spectrophotometry of zonal cloud structure variations on jupiter 1988 1993 global changes of zonal cloud structure on jupiter have been observed and analyzed from data obtained with a 1 m telescope and a low dispersion spectrograph in the spectral range 400 680 nm and with a 70 cm telescope and planetary three channel spectrometer in the spectral range 320 1100 nm during each jovian apparition from 1988 to 1992 variations of the observed meridional intensity profiles and relative spectrophotometric gradients are described as well as the changes of absolute spectral reflectivity of five main belts on jupiter north and south equatorial belts north and south tropical zones and equatorial region

genesis of autochthonous and allochthonous apulian karst bauxites southern italy climate constraints abstract the apulian carbonate platform acp in southern italy has experienced several episodes of subaerial exposure which were in some cases associated with the formation of karst bauxite deposits the acp contains both autochthonous canyon like bauxite and allochthonous salento type bauxite with the latter having been derived from a weathered and eroded pristine bauxite deposit the remnants of this pristine bauxite are preserved as transported pebbles embedded in a clayey matrix the autochthonous bauxite and the pebbles of the allochthonous bauxite have the same texture of sub spheroidal components ooids dispersed in a fine grained matrix the fractal dimension of ooids from both deposits is very similar and corresponds to the growth of aggregates under a diffusion controlled process the ooids of the autochthonous bauxite have a different composition to those in the pebbles of the allochthonous bauxite because they formed under different climatic conditions during the turonian autochthonous bauxite ooids formed in alternating wet tropical conditions promoting al hematite formation and drier conditions favouring boehmite stability in the allochthonous pebbles ooids formed mainly in a dry climate promoting the formation of large boehmite cores the ooids matrix ratio and the geometrical features of the ooids reflect these climate differences the differences in composition and age post turonian of the salento type bauxite bedrock suggest that the pristine bauxite that produced the salento type pebbles was different in composition to and younger in age than the canyon like bauxite the latter probably formed during a middle campanian emersion event evidenced by large karstic cavities which is correlated with the subaerial exposure of karst recorded on the adriatic island of brac

geological geochemical and mineralogical characteristics of the mandan and deh now bauxite deposits zagros fold belt iran the mandan and deh now bauxite deposits are located 40 km northeast of the dehdasht city in the zagros simply fold belt these deposits occur in eroded major nw se trending anticlines and occupy karst cavities near or at the boundary between the sarvak and ilam formations local uplifts at the end of the cenomanian and the mid turonian caused erosion and karstification of the sarvak formation these unconformities in the upper cretaceous favoured the formation and enrichment of bauxite deposits in the zagros fold belt the bauxite sequence in the mandan deposit consists of white gray black pisolitic red and yellow bauxites this sequence was repeated in the deh now area but without gray and black bauxites the present mineralogical studies of the sarvak formation and the mandan and deh now bauxite deposits indicate oxidizing to reducing conditions during the upper cretaceous in the zagros fold belt which had a significant effect on the compositions of the bauxites at least two phases of bauxitization can be distinguished in the study area i an oxidizing phase represented by boehmite diaspore hematite and kaolinite and ii a reducing phase represented by pyrite and chlorite geochemical data show that trace elements like zr hf nb ta th and u were enriched during bauxitization the bauxite deposits and carbonate rocks show similar ree patterns namely they are enriched in rees although the lrees are more enriched than the hrees mass change calculations demonstrate that mg mn ca k and p2o5 were leached out of the weathered system whereas al fe and si become concentrated in the residual system this study indicates that the mandan and deh now deposits are karst type bauxites formed by karstification and weathering of the sarvak formation

mapping potential vorticity dynamics on jupiter i zonal mean circulation from cassini and voyager 1 data maps of ertel potential vorticity on isentropic surfaces ipv and or quasi geostrophic potential vorticity qgpv are well established in dynamical meteorology as powerful sources of insight into dynamical processes involving balanced flow in the present study we derive maps of zonal mean ipv and qgpv in jupiter s upper troposphere and lower stratosphere by making use of a combination of velocity measurements derived from the tracking of cloud features in images from the voyager 1 and 2 and cassini missions and thermal measurements from the voyager 1 iris and cassini cirs instruments ipv and qgpv are mapped and compared for the entire globe between latitudes 55 profiles of zonally averaged pv show some evidence for a step like pattern suggestive of local pv homogenization separated by strong pv gradients in association with eastward jets though on differing scales in the northern and southern hemispheres the northward gradient of pv ipv or qgpv is found to change sign in several places in each hemisphere even when baroclinic contributions are taken into account the relationship of lateral gradients of ipv and qgpv with the corresponding mean zonal flows indicate that the northern hemisphere may be closer to marginal stability with respect to arnol d s second stability theorem than the southern hemisphere copyright 2006 royal meteorological society

mineralogical characteristics of the karstic bauxite deposits in the xiuwen ore belt central guizhou province southwest china abstract the karstic bauxite deposits in the xiuwen ore belt of central guizhou province are hosted by the lower carboniferous jiujialu formation and show parallel unconformity with the overlying and underlying strata the ore bearing rock series that exhibits a typical coal bauxite iron structure is divided into three segments from the bottom upward namely an iron layer a bauxite layer and a coal layer based on the textural features and iron abundances the bauxite ores occurring in the middle segments are divided into three types of ores clastic compact and high iron the bauxite ores primarily comprise diaspore boehmite kaolinite illite and hematite with minor zircon pyrite rutile and feldspar the existence of rutile within diaspore lumps which were inherited from laterization suggests that diaspore was transformed from gibbsite and that karstic bauxite was transformed from laterite bauxite the results of x ray diffraction xrd scanning electron microscopy sem and electron probe x ray microanalyses epma suggest that diaspore and boehmite differ with regard to appearance and element abundance diaspore 2 10 m displays short prismatic or platy shapes and contains low sio2 abundances ranges from 0 2 to 0 51 wt whereas boehmite 0 2 5 m exhibits granular or irregular shapes and contains high contents of sio2 that vary between 2 71 and 10 4 wt the fe cu pb zn ba sulfide and sulfate mineral assemblages associated with cryptocrystalline kaolinites are discovered in the xiaoshanba deposit from the xiuwen ore belt mineralogical and geochemical studies reveal that the genesis of these assemblages is controlled by the decomposition processes of organic matter and the activities of microorganisms within the ore bearing rock series geochemical data suggest that elements rich in high organic cryptocrystalline kaolinite are produced from the adsorption effect of organic matter whereas the low concentration of these elements in pure kaolinite can be attributed to the scavenging effect during kaolinite crystallization in addition coexisting organic matter cryptocrystalline kaolinite and sulfide and sulfate minerals see sample xsb 14 indicate that the forming environment of the bauxite was hot humid tropical or subtropical climates

karst bauxite deposits in the zagros mountain belt iran more than 190 occurrences of bauxitic lateritic deposits were investigated in seven areas within the zagros simply folded mountain belt in southwestern of iran the bauxitic horizons are situated in eroded major nw se trending anticlines and occur in karst cavities near or at the boundary between the sarvak and ilam formations uplift in the cenomanian turanian period had exposed the sarvak limestone to karst weathering and during a period of unconformity layers of ferruginous argillaceous limestone debris developed and accumulated on its surface the ferruginous argillaceous debris was partly converted to bauxite folding and faulting in oligocene miocene time with ensuing erosion exposed the bauxitic horizons on the limbs and cores of anticlines the karst bauxite deposits are probably of authigenic origin as evidenced by their lithologic associations textural and mineralogy

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

terrestrial deposition processes of quaternary gibbsite nodules in the yongjiang basin southeastern margin of tibet and implication for the genesis of ancient karst bauxite abstract the terrestrial deposition process for karst bauxite is difficult to constrain due to its allochthonous origin multiple controls and the difficulty in geodynamic reconstruction this ambiguity has been clarified from investigation of the provenance and geologic geographic conditions for the formation of quaternary gibbsite nodules in the yongjiang basin this karst basin located at the southeastern propagation front of the tibet plateau was affected by the se asia monsoon climate developed since the late oligocene and a later quaternary glaciation a thick blanket of quaternary laterite is located on paleozoic carbonate bedrock and covers an area about 1000 km2 along the east flowing river systems in the basin the laterite profiles are well layered with a layer of iron rich gibbsite nodules overlying on a basal clay zone and irregularly covered by a thin clayey topsoil gibbsite nodules from most localities yield detrital zircons with age peaks at ca 1000 ma 450 ma and 250 ma corresponding to those of the mesozoic clastic and magmatic rocks exposed on the western and southern surrounding highlands nevertheless those from the pingtianshan area produce an exclusive spike at ca 100 ma consistent with the emplacement age of nearby granites apatite fission track modeling for the mesozoic clastic rocks and darongshan granites shows a rapid cooling since the early miocene and that for the pingtianshan cretaceous granite reveals fast exhumation since the late miocene these data indicate differential erosion reshaped the topography and consequently a low relief karst basin was developed allowing a diverse material supply from the surrounding and local highlands via sheet flow and east flowing rivers under a monsoon influenced subtropical climate aluminum and iron oxides hydroxides were accumulated as nodules or concretions which were cemented by and coated with fe oxides due to variations in redox potential and alternating consolidation and swelling while silica was leached at greater depth groundwater solutions preferentially removed and brought upward fe under a reducing environment during the wet seasons while an underlying clay layer occurred due to the reduced solubility of silica later this bauxitization process was probably hindered by the quaternary glaciation which could have promoted the formation of the top clay layer this terrestrial deposition process of quaternary gibbsite nodules serves as one analogue for ancient karst bauxite in which the following submergence would improve the quality via further precipitation of alumina hydroxide and leaching of extra fe

trace and rare earth elements constraints on the sources of the yunfeng paleo karstic bauxite deposit in the xiuwen qingzhen area guizhou china abstract a number of carboniferous paleo karstic bauxite deposits occur in the xiuwen qingzhen area central guizhou province which constitute an important part of the central guizhou southern chongqing bauxite belt in southwestern china these deposits consist of lenticular and stratiform orebodies hosted in the lower carboniferous jiujialu formation which lies unconformably above carbonate rocks mainly dolomite of the middle and upper cambrian loushanguan group shilengshui formation and lower cambrian qingxudong formation although it is generally agreed that the bauxite resulted from weathering of cambrian rocks below the unconformity it remains unclear whether the carbonates alone can provide sufficient material for the formation of the deposits in this study we examined the mineralogy and major trace and rare earth elements geochemistry of bauxite and bauxitic clays from the yunfeng deposit in the xiuwen qingzhen area and compared them to previously published data of a paleo weathering profile consisting of loushanguan dolomite underlying the sub carboniferous unconformity and the black rock sequence of the lower cambrian niutitang formation in order to evaluate the sources of the bauxite the bauxite ores are composed of diaspore as the main ore mineral along with small amounts of pyrite arsenopyrite galena stibnite xenotime and uranium bearing minerals and are characterized by high contents of uranium and phosphorus chondrite normalized ree patterns and various bivariant diagrams commonly used to study the provenance of bauxite including eu eu vs tio2 al2o3 eu eu vs sm nd tio2 vs al2o3 tio2 th th vs ta th vs nb and nb vs ta suggest that the loushanguan dolomite and the niutitang black rock sequence are both potential source rocks however a comparison in u and th contents between the paleo weathering profile of the loushanguan dolomite and the bauxite samples suggests that the dolomite alone cannot provide the materials for the bauxite ores instead the black rock sequence may have contributed most of the ore forming materials which are mainly transported from source regions where the niutitang formation was exposed weathered and eroded therefore the yunfeng bauxite deposit is of mixed autochthonous and allochthonous origin

the 10 october 1999 hip 9369 occultation by the northern polar region of jupiter ingress and egress lightcurves analysis abstract the occultation of bright star hip9369 by the northern polar region of jupiter was observed from four locations in north and south america providing four data sets for ingress and egress the inversion of the eight occultation lightcurves provides temperature profiles at different latitudes ranging from 55 n to 73 2 n we estimate the errors on the profiles due to the uncertainties of the inversion method and compare the value of the temperature at the deepest level probed 50 bar with previous observations the shape of the temperature gradient profile is found similar to previous investigations of planetary atmospheres with propagating and breaking gravity waves we analyze the small scale structures in both lightcurves and temperature profiles using the continuous wavelet transform the calculated power spectra of localized fluctuations in the temperature profiles show slopes close to 3 for all eight profiles we also isolate and reconstruct the three dimensional geometry of a single wave mode with vertical and horizontal wavelengths of respectively 3 and 70 km the identified wave is consistent with the gravity wave regime with a horizontal phase speed nearly parallel to the planetary meridian nevertheless the dissipation of the corresponding wave in jupiter s stratosphere should preclude its detection at the observed levels and an acoustic wave cannot be ruled out

mid infrared mapping of jupiter s temperatures aerosol opacity and chemical distributions with irtf texes abstract global maps of jupiter s atmospheric temperatures gaseous composition and aerosol opacity are derived from a programme of 5 20 m mid infrared spectroscopic observations using the texas echelon cross echelle spectrograph texes on nasa s infrared telescope facility irtf image cubes from december 2014 in eight spectral channels with spectral resolutions of r 2000 12 000 and spatial resolutions of 2 4 latitude are inverted to generate 3d maps of tropospheric and stratospheric temperatures 2d maps of upper tropospheric aerosols phosphine and ammonia and 2d maps of stratospheric ethane and acetylene the results are compared to a re analysis of cassini composite infrared spectrometer cirs observations acquired during cassini s closest approach to jupiter in december 2000 demonstrating that this new archive of ground based mapping spectroscopy can match and surpass the quality of previous investigations and will permit future studies of jupiter s evolving atmosphere the visibility of cool zones and warm belts varies from channel to channel suggesting complex vertical variations from the radiatively controlled upper troposphere to the convective mid troposphere we identify mid infrared signatures of jupiter s 5 m hotspots via simultaneous m n and q band observations which are interpreted as temperature and ammonia variations in the northern equatorial zone and on the edge of the north equatorial belt neb equatorial plumes enriched in nh3 gas are located south east of nh3 desiccated hotspots on the edge of the neb comparison of the hotspot locations in several channels across the 5 20 m range indicate that these anomalous regions tilt westward with altitude aerosols and ph3 are both enriched at the equator but are not co located with the nh3 plumes the equatorial temperature minimum and ph3 aerosol maxima have varied in amplitude over time possibly as a result of periodic equatorial brightenings and the fresh updrafts of disequilibrium material temperate mid latitudes display a correlation between mid ir aerosol opacity and the white albedo features in visible light i e zones we find hemispheric asymmetries in the distribution of tropospheric ph3 stratospheric hydrocarbons and the 2d wind field estimated via the thermal wind equation that suggest a differing efficiency of mechanical forcing e g vertical mixing and wave propagation between the two hemispheres that we argue is driven by dynamics rather than jupiter s small seasonal cycle jupiter s stratosphere is notably warmer at northern mid latitudes than in the south in both 2000 and 2014 although the latter can be largely attributed to strong thermal wave activity near 30 n that dominates the 2014 stratospheric maps and may be responsible for elevated c2h2 in the northern hemisphere a vertically variable pattern of temperature and windshear minima and maxima associated with jupiter s quasi quadrennial oscillation qqo is observed at the equator in both datasets although the contrasts were more subdued in 2014 large scale equator to pole gradients in ethane and acetylene are superimposed on top of the mid latitude mechanically driven maxima with c2h2 decreasing from equator to pole and c2h6 showing a polar enhancement consistent with a radiatively controlled circulation from low to high latitudes cold polar vortices beyond 60 latitude can be identified in the upper tropospheric and lower stratospheric temperature maps suggesting enhanced radiative cooling from polar aerosols finally compositional mapping of the great red spot confirms the local enhancements in ph3 and aerosols the north south asymmetry in nh3 gas and the presence of a warm southern periphery that have been noted by previous authors

submesoscale streamers exchange water on the north wall of the gulf stream the gulf stream is a major conduit of warm surface water from the tropics to the subpolar north atlantic here we observe and simulate a submesoscale 20 km mechanism by which the gulf stream exchanges water with subpolar water to the north along isopycnals the front has a sharp compensated temperature salinity contrast with distinct mixed water between the two water masses 2 and 4 km wide this mixed water does not increase downstream despite substantial energy available for mixing a series of streamers detrain this water at the crest of meanders subpolar water replaces the mixed water and resharpens the front the water mass exchange accounts for a northward flux of salt of 0 5 2 5 psu m2 s 1 large scale diffusivity o 100 m2 s 1 this is similar to bulk scale flux estimates of 1 2 psu m2 s 1 and supplies fresher water to the gulf stream required for the production of 18 subtropical mode water

water mass transformation by cabbeling and thermobaricity water mass transformation is an important process for the global ocean circulation nonlinearities in the equation of state of seawater lead to water mass transformation due to cabbeling and thermobaricity here the contribution of cabbeling and thermobaricity to water mass transformation is calculated in a neutral density framework using temperature gradients derived from observationally based gridded climatologies and observationally based estimates of the spatially varying eddy diffusivities it is shown that cabbeling and thermobaricity play a significant role in the water mass transformation budget with cabbeling having a particularly important role in the formation of antarctic intermediate water and antarctic bottom water a physical hypothesis is presented which explains why cabbeling is important for antarctic intermediate water formation it is shown that spatially varying estimates of eddy diffusivities are essential to correctly quantify the role of cabbeling to the formation of antarctic intermediate water

critical metals distribution in tethyan karst bauxite the cretaceous italian ores abstract bauxite is a residual rock consisting mainly of a mixture of aluminium hydroxides whose industrial significance is primarily due to its profitably exploitable alumina contents in the last decades bauxite mainly karst bauxite has been also considered as possible resource of a great number of economically interesting elements including some critical metals such as rare earth elements sc co ni and nb in this study we present results of univariate and multivariate r mode factor analysis statistics performed on a large data set including chemical composition of the principal cretaceous karst bauxites from central and southern italy with the twofold aim to evaluate the inter elemental relationship among major oxides and critical metals and describe factors affecting their distribution univariate statistics reveal that some critical metals co ni and lree have a significant number of outliers the co ni relationship associated to the outliers dataset suggests that co is likely hosted in ni rich phases whereas ce accumulation in authigenic minerals carbonate fluoride and phosphate is at the origin of lree outliers multivariate r mode statistics applied to the outliers devoid database instead demonstrate that in absence of specific mineralization events the distribution of most critical metals is controlled by al fe and ti oxi hydroxides and to a lesser extent by detrital phases among the critical metals cr and y are the exceptions their geochemical behaviour seems to be influenced primarily by their own chemical features that are responsible for the mobility of cr during bauxitization and for the decoupling of y from the rees

structural framework of the zagros fold thrust belt iran abstract data gleaned from the literature on the zagros have been compiled and used in conjunction with new interpretations to provide a better picture of the structures sedimentation history and deformation of this hydrocarbon rich mountain belt the belt parallel mountain front the n s trending kazerun izeh and e w trending bala rud fault zones are defined as the master structural elements of the belt these fault zones divide the zagros basin into zones with different stratigraphic successions and different rheological profiles this resulted in different structural styles developing along the belt during the subsequent collision the kazerun and izeh fault zones acted as the depositional system transition zone between the lurestan and fars regions in jurassic cretaceous time and partly controlled the distribution of the kazhdumi formation one of the major source rocks by the end of the cretaceous the nw se trending mountain front fault divided the present folded belt of the zagros into a major foreland basin to the southwest and a piggyback basin to the northeast activity along other major transfer fault zones including the izeh kazerun and bala rud fault zones occurred at this time and controlled the sedimentation and subsidence of the dezful embayment the main target region for hydrocarbon exploration these fault zones controlled the thickness of the asmari formation one of the main reservoirs and also the considerable thickness and facies changes of the gachsaran formation the major seal to the asmari formation the present morphology of the mountain belt is interpreted as being mainly related to the pinning of the mountain front fault to the northwest of the dezful embayment and to the north of the strait of hormuz

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

mixing and remineralization in waters detrained from the surface into subantarctic mode water and antarctic intermediate water in the southeastern pacific a hydrographic data set collected in the region and season of subantarctic mode water and antarctic intermediate water samw and aaiw formation in the southeastern pacific allows us to estimate the preformed properties of surface water detrained into these water masses from deep mixed layers north of the subantarctic front and antarctic surface water south of the front using 10 measured seawater properties we estimate the fractions of samw aaiw that originate as surface source waters as well as fractions that mix into these water masses from subtropical thermocline water above and upper circumpolar deep water below the subducted samw aaiw ages associated with the detrained surface water and remineralization and dissolution rates and ratios the mixing patterns imply that cabbeling can account for 0 005 0 03 kg m 3 of additional density in aaiw and 0 0 02 kg m 3 in samw we estimate a shallow depth 300 700 m above the aragonite saturation horizon calcium carbonate dissolution rate of 0 4 0 2 mol caco3 kg 1 yr 1 a phosphate remineralization rate of 0 031 0 009 mol p kg 1 yr 1 and remineralization ratios of p n o2 corg of 1 15 5 0 6 143 10 104 22 for samw aaiw our shallow depth calcium carbonate dissolution rate is comparable to previous estimates for our region our o2 p ratio is smaller than many global averages our model suggests neglecting diapycnal mixing of preformed phosphate has likely biased previous estimates of o2 p and corg p high but that the corg p ratio bias may have been counteracted by a second bias in previous studies from neglecting anthropogenic carbon gradients

uranus in 2003 zonal winds banded structure and discrete features abstract imaging of uranus in 2003 with the keck 10 m telescope reveals banded zonal structure and dozens of discrete cloud features at j and h bands several features in the northern hemisphere are also detectable at k by tracking features over four days we extend the zonal wind profile well into the northern hemisphere we report the first measurements of wind velocities at latitudes 13 19 and northward of 43 the first direct wind measurements near the equator and the highest wind velocity seen yet on uranus 218 m s at northern mid latitudes 20 to 40 the winds appear to have accelerated when compared to earlier hst and keck observations southern wind speeds 20 to 43 have not changed since voyager measurements in 1986 the equator of uranus exhibits a subtle wave structure indicated by diffuse patches roughly every 30 in longitude the largest discrete cloud features on uranus show complex structure extending over tens of degrees reminiscent of activity seen around neptune s great dark spot during the voyager encounter with that planet there is no sign of a northern polar collar as is seen in the south but a number of discrete features seen at the expected latitudes may signal the early stages of development of a northern collar

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

microfacies and geochemistry of the middle cretaceous sarvak formation in zagros basin izeh zone sw iran abstract the sarvak formation albian to cenomanian forming part of the bangestan group comprises a thick succession of carbonate rocks in the zagros basin of southern iran the sarvak formation forms one of the main hydrocarbon reservoirs of this region three sections in the northern 252 m thickness and southern flanks 348 m thickness of the mish and anneh anticlines 245 m thickness in the izeh zone of sw iran were selected for this study petrographic analysis led us to define 10 microfacies units deposited in four facies belts i tidal flat ii lagoonal iii shoal and iv open marine all of these form part of a platform ramp environment geochemical investigations limited to outcrops of the mish anticline aided in understanding geochemical and diagenetic characteristics of carbonate rocks from the sarvak formation variations of oxygen and carbon isotope data from limestones of the sarvak formation indicate near primary marine phreatic and partially meteoric digenesis for both flanks of the mish anticline respectively lower abundances of mn and fe suggest that the carbonates at both sites appear to have stabilized under mainly oxic conditions the sarvak carbonates from the north flank of the mish anticline indicate higher rock water interaction and a closed diagenetic system in comparison to the south flank of the mish anticline vertical and lateral variations in stratigraphic thicknesses in selected outcrops can be related to the presence of syn sedimentary faults in the zagros basin that resulted in regional instability or due to rates of sedimentation with lower rates of deposition in the basin during middle cretaceous times

dynamics of the atmospheres of the outer planets post voyager measurement objectives current knowledge about dynamics and thermal structure on the outer planets is reviewed with the aim of identifying important measurements which should be made in the post voyager era the existence of jets and cloud bands is the puzzle that underlies all others discussion focuses on the particular case of jupiter because documentation is most complete recent dynamical work has successfully reproduced much of the behavior of jets and spots with simple models that contain few parameters it is argued that the gross dynamical parameters such as density stratification and rotation rate are the keys to their behaviors rather than the particular specifics of radiative forcing cloud distributions thermodynamic transformations voyager data have shown that the jet systems decay with height in the region above the visible clouds therefore the highest priority must be given to establishing dynamical parameters that characterize levels within and beneath the clouds these require determination of the deep structure of the jets of the density stratification and of the horizontal density contrasts the deep regions are not easily accessible and these measurements present challenging opportunities indirect inferences about the controlling processes may sometimes be possible by observing waves and other activity in the more easily accessible stratosphere and some of these issues are also discussed

trace element content of karst bauxites and their parent rocks in the mediterranean belt this work deals with a concise but comprehensive study of trace element distribution in the bauxite deposits of mediterranean belt although the alloctonous and mainly detritic characters of several karst bauxite deposits are well established their parent rock has remained largely enigmatic evidence is available that some chemical elements notably zr cr and ga are largely immobile during the weathering and diagenesis and study of such trace elements in karst bauxites permits to make an approach to the lithological nature of their parent rocks it is shown by reference to analyses of bauxites from mediterranean areas that all the deposits studied are aligned from a cr rich pole related to ultramafics to another pole rich in ga and zr contents and in genetical relation with acidic parent rocks the results obtained by this way have been controlled by application of trace element accumulation coefficient which permits to distinguish four principal zones of bauxite derived from the parent rock of different lithological characters fig 3

genesis of the guangou karstic bauxite deposit in western henan china abstract the guangou bauxite deposit in western henan china is located in the north china block and to the north of the north qinling orogenic belt the orebody is hosted within the lower member of the carboniferous benxi formation which overlies unconformably upon the ordovician majiagou formation in the lower member of the benxi formation the bauxite orebody with a diaspore illite anatase mineral assemblage is sandwiched between underlying ferric clay illite hematite goethite and overlying top clay kaolinite quartz goethite according to field observations and geochemical evidence including trace and rare earth element ree compositions especially zr hf ratios the ferric clays were weathered from the underlying argillaceous limestones in the majiagou formation during this weathering process trace elements s zn ni cr v sc f ba and be are depleted li rb and b are enriched and zr hf bi ta ga nb and th are relatively immobile rees exhibit evident differentiation with enrichment of la ce pr and nd and depletion of gd tb dy ho er tm yb and lu the bauxite formed in weak reducing slightly basic water conditions according to the geneses of coexisting diaspore and anatase and it was altered during the epigenetic and second exposure periods forming kaolinite and goethite respectively interelemental relationship analyses of the ores suggest that the elemental behaviors of trace elements and rees in the bauxitization process are mainly controlled by the mineral compositions in bauxite ore and chemical properties of the elements for instance zircon rutile and anatase contain zr hf nb ta w and u based on geochemical evidence together with age data and chemical compositions of the detrital minerals both distant igneous rocks in the plate margin and paleozoic carbonates and precambrian rocks inside north china block provide the miscellaneous material for the bauxite ore and the top clay

jupiter s atmospheric temperatures from voyager iris to cassini cirs abstract retrievals performed on cassini composite infrared spectrometer data obtained during the distant jupiter flyby in 2000 2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere but to higher latitudes than were shown previously by flasar et al flasar f m 39 colleagues 2004a nature 427 132 135 flasar f m 44 colleagues 2004b space sci rev 115 169 297 similar retrievals were performed on voyager 1 iris data to provide the first detailed iris map of the stratosphere and high latitudes in the troposphere thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes and meridional temperature gradients indicate the presence of circumpolar jets as well the temperatures retrieved from the two spacecraft were also compared with yearly ground based data obtained over the intervening two decades tropospheric temperatures reveal gradual changes at low latitudes with little obvious seasonal or short term variation orton et al 1994 science 265 625 631 stratospheric temperatures show much more complicated behavior over short timescales consistent with quasi quadrennial oscillations at low latitudes as suggested in prior analyses of shorter intervals of ground based data orton et al 1991 science 252 537 542 friedson a j 1999 icarus 137 34 55 a scaling analysis indicates that meridional motions mechanically forced by wave or eddy convergence play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter timescales at latitudes away from the equator the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative ground based observations with improved vertical resolution and or long term monitoring from spacecraft are required for this purpose though the voyager and cassini data given indications that the magnitude of the forcing is very small

the ventilated pool a model of subtropical mode water an analytical model of subtropical mode water is presented based on ventilated thermocline theory and on numerical solutions of a planetary geostrophic basin model in ventilated thermocline theory the western pool is a region bounded on the east by subsurface streamlines that outcrop at the western edge of the interior and in which additional dynamical assumptions are necessary to complete the solution solutions for the western pool were originally obtained under the assumption that the potential vorticity of the subsurface layer was homogenized in the present theory it is instead assumed that all of the water in the pool region is ventilated and therefore that all the sverdrup transport is carried in the uppermost outcropping layer the result is the formation of a deep vertically homogeneous fluid layer in the northwest corner of the subtropical gyre that extends from the surface to the base of the ventilated thermocline this ventilated pool is an analog of the observed subtropical mode waters the pool also has the interesting properties that it determines its own boundaries and affects the global potential vorticity pressure relationship when there are multiple outcropping layers ventilated pool fluid is subducted to form a set of nested annuli in ventilated subsurface layers which are the deepest subducted layers in the ventilated thermocline

elemental geochemistry and strontium isotope stratigraphy of cenomanian to santonian neritic carbonates in the zagros basin iran abstract a neo tethyan upper cenomanian santonian neritic carbonate ramp succession sarvak and ilam formations drilled in the zagros basin in southwest iran was investigated via detailed sedimentology microfacies analysis elemental geochemistry and sr isotope stratigraphy sis the succession contains two exposure surfaces which are known as the ct es and mt es cenomanian turonian and middle turonian respectively and associated prominent negative carbon isotope excursions that represent important regional stratigraphic marker horizons precise knowledge about the onset of platform exposure and the duration of the exposure related hiatus however is currently lacking due to a rather low resolved shallow water biostratigraphic framework and a bulk carbonate carbon isotope pattern that clearly differs from global late cretaceous reference curves therefore the existing bio chemostratigraphic framework was complemented by bulk carbonate strontium isotope stratigraphy sis as bulk carbonate material is in particular prone to diagenetic alteration a careful selection of least altered samples has been carried out by means of elemental geochemistry and petrography in contrast to what could be expected the meteoric alteration of limestones beneath both exposure surfaces is not clearly expressed by increasing iron and manganese and coeval decreasing strontium contents on the contrary the impact of meteoric diagenesis is well illustrated via pronounced increases in rb concentrations and concomitant prominent positive shifts to radiogenic strontium isotope values an observation that clearly reflects the decay of continentally derived 87 rb into 87 sr rubidium corrected strontium isotope values place the ct es around the cenomanian turonian boundary and point to an exposure duration of less than 0 4 myr this rather short term ct es related hiatus is supported by petrographic evidence which indicates a youth karstification stage of strata beneath the ct es following sis the ilam sarvak transition at the top of nezzazatinella dicyclina interval zone coincides with the mt es carbonates placing above this transition ilam formation are ascribed to the earliest to latest early santonian while carbonates immediately beneath the mt es sarvak formation are dated as late turonian sis thus indicates a long lasting hiatus of 4 5 myr associated with the mt es emergence represented by the ct es is here proposed as harbinger of the mt es in the zagros basin which most likely resulted from stepwise peripheral bulging due to ophiolite obduction in combination with a small scale global sea level fall around 94 ma

growth of hematite and boehmite in concretions from ancient karst bauxite clue for past climate abstract in the peri adriatic apulia carbonate platform southern ltaly late cretaceous karst bauxites mark an emergence period during a wet tropical climate bauxite formed through clay accumulation in the karst in situ bauxitization and late formation of iron rich concretions in a water unsaturated pedogenic environment the concretions which are geochemical recorders of the environment of formation have a large core of al hematite surrounded by a cortex of alternating al hematite and boehmite boehmite forms instead of al hematite at lower water activity values using a model of molecular diffusion and assuming the fluid flow negligible the time necessary for growth of the concretions has been calculated the average sized core grew in 180 ka the al hematite accretionary band grew in 8 ka whereas the boehmite accretionary band grew in 4 5 ka the average bulk concretions possibly formed in 300 400 ka the growth of the concretions is assumed to be a two stage process in the first stage the core grew in a relatively long period of wet tropical climate in the second stage drier conditions favouring boehmite stability alternated to a wetter climate favouring al hematite stability the growth of the bulk concretions is consistent with the earth s long eccentricity cycle

mass change calculations in altered rock series a technique is presented whereby precursors of altered rocks in a fractionated rock series can be identified and changes in chemical components mass and volume accurately calculated the procedure utilizes elements with high degrees of immobility in hydrothermal and associated interactive water rock systems igneous rock series and sedimentary and metamorphic rocks with primary continuity of chemical composition are amenable to this treatment in the procedure for igneous rocks best fit fractionation lines are established for an immobile igneous compatible incompatible element pair the latter element functioning as the fractionation monitor alteration paths are linear and pass through the origin intersections of the fractionation and alteration lines yield the immobile element concentrations in the precursors to the altered rocks mobile components are determined from fractionation lines and monitor values total mass changes are proportional to the displacement of altered samples from the fractionation line masses of other elements in an altered sample reconstructed values are recalculated to the concentration of the monitor element in the precursor chemical changes are the differences between the calculated precursor compositions and the reconstructed altered rock compositions errors are mainly a function of the positioning of the fractionation lines

eddy resolving model estimate of the cabbeling effect on the water mass transformation in the southern ocean abstractcabbeling effect on the water mass transformation in the southern ocean is investigated with the use of an eddy resolving southern ocean model a significant amount of water is densified by cabbeling water mass transformation rates are about 4 sv 1 sv 106 m3 s 1 for transformation from surface thermocline water to subantarctic mode water samw about 7 sv for transformation from samw to antarctic intermediate water aaiw and about 5 sv for transformation from aaiw to upper circumpolar deep water these diapycnal volume transports occur around the antarctic circumpolar current acc where mesoscale eddies are active the water mass transformation by cabbeling in this study is also characterized by a large amount of densification of lower circumpolar deep water lcdw into antarctic bottom water aabw about 9 sv large diapycnal velocity is found not only along the acc but also along the coast of antarctica at the boundary between lcdw and aabw it is found that about 3 sv of lcdw is den

shear flow dispersion internal waves and horizontal mixing in the ocean abstract two models of advection diffusion in the oscillatory sheared velocity field of an internal wave are discussed our goal is to develop intuition about the role of such currents in horizontal ocean mixing through the mechanism of shear dispersion the analysis suggests simple parameterizations of this process i e those in eqs 7 36 and 42 the enhanced horizontal diffusion due to the interaction of the vertical diffusion and vertical shear of the wave field can be described by an effective horizontal diffusivity which is equal to the actual horizontal diffusivity plus a term equal to the mean square vertical shear of horizontal displacement times the vertical diffusivity provided the vertical length scale of the horizontal velocity field is not too small in the limit of small vertical length scale the expression reduces to taylor s 1953 result in which the effective horizontal diffusivity is inversely proportional to the actual vertical diffusivity the solutions also incidentally

geochemistry of the apulian karst bauxites southern italy chemical fractionation and parental affinities article i nfo this study focuses on a late cretaceous karst bauxite deposit in the murge area of the apulia district southern italy the first analysis of the vertical distributions of a wide range of elements including rees and selected trace elements throughout the deposit was shown in order to identify the processes determining element frac tionation during the evolution of the bauxite the studied karst bauxite deposit exhibits an ooidal texture is mineralogically homogeneous and contains higher abundances of boehmite than of hematite kaolinite and anatase the major element composition of the bauxite is dominated by elevated concentrations of sio2 t io2 a l2o3 a nd fe2o3 and analyses of element mo bility within the bauxite indicate that all elements except for nb and ni and to a lesser extent cr are depleted relative to the immobile element ti r mode factor analysis revealed a number of key findings i some low solubility elements e g zr th ti v ga were concentrated in detrital zircon and monazite zr th in anatase ti v and possibly in boehmite and hematite ga during the later stages of bauxitisation ii fe and cr were concentrated during wet conditions whereas al and co accumulated during dry conditions iii distributions of the light rees lrees and the heavy rees hrees are controlled by the same processes suggesting that little lree hree fractionation occurred during bauxite formation and iv the behaviour of cerium is different from that of the other rees and highly variable cerium anomalies are observed across the deposit with three characteristic ce ce maxima with values ofn2 parisite was the only authigenic cerium mineral detected during this study thus we propose a three step model to explain the distribution of ce cerianite is dissolved by cerium reduction is transported by downward moving meteoric water per descensum and finally parisite is precipi tated this cycle was repeated several times in the apulian karst bauxite in response to eh decreases under alka line conditions promoted by fluctuations in the groundwater level finally we used the value of the eu anomaly todiscuss theparental affinity or protolith of thebauxite the value of the eu anomaly min eu eu 0 76 max eu eu 0 89 indicates that the bauxite was not derived from carbonates but rather that the majority of the bauxite was influenced by intermediate to mafic magmatic sources eu eu vs sm nd diagram suggests that the parental material for the bauxite was derived from a combination of a distant magmatic source and clastic material derived from a continental margin northern africa to the south

a new mechanism for mode water formation involving cabbeling and frontogenetic strain at thermohaline fronts abstracta simple analytical model is used to elucidate a potential mechanism for steady state mode water formation at a thermohaline front that involves frontogenesis submesoscale lateral mixing and cabbeling this mechanism is motivated in part by recent observations of an extremely sharp density compensated front at the north wall of the gulf stream here the intergyre along isopycnal salinity temperature difference is compressed into a span of a few kilometers making the flow susceptible to cabbeling the sharpness of the front is caused by frontogenetic strain which is presumably balanced by submesoscale lateral mixing processes the balance is studied with the simple model and a scaling is derived for the amount of water mass transformation resulting from the ensuing cabbeling the transformation scales with the strain rate equilibrated width of the front and the square of the isopycnal temperature contrast across the front at the major ocean fronts where mode waters are found this isopy

mineralogical and geochemical evolution of the bidgol bauxite deposit zagros mountain belt iran implications for ore genesis rare earth elements fractionation and parental affinity the present study focuses on the late cretaceous bidgol bauxite deposit in the zagros simply fold belt sw iran the orebody is located in the eroded major nw se trending koh e hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the cenomanian turonian sarvak formation detailed mineralogical analysis reveals that diaspore hematite goethite anatase clinochlore chamosite and calcite are the major mineral components accompanied by minor amounts of detrital and ree bearing minerals such as rutile zircon and parisite the ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions the spheroidal pisolites of the bidgol bauxite formed under conditions of low water activity favouring the formation of large diaspore cores and a single dry to wet climatic fluctuation the mass change calculations relative to the immobile element ti show that elements such as si fe mg k na and sr are leached out of the weathered system al ni zr ga cr and ba are concentrated in the residual system and hf ta co rb cs be and u are relatively immobile during the bauxitisation processes the nb th y v sc sn and ree are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores but were slightly mobile at the later stage of bauxitisation geochemical data reveal progressive enrichment of the ree and intense lree hree fractionation toward the lower parts of the bauxite profile cerium behaves differently from the other rees especially lree and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile the distribution and fractionation of trace elements and rees during the bauxitisation process in the bidgol deposit are mainly controlled by the presence of ree bearing minerals fluctuations in soil solution ph ree ionization potential and the presence of bicarbonates or organic matter geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the bidgol bauxite was provided from a siliciclastic material derived from a continental margin the mid turonian uplift led to the formation of karstic topography rubbly breccia and a layer of ferruginous argillaceous debris that was affected by lateritic weathering under humid tropical climate subsequently mobile elements are removed from the profiles while al fe and ti are enriched resulting in the formation of the pristine bauxite materials when the platform subsided into the water again the pristine bauxitic materials were partly converted to bauxite during the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in oligocene miocene important factors such as intensity of the weathering drainage and floating flow may have improved the qualities of the bauxite ores

combined tectonic and paleogeographic controls on the genesis of bauxite in the early carboniferous to permian central yangtze island abstract two bauxite horizons with a total reserve of 1 29 bt occur in the lower carboniferous and lower permian in the central south china block different from other intracontinental bauxites in china which are genetically linked to the orogenesis along the continental margin these bauxites were generated in the absence of marginal orogenesis the genesis of these bauxites were studied based on tectonic paleogeographic and paleoclimatic controls the orebody in huofengchong hfc region is hosted within the lower carboniferous which overlies upon the cambrian dolomite unconformably the orebody in the regions of yanfengba yfb and baiyantou byt occurs in lower permian which overlies upon the silurian shale or devonian dolomite unconformably the mineral assemblages in the carboniferous hfc bauxite consist of diaspore illite anatase and in permian yfb and byt bauxite the minerals are diaspore anatase illite clinochlore and kaolinite the data from the u pb isotope measurements of detrital zircons from these bauxites provide two main ages 1 a maximum u pb age peak of ca 800 ma from the carboniferous hfc and 2 a maximum age peak of ca 1100 ma for the permian byt and yfb the ca 800 ma detrital zircons from the carboniferous bauxite are dominating in the paleozoic sedimentary units which likely derive from the erosion of the mid to neo proterozoic felsic volcanic and intrusive rocks panxi hannan arc occurring in the western margin of the south china block by contrast the zircons with ages of ca 1100 ma are prevalent in the paleozoic sediments from the center of the block the above results indicate that the lower carboniferous and lower permian bauxites are sourced from the sedimentary rocks in the western and central parts of the south china block respectively despite the difference in the provenance these two episodes of deposits were both deposited in a tidal flat restricted platform attached to an ew trending yangtze island occupies the western to central parts of the south china block this indicates that the shift from a marginal to central uplift within the paleo island from early carboniferous to early permian has induced the transition in the provenance of the source material in addition the weathered materials from the two provenances both accumulated in the coastal region receiving further bauxitization the bauxitization was boosted by the persistent preferable tepid and humid paleoclimate defined by the equatorial position of south china block and the drop of global temperature during the metallogenic period

spatial organization and time dependence of jupiter s tropospheric temperatures 1980 1993 the spatial organization and time dependence of jupiter s temperatures near 250 millibar pressure were measured through a jovian year by imaging thermal emission at 18 micrometers the temperature field is influenced by seasonal radiative forcing and its banded organization is closely correlated with the visible cloud field evidence was found for a quasi periodic oscillation of temperatures in the equatorial zone a correlation between tropospheric and stratospheric waves in the north equatorial belt and slowly moving thermal features in the north and south equatorial belts there appears to be no common relation between temporal changes of temperature and changes in the visual albedo of the various axisymmetric bands

geochemistry of trace elements and their relations with organic matter in kuh e sefid phosphorite mineralization zagros mountain iran abstract the kuh e sefid phosphorite is located in zagros fold thrust belt in the ramhormoz area northeast of khuzestan province phosphorite mineralization occurred as phosphorite lenses of eocene age hosted by the pabdeh formation the aim of this study is to investigate the role of organic matter in trace metal portioning during phosphorite mineralization in the kuh e sefid deposit field observations and petrographic studies indicate that the host rock of mineralization is mainly consists of shale marl and limestone with textures varying from wackestone to packestone phosphoritic components such as authigenic apatite pellets intraclasts fish skeletal fragments and micro fossils are present moreover non phosphorite minerals including calcite glauconite pyrite iron oxide and to a lesser extend montmorillonite with microcrystalline quartz occurred in phosphorite lenses nasc normalized patterns of rees showed the enrichment of heavy rare earth elements hree and negative ce anomaly with co existence of slightly negative and positive eu anomalies represent a transitional change from oxic to anoxic sedimentation conditions during mineralization importantly ni co versus v cr ratios and v v ni diagrams confirmed dysoxic to anoxic conditions for the hydrocarbon bearing phosphorite and hosted shales while non hydrocarbon bearing phosphorites exhibit oxic conditions the ftir studies revealed qualitative information about the component bonds and nature of the organic matter and mineral organic bonds like oh carboxylic oh carboxylic acid c o c c alkaline group ch2 c c aromatic ch aliphatic and aromatic stretching associated with phosphate mineralization it seems that there is a link between a relatively high concentration of trace metals i e rees u co zn ni v sr and mo and phosphorites enriched in organic matter especially those of aromatic hydrocarbon groups

mineralogical characteristics of the superlarge quaternary bauxite deposits in jingxi and debao counties western guangxi china abstract in recent decades more than 0 5 billion tons of ores scattered in the quaternary laterite in western guangxi china have been explored the ores were derived from a bauxite horizon in permian via physical break up and re sediment process utilizing various test methods i e xrd dta tg dtg sem eds and epma the mineralogical characteristics of the quaternary bauxite ores in jingxi and debao counties were investigated xrd was used together with tg dtg to obtain relatively accurate ore mineral abundance diaspore is the major phase whereas hematite kaolinite anatase chamosite gibbsite goethite illite and rutile are minor diaspore is characterized by a small particle size low degrees of crystallinity and complex chemical composition both gibbsite and goethite have a varied particle size and goethite crystals contain high al substitution and si it is clarified that diaspore chamosite and anatase were formed in a mildly reduced and alkaline depositional environment in permian while gibbsite hematite goethite and part kaolinite were precipitated from al 3 si 4 and fe 3 enriched solutions within an quaternary oxidized environment the ions al 3 si 4 and fe 3 are mostly released from chamosite in its dissolution process the different physicochemical conditions between the permian depositional and the quaternary weathering periods resulted in a complex mineral assemblage in the quaternary bauxite

biochemostratigraphy of an upper albian turonian succession from the southeastern neo tethys margin sw iran abstract a neo tethyan upper albian turonian hemi pelagic carbonate succession sarvak formation accessible in outcrop in the zagros sw iran was investigated using sedimentology microfacies analysis planktonic foraminifera biostratigraphy and carbon isotope stratigraphy the succession contains six biozones including thalmanninella th appenninica th globotruncanoides rotalipora cushmani whiteinella archaeocretacea helvetoglobotruncana helvetica and marginotruncana schneegansi some of these biozones show variable stratigraphic positions throughout the tethyan and boreal realms that hinder correlation of the studied iranian section with european reference sections therefore the correlation of the existing biostratigraphic framework was complemented by carbonate carbon isotope stratigraphy based on bulk carbonate material despite the low resolution of the presented carbon isotope record pronounced global events including the late turonian events cenomanian turonian boundary ctb event oae 2 and albian cenomanian boundary acb event can be distinguished the 13c excursions provide global synchronous time lines for correlation the distinguished biozones were compared among the sections regarding their stratigraphic positions relative to these time lines the correlation tentatively suggests that the biostratigraphic datum marking the acb is diachronous with an se nw trend first appearance datum fad of th appenninica varies from the upper albian to the lower cenomanian the fad of th globotruncanoides is also variable from the upper albian to the lower cenomanian however the middle cenomanian turonian biozones including rotalipora cushmani and whiteinella archaeocretacea zones are synchronous elevated pco2 contributed to the gradual increase of the sst sea surface temperature during the cenomanian and the dramatic climax at the earliest turonian this trend closely correlates with the change from the diachronous acb biozones to synchronous ctb biozones possibly increasing ssts provided temperature tolerance range for the species throughout different latitudes and assisted their rapid distribution moreover the warming raised the sea level from the latest albian to turonian that inundated landbridges resulting in an enhanced marine circulation and faster distribution of planktonic species throughout the neo tethys ocean

symmetric instability in the gulf stream abstract analyses of wintertime surveys of the gulf stream gs conducted as part of the clivar mode water dynamic experiment climode reveal that water with negative potential vorticity pv is commonly found within the surface boundary layer sbl of the current the lowest values of pv are found within the north wall of the gs on the isopycnal layer occupied by eighteen degree water suggesting that processes within the gs may contribute to the formation of this low pv water mass in spite of large heat loss the generation of negative pv was primarily attributable to cross front advection of dense water over light by ekman flow driven by winds with a down front component beneath a critical depth the sbl was stably stratified yet the pv remained negative due to the strong baroclinicity of the current suggesting that the flow was symmetrically unstable a large eddy simulation configured with forcing and flow parameters based on the observations confirms that the observed structure of the sbl is consistent with the dynamics of symmetric instability si forced by wind and surface cooling the simulation shows that both strong turbulence and vertical gradients in density momentum and tracers coexist in the sbl of symmetrically unstable fronts si is a shear instability that draws its energy from geostrophic flows a parameterization for the rate of kinetic energy ke extraction by si applied to the observations suggests that si could result in a net dissipation of 33 mw m 2 and 1 mw m 2 for surveys with strong and weak fronts respectively the surveys also showed signs of baroclinic instability bci in the sbl namely thermally direct vertical circulations that advect biomass and pv the vertical circulation was inferred using the omega equation and used to estimate the rate of release of available potential energy ape by bci the rate of ape release was found to be comparable in magnitude to the net dissipation associated with si this result points to an energy pathway where the gs s reservoir of ape is drained by bci converted to ke and then dissipated by si and its secondary instabilities similar dynamics are likely to be found at other strong fronts forced by winds and or cooling and could play an important role in the energy balance of the ocean circulation

on cabbeling and thermobaricity in the surface mixed layer abstractthe surface mixed layer ml governs atmosphere ocean fluxes and thereby affects earth s climate accurate representation of ml processes in ocean models remains a challenge however the o 100 m deep ml exhibits substantial horizontal thermohaline gradients despite being near homogenous vertically making it an ideal location for processes that result from the nonlinearity of the equation of state such as cabbeling and thermobaricity traditional approaches to investigate these processes focus on their roles in interior water mass transformation and are ill suited to examine their influence on the ml however given the climatic significance of the ml quantifying the extent to which cabbeling and thermobaricity influence the ml density field offers insight into improving ml representations in ocean models a recent simplified equation of state of seawater allows the local effects of cabbeling and thermobaric processes in the ml to be expressed analytically as functions of the local temperatu

interannual variations in upper ocean heat content and heat transport convergence in the western north atlantic subsurface temperature data in the western north atlantic ocean are analyzed to study the variations in the heat content above a fixed isotherm and contributions from surface heat fluxes and oceanic processes the study region is chosen based on the data density its northern boundary shifts with the gulf stream position and its southern boundary shifts to contain constant volume the temperature profiles are objectively mapped to a uniform grid 0 5 latitude and longitude 10 m in depth and 3 months in time the interannual variations in upper ocean heat content show good agreement with the changes in the sea surface height from the ocean topography experiment topex poseidon altimeter both indicate positive anomalies in 1994 and 1998 99 and negative anomalies in 1996 97 the interannual variations in surface heat fluxes cannot explain the changes in upper ocean heat storage rate on the contrary a positive anomaly in heat released to the atmosphere corresponds to a positive upper ocean heat content anomaly the oceanic heat transport mainly owing to the geostrophic advection controls the interannual variations in heat storage rate which suggests that geostrophic advection plays an important role in the air sea heat exchange the 18 c isotherm depth and layer thickness also show good correspondence to the upper ocean heat content a deep and thin 18 c layer corresponds to a positive heat content anomaly the oceanic transport in each isotherm layer shows an annual cycle converging heat in winter and diverging in summer in a warm layer it also shows interannual variations with the largest heat convergence occurring in even warmer layers during the period of large ocean to atmosphere flux

metallogeny of the large scale carboniferous karstic bauxite in the sanmenxia area southern part of the north china craton china abstract above two billion tons of bauxite were formed during the exposure of the north china craton ncc in 445 300 ma mineralogical geochemical and isotopic analyses of karstic bauxite deposits in the sanmenxia area situated within southern ncc were conducted to explore the genetic processes of carboniferous bauxite the bauxite contains three layers a lower fe bearing claystone layer a middle bauxite ore layer and an upper claystone layer fe bearing claystone is dominated by illite and hematite in the uplift and illite siderite and pyrite in the depression bauxite ore is composed of diaspore illite pyrite and anatase and the upper claystone consists of illite diaspore and anatase distinct pyrite 34s values 11 7 15 2 and 11 5 to 1 0 illite 87sr 86sr i 0 711917 0 713588 and 0 708000 0 711057 and end t 12 2 to 11 4 and 11 8 to 9 7 values and the immobile elemental ratios were obtained between the lower fe bearing claystone and upper bauxite ore and claystone together with chemistry of detrital rutile it is denoted the fe bearing claystone was formed from the underlying limestone whereas the bauxite ore and claystone were derived from both igneous rocks along craton margin and regional precambrian metamorphic rocks the visible microorganisms and wide development of framboidal pyrite with negative 34s within the bauxite ore provide evidences of microbial activity during bauxite formation bio leaching process after the deposition of allochthonous source materials caused the downward migration of ions al3 fe2 ti4 ree3 etc these ions encountered an alkaline and reducing condition in the karstic depression forming diaspore pyrite and anatase and ree enrichment at the bottom of bauxite ore this large input of raw materials warm and humid climate and microorganisms led to large scale bauxite formation in the ncc during late carboniferous

a new mechanism for mode water formation involving cabbeling and frontogenetic strain at thermohaline fronts part ii numerical simulations abstractsubmesoscale resolving numerical simulations are used to investigate a mechanism for sustained mode water formation via cabbeling at thermohaline fronts subject to a confluent strain flow the simulations serve to further elucidate the mechanism and refine the predictions of the analytical model of thomas and shakespeare unlike other proposed mechanisms involving air sea fluxes the cabbeling mechanism in addition to driving significant mode water formation uniquely determines the thermohaline properties of the mode water given knowledge of the source water masses on either side of the front the process of mode water formation in the simulations is as follows confluent flow associated with idealized mesoscale eddies forces water horizontally toward the front the frontogenetic circulation draws this water near adiabatically from the full depth of the thermohaline front up to the surface 25 m where resolved submesoscale instabilities drive intense mixing across the thermohaline front creatin

argillite debris converted to bauxite during karst weathering evidence from immobile element geochemistry at the olmedo deposit sardinia the olmedo bauxite deposit occurs in the nurra district of northwest sardinia it forms a stratiform horizon in cretaceous limestone and marl uplift in mid cretaceous had exposed recently deposited limestone to karst weathering and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite intermediate products were desiccated marl bauxitic argillite and argillaceous bauxite subsidence followed and the bauxite was preserved by the deposition of late cretaceous limestone and other sediments uplift in oligocene miocene time with ensuing erosion exposed the bauxite horizon to its present configuration concentrations of normative minerals illustrate chemical processes and the build up of al in the bauxite horizon plots of chemical data and correlation coefficients show that al ti zr nb th cr and v were immobile during the bauxitization process mass changes point to large net removal of si mg and k from the system although some of this material and slightly mobile al were reprecipitated in the underlying argillite and altered marl immobile element ratios trace the source of the bauxite to the underlying argillaceous limestone al in the bauxite was accumulated from the degradation of 25 to 50 m of the argillaceous limestone

origin and geochemical evolution from ferrallitized clays to karst bauxite an example from the lower cretaceous of ne spain abstract four outcrops of lower cretaceous barremian karst bauxites located in teruel ne spain were analysed the deposits show a heterogeneous chaotic lithostructure consisting of pisolitic bauxite blocks embedded in lateritic red clays filling karst cavities the research has focused on the geochemical study of major minor and trace elements including some critical to industry of both the bauxites and clays the objective was to investigate the bauxite precursor material and to characterize the system s geochemical evolution geochemical analyses were carried out by inductively coupled plasma optical emission and mass spectroscopy an absolute weathering index has been calculated to estimate element mobility assuming ti as an immobile element and the upper continental crust ucc as parent material further selected samples were observed by field emission scanning electron microscopy the data indicate that both the bauxites and red clays originated by intense chemical weathering from more mafic argillaceous sediments than the ucc ongoing weathering caused the bauxitization of the upper parts of the original profile preventing the lower parts from being bauxitized thus producing the ferrallitized clays underlying the pisolitic bauxites subsequent karst reactivation gave rise to the current lithostructure ferrallitization is related to fe sc and v enrichment on the other hand although bauxites are relatively enriched in some elements compared to clays the more intense chemical weathering associated with bauxitization led to chemical homogenization and widespread element depletion during the bauxitization al ti zr cr and probably hf and the critical element nb behaved as more immobile elements in the system bauxitization also enhanced homogenization and depletion of the ree which is more pronounced for the lree hree trends seem to be partly related to the concentration of ti oxides in the bauxites whereas p bearing phases more frequent in the clays control the lree subsequent to bauxitization partial kaolinization of the bauxite took place related to the circulation of acid solutions that also caused the karst reactivation these late processes caused some al depletion in the bauxites and enhanced fe loss together with v and to a lesser extent ge

content and mode of occurrences of rare earth elements in the zagrad karstic bauxite deposit niksic area montenegro abstract three vertical sections through the zagrad deposit of jurassic karst bauxite in central montenegro have provided knowledge of the vertical distribution of major and some selected trace elements including rare earth elements ree variations in the mineralogy particularly those hosting ree have been studied this has revealed the presence of authigenic mineral phases such as xenotime mottramite and monazite best proved using raman microprobe analysis as well as residual phases such as zircon titanite and monazite the mobility of the elements during bauxitization processes has been studied to show that the ree minerals ensure progressive concentration of these elements during removal of major elements through weathering the similarity of normalized ree in the bauxite to the typical post archean australian shales paas and upper continental crust ucc profile and the preserved eu anomaly are evidence that the bauxite was not derived from carbonates and represents alteration of shale marly limestone and volcanogenic or proximal igneous sourced detritus that accumulated in the original karst landform mass change during bauxitization using ti as index element and compared to paas composition revealed almost 100 depletion of si and weak enrichment in al deeper parts of the deposit with authigenic minerals exhibit very strong enrichment in all ree the bauxite ores have high ree contents 693 5 6953 4 ppm especially lree contents 582 8 4882 9 ppm while hree contents 106 6 2070 5 ppm are much lower

mineralogical and geochemical studies of boron rich bauxite ore deposits in the songqi region sw henan china the songqi region sw henan is an important bauxite province in china the bauxite ore deposits occur unconformably on the top of middle ordovician argillaceous carbonates the bauxite ores from the songqi region are characterized by unusually high boron contents in this paper we report the mineralogical and chemical compositions of selected bauxite ores from the region these new data together with existing geochemical data of soils in the region are used to evaluate the origin of boron enrichment in the bauxite ores the compositional characteristics of tourmaline in the bauxite ores suggests that this mineral was likely derived from a meta sedimentary protolith mass balance calculation reveals that tourmaline only accounts for a small portion of boron in the bauxite ores the majority of boron in the ores must occur in other forms possibly by ion absorption on the surfaces of diaspore and clay minerals in the songqi region the precambrian meta sedimentary rocks are known to contain abundant tourmalines whereas the cambrian ordovician argillaceous carbonates and the upper proterozoic shales are all enriched in boron in free ion state we suggest that these rocks provided tourmaline and boron ion to the bauxite deposits in the region most known bauxite deposits in the songqi region occur at the margins of boron rich soil domains suggesting that boron in soils is a potential exploration indicator for unknown bauxite deposits in this region

thermal maps of jupiter spatial organization and time dependence of stratospheric temperatures 1980 to 1990 the spatial organization and time dependence of jupiter9s stratospheric temperatures have been measured by observing thermal emission from the 7 8 micrometer ch4 band these temperatures observed through the greater part of a jovian year exhibit the influence of seasonal radiative forcing distinct bands of high temperature are located at the poles and mid latitudes while the equator alternates between warm and cold with a period of approximately 4 years substantial longitudinal variability is often observed within the warm mid latitude bands and occasionally elsewhere on the planet this variability includes small localized structures as well as large scale waves with wavelengths longer than 30 000 kilometers the amplitudes of the waves vary on a time scale of 1 month structures on a smaller scale may have lifetimes of only days waves observed in 1985 1987 and 1988 propagated with group velocities less than 30 meters per second

geological geochemical and mineralogical characteristics of ree bearing las mercedes bauxite deposit dominican republic abstract bauxite deposits traditionally the main source of aluminum have been recently targeted for their remarkable contents in rare earth elements ree with ree lanthanoids sc y concentrations systematically higher than 1400 ppm av 1530 ppm the las mercedes karstic bauxites in the dominican republic rank as one of the ree richest deposits of its style the bauxitic ore in the las mercedes deposit is mostly unlithified and has a homogeneous massive lithostructure with only local cross stratification and graded bedding the dominant arenaceous and round grained texture is composed of bauxite particles and subordinate ooids pisoids and carbonate clasts mineralogically the bauxite ore is composed mostly of gibbsite and lesser amounts of kaolinite hematite boehmite anatase goethite chromian spinel and zircon identified ree minerals include cerianite and monazite ce whose composition accounts for the steady enrichment in light relative to medium and heavy ree of the studied bauxites considering the paleo geomorphology of the study area we propose that bauxites in the las mercedes deposit are the product of the erosion and deposition of lithified bauxites located at higher elevations in the bahoruco ranges based on the available data we suggest a mixed lithological source for the bauxite deposits at the district scale bedrock carbonates and an igneous source of likely mafic composition