thermal evolution of the ore hosting isa superbasin central and northern lawn hill platform hydrocarbon migration pathways and organic mineral matter associations were used to identify brine pathways in paleoproterozic to early mesoproterozoic rocks from the lawn hill platform mount isa several types of organic matter are identified and their thermal imprints are used to reconstruct the thermal history of the northern to central parts of the isa superbasin three major thermal hydrothermal episodes are recognized from the organic maturation studies isotherm plots on a 175 km long structural sedimentological north south section of the isa superbasin highlight specific fault systems that acted as hot fluid conduits during the geologic history of the basin some of these systems indicate continuing activity into the south nicholson basin supported by the presence of low reflectance type b bitumen this bitumen has not been overprinted by later hydrothermal episodes and therefore represents the latest thermal event along the north south profile a general southward increase in temperature is evident the lowest temperatures are recorded in proximity to the basin margin on the southern flank of the murphy inlier thermal processes and their sequence of events in the basin are recorded by organic maturation subsequent hydrocarbon generation its migration and destruction coincident with transport and precipitation of minerals as some timing and trapping mechanisms for minerals may have analogues with hydrocarbon entrapment relative timing of processes leading to organic maturation hydrocarbon generation and migration are utilized in this study to enhance understanding of ore grade mineralization in the proterozoic successions of the mount isa basin multiple hydrocarbon generation events are recognized these events record the transient passage of potential metal bearing fluids rather than background conductive heat flow from the basement such hydrothermal fluids are responsible for inverse maturation profiles in the vicinity of the termite range fault and extreme maturation reflectance values up to 6 percent ro at the grevillea prospect at century intermediate ro values of 2 percent document the passage of fluids of less than 200 degrees c interaction between these hydrothermal fluids and organic matter resulted in the creation of transient microporosity that was subsequently filled with sulfide minerals principally sphalerite porous sphalerite texture of previous workers pervasive destruction of organic matter in the host sediments at century records high water rock ratios during this mineralizing event previous models for century mineralization interpreted an in situ gas and oil accumulation at the time of mineralization this study shows that initial maturation of organic matter at century coincided with the influx of hydrothermal fluids responsible for mineralization there is no evidence for the existence of an earlier hydrocarbon accumulation in this study samples were only collected from organic matter rich intervals mainly shales and siltstones interbedded sandstones were not sampled therefore it is not possible to determine which siliciclastic lithologic units transmitted the hydrothermal fluids however elevated reflectance values consistently occur adjacent to faults both supersequence boundaries surfaces of major lithologic contrast suggesting that these features controlled fluid migration carbonate lithologic units sampled in this study are primarily from the loretta supersequence walford dolomite these rocks preserve the residue of a primary migrated hydrocarbon overprinted by a hydrothermal fluid event responsible for destruction of the oil and the formation of mesophase textures characteristic of mississippi valley type deposits

mapping ocean observations in a dynamical framework a 2004 06 ocean atlas abstract this paper exploits a new observational atlas for the near global ocean for the best observed 3 yr period from december 2003 through november 2006 the atlas consists of mapped observations and derived quantities together they form a full representation of the ocean state and its seasonal cycle the mapped observations are primarily altimeter data satellite sst and argo profiles gcm interpolation is used to synthesize these datasets and the resulting atlas is a fairly close fit to each one of them for observed quantities especially the atlas is a practical means to evaluate free running gcm simulations and to put field experiments into a broader context the atlas derived quantities include the middepth dynamic topography as well as ocean fluxes of heat and salt freshwater the atlas is publicly available online www ecco group org this paper provides insight into two oceanographic problems that are the subject of vigorous ongoing research first regarding ocean circulation estimates

transformation of deep water masses along lagrangian upwelling pathways in the southern ocean upwelling of northern deep waters in the southern ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient rich deep waters to the sea surface we quantify water mass transformation along upwelling pathways originating in the atlantic indian and pacific and ending at the surface of the southern ocean using lagrangian trajectories in an eddy permitting ocean state estimate recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the antarctic circumpolar current while upwelling through the surface layer is more broadly distributed in the ocean interior upwelling is largely isopycnal atlantic and to a lesser extent indian deep waters cool and freshen while pacific deep waters are more stable leading to a homogenization of water mass properties as upwelling water approaches the mixed layer there is net strong transformation toward lighter densities due to mixing of freshwater but there is a divergence in the density distribution as upper circumpolar deep water tends become lighter and dense lower circumpolar deep water tends to become denser the spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced however the majority of cumulative density change along trajectories is achieved by background mixing we compare the lagrangian analysis to diagnosed eulerian water mass transformation to attribute the mechanisms leading to the observed transformation

subantarctic mode water formation destruction and export in the eddy permitting southern ocean state estimate subantarctic mode water samw is examined using the data assimilating eddy permitting southern ocean state estimate for 2005 and 2006 surface formation due to air sea buoyancy flux is estimated using walin analysis and diapycnal mixing is diagnosed as the difference between surface formation and transport across 30 s accounting for volume change with time water in the density range 26 5 27 1 kg m 3 that includes samw is exported northward in all three ocean sectors with a net transport of 18 2 17 1 sv 1 sv 106 m3 s 1 for years 2005 2006 air sea buoyancy fluxes form 13 2 6 8 sv diapycnal mixing removes 14 5 12 6 sv and there is a volume loss of 19 3 22 9 sv mostly occurring in the strongest samw formation locations the most vigorous samw formation is in the indian ocean by air sea buoyancy flux 9 4 10 9 sv where it is partially destroyed by diapycnal mixing 6 6 3 1 sv there is strong export to the pacific where samw is destroyed both by air sea buoyancy flux 1 1 4 6 sv and diapycnal mixing 5 6 8 4 sv in the south atlantic samw is formed by air sea buoyancy flux 5 0 0 5 sv and is destroyed by diapycnal mixing 2 3 1 1 sv peaks in air sea flux formation occur at the southeast indian and southeast pacific samws seisamws sepsamws densities formation over the broad samw circumpolar outcrop windows is largely from denser water driven by differential freshwater gain augmented or decreased by heating or cooling in the seisamw and sepsamw source regions however formation is from lighter water driven by differential heat loss

lower palaeozoic and precambrian petroleum source rocks and the coalification path of alginite organic rich samples derived from a middle cambrian formation in the georgina basin and from the middle proterozoic of the mcarthur basin in northern and central australia yielded alginite ranging from immature oil shale material to overmature residue a maturation scale has been developed based on the thermal evolution of alginite as determined from reflectance and fluorescence the coalification path of alginite is marked by jumps in contrast to the linear path of wood derived vitrinite six zones have been recognised ranging from undermature zone i through the mature zones ii iii followed by a stable stage of no change zone iv to the overmature zones v and vi the onset of oil generation in alginite as evident from the present study is at 0 3 ro alg and is expressed in a change of fluorescence from yellow to brown and a coalification jump from 0 3 to 0 6 ro of alg in many boreholes zone iii can be distinguished between 0 6 and 0 8 ro of alg where subsequent oil generation occurs zones ii and iii represent the oil window a zone of little or no change designated zone iv at 0 91 0 ro of alginite follows zones ii iii a marked coalification jump characterises zone v where a pronounced change in reflectance occurs to 1 0 ro alg signifying peak gas generation the border of oil preservation lies at the transition of zone v and vi at 1 6 ro alg in zone vi gas generation only occurs comparison of reflectance results with experimental and geochemical pyrolysis data supports high activation energies for hydrocarbon generation from alginite and therefore a later onset of oil generation than other liptinite macerals i e cutinite exinite resinite as well as a narrow oil window transmission electron microscopy tem confirms that alginite does not go through a distinct intermediate stage but that the percentage of unreacted organic matter decreases as maturation proceeds a clear distinction can be made in tem between immature alginite alginite after oil generation and alginite residue following gas generation alginite beyond 1 6 ro acquires very high densities and the appearance of inertinite in tem bitumens pyrobitumens make a pronounced contribution to the organic matter throughout the basins and have been shown to effect pyrolysis results by suppressing tmax the bitumens pyrobitumens have been divided into four groups based on their reflectance and morphology which in turn appears to be an expression of their genetic history their significance is in aiding the understanding of the basins thermal history and the timing of oil and gas generation

a basin system and fluid flow analysis of the zn pb ag mount isa type deposits of northern australia identifying metal source basinal brine reservoirs times of fluid expulsion and organic matter reactions paleoproterozoic rocks of northern australia host one of the world s largest base metal repositories and are the world s most important zinc repository the mcarthur mount isa cloncurry mineral belt contains several world class zn pb ag u cu and cu au deposits ewers and fergusson 1980 williams 1998 betts et al 2003 large et al 2005 fig 1 the province has the potential to host additional base metal and uranium reserves advances in exploration techniques in the 1980s led to the discovery of several major new zn and cu au deposits including cannington century ernest henry and osborne however recent exploration results have been disappointing and new exploration strategies are required if the region is to further its growth potential and if new resources are to be realized beneath shallow cover fig 1 map of northeastern australia showing the principal tectonostratigraphic subdivisions for the region the map highlights the areas of study covered by the thematic papers in this volume and the location of the principal zn pb ag cu and cu au deposits the locations of profiles p1 and p2 the comalco seismic grid and deep boreholes including desert creek 1 are shown in the inset map bottom left between 1975 to 1995 geoscientists from geoscience australia the geological survey of queensland and the northern territory geological survey mapped the paleoproterozoic outcrop belt of northern australia at a scale of 1 100 000 subsequently researchers at monash university undertook detailed studies of the deformation history of the mount isa block placing the ore deposits within a tectonic context e g o dea et al 1997 betts et al 1998 2003 betts and lister 2002 researchers at james cook university carried out structural metamorphic and mineralization studies across the mount isa block with their principal focus concentrating on the deposits and their immediate environs bell et al 1988

the application of electron microscopy and microanalysis in conjunction with organic petrology to further the understanding of organic mineral association examples from mount isa and mcarthur basins australia organic petrology supported by electron microscopical and micro analytical techniques was applied to organic matter in proterozoic sediments to better understand hydrothermal processes responsible for ore grade mineralisation it was shown that organic maturation was not only closely linked to the geological history of the sediments but also highlighted heat transfer by convection as differentiated from conduction solely through sediment burial and step wise subsidence water rock ratios effect organic maturation in hydrothermal systems and erratic reflectance profiles are indicators of convective heat transfer identification and characterisation of organic materials in terms of source rock and migrated hydrocarbons was shown to be a powerful tool in reconstructing the thermal history of sediments identifying hydrothermal episodes fluid pathways and heat source in the northern australian proterozoic basins higher reflectance of organic matter towards the central parts of the mount isa basin and some of the most northerly parts point to proximity to higher heat flow at times in contrast to relatively low temperatures prevailing in the western parts of the basin next to the murphy inlier a close correlation shown between peak organic reflectance values and super sequence boundaries farther highlighted the valuable information to be gained from organic petrology by allowing the separation of processes responsible for metal dissolution and transportation from those inducing precipitation c 2001 elsevier science b v all rights reserved

an inverse estimate of the dynamic topography of the ocean the mean dynamic topography of the surface of the ocean is estimated using a finite difference inverse model of the ocean circulation constrained by a prior topex poseidon egm96 estimate and an ocean density climatology the egm96 geoid uncertainties are represented by their full covariance matrix the model finds a solution that yields a new 1 resolution dynamic topography estimate with a 5 cm precision the existence of this solution suggests that the uncertainties in egm96 despite being much smaller than in previous geopotential models are nonetheless realistic the geodetic information constrains the inverse estimate of the ocean circulation particularly at high latitudes

circulation characteristics in three eddy permitting models of the north atlantic a systematic intercomparison of three realistic eddy permitting models of the north atlantic circulation has been performed the models use different concepts for the discretization of the vertical coordinate namely geopotential levels isopycnal layers terrain following sigma coordinates respectively although these models were integrated under nearly identical conditions the resulting large scale model circulations show substantial differences the results demonstrate that the large scale thermohaline circulation is very sensitive to the model representation of certain localised processes in particular to the amount and water mass properties of the overflow across the greenland scotland region to the amount of mixing within a few hundred kilometers south of the sills and to several other processes at small or sub grid scales the different behaviour of the three models can to a large extent be explained as a consequence of the different model representation of these processes

diagnosing the observed seasonal cycle of atlantic subtropical mode water using potential vorticity and its attendant theorems analyzed fields of ocean circulation and the flux form of the potential vorticity equation are used to map the creation and subsequentcirculation of lowpotential vorticity waters known as subtropical mode water stmw in the north atlantic novel mapping techniques are applied to i render the seasonal cycle and annual mean mixed layer vertical flux of potential vorticity pv through outcrops and ii visualize the extraction ofpv from the mode water layer in winter over and to the south of the gulf stream both buoyancy loss and wind forcing contributetotheextractionofpv buttheauthorsfindthattheformergreatlyexceedsthelatter thesubsequent path of stmw is also mapped using bernoulli contours on isopycnal surfaces

poleward flows in the southern california current system glider observations and numerical simulation 1 three years of continuous spray glider observations in the southern california current system ccs are combined with a numerical simulation to describe the mean and variability of poleward flows in the southern ccs gliders provide upper ocean observations with good across shore and temporal resolution along two across shore survey lines while the numerical simulation provides a dynamically consistent estimate of the ocean state persistent poleward flows are observed in three areas within 100 km of the coast at point conception within the southern california bight scb and offshore of the scb and the santa rosa ridge srr poleward transport by the flows within the scb and offshore of the srr exceeds the poleward transport off point conception suggesting that the poleward flows are not continuous over the 225 km between observation lines the numerical simulation shows offshore transport between the survey lines that is consistent with some of the poleward flow turning offshore before reaching point conception the poleward current offshore of the srr is unique in that it is strongest at depths greater than 350 m and it is observed to migrate westward away from the coast this westward propagation is tied to westward propagating density anomalies originating in the scb during the spring summer upwelling season when wind stress curl is most strongly positive the across shore wave number frequency and phase speed of the westward propagation and the lack of across shore transport of salinity along isopycnals are consistent with first mode baroclinic rossby dynamics

sensitivity of western boundary transport at the mean north equatorial current bifurcation latitude to wind forcing abstractthe bifurcation of the north equatorial current nec plays an important role in the heat and water mass exchanges between the tropical and subtropical gyres in the pacific ocean the variability of western boundary transport wbt east of the philippine coast at the mean nec bifurcation latitude 12 n is examined here a tropical pacific regional model is set up based on the massachusetts institute of technology general circulation model and its adjoint which calculates the sensitivities of a defined meridional transport to atmospheric forcing fields and ocean state going backward in time the adjoint derived sensitivity of the wbt at the mean nec bifurcation latitude to surface wind stress is dominated by curl like patterns that are located farther eastward and southward with increasing time lag the temporal evolution of the adjoint sensitivity of the wbt to wind stress resembles wind forced rossby wave dynamics but propagating with speeds determined by the background stratification and curre

timing of the permian triassic biotic crisis implications from new zircon u pb age data and their limitations abstract the most profound biotic crisis in the earth s history causing the near extinction of both terrestrial and marine life occurred at the end of the permian period about 253 myr ago and marks the paleozoic mesozoic era boundary the cause of this event is still a matter of vigorous debate with both brief and catastrophic as well as gradual mechanisms having been proposed similar to a recent landmark study this study uses the u pb method on zircons from the uppermost permian lowermost triassic ash fall deposits at meishan zhejiang province se china in order to examine time and rate constraints for these events the results of both this study and previous work show that for these ash layers the effects of pb loss are combined with varying amounts and sources of inheritance resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases though the effects of pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid as opposed to commonly applied air abrasion prior to analysis the presence within a single ash layer of multiple generations of older xenocrysts in many cases only slightly older than the depositional age has made quantitative interpretation even more difficult when these combined phenomena bias individual zircon ages by less than a percent they are extremely difficult to deconvolute and if multi grain analyses are used can become impossible to recognize because of the resulting age averaging monte carlo simulations using actual measurements of individual zircon crystals show that age excursions due to pb loss and xenocrystic contamination for the meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi grain zircon samples are compared thus this study uses only high precision analyses of single crystals whether from our work or that of previous studies three main conclusions have emerged first our data require a significant increase in the age of the permian triassic boundary by more than 2 myr compared to the previous study which shifts the age to a value older than 253 ma second neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis third even large suites of very high quality single zircon u pb analyses for these tuffs cannot in most cases yield objective reliable and robust dates with accuracies at the sub myr level though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible the last conclusion is not an indictment of zircon u pb dating in general other rocks and other zircon populations can and do behave very differently and further technical advances will likely improve our ability to prepare grains or sub grains of adequately enhanced quality for analysis consequently the results of the present study strongly suggest that for problems requiring time scale accuracy inferences from zircon u pb dating must be based on sufficiently large suites of single crystal or crystal domain high precision analyses

dynamical reconstruction of upper ocean conditions in the last glacial maximum atlantic abstractproxies indicate that the last glacial maximum lgm atlantic ocean was marked by increased meridional and zonal near sea surface temperature gradients relative to today using a least squares fit of a full general circulation and sea ice model to upper ocean proxy data with specified error estimates a seasonally varying reconstruction is sought of the atlantic ocean state that is consistent with both the known dynamics and the data with reasonable uncertainty assumptions for the observations and the adjustable control variables a consistent lgm ocean state is found one not radically different from the modern one inferred changes include a strengthening of the easterly and westerly winds leading to strengthened subtropical and subpolar gyres and increased upwelling favorable winds off the coast of africa leading to particularly cold ssts in those regions

response of circulation and heat transport in the north atlantic to changes in thermohaline forcing in northern latitudes a model study to avoid an explicit simulation of the overflows across the greenland scotland ridge many models of the large scale ocean circulation seek to include the net effect of the inflowing dense water masses by restoring temperature and salinity near the ridge to observed conditions in this paper the authors examine the effect of different datasets for the northern restoring condition in two versions eddy resolving and non eddy resolving of the model of the north and equatorial atlantic that has been developed in recent years as a community modeling effort for woce it is shown that the use of smoothed climatological fields of temperature and salinity south of the denmark strait leads to strong deficiencies in the simulation of the deep flow field in the basin a switch to actual hydrographic data from the denmark strait ignites a rapid dynamic response throughout the north atlantic affecting the transport and vertical structure of the deep western boundary current and by virtue of the jebar efffect the transport of the horizontal gyres meridional overturning and northward heat transport too weak in the cases with climatological boundary conditions increase to more realistic levels in the subtropical north atlantic the initial response to switches in the high latitude thermohaline forcing is mediated by fast waves along the westurn boundary leading to changes in the deep western boundary current in low latitudes after about two years in the non eddy resolving cast the initial timescale depends on the horizontal grid spacing of the model in the high resolution case the first signal reaches the equator in a few months the adjustment to a new dynamic quasi equilibrium involves kelvin waves along the equator and rossby wave in the interior and is attained in less than two decades throughout the north atlantic it is suggested that these fast dynamic adjustment processes could play an important role in possible fluctuations of the thermohaline circulation or transitions between different equilibrium states of the coupled ocean atmosphere system and may have determined the timescale of the observed climatic transitions before and during the last deglaciation

two decades of the atlantic meridional overturning circulation anatomy variations extremes prediction and overcoming its limitations the zonally integratedmeridional volumetransport in the north atlantic atlantic meridionaloverturning circulation amoc is described in a 19 yr long ocean state estimate one consistent with a diverse global dataset apart from a weak increasing trend at high northern latitudes the amoc appears statistically stable over the last 19yr with fluctuations indistinguishable from those of a stationary gaussian stochastic process this characterization makes it possible to study using highly developed tools extreme values predictability and the statistical significance ofapparenttrends gaussianbehaviorisconsistentwith the central limittheorem for a process arising from numerous independent disturbances in this case generators include internal instabilities changes in wind and buoyancy forcing fields boundary waves the gulf stream and deep western boundary current transports the interior fraction in sverdrup balance and all similar phenomena arriving as summation effects from long distances and times as a zonal integral through the sum of the large variety of physical processes in the three dimensional ocean circulation understanding of the amoc if it is of central climate importance requires breaking it down into its unintegrated components over the entire basin

basin scale numerical modeling to test the role of buoyancy driven fluid flow and heat transfer in the formation of stratiform zn pb ag deposits in the northern mount isa basin numerical fluid flow and heat transport modeling was undertaken on a well constrained geologic section through the northern mount isa basin in order to test the possibility of forming stratiform zn pb ag deposits by buoyancy driven free convection of marine fluids the major two dimensional geologic section used for the modeling was based on recent geologic mapping and sequence stratigraphic interpretation combined with geophysical interpretation from regional seismic aeromagnetic and gravity data sets the basin fill termed the leichhardt calvert and isa superbasins forms a south dipping wedge of sedimentary and minor volcanic rocks up to 25 km thick a number of major subvertical synsedimentary normal faults cut through this fill and are rooted in the basement two potential aquifer sequences have been identified sandstones and volcanic rocks of the big supersequence at the base of the calvert superbasin and sandstones and conglomerates comprising the mount guide quartzite at the base of the older leichhardt superbasin there are three stratiform zn pb ag deposits in the younger isa superbasin close to the section line selected for modeling century is a world class and high grade stratiform zinc deposit which contains over 14 mt of zn metal hosted by 1595 ma black shales and siltstones pb pb isotope studies suggest the deposit formed about 1575 ma walford creek and blue bush are large but low grade pyrite rich and zinc poor stratiform deposits hosted in 1640 ma carbonaceous shales and siltstones numerical modeling of fluid flow at about 1575 ma shows that buoyancy driven convection is controlled by the relationship between the faults and aquifers the synsedimentary faults given high permeabilities in the model because they were active during the mineralizing event act as either recharge or discharge zones for fluid flow marine fluids commonly recharge the basin via the minor faults and flow through the sandstone and volcaniclastic aquifer sequences at depths of 5 to 10 km these fluids have the potential to leach zinc and lead from the clastic material comprising aquifer and adjacent volcanic rock layers the heated metalliferous fluids discharge to the surface where the aquifers intersect the major faults hydrothermal discharge temperatures from the termite range fault were computed to be in the range 100 to 180 c with fluid velocities of 1 to 8 m per year these conditions are suitable for the formation of a century sized zn deposit at the discharge point adjacent to the termite range fault over a period of 0 65 m y provided a suitable chemical trap environment is present several numerical simulations were run with different aquifer and fault properties designed to understand the hydrological constraints for the formation of major zn deposits aquifer permeability fault permeability and fault penetration depth were shown to be the major factors controlling the fluid flow and temperature regime significantly higher discharge fluid temperatures and velocities were obtained when the depth of penetration of the termite range fault was increased from 15 to 30 km the results of the numerical modeling are significant in understanding geologic and hydrological controls on the formation and location of major stratiform zn deposits the permeability and thickness of potential aquifers their depth in the basin the presence of stacked aquifer sequences and the relationship between aquifers and synsedimentary faults all have important exploration implications in particular the termite range fish river and elizabeth creek faults are interpreted to be major deep faults that have controlled basin wide convective fluid flow and therefore the location of major base metal deposits

pyrobitumen in south china organic petrology chemical composition and geological significance abstract pyrobitumen has been discovered in the dolostone reservoir of the central sichuan basin southwest china accumulates coevally with hydrothermal minerals in pores the pyrobitumen has strong anisotropy with an evolutionary sequence from mosaic to a fibrous texture a similar sequence of anisotropy has also been observed in mesophase pitch during the process of coking coal reflectance of the pyrobitumen shows a positive correlation with anisotropic evolution and increasing depth hopane and sterane biomarkers are abundant in extracts of highly anisotropic pyrobitumen with smooth rough hyperplastic surface and honeycomb micropores methylpyrene and methylchrysene maturity indicators and the reflectance values of pyrobitumen show a positive linear correlation in cambrian samples but show random correlation in sinian samples fluid inclusion microthermometry of hydrothermal minerals together with the burial and heat flow history of the reservoir indicate an abrupt thermal event that may have impacted the generation and evolution of pyrobitumen this appears to be confirmed by the reflectance values of pyrobitumen in the source rock and reservoir the pyrobitumen in source rock was less heated by the hydrothermal fluid due to its poor porosity and have lower reflectance values however the pyrobitumen in weathering crust reservoir was more heated by the hydrothermal fluid and have higher reflectance values because the reservoir rocks have higher porosity the occurrence and characteristics of pyrobitumen indicate an in situ pyrolysis of oil which was triggered by an abrupt thermal event in the reservoir the reconstruction of burial history and heat flow as well as the hydrothermal fluid minerals of the dolomite reservoir all indicate the thermal event of the sichuan basin might correlate with the emei mantle plume in late permian

estimated global hydrographic variability an estimate is made of the three dimensional global oceanic temperature and salinity variability omitting the seasonal cycle both as a major descriptive element of the ocean circulation and for use in the error estimates of state estimation historical hydrography recent data from the world ocean circulation experiment and argo profile data are all used root mean square vertical displacements in the upper 300 m of the ocean are generally smaller than 50 m except in energetic boundary currents and in the north atlantic subpolar gyre variability in temperature and salinity is strongly correlated below the top 100 m salinity contributions to sea surface height variability appear more significant at low latitudes than expected possibly resulting from advective and diffusive processes results are generally consistent with altimetric variability under two simple kinematic hypotheses and much of the observed structure coincides with known dynamical features a large fraction of the sea surface height variability is consistent with the hypothesis of dominance of the first baroclinic mode

uncertainties in the mean ocean dynamic topography before the launch of the gravity field and steady state ocean circulation explorer goce 1 in anticipation of the future observations of the gravity mission gravity field and steady state ocean circulation explorer goce the present day accuracy of mean dynamic topography mdt is estimated from both observations and models a comparison of five observational estimates illustrates that rms differences in mdt vary from 4 2 to 10 5 cm after low pass filtering the fields with a hamming window with wavenumber n 120 corresponding to an effective resolution of 167 km rms differences in observational mdt reduce to 2 4 8 3 cm for n 15 1334 km differences in data sources geoid model in situ data are mostly visible in the small scale oceanic features while differences in processing filtering inverse modeling techniques are reflected at larger scales a comparison of seven different numerical ocean models demonstrates that model estimates differ mostly in western boundary currents and in the antarctic circumpolar current rms differences between modeled and observed mdt are at best 8 8 cm for n 120 and reduce to 6 4 cm for n 15 for models with data assimilation a minimal rms difference of 6 6 cm n 120 to 3 4 cm n 15 is obtained with respect to the observational mdts the reduction of differences between mdts with increasing filtering scales is smaller than expected while it is expected that goce will improve mdt estimates at small spatial scales improvement of mean sea surface estimates from satellite altimetry may be needed to improve mdt estimates at larger scales

organic alteration in hydrothermal sulfide ore deposits many ore deposits are enriched in transition metals especially iron whereas organic carbon is a minor component based on currently available analyses variations in bulk chemistry of organic matter in ore deposits correlates with differences in phase equilibria in the system fe s h 2 o in the pyrrhotite and magnetite stability fields extractable organic compositions are restricted to molecules with relatively few carbons organic matter in pyrite rich deposits reflects biochemical precursors pyrite also being the stable fe s phase in fossil fuels oxidation of relatively iron poor deposits results in microbial oxidation of the organic matter in iron copper deposits oxidation results in aromatization and the generation of organosulfurs in h 2 o dominated systems the fluid is a hydrogen source to the organic matter whereas organic products in co 2 dominated fluids are hydrogen depleted the organic matter in ore deposits therefore is often considered to be an alteration product reflecting the dominant iron phase temperature and the alteration fluid composition

water mass transformation by sea ice in the upper branch of the southern ocean overturning sea ice formation is a key factor in the lower branch of the southern ocean overturning circulation observation based data in conjunction with a water mass transformation framework reveal that sea ice plays a central role in the upper branch too

influence of the 26 degrees n rapid mocha array and florida current cable observations on the ecco godae state estimate the incorporation of local temperature and salinity observations from the rapid climate change meridional overturning circulation and heatflux array rapid mocha as well as the cable estimates of volumetransport in the florida current fc is tested in the estimating the circulation and climateof the ocean global ocean data assimilation experiment ecco godae estimation system for their impact on the estimate of the meridional overturning circulation moc and the meridional heat transport in the atlantic an experimental setup covering the first deployment period of rapid mocha from march 2004 to march 2005 is used to test different strategies for incorporating these datasets incorporating both monthly meansofthefcdataandmonthlymeansoftherapid mochatemperatureandsalinitymeasurementsat the eastern and western boundaries of the basin as an observational constraint in a 1 yr experiment results in an adjustment to the referenceestimate whichdoes not include these datasets of approximately 1 sv 1 sv 10 6 m 3 s 21 in the moc at 268n and the adjacent latitudes approximately 6158 with a larger northward branch of the moc above 1000 m compensated by a larger flow in the southward branch of the moc between approximately 2000 and 3000 m the meridional heat transport from 268n to near 408n is approximately 0 05 pw larger than in the reference experiment

bottom pressure signature of annual baroclinic rossby waves in the northeast tropical pacific ocean the annual cycle in bottom pressure pb in the northeast tropical pacific ocean ntpo is studied focus is on a zonal section along 12 n between 105 w and 145 w that is characterized by a strong annual cycle in sea level from satellite altimetry estimates of pb from the gravity recovery and climate experiment grace a state estimate produced by the estimating the circulation and climate of the ocean ecco consortium and a linear rossby wave model lrwm are used the grace ntpo pb annual cycle shows amplitudes as large as 1 cm water equivalent the grace data also evidence westward propagation that is consistent with the behavior of long mode 1 rossby waves at this latitude with phase increasing from east to west at a rate of 0 34 m s 1 the ecco and lrwm pb estimates corroborate the notion that grace reveals the pb signature of annual rossby waves driven by interior wind stress curl and possibly damped by frictional processes results have implications for attempts to constrain global ocean mass using a single point mooring

planetary geometric constraints on isopycnal slope in the southern ocean abstracton planetary scales surface wind stress and differential buoyancy forcing act together to produce isopycnal surfaces that are relatively flat in the tropics subtropics and steep near the poles where they tend to outcrop tilted isopycnals in a rapidly rotating fluid are subject to baroclinic instability the turbulent mesoscale eddies generated by this instability have a tendency to homogenize potential vorticity pv along density surfaces in the southern ocean so the tilt of isopycnals is largely maintained by competition between the steepening effect of surface forcing and the flattening effect of turbulent spatially inhomogeneous eddy fluxes of pv here quasigeostrophic theory is used to investigate the influence of a planetary geometric constraint on the equilibrium slope of tilted density buoyancy surfaces in the so if the meridional gradients of relative vorticity and pv are small relative to then quasigeostrophic theory predicts ds dz f0 cot 0 a or equivalently r z

upper ocean flow statistics estimated from superresolved sea surface temperature images ocean turbulence on scales of 10 50 km plays a key role in biogeochemical processes frontal dynamics and tracer transport in the upper ocean but our understanding of these scales is limited because they are too small to be resolved using extant satellite altimetry products by contrast microwave imagery of the sea surface temperature field does resolve these scales and can be used to estimate the upper ocean flow field due to the strong correlation between the surface density field and the interior potential vorticity however because the surface density or temperature is a smoothed version of the geostrophic stream function the resulting velocity field estimates are limited to scales of 100 300 km in the first few hundred meters of the water column a method is proposed for generating superresolved sea surface temperature images using direct low resolution microwave temperature observations in combination with an empirical parameterization for the unresolved scales modeled on statistical information from high resolution infrared imagery because the method relies only on the statistics of the small scale field it is insensitive to data outages due to cloud cover that affect infrared observations the method enhances the effective resolution of the temperature images by exploiting the effect of spatial aliasing and generates an optimal estimate of the small scale temperature field using standard bayesian inference the technique is tested in quasigeostrophic simulations driven by realistic climatological shear and stratification profiles for three contrasting regions at high middle and low latitudes the resulting superresolved sea surface temperature images are then used to estimate the three dimensional velocity field in the upper ocean on scales of 10 50 km

surface vertical pv fluxes and subtropical mode water formation in an eddy resolving numerical simulation abstract subtropical mode waters are characterized by low potential vorticity pv and so the mechanisms by which pv is extracted from the ocean by air sea interaction are of great relevance to our understanding of how mode waters are formed this study analyzes those mechanisms by comparing the magnitude and spatial patterns of surface pv fluxes of diabatic and frictional origin in a high resolution numerical simulation of the north atlantic the model resolves mesoscale eddies and exhibits realism in the volume and regional distribution of subtropical mode water both in the annual mean and seasonal cycle it is found that the diabatic and mechanic fluxes of pv through the sea surface are of similar amplitude locally but their spatial structures are very different the diabatic pv flux has a large scale pattern that reflects that of air sea heat fluxes directed from the ocean to the atmosphere along and to the south of the separated gulf stream in contrast the mechanical pv flux because of its dependence on horizontal surface density gradients exhibits much smaller scales but embedded within a coherent large scale pattern when mapped over the north atlantic subtropical mode water edw outcropping region the diabatic pv flux pattern is found to be directed out of the ocean everywhere whereas the mechanical pv fluxes exhibits small scale patterns of both sign the amplitude of the diabatic pv fluxes is found to be at least one order of magnitude larger than the mechanical pv fluxes demonstrating the overwhelming importance of diabatic processes in creating mode waters finally we note that the large scale climatological patterns and magnitudes of both diabatic and mechanical pv flux mapped over the edw outcropping region are very similar to patterns obtained from coarse grained ocean state estimates that do not resolve the eddy field

timing and chemistry of fluid flow events in the lawn hill platform northern australia mudrocks and carbonates of the isa superbasin in the lawn hill platform in northern australia host major base metal sulfide mineralization including the giant strata bound century zn pb deposit mineral paragenesis stable isotope and k ar dating studies demonstrate that long lived structures such as the termite range fault acted as hot fluid conduits several times during the paleoproterozoic and mesoproterozoic in response to major tectonic events illite and chlorite crystallinity studies suggest the southern part of the platform has experienced higher temperatures up to 300 degrees c than similar stratigraphic horizons in the north the irregular downhole variation of illite crystallinity values provides further information oil the thermal regime in the basin and shows that clay formation was controlled not only by temperature increase with depth but also by high water rock ratios along relatively permeable zones k ar dating of illite in combination with other data may indicate three major thermal events in the central and northern lawn hill platform lit 1500 1440 to 1400 and 1250 to 1150 ma this study did not detect the earlier century base metal mineralizing event at 1575 ma 1500 ma ages are recorded only in the south and correspond to the age of the late isan orogeny and deposition of the lower roper superbasin they may reflect exhumation of a provenance region the 1440 to 1300 ma ages are related to fault reactivation and a thermal pulse at similar to 1440 to 1400 ma possibly accompanied by fluid flow with subsequent enhanced cooling possibly due to thermal relaxation or further crustal exhumation the youngest thermal and or fluid flow event at 1250 to 1150 ma is recorded mainly to the cast of the tern lite range fault and may be related to the assembly of the rodinian supercontinent fluids in equilibrium with illite that formed over a range of temperatures at different times in different parts of the platform have relatively uniform oxygen isotope compositions and more variable hydrogen isotope compositions delta o 18 3 5 9 7 parts per thousand v smow delta d 94 to 36 parts per thousand v smow the extent of the 180 enrichment and the variably depleted hydrogen isotope compositions suggest the illite interacted with deep basin hypersaline brines that were composed of evaporated seawater and or highly evolved meteoric water siderite is the most abundant iron rich gangue phase in the century zn pb deposit which is surrounded by all extensive ferroan carbonate alteration halo modeling suggests that the ore siderite formed at temperatures of 120 degrees to 150 degrees c whereas siderite and ankerite in the alteration halo formed at temperatures of 150 degrees to 180 degrees c the calculated isotopic compositions of the fluids are consistent with o 18 rich basinal brines and mixed inorganic and organic carbon sources 6180 3 10 parts per thousand v smow delta c 13 7 to 3 parts per thousand v pdb in the northeast lawn hill platform carbonate rich rocks preserve marine to early diagenetic carbon and oxygen isotope compositions whereas ferroan carbonate cements in siltstones and shales in the desert creek borehole are o 18 and c 13 depleted relative to the sedimentary carbonates the good agreement between temperature estimates from illite crystallinity and organic reflectance 160 degrees 270 degrees c and inverse correlation with carbonate delta o 18 values indicates that organic maturation and carbonate precipitation in the northeast lawn hill platform resulted from interaction with the 1250 to 1150 ma fluids the calculated isotopic compositions of the fluid are consistent with evolved basinal brine delta o 18 5 1 9 4 parts per thousand v smow delta c 13 13 2 to 3 7 parts per thousand v pdb that contained a variable organic carbon component from the oxidation and or hydrolysis of organic matter in the host sequence the occurrence of extensive o 18 and c 13 depleted ankerite and siderite alteration in desert creek is related to the high temperature of the 1250 to 1150 ma fluid flow event in the northeast lawn hill platform in contrast to the lower temperature fluids associated with the earlier century zn pb deposit in the central lawn hill platform

direct estimate of lateral eddy diffusivity upstream of drake passage abstractthe first direct estimate of the rate at which geostrophic turbulence mixes tracers across the antarctic circumpolar current is presented the estimate is computed from the spreading of a tracer released upstream of drake passage as part of the diapycnal and isopycnal mixing experiment in the southern ocean dimes the meridional eddy diffusivity a measure of the rate at which the area of the tracer spreads along an isopycnal across the antarctic circumpolar current is 710 260 m2 s 1 at 1500 m depth the estimate is based on an extrapolation of the tracer based diffusivity using output from numerical tracers released in a one twentieth of a degree model simulation of the circulation and turbulence in the drake passage region the model is shown to reproduce the observed spreading rate of the dimes tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m2 s 1 and peaks at the steering level near 2 km where the eddy ph

volcanically induced environmental change at the permian triassic boundary xiakou hubei province south china related to west siberian coal field methane releases a detailed geochemical investigation of the permian triassic boundary in a carbonate ramp setting at xiakou south china provides new insights regarding the role of volcanism in the largest mass extinction in earth history the xiakou section records 9 intervals of volcanic activity some producing up to 25 cm thick composite ash layers during the latest permian and earliest triassic each volcanic episode coincided with major changes in marine environments the largest changes occurred in conjunction with volcanic interval vi 4 correlative with the latest permian mass extinction during which 1 the oceanic oxygen minimum zone expanded as shown by framboidal pyrite flux 2 marine productivity declined sharply as shown by multiple productivity proxies and 3 climate conditions became more humid as shown by increased clay fluxes the mechanism by which volcanic eruptions forced marine environmental changes may be inferred from the relationship between ash layer thickness and the magnitude of the associated negative c isotope excursion the most likely connection is through volcanogenic methane release to the atmosphere possibly as a result of magmatic intrusions into the west siberian coal basin triggering increases in global temperature and humidity these climate changes in turn resulted in stronger oceanic stratification oxygen minimum zone expansion and a decline in marine productivity the xiakou section is important in demonstrating links between volcanism and the marine environment during the permian triassic transition interval

microbial remains in some earliest earth rocks comparison with a potential modern analogue abstract carbonaceous matter cm from ca 3 5 ga hydrothermal black cherts of the pilbara craton of western australia and the barberton greenstone belt of south africa yielded transmission electron microscopy tem images that are suggestive of microbial remains and possible remnants of microbial cell walls these are compared to a potential modern analogue the hyperthermophilic methanocaldococcus jannaschii derived from an active seafloor hydrothermal environment and cultured under similar conditions a striking resemblance to the early archaean forms was evident in wall structure and thermal degradation mode cell disintegration of the cultures occurred at 100 c marking the limits of life complete disintegration deformation and shrinkage occurred at 132 c a multidisciplinary approach to the characterisation of the cm was undertaken using organic petrology tem coupled with electron dispersive spectral analysis eds high resolution tem hrtem to determine molecular ordering and elemental and carbon isotope geochemistry reflectance measurements of the cm to determine thermal stress yielded a range of values corresponding to several populations and pointing to different sources and processes the 13c values of dresser formation cm 36 5 to 32 1 are negatively correlated with toc 0 13 0 75 and positively correlated with c n ratio 134 569 which is interpreted to reflect the relative abundance of high ro oxidised recycled cm and preferential loss of 12c and n during thermal maturation tem observations inferred carbon isotopic heterogeneity and isotope fractionations of 27 to 32 are consistent with the activity of chemosynthetic microbes in a seafloor hydrothermal system where rapid silicification at relatively low temperature preserved the cm

lee wave generation rates in the deep ocean using the world s largest data set of in situ ocean current measurements combined with a high resolution topography roughness data set we use a model assisted hierarchical clustering methodology to estimate the global lee wave generation rate at the ocean floor our analysis suggests that internal wave generation contributes 0 75 0 19 tw 2 standard deviation to the oceanic energy budget but with a strong dependence on the brunt vaisala buoyancy frequency climatology used this estimate is higher than previous calculations and suggests that internal wave generation may be a much more significant contributor to the global oceanic mechanical energy budget than had previously been assumed our results imply that lee wave generation and propagation may be a dominant sink of at least half and potentially the overwhelming majority of ocean surface wind work on the geostrophic circulation

on the patterns of wind power input to the ocean circulation pathways of wind power input into the ocean general circulation are analyzed using ekman theory direct rates of wind work can be calculated through the wind stress acting on the surface geostrophicflow however because that energy is transported laterally in the ekman layer the injection into the geostrophic interior is actuallycontrolledby ekmanpumping with a patterndeterminedby the windcurl ratherthanthe wind itself regions of power injection into the geostrophic interior are thus generally shifted poleward compared to regions of direct wind power input most notably in the southern ocean where on average energy enters the interior 108 south of the antarctic circumpolar current core an interpretation of the wind power input to the interior is proposed expressed as a downward flux of pressure work this energy flux is a measure of the work done by the ekman pumping against the surface elevation pressure helping to maintain the observed anomaly of sea surface height relative to the global mean sea level

the partition of regional sea level variability abstract the existing altimetric record offers an unprecedented view of sea level variability on a global scale for more than 2 decades optimal inference from the data involves appropriate partition of signal and noise in terms of relevant scales physical processes and forcing mechanisms such partition is achieved here through fitting a general circulation model to altimeter and other datasets to produce a best estimate of variability directly forced by the atmosphere the signal of primary interest here in this context noise comes primarily from instrument errors and meso scale eddies as expected but spatial smoothing effectively reduces this noise a separate constraint is thus formulated to measure the fit to monthly large scale altimetric variability that unlike the daily pointwise constraint shows a high signal to noise ratio the estimate is explored to gain insight into dynamics forcing and other factors controlling variability contributions from thermo steric halo steric and bottom pressure terms are all important depending on region but slopes of steric spectra red and bottom pressure spectra white are nearly invariant with latitude much variability can be represented by a seasonal cycle and linear trend plus a few eofs that can be associated with known modes of climate variability and or with topographic controls both wind and buoyancy forcing are important the response is primarily basin bound in nature but uneven patterns of propagation across basin boundaries are clearly present with the pacific being able to affect large portions of the indian and atlantic basins but the atlantic affecting mostly the arctic

raman characterization of carbonaceous material in the macraes orogenic gold deposit and metasedimentary host rocks new zealand abstract raman spectroscopic and petrographic analyses were performed on samples collected from zones distal and proximal to the macraes gold deposit in the otago schist of new zealand to characterize the features and possible origins of carbonaceous material cm and to assess the potential role of cm in the formation of gold deposits cm is a common component in meta sedimentary orogenic gold deposits and it has been proposed that cm contributes to gold mineralization processes but the details of the mechanisms responsible are not fully understood documentation of the origins of the otago schist cm will improve our understanding of the role of cm in gold deposits this work has identified four types of cm of varying thermal maturity and origins from prehnite pumpellyite grade to lower greenschist grade samples in prehnite pumpellyite and pumpellyite actinolite grade rocks low maturity cm 1 coexists with framboidal pyrite indicating an in situ sedimentary origin with a potential association with the source of gold low crystallinity cm 2 is also found in low grade samples and is likely to have been deposited from fluids unrelated to gold mobilization cm 3 is the highest maturity cm recognized cm 3 is found in samples from the highest metamorphic grades studied lower greenschist facies where bands of cm 3 cross cut the foliation cm 3 is therefore thought to have been transported by fluids though possibly only at short length scales cm 4 is less mature than cm 3 and is found in mineralized rocks in association with sulfide minerals and gold cm 4 is likely to have a depositional origin but its precise role with respect to gold mineralization has not been identified

estimates of ocean macroturbulence structure function and spectral slope from argo profiling floats abstractthe argo profiling float network has repeatedly sampled much of the world ocean this study uses argo temperature and salinity data to form the tracer structure function of ocean variability at the macroscale 10 1000 km mesoscale and above here second order temperature and salinity structure functions over horizontal separations are calculated along either pressure or potential density surfaces which allows analysis of both active and passive tracer structure functions using argo data a map of global variance is created from the climatological average and each datum when turbulence is homogeneous the structure function slope from argo can be related to the wavenumber spectrum slope in ocean temperature or salinity variability this first application of structure function techniques to argo data gives physically meaningful results based on bootstrapped confidence intervals showing geographical dependence of the structure functions with slopes near on average independent of depth

u pb zircon geochronology and geochemistry from ne vietnam a tectonically disputed territory between the indochina and south china blocks volcanoplutonic complexes in ne vietnam have recently been interpreted as intraplate products of the emeishan plume alternatively mafic ultramafic rocks have been considered as dismembered palaeotethyan ophiolites juxtaposed along a tectonic melange zone new u pb zircon geochronological and geochemical datasets presented here suggest a complex geological history that records collision between the indochina south china blocks mafic ultramafic rocks exposed within a tectonic melange song hien tectonic zone include sub alkaline pillow basalts that define two geochemically distinct ophiolitic suites sh 1 n morb like sh 2 transitional e morb like both suites have geochemical signatures suggestive of crustal contamination compatible with a volcanic passive margin rift setting we suggest that sh 1 basalts may correlate with the devonian carboniferous jinshajiang ailaoshan song ma branch of the palaeotethys and form part of the associated dian qiong belt whereas sh 2 basalts are co magmatic with middle late permian mafic ultramafic intrusive rocks dolerites gabbros peridotites that developed in a rift basin most likely on the margin of the down going south china plate during west vergent subduction beneath indochina during continental orogenesis and thrust stacking these ophiolitic rocks were juxtaposed with other lithotectonic blocks within the song hien tectonic zone post collisional relaxation led to the development of a rift basin song hien rift comprising late permian triassic volcano sedimentary strata including 270 265 ma terrigenous sandstones 252 ma mudstones and c 254 248 ma felsic effusives granites and granodiorites were emplaced across ne vietnam between c 252 and 245 ma in a syn to post collisional setting the late permian early triassic felsic magmatic rocks best correlate with coeval rocks in sw guangxi and the central and western ailaoshan fold belts china and the truong son fold belt vietnam together they signal the final to post collisional stages of indochina south china collision we demonstrate that the analysed magmatic rocks in the lo gam song hien domains of ne vietnam are not genetically linked to the emeishan large igneous province in the yangtze block of south china as has been previously widely proposed

isopycnal mixing in ocean circulation models abstract a subgrid scale form for mesoscale eddy mixing on isopycnal surfaces is proposed for use in non eddy resolving ocean circulation models the mixing is applied in isopycnal coordinates to isopycnal layer thickness or inverse density gradient as well as to passive scalars temperature and salinity the transformation of these mixing forms to physical coordinates is also presented

the role of sandstone diagenesis and aquifer evolution in the formation of uranium and zinc lead deposits southern mcarthur basin northern territory australia the paleo to mesoproterozoic mcarthur basin in the northern territory australia is filled with mixed carbonate siliciclastic successions and felsic and mafic volcanic units that contain authigenic minerals that formed during burial diagenesis petrographic investigations indicate that some of these lithologic units were cemented early by quartz overgrowths and became diagenetic aquitards whereas secondary porosity was developed in others that became diagenetic aquifers for basinal brines the authigenic minerals in both lithology types preserve geochemical information about the types of fluids that occurred in the basin with those that resided in the diagenetic aquifers having similar geochemical composition to those indicated by alteration minerals in the mcarthur river pb zn deposit and the westmoreland u deposits quartz overgrowths formed early during shallow burial in all clastic lithologic units and are particularly common in the well sorted marine sediments these became diagenetic aquitards due to the porosity occluding cement in the calcareous units early dolomite replaced calcite and aragonite at shallow burial depths fluid inclusion microthermometry indicates that most quartz overgrowths formed between 80 and 125 c from a fluid with a salinity between 0 and 13 1 wt percent nacl equiv the isotopic composition of dolomite indicates 18ofluid of 4 5 1 5 per mil and 13cfluid of 6 9 1 0 per mil suggesting formation from a mixed marine and meteoric fluid illite cemented by early quartz has a 40ar 39ar age of 1738 10 ma in one diagenetic aquitard which reflects the age when the host sediment was deposited and confirms that quartz cementation occurred early during burial with increased burial the poorly sorted sandstones and conglomerates that were initially poor aquifers at or near the surface experienced framework grain dissolution and the creation of secondary porosity at depth as a result the sediments of the westmoreland conglomerate the lower yiyintyi sandstone significant proportions of the warramana sandstone and most of the sandstone interbeds of the gold creek volcanics became diagenetic aquifers and conduits for basinal brines illite dolomite and chlorite formed late in the paragenesis and filled the secondary porosity quartz veins formed last and primarily in faults and fractures the dolomite and quartz veins contain fluid inclusions that have low eutectic temperatures indicative of ca2 and na dominated brines and salinities between 18 5 and 30 9 wt percent nacl equiv illite crystallinity data and chlorite chemical compositions indicate formation between 150 and 250 c the isotopic compositions of illite and chlorite indicate 18ofluid values between 2 9 and 9 1 per mil and dfluid values between 61 and 25 per mil which suggest formation from a mixed meteoric and marine fluid these 18ofluid values are indistinguishable from those determined from the isotopic composition of alteration minerals at the mcarthur river pb zn deposit 5 5 or synore illite at the westmoreland uranium deposit 4 2 suggesting that the diagenetic aquifers and the deposits may be linked argon ages of illite from the diagenetic aquifers indicate that fluid migration began as early as 1680 ma and continued to approximately 1541 ma coinciding with and extending past the time when the mcarthur river pb zn deposit 1640 ma and the westmoreland u deposits 1655 1606 ma formed the results presented in this study show that clastic sediments dominated by poorly sorted sandstone and conglomerate facies evolved through burial diagenesis to become aquifer lithologic units that hosted basinal brines with chemical characteristics and ages similar to those that are reported from the pb zn and u deposits of the southern mcarthur basin

on the sensitivity of the drake passage transport to air sea momentum flux an eddy permitting state estimate and its adjoint are used to analyze the influence of wind stress perturbations on the transport of the antarctic circumpolar current acc system through drake passage the transport is found to be sensitive to wind stress perturbations both along the acc path and also in remote regions the time scale of influence of wind stress perturbations is on the order of 100 days regarding spatial scales the sensitivity of transport to wind stress is relatively smooth in regions offlat topography in boundary regions and regions with complex topography however the sensitivity is enhanced and characterized by shorterlengthscalesoforder100 km positiveperturbationstothezonalwindstressusuallyincreasetheacc transport though the wind stress curl is of primary influence where the currents are steered by topography highlighting locations where the acc is especially responsive to air sea momentum fluxes reveals where an accurate determination of atmospheric winds may best enhance ocean modeling efforts

review and update of the applications of organic petrology part 2 geological and multidisciplinary applications abstract the present paper is focused on organic petrology applied to unconventional and multidisciplinary investigations and is the second part of a two part review that describes the geological applications and uses of this branch of earth sciences therefore this paper reviews the use of organic petrology in investigations of i ore genesis when organic matter occurs associated with mineralization ii the behavior of organic matter in coal fires self heating and self combustion iii environmental and anthropogenic impacts associated with the management and industrial utilization of coal iv archeology and the nature and geographical provenance of objects of organic nature such as jet amber other artifacts and coal from archeological sites and v forensic science connected with criminal behavior or disasters this second part of the review outlines the most recent research and applications of organic petrology in those fields

on the time mean state of ocean models and the properties of long range acoustic propagation 1 receptions on three vertical hydrophone arrays from basin scale acoustic transmissions in the north pacific during 1996 and 1998 are used to test the time mean sound speed properties of the world ocean atlas 2005 woa05 of an eddying unconstrained simulation of the parallel ocean program pop and of three data constrained solutions provided by the estimating the circulation and climate of the ocean ecco project a solution based on an approximate kalman filter from the jet propulsion laboratory ecco jpl a solution based on the adjoint method from the massachusetts institute of technology ecco mit and an eddying solution based on a green s function approach from ecco phase ii ecco2 predictions for arrival patterns using annual average woa05 fields match observations to within small travel time offsets 0 3 1 0 s predictions for arrival patterns from the models differ substantially from the measured arrival patterns from the woa05 climatology and from each other both in terms of travel time and in the structure of the arrival patterns the acoustic arrival patterns are sensitive to the vertical gradients of sound speed that govern acoustic propagation basin scale acoustic transmissions therefore provide stringent tests of the vertical temperature structure of ocean state estimates this structure ultimately influences the mixing between the surface waters and the ocean interior the relatively good agreement of the acoustic data with the more recent ecco solutions indicates that numerical ocean models have reached a level of accuracy where the acoustic data can provide useful additional constraints for ocean state estimation

intermediate depth circulation of the indian and south pacific oceans measured by autonomous floats as part of the world ocean circulation experiment 306 autonomous floats were deployed in the tropical and south pacific ocean and 228 were deployed in the indian ocean to observe the basinwide circulation near 900 m depth mean velocities seasonal variability and lateral eddy diffusivity from the resultant 2583 float years of data are presented area averages local function fits and a novel application of objective mapping are used to estimate the mean circulation patterns of mean circulation resemble those at the surface in both basins well developed subtropical gyres twice as strong in the indian ocean as in the pacific feed western boundary currents tropical gyres are separated by eastward flow along the equator in both hemispheres of both basins although the indian subcontinent splits the north indian tropical gyre the antarctic circumpolar current acc and west wind drifts are prominent in both basins generally tending slightly southward but deviating to the north behind the del cano kerguelen and campbell plateaus and of course south america remarkably the eastern boundaries of the southern subtropical gyres in all three basins apparently occur in the ocean interior away from land the indian ocean s subtropical gyre and perhaps part of the south atlantic s reaches east to a retroflection just upstream of the campbell plateau south of new zealand seasonal variability at 900 m is focused around the equator with weaker variability found near certain bathymetric features there is a remarkable agreement between the observed seasonable variability and that predicted by the jet propulsion laboratory jpl estimating the circulation and climate of the ocean ecco data assimilating numerical model aside from seasonal effects eddy variability is greatest along the equator in tropical and subtropical western basins and along the acc integrals of velocity across regional passages tasman sea mozambique channel provide useful reference for hydrographic analyses of transport across whole ocean basins however the uncertainty associated with the appropriate continuity relation for horizontal flow e g geostrophy vs nondivergence is comparable to the mean flow

adjoint sensitivity of the nino 3 surface temperature to wind forcing theevolutionof sea surface temperature sst overthe easternequatorialpacific playsa significant rolein the intense tropicalair sea interaction there and is of central importance to the el nino southern oscillation enso phenomenon effects of atmospheric fields especially wind stress and ocean state on the eastern equatorial pacific sst variations are investigated using the massachusetts institute of technology general circulation model mitgcm and its adjoint model which can calculate the sensitivities of a cost function in this case the averaged 0 30 m temperature in the nino 3 region during an enso event peak to previous atmospheric forcing fields and ocean state going backward in time the sensitivity of the nino 3 surface temperature to monthly zonal wind stress in preceding months can be understood by invoking mixed layer heat balance ocean dynamics and especially linear equatorial wave dynamics the maximum positive sen sitivity of the nino 3 surface temperature to local wind forcing usually happens 1 2 months before the peak of the enso event and is hypothesized to be associated with the ekman pumping mechanism in model experiments itsmagnitudeiscloselyrelatedtothesubsurfaceverticaltemperaturegradient exhibitingstrong event to eventdifferenceswithstrong weak positivesensitivityduringla nina strongelnino events the adjoint sensitivity to remote wind forcing in the central and western equatorial pacific is consistent with the standardhypothesisthattheremotewindforcingaffectsthenino 3surfacetemperature indirectlybyexciting equatorial kelvin and rossby waves and modulating thermocline depth in the nino 3 region the current adjoint sensitivity study is consistent with a previous regression based sensitivity study derived from per turbation experiments finally implication for enso monitoring and prediction is also discussed

monitoring the transport of the antarctic circumpolar current at drake passage abstract data from an extensive moored instrument array and three hydrographic cruises are used to calculate a time series of the net transport through the upper 2500 m of the drake passage the baroclinic geostrophic transport was monitored with heavily instrumented moorings at each side of the passage pressure gauge measurements at the northern and southern ends of the passage provided a reference speed at 500 m to adjust the relative transport the net transport of the upper 2500 m for the 370 day record ending in january 1980 averaged 121 106 m3 s 1 the total transport through the entire cross sectional area of drake passage is probably between 118 and 146 106 m3 s 1 fluctuations in the relative transport are related to changes in latitude of the northernmost front in the passage the subantarctic front variability of the net transport is coherent with the zonally averaged eastward wind stress

dynamically consistent hydrography and absolute velocity in the eastern north atlantic ocean the problem of mapping a dynamically consistent hydrographic field and associated absolute geostrophic flow in the eastern north atlantic between 24 deg and 36 deg n is related directly to the solution of the so called thermocline equations a nonlinear optimization problem involving needler s p equation is solved to find the hydrography and resulting flow that minimizes the vertical mixing above about 1500 m in the ocean and is simultaneously consistent with the observations a sharp minimum at least in some dimensions is found apparently corresponding to a solution nearly conserving potential vorticity and with vertical eddy coefficient less than about 10 exp 5 sq m s estimates of residual quantities such as eddy coefficients are extremely sensitive to slight modifications to the observed fields boundary conditions vertical velocities etc are a product of the optimization and produce estimates differing quantitatively from prior ones relying directly upon observed hydrography the results are generally insensitive to particular elements of the solution methodology but many questions remain concerning the extent to which different synoptic sections can be asserted to represent the same ocean the method can be regarded as a practical generalization of the beta spiral and geostrophic balance inverses for the estimate of absolute geostrophic flows numerous improvements to the methodology used in this preliminary attempt are possible

fluid flow during deformation associated with structural closure of the isa superbasin at 1575 ma in the central and northern lawn hill platform northern australia proterozoic rocks of the isa superbasin in northern australia host globally significant pb zn ag deposits as well as a series of cu cu au and u deposits this numerical modeling study explores fluid flow patterns during the shortening deformation event associated with the initial stages of the structural inversion of the isa superbasin at ca 1575 ma the major objective of this work is to explore a series of scenarios for the isa superbasin the models of coupled deformation and fluid flow processes presented in this paper include 1 basin fluid flow in a basin inversion environment subject to shortening 2 syntectonic dehydration related fluid production 3 hydrofracturing and permeability creation 4 aquifer permeability changes with depth and 5 the effect of a buried fault versus an open fault in a scenario only considering the interaction of deformation and fluid flow during basin inversion intense upward flow along basin scale faults and strong lateral flow along the well connected segments of major aquifer horizons dominate the fluid flow field the combinations of deformation features aquifer geometry and fault distribution result in different fluid flow patterns across the simulated section this seems to suggest some fluid compartmentalization resulting in variations in fluid chemistry and mineralization across the region the incorporation of dehydration fluid production and hydrofracturing permeability creation both significantly increase fluid flow expressed as greater fluid fluxes and volumes along faults and aquifer units scenarios that consider hydrofracturing permeability development also indicate more efficient fluid migration during basin inversion permeability creation as a result of hydrofracturing allows fluids to migrate more efficiently through rocks along newly developed high permeability horizons and to converge more efficiently into basin scale faults assuming an open fault i e a fault with access to the surface also increases upward fluid flux along the fault the models also demonstrate the effects of changing permeability of aquifer units with depth on fluid flow the key implication of the current modeling results is that shortening deformation during the inversion of the isa superbasin assisted by dehydration related fluid release at deep levels and hydrofracturing related permeability generation could have created efficient multiple fluid pathways through the stratigraphic sequence with multiple aquitard units and increased fluid flow along and near faults in the region

microbial remains and other carbonaceous forms from the 3 24 ga sulphur springs black smoker deposit western australia well preserved carbonaceous materials including filamentous microbial remains have been isolated from an archaean sedimentary package overlying the sulphur springs volcanic hosted massive sulphide vhms deposit in the pilbara of western australia one of the oldest best preserved vhms deposits on earth the isotopically light carbonaceous material 13 c values of 26 8 to 34 0 v pdb occurs as finely striated lenticular to banded organic matter om within fine grained epiclastic sediments and silicified materials that overlie the deposit the predominant banded lenticular carbonaceous material occurs parallel to original sedimentary bedding planes and is distinctly visible in light microscopy transmission electron microscopy tem reveals this om as bundles of filamentous and tubular structure closely resembling both modern day and more ancient microbial forms documented from sea floor hydrothermal environments total organic carbon toc has a range of 1 0 to 2 3 while the thermal maturity of the filamentous microbial bundles indicated by reflectance ro points to maximum temperatures since deposition ca 3 24 ga of around 90 100 c a factor that has enabled the preservation of their morphology these results and the intimate association of sulphides with the om are suggestive of a well developed archaean sediment hosted microbial community situated within a basinal environment associated with an active centre of seafloor hydrothermal activity 2007 elsevier b v all rights reserved

temporal variability of the atlantic meridional overturning circulation at 26 5 n the vigor of atlantic meridional overturning circulation moc is thought to be vulnerable to global warming but its short term temporal variability is unknown so changes inferred from sparse observations on the decadal time scale of recent climate change are uncertain we combine continuous measurements of the moc beginning in 2004 using the purposefully designed transatlantic rapid climate change array of moored instruments deployed along 26 5 n with time series of gulf stream transport and surface layer ekman transport to quantify its intra annual variability the year long average overturning is 18 7 5 6 sverdrups sv range 4 0 to 34 9 sv where 1 sv a flow of ocean water of 106 cubic meters per second interannual changes in the overturning can be monitored with a resolution of 1 5 sv

convergent continental margin volcanic source for ash beds at the permian triassic boundary south china constraints from trace elements and hf isotopes abstract volcanic activity around the time of the permian triassic boundary ptb has been proposed as a trigger for the associated biocrisis multiple claystone beds are prominent near the ptb sections in south china twenty one ptb ash beds from three sections at shangsi jianshi and meishan in south china were sampled and analyzed volcanic ash geochemistry indicate dacite and rhyolite compositions zircons from the ash layers yield comparatively low nb hf and high th nb ratios falling in the range of arc orogenic related settings zircon hf isotope compositions show that ehf t values vary from 11 7 to 1 8 indicating involvement of both juvenile and ancient crustal components the ash beds ss27a js129 js130 js133 ms25 ms26 near the biotic extinction horizon display a large variation in ehf t and relatively positive average values indicating input of juvenile mantle or crust and implying rapid transit through the older basement of the south china craton spatial and temporal distribution of ash beds from thirty one ptb sections worldwide reveal that volcanic ash beds occur mainly in or proximal to the tethys region and were sourced locally integration of hf isotope and trace element compositions from magmatic zircons suggests that the ptb volcanism occurred along the convergent continent margin in or near southwestern south china as a result of the closure of the paleo tethys ocean

global ocean circulation during 1992 1997 estimated from ocean observations and a general circulation model 1 a three dimensional oceanic state is estimated for the period 1992 1997 as it results from combining large scale ocean data sets with a general circulation model at the cost of increased computational load the estimation assimilation method is chosen specifically so that the resulting state estimate is consistent with the model equations having no artificial sources or sinks to bring the model into close agreement with observations its initial temperature and salinity conditions are permitted to change as are the time dependent surface fluxes of momentum heat and freshwater resulting changes of these control vectors are largely consistent with accepted uncertainties in the hydrographic climatology and meteorological analyses the assimilation procedure is able to correct for many of the traditional shortcomings of the flow field by changing the surface boundary conditions changes in the resulting flow field are predominantly on the gyre scale and affect many features that are often poorly simulated in traditional numerical simulations such as the strengths of the gulf stream and its extension the azores current and the anticyclonic circulation associated with the labrador sea tests of the results and their consistency with prior error assumptions show that the constrained model has moved considerably closer to the observations imposed as constraints but has also moved closer to independent data from the world ocean circulation experiment not used in the assimilation procedure in some regions where the comparisons remain indeterminate not enough ocean observations are available and it is difficult to ascribe the residuals to either the model or the observations although problems remain a useful first solution to the global time dependent ocean state estimation problem has been found the estimates will continue to improve through the evolution of numerical models computer power increases more data and more efficient estimation methods

on the influence of dsow in a numerical model of the north atlantic general circulation abstract two numerical experiments regarding the north atlantic circulation are compared the two experiments are initialized with climatological temperatures and salinities and are integrated for ten years with different surface boundary conditions in the lceland sea one case climatological wind stress sst and surface salinity to force the model it reproduces the atlantic circulation found in similar studies a change in surface boundary values in the iceland sea in order to improve the denmark strait overflow water properties in the second case results in major changes in circulation and hydrography the meridional overturning more than doubles and horizontal gyres are intensified recirculation cells occur north and south of the gulf stream the gulf stream separates from the north american coast in a more realistic manner and its further course is in better agreement with observations than in the reference run the subsurface temperature distribution differs by several kelvin in the subpolar and

a multidimensional spectral description of ocean variability abstractan updated empirical analytical model for the frequency and wavenumber distribution of balanced motion in the ocean is presented the spectrum model spans periods longer than the inertial but shorter than a decade and wavelengths between 100 and 10 000 km assuming geostrophic dynamics a spectrum model for the streamfunction is constructed to be consistent with a range of observations including sea surface height from satellite altimetry velocity from moored and shipboard instruments and temperature from moorings first order characteristics of the observed spectra including amplitude and spectral moments vary slowly geographically the spectrum model is horizontally anisotropic accommodating observations that zonal wavenumber frequency spectra are dominated by a nondispersive line qualitative and quantitative agreement is found with one dimensional frequency and wavenumber spectra and observed vertical profiles of variance illustrative application is made of the model spectrum to obse

volume transport of the antarctic circumpolar current from bottom pressure measurements abstract meausrements from bottom pressure gauges located at the north and south sides of drake passage are used to extend the one year time series of volume transport of the antarctic circumpolar current acc given previously by whitworth a small error in that paper is corrected and a revised transport time series is presented which shows the importance of including the transport in the northern and southern margins of drake passage direct measurements of vertical shear averaged across the passage are in good agreement with geostrophic shear and suggest that the acc is in geostrophic balance although most of the acc transport is in the baroclinic field transport fluctuations are mainly barotropic transport estimates based on pressure difference alone differ from the estimates of whitworth by less than 10 106 m3 s 1 fluctuations in transport of almost half of the mean value occur over periods as short as two weeks

diapycnal and isopycnal transports in the southern ocean estimated by a box inverse model quantitative descriptions of circumpolar deep water upwelling and evolution into a lighter mode and heavier bottom waters in the southern ocean are still not well constrained here data from two occupations of eight hydrographic sections are combined and used in a box inverse model to estimate isopycnal and diapycnal transportsinthesouthernocean amixedlayerboxallowsdiapycnaltransportsinthesurfacemixedlayertobe estimated separately current velocity at 1000 dbar was constrained by the mean velocity field estimated from subsurfacefloatdriftdata theestimatedisopycnaltransportsarelargelyconsistentwithpastestimatesandwith outputs of three ocean general circulation models the estimated subduction and upwelling at the base of the southernoceanmixedlayershowthatuppercircumpolardeepwaterupwells 16615and17621sv where 1sv 10 6 m 3 s 21 by different inversion methods and evolves into heavier lower circumpolar deep water 5 6 13 and 6 6 18sv and bottom water 86 9a nd 86 13sv or lighter mode and intermediate waters 96 18 and 13 6 24sv meridional transport in the surface mixed layer is due to northward ekman transport and mostly southward eddy transport in seasonal ice covered areas near antarctica a significant 14 6 14sv southward transport was found the southward eddy transport is largest north of the antarctic circumpolar currentanddecreasespolewardbecauseofthepolewarddecreaseintheeddydiffusivity theinteriordiapycnal transports which can be either upward gaining buoyancy or downward gaining density are comparable in magnitude to the horizontal diapycnal transports within the surface mixed layer

an eddy permitting southern ocean state estimate abstract an eddy permitting general circulation model of the southern ocean is fit by constrained least squares to a large observational dataset during 2005 06 data used include argo float profiles ctd synoptic sections southern elephant seals as oceanographic samplers seaos instrument mounted seal profiles xbts altimetric observations envisat geosat jason 1 and ocean topography experiment topex poseidon and infrared and microwave radiometer observed sea surface temperature an adjoint model is used to determine descent directions in minimizing a misfit function each of whose elements has been weighted by an estimate of the observational plus model error the model is brought into near agreement with the data by adjusting its control vector here consisting of initial and meteorological boundary conditions although total consistency has not yet been achieved the existing solution is in good agreement with the great majority of the 2005 and 2006 southern ocean observations and better repr