geochemistry and nano mineralogy of feed coals mine overburden and coal derived fly ashes from assam north east india a multi faceted analytical approach abstract in order to address the scarcity of information on the nature and mode of occurrence of minerals and elements in coal coal mine overburden and coal ashes from north east india and also the relations between coal mineralogy and ash chemistry the petrology mineralogy and nano mineralogy and ash chemistry of some industrially important high sulfur coals mine overburden materials and fly ash samples from assam india have been evaluated a combined approach using petrography low temperature ashing plus x ray diffraction lta xrd field emission scanning electron microscopy fe sem high resolution transmission electron microscope hr tem raman spectroscopy and inductively coupled plasma mass spectrometry icp ms has provided new information on the mineralogy and nano mineralogy of these sub bituminous coals and associated mine overburden the presence of rare earth elements and yttrium rey in northeast indian coal mine overburden and fly ash samples is also reported for the first time the identification of these components may be significant from an economic point of view some northeast indian fly ashes with ree oxides up to 1580 ppm on an ash basis might possibly represent sources for recovery of rare earth elements

response of roll wave to suspended load and hydraulics of overland flow on steep slope abstract a roll wave is frequently observed in overland flow and it can accelerate the soil erosion on slopes however the feedback effect of eroded sediment on roll wave has not been studied the aim of this study was to investigate the response of roll wave to sediment concentration and overland flow hydraulics on steep slope the experiment was carried out in a hydraulic flume the unit flow rate varied from 1 0 to 3 0 10 3 m 3 s 1 and sediment concentration from 0 to 400 kg m 3 the sediment transport was dominated by suspension slope gradient was 9 as the sediment concentration increased the critical slope length for roll wave formation increased implying that the suspended sediment in flow could inhibit the formation of a roll wave the roll wave in overland flow is a short water long wave the roll wave length increased with the increasing sediment concentration while the wave frequency and velocity decreased the decreased wave velocity meant a decrease in flow erosion potential caused by a roll wave roll wave frequency and velocity significantly increased with reynolds number froude number and mean flow velocity and decreased with the hydraulic resistance while there were no notable relationships between roll wave length and overland flow hydraulics both roll wave frequency and velocity had the strongest dependency on froude number and could be estimated by the linear equations between them when the sediment concentration was larger than 300 kg m 3 all the roll waves in overland flow disappeared due to the high sediment supply the results indicated that the suspended sediment can ease the acceleration influence of a roll wave on soil erosion and should be considered in the soil erosion models

seismic and geodetic progression of the 2018 summit caldera collapse of kīlauea volcano abstract the 2018 eruption of k lauea volcano hawai i resulted in a major collapse of the summit caldera along with an effusive eruption in the lower east rift zone the caldera collapse comprised 62 highly similar collapse cycles of strong ground deformation and earthquake swarms that ended with a magnitude 5 collapse event and one partial cycle that did not end with a collapse event we analyzed geodetic and seismic data to better understand how the caldera collapse progressed over 3 months of activity focusing on the cyclical activity we identified 3 main phases of collapse initial ring fault activation and small explosions phase 1 an eastward shift in activity and freeing of the central piston phase 2 and a recoupling of the piston to the reservoir followed by relatively steady behavior until the eruption s end phase 3 additionally we observed geodetic evidence of tangential motion from the localization of the main ring fault phase 2 and the formation of a major peripheral ring fault on the eastern side of the collapse caldera during phase 3 both geodetic and seismic parameters suggest that the collapse may have had an eastward component of motion after the ring fault system had formed the cyclical seismic and geodetic parameters show no obvious signs that the collapse was coming to an end with the only notable change being a significant increase in the ratio of cyclical displacement to co collapse displacement observed during the last complete cycle on gnss stations outside the caldera region

deep magma body beneath the summit and rift zones of kilauea volcano hawaii a magnitude 7 2 earthquake in 1975 caused the south flank of kilauea volcano hawaii to move seaward in response to slippage along a deep fault since then a large part of the volcano s edifice has been adjusting to this perturbation the summit of kilauea extended at a rate of 0 26 meter per year until 1983 the south flank uplifted more than 0 5 meter and the axes of both the volcano s rift zones extended and subsided the summit continues to subside these ground surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the rift zones kilauea s magmatic system is therefore probably deeper and more extensive than previously thought the summit and both rift zones may be underlain by a thick near vertical dike like magma system at a depth of 3 to 9 kilometers

purely erosional cyclic and solitary steps created by flow over a cohesive bed an erodible surface exposed to supercritical flow often devolves into a series of steps that migrate slowly upstream each step delineates a headcut with an associated hydraulic jump these steps can form in a bed of cohesive material which once eroded is carried downstream as washload without redeposition here the case of purely erosional one dimensional periodic or cyclic steps in cohesive material is considered the st venant shallow water equations combined with a formulation for sediment erosion are used to construct a complete theory of the erosional case the solution allows wavelength wave height migration speed and bed and water surface profiles to be determined as functions of imposed parameters the analysis also admits a solution for a solitary step or single headcut of self preserving form

syntectonic monazite in low grade mudrocks a potential geochronometer for cleavage formation monazite paragenesis during low grade metamorphism is poorly understood the first unequivocal instance of the mineral having crystallized synchronously with compressional cleavage formation is reported compositionally these monazites resemble diagenetic forms but differ texturally by displaying syntectonic microfabrics their predominant association with organic walled fossils implies that organic material may play an important role in controlling the behaviour of light rare earth elements lree during low grade metamorphism probably by releasing diagenetically sequestered lree and organically bound phosphorus during thermal maturation devolatilization and or by promoting a favourable environment for monazite precipitation potentially such monazites could provide a powerful geochronometer for cleavage formation

trace elements geochemistry of the dobrudza coal basin bulgaria abstract the paper discusses the abundance mode of occurrence and origin of trace elements in the dobrudza coal deposit the deposit is the deepest in bulgaria it is overburden by paleozoic up to cenozoic sediments of 1300 m to 1600 m thickness the coal rank reaches the stage of high volatile a bituminous coal the contents of ba cl br mn ge pb w mo as zr li cs cu zn sb ti v th u ag be and y are enriched from 1 5 to 9 2 times as compared with the clarkes for bituminous coals the content of the other elements are slightly higher lower than the respective world wide means chondrite normalized patterns of the ree reveal a strong fractionation among the hree and lree most pronounced for the coals than for the coaly shales and partings a specific feature is the small eu anomaly in the shales and the tonsteins underlying the coal bed most elements are of mixed organic and inorganic association ge cl br mo be and au are predominantly bound to the organic matter arsenic correlates strongly with fe suggesting presence in pyrite ba occurs mainly as barite which is most probably of epigenetic origin sr and mn are presented mainly as isomorphous admixtures in barite and calcite the abundance of the lithophile elements excluding ge mo ba cl br is controlled largely by the detrital and clay mineral content of the coals many elements of different groups correlate positively each other calculation of partial correlation coefficients excluding ash shows that many of these correlations are spurious due to the positive correlation of every single element with ash for this reason the correlation coefficients must be critically evaluated when deducing the mode of occurrence of elements the accumulation of the trace elements in the dobrudza coals was influenced by multi component geological factors 1 as a result of upper pennsylvanian volcanism there are widespread tonsteins underlying the coal layers and as thin layers in the coal most likely many elements were leached from the tonsteins and trapped by the coal 2 olivinobasalt and andesito basalt dikes intruding the coal bearing sediments may cause enrichment or depletion of many elements 3 highly mineralized underground waters are the source of cl br b sr and probably some other elements 4 the numerous regional faults favor the penetration of solutions of different origin which were carriers of trace elements 5 postgenetic erosive processes may cause leaching of trace elements from the rocks which are consequently fixed by the coal

geochemistry of source rock controlled late triassic coal an example from the dabaoding coal mine in panzhihua sichuan province southwestern china abstract the geochemistry of source rock controlled coals from the late triassic daqiaodi formation in the dabaoding coal mine of the southwestern sichuan province was investigated a total of 15 coal samples 6 parting samples and 4 roof and floor rock samples from the d15 3 and d18 coals were subjected to proximate and ultimate analyses for coal quality by using lta xrd with siroquant software for minerals xrf for major element oxides icp ms for trace elements icp cct ms for as and se ise for f and a dma 80 analyzer for hg results indicate that the dabaoding d15 3 and d18 coals are classified as low ash and low volatile bituminous coal minerals in coals are dominated by quartz kaolinite illite and dolomite most trace elements in the dabaoding coals are depleted or at normal levels relative to chinese coals or world hard coals except for cr with slight enrichment the dabaoding coals and host rocks are characterized by weakly positive ce and y anomalies strongly positive gd anomalies and weakly negative eu anomalies based on paleogeographical mineralogical and geochemical evidence the sediment source rocks of the daqiaodi coal bearing strata are identified as the panzhihua trachyte at the top of the kangdian upland which exerted crucial impacts on the dabaoding coals

how summit calderas collapse on basaltic volcanoes new insights from the april 2007 caldera collapse of piton de la fournaise volcano in april 2007 piton de la fournaise volcano experienced a caldera collapse during its largest historical eruption we present here a structural analysis both of the caldera and the surrounding area and precise gps data recorded with a dense gps network specifically dedicated to the analysis of deformation related to the summit collapse structures despite a collapse of more than 300 m in the central zone the geometry of the new caldera is similar in map view to that of the pre existing collapsed structure which was formed from the coalescence of several pit craters the caldera shows an asymmetric inner geometry with sub vertical walls in the nw quadrant and steep scarps composed of inward tilted blocks in the southern half the presence of preserved polished surfaces on the lower part of the sub vertical scarp indicates that it corresponds to the caldera north western ring fault the april 2007 caldera collapse led to the development and the reactivation of concentric fractures on the caldera rim mostly along the southern limit of the caldera gps data show that fractures result from radial extensional stresses that are restricted within the first tens of meters of the caldera edge gps data also reveal that the caldera collapse was coeval with a centripetal deflation whose magnitude is largest along the southern half of the caldera the displacements recorded by gps result from both a general deflation due to magma withdrawal from piton de la fournaise s summit magma chamber and additional local effects related to the caldera collapse comparison of the caldera collapses at piton de la fournaise miyakejima and fernandina reveals striking similarities with cyclic seismic signals accompanying small scale deflation inflation cycles this strongly suggests a common mode of collapse hence we propose a unifying model of caldera collapse in basaltic setting in which the inward deflation due to magma withdrawal from the magma chamber prevents the collapse of the caldera roof until the gravitational stress acting on the rock column above the magma chamber exceeds the shear strength along pre existing ring faults the downward displacement stops when the pressure increase into the magma chamber is able to again sustain the rock column the succession of 1 inward deflation that prevents the collapse 2 collapse due to gravitational stress and 3 stopping of the downward motion is repeated many times the frequency of the cycles is influenced by the rate of magma withdrawal and by the amount of intrusion of magma along the ring faults

distribution of rare earth elements in eastern kentucky coals indicators of multiple modes of enrichment abstract four eastern kentucky pennsylvanian coals from oldest to youngest the manchester pond creek fire clay and hazard coals were examined for their total rare earth element rey concentration and the possible mechanisms for enrichment of the rare earths based on previous studies four possible modes are considered terrigenous tuffaceous infiltrational and hydrothermal with the dean coal a correlative of the fire clay coal considered to be a typical example of the tuffaceous mode the fire clay owes much of its high rey content to the presence of a volcanic ash fall tonstein with rey bearing zircon and phosphates in the coal in numerous locations some of the original rey elements may have components of the detrital minerals deposited in the peat leaching of rey from the tonstein into the surrounding coal and the hydrothermal overprint of mineralizing fluids associated with the northwestwardly movement of the pine mountain thrust sheet contributed to the total rey signature in the fire clay coal not all coals are going to have the complex history of the fire clay coal but it should be considered that the total history of rey enrichment by multiple mechanisms is what gives us both the total rey concentration and the relative distribution of the individual lanthanide elements

understanding caldera structure and development an overview of analogue models compared to natural calderas abstract understanding the structure and development of calderas is crucial for predicting their behaviour during periods of unrest and to plan geothermal and ore exploitation geological data including that from analysis of deeply eroded examples allow the overall surface setting of calderas to be defined whereas deep drillings and geophysical investigations provide insights on their subsurface structure collation of this information from calderas worldwide has resulted in the recent literature in five main caldera types downsag piston funnel piecemeal trapdoor being viewed as end members despite its importance such a classification does not adequately examine a the structure of calderas particularly the nature of the caldera s bounding faults and b how this is achieved including the genetic relationships among the five caldera types various sets of analogue models specifically devoted to study caldera architecture and development have been recently performed under different conditions apparatus materials scaling parameters stress conditions the first part of this study reviews these experiments which induce collapse as a result of underpressure or overpressure within the chamber analogue the experiments simulating overpressure display consistent results but the experimental depressions require an exceptional amount of doming seldom observed in nature to form therefore these experiments are not appropriate to understand the structure and formation of most natural calderas the experiments simulating underpressure reveal a consistent scenario for caldera structure and development regardless of their different boundary conditions these show that complete collapse proceeds through four main stages proportional to the amount of subsidence progressively characterized by 1 downsag 2 reverse ring fault 3 peripheral downsag 4 peripheral normal ring fault the second part of this study verifies the possibility that these latter calderas constitute a suitable analogue to nature and consists of a comprehensive comparison of the underpressure experiments to natural calderas this shows that all the experimental structures as well as their progressive development are commonly observed at natural calderas highlighting a consistency between models and nature as the shallow structure of experimental calderas corresponds to a precise architecture at depth it provides a unique key to infer the deeper structure of natural calderas recognizing diagnostic surface features within a caldera will thus allow it to be categorized within a precise structural and evolutionary context the general relationship between the evolutionary stage of a caldera and its d s diameter subsidence ratio allows such a quantification with stage 1 calderas characterized by d s 40 stage 2 by 18 the four stages adequately explain the architecture and development of the established caldera end members along a continuum where one or more end members downsag piston funnel piecemeal trapdoor may correspond to a specific stage while such a continuum is controlled by progressive subsidence specific collapse geometries will result from secondary contributory factors roof aspect ratio collapse symmetry pre existing faults these considerations allow proposing an original classification of calderas incorporating their structural and genetic features

organic and inorganic associations of rare earth elements in central appalachian coal abstract coal contains trace amounts of rare earth elements ree they are either in the form of discrete minerals or chemically bound to organic matter methods of distinguishing the organic and inorganic associations of ree in coal have been mostly based on the correlations between the ree concentrations and the ash yields quantitative characterization of organically associated ree is still very challenging in this work we confirm the existence of organically associated ree in coal and present an approach to quantifying its mass fraction the coal sample used in this study was a cleaned low ash coal collected from a coal preparation plant in kentucky usa and originally from the central appalachian basin coal region the results from particle size and density separations of the coal suggested that the ree are associated with both organic and inorganic matters it was found that as the ash yield increases both the total ree concentration on the whole coal basis and the lree hree ratio increase while the total ree concentration on the ash basis reduces dramatically the results also suggested that the organic matter is relatively enriched in hree based on these observation and findings a method was developed to quantitatively determine the distribution of ree in the organic and inorganic phases of the coal it was found that the total ree concentrations in the organic and inorganic phases are 31 ppm and 1141 ppm respectively the results also showed that in the low ash appalachian coal sample used in this work 25 of the ree is associated with the organic matter the method developed in this work for quantitative evaluation of the organic inorganic mode of occurrence may be applied to other coal samples and for many other trace elements in coals

rare earth elements and yttrium in pennsylvanian coals and shales in the eastern part of the illinois basin abstract the objective of this study was to evaluate rare earth elements and yttrium rey concentrations in pennsylvanian coal bearing strata in the eastern part of the illinois basin indiana specifically targeting coals and marine shales associated with the coals samples were collected from several coal mines and three boreholes in total 105 samples were analyzed using inductively coupled plasma optical emission spectrometry icp oes including 69 coals 31 shales and 5 paleosols concentrations of rey in the coals vary from less than 200 ppm to more than 3000 ppm on ash basis indirect evidence including rey versus ash relationships rey distribution patterns and rey content in raw coal compared to that in washed coal suggests that the organic association may be an important mode of rey occurrence in these coals the lower block and the upper block coal members of the brazil formation and some coals of the staunton formation have the highest rey concentrations among those studied concentrations of rey in marine shales range from less than 200 to 800 ppm on ash basis the majority of shale samples studied vary little from the rey values of the continental crust but some show enrichments our results suggest that while post combustion coal ash of the high rey coals are a potential source of these elements significant efforts and resources are needed to make the studied shales a viable rey resource

caldera collapse geometry revealed by near field gps displacements at kīlauea volcano in 2018 we employ near field gps data to determine the subsurface geometry of a collapsing caldera during the 2018 kilauea eruption collapse occurred in 62 discrete events with inflationary deformation

the 1989 loma prieta earthquake imaged from inversion of geodetic data we invert geodetic measurements of coseismic deformation from the 1989 ms7 1 loma prieta earthquake to determine the geometry of the fault and the distribution of slip on the fault plane the data include electronic distance measurements global positioning system and very long baseline interferometry vectors and elevation changes derived from spirit leveling the fault is modeled as a rectangular dislocation surface in a homogeneous elastic half space first we assume that the slip on the fault is uniform and estimate the position orientation and size of the fault plane using a nonlinear quasi newton algorithm the best fitting dislocation strikes n48 4 w and dips 76 9 sw consistent with the trend of the aftershock zone and moment tensor solutions bootstrap resampling of the data is used to graphically illustrate the uncertainty in the location of the rupture plane the 95 confidence envelope overlaps the aftershock zone arguing that there is not a significant discrepancy between the geodetic data and the aftershock locations second we estimate the slip distribution using the best fitting uniform slip fault orientation but increase the fault length to 40 km and the downdip width to 18 km the fault is divided into 162 subfaults 18 along strike and 9 along dip each subfault is allowed to have constant right lateral and reverse components of slip we then solve for the slip on each subfault that minimizes a linear combination of the norm of the weighted data residual and the roughness of the slip distribution the smoothing parameter which determines the relative weight put on fitting the data versus smoothing the slip distribution is chosen by cross validation simulations indicate that cross validation estimates of the smoothing parameter are nearly optimal the preferred slip distribution is very heterogeneous with maximum strike slip and dip slip of about 5 and 8 m respectively located roughly 10 km north of the hypocenter there is insignificant dip slip in the southeastern most part of the fault causing the rake to vary from nearly pure right lateral in the southeast to oblique right reverse in the northwest the change in rake is consistent with a uniform stress field if the fault dip increases by about 10 toward the southeast as indicated by the aftershock locations there was little slip above 4 km depth consistent with the observation that there was little if any surface rupture

hyperconcentrated sand water mixture flows over erodible bed field surveys and experiments in a tilting flume on hyperconcentrated sand water mixture swm flows were conducted at slopes slightly smaller than the equilibrium slope a rapid development of sand bars propagating upstream was observed these bars consist of an almost horizontal terrace with subcritical flow a steep lee side slope with supercritical flow and a hydraulic jump between subsequent bars the erosion processes on the bar are limited by the high sand concentrations and flow velocities on the steep slopes as a result the erosion rate is more moderate than predicted by the pickup functions used in classical sediment transport theory a simple one dimensional model is presented to study the behavior of triangular schematized bars from an analysis of the equations it is concluded that an increase in erosion rate requires an increase in bed slope to maintain equilibrium flow conditions finally simulations with the model are compared with observations in the field and in the tilting flume t

mineralization of ree y nb ta zr hf in wuchiapingian coals from the liupanshui coalfield guizhou southwestern china geochemical evidence for terrigenous input abstract abundances modes of occurrence enrichment and origin of critical elements in coal and coal bearing sequences have attracted much attention in recent years previous investigations have attributed ree y nb ta zr hf mineralization in coals and in intra and inter seam tuffs in coal bearing sequences to alkali volcanic ash eruptions and subsequent hydrothermal alteration in this study two major minable coal seams d101 and w407 that are located in the lowermost and uppermost wuchiapingian longtan formation in the liupanshui coalfield guizhou southwestern china were investigated in order to better understand the mechanism of ree y nb ta zr hf enrichment in these coals elevated concentrations of ree y nb ta zr hf in the d101 coal are dominantly due to the alkaline volcanic material forming the top of the emeishan large igneous province elip which served as a terrigenous source region for the coal basin and to airborne volcanic ash which occurs as an intra seam tonstein within the coal seam both of the two source materials were subsequently subjected to groundwater leaching resulting in redistribution of the rare earth elements and y rey leading to an uneven distribution of rey and zr along the studied coal seam sections the average rey oxides in the d101 and w407 coals are 2682 and 1260 ppm both on ash basis respectively and the outlook coefficients are 0 79 and 1 15 respectively indicating that both ashes from the two coals are potential raw sources for rey

mechanical and geometric controls on the structural evolution of pit crater and caldera subsidence 1 pit craters and calderas are volcanic depressions produced by subsidence of a magma reservoir roof to identify how geometric and mechanical factors may influence the structural evolution of this subsidence we used two dimensional distinct element method numerical models the reservoir host rock was represented as an assemblage of bonded circular particles that interact according to elastic frictional laws varying particle and bond properties produced a range of bulk material properties characteristic of natural rock masses fracturing results when bonds break once their shear or tensile strength is exceeded the magma reservoir was represented as a region of nonbonded low friction particles withdrawal of magma was simulated by incrementally reducing the area of the reservoir particles resultant gravity driven failure and subsidence of the reservoir roof were explicitly replicated interaction of the roof s strength young s modulus thickness diameter ratio t d and the reservoir s shape yields a variety of model structures and subsidence styles in conceptual terms four end member subsidence styles developed 1 central sagging favored by low strength and low t d 2 central snapping favored by high strength low t d and a sill like reservoir shape 3 single central block favored by low to intermediate strength high young s modulus and intermediate t d and 4 multiple central blocks favored by high strength low young s modulus and high t d most model realizations incorporated some combination of each style however the models provide a geomechanical framework for understanding natural pit crater or caldera structures as at nindiri nicaragua fernandina galapagos dolomieu la reunion and miyakejima japan

characterization of intrusive rocks and ree geochemistry of coals from the zhuji coal mine huainan coalfield anhui china abstract rare earth element ree concentrations in coals are a source of information relevant to the evolution of source rocks depositional environment and epigenetic tectonic activity as well as the effects of igneous intrusions in this study 186 coal samples 11 intrusion affected coal samples 4 samples representative of the intrusive rocks one coal roof and one parting samples were collected from 29 boreholes at the zhuji coal mine huainan coalfield anhui province china the main objective is to characterize the intrusive rocks in the coal bearing sequence and to investigate the correlation of ree parameters in the coals with the source rocks depositional environment localized faults igneous intrusions and thickness of the coal beds a sequence from base to top of acidic to basic intrusive rocks through the coal bearing strata was identified which possibly corresponds to different intrusive episodes of granite diorite monzonite and gabbro both the ree contents and degree of fractionation of light rare earth elements lree and heavy rare earth elements hree increase from acidic to basic rocks most rocks are slightly depleted in ce but highly depleted in eu the ree concentrations in coals from the zhuiji mine average of 118 g g are nearly identical to recently updated average chinese values but significantly higher than global values the ree content of the intrusion affected coals is not distinctively different from that of the other coals p 0 2 and ree concentrations of the igneous rocks appear to have no clear relationship to those of the intrusion affected coals the depositional environment and source rocks are presumably the main ree contributors to the coal accumulation basin the ree content in coals from fault affected boreholes is higher than that in other boreholes and this trend is stronger in the coal seams of the upper strata the hree tend to be incorporated into thinner coal seams and the degree of fractionation between lree and hree of the coal forming materials increases with coal thickness

cyclic steps and roll waves in shallow water flow over an erodible bed the st venant equations in conjunction with a phenomenological law for erosion are used to explore the nonlinear dynamics of cyclic steps linearly unstable bedform patterns which emerge when uniform flow over an erodible bed becomes supercritical the instability saturates by blocking the overlying flow and creating hydraulic jumps just downstream of the steepest part of the steps near onset steadily migrating nonlinear step patterns are constructed and shown to suffer a short wavelength secondary instability that roughens the bed and renders the staircase patterns less regular and time dependent an eddy viscosity is needed to regularize both the onset of the primary steps and the secondary instabilities further beyond the critical froude number the steps block the flow sufficiently to arrest erosion significantly creating complicated patterns mixing migrating steps and stationary bedforms the reduction in flux also stabilizes roll waves a second hydrodynamic instability of uniform supercritical flow it is further shown that roll waves are purely convective instabilities whereas cyclic steps can be absolute thus in the finite geometries of the laboratory or field it may be difficult to excite roll waves on the other hand the complicated spatiotemporal patterns associated with the cyclic step instability should develop naturally the complicated patterns resulting from the secondary instability do not appear to have been observed experimentally calling into question the validity of the model

finite amplitude river dunes the linear and weakly nonlinear stability of a uniform flow in an infinitely wide open channel with erodible bottom is studied under suitable conditions the flow is found to be unstable leading to the formation of dunes and antidunes at a linear level the corresponding regions of existence are presented and compared with experimental data a weakly nonlinear analysis is then performed in a neighbourhood of the critical conditions for dune and antidune formation the analysis shows that for values of the ratio of the shear velocity to the depth averaged velocity of practical interest dune bifurcation is supercritical whereas antidune bifurcation is subcritical the latter result suggests a possible interpretation of the plane antidune transition where plane bed and antidune configurations are observed to coexist for the same values of the flow and the sediment parameters the supercritical behaviour of the dune bifurcation allows for the prediction of an equilibrium amplitude that successfully compares with the amplitudes measured in laboratory experiments

comments on the geochemistry of rare earth elements la ce sm eu tb yb lu with examples from coals of north asia siberia russian far east north china mongolia and kazakhstan abstract the geochemistry of the ree la ce sm eu tb yb and lu is reviewed with supporting data from coals of north asia the 7189 samples from north asia included in this study represent all coal ranks lignites subbituminous coals bituminous coals and anthracites as well as coals formed under different geotectonic regimes and in different sedimentary conditions these coals are characterized by higher contents of the ree as compared to the coal clarke the distribution characteristics and accumulations of the ree have been studied in several coal deposits and basins within some basins with the near background average contents of the ree isolated coal beds enriched in lanthanides have been observed in coal basins and deposits the relative enrichment in the lanthanides are observed in the fields or zones adjacent to the source area of the terrigenous material accumulation of high ree contents in coal deposits can be attributed to the presence of rocks in the source area containing high concentrations of ree and also alkaline or acidic volcanic ash contemporaneous with the peat accumulation in the basin transformation of volcanic ashes under the aggressive hydro environment of a peat bog results in the mobilization and redeposition of the ree adjacent to the altered volcanic ashes tonsteins with the formation of high concentrations of ree in the coal beds the formation of the ree anomalies may also be related to hydrothermal processes the modes of occurrence of the ree change during the coalification process brown coals with a low degree of coalification are dominated by the organic modes of occurrence of the ree whereas in hard coals and anthracites authigenic mineral forms dominate

role of olivine cumulates in destabilizing the flanks of hawaiian volcanoes the south flank of kilauea volcano is unstable and has the structure of a huge landslide it is one of at least 17 enormous catastrophic landslides shed from the hawaiian islands mechanisms previously proposed for movement of the south flank invoke slip of the volcanic pile over seafloor sediments slip on a low friction decollement alone cannot explain why the thickest and widest sector of the flank moves more rapidly than the rest or why this section contains a 300 km3 aseismic volume above the seismically defined decollement it is proposed that this aseismic volume adjacent to the caldera in the direction of flank slip consists of olivine cumulates that creep outward pushing the south flank seawards average primary kilauea tholeiitic magma contains about 16 5 wt mgo compared with an average 10 wt mgo for erupted subaerial and submarine basalts this difference requires fractionation of 17 wt 14 vol olivine phenocrysts that accumulate near the base of the magma reservoir where they form cumulates submarine erupted kilauea lavas contain abundant deformed olivine xenocrysts derived from these cumulates deformed dunite formed during the tholeiitic shield stage is also erupted as xenoliths in subsequent alkalic lavas the deformation structures in olivine xenocrysts suggest that the cumulus olivine was densely packed probably with as little as 5 10 vol intercumulus liquid before entrainment of the xenocrysts the olivine cumulates were at magmatic temperatures 1100 c when the xenocrysts were entrained olivine at 1100 c has a rheology similar to ice and the olivine cumulates should flow down and away from the summit of the volcano flow of the olivine cumulates places constant pressure on the unbuttressed seaward flank leading to an extensional region that localizes deep intrusions behind the flank these intrusions add to the seaward push this mechanism ties the source of gravitational instability to the caldera complex and deep rift systems and therefore limits catastrophic sector failure of hawaiian volcanoes to their active growth phase when the core of olivine cumulates is still hot enough to flow

calderas and caldera structures a review abstract calderas are important features in all volcanic environments and are commonly the sites of geothermal activity and mineralisation yet it is only in the last 25 years that a thorough three dimensional study of calderas has been carried out utilising studies of eroded calderas geophysical analysis of their structures and analogue modelling of caldera formation as more data has become available on calderas their individuality has become apparent a distinction between caldera caldera complex cauldron and ring structure is necessary and new definitions are given in this paper descriptions of calderas based on dominant composition of eruptives basaltic peralkaline andesitic dacitic rhyolitic can be used and characteristics of each broad group are given styles of eruption may be effusive or explosive with the former dominant in basaltic calderas and the latter dominant in andesitic dacitic rhyolitic and peralkaline calderas four end member collapse styles occur plate or piston piecemeal trapdoor and downsag but many calderas have multiple styles features of so called funnel and chaotic calderas proposed in the literature can be explained by other collapse styles and the terms are considered unnecessary ground deformation comprises subsidence or collapse essential characteristics of a caldera and uplifting doming and fracturing due to tumescence and or resurgence frequent but not essential collapse may occur on pre existing structures such as regional faults or on faults created during the caldera formation and the shape of the collapse area will be influenced by depth size and shape of the magma chamber the final morphology of a caldera will depend on how the caldera floor breaks up whether collapse takes place in one event or multiple events whether vertical movement is spasmodic or continuous throughout the eruptive sequence and whether blocks subside uniformly or chaotically at one or more collapse centres a meaningful description of any caldera should therefore include number of collapse events presence or absence of resurgence caldera floor coherency caldera floor collapse geometry and dominant composition of eruptives

enrichment origin of critical elements li and rare earth elements and a mo u se re assemblage in pennsylvanian anthracite from the jincheng coalfield southeastern qinshui basin northern china abstract the qinshui basin is the largest reservoir of commercial coalbed methane in china the no 15 seam one of the major coal seams for coalbed methane exploration in the jincheng coalfield se qinshui basin has recently been found to be enriched in the critical element li this study further investigates the inorganic geochemistry of the no 15 coal and associated rocks and reveals the enrichment origin of critical elements in these horizons the jincheng no 15 coal is rich in li mo u se re and rare earth elements and y rey concentrations of mo u se and re are higher in the two topmost coal benches probably due to marine transgression in the early diagenetic stage after the peat had been established the enrichment of li and rey in a few lowermost coal benches is suggested to be derived from hydrothermal fluids that were related to magmatic activity 110 140 ma during the yanshanian orogeny late jurassic early cretaceous or a late triassic early jurassic abnormal thermal event occurring at 190 215 ma light rey la ce pr and nd in the jincheng no 15 coal are predominantly associated with phosphate minerals heavier rey sm to lu show a mixed phosphate and organic affinity in the studied coal samples non coal samples are characterized by light rey and hrey enrichment which is probably inherited from the source material in the trans north china orogen trace elements in the coal can be highly enriched in the ash if the coal is combusted due to the low to medium ash yield of the coal critical elements including li ga and rey in the jincheng no 15 coal are considered as promising material for industrial recovery and have been previously under estimated on the other hand environmentally sensitive elements including as hg and pb while having concentrations within the normal range compared with average worldwide coals can be highly enriched in the coal combustion residues if the coal is combusted and thus careful consideration needs to be given to the utilisation of such coals

rapid deformation of the south flank of kilauea volcano hawaii the south flank of kilauea volcano has experienced two large magnitude m 7 2 and m 6 1 earthquakes in the past two decades global positioning system measurements conducted between 1990 and 1993 reveal seaward displacements of kilauea9s central south flank at rates of up to about 10 centimeters per year in contrast the northern side of the volcano and the distal ends of the south flank did not displace significantly the observations can be explained by slip on a low angle fault beneath the south flank combined with dilation deep within kilauea9s rift system both at rates of at least 15 centimeters per year

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

geochemistry of rare earth elements in permian coals from the huaibei coalfield china abstract the rare earth elements rees in coals are important because of a ree patterns can be an indicator of the nature of source rocks of the mineral matter as well as sedimentary environments b rees abundance in coal may have industrial significance in this study a total of thirty four samples of permian coal partings roof and floor were collected from the huaibei coalfield anhui province china abundances of rare earth elements rees and other elements in the samples were determined by inductively coupled plasma mass spectrometry icp ms and inductively coupled plasma atomic emission spectrometry icp aes the results show that the rees are enriched in coals in the huaibei coalfield as compared with chinese and u s coals and the world coal average coals in the lower shihezi formation no 7 5 and 4 coals and upper shihezi formation no 3 have higher ree abundances than the coals in shanxi formation no 10 magmatic intrusion resulted in high enrichment of rees concentrations in no 5 and 7 coals the ree abundances are positively correlated with the ash content the mineral matter in these coals is mainly made up of clay minerals and carbonates the rees are positively correlated with lithophile elements including si al ti fe and na which are mainly distributed in clay minerals indicating that rees are contained mainly in clay minerals the ree abundances in coals normalized by the ash are higher than that in partings rees abundances of coals cannot be accounted for by the ree content in the mineral matter and some rees associated with organic matter in coals

rare earth elements in bituminous coals and underclays of the sydney basin nova scotia element sites distribution mineralogy abstract bituminous coals of the sydney basin nova scotia canada contain some 30 ppm of rare earth elements ree dispersed in illite clay and macerals or concentrated in fossil apatite and resistate minerals monazite florencite xenotime zircon for high ash coals the bulk of ree are derived from suspended river sediments low ash bituminous coals contain some heavy ree complexed with the organic phase or adsorbed by authigenic clays and derived largely from dissolved river load the concentration of ree in coal ash 72 to 483 ppm is similar to that of roof and seat clays except for slight local enrichments in heavy ree individual seams have diverse ree distribution patterns that reflect the depositional and diagenetic mineralogy or reveal enrichment at seam margins by organic complexing or fossil apatite uptake chondrite normalized profiles range from light ree enriched to heavy ree enriched highly pyritized bands yield ash low in ree with flat profiles clay rich bands yield ash with distribution patterns similar to shales with light ree enrichment a weak negative eu anomaly and a profile slope correlated to al content rare earth element partitioning between organic and mineral phases or between coals and associated strata differs over the coalfield reflecting the combined effects of sedimentation water chemistry ion exchange and chelation coal seam correlation using ree distribution is limited by geochemical facies distribution patterns must be interpreted with caution because of analytical problems inherent to coal

incisional cyclic steps of permanent form in mixed bedrock alluvial rivers most bedrock river channels have a relatively thin discontinuous cover of alluvium and are thus termed mixed bedrock alluvial channels such channels often show a series of steps formed at relatively regular intervals this bed form is the bedrock equivalent of cyclic steps formed on beds composed of cohesive soil in gullies in this paper we perform a full nonlinear analysis for the case of cyclic steps in mixed bedrock alluvial channels to explain the formation of these steps we employ the shallow water equations in conjunction with equations describing the process of bedrock incision as a model of bedrock incision we employ the recently introduced macro roughness saltation abrasion alluviation model which allows direct interaction between alluvial and bedrock morphodynamics the analysis is greatly simplified by making the quasi steady assumption that alluvial processes occur much faster than bedrock erosional processes from our analysis we obtain the conditions for the formation of cyclic steps in bedrock as well as the longitudinal profiles of bed elevation water surface elevation and areal fraction of alluvial cover it is found from the analysis that when the sediment supply is small relative to the transport capacity cyclic steps form only on slopes with very high gradients the analysis indicates that the shape of a step formed on bedrock is characterized by a relatively short upstream portion with an adverse slope and a long almost planar downstream portion with a constant slope

distribution of rare earth elements in coal combustion fly ash determined by shrimp rg ion microprobe abstract during coal combustion for electric power generation rare earth elements ree are strongly retained in the ash fraction leading to significant enrichment compared to the ree content of the respective feed coals knowing how the ree are distributed in coal ash is essential to devising effective approaches for ree extraction from this potential resource to better understand the distribution of ree in coal ash we used the stanford usgs shrimp rg ion microprobe to determine grain scale ree partitioning in a suite of 19 u s and international coal fly ash samples shrimp rg microanalysis used a nominal spot size of 15 m and an oxygen negative ion primary beam nist multi element glass standards srm 611 and srm 613 were used for ree calibration prior to shrimp rg analysis samples were characterized by backscattered electron imaging and wavelength dispersive elemental mapping to delineate constituents of interest for ree microanalysis results confirm the occurrence of ree in aluminosilicate glasses consistent with previous results that showed a strong positive correlation between al and ree content in a larger group of u s and international coal fly ash samples among these glasses aluminosilicates consisting of al and si and lacking other major constituents tend to have ree contents similar to or slightly lower than the bulk sample ree content whereas ca and or fe enriched aluminosilicate glasses are similar to or more ree enriched than the bulk sample co occurring quartz and or high silica glass is almost always the most ree depleted fly ash constituent having much lower ree contents than the aluminosilicate glasses fe oxide magnetospheres have ree content with relative proportions of light lree to heavy hree rare earths that are more variable than in the aluminosilicate glasses results suggest that extraction of ree from the aluminosilicate glass fraction in coal ash will yield a significant portion of the ree present and therefore this fraction should be targeted in ongoing efforts to recover ree from coal fly ash

ree geochemistry of the cretaceous lignite from wulantuga germanium deposit inner mongolia northeastern china abstract the wulantuga germanium deposit wgd hosted in coal seams with ge resources up to 1600 mt is located in the shengli coalfield in xilingol inner mongolia china forty two channel samples of ge bearing lignites of the no 6 1 coal seam lower cretaceous bayanhua formation were collected and their ree compositions were analyzed by inductively coupled plasma mass spectrometry icp ms the modes of occurrence of ree in selected lignite samples were studied by scanning electron microscope with energy dispersive x ray spectrometer sem edx and statistical methods the distribution of ree and y in all 42 samples from wgd are in accordance with the log normal distribution the total rare earth element content ree of most lignite samples from wgd range from 9 02 to 118 ppm only four samples show relatively higher 149 533 ppm ree concentration the average ree contents of 42 lignite samples from wgd are slightly higher than those of the usa coals world wide coals sandstone from wgd and the contemporary ge barren lignite from hongqi coal mine the lignite samples from wgd have shale like chondrite or nasc normalized ree patterns similar to those of sandstone overburden and ge barren lignite from hongqi coal mine ree contents of most lignite samples are highly positive correlated with ash yields indicating a mainly detrital source and association with syngenetic mineral matter ree rich phosphates monazite were identified by sem edx in some medium to high ash ash yields range from 23 58 to 38 18 lignite samples with high ree y contents from wgd ree can be concentrated in the upper and lower proportions of the no 6 1 coal seam the vertical profiles of ree mainly follow that of tio 2 and the average ree tio 2 ratio of lignite sample in three sections is very close to that of the sandstone from wgd or lignite from hongqi coal mine it was determined that most ree in the lignite from wgd were derived from a detrital source and associated with syngenetic mineral matter however when normalized to the overlying sandstone some lignite samples from wgd display a small but distinct enrichment in middle to heavy ree indicating small quantity of middle to heavy ree may be added and or retained during epigenesis the lignite samples from wgd are characterized by higher ratios of lree hree and eu eu and horizontal nasc normalized ree patterns and distinguished from those of the ge bearing lignites from lincang germanium deposit yunnan china and ge deposits of russian far east there is no distinct correlations between ge and any individual ree or ree y content of lignite from wgd

geological controls on the distribution of rey zr hf nb ta enrichment horizons in late permian coals from the qiandongbei coalfield guizhou province sw china abstract the abnormal enrichment of the rey rare earth elements and yttrium zr hf nb ta assemblage in late permian coals occurring in some coalfields in sw china has been extensively investigated but the geological controlling factors of this assemblage are still under debate this study reports on the mineralogical and geochemical features of coals and noncoal rocks collected from the yudai and jinqi coal mines within the qiandongbei coalfield in guizhou province to elucidate the geological controls on the distribution of rey zr hf nb ta enrichment horizons the studied coals show rather consistent clay mineral assemblage of kaolinite together with varying amounts of quartz gypsum pyrite and calcite notably the coals are anomalously enriched in rey nb ta zr and hf and enriched in other incompatible elements e g ga th and u phosphates e g florencite and to a lesser extent zircon are the primary carriers of rey zirconium and hf are mainly incorporated into zircon and then anatase the latter of which is a predominant carrier of nb and ta the detrital materials originate from a mixture of the erupted felsic volcanic ash resembling a peralkaline rhyolite composition and the eroded materials of emeishan large igneous province elip basalts the studied coals owe their highly enhanced concentrations of the rey zr hf nb ta assemblage to the input of felsic volcanic ash wherein the highly acidic aqueous solutions allowed these elements to become mobile and be redistributed both geological processes governed the distribution of rey zr hf nb ta enrichment horizons the highly acidic solutions were possibly derived from the oxidation of peat bogs and volcanism related acidic rain the concentrations of rey zr and nb in the coal ashes exceed their corresponding cut off grades thus these coals can be considered highly promising raw material sources for the rey zr hf nb ta assemblage

a fault model for the 1989 kilauea south flank earthquake from leveling and seismic data the geometry of the fault that ruptured during the m6 1 south flank earthquake on kilauea volcano in 1989 is determined from leveling data the elastic dislocation in a homogeneous elastic half space that best fits the data is found using a nonlinear inversion procedure the best fitting model is a gently dipping thrust fault that lies at 4 km depth this is significantly shallower than the 9 km hypocentral depth determined from the local seismic network two dimensional finite element calculations indicate that at least part of this discrepancy can be attributed to the focusing of the surface deformation by the upper few kilometers of compliant low density lavas we conclude that it is important to include realistic elastic structure to estimate source geometry from geodetic data

rare earth elements in a sampled coal from the pirin deposit bulgaria abstract rare earth elements la ce sm eu tb yb and lu in a columnar section of the coal of the pirin deposit bulgaria have been determined by neutron activation analyses the ree content in the coals is lower than the average ree content of shales from north america europe and the soviet union the ree abundances increase with the increasing ash content of the coals the bottom of the seam is slightly enriched in ree the trend being more pronounced in hree tb yb lu the ree content depends on the thickness of the coal layers the thin coal layers are enriched in ree as compared to the thick ones the chondrite normalized distribution patterns are very uniform they are characterized by a negative eu anomaly whose mean value is 0 30 varying in the individual samples from 0 21 to 0 49 and a positive lu anomaly it is supposed that the eu anomaly is inherited from the source rocks the shale normalized distribution patterns show a distinct relative enrichment in hree and a negative eu anomaly the relative enrichment in hree is a specific feature of the ree geochemistry in the pirin deposit the lree hree ratio is lower than that of composite shale it increases with the increasing ash content of the coals and from the bottom to the top of the coal bed ree are bound predominantly to the aluminosilicates of the mineral matter in the coals all ree are positively correlated to the ash si al fe and na the source of ree in coals is mainly the suspended terrigenous material the specific enrichment of ree in the ash of low ash coals is a result of the interaction between the dissolved ree and the products of disintegration and decay of organic substances mainly the humic acids

mineralogical and geochemical compositions of late permian coals and host rocks from the guxu coalfield sichuan province china with emphasis on enrichment of rare metals abstract this paper reports the geochemical and mineralogical compositions of the late permian no 25 coal semi anthracite and its host rocks roof and floor strata from the guxu gulin xuyong coalfield sichuan province china the coal is characterized by medium sulfur content average 2 73 and has an average ash yield of 20 95 in contrast to other late permian coals from southwestern china that are enriched in sc v cr co ni and cu the no 25 coal does not contain an abundance of these transition elements but is rich in lithophile elements be y nb zr hf and u the elevated concentrations of trace elements in the no 25 coal were probably derived from the felsic intermediate rocks at the top of the emeishan basalt sequence rather than from the emeishan mafic basalts the floor strata of the no 25 coal can be divided into two sub sections the upper sub section of the sequence immediately below the no 25 coal consists of material with a felsic intermediate composition probably derived from terrigenous sources and the lower sub section is composed of mafic tuff the terrigenous mineral matter in the no 25 coal appears to have the same sediment source region as the upper sub section of the floor strata based on their similar geochemical compositions the roof strata of the no 25 coal are more quartzose and were probably derived from a different sediment source region the mineral matter in the coal is dominated by kaolinite and to a lesser extent calcite and pyrite the roof and floor strata each have quite different mineralogy with kaolinite dominant in the latter and illite kaolinite and quartz in the former pyrite contents are variable both in the coal and in the host rocks the floor strata and the coal have been affected by hydrothermal solutions leading to the enrichment of rare earth elements and yttrium rey nb ta zr hf and u the rey in the coal and floor strata as well as the nb ta zr hf and u in the floor strata represent potentially economic rare metal resources

coal deposits as potential alternative sources for lanthanides and yttrium abstract this paper presents data on widespread abnormal accumulations of lanthanides and yttrium rey in many coal deposits worldwide high rey contents 0 1 have been found in coal seams and coal ashes as well as in the host and basement rocks of some coal basins for a preliminary evaluation of coal ashes as an rey raw material not only the abundance but also the individual rey compositions were taken into account in this paper three rey distribution patterns for high rey coal ashes are fixed with lrey lan lun 1 mrey lan smn 1 and hrey lan lun

very long period seismic signals and caldera formation at miyake island japan over a period of roughly 40 days starting on 8 july 2000 a caldera structure 1 7 kilometers in diameter developed by means of gradual depression and expansion of the summit crater at miyake island japan at the same time very long period vlp seismic signals were observed once or twice a day source mechanism analyses of the vlp signals show that the moment tensor solutions are smooth step functions over a time scale of 50 seconds with dominant volumetric change components we developed a model to explain the caldera and the vlp signals in which a vertical piston of solid materials in the conduit is intermittently sucked into the magma chamber by lateral magma outflow this model offers potential for making quantitative estimations of the characteristic physical properties of magma systems

ill posedness in modelling two dimensional morphodynamic problems effects of bed slope and secondary flow a two dimensional model describing river morphodynamic processes under mixed size sediment conditions is analysed with respect to its well posedness well posedness guarantees the existence of a unique solution continuously depending on the problem data when a model becomes ill posed infinitesimal perturbations to a solution grow infinitely fast apart from the fact that this behaviour cannot represent a physical process numerical simulations of an ill posed model continue to change as the grid is refined for this reason ill posed models cannot be used as predictive tools one source of ill posedness is due to the simplified description of the processes related to vertical mixing of sediment the current analysis reveals the existence of two additional mechanisms that lead to model ill posedness secondary flow due to the flow curvature and the effect of gravity on the sediment transport direction when parametrising secondary flow accounting for diffusion in the transport of secondary flow intensity is a requirement for obtaining a well posed model when considering the theoretical amount of diffusion the model predicts instability of perturbations that are incompatible with the shallow water assumption the effect of gravity on the sediment transport direction is a necessary mechanism to yield a well posed model but not all closure relations to account for this mechanism are valid under mixed size sediment conditions numerical simulations of idealised situations confirm the results of the stability analysis and highlight the consequences of ill posedness

rare earth element bearing coals from the russian far east deposits abstract coal seams up to 10 m in thickness with high rare earth element ree concentrations 300 1000 ppm were detected in some of the russian far east deposits this paper reports on the ree composition of the coals from a number of deposits the ree bearing coals are subdivided into three geochemical types studies of ree distributions across the coal seams examination of gravitation fractions and sem edx studies have revealed that the enriched coals seams contain ree mainly as sorbed forms by organic matter and clay particles and fine grained authigenic minerals the ree coals formed in 1 erosion tectonic depressions with wide spread weathering crusts in their basins and 2 volcano tectonic grabens in which coal accumulation occurred simultaneously with bimodal volcanism in the former case ree are thought to originate from the borderland in the second case from chambers of subalkaline magma the ree accumulation in the organic material occurred mostly during the peat stage due to mineralized ree bearing water coming to the basins the high ree contents up to 1 0 and even more of the combustion wastes their low lree hree ratios and the considerable estimated resources all place the ree bearing coals of the russian far east among new and very promising mineral resources for y and heavy lanthanoids as by products

geodetic analysis of dike intrusion and motion of the magma reservoir beneath the summit of kilauea volcano hawaii 1970 1985 we use leveling and trilateration data collected on kilauea volcano to constrain the location of deformation sources caused by magma accumulation intrusion and eruption for the 13 inflationary epochs examined combinations of an expanding point source and one or two opening rectangular dislocations mimic inflation of the summit reservoir and formation of dike s respectively the combined model adequately accounts for the deformation data and is consistent with the seismicity observed during each epoch for 10 deflationary epochs however the data require only a contracting point source confidence in these results is gained by noting that locations of the sources of both inflation and deflation are coincident within the observed uncertainties of the data the function of network geometry and the inversion procedure it appears therefore that magma accumulation at kilauea volcano may be characterized by the growth of dikes during inflation of the summit reservoir drainage of the reservoir on the other hand is not accompanied by significant closure of dikes in contrast to previous studies e g fiske and kinoshita 1969 dvorak et al 1983 that do not include the dislocation or dike growth component of summit magma accumulation and concluded that the source of inflation migrates over a 5 km2 area we find that a single magmatic reservoir source accounts for data collected during all inflationary and deflationary epochs results which compare favorably with those obtained from the point ellipsoid model can be used to estimate the distribution of stresses within the volcano in the near field of the source

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

trace elements in the goze delchev coal deposit bulgaria abstract the geochemistry of trace elements in the underground and open pit mine of the goze delchev subbituminous coal deposit have been studied the coals in both mines are highly enriched in w ge and be and at less extent in as mn and y as compared with the world wide clarkes for subbituminous coals ni and ti are also enhanced in the underground coals and zr cr and mo in the open pit mine coals characteristic for the trace element contents in the deposit is a regular variation with depth the following patterns were distinguished for profile i a the element content decreases from the bottom to the top of the bed paralleling ash distribution fe co as sb v y mo cs ree hf ta th p and au b ge and w are enriched in the near bottom and near top coals c in the middle part of the bed the content of k and rb is maximal while that of u is slightly enriched d ba content decreases from the top to the bottom of the bed in profile ii w and be contents decrease from the bottom to the top the near bottom and especially the near roof samples of profile iv are highly enriched in ge while for w the highest is the content of the near bottom sample ge be as mn cl and br are mainly organically associated the organic affiliation is still strong for co b sr ba sb u th mo la ce sm tb and yb in the underground coals and fe co na w sr y and ag in the coals from the open pit mine k rb ti zr hf and ta are of dominant inorganic affinity the chalcophile and siderophile elements correlate positively with fe and each other and may be bound partly with pyrite or other sulphides and iron containing minerals compared statistically by the t criteria the elements na li cu zn pb cr ni co mo fe and be are of higher content in the open pit mine tungsten is the only element of higher concentration in the underground mine the contents of ge as sr v mn y zr and p are not statistically different in both mines it was supposed that there were multiple sources of the trace elements in the deposit the source of the highly enriched elements w ge be and as most probably were the thermal waters in the source area the contemporary mineral springs are of high content of these elements another source were the hosting mesta volcanic rocks which are enriched in sb mo hf u th as li and rb some of the volcanics were hydrothermally altered and enriched or depleted of many elements thus the hydrothermal solutions were also suppliers of elements for the coals it is obvious that the contents distribution and paragenesis of the trace elements in both goze delchev coals reflect the geochemical specialization of the source area including rocks paleo and contemporary thermal waters

sorting and bed waves in unidirectional shallow water flows the stability of a uniform flow above an erodible bed composed of a bimodal mixture of sediments is investigated by means of linear analysis results show that for any given set of the flow and sediment parameters two distinct modes of instability arise each one characterized by its own wave speed growth rate and longitudinal wavelength each one involving spatial variations of both grain size density and bed elevation although at a linear level no information on the amplitude of the perturbations is gathered the analysis of the eigenvectors associated with the two modes of instability allows for an easy classification in terms of the relative amplitudes of the perturbations of bed elevation and size density one eigenvalue is shown to be associated with the modifications of bed forms induced by the presence of the heterogeneous mixture such as the local accumulation of finer and coarser material along the unit wavelength the other with the formation of the low amplitude sorting waves known as bedload sheets in the present unidirectional shallow water framework only the sorting wave is found to be unstable since dunes and antidunes the relevant bed forms for this case require a more refined rotational flow model in order to become unstable on the other hand the simple flow model adopted allows for the formulation of an algebraic eigenvalue problem that can be solved analytically allowing for a deep insight into the mechanisms that drive both instabilities

magma reservoir failure and the onset of caldera collapse at kīlauea volcano in 2018 introduction the 2018 rift zone eruption of k lauea volcano hawai i drained large volumes of magma from the volcano s summit reservoir system causing high rate subsidence of the ground surface and withdrawal of an active lava lake over the span of 1 week the surface of the lava lake fell more than 300 m continued withdrawal of magma caused the rock above the reservoir to fail triggering the onset of episodic caldera collapse surface collapse began near the evacuated lava lake vent but as the eruption continued over 3 months the area of the new caldera expanded to 5 km2 and its volume grew to 0 8 km3 the precursory activity and subsequent growth of the caldera were recorded in far greater detail than was possible at the handful of other caldera collapses observed in the past century these comprehensive observations permit new insights into the conditions that lead to magma reservoir host rock failure and caldera collapse rationale volcanic caldera collapses can be highly destructive and create prominent topographic features but little is known about the architecture of subcaldera magma storage zones or the critical decrease in pressure that triggers collapse withdrawal of k lauea s lava lake in 2018 can be used to gauge pressure change in the underlying magma reservoir we developed a model of time evolving reservoir depressurization to jointly explain lava lake withdrawal rate and the rate and spatial pattern of ground subsidence obtained from radar satellites and a dense local monitoring network results we tracked the evolution of the magmatic system from steady elastic decompression to inelastic failure we were able to estimate the location geometry volume and time evolving pressure within the reservoir as well as conditions required to trigger failure of the overlying crust before the onset of collapse the ground at k lauea s summit was subsiding at nearly 10 cm day and the lava lake surface was retreating at 50 m day we found that these phenomena were caused by drainage of magma at a high rate from a storage reservoir centered 2 km below the surface with a volume of several cubic kilometers drainage rapidly reduced reservoir pressure stressing the surrounding crust two weeks after the rift zone intrusion and eruption began to drain magma from the summit withdrawal of conclusion our results tightly constrain the pressure decrease in the magma reservoir before the onset of collapse together with geodetic data this bounds the magma storage volume and the stress changes needed to cause failure of the host rock above the reservoir our results demonstrate that a magma reservoir s roof may begin to fail after withdrawal of only a small fraction of the stored magma at k lauea this process was likely influenced by a relatively thin and wide reservoir roof and preexisting crustal weaknesses including an established caldera ring fault system and the lava lake vent roof collapses maintained magma pressure sustaining the eruption but they did not as is sometimes assumed completely repressurize the reservoir this indicates residual frictional strength on the collapse bounding faults the eruption was not terminated by complete evacuation of stored magma contrary to assumptions sometimes made when interpreting data from past caldera collapses and indicates that a different process was responsible for the cessation of the eruption joint monitoring of ground deformation and lava lake elevation at other volcanoes when possible may yield rich insights into magmatic processes and conditions

seismic detection of the summit magma complex of kilauea volcano hawaii application of simultaneous inversion of seismic p wave arrival time data to the investigation of the crust beneath kilauea volcano yields a detailed picture of the volcano s heterogeneous structure zones of anomalously high seismic velocity are found associated with the volcano s rift zones a low velocity zone at shallow depth directly beneath the caldera coincides with an aseismic region interpreted as being the locus of kilauea s summit magma complex

rare earth element and yttrium content of coal in the banko coalfield south sumatra basin indonesia contributions from tonstein layers abstract the south sumatra basin is one of the most prolific coal basins in indonesia most of the coal from this area is used as thermal coal seredin and dai 2012 explained the importance and significance of coal deposits as potential sources for rare earth elements and yttrium rey the concentrations of these elements in coal are similar to their abundances in conventional rey deposits production of the rey in coal deposit is mainly from the coal s fly bottom ash examination of coal with high rey concentrations is becoming a very important issue the study area is located in the banko coalfield sumatra indonesia this area is one of the best candidates for studying rey in coal because there are tuffaceous mudstone layers tonsteins reported by previous researchers that may have enriched the coal in rey for this study coal and non coal beds from the same stratigraphic interval were sampled and analyzed using thin and polished section x ray diffraction xrd inductively coupled plasma atomic emission spectroscopy icp aes and inductively coupled plasma mass spectrometry icp ms special attention was given to coals near the tonstein layers based on the data collected it was concluded that all the tonsteins studied are of volcanic origin and are silicic and alkali tonsteins the elements al and si are higher in coal samples collected just beneath the tonstein layers and the highest rey concentration found was in a sample beneath a silicic tonstein layer these data suggest that there is an opportunity to extract rey from coal s fly bottom ash because the rey content of the ash is as much as 10 times higher than the rey content of the coal feed to power plants

flexure and seismicity beneath the south flank of kilauea volcano and tectonic implications we present a refined model for the tectonic behavior of kilauea volcano s south flank including flexure calculations and microearthquake data supportive of the model in our model the south flank moves seaward over the downwardly flexed ocean crust in a manner analogous to an accretionary prism in a subduction zone the flank is driven seaward by the gravitational stresses inherent in its shape this driving force is augmented by high density material in kilauea s rift zones elastic flexure calculations predict a configuration for the downwardly flexed crust which agrees with previous seismic refraction and gravity modeling this configuration in turn is consistent with the hypothesis that many earthquakes occur along the volcanic pile ocean crust interface focal mechanisms for these events predominantly indicate southeastward directed overthrusting we also propose a relationship between rift zone intrusion and south flank displacement including a suggestion that the decollement configuration controls the relative activity of kilauea s east and southwest rift zones

aspects of the geochemistry of rare earth elements in coal an experimental approach abstract many coals worldwide are slightly enriched in heavy rare earth elements hree relative to light rare earth elements lree as compared with chondrites and shales a factor contributing to this fractionation could be the ability of the hree to form complexes with organic compounds which are more stable than those of the lree in order to test this hypothesis experiments on the sorption of several light and heavy rare earth elements la ce sm eu gd ho er lu on xylain and humic acids were performed the sorption on xylain was found to be ph and time dependent maximum quantity was sorbed in the range of ph 3 to 5 sorption equilibrium was reached in 5 to 7 days the shape of the sorption isotherms for all ree studied were similar the maximum content sorbed for each ree was about 0 2 meq 0 5 g xylain when all ree were present in equal concentration in the initial solution the quantity sorbed was also 0 2 meqv 0 5 g xylain nearly the same quantity of na k ca and mg were displaced from the sorbent these results suggest a cation exchange mechanism in which na k ca and mg bound to cooh and oh groups were replaced by the ree cations the capacity of humic acids leached from xylain was found to be about 0 05 meq ree on 0 250 mg humic acids ha the individual ree were sorbed in nearly equal quantities

geochemistry of rare earth elements in a marine influenced coal and its organic solvent extracts from the antaibao mining district shanxi china twenty six samples including roof bottom and coal plies of a marine influenced coal bed were collected from the antaibao mining district shanxi china the rare earth elements rees were determined in solids and organic solvent extracts the distribution pattern showed three distinct patterns shale like lree rich and hree rich this is attributed to the variable microenvironment of peat forming swamp the degree of marine influences and different ree sources rees in the coal are mainly controlled by detrital minerals but also affected by seawater the chondrite normalized ree patterns of the organic solvent extracts are distinctly different from those of corresponding original coal samples which show a negative eu anomaly a depletion of middle rees and an enrichment of hrees the lrees in coal extracts are likely adsorbed by hydrogen containing functional groups and hrees are likely bonded to carbon atoms

mineralogy of a rare earth element rich manchester coal lithotype clay county kentucky abstract many eastern kentucky coals have high ree contents with lithotypes of the pennsylvanian age manchester coal rivaling some of the richest concentrations in the fire clay coal arguably the premier resource in terms of concentration and aerial extent a 2000 ppm ree y rey ash basis 2 13 ash manchester coal lithotype analyzed first by scanning electron microscopy was selected for detailed transmission electron microscopy energy dispersive x ray spectroscopy fast fourier transform selected area electron diffraction investigation tem eds fft saed the mineral grains extracted from the coal seemingly fragments of one or more 2 to 3 m spherical nodules proved to have a phosphate rhabdophane rim with a light ree la through sm and gd association the core of the nodule and the region surrounding the nodule is al si rich but the mineralogy could not be determined the nodule may be a mineralized coprolite the product of the microfauna inhabiting the peat

cyclic steps review and aggradation based classification abstract cyclic steps are a type of upper flow regime bedform consisting of trains of upstream and upslope migrating bed undulations the overriding flow is characterised by a series of hydraulic jumps occurring in the troughs of the undulations cyclic steps form in open channel flows such as rivers and comprise a common bedform in subaqueous density flows in oceans lakes and reservoirs cyclic steps are associated with alternating froude subcritical and froude supercritical flow on respectively the stoss side and lee side of individual bedforms the transition between these flow states is embodied by the hydraulic jump in the trough of the bedform leading to the permanent or quasi permanent morphology of cyclic steps over the past decade numerous studies affirmed the dominant role of cyclic steps in generating bed undulations in modern and ancient glacial outwash fluvial delta and turbidite environments as reviewed here cyclic steps were previously discriminated as net depositional climbing transportational and net erosional falling in different parts of sedimentary systems the following cyclic step descriptors with distinct depositional signatures are proposed fully depositional partially depositional transportational partially erosional and fully erosional partially depositional cyclic steps are most common they are associated with backset bedded sets high aggradation rate and nested scours filled with massive to backset bedded deposits low aggradation rate the new classification can be used as a predictive tool in the reconstruction of modern and ancient sedimentary successions using repeat bathymetry seismic reflection or outcrop data it is applied in three turbidite case studies classical deep sea system small scale delta slope and line sourced carbonate slope

aspects of rare earth element enrichment in central appalachian coals abstract the concentration of lanthanides y and sc collectively rare earth elements ree and their modes of emplacement in appalachian coals with emphasis on manchester and fire clay coals in eastern kentucky are the focus of this investigation those coals have distinct ree concentrations and relationships related to the position of the lithotype within the coal seam such as the ratio of light to heavy lanthanides lree hree in the manchester coal the high s upper lithotypes have lower ree concentrations and different lree hree than the low s lithotypes in the fire clay coal the position of the lithotype relative to the ree enriched tonstein is important with the coal immediately below the tonstein having significantly higher ree than other lithotypes lithotypes in the middle of the coal bench above the tonstein have high lree hree possibly indicating a hydrothermal influence on the ree emplacement

geochemistry of trace elements in the kesan coal and its effect on the physicochemical features of ground and surface waters in the coal fields edirne thrace region turkey abstract in this study concentration and origin of trace elements of the kesan coals in edirne thrace basin have been investigated in order to determine possible environmental impacts on water pollution the coal ground and surface waters and clay samples were taken from the coal mining area the concentration of trace elements in 14 coal ashes 15 water samples and seven clays was determined by inductively coupled plasma mass spectrometry additionally 11 of these coal samples were studied by proximate and seven coal samples were also studied by x ray diffraction analyses the mineralogical composition of the studied coal samples is made up mainly of quartz clay minerals feldspar group minerals pyrite and amorphous matter the kesan coal ash samples have higher average concentrations of cr 180 ppm ni 192 ppm rb 91 ppm and sr 1701 ppm average values of other trace elements are lower than the world average of brown coal ashes the sulfur content of the kesan coals ranges from 0 4 to 3 90 2 02 on average the ph values of the waters vary between 6 55 and 8 36 in coal fields 7 21 and 7 54 in springs the f cl no 3 so 4 ca mg na and k values of the waters vary between 0 11 and 0 25 mg l 33 49 and 52 90 mg l 0 05 and 59 27 mg l 85 and 2829 mg l 66 and 349 mg l 64 and 222 mg l 41 and 1187 mg l 2 and 13 mg l respectively in coal fields some elements are anomalous in concentrations in some water samples e g cr up to 49 6 ppb mn up to 1185 ppb fe up to 10 352 ppb ni up to 55 8 ppb as up to 9 7 ppb ppb it has been interpreted that the lower trace element concentrations in the water samples may be due to clay intercalated with coal the clays are smectite type and they are enriched in cr co ni as sr and th e g up to 394 ppm cr up to 305 ppm ni and up to 35 5 ppm as

elements and phosphorus minerals in the middle jurassic inertinite rich coals of the muli coalfield on the tibetan plateau abstract the content modes of occurrence and origin of elements and phosphorus minerals in the jurassic coals of the muli coalfield on the tibetan plateau were investigated using optical microscopy field emission scanning electron microscopy in conjunction with energy dispersive x ray spectrometry x ray powder diffraction x ray fluorescence spectrometry and inductively coupled plasma mass spectrometry the muli coals l1 and l2 coals are of high volatile a bituminous to medium volatile bituminous rank characterized by low sulfur contents and are generally dominated by the inertinite group macerals predominantly semifusinite and fusinite the l1 coal contains abundant apatite 7 9 on average on an organic matter free basis and alumino phosphate minerals of goyazite gorceixite crandallite group 4 9 on average and accordingly the concentrations of elements f 253 g g on average p 2349 g g sr 526 g g and ba 790 g g are elevated as compared with common world hard coals the deposition of phosphorous bearing minerals in the muli coals was not derived from volcanic input penetration of ca and al rich solutions release of phosphorus from organic matter during plant decay and an appropriate sedimentary environment such as low ph low water table for peat and oxidizing conditions were critical factors in deposition of the phosphorus minerals

lanthanide yttrium and zirconium anomalies in the fire clay coal bed eastern kentucky abstract the fire clay coal bed in the central appalachian basin region contains a laterally persistent tonstein that is found in the coal throughout most of its areal extent the tonstein contains an array of minerals including sanidine quartz anatase and euhedral zircon that constitutes strong evidence for a volcanic origin of the parting for this study five samples of the tonstein and four sets of coal samples underlying the tonstein were collected from five sites in eastern kentucky inductively coupled plasma mass spectroscopy icp ms analysis of the tonstein and underlying coal collected from four sites in eastern kentucky show that although zr concentrations are high in the tonstein 570 1820 ppm on a coal ash basis cab they are highest in the coal directly underlying the tonstein 2870 4540 ppm cab a similar enrichment pattern is observed in the concentration of y plus the sum of the rare earth elements y ree total y ree concentrations in the five tonstein samples range from 511 to 565 ppm cab however y ree contents are highest in the coals directly underlying the tonsteins values range from 1965 to 4198 ppm cab scanning electron microscopy of samples from coal which directly underlies two of the tonstein samples show that ree rich phosphate tentatively identified as monazite commonly infills cracks in clays and cells in clarain and vitrain zircon is rare and commonly subhedral on the basis of coal chemistry and grain morphology we suggest that volcanic components in the tonstein were leached by ground water the leachate rich in y and ree precipitated as authigenic mineral phases in the underlying coal

rare earth elements and yttrium in lithotypes of bulgarian coals abstract rare earth element and yttrium abundances in vitrain xylain liptain fusain and whole coal samples from bulgarian coal deposits have been studied vitrain xylain and liptain are depleted while fusain is enriched in ree and y as compared to the whole coal samples from which they were selected chondrite normalized patterns show relative enrichment of light lree against heavy hree rare earth elements negative eu anomaly and positive lu anomaly the shale normalized patterns of the lithotypes reveal an increase from lree to hree while those of the whole coal samples and mineral interlayers are less fractionated the petrographic composition of the coals is of secondary importance for the concentration of the ree and y the main factors are the source area and the input of dissolved ree and y into the coal depositional sites

motion of kilauea volcano during sustained eruption from the puu oo and kupaianaha vents 1983 1991 kilauea erupted almost continuously from january 1983 through 1991 although the summit began subsiding during the rift zone dike intrusion that initiated this eruption remarkably steady ground surface motions began in late 1983 after a magnitude 6 6 earthquake beneath the slopes of nearby mauna loa volcano and continued until the onset of brief upper east rift zone earthquake swarms in late 1990 during these 7 years the summit and upper rift zones subsided up to 10 11 and 4 8 cm yr 1 respectively and summit baselines contracted up to 6 cm yr 1 baselines directed northward from the summit to stations on mauna loa extended at rates up to 7 cm yr 1 and a baseline from south of the summit to mauna loa extended 4 cm yr 1 much of this extension is inconsistent with deformation caused solely by summit magma reservoir collapse and more likely reflects rifting as the south flank of the volcano moved seaward from the summit and rift zones farther from the summit baselines crossing the south flank extended up to 2 cm yr 1 and a south flank tide gauge rose 2 cm yr 1 the lower east rift zone 40 50 km from the summit subsided about 2 cm yr 1 motion on kilauea then is broadly consistent with slip along low angle south flank faults generating subsidence that is focused at the summit and along the rift system behind the faulting and uplift along the coastal south flank ahead of it dislocation models that combine these elements show that much of kilauea s edifice migrated seaward producing ground surface motions along the south flank of up to about 6 cm yr 1 the magnitude 6 1 earthquake of 1989 punctuated these motions along the eastern south flank producing more than 25 cm of seaward displacement and 15 km east of the epicenter up to 24 cm of subsidence south of the lower east rift zone unlike the magnitude 7 2 south flank earthquake of 1975 the 1989 event was preceded neither by summit magma reservoir inflation nor by rift zone dike intrusions and accompanying compression of the south flank deformation was probably caused by the weight of the volcanic overburden and by ongoing dilation and slip within the rift system

a review of anomalous rare earth elements and yttrium in coal abstract coal deposits have attracted much attention in recent years as promising alternative raw sources for rare earth elements and yttrium rey not only because the rey concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of rey ores but also because of the world wide demand for rey in recent years has been greater than supply in addition to anomalies of enrichment or depletion of light medium and heavy rey in coal deposits normalized to upper continental crust post archean australian shale or north american shale composite anomalies of redox sensitive ce and eu and in some cases of non redox sensitive la gd and y could be used as geochemical indicators of the sediment source region sedimentary environment tectonic evolution and post depositional history of coal deposits factors controlling rey anomalies in coal deposits include the geochemistry of terrigenous source rocks ingress of hydrothermal fluids influence of marine environments percolating natural waters volcanic ashes and sedimentary environments of peat formation additionally the smoothness of a normalized rey distribution pattern provides a simple but reliable basis for testing the quality of rey chemical analyses for coal and other sedimentary rocks

late cretaceous coal overlying karstic bauxite deposits in the parnassus ghiona unit central greece coal characteristics and depositional environment abstract the pera lakkos coal located on top of bauxite deposits in the ghiona mining district central greece is the only known mesozoic late cretaceous coal in the country it was derived from herbaceous plants and algae growing in mildly brackish mires that formed behind a barrier system during a regression of the sea on a karstified limestone partly filled in with bauxitic detritus petrological mineralogical and geochemical data point to the predominance of reducing conditions and intense organic matter degradation in the palaeomires o c vs h c and oi vs hi plots based on elemental analysis and rock eval data characterize kerogen types i ii this reflects the relatively high liptinite content of the coal besides kerogen composition o c vs h c plot for the pera lakkos coals is in accordance with a catagenesis stage of maturation in contrast with vitrinite reflectance and t max from rock eval pyrolysis which indicate the onset of oil window maturation stage suppression of vitrinite reflectance should be considered and the high liptinite content corroborates this hypothesis despite some favourable aspects for petroleum generation presented by the pera lakkos coal its maximum thickness up to 50 cm points to a restricted potential for petroleum generation coal oxidation took place either during the late stage of peat formation due to wave action accompanying the subsequent marine transgression or epigenetically after the emergence of the whole sequence due to percolation of drainage waters both options are also supported by the ree shale normalized profiles which demonstrate an upwards depletion in the coal layer oxidation also affected pyrite included in the coal this led to the formation of acidic sulfate rich solutions which percolated downwards resulting in bleaching of the upper part of the underlying bauxite

kinematic analysis of vertical collapse on volcanoes using experimental models time series 1 volcanoes are often associated with vertical collapse due to deeper magma withdrawal calderas are the most notable type of vertical collapse on the summit of volcanoes caldera collapse has been observed and monitored only at miyakejima japan 2000 dolomieu reunion 2007 and fernandina galapagos 1968 highlighting our limited knowledge on its kinematic behavior here we use experimental models to investigate the kinematic evolution of calderas and vertical collapses in general we extract velocity and strain fields using the particle image velocimetry piv technique generating time series experimental vertical collapses undergoing constant subsidence velocity show three main kinematic behaviors 1 continuous collapse whose velocity is similar to the source subsidence velocity 2 incremental collapse with episodic stepwise accelerations along pre existing ring structures 3 sudden collapse resulting from the upward migration of a cavity only for t d 2 t and d are the depth and width of the magma chamber respectively and without ring structures the velocity in the collapsing column may increase up to four orders of magnitude with regard to the constant subsidence velocity of the source comparison to nature suggests that 1 there are close kinematic similarities with monitored collapse calderas explaining their incremental subsidence after the development of ring structures 2 sudden pit crater formation is induced by the upward propagation of cavities due to magma removal at depth and in absence of ring structures 3 all these types of vertical collapses have a consistent mechanism of formation and kinematic behavior function of t d and the presence absence of ring structures

froude supercritical flow processes and sedimentary structures new insights from experiments with a wide range of grain sizes recognition of froude supercritical flow deposits in environments that range from rivers to the ocean floor has triggered a surge of interest in their flow processes bedforms and sedimentary structures interpreting these supercritical flow deposits is especially important because they often represent the most powerful flows in the geological record insights from experiments are key to reconstruct palaeo flow processes from the sedimentary record so far all experimentally produced supercritical flow deposits are of a narrow grain size range fine to medium sand while deposits in the rock record often consist of a much wider grain size distribution this paper presents results of supercritical flow experiments with a grain size distribution from clay to gravel these experiments show that cyclic step instabilities can produce more complex and a larger variety of sedimentary structures than the previously suggested backsets and scour and fill structures the sedimentary structures are composed of irregular lenses mounds and wedges with backsets and foresets as well as undulating planar to low angle upstream and downstream dipping laminae the experiments also demonstrate that the froude number is not the only control on the sedimentary structures formed by supercritical flow processes additional controls include the size and migration rate of the hydraulic jump and the substrate cohesion this study further demonstrates that froude supercritical flow promotes suspension transport of all grain sizes including gravels surprisingly it was observed that all grain sizes were rapidly deposited just downstream of hydraulic jumps including silt and clay these results expand the range of dynamic mud deposition into supercritical flow conditions where local transient shear stress reduction rather than overall flow waning conditions allow for deposition of fines comparison of the experimental deposits with outcrop datasets composed of conglomerates to mudstones shows significant similarities and highlights the role of hydraulic jumps rather than overall flow condition changes in producing lithologically and geometrically complex stratigraphy

the fascination of a shallow water theory for the formation of megaflood scale dunes and antidunes abstract exceptional megaflood scale bedforms on earth are commonly associated with the catastrophic draining of glacial lakes in the late pleistocene the widest studied events have been the missoula and altai floods with 300 700 m flow depth 1 20 m bedform height and 10 300 m wavelength nowadays the saint venant equations have succeeded at simulating the catastrophic glacial lake drainage process numerically but we still lack a depth averaged morphodynamic theory able to predict the growth of dunes and antidunes the disparity of spatial scales in megafloods prevents the use of non depth averaged rotational flow equations motivating the present shallow water theory for the formation of megaflood scale bedforms we adopt a non equilibrium sediment transport equation rooted in einstein s pioneering work here we prove that the bed instability triggers to form dunes and antidunes simply by lagging the entrainment term for sediment mass conservation or the bottom shear stress with respect to the depth averaged flow velocity we formalise this result using a linear stability theory that captures the existence regions of dune and antidune in addition to the roll wave instability furthermore in the spirit of kennedy annu rev fluid mech vol 1 1969 pp 147 168 we derive a closed form solution of growth rate and wave speed of the bedform the nondimensional groups controlling the linear instabilities are the froude number r the shields parameter sh and the grain roughness relative to flow depth d subsequently we simulate the drainage of the largest missoula flood numerically to explain the formation of giant antidunes in the camas prairie montana us during the late stage of the megaflood also considered are large fields of gravel dunes in the kuray chuja lake basin altai mountains siberia the simulated hydraulic conditions over bedforms in both basins yield values of the nondimensional parameters that lie in the theoretical region of dunes and antidunes according to the proposed theory and in situ measurements in sandy rivers and flume experiments

the geochemistry of tungsten in bulgarian coals abstract this paper discusses the tungsten geochemistry in coal based on the behavior of this element in 14 bulgarian deposits the w contents range from 0 5 4335 ppm in the ash and from 0 01 784 ppm in the coals in four of the deposits the tungsten content proved to be 16 to 100 times higher than the clarke value for sedimentary rocks no correlation has been found between the w concentration and either the age of the coal bearing strata or the coal rank the deposits were divided in three groups on the basis of the relationship between tungsten and ash content the role of sorption ash and terrigenous ash in tungsten binding was evaluated for each group the correlation between tungsten and organic matter is demonstrated by the increased contents of tungsten in the ash of the low ash coals its concentration in the lighter coal fractions its extraction from the coals by hf and naoh only and by model experiments sorption ash concentrates tungsten terrigenous ash is a carrier of tungsten of the petrographic constituents of coal vitrain was found to concentrate the largest amounts of tungsten in two of the deposits richest in tungsten there is a very distinct zonality in its vertical distribution tungsten concentration decreases from the bottom to the top of the coal bed this zonality might be explained by the diffusion syngenetic or diagenetic with respect to the coal forming process through the coal bed of aqueous solutions enriched in tungsten the wide range of variation of the tungsten concentrations the considerable differences in the mean contents and the dispersions between the individual deposits show that tungsten is very sensitive to the differences of the source area coal deposits enriched in tungsten may be expected in the following favourable environments 1 in areas with nitrogen bearing thermal waters containing increased amounts of tungsten 2 source areas with tungsten mineralizations and 3 country rocks consisting of acid granitoids whose clarke values of tungsten are the highest as compared to the other types of rocks