the biogeochemistry of aluminum in the pacific ocean abstract vertical distributions and horizontal surface transects of dissolved and particulate al at several locations in the pacific ocean are presented here concentrations of dissolved al in the pacific range from 0 3 to 5 nmol kg in the surface waters from 0 1 to 1 nmol kg in mid depths and from 0 5 to 2 nmol kg in the deep waters from these data and published data from other regions it is evident that al has a unique oceanic chemistry relative to that of other metals external sources and rapid particle scavenging throughout the water column are the major controls on dissolved al distributions in the oceans vertical profiles generally exhibit a surface maximum a mid depth minimum and increasing concentrations toward the sediment water interface this suggests two sources of dissolved al one to the surface waters and one to the deep waters concentrations of dissolved al in surface waters are lowest within the eutrophic low salinity california current 0 3 1 nmol kg and increase westwardly into the subtropical gyre of the north pacific 5 nmol kg values in the south pacific gyre are fivefold lower these horizontal trends indicate that the primary source of dissolved al to the surface waters of the central pacific is from eolian input dissolved al supplied by rivers to the eastern north pacific appears to be rapidly scavenged in estuaries and or the highly productive coastal region the source of dissolved al to the deep waters is not known but could be due to a flux out of the sediments or a remineralization process suspended particulate al concentrations increase with depth at all stations and decrease with distance from the ocean boundary surface values range from 1 5 nmol kg near shore to 0 3 nmol kg in the central gyres of the pacific deep water concentrations range from 22 nmol kg near shore to 4 nmol kg in the north pacific central gyre and decrease to 1 3 nmol kg in the south pacific central gyre observed distributions indicate that suspended particulate al varies with the intensity of bottom sediment resuspension and the horizontal mixing of the resulting nepheloid layer out from ocean boundary regions particle residence times estimated are consistent with other reported values

new tectonic configuration in ne iran active strike slip faulting between the kopeh dagh and binalud mountains in this paper a combined approach of geomorphic analyses detailed geological mapping on spot 5 satellite images and field surveys complemented by radiometric dating ar 40 ar 39 allows proposing a new and consistent tectonic configuration for the northeastern arabia eurasia collision zone it favors a simple strike slip faulting mechanism in ne iran accommodating the northward motion of central iran with respect to eurasia between the binalud and kopeh dagh mountains our results demonstrate that similar to 2 mm a similar to 25 of this northward motion has been transferred from the binalud to the kopeh dagh through the meshkan transfer zone since similar to 5 ma the modern state of stress deduced from fault kinematics analyses shows n30 degrees e trending maximum stress axis and confirms a dominant strike slip faulting mechanism combining our geological data with other available data we conclude that kinematics of deformation can be appropriately described by rigid block faulting in ne iran instead the continuous deformation as it has been thought during the last 3 decades

aluminium as a tracer of the deep outflow from the mediterranean dissolved aluminium has been determined in sea water samples from the southwestern alboran sea and the gulf of cadiz partial dissolution of eolian dust is responsible for the elevated levels of dissolved al that were found in both the western mediterranean deep water wmdw 111 5 nm and levantine intermediate water liw 86 2 nm masses in the alboran sea the al concentration in the outflowing plume of mediterranean water sampled in the gulf of cadiz is also elevated 72 nm these enhanced signals and the differences between them are used in a three water mass system to calculate a maximum 10 contribution of western mediterranean deep water to the outflow plume considerably less than has been previously supposed while the synoptic nature of this study and the possibility of involvement of other water masses in the outflow plume leave scope to increase the participation of wmdw in the outflow plume these measurements indicate the potential of a nontransient tracer in elucidating the component parts of complex flow systems copyright american geophysical union 1988

diagenesis of dissolved aluminum in organic rich estuarine sediments abstract the sedimentary geochemistry of dissolved al is complicated by a number of different reactions in this study we show that complexation by organic matter adsorption to fe oxyhydroxides and reaction with si in solution have important effects on the distribution of dissolved al in sediments in the absence of physical resuspension of sediment into overlying waters dissolved al is rapidly consumed at the sediment water interface and is subsequently released upon reduction of fe oxyhydroxides this release does not cause noticeable perturbations in dissolved al concentrations in sediments because of rapid consumption reactions which mask the true mobility of al results suggest that one of the consumption reactions may be due to formation of an fe al silicate the amount of authigenic aluminosilicate formed in estuarine sediments must be very small relative to the detrital component in the deep sea however the long residence time of fe oxyhydroxides at the sediment water interface with resulting greater accumulation of adsorbed al may explain the abundance of al in fe smectites reported from many different areas

extrusion tectonics and subduction in the eastern south caspian region since 10 ma comment hollingsworth et al 2008 1 proposed a new kinematic model for the complicated tectonic pattern in the eastern south caspian sea region our comment is focused on the ashkhabad fault and the kopeh dagh mountains examining the data and hypothesis used by the authors to support their model

recent spatial and temporal changes in the stress regime along the southern tunisian atlas front and the gulf of gabes new insights from fault kinematics analysis and seismic profiles tectonic deformations in the southern atlassic front of tunisia saft and the gulf of gabes result from the nubia eurasia convergence this study based on the inversion of geologically determined fault slip vectors presents evidences for spatial and temporal changes in the stress state fault kinematics analyses reveal a temporal change in states of stress during the late cenozoic a paleostress miocene pliocene state is characterized by a regional compressional tectonic regime with a mean n134 09 e trending horizontal maximum stress axis 1 a modern quaternary to present day state of stress also corresponds to compressional tectonic regime with a regionally mean n05 10 e trending horizontal 1 the saft corresponds to two distinct domains a far foreland atlassic front related to contractional deformation associated with southward propagate thrusting and eastward the gulf of gabes characterized by normal component nw to wnw trending faults at the crustal margin scale probably related with a transtensional tectonic regime we propose that the spatial and temporal changes in the stress during the miocene pliocene and quaternary may result from the geodynamic evolution of the tunisian atlas in relation to the rotation of corsica sardinia blocks and the separation of the sicilian continental lithosphere from the ionian oceanic lithosphere these temporal and spatial stress changes along the saft and the gulf of gabes are probably the engine behind the moderate seismicity leading at the same time to a reactivation of the inherited major structures created during the evolution of the southern tethyan margin

extrusion tectonics and subduction in the eastern south caspian region since 10 ma reply we examine active deformation of the region surrounding the eastern south caspian sea using a combination of seismic geological geodetic and geomorphological data global positioning system gps velocities indicate a westward component of motion of the south caspian basin relative to eurasia and central iran we identify major zones of shear the ashkabad and shahrud fault zones that accommodate this westward extrusion on either side of the south caspian block estimates of total strike slip motion could at present day slip rates derived from gps observations be achieved in 10 m y therefore the northwest extrusion of the south caspian region which is accommodated by subduction beneath the north caspian region stable eurasia along the apsheron balkan sill may also date from that time this suggests that the onset of subduction may be older than previous estimates ranging from 1 8 to 5 5 ma our results are summarized in a new kinematic model that significantly clarifies the active tectonics of this complicated region

dissolved al in sediments and waters of the east china sea implications for authigenic mineral formation abstract numerous previous studies indicate that several different authigenic aluminosilicates form in the oceans in this study we show using dissolved al distributions in sediments and waters from the nearshore regions of the east china sea that the process of aluminosilicate formation probably begins rapidly upon contact of detrital clays with seawater statistical analyses of dissolved al si h relations in surface sediments indicate that the minerals forming in east china sea sediments low in dissolved fe are dioctahedral chlorites with an average composition ex 0 91 mg 0 77 al 5 0 si 2 7 o 10 oh 8 where ex exchangeable 1 cation this composition is also consistent with dissolved al and si measurements as a function of salinity in turbid overlying waters results suggest a dissolution reprecipitation mechanism for clay mineral reconstitution this mechanism can help to explain why different authigenic clays are found in different areas of the oceans in the east china sea the total amount of authigenic clays present must constitute a very minor fraction of the bottom sediments thus the formation of these minerals has a relatively small impact upon dissolved si distributions clay mineral reconstitution in nearshore regions may provide a mechanism for buffering sediments and overlying waters with respect to ph as the composition of minerals formed should be a direct function of the h activity in the surrounding environment

dissolved aluminium in the tamar estuary southwest england abstract distributions of dissolved al in the tamar estuary have been recorded through spring neap tidal cycles in winter and summer dissolved al is a highly reactive constituent in this estuary undergoing net removal in the very low salinity region and net input to the mid estuary the extent of both the depletion and the augmentation varied systematically with tidal energy input indicating that tidal sediment disturbance was the principal controlling agency these field data supported by the results of laboratory simulations show that the removal is regulated by sorption onto resuspended sediment particles which dominates kinetically over authigenic aluminosilicate formation removal of dissolved al by flocculation of riverborne colloids is not significant the mid estuarine input is consistent with dissolution of authigenic aluminosilicate following net remobilization of estuarine sediment the internal cycling of al in the estuary generated by these processes alters both the time course and the soluble particulate balance of the riverine discharge of al to the adjacent coastal water

dissolved aluminium in the mediterranean abstract three vertical profiles of dissolved al and nutrients are reported from the eastern basin of the mediterranean profiles of al concentrations resemble those of the nutrient elements except that a proportionally higher residual concentration remains in the surface layer concentrations of al in the surface water inflow from the north atlantic which contains between 10 and 20 nm around gibraltar are elevated to 55 59 and 75 nm at the stations occupied calculations indicate that these concentrations are probably produced by dissolution al from aeolian dust and advective mixing of al rich deep waters into the surface layer balanced by a biologically associated removal process the al removed from the surface layer redissolves in the deep water to raise al concentrations to about 160 nm samples were also recovered from anoxic deep brines in the tyro and bannock basins in the brines al concentrations fall to about 15 nm while si concentrations approach 270 nm

distribution of aluminium in waters of the north east atlantic 25 n to 35 n abstract dissolved al concentrations from the ne atlantic between 25 n and 35 n off the coast of nw africa range from 16 nm to 32 nm in a well mixed surface layer extending to 150 m depth increasing towards the maximum of the saharan dust plume mediterranean outflow water is detected as a high al anomaly corresponding to the salinity signal of the mediterranean water other than in surface and mediterranean waters al concentrations are invariant with depth but increase from 6 nm to 11 nm towards the continental margin the magnitude of the dissolved al signal in the surface layer is compatible with dissolution of al from the highest of present estimates of dust input to this area comparison with data from other areas indicates that al cannot be cycled through the oceans in parallel to silica as has been previously suggested

aluminium in the northwest atlantic abstract a series of profiles between woods hole and bermuda has been measured on board ship for al the extrema in the upper waters can be explained by the accumulation of aeolian inputs in the thin summer mixed layer the depletion of the underlying winter water by scavenging during the spring bloom and the enrichment of the subtropical mode 18 c water by aeolian accumulation during winter and local convection before the spring bloom the pronounced minimum at mid depth is associated with the antarctic intermediate water and the underlying labrador sea med water complex presumably the aaiw and the med water are depleted by the ageing effect on this short residence time element during their transit to the area the lsw is formed from surface waters containing a large component of arctic waters extremely depleted in al advected south in the east greenland current the linear increase to the bottom is caused by mixing of enriched lower north atlantic deep water with the depleted bottom water and lsw cores the enrichment in the deep water appears to be produced by the entrainment of high al waters from the north european shelf by the gyre in the norwegian greenland sea and its injection into the denmark straits overflow waters in a manner recently described for the radiocaesium releases from the windscale reprocessing plant on the irish sea an additional contribution probably comes from the shelf north of iceland

plio quaternary stress states in ne iran kopeh dagh and allah dagh binalud mountain ranges abstract ne iran including the kopeh dagh and allah dagh binalud deformation domains comprises the northeastern boundary of the arabia eurasia collision zone this study focuses on the evolution of the plio quaternary tectonic regimes of northeast iran we present evidence for drastic temporal changes in the stress state by inversion of both geologically and seismically determined fault slip vectors the inversions of fault kinematics data reveal distinct temporal changes in states of stress during the plio quaternary since 5 ma the paleostress state is characterized by a regional transpressional tectonic regime with a mean n140 10 e trending horizontal maximum stress axis 1 the youngest modern state of stress shows two distinct strike slip and compressional tectonic regimes with a regional mean of n030 15 e trending horizontal 1 the change from the paleostress to modern stress states has occurred through an intermediate stress field characterized by a mean regional n trending 1 the inversion analysis of earthquake focal mechanisms reveals a homogeneous transpressional tectonic regime with a regional n023 5 e trending 1 the modern stress state deduced from the youngest fault kinematics data is in close agreement with the present day stress state given by the inversions of earthquake focal mechanisms according to our data and the deduced results in northeast iran the arabia eurasia convergence is taken up by strike slip faulting along ne trending left lateral and nnw trending right lateral faults as well as reverse to oblique slip reverse faulting along nw trending faults such a structural assemblage is involved in a mechanically compatible and homogeneous modern stress field this implies that no strain and or stress partitioning or systematic block rotations have occurred in the kopeh dagh and allah dagh binalud deformation domains the plio quaternary stress changes documented in this paper call into question the extrapolation of the present day seismic and gps derived deformation rates over geological time intervals encompassing tens of millions of years

oceanographic distributions of zinc cadmium copper and aluminium in waters of the central arctic vertical profiles are presented of dissolved cadmium zinc copper and aluminium at the lorex 79 site in the central arctic ocean cd zn and cu show unusually high surface concentrations of 0 3 3 and 5 nmoll 1 respectively these levels are related to contributions from surface run off and from the underlying nutrient rich bering sea winter water al has lower surface concentrations than observed elsewhere and shows no correlation with the nutrients the importance of aeolian supply is questioned and the results point to a major role for inorganic removal of al at least in the arctic ocean

dominance of terrigenous particulate organic carbon in the high turbidity shuangtaizihe estuary suspended sediment samples were collected from the high turbidity shuangtaizihe estuary to analyze particulate organic carbon poc and stable carbon isotope composition 13c of organic materials the poc values of the shuangtaizihe estuary are relatively low 1 2 1 4 but remain stable over the whole salinity range sampled which suggests the predominance of a terrigenous source over the mass transport of organic materials in the estuary the 13c values of particulate organic materials 25 0 to 23 5 are heavy compared to detritus of higher plants e g tree leaves but similar to other chinese rivers the compositional characteristics of poc and 13c indicate a large and isotopically constant material source from the organic matter reservoir of soils over the drainage basin

plio quaternary tectonic regime changes in the transition zone between alborz and kopeh dagh mountain ranges ne iran abstract this paper is concerned with the changes in the plio quaternary stress states in ne iran and provides evidence for regional active deformation across a wide transition zone between the alborz and kopeh dagh mountains the arabia eurasia convergence is involved in the strike slip faulting along ne trending left lateral faults in the eastern alborz as well as nw trending right lateral faults in the western kopeh dagh the inversion result of fault kinematic data slip vector measurement of fault plane and focal mechanisms strongly indicates an active transpressional tectonic regime in the study area we provide evidence for drastic temporal changes in the stress state during the plio quaternary based on the inversions of fault kinematic data a regional transpressional tectonic regime with a mean n036 20 e trending horizontal 1 is representative for the modern stress state the older state reveals compressional to transpressional tectonic regimes comprising a n135 20 e trending horizontal 1 the modern transpressional tectonic regime characterized by a regional ne trending 1 is consistent with the inversion of earthquake focal mechanisms that yield a n47 e trending 1 for the present day stress state the kinematic results are significantly homogeneous and mechanically compatible with the active geological structures in the way that reverse and strike slip faulting are coherent with a single 1 direction

geochemistry of trace metals from chinese river estuary systems an overview abstract based on the data from extensive estuarine studies over 10 years 1983 93 the present work provides an overview of the geochemical features of large chinese river estuary systems elevated concentrations of major elements are observed in chinese rivers from north to south which is attributed to intense weathering and erosion over the drainage basins trace metal levels in chinese rivers are relatively low and similar to those from large and less disturbed world aquatic systems e g amazon and orinoco in the estuaries particulate elements show stable distributions in the mixing zone especially when absolute concentrations are normalized to aluminium and or scandium dissolved trace metals may have either conservative and or active non conservative distributions or both in chinese estuaries wherever non conservative distributions are observed trace elements may be remobilized and or scavenged from solution depending upon river discharge sedimentary dynamics and element biological uptake and regeneration of trace metals becomes more important in high salinity areas further offshore the riverine effluent plumes than inside correlation of heavy metals with grain size and operational chemical forms reveals a high proportion of elements associated with the fine size fraction compared to total sediments and elevated labile fractions in bottom sediments in anthropogenically disturbed systems finally an estimate is made towards the chemical flux of trace metals to the ocean through chinese estuaries

global positioning system constraints on the active tectonics of ne iran and the south caspian region article history we present a velocity field compiled from a network of 27 permanent and 20 campaign gps stations across ne iran this new gps velocity field helps to investigate how arabia eurasia collision deformation is accommodated at the northern boundary of the deforming zone the present day northward motion decreases eastward from 11 mm yr at tehran 52 e to 1 5 mm yr at mashhad 60 e n s shortening across the kopeh dagh binalud and koh e sorkh ranges sums to 4 5 0 5m m yr at longitude 59 e the available gps velocities allow us to describe the rigid body rotation of the south caspian about an euler pole that is located further away than previously thought we suggest that two new stations mavt and mar2 which are sited far from the block boundaries are most likely to indicate the full motion of the south caspian basin these stations suggest that nw motion is accommodated by right lateral slip on the ashkabad fault at a rate of up to 7 mm yr and by up to 4 6 mm yr of summed left lateral slip across the shahroud left lateral strike slip system our new gps results are important for assessing seismic hazard in ne iran which contains numerous large population centers and possesses an abundant historical earthquake record our results suggest that the fault zones along the eastern alborz and western kopeh dagh may accommodate slip at much faster rates than previously thought fully assessing the role of these faults and the hazard that they represent requires independent verification of their slip rates through additional gps measurements and geological fieldwork

observations of grain size sensitive power law creep of olivine aggregates over a large range of lattice preferred orientation strength grain size sensitive gss power law creep of san carlos olivine aggregates was investigated by comparing strain rates measured in laboratory deformation experiments to strain rates determined from a micromechanical model of intragranular dislocation processes the plastic flow behavior of olivine aggregates due solely to intragranular slip was determined using flow laws for olivine single crystals in combination with grain orientations measured by electron backscatter diffraction measured strain rates were compared to results from the micromechanical model for samples deformed in compression to an axial strain of 0 2 and in torsion to a shear strain of up to 7 4 olivine aggregates deform up to a factor of 4 6 times faster than the maximum possible rates determined from the micromechanical model of intragranular slip comparison of our data to published flow laws indicates that diffusion creep cannot account for this difference the ratio of experimentally determined strain rates to those from the micromechanical model is strongly dependent upon grain size but is independent of stress and strength of lattice preferred orientation these observations indicate that gss power law creep consistent with dislocation accommodated grain boundary sliding occurs in both weakly and strongly textured olivine aggregates at the studied conditions

dissolved aluminum in four chinese estuaries evidence of biogeochemical uncoupling of al with nutrients abstract four chinese estuaries the jiaojiang luanhe shuangtaizihe and yalujiang were investigated to determine al geochemistry and inter relations between al and nutrients these estuaries are characterised by low particulate organic carbon and high turbidity with various tidal regimes dissolved al was determined by fluorescence method after liquid liquid extraction into n hexanol concentrations of al in the luanhe estuary are relatively high 1 5 2 0 m and approximately uniform over the salinity range sampled suggesting the influence of in situ sources processes in the shuangtaizihe estuary riverine concentrations of al 1 8 2 2 m decrease with higher chlorinity indicating the predominance of simple dilution by seawater the jiaojiang and yalujiang provide evidence that al is removed from water column at early stages of estuarine mixing owing to probably the particle solution reactions e g flocculation in the estuary the al data are further compared with total suspended matter and nutrients in these estuaries the data sets indicate that aluminum is not dominantly coupled to the cycle of nutrients

quaternary slip rates along the northeastern boundary of the arabia eurasia collision zone kopeh dagh mountains northeast iran summary the kopeh dagh is accommodating a large portion of the northward motion of central iran with respect to eurasia involving a major right lateral strike slip fault system bakharden quchan this fault system corresponds to the northeastern boundary of the arabia eurasia collision and can be considered as a lithospheric scale tectonic feature we present a wellconstrained estimation of late quaternary slip rates along two major strike slip faults the baghan and quchan faults in this fault system using in situ produced 36 cl nuclide to date two offset alluvial fan surfaces combining detailed satellite image and digital topographic data analyses complemented with geomorphic fieldwork allows quantifying the cumulative offset values of 940 100 and 360 50 m of the fan surfaces along the baghan and quchan faults respectively a total of 12 carbonate boulders from the fan surfaces were collected and dated this yields minimum age of two episodes of fan abandonment at 280 16 baghan fault and 83 4 ka quchan fault age estimates and measured offsets of the fans are consistent with respective maximum long term fault slip rates of 2 8 1 0 and 4 3 0 6 mm yr 1 for the baghan and quchan faults over the middle late pleistocene applying the slip rates to cumulative post folding offsets along the baghan and quchan faults indicates that strike slip motion within the kopeh dagh may have started 4 ma this constrains the timing of a major tectonic reorganization in the kopeh dagh previously recorded through arabia eurasia collision between 3 and 7 ma at the regional scale the sum of total cumulative strike slip offsets is about 35 40 km which implies a total maximum slip rate of about 9 2m m yr 1 in the central eastern kopeh dagh this is resolved to average northward and westward slip rates of 8 and 4m m yr 1 respectively for the western kopeh dagh with respect to eurasia our results also suggests that the localized strike slip faulting in the central kopeh dagh can be considered as an intercontinental movement between northeast iran and eurasia accommodating about 80 per cent of northward motion of central iran with respect to eurasia