ammonium in granites and its petrogenetic significance abstract ammonium is present as a trace constituent in all granites with an average concentration of 45 ppm nh4 equivalent to 35 ppm of elemental n it shows wide variations related to petrography and region but the only significant correlation between ammonium and other geochemical parameters is that it is most abundant in peraluminous granites and least abundant in peralkaline granites these variations can be related to a the amount of sedimentary material in the magmatic source region and b redox conditions in the source region the ammonium content of granitic magmas can also be modified by fractionation or contamination hydrothermal alteration has a major effect on the ammonium content of granitic rocks and variation due to this cause may exceed the magmatic variation most hydrothermally altered granites are enriched in ammonium as a result of the transfer of ammonium from sedimentary country rocks by the hydrothermal fluids

a simple multicloud parameterization for convectively coupled tropical waves part i linear analysis abstract recent observational analysis reveals the central role of three multicloud types congestus stratiform and deep convective cumulus clouds in the dynamics of large scale convectively coupled kelvin waves westward propagating two day waves and the madden julian oscillation a systematic model convective parameterization highlighting the dynamic role of the three cloud types is developed here through two baroclinic modes of vertical structure a deep convective heating mode and a second mode with low level heating and cooling corresponding respectively to congestus and stratiform clouds a systematic moisture equation is developed where the lower troposphere moisture increases through detrainment of shallow cumulus clouds evaporation of stratiform rain and moisture convergence and decreases through deep convective precipitation a nonlinear switch is developed that favors either deep or congestus convection depending on the relative dryness of the troposphere in particular a dry troposphere

nitrogen isotopic composition of ammoniated phyllosilicates case studies from precambrian metamorphosed sedimentary rocks ammonium concentrations in phyllosilicates from archean and proterozoic schists and carbonates were evaluated by fourier transform infrared microspectrometry aftir the y 15 nair values of structural nitrogen in these phases were subsequently measured by laser mass spectrometry a rapid estimate of the concentration of nh4 in biotite by aftir allows the preselection of the samples to be analyzed for their isotopic composition micas from 1 90 2 09 ga metasediments from finland and from 1 025 1 500 ga biotite schists from the moine succession in scotland have high concentrations of structural ammonium between 176 and 1549 ppm suggestive of a biological origin for the nitrogen the heavy nitrogen isotopic signatures y 15 n 4 9x to 19 7x of structural nh4 in these micas are considered consistent with biological denitrification in operation at the time of sedimentation evidence for denitrification in the mesoproterozoic is in agreement with geological and geochemical data for abundant free oxygen in the atmosphere facilitating the stability of marine no3 sequences of early archean ca 3 8 ga garnet mica schists from the isua supracrustal belt isb in southern west greenland contain biotite rich in nh4 between 233 and 512 ppm and nitrogen isotopic signatures y 15 n 1 9x to 5 9x which possibly point to an early evolution of ammonium assimilation and or nitrogen fixation this result appears to be consistent with molecular phylogenetic studies in the bacterial and archaeal domains which suggest that nitrogen fixation and ammonium assimilation were metabolic features of the last common ancestor lca of all organisms d 2004 elsevier b v all rights reserved

nitrogen in rock occurrences and biogeochemical implications 1 there is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations nitrogen bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification nitrogen in rock originates as organically bound nitrogen associated with sediment or in thermal waters representing a mixture of sedimentary mantle and meteoric sources of nitrogen rock nitrogen concentrations range from trace levels 200 mg n kg 1 in granites to ecologically significant concentrations exceeding 1000 mg n kg 1 in some sedimentary and metasedimentary rocks nitrate deposits accumulated in arid and semi arid regions are also a large potential pool nitrogen in rock has a potentially significant impact on localized nitrogen cycles elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen in some environments nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems more nitrogen available than required by biota nitrogen saturation results in leaching of nitrate to surface and groundwaters and where soils are formed from ammonium rich bedrock the oxidation of ammonium to nitrate may result in soil acidification inhibiting revegetation in certain ecosystems collectively studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems

oscillations of the intertropical convergence zone and the genesis of easterly waves part ii numerical verification a companion paper part i toma and webster 2008 argued that the characteristics of the mean intertropical convergence zone itcz arise from instabilities associated with the strong cross equatorial pressure gradient cepg that exists in the eastern pacific ocean as a result of the latitudinal sea surface temperature sst gradient furthermore it was argued that instabilities of the mean itcz resulted in the in situ development of easterly waves thus in part i it was hypothesized that the mean and transient state of eastern pacific convection was due to local processes and less so to the advection of waves from the north atlantic ocean to test this hypothesis and at the same time consider others such as a possible role of the equatorial and subtropical orography in generating local instabilities a series of controlled numerical experiments are designed using the wrf regional model the domain of the model was configured to include the western atlantic ocean the isthmus of panama and the eastern pacific ocean to 155 w lateral boundaries were set at 40 n and 40 s thus containing the mountains of central america the andes and the sierra madre of mexico in a series of experiments analysis products were used as boundary conditions that were successively updated four times per day set as 10 day running average fields or as running mean monthly fields finally the model was run with topography essentially eliminated over the land areas although there are differences between the details of the resultant fields the location of mean convection and the form of the transients remain the same it is concluded in support of the theoretical and diagnostic studies of part i that orographic forcing or waves generated in the north atlantic ocean are not the major causes of the mean and transient nature of disturbances in the eastern pacific

nitrogen in future biosphere studies this article suggests a theme for future nitrogen studies involving the functioning and evolution of the biosphere together with certain aspects of human biology it is hoped that this theme could be developed into a multi authored book at some point in the future although numerous new case studies may be required the biosphere can be considered to be a single interactive system comprised of numerous component parts including the atmosphere rain rivers lakes oceans continental ecosystems marine ecosystems soils and sediments in order to study the internal complexity of each of the components and the relationships that exist between them one can choose a common theme the author believes that nitrogen is a good prospect because of its ubiquitous nature and complex chemistry the burial of sedimentary volatiles in the continental crust has contributed to the long term chemical evolution of the exterior environments of the earth the most marked effects notably the accumulation of atmospheric oxygen have been due to the burial of reduced carbon an understanding of the passage of sedimentary volatiles through the crust will provide important constraints on the evolution of the biosphere and may lead to a more meaningful comparative planetology carbon is difficult to trace through crustal processes because its high temperature form graphite is incompatible with the crystal structures of silicate minerals however the high temperature form of sedimentary nitrogen ammonium readily enters into potassic minerals and it can be easily traced through crustal processes herein the fate of sedimentary nitrogen is traced from wet sediments through metamorphic rocks into granites and other crustal melts without the trapping of nitrogen in the crust and the liberation of oxygen that is a consequence of biological nitrogen fixation the n2 o2 of the atmosphere may have been about 82 9 to 16 3 and the total atmospheric pressure about 1 2 atm most of the changes in the oxygen content is due to dilution by nitrogen with only about 5 of the present atmospheric oxygen being a consequence of nitrogen fixation the ancient continental surfaces would have been volcanic deserts containing little 1 ppm or no nitrogen today nitrogen rich soils support continental ecosystems one can use nitrogen as a window to speculate on the colonisation of the continents by land plants herein nitrogen fixation by legumes is considered in detail and by drawing analogies with the present day the author speculates on the colonisation of the continents by land plants having speculated on the co evolution of the atmosphere soils and continental ecosystems one can place a human being in the centre of a tropical forest and begin to examine how they relate to the modern biosphere the chosen example is the metabolism of plant protein and the roles of glutamate dehydrogenase gdh vitamin b2 and flavin mononucleotide fmn the realisation of this theme would imply numerous new case studies notably those concerning the continental crust where nitrogen studies were linked to mineralogy petrology and other geochemical tracers including sr o al and k and where the short range order of 15n were taken into consideration

regional groundwater focusing of nitrogen and noble gases into the hugoton panhandle giant gas field usa the hugoton panhandle giant gas field located across sw kansas and the texas and oklahoma panhandles in the usa is the case type example of high nitrogen concentrations in a natural gas being linked with high helium concentrations we collected 31 samples from producing wells in a north south traverse of the 350 km long field the samples reflect the previously observed north south change in 4he n2 with values changing from 0 020 to 0 049 respectively 3he 4he 21ne 22ne and 40ar 36ar vary between 0 14 0 25 ra 0 0373 0 0508 and 818 1156 respectively and are caused by quantifiable contributions from mantle crustal and atmosphere derived sources the atmosphere derived 20ne 36ar ratios are indistinguishable from groundwater values the crustal 4he 21ne and 4he 40ar ratios show a 60 excess of 4he compared to predicted production ratios in the crust and are typical of noble gases released from the shallow crust the mantle 3he n2 and groundwater recharge 36ar n2 ratios enable us to rule out significant magmatic or atmosphere contributions to the gas field n2 which is dominantly crustal in origin correlated 20ne n2 and 4he n2 shows mixing between two distinct crustal n2 components one n2 component n2 is associated with the crustal 4he and groundwater derived 20ne and the other with no resolvable noble gas contribution measured 15nn2 values vary from 2 7 to 9 4 the n2 and non he associated n2 endmembers are inferred to have 15nn2 3 and 13 and contribute from between 25 60 and 75 40 of the nitrogen respectively the non he associated nitrogen is probably derived from relatively mature organic matter in the sedimentary column the 15nn2 value is not compatible with a crystalline or high grade metamorphic source and similar to the 4he is inferred to be from a shallow or low metamorphic grade source rock 4he mass balance requires a regional crustal source its association with significant magmatic 3he pointing to a tectonically active source to the west of the hugoton system the volume of groundwater required to source the 20ne in the gas field demonstrates the viability of the groundwater system in providing the collection transport and focusing mechanism for the 4he and n2 the n2 20ne ratio shows that the n2 transport must be in the aqueous phase and that the degassing mechanism is probably contact between the regional groundwater system and the preexisting reservoir hydrocarbon gas phase

a 3 800 million year isotopic record of life from carbon in sedimentary rocks an increased ratio of 12c to 13c an indicator of the principal carbon fixing reaction of photosynthesis is found in sedimentary organic matter dating back to almost four thousand million years ago a sign of prolific microbial life not long after the earth s formation partial biological control of the terrestrial carbon cycle must have been established very early and was in full operation when the oldest sediments were formed

observations of a convectively coupled kelvin wave in the eastern pacific itcz abstract a case study of a convectively coupled kelvin wave in the eastern pacific intertropical convergence zone itcz is presented as observed during the 1997 pan american climate studies pacs tropical eastern pacific process study tepps the large scale convective envelope associated with this disturbance with a zonal scale of approximately 1000 2000 km propagates eastward at 15 m s 1 along the mean convective axis of the itcz this envelope consists of many smaller scale westward moving convective elements with zonal scales on the order of 100 500 km as the convectively coupled kelvin wave disturbance propagates eastward it exerts a strong control on local convection radar and vertical profiler data collected aboard the noaa r v ronald h brown during the wave passage show that convection deepens rapidly as the kelvin wave approaches from the west progressing from isolated shallow cumuli to organized deep convective features within just 12 h initially rainfall in the vicinity of the s

experimental determination of the ammonium partitioning among muscovite k feldspar and aqueous chloride solutions abstract the cation exchange equilibria muscovite nh 4 cl tobelite kcl kal 2 alsi 3 o 10 oh 2 nh 4 cl aq nh 4 al 2 alsi 3 o 10 oh 2 kcl aq k feldspar nh 4 cl buddingtonite kcl kalsi 3 o 8 nh 4 cl aq nh 4 alsi 3 o 8 kcl aq are determined by hydrothermal experiments at 400 500 600 c at 400 mpa and piston cylinder experiments at 500 600 c at 1500 mpa along the entire k nh4 compositional range the composition of solid phases are determined by xrd emp and ftir methods nh4 k ratios in coexisting 2 3 molal chloride solutions by ion chromatography muscovite tobelite and k feldspar buddingtonite form complete solid solutions series at all conditions consistent phase relations and mass balances indicate equilibrium between solid solutions and fluids in both the k nh4 muscovite and k nh4 feldspar fluid systems nh4 strongly fractionates into the fluid in the range from 400 to 600 c 400 to 1500 mpa fractionations are slightly temperature and pressure dependent the distribution coefficient k d solid fluid x nh 4 solid x k solid x k fluid x nh 4 fluid varies within the experimental range from 0 10 at xkbulk 0 81 to 0 46 at xkbulk 0 20 for muscovite fluid and from 0 05 at xkbulk 0 91 to 0 70 at xkbulk 0 15 for feldspar fluid nh4 is preferentially incorporated into feldspar relative to mica with kdfsp ms ranging between 1 36 and 2 0 at 400 mpa and between 1 13 and 1 5 at 1500 mpa as xkbulk varies from 0 15 to 0 89 results are evaluated thermodynamically assuming equal mixing of nh4cl and kcl in the fluid mixing energies of solids were estimated using multidimensional regression and a regular solution model for the muscovite tobelite equilibrium values of s 11 7 j k 1 mol 1 v 2 1 j mpa 1 mol 1 and w 4 6 kj mol 1 and for the k feldspar buddingtonite equilibrium s 8 8 j k 1 mol 1 v 1 1 j mpa 1 mol 1 and w 5 4 kj mol 1 were derived results are used to calculate partition coefficients d among phases at very low nh4 bulk concentrations between 400 and 600 c dnh4fluid ms ranges from 7 to 8 at 400 mpa and is 5 at 1500 mpa dnh4fluid ms is 6 to 7 at 400 mpa and about 5 at 1500 mpa dnh4fsp ms is between 1 and 1 2 at all conditions partition coefficients are valid for nh4 contents of up to several hundred ppm in mica and feldspar well within the concentration range observed in many rocks combining the data with that of k nh4 partitioning between phlogopite and fluid results in dnh4phl ms 3 5 and dnh4phl ms 3 at 550 c 200 to 400 mpa nh4 concentrations in coexisting muscovite biotite and k feldspar from a variety of rocks show near equilibrium distributions nh4 k partitioning between major k bearing minerals and saline fluids allows for assessment of the dehydration history of metamorphic rocks during prograde metamorphism water is progressively produced by dehydration reactions and expelled along rock s p t path nitrogen is subsequently removed due to preferred fractionation of nh4 into fluids the remaining nh4 is continuously redistributed among muscovite and biotite and at higher grades k feldspar with biotite as the main solid phase carrier of ammonium the large fractionation effect of nh4 among most phases highlights its potential as tracer of devolatilization processes and fluid rock interactions

distribution of ammonium in minerals of metamorphic and granitic rocks abstract sixty nine analyses are given for nh4 in minerals of metamorphic and granitic rocks mostly from the ryoke belt japan the distribution of nh4 in coexisting minerals is quite systematic suggesting that nh4 is one of the stable geochemical components in high temperature processes biotite has the highest content of nh4 followed by muscovite k feldspar and plagioclase pure quartz is almost free from nh4 calcic plagioclase contains less nh4 than does sodic plagioclase the partition coefficients d pl bi d kf bi and d kf bi are on the average 0 11 0 38 and 0 43 respectively the fractionation of nh4 in these minerals is quite similar to that of rb but much smaller than that of cs distribution of nh4 as well as those of rb and cs appears to be explained by its ionic radius and the shortest cation o distances in alkali positions of minerals

nitrogen distribution in lower palaeozoic slates phyllites of the meguma supergroup nova scotia canada implications for au and zn pb mineralisation and exploration abstract major and trace elements and nitrogen were analysed in 59 cambrian and ordovician slates phyllites of various lithostratigraphic levels within the meguma supergroup 14 ordovician slates phyllites of the ovens gold mineralisation and 16 ordovician slates phyllites of the eastville pb zn cu mineralisation the fixed nitrogen content and the normative n fix k 2 o ratio of muscovite separates members of the goldenville sandstone greywacke quartzite dominated and halifax formation slate phyllite dominated low fixed nitrogen concentration is related to high manganese concentration black slates phyllites of the saddle reef type au mineralisation in the ovens area are characterised by high fixed nitrogen and a high normative n fix k 2 o ratio of muscovite the nitrogen is of secondary hydrothermal origin therefore it might be possible to use the fixed nitrogen as an exploration tool for black slates phyllite hosted gold mineralisation in nova scotia mineralised slates phyllites of the eastville stratabound pb zn mineralisation cannot be distinguished from nonmineralised time equivalent lithologies on the basis of the fixed nitrogen distribution or the n fix k 2 o ratio of muscovite

nitrogen production from geochemical weathering of rocks in southwest montana usa 1 a 30 day time course laboratory weathering experiment was conducted using rock samples collected from the west fork of the gallatin river watershed wfw in southwestern montana usa the goal of these experiments was to quantify the amount of labile nitrogen in rock samples collected from the watershed and determine if chemical weathering is a source of dissolved nitrogen in stream water several rock samples investigated produced nitrate in significantly higher concentrations than the silica bead control p 0 05 and the data were consistent with elevated no3 concentrations measured in associated wfw streams isotopic analyses of 15n no3 in 22 stream water samples from the wfw and four rock water extracts from the laboratory experiments indicated that the isotopic composition of no3 was comparable with rocks and stream water samples in the same watershed and differed strongly from waters downstream of development we suggest that the no3 measured in wfw streams includes nitrogen derived from mineral dissolution products from soils and rock the results presented herein further indicate that rock weathering is a source of stream water n in the west fork watershed and inform water quality assessment total maximum daily load development and the relative influences of natural and anthropocentrically derived n sources across this developing mountain watershed

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

relationships between water and gas chemistry in mature coalbed methane reservoirs of the black warrior basin water and gas chemistry in coalbed methane reservoirs of the black warrior basin reflects a complex interplay among burial processes basin hydrodynamics thermogenesis and late stage microbial methanogenesis these factors are all important considerations for developing production and water management strategies produced water ranges from nearly potable sodium bicarbonate water to hypersaline sodium chloride brine the hydrodynamic framework of the basin is dominated by structurally controlled fresh water plumes that formed by meteoric recharge along the southeastern margin of the basin the produced water contains significant quantities of hydrocarbons and nitrogen compounds and the produced gas appears to be of mixed thermogenic biogenic origin late stage microbial methanogenesis began following unroofing of the basin and stable isotopes in the produced gas and in mineral cements indicate that late stage methanogenesis occurred along a co2 reduction metabolic pathway hydrocarbons as well as small amounts of nitrate in the formation water probably helped nourish the microbial consortia which were apparently active in fresh to hypersaline water the produced water contains nh4 and nh3 which correlate strongly with brine concentration and are interpreted to be derived from silicate minerals denitrification reactions may have generated some n2 which is the only major impurity in the coalbed gas carbon dioxide is a minor component of the produced gas but significant quantities are dissolved in the formation water degradation of organic compounds augmented by deionization of nh4 may have been the principal sources of hydrogen facilitating late stage co2 reduction

n2 and co2 in deep crustal fluids evidence from the caledonides of norway abstract high pressure metamorphic rocks eclogites and high pressure granulites occur along the entire length of the norwegian caledonides and have formed from a variety of protoliths in some cases the relationship between protoliths high pressure rocks and their later retrogression products have been preserved in situ fluid inclusion data suggest a simple correlation between metamorphic grade and metamorphic fluid composition 1 eclogites and high pressure granulites contain n 2 bearing fluids pure n 2 or mixtures with co 2 or h 2 o with x n 2 5 in some eclogite facies rocks co 2 1bn 2 inclusions are associated with aqueous brine inclusions ca 30 wt nacl the two compositions representing immiscible fluids at peak metamorphic conditions 2 granulite facies protoliths and eclogites reworked in the granulite facies contain pure co 2 or co 2 dominated fluids with less than 2 5 n 2 3 rocks retrograded in the amphibolite facies contain h 2 o 1bnacl fluids immiscibility between brine and anhydrous n 2 1bco 2 fluid and between anhydrous fluid and waterbearing aluminosilicate melt have taken place in some eclogites during high grade metamorphism nitrogen may be incorporated in minerals as nh 4 substituting for k or it may occur as n 2 in the free fluid phase the partitioning of nitrogen between minerals and fluids depends upon the water activity and oxygen fugacity during metamorphism low a h 2 o and or high f o 2 partitioning nitrogen to the fluid phase a rock interacting with a carbonic fluid at granulite facies pt conditions will be depleted in mineralogically bound nitrogen in cases where the protoliths of high pressure rocks have been through a previous granulite facies event a local source for the nitrogen contained in high pressure fluid is therefore unlikely

the behavior of nitrogen and nitrogen isotopes during metamorphism and mineralization evidence from the otago and alpine schists new zealand abstract metamorphism is a major mechanism for the re distribution of fluids and mass in the earth s crust with these processes most prominently highlighted by the occurrence of major gold resources within these terranes however although orogenic gold deposits have contributed over 20 of the global gold production their origins remain controversial the nitrogen concentration and isotopic composition of rocks and minerals are potentially powerful tracers of crustal metamorphism and mineralization but there have been few detailed applications of this approach to date although nitrogen isotopes have recently been used to elucidate the source of fluids in some neoarchean orogenic gold deposits and proterozoic to paleozoic mountain belts due to their age and geological complexity of these terranes major uncertainties as to the behavior of nitrogen remain the otago and alpine schists in the south island of new zealand comprise a large comparatively young the range of 15n values for mica and whole rock samples from the schists spans 0 2 to 7 0 and the nitrogen concentration from 23 to 3483 ppm sample provenance and rock type have minimal influence on the nitrogen concentration and isotopic value which appears to have been inherited from the original sedimentary kerogen there is no systematic variation between metamorphic temperature and 15n or n concentration in micas suggesting that there has been little discernible loss of 15n depleted fluids from silicates with increasing metamorphic temperature comparison of fluid mobile alkali element k rb and cs carbon and nitrogen whole rock concentrations indicates that for the otago and alpine schists in rocks up to upper greenschist facies significant nitrogen remains hosted in phases other than micas most likely poorly matured carbonaceous material samples from macraes flat a major gold producer have a similar range of 15n values to the host terrane but show distinctly higher nitrogen concentrations relative to unmineralized samples due to the incorporation of nitrogen from the mineralizing hydrothermal fluid this suggests that there is only a subtle metamorphic re distribution of nitrogen during mineralization albeit with minimal isotopic fractionation in the case of nitrogen at least the isotopic signatures of mineralized rocks support a metamorphic fluid source and are inconsistent with mantle or meteoric fluid reservoirs however due to the high relative abundance of nitrogen in sedimentary rocks compared to other potential reservoirs unless fluid fluxes are very large and well channeled nitrogen signatures are not sensitive recorders of fluid inputs from mantle magmatic or meteoric reservoirs conversely the absence of a sedimentary source nitrogen isotope signature similar to the host rock in an orogenic deposit would be a very strong indicator of an external exotic source for the mineralizing fluids

precambrian ammonium biogeochemistry a study of the moine metasediments scotland abstract the content and isotopic composition of ammoniacal nitrogen have been determined in a suite of amphibolite facies metasediments of precambrian age whole rock samples and mica separates from the moine succession proterozoic of scotland were analysed by a combination of capacitance manometry and static vacuum mass spectrometry prior to the analyses the presence of the ammonium ion was confirmed by obtaining infrared ir absorption spectra from the micas principally biotites whole rock ammonium contents are high for amphibolite facies metasediments 140 422 ppm the ammonium ion was not detected in the ir absorption spectra of biotites from one schist however this sample contains neither garnet nor white mica for most of the samples the 15n values are very positive between 12 4 and 16 6 with one sample having a lower value of 8 4 the major variations between samples can be interpreted in terms of original sedimentary features for the ammonium bearing samples muscovites have concentrations between 365 and 633 ppm biotites between 845 and 1739 ppm for individual samples nh4 mu nh4 bi varies between 0 31 and 0 43 a much narrower range than has been reported previously there are no significant or consistent differences in 15n between co existing biotite and white mica nor between the 15n values of the mineral separates and their respective whole rock values the latter suggests minimal selective partitioning of isotopes between micas and plagioclase feldspar the only other potential host for ammonium in the rocks assuming that the ammonium has been derived from organic matter originally present at the time of deposition and by comparison with previous studies it can be inferred that the original 15n value of the moine sediments was somewhere between 5 and 10 similar to recent sediments this suggests that the nitrogen cycle in the proterozoic shelf sea from which the moine sediments were deposited was broadly similar to the present day overall the study underlines how under developed the n system is compared to other stable isotope systems notably c and s and we use the opportunity to highlight some areas that could be developed in the future however one aspect is clear future ammonium studies of metamorphic rocks will need to be performed at high resolution visible scale of heterogeneity with strong mineralogical petrological and field controls

upscale impact of mesoscale disturbances of tropical convection on convectively coupled kelvin waves abstracttropical convection associated with convectively coupled kelvin waves cckws is typically organized by an eastward moving synoptic scale convective envelope with numerous embedded westward moving mesoscale disturbances such a multiscale structure of tropical convection is a challenge for present day cloud resolving simulations and its representation in global climate models it is of central importance to assess the upscale impact of mesoscale disturbances on cckws as mesoscale disturbances propagate at various tilt angles and speeds besides it is still poorly understood whether the front to rear tilted vertical structure of cckws can be induced by the upscale impact of mesoscale disturbances in the presence of upright mean heating here a simple multiscale model is used to capture this multiscale structure where mesoscale fluctuations are directly driven by mesoscale heating and synoptic scale circulation is forced by mean heating and eddy transfer of momentum and temperature the results s

non biogenic graphite in 3 8 ga metamorphic rocks from the isua district greenland abstract a 3 8 ga old metamorphic rock that contains up to 5 5 wt reduced carbon as graphite was found in the isua district greenland this rock exhibits a strong schistosity comprises mostly talc contains high mgo 28 0 wt ni 553 ppm and cr 267 ppm and low al2o3 2 13 wt and bears a high fe 2 o 3 feo ratio 0 94 the original rock was probably a submarine ultramafic tuff the carbon content and the 13c value of the rock vary on a microscopic scale a few mm3 scale from 0 7 to 5 5 wt and from 15 to 12 respectively the second rock a quartzite contains 0 13 wt c as reduced carbon with a 13c value of 11 25 these 13c values fall within the range 27 to 10 reported by previous investigators for graphite from the isua district the 13c values of the isua graphite have been interpreted by previous investigators e g schidlowski and aharon 1992 as metamorphic modification of organic matter with initial 13c values of 30 an important implication of this model has been that the 3 8 ga ocean already supported some biological activity however an examination of the carbon content vs 13c relationship of the graphite bearing rocks from isua has revealed that the 13c value generally increases with increasing carbon contents the rocks with 13c values less than 20 contain extremely small amounts of carbon the mineralogical and elemental characteristics of the rocks of this study a thermodynamic consideration of the temperature and composition of metamorphic fluids and carbon isotope mass calculations suggest that the major component of graphite with 13c values around 12 was formed by an inorganic rather than by a biological process the graphite appeared to have formed at temperatures between 700 and 400 c by one or both of the following two processes 1 reactions between co2 and ch4 co2 ch4 2c 2h2o during cooling of fluids with a co 2 ch 4 molar ratio of 1 and or 2 reactions between the feo component in the ultramafic rock with co2 rich fluids 4 feo co2 2 fe2o3 c the 13c c values for the fluids for both i and 2 were probably between 12 and 5 suggesting that the carbon bearing fluids could have been derived from the mantle

ammonium concentration and nitrogen isotope composition in metasedimentary rocks from different tectonometamorphic units of the european variscan belt the content and isotopic composition of ammonium nh4 were measured by using kjeldahl distillation for 63 samples of predominantly metasedimentary rocks from two different geological settings of the european variscides i e the erzgebirge and the zone of erbendorf vohenstrauss in germany the studied erzgebirge schists represent an early paleozoic passive margin sequence that reappears in different deep subducted metamorphic units this allows an efficient examination of nitrogen loss and isotope fractionation during prograde metamorphism ammonium is found to be progressively depleted accompanied by a shift in 15n from the low grade units 2 kbar 300 c with 638 124 ppm and 15n 2 2 0 6 to the garnet phyllite unit 9 kbar 470 c with 621 190 ppm and 15n 3 5 0 9 the mica schist eclogite unit 12 kbar 550 c with 394 113 ppm and 15n 3 9 0 8 and to the gneiss eclogite unit 12 kbar 730 c with 99 32 ppm and 15n 7 7 2 0 using equilibrium models for rayleigh distillation and batch volatilization suggest that the nitrogen depletion took place by ammonia release only for the mica schists this isotope fractionation can be explained by the loss of molecular nitrogen in comparison with the early paleozoic schists the proterozoic ortho and paragneisses of the erzgebirge gneiss unit 6 8 kbar 650 c contain significantly lower amounts of ammonium 70 ppm and reach relatively low 15n values 2 5 to 3 6 the paragneisses from the zone of erbendorf vohenstrauss zev sampled from the ktb pilot hole represents a separate tectonometamorphic unit that has undergone polyphase metamorphic conditions with the major imprint being amphibolite facies 7 kbar 650 700 c the metagraywackes have nh4 contents of 80 ppm and 15n of approximately 6 gneisses in the vicinity of a late cataclastic shear zone at 2000 m depth are characterized by a shift in nh4 250 ppm and 15n up to 12 which suggest late fluid rock interactions with a nitrogen and 15n enriched fluid

the santa rita gold deposit in the proterozoic paranoa group goias brazil an example of fluid mixing during ore deposition abstract the santa rita gold deposit central goias brazil is hosted by middle to upper proterozoic carbonate pelite sequences of the paranoa group that have been metamorphosed in the greenschist facies the ore is contained in pyrite bearing quartz carbonate veins the mineralization is structurally controlled by wnw ese high angle faults and fractures resulting from the reactivation of older ne sw lineaments pyrite is the sole sulphide and it shows growth zones enriched in co ni and as up to 4 wt hydrothermal alteration zones are enriched in co ni and as and are characterized by diffuse albitization carbonatization silicification and pyritization a fluid inclusion study on quartz from pyrite bearing quartz carbonate veins led to the identification of two fluids 1 a highly saline co 2 n 2 rich aqueous fluid with halite and sylvite daughter minerals and 2 a co 2 n 2 rich aqueous fluid with moderate salinity the two fluid types occur in the same quartz domain and display great variation in the degree of filling and notable dispersion of the microthermometric data on heating all the inclusions decrepitate between 200 and 300 c raman spectrometry detected high concentrations of n 2 in the gas phase with a co 2 n 2 molar ratio between 1 and 19 and a small proportion of ch 4 up to 2 mole the simultaneous entrapment of compositionally variable fluids in the system h 2 o co 2 n 2 nacl kcl allow us to propose a mechanism of heterogeneous trapping the entrapment may result from the mixing of a high salinity fluid h 2 o nacl kcl system with a carbonic fluid h 2 o co 2 n 2 system produced by the devolatilization process of carbonate and phyllitic host rocks considering the absence of spatially and temporally related igneous activity and the low p t regional metamorphism in the paranoa group the brines are inferred to result from leaching of evaporites occurring in the lower part of the paranoa lithostratigraphic column gold was probably initially transported as an aucl 2 complex t 300 c low ph moderate o 2 pyrite field stability as temperature decreased below 290 c the switch over process would lead to the predominance of au hs 2 in the fluid pyrite precipitated in this temperature interval the oscillatory zoning of the as co ni bearing pyrites indicates episodic fluctuation of the fluid composition such changes in fluid composition are favoured by a mechanism of fluid mixing by intermittent supplies in the hydrothermal system the proposed mechanism of heterogeneous trapping of two separate fluids in the system h 2 o co 2 n 2 nacl kcl and the resulting changes in the physicochemical conditions caused by the fluid mixing appears as a conspicuous process for the santa rita hydrothermal fluid evolution a model based on the existence of a proterozoic geothermal system involving the regional thermal gradient is proposed

the geochemical behaviour of nitrogen compounds during the formation of black shale hosted quartz vein gold deposits north wales abstract previous fluid inclusion studies of the black shale hosted quartz vein au mineralisation at the clogau st davids mine have revealed an association between n 2 levels in the fluids and the grade of au mineralisation suggesting mobilisation and or involvement of n compounds during the mineralising event we have analysed the nh 4 contents of silicates in altered and unaltered rocks hosting the veins in an attempt to constrain the origin of the n ammonium levels in altered wall rocks differ from those in similar rocks remote from mineralisation implying n mobility but only in the zones of most intense alteration are wall rock shales severely depleted in nh 4 however fluids feeding the vein system are low in n and leaching of nh 4 from shales is the most likely source of n during mineralisation thermodynamic modelling of fluid phase equilibria shows that oxidation of nh 4 from silicates is a viable source of n in the fluid such a reaction will have a dramatic reducing effect on the redox state of the fluid and may in conjunction with reduction by graphite be an important trigger of ore deposition the results suggest that amine complexes are unlikely to have been important in metal transport as has been proposed for some epithermal volcanic au deposits however the deposits studied here are of metamorphic origin and the geochemical behaviour of n compounds appears to be markedly different in this case

diagenesis of ammonium during hydrocarbon maturation and migration wilcox group louisiana u s a abstract as organic matter matures n is released in the reduced form as nh4 and substitutes for k in clay minerals as oil forms an abundance of n is generated coincident with the formation of authigenic illite this study suggests that nh4 released from organic matter during maturation migrates through sandstones together with the pore fluids and volatile phases generated from the migrating crude oil this causes anomalously high nh4 substitution in authigenic illites fixed nh4 concentrations in illite are a product of both hydrocarbon maturation and migration concentrations of fixed nh4 from organic rich mudstones in two wilcox group oil fields show a general increase with depth coincident with increasing organic maturation reservoir sandstones containing crude oils have fixed nh4 concentrations as much as two times those of the mudstones when values are normalized to the quantity of clay minerals fixed nh4 concentrations in the gaseous portion of the reservoir are three times as high two out of five sandstones from a dry hole adjacent to a producing oil field contain anomalously high 2 above mean concentrations of fixed nh4 with respect to total organic centent this together with a high production index and hydrogen index in those units suggests that migrating hydrocarbons may have influenced the fixed nh4 concentrations

a multiscale model for the intraseasonal impact of the diurnal cycle over the maritime continent on the madden julian oscillation abstractthe eastward propagating madden julian oscillation mjo typically exhibits complex behavior during its passage over the maritime continent sometimes slowly propagating eastward and other times stalling and even terminating there with large amounts of rainfall this is a huge challenge for present day numerical models to simulate one possible reason is the inadequate treatment of the diurnal cycle and its scale interaction with the mjo here these two components are incorporated into a simple self consistent multiscale model that includes one model for the intraseasonal impact of the diurnal cycle and another one for the planetary intraseasonal circulation the latter model is forced self consistently by eddy flux divergences of momentum and temperature from a model for the diurnal cycle with two baroclinic modes which capture the intraseasonal impact of the diurnal cycle the mjo is modeled as the planetary scale circulation response to a moving heat source on the synoptic and planetary scales

relations of ammonium minerals at several hydrothermal systems in the western u s abstract ammonium bound to silicate and sulfate minerals has recently been located at several major hydrothermal systems in the western u s utilizing newly discovered near infrared spectral properties knowledge of the origin and mineralogic relations of ammonium minerals at known hydrothermal systems is critical for the proper interpretation of remote sensing data and for testing of possible links to mineralization submicroscopic analysis of ammonium minerals from two mercury and gold bearing hot springs deposits at ivanhoe nevada and mclaughlin california shows that the ammonium feldspar buddingtonite occurs as fine grained euhedral crystals coating larger sulfide and quartz crystals ammonium feldspar seems to precipitate relatively late in the crystallization sequence and shows evidence for replacement of nh4 by k or other monovalent cations some buddingtonite is observed in close association with mercury but not with gold ammonioalunite is found in a variety of isolated crystal forms at both deposits nitrogen isotopic values for ammonium bearing minerals show a 14 range in composition precluding assignment of a specific provenance to the nitrogen the correlations of nitrogen isotopic values with depth and ammonium content suggest some loss of nitrogen in the oxidizing supergene environment possibly as a metastable mineral the high ammonium content in these hydrothermal systems the close association to mercury and the small crystal size of the ammonium bearing minerals all suggest that ammonium may be transported in a late stage vapor phase or as an organic volatile such a process could lead to the formation of a non carbonaceous organic aureole above a buried geothermal source the discovery of a 10 km outcrop of ammonium minerals confirms that significant substitution of ammonium in minerals is possible over an extensive area and that remote sensing is a feasible means to detect such aureoles

modeling of the transport and deposition of tungsten in the scheelite bearing calc silicate gneisses of the montagne noire france scheelite bearing calc silicate gneisses csg oceur in the montagne noire within a series of dominant micaschists detailed petrographical and mineralogical studies reveal three successive stages of metamorphism and hydrothermal alteration 1 stage 1 a regional metamorphism at 550 c and 4 5 kb where no mineralization is formed 2 stage 2a a hydrothermal alteration at 500 to 450 c and 4 to 3 kb which is characterized by an intense sericitization of feldpars and deposition of sn in sn bearing cale silicates and 3 stage 2b a hydrothermal alteration characterized by the crystallization of idocrasegrossular in csg with concomittant precipitation of scheelite tungsten was transported through the micaschist environment and deposited as scheelite only in the csg of stage 2b at relatively low pressures to characterize the mechanism of tungsten transport tungsten speciation at high p t and scheelite solubility in aqueous solations buffered by the csg and by the micaschists assemblages were calculated it was found that h2wo 0 4 hwo 4 and wo 2 4 are the dominant tungsten aqueous species in h2o nacl one molal solutions at 500 c and 2 4 kb calculations also indicate that scheelite deposition is controlled by decreasing pressure and increasing activity of aqueous calcium in this system this is consistent with the petrographical and mineralogical observations the consequences of the presence of volatiles n2 ch4 co2 in the regional fluids were examined by determining the effect of n2 on tungsten speciation and scheelite solubility the addition of n2 up to 10 mol to the mineralizing fluids results in a marked increase in h2wo 0 4 and hwo 4 concentrations relative to wo 2 4 and in a large decrease of scheelite solubility this mechanism favours scheelite precipitation and accounts for the commonly observed association of w and sn deposits with graphitic series generating mixed volatiles fluids

nitrogen isotope geochemistry of organic matter and minerals during diagenesis and hydrocarbon migration the magnitude of isotopic variations between organic and inorganic nitrogen was examined in samples from three stacked hydrocarbon reservoirs in the fordoche field louisiana gulf coast basin usa measurements were made of 15n in kerogen bitumen oil formation water and fixed nh4 extracted from mudstones nonproductive sandstones and productive sandstones nitrogen isotope fractionation occurs because 14n is released preferentially to 15n from organic molecules during thermal maturation released 14n goes into solution or may be adsorbed by minerals leaving crude oil enriched in 15n diagenetic clay minerals e g illite commonly form in the temperature range of hydrocarbon generation and nh4 may be fixed in clay interlayers with an isotopic ratio similar to that of the migrating fluids results indicate that the influence of organic matter on mineral 15n depends on the timing of authigenic mineral formation relative to fluid migration the average 15n of kerogen 3 2 0 3 and fixed nh4 from mudstones 3 0 1 4 is similar while bitumen increases from 3 5 to 5 1 with depth in deep reservoir sandstones 100 c the 15n of crude oil averages 5 2 0 4 similar to the 15n of bitumen in the proposed source rocks formation waters are 14n enriched with an average 15n of 2 2 2 6 fixed nh4 15n values lie between that of the oil and water the average 15n of fixed nh4 is 3 0 1 2 in productive sandstones and 0 2 2 4 innonproductive sandstones in the shallower reservoir sandstones 90 c fixed nh4 is apparently not influenced by the presently associated fluids productive and nonproductive sandstones have distinctly low average 15n values 1 2 0 8 yet crude oil 11 1 0 3 and water 3 8 0 1 have been 15n enriched by 6 relative to the deeper reservoirs this suggests that the present fluids migrated into the reservoir after authigenic illite had formed fluids become enriched in 15n during migration and the amount of enrichment may be a function of the amount of interaction with argillaceous sediments

ammonium contents of biotites from precambrian rocks in finland the significance of nh4 as a possible chemical fossil abstract the ammonium contents of biotites in precambrian rocks from finland have been determined to examine the possibility that ammonium in biotites represents a chemical fossil if biologic activity existed in precambrian sedimentary environments biotites formed from the sediments should contain distinctly larger quantities of nh 4 than biotites from igneous rocks biotites from svecokarelidic metasediments which were originally products of sedimentation about 2400 1900 ma ago have high nh 4 contents hundreds of ppm while biotites from svecokarelidic plutonic rocks of 1800 1900 ma old and postsvecokarelian rapakivi granites of 1650 1700 ma old have low nh 4 contents tens of ppm the results may indicate that biologic activity was plentiful during sedimentation of the svecokarelian strata this agrees with evidence for ancient life found in dolomites and greywacke slates of the svecokarelides biotites from presvecokarelidic schists of more than 2600 2800 ma old have only tens of ppm of nh 4 this value is at the same level as those of biotites from the rapakivi granites and the svecokarelidic plutonic rocks considering the rarity of fossils in presvecokarelidic rocks the low nh 4 content of biotite from a presvecokarelidic pelitic schist may indicate less biologic activity during the sedimentation of the original sediments these data emphasize that ammonium in biotites of precambrian metasediments may be a useful chemical fossil for identifying the geologic sites of ancient life

sub greenschist facies metamorphism from the variscides of sw ireland an early syn extensional peak thermal event illite crystallinity studies on metaclastics from the variscides of sw ireland range in value from 0 18 to 0 25 2 indicating a metamorphic grade in the upper anchizone lower epizone c 275 325 c chlorite geothermometry yields a similar metamorphic temperature range 280 315 c combining these data with known overburden estimates for the area c 5km implies late palaeozoic geothermal gradients in excess of 60 ckm 1 fluid inclusion studies on quartz veins in these metaclastics reveal two vein types characterized by fluid densities of 0 7 0 93 g cm 3 group 1 and 0 9 1 0gcm 3 group 2 respectively this variation in fluid density is thought to be dominantly controlled by temperature with group 1 veins linked to late palaeozoic extension and high geothermal gradients and group 2 veins associated with subsequent variscan deformation and lower temperature conditions

the measurement of δ15n in crustal rocks by static vacuum mass spectrometry application to the origin of the ammonium in the cornubian batholith southwest england the release of ammoniacal nitrogen from muscovite biotite orthoclase microcline and a whole rock granite by vacuum pyrolysis has been investigated under the heating regimes employed it was found that micas lose most of their nitrogen below the temperature at which the powders begin to sinter ca 1100 c the peak release of n occurring in either the 900 c or 1000 c heating step it is possible that the loss of ammonium is linked to the loss of h2o and perhaps f for the feldspars there was insignificant release of n below the melting point of the minerals about 1150 c suggesting that diffusion of ammonium or ammonia is the principal control for both micas and feldspars there was significant kinetic fractionation of the nitrogen isotopes during stepped heating from these results a technique has been devised for the routine determination of 15n and ammonium concentration in whole rock granites by static vacuum mass spectrometry the ammonium concentrations and 15n values have been determined in whole rock samples from the cornubian batholith southwest england the ammonium concentrations were in the range 8 to 187 ppm and the 15n values were in the range 5 1 to 10 2 most of the granite samples had 15n values between 8 4 and 10 2 and are within the range that have been obtained from amphibolite facies metasediments these granites are also typified by high 87sr86srinit 0 7130 to 0 7166 and high normative corundum 2 31 to 2 55 taken together the data suggest that the ammonium present within these granites is of biological origin and that it was incorporated via the anatexis of metasediments which originally contained organic material the samples were collected over a distance of 120 km and the limited range in 15n suggests either 1 1 the 15n values within the metasedimentary protolith were rather homogeneous or 2 2 the nitrogen isotopes were homogenised during the incorporation of ammonium into the granite magmas two of the granites had lower 15n values of 5 1 and 7 0 these granites also have lower ammonium concentrations 8 and 15 ppm lower 87sr86srinit 0 7094 0 7095 and lower normative corundum 1 44 and 1 63 the preferred explanation is that they were derived from or have had a contribution from a second crustal source containing sedimentary or metasedimentary material with a lower proportion of pelitic to other constituents

temporal trends in nitrogen isotope values of nitrate leaching from an agricultural soil the concentration and d 15 no f no y in leachate from two undisturbed and unfertilized soil lysimeters one convention 3

fluid evolution during burial and variscan deformation in the lower devonian rocks of the high ardenne slate belt belgium sources and causes of high salinity and c o h n fluids fluid inclusions in quartz veins of the high ardenne slate belt have preserved remnants of prograde and retrograde metamorphic fluids these fluids were examined by petrography microthermometry and raman analysis to define the chemical and spatial evolution of the fluids that circulated through the metamorphic area of the high ardenne slate belt the earliest fluid type was a mixed aqueous gaseous fluid h2o nacl co2 ch4 n2 occurring in growth zones and as isolated fluid inclusions in both the epizonal and anchizonal part of the metamorphic area in the central part of the metamorphic area epizone in addition to this mixed aqueous gaseous fluid primary and isolated fluid inclusions are also filled with a purely gaseous fluid co2 n2 ch4 during the variscan orogeny the chemical composition of gaseous fluids circulating through the lower devonian rocks in the epizonal part of the slate belt evolved from an earlier co2 ch4 n2 composition to a later composition enriched in n2 finally a late variscan aqueous fluid system with a h2o nacl composition migrated through the lower devonian rocks this latest type of fluid can be observed in and outside the epizonal metamorphic part of the high ardenne slate belt the chemical composition of the fluids throughout the metamorphic area shows a direct correlation with the metamorphic grade of the host rock in general the proportion of non polar species i e co2 ch4 n2 with respect to water and the proportion of non polar species other than co2 increase with increasing metamorphic grade within the slate belt in addition to this spatial evolution of the fluids the temporal evolution of the gaseous fluids is indicative for a gradual maturation due to metamorphism in the central part of the basin in addition to the maturity of the metamorphic fluids the salinity of the aqueous fluids also shows a link with the metamorphic grade of the host rock for the earliest and latest fluid inclusions in the anchizonal part of the high ardenne slate belt the salinity varies respectively between 0 and 3 5 eq wt nacl and between 0 and 2 7 eq wt nacl while in the epizonal part the salinity varies between 0 6 and 17 eq wt nacl and between 3 and 10 6 eq wt for the earliest and latest aqueous fluid inclusions respectively although high salinity fluids are often attributed to the original sedimentary setting the increasing salinity of the fluids that circulated through the lower devonian rocks in the high ardenne slate belt can be directly attributed to regional metamorphism more specifically the salinity of the primary fluid inclusions is related to hydrolysis reactions of cl bearing minerals during prograde metamorphism while the salinity of the secondary fluid inclusions is rather related to hydration reactions during retrograde metamorphism the temporal and spatial distribution of the fluids in the high ardenne slate belt are indicative for a closed fluid flow system present in the lower devonian rocks during burial and variscan deformation where fluids were in thermal and chemical equilibrium with the host rock such a closed fluid flow system is confirmed by stable isotope study of the veins and their adjacent host rock for which uniform 180 values of both the veins and their host rock demonstrate a rock buffered fluid flow system

isotopic variations of the fixed nitrogen in metamorphic rocks the content and isotopic composition of fixed nitrogen nh 4 n in metasedimentary rocks phyllites mica schists and gneisses from prograde metamorphic zones in the erzgebirge saxon ore mountains g d r were measured and show that the nitrogen content decreases and 15n increases with increasing metamorphic grade the geochemical and isotopic behaviour of nitrogen during contact metamorphism was investigated in a mica schist profile through the contact aureole of a granitic pluton the nitrogen concentrations of the wall rocks decrease towards the contact whereas the 15n values become higher various model experiments were carried out in the laboratory to explain the changes observed in the rock samples the nitrogen isotope fractionation factor was determined for the isotopic exchange in the system ammonium sulphate ammonia at 250 c 1 0143 0 0012 and 350 c 1 0128 0 0006 in accordance with the model experiments the conclusion seems warranted that the change in nitrogen content and its isotopic composition in rocks during metamorphic processes depend mainly on the metamorphic temperature

source and short distance propagation of the july 9 1956 southern aegean tsunami abstract properties of the tsunamigenic source as well as the attenuation of the tsunami intensities of the large tsunami of july 9 1956 in the southern aegean are investigated this tsunami was generated by a shallow earthquake with a surface wave magnitude of 7 5 which was caused by a normal fault fault plane solution isoseismal lines and bathymetric information indicate that the tsunamigenic source had an elliptical shape with the large axis equal to 110 km and oriented in an ene wsw direction this is also the strike of the normal fault which produced the earthquake and it is probable that the southern block was downthrown linear relations between a the tsunami intensity and the epicentral distance for distances up to 330 km b the observed tsunami height and the epicentral distance and c the tsunami height and intensity have been determined this information concerning the source parameters of tsunamis and the attenuation of the tsunami intensity and tsunami height with distance are of great importance for determining the tsunami hazard in this area

calculated fluid evolution path versus fluid inclusion data in the cohn system as exemplified by metamorphic rocks from rogaland south west norway fluid evolution paths in the cohn system can be calculated for metamorphic rocks if there are relevant data regarding the mineral assemblages present and regarding the oxidation and nitrodation states throughout the entire p t loop the compositions of fluid inclusions observed in granulitic rocks from rogaland south west norway are compared with theoretical fluid compositions and molar volumes the fluid parameters are calculated using a p t path based on mineral assemblages which are represented by rocks within the pigeonite in isograd and by rocks near the orthopyroxene in isograd surrounding an intrusive anorthosite massif the oxygen and nitrogen fugacities are assumed to be buffered by the coexisting fe ti oxides and cr carlsbergite respectively many features of the natural fluid inclusions including 1 the occurrence of co2 n2 rich graphite absent fluid inclusions near peak m2 metamorphic conditions 927 c and 400 mpa 2 the non existence of intermediate ternary co2 ch4 n2 compositions and 3 the low molar volume co2 rich fluid inclusions 36 42 cm3 mol 1 are reproduced in the calculated fluid system the observed co2 ch4 rich inclusions with minor n2 5 mol should also include a large proportion of h2o according to the calculations the absence of h2o from these natural high molar volume co2 ch4 rich inclusions and the occurrence of natural ch4 n2 rich inclusions are both assumed to result from preferential leakage of h2o this has been previously experimentally demonstrated for h2o co2 rich fluid inclusions and has also been theoretically predicted fluid deficient conditions may explain the relatively high molar volumes but cannot be used to explain the occurrence of ch4 n2 rich inclusions and the absence of h2o

ammonium loss and nitrogen isotopic fractionation in biotite as a function of metamorphic grade in metapelites from western maine usa abstract ammonium fixed in micas of metamorphic rocks is a sensitive indicator both of organic inorganic interactions during diagenesis as well as of the devolatilization history and fluid rock interaction during metamorphism in this study a collection of geochemically well characterized biotite separates from a series of graphite bearing paleozoic greenschist to upper amphibolite facies metapelites western maine usa were analyzed for ammonium nitrogen nh 4 n contents and isotopic composition 15nnh4 using the hf digestion distillation technique followed by the ea irms technique biotite separates sampled from 9 individual metamorphic zones contain 3000 to 100 ppm nh 4 n with a wide range in 15n from 1 6 to 9 1 average nh 4 n contents in biotite show a distinct decrease from about 2750 ppm for the lowest metamorphic grade 500 c down to 218 ppm for the highest metamorphic grade 685 c decreasing abundances in nh 4 are inversely correlated in a linear fashion with increasing k in biotite as a function of metamorphic grade and are interpreted as a devolatilization effect despite expected increasing 15nnh4 values in biotite with nitrogen loss a significant decrease from the garnet zones to the staurolite zones was found followed by an increase to the sillimanite zones this pattern for 15nnh4 values in biotite inversely correlates with mg mg fe ratios in biotite and is discussed in the framework of isotopic fractionation due to different exchange processes between nh 4 nh 3 or nh 4 n 2 reflecting devolatilization history and redox conditions during metamorphism

the influence of amazon rainfall on the atlantic itcz through convectively coupled kelvin waves abstract using outgoing longwave radiation olr and tropical rainfall measuring mission trmm daily rain rate data systematic changes in intensity and location of the atlantic intertropical convergence zone itcz were detected along the equator during boreal spring it is found that the changes in convection over the tropical atlantic may be induced by deep convection in equatorial south america lagged regression analyses demonstrate that the anomalies of convection developed over the land propagate eastward across the atlantic and then into africa the eastward propagating disturbances appear to be convectively coupled kelvin waves with a period of 6 7 5 days and a phase speed of around 15 m s 1 these waves modulate the intensity and location of the convection in the tropical atlantic and result in a zonal variation of the atlantic itcz on synoptic time scales the convectively coupled kelvin wave has substantial signals in both the lower and upper troposphere both a reanalysis dataset and the qui

organized convection parameterization for the itcz abstractmesoscale convective systems mcss are of fundamental importance in the dynamics of the atmospheric circulation and the climate system they are often observed to develop over significant terrain in ambient shear flows in midlatitudes and embedded within the madden julian oscillation mjo and convectively coupled equatorial wave ccew envelopes as well as in the intertropical convergence zone itcz yet general circulation models gcms fail to resolve these systems and their underlying convective parameterizations are not directed to represent organized circulations shear parallel mcss which are common in the itcz have a three dimensional structure and as such present a serious modeling challenge here a previously developed multicloud model mcm is modified to parameterize mcss one of the main modifications is the parameterization of stratiform condensation to capture extended stratiform outflows which characterize mcss resulting from strong upper level jets linear analysis show

nitrogen isotope record of fluid rock interactions in the skiddaw aureole and granite english lake district the skiddaw granite and its contact metamorphic aureole in the english lake district provide an excellent opportunity to test the capability of the n isotope system to trace devolatilization and large scale transfer of crustal fluids in the aureole skiddaw group metasedimentary rocks with relatively uniform lithology and major element compositions show a dramatic decrease in n content toward the granite contact from or 800 ppm at distances 2 5 km from the contact to 1 5 km these rocks have extremely uniform delta 15 n air near 3 7 per mil whereas closer to the contact or 1 km delta 15 n is shifted to higher values up to 8 7 per mil the coupled decreases in n content and increases in delta 15 n are compatible with the removal of n having low delta 15 n in fluids during continuous prograde devolatilization reactions involving the break down of white mica and the stabilization of biotite cordierite and andalusite bearing assemblages in the same metasedimentary rocks the lack of obvious trends in major element concentrations including sio 2 tio 2 sio 2 al 2 o 3 and the ratios of other major oxides to tio 2 and al 2 o 3 with distance from the granitic contact is consistent with minimal change in major element composition during the contact metamorphism ratios of whole rock n b rb and ba concentrations to whole rock k 2 o content are believed to reflect the differing fluid mica partitioning and involving varying relative proportions of white mica and biotite of these trace elements during devolatilization reactions greisenized skiddaw granite from a borehole is enriched in n range of 17 225 ppm for whole rocks and white mica separates relative to the unaltered granite whole rock 30 ppm and has delta 15 n of 1 0 to 4 8 per mil the n concentrations and delta 15 n of the wall rocks and greisenized granites combined with c isotopic data carbonate and carbonaceous matter for the same rocks are consistent with the mobilization of fluids having low delta 15 n and delta 13 c pdb values from the devolatilized aureole into the cooling intrusive body such transport is consistent with the predictions of recent theoretical models of late stage hydrothermal evolution in cooling intrusive systems

upscale impact of mesoscale convective systems and its parameterization in an idealized gcm for an mjo analog above the equator abstractthe madden julian oscillation mjo typically contains several superclusters and numerous embedded mesoscale convective systems mcss it is hypothesized here that the poorly simulated mjo

ammonium partitioning and nitrogen isotope fractionation among coexisting micas during high temperature fluid rock interactions examples from the new england appalachians abstract despite recent advances in the field of n isotope geochemistry our understanding of the behavior of this element in the solid earth remains limited by a lack of fundamental information regarding the partitioning of ammonium and isotopic fractionation of n among coexisting mineral and fluid phases study of n behavior in regionally metamorphosed rocks provides the opportunity to assess intermineral nh 4 partitioning and n isotope fractionation among coexisting micas during metamorphism and affords an application of the n system as a tracer of high t fluid rock interactions analyzed mica samples range in 15 n air from 3 3 to 11 9 and contain 9 to 1820 ppm n the outcrop at townshend dam vermont allows examination of n behavior across strike on a relatively small scale and samples from western maine demonstrate the effect of varying metamorphic conditions on n behavior in metapelites 15 n bt w mica 15 n biotite 15 n white mica ranges from 0 9 to 2 7 for all samples from both suites mean 0 36 with 1 0 79 with samples containing a separate paragonite white mica phase showing the greatest range 0 12 to 1 02 mean 0 58 1 1 03 thirteen samples containing only na poor muscovite six from townshend dam seven from western maine have mean 15 n bt w mica of 0 07 1 0 41 in both suites biotite nearly always contains more n than coexisting white mica but n w mica n bt also shows some significant scatter mean n w mica n bt 0 46 with 1 0 34 the thirteen samples containing only a na poor muscovitic white mica phase have mean n w mica n bt 0 39 with 1 0 26 similar to that reported by others for other metamorphic suites containing only muscovite as the white mica phase there is no obvious suggestion of equilibrium n isotopic fractionation among coexisting micas at epidote amphibolite to amphibolite facies metamorphic conditions although nh 4 appears to partition systematically among coexisting biotite and white mica significant scatter in both 15 n bt w mica and nh 4 partitioning conceivably the result of differential closure to exchange during cooling or of retrograde replacements could however obscure observation of small equilibrium intermica fractionations related to the characteristics of the interlayer sites in which nh 4 resides samples most unlike the mean in both 15 n bt w mica and n w mica n bt contain abundant chlorite some of which is likely retrograde based on petrographic observations chl chl bt 0 3 thus retrograde replacement of biotite by chlorite may have been accompanied by fluid mineral n isotope exchange perhaps involving the production of fine grained retrograde n bearing white mica observed petrographically for some samples it is also possible that sampling at scales greater than those of n isotope equilibrium domains e g across fine interlayers results in some scatter because of varying relative modal proportions of the two micas in adjacent fine interlayers although further investigation of the extent of retrograde reequilibration of mica n systematics is warranted the observed lack of systematic n isotope fractionation among coexisting micas and the reasonably systematic nh 4 partitioning data for these phases provide important preliminary constraints for attempts to model n isotope behavior in fluid rock systems these results and other attempts to calibrate n isotope fractionation through field studies point to the conspicuous lack of experimentally determined mica fluid n isotope fractionation factors

genesis of the vein type tungsten mineralization at nyakabingo rwanda in the karagwe ankole belt central africa the vein type tungsten deposit at nyakabingo in the central tungsten belt of rwanda is located in the eastern flank of the complex bumbogo anticlinal structure the host rock is composed of alternating sequences of sandstones quartzites and black pyritiferous metapelitic rocks two types of w mineralized quartz veins have been observed bedding parallel and quartz veins that are at high angle to the bedding which are termed crosscutting veins both vein types have been interpreted to have been formed in a late stage of a compressional deformation event both vein types are associated with small alteration zones comprising silicification tourmalinization and muscovitization dating of muscovite crystals at the border of the veins resulted in a maximum age of 992 4 1 5 ma this age is within error similar to the ages obtained for the specialized g4 granites i e 986 10 ma the w bearing minerals formed during two different phases the first phase is characterized by scheelite and massive wolframite while the second phase is formed by ferberite pseudomorphs after scheelite these minerals occur late in the evolution of the massive quartz veins sometimes even in fractures that crosscut the veins the ore minerals precipitated from a h2o co2 ch4 n2 nacl kcl fluid with low to moderate salinity 0 6 13 8 eq wt nacl and minimal trapping temperatures between 247 and 344 c the quartz veins have been crosscut by sulfide rich veins based on the similar setting mineralogy stable isotope and fluid composition it is considered that both types of w mineralized quartz veins formed during the same mineralizing event given the overlap in age between the g4 granites and the mineralized quartz veins and the typical association of the w deposits in rwanda but also worldwide with granite intrusions w originated from the geochemically specialized g4 granites intense water rock interaction and mixing with metamorphic fluids largely overprinted the original magmatic hydrothermal signature

a simple multicloud parameterization for convectively coupled tropical waves part ii nonlinear simulations observations in the tropics point to the important role of three cloud types congestus stratiform and deep convective clouds besides ubiquitous shallow boundary layer clouds for both the climatology and large scale organized anomalies such as convectively coupled kelvin waves two day waves and the madden julian oscillation recently the authors have developed a systematic model convective parameterization highlighting the dynamic role of the three cloud types through two baroclinic modes of vertical structure a deep convective heating mode and a second mode with lower troposphere heating and cooling corresponding respectively to congestus and stratiform clouds the model includes both a systematic moisture equation where the lower troposphere moisture increases through detrainment of shallow cumulus clouds evaporation of stratiform rain and moisture convergence and decreases through deep convective precipitation and also a nonlinear switch that favors either deep or congestus convection depending on whether the lower middle troposphere is moist or dry here these model convective parameterizations are applied to a 40 000 km periodic equatorial ring without rotation with a background sea surface temperature sst gradient and realistic radiative cooling mimicking a tropical warm pool both the emerging walker cell climatology and the convectively coupled wave fluctuations are analyzed here while various parameters in the model are varied the model exhibits weak congestus moisture coupled waves outside the warm pool in a turbulent bath that intermittently amplify in the warm pool generating convectively coupled moist gravity wave trains propagating at speeds ranging from 15 to 20 m s 1 over the warm pool while retaining a classical walker cell in the mean climatology the envelope of the deep convective events in these convectively coupled wave trains often exhibits large scale organization with a slower propagation speed of 3 5 m s 1 over the warm pool and adjacent region occasional much rarer intermittent deep convection also occurs outside the warm pool the realistic parameter regimes in the multicloud model are identified as those with linearized growth rates for large scale instabilities roughly in the range of 0 5 k day 1

new multiscale models and self similarity in tropical convection abstract one of the unexplained striking features of tropical convection is the observed statistical self similarity in clusters superclusters and intraseasonal oscillations through complex multiscale processes ranging from the mesoscales to the equatorial synoptic scales to the intraseasonal planetary scales here new multispatial scale multitime scale simplified asymptotic models are derived systematically from the equatorial primitive equations on the range of scales from mesoscale to equatorial synoptic to planetary intraseasonal which provide a useful analytic framework for addressing these issues new mesoscale equatorial synoptic dynamical mesd models and balanced mesd bmesd models are developed for the multitime multispace interaction from mesoscales to equatorial synoptic scales new multitime versions of the intraseasonal planetary equatorial synoptic dynamics ipesd models are developed for multiple spatiotemporal interactions on equatorial synoptic scales and planetary scales the m

the chemical and isotopic composition of fumarolic gases and spring discharges from galeras volcano colombia abstract galeras fumarole discharges have been collected since its reactivation in 1988 through december 1995 the gases are dominated by h2o co2 s as so2 and h2s and hcl the relative proportions of these gases classify them as magmatic thermodynamic equilibrium temperatures of the gases range from 260 to 600 c the relative abundance of inert gases n2 ar and he can be used as tracers to identify the source of the fumarole discharges at galeras the majority of the samples have a composition characteristic of gases originating from arc related magmas with relatively high n2 contents and minor he and ar during 1993 the year of frequent eruptions the gas composition changed to basaltic or mantle derived gases with significantly higher he contents this is interpreted to be the result of injection of volatiles from a basaltic magma body at depth prior to and during the increased eruptive activity of 1993 the 13c values for co2 in fumarole discharges are typical of andesitic volcanoes and may indicate addition of morb derived co2 the 15n values for n2 may indicate significant contribution of n2 from marine sediments and only minor contribution of morb derived n2 the d and 18o values of the discharging steam lie on a mixing trend between the isotopic composition of arc related magmatic water and18o shifted meteoric water the most magmatic discharges have d values of 30 to 35 while the most meteoric discharges have values of 70 to 75 similar to galeras thermal spring waters galeras thermal water discharges consist of acid sulfate and bicarbonate waters s cl ratios in the acid sulfate waters are similar to fumarole ratios suggesting direct absorption of magmatic gases into shallow ground waters this is supported by the essentially meteoric d and 18o values of the discharges and by elevated3he 4he ratios of thermal spring waters the absorption of acid s and cl rich gases yield acid waters which are capable of dissolving rocks the thermal waters however are far from equilibrium with galeras lavas and pyroclastic rocks providing evidence of the immaturity of the galeras hydrothermal system the so4 and cl content as well as the o and h isotopic composition of galeras thermal springs vary with the activity of the volcano the 7 year sampling program at galeras revealed intriguing results concerning the activity of galeras its magmatic hydrothermal system and the origin of the volatiles despite decreasing outlet temperatures since 1992 deep temperatures remain high implying continued unrest in the galeras magmatic system

tsunamis observed in greece and the surrounding area from antiquity up to the present times abstract a new and improved catalogue of tsunamis observed in greece and the surrounding area from antiquity up to the present time is presented reliable information derived from previous catalogues as well as original historical information which has not been previously taken into account has been used as data source as far as the associated earthquakes are concerned some recent and reliable seismological catalogues have been used as data sources the main cause of the generation of tsunamis is the shallow seismic activity that occurs along the hellenic arc as well as in the internal seismic zone of the aegean area the statistics for tsunamis indicate that the tsunami hazard is low considering the area in question as a whole ten distinct coastal regions in which this hazard can be suggested as medium or high have been defined

carbon and nitrogen isotope systematics in diamond different sensitivities to isotopic fractionation or a decoupled origin abstract using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources it has been argued that carbon and nitrogen in diamond are decoupled here we re investigate the carbon nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds n 94 from a single locality our diamond samples derived from two kimberlites in the chidliak field ne canada show large variability in 13 c 28 4 to 1 1 mode at 5 8 15 n 5 8 to 18 8 mode at 3 0 and nitrogen contents n 3800 to less than 1 at ppm in combination cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low 13 c and n to mantle like 13 c and high n overall 13 c appears to be uncorrelated to 15 n and n on both the inter and intra diamond levels co variations of 15 n log n however result in at least two parallel negatively correlated linear arrays which are also present on the level of the individual diamonds falling on these two trends these arrays emerge from the two principal data clusters are characterized by slightly negative and slightly positive 15 n about 3 and 2 respectively and variable but overall high n using published values for the diamond fluid nitrogen isotope fractionation factor and nitrogen partition coefficient these trends are perfectly reproduced by a rayleigh fractionation model overall three key elements are identified in the formation of the diamond suite studied 1 a low 13 c and low n component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event 2 repeated influx of a variably nitrogen rich mantle fluid mildly negative 13 c and 15 n 3 in waning stages of influx availability of the mantle type fluid at the site of diamond growth became limited leading to rayleigh fractionation these fractionation trends are clearly depicted by 15 n n but are not detected when examining co variation diagrams involving 13 c also on the level of individual diamonds large 5 variations in 15 n are associated with 13 c values that typically are constant within analytical uncertainty the much smaller isotope fractionation factor for carbon considering carbonate or methane rich fluids as possible carbon sources compared to nitrogen leads to an approximately one order of magnitude lower sensitivity of 13 c values to rayleigh fractionation processes i e during fractionation a 1 change in 13 c is associated with a 10 change in 15 n as a consequence even minor heterogeneity in the primary isotopic composition of diamond forming carbon e g due to addition of minor subducted carbon will completely blur any possible co variations with 15 n or n we suggest this strong difference in isotope effects for c and n to be the likely cause of observations of an apparently decoupled behaviour of carbon and nitrogen isotopes in diamond

effects of rotation on the multiscale organization of convection in a global 2d cloud resolving model abstractatmospheric convection exhibits distinct spatiotemporal variability at different latitudes a good understanding of the effects of rotation on the multiscale organization of convection from

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

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

15n 14n variations in cretaceous atlantic sedimentary sequences implication for past changes in marine nitrogen biogeochemistry at two locations in the atlantic ocean dsdp sites 367 and 530 early to middle cretaceous organic carbon rich beds black shales were found to have significantly lower 15n values lower15n 14n ratios than adjacent organic carbon poor beds white limestones or green claystones while these lithologies are of marine origin the black strata in particular have 15n values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools in contrast black organic carbon rich beds at a third site dsdp site 603 contain predominantly terrestrial organic matter and have c and n isotopic compositions similar to organic matter of modern terrestrial origin the recurring15n depletion in the marine derived cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry existing isotopic and other data indicate that the low15n relative abundance is the consequence of pelagic rather than post depositional processes reduced ocean circulation increased denitrification and hence reduced euphotic zone nitrate availability may have led to cretaceous phytoplankton assemblages that were periodically dominated by n2 fixing blue green algae a possible source of this sediment15n depletion lack of parallel isotopic shifts in cretaceous terrestrially derived nitrogen site 603 argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

upscale impact of mesoscale disturbances of tropical convection on synoptic scale equatorial waves in two dimensional flows abstractsuperclusters on the synoptic scale containing mesoscale systems are frequently organized by convectively coupled equatorial waves ccews present day global models struggle to simulate multiscale tropical convection and the upscale effects of mesoscale systems are not well understood a simple two dimensional multiscale model with prescribed two scale heating and eddy transfer of momentum and temperature drives the synoptic scale circulation successfully reproduces key features of flow fields with a front to rear tilt and compares well with results from a cloud resolving model crm in the scenario with an elevated upright mean heating the tilted vertical structure of synoptic scale circulation is still induced by the upscale impact of mesoscale disturbances in a faster propagation scenario the upscale impact becomes less important as a result of competing effects of eddy transfer of momentum and temperature while the synoptic scale circulation response to mean heating dominates in agre

pathways for nitrogen cycling in earth s crust and upper mantle a review and new results for microporous beryl and cordierite figure 1 earth s atmosphere contains 27 30 of the planet s nitrogen and recent estimates are that about one half that amount 11 16 is located in the continental and oceanic crust combined the percentage of n in the mantle is more difficult to estimate but it is thought to be near 60 at very low concentrations knowledge of the behavior of n in various fluid melt rock settings is key to understanding pathways for its transfer among the major solid earth reservoirs nitrogen initially bound into various organic materials is transferred into silicate minerals during burial and metamorphism often as nh4 substituting for k in layer silicates clays and micas and feldspars low grade metamorphic rocks appear to retain much of this initial organic n signature in both concentrations and isotopic compositions thus in some cases providing a relatively un or little modified record of ancient biogeochemical cycling devolatilization can release significant fractions of the n initially fixed in crustal rocks through organic diagenesis during progressive metamorphism at temperatures of 350 550 c depending on pressure loss of fractionated n during devolatilization can impart an appreciable isotopic signature on the residual rocks producing shifts in 15n values mostly in the range of 2 to 5 these rocks then retain large fractions of the remaining n largely as nh4 despite further heating and ultimately partial melting with little additional change in 15n this retention leads to the storage of relatively large amounts of n largely as nh4 in the continental crust nitrogen can serve as a tracer of the mobility of organic sedimentary components into and within the upper mantle this contribution focuses on our growing but still fragmentary knowledge of the n pathways into shallow to deep continental crustal settings and the upper mantle we discuss the factors controlling the return of deeply subducted n to shallower reservoirs including the atmosphere via metamorphic devolatilization and arc magmatism we discuss observations from natural rock suites providing tests of calculated mineral fluid fractionation factors for n building on our discussion of n behavior in continental crust we present new measurements on the n concentrations and isotopic compositions of microporous beryl and cordierite from medium and high grade metamorphic rocks and pegmatites both phases containing molecular n2 and nh4 bearing micas coexisting with them we suggest some avenues of investigation that could be particularly fruitful toward obtaining a better understanding of the key n reservoirs and the more important pathways for n cycling in the solid earth 1 pending yes

ammonium as a biomarker in precambrian metasediments abstract the following article assesses the potential of ammonium as a biomarker in precambrian metasediments a modern marine environment is considered to highlight the processes that contribute to the isotopic composition of organic nitrogen notably the roles played by nitrogen fixing organisms cyanobacteria and denitrifying bacteria the carbon and nitrogen biogeochemical cycles are compared and contrasted unlike carbon the major nitrogen isotope variations may be controlled by local environmental conditions such as season of the year and water depth however such local environmental factors may have been superimposed on more gradual changes related to the long term chemical evolution of the exterior environments of the earth the great potential of nitrogen as a biomarker is that the breakdown product of organic nitrogen ammonium behaves like a trace element and is stable in high temperature crustal processes thus ammonium may survive as a biomarker when all other evidence for former life has been destroyed and ammonium studies may be able to identify sedimentary pelitic components in high grade precambrian terrains previous results from precambrian rocks are reviewed to highlight that very little work has been completed to date and that only very general conclusions can be drawn much work needs to done in order to understand the basic biogeochemistry and geochemistry of crustal nitrogen and it is suggested that the best way to proceed is by numerous detailed case studies the interpretation of isotope ratios in ancient sediments usually assumes uniformitarianism and the justification of this approach is considered briefly overall this article highlights the under developed potential of precambrian ammonium biogeochemistry and suggests area for future research not only does the development of the subject have implications for the search for former life on mars but it may also open up new areas of precambrian research

the mjo and convectively coupled waves in a coarse resolution gcm with a simple multicloud parameterization abstract the adequate representation of the dominant intraseasonal and synoptic scale variability in the tropics characterized by the madden julian oscillation mjo and convectively coupled waves is still problematic in current operational general circulation models gcms here results are presented using the next generation ncar gcm the high order methods modeling environment homme as a dry dynamical core at a coarse resolution of about 167 km coupled to a simple multicloud parameterization the coupling is performed through a judicious choice of heating vertical profiles for the three cloud types congestus deep and stratiform that characterize organized tropical convection important control parameters that affect the types of waves that emerge are the background vertical gradient of the moisture and the stratiform fraction in the multicloud parameterization which set the strength of large scale moisture convergence and unsaturated downdrafts in the wake of deep convection respectively three

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

ammonium vermiculite in schists from the betic cordillera spain nh 4 bearing phases from pre permian schists of the internal zones of the betic cordillera spain have been characterized by x ray diffraction differential thermal analysis and thermogravimetry infrared spectroscopy and transmission analytical electron microscopy the content and distribution of nh 4 in these phases have been estimated by combining elemental analysis of n with mineral quantification based on x ray diffraction whole rock composition and electron microprobe data the obtained results indicate that the nh 4 content in vermiculite ranges between 0 5 and 1 0 wt leading to terms with nh 4 k in the interlayer the nh 4 content is 4 contents 0 04 wt through the complete sequence we interpret that initially contained in low grade dioctahedral mica nh 4 was incorporated in the structure of the trioctahedral phases formed at increasing metamorphic conditions the entry of nh 4 in the interlayer was favored in chlorite vermiculite mixed layered structures and transitional phases with vacancies in the a site vermiculite and weak cohesion between layers nh 4 appears to favor the formation of intermediate phases instead the direct transformation of chlorite to biotite

deformation related recrystallization processes abstract recrystallization is a common microstructural transformation that occurs during deformation metamorphism and diagenesis of rocks studies on minerals and rock analogues have demonstrated that a wide range of recrystallization mechanisms can occur the range of mechanisms is related to the various ways in which two basic processes grain boundary migration and new grain boundary formation combine to transform the microstructure two recent papers drury et al 1985 urai et al 1986 have proposed different schemes for the description of recrystallization mechanisms the purpose of this paper is to provide a unified framework for the description of mechanisms recrystallization mechanisms are divided into three main types rotation mechanisms which principally involve the formation of new grain boundaries migration mechanisms which principally involve grain boundary migration and general mechanisms which involve both basic processes a further distinction is made on the basis of the continuity of the microstructural transformation with respect to time each of the three main types of mechanism can be divided into a number of sub types depending on whether the processes of grain boundary migration new grain boundary formation and new grain formation occur in a discontinuous or continuous manner with respect to time as the terms continuous and discontinuous have been used in the metallurgical literature to signify the spatial continuity of the microstructural transformation the terms discontinuai and continual are used to refer to the temporal continuity of the transformation it is recommended that the following aspects should be specified if possible in a general description of recrystallization mechanisms 1 1 how do the basic processes combine to transform the microstructure 2 2 if new grain development occurs what is the development mechanism and does new grain formation occur in a continual or discontinuai manner 3 3 if grain boundary migration is involved in the transformation what is the migration mechanism i e fast solute escape migration slow solute loaded migration fluid assisted migration etc and is migration a continual or discontinuai process the application of the unified scheme is illustrated by reviewing studies that have provided detailed information on the recrystallization mechanisms involved the complicating effects of solid solution impurities dispersed second phase particles and grain boundary fluid films are also considered and it is demonstrated that variations in content of these types of impurity can significantly effect the types of recrystallization that occur in a given material

nitrogen rich fluid in the upper mantle fluid inclusions in spinel dunite from lanzarote canary islands fluid inclusions ranging from pure n2 to pure co2 occur in olivine porphyroclasts in spinel dunite xenoliths chrome diopside suite from two localities within the quaternary to historic alkaline lavas of lanzarote canary islands this is the first report of fluid inclusions containing major amounts of n2 in mantle xenoliths the nitrogen rich fluid inclusions predate at least one generation of nitrogen free carbon dioxide inclusions textural evidence indicates that the inclusions were trapped within the upper mantle some of the nitrogen rich fluid inclusions are intimately associated with solid inclusions of spinel the nitrogen rich fluid was most likely produced in situ by oxidation dehydration reactions destabilizing ammonium bearing silicate minerals phlogopite amphibole increasing oxygen fugacity or possibly increasing temperature of the mantle this process could be related to an event of co2 and silicate melt injection at 6 8 kbar neumann et al in press or to some earlier event in the evolution of the mantle beneath lanzarote the existence of a n2 rich fluid phase in at least some mantle lithology ies at certain conditions is demonstrated by these data this discovery has consequences for the understanding of the evolution of the mantle below the canary islands as well as for the global nitrogen budget

nitrogen isotope tracers of high temperature fluid rock interactions case study of the catalina schist california abstract nitrogen isotope data for metasomatized rocks veins and pegmatites in the catalina schist subduction zone metamorphic complex allow futher characterization of complex high p t metasomatic proceses and evaluation of the scales of isotopic equilibration and fluid transport during subduction zone metamorphism throughout the catalina schist n resides predominantly as nh4 in white mica which occurs in nearly all bulk compositions i e metasedimentary metamafic and to a lesser extent metaultramafic melange at all grades within each metamorphic unit of the catalina schist ranging in grade from lawsonite albite to amphibolite facies 15n values of mica in metasomatized metamafic and metaultramafic rocks are consistent with the metasomatic addition of n from nearby devolatilizing metasedimentary rocks into the initially n poor mafic and ultramafic rocks within each unit uniformity of mica 15n in metasomatized rocks relative to the 15n of metasedimentary rocks in the same unit implies mixing of n from nearby heterogeneous metasedimentary sources perhaps producing fluids with unifrom 15n at up to the kilometer scale however the trend in 15n of metasedimentary sources with increasing metamorphic grade is inconsistent with larger scale up temperature transfer of fluid in this case n2 bearing in the catalina schist paleosubduction zone such flow at scales of up to tens of kilometers has been inferred through previous oxygen isotope study nitrogen isotope compositions are instead believed to have been controlled at a more local scale than the o isotope systematics due to the more rock dominated fluid rock mass balance for n the 15n of muscovite in leucosomes and pegmatites in amphibolite grade metasedimentary exposures matches that of muscovite in metasedimentary hosts implying minimal n isotope fractionation during migmatization processes and possible transfer of metasedimentary n isotope signatures in silicate melts these results illustrate the potential of the n isotope system to yield valuable information regarding fluid rock interactions in the crust and mantle the data for the catalina schist demonstrate the ability of n isotopes to trace the transfer of sediment derived c o h s n fluids and silicate melts and show the expected benefit of the n isotope system in having a differing fluid rock mass balance relative to the more commonly used stable isotope systems that can yield unique constraints in quantitative models of crustal fluid processes

high integrated fluid rock ratios during metamorphism at naxos evidence from carbon isotopes of calcite in schists and fluid inclusions a dicussion of the paper by kreulen 1988 contributions to mineralogy and petrology 98 28 32

upscale impact of mesoscale disturbances of tropical convection on 2 day waves abstractwestward propagating 2 day waves with embedded mesoscale disturbances contribute a large portion of synoptic variability of tropical convection over the western pacific it is of crucial im

large scale organization of tropical convection in two dimensional explicit numerical simulations the large scale organization of tropical deep convection is investigated in idealized two dimensional cloud resolving simulations a 20 000 km periodic computational domain allows interactions among moist convection mesoscale organization and surface exchange on a wide range of scales a uniform 10 m s 1 easterly wind and a uniform sea surface temperature of 30 c are assumed a prescribed temperature tendency mimicking the mean radiative cooling of the tropical troposphere is used in this pilot study the large scale organization of convection resembles the observed tropical atmosphere as well as results from some previous numerical studies using parametrized convection the simulation highlights mesoscale convective systems with horizontal scales of several hundred kilometres moving east to west with speeds similar to the mean flow and an envelope of convection with a horizontal extent of a few thousand kilometres and propagating west to east the propagation speed of the large scale envelope compares well with the phase velocitites of convectively coupled kelvin waves observed in the equatorial waveguide convective momentum transport and the impact of convective systems on temperature and moisture near the surface are key processes responsible for the large scale organization of convection these results are discussed in the context of recent observations and numerical studies of convection organization in the tropics

anomalous nitrogen isotopes in ultrahigh pressure metamorphic rocks from the sulu orogenic belt effect of abiotic nitrogen reduction during fluid rock interaction modern nitrogen n fixation is primarily mediated by biological processes however in the early earth where biological activity was absent or limited abiotic n reduction in hydrothermal systems is thought to be a key process to transform atmospheric n2 and nox to ammonium an essential nutrient to support the emergence of life and also an n form that can be incorporated into rocks surprisingly evidence for abiotic n reduction in the rock record has not been clearly identified in this study we reported anomalously low n isotope compositions n15 values as low as 15 8 15 8 of mica samples in ultrahigh pressure metamorphic rocks from the donghai area in the sulu orogenic belt eastern china compared with mica samples with typical crustal n15 values 3 9 3 9 in similar metamorphic rocks from the western dabie orogen the 15n depleted mica samples from the sulu orogen are characterized by significant n enrichment 10 times higher and extreme 18o depletion o18 values as low as 9 9 these features can be best explained by assimilation of n from a source characterized by extremely low n15 values less than 16 16 the extremely low n15 value would be produced by abiotic n reduction during reaction of a meteoric hydrothermal fluid with crustal rocks before subduction this observation provides a clue to the occurrence of abiotic n reduction in continental supracrustal rocks and infer that abiotic n reduction process could be a fundamental process driving the geological n cycling in early earth

nitrogen release from rock and soil under simulated field conditions abstract a laboratory study was performed to simulate field weathering and nitrogen release from bedrock in a setting where geologic nitrogen has been suspected to be a large local source of nitrate two rock types containing nitrogen slate 1370 mg n kg 1 and greenstone 480 mg n kg 1 were used along with saprolite and bc horizon sand from soils derived from these rock types the fresh rock and weathered material were used in batch reactors that were leached every 30 days over 6 months to simulate a single wet season nitrogen was released from rock and soil materials at rates between 10 20 and 10 19 mol n cm 2 s 1 results from the laboratory dissolution experiments were compared to in situ soil solutions and available mineral nitrogen pools from the bc horizon of both soils concentrations of mineral nitrogen no 3 nh 4 in soil solutions reached the highest levels at the beginning of the rainy season and progressively decreased with increased leaching this seasonal pattern was repeated for the available mineral nitrogen pool that was extracted using a kcl solution estimates based on these laboratory release rates bracket stream water no 3 n fluxes and changes in the available mineral nitrogen pool over the active leaching period these results confirm that geologic nitrogen when present may be a large and reactive pool that may contribute as a non point source of nitrate contamination to surface and ground waters

oscillations of the intertropical convergence zone and the genesis of easterly waves part i diagnostics and theory we examine the mean and transient state of the intertropical convergence zone itcz by analyzing data and using simple theory we concentrate on the tropical eastern pacific ocean noting that there exists in this region a well developed mean itcz furthermore it is a region where there has been considerable discussion in the literature of whether easterly waves develop in situ or propagate westwards from the atlantic ocean the region is typical of tropical regions where there is a strong cross equatorial pressure gradient cepg mean convection well removed from the equator but located equatorward of the maximum sea surface temperature sst and minimum sea level pressure mslp further to the west near the dateline where the cepg is much smaller convection is weaker and collocated with sst and mslp extrema it is argued that in regions of significant cepg that the near equatorial tropical system is inertially unstable and that the rectification of the instability for a given cepg determines the location and intensity of the climatological itcz using simple theoretical arguments we develop an expression for the mean latitude of the itcz as a function of the cepg we note on a day by day basis that the itcz is highly transient state with variability occurring on 3 8 day time scales transients with amplitudes about half of the mean itcz propagate northwards from the near equatorial southern hemisphere as anomalous meridional oscillations eventually amplifying convection in the vicinity of the mean itcz it is argued that in these longitudes of strong cepg the mean itcz is continually inertially unstable with advections of anticylonic vorticity across the equator resulting in the creation of an oscillating divergence convergence doublet the low level convergence produces convection and the resultant vortex tube stretching generates cyclonic vorticity which counteracts the northward advection of anticylonic vorticity during a cycle the mid troposphere heating near 10on oscillates between 6 and 12 k day at the inertial frequency of the latitude of the mean convection as a result there exists an anomalous and shallower oscillating meridional circulation with a magnitude about 50 of the mean itcz associated with the stable state following the generation of anticylonic vorticity further it is argued that the instabilities of the itcz are directly associated with in situ development of easterly waves which occur with the inertial period of the latitude of the mean itcz the dynamical sequences and the genesis of easterly waves are absent in the regions further to the east where the cepg is much weaker or absent altogether in a companion study part ii numerical experiments are conducted to test the hypothesis raised in the present study

multiscale convective wave disturbances in the tropics insights from a two dimensional cloud resolving model abstract multiscale convective wave disturbances with structures broadly resembling observed tropical waves are found to emerge spontaneously in a nonrotating two dimensional cloud model forced by uniform cooling to articulate the dynamics of these waves model outputs are objectively analyzed in a discrete truncated space consisting of three cloud types shallow convective deep convective and stratiform and three dynamical vertical wavelength bands model experiments confirm that diabatic processes in deep convective and stratiform regions are essential to the formation of multiscale convective wave patterns specifically upper level heating together with low level cooling serves to preferentially excite discrete horizontally propagating wave packets with roughly a full wavelength structure in troposphere and dry phase speeds cn in the range 16 18 m s 1 these wave packets enhance the triggering of new deep convective cloud systems via low level destabilization the new convection in turn caus

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

nitrogen diffusion in silicate minerals with implications for nitrogen transport and cycling in the lithosphere abstract diffusion laws for nitrogen in orthoclase quartz olivine and clinopyroxene were determined using a combination of experimental strategies that included in diffusion from c h o n vapor in diffusion from molten nh4cl and ion implantation followed by heating to mobilize n most experiments were conducted at pressures near 1 bar but seven experiments were also run in a piston cylinder device at ptotal 1 gpa the c h o n source experiments were wet h2o present those on ion implanted samples were dry all n sources were highly enriched in 15n to avoid spurious 14n signals resulting from surface contamination use of 15n also enabled depth profiling by nuclear reaction analysis nra using the 15n p 12c reaction which has a detection limit of 10 ppm nitrogen profiles in three samples were characterized by both nra and sims with similar results a total of 17 to 28 diffusion coefficient measurements were made on each of the four minerals 83 in all yielding results that conform for each mineral to an arrhenius relation of the form d d0exp ea rt the following values for the pre exponential constant d0 and activation energy ea were obtained mineral log d0 m2 s ea kj mol t range c orthoclase 13 9 0 4 95 4 6 6 500 900 quartz 12 4 0 3 147 3 5 7 550 1150 olivine 14 2 0 3 135 2 6 6 650 1400 clinopyroxene 14 1 0 3 135 6 7 4 750 1300 the various experimental strategies yield generally indistinguishable results at a given temperature and no significant effects of total pressure or h2o are discernible in the overall diffusion data set experiments that involved in diffusion from external n sources provide qualitative insight into the compatibility of n in the structures of the four minerals nitrogen concentrations attain the highest levels in orthoclase 100 8000 ppm atomic with quartz olivine and clinopyroxene falling in the tens to hundreds of ppm range the new diffusion laws enable us to model the diffusive release of n acquired at depth in the crust during fluid absent exhumation and cooling in general orthoclase is the least retentive of the minerals investigated and will lose most of its n during cooling from 600 c at tectonically typical rates olivine and clinopyroxene are the most retentive of n quartz is intermediate in retentivity between the mafic minerals and feldspar but in all cases the extent of n exchange with the surroundings depends critically on the specific t t path of the mineral of interest in subduction settings where n bearing fluid is released to the mantle wedge diffusion is sufficiently fast to homogenize individual mafic mineral grains with respect to n over geologically plausible time scales but equilibration on the outcrop or regional scale via volume diffusion is precluded by our data

high ammonium contents in the 3800 ma isua supracrustal rocks central west greenland abstract ammonium contents of whole rock and biotite samples from the metasedimentary sequence of the 3800 ma isua supracrustal belt central greenland have been determined and compared with the ammonium contents of volcanic sedimentary metamorphic and granitic rocks from the late archaean early proterozoic a sample of the amitsoq gneiss has an nh4 content whole rock 9 ppm biotite 29 ppm that is similar to many younger igneous rocks ammonium contents of the supracrustal rocks vary with chemistry and mineralogy of the rock and most likely were inherited from the original sediments a series of carbonate bearing and basic plagioclase bearing biotite rich schists from sequence a have varying nh4 contents whole rock 6 24 ppm that increase with an increasing chemical clastic component and decreasing volcanogenic component biotites in these rocks together with biotites in mica schists of the same sequence have high nh4 contents which vary over a small range of 54 95 ppm suggesting that the nh4 in these rocks was contained mostly in authigenic clays of the original sediments all these data imply that clay minerals were the major sink of nh4 or other nitrogen compounds on the earth s surface at 3800 ma two samples of graphite bearing garnet staurolite mica schist from sequence b have remarkably high nh4 contents whole rock 68 and 86 ppm biotite 234 and 253 ppm which are as high as or even higher than those of common late archaean early proterozoic argillites it appears almost certain that the original thick clay rich bottom sediments contained a large amount of nh4 or other nitrogen compounds the most likely major source of nitrogen in these nh4 enriched graphite bearing mica schists might be organic nitrogen

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

simulation modeling and dynamically based parameterization of organized tropical convection for global climate models abstracta new approach for treating organized convection in global climate models gcms referred to as multiscale coherent structure parameterization mcsp introduces physical and dynamical effects of organized convection that are missing from contemporary parameterizations the effects of vertical shear are approximated by a nonlinear slantwise overturning model based on lagrangian conservation principles simulation of the april 2009 madden julian oscillation event during the year of tropical convection yotc over the indian ocean using the weather research and forecasting wrf model at 1 3 km grid spacing identifies self similar properties for squall lines mcss and superclusters embedded in equatorial waves the slantwise overturning model approximates this observed self similarity the large scale effects of mcsp are examined in two categories of gcm first large scale convective systems simulated in an aquaplanet model are approximated by slantwise overturning with attention to convective mome

fixed ammonium in clays associated with crude oils abstract the association of ammonium nh 4 silicates with organic rich sedimentary environments has stimulated interest in the chemical cycle of n and its possible application as an indicator of in situ organic maturation reactions or crude oil migration fixed nh 4 in clay minerals was determined from three hydrocarbon occurrences of similar depositional environment but different ages depth and thermal maturity to determine whether anomalously high nh 4 substitution occurs near mature hydrocarbons results show higher fixed nh 4 concentrations in marginally mature mudstones than in immature sediments the highest fixed nh 4 concentrations were found in clays from sandstone reservoirs containing migrated crude oil fixed nh 4 in clays from holocene oil seep sediments in the gulf of mexico continental slope offshore louisiana averages 0 08 wt and increases with depth in shallow cores 420 cm reflecting an early diagenetic trend that is apparently not influenced by migrating crude oil programmed pyrolysis shows that the sediments are thermally immature av t max 419 c high hydrogen index values av 359mg g are the result of biodegraded crude oil and a high oxygen index av 182mg g reflects the presence of authigenic carbonate fixed nh 4 averages 0 16 wt in wilcox group eocene mudstones enclosing two sandstone reservoirs at fordoche field onshore louisiana in comparison to these mudstones anomalously high nh 4 fixation appears to occur in reservoir clay minerals pyrolysis shows that the sediments are marginally mature for crude oil generation av t max 432 c average hydrogen index 187 mg g and oxygen index values 75 mg g are consistent with oil prone type ii and type iii kerogen increased pyrolysis production index values and solvent extraction shows the presence of migrated crude oil this suggests that a reaction which releases nh 3 during crude oil generation or migration is recorded bynh 4 substitution in clays fixed nh 4 and total organic carbon toc at fordoche field show no statistically significant correlation suggesting that nh 4 substitution in clay minerals is not simply related to the amount of organic matter in the section but is also influenced by the presence of crude oil once nh 4 has been fixed in clays it is a more stable hydrocarbon proximity indicator than pore fluid tracers because it is less influenced by later chemical or geological changes

nitrogen isotope compositions of metasedimentary rocks in the catalina schist california implications for metamorphic devolatilization history abstract in the catalina schist subduction zone metamorphic complex california metasedimentary rocks show a decrease in n concentration and an increase in 15nair with increasing metamorphic grade lowest grade lawsonite albite rocks contain 632 185 ppm n with 15 n 1 9 0 6 whereas highgrade amphibolite equivalents contain 138 76 ppm n with 15 n 4 3 0 8 loss of n accompanied devolatilization reactions that evolved h2o rich c o h s n fluids through consumption of chlorite and phengitic white mica and production of mineral assemblages containing muscovite biotite garnet and kyanite whole rock n concentrations of up to 200 ppm in veins and pegmatites produced during high p t metamorphism reflect the redistribution of n during devolatilization and partial melting of the metasedimentary rocks bulk fluid rock n isotope fractionations 15n 15nfluid 15nrock of 1 5 1 were calculated with the rayleigh distillation equation taking into account variability in rock composition by comparison of samples with similar k2o concentrations these fractionations are similar to but slightly lower than published calculated fractionations for n2 nh4 exchange at the temperature range of 350 600 c over which most of the devolatilization occurred in the catalina schist approximately 3 4 to 2 25 the n systematics appear to be explained by n2 nh4 exchange and a devolatilization process intermediate in behavior to batch volatilization and rayleigh distillation the observed shifts in n concentration and 15n cannot be explained by nh3 nh4 exchange at these temperatures using the equilibrium models the distillation devolatilization process implicated in this study may govern the behavior of other trace elements partitioned into hydrous fluids during devolatilization e g b cs u similarity of the calculated fluid 15n 1 5 to 5 5 with compositions of natural gases inferred to be derived from metasedimentary sources indicates the possibility of using n as a tracer of large scale volatile transport

multicloud models for organized tropical convection enhanced congestus heating abstract despite the recent advances in supercomputing the current general circulation models gcms poorly represent the large scale variability associated with tropical convection multicloud model convective parameterizations based on three cloud types congestus deep and stratiform introduced recently by the authors have been revealed to be very useful in representing key features of organized convection and convectively coupled waves here a new systematic version of the multicloud models is developed with separate upper and lower troposphere basis functions for the congestus and stratiform clouds it naturally leads to a new convective closure for the multicloud models enhancing the congestus heating in order to better pinpoint the congestus preconditioning and moistening mechanisms the models are studied here for flows above the equator without rotation effects first the new model results consist of the usual synoptic scale convectively coupled moist gravity wave packets moving at 15 20 m

systematic multiscale models for the tropics systematic multi scale perturbation theory is utilized to develop self consistent simplified model equations for the interaction across multiple spatial and or temporal scales in the tropics one of these models involves simplified equations for intraseasonal planetary equatorial synoptic scale dynamics ipesd this model includes the self consistent quasi linear interaction of synoptic scale generalized steady matsuno webster gill models with planetary scale dynamics of equatorial long waves these new models have the potential for providing self consistent prognostic and diagnostic models for the intraseasonal tropical oscillation other applications of the systematic approach reveal three different balanced weak temperature gradient wtg approximations for the tropics with different regimes of validity in space and time a synoptic equatorial scale wtg sewtg a mesoscale equatorial wtg mewtg which reduces to the classical models treated by others and a new seasonal planetary equatorial wtg spewtg both the spewtg and mewtg model equations have solutions with general vertical structure yet have the linearized dispersion relation of barotropic rossby waves thus these models can play an important role in theories for midlatitude connections with the tropics the models are derived both from the equatorial shallow water equations in a simplified context and also as distinguished limits from the compressible primitive equations in general