late proterozoic lavas of the central arabian shield evolution of an ancient volcanic arc system a petrological assessment of 11 volcano sedimentary belts in the central arabian shield cas using 118 new analyses is presented the same samples have been used in a rb sr dating programme also reported in this volume the oldest volcano sedimentary belts sequence c 900 ma are chemically immature bimodal suites of low k tholeiites and sodic dacite rhyolite depleted in lithophile elements these lavas have chemical characteristics similar to immature island arcs such as the tonga kermadee and lesser antilles arcs younger lavas of sequence b 900 700 ma are slightly more mature in composition being predominantly calc alkaline and low k arc tholeiite series with higher lithophile element contents they are comparable with pacific island are averages the youngest voluminous lavas sequence a 700 570 ma are generally calc alkaline or high k calc alkaline series lavas with moderately high lithophile element abundances they are comparable to volcanic arcs such as central america and indonesia which are transitional between island arcs and continental margin volcanic arcs the cratonization process in the cas thus involved the superimposition of three volcano sedimentary sequences formed in progressively maturing volcanic arcs early formed immature island arcs were succeeded by chemically more mature island arc deposits and then by deposits formed in volcanic arc s transitional between island arcs and continental margins the evolution ceased at this stage and probably did not advance to the equivalent of an andean continental margin

u pb shrimp and nd isotopic data from the western bohemian massif bayerischer wald germany implications for upper vendian and lower ordovician magmatism u pb shrimp dating of zircons of metamagmatites from the bayerischer wald germany reveals a complex evolution of this section of the moldanubian zone exposed in the western bohemian massif of the central european variscan belt in the south western part of the bayerischer wald upper vendian magmatism is constrained by pooled 206pb 238u mean ages of 555 12 549 7 and 549 6 ma from metarhyolites and a metabasite inherited zircon cores were not observed zircon overgrowths yielding pooled 206pb 238u ages of 316 10 and 319 5 ma provide evidence for variscan metamorphic zircon growth cathodoluminescence imaging reveals a two stage metamorphic overprint

a model for flow in the chalk unsaturated zone incorporating progressive weathering summary groundwater from unconfined chalk aquifers constitutes a major water resource in the uk the unsaturated zone in such systems plays a crucial role in the hydrological cycle determining the timing and magnitude of recharge and the transport and fate of nutrients however despite more than three decades of study our physical understanding of this system is incomplete in this research state of the art instrumentation provided high temporal resolution readings of soil moisture status rainfall and actual evaporation from two sites in the pang and lambourn catchments berkshire uk for a continuous two year period 2004 5 a parsimonious physically based model for the flow of water through the chalk unsaturated zone including a novel representation of the soil and weathered chalk layers was developed the parameters were identified by inverse modelling using field measurements of water content and matric potential the model was driven by rainfall and evaporation data and simulated fluxes throughout the profile including the discrete matrix and fracture components down to the water table but not the water table response results showed that the model was able to reproduce closely the observed changes in soil moisture status recharge was predominantly through the matrix and the recharge response was strongly attenuated with depth however the activation of fast recharge pathways through fractures in the chalk unsaturated zone was highly sensitive to rainfall intensity relatively modest increases in rainfall led to dramatically different recharge patterns with potentially important implications for groundwater flooding the development and migration of zero flux planes with time and depth were simulated the simulations also provided strong evidence that for water table depths greater than 5 m recharge fluxes persist throughout the entire year even during drought conditions with important implications for the calculation of specific yield from baseflow estimates and the representation of recharge in groundwater models

the geotectonic environments of late proterozoic mineralisation in the southern arabian shield abstract using the results of recent research the geotectonic setting of selected mineral occurrences in the saudi arabian late proterozoic shield south of latitude 21 n is described and an initial metallogenic cycle is presented the occurrences selected are types common in the region or are economically significant they include volcanic hosted copper zinc sulfides stratabound copper in sedimentary and minor volcanic rocks zinc in sedimentary rocks and tungsten hosted by mafic plutonic rocks the copper zinc occurrences are typical of volcanogenic mineralisation they are hosted by intraoceanic volcanic arc complexes one 100 200 ma younger and geochemically more evolved than the other the stratabound copper which has some features comparable with sedimentary hosted copper deposits elsewhere developed in the lower part of a transgressive sequence in a basin marginal to the younger volcanic arc complex the sedimentary hosted zinc mineralisation belongs to a small unit of rocks accreted to the younger arc complex from a terrane east of the shield the mafic plutonic rocks hosting tungsten are part of the post tectonic pan african phase of magmatism in the region the discussion of these occurrences assumes that the region developed through the processes of ocean plate subduction plate collision and cratonisation of the resulting deformed and metamorphosed accreted rocks by the intrusion of large volumes of post tectonic pan african granitic plutons a metallogenic cycle similar to those developed for other regions of accreted arc terranes results

origin of late variscan granitoids from ne bavaria germany exemplified by ree and nd isotope systematics sm nd isotopic results are presented for late and post tectonic granitoids comprising peraluminous granites and subordinate metaluminous dioritic rocks redwitzites from the fichtelgebirge fg and northern oberpfalz nop ne bavaria the data combined with a number of earlier geochromological studies on these granitoids place severe constraints on the crustal evolution of this region during the carboniferous and pre carboniferous epoch redwitzites range in nd t from 4 to 0 inclusive data from p k holl and coworkers the nd t values of the granites s s are restricted to overlapping ranges of 8 to 3 fg and 8 to 2 nop in both domains the older granites 330 325 ma are characterized by nd t values of 4 whilst the younger granites 315 305 and 290 ma have nd t values of 4 the diversity observed in nd isotopic characteristic is interpreted in terms of different source material the nd isotopic compositions of the redwitzites exhibit source heterogeneity suggesting mixing between mantle magma and crust the nd isotopic features of the older granites are consistent with the magmatic precursors having been generated by partial melting of pre existing mature crust variably contaminated by mantle material or alternatively by melting of chemically less evolved crust resembling paragneisses of teh zev structural unit the origin of the younger granites can be confidently linked to anatexis of common moldanubian and saxothuringian metasediments two stage nd model ages tdm of the granitoids are in the range 1 1 1 7 ga these ages provide further support of substantial involvement of pre phanerozoic crust in the generation of the granitoids the leuchtenberg granite and the g2 and g3 granites yield late variscan sm nd isochron ages which are concordant with previous rb sr data on these granites by contrast the nd isotopic data for barnau and flossenburg define pseudo isochrons suggestive of mixing between contrasting felsic melts

the krunkelbach uranium deposit schwarzwald germany correlation of radiometric ages u pb u xe kr k ar 230 th 234 u pitchblendes and secondary uranium minerals from the krunkelbach vein type uranium deposit in southwest germany were investigated by the u xe kr u pb and 234 u 230 th methods and by microprobe analysis both u pb and u xe kr results indicate a late carboniferous formation age of 295 or 7 ma for all veins of the deposit and an episodic pb loss during the tertiary 50 or 8 ma 234 u 230 th dating yields quaternary formation ages of 250 to 350 ka kiloyears for five secondary u minerals u pb isotope investigations on three of these samples show a strong component of inherited radiogenic pb which means that during the quaternary pitchblende oxidation pb was not completely separated from u the three isotopically dated events probably correlate with three generations of fluid inclusions the carboniferous hydrothermal veins were formed from low salinity solutions at temperatures of 100 degrees to 300 degrees c uranium probably was derived from leaching of magmatic uraninite in the brhalde granite by near surface oxidizing ground waters and later precipitated due to mixing with hot strongly reducing solutions or by reaction with a previously deposited reduced ore assemblage a gap of 30 to 40 m g between granite emplacement and pitchblende formation indicates that circulation of hydrothermal fluids in the late carboniferous early permian probably was caused by a high regional heat flow rather than by magmatic heat during the formation of the rhinegraben in the early tertiary barite fluorite and calcite but not ore minerals were deposited from highly saline na ca cl brines of 150 degrees to 200 degrees c these brines leached radiogenic and fissiogenic uranium daughters from the pitchblendes and there are indications of minor uranium remobilization eight illite samples from hydrothermally altered wall rocks yield k ar ages of 119 to 208 ma these values are interpreted as mixing ages of the u pb and u xe kr documented carboniferous and tertiary events although a mesozoic event not recorded in the other isotopic systems cannot be ruled out with certainty in the late tertiary early quaternary the present hydrological conditions were installed with infiltration of oxygen rich meteoric waters causing uranium remobilization and precipitation of secondary uranyl minerals i e phosphates arsenates silicates and tungstates yielding 230 th 234 u ages of at least 250 ka

oxygen isotope variations in phosphate of biogenic apatites ii phosphorite rocks abstract phosphorites from sedimentary sequences ranging in age from archaean to recent were analysed for 18 o in both the po 4 18 o p and co 3 18 o c in the apatite lattice the oxygen isotope record is considerably better preserved in phosphates than in either carbonates or cherts the use of the longinelli and nuti 8 temperature equation yields temperatures for recent phosphorites that are in good agreement with those measured in the field the 18 o p values of ancient phosphorites decrease with increasing age these changes with time are not likely to be due to post depositional exchange changes in 18 o values of seawater and variations of temperature with time can account for the 18 o p time trend but the latter explanation is preferred in ancient phosphorites 18 o c in structurally bound carbonate in apatite is not a reliable geochemical indicator

u pb whole rock and mineral dating of the falkenberg granite in northeast bavaria u pb and pb pb isotope ratios of 10 whole rock samples 3 k feldspars 3 muscovites 3 biotites and 7 apatites from the falkenberg granite northeast bavaria define a three dimensional discordia plane yielding intersection ages of307 22ma and59 91ma an age of 316 9 ma was calculated from a pb pb isochron for these samples the whole rock samples appear to be only slightly disturbed by a later event which is documented by fission track ages of the apatites about 50 ma the apparent u pb isochron age of 304 ma and the th pb isochron age of 303 ma cannot be accepted as ages because the high mswd values classify them as scatterchrons the results are in agreement with the results of rb sr and k ar dating however dates derived from zircons scatter between 320 and 360 ma these older ages are interpreted as due to relicts in the zircons

weathering of bi bearing tennantite abstract the tennantite tetrahedrite solid solution series called fahlore cu ag 6cu4 fe zn cu hg cd 2 sb as bi te 4 s se 13 is widespread in many geological environments since it incorporates heavy metals and toxic elements a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks emerging mainly from the mobilization of as sb bi and local and global metal fluxes in stream waters and oceans in this study weathering of bi rich members of this mineral group was investigated using microscopy empa sem tem la icp ms raman xrd and mla observations reveal a succession of four distinct stages of weathering during stage 1 irregular tubes within fahlore show an assemblage of nm to m sized romeite group minerals tripuhyite crystalline cu oxides and cu sulfides stage 1 textures and secondary sulfides indicate a low redox potential and a low fluid rock ratio typical of cementation zones mass balance calculations show that during this stage all zn and the majority of as and s are released to the weathering fluids bismuth is immobile in this stage and sb and fe are immobile if bi is sufficiently available from fahlore but both are partly released if the fahlore did not contain sufficient bi during stage 2 amorphous and nano crystalline arsenates replace fahlore as weathering fronts such assemblages indicate a higher redox potential than in stage 1 typical for oxidation zones mass balance calculations reveal that zn sb s and partially cu are lost arsenic and bi are immobile stage 3 occurs only locally dissolving former weathering stages and or precipitating amorphous cu arsenates silicates reflecting processes in micro compartments not characteristic for the general weathering process stage 4 is characterized by the formation of crystalline bi cu ba ca or al bearing arsenates and cu carbonates spatially independent of the precursor fahlore copper and as originate from older weathering assemblages whereas many other elements are derived externally ca ba al this stage reflects the increasing importance of the local host rock and gangue mineralogy as it is typical in near surface environments of oxidation zones or on mine dumps where elements are highly mobile and a high fluid rock ratio prevails gossan mineralization the temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone oxidation zone and gossan assemblages in one hand specimen thus one fahlore grain can record the uplift and erosion and the increasing fluid rock interaction of a weathered ore deposit with time tube like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element oxide arsenide and sulfide phases they also were produced during experimental work in ilmenite this is clear evidence that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore the importance of bi to stabilize sb bearing supergene phases and thereby for the immobilization of toxic sb shown in the present work may stimulate further investigations on the environmental immobilization of toxic elements by companion metals during weathering processes

island arc character and late precambrian age of volcanics at wadi shwas hijaz saudi arabia geochemical and sr and nd isotopic evidence abstract a summary description of two volcanic sequences named the surgah and the shwas formation situated in the wadi shwas area at long 42 0 lat 20 0 in the arabian shield is given major and trace element concentrations including ree abundances are presented as well as sr and some nd isotope results one sequence the surgah formation shows a tholeiitic differentiation trend from basaltic to rhyolitic rocks whereas the shwas formation has calc alkaline affinities both sequences have low concentrations of incompatible elements notably rb nb zr and ti the coexistence of a tholeiitic and a calc alkaline suite along with these low concentrations is strongly reminiscent of some present day island arc environments an rb sr errorchron age of 721 55ma was obtained on the surgah formation with high initial87sr 86sr ratios around 0 705 the rare earth abundances are overall very low and the patterns show a relative depletion of the light ree in the least evolved rocks indicating a relatively light ree depleted mantle source a time integrated light ree depleted source is also indicated by the fairly radiogenic143nd 144nd ratios end values around 8 the nd model age of source depletion tchurnd is around 2 2 ga

controls on preferential recharge to chalk aquifers summary there is evidence that under certain conditions rapid preferential recharge via the fracture network can occur in chalk aquifers this has potentially important implications for contaminant migration through the chalk unsaturated zone cuz and for groundwater flooding in chalk catchments in the case of groundwater flooding deficiencies in modelling aquifer response have been attributed to inadequate representation of flow processes in the cuz in this paper we consider two complementary approaches for assessing controls on preferential recharge to chalk aquifers an empirical approach and a physically based modelling approach we show that the main controls on preferential recharge to chalk aquifers are the characteristics of rainfall events in terms of duration and intensity the physical properties of the near surface and the antecedent soil moisture in the near surface we demonstrate a number of deficiencies when past models of the cuz are applied to the problem of simulating preferential recharge notably that the assumption of instantaneous equilibrium between fractures and matrix is not valid particularly during extreme recharge events in order to simulate preferential recharge fractures and matrix must be modelled as separate but interacting domains this was achieved using a dual continua model the model was computationally demanding but was able to reproduce observed behaviour including apparently hysteretic soil moisture characteristic relationships in the near surface and rapid preferential recharge fluxes in response to high intensity rainfall events

major minor and trace element composition of pyromorphite group minerals as recorder of supergene weathering processes from the schwarzwald mining district sw germany more than 150 samples of pyromorphite mimetite vanadinite and minerals of the hedyphane group which collectively are summarized here under the term pygm for pyromorphite group minerals from the schwarzwald mining district southwest germany have been analyzed by electron microprobe and la icp ms in this largest study of its kind the relations of pygm composition to host rock and fluid compositions and the amount of solid solution between the various end members were investigated in addition we report the colors of the many analyzed mineral compositions here is a list of the most important results pyromorphite and mimetite are completely miscible at conditions of the oxidation zone in ore deposits the solvus between pyromorphite and vanadinite appears to asymmetrical with up to about 3 mol of vanadinite component in pyromorphite and up to about 39 mol of pyromorphite component in vanadinite in cases where both minerals coexist due to a lack of suitable samples the solvus between vanadinite and mimetite could not be completely constrained but we report vanadinite analyses with up to 12 mol mimetite and 8 mol pyromorphite component there is complete miscibility between pyromorphite and phosphohedyphane and between mimetite and hedyphane f rich varieties appear only to exist in hedyphanes and phosphohedyphanes while pyromorphites mimetites and vanadinites are cl or oh dominated we report for the first time analyses suggesting the occurrence of an oh end member corresponding to mimetite while pyromorphites are preferably green and mimetites yellow this is not at all a diagnostic feature as many exceptions exist major elements are not correlated at all with the color of a specific crystal most pygm are strongly zoned and display for example significant variations in ca that are likely to be related to variations of the compositions of various fluid pulses from which the crystals formed pygm composition is generally uncorrelated with host rock composition but pygm enrich other metals like ree cr sb bi or u up to a factor of 10 6 therefore they can be regarded as very sensitive recorders of the metal inventory of an oxidation zone and they even record metals only present as traces in the primary ore deposit very reliably ree patterns of pygm show significant variability even at one location this may suggest that each zone of a pygm crystal records the ree pattern of a single fluid pulse or it may indicate fractionation of the ree during pygm growth in the absence of conclusive data the former possibility appears the more likely one pygm are extremely efficient filters for heavy metals from supergene solutions in and in the vicinity of ore deposits

new analytical procedures to increase the resolution of zircon geochronology by the evaporation technique abstract in the evaporation technique kober b 1987 single zircon evaporation combined with pb emitter bedding for 207 pb 206 pb age investigations using thermal ion mass spectrometry and implications for zirconology contrib mineral petrol 96 63 71 of zircon dating individual zircon crystals are heated in a series of steps causing the thermal breakdown of the zircon along a sharply defined reaction front chapman h j roddick j c 1994 kinetics of pb release during the zircon evaporation technique earth planet sci lett 121 601 611 radiogenic 207 pb 206 pb ages for each step represent the average pb isotopic composition of the zircon consumed resulting in geologically meaningless mixed ages where the reaction front intersects multiple domains within a zircon recognition of whether 207 pb 206 pb ages are derived from single or heterogeneous components is central to age determinations by the evaporation technique replication of an age indicates that a single component is being dated as it is unlikely that several components will be repeatedly mixed in identical proportions thus increasing the number of heating steps taken for each zircon increases the resolution of information obtained presentation of data as age against order of acquisition allows clear visual interpretation of the degree of mixing behaviour within each zircon analysed ranking the heating steps in order of ascending age clarifies trends within the zircon population as a whole and also allows the use of an r2 test to delimit those steps which do or do not contain mixed components mixing behaviour may be further emphasised by superimposing the model initial th u ratio for each step on the same graph

review and comparison of models for describing non equilibrium and preferential flow and transport in the vadose zone abstract in this paper we review various approaches for modeling preferential and non equilibrium flow and transport in the vadose zone existing approaches differ in terms of their underlying assumptions and complexity they range from relatively simplistic models to more complex physically based dual porosity dual permeability and multi region type models a relatively simple dual porosity flow model results when the richards equation is combined with composite double hump type equations for the hydraulic properties to account for both soil textural matrix and soil structural fractures macropores peds effects on flow the simplest non equilibrium flow model a single porosity model which distinguishes between actual and equilibrium water contents is based on a formulation by ross and smettem soil sci soc am j 64 2000 1926 that requires only one additional parameter to account for non equilibrium a more complex dual porosity mobile immobile water flow model results when the richards or kinematic wave equations are used for flow in the fractures and immobile water is assumed to exist in the matrix we also discuss various dual permeability models including the formulation of gerke and van genuchten water resour res 29 1993a 305 and the kinematic wave approach as used in the macro model of jarvis technical description and sample simulations department of soil science swedish university of agricultural science uppsala sweden 1994 51 both of these models invoke terms accounting for the exchange of water and solutes between the matrix and the fractures advantages and disadvantages of the different models are discussed and the need for inter code comparison is stressed especially against field data that are sufficiently comprehensive to allow calibration validation of the more complex models and to distinguish between alternative modeling concepts several examples and comparisons of equilibrium and various non equilibrium flow and transport models are also provided

constraints on the origin of zonation of the granite complexes in the fichtelgebirge germany and czech republic evidence from a gravity and geochemical study compositional zoning of granitic plutons is a common feature but the spatial variation of zoning is rarely studied in detail it is suggested that important additional information can emerge if the compositional zoning is regarded with relation to the root zones i e with the granite shape at depth a combined geochemical and gravity investigation was performed on the hercynian fichtelgebirge granites which are composed of an older intrusive complex oic and younger intrusive complex yic the oic and yic are distinct from each other with respect to magma origin differentiation pattern shape of the granite complexes at depth and the zonation pattern in relation to the root zone the oic shows normal compositional zoning whereas the yic both reverse yic 1 and normal zoning yic 2 the general zonation pattern of the oic and the yic is the result of a combination of multiple injections of single magma batches and in situ differentiation during magma emplacement in addition to the general zonation pattern local zonation in individual granite bodies of the yic was caused by sidewall crystallisation producing a less differentiated marginal facies g2 and a more differentiated core facies g3 and g4 it is suggested that the complex zonation patterns of the fichtelgebirge granite complexes reflect interactions between the rate of magma output which is partly governed by their rheological properties and the rate of deformation which provides the room for the magma to be emplaced

erratum to metamictisation of natural zircon accumulation versus thermal annealing of radioactivity induced damage annealing of the radiation damage generated in decay events is a common phenomenon in natural zircons we have studied relationships between radiation damage age and radionuclide content of natural zircons on a micro scale the degree of metamictisation was estimated by means of confocal laser raman spectroscopic measurements raman band broadening in well ordered to moderately metamict zircons that have not experienced significant healing of the radiation damage since the time of their growth shows a nearly linear dependence on the fluence this dependence is proposed as a calibration line for examining unknown zircons in order to consider complete or incomplete damage storage which may contribute to the understanding of the low t thermal history of their host rocks seven examples for the application are presented radiation damage may anneal heterogeneously with preferred re ordering in more damaged micro areas results suggest that single point defects do not anneal continuously over geologic periods of time but are in contrast a comparably stable type of radiation damage in contrast to recrystallisation processes structural recovery due to simple thermal annealing is not necessarily connected with loss of radiogenic pb the most prominent example for this are concordant zircons from sri lanka although they are excellent standards for u pb dating sri lankan zircons should not be used as standards for structural radiation damage the experimental work is completed by monte carlo simulations of decay events in zircon

time of formation and peak of variscan hp ht metamorphism of quartz feldspar rocks in the central erzgebirge saxony germany the variscan erzgebirge represents an antiform with a core of gneisses and mica schists surrounded by a phyllitic mantle the gneiss eclogite unit geu in the central part is a composite tectonometamorphic assemblage characterized by a hp ht imprint and comprises migmatitic para and orthogneisses ht mylonites hp granulites eclogites and garnet peridotites it is tectonically sandwiched between two major units with distinctly lower pt histories the geu experienced a characteristic kinked retrograde pt path after hp ht equilibration with 1 strong near isothermal decompression at high temperatures 2 extensive re equilibration at medium pressures followed 3 by rapid cooling during continued uplift we dated zircons pb pb evaporation from granitoid orthogneisses and metapelites of the geu the orthogneisses contain euhedral long prismatic zircons of igneous origin that provided protolith ages between 470 and 524 ma metapelites retain well preserved granulite facies mineral assemblages and contain spherical multifaceted metamorphic zircons that grew near the peak of hp ht metamorphism inclusions of prograde hp phengite 15 kbar and rutile are included in one such zircon metamorphic zircons of three samples from different localities yielded identical 207pb 206pb ages of 340 5 0 7 ma 341 2 0 5 ma and 341 6 0 5 ma respectively consideration of these zircon ages with published 39ar 40ar white mica ages suggests fast cooling and uplift rates in excess of 50 c ma and 4 km ma this is typical for large scale extensional tectonic unroofing of the ultra deep part of a fossil thickened variscan continental crust 60 km during continuing continental collision and orogenic collapse

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

caledonian ages in variscan rocks rb sr and sm nd isotopic variations in dioritic intrusives from the northwestern bohemian massif west germany abstract dioritic intrusives and granites from the northwestern bohemian massif west germany were analyzed for the chemical and isotopic composition of rb sr and sm nd the marktredwitz intrusive suite and the tirschenreuth mahring sill intrusions yield apparent rb sr whole rock isochron ages of 468 9 ma and 470 33 ma respectively while the reuth erbendorf granodiorites display a scatter with an apparent age of 545 16 ma the rb sr whole rock ages conflict with geological evidence the diorites intruded metamorphic country rocks which experienced an early devonian metamorphism contact relationships between the diorites and porphyritic granites indicate nearly contemporary emplacement the intrusion ages of two porphyritic granites from this area have been dated at 319 ma and 311 ma the diorites display a variation in nd 320 ma ranging from 1 0 to 4 4 whereas the two granites yield homogeneous initial nd values of 3 7 and 6 6 the variations in elemental concentrations and initial isotopic ratios clearly show a mixing trend within the dioritic rock suites the mixing partners are a presumably mantle derived magma and crustal components of varying composition the isotope systematics of the diorites and the concordance of their rb sr whole rock age values with caledonian rock forming events in central europe point to a pre intrusive caledonian event inherited in these rocks we suggest that the diorites were formed by multistage anatectic processes

zircon ages and nd isotopic and chemical compositions of orthogneisses from the black forest germany evidence for a cambrian magmatic arc single zircon u pb dating combined with 207pb 206pb ages obtained by the evaporation method constrains the emplacement of tonalitic trondhjemitic and granodioritic orthogneisses of the moldanubian zone in the black forest between 500 and 510 ma two detrital zircon populations of 1 9 and 1 6 ga indicate early middle proterozoic material in the former setting of the basement the initial end values range from 0 1 to 3 4 and mean crustal residence ages of 1 0 1 4 ga are consistent with involvement of early middle proterozoic crust and a subordinate juvenile component probably originating from subduction related melting of the mantle the orthogneisses have fractionated ree patterns and slightly higher k2o na2o ratios than typical low k tonalite trondhjemite granite suites the chemical data are interpreted as evidence for melting of amphibolite and contributions from evolved crust the emplacement of the orthogneisses was superceded by a high temperature metamorphic event at 480 ma which we interpret as a result of lithospheric thinning in a marginal basin behind a cambrian magmatic arc

granitoid magmatism of the nw bohemian massif revealed gravity data composition age relations and phase concept the late variscan granitoids of the nw bohemian massif northeast bavaria west bohemia constitute four partly contiguous granitoid complexes fichtelgebirge northern oberpfalz waidhaus rozvadov and bor incorporating more than 20 intrusive units based on gravity data the granites can be modeled as steeply inclined slab and wedge like bodies with thicknesses between 2 and 8 km a rough estimate of the total volume of the granites is approximately 18 000 km3 within the four areas named above composition ranges from less evolved dioritic rocks known as the redwitzite suite to highly evolved granites the redwitzites comprise metaluminous rocks with dominant i type features these rocks yield aberrantly old rb sr ages 545 415 ma low initial sr ratios 0 706 0 708 and high and variable nd t values 1 to 4 sr nd isotopes of the redwitzites show contamination trends towards the granites suggesting mixing between mantle magma and crustal granitic melts an older plutonic association granites of bor leuchtenberg weissenstadt marktleuthen zainhammer is mildly peraluminous displaying features of both i and s type granitoids these granites are characterized by lower carboniferous ages rb sr k ar u pb low to intermediate initial sr ratios 0 707 0 708 and high nd t values 2 to 4 which overlap with those of paragneisses from the zone of erbendorf vohenstrauss zev and from the western part of the tepla barrandian it is postulated that the older granites were formed either by partial melting of zev or tepla barrandian crust or alternatively of preexisting mature crust contaminated by mantle material the younger granites are strongly peraluminous and of s type they yield upper carboniferous rb sr and k ar ages and exhibit a range towards high initial sr ratios 0 710 0 720 and low nd t values 4 to 8 similar values are found in moldanubian paragneisses and in saxothuringian metasediments both of which provide potential source rock lithologies for these granites

high temperature memory in calcic amphiboles and constraints on compositional control of their 40ar 39ar ages well characterized calcic amphiboles from an incompletely mixed magmatic rock association of mainly intermediate dioritic composition were studied by incremental heating experiments of 40 ar 39 ar the rocks in question were thermally overprinted by late hercynian granites microprobe and scanning electron microscopy analyses show that the amphibole grains consist of two different calcic hornblende varieties 1 a si and mg rich variety and 2 a variety enriched in al ti fe k and na the mg si rich hornblende can be further characterized by its higher cao k 2 o ratios 30 50 compared to the al ti fe k na rich hornblende 12 15 three hornblende separates that previously had yielded conventional k ar ages of 320 317 and 302 ma have been dated by the 40 ar 39 ar step heating technique the low and medium temperature parts of the 40 ar 39 ar age spectrum show discordant ar systematics with single step ages generally younger than 325 ma the gas released at the highest temperature steps preserves an exceptional record of old and remarkably similar integrated ages 342 346 and 344 ma the high temperature ages correspond to phases with higher apparent cao k 2 o ratios 30 45 and are interpreted to result from ar release from mg si hornblende domains that are assumed to have been very resistent to ar loss during the late hercynian thermal events the results of this study suggest that ar retentivity differs among calcic amphiboles and mg si rich hornblendes are more ar retentive than their al ti fe k na rich counterparts

late variscan magmatism revisited new implications from pb evaporation zircon ages on the emplacement of redwitzites and granites in ne bavaria pb evaporation zircon analyses coupled with a detailed cathodoluminescence cl study on the complete series of granitoids from the northern oberpfalz ne bavaria provide new evidence for the commencement and timing of late variscan magmatism all granitoids analysed in this study were dated before by rb sr and or k ar methods investigated samples comprise medium grained i type dioritic rocks redwitzites i s type granites leuchtenberg marktredwitz g1 zainhammer and s type granites falkenberg liebenstein mitterteich friedenfels steinwald flossenburg barnau the zircon evaporation technique reveals three groups of 207pb 206pb ages which are interpreted to represent magmatic crystallisation 1 ages of 324 321 ma are found in all analysed redwitzites and in almost all i s type granites 2 the granites of falkenberg and liebenstein yield ages of 315 ma 3 ages between 312 and 310 ma are recorded in the mitterteich friedenfels steinwald and flossenburg granites titanite crystals from different redwitzite bodies yield conventional u pb ages of 325 322 ma identical to the pb evaporation zircon data of these rocks the s type granites of groups 2 and 3 contain zircons with relict cores but only a small number of them yield older ages indicating that some of the cores must have lost their radiogenic pb from the geochronological data we infer that metamorphic conditions of the variscan crust produced different granite types at different times the data support a model involving an early period of mantle related magmatism which postdates the final convergence stage of the variscan orogen this magmatic activity was at the same time as the thermal peak of regional metamorphism and is followed by a late period of crustal anatexis which is probably related to post collisional extension of the thickened variscan crust

the source of phosphate in the oxidation zone of ore deposits evidence from oxygen isotope compositions of pyromorphite abstract pyromorphite pb5 po4 3cl is an abundant mineral in oxidized zones of lead bearing ore deposits and due to its very low solubility product effectively binds pb during supergene alteration of galena pbs the capacity of a soil or near surface fluid to immobilize dissolved pb depends critically on the availability of phosphate in this soil or fluid potential phosphorus sources in soil include i release during biological processes i e leaching from litter lysis of microbial cells after intracellular enzyme activity in soil and hydrolysis from soil organic matter by extracellular enzymes and ii inorganic phosphate from the dissolution of apatite in the adjacent basement rocks intracellular enzyme activity in plants microorganisms associated with kinetic fractionation produces an oxygen isotope composition distinctly different from inorganic processes in soil this study presents the first oxygen isotope data for phosphate 18op in pyromorphite and a comprehensive data set for apatite from crystalline rocks we investigated 38 pyromorphites from 26 localities in the schwarzwald southwest germany and five samples from localities outside the schwarzwald in addition to 12 apatite separates from gneissic and granitic host rocks pyromorphites had 18op values between 10 and 19 comparable to literature data on 18op in the readily available p fraction in soil resin extractable p from which minerals potentially precipitate in soils 18op values below the range of equilibrium isotope fractionation can be attributed either to apatites that formed geochemically 18op of apatites 6 to 9 or less likely to biological processes extracellular enzyme activity however for most of our samples isotopic equilibrium with ambient water was indicated which suggests biological activity therefore we conclude that the majority of pyromorphites in oxidized zones of ore bodies formed from biologically cycled phosphate this study highlights that biological activity and pb mobilization are intimately connected in humid regions with high biological activity in soil pb might be precipitated rapidly due to biologically released phosphate whereas pb will be released to the environment from ore deposits or mine dumps much more easily in arid regions with low biological activity because pyromorphite cannot form due to limited supply of phosphorus

modelling flow and heat transfer through unsaturated chalk validation with experimental data from the ground surface to the aquifer abstract during the winter and spring of 2000 2001 large floods occurred in northern france somme river basin and southern england patcham area of brighton in valleys that are developed on chalk outcrops the floods durations were particularly long more than 3 months in the somme basin and caused significant damage in both countries to improve the understanding of groundwater flooding in chalk catchments an experimental site was set up in the hallue basin which is located in the somme river basin france unsaturated fractured chalk formation overlying the chalk aquifer was monitored to understand its reaction to long and heavy rainfall events when it reaches a near saturation state the water content and soil temperature were monitored to a depth of 8 m and the matrix pressure was monitored down to the water table 26 5 m below ground level the monitoring extended over a 2 5 year period 2006 2008 under natural conditions and during two periods when heavy artificial infiltration was induced the objective of the paper is to describe a vertical numerical flow model based on richards equation using these data that was developed to simulate infiltrating rainwater flow from the ground surface to the saturated aquifer the marthe computer code which models the unsaturated saturated continuum was adapted to reproduce the monitored high saturation periods composite constitutive functions hydraulic conductivity saturation and pressure saturation that integrate the increase in hydraulic conductivity near saturation and extra available porosity resulting from fractures were introduced into the code using these composite constitutive functions the model was able to accurately simulate the water contents and pressures at all depths over the entire monitored period including the infiltration tests the soil temperature was also accurately simulated at all depths except during the infiltrations tests which contributes to the model validation the model was used to calculate the aquifer recharge over a long period that included droughts and floods the calculated recharge is realistic as it makes it possible to simulate the corresponding monitored groundwater level data which increases confidence in the modelling approach

two distinctive granite suites in the sw bohemian massif and their record of emplacement constraints from geochemistry and zircon 207pb 206pb chronology

the tectono metallogenic evolution of the arabian shield abstract the arabian shield comprises a group of diverse terranes accreted during the late proterozoic their boundaries are suture zones characterised by tectonised ultramafic bodies aligned within distinct orogenic belts the asir hijaz and midyan terranes consist of a series of late proterozoic immature island arcs and together form the western half of the shield in the east however the afif and ar rayn terranes have a continental affinity with the afif terrane being much older at least early proterozoic and possibly archaean metallogeny within the arabian shield is also diverse and includes cu ni and cr mineralisation associated with proterozoic oceanic crust or ophiolite arc type volcanogenic base and precious metal deposits associated with formerly active plate margins shear zone hosted mesothermal gold mineralisation related to accretionary and strike slip tectonics as well as sn w ta mo ree mineralisation associated with post cratonisation alkali granite magmatism of late proterozic to early phanerozoic age it is possible to trace a systematic evolution in metallogeny both within each terrane and throughout the craton as a whole as a function of crustal development and tectonics although the age range of rocks exposed in the shield is from early proterozoic to tertiary all known styles of primary metallogeny are associated with its cratonisation in the late proterozoic

recharge of the upper chalk aquifer at a site in hampshire england 1 water balance and unsaturated flow abstract measurements of the annual cycle of changes in water content and potential in the 40 m thick unsaturated zone of upper chalk at a site in southern england are described measured evaporation continued at the penman potential rate until the soil moisture deficit reached 175 mm this suggested that a root constant of 200 mm would be more appropriate than the much lower values generally used the field capacity concept could not be reconciled with the timing of renewed water recharge and the reasons for this are discussed the mechanisms of water flow through the unsaturated zone of the chalk are examined and it is shown that at this upper chalk site matrix flow is the dominant recharge mechanism

distribution of oceanic and continental leads in the arabian nubian shield new common lead data for feldspar whole rock and galena samples from the arabian nubian shield together with data from previous work can be divided into two main groups group i leads have oceanic mantle characteristics whereas group ii leads have incorporated a continental crustal component of at least early proterozoic age the group i leads are found in rocks from the red sea hills of egypt and the western and southern parts of the arabian shield group ii leads are found in rocks from the northeastern and eastern parts of the arabian shield as well as from the southeastern shield near najran they are also found in rocks to the south in yemen to the east in oman and to the west at aswan egypt this distribution of data suggests that the arabian nubian shield has an oceanic core flanked by rocks that have developed at least in part from older continental material two mechanisms are suggested by which this older lead component could have been incorporated into the late proterozoic rocks and each may have operated in different parts of the shield the older lead component either was derived directly from an underlying early proterozoic basement or was incorporated from subducted pelagic sediments or sediments derived from an adjacent continent

time calibration of a p t path from a variscan high temperature low pressure metamorphic complex bayerische wald germany and the detection of inherited monazite a temperature time path was constructed for high temperature low pressure ht lp migmatites of the bayerische wald internal zone of the variscan belt germany the migmatites are characterised by prograde biotite dehydration melting peak metamorphic conditions of approximately 850 c and 0 5 0 7 gpa and retrograde melt crystallisation at 800 c the time calibration of the pressure temperature path is based on u pb dating of single zircon and monazite grains and titanite separates on 40ar 39ar ages obtained by incremental heating experiments on hornblende separates single grains of biotite and k feldspar and on 40ar 39ar spot fusion ages of biotite determined in situ from sample sections additionally crude estimates of the duration of peak metamorphism were derived from garnet zoning patterns suggesting that peak temperatures of 850 c cannot have prevailed much longer than 2 5 ma the temperature time paths obtained for two areas approximately 30 km apart do not differ from each other considerably u pb zircon ages reflect crystallisation from melt at 850 800 c at 323 ma southeastern area and 326 ma northwestern area the u pb ages of monazite mainly coincide with those from zircon but are complicated by variable degrees of inheritance the preservation of inherited monazite and the presence of excess 206pb resulting from the incorporation of excess 230th in monazite formed during ht lp metamorphism suggest that monazite ages in the migmatites of the bayerische wald reflect crystallisation from melt at 850 800 c and persistence of older grains at these temperatures during a comparatively short thermal peak the u pb ages of titanite 321 ma and 40ar 39ar ages of hornblende 322 316 ma and biotite 313 309 ma reflect cooling through the respective closure temperatures of approximately 700 570 500 and 345 310 c published in the literature most of the feldspars ages 305 296 ma probably record cooling below 150 300 c while two grains most likely have higher closure temperatures the temperature time paths are characterised by a short thermal peak by moderate average cooling rates and by a decrease in cooling rates from 100 c my at temperatures between 850 800 and 700 c to 11 16 c my at temperatures down to 345 310 c further cooling to feldspar closure for ar was probably even slower the lack of decompressional features the moderate average cooling rates and the decline of cooling rates with time are not easily reconciled with a model of asthenospheric heating rapid uplift and extension due to lithospheric delamination as proposed elsewhere instead the high peak temperatures at comparatively shallow crustal levels along with the short thermal peak require external advective heating by hot mafic or ultramafic material

constraints on variscan granite emplacement in north east bavaria germany further clues from a petrogenetic study of the mitterteich granite petrochemical and rb sr k ar and sm nd isotopic data presented for the mitterteich granite provide information on whole rock and mineral compositional characteristics intrusion and cooling history and protolith nature and put further constraints on the variscan magmatic evolution in north east bavaria

oxygen isotope composition of natural phosphates from volcanic ash soils of the great rift valley of africa and east java indonesia abstract volcanic ash soils of the great rift valley of africa and east java indonesia are highly fertile due to an ample supply of available phosphorus the origin of the natural phosphates has been determined from oxygen isotope analyses 18o which reflect the formation temperature of the p o bond the 18o values of phosphates extracted from fourteen surface or near surface soil samples ranges from 10 1 to 24 8 the values are higher than those of recent volcanic ashes from oldoinyo lengai tanzania and merapi indonesia 18o 5 3 to 6 2 and those of igneous apatites from carbonatites geodes and hydrothermal deposits 18o 0 2 to 12 2 n 10 the soils with 18o values at the lower end of the range are from ngorongoro crater highlands and the footslope of mt meru northern tanzania 10 4 to 15 9 and east java indonesia 10 1 to 16 9 respectively where the soil surfaces have both been rejuvenated by frequent deposition of volcanic phosphates in recent ashes higher 18o values 16 7 to 24 8 which are comparable with those of wild mammal s skeletons 18o 18 6 to 24 0 are observed for soils in advanced stages of pedogenesis oxygen isotope fractionation between phosphate and associated calcite has been evaluated for selected soil samples the resulting isotopic temperatures are unreasonable however and indicate that the soil phosphates are not in isotopic equilibrium with the fluids responsible for authigenic calcite available phosphorus in the soils studied is derived from both of biogenic plants and mammal bones and volcanic sources

pb diffusion in zircon abstract chemical diffusion of ti under anhydrous conditions at 1 atm and under fluid present elevated pressure 1 1 1 2 gpa conditions has been measured in natural zircon the source of diffusant for 1 atm experiments was a zro2 tio2 zircon mixture with experiments run in crimped pt capsules diffusion experiments done in the presence of h2o co2 fluid were run in a piston cylinder apparatus using a source of ground tio2 zrsio4 and sio2 with oxalic acid added to produce h2o co2 vapor and partially melt the solid source material yielding an assemblage of rutile zircon melt vapor nuclear reaction analysis nra with the resonant nuclear reaction 48ti p 49v was used to measure diffusion profiles for both sets of experiments the following arrhenius parameters were obtained for ti diffusion normal to cover the temperature range 1350 1550 c at 1 atm d ti 3 33 10 2 exp 754 56 kj mol 1 r t m 2 s 1 ti diffusivities were found to be similar for experiments run under fluid present conditions a fit to all of the data yields the arrhenius relation d 1 34 102 exp 741 46 kj mol 1 rt m2 s 1 these data suggest that zircon should be extremely retentive of ti chemical signatures indicating that the recently developed ti in zircon crystallization geothermometer watson e b harrison t m 2005 zircon thermometer reveals minimum melting conditions on earliest earth science 308 841 844 will be quite robust in preserving temperatures of zircon crystallization titanium diffuses somewhat faster in zircon than larger tetravalent cations u th and hf but considerably more slowly than pb the ree and oxygen hence ti crystallization temperatures may be retained under circumstances when radiometric ages or other types of geochemical information are lost

weathering of galena mineralogical processes hydrogeochemical fluid path modeling and estimation of the growth rate of pyromorphite in many natural and anthropogenically affected environments alteration of galena produces thermodynamically more stable secondary lead phases these secondary minerals control the mobility of the toxic heavy metal lead in water these textural paragenetic and stability relations have not been investigated in detail in the literature yet an extensive petrographic study of 41 thin sections of weathered zoned galena and adjacent country rock from the schwarzwald mining area southwest germany is presented the observed textures were evaluated using phreeqc fluid path modeling and sequences of stable secondary mineral assemblages were predicted the most common secondary supergene lead minerals of interest here are cerussite anglesite and pyromorphite group minerals pygm pyromorphite mimetite and vanadinite these lead phases show a spatially well ordered zoned texture around the preexisting relic galena cerussite and anglesite commonly occur either as in situ replacement of galena and or as euhedral crystals in cavities of former partially dissolved galena the pygm are present either as crusts around the margin of the former relic galena or are common as infiltration products into the host rock gangue during progressive weathering anglesite typically disappears first followed by cerussite finally only the highly insoluble pygm persist as a perimorphose hence a spatially and temporally zoning texture is formed thermodynamic models of various fluid evolution paths using phreeqc show the influence of temperature ph variable p co2 phosphorous contents and or different mineral reactions on the sequence of formation and stability of the secondary lead phases already small changes in one or more of these parameters can lead to different mineral assemblages or sequences of secondary lead minerals over almost the whole relevant ph range pygm are the most stable lead phases precipitating at very low ion activities explaining their textural position whether cerussite or anglesite forms depends mainly on the ph value of the supergene fluids which is affected by the quite variable fluid pathways furthermore a solubility diagram for a typical near surface fluid was calculated showing that anglesite is the most soluble phase followed by cerussite and pygm this again reflects the microscopic observations as a further step the time span for the formation of a natural millimeter thick pyromorphite crust was evaluated using subsoil phosphorous fluxes from the literature the calculation indicates that millimeter thick pyromorphite crusts can be formed in few tens to about hundred years which is in agreement with observations in the nature in this study a framework for predicting stable secondary lead mineral assemblages and textures by fluid path modeling is given these models are potentially important for predicting the retention and mobilization of lead in systems around contaminated sites or natural ore deposits

the significance of flow in the matrix of the chalk unsaturated zone the significance of flow in the matrix of the chalk unsaturated zone in comparison with flow in fractures has been the subject of much debate in this article important elements of the literature are discussed in detail and several simple modelling analyses based on steady state flow are presented a study of the sensitivity of solute spreading to fracture spacing in models that ignore matrix flow shows that this latter assumption is generally incompatible with observed solute profiles unless unrealistically small fracture spacings are assumed the effect of air phase continuities e g bedding planes on matrix flow has also been examined these discontinuities are frequently interrupted by points of connectivity between matrix blocks an issue therefore is the relationship between connectivity and its effect on inter block conductance a simple analysis of the laplace equation shows that just 1 connectivity represents an effective pathway equivalent to 18 of the local rock hydraulic conductivity obviously when there is no fracture flow solute spreading is significantly reduced however dual permeability model simulations show that matrix flow reduces solute spreading in the presence of persistent fracture flow all of the above studies suggest that flow in the matrix of the chalk unsaturated zone is significant and that ignoring it may result in a serious misunderstanding of the system

anticorrelated rb sr and k ar age discordances leuchtenberg granite ne bavaria germany the leuchtenberg granite oberpfalz ne bavaria displays a continuous differentiation trend ranging from mildy peraluminous coarse grained porphyritic biotite granites bg to strongly peraluminous medium to fine grained garnet bearing muscovite granites gmg the rb sr and k ar age determinations of whole rock and mineral samples from the granite and associated intermediate rocks redwitzites have revealed two divergent age gradients rb sr wholerock dates decrease and initial 87sr 86sr ratios increase for successively more evolved subsets of the granite all bg samples 87rb 86sr 2 16 yield a date of 326 2 ma with a low initial 87sr 86sr ratio of 0 70778 0 00013 1 while all gmg samples 87rb 86sr 70 to 1000 yield a younger date of 317 2 ma with an enhanced initial 87sr 86sr ratio of 0 7146 0 0039 the k ar measurements on biotites and muscovites give closely concordant dates for the gmg 326 323 ma and the southern lobe of the bg 324 320 ma the northern lobe of the bg including the redwitzites shows a well defined trend of decreasing k ar dates from 320 ma to 300 ma towards the northwest critical consideration of both isotope systems leads to the conclusion that the rb sr system of the gmg was disturbed by a later hydrothermal event the ca 326 ma whole rock rb sr date for the bg is not in conflict with any of the k ar mineral dates and is taken as approaching the crystallization age of the leuchtenberg granite the k ar age progression within the northern lobe of the bg indicates that this part either cooled down over a protracted period of some 20 ma or experienced reheating at ca 300 ma the study highlights the potential of combined rb sr and k ar dating in deciphering detailed chronology on the scale of a single igneous intrusion

major and trace element compositions including ree of mineral thermal mine and surface waters in sw germany and implications for water rock interaction abstract the near surface water cycle in a geologically complex area comprises very different sources including meteoric metamorphic and magmatic ones fluids from these sources can react with sedimentary magmatic and or metamorphic rocks at various depths the current study reports a large number of major minor and trace element analyses of meteoric mineral thermal and mine waters from a geologically well known and variable area of about 200 150 km in sw germany the geology of this area comprises a variscan granitic and gneissic basement overlain in parts by triassic and jurassic shales sandstones and limestones in both the basement and the sedimentary rocks hydrothermal mineralization occurs including pb cu as zn u co and many others which were mined in former times mineral waters thermal waters and meteoric waters flowing through abandoned mines mine waters are distributed throughout the area although the mine waters concentrate in and around the schwarzwald the present analyses show that the major element composition of a particular water is determined by the type of surrounding rock e g crystalline or sedimentary rocks and the depth from which the water originates for waters from crystalline rocks it is the origin of the water that determines whether the sample is na cl dominant deeper origin or ca hco3 dominant shallow origin in contrast compositions of waters from sedimentary rocks are determined by the availability of easily soluble minerals like calcite ca hco3 dominant halite na cl dominant or gypsum ca so4 dominant major element data alone cannot therefore be used to trace the origin of a water however the combination of major element composition with trace element data can provide further information with respect to flow paths and fluid rock interaction processes accordingly trace element analyses showed that ce anomalies can be used as an indicator for the origin of a water whereas surface waters have negative or strongly negative ce anomalies waters originating from greater depths show no or only weak negative ce anomalies eu anomalies can be used to differentiate between host rocks waters from gneisses display positive eu anomalies whereas waters from granites have negative ones waters from sedimentary rocks do not display any eu anomalies rb and cs can also be indicators for the rock with which the fluid interacted rb and cs correlate positively in most waters with rb cs ratios of 2 which suggests that these waters are in equilibrium with the clay minerals in the rocks rb cs ratios 5 indicate reaction of a water with existing clay minerals whereas rb cs ratios the chemical compositions of carbonate precipitates from thermal waters indicate that rare earth elements rees rb and cs concentrations in the minerals are controlled by the incorporation of clay particles that adsorb these elements

mechanisms of water storage and flow in the unsaturated zone of the chalk aquifer abstract it is known that the volumes of water draining from some chalk catchments in recessions are significantly greater than can be explained by gravity drainage from fissure porosity the most likely source of this water is slow drainage from the matric porosity above the water table this paper suggests that the location of this storage is in the irregularities on the fissure surfaces studies of resin impregnated blocks of chalk failed to reveal the presence of hydrologically significant microfissures or macropores that could be the source of additional drainage ultrasonic measurements at varying values of effective stress show no indication of changes in the acoustic transmission properties that could be attributed to closure of microfissures drainage and mercury intrusion measurements indicate that there is significant storage on block surfaces the drainage measurements confirm that the storage is of the order of magnitude about 0 3 needed to explain the slow drainage this additional storage explains why the water table is slow to respond after recharge events and why the chalk is resilient to drought the presence of storage in the unsaturated zone implies that the position of the water table may not be an accurate indicator of groundwater resources the concept of filling and draining of irregularities on fissure surfaces also leads to a new model for the generation of fissure flow in the unsaturated zone of the chalk this suggests that fissure flow can be generated at any depth in the profile and in a sequence of uniform vertical permeability is likely to originate near the water table rather than high in the unsaturated zone

composition age and origin of two proterozoic diorite tonalite complexes in the arabian shield abstract large amounts of diorite tonalite magma were intruded into the island arc successions of the southern arabian shield between ca 900 and 700 ma ago major oxide trace element rare earth ree and isotopic data are presented for two plutons exemplifying older and younger members of this plutonic phase the thurrat pluton which was emplaced into virtually unmetamorphosed volcanics of sequence b has yielded a 10 point rb sr isochron indicating emplacement 744 22 ma ago and an initial 87 sr 86 sr ratio of 0 70281 it consists of gabbros diorites quartz diorites tonalites and low al 2 o 3 trondhjemites which are compositionally primitive with depleted lithophile element contents and flat ree patterns with a negative eu anomaly in the trondhjemites the magma was most probably mantle derived and analogies with other trondhjemitic plutons suggest that it was probably emplaced in an island arc setting the bidah pluton which was emplaced into a compositionally very immature succession of metamorphosed volcanics and volcaniclastics of sequence c has yielded a nine point near isochron mswd 2 86 indicating an age of 901 37ma and an initial 87 sr 86 sr ratio of 0 70246 this date is accepted as the age of emplacement the rocks are compositionally primitive gabbros diorites quartz diorites tonalites and granodiorites with depleted lithophile element contents and flat ree patterns with a negative eu anomaly in the more siliceous components the country rock volcanics were formed in an immature island arc environment and the composition of the bidah pluton is suggestive of a mainly mantle derived magma emplaced into that arc the data for these two plutons therefore provide further evidence that most of the rock material added to the arabian shield between 900 and 700 ma ago was derived from the mantle

revised phosphate water fractionation equation reassessing paleotemperatures derived from biogenic apatite oxygen isotopes of biogenic apatite have been widely used to reassess anomalous temperatures inferred from oxygen isotope ratios of ancient biogenic calcite more prone to diagenetic alteration however recent studies have highlighted that oxygen isotope ratios of biogenic apatite differ dependent on used analytical techniques this questions the applicability of the phosphate water fractionation equations established over 25 years ago using earlier analytical techniques to more recently acquired data in this work we present a new phosphate water oxygen isotope fractionation equation based on oxygen isotopes determined on fish raised in aquariums at controlled temperature and with monitored water oxygen isotope composition the new equation reveals a similar slope but an offset of about 2 to the earlier published equations this work has major implications for paleoclimatic reconstructions using oxygen isotopes of biogenic apatite since calculated temperatures have been underestimated by about 4 to 8 c depending on applied techniques and standardization of the analyses

zircon u pb and pb isotope fractionation during stepwise hf acid leaching and geochronological implications abstract two homogeneous zircons zircon 91500 kuehl lake ontario and phalaborwa zircon south africa were analysed to study u and pb behaviour during stepwise hf acid leaching from the phalaborwa zircon 11 of radiogenic pb and 7 of u were extracted into solution at the first leaching step and a reverse discordance was obtained after extraction of 27 0 of the total radiogenic pb budget and 24 5 of the u the zircon residue gave concordant ages it contained 75 8 of total radiogenic 206pb budget 76 4 of total radiogenic 207pb budget and 68 0 of total radiogenic 208pb budget indicating different mobility of pb isotopes the 208pb 206pb ratios of the solutions and the residue decrease systematically from 1 10 to 0 60 this pattern probably demonstrates that domains with different th u ratios were successively sampled during acid attack in contrast to phalaborwa zircon only 1 of the total radiogenic pb budget was extracted in leaching steps from each of three zircon 91500 fragments highly reverse discordant ages are observed in the first leaching step of the phalaborwa zircon this phenomenon is consistent with the recent studies of mattinson partial dissolution analysis pdf of zircon past present future 11th annual v m goldschmidt conference abstract volume 3368 pdf 2001 and davis and krogh chem geol 172 2000 41 due to the fractionations between u and pb and between radiogenic pb isotopes observed in the first leaching step discordant domains or zonings of zircons have to be completely removed in the leaching steps to avoid any artificial high 207pb 206pb ratio in the residues evaluation of data from leaching studies shows that the extractability of pb is positively correlated with the total radiogenic pb budgets in zircons and subsequently with u contents and ages of zircons indicating an important role of radiation damage this correlation is consistent with the fact that old zircons with high u contents are much more susceptible to pb loss than younger ones with low u contents

unsaturated flow and solute transport through the chalk tracer test and dual permeability modelling a tracer test was carried out in the unsaturated chalk at the fleam dyke research site in cambridgeshire uk to investigate the role of the chalk fractures and matrix in unsaturated flow and solute transport the experiment under natural rainfall conditions involved distributing deuterated water on a grass covered lysimeter a cube of volume 125 m3 and on an adjacent 4 m 4 m field plot tracer migration was monitored through regular core sampling and collection of lysimeter drainage water the presence of occasional secondary peaks in sampling of the vertical tracer profile suggested the occurrence of fracture flow allowing some tracer to bypass the chalk matrix however in the 15 months following application none of the tracer was detected in the lysimeter drainage at 5 m depth modelling of the tracer results was undertaken with the 1 d numerical transient dual permeability model macro 5 0 initially developed for macroporous soils modelling results showed that macro 5 0 could reliably simulate transient recharge through the chalk the simulations suggested that fracture flow is important at the site but that it is only initiated at 1 m depth or deeper the extent of fracture flow appeared to be highly variable in different layers of the profile varying between 40 and 85 of the cumulative flux mainly depending on the saturated hydraulic conductivity of the matrix diffusion between the fractures and the matrix tended to equalize solute concentrations in both flow domains although solute bypass through the fractures occurred in some chalk strata besides diffusive exchange the modelling stressed the importance of advective exchange of solutes the results suggest that the chalk aquifer at the fleam dyke site is only moderately vulnerable to pollution even though for moderate rainfall conditions some bypass flow was possible

geological control of massive sulfide mineralization in the neoproterozoic wadi bidah shear zone southwestern saudi arabia inferences from orbital remote sensing and field studies abstract this study combines new field and orbital remote sensing data to determine geologic controls on sulfide mineralization in the wadi bidah mineral district wbmd located in the neoproterozoic 900 550 ma arabian shield of southwestern saudi arabia the brittle and ductile deformation of these massive sulfide deposits and host rock reflect tectonic events occurring in the arabian shield during the neoproterozoic 900 550 ma remote sensing data were used in conjunction with gis software arcview to map lithologic units and mineral deposits analyze and define regional structural trends and establish geologic controls on sulfide mineralization orbital remote sensing data sets include scenes from landsat 7 and aster the sulfide deposits of the wbmd are found within a group of felsic volcaniclastics a marble unit within the felsic volcaniclastic group is used as a marker horizon based on the distribution of the sulfide deposits relative to the marble unit all sulfide deposits appear to be stratabound deposits have been folded and faulted into their present positions structural control of mineralization appears to be limited to post mineralization folding and shearing

transient simulations of flow and transport in the chalk unsaturated zone chalk is a fractured porous medium composed of matrix blocks bounded by interconnected fractures furthermore there are a number of commonly observed and apparently contradictory phenomena these include a fast water table response slow solute migration and very little solute dispersion to the authors knowledge no unified physically based numerical model has been able to reconcile all of these points in this paper these issues were addressed through the development of a transient dual permeability model of flow and transport the behaviour of the model was explored through a hypothetical scenario the one dimensional model featured a fixed water table at 10 m depth a recharge time series derived using the penman grindley model in conjunction with daily precipitation and monthly potential evaporation data from the kennet valley berkshire was applied at the top of the model a conservative solute that could be tritium chloride or nitrate was applied to the recharge for 1 year subsequent years involved the input of clean water the simulations suggested that although transient effects have been previously neglected overlying soil and gravelly chalk layers are likely to cause significant attenuating effects on flow such that most flow occurs through the matrix fracture flow was found to be episodic and infrequent and represented between 17 and 30 of the annual recharge

zircon hf isotope perspective on the origin of granitic rocks from eastern bavaria sw bohemian massif the petrogenetic potential of in situ laser ablation hf isotope data from melt precipitated zircons was explored through the analyses of about 700 individual crystals derived from about 20 different granitic intrusions covering the variscan basement segment of eastern bavaria se germany in combination with geochemical features four major suites of granitic rocks can be distinguished 1 ne bavarian redwitzites 52 57 wt sio2 intrusion ages around 323 ma have chondritic ehf t values 0 8 to 0 4 the redwitzites are hybrid rocks and the hf data are permissive of mixing of a mantle progenitor and crustal melts 2 various intermediate rock types dioritic dyke granodiorite palite 59 63 wt sio2 334 320 ma from the bavarian forest yield negative ehf t values between 3 4 and 5 1 these values which apparently contradict a mantle contribution fingerprint an enriched metasomatized mantle component that was mixed with crustal material 3 voluminous major crust forming granites sensu stricto 67 75 wt sio2 328 298 ma are characterized by a range in ehf t values from 0 5 to 5 6 different crustal sources and or modification of crustal melts by various input of juvenile material can explain this variation 4 post plutonic c 299 ma porphyritic dykes of dacitic composition 64 67 wt sio2 from the southern bavarian forest have chondritic ehf t values 0 6 to 1 1 and display large intergrain hf isotope variation the dykes form a separate petrogenetic group and the hf data suggest that the zircons crystallized when a pristine mantle derived parental melt was modified by infiltration of crustal material the zircon hf data form a largely coherent positive array with the whole rock nd data and both systems yield similar two stage depleted mantle model ages 1 1 1 7 ga

whole grain evaporation for 207 pb 206 pb age investigations on single zircons using a double filament thermal ion source a technique has been developed and tested to analyse 207pb 206pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains 0 3 mm the evaporation analyses are performed in the double filament arrangement of a thermal ion mass spectrometer thims the method is a powerful tool to distinguish between different lead components occurring in the same grain because differing activation energies of the competing lead components cause their sequential evaporation from the zircons the evaporation of test samples results in 207pb 206pb apparent ages in good agreement with u pb ages known from literature single zircons from a granite of the marble mountains california yield an age of crystallization of 1 410 30 ma ceylon zircons from heavy mineral bearing gravels yield 560 40 ma as age of crystallization of the pegmatitic gravel sources individuals from a heterogeneous zircon population of a diatexite from the southern schwarzwald sw germany indicate metamorphic zircon formation around 500 ma and the existence of middle proterozoic relics 1 95 0 05 ga

k ar geochronology of different tectonic units at the northwestern margin of the bohemian massif abstract the polymetamorphic moldanubian mo of the northeasthern margin of the bohemian massif has been thrust to the north onto the mainly paleozoic sedimentary saxothuringian of the fichtelgebirge fg these two units have undergone polyphase deformation and the last regional event to affect both units was a low pressure metamorphism in which temperatures decreased towards the north in contrast the nappe units of the erbendorf vohenstrauss zone zev and the erbendorf greenschist zone egz which partly cover the border of the moldanubian and the saxothuringian and the munchberg nappe pile mm which lies on the saxothuringian were in parts subjected to a late medium pressure metamorphic event the zev the egz the mo and the fg are intruded by late carboniferous granites conventional k ar analyses mainly of hornblendes and muscovites from the autochthonous fg and mo the units beneath the nappes have yielded exclusively carboniferous dates the oldest dates point to a regional cooling of the rocks which outcrop at the present day surface at about 330 320 ma i e at the early late carboniferous boundary the late carboniferous cooling history was largely governed by the thermal influence of the post kinematic granites 320 295 ma especially in the fg and the northern mo the high grade metamorphic rocks in the western part of the zev and in the upper three nappes of the mm mostly yield dates around 380 ma i e early devonian the results show a relatively wide scatter moreover biotites frequently appear to be older than the coexisting muscovites both observations indicate that the rocks underwent a later thermal influence whether some groups of older dates e g 400 ma are due to excess argon or to inherited argon is still open to discussion slightly scattered muscovite dates around 366 ma were obtained for the prasinite phyllite series one of the lower nappes of the mm a single hornblende from the egz gave the same age these two nappes have therefore probably been affected by a late devonian thermal and or tectonic event the muscovite dates obtained from the paleozoic bavarian lithofacies the lowermost nappe of the mm and the hornblende dates from the eastern part of the zev are indistinguishable from those of the autochthonous units fg and mo

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

secondary ca al silicates in plutonic rocks implications for their cooling history secondary ca al silicates are used to constrain the p t x conditions of the very early post magmatic stage of the intermediate to basic hercynian plutonic complexes of charroux civray nw massif central france and fichtelgebirge ne bavaria germany the secondary ca al silicates hydrogarnet prehnite pumpellyite epidote and laumontite form lenses within unaltered or only slightly chloritized biotite hydrogarnet as the first occurring ca al silicate phase crystallizes at temperatures above 340 c the common paragenesis prehnite pumpellyite post dates hydrogarnet and indicates rather narrow ranges of temperature 200 280 c and pressure 2 3 kbar laumontite is formed at the end of ca al silicate crystallization 180 260 c 1 3 kbar mostly in small fractures in association with prehnite and adularia the observed crystallization sequence of the ca al silicates and their stabilities define a retrograde alteration path for the plutonic rocks the ca al silicate assemblage results from an early pervasive alteration of the plutonic rocks by low xco2 fluids during post magmatic cooling subsolidus cooling starts at about 4 kbar at solidus temperatures as indicated by magmatic epidote stability hornblende barometry and fluid inclusion data and continues under slightly decreasing pressure uplift down to 2 3 kbar at 200 280 c prehnite pumpellyite paragenesis this shows that ca al silicate assemblages may be a unique tool to constrain the p t conditions of the subsolidus cooling of intermediate to basic plutonic bodies