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

postglacial relative sea level histories along the eastern canadian coastline abstract we have assembled a database of relative sea level rsl data points from the eastern coast of canada from hudson bay to the border with the usa in compiling this database we have critically reviewed 1092 radiocarbon dated samples from raised beaches isolation basins intertidal and marine deposits and archaeological indicators to produce 405 sea level index points and 687 sea level limiting points our comprehensive systematic and quality controlled rsl database allowed for the reconstruction of the postglacial evolution of 34 regions of eastern canada providing new basin scale insights into the processes driving rsl changes in the last 16 ka the combination of a database of sea level index points with an innovative empirical bayesian spatio temporal statistical model provided new insights into rates and magnitude of the spatially variable glacial isostatic adjustment gia which dominated the postglacial rsl evolution in this sector of north america a continuous postglacial rsl fall is observed at latitudes 50 n with higher rates up to 35 mm a 1 recorded in southeastern hudson bay at lower latitudes the evolution is non monotonic with rsl that dropped to a spatially variable early holocene lowstand followed by a mid holocene highstand and eventually a gradual drop to present rsl this pattern is particularly evident in the st lawrence corridor along the majority of the newfoundland new brunswick and western nova scotia coasts a late pleistocene early holocene rsl lowstand was followed by a continuous rise through the holocene at the margin of the former ice sheet i e eastern nova scotia our data identify a continuous rsl rise through the holocene these records are characterized by decreasing rates of rsl rise through time commencing with a rapid rise during the early holocene up to 17 mm a 1 a slowdown in the mid holocene average rates 9 mm a 1 and a further reduction in the late holocene average rates

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

tracking of polar cap ionospheric patches using data assimilation 1 ionospheric f region patches are 2 10 larger than background electron densities in the polar ionosphere the eiscat svalbard incoherent radar esr observed a sequence of patches between 2000 2200 ut on 12 december 2001 in this paper the source of these structures is investigated using several other data sets together with a convection driven trajectory analysis the data are assimilated into ionospheric data assimilation three dimensional ida3d the background model used is the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model ncar timegcm the trajectory analysis is based on maps of ionospheric convection obtained from the assimilative mapping of ionospheric electrodynamics amie in addition to patches a tongue of ionization toi is investigated it is shown that patches formed part of the toi it is tempting to conclude the toi and the patches originate at midlatitudes however the ida3d and trajectory analysis suggest that they were transported toward noon from the morning and afternoon sectors near 62 geographic latitude thus for this case the toi and patches did not originate at midlatitudes this work represents advances in the field of patch research a new capability to perform an analysis of patch origin and fate using three dimensional 3 d ionospheric assimilation and 2 d trajectory analysis codes is demonstrated for a sequence of patches observed 12 december 2001 the current resolution of the technique is not able to identify detailed patch formation mechanisms however by it can track the plasma back in time to locations and times where patch formation mechanisms operate

light element distributions n b li in baltic basin bentonites record organic sources abstract distributions of nitrogen boron and lithium were studied in illite smectite from ordovician silurian k bentonites in the baltic basin these trace elements are linked to thermal maturation of organic matter creating fluid signatures that are distinct from those in regionally buried sediments the fluid chemistry is ideally recorded in authigenic illite within the k bentonite because b substitutes in tetrahedral sites of illite li in octahedral sites and n is fixed in the interlayers as nh 4 three nanometric size fractions of illite 10 among these size fractions relate mainly to changes in fluid composition during illite growth bentonite volcanic ash layers mark stratigraphic timelines while illitization of the bentonite k bentonite varies as a function of burial and tectonic temperature gradients in the central baltic basin bentonites were deposited across a carbonate platform near estonia grading to deep basin shales near denmark and poland compositional variations in illite reflect fluids from different sources high n illite 2000 ppm in the southwest basin transitions to high b 250 ppm and high li 100 ppm illite to the northeast these trends follow a thermal gradient decreasing from southwest 200 c to northeast 90 c isotope ratios of b and li show opposing trends in samples across this thermal gradient the bisotopes decrease from southwest to northeast 18 to 4 while li isotopes increase from 5 to 32 the cambrian alum shale a regional hydrocarbon source rock was studied as a potential source of b and li as more than 50 of its b and li was associated with organic matter with increasing thermal maturity illite 11b decreased from 0 to 13 while 7li increased from 20 to 5 these opposing trends are similar to those observed in the k bentonites this suggests that organic sources of n b and li dominate fluids in bentonites from the southwestern baltic basin whereas basement derived fluids dominate in the northeastern baltic basin these trace elements record paleofluid changes during illite crystal growth and can identify pathways of chemically distinct oil and gas related fluids

comment on late deglaciation of the central labrador coast and its implications for the age of glacial lakes naskaupi and mclean and for prehistory by p u clark and w w fitzhugh

10be dating of former glacial lake naskaupi quebec labrador and timing of its discharges during the last deglaciation abstract the last deglaciation of the laurentide ice sheet in northern quebec and labrador led to the formation of several glacial lakes that drained into ungava bay and the nearby labrador sea assessing the potential impact of their drainage on ocean surface conditions and climate however is limited by the few existing age constraints on ice retreat and associated evolution of these lakes here we report 21 10be ages from shorelines and an outburst flood landform formed by lake naskaupi one of the largest glacial lakes in this region the results indicate that the lake drained from its full extent at 8300 300 a suggesting that it may have contributed to the freshwater forcing initiated by the drainage of lake agassiz ojibway that caused the 8 2 ka cold event additionally the results provide important constraints on the position of the ice margin of the labrador sector during its retreat across this region

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 enrichment associated with diagenetic alteration in tertiary pyroclastic rocks from greece the ammonium ion has been measured in fresh volcanic rocks in vitric tuffs and in tuffs which have undergone secondary alteration the ammonium content of fresh lavas of a wide range of composition is shown to be negligible in contrast high concentrations of ammonium are found in pyroclastic rocks that have undergone diagenetic alteration data are given for three types of diagenetic alteration namely 1 hydration 2 zeolitization and 3 alteration to secondary k feldspar different levels of ammonium enrichment are associated with each type hydrated vitric tuffs from kozani in northern greece and heraklion in crete contain from 158 to 390 ppm nh 4 zeolitized ash and lapilli tuffs from santorini and from lefkimi ne greece are much lower in their ammonium content ranging from 12 to 56 ppm tuffs containing secondary k feldspar in addition to zeolites from metaxades n e greece have ammonium contents from 51 to 512 ppm measurements of fixed and exchangeable ammonium were used to distinguish between the ammonium held by zeolites and that held by k feldspars in the clinoptilolite and mordenite bearing tuffs from santorini and lefkimi most of the ammonium is in cation exchangeable form and must be held by the zeolites by contrast in the feldspar bearing tuffs from the metaxades area almost all the ammonium is fixed and it is inferred to be held mainly by secondary k feldspar

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

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

the significance of fixed ammonium in palaeozoic sediments for the generation of nitrogen rich natural gases in the north german basin in contrast to predominantly hydrocarbon rich natural gases in the western part of the central european basin ceb accumulations of natural gases from the eastern part of the north german basin ngb are nitrogen rich with up to 90 n2 this study is focused on the behaviour of fixed ammonium in clay minerals of organic rich palaeozoic sediments in the eastern part of the ngb as a major source of nitrogen rich natural gases carboniferous shales have been investigated for a better understanding of nitrogen fixing during diagenesis storage during burial and release during devolatilization processes or fluid rock interactions the total nitrogen contents in the studied carboniferous shales of the ngb reach up to 2700 ppm with an inorganic fixed portion in the form of nh4 n of more than 60 the results of this study indicate an increasing proportion of the mineralogically fixed ammonium with increasing thermal maturity and storage up to catagenetic conditions the isotopic composition of fixed nh4 is relatively homogeneous in the majority of the shales and ranges from 1 to 3 5 in contrast samples from the basin centre show a significant decrease in ammonium contents down to 460 ppm coupled with a shift in 15n up to 5 6 suggesting a release of nitrogen on a large scale calculation of nitrogen loss and isotopic fractionation indicate that more than 30 of nitrogen was released as ammonium probably as a consequence of fluid rock interaction with highly saline brines

hyperspectral imaging of drill core from the steen river impact structure canada implications for hydrothermal activity and formation of suevite like breccias

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

petrology and geochemistry of diagenetically altered tuffaceous rocks from the middle triassic of central spain abstract petrographical and geochemical analysis of altered tuffaceous rocks of the middle triassic from the iberian range in central spain shows that pedogenic processes and subsequent diagenesis have strongly modified the original mineralogy and textures these rocks are related to a magmatic episode that occurred at the buntsandstein muschelkalk unconformity in this region during the evolution of the iberian trough the tuffaceous rocks accumulated in saline ponds in an open and terminal flood plain setting their alteration is typified by neoformation of k feldspar and illite precipitation of chert and carbonate cements and replacements were also important processes resulting in intercalated chert beds and nodules much of the silica appears to be derived from extensive devitrification and weathering of glassy volcanic ash x ray diffraction analysis microscopic observations and edx microanalysis reveal that the chert consists of various types of chalcedony tridymite micro and megaquartz illite k feldspar and small amounts of albite in some of the nodules dolomite ankerite is also common enclosing anhydrite and barite relicts which are partially silicified different levels of ammonium enrichment have been found in each petrofacies type tuffs and tuffaceous rocks contain from 27 to 326 ppm mean 139 of nh4 underlying arkosic sandstones with authigenic k feldspar contain nh4 ranging from 48 ppm to 191 ppm mean 124 the nh4 was probably derived from decay of organic matter in the evaporitic environment of deposition and its incorporation into feldspar and illite as they formed from unstable volcanic glass sanidine plagioclase and vitric volcanic fragments this transformation could have occurred via the intermediate phases of smectite and zeolites the tuffaceous rocks also have a high content of b ranging from 61 ppm to 170 ppm mean 101 however high levels of b are not positively correlated with high levels of nh4 in the samples both b and nh4 can be contained in either k feldspar or illite but it is not possible to know how much is present in each mineral without separating the minerals comparison of spidergrams of the tuffaceous rocks with those in the underlying arkosic sandstones indicates similar patterns with positive anomalies in la sm and y and negative in nb p ti and yb although the tuffaceous rocks are slightly richer in total ree these data suggest that the distribution of ree must also be controlled by weathering and diagenetic reactions and cannot be used for discrimination between volcanic and nonvolcanic sandstones

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

multiradar observations of the polar tongue of ionization 1 we present a global view of large scale ionospheric disturbances during the main phase of a major geomagnetic storm we find that the low latitude auroral and polar latitude regions are coupled by processes that redistribute thermal plasma throughout the system for the large geomagnetic storm on 20 november 2003 we examine data from the high latitude incoherent scatter radars at millstone hill sondrestrom and eiscat tromso with superdarn hf radar observations of the high latitude convection pattern and dmsp observations of in situ plasma parameters in the topside ionosphere we combine these with north polar maps of stormtime plumes of enhanced total electron content tec derived from a network of gps receivers the polar tongue of ionization toi is seen to be a continuous stream of dense cold plasma entrained in the global convection pattern the dayside source of the toi is the plume of storm enhanced density sed transported from low latitudes in the postnoon sector by the subauroral disturbance electric field convection carries this material through the dayside cusp and across the polar cap to the nightside where the auroral f region is significantly enhanced by the sed material the three incoherent scatter radars provided full altitude profiles of plasma density temperatures and vertical velocity as the toi plume crossed their different positions under the cusp in the center of the polar cap and at the midnight oval polar cap boundary greatly elevated f peak density 1 5e12 m 3 and low electron and ion temperatures 2500 k at the f peak altitude characterize the sed toi plasma observed at all points along its high latitude trajectory for this event sed toi f region tec 150 1000 km was 50 tecu both in the cusp and in the center of the polar cap large upward directed fluxes of o 1 e14 m 2 s 1 were observed in the topside ionosphere

recent hydrocarbon alteration sulfate reduction and formation of elemental sulfur and metal sulfides in salt dome cap rock abstract geochemical analysis of hydrocarbons and scanning electron microscopy sem provide insight to recent alteration of crude oil microbial sulfate reduction and mineral deposition in carbonate cap rock at damon mound brazoria county texas u s a previous work showed that intense aerobic biodegradation of hydrocarbons occurs in shallow cap rock where s 0 and metal sulfides are not abundant the present study focuses on some deeper carbonate cap rock characterized by more limited oxygen availability the c 1 c 4 hydrocarbons in deeper cap rock are a biodegraded residue of hydrocarbons derived from crude oil alteration of higher molecular weight crude oil components is best explained by the effects of water washing accompanied by some biodegradation sem of cavities in carbonate cap rock shows microbes in association with globular masses of solid crude oil and sulfate minerals late forming minerals in cavities include s 0 pyrrhotite pyrite sphalerite and aragonite the presence of s 0 and sulfide minerals indicates that microbial sulfate reduction is associated with limited hydrocarbon biodegradation in this deeper cap rock environment similar processes could explain the origin of some s 0 and metal sulfides at damon mound in the geologic past

organic geochemistry of the san vicente zinc lead district eastern pucara basin peru abstract isotopic and chemical studies of organic matter of the san vicente mississippi valley type zn pb district hosted in the dolomitic units of the eastern pucara basin peru provide insight into the source of organic matter and of the organic matter ore relationship a large scatter exists in the 13c and 15n values of the highly mature kerogens these bulk data were combined with 13c covariations of the saturated and aromatic fractions of the rock extracts to indicate a contribution of continental higher plant lipids to the marine algal source of the organic matter disseminated in the host carbonate rocks an enrichment in 15n of the kerogens of mineralized samples compared to barren samples suggests that isotopically heavy nitrogen compounds were introduced to the ore fluid the fluid likely leached these compounds from the underlying clastic rocks and other detrital units of the pucara the extracts from mineralized samples are enriched in 13c compared to the associated kerogens this suggests that the rocks in the mineralized areas were stained by a mixture of extrinsic and indigenous bitumens by the use of novel instrumentation such as a gas chromatograph gc coupled to a stable isotope ratio mass spectrometer irms through a combustion c interface gc c irms stable carbon isotope analyses of individual hydrocarbons were also obtained both the molecular and isotopic signatures of the individual hydrocarbons are related to mineralization the variability in the organic molecular parameters and the 13c values of the individual n alkanes and isoprenoids indicate mixing of indigenous hydrocarbons with extrinsic 13c depleted microbially derived hydrocarbons the extrinsic source hydrocarbons were introduced to the mineralization site by the ore fluid or later fluids using the same porosity network oxidative alteration of the migrating hydrocarbons was involved in the thermochemical reduction of sulfate to h2s and precipitation of pyrobitumen large differences 12 in the carbon isotope compositions of long chain c20 n alkanes can be utilized in distinguishing sources of organics in the barren and mineralized samples

ionospheric electron concentration imaging using gps over the usa during the storm of july 2000 a new technique for ionospheric imaging is demonstrated during a severe geomagnetic storm of 15th july 2000 the three dimensional time dependent imaging algorithm is applied to multi directional ground based gps data and yields spatial maps of electron concentration this technique is demonstrated by showing a series of images of the mid latitude ionosphere over the usa during the storm of july 2000 a strong uplift in the height of the f layer is observed after 20 ut on 15th july followed by a severe latitudinal electron concentration gradient independent verification of the images is provided by the ionosondes and incoherent scatter radar data the gps images reveal the large scale dynamics of the ionosphere during the disturbed conditions and show the potential of geophysical imaging for storm time ionospheric studies

ammonium halos in lithogeochemical exploration for gold at the horse canyon carbonate hosted deposit nevada u s a use and limitations abstract rock samples taken from the oxidized open pit to depths of 55 m of the carbonate hosted horse canyon gold deposit contain no nh4 samples from the unoxidized zone at the bottom of the pit in the protore however contain as much as 1 44 nh4 1 12 n the presence of nh4 was confirmed by mass spectrometry from these results it is concluded that samples from any oxidized environment e g outcrops soils likely will have lost all or most of any nh4 originaly present in minerals such as buddingtonite of nh4 containing clays this limits the use of nh4 halos in lithogeochemical exploration programs the most reliable application of lithogeochemical studies based on nh4 halos will likely be based on samples from drill cores and other situations where the samples have always been in a reducing environment analysis for nh4 by ir spectroscopy the method preferred by most previous workers is subject to several inherent problems the main one being the presence of the co32 ion whose absorbance at about 1430 cm 1 coincides with that used to determine nh4 the removal of co32 and other phases e g organic matter which may cause analytical difficulties by chemical treatment is not recommended because it is not possible to predict the effect of such treatment on any one of several possible minerals which may contain nh4 it is suggested that the most efficient method of analysis of rock samples for nh4 or n which can be assumed to represent nh4 will be to analyze the samples after heating to 550 c at which temperature all organic nh4 and n is removed by oxidation any remaining nh4 n determined on this residue can be assumed to originate in nh4 containing mineral structures

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

un lac glaciaire dans la region du lac minto nouveau quebec the presence of raised beaches around lake minto northern quebec and the washing of till in the upper part of the leaf river valley are attributed to the existence of a glacial lake it drained westward into the tyrrell sea and was dammed in the east by glacial ice that occupied the main part of the leaf river valley the disappearance of this ice prior to 5200 years bp led to rapid drainage of the glacial lake into an arm of the d iberville sea postglacial isostatic rebound has subsequently led to warping of the highest water plane associated with this glacial lake as well as those of the postglacial seas

mineralization of organogenic ammonium in the monterey formation santa maria and san joaquin basins california usa abstract inorganic fixed ammonium nh4 contents as high as 0 28 wt were measured in organicrich quartz grade siliceous rocks of the miocene monterey formation from the santa maria and san joaquin basins california the greatest amount of fixed nh4 was found in rocks associated with hydrocarbons in the point arguello and lost hills oil fields where the nh 4 nh 4 k molar ratio of bulk samples ranges from 0 17 0 35 the formation of nh4 illite is suggested by the parallel increase in the percent of illite in the mixed layered illite smectite i s and in the nh 4 nh 4 k molar ratio of the clay sized fraction with increasing burial depth mineralization of nh4 appears to be promoted by the coincident timing of the smectite to illite clay mineral transformation and the release of nh4 during catagenesis nh4 feldspar may form at shallow burial depths in rocks from the point arguello field that contain a greater amount of detrital k feldspar and in which the i s contains only 10 20 illite quartzgrade siliceous monterey rocks from coastal outcrops in the lions head area lack significant amounts of hydrocarbons and have nh 4 nh 4 k molar ratios of 0 14 0 21 rocks from the lions head area show a strong positive correlation between diagenetic illite and fixed nh4 contents with nh4 constituting 18 21 mol of the fixed interlayer cations in the i s low grade opal a and opal ct siliceous miocene rocks from coastal outcrops in the pt pedemales area have low fixed nh4 contents 0 01 wt because these rocks contain minor amounts of diagenetic k bearing minerals i s contains 10 illite and they lack significant amounts of generated or migrated hydrocarbons the increase in the organic c n ratio with burial depth most likely reflects the preferential release of n compared to c and suggests that nh4 release is greatest during shallow burial bacterial degradation and deep burial catagenesis oil generation the results of this study support the suggestion of williams et al 1989 that high fixed nh4 contents may provide a long term geologic record of low temperature

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

determination of the content and distribution of fixed ammonium in illite smectite by x ray diffraction application to north sea illite smectite a new x ray diffraction method for the determination of the amount and distribution of fixed nht in illite smectite has been developed illite smectite was saturated with k and heated at iso c the 002 and 005 reflections were recorded with steps of 0 01028 and the experimental d values and the values for full width at half height fwhh were determined using a peak profile fitting procedure peak profiles were calculated with the newmod program for illite structures having different amounts of nh and different patterns for the distribution of nh in interlayers for upper jurassic illite smectite from north sea oil source rocks the amount and the distribution of nh in illite interlayers were determined by comparing the experimental values for doo5 and fwhh with the values calculated for the selected illite structures the amounts of nh determined in this manner correlate well with the amounts determined by an isotopic dilution method the results demonstrate that these illite smectite samples have k end member illite and nh4 endmember illite tobelite layers and that the illite layers formed during diagenesis and oil generation actually are tobelite layers

the framework of hydrocarbon generation and migration gulf of mexico continental slope abstract the occurrence of large volumes of crude oil and thermogenic gas in plio pleistocene reservoirs and holocene seeps of the gulf of mexico slope argues that the process of hydrocarbon generation and migration continues at the present time calculated thermal maturity models based on deep seismic stratigraphy indicate that cretaceous and possibly early tertiary sediments are presently within the thermal maturity range for generation and expulsion of crude oil the cretaceous and early tertiary sediments are suggested as possible source rocks because younger sediments are thermally immature for crude oil generation and older sediments are thermally overmature for crude oil preservation the calculated thermal maturity profile for the slope indicates that some generation of crude oil could occur as shallow as 6 km and that liquid hydrocarbons could be preserved as deep as 9 km thermogenic gas is stable at even greater depths migration with a strong vertical component must be invoked to explain thermogenic hydrocarbons in shallow reservoirs and seeps of the slope the great depth at which liquid hydrocarbons and dry gas can be preserved in reservoirs of the gulf of mexico salt basin indicates that huge volumes of prospective section remain essentially unexplored

midlatitude tec enhancements during the october 2003 superstorm 1 we use observations from the array of north american gps receivers to examine the formation and severity of midlatitude enhancements and steep gradients in total electron content tec during the october 30 31 2003 superstorm a large 10x enhancement in dayside tec was observed over the us mainland during these events as dst decreased sharply and strong saps electric fields eroded the outer reaches of the post noon plasmasphere boundary layer pbl forming poleward streaming plumes of storm enhanced density tec increased to 250 tecu equatorward of the pbl tec gradients across the pbl over the central us exceeded 60 tecu per deg latitude while intense these features are qualitatively similar to those seen in lesser storms

inorganic nitrogen in anthracite from eastern pennsylvania usa abstract up to 20 of the total nitrogen content of anthracite rank coal from eastern pennsylvania occurs in authigenic nh 4 rich illite this enrichment is due to the concurrence of two independent reactions in the coal and surrounding organic rich shale during late stage organic maturation and diagenesis t 200 c 1 the release of n from organic matter by devolatilization reactions and 2 the formation of illite from kaolinite our estimates of inorganically bound n are conservative because minerals in fractures which can be volumetrically important were removed prior to analysis inorganic n estimates using x ray diffraction analysis are similar to those obtained by elemental analysis of combusted material the occurrence of inorganically bound n in organic rich rocks has important implications for geochemical characterizations of high rank coal n content and isotopic composition and laboratory investigations of the kinetics of n loss from organic material during thermal maturation in addition because nh 4 rich illite authigenesis is temporally linked to coalification the radiometric age of this mineral can theoretically be used to determine the absolute age of coalification in this region for detailed characterization of high rank coal we recommend that mineral matter be isolated by low temperature ashing and analyzed by x ray diffraction or c h n elemental analysis for inorganically bound n

the marine record of deglaciation from the continental margin off nova scotia continental margin sediments off nova scotia accumulate at high rates up to 360 cm kyr 1 and contain a history of millennial scale environmental changes which are dominated by the proximity of the laurentide ice sheet during the latest quaternary using stable isotope ratios of oxygen accelerator mass spectrometer radiocarbon dating micropaleontology and sedimentology we document these changes in six piston cores ranging in water depth from 450 to 4300 m we find that maximum 18o in n pachyderma occurred about 15 ka and preceded the maximum abundance of this species in these cores by 1000 years between 13 and 14 ka we find a second peak in abundance of n pachyderma minimum 18o and two pulses of ice rafting the sediment lithology supports terrestrial studies which indicate that there was a general withdrawal of ice beyond the upper paleozoic and mesozoic red beds by 14 ka in southeastern canada so the ice rafting events between 13 and 14 ka probably reflect ice stream activity in the st lawrence valley the younger dry as event is recognized as a peak in abundance of n pachyderma and ice rafting dated as 11 3 ka but meltwater discharge to the gulf of st lawrence was either too small or occurred over too long a time to leave a distinct 18o minimum off nova scotia at 7 1 ka in the middle of holocene warming we find a third peak in abundance of n pachyderma and another 18o minimum but no ice rafting we interpret these data as evidence of a late occurring meltwater event which if correct could have originated in the great lakes in the labrador ungava region or in both the final millennial scale phenomenon off nova scotia is the onset of neoglaciation marked by increased ice rafting and increased n pachyderma beginning about 5 kyr ago

coccolith evidence for instabilities in surface circulation south of iceland during holocene times abstract the coccolith based micropaleontological investigation of an exceptionally thick deep sea holocene sediment core was conducted in order to document the pattern and timing of surface circulation changes south of iceland over the gardar contour drift during the last 12 000 years fluctuations in bulk carbonate content at the core location are primarily driven by the coccolith fraction the observed overall correlation between bottom flow speed as given by the sortable silt mean size index and the bulk coccolith concentration abundance g dry sediment suggests that the accumulation of this fine carbonate fraction is as a first order controlled by processes of sediment redistribution by bottom current the down core variations in coccolith assemblage structure species indicate that changes in properties of surface waters south of iceland occurred as two distinct steps at ca 11 2 and 6 ka the onset of north atlantic drift water influence over the gardar drift after 11 2 ka was associated with excess export flux of coccolith carbonate in the vicinity of an active frontal system the period from 10 to 6 ka saw the progressive warming of the study area which culminated between 6 and 7 ka cooling of the surface waters after 6 ka as indicated changes in the relative abundances of the dominant coccolith species took place in two phases the present hydrological regime being only established after a last cooling step between 3 5 and 2 8 ka these long term reorganisations of the surface hydrology are interpreted as the response of the north atlantic to the combined force of the solar insolation and the waning laurentide ice sheet millennial scale perturbations of the surface hydrology are documented by changes in accumulation of the species emiliania huxleyi these successive decreases in the export fluxes of e huxleyi exhibit a distinct millennial pacing in phase with previously recorded holocene advection of cool ice bearing waters from the greenland iceland seas to the british islands from a clear analogy with the most recent extreme variation in global ocean climate we argue that mechanisms responsible for these observed millennial scale perturbations might be found in long term modulations of the atmospheric processes associated with the north atlantic oscillation nao

near infrared detection of ammonium minerals diagnostic near infrared spectral features have been identified for minerals with ammonium nh4 bound in the crystal structure spectral bands near 2 12 2 02 and 1 56 m are characteristic of synthetic and natural nh4 bearing minerals laboratory spectra of nh4 bearing minerals are distinct from spectra of oh bearing minerals and have diagnostic shifts in band position among different mineral types nh4 bearing minerals were detected at several mineralized hot spring deposits in the western u s by means of hand held and airborne instruments near infrared detection of nh4 bearing minerals may provide useful information for prospecting for certain ore deposits and may provide a better understanding of the nitrogen cycle within geologic environments

the distribution of ammonium in granites from south west england the ammonium contents of granites pegmatites and hydrothermally altered rocks from sw england have been measured ammonium levels in the granites are generally high compared with those from other regions averaging 36ppm and they differ markedly between intrusions the pegmatites show higher ammonium contents than any other igneous rocks which have yet been investigated ammonium contents are strongly enriched in the hydrothermally altered rocks including greisens and kaolinized granites there is a good correlation between the average ammonium content of the intrusions in sw england and their initial 87 sr 86 sr ratios and peraluminosity this relationship supports the hypothesis that the ammonium in the granites is derived from a sedimentary source either in the magmatic source region or via contamination of the magma

deducing storm time f region ionospheric dynamics from 3 d time varying imaging 1 the inversion algorithm for estimating model parameters from ionospheric reverse engineering empire has been created to gain insight into ionospheric dynamics particularly when direct measurement is unavailable we extend the capabilities of empire here in order to demonstrate its effectiveness on densities obtained from real data we apply this method to real ionospheric data assimilation 4 dimensional ida4d data from storm time measurements focusing on the midlatitude f2 layer empire is used to estimate midlatitude field aligned and field perpendicular drifts the estimated upward drifts from empire are validated against measurements obtained from the millstone hill incoherent scatter radar zenith antenna the horizontal drifts are compared to the assimilative mapping of ionospheric electrodynamics amie model which estimates drifts from data sources independent of those used in ida4d results show that the direction and magnitude of the drifts and therefore the electric fields may be deduced from imaging based primarily on total electron content data although altitude variation is not significantly discernible we also indicate that the initial uplift of the storm enhanced density may have been more strongly influenced by field aligned contributions of neutral winds and diffusion than the electric fields

nitrogen geochemistry as a tracer of fluid flow in a hydrothermal vent complex in the karoo basin south africa abstract we have investigated the n geochemistry of minerals and rocks from contact metamorphic aureoles and hydrothermal vent complexes hvc in the karoo basin in south africa the hvc formed during phreatic eruptions associated with rapid devolatilization and pressure build up in contact aureoles around early jurassic sill intrusions by combining outcrop data from a hvc and core data from contact aureoles we investigate the relationship between light element release during metamorphism and vertical fluid migration sandstone and breccia from the hvc contain early diagenetic ammonium nh 4 bearing feldspar buddingtonite and illite ammonium occupies up to 95 of the a site in feldspar corresponding to concentrations up to 5 2 wt n bulk rock n isotope data for rocks from inside and outside the hydrothermal vent complex fall into two distinct groups background samples have 15nair between 1 5 and 4 9 whereas minerals from the vent complex have 15n in the range 7 5 to 10 6 the n geochemistry of contact metamorphic shale from the lower stratigraphic units of the karoo basin shows that the vitrinite reflectance and 15n values are positively correlated shale with reflectivity values 4 ro are enriched in 15n with 15n values between 6 and 14 implying the release of isotopically light n into metamorphic fluids probably as n2 we suggest that the relatively high 15n values of the early diagenetic buddingtonite in the hvc reflect exchange of buddingtonite with n bearing fluids ascending from greater depth after their release during contact metamorphism and dehydration we present a qualitative model whereby hydrothermal vent complexes represent fluid flow structures after their formation focusing n bearing metamorphic fluids sourced in deeper levels of the basin the release of organic n from sediments at depth in volcanic basins could play a role in the geochemical cycle of n becoming particularly important during periods of intense volcanic activity

abrupt deglaciation events and holocene palaeoceanography from high resolution cores cartwright saddle labrador shelf canada the uppermost quaternary sediments in cartwright saddle labrador shelf are acoustically laminated with reflectors that can be traced over long distances two piston cores from the saddle record changes in sediment and meltwater delivery from the northeast margin of the laurentide ice sheet lis during deglaciation variations in sediment properties indicate a similar history of sediment accumulation over the last 12 kyr the temporal sampling interval reaches decadal resolution in the last deglacial period 7 9 ka analyses of total carbonate content sediment magnetic variables foraminiferal species and stable isotope measurements on planktic foraminifers show that abrupt changes occurred ca 10 9 9 2 8 8 7 9 and 7 ka with 450 yr correction there was no distinct change in sediment character during much of the younger dryas chronozone in the 18o record the 8 8 ka event is a dramatic 1 shift toward lower values which we associate with the noble inlet glacial event within hudson strait we do not see the pronounced low 18o event at 7 1 ka reported off nova scotia but surprisingly neither the nova scotia records nor other records in the labrador sea capture the impressive 8 8 ka change serious consideration must be given to the final collapse of the lis as the cause of the 8 2 cal ka cold event recorded in greenland and northwest europe copyright 1999 john wiley sons ltd

time perspectives on glacial landscape formation glacial flow chronology at lac aux goelands northeastern quebec canada we used mapping from aerial photographs and field investigations around lac aux goelands whitegull lake northeastern quebec to establish a glacial flow chronology that involves three different glacial landform systems we interpret the youngest of these systems as related to the late wisconsinan deglaciation this system has an up glacier discontinuity that marks a temporal shift from warm based subglacial conditions to non erosive cold based subglacial conditions whereby older glacial landscapes are preserved in the interior of quebec labrador furthermore our results support theories suggesting a northward migrating ice divide to a final position south of ungava bay during the final deglaciation the recognition that a glacial landscape is fragmented and consists of smaller temporally unrelated units is of considerable significance in understanding ice sheet dynamics and patterns of subglacial preservation and destruction this is because a fragmented landscape implies a fragmented formation history where formation of subglacial landforms occurred in restricted subglacial zones during restricted time periods periods of formation must have been separated by periods of preservation and inhibited subglacial reshaping based on estimates of the ice margin retreat velocity and the velocity of the warm based inward migrating zone we suggest that periods of preservation were orders of magnitude longer than periods of subglacial landform formation copyright 2003 john wiley sons ltd

late glacial ice margins and deglacial chronology for southeastern baffin island and hudson strait eastern canadian arctic radiocarbon dates from marine piston cores and from onshore raised marine stratigraphic sections in the hudson strait region were used to reconstruct deglacial isochrons for 9900 9500 8800 8500 and 8000 bp at the culmination of the gold cove readvance 9900 bp labrador ungava ice flowed northeastward across hudson strait and outer frobisher bay and stood for the last time on the baffin island continental shelf subsequent retreat by calving was rapid and profound opening the entire hudson strait marine trough by 9500 bp at this time ice dispersal from foxe basin labrador ungava and local ice on meta incognita peninsula supported tidewater margins along much of the coastline with the exception of northernmost ungava peninsula where the ice margin stabilized onshore this onshore margin remained in place throughout the cockburn substage while a major northeastward readvance of ungava bay ice the noble inlet readvance from 8800 to 8500 bp crossed outer hudson strait grounding on the hudson st

early holocene glacial lake meltwater injections into the labrador sea and ungava bay 1 in this paper we analyze drainage routes and estimate fluxes of meltwater released from labrador ungava glacial lakes into the labrador sea ungava bay and hudson bay between 7 5 and 6 0 kyr bp 8 4 7 0 calendar cal years ka the analysis and estimates are based on landform based reconstructions of the laurentide ice sheet lis decay pattern and the associated glacial lake evolution geomorphological data constraining the spatial extent of glacial lakes are coupled to a digital terrain model for meltwater volume calculations the lis ice recession between 7 5 and 6 0 kyr bp led to the formation of a large number of glacial lakes which drained in approximately 30 meltwater pulses with fluxes exceeding 0 015 sv 1 sv 106 m3 s 1 into labrador sea ungava bay and hudson bay the inferred rapid ice margin retreat during late stages of deglaciation indicates that these drainage events were relatively short lived the early holocene glacial lakes of labrador ungava released meltwater resulting in a total inflow of 6000 km3 freshwater to the north atlantic the pulsed nature of meltwater release from the lakes is likely to have resulted in rapid repeated cooling of the labrador sea surface water

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

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

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

late deglaciation of the central labrador coast and its implications for the age of glacial lakes naskaupi and mclean and for prehistory the age of the marine limit and associated deglaciation has been estimated from relative sea level curves for the hopedale and nain areas of the central labrador coast as approximately 7600 200 and 8500 200 yr ago respectively these ages indicate that the ice margin remained on the coast for up to 3000 yr longer than previously estimated because the central coast is due east of glacial lakes naskaupi and mclean the earliest the lakes could have formed was 8500 200 yr ago with their largest phases being fully established only after 7600 200 yr ago this suggests that the age of the lakes and associated deglaciation of the central labrador ungava region is younger by at least 1500 yr than previously estimated a late glacial marine based ice mass in ungava bay that dammed the lakes collapsed ca 7000 yr ago within this time frame therefore the glacial lakes only existed for 500 yr the persistence of the laurentide ice sheet margin on the central labrador coast until 7600 yr ago probably restricted the northward movement of early prehistoric people into northern labrador

illite smectite structural changes during metamorphism in black cambrian alum shales from the baltic area illite smectite i s from cambrian black shale of both early diagenetic and anchimetamorphic grade was investigated to determine the mechanism of the clay transformation the layer sequences the distribution of thicknesses of coherent scattering domains csds and the three dimensional ordering were determined by x ray diffraction xrd the proportions of cis vacant cv and transvacant tv 2 1 layers were determined by thermal analysis and the proportion and distribution of interlayer ammonium by xrd and by infared spectroscopy ir the structural formulae were determined from total chemical analysis and mossbauer and 27al nmr spectroscopies and the particle shape and size investigated by atomic force microscopy afm in the early diagenetic samples the i s is composed of two phases one of which contains 0 05 and the other 0 25 smectite s interlayers the first phase does not change during metamorphism in the second phase 0 20 s are converted to tobelite t layers through fixation of formula 1 but the i layers are not changed simultaneously the proportion of cv layers changes from 0 18 to 0 02 and the tetrahedral substitution of al for si is parallel to the increase in t layers all i interlayers contain 0 75k per o10 oh 2 further more the metamorphism results in increasing mean thickness of csds from 5 1 6 8 nm for the low diagenetic samples to 6 7 8 4 nm for the anchimetamorphic samples we conclude that the tobelitization was accompanied by transformation of cv to tv 2 1 layers adjacent to the smectite interlayers and formation of tv layers adjacent to the newformed tobelite interlayers in otherwise intact crystallites this mechanism only partly resembles the tobelitization previously observed in the upper jurassic north sea oil source rocks i s in these rocks contained tv 2 1 layers and t interlayers formed through solid state al for si substitution in the tetrahedral sheet and by ammonium fixation in the corresponding interlayers these different mechanisms are probably because the north sea i s originated from weathered illite like the cambrian high illitic phase whereas the cambrian low illitic phase undergoing the transformation originated from cv smectite of volcanic origin the results indicate that the illitization in oil source rocks is linked to oil generation and that it deviates from the illitization in other rocks because of the supply of ammonium formed during oil generation and the fixation of this ammonium in the former smectite interlayers 1 embed tex math 1 gif

ice sheet dynamics and glacial history of southeasternmost baffin island and outermost hudson strait southeasternmost baffin island is mantled by hudson strait drift it contains abundant limestone erratics and 20 to 50 carbonate in the matrix to the northwest it is replaced by drift dominated by locally derived rock of the canadian shield the sense and orientation of ice erosional features demonstrate that hudson strait drift is associated with northeasterly ice flow that crossed the tip of meta incognita peninsula local drift associated with ice flow s10 w along the hudson strait coast was derived from a dispersal center on the peninsula erratic lithologies contained in the hudson strait drift indicate a labradorean provenance large scale bedrock molding and the distribution of cirques indicate ne flowing ice has been dominant throughout the middle and late quaternary radiocarbon dates of in situ shells confirm that deglaciation began more than 11 000 yr ago with the frobisher bay coast becoming ice free by 9300 yr ago five dates from hudson strait suggest that the strait was deglaciated before 9000 yr bp however ice from the labradorean sector recrossed hudson strait during the cockburn substage about 8500 yr ago damming drainage from the west final retreat of labradorean ice from baffin island was complete by 8000 yr ago at which time the sea was able to penetrate hudson bay

centennial scale holocene climate variability revealed by a high resolution speleothem δ18o record from sw ireland evaluating the significance of holocene submillennial 18 o variability in the greenland ice cores is crucial for understanding how natural climate oscillations may modulate future anthropogenic warming a high resolution oxygen isotope record from a speleothem in southwestern ireland provides evidence for centennial scale 18 o variations that correlate with subtle 18 o changes in the greenland ice cores indicating regionally coherent variability in the early holocene evidence for previously undetected early holocene cooling events is presented but mid to late holocene ice rafting in the north atlantic appears to have had little impact on 18 o at this ocean margin site

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

ionospheric signatures of plasmaspheric tails 1 we make direct comparisons between gps maps of total electron content tec over the north american continent millstone hill radar observations of storm enhanced density and low and high altitude satellite measurements of the perturbation of the outer plasmasphere during the march 31 2001 geomagnetic storm we find that storm enhanced density sed and plumes of greatly elevated tec are associated with the erosion of the outer plasmasphere by strong sub auroral polarization electric fields the sed tec plumes identified at low altitude map closely onto the magnetospheric determination of the boundaries of the plasmapause and plasmaspheric tail determined by euv imaging from the image spacecraft characteristics of the sed tec plumes tails for the march 31 2001 event are tec 100 tecu f region sunward velocity 1000 m s sunward flux 5 1024 ions s 1 total transport to dayside magnetopause merging region 3 hr event 5 1028 ions

investigation of the pyrolytic liberation of molecular nitrogen from palaeozoic sedimentary rocks open system non isothermal pyrolysis up to 1 200 c in combination with elemental analysis was used to study the thermal liberation of molecular nitrogen n2 from sedimentary rocks and kerogen concentrates of palaeozoic age from the central european basin system and an eocene shale liaohe basin china with a high content 36 of ammonium feldspar buddingtonite the n corg atomic ratios of the kerogen concentrates ranged from 0 005 to 0 014 which represents the range commonly observed for coals bulk n corg ratios of the palaeozoic shales extended from 0 035 to 0 108 indicating the presence of significant amounts of inorganic nitrogen namurian a and a b cna cna b samples typically exhibited the earliest onset of n2 generation with intense characteristic peaks around 600 c n2 liberation from the buddingtonite rich sample occurred at higher temperatures with a broad peak around 700 c pyrograms of the kerogen concentrates showed no or strongly reduced n2 generation in the 500 700 c range on line isotope specific analysis of the pyrolytically liberated n2 on one sample revealed a variability of 10 in the 15n values and a steady increase in 15n with temperature during the main phase of n2 generation

late quaternary chronology and environments of square lake torngat mountains labrador sediment pollen and diatom records from square lake a small lake dammed by a segment of saglek moraine cover the period of deposition of and deglaciation from the saglek moraine the basal radiocarbon date 18 210 1900 years bp is on sediment contaminated by reworked pollen and is thus a maximum age however the date was measured on organic carbon recovered from glaciolacustrine couplets associated with deposition of the saglek moraine and thus establishes a late wisconsinan age for the saglek moraine vegetation on the ice free upland surrounding square lake at this time was a sparse tundra vegetation dominated by grasses and herbs the absence of diatoms indicates perennial lake ice cover a major transition is recorded by pollen and diatoms at 8 5 ka vegetation probably remained sparse tundra but birch and willow may have arrived in the area by 8 ka diatoms are first dominated by alkaliphil species reflecting continued influence of glaciolacustrine sedimentation an abrupt change in depos

origin of crude oil in the wilcox trend of louisiana and mississippi evidence of long range migration abstract geochemical characterization of crude oils from wilcox reservoirs in central louisiana and southwest mississippi suggests that they represent a single crude oil family that is distinct when compared to crude oils in deeper tuscaloosa and smackover reservoirs this observation is consistent with geologic constraints that suggest an origin of crude oil from within the wilcox group itself although shales of the shallow wilcox group in central louisiana and southwest mississippi contain gas prone kerogen and are thermally immature a more oil prone source facies is present in marine shales of the deep wilcox group in southcentral louisiana thermal maturity measurements based on pyrolysis suggest a broad area of effective wilcox source rock in southcentral louisiana migration distances from source to reservoir rocks of the downdip wilcox trend of southcentral louisiana appear to be relatively short however long range updip migration sometimes greater than 100 km from deeply buried wilcox source facies provides the best explanation for emplacement of crude oil in the shallow wilcox trend of central louisiana and southwest mississippi

early holocene glacial lakes and ice marginal retreat pattern in labrador ungava canada abstract the existence of glacial lakes naskaupi mclean minto melezes and wapussakatoo during the deglaciation of labrador ungava canada was recognized at the end of 1950s however glacial lakes have seldom been included in regional reconstructions to constrain the outline of successive ice margins during the glacial retreat in labrador ungava reconstruction of the ice flow succession in labrador ungava has often primarily focused on till lineation systems these reconstructions often depict a late glacial ice dispersal center situated over central labrador ungava more recent studies on glacial geomorphology including meltwater features however suggest that north central labrador ungava exhibited cold based conditions at least during the latest deglaciation cold based conditions inhibit basal sliding and formation of landforms except for meltwater traces such as meltwater channels glacial lake shorelines and deltas this situation implies that meltwater traces are the main source of information when reconstructing the spatial retreat pattern during a cold based deglaciation evidence presented in this study such as glacial lake shorelines fossil deltas and spillway and drainage channels in north central labrador ungava indicates the existence of numerous previously unmapped glacial lakes the mapped glacial lake features are synthesized to a reconstruction of several glacial lake stages which in turn are used to constrain the late glacial ice margin retreat pattern over the inferred cold based areas of north central labrador ungava a total of 26 glacial lakes 65 sub stages existed during the deglaciation of labrador ungava these lakes were impounded along the southern margin of the shrinking ice sheet the required damming ice margins indicate that the last ice remnant of the laurentide ice sheet in labrador ungava was situated over the southern ungava bay and the adjacent southern shore

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

observations of the f region height redistribution in the storm time ionosphere over europe and the usa using gps imaging 1 ionospheric imaging with gps provides a near global view of the three dimensional time evolving ionosphere this is of particular interest during storms the focus of this paper is on the height redistribution of the plasma and in particular the longitudinal and latitudinal variations in the time of plasma uplifts three storms 15 july 2000 30 october 2003 and 20 november 2003 are studied here dramatic elevation of the f layer by more than one hundred kilometers was seen in the images during daytime over europe and the usa for all three storms all three showed an east west time delay of around one hour in the peak height elevation over some 85 longitude the 20 november 2003 storm also showed a north south time delay in the change in the f region height with the uplift seen first at high latitudes and then low latitudes independent evidence from other instruments and techniques are provided as supporting evidence that the peak height uplifts occurred candidate mechanisms of the peak height changes are electric fields and neutral winds and the roles of these drivers will be investigated in future modelling studies

geomorphological reconstruction of the labrador sector of the laurentide ice sheet abstract the labrador sector formed one of three major domes of the laurentide ice sheet during the last wisconsinan glaciation reconstruction of its evolution is important because it modulated atmospheric and oceanic circulation over 1 100 ka time scales this paper reports new geomorphological evidence of ice flow which is used to reconstruct glimpses of the behaviour of the labrador sector during its evolution flow evidence indicates a southern position 51 n of the labrador ice divide presumed to be the usual location when the ice sheet was close to its maximum extent a previously inferred dramatic surge of labrador ice across hudson strait and onto baffin island at 9 9 9 4 ka is verified seemingly contradictory evidence regarding deglaciation in northern quebec has been analysed and a reconstruction developed that solves this problem deglacial retreat of the labrador ice sheet was highly asymmetric with rapid retreat of the southern margin northwards migration of the centre of mass by 500 km and slow retreat along the northern margin as it shrank its thermal regime changed from cold centred to entirely cold based and it finally fragmented into many residual ice caps and glaciers this dynamic and asymmetric behaviour may be due to destabilisation of the labrador ice sheet triggered by heinrich event ice streaming through hudson strait

high primary productivity and nitrogen cycling after the paleoproterozoic phosphogenic event in the aravalli supergroup india the causes of atmospheric oxygenation in the paleoproterozoic are multifaceted yet poorly understood an increase in the level of primary productivity however may have been an important factor in producing large amounts of oxygen in the atmosphere a likely environmental consequence of atmospheric oxygenation is an increased abundance of seawater nitrate which would have resulted in a fundamental change from the archean nitrogen cycle in this study we investigate these questions using the carbon and nitrogen isotope compositions of carbonaceous shales from the paleoproterozoic aravalli supergroup india the shales occur stratigraphically above one of the oldest phosphogenic events that took place around 2 0 ga shales in the phosphate domain of the jhamarkotra formation from the lower aravalli group have distinct characteristics from coeval shales in the non phosphate domain carbonaceous shales of the phosphate domain contain relatively high v and u th typical of oxygen deficient environments these shales also have a high organic content of up to 14 wt generally homogeneous 13 corg values around 29 c nwr up to 360 and a large range of 15