calculation of finite incremental deformations in ductile geological materials and structural models abstract although the total continuous deformation of rocks can be the net result of several tectonic pulses finite increments it will be assumed that there are only two it is further assumed that differential displacements are unknown but that two generations of rotation gauges are available in a rock body together with two respective generations of strain gauges a mathematical procedure is outlined herein for calculating the first or second deformation increment in natural structures and putty models with elliptical markers to illustrate their practical value one set of equations is used to determine the pattern of large incremental strain associated with the lateral spreading of a mature model diapir this model pattern may help to interpret igneous fabric patterns of undeformed granitoid plutons

flow and fabric development during the diapiric rise of magma scaled isothermal experiments of the internal circulation induced by viscous drag at a diapir country rock interface are compared with published theoretical studies of flow induced finite deformation inside a rising sphere and new numerical results are presented for the incremental strain pattern developed in spherical diapirs the results predict a time dependent deformation history within rising diapirs that produces finite strains characterized by strong oblate flattening strains at the margin and strong vertical prolate strains in the center with an intervening zone of low plane strain finite strains are discussed in terms of the different sub fabrics expected to form in granitoids after considering the history of rheology and temperature distribution in rising magma strong rheological and temperature gradients are predicted for the margins of internally circulating diapirs that can lead to the formation of strong penetrative foliations at the margin and magmatic or even isotropic fabrics in the i

calculation of volume change in ductile band structures abstract volume changes incurred during the development of ideal band structures infinite shear zones can be readily calculated if one knows the principal directions and principal ratios of total strain within and adjacent to the ideal band structures the calculation is greatly simplified if one knows the directions and ratios of the strain that generated the band structures or if the total strain of the host rocks is zero in some natural deformation zones apparent volume losses according to the band model exceed 30 and may be unreasonably high further determinations of apparent volume change will help to judge the physical viability of the band model and its strict geometrical requirements for example the propagation of embryonic deformation zones may lead to total strain patterns that differ greatly from those of band structures

fission track lengths in the apatite annealing zone and the interpretation of mixed ages abstract measurements of confined fission tracks in apatites from deep boreholes show that their mean length is reduced and the length distribution becomes progressively broader through the fission track annealing zone at subsurface temperatures of around 100 c and above the length distribution characteristically becomes very broad without a pronounced peak the lengths of the longest tracks remain essentially constant at all stages of natural annealing observed in the boreholes this pattern is similar to that found in laboratory annealing of spontaneous fission tracks in apatite from an outcrop sample of the same formation these observations show that confined track lengths can be used as important indicators of the type of thermal history that a sample has experienced in the temperature zone of increasing track stability the length distributions reported here provide a basis for interpretation of fission track ages that might otherwise be ambiguous an apatite age which results from a uniform slow cooling history will have a broad negatively skewed length distribution while a bimodal distribution provides clear evidence of a two stage history involving partial annealing by a discrete thermal event the apparent fission track age associated with a bimodal length distribution will be a mixed age intermediate between the original age and that of the later event

is there a relationship between magmatic fabrics and brittle fractures in plutons a view based on structural analysis anisotropy of magnetic susceptibility and thermo mechanical modelling of the tanvald pluton bohemian massif abstract the present study focuses on the thermal and mechanical aspects of cooling of plutonic systems with respect to their internal structure analysis of the tanvald pluton and the nearby liberec granite the krkonose jizera plutonic complex bohemian massif using the anisotropy of magnetic susceptibility ams method indicates the decoupled magnetic fabrics formed by different processes in these two plutons two regional sets of vertical fractures cut across the plutons and their host rocks they are interpreted as having been formed as opening mode fractures joints after emplacement and cooling our thermo mechanical finite element modelling indicates that the thermal stresses within the tanvald pluton were compressive and that fracture criteria were not met during pluton cooling these results imply that the emplacement depth and confining pressure significantly affect the state of stress within a pluton during cooling and may play a crucial role in the formation of early fractures in plutons consequently the formation of early fractures during pluton cooling is driven by external conditions overriding the role of internal magmatic fabrics we argue that no genetic geometric or temporal correlation can exist between magmatic fabrics and fractures in granitoid plutons and thus that the original concept of hans cloos based on fabric joints relationships should be reconsidered instead an alternative classification of fractures in plutons should include cooling fractures syntectonic fractures uplift fractures and post uplift fractures

determining the effect of topography on isotherms in the shallow crust using low temperature thermochronometry in tunnels apatite u th he and fission track age determinations of samples from a 20 km long near horizontal tunnel in the hochalm ankogel dome eastern tauem window austria are presented in order to determine the role of paleo topography in perturbing isotherms in the shallow crust apatite fission track ages 26 8 ma show no systematic correlation with distance along the tunnel or elevation two age components in the fission track data indicate cooling through 120 c at approximately 20 ma and 80 c at approximately 6 ma surface and tunnel u th he ages 17 9 ma and 13 5 ma respectively are consistently younger than the equivalent fission track ages u th he ages vary systematically along the tunnel with older ages at the northern and southern tunnel portals and younger ages in the central section geological factors faulting lithology appear to have had little effect on this age distribution the u th he age pattern is inconsistent with rock cooling underneath the present day hochalm ankogel dome topography the age minimum is interpreted to coincide with a paleotopographic maximum in the hochalm ankogel dome and suggests that the 40 60 c isotherms were warped sufficiently to affect apatite u th he ages the tunnel apatite u th he ages match synthetic he ages derived from a two dimensional numerical model of landscape evolution integrating the thermal model results with the data allows the relief development to be constrained and we calculate that the present day hochalm ankogel dome topography was formed at 7 to 10 ma copyright 2007 by the american geophysical union

determination of the earth s plasmapause location from the ce 3 euvc images the moon based extreme ultraviolet camera euvc aboard china s chang e 3 ce 3 mission has successfully imaged the entire earth s plasmasphere for the first time from the side views on lunar surface an euvc image on 21 april 2014 is used in this study to demonstrate the characteristics and configurations of the moon based euv imaging and to illustrate the determination algorithm of the plasmapause locations on the magnetic equator the plasmapause locations determined from all the available euvc images with the minimum l algorithm are quantitatively compared with those extracted from in situ observations defense meteorological satellite program time history of events and macroscale interactions during substorms and radiation belt storm probes excellent agreement between the determined plasmapauses seen by euvc and the extracted ones from other satellites indicates the reliability of the moon based euvc images as well as the determination algorithm this preliminary study provides an important basis for future investigation of the dynamics of the plasmasphere with the moon based euvc imaging

the plasmapause response to the southward turning of the imf derived from sequential euv images 1 we statistically examined the plasmapause response to the southward turning of the interplanetary magnetic field imf using sequential global images of the plasmasphere in order to understand how the convection electric field propagates to the inner magnetosphere the extreme ultraviolet euv imager on the imager for magnetopause to aurora global exploration satellite clearly observed inward motion of the plasmapause driven by the southward turning of the imf we surveyed the euv data in the 2000 2001 period and found 16 events using the sequential euv images we calculated the plasmapause radial velocity and then estimated the time development of the convection electric field at the plasmapause epp epp and the solar wind electric field derived from the measurement by the ace satellite had very similar variations each other but there surely was a time lag consequently our research indicates that the plasmapause response to the southward turning of the imf takes 10 30 min this timescale suggests that the convection electric field penetrates from the magnetopause to the inner magnetosphere through the ionosphere

thermochronological constraints on the long term erosional history of the karkonosze mts central europe abstract a combination of zircon u th he zhe apatite fission track aft and apatite u th sm he ahe thermochronology is used to constrain the long term exhumation and erosional history of the karkonosze mts in north eastern bohemian massif by analyzing samples from the highly elevated summit planation surface zhe ages from the south eastern part of the planation surface are 285 19 295 20 and 308 21 ma indicating that the area remained at temperatures below 190 c since the permian in contrast zhe ages in the western part of the planation surface are mid cretaceous proving that this part was residing at temperatures above 190 c prior to exhumation the exhumation occurred in the late cretaceous as evidenced by aft and ahe ages ranging from 82 5 to 90 8 ma and from 77 5 to 91 6 ma respectively modelled cooling trajectories are characterized by a two stage cooling history fast cooling through the apatite partial annealing zone and helium partial retention zone to surface conditions between 90 and 75 ma and slow cooling or even thermal stagnation from 75 ma to present although our data do not allow us to resolve the age of the planation surface completely we narrowed down the number of explanatory options and propose two alternative solutions for the formation of the planation surface i the planation surface represents the remnant of a permian peneplain which was buried by mesozoic sediments of the central european basin system and was re exposed in the late cretaceous or ii the planation surface formed after 75 ma after termination of a period of massive erosion documented by thermochronological data and by the sedimentary record in adjacent basins cenozoic relief production and uplift of the planation surface evident from regional landforms and the sedimentary record is not recorded by thermochronological data this shows that erosion on the uplifted planation surface since 75 ma was less than 1 2 km

moon based euv imaging of the earth s plasmasphere model simulations the euv imager on board the chang e 3 lunar lander will image the earth s plasmasphere from a lunar perspective to focus on some of the open questions in plasmaspheric researches i e global structures erosion and refilling of plasmasphere in order to achieve the understanding of the plasmaspheric dynamics in relation to these euv images in lunar perspective the he 30 4nm emission intensities and global structures of the plasmasphere viewed from the moon are investigated using a dynamic global core plasma model embedded with ts07 magnetic field model and w05 electric field model two typical storms observed by the image euv imager are systematically simulated from the perspectives of the moon it is found from the simulations that the maximum emission intensity of the plasmasphere is similar to 12 3 r which is greater than that detected from polar orbit and the global shapes and temporal evolutions of large scale plasmaspheric structures plasmapause shoulder and plume also have different patterns in moon based simulated images it is also shown that the plasmaspheric structures extracted from moon based euv images are in agreement with those from image euv images systematic simulations demonstrate that specific latitudinal distribution of the plasmaspheric structures can only be imaged at specific positions in lunar orbit it is expected that this investigation provides us with an overall understanding on moon based euv images and helps to identify the plasmaspheric structures and evolution patterns in future moon based euv imaging

inversion tectonics along the western margin of the bohemian massif abstract the block faulted southwestern margin of the bohemian massif is superimposed on a permo carboniferous graben major faults of which became repeatedly reactivated during the mesozoic and cenozoic inversion of sedimentary basins associated with this fault system occurred during the early cretaceous and again during the latest cretaceous early cenozoic

post variscan tectonic and landscape evolution of the elbe fault zone and the lusatian block based on apatite fission track data and geomorphologic constraints abstract the elbe fault zone is a continental scale nw striking structure that contains faults of different kinematics some faults were active at different times since at least the variscan orogenesis in the late carboniferous the lusatian fault lf was one of the major structures of the elbe fault zone in the late cretaceous when nw striking faults of central europe experienced basin inversion and thrusting during a short lived pulse of contraction the lf displays a curved appearance on earth surface what is not compatible with its activity at only one well defined event possibly different faults where active along strike of the lf at different times apatite fission track thermochronology can distinguish differential exhumation or burial of neighbouring fault blocks if the vertical difference comprised at least 1 2 km this study presents apatite fission track data from the footwall and the hangingwall block of the lf and some other faults in its vicinity our new data show a clear difference between the hangingwall block of the lf the lusatian block with uniform 70 85 ma apparent ages and relatively long track lengths and the footwall block of the lf with 66 173 ma apparent ages and shorter and more variable track lengths for one section of the lf we can show that the cretaceous fault is not visible geomorphologically but was substituted by a neighbouring cenozoic reverse fault with a distinct fault scarp we used thermal history modelling to determine the timing and magnitude of exhumation and burial events from apparent apatite fission track ages and track length distributions we infer that the present morphological expression of the lf consist of smaller faults of different kinematics and age and present an evolution model for this section of the lf this study establishes the existence of similar striking reverse faults in direct vicinity and partly intersecting each other in the elbe fault zone this observation emphasizes the significance of the elbe fault zone as a continental scale zone of crustal weakness it has not only been reactivated several times since the variscan orogenesis but represents a cluster of similar striking faults of different age and kinematics

effect of plasmaspheric drainage plumes on solar wind magnetosphere coupling evidence is uncovered that plasmaspheric drainage plumes flowing into the dayside reconnection site mass load the reconnection rate and thereby reduce the coupling of the solar wind to the earth s magnetosphere solar wind magnetosphere coupling is statistically analyzed with the 1963 2003 omni2 data set matched up with the ae au and pci geomagnetic indices times when plasmaspheric drainage plumes are flowing are discerned using multiple spacecraft with plasma detectors in geosynchronous orbit it is found that for a given value of vbz of the solar wind the geomagnetic indices ae au and pci are statistically lower when plasmaspheric drainage plumes are present than when plumes are not present this is taken as a measure of a weakened coupling of the solar wind to the earth s magnetosphere caused by the plumes an addendum examines the effects of polar cap saturation on the auroral electrojet index

geochemistry and provenance of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany an integrated mineralogical and geochemical study of the altendorf feldspathic sandstone in the middle bunter of the thuringian basin germany was carried out to obtain more information on its provenance sedimentological history and geochemistry the fine to coarse grained sandstone has an average composition of 66 63 71 quartz 30 27 35 feldspar and a fine grained illitic matrix the heavy mineral assemblage consists mainly of tourmaline zircon rutile apatite and opaque fe ti minerals it is inferred that this terrigenous material was laid down at the margin of the bunter basin high abundances of igneous quartz grains determined by cathodoluminescence cl the lack of metamorphic heavy minerals as well as alkali feldspar with an average k2o na2o ratio of 14 9 point to material of mostly granitic origin regional geologic and paleogeographic observations suggest that granites of the older and younger intrusive complex of the western erzgebirge are possible source rocks of the feldspathic sandstone the geochemical signature of the alkali feldspar k2o na2o ratio bao content points to the bergen and kirchberg granites as possible parent rocks comparing the mineralogical and geochemical data of the presumed source granites with those of the altendorf sandstone provides information on the sedimentation processes weathering fluvial transport and sedimentation under arid climatic conditions have caused complete decomposition and removal of plagioclase and biotite lowered the bulk ree content and led to the development of a positive eu anomaly the immobile trace elements e g ta th zr sc co ti are best suited for provenance determination because of their relatively low mobility during sedimentary processes elemental ratios such as la sc th sc co th and th ta have inherited the signature of the parent rocks and thus may be particularly useful for provenance studies to evaluate the control of specific minerals and grain size fractions on the distribution of trace elements in the sandstone separated fractions of quartz feldspar the 20 m fraction and heavy minerals were additionally analyzed the concentration densities elemental concentration in the fraction fraction weight reveal that with exception of hf the influence of the heavy mineral fraction on the whole rock geochemistry is insignificant although this fraction generally plays the most important role as carrier of trace elements quartz feldspar and the 20 m fraction have similar concentration densities between 20 and 40 for the ree with exception of eu which is mainly hosted in feldspar strong positive eu anomaly the influence of the 20 m fraction on the distribution of the ree and the elements u th sc ta strongly depends on the abundance of this fraction in the sediment alkali feldspar contains most of the ba sr rb and cs in the samples concentration densities of up to 97 thus differences in the abundances of these elements in whole rock samples can be related to changes in the mineralogical composition quartz feldspar ratio of the sediment

repetitive hydraulic fracturing and shear zone inflation in an archean granitoid hosted ribbon banded au quartz vein system renabie area ontario canada abstract economically significant tonalite 2722 ma and trondhjemite 2728 ma hosted archean au quartz vein mineralization in the renabie area ontario located in a marginal part of the 10 15 km thick wawa domal gneiss terrane shows strong structural control major ore zones occur in e w and nw nnw striking ductile brittle high strain zones that are superimposed on an earlier regional foliation mineralized zones are up to 20 30 m wide mineable to a depth of 1300 vertical metres and dip typically at 60 80 angles production and reserves for the renabie mine totalled 6 million tonnes at 6 6 g t au and 2 g t ag net shear from kinematic indicators is oblique reverse south side up sinistral on e w structures e g nudulama renabie main zone depth 2475 level and west side up sinistral on nw nnw structures e g braminco 21 zone the strain features of the shear zone hosted mineralization together with evidence of reaction enhanced ductility associated with hydrothermal fluid wallrock interaction indicate that mineralization and hydrothermal alteration occurred synchronously with shear deformation the characteristic banded appearance book ribbon structure of the renabie veins which is typical of many archean and cordilleran au quartz vein systems is interpreted to be the result of inflationary vein formation by repeated increments of hydraulic fracturing and mineral deposition 250 750 associated with hydrothermal fluid overpressuring within and below the actively deforming ductile brittle shear zones crack seal type process fracture orientation was largely controlled by the anisotropy in rock tensile strength associated with the approximately planar shear fabric the element mineral association of renabie is typical of oxidized archean au quartz vein systems containing anhydrite hematite carbonate and tourmaline with a chalcophile association consisting of mos 2 cu pb sulphides native au ag and pb bi au ag tellurides key factors in the development of significant mineralization at renabie as compared with other usually small low grade archean granitoid hosted au quartz vein systems include the repetitive nature of the mineralizing process and the focusing of au bearing fluids within the actively deforming shear zones a specific and sufficiently large reservoir of overpressured hydrothermal archean au bearing fluid was generated at some location not yet identified in the archean crustal structure represented by the kapuskasing section

deformation around a rising diapir modeled by creeping flow past a sphere a new experimental method for determining the pattern of flow and three dimensional progressive finite deformation of fluid elements in low reynolds number re viscous flow has been applied to creeping flow past a rigid sphere falling in a cylinder this is intended as a model analogue of natural rock deformation associated with magmatic and solid state diapirs rising through ductile crust the kinematics of finite strain in such analogue experiments may give useful information on the development of natural structures the experiment and a new method for quantifying the progressive finite deformation of fluid volumes in the transparent newtonian test fluid used sgm36 are discussed in detail the progressive finite deformation of fluid flowing along specific streamlines passing the sphere appears to be complex and largely a function of the initial distance of fluid volumes and the particular streamlines which they follow from the flow axis the progressive deformation history in the material surrounding a rising spherical diapir is characterized by progressive flattening and rotation of material above and progressive stretching below the sphere the results compare favorably with the external strain pattern associated with post tectonic mesozonal diapiric intrusions

different modes of the late cretaceous early tertiary inversion in the north german and polish basins several selected seismic lines are used to show and compare the modes of late cretaceous early tertiary inversion within the north german and polish basins these seismic data illustrate an important difference in the allocation of major zones of basement thick skinned deformation and maximum uplift within both basins the most important inversion related uplift of the polish basin was localised in its axial part the mid polish trough whereas the basement in the axial part of the north german basin remained virtually flat the latter was uplifted along the sw and to a smaller degree the ne margins of the north german basin presently defined by the elbe fault system and the grimmen high respectively the different location of the basement inversion and uplift within the north german and polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the wnw ese trending elbe fault system and by the nw se striking teisseyre tornquist zone the latter underlying the mid polish trough therefore the inversion of the polish and north german basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis the inversion of the mid polish trough was connected with the reactivation of normal basement fault zones responsible for its permo mesozoic subsidence these faults zones inverted as reverse faults facilitated the uplift of the mid polish trough in the order of 1 3 km in contrast inversion of the north german basin rarely re used structures active during its subsidence basement inversion and uplift in the range of 3 4 km was focused at the elbe fault system which has remained quiescent in the triassic and jurassic but reproduced the direction of an earlier variscan structural grain in contrast n s oriented mesozoic grabens and troughs in the central part of the north german basin avoided significant inversion as they were oriented parallel to the direction of the inferred late cretaceous early tertiary compression the comparison of the north german and polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field a thick zechstein salt layer in the central parts of the north german basin and the mid polish trough caused mechanical decoupling between the sub salt basement and the supra salt sedimentary cover resultant thin skinned inversion was manifested by the formation of various structures developed entirely in the supra salt mesozoic cenozoic succession the zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution only in parts of the ngb and mpt characterised by either thin or missing zechstein evaporites thick skinned inversion directly controlled inversion related deformations of the sedimentary cover inversion of the permo mesozoic fill within the mid polish trough was achieved by a regional elevation above uplifted basement blocks conversely in the north german basin horizontal stress must have been transferred into the salt cover across the basin from its sw margin towards the basins centre this must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion related basement faults are seismically detected apart from the basin margins this strain decoupling in the interior of the north german basin was enhanced by the presence of the elbe fault system which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred late cretaceous early tertiary far field compression

patterns of total and incremental strain in subsiding troughs experimental centrifuged models of inter diapir synclines the experimental technique of centrifuge modelling has been used to elucidate patterns of total strain and progressive deformation associated with troughs that form by gravitational subsidence of a dense cover into a less dense basement model structures are analogous to synclines found between mantled gneiss domes and the models provide data with which to test the hypothesis that archean greenstone belts are products of vertical gravity tectonics experimental results include the following 1 strain within the main body of subsiding belts is dominated by strong horizontal contraction and vertical extension in natural structures this strain pattern would produce vertical foliation and steeply plunging mineral lineation 2 within cover units near trough margins the flattening plane trends parallel with or at a low angle to the cover basement interface at all levels in the trough 3 patterns of strain within subsiding troughs at least as expressed in surface deformation reflect the geometry of the

formation of density troughs embedded in the outer plasmasphere by subauroral ion drift events a dynamic global core plasma model dgcpm is used to investigate the effects of subauroral ion drift said events on the formation of trough density profiles in the outer plasmasphere during periods of high magnetic activity the dgcpm includes the influences of convection on the changing flux tube volumes as well as daytime refilling and nighttime draining of plasma to calculate the plasma tube contents and equatorial plasma density distribution versus time throughout the magnetosphere saids are regions of latitudinally narrow westward flow of plasma equatorward of the auroral zone we present dgcpm results for various presumed said locations and durations relative to enhanced substorm convection onset and decay to parametrically elicit the formation of plasmaspheric density trough structures resulting from said effects it is found that imposing a said event in the dusk evening sector for 30 min leads to the formation of a narrow less than 1 re near the equatorial plane embedded plasma density trough in the dusk bulge region the modeled plasmasphere density profiles with troughs generally resemble plasmasphere density profiles observed from de 1 measurements

dating multiply overprinted sn mineralized granites examples from the erzgebirge germany granites and primary tin mineralization in the erzgebirge were dated using 1 conventional u pb dating of uraninite inclusions in mica 2 rb sr dating of inclusions in quartz that represent highly evolved melts 3 re os dating of magmatic hydrothermal molybdenite and 4 chemical th u pb dating of uraninite conventional isotope dilution and thermal ion mass spectrometry and chemical th u pb dating of uraninite in granites from the ehrenfriedersdorf mining district provide ages of 323 9 3 5 ma 2 greifenstein granite and 320 6 1 9 and 319 7 3 4 ma 2 both sauberg mine in agreement with u pb apatite ages of 323 9 2 9 and 317 3 1 6 ms 2 both sauberg mine rb sr analysis of melt inclusions from zinnwald gives highly radiogenic sr isotopic compositions that with an assumed initial sr isotopic composition permit calculation of precise ages from single inclusions the scatter of the data indicates that some quartz hosted melt inclusions have been affected by partial loss of fluid exsolved from the melt inclusion re os dating of two molybdenite samples from altenberg provides ages of 323 9 2 5 and 317 9 2 4 ma 2 together with age data from the literature our new ages demonstrate that primary tin mineralization and the emplacement of the large sn specialized granites in the erzgebirge fall in a narrow range between 318 and 323 ma primary sn mineralization occurred within a short interval during post collisional collapse of the variscan orogen and was essentially synchronous over the entire erzgebirge in contrast to earlier claims no systematic age difference between granites of the eastern and western erzgebirge was established furthermore our data do not support a large age range for late variscan granites of the erzgebirge 330 290 ma as has been previously suggested

trace element geochemistry of sphalerite in contrasting hydrothermal fluid systems of the freiberg district germany insights from la icp ms analysis near infrared light microthermometry of sphalerite hosted fluid inclusions and sulfur isotope geochemistry the historic silver mining district of freiberg germany comprises hydrothermal vein style mineralization of permian and cretaceous age we compare sphalerite compositions with associated ore forming fluids and constrain the behavior of critical metals such as in ge and ga in contrasting hydrothermal environments fluid inclusion studies reveal that the permian veins formed due to boiling and cooling of a low salinity 0 to 6 eq w nacl magmatic hydrothermal fluid at 350 to 230 c in contrast cretaceous veins formed by mixing of highly saline 17 to 24 eq w nacl cacl2 and variable na na ca ratios brines at low temperatures 120 c sulfides of the permian ore stage have a narrow range of 34svcdt from 2 3 to 0 9 while the sulfides of the cretaceous stage have a large scatter and significantly more negative 34svcdt values 30 9 to 5 5 supporting the different nature of the hydrothermal systems contrasting fluid systems and ore forming mechanisms correspond to markedly different trace element systematics in sphalerite permian sphalerite is significantly enriched in in up to 2500 g g in relative to two sphalerite generations of cretaceous veins the latter have higher ge up to 2700 g g ge and ga up to 1000 g g ga concentrations the observed trace element systematics of different sphalerite generations imply that in is enriched in high temperature low to intermediate salinity fluids with a significant magmatic hydrothermal fluid component while ge and ga are more concentrated in low temperature high salinity crustal fluids with no obvious magmatic hydrothermal affiliation

post variscan thermal history of the moravo silesian lower carboniferous culm basin ne czech republic sw poland abstract apatite fission track analysis aft and zircon u th he thermochronology zhe have been carried out for a lower carboniferous greywacke succession of the moravo silesian culm basin in the nizk jesenik mountains the range of apparent zircon helium ages is 303 233 ma late carboniferous to early triassic in the eastern part of the basin whilst they are significantly younger in the western part ranging from 194 to 163 ma early middle jurassic apatite fission track central ages range from 152 latest jurassic to 44 ma eocene with the majority being grouped between 114 aptian and 57 ma paleocene all samples experienced substantial post depositional thermal reset both the aft ages and the zhe are considerably younger than the depositional ages the mean track length varies in the range between 12 5 and 15 4 m the unimodal track length distribution the relatively short mean track length in most samples and their rather low standard deviation values 1 2 to 2 1 m indicate that their thermal history was determined by variscan and post variscan heating event s followed by a prolonged residence in the apatite partial annealing zone in the mesozoic and finally by cooling in the paleogene geological evidence combined with thermal modeling based on aft and zhe data indicate that the lower carboniferous strata had already reached maximum palaeotemperatures in the late carboniferous however they were presumably later re heated during the permian triassic post variscan extensional tectonics events were responsible for high heat flow that together with carboniferous burial could account for the reset of both thermochronometers a major phase of cooling occurred in the late cretaceous finally exhumation was probably faster in the paleogene causing the present day exposure of the studied rocks

effect of alpha damage annealing on apatite u th he thermochronology recent data on he diffusion challenge the temperature sensitivity of apatite u th he thermochronology the damage induced by recoil of u and th decay series during emission of particles recoil damage has been proposed to modify he diffusion properties through time however we propose that annealing of these irradiation defects may be an important phenomenon and may be significant in case of slowly cooled or reheated basement rocks to test this hypothesis we developed a quantitative model including an explicit treatment of recoil damage annealing and their effect on he diffusion kinetics and calibrate it against literature data our model is based on two hypotheses 1 helium is in equilibrium between an apatite crystal and its defects and 2 alpha recoil damage annealing can be described analogously to fission track annealing this model has been embedded into a monte carlo simulation of helium production ejection diffusion and applied to data from the french massif central a complex slowly cooled terrain with burial reheating where the thermal history has been constrained by previous fission track ft data including ft length distributions u th he ages are close to the ft ages from the same samples and are generally reproducible among replicates but some samples present he age dispersion that is not correlated with crystal size our model reproduces the massif central data very well except for three samples where he ages are older than corresponding ft ages we show that annealing of irradiation damage has an important impact on retentivity of helium and that the he content he is only a rough approximation of the damage level in particular our results show that independence of he ages on crystal sizes in case of reheated samples is a clear indication of the higher he retentivity induced by recoil defects and that an explicit treatment of defect annealing is required for a correct interpretation of u th he ages in such a case more generally a correlation with the crystal size can bring information on the thermal path only if the age of defects well represented by the fission track age is available due to the dependence of the partial retention zone on damages conversely in case of rapid cooling or for samples having low u and th contents damage effects can be ignored without significant effects on he ages

structure of hood lake syenite an undeformed archean pluton in the western superior province southern canadian shield abstract the hood lake syenite is a late archean pluton that has escaped significant tectonic deformation the intrusive contact dips inward in most localities which provides some constraint of its three dimensional geometry the pluton has a concordant planar fabric of perthite megacrysts and could have grown by mature diapirism mushrooming as well as by in situ ballooning only magmatic diapirism seems to be capable of explaining the heart like map pattern of the pluton and its location at the junction of two vertical zones of weakness a regional fault and a ductile shear zone

apatite u th he thermochronometry using a radiation damage accumulation and annealing model helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal a quantity that varies over the lifetime of the apatite using recently published laboratory data we develop and investigate a new kinetic model the radiation damage accumulation and annealing model rdaam that adopts the effective fission track density as a proxy for accumulated radiation damage this proxy incorporates creation of crystal damage proportional to production from u and th decay and the elimination of that damage governed by the kinetics of fission track annealing the rdaam is a version of the helium trapping model hetm shuster d l flowers r m and farley k a 2006 the influence of natural radiation damage on helium diffusion kinetics in apatite earth planet sci lett 249 148 161 calibrated by helium diffusion data in natural and partially annealed apatites the chief limitation of the hetm now addressed by rdaam is its use of he concentration as the radiation damage proxy for circumstances in which radiation damage and he are not accumulated and lost proportionately from the crystal by incorporating the rdaam into the hefty computer program we explore its implications for apatite u th he thermochronometry we show how u th he dates predicted from the model are sensitive to both effective u concentration eu and details of the temperature history the rdaam predicts an effective he closure temperature of 62 c for a 28 ppm eu apatite of 60 m radius that experienced a 10 c ma monotonic cooling rate this is 8 c lower than the 70 c effective closure temperature predicted using commonly assumed durango diffusion kinetics use of the rdaam is most important for accurate interpretation of u th he data for apatite suites that experienced moderate to slow monotonic cooling 1 0 1 c ma prolonged residence in the helium partial retention zone or a duration at temperatures appropriate for radiation damage accumulation followed by reheating and partial helium loss under common circumstances the rdaam predicts u th he dates that are older sometimes much older than corresponding fission track dates nonlinear positive correlations between apatite u th he date and eu in apatites subjected to the same temperature history are a diagnostic signature of the rdaam for many but not all thermal histories observed date eu correlations in four different localities can be explained with the rdaam using geologically reasonable thermal histories consistent with independent fission track datasets the existence of date eu correlations not only supports a radiation damage based kinetic model but can significantly limit the range of acceptable time temperature paths that account for the data in contrast these datasets are inexplicable using the durango diffusion model the rdaam helps reconcile enigmatic data in which apatite u th he dates are older than expected using the durango model when compared with thermal histories based on apatite fission track data or other geological constraints it also has the potential to explain at least some cases in which u th he dates are actually older than the corresponding fission track dates

strain patterns of crescentic granitoid plutons in the archean greenstone terrain of ontario abstract granitoid plutons of crescentic outcrop pattern in the archean terrain of northwestern ontario are dominated by constrictive strains that are interpreted to be due to intrusion rather than regional deformation the strain patterns of antiformal plutons are characterized by subvertical lineations in contrast the strain patterns of synformat plutons are characterized by subhorizontal lineations presumably only the last flow increments were recorded by the deformed mineral aggregates employed as strain gauges and occurred when the granitoid magma was largely crystalline simple kinematic models are capable of explaining many but not all elements of the natural strain patterns

age and genesis of polymetallic veins in the freiberg district erzgebirge germany constraints from radiogenic isotopes the freiberg mining district in the erzgebirge hosts three principal types of polymetallic veins these are 1 the quartz bearing polymetallic sulfide type 2 the carbonate bearing polymetallic sulfide type and 3 the barite fluorite sulfide type we investigated the genesis of each vein type using rb sr sphalerite geochronology sm nd fluorite geochronology and pb sr and nd isotope systematics of ore and gangue minerals field relationships and the rb sr and pb isotope systematics of sulfides from quartz bearing polymetallic sulfide veins and carbonate bearing polymetallic sulfide veins confirm their close genetic affiliation and yield a combined rb sr errorchron age of 276 16 ma the high mean squared weighted deviation mswd value of 42 on the regression is considered to reflect initial isotopic heterogeneity which is probably related to fluid rock interaction during the hydrothermal mineralization process although some sphalerites from barite fluorite sulfide veins have strongly disturbed rb sr isotope systematics six sphalerites and one co genetic fahlore yield a robust isochron age of 121 3 4 2 ma with an mswd of 2 9 this age is supported by a fluorite sm nd isochron age of 101 18 ma mswd 1 3 the new ages and radiogenic isotope data place robust constraints on the long held hypothesis that veins in the freiberg district formed during two hydrothermal events the lower permian age of first stage quartz bearing polymetallic sulfide veins and carbonate bearing polymetallic sulfide veins coincides with post variscan crustal reorganization and rotliegend volcanism the mid cretaceous age of second stage barite fluorite sulfide veins coincides with opening of the north atlantic ocean during the break up of pangea

long term landscape evolution of the northeastern margin of the bohemian massif apatite fission track data from the erzgebirge germany to study the relative and absolute timing of post variscan cooling and denudation processes in the erzgebirge of the mid european variscides eight samples for apatite fission track aft analysis were collected from a 1 300 m drill core the fission track data reveal two stages of accelerated cooling through the apatite partial annealing zone apaz i e 110 10 60 c in the late jurassic late cretaceous and in the late cenozoic respectively late jurassic late cretaceous cooling corresponding to denudation of 1 5 5 9 km has been related to wrench tectonics along the elbe zone during triassic jurassic pangea breakup late cenozoic exhumation of 2 1 5 6 km and the increase of the geothermal gradient from 17 5 c km 1 oligocene miocene to 25 27 c km 1 recent is likely connected to the formation of the eger graben starting from the oligocene as a result of the late alpine orogenic phases

the age of the latest thermal overprint of tin and polymetallic deposits in the erzgebirge germany constraints from fluorite u th sm he thermochronology the erzgebirge region of germany records two major episodes of hydrothermal activity which includes a late carboniferous to early permian event associated with significant sn w mineralization that is related to late variscan granite magmatism and a mesozoic episode of polymetallic vein mineralization in contrast to the first event the age of the younger hydrothermal activity is poorly constrained for the latter various geochronological methods yielded a wide age range from permian to early tertiary here we apply fluorite u th sm he thermochronology fhe on both types of mineralization with a twofold goal 1 to investigate the sensitivity and applicability of the new fhe method evans et al 2005 and 2 to constrain the thermal history of ore deposits in the erzgebirge region two hundred and thirty three aliquots from seven mineralization localities have been dated fluorite from six deposits yielded cretaceous fhe ages between 112 to 79 ma which are independent of their paragenesis in contrast fluorite from the sadisdorf sn w deposit yielded an age of 234 ma the younger ages are interpreted as cooling ages indicating the time of the last thermal overprint including possible hydrothermal activity in the erzgebirge the oldest triassic fhe ages at sadisdorf indicate that the mesozoic thermal overprint only partially reset the u th sm he system of the late variscan mineralization thermal modeling based on fhe ages and he diffusion parameters in fluorite results in thermal histories comparable to the results from the well established apatite based thermal modeling this study emphasizes the applicability of fluorite u th sm he thermochronology which is especially suited for ore deposits where apatite is lacking

weathering mantles and their significance for geomorphological evolution of central and northern europe since the mesozoic abstract weathering mantles saprolites are very widespread in central western and northern europe where they form thick near surface residual deposits often in excess of 50 m they vary in the type of weathering the bedrock lithology involved the topographic setting and the age and stratigraphic context this review paper provides information about the distribution and major characteristics of weathering mantles from a number of key areas including the british isles the central european belt of mid mountains and uplands the scandinavian mountains and the fennoscandian shield it also examines the evidence for weathering etched origin of various landforms including boulders tors inselbergs basins and some regional landforms assemblages major types of regionally important weathering mantles include ferrallitic lateritic saprolites kaolinite rich saprolites sandy to grus mantles and various residuals left after partial dissolution of carbonate rocks although dating of weathering mantles is often circumstantial it appears sufficiently precise to argue for various ages of deep weathering mesozoic pre late cretaceous mantles are particularly widespread but there are also early tertiary and miocene saprolites widely present whilst most grus weathering is likely to be of miocene to pleistocene age individual upland areas have been subjected to multiple episodes of weathering whose legacy is the present day co existence of different weathering products continental and shallow marine deposits around the uplands particularly in the north sea and intra continental graben structures are often dominated by quartz and kaolinite pointing to deeply weathered land surfaces as the source areas and extending the record of weathering on the geological time scale they demonstrate that weathering mantles repeatedly formed and were subjected to erosion and new cycles of weathering were initiated we suggest that deep unroofing of basement structures in many parts of europe has been mainly accomplished by deep weathering and stripping of pre weathered rock the phenomenon of deep weathering has been very important for geomorphology etched landforms vary in size from small residual boulders up to regional characteristic landscapes etchsurfaces such as joint valley landscapes of southern sweden or undulating multi convex and multi concave landscapes of many uplands in central europe deep weathering has played a major part in the geomorphological evolution of europe since at least the late triassic and the concept involving long term etching and stripping provides an appropriate framework to describe and explain both erosional landscapes and sediment features

variable helium diffusion characteristics in fluorite abstract precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite u th sm he thermochronometer fhe which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism the diffusion behaviour is highly variable and the parameters range between log d 0 a 2 0 30 0 27 7 27 0 46 s 1 and e a 96 3 5 182 3 8 kj mol despite the fact that the caf 2 content of natural fluorites in most cases exceeds 99 weight percent the closure temperature t c of the fluorite u th sm he thermochronometer as calculated from these diffusion parameters varies between 46 14 c and 169 9 c considering a 125 m fragment size here we establish that minor substitutions of calcium by rare earth elements and yttrium ree y and related charge compensation by sodium fluorine oxygen and or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral with increasing ree y concentrations f vacancies are reduced and key diffusion pathways are narrowed consequently a higher closure temperature is to be expected an empirical case study confirms this variability two fluorite samples from the same deposit horni krupka czech republic with ca 170 c and ca 43 c t c yield highly different u th sm he ages of 290 10 ma and 79 10 ma respectively accordingly the fluorite sample with the high t c could have quantitatively retained helium since the formation of the fluorite bearing ores in the permian despite subsequent mesozoic burial and associated regional hydrothermal heating in contrast the fluorite with the low t c yields a late cretaceous age close to the apatite fission track aft and apatite u th he ages ahe from the same locality remarkably thermal modelling of fhe yields comparable results to the well established modelling based on aft and ahe

post variscan thermal history of the intra sudetic basin sudetes bohemian massif based on apatite fission track analysis the intra sudetic basin a 12 km deep variscan intramontane basin has the best preserved post orogenic sedimentary record available at the ne margin of the bohemian massif apatite fission track aft analyses have been performed on 16 sedimentary and volcanic samples of carboniferous to cretaceous age from the intra sudetic basin to improve understanding of the post variscan thermal evolution aft central ages range from 50 1 8 8 to 89 1 7 1 ma early eocene to coniacian with 13 of them being late cretaceous the mean track length values range from 12 5 0 4 to 13 8 0 5 except for one sample 14 4 0 2 m this relatively short mean track length together with the unimodal track length distributions and rather low standard deviation 0 8 to 1 7 m in most samples indicate a long stay in the partial annealing zone during slow cooling however in the northern part of the intra sudetic basin samples show a wider track length distribution standard deviation of 1 8 to 2 1 m that could indicate a more complex thermal evolution possibly related to mesozoic reheating vitrinite reflectance data combined with thermal models based on the aft results indicate that the carboniferous strata reached maximum palaeotemperatures in the latest carboniferous to early permian time corresponding to a major coalification event the second phase of temperature rise occurred due to late mesozoic sedimentary burial but it had no influence on maturation of the carboniferous organic matter final cooling phase in the late cretaceous paleogene was related to tectonic inversion of the intra sudetic basin which occurred after deposition of a significant thickness of cenomanian turonian sediments thermal modelling demonstrates that 4 km thick cover of upper cretaceous sediments is required to obtain a good match between our aft data and modelled time temperature paths this outcome supports a significant amount of late cretaceous paleogene inversion within the variscan belt of central europe

superposition of burial and hydrothermal events post variscan thermal evolution of the erzgebirge germany the post variscan thermal history of the erzgebirge germany is the result of periods of sedimentary burial exhumation and superimposed hydrothermal activity the timing and degree of thermal overprint have been analysed by zircon and apatite u th he and apatite fission track thermochronology the present day surface of the erzgebirge was exhumed to a near surface position after the variscan orogeny thermal modelling reveals permo mesozoic burial to temperatures of up to 80 100 c although the sedimentary cover thins out towards the north resulting in maximum burial temperatures of less than 40 c this thermal pattern was locally modified by cretaceous hydrothermal activity that reset the zircon u th he thermochronometer along ore veins the thermal models show no significant regional exhumation during cenozoic times indicating that the peneplain like morphology of the basement is a late cretaceous feature

global response of the plasmasphere to a geomagnetic disturbance 1 global images of the plasmasphere obtained by the extreme ultraviolet euv imager on the image satellite are used to study the evolving structure of the plasmasphere during two geomagnetic disturbances by tracking the location of the plasmapause as a function of l shell and magnetic local time quantitative measurements of radial and azimuthal motions of the boundary are made for intervals 7 hours in duration with a time resolution of 10 min the two cases presented are 26 27 june 2001 a relatively weak but isolated geomagnetic disturbance and 9 10 june 2001 a moderate event with a multistaged onset and recurring substorm activity after the main disturbance in both cases the onset of the disturbance correlated with a southward turning of the imf is characterized by inward motion or erosion of the plasmapause and a smoothing of any existing azimuthal variations across the nightside over a period of many hours a plasmaspheric plume forms in the afternoon sector as a result of sunward flows from dusk and corotational flows across the dayside azimuthal variations in the plasmapause radius tend to form in the local time sector from dawn to the western edge of the plume including mesoscale 0 5 in l and 2 hours in local time crenulations and larger scale shoulder features while the nightside boundary remains featureless in the 26 27 june 2001 case the magnetosphere entered a period of deep quiet after the main disturbance and the plasmaspheric plume began to corotate with the main plasmasphere from the afternoon sector across the nightside in contrast the plume in the 9 10 june 2001 event became wrapped around the main plasmasphere and a second plume formed in the afternoon sector perhaps due to continued substorm activity in situ density data for these events show highly irregular density structure within the plumes as measured at geosynchronous orbit whereas a measurement by image rpi suggests that there may be less structure near the base of the plume closer to the main plasmasphere

precise electron microprobe age determination in altered uraninite consequences on the intrusion age and the metallogenic significance of the kirchberg granite erzgebirge germany an integral method of data evaluation for chemical dating of accessory uraninite by electron microprobe analysis and electron microscopy is proposed the internal structure of uraninite grains the contents of si ca and fe and tests for loss or gain of pb and u are suitable criteria to decide whether or not a given crystal area was affected by secondary alteration the method was applied to uraninite from the kirchberg granite erzgebirge germany and an age of 330 5 ma 2 was constrained this result supports earlier assumptions that there were at least two events of hercynian granite magmatism separated by a time gap of about 40 ma and that the magmatic evolution of the kirchberg granite is not related to the formation of the w mineralisation developed in the endocontact of this granite secondary alteration of uraninite is probably closely related to the formation of u deposits in the vicinity of the kirchberg massif which was extensively mined in the past

burial and exhumation of corsica france in the light of fission track data 1 the mesozoic and cenozoic exhumation and cooling history of corsica is reconstructed by fission track ft data on basement and sedimentary rocks apatite ages are 105 16 ma zircon ages are 160 145 ma the jurassic and cretaceous ages show that parts of the variscan basement escaped alpine influence the basement was thermally affected by rifting prior to jurassic opening of the ligurian piedmont ocean then it cooled to near surface temperatures in paleocene eocene times subduction buried parts of the basement and overlying flysch to greater depth in the oligocene both collapse of the nappe stack and rifting prior to opening of the ligurian provencal basin affected the apatite ft system of the basement in different partly overlapping areas causing a complex age pattern the study shows that thorough analysis of ft data and thermal modeling allow to assign age populations to distinct cooling processes even when several thermotectonic events contributed to generate an intricate age pattern

thermochronological constraints on the multiphase exhumation history of the ivrea verbano zone of the southern alps abstract the ivrea verbano zone of the western southern alps nw italy exposes a well preserved tilted section across the lower continental crust making it a key region for studying deep crustal and exhumation processes this paper refines the cooling and exhumation history of the ivrea verbano zone using k ar dating of mica and illite rich fault gouges as well as zircon fission track and u th he thermochronology the adjacent strona ceneri zone sesia lanzo zone and lower penninic nappes are included in the study to derive a broader picture of the low temperature history of the area in the strona profile of the ivrea verbano unit the biotite k ar zircon fission track and u th he geochronometers show well preserved but unusually wide partial retention zones the youngest ages representing the formerly deepest position are situated along the insubric line the main foliation of the ivrea verbano zone is vertical the exhumation of the ivrea verbano zone which section has a horizontal position on the surface now took place in three steps during jurassic time the ivrea verbano zone was exhumed to a shallow to mid crustal position by continental scale extension in this displacement the pogallo line probably played a dominant role the studied section occupied an oblique position with a calculated angle of ca 15 to 23 in the jurassic later the ivrea verbano zone experienced a minor cooling event in the late eocene 38 ma zircon fission track ages that was probably related to thrusting and erosion the final exhumation towards the surface took place in the mid miocene as documented by the ca 14 ma zircon u th he ages and a 12 8 ma k ar fault gouge age the magnitude and the high rate of final exhumation suggest orogen parallel extension as a driving force which is widespread in the alps in the lower to middle miocene and is most probably connected to orogenic collapse

strain analysis of deformed granitic rocks helikian muskoka district ontario abstract three dimensional analysis of irrotational longitudinal finite strain was carried out on samples from a crescentic sheet which intruded and was deformed with a host gneiss unit of probable helikian age analytical methods were compared using deformed feldspar grains representing four ideal degrees of strain intensity observed in the porphyritic sheet the polar plot and r f r s methods proved most reliable and sensitive data derived from fabric and strain analysis at 38 sites in the units suggest a two stage deformational sequence the first stage produced recumbent isoclinal similar class 2 folds with northwest trending hinge surface traces this fold form was modified during the second stage to produce an overall type 2 fold interference pattern the second stage produced upright open buckle folds as well as the resultant strain fabric currently observed strain analysis confirms the general fold geometries of the model and also documents competency contrasts between the matrix and feldspar grains with increased strain intensity and magnitude deformation of feldspar grains in the sheet involved modification of a fabric of low strain magnitude s 0 3 and a k value near unity to magnitudes of s 2 6 and k 0 6 matrix strain intensities and magnitudes are consistently higher than those of the feldspar markers in the sheet this variation is related to competency differences between the matrix and the feldspar grains fabric anisotropy accounts for the strain gradient observed between the sheet and gneiss

analyzing electric field morphology through data model comparisons of the geospace environment modeling inner magnetosphere storm assessment challenge events 1 the storm time inner magnetospheric electric field morphology and dynamics are assessed by comparing numerical modeling results of the plasmasphere and ring current with many in situ and remote sensing data sets two magnetic storms are analyzed 22 april 2001 and 21 23 october 2001 which are the events selected for the geospace environment modeling gem inner magnetosphere storms im s assessment challenge imsac the imsac seeks to quantify the accuracy of inner magnetospheric models as well as synthesize our understanding of this region for each storm the ring current atmosphere interaction model ram and the dynamic global core plasma model dgcpm were run together with various settings for the large scale convection electric field and the nightside ionospheric conductance while keeping all other simulation settings the same dgcpm plasmaspheric parameters were compared with image euv plasmapause extractions and lanl mpa plume locations and velocities ram parameters were compared with dst lanl mpa fluxes and moments image mena images and image hena images both qualitative and quantitative comparisons were made to determine the electric field morphology that allows the model results to best fit the plasma data at various times during these events the simulations with self consistent electric fields were in general better than those with prescribed field choices this indicates that the time dependent modulation of the inner magnetospheric electric fields by the nightside ionosphere is quite significant for accurate determination of these fields and their effects it was determined that a shielded volland stern field description driven by the 3 hour kp index yields accurate results much of the time but can be quite inconsistent the modified mcilwain field description clearly lagged in overall accuracy compared to the other fields but matched some data sets like dst quite well the rankings between the simulations varied depending on the storm and the individual data sets indicating that each field description did well for some place time and energy range during the events as well as doing less well in other places times and energies several unresolved issues regarding the storm time inner magnetospheric electric field are discussed

incomplete retention of radiation damage in zircon from sri lanka a suite of 18 zircon gemstones from placers in the highland southwestern complex sri lanka were subjected to a comprehensive study of their radiation damages and ages the investigation included x ray diffraction raman and pl spectroscopy electron microprobe pixe and hrtem analysis as well as u th he and shrimp u th pb age determinations zircon samples described in this study are virtually homogeneous they cover the range from slightly metamict to nearly amorphous generally concordant u th pb ages averaging 555 11 ma were obtained late ordovician zircon u th he ages scattering around 443 9 ma correspond reasonably well with previously determined biotite rb sr ages for rocks from the hswc slightly to moderately metamict zircon has retained the radiogenic he whereas only strongly radiation damaged zircon calculated total fluences exceeding 3 5 10 18 events g has experienced significant he loss when compared to unannealed zircon from other localities sri lanka zircon is about half as metamict as would correspond to complete damage accumulation over a 555 m y lasting self irradiation period suggesting significant annealing of the structural radiation damage insufficient consideration of this has often resulted in significant underestimation of radiation effects in zircon we suggest to estimate effective doses for sri lanka zircon by multiplying total fluences which were calculated using the zircon u th pb age by a correction factor of 0 55 this conversion may be applied to literature data as well because all gem zircon samples from sri lanka this work and previous studies seem to reveal the same general trends of property changes depending on the radiation damage the use of effective doses for sri lanka zircon contributes to more reliable quantitative estimates of radiation effects and makes possible direct comparison between natural and synthetic radiation damaged zircon