observed cross shelf flow induced by mesoscale eddies in the northern south china sea abstractcross shelf flow induced by mesoscale eddies has been investigated in the northern south china sea nscs using velocity observations from long ranger adcp moorings mesoscale eddies influe

oxygen and hydrogen isotope stratigraphy of the rustenburg layered suite bushveld complex constraints on crustal contamination new do values for plagioclase pyroxene and olivine and limited whole rock dd values are presented for samples from the rustenburg layered suite of the bushveld complex south africa in combination with existing data these provide a much more complete composite o isotope stratigraphy for the intrusion throughout the layered suite mineral do values indicate that the magmas from which they crystallized had do values that were about 7 1 that is 1 4 higher than expected for mantle derived magmas suggesting extensive crustal contamination more limited h isotope data suggest that the oh present within whole rocks regardless of the degree of alteration is of magmatic origin and not an alteration phenomenon there appears to be no systematic change in do value with stratigraphic height and this requires the contamination to have taken place in a staging chamber before emplacement of the magma s into the present chamber large amounts 30 40 of contamination by the lower to middle crust are needed to explain these do values which is in general agreement with previous estimates based on srand nd isotope data alternatively smaller amounts of contamination 20 by sedimentary rocks or their partial melts represented by the country rock can explain the data but it is not apparent how such material could have been present at the depth of the staging chamber in the lower to middle crust

magmatic metasomatism and formation of the merensky reef bushveld complex the rare earth element ree contents of pyroxenes and other minerals from the merensky reef and stratigraphically adjacent rocks of the atok section bushveld complex have been determined with the ion microprobe merensky reef clinopyroxene and orthopyroxene contain much higher and more variable concentrations of the ree than their cumulus counterparts in rocks several meters below the reef chondrite normalized merensky clinopyroxene ce contents vary from 10 to 90 for ce and from 4 to 17 for yb they also possess deep negative eu anomalies the eu anomalics being deeper for crystals having high ree contents and relatively shallow for pyroxenes with low ree contents similar compositional characteristics are displayed by cl rich apatite which is an accessory phase in the rocks interstitial pyroxene in cumulates above and below the reef also tends to have elevated ree contents and in general is not in equilibrium with coexisting cumulus minerals the melt from which the cumulus minerals crystallized falls within the compositional range of continental basalts that from which merensky and postcumulus pyroxenes crystallized is inferred to be much more highly enriched in ree than any normal tholeiitic or alkalic basalt despite their highly evolved nature in terms of the ree the merensky reef pyroxenes are not evolved in terms of major elements the decoupling of incompatible trace and major elements is best explained by a metasomatic process it is speculated that metasomatism involved upward percolation of hydrated silicate melt through and its reaction with the crystalline cumulate pile the fact that the rocks enriched in the platinum group elements are also those that show evidence for metasomatism suggests that these elements were also metasomatically redistributed

the cape ghir filament system in august 2009 nw africa in the framework of the canaries iberian marine ecosystem exchanges caibex experiment an interdisciplinary high resolution survey was conducted in the nw african region of cape ghir 30 38 n during august 2009 the anatomy of a major filament is investigated on scales down to the submesoscale using in situ and remotely sensed data the filament may be viewed as a system composed of three intimately connected structures a small shallow and cold filament embedded within a larger deeper and cool filament and an intrathermocline anticyclonic eddy ite the cold filament which stretches 110 km offshore is a shallow feature 60 m deep and 25 km wide identified by minimal surface temperatures and rich in chlorophyll a this structure comprises two asymmetrical submesoscale 18 km fronts with jets flowing in opposite directions the cold filament is embedded near the equatorward boundary of a much broader region of approximately 120 km width and 150 m depth that forms the cool filament and stretches at least 200 km offshore this cool region partly resulting from the influence of cold filament is limited by two asymmetrical mesoscale 50 km frontal boundaries at the ite located north of the cold filament we observe evidence of downwelling as indicated by a relatively high concentration of particles extending from the surface to more than 200 m depth we hypothesize that this ite may act as a sink of carbon and thus the filament system may serve dual roles of offshore carbon export and carbon sink

sequence stratigraphy and controls on reservoir sandstone distribution in an eocene marginal marine coastal plain fairway taranaki basin new zealand abstract middle to upper eocene strata in taranaki basin new zealand consist of terrestrial marginal marine shallow marine and offshore sediments deposited in a series of transgressive and regressive cycles within a passive margin setting coastal plain facies are largely confined to eastern and southern sides of the basin and marine mudstones to western and northern parts shoreface to fluvial sandstones within a ne sw oriented coastal facies belt form the pre eminent petroleum reservoir fairway in taranaki basin and provide the bulk of new zealand production the terrestrial coastal plain part of the succession also contains coal rich proven source rocks we have interpreted twelve depositional sequences 3rd and 4th order within the middle to upper eocene strata the base of our study interval marks a relative transgression within the middle eocene and is overlain by composite sequences and parasequences represented by cyclically stacked packages overall regression occurs up to the top of the middle eocene which is overprinted by intermittent shorter term transgressions the overlying upper eocene strata are characterised by overall shoreline retreat with final transgression over the entire taranaki basin in the latest eocene early oligocene stratigraphic cyclicity within the terrestrial to shallow marine facies is noted from paleoenvironmental interpretations determined from well log core biostratigraphic and coal sulphur data whilst eustasy may have played a role in development of the taranaki stratigraphy tectonically induced subsidence was probably the over riding factor especially in the upper eocene petroleum producing reservoirs occur at several distinct horizons within the middle to upper eocene succession interpreted here to represent significant events during sequence development most reservoir sandstones were deposited as channelised facies following 3rd order lowstands sequence boundaries are interpreted at the base of many of these sandstone intervals some of which may represent type 1 boundaries developed as incised valley systems this regional study has used an integrated approach to show how sequence stratigraphy can be applied to a non marine to shallow marine succession to assist with exploration and reservoir development through our recent and multi disciplinary work we have been able to discriminate subtle base level fluctuations and greater marine control of depositional architecture than has previously been recognised with implications for source rock quality fairway exploration reservoir charge and production effectiveness

sulfur in coals a review of geochemistry and origins geochemical studies of sulfur in coals comprise several major aspects relating to the nature and origin of sulfur in coals including the abundance and distribution of sulfur in coal seams abundance of sulfur in coal lithotypes and macerals characteristics and geochemical significance of sulfur containing organic compounds sulfur isotopic studies relating to the sources of sulfur in coals and sedimentary environments controlling the geochemistry of sulfur in coal a review of the evidence suggests that the variation of sulfur in coals is closely related to the depositional environments of coal seams for low sulfur coal 1 s sulfur is derived primarily from parent plant material for medium sulfur 1 to 3 s and high sulfur 3 s coals there are two major sources of sulfur 1 parent plant material and 2 sulfate in seawater that flooded peat swamps abundances of sulfur in coal are largely controlled by the degree of seawater influence during peat accumulation and by postdepositional changes diagenesis in high sulfur coals seawater sulfate diffuses into the peat which is subsequently reduced by bacteria into hydrogen sulfide polysulfides and elemental sulfur reaction of hydrogen sulfide with ferrous iron generates fine pyrite crystals and mackinawite fes0 9 mackinawite reacts with elemental sulfur to converts to greigite fe3s4 and then to framboidal pyrite the reduced sulfur species in the peat hydrogen sulfide elemental sulfur and polysulfides react with the organic matter to form organic sulfur compounds during coal diagenesis nodular pyrite forms permineralized peat was formed during diagenesis which contains appreciable fraction of pyrite after coal is solidified pyrite can deposit in the cleats from circulating groundwater epigenetic pyrite veins may be deposited from basinal fluids thus pyrite forms during various stages of coal formation from peat to coal as well as late epigenetic activity the relationships between sulfur abundance in coal seams and depositional environments of coals were reviewed for cases from the u s china u k germany hungary turkey indonesia and brazil in most cases low sulfur coals formed in a fluvial environment and high sulfur coals were deposited in seawater influenced environments there are exceptions for example turkish lignites formed in freshwater environments are high sulfur sulfur sources other than seawater are needed for these high sulfur coals the superhigh organic sulfur shos coals are highly enriched in organic sulfur but depleted in pyritic sulfur the shos coals were deposited in sulfur rich iron poor environments such as carbonate platforms or in an iron poor and clastic starved environment in which algae accumulate speciation of organic sulfur compounds in coal appears to be related to coal rank thiophenic compounds are more abundant in bituminous coal and anthracite than in low rank coals

guidelines for assessing the petroleum potential of coaly source rocks using rock eval pyrolysis abstract coaly source rocks are sufficiently different from marine and lacustrine source rocks in their organic matter characteristics to warrant separate guidelines for their assessment using rock eval pyrolysis the rank threshold for oil generation is indicated by the increase in bi s1 toc at rank sr 9 10 tmax 420 430 c ro 0 55 0 6 and the threshold for oil expulsion is indicated by the peak in qi s1 s2 toc at rank sr 11 12 5 tmax 430 440 c ro 0 65 0 85 the pronounced rank related increase in hi s2 toc prior to oil expulsion renders the use of immature samples inappropriate for source rock characterisation a more realistic indication of the petroleum generative potential and oil expulsion efficiency of coaly source rocks can be gained from samples near the onset of expulsion alternatively effective hi values i e his near the onset of expulsion can be estimated by translating the measured his of immature samples along the maturation pathway defined by the new zealand or other defined coal band coaly source rocks comprise a continuum of coaly lithologies including coals shaly coals and coaly mudstones determination of the total genetic potential of coaly source rock sequences is best made using lithology based samples near the onset of expulsion

sulfurized carbohydrates an important sedimentary sink for organic carbon abstract in contrast to the general belief that carbohydrate carbon ccho is preferentially degraded and is not extensively preserved in the sedimentary record it is shown here that ccho forms a large fraction of the organic matter om of the total organic carbon toc rich upper jurassic kimmeridge clay formation as a result of early diagenetic sulfurization a previously unrecognized pathway of om preservation this is evident from both changes in the molecular composition of the insoluble om and from 13ctoc shifts of 6 with varying ccho contents furthermore experiments simulating the natural sulfurization of the ccho rich alga phaeocystis spp demonstrated that sulfurization can indeed lead to a substantial preservation of ccho with a molecular fingerprint identical to that of the kimmeridge clay and many other recent and ancient marine om rich sediments these results imply that preservation of ccho can exert a fundamental control on 13ctoc in om rich sediments complicating the interpretation of 13ctoc records with regard to estimating terrestrial versus aquatic om fractions reconstruction of past atmospheric co2 levels and global carbon budget models

physical oceanography of the western iberia ecosystem latest views and challenges the present review is focused on the mesoscale physical processes recognized in the western iberia ecosystem complementing earlier reviews dedicated to larger scales recent studies support the idea that the mesoscale processes superimposed on the larger scale variability are the major factor controlling the ecosystem functioning in the region a complex structure of interleaved alongshore slope shelf and coastal currents that interact with eddies buoyant plumes upwelling filaments and fronts surface layer expressions of the subsurface circulation and internal waves is revealed by the latest research all of these contribute in different ways to have an effect on the ecosystem the supposedly less variable winter circulation also exhibits significant mesoscale activity in the form of eddy shedding from the poleward slope current intermittent upwelling events and transient nearshore poleward flows the present incomplete knowledge of this complex system presents a number of challenges and questions that must be addressed if we are to arrive at a satisfactory understanding and predictive capability for the system as a whole 2007 elsevier ltd all rights reserved

hydrogen isotope composition of the merensky reef and related rocks atok section bushveld complex hydrogen isotope compositions of rocks from the bushveld complex at the atok mine have been determined to evaluate the relative importance of hydromagmatic and subsolidus hydrothermal processes for defining the geochemical characteristics of the merensky reef and adjacent rocks the rocks include mineralized pyroxenite and pegmatoid of the merensky reef as well as underlying and overlying pyroxenite norite and anorthosite cumulates from the merensky and bastard cyclic units of the upper critical zone the samples were chosen specifically because of the absence of deuteric alteration phases the water contents of all rocks including the pegmatoid are less than 0 26 wt percent and typically in the range 0 05 to 0 15 wt percent the major hydrous phase observable optically is phlogopite however there is not enough phlogopite in most samples to account for even these low water contents additional water is believed to be present either in solution in pyroxene or in submicroscopic phlogopite lamellae within pyroxene the upper critical zone rocks have relatively homogeneous hydrogen isotope compositions having delta d smow values in the range of 93 to 55 per mil there is a small but systematic difference in composition between pegmatoid and pyroxenite of the merensky reef avg delta d 65ppm and of the generally more leucocratic rocks elsewhere in the section avg delta d 79ppm within each lithology there is no relationship between isotopic composition and water content and the data cannot be rationalized in terms of simple mixing of light magmatic water with heavier meteoric crustal water the narrow range of the d h ratio of all the rocks suggests that their isotopic signatures were established under similar conditions this and the fact that different lithologies exhibit different isotopic compositions but possess the same mineralogy the rocks differ from each other mainly in modal abundances of the major phases are used to argue that their isotopic compositions could not have been imposed by subsolidus processes this contention is supported by the composition of merensky reef phlogopite the halogen contents of phlogopite do not vary with the crystal chemical factors known to influence their substitutional behavior phlogopite composition was in part controlled by its equilibration with an intergranular fluid of variable composition implying that there was no significant flow to homoginize pore fluid during subsolidus cooling in the massive rocks subsolidus circulation was therefore limited to large through going fractures the geochemical features of the merensky reef and adjacent rocks at atok were established during late stage solidification the hydrogen isotope data are consistent with a model involving addition of hydrous vapor to the merensky protoreef horizon this vapor originated from crystallization of the intercumulus melt below the reef and may also have included a small portion of water from the country rocks

coal as a source rock for oil a review the geological debate about whether and to what extent humic coals have sourced oil is likely to continue for some time despite some important advances in our knowledge of the processes involved it is clear that not only liptinites but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification some liptinites especially alginite cutinite and suberinite contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are therefore more oil prone it is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed review of the distribution of oil prone coals in time and space reveals that most are jurassic tertiary with key examples from australia new zealand and indonesia methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals results are not entirely consistent among the different approaches and there is much overlap in the ranges of degradation but it seems probable that in the natural environment vitrinites begin to generate early followed by labile liptinites such as suberinite then cutinite sporinite and finally alginite petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro techniques especially fluorescence and infrared ir spectroscopy or bulk techniques such as elemental analysis and 13c nmr spectroscopy the latter three techniques enable a measure of the polymethylene component of the coal which now appears to be one of the best available approaches for determining petroleum potential no method of experimental simulation of petroleum generation from coals is without criticism and comparative results are highly variable however hydrous pyrolysis confined pyrolysis and forms of open system hydrous pyrolysis approach acceptable simulations whether and to what degree generated liquid hydrocarbons are expelled has long been the central problem in oil from coal studies the structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained recent studies show the pores are not interconnected combined with a dynamic model of pore generation it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries the main reason for poor expulsion is the adsorption of oil on the organic macromolecule which may be overcome 1 if coals are thin and interbedded with clastic sediments or 2 if the coals are very hydrogen rich and generate large quantities of oil the existence of oil in vitrinite is attested to by solvent extractions fluorescence properties and by microscopic observations of oil and bitumen experimental simulation of expulsion of oil from coals has only recently been attempted the relative timing of release of generated co2 and ch4 could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear as it is universally agreed that dispersed organic matter dom in some shales readily generates and expels petroleum it is curious that few consistent geochemical differences have been found between coal macerals and dom in interbedded shales unambiguous evidence of expulsion from coals is limited and in particular only a few commercial oil discoveries can be confidently correlated to coals these include upper cretaceous fruitland formation coals in the usa from which oil is produced new zealand tertiary coals and middle jurassic coals from the danish north sea it is likely that coals have at least contributed to significant oil discoveries in the gippsland basin australia in the turpan basin china and in the kutei and ardjuna basins in indonesia but this remains unproven early reports that early jurassic coals in mid norway were a major source of the reservoired oils have been shown to be inaccurate none of the proposed rules of thumb for generation or expulsion of petroleum from coals seem particularly robust decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information the assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain

mineral chemistry and stable isotope constraints on the magmatism hydrothermal alteration and related pge base metal sulphide mineralisation of the mesoarchaean baula nuasahi complex india the baula nuasahi complex on the southern flank of the singhbhum archaean nucleus in north eastern india exposes a series of mesoarchaean igneous suites these are 1 a gabbro anorthosite unit which is petrographically homogeneous although mineral chemistry data hint at a subtle eastward differentiation 2 a peridotite unit with three chromitite layers together with 3 a pyroxenite unit which display cumulate textures modal layering and for the peridotite unit differentiation trends in both mineralogy and mineral chemistry and 4 the bangur gabbro 3 1 ga which defines an oblong intrusion crosscutting the older igneous suites in the southern part of the complex with a curvilinear nw trending apophysis 2 km long and up to 40 m wide magmatic breccia comprising ultramafic and chromitite wall rock clasts in a gabbro matrix is exposed at the contact of the main bangur gabbro body and also forms the entire bangur gabbro apophysis concentrations of platinum group minerals pgms are found where the breccia contains abundant chromitite clasts and two types of platinum group element pge mineralisation are recognised type 1 pt 1 1 14 2 pd 0 1 2 1 ppm with an average pt pd 8 9 is a contact type mineralisation which occurs in the breccia at the contact between the bangur intrusion and its ultramafic host the pgms pt alloys isoferroplatinum and sulphides braggite malanite are enclosed by pyroxene and plagioclase reflecting a magmatic origin significant wall rock assimilation by the magma giving rise to the bangur gabbro is indicated by changes in pyroxene composition and by the presence of relicts of chromite from the host now altered to secondary ferritchromite in the contact zone type 2 pge mineralisation pt 0 3 1 6 pd 1 8 6 0 ppm with pt pd 0 5 3 0 is restricted to the breccia apophysis of the bangur gabbro where it occurs in the breccia matrix associated with an intense hydrothermal alteration which does not exist in the contact zone pgms pge arsenides tellurides bismuthides and antimonides and where present base metal sulphides bmss form intergrowths with hydrous silicates reflecting a hydrothermal origin oxygen isotope geothermometry documents the main stages of hydrothermal alteration within a decreasing temperature range between 700 1 000 and 500 600 c and oxygen hydrogen and sulphur isotopes show that the hydrothermal fluids were derived from the magma rather than an external source pervasive hydrothermal alteration in the breccia apophysis likely represents upward channelling of late magmatic fluids along a narrow near vertical subplanar conduit which led away from the main magma chamber we suggest that type 2 mineralisation was produced by late magmatic hydrothermal remobilisation and reconcentration of type 1 pge mineralisation and that the composition of the hydrothermal fluids controlled whether bmss were enriched along with the pgms

sequence stratigraphic analysis and the origins of tertiary brown coal lithotypes latrobe valley gippsland basin australia abstract the methods of sequence analysis have been applied to the onshore gippsland basin and in particular to the latrobe valley group coal measures which include up to five coal seams each exceeding 100 m in thickness the methods appear to provide new depositional concepts to the evolution of these seams and the development of coal lithotypes in the eastern half of the latrobe valley evidence for marine transgressions into the coal measures are recorded in most of the interseam sediment splits by the presence of contained foraminifera and dinoflagellates to the west inland these splits pinch out into continuous coal however they can be followed westwards as enhanced organic sulphur levels along sharply defined boundaries between light coal lithotypes below and dark coal lithotypes above the dark lithotype immediately overlying each of these boundaries contains the highest sulphur value and warmer climate pollen assemblages sluiter et al 1995 this volume colorimeter and lithotype logging strongly supports an upwards lightening cyclicity to coal colour at 12 20 m intervals through the approx 100 m thick seams with cycle boundaries defined at sharp planar to undulating surfaces the lightening upward lithotype cycles together with their unique boundary conditions i e enhanced organic sulphur levels warm climatic indicators and laterally equivalent marine clay splits are interpreted as parasequences and parasequence boundaries respectively each major coal seam can comprise up to five parasequences and is interpreted to represent deposition during an outbuilding high stand systems tract at one of several maximum periods of tertiary coastal onlap the top of each major seam shows evidence of truncation erosion on a regional scale and these surfaces are interpreted to represent the sequence boundaries the major seams are usually conformably underlain by marine clays and extensive aquifer sands being deposits of the late transgressive systems tracts the low stands and early parts of the transgressive systems tracts appear not to be represented in the latrobe valley due to its more basin margin location but are probably present down dip in the equivalent marine facies of the seaspray group stratigraphic correlation of the sequence boundaries identified in the coal measures to the adjacent internationally dated marine seaspray group provides a basis for chronostratigraphic correlation of the coal successions to the coastal onlap charts of haq et al exon mesozoic cenozoic chronostratigraphic chart version january 1988 and august 1989 from this dating it appears that each major seam is confined to high stands of third order eustatic cycles it therefore follows that the lithotype cycles parasequences that comprise each seam are related to fourth order eustatic cycles by analogy all the coal cycles may have developed under subtropical conditions as ombrogenous forested peat swamps in a similar manner to the holocene though tropical swamps of indonesia

the halogen geochemistry of the bushveld complex republic of south africa implications for chalcophile element distribution in the lower and critical zones solidification of the interstitial liquid the stratigraphic distribution halogen bearing minerals especially apatite are minor but ubiof s cu and the pge in the critical zone cannot readily be quitous phases throughout the bushveld complex interstitial apatite explained either by precipitation of sulfide as a cotectic phase or as is near end member chlorapatite below the merensky reef lower a function of trapped liquid abundance evidence from potholes and and critical zones and has increasingly fluorian compositions with the pge rich driekop pipe of the bushveld complex imply that increasing structural height above the reef main and upper zones migrating cl rich fluids mobilized the base and precious metal cl f variations in biotite are more limited owing to crystal chemical sulfides we suggest that the distribution of sulfide minerals and controls on halogen substitution but are also consistent with a the chalcophile elements in the lower and critical zones reflects a decrease in the cl f ratio with structural height in the complex general process of vapor refining and chromatographic separation of a detailed section of the upper lower zone to the critical zone is these elements during the evolution and migration of a metalliferous characterized by an upward decrease in sulfide mode from 0 01 cl rich fluid phase 0 1 to trace 0 001 cu tends to correlate with other incompatible elements in most samples whereas the platinum group elements pge can behave independently particularly in the critical zone the decrease in the cl f ratio of apatite in the

generation and unstable evolution of a density driven eastern poleward current the iberian poleward current 1 the generation and evolution of a density driven eastern poleward current is investigated using a high resolution primitive equation numerical model the simulations focus on the iberian poleward current ipc as a case study the flow is generated by a meridional upper ocean density gradient balanced by an eastward surface intensified flow that adjusts at the coastal margin the resulting current system has a baroclinic character with poleward flow at the surface layer and equatorward flow underneath a few weeks after initialization the sheared along slope flow generates several vorticity structures downstream of the main topographic features in the lee of the topography persistent anticyclones are observed and deep cyclogenesis is induced in relation to the meandering of the upper layer jet these structures evolve preferentially as cyclone anticyclone eddy pairs and after interaction some dipoles are ejected offslope within a period of a few months the initial meridional gradient evolves into a complex system of fronts eddies and slope flows the dynamics of flow topography interaction is analyzed a comparison with satellite imagery of the ipc is conducted and similarity in scales and patterns is noted

origin of phlogopite orthopyroxene inclusions in chromites from the merensky reef of the bushveld complex south africa about 30 of the chromite grains of variable sizes in a chromitite seam at the base of the merensky reef of the bushveld complex on the farm vlakfontein contain abundant composite mineral inclusions the inclusions are polygonal to circular with radial cracks that protrude into the enclosing chromite they vary from a few microns to several millimeters in diameter and are concentrated in the cores and mantles of chromite crystals electron backscattered patterns indicate that the host chromites are single crystals and not amalgamations of multiple grains na phlogopite and orthopyroxene are most abundant in the inclusions edenitic hornblende k phlogopite oligoclase and quartz are less abundant cl rich apatite rutile zircon and chalcopyrite are present at trace levels na phlogopite is unique to the inclusions it has not been found elsewhere in the bushveld complex other minerals in the inclusions are also present in the matrix of the chromitite seam but their compositions are different the mg mg fe2 ratios of orthopyroxene in the inclusions are slightly higher than those of orthopyroxene in the matrix k phlogopite in the inclusions contains more na than in the matrix the average compositions of the inclusions are characterized by high mgo 26 wt na2o 2 4 wt and h2o 2 6 wt and low cao 1 1 wt and feo 4 4 wt the 18o value of the trapped melt estimated by analysis of inclusion rich and inclusion poor chromites is 7 this value is consistent with the previous estimates for the bushveld magma and with the 18o values of silicate minerals throughout the reef the textural features and peculiar chemical compositions are consistent with entrapment of orthopyroxene with variable amounts of volatile rich melts during chromite crystallization the volatile rich melts are thought to have resulted from variable degrees of mixing between the magma on the floor of the chamber and na k rich fluids expelled from the underlying crystal pile the addition of fluid to the magma is thought to have caused dissolution of orthpyroxene leaving the system saturated only in chromite both oxygen and hydrogen isotopic values are consistent with the involvement of a magmatic fluid in the process of fluid addition and orthopyroxene dissolution most of the cr and al in the inclusions was contributed through wall dissolution of the host chromite dissolution of minor rutile trapped along with orthopyroxene provided most of the ti in the inclusions the na and k rich hydrous silicate minerals in the inclusions were formed during cooling by reaction between pyroxene and the trapped volatile rich melts

peat accumulating depositional systems of sarawak east malaysia many coal deposits originate in deltaic estuarine and coastal plain settings and a knowledge of interrelationships between the tectonic and depositional elements active at the time of sediment deposition is necessary to formulate basin scale models the prograding coastal depositional systems of sarawak all contain domed peat accumulating environments in which low ash low sulfur peats are being deposited in areas of active clastic siliciclastic sedimentation these depositional systems are as large as 11 400 km2 and individual peat deposits within systems are in excess of 20 m thick and 1000 km2 in area the geographic positions and drainage basin areas of each depositional system are controlled by fault and fold systems although prograding into the same receiving basin individual system geomorphology is variable and ranges from a wave dominated microtidal delta to a wave dominated meso to macro tidal delta coastal plain system to a tide dominated macrotidal estuarine embayment along a 450 km stretch of coastline system variation is a function of sediment supply shelf and embayment geometry wave climate and tidal range these factors which control depositional system geomorphology also control the resulting long axis orientation of the thick domed peat deposits the surface vegetation and internal characteristics of most domed peat deposits however are similar internal characteristics consist of basal high ash high sulfur degraded peats overlain by low ash low sulfur well preserved peats in vertical profile these systems demonstrate variable responses to late pleistocene holocene sea level rise and in these instances the variation is most attributable to local differences in siliciclastic sediment supply which is a function of the drainage basin area

the norwegian atlantic current in the lofoten basin inferred from hydrological and tracer data 129i and its interaction with the norwegian coastal current 1 from three hydrological sections taken across the lofoten basin in may 2000 we estimated geostrophic transports of 7 2 sv sverdrup 106 m3 s 1 for the norwegian atlantic current nac and its division between northern 4 8 sv and eastern 2 4 sv branches from 129i 127i concentration ratio measurements and transport estimations we calculated 129i mass flux across the three sections it appears that in the lofoten basin a 129i tracer laden norwegian coastal current ncc is transporting northward 55 kg y of 129i assuming a volume flux of 0 7 sv b the estimated mass fluxes of 129i by the nac and the ncc are comparable c the total mass flux of 129i by the nac and ncc accounts only for about 1 3 of the 129i annual discharge 350 kg y from two reprocessing plants based in france and uk if these measurements are representative of annual mean it suggests an important transfer of 129i outside the nac ncc system

did the giant broken hill australia zn pb ag deposit melt abstract recent published research has proposed that some metamorphosed massive sulfide deposits including the broken hill deposit australia have partially melted here we discuss the evidence for and against this process the broken hill deposit is located in the curnamona craton within a rift in an apparent upward coarsening sequence of clastic metasediments into which paleoproterozoic mafic and felsic melts intruded the deposit was metamorphosed to granulite facies conditions 750 800 c and 5 6 kbar and was subjected to at least five periods of deformation at peak p t conditions a melt phase was produced in silicate rocks especially granitoids and psammopelites and in ore characterized by the systems cu as s ag pb s ag sb as s cu sb pb s sb as s cu sb s and fe as s however the proportion of minerals in these s bearing systems is insignificant 2 feo mno cao al 2 o 3 p 2 o 5 co 2 zns pbs fes feass feas 2 which is the most relevant system to broken hill ores p t conditions were never high enough to produce a melt phase in this system authors arguing for sulfide rock melting suggest that mn rich lithologies garnetite and quartz garnetite which are intimately associated with the pb rich ores at the broken hill deposit were produced by a reaction between mn rich sphalerite and aluminous wall rocks however to produce such rocks would require mn contents of sphalerite compositions that are unrealistically high and yet to be found in nature moreover the implication of the melt model is that wherever mn rich quartz garnetite and garnetite are found sphalerite should be located next to them this is clearly not the case the presence of polyphase sulfide inclusions within garnet in garnetite has also been considered by some in the literature to be sulfide melt inclusions with the implication that the enclosing garnet was a product of melting however we consider these sulfides to be products of hydrothermal processes during retrograde metamorphism it is impossible to form garnetite and quartz garnetite in rocks within the curnamona craton that formed at upper greenschist lower amphibolite facies conditions by partial melting p t conditions were too low we consider that the fe and mn component of garnetite and quartz garnetite are products of exhalation and inhalation at or near the sea floor and that these rocks are meta exhalites or meta inhalites some garnet rich rocks also formed by metasomatic processes throughout the protracted metamorphic history that affected the curnamona craton

the merensky reef at winnaarshoek eastern bushveld complex a primary magmatic hypothesis based on a wide reef facies the merensky reef on the winnaarshoek property in the central sector of the eastern limb of the bushveld complex belongs to what may be described as a wide reef facies in which platinum group element pge mineralization is largely contained within a relatively thick succession of medium grained nonpegmatoidal feldspathic orthopyroxenite bounded top and bottom by thin chromite stringers the wide reef merensky reef facies at winnaarshoek presents the opportunity to study subtle processes which could potentially be obscured or obliterated in the thinner reef facies found in many areas of the western limb especially in places where the reef zone contains a component of pegmatoidal orthopyroxenite at winnaarshoek a pegmatoidal feldspathic orthopyroxenite is developed below the lower chromite stringer and a second pegmatoidal orthopyroxenite is intermittently developed several centimeters above the upper chromite stringer in contrast to most occurrences in the western limb however both these pegmatoidal orthopyroxenites are only sporadically mineralized if at all in addition rather than being at the base of a feldspathic orthopyroxenite unit as is the case throughout most of the western limb the merensky reef at winnaarshoek occurs toward the top of a sequence of feldspathic orthopyroxenite despite the gross relative uniformity of the merensky reef on a property wide scale at winnaarshoek we demonstrate using underground channel samples that individual intersections spaced a matter of meters apart commonly display remarkable variations in grade distribution our study is based primarily on whole rock and mineral chemical profiles from drill cores through three separate and distinctive subfacies of essentially normal i e nonpothole reef one of the drill core intersections represents typical reef in which pge mineralization forms an upper reef extending from the upper chromitite stringer approximately 1 m into the underlying feldspathic pyroxenite and a much thinner lower reef centered on the lower chromitite stringer the other two drill core intersections represent extremes in terms of the vertical distribution of the pge one having mineralization confined to the immediate vicinity of the two chromitite stringers while the other is richly mineralized throughout the reef zone peaks in pge concentrations in all three intersections are coincident with the most primitive compositions of orthopyroxene plagioclase and chromite the dominant rock forming minerals whereas the cumulate layers below major pge peaks are the most evolved as indicated by mineral compositions and elevated whole rock incompatible element concentrations furthermore the lowest grade merensky reef intersection has the most chemically evolved footwall whereas the richest intersection has a relatively primitive footwall we consider the origin of the merensky reef in the context of its position as the culmination of a sequence of several pge mineralized chromite bearing layers in the upper critical zone and suggest that the regular upward variations in the chemistry of the chromitite from one layer to the next and the overall cyclicity are indicative of complex magma replenishment and mixing processes in the chamber we apply a model of lateral streaming of magma with chromite crystallization and consequent sulfide and platinum group mineral pgm precipitation resulting from magma mixing specifically the merensky reef cannot be properly interpreted outside the context of the sequence of successive events that evolved throughout the development of the upper critical zone genetic models also need to account for lateral facies variations in the reef

on the inner shelf circulation in the northern gulf of cadiz southern portuguese shelf abstract a new look at the inner shelf circulation in the northern gulf of cadiz sw iberian peninsula is taken results reveal the introduction of a sharp spatial heterogeneity in the wind field by the coastal geometry around cape st vincent and nearby mountain chains direct observations taken in november december 2001 reveal the alternating nature of the coastal flow along the sw iberian peninsula featuring a sharp current inversion on time scales of less than 2 days along shore gradients of the oceanic wind stress were detected which may contribute to the coastal circulation patterns in the region over the observational period the sea level variability in the gulf of cadiz is better explained by the action of along shore winds outside the gulf than by local winds this is confirmed by a scale analysis done on the vertically integrated momentum equation it is shown that to a first approximation the expected behaviour of the inner shelf flow responds to linear dynamics in this approximation the along shore sea level slope 5 cm over 100 km is the dominant term overriding the linear bottom and surface stress terms this suggests control by large scale atmospheric pressure systems and negligible dynamical influence from local wind stress

biological processes controlling the development of modern peat forming ecosystems abstract although no precise modern analogue exists for the peat forming ecosystems mires of tertiary times it is argued that the principles underlying peat formation are essentially unchanged in the sense that a peat forming ecosystem has an incomplete decomposition process normally because of waterlogging leaving a residue of organic material in its overall energy flow budget the study of modem mires is therefore of relevance to tertiary coal geologists the classification of modern mires is best achieved by reference to their hydrological characteristics particularly the source of water entering the system flow fed rheotrophic mires are often relatively rich in nutrients and clastic while rainfed ombrotrophic mires are poor the transition from one hydrological state to the other can occur during mire development and involves a physical elevation of the mire surface by the growth of peat such mires have a two layered diplotelmic structure in which the surface layer acrotelm is periodically aerobic has a loose structure and a high hydraulic conductivity while the lower layer catotelm is compacted anaerobic and has a low hydraulic conductivity the hydrological outcome is that precipitation landing upon a raised ombrotrophic mire drains from the elevated mire surface laterally through the acrotelm the water retention of the mire and its elevated water table is dependent on the poor water conductivity of the catotelm the transition to the ombrotrophic condition is accompanied by higher rates of peat accumulation and increasing mire acidity it begins with isolated colonization of hummock forming plants that later converge into an extended cupola this ecological transition may be a consequence of external changes such as climatic alteration increased precipitation evaporation ratio or autogenic internal successional developments basin subsidence however or eustatic sea level rise in the case of coastal systems can operate in the reverse direction and prevent the permanent establishment of an ombrotrophic system the ombrotrophic mire is ultimately limited in the depth of its peat development by microbial respiration within the catotelm as the catotelm extends with peat accumulation the total respiratory activity of the profile will equilibrate with primary productivity and peat formation slows down to an eventual standstill on the assumption that peatland hydrology operated in a similar way in former times the deep peats and eventually coals of tertiary times can best be explained therefore in terms of stacks of sequential mires rather than single continuously forming ecosystems

marine influence helps preserve the oil potential of coaly source rocks eocene mangahewa formation taranaki basin new zealand abstract many cretaceous cenozoic coaly source rocks in australasian and southeast asian basins were deposited in coastal plain environments yet the effect of early diagenetic marine influence on their oil potential is not well understood an integrated organic geochemical and petrographic study of humic coals from the eocene mangahewa formation taranaki basin new zealand was undertaken with coals predominantly from raised mire petrofacies with subordinate proportions from planar mires the total s content of 0 63 4 4 dry ash free indicated very slight to strong degrees of marine influence other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite the degree of marine influence had no obvious effect on maceral or plant tissue abundance however hydrogen index hi values were up to ca 150 109 mg hc g toc higher and total c 6 oil potential up to ca 140 43 mg g toc higher among the more strongly marine influenced coals correlation of organic s with solvent extract parameters pristane phytane c 27 c 29 diasteranes steranes c 29 steranes hopanes c 35 c 35 c 34 homohopanes and oleanane index suggested that inundation of brackish water into the early diagenetic peat forming environment enhanced the bio resistance of higher plant and other lipids through sulfurization thereby helping to preserve more of the inherent h content and total oil potential of the original peat biomass conversely marine influence had only a minor effect on the capacity of mangahewa coals to generate paraffinic oil total n c 6 and non volatile n c 15 paraffinic oil potentials were instead controlled primarily by the abundance of leaf derived cutinite and associated liptodetrinite this in turn was dependent on the type of peat mire facies with planar mire facies having better potential for preservation of leaf litter than raised mire facies because of their generally higher groundwater level marine influence is nonetheless beneficial for paraffinic oil charge from coaly source rock sequences in that the associated higher his enhance the efficiency and quantum of paraffinic oil expulsion through increased saturation of the coal pore system

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

a test for the analogy of tropical domed peat deposits to dulling up sequences in coal beds preliminary results abstract megascopic and microscopic characteristics of a domed peat deposit in sarawak malaysia were examined to test their analogy to dulling up sequences in low ash coal beds preliminary petrographic results show high concentrations 95 of vitrinite precursor material for all peat types but that fibrous peats in the upper central portion of the deposit contain more preserved plant material than peats toward the base and margins which although more decomposed contain large fragments 5 150 cm of wood these results present contradictory evidence in support of a dulling up model and suggests that modern tropical peat domes are perhaps poor petrographic analogues for dulling up sequences this deposit would produce an all bright coal seam with bright vitrain bands of variable thickness and amount set in bright high vitrinite matrix

upwelling filaments off cap blanc interaction of the nw african upwelling current and the cape verde frontal zone eddy field 1 the hydrographical and dynamical properties of the upwelling filaments forming off cap blanc mauritania are investigated using remotely sensed and in situ data collected in april may 2009 during the strongest upwelling season the area is situated at the southern edge of the nw african upwelling system where the cape verde frontal zone cvfz separates warmer saltier north atlantic central water nacw and cooler fresher south atlantic central water sacw sea surface temperature images indicated the presence of an upwelling filament extending 280 km offshore rooted over the cap blanc promontory and entrained around a warm core anticyclonic eddy after this filament started to decay a new cold filament developed at the approximate same location high resolution moving vessel profiler mvp and acoustic doppler current profiler adcp surveys of these mesoscale structures revealed that both filaments were carrying south atlantic central water sacw offshore through an intense jet like flow similarity of the relative vorticity structure across the filament with that of the tangent eddy suggested that the latter was responsible for the offshore current tracking of this eddy in altimetric data demonstrated that it originated from the cvfz as implied by its hydrographic structure altimetric data also revealed that another anticyclonic structure centered over the cap blanc promontory was responsible for the northwestward advection of sacw into the base of the filament the results support the idea that some upwelling filaments can be produced by the interaction of an external eddy field including topographic eddies with the upwelled water

eddy induced cross shelf export of high chl a coastal waters in the se bay of biscay abstract different remote sensing data were combined to characterise a winter anticyclonic eddy in the southeastern bay of biscay and to infer its effects on cross shelf exchanges in a period when typical along shelf slope currents depict a cyclonic pattern while the joint analysis of available satellite data infrared visible and altimetry permitted the characterisation and tracking of the anticyclone properties and path data from a coastal high frequency radar system enabled a quantitative analysis of the surface cross shelf transports associated with this anticyclone the warm core anticyclone had a diameter of around 50 km maximum azimuthal velocities near 50 cm s 1 and a relative vorticity of up to 0 45f the eddy generation occurred after the relaxation of a cyclonic wind driven current regime over the shelf slope then the eddy remained stationary for several weeks until it started to drift northwards along the shelf break the surface signature of this eddy was observed by means of high frequency radar data for 20 consecutive days providing a unique opportunity to characterise and quantify from a lagrangian perspective the associated transport and its effect on the chl a surface distribution we observed the presence of mesoscale structures with similar characteristics in the area during different winters within the period 2011 2014 our results suggest that the eddy induced recurrent cross shelf export is an effective mechanism for the expansion of coastal productive waters into the adjacent oligotrophic ocean basin

the geology botany and chemistry of selected peat forming environments from temperate and tropical latitudes abstract peat has been studied in several geologic settings 1 glaciated terrain in cold temperate maine and minnesota u s a 2 an island in the atlantic ocean off the coast of maine where sea level is rising 3 the warm temperate u s atlantic and gulf coastal plains where sea level has changed often and 4 the tropical coast of sarawak malaysia and the tropical delta of the batang hari river sumatra indonesia most of these deposits are domed ombrotrophic or partly ombrotrophic bogs in which peat accumulation continued above the surface of the surrounding soil however the bogs of the u s atlantic and gulf coastal plains are comparatively not as domed and many have almost level surfaces in some bogs aquatic or semi aquatic plant materials accumulated replaced water in the depressions and formed a surface on which marsh or swamp vegetation could subsequently live die and accumulate in others the plant materials accumulated initially on level silt or sand surfaces supporting marshes or swamps as the peat dome formed plants growing on it changed from luxuriant ones near the base of the dome where nutrients were brought into the bog by surface and ground water to stunted ones at the top of the dome where the raised bogs are fed by nutrient poor precipitation the physical and chemical changes that take place in the sequence of environments from the pond stage of deposit development through the grassy marsh stage through the forested swamp stage and finally through the heath dome stage can be measured in terms of acidity and ash volatile matter carbon hydrogen nitrogen sulfur and oxygen contents as well as in the kind and distribution of trace elements the organic and inorganic contents of the deposits relate to geomorphology and geomorphology relates to their settings as models of coal formation some domed peat deposits may help in solving problems of distribution and character of ancient coal beds but clearly not all peat deposits are precursors of coal most holocene peat deposits are subject to destruction by erosion fire and decomposition through microbial and chemical oxidation before burial the best environments for coal precursors have biomass accumulation a continuously rising water table within the mass and minimum influx of clay and silt until preservation by burial the most suitable settings for future economic coal deposits are domed bogs that accumulate thick widespread peat having low ash and low sulfur contents the ombrotrophic peat deposits of tropical sarawak and sumatra are thick and extensive contain low ash and low sulfur peat and have high heating values they are considered to be the best tropical coal analogs because of their extent and chances of preservation the base of the peat is below adjacent river levels and chemical and structural conditions are favorable for accumulation

petroleum source rock assessment in non marine sequences pyrolysis and petrographic analysis of australian coals and carbonaceous shales a series of australian coals and terrestrial sediments ranging in age from permian through tertiary have been analyzed to assess their petroleum source character and the suitability of various techniques for assessment of source rock potential in non marine sequences the procedures used include organic petrography rock eval pyrolysis elemental analysis and quantitative pyrolysis gas chromatography the latter procedure was used to assess the potential yield of paraffins which is critical to the assessment of most non marine source rocks principal components analysis was used to assist in the analysis of the data although the petroleum potential of the samples follows the broad trends in petrographic composition established for australian coals i e relative proportions of vitrinite inertinite and liptinite there is much variation which cannot be explained petrographically at the maceral group level further pyrolytic hydrocarbon yield is not related to overall elemental composition below an atomic h c ratio of 1 0 the yield of phenols in flash pyrolysis is related to depositional setting as well as degree of maturation the yield and carbon number distribution of normal hydrocarbons in flash pyrolysis varied widely depending on the age nature and amount of liptinite macerals particularly in samples with hydrogen indices below 300 liptinite poor 10 samples may yield significant amounts of hydrocarbons but typically they have a low wax content sporinite rich and liptodetrinite rich samples give lower yields of normal hydrocarbons these are predominantly of lower molecular weight suberinite and to a lesser extent cutinite are associated with high yields of waxy normal hydrocarbons but some samples with high yields did not contain large amounts of these maceral the correlation of tmax to vitrinite reflectance varies with petrographic composition the results have implications for the way source rock analyses are conducted and interpreted in non marine sequences

morphology and microstructure of chromite crystals in chromitites from the merensky reef bushveld complex south africa the merensky reef of the bushveld complex consists of two chromitite layers separated by coarse grained melanorite microstructural analysis of the chromitite layers using electron backscatter diffraction analysis ebsd high resolution x ray microtomography and crystal size distribution analyses distinguished two populations of chromite crystals fine grained idiomorphic and large silicate inclusion bearing crystals the lower chromitite layer contains both populations whereas the upper contains only fine idiomorphic grains most of the inclusion bearing chromites have characteristic amoeboidal shapes that have been previously explained as products of sintering of pre existing smaller idiomorphic crystals two possible mechanisms have been proposed for sintering of chromite crystals 1 amalgamation of a cluster of grains with the same original crystallographic orientation and 2 sintering of randomly orientated crystals followed by annealing into a single grain the ebsd data show no evidence for clusters of similarly oriented grains among the idiomorphic population nor for earlier presence of idiomorphic subgrains spatially related to inclusions and therefore are evidence against both of the proposed sintering mechanisms electron backscatter diffraction analysis maps show deformation related misorientations and curved subgrain boundaries within the large amoeboidal crystals and absence of such features in the fine grained population microstructures observed in the lower chromitite layer are interpreted as the result of deformation during compaction of the orthocumulate layers and constitute evidence for the formation of the amoeboid morphologies at an early stage of consolidation an alternative model is proposed whereby silicate inclusions are incorporated during maturation and recrystallisation of initially dendritic chromite crystals formed as a result of supercooling during emplacement of the lower chromite layer against cooler anorthosite during the magma influx that formed the merensky reef the upper chromite layer formed from a subsequent magma influx and hence lacked a mechanism to form dendritic chromite this accounts for the difference between the two layers

petroleum generation and migration from talang akar coals and shales offshore n w java indonesia abstract the oligocene talang akar formation is the major source for petroleum oil and gas in the ardjuna sub basin source rock quality varies within the deltaic to marginal marine complex with coals deposited on the lower delta plain being distinctly oil prone whereas the surrounding delta plain shales are largely gas prone shales and drifted coals laid down in marine influenced interdistributary bay environments show increasingly oil prone characteristics possibly due to preferential transport of hydrogen rich plant components to more distal setting molecular characteristics of the coals and shales are similar with higher plant angiosperm biomarkers and their aromatic derivatives occuring widely kinetic studies of hydrocarbon generation and stimulated maturation experiments using hydrous pyrolysis indicate that the delta plain coals are the major source for crude oils in the basin with a secondary but minor contribution from marine influenced interdistributary bay shales delta plain shales are interpreted to expel gaseous products only the stratigraphic and spatial location of oil and gas fields were examined with respect to their position relative to oil and gas generating source rocks the field distribution could not be explained in terms of source rock geochemistry alone and phase behavior of petroleum during secondary migration was shown to exert an important influence on the distribution of oil and gas deposits in the basin

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

extreme cross shelf transport induced by eddy interactions southwest of iberia in winter 2001 1 unusually high for winter time satellite derived chlorophyll a concentrations southwest of iberia were detected in february 2001 analysis of satellite data seawifs avhrr sea level anomaly from topex poseidon and ers revealed that the phytoplankton rich waters were associated with an extremely long filament up to 400 km induced by eddy eddy interactions occurring in the vicinity of the continental margin the eddy interaction occurred simultaneously with an accumulation of coastal fresh water over the shelf the event promoted an export of biogenic material offshore along with an estimated shelf flushing in a 5 to 6 day period that resulted in a dramatic offshore growth of phytoplankton a description of the event is given and preliminary estimates of the cross shelf transport are presented and discussed

some observations regarding the potential effects of doming of tropical peat deposits on the composition of coal beds abstract several important concepts relative to the origin of coal beds can be gleaned from studies of modern domed and planar peat deposits in tropical subtropical settings these are 1 laterally some portions of a single continuous peat deposit may be domed and some portions may be planar 2 domed deposits are most often found to have begun as planar deposits 3 domed formed peat facies may be overridden by planar formed peat facies due to such factors as sea level rise and or increased rate of local and basinal subsidence 4 domed peat facies tend to have less mineral matter and contain fewer inorganic splits than planar facies 5 sulfur intrusion from marine waters can be retarded by doming allowing low sulfur peats to form relatively near to the coastline 6 marine transgression can cause high sulfur marine influenced planar peat facies to override freshwater domed or planar facies resulting in enrichment of the upper parts of these underlying facies in sulfur and ash 7 dome formed peat facies tend to be thicker and more uniform in composition than planar formed facies with dome formed peat facies having the potential to produce the more uniform bright coal types clarains and vitrains and planar formed peat facies often producing duller coal types and or alternating durainic inertinite rich and vitrainic wood derived bands 8 actively developing peat domes in wet settings often exhibit no appreciable increase in inertinitic material toward their tops although the tops of either domed or planar peat deposits can be enriched in inertinitic material if the water table is lowered by either local or regional changes in hydrology or climate

halogens of bushveld complex south africa δ37cl and cl f evidence for hydration melting of the source region in a back arc setting abstract the bushveld complex is one of only a few layered intrusions anomalously enriched in chlorine this study presents the first chlorine stable isotope analyses of bushveld and associated rocks designed to constrain the source of bushveld cl most samples overlap the range of values for pristine morb and altered seafloor samples 37 cl 4 relative to sea water this contrasts with distal metasedimentary floor rocks 37 cl 0 with little evidence of contamination away from the marginal rocks the cl isotope composition and high cl f ratio is therefore a fundamental characteristic of the lower and critical zone magmas and not derived from infiltration from the country rock these results the high cl f ratio and the boninitic arc like character of bushveld magma are consistent with hydration partial melting of a depleted source in a subduction related setting with cl supplied either by the dehydration of a subducted slab with a heavy cl signature or an overridden wet mantle hotspot

oleananes in oils and sediments evidence of marine influence during early diagenesis abstract the oleananes as markers for the angiosperms provide valuable source and age information when present in an oil nevertheless they are not quantitatively related to the land plant input and indeed their presence reflects only a small leak in diagenetic processes leading primarily to aromatic oleanoids because they are minor products the abundance of oleananes in terrigenous oils and sediments may be highly sensitive to changes in early diagenetic conditions here we present evidence that contact of plant matter with seawater during early diagenesis enhances the expression of oleananes in a mature sediment or oil oleananes are absent or present at very low concentrations in samples from the base of an eocene coal seam affected by postdepositional seawater intrusion however their abundance increases toward the top of the seam in correlation with organic sulphur dibenzothiophene phenanthrene and the homohopane index similarly in deltaic sediments from the south sumatra basin oleanane hopane is strongly correlated with indicators of marine influence such as c 27 c 29 steranes and the homohopane index in each case increasing oleanane abundance is accompanied by a reduction in the extent of aromatisation and for the south sumatra basin the proportion of a ring contracted oleananes an angiosperm derived miocene coal from the philippines deposited under freshwater conditions shows abundant aromatic oleanoids but no oleananes these results show that oleananes need to be used with caution as age and source markers in fluvio deltaic and lacustrine petroleum systems on the other hand their sensitivity to early diagenetic conditions may make them useful in locating effective source rocks in such systems

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

crustal contamination and fluid rock interaction during the formation of the platreef northern limb of the bushveld complex south africa the platreef is the main platinum group element pge bearing and contains some of the most important magmatic ore deposits yet discovered the intrusion covers an area of facies of the northern limb of the bushveld complex but unlike the merensky reef of the eastern and western limbs it is in direct roughly 65 000 km e g tankard et al 1982 and lies almost entirely within the bounds of the transvaal basin contact with the country rock mineral separate o values for samples from the upper zone and main zone of the northern limb fig 1 the layered igneous rocks the rustenburg layered suite sacs 1980 can be divided into eastern indicate crystallization from a well mixed already contaminated magma having a o value of 7 5 pyroxenes from the pyroxenites and western limbs of approximately the same size and a smaller northern limb the northern limb differs in facies of the platreef at sandsloot mine have o values that are up to 2 4 higher than pyroxenes from the upper and main several important aspects from the more well known eastern and western limbs e g van der merwe 1976 zones these differences can be explained by additional assimilation of up to 18 dolomite which is in contact with the intrusion at buchanan et al 1981 cawthorn et al 1985 eales cawthorn 1996 first the layered rocks show a this locality samples from the platreef that have plagioclase and pyroxene not in oxygen isotope equilibrium appear to have interacted pronounced transgression across the floor rocks from a with fluids during slow cooling quartz veins with granophyric level above the magaliesberg quartzite formation south margins have o values between 10 1 and 12 2 which of the town of potgietersrus across the whole pretoria suggest that the fluid that passed through the cooling platreef had group and the banded iron formations and dolomites a o value of 7 9 these data together with hydrogen isotope of the older chuniespoort group onto archaean granitic data from minerals and whole rock samples d of biotite 60 rocks fig 1 second the igneous layering shows an to 88 of the platreef suggest interaction with magmatic fluid apparent transgressive relationship with respect to the at low water rock ratios interaction of this fluid with the calcsilicate contact such that ultramafic rocks of the lower zone footwall rocks lowered their o values abut against the contact south of potgietersrus whereas to the north rocks forming the base of the intrusion are progressively higher in the stratigraphic succession of the

observations and laboratory modeling of meddy generation at cape st vincent abstract the amuse canigo and ampor observations provided a large amount of subsurface float data showing evidence of several distinctly different flow behaviors within the mediterranean water layers in the vicinity of cape st vincent southwest portugal some of the floats followed the coastline and moved northward and some were trapped either in anticyclonic lenses of mediterranean water meddies generated at cape st vincent or in cyclonic structures these observations clearly indicated that the anticyclones were accompanied by cyclones at least during their early stages as the dipolar structure moves away from the cape the cyclone tends to shift slowly away from the anticyclone while decaying so that after some time only the meddy persists these in situ observations are compared with large scale laboratory experiments and the agreement between the two sets of observations is remarkably good near the cape and shortly after the generation the nondimensional radius relative vorticity and r

determining the petroleum generating potential of coal using organic geochemistry and organic petrology abstract the ardjuna basin of northwest java is typical of many tertiary basins in that it contains high wax crude oil pyrolysis gas chromatography revealed that potential precursors of long chain waxy paraffins are present in coals of the talang akar formation and are most abundant in those that are rich in matrix liptinite conversely it was not possible to estimate waxy oil generating potential using rock eval because pyrolysates from talang akar coal are mainly comprised of naphthenic and aromatic compounds these being derived from resinite and fluorescing vitrinite because of a controlling influence by the abundance of these macerals changes in hydrogen index could not be used to assess maturity resinite and related macerals might play an especially important role in petroleum expulsion as evidenced by their high genetic potential and hence inherent capability of saturating the source rock pore system it is speculated that their maturation products while not constituting typical crude oil might pervade the coal fabric deactivate adsorptive sites and hence facilitate the expulsion of waxy oil that is generated from matrix liptinite

chemostratigraphic evidence of higher plant evolution in the taranaki basin new zealand correlation between palynological and biomarker records of higher plant development during the cretaceous and paleogene in taranaki basin new zealand is good gymnosperms particularly podocarps were the chief members of coastal plain swamp flora during the late cretaceous and contributed significant quantities of diterpanes often dominated by isopimarane to organic rich sediments angiosperms increased in relative abundance through the paleocene and became the dominant higher plants in the eocene their contributions to coaly sediments are characterized by various triterpanes particularly 18 h oleanane and its c24 a ring degraded counterpart this change in dominance of higher plant groups can be followed by the use of an angiosperm gymnosperm index agi based on the relative concentrations of selected triterpanes and diterpanes in mz 191 and mz 123 mass chromatograms plant biomarker distributions do not provide as precise age indications as do pollen assemblages but they may be more representative of the vegetation growing in a particular area of a peat swamp

observed cold filaments associated with mesoscale eddies in the south china sea unusual cold filaments are uncovered during the spring intermonsoon season in the south china sea scs using a suite of satellite observations they have a width of about 100 km on average and extend several hundreds of kilometers offshore on the sea surface providing significant cross shelf transport of heat and nutrients the eastward current associated with mesoscale eddies in spring in the western scs is found to play an important role in the filament formation by advecting coastal cold waters far offshore the meridional location of the cold filament displays considerable interannual variability ranging between 9on and 18on which can be attributed to the interannual south north shift of the eastward current associated with eddies it is also found that in the spring cold filaments have profound effects on the chlorophyll a concentration in the upper ocean and the overlying atmosphere these findings provide new insights into the role of eddies in cross shelf exchange and mesoscale air sea interaction in the marginal seas

lead isotopic disequilibrium between sulfide and plagioclase in the bushveld complex and the chemical evolution of large layered intrusions abstract the pb isotopic compositions of coexisting plagioclase and sulfide from the bushveld complex were determined by laser ablation multi collector icpms la mc icpms the samples are of the upper critical zone in the northeast corner of the complex and were collected from drill core and underground mine exposures all the rocks are fresh and exhibit no evidence for alteration weathering or disruption of the pb isotope systematics subsequent to the initial cooling of the intrusion furthermore individual plagioclase and sulfide crystals do not contain enough u to warrant correction for radiogenic in growth for these reasons the measured pb isotope ratios approximate the initial ones for plagioclase 207pb 206pb ranges from 0 98 to 1 02 and 208pb 206pb from 2 26 to 2 35 low 207pb 206pb and 208pb 206pb ratios characterize grain boundaries and partially annealed microcracks some of which contain minute fragments of sulfide and other phases and this accounts for most if not all the heterogeneity exhibited by individual samples real compositional differences exist however in plagioclase from different lithologic layers for example plagioclase 207pb 206pb values vary from 1 004 in norite beneath the merensky pyroxenite to 1 009 in the mineralized pyroxenite and 0 997 in overlying norite in most samples in which sulfide and plagioclase coexist the sulfide 207pb 206pb ratio is lower and 208pb 206pb ratio higher than the corresponding ones in plagioclase for example in a mineralized merensky reef sample average sulfide 207pb 206pb and 208pb 206pb ratios are 0 993 and 2 313 respectively while those in plagioclase are 1 000 and 2 292 in one sample the sulfide is extremely heterogeneous with 207pb 206pb and 208pb 206pb ratios as low as 0 84 and 2 12 in this particular sample the compositions must represent an isolated occurrence of addition of a young pb component the array of sulfide and plagioclase compositions requires multiple sources of pb at the time of crystallization or soon thereafter the disequilibrium between plagioclase and sulfide implies that some of the pb originated from the isotopically distinct country rocks and was introduced at temperatures at which the composition of sulfide but not plagioclase could be modified thus bushveld sulfide and to some extent plagioclase do not reliably record the initial pb isotopic composition s of the parent magma s

mapping mesoscale variability of the azores current using topex poseidon and ers 1 altimetry together with hydrographic and lagrangian measurements the semaphore mesoscale air sea experiment was conducted in the azores madeira region from july to november 1993 topex poseidon tip and ers 1 were flying simultaneously at that time the main purposes of this paper are to evaluate the estimation of the oceanic mesoscale circulation from the two different sets of altimetric data tip and ers 1 and to compare the results with in situ measurements provided by the semaphore hydrographic surveys and smface drifters three expendable bathytermograph conductivity temperature depth surveys in a 500 km2 box and a set of 47 lagrangian surface drifters drogued at 150m comparisons are carried out through the maps obtained by objective analysis ti om the four data sets the mapping accuracy of tip ers i tip and ers 1 combined and in situ data is investigated as weii as the sensitivity of the mapping to the correlation functions used there is a good qualitative agreement between altimetric maps and corresponding drifter and hydrographic maps for the three hydrographic surveys correlations are about 0 8 and the regression fit is about 0 6 0 7 the lower values are clue to the smooth climatology used to reference the altimetric maps the correlation for time differences is better with regression lines not significantly different from i especiaily when ers 1 and tip are combined tip mapping is almost as good as ers 1 mapping which was rather unexpected since the ers 1 space time sampling is better suited for the mesoscale this may reflect the fact that the signal mapped by the hydrography and drifters does not contain the high frequency wavenumber components tip and ers 1 combined provide better results although the improvement is not as large as expected probaply for the same reason