fluid rock interactions during uhp metamorphism a review of the dabie sulu orogen east central china comprehensive review on the characteristics of petrology oxygen isotope fluid inclusion and nominally anhydrous minerals nams for many dabie sulu ultrahigh pressure uhp metamorphic rocks including drill hole core samples reveals that fluid has played important and multiple roles during complicated fluid rock interactions attending the subduction and exhumation of supracrustal rocks we have identified several distinct stages of fluid rock interactions as follows 1 the neoproterozoic supercrustal protoliths of uhp rocks experienced variable degrees of hydration through interactions with cold meteoric water with extremely low oxygen isotope compositions during neoproterozoic snow ball earth time 2 a series of dehydration reactions took place during triassic subduction of the yangtze plate beneath the sino korean plate the released fluid entered mainly into volatile bearing high pressure hp and uhp minerals such as phengite zoisite epidote talc lawsonite and magnesite as well as into uhp nams such as garnet omphacite and rutile 3 silicate rich supercritical fluid hydrous melt existed during the uhp metamorphism at mantle depths 100 km which mobilized many normally fluid immobile elements and caused unusual element fractionation 4 the fluid exsolved from the nams during the early exhumation of the dabie sulu terrane was the main source for hp hydrate retrogression and generation of hp veins 5 local amphibolite facies retrogression at crustal depths took place by infiltration of aqueous fluid of various salinities possibly derived from an external source 6 the greenschist facies overprinting and low pressure lp quartz veins were generated by fluid flow along ductile shear zones and brittle faults during late stage uplift of the uhp terrane

some ir features of sio 4 and oh in coesite and its amorphization and dehydration at ambient pressure abstract coesite coe with grain size in the range of 30 80 m has been synthesized at 5 gpa and 1600 c for 12 h by using a cubic press its unpolarized single crystal absorption infrared ir spectra show 14 ir bands in the range of 1200 650 cm 1 five of which have high intensity at 1161 1109 1063 1028 and 994 cm 1 and are preliminarily assigned to the sio4 asymmetric stretching 3 in addition three sharp but relatively weak bands at 838 814 and 796 cm 1 are tentatively attributed to the sio4 asymmetric bending 4 the ir data also show six oh peaks in the range of 3700 3300 cm 1 with an estimated h2o content of 30 4 wt ppm following previous studies we have assigned the peaks at 3464 7 3421 8 3406 9 and 3377 cm 1 10 to the type ii hydrogarnet substitution and the peaks at 3500 6a and 3534 cm 1 6b to the b based defects with the latter aroused by possible b contamination in the synthesizing experiments annealing experiments conducted consecutively at 200 400 600 800 1000 and 1200 c with every heating step lasting for 24 h demonstrate that water diffuses quickly out of coe at t as low as 600 c the material annealed at 1200 c is completely dehydrated and amorphous a quick response of the water content in coe to the changes of p t and composition is thus possible which may be critical to the preservation of natural coe in relevant geological processes it further implies that water in coe and possibly in other nominally anhydrous minerals nams may behave distinctively different from the water located in the hydrous phases such as amphibole and mica and potentially makes significant contribution to the subduction zone related fluids

supersilicic clinopyroxene and silica exsolution in uhpm eclogite and pelitic gneiss from the kokchetav massif kazakhstan abundant exsolved quartz rods occur in matrix clinopyroxene of eclogite from the kokchetav massif kazakhstan these rocks are diamond grade ultrahigh pressure uhp metamorphic rocks that recrystallized at p 6 gpa and t 1000 c zircon is an excellent container which effectively protects peak uhp metamorphic phases from retrogression therefore to ascertain the pre exsolution composition of the clinopyroxene we analyzed clinopyroxene inclusions in zircon of the eclogite and a diamond bearing biotite gneiss clinopyroxene in zircon has an excess of fe 3 vi al over iv al na k and calculated cation totals significantly less than 4 0 per six o atoms the stoichiometry of these pyroxenes can be reconciled if the ca eskola end member ca 0 5 0 5 alsi 2 o 6 is considered the zircon hosted clinopyroxene in the eclogite contains up to 9 6 mol of the ca eskola component and in the biotite gneiss up to 18 2 mol whereas the matrix clinopyroxene contains much less 1 3 mol on average recalculation of the composition of the matrix clinopyroxene prior to exsolution of quartz rods yields 6 8 mol ca eskola component which is consistent with the composition of the clinopyroxene inclusions in zircon we conclude that the ca eskola component in the peak metamorphic clinopyroxenes broke down by a retrograde reaction 2 ca 0 5 square 0 5 alsi 2 o 6 rightarrow caal 2 sio 6 3 sio 2 resulting in exsolution of the quartz rods in the matrix clinopyroxene subducted crustal and supracrustal rocks form the ca eskola clinopyroxene at high pressures and temperatures the vacancy containing clinopyroxene may have an important bearing on the physico chemical properties of the subducted slab at upper mantle depth

factors in the preservation of coesite the importance of fluid infiltration the survival of coesite in ultrahigh pressure uhp rocks is most commonly attributed to rapid exhumation continuous cooling during uplift and inclusion in strong phases that can sustain a high internal over pressure during decompression exceptions to all of these criteria exist perhaps less attention has been paid to the role of fluid infiltration in the preservation of coesite we used infrared spectroscopy to measure water contents of coesite and coesite pseudomorphs in a variety of uhp rocks in all cases oh concentrations in coesite are below the detection limit of 100 ppm h2o the silica phases surrounding coesite however show varying amounts of h2o this is most spectacularly observed in pyrope quartzites from the dora maira massif that contain at least three phases of silica replacing coesite also distinguished by varying color of cathodoluminescence cl palisade textured quartz 100 ppm h2o red violet cl mosaic quartz which is actually chalcedony up to 0 4 wt h2o yellow brown cl and a rare highly hydrated silica phase interpreted to be opal 7 wt h2o dark blue cl very similar signatures are observed in a grospydite xenolith from the roberts victor kimberlite the quartz replacing coesite in other uhp samples studied contains on the order of 500 ppm h2o or less and most measurements are under the detection limit of our technique we infer that palisade quartz forms under dry or nearly dry conditions and at high temperatures during dilation of the host phase the formation of hydrous silica phases such as chalcedony and opal however must take place at much lower temperatures after cracking of the host phase which allows external fluids to infiltrate delay of fluid infiltration to low temperatures where kinetics are slow even in the presence of water is the most critical factor in the preservation of coesite

water content in natural eclogite and implication for water transport into the deep upper mantle abstract infrared spectroscopy and ion micro probe measurements showed that the major constituent minerals of eclogites from the kokchetav massif which have been subducted to 180 km depths contain significant amounts of water up to 870 ppm h 2 o by weight in omphacite 130 ppm h 2 o in garnet and 740 ppm h 2 o in rutile omphacite shows three hydroxyl absorption bands at 3440 3460 3500 3530 and 3600 3625 cm 1 garnet has a single band at 3580 3630 cm 1 and rutile has a single sharp band at 3280 cm 1 the hydroxyl absorbance at these wavenumbers changes with the crystal orientation in polarized infrared radiation indicating that the water is structurally incorporated in these minerals the water contents in omphacite and garnet increase systematically with the metamorphic pressure of the host eclogites the partitioning coefficient of the water content between coexisting garnet and omphacite is similar in different eclogites d grt omp 0 1 0 2 but decreases slightly at high pressure based on the mineral proportions of the eclogites we estimate bulk rock water content in the eclogites ranging from 3070 to 300 ppm h 2 o by weight although hydrous minerals are absent in the diamond grade eclogite 60 kbar and 1000 c trace amounts of water are incorporated in the nominally anhydrous minerals such as omphacite and garnet the presence of significant water in these minerals implies that the subducting oceanic crust can transport considerable amounts of water into the deep upper mantle beyond the stability of hydrous minerals such water may be stored in the deep upper mantle and have an important influence on dynamics in the earth s interior

solar and climate signals revealed by seasonal 10be data from the neem ice core project for the neutron monitor period abstract 10be in ice cores has been instrumental for reconstructing past changes in solar activity prior to direct observations for a robust use of these records it is pivotal to understand the 10be transport and deposition however there are only few high resolution seasonal 10be data longer than one full solar cycle 11 years that could enable a quantification of the influences of atmospheric circulation and deposition processes on the 10be signal in ice here we present a seasonally resolved 10be data set covering the neutron monitor period 1951 2002 from a firn core connected to the neem north greenland eemian ice drilling project the results suggest that both summer and winter 10be reflect the production signal induced by solar modulation of galactic cosmic rays however superimposed on this solar signal we find additional meteorologically driven influences on 10be transport and deposition we found that the tropopause pressure over 30 n represents an important factor influencing neem 10be concentrations on seasonal and annual scales 10be deposited in summer also correlates significantly with the tropopause pressure over greenland suggesting a direct contribution of stratospheric intrusions during summer to the 10be deposition in greenland to correct for these transport deposition influences we apply a first order correction to the 10be data using a multi linear regression model the climate corrected 10be data shows a comparable skill for reconstructing production rate changes as the 10be composite record from five different ice cores in greenland the results suggest that the correction approach can be a complementary method to the stacking to better isolate the production rate signal from the 10be data when only limited data are available

large variations in holocene solar activity constraints from 10be in the greenland ice core project ice core 1 cosmogenic radionuclides extracted from ice cores hold a unique potential for reconstructing past solar activity changes beyond the direct instrumental period taking the geomagnetic modulation into account the solar activity in terms of the heliospheric modulation function can quantitatively be reconstructed in high resolution throughout the holocene for this period our results reveal changes in heliospheric modulation of galactic cosmic rays significantly larger than the variations reconstructed on the basis of neutron monitor measurements of galactic cosmic rays for the last 50 years moreover the 10be data from the greenland ice core project ice core as well as 14c support a high current solar activity however although the reconstruction of solar activity on long timescales is difficult our result suggests that the modern activity state of the sun is not that exceptional regarding the entire holocene this extended solar activity record provides the basis for further detailed investigations on solar and cosmic ray physics as well as on solar forcing of the earth s climate whose importance is suggested by increasing paleoclimatic evidences

correlation based interpretations of paleoclimate data where statistics meet past climates abstract correlation analysis is omnipresent in paleoclimatology and often serves to support the proposed climatic interpretation of a given proxy record however this analysis presents several statistical challenges each of which is sufficient to nullify the interpretation the loss of degrees of freedom due to serial correlation the test multiplicity problem in connection with a climate field and the presence of age uncertainties while these issues have long been known to statisticians they are not widely appreciated by the wider paleoclimate community yet they can have a first order impact on scientific conclusions here we use three examples from the recent paleoclimate literature to highlight how spurious correlations affect the published interpretations of paleoclimate proxies and suggest that future studies should address these issues to strengthen their conclusions in some cases correlations that were previously claimed to be significant are found insignificant thereby challenging published interpretations in other cases minor adjustments can be made to safeguard against these concerns because such problems arise so commonly with paleoclimate data we provide open source code to address them ultimately we conclude that statistics alone cannot ground truth a proxy and recommend establishing a mechanistic understanding of a proxy signal as a sounder basis for interpretation

rheological contrast between garnet and clinopyroxene in the mantle wedge an example from higashi akaishi peridotite mass sw japan abstract garnet clinopyroxenites occur within foliated dunite in the higashi akaishi peridotite mass located within the subduction type high pressure low temperature sanbagawa metamorphic belt the garnet clinopyroxenites contain 3 80 garnet and garnet and clinopyroxene are homogeneously distributed garnet crystals contain extensive regular dislocation arrays and dislocation networks suggesting that dislocation creep was the dominant deformation mechanism analyses of crystallographic orientation maps indicate similar grain sizes and aspect ratios for garnet and clinopyroxene regardless of modal composition indicating that these minerals deformed with similar degree of plasticity moreover indexes of crystallographic fabric intensity i e j index and m index for both garnet and clinopyroxene tend to increase with increasing modal composition of garnet fourier transform infrared spectroscopy analysis revealed that water content in garnet is 60 ppm whereas that in clinopyroxene is 70 ppm olivine crystal preferred orientations in the higashi akaishi peridotite mass characterized by 0 0 1 0 1 0 are thought to have developed during deformation under wet conditions consequently we argue that the presence of water could act to enhance garnet plasticity during deformation the results reveal contrasting influences of water on the deformation of garnet and diopside under wet conditions compared with dry the strain rate increases by two orders of magnitude for garnet but by an order of magnitude for diopside given the influence of water on the creep strength of garnet garnet within the higashi akaishi mass may have become significantly as weak as clinopyroxene during deformation

beryllium 10 transport to antarctica results from seasonally resolved observations and modeling 1 cosmogenic 10be measured in polar ice cores has important application in the reconstruction of past solar activity however the processes controlling its atmospheric transport and deposition to the ice sheets are not fully understood here we use the seasonal changes in 10be concentrations in a 10 year monthly resolved ice core record from the law dome site east antarctica in conjunction with echam5 ham general circulation model gcm simulations of 10be and 7be deposition as tools to examine this problem maximum 10be concentrations are observed in the ice core during the austral late summer to early autumn summer autumn while minimum concentrations are observed during the austral winter the gcm simulations corroborated by earlier observations of 10be 7be ratios in antarctica from the georg von neumayer air sampling station suggest that the 10be concentration maximum is linked to direct input of stratospheric 10be from the antarctic stratosphere to the lower levels of the antarctic troposphere during the austral summer autumn this result contrasts with the modeled transport of 10be to greenland where the seasonal maximum in stratospheric input is seen in the late winter to spring synchronous with the timing of the seasonal maximum in midlatitude stratosphere to troposphere exchange our results suggest that a different combination of processes is responsible for the transport of 10be to the antarctic and greenland ice sheets

the seismically active atalanti fault in central greece a steeply dipping fault zone imaged from magnetotelluric data abstract the wnw ese striking atalanti fault is one of the large fault segments of the ca 110 km long wnw ese trending sperchios chalkis fault system that subsided along the ne slopes of the kalidromon and chlomo mts in central greece forming an extensive graben similar to the corinthiakos gulf although the fault is characterized by recent seismic activity it has up to now not been investigated by means of geophysical methods that could define the geometrical features of the structure in depth magnetotelluric measurements performed along three 14 km long profiles a b and c and across the fault with a total of 28 stations indicate that its geoelectric strike is wnw ese two dimensional bimodal and the determinant of the impedance tensor inversions were applied to the data the best data fit was achieved using the determinant data the resulting 2d models were further interpreted both separately and all together in order to define the geometry of the structure down to a depth of several kilometers the derived resistivity model defines that the atalanti fault strikes wnw ese and forms a damage zone that contains two high angle fault branches that dip at angles of 60 and 80 respectively thus the interpreted geometry of the atalanti fault and consequently the sperchios chalkis fault system differs from previous interpretation of a low angle extensional crustal structure in addition the electrical resistivity model indicates the subsidence of the overthrust of the internal hellenides over the parnassos zone toward the nne from a depth of 2 km to deeper crustal levels due to the atalanti fault

oriented quartz calcic amphibole inclusions in omphacite from the saualpe and pohorje mountain eclogites eastern alps an assessment of possible formation mechanisms based on ir and mineral chemical data and water storage in eastern alpine eclogites abstract the composition of mineral phases and their modal proportions have been determined for three representative eoalpine eclogites from the saualpe type locality eastern austria sample skp31 and the pohorje massif slovenia cm31 03 and cm15 01 using electron microprobe laser icp ms ir spectroscopy and modal analysis to evaluate possible mechanisms for the formation of composite oriented calcic amphibole quartz inclusions cois in omphacite and to assess the relative importance of hydrous and nominally anhydrous phases as h 2 o carriers in these eclogites for omphacites in cm31 03 with a zonal distribution of cois a comparison of water and trace element concentrations of areas containing cois and those free of cois and a comparison with the trace element concentration of calcic amphibole indicate that cois have formed through an open system alteration of clinopyroxene and not through a closed system exsolution process in sample skp31 both textural and mineral chemical evidence suggests that cois did not form by exsolution involving a ca eskola component in clinopyroxene but formed by progressive growth under eclogite facies p t conditions and prior to the onset of retrogressive symplectite formation analogous to the formation of poikiloblastic quartz calcic amphibole grains in the matrix bulk h 2 o contents of the eclogites are between ca 750 and 2150 ppm with 6 25 of the total water contributed by nominally anhydrous minerals nams because of high modal amounts of 37 65 omphacite is the major nominally anhydrous water carrier containing 145 580 ppm h 2 o with significant concentration variations on a thin section scale due to their very low h 2 o concentrations of 2 o content calcic amphibole forming part of cois may be a major carrier of h 2 o as evidenced by cm31 03 containing both cois and texturally primary calcic amphibole in this sample calcic amphibole of the cois contributes 63 whereas primary calcic amphibole only accounts for 13 of the bulk water the relative order of h 2 o concentrations in nams is h 2 o rutile h 2 o omphacite h 2 o garnet for cm31 03 and cm15 01 and h 2 o rutile h 2 o omphacite h 2 o garnet in skp31

archean mantle heterogeneity and the origin of diamondiferous eclogites siberia evidence from stable isotopes and hydroxyl in garnet data are presented for the o isotopic composition of clinopyroxene and garnet the c isotopic composition of diamond and the oh content of garnet from eclogite xenoliths brought to the surface by the udachnaya kimberlite pipe yakutia siberia radiogenic isotopic data suggest that the eclogites could have been derived from an ultradepleted mantle at approximately 2 9 ga pearson et al 1995 snyder et al in preparation o isotopic compositions generally show equilibration between the eclogitic minerals cpx grt 0 11 0 41 and have 18 o smow for both garnet and clinopyroxene that lie near the range of accepted mantle values of 5 7 0 7 however several eclogites indicate significant deviations from this range at higher values of 6 8 7 0 also two eclogites lie at the lower end of the mantle range at values of 4 8 and 5 0 all in clinopyroxene c isotopic compositions of diamonds all have 13 c pdb in the range of 1 to 7 and are centered at approximately 5 also within the range of accepted mantle values the oh contents of the garnet are generally between 0 and 22 ppm as h 2 0 although two samples exceed 70 ppm this range of oh is similar to eclogitic garnet from the kaapvaal craton of southern africa the mantle c isotopic values of associated diamonds the majority of o isotopic data and the low oh content of the minerals although suggesting a general lack of crustal participation in the formation of the udachnaya eclogites do not rule out the participation of some ancient crustal material that these eclogites include both 18 o enriched and 18 o depleted types suggests that the protoliths may have been overprinted by both low and high temperature hydrothermal events cf jacob et ai 1994 a positive correlation between 18 o and 87 sr 86 sr allows the interpretation of these eclogites as representing a cross section of an archean ophiolite however the lack of a single coherent grouping on a plot of 18 o vs 87 sr 86 sr suggests that if the udachnaya eclogites were derived from oceanic crust they cannot be cogenetic and must represent at least two separate ophiolite sequences conversely if the eclogites are found to be cogenetic then a totally different process affected their formation and a probable metasomatic mechanism was operative because of the total lack of correlation of 18 o with other geochemical parameters we find no compelling evidence that all eclogites are derived ultimately from oceanic crust

corundum inclusions in diamonds discriminatory criteria and a corundum compositional dataset abstract mineral inclusions of corundum are reported from diamonds from alluvial deposits of tributaries of the rio aripuana juina brazil we present the first recorded occurrence of sapphire as an inclusion in diamond and expand on the database of ruby and white corundum inclusions ruby inclusions are found to occur both as isolated and touching grains with aluminous pyroxene and associated with ferropericlase mineral chemistry and phase relations place the origin of such ruby bearing diamonds within the lower mantle at 770 km mineral associations indaving other corundum inclusions were not observed hence their depth of origin is less certain compositions of corundum samples were characterised by electron and ion microprobe given the scarcity of literature data corundum samples from a variety of other geological settings were also analysed samples comprised corundums associated with granitic emplacement metasomatism amphibolite facies and granulite facies rocks gem and industrial synthetic origins and carmine coloured corundums recovered from kimberlite drill cores in addition to variable amounts of cr fe ti mg and si measurable quantities of other transition elements and high field strength elements were also detected corundums from similar geological settings show very similar compositions and are easily distinguishable from other settings irrespective of locality rubies from norwegian tanzanian and kenyan amphibolite facies rocks are compositionally indistinguishable additionally corundums from metasomatised zones associated with contact metamorphism from arizona and japan were very similar particularly characterised by unusually high abundance of mobile zr and nb tens of ppm all juina inclusions are particularly distinguishable from other corundums by high concentrations of ni 18 171 ppm weight typically at least an order of magnitude enriched over the same corundum varietal types from elsewhere furthermore the sapphire inclusion exhibited much larger ratios of ga and ge to hfse elements compared to otherwise similar samples and ruby inclusions are distinguished by high mg fe ratios 0 27 1 56 by weight compositional differences between inclusions in diamonds and corundums from other settings in addition to corundum s physical and chemical durability suggest that with the employment of rapid identification tools such as energy dispersive spectrometry eds and laser icpms corundum has promise as an indicator of diamond prospectivity

a 600 year annual 10be record from the ngrip ice core greenland understanding the link between the sun and climate is vital in the current incidence of global climate change and 10be in natural archives constitutes an excellent tracer for this purpose as cosmic rays enter the atmosphere cosmogenic isotopes like 10be and 14c are formed variations in solar activity modulate the amount of incoming cosmic rays and thereby cosmogenic isotope production atmospherically produced 10be enters natural archives such as sediments and glaciers by wet and dry deposition within about a year of production 10be from natural archives therefore provides information on past solar activity and because these archives also contain climate information solar activity and climate can be linked one remaining question is to what degree 10be in natural archives reflects production and to what extent the local and regional environment overprints the production signal to explore this 10be was measured at annual resolution over the last 600 years in a greenland ice core measurement potentials for these samples benefited from the development of a new laboratory method of co precipitating 10be with niobium to diversify geographic location and archive media type a pioneer study of measuring 10be with annual resolution in varved lake sediments from finland was conducted with samples from the entire 20th century pathways of 10be into lake sediments are more complex than into glacial ice inferring that contemporary atmospheric conditions may not be recorded here it is shown for the first time that tracing the 11 year solar cycle through lake sediment 10be variations is possible results also show that on an annual basis 10be deposition in ice and sediment archives is affected by local environmental conditions on a slightly longer timescale however diverse 10be records exhibit similar trends and a negative correlation with solar activity cyclic variability of 10be deposition persisted throughout past grand solar minima when little or no sunspot activity was recorded 10be levels indicate that although solar activity has been high during the 20th century levels are not unprecedented in the investigated 600 years aerosol 10be 7be values indicate possible influence of stratosphere troposphere exchange on isotope abundance and the production signal

crystal structure refinement of na bearing clinopyroxenes from mantle derived eclogite xenoliths nine omphacitic clinopyroxenes with a jadeitic content between 25 and 57 from the udachnaya and zagadochnaya diamond bearing kimberlites were investigated using single crystal x ray diffraction electron microprobe analysis and mossbauer and infrared spectroscopy crystal structure refinements incorporating constraints from chemical analyses and mossbauer data show a significant concentration of vacancies at the m2 site in three of the samples the cell volumes of the non stoichiometric samples plot below the linear trend defined by stoichiometric diopside jadeite compositions where the deviation from the linear trend is positively correlated with the concentration of vacancies charge balance appears to be achieved primarily through substitution of al3 for mg2 on the m1 site which causes a contraction of the m1 site volume compared to stoichiometric clinopyroxenes with the same composition vacancies are not associated with oh incorporation as the sample with the highest concentration of vacancies contains only 89 ppm wt h2o significant hydrogen loss through iron oxidation during ascent is ruled out based on the low fe3 concentrations h content in omphacite samples from kimberlites could provide a sensitive tool for determining f h2o during diamond formation

the structure of hydrous species in nominally anhydrous minerals information from polarized ir spectroscopy hydrogen is a major constituent in a wide variety of minerals in the earth s crust usually h is bonded to oxygen forming h2o molecules or oh groups in rare cases h3o h3o2 and h5o2 units are also formed the occurrence of nh4 chx etc in minerals will not be considered here hydrogen occurs stoichiometrically in hydrous compounds such as hydrates e g gypsum oxy hydroxides e g goethite and in many rock forming silicates e g micas as well as in nonstoichiometric major amounts in microporous minerals such as zeolites and clay minerals which are of considerable economic and ecologic importance hydrogen also occurs as a minor or trace constituent in minerals that by definition and by their formulae do not contain hydrogen at all i e the so called nominally anhydrous minerals nams nams include common rock forming minerals in the earth s crust e g quartz feldspars and upper mantle e g olivine pyroxene and garnet but also high p and high t phases e g wadsleyite ringwoodite and majorite garnet stable in the mantle transition zone 410 660 km depth the aim of the present chapter is to review the use of polarized infrared ir spectroscopy as it applies to detecting traces of hydrogen in minerals and to characterizing its speciation and structural environment in nominally anhydrous minerals the basic theoretical background will be supplemented by a number of examples from recent research it is important to note that many of the concepts described here for nams can also be applied to synthetic compounds of importance in the materials sciences the importance of hydrous species in nams hydrogen may be incorporated as defects in nominally anhydrous minerals of the earth s mantle due to the large volume of rock in the earth s mantle even trace concentrations of h

the influence of oh in coesite on the kinetics of the coesite quartz phase transition metastable coesite is an important pressure indicator for ultrahigh pressure rocks however in many cases coesite does not survive exhumation but reacts back to quartz although it was shown experimentally that incorporation of h in coesite increases with increasing pressure most coesite relics found in nature are essentially dry i e oh concentrations are below detection limit 1 wt ppm h2o thus does the incorporation of h promote the back reaction of coesite to quartz during exhumation the influence of intrinsic oh on the kinetics of the coesite quartz phase transition was determined using synthetic dry coesite with approximate to10 wt ppm h2o and wet coesite with approximate to105 wt ppm h2o tem analysis of the quenched samples proved the presence and absence of water in the wet and dry samples respectively the kinetics of the coesite quartz transition was investigated in situ using the multi anvil apparatus max 80 at the hamburger synchrotron radiation laboratory hasylab the transition rates were measured by observing changes in selected diffraction line intensities as a function of time the transformation and growth rates were derived using cahn s model of nucleation and growth at grain boundaries under the same experimental conditions the transformation rate of the wet coesite is more than ten times higher than that of the dry coesite this difference may explain why oh bearing natural coesite is rare this study reveals the importance of structurally bound oh for the kinetics of phase transitions of nominally anhydrous minerals

charge contrast imaging of fine scale microstructure and compositional variation in garnet using the environmental scanning electron microscope gaseous secondary electron gse imaging of eclogite garnets under the environmental scanning electron microscope esem at low chamber gas pressures reveals detailed image contrast patterns charge contrast images cci that are not present in back scattered or secondary electron images image intensity is a function of the amount of surface charge accumulation successful acquisition of cci depends on frame size and beam scan rate at a given chamber gas pressure and beam current images are obtained in a few seconds and are stable and reproducible cci patterns do not correlate with cracks or grain boundaries but do correspond closely to variations in major element composition both in the form of concentric growth zoning and branching linear features interpreted as cracks that have been healed by new garnet growth causes of cci are not yet well understood but may be related to variations in lattice defect density and their influence on charge trapping and dissipation these in turn influence the rate of charge build up at or very close to the specimen surface one interesting possibility is that cci images detect vacancies related to non homovalent coupled substitutions involving for example ree and hydroxyl so the method offers a way of imaging the distribution of these trace species in garnets the cci images are rich in microstructural detail and offer the potential for rapid high resolution low noise reconnaissance mapping of intragranular microstructure and compositional variation in both natural and synthetic garnets

quantitative analysis of trace oh in garnet and pyroxenes to calibrate infrared ir spectroscopy for quantitative analysis of trace structural oh in specific minerals we have determined concentrations of h in pure separates of mantle derived pyrope garnet 56 6 ppm h 2o by weight augite 268 8 ppm h 2o and enstatite 217 11 ppm h 2o by manometry after heating the samples and extracting h 2 gas under vacuum ir spectroscopy confirmed the presence of intrinsic oh in these samples prior to extraction and indicated between 86 and 100 removal of h during the extraction procedure the integral specific absorption coefficients of 1 39 0 14 l 7 09 0 32 and 15 6 0 94 ppm h 2o cm 2 for pyrope augite and enstatite respectively allow precise spectroscopic determination of the oh content of upper mantle garnets and pyroxenes to concentration levels of a few parts per million uncertainties in accuracy depend on mineral composition and characteristics of the oh absorption spectrum and are estimated to range between 10 and 50

sodic amphibole exsolutions in garnet from garnet peridotite north qaidam uhpm belt nw china implications for ultradeep origin and hydroxyl defects in mantle garnets two types of amphibole exsolution lamellae were discovered in garnet from a few garnet peridotites from the north qaidam ultrahigh pressure metamorphic belt northern tibet nw china the amphibole lamellae are strictly oriented in four directions corresponding to the isometric form 111 i e octahedron planes of garnet observations by transmission electron microscopy tem show that amphibole lamellae are topotaxtially concordant with the host garnet and possess 9 8 to 10 a lattice c spacing electron microprobe analysis reveals that these exsolved amphibole lamellae are high in na and ti the tem observations and recalculated compositions indicate that the oriented amphibole lamellae exsolved from original supersilicic majorites with high concentrations of na2o 0 3 wt and hydroxyl up to 1000 ppm by weight these results imply that the host garnet peridotites were formed at depths greater than 200 km and that garnet can be an important reservoir of water at such depths in the mantle

hydroxyl contents of accessory minerals in mantle eclogites and related rocks infrared spectra in the region 3000 to 3800 cm 1 have been measured on coesite kyanite sanidine and rutile occurring in inclusions of eclogite and on garnet and spinel in an inclusion of alkremite from south african kimberites coesite and sanidine contain virtually no h 2o or oh although one sanidine crystal was observed to contain abundant h2o apparently as fluid inclusions of molecular h2o kyanite contains significant oh consistent with previous results for similar samples corundum gives no indication of the presence of h 2o or oh rutile containing significant amounts of fe cr al and nb also contains significant amounts of structural oh garnet in alkremite contains small amounts of molecular h 2o whereas the spinel coexisting with this garnet gives no indication of h 2o or oh indicating that the spinel structure is not able to accommodate significant amounts of oh ammonium contents of all samples were less than the detection limit about 10 ppm

hydroxyl defects in garnets from mantle xenoliths in kimberlites of the siberian platform a suite of more than 200 garnet single crystals extracted from 150 xenoliths covering the whole range of types of garnet parageneses in mantle xenoliths so far known from kimberlites of the siberian platform and collected from nearly all the kimberlite pipes known in that tectonic unit as well as some garnets found as inclusions in diamonds and olivine megacrysts from such kimberlites were studied by means of electron microprobe analysis and single crystal ir absorption spectroscopy in the voh vibrational range in search of the occurrence energy and intensity of the voh bands of hydroxyl defects in such garnets and its potential use in an elucidation of the nature of the fluid phase in the mantle beneath the siberian platform the voh single crystal spectra show either one or a combination of two or more of the following major voh bands i 3645 3662 cm 1 ii 3561 3583 cm 1 iii 3515 3527 cm 1 and minor bands ia 3623 3631 cm 1 iia 3593 3607 cm 1 the type of combination of such bands in the spectrum of a specific garnet depends on the type of the rock series of the host xenolith mg mg ca ca mg fe or alkremite on the xenolith type as well as on the chemical composition of the respective garnet nearly all garnets contain band systems i and ii band system iii occurs in ti rich garnets with wt tio2 ca 0 4 from xenoliths of the mg ca and mg fe series only the voh spectra do not correspond to those of oh defects in synthetic pyropes or natural ultra high pressure garnets from diamondiferous metamorphics there were no indications of voh from inclusions of other minerals within the selected 60 60 m measuring areas in the garnets the voh spectra of pyrope knorringite and pyrope knorringite uvarovite rich garnets included in diamonds do not show band systems i to iii instead they exhibit one weak broad band voh 200 460 cm 1 near 3570 cm 1 a result that was also obtained on pyrope knorringite rich garnets extracted from two olivine megacrysts the quantitative evaluation on the basis of relevant existing calibrational data bell et al 1995 of the sum of integral intensities of all voh bonds of the garnets studied yielded a wide range of water concentrations within the set of the different garnets between values below the detection limit of our single crystal ir method near 2 10 4 wt up to 163 10 4 wt the water contents vary in a complex manner in garnets from different xenolith types obviously depending on a large number of constraints inherent in the crystal chemistry as well as the formation conditions of the garnets during the crystallization of their mantle host rocks secondary alteration effects during uplift of the kimberlite play if any only a minor role despite the very complex pattern of the water contents of the garnets preventing an evaluation of a straightforward correlation between water contents of the garnets and the composition of the mantle s fluid phase during garnet formation at least two general conclusions could be drawn 1 the wide variation of water contents in garnets is not indicative of regional or local differences in the composition of the mantle s fluid phase 2 garnets formed in the high pressure high temperature diamond pyrope facies invariably contain significantly lower amounts of water than garnets formed under the conditions of the graphite pyrope facies this latter result 2 may point to significantly lower fh2o and fo2 in the former as compared to the latter facies

use of the elastic recoil detection analysis erda microbeam technique for the quantitative determination of hydrogen in materials and hydrogen partitioning between olivine and melt at high pressures abstract a nuclear microbeam technique called elastic recoil detection analysis erda or forward recoil spectroscopy which is capable of yielding bulk h in silicates at ppm sensitivities is described this technique is nondestructive and uses a 4he beam which may be routinely focused to dimensions less than 5 5 m the technique is suitable for the analysis of both materials of appreciable h content e g amphiboles and materials with trace h content the technique is calibrated in the range 0 2 wt h2o using a set of mineral standards of known h2o concentration with sensitivities of 0 04 wt h2o achieved there is a good correlation between h2o contents derived by spectra simulations and concentrations derived by empirical calibration although the former yield data 10 20 lower when compared to known values the equilibration of olivine with a potassic silicate melt at high pressures 1 5 to 10 gpa in experiments shows more h is accommodated in the mineral with increasing pressure the olivine melt kh2o expressing h as wt h2o concentration in mineral concentration in melt at 1 5gpa 1400 c was ca 0 04 0 015 at 5 8 6 gpa 1740 c olivine melt kh2o increased to 0 13 0 03 a single experiment at 10 gpa ca 2000 c yielded a minimum kh2o of 0 12 the amount of h which minerals accommodate is also highly correlated with bulk system composition which controlled melt composition in alkali absent bulk systems the kh2o for olivine equilibrated with a mg si melt was 0 30 at 1 gpa 1400 c an order of magnitude increase over the alkali bearing system at this pressure this reflects the reduced facility of a wholly mg si melt to accommodate h2o relative to an alkali bearing melt the increase in kh2o with pressure for olivine melt combined with data for kh2o of natural olivine and orthopyroxene in basaltic glass at p

cation deficient phlogopitic mica exsolution in diopside from garnet peridotite in sulu china article i nfo deep subduction and return to the surface of sediments and other continental rocks is now well known forming terranes of ultrahigh pressure metamorphism uhpm a common constituent of these terranes is garnet peridotite mantle rock that has been brought to the surface along with the returning subducted material microstructures of these peridotites especially precipitates within their constituent minerals offer promise of providing information not only about their depth of origin but also about the subduction environment here we report exsolution lamellae of cation deficient phlogopitic mica within diopside of a drill core from the uhpm terrane of sulu china detailed analysis by transmission electron microscopy tem shows these precipitates to be phlogopitic mica that is highly complex both structurally and compositionally with a significant component of the 10 a phase a talc like phase stable only at quite high pressures several mica polytypes are present the simplest one 1m being the most cation deficient the presence of a significant 30 10 a phase component in the mica suggests a means of expanding the 10 a phase bridge for subduction of h2o to deep mantle depths published by elsevier b v

solar and climate influences on ice core 10be records from antarctica and greenland during the neutron monitor era abstract cosmogenic 10be in polar ice cores is a primary proxy for past solar activity however interpretation of the 10be record is hindered by limited understanding of the physical processes governing its atmospheric transport and deposition to the ice sheets this issue is addressed by evaluating two accurately dated annually resolved ice core 10be records against modern solar activity observations and instrumental and reanalysis climate data the cores are sampled from the dss site on law dome east antarctica spanning 1936 2009 and the das2 site southeast greenland 1936 2002 permitting inter hemispheric comparisons concentrations at both dss and das2 are significantly correlated to the 11 yr solar cycle modulation of cosmic ray intensity r xy 0 54 with 95 ci 0 31 0 70 and r xy 0 45 with 95 ci 0 22 0 62 respectively for both sites if fluxes are used instead of concentrations then correlations with solar activity decrease the strength and spectral coherence of the solar activity signal in 10be is enhanced when ice core records are combined from both antarctica and greenland the amplitudes of the 11 yr solar cycles in the 10be data appear inconsistent with the view that the ice sheets receive only 10be produced at polar latitudes significant climate signals detected in the 10be series include the zonal wave three pattern of atmospheric circulation at dss r xy 0 36 with 95 ci 0 57 0 10 and the north atlantic oscillation at das2 r xy 0 42 with 95 ci 0 64 0 15 the sensitivity of 10be concentrations to modes of atmospheric circulation advises caution in the use of 10be records from single sites in solar forcing reconstructions

erratum anatomy of the dead sea transform from lithospheric to microscopic scale rewiews of geophysics 2009 47 rg2002 doi 10 1029 2008rg0002264

decrease of hydrogen incorporation in forsterite from co2 h2o rich kimberlitic liquid to test if hydrogen incorporation by ionic diffusion can occur between a volatile rich kimberlitic liquid and forsterite results of high pressure and high temperature experiments using a piston cylinder apparatus at 1200 1300 c and 1 gpa for durations of 1 min 5 h and 23 h are reported here kimberlitic liquid in the system cao mgo al2o3 sio2 co2 h2o and synthetic forsterite single crystals were chosen as a first simplification of the complex natural kimberlite composition unpolarized fourier transform infrared spectroscopy was used to quantify the concentrations of oh in the crystallographically oriented forsterite scanning electron microscopy electron backscattered diffraction electron microprobe analyses and transmission electron microscopy were performed to identify the run products after 5 and 23 h a forsterite overgrowth crystallized with the same orientation as the initial forsterite single crystal the kimberlitic liquid has crystallized as micrometer scale euhedral forsterite neocrystals with random crystallographic orientations as well as a nanoscale aluminous phase and a calcic phase despite theoretical water saturation of the system and long duration none of the initial forsterite single crystals display signs of hydration such as hydrogen diffusion profile from the border toward the center of the crystal most likely the presence of co2 in the system has lowered the h2o fugacity to such an extent that there is no significant hydration of the starting forsterite single crystal or its overgrowth also the presence of co2 enhances rapid forsterite crystal growth forsterite growth rate is around 2 108 m3 h at 1250 c these experimental results suggest a deep mantle origin of the high oh content found in natural mantle derived xenoliths transported in kimberlites as reported from the kaapvaal craton in agreement with previous studies it also points out to the fact that significant hydration must take place in a co2 poor environment

hydroxyl in olivines from mantle xenoliths in kimberlites of the siberian platform from a total of 335 olivine crystal grains crystallographically orientated platelets and where possible parallelepipeds were prepared chemically analysed by electron microprobe examined under the polarisation microscope and studied by polarised ftir microscope absorption spectrometry in the oh vibrational range 3 000 3 800 cm 1 the 335 crystal grains were extracted from 174 different specimens of yakutian upper mantle material including 97 xenoliths that represent all the rock types occurring in all the kimberlites of the siberian shield the other specimens were mega and macrocrysts or inclusions in diamonds and garnets analysis of the polarised oh spectra allowed distinction between hydroxyl in non intrinsic separate inclusions nsi and in isolated local or condensed extended defects intrinsic to the olivines ild or ced respectively as the two latter types cannot be distinguished by vibrational spectroscopy and as they are presumably interconnected by intracrystalline condensation reactions of the type n ild ced n we propose to symbolise them as ild ced of the total of 70 polarised oh bands that were found in the whole set 17 are caused by nsi 53 by ild ced total mean integrated oh band intensities int total with int a b c int 3 were determined from the spectra they yielded the contents of structurally unallocated water using the recent calibration of the ir method bell et al 2003 the range is 0 a b at 3 327 3 328 cm 1 an energy typical of oh in hydrous wadsleyite we assume this phase to be present as nis in the respective olivines possibly as relic phase 4 weak bands between 3 175 and 3 260 cm 1 polarised along c are tentatively assigned to molecular water nsi with relatively strong hydrogen bonds to the matrix we did not find larger clusters of molecular water i e liquid like water with its characteristic broad band centred at ca 3 400 cm 1 we did also not find any humite minerals as an nsi of the 53 oh bands intrinsic to olivine the 29 most abundant and strong ones were subject to further analysis in terms of oh bearing structural defects ild ced nearly all these bands are strongly polarised along a two bands at 3 672 and 3 535 cm 1 are assigned to boron related defects ild ced b five bands at 3 573 3 563 3 541 3 524 and 3 512 cm 1 are intensity correlated and are assigned to si depleted titan clinohumite like defects ild ced thl the other so far unidentified oh of ild ced are suggested to originate from oh in different types of mg fe depleted defects recently predicted and discovered by tem these are called ild ced kwk eight mostly strong bands of them occur at energies higher than 3 573 cm 1 ild ced kwk h 13 strong to medium strong bands occur below 3 500 cm 1 ild ced kwk l such intrinsic defects may occur alone ild ced thl and ild ced kwk h or in different combinations with each other ild ced kwk h ild ced thl ild ced kwk h ild ced kwk l and ild ced kwk h ild ced thl ild ced kwk l though there are indications that the occurrences of such types and combinations of the intrinsic oh bearing defects in the olivines are related to the types and genetic peculiarities of their host rocks straightforward and simple correlations do not exist the reasons for this and also for the great number of varieties of intrinsic ild ced are discussed

solar activity during the last 1000 yr inferred from radionuclide records identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors solar forcing prior to the period of direct solar observations radionuclide abundances in natural archives provide the best known proxies for changes in solar activity here we present two independent reconstructions of changes in solar activity during the last 1000 yr which are inferred from be 10 and c 14 records we analyse the tree ring c 14 data shcal intca104 from 1000 to 1510 ad and annual data from 1511 to 1950 ad and four be 10 records from greenland ice cores camp century grip milcent and dye3 together with two be 10 records from antarctic ice cores dome concordia and south pole in general the be 10 and c 14 records exhibit good agreement that allows us to obtain reliable estimates of past solar magnetic modulation of the radionuclide production rates differences between be 10 records from antarctica and greenland indicate that climatic changes have influenced the deposition of be 10 during some periods of the last 1000 yr the radionuclide based reconstructions of past changes in solar activity do not always agree with the sunspot record which indicates that the coupling between those proxies is not as close as has been sometimes assumed the tree ring c 14 record and be 10 from antarctica indicate that recent solar activity is high but not exceptional with respect to the last 1000 yr c 2006 elsevier ltd all rights reserved less

micro and nano size hydrogrossular like clusters in pyrope crystals from ultra high pressure rocks of the dora maira massif western alps the supracrustal metamorphic rocks of the dora maira massif western alps have been intensively studied certain ultra high pressure lithologies contain coesite and nearly end member composition pyrope mg3al2si3o12 making this locality petrologically and mineralogically unique structural oh loosely termed water in pyrope crystals of different composition has been investigated numerous times using different experimental techniques by various researchers however it is not clear where the minor oh is located in them ir single crystal spectra of two pyropes of composition mg2 79 fe2 0 15 ca0 04 2 98 al 2 02 si 2 99o12 and mg2 90 fe2 0 04 ca0 02 2 96 al 2 03 si 3o12 were recorded at room temperature rt and 80 k the spectra show five distinct oh bands located above 3600 cm 1 at rt and seven narrow bands at 80 k and additional fine structure the spectra were curve fit and the oh stretching modes analyzed and assigned it is argued that oh is located in microscopic and nano size ca3al2h12o12 like clusters the basic substitution mechanism is the hydrogarnet one where h4o4 4 sio4 4 and various local configurations containing different numbers of h4o4 4 groups define the cluster type the amounts of h2o range between 5 and 100 ppm by weight depending on the ir calibration adopted and are variable among crystals hydrogrossular like clusters are also present in a synthetic pyrope with a minor ca content grown hydrothermally at 900 c and 20 kbar as based on its ir spectra at rt and 80 k experiment and nature are in agreement and oh groups are partitioned into various barely nano size hydrogrossular like clusters this proposal is new and significant mineralogical petrological and geochemical implications result ca and proton ordering occur hypothetical defect and or coupled substitution mechanisms to account for structural oh are not needed to interpret experimental results oh incorporation in pyrope of different generations at dora maira is discussed and oh could potentially be used as an indicator of changing p text h text 2 text o text a text h text 2 text o text t conditions in a metamorphic cycle published experimental hydration dehydroxylation and hydrogen diffusion results on dora maira pyropes can now be interpreted atomistically

h2o contents and d h ratios of nominally anhydrous minerals from ultrahigh pressure eclogites of the dabie orogen eastern china abstract garnet and omphacite from ultrahigh pressure eclogites from the dabie orogen eastern china were investigated by micro ftir the results show that all garnet and omphacite grains contain structural water occurring as hydroxyl oh with h2o contents varying from 14 to 1915 ppm h2o wt and from 105 to 695 ppm respectively within the same sample the water contents are either homogeneous at the grain scale or vary systematically from higher in the core to lower in the rim low water contents at crystal rims possibly result from hydroxyl exsolution after pressure decrease upon rock exhumation the d values of omphacites are between 108 4 and 114 2 and independent of water contents heterogeneous water contents of garnet occur at the centimeter scale and fluid mobility during uhp metamorphism was very limited the estimated whole rock water content based on mineral h2o contents is between 260 and 750 ppm thereby implying that eclogitic rocks formed during continental subduction have the potential to recycle at least several hundreds ppm water to mantle depths the preserved chemical differences likely indicate that the eclogitic rocks resided at mantle conditions for a limited time span and imply that they were exhumed shortly after subduction the water released during decompression might represent the early stage retrograde fluid

water hydrogen in the lunar mantle results from petrology and magma ocean modeling abstract measurements of hydroxyl or water in lunar materials are being used to suggest that melting source regions within the moon contained tens to hundreds of ppm water the compositions of magmatic source regions in the moon can be calculated using magma ocean fractional solidification models given an initial bulk composition our magma ocean models demonstrate that to make a source region with 10 to 200 ppm water the bulk magma ocean must contain 100 to 1000 ppm water or more and in a 1000 km deep lunar magma ocean 1000 ppm water is equivalent to 5 of an earth ocean by weight as solidification of the magma ocean continues water and other incompatible elements are progressively enriched in the evolving liquids the final kreep like liquids would contain the greatest fraction of water we suggest that a bulk magma ocean with over 100 ppm water is prohibited by constraints on these kreep like final magma ocean liquids and by the thermodynamic equilibrium requirement with metallic iron in mare basalts we conclude that bulk lunar interior water contents must be at the low end of the range posited by recent observations

owen fracture zone the arabia india plate boundary unveiled we surveyed the owen fracture zone at the boundary between the arabia and india plates in the nw indian ocean using a high resolution multibeam echo sounder owen cruise 2009 for search of active faults bathymetric data reveal a previously unrecognized submarine fault scarp system running for over 800 km between the sheba ridge in the gulf of aden and the makran subduction zone the primary plate boundary structure is not the bathymetrically high owen ridge but is instead a series of clearly delineated strike slip fault segments separated by several releasing and restraining bends despite an abundant sedimentary supply by the indus river flowing from the himalaya fault scarps are not obscured by recent deposits and can be followed over hundreds of kilometres pointing to very active tectonics the total strike slip displacement of the fault system is 10 12 km indicating that it has been active for the past 3 to 6 ma if its current rate of motion of 3 1 mm yr 1 has remained stable we describe the geometry of this recent fault system including a major pull apart basin at the latitude 20 n and we show that it closely follows an arc of small circle centred on the arabia india pole of rotation as expected for a transform plate boundary

kinetics of the coesite to quartz transformation abstract the survival of coesite in ultrahigh pressure uhp rocks has important implications for the exhumation of subducted crustal rocks we have conducted experiments to study the mechanism and rate of the coesite quartz transformation using polycrystalline coesite aggregates fabricated by devitrifying silica glass cylinders containing 2850 h 10 6 si at 1000 c and 3 6 gpa for 24 h conditions were adjusted following synthesis to transform the samples at 700 1000 c at pressures 190 410 mpa below the quartz coesite equilibrium boundary reaction proceeds via grain boundary nucleation and interface controlled growth with characteristic reaction textures remarkably similar to those seen in natural uhp rocks we infer that the experimental reaction mechanism is identical to that in nature a prerequisite for reliable extrapolation of the rate data growth rates obtained by direct measurement differ by up to two orders of magnitude from those estimated by fitting a rate equation to the transformation time data fitting the rates to turnbull s equation for growth therefore yields two distinct sets of parameters with similar activation energies 242 or 269 kj mol but significantly different pre exponential constants extrapolation based on either set of growth rates suggests that coesite should not be preserved on geologic time scales if it reaches the quartz stability field at temperatures above 375 400 c the survival of coesite has previously been linked to its inclusion in strong phases such as garnet that can sustain a high internal pressure during decompression other factors that may play a crucial role in preservation are low fluid availability possibly even less than that of our nominally dry experiments and the development of transformation stress which inhibits nucleation and growth these issues are discussed in the context of our experiments as well as recent observations from natural rocks

water in the lower crustal granulite xenoliths from nushan eastern china 1 nominally anhydrous clinopyroxene cpx orthopyroxene opx and plagioclase pl from 10 lower crustal granulite two pyroxene granulite and hypersthene granulite xenoliths in cenozoic basalts from the nushan volcano eastern china have been analyzed for their hydrogen content by microscopic fourier transform infrared spectroscopy micro ftir the results demonstrate that hydrogen was incorporated in all these minerals in the manner of oh and that the content h2o weight is up to 2360 ppm for cpx 1170 ppm for opx and 880 ppm for pl on the basis of the water content of constitutive minerals and their proportions whole rock water contents of the nushan granulites were estimated to be 150 950 ppm estimated equilibrium temperatures of the nushan granulites are in the range of 810 892 c corresponding to the lowermost crust at nushan about 25 30 km therefore this study provides direct evidence that the lower continental crust even the lowermost part devoid of hydrous minerals can contain a certain amount of water in nominally anhydrous minerals

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

understanding the climatic signal in the water stable isotope records from the neem shallow firn ice cores in northwest greenland 1 samples of precipitation and atmospheric water vapor were collected together with shallow firn ice cores as part of the new deep drilling project in northwest greenland the neem project these samples were analyzed for their isotope composition to understand the processes affecting the climatic signal archived in the water stable isotope records from the neem deep ice core the dominant moisture source for the snow deposited at the neem site may be originating as far south as 35 n from the western part of the atlantic ocean the surface atmospheric water vapor appears in isotopic equilibrium with the snow surface indicating a large water exchange between the atmosphere and snowpack the interannual variability of neem shallow firn ice cores stable isotope data covering the last 40 years shows an unexpectedly weak nao signal regional to global atmospheric models simulate a dominant summer precipitation in the neem area suggesting that the intermittency of modern winter precipitation is responsible for the lack of a strong nao imprint the interannual variability of neem isotope data however shows a strong correlation with interannual variations of baffin bay sea ice cover a relationship consistent with air mass trajectories neem deep ice core isotopic records may therefore provide detailed information on past baffin bay sea ice extent neem stable water isotope content increasing trend points to a local warming trend of 3 0 c over the last 40 years

coupled substitution of h and minor elements in rutile and the implications of high oh contents in nb and cr rich rutile from the upper mantle infrared absorption spectra of rutile crystals from a variety of geological environments carbonatite hydrothermal vein kyanite rutile lazulite association xenoliths that are kimberlite hosted and dominated by nb and cr rich rutile exhibit strong absorption in the 3300 cm 1 region due to interstitial protons bonded to structure o in general the proton is located at sites slightly displaced from 1 21 20 of the unit cell although some samples show evidence of additional protons at tetrahedral interstitial sites h contents of rutile range up to 0 8 wt h 2o the highest concentrations occurring in mantle derived nb and cr rich rutile of metasomatic origin the role of h in rutile was examined particularly with respect to its relations to other impurities protons are present in the rutile structure to compensate for trivalent substitutional cations cr fe v ai which are only partly compensated by pentavalent ions nb ta the possibility of using the h content of rutile as a geohygrometer is illustrated for the case of coexisting hematite and rutile

uvarovite from chromite bearing ultramafic intrusives orissa india a crystal chemical characterization using 57fe mossbauer spectroscopy epma analyses of uvarovite from the chromite bearing ultramafic intrusive of sukinda india show that uvarovite containing 9 83 to 17 68 wt cr 2 o 3 represents a solid solution of the binary uvarovite andradite series with uva 34 58 and 42 58 associated chromite grains with 57 59 wt cr 2 o 3 do not show any compositional variation from core to rim 57 fe mossbauer spectroscopic studies on the uvarovite samples undertaken both at room temperature 298 k and low temperature 110 k indicate the presence of fe 3 only in octahedral coordination uvarovite grew from chromite cr source and pyroxenes al fe and ca source of the ultramafic host rocks

mineral oxygen isotope and hydroxyl content changes in ultrahigh pressure eclogite gneiss contacts from chinese continental scientific drilling project cores a combined study of mineral o isotopes and hydroxyl contents was carried out for the contacts between ultrahigh pressure eclogite and gneiss from main hole of the chinese continental scientific drilling project in the sulu orogen while there is a large d 18 o variation from 8 3 to 7 3 for all minerals different styles of mineral pair fractionation occur at the boundaries of different lithologies both equilibrium and disequilibrium o isotope fractionations are observed between quartz and the other minerals with reversed fractionations between omphacite and garnet in some samples of eclogite this suggests that both eclogite and gneiss acquired their negative d 18 o values by meteoric hydrothermal alteration of their protoliths at high temperatures before subduction and that fluid assisted o isotope exchange did take place across the boundary of different lithologies at local scales during amphibolite facies retrogression fourier transform infrared spectroscopy analysis yielded h2o concentrations of 50 to 1144 p p m by weight for garnet and 139 to 751 p p m for omphacite the state of equilibrium or disequilibrium o isotope fractionations between omphacite and garnet are correlated with variations in their water content at local scales indicating that the internally derived fluid plays a critical role in retrograde metamorphism during exhumation the retrograde metamorphism results in mineral reactions and o isotope disequilibria between some of the minerals but the fluid for retrogression was derived from the decompression exsolution of structural hydroxyl and thus internally buffered in the o isotope composition a quantitative estimate suggests that a hand specimen 3 6 9 cm of eclogite composed of 70 garnet and 30 omphacite can release 0 316 g water by the decompression exsolution of structural hydroxyl which can form 14 4 g amphibole during exhumation this provides sufficient amounts of water for the amphibolite facies retrogression

hydrogarnet substitution in pyrope a possible location for water in the mantle abstract single crystal spectra of pyropes synthesized on the 3 1 3 composition of the system mgo al2o3 sio2 atph2o ptotal 25kbar and 1000 c show a broad band centered at around 3400 cm 1 due to h2o of h2o n aggregates in fluid inclusions and a sharp intense band near 3600 cm 1 due to oh of ho 44 clusters introduced by the hydrogarnet substitutionsi4 4h the water contents in the synthetic pyrope due to ho 44 clusters are estimated near 0 05 wt h2o from spectroscopic data si deficits in microprobe analyses of the pyropes studied support the hydrogarnet substitution these results show that the hydrogarnet substitution in pyrope may contribute to water contents in the mantle

retrieving a common accumulation record from greenland ice cores for the past 1800 years 1 in the accumulation zone of the greenland ice sheet the annual accumulation rate may be determined through identification of the annual cycle in the isotopic climate signal and other parameters that exhibit seasonal variations on an annual basis the accumulation rate in different greenland ice cores is highly variable and the degree of correlation between accumulation series from different ice cores is low however when using multiyear averages of the different accumulation records the correlation increases significantly a statistical model has been developed to estimate the common climate signal in the different accumulation records through optimization of the ratio between the variance of the common signal and of the residual using this model a common greenland accumulation record for the past 1800 years has been extracted the record shows significant 11 9 years periodicity a sharp transition to very dry conditions is found just before a d 1200 and very dry conditions during the 13th century together with dry and cold spells during the 14th century may have put extra strain on the norse population in greenland and may have contributed to their extinction accumulation rates gradually decrease from a distinct maximum in a d 1394 to very dry conditions in the late 17th century and thus reflect the little ice age

solubility of water in pyrope rich garnet at high pressures and temperature 1 the water solubility in pyrope rich garnet was determined between pressures of 5 9 gpa and temperatures of 1373 1473 k under silica activity and oxygen fugacity similar to those expected in the earth s upper mantle we found that pyrope rich garnet has substantial water solubility up to 0 1 wt under these conditions in addition the water content in garnet varied as a function of chemical conditions in particular the variation in water fugacity and mg caused a variation in water partitioning with olivine the substantial water solubility in pyrope rich garnet under deep upper mantle conditions might have significant influence on physical and transport properties

water transport by subduction clues from garnet of erzgebirge uhp eclogite a key question concerning the water budget of earth s mantle is how much water is actually recycled into the mantle by the subduction of eclogitized oceanic crust hydrous phases are stable only in quartz eclogite not coesite eclogite so that water transport to greater depths is mainly governed by structural water in omphacite and garnet here we explore if garnet can be used as a proxy to assess the amount of this water available data on the water contents of garnet in coesite eclogite vary over orders of magnitude from a few up to ca 2000 ppm by implication the maximum bulk rock water contents are unrealistically high wt level new data from the erzgebirge indicate moderate amounts of structural h 2 o stored in garnet 43 84 ppm omphacite 400 820 ppm and in the bulk coesite eclogite ca 280 460 ppm higher garnet water contents occur but these are not primary features they are related to molecular water in fluid inclusions that can be attributed to eclogite facies fluid influx postdating the metamorphic peak fluid influx also caused the uptake of additional structural water in garnet domains close to fluid inclusions such secondary h 2 o incorporation is only possible in the case of primary water deficiency indicating that garnet hosted less water than it was able to store this is insofar astonishing as comparably high h 2 o amounts are liberated by the breakdown of prograde eclogite facies hydrous minerals as a result of ultrahigh pressure uhp metamorphism judging from erzgebirge quartz eclogite dehydration of 5 10 hydrous minerals equal portions of zoisite calcic amphibole produces 1500 3000 ppm water we infer that the largest part of the liberated water escaped probably due to kinetic reasons and hydrated exhuming uhp slices in the hanging wall depending on the physical conditions water influx in eclogite during exhumation 1 produces fluid inclusions and simultaneously enhances the structural water content of nominally anhydrous minerals as in the erzgebirge and or 2 it may give rise to retrograde hydrous minerals we conclude that eclogite transports moderate quantities of water several hundred parts per million to mantle depths beyond 100 km an amount equivalent to that in ca 1 calcic amphibole

high concentration of water in stishovite in the morb system 1 stishovite synthesized from natural basalt showed the highest concentration of hydrogen ever reported the water concentration obtained from the polished single crystal of stishovite in this study was up to a maximum of 5628 291 atoms of hydrogen per 106 silicon atoms 844 44 ppm water the concentration of hydrogen increased with increasing substitution of trivalent cations which is almost aluminum and temperature has a significant effect on the incorporation of hydrogen into stishovite the result of this study suggests that stishovite in subducted basaltic crust could be an important water containing phase and contribute to the transport of hydrogen to the lower mantle

heterogeneity of water in garnets from uhp eclogites eastern dabieshan china abstract garnets in uhp eclogites from bixiling in dabieshan were investigated by fourier transform infrared spectroscopy ftir the results indicate that all garnets contain structural water that occurs as hydroxyl oh and non structural molecular water h 2 o possibly in the form of sub microscopic fluid inclusions the structural hydroxyl contents range from 92 to 1735 ppm h 2 o wt and most are between 200 and 1000 ppm therefore garnet in eclogite can recycle surface water into the mantle various water contents were observed among different samples of the same outcrop 150 m and in different domains of the same sample 1 cm this variability in structural h 2 o contents suggests that the mobility of fluids during uhp metamorphism was very limited and that both subduction and exhumation processes of uhp rocks occurred in a short time interval

water content of mantle garnets garnet megacrysts from colorado plateau diatremes green knobs garnet ridge and the wesselton kimberlite south africa commonly contain a structural hydrous component the colorado plateau samples range from 0 0 to 0 26 wt h 2 o and the wesselton samples contain from 0 01 to 0 07 concentrations were measured using p 2 o 5 cell coulometry h 2 gas manometry and thermogravimetry these were used to calibrate infrared integrated absorbance in the 3 m region which is a more sensitive measure of total o h content than the other analytical methods infrared absorbance patterns were also used to differentiate structural hydrous component from water contained in alteration and included phases the structure of the hydrous component in these garnets appears to be the classic h 4 o 4 4 sio 4 4 profiles at 100 m intervals across these samples show flat concentration profiles or slightly increasing concentration toward the center a large range of water content among samples appears to represent real differences in water fugacity at the point where the garnets equilibrated garnets in eclogite nodules from south africa and the solomon islands were also studied but were either anhydrous or too badly altered to determine the content of structurally bound water the high concentration of hydrous component in the colorado plateau samples is consistent with other indicators of high volatile content in that region of the mantle the water content of mantle garnets may prove to be an accurate indicator of mantle water fugacities

the distribution of hydroxyl in garnets from the subcontinental mantle of southern africa 166 garnets of dominantly mantle origin were analyzed for oh content by infrared ir spectroscopy ir spectra in the 3400 3700 cm 1 region display consistent absorption patterns attributable to oh structurally bound within the garnet crystal occasionally contaminated by low intensity oh absorptions from microscopic inclusions the principal structural oh absorption occurs near 3570 cm 1 with the appearance of additional absorptions near 3512 cm 1 and 3650 cm 1 dependent on garnet composition or paragenesis samples derive from a wide variety of rock types occurring as xenoliths in kimberlites of southern africa oh abundances using the best currently available calibration range from less than 1 up to 135 ppm h 2o and increase in the general order as follows on craton eclogites group 1 basaltic kimberlite alnoite alkali basalt the oh contents of common lithospheric granets from coarse peridotites including several phlogopite bearing samples are typically less than 20 ppm h 2o for tectonic settings of kimberlites both on and off the archaean kaapvaal craton ti rich garnets from deformed peridotites are richer in oh supporting previous suggestions of association of these xenoliths with putative megacryst magmas subcalcic cr rich xenocrysts diamond inclusion garnets and garnets from diamondiferous eclogites have very low oh contents similar to eclogites and depleted peridotites without macroscopic diamonds the oh content of southern african peridotite and eclogite garnets are significantly lower on average than those previously examined from the colorado plateau diatremes while details of emplacement related h mobility in garnets remain to be established our results suggest that garnets record useful information on the role of water or other hydrous volatile species in petrological processes at their source regions in the mantle although garnets do not appear to constitute a large reservoir of mantle hydrogen the large stability range of oh bearing garnet in the crust and mantle implies wide applicability as a qualitative hydrobarometer

persistent link between solar activity and greenland climate during the last glacial maximum changes in solar activity have previously been proposed to cause decadal to millennial scale fluctuations in both the modern and holocene climates1 direct observational records of solar activity such as sunspot numbers exist for only the past few hundred years so solar variability for earlier periods is typically reconstructed from measurements of cosmogenic radionuclides such as 10be and 14c from ice cores and tree rings2 3 here we present a high resolution 10be record from the ice core collected from central greenland by the greenland ice core project grip the record spans from 22 500 to 10 000 years ago and is based on new and compiled data4 5 6 using 14c records7 8 to control for climate related influences on 10be deposition we reconstruct centennial changes in solar activity we find that during the last glacial maximum solar minima correlate with more negative 18o values of ice and are accompanied by increased snow accumulation and sea salt input over central greenland we suggest that solar minima could have induced changes in the stratosphere that favour the development of high pressure blocking systems located to the south of greenland as has been found in observations and model simulations for recent climate9 10 we conclude that the mechanism behind solar forcing of regional climate change may have been similar under both modern and last glacial maximum climate conditions

origin of retrograde fluid in ultrahigh pressure metamorphic rocks constraints from mineral hydrogen isotope and water content changes in eclogite gneiss transitions in the sulu orogen abstract by taking advantage of having depth profiles between contrasting lithologies from core samples of the chinese continental scientific drilling ccsd project a combined study was carried out to examine changes in mineral h isotope total water and hydroxyl contents in garnet and omphacite across the contacts between ultrahigh pressure uhp eclogite and gneiss in the sulu orogen east central china the samples of interest were from two continuous core segments from the ccsd main hole at depths of 734 21 737 16 and 929 67 932 86 m respectively the results show d values of 116 to 64 for garnet and 104 to 82 for omphacite consistent with incorporation of meteoric water into protoliths of uhp metamorphic rocks by high t alteration both equilibrium and disequilibrium h isotope fractionations were observed between garnet and omphacite suggesting fluid assisted h isotope exchange at local scales during amphibolite facies retrogression while bulk water analysis gave total h2o concentrations of 522 1584 ppm for garnet and 1170 20745 ppm for omphacite structural hydroxyl analysis yielded h2o contents of 80 413 ppm for garnet and 228 412 ppm for omphacite it appears that significant amounts of molecular h2o are present in the minerals pointing to enhanced capacity of water storage in the uhp eclogite minerals hydrogen isotope variations in the transition between eclogite and gneiss show correlations with variations in their water contents petrographically the degree of retrograde metamorphism generally increases with decreasing distance from the eclogite gneiss boundary thus retrograde metamorphism results in mineral reactions and h isotope variation because hydroxyl solubility in nominally anhydrous minerals decreases with dropping pressure significant amounts of water are expected to be released from the minerals during decompression exhumation decompression exsolution of structural hydroxyl from 1 m3 volume of eclogite composed of only garnet and omphacite results in release of a quantitative estimate of 3 07 3 44 kg water that can form 140 156 kg amphibole during exhumation therefore it is concluded that fluid for retrogression of the eclogites away from the eclogite gneiss boundary was derived from the decompression exsolution of structural hydroxyl and molecular h2o in nominally anhydrous minerals for the eclogites adjacent to gneiss in contrast the retrograde metamorphism was principally caused by aqueous fluid from the gneiss which is relatively rich in water consequently both the origin and availability of metamorphic fluid during exhumation of deeply subducted continental crust are deciphered by this combined study focusing on the transitions and the retrograde processes between the felsic and mafic uhp rocks

changes in continental and sea salt atmospheric loadings in central greenland during the most recent deglaciation model based estimates by fitting a very simple atmospheric impurity model to high resolution data on ice accumulation and contaminant fluxes in the gisp2 ice core we have estimated changes in the atmospheric concentrations of soluble major ions insoluble particulates and 10 be during the transition from glacial to holocene conditions for many species changes in concentration in the ice typically overestimate atmospheric changes and changes in flux to the ice typically underestimate atmospheric changes because times of increased atmospheric contaminant loading are also times of reduced snowfall the model interpolates between the flux and concentration records by explicitly allowing for wet and dry deposition processes compared to the warm preboreal that followed we estimate that the atmosphere over greenland sampled by snow accumulated during the younger dry as cold event contained on average four seven times the insoluble particulates and nearly seven times the soluble calcium derived from continental sources and about three times the sea salt but only slightly more cosmogenic 10 be

the rift like structure and asymmetry of the dead sea fault abstract whereas the dead sea fault is a major continental transform active since ca 13 18 ma ago it has a rift like morphology along its southern part it has been argued that this results from a transtensional component active since 5 ma ago due to a regional plate kinematics change we present the results of 3d laboratory experiments carried out to test this hypothesis and to explore its consequences for the structure and morphology of the dead sea fault we conclude that a two stage tectonic history invoking a first stage of pure strike slip and a second stage marked by the addition of a minor transtensional component is consistent with most of the striking geological and geophysical features of the dead sea fault the structural and morphological asymmetry of the dead sea fault can be explained by a transverse horizontal shear in the ductile lower crust below the transform zone a large scale heating event of the arabian mantle is not required to explain these features of the dead sea fault

the oh content of pyrope at high pressure the oh contents of pyrope garnets synthesised at 1000 c and pressures between 2 and 13 gpa have been measured by infrared spectroscopy we find that under the same conditions of pressure temperature ah2o and asio2 the oh content of pyrope is similar to that of grossular this shows that observed differences in nature between water contents of pyrope and grossular are related to paragenesis rather than reflecting higher intrinsic solubility in grossular in the presence of excess sio2 the h2o content increases with pressure to 5 gpa 1000 ppm then decreases to below the detection limit at pressures above 7 gpa thus garnet becomes more hydrous with pressure to some critical value beyond which dehydration occurs even under h2o saturated conditions this observation is consistent with the measured partial molar volume of water in hydrogarnet which becomes greater than that in fluid water within the pressure range of this study when corrected to upper mantle conditions we find that pyrope should dehydrate with increasing depth below about 250 km pyrope is unlikely therefore to be a major site of water storage in the transition zone and upper mantle