a scaling law for slow earthquakes with the availability of the global positioning system and other technical advances a growing number of unusual earthquake phenomena occurring at relatively long periods have been recognized they include deep episodic tremor low frequency earthquakes slow slip events and silent earthquakes based on data chiefly from western japan ide et al report that these slow seismic events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes a diverse array of unusual earthquake phenomena occurring at relatively long periods slow events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes indicating that they comprise a new earthquake category recently a series of unusual earthquake phenomena have been discovered including deep episodic tremor1 low frequency earthquakes2 very low frequency earthquakes3 slow slip events4 and silent earthquakes5 6 7 8 9 each of these has been demonstrated to arise from shear slip just as do regular earthquakes but with longer characteristic durations and radiating much less seismic energy here we show that these slow events follow a simple unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes we find that their seismic moment is proportional to the characteristic duration and their moment rate function is constant with a spectral high frequency decay of f 1 this scaling and spectral behaviour demonstrates that they can be thought of as different manifestations of the same phenomena and that they comprise a new earthquake category the observed scale dependence of rupture velocity for these events can be explained by either a constant low stress drop model or a diffusional constant slip model this new scaling law unifies a diverse class of slow seismic events and may lead to a better understanding of the plate subduction process and large earthquake generation

investigation of the catalytic effects of indigenous minerals in the pyrolysis of aleksinac oil shale substrates steranes triterpanes and triaromatic steroids in the pyrolysates abstract evidence for catalytic effects of indigenous minerals in the pyrolysis of aleksinac oil shale kerogen was found by investigating the liquid products obtained in the micro activity test mat pyrolysis of raw shale and its demineralized substrates by comparing the corresponding fragmentograms of a demineralized sample with those of a substrate containing only silicate minerals differences in the side chain isomerisation of the steranes and triterpanes and in the side chain cleavage of the triaromatic steroids were observed these findings corroborated the previous conclusion based on mat parameters and tg weight losses that the catalytic effect of the indigenous mineral components during the pyrolysis of aleksinac oil shale kerogen is very low

recurrence behavior of short term slow slip and correlated nonvolcanic tremor episodes in western shikoku southwest japan 1 from the national research institute for earth science and disaster prevention hi net tiltmeter data we determine time dependent source processes of seven repeating short term slow slip events sse in the western shikoku region southwest japan over the period from 2002 to 2007 the tiltmeters record clear signals of sses characterized by a slow rise a week long duration and a magnitude on the order of 10 2 10 1 rad we apply a time dependent slip inversion method to the tilt records for the seven sses for each sse a slip area migrates in the strike direction of the subducting slab at a rate of 10 km d 1 comparing the slow slip area with epicenters of accompanying nonvolcanic tremors in subday time resolution we find that the two phenomena are located on a smaller area than previously reported and migrate as a group a moment rate function for each sse exhibits good correlation with the temporal change in tremor activity a comparison of the slip distributions of all of the analyzed sses shows that there is a patch of slow slip area 30 km in diameter that is shared by all of the episodes in addition the location of the slip patch is in good agreement with the epicenters of tremors and very low frequency earthquakes these lines of evidence suggest that the identified slip patch is one of the main slow slip patches in the region and a recurrence of sses may be controlled by the patch and that these slow earthquakes might be different manifestations of a single slip process on the deep plate interface

biological marker distribution in coexisting kerogen bitumen and asphaltenes in monterey formation diatomite california organic rich 18 2 monterey formation diatomite from california was studied the organic matter consist of 94 bitumen and 6 kerogen biological markers from the bitumen and from pyrolysates of the coexisting asphaltenes and kerogen were analyzed in order to elucidate the relationship between the various fractions of the organic matter while 17 alpha h 18 alpha h 21 alpha h 28 30 bisnorhopane was present in the bitumen and in the pryolysate of the asphaltenes it was not detected in the pyrolysates of the kerogen a c40 isoprenoid with head to head linkage however was present in pyrolysates of both kerogen and asphaltenes but not in the bitumen from the diatomite the maturation level of the bitumen based on the extent of isomerization of steranes and hopanes was that of a mature oil whereas the pyrolysate from the kerogen showed a considerably lower maturation level these relationships indicate that the bitumen may not be indigenous to the diatomite and that it is a mature oil that migrated into the rock we consider the possibility however that some of the 28 30 bisnorhopane rich monterey formation oils have not been generated through thermal degradation of kerogen but have been expelled from the source rock at an early stage of diagenesis

petrology of mn carbonate silicate rocks from the gangpur group india abstract metamorphosed mn carbonate silicate rocks with or without oxides assemblage i and mn silicate oxide rocks with minor mn carbonate assemblage ii occur as conformable lenses within metapelites and metacherts of the precambrian gangpur group india the petrology of the carbonate minerals rhodochrosite kutnahorite and calcite that occur in these two assemblages is reported early stabilisation of spessartine aegirine quartz and carbonates in a wide solid solution range was followed by pyroxmangite tephroite rhodonite through decarbonation reactions subsequently jacobsite hematite braunite hollandite and hausmannite have formed by decarbonation oxidation processes during prograde metamorphism textural characteristics and chemical composition of constituent phases suggest that the mineral assemblages reflect a complex relationship between protolithic composition variation of xco2

episodic slow slip events accompanied by non volcanic tremors in southwest japan subduction zone 1 episodic slow slip events have been recognized by means of tilt changes in the western shikoku area southwest japan the crustal tilt deformation was observed repeatedly with a recurrence interval of approximately six months coincident with the occurrences of major non volcanic deep tremor activities in this area observed tilt changes can be explained by slow slip events occurring around the source area of tremors in each episode the source of the slow slip event and tremor migrate simultaneously the spatial and temporal coincidence of tremors and slow slip events indicates that they both may be coupling phenomena reflecting the stress accumulation process at the subducting plate

along strike variations in short term slow slip events in the southwest japan subduction zone 1 short term slow slip events accompanied by nonvolcanic deep low frequency tremors and deep very low frequency earthquakes in southwest japan were investigated systematically by means of ground tilting studies the change in tilt usually lasts for several days by using a genetic algorithm and a least squares method we inverted the data for tilt steps that were caused by slow slip events and were detected by at least four stations situated near the source of the tremor fault parameters were estimated for 54 slow slip episodes that occurred mainly in the western shikoku northeastern kii and tokai regions from 2001 to 2008 in eastern shikoku two slow slip episodes were detected quantitatively for the first time the fault geometries of all the slow slip events were located within the belt like distribution of tremors in the transition zone between the locked and aseismic slip zones at the plate interface of the subducting philippine sea plate the spatial extent of the fault geometry corresponds roughly to the distribution of clusters of nonvolcanic tremors and very low frequency earthquakes the moment magnitudes ranged from 5 4 to 6 2 and the slip was 1 cm for each slow slip event the rate of moment release by the detected slow slip events was 40 60 of the moment accumulation expected from the relative plate motion and it showed regional differences they may reflect the along strike variations in plate convergence and or the characteristic size of the slow slip fault plane on the plate interface

aluminous granulites of the archean craton of kasai zaire petrology and p t conditions aluminous granulites of the archean 2 8 ga kasai craton zaire consist of two main mineral assemblages grt opx and sil grt crd rocks the high grade metamorphic conditions as deduced from grt opx and grt opx pl qtz equilibria are 720 c 6 7 kb considering the zoning of the same minerals the slope of the p t path is estimated at 15 b c thermobarometry involving crd is consistent with those p t conditions three cordierite forming reactions have been observed petrographically grt qtz crd opx r1 grt sil crd spl r2 grt sil crd mag r3 these equilibria are continuous reactions end member reactions have slopes less than 15 b c they are decompression reactions occurring after the metamorphic climax using available thermodynamic data r3 fixes the oxygen fugacity to a value below the qfm buffer log 10f o2 17 6 at 720 c 6 7 kb and xh2ofl 0 3 in the graphite stability field the absence of graphite in the rocks shows that the end of the granulite facies metamorphism did not occur under important co 2 streaming the polymetamorphic history of this archean craton is considered 1988 oxford university press

compositional variations in manganese carbonate micronodules from the lower proterozoic nsuta deposit ghana product of authigenic precipitation or post formational diagenesis abstract detailed petrographic and microprobe studies of micronodules identified in the manganese carbonate orebody and adjacent mn rich rocks at the 2 2 ga nsuta deposit ghana indicate distinct lithologic control on nodule structure and chemical composition nodules in the mn rich rocks adjacent to the manganese carbonate orebody conform with the well banded nature of the rock and are distinctly zoned into alternating bands compositionally dominated by mg kutnahorite and mg ca rhodochrosite individual nodules are partially or completely cemented by thin dark silica and carbonates of ca mg mn solid solution nodules in the orebody on the contrary are generally massive homogeneous consist predominantly of rhodochrosite and are only partially cemented by dark silica based on the stratigraphic relationship of the nodule bearing rocks to the manganese carbonate orebody and the variations in texture and composition observed in the nodules it would appear that the mn carbonate nodules precipitated diagenetically in response to changing pore water chemistry and or metal mn and ca supply the overall mineralogical and geochemical features indicate in addition that the nodules may have preserved original carbonate compositions both metastable and stable during burial diagenesis and low grade regional metamorphism

pore types and pore network evolution in upper devonian lower mississippian woodford and mississippian barnett mudstones insights from laboratory thermal maturation and organic petrology abstract pore evolution models from immature organic matter om rich barnett 0 42 r o and woodford 0 49 r o mudstones were compared with models previously developed from low maturity om lean boquillas eagle ford equivalent mudstones to investigate whether 1 different mineralogy siliceous vs calcareous exerts different catalytic and sorption effects and influences om pore origin and evolution and 2 different types of macerals show different om pore evolution history laboratory gold tube pyrolysis scanning electron microscopy sem and thin section petrography organic petrography and geochemical characterization were used to investigate the role of bulk mineralogy maceral type and thermal maturation on om pore evolution results suggest that mineralogy has little impact on om pore development and evolution macerals identified using both sem platy om particulate om organic mineral admixtures tasmanites and organic petrology vitrinite inertinite amorphous organic matter aom bituminite telalginite leiosphaeridia tasmanites do affect the origin and evolution of om pores owing to differences in chemical compositions generation kinetics and activation energy distributions between tasmanites matrix bituminite and other types of macerals leiosphaeridia and tasmanites in woodford mudstone samples exhibit a delay in onset and a shorter period of petroleum generation and pore development compared to the matrix bituminite in the barnett and woodford mudstone samples pre oil solid bitumen was observed to have migrated into initial primary mineral pore networks at the bitumen generation stage in both barnett and woodford samples at higher levels of thermal maturation the volume of primary mineral pores decreases and the pore volume composed of modified mineral pores and om pores becomes greater pore evolution and pore type heterogeneity in these mudstones is a function of the initial mineral pore network types of kerogen and macerals and generation kinetics of individual macerals upon thermal maturation

evaluation of the application of rare earth elements to paleoceanography anomalous departures of rare earth elements ree from similarity of chemical behaviour are most evident in a comparison of ce with its neighbors under reducing conditions ce3 acts like other ree but oxidized ce4 is adsorbed on mn fe oxyhydroxides or organic particulates and consequently the remaining solution will tend to exhibit a negative ce anomaly in addition more subtle fractionations may emphasize the light or the heavy or the middle ree a pattern of ree may be recorded by immediate diagenesis on a suitable chemical substrate such as apatite fish debris conodonts carbonate or chert this record was originally thought to reflect the paleoredox conditions of primary deposition however any such primary record may be overprinted by late diagenetic alteration early analyses of ree in conodonts from a wide range of sediments suggested a prevalence of reducing conditions no ce anomaly in pre carboniferous oceans and more common oxidation negative ce anomaly in the late paleozoic however recent research by other investigators indicates that variations in cean are more diverse in origin and in particular many are distorted to an unknown extent by late diagenesis in any case it is now clear that geological age does not show a consistent relationship to the level of the ce anomaly the ce anomaly apparently does not play any regular role in the isotopic events that accompany prominent mass extinctions further research is required to understand and thus make useful the controls on the ce anomaly

assessing effects of sulfate minerals on petroleum generation in sedimentary basins using hydrous pyrolysis i light alkanes abstract a series of hydrous pyrolysis experiments were conducted to assess the role of sulfate minerals on the chemical and isotopic compositions of light hydrocarbons generated during thermal degradation of kerogen the shale source rock with low maturity tmax 425 c from eagle ford formation in southeast texas was used in the experiments at 330 c for the duration of 72 h while the abundance of gypsum in each experiment varies from 0 0 5 to 1 wt under experimental conditions the positive effect of gypsum on the yields of gaseous alkanes c1 c4 and co2 has been explicitly observed with an exponential relationship between the yield of each gas and the amount of gypsum while the relative abundance of c2 c4 alkanes has shown an increasing trend with gypsum the gas dryness c1 c1 4 however decreased from 73 1 with no gypsum to 49 6 with gypsum of 1 wt it was attributed to lower overall yields and corresponding higher increased generation rates of c2 c4 alkanes than methane through thermal cracking of kerogen and other organic compounds the carbon isotope value of each alkane reached the highest in the experiment with 1 wt gypsum compared to the experiment without gypsum there was an increase of 11 5 for the 13c value of methane with 1 wt gypsum the extent of this 13c enrichment between experiments with different amount of gypsum became less for c2 to c4 the 13c value of co2 was the highest among generated gases ranging from 4 7 to 2 1 combined with chemical compositions of gases it suggested that enhanced thermal cracking reactions were predominant in generation of light alkanes with the presence of gypsum whereas dissolution of carbonates was the main source of co2 the reactions involving thermochemical sulfate reduction tsr were minor if present under experimental conditions most likely due to the small quantity of gypsum up to 1 wt and neutralization of acidity by carbonates nonetheless the changes in chemical and isotopic compositions of light alkanes which were ultimately caused by the presence of gypsum need to be incorporated into geochemical proxies for assessing source rocks maturation in particular and their generation potential

organic geochemistry and organic petrology of organic rich sediments within the hauptdolomit formation triassic norian of the northern calcareous alps organic rich intercalations toc up to 50 occur within the hauptdolomit the principal components of the organic matter are lamellar alginite prebitumen or solid bitumen epi impsonite organic geochemistry shows the om to be marine and to have a high bacterial contribution a mesohaline environment low terrigenous supply high production of hc rich om high microbial activity and anoxic conditions are seen as factors favouring the formation of these rocks pyrolysis gas chromatography is used to characterize the om based on the abundance of alkene alkane doublets alkyl thiophenes alkyl benzenes and or c15 alkanes biomarker data shows that the samples cover a range from immature to overmature restricted lagoons and special basins within the hd carbonate platform are suggested as the two different paleoenvironmental settings for the deposition of these rocks

the role of minerals in the thermal alteration of organic matter iii generation of bitumen in laboratory experiments abstract a series of pyrolysis experiments utilizing two different immature kerogens from the monterey and green river formations mixed with common sedimentary minerals calcite illite or namontmorillonite was conducted to study the impact of the mineral matrix on the bitumen that was generated calcite has no significant influence on the thermal evolution of bitumen and also shows virtually no adsorption capacity for any of the pyrolysate in contrast montmorillonite and illite to a lesser extent alter bitumen during dry pyrolysis montmorillonite and illite also display strong adsorption capacities for the polar constituents of bitumen by this process hydrocarbons are substantially concentrated within the pyrolysate that is not strongly adsorbed on the clay matrices the effects of the clay minerals are significantly reduced during hydrous pyrolysis the strong adsorption capacities of montmorillonite and illite as well as their thermocatalytic properties may in part explain why light oils and gases are generated from certain argillaceous source rock assemblages whereas heavy immature oils are often derived from carbonate source rocks

supergene manganese ore records 75 myr long campanian to pleistocene geodynamic evolution and weathering history of the central african great lakes region tectonics drives climate assists abstract the southeastern part of the democratic republic of the congo locally hosts proterozoic manganese deposits the deposits of kisenge kamata are the most significant but manganese ores are also known to occur at kasekelesa former katanga province and mwene ditu former kasai province for the present study cryptomelane rich samples from these two localities were dated using the 40ar 39ar step heating method with a co2 laser probe the ages obtained are within a range of c 77 myr to c 2 myr cryptomelane formation took place at c 76 4 ma c 59 6 ma c 45 ma c 35 ma c 23 8 ma c 15 4 ma and c 13 3 ma at kasekelesa and it occurred at c 35 ma c 22 4 ma c 15 ma c 5 5 7 2 ma c 3 6 ma and c 2 1 2 3 ma at mwene ditu the campanian age c 76 4 ma recorded at kasekelesa is the oldest 40ar 39ar age that has up to now been recorded for mn ores from africa it documents the formation of oxidized ore along a campanian or older erosion surface which could be part of the african erosion surface the complete age record suggests that continent wide tectonics accounts for most of the recognized supergene ore formation episodes controlled by vertical lithospheric movements that are ultimately responsible for alternating stages of landscape stability and erosion tectonics is thus regarded as the first order control for secondary ore formation in central africa over the last 80 myr climate is a second order control because sufficient water supply is needed for supergene enrichment whereby climatic conditions are recognized to have been favourable during some relatively cold late mesozoic and paleogene periods as well as during some humid and warm neogene stages

a slow thrust slip event following the two 1996 hyuganada earthquakes beneath the bungo channel southwest japan we report a slow thrust slip event that occurred beneath the bungo channel region southwestern japan on oct and dec 1996 two hyuganada earthquakes both mw 6 7 followed by afterslips occurred in addition a crustal movement characterized by an extremely slow rise was observed around the bungo channel about 200 km north from the epicenters and continued for about 300 days long assuming a slow slip on the plate boundary we estimate its duration and surface displacements from gps time series data by curve fitting and then determine the fault slip distribution we found that a slow slip without any earthquakes continued for nearly one year and released the seismic moment comparable to that of the hyuganada earthquakes occurrence of the slow thrust slip event suggests that this kind of event may be a characteristic mode of stress release at a transition region of interplate coupling

role of minerals in thermal alteration of organic matter ii a material balance pyrolysis experiments were performed on green river and monterey formation kerogens types i and ii respectively with and without calcite illite or montmorillonite at 300 c for 2 to 1 000 hours under dry and hydrous conditions pyrolysis products were identified and quantified and a material balance of product and reactants resulted significant differences were found in the products generated by pyrolysis of kerogens with and without minerals both illite and montmorillonite adsorb a considerable portion up to 80 of the generated bitumen the adsorbed bitumen is almost exclusively composed of polar compounds and asphaltenes that crack to yield low molecular weight compounds and insoluble pyrobitumen during prolonged heating montmorillonite shows the most pronounced adsorptive and catalytic effects with calcite however the pyrolysis products are similar to those from kerogen heated alone and bitumen adsorption is negligible applying these results to maturation of organic matter in natural environments we suggest that a given type of organic matter associated with different minerals in source rocks will yield different products furthermore the different adsorption capacities of minerals exert a significant influence on the migration of polar and high molecular weight compounds generated from the breakdown of kerogen therefore the overall accumulated products from carbonate source rocks are mainly heavy oils with some gas whereas light oils and gases are the main products from source rocks that contain expandable clays with catalytic and adsorptive properties

reconsidering earthquake scaling the relationship scaling between scalar moment m0 and duration t potentially provides key constraints on the physics governing fault slip the prevailing interpretation of m0 t observations proposes different scaling for fast earthquakes and slow mostly aseismic slip populations and thus fundamentally different driving mechanisms we show that a single model of slip events within bounded slip zones may explain nearly all fast and slow slip m0 t observations and both slip populations have a change in scaling where the slip area growth changes from 2 d when too small to sense the boundaries to 1 d when large enough to be bounded we present new fast and slow slip m0 t observations that sample the change in scaling in each population which are consistent with our interpretation we suggest that a continuous but bimodal distribution of slip modes exists and m0 t observations alone may not imply a fundamental difference between fast and slow slip

stereochemical studies of acyclic isoprenoids xii lipids of methanogenic bacteria and possible contributions to sediments abstract abundant volatile lipids of methanobacterium thermoautotrophicum and methanosarcina barkeri include isoprenoid hydrocarbons c30 and c15 c20 and c25 isoprenoid alcohols m barkeri contains 2 6 10 15 19 pentamethyleicosane whose relative stereochemistry is the same as found in marine sediments indicating that it is a marker of methanogenic activity the c20 c30 and c25 alkenes in m thermoautotrophicum also have a preferred sterochemistry the latter have the 2 6 10 14 18 pentamethyleicosanyl skeleton suggesting that the alkane in marine sediments may derive from methanogens the stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens in contrast the stereochemistry of pristane in m thermoautotrophicum indicates a fossil fuel contaminant origin suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin there is therefore little evidence at present that the pristane in immature marine sediments originates in methanogens the c15 and c20 saturated alcohols in m thermoautotrophicum have mainly the all r configuration if this is generally true for methanogens the c20 alcohol in the messel shale may originate mainly from methanogens whereas that in the green river shale may originate mainly from photosynthetic organisms

phenomenology of deep slow earthquake family in southwest japan spatiotemporal characteristics and segmentation 1 the phenomenology of deep slow earthquakes including low frequency tremors very low frequency earthquakes and short term slow slip events on the subducting plate interface in southwest japan is investigated on the basis of their spatiotemporal characteristics the belt like distribution of tremors is divided into segments bounded by gaps the repetition of tremor episode depends on the magnitude of the episode which is defined by the number of detected tremors within each episode major tremor episodes with a large number of detected tremors recur at an interval of approximately 6 months accompanying the short term slow slip events in large segments in small segments tremor episodes with small numbers of tremors have recurrence intervals of a few months some of them occasionally accompany the slight ground tilting caused by a small size slow slip event even in the same segment there exist different recurrence intervals according to the magnitude of the tremor episode the migration pattern varies greatly in initiation termination direction and speed however the migration direction has a general tendency for each segment on both sides of the gap the tremor starts next to the gap and propagates to the other side assuming all tremor episodes are caused by slow slip events the equivalent moment and slip are estimated from the number of detected tremor counts and the area of each tremor episode the equivalent slip history estimated from all tremor episodes is almost constant in each segment this indicates that tremor activity is a good proxy for slow slips

depth dependent activity of non volcanic tremor in southwest japan 1 with a new location method we obtained a high resolution map of non volcanic tremor along the subducting philippine sea plate in southwest japan and clarified the depth dependent behavior of the tremor activity a bimodal distribution of tremor along dip is apparent in regions where short term slow slip events sses and very low frequency earthquakes are frequently detected the separation of bimodal peaks is 5 to 10 km in depth the updip tremor activity occurs episodically coincident with major bursts that often accompany geodetically detectable sses the downdip tremor activity is however rather stable with frequent minor bursts this depth dependent tremor activity likely reflects variation of interplate slip properties specifically weakening with increasing depth and temperature in westernmost shikoku anomalous tremor activity was detected in only the updip section in late 2003 this is interpreted as being triggered by a long term sse in the shallower edge of the tremor zone

the role of minerals in the thermal alteration of organic matter iv generation of n alkanes acyclic isoprenoids and alkenes in laboratory experiments a series of pyrolysis experiments utilizing two different immature oil prone kerogens type i green river formation kerogen type ii monterey formation kerogen mixed with common sedimentary minerals calcite illite or na montmorillonite was conducted to study the effects of minerals on the generation of n alkanes acyclic isoprenoids and alkenes during laboratory simulated catagenesis of kerogen the influence of clay minerals on the aliphatic hydrocarbons is critically dependent on the water concentration during laboratory thermal maturation under extremely low contents of water i e dry pyrolysis where only pyrolysate water is present c12 range n alkanes and acyclic isoprenoids are mostly destroyed by montmorillonite but undergo only minor alteration with illite both clay minerals significantly reduce alkene formation during dry pyrolysis under hydrous conditions mineralwater 2 1 the effects of the clay minerals are substantially reduced in addition the dry pyrolysis experiments show that illite and montmorillonite preferentially retain large amounts of the polar constituents of bitumen but not n alkanes or acyclic isoprenoids therefore bitumen fractionation according to polarity differences occurs in the presence of these clay minerals by this process n alkanes and acyclic isoprenoids are concentrated in the bitumen fraction that is not strongly adsorbed on the clay matrices the extent of these concentration effects is greatly diminished during hydrous pyrolysis in contrast calcite has no significant influence on the thermal evolution of the hydrocarbons in addition calcite is incapable of retaining bitumen therefore the fractionation of n alkanes or acyclic isoprenoids relative to the polar constituents of bitumen is insignificant in the presence of calcite

high abundance of low molecular weight organic acids in hypersaline spring water associated with a salt diapir abstract spring waters with a high salt content 390 g l and a strong pungent odor were collected from the flanks of the mt sedom diapir near the dead sea and analyzed for low molecular weight lmw mono and di carboxylic acids lipid class compounds and dissolved organic carbon concentrations of lmw carboxylic acids were found to be very high c1 c9 monoacids 305 mgc l c2 c9 diacids 27 mgc l the dominant species is acetic acid 220 mgc l followed by propanoic 49 mgc l succinic 18 mgc l and methylpropanoic acid 11 mgc l these organic acids comprised major portions of dissolved organic carbon doc 480 mgc l of the hypersaline brine monoacids contribute 64 of doc and diacids 5 4 volatile organic acids such as acetic propanoic butyric and valeric acids were found to be the source for the pungent smell of the spring water these organic acids were most likely produced in a deeply buried block of the upper cretaceous bituminous chalks in the dead sea rift valley by thermal alteration of the organic matter and were transported upward to the surface together with connate brines along the margins of the diapir the monoacid diacid proportions in the brine water and the predominance of oxalate in the precipitates from the brines suggested a selective removal of dicarboxylic acids by forming organic salt precipitates such as calcium oxalate during upward transport of the brines to the surface

paleoproterozoic manganese and base metals deposits at kisenge kamata katanga d r congo the kisenge kamata manganese deposit katanga d r congo belongs to a group of paleoproterozoic sedimentary manganese ore occurrences that have been recognized for various parts of africa it is a relatively small deposit with total estimated reserves of similar to 12 mt ore but it is of major importance for understanding key aspects of the geology of the kasai block of the congo craton the available constraints indicate that the deposit formed in the 2 0 1 9 ga time interval in the orosirian period the manganese rich facies of the kisenge kamata deposits range in composition from manganese carbonate rocks to non calcareous deposits dominated by manganese rich garnet associated rocks are mainly grey graphitic shales the kisenge kamata sediments are significantly enriched in cu co ni zn and other accessory metals v mo ga field constraints and geochemical data suggest that the kisenge kamata sediments were probably deposited in a relatively small intracratonic basin graben within the kasai block with an inlet allowing periodical access for ocean water influx carrying mn ree and other metals primary carbonate ore has relatively low delta c 13 3 to 6 parts per thousand and high delta o 18 13 to 20 parts per thousand values confirming their derivation from marine fluids

sequential leaching of marine ferromanganese precipitates genetic implications abstract sequential leaching experiments were carried out on twenty one hydrogenetic crust samples from different locations in the central pacific and the results are compared with four crust and nodule samples of different genetic origin fe vernadite mno2 is the most important minor and trace metal bearing mineral phase and shows high concentrations of co ni cd ti ba zn and cu which are present in seawater mainly as hydrated and labile complexed cations elements forming carbonate and hydroxide complexes and oxyanions in seawater like pb mo v and minor proportions of cu and zn are bound in the fe00h fraction the ca carbonate phase and the residual fraction which consists of aluminosilicates and crystalline oxides show only minor heavy metal associations e g cu and zn only a small part of the high ti concentrations in hydrogenetic crusts is of detrital origin ti mainly forms a hydrogenetic phase probably consisting of ti02 2h20 intergrown with the amorphous fe00h phase analyses of different sample types and crust layers show that aging and diagenetic effects can change the phase associations of some elements the most notable change was observed for pb which during phosphatization of crusts is transferred from the mn fe oxide fraction to the apatite fraction a colloid chemical model for the hydrogenetic precipitation of ferromanganese crusts on seamounts is proposed in the first stage mn2 rich water from the oxygen minimum zone is mixed with oxygen rich deep water and oxidized mn iv and other metals like fe ti al and si form oxide and hydroxide colloids these form mixed colloidal phases and scavenge trace metals by sorptive processes which are dominated by coulombic and chemical interactions between colloid surfaces and dissolved metal species in stage two the colloidal phases precipitate on the substrate rocks of the seamounts as ferromanganese oxide encrustations incorporating the sorbed heavy metals into the mineral phases

geodynamic and climate controls in the formation of mio pliocene world class oxidized cobalt and manganese ores in the katanga province dr congo the katanga province democratic republic of congo hosts world class cobalt deposits accounting for 50 of the world reserves they originated from sediment hosted stratiform copper and cobalt sulfide deposits within neoproterozoic metasedimentary rocks heterogenite the main oxidized cobalt mineral is concentrated as cobalt caps along the top of silicified dolomite inselbergs the supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world class manganese cap deposits in western katanga i e the black earths that are exploited by both industrial and artisanal mining here we provide constraints on the genesis and the timing of these deposits ar ar analyses of oxidized mn ore and in situ u pb sims measurements of heterogenite yield mio pliocene ages the ar ar ages suggest a multi phase process starting in the late miocene 10 5 ma when the metal rich substratum was exposed to the action of meteoric fluids due to major regional uplift further oxidation took place in the pliocene 3 7 2 3 ma and formed most of the observed deposits under humid conditions co and mn caps on metal rich substrata and coeval fe laterites on barren areas these deposits formed prior to the regional shift toward more arid conditions in central africa arid conditions still prevailed during the quaternary and resulted in erosion and valley incision which dismantled the metal bearing caps and led to ore accumulation in valleys and along foot slopes

low temperature pyrolysis of green river kerogen geologic note the extrapolation of high temperature pyrolysis data to kerogen maturation conditions occurs over many orders of magnitude quite possibly the chemical kinetics of a high temperature regime may be different for a low temperature regime making the extrapolation meaningless we have mildly thermally treated green river kerogen to remove the low activation energy non oil bearing material low temperature 209 388 c isothermal reaction measurements on this refined material indicate that the same reaction kinetics for the oil production from green river kerogen obtained at high temperature 400 500 c are valid as low as 209 c the same arrhenius parameters apply over the entire range k 1 1013 exp 51300 rt sec 1 this means that the overall decomposition mechanism most probably a radical decomposition mechanism applicable at high temperature is also applicable at low temperature 209 c and perhaps geological i e 50 160 c temperatures olefins are initially produced in a ydrocarbon radical decomposition process we show that with time these olefins are converted to paraffins presumably using the residual hydrogen in the converted kerogen

a sm 1bnd isotopic study of heterogeneous granulites from the archean kasai lomami gabbro norite and charnockite complex zaire africa abstract sm 1bnd model ages t dm of acid granulites from the kasai complex agree with previous rb 1bsr and u 1bpb ages of 2 8 ga for the early and main stage of granulite facies metamorphism these sm 1bnd results give an upper limit of 3 1 ga for the age of the protoliths of the charno enderbites and metapelitic gneisses which represent the majority of the acid rocks of the complex a sm 1bnd study whole rock and internal isochrons and t dm ages of the associated basic granulites meta gabbro norite massif and metadolerite dykes crosscutting the acid granulites demonstrates that the second stage of granulite metamorphism corresponding to regional deformation of all the rocks is nearly coeval with the emplacement of the basic rocks at 2 4 ga

manganese deposits in the global lithogenetic system quantitative approach abstract a computerized data base including 330 localities and believed to represent at least 95 of the presently recorded spot accumulations of ore grade mn on land is the basis for a quantitative analysis of terrestrial mn resources this file is reprinted in full appendix the present subaerially exposed global ore mn resources are calculated as 17 9 109 t mn 1 in this figure are included the actually mineable straight mn deposits 8 7 109 t mn potentially mineable land based mn accumulations 9 2 109 t mn and actual or potential mn that could be extracted as a byproduct of mining other metals 0 6 109 t mn this distribution is strongly influenced by giant accumulations where the single exceptional kalahari mn field contains over 50 of the presently economic mn ore reserves or 23 42 of the global land mn resources a set of attributes has been selected to treat the global ore mn population in terms of genesis geotectonic and environmental setting and lithologic associations in terms of genesis precipitation from aqueous solutions was responsible for at least 99 of the contemporaneous and probably also the past mn accumulations now exposed on land weathering of mn orebodies has left its mark on 93 of the mn localities and 24 are now represented entirely by supergene assemblages less than 0 01 of the ore mn resources however are formed by weathering related accumulation over silicate rocks ultramafics in terms of geotectonic environments the bulk of the land based mn deposits 97 formed in intraplate and stable continental margin settings 3 1 formed along pacific type and rift type continental margins and only 0 00045 of the deposits formed in an oceanic setting this is in contrast with the outstanding mn accumulating capacity of the present ocean and is a consequence of the low preservation potential of the oceanic domain in terms of lithologic associations 96 of the mn in land based deposits is present in marine sedimentary associations 70 of mn is in banded iron formations 14 4 is in detrital and 11 1 is in carbonate dominated associations chert and jasper limestone sandstone shale and banded iron formation are statistically the most common immediate hosts to mn ores with recorded hosting frequencies of 79 50 45 37 and 35 respectively in terms of geological history the lower proterozoic accounts for 58 9 of the prreserved ore mn on land followed by oligocene 17 2 jurassic 6 2 and middle proterozoic 4 5 in terms of the intensity of mn accumulation per one million years of geological time oligocene 110 106 t mn ma is two orders of magnitude greater than the nearest time periods jurassic 8 9 106 t mn ma and lower proterozoic 6 5 106 t mn ma the historical distribution pattern of the land based mn deposits seems to indicate that accumulation of the bulk of the present ore grade mn is the result of repeated recycling with a land ocean trend abruptly initiated at the time of early cratonization about 2 5 ga this has been supplemented by a substantially less significant but remarkably steady reverse trend of addition of juvenile mn released from the mantle into the crust mafics and particularly basalts are the most important intermediaries in the cumulative secular increase of liberated and accumulated mn in the crust direct to indirect proven to hypothetical spatial coincidence of basalts and mn ores can be demonstrated on at least 169 localities out of 330 51 evaluated

detection of short term slow slip events along the nankai trough southwest japan using gnss data 1 we detected short term slow slip events sses previously observable only with tilt and strain data along the nankai trough southwest japan using gnss global navigation satellite system data offsets detected in gnss time series using akaike s information criterion helped automatically identify 207 episodes with a motion direction opposite to that of the relative plate motion from june 1996 to january 2012 by nonlinear inversion of the detected displacement we estimated rectangular fault models for 133 probable and 25 possible short term sses over 15 years the sse moment magnitudes range from 5 5 to 6 3 most sse fault models are located in a narrow band of non volcanic tremors on the interfaces of the subducting philippine sea plate large sses moment magnitude mw 6 often occur in western and central shikoku the cumulative slip is distributed heterogeneously along the strike generally decreasing eastward with the maximum slip 50 cm in western shikoku no definite short term sses were found in the kii channel but several short term sses occurred in ise bay both regions are known as tremor gaps the local maximum of the cumulative slip fills in the tremor gap located in ise bay the long term rate of short term sse cumulative moment increased by threefold around 2003 in eastern shikoku whereas it was almost constant in other regions comparison with short term sse catalogues using tilt data suggests that both this study and previous studies missed some sses along the nankai trough a combination of geodetic data is important in the monitoring of the spatiotemporal distribution of short term sses

a paleoweathering profile from griqualand west south africa evidence for a dramatic rise in atmospheric oxygen between 2 2 and 1 9 bybp a core drilled near wolhaarkop in griqualand west south africa intersected highly oxidized kuruman iron formation below red beds of the gamagara formation the lateral equivalents of the kuruman iron formation in this drill hole consist largely of siderite ankerite magnetite greenalite and quartz the oxidation of the kuruman iron formation in wol 2 occurred almost certainly during weathering prior to the deposition of the gamagara formation the date of this weathering episode is bracketed between about 2 2 and 1 9 bybp by the age of the ongeluk lavas in the transvaal sequence below the unconformity and by the age of the hartley lavas in the olifantshoek group above the unconformity the ratio of iron to sio2 in the several facies of the weathered kuruman iron formation in wol 2 is nearly the same as that in their unweathered equivalents since sio2 loss during weathering was almost certainly minor the similarity of the fe sio2 ratio in the weathered and unweathered bif indicates that nearly all the feo in the kuruman iron formation was oxidized and retained as feo3 during weathering such a high degree of iron retention is best explained by an o2 content of the atmosphere or 0 03 atm at the time of weathering such an o2 pressure is very much greater than that suggested by the composition of paleosols developed on basalt or 2 2 bybp but is consistent with the highly oxidized nature of the 1 85 by flin flon paleosol the new data suggest that po2 rose dramatically from about 1 percent pal present atmospheric level to or 15 percent pal between 2 2 and 1 9 bybp

diagenetic and detrital origin of moretane anomalies through the permian triassic boundary abstract many biogeochemical anomalies coincide with the late permian extinction lpe 252 28 ma several mechanisms have been proposed to explain the moretane hopane anomaly that has been identified in samples from meishan gssp section in southeastern china here we report homohopane 2 and 3 methylhomohopane and lithological data for a drill core from the meishan section in southeastern china three intervals of elevated c 30 moretane hopane ratios are recorded in the lungtan yinkeng and helongshan formations moretane hopane ratios of c 31 34 homohopanes and the 2 and 3 methylhomohopanes display the same stratigraphic patterns as the c 30 moretane hopane record in light of the multiple and parallel moretane anomalies for the homohopane and 2 and 3 methylhomohopane series enhanced input from higher plant organic matter such as coal and peat does not adequately explain the observed isomer patterns correlation of high moretane hopane ratios with low c 35 homohopane index hhi and high hopane sterane values suggest increased input of hopanoids from oxic soils additionally moretane hopane ratios show excellent correlations with total clay percentages and specific clay types particularly chlorite illite and mixed layer illite smectite we conclude that a combination of episodic hopanoid input from soil bacteria and diagenetic effects related to redox and detrital clays generated the unique moretane hopane patterns at meishan similar relationships of ts ts tm with redox source indicators and lithology indicate that ts ts tm is affected by the same factors controlling the moretane hopane ratios berthierine a clay that requires reducing conditions for formation was detected in samples from the lungtan formation we are unable to determine from our results whether the berthierine is authigenic or detrital but future determination of the origin of berthierine at meishan may offer additional environmental insight no link between diasteranes and lithology was observed in this study suggesting that diasteranes are relatively unaffected by the detrital clay component of the meishan sediments in total the results point toward the complex role of source input lithology and depositional redox conditions in the transformation of organic matter during maturation future work is required to elucidate the lithological effects on diagenetic processes including biomarker genesis isomerization and thermal degradation

geochemistry of asphaltenes abstract asphaltenes derived from both oil and source rocks have been studied by pyrolysis gas chromatography the pyrograms obtained at 450 and 550 c show that asphaltene structure is very close to the structure of the kerogen of the same sample they can be interpreted as kerogen moieties resulting from its early evolution therefore they can be used as substitutes of kerogen in genetic studies consequently asphaltenes pyrolysis appear to be a tool in correlation studies for oil oil correlation it can supplement and even replace in the case of degraded oils the information given by hydrocarbon distributions for oil source rock correlations the match between pyrograms of asphaltenes from both oil and source rocks offers more direct possibilities than usual techniques

metacraton nature genesis and behavior article i nfo in this paper we show with examples that cratons involved in intercontinental collisions in a lower plate position are often affected by orogenic events leading to the transformation of their margins in some cases craton interiors can also be shaped by intense collisional processes leading to the generation of intra cratonic orogenic belts we propose to call these events metacratonization and the resulting lithospheric tract metacraton metacratons can appear similar to typical orogenic belts i e active margin transformed by collisional processes but are actually sharply different their main distinctive characteristics not all are present in each metacraton are 1 absence of pre collisional events 2 absence of lithospheric thickening high pressure metamorphism being generated by subduction leading to high gradient in strain and meta morphic intensity 3 preservation of allochthonous pre collisional oceanic terranes 4 abundant post collisional magmatism associated with shear zones but not with lithospheric thickening 5 presence of high temperature low pressure metamorphism associated with post collisional magmatism 6 intraconti nental orogenic belts unrelated to subduction and oceanic basin closures reactivation of the rigid but fractured metacratonic lithosphere will cause doming asthenospheric volcanism emplacement and mineral izations due to repetitive mineral enrichments this paper provides several geological cases exemplifying these different metacratonic features in scandinavia sahara central africa and elsewhere a special focus is given to the saharan metacraton because it is where the term metacraton originated and it is a vastly ex panded tract of continental crust 5 000 000 km 2

hydrothermal pyrolysis of organic matter in guaymas basin i comparison of hydrocarbon distributions in subsurface sediments and seabed petroleums abstract the bitumens of a selection of subsurface sediments from guaymas basin gulf of california have been analyzed in order to assess the hydrothermal effects on the organic matter and to better delineate the processes influencing the generation deposition and alteration of the hydrothermal petroleums at the seabed although the thermally generated subsurface bitumens are generally rich in polar asphaltic materials as are the seabed oils the hydrocarbon transformations parallel the extent of hydrothermal alteration as reflected in the downcore mineralogy at dsdp sites 477 and 478 at site 477 a progressive change from n alkane to aromatic hydrocarbon dominated patterns in the high resolution gas chromatography resolvable fractions of the bitumens accompanies decreases in organic carbon and bitumen yields with depth these transformations are indicative of sequential hydrothermal alteration of the sediments with depth due to increasing temperature and or progressive passage of hydrothermal fluid through the sedimentary column the polycyclic aromatic hydrocarbon pah distributions undergo extensive transformations e g dealkylation consistent with hydrothermal alterations are dominant at depth and have the broadest range as thermal maturation indices the aliphatic and aromatic components of the seabed oils can be transported to the seabed independently as a result of their generation under different temperature or depth regimes and sequentially over time during pyrolysis the concentrations of the parent pah in the thermally altered subsurface bitumens are comparable to those in the seabed oils the differential dissolution of the more soluble aromatics and selective solidification condensation of the higher molecular weight pah out of the high temperature fluids exiting at the seabed chimneys result in aromatic distributions of the oils significantly skewed towards the larger components e g benzo ghi perylene relative to the subsurface bitumens comparison of the downcore hydrocarbon distributions with those in the seabed petroleums support the contention that the hydrothermal oils are mixtures of pyrolysates from different depths or thermal regimes and are significantly altered by differential solubilization during transport and at the seabed

hydrous pyrolysis of monterey asphaltenes abstract hydrous pyrolysis of asphaltenes has been tested as a method to reconstruct the chemical composition of biodegraded oils and oil seeps the asphaltenes of three oils a nondegraded oil a biodegraded oil and a biodegraded oil seep from the monterey formation were studied results show that the aliphatic fraction generated by hydrous pyrolysis is very similar in chemical composition to the non degraded oil this makes the method very useful in correlation studies of biodegraded and nondegraded oils it also allows to roughly estimate the maturity of the source of the biodegraded oil or oil seep

coticules of the belgian type area stavelot venn massif limy turbidites within the nascent rheic oceanic basin abstract coticule is the name originating in belgium for a fine grained metasedimentary yellowish rock mainly composed of quartz spessartine and mica which is repeatedly interstratified in the hematite rich purple slates of the lower ordovician of the ardenne region it was described for the first time in the nineteenth century in the stavelot venn massif ardenne which is accordingly the type area for this peculiar lithology since then numerous occurrences were described all over the world in metamorphic rocks of various grades and ages the exact nature of the belgian coticule protolith remained hypothetical although intensively discussed for a long time in the literature after an extensive review of all the stratigraphical sedimentological and geochemical results and new field geochemical major and trace elements and nd isotopic investigations we propose a significantly improved and sustained genetic model the thin coticule layers were deposited offshore in a deep oceanic basin as limy mud turbidites during the early floian c 477 ma early ordovician density currents came from the north from the shelf which bordered the emergent brabant massif at that time and flowed down the slope to the deep basin plain the purple shales enclosing the coticule layers represent the normal pelagic sedimentation in the basin these shales are exceptionally rich in fe and mn because of the hydrothermal activity of the nearby and young rheic ocean ridge indeed the rheic ocean opened in the early ordovician c 482 ma during diagenesis the strongly oxidizing depositional environment favoured the mobility of mn 2 as opposed to fe 3 that remained insoluble and immobile this allowed for the migration of divalent manganese from the pelagic shales and for replacing calcium in the turbiditic carbonate fraction to form rhodochrosite later epizonal metamorphism transformed the clay quartz rhodochrosite paragenesis of the protolith into the muscovite quartz spessartine paragenesis of the coticule hence in the type area coticule genesis needed a peculiar environment including a continental shelf with limy mud deposits a continental slope generating periodical turbidites and a nearby oceanic ridge here the nascent rheic ocean delivering hydrothermal iron and manganese

an earthquake like magnitude frequency distribution of slow slip in northern cascadia 1 major episodic tremor and slip ets events with mw 6 4 to 6 7 repeat every 15 2 months within the cascadia subduction zone under the olympic peninsula although these major ets events are observed to release strain smaller tremor swarms without detectable geodetic deformation are more frequent an automatic search from 2006 2009 reveals 20 000 five minute windows containing tremor which cluster in space and time into 96 tremor swarms the 93 inter ets tremor swarms account for 45 of the total duration of tremor detection during the last three ets cycles the number of tremor swarms n exceeding duration follow a power law distribution n 0 66 if duration is proportional to moment release the slip inferred from these swarms follows a standard gutenberg richter logarithmic frequency magnitude relation with the major ets events and smaller inter ets swarms lying on the same trend this relationship implies that 1 inter ets slip is fundamentally similar to the major events just smaller and more frequent and 2 despite fundamental differences in moment duration scaling the slow slip magnitude frequency distribution is the same as normal earthquakes with a b value of 1

a thermal and chemical degradation approach to decipher pristane and phytane precursors in sedimentary organic matter a thermal and chemical degradation approach was followed to determine the precursors of pristane pr and phytane ph in samples from the gessoso solfifera ghareb and green river formations hydrous pyrolysis of these samples yields large amounts of pr and ph carbon skeletons indicating that their precursors are predominantly sequestered in high molecular weight fractions however chemical degradation of the polar fraction and the kerogen of the unheated samples generally does not release large amounts of pr and ph additional information on the precursors of pr and ph is obtained from flash pyrolysis analyses of kerogens and residues after hydrous pyrolysis and after chemical degradation multiple precursors for pr and ph are recognised in these three samples the main increase of the pr ph ratio with increasing maturation temperature which is associated with strongly increasing amounts of pr and ph is probably due to the higher amount of precursors of pr compared to ph and not to the different timing of generation of pr and ph

aseismic slip and low frequency earthquakes in the bungo channel southwestern japan 1 analysis of global positioning system gps data has shown transient crustal deformation in the bungo channel in southwestern japan since late august 2003 six years after a similar event in 1996 1997 considering the southeastward motion at many of the gps sites and the similarity between the 1996 1997 and 2003 events it is highly likely that the transients were caused by aseismic interplate slip between the philippine sea plate and the amurian plate the 2003 aseismic slip is estimated beneath the bungo channel and the relative slip increased with time on the west side with a moment magnitude mw amounting to 7 0 in contrast to the gradual subsidence of low frequency earthquakes which began and ended in coincidence with the 2003 event the 2003 transient crustal deformation proceeded at a roughly constant rate until the end of november 2003 the bungo channel area may release energy accumulated from the subduction of the philippine sea plate by aseismic slip

spatiotemporal distribution of seismic energy radiation from low frequency tremor in western shikoku japan 1 the spatiotemporal patterns of the radiated seismic energy from low frequency tremor associated with slow slip events in western shikoku japan have been estimated a spatially decaying mean square amplitude and differential traveltime measurement from envelope correlations observed at hi net stations were used to locate tremors and to estimate their seismic energies tremor amplitude was corrected for the site amplification factors estimated using the coda normalization method the location of the tremor is estimated as the position where both the decay of the observed energy and the differential travel times are well explained the temporal pattern of the total energy released agrees very well with the observed tilt records although the spatial patterns of the energy radiation vary strongly among the six slow slip events sses in western shikoku the region where they overlap always radiates relatively high levels of energy the estimated band limited energy rate of the tremor for a 2 to 10 hz bandwidth was typically between 105 and 106 j min though there is temporal variation of the radiation energy the released total energy associated with the sses whose magnitude is 5 9 6 1 is on the order of 108 j within the duration of sses of 8 13 days this is quite small energy radiation compared to the moment release of accompanying sse the scaled energy which is the ratio of the seismic moment and the seismic energy for the slow slip and a very low frequency earthquake was estimated to be 5 orders of magnitude smaller than that of a regular earthquake

simple relationship between seismic activity along philippine sea slab and geometry of oceanic moho beneath southwest japan summary many earthquakes with various types of focal mechanisms occur along the subducting philippine sea slab phs beneath southwest japan and the hypocentre distribution is quite inhomogeneous in this region distinct non volcanic deep low frequency tremors are often observed to clarify the cause of these apparently complicated and peculiar seismic activities we first construct a detailed configuration of the oceanic moho slab moho within the phs based on a receiver function rf analysis to convert the time domain rfs into their depth domain equivalents we adopt a fine scaled velocity model based on the traveltime tomography the depth contours of the oceanic moho exhibit complexities but the active region of the intraslab earthquakes corresponds well to the oceanic moho geometry in the western part of shikoku the intraslab seismicity is very high and the focal mechanisms mainly exhibit normal faults with east west extension axes since the phs is subducting to the west and the dip angle of the slab becomes steep in the western part of this region the stress field in this region can be attributed to the slab pull induced by the westwards slab subduction similar types of focal mechanisms are observed in the tokai district with a focal depth greater than 35 km since the oceanic moho exhibits a ridge shape in this region its stress field can be attributed to the slab pull and the effect of slab bending shallow earthquakes in the tokai and eastern shikoku regions have strike slip focal mechanisms and their extension axes are parallel to the strike of the oceanic moho these focal mechanisms may be influenced by both the oblique subduction of the slab and low slab dip angle earthquakes beneath the kii peninsula exhibit strike slip or downdip compression focal mechanisms with east west compression axes since the moho beneath this peninsula shows a valley shape compressional stress occurs around the moho moreover the slab convergence compresses this valley this also induces the east west compression field in this region we have newly confirmed the existence of an aseismic slab beneath the northern part of the kinki district central part of japan in this aseismic region the dip direction of the slab is parallel to that of the slab convergence direction this tendency is observed in the central part of shikoku where the slab seismicity is relatively low these features imply that the intraslab seismicity is constrained by the interaction between the slab geometry and slab motion we also revealed the possibility that the oceanic moho beneath not only ise bay but also the kii channel has a ridge shape in both these regions the non volcanic low frequency tremor activity becomes low more than 80 per cent of the tremor epicentres are distributed within contour depths of 38 3 km of the oceanic moho we find that the interaction between the moho geometry and the plate motion of the subducting phs plays an important role in determining the local stress field and the location of both seismicity and low frequency tremors

slow earthquakes linked along dip in the nankai subduction zone we identified a strong temporal correlation between three distinct types of slow earthquakes distributed over 100 kilometers along the dip of the subducting oceanic plate at the western margin of the nankai megathrust rupture zone southwest japan in 2003 and 2010 shallow very low frequency earthquakes near the nankai trough as well as nonvolcanic tremor at depths of 30 to 40 kilometers were triggered by the acceleration of a long term slow slip event in between this correlation suggests that the slow slip might extend along dip between the source areas of deeper and shallower slow earthquakes and thus could modulate the stress buildup on the adjacent megathrust rupture zone

effects of the mineral matrix on the distribution of geochemical markers in thermally affected sedimentary sequences the distribution of geochemical markers in bitumen fractions both free and associated with minerals was studied in bituminous chalk and black shale samples upper cretaceous israel upper cretaceous west greenland affected by combustion metamorphism and the latter also by dyke intrusion the bitumen fractions were obtained by stepwise extraction in conjunction with stepwise dissolution of the carbonate and subsequently silicate minerals they show differences in their bulk composition and in the distribution of n alkanes alkylcyclohexanes isoalkanes isoprenoids steranes and triterpanes at low maturity in the country rocks the distribution of the biomarkers in the various bitumen fractions reflects mainly the source or organic matter and minerals detrival vs autochthonous associated during transport and sedimentation with increasing maturation processes take place like i the formation of hydrogen bonded associations of clay minerals with organic matter ii the isomerisation of steranes which reaches different degrees free bitumen carbonate associated silicate associated in the bituminous chalk while bound free in the black shales iii the formation of isoalkanes and alkylcyclohexanes which occur only in the mineral associated fractions the particular effects of mineral groups on the geochemical markers during sedimentation generation and primary migration necessitates the consideration of the composition of the mineral matrix for the interpretation of the geochemical markers the generation of hydrocarbons during maturation probably involves the mobilization of bitumen from minerals and kerogen

release of aliphatic aromatic and sulphur compounds from kimmeridge kerogen by hydrous pyrolysis a quantitative study abstract the results discussed in this paper form part of a larger study aimed at obtaining qualitative and quantitative data on the types and amounts of aliphatic and aromatic hydrocarbons including biological markers and sulphur containing heterocyclic compounds released when kerogens asphaltenes and the polar fractions of extracted bitumens and crude oils are heated in the presence of excess water some of the results from the experiments in which kimmeridge kerogen was heated in the presence of excess water at times ranging from 7 h to 3 months and at temperatures ranging from 200 to 340 c are reported here the maximum yield of pyrolysate was obtained in experiments conducted at 330 c for 72 h and became increasingly aromatic as pyrolysis temperatures increased aliphatic hydrocarbon distributions became increasingly oil like interestingly unsaturated isoprenoid hydrocarbons were present but only in the low temperature reaction mixtures quantitative estimates of individual hydrocarbon types showed that with increasing temperatures the n alkanes were approximately five to tenfold more abundant than the isoprenoid hydrocarbons by that the rate of release of the latter in the lower temperature work was greater than for the n alkanes the very small amoounts of c21 c22 steranes released increased for all reaction temperatures and with increased heating times unlike the c27 c29 steranes and hopanes they did not pass through a maximum yield at lower pyrolysis temperatures approximately five times more alkylnaphthalenes than phenanthrenes plus anthracenes were released the most abundant sulphur containing compounds in the pyrolysates were alkylbenzothiophnes and dibenzothiophenes the former being tenfold more abundant than the latter and almost double the total amount of alkylnaphthalenes produced at high pyrolysis temperatures microscopy of all of the kerogen residues indicated that vitrinite like material had been generated in the heated kerogens and this increased in rank with increased temperatures and times of heating

effect of mineral matrix and seam thickness on reflectance of vitrinite in high to low volatile bituminous coals an enigma abstract the variation of vitrinite reflectance with respect to mineral matrix lithology the thickness of coal seams and coal lenses and the type of organic matter was studied from two cores in a 550 m sedimentary succession from the upper jurassic to lower cretaceous kootenay group the data obtained indicate that reflectance in high to low volatile bituminous coals ro max 0 8 1 35 with depth of burial is affected by the percentage of organic matter in the samples a positive correlation between the vitrinite reflectance and the percentage of organic matter and a negative correlation with the percentage of mineral matter exist and the thicker the coal interval the higher the vitrinite reflectance thick coal seams 1 m with a mineral content 20 vitrinite dispersed in sandstone and to a lesser extent siltstone and carbonaceous shale has the lowest reflectance variations in vitrinite reflectance may be attributed to chemical differences in the organic matter possibly induced by degradation and diagenesis syn or post depositionally and to the effect of some clay minerals present in the sediments which may act as catalysts differences in the thermal conductivity of the strata have demonstratably not accounted for the observed variations in reflectance with lithology the differences in the vitrinite reflectance of organic matter between lithotypes is substantial and is thus an important consideration in resolving the time temperature history and generation of hydrocarbons from a sedimentary succession

continuous growth of hydrogenetic ferromanganese crusts since 17 myr ago on takuyo daigo seamount nw pacific at water depths of 800 5500 m ferromanganese crusts cover all outcrops on takuyo daigo seamount traversed during remotely operated underwater vehicle rov dives except in places covered by foraminifera sand takuyo daigo is a cretaceous seamount located in the northwest pacific ocean geological and bathymetric mapping provide the framework for this study chemical and mineralogical analyses of the hydrogenetic ferromanganese crusts show temporal and spatial variations typical of those found in previous studies outcrops from 800 to 5500 m water depths are covered with ferromanganese crusts up to 105 mm thick beryllium isotope dating shows that the crusts have apparently been growing continuously at all water depths even through the modern oxygen minimum zone omz contrary to some earlier models for deposition growth rates vary from 2 3 to 3 5 mm myr with fe or mn fluxes of 0 07 0 11 g cm2 myr since the early middle miocene co mn ratios decrease with water depth while fe mn and other metallic elements increase or show no change based on the analysis of the uppermost crust surface this is probably because co is the most abundant redox sensitive element derived from seawater that occurs in crusts

quasi periodic slow slip events in the afterslip area of the 1996 hyuga nada earthquakes japan 1 the time evolution of afterslip on a plate boundary experiencing interplate earthquakes is expected to show logarithmic decay the global positioning system network in japan has been monitoring transient deformation since the occurrence of two large interplate earthquakes with moment magnitudes of 6 8 and 6 7 in the hyuga nada area southwest japan in 1996 the spatial and temporal evolution of aseismic interplate slip based on crustal deformation data indicates that afterslip followed the two earthquakes and gradually declined to background rates by around 2004 with total moment magnitude of 7 3 however quasi periodic slow slip events suddenly began within the afterslip area in 2005 with approximately one year duration and two year recurrence interval the moment magnitudes of the three slow slip events since january 2005 range from 6 7 to 6 8 this differs greatly from the expected behavior of logarithmic decay over time both velocity strengthening and velocity weakening rate and state modes have been implicated as the cause of afterslip whose location is complementary to the main shock area of velocity weakening while a slow slip event occurs in the velocity weakening area with different frictional properties from those of an afterslip area in light of the seemingly different frictional properties the coexistence of afterslip and slow slip events in the same area would provide additional information about precisely how the plate interface is behaving the monitoring of these slow slip events should give the clues to understanding the coexistence of long term afterslip and slow slip events and the increasing risk of earthquakes in neighboring areas

slow slip event within a gap between tremor and locked zones in the nankai subduction zone we report on two small long term slow slip events sses within a gap between tremor and locked zones in the nankai subduction zone southwest japan the sses were detected by subtracting the steady state component and postseismic effects of large earthquakes from long term and high density global navigation satellite system data both sses occurred in adjacent regions of the bungo channel following long term sses in the bungo channel in 2003 and 2010 the estimated slip was 1 5 cm year that lasted at least 1 2 years after 2004 and 2011 partly accommodating plate convergence as the low frequency tremor in the downdip region is activated at the same time as the bungo channel long term sse a spatiotemporal correlation was observed between the detected sses and long term tremor activity in the downdip region this correlation indicates along dip interaction of the slips on the subducting plate interface

timing and pt evolution of whiteschist metamorphism in the lufilian arc zambezi belt orogen zambia implications for the assembly of gondwana abstract one of the world s most extensive occurrences of whiteschists talc kyanite schists is located in south central africa with several exposures along a ca 700 km northwest southeast striking zone the metamorphic evolution and age relations of whiteschists and associated rocks from four localities three in the lufilian arc and one in the zambezi belt were investigated in the lufilian arc whiteschists associated garnet amphibolites and biotite kyanite garnet gneisses record peak metamorphic conditions of about documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes

multistage genesis of the late cretaceous manganese karst hosted tasdremt deposit high atlas morocco the eastern part of the souss basin morocco contains several mn deposits in the tasdremt district three mn orebodies occur within the cenomanian turonian dolostones and the senonian coniacian to maastrichtian detrital series the main orebody being located at the boundary between them the mn ores consist of coronadite group minerals mostly coronadite and hollandite in a karstified dolostone new field observations petrographic analyses and geochemical data define the tasdremt deposits as a karst hosted accumulation 11 60 wt mn particularly enriched in ba 1 5 8 2 wt and pb 1 0 5 0 wt with poor contaminations in al fe and p this study shows that the ore forming process is similar to that occurring in the imini c3 level located 100 km to the north east such similarities with the high grade pyrolusite bearing ore suggest that the tasdremt deposit is a lateral equivalent of the imini deposits however the scarcity of pyrolusite in tasdremt results in lower mn grades the tasdremt ores being considered an aborted incomplete system in comparison with the imini deposits 40ar 39ar geochronology of k bearing mn oxides yields late cretaceous ages defining three phases at 91 5 ma 77 5 82 ma and 65 67 ma although the source of metals remains hypothetical mineralizing fluids were carried by o2 free groundwater that mixed with o2 rich shallow meteoric waters at the tasdremt depositional site the dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of mn oxides causing the coeval increase of ph and eh respectively the early atlasic deformation during the late cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from tasdremt to imini this period enabled karstification and mineralization connecting the tasdremt deposits to other african mn deposits is difficult since the latter consist of laterite resting above paleoproterozoic mn protores and consequently formed under different conditions from karst hosted deposits it is likely that other mn occurrences formed along the atlas belt in similar settings

coseismic slip resolution along a plate boundary megathrust the nankai trough southwest japan geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 tonankai mw 8 1 and 1946 nankaido mw 8 3 earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust data used include 798 angle changes from triangulation surveys 328 leveling section differences and 5 coseismic tidal gage offsets many of the nominally coseismic triangulation data span 50 years nearly half the earthquake cycle and correction for interseismic deformation using post 1950 observations is applied microseismicity is used to define the configuration of the plate boundary interface and approximate it with a continuous multisegment fault model because the onshore geodetic data have very limited resolving power for offshore fault segments offshore coseismic slip was constrained by satake s 1993 estimation based on tsunami data the majority of the coseismic slip occurs between 15 and 25 km depth although resolution declines toward the trench axis it is sufficiently good to define two distinct high slip regions one off southeastern shikoku island 11 m maximum and the other offshore of kii peninsula 3 m maximum the slip magnitude off southeastern shikoku coupled with the plate convergence rate would imply an recurrence interval of about 270 years much longer than the average repeat time of 120 years for historical great earthquakes on the nankai trough however the maximum coseismic slip is sensitive to the assumed fault geometry and slippage on trough parallel splay faults could significantly decrease the maximum slip to about 6 m

efficiency of petroleum expulsion from shale source rocks the limited data available on the mechanism and the efficiency of the processes by which petroleum is expelled in the subsurface from source rocks into adjacent reservoir rocks are mostly qualitative1 2 we present here material balance type comparisons of sample series extending from the centre portions of two adjacent hydrocarbon source rock units towards their outer edges3 which enable expulsion efficiencies to be determined in certain parts of the shale the expulsion efficiencies for total extract and its saturated and aromatic hydrocarbon fractions have much higher values than previously thought reaching up to 80 for the total extract which increase towards possible secondary migration avenues the expulsion is associated with fractionation effects such as those based on polarity differences also expulsion efficiencies were found to be related to the degree of hydrocarbon saturation of the pore system they are higher for a rich oil prone source rock unit compared with a poorer quality one which had generated less hydrocarbons

comparative study of serbian miocene coals insights from biomarker composition abstract the origin of the organic matter om and the characteristics of the paleoenvironment of serbian brown coals covering a time span from the lower to the upper miocene were evaluated and compared based on comprehensive petrological and biomarker analyses investigated coals are typical humic coals peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by variable amount of angiosperms coal forming plants belonged to the gymnosperm families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae peatification proceeded in fresh water environment under variable eh settings from anoxic to slightly oxic condition upper miocene lignites were formed in neutral to slightly acidic environment whereas lower and middle miocene coals were deposited under neutral to slightly alkaline and more reductive conditions which is the result of calcium rich surface waters derived from the surrounding jurassic to cretaceous calcareous country rock and higher water column level diagenetic changes of the om were governed by bacterial activity rather than thermal alteration biomarker pattern does not significantly differ in serbian coals of different ages the main differences between upper middle and lower miocene coals are expressed by higher gelification index gi proxy ratio p aq n c 23 n c 27 n c 31 and pimarane 16 h phyllocladane ratio as well as lower relative abundance of c 31 r hopane of the latter one om of lower miocene coals is more mature corresponding to immature early mature stage huminite vitrinite reflectance 0 45 whereas om of upper miocene lignites is in immature diagenetic phase huminite reflectance 0 3 consequently higher gelification of lower miocene coals is probably an effect of higher rank however high humidity wet climate and low acidity within the mire could not be excluded a good correlation between biomarker parameters and paleoclimate data is observed indicating that biomarker patterns represent a valuable tool that reflect even slight paleoclimate changes in serbia during miocene

contrasting parageneses in the manganese silicate carbonate rocks from parseoni sausar group india and their interpretation mn silicate carbonate rocks at parseoni occur as conformable lenses within metapelites and calc silicate rocks of the precambrian sausar group india the host rocks are estimated to have been metamorphosed at uppermost p t conditions of 500 550 c and 3 4 kbar the mn rich rocks contain appreciable fe reflected in the occurrence of magnetite 1 mno 1 magnetite 2 mno 15 and magnetite 3 mno 10 two contrasting associations of pyroxmangite with and without tephroite developed in the mn silicate carbonate rocks under isothermal isobaric conditions the former assemblage formed in relatively fe rich bulk compositions and equilibrated with a metamorphic fluid having a low xco2 0 2 and the latter equilibrated with a co2 rich fluid rhodochrosite magnetite 1 quartz protoliths produced the observed mineral assemblages on metamorphism partitioning of major elements between coexisting phases is somewhat variable fe shows preference for tephroite over pyroxmangite at the ambient physical conditions of metamorphism oxygen fugacity during metamorphism was monitored at or near the qfm buffer in tephroite bearing domains and the fluid composition was buffered by mineral reactions in respective domains as compared to other metamorphosed mn deposits of the sausar group the mn silicate carbonate rocks at parseoni were therefore metamorphosed at much lower fo2 through complex mineral fluid interactions

a statistical analysis of the carbon isotope record from the archean to phanerozoic and implications for the rise of oxygen organic and inorganic carbon isotope records reflect the burial of organic carbon over geological timescales permanent burial of organic carbon in the crust or mantle oxidizes the surface environment atmosphere ocean and biosphere by removing reduced carbon it has been claimed that both organic and inorganic carbon isotope ratios have remained approximately constant throughout earth9s history thereby implying that the flux of organic carbon burial relative to the total carbon input has remained fixed and cannot be invoked to explain the rise of atmospheric oxygen schidlowski 1988 catling and others 2001 holland 2002 holland 2009 kump and others 2009 rothman 2015 however the opposite conclusion has been drawn from the same carbon isotope record des marais and others 1992 bjerrum and canfield 2004 to test these opposing claims we compiled an updated carbon isotope database and applied both parametric and non parametric statistical models to the data to quantify trends and mean level changes in fractional organic carbon burial with associated uncertainties and confidence levels we first consider a conventional mass balance model where carbon input to surficial reservoirs is balanced by burial of sedimentary carbonates and organic carbon for this model statistical analysis implies fractional organic burial has increased over earth history by a factor of 1 5 relative to organic burial at 3 6 ga with the 95 percent confidence interval ranging from factors of 1 2 to 2 0 an increase in organic burial by a factor of 1 2 cannot explain the rise of oxygen whereas an increase by a factor of 2 could conceivably explain the rise of oxygen there is however a highly significant and well constrained increase in organic burial from the proterozoic to the phanerozoic we also analyze changes in the difference between carbonate and organic carbon isotopic ratios over earth history there is a statistically significant increase in this difference from the early to late archean possibly caused by increased biological fractionation due to methanotrophic recycling this transition is consistent with the evolution of oxygenic photosynthesis at 2 8 ga or earlier finally we explore how these conclusions change if we modify the traditional mass balance model to include other carbon cycle fluxes specifically ocean crust carbonatization and authigenic carbonates because the size of these fluxes has a large poorly constrained range our statistical analysis with this uncertainty implies that the carbon isotope record does not constrain the history of organic burial at all however it remains possible that the magnitude of these additional processes has been inconsequential throughout geologic time in which case conclusions from the conventional model would be valid

variability of near term probability for the next great earthquake on the cascadia subduction zone the threat of a great m 9 earthquake along the cascadia subduction zone is evidenced by both paleoseismology data and current strain accumulation along the fault on the basis of recent information on the characteristics of this subduction system we estimate the conditional probabilities of a great earthquake occurring within the next 50 years and their variabilities the most important vari ation is associated with the existence of episodic slow slip on the deep portion of the subduction interface we show that these events modulate the conditional probability dramatically over their 14 month cycle during the 2 week slow slip events the weekly probability of a great earthquake is about 30 to 100 times as high as it is during any week of the rest of the year near term probabilities also vary significantly with the assumed distribution of earthquake recurrence intervals under a reference scenario of unimodal distribution of recurrence intervals about 500 600 years the 50 year conditional probability is low 0 12 at a 95 confidence interval how ever under a tantalizing bimodal distribution hypothesis this probability could be either four times as high 6 45 or four times as low less than 1 depending on whether the current interval is short 350 years or long 850 years

sedimentary manganese metallogenesis in response to the evolution of the earth system abstract the concentration of manganese in solution and its precipitation in inorganic systems are primarily redox controlled guided by several earth processes most of which were tectonically induced the early archean atmosphere hydrosphere system was extremely o2 deficient thus the very high mantle heat flux producing superplumes severe outgassing and high temperature hydrothermal activity introduced substantial mn2 in anoxic oceans but prevented its precipitation during the late archean centered at ca 2 75 ga the introduction of photosystem ii and decrease of the oxygen sinks led to a limited buildup of surface o2 content locally initiating modest deposition of manganese in shallow basin margin oxygenated niches e g deposits in india and brazil rapid burial of organic matter decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the archean proterozoic transition concurrently a massive drawdown of atmospheric co2 owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused paleoproterozoic glaciations 2 45 2 22 ga the spectacular sedimentary manganese deposits at ca 2 4 ga of transvaal supergroup south africa were formed by oxidation of hydrothermally derived mn2 transferred from a stratified ocean to the continental shelf by transgression episodes of increased burial rate of organic matter during ca 2 4 and 2 06 ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere black shale hosted mn carbonate deposits in the birimian sequence ca 2 3 2 0 ga west africa its equivalents in south america and those in the francevillian sequence ca 2 2 2 1 ga gabon are correlatable to this period tectonically forced doming up attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric co2 drawdown causing glaciation on the neoproterozoic rodinia supercontinent tectonic rifting and mantle outgassing led to deglaciation dissolved mn2 and fe2 concentrated earlier in highly saline stagnant seawater below the ice cover were exported to shallow shelves by transgression during deglaciation during the sturtian glacial interglacial event ca 750 700 ma interstratified mn oxide and bif deposits of damara sequence namibia was formed the varangian marinoan ca 600 ma cryogenic event produced mn oxide and bif deposits at urucum jacadigo group brazil the datangpo interglacial sequence south china liantuo nantuo varangian event contains black shale hosted mn carbonate deposits the early paleozoic witnessed several glacioeustatic sea level changes producing small mn carbonate deposits of tiantaishan early cambrian and taojiang mid ordovician in black shale sequences china and the major mn oxide carbonate deposits of karadzhal type central kazakhstan late devonian the mesozoic period of intense plate movements and volcanism produced greenhouse climate and stratified oceans during the early jurassic oae organic rich sediments host many mn carbonate deposits in europe e g urkut hungary in black shale sequences the late jurassic giant mn carbonate deposit at molango mexico was also genetically related to sea level change mn carbonates were always derived from mn oxyhydroxides during early diagenesis large mn oxide deposits of cretaceous age at groote eylandt australia and imini tasdremt morocco were also formed during transgression regression in greenhouse climate the early oligocene giant mn oxide carbonate deposit of chiatura georgia and nikopol ukraine were developed in a similar situation thereafter manganese sedimentation was entirely shifted to the deep seafloor and since ca 15 ma b p was climatically controlled glaciation deglaciation assisted by oxygenated polar bottom currents aabw nadw the changes in climate and the sea level were mainly tectonically forced

effect of maceral subtypes and mineral matrix on measured reflectance of subbituminous coals and dispersed organic matter abstract the variability in reflectance of huminite texto ulminite eu ulminite a and b different types of corpohuminite and liptinite groups of macerals in subbituminous coals was examined using reflected light microscopy all macerals were selected from coal and interbedded carbonaceous shale and carbonate sediment samples from the 515 m thick coal deposit no 2 located in the hat creek valley of south central british columbia the measurements obtained reveal that in addition to burial depth reflectance distribution depends on maceral subtypes and associated mineral matrix huminite in the coals and sediments kerogen consists mainly of humotelinite with eu ulminite b being the dominant maceral sub type reflectance values determined on huminite in coals and type iiib kerogen increase from eu ulminite a and phlobaphinite type 1 through eu ulminite b and phlobaphinite type 2 to gelinite the reflectance of all five huminite maceral subtypes studied increases with depth however the increase of phlobaphinite type 1 and gelinite reflectance with depth is irregular a comparison of the reflectance values obtained for the same maceral subtype eu ulminite b from the interbedded coal shale and carbonate samples records consistent differences implying some dependence of the reflectance and perhaps rate of organic maturation on the mineral matrix generally the highest eu ulminite b reflectance was recorded from carbonate rocks and the lowest from shale whereas coal matrix produced intermediate values at present it is not known whether differences in reflectance of eu ulminite found in the above lithologies are due to differential retention efficiency of reaction products removal thermal conductivity of the lithologies or existence of a calcium carbonate catalyst

malachite an indicator of major pliocene cu remobilization in a karstic environment katanga democratic republic of congo abstract malachite cu3 oh 2 co3 is a common mineral in the central african copperbelt where it constitutes a high grade 57 cu copper ore and is exploited industrially and by artisanal miners the genesis of this supergene ore in katanga has yet received little attention here we focus on the genetic processes giving rise to this regionally important mineral malachite is secondary to primary copper sulfides which indicates that it ultimately formed by oxidation of the latter in fine grained siliciclastic host rocks it is often partly impregnative commonly with variations in malachite content parallel to the bedding this type may form either by absolute enrichment or by in situ replacement of sulfides within voids of various types including dissolution cavities in carbonate host rocks it precipitates in distinctive forms such as thick laminated crusts and speleothemes up to several tens of centimeters in length ree geochemistry suggests that malachite formed in groundwater environments through in situ recombination of carbonate ions originating from dissolving host rock carbonates and downward percolating cu2 leached from copper sulfides thermodynamic modeling confirms this genetic environment and shows that chrysocolla cu al 2h2si2o5 oh 4 nh2o coexists with malachite when si content increases in the groundwater fluids the importance of karstic features in katanga is also re evaluated karstic features appear to be rather frequent and to constitute ideal site traps for the formation of secondary base metal ores

high precision slip distribution of the 1944 tonankai earthquake inferred from tsunami waveforms possible slip on a splay fault abstract inversion of tsunami waveforms is a well established technique for estimating the slip distributions of subduction zone earthquakes with some of the most detailed results having been obtained for earthquakes in the nankai trough sw japan the present study although it uses a method and tsunami waveform data set almost identical to previous study aims to improve on previous work by using a more precise specification of initial conditions for the calculation of tsunami green s functions specifically we incorporated four improvements in the present study 1 we used a realistic plate model based only on seismic survey results and assumed it to be the fault plane of the 1944 tonankai earthquake 2 the smallest subfaults consistent with the long wavelength approximation were used in the tsunami inversion analysis 3 we included the effect of horizontal displacement of the ocean bottom on tsunami generation and 4 we performed a checkerboard resolution test as obtained in previous studies a zone of high slip 2 0 m was resolved off the shima peninsula however the more precise calculation of tsunami green s functions has revealed additional detail that was not evident in previous studies which we demonstrate is resolvable and correlates with the position of known faults in the accretionary prism while there was little or no slip near the trench axis in the eastern part of the rupture zone there was up to 1 5 m of slip resolved within 30 km of the trough axis in the western part along the coast of the kii peninsula this troughward slip zone coincides with the position of a large splay fault mapped in multichannel reflection surveys furthermore it is also clear that the upper edge of the enshu fault off shima and atsumi peninsulas is consistent with the up dip limit of slip in the eastern part of our model we tested the possibility that slip occurred on the former splay fault instead of on the plate interface during the 1944 tonankai earthquake and find that slip on this splay fault is also consistent with the data although we cannot distinguish whether slip was dominant on the splay fault or on the plate interface we further suggest that the position of the enshu fault may be determined by the subduction of topographic highs and that such faults may have an important influence on the up dip rupture limit of the 1944 tonankai and potentially other subduction zone earthquakes

experimental investigation of oil generation retention and expulsion within type ii kerogen dominated marine shales insights from gold tube nonhydrous pyrolysis of barnett and woodford shales using miniature core plugs abstract although oil retention has recently emerged as a key topic of unconventional shale resource assessment oil retention and expulsion controls in organic rich shales during thermal maturation remain poorly constrained this study presents an experimental comparison of oil generation retention and expulsion in two immature type ii kerogen dominated marine shales the mississippian barnett shale and the upper devonian lower mississippian woodford shale mainly with respect to the combined effects of the organic macerals and rock fabric involved in both cases miniature core plugs drilled from the given samples were isothermally pyrolyzed at 130 to 425 c for 72 h under a confining pressure of 68 mpa during gold tube nonhydrous pyrolysis corresponding to the thermally immature early stage of the oil window the main stage of the oil window the late stage of the oil window the main stage of oil cracking to wet gas and the late stage of oil cracking yields of generated oil retained oil and expelled oil for the two studied samples were systematically quantified on the basis of mass balance calculation of measured oil and gas yields as well as rock eval analyses on pyrolyzed subsamples through the six stages of petroleum formation investigated the principal difference in oil generation was observed in the two studied samples with approximately 38 to 68 greater yields of generated oil equivalent to 130 mg oil g toco for the woodford shale when it evolved into the main and late stages of the oil window these elevated yields of generated oil for the woodford shale were compensated for by additional oil generation resulting from conversion of abundant type i kerogen like algae such as tasmanites and leiosphaeridia which lag in onset and have a shorter period of petroleum generation upon maturation as a response to the difference in oil generation oil retention was found to be significantly enhanced for the woodford shale at equivalent stages with 0 2 to 1 7 times more free oil equivalent to 24 105 mg oil g toco and 0 7 to 3 9 times more sorbed oil equivalent to 58 76 mg oil g toco being retained than that of the barnett shale although this effect was not pronounced for oil expulsion in contrast to the barnett shale relatively low expelled oil yields and expulsion efficiencies both indicate highly limited oil expulsion in the woodford shale implying that the woodford shale whose mineral composition and lithofacies are similar to those of the barnett shale may have a relatively low permeability rock fabric to prevent oil from being expelled furthermore not only significantly higher oil saturation index osi values but also a wider range of maturity at which the oil crossover effect osi 100 mg g toc occurs is expected for the woodford shale when extrapolation to a geological setting occurs these data suggest that the presence of abundant type i kerogen like algae and relatively low permeability rock fabric in the woodford shale are critical to significant oil retention during oil generation and expulsion which jointly raise the possibility of potential commercial shale oil within type ii kerogen dominated marine shales

chemostratigraphy of paleoproterozoic carbonate successions of the wyoming craton tectonic forcing of biogeochemical change the archean wyoming craton is flanked on the south and east by belts of paleoproterozoic supracrustal successions whose correlation is complicated by lack of geochronologic constraints and continuous outcrop however carbonate units in these successions may be correlated by integrating carbon isotope stratigraphy with lithostratigraphy the 10 km thick paleoproterozoic snowy pass supergroup in the medicine bow mountains was deposited on the present day southern flank of the wyoming craton it contains three discrete levels of glacial diamictite correlative with those in the huronian supergroup on the southern margin of the superior craton the nash fork formation of the upper snowy pass supergroup is significantly younger than the uppermost diamictite and was deposited after the end of the paleoproterozoic glacial epoch carbonates at the base of the nash fork formation record remarkable 13 cenrichment up to 28 v pdb whereas those from overlying members of the lower nash fork formation have d 13 c values between 6 and 8 carbonates from the upper nash fork formation above the carbonaceous shale have carbon isotope values ranging between 0 and 2 5 the transition from high carbon isotope values to those near 0 in the nash fork formation is similar to that at the end of the ca 2 2 2 1 ga carbon isotope excursion in fennoscandia this chemostratigraphic trend and deposition of bifs mn rich lithologies carbonaceous shales and phosphorites at the end of the global ca 2 2 2 1 ga carbon isotope excursion are likely related to ocean overturn associated with the final breakup of the kenorland supercontinent correlative carbonates from the slaughterhouse formation in the sierra madre wy and from the whalen group in the rawhide creek area in the hartville uplift wy have highly positive carbon isotope values in contrast carbonates from other exposures of the whalen group in the hartville uplift and all carbonate units in the black hills sd have carbon isotope values close to 0 combined with existing geochronologic and stratigraphic constraints these data suggest that the slaughterhouse formation and the succession exposed in the rawhide creek area of the hartville uplift are correlative with the lower and middle nash fork formation and were deposited during the ca 2 2 2 1 ga carbon isotope excursion the estes and roberts draw formations in the black hills and carbonates from other exposures in the hartville uplift postdate the ca 2 2 2 1 ga

the age of supergene manganese deposits in katanga and its implications for the neogene evolution of the african great lakes region abstract supergene manganese deposits commonly contain k rich mn oxides with tunnel structure such as cryptomelane which are suitable for radiometric dating using the 39ar 40ar method in africa mn deposits have been dated by this method for localities in western and southern parts of the continent whereas only some preliminary data are available for central africa here we present new 39ar 40ar ages for mn oxide samples of the kisenge deposit in southwestern katanga democratic republic of the congo the samples represent supergene mn oxide deposits that formed at the expense of primary paleoproterozoic rhodochrosite dominated carbonate ores main phases of mn oxide formation are dated at c 10 5 ma 3 6 ma and 2 6 ma for a core that crosses a mineralized interval the latter shows a decrease in age with increasing depth recording downward penetration of a weathering front surface samples of the kisenge deposits also record a c 19 2 ma phase as well as c 15 7 ma 14 2 ma and 13 6 ma phases the obtained ages correspond to distinct periods of paleosurface development and stability during the mio pliocene in katanga because katanga is a key area bordered to the north by the congo basin and to the east by the east african rift system these ages also provide constraints for the geodynamic evolution of the entire region for the mio pliocene the kisenge deposits record ages that are not systematically found elsewhere in africa although the 10 5 11 ma event corresponds to a roughly simultaneous event in the kalahari manganese field south africa the rest of the katanga paleosurface record differs somewhat from records for other parts of africa for which older eocene ages have been obtained this difference is most probably related to the specific regional geodynamic context uplift of the east african plateau with associated erosion and the opening of the east african rift system at c 25 ma are events whose effects in the study area interfere with those of processes responsible for the development of continent wide paleosurfaces

comparison between datangpo type manganese ores and modern marine ferromanganese oxyhydroxide precipitates based on rare earth elements abstract datangpo type sedimentary manganese deposits which are located in northeastern guizhou province and its adjacent areas are mn carbonate type deposits hosted in black carbonaceous shale that represent a series of medium to large deposits containing a huge tonnage of reserves paas normalized rare earth element distribution patterns of manganese ores record hat shaped rey ree y plots characterized by pronounced middle rare earth element enrichment evident positive ce anomalies weak to strong positive eu anomalies and negligible negative y anomalies these rey geochemical characteristics are different from those of country rocks and record the processes and features of sedimentation and diagenesis manganese was precipitated as mn oxyhydroxide particles in oxidized water columns with the sorption of a certain amount of rare earth elements subsequently transforming from mn oxyhydroxides to rhodochrosite and redistributing rey in reducing alkaline pore water during early diagenesis a number of similarities can be observed through a comparison of datangpo type manganese ores and modern marine ferromanganese oxyhydroxide precipitates based on their rare earth elements the precipitation of datangpo type manganese ores is similar to that of hydrogenetic crusts and nodules based on their positive ce anomalies and relatively higher total rey concentrations however several differences also exist compared to hydrogenetic crusts and nodules datangpo type manganese ores record smaller positive ce anomalies lower total rey concentrations unobvious fractionation between y and ho and weak to strong positive eu anomalies these were caused by quicker sedimentary rates in the oxic water columns of the shallower basin after which pore water became strongly reducing and alkaline due to the degradation of organic matter in the early diagenetic stage in addition compared to typical deposits in the world datangpo type manganese ores are similar to hydrogenetic deposits and different than hydrothermal deposits all of these characteristics of manganese ores indicate that datangpo type manganese ores the principal metallogenic factors of which include oxidation conditions during deposition and reducing conditions during early diagenetic stages represent hydrogenetic deposits

crustal velocity field of southwest japan subduction and arc arc collision we investigate crustal deformation in southwest japan over a 3 year period revealed by a permanent dense global positioning system gps array southwest japan is a part of the amurian plate a microplate moving about 10 mm yr toward the east with respect to the eurasian plate it overrides the philippine sea plate at the nankai trough and collides with the northeast japan arc in the central part of japan in this paper we first derive gps site velocities relative to the stable part of the amurian plate in order to isolate signals of crustal deformation caused by the subduction and or the collision the velocity field has a conspicuous feature indicating the interseismic elastic loading by the philippine sea plate slab at the nankai trough characterized by the northwestward movements of points throughout the studied area their amplitudes are the largest at the pacific coast and decay toward the japan sea coast with a subtle systematic shift of azimuths a model assuming an elastic half space the convergence rate at the nankai trough based on a refined euler vector and the strength of the coupling inferred from a thermal model could explain the velocity field in the western part of the studied area to a large extent those in the eastern part systematically deviate from them and the residual components there show east west shortening and north south extension this may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and northeast japan this suggests that the collision between southwest and northeast japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block a velocity contrast was found across the median tectonic line the largest inland active fault in japan but the current permanent gps network is not dense enough for us to discuss its coupling depth

the petrographical and organic geochemical composition of coal from the east field bogovina basin serbia abstract a petrological and organic geochemical study was performed on coal samples from the east field deposit bogovina basin serbia fourteen coal samples were collected from different parts of the main and upper coal seams from fresh working faces in the underground subbituminous coal mine the lower miocene coal of the east field is a typical humic coal with huminite liptinite and inertinite concentrations of up to 81 4 vol 16 1 vol and 13 5 vol respectively densinite is the most abundant maceral with variable amounts of ulminite and gelinite sporinite and liptodetrinite are the most common macerals of the liptinite group exsudatinite was detected in the lower part of the lower coal seam inertodetrinite is the most abundant maceral of the inertinite group the mineral matter consists mostly of clay minerals and carbonates the mean random huminite reflectance ulminite b for the main coal seam is 0 42 0 04 rr and 0 41 0 04 rr for the upper coal seam which are typical for an immature to early mature stage of the organic matter the distribution and abundance of n alkanes and steranes indicates a significant contribution of epicuticular waxes from higher plants high amount of phyllocladane type diterpenoids 16 h phyllocladane suggests that coal forming plants were conifer families taxodiaceae podocarpaceae cupressaceae araucariaceae sciadopityaceae and phyllocladaceae while a higher amount of pimarane and norpimarane suggests pinaceae taxodiaceae and cupressaceae the pristane phytane pr ph ratio implies variable anaerobic to oxic conditions during sedimentation the distribution of the hopanes detected in the bogovina east field coal indicates an immature to early mature stage of the organic matter which is in agreement with huminite reflectance the high coal sulphur contents from the east field are characteristic for slightly alkaline depositional environments generated by bentonite from the basement of the main coal seam the petrological observation and biomarker composition provide evidence for the generation of immature hydrocarbons which most probably originated from the resins and waxes of higher plants mostly gymnosperms

automated detection of slow slip events within the nankai subduction zone 1 we have developed a new automated method for the identification and location of slow slip events sses during episodic tremor and slip ets in the nankai subduction zone without any tremor information sse models are estimated from continuous tilt data using the kalman filter algorithm and a grid search and are eventually identified through statistical evaluations we applied this method to data recorded for two years in shikoku japan and successfully detected four sses coincident with major tremor bursts before the onset of sses precursory minor tremor activities usually occur around the fault where sses are subsequently detected when tremor migrates into the sse faults this suggests that an ets episode begins with geodetically undetectable small slip around the main fault and grows to a detectable sse such evolution of sse and tremor activity would reflect the spatial change in the slip property on the plate interface

how earth s atmosphere evolved to an oxic state a status report the evolution of the earth s atmosphere is essentially the story of atmospheric oxygen virtually every realm of the earth sciences biology geology geochemistry oceanography and atmospheric science is needed to piece together an understanding of the history of oxygen over the past decade new data from these fields has shown that there were two significant increases in atmospheric o2 levels at around 2 4 2 3 and 0 8 0 6 billion years ago respectively throughout earth history oceanic sulfate concentrations appear to have increased in accord with greater o2 levels while levels of methane a strong greenhouse gas may have inversely mirrored o2 both oxic transitions occurred in eras characterized by bsnowball earthq events and significant disturbances in the carbon cycle perhaps associated with increases in o2 and losses of methane to understand what controlled the oxygenation of the atmosphere it is necessary to determine how o2 is consumed on geologic time scales through reaction with reductants released from the earth s crust and mantle there was apparently a long delay between the appearance of oxygenic photosynthesis and oxygenation of the atmosphere and a plausible explanation is that excess reductants scavenged photosynthetic o2 from the early atmosphere however a quantitative understanding of how and why o2 became abundant on our reducing planet is still lacking thus the study of the early atmosphere remains a frontier field with much to be discovered d 2005 elsevier b v all rights reserved

steranes and triterpanes generated from kerogen pyrolysis in the absence and presence of minerals abstract steranes and triterpanes generated from pyrolysis of immature monterey formation kerogen in the presence and absence of calcite illite and montmorillonite reveal results that are both consistent and divergent with published data that reflect the use of these biological markers as maturation indicators the extent of isomerization of biomarkers generated from pyrolysis of kerogen at 300 c for 2 hours at c 20 in 14 h 17 h steranes at c 22 in 17 h 21 h hopanes and of 17 h 21 h hopanes correspond to early diagenetic stages in rock extracts from sedimentary basins isomerization increases with heating time and after 1000 hours attains values which correspond to the catagenetic stage in sedimentary basins or equivalent to that of mature oil stepwise pyrolysis of the kerogen indicates faster isomerization rates for steranes and triterpanes in the bitumen than for those retained in the kerogen structure confirming earlier studies presence of a mineral matrix can influence the isomerization of steranes and triterpanes considerably comparisons with results from kerogen heated alone for a given maturation stage show that calcite inhibits illite catalyzes slightly and montmorillonite has a pronounced catalytic effect on these reactions this effect results in early isomerization of steranes and hopanes corresponding to the catagenetic stage in the presence of montmorillonite while kerogen or kerogen with calcite held at the same temperature 300 c and time 10 hours only yield isomerized products which correspond to a diagenetic stage further illite and montmorillonite affect various isomerization reactions differently the fastest reaction is the isomerization at c 20 in 14 h 17 h steranes followed by that at c 22 in 17 h 21 h hopanes and the slowest is the formation of 14 h 17 h steranes these results show that maturation measurements of rock or oil samples from sedimentary basins which use biological markers have to take into account the mineral matrix effects which have been largely ignored until present

modeling of gas generation from the barnett shale fort worth basin texas the generative gas potential of the mississippian barnett shale in the fort worth basin texas was quantitatively evaluated by sealed gold tube pyrolysis kinetic parameters for gas generation and vitrinite reflectance ro changes were calculated from pyrolysis data and the results used to estimate the amount of gas generated from the barnett shale at geologic heating rates using derived kinetics for ro evolution and gas generation quantities of hydrocarbon gas generated at ro 1 1 are about 230 l t 7 4 scf t and increase to more that 5800 l t 186 scf t at ro 2 0 for a sample with an initial total organic carbon content of 5 5 and ro 0 44 the volume of shale gas generated will depend on the organic richness thickness and thermal maturity of the shale and also the amount of petroleum that is retained in the shale during migration gas that is reservoired in shales appears to be generated from the cracking of kerogen and petroleum that is retained in shales and that cracking of the retained petroleum starts by ro 1 1 this result suggests that the cracking of petroleum retained in source rocks occurs at rates that are faster than what is predicted for conventional siliciclastic and carbonate reservoirs and that contact of retained petroleum with kerogen and shale mineralogy may be a critical factor in shale gas generation shale gas systems together with overburden can be considered complete petroleum systems although the processes of petroleum migration accumulation and trap formation are different from what is defined for conventional petroleum systems

biomarker generation from type ii s kerogens in claystone and limestone during hydrous and anhydrous pyrolysis abstract a claystone and a limestone containing immature type ii s kerogen were thermally matured in the presence and absence of water to study the influence of water and clay minerals on the generation of biomarkers in contrast to hydrous pyrolysis anhydrous pyrolysis of the claystone did not generate biomarkers which resulted in the loss of important information desulfurization of the polar fraction of the claystone showed that anhydrous pyrolysis is not capable of converting s bound biomarkers to free biomarkers for the limestone the differences between hydrous and anhydrous pyrolysis are less dramatic adsorption of the polar fraction of the claystone to smectite interlayers probably leads to cross linking reactions preventing the generation of free biomarkers during hydrous pyrolysis the smectite interlayers are occupied by water so that generation of biomarkers can take place in addition cross linking reactions during anhydrous pyrolysis of the claystone may be enhanced because of the presence of s s bonds in the organic matter of the claystone these results show that water is important in closed system laboratory experiments designed to simulate natural maturation of sedimentary organic matter

geodetic data inversion using abic to estimate slip history during one earthquake cycle with viscoelastic slip response functions summary we developed a new method of geodetic data inversion to estimate slip history at a plate interface by using akaike s bayesian information criterion abic in this method we considered the effects of viscoelastic stress relaxation in the asthenosphere which cannot be neglected to estimate slip history at a plate interface during one earthquake cycle we also introduced a proper formulation to incorporate two sorts of partially dependent prior information into observed data by bayes rule by applying the new inversion method to levelling data for 1893 1983 in shikoku southwestern japan we reconstructed the pattern of space time variation in slip motion during one earthquake cycle including the 1946 nankai earthquake at the interface between the eurasian and the philippine sea plates the result shows that a steady slip motion at a plate convergence rate 40 mm yr 1 proceeds in the shallow and the deep regions through the entire earthquake cycle in the intermediate depth range 10 30 km on the other hand an instantaneous slip of approximately 4 m occurs at the time of the nankai earthquake after that this portion keeps in stationary contact until the occurrence of the next nankai earthquake if we neglect the effects of viscoelastic stress relaxation the inversion analysis gives geophysically unrealistic results

oxygen isotope perspective on crustal evolution on early earth a record of precambrian shales with emphasis on paleoproterozoic glaciations and great oxygenation event abstract we present stable isotope and chemical data for 206 precambrian bulk shale and tillite samples that were collected mostly from drillholes on all continents and span the age range from 0 5 to 3 5 ga with a dense coverage for 2 5 2 2 ga time interval when earth experienced four snowball earth glaciations and the irreversible rise in atmospheric o2 we observe significant downward shift of several and a smaller range of 18 o values 7 to 9 in shales that are associated with the paleoproterozoic and potentially neoproterozoic glaciations the paleoproterozoic samples consist of more than 50 mica minerals and have equal or higher chemical index of alteration than overlying and underlying formations and thus underwent equal or greater degrees of chemical weathering their pervasively low 18 o and d down to 85 values provide strong evidence of alteration and diagenesis in contact with ultra low 18 o glacial meltwaters in lacustrine deltaic or periglacial lake sikussak type environments associated with the paleoproterozoic glaciations the d silicate values for the rest of precambrian shales range from 75 to 50 and are comparable to those for phanerozoic and archean shales likewise these samples have similar ranges in 13 c org values 23 to 33 pdb and corg content 0 0 to 10 wt to phanerozoic shales precambrian shales have a large range of 18 o values comparable to that of the phanerozoic shales in each age group and formation suggesting similar variability in the provenance and intensity of chemical weathering except for the earliest 3 3 3 5 ga archean shales which have consistently lower 18 o values moreover paleoproterozoic shales that bracket in age the great oxidation event goe overlap in 18 o values absence of a step wise increase in 18 o and d values suggests that despite the first order change in the composition of the atmosphere weathering cycle was not dramatically affected by the goe at 2 4 2 3 ga shales do not show comparable 18 o rise in the early phanerozoic as is observed in the coeval 18 o trends for cherts and carbonates there is however a sharp increase in the average 18 o value from the early archean to the late archean followed by a progressively decelerating increase into the phanerozoic this decelerating increase with time likely reflects declining contribution of mantle extracted normal 18 o crust and lends support to crustal maturation and increasing 18o sequestration into the crust and recycling of high 18 o and 87sr 86sr sedimentary rocks this secular increase in the 18 o composition of the continental crust could have also had a mild effect on seawater 18 o composition

exsolution lamellae of kirschsteinite in magnesium iron olivine from an angrite meteorite exsolution phenomena of kirschsteinite cafesi04 in olivine have been studied by single crystal x ray diffraction techniques and scanning electron microscopy sem of oriented polished thin sections pts of three single crystals separated from the antarctic angrite lew86010 supplemented by micro area x ray diffraction with the laue method mxl by synchrotron radiation sr for pts of a rock chip of lew8601o the cell dimensions of the host olivine and exsolved kirschsteinite are a 4 79 3 b 10 39 5 and c 6 06 3 a and a 4 87 5 b 11 14 10 and c 6 36 5 a respectively from the precession photos the pts of olivine single crystals oriented parallel to 100 show exsolution lamellae of kirschsteinite up to i 0 m in width the two sets of lamellae are symmetrically related and parallel to 031 and 031 electron microprobe analysis gave si02 33 1 ti02 0 07 al203 0 03 feo 49 4 mno 0 61 mgo 13 4 cao 2 2 cr203 0 02 v203 0 01 nio 0 05 sum 99 4 wt for the host olivine and si02 33 3 ti02 0 03 feo 31 5 mno 0 39 mgo 5 4 cao 28 5 cr203 0 02 nio 0 05 sum 99 2 wt for the exsolved kirschsteinite the results from mxl for the olivine crystals on the rock pts are compatible with the observation on the single crystals that the lamellae are parallel to 031 and 031 the 031 and 031 planes have been known to be twin planes for olivine and the twinning is by reticular pseudomerohedry based on a quadruple lattice although other reported exsolved precipitates in meteoritic olivines exist as inclusions kirschsteinite in lew86010 olivine takes the form of lamellae our explanation is that lew86010 olivine is fe rich and that lamellar precipitates are more easily formed than inclusions because exsolution lamellae along 031 in fe rich olivine maintain lattice coherency

evaluation of the effects of native minerals on the organic matter of aleksinac oil shale based on the composition of free and bound bitumens abstract in order to evaluate the adsorption and catalytic effects of indigenous carbonates and silicates on the organic matter of aleksinac oil shale the free and the bound bitumens were isolated and analyzed by organic geochemical methods the differences in the gross compositions indicated an adsorption effect of both the carbonates and silicates in the examined oil shale the maturation parameters based on n alkanes and isoprenoid alkanes pristane and phytane indicated that bitumen 3 was of the highest and bitumen 1 of the lowest apparent maturity the silicates were shown to have had a thermocatalytic effect on the organic matter of this sediment clay minerals had a catalytic effect primarily on sterane aromatization rearrangement of steranes into diasteranes and their 20r 20s isomerization all evidence obtained by analysis of steranes and aromatic steroids suggested that the differences in bitumen compositions should be explained by the effect of clay minerals rather than by variations in the origin of the precursor biomass