thermospheric zonal mean winds and tides revealed by champ we present direct global observations of longitudinally averaged champ zonal winds gathered between 2003 and 2007 a diurnal variation dominates the global zonal wind westward flows are observed from the early morning through afternoon hours while eastward flows peak in the evening a semidiurnal harmonic is also present with magnitudes that are approximately one third of the diurnal harmonic the time mean wind indicates westward winds over much of the globe with weak superrotation e or eastward winds that is symmetric about the equator during equinox and confined to the winter hemisphere at solstice diurnal and time mean champ winds agree fairly well with the whole atmosphere model some differences are observed in the semidiurnal and higher order tidal winds that underscore the challenges of modeling the sources sinks and mean wind effects upon tides between the surface and 400 km

crystallization of interstitial liquid and latent heat buffering in solidifying gabbros skaergaard intrusion greenland new compositional profiles across plagioclase grains from the layered series ls marginal border series mbs and upper border series ubs of the skaergaard intrusion are used to understand the mechanisms of cumulate rock solidification and the fate of the interstitial liquid the data show that plagioclase crystals display three types of compositional profile over the whole intrusion as follows 1 grains with normal zoning which dominate the mbs and ubs these are interpreted as having formed at the top of a crystal mush and then buried in the cumulate pile crystallization of the interstitial melt resulted in liquid differentiation and produced normally zoned rims on plagioclase cores 2 unzoned crystals which dominate the upper part of the ls also crystallized at the top of the mush and were then buried in mush with a low interstitial liquid fraction or one experiencing convective movements that kept the liquid to a constant composition 3 crystals with a mantle of decreasing an content followed by a rim of constant composition grains showing this complex zoning mostly occur in the lower parts of the ls depending on the stratigraphic position within the intrusion the composition of the rim can be an56 an51 or an40 in the main magma body these compositions an contents correspond to those of plagioclase primocrysts e g cores at the appearance of cumulus clinopyroxene an56 fe ti oxides an51 and apatite an40 compositional buffering of plagioclase rims is interpreted as being a consequence of enhanced release of latent heat of crystallization at the appearance of new interstitial phases in the crystal mush when a new phase saturates the latent heat contribution to the global enthalpy budget of the system becomes sufficiently high to keep the interstitial melt at its liquidus temperature for a period of time that could exceed thousands of years under these conditions equilibrium adcumulus growth together with diffusion and possibly advection of chemical components result in the formation of plagioclase rims of constant composition an content efficient thermal buffering of the mush liquid depends on the porosity i e fraction of liquid within the mush and the degree of compositional homogeneity of the mush in a heterogeneous and highly porous mush saturation of the new phase occurs in the coldest part of the mush and the enhanced latent heat release at the saturation of this phase is quickly dissipated to the whole volume of liquid including the warmest part that is not yet saturated in a new phase as a consequence no thermal buffering occurs and interstitial crystallization produces grains with normal zoning the distribution of the various types of plagioclase grains throughout the skaergaard intrusion can therefore be used to infer the spatial variability in the physical properties of the crystal mush such as the residual porosity both at an intrusion wide scale and at a millimetre to centimetre scale

equatorial zonal plasma drifts measured by the c nofs satellite during the 2008 2011 solar minimum 1 we use the measurements by the vector electric field investigation vefi on board the communication navigation outage forecasting system c nofs satellite to study the local time and seasonal and longitudinal dependent climatology of equatorial f region zonal plasma drifts during 2008 2011 these drifts are essentially westward during the day and eastward at night over jicamarca radio observatory the satellite measurements are in good agreement with incoherent scatter radar drifts our data show strong longitudinal variations particularly in the south american sector during the solstices the equinoctial data exhibit short lived and largely enhanced westward drifts near sunrise and wave 4 structures from the early afternoon to late night equinoctial periods the nighttime eastward drifts are largest near the western american sector at all seasons the june solstice postmidnight eastward drifts decrease sharply at longitudes of about 310 and have much smaller values in the entire eastern hemisphere we also briefly discuss the relationship between the longitude dependent vertical and zonal plasma drifts

the kraemer island macrodyke east greenland solidification of a flood basalt conduit the kraemer island macrodyke that is exclusively exposed on kraemer island about 7 km west of the skaergaard intrusion belongs to a regional dyke swarm termed the skaergaard like dykes or fg 1 dykes weakly modally layered olivine gabbros dominate the exposed parts of the intrusion that has a width of 650 m to 1000 m plagioclase core an 68 2 and ca rich pyroxene core mg no 79 1 grains are normally zoned whereas olivine grains fo50 65 are homogeneous calculated mineral magma equilibria based on experimentally determined mg fe magma olivine and magma clinopyroxene partition coeffi cients suggest that the observed olivine and clinopyroxene compositions in the gabbros cannot have formed from a common parental magma the unzoned nature of olivine grains and their iron rich com positions relative to clinopyroxene suggest post cumulus mg fe exchange between olivine and interstitial melt a gabbroic pegmatite is developed in the centre of the intrusion along its entire exposed 5 km strike length here mineral zonation is limited and compositions are similar to rims of cumulus minerals in the enveloping olivine gabbros the pegmatite could therefore represent interstitial melt mobilized from gab broic cumulates that later accumulated and crystallized at its present stratigraphic location cumulus olivines in the gabbros are close to equilibrium with ca rich pyroxene in the pegmatite this is interpreted as reflecting interstitial melt mobility during the late stages of solidification of the macrodyke chilled margins are well preserved at the intrusion margins and are rich in fe 14 15 3 feo tot ti 3 3 3 tio2 and light rare earth elements la sm n 1 2 1 3 similar to magmas well represented in the overly ing sequence of contemporaneous high ti series flood basalts it is therefore likely that extensive wall rock melting adjacent to the macrodyke reflects continuous feeding of the overlying flood basalts through the kraemer island macrodyke

variations in os isotope ratios of pyrrhotite as a result of water rock and magma rock interaction constraints from virginia formation duluth complex contact zones abstract os isotope ratios in pyrrhotite bearing pelitic rocks of the 1 85 ga virginia formation are variable with perturbations linked to the emplacement of the 1 1 ga duluth complex pyrrhotite in footwall rocks of the contact aureole show evidence for a mixing event at 1 1 ga involving a low 187 os 188 os fluid however because rocks with perturbed pyrrhotite os isotope ratios occur 1 km or more from the duluth complex the fluid is unlikely to have been of magmatic origin fluid inclusions in layer parallel quartz veins provide evidence of the involvement of a boiling fluid at temperatures between 300 and 400 c analyses of fluid inclusions via la icp ms show that the fluids contain up to 1 7 wt na 1 1 wt k 4330 ppm fe 2275 ppm zn and 415 ppm mg the veins also contain pyrite or pyrrhotite plus minor amounts of chalcopyrite bornite pentlandite and sphalerite the re os isotopic ratios of pyrite from the veins indicate that they crystallized from low 187 os 188 os fluids 18 o values of vein quartz range from 7 7 to 9 5 consistent with an origin involving fluid with a relatively low 18 o value between 2 and 5 meteoric water with such a low 18 o value could have interacted with the igneous rocks of the complex and would have acquired os with a low 187 os 188 os ratio strongly serpentinized olivine rich rocks of the complex are commonly characterized by such low 18 o values and we propose that the fluid involved in serpentinization was also responsible for the perturbation of the os isotopic system recorded by pyrrhotite in the virginia formation two important observations are that only pyrrhotite bearing assemblages in the contact aureole show isotopic perturbation and that intervals showing os exchange are spatially restricted and not uniformly distributed os exchange and mixing has occurred only where temperatures were sufficient to convert pyrite to pyrrhotite and where time integrated water rock ratios in the aureole were high enough to provide a supply of os troctolitic and gabbroic rocks of the partridge river intrusion duluth complex are characterized by os isotope ratios that are indicative of variable degrees of crustal contamination os values of 0 543 xenoliths of carbonaceous and sulfidic pelitic rocks of the virginia formation found in the igneous rocks provide evidence that os was released by organic matter and pyrite in the sedimentary rocks and assimilated by mantle derived magma however residual pyrrhotite produced as a result of pyrite breakdown in the xenoliths is characterized by 187 os 188 os ratios that are much lower than anticipated and similar to those of pyrrhotite in the contact aureole the os exchange and addition shown by pyrrhotite in the xenoliths highlight an unusual cycle of re os liberation during devolatilization kerogen maturation and pyrite to pyrrhotite conversion processes that contribute to magma contamination followed by os uptake by pyrrhotite during back reaction involving magma and or fluid characterized by a relatively low 187 os 188 os ratio the extreme os uptake recorded by pyrrhotite in the xenoliths as well as the lesser degree of uptake recorded by pyrrhotite in the contact aureole is in line with the high os diffusivity in pyrrhotite experimentally determined by brenan et al 2000 our data confirm that os isotope ratios in pyrrhotite bearing rocks may be readily perturbed for this reason caution should be exercised in the interpretation of os isotope ratios in rocks where pyrrhotite may be the primary host of os

magma dynamics at the base of an evolving mafic magma chamber incompatible element evidence from the partridge river intrusion duluth complex minnesota usa abstract a characteristic feature of the partridge river intrusion of the keweenawan duluth complex is the approximately fivefold to ninefold increase in the concentrations of incompatible elements in the lower zone compared with cumulates stratigraphically higher the concentrations of incompatible elements decrease from the lower zone upward to steady state values which is ascribed to variations in the proportions of trapped liquid rather than variable degrees of fractional crystallization of a single parental magma the calculated average composition of trapped liquid using our algorithm is similar to typical keweenawan low alumina high ti p basalts associated with the duluth complex but is different from the leading edge ferrodioritic liquid quenched in the chilled margin of the intrusion this difference suggests that the chilled margin does not represent the original parental magma composition from which the whole intrusion solidified and that the enrichment of incompatible elements may be related to the local flotation of magmatic suspensions to test the latter hypothesis numerically we have used heat mass transfer models assuming a sheet like magma chamber to calculate the parameters of the model that best reproduce the observed distribution of incompatible elements in a mush zone at the base of the partridge river intrusion the results indicate that a mush zone enriched in the incompatible elements is produced if the velocity of movement of the lower solidification front into the magma body was less than the floating velocity of the bulk crystal mush the dynamic parameters that best reproduce the observed distribution of incompatible elements include a magma emplacement pressure of 2 kbar critical crystallinities of 50 68 in the mush zone from which the liquid is being expelled and an emplacement temperature of 1160 c for the initial magma

climatology of the nighttime equatorial thermospheric winds and temperatures over brazil near solar minimum 1 we report on the climatology of equatorial thermospheric winds and temperatures based on fabry perot interferometer measurements of doppler shifts and doppler broadenings of the 630 0 nm spectral emission from the cajazeiras observatory located in the northeastern part of brazil 6 89 s 38 56 w these results apply to the lower thermosphere region near 240 km and were obtained during a period of weak solar activity with the solar flux typically within the range of 72 and 82 solar flux units examination of the monthly averaged meridional thermospheric winds for 1 year of measurement from october 2009 to september 2010 found the wind direction to be equatorward during summer months throughout the early evening hours with maximum speeds reaching 65 ms 1 during winter months the early evening meridional wind direction reversed to poleward with similar speeds this result is attributed to the cross hemispheric flow from the summer to winter hemisphere superimposed upon this wintertime meridional wind flow was an equatorward surge shortly before midnight this surge shifted to earlier local times in the transition from the vernal equinox to summer and to later local times between the summer solstice and the autumnal equinox this flow feature is attributed to tidal wave forcing the temperature observations exhibited the expected behavior with the midnight temperature maximum showing a greater amplitude 120 k in the vernal equinox with somewhat weaker amplitudes 75 k seen at earlier local times during the summer also observed was a phase lag of 60 to 90 min between the appearance of the equatorward meridional wind flow and occurrence of the midnight temperature maximum peak

midnight temperature maximum mtm in whole atmosphere model wam simulations 1 discovered almost four decades ago the midnight temperature maximum mtm with typical magnitudes of 50 100 k has been regularly observed by satellite and ground based instruments in the tropical upper thermosphere although several mechanisms have been suggested to explain the phenomenon previous attempts to reproduce it with comprehensive thermosphere ionosphere models have been unsuccessful first long term simulations with the whole atmosphere model wam reveal the presence of a realistically prominent mtm and reproduce the salient features of its daily seasonal and latitudinal variability preliminary analysis indicates that the feature may be traced down to the lower thermosphere where it is manifested primarily in the form of an upward propagating terdiurnal tidal wave its spectrum expands to higher order zonal wavenumbers and frequencies and its phase advances to near midnight higher up in the thermosphere possible mechanisms generating this wave may involve nonlinear interactions between other tidal harmonics originating in the middle and lower atmosphere our results thus suggest that the mtm is yet another phenomenon driven by dynamical links between the lower and upper atmosphere and ionosphere

comparison of zonal neutral winds with equatorial plasma bubble and plasma drift velocities 1 a one year dataset spanning march 2011 to march 2012 of coincident observations of nighttime thermospheric zonal neutral winds equatorial plasma bubble epb velocities and zonal plasma drifts is used to examine the relationship between the thermosphere and the ionosphere near the geomagnetic equator over peru thermospheric neutral winds are determined by using a bistatic fabry perot interferometer fpi experiment located at merihill and nazca in peru the ambient plasma drift velocities were obtained using the incoherent scatter radar at the jicamarca radio observatory in peru the epb zonal velocities were estimated utilizing images of the oi 630 0 nm emission recorded by a narrow field optical imaging system at the cerro tololo inter american observatory in chile the joint analysis of these datasets illustrates that the nighttime and night to night variations in the zonal neutral winds epb velocities and plasma drifts are well correlated this consistent result of the local time variations of the neutral winds with that of epb and plasma drifts illustrates that the f region dynamo is in general fully activated however at times the magnitude of the epb velocities and the plasma drifts are different from the neutral winds it is plausible that such a difference is due either to the effect of polarization electric fields developed inside the epb or due to the latitudinal gradient of the neutral winds and epb velocity measurements since the epb velocities are estimated at a higher latitude corresponding to an apex altitude of 400 km than the wind estimates which derive from an apex altitude of 250 km

experimental data at 3 kbars pressure on parental magma to the bushveld complex experimental studies mainly under 3 kbars pressure have been undertaken on representative samples to determine if any of these compositions could be parental magma to the bushveld complex one such composition with 12 5 mgo mg mg fe of 0 72 and quartz normative crystallizes olivine fo88 as liquidus mineral at about 1 300 c followed at only slightly lower temperature by orthopyroxene at 3 kbars pressure there is a temperature drop of over 100 c before the appearance of plagioclase and finally clinopyroxene this crystallization sequence is in excellent agreement with the observed sequence in the lower part of the bushveld complex

evidence from the rare earth element record of mantle melting for cooling of the tertiary iceland plume widespread flood basalt volcanism and continental rifting in the northeast atlantic in the early tertiary period 55 myr ago have been linked to the mantle plume now residing beneath iceland1 2 3 4 5 although much is known about the present day iceland plume6 7 8 9 its thermal structure composition and position in the early tertiary period remain unresolved estimates of its temperature for example range from 1 600 c in some plume models3 to 1 500 c based on the volume and composition of basaltic crust10 11 12 several recent studies4 have emphasized similarities in the thermal and chemical structure of the tertiary and present day plumes to argue for stability of the mantle anomaly whereas others12 13 relate variations in basalt volumes and compositions to changes in plume flux moreover some authors1 2 13 have assumed that the plume was rift centred for its entire history whereas others argue that it became ridge centred only after plate separation14 15 here we report compositional data for 6 000 metres of flood basalts erupted in east greenland close to the inferred plume axis that we use to constrain the tertiary plume structure rare earth element systematics place limits on the pressures and extents of mantle melting and show that the mantle was initially moderately hot 1 500 c but that its temperature declined during flood volcanism these observations are difficult to reconcile with current plume head models and call for important lithospheric control5 10 16 17 18 on actively upwelling mantle along the rifted margin

rapid highly structured meridional winds and their modulation by non migrating tides measurements from the streak mission 1 measurements of the earth s low latitude thermosphere returned by the ionization gauge on the streak mission are reported and discussed the measurements are of the amount of gas rammed into the sensor by its passage through the thermospheric medium they were obtained in the dusk sector in the altitude range 130 330 km and are shown to be strongly structured by the geomagnetic field similarities to the structure of the equatorial ionization anomaly are discussed the structure is interpreted as being due to rapid several hundred meters per second meridional winds having an antisymmetric pattern with respect to the geomagnetic equator the measurements are interpreted in light of results from other missions and are shown to fit well with ideas based on complementary measurements from the dynamics explorer 2 mission discussed as the equatorial temperature and wind anomaly several features of these winds are described and discussed including their altitude dependence how they form convection cells that extend to high latitude and how the wind amplitudes vary with geographic longitude with an apparent wavenumber one variation the latter characteristic is shown to be consistent with being the signature of tidal variations observed by others approximate calculations utilizing published values for the pertinent parameters are used to show that heating from the dissipation due to ion drag within the ionospheric f region is a dominant driver of the inferred winds

using melt inclusions to determine parent magma compositions of layered intrusions application to the greenhills complex new zealand a platinum group minerals bearing island arc intrusion the permian greenhills complex of southland new zealand is a small ultramafic to mafic layered intrusion that hosts primary magmatic platinum group minerals pgms as inclusions in cumulus chromian spinel grains we have determined the major and trace element chemistry of the parent magmas of the complex using the composition of rehomogenized melt inclusions trapped in cumulus spinel grains from dunite these melt inclusions have compositions similar to those of primitive ankaramite dikes that cut the complex verifying that our data are representative of the parent melt chemistry these magmas have high mgo and cao and are enriched in pb sr and large ion lithophile elements compared to high field strength and rare earth elements we suggest that the parent magmas to the complex were primitive low k island arc tholeiite basalts that formed by high degrees of melting of a spinel peridotite source the platinum group element contents of such magmas are expected to be very high therefore the primary pgms at greenhills are suggested to have precipitated directly from the melt following differentiation and cooling in a shallow magma chamber

characteristics of sediment profiles in reservoirs abstract published data for sediment profiles in the harry strunk guernsey elephant butte and lake mead reservoirs u s a are analyzed it is shown that the profiles can be described by the equation y axb where x and y are horizontal and vertical distances respectively from the pivot point this equation can be used to determine the slope of the profile at any specified point and to determine the location of the transition point between the foreset and bottomset beds correlations are given which permit an estimate of the longitudinal and vertical extent and the shape of the topset foreset and bottomset components of the sediments this information can be used to predict the complete sediment profile in a reservoir provided that the horizontal distance of the pivot point from the dam is known or estimated

mineralogic and oxygen isotopic studies of open system magmatie processes in the south kawishiwi intrusion spruce road area duluth complex minnesota the south kawishiwi intrusion located along the western margin of the duluth complex minnesota is one of several composite intrusions that are found in the complex the duluth complex is the principal exposed plutonic portion of the 1 1 ga midcontineni rift system in the spruce road area the south kawishiwi intrusion is divided into seven distinct units that are part of the broader south kawishiwi troctolite series defined by severson tech rep nrri tr 91 13a natural resources research institute university of minnesota duluth 1994 units may be characterized as follows unit i basal accumulation of heterogeneous gabbro troctolite and norite unit ii norite with abundant inverted pigeonite unit iii troctolite and olivine gabbro with local oxide rich layers unit iv melatroctolite troctolite olivine gabbro unit v increased plagioclase abundance in troctolites and leucocratic troctolites unit vi strongly altered troctolite unit vii similar to unit v troctolite and leucocratic troctolite country rocks in the spruce road area are granodiorite to quartz monzonite of the archean giants range batholith sutfide mineralization consisting of 1 5 vol of disseminated pyrrhotite cubanite chalcopyrite andpentlandite occurs in units i ii iii and vi oxygen isotopic analyses indicate that unit ii has experienced extensive crustal contamination 5o values of unit ii range from 69 to 7 l o and are 0 enriched compared with values of 5 1 6 8 o found in other units silica contamination is indicated based not only on 5 0 values but also by the predominance of orthopyroxene in the unit possible high 0 contaminant rocks include the giants range batholith and pelitic rocks of the lower proterozoic virginia formation or biwabik iron formation mass balance computations suggest that units in the spruce road area may be related through varying degrees offractionation of a high al olivine tholeiite magma modeling of trace element concentrations and variations in mineral chemistry suggest that discontinuities within the major units developed by in situ boundaryaayer equilibrium crystallization of solidification zones 20 50 m in thickness followed by recharge of fresh magma upward enrichment of incompatible elements olivine fa content and plagioclase ab content may be effectively explained by this process 5 0 values of uncontaminated rock types are strongly correlative with modal mineralogy and can also be modeled by boundary layer fractionation a parental magma 5 0 value of 6 3 o is calculated for unit vii based on olivine and plagioclase values and is similar to that of several other large layered mafic intrusives

geochemistry of tholeiites from lanai hawaii lanai is the third smallest of the fifteen principal subaerial shield volcanoes of the hawaiian hotspot this volcano apparently became extinct during the shield building stage of volcanism as shown by the absence of both alkalic cap and post erosional lavas major and trace element analyses of 22 new samples collected primarily from 3 stratigraphic sections show that lanai tholeiites span a large range in composition some lanai lavas are unique geochemically among hawaiian tholeiites in having the lowest abundances of incompatible trace elements of any hawaiian lavas and well developed positive eu anomalies the geochemical characteristics of these low abundance lanai tholeiites are not the result of alteration differences in mantle source modal mineralogy the presence of residual accessory mantle phases or fractional crystallization of such phases assimilation of depleted morb wall rock or accumulation resorption of phenocrysts or xenocrysts incompatible trace element ratios e g nb la nb th la th la hf ce pb in lanai tholeiites span considerable ranges and form coherent trends with each other and with absolute abundances of these elements large variations in la sm la yb and absolute ree abundances at constant mgo suggest that lanai tholeiites formed by variable amounts of partial melting however large ranges in incompatible element ratios cannot be explained solely by variations in partial melting of a geochemically homogeneous source but must reflect geochemical heterogeneities in the lanai source partial melting modeling indicates that the mixed lanai source is probably lree enriched i e la yb cn 1 one component in the lanai source exemplified by the low abundance tholeiites has markedly lower ree hfse th hfse alkali hfse and ce pb ratios than other lanai or hawaiian tholeiites and may indicate the presence of recycled residual subduction zone materials in the hawaiian plume source the positive eu anomalies that characterize the low abundance lanai tholeiites are not the result of plagioclase accumulation or assimilation but are a feature of this source component progressive temporal geochemical variations in lanai tholeiites from 2 stratigraphic sections indicate that the source composition of these lavas probably evolved over time this change could have resulted from a progressive decrease in the extent of partial melting of the lanai source the compositional variability of lanai tholeiites suggests that geochemical heterogeneities in their source are larger than the scale of partial melting lanai tholeiites could not have formed by smaller degrees of partial melting of plume material than did the larger volume hawaiian shields therefore volume differences between hawaiian shields must be controlled primarily by differences in the volume of supplied plume material rather than by differences in the degree of partial melting the premature cessation of eruptive activity at lanai may be attributed to relatively large degrees of partial melting of a small plume

comparison of nighttime zonal neutral winds and equatorial plasma bubble drift velocities over brazil 1 we present results from the first extended period of coincident observations of thermospheric zonal neutral winds and equatorial plasma bubble epb zonal drift velocities over northeastern brazil during the october to december months of 2009 and 2010 the epb zonal drift velocities are estimated utilizing images of the o i 630 0 nm emissions recorded by a wide angle imaging system at cajazeiras thermospheric neutral wind estimates are based upon common volume observations made by a bistatic fabry perot interferometer fpi experiment using fpis located at cajazeiras and cariri in brazil observing the doppler shift of the o i 630 0 nm emission the results illustrate a similar pattern of nighttime and night to night variations in the zonal neutral winds and epb zonal drift velocities in general the geomagnetic zonal neutral winds and the epb velocities show an excellent agreement illustrating that the f region dynamo is fully developed however in the early evening hours the epb zonal speed is slower than that of the background winds on several occasions we conclude that this indicates that during the bubble evolution period in the early evening the f region dynamo is not fully activated

differentiation of tholeiitic basalt to a type granite in the sept iles layered intrusion canada the undeformed 564 ma sept iles layered intrusion quebec canada is a large igneous body of c 20 000km3 from the base to the top it consists of a layered series dominated by troctolite and gabbro an anorthositic upper border series and a dominantly granitic upper series the parent magma of the layered series is inferred to be an iron rich tholeiitic basalt 48 wt sio2 15wt feot whole rock compositions from the chilled margin dykes cross cutting the layered series and silicic rocks from the upper series display continuous major and trace element geochemical trends ranging from basalts to ferroan metaluminous a type granites 77 wt sio2 initial 143nd 144nd 0 51201 0 51207 and 87sr 86sr 0 70353 0 70548 indicate a juvenile mantle source and minimal contamination by old crust 1 2 during crystallization geochemical modeling using the melts thermodynamic calculator combined with equations predicting mineral melt equilibria from experiments on tholeiitic basalts indicate that basaltic to monzonitic melt compositions are in equilibrium with the troctolites and gabbros of the layered series fe ti oxides saturate early in the layered series after 14 fractionation of plagioclase olivine cumulates further fractionation of fe ti oxide bearing gabbros drives the residual liquids toward silica enrichment and iron depletion major and trace element modeling indicates that the a type granites from the upper series were produced by protracted fractional crystallization of an iron rich basaltic parent magma at a fraction of residual liquid of only 8 the observed relative volumes of mafic cumulates and silicic rocks in the intrusion are in agreement with the calculations most of the intermediate compositions correspond to magmatic mafic enclave bearing granitoids and display geochemical evidence of hybridization intermediate compositions produced by fractional crystallization are scarce and a daly gap occurs from 57 to 67 wt sio2 this gap could result either from the fractional crystallization process or from silicate liquid immiscibility during that compositional interval

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

assimilation of crustal xenoliths in a basaltic magma chamber sr and nd isotopic constraints from the hasvik layered intrusion norway contaminated layered intrusions known thousands of recrystallized strontium and neodymium isotopic data for mafic cumulates chilled tabular xenoliths of metasedimentary origin enclosed in the cumulates margins and adjacent crustal rocks of the hasvik layered intrusion are thought to represent the remnants of the assimilated material north norwegian caledonides are reported together with new the xenoliths spalled off the roof during magma emplacement and mineralogical and whole rock analytical data to constrain the extent together with the elevated temperatures 400 600 c of the midand effect of the assimilation of crustal xenoliths in a basaltic crustal country rocks led to a high degree of assimilation in the magma chamber initial sr sr 700 ma of 0 7045 and end hasvik magma chamber 700 ma of 3 03 for the chilled margin which has a tholeiitic composition akin to the chilled rocks of the skaergaard intrusion demonstrate that the parental magma was derived from a depleted mantle source the basal cumulates 0 335 m show an up section decrease in sr sr from 0 7045 to 0 7038 and a correlative

chemical evolution of intercumulus liquid as recorded in plagioclase overgrowth rims from the skaergaard intrusion the intercumulus liquid of a crystal mush fills pore spaces and typically solidifies to form overgrowths on cumulus grains and poikilitic post cumulus minerals if the liquid is immobile solidification produces zoned intercumulus minerals as a result of progressive fractionation of the residual liquid convection within the mush results in buffering of the liquid composition and thus limits mineral zonation for fully solidified cumulates fossil changes in liquid composition or porosity are difficult to identify however detailed study of immobile minor components of plagioclase overgrowth rims can provide information about the progressive solidification of intercumulus material ti contents of plagioclase overgrowths in samples from the lowermost parts of the skaergaard intrusion show strong variations with anorthite content with decreasing xan ti concentrations first rise and then fall consistent with changing tio2 contents of the intercumulus liquid during solidification tio2 in plagioclase decreases sharply at an55 reflecting local saturation of fe ti oxides ti in clinopyroxene oikocrysts also falls rimward but zoning in faster diffusing species fe mg is limited other than slight reverse zones that may occur on the plagioclase margins xan falls continuously during crystallization the reverse zoning is interpreted as the result of compaction driven dissolution and reprecipitation of plagioclase the continual decrease in xan is exploited together with back scattered electron images of the cumulates to produce calibrated images showing regions of progressive crystallization this allows the regions crystallizing at each stage of solidification to be visualized these images show that the final remnants of interstitial melt were present in triangular pockets and as thin grain boundary melt films this approach can provide information about the progressive reduction of porosity during cumulate solidification

crystal mush compaction and the origin of pegmatitic segregation sheets in a thick flood basalt flow in the mesozoic hartford basin connecticut

compositional and kinetic controls on liquid immiscibility in ferrobasalt rhyolite volcanic and plutonic series we present major element compositions of basalts and their differentiation products for some major tholeiitic series the dry low pressure liquid lines of descent are shown to approach or intersect the experimentally defined compositional space of silicate liquid immiscibility ferrobasalt rhyolite unmixing along tholeiitic trends in both volcanic and plutonic environments is supported by worldwide occurrence of immiscible globules in the mesostasis of erupted basalts unmixed melt inclusions in cumulus phases of major layered intrusions such as skaergaard and sept iles and oxide rich ferrogabbros closely associated with plagiogranites in the lower oceanic crust liquid immiscibility is promoted by low pressure anhydrous fractional crystallization that drives the low al2o3 high feo liquids into the two liquid field kinetic controls can be important in the development of two liquid separation the undercooling that occurs at the slow cooling rates of plutonic environments promotes early development of liquid immiscibility at higher temperature in contrast rapid cooling in erupted lavas leads to large undercoolings and liquid immiscibility develops at significantly lower temperatures unmixing leads to the development of a compositional gap characterized by the absence of intermediate compositions a feature of many tholeiitic provinces the compositions of experimental unmixed silica rich melts coincide with those of natural rhyolites and plagiogranites with high feotot and low al2o3 suggesting the potential role of large scale separation of immiscible si rich liquid in the petrogenesis of late stage residual melts no trace of the paired ferrobasaltic melt is found in volcanic environments because of its uneruptable characteristics instead fe ti p rich gabbros are the cumulate products of immiscible fe rich melts in plutonic settings the immiscibility process may be difficult to identify because both melts crystallize the same phases with the same compositions the two liquids might form incompletely segregated emulsions so that both liquids continue to exchange as they crystallize and remain in equilibrium even if segregated both melts evolve on the binodal surface and exsolve continuously with decreasing temperature the two liquids do not differentiate independently and keep crystallizing the same phases with differentiation further evolution by fractional crystallization potentially drives the bulk liquid out of the twoliquid field so that very late stage liquids could evolve into the single melt phase stability field

the fedorivka layered intrusion korosten pluton ukraine an example of highly differentiated ferrobasaltic evolution abstract this study documents the petrography and whole rock major and trace element geochemistry of 38 samples mainly from a drill core through the entire fedorivka layered intrusion korosten pluton as well as mineral compositions microprobe analyses and separated mineral fraction analyses of plagioclase ilmenite magnetite and apatite of 10 samples the fedorivka layered intrusion can be divided into 4 lithostratigraphic units a lower zone lz 72 m thick a main zone mz 160 m thick and an upper border zone itself subdivided into 2 sub zones ubz2 40 m thick ubz1 50 m thick igneous lamination defines the cumulate texture but primary cumulus minerals have been affected by trapped liquid crystallization and subsolidus recrystallization the dominant cumulus assemblage in mz and ubz2 is andesine an39 42 iron rich olivine fo32 42 augite en29 35fs24 29wo42 44 ilmenite hem1 6 ti magnetite usp52 78 and apatite the data reveal a continuous evolution from the floor of the intrusion lz to the top of mz due to fractional crystallization and an inverse evolution in ubz resulting from crystallization downwards from the roof the whole rock fe mg ratio and incompatible element contents e g rb nb zr ree increase in the fractionating magma whereas compatible elements e g v cr steadily decrease the intercumulus melt remained trapped in the ubz cumulates due to rapid cooling and lack of compaction and cumulus mineral compositions re equilibrated e g olivine fe ti oxides in lz the intercumulus melt was able to partially or totally escape the major element composition of the mz cumulates can be approximated by a mixing linear relationship between a plagioclase pole and a mafic pole the latter being made up of all mafic minerals in nearly constant relative proportions by analogy with the ferrobasaltic jotunitic liquid line of descent defined in rogaland s norway and its conjugated cumulates occurring in the transition zone of the bjerkreim sokndal intrusion rogaland a monzonitic 57 sio2 melt is inferred to be in equilibrium with the mz cumulates the conjugated cumulate composition falls within error on the locus of cotectic compositions fixed by the 2 pole linear relationship ulvospinel is the only ti phase in some magnetites that have been protected from oxidation quilf equilibria in these samples show that magnetite and olivine in mz have retained their liquidus compositions during subsolidus cooling this permits calculation of liquidus fo2 conditions which vary during fractionation from fmq 0 7 to 1 4 log units low fo2 values are also evidenced by the late appearance of cumulus magnetite fo42 and the high v3 content of the melt reflected in the high v content of the first liquidus magnetite up to 1 85 v

evolution of the skaergaard magma evidence from crystallized melt inclusions polymineralic aggregates composed of clinopyroxene fe ti oxide minerals apatite and accessory k feldspar biotite and amphibole are enclosed in cumulus plagioclase grains in the middle zone of the skaergaard intrusion the chemistry of the minerals in the aggregates and the textural relations between the aggregates and the host plagioclase grains indicate that they represent inclusions of the contemporaneous melt of the skaergaard intrusion through mass balance calculations a quantitative estimate of the melt composition for this level in the intrusion can be obtained and this estimate confirms that the silica content in the middle zone melt was similar to or possibly even lower than the silica content in the initial skaergaard melt and relatively enriched in iron

an ocean ridge type magma chamber at a passive volcanic continental margin the kap edvard holm layered gabbro complex east greenland the gabbros of the tertiary kap edvard holm layered serieshave a stratigraphic thickness of more than 5000 m earlier work has shown that the range in cumulus mineral compositions is restricted plagioclase an 81 an 51 olivine fo 85 fo 66 pyroxenes ca 43 mg 46 fe 11 to ca 43 mg 37 fe 20 field evidence of magma injections is common which together with the restricted range in mineral chemistry suggests that the magma chamber was frequently replenished by a less fractionated magma a detailed study of a 600 m section 900 1500 m in the lower layered series reveals a period of crystallization when the magma chamber behaved as a closed system 900 1300 m the rocks formed during this periodare well laminated olivine gabbros 900 110 m which evolved to well laminated oxide gabbros 1100 1300 m compositional trends in the cumulusminerals are towards more evolved compositions plagioclase an 64 an 58 pyroxene mg from 80 to 76 with stratigraphic height from 1300 m to 1500 m granular olivine gabbros dominate with moreprimitive mineral compositions plagioclase an 67 an 76 pyroxene mg from 78 to 82 the transition olivine gabbro to oxide gabbro at 1100m is a consequence of fractional crystallization and it is shown how changes in activities of feo and fe 2 0 3 in the magma are reflected in the total iron content of plagioclases the transition from oxide gabbro to olivine gabbro at 1300 m results from replenishment by less evolved basaltic magma on the basis of calcic pyroxene chemistry and the mineral crystallization sequence it is concluded that the kap edvard holm layered series crystallized from a tholeiitic magma similar to morb melanogabbroic units occur throughout the intrusion as discordant to subconcordant sill like bodies 0 2 2 0 m thick the melanogabbroic units consist of cr rich augite olivine plagioclase heteradcumulates and contain deformed mica crystals of pre emplacement origin these units crystallized from a wet mgo rich magma which was injected into the layered host gabbros after the formation of the cumulus pile but before the magma was completely solidified the kap edvard holm layered series has several parallels with the plutonic part of ophiolite sequences these include cumulus mineral assemblage compositions of the minerals and the restricted range in compositions with stratigraphic height field evidence of repeated replenishment of basaltic magma dyke swarms overlying the roof zone of the magma chamber and the existence of a late intrusive suite of wet mgo rich magma these parallels suggest that the processes involved in the formation of the kap edvard holm layered series were similar to those involved in the formation of the crustalpart of many ophiolites and beneath present day spreading ridges the kap edvard holm layered series is therefore believed to represent a shallow level magma chamber which acted as a reservoir for basaltic flows at the continental margin during the opening of the north atlantic ocean

interaction of zonal winds with the equatorial midnight pressure bulge in the earth s thermosphere empirical check of momentum balance a minimum is observed at midnight in the time variation of averaged zonal winds measured in situ near the equator at an average altitude of about 350 km and we inquire whether observations of the equatorial midnight pressure bulge are consistent with this feature the observed zonal wind maintains an eastward direction all night it increases steadily in the early evening reaching a maximum of about 160 m s at 2100 hrs local time lt dropping to a minimum of about 70 m s around 2400 lt then up to about 120 m s around 0300 lt decreasing thereafter and turning westward in the morning around 0500 lt the nighttime eastward ion drift at jicamarca averaged over periods of similar solar activity 1970 71 shows the same signature but generally with amplitude between 70 and 90 of the zonal wind amplitude the 1978 81 jicamarca ion drifts are similar except from 2400 to 0300 lt when they are about 30 larger than the in situ zonal wind averages the ion drift is used together with the measured zonal winds to estimate the ion drag effect in the momentum equation the pressure term of this equation is estimated using in situ measurements of the neutral temperature and density the pressure term is found to be large before 2100 lt 0 05 m s consistent with the steady increase in zonal wind before 2100lt drops rapidly to near zero roughly 0 005 m s before 2200 lt and then increases slowly beginning at 2300 to about 0 015 m s just before 0300 lt when it is observed to reverse the small pressure term observed from 2100 to 2400 lt is associated with the midnight pressure bulge and accounts for the decay of the wind from 160 m s at 2100lt to 70 m s at midnight the larger value at 0300lt is consistent with the second maximum in the wind it is found that the existing data sets are consistent in terms of zonal momentum balance the striking similarity between the zonal wind and the eastward ion drift is responsible for the small ion drag term before midnight which is required to maintain the large zonal winds observed

reequilibration of olivine with trapped liquid in the duluth complex minnesota a 525 m long drill core ddh 221 through the partridge river intrusion in northeastern minnesota consists of mesocumulates and or orthocumulates of troctolite olivine gabbro and olivine gabbronorite the cumulus olivine whose composition fo 31 to fo 71 is a function of the amount of intercumulus liquid followed an equilibrium crystallization path with this liquid estimates of the primary magmatic compositions of the olivine are fo 57 to fo 79 none of the olivine in the drill core samples has retained an original cumulus composition i e one that was in equilibrium with the parental magma the plagioclase is strongly zoned and the cumulus cores an 59 to an 73 are thought to record crystallization from the parental magma

crystallization sequence and magma chamber processes in the ferrobasaltic sept iles layered intrusion canada the sept iles layered intrusion quebec canada 564 ma is a large plutonic body with a diameter of 80 km and a thickness of 6 km made up from its base to top of a layered series with troctolite and gabbro and an upper border series with anorthosite capped by cupolas of a type granite chilled margin compositions suggest a ferrobasaltic parental magma close to that of the skaergaard intrusion but much richer in iron and titanium samples from drill cores and surface sampling of the 4 7 km thick layered series reveal a succession of massive troctolites and layered gabbros that contain 24 fe ti oxide layers cm to m thick and many anorthositic autolithic blocks the sequence of crystallization in the layered series is plagioclase an72 34 and olivine fo75 21 followed by magnetite and ilmenite then ca rich pyroxene and finally apatite an olivine gap is observed between fo66 and fo59 the saturation of fe ti oxides before ca rich pyroxene is interpreted to be the result of the high feot and tio2 contents and the low cao content of the parental magma contamination by old continental crust has occurred during crystallization of the layered series as indicated by sr isotopic compositions 87sr 86sr564 0 70360 0 70497 the differentiation trend of the intrusion is interrupted by two large and many small reversals to more primitive compositions of cumulus phases cr content of magnetite and lower sr isotope ratios these reversals and the intermittent disappearance of some phases are interpreted as resulting from magma chamber replenishments by undifferentiated primitive basaltic magma and mixing with the resident magma the author 2010 published by oxford university press all rights reserved for permissions please e mail journals permissions oxfordjournals org

experimental study of liquid evolution in an fe rich layered mafic intrusion constraints of fe ti oxide precipitation on the t f o 2 and t ϱ paths of tholeiitic magmas the newark island layered intrusion a composite intrusion displaying a similar fractionation sequence to the skaergaard has both dikes which preserved liquids fed into the intrusion and chilled pillows of liquids resident in the chamber this study reports experimentally determined one atmosphere liquid lines of descent of these compositions as a function of oxygen fugacity which varies from qfm quartz fayalite magnetite to 0 5 log10 units above iw iron wustite these experiments reveal a strong oxygen fugacity dependence on the order of appearance and relative abundances of the fe ti oxide minerals titanomagnetite saturates prior to ilmenite at qfm but the order is reversed at lower oxygen fugacities in the layered series of the newark island intrusion ilmenite arrives shortly before titanomagnetite and the titanomagnetite ilmenite ratio decreases monotonically after the cumulus appearance of titanomagnetite comparison of the crystallization sequence in the intrusion with that of the experiments requires that the oxygen fugacity in the intrusion increased relative to qfm before titanomagnetite saturation and decreased afterward but always remained between the qfm and iw buffers similar trends in the modes of the fe ti oxides ilmenite and titanomagnetite in the skaergaard kiglapait and somerset dam intrusions along with fe2o3 feo ratios in morbs suggest that such a temperature oxygen fugacity path may be typical of tholeiitic magma differentiation calculations of the temperature density paths of the experimental liquids indicate that at all possible oxygen fugacities the density must have decreased abruptly after fe ti oxide saturation accordingly liquids replenishing the intrusion after fe ti oxide saturation should pond at the bottom of the chamber quenching against older cumulates field observation at the newark island intrusion confirm this prediction the similarities in the fractionation paths of several other layered intrusions to that of the newark island intrusion suggest that the density of the liquids in these intrusions also decreased after fe ti oxide saturation experiments on a suggested initial skaergaard liquid are consistent with this model

airglow observations of nighttime medium scale traveling ionospheric disturbances from yonaguni statistical characteristics and low latitude limit the characteristics of nighttime medium scale traveling ionospheric disturbance mstid features observed over yonaguni 24 5 n 123 0 e 19 3 n dip latitude japan are studied using all sky imaging of oi 630 0 nm airglow emission the uniqueness of these observations is that the area observed by the imager covers the transition region between low to middle latitudes in the ionosphere typical low latitude limit of midlatitude type nighttime mstids possessing phase front alignments along the northwest to the southeast occurs in this region these mstid features are rarely sighted at dip latitudes below 15 we selected 2 year period for analysis in which 1 year corresponded to the solar minimum conditions and another year to the solar maximum conditions the mstids were observed to extend to farther lower latitudes during the solar minimum conditions than during the solar maximum periods their observed range of wavelengths phase velocities phase front alignment and propagation directions are similar to those observed at typical midlatitude sites however on many occasions the phase fronts of the observed mstids did not extend over the whole field of view of the imager indicating that some process inhibits their extension to further lower latitudes detailed investigation suggests that the poleward propagating enhancement of airglow intensity probably associated with the midnight pressure bulge causes the mstid features to disappear when they reach lower latitudes later in the night when the mstids reach lower latitudes well before midnight they are found to be inhibited by the equatorial ionization anomaly crest region

crustal evolution of island arc ultramafic magma galmoenan pyroxenite dunite plutonic complex koryak highland far east russia alaskan type platinum bearing plutons and potassium enriched mafic to ultramafic volcanic rocks are temporally and spatially associated within the late cretaceous paleocene achalvayam valaginskii intra oceanic palaeo arc system allochthonousy present in the kogak highland and kamchatka peninsula far east russia the compositions of the parental magmas to the alaskan type complexes are estimated using the galmoenan platonic complex as an example this complex composed of dunites pyroxenites and minor gabbros is the largest 20 km3 in the system and the best studied owing to associated platinum placer deposits the compositions of the principal mineral phases in the galmoenan intrusive rocks olivine fo 79 92 clinopyroxene 1 3 5 wt al2o3 0 1 0 5 wt tio2 and cr spinel 5 15 wt al2o3 and 0 3 0 7 wt tio2 are typical of liquidus assemblages in primitive island arc magmas in intra oceanic settings and closely resemble the mineral compositions in the achaivayam valaginskii ultramafic volcanic rocks the temporal and spatial association of intrusive and extrusive units and the similarity of their mineral compositions suggest that both suites were formed from similar parental magmas ne composition of the parental magma for the galmoenan platonic rocks is estimated using previously reported data for the achaivayam valaginskii ultramafic volcanic rocks and phenocryst hosted melt inclusions quantitative simulation of crystallization of the parental magma in the galmoenan magma chamber shows that the compositions of the cumulate units are best modelled by fractional cryallization with periodic magma replenishment the model calculations reproduce well the observed mineral assemblages and the trace element abundances in clinopyroxene based upon the estimated composition of the parental magmas and their mantle source we consider that fluxing of a highly refractory mantle wedge similar to the source of boninites by chlorine rich aqueous fluids is primarily responsible for both high degrees of partial melting and the geochemical characteristics of the magmas including their enrichment in platinum group elements

conjunctive use of deterministic and stochastic models for predicting sediment storage in large reservoirs 1 a stochastic sediment storage model abstract the papers presented discuss the development of a model to predict the deposition of sediment in reservoirs as a function of time in years the papers consist of three parts which are published together the present paper part 1 deals with the development of a stochastic model for the total deposition of sediment in reservoirs this cumulative deposition of sediment in time is shown to be an additive process defined on a finite markov chain the model is analysed to obtain the mean and the range of the cumulative deposition as a function of discrete time in years part 2 discusses a deterministic model for the deposition process along the length of the reservoir the pattern of deposition is shown to be a function of the inflow and the concentration of sediment in the inflow as well as the initial level in the reservoir and the initial composition of sediment the inflow in the reservoir is treated as unsteady and non uniform as much of the physical characteristics of the reservoir as possible is included in the analysis part 3 discusses the application of the two models in conjunction to the john martin reservoir bent county colorado for which measurements are available though limited in extent the comparison between results obtained from the model and the actual measured data is found to be in good agreement with each other the symbols used and references are provided separately in the notation and references section of each part

anorthosite formation by plagioclase flotation in ferrobasalt and implications for the lunar crust abstract the sept iles layered intrusion quebec canada is dominated by a basal layered series made up of troctolites and gabbros and by anorthosites occurring 1 at the roof of the magma chamber 100 500 m thick and 2 as cm to m size blocks in gabbros of the layered series anorthosite rocks are made up of plagioclase with minor clinopyroxene olivine and fe ti oxide minerals plagioclase displays a very restricted range of compositions for major elements an 68 an 60 trace elements sr 1023 1071 ppm ba 132 172 ppm and sr isotopic ratios 87 sr 86 sr i 0 70356 0 70379 this compositional range is identical to that observed in troctolites the most primitive cumulates of the layered series whereas plagioclase in layered gabbros is more evolved an 60 an 38 the origin of sept iles anorthosites has been investigated by calculating the density of plagioclase and that of the evolving melts the density of the feo rich tholeiitic basalt parent magma first increased from 2 70 to 2 75 g cm 3 during early fractionation of troctolites and then decreased continuously to 2 16 g cm 3 with fractionation of fe ti oxide bearing gabbros plagioclase an 69 an 60 was initially positively buoyant and partly accumulated at the top of the magma chamber to form the roof anorthosite with further differentiation plagioclase 60 became negatively buoyant and anorthosite stopped forming blocks of anorthosite autoliths even fell downward to the basal cumulate pile the presence of positively buoyant plagioclase in basal troctolites is explained by the low efficiency of plagioclase flotation due to crystallization at the floor and or minor plagioclase nucleation within the main magma body dense mafic minerals of the roof anorthosite are shown to have crystallized from the interstitial liquid the processes related to floating and sinking of plagioclase in a large and shallow layered intrusion serve as a proxy to refine the crystallization model of the lunar magma ocean and explain the vertically stratified structure of the lunar crust with gabbro noritic rocks at the base and anorthositic rocks at the top we propose that the lunar crust mainly crystallized bottom up this basal crystallization formed a mafic lower crust that might have a geochemical signature similar to the magnesian suite without kreep contamination while flotation of some plagioclase grains produced ferroan anorthosites in the upper crust

conjunctive use of deterministic and stochastic models for predicting sediment storage in large reservoirs abstract the papers presented discuss the development of a model to predict the deposition of sediment in reservoirs as a function of time in years the papers consist of three parts which are published together part 1 dealt with the development of the stochastic model for the total deposition of sediment in reservoirs this cumulative deposition of sediment in time was shown to be an additive process defined on a finite markov chain the model was analysed to obtain the mean and the range of the cumulative sediment deposition as a function of discrete time in years the present part 2 discusses a deterministic model for the deposition process along the length of the reservoir the pattern of deposition is a function of the inflow and the concentration of sediment in the inflow as well as the initial level in the reservoir and the initial composition of the sediment the inflow in the reservoir is treated as unsteady and non uniform as much of the physical characteristics of the reservoir as possible is included in the analysis part 3 discusses the application of the two models in conjunction to the john martin reservoir bent county colorado for which measurements are available though limited in extent the comparison between results obtained from the model and the actual measured data is found to be in good agreement with each other the symbols used and references are provided separately in the notation and references section of each part

the effect of trapped liquid crystallization on cumulus mineral compositions in layered intrusions a series of calculations have been carried out to evaluate the effect on cumulus mineral compositions of solidification of trapped intercumulus liquid in orthocumulates the calculation assumes local equilibrium between phases and that the system remains chemically closed during crystallization of the trapped liquid the latter assumption is held to be valid on a scale of tens to hundreds of centimeters it is not necessary to know the composition of the trapped liquid as the calculation only requires an estimate of feo content and trapping temperature the change in composition of a mineral from that of the initially precipitated cumulus crystals to the final composition after complete solidification is termed the trapped liquid shift its magnitude depends on the modal proportions of cumulus phases and the initial porosity and is only weakly dependent on initial phase compositions trapped liquid shifts are significant when compared with mineral composition changes occurring during fractional crystallization crystallization of 30 trapped liquid gives rise to shifts of up to 10 mol percent in mg number of olivine or pyroxene the size of the shift becomes greater when the initial cumulus assemblage has a lower total feo mgo content and vice versa as a result of the relationship between trapped liquid shift and cumulus mode mineral composition variations and trends may be generated in sequences of cumulates which originally had constant compositions of cumulus minerals for example in a cyclic unit grading from a pyroxenitic base to an anorthositic top crystallization of a uniform proportion of trapped liquid will result in an apparent iron enrichment trend from bottom to top of the cycle as has been observed in the upper critical zone of the bushveld complex

extreme iron enrichment and liquid immiscibility in mafic intrusions experimental evidence revisited abstract this paper examines phase equilibria and mass balance constraints on fe enrichment in tholeiitic liquids in plutonic environments the peak of fe enrichment is thought to roughly coincide with magma saturation in fe ti oxides and olivine starts to react with the liquid at about the same time this crucial stage of crystallization is examined in detail using a compilation of chemical analyses of 64 experimental charges that comprise liquids quenched glasses equilibrated with the liquidus assemblage of olivine plagioclase high ca pyroxene and low ca pyroxene some samples also contain fe ti oxides it is shown that the 4 phase liquidus assemblage does not constrain a narrow range of liquid compositions the concentrations of sio 2 in the selection of experimental glasses vary broadly from 42 to 66 wt silica content shows strong negative correlations with feo and cao al 2 o 3 and strong positive correlation with alkalis extreme fe enrichment above 22 wt feo is observed only in alkali free or alkali poor liquids broad compositional variations for the multiply saturated liquids are attributed to strong non ideality and complex concentration activity relationships in ferrobasaltic melts liquid immiscibility characteristic of fe rich silicate liquids is the ultimate consequence of non ideality petrogenetic implications of phase equilibria and mass balance constraints are discussed for a classical example of the skaergaard intrusion in east greenland where the trend of extreme fe enrichment has been in contention it is proposed that seemingly conflicting results of experiments on skaergaard natural cumulate rocks and model melt compositions can be reconciled if it is assumed that silicate liquid immiscibility in skaergaard started not at the very end of crystallization but earlier soon after the start of ilmenite and magnetite crystallization

simulation of primary phase relations and mineral compositions in the partridge river intrusion duluth complex minnesota implications for the parent magma composition in order to describe the composition and crystallinity of the initial parental magma of the partridge river intrusion of the keweenawan duluth complex and thereby understand the mode of emplacement and solidification of the intrusion we have applied a numerical simulation technique called geochemical thermometry frenkel et al 1988 the parental magma was a low alumina high ti p olivine tholeiite similar to typical keweenawan low alumina high ti p basalts associated with the duluth complex and from the nearby portage lake area of the lake superior region the parental magma was emplaced as a crystal liquid suspension followed by chilling of an evolved leading edge ferrodioritic liquid in the basal zone of the intrusion the conditions of emplacement at the present crustal location were 1 150 c 2 kbar and fo2 slightly above the wustite magnetite wm buffer the main differentiation process after emplacement was the sorting and redistribution of plagioclase and olivine crystals on a local scale accompanied by less efficient convection and minor settling of olivine calculated crystallization sequence for the parental magma is olivine plagioclase 1 240 c olivine plagioclase magnetite 1 146 c wm 0 5 olivine plagioclase magnetite augite 1 140 c wm 0 5 the calculated compositions of the cumulus olivine and plagioclase in equilibrium with the parent magma at 1 150 c are fo66 7 1 1 and an64 5 2 5 respectively and are similar to the estimated average composition of primary olivine fo69 1 2 8 and the average composition of plagioclase core an66 3 2 8 measured in drill core samples through the intrusion chalokwu and grant 1987

assimilation and fractionation in adjacent parts of the same magme chamber vandfaldsdalen macrodike east greenland the vandfaldsdalen macrodike which lies in the skaergaard region of east greenland is a remarkably zoned fossil magma chamber with a granophyric cap overlying cumulate gabboros the intrusion is distinctly bimodal with a large compositional discontinuity at the contact between the gabbro and granophyre although the exposed part of the macrodike is in contact with tertiary basalts and sediments the granophyre originated by assimilation of xenoliths derived from the underlying archean basement sr and nd isotopic ratios throughout the cumulate sequence are remarkably similar indicating insignificant contamination of the gabbro by the granophyre modelling of the compositional effects of cooling and crystallization indicate that the cumulate pile resulted from fractional crystallization with the complicating effects of trapped liquid and post cumulus fractionation the uppermost rocks in the mafic part of the chamber sio2 62 feo 12 4 resulted from about 85 fractional crystallization a transgressive sill of strongly fractionated magma sio2 67 feo 8 8 formed from extracted intercumulus liquid that was the result of 90 fractional crystallization of the original magma mass balance indicates that typical granophyre is made up of about 75 dissolved xenoliths by weight and 25 mantle derived basaltic magma the magmas were not measurably affected by material exchange across the interface between the gabbro and granophyre this magma chamber evolved by both assimilation and fractional crystallization but the residual liquids formed by fractional crystallization were unaffected by assimilation heat exchange between were unaffected by assimilation heat exchange between the two parts of the chamber was obviously important but there was insignificant material exchange the inability of fractional crystallization and assimilation to affect the same liquid is related to the dynamic behavior of this particular magma chamber particularly the buoyancy of granophyre relative to evolving tholeiitic magma

phase relations and liquid lines of descent in hydrous ferrobasalt implications for the skaergaard intrusion and columbia river flood basalts crystallization experiments using a hydrous ferrobasalt as starting material conducted at 200mpa 940 12008c at a wide range of water activities 0 1 1 and redox conditions qfm 3 to qfm 4 where qfm is the quartz fayalite magnetite oxygen buffer show that h2o influences significantly the differentiation history of ferrobasaltic magmas a combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical fe rich tholeiitic system under both dry and hydrous conditions the addition of h2o decreases liquidus temperatures and changes significantly the proportions temperature range and sequence of crystallizing mineral phases the dry liquidus is at about 11708c whereas the liquidus for h2o saturated melts is at 10608c the main phases crystallizing from h2o bearing ferrobasalt at the investigated conditions are olivine ol clinopyroxene cpx plagioclase pl magnetite mt hematite hm ilmenite ilm and amphibole am the phase assemblage is similar to that of the dry system except for the presence of hm at extremely oxidizing conditions and am at low temperatures 59508c and h2o saturated conditions the important observation made in this study is that the stability of fe ti oxides and in particular mt as well as the simultaneous coprecipitation of mtand ilm are almost independent of the activity of h2o ah2o in the system whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing ah2o the stabilities of oxides are controlled mainly by the redox conditions prevailing in the system the most pronounced effect of ah2o on the liquidus temperatures of silicates is observed for pl which shows a considerable delay in crystallization with progressive magma differentiation early crystallization of fe ti oxides in h2o bearing ferrobasaltic compositions precludes any significant fe enrichment during differentiation as fe enrichment is a characteristic feature of the skaergaard intrusion it implies that the skaergaard parental magma did not contain considerable amounts of water on the other hand our experiments indicate that the differentiation of some ferrobasaltic series from the columbia river flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles 0 5 3 wt h2o

seasonal variation in the occurrence time of the equatorial midnight temperature bulge we have reexamined incoherent scatter radar data on electron and ion temperature from the jicamarca radar observatory 12 s 77 w 1 n diplat for the period 1967 68 and early 1969 we find clear evidence of systematic nighttime temperature increases presumably associated with the midnight pressure bulge and the collapse of the middle latitude f region a significant new finding is that the temperature enhancements tend on the average to occur about two hours before midnight in the local summer and about one hour after midnight in the local winter the bulges appear in various shapes and the enhancement magnitudes vary considerably from barely detectable to many tens of degrees kelvin but show a definite tendency to be smaller in winter than in summer when increases of up to 200 k are sometimes observed changeover from summer to winter behavior occurs within two months or less around equinox our results are consistent with the hypothesis of a nighttime equatorial temperature bulge moving with the antisolar meridian but at jicamarca systematically centered 30 west of this meridian 2 hrs before midnight near the december solstice and 15 east of it near the june solstice our data have relevance to the questions of seasonal changes in the phase and amplitude of the tidal modes responsible for the midnight pressure and temperature bulge

coordinated measurements of f region dynamics related to the thermospheric midnight temperature maximum abstract as part of the nsf cedar program coupling energetics and dynamics of atmospheric regions in multi instrumented studies of equatorial thermospheric aeronomy miseta an all sky ccd airglow imaging system has been in operation in arequipa peru since october 1993 here we report on the first such use of a wide field imager to document the optical signature and variability of a brightness feature associated with the so called midnight temperature maximum mtm while the observational driver of this study is a rightness wave bw seen in 6300 a and 5577 airglow images detailed case studies are conducted during two campaign periods when fabry perot interferometer fpi and digital ionosonde data were also available during the passage of a bw the fpi observed enhancements in thermospheric temperatures reversals from equatorward to poleward of the meridional neutral winds and local minima in the zonal neutral winds the ionosonde recorded decreases in the height of the f layer during bw events this lends support to the concept that the poleward winds generated by the mtm pressure bulge cause the lowering of the f layer to regions of enhanced loss h 300 km and corresponding airglow production the two dimensional field of view of the imager allows identification of the geographical orientation of the bw pattern we use the orientation angle of the bw as an indicator of the geographical orientation of the mtm significant day to day variability in these patterns suggest a complex mix of tidal mode interactions that lead to the overall mtm phenomena

the petrology of high mg dikes from the beartooth mountains montana a search for the parent magma of the stillwater complex six geochemically distinct groups of precambrian high mg dikes have been examined to determine if any could have been a sample of or closely related to the parent magma of the stillwater complex only two groups have sufficiently magnesian olivine and orthopyroxene but neither of these has sufficiently calcic plagioclase in terms of major elements there appear to be only two distinct magma types one has a high orthopyroxene component and is petrographically similar to noritic dikes and sills near the great dyke of zimbabwe and the bushveld complex of south africa the other is similar to primitive tholeiites with higher plagioclase and diopside components than the first all of the groups are enriched in light ree and have unusually high k2o concentrations model calculations indicate that crustal contamination 30 50 of fractionating komatiitic magmas is consistent with the major and trace element characteristics of the first magma type less extensive contamination of komatiitic magmas may produce the parental magmas of the large layered intrusions

the chronology of magma influxes to the eastern compartment of the bushveld complex as exemplified by its marginal border groups the floor contact of the eastern compartment of the bushveld complex has been mapped in detail for 130 km field relations petrographical and geochemical data have enabled 3 important marginal border groups and a possible parent to the lower zone to be demarcated these represent the 4 main magma influxes which formed the malic phase of the bushveld complex and are in chronological order 1 a contaminated magnesian basalt b1 which gave rise to a saucer shaped laminated marginal zone at the base of the complex with diverse related sills 2 a harrisitic peridotite representing quenched lower zone magma 3 a border group to the more evolved probably basaltic critical zone magma which was intruded in two phases an early quenched norite facies n being followed by a chilled bulk critical zone facies b2 which forms a skin to the whole critical zone finally 4 a border group to the main and upper zone b3 which represents an early magnesian pulse of this last immense volume of tholeiitic liquid there is also evidence for minor influxes of magma within the critical zone and main zone

further work on experimental plagioclase equilibria and the skaergaard liquidus temperature equilibria between plagioclase and ferrobasaltic melt in low pressure dry melting experiments can be demonstrated near the liquidus further analyses of melting experiments using optimized beam conditions reveals that previous data for understanding the skaergaard intrusion potentially suffered from the analytical inclusion of non equilibrated components in the average plagioclase compositions new reversal experiments demonstrate convergence between plagioclase rim compositions in melting and crystallization products for a ferrobasaltic melt and thus support equilibrium relations the new data set provides tighter bounds on experimental plagioclase composition and documents composition dependent partitioning of na and ca between plagioclase and melt application of the results to modeling the skaergaard requires only minor adjustments to the previously proposed liquidus temperatures and liquid line of descent

the triple group and the platinova gold and palladium reefs in the skaergaard intrusion stratigraphic and petrographic relations this paper describes the setting structure and textural relations of the platinova reefs in the skaergaard intrusion the reefs comprise a strata bound occurrence of au pge estimated at 91 million tons of rock with 1 8 ppm au and similar amounts of pd the precious metals occur in two major zones a lower major pd reef which is concordant with the modal layering and followed by at least ten minor pd reefs also concordant and an au concentration which fringes the pd reefs outward and upward through the triple group units the major pd concentration and the au concentration are separated in a systematic way across the intrusion near the center of the intrusion the au concentration occurs some 60 m higher in the stratigraphy than the main pd reef but the separation decreases gradually outward being only a few meters near the margins the dominant precious metal minerals are small grains of cu fe au pd pt alloys which typically are included in interstitial sulfides bornite digenite and smaller amounts of chalcopyrite the textural relations suggest a close genetic association between the sulfides and au pge minerals an association which is confirmed by whole rock compositional data our observations demonstrate that the platinova reefs formed after significant concentration of the au pge and s in the residual magma during fractional crystallization before it became saturated with respect to a sulfide fe cu s o liquid this sulfide liquid acted as a collector of au pge and settled into the layered series cumulates we propose that the structure of the deposit evolved through fractional crystallization of the au pge bearing sulfide liquid as it was filter pressed along with the interstitial silicate melt upward into the overlying unconsolidated cumulates the fractional crystallization resulted in an evolution of the au pge bearing phases with progressive fractionation from pd rich alloys at the base of the deposit to au rich alloys at the top we argue that the sulfides evolved to their present extreme cu rich fe poor composition during oxidation desulfurization reactions in the same event which oxidized the iron titanium oxides of the intrusion this oxidation desulfurization probably had no overall effect on the distribution of au and pge

deciphering magmatic and metasomatic processes recorded by fluid inclusions and apatite within the cu ni pge sulfide mineralized bathtub intrusion of the duluth complex ne minnesota usa

the differentiation of the skaergaard intrusion we find no support for the claim that the skaergaard magma followed the trend of common tholeiitic volcanic magmas such as those of iceland and the scottish tertiary the end product of differentiation was not a large mass of rhyolite but an iron rich silica poor liquid not unlike that deduced by wager in 1960 the proposal that a large mass of rhyolitic liquid occupied the upper levels of the intrusion finds no support in the field the thick series of ferrogabbos which became richer in iron and poorer in silica until they reached a field of immiscibility cannot be reconciled with crystallization of a large mass of felsic magma mass balance calculations that indicate otherwise are invalid because they fail to take into account large volumes of rocks that differ in composition from those assumed in the calculations while ignoring the existence of major units of the intrusion hunter and sparks propose that lavas in scotland and iceland are more relevant to the liquid compositions than rocks that are intimately associated with the intrusion their argument that the skaergaard intrusion followed a trend of silica enrichment that is universal to tholeiitic magmas is based on an incomplete knowledge of the rocks and faulty calculations of mass balance relations we agree that much remains to be learned about the skaergaard intrusion and the basic mechanisms of magmatic differentiation in this case however we are ready to hang our case on well established field relations and a mass of laboratory data for what must be the most intensely studied body of rock on earth

equatorial plasma bubble zonal velocity using 630 0 nm airglow observations and plasma drift modeling over ascension island 1 we present oi 630 0 nm airglow image data from ascension island geographic 7 9 s 14 4 w dip latitude 16 s in the southern atlantic ocean taken with the utah state university all sky ccd camera during 20 march to 7 april 1997 in order to study plasma bubbles occurring in the low latitude nighttime ionosphere the initial plasma bubble onset occurs in the early evening hours at 19 15 20 00 lst and is followed by eastward propagation with an average speed of 90 120 m s prior to local midnight rapidly decreasing around the midnight and postmidnight periods the ascension results are compared with similar observations from christmas island in order to examine the longitudinal variations of epb development and propagation the observed epb velocities from ascension island are also compared with the results of a plasma drift model in a case study during the night of 4 5 april the velocity reveals unusual latitudinal shear up to 0 12 m s km with a reversal to westward flow at low latitudes while eastward flow is maintained at higher latitudes consequently the bubble rotates counterclockwise and tilts eastward significantly away from alignment with the geomagnetic field lines the westward reversal of the drift motion near the geomagnetic equator is most likely the result of a reversal in the f region dynamo or from a large increase in the altitude of the shear node in the f region plasma drift at the geomagnetic equator

chemical and mineralogical heterogeneity in the basal zone of the partridge river intrusion implications for the origin of cu ni sulfide mineralization in the duluth complex midcontinent rift system copper nickel sulfide mineralization in the partridge river intrusion of the 1 1 ga duluth complex is restricted primarily to a 100 m thick zone near the base of the intrusion which is heterogeneous at meter scales in terms of both sulfide contents and rock types which include dunite melatroctolite troctolite leucotroctolite gabbro olivine gabbro gabbronorite and rare norite olivine rich troctolites and melatroctolites appear to have required mineral accumulation on a substrate whereas augite troctolite and gabbros are thought to have formed via in situ crystallization of magmas ranging in composition from high al olivine tholeiite to high ti tholeiite 18o values of orthopyroxene poor rocks in the partridge river intrusion range from 5 2 to 6 7 18o values of 6 7 are consistent with less than 20 contamination by high 18o metasedimentary country rock either via devolatilization or local partial melting rocks with greater than 15 orthopyroxene gabbronorites and norites are characterized by 18o values in excess of 6 9 and required the assimilation of larger amounts of siliceous country rocks sulfur isotopic values in leucotroctolitic rocks that contain less than 400 ppm s and that overlie the basal zone range between 1 5 and 2 values that are consistent with those of mantle derived sulfur in contrast 34s values in the basal zone range from 1 4 to 10 5 where the 34s enriched samples require an input of sulfur from metasedimentary country rocks 34s values of the rocks in the basal zone correlate with variations in olivine fo content but not with s abundance the wide range in 34s values of rocks in the basal zone strongly suggests that magmas interacted with layers in the sedimentary country rocks that were themselves characterized by variable sulfide contents and 34s values the s isotopic data suggest that the heterogeneity observed in the basal zone results from the emplacement of relatively thin sheets of compositionally distinct magma all rock types present in the basal zone can be produced as a result of variable degrees of fractionation of a parental high al olivine tholeiite followed by varying degrees of contamination of derivative liquids by country rocks the s contamination process was essential for the development of cu ni mineralization and was restricted to the earliest stages in the development of the duluth complex at a time when volatile species such as s and h2o and low t partial melts of country rocks were available to magmas

the effects of metamorphism on o and fe isotope compositions in the biwabik iron formation northern minnesota the biwabik iron formation of minnesota 1 9 ga underwent contact metamorphism by intrusion of the duluth complex 1 1 ga apparent quartz magnetite oxygen isotope temperatures decrease from 700 c at the contact to 375 c at 2 6 km distance normal to the contact in 3d metamorphic pigeonite at the contact however indicates that peak temperatures were greater than 825 c the apparent o isotope temperatures therefore reflect cooling and not peak metamorphic conditions magnetite was reset in d 18 o as a function of grain size indicating that isotopic exchange was controlled by diffusion of oxygen in magnetite for samples from above the grunerite isograd apparent quartz magnetite o isotope temperatures are similar to calculated closure temperatures for oxygen diffusion in magnetite at a cooling rate of 5 6 c kyr which suggests that the biwabik iron formation cooled from 825 to 400 ci n 75 kyr at the contact with the duluth complex isotopic exchange during metamorphism also occurred for fe where magnetite fe silicate fractio nations decrease with increasing metamorphic grade correlations between quartz magnetite o isotope fractio nations and magnetite iron silicate fe isotope fractionations suggest that both reflect cooling where the closure temper ature for fe was higher than for o the net effect of metamorphism on d 18 o d 56 fe variations in magnetite is a strong increase in d 18 omt and a mild decrease in d 56 fe with increasing metamorphic grade relative to the isotopic compositions that are expected at the low temperatures of initial magnetite formation if metamorphism of iron formations occurs in a closed system bulk o and fe isotope compositions may be preserved although re equilibration among the minerals may occur for both o and fe isotopes

the origin of basic ultrabasic sills with s d and i shaped compositional profiles by in situ crystallization of a single input of phenocryst poor parental magma an attempt is made to develop an in situ crystallization model based on the concept of soret fractionation to explain the origin of commonly observed s d and i shaped compositional profiles in sills formed from a single pulse of phenocryst poor parental magma the model envisages that the various compositional profiles observed in sills can be interpreted in terms of different combinations of four principal units basal zone and layered series forming the floor sequence and top zone and upper border series constituting the roof sequence the basal and top zones represent mirror images of the layered and upper border series respectively and therefore are referred to as basal and top reversals it is proposed that the formation of basal and top reversals takes place through the non equilibrium soret differentiation of liquid boundary layers which form as a consequence of the temperature gradient imposed by the cold country rock in contrast the layered and upper border series originate predominantly through the crystal liquid boundary layers developing in equilibrium conditions the model permits the production of s d and i shaped compositional profiles from the same magma composition all that is necessary to produce a specific shape of compositional profile is an appropriate temperature gradient imposed by the cold country rock on the liquid boundary layers of a parental magma of a given composition

conjunctive use of deterministic and stochastic models for predicting sediment storage in large reservoirs 3 application of the two models in conjunction abstract these papers discuss the development of a model to predict the deposition of sediment in reservoirs as a function of time in years the papers consist of three parts which are published together part 1 dealt with the development of the stochastic model for the total deposition of sediment in reservoirs this cumulative deposition of sediment in time was shown to be an additive process defined on a finite markov chain the model was analysed to obtain the mean and the range of the cumulative sediment deposition as a function of discrete time in years part 2 of the paper discussed a deterministic model for the deposition process along the length of the reservoir the pattern of deposition was developed as a function of the inflow and the concentration of sediment in the inflow as well as the initial level in the reservoir and the initial composition of the sediment the inflow in the reservoir was treated as unsteady and non uniform as much of the physical characteristics of the reservoir as possible is included in the analysis part 3 presented here is the application of the two models in conjunction to john martin reservoir bent county colorado for which measurements are available though limited in extent the comparison between results obtained from the model and the actual measured data is found to be in good agreement with each other the symbols used and references are provided separately in the notation and references section of each part

climatologies of nighttime upper thermospheric winds measured by ground based fabry perot interferometers during geomagnetically quiet conditions 1 local time latitudinal seasonal and solar cycle dependence 1 we analyze ground based fabry perot interferometer observations of upper thermospheric 250 km horizontal neutral winds derived from doppler shifts in the 630 0 nm red line nightglow the winds were measured over the following locations south pole 90 s halley 76 s 27 w arequipa 17 s 72 w arecibo 18 n 67 w millstone hill 43 n 72 w sondre stromfjord 67 n 51 w and thule 77 n 68 w we derive climatological quiet time kp 150 the seasonal dependence of the winds is generally annual but there are isolated cases in which a semiannual variation is observed within the austral winter winds measured from the south pole show a substantial intraseasonal variation only along longitudes directed toward the magnetic pole imf effects are described in a companion paper

models of basalt petrogenesis lower keweenawan diabase dikes and middle keweenawan portage lake lavas upper michigan lower keweenawan diabase dikes from marquette baraga counties and middle keweenawan portage lake lavas from upper michigan can each be subdivided into two chemically distinct groups a low tio2 p2o5 group characterized by higher a12o3 content higher mg ratio and lower total fe and ree abundances than a high tio2 p2o5 group both groups which are indistinguishable in the field are enriched in the lree relative to the hree and have similar normalized ree abundance patterns

evidence for the trapped liquid shift effect in the mount ayliff intrusion south africa postcumulus trapped liquid shift in layered complexes produces cumulate minerals with more fractionated compositions than the original primary phases this effect is shown by olivine compositions from the base of the mount ayliff intrusion where varying proportions of olivine to interstitial liquid produce a suite of rocks which define a tight linear trend on a binary whole rock plot of mgo versus feo extrapolation of this trend constrains the composition of the primary cumulus olivine to the range fo84 86 whereas olivine actually present have compositions fo77 83 the magnitude of the discrepancy between the theoretical and observed olivine compositions correlates directly with the weight fraction of interstitial liquid these observations are quantitatively predicted by the trapped liquid shift model they also argue against significant migration of residual liquid trapped liquid shift is documented over a vertical interval of 60 m it occurred in rocks lying only 1 m above the basal contact of the intrusion and hence must be a comparatively rapid process

climatology of f region zonal plasma drifts over jicamarca 1 we use extensive incoherent scatter radar observations made at the jicamarca radio observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the f region peak using bernstein polynomials as base functions our quiet time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent the nighttime drifts are eastward have larger magnitudes and increase strongly with solar flux particularly near equinox and december solstice enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night the nighttime drift perturbations are largest near midnight and increase strongly with solar flux near equinox and december solstice but are essentially absent near june solstice the jicamarca zonal disturbance drifts can be largely accounted for by disturbance dynamo electric fields with a dominant time delay of about 3 15 hours following enhanced geomagnetic activity in the postmidnight sector there are also smaller westward disturbance drifts associated with time delays of about 15 24 hours and perhaps even longer our results strongly suggest that the longitudinal dependence of both the quiet and disturbed equatorial nighttime zonal drifts varies with season

origin of pegmatitic segregation veins within flood basalts subhorizontal veins and lenses of coarse grained rock composed of plagioclase augite and fe ti oxides in a glassy and vesicular mesostasis occur within several thick subaerial basalt flows in the columbia river basalt province of washington and in the eastern north american mesozoic basalt province the veins and lenses referred to as pegmatitic segregation veins are typically 1 10 cm thick and are enriched in fe ti k p cu zr ba and ree by a factor of about 1 1 to 3 over the host basalt al ca sr mg ni and cr are lower and si and na are typically unchanged we interpret the pegmatitic segregation veins as the product of residual melt carried in vapor bubbles from the lower crystallization front of partially crystallized flows to the crystal mush within the upper crystallization front movement through the elevated temperatures of flow interiors fused any crystal nuclei in the segregation melt diminished nucleation density during crystallization may partially account for coarse grain sizes in addition diffusion of ions to large rapidly growing skeletal crystals was probably enhanced by the viscosity reduction effect of water enrichment the water content of accumulated segregation melt may have increased whenever the escape of volatiles from partiallymore crystallized flows was temporarily sealed off under a rigid barrier of solidified basalt rupture of the barrier by downward propagation of columnar joints would allow the resumption of effervescence and any remaining partially crystallized segregation melt phase would be degassed and quenched into a glassy and vesicular mesostasis 59 refs 8 figs 2 tabs less

pressure conditions for the solidification of the skaergaard intrusion eruption of east greenland flood basalts in less than 300 000 years abstract primary granophyres are differentiated from olivine tholeiitic magma and occur interstitially throughout the cumulus stratigraphy of the skaergaard intrusion east greenland samples from the lower zones a c lza c the middle zone mz and the sandwich horizon sh are included in the present study together with granophyric accumulations in gabbroic pegmatite from lza c fluid inclusions in quartz and the mineral assemblage in the granophyres record the pressure under which the skaergaard intrusion crystallised pegmatitic granophyre from lza c consists mainly of quartz plagioclase an 4 7 and alkali feldspar or 40 80 enclosing an earlier formed assemblage of ferrohastingsitic and ferroedenitic hornblende fayalite fo 4 5 titanite biotite and fluor apatite granophyric quartz albite and alkali feldspar crystallised from water saturated granitic melts near eutectic minimum conditions between 680 and 660 c the pressure of granophyre crystallisation was modelled by the intercept between fluid inclusion isochores and the minimum melt solidus for granitic compositions pressures recalculated to the roof pendant of the intrusion are 0 7 0 5 for lza 2 0 0 2 for lzb c 2 3 0 8 for mz the triple group level and 3 3 1 3 kb for sh amphibole geobarometry independently confirm the pressure estimates for pegmatitic granophyres in lza c the granophyres formed as the intrusion cooled through the minimum melt solidus in lza lzb lzc mz and sh respectively the pressure increase from lza to sh granophyres is explained by progressive burial during cooling of the intrusion and contemporaneous outpouring of 5 3 6 3 2 7 km of flood basalts during the initial opening of the northeast atlantic ocean accordingly the skaergaard intrusion evolved from a subvolcanic magma chamber at emplacement to a more deep seated igneous system during terminal crystallization when the majority of the intercumulus phases formed the present cooling history suggests the intrusion cooled through the temperature of granophyre formation in less than 300 000 years the increase in the pressure of granophyre formation therefore implies that 5 3 6 3 2 7 km of flood basalts were emplaced within this time window

the skaergaard pge and gold deposit the result of in situ fractionation sulphide saturation and magma chamber scale precious metal redistribution by immiscible fe rich melt the skaergaard intrusion greenland is the type locality for skaergaard type mineralizations mineralization levels are perfectly concordant with igneous layering up to 5 m thick internally fractionated and contain crystallized sulphide droplets and precious metal alloys sulphides arsenides and telluride immiscible cu rich sulphide droplets formed in a mush zone below the roof scavenged precious metals they were subsequently dissolved and transported to the floor in late formed immiscible fe rich mush melts mineralized stratigraphic intervals of floor gabbro formed in proto macrolayers owing to local sulphide saturation in melt concentrated between floating plagioclase and sinking clinopyroxene the floor mineralization is divided into four stratigraphic sections formation of the lower platinum group element mineralization lpgem involved 1 crystallization of the bulk liquid liquidus paragenesis and in situ fractionation 2 sulphide saturation and formation of sulphide droplets in melt in the upper part of proto macrolayers after further in situ fractionation the following steps occurred 3 the onset of silicate silicate immiscibility and the consequent loss of buoyant and immiscible si rich melt 4 dissolution of unprotected droplets of sulphide melt present in the fe rich mush melt 5 compaction driven upwards loss of residual mush melt enriched in for example au the lpgem preserves upward increasing bulk pd pt 6 13 owing to a continued supply of pge and au with high pd pt the further development of the lpgem ceased as the supply of precious metals to the floor waned the upper pge mineralization upgem subsequently formed from precious metals recycled in the floor the upgem is characterized by increasing au substitution in pge phases and a decrease in total pge and pd pt owing to upward fractionation in migrating mush melts and exhaustion of pd and pt an upper au rich mineralization level uaum was caused by late remobilization of au and deposition on grain boundaries in fully crystallized gabbro cu concentrations 150 ppm are not correlated with pge and au repeated cu mineralization levels cum attaining 1000 ppm occur above the au levels caused by local mush layer sulphide saturation pge au and cu distributions in the floor mineralization reflect sub liquidus but supra solidus processes and reactions in mushes at the roof wall and floor constraints provided by a new model for the mineralization provide the basis for re evaluation of the solidification processes in the skaergaard intrusion we have identified the importance of extensive in situ fractionation and intrusion wide elemental redistributions in immiscible fe and si rich silicate melts our model characterizes the floor cumulates as bulk liquid orthocumulates containing an upwards increasing proportion crystallized from fe rich immiscible mush melt the roof rocks are complementary to the floor with downwards increasing proportions crystallized from the conjugate si rich melt petrographic observations and the relative timing of crystallization support the hypothesis that crystallization was restricted to marginal mush zones bulk melt remaining in the magma chamber evolved not as generally assumed as a result of loss of crystals grown from the bulk melt but as the consequence of mixing with recycled and evolved melt expelled from the mush by compaction redistribution of fe in immiscible melts may be common to mafic intrusions and puts into question the validity of petrogenetic modelling of bulk liquids in mafic intrusions based only on consideration of floor cumulates

local time and altitude variation of equatorial thermosphere midnight density maximum mdm san marco drag balance measurements we present the first study of the local time and altitude variation of the mdm the density component of the equatorial midnight pressure bulge an important feature in the nighttime motions of the ionosphere thermosphere system in the equatorial region the neutral density data of the san marco 3 sm3 and san marco 5 sm5 satellites were averaged to obtain 24 hr density variations from april to december in 1971 and 1988 from these variations the mdm amplitude as a function of altitude and local time was obtained at altitudes from 220 to 400 km at the geographic equator we show the first evidence of downward phase propagation of the mdm together with a vertical structure not observed before which may suggest an ionospheric interaction or perhaps a viscous dissipation effect in 1971 the mdm propagates rather gradually from about 350 to 220 km in about two hours in 1988 there appear two regions in which the mdm time shows little change with height with a discontinuous jump in between the two regions the net effect is still a downward displacement of the mdm with local time the results show significant seasonal and solar activity effects during low solar activity periods 1971 the mdm occurs earlier in equinox than in solstice for all altitudes consistent with the seasonal variation of the midnight temperature maximum mtm however with higher solar activity 1988 and at altitudes below 340 km the mdm occurs earlier in solstice than in equinox raising new questions on solar activity effects on the relative phases of the tidal oscillations of the neutral density and the neutral temperature

major and trace element variation in ilmenite in the skaergaard intrusion petrologic implications abstract ilmenite separates from the floor ls roof ubs and wall mbs sequences of the skaergaard intrusion were analyzed for major and trace elements using dcp aes and icp ms techniques in all three sequences feo progressively increases and mgo and al 2 o 3 progressively decrease with differentiation although trace element abundances are in general higher in ubs ilmenite than in mbs and ls ilmenite all three sequences have similar trends for trace element abundance vs crystallization ba cs rb sr th u y and the rees are excluded elements in ilmenite and remained at low abundances during differentiation cr ni sc and v are included elements in ilmenite and other mafic phases and decreased during differentiation v contents in ilmenite however do not decrease significantly until the upper part of the middle zone suggesting that magnetite did not begin to affect the magma differentiation trend until much later than when it first appears in the intrusion hf nb ta and zr which are strongly excluded elements in silicates are included elements in ilmenite the element ratios zr hf y ho nb ta and u th are relatively constant in skaergaard ilmenite from different parts of the intrusion suggesting that fluid transport did not significantly effect these elements during differentiation or post solidification cooling calculated partition coefficients for ilmenite in the skaergaard intrusion are similar to those reported from previous studies of lunar and terrestrial basalts and kimberlites and for most elements are significantly lower than those reported for ilmenite in rhyolitic magma similar d i s for zr hf nb and ta suggest that ilmenite crystallization did not significantly affect zr nb or hf ta in the skaergaard magma but the ratios of zr hf nb or ta to other high field strength elements such as th u y or the rees may have been altered by ilmenite fractionation

variations of the nighttime thermospheric mass density at low and middle latitudes 1 the latitudinal structure of the nighttime thermospheric mass density at 385 km has been investigated using observations made by the accelerometer onboard the champ satellite between 2002 and 2007 the nighttime thermospheric mass density had a clear latitudinal variation there was a local density peak around the geographic equator and two minima at about 30 this nighttime equatorial mass anomaly nema was opposite to the latitudinal variations of the daytime ionospheric equatorial anomaly and thermospheric mass density anomaly as both have minima at the magnetic dip equator and maxima around 20 in magnetic latitudes this anomalous behavior of the nighttime thermospheric mass density had strong local time seasonal hemispheric and solar cycle dependences the largest crest to trough ratio between the peak density at the equator and the minima at the anomaly latitudes 30 occurred between 0000 and 0200 local time the nema appeared to be more pronounced during solstice seasons it was also stronger during solar minimum than during solar maximum in addition under the same geophysical conditions the empirical nrlmsise 00 model shows similar but much weaker nighttime mass density anomaly features at low and middle latitudes a high resolution national center for atmospheric research thermosphere ionosphere mesosphere energetics global circulation model timegcm simulation reproduced most of the observed latitudinal variations of the nighttime mass density as well as the thermospheric midnight temperature maximum mtm model results suggest that superposition of diurnal and semidiurnal migrating tides of modes up to wave number 6 is the likely cause of both the nema and mtm phenomena

optical interferometric measurements of nighttime equatorial thermospheric winds at arequipa peru we obtained nighttime measurements of equatorial thermospheric wind dynamics at arequipa peru with an automated field widened fabry perot interferometer between april 1983 and august 1983 and reduced data from 62 nights significant seasonal variations in both zonal and meridional components of the thermospheric neutral wind vector were observed near the equinox between 2000 and 2300 lt the zonal wind component is eastward with an amplitude between 100 and 150 m s that gradually ebbs to zero by dawn the meridional component is generally small throughout the night in the winter months may august and at the winter solstice the zonal wind persists eastward throughout the night with speeds between 50 and 150 m s the meridional component is directed poleward southward toward the winter hemisphere with a speed of 50 75 m s that decays to zero by midnight comparison with the predictions of the national center for atmospheric research thermospheric general circulation model for equinoctial and solstice conditions shows good agreement we conclude that the observed seasonal changes are caused by the changing nature of the solar forcing function the arequipa results found the day to day variability in the winter thermospheric winds to be less than that found for the summer equatorial observations obtained at kwajalein interferometric measurements of the 630 0 nm intensity at equinox showed a major reduction of the emission lasting 1 or 2 hours in all directions but south shortly after evening twilight this decrease was not observed during winter

postmagmatic sulphur loss in the skaergaard intrusion implications for the formation of the platinova reef abstract the stratabound platinova au pd reef in the skaergaard intrusion is intimately linked to cu fe sulphide minerals and occurs at a level that shows changes in the sulphur concentration and the cu s ratio these features suggest that the reef is related to silicate sulphide liquid immiscibility in the skaergaard magma however although the evidence is strong present day sulphur concentrations are too low to support such a model the detailed knowledge of the shape volume and compositional relations of the skaergaard lithologies allows for numerical modeling of sulphur and copper concentrations during fractionation of the magma these data can be evaluated with the current models for sulphur saturation in iron rich mafic magmas to assess the original sulphur concentrations the extent of fractionation the composition of sulphide liquids and the extent of postmagmatic sulphur loss mass balance modeling yields initial copper and sulphur concentrations of 250 and 894 ppm for the parental magma to the lower zone a prior to sulphur saturation cu behaves as an incompatible element with a bulk partition coefficient in the cumulus material dcumuluscu of 0 13 indicating some incorporation of cu into mafic silicates probably augite sulphur can be assumed to be perfectly incompatible in the cumulus minerals although it will be included as a component of the interstitial liquid these values yield sulphur saturation at around 635 ppm cu and 2607 ppm s assuming the sulphur to originally be present as a mixture of monosulphide mss and intermediate solid solution sulphide iss the primary sulphides in the cumulates would amount to 0 07 modal through lower and middle zones and 0 53 modal on average through upper zone the expected weight proportion of primary chalcopyrite pyrrhotite evolves from 30 70 at the base of lza through 26 74 at the level of the platinova reef to 18 82 at the sandwich horizon the present day bornite magnetite mineral assemblage is likely to have been derived from a primary pyrrhotite chalcopyrite assemblage through reequilibration and postmagmatic oxidation significant sulphur appears to have been lost from the lower and middle parts of the layered series lower zone a to upper zone b whereas the sulphides of the upper zone c can be explained in the context of a sulphur gain local scale reequilibration of cu from mafic silicates into sulphides may have contributed to the sulphide mineralogy of the lower and middle zones the structure of the platinova reef probably formed from an original single stratabound reef sulphur loss through oxidation in upward migrating deuteric or hydrothermal fluids could have caused dissolution and reprecipitation of pd and au in a cumulate with several stratiform redox barriers this process can thus explain the successive pd peaks of the reef as well as the variable stratigraphic offset of pd and au across the intrusion