molybdenum and tungsten in volcanic rocks and in surface and 100 c ground waters in iceland abstract the concentrations of mo and w in tholeiite series basaltic to silicic volcanics in iceland increase with the concentrations of incompatible magmatic elements in normal mid ocean ridge basalt morb mo and w levels are as low as 0 03 and 0 01 ppm but in rhyolites they are up to 4 and 1 3 ppm respectively in the slightly evolved tertiary tholeiites of the main study area of skagafjordur northern iceland mo and w concentrations are 1 01 and 0 32 ppm respectively on average surface waters in this area typically contain 10 000 years waters in river and ground waters the average mo w ratio is the same as that of the basalt host rock on the other hand in peat soil waters the average mo w ratio is higher due to adsorption processes involving w in river and ground waters both mo and w display conservative behavior progressive water rock interaction leads to successively lower aquatic b mo and b w ratios however the b mo and b w ratios of the most reacted waters are considerably higher than those of the basalt due to non stoichiometric rock dissolution b is dissolved preferentially to both mo and w because b is largely present in a soluble form but mo and w are concentrated in the fe ti oxides these minerals are stable under both surface and sub surface conditions i e the waters are over saturated with respect to these minerals the main supply of mo and w to surface waters is from dissolution of plagioclase and pyroxene as well as volcanic glass olivine is not an important source due to its scarcity in the basalts in

adakite like and normal arc magmas distinct fractionation paths in the east serbian segment of the balkan carpathian arc are used to assess petrogenetic and regional geodynamic processes associated with late cretaceous subvolcanic intrusions within the sparsely studied timok magmatic complex tmc and ridanj krepoljin zone rkz of eastern serbia the tmc and rkz form part of the apuseni banat timok srednogorie abts magmatic belt a cu au mineralized calc alkaline magmatic arc related to closure of thetethys ocean that extends through romania serbia and bulgaria in se europe zircon ages based on u pb laser ablation inductively coupled plasma mass spectrometry supplemented by existing isotope dilution thermal ionization mass spectrometry data respectively range from 89 to 79 ma and from 76 to 71 ma for the tmc and rkz this age pattern corresponds to cross arc younging away from the european continent adakite like trace element signatures y 18 ppm are linked with samples that extend across the arc these overlap in space and time with samples that conform to a normal arc differentiation trend we performed energy constrained assimilation fractional crystallization ec afc modeling of sr la nd yb concentrations and sr and nd isotopic data results suggest that the two distinct fractionation trends may be explained in terms of a common mantle derived parental magma but distinct fractionation and assimilation paths in the lower and upper crust petrogenesis of the adakite like magmas is consistent with extensive high pressure amphibole fractionation in the lower crust followed by ascent and plagioclase dominant fractionation and assimilation in the upper crust in contrast normal arc signatures appear to have evolved exclusively via an upper crustal differentiation process overall our interpretation supports mantle wedge melting related to weak extension during progressive rollback of a subducting slab

shear stress in the graphitization of carbonaceous matter during the low grade metamorphism from the northern parang mountains south carpathians implications to graphite geothermometry abstract low grade metamorphic rocks from the northern parang mountains south carpathians were examined to infer the temperature of metamorphism and to obtain new data to study the applicability of the geothermometers relying on the graphite crystallinity to rocks that underwent different shear stress conditions there were analyzed samples of graphitic carbonaceous matter bearing rocks that exposed dissimilar degrees of strain for which the temperature of metamorphism was calculated using the graphite geothermometers based on the lattice parameter c0 determined through x ray diffractometry and based on the peak area ratio of the first order raman spectrum the temperature was also inferred from the chemical composition of the chlorite and from the fe mg partitioning between chlorite and chloritoid the mineral chemistry being determined through electron microprobe analyses the results obtained have shown i differences of up to more than 150 c between vicinal strained and less strained zones when applying the geothermometers based on the graphite crystallinity and ii considerable discrepancies between the temperatures calculated based on the graphite crystallinity and those based on the chlorite and chloritoid chemical compositions these inconsistencies are most likely caused by the fact that the calibration of the graphite geothermometers considers temperature as being exclusively responsible for enhancing the degree of graphite crystallinity and therefore these graphite geothermometers should be adjusted accordingly by introducing a correction factor that quantifies the degree of strain of the samples analyzed in order to obtain more accurate results

exchange of neodymium and its isotopes between seawater and small and large particles in the sargasso sea the concentrations and isotopic ratios of nd were measured in small 1 53 m and large 53 m in situ filtered particles sediment trap material sediment and aerosol samples collected during oligotrophic and productive conditions in the sargasso sea atmospheric input is the main source of exogeneous nd into the sargasso sea based on ndal ratios in trapped material we suggest that up to 50 of atmospheric nd could dissolve at the air sea interface the concentration and isotopic composition of nd vary with both depth and the particle size neodymium concentrations of small and large particles increase with depth from 2 9 12 g g and 5 8 11 8 g g respectively at 40 m the nd signature of large particles is significantly more negative nd 0 13 1 0 2 than that of the small ones nd 0 11 7 0 3 and the particles filtered deeper below 237 m the nd 0 values for small particles match the seawater whereas the nd 0 values of large particles remain less radiogenic these differences are related to the different behaviors of the particulate fractions small particles apparently exchange nd with seawater and then sink rapidly to depth as biologically formed aggregates large particles these aggregates isolate the small particles slowing the exchange with the water to produce different signatures between large particles and seawater since these exchange processes modify the particulate nd signature the shallow radiogenic nd 0 signature observed in the surface and subsurface waters in the nw atlantic is not due to external contributions and is likely of advective origin at depth below 800 m the magnitude of the aggregation disaggregation process varies significantly with season the fraction of small particles repackaged into large aggregates can vary from 0 8 to 80 100 in productive and oligotrophic conditions respectively this seasonal variation may correspond to sinking particles of different zooplanktonic origin vertical fluxes of nd into and out of the sargasso sea as well as exchange fluxes in the water column are examined about 50 of the particulate flux from the surface is remineralized at depth a net scavenging flux of 0 8 10 4 g m2 y is required this value corresponds to a scavenging nd residence time of 1900 y considerably longer than previous estimates of global oceanic residence time of nd on the order of 400 y

new gas geothermometers for geothermal exploration calibration and application calibration of five gas geothermometers is presented three of which used co2 h2s and h2 concentrations in fumarole steam respectively the remaining two use co2h2 and h2sh2 ratios the calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures after establishing the gas content in the aquifer gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions it is shown that the concentrations of co2 h2s and h2 in geothermal reservoir waters are fixed through equilibria with mineral buffers at temperatures above 230 c epidote prehnite calcite quartz are considered to buffer co2 two buffers are involved for h2s and h2 and two functions are therefore presented for the geothermometers involving these gases for waters containing less than about 500 ppm chloride and in the range 230 300 c pyrite pyrrholite epidote prehnite seem to be involved but pyrite epidote prehnite magnetite or chlorite for waters above 300 c and waters in the range 230 300 c if containing over about 500 ppm the gas geothermometers are useful for predicting subsurface temperatures in high temperature geothermal systems they are applicable to systems in basaltic to acidic rocks and in sediments with similar composition but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones the geothermometry results may be used to obtain information on steam condensation in upflow zones or phase separation at elevated pressures measured aquifer temperatures in drillholes and gas geothermometry temperatures based on data from nearby fumaroles compare well in the five fields in iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected the results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled icelandic fields

the chemistry of geothermal waters in iceland ii mineral equilibria and independent variables controlling water compositions abstract the major element chemistry of icelandic geothermal waters is predictable provided two parameters are known this follows from an attainment of or a close approach to an overall chemical equilibrium in the geothermal systems at temperatures as low as 50 c it is considered that the geothermal system composition temperature and kinetic factors determine which alteration minerals form the system composition is not so much fixed by rock composition as by the rate of leaching of the various constituents from the fresh rock and the composition of inflowing water the water chemistry is determined by the system composition and the external variables acting on the system they include temperature and the mobility of chloride pressure which theoretically should be regarded as an external variable has insignificant effect on water compositions in the range 1 200 bars occurring in the geothermal systems

the geochemistry of trace elements in geothermal fluids iceland abstract trace element geochemistry was studied in geothermal fluids in iceland the major and trace element compositions of hot springs sub boiling and two phase liquid and vapor wells from 10 geothermal areas were used to reconstruct the fluid composition in the aquifers at depth aquifer fluid temperatures ranged from 4 to 300 c ph values between 4 5 and 9 3 and fluids typically contained total dissolved solids

the use of mixing models and chemical geothermometers for estimating underground temperatures in geothermal systems abstract application of various chemical geothermometers and mixing models indicate underground temperatures of 260 c 280 c and 265 c in the geysir hveravellir and landmannalaugar geothermal fields in iceland respectively mixing of the hot water with cold water occurs in the upflow zones of all these geothermal systems linear relations between chloride boron and 18o constitute the main evidence for mixing which is further substantiated by chloride silica and sulphate relations in the geysir and hveravellir fields a new carbonate silica mixing model is proposed which is useful in distinguishing boiled and non boiled geothermal waters this model can also be used to estimate underground temperatures using data from warm springs this model as well as the chloride enthalpy model and the na li and co2 gas geothermometers invariably yield similar results as the quartz geothermometer sometimes also does by contrast the na k and the na k ca geothermometers yield low values in the case of boiling hot springs largely due to loss of potassium from solution in the upflow the results of these geothermometers are unreliable for mixed waters due to leaching subsequent to mixing

chronology of warm core ring 82b a chronology constructed from satellite derived thermal imagery is presented to describe the formation and life history of warm core ring 82b this overview provides insight into a classification of features and discrete events associated with gulf stream warm core rings and allows these events as well as our limited shipboard observations to be placed in a broader spatial and temporal context than would otherwise be possible without the satellite data events influencing the evolution of 82b include environmental factors such as meteorological influences and gulf stream interactions as well as those stimulated by encounters with changes in bottom topography the interactions of the ring with surrounding waters are especially noteworthy and the existence of vortex vortex interactions is shown to be a significant cause of local water advection through streamer activity ring events are documented by following changes in ring size shape translation and surface thermal structure our satellite observations are supported by extensive contemporaneous shipboard observations including xbt ctd bops biooptical profiling system temperature profiles and along track sea surface temperature measurements in addition acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and environs these ship and satellite data form a coherent space time overview of the ring and its environment and show them to be closely related and continually interacting

variscan vs alpine tectonothermal evolution of the southern carpathian orogen constraints from 40ar 39ar ages abstract 40 ar 39 ar hornblende and muscovite ages indicate that basement units exposed within all major alpine nappes of the southern carpathian orogen were penetratively deformed and metamorphosed during late variscan carboniferous tectonothermal events subsequent exhumation resulted in cooling from ca 500 c hornblende k ar retention temperature to ca 375 c muscovite k ar retention temperature between ca 320 and 295 ma late variscan exhumation of middle crustal levels is interpreted to have resulted from intracontinental contraction and regional uplift subsequent to variscan continental collision between gondwana derived tectonic elements e g africa and laurussia muscovite ages within mylonite zones suggest that late variscan shear zones were probably associated with a regional shear system that developed along the southern margins of laurussia alpine metamorphic effects within the southern carpathians are generally nonpenetrative and are only significant within narrow zones of retrogression that are interpreted to have formed during initial attenuation of variscan crust associated with formation of the jurassic severin rift

the anatomy of a gondwanan terrane the neoproterozoic ordovician basement of the pre alpine sebes lotru composite terrane south carpathians romania abstract the sebes lotru terrane in the south carpathians mountain range comprises a lower neoproterozoic metamorphic unit lotru and an upper ordovician metamorphic unit cump na that were juxtaposed during the variscan orogeny two orthogneisses from the lotru metamorphic unit yield u pb la icp ms zircon crystallization ages of 549 3 3 8 ma and 587 5 3 ma respectively two orthogneisses from the cump na metamorphic unit yield zircon crystallization ages of 458 9 3 5 ma and 466 0 4 2 ma respectively high u zircons from two other orthogneisses from the cump na metamorphic unit have ages ranging from 400 ma to 320 ma which are interpreted to reflect protracted zircon recrystallization during the regionally significant variscan collisional event detrital zircons from a metasedimentary gneiss in the cump na metamorphic unit have ages ranging from 0 5 ga to 2 8 ga the 0 5 ga age constrains the maximum sediment deposition age to be late cambrian the source most compatible with the range of precambrian detrital ages in the sebes lotru terrane is northeastern gondwana the sebes lotru terrane was part of a continental subduction collision system as a lower plate after about 400 ma and reached peak metamorphic conditions between 350 and 320 ma e g medaris et al 2003 a cross cutting granite vein has a zircon u pb crystallization age of 321 5 3 1 ma which constrains minimum age of ductile deformation during the variscan collision in this region the trace of the rheic suture within the south carpathians is located between the ordovician upper part of the sebes lotru terrane and the dr gsan pre alpine terrane of the danubian domain

the contrasting biogeochemistry of iron and manganese in the pacific ocean abstract vertical and horizontal distributions of dissolved and suspended particulate fe and mn and vertical fluxes of these metals obtained with sediment traps were determined throughout the pacific ocean in general dissolved fe is low in surface and deep waters 0 1 to 0 7 nmol kg with maxima associated with the intermediate depth oxygen minimum zone 2 0 to 6 6 nmol kg vertical distributions of dissolved mn are similar to previous reports exhibiting a surface maximum a subsurface minimum a mn maximum layer coincident with the oxygen minimum zone and lowest values in deep waters near shore removal processes are more intense for dissolved fe than for dissolved mn dissolved mn in the surface mixed layer remains elevated much farther offshore than dissolved fe elevated near surface dissolved mn concentrations occur in the north pacific equatorial current suggesting transport from the eastern boundary near surface mixed layer dissolved mn concentrations are higher in the north pacific gyre reflecting enhanced northern hemisphere aeolian sources residence time estimates for the settling of refractory paniculate fe and mn from the upper water column are 62 220 days fe and 105 235 days mn in contrast residence times for the scavenging of dissolved fe and mn are 2 13 years fe and 3 74 years mn scavenging residence times for dissolved mn based on horizontal mixing in the surface mixed layer of the northeast pacific are 0 4 years nearshore to 19 years 1000 km offshore there is no evidence for in situ fe redox dissolution within sub oxic waters in the eastern tropical north pacific dissolved fe appeared to be controlled by dissolution from sub oxic sediments with oxidative scavenging in the water column or upper sediment layers however in situ mn dissolution within the oxygen minimum zone was evident

molybdenum isotope behaviour in groundwaters and terrestrial hydrothermal systems iceland abstract molybdenum mo isotopes have proved useful in the reconstruction of paleoredox conditions their application generally relies upon a simplified model of ocean inputs in which rivers dominate mo fluxes to the oceans and hydrothermal fluids are considered to be a minor contribution to date however little attention has been paid to the extent of mo isotope variation of hydrothermal waters or to the potential effect of direct groundwater discharge to the oceans here we present mo isotope data for two icelandic groundwater systems m vatn and eistareykir that are both influenced by hydrothermal processes relative to nist 3134 0 25 the cold n 13 show little if any fractionation from the host basalt 98 95 mobasalt 0 16 to 0 12 and are on average lighter than both global and icelandic rivers in contrast waters that are hydrothermally influenced 10 c possess isotopically heavy 98 95mohydrothermal values of 0 25 to 2 06 n 18 with the possibility that the high temperature endmembers are even heavier although the mechanisms driving this fractionation remain unresolved the incongruent dissolution of the host basalt and both the dissolution and precipitation of sulfides are considered regardless of the processes driving these variations the 98mo data presented in this study indicate that groundwater and hydrothermal waters have the potential to modify ocean budget calculations

pan african displaced terranes in the tuareg shield central sahara concepts developed in the recently published model of the air region eastern tuareg shield niger africa as a college of three displaced terranes integrated in a single geodynamic model lead us to propose a terrane map of the tuareg shield 500000 km 2 the 23 terranes recognized have their own lithological metamorphic magmatic and tectonic characteristics and are separated by subvertical strike slip megashear zones that can be traced for hundreds of kilometres or by major thrust fronts some of these boundaries have ophiolitic assemblages or molassic deposits the tuareg shield was shaped and partly accreted during the pan african orogeny 750 550 ma but not as a homogeneous body

lower cretaceous provenance and sedimentary deposition in the eastern carpathians inferences for the evolution of the subducted oceanic domain and its european passive continental margin

genesis of a variscan batholith field petrological and mineralogical evidence from the corsica sardinia batholith abstract the genesis of the corsica sardinia batholith csb can be explained in a continental collision setting during the time of construction of the batholith which is dated at about 70 ma three magmatic associations were emplaced mg k calc alkaline u1 composite mafic silicic calc alkaline u2 and post collisional alkaline u3 in addition the level of intrusion became progressively shallower from 5 6 kbar for u1 to less than ikbar for u3 in a large scale uplift associations u1 and u2 exhibit non cogenetic mafic and felsic components the processes and products of interaction between mantle and crustal derived melts are however different and may be related to the thickness of the crust which controls both the parameters t pco2 ph2o andptot and the time of mingling of the products of anatexis and basaltic melts both u1 and u2 granitoids were formed by crystallization of a magma derived by fusion of a source of greywacke composition the melting occurred successively under granulitic u1 and amphibolite facies conditions u2 in association u1 basaltic melts displaying potassic lamprophyre like composition up to 8 k2o are of uncertain affinity furthermore crustal interaction with the basic magma precludes precise definition of the source in the u2 composite association the primary tholeiitic character of the mantle derived basic rocks is constrained by both mineralogical and geochemical data dry and hydrated subunits are distinguished among the basic rocks associated with the granitoids no hybridization processes have been identified in the core of the mafic complexes of the dry subunits but they are recognized at the level of emplacement at the margins at the contact with the granitoids contamination in the mafic hydrated subunit is due to the increase in water content of crustal origin in the magma during the ascent and emplacement of the basic complexes leading to the development of abundant green amphibole extensive hybridization is restricted to the base of the crust where it led to incomplete mixing yielding granodiorites and enclaves the genesis and emplacement of the composite calc alkaline u2 association took place in an extensional setting in an uplifting basement postdating a collisional event during the devonian an eastern austro alpine block was thrust onto the western ebro balearic continent the u1 mg k granitoids resulted from anatexis under conditions of pco2 ph2o this took place at the base of the austro alpine crust which was undergoing fusion due to its adiabatic ascent the u2 calc alkaline granitoid rocks were derived in a hydrated environment by fusion of the same austro alpine crust in corsica and of the ebro balearic crust on sardinia and in the pyrenees the conditions of interaction between mafic and felsic magmas may serve as a geodynamic marker providing information on the thickness of the crust in time and space and on the genesis of continental crust the persistence during the palaeozoic of dominantly tholeiitic mafic magmatism suggests that hot spot activity occurred in this area of southwestern europe during pre variscan and variscan times up to the time of opening of the liguro piedmontese ocean birthplace of the alpine orogen

small phytoplankton drive high summertime carbon and nutrient export in the gulf of california and eastern tropical north pacific summertime carbon nitrogen and biogenic silica export was examined using 234th 238u disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps isp within the eastern tropical north pacific and the gulf of california fine scale isp sampling provides evidence that in this system particulate carbon pc and particulate nitrogen pn concentrations were more rapidly attenuated relative to 234th activities in small particles compared to large particles converging to 1 5 mol dpm 1 by 100 m comparison of elemental particle composition coupled with particle size distribution analysis suggests that small particles are major contributors to particle flux while absolute pc and pn export rates were dependent on the method used to obtain the element 234th ratio regional trends were consistent across measurement techniques the highest c fixation rates were associated with diatom dominated surface waters yet the highest export efficiencies occurred in picoplankton dominated surface waters where relative concentrations of diazotrophs were also elevated our results add to the increasing body of literature that picoplankton and diazotroph dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton e g diatoms in low productivity pico nanoplankton dominated regions where small particles are major contributors to particle export findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate therefore we argue the necessity of collecting multiple particle sizes used to convert 234th fluxes into carbon or other elemental fluxes including 50 m since they can play an important role in vertical fluxes especially in oligotrophic environments our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method

short lived eburnian orogeny in southern mali geology tectonics u pb and rb sr geochronology abstract this work is based on a comprehensive field survey including mapping of the massigui degree sheet in southern mali the investigated area belongs to the northern part of the man shield which is mainly composed of lower proterozoic volcano sedimentary sequences birimian and of large areas of granitoids the whole being affected by the eburnian orogeny structural and geochronological u pb and rb sr results from this study point to a short period of time 30 ma for the eburnian orogenesis between 2100 and 2070 ma the events recorded later 1984 30 ma being due to tectonic reactivations on the other hand no trace of events older than 2100 ma have been found coupled with geochemical and rb sr isotopic systematics this leads to invoke a fundamental link between birimian volcanics and eburnian granitoids both being high k calc alkaline in composition and coming from a single evolving mantle source in a palaeo environment which has some of the characteristics of modern subduction including back arc or docking zones the main regional structure of the area strikes roughly nne ssw with an important strike slip component escorted by a greenschist metamorphism the deformation is the most intense in the n40 to n10 5 km large banifin shear zone where metamorphism reached the lower amphibolite facies here one observes subvertical strong foliation non cylindrical folding locally sheath folds and subhorizontal pencil lineations the deformation being regionally recorded by light subisoclinal folds with subvertical axes compatible with a sinistral movement this regional shear tectonics d2 2074 9 8 ma is preceded by an isoclinal deformation d1 bracketed between 2098 5 ma and d2 only known as relics from which it likely derived a later phase d3 occurred along the banifin shear belt at a more superficial level even if still ductile generated by a dextral movement and having induced retrograde metamorphism this last tectonic phase which is not accompanied by plutonism nor volcanism has been dated at 1982 30 ma being responsible for the complete resetting of the rb sr isotopic system in the plutons present in the banifin corridor

vertex manganese transport through oxygen minima abstract manganese transport through a well developed oxygen minimum was studied off central mexico 18 n 108 w in october november 1981 as part of the vertex vertical transport and exchange research program refractory leachable and dissolved mn fractions associated with particulates caught in traps set at eight depths 120 1950 m were analyzed particles entering the oxygen minimum had relatively large mn loads however as the particulates sank further into the minimum total mn fluxes steadily decreased from 190 nmol m 2 day 1 at 120 m to 36 nmol m 2 day 1 at 400 m manganese fluxes then steadily increased in the remaining 800 1950 m reaching rates of up to 230 nmol m 2 day 1 at 1950 m manganese concentrations were also measured in the water column dissolved mn levels 1 were consistently observed within the 150 600 m depth interval in contrast suspended particulate leachable mn amounts were especially low at those depths and never exceeded 0 04 nmol kg 1 the combined water column and particle trap data clearly indicate that mn is released from particles as they sink through the oxygen minimum rate of change estimates based on trap flux data yield regeneration rates of up to 0 44 nmol kg 1 yr 1 in the upper oxygen minimum 120 200 m however only 30 of the dissolved mn in the oxygen minimum appears to be from sinking particulate regeneration the other 70 probably results from continental slope release horizontal transport processes dissolved mn scavenges back onto particles as oxygen levels begin to increase with depth scavenging rates ranging from 0 03 to 0 09 nmol kg 1 yr 1 were observed at depths from 700 to 1950 m these scavenging rates result in mn residence times of 16 19 years and scavenging rate constants on the order of 0 057 yr 1 manganese removal via scavenging on sinking particles below the oxygen minimum is balanced by mn released along continental boundaries and transported horizontally via advective diffusive processes manganese appears to be very weakly associated with particulates nevertheless the amounts of mn involved with sinking biogenic particles are large and the resulting fluxes are on the same order of magnitude as those necessary to explain the excess mn accumulating on the sea floor the overall behavior of mn observed in this and other studies strongly suggests some type of equilibrium occurring between dissolved and particulate phases this equilibrium appears to shift in direct or indirect response to dissolved oxygen levels

size fractionated major particle composition and concentrations from the us geotraces north atlantic zonal transect the concentration and the major phase composition particulate organic matter caco3 opal lithogenic matter and iron and manganese oxyhydroxides of marine particles is thought to determine the scavenging removal of particle reactive teis particles are also the vector for transferring carbon from the atmosphere to the deep ocean via the biological carbon pump and their composition may determine the efficiency and strength of this transfer here we present the first full ocean depth section of size fractionated 1 51 m 51 m suspended particulate matter spm concentration and major phase composition from the us geotraces north atlantic zonal transect between woods hole ma and lisbon portugal conducted in 2010 and 2011 several major particle features are notable in the section intense benthic nepheloid layers were observed in the western north american margin with concentrations of spm of up to 1648 g l two to three orders of magnitude higher than surrounding waters that were dominated by lithogenic material a more moderate benthic nepheloid layer was also observed in the eastern mauritanian margin 44 g l that had a lower lithogenic content and notably significant concentrations of iron and manganese oxyhydroxides 2 5 each an intermediate nepheloid layer reaching 102 g l an order of magnitude above surrounding waters was observed associated with the mediterranean outflow finally there was a factor of two enhancement in spm at the tag hydrothermal plume due almost entirely to the addition of iron oxyhydroxides from the hydrothermal vent we observe correlations between poc and caco3 in large 51 m particles in the upper 2000 m but not deeper than 2000 m and no correlations between poc and caco3 at any depth in small 51 m particles there were also no correlations between poc and lithogenic material in large particles overall there were very large uncertainties associated with all regression coefficients for mineral ballast carrying coefficients suggesting that mineral ballast was not a strong predictor for poc in this section

source and fate of inorganic solutes in the gibbon river yellowstone national park wyoming usa ii trace element chemistry the gibbon river in yellowstone national park receives inflows from several geothermal areas and consequently the concentrations of many trace elements are elevated compared to rivers in non geothermal watersheds water samples and discharge measurements were obtained from the gibbon river and its major tributaries near norris geyser basin under the low flow conditions of september 2006 allowing for the identification of solute sources and their downstream fate norris geyser basin and in particular tantalus creek is the largest source of many trace elements al as b ba br cs hg li sb tl w and rees to the gibbon river the chocolate pots area is a major source of fe and mn and the lower gibbon river near terrace spring is the major source of be and mo some of the elevated trace elements are aquatic health concerns as sb and hg and knowing their fate is important most solutes in the gibbon river including as and sb behave conservatively or are minimally attenuated over 29 km of fluvial transport some small attenuation of al fe hg and rees occurs but primarily there is a transformation from the dissolved state to suspended particles with most of these elements still being transported to the madison river dissolved hg and rees loads decrease where the particulate fe increases suggesting sorption onto suspended particulate material attenuation from the water column is substantial for mn with little formation of mn as suspended particulates

dissolved manganese in the north atlantic ocean 0 35 n abstract dissolved manganese was measured in samples taken from vertical profiles at 13 stations between 0 and 35 n in the atlantic ocean concentrations of dissolved manganese were highest in the surface waters 1 10 to 3 17 nmol l and decreased rapidly over the top few hundred metres to generally low less than 0 5 nmol l and uniform levels for the remainder of the water column highest concentrations in surface waters occurred in latitudes which have particularly high loadings of atmospheric dust of saharan origins and it is suggested that eolian inputs are the most significant source of manganese to the upper water column in this area in the sections of profiles affected by advection of mediterranean water the concentrations of dissolved manganese were similar to those found generally for the atlantic water masses and are consistent with recent data for the mediterranean the generally low concentrations in deep water indicate that in the areas studied there are no major influences of advection of dissolved manganese from sources on the slope or the mid ocean ridge

cretaceous to miocene thrusting and wrenching along the central south carpathians due to a corner effect during collision and orocline formation field studies in the romanian south carpathians longitude 22 5 to 24 2 e and latitude 45 2 to 45 6 n demonstrate 1 cretaceous top to ne shearing parallel to the present strike of the thrust system connected with coaxial flattening within the generally northwest dipping foliation 2 paleogene ductile brittle dextral wrenching e w compression 1 87 15 and basin formation petrosani basin along the cerna jiu fault system 3 large scale miocene dextral wrenching along the northern margin of moesia 1 143 16 and 4 probably pliocene early pleistocene n s compression 1 205 25 we discuss the tectonics of the south carpathians stressing the corner effect of the moesian foreland promontory during convergence and formation of the carpathian orocline up to the late early cretaceous subduction of oceanic crust was active between europe moesia on one side and east carpathia rhodopia on the other side collision and intracontinental deformation occurred during the late early and late cretaceous the pinning of the thrust front at the western tip of moesia and the foreland recess north of it caused superposition of thrusting and wrenching during collision and lateral translation tangential stretching during orocline formation and spreading into the recess further convergence during the early tertiary resulted in dislocation of the previously welded east carpathian rhodopian and moesian fragments along the cerna jiu fault system and the further northeast translation of the western segment the intramontane petrosani basin opened as a northeasterly propagating transient pull apart structure along the cerna jiu fault system which acquired a curved northwesterly convex transtensional trace due to the shape of the moesian promontory tightening of the carpathian orocline and or rearrangement of the microplate geometry during the formation of the pannonian basin system led to large scale dextral wrenching along the northern margin of moesia pliocene n s compression reflects final shortening in the carpathian system before ongoing convergence between europe and africa was transferred to the mediterranean rotation of material lines around the moesian corner is corroborated by paleomagnetic studies

late proterozoic arc continent and continent continent collision in the pan african trans saharan belt of mali the tilemsi magmatic arc preserved along the suture zone of the pan african trans saharan belt of northern mali crops out as a series of northeast to north northeast trending strips along the tilemsi mesozoic trough and is about 100 km in width the volcanic arc series includes pillowed metabasalts of tholeiitic character and associated with rhyodacites overlying sedimentary rocks are turbiditic volcanic greywackes they are progressively recrystallized into grey gneiss in the vicinity of gabbro noritic and dioritic intrusions u pb zircon dating of a crosscutting metaquartz diorite gives a nearly concordant age of while that of a plagiogranite mobilizate associated with the grey gneiss is initial nd and sr isotopic compositions of two metaquartz diorites end730 6 6 6 3 87sr 86sr i 0 7024 are in a agreement with a depleted mantle source similar to modern intraoceanic arcs isotopic compositions of two tilemsi metagreywackes end730 5 8 4 3 87sr 86sr 0 7027 exclude any significa

molybdenum in icelandic geothermal waters molybdenum concentrations in icelandic geothermal waters lie in the range 1 70 ppb warm waters and dilute high temperature waters which contain high concentrations of sulphide are lowest in molybdenum no correlation is otherwise observed between molybdenum concentrations and temperature surface waters and cold ground waters do not contain detectable molybdenum 1 ppb it seems likely that leaching rate is the prime factor in limiting molybdenum levels in these waters within individual geothermal fields molybdenum concentrations are either approximately constant or they vary regularly across the field this regular variation may often be correlated with variations in other solute concentrations and subsurface temperatures and is taken to indicate a control of molybdenum mobility by a temperature dependent equilibrium the evidence suggests that the solubility of molybdenite is responsible molybdenite has not been found in active geothermal systems in iceland but is known to occur in some new zealand geothermal systems and it has been identified in hydrothermally altered tertiary basalt formations at reydarartindur in southeast iceland boiling and mixing with cold water leads to molybdenite undersaturation and thus these processes favour leaching of molybdenum from the rock on the other hand conductive cooling leads to supersaturation which favours removal of molybdenum from solution

the trace metal composition of suspended particles in the oceanic water column near bermuda trace metal partitioning between seawater and particles both suspended and sinking must be determined to understand and model oceanic trace metal scavenging processes in order to improve the oceanic particulate trace metal data base a newin situ pump was developed and deployed to collect suspended particles from 0 4000 m in the sargasso sea near bermuda these particles were analyzed for al fe mn co zn cu ni cd and pb major particulate carrier phases were estimated from ca opaline si and p cd is the only trace element of this group with a particulate maximum in near surface waters the other metals have low particulate concentrations mol l in near surface waters and increase with depth into the upper thermocline particulate al and fe are then uniform with depth below about 1000 m until increasing in the bottom nepheloid layer the remaining elements mn co zn cu ni and pb decrease from the mid thermocline values to lower and relatively uniform concentrations in deep waters the similarities among the vertical profiles for these metals suggest that authigenic mn oxides influence their uptake from the dissolved pool although an important or dominant role for other host phases specifically particulate organic matter is not ruled out by the data mean intermediate and deep water concentrations are al 3600 fe 1200 mn 146 co 1 5 zn 7 4 cu 15 ni 6 0 cd 0 06 and pb 2 1 pmol l these particulate al and mn values agree with previous measurements in this region but the other elements are lower by a factor of 3 fe co to 30 zn suggesting that earlier data were compromised by contamination the suspended metal data are used in a simple steady state two flux model to evaluate the role of suspended particles in determining the vertical flux of metals in the sargasso sea the model calculations indicate that removal of suspended particles in the deep 500 m water column contributes less than half of the total deep flux for all of the elements investigated except for cd this result implies that uptake of these metals onto particles in the deep central ocean is a minor factor in their oceanic mass balance if this finding is generally true for oligotrophic ocean environments whole ocean residence times for these elements must be governed largely by processes occurring either in near surface waters or at ocean margins

the chemistry of trace elements in surface geothermal waters and steam iceland abstract the geochemistry of trace elements in surface geothermal fluids in iceland was studied the sampled fluids included hot springs mud pots steam vents and soil solutions with temperatures ranging from 4 to 100 c ph between 2 01 and 9 10 and total dissolved solids between 86 and 4375 ppm the surface geothermal waters may be categorized into three groups based on their chemical composition namely nacl waters steam heated acid sulfate waters and mixed waters nacl waters with ph 8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow they contained only low concentrations of most metals

exhumation of the danubian nappes system south carpathians during the early tertiary inferences from kinematic and paleostress analysis at the getic danubian nappes contact abstract a detailed kinematic study based on the analysis of brittle structures combined with a description of structures in the adjacent foredeep allows for the definition of three major tectonic episodes during the late cretaceous tertiary evolution of the central part of the south carpathians following middle cretaceous and older orogenic phases the first tectonic event that affected the studied area was a late cretaceous nnw sse oriented contraction which led to the final major emplacement of the danubian and getic nappes during the paleogene early miocene an extension event induced rapid exhumation of the danubian units leading to the formation of large normal faults dipping towards both the foreland and the hinterland this extension together with dextral rotation of the south carpathians around the western corner of the moesian platform allows for the ne ward movement of the internal continental blocks with respect to the foreland platforms in the late miocene e ward translation of the internal south carpathians units with respect to the moesian platform was accommodated through a large scale e w oriented strike slip corridor within the south carpathians the general paleogene early miocene ne to e ward rotation and the late miocene e ward translation of the rhodopian fragment allowed for the accommodation of roll back and contraction taking place in the east carpathians

peri amazonian avalonian type and ganderian type terranes in the south carpathians romania the danubian domain basement abstract the danubian domain basement of the south carpathians romania comprises two neoproterozoic continental crustal fragments the dr gsan and lainici p ius terranes which were sutured by the closure of an intervening oceanic domain the tisovi a terrane magmatic and detrital zircons extracted from an orthogneiss four granitoid plutons two metasedimentary units and a liassic sandstone were dated by zircon u pb la icp ms the f ge el augen gneiss from the dr gsan terrane basement yielded an age of 803 2 4 4 ma the oldest well constrained crystallization age reported from the romanian carpathians basement the tismana usi a novaci and olte granitoid plutons which intrude the lainici p ius terrane basement yielded ages of 600 5 4 4 591 0 3 5 592 7 4 9 and 588 2 9 ma respectively the tismana granitoid age of 600 ma and the youngest detrital zircon ages of 637 622 ma from a metaquartzite within the lainici paius terrane constrain the deposition of the metaquartzite protolith to ca 620 600 ma the 803 ma age represents an old pan african age whereas the younger neoproterozoic ages suggest pan african cadomian thermotectonic events detrital and inherited zircon ages within the dr gsan and lainici paius terranes attest to a peri amazonian avalonian type provenance for the dr gsan terrane and possibly a ganderian type provenance for the lainici p ius terrane the lainici p ius terrane rifted off gondwana before the dr gsan terrane both terranes were attached to moesia during the early paleozoic

evolution of late neoproterozoic to early paleozoic tectonic elements in central and southeast european alpine mountain belts review and synthesis abstract late neoproterozoic to early paleozoic cadomian tectonic elements are widespread in the southeastern alpine mediterranean mountain belts with discontinuous exposure extending from the alps to the menderes massif in turkey the sequences include voluminous plutonic island and continental arc successions some ophiolites of variable late neoproterozoic and cambrian to early ordovician ages high to medium grade metamorphic sequences and subordinate metasediments geological and geochronological data suggest that these cadomian elements partly experienced tectonothermal activity including metamorphism and magmatism between ca 650 and 600 ma followed by further i and s type plutonism in an andean type continental margin setting ca between 570 and 520 ma subsequently a major rift zone developed which resulted in continental stretching and subsequent formation of a back arc basin which is dated as late cambrian rifting is followed by oceanic spreading which commenced ca at the cambrian ordovician boundary possibly in a back arc setting this tectonic scenario suggests that alpine mediterranean cadomian tectonic elements were accreted to gondwana during early cadomian events ca 600 650 ma subsequently they were likely part of a long lasting outer subduction zone of gondwana at the margin of a panthalassa type ocean during late neoproterozoic iii and cambrian due to back arc spreading continental pieces started to split off from gondwana ca at the cambrian ordovician boundary

thermohaline intrusions in the frontal zones of a warm core ring observed by batfish hydrographic data collected with a towed depth cycling instrument batfish in the frontal regions of warm core ring 82h during and immediately after its formation were analyzed to study small scale structure and processes the frontal and slope water regions are characterized by a complex water mass structure resulting from mixing of the shelf the slope and the sargasso sea waters thermohaline intrusions along constant density surfaces are frequently observed two forms of thermohaline intrusions are studied in detail subsurface tonguelike intrusions and cold filaments a subsurface tongue of shelf water origin was found in the slope water region outside the frontal zone at 70 m depth it had a width of 4 km a thickness of 20 m and a length of at least 40 km and moved in a southeast direction toward the front alongside the subsurface tongue a cold filament 10 km wide extending from the surface to 120 m depth was observed as the subsurface tongue and the filament moved toward the frontal zone their orientation became more and more aligned with the front when they reached the front the strong frontal current carried them downstream and hence prevented further intrusion into the ring mixing in the form of interleaving then became the most important process for cross front mixing interleaving occurs along the side walls of the subsurface tongue and filament with more intense interleaving associated with stronger intrusions this suggests a double diffusive generation mechanism of the interleaving

wintertime convection in warm core rings thermocline ventilation and the formation of mesoscale lenses large heat losses from warm core ring 82b during february march and april 1982 formed a 400 m thick thermostad in the center of the ring two different models were constructed to simulate the formation of the thermostad water mass properties a one dimensional vertical model forced with a meteorological time series and a volumetric mixing model with climatological input both models indicate that a flux of slope water into the ring is necessary to yield the observed thermostad salinities the subsequent slow decay of the ring core in the slope water suggests that such winter convected rings can easily maintain the warm band water identified by wright and parker 1976 the large loss of core water during interactions with the gulf stream suggests that the reabsorption of such winter cooled warm rings is an important source of high salinity high oxygen anomalies in the main thermocline of the sargasso sea the volume of water in a typical ring reabsorption is sufficient to generate many 20 intrathermocline eddies with t s properties close to those of recently reported lenses this suggests that many of these small eddies are much more local in origin and may be more highly dissipative than has previously been suggested an estimate of the flux of high salinity high oxygen water into the main thermocline by this mechanism leads to ventilation at a rate that is a significant fraction of the ekman pumping at these density levels thus the reabsorption of winter cooled warm core rings by the gulf stream is an important eddy ventilation mechanism for the sargasso sea

asymmetrical to symmetrical magnetic fabric of dikes paleo flow orientations and paleo stresses recorded on feeder bodies from the motru dike swarm romania the fabric in a dike is representative of the magmatic flow considered as newtonian the anisotropy of magnetic susceptibility of the rocks gives a good representation of the shape preferred orientation which in turn is a marker of the magmatic flow generally a symmetrical pattern of the fabric across the dike is in agreement with a flow of magma within a channel the flow direction is then reliable with this imbrication an asymmetrical fabric is dependent on the flow and displacement of the wall we present the case of both symmetrical and asymmetrical dike fabrics recording different emplacements from a pan african calc alkaline dike swarm of basaltic andesitic dacitic rhyolitic composition of the alpine danubian window from south carpathians romania two populations of dikes have been described thick 1 30 m n s trending dikes and thin 1 m e w dikes the first display asymmetrical fabric and record the regional sinistral movement of the walls in contrast the thin dikes are symmetrical and frequently display an arteritic morphology that limits the dike length with no cartographic extension we propose to relate the two types of dikes to the same regional stress field in a continuum of emplacement during a regional brittle event

proterozoic ophiolites and mafic ultramafic complexes marginal to the istanbul block an exotic terrane of avalonian affinity in nw turkey abstract among the proterozoic inliers in the istanbul block the lowest structural levels are exposed in the sunnice massif north of bolu amphibolite facies mafic and subordinate ultramafic rocks of the cele meta ophiolite underlie the greenschist facies ediacaran calc alkaline yellice metavolcanics which are intruded by the 565 576 ma dirgine granitoids hornblende gneisses of the cele meta ophiolite comprise island arc meta tholeiites and transitional to calc alkaline metabasalts which together with minor serpentinite are disposed in a broadly antiformal structure the meta ophiolitic rocks are therefore the oldest ophiolites in nw turkey and are themselves thrust on to a putative pre existing continental margin now represented by the metasedimentary migmatites of the demirci gneisses which may thus be the oldest rocks of the complex the istanbul block is an exotic terrane unlike other western turkish terranes it lacks variscan metamorphism its different provenance indicated by its geological record faunal affinities and inherited mid proterozoic isotopic dates suggests a former link with avalonian basement in england nw europe and the maritime provinces of canada hence together with other terranes now situated further east than the avalonian terranes of nw europe the istanbul block may represent the easternmost extremities of avalonia which were detached during its end ordovician collision with the bruno silesian promontory on the sw margin of baltica subsequent migration of the istanbul block to its present location occurred by eastward displacement by sinistral transpression along the southern margin of baltica to a point east of the dobrogea and south of the scythian platform followed by collision with the sakarya block in the mesozoic and late cretaceous southward displacement with the opening of the black sea basin

shoshonitic liquid line of descent from diorite to granite the late precambrian post collisional tismana pluton south carpathians romania abstract the post collision late kinematic tismana pluton belongs to the shoshonitic series it is part of a late precambrian basement within the alpine danubian nappes of the south carpathians romania this pluton displays an exceptionally complete range of compositions from ultramafic to felsic rocks granites widespread mingling mixing relationships at all scales give rise to a variety of facies a liquid line of descent from the diorites to the granites is reconstructed by considering the variation in major and trace elements ree sr rb ba nb zr hf zn v co cr u th ga pb from 33 selected samples as well as mineral melt equilibrium relationships the first step of fractional crystallization is the separation from a monzodioritic parent magma of a peridotitic cumulate similar to the ultramafic rock found in the massif a possible contamination by lower crustal mafic component takes place at this stage the second step marks the appearance of apatite and fe ti oxide minerals as liquidus phases and the third step saturation of zircon mixing by hybridisation of magmas produced at different stages of the evolution along the liquid line of descent is also operating endo hybridisation as depicted by nd and sr isotopes fractional crystallization was combined to an important early contamination by a mafic lower crust in a deep seated magma chamber and to a later and mild contamination by a felsic medium crust in an intermediate chamber the mingling essentially occurred during the final emplacement in the high level magma chamber the monzodioritic parent magma identified by major and trace element modelling is shown by sr and nd isotopes to have its source in the lithospheric mantle or in a juvenile mafic lower crust derived from it the necessarily recent enrichment in k2o and associated elements of the lithospheric mantle is likely to be related to the preceding pan african subduction period the partial melting of this newly formed deep source has to be linked to a major change in the thermal state of the plate

the neoproterozoic pan african basement from the alpine lower danubian nappe system south carpathians romania abstract the south carpathians which were thrust to the moesian platform in the alpine orogeny late cretaceous to tertiary include the danubian nappe system the danubian pre alpine basement comprises two variscan nappes each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an ordovician devonian volcano sedimentary cover no lithological correlation can be established between the pre ordovician basements of these two units the metamorphic basement from the first variscan nappe the dr gsan group is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons the banded structure of the amphibolites together with their geochemistry suggests a volcano sedimentary sequence zircon u pb data on an intercalated augen gneiss have given an age of 777 3 ma for the emplacement of the protolith of this gneiss nd model ages t dm for the amphibolites range from 717 ma to 817 ma at 777 ma nd values cluster is at 8 3 to 9 8 and sr initial ratios range between 0 7007 and 0 7023 indicating an oceanic origin without continental crust contamination major and trace elements from the dr gsan amphibolites consistently display an island arc signature with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low k calc alkaline one the dr gsan terrane is similar to the early pan african juvenile terranes of the sahara the basement of the second variscan nappe the lainici p ius group is made up of metasedimentary rocks mainly quartzites marbles and graphitic mica gneisses cut by early leucogranitic dykes medium k calc alkaline and alkali calcic mainly granitic plutons and late medium k porphyry diorite dykes this magmatism can be bracketed between 588 ma and 567 ma u pb zircon ages the best preserved pluton tismana 567 ma old displays a composite alkali calcic very high k calc alkaline magmatic sequence ranging from gabbro diorite to monzogranite including an ultramafic pod ages and geochemical signatures resemble the saharan late pan african granitoids the existence of late precambrian partly juvenile terrains is thus confirmed within the basement of south carpathians which renders then a segment of the european alpine belt that can be successfully compared to the pan african trans saharan belt

remineralization of particulate authigenic trace metals in the middle atlantic bight implications for proxies of export production abstract samples collected by time series sediment traps deployed in the middle atlantic bight were studied to better understand the formation and preservation of particulate authigenic forms of trace metals cu ni ba that hold potential to serve as proxies in the sedimentary record of past changes in the flux of biogenic detritus sinking from the surface ocean into the deep sea export production particulate biogenic and authigenic phases are extremely labile as evidenced by the observation that as much as 70 of the particulate fluxes of organic carbon and of certain metals cu ni and mn and up to 25 of the particulate fluxes of authigenic ba and of opal collected by sediment traps are released rapidly into solution during the time period between particle collection and trap retrieval further remineralization on the seabed reduces concentrations of authigenic cu and ni in surface sediments below the limit of detection approximately 80 of authigenic ba is remineralized during early diagenesis on the seabed much more than is expected for conditions of high sediment mass accumulation rate that exist in the study area extensive remineralization during early diagenesis combined with large corrections required to remove the aluminosilicate contribution to the concentrations of cu ni and ba in sediments preclude the successful use of down core profiles of these trace metals to reconstruct past changes in export production of the middle atlantic bight similar problems are likely to plague paleoproductivity reconstructions in other ocean margin regions or wherever high fluxes of aluminosilicate phases occur

le hoggar oriental bloc cratonise a 730 ma dans la chaine pan africaine du nord du continent africain abstract the djanet tafassasset unit in eastern hoggar is a segment of a pre pan african fold belt trending nw se and is cut by syn to late tectonic calc alkaline batholiths u pb dating of zircons from a granite of this suite gives a crystallisation age of 729 8 ma the eastern hoggar was hence stabilized at about 730 ma i e at the time of growth of both the arabo nubian shield and north mali systems of magmatic arcs during the pan african continental collision 600 ma the eastern hoggar behaved as a rigid block in between the saharan nigerian belt and the mozambique belt

the east carpathian crystalline mesozoic zone romania paleozoic amalgamation of gondwana and east european craton derived terranes abstract the alpine orogen of the eastern carpathians contains pre alpine terranes framed by younger rocks the geological data on these terranes are reviewed and interpreted in order to elucidate their geodynamic evolution during the paleozoic the rebra tulghes terrane shows a stratigraphic sequence similar to avalonia neoproterozoic platformal metasediments rebra group overlain by late neoproterozoic volcano sedimentary rocks pietrosu bistritei porphyroids and lower paleozoic cover tulghes group the bretila terrane made up of orthogneisses pelitic gneisses granites amphibolites and micaschists shows affinities with the basement of the east european craton the modern juxtaposition of the bretila terrane and the rebra tulghes terrane may be explained in terms of collision between the latter and the east european craton during the ordovician times as an effect of collision the bretila terrane was thrust over the rebra tulghes terrane and induced the occurrence of thrust faults within it a lower paleozoic emplacement of the east carpathian pre alpine thrust nappes is thus inferred

description and interpretation of the composition of fluid and alteration mineralogy in the geothermal system at svartsengi iceland abstract the bulk composition and mineralogy of hydrothermally altered tholeiite along with the composition and speciation of fluid have been determined for a well defined alteration zone at 240 c and 110 bars at svartsengi iceland mass balances between the geothermal fluid and altered tholeiite relative to a seawater fresh water mixture and unaltered tholeiite indicate the overall reaction per 1000 cm 3 is 1325 gm plagioclase 1228 gm pyroxene 215 gm oxide minerals break down to form 685 gm chlorite 636 gm albite 441 gm quartz 249 gm epidote 266 gm calcite 201 gm oxide minerals 15 gm pyrite requiring an influx of 123 gm co 2 10 gm h 2 s and 4 gm na 2 o and a release of 57 gm sio 2 35 gm feo 21 gm cao 8 gm mgo and 4 gm k 2 o principal reactions deduced from textural evidence include na ca exchange in plagioclase precipitation of quartz calcite and anhydrite and formation of chlorite and epidote by reactions between groundmass minerals and fluid thermodynamic analyses of authigenic minerals and downhole fluid indicate that the fluid maintains a state close to equilibrium with the secondary mineral phases chlorite epidote albite quartz calcite prehnite anhydrite pyrite and magnetite whereas remnant primary labradorite and augite are out of equilibrium with the fluid water rock ratios for the system are determined under a variety of assumptions however the open nature of the system makes comparisons with experimental and theoretical closed system studies ambiguous

kinetic and thermodynamic factors controlling manganese concentrations in oceanic waters abstract data are presented describing the changes in the distribution of dissolved and particulate mn observed over a 16 month period in the periodically anoxic waters of saanich inlet a fjord located on the coast of vancouver island british columbia during the spring and summer when the bottom waters were anoxic a dense cloud of particulate mn was found at mid depths where mn 2 enriched anoxic bottom waters were mixing with oxygenated waters then during the autumn aand winter following an intrusion which reoxygenated the bottom water an intense precipitation of mn was observed throughout the entire water column during this latter period dissolved mn concentrations in the bottom water which exceeded 1000 nmol l under anoxic conditions decreased towards a lower limit of 1 6 nmole l a value comparable to that observed in pacific ocean waters of similar ph and dissolved oxygen content mn in the particulate matter collected just above the oxic anoxic interface was found to have an average oxidation number of 3 05 and on this basis it is proposed that dissolved mn concentrations in oceanic waters are controlled by the precipitation of the metastable oxide mineral manganite mnooh a hypothesis consistent with the fact that dissolved mn values in subsurface pacific ocean waters closely approach the equilibrium solubility of this phase temporal and spatial gradients in the particulate mn distribution were used to calculate the in situ rate of mn precipitation and the results of these calculations then were fitted to theoretical rate equations which suggest that the precipitation of mn is controlled by 2 parallel processes bacterial oxidation and an inorganic autocatalytic oxidation reaction

pathways of manganese in an open estuarine system the distribution of mn was examined in the bottom sediments and water column suspended paniculate matter of the laurentian trough gulf of st lawrence a characteristic profile of mn with depth in the sediment consisted of a mn enriched surface oxidized zone less than 20 mm thick and a mn depleted subsurface reducing zone a subsurface mn maximum occurred within the oxidized zone below this maximum the concentration dropped sharply to nearly constant residual levels in the reducing zone the accumulating estuarine sediments are deficient in mn compared to the river input of suspended matter and are definitely not the ultimate sink for manganese manganese escapes from the sediment by diffusion and resuspension forming mn enriched fine grained particles which are flushed out in the estuarine circulation 5 0 109gyr 1 of mn or 50 more than the river input of dissolved mn are exported to the open ocean in spite of the efficient mobilization and export of mn the quantity exported is a small fraction 0 2 of the total flux to the deep sea sediments this is related to the low levels of paniculate matter transported by the st lawrence river the export phenomenon however is probably true of many coastal regions of muddy sediments and thus has interesting implications for the oceanic budget of mn

the continental margin is a key source of iron to the hnlc north pacific ocean here we show that labile particulate iron and manganese concentrations in the upper 500m of the western subarctic pacific an iron limited high nutrient low chlorophyll hnlc region have prominent subsurface maxima between 100 200 m reaching 3 nm and 600 pm respectively the subsurface concentration maxima in particulate fe are characterized by a more reduced oxidation state suggesting a source from primary volcagenic minerals such as from the kuril kamchatka margin the systematics of these profiles suggest a consistently strong lateral advection of labile mn and fe from redox mobilized labile sources at the continental shelf supplemented by a more variable source of fe from the upper continental slope this subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing and is likely a key source of bioavailable fe to the hnlc north pacific

precambrian tholeiitic dacitic rock suites and cambrian ultramafic rocks in the pennine nappe system of the alps evidence from sm nd isotopes and rare earth elements major element trace element and sm nd isotope analyses were made of polymetamorphic hornblendefelses plagioclase amphibolites and banded amphibolites from the berisal complex in the simplon area italy switzerland to determine their age origin and genetic relationships in light of major and rare earth element data the hornblendefelses are inferred to have originally been pyroxene rich cumulates the plagioclase amphibolites and the dark layers of the banded amphibolites to have been tholeiitic basalts and the light layers dacites the sm nd isotope data yield isochron ages of 475 81 ma for the hornblendefelses 1 018 59 ma for the plagioclase amphibolites and 1 071 43 ma for the banded amphibolites the 1 ga magmatic event is the oldest one ever found in the crystalline basement of the pennine nappes the sm nd isotope data support the consanguinity of the tholeiitic dark layers and the dacitic light layers of the banded amphibolites with the tholeiitic plagioclase amphibolites and the ultramafic hornblendefelses

atmospheric trace elements at enewetak atoll 2 transport to the ocean by wet and dry deposition the concentrations of trace elements in precipitation and dry deposition are presented for samples collected at enewetak atoll 11 n 162 e during searex experiments in 1979 the concentrations of al sc mn fe co and th in rain are dominated by crustal material and for these elements wet deposition evidently exceeds dry deposition for most of these elements the present rates of atmospheric deposition at enewetak are similar to their mean rate of accumulation in sediments over the past 5 10 000 years suggesting that the air to sea exchange of particles is closely tied to the sedimentary cycle of the mid pacific noncrustal sources govern the concentrations of pb zn cu se and cd in wet and dry deposition samples analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples and even though these estimates do not necessarily reflect the dry deposition to the ocean surface the results suggest that recycled sea spray often amounts to more than 50 of the total dry deposition of the enriched elements recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements the net deposition rates of elements such as cu and zn are greater than or equal to their inputs from vertical mixing but the net deposition of pb clearly exceeds the input from upwelling the current net deposition rates of the enriched elements are also similar to their rates of removal to sediments these results indicate that air sea exchange processes may significantly affect the chemistry of trace metals in the open ocean

222rn surpluses in warm core rings measurements of 222rn and 226ra were made in the western atlantic ocean as part of the warm core rings program a significant number of measurements on waters taken from the surface and deeper waters showed 222rn concentrations in excess of those supported by the parent 226ra since the source of these 222rn surpluses is near bottom shelf or slope water and since the half life of 222rn is only 3 8 days such 222rn surpluses are indicative of rapid offshore advective and or mixing processes concentrations of 226ra exhibit a small but measurable increase when moving from the sargasso sea through the slope water and up onto the shelf

pre variscan back arc and island arc magmatism in the tauern window eastern alps abstract pre variscan sequences of the central and eastern part of the tauern window consist of amphibolites plagioclase gneisses and minor intercalations of metapelites and metacherts they were analyzed geochemically and in addition morphological studies of their zircon crystals were carried out the metabasaltic rocks in the eastern tauern window storz group geochemically represent a transitional island arc back arc geotectonic setting they are intercalated with acid plagioclase gneisses in some places which as is implied from the characteristics of their zircon crystal faces are most probably mantle derived metarhyolites biotite plagioclase gneisses with detrital zircon populations predominate over the amphibolites and are interpreted as metagreywackes derived from the nearby volcanic arc a dismembered ophiolite complex stubach group in the central tauern window shows chemical characteristics of a back arc oceanic crust it is overlain mainly by metabasalts metaandesites and metarhyolites habach group with low k to calc alkaline geochemistry representing a primitive island arc in conclusion the pre variscan sequences of the tauern window were formed in an oceanic setting and represent supra subduction oceanic crust and a primitive island arc cratonization of the area did not occur until the intrusion of large masses of s and i type granitoids during the variscan orogeny

early and late pan african orogenies in the air assembly of terranes tuareg shield niger our study of the 60 000 km 2 air massif which comprises the southeastern extension of the tuareg shield in the niger republic has identified three major displaced terranes aouzegueur barghot and assod6 these terranes were all affected differentially by the pan african orogeny during an early major phase 750 660 ma and a late follow up phase 650 580 ma the greenschist facies aouzegueur terrane comprises an ophiolite and is intruded by a late kinematic mediumk calc alkaline tonalite trondhjemite granodiorite ttg suite 730 ma the amphibolite facies barghot terrane made up of a basement and a supracrustal sequence is intruded by late to post kinematic high k calcalkaline granitoids 715 665 ma both terranes form a nne to e verging belt thrust 680 670 ma upon an unknown eastern rigid continent and are covered unconformably by an early pan african molasse in contrast the amphibolite facies assod6 terrane composed of a basement and several supracrustal sequences collided with the eastern rigid block without being thrust upon it tibetan type crustal thickening occurred and ht lp metamorphism proceeded to regional anatexis enhanced by widespread emplacement of anatectic granites of lower crustal origin 670 ma this thermal event is attributed to the delamination of the continental lithospheric mantle and consequent rise of the asthenosphere the late pan african phase affecting mainly the assod6 terrane is marked by the intrusion of high k calc alkaline n s elongated batholiths 645 580 ma and by right lateral displacement along the n s raghane mega shear zone located on the edge of the eastern rigid continent this movement along the northern extent of the rigid continent in eastern hoggar 8 30 e created the tiririne intracontinental linear fold belt made up of early panafrican molasse in the model proposed we estimate that the assod6 terrane driven by an oblique spreading ridge moved to the north over a distance of 1000 km during 60 ma along the lithospheric raghane shear zone the latter was the subsequent locus of the silurian devonian alkaline ring complexes the calc alkaline granitoids are regarded as subduction related mantle products contaminated by lower and medium level crust the model and mechanisms proposed can be applied to the entire tuareg shield

geochronology of the karadere basement nw turkey and implications for the geological evolution of the istanbul zone earlier geological work in the istanbul zone western pontide tectonic belt has revealed the presence of extensive basement outcrops exposed underneath palaeozoic and mesozoic to tertiary cover sequences the basement of suspected neoproterozoic age plays an important role in understanding the crustal accretion process in nw turkey we report the first results of a detailed pb pb and u pb zircon study complemented by nd sr whole rock and mineral data from basement rocks exposed in the karadere valley safranbolu area five samples were selected for this study comprising three metagranitoids and two metasediments zircon geochronology indicates that the metagranitoids were formed during late proterozoic pan african magmatic events between 590 and 560 ma the rocks are of tonalitic and granitic composition and have low nb y ratios and ti contents consistent with those of arc rocks a continental arc setting is supported by their sr and nd isotope data that indicate a contribution of a mantle source as well as crustal assimilation during magma genesis the metasediments can clearly be distinguished from the metagranitoids by their higher 87sr 86sr ratios and lower end values at 580 ma which supports the suggestion that the arc was underlain by mature continental crust zircons from the metasediments yield a range of pb pb ages between 1 860 and 710 ma thirty per cent of them fall between 890 and 710 ma possibly suggesting a derivation from gondwana afro arabian regions a sm nd garnet whole rock analysis obtained on a metagranite gives an age of 559 8 ma which either reflects pre metamorphic magmatic growth of garnet in a felsic melt or a syntectonic high temperature metamorphic event uplift and cooling of the basement is further constrained by rb sr biotite ages of 548 545 ma these lower cambrian mineral ages demonstrate that the istanbul zone was not thermally reactivated during the hercynian cimmerian or alpine orogeny in contrast to its neighbouring tectonic zones confirming its role as a suspect terrane in the modern western pontide tectonic belt

alpine polyphase tectono metamorphic evolution of the south carpathians a new overview abstract the main terrains involved in the cretaceous tertiary tectonism in the south carpathians segment of the european alpine orogen are the getic supragetic and danubian continental crust fragments separated by the severin oceanic crust floored basin during the early middle cretaceous times the danubian microplate acted initially as a foreland unit strongly involved in the south carpathians nappe stacking multistage folding thrusting events uplift erosion and extensional stages and the development of associated sedimentary basins characterize the south carpathians during cretaceous to tertiary convergence and collision events the main cretaceous tectogenetic events responsible for contraction and crustal thickening processes in the south carpathians are mid cretaceous austrian phase and latest cretaceous laramide or getic phase in age the architecture of the south carpathians suggests polyphase tectonic evolution and mountain building and includes from top to bottom the getic supragetic basement cover nappes the severin and arjana cover nappes and danubian basement cover nappes all tectonically overriding the moesian platform the severin nappe complex including obarsia and severin nappes with late jurassic early cretaceous ophiolites and turbidites is squeezed between the danubian and getic supragetic basement nappes as a result of successive thrusting of dismembered units during the inferred mid to late cretaceous subduction collision followed by tectonic inversion processes early cretaceous thick skinned tectonics was replaced by thin skinned tectonics in late cretaceous thus the former middle cretaceous austrian nappe stack and its albian lower senonian cover got incorporated in the intra senonian laramide getic stacking of the getic supragetic severin arjana nappes onto the danubian nappe duplex the two contraction events are separated by an extensional tectonic phase in the upper plate recorded by the intrusion of the banatitic magmas 84 73 ma the overthrusting of the entire south carpathian cretaceous nappe stack onto the fold thrust foredeep units and to the moesian platform took place in the late miocene intra sarmatian times and was followed by extensional events and sedimentary basin formation

particulate manganese dynamics in gulf stream warm core rings and surrounding waters of the n w atlantic manganese has been measured in size fractionated paniculate matter profiles obtained by large volume in situ filtration of the upper 1000 m of the n w atlantic as part of the warm core rings experiment wcre in 1982 environments sampled included warm core rings wcr 82b and 82h the entrainment zone at the edge of these rings the slope water surrounding rings and the gulf stream gs and sargasso sea ss from which the rings formed manganese concentrations ranged from 10 pmol kg 1 to 10 000 pmol kg 1 with the extreme values observed in the quasi isolated core waters of wcr 82b and in a tongue of shelf water at the periphery of wcr 82b respectively the majority of the mn was in the 1 53 m particle size fraction and most mn was probably close to 1 m in size mn showed no correlation with major biogenic phases indicating that formation by local biological processes was not an important source instead most paniculate mn present in the waters sampled originated in reducing sediments at the continental margin a manganese budget for the quasi isolated core waters of wcr 82b between february and june 1982 showed that most mn removal was by the aggregation of the small mn oxyhydroxide particles into fecal material followed by sedimentation calculations show that wcrs cause offshore particulate mn transports from the continental margin between 66 w and cape hatteras of 8 5 104 to 14 104 mol d 1 with most derived from the continental shelf only 4 of the shelf derived mn becomes entrained into wcrs and the rest is left to disperse in the slope water or enter the circulation of the gulf stream the wcr induced offshore mn transports may account for a large fraction of the mn flux to sediments on the continental slope and upper continental rise

1 57 ga magmatism in the south carpathians implications for the pre alpine basement and evolution of the mantle under the european continent abstract chemical and isotopic analyses of amphibolites and gneisses from the oldest lithostratigraphic group in the south carpathians produce new insights regarding the chronology and evolution of the mobile proterozoic crust in central eastern europe these results date an episode of magmatism related to oceanic crust consumption reveal a period of continental stabilization and put constraints on the underlying mantle composition amphibolites from the cump na group have their origin in basalts chemically similar to island arc tholeiites a whole rock isochron age of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand

exhumation and relief history of the southern carpathians romania as evaluated from apatite fission track chronology in crystalline basement and intramontane sedimentary rocks the combination of apatite fission track ft thermochronology from basement units and the ft age distributions of apatites in the miocene intramontane sedimentary rocks allows describing the exhumation history of the central segment of the southern carpathians romania exhumation and cooling from the total track annealing temperature 120 c of the cozia and cibin massifs occurred in the palaeocene early eocene between the eocene and middle miocene there was a stagnation period concerning vertical displacement the presently exposed part of the basement was buried in shallow depth the present crests of the cozia and cibin mountains were at temperatures around 80 c and 50 c respectively the second exhumation period occurred in middle miocene times the magnitude of the miocene vertical displacement is on the order of the present day relief the vertical apatite ft age distribution in the basement and the age clusters in the sedimentary rocks prove that the levels of the crests were already close to the surface in palaeogene times therefore the post palaeocene erosional removal from the crest zones is very limited

trace element and isotope sr nd geochemistry of porphyry and skarn mineralising late cretaceous intrusions from banat western south carpathians romania geochemical and isotopic strontium neodymium data have been obtained from 24 samples of seven late cretaceous intrusions associated with skarn tincova bocsa ocna de fier dognecea and porphyry copper molybdenum skarn deposits oravi a ciclova sasca and moldova nou in the south carpathians of romania the intrusions cut the supragetic getic nappes and form a 100 km long nne ssw trending lineament in the banat metallogenic province the samples range in composition from gabbro to granodiorite and define in major and trace element variation diagrams a calc alkaline to high potassium calc alkaline trend ranging from 50 to 67 sio2 they are magnetite bearing i type granitoids enriched in lile lree and depleted in nb ta and zr common features for magmas associated with subduction zones the lack of cumulate textures and of positive europium anomalies seems to indicate that the samples represent liquid compositions the observed trend thus approximates a liquid line of descent resulting from fractional crystallisation of parental magmas with similar major and trace element compositions initial strontium isotopic ratios sri vary from 0 7042 to 0 7058 and end t values range from 3 9 to 0 2 variations of sri and end t values with sio2 show minor crustal assimilation the generally positive end t values together with moderate sri indicate that the parental magmas result from partial melting of a rubidium enriched and lree depleted source such as a heterogeneous lithospheric mantle or a young mafic lower crust derived from it selective rubidium enrichment probably occurred during a previous subduction event by metasomatism of the overlying mantle wedge either in the early cretaceous or earlier as suggested by tdm model ages ca 600 ma the cu mo pb zn fe deposits are intimately associated with the intrusions and the banat romania region can be subdivided in two metallogenic zones in northern banat fe cu pb zn skarns occur whereas in southern banat porphyry style copper and molybdenum deposits predominate these differences result from a combination of several parameters 1 magma composition whereby copper and molybdenum rich deposits tend to be associated with calc alkaline compositions 2 an increase of the present day erosion level from south to north as indicated by the presence of large equigranular plutons in northern banat and of porphyritic cupolas and apophyses associated with porphyry style mineralisation in southern banat 3 the nature of the host rocks with skarns preferentially developed in calcareous host rocks and 4 local variations of conditions controlling the infiltration of fluids and the precipitation of ore minerals

sinking fluxes of minor and trace elements in the north pacific ocean measured during the vertigo program as part of the vertical transport in the global ocean vertigo program we collected and analyzed sinking particles using sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 in this paper we present the results of minor and trace element determinations made on these samples minor and trace elements in the sinking material showed 2 trends in flux with depth increasing and constant the sinking particulate phase of some elements al fe mn was dominated by material of lithogenic origin and exhibited flux that was constant with depth and consistent with eolian dust inputs aloha or increasing in flux with depth as a result of lateral inputs from a shelf k2 this shelf derived material also appears to have been confined to very small particles whose inherent sinking rates are slow and residence time within the mesopelagic twilight zone would be consequently long furthermore the flux of this material did not change with substantial changes in the rain of biogenic material from the surface k2 suggesting mechanistic decoupling from the flux of organic carbon and macronutrients micronutrient fe co zn and cu fluxes examined in a 1 d mass balance suggest widely differing sources and sinks in the water column as well as impacts from biological uptake and regeneration for example total fe fluxes into and out of the euphotic zone appeared to be dominated by lithogenic material and far exceed biological requirements the export flux of fe however appeared to be balanced by the eolian input of soluble fe for zn and cu the situation is reversed with atmospheric inputs insufficient to support fluxes and the cycling therefore dominated by the draw down of an internal pool for co the situation lies in between with important but ultimately insufficient atmospheric inputs

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

manganese geochemistry near high temperature vents in the mid atlantic ridge rift valley in july 1985 the first high temperature hydrothermal vents ever discovered on the mar were found at 26 n tag a transponder navigated survey of a 4 8 km area was begun when on board measurements of manganese revealed concentrated hydrothermal plumes in the water column comparable in size and intensity to those found over geothermal fields on the epr these plumes also possess anomalously high light scattering properties and anomalously warm potential temperatures using relay transponder navigation with a rosette ctd system it was possible to sample bottom waters with temperature anomalies of several decidegrees samples collected near vent orifices possessed silica anomalies of up to 17 m and dissolved manganese anomalies as large as 360 nmol kg these manganese and silica anomalies are linearly related and predict amn si ratio of 20 mmol mol for these mar vent fluids a value essentially identical to that measured in 350 c fluid from the epr at 21 n the distribution of temperature anomalies in the water column over this area requires the presence of more than one active vent site a rough estimate of the convective heat loss from this section of the mar based on z profiles is 1 2 108 cal s which is similar to the heat loss estimated for the vent field on the epr at 21 n

the granitoids of the moravian zone of northeast austria products of a cadomian active continental margin abstract a large number of cadomian granitoids occur in the bruno vistulicum brno unit this unit is a pre variscan consolidated block adjoining the central european variscan orogen on the eastern side of the bohemian massif it most probably represents a marginal part a prong of the fennosarmatian platform some of the bruno vistulian granitoids are exposed within austria in the so called moravian zone which is located at the western margin of the bruno vistulicum it was deformed and metamorphosed to various degrees during the variscan orogeny the granitoids of the moravian zone are quartz diorites tonalites quartz monzodiorites granodiorites and granites felsic granodiorites and granites prevail the granitic plutonism as a whole exhibits a great number of geochemical similarities to circum pacific continental arc i type batholiths cadomian plutonic activity in the bruno vistulicum probably occurred in connection with subduction of oceanic lithosphere beneath the southwestern margin of the fennosarmatian continent