concentration mechanisms of rare earth element nb zr be mineralization in the baerzhe deposit northeast china insights from textural and chemical features of amphibole and rare metal minerals

the role of hydrothermal processes in concentrating high field strength elements in the strange lake peralkaline complex northeastern canada abstract the middle proterozoic peralkaline pluton at strange lake quebec labrador comprises hypersolvus to subsolvus phases which are unusually enriched in zr y rees nb be and f as exotic alkali and alkaline earth silicate minerals the highest concentrations of these elements are in subsolvus granite which underwent intense low temperature 200 c hydrothermal alteration involving hematization and the replacement of alkali high field strength element hfse minerals by calcic equivalents this alteration is interpreted to have been caused by meteoric or formational waters high temperature 350 c alteration attributed to orthomagmatic fluids is evident in other parts of the subsolvus granite by the replacement of arfvedsonite by aegirine comparisons of the chemical compositions of fresh and altered rocks indicate that rocks subjected to high temperature alteration were chemically unaffected except for depletion in zr y and hrees these elements were appreciably enriched in rocks that underwent low temperature alteration other elements affected by low temperature alteration include ca and mg which were added and na which was removed available data on hfse speciation in aqueous fluids and the chemistry of the pluton suggest that the hfses were transported as fluoride complexes if this was the case the low temperature fluid could not have been responsible for hfse transport because the high concentration of ca and low solubility of fluorite would have buffered f activity to levels too low to permit significant complexation we propose that hfse mineralization and accompanying alteration were the result of mixing in the apical parts of the pluton of a f rich essentially ca free orthomagmatic fluid containing significant concentrations of hfses with an externally derived meteoric dominated fluid enriched in ca as a result of interaction with calc silicate gneisses and gabbros according to this interpretation the latter fluid was responsible for the exchange of ca for alkalis mainly na in hfse rich minerals and by sharply reducing f activity in the mixed fluid through fluorite precipitation and or increasing ph destabilised the hfse fluoride complexes causing deposition of hfse bearing minerals an important implication of this study is that major hfse enrichment may be restricted to those rare cases where f rich ca free metal leaching environments and ca rich depositional environments are juxtaposed

study of the impact of ice formation in leads upon the sea ice pack mass balance using a new frazil and grease ice parameterization abstractleads are cracks in sea ice that often form because of deformation during winter months leads expose the ocean to the cold atmosphere resulting in supercooling and the formation of frazil ice crystals within the mixed layer here the authors investigate the role of frazil ice formation in leads on the mass balance of the sea ice pack through the incorporation of a new module into the los alamos sea ice model cice the frazil ice module considers an initial cooling of leads followed by a steady state formation of uniformly distributed single size frazil ice crystals that precipitate to the ocean surface as grease ice the grease ice is pushed against one of the lead edges by wind and water drag that the authors represent through a variable collection thickness for new sea ice simulations of the sea ice cover in the arctic and antarctic are performed and compared to a model that treats leads the same as the open ocean the processes of ice formation in the new module slow down the refreezing o

synthetic fluid inclusions xvii pvtx properties of high salinity h2o nacl solutions 30 wt nacl application to fluid inclusions that homogenize by halite disappearance from porphyry copper and other hydrothermal ore deposits fluid inclusions that homogenize by disappearance of the halite crystal after the vapor bubble has disappeared have been reported from a wide range of ore forming systems while this inclusion type is most commonly observed in porphyry copper and similar magmatichydrothermal ore deposits they have also been reported from iron oxide copper gold iocg mississippi valley type orogenic lode greenstone gold massive sulfide unconformity u and mantotype deposits as well as from non ore associated granitoids and oceanic crust the lack of experimental data to interpret microthermometric data from these inclusions combined with poor petrographic characterization of inclusion origin has led to a wide range of inferred pt trapping conditions for the inclusions the relationship between liquid vapor homogenization temperature thl v halite dissolution temperature tmhalite and pressure has been determined using synthetic h2o nacl fluid inclusions that homogenize by halite disappearance the experimental data cover the range thl v 150 to 500 c and tmhalite 275 to 550 c an empirical equation describing the relationship between pressure thl v and tmhalite has been developed to estimate formation pressures from microthermometric data and is valid from pressures along the liquid vapor halite curve to 300 mpa a detailed literature review reveals that the results of this study cannot be applied retroactively to estimate pressures of previously reported inclusions that homogenize by halite dissolution for several reasons first most workers have not collected and reported the data in a manner that allows one to determine if the inclusions have trapped a single homogeneous phase and have not leaked or changed volume following trapping thus it is not possible to determine if the inclusions show consistent microthermometric behavior within a group of coeval inclusions additionally many published studies provide only summaries of results from numerous samples or present the data graphically precluding application of our results to individual inclusions however based on our review it appears that much of the published data for inclusions that homogenize by halite dissolution represent inclusions that have either trapped a halite crystal along with the liquid or have reequilibrated by necking and or stretching results from this study have been used to estimate minimum formation pressures for inclusions from the ditrau alkaline massif transylvania romania the musoshi stratiform copper deposit zaire the bismark skarn deposit northern mexico the naica chimneymanto deposit mexico the questa porphyry molybdenum deposit new mexico and the bingham canyon porphyry cu mo deposit utah in each case pressures estimated using results from the present study are in good agreement with previous pressure estimates however in some cases estimated pressures both our estimates as well as those of other authors appear to be unreasonably high based on the geologic setting at the time of formation these results highlight the currently limited understanding concerning pressures depths of ore formation

petrographic and geochemical contrasts and environmentally significant trace elements in marine influenced coal seams yanzhou mining area china abstract the yanzhou mining area in west shandong province china contains coals of permian and carboniferous age the 31 and 32 seams of the permian shanxi formation and seams 6 15 17 of the carboniferous taiyuan formation were analyzed for coal petrology mineralogy and geochemical parameters the parameters indicate that the coal is high volatile bituminous in rank the coal is characterized by high vitrinite and low to medium inertinite and liptinite contents these properties may be related to evolution of the coal forming environment from more reducing conditions in a marine influenced lower delta plain environment for the early taiyuan coals to more oxidizing paleoenvironments in an upper delta plain for the upper shanxi coal seams the major mineral phases present in the coal are quartz kaolinite pyrite and calcite sulfur is one of the hazardous elements in coal the major forms of sulfur in coal are pyritic organic and sulfate sulfur pyritic and organic sulfur generally account for the bulk of the sulfur in coal elemental sulfur also occurs in coal but only in trace to minor amounts in this paper the distribution and concentration of sulfur in the yanzhou mining district are analyzed and the forms of sulfur are studied the sulfur content of the taiyuan coal seams is considerably higher than that of the shanxi coals organic sulfur content is positively correlated to total and pyritic sulfur the vertical variation of cu zn pb as th u and sulfur contents in coal seam 3 of the shanxi formation in the xinglongzhuang mine show that all these trace elements with the exception of th are enriched in the top and bottom plies of the seam and that their concentrations are also relatively high in the dirt bands within the seam the pyritic sulfur is positively correlated with total sulfur and both are enriched in the top bottom and parting plies of the seam the concentrations of the trace elements are closely related to sulfur and ash contents most of the trace elements are correlated with the ash content and may be associated with the mineral matter in the coal

frazil dynamics and precipitation in a water column with depth dependent supercooling when seawater becomes supercooled collections of small ice crystals known as frazil ice form and grow a model of frazil ice dynamics is presented that deals explicitly with the buoyant settling of frazil crystals onto an overlying surface this yields further insight into transport associated with the ice pump mechanism whereby ice is melted at depth and transferred to a shallower location as a result of the pressure variation of seawater s freezing temperature the model is applied to a vertical cross section through an ice shelf water plume beneath filchner ronne ice shelf antarctica and helps to elucidate the depth variation in its properties for the first time as well as predicting the precipitation rate of frazil crystals the model predicts that frazil ice should be preferentially located in a narrow layer near the ice shelf base as a result of the maximum supercooling there and an influx of crystals rising under their own buoyancy the deposition of these crystals onto the ice shelf is governed by the balance between crystal rising and turbulent transfer of frazil away from the shelf which is investigated in some detail

the role of hydrothermal processes in the granite hosted zr y ree deposit at strange lake quebec labrador evidence from fluid inclusions abstract the strange lake zr y ree nb and be deposit is hosted by a small high level late proterozoic peralkaline granite stock that intruded into high grade metamorphic gneisses on the quebec labrador border the stock is extensively altered early alteration is manifested by the replacement of arfvedsonite with aegirine later alteration involved ca na exchange zr ti y rees nb and be are concentrated in ca bearing minerals that together with quartz commonly pseudomorph na bearing minerals fluid inclusions in pseudomorphs comprise several distinct types high salinity 13 to 24 wt nacl eq ca rich aqueous inclusions that homogenize to liquid between 135 and 195 c mixed aqueousmethane inclusions methane inclusions and solid bearing inclusions aqueous methane inclusions represent heterogeneous entrapment of immiscible high salinity aqueous liquid and methane bastnasite tentatively identified by sem analysis occurs as a daughter mineral other daughter or trapped minerals include a y hree bearing mineral possibly gagarinite and hematite galena sphalerite fluorite pyrochlore kutnahorite and griceite the first three inclusion types also occur in quartz in pegmatites and veins together with lower temperature lower salinity na dominated aqueous inclusions the entrapment temperature inferred for the aqueous inclusions from microthermometry and the na k ca geothermometer range from 155 to 195 c for the higher salinity inclusions and 100 to 165 c for the low salinity inclusions a model is proposed in which the intrusion of a peralkaline granite to high crustal levels initiated a ground formational water dominated hydrothermal system in adjacent gabbroic calc silicate and graphitic gneisses reaction of the high salinity ca rich liquid with the graphitic gneisses led to the production of an immiscible methane gas subsequent interaction of this liquid with the granite led to extensive replacement of sodic minerals by calcium analogues at temperatures of less than 200 c some time after the onset of ca metasomatism the high salinity liquid mixed with a ca poor low salinity low temperature liquid that had leached f and rare metals from the granite yttrium and ree mineral deposition occurred as a result of the decreased ligand concentration that accompanied fluorite deposition during mixing of the ca rich and ca poor aqueous liquids

first report of cisuralian early permian charcoal layers within a coal bed from baode north china with reference to global wildfire distribution abstract fossil charcoal is reported for the first time from a cisuralian coal bed of the shanxi formation in the qiaotou section baode shanxi north china based on anatomical characteristics these charcoal fragments consist of coniferous or cordaitalean xylem unidentified primary xylem and cordaitalean and possible fern leaves these charcoal fragments represent the evidence of palaeowildfire taking place in tropical peat swamps during the cisuralian in cathaysia the palaeowildfire is most likely to be a surface fire and burning litter and shrubby vegetation fire frequency for this early permian peat swamp might have been on the order of 176 294 588 1429 years close to modern values compared with modern analogues the north china block during the cisuralian was probably wet in general but could be occasionally seasonally dry for short time intervals previous charcoal and inertinite records moreover indicate that palaeowildfires were globally common during the cisuralian overall more wildfire evidence was found in the artinskian kungurian than the asselian sakmarian except in the euramerican realm probably due to more suitable regional climate vegetation to fuel fires and taphonomic circumstances

modeling the basal melting and marine ice accretion of the amery ice shelf the basal mass balance of the amery ice shelf ais in east antarctica is investigated using a numerical ocean model the main improvements of this model over previous studies are the inclusion of frazil formation and dynamics tides and the use of the latest estimate of the sub ice shelf cavity geometry the model produces a net basal melt rate of 45 6 gt year 1 0 74 m ice year 1 which is in good agreement with reviewed observations the melting at the base of the ice shelf is primarily due to interaction with high salinity shelf water created from the surface sea ice formation in winter the temperature difference between the coldest waters created in the open ocean and the in situ freezing point of ocean water in contact with the deepest part of the ais drives a melt rate that can exceed 30 m of ice year 1 the inclusion of frazil dynamics is shown to be important for both melting and marine ice accretion refreezing frazil initially forms in the supercooled water layer adjacent to the base of the ice shelf the net accretion of marine ice is 5 3 gt year 1 comprised of 3 7 gt year 1 of frazil accretion and 1 6 gt year 1 of direct basal refreezing

geochemical and petrographical characteristics of low rank balingian coal from sarawak malaysia its implications on depositional conditions and thermal maturity abstract geochemical and coal petrographical analyses were undertaken on low rank upper pliocene balingian coal from sarawak malaysia in an attempt to reconstruct the conditions during peat accumulation and the subsequent coalification processes chemically the coal in this study is characterised by high moisture low ash yield and low sulphur content the low ash yield and low sulphur content together with the lack of epiclastic partings clearly indicate that it was deposited in ombrotrophic raised bogs the coal was plotted in the type iii terrigenous kerogen zone of the van krevelen diagram with h c value below 0 9 this shows that the coal was derived from plant materials of terrigenous origin and is still immature for petroleum generation the petrographical study reveals nonetheless the expulsion of early generated hydrocarbons from the disintegration of suberinite and also from phlobaphinite and cutinite petrographically the coal is dominated by huminite with low to moderate amounts of liptinite and low amounts of inertinite pointing to predominantly anaerobic deposition conditions in the paleomires with limited thermal and oxidative tissue destruction most of the studied samples are characterised by low tpi and high gi values and are plotted on the marsh field of the diessel s diagram or it could also originate from decomposed wood in forested swamps nevertheless coals originating from both these sources usually generate high ash yield which is not the case for the studied coal this shows that the interpretation as suggested by the diessel s diagram is not valid for the studied coal the coal has a mean random huminite reflectance between 0 26 and 0 35 suggesting a lignite coal rank for the coal nevertheless geochemical classification based on total moisture and calorific value suggests a subbituminous c rank

melting of ice and sea ice into seawater and frazil ice formation the thermodynamic consequences of the melting of ice and sea ice into seawater are considered the international thermodynamic equation of seawater 2010 teos 10 is used to derive the changes in the conservative temperature and absolute salinity of seawater that occurs as a consequence of the melting of ice and sea ice into seawater also a study of the thermodynamic relationships involved in the formation of frazil ice enables the calculation of the magnitudes of the conservative temperature and absolute salinity changes with pressure when frazil ice is present in a seawater parcel assuming that the frazil ice crystals are sufficiently small that their relative vertical velocity can be ignored the main results of this paper are the equations that describe the changes to these quantities when ice and seawater interact and these equations can be evaluated using computer software that the authors have developed and is publicly available in the gibbs seawater gsw oceanographic toolbox of teos 10

ocean circulation beneath filchner ronne ice shelf from three dimensional model results a high resolution three dimensional ocean circulation model is applied to the cavity beneath filchner ronne ice shelf fris the model predicts predominantly barotropic currents which form a series of cyclonic gyres in the deep basins and anticyclonic circulations around the islands the surface circulation can be such that the water moves in the direction of decreasing or increasing ice thicknesses in the former case leading to freezing while melting at the ice shelf base results in the latter case the pattern of melting and freezing is consistent with known distributions of marine ice and melting areas beneath fris an anticyclonic circulation around the korff and henry ice rises with melting west of korff ice rise and freezing on the eastern side and north of henry ice rise is the main source for an ice pumping mechanism that produces the observed large marine ice body in the central filchner ronne ice shelf the estimates for net melting for realistic conditions at the open ocean boundary are 40 50 km 3 yr 1 indicating that ice shelf ocean interaction is an important contribution to the mass balance of the ice shelf

variations in elemental composition of macerals with vitrinite reflectance and organic sulphur in the greta coal measures new south wales australia abstract the elemental composition of the individual macerals in the early permian greta coal measures of the northern sydney basin and adjoining cranky corner basin new south wales including some seams with high to very high organic sulphur contents have been analysed in polished sections using light element electron microprobe techniques and the results evaluated in the light of vitrinite reflectance and other characteristics of the coals concerned as with other australian coals the vitrinite macerals in each sample have the lowest proportions of carbon and highest proportions of oxygen and the inertodetrinite and fusinite macerals the highest c and lowest o contents semifusinite and the liptinite macerals have intermediate c and o percentages organic sulphur and organic nitrogen are also highest in the vitrinite macerals of the individual samples and lowest in the fusinite and inertodetrinite components the vitrinite macerals in the puxtrees seam of the greta coal measures on the muswellbrook anticline in the upper hunter valley have similar elemental compositions 78 c and similar reflectance values rv max around 0 7 to vitrinites in the late permian bituminous coals in other parts of the sydney bowen basin the vitrinites in the seams of the cranky corner basin also have similar carbon contents to the puxtrees seam material suggesting a similar rank level but have much lower vitrinite reflectance values rv max 0 4 0 5 probably due to marine influence associated with the depositional system the vitrinites in the greta seam on the lochinvar anticline in the lower hunter region have higher carbon contents 83 than the puxtrees material suggesting a higher rank level but similar to lower vitrinite reflectance values rv max 0 6 0 7 vitrinite carbon is also constant through the seam profile despite upwardly decreasing reflectance values in the seam due to progressive increases in marine influence the vitrinites in the upper greta seam and the cranky corner basin coals have high to very high organic sulphur contents again probably due to marine influence on the depositional process the vitrinites in the cranky corner basin coals which have particularly high organic sulphur contents also have somewhat lower oxygen contents in relation to their carbon percentages than those of other australian seams suggesting that the additional organic sulphur has replaced oxygen in the macerals molecular structure the macerals especially the vitrinites in the coals with high organic sulphur and anomalously low vitrinite reflectance also have up to 0 5 al and 1 ca intimately associated with the organic matter similar organically associated inorganic elements are commonly found in lower rank e g sub bituminous coals but are usually lost from the organic matter at higher rank levels the coals of the greta coal measures therefore have vitrinite carbon contents consistent with a high volatile bituminous rank but those seams or parts of seams with high organic sulphur due to substantial marine influence appear to have preserved the vitrinite reflectance values and organically associated inorganic elements more typical of lower rank sub bituminous materials

petrography carbonate mineralogy and geochemistry of thermally altered coal in permian coal measures hunter valley australia abstract carbonate minerals commonly occur in coals of many ages and from a utilisation viewpoint can be deleterious several studies have been undertaken of the carbonates in the permian coals of the hunter valley australia but few studies use a multi technique approach for this study a combined petrographic geochemical and mineralogical approach was used to determine the distribution and residence of carbonate minerals in coal that had been intruded by a dyke the dominant carbonate assemblages comprise primary siderite in inertinite rich microlithotypes and secondary calcite ankerite dolomite dawsonite in vitrinite rich microlithotypes the secondary carbonates were found in both the aureole of heated coal and also in an unheated mine face sample it is believed that the secondary carbonate minerals precipitated from magma derived fluids percolating through the coal following the emplacement of the intrusions the textures and distribution of the secondary carbonate minerals suggest that the temperature and pressure of the fluids may be just as important in developing fractures near dykes particularly those that have multiple phases of geometries cleat mineralogy and coal textures as direct heating from the intrusion the partitioning of primary siderite with inertinite and secondary carbonates with vitrinite indicates that it can be reasonably expected that there would be a partitioning of minerals in various density fractions derived from float sink tests and consequently a partitioning of elements with inertinite rich fractions containing elevated fe levels and vitrinite rich fractions containing elevated ca mg and al this partitioning has implications for the behaviour of the coal during washing and combustion and the composition of combustion products

elemental composition of coal macerals in relation to vitrinite reflectance gunnedah basin australia as determined by electron microprobe analysis abstract the elemental composition of macerals in high volatile bituminous coals from the gunnedah basin new south wales australia has been analysed by light element electron microprobe techniques the results have been evaluated in relation to maximum vitrinite reflectance trends in vertical section including the effects of marine influence and igneous intrusions on the coal bearing sequence mean maximum vitrinite telocollinite and desmocollinite reflectance for the analysed samples ranges from 0 63 to 0 99 and to 2 2 for coal affected by igneous intrusions the carbon content of the vitrinite as determined by electron microprobe ranges from 79 74 to 86 07 and up to 89 06 for the heat affected coal studied a simple relationship cannot be established between the reflectance of the vitrinite and its carbon content over this range of coal samples vitrinite in marine influenced coals with suppressed reflectance appears to have a slightly higher carbon content than vitrinite in isorank coals without marine influence the increase in carbon may be due to incorporation of carbon and sulphur rich lipoid material into the vitrinite component notwithstanding these differences the carbon content of vitrinite telocollinite seems to be affected only slightly by the depositional changes that cause suppression of vitrinite reflectance in marine influenced coals telocollinite carbon content may therefore be a useful alternative to vitrinite reflectance as a rank indicator in maturation studies the carbon content of whole coal samples determined by ultimate analysis shows in vertical section a trend intermediate between the carbon of the vitrinite determined by electron microprobe and that of the associated inertinite macerals whole coal analysis data in this range depend on the relative proportions of the different macerals present as well as the rank of the coal concerned coals affected by igneous intrusion show a different relationship between carbon and oxygen of vitrinite telocollinite relative to coals where the rank is determined by depth of burial alone the difference in c o relationships suggests that the short term heating associated with intrusions produces chemical changes in macerals that are not paralleled in more normal rank advance

zr nb ree mineralization in peralkaline granites from the amis complex brandberg namibia evidence for magmatic pre enrichment from melt inclusions the amis complex is a late intrusive phase associated with the brandberg anorogenic granite intrusion it consists of peralkaline arfvedsonite bearing granitic and pegmatitic dikes and sills and is characterized by locally extreme enrichments in ree and rare metals with high charge ionic radius ratios such as zr and nb the highest concentrations e g 1 7 wt zr 0 3 wt nb 0 5 wt total ree are found in aegirine albite aplites that formed around arfvedsonite pegmatite cores quartz hosted melt inclusions in coarse grained arfvedsonite granite and pegmatite give unequivocal evidence that the peralkaline composition and rare metal enrichments are primary magmatic features electron microprobe and sims analyses of rehomogenized inclusion glasses reveal their peralkaline high si rhyolite compositions avg molar na k al 1 1 and very high contents of h2o max 10 6 wt and f 2 2 wt inclusion glasses also have high concentrations of incompatible trace elements including nb min 803 ppm zr min 3 187 ppm and ree y min 1 271 ppm the ree zr and nb compositions of the aegirine albite aplites plot along the same linear enrichment trends as the melt inclusion glasses and y ho ratios mostly display unfractionated near chondritic values the chemical and textural features of the aegirine albite aplites are compatible with an origin by rapid crystallization compositional quenching after volatile loss from a residual peralkaline granitic melt of a composition like that of the melt inclusions interaction of postmagmatic fluorine rich aqueous fluids with the arfvedsonite granites caused local remobilization of ree and secondary mineralization of fluorocarbonate phases such as bastnaesite and fractionation of y and ho

the origin of skarn hosted rare metal mineralization in the ambohimirahavavy alkaline complex madagascar the cenozoic ambohimirahavavy alkaline complex in madagascar consists of several syenitic to granitic intrusions 24 2 0 6 ma the largest of which the ampasibitika intrusion is characterized by the presence in its outer flanks of late peralkaline granitic dikes intruding mudstone and limestone of the isalo group a network of dikelets and veinlets propagates from these dikes intruding along bedding or obliquely to bedding at the contact between the dikes and dikelets and a limestone a reaction zone enriched in rare metals dominated by calc silicate minerals such diopside and andradite grossular forms a rare example of skarn resulting from peralkaline igneous activity much of the rare metal mineralization ree zr nb th sn and ti occurs as secondary phases in the dikelets and skarn in the dikelets and endoskarn high field strength element hfse rich phases consist mainly of zircon bastnasite ce and ca ree and ca hfse rich phases in pseudomorphs after aegirine augite in the exoskarn the main hfse rich phases are bastnasite ce zircon pyrochlore nb rich titanite and an unidentified f rich ca zirconosilicate finely disseminated in a matrix composed of calcite diopside andradite phlogopite quartz fluorite and fluorapatite the secondary zircon is characterized by a low zr content and by the presence of ree ca al and fe three types of primary fluid inclusions were observed in dikelets and skarn in quartz calcite and diopside 1 liquid rich inclusions l v 20 to 40 vol vapor occur in all three minerals and homogenize to liquid 2 vapor rich inclusions v 90 vol vapor occur in diopside and quartz and homogenize to vapor and 3 halite bearing l v inclusions l v h occur in diopside and quartz and homogenize either by disappearance of the vapor bubble or by halite dissolution the l v inclusions have low to intermediate salinity and homogenize at temperatures ranging from 200 to 380 c the v inclusions have low salinity and homogenize at higher temperature 350 395 c the l v h inclusions mainly contain nacl 35 45 wt nacl equiv and homogenize by three modes namely bubble disappearance mode a halite dissolution mode b and simultaneous bubble and halite disappearance mode c the homogenization temperatures range from 260 to 380 c we propose a model in which rare metals were transported by a cl f and hfse rich orthomagmatic fluid exsolved at 400 to 450 c and about 20 mpa at these conditions the fluid was in the two phase region and vapor dominated the rare metals were deposited as a result of the interaction of this fluid with limestone and mixing with an external fluid this interaction mixing buffered the orthomagmatic fluid to higher ph and lower temperature resulting in the destabilization of ree chloride complexes and deposition of fluorocarbonate minerals in the limestone zr and nb which were likely transported as hydroxyl fluoride complexes precipitated as zircon and pyrochlore due to deposition of fluorite and a consequent decrease in fluoride activity

the record of triassic charcoal and other evidence for palaeo wildfires signal for atmospheric oxygen levels taphonomic biases or lack of fuel abstract as wildfires are today important sources of disturbance in many terrestrial ecosystems it is of great interest to understand how different environmental parameters and fire activity interacted during past periods of the earth history fossil charcoal inertinites and pyrogenic polycyclic aromatic hydrocarbons pahs represent the only direct evidence for the occurrence of such palaeo wildfires in the present study a review of published data together with new data on the occurrence of fossil charcoal for the permian and the triassic is presented for a long time it has been speculated that an assumed lack of evidence for palaeo wildfires during the triassic should be explained by a large drop in atmospheric oxygen concentration following or during the end permian mass extinction event preventing the occurrence of wildfires however evidence for palaeo wildfires is relatively common in many middle and late triassic strata whereas such evidence is almost totally lacking from early triassic sediments the interpretation of this charcoal gap or depression is difficult as many factors e g atmospheric oxygen concentration taphonomical biases lack of sediments suitable for the preservation of macroscopic charcoal lack of fuel and ignorance of scientists may have influenced not only the production but also the preservation and recovery of evidence for palaeo wildfires during this period thus it is not clear whether this early triassic charcoal gap can also be seen as evidence for an assumed wildfire gap or not without any doubt further investigations on the early triassic record of charcoal and other evidence for palaeo wildfires will be necessary before this problem can be solved in fact it can be expected that the number of published records of early triassic evidence for palaeo wildfires will increase in the future as more and more scientist working on sediments of this age may become aware of the interest in fires from this time this will certainly make it possible to give a much better picture of the temporal and regional distribution of wildfires during this period in the future

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

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

light and trace element composition of carboniferous coals from the donets basin ukraine an electron microprobe study abstract the ukrainian donets basin donbas is one of the major coal mining provinces worldwide while the depositional setting of donbas coals is well studied information on modes of trace element occurrence and changes in element composition with increasing maturation is lacking within the frame of the present study both major light elements c o s and trace elements e g as cu hg mo pb were investigated using the electron microprobe epma which allows in situ determination of the chemical composition of a maceral or mineral phase deviating maturity trends in c o and s contents were found for different maceral groups in relatively immature samples 0 9 rr s contents of vitrinites and liptinites are comparable but lower in inertinite macerals vitrinites in a marine influenced coal host a higher amount of organic s whereas the trace element concentrations are lower than in the investigated non marine coals as expected a trend of increasing c and decreasing o contents was observed for vitrinite macerals within a maturity range from 0 5 to 1 4 rr referred to a decrease in volatile compounds during thermal maturation the light element composition generally tends to higher homogenity with increasing coal rank highly variable trace element concentrations of ash residues were determined for donbas coals with measured as contents up to several thousand ppm despite enrichment in epigenetic pyrite a clearly isolated inorganic source could not be identified suggesting that trace element storage in macerals is an important factor epma measurements revealed an organic matter affinity for at least part of the investigated elements e g hg mo pb

mobility and h2o loss from fluid inclusions in natural quartz crystals petrographic observations on quartz crystals from the mole granite australia and other localities shed new light on the mechanisms of post entrapment modification of fluid inclusions these modifications include migration away from pseudosecondary trails changes in fluid salinity and density shape distortion and the formation of sweat haloes around strongly deformed inclusions increases in fluid salinity which usually are associated with inclusion migration indicate water losses of up to 50 however la icp ms analysis of unmobilized and mobilized inclusions of the same trail reveals basically unchanged ratios of major and trace element cations with the exception of li which seems to be incorporated into the crystal lattice during migration despite the fact that all these modifications are closely related to deformation processes they occur not only in mechanically deformed quartz but also in free standing crystals in the latter samples stress has been generated internally as a result of brazil twinned growth and compositional zonation these observations and their interpretation leads to a list of practical criteria that should help in differentiating between reliable and suspect fluid inclusions in other samples

variations in coal maceral chemistry with rank advance in the german creek and moranbah coal measures of the bowen basin australia using electron microprobe techniques abstract variations in the elemental composition of individual macerals in seams from the permian german creek and moranbah coal measures in the bowen basin of queensland have been studied over a wide range of coal ranks using light element electron microprobe techniques to establish the coalification tracks of key macerals in a single coal bearing interval from subbituminous through bituminous coal to anthracite vitrinite reflectance rv max in the seams studied increases from 0 39 in the western part of the basin to over 3 5 in the east apparently due to increases in burial depth the study extends significantly the rank range covered by previous work on elemental analysis of individual macerals in the gunnedah basin and provides a more useful basis than whole coal analysis to evaluate the performance of coals in different utilisation processes the microprobe results show that the carbon content of the telocollinite increases dramatically from 66 to 90 as the vitrinite reflectance of the coals rv max increases from 0 39 to around 1 75 but increases only slightly from 90 to 91 as rv max increases from 1 75 to 3 52 oxygen decreases from around 26 to approximately 5 as rv max increases from 0 39 to around 1 75 and then decreases only very slightly into the anthracite range the nitrogen content of the telocollinite in these coals also appears to decrease slightly with rank advance and appears moreover to display a relatively abrupt drop at around 2 rv max this may be associated with the development of ammonium illite in the mineral matter organic sulphur in the telocollinite on the other hand seems to remain essentially constant with rank advance at least in this particular succession in contrast to vitrinite fusinite and inertodetrinite have significantly higher but somewhat more constant carbon contents varying only from around 81 to 93 c over the rank range studied oxygen in these macerals decreases from around 12 to a little over 2 with the same degree of rank advance sulphur and possibly nitrogen also appear to be significantly lower in fusinite and inertodetrinite than in the vitrinite of the same coal samples semifusinite is somewhat more variable in composition with characteristics intermediate between those of the fusinite inertodetrinite and those of the vitrinite in the same coal over the rank range studied

mass budget of the grounded ice in the lambert glacier amery ice shelf system we used remote sensing and in situ measurements of surface accumulation rate ice surface velocity thickness and elevation to evaluate the mass budgets of grounded ice flow regimes that form the lambert glacier amery ice shelf system three distinct drainage regimes are considered the western and eastern margins of the ice shelf and the southern grounding line at the major outlet glacier confluence which can be identified with drainage zones 9 11 and 10 respectively of giovinetto and zwally 2000 our findings show the entire grounded portion of the basin is approximately in balance with a mass budget of 4 2 9 8gta 1 drainages 9 10 and 11 are within balance to the level of our measurement uncertainty with mass budgets of 2 5 2 8 gta 1 2 6 7 8 gta 1 and 0 9 2 3 gta 1 respectively the region upstream of the australian lambert glacier basin lgb traverse has a net mass budget of 4 4 6 3 gt a 1 while the downstream region has 8 9 9 9 gt a 1 these results indicate that glacier drainages 9 10 and 11 upstream and downstream of the australian lgb traverse are in balance to within our measurement error

petroleum migration and accumulation in the bozhong sub basin bohai bay basin china significance of preferential petroleum migration pathways ppmp for the formation of large oilfields in lacustrine fault basins abstract this paper discusses migration styles and primary controls of petroleum migration pathways in heterogeneous carrier beds in bozhong sub basin bohai bay basin modeling of secondary petroleum migration pathways has been conducted using a simple three dimensional model which assumes that the positions of petroleum migration pathways are controlled by the morphology of the sealing surfaces the modeling results have accurately predicted the petroleum occurrences and have been supported by petroleum geochemical studies most commercial petroleum accumulations are on the predicted preferential petroleum migration pathways ppmp formed by focusing of numerous small petroleum streams close to the kitchens and most large fields petroleum reserves greater than 1 10 8 ton have more than one preferential petroleum migration pathway to convey petroleum to the traps the focusing of petroleum originated from a large area of the generative kitchens into restricted channels is essential for the formation of large oilfields the strong porosity and permeability heterogeneities of the carrier beds and the relatively high prediction accuracy by a model that does not take into consideration of the effect of heterogeneity suggest that the positions of petroleum migration pathways in heterogeneous carrier beds in the lacustrine fault basins are determined primarily by the morphology of the sealing surfaces at regional scales

the genesis of hydrothermal fluorite ree deposits in the gallinas mountains new mexico breccia hosted fluorite bastnaesite deposits associated with epizonal quartz syenite intrusions in the gallinas mountains new mexico provide an important example of hydrothermal rare earth element ree mineralization and an excellent opportunity to investigate the transport and deposition of the ree under hydrothermal conditions fluid inclusion studies show that mineralization commenced with the deposition of quartz at a temperature of approximately 400 c from sulfate rich nacl kcl brines having a salinity of 15 wt percent nacl equiv these fluids are interpreted to have been of orthomagmatic origin fluorite and bastnaesite deposition occurred at slightly lower temperatures and coincided with the introduction of separate co2 bearing and sulfate poor nacl brines into the system these fluids are considered to have been of external origin the latter being a formation water that circulated in surrounding permian sandstones and limestones evaluation of the available thermodynamic data on the aqueous speciation of ree and the preliminary data on the chemistry of the fluids obtained in this study suggest that the ree were dissolved primarily as fluoride complexes a model is proposed in which the ree were transported by the orthomagmatic fluids and deposited as bastnaesite owing to destabilization of ree fluoride complexes the latter occurred in response to the sharp reduction in f activity that accompanied large scale deposition of fluorite as a result of mixing of the orthomagmatic fluids and formation waters this mixing also led to the deposition of anhydrite and barite owing to the interaction of externally introduced calcium and barium ions with orthomagmatic sulfate ions the later stages in the evolution of the gallinas mountains hydrothermal system were marked by increased incursion of external fluids and the alteration of bastnaesite to ca bastnaesite and minor deposition of ca bastnaesite and parisite owing to lowered f batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document co 3 2 mbox end document ratios and or increased ca2 activity the study suggests that ca free ree fluoride bearing fluids are an important ingredient for ree mineralization that mixing of such fluids with ca carbonate bearing fluids or interaction with carbonate rocks is a major control of ree fluorocarbonate mineral deposition and that the occurrence of fluorite could provide an important guide in the exploration for economic ree deposits

modeling the effects of frazil ice crystals on the dynamics and thermodynamics of ice shelf water plumes the seawater that comes into contact with the base of a floating ice shelf is modified as a result of the phase changes that occur melting is prevalent in the deepest parts of the subice cavity and this drives a buoyant flow of ice shelf water isw along the sloping ice shelf base the ascent of the isw toward the surface of the ocean causes supercooling because the freezing point rises with the falling pressure and this induces a change from melting to freezing assuming that seed crystals exist the isw now fulfills the condition for the rapid growth of disc shaped frazil ice crystals which may subsequently settle upward out of suspension under the action of gravity a simple numerical model of these processes has been developed based on the theory of inclined plumes the isw is treated as a turbulent particle laden gravity current ascending a reactive boundary and containing a suspended crystal load which evolves in response to the supercooling of the water and the inverted sedimentation of the crystals the frazil ice has two important effects on the behavior of the isw plume because the generation of crystals through out the plume provides such a large area over which phase changes can occur the conversion of supercooling into ice happens much more readily than is possible through turbulent transfer of heat and mass at the ice shelf base a suspended crystal load reduces the bulk density of the isw so that a growing suspension causes the plume to accelerate while deposition of crystals onto the ice shelf effects a deceleration there are positive feedbacks in that an acceleration of the plume induces more rapid crystal growth while a deceleration allows suspended crystals to settle out more easily

variation in elemental composition of macerals an example of the application of electron microprobe to coal studies abstract elemental composition of macerals in lignite sub bituminous high volatile bituminous medium volatile bituminous and anthracitic rank coals have been investigated using the electron microprobe technique the concentration of c o n s fe si and al have been measured directly and hydrogen was calculated by difference the chemical composition was compared to reflectance values and whole coal chemistry in lignite the sequence ulminite 66 27 c porigelinite 67 32 c micrinite 67 92 c corpocollinite 68 21 c macrinite 70 24 c and fusinite 73 03 c represents a series with increasing carbon content sulphur concentration is the highest in porigelinite 2 95 and the lowest in fusinite 0 21 whereas nitrogen is the highest in corpocollinite 3 12 and the lowest in micrinite and porigelinite in sub bituminous coal the sequence of decreasing carbon content is as follows macrinite 80 01 c sporinite 73 00 c semifusinite 72 76 c and telocollinite 67 49 c sulphur content is the highest in telocollinite 3 29 in high volatile bituminous coal carbon content is highest in fusinite 93 68 and lowest in cutinite 82 82 vitrinite macerals have the highest sulphur content and fusinite has the lowest in medium volatile bituminous coal a sequence of decreasing carbon and increasing oxygen content fusinite 90 02 c semifusinite 89 73 c and vitrinite 88 56 c is detectable but differences in carbon and oxygen content between macerals are small in anthracite no statistical differences in carbon and oxygen content between vitrinite and inertinite macerals exist about 94 c and 1 o for both macerals comparison of reflectance values to carbon and oxygen contents for individual macerals demonstrates that vitrinite and sporinite enter a common coalification path at 88 5 c and a reflectance of 1 25 semifusinite joins the path at about 89 c and a reflectance of 1 8 2 0 more data are needed to determine the relationship between reflectance and elemental composition for other macerals

vitrinite reflectance anomalies in the high volatile bituminous coals of the gunnedah basin new south wales australia abstract the rank of the permian coals in the gunnedah basin has been analyzed using both petrographic and chemical methods apart from the effects of local igneous intrusions a number of seams in the sequence have vitrinite reflectance values rv max that deviate significantly from the trend expected with a steady downward increase in coalification correlation of these anomalies with interpreted depositional environments suggests that abnormally low vitrinite reflectance values in the sequence occur in seams either overlain by or intimately associated with marine strata the three dimensional distribution of such low reflectance values in part of the section at least can be related either to the lithofacies pattern or post depositional groundwater flow associated with a major fan delta system coals with anomalously high vitrinite reflectance values appear to contain material described elsewhere as pseudovitrinite a component not previously reported in australian permian bituminous coals both low value and high value anomalies need to be taken into account when interpreting maturation patterns from vitrinite reflectance data in some cases other rank indicators such as air dried moisture may be useful to complement vitrinite reflectance in rank studies of high volatile bituminous coals abnormally low vitrinite reflectance values due to environmental factors such as marine influence on the other hand may be used to identify flooding surface sequence boundaries in the basin for stratigraphic and sedimentological investigations

zircon solubility in alkaline aqueous fluids at upper crustal conditions field evidence and thermodynamic data at ambient conditions suggest that complexing of zr with hydroxyl ions at high ph enhances the solubility of zircon we tested this hypothesis by measuring the solubilities of the assemblages zircon zrsio 4 baddeleyite z b and zircon quartz z q in neutral to alkaline fluids at 0 2 gpa and 450 750 c in neutral to alkaline fluids 0 0 1 1m naoh zircon dissolved incongruently in quartz undersaturated fluids to form baddeleyite at 450 c various na zr silicates precipitated from fluids saturated and undersaturated in quartz we observed no significant dependence of solubility on temperature the measured solubilities of zircon in pure h 2o at 600 and 750 c are only slightly higher than the procedural blank of 3 3 10 7 m zr however the measured solubility of zircon increases with increasing aqueous silica suggesting that zirconium complexes with silica in the fluid at 600 c linear regression of experimental results yielded ln zr 0 25 2 9 ln si where terms in parentheses represent molal concentrations zircon solubility also seems to increase with increasing hydroxyl concentration in the fluid enhanced solubility in silica rich alkaline fluids may cause dissolution reprecipitation of zircon and resetting of its isotopic clocks suggesting that some zircon u pb ages may correspond to fluid events

impact of tide topography interactions on basal melting of larsen c ice shelf antarctica 1 basal melting of ice shelves around antarctica contributes to formation of antarctic bottom water and can affect global sea level by altering the offshore flow of grounded ice streams and glaciers tides influence ice shelf basal melt rate wb by contributing to ocean mixing and mean circulation as well as thermohaline exchanges with the ice shelf we use a three dimensional ocean model thermodynamically coupled to a nonevolving ice shelf to investigate the relationship between topography tides andwb for larsen c ice shelf lcis in the northwestern weddell sea antarctica using our best estimates of ice shelf thickness and seabed topography we find that the largest modeled lcis melt rates occur in the northeast where our model predicts strong diurnal tidal currents 0 4 m s 1 this distribution is significantly different from models with no tidal forcing which predict largest melt rates along the deep grounding lines we compare several model runs to explore melt rate sensitivity to geometry initial ocean potential temperature 0 thermodynamic parameterizations of heat and freshwater ice ocean exchange and tidal forcing the resulting range of lcis averagedwb is 0 11 0 44 m a 1 the spatial distribution of wb is very sensitive to model geometry and thermodynamic parameterization while the overall magnitude of wb is influenced by 0 these sensitivities in wbpredictions reinforce a need for high resolution maps of ice draft and sub ice shelf seabed topography together with ocean temperature measurements at the ice shelf front to improve representation of ice shelves in coupled climate system models

hierarchies of overpressure retardation of organic matter maturation case studies from petroleum basins in china the effects of overpressure on different aspects of organic matter maturation have been examined in three basins using multiple parameters overpressure in the yinggehai basin has retarded kerogen maturation hydrocarbon generation and thermal cracking of long chain normal hydrocarbons as well as evolution of isoprenoid hydrocarbons overpressure in the dongpu depression bohai bay basin seems to have retarded the maturation of bulk kerogens reflected by rock eval tmax the thermal cracking of long chain normal hydrocarbons and the evolution of isoprenoid hydrocarbons but seems to have had no detectable effects on vitrinite reflectance overpressure in the qiongdongnan basin has had no detectable retardation effects on all aspects of organic matter maturation the observed phenomena suggest differential retardation of organic matter maturation that is different organic matter maturation reactions and different maturity parameters have been retarded by overpressure to different degrees in the same overpressured system and four hierarchies of overpressure retardation hierarchy i retardation is defined as the state where the overpressure has retarded all aspects of organic matter maturation and is proposed to have been caused by the combination of high formation pressure and excess pressure a high water organic matter ratio and strong retention of reaction products in an early developed strong persistent overpressured system hierarchy ii retardation refers to the case in which all aspects of organic matter maturation except the maturation of hydrogen poor kerogens especially vitrinite have been retarded and seem to have been caused by early developed moderate to strong persistent overpressure hierarchy iii retardation refers to the situation where overpressure has retarded only the thermal cracking of liquid hydrocarbons but has had no detectable effect on the maturation of both hydrogen rich and hydrogen poor kerogens and is proposed to have been caused by moderate to strong persistent overpressures that began to develop around peak oil generation hierarchy iv retardation is defined as the situation where overpressure has had no detectable retardation on all aspects of organic matter maturation and may have been caused by cases wherein the overpressure developed too late the intensity of the overpressure was too low the duration of the overpressure was too short or overpressured fluids had been expelled frequently resulting from both the diversities of organic matter maturation reactions and the complexities of overpressure generation and development the hierarchies of overpressure retardation in different basins may be quite different and it is necessary to use multiple parameters to understand the evolution of the petroleum systems in overpressured basins

zircon of the no 782 deposit from the great xing an range in ne china implications for nb ree zr mineralization during magmatic hydrothermal evolution abstract niobium rare earth elements ree lanthanides y and zirconium are widely used in high tech applications the nb ree zr mineralization in the no 782 deposit of ne china developed in a fine grained porphyry porphyry that occurs as a ring shaped stock the ore forming porphyry is hosted in a coarse grained granite granite that dominates the study area zircon is the only zr bearing mineral in both the porphyry and the granite in contrast to the granite that hosts only magmatic zircon both magmatic type i and metasomatic type ii zircon crystals or aggregates are present in the porphyry most type i zircon occurs as individual crystals and are hosted mainly in interstitial quartz with evident oscillatory zoning most type ii zircon occurs as aggregates rather than individual crystals and exhibits vague zoning distribution of the type ii zircon in the porphyry is heterogeneous with great abundance in places where there are substantial albitization and snowball quartz crystals textural and chemical features of the type ii zircon and of the associated albite and snowball quartz crystals suggest that all these minerals are metasomatic nb is hosted mainly by fergusonite y and ree by fergusonite y and to a lesser extent by bastnasite ce and parisite ce where parisite ce occurs as a replacement of bastnasite ce the nb ree mineralization occurs either as a replacement of the type ii zircon or in chlorite quartz dominant veinlets that postdated both the type i and the type ii zircon most type i zircon crystals in the porphyry were intact from the replacement or alteration by the postdated nb ree minerals possibly because the type i crystals were encased earlier by other magmatic minerals the chronological and oxygen isotopic data of zircon suggest that the porphyry 453 8 3 1 ma is younger than the granite 487 0 4 0 ma and that the two granitic phases derived from different magma chambers the subtle age difference between magmatic type i and metasomatic type ii zircon cannot be shown by shrimp u pb data of zircon the mineral assemblages associated with type ii zircon and the chronological data suggest that the medium from which type ii zircon precipitated is likely an internally derived hydrosilicate liquid hsl that lies compositionally in between a silicate melt and a hydrothermal fluid during the magmatic hydrothermal transition textural features of the nb ree minerals combined with the fact that nb ree mineralization developed only inside the porphyry but not in surrounding country rocks i e the granite suggest that the nb ree mineralization originated from an aqueous fluid that was constrained to the porphyry

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

modeling water mass formation in the mertz glacier polynya and adelie depression east antarctica 1 high rates of sea ice growth and brine rejection in the mertz glacier polynya drive the production of dense continental shelf waters in the adelie depression we consider the rate of outflow of waters having sufficient density to sink into the neighboring abyssal ocean and form adelie land bottom water albw along with weddell and ross sea bottom waters the albw is an important source of antarctic bottom water the relevant processes are modeled using a variant of the max planck institute ocean model mpiom under daily ncep ncar reanalysis forcing for the period 1991 2000 the orthogonal curvilinear horizontal grid allows for the construction of a global domain with high resolution in our region of interest the modeled mertz glacier polynya is realistic in location and extent exhibiting low ice thickness 0 4 m and low ice fraction 50 the net surface ocean to atmosphere heat flux exceeds 200 w m2 and is dominated by sensible heat exchange in wintertime may through september inclusive 7 5 m of sea ice forms over the adelie depression at a rate of 4 9 cm d 1 this results in annual average volumetric production of 99 km3 of sea ice the associated brine release drives dense shelf water formation the off shelf flow of dense water exhibits strong interannual variability in response to variability in both atmospheric forcing and ocean preconditioning averaged over the period 1991 2000 the off shelf flow of dense water is 0 15 sv for a period of strong outflow 1993 1997 this increases to 0 24 sv most of the outflow occurs during july through october at a rate of 0 40 0 63 sv over the period 1991 2000 1993 1997 the peak mean monthly outflow can exceed 1 sv

modelling the response of ice shelf basal melting to different ocean cavity environmental regimes we present simulation results from a version of the regional ocean modeling system modified for ice shelf ocean interaction including the parameterisation of basal melting by molecular diffusion alone simulations investigate the differences in melting for an idealised ice shelf experiencing a range of cold to hot ocean cavity conditions both the pattern of melt and the location of maximum melt shift due to changes in the buoyancy driven circulation in a different way to previous studies tidal forcing increases both the circulation strength and melting with the strongest impact on the cold cavity case our results highlight the importance of including a complete melt parameterisation and tidal forcing in response to the 2 4 c ocean warming initially applied to a cold cavity ice shelf we find that melting will increase by about an order of magnitude 24 with tides and 41 without tides

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

the role of meltwater advection in the formulation of conservative boundary conditions at an ice ocean interface abstract upper boundary conditions for numerical models of the ocean are conventionally formulated under the premise that the boundary is a material surface in the presence of an ice cover such an assumption can lead to nonconservative equations for temperature salinity and other tracers the problem arises because conditions at the ice ocean interface differ from those in the water beneath advection of water with interfacial properties into the interior of the ocean therefore constitutes a tracer flux neglect of which induces a drift in concentration that is most rapid for those tracers having the lowest diffusivities if tracers are to be correctly conserved either the kinematic boundary condition must explicitly allow advection across the interface or the flux boundary condition must parameterize the effects of both vertical advection and diffusion in the boundary layer in practice the latter alternative is often implemented although this is rarely done for all tracers

a numerical model to estimate trapping conditions of fluid inclusions that homogenize by halite disappearance abstract fluid inclusions fi that homogenize by halite disappearance are common in some geological environments and interpretation of microthermometric data from these inclusions has been limited by the lack of a model describing the pvtx relationships over the complete range of ptx conditions found in nature in this study a system of equations has been developed that can be used to estimate salinity pressure and density of fi that homogenize by halite disappearance the salinity pressure density and d p d t slope of the fi isochore are calculated as functions of liquid vapor homogenization temperature th and halite dissolution temperature tm the equations are based on a numerical model describing the isochoric pressure temperature trajectory followed by halite saturated fluids during heating the model is valid for th and tm from 100 to 600 c and for pressures along the liquid vapor halite curve to 300 mpa

the effects of rotation and ice shelf topography on frazil laden ice shelf water plumes a model of the dynamics and thermodynamics of a plume of meltwater at the base of an ice shelf is presented such ice shelf water plumes may become supercooled and deposit marine ice if they rise because of the pressure decrease in the in situ freezing temperature so the model incorporates both melting and freezing at the ice shelf base and a multiple size class model of frazil ice dynamics and deposition the plume is considered in two horizontal dimensions so the influence of coriolis forces is incorporated for the first time it is found that rotation is extremely influential with simulated plumes flowing in near geostrophy because of the low friction at a smooth ice shelf base as a result an ice shelf water plume will only rise and become supercooled and thus deposit marine ice if it is constrained to flow upslope by topography this result agrees with the observed distribution of marine ice under filchner ronne ice shelf antarctica in addition it is found that the model only produces reasonable marine ice formation rates when an accurate ice shelf draft is used implying that the characteristics of real ice shelf water plumes can only be captured using models with both rotation and a realistic topography

the burning of gondwana permian fires on the southern continent a palaeobotanical approach abstract fossil charcoal has widely been accepted as a direct indicator for the occurrence of palaeo wildfires in upper palaeozoic sediments of euramerica and cathaysia records of these remains are relatively common and regionally and stratigraphically more or less homogeneously distributed in terrestrial sequences on the other hand just a few records have been published for the permian of gondwana and only recently has it been demonstrated that macroscopic charcoals are also common here most permian macroscopic charcoal from gondwana is gymnospermous and has been reported from coal bearing strata macroscopic charcoal occurrences are spread out in different sequences and also in distinct stratigraphic intervals in the permian e g parana basin sakmarian artinskian of brazil karoo basin artinskian of south africa damodar basin lopingian of india and dead sea area changhsingian of jordan they range from peri glacial post glacial to warm temperate climatic systems throughout the permian macro and micro charcoal occurrences are compared to inertinite incidences to support the pyrogenic origin for these coal macerals and to provide an up to date overview on the known evidences of permian wildfires on gondwana in space and time

alteration hfse mineralisation and hydrocarbon formation in peralkaline igneous systems insights from the strange lake pluton canada abstract two characteristics of peralkaline igneous rocks that are poorly understood are the extreme enrichment in hfse notably zr nb y and ree and the occurrence of fluid inclusions dominated by methane and higher hydrocarbons although much of the hfse enrichment can be explained by magmatic processes the common intense alteration of the parts of the peralkaline intrusions most enriched in these elements suggests that hydrothermal processes also play an important role in hfse enrichment likewise although the origin of the higher order hydrocarbons that occur as inclusions in these rocks is still debated there is strong evidence that at least in some cases their formation involved hydrothermal processes the issues of hfse enrichment and hydrocarbon formation in peralkaline intrusions are examined using data from the strange lake pluton a small middle proterozoic intrusion of peralkaline granite in northeast canada this pluton contains some of the highest concentrations of zr ree and y ever reported in an igneous body and is characterised by abundant hydrocarbon dominated fluid inclusions in rocks that have been hydrothermally altered including those that form a potential hfse ore zone we show that hfse at strange lake were partly concentrated to near exploitable levels as a result of their transport in a high salinity magmatic aqueous liquid and that this fluid coexisted immiscibly with a carbonic phase which reacted with hydrogen and iron oxides generated during the associated hydrothermal alteration to produce hydrocarbons via a fischer tropsch synthesis as a result hydrocarbons and hfse mineralization are intimately associated we then go on to show that hydrothermal alteration hfse mineralisation and hydrocarbons are also spatially associated in other peralkaline complexes and present a model to explain this association which we believe may be applicable to any peralkaline intrusion where hfse enrichment was accompanied by calcium metasomatism hematisation and hydrothermal fluorite we also suggest that even where these criteria are not satisfied hydrothermally enriched hfse and hydrocarbons will be intimately associated simply because they are products of the same initial magmatic fluid finally we speculate that the association of hfse and hydrocarbons may in some cases actually be genetic if as seems possible unmixing or effervescence of a reduced carbonic fluid from the original magmatic fluid caused changes in temperature ph f o 2 or the activity of volatile ligands sufficient to induce the deposition of hfse minerals

ocean stratification and low melt rates at the ross ice shelf grounding zone ocean driven melting of ice shelves is a primary mechanism for ice loss from antarctica however due to the difficulty in accessing the sub ice shelf ocean cavity the relationship between ice shelf melting and ocean conditions is poorly understood particularly near the grounding zone where the ice transitions from grounded to floating we present the first borehole oceanographic observations from the grounding zone of the ross ice shelf antarctica s largest ice shelf by area contrary to predictions that tidal currents near grounding zones mix the water column we found that ross ice shelf waters were vertically stratified current velocities at middepth in the ocean cavity did not change significantly over measurement periods at two different parts of the tidal cycle the observed stratification resulted in low melt rates near this portion of the grounding zone inferred from phase sensitive radar observations these melt rates were generally 10 cm year which is lower than average for the ross ice shelf 20 cm year melt rates may be higher at portions of the grounding zone that experience higher subglacial discharge or stronger tidal mixing stratification in the cavity at the borehole site was prone to diffusive convection as a result of ice shelf melting since diffusive convection influences vertical heat and salt fluxes differently than shear driven turbulence this process may affect ice shelf melting and merits further consideration in ocean models of sub ice shelf circulation

changes in geochemistry and mineralogy of thermally altered coal upper hunter valley australia abstract igneous intrusions thermally and geochemically alter coal commonly causing economic and safety problems for many coal mines the effects of two dykes on the inorganic content of the late permian bituminous upper wynn seam were determined from analyses of 44 samples that were collected along transects approaching the intrusions petrographic and xrd data were used to determine sample mineralogy and inaa and xrf spectrometry were utilised to determine the contents of 57 elements the mineralogy of the unaltered coal altered coal and dyke is dominated by carbonates particularly dawsonite which formed by epigenetic precipitation at a late stage after thermal alteration ankerite and siderite are the products of thermal alteration and are restricted to the altered coal and dykes principal component analysis correlations and compositional trends approaching the intrusions were used to subdivide the elements into groups and to identify the mineralogical affinity of each group geochemical data are more sensitive than mineralogy for defining the size of the alteration halo and three zones ranging from unaltered coal through altered coal to highly coked coal are recognised as each intrusion is approached the alteration halos differ in extent 9 5 and 56 m wide but their size is not a multiple of the size of the causative intrusion at the contact between coal and intrusion concentrations of elements with affinities to some aluminosilicates oxides carbonates sulphides and organic components are enriched while other aluminosilicate related elements are depleted in the altered coal towards the edge of the alteration halo some aluminosilicate elements are enriched and oxide elements are depleted

a numerical model of the weddell sea large scale circulation and water mass distribution a circumpolar model for regional studies of the wind driven and thermohaline circulation of the southern ocean including the major sub ice shelf areas is described a first series of numerical experiments focusing on the weddell sea reveals a pronounced and persistent double cell structure of the weddell gyre with a maximum transport of 60 sv in agreement with observations experiments with artificial passive tracers point to the shallow shelf areas off the filchner ronne ice shelf as main locations for bottom water production the trajectories of lagrangian floats are used to determine the pathways and timescales of water mass spreading in the model in addition the effect of sub ice shelf forcing on the water mass characteristics is evaluated it is shown that water modified in the sub ice cavities contributes significantly to the deep and bottom water formation along the continental slope and affects the water mass characteristics throughout the weddell sea by increasing the stability of the near surface stratification and preventing deep convection

thermohaline circulation and interaction between ice shelf cavities and the adjacent open ocean the circulation system in an ice shelf cavity is driven by buoyancy fluxes due to melting and freezing of ice and horizontal pressure gradients at the interface between the cavity and the open ocean hence the inflow and outflow pattern and the hydrography in the open ocean influence the general hydrographic condition in the cavity which at least provides the potential for melting and freezing processes applying a three dimensional ocean general circulation model to an idealized ice shelf cavity geometry coupled with an open ocean at a topographic ice shelf barrier we found an important parameter controlling the interaction between these two systems idealized studies for different ice shelf and sea bottom topographies and forcing mechanisms for the open ocean show that the ice shelf edge represents a natural barrier for barotropic interaction because of the sudden decrease in water column thickness since the water column thickness and the coriolis force determine the characteristics for geostrophic flow separated circulation systems arise for the open ocean and the ice shelf cavity only in areas where constant water column thickness and from the oceanographic point of view constant f h contours can be observed across the barrier an increased barotropic current can surmount the ice edge and ventilate the water mass beneath the ice shelf this is only the case at lateral sloping sidewalls or at deep depressions which can be found for example in the southern weddell sea in all other cases the circulation in the ice shelf cavity is closed and almost unaffected by the hydrography outside the barrier

deltaic depositional systems coal distribution and quality and petroleum potential permian gunnedah basin n s w australia abstract upper permian sediments of the lower black jack formation were deposited as a major delta system in the gunnedah basin a foredeep of the rising new england fold belt two principal depositional units are recognized in the lower black jack formation the lower delta plain facies and the shallow marine facies a third but minor depositional unit the western bed load fluvial facies is correlative with the upper part of the shallow marine facies geometry of the framework sandstones indicates that the lower delta plain facies was deposited in a combination of fluvial dominated and wave modified delta systems and that the shallow marine facies was deposited in a tide dominated system sediment source was predominantly from the northeast except for the western bed load fluvial facies which was derived from the lachlan fold belt region to the west the lower delta plain facies was deposited during a major episode of delta construction principal components recognized in drillcore are distributary channel crevasse splay and splay subdelta interdistributary bay lagoon and marsh deposits transgression of the delta possibly initiated by a major eustatic sea level rise led to deposition of the shallow marine facies this facies consists chiefly of beach barrier beach tidal sand ridge and tidal channel fill deposits subsequent lowering of sea level was accompanied by deposition of the western bed load fluvial facies this facies consists predominantly of upward fining fluvial channels which display considerable marine reworking toward the basin centre a vast coal swamp was established rapidly after the marine conditions regressed and is represented by the hoskissons coal member coals of commercial interest are developed within the lower delta plain facies and above the shallow marine facies the lobate geometry of the coal deposits in the lower delta plain facies mirrors the geometry of the framework sandstones and indicates a deltaic origin for coal formation two mechanisms for coal formation are recognized in the lower delta plain facies thick laterally extensive coals such as the melvilles coal member are thought to have originated as blanket peats following delta abandonment thin discontinuous coals formed in interdistributary depressions during active deltaic progradation coal above the shallow marine facies is contained in one major seam the hoskissons coal member this seam probably formed mostly as a back barrier or lagoonal peat depositional setting strongly influenced coal quality isoash trends for the melvilles coal member suggest a marginal marine influence during peat accumulation ash content of the hoskissons coal member has a similar distribution to the percentage of sandstone in the underlying shallow marine facies potential exists for petroleum accumulation in the lower black jack formation suitable reservoir rocks are present in the lower delta plain and shallow marine facies underlying prodelta facies are potential source rocks

ocean circulation and ice ocean interaction beneath the amery ice shelf antarctica simulations of the ocean dynamics in the cavity under the amery ice shelf antarctica were carried out using a three dimensional numerical ocean model two different boundary conditions were used to describe the open ocean barotropic exchange at the ice front the simulations show that the circulation in the ocean cavity is predominantly barotropic and is generally steered by the cavity topography the circulation is driven by the density gradient in the cavity which is strongly influenced by the heat and salt fluxes from melting and freezing processes at the ice ocean interface and by the horizontal exchange of heat and salt across the open ocean boundary at the ice front the interaction at the ice ocean interface allows the basal component of the mass loss of the amery ice shelf to be estimated in the two simulations the computed losses were 5 8 gt yr 1 and 18 0 gt yr 1 values consistent with observations the bulk of the melting occurred near the southern grounding line of the ice shelf although substantial melting also occurred in areas where heat transport by horizontal circulation was large accretion was restricted to areas where water from upstream melting became supercooled as it ascended the ice shelf base

neoproterozoic nb ta w sn bearing tourmaline leucogranite in the western part of jiangnan orogen implications for episodic mineralization in south china abstract there are four episodes neoproterozoic early paleozoic early and late mesozoic of sn w nb ta mineralization in south china accounting for more than 50 w and 20 sn reserves of the world and hosting considerable nb and ta resources the genesis for such large scale mineralization that may have seen multiple phases of recycling of ore elements is not well unterstood the study of the earliest mineralized granites in south china however may be helpful to better understand the mechanism of mineralization we present detailed mineralogical geochemical and isotopic data from two typical neoproterozoic mineralized intrusions i e the fanjingshan and yuanbaoshan tourmaline leucogranites there is a characteritstic mineral succession of diverse magmatic columbite group minerals cgms nb ta bearing cassiterite and hydrothermal wolframite wolframoixiolite nb ta poor cassiterite sn w nb ta oxides hydrothermal cassiterite and w bearing oxides wolframite wolframoixiolite in the yuanbaoshan intrusion were deposited separately by two types i e sn rich and nb w rich fluids in situ u pb dating of zircon columbite and wolframoixiolite yields ages of 830 5 832 5 and 821 5 ma respectively whole rock end t values of 2 5 to 6 4 correspond to crustal nd model ages of 1 6 1 9 ga paleoproterozoic model ages 1 6 2 2 ga for most episodes of w nb ta mineralization in south china indicate that i paleoproterozoic or older sediments may have been involved in the formation of w nb ta bearing granites and ii contributions of juvenile material was not important for these w nb ta mineralization neoproterozoic peraluminous granites along the jiangnan orogen formed in post collision environments but only those in the western part show sn w nb ta mineralization the mineralized neoproterozoic granites of the western part have experienced more extensive fractional crystallization lower nb ta zr hf ratios and more depleted in fe mg ca sr ba eu ti and are richer in volatiles h2o b than the barren peraluminous intrusions of the eastern part as similarly evolved mesozoic metaluminous granites of the nanling area have considerably more important tin mineralization than the mineralized neoproterozoic granites fractionation is not the only factor controlling mineralization instead other factors such as protolith and conditions of partial melting may account for the more important mesozoic tin mineralization

barotropic tides of the southern indian ocean and the amery ice shelf cavity the 8 main tidal constituents were computed using a finite element hydrodynamic ocean tide model over the south indian ocean region the discretization of the domain is of the order of 100 km over the deep ocean and a few hundred meters near the coast such refinement in the grid resolution enables wave propagation and damping on the continental shelves to be solved correctly the model used the gebco 1 minute global bathymetric grid which was improved with updated topographic data the model solutions show good agreement with in situ observations and topex poseidon altimeter measurements and are significantly better than previously published solutions we obtain a combined standard deviation of 1 4 cm for differences of our new regional model against independent observations compared to about 2 5 cm for the other tide models the greatest improvements are found around the kerguelen islands around antarctica and beneath the amery ice shelf and can be explained by the high grid resolution used and the particular attention given to the accuracy of the bathymetry in those regions

current measurements near ronne ice shelf implications for circulation and melting we present the first year long current meter records ever obtained near the floating filchner ronne ice shelf in the weddell sea the currents are steered along the ice front but in the lower layer where the bottom topography is descending toward the west the current has a component toward the ice front of about 3 cm s 1 during winter the temperature stayed near the surface freezing point while the salinity increased indicating that ice was formed and brine released the seasonal variation in salinity was 0 15 0 05 psu corresponding to the formation of 1 2 m of ice on a shelf depth of 400 m the transport of high salinity shelf water hssw into the ice shelf cavity was found to be of the order 0 5 106 m3 s 1 the production of this water due to oscillating tides and off shelf winds was found to be of the same order of magnitude in contact with glacial ice at great depths and because of the depression of the freezing point the hssw is transformed to ice shelf water isw by cooling and melting processes the melting rate was estimated to 1 1011 ton yr 1 this corresponds to the melting of 0 2 m ice per year if the melting is evenly distributed over the filchner ronne ice shelf if the melting is concentrated along a path from the berkner shelf around the berkner island to the filchner depression then melting rates up to 7 m yr 1 must be expected a comparison of hssw characteristics in the ronne depression our winter observations on the berkner shelf and the isw flowing out of the filchner depression indicates that very little water passes through the cavity from the ronne to the filchner depression it appears that most of the isw originating from processes on the berkner shelf escapes the cavity in the filchner depression this leaves the berkner shelf as the important source of isw and subsequently of the weddell sea bottom water formed from isw

the combined effects of water and fluorine on the viscosity of silicic magmas abstract the newtonian viscosity of water plus fluorine bearing silicate melt of haplogranitic composition hpg8 has been determined viscosities of hpg8 melt with addition of 3 11 and 4 25 wt of f and up to 3 wt h2o have been obtained using a micropenetration technique in the interval 109 74 to 1011 84 pa s and temperatures varying from 370 to 700 c at ambient pressure determination of the temperature dependence of viscosity from this and previous studies permits the parameterization of the viscosity of melts containing water and fluorine having similar composition within a 0 3 log units standard error the viscosity of water bearing f rich haplogranitic samples is represented by a modified vogel fulcher tammann vft equation which provides a non arrhenian description of the temperature dependence of the viscosity the results of this study indicate that taken individually or together both h2o and f have a strong and similar effect on the viscosity of sio2 rich compositions this similarity between f2o 1 and h2o greatly simplifies the task of predicting viscosity for volatile rich highly silicic magmas the low viscosities of hydrous fluorine bearing granitic melts favour efficient crystallization fractionaction paths for these liquids controlling degassing paths and consequently the eruptive behaviour numerical simulations of eruptive events normally do not take into account the contribution of fluorine this may introduce a significant error in the description of the fluid dynamic properties of magma and therefore in the accurate prediction of eruptive scenarios as well as in hazard assessment studies fluorine unlike water remains dissolved in the melt at high concentrations and low confining pressures the incorporation of fluorine data and the modelling of fluorine bearing viscosity data are therefore of fundamental importance for simulations of magma dynamics and prediction of eruptive scenarios

influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the ross sea antarctica 1 satellite imagery shows that there was substantial variability in the sea ice extent in the ross sea during 2001 2003 much of this variability is thought to be due to several large icebergs that moved through the area during that period the effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model it would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs here sea ice concentration is specified from satellite observations to examine the effects of changes in sea ice due to iceberg c 19 simulations were performed using either climatological ice concentrations or the observed ice for that period the heat balance around the ross sea polynya rsp shows that the dominant term in the surface heat budget is the net exchange with the atmosphere but advection of oceanic warm water is also important the area average annual basal melt rate beneath the ross ice shelf is reduced by 12 in the observed sea ice simulation the observed sea ice simulation also creates more high salinity shelf water another simulation was performed with observed sea ice and a fixed iceberg representing b 15a there is reduced advection of warm surface water during summer from the rsp into mcmurdo sound due to b 15a but a much stronger reduction is due to the late opening of the rsp in early 2003 because of c 19

the peralkaline granite related khaldzan buregtey rare metal zr nb ree deposit western mongolia the khaldzan buregtey rare metal nb zr ree etc deposit in peralkaline granitoids is located in western mongolia 45 km northeast of the town of kobdo the deposit which was discovered by the authors is composed of dome shaped stocks of rare metal peralkaline granite covering 0 85 km and represents the late plutonic phases of the devonian 380 390 ma multiphase khaldzan buregtey peralkaline granite massif the formation of the massif took place during tectonic extension as shown by the development of a major dike complex synchronous with granite emplacement the massif consists of peralkaline granitoids as well as gabbro and basalt and is characterized by a radial circular shape eight intrusive phases are recognized and consist of 1 nordmarkite 2 peralkaline granite 3 dikes of fine grained peralkaline granite 4 dikes of pantellerite 5 rare metal peralkaline granite 6 gabbroids 7 miarolitic peralkaline rare metal granite and 8 syenite and leucite basalt field relationships of the rare metal peralkaline granite bodies indicate an intrusive igneous origin the rare metal peralkaline granites consist of k na feldspar quartz albite arfvedsonite aegirine fluorite and diverse rare metal minerals ranging up to 25 vol percent ore minerals are represented by elpidite gittinsite and zircon pyrochlore nb rare metal flurocarbonate and monazite ree and polylithionite li the zirconium minerals often occur in the endocontact and apical parts of rare metal granite bodies and are reflected in the negative correlation of zr and nb contents in the seventh phase granites the rare metal peralkaline granites of the deposit differ from those of other massifs by their high and variable ca and f contents the granites are rich in zr up to 5 3 wt nb up to 0 8 wt ree up to 0 4 wt y up to 0 3 wt be sn rb and sometimes li pb zn hf and ta they are depleted in sr and ba and have an almost flat ree distribution pattern with a small negative eu anomaly the initial 87 sr 86 sr ratio of fluorite from rare metal peralkaline granite is 0 70433 or 7 the end value for these rocks at 386 ma ranges from 4 3 to 5 7

basal melting and freezing under the amery ice shelf east antarctica the basal melting and freezing rates under the amery ice shelf east antarctica are evaluated and their spatial distributions mapped ice velocity surface elevation and accumulation rate datasets are employed in the analysis along with a column averaged ice density model our analysis shows that the total area of basal melting is 34 700 km 2 with a total annual melt of 62 5 9 3 gt and an average melting rate of 1 8 0 3 m a 1 basal freezing mainly occurs in the northwestern part of the ice shelf over a total area of 26 100 km 2 and with a maximum freezing rate of 2 4 0 4 m a 1 the total marine ice that accretes to the ice shelf base is estimated to be 16 2 2 4 gt a 1 using a redefined grounding line and geometry of the amery ice shelf we estimate the net melt over the ice shelf base is about 46 4 6 9 gt a 1 which is higher than previous modeling and oceanographic estimates net basal melting accounts for about half of the total ice shelf mass loss with the rest being from iceberg discharge our basal melting and freezing distribution map provides a scientific basis for quantitative analysis of ice ocean interaction at the ice shelf ocean interface

occurrence and distribution of organic sulphur in macerals of australian coals using electron microprobe techniques the organic sulphur content of the individual macerals in permian high volatile bituminous coals from the gunnedah basin of new south wales has been studied using an electron microprobe technique liptinite chiefly sporinite in the coal has the highest organic sulphur content and inertinite mainly semifusinite the lowest the vitrinite macerals have intermediate sulphur contents these variations are responsible for the relatively low overall organic sulphur in inertinite rich coals typical of australian permian deposits neither marine influence on coal formation nor increases in coal rank appear to be associated with significant changes in organic sulphur of the individual macerals concerned

a model for entrainment of sediment into sea ice by aggregation between frazil ice crystals and sediment grains avertical numerical model has been developed that simulates tank experiments of sediment entrainment into sea ice physical processes considered were turbulent vertical diffusion of heat salt sediment frazil ice and their aggregates differential growth of frazil ice crystals secondary nucleation of crystals and aggregation between sediment and ice the model approximated the real size distribution of frazil ice and sediment using five classes of each frazil crystals 25 m to 1 5 cm were modelled as discs with a constant thickness of their diameter each class had a constant rise velocity based on the density of ice and drag forces sediment grains 1 600 m were modelled as constant density spheres with corresponding sinking velocities the vertical diffusion was set constant for experiments based on calculated turbulent rms velocities and dissipation rates from current data the balance between the rise sinking velocities and the constant vertical diffusion is an important feature of the model the efficiency of the modeled entrainment process was estimated through a an aggregation factor values for a are in the range but average values are often close to 0 01 entrainment increases with increasing sediment concentration and turbulence of the water and heat flux to the air

chemical composition of macerals in bituminous coals of the gunnedah basin australia using electron microprobe analysis techniques abstract the chemical composition of the organic matter in the principal macerals of high volatile bituminous coals from the gunnedah basin new south wales rvmax of telocollinite between 0 6 and 1 1 has been evaluated from polished section specimens using an electron microprobe technique highest proportions of carbon occur in the inertinite macerals especially fusinite and secretinite formerly resino sclerotinite as well as in sporinite lowest proportions of carbon occur in the different macerals of the vitrinite group oxygen shows the reverse trend being most abundant in vitrinite and least abundant in the inertinite components whereas sulphur is lowest in the inertinites and highest in the liptinite mainly sporinite present evaluations of maceral composition using the carbon content of telocollinite as a rank indicator show that carbon is more abundant in both sporinite and semifusinite relative to vitrinite in low rank high volatile bituminous coals the difference decreases with increasing rank and the proportion of carbon in telocollinite becomes essentially the same as that in sporinite and semifusinite at carbon contents of about 89 and 91 respectively the carbon content of fusinite and secretinite on the other hand does not seem to vary appreciably with rank advance no significant difference in composition occurs in the rank range studied between the three vitrinite varieties present desmocollinite telocollinite and a more highly reflecting telocollinite resembling pseudovitrinite no evidence was found to indicate a higher hydrogen content relative to telocollinite for the vitrinite matrix of desmocollinite

modeling sea ice production and dense shelf water formation in coastal polynyas around east antarctica 1 using an ice ocean coupled model with fine horizontal resolution around east antarctica sea ice production and dense shelf water dsw formation in coastal polynyas are investigated the model reproduces well the locations of coastal polynyas and the high sea ice production there dsw is formed over the continental shelves under a number of coastal polynyas a threshold density beyond which net production of dsw takes place is largely different among coastal polynyas the densest and most vigorous dsw formation occurs in the cape darnley and mertz ninnis glacier polynyas followed by somewhat less but still significant dsw formation in the prydz barrier and vincennes polynyas assuming mixing of the dsw outflowing across the shelf break with typical modified circumpolar deep water over the continental slope the maximum possible formation rate of antarctic bottom water aabw is estimated to be 7 58 sv around east antarctica between 60 e and 150 e with the cape darnley and mertz ninnis glacier polynyas exhibiting the most active formation rates of 2 13 and 1 97 sv respectively from a series of numerical experiments it is found that the treatment of coastline and grounded icebergs has a large impact on both sea ice production and formation of dsw and aabw

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

zr and ree mineralization in sodic lujavrite from the saima alkaline complex northeastern china a mineralogical study and comparison with potassic rocks abstract the triassic saima alkaline complex on the liaodong peninsula northeastern china consists mainly of potassic phonolite nepheline syenite and sodic lujavrite the lujavrite shows significant zr ree mineralization which is present in the form of early magmatic zr ree enriched clinopyroxene 30 40 titanite 5 and loparite ce and late magmatic to hydrothermal wadeite widespread eudialyte group minerals 5 10 and catapleiite ultimately the fractionation of the alkaline magma leads to the crystallization of mosandrite and hezuolinite textural relations and compositional variation among the characteristic zr ree bearing minerals record that both zr and rees were strongly incompatible in the sodic melt but that zr mineralization preceded ree mineralization the main zr ree mineralization in the saima lujavrite resulted from the high peralkalinity na k ratio and hfse content low oxygen fugacity and the intensive activity of water and volatiles of its evolving magma the discontinuous and abrupt changes in melt composition and mineral assemblage from the potassic nepheline syenite of the complex to the sodic lujavrite suggest that their magma was derived from different episodes of magmatic activity with different physico chemical characteristics rather than from the continuous evolution of a single magmatic event

on the relationship between alteration facies and metal endowment of iron oxide alkali altered systems southern great bear magmatic zone canada the great bear magmatic zone in northern canada hosts large iron oxide and alkali altered systems that developed within a 10 m y period during the paleoproterozoic in the eastern treasure lake and duke sectors and at the nico deposit early albitization associated with magmatism was followed by tungsten mineralization that was spatially associated with extensive skarn and fe skarn alteration subsequent fluid rock reactions led to substantial iron enrichment that culminated in iron oxide apatite mineralization at the transition from compressional transpressional to extensional transtensional stress regimes changes in magma composition increased the metal budget of exsolved magmatic hydrothermal fluids and played a key role in the formation of au co bi mineralization at the nico deposit and its satellite showings in the duke zone this process happened as the systems regionally transitioned to magnetite bearing potassic iron alteration the continued evolution of magmatism and fluid chemistry then contributed to the formation of iron oxide copper gold iocg and variant mineralized zones in the sue dianne and nico deposits and other showings and albite hosted uranium mineralized zones elsewhere the great bear magmatic zone illustrates that the evolution of magmatically derived fluids during a transition between different stress regimes can play a significant role in metal endowment and the ability of metasomatic systems to form skarn iron oxide apatite iocg and albitite hosted uranium mineralization

modeling ice shelf cavities in a z coordinate ocean general circulation model 1 processes at the ice shelf ocean interface and in particular in ice shelf cavities around antarctica have an observable effect on the solutions of basin scale to global coupled ice ocean models despite this these processes are not routinely represented in global ocean and climate models it is shown that a new ice shelf cavity model for z coordinate models can reproduce results from an intercomparison project of earlier approaches with vertical or isopycnic coordinates as a proof of concept ice shelves are incorporated in a 100 year global integration of a z coordinate model in this simulation glacial meltwater can be traced as far as north as 15 s the observed effects of processes in the ice shelf cavities agree with previous results from a coordinate model notably the increase in sea ice thickness however melt rates are overestimated probably because the parameterization of basal melting does not suit the low resolution of this configuration

pathways of meltwater export from petermann glacier greenland abstractintrusions of atlantic water cause basal melting of greenland s marine terminating glaciers and ice shelves such as that of petermann glacier in northwest greenland the fate of the resulting glacial meltwater is largely unknown it is investigated here using hydrographic observations collected during a research cruise in petermann fjord and adjacent nares strait onboard icebreaker i b oden in august 2015 a three end member mixing method provides the concentration of petermann ice shelf meltwater meltwater from petermann is found in all of the casts in adjacent nares strait with the highest concentration along the greenland coast in the direction of kelvin wave phase propagation the meltwater from petermann mostly flows out on the northeast side of the fjord as a baroclinic boundary current with the depth of maximum meltwater concentrations approximately 150 m and shoaling along its pathway at the outer sill which separates the fjord from the ambient ocean approximately 0 3 msv 1 sv

meteoric and marine ice crystal orientation fabrics from the amery ice shelf east antarctica the northwestern sector of the amery ice shelf east antarctica has a layered structure due to the presence of both meteoric ice and a marine ice layer resulting from sub shelf freezing processes crystal orientation fabric and grain size data are presented for ice cores obtained from two boreholes 70 km apart on approximately the same flowline multiple maxima crystal orientation fabrics and large mean grain sizes in the meteoric ice are indicative of stress relaxation and subsequent grain growth in ice that has flowed into the amery ice shelf strongly anisotropic single maximum crystal orientation fabrics and rectangular textures near the base of the 200 m thick marine ice layer suggest accretion occurs by the accumulation of frazil ice platelets crystal orientation fabrics in older marine ice exhibit vertical large circle girdle patterns influenced by the complex stress configurations that exist towards the margins of the ice shelf post accumulation grain growth and fabric development in the marine ice layer are restricted by a high concentration of brine and insoluble particulate inclusions differences in the meteoric and marine ice crystallography are indicative of the contrasting rheological properties of these layers which must be considered in relation to large scale ice shelf dynamics

mapping of sea ice production for antarctic coastal polynyas 1 active sea ice production in antarctic coastal polynyas causes dense water formation finally leading to antarctic bottom water aabw formation this study gives the first mapping of sea ice production in the antarctic ocean based on heat flux calculation with ice thickness data derived from satellite data the highest ice production occurs in the ross ice shelf polynya region the ice production there decreased by 30 from the 1990s to the 2000s which can be one candidate for causing the recent freshening of aabw the cape darnley polynya in east antarctica is found to be the second highest production area suggesting a possible aabw formation area according to our estimation around 10 of southern ocean sea ice is produced in the major antarctic coastal polynyas the mapping provides surface heat and salt flux conditions in the ice covered region which have not been well understood

how precisely can the temperature of a fluid event be constrained using fluid inclusions u s national science foundation ear 1624589 chemical sciences geosciences and biosciences division office of basic energy sciences office of science u s department of energy de fg02 03er15430 bureau of economic geology jackson school of geosciences university of texas austin

supercooled southern ocean waters in cold polar waters temperatures sometimes drop below the freezing point a process referred to as supercooling however observational challenges in polar regions limit our understanding of the spatial and temporal extent of this phenomenon we here provide observational evidence that supercooled waters are much more widespread in the seasonally ice covered southern ocean than previously reported in 5 8 of all analyzed hydrographic profiles south of 55 s we find temperatures below the surface freezing point potential supercooling and half of these have temperatures below the local freezing point in situ supercooling their occurrence doubles when neglecting measurement uncertainties we attribute deep coastal ocean supercooling to melting of antarctic ice shelves and surface induced supercooling in the seasonal sea ice region to winter time sea ice formation the latter supercooling type can extend down to the permanent pycnocline due to convective sinking plumes an important mechanism for vertical tracer transport and water mass structure in the polar ocean

acoustic detection of ice crystals in antarctic waters during the voyage of the rsv aurora australis to the region of prydz bay antarctica in january march 1991 ice crystals were encountered at depths from the surface to 125 m in the western area of the bay on two occasions crystals were retrieved by netting and echo sounder records have been used to infer additional regions of occurrence acoustic target strength estimates made on the ice crystal assemblies encountered show significant spatial variation which may relate to crystal size and or aggregation data from a suite of conductivity temperature depth casts have been used to map regions of the study area where in situ water temperatures fell below the computed freezing point such regions correlate well with those selected on the basis of echogram type and imply that ice crystals occurred at depth over large areas of the bay during the cruise period the ice crystal distribution described is consistent with that expected from a plume of supercooled water emerging from under the amery ice shelf and forming part of the general circulation of the bay the magnitude of the supercooled water plume is greater than those reported previously in the prydz bay region if misinterpreted as biota on echo sounder records ice crystals could significantly bias biomass estimates based on echo integration in this and potentially other areas

a field and laboratory study of wave damping by grease ice in a field and laboratory study we discuss the formation growth and wave absorption properties of grease ice our field observations show that grease ice formation occurs under cold windy conditions in both leads and polynyas in leads grease ice forms in the open water then is herded to the down wind edge of the lead in polynyas a langmuir circulation herds the grease ice into long plumes parallel to the wind in the laboratory we grow grease ice in a wave tank and measure its wave absorption properties for single frequency two dimensional waves on a large scale we find that the thickness of the grease ice which increases away from the paddle is determined by a balance between the wave momentum flux and the free surface tilt on a small scale our photographs show that the crystals which make up the grease ice consist of discs measuring about 1 mm in diameter and 1 10 m thick which at low rates of shear sinter together into larger clumps yielding a viscosity increase to measure this non linear viscosity we study the decay of wave amplitude between two critical distances measured inwards from the leading edge the first occurs when the depth of grease ice exceeds k 1 where k is the wave number the second further distance is a line of transition from liquid to solid behavior which we call the dead zone between these two distances the wave amplitude decays with a linear slope which increases as a 0 k 2 where a0 is the wave amplitude in open water concurrent measurements of ice concentration show that it increases from values of 18 22 at the leading edge to a local maximum of 32 44 at the dead zone while the values at the dead zone increase non linearly with a0k finally comparison of the observed to that calculated from a yield stress viscosity model shows if the yield stress coefficient is proportional to the incident wave momentum flux the model predicts the observed

chemical evolution of miocene wood example from the belchatow brown coal deposit central poland abstract miocene conifer wood samples from the belchatow brown coal deposit in poland were studied in order to discuss a range of chemical variations that occur as a result of biochemical coalification petrographic analysis ultimate analysis electron microprobe technique and ftir spectroscopy were used in this study our data show several progressive trends in functional groups distribution that take place during the wood transformation from group 1 to group 4 such as an overall increase in aromaticity an increase in lignin cellulose ratio and an increase in oxygen functionalities other observations include an increase in aliphatic stretching and bending functionalities from groups 1 to 3 followed by a decrease in the wood of group 4 appearance of aliphatic out of plane bands in group 3 and increase in group 4 an increase in ch2 ch3 in group 4 compared to the other groups and decrease in o h groups in group 4 compared to other groups these observations together with other chemical and petrological observations indicate that the progressive elimination of cellulose and modification of lignin are dominant processes of the wood transformation

interannual variations in meltwater input to the southern ocean from antarctic ice shelves ocean driven basal melting of antarctica s floating ice shelves accounts for about half of their mass loss in steady state where gains in ice shelf mass are balanced by losses ice shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level and the changing meltwater fluxes influence climate processes in the southern ocean existing continent wide melt rate datasets have no temporal variability introducing uncertainties in sea level and climate projections here we combine surface height data from satellite radar altimeters with satellite derived ice velocities and a new model of firn layer evolution to generate a high resolution map of time averaged 2010 2018 basal melt rates and time series 1994 2018 of meltwater fluxes for most ice shelves total basal meltwater flux in 1994 1090 150 gt yr was not significantly different from the steady state value 1100 60 gt yr but increased to 1570 140 gt yr in 2009 followed by a decline to 1160 150 gt yr in 2018 for the four largest cold water ice shelves we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability providing insights into climate forcing of basal melting and the impact of this melting on the southern ocean

the circulation and water masses of the antarctic shelf and continental slope between 30 and 80 e abstract the circulation and water masses from the antarctic continental shelf to 62 s between 30 and 80 e are described using hydrographic data collected on seven hydrographic sections during the baseline research on oceanography krill and the environment west broke west experiment the eastern limb of the weddell gyre dominates circulation between 30 and 40 e and is significantly cooler and fresher than the region to the east the antarctic circumpolar current acc extends from the north into the survey region east of 40 e reaching as far south as 65 5 s at 60 e this results in increasing observed maximum temperature and salinities progressively towards the east peaking at 80 e due to the intrusion of the southern acc front saccf to 63 s this southward extension is steered by the southern end of kerguelen plateau causing a horizontal shear of over 0 15 m s 1 between the eastward acc and westward flowing antarctic slope current asc the asc is observed at all six meridional sections immediately north of the shelf break it is strongly barotropic and transports a total of 15 8 7 4 sv westwards while the bottom referenced baroclinic component only contributes 1 3 0 3 sv at each section this current intensifies to a narrow westward jet with absolute velocities up to 0 3 m s 1 over the steepest shelf slope gradients at 70 e a v shape is observed in the asf this and the nearby presence of denser shelf water and ice shelf water is characteristic of antarctic bottom water aabw formation but no new aabw is found on this section instead significantly warmer saltier and less oxygenated aabw to the east and newly formed aabw high on the continental slope immediately to the west suggest a formation region just west of 70 e this newly formed aabw progressively becomes warmer and saltier west of 60 e and is observed extending offshore and moving westward below eastward flowing water masses acc frontal positions are found to be 1 2 farther north in the survey region than suggested by historical climatology

measurements of ice shelf water beneath the front of the ross ice shelf using gliders measurements made by an underwater glider deployed near the ross ice shelf were used to identify the presence of ice shelf water isw which is defined as seawater with its potential temperature lower than its surface freezing point temperature properties logged by the glider included in situ temperature electrical conductivity pressure gps location at surfacings and time for most of the first 30 recorded dives of its deployment evidence suggests the glider was prevented from surfacing due to being under the ice shelf for dives under the ice shelf farthest from the ice shelf front isw layers of varying thicknesses and depth locations were observed between 2 m thick centred at 231 m depth to 93 m thick centred at 360 m for dives under the ice shelf close to the ice shelf front either no isw was observed or isw layers were centred at shallower depths 116 127 m thicker isw layers e g up to 250 m thickness centred at 421 m were observed for some glider dives in open water in front of the ross ice shelf no in situ supercooling water colder than the pressure dependent freezing point temperature was observed

recent advances in coalification studies and their application to geology abstract recent advances in coalification studies since 1970 are reported concerning microscopic methods causes of coalification the coalification process as such and application to geology the degree of coalification rank is mostly determined on the basis of vitrinite reflectance measured on finely dispersed material in rocks for rocks bare of vitrinite other microscopic methods are used such as fluorescence properties of liptinites and graptolite reflectance under incident light or coloration of microfossils like palynomorphs and conodonts in transmitted light the validity of the various methods is discussed maximum rock temperature and its duration are the main causes of chemical coalification reactions heating rates during subsidence influence the attainment of rank equilibrium contact metamorphic coals and natural cokes formed from bituminous coals are characterized by a relatively high reflectance and anisotropy strong frictional heat may cause local increase of rank adjacent to thrust planes graphitization is thermodynamically not possible in nature without pressure and shearing confining pressure retards the chemical coalification reactions tectonic stress especially shearing promotes the increase of maximum reflectance and of anisotropy it commonly leads to bi axial optical properties instead of the more typical uni axial negative geometry of vitrinite in undisturbed coal seams bi axial optical properties are common for vitrinite inclusions in clastic rocks on the basis of combined fluorescence microscopical and geochemical studies bituminization has been recognized as the characteristic part of coalification in the range between sub bituminous and bituminous coal it is characterized by the generation of petroleum like substances which enable the coal to soften and to agglomerate during carbonization hydrogenation properties are favoured by the bituminization process the different liptinite macerals behave differently during coalification and pass coalification jumps at different rank stages a considerable part of total inertinites is formed during early coalification brown coal to sub bituminous coal stage as rank inertinite this new knowledge appears to become important in relation to hydrocarbon exploration diagenetic methane some examples for the application of coalification studies to geology refer to vitrinite reflectance as an indicator of rock diagenesis and metamorphism palaeogeographical and structural history palaeogeothermics and hydrocarbon exploration large scale areal coalification studies in foredeeps and backdeeps of ancient and recent orogens suggest estimations of crustal thicknesses and relations to plate tectonics