a self consistent model of melting magma migration and buoyancy driven circulation beneath mid ocean ridges numerical modeling and analysis are used to investigate the processes leading to the eruption of mantle derived magma at mid ocean ridges our model includes the following effects melting due to decompression magma migration by percolation and circulation of the mantle driven by both the oceanic plates and the distribution of buoyancy beneath the ridge the distribution of buoyancy is due to both the low density of the liquid and the difference in the density of the residual solids relative to unmelted mantle material the calculation of densities is based on a simple petrological model in which garnet spinel lherzolite melts to form a basaltic liquid and a harzburgite residue we find that the system spontaneously evolves to a state in which a rapid upwelling beneath the ridge axis faster than the plate velocity is confined laterally by stably stratified residual material beneath the newly formed plates this effect is exaggerated if a modest decrease in the shear viscosity of the solid upon melting is included our results provide a simple explanation for the narrowness of the zone of crustal formation at mid ocean ridges the model also predicts a transition from steady state to episodic crustal formation as the spreading velocity is reduced perhaps giving rise to along axis variations in the character of seafloor spreading the narrow rapid upwelling gives rise to substantial porosities at depths that are a large fraction of the depth to the solidus this may allow the liquid at depth to segregate into macroscopic channels which would account for the consensus from experimental petrology that the liquids parental to morb are derived from well below the base of the crust

transport of atmospheric impurities over the qinghai xizang tibetan plateau as shown by snow chemistry abstract chemical records were recovered from samples collected from snow pits over two transects s n and se nw across the qinghai xizang tibetan plateau the records show that the flux of major ions in the regions to the north of mt tanggula is on the average 6 30 times higher than that of the regions to the south and 0 6 5 times higher than regions to the southeast it appears that mt tanggula provides a barrier to continental dust transported across the plateau from the north and to marine aerosols transported from the southeast the spatial patterns of snow chemistry as well as the total suspended particle tsp distribution along the northern qinghai xizang highway demonstrate that continental dust originates mainly from the deserts to the north while monsoon sources of moisture exert greater influence on snow chemistry on the southern part of the plateau seasonal variations of the major ions were also examined in a firn core drilled at a height of 7000 m on the dasuopu glacier and in a snow pit from the meikuang glacier eastern kunlun the choice of a high altitude site at dasuopu and the sampling season before snowmelt at meikuang avoided post depositional modification processes mainly the elution effect of meltwater thus guaranteeing the reliable recovery of the distribution of impurities in different seasons the peak of the impurities appear at dasuopu during the spring and at meikuang in the winter spring coinciding with the asian dust season however the amplitude of the seasonal variations at meikuang is much higher than at dasuopu ph values at the dongkemadi glacier are greater than 6 but at the dasuopu glacier himalayas they range between 4 and 7 5 the liquid conductivity lc from dongkemadi is positively correlated with the ph while at dasuopu lc is positively correlated with ph when ph is below 6 and negatively correlated with ph when it is greater than 6 this implies that during august to september the himalayan range is a transition zone between the transportation of continental dust and marine aerosols

isotopic composition δ18o and δd of precipitation and groundwater in a semi arid mountainous area guadiana menor basin southeast spain we characterize the precipitation and groundwater in a mountainous peaks slightly above 3000 m a s l semi arid river basin in se spain in terms of the isotopes 18o and 2h this basin with an extension of about 7000 km2 is an ideal site for such a study because fronts from the atlantic and the mediterranean converge here much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs a total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed to sample precipitation we set up a network of 39 stations at different altitudes 800 1700 m a s l with which we were able to collect the rain and snowfall from 29 separate events between july 2005 and april 2007 and take monthly samples during the periods of maximum recharge of the aquifers to characterize the groundwater we set up a control network of 43 points 23 springs and 20 wells to sample every 3 months the main aquifers and both the thermal and non thermal groundwater we also sampled two shallow water sites a reservoir and a river the isotope composition of the precipitation forms a local meteoric water line lmwl characterized by the equation d 7 72 18o 9 90 with mean values for 18o and d of 10 28 and 69 33 respectively and 12 9 for the d excess value to correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line wlmwl characterized by the equation d 7 40 18o 7 24 which takes into account the quantity of water precipitated during each event these values of d d d 18o 8 and d excess d 8 18o 10 in each curve bear witness to the amount effect an effect which is more manifest between may and september when the ground temperature is higher other effects noted in the basin were those of altitude and the continental influence the isotopic compositions of the groundwater are represented by the equation d 4 79 18o 18 64 the groundwater is richer in heavy isotopes than the rainfall with mean values of 8 48 for 18o and 59 27 for d the isotope enrichment processes detected include a higher rate of evaporation from detrital aquifers than from carbonate ones the effects of recharging aquifers from irrigation return flow and or from reservoirs leakage and enrichment in 18o from thermal water copyright 2010 john wiley sons ltd

precipitation origin and evaporation of lakes in semi arid patagonia argentina inferred from stable isotopes δ18o δ2h stable isotope approaches are often used for estimating water balances of lakes such studies require regional background information about hydrogen and oxygen isotope variability of lakes and their potential inflows here a stable isotope database 2h and 18o is presented for estimating evaporation to inflow ratios e i of lakes in semi arid southern patagonia water samples of 23 lakes and ponds located in the patagonian steppe at about 52 s were sampled during three subsequent austral summers two deep crater lakes laguna azul and laguna potrok aike were studied in more detail during a two years monitoring furthermore precipitation groundwater and atmospheric water vapor were sampled for isotope analyses presented data imply that the isotopic composition of rainfall in southeastern patagonia is predominantly determined by precipitation amount and moisture source area for the investigated area the first meteoric water and evaporation lines in 2h vs 18o space are presented the database was further used to estimate the water balances of the two crater lakes laguna azul and laguna potrok aike which are in the focus of recent paleoclimatic investigations according to that approach about 50 and 60 respectively of the water entering laguna azul and laguna potrok aike via surface and subsurface inflow evaporates these results testify a considerable flow of lake waters into the groundwater

mid holocene erosive episodes in tufa deposits from trabaque canyon central spain as a result of abrupt arid climate transitions during the holocene a series of tufa sediments were deposited from a karstic spring along the trabaque canyon central spain a long term lowering of the water table caused the location of the spring to be displaced from the upper sector of the canyon during the early holocene to the lower sector in the late holocene this progressive shift was in response to decreased precipitation in the region the depositional environments and their geomorphologic relationships were characterized thus five morphosedimentary units msus were identified within the holocene tufa deposits erosive episodes were recognized between msus and as most of the msus partially overlap the older ones are perched in relation to the younger ones the chronology of the msus is based on 14c dates and stable isotopes and total organic carbon content provided environmental information during the period of tufa sedimentation the successive dissection episodes in the trabaque canyon tufa deposits took place during transitioning climate conditions from the relatively wet early holocene to the more arid late holocene during this transitional period in the mid holocene wet phases alternated with more arid conditions causing the largest hydrological regime gradients in the holocene thus the four erosive episodes causing tufa dissection in trabaque during the holocene are interpreted as the result of abrupt transitional periods towards arid conditions

climate footprint in karst aquifers derived from time series and spatial data the case of orce maria se spain the alignment of carbonates comprising the orce and maria mountain chains rides the surface hydrological divide between the catchment basins of the guadalquivir river and the segura river they are influenced by atlantic precipitation on the western side and mediterranean on the eastern side these circumstances cause differences in the precipitation recharge which are reflected in the groundwater and they can be studied in the recharge response recorded not only in piezometers but also in springs the hydrochemical and isotopic characteristics of the groundwater can also be conditioned by these different climate environments an analysis of piezometric and hydrometric series and of hydrochemical and isotopic data shows that the precipitation recharge with mediterranean influence is predominant despite the fact that only 30 of the outcrops are in that catchment basin in the main discharge zones are springs in carbonate outcrops and in outcrops associated with pliocene and quaternary material the data reveal a mixing of waters on the borders of the mountain chains deriving from the carbonate aquifer and from the pliocene and quaternary detrital sediments overlying the aquifers on its borders there are differences between the chemical compositions of the water circulating through the maria mountain and through orce mountain carbonates interpreted as the result of a greater or lesser presence of dolomites the isotopic data can be used to identify water infiltrating from mediterranean or atlantic areas of influence the values of 18o are between 9 38 and 6 46 and in the case of 2h between 61 73 and 44 46 in the maria mountains mediterranean influence the average is of 8 75 and 53 63 respectively and of 9 01 and 59 41 in samples related to the carbonates of the orce mountains atlantic influence the mean for the deuterium excess is of 15 8 in the first case and 13 4 in the second one

recharge sources and hydrogeochemical evolution of groundwater in semiarid and karstic environments a field study in the granada basin southern spain abstract the objective of this study is to refine the understanding of recharge processes in watersheds representative for karstic semiarid areas by means of stable isotope analysis and hydrogeochemistry the study focuses on the granada aquifer system which is located in an intramontane basin bounded by high mountain ranges providing elevation differences of almost 2900 m these altitude gradients lead to important temperature and precipitation gradients and provide excellent conditions for the application of stable isotopes of water whose composition depends mainly on temperature samples of rain snow surface water and groundwater were collected at 154 locations for stable isotope studies 18 o d and in the case of ground and surface waters also for major and minor ion analysis thirty seven springs were sampled between 2 and 5 times from october 2004 to march 2005 along an altitudinal gradient from 552 masl in the granada basin to 2156 masl in sierra nevada nine groundwater samples were taken from the discharge of operating wells in the granada basin which are all located between 540 and 728 masl the two main rivers were monitored every 2 3 weeks at three different altitudes rainfall being scarce during the sampling period precipitation could only be sampled during four rainfall events calculated recharge altitudes of springs showed that source areas of mainly snowmelt recharge are generally located between 1600 and 2000 masl the isotope compositions of spring water indicate water sources from the western mediterranean as well as from the atlantic without indicating a seasonal trend the isotope pattern of the quaternary aquifer reflects the spatial separation of different sources of recharge which occur mainly by bankfiltration of the main rivers isotopic signatures in the southeastern part of the aquifer indicate a considerable recharge contribution by subsurface flow discharged from the adjacent carbonate aquifer no evaporation effects due to agricultural irrigation were detected

stable isotopes in rain and cloud water in madeira contribution for the hydrogeologic framework of a volcanic island madeira is a volcanic island whose economy is highly dependent on groundwater previous studies suggest that besides precipitation cloud water interception contributes to groundwater recharge as such the isotopic characterization of the sources of recharge is useful for the hydrogeological framework of the island the 18o and 2h content of rain and cloud water was analyzed during three campaigns rain plots over a local meteoric water line lmwl whose equation is 2h 7 92 18o 10 49 r2 0 97 n 43 the volume weighted average meteoric line wlmwl is given by 2h 7 97 18o 10 57 r2 0 98 n 20 both are similar to the global meteoric water line which indicates along with the d excess values 10 8 and 11 for the lmwl and wlmwl respectively that rain originates essentially in the atlantic seasonal variations were also observed and rain in campaign ii was isotopically enriched and had a higher d excess 18omean 3 63 2hmean 16 3 d excess 12 7 than rain in campaign iii 18omean 7 01 2hmean 46 5 d excess 9 5 campaign i stood in between these variations were probably the result of differences in temperature water vapor source areas and rain forming processes rain was found to become increasingly depleted with altitude 18o at a rate of 0 15 100 m and 0 11 100 m in the windward and leeward sides respectively cloud water was always isotopically enriched when compared with rain at the same altitude this was related to constant water vapor replenishment of orographic clouds to the fact that it usually represents an early stage condensation from air moisture and to the smaller size of cloud water droplets when compared to rain droplets these results will be useful to refine madeira s hydrogeological conceptual model future extended sampling during more years with smaller sampling periods and single rainfall events should be useful to support the conclusions of this study

small scale spatial and temporal variations in mid ocean ridge crest magmatic processes data from a suite of closely spaced lava flows recovered within the axial summit caldera and on the crestal plateau of the east pacific rise around lat 9 31 n indicate that eruptions on this fast spreading part of the mid ocean ridge occur throughout the crestal region and are not restricted to the axis these eruptions contribute to a complex distribution of basalts of various ages and a significant thickening of seismic layer 2a away from the axis in our study area small scale 600 m diversity and nonsystematic distribution of lava types may reflect rapid changes in magma chemistry that occur during crystallization and replenishment in small magma lenses coupled with the effects of frequent low volume eruptions both within and outside of the axial summit caldera

holocene snail shell isotopic record of millennial scale hydrological conditions in western mediterranean data from bauma del serrat del pont ne iberian peninsula land snail shells are a common component in mediterranean holocene archaeological deposits providing the opportunity to explore their potential as source of information concerning human behaviour and palaeoclimatic conditions many well preserved shells of the caenogastropod pomatias elegans were recovered along the holocene succession of bauma del serrat del pont bsp in the iberian peninsula their oxygen 18os and carbon 13cs isotopic compositions were analysed and compared with that of modern shells of the same species collected in two distinct areas near the archaeological site modern shells from site a shady and b sunny show distinctly different oxygen isotopic ratios possibly due to the effect of microenvironmental conditions e g temperature and relative humidity carbon isotopes by contrast reveal similar values isotope mass balance suggests a prevalent contribution of vegetation 70 integrated with foreign carbonates 30 to 13cs of modern snails early late holocene shells 9 2 5 cal ka bp have lower 18os compared with modern counterparts which is consistent with prevailing wetter conditions compared with present day the 13cs reveals distinct hydrological regimes wet and dry conditions from early to late holocene respectively in general shell isotopic records from western and central mediterranean regions suggest wetter conditions during the middle holocene with a possible reduction in humidity from 4 cal ka bp the 18os indicates a possible latitudinal difference in hydrological balance between mediterranean and atlantic europe as inferred by previous studies of regional palaeoclimatic records carbon isotopes by contrast do not provide a clear climatic picture probably due to the effect of distinct vegetation structure and composition comparisons with other environmental archives reinforce the concept of regional shell oxygen isotopic response to millennial scale changes in hydrological condition over the western and central mediterranean during the late quaternary

molten rocks in motion evidence for tectonic activity under the ocean comes from molten rocks that erupt at mid ocean ridges chemical differences between volcanic rocks found at the ridge and nearby support a passive model of mantle flow whereby magma rises to the surface in response to the plates moving apart

antiquity of peridotitic diamonds from the siberian craton diamonds erupted by kimberlites traversing ancient continental tectosphere 1 provide a window into the evolution of continents and their mantle keels however the vintage of this window that is the timing of crystallization of peridotitic mineral inclusion bearing diamonds beneath different cratons has proved controversial because of the model age arguments involved 2 12 isochron age data for peridotitic garnets in combination with nitrogen aggregation data for host diamonds from the udachnaya kimberlite on the siberian craton show that such diamonds are ancient and could not have crystallized as recently 70 ka before eruption as proposed 10 12 the garnets yield a smnd isochron age of 2 0 ga and the diamonds display nitrogen aggregation characteristics requiring lithospheric mantle storage at temperatures of 1100 1200 c for a comparable period the crystallization age of these peridotitic diamonds is similar to that of equivalent diamonds from the premier kimberlite on the kaapvaal craton which postdate the massive 2 05 ga old bushveld complex and represent a diamond generation unrelated to craton keel stabilization 3 2 ga ago 3 9 10

variation of the stable isotopes of water with altitude in the saint elias mountains of canada the stable isotopes of water measured in melt samples taken from snow pits and cores at locations between 1750 and 5930 m altitude on mount logan 5951 m and between 2900 and 4900 m on mount steele 5079 m in the saint elias mountains yukon show a distinctive altitudinal distribution several 18o and d versus altitude profiles indicate the general persistence of a nearly iso step or staircase structure separating a lower region of altitude dependent isotopic fractionation between 1750 and 3350 m from another apparent fractionation sequence appearing above about 5300 m both of these sequences but especially the lower one indicate orderly processes on the one hand postdepositional changes to isotope ratios in snow at different altitudes may cause distortions to an otherwise nearly monotonic isotope fractionation sequence but the main anomaly appears to be far too large to be explained in this way on the other hand an explanation linked to processes occurring in the lower and midtroposphere is based on established meteorological principles as well as on upper air data this hypothesis is proposed as the primary one to explain the gross features of the observed isotope profiles it is compatible with the concept of secondary source moisture arriving via the upper troposphere and it does not exclude the effects of postdepositional stratigraphic and stable isotope ratio changes over interannual time scales any vertical modulation of the observed isotope altitude structure from for example changes in wind regime would give rise to an additional signal in any ice core time series these findings identify a potential difficulty in the interpretation of stable isotope records obtained from high mountain ice core sites it is possible that the results may have application to atmospheric circulation modeling where the effects of extreme topography are being studied

asymmetric electrical structure in the mantle beneath the east pacific rise at 17 s the magnetotelluric component of the mantle electromagnetic and tomography melt experiment measured the electrical resistivity structure of the mantle beneath the fast spreading southern east pacific rise epr the data reveal an asymmetric resistivity structure with lower resistivity to the west of the ridge the uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles mantle resistivities to the west of the ridge are consistent with a low melt fraction about 1 to 2 percent interconnected melt distributed over a broad region and extending to depths of about 150 kilometers the asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates

stable isotope ratios in meteoric recharge and groundwater at mt vulture volcano southern italy summary a rain gauge network consisting of five sites located at different altitudes ranging from 320 to 1285 m a s l was installed at mt vulture volcano southern italy rain water samples were collected monthly over a two year period and their isotopic composition 18o and d was analyzed during the same period circulating groundwater was sampled from 24 springs and wells distributed throughout the study area monthly isotopic composition values were used to determine the local meteoric water line lmwl its slope is slightly lower than the relationship defined by longinelli and selmo longinelli a selmo e 2003 isotopic composition of precipitation in italy a first overall map j hydrol 270 75 88 for southern italy the groundwater samples analyzed were distributed essentially along the lmwl the weighted local meteoric water line wlmwl defined through the mean values weighted by the rainfall amount however may define in a short range the meteoric end member in the local hydrological cycle more precisely since most of the groundwater sampling locations do not show seasonal variations in their stable isotope values the flow system appears to be relatively homogeneous the mean altitude of the recharge by rainfall infiltration was estimated on the basis of the local vertical isotopic gradient 18o a few springs which show anomalous isotopic values reveal more regional circulation systems associated with tectonic structures responsible for the ascent of deeper water

influence of rainfall quantity on the isotopic composition 18o and 2h of water in mountainous areas application for groundwater research in the yunquera nieves karst aquifers s spain abstract the isotopic composition 18 o and 2 h of rainwater and groundwater was determined in the yunquera nieves hydrogeological unit a karstic massif in s spain with complex orography and hydrogeology the aims were to identify 1 the source of the water 2 the main factors determining the isotopic content 3 the catchment area of the springs and 4 the aquifer behaviour the isotopic content of the sampled waters is of mixed atlantic mediterranean origin and is opposite to the quantity of rainwater distribution both in space and time spatially water is isotopically less depleted toward the eastern sector where rainwater quantity is lower which is locally affected by the orography thus it is possible to differentiate the catchment areas of the main springs aquifer recharge is produced by winter precipitation when rainfall water is isotopically more negative and evaporation is lower the decrease in rainfall quantity during the study period provoked an increase in 18 o and 2 h values both in rainwater and in groundwater the recorded variations of the isotopic content of the rainfall are rapidly evident in the spring waters which demonstrates a well developed karst network inside the carbonate aquifers and thus the existence of conduit flow systems

off axis volcanism at the east pacific rise detected by uranium series dating of basalts recent detailed surveys of the east pacific rise have revealed the complexity of the volcanic and magmatic processes occurring along and across fast spreading ocean ridge crests1 7 in parallel with geological and geochemical investigations it is now possible to investigate the temporal and spatial pattern of volcanism at ocean ridges by dating young basalts using mass spectrometric uranium series disequilibria methods8 11 here we use 238u 230th and235u 231pa ages for basalts to quantify the spatial extent of young volcanism and crustal accretion at 9 31 n on the east pacific rise most of the ages are younger than would be expected based on off axis distance and spreading rate we infer from these anomalously young ages that most of the dated basalts on the crestal plateau were erupted 0 5 2 km outside the axial summit caldera with some volcanism occurring as far as 4 km off axis melts erupted outside the axial summit caldera can have crustal residence times and magmatic supply systems that differ from those of axial lavas

using stable isotope analysis δd δ18o to characterise the regional hydrology of the sierra de gador south east spain water stress is rapidly increasing in many mediterranean coastal zones mainly due to expansion in agriculture and tourism in this paper we focus on the sierra de gador campo de dalias aquifer system southeastern spain in order to assess the capability of water stable isotope analysis deltad delta 18 o to refine the understanding on recharge of this karstic aquifer system different types of surface and groundwater were sampled along an altitudinal gradient from the recharge zone in the mountains to the coastal plain surface water is restricted to local runoff collected in closed reservoirs runoff amounts collected in three of these reservoirs were monitored together with the precipitation in their catchments meteorological maps were used to detect the origin of the precipitation generating the majority of the runoff the results were compared to literature data on local and regional precipitation the use of oxygen and hydrogen isotopic composition has proved to be a useful tool to explain the origin of groundwater in a mediterranean karstic system such studies are however not numerous and are often limited to local scale recharge for fast reacting systems this paper focuses on the delta 18 o deltad relationships of local precipitation to explain the isotopic variability of a large karstic aquifer system the isotopic compositions of groundwater sampled along an altitudinal gradient from the recharge zone to the coastal plain are well displayed in a deltad delta 18 o diagram on a mixing line connecting a pole of mediterranean waters to a pole of atlantic waters the atlantic signature predominates in the shallow groundwater of natural springs reflecting the rainfall which produced the local runoff sampled the mediterranean signature is mainly restricted to deep groundwater from boreholes in the coastal plain the existence of a degree of spatial separation of groundwater types demonstrates that groundwater flow in a complex karstic system is not always continuous the mediterranean signature of deep groundwater could be due to past extreme rainfall events during which connectivity between recharge and reservoir exists while at the same time the atlantic signature of recent winter rains dominates in shallow groundwater the assumption that an equilibrium in isotopic composition is established within a continuous aquifer and that therefore a slope lower than 8 in a deltad delta 18 o diagram indicates evaporation is not necessarily valid c 2002 elsevier science b v all rights reserved

on origin of near axis volcanism and faulting at fast spreading mid ocean ridges at fast and superfast spreading mid ocean ridges such as the east pacific rise a plate boundary is defined by a narrow tens to hundreds of meters wide neovolcanic zone within which the bulk of the upper oceanic crust is created however detailed near bottom observations indicate that the volcanic construction may occasionally persist several kilometers off of the ridge axis it has been proposed that off axis volcanism manifests tapping of a wide melting region that supplies magma to the ridge axis or spatial migration of magmatic sources in the crust and upper mantle we demonstrate that off axis eruptions may be a natural consequence of variations in magma supply rate even if the ridge axis is stationary in space and the magma delivery is perfectly focussed at the ridge axis theoretical modeling and field observations indicate that off axis volcanism may result from magma emplacement in sills that propagate toward the surface after their characteristic horizontal size exceeds their emplacement depth volcanic construction and faulting due to sill intrusions may contribute to the formation of abyssal hills arguably the most abundant relief form on earth fl 2001 elsevier science b v all rights reserved

impacts of human activities on recharge in a multilayered semiarid aquifer campo de cartagena se spain the development of intense agriculture in semiarid areas modifies intensity and spatial distribution of groundwater recharge by summing irrigation return flow to limited rainfall infiltration environmental tracers provide key information but their interpretation is complicated by more complex groundwater flow patterns in multilayered aquifers the real origin of the groundwater samples is hard to assess because of local mixing processes occurring inside long screened boreholes we use environmental tracers 14c 13c 2h 18o 3h to investigate the long term evolution of recharge in the five layer campo de cartagena aquifer in south eastern spain in addition to high resolution temperature loggings to identify the depth of origin of groundwater despite the complex background this methodology allowed a reliable interpretation of the geochemistry and provided a better understanding of the groundwater flow patterns the tritium method did not give good quantitative results because of the high variability of the recharge signal but remained an excellent indicator of recent recharge nonetheless both pre anthropization and post anthropization recharge regime could be identified and quantified by radiocarbon before the development of agriculture recharge varied from 17 mm year 1 at the mountain ranges to 6 mm year 1 in the plain whereas the mean annual rainfall is about 300 mm in response to the increase of agricultural activity recharge fluxes to the plain were amplified and nowadays reach up to 210 mm year 1 in irrigated areas these values are strengthened by global water budget and local unsaturated zone studies copyright 2013 john wiley sons ltd

ghosts of lithospheres past imaging an evolving lithospheric mantle in southern africa group ii 143 117 ma and group i kimberlites 108 74 ma intrude across the southwest boundary of the kaapvaal craton sampling the same volume of the subcontinental lithospheric mantle sclm in two time slices major and trace element analyses of 3699 peridotitic garnet xenocrysts were used to construct paleogeotherms for 17 kimberlite localities and to place each garnet at its depth of origin the ti contents of each garnet and the calculated x mg of its coexisting olivine were projected onto a southwest northeast section across the craton boundary and splines were used to interpolate between the virtual boreholes in each age group the sections show that the cratonic sclm extends at least 75 km southwest of the mapped craton boundary suggesting a dipping contact marked differences between the time slice sections show that between 117 and 108 ma the sclm on both sides of the craton boundary was heated and chemically refertilized by infiltrating asthenosphere derived melts thinning the depleted layer by 40 km the thermal and geochemical changes record a significant tectonothermal event that may be related to changes in the stress field associated with opening of the south atlantic or with mantle upwelling

origin and type of rainfall for recharge of a karstic aquifer in the western mediterranean a case study from the sierra de gador campo de dalias southeast spain isotope signatures in precipitation from the global network for isotopes in precipitation around the mediterranean basin and literature data are compared with isotopic data from a large karstic aquifer in southeast spain to explain the origin and type of the precipitation events dominating recharge analysis of the deuterium excess d at the scale of the mediterranean basin and at the regional scale allows us to understand the isotopic context of the study area campo de dalias and the sierra de gador almerfa province the origin of precipitation can be determined from its d value the d value changes as a function of the initial evaporation condition it depends on the relative humidity and temperature during the evaporation producing the water vapour of the clouds the water vapour which dominates the study area is generated in two areas the atlantic ocean d 10 parts per thousand and the western mediterranean basin d 15 parts per thousand with increasing precipitation volume the western mediterranean character dominates these heavier storms contribute mainly to recharge as illustrated by the d value of 13 6 parts per thousand in deep groundwater of the campo de dalias weighted d values increase with the volume of precipitation giving a significant relationship for the southern and eastern coasts of the iberian peninsula this selectivity of d to monthly precipitation was used to estimate the return period of precipitation leading to aquifer recharge at 0 9 4 9 years moderate rainfall which occurs more frequently still represents similar to 60 90 of the total precipitation one of the challenges to meet ever growing water demands is to increase recharge from moderate events yielding intermediate quantities per event but forming the bulk of the annual precipitation copyright c 2006 john wiley sons ltd

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

characterising flow regime and interrelation between surface water and ground water in the fuente de piedra salt lake basin by means of stable isotopes hydrogeochemical and hydraulic data summary this research reports the characterisation of ground and surface water interaction in the fuente de piedra salt lake basin in southern spain by a combined approach using hydraulic hydrogeochemical and stable isotope data during three sampling campaigns february 2004 2005 and october 2005 ground and surface water samples were collected for stable isotope studies 18 o d and for major and minor ion analysis hydraulic measurements at multilevel piezometers were carried out at four different locations around the lake edge conductivity logs were performed at four piezometers located along a profile at the northern lake border and at two deeper piezometers in the miocene basin at a greater distance from the lake to describe processes that control the brine evolution different hydrogeochemical simulations were performed hydrogeochemical data show a variety of brines related to thickness variations of lacustrine evaporites around the lake salinity profiles in combination with stable isotope and hydraulic data indicate the existence of convection cells and recycled brines furthermore restricted ground water inflow into the lake was detected dedolomitisation processes were identified by hydrogeochemical simulations and different brine origins were reproduced by inverse modelling approaches