geomorphometric analysis of the 2014 2015 barðarbunga volcanic eruption iceland abstract topographical information is of fundamental interest for a wide range of disciplines including glaciology agriculture communication network planning or hazard management in volcanology elevation data are of particular importance when assessing material flows throughout a volcanic system to obtain accurate estimates of time varying topography in volcanic active regions high resolution digital elevation models dems are required to monitor and evaluate topographical changes and especially volumetric gains and losses during the 2014 2015 bar arbunga eruption iceland multi temporal tandem x dem sequences were evaluated the 2014 2015 volcanic eruption was associated with the rare event of a caldera collapse visible on the surface of the vatnajokull glacier as well as major lava effusion in the holuhraun plain before investigating topographical change at the two study areas the tandem x dems were analysed for absolute and relative height errors resulting from the radar system parameters the sar processing or the local environment the uncertainty investigation determined that acquisitions over the snow covered bar arbunga caldera were primarily affected by microwave penetration into snow and dems over the holuhraun lava field exhibited increased height errors due to active lava flows and dynamic outwash plain the topographical analysis of the 2014 2015 bar arbunga eruption revealed a maximum vertical displacement of approximately 65 m and 43 m at the study area of the bar arbunga caldera and holuhraun lava field respectively with a total subsidence volume of 1 40 0 13 km3 and a dense rock equivalent dre lava volume of 1 36 0 07 km3 known uncertainties in volume were decreased by approximately 35 and 77 accordingly taking into account the calculation of rates the temporal development of caldera collapse and lava effusion was found to exhibit a near exponential decrease the ratio between subsidence and dre lava volume moreover indicated the coupling between piston collapse and magma drainage

the dissolution kinetics of brucite antigorite talc and phlogopite at room temperature and pressure dissolution experiments were done on a series of layer type mg minerals brucite antigorite talc and phlogopite of progressively more complex structure and chemical composition twenty five gram portions of these minerals were dry ground to 400 mesh and then subjected to controlled dissolution in distilled water at 25 c and i atm co2 partial pressure for antigorite talc and phlogopite mg from the octahedral sheets was released more rapidly than was si from the tetrahedral sheets r e the dissolution was incongruent it appears that the solubility of these layer type minerals is related to the relative number of octahedral to tetrahedral sheets present in the structure i e the dissolution kinetics of layer type silicate minerals is controlled bv the rate of destruction of the tetrahedral silica sheets of the mineral

basaltic calderas collapse dynamics edifice deformation and variations of magma withdrawal 1 the incremental caldera collapses of fernandina 1968 miyakejima 2000 and piton de la fournaise 2007 are analyzed in order to understand the collapse dynamics in basaltic setting and the associated edifice deformation for each caldera the collapse dynamics is assessed through the evolution of the 1 time interval t between two successive collapse increments 2 amount of vertical displacement during each collapse increment and 3 magma outflow rate during the whole collapse caldera process we show from the evolution of t that piton de la fournaise and fernandina were characterized by a similar collapse dynamics despite large differences in the caldera geometry and the duration of the whole collapse caldera process this evolution significantly differs from that of miyakejima where t strongly fluctuated throughout the whole collapse process quantification of the piston vertical displacements enables us to determine the magma outflow rates between each collapse increment displacement data tiltmeter and or gps for piton de la fournaise and miyakejima are used to constrain the edifice overall deformation and the edifice deformation rates these data reveal that both volcanoes experienced edifice inflation once the piston collapsed into the magma chamber such a deformation which lasts during the first collapse increments only is interpreted as the result of larger volume of piston intruded in the magma chamber than magma withdrawn before each collapse increment once the effect of the collapsing rock column vanishes edifice deflates we also determine for each caldera the critical amount of magma evacuated before collapse initiation and compare it to analog models the significant differences between models and nature are explained by the occurrence of preexisting weak zones in nature i e the ring faults that are not taken into account in analog models finally we show that t at piton de la fournaise and fernandina was equally controlled by the frictional resistance along the ring faults and the magma outflow rate in addition to these two parameters the collapse dynamics of miyakejima was also influenced by variations of the magma bulk modulus which changed after the influx of deep gas rich magma into the collapse related magma chamber altogether our results show that the dynamics of caldera collapse in basaltic volcanoes proceeds in two phases phase 1 starting with the first collapse is characterized by the largest collapse amplitude an incremental edifice inflation and a step by step increase of the rate of magma outflow phase 2 shows a rapid decrease of the magma discharge rate to a low level concomitant with the continuous edifice deflation if deep magma is injected into the magma chamber as at miyakejima an additional phase occurs phase 3

the transformation of nesquehonite to hydromagnesite in the system cao mgo h20 co2 an experimental spectroscopic study abstract this study reports the nature of the nesquehonite to hydromagnesite transition at 52 c in an aqueous medium hosting magnesian calcite and nesquehonite the latter mineral occurs with abundant calcite at the floor of the experimental chamber substrate and as a film of needles at the interface between the mother liquor and the atmosphere surface film the experimental vessel was held at 52 c for 336 h and at 60 c for a further 192 h precipitates were analyzed by fourier transform ft raman augmented by ft infrared and x ray diffraction at 52 c hydromagnesite and dypingite occur with abundant quantities of a hitherto unreported transitory magnesium hydrate carbonate tmhc together with huntite magnesian calcite and traces of nesquehonite and monohydrocalcite the ft raman spectra of the first formed hydromagnesite crystals contain the raman forbidden v2 mode interpreted to indicate a relaxation in selection rules caused by rapid precipitation hydromagnesite growth at the expense of t

modelling satellite derived magma discharge to explain caldera collapse many effusive eruptions are characterized by effusion rates that decay exponentially with time a trend which is generally ascribed to elastic relaxation of a deep magma chamber thermal emissions detected by satellite during the a d 2014 2015 bar arbunga holuhraun eruption iceland indicate that the volume of the erupted magma and effusion rates followed an overall exponential trend that fits the observed major subsidence of the bar arbunga caldera floor this trend continued until a critical flow rate was reached hence the subsidence slowed down and the eruption rapidly ceased reflecting the ultimate closure of the magma path we present a model of inelastic magma withdrawal that very closely reproduces all the observed phenomena and provides new insights into the caldera collapses and the driving pressure of other effusive eruptions

experimental determination of the effect of dissolved co2 on the dissolution kinetics of mg and ca silicates at 25 c dissolution rates of diopside forsterite fo100 and fo92 wollastonite and hornblende were measured at 25 c in nacl solutions as a function of ph 1 ph 12 pco2 0 and 1 atm and activity of hco3 and co32 10 5 co2 0 1 m dissolution rates of diopside forsterite and horneblende are not affected within the experimental uncertainty by 1 atm pco2 at ph 4 and by the presence of bicarbonate up to 0 1 m and carbonate up to 0 01 m ions at ph of 8 and 11 12 respectively although wollastonite dissolution rates are unaffected by pco2 at ph 4 its rates are increased by the presence of hco3 at 0 01 hco3 0 1 m and ph 7 8 and decreased slightly by co32 at co32 0 0001 m and ph 12 these results should be useful for modeling the effect of silicate rock weathering on the global biogeochemical cycle of carbon for the first time we were able to distinguish the net effect of pco2 versus that of ph it is observed in general accord with previous results that the direct effect of co2 on basic silicates dissolution rates is very weak as a result the major parameter governing basic silicates dissolution is ph of soil solutions in contact with minerals

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

chronology and products of the 2000 eruption of miyakejima volcano japan lateral migration of magma away from miyakejima volcanic island japan generated summit subsidence associated with summit explosions in the summer of 2000 an earthquake swarm beneath miyakejima began on the evening of 26 june 2000 followed by a submarine eruption the next morning strong seismic activity continued under the sea from beneath the coast of miyakejima to a few tens of kilometers northwest of the island summit eruptive event began with subsidence of the summit on 8 july and both explosions and subsidence continued intermittently through july and august the most intense eruptive event occurred on 18 august and was vulcanian to subplinian in type ash lofted into the stratosphere fell over the entire island and abundant volcanic bombs were erupted at this time another large explosion took place on 29 august this generated a low temperature pyroclastic surge which covered a residential area on the northern coast of the island the total volume of tephra erupted was 9 3 106 m3 dre much smaller than the volume of the resulting caldera 6 108 m3 migration of magma away from miyakejima was associated with crustal extension northwest of miyakejima and coincident shrinkage of miyakejima island itself during july august 2000 this magma migration probably caused stoping of roof rock into the magma reservoir generating subsurface cavities filled with hydrothermal fluid and or magmatic foam and formation of a caldera oyama caldera at the summit interaction of hydrothermal fluid with ascending magma drove a series of phreatic to phreatomagmatic eruptions it is likely that new magma was supplied to the reservoir from the bottom during waning stage of magma s migration resulting in explosive discharge on 18 august the 18 august event and phreatic explosions on 29 august produced a conduit system that allowed abundant so2 emission as high as 460 kg s 1 after the major eruptive events were over at the time of writing inhabitants of the island about 3 000 have been evacuated from miyakejima for more than 3 years

the collapse of barðarbunga caldera iceland lying below vatnajokull ice cap in iceland bar arbunga stratovolcano began experiencing wholesale caldera collapse in 2014 august 16 one of the largest such events recorded in the modern instrumental era simultaneous with this collapse is the initiation of a plate boundary rifting episode north of the caldera observations using the international constellation of radar satellites indicate rapid 50 cm d 1 subsidence of the glacier surface overlying the collapsing caldera and metre scale crustal deformation in the active rift zone anomalous earthquakes around the rim of the caldera with highly nondouble couple focal mechanisms provide a mechanical link to the dynamics of the collapsing magma chamber a model of the collapse consistent with available geodetic and seismic observations suggests that the majority of the observed subsidence occurs aseismically via a deflating sill like magma chamber

how the development of magma chambers affects collapse calderas insights from an overview here we review the studies of pluton emplacement and caldera collapse proposing a model linking the two processes the shallow rise of magma occurs by dyking and its emplacement occurs along major anisotropies many plutons are emplaced at subhorizontal discontinuities forming sills these will eventually grow forming laccoliths the most common mechanism to store shallow magma calderas are a surface expression of these reservoirs and can be approximated by a piston cylinder which sinks due to 1 underpressure in the reservoir producing outward dipping reverse faults 2 overpressure within a silllike chamber undergoing doming and 3 overpressure within a laccolith generating apical tensile stresses in the latter two cases inward dipping normal faults form we suggest that collapse calderas are the surface expression of pressure variations within laccoliths or tabular intrusions their geometric relationships depend on the shape and aspect ratio of the intrusion and its pressure conditions tabular intrusions generating ring faults mainly at their tips form calderas with a similar width to the intrusion laccoliths may generate ring faults along the intrusion roof forming calderas narrower than the intrusion the outward or inward dip of the caldera faults results from the underpressure or overpressure conditions within the

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

formation of oskjuvatn caldera at askja north iceland mechanism of caldera collapse and implications for the lateral flow hypothesis the oskjuvatn caldera at askja volcano north iceland was formed as a result of an explosive eruption at askja on 28th 29th march 1875 oskjuvatn is one of the youngest collapse calderas on earth and its initiation and growth were observed and documented by explorers and geologists working in the askja region between 1875 and 1932 it is an example of caldera formation where the volume of the caldera collapse far exceeds the volume of associated erupted products the discrepancy between the collapse volume and associated erupted products has been used by previous workers as a justification for the hypothesis that the injection of lateral dykes from askja fed the february to october 1875 n jahraun fissure eruptions at the sveinagja graben some 60 km north of askja however historical accounts documenting the caldera formation in sufficient detail show clearly that oskjuvatn formed by piecemeal collapse taking over 40 years to reach its current form we use these accounts to undertake a detailed examination of the stages of caldera collapse and to compare them with the known magmatic output of askja in the years following the 1875 eruption arcgis software was used to calculate the volume of oskjuvatn during the various stages of collapse and the volume of material erupted after 1875 while a dyke extending between askja and sveinagja may be implied to account for the missing volume our results demonstrate that the volume of oskjuvatn in july 1875 closely corresponds to the volume of rhyolitic material erupted on 28th 29th march 1875 in addition geochemical evidence indicates that the n jahraun magmas were sourced from a deeper reservoir rather than by lateral injection from askja s shallow crustal magma chamber we therefore suggest that the injection of sills and dykes in a coherent intrusion complex beneath askja central volcano combined with background deflation of the magma storage zone beneath oskjuvatn caldera over 30 to 40 years following 1875 satisfactorily accommodates the volume required to form oskjuvatn caldera

volcanic and hydrothermal processes in submarine calderas the kulo lasi example sw pacific abstract the study area is located at the transition between the northern end of the tonga trench and the north fiji fracture zone where tectonic movements are reputed to be the fastest in the world to the southeast of futuna island a broad area of volcanism occurs within a region characterized by a change in the tectonic fabric between a ne sw oriented volcanic graben and the n s oriented alofi ridge in 2010 the active volcano kulo lasi which represents the most recent volcanic episode in the futuna area was discovered in the center of this extensive volcanic zone kulo lasi is a 20 km diameter shield volcano that rises 400 m above the seafloor it is composed of basaltic to trachy andesitic lava with no obvious geochemical affinity with the tonga subduction that occurs 500 km to the east the central caldera is 5 km in diameter and 300 m deep and is located at a water depth of 1500 m diving operations with the submersible nautile and high resolution auv mapping have revealed the presence of numerous active and inactive hydrothermal fields on the floor and the walls of the caldera four tectono volcanic stages can be distinguished at kulo lasi caldera in stage 1 the shield volcano is built annular reverse faults develop at the summit and control circulation of water rock dominated hydrothermal fluids and high temperature alteration of rocks along the nascent normal faults mixing of hydrothermal fluids with seawater is favored along normal superficial faults leading to the formation of low temperature fe mn mineralization at the summit of the volcano during stage 2 the caldera collapse gradually revealing outcrops of the altered and mineralized zones formed during stage 1 as the magma chamber cools and collapses less heat is available as a result medium to low temperature

stability and instability of quiescently active volcanoes the case of masaya nicaragua quiescently active volcanoes are enigmatic due to their restlessness but lack of eruptive activity i present a model of coupled conduit convection and foam accumulation to explain degassing behavior of masaya an active volcano in nicaragua that is currently emitting large amounts of gas but not erupting gas rich magma is transported through a conduit 2 6 m in radius and then released into a shallow reservoir the magma is degassed in the reservoir and forms a foam 1 3 m thick at the top with bubbles 20 60 m in diameter the foam layer is stable because the input of gas into the foam is balanced by gas release through a vent to the surface if the foam layer is destabilized the volcano can erupt explosively the most likely cause of foam destabilization is a large injection of volatile rich magma from deeper levels into the shallow conduit reservoir system thereby increasing magma fluxes and gas fluxes exsolving large gas bubbles and reducing surface tension of the magma

carbon dioxide fixation within mine wastes of ultramafic hosted ore deposits examples from the clinton creek and cassiar chrysotile deposits canada carbon dioxide co2 is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at clinton creek yukon territory and cassiar british columbia canada accelerated weathering is attributed to a dramatic increase in surface area which occurs during the milling of ore we provide a detailed account of the natural process of carbon trapping and storage as it occurs at clinton creek and cassiar including mineralogy modes of occurrence methods of formation for carbonate alteration light stable isotope geochemistry and radiocarbon analysis powder x ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite mgco3 3h2o dypingite mg5 co3 4 oh 2 5h2o hydromagnesite mg5 co3 4 oh 2 4h2o and less commonly lansfordite mgco3 5h2o textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings samples of efflorescent nesquehonite are characterized by 13c values between 6 52 and 14 36 per mil 18o values between 20 93 and 26 62 per mil and f14c values fraction of modern carbon between 1 072 and 1 114 values which are consistent with temperature dependent fractionation of modern atmospheric co2 during mineralization samples of dypingite hydromagnesite collected from within 0 2 m of the tailings surface give 13c values between 1 51 and 10 02 per mil 18o values between 17 53 and 28 40 per mil and f14c values between 1 026 and 1 146 which suggests precipitation from modern atmospheric co2 in a soil like environment field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments nesquehonite formed in an evaporative environment on the surface of tailings piles and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate in both cases these minerals

atmospheric carbon sequestration in ultramafic mining residues and impacts on leachate water chemistry at the dumont nickel project quebec canada abstract passive carbon mineralization in ultramafic mining residues which allows the sequestration of co2 through carbonate precipitation is one of the options being considered to limit the accumulation of anthropogenic co2 in the atmosphere the dumont nickel project dnp will generate approximately 1 7 gt of utramafic mining residues over 33 years of production and the mine will release about 127 700 tonnes of co2 each year using two experimental cells filled with ultramafic waste rock ec 1 and milling residues ec 2 the impacts of carbon mineralization on leachate water quality were studied and the quantity of sequestered carbon was estimated hydrotalcite supergroup minerals aragonite artinite nesquehonite dypingite and hydromagnesite precipitated through atmospheric weathering while the inorganic carbon content of the weathered mining waste increased from 0 1 wt to 4 0 wt which indicates active co2 sequestration the leachate water sampled at the bottom of the experimental cells is characterized by an alkaline ph 9 5 a high alkalinity 90 to 750 mg l and a high concentration of magnesium 50 750 mg l which is typical from weathering of ultramafic rocks in a system open to co2 since 2012 the chemical composition of the leachate water has evolved seasonally these seasonal variations are best explained by 1 climatic variations over the year and 2 increased carbonate precipitation between may and july increased carbonate precipitation decreased the alkalinity and magnesium concentrations in the leachate water and produced pore waters which were undersaturated with respect to carbonate minerals such as artinite and hydromagnesite carbonate precipitation thus self limits carbon sequestration through a negative feed back loop the carbon sequestration potential of the dnp residues is also influenced by the hydrogeological properties of the residues in cell ec 2 a high liquid solid ratio which limits carbonate precipitation was maintained by the hydrogeological properties since 2011 an estimate of 13 kg of atmospheric co2 has been sequestered in the milling residues ec 2 which corresponds to a mean rate of 1 4 0 3 kgco2 tonne year using this mean rate the 15 mt of tailings produced each year during the planned 33 years of mining operation could potentially sequester 21 000 tonnes of co2 per year by passive carbon mineralization about 16 of the 127 700 tonnes of co2 annually emitted by the planned mining operation

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

caldera formation by magma withdrawal from a reservoir beneath a volcanic edifice caldera formation has been explained by magma withdrawal from a crustal reservoir but little is known about the conditions that lead to the critical reservoir pressure for collapse during an eruption the reservoir pressure is constrained to lie within a finite range it cannot exceed the threshold value for eruption and cannot decrease below another threshold value such that feeder dykes get shut by the confining pressure which stops the eruption for caldera collapse to occur the critical reservoir pressure for roof failure must therefore be within this operating range we use an analytical elastic model to evaluate the changes of reservoir pressure that are required for failure of roof rocks above the reservoir with and without a volcanic edifice at earth s surface with no edifice at earth s surface faulting in the roof region can only occur in the initial phase of reservoir inflation and affects a very small part of the focal area such conditions do not allow caldera collapse with a volcanic edifice large tensile stresses develop in the roof region whose magnitude increase as the reservoir deflates during an eruption the edifice size must exceed a threshold value for failure of the roof region before the end of eruption the largest tensile stresses are reached at earth s surface indicating that faulting starts there failure affects an area whose horizontal dimensions depend on edifice and chamber dimensions for small and deep reservoirs failure conditions cannot be achieved even if the edifice is very large quantitative predictions are consistent with observations on a number of volcanoes

anomalous earthquakes associated with nyiragongo volcano observations and potential mechanisms abstract a series of five unusual earthquakes 4 6 m 5 3 has been recently located near nyiragongo volcano d r congo in the western rift valley of the east african rift despite their moderate size these earthquakes do not appear in global seismicity catalogs but were located using long period surface waves primarily recorded on the global seismographic network three of the events occurred in the week following the january 2002 eruption of nyiragongo while the final two occurred in 2003 and 2005 respectively and are not linked to a major eruption at nyiragongo or its neighboring volcano nyamuragira several common techniques were used to investigate the characteristics of these seismic sources in the context of the volcanic activity of the region the frequency content of the five anomalous earthquakes was compared to that from local events found in global catalogs and the newly detected earthquakes were shown to be slow events being greatly depleted in frequencies above 0 1 hz each of the newly detected earthquakes was modeled by a series of forces and by a centroid moment tensor a deviatoric moment tensor was shown to provide a better fit to the data the newly detected earthquakes are highly non double couple in nature each having a large compensated linear vector dipole component of the moment tensor drawing on models based on similar observations from other active volcanoes we propose that the earthquakes are caused by slip on non planar faults beneath the volcano we suggest a mechanism in which these newly detected earthquakes are generated by the collapse of the roof of a shallow magma chamber along an inward dipping cone shaped ring fault diking events which result in magma evacuation from shallow magma chambers could trigger such earthquakes our results provide new constraints on the dynamics of the poorly understood magma system beneath nyiragongo an active volcano that is a significant threat to life and property

magma chamber volume changes associated with ring fault initiation using a finite sphere model application to the aira caldera japan abstract we have derived an analytical solution expressing the magma chamber volume change required for ring fault caldera initiation in terms of a finite sphere model we consider the conditions by which magma chamber contraction volume reduction could contribute to the initiation of a ring fault at the surface above the chamber using the elastic plastic theory of host rock behaviour the model does not consider underpressure pressure less than lithostatic in the chamber but only magma chamber volume reduction or shrinkage the model is heuristic in the sense that we do not explore the detailed mechanical condition for the volume reduction apart from its being related to magma flow out of the chamber but rather focus on the consequences of the reduction for ring fault initiation and dip the solution obtained for the finite sphere model consists of a leading term that is proportional to the cube of the magma chamber depth and a second term that is proportional to the cube of the magma chamber radius the second term reflects explicitly the effects of a finite source radius whereas the first term corresponds to a solution for a point source model this follows because in a point source model the magma chamber radius is zero so that the second term drops out the equation that plays the key role in obtaining this solution is a linear function relating the radius of the caldera to the magma chamber depth the proportionality coefficient of this equation is dimensionless and depends not only on the elastic constants of the medium but also on the depth d and radius a of the magma chamber given by e a d in addition because this coefficient controls a geometric parameter related to the overall form of the ring fault our results indicate that the ring fault shape and size is decided by the magma chamber depth and size as well as by the host rock elastic properties and angle of internal friction the results indicate that the associated ring fault is inward dipping and that the magma chamber radius can be estimated from the fault radius and dip we applied the analytical solution to the ring fault of the aira caldera in southern kyushu japan the calculations indicate that the aira ring fault could have been initiated at the surface as a result of 2 8 reduction in the volume of a magma chamber with a radius of 4 7 km and at a depth of 9 1 km these results agree with independent information on the aira magma chamber we conclude that the present solution yields useful first order information on magma chambers associated with ring faults

advanced interferometric synthetic aperture radar insar time series analysis using interferograms of multiple orbit tracks a case study on miyake jima 1 insar time series analysis is an effective tool for detecting spatially and temporally complicated volcanic deformation to obtain details of such deformation we developed an advanced insar time series analysis using interferograms of multiple orbit tracks considering only right or only left looking sar observations incidence directions for different orbit tracks are mostly included in a common plane therefore slant range changes in their interferograms can be expressed by two components in the plane this approach estimates the time series of their components from interferograms of multiple orbit tracks by the least squares analysis and higher accuracy is obtained if many interferograms of different orbit tracks are available additionally this analysis can combine interferograms for different incidence angles in a case study on miyake jima we obtained a deformation time series corresponding to gps observations from palsar interferograms of six orbit tracks the obtained accuracy was better than that with the sbas approach demonstrating its effectiveness furthermore it is expected that higher accuracy would be obtained if sar observations were carried out more frequently in all orbit tracks the deformation obtained in the case study indicates uplift along the west coast and subsidence with contraction around the caldera the speed of the uplift was almost constant but the subsidence around the caldera decelerated from 2009 a flat deformation source was estimated near sea level under the caldera implying that deceleration of subsidence was related to interaction between volcanic thermal activity and the aquifer

conceptual and numerical models of ring fault formation abstract most ring faults of collapse calderas are primarily shear fractures the initiation and development of which depends on the state of stress in the host rock the state of stress in a volcano is controlled by the loading conditions such as magma chamber geometry and pressure but also by the mechanical properties of its rock units and structures such as existing contacts faults and joints ring fault formation is thus essentially a problem in rock physics field observations show that some ring faults are dip slip whereas others are partly faults shear fractures and partly ring dykes extension fractures although slip on existing ring faults is much more common in basaltic edifices shield volcanoes than in true composite volcanoes in both types of volcanoes most caldera unrest periods do not result in ring fault slip here i present new conceptual and numerical models of caldera formation in volcanoes with shallow spherical circular or oblate ellipsoidal sill like magma chambers in the layered models the host rock above the chamber is composed of 30 comparatively thin layers with stiffnesses young s moduli alternating between 1 gpa and 100 gpa the chamber itself is located in a single thick layer the crustal segment hosting the chamber is either 20 km or 40 km wide but has a constant thickness of 20 km the loading conditions considered are 1 a crustal segment subject to 5 mpa tension 2 crustal segment subject to excess magmatic pressure of 10 mpa at the bottom doming of the volcanic field containing the chamber 3 a combination of tension and doming and 4 chamber subject to underpressure negative excess pressure of 5 mpa the main results are as follows 1 excess pressure and underpressure in a chamber normally favour dyke injection rather than ring fault formation 2 for doming or tension a spherical magma chamber favours dyke injection except when the layer hosting the chamber is very soft 10 gpa or one with recent dyke injections in which case the surface stress field favours ring fault formation 3 for a sill like chamber in a 20 km wide crustal segment a ring fault can be generated by either tension or tension and doming for a 40 km wide segment doming alone is sufficient to generate a ring fault 4 since individual layers in a volcano may develop different local stresses stress field homogenisation through all the layers between the chamber and the surface is a necessary condition for ring fault formation 5 because the mechanical properties of the layers that constitute basaltic edifices are more uniform than those that constitute true composite volcanoes it follows that stress field homogenisation and thus ring fault formation or slip is more commonly reached in basaltic edifices than in composite volcanoes 6 both for basaltic edifices and composite volcanoes the stress fields most likely to initiate ring faults are those generated around sill like chambers subject to tension doming or both

observation of the eruption sequence and formation process of a temporary lava lake during the june august 2015 mt raung eruption indonesia using high resolution and high frequency satellite image datasets abstract from june to august 2015 mt raung located at the east end of java indonesia erupted effusively with strombolian activity at the intra caldera cinder cone the effused lava from the base of the cone entirely buried the caldera floor with a lava bed and ultimately formed a temporary lava lake in this study details of the eruption sequence and formation process of the temporary lava lake are analyzed based on a series of high resolution images combined with the high frequency thermal observation results of himawari 8 the volume of effused lava was also estimated using a digital elevation model aster gdem based on the lava bed bathymetry in the caldera and lava bed distribution at several points over the course of the eruption the total effusion volume was estimated to be 7 5 107 m3 and the average effusion rate was 1 4 106 m3 day the activity consisted of four stages the precursory stage was characterized by low level thermal anomalies which are thought to result from high temperature spots at the bottom of several pits formed in the buried vent probably due to magma head partial exposure or gas emission pulses 1 and 2 were effusive stages that formed the lava bed the pattern recognized in the time series variation of thermal anomalies was confirmed to reflect the lava effusion rate using the volumes estimated in this study the lava bed is divided into the lower and upper lava groups which were generated in pulses 1 and 2 respectively except for the fine lobes formed around the margin of the lower lava group the terminal stage also showed low level thermal anomalies most likely caused by gas emissions the intra caldera cone grew to approximately 100 m higher than its initial height by mid august and then collapsed into the conduit at the end of the terminal stage the lava bed increased in thickness through lobe multi layering and later through the addition of lava directly from the vent into the lava bed interior over the course of the lava bed growth the bed outline nearly matched the caldera contours uplift of the lava bed surface caused lateral fluidization of the bed and molten lava was extruded at the bed margins forming fine lobes this process enlarged the zone of fine lobes around the lava bed thus the lava bed growth resulted in the appearance of a lava lake in the middle of pulse 1 a small amount of hot material was thrown onto the slope beyond the caldera rim in the future the caldera floor uplift caused by this activity approximately 49 m will increase the risk of erupted material ejection outside the caldera in a comparison with the 2013 15 nishinoshima eruption which was a similar effusive eruption mt raung was shown to have predominantly large lobes over most of the lava bed while in nishinoshima narrow medium scale lobes occupied the majority of the surface this may be attributed to the high effusion rate of lava for mt raung which was approximately seven times higher on average than the lava effusion rate for nishinoshima

subaqueous calderas in the archean abitibi greenstone belt an overview and new ideas abstract the 300 700 km abitibi greenstone belt in canada contains numerous world class archean volcanogenic massive sulfide vms deposits yet documentation of archean subaqueous calderas hosting such deposits is lacking the modern sunrise deposit in the myojin knoll caldera of the izu bonin arc shows that submarine calderas are first order sites for vms the hunter mine and normetal calderas as well as the blake river megacaldera complex are reviewed with respect to geometry regional geology physical volcanology dyke emplacement and hydrothermal carbonate alteration these subaqueous calderas are placed into the geodynamic context of the abitibi greenstone belt the abitibi belt displays a complex history of oceanic arc formation evolution collision and fragmentation with numerous types of volcanic edifices and sedimentary basins controlled by oblique subduction and mantle plumes analogue models yielding new insights into the sequence of caldera forming events and their synvolcanic fault patterns are applied to explain archean examples underpressure experiments develop a consistent sequence of fault patterns that compare favourably with natural caldera events during subsidence two sets of faults propagate from the magma chamber margin 1 early reverse outward dipping faults and 2 normal inward dipping faults the largest massive sulfide deposits form preferentially at the caldera margin based on experimental studies and detailed facies mapping the hunter mine caldera is of the segmented piecemeal variety and the normetal caldera is akin to a piston structure the blake river megacaldera contains 1 the e w trending misema 2 the nw trending new senator and 3 the ne trending noranda calderas with the latter two being nested graben type calderas consistent with oblique archean subduction the poorly documented hydrothermal carbonate alteration is discussed and a new exploration model for calderas is presented the alteration study was evaluated at three levels microprobe analysis geochemical staining of drill core and whole rock analyses there were two principal stages of alteration related to vms formation an early silicification phase developed either at depth and or at the seawater interface whereby silicification was bedding parallel in fine grained volcaniclastic deposits near the water surface a pervasive and extensive semi conformable carbonate alteration zone with a discordant focused root zone along faults evolved subsequently three distinct carbonate pairings were observed 1 proximal siderite sideroplesite fe ankerite next to the vms deposit 2 an intermediate ankerite fe dolomite zone and 3 a distal calcite dolomite zone the carbonate phase is associated with the mineralizing event transitions between carbonate species are subtle and changes are indicated by mineral assemblage overlap the silica carbonate hydrothermal alteration pattern is a replacement product and is far more widespread than has been documented this alteration can be easily confused with primary carbonates and chemical precipitation deposits e g banded iron formation if detailed volcano sedimentary facies mapping with alteration has not been conducted and if outcrop is insufficient

sounding the plume of the 18 august 2000 eruption of miyakejima volcano japan using gps 1 we processed 79 days of gps data collected at four stations on miyakejima volcano japan before and during its eruption in 2000 this period includes a strong seismic swarm 27 june to 8 july followed by five eruptions 8 and 14 15 july 10 18 and 29 august surface motion is strong during the seismic swarm then remains almost steady during eruptions however during each eruption we found anomalous values of the lc ionosphere free double differences especially on 18 august with a peak of 0 6 cycles i e an apparent 290 mm increase of the satellite station range we cannot explain these anomalies by temporary ground displacements during the events instead we propose that they are due to path delay effects in the hot volcanic plume by adapting a seismic tomography algorithm the refractivity anomaly and the inferred temperature in the plume is mapped in time and space

the new worldwide collapse caldera database ccdb a tool for studying and understanding caldera processes collapse calderas are one of the most important volcanic structures not only because of their hazard implications but also because of their high geothermal energy potential and their association with mineral deposits of economic interest the objective of this work is to describe a new general worldwide collapse caldera database ccdb in order to provide a useful and accessible tool for studying and understanding caldera collapse processes the principal aim of the ccdb is to update the current field based knowledge on calderas merging together the existing databases and complementing them with new examples found in the bibliography and leaving it open for the incorporation of new data from future studies this database does not include all the calderas of the world but it tries to be representative enough to promote further studies and analyses we have performed a comprehensive compilation of published field studies of collapse calderas including more than 200 references and their information has been summarized in a database linked to a geographical information system gis application thus it is possible to visualize the selected calderas on a world map and to filter them according to different features recorded in the database e g age structure the information recorded in the ccdb can be grouped in seven main information classes caldera features properties of the caldera forming deposits magmatic system geodynamic setting pre caldera volcanism caldera forming eruption sequence and post caldera activity additionally we have added two extra classes the first records the references consulted for each caldera the second allows users to introduce comments on the caldera sample such as possible controversies concerning the caldera origin a further purpose of this work is to construct the ccdb web page in this web page where registered users can acquire the current database version as well as to propose corrections or updates and to exchange information with other registered members also involved in the study of caldera collapse processes additionally the ccdb includes a formulary that will facilitate the incorporation of new calderas into the database

kinetic testing to evaluate the mineral carbonation and metal leaching potential of ultramafic tailings case study of the dumont nickel project amos quebec abstract ultramafic mine wastes are known to react passively with co 2 to form stable hydrated magnesium carbonates this study uses kinetic tests to evaluate the carbonation potential of ultramafic mine tailings from the dumont project rnc minerals quebec canada during their weathering and to determine the impact of carbonation on the long term quality of drainage waters the weathering of awaruite ni 2 5 fe pentlandite fe ni 9 s 8 and heazlewoodite ni 3 s 2 which are the main sources of ni in the studied materials were also investigated due to their potential to generate contamination a column test and small scale weathering cell tests were used to simulate the passive weathering of ultramafic mine wastes as well as concentrates of awaruite and ni sulfides results from the kinetics tests confirmed that the dumont tailings have a significant carbon sequestration potential which ranged from 8 5 to 33 6 kgco 2 t the surface normalized carbonation rates varied from 600 to 2200 g of co 2 m 2 year results demonstrated that brucite mg oh 2 content is the main parameter controlling co 2 uptake by the dumont wastes weathering of brucite and serpentine mg 3 si 2 o 5 oh 4 are driven by co 2 dissolution in pore water and by sulfide oxidation the rapid dissolution of brucite results in leachates with alkaline ph values thus preventing metal mobility metals such as ni zn fe and cu are suggested to precipitate as hydroxide or carbonate species within the wastes immediately upon being released through sulfide oxidation the ni fe alloy awaruite is stable and does not release metals in kinetic tests the dumont tailings are found to be non acid generating and co 2 sequestration is shown to play a significant role in drainage water quality which allow generation of significant alkalinity and the rise of ph

an igneous origin for features of a candidate crater lake system in western memnonia mars the association of channels inner terraces and delta like features with martian impact craters has previously been interpreted as evidence in favor of the past existence of crater lakes on mars however examination of a candidate crater lake system in western memnonia suggests instead that its features may have formed through igneous processes involving the flow and ponding of lava accumulations of material in craters and other topographic lows throughout much of the study region have characteristics consistent with those of volcanic deposits and terraces found along the inner flanks of some of these craters are interpreted as having formed through drainage or subsidence of volcanic materials channels previously identified as inlets and outlets of the crater lake system are interpreted instead as volcanic rilles these results challenge previous interpretations of terrace and channel features in the study region and suggest that candidate crater lakes located elsewhere should be reexamined

acid neutralization mechanisms and metal release in mine tailings a laboratory column experiment mining and milling of base metal ore deposits can result in the release of metals to the environment when sulfide minerals contained in mine tailings are exposed to oxygen and water they oxidize and dissolve two principal antagonistic geochemical processes affect the migration of dissolved metals in tailings impoundments sulfide oxidation and acid neutralization this study focuses on acid neutralization reactions occurring in the saturated zone of tailings impoundments to simulate conditions prevailing in many tailings impoundments 0 1 mol l sulfuric acid was passed continuously through columns containing fresh unoxidized tailings collected at kidd creek metallurgical site the results of this column experiment represent a detailed temporal observation of ph eh and metal concentrations the results are consistent with previous field observations which suggest that a series of mineral dissolution precipitation reactions control ph and metal mobility typically the series consists of carbonate minerals al and fe iii hydroxides and aluminosilicates in the case of kidd creek tailings the dissolution series consists of ankerite dolomite siderite gibbsite and aluminosilicates in the column experiment three distinct ph plateaus were observed 5 7 4 0 and 1 3 the releases of trace elements such as cd co cr cu li ni pb v and zn were observed to be related to the ph buffering zones high concentrations of zn ni and co were observed at the first ph plateau ph 5 7 whereas cd cr pb as v and al were released as the ph of the pore water decreased to 4 0 or less

an experimental study of the role of subsurface plumbing on geothermal discharge in order to better understand the diverse discharge styles and eruption intervals observed at geothermal features we performed three series of laboratory experiments with differing plumbing geometries a single straight conduit that connects a hot water bath flask to a vent funnel can originate geyser like periodic eruptions continuous discharge like a boiling spring and fumarole like steam discharge depending on the conduit length and radius the balance between the heat loss from the conduit walls and the heat supplied from the bottom determines whether and where water can condense which in turn controls discharge style next we connected the conduit to a cold water reservoir through a branch simulating the inflow from an external water source colder water located at a higher place than a branching point can flow into the conduit to stop the boiling in the flask controlling the periodicity of the eruption when an additional branch is connected to a second cold water reservoir the two cold reservoirs can interact our experiments show that branching allows new processes to occur such as recharge of colder water and escape of steam from side channels leading to greater variation in discharge styles and eruption intervals this model is consistent with the fact that eruption duration is not controlled by emptying reservoirs we show how differences in plumbing geometries can explain various discharge styles and eruption intervals observed in el tatio chile and yellowstone usa this article is protected by copyright all rights reserved

the spectrum of basaltic feeder systems from effusive lava eruption to explosive eruption at miyakejima volcano japan basaltic feeder systems exposed in the caldera wall of miyakejima volcano are classified into three groups 1 effusive feeders 2 moderately explosive feeders and 3 highly explosive feeders the surface deposits and feeder systems reveal a wide variation in the explosivity of the eruptions that produced them ranging from non explosive lava effusions to violent explosive eruptions despite the apparent lack of influence of external water effusive feeders are filled with coherent non fragmented intrusive rock indicating no significant fragmentation in the feeder system the other two types of feeder systems consist of a coherent dike in their deeper part and a pyroclastic fill in their uppermost part their uppermost parts show an upward flaring shape the transition from coherent intrusion to pyroclastic fill in the feeder systems suggests underground fragmentation of the rising magma the depth of the coherent pyroclastic transition is deeper 20 150 m in highly explosive feeders than in the moderately explosive feeders 20 m and coincides with the depth at which the system flares upwards presence of lithic fragments derived from the host rock in the products of the highly explosive feeder systems indicates the removal of the wall rock by explosive activity this observation suggests that the fragmentation of rising magma promoted the enlargement of the feeder systems to form their upward flaring shapes by mechanical erosion and wall collapse

subsurface cyclic magma sill expansions in the 2000 miyakejima volcano eruption possibility of two phase flow oscillation 1 step like tilt changes were observed at intervals of dozens of hours during the caldera formation stage occurred during the 2000 miyakejima volcano eruption our analysis suggests that these tilt steps were caused by the cyclic expansion of a subsurface sill like magma plumbing system trending from se to nw of the volcano in the same period a caldera gradually grew at the summit area to a very large 1 6 km in diameter and 450 m in depth the source mechanism of these tilt steps is fairly well explained by a two phase flow instability called a pressure drop oscillation this model indicates that the gas phase capacity in the upper part of the conduit acts as a pump that controls the flux of two phase magma in the sill like reservoir caldera formation as well as magma uplift and descent in the conduit may reflect temporal changes in the intervals between tilt steps which are themselves proportional to the volume of this gas capacity

the april 2007 eruption and the dolomieu crater collapse two major events at piton de la fournaise la reunion island indian ocean abstract after 10 years of high activity and 24 eruptions piton de la fournaise pdf produced on april 2 to may 1 2007 one of its most voluminous and intense eruption since at least one century the eruption focused at 590 m elevation in the grand brule on the south east flank of piton de la fournaise 7 km away from summit it was located close to the southern cliff of the grand brule volcano tectonic collapse the rempart du tremblet and to the nearby village called le tremblet and it highly rattled and incommoded the inhabitants there eleven hours after the beginning of the eruption the lava flows reached the sea and created 0 45 km 2 of new land until the end of eruption in the night of april 5 the rock column beneath dolomieu crater started to collapse with a piston like mechanism into the magma chamber forming within less than 24 h the most recent and well documented caldera we report in this paper the chronology of these two related major events in the recent activity of pdf seen by the scientific networks of the volcanological observatory ovpf ipgp and field observations which allowed to back up the scenario of the caldera formation and to quantify these two exceptional episodes

caldera faults capture and deflect inclined sheets an alternative mechanism of ring dike formation the subsurface structures of caldera ring faults are often inferred from numerical and analog models as well as from geophysical studies all of these inferred structures need to be compared with actual ring faults so as to test the model implications here we present field evidence of magma channeling into a caldera ring fault as exhibited at hafnarfjall a deeply eroded and well exposed 5 ma extinct volcano in western iceland at the time of collapse caldera formation over 200 m of vertical displacement was accommodated along a ring fault which is exceptionally well exposed at a depth of approximately 1 2 km below the original surface of the volcano there are abrupt changes in the ring fault attitude with depth but its overall dip is steeply inward several inclined sheets within the caldera became arrested at the ring fault other sheets became deflected up along the fault to form a multiple ring dike we present numerical models showing stress fields that encourage sheet deflection into the subvertical ring fault our findings provide an alternative mechanical explanation for magma channeling along caldera ring faults which is a process likely to be fundamental in controlling the location of post caldera volcanism

sequestration of atmospheric co2 in chrysotile mine tailings of the woodsreef asbestos mine australia quantitative mineralogy isotopic fingerprinting and carbonation rates since closure of the woodsreef asbestos mine located in the great serpentinite belt gsb new south wales australia extensive carbonate rich crusts have formed by recessive weathering of fine grained material on the surface of the tailings pile a relationship exists between the mode of carbonate occurrence the mineralogy and the isotopic fingerprint of carbonates from the tailings pile vertical carbonate crusts covering most of the tailings predominantly consist of the hydrated mg carbonate hydromagnesite mg5 co3 4 oh 2 4h2o which has precipitated from evaporating meteoric waters incorporating atmospheric co2 as reflected in high 18o 13c and f14c signatures respectively low and variable concentrations of magnesite dolomite and calcite represent bedrock carbonate which has formed during alteration of the serpentinite bedrock before mining and is characterised by moderately high 18o low 13c and f14c a signature typical for weathering derived magnesite deposits in the gsb the carbonate fraction of deep cement samples collected from 70 to 120 cm below the surface representing the bulk tailings material at depth predominantly consists of pyroaurite mg6fe2 co3 oh 16 4h2o and despite stable isotope signatures similar to bedrock contains significant radiocarbon this indicates that pyroaurite forming under different conditions as hydromagnesite may represent an additional trap for atmospheric co2 in the woodsreef mine tailings the distribution of carbonates and quartz together with the absence of isotopic mixing trends between bedrock carbonate and atmospheric derived carbonate strongly indicates that dissolution and re precipitation of bedrock carbonate is not a dominant process in the woodsreef tailings the cations for carbonate formation are instead derived from the dissolution of serpentine minerals lizardite and chrysotile and brucite the internal standard method and the reference intensity method have been used with x ray diffraction data to estimate the abundance of the two major carbonate minerals hydromagnesite and pyroaurite respectively considering the formation of hydromagnesite on the outer surface of the tailings pile alone or together with formation of pyroaurite within the tailings pile we conclude that between 1400 and 70 000 t of atmospheric co2 have been sequestered in the mine tailings since closure of the mine 29 a ago carbonation rates of 27 g c m 2 y 1 and 1330 g c m 2 y 1 are significantly higher than background rates of co2 uptake by chemical weathering and demonstrate the potential of passive carbonation of mine tailings as a cost and energy effective alternative for storage of co2 in carbonate minerals

an active ring fault detected at tendurek volcano by using insar 1 although ring faults are present at many ancient deeply eroded volcanoes they have been detected at only very few modern volcanic centers at the so far little studied tendurek volcano in eastern turkey we generated an ascending and a descending insar time series of its surface displacement field for the period from 2003 to 2010 we detected a large 105 km2 region that underwent subsidence at the rate of 1 cm yr during this period source modeling results show that the observed signal fits best to simulations of a near horizontal contracting sill located at around 4 5 km below the volcano summit intriguingly the residual displacement velocity field contains a steep gradient that systematically follows a system of arcuate fractures visible on the volcano s midflanks rapideye satellite optical images show that this fracture system has deflected holocene lava flows thus indicating its presence for at least several millennia we interpret the arcuate fracture system as the surface expression of an inherited ring fault that has been slowly reactivated during the detected recent subsidence these results show that volcano ring faults may not only slip rapidly during eruptive or intrusive phases but also slowly during dormant phases

surface displacements resulting from magma chamber roof subsidence with application to the 2014 2015 bardarbunga holuhraun volcanotectonic episode in iceland abstract the conditions which lead to caldera collapse are still poorly constrained as there have only been four possibly five well documented caldera forming events in the past century the geodetic signals produced during chamber roof subsidence or chamber volume reduction shrinkage in general are not well documented or understood in particular when two or more geodetic sources are operating and providing signals at the same time it is important to be able to estimate the likely contribution of each simultaneous activities of different geodetic sources are common and include pressure changes in magma chambers reservoirs occurring at the same time as dyke emplacement here we present results from numerical models designed to simulate the subsidence of a magma chamber roof either directly chamber shrinkage or through ring fault displacement and the induced surface deformation and crustal stresses we consider chamber depths at 3 km 5 km and 7 km below the crustal surface using both non layered isotropic and layered anisotropic crustal models we also model the effects of a caldera lake and of a thick ice cover ice sheet on top of the caldera the results suggest that magma chamber roof subsidences between 20 m and 100 m generate large tens of centimetres vertical and in particular horizontal displacements at the surfaces of the ice and the crust out to distances of up to tens of kilometres from the caldera chamber centre crustal layering tends to reduce but increasing chamber depth to enlarge the horizontal and vertical surface displacements applying the results to the ice subsidence in the bardarbunga caldera during the 2014 2015 bardarbunga holuhraun volcanotectonic episode indicates that the modelled ice displacements are less than those geodetically measured also the geodetically measured crustal displacements are less than expected for a 60 m chamber roof subsidence the modelling results thus suggest that only part of the ice subsidence is due to chamber roof subsidence the other part being related to flow in and down bending of the ice we show that such a flow is likely within the caldera as a result of the stress induced by the 45 km long regional dyke emplaced primarily in vertical magma flow during the episode this conclusion is further supported by the model results suggesting that the ring fault piston like displacements must have been much less than the total 60 m ice subsidence or else faults with tens of metres displacements would have cut through the ice these are not observed we suggest that the ring fault subsidence was triggered by small doming of the volcanic field and system hosting the bardarbunga caldera and that this doming occurred as a result of magma inflow and pressure increase in a deep seated reservoir the doming is confirmed by gps measurements and supported by the seismicity results the magmatic pressure increase in the reservoir was in terms of the present model responsible for the regional dyke emplacement the holuhraun eruption and part of the stress concentration around and displacement of the bardarbunga caldera

the november 2002 eruption at piton de la fournaise volcano la reunion island ground deformation seismicity and pit crater collapse an eruption on the eastern flank of piton de la fournaise volcano started on 16 november 2002 after 10 months of quiescence after a relatively constant level of activity during the first 13 days of the eruption lava discharge volcanic tremor and seismicity increased from 29 november to 3 december lava effusion suddenly ceased on 3 december while shallow earthquakes beneath the dolomieu summit crater were still recorded at a rate of about one per minute this unusual activity continued and increased in intensity over the next three weeks ending with the formation of a pit crater within dolomieu based on ground deformation measured by rapid static and continuous gps and an extensometer seismic data and lava effusion patterns the eruptive period is divided into five stages 1 slow summit inflation and sporadic seismicity 2 rapid summit inflation and a short seismic crisis 3 rapid flank inflation onset of summit deflation sporadic seismicity accompanied by stable effusion 4 flank inflation coupled with summit deflation intense seismicity and increased lava effusion and finally 5 little deflation intense shallow seismicity and the end of lava effusion we propose a model in which the pre intrusive inflation of stage 1 in the months preceding the eruption was caused by a magma body located near sea level the magma reservoir was the source of an intrusion rising under the summit during stage 2 in stage 3 the magma ponded at a shallow level in the edifice while the lateral injection of a radial dike reached the surface on the eastern flank of the basaltic volcano causing lava effusion pressure decrease in the magmatic plumbing system followed resulting in upward migration of a collapse front forming a subterranean column of debris by faulting and stoping this caused intense shallow seismicity increase in discharge of lava and volcanic tremor at the lateral vent in stage 4 and eventually the formation of a pit crater in stage 5

searching for patterns in caldera unrest the ultimate goal of volcanology is forecasting eruptions this task is particularly challenging at calderas where unrest is frequent affects wider areas and its evidence is often masked by the activity of hydrothermal systems a recent study has compiled a database on caldera unrest derived from seismicity geodetic gravity and geochemical monitoring data at calderas worldwide from 1988 to 2014 here we exploit this database searching for the most recurring features of unrest and in turn its possible dynamics in particular we focus on a the duration of unrest at calderas b recurring patterns in unrest c unrest episodes culminating in eruptions including time or size predictability and a multivariate regression analysis our analysis indicates that pre eruptive unrest is shorter than non eruptive unrest particularly with open or semi open calderas calderas with mafic or mixed composition of past eruptive products or unrest driven by mafic magma conversely lack of data on pre eruptive unrest driven by felsic magma and or at felsic or plugged calderas prevents an analysis of these specific subsets in addition 72 of pre eruptive unrest lasts 10 months and shows high seismicity and degassing the remaining 28 a is essentially aseismic in calderas with open conduit 17 or b lasts between 10 and 18 months with seismicity and degassing constituting a longer duration tail of the pre eruptive unrest with seismicity and degassing 11 surface deformation is not always reliable to characterize pre eruptive unrest our analysis suggests that magma may withstand only a limited period of eruptability before becoming stored in the upper crust

geochemical evolution of a shallow magma plumbing system during the last 500 years miyakejima volcano japan constraints from 238u 230th 226ra systematics abstract in order to unravel magma processes and the geochemical evolution of shallow plumbing systems beneath active volcanoes we investigated u series disequilibria of rocks erupted over the past 500 years 1469 2000 ad from miyakejima volcano izu arc japan miyakejima volcanic rocks show 238u 230th 226ra disequilibria with excess 238u and 226ra due to the addition of slab derived fluids to the mantle wedge basaltic bombs of the 2000 ad eruption have the lowest 230th 232th ratio compared to older miyakejima eruptives yielding the youngest 238u 230th model age of 2 kyr this reinforces our previous model that fluid release from the slab and subsequent magma generation in the mantle wedge beneath miyakejima occur episodically on a several kyr timescale in the last 500 years miyakejima eruptives show 1 a vertical trend in a 230th 232th 238u 232th diagram and 2 a positive linear correlation in a 226ra 230th 0 1 230th diagram which is also observed in lavas from some of the single eruptions e g 1940 1962 and 1983 ad the variations cannot be produced by simple fractional crystallization in a magma chamber with radioactive decay of 230th and 226ra but it is possibly produced by synchronous generation of melts in the mantle wedge with different upwelling rate or addition of multiple slab derived fluids a much more favorable scenario is that some basaltic magmas were intermittently supplied from deep in the mantle and injected into the crust subsequently modifying the original magma composition and producing variations in 230th 232th and 226ra 230th 0 ratios via assimilation and fractional crystallization afc the assimilant of the afc process would be a volcanic edifice of previous miyakejima magmatism due to the relatively short timescales involved the interaction between the assimilant and recent miyakejima magmatism has not been recorded by the sr nd pb isotopic systems in such cases th isotopes and 226ra 230th ratio are excellent geochemical tracers of magmatic evolution

the mineral and aqueous phase evolution of sulfur and nickel with weathering of pyrrhotite in a low sulfide granitic waste rock abstract the release of s and metals from the weathering of waste rock pyrrhotite fe 1 x s is affected by oxidation pathways the presence and concentration of fe substitution metals e g ni and fe oxyhydr oxide products a 4c monoclinic pyrrhotite fe7s8 ni fe substitution of about 1 200 in a low sulfide waste rock was weathered in the laboratory and at a field site to identify the evolution of s oxidation distribution and coordination of ni and possible adsorption of ni on secondary fe minerals mineral phase s was present in the 2 1 0 4 and 6 oxidation states prior to its release as so42 into solution the thiosulfate s2o32 pathway of sulfide oxidation was indicated by the presence of polythionates and s2o32 sulfur as s2o32 was more persistent than sulfite so32 prior to oxidation to so42 the release of ni during the oxidative dissolution of pyrrhotite was influenced by its distribution in the grain diffuse throughout the grain solid solution mineral or concentrated in exsolved pentlandite fe ni 9s8 lamellae within the pyrrhotite with the oxidation of s ni coordination changed from bonding with reduced s species to bonding with oxygen prior to its release with so42 sulfur as so42 typically stayed in solution with release from the pyrrhotite but the solubility of released ni was dependent on leachate ph a near neutral ph induced the adsorption of ni onto fe oxyhydr oxides which formed during oxidation of the pyrrhotite in some grains ni was found concentrated in fe distal precipitates as opposed to the closer alteration layers zones of the sulfide grain subsequent dissolution of the fe oxyhydr oxides or desorption of ni with a change in ph provides a delayed release of ni into solution this improved understanding of the oxidation pathway of s coordination and release of ni and influence of fe oxyhydr oxides in the weathering of pyrrhotite will assist in determining appropriate reaction rate factors and element release rates for prediction of acid rock drainage

caldera structure amount of collapse and erupted volumes the case of bolsena caldera italy calderas are common on volcanoes but their structure is seldom visible the 19 km wide bolsena caldera italy formed between 0 6 and 0 2 ma the largely preserved structural rim and subsurface data make bolsena ideal to investigate caldera structure in relation to the subsidence and erupted volume in this paper we use remote sensing field analysis and available subsurface data at the surface the caldera passes from a downsag south rim to a narrow and densely faulted area north rim with outer normal and inner reverse faults the caldera structure on the widely faulted east rim appears to be scale dependent with a staircase like fault zone larger scale horst and graben like structures intermediate scale and domino like structures smaller scale subsurface data indicate asymmetric collapse with a northward increase in subsidence ranging from diffuse to the south to focused to the north deformation at the surface the collapse rate constant between ca 490 and 175 ka was more than magma output between ca 330 and 130 ka highlighting significant 200 m and prolonged 200 ka posteruptive subsidence as the nearby latera caldera west rim of bolsena was mostly active between ca 265 and 160 ka much of the subsidence at bolsena may be related to this activity suggesting a common magmatic reservoir the subsidence related structural variations along the caldera rim and the significant posteruptive subsidence found at bolsena have not been found in other calderas

very long period seismic signals observed before the caldera formation with the 2000 miyake jima volcanic activity japan 1 very long period seismic signals whose waveform consists of an initial impulsive signal and a later oscillatory wave with 0 2 or 0 4 hz in dominant frequency were observed before the caldera formation in the 2000 activity of miyake jima volcano japan the results of waveform inversion show that the initial and later parts can be explained by a northward single force of 1 5 108 n working at a depth of 2 km beneath the summit and a moment tensor solution at a depth of 5 km below and 2 km southwest of the summit with 1012 nm respectively a clear positive correlation of the amplitudes between the two sources strongly suggests that the shallow single force triggers the deeper moment source in spite of the several km distance between the two sources to analyze the source time functions of the moment tensor that do not always oscillate in phase we introduce a new method of moment tensor diagonalization which is performed in the frequency domain according to the analysis the two principal components have similar amplitudes and are greater than the third principal component suggesting an axially symmetric oscillation one of the possible systems is a combination of two cracks intersecting perpendicularly our interpretation is that the single force was generated when magma containing rock blocks suddenly began to move in a choked subsurface magma path and the resultant pressure waves propagated and excited a resonance oscillation of the two cracks

small inflation sources producing seismic and infrasonic pulses during the 2000 eruptions of miyake jima japan abstract during the 2000 activity of miyake jima volcano japan we detected long period seismic signals with initial pulse widths of 1 2 s accompanied by infrasonic pulses with almost the same pulse widths the seismic signals were observed from 13 july 2000 a day before the second summit eruption the occurrences of the seismic signals were intermittent with a gradual increase in their magnitudes and numbers building toward a significant explosive eruption on 18 august after the eruption the seismic and infrasonic events ceased the results of a waveform inversion show that the initial motions were excited by an isotropic inflation source beneath the south edge of the caldera at a depth of 1 4 km on the other hand the sources of the infrasonic pulses were located in the summit caldera area the times at which the infrasonic pulses were emitted at the surface were delayed by about 3 s from the origin times of the seismic events it is suggested that small isotropic inflations excited seismic waves in the crust and simultaneously caused acoustic waves that traveled in the conduit and produced infrasonic pulses at the crater bottom considering the observed time differences and gas temperatures emitted from the vent the conduit should have been filled with vapor mixed with so 2 gas and volcanic ash the change of the time differences between the seismic and infrasonic signals suggests that the seismic source became shallower within half a day before the august 18 explosive eruption we interpret the source process as a fragmentation process of magma in which gas bubbles burst and quickly released part of the pressure that had been sustained by the tensional strength of magma

magma dynamics and collapse mechanisms during four historic caldera forming events 1 four historic caldera forming events were studied to understand the relationship of magma withdrawal processes and caldera subsidence mechanisms two calderas are silicic katmai in 1912 and pinatubo in 1991 and two are basaltic fernandina in 1968 and miyakejima in 2000 all events have sufficient geophysical geologic and petrologic data with which to examine and model magma withdrawal and caldera collapse the data reveal that the magmas erupted at katmai and pinatubo were in a bubbly state in the reservoir immediately before and during caldera collapse the bubbly magma allowed for its efficient extraction from the reservoir causing significant underpressures to develop rapidly particularly in the case of katmai where the erupted rhyolite was voluminous and nearly aphyric and has very low viscosity the rapidly developing underpressures at katmai and pinatubo caused sudden en masse caldera collapse halfway through the climactic eruptions thereby liberating large amounts of seismic energy at fernandina and miyakejima by contrast caldera collapse was initiated early and continued for an extended period of time from weeks to months consisting of a series of discrete subsidence events manifested by large earthquakes at fernandina and by very long period vlp signals at miyakejima systematic changes in earthquake magnitudes and quiescent intervals at both volcanoes reveal changes in friction as collapse took place during extended time intervals

mobilization and attenuation of heavy metals within a nickel mine tailings impoundment near sudbury ontario canada the oxidation and the subsequent dissolution of sulfide minerals within the copper cliff tailings area have led to the release of heavy metals such as fe ni and co to the tailings pore water dissolved concentrations in excess of 10 g l fe and 2 2 g l ni have been detected within the shallow pore water of the tailings with increasing depth these concentrations decrease to or near analytical detection limits geochemical modelling of the pore water chemistry suggests that ph buffering reactions are occurring within the shallow oxidized zones and that secondary phases are precipitating at or near the underlying hardpan and transition zones mineralogical study of the tailings confirmed the presence of goethite jarosite gypsum native sulfur and a vermiculite type clay mineral goethite jarosite and native sulfur form alteration rims and pseudo morphs of the sulfide minerals interstitial cements composed of goethite jarosite and gypsum locally bind the tailings particles forming hardpan layers microprobe analyses of the goethite indicate that it contains up to 0 6 weight ni suggesting that the goethite is a repository for ni other sinks detected for heavy metals include jarosite and a vemiculite type clay mineral which locally contains up to 1 6 weight ni to estimate the mass and distribution of heavy metals associated with the secondary phases within the shallow tailings a series of chemical extractions was completed the experimental design permitted four fractions of the tailings to be evaluated independently these four fractions consisted of a water soluble an acid leachable and a reducible fraction as well as the whole rock total twenty five percent of the total mass of heavy metals was removed in the acid leaching experiments and 100 of the same components were removed in the reduction experiments the data suggest that precipitation coprecipitation reactions are providing an effective sink for most of the heavy metals released by sulfide mineral oxidation in light of these results potential decommissioning strategies should be evaluated with the recognition that changing the geochemical conditions may alter the stability of the secondary phases within the shallow tailings

geochemical and mineralogical aspects of sulfide mine tailings abstract tailings generated during processing of sulfide ores represent a substantial risk to water resources the oxidation of sulfide minerals within tailings deposits can generate low quality water containing elevated concentrations of so 4 fe and associated metal loid s acid generated during the oxidation of pyrite fes 2 pyrrhotite fe 1 x s and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate oxy hydroxide and silicate minerals the extent of acid neutralization and therefore pore water ph is a principal control on the mobility of sulfide oxidation products within tailings deposits metals including fe iii cu zn and ni often occur at high concentrations and exhibit greater mobility at low ph characteristic of acid mine drainage amd in contrast hydr oxyanion forming elements including as sb se and mo commonly exhibit greater mobility at circumneutral ph associated with neutral mine drainage nmd these differences in mobility largely result from the ph dependence of mineral precipitation dissolution and sorption desorption reactions cemented layers of secondary oxy hydroxide and hydroxy sulfate minerals referred to as hardpans may promote attenuation of sulfide mineral oxidation products within and below the oxidation zone hardpans may also limit oxygen ingress and pore water migration within sulfide tailings deposits reduction oxidation redox processes are another important control on metal loid mobility within sulfide tailings deposits reductive dissolution or transformation of secondary oxy hydroxide phases can enhance fe mn and as mobility within sulfide tailings production of h 2 s via microbial sulfate reduction may promote attenuation of sulfide oxidation products including fe zn ni and tl via metal sulfide precipitation understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings

evolution of the quaternary silicic volcanic complex of shiribetsu hokkaido japan an example of ignimbrite shield volcanoes in an island arc setting this paper describes the geology and eruptive history of a quaternary silicic volcanic complex at shiribetsu hokkaido japan with a focus on volcanic landforms produced by silicic explosive eruptions that were not associated with caldera collapse the shiribetsu volcanic complex comprises a dacitic pyroclastic plateau and an overlying dacitic central dome complex the pyroclastic plateau is 22 25 km in size 200 m high and consists of two ignimbrite units the km 1 and km 2 deposits sio2 67 68 wt total volume 10 km3 the central dome complex is 4 5 km wide rises to 650 m above the pyroclastic plateau and comprises two adjoining edifices which are east and west shiribetsu sio2 62 64 wt total volume 1 6 km3 east shiribetsu has a conical morphology whereas west shiribetsu comprises lava flows and a dome and has a large amphitheater a debris avalanche deposit volume 1 km3 extends from the amphitheater to the western foot of west shiribetsu a dacitic lava dome volume 0 2 km3 occurs within the amphitheater according to the stratigraphic relationships and new fission track dating the shiribetsu volcanic complex evolved as follows 1 dacitic explosive eruptions at ca 130 ka km 2 and 70 ka km 1 produced the pyroclastic plateau 2 effusive dacitic eruptions at 70 ka east shiribetsu and 60 ka west shiribetsu produced the central dome complex 3 sector collapse occurred at west shiribetsu at 50 60 ka and 4 lava dome formation within the amphitheater at 50 ka the evolution of the shiribetsu volcanic complex resembles that of ignimbrite shield volcanoes in the central andes shiribetsu may be the first identified example of ignimbrite shield volcanoes in an island arc setting we suggest that these are an independent class of explosive silicic volcanoes distinct from calderas and form above small magma chambers

h2o emission rate by the volcanic plume during the 2000 2002 miyakejima volcanic activity 1 extremely intense degassing at miyakejima volcano japan was observed after the 2000 eruption the h2o emission rate was estimated using a record of infrared thermal images at 400 kton day in november 2000 by april 2002 h2o emission rate had decreased exponentially to 100 kton day the h2o emission rate varied in parallel with the so2 emission rate except for the early stage in september 2000 the ratio of h2o to so2 emission rate after november 2000 remained constant at about 10 which is consistent with the h2o so2 ratio in the magma the large rate of h2o and so2 emission requires efficient degassing at shallow depth the agreement between the gas composition of the plume and that of dissolved volatiles in melt inclusions indicates h2o discharged from the vent was mostly magmatic in origin after november 2000

submarine flank eruption preceding caldera subsidence during the 2000 eruption of miyakejima volcano japan during the early part of a seismic swarm preceding eruption and caldera formation at miyakejima volcano discoloured sea surfaces were observed 1 5 km off the western coast of miyakejima on 27 june 2000 a later survey of the area using a multi beam side scan sonar and a remotely operated small submarine revealed four craters of 20 30 m diameter aligned east west in a 100 10 30 m area on the seafloor with hot water at 140 c being released from one of the centres each crater consists of submarine spatter overlain in part by scoria lapilli dredged spatter from the craters was fresh and there was no evidence of activity of marine organisms on the spatter surface indicating that the discoloured sea surface resulted from magmatic eruption on the seafloor this eruption occurred when a westward propagating seismic swarm initiated beneath miyakejima s summit passed through the area finding new magma on the seafloor demonstrates that this seismic swarm was associated with intruding magma moving outward from beneath miyakejima submarine spatter shows flattened shapes with a brittle crust formed by cooling in water and its composition is aphyric andesite of 54 wt sio2 the spatter is similar in whole rock and mineral composition to spatter erupted in 1983 however the wide range of cl in melt inclusions in plagioclase of the 27 june submarine spatter shows that it is not simply a remnant of the 1983 magma which has only high cl melt inclusions in plagioclase the mixed character of melt inclusions suggests involvement of a magma with low cl melt inclusions the magma erupted explosively on 18 august from miyakejima s summit considered as the second juvenile magma in this eruption contains low cl melt inclusions in plagioclase based on these observations and the eruption sequence we present the following model 1 a shallow magma chamber was filled with a remnant of 1983 magma that had evolved to a composition of 54 55 wt sio2 2 injection of the 18 august magma into this chamber generated a mixed magma having a wide range of cl in melt inclusions contained plagioclase the magma mixing might have occurred shortly before the submarine eruption and could have been a trigger for the initiation of the removal of magma from the chamber as an extensive dyke which eventually led to caldera subsidence

mount isa silica dolomite and copper orebodies the result of a syntectonic hydrothermal alteration system complex hydrothermal alteration system postdates deposition of the mount isa group and the lead zinc silver orebodies silica dolomite results from differential progressive metasomatic alteration of the entire range of microfacies constituting the lead zinc sequence the main components of this alteration are phyllosilicate development dolomitization and silicification this study concentrates on the latter two components and their role in breccia host formation all stages from incipient bedding and vein controlled alteration to total pervasive brecciation can be related to a deformational history of folding cleavage development and faulting a regional folding event d 2 formed the fold limb which constitutes the ore setting dolomite replacement veins and pseudobreccia complexes developed with varying intensity in favorable zones combinations of bedding and fracture controlled replacement continued until total dolomitization of the former shales occurred all forms and stages of dolomitic pseudobreccias are preserved by pseudomorphic quartz replacement in silicification zones which form the core of the orebody systems the separation in timing and mode of formation of lead zinc and copper orebodies is significant for exploration in the mount isa inlier the lead zinc mineralization appears to accumulate either syngenetically or at a very early stage in diagenesis but the copper has a structural control and a basic igneous association and is estimated to have been introduced at least 150 m y later modified journal abstract

insights into the 3d architecture of an active caldera ring fault at tendurek volcano through modeling of geodetic data abstract the three dimensional assessment of ring fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field geodetic or seismological data or by only partial ring fault rupture or slip here we use a novel combination of spatially dense insar time series data numerical models and sand box experiments to determine the three dimensional geometry and kinematics of a sub surface ring fault at tendurek volcano in turkey the insar data reveal that the area within the ring fault not only subsides but also shows substantial westward directed lateral movement the models and experiments explain this as a consequence of a sliding trapdoor ring fault architecture that is mostly composed of outward inclined reverse segments most markedly so on the volcano s western flanks but includes inward inclined normal segments on its eastern flanks furthermore the model ring fault exhibits dextral and sinistral strike slip components that are roughly bilaterally distributed onto its northern and southern segments respectively our more complex numerical model describes the deformation at tendurek better than an analytical solution for a single rectangular dislocation in a half space comparison to ring faults defined at glen coe fernandina and bar arbunga calderas suggests that sliding trapdoor ring fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring faults at different scales worldwide

growth of intra caldera lava domes controlled by various modes of caldera collapse the stiavnica volcano plutonic complex western carpathians abstract the stiavnica volcano plutonic complex is an erosional relic of miocene caldera stratovolcano in the western carpathians the complex exposes a vertical section from the volcano basement through subvolcanic intrusions and a ring fault to volcanic edifice comprising mostly andesitic lava flows and domes this paper examines internal structure magnetic fabric as derived from the anisotropy of magnetic susceptibility ams and emplacement dynamics of three intra caldera andesite domes referred to as domes 1 3 located near the presumed ring fault magnetic fabrics carried by multi domain titanomagnetite and titanomaghemite are interpreted as recording various mechanisms of dome growth controlled by active caldera collapse dome 1 is explained as a lava coulee fed by conduits located along the ring fault with a long lava outflow down the sloping caldera floor dome 2 represents an elongated ring fault parallel dome wherein the lava flowed a short distance over a flat floor dome 3 is interpreted as a composite dome fed from multiple linear fissures opened at a high angle to the ring fault subsequently the dome was intruded by ring fault parallel dikes that may have potentially fed overlying now largely eroded lava domes and flows finally we suggest that all domes formed during collapse of the stiavnica caldera and the various mechanisms of their growth reflect different stages of the caldera evolution from piston dome 2 through trap door dome 1 to piecemeal dome 3

sector collapse of mud volcanoes azerbaijan abstract field data collected from mud volcanoes in azerbaijan are used to describe a process in mud volcano development that involves portions of the constructional edifices collapsing outwards in thin skinned9 slides these events create kilometre scale scarps that are tens of metres in height arcuate in plan view elongate and facing downdip similar morphological features occur on igneous volcanoes and have been described as sector collapse9 structures the largest sector collapses in igneous volcanoes involve some 10 12 tons of mobilized material equivalent structures in mud volcanoes are several orders of magnitude smaller we employ a shape parameter that can be utilized in field and satellite based mapping to distinguish between slope failure and eruptive deposits three mud volcanoes with kilometre scale sector collapses are described and controlling mechanisms are reviewed the updip domains of these collapses are characterized by fluid escape showing that there is also linkage to deeper mud volcano structure the observations are reconciled in a model consisting of a deflating mud chamber that triggers thin skinned sector collapse the updip domain of the sector collapse is localized above a deep seated zone of volume loss and the downdip domain of the collapse runs down the edifice flank onto the surrounding plain

propagation linkage and interaction of caldera ring faults comparison between analogue experiments and caldera collapse at miyakejima japan in 2000 the formation of ring faults yields important implications for understanding the structural and dynamic evolution of collapse calderas and potentially associated ash flow eruptions caldera collapse occurred in 2000 at miyakejima island japan in response to a lateral intrusion based on geophysical data it is inferred that a set of caldera ring faults was propagating upward to understand the kinematics of ring fault propagation linkage and interac tion we describe new laboratory sand box experiments that were analyzed through digital image correlation dic and post processed using 2d strain analysis the results help us gain a better understanding of the processes occurring during caldera subsidence at miyakejima we show that magma chamber evacuation induces strain localization at the lateral chamber margin in the form of a set of reverse faults that sequentially develops and propagates upwards then a set of normal faults initiates from tension fractures at the surface propagating downwards to link with the reverse faults at depth with increasing amounts of subsidence interaction between the reverse and normal fault segments results in a deactivation of the reverse faults while displacement becomes focused on the outer normal faults modeling results show that the area of faulting and collapse migrates successively outward as peak displace ment transfers from the inner ring faults to later developed outer ring faults the final structural architecture of the faults bounding the subsiding piston like block is hence a consequence of the amount of subsidence in agreement with other caldera structures observed in nature the experimental simulations provide an analogy to the obser vations and seismic records of caldera collapse at miyake jima volcano but are also applicable to caldera collapse in general

sedimentary and volcano tectonic processes in the british paleocene igneous province a review research on the british paleocene igneous province bpip has historically focused on the emplacement chemistry and chronology of its elaborate central intrusive complexes and lava fields however the bpip has also been dramatically shaped by numerous erosion sedimentation and volcano tectonic events the significance of which becomes ever clearer as localities in the bpip are re investigated and our understanding of volcano sedimentary processes advances the resultant deposits provide important palaeo environmental palaeo geographical and stratigraphical information and highlight the wide range of processes and events that occur in ancient volcanic settings such as the bpip in this paper we review the sedimentary and volcano tectonic processes that can be distinguished in the bpip and conceptualize them within a generalized framework model we identify and describe the sedimentary responses to four broadly chronological stages in the history of the bpip volcanoes 1 the development of the lava fields 2 early intrusion induced uplift 3 caldera collapse and 4 post volcano denudation and exhumation of central complexes we highlight and illustrate the range of sedimentary processes that were active in the bpip these operated on and helped shape a dynamic landscape of uplands and lowlands of alluvial fans braided rivers lakes and swamps and of volcanoes torn apart by catastrophic mass wasting events and or caldera collapse

interaction of diamond mine waste and surface water in the canadian arctic abstract factors controlling the chemical composition of water interacting with finely crushed kimberlite have been investigated by sampling pore waters from processed kimberlite fines stored in a containment facility discharge water from the diamond recovery plant and surface water from the containment facility which acts as plant intake water were also sampled all waters sampled are ph neutral enriched in so 4 mg ca and k and low in fe pore water samples representing the most concentrated waters are characterized by the highest so 4 up to 4080 mg l 1 mg up to 870 mg l 1 and ca up to 473 mg l 1 the water discharged from the processing plant has higher concentrations of all major dissolved constituents than the intake water the dominant minerals present in the processed fines and the kimberlite ore are serpentine and olivine with small amounts of ca sulphate and fe sulphide restricted to mud xenoclasts reaction and inverse modeling suggest that much of the water rock interaction takes place within the plant and involves the dissolution of chrysotile and ca sulphate and precipitation of silica and mg carbonate evapoconcentration also appears to be a significant process affecting pore water composition in the containment facility the reaction proposed to be occurring during ore processing involves the dissolution of co 2 g and may represent an opportunity to sequester atmospheric co 2 through mineral carbonation

in situ sequestration of atmospheric co2 at low temperature and surface cracking of serpentinized peridotite in mine shafts abstract the investigation of carbonate formation at low temperature during weathering of ultramafic rocks has become increasingly important as it represents an analog study for a cost efficient carbon disposal strategy here we present new insight into carbonate formation under subarctic surface conditions obtained from extensively carbonated chromite mine shafts in the feragen ultramafic body e norway carbonation proceeded by formation of mm to cm thick carbonate surface coatings on the serpentinized peridotite host rock the surface coatings consist in most cases of pure lansfordite mgco 3 5h 2 o and sometimes nesquehonite mgco 3 3h 2 o heavy o and c isotopes are strongly enriched in the carbonate coatings relative to drip water samples from the mines and water samples from subaerial ponds the major element composition of the water samples reveal that infiltrating rainwater reacts rapidly with the peridotite mainly due to brucite dissolution within the mines discharging alkaline water forms thin films on walls and ceilings that evaporate upon circulation of cold dry air in mines with only one opening the carbonation is limited to the entrance area in mines with a more efficient air circulation due to multiple entrances carbonation is found throughout the mine evaporation of the mine water results in lansfordite saturation and precipitation and is accompanied by a rayleigh type distillation effect causing enrichment of the heavy c and o isotopes in the liquid from which the carbonates precipitate formation of the carbonate coatings involved fragmentation of the underlying serpentinite substrate fragmentation proceeded by subcritical cracking i e by a combination of substrate weakening due to brucite dissolution and stress build up due to lansfordite precipitation in fractures close to the surface reaction induced fracturing represents a positive feedback mechanism as it creates additional reactive surface area during the carbonation mining operations in the area ceased in the mid 1920s indicating that the described carbonation occurs on a time scale relevant for the disposal of anthropogenic co 2

a volcanotectonic survey of ascraeus mons mars 1 ascraeus mons is one of the largest volcanoes on mars it is replete with well preserved features that can be used to understand its volcanotectonic evolution previous studies of this volcano focused on specific features and were limited by the quality and coverage of contemporary data our objective is to review and enhance the existing developmental model for ascraeus by considering all endogenic surface features on the volcano we surveyed the volcano s caldera complex flank terraces pit structures sinuous rilles arcuate grabens and small vents we report the spatial and temporal distributions of these features appraise their proposed formation mechanisms in light of our mapping results and propose a detailed geological history for ascraeus mons an initial shield building phase was followed by the formation of a summit caldera complex and small parasitic cones while compression due to flexure of the supporting basement led to extensive terracing of the shield flanks an eruptive hiatus followed ending with the construction of expansive rift aprons to the northeast and southwest against later extensive flank resurfacing in the late amazonian continued flexure formed arcuate grabens concentric to the edifice localized eruption and surface flow of a fluid agent lava and or water from within the volcano then produced a population of rilles on the lower flanks finally in a change of flank tectonic regime from compression to extension pit crater chains and troughs developed on the main shield and rift aprons eventually coalescing to form large embayments at the northeast and southwest base of the volcano

quantifying carbon fixation in trace minerals from processed kimberlite a comparative study of quantitative methods using x ray powder diffraction data with applications to the diavik diamond mine northwest territories canada abstract the capacity of mine waste to trap co2 is in some cases much larger than the greenhouse gas production of a mining operation in mine tailings the presence of secondary carbonate minerals that trap co2 can therefore represent substantial fixation of this greenhouse gas the abilities of three methods of quantitative phase analysis to measure trace nesquehonite mgco3 3h2o in samples of processed kimberlite have been assessed the method of reference intensity ratios rir the internal standard method and the rietveld method with x ray powder diffraction data tests on synthetic mixtures made to resemble processed kimberlite indicate that both the rir and rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0 5 wt for conditions used in the laboratory below this value estimates can be made to a limit of approximately 0 1 wt using a calibration curve according to the internal standard method the rir method becomes increasingly unreliable with decreasing abundance of nesquehonite primarily as a result of an unpredictable decline in preferred orientation of crystallites for rietveld refinements structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases the resulting pattern of misestimates may be mistaken for the effect of amorphous and or nanocrystalline material in samples this effect is mitigated by collecting data from non serrated specimens which typically give relative errors on refined abundances for major and minor phases in the range of 5 20 however relative error can increase rapidly for abundances less than 5 wt nonetheless absolute errors are sufficiently small that estimates can be made for the amount of co2 stored in secondary nesquehonite using the rir method or the rietveld method for abundances 0 5 wt and a calibration curve for abundances

silicic magmas in the izu bonin oceanic arc and implications for crustal evolution abundant rhyolitehaseruptedfromthe izu bonin marianavolca nic arc ibm arc from its earliest stage eocene to the present geochemically three types of quaternary rhyolites exist in the izu bonin arcfront and theyare closely related tovolcanotypeand crus tal structure the dominantly basaltic islands of the volcanic frontproduce small volumes of rhyolites that we call r1 the submarinecalderas of the volcanic front erupt mostly rhyolite that we call r2 seamounts knolls and pillow ridges in thebackarcextensionalzoneare mostly basaltic but also contain rhyolites that we call r3 thethickest total crust and the thickest intermediate compositionmiddle crust occurs below the dominantly basaltic volcanoes whereas the intermediate composition middle crust tends to be thin nerbeneaththesubmarinecalderas r1rhyolitesmaybederivedfromquaternary andesitic sources whereas r2 and r3 rhyolites may bederivedfromoligoceneones thehighercao al

colloquium 2004 hydrogeotechnical properties of hard rock tailings from metal mines and emerging geoenvironmental disposal approaches tailings are ground rock particles from which the valuable minerals or metals have been extracted an historical overview on hard rock mines shows that since the 1930s it has become current practice to pump the tailings into storage areas circumscribed by dykes made of the tailings themselves however numerous physical and chemical stability problems were observed mainly owing to the particular hydrogeotechnical and mineralogical properties of the tailings therefore modifications to the conventional methods were proposed but these were relatively costly not always efficient and sometimes difficult to implement new management methods that improve the physical and or chemical stability have hence been developed to reduce environmental risks associated with tailings storage namely densified tailings environmental desulphurization covers built with tailings and co disposal of tailings and waste rock even if many aspects need to be optimized these approaches can be considered today as interest

from structure to erosion controlled subsiding calderas evidence thresholds and mechanics collapse calderas evolve by increasing their depth diameter ratio to properly characterize caldera evolution a structural s d ratio between structural subsidence and ring fault diameter ss ds and a topographic s d ratio between topographic caldera depth and topographic caldera width st dt are considered we review the evolution of the a d 2000 miyakejima caldera with two concentric ring faults at earlier collapsing stages and erosion of its wall accumulating debris on the floor at later collapsing stages while st dt and ss ds show a similar increase at initial stages when ss ds 0 33 the ss ds becomes significantly different from st dt while continuous caldera subsidence monotonically increases ss ds the erosion of the wall and the filling of the floor decrease st dt this evolution finds close similarities with recent caldera collapses of krakatau 1883 katmai 1912 fernandina 1968 tolbachik 1975 1976 pinatubo 1991 and dolomieu 2007 analog experiments mimic the observed variation evolving from a depression controlled by the activity of the double ring faults to that controlled by the erosion of the wall and sedimentation at the floor these natural and modeling results show that the control on the shape of mature calderas ss ds 0 07 and approaching ss ds 0 3 0 4 passes from a mainly structural to a mainly erosional control both st dt and ss ds are needed to describe the evolution of a collapse and the processes accompanying it evaluating st dt and ss ds allows proper description of the precise evolutionary stage of a caldera and of the relative importance of the structural and erosional processes and allows making semiquantitative comparisons between evolutionary stages

caldera collapse during the 2000 eruption of miyakejima volcano japan a collapsed caldera 1 6 km in diameter and 450 m in depth was formed at the summit of miyakejima volcano during the 2000 eruption the collapsed caldera appeared on 8 july with a minor phreatic eruption 12 days after seismic activity and magma intrusion occurred northwest of the volcano growth of the caldera took from 8 july to the middle of august with seismic swarms associated with the continuous intrusion of magma northwest of the volcano the growth rate of the caldera was about 1 4 107 m3 day and the final volume of the collapsed caldera was about 6 108 m3 major phreatomagmatic eruptions produced a total of about 1 6 1010 kg 1 1 107 m3 of volcanic ash after caldera growth the caldera structure and the nature of the eruptive materials of the first collapse on 8 july suggest that the surface subsidence was caused by the upward migration of a steam filled cavity with stoping of the roof rock above the magma reservoir the diameter of the stoping column was estimated to be 600 700 m from circumferential faults that developed in the caldera floor and the collapse of the caldera wall enlarged the diameter of the caldera to 1 6 km the total volume of the caldera and the horizontal diameter of the stoping column gave a subsidence of the caldera floor of 1 6 2 1 km

growth of phreatomagmatic explosion craters a model inferred from suoana crater in miyakejima volcano japan abstract a subvertical cross section of a maar diatreme volcano is exposed in the wall of the a d 2000 caldera on miyakejima volcano the maar suoana is one of the lateral vents of this volcano and it was inferred to be formed in the 7th century the subvertical wall of the a d 2000 caldera truncated the suoana maar crater at its center revealing the near comlete cross section of this small maar diatreme volcano exposed in the cross section are a 400 m wide maar crater an associated tuff ring with a maximum thickness of 20 m a diatreme extending vertically to a depth of about 220 m from the floor of the maar crater and a feeder dike connected to the base of the diatreme the depth of the diatreme structure is about 260 m from the original ground surface the outline of the diatreme resembles an upward opening funnel with an almost vertical wall below 560 m asl and an upward flaring wall above 560 m asl coarse grained volcanic breccia fills the diatreme the deposits of which can be divided into 6 units based on lithological and structural characteristics the upper half of the diatreme is filled with landslide deposits mainly derived from the surrounding crater wall the bottom of the diatreme is occupied by massive explosion breccia some coherent blocks were detached from the wall of the diatreme and preserved in the diatreme fill the y shaped cross sectional geometry of the suoana diatreme is the result of a combination of an underground subsidence in the lower part of the diatreme and the surface landslide in its upper part the inwardly inclined stratification of pyroclastic rock units and development of many small faults in the diatreme filling breccia indicate successive collapse and deformation of these materials within the diatreme during the eruption the upper part of the diatreme was formed by the landslides of the crater wall induced by the subsidence of the crater floor discharge of tephra from the bottom of the diatreme caused infill subsidence which induced sliding of the inner wall of the crater as a result the topographic diameter of the crater became much larger than that of the diatreme itself the tephra ring surrounding the crater consists mainly of pyroclastic fall deposits

accelerating mineral carbonation in ultramafic mine tailings via direct co2 reaction and heap leaching with potential for base metal enrichment and recovery accelerated carbonation of ultramafic mine tailings has the potential to offset co2 emissions produced by mining ores from cu ni platinum group element podiform chromite diamondiferous kimberlite and historical chrysotile deposits treatments such as acid leaching reaction of tailings with elevated concentrations of gaseous co2 and optimization of tailings pore water saturation have been shown to enhance co2 sequestration rates in laboratory settings the next challenge is to deploy treatment technologies on the pilot and field scale while minimizing cost energy input and adverse environmental impacts implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures here we describe column experiments designed to trial two geochemical treatments that address these criteria 1 direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation 10 co2 in n 2 and 2 repeated heap leaching of ultramafic tailings with dilute sulfuric acid in the first experiment we report rapid carbonation of brucite mg oh 2 in the presence of 10 co2 gas within tailings sampled from the woodsreef chrysotile mine new south wales australia within four weeks we observe a doubling of the amount of co2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field our simulated heap leaching experiments treated daily with 0 08 m h2so4 produce high mg leachates that have the potential to sequester 21 2 kg co2 m 2 which is approximately one to two orders of magnitude higher than the rate of passive carbonation of the wood sreef mine tailings although some nesquehonite mgco3 center dot 3h 2 o forms from these leachates most of the mg is precipitated as mg sulfate minerals instead therefore an acid other than h2so4 could be used otherwise sulfate removal would be required to maximize co2 sequestration potential from acid heap leaching treatments reactive transport modeling min3p is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years finally our synchrotron x ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals fe ni mn co cr become highly concentrated within secondary fe hydr oxide minerals at the ph neutralization horizon within our column experiments this discrete horizon migrates downward and our reactive transport models indicate it will become increasingly enriched in first row transition metals in response to continued acid leaching acid leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings waste rock or low grade ores

structures and evolution of the plumbing system of piton de la fournaise volcano inferred from clustering of 2007 eruptive cycle seismicity analysis of seismic activity associated with the eruptions of 2007 which led to the collapse of the dolomieu crater on april 5th reveals the link between the seismicity and the magma transfers at piton de la fournaise three eruptive phases occurred on february 18th march 30th and april 2nd 2007 at the summit 2 000 m and 600 m high on the south east flank respectively illustrating the three types of eruptions defined for the current piton de la fournaise activity we use cross correlation of seismic waveforms and clustering to improve the earthquake locations and determine the best constrained focal mechanisms with an average of 78 p phase polarities the pre eruptive seismicity of the february and march eruptions is composed of time extended clusters that also preceded other distal eruptions from 2000 to 2007 our analysis shows that the seismic swarm prior to the february eruption initiated the intrusion that led to the april 2007 eruption the seismicity preceding the dolomieu crater collapse consists of numerous but time limited clusters and specific seismic activity that accompanied the dolomieu crater collapse from april 1st to april 5th earthquakes with clvd mechanisms combined with normal faulting sources occurred between 0 8 and 0 km asl until the complete rupture of the shallow magma storage roof this collapse induced the propagation of a de pressurization front and triggered a migration of seismicity from 0 to 8 km along a very narrow path

verifying and quantifying carbon fixation in minerals from serpentine rich mine tailings using the rietveld method with x ray powder diffraction data most carbon on earth is bound within minerals and increasing the uptake of atmospheric carbon dioxide into minerals may reduce the greenhouse gas content of the atmosphere we document carbon disposal through the mineralization of mine tailings at clinton creek yukon territory and cassiar british columbia we confirm crystallographic binding of carbon in these tailings and quantify carbon dioxide uptake using quantitative phase analysis with the rietveld method for x ray powder diffraction data planar disorder in the structures of the kaolinite serpentine group minerals makes rietveld refinements of x ray powder diffraction data for serpentinites problematic using structureless pattern fitting and with the addition of a known quantity of a well crystallized material the problem of structural disorder is overcome by considering the serpentine minerals as amorphous phases we test the accuracy and precision of this refinement method using synthetic serpentine rich mine tailings of known composition estimates of the abundance of hydrated magnesium carbonates in these tailings have a precision of approximately 5 relative for mineral species present in amounts greater than 10 wt precise estimates of carbonate mineral content and crystallographically bound atmospheric co 2 are made for samples of serpentine rich tailings from clinton creek and cassiar results for mine tailings are also compared to mineralogically similar samples from a carbonate playa at atlin british columbia the potential for decomposition of metastable hydrated magnesium carbonate phases to geologically stable magnesite may represent long term stability of the products of mineral sequestration in mine tailings

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

banded tremor at miyakejima volcano japan implication for two phase flow instability 1 volcanic tremor was recorded during a period of volcanic gas emission from miyakejima volcano activity from 2001 to 2006 similar to volcanic earthquakes and long period events the source of banded tremor lies at a shallow depth beneath the summit caldera tremor packets occurred every 20 to 45 min for 1 to 2 days we modeled the source of this phenomenon with a two phase hydrothermal instability flow model consisting of subcool and superheated water regions and found two modes an excursion mode and a series of damping oscillations mode the interval between banded tremor packets can be interpreted in terms of this two phase flow oscillation with a heat supply in the order of 10 100 mw from the magma beneath the hydrothermal system

the magmatic plumbing of the submarine hachijo nw volcanic chain hachijojima japan long distance magma transport 1 recent geophysical observations on basaltic composite volcanoes in izu bonin arc reveal the process of long distance lateral magma transport within arc crust to clarify a long distance magma transport system of the basaltic arc volcano from geological and petrological aspects we investigated 20 km long submarine volcanic chains hachijo nw chain and hachijo kojima chain and cones on the northeastern slope ne edifices as well as subaerial satellite cones nested hachijo nishiyama volcano in the northern izu arc front basalts from hachijo nw chain have more primitive composition than those from other edifices the composition of the hachijo nw chain basalts is controlled by fractional crystallization while plagioclase accumulation occurred in ne edifices and subaerial satellite cones trace element and isotopic characteristics indicate that the same basaltic primary magma is involved in all sections of the volcano this leads us to consider that magma was transported long distances between the nishiyama volcano and the hachijo nw chain primitive magma was laterally transported nnw for at least 20 km in the middle to lower crust 10 20 km deep from nishiyama volcano with only minimal crustal level modifications and formed hachijo nw chain on the other hand magmas experienced crystal fractionation and accumulation at shallow magma chamber beneath nishiyama volcano seems to have been transported in a short distance 5 km and formed ne trending edifices and subaerial satellite cones the long distance magma transport seems to be controlled by a regional extensional stress regime while short distance transport may be controlled by local stress regime affected by load of main volcanic edifice

localized deformation at miyakejima volcano based on jers 1 radar interferometry 1992 1998 1 stacked radar interferograms at miyakejima volcano japan between 1992 and 1998 showed two localized significantly deforming areas with a magnitude of 4 6 mm yr in the radar line of sight one area is close to the 1983 eruption vent and using a simple closed analytical formulation the deformation is interpreted as due to a thermoelastic contraction of a formerly intruded magma the other one detected in the previous caldera is explained by a depressurization source whose depth 500 m coincides with that of a low resistivity zone interpreted as a hydrothermal reservoir also our computed co2 flux is consistent with in situ measurement data the reservoir volume is significantly less than the collapsed volume in 2000 and its depth is much shallower than the void detected prior to the collapse hence the depressurization would not directly induce the caldera collapse in 2000

mine drainage from the weathering of sulfide minerals and magnetite pyrite and pyrrhotite are the principal minerals that generate acid drainage in mine wastes low ph conditions derived from fe sulfide oxidation result in the mobilization of contaminant metals such as zn cd ni and cr and metalloids such as as which are of environmental concern this paper uses data from detailed mineralogical and geochemical studies conducted at two canadian tailings impoundments to examine the mineralogical changes that pyrite pyrrhotite sphalerite and magnetite undergo during and after sulfide oxidation and the subsequent release and attenuation of associated trace elements the stability of sphalerite in tailings impoundments generally is greater than that of pyrrhotite but less than pyrite dissolved ni and co derived from fe sulfides and to a lesser extent dissolved zn and cd from sphalerite are commonly attenuated by early formed fe oxyhydroxides as oxidation progresses a recycling occurs due to continued leaching from low ph pore waters and because the crystallinity of fe oxyhydroxides gradually increases which decreases their sorptive capacity unlike many other elements such as cu pb and cr which form secondary minerals or remain incorporated into mature fe oxyhydroxides zn and ni become mobile magnetite which is a potential source of cr is relatively stable except under extremely low ph conditions a conceptual model for the sequence of events that typically occurs in an oxidizing tailings impoundment is developed outlining the progressive oxidation of a unit of mine waste containing a mixed assemblage of pyrrhotite and pyrite

timing and characteristics of the archean subaqueous blake river megacaldera complex abitibi greenstone belt canada abstract the archean blake river group of the abitibi greenstone belt represents a megacaldera complex which evolved over 8 11 m y from approximately 2704 to 2696 ma the early misema caldera developed from a series of amalgamated shield volcano complexes identified by the remnants of mafic dyke and sill systems these remnants are found in the jevis clericy montsabrais renault clifford tannahill and colnet regions where summit calderas are delineated by circular ring dyke structures the secondary 330 trending new senator caldera formed within the envelope of the misema caldera and exhibits a box work graben type structure finally the felsic dominated 070 striking noranda caldera well known for its vms endowment represents the final collapse of the megacaldera complex deformation has overprinted the calderas but structural patterns can be used in order to reconstruct the pre existing volcanic architecture structures such as mafic ring dyke complexes and rhyolitic dome flow complexes have nucleated fold geometries and synvolcanic fractures were reactivated within zones of ductile deformation precise u pb geochronological analyses were conducted in selected areas with specific emphasis on the misema and new senator calderas felsic volcanism progressed throughout the evolution of the megacaldera complex and intermediate to felsic units have been dated to limit this evolution the misema caldera formed between 2704 and 2702 ma via the amalgamation of shield volcanoes that were probably active prior to 2704 ma the new senator caldera was generated between 2702 and 2700 ma during paroxysmal felsic volcanism followed by the collapse of the noranda caldera culminating between 2700 2696 ma the misema caldera was generated by a gravitational stress field consistent with the formation of ring and radial dyke architecture whereas the se trending new senator caldera is more compatible with a sw trending principal compression direction related to oblique convergence in the abitibi belt the noranda caldera is interpreted as a ne rift structure that formed in the final stages of megacaldera evolution

a rock glacier pond system nw italian alps soil and sediment properties geochemistry and trace metal bioavailability abstract rock glacier sediment transfer and ice melting can impact surface waters located downstream however there is a lack of knowledge on the influence of rock glacier dynamics on the geochemical hydrochemical and ecological characteristics of adjacent impounded surface waters in the col d olen area long term ecological research site nw italian alps an intact rock glacier terminates into a pond and solute enriched waters originating from the rock glacier flow into the pond through a subsurface hydrological window in this study we performed geophysical and ground surface temperature measurements moreover we sampled soils and sediments in different compartments of the investigated rock glacier pond system and we further sampled benthic invertebrates in the pond cold ground thermal regime ground ice presence and coarse debris cover on the rock glacier together with its lithology serpentinites influence the rock glacier geochemistry and ecology with respect to surrounding areas pond geochemistry is affected by transfer of trace metal enriched fine grained debris and meltwaters from the rock glacier enhanced bioavailability of serpentinite associated trace metals was proved with concentrations of ni and cr in benthic invertebrates up to 384 and 110 mg kg 1 d w respectively potentially exerting toxic effects on pond biota the advancing movement of the rock glacier not only has delivered sediments to the pond but it has progressively filled the valley depression where the pond is located creating a dam that could have modified the level of impounded water this process likely constituted a sediment trap in which serpentinitic rock glacier sediments could be deposited at the pond bottom with related geochemical and ecological implications this study illustrates the importance of rock glaciers in influencing the characteristics of downstream freshwater bodies and highlights the need to improve our knowledge about climate change related impacts of rock glacier dynamics on alpine headwaters