sub sea floor boiling of red sea brines new indication from noble gas data hydrothermal brines from the atlantis ii deep red sea have been sampled in situ and analyzed for noble gases the atmospheric noble gas concentrations ne aratm kr xe in the deepest layer lcl are depleted by 20 to 30 relative to the initial concentrations in ambient red sea deep water without a systematic mass fractionation between the different noble gases sub surface boiling during the hydrothermal circulation and subsequent phase separation is shown to be a consistent explanation for the observed depletion pattern using a conceptual model of phase separation under sub critical conditions in which gases are partitioned according to henry s law we reconstruct the fluid history before injection into the atlantis ii deep after having circulated through evaporites and young oceanic crust where it becomes enriched in hemorb and armorb the ascending fluid boils and the residual liquid becomes depleted in noble gas concentrations the depleted fluid rises to the sediment surface and feeds the atlantis ii basin the relatively low boiling degree of about 3 i e the percentage of fluid removed as vapor derived from the model indicates that the atlantis ii system represents an early stage of boiling with relatively small gas loss in contrast to hydrothermal systems at sediment free mid ocean ridges

tertiary volcanism of the galatia province north west central anatolia turkey abstract large volumes of trachyandesitic dacitic lava flows and pyroclastics of miocene age are associated with small volumes of alkali basalt lava flows in the galatia volcanic province northwest central anatolia turkey the volcanism postdates continental collision occurring in a transtensional tectonic setting associated with movement along the north anatolian fault zone major and trace element including ree and sr nd isotope data and k ar ages for representative samples of mafic intermediate volcanic rocks have been obtained from a series of localities within the province the k ar age data indicate that alkali basalts were erupted during two distinct time periods in the early miocene 17 19 ma and late miocene

early miocene adakite like volcanism in the balkuyumcu region central anatolia turkey petrology and geochemistry the balkuyumcu region located in the southwestern part of ankara in the izmir ankara suture zone central anatolia turkey consists of basic andesitic andesitic dacitic and rhyolitic rocks extruded during the early miocene 20 22 ma as a result of post collisional volcanism balkuyumcu volcanic rocks can be divided into two groups on the basis of their mineralogy and composition the basic andesitic ba and andesitic dacitic and rhyolitic adr groups the adr and ba group of rocks have adakite like and calc alkaline characteristics respectively the adr group has higher sio2 content sr y and la yb ratios and low mgo mg y and yb contents than the ba group both groups have nearly the same sr nd isotopic compositions and display similar normalized multi element patterns with enrichments in lile and lree depletions in nb ti zr p and a lack of eu anomalies major trace element and sr nd isotopic data indicate that both groups of rocks were derived from the same source but affected by different magmatic processes during ascent the adakite like rocks may have been produced by partial melting of thickened lower continental crust fractional crystallization also played a major role in their formation however the ba group rocks were derived from partial melting of lower continental crust that was probably delaminated these rocks appear to have had limited interaction with mantle peridodite during ascent to the surface

alkaline series related to early middle miocene intra continental rifting in a collision zone an example from polatli central anatolia turkey abstract a large volcanic area 7600 km2 the galatean volcanic province gvp developed in northwest central anatolia during the miocene along the neo tethys ocean suture zone possibly by post collisional processes the gvp mainly comprises 20 14 my old acid to intermediate volcanites with a geochemical signature indicating a mantle source modified by earlier late cretaceous subduction related events 100 km south of the gvp near polatli ankara basaltic rocks that cover large areas are intercalated with the miocene deposits of the beypazari basin an intra continental subsidence zone at the southwest of the gvp field observations geochemistry and k ar age dating of the polatli volcanites show that they are early 19 9 ma to mid 14 1 ma miocene in age covering an area as large as 215 km2 variations in lava thickness and the thickness of the underlying silicified baked zones suggest that the basaltic lavas erupted from a southern source possibly from the eskisehir fault zone and flowed northwards most polatli samples have chemical compositions that indicate derivation from a mantle source with crustal contamination during ascent they do not display any characteristic to suggest a subductional component although the gvp and polatli lavas formed close in time and space they were derived from different mantle sources considering the positions of these two magmatic regions with regard to the tethyan suture zone we propose that the mantle beneath the gvp and near the suture zone memorised the earlier subduction while the mantle beneath polatli that is located about 100 km further from the suture zone remained apparently unchanged after a significant volume of magma was consumed in the gvp a later 10 my and last activity guvem activity has produced quantitatively much less basaltic rocks where this subductional signature seems to completely disappear considering that the western anatolian crust is proposed to undergo extension since the late oligocene early miocene times the early miocene intra plate polatli activity may have developed within this extensional tectonic regime combined with regional data polatli data also provide broad estimations on how long a subductional event continues to modify the mantle after the subduction ceased at least 20 my how long the subductional signature is preserved during significant magmatism between 6 and 10 my and how far the subductional effect disappears laterally on the mantle with respect to the collision zone

analysis of the north anatolian shear zone in central pontides northern turkey insight for geometries and kinematics of deformation structures in a transpressional zone abstract the western part of the north anatolian shear zone at the southern boundary of the central pontides in turkey was investigated in the kursunlu arac area by means of a geological structural field study in this area the north anatolian shear zone results in a transpressional deformation zone that extends between two master faults striking parallel to the main shear direction the main systems of structures identified in the deformation zone appear to be oriented parallel to the directions predicted by riedel theoretical model nevertheless the strain partitioning is more complicated than predicted by theory the structural analysis suggests a polyphase deformation characterized by a steady component of transcurrence associated with alternance of compression and extension along each of theoretical directions the combination of double verging structures can be observed with folds and thrust surfaces root into high angle shear zones according to flower type geometries the discrepancies of directions kinematics and geometries from theoretical models are due to transpressive and or transtensive nature of the deformation according to the observed outcropping structures we propose a conceptual model for the north anatolian shear zone interpreting it as a crustal scale positive flower structure

an example of an accretionary forearc basin from northern central anatolia and its implications for the history of subduction of neo tethys in turkey deformed sedimentary sequences of late cretaceous middle eocene age located between the sakarya continent and the anatolian complex have been interpreted as the fill of a forearc basin the history and structure of this basin are critical for understanding the evolution of the neo tethyan subduction in the middle east i test and elaborate upon this interpretation on the basis of three basic outcrop areas of upper cretaceous lower tertiary sedimentary sequences confined to a northeast southwest trending belt in north west ankara these are the alci kinik and orhaniye areas they expose two different sedimentary sequences called alci and orhaniye in the alci area the sequence starts at the base with the continental red clastic rocks on the erosional surface of an underlying ophiolitic melange and continues upward into the shallow marine reefal buildup of the late maastrichtian age the upper half of the alci sequence is separated from its lower half by a local disconformity and dominated by the continental debris flow deposits composed mostly of volcanic material by contrast both the kinik and orhaniye areas are characterized by a thick continuous and coarsening upward sequence overlying conformably the underlying ophiolitic melange the lower half of the orhaniye sequence is dominated by a deep marine flysch its middle part by continental clastic material and the topmost part by the shallow marine reefal buildup lower contact relationships lithologic composition facies distribution internal structures and the regional tectonic settings of both sequences strongly suggest that the above mentioned three outcrops preserve the remnants of a peripheral accretionary forearc basin forming the north northwestern margin of the haymana polath accretionary forearc basin during middle campanian middle eocene time this peripheral basin is here named orhaniye accretionary forearc basin

new stratification in the hydrothermal brine system of the atlantis ii deep red sea temperature and salinity records from the redsed cruise september 1992 reveal a new stratification in the hydrothermal brine system of the atlantis ii deep this stratification consists of the preexisting lower and upper convective layers lcl and ucl1 with temperatures of about 66 c and 55 c respectively and two additional upper convective layers ucl2 and ucl3 that formed more recently and have distinct temperature salinity and thickness in accordance with the physical process that leads to the formation of brine layers i e double diffusive convection a flow rate of about 200 l s has been estimated for the hydrothermal discharge

distributed neotectonic deformation in the anatolides of turkey a palaeomagnetic analysis abstract the palaeotectonic phase of deformation in anatolia accompanied closure of the tethyan ocean and was finally completed with sealing of the bitlis suture bordering the arabian shield at 12 ma arabia has since continued to indent the collage of terranes accreted to the eurasian margin by differential northward movement relative to africa along the dead sea fault zone and counterclockwise ccw rotation accompanying the opening of the red sea this neotectonic phase of deformation has accompanied uplift of the anatolian plateau and establishment of intracontinental transforms comprising the north and east anatolian fault zones deformation has included extrusion and rotation of blocks away from the arabian syntaxis by tectonic escape we produce an updated summary of palaeomagnetic results from this region to show that deformation has been distributed so that block rotations vary systematically across anatolia ranging from strongly ccw in the zone of high strain north of the arabian indenter to near zero in central anatolia and then progressively cw in western anatolia new palaeomagnetic results from the ankara igneous district are also reported and help to constrain the east to west change from ccw to cw rotation within central anatolia the transition of tectonic regimes from compression in the east to extension in the west involves the expulsion of blocks and their rotation along arcuate strike slip faults at an acute angle to the maximum compressive stress 1 between arabia and eurasia the comparable distribution of rotations in palaeotectonic and neotectonic units indicates that the bulk of the observed palaeomagnetic rotations have been concentrated within the last plio pleistocene phase of the neotectonic era as is found in the aegean domain to the west and has involved blocks of the order of 100 km in size the weak collage of accretionary terranes sandwiched between the arabian indenter and the eurasian margin now defined by the north anatolian fault zone has evidently taken up the bulk of the strain imparted by the continuing northward motion of arabia to expand the radius of the tauride arc and the perimeter of extruded crust bordering the limit of the extensional province in western turkey the distributed character of neotectonic deformation is illustrated by equivalent polar distributions both palaeotectonic and neotectonic palaeomagnetic poles show arcuate distributions with poles to best fitting small circles focussed close to the study area differences between the distributed neotectonic deformation resolved from palaeomagnetism and the contemporary gps record reflect the contrasting time periods being evaluated the palaeomagnetic record incorporates evolving and changing tectonic regimes whereas the gps signature has no long term validity within the weak anatolian collage hence the full spectrum of techniques for resolving neotectonic deformation is relevant to unravelling deformation in such regions

visual observations of the red sea hot brines the research vessel akademik kurchatov has investigated the red sea rift zone with the aid of a manned submersible pisces xi in the winter of 1979 80 as the value of such investigations is now well established1 2 our research involved a comprehensive programme of hydrophysical studies in deeps containing thermal brines of the sea axial rift atlantis ii discovery and valdivia see fig 1 measurements were made with standard hydrographic stations the aist temperature and salinity meter with specially selected temperature and electric conductivity scales on board a towed vehicle zvouk 4m and pisces xi the present data on water stratification in the atlantis ii chain and valdivia deeps have in general confirmed previously known data3 9 but have also revealed some new facts for example we have recorded an increase of temperature of the hot brine of up to 62 c in the southwestern basin of the atlantis ii deep since studies aboard the r v sonne in 1977 using data from this expedition hartmann9 gives a curve of temperature growth in the lower brine constructed from the data of different expeditions since 1965 a multilayer temperature structure of the upper brine and horizontal inhomogeneities have also been found8 10 steps in the upper brine of the atlantis ii deep were first described6 9 from the surveys of the r v valdivia 1971 72 and sonne 1977 our observations reveal stratification of the deep brine table 1 in temperature and electrical conductivity salinity and enable their rate of change of thickness to be estimated10

seismic velocity reduction and accelerated recovery due to earthquakes on the longmenshan fault various studies report on temporal changes of seismic velocities in the crust and attempt to relate the observations to changes of stress and material properties around faults although there are growing numbers of observations on coseismic velocity reductions generally there is a lack of detailed observations of the healing phases here we report on a pronounced coseismic reduction of velocities around two locked sections asperities of the longmenshan fault with a large slip during the 2008 mw 7 9 wenchuan earthquake and subsequent healing of the velocities the healing phase accelerated significantly at the southern asperity right after the nearby 2013 mw 6 6 lushan earthquake the results were obtained by joint inversions of travel time data at four different periods across the wenchuan and lushan earthquakes the rapid acceleration of healing in response to the lushan earthquake provides unique evidence for the high sensitivity of seismic velocities to stress changes we suggest that stress redistribution plays an important role in rebuilding fault strength after a fault ruptures the recovery of its strength may be accelerated by earthquakes that redistribute stress according to an analysis of temporal variation in crustal seismic velocity on the longmenshan fault in china

phase relations and adiabats in boiling seafloor geothermal systems abstract observations of large salinity variations and vent temperatures in the range of 380 400 c suggest that boiling or two phase separation may be occurring in some seafloor geothermal systems consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed system conditions salinity and temperature of boiling vents can be used to estimate the pressure temperature point in the subsurface at which liquid seawater first reached the two phase boundary data are reviewed to construct phase diagrams of coexisting brines and vapors in the two phase region at pressures corresponding to those of the seafloor geothermal systems a method is developed for calculating the enthalpy and entropy of the coexisting mixtures and results are used to construct adiabats from the seafloor to the p t two phase boundary results for seafloor vents discharging at 2300 m below sea level indicate that a 385 c vent is composed of a brine 7 nacl equivalent in equilibrium with a vapor 0 1 nacl brine constitutes 45 by weight of the mixture and the fluid first boiled at approximately 1 km below the seafloor at 415 c 330 bar a 400 c vent is primarily vapor 88 wt 0 044 nacl with a small amount of brine 26 nacl and first boiled at 2 9 km below the seafloor at 500 c 520 bar these results show that adiabatic decompression in the two phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor

timing of cenozoic extensional tectonics in west turkey the timing of the transition from compressional to extensional tectonics in the late cenozoic evolution of west turkey has been constrained by k ar geochronology from acidic volcanic rocks and tourmaline leucogranite dykes in the central and east margin respectively of the gordes basin dacites and rhyolites in the centre of the gordes neogene sedimentary basin cut both the basement ophiolites of the izmir ankara suture zone and the neogene sediments on the basin s eastern margin the leucogranites cut metamorphic basement along a major ne sw trending normal fault that controls the regional structure of the basin pebbles of these leucogranites occur in adjacent neogene turfites and conglomerates k ar dates on biotites from the central volcanic rocks vary from 18 4 0 8 ma to 16 3 0 5 ma early miocene whilst muscovite from a leucogranite on the eastern margin of the basin provides ages of 24 2 0 8 ma and 21 1 1 1 ma latest oligocene to early miocene geochronological data and field relationships demonstrate that the earlier compressional regime had been replaced by extensional tectonics by latest oligocene early miocene

geochemistry and tectonic setting of tertiary volcanism in the guvem area anatolia turkey abstract detailed field mapping in the guvem area in the galatia province of nw central anatolia turkey combined with k ar dating has established the existence of two discrete miocene volcanic phases separated by a major unconformity the magmas were erupted in a post collisional tectonic setting and it is possible that the younger phase could be geodynamically linked to the onset of transtensional tectonics along the north anatolian fault zone the early miocene phase 18 20 ma burdigalian is the most voluminous comprising of over 1500 m of potassium rich intermediate acid magmas in contrast the late miocene volcanic phase ca 10 ma tortonian comprises a single 70 m thick flow unit of alkali basalt the major and trace element and sr nd isotope compositions of the volcanics suggest that the late miocene basalts and the parental mafic magmas to the early miocene series were derived from different mantle sources despite showing some similarities to high k calc alkaline magma series from active continental margins the early miocene volcanics are clearly alkaline with higher abundances of high field strength elements zr nb ti y crustal contamination appears to have enhanced the effects of crystal fractionation in the petrogensis of this series and some of the most silica rich magmas may be crustal melts the mantle source of the most primitive mafic magmas is considered to have been an asthenospheric mantle wedge modified by crustally derived fluids rising from a late cretaceous early tertiary tethyan subduction zone dipping northwards beneath the galatia province the late miocene basalts whilst still alkaline have a sr nd isotope composition indicating partial melting of a more depleted mantle source component which most likely represents the average composition of the asthenosphere beneath the region

origin of fluids and the evolution of the atlantis ii deep hydrothermal system red sea strontium isotope study abstract atlantis ii is the largest and most mineralized of the deeps along the axis of the red sea spreading center its basaltic substratum is covered by recent layered metalliferous sediments which precipitated from an overlying brine pool the 87 sr 86 sr ratio and the strontium concentration of interstitial waters within these sediments range between 0 70708 and 0 70725 and between 43 and 53 ppm respectively they are close to what is found for the present day deep brine pool 0 707105 45 10 ppm the strontium concentration and the 87 sr 86 sr ratio of the atlantis ii deep brines can be derived from those of the interstitial waters of the surrounding miocene evaporite by hydrothermal interaction with oceanic basaltic rocks at a maximal water rock ratio of 2 3 this water rock ratio is similar to that calculated for oceanic hydrothermal systems on sediment free ridges interstitial waters show a linear trend on a plot of 87 sr 86 sr vs 1 sr the highest strontium concentration and the most radiogenic interstitial waters correspond to sediment samples enriched in iron and manganese oxide minerals these waters reflect the diagenetic release of strontium by oxide minerals that initially precipitated at the interface between the brine pool and more radiogenic seawater the solid fraction of the sediment has 87 sr 86 sr isotopic compositions intermediate to those of the brines and seawater the most radiogenic strontium values were observed in samples strongly enriched in marine microbiota the gradual isotopic evolution in the lowest part of the western basin sediments testifies to the gradual influence of the hydrothermal activity in the deep in the beginning of the atlantis ii deep sedimentary history the strontium isotopic composition of solid samples from younger metalliferous facies is fairly uniform and close to that of the present day brine this isotopic homogeneity indicates that the isotopic composition of mineralizing fluids did not change during the time of deposition of the metalliferous sediment

basalt magma genesis and fractionation in collision and extension related provinces a comparison between eastern central and western anatolia experimental studies of synthetic and natural basalt systems suggest that conditions of magma genesis and fractionation depend fundamentally on mantle temperatures and lithospheric stress fields in general compressional settings are more conducive to polybaric fractionation than extensional settings and in this regard the anatolian magmatic province offers a natural laboratory for comparing near coeval basalt eruptions as a function of regional tectonics compressional collision related regimes dominating in eastern anatolia and extensional tectonics characterizing a western province related to aegean sea opening projection of plio quaternary basalt normative compositions from the western anatolia extensional province waep the central anatolian ova province caop and eastern anatolia compressional province eacp are projected onto ol ne cpx and pl cpx ol planes in the simplified basalt system ne cpx ol qz each showing distinctive liquid lines of descent waep basalts are mostly constrained by low pressure 0 5 gpa cotectics while caop and eacp compositions conform to moderate and or high pressure 0 8 3 0 gpa cotectics overall a quasi linear shift from moderate and or high pressure to low pressure equilibria matches the westward transgression from compressional east anatolia to the extensional west anatolian aegean region comparison of their respective primary mantle equilibrated magmas simulated by normalizing their compositions to mgo 15 wt mg 15 with parameterized anhydrous and h2o undersaturated experimental melts suggests they segregated from spinel to garnet lherzolite mantle facies at pressures between c 2 and 3 gpa c 70 100 km depth under h2o undersaturated conditions interpolated potential temperatures tp and lithospheric stretching factors range as follows 1 eastern anatolian basalts associated with the arabian foreland show tp varying between 1250 and 1400 c except for the karacalidag alkali basalts south of the bitlis zagros fracture zone for which tp ranges up to 1450 c for values of 1 2 1 8 tp values for central anatolia e g sivas range between 1300 and 1375 c except for karapinar egrikuyu and hasandag which show 1150 c and values of 1 3 1 4 for western anatolian basalts tp range mostly between 1250 and 1330 c except for a single value for canakkale of 1400 c and kula sample showing tp 1200 c and values of 1 3 2 0 variation of these conditions is as great or greater than that between provinces although there are clearly significant constraints on the inferred polybaric to low pressure isobaric fractionation regimes covariation of total feo tio2 la yb ce sm zr y and zr nb reflects small but significant differences in bulk composition and ambient melt fraction while the covariance of ce sm and sm yb is consistent with the segregation of primitive melts at the spinel to garnet lherzolite transition

noble gases in vent water from the juan de fuca ridge abstract hydrothermal vent fluids collected with the dsrv alvin from the southern limb of the juan de fuca ridge are chemically unique having chloride concentrations 2 times ambient seawater the same fluids contain noble gases in relative abundances like 2 c air saturated seawater the expected recharge composition however the absolute noble gas abundances are depleted by 30 relative to seawater the combination of very high chloride and moderately depleted noble gases appears to require the formation of a cl rich gas free brine by phase separation this brine is mixed with recharge seawater at temperatures in excess of 340 c and therefore deep in the hydrothermal system

atlantis ii deep geothermal brine system chemical processes between hydrothermal brines and red sea deep water water samples and suspended matter taken in the atlantis ii deep area red sea during the expedition so 2 with rv sonne in november 1977 were investigated for chemical composition only slight changes have been found for most components since 1966 a strong decrease of the cu content from 100 500 g kg 1 according to brooks et al 1969 to values below 1 g kg 1 has however become evident comparison between theoretical concentrations in the intermediate brine layers resulting when using the lower or the upper homothermal layers respectively as end members of mixing processes with red sea deep water and the concentrations measured prove that precipitation and resolution processes have considerable influence on the concentrations found in solution components strongly involved in such processes are iron manganese copper oxygen sulfate and silica as could be shown from comparison of theoretical and measured concentration profiles along the water column investigations of the metals suspended in the brine confirm these processes compared to 1971 1972 the cu and zn values in suspension preferring the southwestern basin at that time are clearly reduced thus being in agreement with the recently lowered hydrothermal activity remarks on the hypothetical composition of the unknown hydrothermal brine discharging into the deepest basin are also included