hydrogeochemical conditions and evolution at the aspo hrl sweden abstract the overall hydrogeochemical conditions at and in the near vicinity of the underground experimental aspo hard rock laboratory hrl in se sweden have been investigated groundwater data from more than 400 samples have been compiled and evaluated the groundwater samples represent depths down to 1700 m below sea level and sampling has been performed prior to and during the hrl tunnel excavation episodic events have to a great extent influenced the hydrochemical evolution since the last glaciation which ended some 13 ka ago at that time glacial melt water was flushed under hydraulic pressure down into the fracture system to a depth of at least several hundred metres the next episodic event took place when the baltic freshwater lake transformed into the brackish litorina sea some 7 ka ago at this time aspo was covered by the sea and these denser more saline waters partly replaced the glacial water down to a depth where the density equilibrated with the replacement sea water at some time around 3 4 ka ago aspo started to rise above sea level and meteoric water began to infiltrate the rock the overall trend of increasing salinity with depth may easily be misinterpreted as a fairly simple groundwater system evolving from a two component evolution path between non saline and saline groundwaters however when combining the results from environmental isotopes and the chemical parameters using a new modelling tool named m3 multivariate mixing and mass balance calculations a higher resolution was obtained and a more complex groundwater pattern which reflects the present and paleo hydrogeological events can be recognised the measured groundwater composition was modelled to be a mixture of meteoric past and present baltic seawater glacial or cold climate recharge and brine type of waters the modelling result shows that the processes considered to have a dominating impact on the present aspo groundwater chemistry are mixing both in disturbed and undisturbed systems calcite dissolution and precipitation redox reactions and biological processes the undisturbed groundwater conditions prior to the hrl tunnel construction at aspo consisted of 1 a dominating proportion of meteoric fresh water in the upper 250 m of the aquifer 2 a brackish saline water consisting of mixing proportions of present and ancient baltic sea water and glacial melt water present to a depth of 250 600 m 3 saline water still containing proportions of glacial water which could represent even older glaciations and brines a large portion of which have been stagnant for perhaps millions of years below a depth of 600 m during the hrl tunnel construction there were changes in the composition of the water flowing into the tunnel at different locations although the variation in salinity was relatively small the variations in the mixing proportions of the different water types were substantial

modelling of the evolution of ground waters in a granite system at low temperature the stripa ground waters sweden abstract from chemical data collected by nordstrom and his colleagues on stripa ground waterswe have tried to model the evolution of the chemical composition of a ground water in a granitic system at low temperature the existence of two end member ground water compositions made it possible first to test the conventional model of a geothermal system according to which an overall equilibrium between the waters and a given mineral assemblage can be defined and then to show that such a model could be extended to low temperatures 10 c conversely if we know the mineral assemblage the equilibration temperature and the charge of the mobile ions in this case cl the composition of the solution is entirely fixed in our model of the stripa ground waters the existence of two end member ground water compositions can be explained by an evolution from a kaolinite albite laumontite equilibrium to a prehnite albite laumontite equilibium the latter requiring less al than the former we have also emphasized the importance of the cl ion concentrions ofof the ground waters because they cab be considered as indicators of the degree of reaction progress between rock and water thus determining the degree of equilibration of the system

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

tonalite granodiorite suites as cotectic systems a review of experimental studies with applications to granitoid petrogenesis abstract granodiorites and tonalites granotonalites in this review paper form large batholiths at active continental margins and collisional orogens although the relation with subduction is obvious the mechanisms of magma generation remain among the most debated topics in earth sciences today the most outstanding features of these calc alkaline batholiths are summarized in this review the problem has been addressed by laboratory experiments along decades dispersed data from experimental studies are compiled here in order to give phase equilibria constraints of general application it is apparent from chemical data that major element compositional trends follow cotectic patterns whose composition is largely dependent on intensive variables the comparison between experiments and batholith chemical trends produces an empirical thermodynamic framework useful to understand in a first approach the origin and evolution of magmas forming granite batholiths a new projection scheme of rock compositions onto the pseudoternary plane defined by the fe mg anorthite orthoclase is given this can be taken as first approach to phase equilibria model of batholiths it has been revealed useful to distinguish processes controlled by increasing melting or decreasing crystallization magma temperature from processes controlled by assimilation or magma mixing the available experimental data although scarce can be used to tentatively depict phase equilibria in the projected pseudoternary f an or diagram although important limitations are imposed by the projective procedure phase equilibria relations in equilibrium with liquids can be drafted in the diagram the stability fields of mineral in areas close to the liquid are defined according to reported phase assemblages in the experimental studies of reference the diagram is robust to identify cotectic and non cotectic relations phase equilibrium constraints and rock textures have revealed that one of the most important parameter controlling phase equilibria in granite magmas is the initial water content typically calc alkaline granitoids from qtz diorite to granotonalite and granite have crystallized from strongly undersaturated water magmas low initial water contents w i in the range 1 2 wt h 2 o may account for residual saturated melt fractions as low as 0 1 0 2 for plutons emplaced at 400 mpa the water content of these residual melt fractions is enough to stabilize hydrous minerals namely hbl and bt as predicted by experiments the initial water content is a primary feature of the magma and it is directly related to the melting reaction and more precisely to the temperature of magma generation the study of compositional trends supports magma fractionation by crystal liquid separation as a relevant role as a first approach the pressure composition relations in the melts can be seen as a response to the composition of the solid saturating assemblage and particularly related to the ratio grt pl in the solid residue

tracing the cambro ordovician ferrosilicic to calc alkaline magmatic association in iberia by in situ u pb shrimp zircon geochronology gredos massif spanish central system batholith abstract u pb geochronological study of zircons from nodular granites and qtz diorites comprising part of variscan high grade metamorphic complexes in gredos massif spanish central system batholith points out the significant presence of cambro ordovician protoliths among the variscan migmatitic rocks that host the late carboniferous intrusive granitoids indeed the studied zone was affected by two contrasted tectono magmatic episodes carboniferous variscan and cambro ordovician three main characteristics denote a close relation between the cambro ordovician protholiths of the prado de las pozas high grade metamorphic complex strongly reworked during the variscan orogeny and other cambro ordovician igneous domains in the central iberian zone of the iberian massif 1 geochemical features show the ferrosilicic signature of nodular granites they plot very close to the average analysis of the metavolcanic rocks of the ollo de sapo formation iberia qtz diorites present typical calc alkaline signatures and are geochemically similar to intermediate cordilleran granitoids 2 both qtz diorite and nodular granite samples yield a significant population of cambro ordovician ages ranging between 483 and 473 ma and between 487 and 457 ma respectively besides 3 the abundance of zircon inheritance observed on nodular granites matches the significant component of inheritance reported on cambro ordovician metagranites and metavolcanic rocks of central and nw iberia the spatial and temporal coincidence of both peraluminous and intermediate granitoids and specifically in nodular granites and qtz diorite enclaves of the prado de las pozas high grade complex is conducive to a common petrogenetic context for the formation of both magmatic types tectonic and geochemical characteristics describe the activity of a cambro ordovician arc back arc tectonic setting associated with the subduction of the iapetus tornquist ocean and the birth of the rheic ocean the extensional setting is favorable for the generation emplacement and fast rise of subduction related cold diapirs supported by the presence of typical calc alkaline cordilleran granitoids contemporary with ferrosilicic volcanism

structural pattern and ascent model in the central extremadura batholith hercynian belt spain abstract the central extremadura batholith constitutes an important alignment of plutonic rocks occupying part of the internal zones of the iberian hercynian belt it comprises 13 plutons and numerous minor intrusions and covers a wide compositional range from quartz diorites to alkali feldspar granites structural study of the individual plutons reveals that their internal structural patterns may be correlated correlation between the different structural patterns in the plutons and interpretation of the superimposed deformation in the metasedimentary host rocks indicate that the plutons were emplaced and deformed in an e w dextral intracontinental shear zone developed during the second deformation phase 302 320 ma a qualitative ascent model has been established as follows 1 development of extensional fractures at 45 to the e w dextral shear zone 2 intrusion of granitic magmas along these fractures and 3 rotation of the earlier intrusions in a dextral sense inducing antithetic shear zones n s sinistral and a transverse shortening perpendicular to the major axis of the earlier deformed plutons as well as the forced emplacement of the later plutons

linking granulites silicic magmatism and crustal growth in arcs ion microprobe zircon u pb ages from the hidaka metamorphic belt japan there is no consensus as to how the extreme metamorphic conditions required to form granulites are attained or how these rocks relate to crustal growth and differentiation processes studying young granulites offers two advantages the tectonic setting is likely to be well constrained and the ambiguities that result from overprinting by younger metamorphic events are potentially avoided we report the first ion microprobe u pb zircon ages for orthopyroxene bearing granulites tonalites and gabbros of the cenozoic hidaka metamorphic belt hokkaido japan to clarify the magmatic metamorphic connection in this area the data support a two stage evolution for this terrane which is attributed to episodes of supra subduction zone magmatism late eocene and back arc extension early miocene we relate granulite facies metamorphism and garnet orthopyroxene tonalite generation to mafic magma under accretion and lithosphere thinning due to the opening of the japan sea at 19 ma the hidaka granulites are thus among the youngest exposed granulites on earth and manifest the thermal response to continental growth

hydrological factors in the interpretation of stable isotopic proxy data present and past a european perspective in the context of this paper stable isotopic proxies are those preserving directly or via known or calculable fractionation factors a record of 18o 16o and or 2h 1h in the water which contributed to their growth suitable proxies include amongst others tree ring cellulose bone phosphate lake sediment minerals and speleothem fluid inclusions a principal aim of studying isotopic proxies is to gain more information about past climates through a knowledge of how rainfall isotope compositions have changed over time however converting back from proxy to rainfall is not necessarily straightforward because however well the isotopic fractionation due to proxy growth or formation is understood a variety of modifying processes may have intervened between this and the actual rainfall events three main reservoirs of environmental water may contribute to the isotopic compositions of terrestrial proxy indicators surface waters soil moisture and groundwater each of these can in principle be isotopically modified compared to rainfall in the locality this review examines these effects and how they may change under different european climate types at the present day it is concluded that while groundwater isotopic compositions typically represent closely the bulk composition of rainfall under a variety of climatic regimes soil and particularly lake waters require detailed study if their isotope systematics are to be adequately understood the review also finds that to a large extent the present is the key to the past in terms of recharge processes during the late pleistocene though glaciation may have had profound isotopic consequences in certain areas while a more general aridity led to the apparent absence of recharge in most areas for much of the late devensian

igneous garnet and amphibole fractionation in the roots of island arcs experimental constraints on andesitic liquids to evaluate the role of garnet and amphibole fractionation at conditions relevant for the crystallization of magmas in the roots of island arcs a series of experiments were performed on a synthetic andesite at conditions ranging from 0 8 to 1 2 gpa 800 1 000 c and variable h2o contents at water undersaturated conditions and fo2 established around qfm garnet has a wide stability field at 1 2 gpa garnet amphibole are the high temperature liquidus phases followed by plagioclase at lower temperature clinopyroxene reaches its maximal stability at h2o contents 9 wt at 950 c and is replaced by amphibole at lower temperature the slopes of the plagioclase in boundaries are moderately negative in text t text x text h 2 text o space at 0 8 gpa garnet is stable at magmatic h2o contents exceeding 8 wt and is replaced by spinel at decreasing dissolved h2o the liquids formed by crystallization evolve through continuous silica increase from andesite to dacite and rhyolite for the 1 2 gpa series but show substantial enrichment in feo mgo for the 0 8 gpa series related to the contrasting roles of garnet and amphibole in fractionating fe mg in derivative liquids our experiments indicate that the stability of igneous garnet increases with increasing dissolved h2o in silicate liquids and is thus likely to affect trace element compositions of h2o rich derivative arc volcanic rocks by fractionation garnet controlled trace element ratios cannot be used as a proxy for slab melting or dehydration melting in the deep arc garnet fractionation either in the deep crust via formation of garnet gabbros or in the upper mantle via formation of garnet pyroxenites remains an important alternative despite the rare occurrence of magmatic garnet in volcanic rocks

groundwater chemistry and water rock interactions at stripa groundwaters from near surface to a depth of 1232 m in the stripa granite have been sampled and analyzed for major and trace constituents the groundwater composition consists of two general types a typical recharge water of ca hco3 type 700 m depth of high ph 8 10 that reaches a maximum of 1250 mg l in total dissolved solids tds intermediate depths show mixtures of the two types that are highly fracture dependent rather than depth dependent any borehole can vary significantly and erratically in tds for either a horizontal or vertical direction the general transition from ca hco3 type to na ca cl type correlates with the depth profile for hydraulic conductivity that drops from 10 8 m s to 10 11 m s or lower thermomechanical stress from heater experiments clearly shows an effect on the groundwater composition that could be caused by changing flow paths leakage of fluid inclusions or both dissolution and precipitation of calcite fluorite and barite aluminosilicate hydrolysis and addition of a saline source possibly fluid inclusion leakage play the major roles in defining the groundwater composition the low permeability of the stripa granite has produced a groundwater composition that appears intermediate between the dilute shallow groundwaters typical of recharge in a crystalline rock terrain and the saline waters and brines typical of cratonic shield areas at depth

atypical peri gondwanan granodiorite tonalite magmatism from southern iberia origin of magmas and implications abstract an ensemble of fifteen granodiorite tonalite plutons and minor intrusions was generated during cambro ordovician times ca 498 462 ma at the margin of gondwana which occupies a large portion of the central iberian zone of the iberian massif spain and portugal this ensemble is known as the beira extremadura batholith beb which is mainly composed of tonalities and granodiorites 90 vol and shows an atypical composition with values of asi alumina saturation index 1 2 on average and marked calc alkaline affinity in terms of major and trace elements shrimp zircon u pb ages of 476 7 ma 476 6 ma and 474 7 ma for montanchez santa cruz de la sierra and valdemorales tonalites respectively coincide within uncertainty with the age of other lower ordovician beb intrusions analysis of phase relations and comparisons with experimental results on cotectic liquid compositions indicate that these atypical rocks represent calc alkaline magmas that carried exogenous pelitic restites from depth assimilation of partially molten metasediments by invasion of calc alkaline magmas is a plausible explanation model mixing of experimental calc alkaline liquids and ediacaran metasedimentary rocks yields that 20 up to 40 in samples of the santa cruz pluton of assimilated metagreywackes and metapelites is required to account for geochemical atypical compositions departing from a main cotectic array of calc alkaline systems the processes of melting or melting plus assimilation are favored by addition of water rich fluids we propose a tectonic scenario of crustal extension and metasomatized mantle melting that supplied hydrous intermediate magmas to the crust triggering crustal melting and massive assimilation of metasediments

carbon isotopes and geochemical processes in co2 rich cold mineral water n portugal this paper summarizes a new outlook on the conceptual model of melgaco messegaes co2 rich cold 18 c mineral water systems issuing in n of portugal based on their isotopic 2h 3h 13c 14c and 18o and geochemical features stable isotopes indicate the meteoric origin of these co2 rich mineral waters based on the isotopic fractionation with the altitude a recharge altitude between 513 up to 740 m a s l was estimated corroborating the tritium results the lowest 3h content 0 tu is found in the groundwater samples with the highest mineralization the mineral waters circulation are mainly related to a granitic and granodioritic environment inducing two different groundwater types ca na hco3 and na ca hco3 indicating different underground flow paths calcium dissolution is controlled by hydrolysis of rock matrix silicate minerals e g ca plagioclases and not associated to anthropogenic sources the shallow dilute groundwaters exhibit signatures of anthropogenic origins e g no3 and higher na ca ratios the stable isotopes together with the geochemistry provided no indication of mixing between the regional shallow cold dilute groundwater and mineral water systems the heavy isotopic signatures identified in the 13c data 13c 4 7 performed on the total dissolved inorganic carbon tdic of co2 rich mineral waters could be derived from a deep seated upper mantle source or associated to methanogenesis ch4 source the negligible 14c content 2 pmc determined in the tdic of the mineral waters corroborates the hypothesis of a mantle derived carbon source to the mineral groundwater systems or dissolution of carbonate layers at depth

thermal limitations on incorporation of wall rock into magma incorporation of solid wall rocks is an oft cited process in the evolution of magmas but this process is severely limited by the energy required to dissolve xenoliths disaggregation without melting has been proposed as an alternative process for incorporating xenoliths into magma because disaggregation avoids expending the energy required for melting analysis of these processes using enthalpy composition diagrams shows that both processes rapidly lead to high crystal contents in the hybrid magma for example incorporation of 25 granite at 400 c into basalt magma at 1125 c produces a hybrid magma at 1050 c with 50 crystals if the granite disaggregates without melting the crystal content is 65 70 once the crystal content reaches 50 the viscosity of the magma is too high to allow further magma movement or xenolith incorporation thus both processes are self limiting and probably restricted in natural systems to at most a few tens of percent incorporation of xenoliths

measurements of momentum and heat transfer across the air sea interface abstract this study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air sea interface and to assess the ability of rigid boundary turbulence models to predict mean vertical gradients beneath the ocean s wavy surface observations were made at 20 hz at nominal depths of 2 2 and 1 7 m in 16 m of water a new method is developed to estimate the fluxes and the length scales of dominant flux carrying eddies from cospectra at frequencies below the wave band the results are compared to independent estimates of those quantities with good agreement between the two sets of estimates the observed temperature gradients were smaller than predicted by standard rigid boundary closure models consistent with the suggestion that wave breaking and langmuir circulation increase turbulent diffusivity in the upper ocean similarly the monin obukhov stability function h was smaller in the authors measurements than the stability functions used in rig

stable isotope geochemistry of ground and surface waters associated with undisturbed massive sulfide deposits constraints on origin of waters and water rock reactions abstract stable isotopes h o c were determined for ground and surface waters collected from two relatively undisturbed massive sulfide deposits halfmile lake and restigouche in the bathurst mining camp bmc new brunswick canada additional waters from active and inactive mines in the bmc were also collected oxygen and hydrogen isotopes of surface and shallow groundwaters from both the halfmile lake and restigouche deposits are remarkably uniform 13 to 14 and 85 to 95 for 18ovsmow and 2hvsmow respectively these values are lighter than predicted for northern new brunswick and combined with elevated deuterium excess values suggest that recharge waters are dominated by winter precipitation recharged during spring melting deeper groundwaters from the restigouche deposit and from active and inactive mines have heavier 18ovsmow ratios up to 10 8 than shallow groundwaters suggesting recharge under warmer climate or mixing with shield type brines some of the co variation in cl concentrations and 18ovsmow ratios can be explained by mixing between saline and shallow recharge water end members carbon isotopic compositions of dissolved inorganic carbon dic are variable ranging from 15 to 5 13cvpdb for most ground and surface waters much of the variation in the carbon isotopes is consistent with closed system groundwater evolution involving soil zone co2 and fracture zone carbonate minerals calcite dolomite and siderite average 6 5 13cvpdb the dic of saline restigouche deposit groundwater is isotopically heavy 12 13cvpdb indicating carbon isotopic fractionation from methanogenesis via co2 reduction consistent with the lack of dissolved sulfate in these waters and the observation of ch4 degassing during sampling

turbulence measurements in the surf zone abstract velocity measurements within 1 m of the bottom in approximately 4 5 m water depth on a sand beach provide estimates of turbulent reynolds shear stress using a dual sensor technique that removes contamination by surface waves and inertial range estimates of dissipation when combined with wave measurements along a cross shore transect and nearby wind measurements the dataset provides direct estimates of the terms in simplified equations for alongshore momentum and turbulence energetics and permits examination of semiempirical relationships between bottom stress and near bottom velocity the records are dominated by three events when the measurement site was in the outer part of the surf zone near bottom turbulent shear stress is well correlated with squared correlation coefficient r2 0 63 but smaller than regression coefficient b 0 51 0 03 at 95 confidence wind stress minus cross shore gradient of wave induced radiation stress indicating that estimates of one or more of these ter

saline groundwaters in the canadian shield a first overview abstract the chemical and isotopic compositions of saline groundwaters and brines in the canadian shield are described the occurrence of such waters is very widespread not related to any specific rock type or mineralization and generally can be expected at depths below 1 km the most saline brines have salinities exceeding 200 g l 1 dissolved solids and their chemistries tend to suggest that in the past saline waters penetrated the canadian shield the original chemistry of these solutions was subsequently modified through strong rock water interactions and it appears that their final chemical compositions are independent of the original chemistries stable isotope analyses indicate that these waters are not simple evaporated seawater sedimentary basin brines hydrothermal solutions or residual ore forming fluids although any of these could be a precursor of the brines secondary isotope exchange reactions and the hydration of primary silicates accompanied by the formation of clay minerals could have modified not only the primary isotopic composition but may have also profoundly influenced the chemistries of these brines to be effective these processes would have had to occur in closed systems

assessing bulk assimilation in cordierite bearing granitoids from the central system batholith spain experimental geochemical and geochronological constraints

geochronology and geochemistry of the pola de allande granitoids northern spain their bearing on the cadomian avalonian evolution of northwest iberia the pola de allande pre variscan tonalite granodiorite plutons are located in the narcea antiform at the boundary zone between the cantabrian and west asturian leonese zones of the iberian variscan belt these granitoids were intruded into a neoproterozoic siliciclastic sedimentary sequence with subordinate volcanic intercalations and were subsequently overprinted by variscan thrust related shear deformation u pb laser ablation inductively coupled plasma mass spectrometry icp ms dating of zircons from two plutons yielded concordant ages of intrusion of 605 10 and 580 15 ma to the authors knowledge this is the first reported u pb cadomian avalonian age for igneous rocks in this section of the iberian variscan belt these intrusions are coeval with the main episode of dominantly calc alkaline magmatic activity related to cadomian avalonian subduction major and trace element composition of the granitoids is characteristic of i type high k calc alkaline granitoids generated in continental arc se

the genesis of i and s type granitoid rocks of the early ordovician oledo pluton central iberian zone central portugal abstract the early ordovician oledo pluton consists of four distinct granodioritic to granitic phase g1 g4 which intruded a cambrian schist metagraywacke complex but were themselves intruded by a late carboniferous pluton id tims u pb ages for zircon and monazite from these granitic rocks indicate emplacements within a short period of time at 479 480 ma granodiorite g1 is the most deformed rock with shear zones and deformation at the border g1 and g3 contain fine grained biotite tonalite and biotite granodiorite microgranular enclaves which are darker and richer in mafic minerals than the host granodiorites the geological mineralogical geochemical and sr nd and o isotopic data show that tonalitic and granodioritic enclaves and host g1 are of i type and were related predominantly by a fractional crystallization process least square analysis of major elements and modelling of trace elements indicate that granodioritic enclaves and host g1 could be derived from the tonalitic enclave magma by fractional crystallization of plagioclase grunerite biotite and ilmenite granodiorite g2 is of hybrid origin most variation diagrams for granodioritic enclaves and host g3 granodiorite and their biotites show linear trends modelling of major and trace elements of granodioritic enclaves indicate that they result from mixing of relatively primitive granodiorite magma with magma derived from crustal melting tonalitic enclaves correspond to globules of a more mafic relatively primitive magma granite g4 has the most pronounced crustal signature and is of s type

some thermal constraints on crustal assimilation during fractionation of hydrous mantle derived magmas with examples from central alpine batholiths following assimilation at different levels in the crust we test by heat and mass balance the extent of assimilation of crustal country rocks in different local plutonic

role of the ollo de sapo massive felsic volcanism of nw iberia in the early ordovician dynamics of northern gondwana abstract the ollo de sapo fm in the sanabria region of nw iberia consists of subvolcanic volcanic and volcano sedimentary rocks underlying and partly intercalated with early ordovician platform facies sediments granitic plutons of the same age presently transformed into orthogneisses are genetically related the metavolcanic rocks are dacites and rhyolites with potassic and peraluminous character and volcanic arc signature possibly inherited from the melting of calc alkaline crustal material in the study area the ollo de sapo fm is made up of two large superposed volcanic domes separated by a thin screen of contemporaneous metapelites and sandstones the domes underwent endogenous growth with subvolcanic phenocryst rich magma intruding and cooling under a volcanic and volcaniclastic shield the western dome tapers to the east and underlies the younger eastern dome suggesting that the whole formation consists of several volcanic edifices replacing each other along the 570 km outcrop belt of the ollo de sapo fm two new u pb protolith ages of 488 6 ma and 472 12 ma match within error the known age span for the ollo de sapo fm in iberia 495 483 ma the younger age dates an augen gneiss at the core of the eastern volcanic dome whereas the older date comes from the overlying volcanic sequence suggesting intrusion of the augen gneiss protolith into the overlying volcanic rocks an incipient rift involving necking of crustal scale boudinage a few hundred km landward of the edge but still within the wide passive margin of northern gondwana may explain the linear distribution of the ollo de sapo fm and the limited time span of massive volcanism the heat for crustal melting was probably supplied by mafic magmas intruding or underplatting the lower crust the early ordovician felsic magmatism of nw and central iberia seems to form part of a large siliceous province linked to break up and terrane dispersion of the northern gondwana realm

the last stages of the avalonian cadomian arc in nw iberian massif isotopic and igneous record for a long lived peri gondwanan magmatic arc abstract the upper allochthonous units of nw iberian massif contain an extensive cambrian magmatism c 500 ma covering felsic to mafic compositions the magmatic activity generated large massifs of granitoids and gabbros with calc alkaline and tholeiitic compositions respectively petrological and geochemical features of these massifs are characteristic of volcanic arc the plutons intruded siliciclastic sedimentary series deposited in the periphery of the west africa craton u pb hf isotopic compositions of detrital zircon in the siliciclastic host series indicate continental arc activity between c 750 ma and c 500 ma it was characterized by a large variety of isotopic sources including from very old continental input even archean to the addition of a significant amount of juvenile mafic material these isotopic sources experienced an extensive mixing that explains the composition and isotopic features ehft from 50 until 15 of the represented cambrian plutons the cambrian igneous rocks of the upper units of nw iberia are related to the latest activity of the avalonian cadomian arc from the middle cambrian arc activity in the periphery of gondwana was replaced by pronounced extension associated with the development of continental rifting which finally led to separation of the microcontinent avalonia subsequent drifting of avalonia to the north caused progressive opening one of the main paleozoic ocean the rheic ocean

reactive bulk assimilation a model for crust mantle mixing in silicic magmas bulk assimilation of small millimeters to 1 km fragments of crust driven and ultimately masked by reactions during xenolith melting and magma crystallization is an important mechanism for crust mantle mixing xenoliths containing mica or amphibole undergo dehydration melting when incorporated into a host magma yielding mainly plagioclase pyroxene fe ti oxides and hydrous melt the xenolith is physically compromised by partial melting and begins to disintegrate xenolithic melt and crystals are mixed into the host magma xenocrystic zircon is liberated at this stage the cryptic character of assimilation is greatly enhanced in any hydrous magma by hydration crystallization reactions the reverse of dehydration melting all pyroxenes and oxides phenocrysts xenocrysts or crystals having a hybrid signature will be subject to these reactions producing feldspars amphiboles and micas that incorporate material from several sources a particularly effective mixing mechanism implicit in the model is a reduced energy penalty for bulk assimilation much of the assimilant remains in solid form compared to melt assimilation models a large role for bulk assimilation supports stoping as a credible mechanism for the ascent of magmas while the assimilation of low density crust and concomitant fractionation provide the isostatic impetus for ascent the wholesale incorporation and processing of crustal rocks in the magma chamber helps create the room for ascent

evaluation of the groundwaters from the stripa mine using stable chlorine isotopes groundwater samples and a rock leachate sample from the stripa mine and south central sweden have been analysed for their 37cl values results reveal that the salinity found at depth in the groundwater is most likely derived form water rock interaction the overall distribution is one of 37cl enrichment with depth and with chloride concentration this trend is comparable to other sites in the fennoscandian shield where it is believed that deep groundwaters derive their 37cl values from the local bedrock

long term observations of turbulent reynolds stresses over the inner continental shelf abstractin situ observations of turbulent momentum flux or reynolds stresses were estimated from a 10 yr acoustic doppler current profiler adcp record of inner shelf velocities at the martha s vineyard coastal observatory mvco using recently developed analysis techniques that account for wave induced biases these observations were used to examine the vertical structure of stress and turbulent mixing in the coastal ocean during tidal wave and wind driven circulation by conditionally averaging the dataset by the level of forcing or stratification present bottom intensified stresses were found during tidally driven flow having estimated eddy viscosities as high as 1 10 2 m 2 s 1 during slack water an assessment of the mean low wave low wind stress results quantified the magnitude of an unmeasured body force responsible for the mean circulation present in the absence of wind and wave forcing during weak stratification and isolated wind forcing downwind stresses matched the observed wind st

the paroo station mine supergene lead deposits western australia geological and geochemical constraints abstract the paroo station mine lead project is situated near wiluna in the central part of western australia it is located in an outlier of the paleoproterozoic earaheedy group overlying the southeast yerrida basin the total measured and indicated mineral resource is currently as at 31st of december 2014 estimated at 31 8 mt of ore at 4 4 pb the deposits are hosted by deeply weathered carbonate and clastic sediments of the paleoproterozoic yelma formation the lead only mineralisation contains only traces of sulfides and is composed of few supergene minerals predominantly cerussite and anglesite with minor pyromorphite and plumbogummite the paroo station mine demonstrates a high degree of supergene pb mobility which has resulted in almost complete destruction of primary pb distribution pattern and development of characteristic for the oxidation zones coupled depletion zone and subhorizontal enrichment blankets below the deposits are interpreted to have formed from mississippi valley type mvt stratabound relatively low grade sulfide pb zn mineralisation located within dolomites of the sweetwaters well member of the yelma formation the primary mineralisation based on modelling the pb distribution was controlled by a network of northeast northwest and meridional oriented fractures and small faults lead isotope study yielded from 1 80 to1 88 ga ages of the mineralisation based on the stacey and kramers 1975 two stage model the mineralising event is related to the capricorn orogeny this data is well in line with previous u pb dating of monazites interpreted to be related to the mineralisation 1 82 ga muhling et al 2012 high 238u 204pb values 10 26 10 58 are indicative of the archean basement contribution and or more likely with sediments originally derived from that basement the paroo station mine mineralisation is thought to be similar in style and formed synchronously with the mvt prospects in the teague area in the earaheedy basin approximately 120 km to the northeast the mineralisation at the paroo station mine was significantly upgraded through a multi stage supergene remobilisation and reprecipitation of lead in the course of long weathering history of the region lead was almost completely depleted from the upper zone and accumulated below as subhorizontal enrichment blankets at three levels from top to bottom 1 the base of the collapse quartz clay breccia unit marking the dolomite weathering front 2 the contact of siltstone and sandstone packages coincident with the feldspar kaolinite weathering front and 3 the mid to lower parts of the sandstone unit close to the base of weathering the lowest enrichment zone extends as a continuous blanket at a significant up to 500 m distance at a 1 pb cut off beyond the upper mineralisation projection this enrichment is interpreted to be formed by lateral pb transport in waters close to the groundwater table through the most permeable layers of weathered sandstones this active lateral lead dispersion is of high exploration significance for the region providing a much larger exploration target and vector to the primary mineralisation

the upper neoproterozoic lower cambrian of the central iberian zone spain chemical and isotopic sm nd evidence that the sedimentary succession records an inverted stratigraphy of its source the upper neoproterozoic lower cambrian sedimentary succession in the central iberian zone has recently been divided into 12 sedimentary units i to xii units i to iv are of late neoproterozoic age and units v to xii are early cambrian throughout the stratigraphic section shales with similar ranges of sio2 and al2o3 have tio2 and zr contents that are coupled and vary gradually from the bottom unit i tio2 1 0 1 1 zr 245 287 ppm to the top unit xii tio2 0 74 0 86 zr 141 192 ppm these two parameters clearly distinguish upper neoproterozoic from lower cambrian compositions as do certain elemental ratios al2o3 tio2 rb zr nb ti which vary from low values at the bottom of the section to high at the top however other elements the rare earth elements rees y do not fit this general trend with heavy rees and y showing extreme concentrations in some lower cambrian units which also have negative ce anomalies units i to iii and units xi to xii have uniform tdm neodymium model ages 1 1 and 1 7 ga respectively but the units between these two groups have erratic values between 1 4 ga unit vii and 3 4 ga unit viii thus the bottom and top units have neodymium isotope ratios that indicate the presence of two source compositions a composition that records a juvenile contribution younger than 1 1 ga and a composition mainly derived from an old basement some samples from lower cambrian units have disturbed ree abundances and neodymium isotope ratios that are attributed to extensive chemical alteration that resulted in ree and y redistribution this alteration probably affected the material now preserved as unit iv during a period of relative sea level fall at the end of the late neoproterozoic both elemental and isotopic results support the suggestion that the upper neoproterozoic lower cambrian stratigraphic section records an inverse stratigraphy of a source hinterland composed of a cover sequence of relatively juvenile crustal materials underlain by an older basement through time the deeper crust gradually increased its contribution to the sediments in the basin from late neoproterozoic to lower cambrian times these results are compatible with data from many other european zones

natural radioelement solution by circulating groundwaters in the stripa granite natural radioelement concentrations in groundwaters from the fracture flow regime in the stripa granite were monitored during the period 1977 1986 uranium concentrations from depths of 80 m or less and in minewaters from above the hydraulic sink produced by the deepest mining level 410 m range from 10 to 90 ppb 234u238u activity ratios are characteristic of chemical leaching processes at the shallower depths whilst at about 350 m groundwaters occur which have an additional component of 234u by alpha recoil processes at greater depths u concentrations are indicative of the changed redox conditions and are subject to activity ratio enhancement by the alpha recoil process groundwater residence times may be estimated from the rate of such recoil solution of 234u in zones where chemical leaching of u is not active the 222rn contents of the minewaters are extremely high and can be related to the 222rn flux from fracture surfaces and the fracture width the fracture apertures range from 10 mm for the shallow groundwater zone 222rn contents m for water from the deepest borehole section 222rn content 100 kbq kg 1 the activity ratios 234th238u 210pb222rn and 210po222rn have been used to estimate residence times for th pb and po isotopes solution of ra is controlled by chemical rather than alpha recoil processes the 226ra content of the groundwater increases with salinity and is well correlated with groundwater ca content the 228ra226ra activity ratios in the groundwaters suggest that water rock interaction occurs predominantly with the average granitic matrix rather than with highly uraniferous fracture mineralisation the behaviour of ra th and po isotopes may be used to assess that of homologous fission product and actinide constituents of nuclear wastes in groundwaters

spatial scales of stress carrying nearshore turbulence measurements from a horizontal array of velocity sensors indicate that the alongshore scales of turbulence contributing to the near bottom reynolds stress just seaward of the surf zone on an ocean beach range from 0 to approximately 4 times the height of the measurements above the seafloor with shorter scales during stable stratification than during neutral or unstable stratification the dependence of alongshore turbulence scales on the stratification reynolds stress and height above the bottom is consistent with semiempirical results from the atmospheric surface layer implying similar dynamics of near boundary turbulence in the atmosphere and the shallow coastal ocean

the isotope geochemistry of carbon in groundwater at stripa the carbon isotopic composition of the total dissolved inorganic carbon in groundwater associated with a granitic pluton at stripa sweden reflects both inorganic and organic carbon sources following the uptake of soil carbon dioxide calcite dissolution dominates the geochemical evolution of shallow groundwater calcite saturation is reached at a depth of about 100 m in deeper waters geochemical release of ca and increasing ph cause calcite precipitation radiocarbon contents suggest carbon and water ages in excess of 20 000 years for waters at 300 400 m depth in deep groundwaters with enhanced salinities organic carbon is added to the dissolved inorganic carbon either through bacterial activity e g sulphate reducing bacteria or the oxidation of organic compounds such as methane the lowest radiocarbon contents were measured at the 300 400 meter levels and not in the deepest fluids the distribution of 13c in the deep groundwaters suggests the existence of well defined flowsystems with limited active hydraulic interaction isotope analyses on fracture calcites substantiate the complex geochemical history of the pluton

stable isotope geochemistry of carbonate minerals in supergene oxidation zones of zn pb deposits abstract the 18 o 16 o and 13 c 12 c ratios of carbonate minerals formed by supergene oxidation of zn pb deposits and submarine alteration of ancient slags were studied in order to constrain isotope fractionation factors for smithsonite cerussite and phosgenite and to characterize conditions of nonsulfide ore formation we present new isotope data of carbonate hosted ores from the iglesiente district sardinia italy and vila ruiva portugal as well as from the silicate hosted ores of the broken hill district new south wales australia and freihung germany and review previously published isotope data the temperature dependence of oxygen isotope fractionation between pb and zn carbonate minerals and water below 240 c for cerussite and below 100 c for smithsonite and phosgenite can be expressed as 1000ln cerussite water 2 29 10 6 t 2 3 56 1000ln smithsonite water 3 10 10 6 t 2 3 50 1000ln phosgenite water 2 55 10 6 t 2 3 50 with t in kelvin the carbon isotope fractionation between smithsonite phosgenite hydrozincite and calcite is less than about 2 while cerussites are strongly depleted in 13 c by about 10 as compared to the former minerals oxygen isotope variations of individual carbonate minerals within a deposit are relatively small indicating constant formation temperatures and a single meteoric fluid source average formation temperatures of the studied deposits are calculated at 20 5 c using the estimated isotope compositions of local paleometeoric waters we observe a linear relationship between the isotope values of estimated paleometeoric waters and supergene carbonates thus base metal carbonate minerals from supergene deposits may provide paleoclimatic information the carbon isotope values are in most carbonate hosted deposits highly variable more than 10 suggesting at least two isotopically distinct carbon sources the isotopically light component can be related to oxidation of c3 plants soil derived carbon and or microbes that take active part in sulfide oxidation while the isotopically heavy component originates from carbonate carbon from wall rocks and or atmospheric carbon the 13 c enriched component is less dominant in silicate hosted deposits

identify the impacts of waves and tides to coastal suspended sediment concentration based on high frequency acoustic observations abstract high frequency measurements of wind waves tides suspended sediment concentration ssc and turbulence were made using an autonomous meteorological station and optical and acoustic instruments over 34 days during january 20 february 23 2016 in heini bay yellow sea the responses of ssc on different dynamic processes are analyzed by decomposing the velocity and ssc fluctuations into wave and turbulent components in the presence of ssc fronts the horizontal advection by the reciprocating tidal flow would cause an asymmetry of ssc in a flood ebb tidal cycle the presence of swells induced intensified sediment resuspension and a flood ebb symmetry of ssc in the bottom boundary layer the net horizontal sediment fluxes were significantly increased in the presence of strong waves significant amount of suspended sediments were taken away from the study area implying the occurrence of coastal erosion

upper neoproterozoic series in the central iberian cantabrian and west asturian leonese zones spain geochemical data and statistical results as evidence for a shared homogenised source area abstract analyses 100 of six groups of upper neoproterozoic shales from different areas in central and northern spain covering an extension of over 60 000 km2 reveal relatively uniform major and trace element abundances and values of relevant ratios such as al2o3 tio2 k2o al2o3 mol ti zr ti nb rb zr rb th sm nd eu eu la yb n la nb zr y zr nb th nb th yb th u and cr zr the six groups of shales define indistinguishable chondrite normalised and upper continental crust normalised patterns for rare earth and trace elements respectively and show relatively low fractionated geochemical features compared with those of the continental upper crust statistical calculations demonstrate a normal distribution of the abundances of major and trace elements and element ratios they suggest a remarkable geochemical homogeneity for the upper neoproterozoic series studied and they separate this series from the lower cambrian one in the central iberian zone on the basis of 15 element ratios the extension of the upper neoproterozoic detrital series and the similar geochemical features of shales in all the studied areas suggest an extensive and homogenised source region thus the mean of the 100 analyses neoproterozoic iberian average shale nibas is proposed as a standard of comparison to identify the specific recycled and homogenised source for detrital upper neoproterozoic sediments in central and northern iberia and probably also in other european peri gondwanan areas the ranges of statistically distinctive geochemical parameters separating the upper neoproterozoic from the lower cambrian series are given as possible criteria to help in the studies of areas where no other data provide conclusive information about the series ages

radiocarbon application in dating complex hot and cold co2 rich mineral water systems a review of case studies ascribed to the northern portugal abstract the use of radioactive isotopes plays a very important role in dating groundwater providing an apparent age of the systems in the framework of the aquifers conceptual modelling making available important features about the water fluxes such as recharge horizontal flow rates and discharge in this paper special emphasis has been put on isotopic constraints in the use of 13 c and 14 c content as a dating tool in some hot 76 c and cold 17 c co 2 rich mineral waters discharging in the vilarelho da raia pedras salgadas region n portugal the radiocarbon content determined in these co 2 rich mineral waters 14 c activity from 4 3 up to 9 9 pmc is incompatible with the systematic presence of 3 h from 1 7 to 7 9 tu the 13 c values of the studied co 2 rich mineral waters indicate that the total c in the recharge waters is being masked by larger quantities of co 2 14 c free introduced from deep seated upper mantle sources this paper demonstrates that a good knowledge of mineral water systems is essential to allow hydrologists to make sound conclusions on the use of c isotopic data in each particular situation

saline groundwater and brines in crystalline rocks the contributions of john andrews and jean charles fontes to the solution of a hydrogeological and geochemical problem abstract investigations into the suitability of crystalline rock for the long term containment of high level nuclear waste were initiated in the early 1970s a significant task was thereby to assess fluid movements to and from potential repositories this paper focuses on the contributions of j n andrews and j ch fontes to this problem and presents some aspects of their work on fluids in crystalline rock environments waste repository studies saw major progress with the initiation of the stripa project in 1977 andrews joined this project during the first year and participated until its closure in the late 1980s fontes involvement began during the second phase of the project after the first ideas about the geochemistry and evolution of groundwater encountered in the stripa granite had been developed the problems associated with dating of such hydrogeological systems their geochemical evolution and the question of origin of dissolved salts occupied both of them and their co workers those privileged to participate in the long and lively discussions will remember these times as extremely fruitful the results are documented in a multitude of international studies where the stripa ideas were further developed and tested not only in sweden based on the data from swedish and other environments with crystalline rock brines andrews fontes and others had recognised the need to develop at least one additional project designed to clarify major points of uncertainty regarding the age and evolution as well as the origin of saline fluids found in most crystalline rock environments the untimely death of these two applied geochemists is the reason why these discussions have not yet been concluded

reynolds stresses under wind waves this paper describes a series of wave measurements taken from an oceanographic tower concerning water particle kinematics attention is focused on the phase relationship between surface elevation and the velocity components large phase shifts with respect to the expected values are found under active wave conditions while swell behavior closely follows the linear theory the reliability of the measurements is analyzed in detail possible physical reasons for the findings are indicated in the final discussion

large scale intrusion of shallow water into a vertical fracture zone in crystalline bedrock initial hydrochemical perturbation during tunnel construction at the aspo hard rock laboratory southeastern sweden on march 13 1991 construction of the entrance tunnel to the aspo hard rock laboratory opened a vertical fracture zone at a depth of 70 m this provides an opportunity to study geochemical changes resulting from shallow water inflow into a crystalline bedrock aquifer as anticipated during construction and operation of a deep repository for spent nuclear fuel chloride ion is a natural conservative tracer for mixing between the dilute cl 10 mg l 1 shallow groundwater and the saline cl 5000 mg l 1 native groundwater of the fracture zone a sharp dilution front corresponding to 80 dilution of the native groundwater indicated arrival of shallow groundwater in the entrance tunnel after 3 weeks in spite of this large input of shallow water the fracture zone remains predominantly anoxic major element hydrochemistry and carbon and oxygen stable isotope data indicate large inputs of alkalinity and biogenic co2 g input of organic carbon with shallow groundwater provides a possible energy and carbon source for anaerobic respiration there is no evidence for sulfate reduction and fe iii oxyhydroxide fracture minerals are the only other dominant electron acceptor observed

zircon ages of the metavolcanic rocks and metagranites of the ollo de sapo domain in central spain implications for the neoproterozoic to early palaeozoic evolution of iberia dating the pre middle ordovician metavolcanic rocks and metagranites of the ollo de sapo domain has historically been difficult because of the small compositional variation the effects of the variscan orogeny and as revealed in this paper the unusually high fraction of inherited zircon components the first reliable zircon data u pb ion microprobe and pb pb stepwise evaporation indicate that the ollo de sapo volcanism spanned 495 5 ma to 483 3 ma and was followed by the intrusion of high level granites from 483 3 ma to 474 4 ma in both metavolcanic rocks and metagranites no less than 70 80 of zircon grains are either totally precambrian or contain a precambrian core overgrown by a cambro ordovician rim about 80 90 of inherited zircons are early ediacaran 602 614 ma and derived from calc alkaline intermediate to felsic igneous rocks generated at the end of the pan african arc continent collision in the villadepera region located to the west both the metagranites and metavolcanic rocks also contain meso archaean zircons 3 0 3 2 ga which ultimately originated from the west african craton in the hiendelaencina region located to the east both the metagranites and metavolcanic rocks lack meso archaean zircons but they have two different inherited zircon populations one cryogenian 650 700 ma and the other tonian 850 900 ma which suggest older than ediacaran additional island arc components the different proportion of source components and the marked variation of the 87 sr 86 sr init suggest at least tentatively that the across arc polarity of the remnants of the pan african arc of iberia trended east west with respect to the current coordinates during cambro ordovician times and that the passive margin was situated to the west

pluton accommodation at high strain rates in the upper continental crust the example of the central extremadura batholith spain abstract emplacement in the tensional bridge of a stepped dextral shear zone system is proposed for the central extremadura batholith spain the country rocks show a pervasive anisotropy that conditioned the style of the structures developed as a consequence of the transference of displacement from the stepped shear zones to the releasing area the kinematic evolution of the resulting megakink fold provided the volume increase necessary for the granite emplacement thermal and kinematic models suggest that the growth of individual plutons took place in periods of no more than several hundred to a few thousand years fast strain rates 10 10 10 11 s 1 must concentrate in local structures e g initiation of kink folds even in zones deforming as a whole under typical strain rates 10 14 1 s 1 granite plutons might be used as strain rate gauges for syn plutonic structures

deuterium oxygen 18 and tritium in stripa groundwater deuterium oxygen 18 and tritium determinations show that groundwaters in the fractures of the stripa granite are of meteoric origin not affected by secondary isotope effects evaporation or isotope exchange deep ground waters have lower 18o and 2h contents than recent shallow groundwaters the differences are most likely due to recharge during cooler climatic conditions however no age information can be derived because recharge could have occurred before the last major climatic improvement following the last deglaciation during minor climatic variations during the more recent past or could be the result of regional groundwater flow low 18o contents are paralleled by increasing salinities with highest salinities limited to a narrow fracture zone at a depth of about 800 m below ground surface most saline waters sampled appear to represent mixtures of a saline component with an isotopically depleted water and local fresh water the presence of young groundwaters is indicated by bomb produced 3h all surface boreholes contain tritium indicating residence times 35 years however tritium is also found in some boreholes drilled at the 300 m mine levels and its presence may be due to flows induced in response to heater tests low but detectable 3h contents about 0 1 to 1 tu in v2 at about 850 m below groundsurface are discussed either as subsurface production and or as a result of admixtures of small amounts of recent water to old groundwater

mechanisms for folding of high grade rocks in extensional tectonic settings abstract this review of structures developed in extensional high grade terrains combined with results of centrifuge analogue modelling illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust thickened orogen several extensional fold mechanisms such as folding within detachment shear zones are similar to those in contractional settings the metamorphic p t t path and not fold style or mode of formation is therefore required to determine the tectonic setting in which some folds developed other mechanisms such as rollover above and folding between listric normal shear zones and folding due to isostatic adjustments during crustal thinning are unique to extensional tectonic settings several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation it is shown that isoclinal recumbent folds refolded by open upright folds may develop during regional extension in the deep crust folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment or from enhanced back rotation of layers between normal shear zones during back rotation folding layers rotated into the shortening field undergo further buckle folding and all may rotate towards orthogonality to the maximum shortening direction this mechanism explains the presence of many transposed folds folds with axial planar pegmatites and folds with opposite vergence in extensional terrains examples of folds in high grade rocks interpreted as forming during regional extension included in this paper are from the grenville province of canada norwegian caledonides albany mobile belt and leeuwin complex of western australia ruby mountains in the basin and range province of nevada the at sund area of greenland the napier complex of enderby land in east antarctica and the kigluaik mountains in western alaska

geochemical and isotopic constraints on the petrogenesis of early ordovician granodiorite and variscan two mica granites from the gouveia area central portugal abstract a biotite granodiorite and seven sn bearing two mica granites crop out in the gouveia area central portugal a shrimp u th pb zircon age from the granodiorite and monazite ages from four of the two mica granites show that they are of early ordovician 480 ma and permo carboniferous i e variscan 305 and 290 ma age respectively the variscan two mica granites are late and post d3 major and trace element variation in the granitic rocks and their biotite and muscovite indicate mainly individual fractionation trends the granitic rocks are mostly depleted in hree relative to lree the biotite granodiorite is probably derived from igneous lower crust as evidenced by low initial 87 sr 86 sr 0 7036 high e nd t 2 5 and moderate 18 o 8 8 the two mica granites are probably derived by partial melting of heterogeneous mid crustal metasediments mainly metapelite and some metagraywacke as evidenced by their high initial 87 sr 86 sr 0 7076 0 7174 18 o 10 7 13 4 and major element compositions however variation diagrams for major and trace elements from two of the muscovite biotite granites and their micas define fractionation trends rb sr whole rock analyses from the two granites are perfectly fitted to a single isochron and the rocks have sub parallel ree patterns the younger granite is derived from the older by fractional crystallization of quartz plagioclase biotite and ilmenite tested by modelling major and trace elements most of the sn bearing granites are derived from distinct magma batches they result from partial melting of a heterogeneous mid crustal metasediment they do not represent a crustal anomaly in tin fractional crystallization is responsible for the increase in the sn contents of the granites and their micas muscovite has a higher sn content than coexisting biotite and is the principal host mineral for sn in these rocks

age dating of groundwater in fissured rock influence of water volume in micropores age dating of groundwater by 14c measurements is sometimes used to indicate the residence time of the water in fissured rock with a porous rock matrix the flow is in the fissures the water filled pores of the rock may however be accessed by the tracer by diffusion the residence time for a tracer can then be longer than the flow time model calculations were performed using data for granitic rock for flow in large fissures 1 mm the 14c age is 10 70 times larger than the water residence time for small fissures 0 01 mm the 14c age may be more than 1000 times larger

exotic stable isotope compositions of saline waters and brines from the crystalline basement the overwhelming majority of groundwaters reported in literature show isotopic compositions that place them on or right of the meteoric water line mwl in a 2h vs 18o diagram a closer look to the steadily increasing data from the deeper crystalline basement reveals nevertheless that points left of the mwl are not so unusual as has been suggested during the last decades their supposed rareness seems to be due to a bias of sampling the concerned fluids develop only at greater depths and in low permeability environments which makes access to them so difficult paradoxically exotic stable isotope compositions may be the rule in a restricted depth zone in all crystalline basements with slow groundwater movements but not too high temperatures the present study takes stable isotope data on saline fluids from the deep french granitic basement as a starting point in order to situate the french data from the vienne region in a more general context a literature review has been undertaken assembling more than 1300 stable isotope analyses of waters and brines in crystalline rocks from stable cratons and mountain belts world wide the french fluids show some particular features with respect to the majority of other studies as their major ion composition close to seawater or a significant isotopic shift at relatively low salinities detailed knowledge on the hydrological and chemical history of the site allowed to develop a conceptual model of isotopic evolution by interaction of fracture fluids with fracture minerals this model considers interactions of the last fluids flushing the system marine water unaltered evaporated or diluted with previously precipitated mineral phases and the neoformation of the last generation of fracture minerals the model has been tested quantitatively for several combinations of dissolution precipitation reactions involving formation of carbonates clay minerals and fe hydroxides most of the modelled scenarios would leave the residual liquid phase depleted in 18o and either enriched or depleted in 2h and produce waters with isotopic signatures corresponding to the observed 2h vs 18o correlation it is therefore suggested that the general phenomenon of an isotopic shift in deep fissured silicate rocks which seems to be rather independent of lithology may result from a combination of different reaction mechanisms implying not solely the rock matrix but also the different generations of fracture minerals

anatexis of interlayered amphibolite and pelite at 10 kbar effect of diffusion of major components on phase relations and melt fraction we have conducted h2o undersaturated melting experiments on charges consisting of a layer of a sillimanite bearing metapelite and a layer of garnet bearing amphibolite with the goal of studying how layered metamorphic rocks interact during anatexis experiments with the layered charges were performed at 10 kbar 1 gpa at 900 c 334 h 925 c 341 h and 950 c 50 161 332 h dehydration melting of the amphibolite alone and of the pelite alone were studied at the same p t conditions when run alone at 900 c the pelite and the amphibolite yielded ca 40 vol and 15 vol melt respectively corresponding melt fractions at 950 c were ca 50 vol and 30 vol when run side by side melt abundance in the pelite is fairly uniform and ca 20 vol higher than in the solo runs at all temperatures studied in contrast complex zoning patterns parallel to the interface develop in the amphibolite layer far from the interface the melt fraction is 5 10 vol lower than in the amphibolite solo runs closer to the interface the melt fraction in the amphibolite layers are comparable to or somewhat higher than in the amphibolite solo runs and both clinopyroxene and plagioclase react out and are replaced by orthopyroxene and quartz melt fraction closest to the interface reaches 65 70 vol and the only crystalline phase present is garnet with hollow cores the increase in melt fraction in the pelite layers of the layered runs is caused by transfer of na from the amphibolite to the pelite which forces biotite to be eliminated at lower temperature along the biotite garnet reaction boundary k is transferred from the pelite to the amphibolite and the lower melt fraction in the distal end of the amphibolite layers is caused by faster diffusion of na compared to k which results in a net depletion of alkalies ca is transferred from the amphibolite to the pelite and the resulting changes in cao concentrations affect the stabilities of plagioclase pyroxenes garnet and quartz and cause the observed zoning in the amphibolite layer ca entering the pelite layer induces crystallization of large plagioclase neoblasts radiating from the interface into the pelite layer these results show that diffusion of components between contiguous lithologies undergoing anatexis can cause profound changes in phase relations melt fractions and restite compositions

deep drilling at the siljan ring impact structure oxygen isotope geochemistry of granite the siljan ring is a 362 ma old impact structure formed in 1700 ma old i type granites a 6 8 km deep borehole provides a vertical profile through granites and isolated horizontal diabase sills fluid inclusion thermometry and oxygen isotope compositions of vein quartz granite diabase impact melt and pseudotachylite reveal a complex history of fluid activity in the siljan ring much of which can be related to the meteorite impact in granites from the deep borehole 18o values of matrix quartz increase with depth from near 8 0 at the surface to 9 5 at 5760 m depth in contrast feldspar 18o values decrease with depth from near 10 at the surface to 7 1 at 5760 m forming a pattern opposite to the one defined by quartz isotopic compositions values of 18o for surface granites outside the impact structure are distinct from those in near surface samples from the deep borehole in the deep borehole feldspar coloration varies from brick red at the surface to white at 5760 m and the abundances of crack healing calcite and other secondary minerals decrease over the same interval superimposed on the overall decrease in alteration intensity with depth are localized fracture zones at 4662 5415 and 6044 m depth that contain altered granites and which provided pathways for deep penetration of surface water the antithetic variation of quartz and feldspar 18o values which can be correlated with mineralogical evidence of alteration provides evidence for interaction between rocks and impact heated fluids 100 300 c in the upper 2 km of the pluton penetration of water to depths below 2 km was restricted by a general decrease in impact fracturing with depth and by a 60 m thick diabase sill at 1500 m depth that may have been an aquitard at depths below 4 km in the pluton where water rock ratios were low oxygen isotopic compositions preserve evidence for limited high temperature 500 c exchange between alkali feldspar and fluids the high temperature exchange may have been a post impact event involving impact heated fluids or a post magmatic event

origin of peraluminous granites and granodiorites iberian massif spain an experimental test of granite petrogenesis the discrimination between potential source materials involved in the genesis of iberian granites and granodiorites as well as the role of mantle crust inter actions are examined using constraints imposed by melting experiments melting assimilation experiments and sr nd isotope systematics the sr nd isotope re lationships indicate the existence of diaerent genetic trends in which juvenile mantle materials are involved by diaerent mechanisms 1 a source trend traced by a particular evolution of the pre hercynian basement and indicating mantle participation at the time of sedimen tation 2 a set of magmatic trends traced by gabbro tonalite enclave granodiorite associations implying the incorporation of new mantle material at the time of granite generation these relationships strongly support a pure crustal origin for the peraluminous leucogranites derived from partial melting of crustal protoliths and a hybrid origin for the peraluminous granodiorites these granodiorites are the most abundant granitic rocks of the central iberian zone ciz of the iberian massif implying that processes of hybridisation by assimilation and or magma mixing played an important role in granitoid production during the hercynian orogeny these hypotheses have been tested by means of melting and assimilation experiments melting experiments in the range 800 900 c and at pressures of 3 6 10 and 15 kbar indicate that 1 several potential source materials such as bt ms gneisses and metagreywackes are suitable for the production of peraluminous leucogranite melts 2 the melt compositions are always leucogranitic re gardless of pressure 3 pressure exerts a strong influ ence on the fertility of the source experiments at 3 kbar produce more than 20 vol of melt compared with less than 5 vol of melt produced at 10 and 15 kbar and at the same temperature the melting assimilation experi ments carried out at 1000 c and 4 7 and 10 kbar and using a proportion of 50 gabbro and 50 gneiss give high melt proportions more than 50 vol and noritic residues these melts have the composition of le ucogranodiorites and overlap with part of the compo sitional range of peraluminous granodiorites of the iberian massif the generation of more mafic granodiorites may be explained by the incorporation of some residual orthopyroxene to the granodiorite mag mas the low solubility of fe mg prevents the gen eration of granodiorite melts with more than 3 wt of mgo feo at all crustal pressures the large volumes of peraluminous hybrid granodiorites produced by assimilation of crustal rocks by mantle magmas imply that an important episode of crustal growth took place during the late palaeozoic hercynian orogeny in the iberian massif

observations of turbulence within a natural surf zone abstract here the reynolds stresses u w and w where u and w are the cross shore alongshore and vertical turbulence velocities respectively and the angle brackets represent time averaging are used to diagnose turbulence dynamics beneath natural breaking surf zone waves the data were collected at truc vert beach france during a 12 day period in 1 3 m water depth with strong cross shore and alongshore currents under high energy wave conditions offshore significant wave heights ranged between 2 and 8 m the u w term is predominantly negative increases with the ratio of wave height hs to water depth h degree of wave breaking and decreases in magnitude toward the bed this supports the view that the cross shore shear stress is due to breaking induced vortices that transport high speed cross shore flow downward and disintegrate close to the bed the occasional positive sign of u w within the lower 15 20 of the water column indicates that sometimes surface generated turbule

surface wave effects on the translation of wind stress across the air sea interface in a fetch limited coastal embayment abstractthe role of surface gravity waves in structuring the air sea momentum flux is examined in the middle reaches of chesapeake bay observed wave spectra showed that wave direction in chesapeake bay is strongly correlated with basin geometry waves preferentially developed in the direction of maximum fetch suggesting that dominant wave frequencies may be commonly and persistently misaligned with local wind forcing direct observations from an ultrasonic anemometer and vertical array of advs show that the magnitude and direction of stress changed across the air sea interface suggesting that a stress divergence occurred at or near the water surface using a numerical wave model in combination with direct flux measurements the air sea momentum flux was partitioned between the surface wave field and the mean flow results indicate that the surface wave field can store or release a significant fraction of the total momentum flux depending on the direction of the wind when wind blew across dominant fetc

an alongshore momentum budget over a fringing tropical fore reef author s arzeno isabella b collignon audric merrifield mark giddings sarah n pawlak geno

geochemistry and petrology of recycled orogen derived sediments a case study from upper precambrian siliciclastic rocks of the central iberian zone iberian massif spain abstract two areas of upper precambrian siliciclastic rocks separated from each other by 150 km were selected in the central iberian zone ciz for a petrological and geochemical study the petrology of the coarser grained rocks indicates the absence or scarcity of igneous clasts the presence of extrabasinal and intrabasinal clasts and homogeneous features of sandstones ranging from very fine to fine grained the modal data of these rocks plot close to the qt l and qm lt sides of qtfl and qmflt triangular diagrams suggesting provenance from a recycled orogen the geochemical data on the shales and sandstones from the two areas studied are very uniform both groups of rock show similar ranges of relevant major element ratios such as al 2 o 3 tio 2 17 46 21 51 17 46 21 34 for shale and sandstone respectively al 2 o 3 feo t 2 40 3 79 2 18 3 33 and feo t feo t mgo 0 71 0 77 0 68 0 76 together with parallel average rare earth element ree patterns and similar values for some key trace element ratios la th th yb th u zr hf sm nd and cr sc other trace element ratios la sc th sc cr th and cr zr are uniform in the shales group and also in the sandstones group although minor differences become apparent when both groups are compared these differences are probably related to the quartz dilution effect affecting the relative abundance of phyllosilicates in these rocks and indirectly the sc and cr contents given their covariations with al2o3 the zr yb zr y and zr th ratios of the shales are uniform the sandstones show higher and more variable values and there is no correlation between zr abundance and any of these ratios in the shales or sandstones together with the parallel ree patterns shown by both groups of rock these results suggest the absence of heavy mineral fractionation during the transport of detrital material and or the relative importance of other minerals probably phyllosilicates in the control of yb y and th abundances apparently all the groups of rocks show a remarkable geochemical homogeneity despite the distance between the sampling areas thus the petrological and chemical data are consistent and point to a very extensive homogeneous and stable source region as the most plausible contributor to the upper precambrian siliciclastic rocks in the ciz the possible relationship between this zone and n gondwana is also discussed

isotope palaeohydrology and the prediction of long term repository behaviour there are considerable well recognized difficulties involved in the investigation of very low permeability rocks by conventional measurements of water potentials and spatial distribution of hydrological parameters such as permeability and effective porosity therefore most studies of predictive behaviour are based on models which when unconstrained by data are often worse than no model at all geochemistry and environmental isotope geochemistry are techniques well suited for hydrological investigations of potential sites of nuclear waste isolation and for constraining predictive models stable isotopes constitutive of the water molecule 2h and 18o may give information on the origin of the water especially 2h which is practically uninvolved in isotope exchange with rock forming minerals variations in stable isotope contents can be related to palaeohydrological and palaeoclimatic conditions whereas 3h is indicative of recent recharge the 13c content of dissolved carbon is related to its origin s and the 14c activity gives a time scale however the initial carbon isotope contents can be modified by various diagenetic effects such as precipitation dissolution of secondary calcite and oxidation of reduced carbon the heavy isotope content of the total dissolved inorganic carbon tdic cannot be interpreted without a detailed knowledge of the carbon chemistry and of the mineralogy and isotope contents of secondary carbonates species of dissolved organic carbon doc with high molecular weights hmw can generally be attributed to soil derived compounds their 14c content may be measured by ams accelerator mass spectrometry thus providing an estimate of the time elapsed since recharge took place chlorine 36 is an interesting potential tool for dating old ground waters because of its long half life 301 kyr and its hydrophilic behaviour it can be also produced in situ in significant amount if the rocks are rich some tens of ppm in u and th in such cases this time dependent build up provides a more systematic radiochronometer of ci residence time in the rock than the decay of cosmic input 36ci provided no cl is leached from the rock the isotopic composition of aqueous sulphur compounds depends on their origin and on their diagenetic evolution the redox reactions of so2 4 reduction or of s2 oxidation are marked by strong isotope effects especially when generated by bacteria sulphate reduction by organic matter is a potential source of dissolved inorganic carbon and may thus interfere with 14c age interpretations after discussion of the possible age and origin of waters and solutes some scenarios of evolution of local and regional palaeohydrological conditions are proposed examples are given with special emphasis on detailed results from the fennoscanian shield stripa project and from northern switzerland

uniform sense normal simple shear of the continental lithosphere geophysical studies suggest that the thin crust characteristic of the basin and range province extends eastward beneath the west margin of the colorado plateau and rocky mountain regions in arizona and utah zones perhaps over 100 km wide may be defined bounded on the west by the east limit of upper crustal normal faults that account for more that 10 extension and on the east by the east limit of thinning beneath the colorado plateau a discrepancy exists within these zones between the negligible extension measurable in the upper crust and the substantial extension apparent from crustal thinning assuming the discrepant zone crust was as thick as or thicker than the colorado plateau rocky mountain crust prior to extensional tectonism if various theories appealing to crustal erosion are dismissed mass balance problems evident in the discrepant zones are most easily resolved by down to the east normal simple shear of the crust moving lower and middle crustal rocks that initially were within the zones up and to the west to where they now are locally exposed in the basin and range province west of the discrepant zones in both arizona and utah east directed extensional allochthons with large displacement are exposed these geophysical and geological observations complement one another if it is accepted that the entire crust in both arizona and utah failed during extension on gently east dipping east directed low angle normal faults and shear zones over a region several hundred kilometres wide large scale uniform sense normal simple shear of the crust suggests the entire lithosphere may do the same such a hypothesis predicts major lithospheric thinning without crustal thinning will occur in plateau areas in the direction of crustal shear in the case of the arizona utah and red sea extensional systems and possibly the death valley extensional terrain a broad topographic arch typically 1500 2000 m higher than the extended terrain is present suggesting lithospheric thinning in areas predicted by the hypothesis

determination of the fluid absent solidus and supersolidus phase relationships of morb derived amphibolites in the range 4 14 kbar experiments on a morb mid ocean ridge basalt derived amphibolite have been conducted in order to determine fluid absent solidus and supersolidus phase relationships the solidus has been determined in the range 4 14 kbar by using the incremental heating technique tested against classical procedures peritectic clinopyroxene was produced below 10 kbar and epidote was the stable peritectic phase at pressures greater than 10 kbar for temperatures near the solidus garnet was the peritectic phase for temperatures above 800 c and pressures of 10 to 14 kbar the shape of the solidus was similar to previous estimations but the temperature interval between the high and low pressure regions was strongly reduced with these new estimations the possibilities for melting of the oceanic crust at p below 10 kbar are increased and consequently the number of tectonic scenarios needed for magma generation from amphibolite sources is enlarged in the absence of free water the solidus in the pressure region above 10 kbar is at higher t than previous estimations

observations of spatial flow patterns at the coral colony scale on a shallow reef flat 1 although small scale spatial flow variability can affect both larger scale circulation patterns and biological processes on coral reefs there are few direct measurements of spatial flow patterns across horizontal scales 1 had similar spatial patterns to wakes while higher frequency variations 0 05 0 1 hz kc 1 had no observable spatial structure on the reef flat both drag and inertial forces exerted by coral colonies could have significant effects on flow but within different frequency ranges drag dominates for low frequency flow variations and inertial forces dominate for higher frequency variations including the wave band our scaling analyses suggest that spatial flow patterns at colony and patch scales could have important implications for both physical and biological processes at larger reef scales through their effects on forces exerted on the flow turbulent mixing and dispersion

magmatism and early variscan continental subduction in the northern gondwana margin recorded in zircons from the basal units of galicia nw spain in situ uranium lead dating la sf icpms and sims and lu hf isotope analyses la mc icp ms of zircon from eclogite facies rocks from the basal units of the variscan belt in galicia constrain their magmatic and metamorphic evolution and give some clues about the nature and origin of the involved basement the samples studied are two felsic gneisses two eclogites and one eclogitic gneiss of intermediate composition metatonalite oscillatory zoned zircon cores from the felsic samples gave a main clustering of u pb ages at 493 2 and 494 2 ma and some older ages that represent inherited cores zircon grains from the intermediate and one of the mafi c rocks show no inherited cores and yielded ages of 494 3 and 498 6 ma respectively interpreted as time of protolith crystallization variably developed homogeneous zircon rims in one felsic gneiss yielded an age of 372 3 ma and very tiny zircons of one eclogite gave 350 2 ma both of which we interpret as metamorphic ages the new age data demonstrate that the calc alkaline magmatic suite described in the basal unit is ca 20 ma older than the alkaline to peralkaline plutonic suite of the same unit dated at 472 2 ma rodriguez et al 2007 and thus probably represents a distinct geologic event overgrowth rims are interpreted as metamorphic on the basis of their lu hf and th u ratios the 372 3 age is considered as dating the high pressure high p metamorphism and is essentially in agreement with previous ar ar and rb sr data this high p metamorphism marks the initial early variscan subduction of the gondwana margin the inherited zircon ages and hf isotopic composition of zircons point to a considerable input of crustal material with west african craton provenance to the felsic magma

the status of isotope hydrology today abstract the present status of isotope hydrology is reviewed with the accent on techniques which are most frequently used or the potential of which is perhaps as yet not fully utilised applications are grouped under two headings 1 applications of intentionally introduced tracers and nucleonic instruments and 2 applications of environmental isotope techniques under the first classification are included the use of tracers in flow gauging sediment transport as bedload and in suspension measurement of flow and its direction in boreholes and the use of artificial tritium for the estimation of recharge the topics included within the group of environmental isotope techniques are recharge and dating of groundwater elevation of recharge area runoff studies arid zone hydrology interaction of surface water with groundwater leakage between aquifers mechanisms of salinization role of environmental isotope techniques in the assessment of geothermal resources and the hydrology of waste disposal sites with regard to the future the author points to the need for a more quantitative approach to the interpretation and presentation of results and broadening the range of dating capability

the wave driven ocean circulation oceanic surface gravity waves have a mean lagrangian motion the stokes drift the dynamics of winddriven basin scale oceanic currents in the presence of stokes drift are modified by the addition of so called vortex forces and wave induced material advection as well by wave averaged effects in the surface boundary conditions for the dynamic pressure sea level and vertical velocity some theoretical analyses previously have been made for the gravity wave influences on boundary layer motions including the ekman currents the present paper extends this theory to the basin scale depth integrated circulation in a bounded domain it is shown that the sverdrup circulation relation with the meridional transport proportional to the curl of the surface wind stress applies to lagrangian transport while the associated eulerian transport is shown to have a component opposite to the stokes drift transport a wave induced correction to the relation between sea level and surface dynamic pressure is also derived preliminary assessments are made of the relative importance of these influences using a global wind climatology and an empirical relationship between the wind and wave fields recommendations are made for further development and testing of this theory and for its inclusion in general circulation models

geochemistry of the ediacaran early cambrian transition in central iberia tectonic setting and isotopic sources abstract a complete ediacaran early cambrian stratigraphic transition can be observed in the southern part of the central iberian zone iberian massif two different stratigraphic units underlying ordovician series display geochemical and sm nd isotopic features in agreement with an evolving geodynamic setting pusa shales early cambrian rest unconformably on greywackes of the lower alcudian formation late ediacaran both sequences present minor compositional variations for major and trace element contents and similar ree patterns close to those of paas post archean australian shale trace element contents and element ratios suggest mixed sources with intermediate to felsic igneous contributions for both units tectonic setting discrimination diagrams for the ediacaran greywackes indicate that these turbiditic series were deposited in a sedimentary basin associated with a mature active margin volcanic arc however the compositions of the cambrian shales fit better with a more stable context a back arc or retro arc setting end t and tdm ages are compatible with dominance of a similar cratonic source for both sequences probably the west africa craton end 565 values for the ediacaran greywackes 3 0 to 1 4 along with tdm ages 1256 1334 ma imply a significant contribution of juvenile material probably derived from the erosion of the volcanic arc however end 530 values in the cambrian shales 5 2 to 4 0 together with older tdm ages 1444 1657 ma suggest a higher contribution of cratonic isotopic sources probably derived from erosion of the adjacent mainland coeval with the progressive cessation of arc volcanism along the peri gondwanan realm during the cambrian there was a period of more tectonic stability and increasing arrival of sediments from cratonic areas the geochemistry of the ediacaran cambrian transition in central iberia documents a tectonic switch in the periphery of gondwana from an active margin to a more stable context related to the onset of a passive margin

breaking surface wave effects on river plume dynamics during upwelling favorable winds this study examines the dynamics of a buoyant river plume in upwelling favorable winds concentrating on the time after separation from the coast a set of idealized numerical simulations is used to examine the effects of breaking surface gravity waves on plume structure and cross shore dynamics inclusion of a wavebreaking parameterization in the two equation turbulence submodel causes the plume to be thicker and narrower and to propagate offshore more slowly than a plume in a simulation with no wave breaking in simulations that include wave breaking the plume has much smaller vertical gradients of salinity and velocity than in the simulation without breaking this leads to decreased importance of shear dispersion in the plumes with wave breaking much of the wideningrate of the plume is explainedby divergentekmanvelocities at the off and onshore edges some aspects of plume evolution in all cases are predicted well by a simple theory based on a critical richardson number and an infinitely deep ocean however because the initial plume in thesesimulationsisincontactwiththeseafloorintheinnershelf somedetailsarepoorlypredicted especially around the time that the plume separates from the coast

87sr 86sr of brines from the fennoscandian shield a synthesis of groundwater isotopic data from the baltic sea region high salinity ca na cl brines occur in sweden and finland the complex geological history of the fennoscandian shield is reflected by the wide range of saline waters whose chemical compositions have been explained by local water rock interaction simple evolution of relict sea water or freezing of sea water during glacial periods this study deals with the present knowledge of sr isotopes in groundwater from the fennoscandian shield to better constrain the origin of their deep saline component two different mixing trends are seen between aspo island groundwater and the baltic sea the first trend links the north sea to rivers through various dilution levels in the baltic the second trend is a simple linear relationship through aspo groundwaters agreeing with a binary mixing between a baltic end member and a highly sr concentrated fluid strontium isotope compositions are presented for precipitation in finland and sweden the baltic sea and the river waters draining the fennoscandian shield and for g

shrimp u pb geochronological constraints on the timing of the intra alcudian cadomian angular unconformity in the central iberian zone iberian massif spain new shrimp u pb ages of detrital zircons from neoproterozoic low grade metasandstones of the schist graywacke complex central iberian zone iberian massif sampled just below and above the intra alcudian unconformity at two selected locations contribute to reconstruct the geodynamic evolution of iberia during the cadomian orogeny in the north gondwana margin the youngest zircons i e maximum depositional age in the lower alcudian are c 580 576 ma while those in the upper alcudian are c 555 552 ma the obtained remarkable time gap of about 21 ma supports the existence of a tectonic event in between this event resulted in moderate folding without related foliation metamorphism that verticalized the lower alcudian previous to the deposition of the upper alcudian additional evidence of late cadomian tectonothermal events elsewhere in iberia also fit in the interval c 560 550 ma combined with other geological data the most probable maximum depositional ages are c 580 560 ma for the lower alcudian previous to the late cadomian folding event and c 550 540 ma for the upper alcudian previous to the deposition of the overlying pusian group and lower cambrian sandstones and limestones a comparison of the new zircon age spectra with possible source areas verifies recent studies that point to the cadomian foreland in the north gondwana continent affected by the pan african orogeny the west african craton and or the saharan metacraton furthermore ongoing cadomian arc related magmatism in iberia c 605 545 ma could have contributed as a local zircon source the end of the cadomian activity is marked by a transient stage ephemeral lower cambrian platform which preceded widespread cambro ordovician rifting of north gondwana