seismic tomography of the north anatolian fault new insights into structural heterogeneity along a continental strike slip fault major funding was provided by the uk natural environment research council nerc under grant ne i028017 1 equipment was provided and supported by the nerc geophysical equipment facility seis uk this project is also supported by bogazici university scientific research projects bap under grant 6922 and turkish state planning organization dpt under the tam project number 2007k120610

instability of the axisymmetric monsoon flow and intraseasonal oscillation 1 a linear model of intermediate complexity based on quasi equilibrium theory is used in a zonally symmetric aquaplanet configuration to investigate the stability of the mean summer monsoon flow in the south asian region in the control case the mean state has one linearly unstable mode that corresponds in period and structure to the variability in the nonlinear model described by bellon and sobel 2008 and to the observed 30 to 60 d mode of intraseasonal variability this mode features propagation of the precipitation anomalies from the equator to the monsoon trough around 20 n both the period of this mode and its direction of propagation are determined by the direction and magnitude of the mean meridional baroclinic flow the wind induced surface heat fluxes associated with the surface westerlies in the northern tropics are an important contributor to the instability of the mode the mechanisms of propagation and reinitiation of convection are further described 1 meridional advection of vorticity by the mean flow is responsible for the creation of free tropospheric vorticity north of the convection center this vorticity in turn creates boundary layer convergence via coriolis acceleration and subsequent northward movement of the convection 2 meridional advection of zonal momentum creates equatorial free tropospheric easterlies on the equator these easterlies in turn generate low level convergence via the term of the coriolis acceleration and cause the reemergence of convection at the equator

exhumation of eclogites insights from depth time path analysis abstract literature data on geochronology and pressure temperature estimates have been used to assess the depth time paths for high pressure units in the alps and the variscan belt these depth time paths consistently show that exhumation rates decrease through time the first stages of the exhumation are rapid 1 mm yr 1 and last less than a few million to a few tens of million years in contrast the final 10 20 km ascent to the surface is at least one order of magnitude slower for the deepest and most important part of the exhumation trajectory the chronology of the retrogressive metamorphism excludes gravitational collapse as the major driving force material balance and structural arguments also exclude isostatically assisted erosion processes prism dynamics and tectonically assisted erosion are the most likely mechanisms accounting for the kinetics of exhumation isostasy assisted erosion and shallow level extension are nevertheless required to eventually bring the high pressure rocks to exposure

influence of oxygen fugacity on mineral compositions in peralkaline melts the katzenbuckel volcano southwest germany the igneous rocks of the katzenbuckel southwest germany represent a unique and unusual alkaline to peralkaline association within the european volcanic province the magmatic activity can be subdivided into two main phases phase i comprises the main rock bodies of phonolite and nepheline syenite which were later intruded by different peralkaline dyke rocks tinguaites and alkali feldspar syenite dykes of phase ii the dyke assemblage was accompanied by magnetite and apatite veins and was followed by a late stage pneumatolytic activity causing autometasomatic alterations as is typical for alkaline to peralkaline igneous rocks early mafic minerals of phase i rocks comprise olivine augite and fe ti oxides which are substituted in the course of fractionation by na amphibole and na pyroxene for the early magmatic stage calculated temperatures range between 880 and 780 8c with low silica activities 0 4 to 0 6 but high relative oxygen fugacities between 0 5 and 1 9 log units above the fmq buffer even higher oxygen fugacities above the hm buffer are indicated for the autometasomatic alteration which occurred at temperatures between 585 and 780 8c and resulted in the formation of pseudobrookite and hematite the unusually high oxygen fugacities even during the early magmatic stage are recorded by the major element compositions of the mafic minerals forsterite content in olivine between 68 and 78 mol up to 6 2 wt zro2 and 8 5 wt tio2 in clinopyroxene the unusual mineral assemblages pseudobrookite freudenbergite and by the enrichment of fe 3 in the felsic

climatology of tropical intraseasonal convective anomalies 1979 2002 tropical intraseasonal convective anomalies tica have a central role in subseasonal changes in the coupled ocean atmosphere system but the climatology of tica events has not been properly documented this study exploits 24 years of outgoing longwave radiation olr data and a tracking algorithm to develop a climatology of eastward propagating tica events three distinct types of tica occurrences are documented according to their propagation characteristics the first type ind is characterized by events that propagate in the indian ocean without significant influence in the western pacific ocean the second and third types are associated with occurrences of the madden julian oscillation during boreal winters mjo and summers iso the frequency of occurrence of tica events is highest in april june and october december and lowest in july september an analysis of the spatial and temporal characteristics reveals that mjo events tend to have the longest life cycle greatest intensity and largest variability inside the contiguous region of olr anomaly given the data record of 24 years the analysis of interannual occurrences of tica events does not show statistically significant

the mineralogical diversity of alkaline igneous rocks critical factors for the transition from miaskitic to agpaitic phase assemblages geochemically the large family of alkaline plutonic rocks both qtz undersaturated and oversaturated compositions can be subdivided into metaluminous na 2 o k 2 o al 2 o 3 types in this paper we discuss two important aspects of the mineralogical evolution of such rocks with respect to their fe mg phases a major mineralogical transition observed is the precipitation of arfvedsonite or aegirine instead of fayalite or magnetite ilmenite the relative stability of these phases is controlled by oxygen fugacity and na activity in the crystallizing melts if na activity in the melt is high enough arfvedsonite aegirine form a common assemblage in peralkaline rocks under both reduced and oxidized conditions major mineralogical differences within this rock group exist with respect to their high field strength element hfse rich minerals most syenitic rocks known as miaskites contain zircon titanite or ilmenite as hfse rich minerals whereas in agpaites complex na k ca ti zr silicates incorporate the hfse similarly only a small group of peralkaline granites are found to lack zircon titanite or ilmenite but instead contain na k ca ti zr silicates here we present a detailed phase petrological analysis of the chemical parameters na 2 o cao k 2 o that influence the transition from miaskitic to agpaitic rocks based on the occurrence of ti and zr minerals several transitional mineral assemblages are identified and two major evolution trends for agpaites are distinguished a high ca trend which is exemplified by the alkaline rocks of the kola province russia and a ca depletion trend which is displayed by the alkaline rocks of the gardar province south greenland both trends show significant na enrichment during magmatic evolution high ca agpaites evolve from nephelinitic parental melts that did not crystallize large amounts of plagioclase in contrast agpaites showing ca depletion originate by extensive fractionation of plagioclase from basaltic parental melts in some peralkaline granites evolutionary trends are observed that culminate in agpaite like hfse mineral associations in the most evolved rocks

the variation of heat generation density and seismic velocity with rock type in the continental lithosphere abstract the petrophysical properties radioactive heat generation compressional wave velocity and density are related to rock type in crystalline rocks the cation fraction in the rock forming minerals is applied to determine the relationships quantitatively heat generation exhibits considerable variation with rock type as well as with the geologic age of the rocks therefore the relation between heat generation and rock type has been split into a relation for phanerozoic rocks and another for precambrian rocks which exhibit significantly lower heat generation only 1 3 of that of phanerozoic rocks the interrelations between the petrophysical properties are applied to fennoscandia precambrian terrane and southern bavaria northern alpine foreland phanerozoic rocks to estimate the heat generation by radioactivity in the crust and the heat flow density from the upper mantle

very fast exhumation of high pressure metamorphic rocks with excess 40ar and inherited 87sr betic cordilleras southern spain in order to attempt to further constrain the age of the early alpine tectonic evolution of the mulhacen complex and to explore the influence of inherited isotopes micas from a small number of well characterised rocks from the sierra de los filabres with a penetrative tectonic fabric related to the exhumation of eclogite facies metamorphic rocks were selected for 40 ar 39 ar and rb sr dating a single phengite grain from an amphibolite yielded an 40 ar 39 ar laser step heating plateau age of 86 9f1 2 ma 2r 70 39 ar released and an inverse isochron age of 86 2f2 4 ma with an 36 ar 40 ar intercept within error of the atmospheric value induction furnace step heating of a biotite separate from a gabbro relic in an eclogite yielded a weighted mean age of 173 2f6 3 ma 2r 95 39 ar released these ages are diagnostic of excess argon 40 arxs incorporation as they are older than independent age estimates for the timing of eclogite facies metamorphism and intrusion of the gabbros 40 arxs incorporation probably resulted from restricted fluid mobility in the magmatic rocks during their metamorphic recrystallisation rb sr whole rock phengite ages of graphite bearing mica schists from paleozoic rocks secano unit show a dramatic variation 66 1f3 2 40 6f2 6 and 14 1f2 2 ma an albite chlorite mica schist from the mesozoic series of the nevado lubro n unit has a whole rock mica albite age of 17 2f1 9 ma which is within error of an 40 ar 39 ar plateau age published previously and of the youngest rb sr age of the paleozoic series obtained in this study the significant spread in rb sr ages implies that progressive partial resetting of an older isotopic system has occurred the microstructure of the samples with pre miocene rb sr ages reveals incomplete recrystallisation of white mica and inhibited grain growth due to the presence of graphite particles this interpretation agrees with previously published disturbed and slightly dome shaped 40 ar 39 ar age spectra that may point similarly to the presence of an older isotope component the progressively reset rb sr system is a relic of variscan metamorphism of the paleozoic series of the mulhacen complex in contrast the origin of the ca 17 2 ma old sample from the mesozoic series precludes any isotopic inheritance in agreement with its pervasive tectono metamorphic recrystallisation during the miocene exhumation of the eclogite facies mulhacen complex occurred in two stages with contrasting rates of about 22 5 mm year during the early phase and 9 10 mm year during the late phase the latter with a cooling rate in the order of 330 jc ma d 2003 elsevier b v all rights reserved

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

role of the boundary layer moisture asymmetry in causing the eastward propagation of the madden julian oscillation the moisture budget associated with the eastward propagating madden julian oscillation mjo was diagnosed using 1979 2001 40 yr ecmwf re analysis era 40 data a marked zonal asymmetry of the moisture relative to the mjo convection appears in the planetary boundary layer pbl below 700 hpa creatingapotentiallymoreunstablestratificationtotheeastofthemjoconvectionandfavoringtheeastward propagation of mjo the pbl integrated moisture budget diagnosis indicates that the vertical advection of moisture dominates the low level moistening ahead of the convection a further diagnosis indicates that the leading term in the vertical moisture advection is the advection of the background moisture by the mjo ascending flow associated with pbl convergence the cause of the zonally asymmetric pbl convergence is further examined it is found that heating induced free atmospheric wave dynamics account for 75 90 of the total pbl convergence while the warm sst anomaly induced by air sea interaction contributes 10 25 of the total pbl convergence the horizontal moisture advection also plays a role in contributing to the pbl moistening ahead of the mjo convection the leadingterm in the moistureadvectionis the advectionacross the backgroundmoisture gradient by the mjo flow in the western indian ocean maritime continent and western pacific the meridional moisture advection by the mjo northerly flow dominates while in the eastern indian ocean the zonal moisture advection is greater the contribution of the moisture advection by synoptic eddies is in generalsmall ithas a negativeeffect overthetropicalindianoceanand westernpacificandbecomespositive in the maritime continent region

high pressure phengite decomposition in the weissenstein eclogite munchberger gneiss massif germany the petrography mineral chemistry and petrogenesis of a sample from the weissenstein eclogite bavaria germany has been investigated the total mineral assemblage comprises garnet clinopyroxenei ii quartz amphibolei ii rutile phengite epidote allanite plagioclase biotite apatite pumpellyite titanite sphene zircon alkali feldspar and calcite textural observations combined with geothermobarometry fe mg distribution between clinopyroxene garnet and phengite garnet jadeite content of omphacite si content of phengite and an content of plagioclase provide indications of two different stages in the metamorphic evolution of the rock the main phengitequartz eclogite mineral equilibration occurred at minimum p 13 17kbar minimum t 620 50 c the retrograde symplectite stage clinopyroxeneii amphiboleii biotite plagioclase occurred at ptotal between 12 and 8 5 kbar

coupling between northward propagating intraseasonal oscillations and sea surface temperature in the indian ocean using a hybrid atmosphere ocean coupled model it is shown that during the boreal summer northwardpropagating intraseasonal oscillations npisos are strongly coupled to the underlying sea surface temperature sst in the indian ocean sector on the one hand the intraseasonal atmospheric convection changes the sst through solar radiation latent heat flux and mixed layer entrainment on the other the induced sst fluctuations feed back to affect the intraseasonal convection the preferential northward rather than southward propagation of boreal summer isos in the indian ocean is partially explained by an interaction among the summer mean climate state the atmospheric disturbances and the ocean surface temperature a solution to an atmosphere only model forced with daily sst produces much stronger npisos than a similar solution forced with monthly mean sst amip type run the atmosphere only model however even when it is forced by daily sst from the coupled model with a small amount of noise in the initial and or boundary conditions is unable to reproduce the npisos in the coupled case in the coupled system intraseasonal sst anomalies are forced by intraseasonal atmospheric convection and hence are in quadrature with the convection in the stand alone atmospheric model however sst acts only as a boundary forcing and the resultant atmospheric convection has almost the same phase with the underlying sst one consequence is that the intensity of the sst forced intraseasonal convection in the stand alone atmospheric model is considerably weaker than in the coupled model finally solutions indicate that the northward movement of the off equatorial convection in the northern indian ocean is more closely related to local intraseasonal sst anomalies than to the equatorial eastward moving madden julian oscillation positive negative sst anomalies in the northern indian ocean lead the active break phases of the intraseasonal convection by about 2 pentads 10 days therefore intraseasonal sst anomalies in the northern indian ocean are potentially a useful index to forecast active break spells of the south asian summer monsoon

high pressure melting of eclogite and the p t x history of tonalitic to trondhjemitic zoisite pegmatites munchberg massif germany summary the zoisite pegmatites provide an excellent example of theonset of metabasite melting at eclogite facies conditions such conditions can be expected in a down going oceanicslab as well as in collision zones the newly produced meltin a metabasaltic rock of morb composition is tonalitic to trondhjemitic and shares some characteristics withthe ttg series or with adakites the amount of melt forming at a temperature of less than 7508c however is small as a result of the combined effect of relatively lowtemperature and restricted availability of water and themelt does not separate from the rock unit only if themelt fraction increases will the melt segregate and mightmigrate upwards influencing melting in the overlyingmantle wedge because of the poor outcrop situation ofthe mu nchberg area in the variscan chain of centraleurope it is unfortunately impossible to give an estimateof the amount of melt produced this will be a crucialquestion to solve at what degree of melting at whattemperature in a given composition andat what geological mechanical conditions the melt will effectively separate our data suggest the following model high pressurepartial melting and pegmatite formation occurred at con ditions only slightly above the water saturated solidus andcan be a fluid conserving or fluid recycling process any fluid released from hydrous minerals such as zoisite epidote or amphibole is trapped in small fractions offully to nearly water saturated siliceous melt for truedehydration melting a free fluid phase never exists neither the fluid nor the siliceous melt will separate andmigrate into the overlying rock units during uplift cool ing and crystallization the water which is stored in thesiliceous melt is again liberated and encounters a dehy drated eclogite facies assemblage here it hydrates theeclogite facies assemblage leading to crystallization ofhydrous minerals such as amphibole or mica this modelof fluid conservation or fluid recycling implies also thatthe trace element budget of the whole rock does notchange during melting and subsequent crystallization the pegmatites from the hangendserie of the mu nchbergarea still preserve some trace element signatures of theirindividual protoliths which means that the partial meltsdid not mix andwere not homogenized element transportoccurs onlyona restricted scale of probably much lessthanthe present thickness of the hangendserie the coarse grain size of the pegmatitic rocks is how ever a good condition to preserve textural disequilibriumand to record different stages of the uplift and coolinghistory reheating is indicated in the pegmatites by partialresorption of zoisite and crystallization of a second andthird generation with distinctly different composition this observation is in line with the idea that upliftoccurred during the collision event and shortly afteror simultaneously with stacking of the nappes that is in a short time frame which is in many cases close to thetime resolution of available geochronometric methods

mechanisms of northward propagating intraseasonal oscillation a comparison between the indian ocean and the western north pacific abstract mechanisms of northward propagating intraseasonal oscillations isos over the indian ocean io and the western north pacific wnp are examined for the possibility of their existence in observations they include the following 1 the vorticity advection effect which is associated with the advection of anomalous baroclinic vorticity by mean baroclinic meridional winds 2 the vertical wind shear effect which is the vertical advection associated with the meridional gradient of baroclinic divergence and mean easterly vertical wind shear 3 the moisture advection effect induced by mean flow and 4 the air sea interaction via surface latent heat flux because of differences in mean state the influence of each mechanism on the northward propagating isos is different between the io and the wnp the vorticity advection effect is consistently found over both the io and the wnp while the air sea interaction has different impacts on the northward propagating isos over the io and the wnp the vertic

improved modelling of the quaternary evolution of the gulf of corinth incorporating erosion and sedimentation coupled by lower crustal flow abstract numerical modelling incorporating coupling between surface processes and induced flow in the lower continental crust is used to address the quaternary evolution of the gulf of corinth region in central greece the post early pleistocene marine depocentre beneath this gulf overlies the northern margin of an older early pleistocene and earlier lacustrine basin the proto gulf of corinth basin or pgcb in the late early pleistocene relief in this region was minimal but subsequently dramatic relief has developed involving the creation of 900 m of bathymetry within the gulf and the uplift by many hundreds of metres of the part of the pgcb south of the modern gulf which forms the gulf s main sediment supply it is assumed that as a result of climate change around 0 9 ma erosion of this sediment source region and re deposition of this material within the gulf began both processes occurring at spatial average rates of 0 2 mm a 1 modelling of the resulting isostatic response indicates that the local effective viscosity of the lower crust is 4 10 19 pa s indicating a moho temperature of 560 c it predicts that the 10 mm a 1 of extension across this 70 km wide model region at an extensional strain rate of 0 15 ma 1 is partitioned with 3 mm a 1 across the sediment source 2 mm a 1 across the depocentre and 5 mm a 1 across the hinge zone in between the latter value being an estimate of the extension rate on normal faults forming the major topographic escarpment at the southern margin of the gulf this modelling confirms the view suggested previously that coupling between this depocentre and sediment source by lower crustal flow can explain the dramatic development in local relief since the late early pleistocene the effective viscosity of the lower crust in this region is not particularly low the strong coupling interpreted between the sediment source and depocentre results instead from their close proximity in detail the effective viscosity of the lower crust is expected to decrease northward across this model region due to the northward increase in exposure of the base of the continental lithosphere to the asthenosphere in the south the two are separated by the subducting hellenic slab the isostatic consequences of such a lateral variation in viscosity provide a natural explanation for why since 0 9 ma the modern gulf has developed asymmetrically over the northern part of the pgcb leaving the rest of the pgcb to act as its sediment source

seasonality of the structure and propagation characteristics of the mjo the seasonality of the madden julian oscillation mjo is documented in observational data and a nonlinear shallow water model is used to help interpret some of the contrasts in mjo structure between the boreal winter season november march ndjfm and the asian summer monsoon period june september jjas at upper tropospheric levels the flanking rossby waves remain centered around 28 degrees n s year round but they tend to be stronger in the winter hemisphere where the climatological mean jet stream is stronger rendering the subtropical circulation more sensitive to forcing by a near equatorial heat source amplitudes of the mjo related deep convection and lower tropospheric zonal wind are stronger in the summer hemisphere where the column integrated water vapor is larger during ndjfm the equatorial asymmetry is subtle as in the annual mean moisture convergence into swallowtail shaped regions of enhanced deep convection is an integral part of the equatorial rossby wave signature and the eastward propagation is due to moistening of the air to the east of the enhanced convection by poleward moisture advection during the asian summer monsoon in jjas the convection assumes the form of northward propagating west northwest east southeast oriented rainbands embedded within cyclonic shear lines these features are maintained by frictional convergence of moisture and their northward propagation is mainly due to the presence of features in the climatological mean fields that is the west east moisture gradient over india and the arabian sea and the southwesterly low level monsoon flow over the northwest pacific

the 10 20 day mode of the 1979 indian monsoon its relation with the time variation of monsoon rainfall abstract the synoptic structure of the 10 20 day monsoon mode and this intraseasonal monsoon mode s relationship with the indian monsoon rainfall are examined with the 1979 summer first garp global experiment iiib data of the european centre for medium range weather forecasts and the daily 1 1 rainfall estimates retrieved from the satellite data by the goddard laboratory for atmospheres the major findings of this study are as follows 1 the 10 20 day monsoon mode exhibits a double cell either double high or double low structure one cell is centered at about 15 20 n and the other at the equator 2 both cells of the 10 20 day monsoon mode propagate coherently westward along the indian monsoon trough and along the equator respectively 3 based upon the zonal wind and local hadley circulation the vertical structure of the 10 20 day monsoon mode does not exhibit a phase change 4 a significant rainfall occurs around low centers of the 10 20 day monsoon mode through the modulation of this monsoon

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

ductile deformation and 40ar 39ar dating of the changle nanao ductile shear zone southeastern china abstract an investigation of ductile deformation mylonitization and 40ar 39ar geochronology in the changle nanao ductile shear zone southeastern china is reported in this paper at least two phases of ductile deformation occurred in the shear zone in the mesozoic the first is a ne trending foliation widely developed in metasedimentary rocks and orthogneisses and is associated with metamorphism of amphibolite facies at 165 178 ma the second is a strike slip related ductile deformation developed both in the metamorphic rocks and the mesozoic volcanics and includes folds shear foliation or cleavage s c fabrics ne striking stretching lineation and mylonitic microstructures the ductile deformation and dislocation microstructures of quartz and the brittle deformation microstructures of plagioclase in the mylonites from the shear zone indicate that the second phase of ductile deformation and mylonitization occurred under greenschist facies conditions at temperatures of 300 350 c 40ar 39ar plateau ages of five minerals from deformed and mylonitized rocks in the shear zone are in the range of 118 107 ma the plateau ages record the time of ductile deformation and mylonitization associated with strike slip movement along the changle nanao ductile shear zone

partially retrograded eclogites of the munchberg massif germany records of a multi stage variscan uplift history in the bohemian massif eclogites with a wide range in bulk composition are present in the munchberg massif part of the variscan basement of the bohemian massif in north east bavaria new analyses of the primary phases garnet omphacite phengite and amphibole as well as the secondary phases clinopyroxene ii various amphiboles biotite phlogopite plagioclase margarite paragonite prehnite and pumpellyite reveal a complex uplift history new discoveries were made of samples with very jadeite rich primary omphacite as well as a secondary omphacite in a symplectite with albite various geothermobarometric techniques together with thermodynamic databases incorporating separately determined activity composition values and experimental data have clustered the minimum conditions for the primary assemblages to the p t range 650 60 c 14 3 1 kbar however jadeite in omphacite kyanite paragonite in phengite and zoisite grossular in garnet kyanite quartz relationships suggests pressures of 25 28 kbar at the same temperatures the fact that the secondary omphacite plagioclase assemblage yields pressures within a few hundred bars of the minimum pressures for the plagioclase free assemblages strongly suggests that the minimum values are serious underestimates zoning inclusion suites and breakdown reactions of primary phases in addition to new minerals formed during uplift define a polyphase metamorphic evolution which from geochronological evidence occurred solely within the variscan cycle the complex breakdown in other bohemian massif eclogites and the distinct variation in their temperatures during uplift suggest a multi stage thrusting model for the regional evolution of the eclogites such an evolution has significance with respect to incorporation of mantle slices into crustal sequences and fluid derivation from successively subducted units possibly driving the breakdown reactions

an idealized semi empirical framework for modeling the madden julian oscillation abstractthe authors present a simple semi empirical model to explore the hypothesis that the madden julian oscillation can be represented as a moisture mode destabilized by surface flux and cloud radiative feedbacks the model is one dimensional in longitude the vertical and meridional structure is entirely implicit the only prognostic variable is column water vapor w the zonal wind field is an instantaneous diagnostic function of the precipitation field the linearized version of the model has only westward propagating relative to the mean flow unstable modes because wind induced surface latent heat flux anomalies occur to the west of precipitation anomalies the maximum growth rate occurs at the wavelength at which the correlation between precipitation and surface latent heat flux is maximized this wavelength lies in the synoptic to planetary scale range and is proportional to the horizontal scale associated with the assumed diagnostic wind response to precipitation anomalies the nonlinear version

p t evolution and fluid inclusion characteristics of retrograded eclogites munchberg gneiss complex germany kyanite eclogites occur as part of the munchberger nappe pile in ne bavaria west germany eclogites are overprinted by subsequent amphibolite facies metamorphism the preservation of primary eclogitic textures as well as symplectitic textures are indicative of rapid decompression eclogite formation is estimated to have occurred under conditions of high h2o activities at pressures between 20 and 26 kbar and temperatures ranging between 590 and 660 c as is shown by the coexistence of omphacite jd 50 kyanite zoisite and quartz minimum pressure estimates independent of the water activity range between 9 and 16 kbar at the relevant temperatures detailed studies of fluid inclusion reveal two predominant groups of aqueous brine inclusions high salinity 14 17 wt nacl equiv and low salinity 0 8 wt nacl equiv inclusions fluid compositions of both groups of inclusions yield isochores passing close to the estimated amphibolite facies pt field the compositions of these fluids are in good agreement with fluid compositions considered from mineral equilibria none of the fluid inclusions has densities appropriate for eclogite facies metamorphism but probably reflect later amphibolite facies metamorphism

a unified moisture mode framework for seasonality of the madden julian oscillation abstractthe madden julian oscillation mjo exhibits pronounced seasonality while it is largely characterized by equatorially eastward propagation during the boreal winter mjo convection undergoes marked poleward movement over the asian monsoon region during summer producing a significant modulation of monsoon rainfall in classical mjo theories that seek to interpret the distinct seasonality in mjo propagation features the role of equatorial wave dynamics has been emphasized for its eastward propagation whereas coupling between mjo convection and the mean monsoon flow is considered essential for its northward propagation in this study a unified physical framework based on the moisture mode theory is offered to explain the seasonality in mjo propagation moistening and drying caused by horizontal advection of the lower tropospheric mean moisture by mjo winds which was recently found to be critical for the eastward propagation of the winter mjo is also shown to play a dominant role in operating t

regional distribution of white k mica polymorphs and their phengite content in the central alps some 150 white k micas from the central alps were analysed for their polymorph and phengite content

relationships between the petrophysical properties density seismic velocity heat generation and mineralogical constitution the petrophysical properties density p compressional wave velocity v p and heat generation a exhibit considerable variation with rock type to characterize a given rock quantitatively a single parameter the cation fraction expressed by the k value has been found to be suited best 100 crystalline rocks have been sampled to cover the widest possible range in k value from silicic types like granophyres and granites through granodiorites tonalites diorites gabbros amphibolites hornblendites pyroxenites to ultrabasic rocks p k a and v p were determined experimentally the latter at 0 5 kbar 50 mpa the interrelations between these properties were established by regression analysis the relation k and v p k show a linear dependence whereas a k a and a v p follow exponential laws in a w m 3 12 20 230 5 k mole cm 3 in a 22 5 8 15 g cm 3 and in a 16 5 2 74 v p km s all correlation coefficients are better than 0 9

the timescale and mechanism of granulite formation at kurunegala sri lanka incipient charnockite formation at kurunegala in sri lanka is characterized by the growth of orthopyroxene at the expense of amphibole and biotite in an originally homogeneous gneiss mineral equilibria in the charnockite assemblage record pressure temperature p t conditions of 738 60 c and 6 9 1 2 kbar at 17 0 1 2 log fo2 and ah2o 0 18 0 16 wholerock trace element and isotopic measurements show that charnockite formation was accompanied by a systematic depletion of sm rb pb u sr nd with a fractionation of rb sr sm nd and th u ratios and crystallization of the charnockite assemblage at 535 5 ma major element fe mg ca and sm nd equilibration between minerals occurred at 524 9 ma whereas pb and rb sr underwent continued exchange to 501 5 ma and 486 1 ma respectively trace element data for both amphibolite and charnockite minerals show that depletion on a whole rock scale can be accounted for either by changes in mineral modes or trace element abundances within the immediate area of dehydration the fractionation of sm nd on a whole rock scale is controlled by the breakdown of amphibole without the growth of a major new host phase for sm in the charnockite rubidium and sr are dependent on the relative behaviour of biotite plagioclase and alkali feldspar modelling of dehydration melting involving the breakdown of amphibole biotite and alkali feldspar reproduces the observed sm nd and rb sr fractionation and indicates the loss of small melt fractions on a cm scale from the charnockite these observations suggest that partial melting is the most plausible means of effecting both the dehydration and depletion that accompanies charnockite formation

real time multivariate indices for the boreal summer intraseasonal oscillation over the asian summer monsoon region the boreal summer intraseasonal oscillation bsiso of the asian summer monsoon asm is one of the most prominent sources of short term climate variability in the global monsoon system compared with the related madden julian oscillation mjo it is more complex in nature with prominent northward propagation and variability extending much further from the equator in order to facilitate detection monitoring and prediction of the bsiso we suggest two real time indices bsiso1 and bsiso2 based on multivariate empirical orthogonal function mv eof analysis of daily anomalies of outgoing longwave radiation olr and zonal wind at 850 hpa u850 in the region 10 s 40 n 40 160 e for the extended boreal summer may october season over the 30 year period 1981 2010 bsiso1 is defined by the first two principal components pcs of the mv eof analysis which together represent the canonical northward propagating variability that often occurs in conjunction with the eastward mjo with quasi oscillating periods of 30 60 days bsiso2 is defined by the third and fourth pcs which together mainly capture the northward northwestward propagating variability with periods of 10 30 days during primarily the pre monsoon and monsoon onset season the bsiso1 circulation cells are more rossby wave like with a northwest to southeast slope whereas the circulation associated with bsiso2 is more elongated and front like with a southwest to northeast slope bsiso2 is shown to modulate the timing of the onset of indian and south china sea monsoons together the two bsiso indices are capable of describing a large fraction of the total intraseasonal variability in the asm region and better represent the northward and northwestward propagation than the real time multivariate mjo rmm index of wheeler and hendon

moisture dynamics of the northward and eastward propagating boreal summer intraseasonal oscillations possible role of tropical indo west pacific sst and circulation boreal summer intraseasonal oscillation bsiso has complex spatial structure due to the co existence of equatorial eastward and off equatorial northward propagation in the equatorial indian ocean as a result equatorial indian ocean convection has simultaneous northward and eastward ne northward only n only and eastward only e only propagations it is well established that the convection propagates in the direction of increasing moist static energy mse the moisture and mse budget analysis reveals that the horizontal advection of anomalous mse contributes to positive mse tendency which is in agreement with the horizontal advection of column integrated moisture anomaly northward movement of warm sst and the anomalous moisture advected by zonal wind are the major initiative for the northward propagation of convection from the equatorial indian ocean in both ne and n only category at the same time warm sst anomaly in the equatorial west pacific along with moisture advection caused by anomalous meridional wind is important for the equatorial eastward branch of ne propagation as these anomalies in the west pacific moves northward equatorial indian ocean convection establishes over the equatorial west pacific the absence of these processes confines the bsiso in northward direction for n only category in the case of e only movement warm sst anomaly and moisture advection by zonal component of wind causes the eastward propagation of convection boundary layer moisture convergence always remains east of convection center in e only propagation while it coincides with convection centre in other two categories thus the present study concludes that the difference in underlying sst and atmospheric circulation in tropical indo west pacific oceanic regions encourage the differential propagation of bsiso convection through moisture dynamics

seasonality in the madden julian oscillation abstract this study using observational data and global reanalysis products synthesizes existing knowledge on the seasonality in the madden julian oscillation mjo and discusses its possible dependence on the mean background state the seasonality in the mjo is documented in terms of its components in low level zonal wind and precipitation a single peak season boreal winter exists near the equator in the indian and western pacific oceans for the broad tropical region however the seasonality in the mjo is featured by a latitudinal migration across the equator between two peak seasons the primary peak season is in boreal winter december march during which mjo signals are mainly confined to the indian and western pacific ocean and reach their maxima in the south pacific convergence zone the secondary peak season is boreal summer june september during which the strongest mjo occurs north of the equator from the bay of bengal to the south china sea and another separated region of strong mjo

northwestward propagation of the intraseasonal oscillation in the western north pacific during the boreal summer structure and mechanism abstract the convection of the intraseasonal timescale in the western north pacific during the boreal summer tends to propagate northwestward in the philippine sea to near 20 n and then continues propagating westward the formation of enhanced convection in the western north pacific is a result of the merging of a convective system moving eastward along the equator and a westward propagating low level convergence anomaly which is located to the east of a vortex in the subtropics a positive feedback between the anomalous circulation and convection leads to a rapid enhancement of the system the strengthened southwesterly associated with the vortex enhances evaporation over the oceans e g the eastern indian ocean the bay of bengal and the south china sea and transports moisture northeastward the moisture converges at the northwestern corner of the convection and results in a potentially unstable atmosphere the result is the northwestward propagation of the coupled circulation convection system in

formation and exhumation of blueschists and eclogites from ne oman new perspectives from rb sr and 40ar 39ar dating seven eclogite facies samples from lithologically different units which structurally underlie the semail ophiolite were dated by the 40 ar 39 ar and rb sr methods despite extensive efforts phengite dated by the 40 ar 39 ar method yielded saddle hump or irregularly shaped spectra with uninterpretable isochrons the total gas ages for the phengite ranged from 136 to 85 ma clinopyroxene phengite epidote phengite and whole rock phengite rb sr isochrons for the same samples yielded ages of 78i2 ma we therefore conclude that the eclogite facies rocks cooled through 500 u ca tc 7 8i2 ma and that the 40 ar 39 ar dates can only constrain maximum ages due to the occurrence of excess ar inhomogeneously distributed in different sites our new results lead us to conclude that high pressure metamorphism of the oman margin took place in the late cretaceous contemporaneous with ophiolite emplacement previously published structural and petrological data lead us to suggest that this metamorphism resulted from intracontinental subduction and crustal thickening along a ne dipping zone choking of this subduction zone followed by ductile thinning of a crustal mass wedged between deeply subducted continental material and overthrust shelf and slope units facilitated the exhumation of the eclogite facies rocks from depths of c 50 km to 10 15 km within c 10 ma and led to their juxtaposition against overlying lower grade rocks final exhumation of all high pressure rocks was driven primarily by erosion and assisted by normal faulting in the upper plate

reaction textures and fluid behaviour in very high pressure calc silicate rocks of the munchberg gneiss complex bavaria germany calc silicate rocks occur as elliptical bands and boudins intimately interlayered with eclogites and high pressure gneisses in the munchberg gneiss complex of ne bavaria core assemblages of the boudins consist of grossular ric h garnet diopside quartz zoisite clinozoisite calcite rutile and titanite the polygonal granoblastic texture commonly displays mineral relics and reaction textures such as post kinematic grossular rich garnet coronas reactions between these mineral phases have been modelled in the cao al 2 0 3 si02 c 02 h 20 system with an internally consistent thermodynamic data base high pressure metamorphism in the calc silicate rocks has been estimated at a minimum pressure of 31 kbar at a temperature of 630 c with x osq gi small volumes of a c02 n2 rich fluid whose composition was buffered on a local scale were present at peak metamorp hic conditions the p t conditions for the onset of the amphibolite facies overprint are about 10 kbar at the same temperature a co of the h20 rich fluid phase is regarded to have been 0 03 during amphibolite facies conditions these p t estimates are interpreted as representing different stages of recrystalliza tion during isothermal decompression the presence of multiple generations of mineral phases and the preservation of very high pressure relics in single thin sections preclude pervasive post peak metamorphic fluid flow as a cause of a re equilibration within the calc silicates the preservation of eclogite facies very high pressure relics as well as amphibolite facies reactions textures in the presence of a fluid phase is in agreement with fast tectonically driven unroofing of these rocks

modeling tropical convergence based on the moist static energy budget abstract the vertically integrated moist static energy equation provides a convenient starting point for the construction of simple models of the time mean low level convergence in the tropics a vertically integrated measure of the moist static stability the gross moist stability proves to be of central importance minima in this quantity mark the positions of the tropical convergence zones we argue that the positions of these minima are determined by the time mean moisture field which is in turn closely tied to the time mean surface temperature

the effect of titanite and other hfse rich mineral ti bearing andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts abstract we present trace element data for hfse rich minerals titanite eudialyte ti bearing andradite zircon from plutonic rocks of the eocene tamazeght complex high atlas mountains morocco in most lithologies significant amounts of titanite are present and as such titanite fractionation played a major role in the evolution of the hfse budget of the whole complex by combining our data with published titanite melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters zr hf nb ta la lu and th u ratios during differentiation of silicate melts in detail based upon this we further discuss the genetic relationships between the various rock types present in the tamazeght complex and show that the above mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite zircon eudialyte and ti bearing andradite are generally rare or are restricted to localized rock units despite their scarcity each of them can have a significant effect upon the hfse budget in their evolving magmas here we derive first estimations of eudialyte melt partition coefficients for ree application of these data to eudialyte bearing rocks of the ilimaussaq complex south greenland and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations

propagating versus nonpropagating madden julian oscillation events abstractbasinwide convective anomalies over the indian ocean io associated with the madden julian oscillation mjo sometimes propagate eastward and reach the west pacific wp but sometimes do not long term observations and reanalysis products are used to investigate the difference between the propagating and nonpropagating mjo events io convection onset events associated with the mjo are grouped into three categories based on the strengths of the simultaneous dry anomalies over the eastern maritime continent and wp the io convection anomaly preferentially makes eastward propagation and reaches the wp when the dry anomaly is stronger analysis of the column integrated moist static energy mse budget shows that horizontal advection moistens the atmosphere to the east of the positive mse anomaly associated with the active convection over the io and is of sufficient magnitude to explain the eastward propagation of the positive mse anomaly interpretation is complicated however by lack of closure in

low frequency equatorial waves in vertically sheared zonal flow part i stable waves abstract the mechanism by which a vertically sheared zonal flow affects large scale low frequency equatorial waves is investigated with two level equatorial plane and spherical coordinates models vertical shears couple barolinic and barotropic components of equatorial wave motion affecting significantly the rossby wave and westward propagating yanai wave but not the kelvin wave this difference results from the fact that the barotropic component is a modified rossby mode and can be resonantly excited only by westward propagating internal waves the barotropic components emanate poleward into the extratropics with a pronounced amplitude while the baroclinic components remain equatorially trapped a westerly vertical shear favors the trapping of rossby and yanai waves in the upper troposphere whereas an easterly shear tends to confine them in the lower troposphere as such their westward propagation is slowed down by both westerly and easterly shears when the strength of the vertical shear varies w

roles of barotropic convective momentum transport in the intraseasonal oscillation both observational data analysis and model simulations suggest that convective momentum transport cmt by cumulus convection may play a significant role in the intraseasonal oscillations iso by redistributing atmospheric momentum vertically through fast convective mixing process the authors present a simple theoretical model for the iso by parameterizing the cumulus momentum transport process in which the cmt tends to produce barotropic wind anomalies that will affect the frictional planetary boundary layer pbl in the model with equatorial easterly vertical wind shear vws it is found that the barotropic cmt tends to select most unstable planetary scale waves because cmt suppresses the equatorial ekman pumping of short waves which reduces the shortwave instability from the pbl moisture convergence and accelerates the shortwave propagation the model with subtropical easterly vws has behavior that can be qualitatively different from the model with equatorial easterly vws and has robust northward propagation the basic mechanism of this northward propagation is that the cmt accelerates the barotropic cyclonic wind to the north of iso which will enhance the precipitation by pbl ekman pumping and favor the northward propagation the simulated northward propagation is sensitive to the strength and location of the seasonal mean easterly vws these results suggest that accurate simulation of the climatological mean state is critical for reproducing the realistic iso in general circulation models

excess argon incorporation in phengite of the mulhacen complex submicroscopic illitization and fluid ingress during late miocene extension in the betic zone south eastern spain abstract 40 ar 39 ar induction furnace and laser step heating of well crystallised post tectonic phengitic mica single grains from gneisses of the mulhacen complex with an early alpine tectonic fabric has resulted in 1 highly scattered integrated ages 2 an abnormally high atmospheric contamination and 3 often anomalously old apparent ages during early 39 ar release that is associated with a high 36 ar air and 37 ar ca contamination this low temperature excess argon 40 ar xs component is probably released from carbonate formed during slight alteration of the mica more than 50 of the samples yielded plateau ages ranging from 15 8 0 4 to 90 1 1 0 ma samples taken only a few metres apart may differ in age by as much as 50 ma a grain that was split over the basal plane yielded plateau ages for each half that differ by 12 the age variation on these different scales is explained by heterogeneous 40 ar xs incorporation during a period with a high transient partial argon pressure in the metamorphic fluid resulting from a late stage reheating event the very swift cooling of 50 100 c ma during exhumation of the mulhacen complex concomitant with late miocene extension may have prevented the equilibration of different 40 ar xs levels in the mica hrtem images of the oldest and youngest phengite specimens show that at least 20 of the lattice is affected by submicroscopic illitisation which is concentrated in several micrometer wide zones and veins that cross cut the basal cleavage these are made up of aggregates of 0 07 0 30 m thick crystallites of three illitic micas types which are chemically and structurally progressively closer to pure illite and occur in different textures the oldest specimen is affected most severely as the veins contain newly formed pseudo illite that does not inherit its crystallographic orientation and chemistry from the host mica in contrast to the youngest sample hrtem aem analyses revealed that phengite and the different illitic micas may be depleted in k the oldest sample is derived from a coarse grained augen gneiss with extensively developed hydraulic cracks which are lacking in the youngest sample a fine grained mylonitic gneiss fluid rock interaction and consequently sub microscopic illitization were therefore more intense in the coarser grained rocks growth of the illitic micas in equilibrium with a high partial 40 ar pressure could account for 40 ar xs incorporation in k vacancies and other lattice imperfections variation in illitisation and associated textural dissimilarities between the oldest and youngest mica permit the different levels of 40 ar xs incorporation that account for the observed age discordance the finding of 40 ar xs plateau ages despite the degassing of intimately intergrown micaceous minerals is interpreted by gas release invoked by in vacuo chemical and structural changes that led to a joint collapse of the lattices of phengite and the illitic micas between 800 c and 1000 c

diagnosing the column integrated moist static energy budget associated with the northward propagating boreal summer intraseasonal oscillation column integrated moist static energy mse budgets associated with the northward propagating boreal summer intraseasonal oscillation bsiso are diagnosed for the bay of bangel bob and western north pacific wnp regions while an active bsiso convection is in phase with a positive column integrated mse perturbation the mse tendency exhibits a marked north south asymmetry about the convection with positive negative anomaly to its north south an mse budget diagnosis reveals that the advection of anomalous mse by the background southwesterly plays a dominant role in causing such an asymmetry and thus promotes the northward propagation as the anomalous rainband associated with the bsiso has a northwest southeast tilted structure the anomalous bsiso wind plays a negative role because the low level easterly anomaly to the north of the bsiso convection tends to suppress the surface evaporation through reduced near surface wind speed inhibiting the north south asymmetry in addition as maximum background mse appears over the asian land region the advection by the low level easterly anomaly contributes negatively over the wnp while it has little impact over the bob when the bsiso convection is near the equator a much stronger subsidence anomaly appears to the north than the south due to the equatorial asymmetry of the summer mean state this leads to a greater mse tendency north of the equator due to greater anomalous vertical mse advection supporting the initiation of the northward propagation

effect of vertical moist static energy advection on mjo eastward propagation sensitivity to analysis domain previous studies have shown great uncertainty in assessing the effect of vertical moist static energy mse advection term to the zonal asymmetry of mse tendency this study addresses this issue by qualitatively assess the fractional contribution of the vertical mse advection to the zonal asymmetric pattern of the mse tendency field and how its contribution depends on the choice of the analysis domain based on both observational and numerical simulation results it is shown that the vertical mse advection indeed plays a critical role in generating the zonal asymmetry of mse tendency accounting for 60 of the total mse tendency field in observation and even more in aqua planet simulations it is indicated that the underestimated contribution from vertical mse advection by some previous studies is attributed to the unphysical selection of analysis domain for the zonal asymmetric mse tendency pattern

influence of sea surface temperature on the intraseasonal variability of the south china sea summer monsoon the objective of this study is to examine based on recently available high resolution satellite and observational data the evolution and role of sea surface temperature sst in influencing the intraseasonal variability of the south china sea scs summer monsoon sm the study focuses on the 30 60 day timescale when the northward propagating anomalies are dominant over the scs composite analysis of the sst maximum events during scs sm shows that increased sst anomalies over the scs are significantly influenced by the downward shortwave radiation flux anomalies with the suppressed surface latent heat flux anomalies supplementing to it a thermal damping of the positive sst anomalies induces positive upward heat fluxes which then destabilize the lower atmosphere between 1 000 and 700 hpa the positive sst anomalies lead the positive precipitation anomalies over the scs by 10 days with a significant correlation r 0 44 between the sst precipitation anomalies the new findings here indicate an ocean to atmosphere effect over the scs where underlying sst anomalies tend to form a favorable condition for convective activity and sustain enhanced precipitation during the scs sm it is also argued based on our observations that the negative sea level pressure anomalies induced by the positive sst anomalies play a role in enhancing the northward propagation of the intraseasonal anomalies over the scs

exsolution in hornblende and its consequences for 40ar39ar age spectra and closure temperature abstract step heating studies of hornblende and biotite which coexist in an amphibolite near north walpole vermont reveal dramatically different 40 ar 39 ar age spectra the biotite mg 59 is characterized by a plateau over 98 percent 39ar release at 343 5 ma in strong contrast to the amphibole which exhibits both a complex age spectrum and a k ar age significantly younger than the biotite the amphibole release pattern contains three complete age cycles which range between extremes of 199 ma and 408 ma interestingly the k ca ratio calculated from reactor produced isotopes also varies with ar release but follows a trend which is antipathetic to the 40 ar 39 ar age pattern detailed microstructural examination including transmission electron microscopy tem reveals a complex exsolution structure that is consistent with both the complexity of the release pattern as well as the low degree of radiogenic 40ar 40ar retentivity in the amphibole this result underscores the variability of closure temperature tc for 40ar in metamorphic amphiboles and should warn against accepting a single universal value of tc

retrograde evolution of eclogites evidences from microstructures and 40ar 39ar white mica dates munchberg massif northern bavaria phengites from eclogites and pegmatites 3t 2m1 coarse grained and recrystallized of the munchberg massif weissenstein and oberkotzau have been dated by the 40ar 39ar method 3t micas from the eclogites yielded plateau and isochron ages of 365 7 ma 2m1 micas show disturbed degassing spectra micas from pegmatites show a slight excess ar component with an isochron age of 353 to 351 3 ma an age component of approximately 300 ma was also detected in combination with age values from the literature the cooling history of the munchberg massif from eclogite facies conditions 390 ma to cooling below 350 c 350 ma is documented the age component of 300 ma is attributed to a low grade stage of mineral growth accompanied by a transitional ductile brittle deformation the petrological effects include formation of pumpellyite prehnite facies minerals frequently precipitated in microcraks and cleavage planes of earlier formed minerals this stage has to be seen in conjunction with the intrusions of the fichtelgebirge granite

structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation abstract the spatial and temporal structures of the northward propagating boreal summer intraseasonal oscillation bsiso are revealed based on the analysis of both the echam4 model simulation and the ncep ncar reanalysis the bsiso structure and evolution characteristics simulated by the model bear many similarities to those derived from the ncep ncar reanalysis the most notable features are the remarkable meridional asymmetries relative to the bsiso convection in the vorticity and specific humidity fields a positive vorticity perturbation with an equivalent barotropic structure appears a few latitude degrees north of the convection center the maximum specific humidity also shows a clear northward shift in the lower troposphere two internal atmospheric dynamics mechanisms are proposed to understand the cause of the northward propagation of the bsiso the first is the vertical shear mechanism the key process associated with this mechanism is the generation of barotropic vorticity due to the couplin

fundamental causes of propagating and nonpropagating mjos in mjotf gass models abstractthis study investigates the fundamental causes of differences in the madden julian oscillation mjo eastward propagation among models that participated in a recent model intercomparison project these models are categorized into good and poor groups characterized by prominent eastward propagation and nonpropagation respectively column integrated moist static energy mse budgets are diagnosed for the good and the poor models it is found that a zonal asymmetry in the mse tendency characteristic of eastward mjo propagation occurs in the good group whereas such an asymmetry does not exist in the poor group the difference arises mainly from anomalous vertical and horizontal mse advection the former is attributed to the zonal asymmetry of upper midtropospheric vertical velocity anomalies acting on background mse vertical gradient the latter is mainly attributed to the asymmetric zonal distribution of low tropospheric meridional wind anomalies advecting background mse and moisture fields base

alpine deformation and 40ar 39ar geochronology of synkinematic white mica in the siviez mischabel nappe western pennine alps switzerland we explore the timing of deformation and exhumation of the siviez mischabel nappe western swiss alps which has been considered a classic example of a midcrustal crystalline nappe since the studies of argand 1916 this study presents 40ar 39ar ages obtained on both synkinematic white mica from permo triassic cover sediments and more complex white mica populations from basement gneisses of the siviez mischabel and middle pennine nappes primary foliation developed in cover units by nucleation growth and rigid rotation of mica grains during noncoaxial alpine deformation although some samples show a crenulation of this primary foliation mica growth appears to have occurred only during the development of primary foliation the main phase of greenschist facies deformation related to imbrication of the siviez mischabel nappe and other middle pennine nappes good agreement exists between independent estimates of the timing of deformation and reported 40ar 39ar white mica ages from cover units of the central and southern siviez mischabel nappe in cover units from the central and southern siviez mischabel regions of the study area 40ar 39ar ages appear to date synkinematic white mica growth results suggest that the siviez mischabel nappe was emplaced and developed foliation during a 5 m y period from 41 to 36 ma in cover units from the eastern siviez mischabel however 40ar 39ar white mica ages appear to date postkinematic thermal events these thermal events may be related to oligocene magmatic activity in the lower pennine nappes or to miocene development of the simplon fault zone variations in the relation between alpine age and grain size for cover samples from the central eastern and southern siviez mischabel correlate well with the regional variations in temperature inferred from quartz microfabrics and the pattern of regional metamorphism when considered in concert with other recent isotopic studies on the timing of major tectonic and thermal events in the western swiss alps these data support arguments that the relative timing of events such as thrusting and back thrusting of crystalline nappes in hinterland units and exhumation of high pressure units in the suture zone of the western alps are intimately related and synchronous on the scale of a few million years

boreal summer quasi monthly oscillation in the global tropics the boreal summer intraseasonal oscillation iso in the global tropics is documented here using a 7 year suite 1998 2004 of satellite measurements a composite scenario was made of 28 selected events with reference to the oscillation in the eastern equatorial indian ocean eio where the oscillation is most regular and its intensity is indicative of the strength of the subsequent northward propagation the average oscillation period is about 32 days and this quasi monthly oscillation qmo is primarily confined to the tropical indian and pacific oceans topics that were investigated are the partition of convective versus stratiform clouds the vertical structure of precipitation rates and the evolution of cloud types during the initial organization and the development of intraseasonal convective anomalies in the central indian ocean during the initiation of the convective anomalies the stratiform and convective rains have comparable rates the prevailing cloud type experiences a trimodal evolution from shallow to deep convection and finally to anvil and extended stratiform clouds a major northwest southeast slanted rainband forms as the equatorial rainfall anomalies reach sumatra and the rainband subsequently propagates northeastward into the west pacific ocean the enhanced precipitation in the west pacific then rapidly traverses the pacific along the intertropical convergence zone meanwhile migrating northward to the philippine sea a seesaw teleconnection in rainfall anomalies is found between the southern bay of bengal 5 15 n 80 100 e and the eastern pacific 5 15 n 85 105 w local sea surface temperature sst rainfall anomalies display a negative simultaneous correlation in the off equatorial regions but a zero correlation quadrature phase relationship near the equator we propose that atmosphere ocean interaction and the vertical monsoon easterly shear are important contributors to the northeastward propagation component of the intraseasonal rainband the observed evidence presented here provides critical information for validating the numerical models and it supports the self induction mechanism theory for maintenance of the boreal summer iso

seismic velocity and q structure of the middle eastern crust and upper mantle from surface wave dispersion and attenuation observed velocities and attenuation of fundamental mode rayleigh waves in the period range 7 82 sec were inverted for shear wave velocity and shear wave q structure in the middle east using a two station method additional information on q structure variation within each region was obtained by studying amplitude spectra of fundamental mode and higher mode rayleigh waves we obtained models for the turkish and iranian plateaus region 1 areas surrounding and including the black and caspian seas region 2 and the arabian peninsula region 3 the effect of continent ocean boundaries and mixed paths in region 2 may lead to unrealistic features in the models obtained there at lower crustal and upper mantle depths shear velocities are similar in all three regions shear velocities vary significantly in the uppermost 10 km of the crust being 3 21 2 85 and 3 39 km s for regions 1 2 and 3 respectively q models obtained from an inversion of interstation attenuation data show that crustal shear wave q is highest in region 3 and lowest in region 1 q s for the upper 10 km of the crust are 63 71 and 201 for regions 1 2 and 3 respectively crustal q s at 30 km depth for the three regions are about 51 71 and 134 the lower crustal q values contrast sharply with results from stable continental regions where shear wave q may reach one thousand or more these low values may indicate that fluids reside in faults cracks and permeable rock at lower crustal as well as upper crustal depths due to convergence and intense deformation at all depths in the middle eastern crust

poleward propagating intraseasonal monsoon disturbances in an intermediate complexity axisymmetric model abstract a model of intermediate complexity based on quasi equilibrium theory a version of the quasi equilibrium tropical circulation model with a prognostic atmospheric boundary layer as well as two free tropospheric modes in momentum and one each in moisture and temperature is used in a zonally symmetric aquaplanet configuration to simulate aspects of the south asian monsoon and its variability key qualitative features of both the mean state and the 30 60 day mode of the intraseasonal variability are simulated satisfactorily the model has two limit cycles of similar period and structure that can account for this mode both feature northward propagation of the tropical convergence zone from 5 s to 25 n with a period of about 50 days the dynamics of the oscillations are investigated the system reaches a hopf bifurcation when the asymmetry of the sea surface temperature sst forcing is increased beyond the bifurcation the mean flow is linearly unstable and the one linearly unstable mode is simila

some observations on the interpretation of 40ar 39ar age spectra several recent applications of the 40ar 39ar age spectrum technique have utilized the ability of this technique to resolve the internal ar isotope distribution in crystals for the purpose of placing constraints on the timing of thermal events additionally a few of these studies have attempted to use certain properties of the age spectrum to estimate the temperature and duration of heating experienced by the sample during the disturbance although these successful applications are encouraging the interpretation of age spectra of disturbed samples is in many ways still an art form with the beholder apparently relatively free of constraints that might limit an assessment in fact there are a number of restrictions on interpretation imposed by 1 multiple episodic loss 2 slow cooling 3 mixed phases 4 resolution of the age spectrum 5 excess 40ar 6 recoil artifacts 7 grain distribution and size and 8 phase changes while in the vacuum extraction system these effects are discussed with a view to understanding possible ambiguities in ar release patterns in most cases only with independent geochronological knowledge an understanding of the release systematics and complete sample characterization can these constraints be successfully dealt with in a quantitative framework

northward propagation mechanisms of the boreal summer intraseasonal oscillation in the era interim and sp ccsm abstractmechanisms for the northward propagation np of the boreal summer intraseasonal oscillation bsiso and associated asian summer monsoon asm are investigated using data from the interim ecmwf re analysis era interim herein called erai and the superparameterized community climate system model sp ccsm analyzed mechanisms are 1 destabilization of the lower troposphere by sea surface temperature anomalies 2 boundary layer moisture advection and boundary layer convergence associated with 3 sst gradients and 4 barotropic vorticity anomalies mechanism indices are regressed onto filtered olr anomaly time series to study their relationships to the intraseasonal oscillation iso and to equatorial rossby er waves northward propagation in erai and sp ccsm is promoted by several mechanisms but is dominated by boundary layer moisture advection and the barotropic vorticity effect sst linked mechanisms are of secondary importance but are nonnegligible the magnitudes of np mechanisms vary from

prograde mica 40ar 39ar growth ages recorded in high pressure rocks syros cyclades greece abstract phengites from the eclogite and blueschist facies sequences of the cycladic island of syros greece have been dated by the in situ uv laser ablation 40 ar 39 ar method a massive phengite rich eclogite and an omphacite rich metagabbro were investigated the phengites are euhedral and coarse grained several 100 m strain free and exhibit no evidence for late brittle deformation or recrystallization apparent ages in these samples range from 43 to 50 ma for the phengite rich eclogite and 42 to 52 ma for the omphacitic metagabbro this large spread of ages is visible at all scales within individual grains as well as in domains of several 100 m and across the entire sample ca 2 cm such variations have been traditionally attributed to metamorphic cooling or the incorporation of excess argon however the textural equilibrium between the phengites and other high pressure phases and the subtle compositional variations within the phengites especially the preservation of growth textures alternatively suggest that the observed range in ages may reflect variations of radiogenic argon acquired during phengite formation and subsequent growth thus dating a discrete event on the prograde path this implies that the oldest phengite 40 ar 39 ar ages provide the best estimate of a minimum crystallization age which is in agreement with recently reported u pb and lu hf geochronological data our results are consistent with available stable isotope data and further suggest that under fluid restricted conditions both stable and radiogenic isotopic systems can survive without significant isotopic exchange during subduction and exhumation from eclogite facies p t conditions

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

origin of the duvertepe kaolin alunite deposits in simav graben turkey timing and styles of hydrothermal mineralization abstract the duvertepe district located on the western end of the simav graben is the largest known fossil hydrothermal kaolin deposit in turkey active hot springs occur to the north of simav city eynal citgol nasa and geothermal fields occur to the west of the graben hisaralan kaolin in the duvertepe district formed at the expense of miocene rhyolites rhyodacites and tuffs emplaced in a tectonically active system undergoing n s extension upward fan shaped deposits of silicification and kaolin are found along fault zones and define areas of enhanced kaolinization silica sinters located above the kaolin zones suggest that hydrothermal fluids followed the fracture systems and mark outflow of geothermal waters fractured volcanic rocks rich in glass shards bear sufficient porosity and permeability for hydrothermal circulation two mineral facies kaolinite and alunite dominate the deposits which respectively include 1 kaolinite alunite quartz and 2 alunite opal ct quartz halloysite kaolinite crystals are well formed hexagonal vermiform habits and alunite crystals are idiomorphic rhombohedral forms needle and tubular shaped halloysites are common in the alunite facies the 34 s values for alunite range from 1 55 to 6 18 kaolinites have d ranging from 49 0 to 94 3 and the 18 o values range from 5 8 to 14 8 calculated formation temperatures of kaolin mineralization using 18 o values suggest that hydrothermal alteration occurred in the range of 38 to 129 c independent k ar and 40 ar 39 ar ages of alunite are concordant and indicate that alteration occurred from 20 1 to 20 6 ma in the southern part of the graben and 17 3 to 19 2 ma in the northern part these results suggest that metasomatism by steam heated hydrothermal fluids sourced by rhyolitic magma is responsible for the duvertepe kaolin and alunite deposit origins

curie point depth map of turkey summary a curie point isotherm map of the whole of turkey has been prepared from aeromagnetic data by means of a spectral analysis technique the most characteristic signature of this map is that the shallow depths generally correlated with the young volcanic rocks and the thinned crustal thicknesses in the west reveal geothermal fields and several hot springs the orogenic pontide belt of the black sea region in the north the western taurus belt in the south and some high plateaus in eastern turkey show that the deepest curie isotherm depths range between 20 and 29 km depth contour lines elongating in an almost e w direction are due to the overlapping percentage of adjacent data blocks of 50 per cent in the e w direction and to magnetic anomalies trending in the e w direction curie isotherm depths are in the range 6 to 10 km in the aegean region and are characterized by e w and ne sw trending graben structures as expected since the region has crustal thinning and many hot springs and geothermal fields these imply the existence of shallow heat sources that could be utilized for electricity heating of towns and cities greenhouse and health purposes

mass and stress changes in the menderes massif western anatolia turkey abstract comparing the results of the microgravity and gnss measurements is useful for understanding the vertical displacements of the plates in this study for determining the geodynamical behaviors of seismically active tectonic structures of gediz and buyuk menderes grabens which are located in western anatolia turkey graben system the mass changes were examined by processing of gnss and microgravity data besides after modeling the gnss velocity by coulomb stress analysis the stress distributions were investigated for these models therefore first of all the changes of gravity and the vertical components of gnss velocity values were evaluated together with a statistical method secondly gnss velocities were calculated relative to the main tectonic structures and the stress changes of tectonic structures were obtained at different depths with coulomb stress analysis by using these velocities and all results were evaluated with the earthquakes that had occurred in the study area consequently the crustal movements of the areas located at the gnss stations and their surroundings were put forwarded as in compensation or uncompensation concept of surface and subsurface loadings due to the mass or groundwater effects by using both microgravity and gnss measurements as an initial study on western anatolia graben system

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

mjo initiation processes over the tropical indian ocean during dynamo cindy2011 abstracta multination joint field campaign called the dynamics of mjo cooperative indian ocean experiment on intraseasonal variability in year 2011 dynamo cindy2011 took place in the equatorial indian ocean io in late 2011 during the campaign period two strong mjo events occurred from the middle of october to the middle of december referred to as mjo i and mjo ii respectively both the events were initiated over the western equatorial indian ocean wio around 50 60 e using multiple observational data products era interim the ecmwf final analysis and nasa merra the authors unveil specific processes that triggered the mjo convection in the wio it is found that 10 days prior to mjo i initiation a marked large scale ascending motion anomaly appeared in the lower troposphere over the wio the cause of this intraseasonal vertical motion anomaly was attributed to anomalous warm advection by a cyclonic gyre anomaly over the northern io the mjo ii initiation was preceded by a low level specifi

key processes for the eastward propagation of the madden julian oscillation based on multimodel simulations as a prominent climate variability mode with widespread influences on global weather extremes the madden julian oscillation mjo remains poorly represented in the latest generation of general circulation models gcms with a particular challenge in simulating its eastward propagating convective signals in this study by analyzing multi model simulations from a recent global mjo model evaluation project an effort is made to identify key processes for the eastward propagation of the mjo through analyses of moisture entropy me processes under a moisture mode framework for the mjo the column integrated horizontal me advection is found to play a critical role for the eastward propagation of the mjo in both observations and good mjo models with a primary contribution through advection of the lower tropospheric seasonal mean me by the mjo anomalous circulations by contrast the horizontal me advection effect for the eastward propagation is greatly underestimated in poor mjo gcms due to model deficiencies in simulating both the seasonal mean me pattern and mjo circulations leading to a largely stationary mjo mode in these gcms these results thus pinpoint an important guidance towards improved representation of the mjo in climate and weather forecast models while this study mainly focuses on fundamental physics for the mjo propagation over the indian ocean complex influences by the maritime continent on the mjo and also me processes associated with the mjo over the western pacific warrant further investigations

conductive crust imaged in western turkey by mt wide band magnetotelluric mt data across the izmir ankara suture zone iasz the bornova flysch zone and the menderes massif of western turkey images shallow and deep crustal structures inversions of the mt data reveals two subzones of the crust with varying thickness the viscoelastic lower crust appears as a conductive zone 2000 ohm m at a depth from 5 km to 25 km under the iasz a hypocentral cross section of earthquakes along the profile shows more dense seismic activity in and around the twin core structure due to this correspondence we interpret that decoupling of the twin core structure could be responsible for the denser seismic activity around the iasz the depth of the lithosphere asthenosphere boundary is rather shallow in the geoelectrical model about 45 km at the se and nw end of the profile and 55 km in the middle

mechanism for northward propagation of boreal summer intraseasonal oscillation convective momentum transport 1 this study demonstrates that the momentum transport by cumulus convection plays a significant role in the organization and northward propagation of intraseasonal iso convection anomalies over the indian and western pacific regions during boreal summer a version of seoul national university s atmosphere ocean coupled general circulation model simulates northward propagation when convective momentum transport cmt is implemented the northward propagation disappears when cmt is disabled an axially symmetric shallowwatermodel withaparameterized cmtis used to understand the role of cmt in the northward propagation of iso the basic mechanism of northward propagation is the lower level convergence to the north of convection which is induced by the secondary meridional circulation associated with large momentum mixing by convection in the region of large mean vertical shear a large meanverticalshearexistsinsouthasianregionduringboreal summer citation kang i s d kim and j s kug 2010 mechanism for northward propagation of boreal summer intraseasonal oscillation convective momentum transport geophys res lett 37 l24804 doi 10 1029 2010gl045072

regional heat flow in western anatolia using silica temperature estimates from thermal springs regional trends of variation of heat flow in western anatolia have been outlined using the silica temperature estimator on thermal springs silica heat flow values from 187 springs have been calculated the data are corrected for local long term mean annual surface temperature a mean value of heat flow for the western part of anatolia of 107 45 mw m 2 has been obtained which is about 60 above the world average the silica heat flow data are compared with available conventional heat flow values for this region a general agreement is observed and new patterns are recognized a close association exists between areas of high silica heat flow values above 100 mw m 2 and areas of tertiary and younger volcanism high heat flow is also observed in palaeozoic units of the menderes massif which is under tensional stress the highest heat flow estimate of 247 mw m 2 is obtained near gediz 38 57 n 29 13 2 e this area is part of a seismically active region and is located near a middle eocene subduction zone which is an area of later collision tectonics the new heat flow data from western anatolia improve our knowledge of the thermal conditions within the crust this information is important for the analysis of various geophysical and geological phenomena including seismicity

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

3d mechanical modeling of the gps velocity field along the north anatolian fault the north anatolian fault naf extends over 1500 km in a complex tectonic setting in this region of the eastern mediterranean collision of the arabian african and eurasian plates resulted in creation of mountain ranges i e zagros caucasus and the westward extrusion of the anatolian block in this study we investigate the effects of crustal rheology on the long term displacement rate along the naf heat flow and geodetic data are used to constrain our mechanical model built with the three dimensional finite element code adeli the fault motion occurs on a material discontinuity of the model which is controlled by a coulomb type friction the rheology of the lithosphere is composed of a frictional upper crust and a viscoelastic lower crust the lithosphere is supported by a hydrostatic pressure at its base representing the asthenospheric mantle we model the long term deformation of the surroundings of the naf by adjusting the effective fault friction and also the geometry of the surface fault trace to do so we used a frictional range of 0 0 0 2 for the fault and a viscosity varying between 10 19 and 10 21 pa s one of the most striking results of our rheological tests is that the upper part of the fault is locked if the friction exceeds 0 2 by comparing our results with geodetic measurements mcclusky et al j geophys res b 105 2000 5695 5719 and tectonic observations we have defined a realistic model in which the displacement rate on the naf reaches v17 mm yr for a viscosity of 10 19 pa s and a fault friction of 0 05 this strongly suggests that the naf is a weak fault like the san andreas fault in california adding topography with its corresponding crustal root does not induce gravity flow of anatolia rather it has the counter intuitive effect of decreasing the westward anatolian escape we find a poor agreement between our calculated velocity field and what is observed with gps in the marmara and the aegean regions we suspect that the simple lithosphere model is responsible for this discrepancy taking into account the weaknesses of these deforming regions should allow us to build a more realistic model that would match ground observations more appropriately on the other hand our results fit well gps measurements in central anatolia setting the basis of modeling crustal strain in turkey b 2003 elsevier science b v all rights reserved

ordovician 40ar 39ar phengite ages from the blueschist facies ondor sum subduction accretion complex inner mongolia and implications for the early paleozoic history of continental blocks in china and adjacent areas we obtained 453 21 8 ma and 449 41 8 ma 2 laser step heating 40 ar 39 ar plateau ages for phengite from quartzite mylonites from the blueschist facies ondor sum subduction accretion complex in inner mongolia northern china these ages are within error of the inverse isochron ages calculated using the plateau steps and the weighted mean ages of total fusion of single grains the compositional change from glaucophane in the cores to crossite in the rims of blue amphiboles as revealed by electron microprobe analysis points to decompression probably caused by progressive exhumation of the subducted material the late ordovician ages were not affected by excess argon incorporation because in all likelihood the oceanic sediments were wet on arrival at the trench and free of older detrital mica the ca 450 ma ages are hence interpreted as the time of crystallization during mylonitization under high fluid activity at fairly low temperatures this means that accretion of the quartzite mylonite unit occured about 200 ma before final closure of the paleo asian ocean amalgamation of the siberian tarim and north china cratons and formation of the end permian solonker suture zone we argue that the early paleozoic evolution of the ondor sum complex occurred along the northeastern cimmerian margin of gondwana which was composed of micro continents fringed by subduction accretion complexes and island arcs the later evolution took place during the building of the eurasian continent following middle devonian and younger rifting along the east gondwanan margin and northward drift of the detached north china craton an extensive review shows that this type of two stage scenario probably also applies to the geodynamic evolution of other micro continents like south china tarim a number of kazakh terranes alashan qaidam and kunlun as well as south kitakami and correlatives in japan and probably indochina like the north china craton these were bordered by early paleozoic subduction accretion complexes island arcs or contained calc alkaline volcanic mar gins like for example the central tienshan north qinling north qaidam altun north qilian and kunlun belts in china as well as the oeyama and miyamori ophiolites and matsugadaira motai blueschist belt of japan and the dismembered sergeevka ophiolite of the southern part of the russian far east this implies that a vast orogenic system comprising an archipelago of micro continents seems to have existed along the cimmerian margin of east gondwana in early paleozoic time in which the ultrahigh pressure metamorphism that characterizes the early evolution of many of the asian micro continents occurred introduction and aim

k ar geochronology of different tectonic units at the northwestern margin of the bohemian massif abstract the polymetamorphic moldanubian mo of the northeasthern margin of the bohemian massif has been thrust to the north onto the mainly paleozoic sedimentary saxothuringian of the fichtelgebirge fg these two units have undergone polyphase deformation and the last regional event to affect both units was a low pressure metamorphism in which temperatures decreased towards the north in contrast the nappe units of the erbendorf vohenstrauss zone zev and the erbendorf greenschist zone egz which partly cover the border of the moldanubian and the saxothuringian and the munchberg nappe pile mm which lies on the saxothuringian were in parts subjected to a late medium pressure metamorphic event the zev the egz the mo and the fg are intruded by late carboniferous granites conventional k ar analyses mainly of hornblendes and muscovites from the autochthonous fg and mo the units beneath the nappes have yielded exclusively carboniferous dates the oldest dates point to a regional cooling of the rocks which outcrop at the present day surface at about 330 320 ma i e at the early late carboniferous boundary the late carboniferous cooling history was largely governed by the thermal influence of the post kinematic granites 320 295 ma especially in the fg and the northern mo the high grade metamorphic rocks in the western part of the zev and in the upper three nappes of the mm mostly yield dates around 380 ma i e early devonian the results show a relatively wide scatter moreover biotites frequently appear to be older than the coexisting muscovites both observations indicate that the rocks underwent a later thermal influence whether some groups of older dates e g 400 ma are due to excess argon or to inherited argon is still open to discussion slightly scattered muscovite dates around 366 ma were obtained for the prasinite phyllite series one of the lower nappes of the mm a single hornblende from the egz gave the same age these two nappes have therefore probably been affected by a late devonian thermal and or tectonic event the muscovite dates obtained from the paleozoic bavarian lithofacies the lowermost nappe of the mm and the hornblende dates from the eastern part of the zev are indistinguishable from those of the autochthonous units fg and mo

monazite in a variscan mylonitic paragneiss from the munchberg metamorphic complex ne bavaria records cadomian protolith ages small oval shaped unshielded monazite grains found in a variscan garnet muscovite bearing mylonitic paragneiss from the liegendserie unit of the munchberg metamorphic complex mmc in the northwestern bohemian massif central europe yield only pre variscan ages these ages determined with the electron microprobe have maxima at about 545 520 and 495 ma and two side maxima at 455 and 575 ma and are comparable with previously determined ages of detrital zircon reported from paragneisses elsewhere in the nw bohemian massif the pressure p temperature t history of this mylonitic paragneiss determined from contoured p t pseudosections involved an initial stage at 6 kbar 600 c reaching peak p t conditions of 12 5 kbar 670 c with partial melting followed by mylonitization and retrogression to 9 kbar 610 c the monazite representing detrital grains derived from igneous rocks of a cadomian provenance between 575 455 ma has survived these variscan metamorphic deformational events unchanged because this mineral has probably never been outside its p t stability field during metamorphism this article is protected by copyright all rights reserved

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

mechanism of the northward propagating intraseasonal oscillation insights from a zonally symmetric model abstract the propagation and initiation mechanisms of the boreal summer intraseasonal oscillation bsiso in the south asian summer monsoon are examined with a zonally symmetric atmospheric model in the axially symmetric model the effects of zonally propagating atmospheric waves are intentionally excluded the model specifies mean flows and depicts the lowest baroclinic mode and a barotropic mode in the free troposphere the two vertical modes are coupled by the time mean vertical wind shear the model atmosphere produces a 15 20 day oscillation which is characterized by northward propagation of convection from south of the equator to the indian monsoon trough region and a reinitiation of convection in the region between 10 s and the equator the northward propagation in the model is produced by the free troposphere barotropic divergence which leads convection by about a quarter of a cycle the vertical advection of summer mean easterly vertical wind shear by perturbation vertical motion inside the con

argon retentivity and argon excess in amphiboles from the garbenschists of the western tauern window eastern alps 22 hornblende k ar ages and 10 39ar 40ar spectra were obtained for hornblende garbenschists from the western tauern window the post kinematic amphiboles were produced during the late alpine prograde metamorphism 6 10 kb and 500 570 c two nearly potassiumfree cummingtonites rimming hornblende yield k ar ages of 120 ma while the 20 tschermakitic hornblendes scatter between 17 and 37 ma the reason for this scatter is excess ar possibly incorporated into amphiboles during healing of fractures now traceable by trails of fluid inclusions excess ar is semiquantitatively corrected for by combining cogenetic hornblende and cummingtonite with k ar isochrons it can be quantified in 4 out of 10 hornblendes by 39ar 40ar stepwise heating experiments ages of 18 20 ma result for corrected hornblendes the retentivity of 40ar after correction for excess shows no correlation with chemistry within the narrow compositional range observed rather it shows intriguing correlations with irregularities in ca k spectra pointing to a microstructurally controlled mechanism for ar loss this observation leads to a critical evaluation of the closure temperature constant which apparently depends on an incompletely known number of mineralogical and environmental parameters in particular those 39ar 40ar release spectra which yield low temperature steps with younger ages than the plateaus are not interpretable in terms of a synchronous closure this gives evidence that loss of radiogenic isotopes proceeds by a more complex mechanism than simple volume diffusion through isotropic media

tectonometamorphic evolution of the bohemian massif evidence from high pressure metamorphic rocks the variscan orogenic belt of which the bohemian massif is a part is typically recognized for its characteristic low pressure high temperature metamorphism and a large volume of granites however there are also bodies of high pressure rocks eclogites garnet peridotites and high pressure granulites which are small in size but widely distributed throughtout the massif initially the high pressure rocks were considered to be relicts of a much older orogenic event but the increasing data derived from isotopic and geochronological investigations show that many of these rocks have palaeozoic protoliths metamorphic ages from the high pressure rocks define no single event instead a number of discrete clusters of ages are found between about 430 ma and the time of the dominant low pressure event at around 320 330 ma

ultrahigh pressure metamorphism in the śnieznik mountains sudetes poland p t constraints and geological implications the petrology and p t conditions of eclogites and associated gneisses from the nieznik mountains sudetes sw poland were investigated to establish an exhumation path for these ultrahigh pressure rocks peak pressure conditions are represented by the assemblage garnet omphacite phengite kyanite coesite rutile post dating this assemblage but still in the eclogite facies garnet with lower grossular content and a first generation of amphibole are formed under lower pressure conditions giving rise to the assemblage garnet omphacite phengite kyanite quartz rutile calcic amphibole i continuing depressurization caused the successive destabilization of omphacite garnet kyanite and phengite in some places the primary eclogite assemblage was completely transformed into amphibolite facies mineral assemblages estimated peak pressures in the nieznik and miedzygorze units lie in the coesite stability field p 27 kbar at temperatures of about 700 800 c and are not significantly different to the zlote un

mantle fluids in the karakoram fault helium isotope evidence abstract the karakoram fault kkf is the 1000 km long strike slip fault separating the western himalaya from the tibetan plateau from geologic and geodetic data the kkf is argued either to be a lithospheric scale fault with hundreds of km of offset at several cm a or to be almost inactive with cumulative offset of only a few tens of kilometers and to be just the upper crustal localization of distributed deformation at depth here we show 3he 4he ratios in geothermal springs along a 500 km segment of the kkf are 3 100 times the normal ratio in continental crust providing unequivocal evidence that a component of these hydrologic systems is derived from tectonically active mantle mantle enrichment is absent along the indus yarlung suture zone isz just 35 km southwest of the kkf suggesting that the mantle fluids flow only within the kkf within the last few ma the kkf must have accessed tectonically active tibetan mantle northeast of the mantle suture which we therefore locate vertically beneath the kkf very close to the surface trace of the isz hence in southwestern tibet indian crust may not now be underthrusting substantially north of the isz even though miocene underthrusting may have placed indian crust north of the isz in the lower half of the tibetan plateau crust this is in significant contrast to central and eastern tibet where underthrust indian material not only forms the lower half of the tibetan crust but is also currently underthrusting for 200 km north of the isz our new constraint on kkf penetration to the mantle allows an improved description of the continuously evolving karakoram fault as a tectonically significant yet perhaps geologically ephemeral lithospheric structure

three dimensional structure and evolution of the moisture field in the mjo abstractthe large scale circulation features that determine the structure and evolution of mjo related moisture and precipitation fields are examined using a linear analysis protocol based on daily 850 minus 150 hpa global velocity potential data the analysis is augmented by a compositing procedure that emphasizes the structural features over the indo pacific warm pool sector 60 e 180 that give rise to the eastward propagation of the enhanced moisture and precipitation it is found that boundary layer bl convergence in the low level easterlies to the east of the region of maximum ascent produces a deep but narrow plume of equatorial ascent that moistens the midtroposphere while weakly diffluent flow above the bl spreads moisture away from the equator vertical advection of moisture from this plume of ascent accounts for the eastward propagation of the positive moisture anomalies across the maritime continent into the western pacific when the convection is first developing over the indian ocean ho