factors affecting the durability of selected weak and clay bearing rocks from turkey with particular emphasis on the influence of the number of drying and wetting cycles weathering can induce a rapid change of rock material from initial rock like properties to soil like properties the resistance of a rock to short term weathering is described through a durability parameter called the slake durability index as durability is an important engineering parameter particularly for weak and clay bearing rocks it was assessed by a number of tests the main purpose of this study is to assess the influence of the number of drying and wetting cycles and controls of mineralogical composition and strength on durability for this purpose 141 samples of different types of weak and clay bearing rocks were selected from different parts of turkey and relationships between the above mentioned rock characteristics were statistically investigated the samples were subjected to multiple cycle slake durability testing x ray diffraction xrd analysis and uniaxial compression testing in addition to assess the influence of mineralogical composition on durability the mineral contents of the original material and the material passing from the drum of the slake durability apparatus after each cycle were also determined by xrd the results indicate that the type and amount of clay minerals are the main factors influencing the variations of the slake durability index in all samples the durability of the clay bearing rocks studied correlates best with the amount of expandable clay minerals a strong relationship between the uniaxial compressive strength and the fourth cycle slake durability index is found only for the marls among the rock types studied assessment of gradation results of the spoil pile materials consisting of clay bearing rocks also reveals that the increase in percentage of fines in old piles is indicative of material degradation as is evident by multiple cycle slaking it is emphasized that two cycle conventional slake durability testing did not appear to offer an acceptable indication of the durability of weak and clay bearing rocks when compared with multiple cyclic wetting and drying comments on the performance of the test are made that aim to make the testing process and interpretation of the results more reliable

an insight into crack density saturation rate and porosity model of the 2001 bhuj earthquake in the stable continental region of western india abstract the 2001 bhuj earthquake mw 7 6 source zone is examined in the light of crack density e saturation rate and porosity parameter using new data set derived from a large aftershock sequence recorded by the gujarat seismic network gsnet during november 2006 december 2009 processes of rupture initiations of the mainshock and its aftershock sequence are better understood by synthesizing the dynamic snapshots of the source zone using the new dataset pattern of crustal heterogeneities associated with high e high and high anomalies at depths varying from 20 km to 25 km is similar to those of earlier study by mishra and zhao 2003 the anomalous zone is found extended distinctly by 50 60 km in the lateral direction indicating the reinforcement of cracks and fractured volume of rock matrix due to long aftershock sequence since 2001 bhuj earthquake in the source area it is inferred that the presence of a fluid filled fractured rock matrix with super saturation may have affected the structural and seismogenic strengths of the source zone and is still contributing significantly to the geneses of earthquakes in and around the source zone anomalous pattern of high e with wider distribution of high indicates the existence of micro cracks in the lower crust while high suggests the cementation of cracks through permeation of residual magma metamorphic fluids into the hypocenter zone the results suggest that the existence of residual fluids in the fractured rock matrix in the mid to lower crust might have played a key role in triggering the 2001 mainshock and is still responsible for its continued long aftershock sequences

poisson s ratio and porosity at coso geothermal area california high resolution three dimensional compressional and shear wave velocity models derived from microearthquake traveltimes are used to map the distribution of poisson s ratio and porosity at coso geothermal area inyo county california spatial resolution of the three dimensional poisson s ratio and porosity distributions is estimated to be 0 5 km horizontally and 0 8 km vertically model uncertainties 1 in the interior and 2 3 around the edge of the model are estimated by a jackknife method we use perturbations of r vp vs ratio and vp vs product to derive distributions of poisson s ratio and porosity which are then used to constrain and delineate possible zones of intense heat fracture accumulation and fluid saturation poisson s ratio at coso ranges from 0 15 to 0 35 with an average of 0 224 lower than the crustal average of 0 25 high poisson s ratios are more extensive in shallower depths 1 5 km while lower poisson s ratios are found in the deeper section 1 5 3 0 km of the target area two major features with low poisson s ratio are identified at geothermal production depth 1 3 km around stations s2 s6 and s1 s3 s4 the two low features are separated by a northwest southeast trending high belt with variable width of 1 3 km a high body is found around s2 and s6 and extends down in depth a circular low belt corresponding to the high belt is located around s2 s6 and is linked to a previously reported structure in vs tomography this low highly porous belt is probably a horizontal conduit reservoir of geothermal fluid a vertical low and high channel beneath triangle s1 s3 s4 corresponds to a high attenuation dome like feature we propose an upwell and spread magma intrusion model for the last major magmatism in the coso region the magmatic upwelling is centered in the s1 s3 s4 area the model predicts potential geothermal resources to the south and west of triangle s1 s3 s4 based on local faulting patterns

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

chemical mineralogical and textural properties of the kope formation mudstones how they affect its durability abstract the kope formation is a rock unit that extends over southwest ohio and adjacent areas of kentucky and indiana usa it is characterized by meter scale cycles of mudstones and limestones where thick mudstone is sandwiched between thin limestone layers kope formation mudstones are less durable than the mudstones in the area they cause abundant slope failures in areas of their outcrops this study evaluates chemical mineralogical and textural properties of kope mudstones to determine why it is less durable the two cycle slake durability index id 2 was measured on thirty mudstones belonging to three consecutive cycles of the kope formation chemical composition and mineralogy of kope mudstones do not show significant relationship with the id 2 instead a relationship to fabric was found kope mudstones with two main fabric types were observed in the field laminated mudstones and non laminated mudstones detailed micro fabric analysis on kope mudstones was done using the scanning electron microscope laminated mudstones with turbostratic fabric showed higher id 2 and lower moisture content than the non laminated mudstones with matrix fabric the difference in the id 2 of laminated mudstones and non laminated mudstones is statistically significant both mudstone types exist in many cycles of the kope formation thus core samples should be selected from both types for preliminary tests in geotechnical practice to obtain more accurate estimations of the geotechnical properties of the kope mudstones the results and data interpretations of this study can be correlated with the mudstones and shale in different areas of the world specifically a great attention should be paid to the macro and micro textural properties of any rock type regardless of their classification

silicified conifer forests and potential mining problems in seam m2 of the gore lignite measures miocene southland new zealand abstract silicified conifer podocarpus cf hallii stumps up to 0 8 m in diameter are present at two levels in seam m2 of the miocene gore lignite measures mataura coalfield eastern southland the in situ stumps are believed to be the remains of forests which grew during pauses in peat accumulation when groundwater levels were depressed as a result of climatic change or local basinal processes growth ring measurements show the trees increased in radius between 0 16 and 1 mm per year in two of six specimens the growth rates halved during their final 30 40 years of life rising water levels may have resulted in less favourable growth conditions within the stumps much of the wood structure is well preserved progressive diagenesis involved impregnation of the cell walls by silica infilling of the cell lumens with length slow chalcedony and opaline silica and deposition of opal length fast chalcedony and minor siderite in fractures radial and axial parenchyma contain coalified organic material and minor chalcedony filaments of wood rotting fungi and probable root masses of epiphytes are present in some fossil wood however by analogy with modern podocarpus hallii we maintain the stumps were preserved for later silicification because the wood was highly resistant to fungal and bacterial decay the stumps presumably functioned as conduits to ascending silica saturated meteoric groundwater and water released during compaction because of the contrasts in permeability between the vertical stumps and the surrounding peat

controls on shale durability the response of two ordovician shales in the slake durability test the slake durability test has been proposed as a means of predicting the engineering performance of shales testing of sections in the two major shale units of ontario show that the test is capable of making distinctions between apparently similar shale samples queenston shale has generally lower durability than the georgian bay formation samples inspection of the shale fabric shows that this is due partly to inefficient cementing by calcite in queenston shale but is primarily because the microcracks in queenston shale are more curved than those in georgian bay formation variation in shale durability within the shales is controlled by mineralogy in queenston shale it is controlled almost entirely by calcite cementation in georgian bay where hard bands shaly limestone are present these dominate the test giving a high durability however pure shale durability is controlled by clay content comments on the performance of the test are made that aim to make the testing process and interpretation of

seismic velocity and poisson s ratio tomography of the crust beneath east anatolia abstract eastern anatolia is a region in the early stages of continent continent collision and so provides a unique opportunity to study the early development of continental plateau located within the alpine himalayan fold thrust fault belt the anatolian plateau is geologically very complex with over half of the surface area covered with late cenozoic volcanics of diverse composition the plateau is also seismically active and is dissected by numerous seismogenic faults predominantly of strike slip motion in this study we determine 3 d tomographic images of the crust beneath eastern anatolia by inverting a large number of arrival time data of p and s waves from the obtained p and s wave velocity models we estimated the poisson s ratio structures for a more reliable interpretation of the obtained velocity anomalies our tomographic results are generally consistent with the major tectonic features of the region high p and s wave velocity anomalies are recognized near the surface while at deeper crustal layers low seismic wave velocities are widely distributed poisson s ratio exhibits significant structural heterogeneities compared to the imaged velocity structure the seismic activity is intense along highly heterogeneous zones and is closely associated with pre existing faults in the central and western parts of the study area results of the checkerboard resolution test indicate that the imaged anomalies are reliable features down to a depth of about 40 km the low velocity high poisson s ratio zones in the middle to lower crust are consistent with many geophysical observations such as strong sn attenuation low pn and sn velocity and the absence of mantle lid implying the presence of partial melt in the uppermost mantle

geodynamic evolution of the lithosphere and upper mantle beneath the alboran region of the western mediterranean constraints from travel time tomography an edited version of this paper was published by the american geophysical union copyright 2000 agu see also http www agu org pubs crossref 2000 2000jb900024 shtml http atlas geo cornell edu morocco publications calvert2000 htm

synsedimentary volcanic ash derived illite tonsteins in late permian coal bearing formations of southwestern china abstract illite claystones tonsteins of late permian coal bearing formations are well developed and extensively distributed in southwestern china over the past decades it has been recognized that they are synsedimentary volcanic ash falls in origin altered tuff beds based on the data derived from the comprehensive investigations on their stratigraphic and geographic distribution petrographic types chemical composition accessory mineral assemblage as well as on their morphological characteristics recently mineralogical and petrological identifications and x ray diffraction analyses on these peculiar tonsteins further suggest that they can be classified mainly into three categories based on their clay mineral constitution kaolinitic kaolinitic illitic transitional type and illitic as coal partings in most cases these different types of tonsteins show a distinct zonal distribution on a regional scale their mineral constitution is profoundly modified by the combined effects of many factors during deuterogenic diagenesis as indicated by the variation in volatile component percentage vm of the adjacent coal seams vm is calculated on a combustible component basis those tonsteins intercalated in coal with a vm 10 are dominated by kaolinite but they contain increasing amount of illite at the expense of kaolinite when vm of coal decreases from 10 to 8 when vm declines to less than 8 the clay minerals in these tonsteins are almost entirely illite with some sort of accompanying chloritization it is clear that from a regional point of view the variation in clay mineral constitution of these tonsteins is in response to the continual and progressive change in geological processes in addition to the temperature and pressure conditions the existence of a certain amount of alkali metal ions and ferrous ions in solution is one of the controlling factors

3 d seismic structure of kii peninsula in southwest japan evidence for slab dehydration in the forearc abstract kii peninsula is located in the forearc region of southwest japan and has distinct structural and tectonic features characterized by high seismicity in the crust and the subducting philippine sea slab high surface heat flow high 3he 4he isotopic ratio and a local change in the geometry of the subducting slab we have tried to determine detailed 3 d p and s wave velocity structures of this region using a large number of high quality arrival time data recorded by dense seismic networks on the japan islands from the obtained seismic velocities we further estimated 3 d distributions of poisson ratio crack density saturation rate and porosity parameter in the study area our results show significant heterogeneities in the crust and upper mantle wedge characterized by low seismic velocities high poisson ratio high values of crack density saturation rate and porosity these results suggest the existence of fluids in the crust and mantle wedge resulting from the dehydration of the subducting philippine sea slab which can explain the observed geophysical and geochemical features in kii peninsula

lateral variation of the crust in the iberian peninsula new evidence from the betic cordillera abstract new results from a seismic refraction wide angle reflection survey carried out in the betic cordillera in autumn 1989 contribute to a better picture of its deep structure one nw se profile cuts across the iberian massif the external and internal betics the structure of the crust in the iberian massif shows characteristics similar to those found in previous experiments the lower crust is found as a distinct layer 12 km thick with an average velocity of 6 8 km s 1 the moho is found at about 35 km depth this structure extends southeastward until a 3 4 km upwelling of the moho about 30 km north of the present day surface boundary between the external and internal betic units further southeast the moho deepens to 38 km and the lower crust is no longer seismically detected the absence of differentiated lower crust beneath part of the external betics may be related with the mesozoic rifting of the south iberian passive margin instead this absence under the internal betics may be caused by rifting in conjunction with the collisional evolution of the orogen a wnw ese profile lying in the internal betics shows the presence of a prominent reflector at 10 12 km depth this seems to be a widespread feature in the internal betics and may be interpreted as a detachment surface the moho is found at 38 km depth rising strongly in the easternmost betics seismic data suggest a thin crust in the offshore area southwest of malaga probably containing a massive zone of high velocity rocks which is also supported by available geophysical and geological data

small scale faulting topographic steps and seismic ruptures in the alhambra granada southeast spain the alhambra 14th century ad in granada southeast spain is built at the summit of a pliocene to lower pleistocene conglomeratic formation tens of small scale normal faults crop out along the northern hillslope of the alhambra which have a n130 n150 e strike dipping 65 75 mostly to the southwest these are closely spaced faults approximately 5 30 m with centimetre to several metre displacements several topographic steps in this area coincide with hectometre to kilometre scale faults with the same kinematics as the small scale ones some of these faults appear to be active and related to the present seismicity detected in this region and associated with the cracks and other damage observed in the alhambra several focal mechanisms calculated in this study are in accordance with the dominant nw se orientated normal faults we interpret that the topographic steps of these faults are a consequence of repeated earthquakes during the past 800 ka the last large earthquake of approximately 5 1 magnitude in this area occurred in 1431 destroying the alixares palace the arabian fence and part of the alhambra wall we consider the seismic risk associated with these faults to be moderate as the displacement is partitioned into several hectometre to kilometre scale faults copyright 2004 john wiley sons ltd

improved petrological modal analyses from x ray powder diffraction data by use of the rietveld method part ii selected sedimentary rocks abstract mineral modes have been determined for specimens of five sedimentary rocks arenite graywacke slate mudstone and shale from cu k x ray powder diffraction data using the rietveld method up to eight individual mineral components were measured in each sample with a detection limit of about 0 5 wt depending on the mineral assemblage the x ray results when expressed as reduced oxides wt are in reasonable agreement with xrf oxide compositions the power of the rietveld method in this application to mineral mode determination is its ability to 1 cope with complex diffraction patterns containing substantial peak overlap 2 provide modes that do not generally require independent lengthy calibration 3 determine the chemical composition of the major phases during the analysis thereby providing a degree of self calibration and 4 deal with very fine grained samples disadvantages include 1 the need to know the identity of all the components beforehand and 2 the need for experience in x ray diffraction analysis by the rietveld method

analysis origin and significance of mineral matter in coal an updated review abstract the material classed as mineral matter in coal embraces crystalline mineral materials as well as a range of inorganic elements that occur in non crystalline form this review outlines the methods that may be used to evaluate the percentage of mineral matter for a coal sample as opposed to the ash yield and to identify the minerals their individual percentages and their modes of occurrence within the coal the principal techniques include low temperature oxygen plasma ashing quantitative evaluation of x ray diffraction data observation using optical microscopy and a combination of observation chemical analysis and in some cases mapping based on scanning electron microscopy and related methods a range of other techniques may also be used to provide additional information on particular mineral matter components processes responsible for mineral matter formation include detrital input biogenic activity and authigenic precipitation at different stages of the coal s depositional and post depositional history differential migration of non mineral inorganic elements may also occur in lower rank coals and expulsion of non mineral inorganics may take place with rank advance knowledge of the mineral matter may be of assistance in understanding the modes of trace element occurrence with implications for assessing possible environmental impacts and also the potential for recovery of economic products from coal the behaviour of different mineral matter components at high temperatures is also discussed as well as methods for mineralogical analysis of ashes and other coal utilization products information from mineral matter studies may provide an improved basis for understanding coal formation and for evaluating the response of particular coals to different combustion gasification and coking processes

variations of spectral width with aspect angle for type ii vhf echoes from the eastward electrojet continuous wave radar data from the university of saskatchewan summer 1981 radar auroral campaign were examined to study the variation of spectral width with aspect angle in order to reduce the uncertainties caused by refraction from strong optical forms the data were restricted to stable eastward electrojet events a consistent and sharp increase of spectral width with aspect angle was observed in qualitative agreement with theory

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

crustal structure of the central sector of the betic cordillera se spain deep seismic reflection gravimetric and magnetometric data allow the main features of the deep structure of the central sector of the betic cordillera to be established the moho is horizontal or dips slightly toward the s below the mountain chain and its morphology has no direct relationship with the region s topography the deep reflectors are not deformed by the neogene kilometric scale folds that produced the main topographic features probably due to the existence of detachment levels in the crust the crust is slightly thickened in the betic cordillera almost 35 km and has an abrupt transition to the thin crust of the alboran sea 15 km in the central alboran sea along an e w oriented narrow band subparallel to the coast line where the moho dips more than 60 n the neogene evolution of the mountain chain caused compressive deformation in the external zones in the internal zones pre tortonian low angle normal faults developed after the alpine metamorphism and later high and low angle normal faults and strike slip faults occurred up to the quaternary geophysical and field geology data can be used to establish a geological model for the recent evolution of the crustal deformation in this model the recent evolution of the region is probably determined by thrusting of the thin continental crust of the alboran sea toward the nw over the southern margin of the iberian massif this deformation could be a consequence of the oblique convergent movement between the african and eurasian plates which may have uplifted the entire region causing regressions in the sedimentary basins and the formation of folds and extensional structures in the upper part of the thickened crust

teleseismic p residual study in the iberian peninsula abstract teleseismic p wave residuals cleared of the effects of various source regions and deep mantle paths reflect the composition and structure of the lithosphere and asthenosphere beneath seismological stations we use a method with which we compute two components of the relative residuals for each station namely a directionally independent average and azimuth incidence angle dependent terms and also the ach 3 d inversion method the representative averages show consistent variations over the iberian peninsula with a relatively steep gradient in some areas the iberian massif and the betic cordillera these changes attain values around 1 s over a distance of about 200 km the lateral variations of these residual averages are transformed into a tentative model of the lithosphere thickness a thick lithosphere is observed beneath the iberian massif the pyrenees and beneath part of the betic cordillera waves from events at different teleseismic distances and various azimuths provide consistent residual patterns and a systematic directional dependence of the relative residuals especially at stations in the betic cordillera

mineral matter in coals cleat minerals and their origin in some coals from the english midlands abstract in four coal seam profiles from the cannock coalfield west midlands the cleat joint frequency is a function of lithotype greatest in vitarin and is inversely related to bed thickness the cleat minerals were studied 1 under the microscope optical and electron 2 by x ray diffraction and 3 chemically the minerals present are pyrite marcasite sphalerite galena sulphides quartz kaolinite silicates ankerite calcite carbonates and apatite this sequence has features in common with diagenetic sequences recorded in other rock types and it is concluded that the cleat minerals in coal form in response to pore fluid evolution and movement during burial diagenesis the elements are thought to originate from both the coal and the associated sediments mainly mudrocks similarities in diagenetic sequences are in part a reflection of the importance of organic maturation reactions in all the rock types in the sequence whereas differences are attributed to the dominance of these reactions in the coal itself

improved petrological modal analyses from x ray powder diffraction data by use of the rietveld method i selected igneous volcanic and metamorphic rocks

crustal heterogeneities beneath the 2011 talala saurashtra earthquake gujarat india source zone seismological evidence for neo tectonics abstract during the 1st decade of the 21st century the study area of talala saurashtra of western india witnessed three damaging earthquakes of moderate magnitude year 2007 mw 5 0 mw 4 8 and in the year 2011 mw 5 1 that generated public panic in the region the last damaging moderate earthquake of the 20th october 2011 in talala region 21 09 n 70 45 e located at about 200 km south to the devastating 2001 bhuj 23 412 n 70 232 e mainshock mw 7 6 jolted the entire saurashtra region of gujarat a long series of aftershocks followed hereafter recorded at nine seismograph accelerograph stations hypocenters of aftershocks were relocated accurately using absolute and relative travel time double difference method in this study we for the first time determined 3 d tomographic images of the upper crust beneath the 2011 talala earthquake source zone by inverting about 1135 p and 1125 s wave arrival time data estimates of seismic velocities v p v s and poisson s ratio structures offer a reliable interpretation of crustal heterogeneities and their bearing on geneses of moderate earthquakes and their aftershock sequences beneath the source zone it is found that the 2011 talala mainshock hypocenter depth 6 km is located near the boundary of the low and high velocity v p v s and the source zone is associated with low anomalies guarded by the prominent high anomalies along the active fault zone having strike slip motion beneath the earthquake source zone the pattern of distribution of v p v s and its association with occurrences of aftershocks provide seismological evidence for the neo tectonics in the region having left lateral strike slip motion of the fault

imaging the crustal structure throughout the east anatolian fault zone turkey by local earthquake tomography this paper presents new models of the seismic velocity structure of eastern anatolia turkey we applied a local earthquake tomography method to arrival time data produced by local and regional events in eastern anatolia to understand the three dimensional seismic velocity and vp vs models and their correlation with the geological evolution and tectonic processes in the study area the data are obtained from 78 broadband seismic stations owned by the earthquake department of the disaster and emergency management presidency for the period between 2008 and 2017 seven depth cross sections are taken along various segments of the east anatolian fault zone travel times of 53 099 phase readings 29 122 p phase and 23 977 s phase picks from 4249 high quality earthquake recordings are analysed to develop 3 d vp lithological and vp vs petrological models of the study area the resulting p wave velocities describe intrusive magmatic bodies sediment thickness and the structure of the basin the vp vs structures aid to limit the position of the faults areas of weakness and gas or liquid saturated units with regions of high pore pressure four main seismic crustal layers down to 40 km are determined the upper crust 0 8 km has vp 4 6 km s whereas in the middle crust 9 20 km a vp perturbation between 4 6 and 5 8 km s is observed in the lower crust 20 35 km vp changes from 5 9 to 7 3 km s and in the upper mantle layer below 36 km vp exceeds 7 4 km s in all cases seismic velocities are well resolved in the first 40 km tomograms are compatible with the geological characteristics of the region dominant high p velocity values are observed beneath the collision zone conrad discontinuity is detectable at 20 km depth while moho depth is observed to vary between 30 and 40 km in the study area

p wave tomographic images in the central betics alboran sea south spain using local earthquakes contribution for a continental collision to investigate the relationship between shallow and intermediate depth earthquakes and the crust and upper mantle structure beneath the betic cordillera and alboran sea region we have applied seismic tomography to 2569 p wave arrival times from 367 microearthquakes recorded by both permanent and temporary seismic stations deployed in the region these earthquakes occurred in the depth range of 0 to 110 km beneath the central betic cordilleras and alboran sea our results have revealed significant structural heterogeneities in the crust and upper mantle beneath the study area in the upper crust there is a high velocity anomaly at sierra gorda western boundary of the granada basin penetrating to 15 km depth which is in good agreement with the aeromagnetic anomaly in the granada basin a low velocity anomaly is located in the middle crust which coincides with a previously detected greater cutoff depth of seismicity and are considered to be associated with a highly fractured zone generated by an intracrustal detachment the northern boundary of the alboran sea malaga coast is well imaged as low velocities from 50 to 90 km depths this low velocity zone in the upper mantle is associated with the intermediate depth seismicity which outline a section of continental crust related to the collision subduction beneath the northern part of the alboran sea southern part of the central betics

some genetic implications of silica and aluminosilicates in peat and coal abstract the inorganic content of okefenokee peat in the absence of a significant detrital contribution is a function of sponge spicule phytolith and diatom abundance in addition to the degree of organic matter decomposition and the frequency of fires the detrital component quartz dominates ash composition where it is present no clear correlation has been observed between the inorganic content of coals examined in this study and their maceral composition vitrinite rich coals have a wide range of ash yield these observations suggest that the minerals have been introduced detritally rather than accumulated as a result of peat degradation quartz in the coals appears to be detrital and the presence of 2m 1 mica indicates that there is also a detrital contribution to the clay minerals present

shear wave velocity structure of the south eastern part of the iberian peninsula from rayleigh wave analysis in this study we present the lithospheric structure of the south eastern part of the iberian peninsula by means of a set of 2d images of shear velocity for depths ranging from 0 to 50 km this goal will be attained by means of the inversion of the rayleigh wave dispersion for it the traces of 25 earthquakes occurred on the neighbouring of the study area from 2001 to 2003 will be considered these earthquakes have been registered by 11 broadband stations located on iberia all seismic events have been grouped in source zones to get an average dispersion curve for each source station path the dispersion curves have been measured for periods between 2 and 45 s by combination of two digital filtering techniques multiple filter technique and time variable filtering the resulting set of source station averaged dispersion curves has been inverted according to the generalized inversion theory to get s wave velocity models for each source station path later these models have been interpolated using the method of kriging to obtain a 2d mapping of the s wave velocity structure for the south eastern part of iberia the results presented in this paper show that the techniques used here are a powerful tool to investigate the crust and upper mantle structure through the dispersion analysis and its inversion to obtain shear velocity distributions with depth by means of this analysis principal structural features of the south eastern part of iberia such as the existence of lateral and vertical heterogeneity in the whole study area or the location of the moho discontinuity at 30 km of depth with an average s velocity of uppermost mantle of 4 7 km s have been revealed other important structural features revealed by this analysis have been that the uppermost of iberian massif shows higher velocity values than the uppermost of the alpine domain indicating that the massif is old and tectonically stable the average velocity of the crust in betic cordillera is of 3 5 km s while in the iberian massif is 3 7 km s all these features are in agreement with the geology and other previous geophysical studies

an interpretation of wide angle compressional and shear wave data in southwest germany poisson s ratio and petrological implications shear wave velocity especially when used with compressional wave velocity is an important constraint on estimates of the composition and physical state of the continental lithosphere we present shear velocity s models derived from high quality s wave data along three profiles in southwest germany which combine with existing p wave velocity p models to give poisson s ratio in the crust and uppermost mantle we then construct a laterally varying petrological model of the crust by comparing our p and s models with published laboratory measured rock velocities in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust but reaching a low of 0 15 in the black forest low p zone and varies laterally from 0 24 to 0 30 in the lower crust the average poisson s ratio of the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data implying a strong high low alternation of poisson s ratio in the lower crust this suggests that the lower crustal laminae represent mafic silicic compositional layering for example basic sills in an originally more quartz rich lower crust rather than alternating zones of high and low pore pressure there is no evidence for a shear wave low velocity zone lvz in the black forest mid crust despite the presence of a strong p wave lvz this suggests high quartz content and the presence of pore fluids at low not high pore pressure a clear p to s converted moho reflection pm s is visible on several shots indicating that the moho is at least locally a first order discontinuity no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle the petrological modeling indicates that the upper and middle crust are probably of granitic composition that the mid crustal low p zones have high quartz content and that the lower crust probably consists of granulites of laterally varying bulk composition from granodioritic to gabbroic the lower crust is more mafic in areas of high reflection density on seismic reflection profiles suggesting that the laminations are caused by mafic intrusions into the lower crust either prior to the variscan orogeny or during tertiary volcanic activity

burial of trees by eruptions of mount st helens washington implications for the interpretation of fossil forests lahars and fluvial sediments which buried trees following the 18 may 1980 eruption of mount st helens were investigated during august of 1982 trees buried in older mudflows dated at a d 1885 a d 1450 1550 and 36000 years b p also were examined although many logs clearly were transported large numbers of trees were buried in growth position burial by lahars generally resulted in the death of trees whereas some trees survived burial by fluvial sediments scanning electron microscope studies show that trees buried in lahars are well preserved pre 1885 buried woods show incipient silicification and woods buried 36000 years b p show silica impregnation of cell walls features of in situ and allochthonous burial very similar to those seen in southern washington are found also in eocene silicified forests in yellowstone national park wyoming u s a and in cretaceous fossil forests in southeastern alexander island antarctica observations of recent wood from volcaniclastic deposits of mount st helens provide valuable insights into processes of burial and silicification of fossil forests of various ages around the world

dual radar investigation of e region plasma waves in the southern polar cap origins and characteristics of small scale plasma irregularities in the polar ionosphere are investigated using a dual radar setup in which the e region is probed from opposite directions by two super dual auroral radar network superdarn facilities at the mcmurdo and dome concordia antarctic stations in certain time intervals velocity agreement is observed when velocities are compared at the same physical location in the horizontal plane such an agreement is widely expected if velocity at a given location is largely controlled by the convection electric field in other cases however velocity agreement is unexpectedly observed when measurements are considered at the same slant range distance along the radar beam for both radars this implies that it is not the electric field at a given location that is a controlling factor raytracing results show that the same range agreement may be explained for certain e region density conditions when echo altitude increases with radar range backscatter observations under generally unfavorable conditions for irregularity generation and the critical role of propagation conditions in the polar cap are discussed the observed e region velocity in the polar cap is demonstrated to depend indirectly on the plasma density distribution which is important for establishing the fundamental dependence on the convection electric field

the depth of the earthquake activity in the central betics southern spain in this study we used relatively velocity independent methods wadati diagrams to estimate and check the focal depth of the seismic activity in a sector of the betic cordilleras alboran sea in southern spain to understand the behaviour of the seismic activity a total of 335 earthquakes have been analyzed the most interesting feature found in the analyzed sector is the strong variation of the focal depth on average the focal depth distribution in the granada basin is restricted to h 20 km the lower cut off in the seismic activity which is interpreted to mark the brittle ductile transition this cut off is coincident with a midcrustal reflector detected in the zone by previous seismic refraction and deep reflection experiments that was interpreted as an extensional detachment the seismic activity in the malaga zone reaches depths up to 100 km in this case the seismic activity affect to the crust and upper mantle the deepest activity coincides with low values of heat flow possibly thus indicating a thicking of the lithosphere towards the w in the centre of the alboran sea the activity is shallower and corresponds with a higher heat flow we think that our results support models that have proposed active delamination towards the west such a model may explain the increase in the lithosphere thickness in this direction which would be congruent with the depth of the earthquakes

application of complementary methods for more robust characterization of sandstone cores abstract this paper is based on detailed mineralogical structural petrophysical and geochemical studies of sandstone core samples using routine core analysis methods these include x ray computer tomography ct scanning magnetic resonance imaging mri particle size analysis point counting based on petrographic thin sections environmental scanning microscopy esem x ray diffraction xrd and x ray fluorescence xrf in this study we demonstrate the feasibility of combing these complementary methods in the characterization of reservoir properties of sandstone cores four types of sandstones slick rock aeolian fife locharbriggs and berea sandstones that differ in grain size porosity and mineralogy have been characterized the results of the different methods used were found to be consistent with each other but the combination of a variety of methods has allowed a fuller characterization of the rock samples than each method used on its own bringing out subtle variations in petrographic characteristics that add significant value towards a better description of reservoir properties for example it becomes apparent that some types of rocks like berea sandstones thought to be homogeneous are in fact heterogeneous the recognition that rock heterogeneity at the sub centimeter scale may have a significant effect on hydrocarbon recovery requires that field scale reservoir models take account of these small scale effects in order to lay claim to reasonable accuracy in production forecasts

some geotechnical characteristics of fragmented queenston shale this paper presents the results of an experimental study to determine the stress strain behaviour of fragmented queenston shale from russell ontario and to investigate how its strength properties altered when the material was subjected to repeated slaking cycles slaking tests showed that large cobble size blocks of the material degrade rapidly to a particle size of 20 mm upon exposure to water and air consolidated drained tests in a large triaxial apparatus under monotonic loading conditions on specimens of fresh and slaked material were performed they indicate that the shear strength of fragmented queenston shale of particle size smaller than 20 mm is not affected by slaking key words queenston shale compaction shale granular material rockfill slaking shear strength consolidated drained tests

closure of the africa eurasia north america plate motion circuit and tectonics of the gloria fault we examine the closure of the current plate motion circuit between the african north american and eurasian plates to test whether these plates are rigid and whether the gloria fault is an active transform fault we also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries and compare the predicted direction of motion along the african eurasian plate boundary in the mediterranean with the direction of slip observed in earthquakes from marine geophysical data we obtain 13 transform fault azimuths and 40 3 m y average spreading rates 34 of which are determined from comparison of synthetic magnetic anomaly profiles to 140 observed profiles slip vectors from 32 earthquake focal mechanisms further describe plate motion detailed magnetic surveys north of iceland provide 11 rates in a region where prior plate motion models had few data magnetic profiles north of the azores triple junction record a rate of 24 mm yr 4 mm yr slower than used by prior models gloria and sea beam surveys accurately measure the azimuths of seven transform faults our plate motion model fits six of the seven within 2 two transform faults surveyed by gloria side scan sonar lie near famous area transform faults a and b and give azimuths 13 clockwise of them because recent studies show that short offset transforms such as transforms a and b are in many places oblique to the direction of plate motion we exclude azimuths from transforms with less than 35 km offset the best fitting and closure enforced vectors fit the data well except for a small systematic misfit to the slip vectors on right lateral slipping transforms slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths whereas on left lateral slipping transforms slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths we search the long eurasia north america boundary for evidence of an additional plate but find no systematic misfits to the data in particular if a spitsbergen plate exists and moves relative to eurasia its motion is less than 3 mm yr an africa eurasia euler vector determined by adding the eurasia north america and africa north america euler vectors is consistent with the gloria fault trend and with slip vectors from eastern azores gibraltar ridge focal mechanisms a small circle centered at the africa eurasia closure enforced pole fits the trace of the gloria fault the model in which closure was enforced predicts 4 mm yr slip across the azores gibraltar ridge and west northwest convergence near gibraltar 45 more oblique than suggested by a recent model based on compressive axes of focal mechanisms moreover our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between gibraltar and sicily because closure enforced vectors fit the data nearly as well as the best fitting vectors we conclude that the data are consistent with a rigid plate model and with the gloria fault being a transform fault

mineral matter and trace elements in coals of the gunnedah basin new south wales australia abstract the concentrations of major and trace inorganic elements in a succession of permian coals from the gunnedah basin new south wales have been determined by x ray fluorescence techniques applied to both whole coal and high temperature ash samples the results have been evaluated in the light of quantitative data on the minerals in the same coals determined from x ray diffraction study of whole coal samples using a rietveld based interpretation program siroquant to determine relationships of the trace elements in the coals to the mineral species present comparison of the chemical composition of the coal ash interpreted from the quantitative mineralogical study to the actual ash composition determined by xrf analysis shows a high degree of consistency confirming the validity of the xrd interpretations for the gunnedah basin materials quartz illite and other minerals of detrital origin dominate the coals in the upper part of the sequence whereas authigenic kaolinite is abundant in coals from the lower part of the permian succession these minerals are all reduced in abundance however and pyrite is a dominant constituent in coals formed under marine influence at several stratigraphic levels calcite and dolomite occur as cleat and fracture infillings mostly in seams near the top and bottom of the sequence the potassium bearing minerals in the detrital fraction are associated with significant concentrations of rubidium and the authigenic kaolinite with relatively high proportions of titanium zirconium is also abundant with associated p and hf in the gunnedah basin coal seams relationships exhibited by ti zr nd and y are consistent with derivation of the original sediment admixed with the seams from an acid volcanic source pyrite in the coals is associated with high concentrations of arsenic and minor proportions of thallium no other element commonly associated with sulphides in coals however appears to occur in significant proportions with the pyrite in the sample suite small concentrations of cl present in the coal are inversely related to the pyrite content and appear to represent ion exchange components associated with the organic matter strontium and barium are strongly associated with the cleat filling carbonate minerals ge and ga appear to be related to each other and to the coal s organic matter cr and v are also related to each other as are ce la nd and pr but none of these show any relationship to the organic matter or a particular mineral component

crustal structure of the betic rif system western mediterranean from local earthquake tomography abstract we have determined the three dimensional p wave velocity structure of the crust and uppermost mantle beneath the iberia africa collision zone using local earthquake tomography we have inverted arrival times of first arriving p phases listed in the bulletins of the instituto geografico nacional and phases picked by us on permanent stations of other regional networks and on temporary broadband stations deployed in the frame of the topo iberia project in total we have used 38 624 p wave arrival times from 2362 local events recorded at 120 seismic stations the most remarkable result is the imaging of a large high velocity body following approximately the western alboran coastline with a horizontal dimension of at least 200 km and extending in depth from the surface down to 24 km this body not imaged previously with this extent using seismic tomography coincides with surface exposures of subcontinental mantle peridotites in iberia and africa and with a belt of positive gravity anomalies we have also found a marked contrast in the seismic velocities of the middle and lower crust of the alboran basin coinciding with the location of the trans alboran shear zone we attribute this contrast to widespread magmatic intrusions in the eastern part of the basin resulting in higher p wave velocities than in the west this contrast would also explain the different orientation of the trans alboran shear zone with respect to the surface features and faults in the alboran basin we also image thick crust beneath the betics and rif accompanied by downgoing lithosphere of the iberian foreland and gulf of cadiz beneath the betic rif alboran system

experimental and numerical study on the effect of calcite on the mechanical behaviour of coal abstract the effects of the presence of calcite grains on the mechanical behaviour of a coal are investigated in this study coal specimens with and without calcite grains were obtained from the same coal seam and then subjected to confined compression with varying confining pressures mineral composition data of the coal containing calcite grains were obtained from petrographic analysis and subsequently used for constructing udec gbm model the model was calibrated to experimental results and then used to further the understanding of the influence of calcite grains on the mechanical behaviour of the coal it is found that the presence of calcite increases the young s modulus reduces the peak strength and the brittleness of the coal the numerical results suggest that the presence of calcite grains significantly increase the heterogeneities of the coal leading to differential and extensional straining which in turn causes internal tensile stresses and consequently tensile cracking the conformity of the numerical results with the experimental observations suggests the potential use of the udec gbm approach model for better understanding the mechanics of brittle rock failure at micro structure scale

3 d crustal structure of the extensional granada basin in the convergent boundary between the eurasian and african plates three dimensional p and s wave velocity models of the crust under the granada basin in southern spain are obtained with a spatial resolution of 5 km in the horizontal direction and 2 to 4 km in depth we used a total of 15407 p and 13704 s wave high quality arrival times from 2889 local earthquakes recorded by both permanent seismic networks and portable stations deployed in the area the computed p and s wave velocities were used to obtain three dimensional distributions of poisson s ratio r and the porosity parameter vpvs the 3 d velocity images show strong lateral heterogeneities in the region significant velocity variations up to 7 in p and s velocities are revealed in the crust below the granada basin at shallow depth high velocity anomalies are generally associated with mesozoic basement while the low velocity anomalies are related to the neogene sedimentary rocks the south southeastern part of the granada basin exhibits high r values in the shallowest layers which may be associated with saturated and unconsolidated sediments in the same area vpvs is high outside the basin indicating low porosity of the mesozoic basement a low velocity zone at 18 km depth is found and interpreted as a weak ductile crust transition that is related to the cut off depth of the seismic activity in the lower crust at 34 km depth a clear slow vp and vs anomalous zone may indicate variations in lithology and or with the rigidity of the lower crust rocks d 2002 elsevier science b v all rights reserved

deep structure of japan subduction zone as derived from local regional and teleseismic events we have determined a detailed three dimensional p wave velocity structure of the japan subduction zone to 500 km depth by inverting local regional and teleseismic data simultaneously we used 45 318 p wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the japan islands the arrival times are recorded by the japan university seismic network which covers the entire japan islands densely and uniformly we also used 4211 travel time residuals from 100 teleseismic events which are read from seismograms recorded by seismic stations in northeastern japan in comparison with the previous results obtained from only local and regional events the present result for the area around the lower plate boundary and the mantle below the plate is determined more reliably because of the addition of 7035 data from 100 teleseismic events and 41 very deep earthquakes in the crust and uppermost mantle low velocity zones are clearly visible beneath active volcanoes in the mantle wedge the low velocity zones generally parallel with the slab and exist continuously to a depth of about 200 km which is consistent with the petrological geochemical and geodynamic studies we consider that the existence of volcanism related low velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones in light of all the available tomographic results for many subduction zones in the world the pacific slab beneath japan is imaged more clearly than in previous studies as a high velocity zone with a thickness of 80 90 km and a p wave velocity 4 6 higher than the normal mantle lower velocity anomalies are found in the mantle below the slab

minerals in bituminous coals of the sydney basin australia and the illinois basin u s a although other forms of inorganic components may be significant in lower rank coals the mineral matter in most bituminous coals is dominated by silicates carbonates sulphides phosphates and other crystalline mineral groups these may be present in various forms including thin bands and laminae intimately associated with the organic matter as well as lenticles nodules crystal aggregates and cell infillings all of which indicate approximately contemporaneous formation with the peat bed other minerals however occur as veins or cleat and fracture fillings indicating precipitation after most of the compaction and presumably after most of the rank advance ome of the penecontemporaneous mineral matter is of detrital origin representing epiclastic or pyroclastic particles washed or blown into the peat swamp other mineral matter however including much of the pyrite quartz and siderite as well as abundant well crystallized kaolinite appears to have been formed by precipitation processes either within the swamp waters or in the pores of the peat deposit pyrite largely formed by bacterial reduction of dissolved sulphate ions seems to be related in abundance to marine transgressions which allowed permeation of sea water into the swamp and through the peat bed beneath siderite appears to form in the absence of sulphate rich sea water probably from co2 released by organic decay the clay fraction of the noncoal rocks in many coal bearing sequences is typically dominated by illite or interstratified clay minerals with kaolinite chlorite and possibly montmorillonite also present to a variable though typically minor extent although perhaps modified by chemical reactions or ion exchange mechanisms in the peat swamp these clay minerals may also be present in the coal as well especially near the base of top of the seam the kaolinite in the noncoal rocks is usually poorly crystallized and typically a minor constituent but well crystallized kaolinite is characteristically present and often the dominant component in the mineral fraction of bituminous coal beds as well as in some of the lutites including underclays intimately associated with the seams a progressive upward gradation to a particularly kaolinite dominated mineral assemblage occurs in some seams of the sydney basin australia this gradation is thought to be due to either increased blockage of detrital contaminants as the swamp developed or to in situ chemical or biological leaching of the mineral fraction and reconstitution of the residues in the upper parts of the peat bed superimposition of such cycles is also noted within the seam in some instances suggesting repetition of several phases of this type during major peat accumulations

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

quantification of mineral matter in the argonne premium coals using interactive rietveld based x ray diffraction abstract the mineral matter in the eight reference north american coal samples of the argonne premium coal series has been investigated on a quantitative basis using x ray diffraction xrd techniques x ray diffraction data obtained from electronic low temperature oxygen plasma ash lta residues from ashes produced by heating the coals in air at 370 c and also from the raw coals themselves were evaluated using an interactive data processing system siroquant based on rietveld interpretation methods the results from the three types of material lta 370 c ash and raw coal were compared for each sample this allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced particularly in the low rank coals from interaction of organically associated elements ca s etc during the two ashing processes after the allowance for the production of any artifacts the quantitative mineral assemblages identified from xrd of the raw coals were found to be consistent even for coals having a relatively low ash percentage around 5 with the results obtained from the respective mineral concentrates prepared by the ashing methods the effects of heating the coal to 370 c could also be distinguished relative to the raw coal or the lta through changes in components such as pyrite and the clay minerals although some areas of uncertainty exist particularly with magnesium in the low rank coals the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials

petrifaction of wood by silica minerals abstract seventy five woods of australian origin have been examined by means of x ray diffraction optical and scanning electron microscopy and differential thermal analysis the silica is in one or other of the following forms opal a opal ct chalcedony quartz quartz chalcedony opal chalcedony more than half of them consist of opal ct or chalcedony the results indicate that petrifaction by silica involves penetration of the wood via splits or checks permeation of cell walls via a reticulated system of micropores enlargement of the micropore system as cell wall components break down and continuing deposition of silica ata rate and in a manner consistent with maintaining the dimensional stability of the wood deposition of silica in cell lumina and intercellular voids may be sometimes but not always a separate and later event the final stages of lithification involve loss of water and perhaps transformation of one form of silica into another

effects of detrital influx in the pennsylvanian upper freeport peat swamp abstract quartz cathodoluminescence properties and mineralogy of three sets of samples and vegetal and or miospore data from two sets of samples from the upper freeport coal bed west central pennsylvania show that detrital influence from a penecontemporaneous channel is limited to an area less than three km from the channel the sets of samples examined include localities of the coal bed where 1 the coal is thin split by partings and near a penecontemporaneous fluvial channel 2 the coal is relatively thick and located approximately three km from the channel and 3 the coal is thick and located approximately 12 km from the channel samples from locality 1 nearest the channel have relatively high ash yields low temperature ash average 27 3 on a pyrite and calcite free basis and high proportions of quartz and clay minerals the quartz is primarily detrital as determined by cathodoluminescent properties and the ratio of kaolinite to illite is low in addition most of the plant remains and miospores indicate peat forming plants that required low nutrient levels for growth in contrast samples from localities 2 and 3 from the more interior parts of the bed contained predominantly authigenic quartz grains nd yielded low temperature ash values of less than 14 on a pyrite and calcite free basis the low temperature ash contains low concentrations of quartz and clay minerals and the ratio of kaolinite to illite is relatively high although intact core was not available for paleobotanical analyses another core collected within 1 km from locality 3 contained plant types interpreted to have required high nutrient levels for growth these data indicate that mineral formation is dominated by authigenic processes in interior parts of the coal body some of the authigenic quartz may have been derived from herbaceous ferns as indicated by patterns in the palynological and paleobotanical data in contrast detrital processes appeared to be limited to in areas directly adjacent to the penecontemporaneous channel where the coal bed is high in ash split by mineral rich partings and of little or no economic value

tomography of the source area of the 1995 kobe earthquake evidence for fluids at the hypocenter seismic tomography revealed a low seismic velocity 5 and high poisson s ratio 6 anomaly covering about 300 square kilometers at the hypocenter of the 17 january 1995 magnitude 7 2 kobe earthquake in japan this anomaly may be due to an overpressurized fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake

identification of potential for methane ignition by rock friction in australian coal mines abstract the relative propensity for the different rock types in australian underground coal mines to ignite methane bearing atmospheres by frictional contact either with mining equipment or with other rock materials has been evaluated by laboratory testing using an instrumented rotating wheel apparatus a five point incendivity categorisation has been developed for the rocks tested and the results compared to petrographic composition mineralogy and related chemical properties recent experience with ignitions in new south wales collieries has also been taken into account with the progressive decline in ignitions from other sources frictional effects are now the most common source of methane ignition in modern underground coal mines conglomerates lithic or quartzose sandstones with low clay and carbonate contents and siliceous cherty tuffs appear to represent the most potentially incendive materials in roof and floor strata along with siliceous or pyritic impregnations that may occur in the coal seam itself temperatures in excess of 1500 c may be developed within less than 1 s during rock on rock contacts with ignitions emanating from the contact point or related heat trail rather than from incandescent particles sparks ejected during the friction process the average temperature and the coefficient of dynamic friction developed during rock on rock testing also appear to be related to frictional incendivity characteristics

recent and present day stresses in the granada basin betic cordilleras example of a late miocene present day extensional basin in a convergent plate boundary the diffuse convergent boundary between the eurasian and african plates in the western mediterranean is associated with a seismicity zone more than 300 km wide although the two plates are converging nw se the betic and rif cordilleras contain extensional structures that have been active since the miocene the extensional tectonics in the region which occurred simultaneously with the uplift of the cordillera have been analyzed in the southeastern sector of the late miocene to recent granada basin using earthquake focal mechanisms the determination of paleostresses from the study of the orientation and kinematics of microfaults and the study of the major structures both the geological surface data and the focal mechanisms indicate present day regional conditions of ne sw extension with triaxial to prolate stress ellipsoids however the stress field is heterogeneous with local variations in stress over time with different stresses sometimes even acting simultaneously in adjacent areas the most frequent changes consist of pluridirectional or ne sw extension favored by the prolate character of the stress ellipsoids and nw se subhorizontal compression favored by the regional tectonic setting strike slip faults are scarce even though they are the most likely structure to be expected in a region with sw ne extension and nw se compression seismicity is concentrated in the upper crust and may correspond to the activity of low to high angle normal faults similar to the surface faults although they can not be correlated with them the lower cutoff of this seismicity probably coincides with the 300 c isotherm and suggests a low thermal gradient for the region present day regional stresses have 1 vertical at the surface but in depth plunge toward the sw

volcanic ash dispersed in the wyodak anderson coal bed powder river basin wyoming minerals derived from air fall volcanic ash were found in two zones in the upper paleocene wyodak anderson coal bed of the fort union formation in the powder river basin of wyoming and are the first reported evidence of such volcanic material in this thick 20 m coal bed the volcanic minerals occur in zones that are not visually obvious because they contain little or no clay these zones were located by geophysical logs of the boreholes and x ray radiography of the cores the zones correspond to two of a series of incremental core samples of the coal bed that have anomalous concentrations of zr ba nb sr and p2o5 two suites of minerals were found in both of the high density zones a primary suite not authigenic consists of silt sized quartz grains biotite and minor zircon a minor suite consists of authigenic minerals including calcite pyrite kaolinite quartz anatase barite and an alumino phosphate crandallite the original volcanic ash is inferred to have consisted of silica glass containing phenocrysts of quartz biotite zircon and possibly associated feldspars pyroxenes and amphiboles the glass as well as the less stable minerals probably dissolved relatively quickly and contributed to the minor authigenic mineral suite or was removed from the peat as a result of the prevailing hydrologic conditions present in a raised peat formation this type of volcanic ash suggests that suggests that volcanic material could have rained on the peat this fallout may have also had a fertilizing effect on the peat by providing nutrients essential for plant growth thus contributing to the thick accumulations of the wyodak anderson bed notwithstanding the presence of these minerals provides evidence for the contribution by volcanic sources to the mineral content of coal but not as tonsteins

the queenston formation shale dominated mixed terrigenous carbonate deposits of upper ordovician semiarid muddy shores in ontario canada the upper ordovician queenston formation constitutes the westernmost part of the taconic clastic wedge of eastern north america in ontario the queenston formation consists of a mixed terrigenous carbonate succession composed primarily of red silty shales which are locally gypsiferous alternating in the middle and lower parts of the formation with thin grey shales calcareous siltstone and sandstone and bioclastic limestone brachiopods some ostracodes and in the lower beds bryozoans constitute the body fossil assemblage diplocraterion skolithos chondrites and occasional large vertical burrows of unknown origin form the ichnofauna plane beds ripple marks and occasional swaley and hummocky cross stratifications are present in the calcareous units mudcracks gypsum nodules occasional halite hopper casts and gilgai like structures typically occur in horizons where shales alternate with siltstone and limestone these features are indicative of prograding muddy and storm and tide affected

a method for development of a system of identification for appalachian coal bearing rocks abstract the number of observable properties of sedimentary rocks is large and numerous classifications have been proposed for describing them some rock classifications however may be disadvantageous in situations such as logging rock core during coal exploration programs where speed and simplicity are the essence after experimenting with a number of formats for logging rock core in the appalachian coal fields a method of using color photographs accompanied by a rock name and numeric code was selected in order to generate a representative collection of rocks to be photographed sample methods were devised to produce a representative collection and empirically based techniques were devised to identify repeatedly recognizable rock types a number of cores representing the stratigraphic and geographic range of the region were sampled so that every megascopically recognizable variety was included in the collection the frequency of samples of any variety reflects the frequency with which it would be encountered during logging in order to generate repeatedly recognizable rock classes the samples were sorted to display variation in grain size mineral composition color and sedimentary structures class boundaries for each property were selected on the basis of existing widely accepted limits and the precision with which these limits could be recognized the process of sorting the core samples demonstrated relationships between rock properties and indicated that similar methods applied to other groups of rocks could yield more widely applicable field classifications

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

assessment of methane ignition potential by frictional processes from australian coal mine rocks a method for categorising the potential of different rocks to ignite methane gas in mine atmospheres has been developed for a suite of sedimentary and igneous samples from australian coal mine areas based on rock on rock friction behaviour in a rotating wheel test rig the five point ignition potential categorization igcat value is derived from the occurrence of ignitions or non ignitions in a gas chamber with a 7 methane atmosphere when a sample of the rock is pressed with a constant load against a rotating wheel of the same material at contact speeds of 2 2 3 7 and 5 1 m s

preliminary study of tonsteins of the pastora formation stephanian b of the cinera matallana coalfield northwestern spain abstract the correlation of seams of the pastora formation in the cinera matallana basin is affected by facies changes seam discontinuities such as seam splitting and joining and tectonic features exploratory drillings in the matallana syncline and in an underground exposure at the northern flank of the llombera syncline prove for the first time the existence of six tonsteins the investigation provided three kaolin tonsteins one kaolinite illite transition tonstein and two illite tonsteins which are described in detail the determination of coal rank gives evidence that there is no strict co incidence with the degree of diagenesis or metamorphosis of the original volcanic ashes thus further reasons for the alteration have to be considered such as varying compositions of the original volcanic ashes biochemical and chemical processes after deposition local hydrothermal metasomatism caused by the intrusion of basic magma or tectonic stress besides known faunal and facies marker horizons these newly detected tonsteins represent first class markers within the pastora formation the possibility of using these layers for the correlation of strata and for palaeomorphological studies depends on the successful continuation of the search for additional tonsteins as well as on the compilation and evaluation of subsequent investigations

v p v s and lithology published laboratory investigations suggest an association exists between the ratio of seismic compressional and shear wave velocities vp vs and sedimentary rock lithology comparisons of some theoretical models with these laboratory studies suggest that crack or pore geometry has a stronger effect on observed vp vs values than elastic constants of the minerals comprising the matrix further it can be inferred that the observed association between lithology and vp vs is a result of an association between lithology and distribution of pore and crack shapes direct observation of crack shapes for a variety of lithologies is a next step in strengthening these inferences the present study reviews the empirical relations between vp vs and lithology and examines two published theoretical models of cracked elastic media the models suggest that seismic velocities of sandstones may be controlled by cracks and pores with aspect ratios in the range of 10 1 to 1 dolomite in the range of 10 2 to 10 1 and dens

quantitative mineralogy of sandstones by x ray diffractometry and normative analysis abstract quantitative x ray diffraction normative calculation and whole rock chemical analysis have been compared for permo triassic quartz lithic to litho feldspathic sandstones from eastern australia the quantitative xrd technique provides mineralogical percentages that correlate well with the chemical composition of the sandstones and also with most of the mineral percentages derived from normative calculation the need for assumptions on potassium distribution between minerals provides a limitation on estimates of k feldspar and illite using the normative technique although these can be improved on a sample specific basis if necessary using complementary thin section observations or qualitative x ray diffractograms quantitative xrd analysis possibly indicates a small proportion of amorphous material in some of the sandstones especially materials with abundant lithic fragments or clay minerals but the proportion of any amorphous material overall is probably negligible both quantitative xrd and normative calculation avoid problems associated with sample heterogeneity or operator inconsistency that may affect point counting of thin sections they can also be used to provide quantitative information on sediments with abundant rock fragments or matrix components the actual mineralogy of which is not resolvable in conventional microscope investigations

eastern segment of the azores gibraltar line central eastern atlantic an oceanic plate boundary with diffuse compressional deformation new seismic reflection images across the eastern segment of the azores gibraltar line west of the collisional area between the african and iberian plates have revealed a complex pattern of compressional deformation involving the mesozoic oceanic lithosphere the compressional deformation developed in a region of slow plate convergence and is diffused at different lithospheric levels across an area spanning 200 km from the gorringe ridge to the seine plain the convergence between the african and iberian plates has been active since tertiary time and our results indicate that no subduction zone exists across this part of the plate boundary

empirical high latitude electric field models electric field measurements from the dynamics explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn dusk ogo 6 measurements j p heppner 1977 the analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones paralleling the previous analysis the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the y component of the interplanetary magnetic field the objective which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns is met by deriving one pattern model bc for the northern hemisphere with a y interplanetary magnetic field imf and southern hemisphere with a y imf and two patterns models a and de for the northern hemisphere with a y imf and southern hemisphere with a y imf the most significant large scale revisions of the ogo 6 models are 1 on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the imf y component 2 on the nightside where a westward flow region poleward from the harang discontinuity appears under model bc conditions and 3 magnetic local time shifts in the positions of the convection cell foci the modeling above was followed by a detailed examination of cases where the imf z component was clearly positive northward neglecting the seasonally dependent cases where irregularities obscure pattern recognition the observations range from reasonable agreement with the new bc and de models to cases where different characteristics appeared primarily at dayside high latitudes the analysis of these differences for strong bz conditions using passes through different mlt zones led to finding that the deviations from both the bc and de models could be modeled by extending the evening cell foci toward and beyond noon with a deformation that roughly resembles a rotational twist of the extended evening cell the morning cell accommodation to the model bc deformation produces a narrow tongue of eastward convection near 75 invariant latitude on the dayside the model de deformation compresses the morning cell toward the night hours such that the sunward convection in the morning cell is diverted to polar latitudes in the 0400 to 0700 mlt sector in both cases the deformations of the two cell patterns lead to sunward convection in dayside polar regions while maintaining the integrity of the nightside convection pattern thus the nightside dilemmas that plague three and four cell models designed to explain sunward convection in polar regions under bz conditions do not appear

diagenetic quartz and amorphous silica in new zealand coals new zealand coal seams late cretaceous miocene lignite semi anthracite contain numerous and varied occurrences of diagenetic quartz and amorphous silica early diagenetic silicifications include sub horizontal and laterally extensive quartz mineralized bands micro and megascopic euhedral quartz crystals dispersed or concentrated in layers and silicified in situ tree stumps late diagenetic forms include sub horizontal quartz mineralized bands mostly 1 m in length and fracture infillings the origins of the silica remain uncertain but leached basement rocks and coal measure sediments and siliceous phytoliths within the coal forming plants are possible sources the silicification of coal seams may have significant implications for exploration mining and geological studies

seismological evidence for magmatic and hydrothermal structure in long valley caldera from local earthquake attenuation and velocity tomography we compare the results of six different tomographic inversions for the three dimensional seismic attenuation and velocity structure in long valley caldera california in order to constrain interpretations on the location and character of magmatic and geothermal structure in the caldera crust p and s wave amplitudes and arrival times obtained in previous studies from seismograms of local earthquakes recorded on vertical and three component seismographis were inverted for q sv 1 q sh 1 q s 1 q p 1 and v p v s in the upper 9 km of teh caldera crust detailed comparisons of the results of the inversions suggest significant locations of high temperatures and perhaps magma and hydrothermal zones in the caldera a region of low q s with locally variable q p and v p v s is imaged in the 7 9 km depth range beneath the resurgent dome overlying and adjacent to this anomaly are significant low q p and low v p v s anomalies as well as smaller zones of low q s and high v p v s together these suggest zones of high temperature magma below and adjacent to zones of supercritical hydrothermal fluids at 4 5 km depth along the southern rim of the caldera just east of mammoth mountain a significant anomaly with relatively low q p and relatively low v p v s is imaged and is interpreted as a supercritical hydrothermal zone poorly resolved relatively low q p and relatively high v p v s are seen at 4 5 km depth beneath the inyo craters suggesting possible high temperatures and perhaps magma because of lack of data in the individual inversions the resultant images have spatially variable error and resolution however by comparing multiple images of different seismic parameters we have improved our ability to determine the significance of an constrain interpretation of seismic structure anomalies

seismicity and focal mechanisms in south spain abstract recent improvements in regional seismological networks allow a better definition of the seismicity and the determination of focal mechanisms in south spain this region is part of the lithospheric plate boundary between africa and eurasia and shows a continuous seismic activity of moderate magnitude m h h 650 km earthquakes also occurring in the region eight fault plane solutions have been determined that can be related to the tectonics of the area the solutions for the shallow shocks are compatible with regional stresses with horizontal compressions in nw se direction and tensions in e w direction that produce normal faulting along the n30 to 60 w and n10 to 30 e systems of faults the mechanisms of the intermediate depth shocks can be explained in terms of a subduction zone from africa in a nw direction that is under compression

v p v s from mode converted p sv reflections p sv reflections are generated by a compressional wave source and result from p waves that are converted to shear sv waves upon reflection recording both the p and sv components yields compressional and shear data simultaneously verifying that the easily detected events really are p sv reflections is accomplished by noting the good correlation of surface cdp data with vertical seismic profile vsp reflections stacking velocities from p sv cdp gathers determine the vpvs product when source to receiver offset is less than the depth of the reflector but data from synthetic models show that p sv reflections are nonhyperbolic for shallow reflections or when source to receiver offset is too large shear velocity vs can be calculated from p sv reflections by one of two techniques comparison of stacked section p p and p sv reflection times or by using the p p and p sv stacking velocities unfortunately most p sv reflections on a p sv seismic section do not necessarily originate from exactly the same dep

use of mineralogical analysis in geotechnical assessment of rock strata for coal mining abstract the fundamental geotechnical properties of sedimentary rocks from the coal bearing sydney basin of new south wales australia including density porosity water absorption and moisture content as well as compressive strength have been related to the mineralogy of the materials as determined by quantitative x ray diffraction of powdered rock samples and processing by the rietveld based siroquant technique the results show for example that the overall proportions of clay minerals in the rocks as well as the types of clay minerals present affect properties such as water absorption and moisture content the presence of clay minerals also adds to the dry strength of silica cemented quartz sandstones however the strength of finer grained mudrocks is inversely related to the total percentage of clay minerals correlations have been established between the deterioration or slaking behaviour of mudrocks in water and their clay mineral content based on either simple immersion tests or on more sophisticated slake durability index determinations these relationships may be of significance in understanding the longer term behaviour of rock strata when exposed in different types of mining operations the propensity of different rocks to ignite methane in underground mines by frictional effects has also been shown to depend on the mineralogy of the rock materials whether determined by point counting of thin sections or by rietveld based xrd analysis abundant quartz feldspar and rock fragments in sandstones for example increase the likelihood of frictional ignitions whereas clay minerals and especially carbonates in the rock reduce the frictional ignition potential pyrite in the rocks if present also increases the ignition risk pyrite undergoes exothermic oxidation at high temperatures whereas other minerals respond by simple heating due to rock on rock or pick on rock friction processes

the sapphire north radar experiment observations of discrete and diffuse echoes since february 1995 regular observations have been carried out by the university of saskatchewan radar group using a new 50 mhz doppler radar system called sapphire north the sapphire north radar monitors the ionospheric processes in the transitional region between the auroral oval and the polar cap over cambridge bay northwest territories in this paper results of the first 2 months of observations are presented echoes were registered at about 10 of observational time diurnal echo occurrence exhibited two distinct maxima one close to noon and another prior to midnight the noon echoes were usually of a diffuse type while midnight echoes were of a discrete type midnight discrete echoes were found to be associated with an arrival of poleward expanding substorm bulges into the sapphire north field of view noon diffuse echoes were most likely due to electric field enhancements in the vicinity of the cusp cleft region salient spectral features of both the diffuse and discrete echoes are presented and compared with auroral zone results the role of ionospheric refraction for observations of these high latitude echoes is discussed