seismic evidence for distinct anisotropy in the innermost inner core to understand the evolution of the inner core it is important to constrain the structure of its innermost part analysis of two types of seismic waves that traverse the inner core reveals seismic anisotropy of the innermost region and is consistent with the slowest direction of anisotropy being tilted away from the equatorial plane

zeolites in burial diagenesis and low grade metamorphic rocks many zeolite assemblages originated during burial and subsequent low grade metamorphism of rocks particularly those of volcaniclastic origin eskola 1939 first suggested this type of zeolitization and applied the term zeolite facies to assemblages formed under such low temperature and low pressure conditions although several definitions of the zeolite facies have been proposed over the years e g fyfe et al 1958 the phrase as used here includes both low grade metamorphic assemblages and zeolite assemblages formed successively during burial the regional occurrence of zeolites in sedimentary rocks was first recognized by coombs 1954 who made detailed petrographic studies of triassic tuffaceous greywackes and tuffs of andesitic to rhyolitic in composition in the taringatura area of new zealand coombs recognized a zonal arrangement of heulandite and analcime near the top of the sequence and heulandite and laumontite near the bottom he also recognized a similar progressive zeolitization with depth in clastic sediments in other orogenic belts the zeolite assemblages described by coombs represent a rather advanced stage of alteration as opposed to an earlier stage of zeolitization that was subsequently described in neogene silicic volcaniclastic rocks from japan in the latter rocks zones from top to bottom of fresh glass clinoptilolite mordenite analcime heulandite laumontite and albite were recognized utada 1965 1970 progressive zeolitization has also been reported as a result of the thermal effects of intrusive masses see seki et al 1969 and around volcanic calderas utada and ito 1989 recently boles 1991 described the low temperature formation of laumontite and stilbite in fractures and faults related to post jurassic folding and uplift of the southland syncline new zealand the physico chemical conditions of zeolite crystallization in burial diagenesis and low grade metamorphic environments can vary widely both borehole data see iijima 1995 and experimental results liou 1970 1971a b c

antipodal focusing of seismic waves observed with the usarray we present an analysis of the mw 5 3 earthquake that occurred in the southeast indian ridge on 2010 february 11 using usarray data the epicentre of this event is antipodal to the usarray providing us with an opportunity to observe in details the antipodal focusing of seismic waves in space and time we compare the observed signals with synthetic seismograms computed for a spherically symmetric earth model prem a beamforming analysis is performed over the different seismic phases detected at antipodal distances direct spatial snapshots of the signals and the beamforming results show that the focusing is well predicted for the first p wave phases such as pkp or pp however converted phases sksp pps show a deviation of the energy focusing to the south likely caused by the earth s heterogeneity focusing of multiple s wave phases strongly deteriorates and is barely observable

mechanisms of salinization in a middle eocene lake in the tanggu area of the huanghua depression abstract the sha 3 5 submember of the shahejie formation in the tanggu area of the huanghua depression contains analcime bearing dolomite indicating salinization of an ancient lake during deposition solar evaporation and hydrothermal salinization have both been proposed as ways to generate these saline conditions based on a comprehensive analysis of core data thin sections spore and pollen data elemental geochemistry pyrolysis results and vitrinite reflectance we assessed the mechanisms driving salinization in light of provenance evolution geothermal evolution paleoclimate mineral responses to evaporation and the relationship between fluid temperature and salinity the vertical profiles of ree eu eu and tmax exhibit little variation and the maximum paleotemperatures attained by organic matter are comparable to present day drill hole temperature no major changes in provenance or paleotemperature and no petrological fabrics that would indicate a hydrothermal input are observed in the studied section however evidence for a semi humid to semi arid climate primary evaporitic textures and structures and a positive relationship between fluid temperature and salinity all support evaporation as the primary mechanism driving rising salinity solar evaporation rather than hydrothermal eruption appears to have been the primary factor driving lake salinization during middle eocene deposition of the dolomitic sha 3 5 submember

zeolitic diagenesis of late quaternary fluviolacustrine sediments and associated calcrete formation in the lake bogoria basin kenya rift valley late quaternary fluviolacustrine siltstones mudstones and claystones loboi silts on the northern margins of the saline alkaline lake bogoria in the kenya rift valley contain up to c 40 authigenic analcime and minor natrolite the zeolitic sediments are reddish brown and up to 1 m thick the amount of analcime increases upward in the profile but decreases with distance from the lake the altered sediments show many pedogenic features including zeolitic root mats rootmarks concretions and carbonate rhizoliths residual patches of calcrete locally cap the zeolitic rocks the profile is interpreted as an exhumed palaeosol and land surface on the former margins of the lake the analcime occurs as submicroscopic 0 5 2 5 m subhedral and euhedral crystals which have an average si a 1 ratio of 2 33 as determined by x ray microanalysis or 2 18 d value of 639 analcime peak the analcime formed in lake marginal sediments soils by reaction of silicate detritus with na2co3 rich pore waters concentrated close to the land surface by evaporative pumping and evapotranspiration poorly ordered clay minerals were probably the main reactants authigenic illite may have been a by product of the reactions chemical analyses suggest that pore waters supplied some of na and possibly k and sio2 the associated calcrete and rhizoliths were formed during or shortly after the main period of zeolitic alteration the ca2 may have originated from infiltrating dilute runoff and groundwater authigenic smectite was precipitated in open porosity following analcime formation the zeolitic alteration at lake bogoria provides a relatively recent analogue for lake marginal zeolites found in many ancient saline alkaline lake sediments

zeolitization of intracaldera sediments and rhyolitic rocks in the 1 25 ma lake of valles caldera new mexico usa abstract quantitative x ray diffraction analysis of about 80 rhyolite and associated lacustrine rocks has characterized previously unrecognized zeolitic alteration throughout the valles caldera resurgent dome the alteration assemblage consists primarily of smectite clinoptilolite mordenite silica which replaces groundmass and fills voids especially in the tuffs and lacustrine rocks original rock textures are routinely preserved mineralization typically extends to depths of only a few tens of meters and resembles shallow caldera type zeolitization as defined by utada et al utada m shimizu m ito t inoue a 1999 alteration of caldera forming rocks related to the sanzugawa volcanotectonic depression northeast honshu japan with special reference to caldera type zeolitization resource geol spec issue no 20 129 140 geology and 40 ar 39 ar dates limit the period of extensive zeolite growth to roughly the first 30 kyr after the current caldera formed ca 1 25 to 1 22 ma zeolitic alteration was promoted by saturation of shallow rocks with alkaline lake water a mixture of meteoric waters and degassed hydrothermal fluids and by high thermal gradients caused by cooling of the underlying magma body and earliest post caldera rhyolite eruptions zeolitic alteration of this type is not found in the later volcanic and lacustrine rocks of the caldera moat 0 8 ma suggesting that later lake waters were cooler and less alkaline the shallow zeolitic alteration does not have characteristics resembling classic alkaline lake zeolite deposits no analcime erionite or chabazite nor does it contain zeolites common in high temperature hydrothermal systems laumontite or wairakite although aerially extensive the early zeolitic alteration does not form laterally continuous beds and are consequently not of economic significance

observations of exotic inner core waves the seismic structure of earth s inner core is highly complex displaying strong anisotropy and further regional variations however few seismic waves are sensitive to the inner core and fundamental questions regarding the origin of the observed seismic features remain unanswered thus new techniques to observe different types of inner core waves are imperative to improve data coverage here we detail our method for detecting exotic inner core phases such as pkjkp and pkiikp using inner core compressional waves as proof of concept we use phase weighted stacking on long period data from a global distribution of stations and employ several synthetic methods including normal mode summation and specfem to identify and confirm the inner core phases we present evidence for two observations of exotic inner core compressional waves and apply the technique to a previously detected inner core shear wave a possible new inner core shear wave remains unconfirmed additionally we show how our method is important for rejecting potential observations and distinguishing between waves with similar traveltime and slowness the method is most successful for detecting exotic inner core compressional waves and will provide a new approach for studying the compressional wave structures in the upper inner core

seismic velocity and attenuation structures in the top of the earth s inner core 1 we collect a global data set of pkikp and pkikp phases recorded by the global seismic network and many regional seismic arrays to study seismic structure in the top of the earth s inner core the pkikp and pkikp observations show different characteristics between those sampling the eastern hemisphere 40 e 180 e of the inner core and those sampling the western hemisphere 180 w 40 e pkikp phases 1 arrive about 0 4 s earlier than the theoretical arrivals based on preliminary reference earth model prem for those sampling the eastern hemisphere of the inner core and about 0 3 s later for those sampling the western hemisphere 131 141 2 bifurcate at smaller epicentral distances for those sampling the eastern hemisphere compared to those sampling the western hemisphere and 3 have smaller amplitudes for those sampling the eastern hemisphere waveform modeling of these observations suggests two different types of models for the two hemispheres of the top of the inner core with a model in the eastern hemisphere having a p velocity increase of 0 765 km s across the inner core boundary a small radial velocity gradient of 0 000055 km s km and an average q value of 250 and a model in the western hemisphere with a p velocity increase of 0 633 km s across the inner core boundary a radial velocity gradient of 0 000533 km s km and an average q value of 600 the hemispherical difference of seismic structures may be explained by different geometric inclusions of melt and or different alignments of iron crystals with anisotropic properties in both velocity and attenuation we speculate that this large scale pattern of seismic heterogeneities may be caused by a large scale heat flow anomaly at the bottom of the outer core and or different vigorousness of convection in the top of the inner core between the two hemispheres

a magmatic hydrothermal lacustrine exhalite from the permian lucaogou formation santanghu basin nw china the volcanogenic origin of fine grained clastic sedimentary rocks abstract shales in the middle permian lucaogou formation in the intracontinental santanghu rift basin have been considered as typical organic rich profundal shales for decades our study of well cores using petrographic microscope and scanning electron microscopy suggests an otherwise complex hydrovolcanic and hydrothermal origin this paper describes characteristics of a particular type of the shales composed of fine grained detrital minerals and lithic grains some of them are orthopyroxene calcite peralkaline feldspars and analcime that are interpreted as derived from peralkaline alkaline carbonatite pyroxenite analcime phonolite and andesite whereas others are quartz dolomite ankerite serpentine and calcite that were precipitated from syndepositional or penecontemporary hydrothermal fluids grain size ranges from 0 001 to 2 mm mostly 0 01 0 1 mm well developed laminae are mostly 0 5 3 mm thick and alternate with tuffaceous dolomicrite the rocks are interpreted as sublacustrine hydrovolcanic deposits which had been altered by syndepositional hydrothermal fluids the interpretation is substantiated by abundant cone shaped stratigraphic buildups on seismic sections in the basin this study shows an ancient example of volcanic hydrothermal deposits in a rift basin

formation of zeolites in open hydrologic systems in contrast to those deposits formed by the alteration of volcanic ash in saline alkaline lakes discussed in the chapter by hay and sheppard this volume large volumes of tuffaceous sediments around the world have been transformed to zeolites and other authigenic silicate minerals by the action of percolating water in open hydrologic systems these include systems that have experienced significant chemical and hydrologic exchanges with the surrounding environment tephra sequences exposed to open system alteration commonly show a vertical zonation of zeolites and other authigenic minerals that reflects the chemical changes in meteoric water moving through the system flow in an open hydrologic system can either be downward or have a downward component where meteoric water enters the system resulting in a vertical or nearly vertical zonation of water composition and authigenic minerals the original pyroclastic materials of tuffaceous sediments may have been laid down in the sea close to the volcanic sources air laid onto the land surface or reworked into fluviatile and freshwater lacustrine environments open system zeolite deposits are most common in nonmarine rocks although many are known in sediments that were deposited in shallow marine environments zeolite deposits of the open system type are commonly several hundred meters thick and can be traced laterally for several tens of kilometers many examples of zeolite deposits that formed from land laid tephra have been recognized in the western united states but most of the large marine deposits are in japan and in southern and southeastern europe because of their relatively large and commonly discontinuous areal extent open system deposits have not been studied in as much detail as some other types of zeolite deposits in sedimentary rocks however studies of several key areas have provided a sound basis for the current understanding of this type of zeolite body zeolitic alteration can take place

genetic mechanism of high quality reservoirs in permian tight fan delta conglomerates at the northwestern margin of the junggar basin northwestern china fan delta conglomerate reservoirs in the permian jiamuhe formation in the zhongguai area at the northwestern margin of the junggar basin northwestern china are reservoirs for large accumulations of natural tight gas the tight conglomerates and sandstones are mainly litharenites with a large amount of texturally and compositionally immature volcanic clastic materials core porosities demonstrate the development of anomalously high porosities at depths of 3200 4200 m 10 500 13 800 ft and 4500 4900 m 14 800 16 100 ft the permian reservoirs experienced initial rapid subsidence uplift and further subsidence and diagenetic reactions occurred in these reservoirs involving compaction precipitation of chlorite clays calcites zeolites iron oxides kaolinite and quartz cements and dissolution of unstable minerals including analcite laumontite feldspars and rock fragments low porosity reservoirs with extensive compaction and or cementation of calcite and heulandite ca consist of only few visible secondary pores formed by dissolution of feldspars and rock fragments reservoirs with anomalously high porosity however experienced relatively weak compaction and contain significant amounts of secondary pores formed by dissolution of mainly laumontites some feldspars and rock fragments comprehensive studies of sedimentary features and diagenesis of the reservoirs indicate that these anomalously high porosities originate from chronological coupling of four important geological processes 1 sedimentary facies and detrital compositions controlled distribution of various zeolites in reservoirs with abundant laumonites developed in reservoirs in the fan delta front subfacies 2 early precipitation of the laumontites inhibited compaction during deep burial however they provided unstable minerals for secondary porosity development 3 the permian reservoirs experienced subaerial exposure erosion during the uplift stage and meteoric freshwater leached laumontite cements and aluminosilicate grains to form secondary pores in reservoirs beneath the unconformity 4 hydrocarbon emplacement at relative shallow depth during a second subsidence period preserved the secondary pores in reservoirs by retarding late carbonate cementation

genesis of poikilotopic zeolite in aeolianites an example from the parnaiba basin ne brazil abstract zeolite cement is one of the main components of the jurassic to lower cretaceous fluvial aeolian succession in the parnaiba basin northeastern brazil core and outcrop based stratigraphic analyses permitted the paleo environmental and diagenetic interpretation of aeolian sandstone and showed the influence of the volcanic substrate in the origin of the zeolite cement the substrate is represented by an extensive volcanic plain developed in the last stages of the central atlantic magmatic province camp in west gondwana the siliciclastic deposits consist of dune field sand sheet and wadi deposit facies associations the zeolite cement of the aeolian succession forms poikilotopic crystals with anomalous up to 50 modal content x ray diffraction and sem eds cl analyses showed laumontite and ca stilbite exhibiting respectively massive and radial textures during eodiagenesis the main processes included clay infiltration linked to water table fluctuations and flash flood events producing clay coatings and displacive stilbite cementation massive laumontite cementation and smectite chlorite conversion occurred in the mesodiagenesis while in the final stages the zeolite was partially replaced by calcite cement telodiagenesis is recorded by iron exsudation and the corrosion of clay films several processes can be inferred to explain the origin of the zeolite cement in the jurassic lower cretaceous sandstone of the parnaiba basin after the first magmatic pulse triassic magmatism the zeolite bearing basalts were submitted to chemical weathering causing cation leaching afterwards the deposition of aeolian sands related to a wet desert system occurred above this weathered substrate fractured basaltic substrate favored the release of ions to the surface with fluids enriched in sodium and calcium that percolated the permeable aeolian sandstone beds during the diagenesis furthermore zeolite cement is geographically associated with the volcanic substrate in the western parnaiba basin however it is absent in the eastern part where the aeolianites overlie sedimentary rocks we suggest that the system was thermally reactivated by the last thermal camp phase with basalt emplacement in the eastern parnaiba basin linked to the opening of the equatorial atlantic ocean cretaceous magmatism the progressive heating towards the western part of the basin triggered fluids convection and the enrichment in ions such as ca2 si4 na al3 hco 3 and so42 promoting optimal conditions for zeolite crystal growth 100 c 300 c sandstone textural aspects as well as extensional faults and fractures allowed fluids migration resulting in the massive poikilotopic zeolite cementation characterizing one of the most singular features of the diagenetic history of the west gondwana record

waveform search for the innermost inner core abstract waveforms of the pkikp seismic phase are inconsistent with the effects of a sharp boundary at 300 km radius of an inner most inner core seismograms synthesized for the distance range 150 to 180 in models having a discontinuity at 300 km radius in the inner core exhibit focused diffractions around the innermost sphere at antipodal range that are inconsistent with observed pkikp waveforms a few examples however can be found of pkikp complexity near 165 consistent with a triplication created by a 475 km radius discontinuity a rapid change in the magnitude and variance of seismic attenuation of pkikp whose rays turn between 400 and 600 km radius is also observed consistent with an innermost sphere of low regionally uniform seismic attenuation models predicting waveforms in agreement with observed waveforms have either a transition in elastic and anelastic properties spread over a depth interval greater than 100 km or an innermost sphere of differing elastic properties that exceeds 450 km radius the weak but suggestive evidence for an innermost inner core may simply represent a transition in fabric spread over 100 km or more centered near 500 km radius this change may signify the end stage of solidification flow and re crystallization resulting in the highest ordering and largest grain sizes of intrinsically anisotropic crystals

formation of analcime and moganite at lake lewis central australia significance of groundwater evolution in diagenesis abstract lake lewis basin in the northern territory is a hydrologically closed intermontane basin in which clay rich palaeolacustrine sediments are infused with highly evolved brines acquisition of dissolved silica and sodium by groundwaters from the proterozoic arunta granite gneiss terrain and from arkosic alluvium and weathering products sourced from these bedrocks is important to diagenesis at the salt lake supersaturation of groundwaters with respect to sio 2 and the availability of catalytic ions coupled with high rates of evaporation favour neoformation of opal and chalcedonic silica from solution near the groundwater discharge zone moganite a distinctive silica polymorph that is commonly associated with evaporites has been identified amongst precipitated silica species down gradient from the zone of silica precipitation beneath the playa brines are sio 2 deficient long periods of weathering and diagenesis of lacustrine clays immersed in semi stagnant brines has transformed detrital minerals into substantial proportions of amorphous or gelatinous aluminosilicate material aluminosilicate phases have become metastable in the presence of evolved sio 2 deficient interstitial brine analcime a sodium bearing zeolite group mineral is stable in the presence of the na rich brine and is crystallizing authigenically below the watertable from the amorphous aluminosilicate material in the lacustrine sediment no volcanic rocks or pyroclastic sediments are involved in this diagenetic occurrence of analcime the appearance of analcime in the evolution of the salt lake system probably commenced within the last 100 000 years and is occurring in the present day hydrologic and climatic regime of this arid zone area

occurrence composition and origin of analcime in sedimentary rocks of non marine petroliferous basins in china abstract natural analcime a highly brittle aluminosilicate mineral that dissolves easily during diagenesis occurs in the sedimentary rocks of eight main non marine petroliferous basins in china this mineral has been well documented for the past 30 years and has proved to be significant for the formation of high quality hydrocarbon reservoirs the present study fully reviews analcime occurrences chemical compositions si al ratios origin and controlling factors and influence on the hydrocarbon reservoir quality in permian to paleogene sedimentary rocks previous research has shown that analcime is commonly distributed within argillaceous laminae l type occurs as intergranular cement c type replacement r type and crack filling f type forms or is closely intergrown with other authigenic exhalative minerals a type analcime in lacustrine basins is slightly al rich and na poor and its si al ratios range from 1 95 to 2 80 the geochemical compositions of the analcime and ankerite bearing exhalites are characterised by enrichment in light rare earth elements and 13c and depletion in heavy rare earth elements and 18o with negative eu and positive ce anomalies diagenetic analcime forms by the alteration of volcanic glass clays or zeolite precursors in saline alkaline lakes or during buried diagenetic stages in sedimentary rocks in addition it coexists with other authigenic zeolite carbonate and clay minerals as well as albite hydrothermal analcime presumably precipitates from hydrothermal fluids and is not dependent on a local precursor mineral or volcanic glass this type is commonly related to exhalative mineralisation of hydrothermal springs the formation of natural analcime is controlled by various factors such as the composition of the parent material temperature prevalent during crystallisation chemistry of the fluid phase and thermodynamic characteristics of the geological environment as zeolites are formed in alkaline fluid phases they become unstable in acidic pore water secondary pores created by analcime mineral dissolution and intercrystalline micropores among analcime minerals are highly significant in hydrocarbon reservoirs analcime bearing mudstone siltstone dolostone and exhalite are favourable lithofacies for unconventional hydrocarbon accumulation owing to its high brittleness and selective dissolution of analcime and other associated minerals

a diagenetic study of intrabasaltic siliciclastics sandstones from the rosebank field abstract the rosebank field contains producible hydrocarbons from paleocene eocene intrabasaltic fluvial and shallow marine siliciclastic sandstone reservoirs despite close proximity to volcanic lithologies the siliciclastic sandstones display very good reservoirs properties with permeability in the darcy range and porosity values ranging from 19 to 23 preservation of high quality reservoir properties is the result of low quantities of volcanic minerals in the siliciclastic sandstones and limited element diffusion e g fe and mg from adjacent basalts into siliciclastic reservoir sandstones the low content of volcanic derived detritus is most likely a result of the main sediment source being situated outside the volcanic terrain the effect is that formation of clay minerals smectites and or chlorites reducing permeability and porosity is low in contrast to the siliciclastic sandstones the pore space of the volcaniclastics is occupied by authigenic clays chlorite smectite and carbonates calcite and mg calcite resulting in poor reservoir quality this paper demonstrates that high quality reservoirs can be found in intrabasaltic siliciclastic reservoirs in depth analyses of core samples show that authigenic phases formed during progressive burial with temperatures up to 120 c the suite of diagenetic phases in siliciclastic sandstones between wells and the different colsay units vary and are interpreted to result from differences in pore water chemistry and or detrital mineralogy laumontite was formed as a late stage authigenic mineral restricted to cored colsay 1 and 3 units in well 213 26 1z and has not been observed in the neighbouring 213 27 2 core which may be explained by differences in pore water ph or co2 partial pressure the occurrence of laumontite is often associated with poor reservoir quality but due to the patchy distribution of this mineral in the rosebank reservoir sands it appears not to have affected reservoir quality

antipodal seismic observations of temporal and global variation at earth s inner outer core boundary 1 we have found two pairs of earthquake doublets closely located antipodally on one diametral axis between tonga algeria and several other events on other axes these doublets show significant correlation and exhibit seismic phases traversing the core that cannot be explained by a standard radial earth model such as prem the antipodal waveform data are highly variable between axes the observed variability of the waveforms indicates global variations in the structure above and below the inner outer core boundary region we have found evidence for a regional low velocity zone at the base of the outer core corresponding with a decadal temporal variation 0 55 s in seismic energy traversing the top of the inner core we propose an antipodal seismic array to constrain and to provide further progress for the study of the inner and outer core

discovery of sublacustrine hydrothermal activity and associated massive sulfides and hydrocarbons in the north tanganyika trough east african rift massive sulfides and carbonate mineral deposits associated with sublacustrine thermal springs were recently discovered along the zaire side of the north tanganyika trough western branch of the east african rift this hydrothermal activity investigated by scuba diving at a maximum depth of 20 m is located at the intersection of major north south normal faults and northwest southeast faults belonging to the tanganyika rukwa malawi trm strike slip fault zone the preliminary results presented here come from analyses of sulfide deposits hydrothermal fluids and associated hydrocarbons that result from geothermal activity in this part of the east african rift filled by a thick pile of sediment the north tanganyika trough

the innermost inner core of the earth evidence for a change in anisotropic behavior at the radius of about 300 km since the discovery of the inner core in 1936 no additional spherical subshell of the earth has been observed based on an extensive seismic data set we propose the existence of an innermost inner core with a radius of 300 km that exhibits a distinct transverse isotropy relative to the bulk inner core specifically within the innermost inner core the slowest direction of wave propagation is 45 from the east west direction in contrast the direction of the slowest wave propagation in the overlying inner core is east west the distinct anisotropy at the center of the earth may represent fossil evidence of a unique early history of inner core evolution

detection of inner core solidification from observations of antipodal pkiikp pkiikp waves reflected from the underside of the inner core boundary are very sensitive to the s velocity in the uppermost 80 km of the inner core at antipodal distances undergoing a phase change and a factor of 4 amplification as the distance approaches 180 modeled pkiikp waveforms are consistent with a near zero shear modulus in the uppermost inner core in a 20 40 km thick patch beneath the eastern equatorial hemisphere this bright spot of pkiikp reflection correlates with a thin zone of low p velocity inferred from the complexity of pkikp waveforms sampling this patch estimates of grain sizes from seismic attenuation the absence of backscattered pkikp coda in this region and a prediction for enhanced heat flow through this patch suggest that it is a region of solidification rather than melting

detecting seismic anisotropy above the 410 km discontinuity using reflection coefficients of underside reflections abstract we investigate the effect of various types of deformation mechanisms on the reflection coefficients of p and s waves underside reflections off the 410 km discontinuity to develop a diagnostic tool to detect the style of deformation at boundary layers we calculate the reflection coefficient for p and sh underside reflections using velocity perturbations resulting from aligned minerals above the 410 km discontinuity for different deformation scenarios the results show that in the case of an anisotropic olivine layer above an isotropic wadsleyite layer the p wave reflection coefficient amplitudes are only slightly influenced by the joint effect of angle of incidence and the strength of imposed deformation without any polarity reversal and for all deformation styles for the sh wave underside reflections the incidence angle for which a polarity reversal occurs changes with distance for all scenarios and in addition changes with azimuth for shear deformation scenarios these differences in amplitude and polarity patterns of reflection coefficients of different deformation geometries especially for s wave at shorter distances potentially provide a possibility to distinguish between different styles of deformation at a boundary layer we also show a first test using currently available elastic constants of anisotropic wadsleyite beneath anisotropic olivine

structure and dynamics of earth s inner core abstract the seismological exploration of the earth s inner core has revealed unexpected and puzzling structural complexities its elastic anisotropy is now well established and has been shown to vary spatially there is a well defined hemispherical dichotomy in anisotropy and attenuation and significant variations in the radial direction with weaker anisotropy in the uppermost regions and possibly different properties in an innermost inner core of radius 300 600 km perhaps even more puzzling is the observation of a stably stratified layer at the base of the outer core which has recently been proposed to result from melting of inner core material if confirmed the presence of this layer has major implications for our understanding of convection in the outer core inner core differential rotation with respect to the mantle remains controversial we will review here recent progress in understanding the dynamics of the inner core a number of different models have been proposed for the development of the inner core s structure and formation of the stable layer at the base of the outer core and particular care will be taken to clarify under which conditions the proposed mechanisms can be active

shear wave anisotropy of textured hcp fe in the earth s inner core abstract many seismological studies have confirmed that vp travels 3 4 faster along the rotation axis of the earth than along the equatorial plane in the inner core indicating that the inner core is elastically anisotropic however seismic and mineral physics observations of the polarized vs are still emerging thus far the vs anisotropy of the constitute iron crystals at relevant pressures of the earth s core has remained mostly theoretical mainly because of the technical difficulties involved in measuring reliable vs velocities of iron crystals here we have measured azimuthal vs anisotropy of highly textured hcp fe at high pressures using nuclear resonant inelastic x ray scattering a technique sensitive to vs in a diamond anvil cell our results show that the azimuthal vs is 2 4 faster along the crystallographic c axis than along the a axis at 158 gpa and 172 gpa if one describes the vp anisotropy of the inner core as a result of the textured hcp fe crystals it is conceivable that azimuthal and polarized vs anisotropies with a magnitude of a few percent also exist in the region since vp and vs of candidate iron phases behave quite differently in theoretical predictions our results here indicate that future seismic observations of the vs and vp anisotropies of the inner core thus hold the key to deciphering the causes for the seismic and dynamic signatures as well as constitute iron phase s of the region

occurrence of zeolites in sedimentary rocks an overview zeolites have been known since the mid 1750s but prior to the early 1950s most reported occurrences of zeolites were in fracture fillings and amygdules in igneous rocks particularly basaltic lava flows indeed most of the large attractive zeolite specimens in museum collections were obtained from lavas in recent years zeolites have been recognized as important rock forming constituents in low grade metamorphic rocks and in a variety of sedimentary rocks most zeolites in sedimentary rocks are finely crystalline that is they occur as microscopic or submicroscopic crystals and they are therefore of little appeal to mineral collectors however deposits of this type are voluminous and have great geologic significance and economic potential zeolites are among the most common authigenic silicate minerals that occur in sedimentary rocks and they form in sedimentary rocks of diverse lithology age and depositional environment about twenty species of zeolites have been reported from sedimentary rocks but only eight zeolites commonly make up the major part of zeolitic rocks these are analcime chabazite clinoptilolite erionite heulandite laumontite mordenite and phillipsite this chapter will consider chiefly the zeolites in sedimentary rocks with emphasis on volcaniclastic deposits which contain the largest concentrations of zeolites the occurrence of zeolites in lava flows is mentioned only briefly journal articles on the occurrence and origin of natural zeolites have multiplied at a rapid rate since the mineralogy and geology of natural zeolites was first published in 1977 as volume 4 of the mineralogical society of america s reviews in mineralogy the present review will highlight areas of more recent research on the occurrence and origin of zeolites and some of the coexisting minerals a wide variety of zeolites has been identified in sedimentary deposits with the most common being clinoptilolite analcime heulandite laumontite and phillipsite less abundant zeolites include chabazite erionite mordenite natrolite

zeolites in petroleum and natural gas reservoirs zeolites have been reported in petroleum and natural gas reservoirs of a wide range of geological ages from many parts of the world such zeolite bearing oil and gas reservoirs are not comparatively large in number and scale however where present in petroleum and natural gas reservoirs zeolites can have profound effects on the quality of the reservoirs affecting rock porosity and permeability zeolite containing reservoir rocks vary widely lithologically including not only porous pelitic sedimentary rocks but also volcanogenic rocks and even fractured intrusive and plutonic rocks several different genetic types of zeolite occurrences have been distinguished and classified e g hay 1966 1986 1995 iijima 1980 1986 as hay and sheppard discussed and summarized in an earlier chapter this volume in addition the organic origin theory for the formation of economic oil and gas resources seems to have been universally accepted including the prominent kerogen decomposition theory summarized by tissot and welte 1978 sedimentary basins filled by very thick sequences of sedimentary strata containing organic rich source rocks and porous reservoir rocks are considered necessary for producing hydrocarbon resources such sedimentary basins develop primarily through rifting or in relation to arc formation at active plate boundaries and they are often accompanied by heating and extensive volcanic activity most types of zeolite occurrence are consequently constrained to burial diagenesis uplift related late stage diagenesis surdam and boles 1979 boles 1993 and hydrothermal alteration as will be discussed in this chapter zeolites in hydrocarbon reservoir rocks occur commonly as cements and grain replacements in the form of disseminated microcrystalline aggregates and occasionally as macroscopic crystals in vugs and veins it was in 1950s that coombs and co workers pioneered the petrologic study of rock forming zeolites through their classic research on burial metamorphism of the triassic geosynclinal deposits in south syncline new

clay mineral assemblages and analcime formation in a palaeogene fluvial lacustrine sequence maiz gordo formation palaeogen from northwestern argentina abstract the palaeogene maiz gordo formation is one of the main lacustrine events recorded in northwestern argentina it consists of sandstone mudstone and limestone beds 200 m thick deposited in a brackish alkaline lake and braided alluvial systems the maiz gordo lake evolved mainly as a closed system with brief periods as an open one x ray diffraction xrd and scanning electron microscopy sem were used to study samples from seven sites corresponding respectively to proximal intermediate and transitional positions of the fluvial environment and marginal and inner lake environment focusing on the clay mineralogy and analcime formation the basinward zonation of diagenetic minerals identified in the maiz gordo lake was mordenite analcime k feldspar although not a typical zonation of saline alkaline lakes it does indicate an increase in salinity and alkalinity towards the centre in proximal fluvial settings smectite predominates at the base of the sequence with scarce kaolinite towards the top a striking increase in kaolinite content suggests a change from a relatively arid climate with alternating humid and dry seasons towards a warm and humid climate kaolinite content clearly decreases in a basinward direction such a variation is attributable to changes in hydro geochemistry denoting the progressive influence of the brackish and alkaline lake water on interstitial pores sem images of intermediate fluvial samples reveal authigenesis of illite at the expense of kaolinite booklets in littoral and inner lake settings the clay fraction is composed of muscovite sometimes with subordinate smectite analcime occurs in variable amounts in all sedimentary facies in rock pores or filling veins it forms subhedral square to hexagonal or anhedral rounded crystals denoting that they coarsened at low to moderate degrees of supersaturation although the mordenite identified in a fluvial level would have been the precursor of analcime in the maiz gordo basin no textural evidence of analcime formation through replacement of mordenite or other precursor zeolite was found hence it is more probable that analcime formation took place by direct authigenic precipitation or through the reaction between interstitial brines and clay minerals or plagioclase

geochemistry of high h2 and ch4 vent fluids issuing from ultramafic rocks at the rainbow hydrothermal field 36 14 n mar the flores diving cruise was part of the mast iii amores 1995 1998 program funded by the european union one of the major achievements of the flores cruise was the discovery of the rainbow hydrothermal field hosted in ultramafic rocks south of the amar segment on the mid atlantic ridge mar the rainbow hydrothermal fluids exhibit temperatures of 365 c ph of 2 8 high chlorinity 750 mmol kg and low silica 6 9 mmol kg the uniformity in endmember major minor trace element concentrations and gas contents suggests that all rainbow fluids originate from the same deep source although h2s content is relatively low 1 20 mmol kg all vent fluids show extraordinary high h2 16 mmol kg ch4 2 5 mmol kg and co 5 mol kg endmember concentrations compared to fluids collected from other vent sites along the mar hydrogen represents more than 40 of the total gas volume extracted from the fluids at rainbow h2 production is likely associated with alteration of olivine and orthopyroxene minerals during serpentinization given that exposures of ultramafic rock may be common particularly along slow spreading ridges the production of h2 may have important implications for microbial activity at and beneath the seafloor

great tsunamigenic earthquakes during the past 1000 yr on the alaska megathrust large to great earthquakes and related tsunamis generated on the alaska megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the pacific ocean recent modeling studies suggest that single segment ruptures as well as multi segment 1964 type ruptures can produce great earthquakes m8 and significant hazards both in the near field and to distant locations through the generation of tsunamis we present new paleoseismological data from kodiak island and a new analysis of radiocarbon data based on bayesian age modeling to combine our observations with previous geological historical and archaeological investigations we suggest that in addition to multi segment ruptures in a d 1964 and 1020 1150 95 age estimate a single segment rupture occurred in 1788 with coseismic land surface deformation across kodiak island and a tsunami that is recorded in historical documents and in sediment sequences and another similar rupture of the same kodiak segment at a d 1440 1620 these indicate shorter intervals between ruptures of the kodiak segment than previously assumed and more frequent ruptures than for the prince william sound segment

core structure re examined using new teleseismic data recorded in antarctica evidence for at most weak cylindrical seismic anisotropy in the inner core we present a significant addition to the data set of traveltimes of seismic pkp waves that sample the earth s lowermost mantle and core along the earth s rotation axis recorded at permanent global seismic network gsn and temporary sscua deployment broad band seismographic stations in antarctica the new data improve the previously poor and biased coverage that underlies the seismic constraints on recent models of inner core structure and anisotropy on the one hand new differential pkp traveltime measurements improve the sampling of predominantly the eastern inner core hemisphere pkpab df and pkpbc df differential traveltime residuals with respect to the spherically symmetric model ak135 are consistently smaller than two seconds along the north south paths sampled axially symmetric models of inner core seismic anisotropy with fast axis parallel to the earth s rotation axis require a weak anisotropy of 0 7 0 1 per cent to be consistent with our pkpbc df observations pkpbc df residuals from the quasi eastern hemisphere indicate 0 4 0 1 per cent anisotropy if only pkpbc df observations from the top 200 km of this hemisphere are considered this is reduced to 0 1 0 2 per cent consistent with an isotropic layer on the other hand new absolute pkp traveltime measurements add to the sampling of both hemispheres of the inner core but it is difficult to use them with more confidence to assess structure of the core since they are affected by crustal and mantle structure and source uncertainties the newly collected data set also increases constraints on d structure beneath the south pole in contrast to previous inferences based on data from northern stations we find no evidence of a velocity heterogeneity in the outer core near the inner core boundary associated with the cylinder tangent to the inner core in the southern hemisphere

anatomy of a submarine pyroclastic flow and associated turbidity current july 2003 dome collapse soufriere hills volcano montserrat west indies the 12 to 13 july 2003 andesite lava dome collapse at the soufriere hills volcano montserrat provides the first opportunity to document comprehensively both the sub aerial and submarine sequence of events for an eruption numerous pyroclastic flows entered the ocean during the collapse depositing approximately 90 of the total material into the submarine environment during peak collapse conditions as the main flow penetrated the air ocean interface phreatic explosions were observed and a surge cloud decoupled from the main flow body to travel 2 to 3 km over the ocean surface before settling the bulk of the flow was submerged and rapidly mixed with sea water forming a water saturated mass flow efficient sorting and physical differentiation occurred within the flow before initial deposition at 500 m water depth the coarsest components 60 of the total volume were deposited proximally from a dense granular flow while the finer components 40 were efficiently elutriated into the overlying part of the flow which evolved into a far reaching turbidity current

thermogenetic degradation of early zeolite cement an important process for generating anomalously high porosity and permeability in deeply buried sandstone reservoirs abstract diagenetic explanations to anomalously high porosities and permeabilities in deeply buried sandstones have been presented for many reservoirs for example grain coatings of microquartz or chlorite can preserve porosity by preventing succeeding quartz overgrowths and dissolution of grains or cement can generate secondary porosity anomalously high porosity and permeability up to 25 and 500 md respectively characterize the deeply buried 5 km upper jurassic shoreface sandstones of the gert member heno formation in the hejre field in the danish central graben optical cathodoluminescence and scanning electron microscopy were used to characterize the petrography and diagenetic changes that resulted in this high pressure and high temperature hpht reservoir this was supplemented by chemical analyses icp oes and icp ms mineralogical composition xrd and oxygen isotope composition of quartz and calcite cement sims the petrographic investigation shows that none of the known explanations for anomalously high porosity and permeability can be applied hence a new hypothesis for deeply buried sandstones in contact with lavas and volcaniclastic lithologies is proposed the new hypothesis includes reducing mechanical compaction due to early patchy zeolite cement which was sourced from adjacent lavas and volcaniclastic rocks locally stylolites developed where zeolite cement was less effective hence the present overpressure formed at a later stage increased temperatures during burial resulted in thermal instability of the zeolite cement which was dissolved and authigenic k feldspar and quartz precipitated instead this resulted in a reduction of the cement volume of up to 70 if the zeolite was k heulandite and a corresponding relative porosity increase thus a reduction in cement volume was generated by replacing zeolite of an open crystal structure with mineral phases k feldspar and quartz of denser crystal structures the thermogenetic breakdown of zeolite was forced by increased temperatures during burial this process may explain previously enigmatic highly porous and permeable deeply buried sandstone reservoirs

tectonic history of the earth s inner core preserved in its seismic structure seismic data show that the earth s inner core is structurally complex numerical simulations suggest that whereas the deeper structure may be inherited from past episodes of inner core growth the origin of the shallow structure is due to ongoing deformation

hemispherical structure in inner core velocity anisotropy 1 we investigate the hemispherical pattern in inner core velocity anisotropy using a new and independent high quality data set of pkpbc pkpdf and pkpab pkpdf body wave observations our data show no evidence for a tilted anisotropy axis with respect to the earth s rotation axis and is significantly better fit by a model with 4 4 anisotropy in the western hemisphere and only 1 0 in the eastern hemisphere than by a model of uniform anisotropy we carry out variance minimization and find the boundaries between the hemispheres at lines of constant longitude at 14 e and 151 w variance minimization enables us to extract the imprint of hemispherical structure from all of the data and not just polar paths resulting in boundaries which are nearly 30 from the results of previous studies the high quality of the data allows us to provide robust evidence that the isotropic velocity in the eastern hemisphere is 0 2 lower than in the western hemisphere in the top 660 km of the inner core our data set also suggests an increase in inner core anisotropy in the eastern hemisphere from 1 to around 6 at depths deeper than 660 km indicating that the hemispherical pattern in anisotropy may disappear at greater depths the presence of hemispherical structure rules out mechanisms for creating anisotropy which are unable to sustain longitudinal variations in the inner core furthermore steady inner core superrotation of the order of 0 1 year would eradicate the hemispherical differences though inner core oscillation would still be permissible

origin of zeolite cements in the miocene sandstones north tejon oil fields california zeolite cement zoning from heulandite via heulandite laumontite to laumontite is found in miocene volcaniclastic sandstones at the north tejon oil field southern san joaquin basin california the zeolite transition occurs at the depth range from 2703 2743 m present temperature range 90 92 degrees c heulandite and minor smectite forms together from the dissolution of volcanic glass during early diagenesis at depths shallower than 2743 m early laumontite forms directly at the expense of heulandite by a reaction of the form 1250 cc 1470 cc ca sub 3 75 al sub 7 5 si sub 28 5 o 72 24h 2 o 3 35ca super 2 6 7al oh 4 super 7 1caal 2 si 4 o 12 4h 2 o 9h 2 o heulandite laumontite this reaction is based on the volumetrical relation between both zeolites and the absence of quartz cements during the zeolite transition the sources of the ca and al appear to be partial dissolution of plagioclase and smectite occurring prior to the above reaction and incorporation of residual smectite coatings at that reaction time active albitization and late laumontite formation begin to occur in the laumontite bearing sandstones at depths greater than 2743 m present temperatures greater than 94 degrees c this albitization reaction accompanying the late laumontite is as follows 100 cc 70 cc 62 cc na sub 0 7 ca sub 0 3 al sub 1 3 si sub 2 7 o 8 0 6h 4 sio 4 0 7naalsi 3 o 8 0 3caal 2 si 4 o 12 4h 2 o plagioclase albite lumontite clay mineral transitions from smectite via mixed layer clay minerals c s or i s to chlorite or illite probably produced the h 4 sio 4 necessary for the above reaction in addition to the albitization the source of late laumontite was derived in part from a mass transfer from outside during the late laumontite formation calcite locally forms and acts as an additional sink for ca immediately adjacent to deformed biotite flakes

inner core differential rotation inferred from antipodal seismic observations abstract the earth s inner core may rotate at a different speed than earth s crust mantle we use observations for antipodal earthquake and station pairs to examine the arrival time shift of the whispering gallery wave which propagates tangentially along the top of the inner core observations of these waves for earthquakes which occurred at the same location reveal that travel times vary by 0 2 s over the past 20 years we propose that these time shifts are caused by the interaction of a zero rigidity patch lateral heterogeneity at the inner core surface with the inner core differential rotation the simplest interpretation infers a rotation rate of 0 05 year which is one order of magnitude smaller than those reported by previous studies our result may also give constraint to the provenance of a zero rigidity patch at the inner core surface the fresnel zone coverage of whispering gallery pkiikp antipodal measurements beneath the inner core boundary extend over 60 of the boundary surface in contrast to pkikp pkp paths which individually measure specular reflections 1 hz from the top of the icb over fresnel zones each encompassing 0 002 of the inner outer core boundary

a new type of reservoir rock in volcaniclastic sequences development of pronounced secondary porosity and permeability accompanied by dramatic changes in wave propagation velocity and other physical properties in laumontite tuffs occurs in the oil fields of eastern georgia soviet union these rocks originated during intense hydrothermal alterations of andesite tuffs and comprise local few meters thick commonly lens shaped bodies hydrothermal alteration was lithologically and structurally controlled resulting in the formation of specific reservoir rocks identifiable on geophysical logs and capable of producing oil and gas the considerable relief of the in situ stress within these bodies was estimated from differential velocity analysis using sonic log and laboratory data this stress relief as well as borehole enlargem nts accompanied by the development of zones of nonelastic deformation around the hole tends to enhance near well permeability and hence the productive potential of these uncommon and poorly studied reservoirs

diagenetic model of the bajo barreal formation cretaceous in the southwestern flank of the golfo de san jorge basin patagonia argentina abstract this paper analyses the diagenetic evolution of sandstones belonging to the bajo barreal formation cretaceous in the golfo de san jorge basin patagonia argentina the bajo barreal formation includes the main reservoirs which are located along the western area of the basin and is composed of sandstones conglomerates mudstones tuffaceous mudstones and some layers of tuffs the principal reservoirs comprise medium to coarse grained sandstones which are dominated by feldspathic litharenites and contain minor amounts of litharenites and lithic arkoses the authigenic minerals include kaolinite smectite chlorite quartz overgrowths microquartz and calcite with minor proportions of megaquartz siderite analcime laumontite feldspar overgrowths and illite smectite and chlorite smectite mixed layers secondary porosity is much more important than primary porosity and is produced by the dissolution of feldspar lithic clasts and clay cements the diagenetic history of the bajo barreal sandstones can be divided into seven diagenetic stages each of which is characterized by a specific assemblage of authigenic minerals and diagenetic processes eogenetic conditions occur in stages 1 2 3 and 4 stage 1 corresponds to shallow burial characterized by the physical reduction of primary porosity by compaction during stage 2 rim clay cements of chlorite smectite and clinoptilolite as well as thin quartz overgrowths were formed the precipitation of pore filling cements of kaolinite chlorite and smectite occurred during stage 3 while stage 4 records the intense dissolution of feldspar lithic fragments and kaolinite cements mesogenesis occurs in diagenetic stages 5 and 6 the former corresponds to a new phase of authigenic kaolinite while the latter records the significant dissolution of feldspar lithic clasts and previous cements which produced the highest values of secondary porosity finally stage 7 corresponds to the highest degree of diagenesis in the bajo barreal formation mesogenesis which resulted in the precipitation of cements of zeolites and calcite as well as quartz and plagioclase overgrowths

the effect of d on pkp ab df travel time residuals and possible implications for inner core structure abstract the hypothesis that the deep inner core is anisotropic is based on pkp travel time observations at large distances and relies on a small number of very anomalous measurements for paths quasi parallel to the earth s rotation axis here we analyze a global dataset of pkp ab df travel times residuals and discuss their significant dispersion 2 s and coherent large scale patterns we show that the trends observed for quasi equatorial paths are consistent with predictions from recent tomographic mantle models when the latter are modified to account for strong heterogeneity at the base of the mantle under the pacific ocean and africa as documented in several recent studies likewise for polar paths we show that a large part of the signal could be explained by deep mantle structure the effects of complex structure in the deep mantle on pkp ab df travel times should be carefully considered in order to reliably estimate the anisotropic structure of the central part of the inner core

seismic anisotropy estimated from p wave arrival times in crosshole measurements summary seismic anisotropy is evidenced in the inner core upper mantle and the lower crust in large scale and the evidence is generally provided by shear wave splitting analysis here this paper searches for the evidence of anisotropy in the uppermost crust by using p wave arrival times from crosshole seismic measurement to directly estimate velocity anisotropy associated with the fine layering effect of multiple sedimentary beds conceptually fine layering causes the so called vti vertical transverse isotropy anisotropy with a vertical symmetry and the effect is parametrized by the horizontal and vertical velocity ratio it is found however that the vti anisotropic parameter does not have a simple vertical symmetry but is also azimuth dependent this azimuthal anisotropy may reflect the fracture orientation due to large scale tectonic movements and is very important in the production of oil reservoirs as the seismically fast directions can indicate preferred directions of fluid flow this paper presents innovative methods for anisotropy analysis in both vertical and horizontal plane integrated seismic anisotropy interpretation clearly indicates distinguished strain orientations forming fractures in oligocenic miocenic and pliocenic sediment in the edge of the extensional basin immediately next to tan lu fault an active continental strike slip fault zone

zeolites in closed hydrologic systems zeolites were first described from vugs and fissures in basaltic flows in the mid eighteenth century cronstedt 1756 and they are now known to be widespread in a variety of geological environments more zeolite species occur in vesicles and fractures of basaltic rocks than in any other geologic setting however zeolites from sedimentary rocks in particular represent the most important occurrences both in terms of aerial extent of deposits and in terms of the abundance of certain zeolite species the introduction of new analytical techniques in the latter part of the 20th century provided a significant stimulus to zeolite research these techniques allowed identification of large quantities of zeolites in widespread deposits of sedimentary rocks and in particular in sediments from saline alkaline lakes of the western united states sheppard and gude 1968 1969a 1973 based on geological and hydrologic environments zeolite occurrences in sedimentary rocks can be classified in the following framework a saline alkaline lakes b alkaline soils and land surfaces c deep sea sediments d open hydrologic systems e as products of hydrothermal alteration and f burial diagenetic or low metamorphic environments from a broader perspective zeolite deposits can be classified into two main groups namely closed hydrologic systems and open hydrologic systems the work of sheppard and gude 1968 1969a 1973 and later surdam 1977 discussing not only the mineralogy of the deposits but also the geology hydrology and chemistry of the depositional basins represent milestones in the study of closed hydrologic system formation of zeolites surdam 1977 considered closed hydrologic basins in two different tectonic settings a block faulted regions in arid and semiarid regions and b trough valleys associated with rifting examples of the first setting are the closed lakes of the basin and range province of the western united states whereas the

fine scale heterogeneity in the earth s inner core the seismological properties of the earth s inner core have become of particular interest as we understand more about its composition and thermal state1 2 observations of anisotropy and velocity heterogeneity in the inner core are beginning to reveal how it has grown and whether it convects3 4 the attenuation of seismic waves in the inner core is strong and studies of seismic body waves5 6 have found that this high attenuation is consistent with either scattering or intrinsic attenuation5 the outermost portion of the inner core has been inferred to possess layering and to be less anisotropic than at greater depths7 8 9 10 here we present observations of seismic waves scattered in the inner core which follow the expected arrival time of the body wave reflection from the inner core boundary the amplitude of these scattered waves can be explained by stiffness variations of 1 2 with a scale length of 2 kilometres across the outermost 300 km of the inner core these variations might be caused by variations in composition by pods of partial melt in a mostly solid matrix or by variations in the orientation or strength of seismic anisotropy

diagenesis of analcime bearing reservoir sandstones the upper permian pingdiquan formation junggar basin northwest china abstract the junggar basin is one of the largest and most important oil producing basins in china in which upper permian lacustrine oil shales are among the thickest and richest source rocks in the world the upper permian pingdiquan formation was deposited predominantly in fan delta sequences within a lacustrine setting in the northeastern junggar basin the pingdiquan formation sandstones volcanic and feldspathic litharenites constitute the principal oil reservoirs whereas the interbedded black shales are the predominant oil source rocks the early diagenetic minerals in the sandstones include siderite pyrite analcime albite calcite and trace amounts of halite late diagenetic minerals include k feldspar ankerite and minor mixed layer clay minerals a similar diagenetic sequence as recognized in the intercalated mudrocks which contain abundant analcime albite and microcrystalline dolomite early authigenic mineral formation e g calcite versus analcime albite was controlled by alternating periods of lower and higher salinity in the lacustrine environment cementation by siderite analcime calcite and albite substantially occluded sandstone porosity early in diagenesis however extensive dissolution of analcime cement and detrital feldspars during burial produced significant secondary porosity in the sandstones improving their reservoir potential organic acids generated during oil shale maturation may be responsible for secondary porosity in the interbedded sandstones

hemispherical variations in seismic velocity at the top of the earth s inner core knowledge of the seismic velocity structure at the top of the earth s inner core is important for deciphering the physical processes responsible for inner core growth1 2 3 previous global seismic studies4 5 6 7 8 9 have focused on structures found 100 km or deeper within the inner core with results for the uppermost 100 km available for only isolated regions10 11 12 here we present constraints on seismic velocity variations just beneath the inner core boundary determined from the difference in travel time between waves reflected at the inner core boundary and those transmitted through the inner core we found that these travel time residuals observed on both global seismograph stations and several regional seismic networks are systematically larger by about 0 8 s for waves that sample the eastern hemisphere of the inner core 40 e to 180 e compared to those that sample the western hemisphere 180 w to 40 e these residuals show no correlation with the angle at which the waves traverse the inner core this indicates that seismic anisotropy is not strong in this region and that the isotropic seismic velocity of the eastern hemisphere is about 0 8 higher than that of the western hemisphere

support for equatorial anisotropy of earth s inner inner core from seismic interferometry at low latitudes abstract anisotropy of earth s inner core provides a key role to understand its evolution and the earth s magnetic field recently using autocorrelations from earthquake s coda we found an equatorial anisotropy of the inner inner core iic in apparent contrast to the polar anisotropy of the outer inner core oic to reduce the influence of the polar anisotropy and reduce possible contaminations from the large fresnel zone of the pkikp 2 and pkiikp 2 phases at low frequencies we processed coda noise of large earthquakes 10 000 40 000 s after magnitude 7 0 from stations at low latitudes within 35 during 1990 2013 using a number of improved procedures of both autocorrelation and cross correlation we extracted 52 array stacked high quality empirical green s functions egfs an increase of over 60 from our previous study the high quality data allow us to measure the relative arrival times by automatic waveform cross correlation the results show large variation 10 9 s in the differential times between the pkikp 2 and pkiikp 2 phases the estimated influence of the fresnel zone is insignificant

diagenesis and reservoir potential of permian triassic fluvial lacustrine sandstones in the southern junggar basin northwestern china the junggar basin is one of the largest oil producing areas in china and contains upper permian lacustrine oil shales with some of the greatest hydrocarbon potental in the world in this study we present the diagenetic characteristics of permian triassic sandstones from the southern junggar basin and evaluate their reservoir potential the uppermost permian and lower triassic cangfanggou group in the southern junggar basin is characterized by alternating fluvial and lacustrine deposits whereas the middle upper triassic xiaoquangou group was deposited predominantly in a lacustrine environment fluvial and deltaic sedimentation was subordinate the sandstones of the cangfanggou and xiaoquangou groups are volcanic litharenites their detrital modes and textures of volcanic fragments suggest a primarily andesitic basaltic volcanic arc provenance early diagenesis of the sandstones is characterized by nonferroan calcite cementation grain coating pore lining clay minerals and the initial dissolution of detrital grains authigenic quartz pore filling phyllosilicates pore filling grain replacive zeolites albitized detrital plagioclase authigenic k feldspar copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received april 15 1996 revised manuscript received november 4 1996 final acceptance may 2 1997 2department of earth sciences university of western ontario london ontario n6a 5b7 canada 3school of geosciences queen s university of belfast belfast bt7 1nn united kingdom this work was done at the queen s university of belfast with funding from exxon bhp mobil and itotal which we gratefully acknowledge the karamay institute of petroleum exploration and development generously provided borehole samples geng ansong at the institute of geochemistry guangzhou academia sinica and zhou yisheng at the xinjiang institute of petroleum are thanked for assistance with field work and for valuable discussions special thanks go to the staff of the electron microscopy unit at the queen s university of belfast we also thank a h ruffell and s r lawrence for their constructive comments on an earlier version of the manuscript stable isotope analysis and ongoing research concerning the junggar basin at the university of western ontario have been supported by the natural science and engineering research council of canada the manuscript benefited substantially from critical commentary by kevin t biddle suzanne kairo w r kaiser and an anonymous reviewer

earthʼs inner core innermost inner core or hemispherical variations the structure of earth s deep inner core has important implications for core evolution since it is thought to be related to the early stages of core formation previous studies have suggested that there exists an innermost inner core with distinct anisotropy relative to the rest of the inner core using an extensive new data set of handpicked absolute travel time observations of the inner core phase pkikp we find that the data are best explained by variations in anisotropy between two hemispheres and do not require an innermost inner core we demonstrate that observations of an innermost inner core are an artifact from averaging over lateral anisotropy variations more significantly we show that hemispherical variations in anisotropy previously only imaged in the upper inner core continue to its centre the eastern region has 0 5 1 5 anisotropy whereas the western region has 3 5 8 8 anisotropy increasing with depth with a slow direction at 57 61 to the earth s rotation axis at all depths such anisotropy is consistent with models of aligned hcp or bcc iron aggregates