sample scale carbon isotopic variability and diverse biomass in the paleoproterozoic zaonega formation russia abstract the stratigraphic record of organic matter in the c 1 97 ga zaonega formation zf onega basin northwestern russia exhibits a distinct negative 13c excursion 13corg from 25 to 40 vpdb which was previously interpreted either to reflect a disturbance in the global carbon cycle after the great oxidation event or to have been caused by an increase in basinal methanotrophic activity in order to assess the nature of primary biomass and the effects of post depositional alteration we here report the sample scale carbon isotopic characteristics of organic matter in two drill cores from the zf covering 500 m of stratigraphy by using secondary ion mass spectrometry sims the results confirm that the organic matter has to a large extent preserved the primary isotopic signatures whereas secondary effects are limited

extreme 13ccarb enrichment in ca 2 0 ga magnesite stromatolite dolomite red beds association in a global context a case for the world wide signal enhanced by a local environment abstract the palaeoproterozoic positive excursion of 13 c carb is now considered as three positive shifts of 13 c carb separated by returns to 0 which all occurred between 2 40 and 2 06 ma this isotopic event is unique in terms of both duration 300 ma and 13 c enrichment up to 18 the mechanism responsible for one of the most significant carbon isotopic shifts in earth history remains highly debatable to date 13 c of 10 to 15 cannot be balanced by organic carbon burial forg as there is no geological evidence for an enhanced corg accumulation prior to or synchronous with the excursion instead termination of these excursions is followed by formation of a vast reservoir of 13 c depleted organic material 45 at shunga and by one of the earliest known oil generation episodes at 2 0 ga none of the three positive excursions of 13 c carb is followed by a negative isotopic shift significantly below 0 as has always been observed in younger isotopic events reflecting an overturn of a major marine carbon reservoirs this may indicate that forg was constant implying that the mechanism involved in the production of corg was different onset of intensive methane cycling resulting in c change is another possibility the majority of sampled 13 c carb rich localities represents shallow water stromatolitic dolostones red beds and evaporites formed in restricted intracratonic basins and may not reflect global 13 c carb values closely spaced drill core samples n 73 of stromatolitic dolostones from the 1980 27 ma tulomozerskaya formation in the onega palaeobasin russian karelia have been analysed for 13 c carb and 18 o carb in order to demonstrate that different processes were involved in the formation of 13 c carb rich carbonates the 800 m thick magnesite stromatolite dolomite red beds succession formed in a complex combination of environments on the karelian craton peritidal shallow marine low energy protected bights barred basins evaporative ephemeral ponds coastal sabkhas and playa lakes the carbonate rocks exhibit extreme 13 c enrichment with 13 c values ranging from 5 7 to 17 2 vs v pdb mean 9 9 2 3 and 18 o from 18 6 to 26 0 vs v smow mean 22 0 1 6 the tulomozerskaya isotopic excursion is characteristic of the global 2 4 2 06 ga positive shifts of carbonate 13 c 12 c although it reveals the greatest enrichment in 13 c known from this interval an external basin s is considered to have provided an enhanced corg burial and global seawater enrichment in 13 c the global background value for the isotopic shift at tulomozero time ca 2 0 ga is roughly estimated at around 5 an explosion of stromatolite forming microbial communities in shallow water basins evaporative and partly restricted environments high bioproductivity enhanced uptake of 12 c and pene contemporaneous recycling of organic material in cyanobacterial mats with the production and consequent loss of co2 and ch4 are believed to be additional local factors which may have enhanced 13 c from 5 up to 17 such factors should be taken into account when interpreting carbon isotopic data and attempting to discriminate between the local enrichment in 13 c and globally enhanced 13 c values we propose that many previously reported 13 c values from other localities where environmental interpretations are not available or have not been taken into account may not represent the global 13 c values

oblique convergence and deformation along the kuril and japan trenches the hypothesis that present day deformation within the southern kuril forearc is driven by oblique subduction of the pacific plate is tested using 397 horizontal slip directions derived from shallow thrust earthquakes from the kuril and japan trenches for the period 1963 1991 a simple two plate model fits the 397 slip vectors significantly worse than a model that permits strike slip motion of the southern kuril forearc relative to the overlying plate weighted mean slip directions along the southern kuril trench are systematically rotated toward the direction orthogonal to the trench which implies that the net convergence is partitioned into less oblique subduction and trench parallel displacement of the southern kuril forearc the angular discrepancy between the observed slip direction and the direction predicted by the nuvel 1 pacific north america euler vector implies that the southern kuril forearc translates 6 11 mm yr 1 to the southwest relative to the overlying north american plate these results are consistent with geologically geodetically and seismologically observed convergence at the leading edge of the forearc sliver in southern hokkaido and with previously inferred extension at the trailing edge of the sliver which is located at the bussol strait at 46 n the percentage of the oblique component of the rigid plate convergence vector that is transferred into forearc strike slip motion is only 30 which may be evidence that the hokkaido honshu bend in the trench hinders southwest forearc motion or that the greater strength of oceanic forearcs impedes motion along forearc strike slip faults

karelian shungite an indication of 2 0 ga old metamorphosed oil shale and generation of petroleum geology lithology and geochemistry abstract the ca 2 0 ga old 600 m thick upper zaonezhskaya formation near lake onega nw russia contains unusually high concentrations of corg up to 98 averaging around 25 the formation contains an estimated 25 1010 tonnes of organic carbon accumulated within an area of 9000 km2 organic material is represented by shungite which forms a black dense amorphous or nanocrystalline mass consisting of c with traces of n o s and h autochthonous shungite occurs as disseminated organic material 0 1 50 corg which when mixed with migrated bitumen now pyrobitumen appears as coal like seams and lenses of semilustrous and semimat layer shungite rocks oil shales 50 75 corg the migrated bitumen originally petroleum represented by the lustrous vein and layer shungite conformably fills interbedding spaces or cross cutting joints and usually contains 80 98 corg the shungite bearing rocks of the upper zaonezhskaya formation represent one of the most richest accumulations of organic material reported from the palaeoproterozoic and one of the geologically earliest stages of petroleum generation the sediments of the zaonezhskaya formation were initially deposited in brackish water in a non euxinic lagoonal environment the high c s ratio 8 1000 with a zero intercept on the c s cross plot indicates that deposition occurred in sulphur poor water intensive synchronous volcanism may have contributed to both the enhanced delivery of nutrients and elevated sedimentation rate and eventually to the high degree of preservation of organic material the integrated data suggest that the organic material has a biogenic origin most likely algal or bacterial the organic material suffered complex catagenetic and metamorphic alteration which is reflected in 1 the four modal distribution of corg content with maxima at 5 30 65 and 95 2 highly variable 13 c org 45 to 17 3 bimodal distribution of 13 c org with maxima at 28 and 39 and 4 low h c ratios 0 005 0 2 abundant diagenetic carbonates associated with shungite rocks 13 c carb 5 to 26 and the presence of pyrite 34 s 22 to 31 reflects substantial loss of organic matter via bacterial reduction of sulphate during diagenesis the shungite rocks are characterised by a further substantial loss 50 of biologically produced organic material in the course of thermal maturation and by a depletion in 12 c 10 the isotopic composition of carbonate concretions does not indicate the involvement of fermentative diagenesis conservative estimates give 13corg of 34 as the best value of the initial biomass lustrous vein and layer shungite containing more than 80 corg are considered to be allochthonous migrated bitumen originally petroleum the semilustrous and semimat layer shungite rocks containing 55 75 corg represent oil shales with both migrated bitumen originally petroleum and autochthonous kerogen residues the oil source rocks were apparently hosted in the zaonezhskaya formation the generated oil has migrated both vertically and laterally with the highest concentration in cupola structures the locality at shunga represents the most significant volume of trapped petroleum from the study area

seismological monitoring on the 2003 tokachi oki earthquake derived from off kushiro permanent cabled obss and land based observations abstract japan marine science and technology center installed a cabled geophysical observatory system off kushiro hokkaido island in july 1999 this observatory system comprises three ocean bottom seismographs obss two tsunami gauges and a geophysical geochemical monitoring system 4 years and 2 months after the installation a megathrust earthquake the 2003 tokachi oki earthquake 26th september in japan standard time jst mjma 8 0 occurred along a plate boundary underneath a forearc basin where the system is located the system recorded clear unsaturated seismograms just at 28 6 km from the epicenter this paper demonstrates advantages brought by the cabled observatory to record the megathrust earthquake showing how earthquake detectability is improved dramatically combining permanent obs and land based observations around the region and importance of the in situ monitoring on the seismogenic zone in the present study processing obss and land based network together and comparing magnitudes of common observed earthquakes with national authorized network event detection level improved down to m 1 5 which is much lower than the previously designed as down to m 2 comparing detection level before and after installing obss we found dramatic improvement of the earthquake detection level in the interesting region real time continuous observations of microearthquakes since 1999 have brought us tremendous findings first a seismic quiescence started about 10 days before the 2003 tokachi oki earthquake second aftershock distribution is not uniform over the focal area and can be divided into several sub regions which might indicate an existence of several asperities we think that the geophysical observations helped to understand the initiation process of the rupture of the 2003 tokachi oki earthquake and that observations including seismological geodynamic hydrogeological and the other multidisciplinary observations would provide a clue to future understanding of seismogenic processes at subduction zones

petroleum surface oil seeps from a palaeoproterozoic petrified giant oilfield early palaeoproterozoic rocks from the onega basin in russian fennoscandia contain evidence for substantial accumulation and preservation of organic matter up to 75 wt total organic carbon with an estimated original petroleum potential comparable to a modern supergiant oilfield the basin contains a uniquely preserved petrified oilfield including evidence of oil traps and oil migration pathways here we report the discovery of the surface expression of a migration pathway along which petroleum was flowing from the sub surface this surface oil seep the first occurrence ever reported from the palaeoproterozoic appears as original bitumen clasts redeposited in palaeoproterozoic lacustrine turbidites the 13corg of clastic pyrobitumen ranges between 35 4 and 36 0 n 14 which is within the range of interbed and vein trapped fossil oil 46 and 24 suggesting similar source biogenic organic matter whose isotopic composition was modified during thermal maturation is the likely source for the migrated hydrocarbon

source complexity of the 1988 armenian earthquake evidence for a slow after slip event we analyzed teleseismic p and s waves using a multiple event deconvolution method to investigate the source process of the spitak armenia earthquake of december 7 1988 teleseismic long period body waves exhibit complex waveforms significantly more complex than those normally seen for an event of this size we identified two groups of subevents one is a group of strike slip events during the first 20 s the other is a dip slip event initiating at about 30 s after the initial rupture the tensor sum of all the subevents is essentially strike slip strike 302 dip 59 rake 143 with a scalar moment of 1 47 10 19 n m the seismic moment of the dip slip event strike 89 dip 60 rake 88 is 5 6 10 18 n m nearly 40 of the total and the moment release rate is slower than the other subevents with a strike slip mechanism we call this event a slow after slip event the mechanism of the after sup event is consistent with the present day deformation pattern in the caucasus where north south compression is predominant due to the continental collision between the arabian plate and the russian platform this result suggests that in a region where both strike slip motion and crustal shortening are taking place like southern california a large strike slip event may accompany large thrust events and vice versa in order to determine the total coseismic deformation pattern it is essential to resolve these multiple events in time space and mechanism

evidence for pervasive petroleum generation and migration in 3 2 and 2 63 ga shales petroleum generation largely occurs through the thermal decomposition of organic matter the presence of oil bearing fluid inclusions and pyrobitumen in archean rocks suggests that similar processes operated as early as ca 3 25 ga however direct evidence of petroleum generation from potential source rocks is lacking and an abiogenic origin has been proposed for some archean carbonaceous residues pilbara craton ca 3 2 ga and ca 2 63 ga black shales were found to contain abundant kerogenous streaks and laminae as well as bitumen nodules comprising a radioactive mineral core surrounded by a carbonaceous rim and pyrobitumen formerly petroleum globules films and aggregates the bitumen nodules formed around detrital radioactive grains via polymerization of fluid hydrocarbons generated within the shale and represent diagnostic indicators of oil generation in ancient shales the bitumen globules films and masses are preserved within authigenic pyrite and demonstrate that a separate hydrocarbon phase had developed in the shale matrix during burial providing compelling evidence for in situ petroleum generation and expulsion the abundance of bitumen nodules and residual pyrobitumen in black shales across the pilbara craton suggests that hydrocarbon generation from kerogenous shales was a common phenomenon during the middle to late archean the petroleum was generated from organic matter that accumulated in marine environments most probably comprising the remains of photosynthetic and chemosynthetic organisms pointing to a sizeable biomass as early as 3 2 ga

collision and extrusion at the kuril japan arc junction hokkaido japan is a region where collision tectonics is ongoing at an arc arc junction and where lower crust is presently exposed as a result of the collision of the forearc sliver of the kuril arc with the northeast japan arc deep seated ductile deformation in metamorphic rocks has already been described but more shallow deformation is not sufficiently well observed to clarify a total history of the collision we focus on the shallow deformation in the cape erimo area in central hokkaido and discuss in detail the process of collision at this arc arc junction four phases of deformation are discriminated in the study area as follows 1 ene wsw extension immediately after sediment deposition 2 nw trending dextral strike slip 3 ne sw compression in association with the formation of conjugate sets of strike slip faults and 4 e w compression represented by the formation of low angle reverse faults the first and the second phases of faulting may be a manifestation of the oligo miocene dextral transform plate boundary between the eurasia and okhotsk plates a conjugate system of strike slip faults formed in the third phase newly clarified in this study by ne trending horizontal compression nearly normal to the nw trending dextral strike slip fault zone of the previous phase development of the strike slip faults especially the predominance of sinistral strike slip faults in the southern half of the arc arc junction must be explained by extrusion in association with collision of the forearc sliver of the kuril arc such extrusion may be a common tectonic feature even in the case of a small scale collision at an arc arc junction

the 2003 m8 0 tokachi oki earthquake how much has the great event paid back slip debts 1 a great earthquake with m8 0 the 2003 tokachi oki earthquake occurred on september 26 2003 on the plate boundary south of hokkaido at about the same epicenter as that of the 1952 m8 2 tokachi oki earthquake we estimated the coseismic slip distribution using gps data to obtain consistent results with that inferred from waveform inversions a maximum slip larger than 5m exists around 30km nne from the epicenter though the slip deficit estimated there 80 mm yr by our recent study is based on a rather short period of observation 5 years to discuss the whole seismic cycle the maximum coseismic slip roughly accounts for the slip deficit accumulated in the past 51 years assuming that the back slip rate has been nearly constant since 1952 besides the area of the largest slip however an accumulated slip deficit still remains and should be released by seismic or aseismic slip which is now actually observed in part as postseismic slip

the solubility of nickel ni in crude oil at 150 200 and 250 c and its application to ore genesis abstract the very low solubility of ni in saline brines and the correspondingly high concentration of ni in some crude oils raise the possibility that liquid hydrocarbons may be the ore fluids for black shale hosted ni deposits to test the feasibility of this hypothesis ni wires were reacted with three crude oils of differing composition at 150 200 and 250 c for up to 30 days and the concentration of ni in the oil determined at 150 c ni concentrations in the three oils remained relatively low above 200 c however ni concentrations were elevated and correlated positively with the thiol content of the oil our most thiol rich oil dissolved 217 40 4 ppm ni after 30 days at 250 c x ray photoelectron spectroscopic xps analyses performed on the residual oil coating the ni wires after reaction independently corroborate the conclusion that ni has a strong chemical affinity for thiols in crude oil in crude oils with no thiols the ni reacted with other sulfur compounds potentially sulfonic acids to form thiols significantly our xps analyses show that iron fe from the oil was embedded in the ni wire synchronously with the attachment of thiols this suggests that fe has an affinity for ni and that the thiolation of ni by crude oil may depend on the availability of fe in the oil in addition to thiols porphyrins also likely play an important role in the dissolution of ni as shown by the fact that the oil in which ni was most soluble has a high nitrogen content whereas in the other oil which is characterized by a high thiol content the ni solubility was relatively low and the nitrogen content of this oil was below the detection limit immature biodegraded oils that are sourced from carbonate rocks generally tend to be enriched in asphaltenes ni and sulfur nevertheless some mature oils acquire anomalously large thiol contents through thermochemical sulfate reduction tsr a high temperature 100 to 140 c reaction occurring commonly in carbonate reservoirs which involves the abiotic reduction of sulfate minerals at the expense of oil or bitumen thus given the affinity of ni for thiols large volumes of ni poor oil can potentially be altered by tsr to produce smaller volumes of residual oil enriched in thiols and ni

a giant palaeoproterozoic deposit of shungite in nw russia genesis and practical applications abstract occurrences of 2 0 ga mature organic material from the lake onega area nw russia constitute one of the most remarkable accumulations of organic carbon from the palaeoproterozoic the deposit occurs in a 1000 m sedimentary volcanic succession developed over an area of 9000 km 2 with an estimated total carbon reserve exceeding 25 10 10 tonnes the organic material occurs in the form of the mineraloid shungite which is a black non crystalline semi metallic material that contains 98 wt c the shungite bearing rocks were accumulated within a volcanic continental rift setting in a non euxinic brackish water lagoonal environment developed on the rifted margin of the archaean craton the occurrences of shungite bearing rocks represent a combination of a petrified oil field petrified organosiliceous diapirs and oil spills these are exemplified by three types of deposit i in situ stratified ii migrated diapirs and iii redeposited clastic in situ stratified deposits are composed of metamorphosed oil shales 80 wt c diapiric deposits form non stratified cupolas or mushroom shaped bodies composed of shungite containing 35 75 wt sio 2 and 20 55 wt c these are considered to represent organosiliceous rocks originally gels or mud the shungite rocks show abundant shrinkage cracks cryptic fluidal textures and brecciation caused by multiple fluidisation processes the current data are consistent with either diapiric or mud volcanic origins occurrences of clastic shungite are hosted by lacustrine volcanoclastic greywackes deposited from turbiditic flows shungite occurs in rocks as shungite has a heterogeneous molecular structure in which carbon occurs as 10 nm globules irregularly distributed within carbon showing no structure the unusual physicochemical and structural properties of shungite are used in diverse industrial and environmental applications including metallurgy water purification thermolysis and organosynthesis of cyclic hydrocarbons shungite is an effective sorbent for removal of organic and inorganic substances pathogenic bacteria and heavy metals from contaminated water

space time distribution of afterslip following the 2003 tokachi oki earthquake implications for variations in fault zone frictional properties 1 gps time series following the september 25 2003 ut tokachi oki earthquake m w 8 0 reveal significant deformation we use the network inversion filter to invert for the spatial and temporal evolution of afterslip in the 30 days following the earthquake afterslip is concentrated adjacent to the coseismic rupture zone between the 2003 rupture and the inferred source regions of the 1968 tokachi oki and the 1973 nemuro oki earthquakes the inversion shows a rapid decay of slip rate in the 2003 rupture zone with slower deceleration in the surrounding regions the stress velocity paths for the afterslip regions approximately follow d d in v 0 6 mpa suggestive of steady state velocity strengthening friction the complementary spatial pattern of coseismic rupture and afterslip may indicate along strike spatial variations of frictional properties although other interpretations can not be ruled out

archean oil evidence for extensive hydrocarbon generation and migration 2 5 3 5 ga archean sedimentary rocks from the pilbara craton australia contain evidence for petroleum generation and migration in the form of bitumen nodules produced by radiogenic immobilization of fluid hydrocarbons around detrital uraninite thorite and monazite grains the nodules are preserved in sandstones at several stratigraphic levels in the fortescue group 2 75 ga and lalla rookh formation 3 0 ga both nonmarine successions and in deltaic sediments of the mosquito creek formation 3 25 ga the most ancient evidence comes from the warrawoona group 3 46 ga where hydrocarbon droplets were apparently formed in situ from kerogenous sediments by flash maturation during early hydrothermal silicification bituminous relics of petroleum are also commonly preserved in shallow marine sandstones of the black reef formation 2 59 ga and the witwatersrand supergroup 2 85 ga from the kaapvaal craton south africa along with subeconomic methane accumulations in all cases the petroleum was apparently sourced from archean shales generated during the archean and migrated before the late archean or early early proterozoic metamorphism occluded fluid pathways given this widespread and abundant evidence for hydrocarbon generation and migration in archean depositional basins it seems that primordial bacterial biomass producing labile type i kerogen was often buried in sufficient quantities to successfully generate and expel petroleum depositional basins on ancient cratons clearly contained permeable rocks amenable to the migration and probably to the accumulation of petroleum thus the main factors precluding the discovery of economically exploitable hydrocarbon accumulations in archean basins are the subsequent destructive effects of deformation and metamorphism which causes trap breaching imperfect sealing or thermal obliteration however there are ancient stable cratons where such disruption may not have occurred and so petroleum explorers may wish to reassess the possibility of finding valuable hydrocarbon resources in archean rocks

wadsleyite ii a new high pressure hydrous phase in the peridotite h2o system a new hydrous silicate phase with formula mg1 71fe0 177al0 01si0 965h0 332o4 has been synthesized at 1400 c and 17 5 gpa from a hydrous iron rich mantle peridotite composition the space group is imma and unit cell parameters a 5 6884 4 b 28 9238 15 and c 8 2382 6 a so that a and c are approximately those of wadsleyite whereas b is 2 5 times that of wadsleyite the calculated density of this phase is 3 513 g cm3 in addition to five mg fe octahedra and two silicate tetrahedra the structure contains one partially occupied mg fe octahedron and one partially occupied silicate tetrahedron these two partially occupied sites may be the result of decompression of a single mg si octahedron the synthesis of this phase which has not been previously noted or described indicates that the crystal chemistry of h incorporation into high pressure spinelloid structures is more complex than previously thought whereas the transition zone of the earth s mantle may serve as a very large reservoir for hydrogen further work will be required to outline the relative stabilities and physical properties of the various hydrous silicates that may xist there

coseismic crustal deformation from the 1994 hokkaido toho oki earthquake monitored by a nationwide continuous gps array in japan using a brand new nationwide continuous gps array we monitored coseismic displacements from the october 4 1994 hokkaido toho oki kurile islands earthquake mjma 8 1 based on 2 week time series of site coordinates of 21 gps stations we present a coseismic deformation field of whole hokkaido within 1 cm precision for example the station at nemuro 170 km west of the epicenter moved 44 cm to the east and subsided 10 cm even stations in southern hokkaido 600 km apart from the epicenter moved a few cm horizontally toward the epicenter we compare the gps result with displacements calculated from two preliminary models assuming fault planes parallel or perpendicular to the kurile trench since the observed were far field displacements on land both models can explain the gps result

petrography and geochemistry of carbonate rocks of the paleoproterozoic zaonega formation russia documentation of 13c depleted non primary calcite the norwegian research council grant 191530 v30 to v a melezhik fully funded the work of aec vam and al atb was supported by nerc grant ne g00398x 1 to aef and arp we are grateful for sample preparation and analyses to all the personnel at ngu lab we appreciate the work on carbon and oxygen isotope analyses by julie dougans and chris taylor bojan otonicar organized and helped with the cl work at the karst research institute at postojna arrangement of toc ic and tc analyses at university of munster is acknowledged to harald strauss

new discoveries in dynamics of an m8 earthquake phenomena and their implications from the 2003 tokachi oki earthquake using a long term monitoring cabled observatory at the 2003 tokachi oki earthquake of m8 seafloor phenomena such as a generation process of tsunami seafloor uplifts turbidity current etc were observed using a cabled observatory installed on the seafloor the turbidity current was observed as a benthic storm caused presumably by the mainshock the seafloor uplifts were observed at the mainshock and continuously after the mainshock the uplifts were 0 35 0 37 and 0 12 m for epicentral distances of 25 5 31 4 and 81 7 km respectively after the mainshock a continuous uplift of the seafloor is observed at all three pressure gauge locations indicating that there was a change in the state of friction on the plate boundary interface by the mainshock in this paper we first show what was observed using the cabled observatory installed right above the focal area of the earthquake and then we discuss to summarize these phenomena associated with the earthquake its possible causes and future directions in long term monitoring of seismogenic processes

oil bearing co2 ch4 h2o fluid inclusions oil survival since the palaeoproterozoic after high temperature entrapment the 2 45 ga fluvial quartz arenites and conglomerates of the matinenda formation at elliot lake canada contain evidence for two episodes of oil migration with entrapment of oil bearing fluid inclusions the first episode was during diagenesis the second during a subsequent sub greenschist facies metamorphic event at ca 2 2 ga at temperatures exceeding 250 c remnants of the migrating hydrocarbon fluids are preserved as radiogenic pyrobitumen nodules occupying former inter granular pore spaces and as complex fluorescing oil bearing fluid inclusions the latter include two dominant types 1 aqueous oil inclusions with a minor oil phase located within original detrital grains and clasts and within rare quartz overgrowths and 2 aqueous carbonic inclusions with a minor oil phase light hydrocarbons and solids located within microfractures in detrital quartz grains and clasts the majority of type 1 inclusions were trapped with a high salinity fluid up to 25 wt nacl equivalent at relatively low temperatures between 80 and 200 c and pressures of less than 2 kbar early in the burial history of the matinenda formation type 2 inclusions were trapped during metamorphism with a much lower salinity aqueous carbonic fluid 1 2 to 17 wt nacl equivalent at temperatures between 280 and 350 c and pressures between 1 and 1 5 kbar under these conditions oil may have been miscible in the mixed fluid 13c of 25 5 and 24 9 for the pyrobitumen nodules and fluid inclusion hydrocarbon gas indicate a biogenic origin for the petroleum 13c of 16 2 for the bulk inclusion gas suggests a value of 12 for the carbonic phase hence a mix of inorganic co2 and organic co2 from either thermal alteration of organic matter or in situ chemical oxidation of hydrocarbons this study has implications for the depth and temperature at which oil may be present suggesting that deep old reservoirs may not be completely barren of petroleum the fact that hydrocarbons in the matinenda formation fluoresce indicates that aromatic compounds are able to survive temperatures of up to 350 c in a suitable geological environment

oily old ores evidence for hydrothermal petroleum generation in an archean volcanogenic massive sulfide deposit oil is formed in some modern seafloor vent systems after rapid thermal maturation of sedimentary organic matter by hydrothermal fluids although most of this petroleum escapes into the ocean some hydrocarbons may be trapped as fluid inclusions in hydrothermal precipitates or as bituminous residues in cavities however the geological record lacks evidence of this phenomenon which is unfortunate because it could be significant for understanding the history of petroleum genesis the processes of hydrothermal mineralization and perhaps the origin and early evolution of life from the pilbara craton of australia we report the discovery of pyrobitumen and oil in an early archean ca 3235 ma deep sea volcanogenic massive sulfide deposit the oil occurs in fluid inclusions within hydrothermal barite and pyrobitumen is intergrown with polymetallic sulfides petrographic textures show that the oil was emplaced and thermally altered coked before late stage sulfide mineralization the results demonstrate that subseafloor hydrothermal petroleum generation was active during the early archean possibly providing an energy and carbon source for a subsurface microbiota metabolizing hydrothermal sulfur species

mineral templated growth of natural graphite films abstract organic material in sediments is progressively altered during diagenesis and metamorphism leading to the formation of kerogen and ultimately crystalline graphite bulk carbonaceous material in metamorphic terrains typically has attained an overall degree of structural order that is in line with peak metamorphic temperature on a micron to nano scale however carbonaceous material can display strong structural variation the main factor that drives this variation is the chemical and molecular heterogeneity of the precursor biologic material specific conditions during metamorphism however can also play a role in shaping the microstructure of carbonaceous material here we describe the structural variation of carbonaceous material in rocks of the 2 0 ga zaonega formation karelia russia raman spectroscopy indicates that bulk carbonaceous matter in these rocks has experienced peak temperatures between 350 and 400 c consistent with greenschist facies metamorphism on a nano scale however a strong structural heterogeneity is observed transmission electron microscopy tem reveals the occurrence of thin films of highly ordered graphitic carbon at mineral surfaces these graphite films consisting of 20 100 individual layers completely envelop quartz crystals and occur on specific crystal surfaces of chlorite it is proposed that minerals can act as templates for the parallel ordering of carbon crystallites causing enhanced graphitization within narrow zones at mineral surfaces alternatively oriented organic precursor molecules could have been adsorbed onto charged mineral surfaces leading to thin graphitic films during later metamorphic heating episodes overall the presented observations demonstrate that mineral surfaces can initiate and accelerate localized graphitization of sedimentary organic material during metamorphism and therefore cause distinct nano scale variation in structural order

the 1993 kushiro oki japan earthquake a high stress drop event in a subducting slab a spatial slip distribution of the 1993 kushiro oki earthquake mw 7 6 is undoubtedly constrained using near field data and the detailed aftershock distribution this earthquake has peculiar features in that the slip on the fault plane is restricted within an extremely small area about 40 km 20 km between the upper and lower planes of the double seismic zone in the subducting slab beneath hokkaido the total seismic moment averaged slip and stress drop in this area are 3 3 1020 nm 5 5 m and 4 2 107 pa respectively this earthquake indicates that the region of the slab between the planes of the double seismic zone beneath hokkaido is strong enough to sustain a stress of about 4 107 pa the slip motion of this event is consistent with retrograde slab migration along the southern kuril trench and may represent a process by which retrograde motion of subducting slabs could occur

a five years super slow aseismic precursor model for the 1994 m8 3 hokkaido toho oki lithospheric earthquake based on tide gauge data 1 here we present a super slow aseismic event model prior to the magnitude 8 3 kurile island hokkaido toho oki earthquake on 4 october 1994 based on data recorded by two tide gauges located 50 150 km from the earthquake epicenter both instruments recorded several cm of subsidence during a five year period prior to the earthquake the observed signals are consistent with a precursory quasi stable slip on the western half of the hokkaido toho oki fault plane when recognized such aseismic events can considerably improve our intermediate term several years prediction capability

detectability of very slow earthquake from tide gauge records a very slow earthquake or crustal deformation with a rise time longer than the period of the free oscillation of the earth is difficult to observe on seismograms however we show that it can be detected from tide gauge records because the free oscillation of an ocean basin such as the japan sea contains longer eigenperiods than those of the solid earth actually such an oscillation was excited by the niigata earthquake of 1964 and recorded on tide gauges comparison of the tide gauge spectra of the free oscillation with the noise spectra shows that the free oscillation of the japan sea excited by a magnitude 7 class earthquake can be detected in the present tide gauge observation system further a simulation for a very slow earthquake with a source process time of 1 hour shows that the slow event which cannot be detected on seismograms is detectable on tide gauges however the smaller the slip the more difficult it is to detect the movement because of the limited dynamic range of the existing tide gauge system if a slow deformation precedes a large earthquake tide gauge records would be useful for earthquake prediction so improvements in the observation system are desirable

carbonate deposition in the palaeoproterozoic onega basin from fennoscandia a spotlight on the transition from the lomagundi jatuli to shunga events abstract several deep drillholes were made in the onega palaeobasin by the fennoscandian arctic russia drilling early earth project far deep of the international continental scientific drilling program icdp these provided fresh core material documenting the lomagundi jatuli isotopic event ljie its termination and the start of the shunga event she of an enhanced accumulation of organic matter the cored section represents the most complete known record of the end of the ljie the late phase of the ljie recorded in far deep core 11a is represented by the upper part of the tulomozero formation tf a 300 m thick unit composed of variegated dolostones siltstones and shales accumulated under oxic conditions on a shallow water carbonate platform the tf hosts the earliest known thick formations of halite and massive anhydrite low temperature greenschist facies metamorphism caused partial recrystallisation of the rocks however a primary carbonate phase the dolomite exhibits a negligible degree of post depositional alteration of the carbon isotope system the dataset of 46 bulk carbonate analyses of carbon and oxygen isotopes yielded 13 c carb ranging between 6 8 and 11 8 and revealed a positive excursion from 8 to 11 8 followed by a decline to 8 towards the top of the 300 m thick succession the cored part of the overlying zaonega formation zf recovered in holes 12ab and 13a is an 800 m thick unit composed of mixed siliciclastic carbonate facies with numerous mafic lava flows and tuff beds intruded by gabbro sills the formation represents an unprecedented episode of enhanced accumulation of organic rich rocks and preserves the earliest known supergiant petrified oilfield all typifying the she the sedimentological petrographic geochemical and c and o isotopic study of over 800 m of core throughout the zf suggests that the initial carbonate deposition occurred in a lacustrine environment then rapidly proceeding through a lagoonal setting to a rifted deepwater shelf and finally to a carbonate platform both the deepwater shelf and the platformal settings are marked by organic rich environments the primary dolomite was potentially exposed to syn and post depositional hydrothermal metasomatic alterations organic matter diagenesis metamorphic mineral reactions co 2 degassing and finally a low temperature post metamorphic calcitisation resulting in overall large fluctuations of 13 c carb between 22 and 8 the dataset of over 413 bulk carbonate analyses of carbon and oxygen isotopes screened petrographically and geochemically against post depositional alteration revealed 28 least altered samples within three stratigraphic intervals suggesting multiple positive and negative 13 c carb excursions throughout over 1000 m of stratigraphy a shift from 5 to 9 followed by a drop to near zero values marks the lower part of the zf a 13 c carb decline from 8 to below zero in the middle and upper part of the zf defines the end of the ljie a subsequent prominent negative excursion down to 6 does not show convincing isotopic evidence for influence of methanogenesis and hence appears to be of primary depositional origin an erratic positive excursion in the uppermost part of the drilled section indicates return of 13 c carb to a near normal marine value

organic rich microfossils produced by oil infiltration of hollow silicified bacteria evidence from the ca 340 ma red dog zn pb deposit alaska

precursory transient slip during the 2001 mw 8 4 peru earthquake sequence from continuous gps 1 two hour position estimates from a continuous gps station located at arequipa peru document precursory deformation beginning 18 hours prior to an mw 7 6 aftershock of the june 23rd 2001 mw 8 4 earthquake this preseismic signal appears on the north and east components as a slow displacement with an amplitude twice that of the subsequent coseismic analysis of three years of 18 hour rate measurement shows this signal to be unprecedented and beyond four standard deviations from the mean rate the best fitting centroid is directionally consistent with slow slip along the plate interface and suggests the preseismic deformation arises from creep near the aftershock rupture this implies the nazca south american plate interface slipped slowly prior to seismogenic faulting these observations indicate the mw 7 6 earthquake grew out of slow slip along the plate interface and clearly demonstrate the breadth of slip rates accommodated by subduction zone plate interfaces