provenance of quartz in sedimentary mantles and laterites overlying bedrock in west africa evidence from oxygen isotopes abstract silty to sandy mantle and laterite sediments overlying bedrock in west africa cameroon to mali were studied to establish their origin oxygen isotope values of fine quartz 1 to 10 m in diameter separated from the samples have a relatively narrow range 15 to 17 vs smow and are indistinguishable from quartz separated from two harmattan wind dust samples collected in nigeria 15 4 however the oxygen isotope values are distinctly different from those of quartz in samples of basement precambrian granites 10 5 to 12 8 gneiss 13 3 o and a cretaceous shale 23 2 from the same area the 18 o values of quartz from the studied soils and sediments systematically decrease with increasing particle size small oxygen isotopic variations were observed for quartz up to 105 m in size whereas greater stable isotope variations are present in quartz fractions larger than 105 m oxygen isotope and particle size frequency evidence indicate that the fine sand silt size quartz fraction 105 m had a local origin we conclude that the eolian fine quartz was transported by the harmattan winds which blow from the chad basin to the atlantic ocean

evidence of saharan dust in upper pleistocene reworked palaeosols of north west sardinia italy palaeoenvironmental implications abstract a multi disciplinary approach was followed to investigate two thick palaeosolstrata that alternate with wind blown dominated deposits developed along thealghero coast north west sardinia italy optically stimulated luminescenceages reveal that both palaeosols were developed during cooler drier periods the rst one at around 70 ka marine isotope stage 4 and the latter around 50 ka marine isotope stage 3 in contrast the pedological features indicate that thepalaeosols underwent heavy weathering processes under warm humid to sub humid conditions characteristic of the sardinian climate during the lastinterglacial stage marine isotope stage 5e to reconcile this apparent datadiscrepancy a range of sedimentological and pedological analyses wereconducted these analyses reveal that the palaeosols possess a complexhistory with accumulation and weathering occurring during marine isotopestage 5e and erosion colluviation and nal deposition taking place during thefollowing cold stages thus even if these reddish palaeosols were last formedduring the glacial period the sediments building up these strata probablyrecord the climate of the last interglacial stage marine isotope stage 5e traceelement and x ray diffraction analyses together with scanning electronmicroscope images reveal the presence of saharan dust in the parentmaterial of the palaeosols however no evidence of any far travelled africandust has been observed in the marine isotope stage 4 3 aeolian deposits it ispossible to conclude that in the west mediterranean islands saharan dustinput even if of modest magnitude is preserved preferentially in soilsaccumulated and weathered during interglacial stages keywords marine isotopic stage mediterranean osl dating trace elementgeochemistry xrd analysis sedimentology 2012 59 917 938

aeolian dust in europe african sources and european deposits abstract a conceptual model is presented for the provenance and dispersal patterns of small dust that falls on europe generally its sources are in north africa and it is distributed across all europe several key sources can be distinguished sahelian dust comes largely from the old lake chad region this is a clay rich unimodal material saharan dust comes from the great sand sheets it contains small monomineralic particles and may have a bimodal size range three simple deposition zones can be recognised a d1a zone where sufficient dust is deposited to form a discrete soil layer not well classified as a rendoll in the extreme south of europe a d1b zone where the airborne dust simply provided a silty admixture to soil systems across middle europe and a northern zone d1c where the dust is a fugitive cloud but very occasionally forms noticeable deposits two particle formation methods can be noted particle control in sahelian dust is via the sedimentation in the original lake this gives an open structure which can be modelled using a simple monte carlo approach the open structure ensures that only small particles are produced size control is via particle packing a chipping mechanism can produce fine quartz particles from sandy deserts the aeolian energy is by and large not sufficient to cause major impact fracturing but small mineral chips can be produced in the small dust size fine and very fine silt which go into high level suspension and travel to europe and beyond the saharan material can have a wider more variable size distribution than the sahelian material the canary islands loess is largely sahelian material the cape verde islands deposits from the nearby sandy regions are saharan deposits large dust has fallen on europe and produced widespread loess deposits large dust is essentially an in continent deposit small dust comes from outside from africa

late holocene environmental change and the anthropization of the highlands of santo antao island cabo verde abstract cabo verde was the first tropical archipelago colonized by europeans historians have suggested that the first colonizers initiated archipelago wide ecosystem degradation loss of vegetation cover and erosion however the human environment interactions that led to the archipelago s current environmental status remain poorly understood here we report the first palaeoecological study of past vegetation change and disturbance regimes for cabo verde we present a 2130 yr old sediment sequence from a volcanic caldera cova de paul located at 1200 m asl on santo antao island for which we analyzed fossil pollen non pollen palynomorphs npps charcoal silica bodies and grain size distribution our analyses do not show evidence of the presence of temperate tropical or subtropical forests growing on the summits of santo antao in pre human times the pollen record shows that scrubland and grasslands dominated the highlands and underwent compositional changes ca 1850 and 1300 cal yr bp these shifts overlap with erosion phases and are linked to intensified seasonality steady rates of sedimentation marked the period 1230 to ca 350 cal yr bp but an increase in charcoal concentrations indicate a drying phase increases in regional and local fire peaks of coprophilous fungi and the presence of new world crop pollen zea mays are interpreted as the onset of portuguese settlement of the highlands after 450 bp sustained erosion between ca 350 and 100 cal yr bp indicate soil degradation and the pollen record shows the increase in introduced herbaceous taxa rosaceae centaurea verbenaceae and exotic tree taxa e g pinus while shifting abundances of coprophilous fungi indicate changes in land use the record shows stabilization of soils in the last century due to recent afforestation of the highlands further palaeoecological studies have the potential to provide further detail of the long term dynamics of cabo verde ecosystems and to inform conservation initiatives

tracing dust sources and transport patterns using sr nd and pb isotopes continental dust transported through the atmosphere can be a tracer of atmospheric circulation and transport as well as being a source of information about climate in the dust s source area this information about the provenance of dust transported from desert areas and deposited elsewhere on the oceans and continents can be evaluated using several observational techniques satellite imagery has been used to this end in recent decades and air mass back trajectories have been calculated to trace dust deposits back to their source area another method consists of analysis of the concentration and composition of certain tracers in the dust itself and comparing them to soils and sediments from possible source areas this method has the advantage of being useable for paleo atmospheric circulation and paleo dust transport studies whereas satellite imagery and air mass back trajectories are restricted to relatively recent times we review here different kinds of isotopic tracers that have been used to trace dust provenance but special attention is focused on the use of sr nd and pb isotopes we evaluate their use in studies of both spatially as well as temporally varying continental dust source and transport

dynamic link between the level of ductile crustal flow and style of normal faulting of brittle crust abstract in a rheologically layered crust compositional layers have an upper elasto plastic part and a lower viscous one when broken the upper elastic part undergoes flexure which is upward for the foot wall and downward for the hanging wall as a consequence of bending stresses will develop locally that can overcome the strength of the plate and therefore impose the migration of active fault in the lower viscous part of each compositional layer rocks can potentially flow numerical modelling of the behaviour of a crust made up of two compositional layers during and following extension shows that flow can take place not only in the lower crust but also and more importantly in the lower part of the upper crust the ability of crustal rocks to flow influences the style and kinematics of rifted regions when no flow occurs subsidence will affect the extending areas both hanging wall and foot wall will subside with respect to an absolute reference frame such as sea level and there will be a strict proportionality between extension and thinning in addition the downward movement of the fault blocks will decrease the local stresses created in the foot wall and increase those of the hanging wall thereby imposing a migration of fault towards the hanging wall this is the behaviour of extensional settings developed on stabilised crust and which evolved in a passive margin when flow does take place middle crustal rocks will move towards the rifting zone causing isostatically driven upward movements that will be superimposed on movements associated with crustal and lithospheric thinning consequently fault blocks will move upwards and the crust will show more extension than thinning the upward movements will decrease the stresses developed in the hanging walls and increase those of the foot wall faults will then migrate towards the foot wall such a mode of deformation is expected in regions with thickened crust and has its most apparent expression in core complexes

sr and nd isotope composition of late pleistocene sapropels and nonsapropelic sediments from the eastern mediterranean sea implications for detrital influx and climatic conditions in the source areas isotopic ratios of sr and nd from lithogenic components of three isochronous core sections recovered from an east west transect in the eastern mediterranean sea ems have been analyzed the data are used for a quantitative estimate of the temporal and spatial variation of detrital flux to the ems assuming saharan dust and aegean nile particulate matter as dominant end members it was established that the carbonate free saharan dust flux during deposition of the nonsapropel layers of marine oxygen isotope stage 5 4 mis 5 4 was similar to the present flux during the deposition of sapropels s5 and s6 however the saharan dust input was drastically reduced and was not balanced by a change in the riverine influx at this time denser vegetation cover during more humid conditions may have reduced physical erosion and sediment removal in the source area during marine oxygen isotope stage 6 2 mis 6 2 a pronounced increase of saharan dust and detrital influx from the aegean region is evident and implies more arid conditions in the southern and northern catchment areas during this period intersite variations are interpreted in terms of their geographic location relative to the seaways connecting the aegean sea and ems the width of the straits and hence the amount of sediment entering the eastern basins may have been affected by a low sea level that impeded interbasin sediment dispersal

dust rains in mallorca western mediterranean their occurrence and role in some recent geological processes abstract dust rains were observed in palma de mallorca island of mallorca western mediterranean on 253 days in the 22 year period from 1982 to 2003 these and other data from the western mediterranean show that dust rains are on the increase most occur in the warmest season of the year meteorological conditions associated with this phenomenon combine hot advection from the south at low tropospheric levels with southwest winds associated with a depression in the middle troposphere dry deposition of dust often in aggregates 40 300 m across is occasionally observed analysed samples are silty and mainly composed of quartz and kaolinite they also contain minor proportions of feldspars and palygorskite which do not occur as rock forming minerals in the balearic islands comparisons of the dusty rainwater samples with soils and recent marine and karstic sediments suggest that dust deposition is an important sedimentary process in the balearic islands

the characterisation of saharan dusts and nile particulate matter in surface sediments from the levantine basin using sr isotopes abstract the provenance of sediments within the levantine basin of the eastern mediterranean was studied using 87 sr 86 sr isotopic ratios together with major elements measurements were made on the detrital fraction of surface sediments and the two most important sources of detrital matter to the region saharan dust was characterised by an 87 sr 86 sr isotopic ratio in the range 0 7160 0 7192 there was a small systematic decrease in 87 sr 86 sr from west to east which is interpreted as due to a change in the balance of aeolian source material the nile particulate matter had a 87 sr 86 sr isotopic ratio in the range 0 7057 0 7071 87 sr 86 sr isotopic signatures together with sr concentration were used to calculate the contributions made by saharan dust and nile particulate matter to the surface sediments of the levantine basin it was shown that nile derived sediment was dispersed widely across the levantine basin enabling the area affected by retention of sediment behind the aswan dam to be determined

a new approach to the nd residence time in the ocean the role of atmospheric inputs concentrations of rare earth elements ree and nd isotopic ratios were analyzed for seawater filtered suspension and sediment trap samples collected in the tropical atlantic ocean eumeli program eutrophic mesotrophic and oligotrophic sites 20 n 18 21 w this is the first ree nd dataset on solution and different sized particles collected at the same site we present direct evidence of the nd isotopic exchange between particulate lithogenic fraction and seawater without significant mass transfer this exchange is probably one of the main factors that simultaneously constrains the nd concentration and isotopic ratio budget we propose a new approach to estimate the residence time of nd in the ocean nd based on isotopic exchange 200 yr nd 1000 yr the exchange requires a partial dissolution of lithogenic nd we estimate that the fraction of soluble nd proportion in atmospheric dust is of the order of 20 based on the isotopic ratios we suggest that the partial dissolution of atmospheric fallout is probably one of the main ree sources of the ocean

multicomponent analysis of ftir spectra quantification of amorphous and crystallized mineral phases in synthetic and natural sediments abstract the study of weathering and erosion processes requires the establishment of a mass balance of minerals from the soils towards the sedimentation area this calls for the development of quantitative tools that can be applied to mixtures of finely divided and sometimes poorly crystallized minerals found in soils and sediments we present here the use of fourier transform infrared ftir absorbance spectroscopy in the mid infrared as a method to calculate mineral modes for such materials samples were prepared using the kbr disc method this ensures that lambert beer s law is valid a quantitative determination of the mineral content from various blends was performed by making a multicomponent analysis of the experimental spectrum using the spectra of each component in the mixture to check the validity of the procedure the multicomponent analysis was performed on spectra from synthetic mixtures of standard minerals quartz kaolinite gibbsite amorphous silica good agreement between actual and computed wt was obtained in the range 1315 315 cm 1 this application of ftir spectroscopy was used to quantify the mineral components of a lacustrine sediment cored at salitre minas gerais brazil the major phases are organic matter kaolinite gibbsite quartz anatase and amorphous silica phytoliths and sponge spicules fifty three samples were analyzed quantitative results from ftir spectroscopy were compared to chemical analyses to assess the validity of the method for the natural sediments phases with no sharp diagnostic spectral features such as anatase or amorphous silica were quantified using the multicomponent analysis the variations of the main mineral phases along the core reflect the mechanisms of transfer from the surrounding soils to the sediment area and the role of the vegetal cover over the drainage area

atmospheric contribution to cations cycling in highly weathered catchment guadeloupe lesser antilles abstract the important fertilizing role of atmospheric dust and particularly african dust in tropical rainforests is increasingly recognized but still poorly quantified to better evaluate dust input into the caribbean basin we sampled critical zone compartments of a small forested volcanic catchment in guadeloupe soils parent rock atmospheric dust plants soil solutions stream and rain waters the aims of this study are to track sources of cation nutrients ca mg k sr developed on highly weathered soil in the rainforest of guadeloupe to quantify plant recycling of these nutrients and to identify constraints on regolith development and its associated nutrient pool in the quiock creek catchment a large isotopic range of 87sr 86sr and end values was observed despite the small scale of observation sr isotopic composition of the dissolved load varied from 0 7084 in rainfall to 0 7110 in soil solution whereas it ranges between 0 7068 and 0 7153 for soil samples and between 0 7096 and 0 7102 for plants the nd isotopic composition varied between 8 39 in near surface soil samples to 2 71 in deeper soil all samples had an intermediate signature between that of the bedrock endmember 87sr 86sr 0 7038 end 4 8 and the atmospheric endmember sea salt 87sr 86sr 0 7092 and saharan dust 87sr 86sr 0 7187 end 11 5 the regolith was built on pyroclastic deposits but because of extreme leaching the regolith has lost its original bedrock signature and inherited an exogenous atmospheric signature our results show that only the chemical weathering of the fresh near surface minerals can provide nutrients to the ecosystem first 30 cm however this dust weathering is too low to sustain the tropical forest ecosystem on its own the cationic mass balance at the catchment scale as well as the sr isotopic signature show that cation and sr fluxes are of atmospheric origin only and that original bedrock no longer participates in nutrient cycles the vegetation reflects the 87sr 86sr of the dissolved pool of atmospheric sr at the soil plant scale the cation nutrient fluxes provided by vegetation litter fall leaf excretion are major compared to input and output fluxes the annual ca k sr and mg fluxes within the vegetation are respectively 31 28 20 and 3 times greater than the exported fluxes at the outlet of the basin the residence time of nutrients in the vegetation is 16 years for k and close to 45 years for sr ca and mg these results emphasize the highly efficient vegetative turnover that dominates the nutrient cycle in the quiock creek catchment this first characterization of biogeochemical cycles in the guadeloupean rainforest suggests that the forest community of quiock creek is sustained by a small near surface nutrient pool disconnected from the deep volcanic bedrock we also demonstrated that even with efficient nutrient recycling saharan dust plays a significant role in maintaining ecosystem productivity in guadeloupe over long time scales

sr isotopes as a tracer of weathering processes and dust inputs in a tropical granitoid watershed luquillo mountains puerto rico abstract sr isotope data from soils water and atmospheric inputs in a small tropical granitoid watershed in the luquillo mountains of puerto rico constrain soil mineral development weathering fluxes and atmospheric deposition this study provides new information on pedogenic processes and geochemical fluxes that is not apparent in watershed mass balances based on major elements alone 87sr 86sr data reveal that saharan mineral aerosol dust contributes significantly to atmospheric inputs watershed scale sr isotope mass balance calculations indicate that the dust deposition flux for the watershed is 2100 700 mg cm 2 ka 1 nd isotope analyses of soil and saprolite samples provide independent evidence for the presence of saharan dust in the regolith watershed scale sr isotope mass balance calculations are used to calculate the overall short term chemical denudation velocity for the watershed which agrees well with previous denudation rate estimates based on major element chemistry and cosmogenic nuclides the dissolved streamwater sr flux is dominated by weathering of plagioclase and hornblende and partial weathering of biotite in the saprock zone a steep gradient in regolith porewater 87sr 86sr ratio with depth from 0 70635 to as high as 0 71395 reflects the transition from primary mineral derived sr to a combination of residual biotite derived sr and atmospherically derived sr near the surface and allows multiple origins of kaolinite to be identified

bulk composition of northern african dust and its source sediments a compilation abstract this paper presents a review of bulk compositional data of northern african dust and its potential source sediments and includes elemental isotope and mineralogical data northern african dust represents about one half of the total global atmospheric mineral dust burden and its uplift transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems the chemical data set shows that an average northern african dust exhibits comparable si fe and mn contents with respect to the average composition of the upper continental crust is slightly depleted in the alkali metals k and na and enriched in ti and p however the complete data set yields clear evidence that northern african dust and its source sediments are compositionally heterogeneous on a regional scale and that this heterogeneity can be used to differentiate between major potential source areas on the basis of so called source markers an evaluation of these compositional fingerprints shows that the following parameters and especially their combination are effective in the discrimination of the most active source areas in northern africa ratio of ca mg fe wt calcite or carbonate content palygorskite occurrence and abundance illite kaolinite ratio nd 0 value and 87sr 86sr ratio for example the data set corroborates previous ideas which assign carbonate illite and palygorskite rich mineral dusts to north west ern source regions because most of the above listed source markers do not change substantially during transport even far traveled dusts may be assigned to specific potential source areas in northern africa some limitations of the presented data set are also discussed our compilation reveals some substantial gaps in the knowledge of the composition of source sediments and mineral dusts from important potential source areas that should be filled in the future the here compiled data set can be used as a reference frame when incorporating the composition of source sediments e g mineralogy into global or regional dust transport models and can be compared with source analysis by remote sensing or back trajectory analysis however source apportionment studies supported by our data set will not only be useful for actual dust samples but will also be helpful for the understanding of paleo wind directions and hence paleo climatological conditions through the investigation of quaternary eolian sediments deposited in and around northern africa

evolution of deepwater mixing and weathering inputs in the central atlantic ocean over the past 33 myr the isotopic composition of nd in present day deep waters of the central and northeastern atlantic ocean is thought to fingerprint mixing of north atlantic deep water with antarctic bottom water the central atlantic romanche and vema fracture zones are considered the most important pathways for deep water exchange between the western and eastern atlantic basins today we present new nd isotope records of the deepwater evolution in the fracture zones obtained from ferromanganese crusts which are inconsistent with simple water mass mixing alone prior to 3 ma and require additional inputs from other sources the new pb isotope time series from the fracture zones are inexplicable by simple mixing of north atlantic deep water and antarctic bottom water for the entire past 33 myr the distinct and relatively invariable nd and pb isotope records of deep waters in the fracture zones appear instead to have been controlled to a large extent by contributions from saharan dust and the orinoco amazon rivers thus the previously observed similarity of nd and pb isotope time series from the western and eastern north atlantic basins is better explainable by direct supply of labrador seawater to the eastern basin via a northern pathway rather than by advection of north atlantic deep water via the romanche and vema fracture zones

neodymium isotopes as tracers in marine sediments and aerosols north atlantic nd and sm concentrations and nd isotopic compositions were measured on the detrital fraction of deep sea surface sediments and on aerosols sampled over the north atlantic and mediterranean sea the data expressed asend 0 and as model ages ranged from 14 5 end 0 4 9 and from 0 01 to 2 21 ga respectively two areas where the sediments contain relatively less radiogenic nd are to the west off north africa and eastward of the canadian shield this distribution is consistent with other tracers in suggesting that a significant fraction of the sediments are derived from aeolian material transported by major wind systems saharan dust transported in the equatorial trade winds belt and north american soil material transported in the latitudes of the westerlies between these aeolian dominated belts along an axis from the azores to gibraltar and the mediterranean lies a zone of more radiogenicend 0 values in sediments and aerosols influenced by the recent volcanism of this region previously reported distributions of nd isotopes in bottom formed iron manganese crusts and coatings are similar to distributions of nd isotope values in detrital sediments and aerosols this suggests that the detrital fraction has undergone partial dissolution and desorption in the water column and or in the pore waters of near surface sediments and that a significant proportion of nd in the authigenic ferromanganese phases is derived from this source and may therefore not represent strictly dissolved seawater nd isotope ratios useful as watermass tracers

the magnetism of a glacial aeolianite sequence from lanzarote canary islands coupling between luvic calcisol formation and saharan dust trapping processes during wet deposition events off northwestern sahara summary in order to better document the climatic origin of pedogenized loess deposits west of sahara rock magnetic measurements were performed on a last glacial coastal sand sequence from la mala lm quarry lanzarote canary islands containing six interbedded loess palaeosol units hysteresis and susceptibility data point to a coarse grained magnetic enhancement in the coastal sand which contrasts with the superparamagnetic sp to pseudo single domain psd behaviour of the saharan loess and palaeosol high and low temperature experiments show that oxidized titanomagnetite contributions dominate in the sand while fine grained sp to psd iron oxidation products such as maghemite and goethite are evidenced in the saharan loess palaeosol units at room temperature the detrital psd multidomain titanomagnetite contribution of local origin is tentatively estimated from the ac field dependence of magnetic susceptibility surface oxidation of detrital spinel grains and authigenesis of fine grained iron oxides including sp goethite are proposed to explain the magnetic properties of the primarily fine saharan dust bearing material the dry local climate of the present day and late holocene means that loess deposits are not preserved the six pedogenized loess units however point to dust trapping under semi arid wetter conditions probably illustrating periods of reduced latitudinal temperature gradients and climate variability of the north atlantic climate respectively these findings suggest that both the canary palaeosol and its content of ultra fine iron oxide might be constrained by wet deposition and trapping of fine saharan dust

deciphering human climate interactions in an ombrotrophic peat record ree nd and pb isotope signatures of dust supplies over the last 2500 years misten bog belgium abstract a high resolution peat record from eastern belgium reveals the chronology of dust deposition for the last 2500 years ree and lithogenic elements in addition to nd and pb isotopes were measured in a 173 cm age dated peat profile and provide a continuous chronology of dust source and intensity calculated dust flux show pronounced increases c 300 bc 600 ad 1000 ad 1200 ad and from 1700 ad corresponding to local and regional human activities combined with climate change the industrial revolution samples 1700 1950 ad are characterised by a significant enrichment in sc normalised ree abundance sum ree sc 25 due to intensive coal combustion for the pre industrial revolution samples the sc normalised ree abundance 10

absence of saharan dust influence on the strontium isotope ratios on modern trees from the bahamas and turks and caicos islands we report on strontium 87 sr 86 sr isotope results from 91 modern trees growing on the bahamas and turks and caicos islands the average 87 sr 86 sr ratio of 0 709169 0 000010 is consistent with the late quaternary limestone of the islands and with the modern ocean value the absence of any detectable influence of 87 sr enriched saharan dust is notable given the known contribution of this material to both past and recent soils of the caribbean our results indicate that the impact of saharan dust to the modern biosphere of the bahamian archipelago is at least an order of magnitude less than modeled in currently available strontium isoscapes for the circum caribbean we suggest that the bioavailability of sr in saharan dust may be considerably less than previously thought nevertheless further work could usefully be carried out in the bahamian archipelago on plants with different rooting depths growing on different soil types and on limestone of different ages our results have particular relevance for the refinement of existing strontium isoscapes and the archaeological provenience of artifacts animals and people in the circum caribbean

geochemical and mineralogical evidence for sahara and sahel dust additions to quaternary soils on lanzarote eastern canary islands spain africa is the most important source of dust in the world today and dust storms are frequent on the nearby canary islands previous workers have inferred that the sahara is the most important source of dust to canary islands soils with little contribution from the sahel region soils overlying a late quaternary basalt flow on lanzarote canary islands contain in addition to volcanic minerals quartz and mica exotic to the island s bedrock kaolinite in the soils also likely has an exotic origin trace element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and african dust major element geochemistry clay mineralogy and interpretation of satellite imagery suggest that dust additions to the canary islands come not only from the sahara desert but also from the sahel region

anti atlas moroccan chain as the source of lithogenic derived micronutrient fluxes to the deep northeast atlantic ocean identifying the source of atmospheric dust is crucial to better understand the global marine biogeochemical cycle as phytoplankton growth relies on dissolved micronutrient elements available in the open ocean mineralogical geochemical and sr isotope analyses of a one year time series april 2003 april 2004 of deep ocean particle flux at the madeira abyssal plain in the subtropical northeast atlantic are presented the lithogenic fraction has a high occurrence of palygorskite and smectite and an absence of kaolinite together with sr isotopic compositions similar to the northeast atlantic aerosols this indicates the anti atlas moroccan chain of paleozoic age as the source region the lithogenic fraction supplies 4 times more fe during a dust event than during the spring summer aeolian input a continuous input of only 1 of the lithogenic iron made available over a year period could lead to an increase in primary productivity of 40 relative to today s value

evidence from the sunshine mine for dip slip movement during coeur d alene district mineralization the coeur d alene district of idaho is a world class silver base metal district with production exceeding 1 0 billion troy ounces of silver despite the prolific production history little is known about the structural controls of ore deposition or the style of deformation which accompanied metallization the role of strike slip faulting has been emphasized by past workers as an important structural control of the mineralization structural data from the sunshine mine show that the main sense of movement of structures during ore deposition was along a steep southwesterly line during a dip slip tectonic metamorphic event kinematic indicators suggest mainly reverse motion during deformation and synchronous mineralization siderite quartz veins variously oriented in the sunshine mineralized zone intersect in a common line that plunges steeply to the southwest parallel to slickenlines tetrahedrite rich ore shoots within the siderite quartz veins also plunge southwest regardless of vein orientation the dip slip fabrics associated with the mineralizing event cut the big creek anticline yet evidence shows that preexisting fold fabrics were reactivated during metallization

origin of high ag fahlores from the galena mine wallace idaho u s a tetrahedrite fahlores from the galena mine of the coeur d alene mining district wallace idaho have been found to be enriched in ag by the ag cu exchange reaction 1 10 cu 10 zn fe 2 sb 4 s 13 cu fahlore agsbs 2 in galena pbs galena cupbsbs 3 bournonite 1 10 ag 10 zn fe 2 sb 4 s 13 ag fahlore which occurred during cooling following fahlore mineralization this solid state reaction produced a distinct population of high ag fahlores found in galena rich samples quantitatively removed ag in an agsbs 2 component from galena and accounts for all of the bournonite mineralization this reaction has produced the most argentian fahlore yet found molar ag ag cu 0 443 in the district and forms a secondary overprint on any primary fahlore zoning that may have existed the results obtained here indicate that the galena and fahlore siderite stages of mineralization were virtually synchronous as this reaction has produced the same result despite the opposite relative age relationships of these mineralization stages exhibited in two of the mines studied multiple lines of evidence suggest a temperature between 320 and 350 c for this stage based on the ag ag cu of fahlores and fe zn partitioning between fahlore and sphalerite we estimate that fahlore compositions were frozen in by about 235 c roughly 40 c above corresponding temperatures obtained for the gold hunter vein of the lucky friday mine this result and the absence of readily detectable diaphorite pb 2 ag 3 sb 3 s 8 in the galena mine sample containing the highest ag fahlore indicate a faster cooling rate for the terrane in the vicinity of the galena mine

holocene saharan dust deposition on the cape verde islands sedimentological and nd sr isotopic evidence holocene aeolian silts deposited on the cape verde islands provide information about the origin of african palaeodusts that have fallen on the north eastern atlantic ocean over the last 10 000 years sedimentological composition indicates that most of these aeolian silts are unquestionably of continental origin their sr and nd isotopic composition identifies a saharan origin suggesting transport by harmattan winds we estimate that saharan dust comprises 75 95 of material in these holocene silts the rest coming from the weathering of local basaltic bedrock

age and tectonic setting of the camaguey volcanic intrusive arc cuba late cretaceous extension and uplift in the western greater antilles abstract ar ar ages determined on rocks and minerals from the camaguey area in central cuba provide age constraints on events that accompanied the northward migration of cuba into the caribbean region and its subsequent collision with the bahamas bank whole rock samples from the camujiro and piragua formations part of the camaguey volcanic sequence yielded ar ar ages of 74 72 ma distinctly younger than the 100 80 ma ages indicated by fossils in interlayered sedimentary rocks syenite and granodiorite in the camaguey batholith which cut these volcanic rocks yield generally similar ar ar ages of 75 72 ma for hornblende biotite and feldspar these ages are interpreted to reflect relatively rapid uplift and cooling of most of the volcanic intrusive arc additional constraints on the timing of this uplift are provided by ar ar ages of 71 75 ma for rhyolite rhyodacite domes of the la sierra formation and 52 ma for andesitic basalt of la mulata formation which appear to have been emplaced onto erosion s

the 7 13 march 2006 major saharan outbreak multiproxy characterization of mineral dust deposited on the west african margin mineral dust deposits were collected at mbour senegal throughout the spring of 2006 and especially during the well documented march 7 13 large saharan dust outbreak during this 7 day period significant changes in mass flux grain size clay mineralogy and sr and nd isotopic compositions were recorded indicating distinct provenances for the dust transported and deposited during and outside the event all these terrigenous proxies as well as freshwater diatom taxa also showed significant temporal variations during the outbreak implying contributions from at least two different provenance regions tri dimensional back trajectories and satellite imaging enabled us to link those distinct signatures to regions increasingly to the southeast within a large area covering mauritania mali and southern algeria identified by the total ozone mapping spectrometer toms as the main source of the prominent winter spring plume over the tropical atlantic the multiproxy characterization of the march 7 13 dust fall therefore enables us to typify the terrigenous signature of two different regions supplying dust off west africa and provide valuable clues for the interpretation of northeastern tropical atlantic ocean dust sedimentary records in terms of changes in provenance regions and transport systems additionally because dust deposition data are scarce flux and grain size data obtained in this study among other parameters such as clay assemblages provide important constraints for atmospheric transport models and dust deposition budget estimates in this area

isotopic evidence for the eolian origin of quartz and mica in soils developed on volcanic materials in the canary archipelago quartz and mica contents of soils developed on volcanic materials in the canary archipelago lanzarote tenerife gomera and la palma islands off western africa are often higher in surficial horizons with higher rainfall and older landscape age the soil quartz particles are fine grained less than 53 m in diameter and well sorted the oxygen isotopic abundance 18osmow of fine aerosol sized quartz 1 10 m in diameter showed a range of 16 0 to 18 2 the values are compatible with those of the same sized quartz from two holocene deep sea sediments in cape verde rise 16 0 and 16 1 and saharan dusts 15 8 la laguna tenerife 16 2 barbados west indies a distinct 87sr 86sr ratio of 0 717 for a micaceous horizon from lanzarote is comparable with those of saharan dusts 0 715 to 0 721 but not with reported values 0 7032 from local volcanics these geochemical parameters show that the fine grained quartz together with mica in soils of the canary archipelago are transported from north african sahara deserts by trade winds and negate both possibilities of authigenesis and inheritance from weathering of local volcanics

subduction style magmatism in a non subduction setting the colville igneous complex ne washington state usa of the klondike mountain formation which show no decoupling the colville igneous complex is located within the eocene magof the lile and hfse i e no subduction signature precluding matic belt of the north american cordilleran interior it straddles the presence of a subduction slab beneath this part of the north the us canadian border in northeast washington and southern american cordillera during the eocene we propose the alternative british columbia the complex consists of three intrusive and two model that the colville igneous complex formed as a result of extrusive phases the first extrusive phase being contemporaneous decompression melting of crust and mantle during post laramide with the latter two intrusive phases as a consequence of suborogenic collapse of an overthickened crust solidus re equilibration in the plutonic rocks this study concentrates on the two extrusive phases the sanpoil volcanic formation and the klondike mountain formation the sanpoil volcanic formation consists of andesites dacites and rare trachyandesites sio2

relations between geological characteristics and satellite derived infrared and microwave emissivities over deserts in northern africa and the arabian peninsula 1 infrared and microwave emissivities have been previously calculated over the globe from satellite observations to estimate the longwave radiative budget of the planet in global circulation models gcm or to facilitate the assimilation of surface sensitive satellite observations over land in numerical weather prediction nwp models this study examines the relationship between these emissivities and the soil lithology over the deserts in northern africa and the arabian peninsula at large scales for this purpose a lithology map of the area has been carefully derived from combining several geological maps and in situ lithostratigraphic columns infrared and microwave emissivities show large spatial variability much more than often assumed in gcm or in nwp models that relate well to the surface properties especially the lithology changes in the lithology explain 40 and up to 50 of the emissivities variability at the considered frequencies in the infrared and in the microwaves in particular siliceous and carbonate outcrops have specific signatures that can be identify in these wavelength ranges with a surprisingly good sensitivity of the microwaves to the presence of carbonates this study clearly indicates that geological information is necessary for emissivity modeling not only in the infrared but also in the microwaves for gcm and nwp applications the lithology maps created from the geological maps for this study is available under request our study also suggests that the combination of infrared and microwave emissivities has some potential for lithology mapping at large scales especially for land surface models

marine sr ca input in quaternary volcanic rock weathering profiles from the mediterranean coast of morocco sr isotopic approach carbonate commonly accumulates in weathering profiles developed on noncalcareous parent material under arid and semiarid climatic conditions such weathering profile types are widespread in morocco making it critical to know the sources of the calcium in order to understand the genesis of carbonate rich soils in this study we use 87sr 86sr as a geochemical tracer of the ca sources in weathering profiles developed on volcanic rocks basalt tuff andesite and latite in the mediterranean coast of morocco the results show that the most of the sr and hence ca is of an external origin derived from i sea water for the profiles located near to the coast or ii sea water plus liassic carbonate outcropping in the catchment for the profiles more distant from the coastline the contribution of the host rock is small being less than 25 the ratio of the sr ca from the parent material to that from the external sources is controlled by the degree of porosity developed in the profile

mineralogy fluid inclusion petrography and stable isotope geochemistry of pb zn ag veins at the shizhuyuan deposit hunan province southeastern china the shizhuyuan polymetallic deposit is located in the central part of the nanling region southeastern china and consists of proximal w sn mo bi skarns and greisens and distal pb zn ag veins the sulfides and sulfosalts in the distal veins formed in three distinct stages 1 an early stage of pyrite and arsenopyrite 2 a middle stage of sphalerite and chalcopyrite and 3 a late stage of galena ag sn and bi bearing sulfides and sulfosalts and pyrrhotite combined sulfide and sulfosalt geothermometry and fluid inclusion analyses indicate that the early stage of mineralization occurred at a temperature of 400 c and involved boiling under hydrostatic pressure 200 bar with the temperature of the system dropping during the late stage to 200 c laser raman analysis indicates that the fluid inclusions within the studied minerals are dominated by h2o although some contain carbonate solids and ch4 gas vein hosted sulfides have 34s values of 3 8 6 3 that are interpreted as indicative of a magmatic source of sulfur the mineralization process can be summarized as follows an aqueous fluid exsolved on final crystallization of the qianlishan pluton ascended along fracture zones cooled to 400 c and boiled under hydrostatic conditions and with decreasing temperature and sulfur fugacity sulfide and sulfosalt minerals precipitated successively from the ag cu zn fe pb sb as s bearing fluid system

cycling of lithogenic marine particles in the us geotraces north atlantic transect in this paper we present describe and model the first size fractionated 0 8 51 m 51 m water column particulate trace metal results from the us geotraces north atlantic zonal transect in situ pumping survey with a focus on the lithogenic tracer elements al fe and ti this examination of basin wide full depth distributions of particulate elements elucidates many inputs and processes some for bulk lithogenic material others element specific which are presented via concentration distributions elemental ratios size fractionation dynamics and steady state inventories key lithogenic inputs from african dust north american boundary interactions the mediterranean outflow hydrothermal systems and benthic nepheloid layers are described using the refractory lithogenic tracer ti we develop a 1 d model for lithogenic particle distributions and test the sensitivities of size fractionated open ocean particulate ti profiles to biotically driven aggregation disaggregation rates vertical sinking speeds and dust input rates we discuss applications of this lithogenic model to particle cycling in general and to poc cycling specifically

geochemical and isotopic characterization of the bodele depression dust source and implications for transatlantic dust transport to the amazon basin the bodele depression chad in the central sahara sahel region of northern africa is the most important source of mineral dust to the atmosphere globally the bodele depression is purportedly the largest source of saharan dust reaching the amazon basin by transatlantic transport here we have undertaken a comprehensive study of surface sediments from the bodele depression and dust deposits chad niger in order to characterize geochemically and isotopically sr nd and pb isotopes this dust source and evaluate its importance in present and past african dust records we similarly analyzed sedimentary deposits from the amazonian lowlands in order to assess postulated accumulation of african mineral dust in the amazon basin as well as its possible impact in fertilizing the amazon rainforest our results identify distinct sources of different ages and provenance in the bodele depression versus the amazon basin effectively ruling out an origin for the amazonian deposits such as the belterra clay layer by long term deposition of bodele depression material similarly no evidence for contributions from other potential source areas is provided by existing isotope data sr nd on saharan dusts instead the composition of these amazonian deposits is entirely consistent with derivation from in situ weathering and erosion of the precambrian amazonian craton with little if any andean contribution in the amazon basin the mass accumulation rate of eolian dust is only around one third of the vertical erosion rate in shield areas suggesting that saharan dust is consumed by tropical weathering contributing nutrients and stimulating plant growth but never accumulates as such in the amazon basin the chemical and isotope compositions found in the bodele depression are varied at the local scale and have contrasting signatures in the silica rich dry lake bed sediments and in the calcium rich mixed diatomites and surrounding sand material this unexpected finding implies that the bodele depression material is not pre mixed at the source to provide a homogeneous source of dust rather different isotope signatures can be emitted depending on subtle vagaries of dust producing events our characterization of the bodele depression components indicate that the bodele calcium rich component identified here is most likely released via eolian processes of sand grain saltation and abrasion and may be significant in the overall global budget of dusts carried out by the harmattan low level jet during the winter

geochemistry of the xining xifeng and jixian sections loess plateau of china eolian dust provenance and paleosol evolution during the last 140 ka abstract loess and paleosol samples from three distant sections xining xifeng jixian of the chinese loess plateau were analyzed for chemical and nd sr isotopic compositions in order to obtain information about the paleoclimatic variation during the last 140 ka these three sections represent three different climatic conditions from arid in the west xining to more humid in the east jixian across the loess plateau isotopic analyses show that all the three sections display a restricted range of 143 nd 144 nd ratios or e nd 10 0 5 indicating the dominance of relatively young and uniform upper crustal sources for the eolian dust the loess and paleosol samples have typical upper crustal 87 sr 86 sr ratios 0 714 0 718 and their variation can partly be attributed to different carbonate silicate ratios in the samples ree data from the three sections are indistinguishable from each other they show typical upper crust patterns characterized by la yb n 10 and eu eu 0 65 the high degree of chemical and isotopic homogeneity suggests that the dust source region must have undergone multiple recycling and thorough sedimentary mixing processes various chemical indicators have been used to monitor the pedogenetic intensity in these sections although results for the jixian section agree reasonably well with the known climatic conditions on the loess plateau the other two sections yield results not in agreement with some well accepted proxies like magnetic susceptibility or grain size distribution some chemical proxy indicators established in our previous work on the luochuan section such as the systematic u depletion and negative ce anomalies in ree patterns in soils are not clearly recorded in the present case the discrepancy between different climatic proxies could be related to the effective soil water budget temperature as well as the rate of development of each proxy

ca sr and 87sr 86sr ratios as tracers of ca and sr cycling in the rio icacos watershed luquillo mountains puerto rico abstract we investigated ca and sr cycling in a humid tropical forest by analyzing ca sr ratios and 87sr 86sr ratios in soil minerals soil exchangeable cations soil porewater and plant roots wood and leaves and calculating the relative contributions of sr from atmospheric inputs and weathering of local bedrock an unexpectedly large contribution of bedrock derived sr and presumably ca is cycled through the vegetation reflecting the important role of geological processes in controlling the cycling of base cation nutrients even in a system with intensely weathered soil this is surprising because over 99 of the ca and sr that was originally in the bedrock is leached out of the soil and saprolite during early stages of weathering at this site and because there are large atmospheric inputs to the site of both sea salt and saharan dust substantial differences in ca and sr cycling are seen on small spatial scales between a ridgetop and an adjacent steep hillslope site measured ca sr ratios reflect fractionation between these elements during biogeochemical cycling fractionation was particularly evident between wood and foliar tissue but fractionation during soil exchange processes is also likely in comparing the ca sr ratios of plants exchangeable cations and bulk soils we found that foliar ca sr ratios were greater than exchangeable cation ca sr ratios which in turn were greater than soil ca sr ratios similar to patterns observed at other highly weathered tropical sites

u pb geochronological constraints on the timing of episodic regional metamorphism and rapid high t exhumation of the grand forks complex british columbia abstract the grand forks complex gfc is a fault bounded metamorphic core complex in the southern omineca belt of british columbia canada it experienced prograde metamorphism ranging from upper amphibolite to granulite facies conditions during the mesozoic to early tertiary compressional stage of the cordilleran orogeny peak metamorphism was followed by multi stage exhumation in the early eocene this study provides u pb monazite and zircon constraints on the timing of metamorphic episodes in the gfc and subsequent high t amphibolite facies decompression in the early eocene monazite la icp ms ages from metapelitic gneisses record episodic metamorphism from the late jurassic to paleocene with peak metamorphism occurring between 59 and 50 ma peak metamorphism was followed by rapid near isothermal decompression of the gfc between 52 and 50 ma and leucosome crystallization at 50 ma thermodynamic modeling of metapelites in the system mnnckfmashpyce predicts that monazite was not stable at peak metamorphic conditions consistent with the dominant population of 59 ma ages representing growth along the prograde path most likely at subsolidus conditions growth of widespread high y monazite rims 50 ma is predicted along suprasolidus decompression and cooling paths zircon shrimp ages from igneous bodies in the gfc and hanging wall of the bounding kettle river fault krf suggest ductile deformation related to high t decompression of the gfc was ongoing at 51 ma but had ceased by 50 ma truncated by post kinematic granitoids this high t deformation predates subsequent greenschist facies extension on the overlying krf a pre krf hanging wall ductile shear zone is constrained to 59 51 ma it deforms 59 ma ladybird suite leucogranites and may be related to high t exhumation of the core complex rapid 100 c ma cooling rates are required to accommodate high t amphibolite facies exhumation of the gfc at 52 50 ma followed by low t greenschist facies exhumation at 49 ma

systematic variation in galena solid solution compositions at santa eulalia chihuahua mexico argentiferous galena is the main silver bearing phase at both the east and west camps of the santa eulalia district chihuahua mexico the silver occurs as a coupled substitution of ag and sb for pb in pbs with compositions ranging from 0 04 to 5 9 atomic percent at ag and 0 10 to 7 2 at percent sb correlation analysis between ag and sb resulted in r values of 0 97 and 0 99 significant at the 98 confidence level for direct current plasma atomic emission spectroscopy dcp aes and microprobe analysis of galena respectively discrete and crystallographically oriented inclusions of diaphorite usually 1 m or smaller were common in high silver antimony galenas and rare in low silver types when present tend to be larger these inclusions were most abundant in the core zones of the crystals and rare on the edges spatial and temporal variations in ag sb concentrations and ratios in galena were found mainly in the west camp of the district high silver galenas maximum 5 9 at are confined to skarn zones or deep manto and chimney areas the ag sb ratio increases in galena from depth 0 88 to the surface 1 04 and from south 0 76 to north 0 94 following zonation and flow patterns established in previous investigations differences in ag sb substitution in galena are also seen in different mineralization types breccia zones deep mantos and chimneys contain more ag sb 3 5 at avg and have lower ag sb ratios avg ratio 0 88 than the upper mantos silicate and calc silicate orebodies which have lower ag sb concentrations 2 2 avg at but higher ratios avg ratio 1 00 silver and antimony substitution also correlates with sulfur isotope variation in the district within individual orebodies the 34s value increases with decreasing silver and antimony concentrations in galena the solid solution compositional variations in galena coupled with sulfur isotope values are a useful tool for inferring fluid paths and appear to reflect fluid evolution at santa eulalia silver is disseminated to various degrees throughout the orebodies and galena solid solution concentrations appear to be controlled by subtle physical and or chemical gradients this contrasts with volcanic epithermal systems in which significant physiochemical perturbations large thermal and pressure gradients boiling etc lead to dumping of precious metals and semimetals as sulfosalts in bonanza zones relatively low concentrations of other potential ore forming elements namely copper and bismuth also precluded the formation of a complex suite of silver sulfosalts and antimonian argentiferous galena precipitated instead sulfosalts at santa eulalia are localized to upper mineralized zones as breccia void fillings indicative of limited zones of boiling

sr nd elements and isotopes as tracers of dust input in a tropical soil chronosequence abstract although hainan island is located in one of the relative least dusty regions in china asian dust has been identified in hainan soils we used sr and nd isotopes of soils saprolite bedrocks and asian dust to not only identify long range transported dust but also quantify the dust contribution to hainan soils sr and nd isotopic compositions of the soils are clearly affected by dust deposition the soils in near surface horizons have 87 sr 86 sr values as high as 0 7193 that are more radiogenic than the basalts indicating involvement of asian dust whereas deep horizons show a dominantly basaltic signature 87 sr 86 sr 0 7038 the e nd 0 values for hainan soils range from 6 46 to 1 85 the higher value closely approximates the values measured for the hainan lava and the lower value indicates the fingerprint of the asian dust the 87 sr 86 sr and e nd 0 values for soils also show a progressive trend with time which implies that dust accumulates with soil age we calculated the dust accretion rates for sr based and nd based to quantify the dust contributions to soils the estimate of dust accreted shows an approximate increasing trend with the ages of soils for sr based and nd based methods the soils in the old sites are likely to have undergone long term dust input and accumulated high dust levels we also find excellent agreement in the amount of dust present and dust accretion rates based on the two tracers at the 300 ka site and the 1120 ka site respectively besides lower dust deposition in the pliocene epoch than the late quaternary over eastern eurasian the loss of mineralogical and geochemical tracers over million year time scales also may lead to underestimates of time averaged dust deposition rates in the old sites therefore the young sites 180 ka and 300 ka should provide more realistic estimates of average dust accretion rates the importance of dust in the tropical hainan soil chronosequence highlights the significance of dust accretion to soils globally

the role of atmospheric deposition in the biogeochemistry of the mediterranean sea abstract estimates of atmospheric inputs to the mediterranean and some coastal areas are reviewed and uncertainities in these estimates considered both the magnitude and the mineralogical composition of atmospheric dust inputs indicate that eolian deposition is an important 50 or even dominant 80 contribution to sediments in the offshore waters of the entire mediterranean basin model data for trace metals and nutrients indicate that the atmosphere delivers more than half the lead and nitrogen one third of total phosphorus and 10 of the zinc entering the entire basin measured data in sub basins such as the north western mediterranean and northern adriatic indicate an even greater proportions of atmospheric versus riverine inputs when dissolved fluxes are compared the form most likely to impinge on surface water biogeochemical cycles the atmosphere is found to be 5 to 50 times more important than rivers for dissolved zinc and 15 to 30 times more important for lead fluxes neglecting co limitation by other nutrients new production supported by atmospheric nitrogen deposition ranges from 2 4 g c m 2 yr 1 whereas atmospheric phosphorus deposition appears to support less than 1 g c m 2 yr 1 in spite of the apparently small contribution of atmospheric deposition to overall production in the basin it has been suggested that certain episodic phytoplankton blooms are triggered by atmospheric deposition of n p or fe future studies are needed to clarify the extent and causal links between these episodic blooms and atmospheric oceanographic forcing functions a scientific program aimed at elucidating the possible biogeochemical effects of saharan outbreaks in the mediterranean through direct sampling of the ocean and atmosphere before and after such events is therefore highly recommended

toroda creek half graben northeast washington late stage sedimentary infilling of a synextensional basin the toroda creek half graben is one of several north northeast trending eocene extensional basins associated in time and space with the okanogan and kettle metamorphic core complexes in the southern omineca crystalline belt of washington and british columbia sedimentary rocks of the middle eocene klondike mountain formation are the youngest stratified nonvolcanic rocks in the toroda creek half graben these sedimentary rocks preserve details of the character of toroda creek half graben basin development in a humid temperate setting help constrain the timing of brittle faulting in the basin and provide insight into approximate rates of okanogan core complex uplift facies distributions and provenance determinations indicate that the klondike mountain formation accumulated in a localized basin there is no evidence that the klondike mountain formation strata in the toroda creek half graben were once part of a more widespread deposit that later was segmented by faulting into its present configuration klondike mountain sedimentary strata consist of sedimentary gravity dominated rock avalanche slide and debris flow deposits that accumulated on alluvial fans that delivered their sediments into either a single elongate lake or a series of possibly interconnected lakes provenance determinations and facies distribution patterns suggest that klondike mountain detritus primarily was derived from steep unstable highlands exposed in the footwall of the bodie mountain fault on the east side of the basin sediments at the southern end of the basin were shed from an upland created by a west northwest trending transfer fault granite creek fault rates of footwall uplift and or basin subsidence estimated from unroofing of plutonic and presumed mylonitic rocks suggest rapid and significant basin margin uplift

paleocene eocene migmatite crystallization extension and exhumation in the hinterland of the northern cordillera okanogan dome washington usa the okanogan gneiss dome washington is located in the hinterland of the north american cordillera and is part of a chain of metamorphic core complexes containing gneiss and migmatite domes exhumed during eocene extension of thickened crust u pb sensitive high resolution ion microprobe shrimp analyses of zircon monazite and titanite and 40 ar39 ar analyses of biotite from migmatites exposed in the footwall of the okanogan detachment coupled with a detailed structural analysis document the timing and duration of migmatite crystallization and indicate coeval crystallization extensional deformation and exhumation of the dome okanogan migmatites are folded and deformed and preserve successive generations of leucosomes generated by synkinematic anatexis analyses of migmatite samples from a highmelt fraction subdome near stowe mountain suggest that the okanogan dome records a history of migmatite crystallization spanning at least 12 m y as indicated by 206 pb

a fractional crystallization model for the deposition of argentian tetrahedrite electron microprobe analyses of natural hydrothermal tetrahedrites reveal that most specimens are heterogenous in composition a simplified formula for natural tetrahedrite showing the three common solid solutions is cu ag 10 fe zn 2 sb as 4 s 13 variations in ag and sr are positively correlated within each individual sample however the mathematical slopes and intercepts of the linear correlations are different for different samples and the bulk composition of the samples varies with position within the ore deposit nearly 5 000 new point analyses are presented for tetrahedrites from coeur d9alene idaho and orcopampa and julcani peru to document these observations heterogeneity within a single sample could arise when a particular depositional site receives more and less evolved fluids at different times modified journal abstract

dust deposition in the central mediterranean tyrrhenian and adriatic seas relationships with marine sediments and riverine input major al ca fe mg mn si and minor cd pb zn elements of aeolian dust samples collected onboard ship around italy were analysed and the concentrations of metal in the dusts were in good agreement with previously published data from the mediterranean sea the elemental composition of dust samples collected in four subareas adriatic ionian tyrrhenian and sicily channel was compared with the composition of marine deep sediments obtained in the same regions mn al cd and zn contents differentiated between the four areas in both sets of samples suggesting a possible geochemical signature of the atmospheric crustal contribution in marine deep sediments an estimate of the relative contribution of atmospheric dry deposition of cd pb and zn and riverine discharge indicates that a the metals deposited from the atmosphere to the adriatic basin are a small fraction 2 5 of those discharged by the po and adige rivers b almost the same amounts of cd pb and zn are delivered to the tyrrhenian sea by the atmosphere and by the arno and tiber rivers

magnetic mineral inventory of equatorial atlantic ocean marine sediments off senegal glacial and interglacial contrast summary in complex sedimentary environments with different sources of the magnetic particles it is vital that all factors contributing to and affecting the magnetic signals be well understood for a better constrained interpretation of palaeomagnetic and climatic data palaeoclimatically driven signals may be convolved with volcanic and cosmogenic sources and diagenesis may alter the primary magnetic mineral assemblage rock magnetic methods and electron microscopy provide suitable means to characterize magnetic assemblages in this study of core retrieved sediments from the last 150 kyr off the coast of senegal nw africa the occurrence of magnetic spherules of volcanic origin and cosmogenic particles appeared to be insignificant in glacial stages ferrimagnetic iron and iron titanium oxides magnetically dominate with few signs of a diagenetic overprint low and room temperature magnetic results reveal evidence for haematite and goethite while haemoilmenite and titanomagnetite were identified from low temperature ac susceptibility measurements and sem observations in contrast the interglacial samples appeared to have been severely affected by diagenesis with pyrite making up over 50 per cent of the iron bearing phases the verwey transition observed at 110 k confirms the presence of magnetite the glacial and interglacial contrast reveals the close link between northwest african climate and the magnetic mineralogy of the sediments

constraining compositions of hydrothermal fluids in equilibrium with polymetallic ore forming sulfide assemblages to provide an improved understanding of the genesis of high temperature ag pb zn ore deposits we have obtained revised estimates for the thermodynamic properties for cu ag 10 fe zn 2sb4s13 fahlore endmember components calculations of aqueous solution mineral equilibria 250 300 c for fahlore bearing assemblages from ag pb zn ore deposits from the coeur d alene idaho united states and keno hill yukon territory canada mining districts demonstrate consistency between predicted and observed mineral assemblages and hydrothermal fluids based on these new estimates these calculations confirm that much of the ag mined from the coeur d alene district was originally present in galena they also confirm that sphalerite was typically undersaturated in fluids crystallizing fe rich fahlores in the coeur d alene ag pb zn ores and constrain the parameters of the fluids equilibrated with these ores to within narrow limits for the keno hill deposits these calculations demonstrate that the early high temperature 300 310 c fluids 0 07 0 7 in pb2s2 agsbs2 galena or their compositionally equivalent sulfosalt assemblages diaphorite pb2ag3sb3s8 miargyrite agsb pb2 s2 or diaphorite pb2ag3sb3s8 frieslebenite pbagsbs3 were deposited initially in ag rich fahlore bearing ores these minerals were replaced by ag poor galena and epithermal ag minerals that include acanthite stephanite and polybasite

mass balance for nd in the mediterranean sea abstract the mass balance for nd in the mediterranean sea has been assessed through the measurement of nd isotope ratios in particulates from rivers entering the mediterranean sea floor clays and ferromanganese crusts and samples of atmospheric dusts nd values for the po and rhone rivers respectively are 10 8 and 9 7 whereas the nile seyhan and tarsus have 3 3 6 2 and 6 3 sea floor clays and ferromanganese crusts range from 2 0 to 10 1 and dust samples vary from 8 2 to 11 0 the relatively radiogenic nd isotope composition of the mediterranean seawater ed 6 to 7 compared to the atlantic nd 12 reflects partial equilibration of the particulate input into the basin rather than merely the dissolved input

connection between south mediterranean climate and north african atmospheric circulation during the last 50 000 yr bp north atlantic cold events abstract high resolution clay mineralogical analyses were performed on sediment deposited during the last 50 000 yr in the alboran sea odp site 976 the clay mineral record is compared with pollen assemblages and with annual precipitation pann and mean temperatures of the coldest month mtco reconstructed with the modern analog technique mat enhanced contribution of palygorskite a typical wind blown clay mineral characterizes the north atlantic cold climatic events coeval development of the semi arid vegetation artemisia rich associated with a drastic fall of reconstructed precipitations and temperatures suggest cold and arid continental conditions in the west mediterranean area during north atlantic cold events the clay mineral association especially the palygorskite content and the illite to kaolinite ratio indicate western morocco as one of the major source of the clay size fraction during the north atlantic cold events the maximum abundance of artemisia associated with the presence of argania pollen both indicate morocco as the main origin for pollen during these cold periods the comparison of these pollen and clay mineral specific features allows us to pinpoint western morocco as the dominant source of wind blown particles during north atlantic cold events these specific mineralogical composition and palynological assemblages reveal enhanced aridity over north africa and intensification of winds favouring dust erosion and transport from north africa toward the alboran sea during the north atlantic cold events according to atmospheric models such a meridian transport 1 likely results from the development of strong and stable anticyclonic conditions over the tropical atlantic and north africa similar to today s summer meteorological configuration and 2 implies a northward position of the westerly winds during north atlantic cold events finally the synoptic situation over the west mediterranean during the north atlantic cold events is compared with the north atlantic oscillation nao suggesting that during the cold atlantic events weather regimes over europe and north africa may have been systematically shifted towards a positive nao situation

thermochronological constraints on the eocene exhumation of the grand forks complex british columbia based on 40ar 39ar and apatite fission track geochronology the grand forks complex gfc is a metamorphic core complex within the composite shuswap complex in the southern omineca belt of the canadian cordillera it is juxtaposed against the surrounding lo

age and origin of base and precious metal veins of the coeur d alene mining district idaho ore bearing quartz carbonate veins of the coeur d alene mining district yield 87sr 86sr ratios of 0 74 to 1 60 for low rb sr carbonate gangue minerals similar to current ranges measured in middle proterozoic high rb sr rocks of the belt supergroup stable isotope and fluid inclusion studies establish a genetic relationship between vein formation and metamorphic hydrothermal systems of the region these extraordinary 87sr 86sr ratios require accumulation of radiogenic 87sr in a high rb sr system over an extended period prior to incorporation of sr into the hydrothermal veins evaluation of the age and composition of potential sources of highly radiogenic sr indicates that the ore bearing veins of the coeur d alene district formed during the cretaceous from components scavenged from rocks of the belt supergroup the primary host rocks of the district proterozoic pb isotope ratios observed in galena from many coeur d alene veins were established when pb separated from uranium during deposition or diagenesis of the belt supergroup at 1400 to 1500 ma possibly as disseminated syngenetic deposits k ar and rb sr apparent ages and 18o values of belt supergroup rocks decrease from the coeur d alene district toward the idaho and kaniksu batholiths approximately normal to the trends of metamorphic isograds fold axes foliation and the major reverse faults of the district isoclinal folding thrust faulting high temperature metamorphism granitic plutonism and regional scale metamorphic hydrothermal activity is documented in the region between 140 and 45 ma representing the only such combination of events in the coeur d alene region subsequent to about 1300 ma the sr and oxygen results and geologic evidence favor formation of the ore bearing carbonate veins by fluids related to a complex metamorphic hydrothermal system during the cretaceous pb with proterozoic isotopic compositions was probably mobilized and incorporated like other metals into the hydrothermal veins during this event the ore bearing veins were sheared and displaced during early tertiary northwest trending dextral strike slip faulting along the osburn fault and related structures of the lewis and clark line

middle eocene sedimentary and volcanic infilling of an evolving supradetachment basin white lake basin south central british columbia the middle eocene white lake and skaha formations in the white lake basin british columbia record the sedimentary and volcanic infilling of a supradetachment basin that developed during the latter stages of shuswap metamorphic core complex exhumation the 1 1 km thick white lake formation is characterized by volcanogenic sediment gravity flow fluvial and sheetflood facies interbedded with volcanic deposits facies relations suggest white lake strata accumulated on coalesced west sloping alluvial fans that drained an active volcanic center the overlying 0 3 km thick skaha formation records increased tectonism and mass wasting pervasively shattered skaha avalanche slide and sheetflood deposits accumulated on alluvial fans shed from hanging wall and footwall sources exposed along the okanagan valley fault clast compositions of the white lake and skaha formations record alluvial and tectonic stripping that locally eliminated hanging wall blocks mylonite clasts in upper skaha beds imply significant okanagan valley fault footwall uplift during the middle eocene and syntectonic erosion of the shuswap metamorphic core complex the syntectonic sedimentary record preserved within the white lake basin elucidates the relations and timing between core complex exhumation and extensional tectonism in this region the white lake and skaha formations are the apparent age equivalent of the klondike mountain formation of northern washington usa white lake basin strata however are more complexly interstratified post depositionally disrupted and contain a more complete record of core complex unroofing variations in the spatial distributions and textural and compositional character of middle eocene strata in this area underscore the need to exercise care when developing regional scale sedimentary tectonic volcanic models