rewriting the climatology of the tropical north atlantic and caribbean sea atmosphere abstract the jordan mean tropical sounding has provided a benchmark reference for representing the climatology of the tropical north atlantic and caribbean sea atmosphere for over 50 years however recent observations and studies have suggested that during the months of the north atlantic hurricane season this region of the world is affected by multiple air masses with very distinct thermodynamic and kinematic characteristics this study examined 6000 rawinsonde observations from the caribbean sea region taken during the core months july october of the 1995 2002 hurricane seasons it was found that single mean soundings created from this new dataset were very similar to c l jordan s 1958 sounding work however recently developed multispectral satellite imagery that can track low to midlevel dry air masses indicated that the 1995 2002 hurricane season dataset and likely jordan s dataset as well was dominated by three distinct air masses moist tropical mt saharan air layer sal and midlatit

the evolution of dropsonde derived kinematic and thermodynamic structures in developing and nondeveloping atlantic tropical convective systems abstractthe processes by which tropical cyclones evolve from loosely organized convective clusters are still poorly understood because of the data sparse regions in which tropical cyclones form observational studies of tropical cyclogenesis are often more difficult than studies of land based convective phenomena as a result many studies of tropical cyclogenesis are limited to either a few case studies or rely on simulations the 2010 predict and grip field experiments have provided a new opportunity to gain insight into these processes using unusually dense observations in both time and space the present study aims at using these recent datasets to perform a detailed analysis of the three dimensional evolution of both kinematic and thermodynamic fields in both developing and nondeveloping tropical convective systems in the western atlantic five tropical convective systems are analyzed in this study two nondeveloping two developing and one dissipating system although the analysis necessarily inclu

the eclogite garnetite transformation at high pressure and some geophysical implications mineral assemblages displayed by morb and alkali poor olivine tholeiites have been investigated over the pressure interval 4 6 18 gpa at 1200 c both compositions crystallize to form normal eclogites between 4 6 and 10 gpa and there is little change in the relative proportions of garnet and pyroxene over this range however the proportion of garnet increases rapidly above 10 gpa as pyroxene dissolves in the garnet structure and pyroxene free garnetites stishovite are produced by 14 15 gpa dependent upon composition the garnetite facies for both compositions possess zero pressure densities of 3 75 g cm3 implying that subducted oceanic crust remains appreciably denser than surrounding mantle to depths exceeding 600 km it is demonstrated that the seismic velocity distributions in the mantle between 400 and 650 km are inconsistent with anderson s hypothesis that this region is of eclogitic composition

mineral inclusions in diamonds from the sloan kimberlites colorado mineral inclusions have been recovered from 40 small 1 5 mm diamonds from the sloan 1 and 2 kimberlite pipes in northern colorado primary inclusions i e proto or syngenetic are olivine clinopy roxene sanidine rutile and possibly native fe and some phlogopite phases interpreted as epigenetic are acmite richterite most phlogopite perovskite mn ilmenite cr spinel magnetite calcite serpentine and possibly mg ilmenite acmite richterite and perovskite have not previously been reported in diamond the epigenetic minerals commonly occur as inclusion assemblages such as phlogopite richterite phlogopite perovskite ilmenite magnetite serpentine and phlogopite clinopyroxene spinel magnetite calcite the majority of the primary inclusions have an eclogitic suite affinity which is uncommon but similar to diamonds in the premier orapa and mbuji mayi kimberlites of southern and central africa and from a few sites in russia and western australia secondary inclusions reflect

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

triassic early liassic extensional systems and their tertiary inversion essaouira basin morocco abstract nne ssw striking late triassic early liassic half grabens of the essaouira basin and the adjacent high atlas are linked by roughly ew striking transfer faults they are overlain by a wide considerably less faulted evaporitic sag basin and extensive basalt flows a pre pliensbachian unconformity truncates the triassic early liassic sequences on the e and ne margin of the basin and is overlain by a mid liassic to cretaceous platform sequence in the cap sim necnafa depression jurassic and early cretaceous salt tectonics caused widespread salt withdrawal structures tertiary nnw to sse compression caused the inversion of ne and nne striking structures and or the formation of salt anticlines the same compression formed ew striking reverse faults and anticlines suggesting the reactivation of late triassic early liassic transfer faults

muddy and dolomitic rip up clasts in triassic fluvial sandstones origin and impact on potential reservoir properties argana basin morocco abstract the significance of rip up clasts as sandstone framework grains is frequently neglected in the literature being considered as accessory components in bulk sandstone composition however this study highlights the great value of muddy and dolomitic rip up clast occurrence as a information source about low preservation potential from floodplain deposits and b key element controlling host sandstone diagenetic evolution and thus ultimate reservoir quality high resolution petrographic analysis on triassic fluvial sandstones from argana basin t6 and t7 t8 units highlights the significance of different types of rip up clasts as intrabasinal framework components of continental sediments from arid climates on the basis of their composition and ductility three main types are distinguished a muddy rip up clasts b dolomitic muddy rip up clasts and c dolomite crystalline rip up clasts spatial distribution of different types is strongly facies related according to grain size origin of rip up clasts is related to erosion of coeval phreatic dolocretes in different development stages and associated muddy floodplain sediments cloudy cores with abundant inclusions and clear outer rims of dolomite crystals suggest a first replacive and a subsequent displacive growth respectively dolomite crystals are almost stoichiometric this composition is very similar to that of early sandstone dolomite cement supporting phreatic dolocretes as dolomite origin in both situations sandstone diagenesis is dominated by mechanical compaction and dolomite cementation a direct correlation exists between 1 muddy rip up clast abundance and early reduction of primary porosity by compaction with irreversible loss of intergranular volume igv and 2 occurrence of dolomitic rip up clasts and dolomite cement nucleation in host sandstone occluding adjacent pores but preserving igv both processes affect reservoir quality by generation of vertical and 3d fluid flow baffles and barriers that compartmentalize the reservoir these findings may provide quantitative useful data for the better understanding of reservoir quality in analogous hydrocarbon bearing basins such as the bay of fundy nova scotia canada

mesoscale interactions in tropical cyclone genesis with the multitude of cloud clusters over tropical oceans it has been perplexing that so few develop into tropical cyclones the authors postulate that a major obstacle has been the complexity of scale interactions particularly those on the mesoscale which have only recently been observable while there are well known climatological requirements these are by no means sufficient a major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development observations exist for only a few forming cases in these the moist convection in the preformation environment is organized into mesoscale convective systems each of which have associated mesoscale potential vortices in the midlevels interactions between these systems may lead to merger growth to the surface and development of both the nascent eye and inner rainbands of a tropical cyclone the process is essentially stochastic but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences for example a monsoon trough provides a region of reduced deformation radius which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices further a strong monsoon trough provides a vertical wind shear that enables long lived midlevel mesoscale vortices that are able to maintain or even redevelop the associated convective system the authors develop this hypothesis by use of a detailed case study of the formation of tropical cyclone oliver observed during toga coare 1993 in this case two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband the eye developed on the edge of the major convective system and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere the importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western north pacific

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

lithospheric domains and controls on kimberlite emplacement slave province canada evidence from elastic thickness and upper mantle composition 1 we have mapped the deep structure of the slave craton by combining analysis the effective elastic thickness te with data on mantle samples from numerous kimberlites three dimensional mapping of the subcontinental lithospheric mantle sclm using mantle derived xenoliths and xenocrysts in kimberlites has shown that much of the craton is underlain by a strongly layered sclm a highly depleted upper layer low in basaltic components ca al fe is separated from a relatively fertile lower layer by a sharp boundary this boundary lies at 140 150 km depth in the lac de gras area and shallows to 100 km in the northern and southern parts of the craton weak lithosphere te 56 km in the younger eastern part of the craton is separated from the older western part by a zone of steep te gradient parallel to the major locus of kimberlite intrusion which may map the deep extension of the boundary between the two domains another strong te gradient across the kilohigok basin accompanies a marked compositional change in the upper layer of the lithospheric mantle the basin probably marks a major translithospheric fault correlations between te and mantle composition suggest that te is strongly influenced by the rheology of the upper mantle

salt tectonics along the atlantic margin of morocco abstract the moroccan salt basin appears to be very unique in the sense that it is not sedimentary loading but tectonic inversion which appears to drive the latest stages of salt related deformation in the central part of the basin the gravity potential to maintain salt tectonics is provided by the differential uplift of the atlas mountains located adjacent and striking almost perpendicular to the margin along the offshore part of the moroccan salt basin there are many play types most of them related to the triassic syn rift salt toe thrust anticlines at the basinwards edge of the salt basin form very large structures traps associated with salt tongues and diapirs define a more classical salt flank play numerous salt tongues sheets and canopy complexes provide for a gulf of mexico style subsalt play despite the numerous untested play types there have been only four deep water exploration wells drilled in the entire moroccan salt basin none of them having subsalt penetrations

subsidence of the atlantic moroccan margin during the mesozoic this paper presents a combined study based on seismic interpretation sequence stratigraphy and the evaluation of subsidence that aims to characterize the structure and development of the essaouira basin in morocco located in the coastal meseta adjoining the continental margin this basin records an initial carnian hettangian deformation phase during rifting in the central part of the north atlantic region the geometry of the basin as a function of time shows a succession of half grabens and horsts that developed westwards from reactivated hercynian structures the postrift stage is characterized by an aggrading sedimentary sequence as shown by concordant seismic sequences stacking over the onshore part of the basin the upper cretaceous coincides with a sequence showing a transition towards a prograding regime that leads to the topography of the present day margin using the high resolution analysis provided by sequence stratigraphy it is possible to recognize fine scale stratigraphic variations in

cyclicity of triassic to lower jurassic continental red beds of the argana valley morocco implications for palaeoclimate and basin evolution abstract cyclical playa deposits form a prominent part of the continental clastic succession of the argana valley western high atlas of morocco the red beds formed in triassic to lower jurassic times during rifting of the north american and african plates detailed stratigraphic work revealed asymmetrical metre scale cycles in mudstone dominated successions that constitute the intermediate and upper portion of the basin fill sedimentary cycles commonly comprise ephemeral lake shales at the base playa mudflat mudstones in the intermediate part and both fluvial and aeolian sandstones at the top cycles of the aglegal member t4 are mainly characterized by analcime rich playa mudflat deposits displaying features indicative of palaeo vertisols cycles of the sidi mansour t7 and hasseine t8 members are represented by ephemeral lake or dry playa mudflat deposits grading into saline mudflat mudstones that are overlain by sheet flow and minor aeolian sandstones sedimentary cycles of the imerhrane member t9 comprise sheet delta sandstones at the base overlain by ephemeral lake and dry playa mudflat mudstones upper cycle portions consist of aeolian dune and sand sheet sandstones cyclicity is attributed to palaeoclimatic and associated palaeohydrological fluctuations probably within the milankovitch frequency band sedimentary facies of each cycle provide evidence for a gradual climatic drying with time the asymmetrical drying upward cycles possibly record the precession cycle since they are modulated by symmetrical i e oscillating drying wetting cycles of a lower frequency indicative of eccentricity a long term change in palaeoclimate ranging from semi arid conditions with seasonal precipitation t4 towards an arid non seasonal climate t8 is preserved within the cyclical units spanning a time interval of several million years individual cycles can be traced laterally for tens of kilometres correlative sections are almost identical in thickness suggesting a phase of tectonic quiescence during their deposition sediment accumulation was not restricted to small scale grabens but took place continuously throughout the exposed area of the argana valley implying that accommodation space has not been controlled by syndepositional tectonism

mineral inclusions and geochemical characteristics of microdiamonds from the do27 a154 a21 a418 do18 dd17 and ranch lake kimberlites at lac de gras slave craton canada a mineral inclusion carbon isotope nitrogen content nitrogen aggregation state and morphological study of 576 microdiamonds from the do27 a154 a21 a418 do18 dd17 and ranch lake kimberlites at lac de gras slave craton was conducted mineral inclusion data show the diamonds are largely eclogitic 64 followed by peridotitic 25 and ultradeep 11 the paragenetic abundances are similar to macrodiamonds from the do27 kimberlite davies r m griffin w l o reilly s y 1999 diamonds from the deep pipe do27 slave craton canada in gurney j j gurney j l pascoe m d richardson s h eds the j b dawson vol proc 7th internat kimberlite conf red roof designs cape town pp 148 155 but differ to diamonds from nearby kimberlites at ekati e g lithos 2004 tappert r stachel t harris j w brey g p 2004 mineral inclusions in diamonds from the panda kimberlite s p canada 8th international kimberlite conference extended abstracts and snap lake to the south dokl earth sci 380 7 2001 806 that are dominated by peridotitic stones eclogitic diamonds with variable inclusion compositions and temperatures of formation 1040 1300 c crystallised at variable lithospheric depths sometimes in changing chemical environments a large range to very 13c depleted c isotope compositions 13c 35 8 to 2 2 and an nmorb bulk composition calculated from trace elements in garnet and clinopyroxene inclusions are consistent with an origin from subducted oceanic crust and sediments carbon isotopes in the peridotitic diamonds have mantle compositions 13c mode 4 0 mineral inclusion compositions are largely harzburgitic variable temperatures of formation garnet tni 800 1300 c suggest the peridotitic diamonds originate from the shallow ultra depleted and deeper less depleted layers of the central slave lithosphere carbon isotopes 13c av 5 1 and mineral inclusions in the ultradeep diamonds suggest they formed in peridotitic mantle 670 km the diamonds may have been entrained in a plume and subcreted to the base of the central slave lithosphere poorly aggregated nitrogen iaa without platelets in a large number of eclogitic 67 and peridotitic 32 diamonds with similar nitrogen contents indicates the diamonds were stored in the mantle at low temperatures 1060 1100 c following crystallisation in the archean type iaa diamonds have largely cubo octahedral growth forms and type ii and type iaab diamonds with higher nitrogen aggregation states mostly have octahedral morphologies however no correlation between these groups and their mineral inclusion compositions c isotopes and n contents rules out the possibility of unique source origins and suggests eclogitic and peridotitic diamonds experienced variable mantle thermal states variation in mineral inclusion chemistries in single diamonds possible overgrowths of 13c depleted eclogitic diamond on diamonds with peridotitic and ultradeep inclusions and type i ultradeep diamond with low n aggregation is consistent with diamond growth over time in changing chemical environments

eclogitic inclusions in diamonds evidence of complex mantle processes over time the first ion probe trace element analyses of clinopyroxene garnet pairs both included within diamonds and from the eclogite host xenoliths are reported these diamondiferous eclogites are from the udachnaya and mir kimberlite pipes yakutia russia the major and trace element analyses of these diamond inclusion and host rock pairs are compared in order to determine the relative ages of the diamonds confirm or deny genetic relationships between the diamonds and the eclogites evaluate models of eclogite petrogenesis and model igneous processes in the mantle before during and after diamond formation the most striking aspect of the chemical compositions of the diamond inclusions is the diversity of relationships with their eclogite hosts no single distinct pattern of variation from diamond inclusion minerals to host minerals is found for all four samples garnet and clinopyroxene inclusions in the diamonds from two samples u 65 3 and u 66 3 have lower mg s lower mg and higher fe contents and lower lree than those in the host eclogite we interpret such variations as due to metasomatism of the host eclogite after diamond formation one sample u 41 3 shows enrichment in diamond inclusion mree enrichment relative to the eclogite host and may indicate a metasomatic event prior to or during diamond formation bulanova 2 found striking differences between inclusions taken from within different portions of the very same diamond clinopyroxene inclusions taken from the central early portions of yakutian diamonds were lower in mg and mg contents by up to 25 than those later inclusions at the rims of diamonds these trends are parallel to those between diamond inclusions and host eclogites determined for four of the five samples from the present study and may merely represent changing magmatic and or p t conditions in the mantle garnet trace element compositions are similar in relative proportions but variable in abundances between diamond inclusions and host eclogites this is probably due to the rapid diffusion of trace elements in garnet under mantle temperatures and consequent alteration of the garnet and not due to juvenile diamonds locking in source heterogeneities c f 3 trace element compositions of clinopyroxenes included in diamonds are generally similar to those in the host eclogite however one host clinopyroxene does show enrichment in the lree compared to that in the inclusion and may be attributed to mantle metasomatism not related to kimberlite transport in another eclogite m 46 the host clinopyroxene is depleted in the lree and fe and enriched in the hree and mg relative to the inclusion and is consistent with partial melting of the eclogite subsequent to diamond formation smnd ratios in clinopyroxenes appear to be little affected by these processes for most samples allowing sm nd isotopic studies to yield important information about ancient protoliths eclogitic mineral inclusions in yakutian diamonds appear consanguineous with the diamonds a contention supported by the observations of bulanova 2 therefore re os whole rock and smnd clinopyroxene age determinations of the udachnaya eclogites also yield the time of diamond formation approximately 2 9 ga 32 33

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

stability of clinopyroxene at pressure temperature conditions of the transition region abstract the stability of diopside at conditions of 16 19 gpa and 1250 1900 c was determined using a 6 8 type multi anvil apparatus at pressures of 17 18 gpa diopside undergoes a decomposition reaction to an assemblage of casio3 perovskite ca mg sio3 garnet or ilmenite depending on temperature the clapeyron slope for the breakdown reaction download download full size image is 2 mpa k 1 when coupled with a re examination of clinopyroxene stability in other more complex peridotite systems the experimental data are consistent with a recent proposal that the 520 km discontinuity in the transition region is caused by the exsolution of casio3 rich perovskite from garnet rich in majorite component

inversion tectonics and the evolution of the high atlas mountains morocco based on a geological geophysical transect an edited version of this paper was published by the american geophysical union agu copyright 1998 agu see also http www agu org pubs crossref 1999 1998tc900015 shtml http atlas geo cornell edu morocco publications beauchamp1999 htm

lithoprobe s impact on the canadian diamond exploration industrythis article is one of a series of papers published in this special issue on the theme lithoprobe parameters processes and the evolution of a continent earth sciences sector contribution 20070261 lithoprobe contribution 1479 lithoprobe aided and will continue to guide diamond exploration in canada via a number of diverse ways and at scales from cratons to individual ore bodies specific transects outlined the domainal nature geometry and age relations of crust subjacent mantle and diamond bearing roots in unusually rich detail for cratonic settings such as those of the superior and slave cratons as well as pericratonic shield settings such as those of the sask craton and buffalo hills terrane the superior and slave examples of craton construction by multiple underthrust layers as inferred from structural geometries observed in lithoprobe seismic and magnetotelluric surveys remain the clearest resolved to date the first definition of the sask craton occurred 10 15 years ago and helped fuel the diamond industry s ongoing revision of clifford s rule for exploration so as to include targets in proterozoic shield settings main lithoprobe transect results and supporting geoscience studies have helped to demonstrate the

recycling of crustal materials through study of ultrahigh pressure minerals in collisional orogens ophiolites and mantle xenoliths a review abstract newly recognized occurrences of ultrahigh pressure uh p minerals including diamonds in ultrahigh temperature uh t felsic granulites of orogenic belts in chromitites associated with ophiolitic complexes and in mantle xenoliths suggest the recycling of crustal materials through deep subduction mantle upwelling and return to the earth s surface this circulation process is supported by crust derived mineral inclusions in deep seated zircons chromites and diamonds from collision type orogens from eclogitic xenoliths in kimberlites and from chromitities of several alpine himalayan and polar ural ophiolites some of these minerals contain low atomic number elements typified by crustal isotopic signatures ophiolite type diamonds in placer deposits and as inclusions in chromitites together with numerous highly reduced minerals and alloys appear to have formed near the mantle transition zone in addition to ringwoodite and inferred stishovite a number of nanometric minerals have been identified as inclusions employing state of the art analytical tools reconstitution of now exsolved precursor uh p phases and recognition of subtle decompression microstructures produced during exhumation reflect earlier uh p conditions for example tibetan chromites containing exsolution lamellae of coesite diopside suggest that the original chromitites formed at p 9 10 gpa at depths of 250 300 km the precursor phase most likely had a ca ferrite or a ca titanite structure both are polymorphs of chromite and at 2000 c would have formed at minimum pressures of p 12 5 or 20 gpa respectively some podiform chromitites and host peridotites contain rare minerals of undoubted crustal origin including zircon feldspars garnet kyanite andalusite quartz and rutile the zircons possess much older u pb ages than the time of ophiolite formation these uh p mineral bearing chromitite hosts evidently had a deep seated evolution prior to extensional mantle upwelling and partial melting at shallow depths to form the overlying ophiolite complexes these new findings together with stable isotopic and inclusion characteristics of diamonds provide compelling evidence for profound underflow of both oceanic and continental lithosphere recycling of surface organic carbon into the lower mantle and ascent to the earth s surface through mantle upwelling intensified study of uh p granulite facies lower crustal basement and ophiolitic chromitites should allow a better understanding of the geodynamics of subduction and crustal cycling

on origin of lower mantle diamonds and their primary inclusions abstract knowledge of mineralogy and petrology of unattainable lower mantle material is usually founded on high pressure experiments with pyrolite in situ material and oceanic morb basalt subducted material primary inclusions in transition zone and lower mantle super deep diamonds represent heterogeneous fragments of diamond parental medium not the unaltered lower mantle material inclusions of magnesiowustite and stishovite intergrowths stishovite paradox give experimentally supported evidence that stishovite similarly to magnesiowustite is not subducted but in situ lower mantle mineral primary ca mg na carbonate inclusions are symptomatic for multicomponent carbonatite carbonate oxide silicate parental melts for the lower mantle diamonds and inclusions we investigated melting phase relations of simple carbonates of ca mg na and multicomponent mg fe na carbonate up to 60 gpa and 3500 4000 k using multianvil press and diamond anvil cell with laser heating and determined a congruent melting of the carbonates and stability of pt extended phase fields of the carbonate melts super deep diamonds are experimentally crystallized in melts of the lower mantle diamond parental carbonate magnesiowustite mg perovskite carbon system based on experimental and mineralogical evidence for the lower mantle diamonds inclusions genetic links between diamonds and inclusions are determined and a generalized composition diagram of parental media for lower mantle diamonds and inclusions is constructed

an investigation of composite dropsonde profiles for developing and nondeveloping tropical waves during the 2010 predict field campaign abstractcomposite dropsonde profiles are analyzed for developing and nondeveloping tropical waves in an attempt to improve the understanding of tropical cyclogenesis these tropical waves were sampled by 25 reconnaissance missions during the 2010 pre depression investigation of cloud systems in the tropics predict field campaign comparisons are made between mean profiles of temperature mixing ratio relative humidity radial and tangential winds relative vorticity and virtual convective available potential energy cape for genesis and nongenesis cases genesis soundings are further analyzed in temporal progression to investigate whether significant changes in the thermodynamic or wind fields occur during the transition from tropical wave to tropical cyclone significant results include the development of positive temperature anomalies from 500 to 200 hpa 2 days prior to genesis in developing waves this is not observed in the nongenesis mean progressive mesoscale moistening of the column is observe

transtensive synsedimentary tectonics associated with ocean opening the essaouira agadir segment of the moroccan atlantic margin the mesozoic cenozoic sedimentary sequences of the agadir essaouira region were studied by field observations in the onshore basin and offshore by seismic profiles and borehole data during the late jurassic and the early cretaceous they were frequently disturbed by repeated synsedimentary tectonic instability extensively demonstrated by structures such as slumps breccias faults etc regionally these movements led to the initiation of ridges in some cases diapiric as well as depocentres these are mainly n 70 e to e w trending contemporaneously with a slight tectonic inversion of some of the offshore half grabens the late jurassic cretaceous regional deformation converted the synsedimentary ridges to anticlines and the depocentres to synclines before the latest atlasic orogenic uplift during the cenozoic this structural evolution distinguishes the agadir essaouira segment from other parts of the atlantic margin of morocco it results from an interference between the n20 e oriented passive margin of morocco and the n70 e oriented atlasic zone the latter acted as a transform zone during late jurassic early cretaceous times and then suffered a n s compression during the atlasic orogeny

the crustal structure of the nw moroccan continental margin from wide angle and reflection seismic data summary the atlantic margin off morocco with its neighbouring jurassic oceanic crust is one of the oldest on earth it is conjugate to the nova scotia margin of north america the sismar marine seismic survey acquired deep reflection seismic data as well as wide angle seismic profiles in order to image the deep structure of the margin characterize the nature of the crust in the transitional domain and define the geometry of the synrift basins we present results from the combined interpretation of the reflection seismic wide angle seismic and gravity data along a 440 km long profile perpendicular to the margin at 33 34 n extending from nearly normal oceanic crust in the vicinity of coral patch seamount to the coast at el jadida and approximately 130 km inland the shallow structure is well imaged by the reflection seismic data and shows a thick sedimentary cover that is locally perturbed by salt tectonics and reverse faulting the sedimentary basin thickens from 1 5 km on the normal oceanic crust to a maximum thickness of 6 km at the base of the continental slope multichannel seismic mcs data image basement structures including a few tilted fault blocks and a transition zone to a thin crust a strong discontinuous reflection at 12 s two way travel time twt is interpreted as the moho discontinuity as a result of the good data quality the deep crustal structure depth and velocity field is well constrained through the wide angle seismic modelling the crust thins from 35 km underneath the continent to approximately 7 km at the western end of the profile the transitional region has a width of 150 km crustal velocities are lowest at the continental slope probably as a result of faulting and fracturing of the upper crust uppermantle velocities could be well defined from the ocean bottom seismometer obs and land station data throughout the model

archean diamonds from wawa canada samples from deep cratonic roots predating cratonization of the superior province with an age of ca 2 7 ga greenschist facies volcaniclastic rocks and lamprophyre dikes in the wawa area superior craton host the only diamonds emplaced in the archean available for study today nitrogen aggregation in wawa diamonds ranges from type iaa to iab suggesting mantle residence times of tens to hundreds of millions of years the carbon isotopic composition 13c of cube diamonds is similar to the accepted mantle value 5 0 octahedral diamonds show a slight shift by 1 5 to isotopically less negative values suggesting a subduction derived isotopically heavy component in the diamond forming fluids syngenetic inclusions in wawa diamonds are exclusively peridotitic and similar to many diamond occurrences worldwide are dominated by the harzburgitic paragenesis compositionally they provide a perfect match to inclusions from diamonds with isotopically dated paleo to mesoarchean crystallization ages several high cr harzburgitic garnet inclusions contain a small majorite component suggesting crystallization at depth of up to 300 km combining diamond and inclusion data indicates that wawa diamonds formed and resided in a very thick package of chemically depleted lithospheric mantle that predates stabilization of the superior craton if late granite blooms are interpreted as final stages of cratonization then a similar disconnect between paleo to mesoarchean diamondiferous mantle lithosphere and neoarchean cratonization is also apparent in other areas e g the lac de gras area of the slave craton and may suggest that early continental nuclei formed and retained their own diamondiferous roots

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

the application of c isotope measurements to the identification of the sources of c in diamonds a review abstract in the past decade the isotopic compositions of c in 600 inclusion bearing diamonds have been determined such analyses have revealed the following isotopic characteristics 1 peridotitic diamonds which typically contain garnet chromite olivine and or orthopyroxene inclusions with refractory compositions high mg cr have 13 c values predominantly between 10 and 1 with a sharp peak in the distribution near 5 2 eclogitic diamonds which commonly contain inclusions of omphacitic clinopyroxene cr poor pyrope and or eclogitic accessory minerals such as rutile kyanite coesite or sanidine have 13 c values between 34 and 3 with a smaller peak near 5 3 the isotopic compositions obtained for suites of diamonds from individual occurrences are in general unique and do not resemble the range and distribution obtained by amalgamating the diamond isotope data from a number of localities 4 isotopic zoning patterns and heterogeneities are found in some diamonds cores of coated diamonds tend to be depleted in 13 c relative to the rims and within single octahedral diamonds 13 c variations of nearly 6 have been reported because expected c isotope fractionations at mantle temperatures are small attempts to model the full range of diamond isotope values through fractionating a homogeneous mantle c source have been unsuccessful nevertheless fractionation is probably responsible for some of the observed variation in 13 c values two other models have also been proposed to account for the diamond characteristics outlined above the primordial model suggests that the range and distribution of c isotope compositions are inherited from primordial c in the mantle which has an inhomogeneous isotopic composition such as that found in meteorites the subduction model suggests that subducted crustal c is the source of c in diamonds as organic and inorganic c compounds in the crust exhibit a range of 13 c values similar to that observed in diamonds this paper reviews the c isotope characteristics of diamonds and compares the models which have been proposed to explain the origins of these characteristics

crust mantle coupling revisited the archean slave craton nwt canada abstract lithospheric domains in the slave province inferred from regional variations in chemistry of mantle derived garnets are parallel with northeasterly structural trends in neoarchean surface rocks and were used previously to infer late neoarchean crust mantle coupling and argue against the presence of diamondiferous mesoarchean lithosphere under the western slave craton prior to its late neoarchean orogenic climax a review of more recent evidence does not support this view but concludes that a mesoarchean lithospheric root was coupled to mesoarchean crust of the central slave superterrane csst prior to accretion of adjacent juvenile neoarchean terranes a significant part of this root survived the neoarchean break up of the csst neoarchean terrane accretion and a complex sequence of post accretion deformation granitoid plutonism and metamorphism it was least modified in the ultra depleted harzburgitic layer udl under the central part of the contwoyto terrane where it is trapped above the deepest part of an underplated paleoproterozoic slab which stabilized the remnants of the archean root and caused downward younging of the lithosphere upper mantle domains recognized on the basis of the distribution of peridotitic garnets are not primary neoarchean features but were either inherited from the original mesoarchean root or resulted from neoarchean and paleoproterozoic tectonic erosion and or metasomatism of this root the slave province resembles other diamondiferous cratons in that its diamond endowment consists of both mesoarchean and paleoproterozoic stones

hydrocarbon generation in the essaouira basin of western morocco the essaouira basin is an important onshore hydrocarbon generating basin in western morocco there are seven producing or shut in oil and gas fields six produce from jurassic and one from triassic reservoirs basin modeling and geochemical evidence suggest that hydrocarbon generation occurred from at least two source rocks 1 jurassic oxfordian shale accumulated within the neknafa syncline and 2 deeply buried carboniferous coals underlying the eastern basin area the oxfordian shale was sufficiently buried in western essaouira to generate voluminous gas and condensate liquids and to expel them into structurally closed jurassic reservoirs toukimt field or offset horst block triassic reservoirs meskala field geochemical evidence suggests that the jurassic age reservoirs across the eastern essaouira basin host commingled gases sourced from jurassic and carboniferous strata coal methane generated from a deeply buried carboniferous interval may have been the main source for the astern essaouira basin traps developed as structures draping salt domes at junctions of offset transtensive faults

the hydrocarbon systems of north africa abstract north africa s hydrocarbon reserves are spread over a wide range of reservoirs and play types but derive from only a few key source rock intervals particularly those in the silurian late cretacous and eocene source rock maturity together with the timing of the generation relative to trap forming and destructive events seem to be the key controlling factors on success or failure at a basin level in most cases generation clearly post dates trap formation although a more complex relationship is evident in various parts of algeria where some traps did not form until gas was being generated source rock deposition and maturation can be tied to two main extensional tectonic cycles which ended in the compressional and destructive events of the hercynian and alpine orogenies remaining exploration potential in mature provinces may be tied largely to subtle and stratigraphic traps in addition significant frontier potential can be identified in two main fairways corresponding to regions where silurian devonian and cretaceous eocene sources respectively are likely to have generated petroleum critical factors in these areas are timing of generation and preservation the gas discoveries in the ahnet basin provide analogues for palaeozoic generation preservation models in the interior silurian devonian source fairway similarly the key to success for the mesozoic basins of the atlas region lies in demonstrating a favourable relationship between trap formation destruction and generation from late cretaceous and eocene source rocks

rift controlled fluvial tidal transitional series in the oukai meden sandstones high atlas of marrakesh morocco abstract the carnian formation of the oukai meden sandstones was deposited in the northwestern corner of the african craton along tectonic troughs grouped as a wsw ene rift system on the southwestern margin of the tethys red sandstones represent mainly distal braided stream deposits where very extensive sand flats with 3d dunes 2d sand waves and high regime horizontally laminated sandstones predominate the similarities in orientation between current patterns and trough border faulting the sudden large variations in the thickness of deposits and the occurrence of lateral alluvial fans along the marginal faults are all evidence of the tectonic control of sedimentation the middle part of this clastic continental rift series includes finer facies containing marine reworked or in situ fossils and tracks as well as sedimentary structures interpreted as being of tidal origin especially overlapping s shaped sets the episodic marine influxes that occur within these continental rift deposits are thought to result from the substantial downdropping of tectonic blocks and the drowning of fluviatile facies by the peritethyan marine domain to the northeast the development of marine facies was of relatively short duration and figures little in the sedimentary record butit is evidence of the earliest mesozoic onlaps of the tethys over the african craton in a carnian rift

mass balance simulation and principal components analysis applied to groundwater resources essaouira basin morocco the water resources of the essaouira coastal basin west of marrakesh are characteristic of a semi arid climate and are severely impacted by the climate in terms of quantity and quality considering the importance of the essaouira aquifer in the groundwater supply of a vast region nearly 1 200 km2 a research study was conducted in order to better understand groundwater evolution in this aquifer system it is a coastal aquifer located on the atlantic coastline southern morocco and salinization problems have been reported covering the palaeozoic bedrock the sedimentary series range from the triassic to the quaternary besides the possibility of seawater intrusion problems the geological structures delineate a syncline bordered by the tidzi diapir of triassic age outcropping to the east and south this is a recharge area for the aquifer whereas the main groundwater flow direction is from se to nw towards the atlantic ocean in spite of the occurrence of calcareous and dolomitic levels all waters in the essaouira basin are of the na cl type based on a range of experimental methodologies combined with pca and geochemical modelling it was possible to identify the mineralization processes occurring in the groundwater system and the importance of the water rock interaction in the water chemistry scenarios were tested using a simple mass balance model through the phreeqc programme the reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters an important contribution of water rock interaction in groundwater mineralization was found corroborating the influence of preferential recharge from the tidzi diapir in the water s signature anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future in a country with scarce water resources

a spatial filter approach to evaluating the role of convection on the evolution of a mesoscale vortex abstracta new spatial filter is proposed that exploits a spectral gap in power between the convective scale and the system vortex scale during tropical cyclone tc genesis simulations using this spatial separation this study analyzes idealized three dimensional numerical simulations of deep moist convection in the presence of a symmetric midlevel vortex to quantify and understand the energy cascade between the objectively defined convective scale and system scale during the early stages of tropical cyclogenesis the simulations neglect surface momentum heat and moisture fluxes to focus on generation and enhancement of vorticity within the interior to more completely close off the energy budget and to be consistent for comparison with prior benchmark studies of modeled tc genesis the primary contribution to system scale intensification comes from the convergence of convective scale vorticity that is supplied by vortical hot towers vhts they contribute more than the convergence of system scale v

observational analysis of tropical cyclogenesis in the western north pacific part i structural evolution of cloud clusters abstract this paper is the first of a two part series summarizing recent attempts to advance omit understanding of the physical processes associated with tropical cyclone formation in the western north pacific a combination of rawinsonde composite and individual case analyses are shown for both pre cyclone tropical cloud clusters genesis and those prominent cloud cluster that do not develop into tropical cyclones nongenesis this research is an extension of previous works at colorado state university by mcbride zehr and love the first part of the study concerns the structural evolution of the genesis cloud clusters and nongenesis cloud clusters results show that nongenesis cloud clusters have about the same mean vertical motion and cumulus activity as the genesis cloud clusters however genesis cloud clusters are found to have much stronger middle to low level cyclonic circulation extending over a radius 2 8 outward from the center the buildup of this strong precyclogenesis circulation is ass

inclusions in diamonds from the k14 and k10 kimberlites buffalo hills alberta canada diamond growth in a plume analyses of mineral inclusions carbon isotopes nitrogen contents and nitrogen aggregation states in 29 diamonds from two buffalo hills kimberlites in northern alberta canada were conducted from 25 inclusion bearing diamonds the following paragenetic abundances were found peridotitic 48 eclogitic 32 eclogitic websteritic 8 websteritic 4 ultradeep 4 and unknown 4 diamonds containing mineral inclusions of ferropericlase and mixed eclogitic asthenosphericwebsteritic and eclogitic websteritic mineral associations suggests the possibility of diamond growth over a range of depths and in a variety of mantle environments lithosphere asthenosphere and possibly lower mantle eclogitic diamonds have a broad range of c isotopic composition d 13 c y21 x to y5x peridotitic websteritic and ultradeep diamonds have typical mantle c isotope values d 13 c y4 9 x av except for two 13 c depleted peridotitic d 13 c y11 8 x y14 6 x and one 13 c depleted websteritic diamond d 13 c y11 9 x infrared spectra from 29 diamonds identified two diamond groups 75 are nitrogen free type ii or have fully aggregated nitrogen defects type iab with platelet degradation and low to moderate nitrogen contents av 330 ppm n 25 have lower nitrogen aggregation states and higher nitrogen contents f30 iab 1600 ppm n the combined evidence suggests two generations of diamond growth type ii and type iab diamonds with ultradeep peridotitic eclogitic and websteritic inclusions crystallised from eclogitic and peridotitic rocks while moving in a dynamic environment from the asthenosphere and possibly the lower mantle to the base of the lithosphere mechanisms for diamond movement through the mantle could be by mantle convection or an ascending plume the interaction of partial melts with eclogitic and peridotitic lithologies may have produced the intermediate websteritic inclusion compositions and can explain diamondsofmixedparageneses andtheoverlapinc isotopevaluesbetweenparageneses strongdeformationandextremelyhigh nitrogen aggregation states in some diamonds may indicate high mantle storage temperatures and strain in the diamond growth environment a second diamond group with type iaa iab nitrogen aggregation and peridotitic inclusions crystallised at the base of the cratonic lithosphere all diamonds were subsequently sampled by kimberlites and transported to the earth s surface crown copyright d 2004 published by elsevier b v all rights reserved

controls on the stratigraphic development of the triassic fundy basin nova scotia implications for the tectonostratigraphic evolution of triassic atlantic rift basins abstract the late triassic synrift succession of the minas sub basin bay of fundy nova scotia includes a fluvio alluvial fan dominated unit lower and middle wolfville formation a transitional fluvio playa unit upper wolfville formation and an upper playa dominated package blomidon formation we describe the facies development in the 240 m thick upper wolfville formation examine vertical facies stacking patterns and develop a depositional model for this succession the unit comprises channelized and unconfined fluvial deposits interbedded with aeolian and playa sediments that grade upward into playa deposits the succession comprises progradational and retrogradational fluvial packages and thin aggradational playa claystones comparison with 11 other atlantic margin continental triassic rift basins allows an assessment of the controls that govern rift basin development the transition from fluvial to playa or lacustrine conditions occurs in all basins at different times the lack of synchronicity indicates that global climate change was not a controlling factor we suggest that the fluvial to lacustrine or playa transition was due to a decrease in source area relief related to a decline in regional tectonic activity and that the basin was hydrologically closed throughout sedimentation this tectonostratigraphic model may be appropriate for other triassic basins developed along the atlantic margin

mid triassic to early liassic clastic evaporitic deposits over the maghreb platform abstract the development of triassic to lower liassic clastic evaporitic series over the epicratonic maghreb platform is closely associated with the eastern opening of a tethyan marine domain between africa and europe west of the platform morocco became separated from north america in late triassic times by rifting along the axis of the proto atlantic ocean in addition ne sw and ene wsw trending atlasic half grabens formed essentially in morocco as part of a late triassic early liassic atlas rifting episode this is the tectonic context in which the red bed to evaporite sequences were deposited a first depositional pattern is illustrated by the areally extensive onlapping of upper triassic clastic evaporitic series over the algerian saharan platform from the carnian to the norian distal mudflats and evaporites graded westward i e landward into proximal fluvial facies seven stratigraphic cycles formed part of a general base level rise of a major retrogradational clastic to evaporitic cycle indicative of general tectonic subsidence of the algerian platform as a whole the evaporites are thus interpreted as markers of persistent onlapping occurring at the edge of the basin as clastic influxes gradually diminished a second depositional pattern is provided by ladinian to rhaetian clastic evaporitic carbonate transgressive sequences of the atlasic domain in tunisia these terminate characteristically in marine facies in this domain intense tectonic activity was consistently offset by a high rate of evaporitic or clastic sedimentation in shallow water environments a third depositional pattern is illustrated in the moroccan high atlas in the central part of this range carnian red conglomerates and sheet like sandstones of a distal braided fluvial plain were deposited in tectonic troughs that linked together as part of a rift system episodic connections occurred with the tethyan domain to the northeast in the western high atlas an upper carnian norian sequence several hundred meters thick displays a general trend from clastics to evaporites reflecting the development of arid paleoclimatic conditions the moroccan meseta provides examples of clastic evaporitic depositional patterns within intracratonic troughs clastic filling of rift induced troughs in the oujda mountains exhibits significant facies and thickness variations ranging from local proximal alluvial and distal anastomosed channel systems through to dominant mudflat systems in the 1000 m thick series of the 60 km long khemisset basin facies range from red beds located mainly along the basin margins to salt dominated deposits in the basin center increasing accommodation controlled the deposition of evaporites and the maximum flooding surface is to be found in typical halite deposits with interbedded bands of clays at that time greater tectonic subsidence rates allowed more marked episodic marine incursions clastic evaporitic series from the passive margin of the moroccan atlantic coast are known only from bore holes and onshore and offshore seismic data recent papers have reported interesting sections across strongly subsiding grabens or tilted blocks related to predominantly ssw nne faults

syn and postrift evolution of the el jadida agadir basin morocco constraints for the rifting models of the central atlantic the el jadida agadir basin shows an evolution related to that of the central atlantic rifting history the synrift period late early triassic to earliest jurassic is dominated by deposition of red clastic sediments and evaporites which are overlain by or intercalated with basalt flows two intense extensional phases are recognized the first probably in middle triassic times is oriented north northwest south southeast and resulted in the formation of east northeast west southwest oriented grabens and half grabens the second a widespread northwest southeast trending extension is ladinian to earliest liassic and induced the formation of westward dipping half grabens extensional tectonics initiated in the southern part of the basin and migrated northwards contrary to classical ideas proposing rifting from north to south the postrift evolution is characterized by jurassic to eocene subsidence tectonism appears to have been restricted to a narrow area close to the present day coast subsidence h

a sedimentological model for the continental upper triassic tadrart ouadou sandstone member recording an interplay of climate and tectonics argana valley south west morocco the continental upper triassic tadrart ouadou sandstone member was deposited in an extensional setting on the pangaean continent strongly influenced by a low latitude climatic regime 10 to 20 north complex interaction of basin subsidence and climatically driven processes led to high facies variability and a lack of correlatable units across the argana valley exposures a process orientated approach integrating detailed facies with architectural element analysis was undertaken which resulted in a multistage depositional model for the tadrart ouadou sandstone member the basin scale model shows that basal alluvial fan and braided river systems are confined to the centre of the argana valley exposures aeolian deposits occur throughout the sequence but dominate in the north after a phase of playa deposition prominent basin wide fluvial incision of up to 8 m marks the onset of perennial fluvial flow these well sorted internally complex and locally highly amalgamated fluvial sandstones are widespread throughout the basin and are focused in a north to south south west flowing channel system after a final stage of aeolian sedimentation sandstone deposition of the tadrart ouadou sandstone member in the argana valley is terminated rapidly by the onlap of lacustrine mudstones of the sidi mansour member the study revealed that except for one pronounced period of perennial conditions sedimentation is controlled largely by ephemeral fluvial flow alternating ground water tables deflation processes and periods with limited periodic local run off the study highlights that facies architecture in the basin is the result of complex interaction of local syn sedimentary tectonics and the climatic regime within the basin but also the climate of the catchment area to the east the data suggest a proximal to mid distal basin setting in the rain shadow to the west of a mountain range massif ancien which exerted a strong control on the depositional environments of triassic deposits exposed in this part of south west morocco

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere