first evidence of high pressure metamorphism in the cover series of the southern menderes massif tectonic and metamorphic implications for the evolution of sw turkey abstract the menderes massif occupies a large part of western turkey it is tectonically overlain by nappes of the izmir ankara suture zone including the bornova flysch zone on its northern flank the afyon zone on its eastern border and the lycian nappes on its southern flank the discovery of magnesiocarpholite kyanite assemblages in the mesozoic cover sequence of the southern menderes massif leads to the very first consideration that a major high pressure hp metamorphic event affected the massif during its alpine evolution estimations of minimum pressure temperature conditions about 10 12 kbar and 440 c suggest a minimum burial of 30 km for the metasedimentary rocks of the menderes massif similar to that for the eocene dilek blueschists which belong to the cycladic complex this finding of high pressure rocks within the menderes cover series as well as the recent description of low grade high pressure parageneses in the basal thrust sheets of the overlying lycian nappe complex has strong implications for the tectono metamorphic evolution of these units the characteristics of this high pressure metamorphism and the deformation features observed in the southern menderes massif allow consideration of a fast burial during alpine subduction and nappe stacking three high pressure units were piled up during the eocene collision of the sakarya continent and the tauride menderes block the lowermost unit consists of the imbricated core and cover of the menderes massif the intermediate unit is the cycladic blueschist complex dilek and samos regions and the uppermost unit is made of the lycian nappes the retrogression of high pressure parageneses from the menderes massif follows an isothermal decompression path and the associated deformation is characterized by a severe stretching oriented n s to ne sw during the high pressure event and its exhumation we propose a tectono metamorphic model in three main stages 1 the southward translation of the high pressure lycian nappes and the burial of the menderes and cycladic metasediments to a depth of at least 30 km to allow their eocene high pressure metamorphism 2 a northward continuum of deformation responsible for top to the north fabrics associated with the main menderes metamorphism peak paleocene eocene and its progressive cooling late eocene north verging folding thrusting imbrication of core and cover series and n s to ne sw intense stretching associated with the menderes high pressure metamorphism and its exhumation these top to the north to top to the northeast movements are probably related to the northward backthrusting of the lycian nappes reactivating the contact between the menderes massif and the lycian nappes as a top to the ne shear zone that allowed exhumation of the lycian high pressure rocks 3 oligo miocene n s extension during which the final exhumation of the metamorphic rocks along kilometre scale low angle detachments occurred

contrasting noble gas compositions of peridotitic and eclogitic monocrystalline diamonds from the argyle lamproite western australia abstract he ne ar compositions were determined in diamonds from the argyle lamproite western australia to assess whether subducted material affects the noble gas budget and composition of stable old sub continental lithospheric mantle sclm twenty diamonds both peridotitic and eclogitic were characterized for their carbon isotopic compositions and n abundance and aggregation from which 10 eclogitic growth zones and 5 peridotitic growth zones were analysed for their he ne ar compositions the eclogitic diamonds have 13c values of 4 7 to 16 6 indicating a subduction signature whereas the peridotitic diamonds have mantle like compositions of 4 0 to 7 8 mantle residence temperatures based on n in diamond thermometry showed that the eclogitic diamonds were mainly formed at 1260 1270 c or above 1300 c near the base of the lithosphere whereas the peridotitic diamonds generally formed at lower temperatures mostly 1135 1230 c a noble gas subduction signature is present to various extents in the eclogitic diamonds and is inferred from a hyperbolic mixing relationship between r ra and 4he and 13c values concentrations with a predominance of low r ra values

implanted 3he 4he and xe in further studies of diamonds from western australia in measurements of the noble gases in additional samples of diamonds from the argyle and ellendale lamproites in western australia we have failed to encounter any neon rich stones such as showed solar like isotopic compositions in earlier work no neon was detected above the relatively high blank levels in our glass apparatus white and brown diamonds showed no differences in noble gas content nor did samples segregated by the color of long wave uf fluorescence the rare gas patterns in the 1 2 ga argyle pipe are largely consistent with implanted 3he 4he and fissiogenic xe from u th in the matrix rock in which the diamonds have been stored for so long these implanted species are absent in diamonds from the much younger approximately 20 ma ellendale pipe we give implantation formulae for several models of inhomogeneously distributed u th differences in 3he content between pipe and alluvial argyle samples are consistent with expected cosmogenic production in the latter an expanded data base for helium and carbon isotopic data on the same samples supports a negative 4he 13 c correlation seen earlier in work from our group but if the argyle samples which contain light carbon are corrected for implanted 4he 13 c the correlation is considerably weakened we no longer see an earlier 3he 4he 13 c correlation

isotopic evolution of mauna loa volcano abstract in an effort to understand the temporal helium isotopic variations in mauna loa volcano we have measured helium strontium and lead isotopes in a suite of mauna loa lavas that span most of the subaerial eruptive history of the volcano the lavas range in age from historical flows to ninole basalt which are thought to be several hundred thousand years old most of the samples younger than 30 ka in age kau basalt are radiocarbon dated flows while the samples older than 30 ka are stratigraphically controlled kahuku and ninole basalt the data reveal a striking change in the geochemistry of the lavas approximately 10 ka before present the lavas older than 10 ka are characterized by high 3 he 4 he 16 20 times atmospheric higher 206 pb 204 pb 18 2 and lower 87 sr 86 sr 0 70365 ratios than the younger kau samples having he pb and sr ratios of approximately 8 5 atmospheric 18 1 and 0 70390 respectively the historical lavas are distinct in having intermediate sr and pb isotopic compositions with 3 he 4 he ratios similar to the other young kau basalt 8 5 atmospheric the isotopic variations are on a shorter time scale 100 to 10 000 years than has previously been observed for hawaiian volcanoes and demonstrate the importance of geochronology and stratigraphy to geochemical studies the data show consistency between all three isotope systems which suggests that the variations are not related to magma chamber degassing processes and that helium is not decoupled from the other isotopes however the complex temporal evolution suggests that three distinct mantle sources are required to explain the isotopic data most of the mauna loa isotopic variations could be explained by mixing between a plume type source similar to loihi and an asthenospheric source with helium isotopic composition close to morb and elevated sr isotopic values an asthenospheric source or variation within the plume source is considered more likely than lithospheric sources due to the elevated 87 sr 86 sr ratios in the recent kau basalts however the distinct isotopic characteristics of the historical lavas are inferred to be related to lithospheric involvement in the latest stages of shield building volcanism

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

he and sr isotopic constraints on subduction contributions to woodlark basin volcanism solomon islands in order to assess the nature and spatial extent of subduction contributions to arc volcanism sr and he isotopic compositions are measured for dredged volcanic rocks from the woodlark basin in the western pacific sup 87 sr sup 86 sr ratios increase geographically from ocean ridge values 7025 7029 at the woodlark spreading center to island arc ratios 7035 7039 in the solomon islands forearc with intermediate values near the triple junction where the woodlark spreading center subducts beneath the solomon islands sup 3 he sup 4 he ratios are also more radiogenic in the forearc 6 9 plus minus 2 r sub a at active kavachi volcano than along the spreading center where values typical of major ocean ridges were found 8 2 9 3 r sub a very low sup 3 he sup 4 he ratios occur in many triple junction rocks 1 to 5 r sub a but consideration of he isotopic differences between crushing and melting analyses suggests that the low ratios were caused by atmospheric 1 r sub a and radiogenic approx 0 2 r sub a helium addition after eruption variations in unaltered magnetic sup 3 he sup 4 he and sup 87 sr sup 86 sr ratios are best explained by subduction related fluid or silicate melt contributions to the magma source region perhaps from ancient pacific lithosphere however more mantle volatiles dominate the generation of woodlark basin rocks despite extensive subduction in the region less

cosmogenic nuclide exposure ages and glacial history of late quaternary ross sea drift in mcmurdo sound antarctica 3he 10be and26al surface exposure ages were determined for rock samples from late quaternary drift sheets deposited on the coast of mcmurdo sound antarctica by the ross sea ice sheet the youngest drift previously believed to be late wisconsin in age has exposure ages of 8 106 kyr 19 samples these results suggest that the apparent late wisconsin ice margin may represent a number of ice sheet advances during the last glacial period 3he exposure ages from analogous stratigraphically older drift range from 104 to 567 kyr seven samples and clearly distinguish the youngest drift from older deposits comparison of10be and3he concentrations in ross sea drift quartz samples indicates significant3he loss in only one sample suggesting that cosmogenic3he is generally retained in young antarctic quartz samples exposure age 100 kyr of appropriate grain size in two of the five quartz samples analyzed significant excesses of26al relative to10be preclude meaningful26al exposure age calculations these excesses may be due to nucleogenic26al produced as a byproduct of uranium and thorium decay

basaltic explosive volcanism but no comet impact at the paleocene eocene boundary high resolution chemical and isotopic records from egypt spain and denmark in the search for a triggering mechanism for the paleocene eocene p e boundary event 55 ma centimeter resolution chemical e g ir os pt and isotope e g os o 187 os 188 he 3 he 4 sr 87 sr 86 records across this boundary have been established for six uplifted marine sections in egypt spain and denmark the sections studied represent some of the stratigraphically most complete records across the onset of the carbon isotopic excursion cie and associated benthic foraminifera extinctions that mark the paleocene eocene boundary high sensitivity analyses failed to uncover evidence of extraterrestrial element or isotope enrichments in the six sections refuting the hypothesis of a major comet impact at the boundary preliminary searches for other impact indicative features such as spherules or shocked quartz also gave negative results in the danish section studied three basaltic ir rich ash layers occur at the paleocene eocene boundary but no similar ashes were found in egypt or spain the three ashes represent the earliest known manifestation of an unusual i to 2 million year long phase of explosive basaltic volcanism in the faero greenland region this volcanism is synchronous with major flood basalt effusions in east greenland and is associated with prominent paleogeographic changes in the high latitude north atlantic region discharge of mantle derived os to seawater during this volcanism may explain a small decrease in os o 187 os o 188 ratio at the paleocene eocene boundary in the zumaya section in spain the environmental perturbations at the paleocene eocene boundary appear to have been triggered by basaltic volcanism but any model for the detailed causal relation remains speculative c 2004 elsevier b v all rights reserved less

petrogenesis and 40ar 39ar geochronology of the volcanic rocks of the usak gure basin western turkiye abstract in spite of much research over the past 30 years the dynamic evolution origin of the volcanism and geometrical stratigraphical relations of the ne sw trending basins in western anatolia are poorly understood the usak gure basin is one of the prominent ne sw trending basins developed on the northern part of the menderes massif core complex three distinct volcanic successions are found in the usak gure basin 1 the beydagi volcanic unit composed of shoshonite latites and rhyolitic lavas followed by dacitic and andesitic pyroclastic deposits 2 the payamtepe volcanic unit composed of potassic intermediate composition lavas latites and trachytes and 3 the karaagac dikes composed of andesite and latite the beydagi volcanic unit occurs in three different ne sw trending volcanic centers beydagi itecektepe and elmadag calderas from southwest to northeast respectively the oldest radiometric ages for the beydagi volcanic unit are from the elmadag volcanic center in the north and range from 17 to 16 ma the data indicate that volcanism was active during the latest early miocene the youngest radiometric age for the beydagi volcanic unit is obtained from the beydagi caldera located 12 ma in the south the data indicate that beydagi volcanism was active in the late middle miocene and migrated from north to south with time 40ar 39ar ages of the payamtepe volcanic unit are restricted to a short period between 16 0 and 15 9 ma volcanic rocks of the usak gure basin are characterized by strong enrichment in lile and lree and depletions of nb ta and ti on morb normalized multi element diagrams geochemical features of the volcanic rocks suggest that they experienced mixing processes between mafic and felsic end members and also fractional crystallization of dominantly plagioclase and pyroxenes from mixed magma compositions crustal contributions to the magma sources may also have occurred during magmatic evolution these processes have resulted in scattered major and trace element variations with respect to increasing silica contents geochemical features of the most mafic samples agree with the results of previous studies from other volcanic areas in western anatolia suggesting that the volcanic rocks in the region were derived from a mainly lithospheric mantle source that had been heterogeneously metasomatized by previous subduction events during convergence between the african and eurasia plates the volcanic activity in the region which developed synchronously with the formation of the menderes massif core complex is best explained by delamination of lithospheric mantle slices that were heterogeneously enriched by previous subduction related processes

seasonal variations of high latitude field aligned currents inferred from orsted and magsat observations 1 in this paper we report on field aligned currents inferred from high precision three component geomagnetic field observations made on board the danish satellite orsted over polar regions because of a slow drift in local time of the satellite orbit through the noon midnight sector we were able to study the seasonal dependence of the dynamic properties of the dayside and nightside field aligned current systems over the northern and southern hemispheres we find an average over the pole distance between dayside and nightside currents of 32 during summer but 37 during winter and 36 during equinox the decrease in the size of the summer polar cap is caused by a shift of both daytime and nighttime current systems to higher magnetic latitudes for comparison the dawn dusk cross polar distance of the region 1 region 2 field aligned currents has been determined from high precision data observed by magsat a satellite flown in 1979 1980 in a dawn dusk orbit the latter results show that the dawn dusk distance between r1 r2 currents exhibits little seasonal dependence and amounts to 34 for all seasons in both polar caps the seasonal dependence is confirmed for the high latitude field aligned intensities they are larger by a factor of 1 5 1 8 in the sunlit summer polar cap in comparison with the winter hemisphere our results suggest that the r1 r2 and dayside field aligned currents are well balanced between the pairs of downward upward currents for all seasons as well as between hemispheres during equinox we were not able to confirm results reported in earlier studies that the net currents tend to increase with an enhancement of ionospheric conductivity caused by the solar illumination or substorm activity

evidence for a mantle component shown by rare gases c and n isotopes in polycrystalline diamonds from orapa botswana in an attempt to constrain the origin of polycrystalline diamond combined analyses of rare gases and carbon and nitrogen isotopes were performed on six such diamonds from orapa botswana helium shows radiogenic isotopic ratios of r ra 0 14 1 29 while the neon ratios 21 ne 22 ne of up to 0 0534 reflect a component from mantle nucleogenic and atmospheric sources 40 ar 36 ar ratios of between 477 and 6056 are consistent with this interpretation the 129 xe 130 xe isotopic ratios range between 6 54 and 6 91 and the lower values indicate an atmospheric component the he ne ar and xe isotopic compositions and the xe isotopic pattern are clear evidence for a mantle component rather than a crustal one in the source of the polycrystalline diamonds from orapa they 13 c and y 15 n isotopic values of 1 04 to9 79xand 4 5 to 15 5x respectively lie within the range of values obtained from the monocrystalline diamonds at that mine additionally this work reveals that polycrystalline diamonds may not be the most appropriate samples to study if the aim is to consider the compositional evolution of rare gases through time our data shows that after crystallization the polycrystalline diamonds undergo both gas loss that is more significant for the lighter rare gases such as he and ne and secondary processes such as radiogenic nucleogenic and fissiogenic as well as atmospheric contamination finally if polycrystalline diamonds sampled an old mantle 1 3 2 ga the determined xe isotopic signatures which are similar to present morb mantle no fissiogenic xe from fission of 238 u being detectable imply either that xe isotopic ratios have not evolved within the convective mantle since diamond crystallization or that these diamonds are actually much younger d 2005 elsevier b v all rights reserved

40ar39ar laser probe dating of individual clinopyroxene inclusions in premier eclogitic diamonds abstract the ages of seven individual clinopyroxene inclusions in premier diamonds of eclogitic association have been determined using the 40 ar 39 ar dating technique syngenetic inclusions weighing between 10 and 130 g were exposed on cleaved surfaces of the diamonds and analysed using a laser probe the inclusion ages were found to be in the range 1111 35 to 1254 38 ma with an average of 1185 94 ma the ages obtained are in good agreement with previous determinations made on aggregates of eclogitic inclusions from premier diamonds and demonstrate the applicability of the laser probe to dating individual diamond inclusions

seasonal and diurnal variations in ampere observations of the birkeland currents compared to modeled results we reduce measurements made by the active magnetosphere and planetary electrodynamics response experiment ampere to give the total birkeland field aligned current flowing in both hemispheres in monthly and hourly bins we analyze these totals using 6 years of data 2010 2015 to examine solar zenith angle driven variations in the total birkeland current flowing in both hemispheres simultaneously for the first time a diurnal variation is identified in the total birkeland current flowing consistent with variations in the solar zenith angle a seasonal variation is also identified with more current flowing in the northern southern hemisphere during bartels rotations in northern southern summer for months close to equinox more current is found to flow in the northern hemisphere contrary to our expectations we also conduct the first test of the milan 2013 model for estimating birkeland current magnitudes with modifications made to account for solar contributions to ionospheric conductance based on the observed variation of the birkeland currents with season and time of day the modified model using the value of d averaged by bartels rotation scaled by 1 7 is found to agree with the observed ampere currents with a correlation of 0 87 in the northern hemisphere and 0 86 in the southern hemisphere the improvement over the correlation with dayside reconnection rate is demonstrated to be a significant improvement to the model the correlation of the residuals is found to be consistent with more current flowing in the northern hemisphere this new observation of systematically larger current flowing in the northern hemisphere is discussed in the context of previous results which suggest that the northern hemisphere may react more strongly to dayside reconnection than the southern hemisphere

tectono stratigraphic evolution of the ne sw trending superimposed selendi basin implications for late cenozoic crustal extension in western anatolia turkey abstract selendi basin is located in the eastern part of western anatolia that is the easternmost part of the aegean extensional province in western anatolia crustal extension resulted in exhumation of the mid crustal units the menderes massif synchronously with volcano sedimentary basin formation the stratigraphic and tectonic features of the volcano sedimentary succession reflect the exhumation processes and the modes of extension we present new stratigraphical sedimentological structural and 40ar 39ar age data from the neogene volcano sedimentary fill of the ne sw trending selendi basin the data show that crustal extension in the region occurred in four distinct episodes and accommodated the exhumation of the menderes massif and the basin formation throughout the late cenozoic late oligocene to early miocene detachment faulting the simav detachment fault sdf is attributed to the first episode clastic sedimentation and bimodal volcanism of 20 0 17 5 ma the hacibekir group age was formed in the hanging wall of the sdf during the exhumation of northern menderes massif in the footwall during second episode the menderes collapse occurred and was manifest by formation of the gediz detachment fault gdf during the middle miocene activity on the gdf has resulted in the exhumation of the central menderes massif in the bozdag area during this period the hanging wall of the gdf was dissected by ne sw trending high angle oblique slip cross faults and accommodated clastic to lacustrine carbonate deposition and syn sedimentary bimodal volcanism of 16 15 ma the inay group the third episode is represented by formation of nw se trending sinistral and ne sw trending dextral strike to oblique slip faults and associated dip to oblique slip normal faults during the late miocene indicating that the area was deformed under a strike slip tectonic regime the faults localized alluvial sedimentation the kocakuz formation and basaltic volcanism of 7 8 ma the kabaklar basalt in the selendi basin the last episode commenced by the start of the plio quaternary this period is represented by the currently active n s extensional tectonic regime that resulted in the formation of e w trending high angle normal faults that controls the present day e w trending graben type basin formation e g gediz and simav grabens and the quaternary 1200 60 ka basaltic volcanism

combining 3 he cosmogenic dating with u th he eruption ages using olivine in basalt this paper presents new u th he crystallization and 3 he exposure ages on olivine for a suite of basalt samples from the snake river plain idaho the results provide the first demonstration that u th he geochronology can be successfully applied to late quaternary basalts using measurements of olivine phenocrysts as opposed to u rich minerals the approach employs abrasion to remove the outer rinds of olivine crystals to avoid problems with 4 he implantation from the groundmass and a specially designed extraction system that allows u th and he concentrations and isotopic compositions to be measured on the same olivine grains we demonstrate the viability of the u th he technique on basalts with ages of 373 ka and 3400 ka previously dated by ar ar and show that concurrent measurements of u th 4 he ages and 3 he cosmogenic exposure ages improve the accuracy of both methods the combinedu th 4 he 3 hetechniqueisappliedtoaseriesofbouldersandflowsfromboxcanyonnearhagerman idaho toevaluate the ages of the basalts and to use exposure ages to make inferences about the age and mode offormation of the canyon the u th he ages of the box canyon basalts are between 86 12 ka and 130 12 ka 1 sigma errors and suggest at least two periods of eruption the ages are similar to a ca 95 ka ar ar age previously assigned and distinguish the box canyon basalts from nearby ca 395 ka basalt exposure ages of boulders within the canyon at the mouth head and middle of box canyon are 21 1 19 3 and 48 3 ka scoured bedrock at the canyon head has an exposure age of 45 5 ka these data indicate that the canyon was carved before the

petrology and geochemistry of potassic rocks in the golcuk area isparta sw turkey genesis of enriched alkaline magmas abstract the lower pliocene volcanic rocks occurring in the golcuk area of sw turkey exhibit alkaline major element trends with a general potassic character the development of volcanism can be divided into 2 major stages such as trachytic ancient lavas domes and tephriphonolitic trachyandesitic to trachytic golcuk eruptions ignimbrites lava dome extrusions phreatomagmatic deposits and finally young domes volcanic rocks consist primarily of plagioclase clinopyroxene which ranges in composition from diopside to augite and are commonly zoned biotite and phlogopite amphibole phenocrysts are restricted to the pyroclastic deposits pseudoleucites are also seen only in the lava dome extrusions oxides and apatites are common accessory phenocryst phases as would be expected from their potassic alkaline nature the volcanic rocks of the golcuk area contain high amounts of lile ba sr rb and k lree and zr concentrations of compatible elements such as cr ni and v are very low possibly indicating fractionation of olivine and clinopyroxene correlation of sio2 rb sr and mgo with 87 sr 86 sr 0 703506 0 704142 exhibit an increasing trend in the direction of crustal contamination however the isotopic compositions of sr are not as high to indicate a high level of crustal contamination geochemical data are consistent with the derivation of golcuk volcanic rocks from a metasomatized and or enriched lithospheric mantle source during crustal extension in the area this metasomatism was probably occurred by fluids released from the northward subduction between african and eurasian plates during tertiary as the golcuk volcanic rocks display features of island arc magmas with having high ba nb 28 ratios and nb and ti depletions lower pliocene volcanism in the golcuk was response to extensional tectonics

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

a dynamical model of high latitude convection derived from superdarn plasma drift measurements 1 a discrete set of climatological patterns of high latitude ionospheric convection are derived using line of sight plasma drift data from the super dual auroral radar network superdarn the patterns are derived independently for the northern hemisphere and southern hemisphere and for varying solar wind interplanetary magnetic field imf and dipole tilt angle conditions by interpolating between discrete patterns a dynamical model of convection is obtained which can uniquely specify the high latitude electrostatic potential distribution for a wide range of solar wind imf and dipole tilt parameter values accounting for solar wind velocity dependencies in convection leads to better resolving the large scale convection pattern as compared to previous statistical models based on superdarn data it is shown that the mesoscale features of the climatological model compare favorably to the features seen in instantaneous patterns of convection observed with superdarn comparison of the model to other statistical or empirical models derived from ground and space based measurements shows good agreement with most models

the 40ar 39ar age of extensional ductile deformation and granitoid intrusion in the northern menderes core complex implications for the initiation of extensional tectonics in western turkey the simav detachment fault in the northern part of menderes core complex in western turkey separates cover sequence rocks with brittle deformation from high grade metamorphic core rocks and young granitoid intrusions the timing of shear zone formation and the intrusion of syn tectonic granitoids is constrained by 40ar 39ar geochronology on muscovite from mylonitic gneiss and biotite from the egrigoz granitoid 40ar 39ar data indicate that mylonitic deformation occurred at 22 86 0 47 ma whilst the cooling age of the granitoid is 20 19 0 28 ma the intrusion and cooling of the egrigoz granitoid occurred between 23 20 ma these data demonstrate that extensional deformation in the northern menderes core complex began before early miocene times and represents an early stage in the tertiary extensional tectonics of western turkey

the large scale current system during auroral substorms we present an empirical model of the equivalent current system in the ionosphere during the peak of a classical bulge type auroral substorm this model is derived from measurements made by 110 ground magnetometer stations during 116 substorms the data are temporally and spatially organized using global auroral images obtained by the polar visible imaging system earth camera the empirical equivalent current system displays three key features a poleward shift of the westward electrojet connecting the postmidnight and premidnight components a polar cap swirl and significantly different magnitudes of the postmidnight and premidnight westward electrojets this leads us to propose a two wedge current system linking the ionosphere to the magnetosphere the bulge current wedge is located in the premidnight region just equatorward of the open closed field line boundary while another three dimensional current system is located in the postmidnight region well within the auroral oval we use biot and savart calculations and tsyganenko mapping and show that this new model is a likely solution for the large scale current system

altitude adjusted corrected geomagnetic coordinates definition and functional approximations analysis of the functional approximations used to transform between geo graphic and altitude adjusted corrected geomagnetic aacgm coordinates reveals that errors of 50 km can occur in the auroral and polar regions these errors are the result of efforts to better approximate aacgm coordinates near the magnetic equator and the south atlantic anomaly in these regions aacgm coordinates are not defined and alternate coordinates have been used this augmentation and emphasis on the so lution in regions near the equator result in spherical harmonic approximating functions that are less accurate than need be in the auroral and polar regions in response a new set of spherical harmonic coefficients have been derived that better represent aacgm coordinates in these regions these new aacgm coefficients are limited to below 2000 km in altitude in order to ensure accuracy for altitudes above 2000 km a magnetic field line tracing solution is recommended a software package developed to take advantage of the new aacgm coefficients provides the capability of tracing magnetic field lines at any altitude for improved accuracy in addition linear interpolation between 5 year epochs is used to produce coordinates that vary smoothly over the entire period from 1965 present the intent of this work is to provide a more accurate procedure for de termining aacgm coordinates in the auroral and polar regions for the study of mag netospheric and ionospheric processes

cosmic ray exposure dating with in situ produced cosmogenic 3he results from young hawaiian lava flows in an effort to determine the in situ production rate of spallation produced cosmogenic 3 he and evaluate its use as a surface exposure chronometer we have measured cosmogenic helium contents in a suite of hawaiian radiocarbon dated lava flows the lava flows ranging in age from 600 to 13 000 years were collected from hualalai and mauna loa volcanoes on the island of hawaii because cosmic ray surface exposure dating requires the complete absence of erosion or soil cover these lava flows were selected specifically for this purpose the 3 he production rate measured within olivine phenocrysts was found to vary significantly ranging from 47 to 150 atoms g 1 yr 1 normalized to sea level although there is considerable scatter in the data the samples younger than 10 000 years are well preserved and exposed and the production rate variations are therefore not related to erosion or soil cover data averaged over the past 2000 years indicate a sea level 3 he production rate of 125 30atoms g 1 yr 1 which agrees well with previous estimates the longer record suggests a minimum in sea level normalized 3 he production rate between 2000 and 7000 years 55 15atoms g 1 yr 1 as compared to samples younger than 2000 years 125 30 atoms g 1 yr 1 and those between 7000 and 10 000 years 127 19atoms g 1 yr 1 the minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength as indicated by archeomagnetic data however the production rate variations a factor of 2 3 0 8 are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples calculations using the atmospheric production model of o brien 1979 35 and the method of lal and peters 1967 11 predict smaller production rate variations for similar variation in dipole moment a factor of 1 15 1 65 because the production rate variations archeomagnetic data and theoretical estimates are not well determined at present the relationship between dipole moment and production rate will require further study precise determination of the production rate is an important uncertainty in the surface exposure technique but the data demonstrate that it is feasible to date samples as young as 600 years of age providing that there has been no erosion or soil cover therefore the technique will have important applications for volcanology glacial geology geomorphology and archaeology

chemical and isotopic analyses of hydrocarbon bearing fluid inclusions in olivine rich rocks we examined the mineralogical chemical and isotopic compositions of secondary fluid inclusions in olivine rich rocks from two active serpentinization systems the von damm hydrothermal field mid

conditions of diamond growth a proton microprobe study of inclusions in west australian diamonds crystalline primary inclusions in diamonds from the argyle and ellendale lamproites have been analyzed for mn ni cu zn ga pb rb sr y zr nb ta ba and mo by proton microprobe eclogite suite inclusions dominate at argyle and occur in equal proportions with peridotite suite inclusions at ellendale eclogitic phases present include garnet omphacitic clinopyroxene coesite rutile kyanite and sulfide eclogitic clinopyroxenes are commonly rich in k and contain 300 1060 ppm sr and 3 70 ppm zr k rb increases with k content up to 1400 at 0 7 1 1 k rutiles have high zr and nb contents with zr nb 1 5 4 and nb ta 16 of the peridotite suite inclusions olivine commonly contains 10 ppm sr and mo cr pyropes are depleted in sr y and zr and enriched in ni relative to eclogitic garnets

he ar and c isotopes in coated and polycrystalline diamonds helium ar and c isotopic measurements have been undertaken on different qualities of industrial grade and polycrystalline diamond from localities in africa and brazil these include coated and cloudy diamonds which contain abundant volatile rich micro inclusions and framesites and carbonados which consist of aggregates of micron sized diamond crystals interspersed with mineral inclusions in an attempt to release selectively the primary trapped he from the diamonds they were analysed using an in vacuo crushing technique the he data are combined with ar k and u data obtained from 40ar 39ar stepped heating studies of irradiated fractions of the diamonds and bulk carbon isotope data obtained from the crushed residues results indicate that coated and cloudy diamonds best preserve a mantle signature with 3he 4he values of 1 7 ra and 13c of 5 to 6 coated diamonds have uniformly high he and ar concentrations of 10 6 10 5 cm3 g 1 framesites have lower 3he 4he values 0 1 3 ra and bimodal 13c values with modes at 6 and 20 carbonados show both the lowest 13c values 25 and 3he 4he of 0 1 ra u and k concentrations show a progressive increase from coats framesites carbonados while it is tempting to attribute low 13c low 3he 4he and high u to the influence of subducted crustal material it is likely that implantation of 4he by u th rich minerals adjacent to the micro diamonds is also a possible cause of the low he isotope ratios

high precision 40ar 39ar dating of oligocene rhyolites from the mogollon datil volcanic field using a continuous laser system replicate 40ar 39ar analyses of sanidine from seven oligocene 28 2 ma rhyolite flows using a continuous laser dating system routinely yield analytical precisions of less than 0 45 1s on samples smaller than 0 5 mg this is as good or better than has been obtained by any other method even though the sample mass is several orders of magnitude smaller the system has the potential of resolving differences in apparent age of as little as 0 2 for high k ca samples as young as a few ma the analyses suggest that the seven volcanic units analyzed were erupted in an interval of about 0 1 m y or less

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

petrology and geochemistry of augite trachytes and porphyritic trachytes from the golcuk volcanic region isparta sw turkey a case study abstract the plio quaternary alkaline volcanic rocks at golcuk isparta sw turkey include older porphyritic trachytes augite trachytes and younger trachyandesitic and tephriphonolitic dikes in order to better understand their pre eruptive evolution the geochemical variations of porphyritic trachytes and augite trachytes have been modeled quantitatively using the melts algorithm ghiorso and sack 1995 their geochemical variations are also compared with those of the younger series results show that two distinct magma series trachyte trachyandesite and tephriphonolite governed the petrogenesis of golcuk volcanic rocks geochemistry of the trachytic trachyandesitic series is controlled predominantly by clinopyroxene and plagioclase fractionation at a shallow depth under oxygen fugacity conditions two units above the qfm buffer melts calculations also show that the crystallisation of trachytic trachyandesitic magma produces clinopyroxene plagioclase alkali feldspar biotite apatite and magnetite quartz consistent with the mineralogy of the augite trachyte porphyritic trachyte and trachyandesitic dikes

koroglu caldera mid west anatolia turkey volcanological and magmatological evolution abstract the koroglu caldera is a result of the eruption of seydiler ignimbrites which have been emplaced in two sequences known as lower seydiler ls and upper seydiler us the koroglu caldera measures 13 km 18 km contains a resurgent dome in the center and produced low aspect ratio ignimbrites which have been transported up to 50 km away from the source the ignimbrites show argillaceous weathering which decreases from the bottom towards the top of the deposits such a transition from ignimbrites to reworked tuffs indicates the development of a lacustrine environment over the ignimbrites spot image analysis shows that tectonic activity continued after the caldera collapse two main trends of tectonic elements ne sw and nw se have been distinguished the latter being the younger a nw se striking fault was used by lamprophyric magmas which were extruded into the post ignimbrite lacustrine deposits the lava flows and dikes trachybasalte trachyandesite also occur along the ring fractures of the caldera the dikes are composed of olivine phlogopite cr diopside salite k feldspar ba feldspar hyalophane the lava flows contain scarce cognate inclusions

a new tool for determining ionospheric currents from magnetic satellite data an algorithm for determining ionospheric currents at high latitudes from magnetic measurements made by low altitude satellites is presented and illustrated using magsat data the ionospheric currents are assumed to flow in a height of 115 km perpendicular to the orbit plane of the satellite which corresponds to east west direction in the case of the dawn dusk magsat orbit the method allows for studying the time development of both the strength and the location of the auroral electrojets application to 13 days of magsat data in winter 1979 yields a correlation coefficient of r 0 88 between the ae index and the strength of the auroral electrojets their latitudinal location moves southward with increasing magnetospheric ring current as measured by the dst index

dependencies of high latitude plasma convection consideration of interplanetary magnetic field seasonal and universal time factors in statistical patterns 1 the database of the nine radars of the super dual auroral radar network superdarn in the northern hemisphere has been analyzed for information on factors that influence the convection of plasma in the high latitude ionosphere the velocity measurements were collected over the period 1998 2002 the data were first used to derive a new statistical model of convection that improves upon the earlier one radar model of ruohoniemi and greenwald 1996 in its specification of the dependence of the convection pattern on the magnitude and direction of the imf in the gsm y z plane we then derived average patterns for secondary sortings by season year and radar such dependencies as emerged were most clearly seen by contrasting the results for by and by the seasonal effect in the convection pattern is found to have similarities to that of the sign of by in particular the combination of by summer by winter reinforces the tendency of the by sign factor to sculpt the dusk and dawn cells into more round crescent crescent round shapes and to shift the crescent cell across the midnight mlt meridian however these combinations are associated with lower estimates of the total cross polar cap potential drop pc while the nonreinforcing combinations produce elevated pc especially by summer there is an overall tendency for pc to increase from winter to summer although the pure seasonal effect on the potential drop is weaker than that of the by sign season factor we did not find pronounced differences among the patterns derived for the 5 individual years which spanned the most recent interval of solar cycle maximum sorting by radar we found few differences among the patterns for by but for by variations emerged that are consistent with a possible dependence on universal time ut the impacts of season and ut on convection in the high latitude ionosphere thus depends on the imf especially the sign of by we speculate that variability in the ionospheric conductivity has a greater effect on magnetosphere ionosphere coupling under by conditions

cosmogenic 10be in zaire alluvial diamonds implications for 3he contents of diamonds to determine the amounts of cosmic ray produced cosmogenic 3he which could be created in diamonds during their post eruptive residence in near surface regions we have measured the concentration of 10be half life 1 6 myr in an industrial diamond sample the motivation to study cosmogenic 3he in diamonds comes from the recent observations1 2 of 3he 4he ratios in some diamonds that are even higher than meteoritic values so called planetary helium with 3he 4he 1 4 10 4 we measured 10be in an alluvial diamond sample using radiochemical and accelerator mass spectrometry ams techniques the observed 10be concentration 2 46 0 39 106 atoms g 1 leads to an effective surface exposure of 3 3 105 yr for these diamonds this corresponds to a substantial cosmogenic production of 3he in the alluvial diamonds 29 of the total 3he we conclude that the high 3he 4he ratios in at least some diamonds are due to cosmogenic 3he production in near surface regions during their residence in alluvial or weathering deposits thus in order to establish that such high 3he 4he ratios existed in the mantle at one time it is a priori necessary to study diamonds collected by underground mining methods

an important source of4he and3he in diamonds a large data base has recently accumulated on the concentrations of helium isotopes in diamonds mined from various regions it was noted earlier ozima et al 1985 1 lal et al 1989 2 that the frequency distribution of the4he concentrations is a fairly narrow one whereas that of3he concentrations is a broad one with no pronounced peaks the ratios 3he 4he on the other hand show a broad maximum around 2 ra ra equals atmospheric 3he 4he ratio 1 40 10 6 with a slow decrease over two orders of magnitude on either side does this imply that the diamonds sample a wide variety of helium reservoirs having a range of 3he 4he ratios but somehow attain similar4he concentrations we propose that in a majority of the diamonds studied 4he is primarily due to implantation of radiogenic alpha particles from the host material after emplacement in the crust usually kimberlite and that the concentrations of4he in diamonds often get appreciably altered by this process thus the4he trapped in the diamond at the time of its crystallization is usually overwhelmed by the implanted helium and the measured 3he 4he ratios do not generally correspond to any sources in the mantle however the implanted4he resides in the outer 16 m of the diamond and the intrinsic4he and 3he 4he ratios in the diamond can be studied if its outer layers are removed the wider implications of diamond being the target material for nuclear reaction products from the host material are discussed radiogenic3he produced in the host material is also implanted in the diamond but this contribution is small on a gross basis however since the depth of implantation of3he is greater than that of4he some of the very high 3he 4he ratios observed in diamonds could be due to the implantation of radiogenic3he the radiogenic reactions in the host material can also contribute to appreciable21ne in diamonds

3he in diamonds the cosmogenic component abstract we have measured 3 he and 4 he concentrations in a number of diamonds received directly from mines as well as in industrial samples none of our diamonds recovered from underground mining has a 3 he 4 he ratio r exceeding 3 r a r a atmospheric 3 he 4 he ratio 1 40 10 6 one of the five diamonds from the consolidated diamond mine cdm 5 an alluvial deposit has a ratio of 142 r a based on a number of facts i the zaire alluvial diamonds have 29 cosmogenic 3 he ii some documented high 3 he 4 he ratio diamonds are from alluvial mines and iii the apparent diffusion coefficients of 3 he and 4 he in diamonds are ten orders of magnitude too large to preserve diamond helium ratios in the mantle we conclude that ozima s hypothesis ozima et al 1983 of high primordial 3 he 4 he ratios in diamonds exceeding morb ratios is not required the present data are readily explainable as the result of cosmogenic and nucleogenic production of 3 he within the diamonds

implanted radiogenic and other noble gases in crustal diamonds from northern kazakhstan noble gases were extracted in steps from grain size fractions of microdiamonds 15 m the concentration also decreases with the combustion step both results are clear evidence that 4he has been implanted into the diamonds from decaying elements in the surrounding matrix the saturation concentration of 4he 5 6 10 4 cm3 stp g is among the very highest observed in any terrestrial diamonds fission xenon from the spontaneous fission of 238u accompanies the radiogenic 4he the 136xef 4he ratio of 2 5 0 3 10 9 agrees well with the production ratio of 2 3 10 9 expected in a reservoir where th u 3 3 radiogenic 40ar is predominantly 90 set free upon combustion it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation 3he on the other hand is mainly released during pyrolysis and hence is apparently carried by contaminants the concentration in the diamonds proper is of the order of 4 10 12 cm3 stp g with a 3he 4he ratio of 1 10 8 excess 21ne similarly appears to be present in contaminants as well as in diamonds proper these two nuclides in the contaminants must have a nucleogenic origin but it is difficult to explain their high concentrations

helium and carbon isotopes in indian diamonds we report the first helium and carbon isotopic measurements for indian diamonds the helium concentrations and isotope ratios in ten diamonds from documented sites in andhra pradesh are generally in the ranges of values for diamonds from other locations five samples are alluvial from various sites in the krishna river gravels the rest were mined from three kimberlite pipes despite the limited statistics our results lead to fairly plausible conclusions 1 1 most of the 3he in the alluvial diamonds is of cosmogenic origin and 2 2 the alluvial diamonds may also have a significant 4he component due to implantation of particles during storage in a secondary matrix conglomerates and or alluvium carbon isotope ratios in these diamonds are within the normal mantle range 13c 4 to 7 plus one sample at 10 except for a single sample the only spectral type ii diamond which has 13c 26 5 this sample a mined kimberlite specimen has the lowest 4he content so far recorded in diamonds 0 018 cc g

high k volcanism in the afyon region western turkey from si oversaturated to si undersaturated volcanism volcanic rocks of the afyon province eastern part of western anatolia make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 ma the early stage si oversaturated volcanic rocks around the afyon city and further southward are trachyandesitic volcanic activity 14 23 0 09 ma late stage si undersaturated volcanism in the southernmost part of the afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages melilite leucitites 11 50 0 03 ma spotted trachyandesites tephryphonolites and lamproites 11 91 0 13 ma formed in the first episode trachyandesites in the second episode and finally phonotephrites phonolite basaltic trachyandesites and nosean bearing trachyandesites during the last episode the parameter q normative q ne lc kls ol of western anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10 15 ma the magmatism experienced a sudden change in the extent of si saturation after 14 ma during late stage volcanic activity of afyon volcanic province at around 12 ma though there was some coexistence of si oversaturated and si undersaturated magmas during the whole life of afyon volcanic province

solar wind control of ionospheric equivalent currents and their time derivatives a solid understanding of the solar wind control of ground magnetic field disturbances is essential for utilizing the existing long time series of ground data to obtain information on solar wind magnetosphere ionosphere coupling we have used 20 years of international monitor for auroral geomagnetic effects magnetometer data 54 76 magnetic latitude to study the solar wind control of the ionospheric equivalent current density and its time derivative we found that peaks at the premidnight and prenoon ends of the westward electrojet the prenoon peak was most intense during fast solar wind and radial interplanetary magnetic field imf the location of the peak was not affected by the imf orientation but persisted at 8 10 magnetic local time and 70 75 latitude near the boundary between the westward and eastward electrojets sensitivity of this boundary to disturbances was suggested as a possible explanation for the persistent prenoon location of the peak the premidnight peak was most intense during southward imf orientation while faster solar wind mainly resulted in more intense in the premidnight sector stronger imf caused the region of intense to spread to the postmidnight dawn and dusk sectors a good correspondence was found between development of the nightside intensification and average substorm bulge and oval aurora as determined by gjerloev et al 2007 the bulge aurora covered the western end of the westward electrojet where the equivalent current also had a significant poleward component the substorm oval aurora on the other hand extended eastward along the westward electrojet

helium isotopic evidence for a lower mantle component in depleted archean komatiite archean magnesium rich komatiites require hot and presumably deep mantle sources but their trace element composition and radiogenic isotope composition are similar to those of modern mid ocean ridge basalts which originate in the upper mantle the isotopic composition of helium extracted by sequential crushing of fresh olivines separated from two archean and one mid proterozoic komatiites varies over three orders of magnitude between a radiogenic end member rich in helium 4 and a component rich in helium 3 such helium 3 enrichment suggests the presence of a lower mantle component in archean komatiites

the radial distribution of implanted and trapped 4he in single diamond crystals and implications for the origin of carbonado abstract we have investigated variations of 4 he content in the different zones of single natural diamond crystals using a step combustion technique the results indicate that some diamonds may be strongly irradiated during their residence in the earth s crust since concentrations of 4 he in the 30 m outer layer were found to be as high as 0 014 cm3 g the observation leads to a conclusion that similarly high 4 he concentrations in carbonado diamonds do not necessary demand an exotic origin previous theoretical estimations of the magnitude of he implantation in diamonds which use normal u th concentrations of ca 30 ppm in the surrounding rocks do not agree with experimentally obtained results the he concentrations actually found in the skins outer 30 m layer of the crystals of the samples we studied require concentrations of u and th in the host rock from 160 ppm to 1000 ppm the interiors of the samples have also been analysed and exhibited 4 he concentrations from 3 10 7 cm3 g to 2 10 5 cm3 g indicating heterogeneity even within single diamond crystals and arguing for the changes in the growth environment from 4 he zoning within a diamond from the finsch kimberlite a maximum 4 he diffusion coefficient was estimated to be 4 10 21 cm2 s lower than previous estimates indicating that diamond may retain indigenous 4 he in the structure during its residence under mantle pt conditions

helium isotopic variability within single diamonds from the orapa kimberlite pipe abstract the distribution and isotopic composition of helium has been measured in a suite of well characterized one carat diamonds from the orapa kimberlite botswana crushing of the diamonds in vacuo indicates that most of the helium is contained by the matrix generally greater than 90 rather than by the inclusions step heating experiments performed on inclusion free fragments remaining after crushing indicate that the3he 4he ratio is variablewithin individual diamonds the fragments as small as 10 mg were heated in two timed steps both at 2000 c in every case lower3he 4he ratios are observed in the first graphitization step 0 05 3 atmospheric while the last heating step releases helium with systematically higher3he 4he ratio 30 80 atmospheric we suggest that this internal isotopic variability is the result of stepwise graphitization the first heating step initiates graphitization which nucleates around defects and the second heating step graphitizes the relatively defect free regions of the diamond the3he 4he ratio measured using the partial graphitization technique differs by up to a factor of 100 within a single specimen the inclusion free fragments release small quantities of helium below 2000 c which suggests that helium release is obtained only by graphitization the3he contents of the monocrystalline diamonds are relatively constant at 3 10 13 cm3 stp gram and indicate that most of the isotopic variability is due to radiogenic4he the variations in4he content are either related to zoning of th and u in the diamonds i e in situ decay to zoning of inherited4he or to implantation of particles from a th and u rich environment i e kimberlite because the orapa diamonds were mined from roughly 40 m depth in the kimberlite spallation reactions from cosmic ray interactions are not a significant source of3he however calculations based on the age of the kimberlite 90 m y and reasonable th and u abundances suggest that most of the3he in the orapa diamonds could be produced by6li n t in the diamond although this may not be true of all diamonds nuclear reactions in the crust and mantle including spallation reactions at the surface can explain many of the high3he 4he ratios previously reported for diamonds

noble gas state of the ancient mantle as deduced from noble gases in coated diamonds cores and coats of five coated diamonds one from botswana and four from zaire were separately analyzed for their noble gases noble gases in the diamonds are essentially of a trapped origin including radio and nucleogenic components such as4he 40ar 21neexcess and excesses in xe isotopes 129 131 136 the fairly precise elemental and isotopic abundances allow us to infer the noble gas state in the ancient mantle 20ne 22ne ratios are fairly constant 11 8 0 4 and very close to that of sep solar energetic particle ne but distinctly different from the atmospheric ratio 21ne 22ne ratios range from 0 028 to 0 06 which is attributed to nucleogenic 21ne from 18o n 21ne and 24mg n 21ne reactions the difference in 20ne 22ne between atmosphere and mantle can be attributed to the hydrodynamic escape of hydrogen from the primitive atmosphere during the very early stage in the earth s history 38ar 36ar and kr isotopic ratios are identical to the atmospheric values within 1 after correction for 238u or 244pu fission xe the 131 136xe abundance ratios are indistinguishable from atmospheric ratios lighter xe isotopes 124 128xe are also likely to be atmospheric but a final conclusion must wait until better data are obtained in a 136xe 130xe 129xe 130xe diagram diamond data lie on the same line as defined for morb the observed identical correlation for both diamonds and morb s appears to suggest that the progenitor of the excess131 136xe is 244pu but not238u though the direct xe isotopic measurements was not precies enough to decide unanimously the progenitor

k richterite olivine phlogopite diopside sanidine lamproites from the afyon volcanic province turkey middle miocene volcanic activity in the afyon volcanic province eastern part of western anatolia is characterized by multistage potassic and ultrapotassic alkaline volcanic successions the volcanism is generally related to the northward subduction of the african plate beneath the eurasian plate in afyon the middle miocene volcanic products consist of melilite leucitite tephriphonolite trachyte basaltic trachyandesite phonolite phonotephrite tephriphonolite and lamproite rocks near surface emplacement and relatively quiescent subaerial eruptions of lamproitic magma produced different emplacement forms such as dome plug shaped bodies and lava flows showing variation in volume and texture the mineralogical constituents of the lamproites are sanidine olivine 77 mg no 81 phlogopite 74 mg no 78 k richterite clinopyroxene 74 mg no 78 with accessory apatite calcite and opaque minerals afyon lamproites resemble mediterranean type si rich lamproites their compositional range is 50 52 wt sio2 4 8 wt mgo and they display a typical lamproitic affinity chondrite normalized ree patterns exhibit enrichment in lree relative to hree la yb cn 15 3 17 0 they show extreme enrichment in lile relative to primitive mantle values and troughs of nb and ti the lamproites give a range of high initial 87sr 86sr ratios and low 143nd 144nd ratios the geochemical and isotopic characteristics suggest that lamproitic magma is derived from highly metasomatized mantle the enrichment history may include metasomatic events related to subduction as in other active orogenic areas of the mediterranean

surface exposure chronology using in situ cosmogenic 3he in antarctic quartz sandstone boulders abstract in situ produced cosmogenic helium 3 he c provides a new tool for constraining histories of quaternary geomorphic surfaces before general application of the technique however the systematics and production rates of 3 he c must be well understood in a companion study 3 he and 10 be data from sandstone and granite boulders in the dry valleys region of antarctica have been used to constrain the ages of an important moraine sequence formed by the taylor glacier data from these deposits also provide information about the systematics of 3 he in quartz that has important implications for geochronology based on 3 hec in contrast to previous results from olivine and clinopyroxene crushing quartz in vacuo releases helium with high 3 he 4 he ratios up to 148 r a where r a is the atmospheric 3 he 4 he ratio indicating that crushing cannot be used to determine the isotopic composition of trapped i e noncosmogenic helium in quartz analysis of 3 he in different size fractions of the same samples indicates significant 3 he loss not predicted by existing 3 he diffusion data for quartz the origin of the discrepancy is not clear but loss from these samples is not as significant as suggested by the limited data of previous studies

3he4he ratio noble gas abundance and k ar dating of diamonds an attempt to search for the records of early terrestrial history the 3he4he ratios measured in 27 southern africa diamond stones four from premier mine and the rest of unidentified origin range from 4 2 10 8 to 3 2 10 4 with three stones above 1 10 4 we conclude that the initial helium isotopic ratio 3he4he 0 in the earth was significantly higher than that of the planetary helium a 3he4he 1 42 10 4 but close to the solar helium 3he4he 4 10 4 the apparent k ar ages for the twelve diamonds of unidentified origin show enormously old age indicating excess argon 40 3he4he evolution in diamonds suggests that the diamonds with the high 3he4he ratio 2 10 4 may be as old as the earth noble gas elemental abundance in the diamonds relative to the air noble gas abundance shows monotonie decrease with a decreasing mass number this paper discusses the implications of these observations on the early solar system and the origin of diamonds

primordial and recycled helium isotope signatures in the mantle transition zone isotope compositions of basalts provide information about the chemical reservoirs in earth s interior and play a critical role in defining models of earth s structure however the helium isotope signature of the mantle below depths of a few hundred kilometers has been difficult to measure directly this information is a vital baseline for understanding helium isotopes in erupted basalts we measured he sr pb isotope ratios in superdeep diamond fluid inclusions from the transition zone depth of 410 to 660 kilometers unaffected by degassing and shallow crustal contamination we found extreme he c pb sr isotope variability with high 3he 4he ratios related to higher helium concentrations this indicates that a less degassed high 3he 4he deep mantle source infiltrates the transition zone where it interacts with recycled material creating the diverse compositions recorded in ocean island basalts