petrology geochemistry and na metasomatism of triassic jurassic non marine clastic sediments in the newark hartford and deerfield rift basins northeastern usa many sandstones and associated siltstones and shales of the triassic jurassic newark supergroup in the newark hartford and deerfield rift basins are immature feldspathic alluvial and lacustrine closed basin deposits they were derived from felsic igneous and metamorphic continental blocks on the flanks of their depositional basins the provenance was dominantly calc alkaline basement rocks similar to the sierra nevada of california the physical and chemical environments of erosion and deposition were probably similar to those in moist pleistocene holocene alluvial basins and playas in the great basin of california and nevada new petrographic and geochemical data for 113 samples indicate that albite rich sandstones and shales of the stockton lockatong and passaic formations in the newark basin and in the portland and east berlin formations of the hartford basin and analcime rich shales up to 52 normative analcime of the lockatong formation have unusually high na2o contents 4 7 textural evidence indicates both sodium replacement in feldspars and formation of authigenic albite and analcime in these rocks by comparison with modem sediments derived from similar provenance using mixing models it is estimated that up to 4 na2o was diagenetically added to the detrital clastics trace metals co cr cu ni zn abundances were apparently enhanced by deposition from brines in the lockatong formation analcime deposition occurred in shales with al2o3 na2o sio2 0 46 this ratio is found only in sediments to which na has been added from salts brines source rocks and the weathering products derived from them may be considered as a closed system in which sodium was retained partly in solids as feldspar and part went into solution during weathering the dilute solution migrated into the depositional basin where evaporation yielded concentrated brine during semi arid to arid climate in the drier parts of 21 000 yr milankovitch cycles reaction of brine during diagenesis at near surface and or shallow depths 2 km with ca plagioclase k feldspar and layer silicates at estimated temperatures 50 c to 100 c and ph 7 9 yielded thermodynamically stable authigenic albite and analcime in the sodium metasomatised clastic sediments low activity of k precluded development of authigenic k feldspar however k from solution incorporated into muds and silts as smectites were transformed to illite some lockatong beds contain anomalously high p2o5 ce la y th and u in authigenic apatite or monazite suggestive of mobilization of these elements in diagenesis

contrasting low and high ca granites in the archean barberton mountain land southern africa abstract two distinct groups of granites can be recognized among the late plutons of the barberton mountain land discrimination between the two groups is provided by geochemical and mineralogical parameters which are considered to reflect the source material from which the magmas were derived a high ca suite has geochemical parameters consistent with derivation from an igneous source i type and an accessory mineral assemblage comprising zircon apatite allanite and sphene a low ca suite contains distinctly different accessory minerals comprising zircon apatite zirconosilicates ca th phosphates very rare xenotime and early monazite and has a chemical signature consistent with derivation from a metasedimentary precursor s type major and trace element trends on harker diagrams support the existence of two distinct granite suites the i type suite exhibits inverse relationships between sio2 and cao tio2 fe2o3 mgo and p2o5 while al2o3 k2o and na2o remain relatively constant these characteristics are consistent with magma formation from an intermediate parent composition and in equilibrium with a hornblendite restite the s type granites formed by vapour absent melting of siliceous metapelite and exhibit inverse correlations between sio2 and al2o3 na2o and k2o with the other major elements remaining relatively unchanged this interpretation of restite unmixing is not unambiguous since rb sr trends could be viewed as reflecting crystal fractionation and partial melting processes high field strength elements tend to reflect the character of accessory mineral phases and are not amenable to modelling in terms of crystal melt equilibria the recognition of possible s and i type suites among the late granite plutons of the barberton mountain land supports recent models which propose plate tectonic analogues in the region the two granite suites are distributed along two subparallel linear arrays which suggests scenarios invoking subduction or hot spot related magmatism with the i types forming in the time span 2740 2690 ma along a western array the putative s types occurring entirely along an easterly belt were emplaced at 3074 and 2820 ma the presence of s type plutons as old as 3074 ma implies that sediments such as the moodies and fig tree groups or their equivalents had been buried to depths of at least 15 km and that by this time at least in the barberton area granites had evolved beyond the ttg mode that typifies many early archaean shield areas

precise u pb titanite age constraints on the emplacement of the bushveld complex south africa the c 2 06 ga bushveld complex intrudes the transvaal supergroup south africa calcsilicate xenoliths within the mafic phase of the bushveld complex rustenburg layered suite or rls preserve calcsilicate xenoliths with high temperature c 1200 c mineralogies that were later metasomatized by hydrous retrograde c 600 700 c fluids whose timing has been unconstrained new u pb isotope data from newly grown titanite within a completely retrogressed xenolith indicates that retrogression occurred at 2058 9 0 8 ma this suggests that retrogression was due to hydrothermal circulation associated with the cooling rls and not slightly later bushveld related granites the new data place a tight constraint on the minimum age of emplacement of the rls

3 07 2 97 ga greenstone belt formation in the northeastern kaapvaal craton implications for the origin of the witwatersrand basin

metallogeny of precious and base metal mineralization in the murchison greenstone belt south africa indications from u pb and pb pb geochronology the 3 09 to 2 97 ga murchison greenstone belt is an important metallotect in the northern kaapvaal craton south africa hosting several precious and base metal deposits central to the metallotect is the antimony line striking ene for over 35 km which hosts a series of structurally controlled sb au deposits to the north of the antimony line hosted within felsic volcanic rocks is the copper zinc line where a series of small ca 2 97 ga cu zn volcanogenic massive sulfide vms type deposits occur new data are provided for the malati pump gold mine located at the eastern end of the antimony line crystallizations of a granodiorite in the malati pump mine and of the baderoukwe granodiorite are dated at 2 964 7 and 2 970 7 ma respectively zircon u pb while pyrite associated with gold mineralization yielded a pb pb age of 2 967 48 ma therefore granodiorite emplacement sulfide mineral deposition and gold mineralization all happened at ca 2 97 ga it is thus suggested that the major styles of orogenic au sb and the cu zn vms mineralization in the murchison greenstone belt are contemporaneous and that the formation of meso to epithermal au sb mineralization at fairly shallow levels was accompanied by submarine extrusion of felsic volcanic rocks to form associated cu zn vms mineralization

characterization of multiple fluid granite interaction processes in the episyenites of avila bejar central iberian massif spain episyenites are small granite hosted pipe like masses characterized by hydrothermal alteration and the major loss of silica compared with the host granites such bodies are fairly common in the hercynian granites of western europe this study deals with late hercynian amphibole bearing and biotite granodiorites monzogranites from the central iberian massif using petrological geochemical major oxides trace elements and ree and isotopic o h data to constrain the paragenesis of alteration the apparent changes in bulk composition and the sources and conditions of fluids involved in fluid rock interactions episyenitization leads to reduction of quartz content albitized plagioclases and chloritized ferromagnesian phases and the process results in increasingly ordered alkali feldspars there are noticeable variations in whole rock na20 k2o mgo cao rb and sr contents with sio2 in some cases behaving differently depending on whether the episyenite is hosted in amphibole granite or biotite granite the lree y zr and nb have also been modified in those syenites associated with amphibole bearing granites this being attributed to destabilization of accessory minerals and recrystallization of new stable mineral assemblages the process is complex and two generations of chlorite early high fe and late low fe are observed whole rocks and mineral separates were studied for o and h isotopes the data rule out meteoric fluids as the cause of syenitization and the later resiliciftcation of some and suggest that at least two different fluids were involved in generating the syenites the first is interpreted to be a high temperature 300 450 c late magmatic deuteric fluid as recorded by feldspar o isotope data later a different fluid with 18o 1 4 and d 13 isotopically indistinguishable from seawater on a deglaciated earth produced the chlorite secondary quartz and minor epidote such a fluid was only available for a short period since feldspars did not re equilibrate the fault systems occupied by the episyenites provided suitable pathways for fluids of both shallow and deep origins over a long term during the carboniferous

porphyry intrusions and albitites in the bardoc kalgoorlie area western australia and their role in archean epigenetic gold mineralization minor intrusions in the menzies kambalda greenstone belt of the archean eastern goldfields province western australia range from quartz feldspar porphyry to plagioclase hornblende porphyry the porphyries display enrichment of mobile and incompatible elements k to zr and depletion of relatively compatible elements with negative nb p and ti anomalies on mid ocean ridge basalt normalized spidergrams the composition and timing of emplacement of the porphyries are consistent with a genetic relationship with spatially related granitoids porphyries occur in 30 of gold mines in the menzies kambalda belt the association appears to be largely structural since both the intrusions and the mineralizing fluids exploit zones of weaknesses such as lithological contacts and shear zones porphyries have been modified to varying degrees by hydrothermal alteration especially pervasive albitization textural evidence indicates that secondary albite and associated sodic amphibole formed late in the deformatio

quasi periodic radar echoes from midlatitude sporadic e and role of the 5 day planetary wave using measurements of magnetic aspect sensitive radar echoes from midlatitude sporadic e collected over a two month period from tanegashima japan we show that while their occurrence duration from night to night did not exhibit any systematic variation that of the so called quasi periodic qp echoes varied sinusoidally with a period of 5 days we have interpreted this behavior in terms of effects produced by a planetary wave and identified its presence through neutral wind measurements made with a partial reflection drift radar located nearby at yamagawa we propose that the occurrence of qp echoes is affected both by a contribution of the wind to the dynamo electric field and by the direction of the neutral wind we argue that because the wind vector of the planetary wave is elliptically polarized at midlatitudes a preferred wind direction conducive to the generation of qp echoes occurs once every 5 days on the other hand this wave is linearly polarized and directed zonally over the geographic equator the fact that qp echoes are most fully developed at midlatitudes and less so at lower latitudes suggests that zonal flow is not particularly favorable for qp echo production

signatures of low latitude high latitude coupling in the tropical mlt region during sudden stratospheric warming 1 the present paper analyses the variations of daytime mesopause temperature over an equatorial station during polar stratospheric sudden warming ssw events indicating a possible dynamical coupling between the two regions through the intensification of planetary wave activity the amplified wave signatures of quasi 16 day period have been seen in the equatorial mesopause temperature emt and polar stratospheric temperature at 10 hpa during the course of the ssw the emt measurements were made from trivandrum 8 5 n 76 5 e an equatorial station in india and the stratospheric temperatures were obtained from ncep ncar reanalysis this investigation reveals 1 an overall enhancement and amplified wave activity in the emt prior to the ssw and 2 propagation of a wave disturbance from equatorial stratosphere to north pole in about a month these results are new and reveal some newer aspects of the ssw and its equatorial effects

reconstructing upper ocean vertical velocity field from sea surface height in the presence of unbalanced motion abstractreconstructability of upper ocean vertical velocity w and vorticity fields from high resolution sea surface height ssh data is explored using the global 1 48 horizontal resolution mitg

zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by eos aura microwave limb sounder 1 recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers here we use eos aura microwave limb sounder mls temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70 s to 70 n from 2004 to 2009 we consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals particularly at high latitudes in winter the seasonal evolution of the different wave numbers is investigated and found to be very different between the northern and southern hemispheres in both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 w3 and w4 however in the southern hemisphere the wave is dominated by the w3 component but in the northern hemisphere the w3 component is smaller and the w4 component is often of similar or larger amplitude a small amplitude westward traveling zonal wave number 2 w2 wave is also evident in both hemispheres in the northern hemisphere the w2 amplitudes never exceed 3 k the w3 amplitudes can reach 3 5 k and the w4 can be the largest component reaching amplitudes of 4 k in the southern hemisphere the w2 amplitudes can reach up to 3 5 k the w3 amplitudes can be much larger reaching 12 k and the w4 amplitudes are smaller than in the northern hemisphere in 4 out of 5 years not exceeding 3 k the northern hemisphere w4 can reach large amplitudes in august when the w3 is small which means that the late summer northern hemisphere quasi 2 day wave is usually a w4 oscillation rather than the familiar w3 in contrast in the southern hemisphere the w3 is often larger than the w4 around the summer solstice and there are no episodes observed where the wave becomes dominated by the w4 for an extended period of time a high degree of interannual variability is evident particularly in the southern hemisphere where the w3 peak amplitudes vary from 12 k in january 2006 to 3 k in january 2009 the height latitude structure of the w4 suggests that this wave is a 4 0 rossby gravity wave

a 6 5 day westward propagating planetary wave origin and characteristics a large 10 30 m s 1 6 7 day period westward propagating planetary wave was seen in both ground radar and satellite data within the 80 100 km height regime during august and september 1993 previous analyses of these data argue that it was most likely a manifestation of the 1 2 rossby planetary wave commonly referred to as the 5 day wave perhaps shifted to longer periods by interaction with the mean zonal winds in this study the global scale wave model gswm hagan et al 1993 is used to analyze the characteristics of this westward propagating wave we propose that the observed wave is not a doppler shifted 5 day wave but rather an unstable mode drawing energy from unstable regions in the upper mesosphere whose realization is global in scale the concept of atmospheric instability is used to determine a likely source region and the model is used determine the characteristic period growth rate and perturbation fields of the instability driven wave

uranium deposits associated with na metasomatism from central ukraine a review of some of the major deposits and genetic constraints abstract the paper reviews geological structural mineralogical fluid inclusion geochemical and stable isotope characteristics of u deposits related to na metasomatism in the central ukrainian uranium province cuup the province contains numerous u deposits hosted in gneisses migmatites and granites of the ingul paleoproterozoic megablock and in iron formations along its margin with the fore mid dnieper mesoarchean megablock the richest u deposits are distributed along the nearly e w striking subotin mashorin tectonic zone but they are tightly controlled by n s and more rarely sw ne striking crustal scale shear zones na metasomatism and u mineralisation were controlled by protracted tectonic activity along these shears zones from ductile to brittle regimes of deformation a metasomatic zoning is developed from outermost unaltered lithologies inwards to dequartzified rocks episyenites aegirine albitites na metasomatites andradite epidote ca amphibole calcite rich rocks ca mg metasomatites and ultimately to biotite albitites k metasomatites main u ore deposition predominantly consisting of brannerite and uraninite with lesser amounts of u ferropseudobrookite is associated with the ca mg and k metasomatised zones superimposed on earlier aegirine albitites na metasomatites were formed at temperatures exceeding 500 c possibly triggered by the onset of a plume in the mantle associated with the intrusion of the highly potassic korsun novomyrgorod rapakivi granitic pluton at about 1750 1800 ma as constrained by u pb geochonologic data on the granites and uranium mineralisation these intrusions have been partly reworked tectonically with recrystallisation under lower p t conditions the mineral paragenesis of ca mg and k metasomatites crystallised during the cooling of the system down to 370 340 c ca mg and k metasomatisms resulted in further dequartzification of the rocks and their enrichment mainly in ca mg k u zr fe 2 and hf the hydrothermal fluids were oxidised moderately saline and highly alkaline the high alkalinity of the fluids explains the dissolution of quartz the deposition and stability of albite the high zr hf ratios up to 224 in the metasomatites and the high solubility of u and zr u deposition was controlled by mixing with a reduced fluid which explains the increase of whole rock fe 2 concentration during uranium deposition the last widespread hydrothermal event corresponds to a chlorite epidote paragenesis superimposed on all previous mineral associations at temperatures down to less than 100 c h o and c isotopic ratios in minerals and fluid inclusions extract from albitites suggest a surface formation water origin for the hydrothermal fluids producing na metasomatism and a mixed metamorphic surficial formation water origin for the fluids producing ca mg and k metasomatism and the main u mineralisation

five day mesospheric waves observed in solar mesosphere explorer ozone solar mesosphere explorer sme ozone data were analyzed for short term periodic oscillations in the altitude region from 50 to 90 km a 5 day oscillation was found to be a dominant feature at high southern latitudes near the december solstice in the altitude range from 50 to 80 km the wave feature appears to travel westward with a speed consistent with that of a wave number one planetary scale oscillation circling the globe in 5 days the amplitude also appears to be consistent with the temperature oscillations predicted by geisler and dickinson 1976 this oscillation was not found to be a dominant feature in sme ozone during northern hemisphere summer

albitization in the antimony line murchison greenstone belt kaapvaal craton a geochemical and geochronological investigation abstract the 3 09 2 97 ga murchison greenstone belt is one of several archean volcano sedimentary belts within the kaapvaal craton in southern africa among the diverse ore deposits found within the belt a set of sb au deposits are located in a major quartz carbonate altered brittle ductile structure known as the antimony line the antimony line is thus clearly related to hydrothermal fluid circulation in this study we focus on albitites that run along the antimony line petrological and geochemical investigations indicate that albitization developed at the expense of a granodioritic protoliths under high fluid rock ratios and also that sb enrichment was concomitant with albitization oxygen isotopes on albitites point to a crustal origin for the hydrothermal fluid responsible for the albitization process geochronology on zircon and hydrothermal monazite identifies a 2 97 2 92 ga magmatic crystallization event disconnected from a ca 2 8 ga hydrothermal alteration and a potentially younger event around 2 0 ga these data highlight a likely magmatic related primary enrichment at 2 97 2 92 ga followed by a secondary metamorphic related mobilization event around 2 8 ga leading to a sb enrichment in the albitites and a last episode of alteration around 2 0 ga

regional scale cretaceous albitization in the pyrenees evidence from in situ u th pb dating of monazite titanite and zircon abstract albitization is a common metasomatic process active in various geodynamic contexts in the northern pyrenees there are several occurrences of albitites but until now only one occurrence has been dated 117 ma ar ar dating this paper presents new u th pb ages for several albitite occurrences throughout the pyrenees to test whether they are contemporaneous and if so to specify the regional extent of the albitization event ages obtained from large euhedral titanite and monazite grains from distinct albitites are 110 8 and 98 2 ma respectively the zircon u th pb isotopic system did not record this cretaceous metasomatic event even when grains were selected in metasomatically zr enriched rocks or in hydrothermal structures millimetre sized veins cross cutting granitoids we argue that the total time span of 20 ma recorded by albitites corresponds to a long lived hydrothermal system that was active during the rotation of iberia around europe along the north pyrenean fault because albitization and talc mineralization have the same spatial and temporal distribution in the pyrenees we argue that these two metasomatic phenomena are two independent records of this single regional scale long lived hydrothermal system

role de la deformation du granite dans la genese des episyenites feldspathiques des massifs de lovios geres galice et des zaer maroc central l etude de la deformation du granite dans les zones encaissant les bandes d episyenites feldspathiques de deux massifs hercyniens a permis de degager un modele tectonique rendant compte des caracteristiques structurales de celles ci les bandes d episyenites feldspathiques se forment lors des phases ultimes de la mise en place des intrusions granitiques sous l effet d un champ de contrainte local susceptible d engendrer des surpressions fluides aboutissant a une fracturation de type hydraulique la genese des mineralisations filoniennes intragranitiques a tungstene etain associees spatialement a ces episyenites doit etre rapportee a des evenements tectoniques et a des circulations fluides posterieures

properties of the quasi 16 day wave derived from eos mls observations 1 this paper describes the use of eos microwave limb sounder mls data to observe the field of traveling planetary waves with quasi 16 day periods this study utilizes mls v2 2 temperature and geopotential data between 1 january 2005 and 31 december 2008 in the range 316 hpa to 0 001 hpa approximately 8 to 97 km to examine these waves analysis demonstrates that the quasi 16 day wavefield is made up of a number of components with westward and eastward propagating s 1 and s 2 waves generally dominant in the northern hemisphere the westward and eastward propagating s 1 waves have similar magnitudes and are larger than the other modes while in the southern hemisphere the eastward propagating s 1 and s 2 waves are larger than the westward propagating wave modes all of the modes examined display strong seasonal patterns in the temperature amplitude significant variability in the wave activity from year to year and the presence of strong pulse like patterns in the activity all of the modes also display large median temperature amplitudes poleward of 40 degrees in both hemispheres our analysis also demonstrates that the variability in winter from year to year is larger in the northern hemisphere than the southern hemisphere detailed study also suggests that the exclusion of waves from regions of negative refractive index squared likely forms much of the seasonal pattern observed thus regions of strong westward wind speeds effectively exclude vertically propagating waves as expected from theory the reflection and absorption of waves associated with critical lines is also likely to explain the frequent occurrence of standing wave patterns in the eos mls temperature observations this study highlights the potential of mls observations for observing waves from the upper troposphere to the lower mesosphere

observations of the 6 5 day wave in the mesosphere and lower thermosphere previous observations of atmospheric oscillations with zonal wave number 1 have consistently located waves of periods between 5 and 7 days this study presents a global and seasonal analysis of the 6 5 day wave in high resolution doppler imager daytime mesosphere and lower thermosphere horizontal winds temperatures and nighttime atomic oxygen at 95 km the horizontal structures of all these atmospheric variables are similar to the gravest symmetric wave number 1 rossby wave i e the 1 1 mode the seasonal and spatial analysis displays possible modification by the zonal mean wind finally the observed vertical structures of the 6 5 day wave indicate that it is an internal rossby wave not an external or lamb wave

large scale waves in the mesosphere and lower thermosphere observed by saber observations made by the sounding of the atmosphere using broadband emission radiometry saber instrument on board nasa s thermosphere ionosphere mesosphere energetics and dynamics timed satellite have been processed using salby s fast fourier synoptic mapping ffsm algorithm the mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere mlt since the launch of the timed satellite in december 2001 the results show the presence of various wave modes in the mlt which reach largest amplitude above the mesopause and include kelvin and rossby gravity waves eastward propagating diurnal oscillations non sunsynchronous tides and a set of quasi normal modes associated with the so called 2 day wave the latter exhibits marked seasonal variability attaining large amplitudes during the solstices and all but disappearing at the equinoxes saber data also show a strong quasi stationary rossby wave signal throughout the middle atmosphere of the winter hemisphere the signal extends into the tropics and even into the summer hemisphere in the mlt suggesting ducting by westerly background zonal winds at certain times of the year the 5 day rossby normal mode and the 4 day wave associated with instability of the polar night jet are also prominent in saber data

in situ la icp ms u pb titanite dating of na ca metasomatism in orogenic belts the north pyrenean example in the pyrenees in association with the rotation of the iberian plate around europe during the mid cretaceous a na ca metasomatism is recognized as a complementary record of the hydrothermal activity that led to na metasomatism albitization and talc chlorite mineralization it affected metasedimentary rocks as well as hercynian granites in situ laser ablation icp ms u pb analyses of titanite grains formed in albitites during metasomatism date the na ca metasomatism between 110 and 92 ma the temperature of the na ca metasomatism is estimated to be approximately 550 c both the time constraints and temperature estimates suggest that the na ca metasomatism is related to the low p high t north pyrenean metamorphism

evidence for stratosphere sudden warming ionosphere coupling due to vertically propagating tides 1 observations of the global positioning system gps total electron content tec are used to study the coupling between the 2009 sudden stratospheric warming ssw and ionospheric perturbations the observations reveal both migrating and nonmigrating perturbations to the semidiurnal tide in the equatorial ionization anomaly crest region that are associated with changes in electric fields induced by the tidal dynamo in particular a significant enhancement is observed in the nonmigrating semidiurnal westward propagating tide with zonal wavenumber 1 sw1 in gps tec during the ssw the sw1 perturbations in the low latitude ionosphere are found to oscillate with a similar period as planetary wave 1 activity in the northern hemisphere stratosphere this connection is attributed to the nonlinear interaction between tides and planetary waves and strongly supports the theory that planetary wave tide interaction is the primary mechanism coupling ssws to ionospheric variability enhancements are also observed in the nonmigrating semidiurnal tide with zonal wavenumber 0 s0 during this time period and may be related to the nonlinear interaction between the migrating semidiurnal tide and planetary wave 2 the connection between planetary wave 2 and s0 is however less clear which may be attributed to differences in the zonal mean zonal winds in the mesosphere and lower thermosphere during the times of peak planetary wave 1 and planetary wave 2 activity we conclude that the changing zonal winds during ssws play an important role in the coupling between ionospheric variability and the forcing from planetary waves of lower atmospheric origin during ssws

li na metasomatism related to i type granite magmatism a case study of the highly fractionated la pedriza pluton iberian variscan belt abstract this study describes rare albitites associated with highly fractionated i type granitic melts showing a mineral paragenesis that resembles those of high temperature metasomatized rocks fenites associated with alkaline and carbonatitic intrusions the studied albitites occur as lenticular bodies on the meter scale hosted in peraluminous granites and are scattered in a narrow sector next to the peraluminous and highly fractionated i type la pedriza leucogranite lpl pluton in the spanish central system albitites show sharp contacts and preserve textural features of the host granites i e isovolumetric metasomatism these rocks consist of a variably albitized magmatic feldspar framework 70 85 modal and interstitial domains where singular na li fe3 rich amphiboles and pyroxenes crystallized with albite or quartz titanite andradite grossular garnet mg li rich mica magnetite fluorite and apatite are metasomatic accessory minerals mass balance indicates enrichments of na2o feo mgo mno li f be and some hfse high field strength elements such as zn sc and sn and lile large ion lithophile elements depletion u pb data from metasomatic titanite yield 307 10 ma which is coeval with the lpl and within the range of the regional granite emplacement about 309 298 ma the lpl also shows strong compositional affinities f li na sn and zn enrichment with albitites similar sr nd d isotopic signatures between albitites and host granites suggest that magmatic fluids might be dominant during metasomatism however the heterogeneity of 18o which shifts toward lower values in the more distant outcrops suggests contribution of meteoric in origin low salinity waters during prograde metasomatism p t fo2 conditions are estimated at 0 2 0 3 gpa 645 700 c and relatively oxidized conditions we propose that na hfse flux rich residual melts of the lpl expelled two immiscible hot liquids an alkaline low density liquid and a high density hydrosilicate liquid hsl the low density fluid dissolved magmatic quartz and provided albitization of the magmatic feldspar framework by a diffusive mechanism quartz dissolution created microchannels for infiltration of the relatively low viscosity hsl forming tubular channels this fluid was enriched in network modifiers li na f be and cations ca al released after albitization and it precipitated in these microchannels to form the new metasomatic paragenesis quartz albite uncommon li rich mafic silicates and accessory minerals

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

ionosphere variability during the 2009 ssw influence of the lunar semidiurnal tide and mechanisms producing electron density variability to investigate ionosphere variability during the 2009 sudden stratosphere warming ssw we present simulation results that combine the whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the simulations reveal notable enhancements in both the migrating semidiurnal solar sw2 and lunar m2 tides during the ssw the sw2 and m2 amplitudes reach 50 m s 1 and 40 m s 1 respectively in zonal wind at e region altitudes the dramatic increase in the m2 at these altitudes influences the dynamo generation of electric fields and the importance of the m2 on the ionosphere variability during the 2009 ssw is demonstrated by comparing simulations with and without the m2 time gcm simulations that incorporate the m2 are found to be in good agreement with jicamarca incoherent scatter radar vertical plasma drifts and constellation observing system for meteorology ionosphere and climate cosmic observations of the maximum f region electron density the agreement with observations is worse if the m2 is not included in the simulation demonstrating that the lunar tide is an important contributor to the ionosphere variability during the 2009 ssw we additionally investigate sources of the f region electron density variability during the ssw the primary driver of the electron density variability is changes in electric fields changes in meridional neutral winds and thermosphere composition are found to also contribute to the electron density variability during the 2009 ssw the electron density variability for the 2009 ssw is therefore not solely due to variability in electric fields as previously thought

upper mesospheric lunar tides over middle and high latitudes during sudden stratospheric warming events in recent years there have been a series of reported ground and satellite based observations of lunar tide signatures in the equatorial and low latitude ionosphere thermosphere around sudden stratospheric warming ssw events this lower atmosphere ionosphere coupling has been suggested to be via the e region dynamo in this work we present the results of analyzing 6 years of hourly upper mesospheric winds from specular meteor radars over a midlatitude 54 n station and a high latitude 69 n station instead of correlating our results with typical definitions of ssws we use the definition of polar vortex weaking pvw used by zhang and forbes 2014 this definition provides a better representation of the strength in middle atmospheric dynamics that should be responsible for the waves propagating to the e region we have performed a wave decomposition on hourly wind data in 21 day segments shifted by 1 day in addition to the radar wind data the analysis has been applied to simulations from whole atmosphere community climate model extended version and the thermosphere ionosphere mesosphere electrodynamics general circulation model our results indicate that the semidiurnal lunar tide m2 enhances in northern hemispheric winter months over both middle and high latitudes the time and magnitude of m2 are highly correlated with the time and associated zonal wind of pvw at middle high latitudes m2 in the upper mesosphere occurs after before the pvw at both latitudes the maximum amplitude of m2 is directly proportional to the strength of pvw westward wind we have found that m2 amplitudes could be comparable to semidiurnal solar tide amplitudes particularly around pvw and equinoxes besides these general results we have also found peculiarities in some events particularly at high latitudes these peculiarities point to the need of considering the longitudinal features of the polar stratosphere and the upper mesosphere and lower thermosphere regions for example during ssw 2009 we found that m2 enhances many days before pvw which is not in agreement with most of our results

sodium calcium metasomatism chemical temporal and spatial relationships at the yerington nevada porphyry copper deposit tilting associated with extensional tectonics has exposed 1 800 m of continuous palcovertical relief through the jurassic age yerington porphyry copper deposit the rarely observed root zones of a porphyry system are characterized at yerington by sodium calcium metasomatism the principal hydrothermal reactions involve the replacement of primary k feldspar by oligoclase and of primary biotite by actinolite copper has been removed sodic calcic alteration developed at deep intrusive contacts nearly simultaneously with potassic alteration and copper mineralization at shallow intrusive contacts the reactions accompanying potassic alteration are the reverse of those accompanying sodic calcic alteration plagioclase reacted to form k feldspar hornblende reacted to form biotite the potassic and sodic calcic alteration couplet principally accompanied each of two separate intrusive events 1 luhr hill granite stock and associated porphyry dikes and 2 walker river granite porphyry dikes the younger walker river intrusion was emplaced at slightly deeper levels than the older luhr hill complex vertically stacked and partially superimposed alteration and mineralization patterns resulted from differences in depth and in timing of emplacement at lower temperatures late sodic alteration was superimposed on early sodic calcic alteration at deeper levels in the system whereas late quartz sericite pyrite alteration was superimposed on potassic alteration at higher levels sodic alteration is characterized by the replacement of k feldspar by albite and of biotite by chlorite copper deposited during potassic alteration was remobilized the transition to lower temperature alteration is associated only with the walker river intrusion the hydrothermal system associated with the emplacement of the luhr hill complex had not evolved to lower temperature assemblages prior to emplacement of the walker river dikes phase equilibria and geologic reconstruction of depth of emplacement suggest that temperatures during early sodic calcic alteration were limited to the range of 360 degrees to 480 degrees c at pressures between 300 and 800 bars late sodic alteration took place at similar pressures but at temperatures less than 360 degrees c nearly simultaneous development of potassic and sodic calcic alteration resulted from the flow of fluids away from intrusions at shallow levels potassic alteration and from the flow of fluids toward intrusions at deeper levels sodic calcic alteration because k na and na ca activity ratios of a fluid in equilibrium with granitic rocks decrease with decreasing temperature cooling of high temperature fluids can generate potassic alteration and heating of fluids to high temperatures can generate sodic or sodic calcic alteration

retrograde fluid infiltration in the high grade modum complex south norway evidence for age source and ree mobility the high grade metamorphic basement of the modum complex south norway exhibits retrogradation and alteration due to late stage fluid infiltration extensive alteration zones of albite and calcite rich veining occur especiallywithin and around numerous metagabbros the gabbros intruded at 1224 15ma are now partly altered to amphibolites due to the subsequent high grade metamorphism two generations of albite rich rocks have been recognized 1 a fine grained foliated type 2 a coarse grained crosscutting type both types show a typical greenschist facies mineralassemblage albite actinolite chlorite talc the calcite veins dykesrepresent a younger generation of veins than both albite rich types u pb data for spheneof type 1 yielded an age of 1080 3 ma determining a point on the retrogradep t t path of the modum complex increasing albitisation of themetagabbros leads to a decrease in 143nd 144nd oand an increase in 87sr 86 o albite and calcite rich samples show negative nd and positive sr suggesting that fluids which interacted with the metagabbros originated from a crustal reservoir the nd and sr isotopic data show disequilibrium at the microscale as well as at the macroscale negative sm nd model ages of the albite rich rocks demonstrate that rare earth elements rees were mobile and fractionated during albitisation

tin bearing sodic episyenites associated with the proterozoic a type agua boa granite pitinga mine amazonian craton brazil this paper reports the first occurrence of tin mineralized episyenites in the amazonian craton the agua boa and madeira plutons in the pitinga region are stanniferous proterozoic a type granites of the rapakivi series featuring metasomatic episyenitization the biotite granite facies of the agua boa pluton is metasomatically altered to sodic episyenite and minor potassic episyenite and micaceous episyenite the sodic episyenites formed by a albitization of k feldspar b vug formation by dissolution of magmatic quartz c vug filling by albite chlorite lithian muscovite cassiterite fluorite k feldspar and d deposition of late quartz cassiterite in remaining cavities in the potassic episyenites vugs produced by quartz dissolution are filled by secondary k feldspar which also replaces magmatic phases micaceous episyenites formed by zinnwaldite replacement of secondary albite in the sodic episyenites in contrast to the sodic episyenites the potassic and micaceous episyenites contain only traces of cassiterite relative to unaltered biotite granite the sodic episyenites are strongly depleted in sio2 k2o lree and sr moderately depleted in hree and enriched in na2o al2o3 rb and sn the potassic episyenites resemble the sodic episyenite in sio2 and al2o3but exhibit higher values of k2o ba y and rb their na2o ree and sn concentrations match those of the biotite granite host metasomatic episyenitization is attributed to 1 a high temperature gradient and fluid rock ratio during subsolidus cooling of the agua boa pluton 2 quartz dissolution in the biotite granite facies by reaction with an high temperature silica undersaturated fluid of probable magmatic origin 3 hydrothermal cavity filling by a low temperature silica saturated fluid of meteoric or mixed magmatic meteoric character significant tin values in metasomatic sodic episyenites near the pitinga mine suggest that exploration of similar rocks in other a type granites may be worthwhile

cretaceous albitization and dequartzification of hercynian peraluminous granite in the salvezines massif french pyrenees abstract the salvezines massif in northern french pyrenees has undergone extensive albitization the massif consists of gneisses and a leucogranite hosted in paleozoic sediments schists and carbonates the leucogranite was emplaced at the end of the hercynian orogeny the granite underwent monazite fractionation during magmatic stages which induced lowering of ree and th contents in the most evolved rocks hydrothermal alteration during late magmatic stages is also identified through the development of a tetrad effect in the ree patterns of the granite and through the fractionation of ratios like zr hf out of the charac charge radius controlled range the granite underwent partial to complete sub solidus albitization progressive metasomatic overprint induced metasomatic replacement of feldspars into albite and dissolution of quartz episyenitization together with new albite formation hydrothermal muscovite with a sheaf like structure sometimes crystallised in albitites inherited muscovites from magmatic stage and newly formed muscovites from albitites have distinct chemical compositions with the latter being much more phengitic the initial peraluminous chemistry of the leucogranite was lost during albitization and composition evolved towards a pure albite one a cnk 1 albitization induced gains in na and al and losses in si and k leaching of ree and u is also identified during albitization as well as the non charac behaviour of some elements 18o values of quartz and muscovite in albitized granites are in the magmatic range about 12 and 9 5 respectively feldspars acquired high 18o values during albitization up to 15 muscovite grains from albitites have higher 18o values than inherited ones and tend towards isotopic equilibrium with albite the albitizing fluids have interacted with high 18o rocks probably local carbonates prior to alter granite muscovites inherited from magmatic stages display very characteristic disturbed 39ar 40ar age spectra with saddle shapes when a muscovite associated with albitization provided a plateau age at 117 5 ma for this alteration event albitization in the salvezines massif just preceded the regional talc chlorite hydrothermal mineralization both events might then represent two outward signs of a huge hydrothermal system at the time of the rotation of the iberian plate around europe the north pyrenean metamorphism is identified by 39ar 40ar analyses at ca or younger than 100 ma

the significance of rb sr ages of biotite and phlogopite for the thermal history of the central and southern marginal zones of the limpopo belt of southern africa and the adjacent portions of the kaapvaal craton abstract generally rb sr biotite and phlogopite ages range from 2050 ma to 1950 ma between the murchison thabazimbi and triangle tuli sabi shear zones of southern africa in the rocks comprising the central and southern marginal zones of the limpopo belt and adjacent portions of the kaapvaal craton in some shear zones however similar ages ocurr as young as 800 ma in contrast within the kaapvaal craton south of the murchison thabazimbi shear zone rb sr biotite ages range between 3150 ma and 2100 ma and show no regular distribution in all cases the ages are interpreted to indicate the time elapsed since the biotite last cooled below its closure temperature approximately 320 c the regular pattern of 2050 ma to 1950 ma rb sr biotite ages north of the murchison thabazimbi shear zone suggests that the present erosional surface approximates a paleo isothermal surface this surface was exposed by uplift and erosion which was completed by 1900 ma to 1800 ma ago when the sedimentary and volcanic rocks of the soutpansberg group were deposited the regional uplift was accommodated by motion on the murchison thabazimbi and triangle tuli sabi shear zones and probably was related to tectonism associated with the emplacement of the anorogenic bushveld and phalaborwa complexes other anorogenic granitic magmatism accompanied uplift the depth represented by the paleo isothermal surface and the magnitude of the uplift that exhumed it cannot be constrained precisely it is suggested however that the majority of the 10 to 15 km by which crust in this area is thinner than that of the adjacent cratons is the manifestation of this uplift

juvenile crust formation in the northeastern kaapvaal craton at 2 97 ga implications for archean terrane accretion and the source of the pietersburg gold abstract combined u pb and lu hf isotope data of detrital and magmatic zircon grains provide evidence that the murchison greenstone belt ne kaapvaal craton south africa hosts an important archean suture zone which primarily formed by a collision 2 97 ga ago between a back arc system to the north and an evolved terrane the proto kaapvaal craton to the south this model is supported by the observations that igneous rocks of the northern terrane comprising mafic rocks and tonalites of the rooiwater complex and felsic volcanics of the rubbervale formation were both emplaced at about 2 97 ga and show highly superchondritic hft of 4 4 to 5 1 in contrast u pb hf isotope data of detrital zircon grains from quartzitic schists of the murchison unit and the la france formation both part of the southern terrane provide evidence for a southern provenance which was affected by granitoid intrusions accompanied by crust re working at 3 53 3 42 ga hft 1 8 to 4 8 3 30 3 20 ga hft 1 8 to 6 3 and 3 13 3 05 ga hft 1 3 to 5 6 pointing to a connection with the barberton greenstone belt and swaziland a spatial separation of the two terranes prior to 2 97 ga is furthermore supported by the facts that the youngest detrital zircon grains of the southern terrane having ages between 2 99 and 2 97 ga show subchondritic hft between 6 5 and 1 5 in contrast to the highly superchondritic hft obtained from the contemporaneous magmatic rocks of the northern terrane the juvenile character of the rooiwater and rubbervale magmatic rocks along with the occurrence of vms deposits makes them a likely candidate for the source of the gold pyrite bearing conglomerates exposed in the adjacent pietersburg greenstone belt

tidal wind mapping from observations of a meteor radar chain in december 2011 1 this article proposes a technique to map the tidal winds in the mesosphere and lower thermosphere mlt region from the observations of a four station meteor radar chain located at middle and low latitudes along the 120 e meridian in the northern hemisphere a 1 month dataset of the horizontal winds in the altitude range of 80 100 km is observed during december 2011 we first decompose the tidal winds into mean diurnal semidiurnal and terdiurnal components for each station it is found that the diurnal semidiurnal components dominate at the low latitude midlatitude stations their amplitudes increase at lower altitudes and then decrease at higher altitudes after reaching a peak in the mlt region hough functions of the classical tidal theory are then used to fit the latitudinal distribution of each decomposed component the diurnal component is found to be dominated by the first symmetric 1 1 mode yet for the semidiurnal and terdiurnal components the corresponding dominant modes are the second symmetric modes 2 4 and 3 5 and considerable contributions are also from the first antisymmetric modes 2 3 3 4 and second antisymmetric modes 2 5 3 6 based on the decomposed results we further map the horizontal winds in the domains of latitude altitude and local time the mapped horizontal winds successfully reproduce the local time versus altitudinal distributions of the original observations at the four stations thus we conclude that the meteor radar chain is useful to monitor and study the regional characteristics of the tidal winds in the mlt region

albite rich silica depleted metasomatic rocks at emuford northeast queensland mineralogical geochemical and fluid inclusion constraints on hydrothermal evolution and tin mineralization late paleozoic fluorine rich granites and their host metasediments in the emuford district of the herberton tin field contain small zones of intense albitization that host cassiterite mineralization sodium metasomatism was accompanied by hydrothermal leaching of granite quartz to form vuggy albite rocks episyenites vugs created by quartz dissolution were filled in by hydrothermal minerals including albite k feldspar and or muscovite and cassiterite late phases are dominated by quartz and fluorite swarms of parallel veinlets crosscut the albitized zones these veinlets were formed by repeated fracturing in response to local fluid over pressures they contain infill mineralogy similar to the vugs and probably formed at least partly contemporaneously with vug infill due to the overprinting at various scales of alteration vug infill and vein formation stages chemical changes associated with episyenite formation are only qualitatively constrained however the mineralogical and textural features of the alteration zones suggest that most major and trace elements had substantial mobility during their formation major chemical changes associated with episyenite formation include leaching of sio 2 k 2 o rb and ba with introduction of na 2 o and minor sr during vug and vein filling stages there was an introduction of sio 2 al 2 o 3 na 2 o k 2 o cao f and sn the erratic behavior of ree is probably related to the growth of fluorite and minor accessory phases zircon monazite xenotime with preferential enrichment of heavy ree in rocks with the highest fluorine concentrations fluid inclusion study indicates that vug and vein filling stages of the hydrothermal evolution involved two types of fluids a high salinity fluid 30 50 equiv wt nacl of probable magmatic origin and homogenization temperatures up to 428 degrees c was associated with vug filling in the granite hosted deposits a lower salinity fluid 5 15 equiv wt nacl containing variable amounts of co 2 and having homogenization temperatures between 160 degrees and 420 degrees c was associated with veinlet formation in the granite hosted deposits and with vein and cavity filling in the metasediment hosted deposit this lower salinity fluid may represent a condensed vapor phase derived from boiling of the magmatic fluid or may be a mixture of magmatic and meteoric components the close association of albitization and quartz dissolution suggests a genetic link between the two processes it is proposed that exchange of na for k in the fluorine rich hydrothermal fluids caused a substantial increase in quartz solubility and led to quartz dissolution in the albitized rocks

observations of the 5 day wave in the mesosphere and lower thermosphere the 5 day planetary wave has been detected in the winds measured by the high resolution doppler imager hrdi on the upper atmosphere research satellite uars in the mesosphere and lower thermosphere 50 110 kin the appearances of the 5 day wave are transient with a lifetime of 10 20 days in the two year data set the structures of selected 5 day wave events are in generally good agreement with the 1 1 rossby normal mode for both zonal and meridional components a climatology of the 5 day wave is presented for an altitude of 95 km and latitudes mainly between 40os and 40on

structure and metamorphism of the archean murchison belt kaapvaal craton south africa critical examination of five popular prejudices applied to greenstone belts in general and the murchison belt in particular show that 1 the term murchison schist belt is preferred to that of murchison greenstone belt which differs significantly from the barberton greenstone belt 2 the murchison belt is tectonized such that no simple stratigraphy may be erected 3 the murchison belt lacks a synclinal keel 4 heterogeneous oblique to dip slip shear characterizes much of the murchison belt but strike slip deformation occurred in the letaba shear zone along the northeastern margin of the belt and 5 contact metamorphism was a limited phenomenon that was not responsible for the highest grade rocks of the murchison belt the belt comprises a number of domains each with its own characteristic lithologies structural style and metamorphic history bounded by tectonic breaks which have juxtaposed rocks from different crustal levels

mineralogical and geochemical characteristics of hydrothermal alteration and episyenitization in the konigshain granites northern bohemian massif germany the late hercynian granites of konigshain underwent multistage hydrothermal processes extensive high temperature late magmatic alteration is for example indicated by low zr hf and an ree pattern displaying the tetrad effect intensive post magmatic alteration of the granite occurred along brittle structures at least two main stages of post magmatic hydrothermal alteration are involved the first high temperature stage which is characterized by albitization and or quartz leaching episyenitization resulted from fluid rock interaction with late magmatic fluids that very probably mixed with external low salinity fluids quartz dissolution was triggered by vapour condensation and or the cooling of these fluids below 450 c along brittle structures the high porosity resulting from quartz leaching during stage 1 assisted subsequent circulation of low temperature fluids at stage 2 the latter is characterized by the chloritization and illitization of episyenites almost all major and trace elements were enriched or depleted during one of the main alteration stages however zr hf th and ti were immobile during post magmatic alteration the significant depletion of lree and the enrichment of hree in albitized samples is controlled by the dissolution of monazite and the new formation of hree rich polycrase y or aeschynite y during post magmatic stage 1 negative ce anomalies of episyenites are associated with illitization and suggest oxidizing conditions during stage 2

ore forming fluids in archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec canada archean gold bearing quartz veins at the sigma mine occur in deformed metavolcanics intruded by two generations of preore porphyries the veins were emplaced during a late compressional tectonic event and they consist primarily of quartz tourmaline carbonates pyrite and scheelite vein minerals have been deformed and are also cut by abundant healed fractures outlined by fluid inclusions in the veins gold typically occurs in late fractures and in recrystallized quartz microthermometric sem eda leachate analysis and gas chromatographic techniques were used to study fluid inclusions in quartz most fluid inclusions at sigma occur in late fractures and are secondary the fluid inclusions are commonly found in fractures parallel to or less commonly within gold bearing fractures and are genetically related to the gold three types of fluid inclusions are identified 1 high salinity na ca cl aqueous inclusions 25 34 wt salt with small amounts of co 2 some containing halite calcite and nahcolite as daughter minerals 2 co 2 rich inclusions containing small amounts of h 2 o and ch 4 and 3 low salinity h 2 o co 2 inclusions 10 equiv wt nacl with co 2 contents which are variable but commonly in the range of 15 to 30 mole percent co 2 leachate analyses show that in addition to na and ca the aqueous fluids contain minor amounts of k fe mg and li homogenization temperatures of h 2 o co 2 inclusions with constant phase ratios range from 285 degrees to 395 degrees c those of aqueous inclusions range from 60 degrees to 295 degrees c the aqueous and co 2 rich inclusions are interpreted to have trapped two coexisting fluids resulting from the unmixing of a homogeneous h 2 o co 2 parent fluid itself occasionally trapped in late fractures the ore bearing fluid is interpreted to be a low salinity 10 equiv wt nacl fluid containing 15 to 30 mole percent co 2 at minimum temperatures in the range of 285 degrees to 395 degrees c the relatively low homogenization temperatures of aqueous inclusions are interpreted to be the result of co 2 effervescence from a co 2 saturated aqueous fluid due to pressure fluctuations at the time of entrapment it is also proposed that the onset of gold deposition is related to the onset of fluid unmixing

isotopic peculiarities of an archaean pegmatite union mine mica south africa abstract an isotopic investigation rb sr u pb pb pb and sm nd of the archaean union mine pegmatite northern province south africa is reported the intrusion of this pegmatite devoid of zircon and monazite has been dated at 2912 2 6 ma by pb pb step leaching of magmatic garnet this age is supported by an identical two garnet apatite sm nd isochron of 2917 27 ma a rb sr k feldspar garnet albite isochron of 2023 11 ma corresponds to a later hydro thermal overprint isotope resetting during this overprint was incomplete and revealed that various parent daughter isotope pairs within minerals of the union mine pegmatite behaved in exceedingly different manners under the same physico chemical conditions sr isotope resetting was incomplete and resulted in open system behaviour of the pegmatite k feldspar almost quantitatively lost its radiogenic sr which had accumulated between the time of intrusion and the overprint sr loss from muscovite was variable and incomplete as indicated by a wide range in ages from 2088 74 ma to 2744 13 ma only insignificant portions of this sr were incorporated into adjacent albite as revealed by a micro drilled rb sr profile through a muscovite albite grain boundary the 87 sr 86 sr initial ratio is 0 8301 11 for the proterozoic isochron which is far less radiogenic than the calculated value of 2 24 for a closed system it is therefore concluded that sr was lost from the system and that the rb sr ratio of the whole rock was changed apatite on the other hand seems to have behaved as a closed system and retains a low initial sr ratio of 0 7125 u pb analyses of apatite reveal that this mineral has behaved as an almost closed system for pb diffusion as well but was open for u significant loss during the overprint this has resulted in high reverse discordance of apatite u pb analysis and in a geologically meaningless secondary pb pb isochron the data demonstrate that both preferential loss of daughter sr over parent rb and parent u over daughter pb isotopes can occur in some minerals of one and the same rock this process altered the parent daughter ratios to such an extent that in the case of apatite a secondary pb pb isochron with an erroneous age of 4119 66 ma was established it appears likely that preferential loss of daughter or parent isotopes is the reason for spurious secondary whole rock isochrons reported and reviewed by moorbath and taylor 1986 and moorbath et al 1986 such losses far exceeding predictions based on volume diffusion experiments may occur by means of fast transport diffusion which in part may depend on the micro textures of the host minerals geochemical studies of early archaean rocks require substantial back correction for radiogenic decay and the example of the union mine pegmatite shows that changes of parent daughter isotope ratios may occur long after rock formation however such changes may go unnoticed in high precision geochronology i e garnet dating in this study but will lead to erroneous correction for radiogenic decay and hence to erroneous conclusions regarding the origin of the studied samples

mineralogy and geochemistry of the sodium metasomatism related uranium occurrence of aricheng south guyana the aricheng south uranium occurrence is associated with na metasomatism that affected the granitoids of the kurupung batholith in western guyana the mineral paragenesis indicates that late magmatic albitization was followed by chlorite alteration of biotite a minor amount of uraninite occurs in fractures in the newly formed albite crystals often in company of calcite the main mineralization stage occurred later than albitization and chloritization and is represented by brannerite disseminated in a groundmass of fine grained hydrothermal zircon whole rock geochemistry supports the temporal dissociation of albitization from the main ore stage brannerite zircon and uraninite are often partially altered to secondary brannerite zircon and coffinite respectively stable oxygen chlorite calcite and hydrogen chlorite isotope compositions suggest that a highly evolved meteoric fluid or at least one corresponding to a very high rock fluid ratio 18o of approx 3 4 to 4 and d of approx 80 may have caused the pre ore alteration assemblage the fluids in equilibrium with main ore stage zircon have 18o of approx 6 8 and appear to be of magmatic origin the aricheng occurrence geochemically mineralogically thermally and paragenetically resembles the valhalla u deposit in northern australia despite differences between the deposits host lithologies whereas the lagoa real and espinharas u deposits in brazil have host rock lithology that resembles that of aricheng

ages of altered granites adjoining the witwatersrand basin with implications for the origin of gold and uranium one of the main problems in understanding the origin of the witwatersrand basin mineralization concerns the source of the prodigious concentrations of gold and uranium in the basin another problem is the age and nature of the rocks in the source area recent data1 2 indicate that the source area was largely 3 200 2 900 myr old becoming progressively younger as the basin evolved granites adjoining the basin are commonly overprinted by pervasive and vein related hydrothermal alteration which resulted in an enrichment of both gold and uranium3 4 here we report uranium lead data demonstrating that these hydrothermally altered granites were intruded sporadically both before and during the 360 myr period5 constraining witwatersrand sediment deposition and that hydrothermal alteration was associated with granitoid intrusion and subsequent cooling thus fertilization of the crust occurred during basin evolution a feature that supports the idea19 that gold and uranium mineralization occurred simultaneously with sediment deposition

u th pb geochronology of zircon and monazite from syenite and pincinite xenoliths in pliocene alkali basalts of the intra carpathian back arc basin abstract phreatomagmatic eruptions in the lucenec basin in slovakia ejected fragments of igneous rocks of unknown age and ranging in composition from gabbro to syenite and orthopyroxene granodiorite pincinite two kinds of syenites with different fe3 contents composed of anorthoclase and interstitial metaluminous trachyte to alkali rhyolite glass represent the final products of alkali basalt differentiation at depths of 10 and 15 18 km pincinite composed of plagioclase quartz orthopyroxene ilmenite and interstitial peraluminous dacite glass is a quenched supersolidus anatectic melt formed at the depth of 17 20 km by high temperature dehydration melting of biotite bearing gneissic protolith zircon from pincinite and syenite and monazite from syenite were dated using excimer laser ablation icp ms the obtained ages cluster at 5 8 0 1 and 5 4 0 1 ma thus corroborating the genetic link between the two rock types and constraining the residence time of at least 300 100 ka of the parental basalt in the deep crustal magma storage zones the inferred ages overlap the upper miocene pliocene boundary and are considerably younger than spatially associated basaltic lava flows dated using the k ar method consequently the fluviolacustrine poltar formation overlying the maar structure must have sedimented during the pliocene and not during the upper miocene pontian as previously assumed

structures related to the antimony line murchison schist belt kaapvaal craton south africa abstract sporadic epigenetic antimony gold mineralisation along the ene trending antimony line of the murchison schist belt is structurally controlled and spatially related to carbonated rock types with quartz carbonate veins in tension fractures the antimony line is a discontinuous zone of brittle ductile deformation and is locally oblique to lithological layering within a broad ductile shear zone this tectonically early d 1 shear zone has an oblique to dip slip reverse north side up movement sense with downward facing fold structures in the hangingwall later d 2 fold structures deformed the antimony line and its wallrocks into steep structures the antimony line is intruded by granitoids which post date d 1 and are not directly related to mineralisation the source of which may have been metamorphic fluids

stable isotopes c o and fluid inclusion study of quartz carbonate veins from the antimony line murchison greenstone belt in the homogeneously deformed murchison greenstone belt region fluids circulations were focused along a localized deformation brittle ductile zone and the so called antimony line in order to trace the origin of the fluid its composition the temperature of the precipitation along the antimony line we investigate the stable isotope oxygen and carbon and fluid inclusion compositions of the quartz carbonate veins as well as chemical analyses of the carbonates and 40ar 39ar dating on the fuchsite associated with the veins three types of fluid inclusions are recognized for the h2o co2 dominated plus minor ch4 n2 fluid s microthermometric measurements together with the paragenesis of the veins and host rocks indicate that the pressure temperature of the precipitation is 350 to 450 c 200 to 300 mpa which is an unusually high temperature for an antimony deposit the carbonates are fe mg rich and are characterized by flat mree and hree patterns with slight depletions in lree the oxygen isotope compositions of the quartz are rather homogeneous at the scale of the antimony line 18oquartz 10 9 14 3 in detail subtle differences in the 18o values for the quartz and carbonate exist depending on the sampling sites these differences are likely due to minor temperature and or host rock geochemistry variations along the antimony line data point to a metamorphic origin for the fluids responsible for the mineralization which likely escaped from the nearby greenstone lithologies finally we present an overview of the murchison greenstone belt geological evolution by integrating the antimony metallogeny of the antimony line which can be compared to that of an orogenic gold deposit

the 6 5 day wave in the tropical stratosphere and mesosphere 1 the 6 5 day wave is a westward propagating zonal wave number 1 s 1 planetary wave that is prominent near equinox the spatial temporal structure of the 6 5 day wave seen in the united kingdom meteorological office ukmo data in the stratosphere is found to be consistent with that obtained from upper atmosphere research satellite high resolution doppler imager hrdi measurements of horizontal winds and temperatures in the mesosphere lower thermosphere mlt two wave events are commonly observed before and after equinox at low latitudes in both ukmo and hrdi data this paper focuses on a pair of such events in late 1994 the amplitude growth and phase decrease with altitude of the zonal wind 6 5 day wave appear to be continuous between the two data sets for the period analyzed both wave events appear to grow from the stratosphere to the upper atmosphere at a rate consistent with the suggested vertical phase velocity such consistency between the two data sets establishes that the wave previously observed in the mlt is propagating from the stratosphere further analyses of the ukmo data shows the presence of the 10 day s 1 and 4 day s 2 waves that appear to be either nonlinearly coupled with the 6 5 day wave or related through a common sourcing mechanism