fault controlled soil co2 degassing and shallow magma bodies summit and lower east rift of kilauea volcano hawaii 1997 soil co2 flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower east rift zone of kilauea volcano anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles this result contrasts with what was recently observed on mt etna where most of the surveyed faults were associated with anomalous soil degassing the difference is probably related to the differences in the state of activity at the time when soil gas measurements were made kilauea was erupting whereas mt etna was quiescent although in a pre eruptive stage unlike mt etna flank degassing on kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing east rift eruption or in areas of the lower east rift where other shallow likely independent reservoirs are postulated anomalous soil degassing was also found in areas without surface evidence of faults thus suggesting the possibility of previously unknown structures

development and flow structures of sand injectites the hind sandstone member injectite complex carboniferous uk abstract the hind sandstone member of the carboniferous craven basin occurs within a thick succession of marine mudstone and is here interpreted as a sandstone injectite complex injectites take the form of i sills ii upwards emplaced dykes iii downwards emplaced dykes iv a sedimentary laccolith and v sandstone bodies remobilised in situ the remobilised and injected sand originated from small turbidite scour fills and potentially a more significant sand body such as a submarine slope gully fill the sedimentary laccolith appears to jack up the units it injects and is filled by sandstone with a chaotic fabric suggestive of brecciation of partly cemented sand the laccolith and sill dominated nature are suggestive of relatively shallow remobilisation sills are commonly laterally gradational with upwards emplaced dykes and in some cases these feed apparently downwards emplaced dykes a series of flow structures are preserved within some of the injectites and these provide clues to the emplacement history crack propagation direction is inferred from the orientation of undulating crests developed on the upper and lower surfaces of injectites peak flow is indicated by scour marks resembling flute and tool marks which are superimposed onto these undulating surfaces internal flow structures highlighted by pyrite mineralistion record the waning stage of injection the observed flow structures suggest that the apparent crack propagation direction was generally oblique to the peak flow and nearly perpendicular to the direction of late stage fluidised sediment flow crack propagation relates to the local stress field whilst injection flow may be related to the local pore pressure distribution recognition of this suite of structures may provide a useful interpretational tool for other injectites in both core and outcrop pore fluid overpressure which drove injection developed through the migration of petroleum and mineralising fluids from the underlying bowland shales and older limestones a complex brecciated fracture network within the mudstones underlying the injectites records fluid migration pathways sliced blocks and thin sections from injectites reveal flow structures defined by iron pyrite mineralisation the trigger is here related to growth of compressional structures and associated syn sedimentary slumps which occur at the same stratigraphic level as the injectites

forced folding and fracturing induced by differential compaction during post depositional inflation of sandbodies insights from numerical modelling abstract three series of numerical models based on the discrete element method were constructed to simulate forced folding and fracturing triggered by postdepositional inflation of fluidised sandbody the models consist of numerous particles that have relatively low to high interparticle bonds to represent overburden sediments with a relatively low to high cohesion and cohesionless frictionless particles to represent fluidised sands the modelling results show that normal faults were produced due to the upward inflation of sand domes and the resulting flexed overburden when the cohesion of the host sediments is low opening voids were created as a result of strata collapse when the intrusion related normal faults terminated within the host sediments as blind faults conical fractures that are aligned along sandbody margins were produced which consist of closed lower segments with a reverse displacement and opening middle upper segments with a minor to zero shear component forced folds were generated in most models with a moderate to high cohesion resulting in differential compaction in the overlying sediments that can account for the formation of fold related fractures which are either shear hybrid or pure tensile depending on their structural positions the amplitude of forced folds is closely associated with both cohesion and thickness of sediments in the overburden whilst fold wavelength is mainly controlled by sediment cohesion based on the modelling results three types of preferential sites for the storage of injected sands were suggested which are believed to be instructive for subsurface sandbody detection and prediction this study demonstrates that differential compaction induced by sand inflation can play an important role in overburden folding and fracturing

an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

emplacement of sandstone intrusions during contractional tectonics abstract sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure however the contribution provided by horizontal compressive stress to the build up in overpressure and the resulting emplacement of sand injection complexes is still to be substantiated by robust field observations an opportunity to address this issue occurs in central california where a large volume of sandstone intrusions record regionally persistent supra lithostatic pore pressure detailed fieldwork allows sandstone filled thrusts to be recognized and for the first time permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the great valley basin fluidized sand was extensively injected along thrust surfaces and also fills local dilatant cavities linked to thrusting the main aims of this paper are to provide detailed descriptions of the newly recognized syn tectonic injections and describe detailed cross cutting relationships with earlier sandstone injection complexes in the study area finally an evolutionary model consisting of three phases of sand injection is provided in this model sand injection is linked to contractional tectonic episodes affecting the western side of the great valley basin during the early middle cenozoic this study demonstrates that sand injections driven by fluid overpressure may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation it is shown that different generations of sand injection can develop in the same area under the control of different stress regimes linked to the evolving mountain chain

petrofacies of eocene sand injectites of the tumey giant injection complex california usa abstract the forearc succession of great valley group in central california provides some of the best examples of giant sand injection complexes in the world and is therefore considered valuable analogues for injectite systems in the subsurface several sand injection complexes are well described in the outcrop and subsurface however the petrographic characteristics of injectites are still poorly documented in this paper we present the results of an integrated study of field observations quantitative and qualitative sandstone petrography provenance and petrofacies analysis of the tumey giant injection complex tgic in order to understand its lithostratigraphy and petrological evolution and its impacts on reservoir petrofacies characteristics and fluid migration the tgic intrudes into a 450 m thick deep water succession of slope mudrocks and sandy channel fills of the kreyenhagen shale eocene forming an interconnected network of sandstone sills dykes and injection breccias the complex generated a horizontal and vertical plumbing system for fluid migration connecting isolated sandy channel fills among low permeability mudrocks the primary detrital composition diagenetic products microtextures and provenance signatures allowed for the definition and discrimination of depositional and intrusive petrofacies and their genetic relations petrofacies associations confirm that the gypsum cemented feldspathic litharenites from the kreyenhagen shale channel fills are the only source for the injection complex eodiagenetic compaction and extensive gypsum cementation reduced the primary porosity of the complex while telodiagenetic dissolution of autigenic constituents formed pervasive secondary porosity the underlying calcite cemented arkosic sandstones of the lodo and domengine formations acted as barriers for fluid flow aiding lateral fluid migration and overpressure buildup within the overlying kreyenhagen channel fills intense grain microfracturing occurred during sand remobilization and injection along with erosion of the host mudrocks this study has significance for the generation of reliable stratigraphic and petrological models for sand injection complex genesis and evolution that consequently can help the understanding and exploration of injectite complexes elsewhere

late cenozoic geological evolution of the northern north sea development of a miocene unconformity reshaped by large scale pleistocene sand intrusion despite hundreds of wells and extensive 3d seismic coverage the late cenozoic geological evolution is still not completely understood in the prolific northern north sea hydrocarbon province this is mainly due to post depositional modification of sediment body geometries by injections of large volumes of sand using high quality 3d seismic and well data above the snorre and visund fields we propose a new late cenozoic geological model that describes pre injection geomorphological forms and sand injection events the northern north sea was exposed during mid and late miocene times 10 myr simultaneously with the regional miocene compression phase subaerial and coastal cliff erosion formed escarpments up to 100 m high around the miocene pliocene boundary the northern north sea subsided below sea level and a layer of glauconitic sand was deposited during the early pleistocene glacial period high fluid pressures fractured the regional hordaland group seal fluidized sand either vented to the sea floor or was deposited in irregular sand bodies up to 150 m thick above them the injected sand lifted the overburden and formed irregular mounds that reshaped the top hordaland group unconformity regionally during the glacial period the area was tilted regionally by 0 3 towards the nne

soil co2 degassing along tectonic structures of mount etna sicily the pernicana fault abstract carbon dioxide emissions from the soil have been investigated along lines of equally spaced sampling points perpendicular to the pernicana fault on mt etna anomalous values of soil co2 have been found not only along the fault plane but also along directions parallel to it both to the n and to the s of the main fault the acquired data seem to reveal a shallow step like geometry of the pernicana fault system with parallel faults being generally not deeper than the interface between etna s volcanic cover and its sedimentary basement a few hundred meters the distribution of the anomalous co2 emissions has also revealed that the pernicana fault continues at least as far as the ionian sea in an area where only sedimentary rocks crop out this finding would suggest that the main structure is deeper than the base of the volcanic cover thus cutting at least the uppermost portion of etna s sedimentary basement isotopic analyses of c carried out in samples from locations of high co2 seem to indicate that the emitted co2 is a mixture of an organic shallow component and a minor deeper magmatic one both chemical and isotopic data on soil gases emitted in the easternmost part of the studied area distinguished another tectonic structure which seems to be much deeper than the pernicana fault and is roughly directed nne ssw this direction being coincident with an important structural trend of eastern sicily

a coupled fluid fracture approach to propagation of clastic dikes during earthquakes abstract the propagation of clastic dikes was studied in ami az plain where hundreds of clastic dikes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin two analytic models were established to estimate the dike propagation velocities the dike emplacement duration and the driving pressures that were associated with dike propagation either under laminar or turbulent flow conditions these models depend on the host rock and fluid properties dike width and length based on these properties and field limitations the results indicate that the dikes were propagated under turbulent flow conditions and propagation velocities of 4 65 m s the emplacement duration of the clastic dikes is between 0 8 and 2 s which is similar to the order of the acoustic wave duration that passes through the soft rock during an earthquake event this implies that the propagation of dikes could form during the passing acoustic waves and may thus be considered as an earthquake induced impact structures the calculated driving pressures that were generated during the earthquake events near the surface are 1 2 mpa one order of magnitude larger than the pressure due to the overburden on the source layer

development and post depositional deformation of a middle eocene deep water sandy depositional system in the sorvestsnaget basin sw barents sea abstract three dimensional seismic data from the sorvestsnaget basin sw barents sea supported by well data are used to investigate a middle eocene deep water depositional system the system forms a nnw oriented sediment accumulation characterized by increased seismic amplitudes and abrupt western termination the data indicate that post depositional sand remobilization and injection led to formation of sub circular sediment blocks up to several km wide to the east of the main accumulation the deep water depositional system was deformed by wing like sandstone intrusions extending 200 400 m upwards from the margins of the parent sand bodies the intrusions have polygonal or broadly circular plan view geometries deformation is inferred to have been associated with overpressure of the sand bodies as a result of rapid burial fluid migration into the sealed sand bodies from deeper sources via synsedimentary faults and fluid drainage from the surrounding mudrock during early compaction the final triggering mechanism for sand remobilization and injection is inferred to have been fracture propagation due to differential compaction and or fault induced earthquakes the injectite complexes are often associated with folding of overlying strata which we relate to differential compaction intrusion of sand took place during the middle eocene post depositional sand remobilization and injection have important implications for hydrocarbon exploration because they cause changes in the reservoir primary architecture connectivity and structure

diffuse volcanic gas emission and thermal energy release from the summit crater of pico do fogo cape verde we report the first detailed study of diffuse emission of carbon dioxide co2 hydrogen sulfide h2s helium he and hydrogen h2 from the summit crater of pico do fogo volcano cape verde diffuse co2 h2s he and h2 gas fluxes were measured at 57 sampling sites and ranged up to 12 800 13 1 and 6 g m 2 day 1 respectively soil temperature measurements at each sampling site were used to evaluate the heat flux most of the summit crater shows relatively high co2 efflux with highest values close to the fumarolic area suggesting a structural control of the degassing process in contrast h2s effluxes were negligible or very low at the summit crater except close to the fumarolic area where anomalously high co2 efflux and soil temperatures were also measured we estimate total co2 h2s he and h2 diffuse gas fluxes of 219 t day 1 25 4 and 33 kg day 1 respectively based on a h2o co2 mass ratio of 1 52 measured at the fumaroles we estimate a diffuse steam flux from the summit crater of approximately 330 t day 1 the enthalpy of this steam is equivalent to a heat flux of about 10 3 mw the diffuse gas emission and thermal energy released from the summit crater of pico do fogo volcano are comparable to those observed at other volcanoes sustained surveillance of pico do fogo using these methods will be valuable for monitoring the activity of one of the most active volcanoes in the atlantic ocean

exsolution of ilmenite and rutile in hornblende two basic intrusions in the caledonian of western scotland were studied by optical microscopy electron microprobe analysis scanning and transmission electron microscopy and x ray diffraction ilmenite occurs in 8 orientations 4 pairs in which members of a pair are equivalent by the symmetry of the hornblende rutile occurs in 6 orientations 4 symmetrically distinct orientations the orientations are interpreted in terms of the fully o rotated model amphibole structure in which the oxygen atoms are cubic close packed it is possible that the ilmenite and rutile were exsolved in a closed system from a parental amphibole with a normal structural formula modified journal abstract

physical modelling of sand injectites abstract sand injectites are structures that result from intrusion of fluidized sand into fractures we have studied them in the tampen spur area of the north sea and have reproduced them experimentally by driving compressed air through layers of sand glass microspheres and silica powder the silica powder was cohesive and capable of hydraulic fracturing whereas the sand and glass microspheres were almost non cohesive and therefore able to fluidize the models were dynamically similar to their natural counterparts for as long as equilibrium was static when the processes became dynamic so that inertial forces were significant the scaling was approximate and the corresponding reynolds numbers differed the experimental apparatus was a square box 1 m 1 m wide resting on a grid of fluid diffusers during the experiments the fluid pressure increased until it attained and surpassed the weight of overburden flat lying hydraulic fractures containing air formed within cohesive and least permeable layers heterogeneities in material properties and layer thicknesses were responsible for localizing fracture networks when any one network broke through to the surface rapid flow of air through the fractures fluidized the underlying mobile materials and even depleted some of the layers some of the fluidized material extruded at the surface through vents forming volcanoes and sheets the remainder lodged at depth forming sand injectites or laccoliths conical sand injectites formed preferentially where layers had high resistance to bending laccoliths formed nearer the surface where overlying layers had low resistance to bending the experimental sand injectites were broadly similar to those in the tampen spur area of the north sea as well as other areas

new evidence for the form and extent of the pernicana fault system mt etna from structural and soil gas surveying a multidisciplinary study based on structural and soil gas surveys was carried out in order to investigate the relationship between soil co2 degassing and the tectonic setting of the lower northeastern flank of mt etna volcano the results show that anomalous soil co2 emissions occur mainly along faults trending wnw ese and also where these faults intersect the other main fault set trending ne sw that displaces the study area in particular anomalies in co2 degassing were revealed both along the pernicana fault and along another fault fiumefreddo fault which may represent the prolongation of the former towards the ionian sea coast in the areas where these structures show evident surface faulting they are all characterised by left lateral displacements and aseismic creep behaviour furthermore the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline in the light of these findings we suggest that the pernicana and fiumefreddo faults are discrete segments of a near continuous left lateral shear zone affecting the whole north eastern flank of mt etna as far as the ionian coast

runoff control of soil degassing at an active volcano the case of piton de la fournaise reunion island abstract airborne atmospheric and in situ soil gas analyses demonstrate that distal gas leaks are non existent at piton de la fournaise pf despite frequent eruptions airborne traverses made at a constant altitude indicated that no detectable large scale co 2 degassing occurs from the volcano in situ soil gas traverses co 2 4 he 222 rn across the active rift zones the summit crater and the caldera rims show both a lack of positive anomalies and evidence of strong depleted concentrations for he and co 2 with respect to air depletions in soil he is explained by intense rain water infiltration a more unexpected result lies in the very low co 2 concentrations down to 92 ppm in bare soils in the summit region such a depletion was not previously reported and is attributed to considerable basalt weathering operating as the result of huge runoff a model has enabled both the runoff and the co 2 consumption occurring within the basaltic layers to be calculated data obtained are consistent with values expected from large scale erosion models and with the local calculated diffusive flux of co 2 in soils the huge runoff together with the basaltic lithology of the volcano are found to be the main factor controlling the soil gas signatures at pf

the summit hydrothermal system of stromboli new insights from self potential temperature co2 and fumarolic fluid measurements with structural and monitoring implications accurate and precisely located self potential sp temperature t and co2 measurements were carried out in the summit area of stromboli along 72 straight profiles sp data were acquired every metre and t data every 2 5 m co2 concentrations were acquired with the same density as t but only along seven profiles the high density of data and the diversity of the measured parameters allows us to study structures and phenomena at a scale rarely investigated the shallow summit hydrothermal activity pizzo fossa area is indicated by large positive sp t and co2 anomalies these anomalies are focused on crater faults suggesting that the fracture zones are more permeable than surrounding rocks at stromboli the analysis of the distribution of these linear anomalies coupled with the examination of the geologic photographic and topographic data has led us to propose a new structural interpretation of the summit of stromboli this newly defined structural framework comprises 1 a large pizzo circular crater about 350 m in diameter 2 a complex of two concealed craters nested within the pizzo crater the large and the small fossa craters thought to have formed during the eruption of the pizzo pyroclastites unit the small fossa crater is filled with highly impermeable material that totally impedes the upward flow of hydrothermal fluids and 3 the present complex of active craters on the floor of the fossa short wavelength sp lows are organized in drainage like networks diverging from the main thermal anomalies and converging toward the topographic low in the fossa area inside the small fossa crater they are interpreted as the subsurface downhill flow of water condensed above the thermal anomalies we suspect that water accumulates below the small fossa crater as a perched water body representing a high threat of strong phreatic and phreatomagmatic paroxysms t and co2 anomalies are highly correlated the two types of anomalies have very similar shapes but the sensitivity of co2 measurements seems higher for lowest hydrothermal flux above t anomalies a pronounced high frequency sp signal is observed isotopic analyses of the fluids show similar compositions between the gases rising through the faults of the pizzo and large fossa craters this suggests a common origin for gases emerging along different structural paths within the summit of stromboli a site was found along the large fossa crater fault where high gas flux and low air contamination made gas monitoring possible near the active vents using the alkaline bottle sampling technique

new 230th 238u and 14c age determinations from piton des neiges volcano reunion a revised chronology for the differentiated series 230th 238u age measurements were carried out on 18 samples of lava from piton des neiges these lavas range from basalts to trachytes the ages extend from 270 000 to 12 000 a b p and cover most of the period in which differentiated series magmas were erupted new 14c ages on charcoal sampled in young pyroclastic deposits are also presented the late stage evolution of the volcano is discussed in the light of these new ages and a chronology of the explosive activity is given the oldest pyroclastic flow ste suzanne is more than 220 000 a other pyroclastic units were emitted between 220 000 and 110 000 a there were at least two episodes of caldera formation the first episode is inferred to have occurred about 190 000 a ago the last occurred between 190 000 and 110 000 a although the most recent lava activity was mainly concentrated on the eastern flank of the volcano and around the summit area it also occurred about 70 000 a ago in the southwestern part of the massif the youngest explosive activity about 50 000 to 20 000 a on the eastern flank of the volcano has now been dated by three different methods 14c and th u ages on block and ash flow tuffs k ar ages on associated domes youthful explosive activity about 35 000 to 12 000 a on the western flank of the volcano is also demonstrated by 14c dating on charcoal and by a th u age of 12 000 a on a trachytic nuee ardente deposit this last age indicates that activity may have persisted later than previously supposed and implies a high rate of erosion for the cirque de mafate

heavy mineral assemblages in sandstone intrusions panoche giant injection complex california u s a excellent exposure from part of the panoche giant injection complex in the san joaquin valley is used to examine provenance characteristics of sandstone intrusions with respect to two parent sandstone units that are known to feed the sand injection complex the succession is part of the upper mesozoic to lower tertiary great valley group and was deposited in a deepwater part of an evolving deep water forearc basin the section examined is mudstone dominated and the sand injection is constrained to have occurred in the danian sandstones in the dosados member moreno fm are identified as the main parent unit on the basis of total heavy mineral assemblage compositions and varietal studies of selected minerals tourmaline garnet titanite apatite and zircon fluidized sand is emplaced in turbulent flow conditions creating high velocity inter grain collisions evidence of comminution and diminution of minerals that are less hard than quartz is documented using indices for the relative hardness tah and durability tad of heavy minerals preferential settling of high density zircon relative to lower density tourmaline produces density controlled variations of zircon tourmaline upward through the injection complex heavy mineral dissolution occurred in the most permeable sandstone intrusions and is believed to record the effects of mid eocene deep weathering when subtropical climate prevailed in the study area detrital heavy mineral assemblages which are dominated by titanite and garnet record erosion of the sierran metamorphic terrane with mafic and alkaline plutonic rocks zircon with u pb ages of c 140 160 ma and c 90 110 ma consistent with earlier independent analyses record erosion of sierran granitoids on the paleo seafloor enrichment of ca amphibole and epidote is indicative of sierran provenance concurrent with sand extrusion the presence of na amphibole in the uhalde sandstone supports earlier work that suggested sediment input from obducted seafloor to the west

indicators of propagation direction and relative depth in clastic injectites implications for laminar versus turbulent flow processes clastic injectites are widely recognized in deep water stratigraphic successions although their sediment transport processes propagation direction and depth of injection are poorly constrained understanding how they form is important as injectites are increasingly being recognized as significant components of sedimentary basin fills yet are not predicted by standard sedimentary facies models here analysis of features on the margins of exhumed clastic sills and dikes and clasts within them enables their genesis to be determined a diverse array of diagnostic structures is found on the margins of injectites in the karoo basin south africa where the net direction of injection and position of the parent sand are well constrained injectite margin features include mudstone clast rich surfaces planar or smooth surfaces blistered surfaces and parallel and plumose ridged surfaces combined these features are critical in distinguishing injected sands where injectites are strata concordant from those of primary deposition all features are indicative of propagation through brittle very fine grained sediments at depths where the applied shear stress is at least four times the tensile strength of the host rock additionally the presence of parallel ridges plumose ridges and steps allows local fracture propagation to be constrained and in turn injection direction the features described provide evidence that sands were injected at considerable depth in closed fractures with limited capacity for flow dilution and turbulence enhancement calculated reynolds numbers lack of erosion at injectite walls and the presence of mud clasts at the top and base of sills indicate that many flows were likely fully laminar during injection the sedimentary features of these confined relatively deep laminar flow induced injectites are very different from injectites that reach the surface and produce extrudites surface linked injectites are associated with open conduits where a greater fraction of carrier fluid to particles can be accommodated enabling highly turbulent lower concentration flows

geometry and lithofacies of coarse grained injectites and extrudites in a late pliocene trench slope basin on the southern boso peninsula japan abstract this study investigates the geometry and internal structures of coarse to very coarse grained volcanic sandstones and volcanic breccias with many siltstone clasts interpreted to be sill like injectites and extrudites occurring in an upper pliocene trench slope basin succession on the southern boso peninsula japan the injectites occur in the uppermost shiramazu formation and pinch out laterally into siltstone dominated deposits of the mera formation their thicknesses vary from a few centimeters to 2 m the basal and upper contacts of the injectites with host muddy deposits are sharp and or erosional and are locally discordant with the bedding of the host deposits siltstone clasts which were ripped up or ripped down from the host muddy deposits are commonly incorporated into the injectites although some siltstone clasts have geological ages older than those of the host deposits seven lithofacies have been identified in the injectites based on the internal structures the combinations of internal structures are different from those of high density turbidity current deposits and debrites and suggest that injection was promoted by a combination of turbulent and laminar flow conditions the extrudites show an overall convex up geometry and possess lithological features similar to those of the injectites they have been identified in the rendaiji conglomerate member which is encased in the mera formation and which rests on the uppermost shiramazu formation the extrudites are characterized by gently undulating waveforms that show upstream migration and climbing stacking patterns similar to the cross sectional geometry of cyclic steps or upstream migrating antidunes the active eruption of solid liquid mixtures onto the seafloor and sedimentary piles may have subsequently collapsed to produce supercritical high density gravity currents down the flanks of a neptunian volcano the injectites and extrudites locally contain calyptogena shells and shell fragments as well as fragments of carbonate concretions that exhibit low carbon isotopic ratios suggesting that fluidization of the source sediments was triggered by a combination of seepage of cold methane bearing water into the source sediments and seismic shaking volcaniclastic deposits older than the host muddy deposits are present in the trench slope basin deposits and these are the likely source of the injectites and extrudites

regional sand injectite architecture as a record of pore pressure evolution and sand redistribution in the shallow crust insights from the panoche giant injection complex california abstract observations on outcrop of a regionally developed sand injectite are used to infer and estimate the pore pressure conditions in the shallow crust that caused the fluidization and injection of tens of cubic kilometres of sand the estimated pore fluid pressures at the base of the injection complex at 1500 m burial depth below a regionally developed shale dominated seal are from 22 26 to 25 08 mpa which respectively correspond to 0 81 and 0 95 lithostatic pressure a theoretical basis for prediction of sand injection is defined and applied to the prediction of pore pressure at the time of sand injection the depth at which seal failure occurred and the density and granular content of the fluidized flow lateral variations in the style and abundance of sandstone intrusions are described and these all fit into a remarkably uniform tripartite division of parent units an intrusive complex and an extrusive complex a sill zone intrusions are dominated by sills occurs in a restricted stratigraphic interval 200 270 m thick location of the base of the sill zone is directly related to the thickness of the overburden and an isobaric surface at the time of sand injection the lithostatic equilibrium surface is defined at the base of the sill zone when the sills formed an extended period of supra lithostatic pressure occurred within the sill zone

regional scale subsurface sand remobilization geometry and architecture an architectural hierarchy of clastic sills is recognized in the panoche giant injection complex in which staggered stepped with erosive top surfaces and multi layered geometries occur in that stratigraphic order upward genetic relationships between parent depositional sand bodies the sand injections a zone of hydraulic fracture and a palaeo sea floor are seen at a scale previously observed only by using seismic data sills and randomly oriented dykes intrude into a hydraulically fractured shale unit above and below which dykes predominate erosive surfaces scallops are identified on sills that along with smaller erosional features record low viscosity turbulent flow during sand injection sand extrusions occur where dykes reach the palaeo sea floor

seismic scale funnel shaped collapse features from the paleocene eocene of the north west shelf of australia abstract a multi tiered cluster of funnel shaped seismic anomalies can be observed over 11 000 km2 in the lower tertiary of the carnarvon basin nw shelf of australia the lithology is dominated by deep water carbonates and marls individual funnel shaped depressions typically have a diameter exceeding 1 km and a depth of a few hundred meters the strata inside some of the anomalies can be correlated with surrounding layers in the best documented example the correlation shows that the infill has foundered into the funnel shaped depression the collapse appears to have removed about 1 km3 below sedimentary cover the anomalies were emplaced in deep water when gas was actively migrating in the basin and above a structural high based on this context and using recently described hydrate pockmarks as live analogs the following model is proposed for the emplacement of these collapsed features 1 thermogenic gas migrated up into the fine grained paleogene series and froze up into hydrates upon entering the gas hydrate stability zone 2 the correlative volume increase resulted in conical failure of the overburden and gas migrating along the failure impregnated the surrounding sediments with hydrates 3 as the hydrate stability zone moved up hydrate dissolution dissociation expelled gas and associated liquefied sediment from the cone while the non impregnated core foundered towards the bottom of the cone three such episodes are recorded in the study area during the paleogene two of them lie in close temporal vicinity to the main hyperthermal events of this period volume calculations indicate that the amount of gas released in our study area is two orders of magnitude lower than what would be needed to trigger the paleocene eocene thermal maximum event suggesting that the anomalies are rather developed as a consequence of global hyperthermal events

fluid circulation in a complex volcano tectonic setting inferred from self potential and soil co2 flux surveys the santa maria cerro quemado zunil volcanoes and xela caldera northwestern guatemala the region encompassing santa maria cerro quemado and zunil volcanoes close to quetzaltenango the second largest city of guatemala is volcanically and tectonically complex in addition the huge xela caldera about 20 km in diameter crosses this area and links up to the important zunil fault zone located between the three volcanoes two highly active geothermal sites named zunil i and zunil ii are also located between these three volcanic edifices at the southeastern boundary of xela caldera in order to determine the permeability variations and the main structural discontinuities within this complex volcano tectonic setting self potential and soil co2 flux measurements have been coupled with a step of 20 m along a 16 880 km long profile crossing the entire area two shallow hydrothermal systems with maximum lateral extensions of 1 5 km in diameter are indicated by positive self potential elevation gradients below santa maria and cerro quemado volcanoes such small hydrothermal systems cannot explain the intense geothermal manifestations at zunil i and zunil ii another minor hydrothermal system is indicated by self potential measurements on the flank of santa maria along the edge of the xela caldera co2 flux measurements display slight variations inside the caldera and decreasing values crossing outside the caldera boundary we hypothesize the presence of a magmatic body inside the southeastern border of xela caldera to explain the deeper and more intense hydrothermal system manifested by the zunil i and the zunil ii geothermal fields this magmatic system may be independent from santa maria and cerro quemado volcanoes alternatively the hypothesized xela magmatic system could have a common magmatic origin with the cerro quemado dome complex consistent with previous findings on regional gas emissions sectors bordering the cerro quemado dome complex also have high amplitude minima short wavelength anomalies in self potential interpreted as preferential rain water infiltration along faults of major permeability probably related with the most recent stages of cerro quemado dome growth

statistical analysis reveals spatial and temporal anomalies of soil co2 efflux on mount etna volcano italy abstract extensive geochemical surveys were carried out on the western flank of mt etna volcano for the determination of soil co 2 effluxes in order to study the relationship between soil gas anomalies faults and volcanic activity the areas of santa maria di licodia sml and w rift wr were selected because of their importance within the volcano tectonic framework of etna two gas surveys were performed in each area in different periods november 2005 and may 2006 in sml september 2007 and june 2008 in wr with 2140 measurements in total in each survey data were log normally distributed and were statistically different from the other surveys therefore their standard normal form was used to compare them log probability plots revealed five populations of data in each survey due to varying degrees of mixing between biogenic and magmatic co 2 and indicated anomalous co 2 effluxes for values 36 g m 2 d 1 magmatic output was 39 2 t d 1 in november 2005 15 8 t d 1 in may 2006 98 4 t d 1 in september 2007 and 234 1 t d 1 in june 2008 natural neighbor interpolation of standardized data produced distribution maps that showed some clustering of anomalous values along directions possibly related to hidden faults compatible with volcanic or regional structural trends analysis of magmatic co 2 emissions in time suggested a possible influence from seasonal variations but comparison with volcanic activity of etna also indicated a volcanic influence accompanying the 2008 2009 flank eruption

sub aqueous sand extrusion dynamics extruded sandstone mounds and sandstone sheets are increasingly recognized in the geological record and seismic data yet the underlying mechanisms that control these features and determine whether deposits form discrete accumulations or areally extensive sheets remain poorly understood here we address these issues through study of a well exposed ancient sand sheet in the shannon basin ireland sand volcanoes are shown to have erupted contemporaneously following liquefaction and fluidization of delta front mouth bar sands and silts the expelled sediment forming an extruded sheet of sand the sand sheet formed during a single prolonged eruption event with the interaction of radial gravity currents from the hundreds of vents exerting control on the internal architecture of the extrudite based on our observations here we develop a process based model that demonstrates that sand extrusions can form sheets only if 1 multiple vents are extruding coevally causing gravity currents to interact or 2 topographic forcing such as channelling redirects the otherwise radial gravity currents resulting in sheet like deposition of extruded material away from the vent site this study provides a new model of sand extrudite formation and examines the potential for identifying extrudites from core and bed scale studies and differentiating them from liquefied beds

constraining the origin of reservoirs formed by sandstone intrusions insights from heavy mineral studies of the eocene in the forties area united kingdom central north sea the presence of hydrocarbon bearing sandstones within the eocene of the forties area was first documented in 1985 when a forties field paleocene development well discovered the brimmond field further hydrocarbons in the eocene were discovered in the adjacent maule field in 2009 reservoir geometry derived from three dimensional seismic data has provided evidence for both a depositional and a sand injectite origin for the eocene sandstones the brimmond field is located in a deep water channel complex that extends to the southeast whereas the maule field sandstones have the geometry of an injection sheet on the updip margin of the brimmond channel system with a cone shape feature emanating from the top of the forties sandstone member paleocene the geometry of the eocene sandstones in the maule field indicates that they are intrusive and originated by the fluidization and injection of sand during burial from seismic and borehole data it is unclear whether the sand that was injected to form the maule reservoir was derived from depositional eocene sandstones or from the underlying forties sandstone member these two alternatives are tested by comparing the heavy mineral and garnet geochemical characteristics of the injectite sandstones in the maule field with the depositional sandstones of the brimmond field and the forties sandstones of the forties field the study revealed significant differences between the sandstones in the forties field and those of the maule and brimmond fields both in terms of heavy mineral and garnet geochemical data the brimmond maule and forties sandstones therefore have different provenances and are genetically unrelated indicating that the sandstones in the maule field did not originate by the fluidization of forties sandstones by contrast the provenance characteristics of the depositional brimmond sandstones are closely comparable with sandstone intrusions in the maule field we conclude that the injectites in the maule field formed by the fluidization of depositional brimmond sandstones but do not exclude the important function of water from the huge underlying forties sandstone member aquifer as the agent for developing the fluid supply and elevating pore pressure to fluidize and inject the eocene sand the study has demonstrated that heavy mineral provenance studies are an effective method of tracing the origin of injected sandstones which are increasingly being recognized as an important hydrocarbon play

mechanisms and controls on the formation of sand intrusions sandstone intrusions are found in all sedimentary environments but have been reported most commonly from deep water settings they also appear to be more frequently developed in tectonically active settings where applied tectonic stresses facilitate development of high fluid pressures within the sediments a variety of mechanisms have been cited as triggers for clastic intrusions these include seismicity induced liquefaction application of tectonic stresses excess pore fluid pressures generated by deposition related processes and the influx of an overpressured fluid from deeper within the basin into a shallow sand body the formation of sandstone dykes and sills is investigated here by considering them as natural hydraulic fractures when the seal on an unconsolidated overpressured sand body fails the resulting steep hydraulic gradient may cause the sand to fluidize the fluidized slurry can then inject along pre existing or new fractures to form clastic intrusions the scale and the geometry of an intrusive complex is governed by the stress state depth and pre existing joints or faults within the sedimentary succession as well as the nature of the host sediments for the simplest tectonic setting where the maximum stress in a basin is vertical gravitational loading small irregular intrusions commonly result in the formation of sills at shallow depths within a few metres of the surface whereas at greater depth dykes and sills forming clastic intrusion networks are more typical a simple relationship is derived to calculate the maximum burial depth at which a dyke sill complex forms as a function of the source bed to sill height the bulk density of the surrounding sediments and the ratio of the vertical to horizontal effective stresses k 0 when applied to three examples of large scale dyke sill complexes developed within paleocene and eocene deep water reservoir sand bodies of the north sea maximum burial depths in a range of 375 to c 500 m 450 700 m and 550 850 m are estimated for intrusion of each of the three complexes

anatomy of piton de la fournaise volcano la reunion indian ocean the aim of this work is to propose a general model of piton de la fournaise volcano using information from geological and geophysical studies firstly we make a graphical compilation of all available geophysical information along a w e profile secondly we construct a geological section that integrates both the geophysical information and the geological information the lithosphere beneath piton de la fournaise is not significantly flexed and the crust is underlain by an underplating body which might represent the deep magma reservoir for la reunion volcanism piton de la fournaise is a relatively thin volcano lying on a huge volcanic construction attributed mostly to les alizes volcano indeed if the differentiated rocks observed at the bottom of the riviere des remparts are the top of les alizes volcano the interface with piton de la fournaise may be located at about sea level beneath the summit area the endogenous constructions intrusive complexes related to les alizes and piton de la fournaise volcanoes represent a large volume the huge intrusive complex of les alizes volcano probably rests on the top of the oceanic crust and appears to have a buttressing effect for the present eastern volcano tectonic activity of piton de la fournaise the early piton de la fournaise edifice was built around a focus located beneath the plaine des sables area the center subsequently moved 5 6 km eastward to its current location the dense high velocity body beneath the plaines des sables and the western part of the enclos probably corresponds to the hypovolcanic intrusive complex that developed before the volcanic center shifted to its present day position magma reservoirs may have existed and may still exist as illustrated by the march 1998 crisis at the mechanical and density interface between the oceanic crust and the les alizes edifice strong evidence also exists for the presence of a shallower magma reservoir located near sea level beneath the summit the march 1998 pre eruptive seismic pattern location and upward migration seems to be evidence for a transfer of magma between the two reservoirs the dominant structural feature of the central zone is a collapse structure beneath the summit craters above the inferred magma reservoir near sea level the collapsed column constitutes a major mechanical heterogeneity and concentrates most of the seismic intrusive and hydrothermal activity because of its higher permeability and weaker mechanical strength

identifying rift zones on volcanoes an example from la reunion island indian ocean we describe a methodology for identifying complex rift zones on recent or active volcanoes where structures hidden by recent deposits and logistical conditions might prevent carrying out detailed fieldwork la reunion island was chosen as a test site we used georeferenced topographic maps aerial photos and digital terrain models to perform a statistical analysis of several morphometric parameters of pyroclastic cones this provides a great deal of geometric information that can help in distinguishing the localisation and orientation of buried magma feeding fractures which constitute the surface expression of rift zones it also allowed the construction of a complete gis database of the pyroclastic cones la reunion is a perfect example where past and active volcanic rift zones are mostly expressed by clusters of monogenic centres the data has been validated in the field and compared and integrated with the distribution and geometry of dyke swarms results show the presence of several main and secondary rift segments of different ages locations and orientations whose origin is discussed considering regional tectonics local geomorphology and volcano deformation

deposition or remobilization of the enigmatic hefring member sand eastern north sea a multidisciplinary approach abstract sand remobilization is a well known and well studied phenomenon and seismic observations particularly from the north sea giant sand injectite province nsgsip combined with outcrop investigations have permitted a good understanding of the physical processes of sand remobilization trigger mechanisms and resulting seismic geometries the degree of remobilization and the distinction between depositional and remobilized injected sand from seismic data alone are however still relatively unconstrained in this study we use a multidisciplinary approach based on seismic stratigraphy petrography and biostratigraphy to investigate an enigmatic and apparently isolated eocene sandstone body the hefring member which in the seismic data shows characteristics of both depositional and remobilized origin we use the available well logs cutting samples and side wall cores to investigate whether we can address the degree of remobilization from seismic data alone by linking the mapped seismic facies with remobilization degree as observed from the well data in addition to addressing the degree of remobilization we propose a model for the formation of the hefring member which includes laterally restricted submarine channel sand deposition and secondary remobilization with mainly upward and lateral injection we infer that the remobilization of the hefring member was controlled by local and rapid differential loading potentially emphasized by activity in the nearby d 1 fault system and triggered by a significant drop in sea level understanding the origin and evolution of the hefring member is important for unravelling the geological development of the area and because the sand member represents a new reservoir unit comparable to the nearby prolific siri canyon sandstone

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

the style of late cenozoic deformation at the eastern front of the california coast ranges the 1983 coalinga earthquake occurred at the eastern boundary of the california coast ranges in response to northeast directed thrusting such movements over the past 2 ma have produced coalinga anticline by folding above the blind eastern tip of the coalinga thrust zone the 600 km length of the coast ranges boundary shares a common structural setting that involves westward upturn of cenozoic and cretaceous strata at the eastern front of the coast ranges and a major southwest facing step in the basement surface beneath the western great valley like coalinga anticline pliocene and quaternary folding and faulting along the rest of the boundary also result from northeast southwest compression acting nearly perpendicular to the strike of the san andreas fault we suggest that much of this deformation is related to active thrusts beneath the eastern coast ranges the step in the basement surface beneath the great valley seems to have controlled the distribution of this deformation and the shape of the coast ranges boundary

a new model for the evolution of the volcanic island of reunion indian ocean the island of reunion has been studied using data from airborne and shipborne magnetic surveys the subaerial history of reunion spans the last 2 1 million years the brunhes matuyama geomagnetic reversal enables differentiation of volcanic rocks older and younger than 0 78 ma the lower submarine flanks are poorly magnetized and are interpreted as landslide deposits the core of the island is composed of highly magnetized rocks piton des neiges volcano is composed mostly of rocks older than 0 78 ma only its western flank and central area include thick piles of younger rocks piton de la fournaise is a highly and normally magnetized edifice but its northern and eastern flanks are underlain at shallow depth by reversely magnetized formations the latter are regarded as remnants of les alizes volcano associated with the grand brule hypovolcanic complex at the matuyama brunhes transition the island was composed of at least two main volcanoes piton des neiges and les alizes and perhaps also of a third old volcano takamaka at the center north of the island piton de la fournaise grows on the flank of les alizes and is a relatively young focus of volcanism these volcanoes have had successive phases of construction and destruction the analysis of magnetic anomalies over reunion was decisive in defining a new coherent model for the evolution of the island

fluidization and injection in the deep water sandstones of the eocene alba formation uk north sea the nauchlan member of the late eocene alba formation uk north sea consists of a deep water channel fill that was extensively modified by post depositional sand remobilization and injection sandstone textures facies associations and the geometry of the channel fill were affected a suite of sand rich facies was produced by large scale fluidization and injection within the channel fill and above it these facies termed here unstratified facies are characterized by the absence of stratification surfaces and by discordant relationships with bedding in the adjacent succession they reflect variable degrees of disruption of the primary sedimentary structures caused by escaping pore fluid the velocity of which is estimated at least in the order of 0 1 ms 1 adjacent mudstones were severely disrupted by hydraulic fracturing and fragments of fractured mudstone were incorporated into the fluidized sand average porosity was decreased in the sandstones affected by fluidization two main phases of sand injection are inferred to occur at different burial depths a shallow burial phase below 100 m produced thin dykes with ptygmatic folds the second phase occurred at the boundary between eocene and oligocene 300 m burial depth and resulted in large scale tabular wing like dykes that project from the edges of the channel fill the significant pore fluid overpressure which was required to hydraulically fracture the thick mudstone seal and to fluidize the large volume of sand was likely to be built up by static liquefaction of the source sand and was possibly enhanced by hydrocarbon gas influx

petrology of 1977 to 1998 eruptions of piton de la fournaise la reunion island abstract geochemical and petrological variations in 35 historical eruptions from the april 1977 eruption to the march september 1998 eruption at piton de la fournaise have been analyzed for their major elements abundances mineralogical compositions and oxygen isotopes during these 21 years samplings were repeated several times during eruptions as well as temperature measurements since the end of 1977 to 1998 all erupted lavas except 1998 hudson basalt belong to the group of the steady state basalts however evidences for small degrees of differentiation can be observed during a single eruption the earliest lava emitted contains less phenocrysts and has almost always a lower mgo mgo mgo feot than the lavas emitted later suggesting that it is more differentiated from one eruption to the next between 1977 and 1998 bulk compositions are more and more differentiated towards the first lava of 1998 a process of low pressure fractional crystallisation involving small proportions of olivine clinopyroxene and plagioclase allows to explain this evolution a major result of our study is to show that this evolution does not correspond to a unique fractionation trend over the considered period different types of magmas have been distinguished the first magma type erupted from october 1977 to november 1987 was richer in potassium 0 82 wt in average than the second one and apparently derived from the liquid of the 1977 oceanite the second magma type erupted from february 1988 to september 1998 was poorer in k 2 o 0 69 wt in average in march 1998 a third magma type hudson basalt erupted simultaneously with the second one hudson basalt has undergone a wehrlitic fractionation and is supposed to come from a deeper magma reservoir than other erupted magmas for this period from 1977 to 1998 the 18 o of lavas progressively decreases with time together with the increasing chemical differentiation of the magmas by low pressure fractional crystallisation this variation agrees with the hypothesis of magma contamination at shallow level in the altered volcanic edifice vlastelic i deniel c bosq c telouk p boivin p bachelery p famin v staudacher t 2009 this issue pb isotope geochemistry of piton de la fournaise historical lavas journal of volcanology and geothermal research 184 63 78 this issue overall petrological variations are in good agreement with a model of a shallow reservoir discontinuously supplied between 1977 and 1998 the speed of the variations the coexistence of different liquids the chemical evolution of the lavas during the same eruption lead us to favour a model of chemically stratified reservoir constituted by a complex of dykes sills and laccoliths close to the surface and located above larger magma bodies

cluster analysis of soil co2 data from mt etna italy reveals volcanic influences on temporal and spatial patterns of degassing soil co2 concentration data were collected periodically from july 2001 to june 2005 from sampling site grids in two areas located on the lower flanks of mt etna volcano paterno and zafferana etnea santa venerina cluster analysis was performed on the acquired data in order to identify possible groups of sites where soil degassing could be fed by different sources in both areas three clusters were recognised whose average co2 concentration values throughout the whole study period remained significantly different from one another the clusters with the lowest co2 concentrations showed time averaged values ranging from 980 to 1 170 ppm vol whereas those with intermediate co2 concentrations showed time averaged values ranging from 1 400 to 2 320 ppm vol and those with the highest concentrations showed time averaged values between 1 960 and 55 430 ppm vol we attribute the lowest co2 concentrations largely to a biogenic source of co2 conversely the highest co2 concentrations are attributed to a magmatic source whereas the intermediate values are due to a variable mixing of the two sources described above the spatial distribution of the co2 values related to the magmatic source define a clear direction of anomalous degassing in the zafferana etnea santa venerina area which we attribute to the presence of a hidden fault whereas in the paterno area no such oriented anomalies were observed probably because of the lower permeability of local soil time series analysis shows that most of the variations observed in the soil co2 data from both areas were related to changes in the volcanic activity of mt etna seasonal influences were only observed in the time patterns of the clusters characterised by low co2 concentrations and no significant interdependence was found between soil co2 concentrations and meteorological parameters the largest observed temporal anomalies are interpreted as release of co2 from magma batches that migrated from deeper to shallower portions of etna s feeder system the pattern of occurrence of such episodes of anomalous gas release during the observation period was quite different between the two studied areas this pattern highlighted an evident change in the mechanism of magma transport and storage within the volcano s feeder system after june 2003 interpreted as magma accumulation into a shallow 8 km depth reservoir

sandstone extrusions and slope channel architecture and evolution mio pliocene monterey and capistrano formations dana point harbor orange county california u s a abstract the miocene monterey formation and deepwater channels of the mio pliocene capistrano formation crop out at dana point harbor california and are locally separated by a series of extruded sandstone bodies stratigraphic columns photo panels and high resolution lidar data are used to describe the stratigraphy of the 840 m wide 30 m thick exposure the studied exposure contains 1 a lower unit composed of monterey slope mudstone 2 an up to 13 m thick discontinuous middle unit of structureless sandstone bodies and 3 an upper sandstone unit composed of the laterally and vertically stacked breccia conglomerate and sand filled channels of the capistrano formation several observations collectively suggest that the structureless sandstone bodies in the middle unit are remobilized 1 the lower mudstone unit contains centimeter to meter scale injections of structureless poorly sorted coarse grained sandstones 2 the facies in the middle sandstone unit are identical to the injected sandstones facies observed in the lower mudstone unit 3 the structureless sandstone bodies of the middle unit form disconnected bodies below the upper sandstone unit and have an average aspect ratio of 4 1 whereas the capistrano channels have an aspect ratio greater than 10 1 4 quartz and feldspar grains in the injected sandstone of the lower unit and the structureless sandstone of the middle unit are fractured 5 the structureless sandstone bodies of the middle unit contain meter scale angular mudstone clasts of composition similar to that of the monterey mudstones 6 these clasts contain internal sandstone injections and are deformed 7 the monterey strata around the structureless sandstone bodies display distinct variations of strike and dip relative to the regional trend the remobilized sandstone bodies forming the middle unit are interpreted as extruded sandstone bodies that incorporated large mudstone clasts rafts during the migration from a deep sand source interpreted as being a lower sandy monterey interval these sand extrusions were emplaced at the seafloor in multiple phases following slope channel incision and preceding channel fill deposits these extruded fluidized sands triggered local syndepositional deformation of the channel fills in the form of large load structures the processes that caused the source sands to fluidize are interpreted to be related to deep fluid migration toward a structural high located below the study area the mechanism triggering the upward migration of sand is likely related to slope channel incision

continuous monitoring of soil co2 flux on mt etna the 2004 2005 eruption and the role of regional tectonics and volcano tectonics 1 the soil co2 flux on mt etna as recorded by the etnagas network an automatic system for measuring soil co2 flux and meteorological parameters started to increase strongly about 5 months prior to the onset of the 2004 2005 eruption and decreased a few months before the end of the eruption time delays in the occurrences of anomalies in soil co2 flux at different sites in the geochemical network constrain the relationship between soil co2 flux distributions and the tectonic framework of etna volcano the anomalies observed before the 2004 2005 eruption support the intrusion of new undegassed magma into the upper feeding system of the volcano 20 km below sea level magma subsequently rose slowly in the volcano conduits thereby triggering the onset of the 2004 2005 eruption the time delays in the occurrences of anomalies in combination with spectral analysis indicate the importance of tectonic and volcanotectonic structures in driving the ascent of deep gases within the crust moreover greatest amplitude pulsations of the low frequency components of the co2 flux signals were correlated with the paroxystic activities of the 2004 2005 eruption this study confirms that co2 flux variation is a useful indicator for volcanic activity in the surveillance of the mt etna and similar basaltic volcanoes

geochemistry of gas emanations a case study of the reunion hot spot indian ocean abstract the results of analysis of natural emanations in reunion island show a clear magmatic origin for co2 and he while n2 and ar are predominantly derived from the atmosphere the distribution of magmatic gases in the piton des neiges massif fits the local volcanotectonic context well and suggests that the areas concerned are still subject to volcanic activity at depth a simple method is proposed for correcting gas concentration and isotope composition for water degassing in doing so the isotope and elemental c he composition of gases is homogeneous for the two volcanoes the isotope ratio of he 12 5 0 5r ra in the present discharges is in agreement with the results of previous studies on rocks of various ages from the two volcanoes the isotope ratio of c 13c 5 to 4 vs pdb and the c 3 he ratio 4 109 are similar to those found in other hot spot volcanic systems such as kilauea hawaii and hengill iceland these similarities suggest comparable volatile history for the respective mantle sources the main differences being in the relative proportions of radiogenic 4he in detail hot spots appear enriched in c having a light composition with respect to morb possibly due to the addition of a c rich e g subducted component in addition to a relatively undegassed 3he rich component

relationship between bowl shaped clastic injectites and parent sand depletion implications for their scale invariant morphology and composition 3d seismic reflection data provides a means to assess the impact of injection on parent sands and to quantify the character of the resulting injectite networks the morphology of a series of large injectite structures hosted in the palaeocene lower lista formation were mapped using broadband 3d seismic data from the north sea to investigate their relationship with parent sands fourteen bowl shaped structures were identified within the lista formation in the study area 60 85 m in height and 200 900 m in width sand is absent below resolution below these large scale bowls suggesting that the parent sand is the underlying maureen formation and sand welds formed rather than sand prone channelised deposits within the lista formation identification of injectite networks can be ambiguous which impacts geological model development observations from exhumed systems and core offers high resolution insights into the complexity of injectite networks to advance our understanding of this scale gap we argue for injectites being scale invariant in their shape and grain size this permits the application of outcrop scale knowledge to seismic scale interpretation the demonstrable depletion of parent sands and their scale invariance can be applied to basin fills worldwide to reduce uncertainties of the impact of sand injectites on hydrocarbon reservoirs

reply to discussion on late cenozoic geological evolution of the northern north sea development of a miocene unconformity reshaped by large scale pleistocene sand intrusion journal of the geological society 170 133 145 knowledge of small sand injection is far from new murchison 1827 hurst et al 2011 but that intrusive and extrusive bodies of sand can be more than 100 m thick and extend for kilometres is considered unlikely by rundberg eidvin 2015 who discuss our paper loseth et al 2013 their discussion disagrees with our interpretation of the origin of these sand bodies and instead favours their previously proposed models eidvin rundberg 2001 rundberg eidvin 2005 they claim that 1 the early pleistocene sandstones are turbiditic sands deposited at the toe of the glaciomarine shelf clinoform foresets and not extrusive sands 2 the oligocene sandstones located below mounds at the top hordaland group unconformity are in situ deposits representing turbiditic gravity sands shed from the shetland platform and not intrusive sands and 3 the top hordaland group unconformity in the northern north sea was formed by submarine erosion and not during subaerial exposure we have studied rock properties of eocene to pleistocene claystones and sandstones oygarden et al 2015 carried out detailed seismic and well studies in the north sea loseth et al 2003 2012 2013 studied the physical processes of injection extrusion and depletion of sand in analogue experiments rodrigues et al 2009 and studied outcrops of intrusive sandstones through sand injection research consortiums e g hurst et al 2006 2011 vigorito et al 2008 cartwright 2010 scott et al 2012 our seismic and well observations above the snorre and visund fields were in conflict with existing geological models and therefore we proposed new models this reply builds on knowledge of how the seismic expression of sandstone varies with the type of embedding claystone oygarden et al

investigating the deepest part of a volcano plumbing system evidence for an active magma path below the western flank of piton de la fournaise la reunion island abstract peripheral diffuse degassing of co 2 from the soil occurs across the western flank of piton de la fournaise volcano la reunion island indian ocean along a narrow zone in this area carbon isotopic analysis on soil gas samples highlights significant mixing between magmatic and organic end members the zones with the strongest magmatic signature highest 13 c overlap spatial distribution of hypocenters recorded shortly before and during volcano reactivation and allow discriminating a n135 degassing lineament with a minimum length of 11 km and 140 20 m width such orientation is in accordance with that of an old dyke network along the rift zone and with n120 130 and n140 155 lineaments related to the inheritance of oceanic lithosphere structures our findings show that this n135 lineament represents a preferential magmatic pathway for deep magma transfer below the volcano flank moreover spatial distributions of recent eccentric cones indicate a well founded possibility that future eruptions may by pass the shallow plumbing system of the central area of the volcano taking a lateral pathway along this structure our results also confirm that piton de la fournaise activity is linked to a laterally shifted plumbing system and represent a major improvement in identifying the main high risk area on the densely populated western flank of the volcano

rift zones and magma plumbing system of piton de la fournaise volcano how do they differ from hawaii and etna on ocean basaltic volcanoes magma transfer to the surface proceeds by subvertical ascent from the mantle lithosphere through the oceanic crust and the volcanic edifice possibly followed by lateral propagation along rift zones we use a 19 year long database of volcano tectonic seismic events together with detailed mapping of the cinder cones and eruptive fissures to determine the geometry and the dynamics of the magma paths intersecting the edifice of piton de la fournaise volcano we show that the overall plumbing system from about 30 km depth to the surface is composed of two structural levels that feed distinct types of rift zones the deep plumbing system is rooted between piton des neiges and piton de la fournaise volcanoes and has a n30 40 orientation above 20 km below sea level bsl the main axis switches to a n120 orientation which permits magma transfer from the lithospheric mantle to the base of the oceanic crust below the summit of piton de la fournaise the related nw se rift zone is 15 km wide linear spotted by small to large pyroclastic cones and related lava flows and emits slightly alkaline magmas resulting from high pressure fractionation of clinopyroxene olivine this rift zone has low magma production rate of 0 5 3 6 10 3 m 3 s 1 and an eruption periodicity of around 200 years over the last 30 ka seismic data suggest that the long lasting activity of this rift zone result from regional nne ssw extension which reactivates inherited lithospheric faults by the effect of underplating and or thermal erosion of the mantle lithosphere the shallow plumbing system b11 km bsl connects the base of the crust with the central cone it is separated from the deep plumbing system by a relatively large aseismic zone between 8 and 11 km bsl which may represent a deep storage level of magma the shallow plumbing system feeds frequent short lived summit and flank ne and se flanks eruptions along summit and outer rift zones respectively summit rift zones are very active 0 1 0 25 m 3 s 1 short 2 3 km and present an orthogonal pattern confined to the central active cone of piton de la fournaise outer ne and se rift zones are much less active 4 7 3 10 3 m 3 s 1 and extend from inside the enclos fouque caldera to bound the mobile eastern volcano flank we show that the outer rift zones are almost aseismic and are genetically linked to the seaward flank displacements whose most recent events where detected in 2004 and 2007 east flank sliding is itself triggered by shallow b 2 km depth sill intrusions we propose that the subvertical magma intrusions along the perpendicular summit rift zones sill intrusions and subsequent magma injections along the outer rift zones are controlled by cycles of stress permutations we thus tentatively propose that as for piton de la fournaise the regional stress field acting on etna and hawaiian volcanoes is an important parameter in the control of the magma transfer along their deep plumbing system whereas the dynamics of their summit system is governed by shallow stress variations above 5 10 km bsl due to edifice deformation and magma transfers

monitoring the volcanic unrest of el hierro canary islands before the onset of the 2011 2012 submarine eruption 1 on 10 october 2011 a submarine volcanic eruption started 2 km south from el hierro island spain since july 2011 a dense multiparametric monitoring network was deployed all over the island by instituto geografico nacional ign by the time the eruption started almost 10000 earthquakes had been located and the deformation analyses showed a maximum deformation of more than 5 cm earthquake migration from the north to the south of the island and acceleration of seismicity are in good correlation with changes in the deformation pattern as well as with some anomalies in geochemical and geomagnetic parameters an earthquake of local magnitude 4 3 at 12 km depth 8 october 2011 and shallower seismicity a day after preceded the onset of the eruption this is the first time that a volcanic eruption is fully monitored in the canary islands data recorded during this unrest episode at el hierro will contribute to understand reawakening of volcanic activity in this region and others of similar characteristics

fluid flow features in hydrocarbon plumbing systems what do they tell us about the basin evolution abstract fluid flow features such as sandstone intrusions mud volcano systems and pockmarks represent well known geological structures generated due to flow of fluids in the subsurface however the integration of fluid flow features in quantitative and qualitative basin analysis is still in its infancy this study presents a review and a qualitative integration of fluid flow features in basin analysis of the danish north sea area and of salt mini basins offshore angola based on results from six case studies focusing on the detection mapping and evaluation of features related to focused fluid flow in these areas in the study the diversity of seismically imaged fluid flow features in hydrocarbon plumbing systems is reviewed and their utility is demonstrated this is done by focusing on the aspects of fluid flow related features that can be integrated into basin analysis studies and how these may help us increase the understanding of basin evolution and to achieve the major goals of basin analysis such as understanding the depositional and tectonic context of the basin and the presence and extent of hydrocarbons particularly concerning the determination of fluid flow timing triggers sources and routes fluid flow features represent a major but underused tool in basin analysis

origin and timing of sand injection petroleum migration and diagenesis in tertiary reservoirs south viking graben north sea petrographic fluid inclusion and carbon and oxygen stable isotope studies of tertiary injectite reservoirs in the south viking graben of the north sea allow an understanding of the origin and timing of sand injection petroleum migration and diagenesis injection from shallowly 400 m 1300 ft buried paleocene and eocene unconsolidated sandstones occurred at the end of the eocene probably in response to earthquake activity liquid oil was already present in the parent sands prior to injection and leaked from the injectites to the seabed upward migrating oil and basinal brines mixed with downward invading mixed meteoric marine pore fluids in the injectites causing extensive biodegradation of the oil biodegradation of oil provided the driver for early carbonate cementation in injectites causing diminished reservoir quality however early carbonate cementation also sealed off the injectites as potential escape routes for petroleum from the underlying parent sands oil and gas continued to migrate into the reservoir parent sands upon increased burial causing a mixing of high api oil with the early charged extensively biodegraded low api oil the study of early diagenetic imprints reveals the evolution of injectite reservoirs which forms the basis for understanding how to explore and develop them

explosive activity of the summit cone of piton de la fournaise volcano la reunion island a historical and geological review summit explosive activity and collapses that form pit craters and calderas represent major volcanic hazards on a dominantly effusive frequently active volcano like piton de la fournaise only three summit collapse events 1986 2002 2007 have been recorded since the foundation of the piton de la fournaise volcano observatory ovpf in 1979 and two of them 1986 and 2007 were associated with weak phreatic activity at piton de la fournaise the normal explosive activity consists of short lived and mild 20 m high lava fountains which quickly evolve into strombolian activity during the eruptions based on comprehensive literature review and high resolution image analysis of surface outcrops and summit caldera walls we reconstructed the time distribution of recent explosive events phreatomagmatic phreatic and their link with summit collapses and lateral flank effusive eruptions in historical time post 1640 ce we recognise two main clusters of explosive events frequent and violent phreatomagmatic to phreatic explosions occurred during the oldest cluster 1708 1878 and alternated with long lasting periods years to decades of summit effusive activity in contrast scarce and on average weak explosions occurred during the youngest cluster 1897 2012 when discrete and short lived 6 months effusive eruptions represent the main eruptive dynamics historical summit collapses pit craters and caldera all localised at the top of the summit cone were related to voluminous lateral eruptions and were followed by a significant decrease in eruptive rate however magma draining during lateral eruptions was not systematically associated with summit collapses or explosions the long lasting occurrence of magma at very shallow depth below the volcano summit followed by a rapid lateral drainage apparently represents a critical condition favouring magma groundwater interaction to produce explosive activity the prehistoric growth of the piton de la fournaise summit cone results chiefly from long lasting to continuous activity centred below its western side bory crater containing lava lakes high lava fountains long lasting effusive activity lava lakes ash plumes and block ejections were common types of eruptive dynamics in the historical past between 1640 and 1878 in this perspective short lived small volume eruptions and long pauses up to six years during the last century of activity of piton de la fournaise can be considered as a lull despite the high frequency of eruption 1 eruption 9 months on average temporal and spatial variations in recurrence rate and eruptive dynamics of basaltic volcanism such as those recognised at piton de la fournaise should be considered in the formulation of hazard assessments and in the interpretation of precursory patterns

facies and flow regimes of sandstone hosted columnar intrusions insights from the pipes of kodachrome basin state park sandstone hosted intrusions are found in a wide variety of environments but remain poorly understood compared with their mudstone hosted counterparts in particular they remain largely unrecognized in the subsurface in part because they are problematic to image in seismic data this study reports on the facies and fluid flow associated with a 20 000 km3 sandstone intrusion province in utah usa forming a small portion of this intrusion province the intrusions cropping out in kodachrome basin state park display a very wide array of facies and morphologies factors which would make their identification in core a significant challenge remobilized sediment is shown to have been injected at least 200 m vertically from its source with flow prolonged enough to concentrate heavy minerals in placer style deposits at the pipe margins evidence for lateral pipe migration and for associated broader fluidization regions is also presented a new approach to estimating flow parameters in injectites is implemented herein and indicates that previous work has overestimated velocities and flow reynolds numbers by up to two orders of magnitude flow modelling suggests turbulent flow in the pipes that is consistent with field observations of erosive margins and chaotic internal structures post emplacement these pipes remained as long term fluid conduits as revealed by their diagenetic history focussing and facilitating flow of extraformational fluids despite the relatively high porosity and permeability of the aeolian host strata

the 2 1 ga old injectite network of the franceville basin gabon architecture origin and implications on manganese mineralization abstract detailed sedimentological investigations on numerous outcrops and drill core sections in the 2 1 ga old franceville basin gabon provide evidence for a large scale injectite network the injectites were formed by the injection of sands through a thickness of about 150 m of the fb1 member and now cover a minimum area of 70 km 2 corresponding to the bangombe plateau but are also recognized close to franceville 35 km farther south east the injectite lithology corresponds to a mud or carbonate supported sandstone characterized by a loose and uncompacted fabric contrasting with the host rock because the injectites are often parallel to subparallel to the stratification they were misinterpreted as depositional beds by previous authors at outcrop the injectite bodies exhibit sill dyke wing and protrusive geometries emplaced during early burial within poorly compacted material with partial wall erosion and dissociation the source of the sand material is attributed to a channel levee turbidite depositional system located in the lower part of the fb1 member these deposits were buried by a thick biochemical muddy cap deposited during a starvation phase which increased the seal capacity of the system this type of architecture has a high potential to develop compaction disequilibrium during burial moreover in the case of the francevillian injectites the abundance of microbial organic matter favoured early methane degassing and lateral charging of the sand reservoir the overpressure in the channels was periodically released during early burial through the effect of rapid sedimentary and tectonic loading and possible seismic activity the fluidized sand was injected according to a symmetrical wing pattern thus the injected masses caused a local decrease in the grade of the lateritic manganese ore deposit of the bangombe plateau

pressurization and depressurization phases inside the plumbing system of mount etna volcano evidence from a multiparametric approach during 2013 mount etna volcano experienced intense eruptive activity at the summit craters foremost at the new southeast crater and to a minor degree at the voragine and bocca nuova bn which took place in two cycles february april and september december in this work we mainly focus on the period between these cycles applying a multiparametric approach the period from the end of april to 5 september showed a gradual increase in the amplitude of long period lp events and volcanic tremor a slight inflation testified by both tilt and gps data and a co2 flux increase such variations were interpreted as due to a gradual pressurization of the plumbing system from the shallowest part where lp and volcanic tremor are located down to about 3 9 km below sea level pressure source depths obtained by both geodetic and co2 data on 5 september at the same time as a large explosion at bn we observed an instantaneous variation of the aforementioned signals decrease in amplitude of lp events and volcanic tremor slight deflation and co2 flux decrease and the activation of a new infrasonic source located at bn in the light of it the bn explosion probably caused the instantaneous end of the pressurization and the opening of a new vent at bn that has become a new steady source of infrasonic events this apparently slight change in the plumbing system also led to the gradual resumption of activity at the new southeast crater culminating with the second lava fountain cycle of 2013

constraining the depth and timing of large scale conical sandstone intrusions kilometer scale sandstone intrusions a recently recognized end member of the spectrum of soft sediment deformation structures are important components of many deep water sandstone reservoirs they result from the remobilization of considerable volumes of sand during early stages of burial this paper uses three dimensional seismic data calibrated to nearby wells to describe an extensive system of large downward tapering conical sandstone intrusions from the faeroe shetland basin on the uk atlantic margin the intrusions are derived from a middle eocene submarine fan and are injected vertically upward through overlying highly faulted claystones to form conical bodies that interconnect across the 700 m thick claystone interval to feed a set of shallow intrusions located within a few hundred meters of the paleoseabed the forcible intrusion of these shallow sandstone bodies produced complementary folding of the contemporaneous seabed the subsequent onlap of these seabed domal folds took place immediately after the intrusion event and by correlation to biostratigraphic data from nearby wells we date these intrusions as late miocene this is the first time that both the age and emplacement depth range of a system of large scale sandstone intrusions have been constrained

formation of conical fractures in sedimentary basins experiments involving pore fluids and implications for sandstone intrusion mechanisms large sand intrusions often exhibit conical morphologies analogous to magmatic intrusions such as saucer shaped or cup shaped sills whereas some physical processes may be similar we show with scaled experiments that the formation of conical sand intrusions may be favoured by the pore pressure gradients prevailing in the host rock before sand injection our experiments involve injecting air into a permeable and cohesive analogue material to produce hydraulic fractures while controlling the pore pressure field we control the state of overpressure in the overburden by applying homogeneous basal pore pressure and then adding a second local pore pressure field by injecting air via a central injector to initiate hydraulic fractures near the injection point in experiments involving small vertical effective stresses small overburden or high pore fluid overpressure the fracturing pressure lambda fract is supralithostatic and two dipping fractures are initiated at the injection point forming a conical structure from theoretical considerations we predict that high values of lambda fract are due to strong cohesion or high pore fluid overpressure distributed in the overburden such conditions are favoured by the pore pressure stress coupling induced by both pore pressure fields the dips of cones can be accounted for elastic stress rotation occurring around the source contrary to magmatic chamber models the aqueous fluid overpressure developed in a parent sandbody and prevailing before the formation of injectites may diffuse into the surrounding overburden thus favouring stress rotation and the formation of inclined sheets far from the parent source for experiments involving higher vertical effective stresses thick overburden or low pore fluid overpressure the fracturing pressure is lower than the lithostatic stress and a single fracture is opened in mode i which then grows vertically at a critical depth the fracture separates into two dilatant branches forming a flat cone we make use of a p i v particle imaging velocimetiy technique to analyse plastic deformation showing that these inclined fractures are opened in mixed modes close to the surface they change into steep shear bands where fluids can infiltrate the final morphology of the fracture network is very similar to the common tripartite architecture of various injection complexes indicating that different mechanisms may be involved in the formation of dykes feeder dykes under the sill zones may open as tensile fractures while overlying dykes may be guided by the deformation induced by the growth of sills these deformation conditions may also favour the formation of fluid escape structures and pockmarks c 2011 elsevier b v all rights reserved

role of the structural inheritance of the oceanic lithosphere in the magmato tectonic evolution of piton de la fournaise volcano la reunion island la reunion island is located east of madagascar on the eastern rim of the tectonically inactive mascarene basin this island is composed of three shield volcanoes of which only piton de la fournaise is currently active although the magmatic activity is restricted to piton de la fournaise a scattered seismicity occurs on the whole 200 km wide volcanic edifice and in the underlying oceanic crust we carried out a multiscale analysis to understand 1 the origin of the seismicity in the geodynamic context and 2 the role of the oceanic lithosphere in the deformation of piton de la fournaise and la reunion island analysis of the magmatic system suggests that the magma ascent is controlled by large n25 30 and n125 130 fracture zones located below the enclos depression we also show that the orientation difference between the eruptive fissures and the related dykes result from a rotation of the main principal stress s 1 from vertical to downslope through the surface combining a digital elevation model dem analysis field observations and the geophysical data reveals that the volcano is affected by large fault zones the fault distribution indicates the predominance of a main n70 80 trend magnetic data show the same n80 orientation characterizing the remnant part of the alizes volcano such parallel alignment suggests a control exerted by the underlying alizes volcano on piton de la fournaise furthermore the alignment between the crustal orientations and the structures determined on the island suggests a control of the crustal structures in la reunion s volcano tectonic activity contrary to several volcanic islands such as hawaii and tenerife la reunion volcanoes lie on an upbending crust then we interpret the reactivation of the crustal faults as resulting from a crustal uplift related to the thermal erosion of the base of the lithosphere and or to strong underplating the upward deformation may prevent the spreading of the volcanoes as no evidence of such a mechanism is observed in the bathymetry and the seismic data around the island

cumulate clasts in the bellecombe ash member piton de la fournaise reunion island and their bearing on cumulative processes in the petrogenesis of the reunion lavas abstract among the ejecta from a phreatomagmatic eruption on piton de la fournaise volcano are wehrlitic and gabbroic cumulate clasts these fresh samples comprise olivine fo85 0 to fo69 0 augite en47 1wo44 6wo44 6 to en41 1fs15 4wo43 5 and plagioclase an82 8ab16 8or0 4 to an53 8ab44 8or1 4 with spinel ti rich ferrichromites to ti magnetite and some ilmenite a few percent of highly vesicular interstitial glass is commonly present textures indicate that the cumulates were not wholly crystalline at the time of eruption and that the glass represents a residual intercumulus melt that varies from basaltic to mugearitic sulphide globules typically spherical and up to 40 m diameter represent immiscible melts within the glasses the sulphides contain relatively high contents of cu and ni and appear to be high temperature homogeneous pyrrhotite rich compositions rank order of element abundance in the sulphides is fe s cu ni co and zn wt s although in one sample ni is more abundant than cu lack of correlation between the sulphide globule compositions and their host glasses is probably due to complex partitioning between the silicate melts silicate and oxide crystals sulphide melt and separating volatile phase whereas the cu cu ni at values of the sulphides are similar to those of the sulphide ore bodies from major gabbroic complexes the ni ni fe values are notably high with regard to the low mgo content of their host glasses oxide pairs regarded as reflecting equilibria prior to eruption indicate temperatures of 1017 897 c and log fo2 values of 9 6 12 7 compaction of analogous cumulate mushes with extraction of relatively low density basaltic to mugearitic and ultimately trachytic residual melts is inferred to have yielded the differentiated series lavas and ash flows of the older volcano on reunion piton des neiges the sequence of crystallisation with augite as the second silicate phase rather than plagioclase as is normal in the lava sequences suggests crystallisation at depths 5 km the bellecombe ash cumulate clasts show more evolved assemblages than most other xenolith suites on the volcano in which dunites predominate and are probably products of stagnated magma batches possibly arrested in sill like intrusions in the deeper crust the cumulates are recent components in what is probably a large ca 70 km across layered complex beneath the volcanic edifices accreted during the build up of reunion

relationships between diffuse co2 emissions and volcanic activity on the island of vulcano aeolian islands italy during the period 1984 1994 measurements of co2 flux from the ground were periodically carried out on the island of vulcano aeolian islands italy between 1984 and 1994 three high flux areas were identified at the foot of the volcanic cone la fossa either inside or very close to the main village effect of the choice of the sampling grid was evaluated a different sampling grid resulted in similar distribution patterns but with different co2 fluxes therefore the absolute estimate of the total flux from the investigated area includes a large degree of uncertainty but repeated measurements with permanent sampling sites are accurate and can detect small changes no correlation of the flux with atmospheric parameters was found at sites with high fluxes some periods characterized by high co2 fluxes were observed and a close correlation was found between the gas emissions from the ground and other geochemical and geophysical parameters such as temperature chemical composition steam and so2 flux from fumaroles seismic energy release and ground deformations the results show that major temporal variations of diffuse co2 flux are related to variations in volcanic activity

sand injectites from source to emplacement an example from the miocene age frimmersdorf seam garzweiler open cast mine lower rhine embayment

soil map update procedure and problems encountered for the island of reunion many soil maps were drawn up after world war ii with different soil classifications that have significantly evolved since updating such old maps with a new version or a new classification system is always complex i we do not always possess all the original information ii the criteria for determining references are often different and iii on the most accurate scales correlations come up against the complexity and specificities of each classification system on reunion a volcanic tropical island in the indian ocean we undertook a comprehensive overview of the old existing soil studies this article describes i the procedure used to update the soil maps and the toposequence acquired with the old french commission de pedologie et de cartographie des sols cpcs classification system without any new information using the world reference base for soil resources wrb ii the construction of a new soil map drawn up with completely new information and iii a comparison of these two approaches at elevations below 350 m asl above sea level without any new pedological information we updated brown ferruginous soils reddish brown ferrallitic soils and fersialitic soils into haplic nitisols humic eutric the acquisition of new data showed that this update was incorrect because not all the diagnostic criteria of the nitic horizons were met the correct diagnostic horizons were a mollic horizon when the thickness was 25 cm or more or a cambic horizon leptic phaeozems and leptic cambisols were then the correct reference soil group rsg at elevations from 350 to 900 m asl without any new information brown and reddish brown ferrallitic soils andic ferrallitic soils and brown and andic brown soils were updated into haplic nitisols humic dystric and andic umbrisols humic the acquisition of new data showed that this update was incorrect because andic properties and the diagnostic criteria of the nitic horizons were not met over 900 m asl pozols were correctly updated as were the andosols except from 900 to 1050 m asl where not all the andic properties were met without any new information incorrect updates were observed for both the determination of rsg and the qualifiers despite the field descriptions the lack of any analytical determinations on the old soil studies was a source of updating errors for the more developed soils formerly qualified as ferrallitic in order to update limits for andic properties and andosols the systematic use of analytical determinations has to be considered for updating old soil maps as the diagnostic criteria are more restrictive than in the past resume d auteur

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

the process of sand injection internal structures and relationships with host strata yellowbank creek injectite complex california u s a abstract the yellowbank creek injectite complex ycic has excellent exposure of the external geometries and internal structures in a large scale sandstone injectite the ycic has an irregular geometry that can be defined neither as a sandstone dike nor as a sill substantial erosion occurred along the margins between the ycic sandstone and host mudstones that includes scoured basal margins and a scalloped upper margin that cuts up to 5 m into the overlying host mudstones erosion of host mudstone has incorporated significant volumes of mudstone clasts into sandstones at the margins of the injectite using microtextural data corrasion is identified as a typical process by which mudstone is eroded during sand injection corrasion occurs when particles of mudstone are either cut or broken from a cohesive bed as the result of high velocity turbulent flow of sand grains acting as tools corrasion together with scouring and the general erosion of the host mudstone imply high velocity turbulent flow conditions and confirm that the fluidized sand had a sufficiently low viscosity during sand injection to allow turbulence internal structures include laminae of more tightly packed sand grains than occur in the surrounding sandstones and are interpreted to have formed by flow and deposition of injecting sands during waning of flow thus reflecting an overall reduction of pore fluid pressure deformation of laminae into folds defines bands which are aligned parallel to the margins of the sandstone the force driving deformation is likely to have been shear stresses induced between the injected sandstone and the more rigid host mudstone the principal style of deformation is hydroplastic oversteepened laminae and pipes are interpreted to have formed due to post sand injection consolidation and resulted in only minor mobilization of sand