prompt penetration electric fields ppefs and their ionospheric effects during the great magnetic storm of 30 31 october 2003 1 we explore the ionospheric effects of prompt penetration electric fields ppefs for a variety of interplanetary magnetic field directions we use the great magnetic storm of 30 31 october as an example of ppef effects for intense southward interplanetary magnetic fields imfs inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm concurrent with the above positive phase ionospheric storms occur in the dayside and negative phase ionospheric storms occur on the nightside the topics of this paper the dayside ionospheric storms due to ppefs are characterized by transport of near equatorial plasma to higher altitudes and latitudes forming a giant plasma fountain these features are part of what is called the dayside ionospheric superfountain dis for these southward imfs dusk and dawn plasma are predicted to be transported toward the dayside for northward imfs negative phase ionospheric storms are expected on the dayside if the ppefs indeed reach that region of space imf by components are expected to have weak or neglible ionospheric effects on the basis of ppef arguments intervals of imf by should not be related to geomagnetic storms they are not imf by intervals should however cause a shearing of the magnetotail a feature that has been previously reported in the literature

radiation damage halos in quartz radiation damage halos are present in quartz that surrounds or is adjacent to accessory minerals such as zircon these halos are not visible in transmitted light but are revealed by cathodoluminescence cl they extend up to 45 m away from the source of radioactivity some halos show concentric rings similar to those previously reported in pleochroic halos in biotite radiation damage halos occur in three main settings surrounding inclusions within quartz grains penetrating into quartz from adjacent radionuclide bearing grains and in quartz cement near such grains halos are more common in pre paleozoic rocks than in younger rocks except in cases of unusual enrichment in radioactive elements halos result from damage to quartz crystal structure identical to the process forming pleochroic halos in biotite damage is caused by alpha particles emitted by radioactive elements within mineral grains and is a partial function of time consequently radiation damage halos may have potential uses in geochronology

reply to comment by s tulasi ram et al on westward electric field penetration to the dayside equatorial ionosphere during the main phase of the geomagnetic storm on 22 july 2009

gps phase scintillation at high latitudes during the geomagnetic storm of 17 18 march 2015 the geomagnetic storm of 17 18 march 2015 was caused by the impacts of a coronal mass ejection and a high speed plasma stream from a coronal hole the high latitude ionosphere dynamics is studied using arrays of ground based instruments including gps receivers hf radars ionosondes riometers and magnetometers the phase scintillation index is computed for signals sampled at a rate of up to 100 hz by specialized gps scintillation receivers supplemented by the phase scintillation proxy index obtained from geodetic quality gps data sampled at 1 hz in the context of solar wind coupling to the magnetosphere ionosphere system it is shown that gps phase scintillation is primarily enhanced in the cusp the tongue of ionization that is broken into patches drawn into the polar cap from the dayside storm enhanced plasma density and in the auroral oval in this paper we examine the relation between the scintillation and auroral electrojet currents observed by arrays of ground based magnetometers as well as energetic particle precipitation observed by the dmsp satellites equivalent ionospheric currents are obtained from ground magnetometer data using the spherical elementary currents systems technique that has been applied over the ground magnetometer networks in north america and north europe the gps phase scintillation is mapped to the poleward side of strong westward electrojet and to the edge of the eastward electrojet region also the scintillation was generally collocated with fluxes of energetic electron precipitation observed by dmsp satellites with the exception of a period of pulsating aurora when only very weak currents were observed

spread f occurrence over a southern anomaly crest location in brazil during june solstice of solar minimum activity 1 we present a study of spread f occurrence over a location under the southern crest of the equatorial ionization anomaly cachoeira paulista 22 7 s 45 0 w mag lat 16 s dip angle 32 3 brazil during the last solar cycle which presented an extended solar minimum activity after analyzing hundreds of ionograms obtained with a digital ionosonde dgs 256 between 2001 and 2010 we verified high spread f occurrence around midnight postmidnight during june solstice southern hemisphere winter with a peak occurrence between 2006 and 2009 when the solar flux has reached very low values 70 sfu at the brazilian sector the occurrence of spread f is known to be associated with equatorial plasma bubbles epbs and is observed mainly between september and march on the other hand epbs are rarely observed over cachoeira paulista hereafter referred as cp during june solstice because of the weak magnitudes of the equatorial electric field prereversal enhancement an essential condition to the development of the large scale irregularities at the equatorial region despite the rarity of epbs we observed several strong spread f events occurring under low plasma densities conditions which can extend for several hours we have found evidences that the spread f events over cp during june solstices of low solar activity can be caused by ionospheric disturbances that are unrelated to equatorial processes finally we present a statistical analysis of the events and we suggest that traveling ionospheric disturbances could be one of the main sources of these nonequatorial spread f events

petrogenesis of the proterozoic athabasca basin northern saskatchewan canada and its relation to diagenesis hydrothermal uranium mineralization and paleohydrogeology abstract in the athabasca basin proterozoic sandstones unconformably overlie archean and aphebian rocks multiple fluid events involving isotopically and chemically distinct fluids which have migrated laterally for considerable distances and along fault zones have produced a paragenetically identifiable assemblage of clay silicate and oxide minerals in the basin and basement rocks altered sandstones and the underlying metasedimentary rocks proximal to fault zones host high grade u ni co unconformity type uranium ore deposits and contain an alteration assemblage of highly crystalline 2m 3t illite 1m kaolinite clinochlore and sudoite hematite dravite and euhedral quartz in the sandstones 18o values of coeval quartz hematite quartz illite quartz dravite illite hematite and kaolinite hematite fluid inclusion temperatures in diagenetic quartz and d values of 1m kaolinite 2m 3t illite dravite and in fluid inclusions in the quartz indicate formation from a basinal fluid that had d values of 60 10 and which underwent salinity temperature and 18o increases from 5 to 34 wt nacl 120 to 240 c and 5 to 3 respectively as a result of increasing burial depth and sustained water rock interactions with the basinal sediments over substantial time periods 18 o 16 o and d h ratios of sudoite and clinochlore in meta sedimentary basement rocks within the alteration haloes indicate formation from a basement derived fluid with 18o and d values of 4 4 and 30 10 respectively that was isotopically distinct from the basinal fluids 18o and d values of late kaolinites in reactivated fault zones indicate formation mainly from low temperature 50 25 c fluids having 18o and d values of 16 and 130 respectively similar to relatively modern meteoric waters in the area some kaolinites have 18o and d values which suggest they formed from meteoric waters at mid latitudes and have experienced varying degrees of oxygen and hydrogen isotope exchange with relatively modern meteoric waters in the re activated faults illite sudoite and dravite have d values that vary by 100 without concurrent changes to their 18o values indicating preferential hydrogen isotope exchange with relatively modern meteoric waters at low temperatures and under conditions of high integrated water rock ratios rb sr isochron and model ages of 1477 57 and 952 ma respectively for the crystalline 2m 3t illites indicate the timing of the high temperature basinal fluid events associated with fluid mixing rb sr and k ar ages on illites with the lowest d values are as young as 300 ma and indicate late stage resetting of their radiogenic isotope systematics as a result of substantial interactions with relatively modern meteoric waters the evolution of sr isotopic compositions of fluids in the basin and basement rocks as reflected by the 87 sr 86 sr ratios of chlorite illite and dravite indicates that mixing of two isotopically distinct fluids in the vicinity of faults was the process by which uranium was precipitated similar to that suggested by oxygen and hydrogen isotope systematics in the clays and silicate minerals nd ratios in the high temperature diagenetic and hydrothermal clay and silicate minerals and the cogenetic uranium ores suggest they all have formed from similar fluids which have interacted substantially with the basin sediments in general the isotopic chemical microthermometric and petrologic data indicate that the athabasca basin has had a protracted fluid history comparable to that documented for more modern sedimentary basins the data clearly show that the major sandstone aquifers have been affected by widespread lateral flow of diagenetic fluids over distances of hundreds of kilometers and also that these fluid migration paths have been modified by cross formational fluid flow near active fault zones

radiation damage rims in quartz from uranium bearing sandstones abstract using cathodoluminescence cl mode of a scanning electron microscope sem radiation damage in quartz is made visible in uranium vanadium bearing sandstones located in the salt wash member of the morrison formation jurassic from the colorado plateau u s a detrital quartz grains surrounded by uranium minerals display radiation damage rims three concentric rims with thicknesses of 37 m 24 m and 16 m have been observed the rims are similar to halos surrounding uranium and thorium rich accessory minerals observed by owen 1988 they are due to alpha particles which create damage when penetrating a medium the width of the rims agrees well with the bragg kleeman rule and corresponds to the most energetic alpha particles in the 238u decay series sandstones entirely cemented by vanadium clays also exhibit radioactive rims which demonstrates that uranium has been removed during diagenesis these results have important implications for the uranium ore genesis in the salt wash sandstones because they imply an ancient episode of uranium leaching prior to recent weathering therefore cathodoluminescence in sandstones may be useful in recognizing ancient zones or episodes of accumulation and leaching of alpha emitting nuclides from the uranium series

long duration penetration of the interplanetary electric field to the low latitude ionosphere during the main phase of magnetic storms 1 it is well known that the interplanetary electric field can penetrate to the low latitude ionosphere it is generally believed that the penetration of electric fields can last only for 30 min because of the shielding effect in the ring current in this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field imf in six cases the eastward electric field in the dayside equatorial ionosphere measured by the jicamarca incoherent scatter radar was enhanced for 2 3 hours after the imf turned southward and remained continuously southward in one case the eastward electric field in the dayside midlatitude ionosphere measured by the millstone hill incoherent scatter radar was continuously enhanced for 10 hours during southward imf since millstone hill is close to the equatorward boundary of the auroral zone during magnetic storms the penetration electric field there may be different from that at the equatorial ionosphere the most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay the electric field enhancements in the middle and low latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms the observations show that the interplanetary electric field can continuously penetrate to the low latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions

ar ar and u pb geochronology of a late paleoproterozoic rift basin support for a genetic link with hudsonian orogenesis western churchill province nunavut canada abstract the baker lake group baker sequence represents the record of the formative stage of baker lake basin a series of generally elongate northeast striking half graben and fault bounded troughs filled with continental redbeds and coeval voluminous ultrapotassic volcanic rocks an estimate for the time of basin initiation is given by a u pb zircon age of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape 1833 pm 3 end document ma obtained from a basal volcanic flow at the western end of the basin which is in agreeme

ionospheric responses to the october 2003 superstorm longitude local time effects over equatorial low and middle latitudes 1 ionospheric responses to the major magnetic storm disturbances of october 2003 are investigated using database selected in the brazilian and japanese asian longitude sectors data obtained from latitudinally spaced digisondes in the equatorial and low latitude sites in brazil and from the asian and japanese ionosonde network the total electron content data from the extensive japanese gps receiver chain and magnetometer data from the pacific equatorial electrojet stations are analyzed during the period 28 31 october prompt penetrating pp dawn dusk polar cap electric fields produce large f region plasma uplift on the dayside and eveningside while the associated westward electric field on the nightside produces large downdraft of the f region plasma and causes development of westward electrojet current observed for the first time episodes of pp electric field effects appear to be of larger intensity over brazil than over asian longitudes equatorial anomaly development due to undershielding as well as overshielding electric fields was observed in the brazilian and in the asian sectors disturbance dynamo electric field causes large nighttime f layer uplifts that are modulated by strong meridional winds in both sectors the disturbance electric field local time variation patterns are compared with the results of recent global model mtiegcm simulation by richmond et al 2003 and validated in some cases transients of transequatorial winds flipping direction from southward to northward in the widely separated longitude sectors were diagnosed to be present toward the final recovery phase of the storm these results are presented and discussed in this paper

a strong positive phase of ionospheric storms observed by the millstone hill incoherent scatter radar and global gps network 1 during geomagnetic storms the ionospheric f region electron density may be greatly increased or decreased which are termed positive storms or negative storms it is generally accepted that negative storm phases are caused by neutral composition changes in contrast different mechanisms have been proposed to explain the generation of positive storm phases in this paper we present observations of a strong positive storm at middle latitudes the millstone hill incoherent scatter radar detected significant increases of the midlatitude ionospheric f region electron density during a magnetic storm on 3 april 2004 the positive phase of the ionospheric storm started to occur in the morning sector 0912 lt at millstone hill and lasted for more than 10 hours compared with the quiet time ionosphere the daytime f peak altitude over millstone hill during the storm was 80 km higher the f region electron density was increased by a factor of 2 4 and the f region electron temperature was decreased by 1000 k or 40 the radar also measured an enhanced eastward electric field and a slightly more equatorward neutral wind global gps measurements show that total electron content tec was increased at middle latitudes and decreased at lower latitudes and the large tec enhancements occurred primarily in the atlantic sector we suggest that electric fields may play an important role in the generation of the observed positive storm phase the eastward electric field will cause increases in the midlatitude ionospheric electron density by moving the plasma particles upward and decreases in the equatorial ionospheric electron density by strengthening the fountain effect the daytime poleward wind was reduced or even reversed during the storm which may also contribute to the occurrence of the positive storm

westward electric field penetration to the dayside equatorial ionosphere during the main phase of the geomagnetic storm on 22 july 2009 1 the moderate geomagnetic storm minimum sym h 89 nt that occurred during the period from 21 to 25 july 2009 is anomalous because the storm main phase developed during northward interplanetary magnetic field imf a reduction for 4 h in the daytime e region westward drift eastward electric field over the magnetic equatorial location of trivandrum 8 5 n 77 e dip latitude 0 5 n in india is observed during the storm main phase this reduction in the drift is also indicated by the disappearance of the equatorial sporadic e region esq echoes on the ionograms it is suggested that an additional westward prompt penetration electric field characterized by the northward imf bz is superposed on the ionosphere during the storm main phase which contributed to the observed reduction in the drift these are the first observations which indicate the effects of the dusk to dawn penetration electric fields on the east west drifts during northward imf

stable isotope geochemistry of alteration associated with the key lake uranium deposit canada the key lake uranium deposit occurs within a shear zone that intersects the unconformity between early proterozoic basement gneiss and overlying middle proterozoic athabasca group sandstone uranium is concentrated near the unconformity and is associated with intense illite chlorite and kaolinite alteration the delta d and delta 18 o values of the clay minerals suggest that several different fluids have affected the ores and surrounding host rocks alteration of the basement gneisses associated with the uranium mineralization consists mainly of mg chlorite that equilibrated about 200 degrees c with a fluid having a delta d value near 20 per mil and a delta 18 o value near 5 per mil an illite rich sandstone alteration halo preserved only locally above the deposit equilibrated about 200 degrees c with a basinal brine having a delta d value near 65 per mil and a delta 18 o value near 5 per mil the uranium was concentrated near the unconformity by the mixing of these two distinct fluids the delta 18 o values of coexisting quartz and illite sampled from the shear zone hosting the uranium mineralization yield equilibration temperatures of 190 degrees to 230 degrees c which is postulated to be the temperature of the ore forming event fracturing in the sandstone above the deposit controlled late low temperature 50 degrees c kaolinitization of preexisting hydrothermal illite and chlorite by meteoric waters having delta d values of 50 or 30 per mil and delta 18 o values of 7 or 3 per mil the youngest event to affect the key lake deposit is related to the influx of modern meteoric waters that have lowered the delta d values but not greatly affected the delta 18 o values of some of the clay minerals associated with the shear and breccia zones this latest event has recrystallized much of the hydrothermal mg chlorite associated with the uranium to produce an fe mg chlorite with delta d values as low as 170 per mil

o and pb isotopic analyses of uranium minerals by ion microprobe and u pb ages from the cigar lake deposit we apply a rapid and accurate in situ technique to make u pb isotopic measurements of complexly intergrown uranium minerals and oxygen isotopic analyes of uraninite from the unconformity type cigar lake uranium deposit secondary uranium minerals intergrown with uraninite such as coffinite usio4 nh2o and calciouranoite cau2o7 5h2o were identified by highresolution transmission electron microscopy hrtem in situ u pb results from three stages of uraninite and coffinite define well correlated arrays on concordia with upper intercepts of 1461f47 1176f9 and 876f14 ma f1r these ages are interpreted as the minimum ages of mineralization correlate with the timing of clay mineral alteration f1477 ma associated with these unconformity type uranium deposits the ages of magnetization events at 1600 1450 and 900 ma from the athabasca basin and the grenvillian orogeny at f1100 ma in situ u pb isotopic analyses of uraninite and coffinite can document the pb u heterogeneities that occur on the scale of 15 30 am thus providing relatively accurate information regarding the timing of fluid interactions associated with the evolution of these deposits the high spatial resolution and precision of the ion microprobe allow us to measure d 18 o values of 20 100 am unaltered portions of uraninites from cigar lake the range of d 18 o values 33 9 to 20 4x are among the lowest reported for unconformity type deposits confirming that conventional fluorination analyses of material sampled at the mm scale are insufficient to avoid contamination from isotopically heavier coffinite and calciouranoite d 2002 elsevier science b v all rights reserved

a mississippian black shale record of redox oscillation in the craven basin uk early diagenetic redox oscillation processes have been rarely recognised in the ancient rock record but potentially exert an important control on mineral authigenesis hydrocarbon prospectivity and supply of metals and or reduced s as part of associated mineral systems the upper unit of the mississippian bowland shale formation is a candidate record of diagenetic redox oscillation processes because it was deposited under a relatively high sediment accumulation rate linked to a large delta system and under dominantly anoxic and intermittently sulphidic bottom water conditions in order to characterise the syngenetic and early diagenetic processes sedimentological and geochemical data were integrated through the upper bowland shale at three sites in the craven basin lancashire uk organic matter om comprises a mixture of type ii ii s ii iii and iii om redox zones are defined by patterns of fe speciation and redox sensitive trace element enrichment and split into two groups sulphidic zones eux an iii an i and an it represent sediments deposited under conditions of at least intermittently active sulphate reduction in bottom waters non sulphidic zones ox rx ox f and ox represent sediments deposited under non sulphidic oxic to ferruginous anoxic bottom waters operation of a shelf to basin reactive fe fehr shuttle moderated by sea level fluctuation and delta proximity controlled the position and stability of redoxclines between zones of fe and sulphate reduction and methanogenesis early diagenetic redoxclines were capable of migration through the shallow sediment column relatively quickly in response to sea level fluctuation preservation of syngenetic and early diagenetic geochemical signals shows redoxclines between fe and sulphate reduction and the upper boundary of sulphate methane transition zone were positioned within decimetres i e 10 s cm of seabed falling sea level and increasing fehr supply is recognised as a switch from zones eux high sea level an iii and ultimately an i and an it low sea level zone an i defines the operation of redox oscillation between zones of fe and sulphate reduction in shallow porewaters associated with enhanced degradation of om and complete dissolution of primary carbonate preservation of om and carbonate in this system was a function of changing bottom and pore water redox processes redox oscillation operated in a siliciclastic prodeltaic environment associated with a relatively high sediment accumulation rate and high loadings of labile organic matter and metal oxides these findings are important for understanding late palaeozoic black shales in the context of hydrocarbon and mineral systems

tracing past migrations of uranium in paleoproterozoic basins new insights from radiation induced defects in clay minerals radiation induced defects were identified in kaolinite illite and sudoite by electron paramagnetic resonance spectroscopy of the alteration halo surrounding the uranium orebodies in the athabasca basin saskatchewan canada clay minerals are assumed to behave similarly under irradiation in all samples defects are similar in nature but their concentrations can vary widely over several orders of magnitude the maximum fluctuations in defect concentrations are observed along the regional paleoproterozoic unconformity between the lower sandstones and the metamorphic basement rocks and close to crosscutting brittle structures both of which appear to be the main vectors of uranium bearing fluid transfer in the basin in the basement some hudsonian faults connected to this unconformity also show high defect concentrations attesting that uranium bearing fluids may have circulated in the fracture network the proximity of mineralization can be revealed through defects that record the past presence of uranium in altered rocks at significant distances from the mineralized bodies the absence of correlation between defect concentrations and present dose rates indicates that migrations of uranium bearing fluids took place after the formation of clay minerals

continuous penetration of the interplanetary electric field to the equatorial ionosphere over eight hours during intense geomagnetic storms 1 the interplanetary electric field penetrates to the low latitude ionosphere and has significant influence on the ionospheric electrodynamics during intense geomagnetic storms it is critical to understand how much of the interplanetary electric field can penetrate to the ionosphere and how long penetration electric fields can exist in this study we present the defense meteorological satellite program dmsp satellite measurements of the equatorial ionospheric ion vertical velocity in the dusk sector during two intense geomagnetic storms we find that the equatorial ionospheric electric field at dusk is approximately proportional to the interplanetary electric field for 8 10 hours during the storm main phase the penetration efficiency is relatively constant over the entire interval and is 5 at dusk in one storm case the long lasting storm time penetration electric field causes significant redistribution of the ionospheric plasma this study reveals that penetration electric fields can last for 8 10 hours without effective shielding when the magnetic storm activity is strengthening during continuous southward interplanetary magnetic field the result implies that the interplanetary electric field is linearly coupled with the dusk equatorial ionosphere during the entire main phase of intense magnetic storms which is very important for understanding the storm time ionospheric electric field and electrodynamics

reconstruction of past u migration in a sedimentary deposit coutras france implications for a radwaste repository this study is focused on ancient u mobility in unconsolidated kaolinite bearing sediments from the outcrop area of the coutras u deposit gironde france the analysis of radiation induced defects by electron paramagnetic resonance spectroscopy shows significant variations among the investigated samples and provides the paleodoses due to u at coutras the highest paleodose does not correspond to the highest u concentrations indicative of a past concentration of uranium different from the present one the paleodose gives an estimate of the equivalent u concentrations eu responsible for the defect concentration assuming an age for the kaolinites and considering extreme degrees of disequilibrium among u decay chain as uncertainties of the method the comparison between the equivalent eu and normalized present day u concentrations u norm reveals past migration of u when these two concentrations are different past occurrence of u and daughters is revealed even when this radioelement has been subsequently leached indeed surface sandy beds show a slight barely significant leaching evidence of u eu u norm in contrast several samples show u norm much greater than eu which suggests past accumulation of u younger than the sediment deposition particularly in organic rich clay layers these late enrichments may reach several hundreds ppm u isotopic constraints from the literature imply that accumulation is older than 1 ma in the organic clayey beds although the time of transfer or spatial dispersion of u cannot be specified from the methodology and the limited set of samples the quantitative analysis of radiation induced defects in clays yields intensity of past radioisotope transfers at the geological timescale it is relevant for the analysis of u mobility in sedimentary natural analogues of high level nuclear waste repositories it is also complementary to classical isotopic analysis of u and th series

penetration of magnetospheric electric fields to the equator during a geomagnetic storm 1 penetration of the magnetospheric electric field to the equatorial ionosphere was examined for the geomagnetic storm on 6 november 2001 by analyzing the difference in magnitude of the geomagnetic storm recorded at the dayside geomagnetic equator yap 0 3 gml and low latitude okinawa 14 47 gml the penetrated electric field caused the dp2 currents at the equator i e eastward currents during the main phase of the storm while the overshielding currents i e westward currents dominated during the recovery phase it is shown that the ring current started to develop simultaneously with the onset of the equatorial dp2 within the temporal resolution of a few minutes these results imply prompt transmission of the dawn to dusk convection electric field to the inner magnetosphere as well as to the equatorial ionosphere it is found that the equatorial dp2 started to decrease one hour after the onset of the ring current development indicating shielding effects becoming effective at the equator during the latter half of the storm main phase the dp2 was then overwhelmed by the overshielding which resulted in the counter electrojet cej in the beginning of the storm recovery phase the image magnetometer chain data indicate that the westward auroral electrojet aej in the dawn sector was driven over midlatitude centered at 57 corrected geomagnetic latitude cgml during the main phase while the aej shifted rapidly poleward to the auroral latitude centered at 67 cgml in the beginning of the recovery phase the overshielding must be caused by the abrupt poleward shift of the rl facs as inferred from the poleward shift of the aej in addition to the decrease in their magnitude due to the decrease in magnitude of the southward imf the geomagnetic storm at the dayside geomagnetic equator was enhanced in amplitude with the ratio of 2 7 as compared with the geomagnetic storm at low latitude this amplification is a result of both effects of the dp2 currents and the cej associated with the main and recovery phases respectively it is suggested that the electric field associated with the dp2 currents contributed to the development of the ring current during the main phase while the overshielding electric field may contribute to cease developing the ring current during the recovery phase

radiation induced defects in drusy quartz athabasca basin canada a new aid to exploration of uranium deposits room temperature powder electron paramagnetic resonance epr spectra of drusy quartz i e euhedral quartz crystals as coatings on or infillings in cavities and fractures from five uranium mineralized areas in the eastern athabasca basin saskatchewan canada reveal a suite of radiation induced defects these epr spectra also show that radiation induced defects in drusy quartz from different geologic occurrences are similar in nature but vary widely in abundance for example radiation induced defects in drusy quartz from altered basement rocks significantly below mineralization are close to or below detection limits providing the first line of direct evidence for previous suggestions that fluids from the underlying basement rocks were uranium deficient drusy quartz in ore samples and those from alteration haloes around uranium orebodies are characterized by elevated levels of radiation induced defects similarly drusy quartz from less altered sandstones near the present day surface hundreds of meters above mineralization where uranium rich minerals are generally absent contains abundant radiation induced defects comparison of epr spectra of drusy quartz from less altered sandstones before and after hf treatments reveals that radiation induced defects are uniformly distributed in individual crystals in contrast to the preferred concentration in the grain margins and along fractures in detrital quartz these results suggest that radiation induced defects in drusy quartz were most likely formed by bombardment of alpha particles emitted by uranium bearing fluids during crystal growth therefore detection of radiation induced defects in drusy quartz from less altered sandstones represents a new near surface technique for exploration of uranium mineralization in the athabasca basin

the age of unconformity related uranium mineralization in the athabasca basin northern saskatchewan age data are presented for major athabasca basin uranium deposits at cigar lake cluff lake collins bay dawn lake eagle point mcarthur river midwest and rabbit lake as well as for several minor or undeveloped deposits including hughes lake and nisto the best constrained data indicate that almost all the deposits formed in a restricted time interval between about 1330 and 1380 ma this range of ages is believed to be real and not the result of uncertainties in the calculation of ages based on discordant data the one major exception is the recently discovered nias free deposit at mcarthur river for which a well determined age of 1514 18 ma 2 has been obtained even this deposit yields an age in the1330 1380 ma range for some material periods of reworking redeposition occurred at 1280 1000 575 and 225 ma these may be basin wide affecting to some degree all the deposits that we have studied other times of redeposition are less well determined but may be present as well no ages tha

significance of aluminum phosphate sulfate minerals associated with u unconformity type deposits the athabasca basin canada aluminum phosphate sulfate aps minerals formed around the athabasca unconformity type deposits and those from their australian counterparts are chemically very similar showing the same continuum between the diagenetic sr rich aps minerals of the barren sandstones and the lree rich composition of the aps minerals in the hydrothermally altered sandstone the p and lree rich compositions were controlled by the transport and the redistribution of p and lree elements released from the dissolution of phosphate minerals principally monazite in the basement rocks and in the basin during the syn ore alteration processes the s sr ratio measured in the aps minerals from unaltered sandstone away from the unconformity and any mineralization is preserved during the syn ore alteration processes suggesting that the fluids involved in both the deep burial diagenetic processes and the syn ore alteration system were derived from a similar diagenetic reservoir in both the athabasca and kombolgie regions the trioctahedral chlorite host rock alteration around the australian basement hosted u deposits as compared to the illite and sudoite associated with the athabasca basement hosted along with the more lree rich aps compositions in the australian deposits suggests that the ph and oxygen fugacity f o 2 of the syn ore fluids differed in the alteration systems of the two regions at the time of the u deposition