crystallization environment of kazakhstan microdiamond evidence from nanometric inclusions and mineral associations nanometric solid inclusions in diamond incorporated in garnet and zircon from felsic gneiss of the kokchetav massif kazakhstan have been examined utilizing electron microscopy and focused ion beam techniques host garnet and zircon contain numerous pockets of multiple inclusions which consist of 1 3 diamond crystals intergrown with quartz phengite phlogopite albite k feldspar rutile apatite titanite biotite chlorite and graphite in various combinations recalculation of the average chemical composition of the entrapped fluid represented by multiple inclusion pockets indicates that such fluid contained a low wt of sio2 suggesting a relatively low temperature fluid rather than a melt transmission electron microscopy revealed that the diamond contains abundant nanocrystalline inclusions of oxides rare carbonates and silicates within the 15 diamond crystals studied abundant inclusions were found of sio2 tio2 f e xoy c r 2o3 zrsio4 and single grains of thxoy baso4 mgco3 fecr2o4 and a stoichiometric fe rich pyroxene the diversity of trace elements within inclusions of essentially the same stoichiometry suggests that the kokchetav diamond crystallized from a fluid containing variable amounts of si fe ti cr zr ba mg and th and other minor components such as k na p s pb zn nb al ca cl most of the components in crystals included in diamond appear to have their origin in the subducted metasediments but some of them probably originate from the mantle it is concluded that kokchetav diamond most likely crystallized from a coh rich multicomponent supercritical fluid at a relatively low temperature hence the apparently low content of rock forming elements and that the diversity of major and minor components suggests interactions between subducted metasediments and mantle components

nanometric inclusions of carbonates in kokchetav diamonds from kazakhstan a new constraint for the depth of metamorphic diamond crystallization abstract previous studies have revealed that microdiamonds from the kokchetav ultra high pressure metamorphic terrane of kazakhstan contain nanometric scale inclusions of si fe ti and cr oxides because the structure of sio 2 inclusions was not confirmed to be coesite or stishovite due to their very small size such diamonds formerly served only as an indicator of a minimum pressure ca 4 gpa geothermobarometry applied to kokchetav diamond bearing rocks yielded a wide range of conditions t 700 c 1250 c and p 4 9 gpa our paper presents transmission electron microscopy studies with focused ion beam assistance that indicate that diamonds from marbles contain inclusions of aragonite caco 3 and magnesite mgco 3 and that aragonite and nitrogen bearing nanometric particles are associated with dislocations reflecting diamond growth at relatively high temperature conditions we determined the boundary of dolomite stability using the reaction camg co 3 2 dolomite caco 3 aragonite mgco 3 this allowed us to utilize available experimental data to evaluate the pressure at which diamond was crystallized taking into consideration uncertainties existing between experimental data produced in different laboratories we propose the pressure for kokchetav diamond crystallization to be 6 to 9 gpa this evaluation is based on the assumption that temperature was determined correctly as 980 c minimum and 1250 c maximum for diamond grade dolomitic marbles our data provide strong evidence that the metasedimentary rocks of the kokchetav massif containing diamonds were subducted to the depth of 190 280 km

internal wave observations from flip in mildex abstract during 0ctober november 1983 the research platform flip participated in the mixed layer dynamics experiment mildex off the coast of southern california included among the equipment on board was an array of six doppler sonars and a repeatedly profiling ctd the sonars operate at frequencies between 67 and 80 khz with peak transmitted power of order 2 kw each four of the sonars were directed downward 53 obtaining velocity profiles to depths in excess of 1100 m the ctd was profiled to a depth of 320 m every 3 minutes approximately 6000 ctd profiles were obtained during mildex the mildex internal wavefield is slightly less energetic than the garrett munk canonical standard except in the near inertial frequency band here very low energy levels are seen the semidiurnal baroclinic tide dominates the spectra of both horizontal and vertical velocity in this work slant velocity estimates from back to back sonar beam are combined to form estimates of horizontal velocity and its vertical der

direct observation and analysis of a trapped coh fluid growth medium in metamorphic diamond the mechanism by which diamonds grow in earth s mantle has been a subject of discussion for many years arguments have been advanced for growth from a melt from a coh fluid and in the solid state the discovery of microdiamonds within ultra high pressure terranes of continental collision settings re energized this debate because of their very different but well defined continental crust environment we report here the discovery of filled nanometric fluid bubbles in diamonds from marble of the kokchetav massif kazakhstan and the serendipitous measurement of their contents due to bursting of a bubble very shortly after a measurement of chemical composition in the transmission electron microscope thereby allowing immediate re analysis with exactly the same settings of all parameters of the microscope the chemical composition of the fluid is c h o cl s ca fe and k the direct observation and composition of a low viscosity trapped fluid in microdiamond unambiguously establish their fluid growth medium

observations of energetic high wavenumber internal waves in the kuroshio abstract intense and spatially coherent shear layers were detected in and under the kuroshio in an april 2000 survey in the east china sea the sloping layers revealed by shipboard doppler sonars on the r v roger revelle appeared to cross isopycnal surfaces except in a small region near the kuroshio shelfbreak front the rms finescale shear associated with the layers significantly exceeded the geostrophic shear an april 2002 follow on cruise was organized to establish whether these motions were propagating internal waves shipboard and lowered adcps were both operated from the r v melville in addition to ctd sonar transects a 30 h time series of currents and shear was obtained in the core of the kuroshio near the island of kyushu japan the shear structures were indeed found to be propagating with both up and down going internal wave motions present in comparison with the nearby open ocean the finescale 160 m vertical shear variance is increased by a factor of 3 in the kuroshio and by a fact

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

ultrahigh pressure minerals and metamorphic terranes the view from china abstract ultrahigh pressure uhp metamorphism refers to mineralogical modifications of continental and oceanic crustal protoliths associated mafic ultramafic rocks initially formed or emplaced in shallow levels of the lithosphere but which subsequently have experienced p t conditions within or above the coesite stability field 2 7 gpa 700 c typical products include eclogite garnet peridotite and uhp varieties of metapelite quartzite marble paragneiss and orthogneiss uhp metamorphic assemblages require relatively cold lithospheric subduction to mantle depths some recrystallization even occurs under forbidden p t conditions characterized by a geotherm of the current explosion of research on continental uhp terranes reflects their significance for mantle dynamics and the tectonics of continental subduction collision exhumation mantle slab interactions and geochemical recycling a further characterization of uhp phases and positive identification of uhp minerals requires new experimental studies coupled with state of the art analyses for example the very rare occurrence of microdiamond inclusions in zircons from dabie sulu uhp rocks may reflect high f o 2 attending recrystallization inasmuch as epidote is rather common rutile needles within garnets from sulu uhp eclogitic rocks may not be the result of exsolution so in such cases the apparent uhp pressure may have been over estimated hadean igneous microdiamond inclusions in jack hills detrital zircons could have originated from mantle xenoliths whereas abundant detrital phanerozoic diamonds containing inclusions of coesite and other eclogitic minerals from new south wales might have been derived from unexposed uhp metamorphic terranes micro mineral intergrowth and nano size minerals may hold important key to deciphering the actual p t paths of subduction and mantle return flow although most exhumed terranes have returned surfaceward relatively rapidly after short time of uhp condition the long duration of storage at great depth and slow exhumation for the largest uhp terranes remain as major problems

transmission electron microscope observation of the high pressure form of magnesite retrieved from laser heated diamond anvil cell abstract we applied focused ion beam fib technique to make a thin foil for transmission electron microscope tem observations of mgco3 magnesite and its new high pressure form magnesite ii recovered from laser heated diamond anvil cell lhdac both of which should play fundamental roles in the circulation of carbon in the lower mantle heterogeneous microstructures due to significant temperature gradients were observed along the axial direction of the disk sample 100 m in diameter and 30 m thick in spite of double sided laser heating and the use of thermal insulators between the diamond anvil and the sample the central portion of the mgco3 sample was found amorphous while the peripheral part remained magnesite on the basis of electron diffraction measurements with tem this and our earlier results based on in situ x ray diffraction measurements suggest that magnesite transformed to magnesite ii only at the central part where the temperatures should have been significantly higher than those near the pressure medium magnesite ii was amorphisized on release of pressure in contrast to our interpretation that it was converted back to magnesite based solely on in situ x ray diffraction measurements the new method of combining the fib technique with tem observation thus provides important information on phase transitions under very high pressure using lhdac which may be overlooked by in situ optical and x ray diffraction measurements

nanometer size p k rich silica glass former melt inclusions in microdiamond from the gneisses of kokchetav and erzgebirge massifs diversified characteristics of the formation media of metamorphic microdiamond in uhp rocks due to host rock buffering abstract nanometer size p k rich silica glass former melt inclusions were identified within metamorphic microdiamonds from garnets of ultrahigh pressure uhp gneisses of the kokchetav and the erzgebirge massifs by analytical electron microscopy aem the chemical characteristics of these inclusions within microdiamonds are surprisingly similar among various gneissic rocks from both kokchetav and erzgebirge but are significantly different from the si poor ultrapotassic fluid inclusions within microdiamonds from garnets of the kokchetav uhp marble these contrasting findings not only provide constraints on the characteristics compositions of the formation media of metamorphic microdiamonds but also imply that the formation media must have been buffered by the hosting rocks resulting in the observed diversities as reported here in addition depending on the rock types and thus on the nature of the formation media from which metamorphic microdiamonds were formed the respective characteristic morphologies of the microdiamonds differ the p k rich silica melt tends to form octahedral or cubo octahedral microdiamonds within garnet in gneissic rocks whereas the si poor ultrapotassic fluid tends to form spheroids cuboid microdiamonds with rugged surfaces within garnet in marble consequently the buffered media in hosting rocks played a decisive role in determining the different morphologies and growth rates mechanisms of metamorphic microdiamonds in general

microdiamond daughter crystals precipitated from supercritical coh silicate fluids included in garnet erzgebirge germany microdiamonds associated with phlogopite quartz paragonite phengite apatite and rutile are found as regular constituents of minute polyphase inclusions in garnet of ultrahigh pressure p metamorphic gneiss lenses within migmatites of the gneiss eclogite unit erzgebirge germany these aggregates are interpreted to represent original inclusions of a supercritical dense coh fluid rich in k na and sio 2 from this fluid diamond was precipitated as a daughter crystal due to cooling at ultrahigh p conditions brittle failure of the garnet host due to overpressure during release of confining pressure is demonstrated by healed radial cracks during further cooling the silicate phase assemblage of the inclusions crystallized at reduced internal pressures outside the stability field of diamond as indicated by the presence of quartz paragonite and plagioclase it is proposed that the mica dominated mineral assemblage of the inclusions formed by reaction between the fluid and the garnet host the previously formed diamond daughter crystals being preserved metastably these diamond bearing inclusions provide an unequivocal record of dense supercritical coh fluids rich in alkalies and silica within subducted continental crust during ultrahigh p metamorphism

hadean diamonds in zircon from jack hills western australia this paper reports the discovery of micro diamond inclusions in zircon from the jack hills western australia which is up to 4 252 million years old and includes the oldest known diamonds found in terrestrial rocks the spread of ages indicates that either the conditions required for diamond formation were repeated several times during early earth history or that there was significant recycling of ancient diamond

very high pressure orogenic garnet peridotites mantle derived garnet peridotites are a minor component in many very high pressure metamorphic terranes that formed during continental subduction and collision some of these mantle rocks contain trace amounts of zircon and micrometer sized inclusions the constituent minerals exhibit pre and postsubduction microstructures including polymorphic transformation and mineral exsolution experimental mineralogical petrochemical and geochronological characterizations using novel techniques with high spatial temporal and energy resolutions are resulting in unexpected discoveries of new phases providing better constraints on deep mantle processes

multiphase solid inclusions in uhp rocks su lu china remnants of supercritical silicate rich aqueous fluids released during continental subduction abstract primary multiphase solid ms inclusions without preserved fluid are found within peak minerals in kyanite quartzite topaz and kyanite phengite epidote eclogite from donghai area su lu terrane typical mineral association in inclusions is paragonite muscovite anhydrite corundum alunite type sulphate zircon calcite chlorite sio 2 barite pyrite apatite in quartzites and paragonite rutile apatite amphibole zn staurolite magnetite plagioclase zircon pyrite alunite type sulphate zn mg fe al ti spinel in eclogites on the basis of the fluid inclusion textures and of the daughter phase assemblage calculated fluid composition is as follows in quartzites 24 wt sio 2 30 wt al 2 o 3 9 wt cao 5 wt k 2 o 3 wt na 2 o 11 wt so 3 18 wt h 2 o with traces of tio 2 fe 2 o 3 feo mgo bao p 2 o 5 cl f and co 3 2 and in eclogites 26 wt sio 2 21 wt tio 2 20 wt al 2 o 3 2 wt mgo 4 wt feo 6 wt fe 2 o 3 7 wt cao 3 wt na 2 o 3 wt p 2 o 5 7 wt h 2 o 1 wt cl and traces of zno mno k 2 o so 3 and f originally trapped chloride poor aqueous fluids contained very high amounts in the order of tens of wt of si 4 al 3 and ti 4 solute species reflect the chemical composition of the host rocks mg 2 fe 2 ti 4 p 5 and na are abundant in the fluids present in eclogites while fluids are enriched in al 3 k na so 4 2 co 3 2 in quartzites we propose that multiphase solid inclusions represent remnants of high density supercritical silicate rich aqueous fluids that were in equilibrium with peak minerals at uhp conditions these fluids show characters which are transitional between aqueous fluids and silicate melts and were probably produced by dehydration reactions of the host rocks during the latest stages of subduction

patterns of shear and turbulence across the florida current abstract measurements by the multi scale profiler msp at seven stations spanning the straits of florida characterize levels and patterns of internal wave activity and mixing in this vertically sheared environment contrasting properties suggest five mixing regimes the largest and most vast is the interior regime where the background flow has an inverse richardson number ri 1 ranging up to 0 55 shear is dominated by fluctuations that are 1 4 times stronger than in the open ocean and turbulent diffusivities are similarly moderate at 1 4 10 5 m2 s 1 the high velocity core of the current near the surface at midchannel is associated with weak mixing to its west is a zone of high mean shear where strong stratification results in background ri 1 of only 0 4 fluctuations are weak and diffusivity is moderate intermittent shear features beneath the core have mean ri 1 1 and strong turbulence two regimes are related to channel topography adjacent to the steep eastern slope finescale shear is

decrepitated uhp fluid inclusions about diverse phase assemblages and extreme decompression rates erzgebirge germany minute polyphase inclusions in garnet of quartzofeldspathic rocks saidenbachite from the saxonian erzgebirge germany contain microdiamond or graphite phlogopite quartz paragonite phengite and other minerals in minor amounts these inclusions are interpreted to represent an original dense coh silicate fluid trapped in crystallizing garnet at depths of 150 km inspection of the inclusion population in a single garnet by sem reveals two characteristic features i the shape of most inclusions indicates healed radial cracks in the host garnet and thus the buildup of a significant differential pressure p i e a contrast in pressure between the inclusion pi and the host mineral pe the mineral assemblages sealing the cracks and showing an equilibrated microstructure indicate temperatures of 750 50 c and pressures below 2 5 gpa ii the diverse types of inclusions appear to be randomly distributed in the garnet host thus the variable phase assemblages do not reflect a compositional evolution of the fluid trapped in the garnet combining observations i and ii we propose that the diversity of the phase assemblage in the inclusions is the result of decrepitation at different times and thus of distinct histories of pi as p at decrepitation is primarily controlled by inclusion size and shape applying a flow law for dislocation creep of garnet a low strength of garnet at 750 50 c for low geological strain rates is predicted thus differential pressure should have been kept low i e pi pe by continuous stretching of the inclusion for typical exhumation rates of metamorphic rocks to attain the differential pressure pi pe required for catastrophic brittle failure of the garnet host the decompression rate must have been extremely high as a robust lower bound a minimum exhumation rate on the order of 100 m year 1 is suggested which corresponds to ascent rates of magma

precipitation of pyroxenes and mg2sio4 from majoritic garnet simulation of peridotite exhumation from great depth our experimental simulations of the exhumation path of mantle peridotites show that high temperature 1400 c decompression of lherzolite from 14 to 13 and 12 gpa results in exsolution of interstitial blebs of diopside and mg2sio4 wadsleyite lamellae from majoritic garnet at lower pressures from 8 to 5 gpa at t 1400 c only enstatite exsolves as blebs at garnet boundaries continuous high temperature decompression from 14 to 7 gpa produces zoned majoritic garnet containing blebs of exsolved pyroxenes inside garnet rims no intracrystalline precipitation of pyroxene was observed in garnet although such lamellae are found in some natural garnet peridotites the explanation appears to be the three orders of magnitude difference in grain size between experimental and natural specimens our data suggest that mg2sio4 and diopside exsolutions reflect the deepest point of the exhumation path of garnet peridotites whereas enstatite precipitation may be restricted to garnets with less majoritic component at shallower depths

westward younging high mg adakitic magmatism in central tibet record of a westward migrating lithospheric foundering beneath the lhasa qiangtang collision zone during the late cretaceous abstract magmatic records with high mg and low y signatures provide important insights into the deep mantle dynamics that dictate the evolution of ancient orogenic belts this paper reports the presence of felsic intrusive dikes with high mg and low y signatures intruding the baingoin batholith central tibet at ca 94 ma these dikes show adakitic signatures including high sr and low y and yb contents and high sr y and la yb n ratios the adakitic dacitic dikes can be grouped into high mg mg 48 52 with positive zircon e hf t 8 3 12 4 and whole rock e nd t 0 27 and low mg mg 37 45 with positive zircon e hf t 7 2 13 5 varieties these distinct geochemical features along with geological observations show that the baingoin high mg adakitic dacitic dikes were most likely derived from the partial melting of a foundering juvenile lower crust and subsequent melt mantle reaction whereas the low mg adakitic dacitic dikes can be interpreted as resulting from the partial melting of a thickened lower crust that did not delaminate the generation of these adakitic rhyolitic dikes can be attributed to hornblende dominated fractional crystallization of the adakitic dacitic melts a decrease in y and heavy rare earth element contents of magmatic records from 120 100 ma to 95 80 ma within the lhasa qiangtang collision zone suggest an increase in crustal thickness with time the volumetrically minor westward migrating high mg adakitic magmatism can readily be interpreted as the consequences of the westward migrating foundering of the lithosphere triggered by rayleigh taylor instabilities along the lhasa qiangtang collision zone during the period 94 80 ma

focused ion beam technique and transmission electron microscope studies of microdiamonds from the saxonian erzgebirge germany a focused ion beam of ga ions is a relatively new technique that has been developed for microelectronic industries now researchers of the earth sciences find it to be a promising tool for studying various geological materials using the fib technique and an fei strata db 235 dual beam system we have successfully prepared several electrontransparent foils which crossed wm sized diamonds included in host minerals such as zircon and garnet from quartzofeldspathic rocks of the saxonian erzgebirge germany scanning and transmission electron microscopy applied to these foils revealed that the diamonds contain crystalline nanometric inclusions these inclusions consist of minerals of known stoichiometries such as sio2 and al2sio5 whereas others are characterized by different combinations of si k p ti and fe in the presence of oxygen stoichiometries are not clear at this stage of research one suite of inclusions is assumed to be represented by archerite kh2po4 which is known to be stable at pressures of 4 22 gpa and one nanocrystal containing pb oxygen and carbon is interpreted to be pbxoy or pbco3 along with solid crystalline inclusions the diamonds contain cavities filled by liquid gas that escaped during sample preparation these are associated with dislocations of diamond growth our data are consistent with the concept of diamond crystallization from a coh rich multicomponent supercritical fluid and suggest that the composition of such a fluid is more consistent with a local crustal source rather than that of a mantle origin 2003 elsevier science b v all rights reserved

a comparison of the evolution of diamondiferous quartz rich rocks from the saxonian erzgebirge and the kokchetav massif are so called diamondiferous gneisses magmatic rocks abstract the petrography and chemical composition of minerals of quartz rich diamondiferous rocks from the kokchetav massif especially the zonation of garnet were studied and compared with diamondiferous quartzofeldspathic rocks from the saxonian erzgebirge many compositional and textural features were found to be similar for instance microdiamonds are enclosed systematically in a specific intermediate growth zone of garnet in these rocks on the basis of experimental data a magmatic scenario was constructed to check if the quartz rich diamondiferous rocks are of magmatic origin by this the p t paths derived here for the kokchetav rocks and the textural observations it is concluded that the minerals of the diamondiferous rocks have crystallized from silicate melts these melts originated by anatexis of deeply submerged metasediments erzgebirge at t as high as 1200 c kokchetav massif at 50 100 c lower t and ascended from at least 200 km depth relics of the pre anatectic evolution are still present for instance as garnet cores after ascent and emplacement of the magma in deep portions of thickened continental crust kokchetav massif 45 50 km close to 800 c erzgebirge 55 60 km at 30 50 c lower t considerable quantities of white and or dark micas formed by peritectic reactions from melt for instance garnets could be resorbed at this stage and biotite grew instead after the magmatic stage retrogression took place much stronger in the kokchetav massif this was accompanied by deformation transforming broadly the magmatic texture of quartz rich diamondiferous rocks from the kokchetav massif to a gneissic texture

metamorphic diamonds mechanism of growth and inclusion of oxides we report a detailed series of electron microscope observations of metamorphic microdiamonds included in and separated from garnets and zircons from a single specimen of garnet biotite feldspar gneiss from the kokchetav massif kazakhstan the morphology of the diamonds ranges from skeletal forms composed of thin 111 plates through cuboid and octahedral forms included within the diamonds is a diverse suite of nanometric oxides suggesting that the c o h fluid from which the diamonds grew may have carried chemical components derived from both the sediments and the mantle the spectrum of morphologies and their abundant tiny inclusions can all be explained by a simple model based on the ratio of the rate at which 111 plates grow and the rate of random nucleation of new plates at their edges

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

phase transformation and nanometric flow cause extreme weakening during fault slip faults weaken during earthquakes laboratory simulations of earthquake rupture show that the nanometric scale fault gouge created during slip is inherently weak and flows by grain boundary sliding providing a mechanism to weaken faults

radiation damage to kokchetav uhpm diamonds in zircon variations in raman photoluminescence and cathodoluminescence spectra abstract we conducted detailed in situ raman photoluminescence pl and cathodoluminescence cl studies on microdiamonds in a tourmaline rich quartzofeldspathic rock from the kokchetav massif kazakhstan the microdiamonds occur as inclusions in the cores of k tourmaline and in zoned zircons with varying u contents the results of 2d raman mapping of zircon showed that the u rich parts were more metamictized than the u poor parts all the diamonds showed a strong raman band at approximately 1332 cm 1 however the features of the raman bands were distinctly different depending on the host minerals on the one hand diamonds in tourmaline had a sharp raman band that is similar to that of kimberlite diamonds full width at half maximum fwhm 2 3 cm 1 on the other hand diamonds in zircon had a broad and downshifted band compared to those in tourmaline in particular diamonds in u rich cores of zircons up to 0 15 wt uo 2 showed broader and more downshifted raman bands fwhms and peak positions varied up to 9 3 cm 1 and 1328 cm 1 respectively with additional small bands at approximately 1490 cm 1 and 1630 cm 1 a negative correlation was observed between the peak position and the fwhm of the principal raman band of microdiamonds furthermore the pl and cl spectra showed systematic variations diamonds in zircons with low to moderate u concentrations had very strong pl and cl compared to diamonds in u rich zircons and in tourmalines several characteristic peaks appeared in the pl and cl spectra indicating the presence of irradiation and or nitrogen related point defects in the diamonds pl and cl of microdiamonds in high u zircon were weak but still showed irradiation related peaks the relationship between the occurrence of microdiamonds i e corresponding to the estimated total dose since crystallization and the raman pl and cl spectral characteristics of microdiamonds strongly suggests that radiation damage predominantly caused by particle emission from radioactive decay of actinides mainly u in zircon is a principal factor for the spectral variations radiation damage metamictization is probably a common phenomenon among microdiamonds in zircons in various diamond bearing rocks from the kokchetav massif to discuss the genesis of diamonds based on their raman pl or cl spectra it is highly recommended that microdiamonds included in actinide bearing minerals e g zircon should be treated with the most careful attention because post crystallization radiation damage significantly influences the spectra

thermohaline fine structure in an oceanographic front from seismic reflection profiling we present acoustic images of oceanic thermohaline structure created from marine seismic reflection profiles across the major oceanographic front between the labrador current and the north atlantic current the images show that distinct water masses can be mapped and their internal structure imaged using low frequency acoustic reflections from sound speed contrasts at interfaces across which temperature changes the warm cold front is characterized by east dipping reflections generated by thermohaline intrusions in the uppermost 1000 meters of the ocean our results imply that marine seismic reflection techniques can provide excellent spatial resolution of important oceanic phenomena including thermohaline intrusions internal waves and eddies

evidence of fluid inclusions in metamorphic microdiamonds from the kokchetav massif northern kazakhstan abstract microdiamonds from garnet clinopyroxenites of the kokchetav massif northern kazakhstan and associated alluvial diamonds have been investigated using infrared spectroscopy all diamonds have high nitrogen contents from 747 up to 4488 20 at ppm and are of type ib iaa nitrogen data are consistent with a diamond formation over a narrow temperature range microdiamonds from garnet clinopyroxenites are characterized by water and carbonate inclusions similar to those ocurring in fibrous coated diamonds from kimberlite which suggest that diamonds grew from a c h o fluid in contrast alluvial microdiamonds do not contain any carbonate inclusions and h2o is absent or present in only minor amounts alluvial diamonds are considerably more n rich but have a similar range of nitrogen aggregation states it is suggested that alluvial diamonds belong to a separate diamond population compared with the microdiamonds from garnet clinopyroxenites the kokchetav microdiamonds are distinct from kimberlitic fibrous diamonds in that they contain abundant ib centres have high nitrogen contents and show different populations depending on host rock type these characteristics support a metamorphic origin for the microdiamonds from the uhpm rocks of the kokchetav massif

synthesis of skeletal diamonds implications for microdiamond formation in orogenic belts diamond was synthesized at high temperature and pressure in a walker style multianvil apparatus from various supercritical c o h rich fluid compositional systems depending on the type and amount of impurities added to the system diamonds of vary ing morphology and bearing solid oxide inclusions were found within the run product these characteristics bear a striking re semblance to metamorphic microdiamonds recovered from the kokchetav massif kazakhstan these natural diamonds share mor phological traits with our synthesized diamonds and both the nat ural and synthesized diamonds contain similar solid oxide inclu sions our data favor formation of kokchetav diamonds via crystallization from a supercritical c o h fluid rather than from carbonate or carbonatite melt as others have suggested

nano inclusion suite and high resolution micro computed tomography of polycrystalline diamond framesite from orapa botswana abstract a single polycrystalline diamond aggregate from the orapa kimberlite botswana contains a syngenetic micro and nano inclusion suite of magnetite pyrrhotite omphacite garnet rutile and c o h fluid in order of abundance this suite of inclusions is distinctly different from those in fibrous diamonds although the presence of sub micrometer fluid inclusions provides evidence for a similarly important role of fluids in the genesis of polycrystalline diamond it is the first study of polycrystalline diamond by high resolution ct computed tomography reaching a resolution of 1 3 m using polychromatic x rays combined with focused ion beam assisted transmission electron microscopy the method reveals epigenetic replacement coatings of hematite and late stage sheet silicates around the magnetites showing that magnetites are often but not always interstitial to the diamond and thus were open to late stage overprinting it is proposed that the polycrystalline diamond formed by a redox reaction between a small scale carbonatitic melt and a sulfide bearing eclogite the water released from the melt during diamond precipitation fluxed local melting of the surrounding eclogite and oxidation of sulfide phases to magnetite which mingled with the carbonatitic melt and re precipitated locally

diamond inclusions in garnets from metamorphic rocks a new environment for diamond formation diamonds commonly occur in kimberlites lamproites and alluvial sediments derived from these rocks more recently diamonds or their graphite pseudomorphs have been discovered in ultramafic massifs1 and picrites2 here we report the occurrence of diamonds in situ in crustal rocks highly retrograded high pressure metamorphic garnet pyroxene and pyroxene carbonate garnet rocks biotite gneisses and schists from the kokchetav massif northern kazakhstan ussr the diamonds are cubo octahedral averaging 12 m in size and occur in zircons and with euhedral graphite as inclusions in unzoned garnets we believe that the zircon and garnet matrices protected these diamonds from retrogressive transformation to graphite mica rutile titanite clinopyroxene kyanite and zircon also occur as inclusions in garnet often intergrown with the diamonds equilibration relations of inclusions and host garnets indicate that both diamonds and graphite crystallized from a fluid phase under static conditions at pressures of 40 kbar and temperatures 900 1 000 c

microdiamonds frontier of ultrahigh pressure metamorphism a review abstract this is a comprehensive review paper devoted to microdiamonds from ultrahigh pressure metamorphic uhpm terranes incorporated in orogenic belts formed at convergent plate boundaries in paleozoic mesozoic alpine time when in 1980 the first small diamonds were discovered within amphibolite granulate facies metamorphic rocks it came as a great surprise that buoyant continental crust could be subducted to depths of hundreds of kilometers and then subsequently exhumed since then much progress has been made in understanding the mechanism of these diamonds formation and the number of new diamond bearing uhpm terranes was significantly increased especially within european orogenes moreover new variations in tectonic settings in which uhp rocks can be formed and exhumed came to the attention of geologists simply due to the finding of diamonds in places previously forbidden for their formation e g oceanic islands ophiolites and forearc environments over the past decade the rapidly moving technological advancement has made it possible to examine microdiamonds in detail and to learn that part of them has a polycrystalline nature that they contain nanometric multiphase inclusions of crystalline and fluid phases and that they keep a crustal signature of carbon isotopes scanning and transmission electron microscopy focused ion beam techniques synchrotron infrared spectroscopy micro x ray diffraction and nano secondary ion mass spectrometry studies of these diamonds provide evidence that they keep traces of fluid originated from both crustal and mantle reservoirs and that they probably interacted with deep mantle plumes hypotheses proposed for diamond formation in subduction zones founded on both analytical and experimental studies are discussed the paper also emphasizes that the discovery of these microdiamonds as well as coesite triggered a major revision in the understanding of deep subduction processes leading to a clear realization of how continental materials can be recycled into the earth s mantle and geochemically rejuvenate it

first find of polycrystalline diamond in ultrahigh pressure metamorphic terrane of erzgebirge germany this article describes polycrystalline diamond from the erzgebirge ultrahigh pressure metamorphic uhpm terrane of the bohemian massif related to the variscan 340 ma continent continent collision the foils polycrystalline diamond included in zircon were prepared with focused ion beam fib and studied with transmission electron microscopy tem each domain of the polycrystalline diamond consisted of a series of diamond monocrystals from 1 to 4 up to 15 containing numerous nanometric fluid and crystalline inclusions of sio2 caco3 kcl and kalsi3o8 the integrated chemistry of the nanoinclusions suggests that the polycrystalline diamond was crystallized from a mixture of two end members which includes a carbon rich hydrous silicic fluid containing si al k and a hydrous saline fluid rich in cl k na traces of carbonate sulphate and phosphate coupled with the presence of metallic cations such as fe mg ti cr co zn zr pb as and hg found in the diamond are coherent with the local geochemical diversity of the host metasedimentary rocks the oxidation state of the diamond forming fluid was close to c co buffer for example fo2 6 log units which is at the upper limit of the diamond stability region the presence of dislocation arrays indicating low angle grain boundaries together with zig zag features or kinks at diamond grain boundaries reflects rapid crystallization of the polycrystalline diamond triangular fluid pockets with steps at the surface related to 110 and 111 planes of diamond could promote the formation of c h and c oh bonds that probably could facilitate the process of diamond graphitization the microstructural features of polycrystalline diamond from the erzgebirge uhpm terrane as well as their undisputed formation from crustal organic carbon can be used for better understanding of the origin of any polycrystalline diamond formation from both kimberlitic and alluvial sources including enigmatic polycrystalline black diamond commonly called carbonado