reservoir overprinting of crude oils abstract biomarker concentrations are generally low in high api gravity oils and condensates admixture of even small amounts of low maturity biomarker rich bitumen can drastically alter the biomarker profile of such fluids we suggest that a 41 api dst oil from the sunfish 1 well cook inlet alaska is a mixture of jurassic derived oil with approximately 5 wt tertiary input derived from coals interbedded with the reservoir sands reservoir overprinting has significantly altered the biomarker fingerprint of the sunfish 1 oil therefore biomarker patterns or parameters for biomarker lean high api gravity fluids should be scrutinized closely for internal consistency and conformity with bulk properties

concentration and character of pahs and other hydrocarbons in coals of varying rank implications for environmental studies of soils and sediments containing particulate coal abstract particulate coal can occur in soils and sediments from both natural and anthropogenic sources its presence can influence the concentrations of regulated and more bioavailable pollutants through its geosorbent qualities and its own contribution of total extractable hydrocarbons teh including polycyclic aromatic hydrocarbons pahs and biomarkers extractable pahs in coal also can potentially affect pah based source and maturity ratios of soil or sediment extracts which can be used to assess the source s of pahs this study reports on the absolute concentrations of teh the 16 priority pollutant pahs 27 alkylated pahs and sulfur containing aromatics and selected biomarkers in 15 coals ranging in rank from lignite to anthracite unlike most previous studies in the fuel science or geochemical literature the coals herein were extracted using dichloromethane at room temperature an epa method 3500 type method common in environmental laboratories thereby allowing comparison of these results to environmental studies the concentrations of teh ranged from 8 2 to 2500 g g coal dry wt with a maximum yield among high volatile bituminous coals the teh fingerprints were variable and some of these resembled those of other forms of contamination the concentrations of priority pollutant pahs ranged from 35 to 11 000 ng g coal dry wt or 38 to 12 000 ng g carbon and varied with coal rank reaching a maximum within the high volatile bituminous rank the distributions of extractable pahs and numerous pah ratios conventionally used as source and or maturity parameters also varied with coal rank emphasizing that particulate coal in soils and sediments cannot be universally represented by a single set of diagnostic parameters hopanoid and sterane biomarker yields also varied with rank reaching a maximum in high volatile bituminous coals and were low relative to pahs because particulate coal often co occurs with other sources of hydrocarbons in soils and sediments the data presented herein may prove useful in allocating coal versus non coal sources on a mass balance basis

multiple levels of magma storage during the 1980 summer eruptions of mount st helens wa transitions in eruptive style explosive to effusive sustained to pulsatory are a common aspect of volcanic activity and present a major challenge to volcano monitoring efforts a classic example of such transitions is provided by the activity of mount st helens wa during 1980 where a climactic plinian event on may 18 was followed by subplinian and vulcanian eruptions that became increasing pulsatory with time throughout the summer finally progressing to episodic growth of a lava dome here we use variations in the textures glass compositions and volatile contents of melt inclusions preserved in pyroclasts produced by the summer 1980 eruptions to determine conditions of magma ascent and storage that may have led to observed changes in eruptive activity five different pyroclast types identified in pyroclastic flow and fall deposits produced by eruptions in june 12 july 22 and august 7 1980 provide evidence for multiple levels of magma storage prior to each event highly vesicular clasts have h2o rich 4 5 5 5 wt melt inclusions and lack groundmass microlites or hornblende reaction rims characteristics that require magma storage at p 160 mpa until shortly prior to eruption all other clast types have groundmass microlites ph20 estimated from both h2o bearing melt inclusions and textural constraints provided by decompression experiments suggest pre eruptive storage pressures of 75 40 and 10 mpa the distribution of pyroclast types within and between eruptive deposits can be used to place important constraints on eruption mechanisms fall and flow deposits from june 12 1980 lack highly vesicular microlite free pyroclasts this eruption was also preceded by a shallow intrusion on june 3 as evidenced by a seismic crisis and enhanced so2 emissions our constraints suggest that magma intruded to a depth of 4 km beneath the crater floor fed the june eruption in contrast eruptions of july and august although shorter in duration and smaller in volume erupted deep volatile rich magma if modeled as a simple cylinder these data require a step wise decrease in effective conduit diameter from 40 50 m in may and june to 8 12 m in july and august the abundance of vesicular intermediate to deep clast types in july and august further suggests that this change was effected by narrowing the shallower part of the conduit perhaps in response to solidification of intruded magma remaining in the shallow system after the june eruption eruptions from july to october were distinctly pulsatory transitioning between subplinian and vulcanian in character as originally suggested by scandone and malone 1985 a growing mismatch between the rate of magma ascent and magma disruption explains the increasingly pulsatory nature of the eruptions through time recent fragmentation experiments spieler et al 2004 suggest this mismatch may have been aided by the multiple levels at which magma was stored and degassed prior to these events

changes in tourmaline composition during magmatic and hydrothermal processes leading to tin ore deposition the cornubian batholith sw england abstract to investigate the potential of tourmaline as a geochemical monitor a comprehensive dataset on major minor and trace element concentrations as well as fe3 fe ratios of tourmaline is presented the dataset includes samples from five plutonic complexes related to diverse magmatic to hydrothermal stages of the cornubian batholith sw england tourmaline composition found in barren and cassiterite bearing samples include all three primary tourmaline groups and tourmaline species with the general endmembers schorl dravite elbaite uvite feruvite foitite and mg foitite based on textures and compositions it is possible to distinguish not only between late magmatic and hydrothermal tourmaline but also between several formation stages hence tourmaline monitors late magmatic processes and the partitioning of elements during exsolution of an aqueous phase for example in hydrothermal tourmaline sn is strongly enriched while ti cr v and sc are depleted compared to late magmatic tourmaline of the same sample several tourmaline generations that precipitated from magmatic fluids can be distinguished with differing major and minor elements and ree patterns depending on the composition of the melt from which they were expelled from strongly zoned tourmaline allows for unraveling the hydrothermal history of a distinct location including ore precipitation the precipitation of sno2 in the study area was probably caused by mixing between acidic reduced sn bearing magmatic fluids and oxidized meteoric fluids which is in agreement with london and manning 1995 and williamson et al 2000 hence the ability of tourmaline composition to monitor changes in sn concentration and redox conditions in hydrothermal fluids has potential as an exploration tool

lacustrine basin dynamics and organosulphur compound origin in a carbonate rich lacustrine system late oligocene mequinenza formation se ebro basin ne spain abstract the late oligocene mequinenza formation se ebro basin ne spain records the development of extensive shallow low gradient lacustrine zones which evolved under a subtropical warm climatic regime affected by humidity aridity cycles carbonate dominated inner lacustrine sequences which include thin coal seams are laterally related to muddy carbonate and siliciclastic marginal lacustrine assemblages where evaporites occur water solute concentration of the lacustrine zones changed during the alternative high and low stand episodes with lacustrine waters ranging mainly from fresh to oligosaline nonsulphurised nsc and sulphurised osc organic compounds occur in the inner lacustrine facies and record significant contributions from aquatic and terrestrial higher plants bacteria cyanobacteria photosynthetic anaerobic bacteria and algae these biomarkers show that the lacustrine system was eutrophic and the water column was poorly oxygenated and sometimes stratified as evidenced by occasional finely laminated facies and gammacerane organic matter s c ratio lower in carbonate than in coal and coal related facies suggests significant variations in the lacustrine autotrophic production and or the allochthonous organic matter contribution higher plant biomarkers were recorded mainly as normal nonsulphurised lipids by contrast bacterial and algal lipids hopanoids steroids and isoprenoids under intense sulphate reduction conditions incorporated sulphur in their hydrocarbon skeleton and gave rise to osc with distributions of thienyl and thiolanylhopanoids epithiosteranes and polyprenoids linear thiols are new biomarkers which probably were generated by the early incorporation of sulphur into funtionalised precursors e g alkanols intense methanogenesis was enhanced in some lacustrine zones owing to high organic matter input and as a consequence biomarkers of methanotrophic and methylotrophic bacteria related to methane emission are also found

organic geochemical investigations of brown coal lithotypes a contribution to facies analysis of seam banding in the helmstedt deposit abstract samples of light medium light and dark lithotypes from the eocene helmstedt brown coal deposit were examined by organic geochemical methods soxhlet extraction liquid and gas chromatography gc ms the study is part of a facies analysis of banded brown coals there are significant differences between the lithotypes concerning the extractable organic matter yields the composition of the extracts and the composition of the alkane fractions on average the light brown coals produce three times as much extractable organic matter as the dark ones asphaltenes and resins are the main components of the extracts of the light lithotypes hydrocarbons and n s o compounds of lower molecular weight are less abundant than in the dark lithotypes the alkane fraction of light lithotypes contains more n alkanes of high molecular weight and more saturated triterpenoids hopanes excluding homohopane but less unsaturated polycyclic compounds rearranged sterenes triterpenes and less homohopane the generally low concentrations of cyclic diterpanes norabietane norpimarane do not reveal any relationship to the three lithotypes based on these results there is no support for the conventional assumption that the light and dark brown coal lithotypes originated from different plant communities of the paleomoor the results rather suggest that the banding within the seam of the helmstedt brown coal deposit results from different biogeochemical degradation and transformation processes these processes are considered to be dependent on the environment of the paleomoor

transitions between explosive and effusive eruptions of silicic magmas water rich silicic magmas may erupt explosively giving rise to massive columns of fragmented ash1 5 or effusively as viscous bubbly lavas to form lava domes6 8 complex cycles of explosive and effusive eruptions are often observed8 12 although these two eruption mechanisms have been modelled independently1 8 the conditions under which a volcano exhibits a particular style of eruption are not known and the transitions between eruption styles are poorly understood by modelling the ascent of magma along a permeable conduit we show here that for small magma chamber overpressures the style of eruption explosive or effusive is dependent on the magma flow rate we also identify a critical overpressure above which only explosive eruptions occur complex eruption sequences follow naturally for example if a shallow magmatic system is supplied with magma at an intermediate flow rate the eruption will be slow and effusive until the chamber over pressure becomes too large an explosive eruption then relieves the overpressure and an effusive eruption style resumes we suggest that monitoring of temporal variations in chamber overpressure for example by measuring ground deformation can be used to assess whether a passively effusing volcano has the potential to erupt explosively

crystal chemical characterization of tourmalines from the english lake district electron microprobe analyses and mossbauer spectroscopy electron microprobe analyses empa and mossbauer spectra ms have been acquired for natural tourmalines sampled near crummock water and haweswater english lake district in the former the dravite schorl series is prevalent whereas in the latter the dravite species is dominant all tourmaline samples presently studied are chemically disordered the compositional and ms data give an insight into the thermal and fluid evolution experienced by the tourmalinite rocks the tourmalines from crummock water crystallized in a closed low f o 2 environment under the influence of a magmatic fluid the tourmalines from haweswater are of hydrothermal origin and were formed under low variable t and low f o 2 conditions from a fluid of constant composition

remarkable cyclic ground deformation monitored in real time on montserrat and its use in eruption forecasting telemetered high resolution tiltmeters were installed in montserrat in summer of 1995 in december 1996 and in may 1997 the 1995 installations several km from the soufriere hills vent were too distant to yield useful data however the 1996 and 1997 installations on the crater rim revealed 6 14 h inflation cycles caused by magma pressurization at shallow depths 0 6 km below the base of dome the tilt data correlated with seismicity explosions and pyroclastic flow activity and were used to forecast times of increased volcanic hazard to protect scientific field workers and the general public

the generation of gas overpressure in volcanic eruptions abstract observations of natural eruption products show that different parts of a single magma batch may experience different degassing histories during ascent in a volcanic conduit in non explosive eruptions lava issuing from a volcanic vent may contain overpressured gas bubbles these important features of volcanic eruptions cannot be accounted for by existing flow models which rely on simplifying hypotheses for the relationship between pressures in the gas phase and in the bulk flow volcanic flows involve highly compressible material which undergoes large viscosity variations as degassing proceeds we show that these properties may lead to large gas overpressures in erupting lava the magnitude of this overpressure depends on the initial volatile content of magma and is largest for relatively volatile poor magmas due to the extreme viscosity variations at water contents less than 1 wt we develop a simple analytical model to illustrate the main features of compressible viscous flows 1 at any level gas pressure is larger near the conduit axis than at the walls 2 gas overpressure is an increasing function of mass discharge rate

organic geochemistry of the lower miocene oberdorf lignite styrian basin austria its relation to petrography palynology and the palaeoenvironment abstract in the oberdorf trough at the northwestern margin of the styrian basin austria an up to 36 m thick lower miocene ottnangian lignite seam occurs within the fluvial koflach voitsberg formation previous results indicate that the lignite originated in a topogenous mire within a wet forest swamp palaeoenvironment differences in soluble organic matter som yield of borehole samples from the lignite seam are related to free lipids present in plant waxes or resins and the presence of thermally labile polymers indicated by the contents of liptinite macerals i e resinite suberinite and liptodetrinite the n alkane distribution patterns are dominated by high molecular weight lipids with marked odd over even predominance originating from plant waxes a contribution of algae to the even numbered short chain lipids observed in considerable amounts in the footwall sediments is proposed terpenoid biomarkers characteristic for conifers and angiosperms were detected consistent with palynomorphic spectra which are dominated by forest swamp pollen taxodiaceae cupressaceae and pollen from plants living in a mixed mesophytic forest excellent relationships between higher plant biomarker composition and palynologic data indicate that the organic geochemical results reflect the varying inputs of coniferales vs angiosperms the data further imply that cuparene may be used for taxonomical differentiation of coniferales families organic geochemical data provide evidence that the content of land plant derived biomarkers is controlled by the input of resin rich conifers concentrations of hopanoids dominated by hop 17 21 ene generally increase towards the top of the lignite a section characterised by high extents of aromatisation of triterpenoid biomarkers the results suggest that the aromatisation of angiosperm derived biomarkers may be governed by the activity of anaerobic rather than by aerobic bacteria however changes in the depositional environment and palynologic facies during peat formation probably influenced the origin and fate of angiosperm derived triterpenoids the results indicate how biomarker composition may contribute to the evaluation of environmental changes cross correlations of organic geochemical parameters with palynological data and petrography based facies indicators will provide further insights in the peat forming vegetation and biogeochemical activities in the mire

compositional zoning and element partitioning in nickeloan tourmaline from a metamorphosed karstbauxite from samos greece blue green nickeloan tourmaline from a micaceous enclave of a marble from samos greece contains unusually high concentrations of ni up to 3 5 wt nio co up to 1 3 wt coo and zn up to 0 8 wt zno the polymetamorphic karstbauxite sample has an uncommon assemblage of nickeloan tourmaline calcite zincian staurolite gahnite zincohogbomite diaspore muscovite paragonite and rutile the complex geologic history is reflected in multi staged tourmaline growth with cores that represent detrital fragments surrounded by two staged metamorphic overgrowths zone 1 metamorphic overgrowths which nucleated next to detrital cores are highly asymmetric and exhibit compositional polarity such that narrow overgrowths of brown schorl developed at the c pole are enriched in mg ti and f and depleted in al fe and x site vacancies x relative to wider gray blue schorl to foitite overgrowths developed at the c pole volumetrically dominant zone 2 overgrowths are strongly zoned nickeloan dravites with a continuous increase in mg co ca and f at the expense of fe zn cr and v from the zone 1 interface to the outermost rim within zone 2 ni reaches a maximum of 0 5 apfu before decreasing in the outer 20 40 m zone 2 overgrowths also exhibit compositional polarity such that at the c pole overgrowths are enriched in mg f na ca and cr relative to overgrowths at the c pole that are in turn enriched in al fe ni co and x element partitioning involving tourmaline rims and coexisting minerals indicates that relative partitioning of ni is tourmaline staurolite gahnite co is tourmaline staurolite gahnite and zn is gahnite staurolite tourmaline

major and trace element geochemistry of tourmalines from archean orogenic gold deposits proxies for the origin of gold mineralizing fluids abstract orogenic style gold mineralizations in the archean hattu schist belt e finland are present in all major host rock lithologies including epiclastic sedimentary and volcanogenic rocks as well as felsic intrusives the gold mineralizations occur as dissemination in altered wall rocks and within hydrothermal quartz veins hydrothermal tourmalines are often associated with the gold mineralizations occurring in the quartz veins as alteration minerals in contacts of the metasedimentary host rocks and quartz veins but also within mineral assemblages of the metasedimentary and magmatic rocks we characterize and compare the major trace and rare earth element chemistry of these tourmalines in order to evaluate their suitability as a petrogenetic tool for tracing the fluid sources of the hydrothermal system by comparing the chemistry of tourmalines from gold mineralization with those from metamorphic and magmatic host rocks we test whether tourmaline composition can be used to identify the source rocks of the gold transporting hydrothermal fluids all analyzed tourmalines belong to the alkali super group and plot along the schorl dravite join the hydrothermal tourmalines have li sr and v concentrations comparable to metamorphic tourmalines and clearly distinct from magmatic tourmalines because the concentrations of ni pb cr mn ga zn and sn show a wide overlap between magmatic metamorphic and hydrothermal tourmalines these elements do not permit to discriminate between different source rocks the co variations of many elements in hydrothermal tourmalines when plotted against li show more similarity to metamorphic tourmalines and the whole rock compositions of metasedimentary and metavolcanic host rocks than to their magmatic counterparts this indicates that the major and trace element composition of hydrothermal tourmalines in the hattu schist belt is predominantly controlled by the host rocks and local fluid rock interactions and does not reflect the distal fluid sources the effect of local fluid rock interaction is also manifested by the ree patterns of tourmalines the magmatic tourmalines have distinct lree enriched patterns resembling the whole rock ree patterns of granitic intrusives while the metamorphic and hydrothermal tourmalines have flat or weakly fractionated patterns similar to metavolcanic and metasedimentary host rocks taken together the tourmaline data suggest that hydrothermal tourmalines associated to gold mineralizing fluids are most likely genetically related to metamorphic rock sources without important contributions of magmatic fluids and that local fluid rock interaction exerted a major control on tourmaline chemistry

the productora cu au mo deposit chile a mesozoic magmatic hydrothermal breccia complex with both porphyry and iocg affinities the productora cu au mo deposit is hosted by a cretaceous hydrothermal breccia complex in the coastal cordillera of northern chile the current resource which includes the neighboring alice cu mo porphyry deposit is estimated at 236 6 mt grading 0 48 cu 0 10 g t au and 135 ppm mo local wall rocks consist of a thick sequence of broadly coeval rhyolite to rhyodacite lapilli tuffs 128 7 1 3 ma u pbzircon and two major intrusions the cachiyuyito tonalite and ruta cinco granodiorite batholith 92 0 1 0 ma u pbzircon previous studies at productora concluded the deposit had strong affinities with the iron oxide copper gold iocg clan and likened the deposit to candelaria based on new information we document the deposit geology in detail and propose a new genetic model and alternative classification as a magmatic hydrothermal breccia complex with closer affinities to porphyry systems hydrothermal and tectonic breccias veins and alteration assemblages at productora define five paragenetic stages stage 1 quartz pyrite cemented breccias associated with muscovite alteration stage 2 chaotic matrix supported tectonic hydrothermal breccia with kaolinite muscovite pyrite alteration stage 3 tourmaline pyrite chalcopyrite magnetite biotite cemented breccias and associated k feldspar albite alteration stage 4 chalcopyrite pyrite muscovite illite epidote and chlorite veins and stage 5 calcite veins the productora hydrothermal system crosscuts earlier formed sodic calcic alteration and magnetite apatite mineralization associated with the cachiyuyito stock main stage mineralization at productora was associated with formation of the stage 3 hydrothermal breccia chalcopyrite is the dominant hypogene cu mineral and occurs predominantly as breccia cement and synbreccia veins with pyrite the alice cu mo porphyry deposit is characterized by disseminated chalcopyrite and quartz pyrite chalcopyrite molybdenite vein stockworks hosted by a granodiorite porphyry stock alice is spatially associated with the silica ridge lithocap which is characterized by massive fine grained quartz altered rock above domains of alunite pyrophyllite and dickite rhenium os dating of molybdenite indicates that main stage mineralization at productora occurred at 130 1 0 6 ma and at 124 1 0 6 ma in the alice porphyry chalcopyrite and pyrite from productora have 34ssulfide values from 8 5 to 2 2 consistent with a magmatic sulfur source and fluids evolving under oxidizing conditions no significant input from evaporite or seawater sourced fluids was detected stage 3 tourmalines have average initial sr of 0 70397 consistent with an igneous derived sr source the productora magmatic hydrothermal breccia complex formed as a result of explosive volatile fluid release from a hydrous intrusive complex metal bearing fluids were of magmatic affinity and evolved under oxidizing conditions despite sharing many similarities with the andean iocg clan strong structural control regional sodic calcic alteration locally anomalous u fluid evolution at the productora cu au mo deposit is more consistent with that of a porphyry related magmatic hydrothermal breccia sulfur rich acid alteration assemblages and relatively low magnetite contents

trace elements in tourmalines from massive sulfides deposits and tourmalinites geochemical controls and exploration applications trace element contents of tourmalines from massive sulfide deposits and tourmalinites have been determined in situ by proton microprobe 390 analyses were acquired from 32 polished thin sections concentrations of trace elements in the tourmalines vary widely from 40 to 3 770 ppm mn 4 to 1 800 ppm ni 2 to 1 430 ppm cu 9 to 4 160 ppm zn 3 to 305 ppm ga 6 to 1 345 ppm sr 10 to 745 ppm sn 49 to 510 ppm ba and 3 to 4 115 ppm pb individual grains and growth zones are relatively homogeneous suggesting that these trace elements are contained within the crystal structure of the tourmaline and are not present in inclusions the highest base metal contents are in ore related tourmaline samples from kidd creek ontario broken hill australia and sazare japan tourmaline data from these and many other massive sulfide deposits cluster by sample and display broadly linear trends on zn vs fe plots suggesting chemical control by temperature and hydrothermal and or metamorphic fluid mineral equilibria significant ni occurs only in samples from the kidd creek cu zn pb ag deposit which is associated with a large footwall ultramafic body an overall antithetic relationship between zn and ni probably reflects fluid source controls mn is correlated with fe in tourmalines from barren associations and possibly in some tourmalines associated with sulfide vein deposits sn increases systematically with fe content irrespective of association the highest values are found in schorls from granites other trace elements are generally uncorrelated with major element concentrations e g sr ca base metal proportions in the tourmalines show systematic patterns on ternary cu pb zn diagrams that correlate well with the major commodity metals in the associated massive sulfide deposits for example data for tourmalines from cu zn deposits e g ming mine newfoundland fall mainly on the cu zn join whereas those from pb zn deposits e g broken hill australia plot on the pb zn join no data fall on the cu pb join consistent with the lack of this metal association in massive sulfide deposits the systematic relationship between base metal proportions in the tourmalines and the metallogeny of the host massive sulfide deposits indicates that the analyzed tourmalines retain a strong chemical signature of their original hydrothermal formation in spite of variable metamorphic recrystallization such trace element patterns in massive sulfide tourmalines may be useful in mineral exploration specifically for the evaluation of tourmaline concentrations in rocks soils and stream sediments

geochemical characterization of the devonian mississippian woodford shale from the mcalister cemetery quarry criner hills uplift ardmore basin oklahoma abstract it has been estimated that technically recoverable reserves from shales in the continental u s are believed to be approximately 24 billion barrels of oil bbo and 750 trillion cubic feet tcf of gas in oklahoma the most important hydrocarbon source rock is the woodford shale proposed to be the source of some 70 of the state s liquid hydrocarbon reserves such a regionally widespread source rock provides potential for both academic study and industrial opportunities in this study representative samples of the woodford shale from the mcalister quarry outcrop have been characterized by a variety of geochemical techniques toc values range from 0 07 to 15 6 wt and based on rock eval pyrolysis most of the samples plot within the type i ii kerogen range with several low toc samples plotting in the type iii kerogen range toc and biomarker parameters suggests that two sections of the upper woodford are immature paleosols having been subaerially exposed due to abrupt episodes of sea level fall during the late devonian evidence for these zones of paleoweathering includes highly depleted toc increased oxygen index oi values loss of n alkanes decreases in the aryl isoprenoid ratio air sesquiterpenoids cheilanthanes hopanoids and decreases in many of the polycyclic aromatic hydrocarbons pahs the values of several paleoenvironmental proxies for samples immediately following the frasnian famennian f f stage extinction boundary within the upper woodford suggests that a large influx of weathered terrigenous material occurred at that time the presence of pyrogenic compounds implies that paleowildfires were widespread throughout the middle and late devonian in the north american midcontinent it is possible that these influxes of weathered terrestrial organic material stimulated algal blooms that led to the anoxic water column conditions often attributed to the f f stage extinction event investigation of the stratigraphic framework of these source rocks assists in evaluating their potential as hydrocarbon producers and or unconventional reservoirs integration of geochemical data adds another powerful dimension to this approach it has been proposed that the woodford shale was deposited during a 2nd order depositional sequence the lower member represented the transgressive systems tract tst the upper member the highstand systems tract hst and the middle member bridging the transition between the two numerous 3rd order parasequences were also identified as being part of the overall 2nd order sequence and could be correlated to the devonian sea level curve the major objectives of the study were while this study focuses locally on the mcalister quarry samples it is also of regional importance the woodford is a prolific source rock throughout the anadarko basin and has been the subject of extensive exploration and production efforts particularly in the past decade with the development of horizontal drilling and hydrofracturing techniques continued investigation of the heterogeneity of the shale will greatly enhance the ability to predict more productive facies within the formation throughout the basin

biomarkers stratigraphy of irati formation lower permian in the southern portion of parana basin brazil abstract this study covers the application of biomarkers as stratigraphic markers in a lower permian marine section from the parana basin southern brazil the biomarker variations reveal changes in sedimentary environment that were not detected by sedimentological and paleontological methods and will contribute to high resolution stratigraphy the irati formation contains two lithostratigraphic units 1 the lower unit taquaral member is composed of shales deposited in a marine epicontinental to restricted environment and 2 the upper unit assistencia member which consists of carbonates interbedded with shales and organic rich shale intervals deposited in a restricted marine environment the biomarker differences observed in the taquaral member can be explained by two different types of organic matter the lower and upper parts are characterized by a high relative abundance of high molecular weight n alkanes c27 17 trisnorhopane c31 r homohopane high hopanes steranes ratio and low hydrogen index values this facies contains greater relative amount of terrestrial organic matter the low hopanes steranes ratio together with the high hydrogen index values and amorphous organic matter relative proportion observed in the middle part of the taquaral member indicate a more marine organic matter contribution in the assistencia member based on gammacerane c30 hopane ratio c28 20r methylcholestane c29 20r methylcholestane ratio total organic carbon hydrogen index values palynofacies and sedimentary structures it was possible to distinguish changes in salinity and redox conditions the bituminous shales intervals were deposited in an anoxic environment high total organic carbon high hydrogen index values high preserved amorphous organic matter content with lower salinity lower gammacerane c30 hopane and c28 20r methylcholestane c29 20r ethylcholestane ratios on the other hand the limestones intervals were deposited in an aerobic environment low total organic carbon low hydrogen index values high oxidized organic matter content with higher salinity higher gammacerane c30 hopane and c28 20r methylcholestane c29 20r methylcholestane ratios

correlating terrestrial signatures from biomarker distributions δ13c and palynology in fluvio deltaic deposits from nw australia triassic jurassic abstract a multidisciplinary study using molecular and organic isotope geochemistry petrology and palynology has been used to establish palaeoenvironmental conditions of fluvio deltaic deposits from the delambre 1 well western australia triassic jurassic changes in higher plant biomarker distributions correlate with 1 brackish water environments 2 major changes in composition of spore and pollen assemblages 3 variations in types of sedimentary facies and 4 stable carbon isotopic composition of higher plant biomarkers these changes are all consistent with the occurrence of climatic shifts in northwestern australia during triassic jurassic periods established by parrish j t bradshaw m t brakel a t mulholland s m totterdell j m yeates a n 1996 palaeoclimatology of australia during the pangean interval palaeoclimates 1 241 281 the combustion marker benzo e pyrene is abundant in samples that contain pollen from falcisporites australis the decline of f australis and the rapid emergence of assemblages dominated by corollina spp at the end of the triassic marks a rapid pollen spore extinction event at the triassic jurassic boundary there is an increase in relative abundance of the higher plant biomarkers cadalene and simonellite in a prodeltaic facies the 13 c values of between 26 9 and 24 9 for retene are consistent with a source from class i conifer resinites and relate to samples abundant in araucariacian conifers in the early middle jurassic where facies are characterized as pro distal deltaic

novel aromatic hydrocarbons of probable bacterial origin in a jurassic lacustrine sequence novel series of aromatic hydrocarbons apparently bacterially derived were detected by gc ms analysis of an oil and three samples of its source rock in addition to high levels of known bacterial marker compounds hopanes benzohopanes and d ring monoaromatic 8 14 secohopanoids all samples exhibited a new series of aromatic secohopanoids which appeared to comprise pairs of c28 c31 demethylated counterparts of the regular d ring monoaromatic 8 14 secohopanoids lacking either the c 27 or more probably the c 28 methyl group further new series appeared to be composed of c28 c30 analogues of the regular and demethylated monoaromatic secohopanoids with an additional c c bond in the e ring alkylnapthalene distributions in the rock samples were dominated by 1 1 5 6 tetramethyl 1 2 3 4 tetrahydronaphthalene 1 2 5 trimethylnapthalene and 1 2 5 6 tetramethylnapthalene deriving from degradation of aromatic 8 14 secohopanoids three prominent phenanthrene analogues of these napthalene derivatives appeared to be present exhibiting similar relative abundance trends in the rock samples which suggests common bacterially derived precursors

relationships between coal quality and organic geochemical parameters a case study of the hafik coal deposits sivas basin turkey abstract this study provides coal quality organic petrographic and organic geochemical data on tertiary subbituminous coal of the hafik area northwestern part of the sivas basin turkey coal petrological studies along with proximate and ultimate analyses were undertaken to determine the organic petrographic characteristics of the hafik coals huminite reflectances were found to be between 0 38 and 0 48 corresponding to an organic material rich and coal layers values characteristic of low maturity this parameter shows a good correlation with calorific values average 21 060 kj kg and average t max 422 c mineral matter diagenesis indicating immaturity the studied coals and organic material underwent only low grade transformation a consequence of low lithostatic pressure therefore the hafik coals are actually subbituminous in rank rock eval analysis results show types ii iii and iii kerogens the organic fraction of the coals is mostly comprised of humic group macerals gelinites with small percentages derived from the inertinite and liptinite groups in this study organic petrographic organic geochemical and coal quality data were compared the hafik deposit is a high ash high sulfur coal the mineral matter of the coals is comprised mainly of calcite and clay minerals

effects of conduit geometry on magma ascent dynamics in dome forming eruptions abstract we develop a steady state two phase flow model of magma ascent through an axisymmetric conduit of variable radius r and length l in order to quantify relationships between conduit geometry and magma ascent dynamics holding boundary conditions and chamber magma properties constant we vary conduit geometry systematically and independently such that the upper conduit radius increases or decreases by a factor of r t r b radius ratio 0 4 r t r b 2 5 above a change initiation height h 0 1 h l 0 7 and over length l e l e l 0 2 where r t and r b are conduit radius above t and below b the radius change and h is the height above the top of the magma chamber conduit widening causes a drop in overpressure and corresponding increase in gas volume fraction and magma acceleration over the whole length of the conduit with all changes increasing in magnitude with increasing radius ratio magma ascent rate increases roughly as r 2 and volumetric flow rate subsequently increases as r 4 when r t r b r both increasing r t for a fixed r b increasing radius ratio and increasing r b for a fixed r t decreasing radius ratio increase volume flow and magma ascent rates compared to changes in geometry small changes in chamber pressure

aliphatic and aromatic hydrocarbons in candiota coal samples novel series of bicyclic compounds abstract aliphatic and aromatic fractions obtained from nine samples taken from two different seams of five boreholes in the candiota coalfield lower permian were analysed by gas chromatography mass spectrometry the occurrence of the tetracyclic diterpenoids 16 h phyllocladane and ent 16 h kaurane among the aliphatic hydrocarbons and the tricyclic diterpenoids simonellite and retene in the aromatic hydrocarbon concentrates suggest an important input from conifers to the sedimentary biomass this may explain the origin of a novel series of saturated and aromatic bicyclic compounds detected in the extracts which may be structurally related to the same precursor possibly a conifer resin derived tricyclic diterpenoid

polycyclic aromatic hydrocarbons pahs in late eocene to early pleistocene mudstones of the sylhet succession ne bengal basin bangladesh implications for source and paleoclimate conditions during himalayan uplift abstract distribution and possible sources of polycyclic aromatic hydrocarbons pahs have been investigated in 23 late eocene to early pleistocene mudstones from the sylhet succession of the northeastern bengal basin bangladesh paleoclimatic conditions in the southern himalaya region throughout the himalayan uplift were reconstructed based on combustion derived pahs and aromatic land plant derived biomarkers phenanthrene fluoranthene fla pyrene py benz a anthracene baan chrysene triphenylene chry tpn benzofluoranthenes bflas benzo e pyrene bepy benzo a pyrene bapy perylene pery indeno 1 2 3 cd pyrene inpy benzo ghi perylene bghip coronene cor and retene ret were the identified pahs fla fla py ratios 0 5 and inpy inpy bghip 0 2 from almost all sylhet samples suggest occurrence of natural wildfires low contents of baan and bapy indicate decomposition by long exposure to sunlight before sedimentation or early diagenetic weathering increased cor inpy and bghip contents suggest occurrence of larger high temperature wildfires correlation coefficients of the pahs and p values for statistical hypothesis testing showed that the positive and negative correlations within the pahs may be indicative of high or low temperatures in wildfires fungi derived pery showed negative correlations with py r 0 67 p 4 6 10 4 and fla r 0 56 p 5 0 10 3 but not with cor bflas inpy and bghip based on the correlation coefficients for all pahs and their p values five statistical groups py fla cor bflas inpy bghip baan chry tpn bapy pery and ret were recognized these groups are probably correlated with origins and depositional processes according to the results the sylhet succession was deposited in three differing paleoclimatic regimes 1 first phase late eocene to early miocene early to middle stage of himalayan uplift high contents of combustion derived pahs fla py and bepy significant gymnosperm derived ret and low pery abundances in the jaintia and barail groups indicate arid climatic conditions although wildfires could often occur 5 or 6 ring combustion pahs cor inpy and bghip contents are low suggesting that the wildfires were relatively low temperature 2 second phase middle to late miocene middle to late stage of himalayan uplift combustion derived pahs and fungi derived pery were dominant in the surma group the climate was arid to humid and seasonal with a dry season giving conditions suitable for combustion abundant fla bflas bepy cor inpy and bghip imply high temperatures in large wildfires however frequency of the wildfires decreased because of wet climate 3 third phase late miocene to pleistocene late stage of himalayan uplift moderate to high pery contents and low fla py and bepy abundances in the tipam and dupitila groups indicate establishment of more humid climate inpy bghip cor bflas and bapy were predominant intensified humid and seasonal climate arising from the himalayan monsoon decreased the incidence and frequency of general wildfires but increased the ratio of large to small wildfires

dynamics of two phase conduit flow of high viscosity gas saturated magma large variations of sustained explosive eruption intensity the ascent of gas saturated magma in a conduit can lead to the transition from the laminar flow of a bubble rich melt to the turbulent flow of particle rich hot gas in upper part of the conduit this process is investigated with a help of a disequilibrium two phase flow model for steady and unsteady conditions for the description of different gas magma flow regimes in the conduit separated sets of equations are used the main difference from previous conduit flow models is the consideration of the pressure difference between a growing bubble and the surrounding melt for a bubbly liquid to evolve into a gas particle flow a critical overpressure value must be exceeded this transition region is simulated by means of a discontinuity namely by a fragmentation wave the magma flow calculations are carried out for a given conduit length and overpressure between the magma chamber and the atmosphere the steady solution of the boundary problem is not unique and there are up to five distinct steady regimes corresponding to fixed eruption conditions within the framework of the quasi steady approach governing parameters being varied monotonically the transition from one regime to another can take place suddenly and is accompanied by the fundamental restructuring of the conduit flow resulting in rapid or abrupt changes in the intensity of explosive eruptions abrupt intensification of an explosive eruption occurs when the chamber pressure becomes sufficiently less than saturation pressure and therefore corresponds to the case of shallow depth magma chamber and high initial water content a regime with minimum flow rate may relate to the growth of a lava dome following the explosive phase of eruption these models can explain geological observations that imply large and sudden changes of discharge rate in large magnitude explosive eruptions particularly at the transition between plinian phase and ignimbrite formation

characteristics of upper cretaceous coals from enugu nigeria related to bitumen generation and mobilization abstract a set of nine upper cretaceous coals of sub bituminous rank were studied petrographically and geochemically the coals contain considerable amounts of various liptinites as well as fluorescent vitrinite some bitumen has been generated and mobilized in these low rank coals as evident by the presence of exsudatinite nevertheless no hydrocarbons have been expelled as the amount of bitumen generated is not considered to be sufficient to overcome the threshold saturation of the coals

temporal evolution of flow conditions in sustained magmatic explosive eruptions abstract the temporal evolution of fundamental flow conditions in the magma chamber plus conduit system such as pressure velocity mass flow rate erupted mass etc during sustained magmatic explosive eruptions was investigated to this aim simplified one dimensional and isothermal models of magma chamber emptying and conduit flow were developed and coupled together the chamber model assumed an homogeneous composition of magma and a vertical profile of water content the chamber could have a cylindrical elliptical or spherical rigid geometry inside the chamber magma was assumed to be in hydrostatic equilibrium both before and during the eruption since the time scale of pressure variations at the conduit inlet of the order of hours is much longer than the travel time of magma in the conduit of the order of a few minutes the flow in the conduit was assumed as at steady state the one dimensional mass and momentum balance equations were solved along a circular conduit with constant diameter assuming choked flow conditions at the exit bubble nucleation was considered when the homogeneous flow pressure dropped below the nucleation pressure given the total water content and the solubility law above the nucleation level bubbles and liquid magma were considered in mechanical equilibrium the same equilibrium assumption was made above the fragmentation level between gas and pyroclasts due to the hydrostatic hypothesis the integration of the density distribution in the chamber allowed to obtain the total mass in the chamber as a function of pressure at the chamber top and through the conduit model as a function of time simulation results pertaining to rhyolitic and basaltic magmas defined at the volcanic eruption mechanism modeling workshops durham nh 2002 nice france 2003 are presented important flow variables such as pressure density velocity shear stress in the chamber and conduit are discussed as a function of time and magma chamber and conduit properties results indicate that vent variables react in different ways to the pressure variation of the chamber pressure density and mass flow rate show relative variations of the same order of magnitude as the conduit inlet pressure whereas velocity is more constant in time sill like chambers produce also significantly longer and more voluminous eruptions than dike like chambers water content stratification in the chamber and the increase of chamber depth significantly reduce the eruption duration and volume maximum erupted mass fractions of about 0 2 are computed for small water saturated and shallow chambers

trace element systematics of tourmaline in pegmatitic and hydrothermal systems from the variscan schwarzwald germany the importance of major element composition sector zoning and fluid or melt composition article an extensive data set on the compositional variation of tourmaline from granitic pegmatites from migmatitic gneisses and from various types of hydrothermal veins from the schwarzwald germany is provided the investigated tourmalines are members of the alkali and x vacant groups representing mostly dravite schorl solid solutions with some analyses belonging to the foitite mg foitite series oxygen isotope data on quartz tourmaline pairs indicate formation temperatures between 550 and 350 c for most of the quartz tourmaline veins most of the tourmalines show strong sector zonation fractionating certain major e g na mg minor e g ti ca and trace elements e g sr pb ree among the different crystallographic sectors of the crystals we conclude that comparison of tourmaline compositions for petrogenetic interpretations must be based on the concentrations in the neutral a sector in order to eliminate the effects of intra crystalline fractionation most trace element contents vary over several orders of magnitude with median concentrations generally be tween 0 1 and 10 g g the highest concentrations are found for zn v sr sc sn and li median concentrations of several tens to hundreds of g g whereas very low median concentrations b0 1 g g were found for u th bi tl and cs the concentration of several trace elements e g sr ree co correlates with the major element composition of the tourmaline which implies potential crystal chemical effects on their incorporation conse quently the general assumption that tourmaline is a passive monitor for the chemical compositions of the melts or fluids from which it crystallizes has to be questioned nevertheless our study demonstrates that the trace element composition of tourmaline allows to distinguish between geochemically distinct fluid sources and the trace element composition of tourmaline may therefore be used to unravel the chemical complexity of granite related hydrothermal systems

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

catastrophic lava dome failure at soufriere hills volcano montserrat 12 13 july 2003 the lava dome collapse of 12 13 july 2003 was the largest of the soufriere hills volcano eruption thus far 1995 2005 and the largest recorded in historical times from any volcano 210 million m3 of dome material collapsed over 18 h and formed large pyroclastic flows which reached the sea the evolution of the collapse can be interpreted with reference to the complex structure of the lava dome which comprised discrete spines and shear lobes and an apron of talus progressive slumping of talus for 10 h at the beginning of the collapse generated low volume pyroclastic flows it undermined the massive part of the lava dome and eventually prompted catastrophic failure from 02 00 to 04 40 13 july 2003 large pyroclastic flows were generated these reached their largest magnitude at 03 35 when the volume flux of material lost from the lava dome probably approached 16 million m3 over two minutes the high flux of pyroclastic flows into the sea caused a tsunami and a hydrovolcanic explosion with an associated pyroclastic surge which flowed inland a vulcanian explosion occurred during or immediately after the largest pyroclastic flows at 03 35 13 july and four further explosions occurred at progressively longer intervals during 13 15 july 2003 the dome collapse lasted approximately 18 h but 170 of the total 210 million m3 was removed in only 2 6 h during the most intense stage of the collapse

occurrence and geochemical significance of 1 2 5 6 tetramethylnaphthalene analysis of aromatic hydrocarbon fractions of selected coal and shale samples reveals the predominance of two specific polyalkylnaphthalenes which have been identified as 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnaphthalene the maturity of the samples is such that the source effect on the formation of individual molecules from biological precursors is expected to be recognisable these alkylnaphthalenes are thought to be diagenetically derived from pentacyclic triterpenoids via 8 14 seco triterpenoids which are also detectable in some of the samples investigated it is proposed that 1 2 5 6 tetramethylnaphthalene in the coal samples is formed by cleavage and methyl shift reactions from geminal c 4 methylated triterpenoids which contain a leaving group in position 3 for the shale samples degradation of monoaromatic secohopanoids must be considered as an alternative pathway

a study in early diagenesis biomarker composition of a suite of immature coals and coaly shales abstract a suite of samples from the funan mine n e china has allowed a comparison to be made between hydrocarbon rich coals and coaly shales these are immature coals and the known geological history suggests that they have experienced only a mild geothermal history analyses of the di and sesquiterpenoid components show that compounds based on the kaurane skeleton are absent unlike australian brown coals and the diterpenes isopimarane pimarane and 16 h phyllocladane relate to a different community of higher plants such as pinaceae and taxodiaceae from those recognized in australian brown coals a consideration of geochimical parameters and biomarker composition leads to the conclusion that the geolipid concentrations in the sample suite are environmentally determined it is concluded therefore that 22r 17 h 21 h bishomohopanoic acid and the 22r 17 h 21 h homohopane both predominant components in their respective classes are derived from different sources labdanic acids have been identified in these coals they are likely to be derived from resin constituents of the coal and not from microbial biomass they could potentially be developed as a maturation parameter cis and trans isomers of a triaromatic hydrocarbon based on the oleanane skeleton which has been previously identified in victorian brown coal are present in the funan coals the more oxidizing the environment the less advanced is the isomerization of cis to trans and again the environment of deposition is the controlling factor this study emphasizes the importance of understanding pathways of early diagenesis for the interpretation of data derived from more mature samples

molecular composition of a leaf and root bearing oligocene oxbow lake clay in the weisselster basin germany abstract a plant fossil bearing clay profile from the upper oligocene thierbach strata weisselster basin germany has been sectioned into horizons and the plant macrofossils of each section surface have been identified by morphological and anatomical studies in the upper half of the profile leaves from populus germanica and carpinus grandis and branchlets from the conifer taxodium balticum vel t dubium dominate the horizons while the lower part contains only root remains of unknown higher plants in the soxhlet extracted samples from each section n alkanes n alkanols n carboxylic acids and several terpenoids amyrin 24 25 dinoreleana 1 3 5 10 12 tetraene olean 12 en 3 one simonellite and hop 17 21 ene were identified by combined gas chromatography mass spectrometry the comparison of the extracted chemical compounds and the macrofossil record of the profile shows that simonellite occurs preferentially in the taxodium bearing horizons n alkanes n alkanols n carboxylic acids and amyrin were found in all sections but are enriched in the root containing part of the profile the distribution of hop 17 21 ene is independent of the input of higher plant remains

diverse tourmaline compositions from orogenic gold deposits in the hutti maski greenstone belt india implications for sources of ore forming fluids the late archean hutti maski greenstone belt hosts the largest operational gold mine in india at hutti as well as two satellite mines at hira buddini and uti tourmaline is a common accessory mineral in the auriferous altered wall rocks proximal to the gold bearing veins of these orogenic gold deposits we report here major rare earth element ree and selected trace element compositions of tourmalines from these alteration zones at hutti and hira buddini and from spatially associated volcaniclastic rocks at uti in order to compare and evaluate possible fluid sources related to tourmaline precipitation and gold mineralization tourmalines at hutti occur as tourmaline calcite microveins within proximal alteration zones and as disseminated grains along the biotite chlorite defined mylonitic foliation these tourmalines belong to the dravite oxydravite group with an evolutionary trend towards magnesio foitite and commonly are mg rich up to 2 06 apfu with low na 0 61 apfu and up to 53 x site vacancies characteristics are low abundances of total ree 0 25 0 67 chondrite and a flat trend with minor hree enrichment accompanied by strong positive eu anomalies at hira buddini tourmalines of the oxydravite povondraite series replace amphiboles and hydrothermal biotite based on textural and chemical characteristics three generations of tourmalines are present at hira buddini earliest type i tourmaline has moderate fe content up to 1 46 apfu high na average 0 80 apfu and moderate x site vacancies up to 22 type ii tends to be relatively enriched in fe up to 2 08 apfu have similar na contents average 0 79 apfu and low x site vacancies up to 8 these tourmalines contain higher total ree 0 93 2 23 chondrite and display a flat trend with slight middle rare earth element mree depletion accompanied by a small positive eu anomaly the latest tourmalines type iii are fe poor up to 1 52 apfu and na poor average 0 67 apfu with relatively high x site vacancies up to 21 this tourmaline type has relatively low total rees 0 21 1 05 chondrite and similar abundance patterns to those of hutti tourmalines accompanied by large positive eu anomalies similarity in tourmaline compositions with evolutionary trends in compositional space from different textural associations suggests that a single low salinity and reduced metamorphogenic fluid with inherently low ree was responsible for proximal alteration and gold mineralization at hutti the type i and type ii tourmalines from hira buddini display oxydravite povondraite trends with compositional overlap that suggests fluid mixing at a paragenetically early stage the early hydrothermal fluid was more saline oxidizing and likely had a granite derived component with high ree contents a later evolved relatively low salinity and reduced fluid is recorded by the last generation type iii tourmalines at hira buddini the tourmalines from uti metapelites are characterized by dravitic composition low na contents high x site vacancies 31 47 and an evolutionary trend toward magnesio foitite these tourmalines have higher ree contents 1 16 2 08 chondrite lree enriched patterns together with large positive eu anomalies and low concentrations of most trace elements all features that suggest a metamorphic origin

from vulcanian explosions to sustained explosive eruptions the role of diffusive mass transfer in conduit flow dynamics abstract magmatic explosive eruptions are influenced by mass transfer processes of gas diffusion into bubbles caused by decompression melnik and sparks melnik o e sparks r s j 2002 modelling of conduit flow dynamic during explosive activity at soufriere hills volcano montserrat in druitt t h kokelaar b p eds the eruption of soufriere hills volcano montserrat from 1995 to 1999 geological society london memoirs 21 307 317 proposed two end member cases corresponding to complete equilibrium and complete disequilibrium in the first case diffusion is fast enough to maintain the system near equilibrium and a long lived explosive eruption develops in the latter case pre existing bubbles expand under conditions of explosive eruption and decompression but diffusive gas transfer is negligible this leads to a much shorter eruption here we develop this model to consider the role of mass transfer by investigating transient flows at the start of an explosive eruption triggered by a sudden decompression the simulations reveal a spectrum of behaviours from sustained to short lived highly non equilibrium vulcanian style explosions lasting a few tens of seconds through longer lasting eruptions that can be sustained for tens of minutes and finally to eruptions that can last hours or even days behaviour is controlled by a mass transfer parameter which equals n 2 3 d where n is the bubble number density and d is the diffusivity the parameter is expected to vary between 10 5 and 1 s 1 in nature and reflects a time scale for efficient diffusion the spectrum of model behaviours is consistent with variations in styles of explosive eruptions of silicic volcanoes in the initial stages peak discharges occur over 10 20 s and then decline to low discharges if a critical bubble overpressure is assumed to be the criterion for fragmentation then fragmentation may stop and start several times in the declining period causing several pulses of high intensity discharge for the cases of strong disequilibria the fluxes can decrease to negligible values where other processes such as gas escape through permeable magma prevents explosive conditions becoming re established so that explosive activity stops and dome growth can start for cases closer to the equilibrium the eruption can evolve towards a quasi steady sustained flow never declining sufficiently for gas escape to become dominant

erosion processes in volcanic conduits and application to the ad 79 eruption of vesuvius abstract the flow of gas magma and pyroclasts through a volcanic conduit produces erosion of the conduit wall erosion may be produced by the impact of pyroclasts on the conduit wall fluid shear stress at the wall conduit wall collapse and volcanic tremor using a two phase flow non equilibrium model of magma ascent along the volcanic conduits demonstrated that the erosion due to the impact of particles on the wall can occur only above the magma fragmentation level of the conduit where the particles or pyroclasts remove the wall material by an abrasion process this abrasion process was found to be the largest near the conduit exit where the gas magma velocities are the largest the erosion due to the fluid shear stress at the wall can be produced along the entire length of a conduit depending on the wall roughness and yield strength of wall rocks this shear stress is the largest near the magma fragmentation level where the gas magma viscosity and velocity gradients are very large the collapse of conduit wall due to the difference between the gas magma and lithostatic pressures can occur below and above the magma fragmentation level causing the production of lithics directly when the wall collapses inward and indirectly when the wall collapses outward the effectiveness of different erosion mechanisms was tested with the magma characteristics conduit geometry and wall rock properties pertaining to the ad 79 eruption of vesuvius it was found that during the white and gray magma plinian eruption phases the lithics should had come from the deep as well as from the shallow regions of the conduit the conclusions from erosion modeling are also consistent with the limited field data whereby the gray magma phase deposits are associated with larger lithic content and larger proportion of deep limestone fragments

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

significance of polycyclic aromatic hydrocarbons pahs in permian triassic boundary sections abstract in this study the abundances of several polycyclic aromatic hydrocarbons pahs table 1 i xxi have been measured throughout three permian triassic p tr sections from meishan south china kap stosch area east greenland and peace river basin western canada dibenzothiophene i and dibenzofuran ii were found to decrease in abundance just before or shortly after the p tr transition in all three sections while perylene iii was observed to increase in abundance at the onset of the main extinction horizon bed 25 in meishan perylene has been attributed to a wood degrading fungal source and therefore it seems possible these phenomena are related to the demise of land plants further distinct patterns of various combustion derived pahs occurring in each section imply that forest fire events occurred within the late permian and early triassic in the meishan section high amounts of combustion derived pahs pyrene iv fluoranthene v benzo a anthracene vi benzofluoranthenes sum i e vii benzo a pyrene viii benzo e pyrene ix and coronene x occur within bed 25 also containing ash attributed to the fallout from massive volcanic eruptions in siberia and or china

magmatic hydrothermal fluids and volatile metals in the spirit lake pluton and margaret cu mo porphyry system sw washington usa the halogen bearing minerals tourmaline amphibole and biotite formed during magmatic hydrothermal processes associated with the late stage cooling of the spirit lake granitoid pluton mt st helens wa and with the younger sulphide mineralised rocks of the margaret cu mo porphyry deposit located entirely within the pluton major and trace element discrimination suggests that one tourmaline population crystallised from fractionated late stage melt pockets in granodiorite monzogranitic dykes of the pluton these coarse euhedral oscillatory and complexly sector zoned uvite tourmalines span a limited range in mg mg fe mg space 0 4 0 7 apfu and show the highest ti ca f nb and ta contents and low x site vacancies 0 6 apfu lower ca and f contents and the highest li as and hree contents 80 ppm li 1200 ppm as this population appears to record direct rapid crystallisation from magmatic meteoric fluid s bearing the signature of the breakdown of primary feldspars and pyroxenes with fluid exsolution from fractionated melt patches likely triggered by the formation of the previous generation of tourmaline mineralised porphyry deposit tourmaline compositions from the stockwork span a much larger range in mg space 0 05 0 9 apfu and are almost entirely ca free x sites of these schorl tourmalines are dominated by na or vacancies and the y sites are strongly fe enriched the highest mn and zn concentrations 4000 and 1000 ppm respectively potentially reflect the composition of mineralising fluids during ore deposition a number of boron isotopic analyses yield predominantly heavy boron but 11b values range from 5 2 to 6 2 and average 1 4 whilst most plutonic tourmalines conform to reported a and c sector element partitioning models those from the mineralised porphyry show large and variable sector fractionation differences suggesting that external controls may also be important wider evidence for late stage pervasive metasomatism by halogen bearing exsolved fluid s is provided by the high mg 70 secondary amphiboles and biotites from within the spirit lake pluton where the amphiboles are clear replacement products of primary pyroxenes fluid halogen fugacity ratios calculated from the biotite compositions overlap with other global mineralised porphyry systems despite not being immediately associated with sulphide ores the evidence suggests complex fluid processes and the coincidental development of the mineralised porphyry system within the pluton heat fluids and metals were therefore likely supplied by a later phase of magmatism unrelated to the consolidation of the main spirit lake granitoid these new constraints on magmatic hydrothermal fluid signatures have wider applicability to potentially tracing proximal barren and mineralised processes and for distinguishing between formation mechanisms for primary and secondary halogen bearing minerals

a model of vulcanian eruptions at galeras volcano colombia abstract a series of six vulcanian eruptions at galeras volcano colombia occurred during 1992 1993 these eruptions followed the emplacement of a lava dome in late 1991 which was accompanied by cooling crystallizing and partial solidification of the column of magma plugging the conduit five of the eruptions were preceded by episodes of monochromatic long period seismicity suggesting cyclic pressurization of the magma the quiescent intervals between eruptions generally decreased with each successive eruption we propose a model of gas release from magma into confined stationary pore spaces by 5 10 crystallization of anhydrous minerals causing repeated overpressurization of the magmatic system using initial lithostatic pressures of 20 100 mpa 800 3900 m depth gas buildup by crystallization indicates overpressures of 3 17 mpa which is the approximate fracture criterion for a magma chamber our galeras data suggest two models of pressurization 1 gas exsolution may have occurred at similar depths but with progressively smaller overpressures being developed before each successive eruption according to this model the comparatively long quiescent periods between the first eruptions resulted in relatively large amounts of gas exsolution from the magma and accumulation in pore spaces whereas the shorter quiescent periods for the later eruptions exsolved less gas the decrease in overpressure with time may have resulted from progressive fracturing of partly solidified magma during the eruptions which progressively decreased the tensile strength and increased the permeability of the magma 2 since overpressures are smaller at shallower depths for a given amount of crystallization the first eruptions of 1992 1993 were caused by gas exsolution at shallow depths while the last eruptions having shorter quiescent intervals resulted from a greater amount of gas exsolution at greater depths in this case the rate of gas exsolution varied as a function of depth the two scenarios for pressurization may be combined into a more general model involving edifice weakening and the development of a shallow hydrothermal system from continued degassing of the magma plug as weakening of the edifice formed an extensive system of fractures the shallow hydrothermal system deepened due to meteoric water input and magmatic degassing with time a greater number of fractures were filled and partly sealed by hydrothermal minerals at progressively deeper levels as a result the source of the overpressure also deepened with time

crustal deformation in the mid may 1991 crisis preceding the extrusion of a dacite lava dome at unzen volcano japan abstract tilt observations at fg1 station located about 680 m west of the central crater of unzen volcano southwestern japan revealed details about the process of magma ascent during the mid may 1991 crisis just before the appearance of a lava dome crustal deformations measured during this period can be interpreted by a combination of upward growth of a buried magma column and lateral intrusion of a dike modeled by a vertical line source and a planer tensile dislocation in an elastic half space marked change in tilt was observed at first in the ew direction at fg1 during may 11 14 suggesting the ascent of a magma column with a diameter of about 40 m from about 300 m to 160 m in depth beneath the central crater after the interruption of the rise of the magma column magma began to intrude laterally as a dike on may 15 toward approximately the n80 w direction this resulted in a large tilt change essentially in the ns component at fg1 the horizontal extent of the dike might have exceeded 400 m in a few days with a thickness of about 6 m on may 17 the magma column started to rise again probably because the impediment to magma ascent was fractured by the growth of the dike the top of the magma column finally reached to the crater bottom probably on may 19 and a new lava dome was actually observed on may 20 after which the remarkable upward tilt to the south at fg1 due to the dike intrusion decreased rapidly the deformation after may 20 can be interpreted by a gradual increase in the thickness of the dike up to 13 m by the end of may 1991 although large errors are inevitable in estimated values because of a lack of sufficient data the present results confirm the importance of making continuous observations of crustal deformation near the summit areas of active volcanoes in order to clarify the underground processes of magma movement leading to eruptions

effect of igneous intrusion on the organic geochemistry of a siltstone and an oil shale horizon in the midland valley of scotland abstract the effect of rapid thermal stress on the organic geochemistry of a siltstone intruded by a quartz dolerite dyke and an oil shale intruded by an alkali dolerite sill has been studied using optical petrography rock eval pyrolysis gas chromatrography and gas chromatography mass spectrometry maturity dependent ratios derived from both the aliphatic and aromatic hydrocarbon fractions corroborate the observation of raymond and murchison 1988b that the alkali dolerite sills which were intruded soon after sedimentation had a lesser effect than the later quartz dolerite intrusions the maturity parameters based on the alkylnaphthalene and alkylphenanthrene isomer ratios are more suitable for studying maturity variations in heat affected samples than those based on the commonly used aliphatic biological markers these aromatic compounds survive to higher ranks and the isomer ratios continue changing

petrological and organic geochemical characteristics of coal samples from florina lava moschopotamos and kalavryta coal fields greece abstract coal samples from florina vevi lava moschopotamos and kalavryta basins greece have been subjected to petrographic and organic geochemical analysis the reflectance of the samples ranged from 0 26 to 0 42 which ranks them as soft brown coals and sub bituminous c coals lower reflectance values were encountered in the florina and kalavryta coals whereas higher values were obtained for lava and moschopotamos samples maceral composition of the samples from the florina area shows a high concentration of textinite a and texto ulminite a the samples from the lava and moschopotamos area are comparatively rich in humodetrinite samples from florina are rich in resinite whereas samples from lava are rich in liptodetrinite rock eval pyrolysis data show that the samples from florina and kalavryta have generally high hi si and s2 and low t max values the coal samples from moschopotamos and lava show the opposite having low hi s1 and s2 values these distinct differences are related to the maceral composition tissue rich in resinitic material and rank of the coals gas chromatography of the saturate fraction indicates that the samples from the lava and moschopotamos are rich in n alkanes from n c 23 to n c 33 in contrast the samples from florina are rich in diterpanes whereas those from kalavryta are rich in sesquiterpenoids gas chromatography mass spectrometry of the saturate fraction reveals that the diterpenoids present in the lignites from kalavryta are derivatives of abietanic acid and pimaric acid which are found in pinaceae the lignites from florina mainly contain the diterpane phyllocladane which implies an input from cupressaceae and or taxodiacaea the difference in the composition of these xylitic lignites may be attributed to differences in gymnosperm input as a response to climatic change as the kalavryta coals are of pliocene age whereas the florina coals are of miocene age the study suggests that the petrology and organic geochemistry of these coals are related to the different peat forming plant communities that were present in the florina kalavryta lava and moschopotamos basins a mainly non woody angiosperm dominated vegetation made up the peat that went to form the coal deposits of lava and moschopotamos while the florina and kalavryta lignites were formed by peats derived mainly from gymnosperms

deformation controlled cation diffusion in tourmaline a microanalytical study on trace elements and boron isotopes abs tract plastic deformation of variable intensity has modified primary textures composition and element distribution in tourmaline from a mylonitic pegmatite from the nw argentinean sierras pampeanas the primary concentric tourmaline zonation has been overprinted and partly destroyed by synkinematic cation diffusion that occurred under amphibolite facies p t conditions textural changes include bending of crystals formation of subgrains and subgrain rotation leading locally to recrystallization of tourmaline some parts of deformed crystals were less affected or unaffected by plastic deformation and secondary cation diffusion two principal processes intracrystal trace element diffusion and matrix exchange of trace elements caused the compositional variations in deformed tourmaline domains intracrystal diffusion partly or completely destroyed the primary trace element zonation by cation diffusion from zones of high to low concentration small cations occupying the y position are readily mobilized even by weak deformation whereas large cations on the x site require higher deformation intensity to be mobilized and show less pronounced or no homogenization of the primary zonation matrix exchange between tourmaline and co existing solid or fluid phases generally leads to trace element loss from deformed tourmaline domains the extent of the matrix exchange is primarily controlled by the compatibility of mobilized cation species with matrix phases during mylonitization in contrast the b isotopic compositions in deformed and undeformed crystal domains are uniform indicating absence of significant b diffusion and isotope fractionation during crystal growth and plastic deformation i e the activation energy to move b in tourmaline must be too high even for intense plastic deformation to overcome

saturated and aromatic diterpenoids and triterpenoids in eocene coals and mudstones from china several series of saturated diaromatic triaromatic c ring cleaved and triaromatic diterpenoids and triterpenoids have been detected in 4 immature coal and mudstone samples a number of these compounds appear to represent intermediates in a series of postulated pathways for progressive aromatization of biogenic diterpenoids and triterpenoids diagenetic pathways for the formation of tricyclic aromatic hydrocarbons from abietane and pimarane type diterpenoid precursors and for the formation of diaromatic triaromatic c cleaved and triaromatic hydrocarbons from amyrin and other triterpenoid precursors are proposed saturated and aromatized abietanes pimaranes and phyllocladanes which are the most abundant compounds in all 4 samples indicate a predominant higher plant input which can be related to the coniferales group but not to individual plant families amyrin and other triterpenoid derived triaromatic and triaromatic c ring cleaved hydrocarbons with triterpenoid structures are thought to be characteristic for angiosperms the relative concentrations of the triaromatic and triaromatic c ring cleaved hydrocarbons are higher in samples 9602 mudstone and 9603 coal than samples 9601 coal and 9604 mudstone indicating samples 9602 mudstone and 9603 coal contain relatively more angiosperm derived organic matter than samples 9601 coal and 9604 mudstone the distribution patterns and the relative concentrations of saturated and aromatic diterpenoids and triterpenoids thus are valuable markers for the determination of the relative contents of biological sources of organic material in geological samples

geochemical characteristics of crude oils from the cuyo basin argentina abstract crude oils from the triassic cuyo basin are thought to be derived from a fresh water lacustrine source rock mainly the upper triassic organic rich shales of cacheuta fm by means of gc and gc ms methods the oils were analysed for characteristic compounds which may reflect biological input to the source sediments and maturity variations pristane phytane ratios distributions of n alkanes and the presence of significant amounts of bacteriohopanoid derived compounds hopanes 8 14 secohopanes 8 14 monoaromatic secohopanoids benzohopanes together with bicyclic sesquiterpanes in all the samples studied are taken as an indication of possible reworking of algal organic matter by bacteria sterane distributions were consistent with a lacustrine origin of the oils the occurrence of selected alkylnaphthalene derivatives as dominant compounds in the aromatic hydrocarbon fractions was a matter of special attention in the study the variation of their concentrations with the maturity of the oils is compared to that of monoaromatic 8 14 secohopanoids the results suggest that 1 2 5 trimethylnaphthalene in these oils is a product of hopanoid degradation under mild thermal conditions

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

tourmaline rich features in the heemskirk and pieman heads granites from western tasmania australia characteristics origins and implications for tin mineralization distinctive magmatic hydrothermal tourmaline rich features have developed in the heemskirk and pieman heads granites from western tasmania australia they are categorized as tourmaline rich patches orbicules cavities and veins based on their distinctive morphologies sizes mineral assemblages and contact relationships with host granites these textural features occur in discrete layers in the roof zone of granitic sills within the heemskirk and pieman heads granites tourmaline patches commonly occur below a tourmaline orbicule rich granitic sill tourmaline filled cavities have typically developed above the tourmaline quartz orbicules in the upper layer of the white phase of the heemskirk granite tourmaline quartz veins penetrate all exposed levels of the granites locally cutting tourmaline orbicules and cavities the tourmalines are mostly schorl fe rich and foitite with an average end member component of schorl 45 dravite 6 tsilaisite 1 uvite 0 fe uvite 3 foitite 31 mg foitite 4 olenite 10 element substitutions of the tourmalines are controlled by femg 1 al y x square r2 na 1 and minor alo al y r2 oh 1 where r2 fe2 mg2 mn2 exchange vectors several trace elements in tourmaline have consistent chemical evolutions grouped from tourmaline patches through orbicules and cavities to veins there is a progressive decrease of most transition and large ion lithophile elements and a gradual increase of most high field strength elements these compositional variations in the different tourmaline rich features probably relate to element partitioning occurring in these phases due to volatile exsolution and fluxing of aqueous boron rich fluids that separated from the granitic melts during the emplacement of s type magmas into the shallow crust 4 to 5 5 km tourmalines from the heemskirk granite are enriched in fe na li be sn ta nb zr hf th and rare earth elements relative to the tourmalines from the pieman heads granite but depleted in mg mn sc v co ni pb sr and most transition elements these results imply that bulk compositions of the host granites exert a major control on the chemical variations of tourmalines the trace element compositions of tourmalines from the sn mineralized heemskirk granite are different from those of the barren pieman heads granite trace element ratios e g zn nb co nb sr ta and co la and sn concentrations in tourmaline can distinguish the productive heemskirk granite from the barren pieman heads granite

comparison of resinite related aromatic biomarker distributions in cretaceous tertiary coals from canada and germany a set of 13 cretaceous tertiary coals from western canadian coal deposits and two cretaneous coals from the southern part of the lower saxony basin of germany have been investigated using microscopial and organic geochemical methods the coals are in the ranl range of lignite to medium volatile bituminous 0 37 1 13 rr petrographically the coals are characterized by varying proportions in vitrinite inertinite and liptinite groups in most of the coals resinite constitutes the major liptinite component both of the german wealden coals are composed exclusively of conifer needles gc ms analyses indicate differences in the composition of resin related molecular biomarkers comparing samples from both deposits in the canadian coals of moderate rank 0 4 0 8 rr resin related napthalene derivatives are associated with tricyclic aromatic hydrocarbons such as retene abieta 6 8 11 13 tetraene simonellite and c5 phenanthrene samples higher in rank about 1 1 rr provide fully aromatized and partly desalkylated phenanthrene homologues generation of 1 methylphenanthrene from retene during maturation affects molecular rank parameters like mpr and mpi 1 additionally an intra seam homogenization of resin derived aromatic hydrocarbon is observed in comparison the german wealden coal extracts are dominated by bicyclic aromatic hydrocarbons and they are poor in tricyclic hydrocarbons analyses of hand picked macerals resinites and cutinites by thermodesorption coupled to gc ms indicate the presence of two potential sources for the naphthalene derivatives c4 tetralin is primarily associated with the resins of abietites linkii 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnapthhalene are probably derived from the fluorinite filling of the conifer needles

reconstruction of floral changes during deposition of the miocene embalut coal from kutai basin mahakam delta east kalimantan indonesia by use of aromatic hydrocarbon composition and stable carbon isotope ratios of organic matter the distribution of aromatic hydrocarbons and stable carbon isotope ratios of organic matter in a series of nine miocene embalut coal samples obtained from nine coal seams of kutai basin east kalimantan indonesia were studied the rank of the embalut coals ranged from lignites to low rank sub bituminous coals 0 36 0 50 rr based on measurements of huminite reflectance the aromatic hydrocarbon fractions of all coal samples were dominated by cadalene in the lower boiling point range and picene derivatives in the higher boiling point range of the gas chromatograms cadalene can be attributed to the contribution of dipterocarpaceae and various hydrated picenes to the contribution of additional angiosperms to the coal forming vegetation the picenes originate from alpha and beta amyrin however in some coal samples minor amounts of simonellite and retene were also detected which argues for an additional contribution of gymnosperms conifers to coal forming vegetation preferentially in the middle miocene and at the beginning of the late miocene the results of stable carbon isotope ratios d 13

control of magma flow in dykes on cyclic lava dome extrusion 1 lava dome eruptions are commonly characterized by large fluctuations in discharge rate with cyclic behaviour on time scalesranging from hours to decades examples include bezymianny volcano russia merapi java santiaguito guatemala mt st helens usa mt unzen japan and soufriere hills volcano montserrat previous models have assumed simple cylindrical conduits for magma transport but extrusions are mainly fed by dykes with cylindrical geometries developing only at shallow levels the widths of dykes embedded in an elastic medium are influenced by local magma pressure affecting flow rates and system dynamics strongly we develop a model for magma flow in dykes which predicts intense pulsations of magma extrusion for the case of a constant source pressure the period time scale is determined by the elastic deformation of the dyke walls and the length to width ratio of the dyke the dyke acts like a volumetric capacitor storing magma as pressure increases and then releasing magma in a pulse of extrusion for the soufriere hills volcano cyclic extrusions with time scales of a few weeks are predicted for dykes 300 500 m long and 3 6 m wide matching observations the model explains the sharp onset of tilt pulsations and seismic swarms citation costa a o melnik r s j sparks and b voight 2007 control of magma flow in dykes on cyclic lava dome extrusion geophys res lett 34 l02303 doi 10 1029 2006gl027466

novel families of tetra and hexacyclic aromatic hopanoids predominant in carbonate rocks and crude oils two novel families of monoaromatic geomarkers related to hopanoids have been separated and characterized in sediments and crude oils the benzohopanes c32 c35 1 and the ring d aromatized 8 14 secohopanoids c27 c35 4 and 5 both series are particularly abundant in many carbonate samples where they amount to approximately 100 p p m per component in some crude oils but can also be detected in other environments the benzohopanes have been separated as pure compounds by high performance liquid chromatography and identified by x ray diffraction the structure of the 8 14 secohopanoids mostly relies on spectroscopic data nmr and ms and comparison with synthetic analogs both families must be formed in the subsurface from bacterial c35 hopanoid precursors but the benzohopanes seem to occur at an earlier stage of sedimentation the two series appear in varying distributions in the different samples and may therefore be potentially useful as geochemical correlation parameters

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

organic geochemistry and petrography of tertiary coals and carbonaceous shales from argentina a series of eight tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0 50 and 0 58 were extracted fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by gc and gc ms additionally a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation the saturated hydrocarbon fractions displayed the typical n alkane distribution for coals of this rank with cpi values between 2 0 and 3 1 among the branched cyclic compounds pristane and homohopane were recognised as relevant components pointing to an oxic depositional environment detection of benzohopanes c32 c35 in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass taking into consideration the pr ph ratios ash contents and microscopical characteristics of the samples aspects of the possible degradation of hopanetetrol to homohopane are discussed resin derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and although minor compounds they are interpreted to be a sign of the contribution of podocarpaceae and araucareaceae to the coal swamp aromatic compounds were dominated by alkylnaphthalene derivatives presumably formed by c ring cleavage and aromatisation of higher plant derived pentacyclic triterpenois which were main components in the high boiling range of the fractions investigated angiosperms especially fagaceae are postulated as source for these polycyclic compounds and hence for some of the polyalkylated aromatic bicyclics detected

transient two dimensional dynamics in the upper conduit of a rhyolitic eruption a comparison of closure models for the granular stress to elucidate the role of particle collisions in redistributing momentum after fragmentation a numerical study was performed comparing the behavior of an inviscid or collision less granular material with a granular material whose viscosity and pressure were modeled using kinetic theory the granular viscosity calculation is sensitive to particle size and three particle sizes were considered 0 0002 m 0 002 m and 0 02 m a critical volume fraction of gas 0 75 identifies the onset of fragmentation dividing the region of rhyolitic magma with dispersed bubbles from the region of turbulent gas with dispersed particles the transient simulations can be divided into two dynamic regimes an initial shock followed by a transition to steady state during the initial shock phase treatment of the granular pressure and viscosity led to greater particle velocities relative to the inviscid calculation due to the development of higher gas pressure at fragmentation however as steady state is approached the viscosity slows the particle phase relative to the inviscid counterpart for particles greater than a millimeter the modeled sub millimeter particle velocity was insensitive to the treatment of the granular pressure and viscosity centimeter scale particles have a much higher granular viscosity up to 10 1 pa s and the kinetic theory calculation is thus relevant in these conditions after reaching steady state the differential velocity between gas and particles at the conduit exit correlates with particle size for both the inviscid and granular viscosity calculations negligible differential velocity develops for sub millimeter particles but centimeter scale particles exit the conduit with 5 differential velocity between phases

late magmatic immiscibility during batholith formation assessment of b isotopes and trace elements in tourmaline from the land s end granite sw england quartz tourmaline orbicules are unevenly distributed in the roof segment of the land s end granite sw england this study shows that the orbicules formed from an immiscible hydrous borosilicate melt produced during the late stages of crystallization and differentiates tourmaline formed by dominantly magmatic and dominantly hydrothermal processes trace elements and boron isotope fractionation can be tracked in tourmaline and create a timeline for crystallization tourmaline from the granite matrix has higher v cr and mg content and is isotopically heavier than the later crystallizing inner orbicule tourmaline overgrowths of blue tourmaline occurring together with quartz showing hydrothermal cathodoluminescence textures crystallized from an aqueous fluid during the very last crystallization and are significantly higher in sr and sn and isotopically heavier tourmaline associated with sn mineralization is also high in sr and sn but has boron isotopic compositions close to that of the magmatic tourmaline and is not formed by the same fluids responsible for the blue overgrowths the ore forming fluids precipitating tourmaline and cassiterite are likely derived from the same magma source as the granite but exsolved deeper in the magma chamber and at a later stage than orbicule formation tourmaline from massive quartz tourmaline rocks is concentrically zoned with major and trace element compositions indicating crystallization from a similar melt as for the orbicules but shows a more evolved signature

textures water content and degassing of silicic andesites from recent plinian and dome forming eruptions at mount pelee volcano martinique lesser antilles arc previous petrological and phase equilibrium experimental studies on recent silicic andesites from mount pelee volcano have evidenced comparable pre eruptive conditions for plinian and dome forming pelean herein eruptions implying that differences in eruptive style must be primarily controlled by differences in degassing behaviour of the mount pelee magmas during eruption to further investigate the degassing conditions of plinian and pelean magmas of mount pelee we study here the most recent mount pelee s products p1 at 650 years b p 1902 and 1929 eruptions which cover a range of plinian and pelean lithologies for bulk rock vesicularities glass water contents glass inclusions in phenocrysts and matrix glasses and microtextures water contents of glass inclusions are scattered in the plinian pumices but on average compare with the experimentally deduced pre eruptive melt water content i e 5 3 6 3 wt whereas they are much lower in the dominant pelean lithologies crystalline poorly vesicular lithics and dome samples this indicates that the glass inclusions of the pelean products have undergone strong leakage and do not represent pre eruptive water contents the water content of the pyroclast matrix glasses are thought to closely represent the residual water content in the melt at the time of fragmentation determination of the water contents of both the pre eruptive melt and matrix glasses allows the estimation of the amount of water exsolved upon syn eruptive degassing we find the amount of water exsolved during the eruptive process to be higher in the pelean products than in the plinian ones typically 90 100 and 65 70 of the initial water content respectively the vesicularities calculated from the amount of exsolved water compare with the measured vesicularities for the plinian pumices consistent with a closed system near equilibrium degassing up to fragmentation by contrast the low residual water contents low groundmass vesicularities and extensive groundmass crystallization of the pelean products are direct evidence of open system degassing microtextural features including silica bearing and silica free voids in the pelean lithologies may represent a two stage vesiculation

infrared and mossbauer study of brazilian tourmalines from different geological environments infrared ir spectra in the oh stretching region and mossbauer spectra ms have been acquired for natural tourmalines from magmatic and hydrothermal deposits in the state of minas gerais brazil in the magmatic environment samples of tourmaline were collected from granitic pegmatites and granitoids in the former the elbaite schorl series is prevalent while in the latter the schorl species is dominant tourmalines from hydrothermal gold deposits are typically intermediate members of the dravite schorl series whereas the uvite and fe bearing uvite species are present in tourmaline samples from a magnesite deposit different behaviors are discussed in terms of local lattice environment geological history fluid rock interaction or magma evolution and degree of crystallinity