mica liquid trace elements partitioning and the granite pegmatite connection the st sylvestre complex western french massif central abstract we constrain the genetic relation between granite and pegmatite parental melts from the variscan saint sylvestre leucogranite complex and associated pegmatite bodies massif central france through compositions of micas using mica trace element concentrations and available partition coefficients for li rb ba cs and f we calculated the trace element contents of granitic and pegmatitic melts at equilibrium with micas biotite in leucogranites and pegmatites ranges mostly from fe biotite to siderophyllite more evolved facies contain protolithionite and zinnwaldite and lepidolite occurs in the most fractionated pegmatite white micas have homogeneous compositions from muscovite to li phengite in granites biotite and muscovite trace element distributions are clustered in pegmatites mica trace element contents globally follow differentiation from the least to the most evolved body the reconstructed pegmatitic and granitic melts present strong compositional similarities such as enrichments in li rb cs and depletion in ba that suggest a similar origin however micas are shown to have selectively equilibrated with the last melt or fluid in contact and so trace element concentrations of early magmatic liquids are rarely preserved inversion of the mica data constrains the composition of parental melts and the trace element evolutions during crystallization leucogranite and pegmatite melts show mutual incompatible element evolutions inconsistent with a parent daughter genetic relation the data and the modelling suggest that they represent non cogenetic melts generated by discrete episodes of partial melting differentiation is thus inherited from source processes rather than being the consequence of fractional crystallization of a common parental melt magma we suggest that both the leucogranites and the pegmatites originate from partial melting of a heterogeneous source rather than pegmatites being the product of granite crystallization

a numerical study of a mesoscale convective system during toga coare part ii organization in part i the authors presented a successful numerical simulation of the life cycle of a warm pool mesoscale convective system mcs that occurred on 15 december 1992 during the tropical ocean global atmosphere coupled ocean atmosphere response experiment in this study the simulation results of part i are diagnosed to investigate the organization of the mcs and the convective onsets that occurred during the growing and mature stages of the mcs during the life cycle of the mcs four convective onsets occur in the presence of large scale ascent convective available potential energy cape and surface potential temperature drop off sptd it is found that the first convective onset is caused by the existence of upward motion cape and sptd in the model initial conditions the second convective onset is regulated by the favorable occurrence of sptd the third and fourth convective onsets arise from the development of upward motion associated with the westward propagation of the quasi 2day wave the four mesoscale precipitation features clustered together to form the mcs in response to the evolution of the vertical motion field the organization of the mcs is characterized by the presence of a midtropospheric mesovortex situated near the position of the first convective onset analysis of the relative vorticity rv budget indicates that the mesovortex originates and intensifies largely from vortex stretching induced by deep convective heating a decrease in rv above below the mesovortex arises because of the combined effects of the tilting and horizontal advection terms the tilting stretching and solenoidal terms our results suggest that the mesovortex played little role in the subsequent onsets i e second third and fourth and that other warm pool mcss occurring near the transequatorial flow are likely to be associated with mesovortices

multiscale interactions in the life cycle of a tropical cyclone simulated in a global cloud system resolving model part ii system scale and mesoscale processes abstract the life cycle of tropical storm isobel was simulated reasonably well in the nonhydrostatic icosahedral atmospheric model nicam a global cloud system resolving model the evolution of the large scale circulation and the storm scale structure change was discussed in part i both the mesoscale and system scale processes in the life cycle of the simulated isobel are documented in this paper in the preconditioned favorable environment over the java sea mesoscale convective vortices model mcvs developed in the mesoscale convective systems mcss and convective towers with cyclonic potential vorticity pv anomalies throughout the troposphere model vortical hot towers vhts appeared in the model mcvs multiple model vhts strengthened cyclonic pv in the interior of the model mcv and led to the formation of an upright monolithic pv core at the center of the concentric mcv primary vortex enhancement as the monolithic pv core with a warm core developed near the circulation center the intensif

genesis of tropical storm eugene 2005 from merging vortices associated with itcz breakdowns part i observational and modeling analyses abstract although tropical cyclogenesis occurs over all tropical warm ocean basins the eastern pacific appears to have the highest frequency of tropical cyclogenesis events per unit area in this study tropical cyclogenesis from merging mesoscale convective vortices mcvs associated with breakdowns of the intertropical convergence zone itcz is examined this is achieved through a case study of the processes leading to the genesis of tropical storm eugene 2005 over the eastern pacific using the national centers for environmental prediction reanalysis satellite data and 4 day multinested cloud resolving simulations with the weather research and forecast wrf model at the finest grid size of 1 33 km observational analyses reveal the initiations of two mcvs on the eastern ends of the itcz breakdowns that occurred more than 2 days and 1000 km apart the wrf model reproduces their different movements intensity and size changes and vortex vortex interaction at nearly the right timing and location at

k ar age and geochemistry of the sw japan paleogene cauldron cluster implications for eocene oligocene thermo tectonic reactivation abstract systematic k ar dating and geochemical analyses of paleogene cauldrons in the sanin belt of sw japan have been made to explore the relationship between the timing of their formation and the paleogene subduction history of sw japan documented in the shimanto accretionary complex we also examine the magma sources and tectonics beneath the backarc region of sw japan at the eastern plate boundary of eurasia fifty eight new k ar ages and 19 previously reported radiometric age data show that the cauldrons formed during middle eocene to early oligocene time 43 30 ma following a period of magmatic hiatus from 52 to 43 ma the hiatus coincides with absence of an accretionary prism in the shimanto belt resumption of the magmatism that formed the cauldron cluster in the backarc was concurrent with voluminous influx of terrigenous detritus to the trench as a common tectono thermal event within a subduction system the cauldrons are composed of medium k calc alkaline basalts to rhyolites and their plutonic equivalents these rocks are characterized by lower concentrations of large ion lithophile elements lile including k2o ba rb th u and li lower la yb n ratios lower initial sr isotopic ratios 0 7037 0 7052 and higher end t values 0 5 to 3 5 relative to late cretaceous to early paleogene equivalents there are clear trends from enriched to depleted signatures with decreasing age from the late cretaceous to the paleogene the same isotopic shift is also confirmed in lower crust derived xenoliths and is interpreted as mobilization of pre existing enriched lithospheric mantle by upwelling depleted asthenosphere relatively elevated geothermal gradients are presumed to have prevailed over wide areas of the backarc and forearc of the sw japan arc trench system during the eocene to oligocene newly identified late eocene low silica adakites and high mg andesites in the sanin belt and early eocene a type granites in the sw korea peninsula probably formed due to upwelling of hot asthenosphere and subduction of a young plate the backarc region was an extensional tectonic setting and some paleogene rift basins and sanin belt cauldrons occur in linear arrays the eocene oligocene sanin se korea continental arc lies on the ne extension of the east china sea basin the initial stage of which probably formed by continental arc rifting this rifting may have been triggered by upwelling of hot asthenosphere into the wedge space created by rollback of the subducted slab in response to decreased convergence rate between the pacific and eurasian plates

a petrologic assessment of internal zonation in granitic pegmatites abstract cameron et al 1949 devised the nomenclature and delineated the patterns of internal zonation within granitic pegmatites that are in use today zonation in pegmatites is manifested both in mineralogy and in fabric mineral habits and rock texture although internal zonation is a conspicuous and distinctive attribute of pegmatites there has been no thorough effort to explain that mineralogical and textural evolution in relation to the zoning sequence presented by cameron et al 1949 or in terms of the comprehensive petrogenesis of pegmatite bodies pressure temperature and whole rock composition this overview of internal zonation within granitic pegmatites consists of four principal parts 1 a historic review of the subject 2 a summary of the current understanding of the pegmatite forming environment 3 the processes that determine mineralogical and textural zonation in pegmatites and 4 the applications of those processes to each of the major zones of pegmatites based on the concepts presented in london 2008 the fundamental determinates of the internal evolution of pegmatite zones are 1 the bulk composition of melt 2 the magnitude of liquidus undercooling prior to the onset of crystallization 3 subsolidus isothermal fractional crystallization by which eutectic or minimum melts fractionate by sequential non eutectic crystallization 4 constitutional zone refining via the creation of a boundary layer liquid chemically distinct from but continuous with the bulk melt at the crystallization front and 5 far field chemical diffusion the long range and coordinated diffusion of ions particularly of alkalis and alkaline earths through melt

the interaction of easterly waves orography and the intertropical convergence zone in the genesis of eastern pacific tropical cyclones the interaction of an idealized easterly wave with an orographic feature representing the sierra madre of mexico and a large scale meridionally sheared zonal flow representing the itcz in the eastern north pacific is examined through numerical integration of the shallow water equations on an equatorial beta plane channel the model simulations show that as a wave approaches the orography from the east the relative vorticity in the lee increases due to the wave being modified by the orography this relative vorticity maximum increases the northward advection of the itcz in the lee of the mountain that occurs due to the influence of the mountain anticyclone the result of this interaction is the development of a localized region of enhanced cyclonic vorticity that moves parallel to the contours of the model orography there is a minimal increase in the amplitude of the vorticity occuring during interactions between the wave and orography itcz and orography and wave and itcz the position of the incident wave upstream of the orography at the time that the disturbance in the lee begins to develop and the subsequent motion of the leeside vorticity maximum are in agreement with an observed case of eastern pacific tropical cyclogenesis which is also presented

melt inclusions in quartz from an evolved peraluminous pegmatite geochemical evidence for strong tin enrichment in fluorine rich and phosphorus rich residual liquids abstract we have investigated the magmatic evolution of a late stage f and p rich pegmatite forming aluminosilicate liquid and the geochemical controls on magmatic mineralizing processes by remelting totally crystallized melt inclusions in quartz and analyzing the quenched glass by epma and sims the quartz phenocrysts were sampled from a pegmatite that occurs in a variscan granite genetically associated with cassiterite and wolframite mineralized greisen veins at the ehrenfriedersdorf sn w deposit central erzgebirge se germany the melt inclusion compositions imply that the pegmatite forming liquid achieved extreme levels of chemical differentiation it contained high abundances of sn f p li rb cs nb ta and be and abnormally low concentrations of ca y sr and ree for a granite and it was strongly peraluminous the molar al 2 o 3 cao na 2 o k 2 o ranged from 1 3 to 2 0 fractions of the pegmatite forming liquid were extremely enriched in p 2 o 5 f al 2 o 3 and the molar abundances of f p in the glasses correlate strongly with moles of network modifying al ions implying that the bulk liquid included f p and al bearing complexes formation of these complexes reduced the activities of f p and al in bulk liquid suppressed the crystallization of magmatic topaz and p rich minerals and allowed the liquid to become enriched in these constituents some fractions of the ehrenfriedersdorf aluminosilicate liquid contained 1000 2000 ppm sn these levels of sn enrichment were up to 2 orders of magnitude greater than that ever reported for nonmineralized metaluminous and peraluminous igneous materials and are consistent with some experimentally derived sn solubilities in cassiterite saturated granitic liquids at geologically relevant pressures and temperatures this concordance implies that cassiterite could have crystallized directly from this highly evolved p and f rich peraluminous granitic liquid without the involvement of hydrothermal fluids

genesis of tropical storm eugene 2005 from merging vortices associated with itcz breakdowns part ii roles of vortex merger and ambient potential vorticity abstract in this study the roles of merging midlevel mesoscale convective vortices mcvs and convectively generated potential vorticity pv patches embedded in the intertropical convergence zone itcz in determining tropical cyclogenesis are examined by calculating pv and absolute vorticity budgets with a cloud resolving simulation of tropical storm eugene 2005 results show that the vortex merger occurs as the gradual capture of small scale pv patches within a slow drifting mcv by another fast moving mcv thus concentrating high pv near the merger s circulation center with its peak amplitude located slightly above the melting level the merging phase is characterized by sharp increases in surface heat fluxes low level convergence latent heat release and upward motion lower tropospheric pv surface pressure falls and growth of cyclonic vorticity from the bottom upward melting and freezing appear to affect markedly the vertical structures of diabatic heating convergence absolute vorticity

the crystal chemical basis for ar retention in micas inferences from interlayer partitioning and implications for geochronology cation partitioning data for coexisting muscovite and biotite are shown to be useful indicators of relative interlayer bond length strength in these minerals these data therefore provide a useful crystal chemical perspective on relative mass transfer kinetics of radiogenic isotopes and account for the observation that biotite is generally less retentive of 40ar and 87sr than coexisting muscovite partitioning behavior of trace elements underscores three reasons why overall interlayer bonding in biotite is weaker than in muscovite first the preferences of large rb cs in biotite and of small la3 and na in muscovite indicate a relatively spacious interlayer volume in biotite suggesting a longer mean k o bond second the preference of interlayer vacancies in biotite with some all possibly h2o h3o filled suggests that its adjacent 2 1 sheets are connected by fewer interlayer bonds per unit cell than those of muscovite third the relative exclusion of large ba2 from biotite despite its large interlayer sites is attributed to o h bonds pointing into the interlayer cavity sub normal to 001 k ba2 h repulsion thereby induced by the bare proton both destabilizes ba2 and weakens k o bonds in contrast muscovite offers a more favorable electrostatic environment for ba2 substitution since its o h bonds are directed into the vacant m1 octahedral site sub parallel to 001 this hypothesis is supported by the observation that progressive f oh 1 exchange enhances ba2 partitioning into biotite phlogopite relative to coexisting muscovite these crystal chemical differences between biotite and muscovite are mirrored in calculated values of ionic porosity z i defined here as the percentage of their interlayer unit cell volume not occupied by ions a monitor of ionic packing density and geometry z i is inversely correlated with k o bond strength which appears to be the rate determining kinetic common denominator for a variety of processes affecting micas including those responsible for loss of radiogenic isotopes in biotite and muscovite accordingly the relatively longer weaker k o bonds of biotite are envisioned as being more easily stretched during volume diffusion or broken during recrystallization or retrograde alteration this in turn accounts for common observations of enhanced radiogenic ar sr loss and younger 40ar 39ar and rb sr ages in natural biotite high z i relative to coexisting muscovite lower z i significantly this pattern may arise irrespective of isotopic loss mechanism diffusion or recrystallization etc and it follows that any age discordance observed between muscovite and biotite cannot be ascribed uniquely to one mechanism or the other without appropriate field petrographic and petrologic constraints extension of this partitioning porosity based synthesis leads to prediction of corollary age retentivity composition effects among chemically diverse trioctahedral and dioctahedral micas which are best field tested in terranes that cooled slowly under dry static conditions pressure effects on argon retention are also inferred from the porosity model

genesis of typhoon chanchu 2006 from a westerly wind burst associated with the mjo part ii roles of deep convection in tropical transition abstractin this study the life cycles of a series of four major mesoscale convective systems mcss during genesis and their roles in transforming a vertically tilted vortex associated with a westerly wind burst hereafter the wwb vortex into typhoon chanchu 2006 are examined using 11 day cloud resolving simulations presented in part i it is found that the tilted wwb vortex at early stages is characterized by an elevated cold core layer about 200 hpa thick below and a weak warm column above with large vertical wind shear across the layer which extends over a horizontal distance of about 450 km between the vortex s 400 and 900 hpa centers during the final two days of the genesis process the upper level warm column increases in depth and intensity as a result of the absorption of convectively generated vortices cgvs including a mesoscale convective vortex mcv causing more rapid amplification of cyclonic vorticity in the middle than the lower troposphere the commencement of sustained intens

oceanic cyclogenesis as induced by a mesoscale convective system moving offshore part i a 90 h real data simulation abstract recent observations have revealed that some mesoscale convective systems mcss could undergo multiple cycles of convective development and dissipation and under certain environments they appeared to be responsible for barotropic oceanic or tropical cyclogenesis in this study oceanic cyclogenesis as induced by an mcs moving offshore and then driven by deep convection in a near barotropic environment is investigated by extending to 90 h the previously documented 18 h simulation of the mcss that were responsible for the july 1977 johnstown flash flood it is demonstrated that the mesoscale model can reproduce very well much of the meso scale structures and evolution of the long lived mcs out to 90 h these include the development and dissipation of the continental mcss as well as the associated surface and tropospheric perturbations the timing and location in the initiation of a new mcs after 36 h and in the genesis of a surface mesolow over the warm gulf stream water after 60 h integra

geochemical constraints on the bimodal origin of high himalayan leucogranites major and trace element and rb sr isotope systematics of the manaslu leucogranite central nepal have been examined to constrain the role of mineral fractionation and fluids in peraluminous granite petrogenesis biotite and tourmaline are for the most part mutually exclusive with a predominance of two mica leucogranites over tourmaline leucogranites the 87sr86sr initial isotopic ratios sri indicate that leucogranitic melts were derived from two different sources the two mica leucogranites having a metagreywacke origin with sri 0 752 nd 15 such a bimodal nature of the source zone does not directly influence the magmatic evolution except that probably the higher initial boron content in the metapelitic rocks may increase the na2ok2o ratio in contrast the amount of water present during melting principally controls in part anatectic processes and element behaviour water saturated conditions probably occured during melting of metagreywackeous rocks and favoured crystallization of two mica leucogranites whereas water absent conditions prevailed during melting of metapelitic layers and favoured biotite plagioclase and monazite fractionation in the source zone and tourmaline crystallization in the leucogranite

surface cyclogenesis from convectively driven amplification of midlevel mesoscale convective vortices mesoscale convective vortices mcvs are midtropospheric warm core cyclonic circulations that often develop in the stratiform region of mesoscale convective systems typically divergent anticyclonically circulating mesoscale cold anomalies appear both above and below the mcv the upper level cold anomaly is usually found near the tropopause while the low level anomaly is surface based and exhibits locally higher pressure one aspect of mcvs that has received much attention recently is the role that they may play in tropical cyclogenesis of special interest is how an mcv amplifies when deep convection redevelops within the borders of its midlevel cyclonic circulation and how the amplified mcv transforms the divergent surface based cold pool with anomalously high surface pressure into a convergent cyclonic circulation with anomalously low pressure the pennsylvania state university national center for atmospheric research fifth generation mesoscale model is used to simulate an mcv that was instrumental in initiating within the borders of the midlevel vortex s circulation several successive cycles of convective development and decay over a 2 day period after each cycle of convection both the horizontal size of the cyclonic circulation and the magnitude of the potential vorticity associated with the vortex were observed to increase the simulation reproduces the development and evolution of the mcv and associated convective cycles mesoscale features responsible for the initiation of convection within the circulation of the vortex and the impact of this convection on the structure and evolution of the vortex are investigated a conceptual model is presented to explain how convective redevelopment within the mcv causes low level heights to fall and cyclonic vorticity to grow downward to the surface applying this conceptual model to a tropical marine environment is also considered

late orogenic post orogenic and anorogenic granites distinction by major element and trace element chemistry and possible origins granites classified into four categories based solely on tectonics of occurrence and associated rock types also have compositional characteristics that are consistent within groups and different am

subduction products according to experimental prediction knowledge of the thermal structure and processes in subduction zones is so uncertain that our more extensive knowledge of source materials and phase relationships remains insufficient for prediction of magmatic products the phase relationships do provide important constraints for testing geophysical and petrogenetic models especially when considered along with geochemical constraints physical questions such as the behavior of partially molten rocks are intimately related to the compositions of magmas from source to eruption site tentative predictions and conclusions include 1 andesite is not a primary magma from oceanic crust 2 it is unlikely that liquids from subducted oceanic crust yield andesites by fractionation except by melting of amphibolite in an especially warm subducted crust 3 it is more likely that hydrous siliceous magmas from the crust leak into the overlying mantle 4 andesite magmas can be generated in peridotite only under exceptional circumstances 5 h2o undersaturated basic magmas from peridotite modified by aqueous fluids or hydrous magma may yield andesite by fractionation 6 phlogopite peridotite could escape melting and yield alkalic magmas at deeper levels 7 andesite magmas could be produced in continental crust only by extreme heating through underplating of basalts or by mixing of basalt and rhyolite derived from crust most of these conclusions need revision if convection in the asthenosphere wedge raises the temperature of the subducted slab to 1250 c at 100 km as proposed by marsh 1979a this demonstrates the dependence of experimental predictions on geophysical models

the genesis of lct type granitic pegmatites as illustrated by lithium isotopes in micas abstract isotopic compositions in the monts d ambazac pegmatite field french massif central exhibit a narrow range of mica 7li values ranging from 3 6 to 3 4 the value obtained in biotite from the host saint sylvestre granite falls within this range 7li 1 5 lithium concentrations are consistent with the degree of magmatic evolution of each pegmatite type from 630 ppm in type ii up to 13 500 ppm in the more evolved type vi pegmatite although the rare element contents e g li cs and ta of the micas are consistent with pegmatite differentiation 7li are firstly independent of the degree of magmatic differentiation independent of pegmatite type and secondly independent of the content of li and other flux elements such as be and cs muscovite sampled in pegmatite v from the chabannes locality is the only pegmatite to exhibit a 7li variation from an intermediate unit 1 7 to an internal pegmatitic unit 3 4 the nature of this 7li variation suggests that there was extensive fractional crystallization during the pegmatite s consolidation the independence of 7li evolution from the degree of magmatic evolution and the presence of distinct major rare element bearing phases throughout the pegmatite field tend to confirm that the 7li values recorded in mica are inherited from crustal source rocks common to the granite and pegmatite forming melts we propose that the distinct pegmatite subtypes beryl columbite vs lepidolite petalite subtypes observed throughout the monts d ambazac pegmatite field reflect the diverse contributions of crustal protoliths the lack of evidence of surrounding alteration combined with the absence of increasing li content within the host granite tends to confirm that the 7li values obtained within this pegmatite field are primary and that no li diffusional process and or mixing driven li isotope fractionation has overprinted these isotopic compositions in light of these results the process of partial melting of protoliths enriched in rare element bearing phases e g mica and garnet seems to be more responsible for li isotope fractionation than li diffusion or fractional crystallization at the temperature of pegmatite consolidation finally we discuss the use of li isotopic compositions to identify the most highly evolved pegmatitic systems

an initial continental margin plutonism cretaceous older ryoke granitoids southwest japan the emplacement of the older ryoke granitoids took place in the mid cretaceous period in the outermost side of the inner zone of southwest japan which was located at the eastern margin of the eurasian continent before the opening of the japan sea the ryoke belt constitutes a long segment of the cretaceous to palaeogene felsic magmatic belt of pacific asia the older ryoke granitoids represent its initial magmatism related to the subduction of an oceanic plate underneath the eurasian plate in that time their magmas were generated in the lower to middle crust beneath the ryoke belt in the subduction regime they were emplaced during the ryoke regional metamorphism and converted to orthogneisses

numerical simulations of the genesis of hurricane diana 1984 part i control simulation abstract the complete transformation of a weak baroclinic disturbance into hurricane diana is reproduced by numerical simulations using the fifth generation pennsylvania state university national center for atmospheric research mesoscale model three distinct phases of the evolution are evident first baroclinic and barotropic development strongly modified by the effects of latent heating occurs during the latter part of this phase the low level circulation is strengthened through the axisymmetrization of remote potential vorticity anomalies that are generated by condensational heating and then advected toward the incipient storm the axisymmetrization process evinces properties of both nonlinear discrete vortex merger and vortex rossby wave dynamics the transformation from cold core to warm core vortex occurs in this development stage in the second phase lasting 10 12 h little deepening occurs spiral bands of convection begin to form and the core of the storm moistens eventually reaching 95

genesis of typhoon nari 2001 from a mesoscale convective system 1 in this study the origin and genesis of typhoon nari 2001 as well as its erratic looping track are examined using large scale analysis satellite observations and a 4 day nested cloud resolving simulation with the finest grid size of 1 33 km observational analysis reveals that nari could be traced 5 days back to a diurnally varying mesoscale convective system with growing cyclonic vorticity and relative humidity in the lower troposphere and that it evolved from a mesoscale convective vortex mcv as moving over a warm ocean under the influence of a subtropical high a weak westerly baroclinic disturbance an approaching and departing typhoon danas to the east and the kuroshio current results show that the model reproduces the genesis final intensity looping track and the general convective activity of nari during the 4 day period it also captures two deep subvortices at the eye eyewall interface that are similar to those previously observed a few spiral rainbands and a midget storm size associated with nari s relatively dry and stable environment we find that 1 continuous convective overturning within the mcv stretches the low level vorticity and moistens a deep mesoscale column that are both favorable for genesis 2 nari s genesis does not occur until after the passage of the baroclinic disturbance 3 convective asymmetry induces a smaller sized vortex circulation from the preexisting mcv 4 the vortex vortex interaction with danas leads to nari s looping track and temporal weakening and 5 midlevel convergence associated with the subtropical high and danas accounts for the generation of a nearly upright eyewall

subduction related magmatism of late ordovician age in eastern england deep boreholes show that plutonic and volcanic igneous rocks comprise an important component of the caledonian basement in eastern england the isotopic compositions of these rocks reveal that many of them are of late ordovician age 440 460 ma and their geochemical compositions suggest calc alkaline affinities the intermediate diorite tonalite plutonic rocks are associated with a prominent northwest southeast trending belt of aeromagnetic anomalies extending from derby to st ives hunts which is interpreted to work the plutonic core of a calc alkaline magmatic arc it is inferred that this arc was generated by the subduction of oceanic lithosphere possibly from the tornquist sea in a south or southwest direction beneath the midlands microcraton in late ordovician times the age and geochemical composition of concealed ordovician volcanic rocks in eastern england and hypabyssal intrusions of the midlands minor intrusive suite in central england is compatible with such a hypothesis

geochemical characteristics and variations of the ryoke granitoids southwest japan petrogenetic implications for the plutonic rocks of a magmatic arc abstract geochemical characteristics and variations of the ryoke granitoids southwest japan have been elucidated based on more than 70 analyses from the mikawa and kinki districts for major and trace elements including ree the ryoke granitoids are the products of a continental margin arc magmatism of pacific asia during late cretaceous period and represent its magmatic front they are classified into the older and younger groups according to their intrusive ages and textural and petrographic characteristics the older ryoke granitoids were emplaced at ca 20 km depth during 100 85 ma and deformed and recrystallized together with the host ryoke metamorphic rocks the younger ryoke granitoids are post tectonic plutons emplaced at ca 15 km depth 85 75 ma and accompanied by the formation of contact aureoles the majority belongs to i type and ilmenite series granitoids the granitoids of both groups are geochemically quite similar calcic alkali lime index 65 very low in fe 3 fe 2 ratio and both metaluminous and peraluminous they have low rb

tropical cyclogenesis due to itcz breakdown idealized numerical experiments and a case study of the event in july 1988 abstractthe mechanism of tropical cyclogenesis due to the breakdown of the intertropical convergence zone itcz breakdown and the structure of associated vortices are studied by numerical experiments using a nonhydrostatic mesoscale model first an idealized numerical experiment in which a simple initial state without external disturbances is assumed is performed without cumulus parameterization a zonally uniform forcing of high sea surface temperature sst is imposed to generate an itcz like structure this itcz starts to undulate and eventually breaks down to form several tropical cyclones tcs these tcs merge and end up with a single tc the energy budget analysis shows that barotropic instability of the low level flow associated with the itcz is responsible for the genesis of vortices and tc scale buoyancy production soon takes over to contribute to the intensification of tcs conversion from the cumulus scale kinetic energy into the tc scale kinetic energy is found to be insignificant duri

geochemical comparison between himalayan and hercynian leucogranites abstract isotopic sr pb nd o ree and trace element data from three himalayan nepal and six hercynian brittany france leucogranites are compared for the himalayan granites makulu mustang and especially manaslu the 87sr 86sr versus 87rb 86sr scatter diagrams and hence variability of the initial 87sr 86sr ratios reflect heterogeneity of the source materials these ratios are very high 0 730 0 770 for manaslu the very high 207pb 204pb ratios 15 8 at the corresponding 206pb 204pb ratio of 18 8 the very low 143nd 144nd ratios i nd 13 to 17 and the very high 18o 16o ratios 12 confirm the crustal origin with the paragneisses of the tibetan slab formation i as the probable parent source for the six hercynian granites with an individual rb sr isochron established for many of them the initial 87sr 86sr ratios range from 0 706 to 0 717 the lead neodymium and oxygen isotope compositions confirm their crustal source of presumably palaeozoic age but not specifically identified the rare earth patterns and thorium contents are comparable to those for himalayan granites the similarities of the geochemical signatures isotopes and trace elements of the himalayan and hercynian leucogranites suggest that the petrogenetic processes were comparable and that the himalayan continental collision model can be applied to the hercynian the depletion in ree and th implies either interaction of the granitic liquids with fluid or more probably early precipitation of monazite the increase in sm nd in the granites compared to their parent materials implies that the neodymium model ages of primary mantle extraction are maximum rather than minimum ages in contrast to the hercynian leucogranites the extremely radiogenic sr of the himalayan leucogranites reflects the very long crustal residence time before the melting event the apparent uniformity of the initial 87sr 86sr ratios of the individual hercynian granites may be related to an aging effect where the straight line fitting improves with increase in age of the pluton

genesis of tropical storm eugene 2005 from merging vortices associated with itcz breakdowns part iii sensitivity to various genesis parameters abstract in this study a series of sensitivity simulations is performed to examine the processes leading to the genesis of tropical storm eugene 2005 from merging vortices associated with the breakdowns of the intertropical convergence zone itcz over the eastern pacific this is achieved by removing or modifying one of the two vortices in the model initial conditions or one physical process during the model integration using the results presented in parts i and ii as a control run results reveal that while the itcz breakdowns and subsequent poleward rollup through a continuous potential vorticity supply provide favorable conditions for the genesis of eugene the vortex merger is the most effective process in transforming weak tropical disturbances into a tropical storm the sensitivity experiments confirm the authors previous conclusions that eugene would not reach its observed tropical storm intensity in the absence of the merger and would become much shorter lived without the potential vorticit