source model of deformation at lazufre volcanic center central andes constrained by insar time series 1 recent interferometric synthetic aperture radar insar observations of the lazufre region central andes show large scale uplift at a rate of about 3 cm yr beginning between 1998 and 2002 the initiation of this activity during the ers satellite mission and its proximity to active volcanoes have made lazufre the focus of several studies aimed at understanding its source geometry its relation to nearby volcanoes and whether or not the source area is expanding there now exists a longer time series from multiple ers envisat satellite tracks that allows a more comprehensive examination of the source geometry and its temporal and spatial variation if any we processed 15 years of insar data from three separate tracks modeling the different look geometries provided greater resolution of source depth and geometry we conclude that the source is a shallowly dipping sill at a depth of about 8 km with no evidence of lateral expansion

magma supply dynamics at westdahl volcano alaska modeled from satellite radar interferometry 1 a group of satellite radar interferograms that span the time period from 1991 to 2000 shows that westdahl volcano alaska deflated during its 1991 1992 eruption and is reinflating at a rate that could produce another eruption within the next several years the rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days respectively this behavior is consistent with a deep constant pressure magma source connected to a shallow reservoir by a magma filled conduit an elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath westdahl peak we propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir the pressure gradient and hence the flow rate are greatest immediately after eruptions pressurization of the reservoir decreases both the pressure gradient and the flow rate but eventually the reservoir ruptures and an eruption or intrusion ensues the eruption rate is controlled partly by the pressure gradient between the reservoir and surface and therefore it too decreases with time when the supply of eruptible magma is exhausted the eruption stops the reservoir begins to repressurize at a high rate and the cycle repeats this model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems

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

the structure of sw cornwall and its bearing on the emplacement of the lizard complex six phases of deformation can be recognized in the devonian metasediments to the n of the lizard complex the first two phases d 1 d 2 show a variety of orientations and styles but with a general n or nw vergence these phases while respresenting regional deformation events are considerably modified by the emplacement of the lizard complex there is a general increase in intensity of both d 1 and d 2 structures towards the lizard boundary this is accompanied by variation in the orientation of both early phases of deformation leading to a variety of interference patterns domains of oblique f 1 folds with axes trending n s are developed in the rocks immediately to the ne and nw of the lizard and are considered to have formed by differential nnw directed thrusting of slabs of the complex during the early regional deformation d 2 produced discrete shear zones ahead and below the lizard rocks and may have resulted from the gravitational collapse of the d 1 nappes the d 3 deformation post dates the lizard emplacement being related to the cornubian batholith subsequent phases represent essentially post batholith and hence post lizard emplacement deformation

inflation model of uzon caldera kamchatka constrained by satellite radar interferometry observations 1 we analyzed radarsat 1 synthetic aperture radar sar data to compute interferometric sar insar images of surface deformation at uzon caldera kamchatka russia from 2000 to 2003 approximately 0 15 m of inflation occurred at uzon caldera extending beneath adjacent kikhpinych volcano this contrasts with insar data showing no significant deformation during either the 1999 to 2000 or 2003 to 2004 time periods we performed three sets of numerical source inversions to fit insar data from three different swaths spanning 2000 to 2003 the preferred source model is an irregularly shaped pressurized crack dipping 20 to the nw 4 km below the surface the geometry of this solution is similar to the upper boundary of the geologically inferred magma chamber extension of the surface deformation and source to adjacent kikhpinych volcano without an eruption suggests that the deformation is more likely of hydrothermal origin possibly driven by recharge of the magma chamber

no evidence for thermogenic methane release in coal from the karoo ferrar large igneous province abstract the early jurassic toarcian oceanic anoxic event t oae and concurrent negative carbon isotope 13 c excursion have recently been attributed to either the release of methane ch 4 clathrates or thermogenic ch 4 gas associated with the karoo ferrar large igneous province lip into coals and organic rich shales 12 c enriched thermogenic ch 4 production associated with the karoo ferrar would result in residual material being 12 c depleted nearer the intrusions in this study geochemical analyses carbon isotopes volatile matter vm vitrinite reflectance r o are reported for two coal transects associated with dykes intruding the no 4l coal in the highveld coalfield karoo basin south africa vm decreases from over 35 to around 15 in one transect and the second transect shows a less pronounced decrease from 25 to 16 accompanying the decrease in vm content is an increase in r o from background levels of around 0 7 to over 4 adjacent to the dyke used as a palaeo geothermometer r o values indicate background temperatures of 100 c increasing to 300 c close to the contact despite changes in vm and r o there are no significant changes in 13 c certainly not of the magnitude that would be expected associated with large scale thermogenic ch 4 generation these and other gondwanan coals have low vitrinite and liptinite contents components more prone to ch 4 generation in part explaining the modest decreases in vm adjacent to the dykes this combined with the relatively narrow metamorphic aureole surrounding the intrusions and the likelihood that at least some of the volatiles generated by the intrusion were trapped as coalbed ch 4 or condensed as pyrolytic carbon suggests only limited ch 4 release in addition based on original estimates of moisture contents in these coals and the depth at time of intrusion 1 000 2 000 m the dykes would have lost most of their energy heating and evaporating water thus having very little remaining energy to generate thermogenic ch 4

hypautochthonous allochthonous coal deposition in the permian south african witbank basin no 2 seam a combined approach using sedimentology coal petrology and palaeontology abstract a suite of techniques including coal petrology micropalynology mesofossil analysis and macroscopic appearance has been used to examine the early permian south african witbank basin no 2 seam from a sample locality near ogies this coal appears to be similar in its palynological and petrographic composition to other coals of this interval from this basin however its accumulation appears to have been largely hypautochthonous or allochthonous evidenced by erosive contacts small scale cross laminations and fine lenticular bodies being recognised within the coal seam profile this ex situ deposition probably in part relates to frequent wildfire activity which may have promoted subsequent run off and erosion and led to the numerous mineral rich horizons observed in the sample seam profile in addition to the sedimentological characters described above the petrology of the seam and its mesofossils most particularly megaspores from a lycopsid parent vegetation indicate saturated peat forming conditions however examination of charred mesofossil fragments indicates periods of low humidity and even drying of the peat itself rendering it liable to combustion these contradictory characters may indicate seasonality and suggest a coldness of the climate at least for part of the year that could account for the retardation of peat decay during these drier intervals these characters can be reconciled with deposition during an interglacial phase as the dwyka glaciation terminates as has previously been proposed for the witbank basin no 2 seam

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

models of ground deformation from vertical volcanic conduits with application to eruptions of mount st helens and mount etna we present simple analytical models of ground deformation from inflation of vertical volcanic conduits or pipes we compare three cases corresponding to 1 a pressurized pipe with closed end at the top that resists the internal pressure 2 a pressurized pipe with top open for which the internal deformation is mainly dislocation of the cylindrical walls and 3 a pipe shaped region that dilates for the closed pipe we use eshelby s inclusion theory to model deformation from a thin pressurized elongated prolate ellipsoid in a full space which we express in terms of double forces to satisfy surface boundary conditions we superimpose image solutions by using double forces derived from mindlin s half space solution for the point force for the open pipe we apply the volterra integral to dislocation across a cylindrical surface and generalize it to the half space using mindlin s point force solution these two solutions show marked differences from the line of dilatation solution ratios of maximum horizontal deformation to maximum vertical deformation for the pipe models are significantly greater than values for the center or line of dilatation models this and the more gradual fall off of the deformation with distance may be used as diagnostics for discriminating between pipe like sources and dilatational sources on volcanoes where both components of the deformation field are available as examples we compare the closed pipe model with deformation associated with dome building on mount st helens volcano and tilt predicted by the open pipe model with tilt measured during a period of explosive eruptive activity on mount etna sicily in 1995 comparison between model values and the measurements suggests that the effective elastic moduli of the volcanic cones are very low

reply to the comment by iyer and schmid on thickness matters influence of dolerite sills on the thermal maturity of surrounding rocks in a coal bed methane play in botswana by bulguroglu m e milkov a v marine and petroleum geology 111 2020 219 229

persistent uplift of the lazufre volcanic complex central andes new insights from pcaim inversion of insar time series and gps data we reanalyzed the surface displacements observed at the lazufre volcanic complex in the southern andean central volcanic zone using gps measurements made between 2006 and 2008 and a large insar data set we performed a detailed spatiotemporal analysis of the displacements using a principal component analysis inversion method pcaim the pcaim reveals a source with no significant changes in shape and dimension and with a remarkably linear strength increase over the whole period of observation i e 2003 2010 then we used a three dimensional mixed boundary element method mbem to invert the first component of surface displacement as obtained from pcaim we explored a continuum of geometries from a shallow elliptic crack to a deep massive truncated elliptical cone that could represent a sill or a large magma chamber respectively the best models indicate a large flat topped source with a roof area between 40 and 670 km2 and a depth of between 2 and 14 km below ground surface lastly on the basis of the limited data available for the thermomechanical structure of the crust in the southern andean central volcanic zone we consider some possible scenarios to explain the spatial and temporal pattern of displacements at lazufre

sombrero uplift above the altiplano puna magma body evidence of a ballooning mid crustal diapir the altiplano puna ultralow velocity zone in the central andes south america is the largest active magma body in earth s continental crust space geodetic observations reported an uplift in the altiplano puna proper at a rate of 10 mm year however the nature of the inferred inflation source has been uncertain we present data showing that the uplift has persisted at a nearly constant rate over the past two decades and is surrounded by a broad zone of subsidence we show that the ongoing uplift and peripheral subsidence may result from a large mid crustal diapir fed by partial melt from the altiplano puna magma body

coal magma interaction an integrated model for the emplacement of cylindrical intrusions olivine bearing lamproite magmas intruded into permian coal seams in northeast india occur as root like cylinder stockworks extending for up to several kilometres up dip along the bedding planes of their sedimentary host clusters of eight or more conduits are typical linked by thin tubular cross branches cylindrical geometry may arise by injection of hot low viscosity fluid through a slot with the development of multiple tube like instabilities at the interface between the moving fluid and a higher viscosity host this behaviour appears more complex than the models of chouke van meurs van der pod and saffman taylor which predict the development of a single dominant tube in porous or layered flow cylinder emplacement may be an essentially passive process in which the sediment column is reduced by expulsion of heated pore fluids at the head of the moving intrusion creating a space into which the melt can propagate generation of a superheated vapour envelope by non nucleated film boiling of these fluids around the hot lamproite magma the leidenfrost effect allows melt flow to be maintained in a lengthening tube thermally insulated from the surrounding coal in a manner analogous to submarine lava tubes cooling of the magma through the nukiyama temperature the temperature at which maximum evaporation of the heated fluid occurs may give rise to violent surface boiling and the formation of large vapour bubbles at the magma coal interface implosion of these bubbles could then result in the formation of shock breccias comparable to hyaloclastites produced by bubble or surface film collapse in the vicinity of pillow lava tubes the operation of such a process around lamproite magma is suggested by the presence of complex breccias composed of highly fragmented coal sandstone and lamproite at the termini of certain cylinders surface and subsurface exposures of the cylinders reveal the presence of a carbonate chlorite clay halo surrounding each intrusion resulting from the alteration of mafic mineral phases by fugitive volatiles released from the protective vapour jacket the coal seams proximal to intrusion clusters are relatively undeformed with no evidence of assimilation by the invading melts the coals have experienced extensive carbonization probably as a result of slow conductive heating from the cooling lamproite bodies or fluids derived therefrom field observations indicate that these thermal effects are not merely confined to the coal melt interface but occur for some considerable distance away from the intrusions producing large areas of naturally coked coal

toggling of seismicity by the 1997 kagoshima earthquake couplet a demonstration of time dependent stress transfer 1 two m 6 well recorded strike slip earthquakes struck just 4 km and 48 days apart in kagoshima prefecture japan in 1997 providing an opportunity to study earthquake interaction aftershocks are abundant where the coulomb stress is calculated to have been increased by the first event and they abruptly stop where the stress is dropped by the second event this ability of the main shocks to toggle seismicity on and off argues that static stress changes play a major role in exciting aftershocks whereas the dynamic coulomb stresses which should only promote seismicity appear to play a secondary role if true the net stress changes from a sequence of earthquakes might be expected to govern the subsequent seismicity distribution however adding the stress changes from the two kagoshima events does not fully capture the ensuing seismicity such as its rate change temporal decay or migration away from the ends of the ruptures we therefore implement a stress transfer model that incorporates rate state friction in which seismicity is treated as a sequence of independent nucleation events that are dependent on the fault slip slip rate and elapsed time since the last event the model reproduces the temporal response of seismicity to successive stress changes including toggling decay and aftershock migration nevertheless the match of observed to predicted seismicity is quite imperfect due perhaps to inadequate knowledge of several model parameters however to demonstrate the potential of this approach we build a probabilistic forecast of larger earthquakes on the expected rate of small aftershocks taking advantage of the large statistical sample the small shocks afford not surprisingly such probabilities are highly time and location dependent during the first decade after the main shocks the seismicity rate and the chance of successive large shocks are about an order of magnitude higher than the background rate and are concentrated exclusively in the stress triggering zones

naturally acid waters from copahue volcano argentina volcanic acid sulfate chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals chemical data of such acid waters from copahue volcano argentina covering 8 years of observations show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface the chemical composition changed dramatically during the 2000 eruption of copahue with enhanced concentrations and fluxes of mg na fe and al followed in 2001 by rapidly declining concentrations and element fluxes the subsequent 5 years saw more variable element ratios and strong depletions in k and al most incompatible elements are released from the rock matrix stochiometrically whereas some elements are enriched through vapor input from the magma as pb zn most fluids have lree enrichments relative to the rock matrix but during periods of new magma intrusion the lree enrichment decreases as does the magnitude of the negative eu anomaly in the fluids these observations are interpreted assuming early dissolution of plagioclase olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system the high field strength elements are virtually immobile even in these hot acid fluids with nb and ta more so than hf and zr the mobility of u and th in these fluids is comparable at variance with th behavior in neutral fluids the local rivers and lakes of copahue are fertilized by volcanic dissolved p and most surface waters with ph 3 have high levels of as the acid fluids from copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early mars environments that are thought to have had large acid lakes

the karoo basin of south africa type basin for the coal bearing deposits of southern africa abstract the coal bearing sediments and coal seams of the karoo basin southern africa are described and discussed the karoo basin is bounded on its southern margin by the cape fold belt onlaps onto the kaapvaal craton in the north and is classified as a foreland basin coal seams are present within the early permian vryheid formation and the triassic molteno formation the peats of the vryheid formation accumulated within swamps in a cool temperate climatic regime lower and upper delta plain back barrier and fluvial environments were associated with peat formation thick laterally extensive coal seams have preferentially accumulated in fluvial environments the coals are in general inertinite rich and high in ash however increasing vitrinite and decreasing ash contents within seams occur from west to east across the coalfields the triassic molteno coal seams accumulated with aerially restricted swamps in fluvial environments these molteno coals are thin laterally impersistent vitrinite rich and shaly and formed under a warm temperate climatic regime palaeoclimate depositional systems differential subsidence and basin tectonics influence to varying degrees the maceral content thickness and lateral extent of coal seams however the geographic position of peat forming swamps within a foreland basin coupled with basin tectonics and differential subsidence are envisaged as the primary controls on coal parameters the permian coals are situated in proximal positions on the passive margin of the foreland basin here subsidence was limited which enhanced oxidation of organic matter and hence the formation of inertinitic coals the coals in this tectonic setting are thick and laterally extensive the triassci coals are situated within the tectonically active foreland basin margin rapid subsidence and sedimentation rates occurred during peat formation which resulted in the preservation of thin laterally impersistent high ash vitrinite rich shaly coals

neotectonics in the foothills of the southernmost central andes 37 38 s evidence of strike slip displacement along the antinir copahue fault zone 1 the antinir copahue fault zone acfz is the eastern orogenic front of the andes between 38 and 37 s it is formed by an east vergent fan of high angle dextral transpressive and transtensive faults which invert a paleogene intra arc rift system in an out of sequence order with respect to the cretaceous to miocene fold and thrust belt 3 1 1 7 ma volcanic rocks are folded and fractured through this belt and recent indicators of fault activity in unconsolidated deposits suggest an ongoing deformation in spite of the absence of substantial shallow seismicity associated with the orogenic front neotectonic studies show the existence of active faults in the present mountain front the low shallow seismicity could be linked to the high volumes of retroarc derived volcanic rocks erupted through this fault system during pliocene and quaternary times this thermally weakened basement accommodates the strain of the antinir copahue fault zone absorbing the present convergence between the south america and nazca plates

paleodepositional environments and tectonosedimentary controls of the postglacial permian coals karoo basin south africa abstract coal deposits of the karoo basin in south africa are contained within an 80 250 m thick clastic sequence designated the vryheid formation this formation constitutes part of the ecca group of the karoo sequence and contains several mineable bituminuos coal and anthracite beds and sporadic coking coal seams the sedimentary succession was deposited during the early permian following the late carboniferous dwyka ice age paleoclimate initially influenced the paleodepositional environments which for the lowermost stages comprised glaciofluvinal outwash braided plain deposits overlying minor deltaic and glaciolacustrine fill the early permian floral assemblages attest to a cool temperature climatic regime in the extreme northern parts of the basin the lowermost coals frequently directly overlie dwyka diamictite or pre karoo basement paleodepositional systems associated with the coals above the glaciogenic succession consisted predominantly of regressive fluviodeltaic facies assemblages in the northern regions regressive deltaic lobes prograded rapidly basinward across the relatively shallow intracratonic platform in the northeast areas greater subsidence rates were accompanied by multiple stacking of regressive deltaic cycles in several areas of the coalfields peat accumulation was associated with the bed load braided fluvial systems these subsequently modified the underlying deltaic deposits by intense and deep erosion that removed portions of the underlying stratigraphy smaller scale syndepositional anastomosed rivers which were contemporaneous with certain peat swamps locally controlled seam distribution and adversely affected coal seam quality coal distribution was directly controlled a the tectonic setting b the nature of the pre karoo basement lithologies c the basement paleotopography and d the paleodepositional systems associated with and following peat formation the coalfields are restricted to a relatively small area in the northern and northeastern parts of the karoo basin where a stable intracratonic shelf provided a suitable tectonic setting for peat accumulation resistant basement lithologies orthoquartzite and felzite produced positive topographic relief while easily weatehred archean granite basement terrain left residual topographic depressions that were later extensively filled by sediment differential compaction of fine sediment mud and silt deposited over the diverse basement topography provided further subtle controls on coal seam thickness sediments and coal overlying basement highs compacted significantly causing thinning and a draping effect of the sedimentary cover in contrast paleovalleys contained substantial thickness of sediment and host some of the thickest seams these coals can however thin and shale out against the adjacent elevated valley flanks the paleovalley coals were further affected by multiple seam splits produced by fluvial channels that contemporaneously occupied the lowland areas

how contact metamorphism can trigger global climate changes modeling gas generation around igneous sills in sedimentary basins abstract large volumes of greenhouse gases such as ch4 and co2 form by contact metamorphism of organic rich sediments in aureoles around sill intrusions in sedimentary basins thermogenic gas generation and dehydration reactions in shale are treated numerically in order to quantify basin scale devolatilization we show that aureole thicknesses defined as the zone of elevated metamorphism relative to the background level vary within 30 250 of the sill thickness depending on the temperature of the host rock and intrusion besides the sill thickness in shales with total organic carbon content of 5 wt ch4 is the dominant volatile 85 135 kg m3 generated through organic cracking relative to h2o generation from dehydration reactions 30 110 kg m3 even using conservative estimates of melt volumes extrapolation of our results to the scale of sill complexes in a sedimentary basin indicates that devolatilization can have generated 2700 16200 gt ch4 in the karoo basin south africa and 600 3500 gt ch4 in the voring and more basins offshore norway the generation of volatiles is occurring on a time scale of 10 1000 years within an aureole of a single sill which makes the rate of sill emplacement the time constraining factor on a basin scale this study demonstrates that thousands of gigatons of potent greenhouse gases like methane can be generated during emplacement of large igneous provinces in sedimentary basins

revisiting the thermally metamorphosed coals of the transantarctic mountains antarctica abstract petrographic and geochemical data for late permian coals and carbonaceous shales from the transantarctic mountains antarctica source polar rock repository prr were used to evaluate maturation levels and assess the effects of contact metamorphism coals were evaluated for locations in the southern transantarctic mountains the central transantarctic mountains and south victoria land including samples from the buckley mt glossopteris and queen maud formations and the weller coal measures these formations have been intruded by sills and dikes of the jurassic ferrar group 177 183 ma associated with the breakup of gondwanaland proximate 129 samples total sulfur 69 analyses vitrinite reflectance analysis 92 and petrographic composition 34 were determined one third of the samples have 50 ash yields dry basis a subset of samples 87 with 7 thus vm does not reveal true rank of the antarctic coals vitrinite reflectance rr typically surpasses that of inertinite the vm rr relationship for these coals does not follow that of coals matured by normal burial maturation but more closely follows that of intruded coals coke textures including isotropic coke and anisotropic mosaics vacuoles pyrolytic carbon and coked bitumen are observed indicating alteration by contact metamorphism and providing insights to the rank of the coal at the time of intrusion coarse grained circular and fine grained lenticular mosaic textures suggest coal rank at the time of intrusion was medium volatile bituminous coal maximum vitrinite reflectance 1 2 this would imply a burial depth by time of intrusion of 5 5 5 km assuming 25 c km or 4 km assuming 34 c km modern day background reflectance levels of 2 5 rr indicate continued post intrusion maturation possibly due to exposure to higher regional heat flow coals and carbonaceous shales from the polar rock repository prr can provide reliable petrographic and maturation data using reflectance to help decipher the burial history for various parts of the transantarctic mountains however geochemical data must be used with caution due to the high original inorganic content and possible formation of gypsum and changes in vm during long term storage hcl treatment removes some of the neoformed minerals but samples should be treated extensively with hcl hf to remove all silicate minerals prior to proximate and ultimate analysis to ensure more reliable data

an extraordinary episode of yellowstone caldera uplift 2004 2010 from gps and insar observations 1 geodetic measurements of yellowstone ground deformation from 2006 to june 2010 reveal deceleration of the recent uplift of the yellowstone caldera following an unprecedented period of uplift that began in 2004 in 2006 2008 uplift rates decreased from 7 to 5 cm yr and 4 to 2 cm yr in the northern and southwest caldera respectively and in 2009 rates further reduced to 2 cm yr and 0 5 cm yr in the same areas elastic dislocation modeling of the deformation data robustly indicates an expanding sill at 7 10 km depth near the top of a seismically imaged crystallizing magma reservoir with a 60 decrease in the volumetric expansion rate between 2006 and 2009 reduction of hydrothermal volcanic recharge from beneath the northeast caldera and seismic moment release of the 2008 and 2010 large earthquake swarms are plausible mechanisms for decelerating the caldera uplift and may have influenced the change in recent caldera motion from uplift to subsidence

the interpretation of gravity changes and crustal deformation in active volcanic areas simple models like the well known point source of dilation mogi s source in an elastic homogeneous and isotropic half space are widely used to interpret geodetic and gravity data in active volcanic areas this approach appears at odds with the real geology of volcanic regions since the crust is not a homogeneous medium and magma chambers are not spheres in this paper we evaluate several more realistic source models that take into account the influence of self gravitation effects vertical discontinuities in the earth s density and elastic parameters and non spherical source geometries our results indicate that self gravitation effects are second order over the distance and time scales normally associated with volcano monitoring for an elastic model appropriate to long valley caldera we find only minor differences between modeling the 1982 1999 caldera unrest using a point source in elastic homogeneous half spaces or in elasto gravitational layered half spaces a simple experiment of matching deformation and gravity data from an ellipsoidal source using a spherical source shows that the standard approach of fitting a center of dilation to gravity and uplift data only excluding the horizontal displacements may yield estimates of the source parameters that are not reliable the spherical source successfully fits the uplift and gravity changes overestimating the depth and density of the intrusion but is not able to fit the radial displacements

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

40ar 39ar ages of the sill complex of the karoo large igneous province implications for the pliensbachian toarcian climate change 1 reliable geochronological results gathered so far n 76 have considerably constrained the timing of the emplacement of the karoo large igneous province lip yet strikingly missing from this dating effort is the huge southern sill complex cropping out in the 0 6 106 km2 main karoo sedimentary basin we present 16 new 40ar 39ar analyses carried out on fresh plagioclase and biotite separates from 15 sill samples collected along a n s trend in the eastern part of the basin the results show a large range of plateau and miniplateau ages 176 2 1 3 to 183 8 2 4 ma with most dates suggesting a 3 ma 181 184 ma duration for the main sill events the available age database allows correlation of the karoo lip emplacement with the pliensbachian toarcian second order biotic extinction the global warming and the toarcian anoxic event provided that adequate calibration between the 40k and 238u decay constant is made the mass extinction and the isotopic excursions recorded at the base of the toarcian appear to be synchronous with both the increase of magma emission of the karoo lip and the emplacement of the sills the co2 and so2 derived from both volcanic emissions as well as carbon rich sedimentary layers intruded by sills might be the main culprits of the pliensbachian toarcian climate perturbations we propose that the relatively low eruption rate of the karoo lip is one of the main reasons explaining why its impact on the biosphere is relatively low contrary to e g the camp triassic jurassic and siberia permo triassic lips

thickness matters influence of dolerite sills on the thermal maturity of surrounding rocks in a coal bed methane play in botswana abstract global studies suggest that igneous intrusions usually have thermal aureole thicknesses between 30 and 250 of the intrusion thickness here we discuss data and 1d thermal maturity models from nine coreholes wells drilled in botswana to explore for coal bed gas the coreholes penetrated multiple dolerite sills with thicknesses ranging from 1 2 m to 73 4 m the sills intruded the sedimentary rocks in the jurassic period and significantly affected the rank properties and thermal maturity of permian coals the thermal influence of the sills extends for 5 53 m away from their contacts with surrounding rocks the relatively thick 13 m sills have thermal aureole thicknesses of 31 137 of the sill thickness in line with global observations however the relatively thin 1000 of the sill thickness significantly larger than previously reported from most other locations affected by igneous intrusions thin sill intrusions in coals and organic rich shales may lead to the generation of larger volumes of ch4 other hydrocarbon gases and co2 than previously thought affecting the safety in coal mines and gas resources

formation temperatures of natural coke in the lower silesian coal basin poland evidence from pyrite and clays by sem edx abstract the purpose of this paper is to show how sem edx can be applied in a study of coals altered to coke by a magnetic intrusion sem photographs reveal some textural features of a natural coke which would not be detectable using optical microscopy the similarity between images of natural and artificial coke is proof that temperatures over 350 c were experienced during contact metamorphosis crystal shapes of minerals are presented as evidence of hydrothermal activity in the contact zone and an average temperature level below 575 c pyrite is used as a geological thermometer its shape and composition showing the occurrence of incidental hot spots 750 c in contact with the dyke

the coalification of south african coal abstract it has been generally accepted that the variation in rank of south african coal is essentially due to the metamorphic effect of dolerite dykes and sills however no satisfactory explanation could be given for the fact that true anthracite has not been formed adjacent to dykes and transgressive sills in those south african coal fields where the rank of the coal is normally low in these areas the coal close to the intrusives is often referred to as burnt a detailed examination of the contact metamorphism of south african coal by dolerite intrusives shows that a dyke or sill affects the coal to variable distances generally from 0 6 to 2 times the thickness of the intrusive and that this distance is independent of the rank of the coal outside the contact aureole this is explained by an initial episode of contact metamorphism while the coal was still in the lignite stage of coalification followed by burial metamorphism during which the paleogeothermal gradient increased in an easterly direction this regional increase in paleogeothermal gradient is probably related to the large scale magmatic activity that culminated in the extrusion of the drakensberg basalts and the break up of gondwanaland

effects of igneous intrusions on coalbed methane potential gunnedah basin australia abstract the gunnedah basin nsw australia contains more than 500 gt of coal and has been the subject of recent coalbed methane exploration large areas of the basin contain igneous intrusions and large areas of coal have been heat affected as a consequence a detailed study has been undertaken of coal seams intersected in a cored coalbed methane exploration drillhole in which two sill form igneous intrusions are present comparisons are made between coals that are unaltered and coals that have been heat affected using petrographic and chemical data coal seam gas desorption data and gas chemical analysis data results demonstrate that the two igneous intrusions have had a very positive effect on coalbed methane development the gas content in a number of heat affected coal seams within thermal aureoles above and below the sills is substantially higher than in adjacent unaffected coal seams in addition the intrusions have had little effect on gas quality the coals in the heat affected zone were found to contain gas with approximately 95 methane the coals in the thermal aureoles were found under the microscope to contain characteristic micropores and slits which collectively may serve to enhance gas adsorption capacity permeability and gas desorption gas contents below each of the sills is substantially higher than above the sill confirming earlier results that the sills appear to have acted as a reservoir seal during and for some time after intrusion the background coal rank in acm yannergee ddh 1 is in the high volatile bituminous range the igneous intrusions have resulted in an increase in rank such that large areas of coal have moved into the optimal thermogenic gas generation window this rank increase has affected a major part of the coal bearing sequence

gas geochemistry of the magmatic hydrothermal fluid reservoir in the copahue caviahue volcanic complex argentina abstract copahue volcano is part of the caviahue copahue volcanic complex ccvc which is located in the southwestern sector of the caviahue volcano tectonic depression argentina chile this depression is a pull apart basin accommodating stresses between the southern liquine ofqui strike slip and the northern copahue antinir compressive fault systems in a back arc setting with respect to the southern andean volcanic zone in this study we present chemical inorganic and organic and isotope compositions 13c co2 15n 3he 4he 40ar 36ar 13c ch4 d ch4 and d h2o and 18o h2o of fumaroles and bubbling gases of thermal springs located at the foot of copahue volcano sampled in 2006 2007 and 2012 helium isotope ratios the highest observed for a southern american volcano r ra up to 7 94 indicate a non classic arc like setting but rather an extensional regime subdued to asthenospheric thinning 13c co2 values from 8 8 to 6 8 vs v pdb 15n values 5 3 to 5 5 vs air and co2 3he ratios from 1 4 to 8 8 109 suggest that the magmatic source is significantly affected by contamination of subducted sediments gases discharged from the northern sector of the ccvc show contribution of 3he poor fluids likely permeating through local fault systems despite the clear mantle isotope signature in the ccvc gases the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water gas geothermometry in the h2o co2 ch4 co h2 system suggests that co and h2 re equilibrate in a separated vapor phase at 200 220 c on the contrary rock fluid interactions controlling co2 ch4 production from sabatier reaction and c3h8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250 to 300 c fumarole gases sampled in 2006 2007 show relatively low n2 he and n2 ar ratios and high r ra values with respect to those measured in 2012 such compositional and isotope variations were likely related to injection of mafic magma that likely triggered the 2000 eruption therefore changes affecting the magmatic system had a delayed effect on the chemistry of the ccvc gases due to the presence of the hydrothermal reservoir however geochemical monitoring activities mainly focused on the behavior of inert gas compounds n2 and he should be increased to investigate the mechanism at the origin of the unrest started in 2011

maceral types in some permian southern african coals abstract a suite of permian gondwana coals from southern africa exclusive of the republic of south africa were examined petrographically with the exception of a single low volatile bituminous semi anthracite coal from mozambique the coal rank is high volatile bituminous c most coals were dominated by inertinite group macerals primarily semifusinite and detrital inertinite inertodetrinite but with significant secretinite in some cases vitrinite group macerals were absent in several zambian coals when considering these coals it becomes apparent that not all gondwana maceral types determined necessarily fit the iccp definitions

deformation of copahue volcano inversion of insar data using a genetic algorithm abstract the copahue volcano is one of the most active volcanoes in argentina with eruptions having been reported as recently as 1992 1995 and 2000 a deformation analysis using the differential synthetic aperture radar technique dinsar was performed on copahue caviahue volcanic complex ccvc from envisat radar images between 2002 and 2007 a deformation rate of approximately 2 cm yr was calculated located mostly on the north eastern flank of copahue volcano and assumed to be constant during the period of the interferograms the geometry of the source responsible for the deformation was evaluated from an inversion of the mean velocity deformation measurements using two different models based on pressure sources embedded in an elastic homogeneous half space a genetic algorithm was applied as an optimization tool to find the best fit source results from inverse modelling indicate that a source located beneath the volcano edifice at a mean depth of 4 km is producing a volume change of approximately 0 0015 km yr this source was analysed considering the available studies of the area and a conceptual model of the volcanic hydrothermal system was designed the source of deformation is related to a depressurisation of the system that results from the release of magmatic fluids across the boundary between the brittle and plastic domains these leakages are considered to be responsible for the weak phreatic eruptions recently registered at the copahue volcano

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

evolution of unrest at laguna del maule volcanic field chile from insar and gps measurements 2003 to 2014 the laguna del maule ldm volcanic field in the southern volcanic zone of the chilean andes exhibits a large volume of rhyolitic material erupted during postglacial times 20 2 ka since 2007 ldm has experienced an unrest episode characterized by high rates of deformation analysis of new gps and interferometric synthetic aperture radar insar data reveals uplift rates greater than 190 mm yr between january 2013 and november 2014 the geodetic data are modeled as an inflating sill at depth the results are used to calculate the temporal evolution of the vertical displacement the best time function for modeling the insar data set is a double exponential model with rates increasing from 2007 through 2010 and decreasing slowly since 2010 we hypothesize that magma intruding into an existing silicic magma reservoir is driving the surface deformation modeling historical uplift at yellowstone long valley and three sisters volcanic fields suggests a common temporal evolution of vertical displacement rates

thermal maturity evaluation of dispersed organic matter inclusions from kimberlite pipes lac de gras northwest territories canada abstract dispersed organic matter dom inclusions have been recovered from crater diatreme and diatreme xenoliths within hypabyssal facies of diamondiferous kimberlite pipes in the lac de gras region of northwest territories canada incident white and fluorescent light microscopy has been used to study vitrinite and liptinite dom xenoliths in the pipes percent reflectance in oil ro of wood derived vitrinite visible light region fluorescence properties of sporinite cutinite and resinite and changes in maceral morphology have been used to evaluate thermal alteration within the kimberlite pipes temperature estimates for different thermal zones in the kimberlite pipes have been inferred by comparing vitrinite reflectance with data from rapid pyrolysis experiments conducted on low rank vitrinites crater facies dom consists of very low reflecting 20 to 200 c to a maximum of 650 c the presence of petroleum derived cokes are consistent with estimates of 400 450 c for samples recovered close to and within hypabyssal dykes and macrocrystic breccia and massive hypabyssal facies below this zone tuffisitic kimberlites are marked by a reduction in vitrinite reflectance 0 5 to 1 8 ro and a lower inferred alteration temperature estimated at 200 to 450 c anomalous populations of very low reflecting partially devolatilized vitrinite 0 50 to 0 84 ro in this zone may have suppressed reflectance possibly a consequence of liquefaction like conditions and impregnation by oily bitumens produced during pyrolysis of associated liptinite macerals

magma ascent and the pressurization of mount etna s volcanic system after a period of deflation during the 1991 1993 flank eruption mount etna underwent a rapid inflation seismicity and ground deformation show that since 1994 a huge volume of magma intruded beneath the volcano producing from 1998 onward a series of eruptions at the summit and on the flank of the volcano the last of these started on 27 october 2002 is still in progress and can be considered one of the most explosive eruptions of the volcano in recent times here we show how geodetic data and seismic deformation between 1994 and 2001 indicate a radial compression around an axial intrusion consistent with a repressurization of mount etna s plumbing system at a depth of 6 to 15 kilometers which triggered most of the seismicity and provoked the dilatation of the volcano and the recent explosive eruptive activity

coalification trends in indian coals abstract a study of the coalification trends of indian coals covering a wide range of geological age permian eocene to pleistocene shows a progressive transition in physico chemical and optical properties from peat to semianthracite the relation between the maximum reflectance in oil of huminite vitrinite and volatile matter or fixed carbon has been found to be similar to that of the normally coalified british carboniferous coals also the coalification trend of indian coals measured in terms of elemental carbon and hydrogen appears to follow seyler s band and is similar to the normally coalified british carboniferous coals although coals of the two hemispheres follow the same normal coalification course their physical chemical and petrographical characters differ depending on the petrographic composition i e the macerals microlithotype and mineral matter contents the petrographic composition of a coal appears to be essentially controlled by the nature of the peat paleodepth paleotemperature and paleoheating in the coal basins

the inherent moisture content of south african permian coals abstract the inherent moisture content im of coals impinges on many usages but little is known about the controls on this parameter in gondwana coals in the permian coals of the main karoo basin the chief mediator of im on as as received basis is rank which is determined by regional and contact metamorphism independent of burial depth mineral matter content and maceral composition are ancilliary controls the relationship between im and rank is inverse up to the anthracite meta anthracite boundary where development of secondary porosity causes im to rise sharply northern transvaal coals deposited in structural basis separate from the main karoo basin are strongly deficient in im relative to northern hemisphere coals of equivalent rank and type pressure generated by tectonism may explain this anomaly

the relationship between organic maturation the widths of thermal aureoles and the thicknesses of sills in the midland valley of scotland and northern england the contrasting nature of thermal aureoles that surround mid carboniferous alkaline dolerite sills and early permian quartz dolerite silk of the midland valley of scotland and northern england is described the development of the aureoles is influenced by the degree of consolidation of the sediments their volume of pore water when invaded by the magma the time period between deposition of the invaded sediments and emplacement of the intrusion and the degree of organic maturation at the time of intrusion a correlation exists between the logarithms of the thicknesses of sills and thermal aureoles of the quartz dolerites equivalent data for the alkaline dolerites lie more than two standard errors from the regression line for the quartz dolerite plots

source model for the copahue volcano magma plumbing system constrained by insar surface deformation observations copahue volcano straddling the edge of the agrio caviahue caldera along the chile argentina border in the southern andes has been in unrest since inflation began in late 2011 we constrain copahue s source models with satellite and airborne interferometric synthetic aperture radar insar deformation observations insar time series from descending track radarsat 2 and cosmo skymed data span the entire inflation period from 2011 to 2016 with their initially high rates of 12 and 15 cm yr respectively slowing only slightly despite ongoing small eruptions through 2016 insar ascending and descending track time series for the 2013 2016 time period constrain a two source compound dislocation model with a rate of volume increase of 13 106 m3 yr they consist of a shallow near vertical elongated source centered at 2 5 km beneath the summit and a deeper shallowly plunging source centered at 7 km depth connecting the shallow source to the deeper caldera the deeper source is located directly beneath the volcano tectonic seismicity with the lower bounds of the seismicity parallel to the plunge of the deep source insar time series also show normal fault offsets on the ne flank copahue faults coulomb stress change calculations for right lateral strike slip rlss thrust and normal receiver faults show positive values in the north caldera for both rlss and normal faults suggesting that northward trending seismicity and copahue fault motion within the caldera are caused by the modeled sources together the insar constrained source model and the seismicity suggest a deep conduit or transfer zone where magma moves from the central caldera to copahue s upper edifice

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

genesis and evolution of unrest episodes at campi flegrei caldera the role of thermal fluid dynamical processes in the geothermal system we develop a model for describing water flow in a porous medium under the effect of thermal and pressure gradients the model simulates geothermal systems in calderas given the boundary conditions and the fluid dynamical properties of the medium the model allows computation in fluid dynamical stationary states of parameters characterizing the flow such as flow velocity and temperature and pressure distributions at depth the model is applied to investigate the effects of the local geothermal system on the unrest episodes at campi flegrei caldera using experimentally determined fluid dynamical parameters for the caldera rocks we show that changes of water flow in shallow aquifers under the effect of pressure and or temperature variations within the geothermal system can be very important in the genesis and evolution of unrest crises in particular they can strongly amplify the effect of pressure increase in the magma chamber on ground uplift they can also explain the timescales of evolution of ground movements in terms of transit times of the water front and of the connected temperature fronts due to advective transport on such grounds an integrated mechanic thermal fluid dynamical model was built allowing us to give a semiquantitative global explanation to the genesis and evolution of unrest phenomena results obtained here can be generalized to other similar calderas

notes on the mechanisms of coal metamorphism in the pennsylvania anthracite fields abstract charred devolatilized megasporinite and featureless vitrinite with devolatilization pores filled with pyrolytic carbon suggest that eastern pennsylvania anthracites may have been altered by to localized episodes of metamorphism from superheated steam co2 co hydrocarbons in addition to the pervasive regional metamorphism based on the extant vitrinite textures the lack of mesophase anisotropic textures and on comparisons to laboratory studies of the thermoplasticity of bituminous coals the rank at the time of metamorphism would have been high volatile c or lowermost high volatile b bituminous the temperature of alteration would have been in the 350 400 c range corresponding to the critical point of steam 374 15 c and 22 1 mpa about 1 km depth it is speculated that while increased pressure would have prolonged the duration of fluid properties fluidity is still a transient property and the vitrinite would have returned to a solid state after a few hours the heat would have persisted dissipating over the course of days to months to years depending upon the depth and ambient pre heating geothermal gradient but contributing to the coal metamorphism long after the vitroplast solidified

carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at copahue caviahue volcanic complex argentina abstract the north western sector of caviahue caldera argentina close to the active volcanic system of copahue is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions anomalous soil diffuse degassing of co2 and hot soils in march 2014 measurements of soil co2 fluxes in 5 of these sites namely las maquinas las maquinitas i las maquinitas ii anfiteatro and termas de copahue allowed an estimation that 165 t of deeply derived co2 is daily released the gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges gas equilibria within the h c o gas system indicate the presence of a large probably unique single phase vapor zone at 200 210 c feeding the hydrothermal manifestations of las maquinas las maquinitas i and ii and termas de copahue a natural thermal release of 107 mw was computed by using co2 as a tracer of the original vapor phase the magmatic signature of the incondensable fumarolic gases the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the caviahue caldera