s lower mg and higher fe contents and lower lree than those in the host eclogite we interpret such variations as due to metasomatism of the host eclogite after diamond formation one sample u 41 3 shows enrichment in diamond inclusion mree enrichment relative to the eclogite host and may indicate a metasomatic event prior to or during diamond formation bulanova 2 found striking differences between inclusions taken from within different portions of the very same diamond clinopyroxene inclusions taken from the central early portions of yakutian diamonds were lower in mg and mg contents by up to 25 than those later inclusions at the rims of diamonds these trends are parallel to those between diamond inclusions and host eclogites determined for four of the five samples from the present study and may merely represent changing magmatic and or p t conditions in the mantle garnet trace element compositions are similar in relative proportions but variable in abundances between diamond inclusions and host eclogites this is probably due to the rapid diffusion of trace elements in garnet under mantle temperatures and consequent alteration of the garnet and not due to juvenile diamonds locking in source heterogeneities c f 3 trace element compositions of clinopyroxenes included in diamonds are generally similar to those in the host eclogite however one host clinopyroxene does show enrichment in the lree compared to that in the inclusion and may be attributed to mantle metasomatism not related to kimberlite transport in another eclogite m 46 the host clinopyroxene is depleted in the lree and fe and enriched in the hree and mg relative to the inclusion and is consistent with partial melting of the eclogite subsequent to diamond formation smnd ratios in clinopyroxenes appear to be little affected by these processes for most samples allowing sm nd isotopic studies to yield important information about ancient protoliths eclogitic mineral inclusions in yakutian diamonds appear consanguineous with the diamonds a contention supported by the observations of bulanova 2 therefore re os whole rock and smnd clinopyroxene age determinations of the udachnaya eclogites also yield the time of diamond formation approximately 2 9 ga 32 33

apatite u th he thermochronometry using a radiation damage accumulation and annealing model helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal a quantity that varies over the lifetime of the apatite using recently published laboratory data we develop and investigate a new kinetic model the radiation damage accumulation and annealing model rdaam that adopts the effective fission track density as a proxy for accumulated radiation damage this proxy incorporates creation of crystal damage proportional to production from u and th decay and the elimination of that damage governed by the kinetics of fission track annealing the rdaam is a version of the helium trapping model hetm shuster d l flowers r m and farley k a 2006 the influence of natural radiation damage on helium diffusion kinetics in apatite earth planet sci lett 249 148 161 calibrated by helium diffusion data in natural and partially annealed apatites the chief limitation of the hetm now addressed by rdaam is its use of he concentration as the radiation damage proxy for circumstances in which radiation damage and he are not accumulated and lost proportionately from the crystal by incorporating the rdaam into the hefty computer program we explore its implications for apatite u th he thermochronometry we show how u th he dates predicted from the model are sensitive to both effective u concentration eu and details of the temperature history the rdaam predicts an effective he closure temperature of 62 c for a 28 ppm eu apatite of 60 m radius that experienced a 10 c ma monotonic cooling rate this is 8 c lower than the 70 c effective closure temperature predicted using commonly assumed durango diffusion kinetics use of the rdaam is most important for accurate interpretation of u th he data for apatite suites that experienced moderate to slow monotonic cooling 1 0 1 c ma prolonged residence in the helium partial retention zone or a duration at temperatures appropriate for radiation damage accumulation followed by reheating and partial helium loss under common circumstances the rdaam predicts u th he dates that are older sometimes much older than corresponding fission track dates nonlinear positive correlations between apatite u th he date and eu in apatites subjected to the same temperature history are a diagnostic signature of the rdaam for many but not all thermal histories observed date eu correlations in four different localities can be explained with the rdaam using geologically reasonable thermal histories consistent with independent fission track datasets the existence of date eu correlations not only supports a radiation damage based kinetic model but can significantly limit the range of acceptable time temperature paths that account for the data in contrast these datasets are inexplicable using the durango diffusion model the rdaam helps reconcile enigmatic data in which apatite u th he dates are older than expected using the durango model when compared with thermal histories based on apatite fission track data or other geological constraints it also has the potential to explain at least some cases in which u th he dates are actually older than the corresponding fission track dates

palaeorotation of the troodos microplate cyprus the troodos ophiolite represents one of the best preserved fragments of ocean floor crust that is exposed on land as the extrusive series of the ophiolite retains a stable magnetization that is directed westward the ocean crust is considered to have rotated anticlockwise through 90 since its formation in the late cretaceous1 to determine the timing of the rotation event over 3 000 orientated samples have been collected from the ophiolite and from its in situ turonian to recent sedimentary cover here we report that pelagic chalks immediately overlying the highest extrusive lava units of the ophiolite complex give reliable magnetic vector directions indicating that at least 60 of rotation occurred before the lower eocene and that rotation was completed by the end of the lower eocene rotation cannot have occurred within a single late miocene event as reported previously2 regional geological considerations support the rotation of only a small fragment of oceanic crust that was stranded adjacent to an active continental margin in this tectonic setting the oblique consumption of oceanic crust beneath troodos crust could provide the necessary driving force for tectonic rotation

pb diffusion in zircon abstract chemical diffusion of ti under anhydrous conditions at 1 atm and under fluid present elevated pressure 1 1 1 2 gpa conditions has been measured in natural zircon the source of diffusant for 1 atm experiments was a zro2 tio2 zircon mixture with experiments run in crimped pt capsules diffusion experiments done in the presence of h2o co2 fluid were run in a piston cylinder apparatus using a source of ground tio2 zrsio4 and sio2 with oxalic acid added to produce h2o co2 vapor and partially melt the solid source material yielding an assemblage of rutile zircon melt vapor nuclear reaction analysis nra with the resonant nuclear reaction 48ti p 49v was used to measure diffusion profiles for both sets of experiments the following arrhenius parameters were obtained for ti diffusion normal to cover the temperature range 1350 1550 c at 1 atm d ti 3 33 10 2 exp 754 56 kj mol 1 r t m 2 s 1 ti diffusivities were found to be similar for experiments run under fluid present conditions a fit to all of the data yields the arrhenius relation d 1 34 102 exp 741 46 kj mol 1 rt m2 s 1 these data suggest that zircon should be extremely retentive of ti chemical signatures indicating that the recently developed ti in zircon crystallization geothermometer watson e b harrison t m 2005 zircon thermometer reveals minimum melting conditions on earliest earth science 308 841 844 will be quite robust in preserving temperatures of zircon crystallization titanium diffuses somewhat faster in zircon than larger tetravalent cations u th and hf but considerably more slowly than pb the ree and oxygen hence ti crystallization temperatures may be retained under circumstances when radiometric ages or other types of geochemical information are lost

low water contents in diamond mineral inclusions proto genetic origin in a dry cratonic lithosphere the mantle is the major reservoir of earth s water hosted within nominally anhydrous minerals nams e g bell and rossman 1992 peslier et al 2010 peslier 2010 nestola and smyth 2015 in the form of hydrogen bonded to the silicate s structural oxygen from whence cometh this water is the water in these minerals representative of the earth s primitive upper mantle or did it come from melting events linked to crustal formation or to more recent metasomatic re fertilization events during diamond formation nams are encapsulated at hundreds of kilometers depth within the mantle thereby possibly shielding and preserving their pristine water contents from re equilibrating with fluids and melts percolating through the lithospheric mantle here we show that the nams included in diamonds from six locales on the siberian craton contain measurable and variable h 2o concentrations from 2 to 34 parts per million by weight ppmw in olivine 7 to 276 ppmw in clinopyroxene and 11 17 ppmw in garnets our results suggest that if the inclusions were in equilibrium with the diamond forming fluid the water fugacity would have been unrealistically low instead we consider the h 2o contents of the inclusions shielded by diamonds as pristine representatives of the residual mantle prior to encapsulation and indicative of a protogenetic origin for the inclusions hydrogen diffusion in the diamond does not appear to have modified these values significantly the h 2o contents of nams in mantle xenoliths may represent some later metasomatic event s and are not always representative of most of the continental lithospheric mantle results from the present study also support the conclusions of peslier et al 2010 and novella et al 2015 that the dry nature of the sclm of a craton may provide stabilization of its thickened continental roots

paleoenvironmental changes at the messinian pliocene boundary in the eastern mediterranean southern cyprus basins significance of the messinian lago mare abstract the study of the late messinian early pliocene sediments in south cyprus pissouri and polemi basins and the comparison with the offshore coeval deposits drilled in the odp leg 160 boreholes provide new data illustrating the environmental changes which occurred in the eastern mediterranean at the end of the salinity crisis the messinian pliocene transition is marked by a very rapid environmental change indicated by sharp variations in lithology sedimentology microfaunal assemblages and stable isotope composition the latest messinian interval is dominated by the lago mare oligo mesohaline environments the most striking feature in the pissouri basin is the intercalation between the uppermost gypsum bed and the base of the zanclean deposits of four main horizons of paleosols interbedded with carbonates and conglomerates paleosols indicate periods of subaerial exposure long enough to permit pedogenesis to develop conglomerates indicate intense erosion of the troodos massif and its sedimentary cover as a result of the water level drop tectonic activity and more humid climatic conditions thus several subaerial exposure phases occurred in the marginal areas like the pissouri basin whereas shallow oligohaline conditions persisted in the deeper parts of the basin as indicated at odp site 968 both in the pissouri basin and on the flank of the erathostenes seamount the late messinian paleosols are directly overlain by the lowermost pliocene sediments deposited in well oxygenated deep marine conditions this drastic change of water depth shows that the water level of the late messinian saline to brackish lakes dropped far below that of the world ocean at least more than several hundred meters both these base level fluctuations and the oligohaline conditions caused intensive erosion karstification of the upper gypsum beds as also reported from many other mediterranean regions moreover the study of the polemi sections shows that oligohaline conditions had already started during the deposition of the upper gypsum sub unit typical brackish and fresh water assemblages are present in the last two gypsum layers and intergypsum beds this indicates that freshwater dilution i e the lago mare conditions resulted from a progressive change of the hydrological budget which started during deposition of the upper evaporites and climaxed after the deposition of the uppermost gypsum layer classical lago mare facies during this time periods of increased evaporation over precipitation led to deposition of the uppermost gypsum layers this evolution is interpreted as being due both to the severance from the open ocean and to the increasing contribution of the runoff precipitation versus marine inputs in the hydrological budget of the mediterranean

quaternary uplift and sea level change at an active plate boundary cyprus a combination of northward underthrusting of the african plate and serpentinite diapirism resulted in progressive uplift of cyprus during the quaternary the uplift was associated with the development of succession of alluvial fans and marine terraces marine terraces in coastal southern cyprus are developed at 350 360 m 110 100 m 60 50 m 11 8 m and 2 3 m above present sea level the terraces display sequences of regressive deltaic carbonate and siliciclastic sub littoral to littoral and sub aerial type alluvial fans of the fanglomerate group crop out on the northern flanks of the troodos massif forming extensive dissected peneplaned terraces later uplift resulted in the formation of channel fans and river terraces proximal sheetflood conglomerates pass distally into channelized braid plain environments on the southern margin of the troodos massif the fanglomerate group comprises braided channelized and floodplain sequences which pass laterally into littoral facies provenence studies indicate that uplift and resulting erosion of cyprus was centred on the troodos massif mount olympus radiometric dates indicate that uplift was rapid in the early and mid pleistocene in the late pleistocene holocene eustatic sea level changes and anthropogenic effects dominated while the rate of uplift was reduced with local submergence of southern coastal areas

the mediterranean outflow splitting a comparison between theoretical models and canigo data abstract the mediterranean outflow in the atlantic is vertically subdivided into two main cores that are identified by temperature and salinity maxima hydrological data collected west of the strait of gibraltar and off the south and south west coasts of portugal in september 1997 have been used in two different models to shed some light on the mechanisms that cause a splitting of the mediterranean outflow these models are i a steady one dimensional streamtube model and ii a local time dependent model that includes cross stream variations the streamtube model applied at the northern respectively the southern part of the outflow appears capable of reproducing the observed density difference between the two cores the vertical separation however was underestimated the results from the local model suggest that a bump in the bottom topography may be a determining factor for the splitting tendency of the flow

development of concepts concerning the genesis and emplacement of tethyan ophiolites in the eastern mediterranean and oman regions this article uses evidence mainly from the eastern mediterranean and oman to help understand the origin and emplacement of ophiolites field studies in these regions emphasize the diversity of ophiolite related sedimentary and tectonic processes topics to be discussed here include the sedimentary covers of ophiolites their metamorphic soles related melanges and emplaced continental margin slope rise units modes of ophiolite emplacement will also be considered and tectonic reconstructions that have a direct bearing on the origin and emplacement of ophiolites the writer argues that there is compelling evidence that many ophiolites formed by spreading above intraoceanic subduction zones evidence from their intact sedimentary covers however indicates that such subduction was only incipient in most cases as directly associated volcanic arcs or back arc basins are rare metamorphic soles record fragments of oceanic lithosphere derived from settings ranging from open ocean to continental slope rise settings underlying melanges record the subduction of most of the ocean lithosphere formed at spreading ridges continental margin units beneath ophiolites demonstrate that these ophiolites were formed in ocean basins that were mainly initiated by continental rifting in the eastern mediterranean and oman regions ophiolite emplacement was commonly achieved by trench margin collision although strike slip transpression and large scale accretion along subducting margins played a role in some cases taking account of the mesozoic palaeotectonic setting of the eastern mediterranean region it is widely believed that ophiolites of two main ages mid jurassic and late cretaceous were formed in several small oceanic basins separated by rifted microcontinents the history of tethys in pre mesozoic time remains more open to question lastly giant subduction related ophiolites as in oman cyprus or the balkans may not be forming anywhere in the world ocean today but may instead relate to rare events in earth history when regional to global plate boundaries were drastically reorganised

tectonic setting origin and obduction of the oman ophiolite the semail ophiolite in the oman mountains is the world9s largest and best preserved thrust sheet of oceanic crust and upper mantle 10 000 km 2 550 km long 150 km wide it was emplaced onto the arabian continental margin during late cretaceous time the ophiolite originated 96 94 ma at a spreading center above a northeast dipping subduction zone associated with initiation of immature island arc tholeiitic lavas lasail arc at the highest levels of the ophiolite simultaneous underthrusting of triassic and jurassic mid oceanic ridge basalt and alkalic volcanic rocks beneath 12 km of upper mantle depleted harzburgites produced garnet clinopyroxene amphibolites formed at temperatures of 850 c dated as 95 93 ma subduction cannot have been initiated at a mid oceanic ridge otherwise the protolith of the amphibolites in the metamorphic sole would be the same age and composition as the ophiolite volcanic rocks above in the northern part of the oman mountains in the bani hamid area united arab emirates 870 m of granulite facies rocks enstatite spinel diopside quartzites garnet diopside wollastonite calc silicate marbles clinopyroxene bearing amphibolites were formed at temperatures similar to those of the garnet diopside amphibolites of the oman sole 800 850 c but at slightly higher pressures as much as 9 kbar they are interpreted as deeper level metamorphosed continental margin sedimentary rocks exhumed by out of sequence thrusting placing granulites over mantle sequence harzburgites during the later stages of obduction subduction of the arabian continental crust beneath the obducting semail ophiolite to 78 90 km depth has been proven by thermobarometry of the as sifah eclogites to 20 23 kbar in the eastern sector in the united arab emirates the subducted continental crust began to partially melt producing unusual biotite muscovite garnet tourmaline cordierite andalusite bearing granites that intrude the uppermost mantle sequence harzburgites and lowermost crustal sequence cumulate gabbros of the ophiolite we suggest that the entire leading northeast edge of the arabian plate was subducted beneath the ophiolite during the final stages of obduction leading to eclogitization of the crustal rocks higher temperatures and pressures in the united arab emirates sector possibly due to a thicker or double thickness ophiolite section led to blueschist amphibolite and granulite facies conditions in the metamorphic sole and crustal melting in the subophiolite basement produced leucocratic granites that intruded up as dikes through the obducted ophiolite a model for ophiolite obduction is presented which accounts for all the structural and metamorphic conditions reported from the oman mountains

evidence for upper cretaceous transform fault metamorphism in west cyprus abstract metamorphic rocks of low pressure medium temperature facies occur in west cyprus as blocks and slivers with mafic and ultramafic screens in high angle serpentinite filled fault zones a satisfactory explanation for the origin of the metamorphic rocks has previously remained a subject of controversy the evidence presented here based on a study of their bulk chemistry mineralogy and 40 ar 39 ar geochronology indicates they were produced by greenschist to amphibolite facies dynamothermal metamorphism of alkalic and tholeiitic mafic rocks and associated sediments at between 83 and 90 m y their field relations show similarities with present day oceanic fracture zones suggesting that metamorphism occurred within strike slip faults some of which were probably extensions of the arakapas transform we propose that hot crust generated at an oceanic spreading centre provided the heat for metamorphism when juxtaposed against older cooler rocks during ridge ridge transform movements in addition shear heating may have been facilitated by the strike slip faulting and contributed to the total heat available these interpretations are compatible with many aspects of the broader regional geology of cyprus provide new constraints on the early evolution of the troodos complex and form the basis of a model for transform fault metamorphism

sedimentology of two fan delta systems in the pliocene pleistocene of the mesaoria basin cyprus abstract two fan delta systems have been recognised in the pliocene pleistocene deposits of the mesaoria basin an asymmetrical half graben located on the northern side of the troodos ophiolite cyprus the older fan delta system the pliocene nicosia formation was deposited when the mesaoria basin was actively subsiding it comprises a number of small isolated fan deltas which built across a narrow

multi phased uplift of the southern margin of the central anatolian plateau turkey a record of tectonic and upper mantle processes abstract uplifted neogene marine sediments and quaternary fluvial terraces in the mut basin southern turkey reveal a detailed history of surface uplift along the southern margin of the central anatolian plateau from the late miocene to the present new surface exposure ages 10be 26al and 21ne of gravels capping fluvial strath terraces located between 28 and 135 m above the goksu river in the mut basin yield ages ranging from ca 25 to 130 ka corresponding to an average incision rate of 0 52 to 0 67 mm yr published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0 25 to 0 37 mm yr since late miocene time starting between 8 and 5 45 ma and 0 72 to 0 74 mm yr after 1 66 to 1 62 ma together with the terrace abandonment ages the data imply 0 6 to 0 7 mm yr uplift rates from 1 6 ma to the present the different post late miocene and post 1 6 ma uplift rates can imply increasing uplift rates through time or multi phased uplift with slow uplift or subsidence in between longitudinal profiles of rivers in the upper catchment of the mut and ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1 2 to 1 5 km elevation implying a transient response to a change in uplift rates projections of graded upper relict channel segments to the modern outlet together with constraints from uplifted marine sediments show that a slower incision uplift rate of 0 1 to 0 2 mm yr preceded the 0 7 mm yr uplift rate the river morphology and profile projections therefore reflect multi phased uplift of the plateau margin rather than steadily increasing uplift rates multi phased uplift can be explained by lithospheric slab break off and possibly also the arrival of the eratosthenes seamount at the collision zone south of cyprus

diamond growth from c h n o recycled fluids in the lithosphere evidence from ch 4 micro inclusions and δ 13 c δ 15 n n content in marange mixed habit diamonds abstract mixed habit octahedral cuboid diamonds from the marange alluvial deposits in the eastern zimbabwe craton have high nitrogen and hydrogen contents that provide an opportunity to evaluate diamond growth mechanisms and c n h o bearing fluids in the lithospheric keel light grey cuboid sectors with hydrogen containing defects trap abundant dispersed ch 4 inclusions raman peaks at 2917 cm 1 associated with graphite raman peaks at 1580 cm 1 clear octahedral sectors are richer in nitrogen and free of any such inclusions core to rim co variations of 13 c 15 n and n content can be explained by a mixing trend between earlier fluids that are ch 4 rich and later fluids that are more co 3 or co 2 rich marange diamonds have limited overall 13 c variation but do show fractionation during growth towards higher 13 c values this trend can be explained by diamond precipitation from mixed ch 4 and co 2 fluids where isotopic fractionation occurs as the amount of fluid wanes calculated 15 n values for diamond source fluids evolving in this manner are between 2 3 and 6 4 these n isotopic compositions require ch 4 rich and co 3 co 2 rich end member fluids to have a recycled metasedimentary component perhaps introduced with subduction of eclogite

plate convergence in the cyprean arc abstract the cyprean arc is a part of the plate boundary between afro arabia and eurasia in the eastern mediterranean a re examination of the geophysical properties of the cyprean arc together with an analysis of multichannel seismic reflection profiles now available in the cyprean arc area provides a clearer view of the tectonic setting and processes in this region seismic activity and a gravity anomaly indicate that a northward subduction of oceanic material related to the african plate beneath the turkish plate is the mode of convergence along the western segment of the cyprean arc subduction is interrupted due to the collision of the eratosthenes seamount at the central segment of the cyprean arc which forms a zone of intense deformation the zone of deformation spreads away and disappears in the eastern segment of the cyprean arc no signs for deformation have been found in this portion either in the multichannel seismic reflection profiles in the seismicity or in the bathymetry the change in the mode of convergence and in the type of deformation along the cyprean arc is induced by crustal differences in the underthrusting plate interruption of subduction activity in one segment of the arc also affects the geometry of nearby segments and the processes over there

uranium lead isotopic ages of plagiogranites from the troodos ophiolite cyprus and their tectonic significance zircon populations from two plagiogranites in the plutonic section of the troodos ophiolite yield u pb dates between 90 3 0 7 and 92 4 0 7 ma zircons from one of the two samples yield u pb dates of 90 3 0 7 and 92 1 0 7 ma this difference is greater than our analytical error and the zircons are therefore considered to be slightly discordant two fractions from another sample are internally and externally concordant and have an average date of 91 6 1 4 ma this date is adopted as the age of plagiogranite crystallization the plutonic section of the troodos ophiolite is complex in that several generations of intrusion can be identified the plagiogranites occur at the top of the intrusive section and represent fractionated residua of magma chambers related to the lower pillow lavas they are possibly slightly older than small ultramafic layered complexes that represent the final intrusive episode within the troodos ophiolite there is good agreement between our results and the ages of radiolaria which occur in umbers intercalated with the upper pillow lavas of troodos blome and irwin 1985 this shows that the 75 to 85 ma k ar dates on the lavas and sheeted dikes desmet et al 1978 delaloye and desmet 1979 delaloye et al 1980 staudigel et al 1986 represent age resetting unrelated to ophiolite formation the troodos u pb zircon ages are slightly lower than u pb zircon ages from the samail ophiolite in oman which vary between 93 5 and 97 9 ma and average 95 ma tilton et al 1981 the small difference in age between the troodos and the samail ophiolites and the geochemical similarities of basalts from both complexes to island arc volcanic rocks imply that a 3000 km axis of rift related island arcs formed between 91 and 98 ma emplacement of the ophiolites followed during the early maastrichtian

timing of uplift of the troodos massif cyprus constrained by sedimentary and magnetic polarity evidence abstract plio pleistocene sediments exposed around the ophiolitic troodos massif document spectacular uplift from below sea level to a maximum height of c 2000 m sedimentation reflects a dominant control of focused tectonic uplift modified by the effects of glacio eustatic sea level change and climatic change understanding the uplift and controls on deposition has been hindered by an inadequate age model here we present a preliminary investigation of the polarity of remanent magnetizations recorded within the upper part of the pliocene succession in the pissouri and mesaoria basins and from the pleistocene marine terrace deposits that border the troodos massif when integrated with available lithostatigraphic and biostratigraphic data the main results are as follows focused uplift of the troodos massif began during the late pliocene either between 2 14 and 1 95 ma or immediately prior to 1 77 ma shallow marine ophiolite derived clastic and bioclastic sediments accumulated in both the mesaoria and pissouri basins implying that the troodos massif was uplifted as a single tectonic entity non marine deltaic and fluvial facies prograded into both of the basins during the pleistocene 1 77 ma recent marine terraces in sw and south cyprus were cut and covered by littoral sediments from

gravity anomalies of the cyprus arc and their tectonic implications abstract continental crust forms from structurally thickened remnants of oceanic crust and overlying sediments which are then invaded by arc magmatism understanding this process is a first order problem of lithospheric dynamics the transition in young mountain belts from ocean crust through the agglomeration of arc systems with long histories of oceanic closures to a continental hinterland is well exemplified by the plate margin in the eastern mediterranean the boundary between the african plate and the aegean anatolian microplate is in the process of transition from subduction to collision along the cyprus arc in the west north of the oceanic herodotus basin subduction may be continuing in the east microcontinental blocks such as the eratosthenes seamount are already colliding with cyprus to the north of the suture the changes in crustal structure along and across this convergent zone are not known except by inference from bathymetry and from a couple of deep penetrating wide angle seismic transects on the african plate margin in this contribution we model four bouguer gravity profiles across the cyprus arc the profiles are similar in showing a gravity low over the plate boundary suture attributed to thick sediments with bouguer highs over oceanic or transitional crust to the south and over ophiolites and thinner sediments on thin continental crust to the north bouguer lows at the northern ends of the profiles are characteristic of elevated continental crust well sedimented oceanic or transitional crust on the african plate margin is replaced north of the suture by variably sedimented basement in which continental crustal thickness increases from 10 km to 30 km over the forearc region the models involve assumptions about characteristic densities and trade offs between sediment and crustal thicknesses but they do provide well defined targets for future wide angle seismic tests

glacial to interglacial changes in the settling depth of the mediterranean outflow plume we present micropalaeontological and grain size records for a set of sediment cores from the gulf of cadiz southwest spain that reflect changes in the position and strength of the mediterranean outflow mo current the cores sample a sediment drift the gil eanes drift that is positioned lower on the slope in the gulf of cadiz than the position of the main current today the data indicate that the drift is of glacial age and that the glacial mo current was positioned lower on the slope than today but also that it was active over a considerably reduced area of the slope we argue that this observation is consistent with physical constraints on the gibraltar exchange and on the likely settling and spreading behavior of the mo plume along the iberian margin under glacial environmental and sea level conditions the deeper settling of the mo is likely to have influenced the formation of glacial north atlantic intermediate water and also may have exerted indirect influence on the formation of glacial north atlantic deep water

evidence from the kyrenia range cyprus of the northerly active margin of the southern neotethys during late cretaceous early cenozoic time sedimentary geology and planktonic foraminiferal biostratigraphy have shed light on the geological development of the northern active continental margin of the southern neotethys in the kyrenia range following regional triassic rifting a carbonate platform developed during jurassic cretaceous time followed by its regional burial deformation and greenschist facies metamorphism the platform was exhumed by late maastrichtian time and unconformably overlain by locally derived carbonate breccias passing upwards into upper maastrichtian pelagic carbonates in places the pelagic carbonates are interbedded with sandstone turbidites derived from mixed continental basic volcanic neritic carbonate and pelagic lithologies in addition two contrasting volcanogenic sequences are exposed in the western central kyrenia range separated by a low angle tectonic contact the first is a thickening upward sequence of campanian lower maastrichtian pelagic carbonates silicic tuffs silicic lava debris flows and thick bedded to massive rhyolitic lava flows the second sequence comprises two intervals of basaltic extrusive rocks interbedded with pelagic carbonates the basaltic rocks unconformably overlie the metamorphosed carbonate platform whereas no base to the silicic volcanic rocks is exposed additional basaltic lavas are exposed throughout the kyrenia range where they are dated as late maastrichtian and late paleocene middle eocene in age in our proposed tectonic model related to northward subduction of the southern neotethys the kyrenia platform was thrust beneath a larger tauride microcontinental unit to the north and then was rapidly exhumed prior to late maastrichtian time pelagic carbonates and sandstone turbidites of mixed largely continental provenance then accumulated along a deeply submerged continental borderland during late maastrichtian time the silicic and basaltic volcanogenic rocks erupted in adjacent areas and were later tectonically juxtaposed the campanian early maastrichtian silicic volcanism reflects continental margin type arc magmatism in contrast the upper maastrichtian and paleocene middle eocene basaltic volcanic rocks erupted in an extensional or transtensional setting likely to relate to the anticlockwise rotation of the troodos microplate

evidence from gabbro of the troodos ophiolite for lateral magma transport along a slow spreading mid ocean ridge the lateral flow of magma and ductile deformation of the lower crust along oceanic spreading axes has been thought to play a significant role in suppressing both mid ocean ridge segmentation and variations in crustal thickness direct investigation of such flow patterns is hampered by the kilometres of water that cover the oceanic crust but such studies can be made on ophiolites fragments of oceanic crust accreted to a continent in the oman ophiolite small scale radial patterns of flow have been mapped along what is thought to be the relict of a fast spreading mid ocean ridge here we present evidence for broad scale along axis flow that has been frozen into the gabbro of the troodos ophiolite in cyprus thought to be representative of a slow spreading ridge axis the gabbro suite of troodos spans nearly 20 km of a segment of a fossil spreading axis near a ridge transform intersection we mapped the pattern of magma flow by analysing the rocks magnetic fabric at 20 sites widely distributed in the gabbro suite and by examining the petrographic fabric at 9 sites we infer an along axis magma flow for much of the gabbro suite which indicates that redistribution of melt occurred towards the segment edge in a large depth range of the oceanic crust our results support the magma plumbing structure that has been inferred indirectly from a seismic tomography experiment on the slow spreading mid atlantic ridge

solid molecular nitrogen δ n2 inclusions in juina diamonds exsolution at the base of the transition zone abstract diamonds originating from the transition zone or lower mantle were previously identified based on the chemistry of their silicate or oxide mineral inclusions here we present data for such a super deep origin based on the internal pressure of nitrogen in sub micrometer inclusions in diamonds from juina brazil infrared spectroscopy of four diamonds rich in such inclusions revealed high concentrations of fully aggregated nitrogen average of 900 ppm all in b centers and almost no platelets raman spectroscopy indicated the presence of solid cubic n 2 at 10 9 0 2 gpa corresponding to a density of 1900 kg m 3 transmission electron microscopy of two diamonds found two generations of octahedral inclusions microinclusions average size 150 nm average concentration 100 ppm and nanoinclusions 20 30 nm 350 ppm eels detected nitrogen and a diffraction pattern of one nanoinclusion yielded a tetragonal phase which resembles n 2 with a density of 1400 kg m 3 internal pressure 2 7 gpa we also observed up warping of small areas 150 nm in size on the polished surface of one diamond the 2 nm rise can be explained by a shallow subsurface microinclusion pressurized internally to more than 10 gpa using available equations of state for nitrogen and diamond we calculated the pressures and temperatures of mechanical equilibrium of the inclusions and their diamond host at the mantle geotherm the inclusions originated at the deepest part of the transition zone at pressures of 22 gpa 630 km and temperatures of 1640 c we suggest that both generations are the result of exsolution of nitrogen from b centers and that growth took a few million years in a subducting mantle current the microinclusions nucleated first followed by the nanoinclusions shortly after the exsolution events the diamonds were trapped in a plume or an ascending melt and were transported to the base of the lithosphere and later to the surface

trace elements in sulfide inclusions from yakutian diamonds sulfide inclusions in diamonds may provide the only pristine samples of mantle sulfides and they carry important information on the distribution and abundances of chalcophile elements in the deep lithosphere trace element abundances were measured by proton microprobe in 50 sulfide inclusions sdi from yakutian diamonds about half of these were measured in situ in polished plates of diamonds providing information on the spatial distribution of compositional variations many of the diamonds were identified as peridotitic or eclogitic from the nature of coexisting silicate or oxide inclusions known peridotitic diamonds contain sdis with ni contents of 22 36 consistent with equilibration between olivine monosulfide solid solution mss and sulfide melt whereas sdis in eclogitic diamonds contain 0 12 ni a group of diamonds without silicate or oxide inclusions has sdis with 11 18 ni and may be derived from pyroxenitic parageneses eclogitic sdis have lower ni cu and te than peridotitic sdis the ranges of the two parageneses overlap for se as and mo the mo and se contents range up to 700 and 300 ppm respectively the highest levels are found in peridotitic diamonds among the in situ sdis significant zn and pb levels are found in those connected by cracks to diamond surfaces and these elements reflect interaction with kimberlitic melt significant levels of ru 30 1300 ppm and rh 10 170 ppm are found in many peridotitic sdis sdis in one diamond with wustite and olivine inclusions and complex internal structures have high levels of other platinum group elements pges as well and high chondrite normalized ir pd comparison with experimental data on element partitioning between crystals of monosulfide solid solution mss and sulfide melts suggests that most of the inclusions in both parageneses were trapped as mss while some high cu sdis with high pd rh may represent fractionated sulfide melts spatial variations of sdi composition within single diamonds are consistent with growth histories shown by cathodoluminescence images in which several stages of growth and resorption have occurred within magmatic environments that evolved during diamond formation

kinematic history of a reactivated oceanic suture the mamonia complex suture zone sw cyprus the mamonia complex suture zone in sw cyprus marks an arcuate tectonic suture between an upper cretaceous oceanic microplate of supra subduction zone origin troodos complex and a deformed triassic passive margin sequence mamonia complex mapping of the serpentinite filled fault zones that define the suture zone combined with microstructural studies of its constituent fault rocks has revealed evidence of three main tectonic events of upper cretaceous age 1 high temperature c 600 c transform related dextral strike slip and localized metamorphism of mamonia complex units c 90 83 ma 2 retrograde hydration c 83 73 ma 3 regional contractional reactivation at low temperatures which ceased by the latest maastrichtian c 65 ma the present day structural geometries are interpreted as the result of maastrichtian contractional reactivation of a pre existing steep and irregular structural architecture that formed during transtension the resultant orientation of finite strain axes and thrust displacements display a radial distribution documenting near fault normal contraction along the whole length of the arcuate suture zone this pattern of displacements suggests a model whereby the troodos microplate impinged on the mamonia complex during westerly to southwesterly directed plate motion contractionally reactivating the mechanically weak suture zone

enrichment of h2o and fluid soluble trace elements in the troodos ophiolite evidence for a near trench origin abstract the troodos ophiolite on the island of cyprus is a cretaceous supra subduction zone ophiolite it formed by seafloor spreading in the vicinity of a subduction zone but the exact tectonic setting in which it formed is debated we determined h2o contents together with other volatiles s cl and co2 and sr nd and pb isotope compositions of fresh troodos volcanic glasses previously measured for major and trace element contents glass compositions range from boninite to tholeiitic andesite the least degassed glasses have h2o contents of 1 7 to 2 7 wt and h2o ce ratios of 4400 to 33 600 the most depleted glasses with low zr yb have the highest fractionation corrected h2o contents and h2o ce and the highest subduction zone input highest th la ba zr and 87sr 86sr the high h2o contents enrichment in fluid mobile elements and depletion in zr hf and heavy rare earth elements are consistent with formation above a subduction zone very close to a trench in a fore arc position likely at water depths of 5000 m the enrichment in both fluid mobile e g rb cs and melt soluble e g th elements indicate that the troodos ophiolite formed by propagation of a back arc rift into the fore arc region of an active subduction zone