geothermal model of the continental margins of eastern canada abstract deep temperature distributions on six seismic cross sections on the passive continental margins of eastern canada have been calculated each of the considered profiles of the crustal structure includes sections with continental and oceanic crusts and also a zone of ocean continent transition present calculations show that on each profile the crust and upper mantle beneath the ocean have temperatures considerably higher than those beneath the continent the difference between sub oceanic and sub continental temperatures at the same depth amounts to 100 150 k at the depth of 50 km the temperature in the continental and oceanic regions reaches 500 700 c and 700 900 c respectively in the region with continental crust the crustal radioactivity and the outflow of heat from the mantle constitute approximately equal heat sources in producing the crustal temperatures in the area with oceanic crust the mantle heat flow is the dominant source of heating on these sections of the profiles more than about 75 of the surface heat flow has its origin in the mantle the thickness of the lithosphere across the margins decreases seawards in the region with oceanic crust its thickness reduces to 70 75 km typical of the north atlantic

compression of oceanic lithosphere an analysis of intraplate deformation in the central indian basin intraplate compressional deformation in the central indian basin is expressed as linear e w trending topographic undulations and geoid anomlies with characteristic spacings of approximately 200 km to elucidate the nature of this deformation we develop models of an oceanic lithosphere in a state of horizontal compression the lithosphere is treated as a viscous or plastic layer of uniform strength which overlies a viscous half space in which strength decreases exponentially with depth we compare models in which deformation with a dominant wavelength develops in response to flexural buckling and the hydrodynamic growth of instabilities for the viscous flexural buckling model deformation is constrained to occur in the antisymmetric mode by flexural folding which is characterized by uniform bending of the layer in the hydrodynamic flow model a range of deformational styles are possible in a strong viscous lithosphere deformation of the layer occurs by flexural folding at a wavelength which agrees with that predicted from flexural buckling theory in a lithosphere of intermediate strength the layer deforms by folding characterized by thickening which localizes beneath topographic highs in a relatively weak lithosphere the layer incurs an even greater amount of localized thickening and deforms in the symmetric or pinch and swell mode by inverse boudinage if the layer has a plastic rheology deformation occurs by inverse boudinage independent of the yield stress results from models in which the layer folds either flexurally or with periodic thickening are consistent with the observed depth distribution of seismicity in the central indian basin and with experimental rock rheological data because of the trade off between buoyancy forces and layer strength in determining the dominant wavelength a lithosphere which was overlain by weak sediments when intraplate deformation initiated can be characterized by a compressive layer strength almost a factor of 3 less than a lithosphere which was initially sediment free for a range of plausible models which consider both a sediment covered and sediment free lithosphere the observed wavelength requires deviatoric stresses in the indian plate of several hundreds of mpa

initiation of subduction zones along transform and accreting plate boundaries triple junction evolution and forearc spreading centres implications for ophiolitic geology and obduction

impact of co combustion of petroleum coke and coal on fly ash quality case study of a western kentucky power plant abstract petroleum coke has been used as a supplement or replacement for coal in pulverized fuel combustion at a 444 mw western kentucky power station the combustion of nearly 60 petroleum coke with moderate to high sulfur illinois basin coal produces fly ash with nearly 50 uncombusted petroleum coke and large amounts of v and ni when compared to fly ash from strictly pulverized coal burns partitioning of the v and ni known from other studies to be concentrated in petroleum coke was noted however the distribution of v and ni does not directly correspond to the amount of uncombusted petroleum coke in the fly ash vanadium and ni are preferentially associated with the finer higher surface area fly ash fractions captured at lower flue gas temperatures the presence of uncombusted petroleum coke in the fly ash doubles the amount of ash to be disposed makes the fly ash unmarketable because of the high c content and would lead to higher than typical compared to other fly ashes in the region concentrations of v and ni in the fly ash even if the petroleum coke c could be beneficiated from the fly ash further studies of co combustion ashes are necessary in order to understand their behavior in disposal

on the initiation of subduction estimates of shear resistance associated with lithospheric thrusting and convergence represent lower bounds on the force necessary to promote trench formation three environments proposed as preferential sites of incipient subduction are investigated passive continental margins transform faults fracture zones and extinct ridges none of these are predicted to convert into subduction zones simply by the accumulation of local gravitational stresses subduction cannot initiate through the foundering of dense oceanic lithosphere immediately adjacent to passive continental margins the attempted subduction of buoyant material at a mature trench can result in large compressional forces in both subducting and overriding plates this is the only tectonic force sufficient to trigger the nucleation of a new subduction zone the ubiquitous distribution of transform faults and fracture zones combined with the common proximity of these features to mature subduction complexes suggests that they may represent the most likely sites of trench formation if they are even marginally weaker than normal oceanic lithosphere

simple bouguer gravity anomaly field and the inferred crustal structure of continental ecuador the simple bouguer gravity anomaly field of continental ecuador corresponds closely to the physiographic provinces of the country the sierra which includes the andes and their foothills is characterized by a pronounced low with values to 292 mgal which reflects the deep andean root bouguer anomalies over the oriente become less negative away from the sierra chiefly in response to progressive thinning of continental crust eastward the costa between the sierra and the pacific shore in the north has the most positive on land bouguer anomalies 162 mgal so far known in the western hemisphere this part of the costa is underlain by an ancient oceanic plate now welded to the northwestern corner of the otherwise continental south american plate

the existence of a thin low viscosity layer beneath the lithosphere the horizontal temperature gradient at the base of the lithosphere at an oceanic fracture zone where plate of different ages is juxtaposed is expected to drive a local circulation the characteristics of which can be constrained by the amplitude wavelength and age dependence of the geoid two dimensional numerical models of convection in a fluid layer overlain by a solid conducting lid have been used to generate theoretical geoid profiles at right angles to the fracture zone only a thin low viscosity layer provides a reasonable fit to the data the best model so far obtained has a fluid layer 150 km thick with viscosity 1 5 1019 pa s under a 75 km lid such a layer which is incapable of transmitting strong horizontal shear stresses could provide the decoupling mechanism between plate and deep mantle flow required to balance the forces on the plates

on the initiation of subduction zones analysis of the relation between intraplate stress fields and lithospheric rheology leads to greater insight into the role that initiation of subduction plays in the tectonic evolution of the lithosphere numerical model studies show that if after a short evolution of a passive margin time span a few tens of million years subduction has not yet started continued aging of the passive margin alone does not result in conditions more favorable for transformation into an active margin

evolution of intra oceanic arc trench systems abstract intra oceanic island arc trench systems represent a locus of crustal thickening through the addition of mantle derived magmas which form the volcanoes and subjacent stratiform plutons the crust of immature island arcs and adjacent back arc basins is oceanic in chemistry in that it is dominated by mafic e g tholeiitic magmas a magma sequence is recognized in many arc systems which progress from boninite to arc tholeiite to calc alkaline and in some arcs to shoshonites the adjacent back arc basins are formed of morb like tholeiite arc systems may be dominated by extension rather than compression if the subducted and overriding plates are decoupled extension of the arc system may be associated with seaward retreat or roll back of the trench axis alternate cycles of extension and compression of the arc system can lead to both tectonic erosion of the fore arc and accretion of fragments from the incoming sea floor the izu bonin mariana tonga yap and palau trench arc systems are examples of different stages in a dynamic process which starts when subduction begins along old fracture zone traces crustal extension causes both fore arc subsidence and opening of back arc basins island arc volcanic chains and back arc basins are new crust formed largely of fractional melts of the mantle the evolution of an arc system may stop when blocking of the subduction zone or changes in relative plate motion causes overthrusting of back arc lithosphere on to former volcanic arcs many ophiolites preserve remnants of arc system crust and upper mantle

mineral microspherules in chinese coal and their geological and environmental significance abstract studies of finer grained minerals in coal have great significance for both geology and the environment eleven coal samples of different rank were collected from different regions in china and mineral microspherules were identified in these samples by scanning electron microscopy with energy dispersive x ray spectroscopy sem edx the microspherules usually occur as regular spheres with smooth surfaces and have an average size of less than 5 m in diameter most microspherules are colloidal in origin and include phases such as fe sulfides glauconite fe hydr oxides calcium oxalate and allophane allophane is a product of colloidal al2o3 and sio2 which as a precursor of kaolinite exists ubiquitously in the coals as does kaolinite some microspherules such as garnet and sphene are mainly derived from detrital sources and a few microspherules probably result from volcanogenic ash and or from cosmic dust ultrafine na bearing minerals were also found in the coals such micro sub micro and ultrafine minerals in coal may play an important role in the formation of ultrafine coal fly ash particles

mineral matter major and trace element content of the afsin elbistan coals kahramanmaras turkey abstract the afsin elbistan coal basin is one of the most important coal deposits of turkey the mineral matter major and trace element concentrations of the afsin elbistan coals and their modes of occurrence are discussed in this study the coal seam is located within the upper miocene pliocene aged ahmetcik formation which is represented by fluvial lacustrine facies thickness of the coal zone is 80 m but it reaches 105 m in the kislakoy sector a total of 86 samples were taken from the kislakoy open pit mine and from the 14 boreholes drilled by the general directorate of mineral research and exploration mta for coal exploration the proximate xrd sem eds major and trace element analyses were conducted on the samples the studied coals are characterized by relatively high moisture ash total sulfur volatile matter contents and low gross calorific values the mineral matters of the afsin elbistan coal are represented by calcite quartz pyrite feldspar aragonite opal ct gypsum jarosite and clay minerals strontium rb sm zr hf nb mo u zn pb as mn co cr and ni concentrations detected by edp xrf are higher than the world brown coal values many of the trace elements showing positive correlations with ash content imply inorganic affinity the element concentrations of the coals are mainly related to the carbonate silicate sulfide phosphate ore minerals and fossil shells however some elements have also organic affinities

intraplate deformation and closure of the australia antarctica africa plate circuit to determine the current motion between the australian antarctic and african plates and to test whether this plate circuit obeys closure all plate motion data available along the southeast southwest and central indian ridges are analyzed and reduced to 67 spreading rates 38 transform fault azimuths and 135 earthquake slip vectors carlsberg ridge data were excluded because they record india africa not australia africa motion new data include 10 new transform azimuths along the southwest indian ridge many slip vectors and a dense aeromagnetic survey along the southeast indian ridge all published and many unpublished magnetic profiles are modeled to determine rates consistently over a 3 m y time averaging interval for three reasons 1 magnetic profiles from the southeast and central indian ridges suggest recent spreading rate changes 2 some published rates differ for identical profiles and 3 prior studies have not used identical criteria and time scales to determine spreading rates the new rates differ from published rates by as much as 5 mm yr transform fault azimuths are estimated from bathymetry seasat altimetric data epicenter distributions and offsets of magnetic lineations azimuths of plate motion are also estimated from the horizontal projections of slip vectors from the centroid moment tensor solutions and other focal mechanism studies our new australia antarctica and australia africa euler vectors differ from all prior euler vectors at the 95 confidence level along the southeast and central indian ridges our model gives rates differing by 4 7 mm yr from those of prior models from a systematic analysis of the plate motion data we find no evidence for a nubia somalia antarctica triple junction along the southwest indian ridge we also find no evidence for a triple junction previously proposed to be at 80 e along the southeast indian ridge any deformation within this seismically active region of the australian plate adds up to less than a few millimeters per year along each boundary data are fit well by a single euler vector except for a 5 systematic misfit to azimuthal data along the eastern southeast indian ridge near a seismically active region of the australian plate south of tasmania although seismicity and the azimuthal misfit suggest the australian plate is deforming measurably possibly by distributed deformation or by the westward motion of a small microplate southeast of tasmania the significance of the misfit is marginal and is small enough that systematic errors may cause it these alternative explanations could be distinguished by surveying these transform faults with modern seafloor mapping techniques prior studies found that enforcing plate circuit closure causes systematic misfits to rates along the southeast indian ridge here we find that enforcing closure causes no systematic misfits to any data moreover only insignificant nonclosure is found by an f ratio test which numerical experiments suggest could detect deformation exceeding 2 mm yr we conclude that indian ocean plate circuit nonclosure and the deformation it suggests are much smaller than thought before the absence of significant nonclosure argues against the usefulness of a model of deformation distributed throughout an indo australian plate but favors a model in which the significant deformation occurs in a diffuse plate boundary along the equatorial indian ocean between the central indian ridge and the sumatra trench

zenisu ridge mechanical model of formation abstract seabeam seismic and submersible surveys took place during the kaiko project and revealed significant compressive deformation at the northeastern end of the philippine sea plate related to the recent collision of the izu ogasawara arc against central japan intraoceanic thrusting at the base of the zenisu ridge a linear topographic high running a few tens of kilometers south of the nankai trough is supported by tectonic magnetic and gravimetric data we investigate the formation of the zenisu ridge in terms of compressive mechanical failure of a thin elastic perfectly plastic plate subducting at a trench and subject to a regional compressive axial force the rheological envelope concept is used throughout the numerical calculations based on a detailed study of flexure of the present day bending far from the deformation zone we evaluate the bending forces involved the bulge is 120 to 150 m high and the compressive stress all along the nankai trough is about 100 mpa in the zenisu ridge area an additional compressive stress is superimposed due to the nearby collision at izu peninsula we compute the vertical distribution of the deviatoric stress before failure and find that the deviatoric stress is maximum at a depth of 20 25 km in the trench area and again at the surface 60 to 100 km seaward in the vicinity of the bulge the development of a thrust joining these two maxima through the entire thickness of the lithosphere is discussed the model predicts that the formation of the zenisu ridge did not occur before 4 ma and is caused by progressive tectonic uplift due to the redistribution of bending stresses as the ridge approaches the nankai trough

mineral occurrence and its impact on fracture generation in selected qinshui basin coals an experimental perspective abstract the effect of mineral matter on the fracture evolution was investigated for lower permian and upper pennsylvanian coal samples from the qinshui basin of china optical microscopy scanning electron microscopy with energy dispersive x ray spectrometry sem eds and x ray computed tomography x ray ct were used to investigate the composition and modes of occurrence of minerals within the coals and to characterize the natural and induced fractures present within the samples the spatial distribution of mineral matter investigated by x ray ct demonstrates that the variation of mineralization within the cleats fractures occurred at fine scales and most of minerals were scattered in coal core samples the original fractures normally were present as two sets one set was almost parallel to the bedding plane and the other was almost perpendicular to the bedding plane for created fractures the difference in density between the matrix and mineral matter may weaken the cohesion of coals and it could explain why the created fractures propagate along the junction of minerals and organic coal matrix the internal fracture porosities varied from 0 06 to 20 69 which indicates a strong internal heterogeneity of the coals after a stress is applied the inclination of the main shear fractures ranges from 55 to 95 using energy analysis the fracture energy appears to represent nearly half of the total dissipated energy which can be correlated with the fracture density and orientation the formation and distribution of shear fractures is related to the spatial distribution of mineral matter and the overall mineral content these investigations serve to characterize hydro fracturing and pulverized coal generation during coalbed methane development

quantification of crystalline mineral matter in some turkish coals using interactive rietveld based x ray diffractometry quantitative x ray diffractometry using a rietveld based computational method siroquant has been carried out for a series of coal samples from the various turkish mines standard proximate and ultimate analyses were carried out chemical compositions of the high temperature ash hta of coal samples were determined by x ray fluorescence xrf spectrometry technique crystalline mineral matter and amorphous content of raw coal samples were estimated the ca si al s and fe concentrations are higher than those of the other major elements ti mn mg na p k in the studied coal samples the percentage of crystalline mineral matter for each sample varies from 16 5 to 36 1 of the coal samples the minerals in the sampled coals consist mainly of quartz clay minerals calcite pyrite and gypsum percentages of crystalline mineral matter in ash content remarkably decrease for the elbistan orhaneli and tufanbeyli lower rank coals

depositional evolution of miocene coal successions in the soma coalfield western turkey abstract miocene alluvial and fluvial lacustrine deposits comprising three lignite successions lower middle and upper are exposed in the soma coalfield in western anatolia the total thickness of the coal successions is about 900 m and they rest unconformably on mesozoic carbonate and siliciclastic basement rocks several lithofacies are recognised and are arranged into 15 facies assemblages fa1 to fa15 within coal successions the lower coal succession fa1 to fa3 has been interpreted as the deposits of alluvial fan to ephemeral lacustrine and forest lower mire system resulting in a subbituminous coal which averages thickness of 20 m the freshwater carbonate dominated middle coal succession fa4 to fa7 has been interpreted as the deposits of an anastomosed river system including shallow carbonate mudflats to lake and ponds and frequently drying poor forest mires depositing lignitic coal the volcanic influenced upper coal uc succession fa8 to fa15 has been interpreted as the fluvial channel floodplain and allochthonous peat mire deposits fa8 to fa10 associated with a braided river system that was rapidly buried and eroded by volcaniclastic apron deposits fa11 to fa14 and culminated in large carbonate dominated shallow lake deposits fa15 the miocene coal successions were probably deposited in a slowly subsiding and fault controlled karst based paleovalley and lowlands of the intramontane paleomorphology that resulted from the early tertiary collision of the eurasian and anatolian plates

intraplate earthquakes and the state of stress in oceanic lithosphere abstract the sources of stress responsible for oceanic intraplate earthquakes and their usefulness for inferring the tectonic stress field are investigated through a synthesis of the source mechanisms of 58 of the largest such events determined by inversion of long period p and sh waveforms further constraints are provided by the global distribution of oceanic intraplate seismicity and a calculation of the seismic moment release per unit volume of seismogenic lithosphere as a function of lithosphere age although frequently associated with relict tectonic features large oceanic intraplate earthquakes are generally reliable indicators of the state of stress in the source region most oceanic intraplate seismicity occurs in young lithosphere

the miocene coal seams in the soma basin w turkey insights from coal petrography mineralogy and geochemistry abstract the neogene soma basin western turkey hosts three coal seams km2 km3 and kp1 and several altered tuff layers within the miocene sequences this study focuses on the evaluation of coal petrography mineralogical and elemental compositions as well as the rock eval pyrolysis of the three coal seams from eynez isiklar and denis sectors and to identify the mineralogy of altered tuff layers within km2 and kp1 seams the routine coal quality analyses show that coal samples from the km2 seam are characterized by lower ash yields and total s contents and higher gross calorific values than km3 and kp1 seams the mineralogical composition of the bulk coal samples varies between all three seams the statistical treatment implies that major elements in bulk coal samples such as al fe k mg and na and the vast majority of minor and trace elements have inorganic affinity the trace element contents and elemental enrichments in the coal samples are generally changeable from seam to seam which could be related to differences in ash yield and mineralogy altered tuff layers or tonsteins were identified in km2 and kp1 seams the tonsteins are clay rich and certain trace elements e g as and zr are enriched in the coal layers beneath the tuff layers in the km2 seam this might be related to penetration of leached pore water into these layers and precipitation of epigenetic minerals the coal petrography composition and the coal facies diagrams show that the precursor peat of the km2 seam was accumulating under telmatic mesotrophic anoxic conditions whereas the water level was high and stable the relatively low ash yields and thicker coal beds suggest a lower clastic input from the basin margins and water table fluctuations resulted in calcareous intercalations in the km3 and kp1 seams these imply the development of limno telmatic conditions whereas fluvial activity affected during peat accumulation of both seams considering the maceral composition along with the coal thickness coal seams in the soma basin might display oil generation potential however the pyrolysis analysis shows that the studied coal seams are mainly gas prone and only certain coal beds have mixed hydrocarbon generation capacity all data presented in this study indicates that lithological features differences in coal qualities and elemental contents in the soma basin were mainly controlled by changes in the depositional conditions and the detrital input during miocene

recent tectonics associated with the subduction collision of the d entrecasteaux zone in the central new hebrides abstract recent data from the new hebrides vanuatu subduction zone have enabled a morphological description and tectonic interpretation to be made of the complex plate contact between the d entrecasteaux zone and the west torres massif on the one hand and the old santo malekula block on the other between latitudes 14 30 and 17 s no trench occurs owing to the presence of the old rigid santo malekula block at the edge of the overriding plate the outer limit of plate contact describes a tortuous line westward of the projected line of the adjacent trenches this may be explained by local collision of the north d entrecasteaux ridge and the south d entrecasteaux chain with the west flank of santo this collision is compensated for by lateral plastic flow of the inner wall downward into the small basins which separate the d entrecasteaux zone ridges a process which may be explained by plastic plane strain theory the westward jump of the plate contact zone here may result from pieces of the north d entrecasteaux ridge being cut off and incorporated in the frontal arc a review of the geological evidence and the shallow seismicity of the central new hebrides shows that radiant horizontal stresses resulting from this collision have generated a specific compressive stress regime which influences the whole width of the arc the resultant deformation shows a close resemblance to a theoretical strain field produced by the indentation of a long narrow plastic body cf the arc by a rigid flat die cf the d entrecasteaux zone thus the central new hebrides block is both elastically bent under vertical stresses and plastically deformed and pushed eastwards by horizontal stresses recent uplift of the eastern chain can be explained by this model in contrast at the rear of both the northern and southern sections of the arc the tectonics are mainly controlled by a tensional stress regime the strong plate interaction due to the subduction of the d entrecasteaux zone is thought to be responsible for the compressive stress regime across the central new hebrides the same cause can be invoked to account for the tensional stress regime observed in north and south new hebrides rear arc regions

deep sea drilling project geothermal measurements a review in this article the geothermal measurements made from the scientific drilling ship glomar challenger are evaluated edited and reviewed for a number of sites the heat flow values given in the initial reports of the deep sea drilling project have been revised less than half of the boreholes in which thermal measurements were attempted gave reliable data by the end of the deep sea drilling project dsdp in 1983 reliable borehole heat flow measurements had been obtained at some 80 sites in all of the world oceans except the arctic the reliable values are considered to represent the deeper heat flux to within 20 for a few the accuracy is within 5 most temperature measurements have been obtained using probes penetrating the undisturbed sediments at the bottom of the hole at subbottom depths of between 75 m and 250 m although some data have been obtained at depths less than 30 and over 1000 m temperatures have been obtained a significant distance into the crust in eight holes the main general conclusions are as follows 1 there are no large or systematic differences between borehole heat flow values and oceanographic probe values obtained nearby such a test of shallow penetration oceanographic probe measurements was one of the first objectives of the dsdp heat flow program 2 there are very few clear smooth changes of borehole heat flow with depth in areas with thick sedimentary sections that are indicative of either long term bottom water temperature changes tens to thousands of years or large heat production in the sediments vertical migration of sediment interstitial pore water is suggested by nonlinear temperature depth profiles at a few sites particularly where the sediment is relatively thin and the temperature gradient is high 3 temperatures in the crustal parts of deep sea drill holes exhibit a wide range of behavior generally indicating hydrothermal circulation in the upper crust at five sites seawater is inferred to be moving down the holes into the crust indicating low formation pressures and very high permeability in the upper crust in two deep holes however such flow is limited to above several hundred meters into the crust and heat fluxes close to theoretical cooling lithosphere values for the age of the crust 6 and 7 ma are found at greater depth these sites suggest that hydrothermal circulation may be concentrated at shallow depths in the crust summary tables are presented of the heat flow data considered to be reliable after review and revision and an appendix provides detailed comments on all the measurements for which data are available geothermal measurements are continuing on the new ocean drilling program ship joides resolution

implications of the mechanical and frictional behavior of serpentinite to seismogenic faulting the widespread occurrence of serpentinite along major strike slip seismogenic faults warrants systematic investigation to determine how its frictional characteristics may affect slip along the fault different locations along the motagua fault zone in guatemala were sampled to investigate the sliding mode as a function of composition and texture confining pressure and displacement rate air dried right circular cylinders 7 1 cm in length and 3 3 cm in diameter with a precut 35 to the cylinder and load axes were deformed at confining pressures up to 200 mpa room temperature and displacement rates of 10 4 and 10 7 cm s compositional analyses of specimens cored from five blocks of serpentinite that were tested show that the serpentinite can be divided into two groups one is a mesh textured serpentinite containing up to 70 serpentine mostly lizardite 11 enstatite phenocrysts 19 oxides and minor amounts of olivine and carbonate undifferentiated the other is a flare textured serpentinite containing up to 84 serpentinte mostly antigorite 10 oxides 6 magnesite and dolomite and almost no enstatite or olivine the flare serpentinite undergoes the transition from stable sliding to stick slip sliding at confining pressures as low as 10 mpa the mesh serpentinite results only in stable sliding up to confining pressures of 200 mpa and a displacement rate of 10 4 cm s at a displacement rate of 10 7 cm s only one of the three mesh blocks exhibits stick slip the shear stress required to initiate sliding for the flare textured serpentinites is given by 0 77 n for the mesh textured serpentinites at a displacement rate of 10 4 cm s it is given by 0 56 n and at a displacement rate of 10 7 cm s by 0 50 n differences in fracture strength between the five specimen blocks correlate with differences in frictional strength differences in the sliding behavior and in the deformation observed along the sliding surfaces can be related to the mineralogical components of each serpentinite type extensive deformation occurs in the mesh serpentinites as a result of hard oxide and enstatite indenters ploughing through a soft lizardite substrate lizardite lizardite contacts prevail and these deform by plastic flow the stick slip behavior in the flare textured serpentinites is explained by brittle failure of antigorite antigorite contacts the smaller grain size of the flare serpentinites relative to the mesh serpentinites may also contribute to the higher frictional strength of the flare serpentinites we discuss the implications of the antigorite rich flare textured serpentinite to seismogenic faulting in particular we consider the case of antigorite forming by shear heating induced progressive metamorphism of lizardite chrysotile serpentinites if serpentine dehydration temperatures are approached talc may form having a lower coefficient of friction than serpentine talc may act as a lubricant along the fault plane

recent changes of atmospheric heavy metals in a high elevation ice core from muztagh ata east pamirs initial results al mn rb sr ba cs bi and sb were measured at various depth intervals of a 41 6 m firn ice core drilled at an elevation of 7010 m near the top of muztagh ata glacier east pamirs 38817 0 n 75806 0 e central asia these data spanning the mid 1950s to 2000 were obtained by analyzing 101 sections using a sector field double focusing inductively coupled plasma mass spectrometer icp ms instrument this study provides the first time series for these metals from central asia concentrations are 11 7 329 ng ml 1 for al 0 33 42 7 ng ml 1 for mn 0 42 17 8 ng ml 1 for sr 0 04 1 4 ng ml 1 for rb 0 18 10 4 ng ml 1 for ba 2 167 pg ml 1 for cs 2 51 pg ml 1 for sb and 1 31 pg ml 1 for bi large variations in metal concentrations were found during the study period pronounced increases in concentrations were observed for sb and bi from the mid 1960s to the beginning of the 1990s suggesting increased anthropogenic sources of sb and bi in central asia during the same period however the decrease of sb and bi concentrations during the mid to late 1990s reflects a reduction in anthropogenic activities in central asia

high pore pressure generation in sediments in front of the barbados ridge complex dsdp data for the barbados ridge complex show the existence of high pore pressures in sediments both oceanward and arcward of oceanic trenches we model the evolution of pore pressure by using a finite element procedure three consecutive stages are recognized 1 in the oceanic basin sedimentation rate is low there is little excess pore pressure 2 approaching the trench but before being incorporated into the accretionary prism sediments are subjected to increasing tectonic compression as well as greater sediment overburden thus high pore pressure can be created an important result is that the lowest effective stress occurs within the sedimentary layer instead of at its base and a decollement may develop along this weakened zone 3 arcward of the trench sediments above the decollement are offscraped while those beneath it are subducted fast sedimentation combined with tectonic compression can create pore pressures so high as to cause porosity to increase with depth this facilitates the formation of mud volcanoes even oceanward of the deformation front

the east pacific rise and the thermal model although the thermal mode of lithosphere cooling can be used to predict the east pacific rise topography reasonably well it does not adequately predict the observed gravity when the zero temperature boundary condition is at the seafloor the misfit arises primarily because this model predicts thermally lowered densities in the crust at the rise axis which counteract the gravitational effect of the topography generating a theoretical gravity anomaly smaller than that observed it is shown using data at 12 n as an example that improved agreement with the thermal model is obtained if to first order the crust is treated as an isothermal constant thickness constant density layer with variable depth this result is consistent with seismic data and observations of convective cooling of the crust by seawater circulation it implies that convective cooling of the whole crust is very rapid even at the axis of fast spreading ridges the oceanic moho may represent the depth to which cracking and convective cooling extends

geochemistry and tectonic setting of pre collision cretaceous and paleogene volcanic rocks of ecuador pre collision cretaceous lower tertiary volcanic rocks of western ecuador from the coastal area pinon and san lorenzo formations and western cordillera macuchi and celica formations consist of three rock suites the first suite includes tholeiites of ocean floor affinities that have distinct light ree depleted patterns and low la nb la hf and th hf ratios the island arc tholeiites of the second suite have lower contents of ti zr hf and nb the third suite comprises calc alkalic rocks mainly continental margin andesites and dacites the continental volcanic arc rocks crop out in an area east of the tholeiitic rocks the boundary between the two areas is the major suture separating continental south america from accreted terrenes to the west a model is suggested for the geodynamic evolution of what is now western ecuador during the late cretaceous it includes two east dipping subduction zones of turonian to santonian ages and the accretion of the oceanic island arc to the continent

earthquake source mechanisms from body waveform inversion and intraplate tectonics in the northern indian ocean double couple point source parameters for 11 of the largest intraplate earthquakes in the northern indian ocean during the last 20 y were determined from a formal inversion of long period p and sh waveforms nine of the events have centroid depths at least 17 km below the seafloor well into the upper mantle two have centroid depths as great as 39 km using the source mechanisms of these earthquakes we distinguish two major intraplate tectonic provinces in the northern indian ocean to the west of the ninetyeast ridge in the southern bay of bengal intraplate earthquakes have thrust faulting mechanisms with p axes oriented n s the centroid depths of these earthquakes range from 27 to 39 km below the seafloor lithospheric shortening in this region is thus accomplished by thrust faulting in the strong core of the oceanic upper mantle while other geophysical evidence suggests that shallow sedimentary and crustal layers apparently deform predominantly by folding in the immediate vicinity of the ninetyeast ridge earthquakes display strike slip mechanisms with left lateral motion on planes parallel to the ridge this type of faulting occurs from at least 10 s to the northern end of the ninetyeast ridge near 10 n where the ridge meets the sunda arc seismic activity diminishes to the east of the ninetyeast ridge but is also characterized by strike slip faulting despite these variations in deformational style the inferred orientation of greatest compressive stress in the northern indian ocean displays a consistent long wavelength pattern over a large portion of the indian plate varying smoothly from nearly n s in the bay of bengal to nw se in the northeastern indian ocean this plate wide stress pattern and the high level of intraplate seismicity in the northern indian ocean are likely the results of substantial resistance along the himalayan continental collision zone to the continued northward motion of the western portion of the indian plate oceanic intraplate earthquakes in other regions where the level of deviatoric stress associated with the long wavelength part of the stress field is likely to be smaller need not be comparably reliable indicators of the plate wide stress field

the experimental deformation of dunite deformation experiments have been carried out on two dunites anita bay of 100 m grain size and aheim of 900 m grain size at strain rates from 10 3 to 10 6 s 1 and temperatures from 1000 c to 1300 c in a gas medium deformation apparatus at 300 mpa confining pressure most of the tests were under wet conditions defined by the presence of small amounts of water from hydrous minerals initially present constant strain rate and relaxation experiments covering ranges of flow stress down to about 70 mpa and 7 mpa respectively show that there is a change in flow law in going below about 100 mpa differential stress and that the coarser grained rock is stronger than the finer grained one power law parameters above the transition are n 4 48 0 31 and q 498 38 kj mol 1 for aheim dunite and n 3 35 0 17 and q 444 24 kj mol 1 for anita bay dunite while below the transition relaxation tests on anita bay dunite give n 2 44 0 18 and q 386 27 kj mol 1 it is concluded that there is a weakening effect of water that this effect is mainly in the grain boundaries and that grain boundary sliding is probably a significant deformation mechanism at the lower stresses under wet conditions

allochthonous terranes in the andes of ecuador and northwestern peru in ecuador and northwestern peru the andes and adjacent country particularly on the pacific side are composed of at least five distinctive geologic terranes the terranes are distinguished from one another and from cratonic south america to the east by dissimilar basements cover rocks intrusive rocks and bouguer gravity anomaly fields the pinon terrane occupying most of coastal ecuador has a basaltic basement characterized by the largest known on land positive bouguer anomalies in the western hemisphere the tahuin terrane occupies most of northwestern peru and the southwestern corner of ecuador the terrane has an especially complex basement and is the site of generally positive bouguer anomalies the small biron terrane has an unusual basement composed in part of cordierite gneiss and amphibolite that give consistent late cretaceous k ar mineral ages the wedge shaped chaucha terrane lies in part on the western andean slope between the oceanic pinon terrane on the north and the continental bir

mineralogy and environmental geochemistry of lagooned ashes resulted from combustion of maritza east lignite bulgaria the phase mineral composition of the feed coal fc from maritza east lignite used in the maritza east 1 thermo electric power station teps and lagooned ashes las generated from the burning of this lignite was studied the concentration and behaviour of 19 trace elements in the fc and las as well as in the soils and plants collected from the restored sites of former la disposals are also described the minerals and inorganic phases identified in the lignite include quartz kaolinite pyrite illite plagioclase gypsum calcite sulphur marcasite pyrrhotite magnetite k feldspar barite szomolnokite other fe sulphates sylvite ni carbonate or oxide hydroxide and glass the phase composition of las is represented by original lignite minerals pyrrhotite magnetite quartz kaolinite and newly formed minerals and phases generated during the combustion process pyrrhotite magnetite hematite quartz metakaolinite mullite indialite glass char or storage of las sulphur hematite fe hydroxides gypsum barite fe sulphates calcite sylvite it was found that cr cu and ti in the lignite ashes and co cr cu mn and ni in las are relatively enriched in comparison with their respective clarke values worldwide average contents for lignite and subbituminous coal ashes the concentrations of ag ba be co cu ga mo ni rb sn and ti in the soils have contents higher than their clarke values for soils the abundance of these elements plus mn v and zn in soils is probably related to some occurrence of discrete minerals and phases containing such elements the contents of be cr ga li ni pb ti and v in the plants growing on these restored la sites have concentrations higher than their clarke values for land plants dry basis the water soluble modes of occurrence of ag ba be co cr cu li mn mo ni pb sn ti and zn in soils and or las as well as the plant affinity to these elements should have a leading role for their concentration in plants the present results reveal that various trace elements with environmental concern could be potential pollutants of surface and subsoil waters soils and plants in the areas of restored la sites

stress in the indo australian plate cloetingh s and wortel r 1986 stress in the ind austr ian plate in b johnson and a w bally editors intraplate deformation characteristics processes and causes tectonophysics 132 49 67 we modelled the state of stress in the indo australian plate in order to investigate quantitatively variations observed in tectonic style the numerical procedure incorporates the dependence of slab pull and ridge push on the age of the oceanic lithosphere estimates are presented for the average net resistive forces at the himalayan collision zone the suction force acting on the overriding indo australian plate segment at the tonga kermadec trench and the drag at the base of the lithosphere our modelhng shows a concen ation of compressive stresses of the order of 3 5 lcbar in the ninetyeast ridge area the effects of the compressive resistance associated with himalayan collision and subduction of young lithosphere off the northern part of the sunda arc are focused in this region the stress field as calculated gives a consistent explanation for the observed concentration of seismic activity stein and okal 1978 and significant deformation in the oceanic crust weissel et al 1980 mcadoo and sandwell 1985 in the area the calculated stress field in the area adjacent to the southeast and central india ridges is characterized by tension parallel to the spreading axis this explains the concentration of near ridge normal faulting seismicity with t axes subparaile1 to the spreading ridge in the indian ocean as recently observed by bergman et al 1984 and wiens and stein 1984 the regional stress field along the strike of the sunda arc varies from compression seaward of and parallel to the sumatra trench segment to tension perpendicular to the java flores segment this explains the selective occurrence of well developed grabens seaward off the java flores segment of the trench observed by hilde 1983 our modelling shows that the observed rotation of the stress field denham et al 1979 in the australian continent is mainly the consequence of its geographic position relative to the surrounding trench segments and the variations of the forces acting on the down going slab in each of these the state of compression in west and central australia is induced by the action of resistive forces at the himalayan and banda arc collision zones the joint occurrence of high levels of compression in the plate s interior and normal faulting seismicity in the near ridge areas is a transient feature unique to the present dynamic situation of the indo australian plate

abundances and distribution of minerals and elements in high alumina coal fly ash from the jungar power plant inner mongolia china abstract the fly ash from the jungar power plant inner mongolia china is unique because it is highly enriched in alumina al2o3 50 the fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum quartz char calcite k feldspar clay minerals and fe bearing minerals the mullite content in fly ash is as high as 37 4 because of high boehmite and kaolinite contents in feed coal corundum is a characteristic mineral formed during the combustion of boehmite rich coal samples from the economizer were sieved into six size fractions 500 mesh and separated into magnetic mullite corundum quartz mcq and glass phases for mineralogical and chemical analysis the corundum content increases but amorphous glass decreases with decreasing particle size fractions of small particle sizes are relatively high in mullite probably because mullite was formed from fine clay mineral particles under high temperature combustion condition similarly fine corundum crystals formed in the boiler from boehmite in feed coal the magnetic phase consists of hematite magnetite magnesioferrite and mgfealo4 crystals the mcq phase is composed of 89 mullite 6 1 corundum 4 5 quartz and 0 5 k feldspar overall the fly ash from the power plant is significantly enriched in al2o3 with an average of 51 9 but poor in sio2 fe2o3 cao mgo na2o p2o5 and as arsenic tio2 th al2o3 bi la ga ni and v are high in mullite and the magnetic matter is enriched in fe2o3 cao mno tio2 cs co as cd ba ni sb mgo zn and v the remaining elements are high in the glass fraction the concentration of k2o na2o p2o5 nb cr ta u w rb and ni do not clearly vary with particle size while sio2 and hg decrease and the remaining elements clearly increase with decreasing particle size

phase mineral and chemical composition of composite samples from feed coals bottom ashes and fly ashes at the soma power station turkey abstract the phase mineral and chemical composition of feed coals fcs and their bottom ashes bas and fly ashes fas produced in the soma thermo electric power station tps turkey was characterized fcs are high ash soma subbituminous coals abundant in moisture and ca and depleted in s the inorganic composition in decreasing order of significance of fcs includes calcite quartz kaolinite illite muscovite chlorite plagioclase gypsum pyrite montmorillonite k feldspar dolomite siderite ankerite opal and volcanic glass the results for 57 elements studied show that ca nb cs v li have significantly higher contents in fc ashes than the respective clarke values for coal ashes the water soluble residues isolated from fcs include gypsum calcite inorganic amorphous matter ca mg na k phase and opal these residues are enriched in na se s b mg mo sr ca k the phase mineral composition of bas and fas includes mainly glass quartz char mullite plagioclase calcite and portlandite and to a lesser extent illite muscovite melilite hematite anhydrite lime cristobalite kaolinite and magnetite minor amounts of k feldspar dolomite ankerite fe spinel gypsum and ca k na phase also occur in bas and fas fas are enriched in inorganic matter glass cristobalite mullite fe oxides lime and anhydrite and depleted in mineral matter char quartz clay minerals melilite portlandite and carbonates in comparison with bas only se is significantly enriched in bas and fas compared to fc ashes most of the trace elements in particular as bi cd ge pb sn tl and w are more abundant in fas while bas are more enriched in ca cs fe ho mn p sc se and tb significant percentages 11 59 of elements initially present in fcs namely s sb sn ta mo bi zn ni na lu tm b were emitted by stack emissions and not captured by the cleaning equipment in the soma tps some genetic features properties possible environmental concerns and potential utilization directions related to fcs bas and fas are also discussed

thermoelastic stress how important as a cause of earthquakes in young oceanic lithosphere we present a series of exploratory models which test the hypothesis that thermoelastic stress is a significant contributor to the state of stress in young oceanic lithosphere less than 35 m y in age in support of this hypothesis is the concentration of seismicity in lithosphere younger than 15 m y where cooling rates are relatively high most near ridge earthquakes have focal depths between the moho and the depth of the 800 c isotherm thrust and strike slip events dominate the shallowest seismicity while the focal mechanisms of the deeper events are generally characterized by normal faulting to assess the importance of thermal stress in the generation of near ridge earthquakes we model the lithosphere as an elastic half space in which the response to cooling is computed using the method of thermoelastic displacement potentials a key assumption in the models is that stress is relieved on time scales generally short compared with the age of the lithosphere a further assumption in some models is that material will not contribute thermal stress until it has cooled below an elastic blocking temperature normal faulting is predicted throughout the lithosphere in thermal stress models based on simple half space cooling models in which a cooled surface layer is incorporated to simulate the effect of hydrothermal circulation on shallow thermal structure predict stresses that can match the locations of both thrust and normal faulting earthquakes near mid ocean ridges the addition of a ridge push stress to the computed thermal stress enhances the likelihood of thrust faulting in the uppermost lithosphere at ages greater than about 15 m y but probably contributes little to the stress field at younger ages though these simple models are limited by several simplifying assumptions particularly in the immediate vicinity of the ridge axis they support the hypothesis that thermoelastic stress can play a major role in the tectonics of young oceanic lithosphere

constraints on yield strength in the oceanic lithosphere derived from observations of flexure summary the wavelength and amplitude of outer rises seaward of sub duction zones and arches surrounding islands and seamounts are used to parameterize flexure profiles in terms of the moment and curvature at the first zero crossing the data show the clear age dependence in the mechanical thickness of the lithosphere up to 60 100myr saturation of moment at large curvature is interpreted in terms of a depth dependent yield strength for the lithosphere using relations adopted from laboratory experiments of rock deformation a comparison of theoretical curves with observed moments indicates that old oceanic lithosphere has no long term strength below about 40 km depth with no difference between 100 and 165 myr old crust moderate axial loading forces 200 mpa can explain most variations in the moment curvature observations except in the case of the kuril trench which appears anomalous given the age of the crust regional tension causes greater variability in moment as compared to regional compression because of the greater slope in the brittle failure envelope under tension the observations point to a lithosphere weaker than the prediction from experimental deformation of rocks of the possible weakening mechanisms elevated pore fluid pressure on faults does not predict the correct age dependence and is incompatible with earthquake focal mechanisms our favoured explanation is that the activation energy q appropriate for ductile flow at geological strain rates is lower than the values derived from laboratory extrapolations of dry olivine data taken at high temperatures if recent oceanic geotherms are reliable q in the lower lithosphere must be lower than 100kcal mol 1 the method used here is most appropriate for trench profiles with curvatures greater than 10 7m 1 for lower curvatures such as along seamount profiles small errors in the curvature estimate cause large changes in rheological parameters

thermomechanical evolution of oceanic fracture zones a fracture zone fz model is constructed from existing models of the thermal and mechanical evolution of the oceanic lithosphere as the lithosphere cools by conduction thermal and mechanical boundary layers develop and increase in thickness as age 1 2 surface expressions of this development such as topography and deflection of the vertical i e gravity field are most apparent along major fz s because of the sharp age contrast a simple model including the effects of lateral heat transport but with no elastic layer predicts that variations in seafloor depth and deflection of the vertical will become increasingly smooth and ultimately disappear as the fz ages observations however show that both the fz topography and the deflection of the vertical remain sharp as the fz evolves these two observations as well as the observed asymmetry in deflection of the vertical profiles across the udintsev romanche and mendocino fz s are explained by including a continuous elastic layer in the model the asymmetry in deflection of the vertical is a consequence of elastic thickness variations across the fz modeling also shows that the evolution of the fz topography is extremely sensitive to the initial thermal structure near the ridge transform intersection model geoid steps and their development with age are used to access techniques for measuring geoid offsets across fz s reasonable step estimation techniques will underestimate the overall step amplitude by up to 50 this implies that abnormally thin thermal boundary layers derived from studies of geoid height versus age are not required by the data

continental margin tectonics submarine accretionary prisms submarine accretionary prisms are sites of incipient mountain building where sediments and rocks of the deep ocean are uplifted deformed and ultimately transformed to continental crust accretionary prisms develop at sites of lithospheric convergence that is subduction zones commonly accretionary prisms form along continental margins although accretionary prisms may also occur adjacent to island arcs which are ultimately coalesced into continental landmasses here we review the studies of submarine accretionary prisms during the past four years with primary focus on the contributions of geoscientists from the united states

sulfur and carbon isotope geochemistry of coal and derived coal combustion by products an example from an eastern kentucky mine and power plant abstract the isotopic compositions of s 34 s and c 13 c were determined for the coal utilized by a power plant and for the fly ash produced as a by product of the coal combustion in a 220 mw utility boiler the coal samples analyzed represent different lithologies within a single mine the coal supplied to the power plant the pulverized feed coal and the coal rejected by the pulverizer the ash was collected at various stages of the ash collection system in the plant there is a notable enrichment in 34 s from the base to the top of the coal seam in the mine with much of the variation due to an upwards enrichment in the 34 s values of the pyrite variations in 34 s and in the amount of pyritic s in the coal delivered to the plant show that there was a change of source of coal supplied to the plant between week one and week two of monitoring supporting a previous study based on metal and sulfide geochemistry for the same plant the fly ash has a more enriched 34 s than the pulverized coal and in general the 34 s is more enriched in fly ashes collected at cooler points in the ash collection system this pattern of 34 s suggests an increased isotopic fractionation due to temperature with the fly ash becoming progressively depleted in 34 s and the flue gas s containing components becoming progressively enriched in 34 s with increasing temperatures substantially less variation is seen in the c isotopes compared to s isotopes there is little vertical variation in 13 c in the coal bed with 13 c becoming slightly heavier towards the top of the coal seam an 83 93 loss of solid phase c occurs during coal combustion in the transition from coal to ash owing to loss of co 2 despite the significant difference in total c content only a small enrichment of 0 44 0 67 in 13 c in the ash relative to the coal is observed demonstrating that redistribution of c isotopes in the boiler and convective passes prior to the arrival of the fly ash in the ash collections system is minor

heat transfer and intraplate deformation in the central indian ocean nineteen new heat flow measurements made across deformed oceanic lithosphere in the central indian ocean and previously published data show that heat flow is significantly higher than predicted by models for cooling oceanic lithosphere over much of the region many of the temperature depth profiles are nonlinear upward convection of water is the most likely explanation for the curvature of the temperature profiles since other possible causes including variations in bottom water temperatures conductivity changes with depth in the sediments and experimental error can be eliminated this interpretation requires water velocities of the order of 7 x 10 sup 8 m s which is unusual because the lithosphere is relatively old 72 82 m y and a thick sedimentary cover 1 2 5 km is present these observations suggest that the processes causing deformation of the plate have increased the heat flux through the sediment water interface we infer that extra heat is being generated at shallow depths perhaps less than 35 km in the plate although the specific mechanism by which deformational energy is converted into heat is difficult to determine

properties of a lacustrine subbituminous k1 seam with special reference to the contact metamorphism soma turkey abstract the subbituminous k1 seam in the middle miocene soma formation of western turkey reaches a thickness of 24 m typical samples on an air dried basis have 9 5 14 2 moisture 4 3 13 8 ash and 0 57 2 54 total sulphur the coal rank parameters and non agglomerating behaviour show that the coals are of subbituminous a rank the k1 seam is huminite rich coal with a mean random ulminite reflectance rr between 0 46 and 0 49 fluorescence emission measurements show that the sporinite cutinite resinite and alginite present have typical fluorescence spectra between 460 and 700 nm the soma formation was intruded by an olivine basalt during the pliocene pleistocene which caused local contact metamorphism at the top of the k1 seam on the basis of proximate ultimate and petrographic analyses the intruded seam can be divided into normal coal transition zone and natural coke intervals each differing in their degree of metamorphism moisture volatile matter hydrogen and oxygen contents very rapidly decrease close to the contact point with the intrusion whilst calorific value carbon content and mean random reflectance value increase a diagram ofo c versus h c also shows a distinct increase in rank caused by the intrusion minor illite siderite and plagioclase feldspar are present in the natural coke samples butpyrrhotite is not observed mineralogical geochemical and reflectance studies indicate that the general temperature during formation of natural coke was probably relatively low

coal combustion by product quality at two stoker boilers coal source vs fly ash collection system design fly ashes from two stoker boilers burning pennsylvanian eastern kentucky high volatile a bituminous coal blends were examined for their petrology and chemistry the source coals have similar trace element contents one of the ash collection systems was retrofitted with a baghouse fabric filter system collecting a finer fly ash at a cooler flue gas temperature than the plant that has not been reconfigured the baghouse ash has a markedly higher trace element content than the coarser fly ash from the other plant the enhanced trace element content is most notable in the as concentration reaching nearly 9000 ppm ash basis for one of the collection units differences in the ash chemistry are not due to any substantial differences in the coal source even though the coal sources were from different counties and from different coal beds but rather to the improved pollution control system in the steam plant with the higher trace element contents

geological controls on the mineralogy and geochemistry of the beypazari lignite central anatolia turkey abstract the raw coal from the cayirhan mine beypazari basin turkey contains an average of 28 5 mineral matter consisting up to 80 zeolites the coal seam is split by a 1 m thick tuffaceous siltstone into the upper first tv and lower second tb seams which contain essentially different zeolites the first seam contains ca rich zeolites clinoptilolite heulandite whilst the second seam contains na rich zeolites analcime experimental work has shown that a na rich activation solution will produce na rich zeolites when the original volcanic glass is na rich but will produce ca rich zeolites when the volcanic material is ca rich it is thought that a na rich activation solution derived from contemporaneous volcanics in the beypazari basin reacted with volcanic tuffs of different chemical composition to produce the vertical variability in the mineral matter of the two seams trace element analyses of the raw coal showed that they are enriched in as b cr ni and zr when compared to world wide averages of coal they are also enriched in the major elements na and k these elements are probably also derived from a volcanic source barium and sr show a clear affinity for analcime whilst li cr ni cu zn co and ga show a clear affinity for clinoptilolite heulandite trace elements showing a positive correlation with the organic matter are mn b be ge y zr nb hf w and u manganese u th sc ge and hree heavy rare earth elements show correlations with phosphate trace elements showing correlation with both fe and s contents are co mo ta pb and iree intermediate rare earth elements arsenic and v seem to have mixed affinities with sulphides and zeolites and organic matter and zeolites respectively although a proportion of the as b and s are retained in the ash during coal combustion due to the sorption mechanism of cao derived from the clinoptilolite heulandite decomposition significant emissions of these elements may arise from the cayirhan thermal power station due to the anomalously high concentrations of these elements in the beypazari coal the high total alkali metal content of these coals exceeds the recommended maximum for steam coal but it is believed that sodium occurring in a mineralogical form such as analcime is not as likely to contribute to boiler fouling as organically associated sodium

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

seismic evidence for hydrothermally altered mantle beneath old crust in the tydeman fracture zone abstract to study the structure of old atlantic fracture zones seismic refraction profiles were obtained using ocean bottom seismometers and two ship multichannel expanding spread experiments on two inactive sections of the tydeman fracture zone the results indicate that a crustal seismic velocities are low compared with normal oceanic crust b there is a marked absence of an identifiable layer 3 c the depth to the moho is shallow though not exceptionally so and d anomalously low seismic velocities of 7 2 7 5 km s 1 are observed over ranges at which upper mantle velocities are normally detected s wave arrivals corresponding to both crustal and mantle refractions are also observed which enable the first estimates of poisson s ratio within a fracture zone to be made using these results and those from other surveys we show that the seismic velocity in the upper mantle beneath fracture zones decreases systematically with increasing age these findings suggest that hydrothermal circulation which can lower the upper mantle velocity by serpentinization persists under fracture zones for at least 70 ma and occurs at greater depths than for normal oceanic crust the serpentinization process is not sufficiently rapid to obscure the location of the original crust mantle boundary

seasat derived gravity constraints on stress and deformation in the northeastern indian ocean we use seasat derived gravity data to investigate crustal deformation in the ne indian ocean gravity highs reflecting crustal undulations vary in orientation from e w in the central indian basin to ne sw in the wharton basin the undulations vary in trend similarly to the variation of the maximum compression directions predicted by a plate driving force model cloetingh and wortel 1985 and are essentially restricted to the area of predicted compression for both principal horizontal stresses this agreement implies that the stress model describes the basic features of the deformation observed in the gravity as well as the seismicity the gravity data also provide insight into two enigmatic tectonic features the transition in the morphology of the 90 e ridge at 10 s from a continuous high to a complex blocky structure appears related to the deformation since undulations in the central indian basin can be projected eastward to blocks on the ridge the morphology formerly interpreted as a fossil feature may reflect the recent deformation the discrepancy between the trends of the southernmost 85 e ridge and the 90 e ridge previously thought to exclude similar hot spot track origins appears to result from treating a crustal undulation as part of the 85 e ridge earthquakes do not appear to be preferentially located with respect to the peaks and troughs of the undulations

multi technique study of fly ash from the bokaro and jharia coalfields jharkhand state india a contribution to its use as a geoliner abstract the chemical mineralogical petrographic and textural characteristics of fly ashes from one fluidized bed and two pulverized fuel power stations in india have been evaluated by a range of complementary methods including optical and electron microscopies laser granulometry quantitative x ray diffraction x ray fluorescence spectrometry and inductively coupled plasma techniques mineralogical and geochemical analyses have also been carried out on the feed coals from the respective power stations and the results were used to evaluate the changes produced during different combustion processes differences in particle size and shape for the ashes and also differences in ash petrology and mineralogy have been related to differences in the mineral matter of the feed coals and to the milling characteristics and combustion temperatures in the different power plants there is a potential of using these fly ashes as geoliner because of their fine texture and low permeability leaching tests have also been carried out on the fly ashes as a basis for assessing the potential for adverse impacts on groundwater systems the materials were blended with bentonite to decrease the permeability further the major and trace element compositions of these ashes were determined most of the elements studied were leached in lower concentrations than averages for the same elements from european fly ashes it is thus expected that these ashes will not provide significant source of additional contamination to permeating water if they are used with bentonite as geoliner material

plate tectonic models for indian ocean intraplate deformation abstract the equatorial region of the conventionally defined indo australian plate has long been recognized as containing a type example of intense intraplate deformation we trace the development of tectonic models for the area to illustrate techniques for the analysis of such deformation the identification of anomalous seismicity near the ninetyeast and chagos laccadive ridges demonstrated the existence of the deformation focal mechanisms from recent and historic earthquakes showed strike slip motion occurring along the ninetyeast ridge seismic moment data allowed the rate to be estimated similar studies showed north south tension in the chagos bank region and north south compression in the region between the ninetyeast and chagos ridges global plate motion studies indicated non closure of the indian ocean triple junction suggesting the conventional plate geometry was inadequate for a rigid plate description of the area gravity and marine geophysical data indicated intense north south compressional deformation south of the bay of bengal these observations are reconciled by a plate motion model in which australia and india lie on distinct plates divided by a boundary that intersects the central indian ridge near the equator in this model arabia usually considered a separate plate has negligible motion relative to india the resulting euler vector for australia relative to indo arabia lies just east of the central indian ridge and predicts approximately 0 5 1 5 cm yr compression in the central indian basin and 1 5 2 cm yr strike slip motion along the northern ninetyeast ridge consistent with the seismological and geophysical data in contrast to conventional oceanic plate boundaries the boundary deformation is distributed over a wide zone this diffuse nature may reflect either the boundary s recent inception or slow rate of motion analysis of seismicity and deformation in the boundary zone should offer insights into the mechanics of its development and its implications for the evolution of plate boundaries

rotated oceanic blocks in western ecuador a paleomagnetic study of over 250 cores from 21 sites sampled over a distance exceeding 250 km in the early cretaceous pinon formation in the costa of western ecuador indicates that the sampled lithologies essentially morb type basalts and dolerites carry a stable remanent magnetization whose direction significantly deviates from that of coeval formations of stable south america although both normal and reverse directions have been recorded the two polarities cannot easily be distinguished because of the low latitude of the ocean floor at the time of formation the most likely interpretation is that the entire area has undergone 70 clockwise rotation since its genesis these results thus yield new evidence for an allochtonous origin of this suspect terrane

seismotectonics of portugal and its adjacent area in the atlantic abstract new elements on the seismicity of portugal and new focal mechanism solutions of earthquakes with epicentres situated off the coast of the portuguese mainland and in the azores region are presented historical seismicity data show that in the territory of the portuguese mainland there are active faults that are responsible for earthquakes that have caused important damage and many casualties however most of the intraplate earthquakes with epicentres situated in the portuguese mainland or near the shore are normally of small magnitude and this renders difficult their interpretation in the light of focal mechanisms a solution for one earthquake with magnitude 5 and epicentre at the nazare submarine canyon is presented southwestwards of cape st vincent there is an important seismic zone responsible for high magnitude earthquakes such as that of 1 november 1755 this zone is situated in the region where the extension of the messejana fault into the ocean joins with the azores gibraltar fault the seismicity of the area situated between the western coast of the portuguese mainland and the azores increases approximately along the 15 w meridian from the latitude of the azores gibraltar fault up to 44 n focal mechanisms of earthquakes with epicentres situated along this line show very similar solutions the interpretation of the focal mechanism solutions of the earthquakes with epicentres situated in the studied area shows that the stress field trends approximately nw se it is assumed that this stress field results from the interaction of the eurasian and african plates however this direction is not maintained in the azores region

geology and paleobiology of islands in the ordovician iapetus ocean review and implications a history of islands in the iapetus ocean and their destruction is recorded by widespread occurrences of lower to upper ordovician volcanic and epiclastic rocks and some limestone through the axial parts of the appalachian caledonide orogen in north america and northwestern europe assemblages of arenigian and llanvirnian benthic shelly fossils chiefly brachiopods from these rocks constitute the celtic biogeographic province that is distinguished by its endemic genera and by some that are older than in other biogeographic provinces some that are younger than elsewhere and others that have not hitherto been found together evidence from these fossils and from the geology of the rocks pertaining to them suggests that north american terranes that included islands of arenigian llanvirnian age lay at middle to high latitudes both in mid ocean and within the armorican continental margin whereas coeval rocks in west central ireland and norway that have toquima table head shelly fossils were originally part of the laurentian continental margin eradication of the celtic assemblage and the reduction of ordovician faunal provinciality in the appalachian caledonide region coincide with llanvirnian obduction subduction of hundreds of kilometres of iapetus ocean crust late llanvirnian and younger ordovician rocks in the remnant basin including some of peri insular origin have brachiopods of scoto appalachian affinities no discrete islands of ashgillian age have been recognized although fossiliferous volcaniclastic and polymictic conglomerates indicate intermontane basins in some places shelly fossils in these rocks and those in the siltstones and limestones from the gaspe peninsula are like those of ashgillian age elsewhere

back arc thrusting in the eastern sunda arc indonesia a consequence of arc continent collision the structure of the eastern sunda back arc region is dominated by two large north directed thrusts the wetar and flores thrusts and one or more minor thrusts which may represent early stages of subduction polarity reversal of the arc the relationships between thrusting and magmatic activity surface slopes cross arc faulting uplift forearc structure and collision by the australian continental margin provide constraints on the likely driving mechanisms of thrust formation driving mechanisms are considered in two broad categories one set of possible mechanisms originates within the upper plate and includes gravity sliding gravity spreading and magmatic intrusion the other set focuses on stress propagation between the upper and lower plates and for this arc system the major mechanism is that of continental collision while no one mechanism explains the range of observations we see in the back arc region all of these aspects play some role in the development of the thrusts we can eliminate upper plate mechanisms as primary driving forces because slope effects are similar in areas of both thrusting and nonthrusting in addition the wetar thrust shows a negative relation between thrusting and volcanism and side looking airborn radar images show no evidence of postvolcanic rifting that could accompany intrusion without volcanism collision between the arc and the australian continent provides the clearest driving mechanism but it does not explain the discontinuous nature or the particular location of the thrusts we suggest a sequence that appears to account for the data and to provide insight into the controversies often associated with other such thrust belts thrusting was initiated in those areas where the crust of the forearc region was thick a factor that facilitated stress propagation across the arc and where the crust of the back arc was thin which facilitated back arc thrusting thrusting concentrated at the base of the slope where the slope stress is maximum the early thrusting may have been helped also by thermal weakening of the crust due to volcanism as convergence proceeded volcanism waned then ceased in the eastern part of the arc the crust then strengthened and thrusting required higher stress to maintain and propagate this later stage should show higher seismic energy release which appears to be the case for the wetar thrust region displacement on the flores thrust appears to be matched by deflection of the volcanic arc we have estimated shortening in the back arc from interpretation of reflection profiles and for the flores thrust the value of approximately 30 km is consistent with that estimated for deflection of the arc compressional deformation continues west of the collision zone across the bali basin and into java it is reported in ne sumatra as well this deformation involves much less convergence than the eastern sunda thrusts and it may be related to magmatic processes to subduction of oceanic plateaus such as the roo rise or in the case of the bali basin to efficient lateral propagation of the flores thrust

a diffuse plate boundary model for indian ocean tectonics it is suggested that motion along the virtually aseismic owen fracture zone is negligible so that arabia and india are contained within a single indo arabian plate divided from the australian plate by a diffuse boundary the boundary is a zone of concentrated seismicity and deformation commonly characterized as intraplate the rotation vector of australia relative to indo arabia is consistent with the seismologically observed 2 cm yr of left lateral strike slip along the ninetyeast ridge north south compression in the central indian ocean and the north south extension near chagos

mineralogy and geochemistry of feed coals and their combustion residues from the cayirhan power plant ankara turkey abstract a total of 48 samples feed run of mine coals and their combustion residues fly ash and bottom ash were systematically collected twice a week over a 4 week period june 1998 from two boiler units i and ii of the cayirhan power plant 630 mw that burns zeolite bearing coals of late miocene age the feed coals are high in moisture 22 8 as received content and ash 44 9 yield and total s content 5 1 and low in calorific value 2995 kcal kg the mineralogy of the feed coals contains unusually high contents of the zeolites clinoptilolite heulandite and analcime which are distributed within the organic matter of coal other minerals determined are gypsum quartz feldspar pyrite dolomite calcite cristobalite and clays common minerals in the crystalline phase of the combustion residues are anhydrite feldspar quartz hematite lime and ca mg silicate minor and trace amounts of magnetite cristobalite maghemite gehlenite calcite and clinoptilolite heulandite are also present in the combustion residues trace element contents of the feed coals except for w fall within the estimated range of values for most world coals however the mean values of mn ta th u and zr are near maximum values of most world coals elements such as as bi ge mo pb tl w and zn are enriched more in the fly ash compared to the bottom ash