the uwekahuna ash member of the puna basalt product of violent phreatomagmatic eruptions at kilauea volcano hawaii between 2800 and 210014c years ago abstract kilauea volcano s reputation for relatively gentle effusive eruptions belies a violent geologic past including several large phreatic and phreatomagmatic eruptions that are recorded by holocene pyroclastic deposits which mantle kilauea s summit area and the southeast flank of adjacent mauna loa volcano the most widespread of these deposits whose original distribution can be reconstructed is the uwekahuna ash member of the puna basalt a basaltic surge and fall deposit emplaced during two or more eruptive episodes separated by a few decades to several centuries the first episode occurred between 2770 70 and 2265 50 14 c yr ago it included two major pyroclastic surges each preceded by unusually vigorous lava fountaining from a vent near the volcano s summit before the second eruptive episode 2110 120 14 c yr ago plants had re colonized the rainforest environment northeast of the summit and at least two lava flows from mauna loa had buried parts of the first episode deposits the second episode also began with vigorous lava fountaining followed by widespread lithic ashfall a third major surge and finally a fourth fountaining event before the final pumice deposit could be significantly reworked it was partly buried by picritic basalt flows that are unusual in kilauea s summit area in proximal areas the uwekahuna ash member is more than 1 m thick locally 5 m and includes lithic blocks up to 0 8 m in diameter coarse primarily lithic debris was deposited around the vent by laterally expanding surges fallout deposits accumulated preferentially to the northeast under the influence of high altitude counter tradewinds the area devastated by surges and originally buried by at least 15 cm of the uwekahuna was about 420 km 2 the bulk volume of the deposits was approximately 0 3 km 3 including less than 0 1 km 3 of juvenile material juvenile constituents are olivine tholeiitic basalts similar in major element composition to typical kilauea summit lava flows but variations in both major elements and trace elements suggest that the eruptions tapped more than a single uniform source region we infer that the eruptions which produced the uwekahuna were driven by water interacting with a fluctuating magma column magma withdrawal episodes may have been accompanied by large volume submarine effusive eruptions and by summit collapse the volume extent and character of the uwekahuna deposits underscore the hazards posed by relatively infrequent but potentially devastating explosive eruptions at kilauea as well as at other basaltic volcanoes

calculated volumes of individual shield volcanoes at the young end of the hawaiian ridge abstract high resolution multibeam bathymetry and a digital elevation model of the hawaiian islands are used to calculate the volumes of individual shield volcanoes and island complexes niihau kauai oahu the maui nui complex and hawaii taking into account subsidence of the pacific plate under the load of the hawaiian ridge our calculated volume for the island of hawaii and its submarine extent 213 103 km3 is nearly twice the previous estimate 113 103 km3 due primarily to crustal subsidence that had not been accounted for in the earlier work the volcanoes that make up the island of hawaii mahukona kohala mauna kea hualalai mauna loa kilauea and loihi are generally considered to have been formed within the past million years and our revised volume for the island indicates that magma supply rates are greater than previously estimated 0 21 km3 yr as opposed to 0 1 km3 yr this result also shows that compared with rates calculated for the hawaiian islands 0 6 ma 0 095 km3 yr the hawaiian ridge 0 45 ma 0 017 km3 yr and the emperor seamounts 45 80 ma 0 010 km3 yr magma supply rates have increased dramatically to build the island of hawaii

prehistoric fault offsets of the hilina fault system south flank of kilauea volcano hawaii historical accounts of earthquakes on the island of hawaii date only to 1823 but lava flows as old as 1500 3000 years b p contain fault offsets from prehistoric earthquakes the m7 2 1975 kalapana earthquake produced over 25 km of fault rupture along the hilina fault system we compare fault offsets in prehistoric lava flows with kalapana earthquake fault offsets in neighboring 1969 1974 mauna ulu lava flows to estimate the frequency of prehistoric major earthquakes on the hilina fault system horizontal and vertical fault offset rates across the hilina fault system are 4 0 to 12 0 and 2 0 to 20 0 mm yr respectively based on lava flows 750 years b p age assuming prehistoric earthquakes produced similar fault offsets compared to the kalapana earthquake three to five events are recorded in 400 750 years b p old lava flows yielding recurrence intervals of 260 80 years vertical fault offsets in prehistoric lava flows suggest that hanging wall rotation of the hilina fault system contributes to fault offset the assumption that past faulting resulted from prehistoric earthquakes with similar magnitude and fault offset to the kalapana earthquake is an oversimplification large south flank earthquakes most likely do not have uniform recurrence intervals

volcanic spreading at kilauea 1976 1996 the rift system traversing about 80 km of the subaerial surface of kilauea volcano has extended continuously since the m 7 2 flank earthquake of november 1975 widening across the summit has amounted to more than 250 cm decelerating after 1975 from about 25 to 4 cm yr 1 since 1983 concurrently the summit has subsided more than 200 cm even as the adjacent south flank has risen more than 50 cm the axes of the upper zones about 10 km from the summit subsided before 1983 at average rates of 9 and 4 cm yr 1 respectively and at rates of 4 and 3 cm yr 1 since the middle southwest rift zone is also subsiding and at the other end of kilauea s subaerial rift system subsidence along the lower east rift zone has averaged 1 2 cm yr 1 deformation of kilauea s south flank has been continuous although subject as well to displacements caused by major rift zone seismic swarms whereas horizontal strains across the subaerial south flank seem to have been generally compressive after 1975 they have been extensional since about 1980 or 1981 interrupted only by the east rift zone dike intrusion of 1983 because the magnitudes of these contractions and extensions are much less than the extension across the rift system the subaerial south flank is apparently sliding seaward on its basal decollement more than it is accumulating horizontal strains within the overlying volcanic pile kilauea suffers from gravitational spreading made even more unstable by accumulation of magma along the rift system at depths in excess of about 4 5 km in the presence hot rock incapable of withstanding deviatoric stresses this seismicly quiescent zone decouples the south flank from the rest of hawaii s volcanic edifice the rift zones at lesser depths exhibit a more brittle and therefore sporadic extensional behavior judging from the modern extension record of the summit which both predates the m 7 2 earthquake of 1975 and has outlived its 10 year period of aftershocks kilauea will continue to spread along its rift system as its south flank slips seaward to accommodate the accretion of magma and its relatively dense olivine rich differentiate

rapid mass wasting following nearshore submarine volcanism on kilauea volcano hawaii abstract the rapid mass wasting of shallow submarine basalts was documented during scuba dives along the flanks of kilauea volcano hawaii during the kii lava entry of the current eruption 19 20 5 n 154 59 8 w lava entered the ocean at this site from mid february to late march 1990 with several pauses dives on 19 20 march 1990 confirmed the widespread formation of lava pillows at this site over a water depth range of 20 40 m and visual observations suggested that the resulting volcanic deposits were generally stable despite the steep 40 incline of the seafloor the pre eruptive nearshore seafloor slope was 14 however dives on 2 april 1990 revealed that nearly all submarine volcanic features had been subject to mass wasting as the offshore area had been transformed into a debris field composed of material ranging in size from fine sand to boulder fragments this generally featureless seascape extended uniformly to beyond the visual range of divers 60 m water depth high resolution multibeam bathymetry and sidescan imaging indicate that steeply sloped coarse sediment extends down the flanks of kilauea in this area to abyssal depths implying a linkage between nearshore submarine volcanism and deep water deposits

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

modelling the interaction of hyperalkaline fluids with simplified rock mineral assemblages abstract designs for geological disposal facilities for radioactive wastes often envisage the extensive use of cementitious materials after closure the repository will saturate with groundwater and cement porewater will migrate into the geosphere to form an alkaline ph 12 5 13 plume this plume will react with the components of the surrounding host rock leading to mineralogical chemical and physical changes which will be complex in nature coupled computer models of geochemistry and hydrogeological transport will be needed to scope these changes in the recent past a series of laboratory column experiments were carried out by the british geological survey in order to test the capabilities of coupled models to predict the evolution of outflow fluid compositions and product solids these experiments reacted single minerals i e quartz albite calcite and muscovite quartz and potential host rock lithologies i e borrowdale volcanic group fault rock aspo granite and wellenberg marl with cement pore fluids the objectives of the present work were to develop the understanding of these experiments and to improve simulations of the data by computer models to this end a systematic approach was adopted in which dissolution rates for individual minerals were calibrated to the results of the single mineral columns and the resulting parameter values applied to the more complex columns it was found that for the systems studied reasonable agreement between the experimental data and the calculated results could be obtained however the calibrated dissolution rate constants used in the models first vary between experiments by up to half an order of magnitude and secondly differ from literature values by up to one order of magnitude with the calibrated values being generally slower than those found in the literature

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

piggyback tectonics long term growth of kilauea on the south flank of mauna loa abstract compositional and age data from offshore pillow lavas and volcaniclastic sediments along with on land geologic seismic and deformation data provide broad perspectives on the early growth of kilauea volcano and the long term geometric evolution of its rift zones sulfur rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater growth of a large compositionally diverse alkalic edifice the alkalic rocks yield 40ar 39ar ages as old as about 275 ka transitional composition lavas which mark beginning of the shield stage while most or all the edifice remained below sea level probably first erupted after about 150 ka and tholeiitic lavas of present day type are probably younger than 100 ka breccia clasts from papau seamount and along the lower southwest corner of the hilina bench are derived from subaerial mauna loa requiring that mauna loa s flank underlies western parts of kilauea at shallow depth the volume of the kilauea edifice is therefore smaller 10 000 km3 than previous estimates 15 40 000 km3 lava thickness accumulation rates appear to have remained nearly constant during edifice growth as effusion rates increased from 25 106 m3 yr at end of the alkalic stage to the present day tholeiite rate of 100 106 m3 yr seismic and gravity data show that the deep plumbing system for kilauea s magma supply extends nearly vertically through the oceanic crust at least to mantle depths of 30 35 km directly below its present day caldera proximity of kilauea s caldera to the surface boundary with mauna loa and the presence of mauna loa rocks at shallow depth beneath the south flank are difficult to reconcile with a submarine origin for early kilauea alkalic lavas unless geometric relations between the two volcanoes have changed substantially during growth of the kilauea shield seismic and ground deformation data suggest seaward spreading of the entire south flank of hawaii island independently of the boundary between kilauea and mauna loa along a landward dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying oceanic crust current steady state horizontal displacements increase seaward at rates of 1 5 cm yr on the lower flank of mauna loa and reaching 5 8 cm yr at the kilauea coastline infrequent 100 yr large earthquakes generate similar geometries but 102 larger displacements per event present day kilauea is the more dynamic edifice but prior to inception of kilauea and during its early growth mauna loa is inferred to have undergone intense volcano spreading involving the kaoiki honuapo fault system considered a geometric analog of the hilina system on kilauea cumulative deformation of mauna loa s south flank during growth of kilauea since 200 300 ka is estimated to have involved 10 km of seaward spreading displacing the rift zones of k lauea while its deep plumbing system and summit magma reservoir remained nearly fixed in space kilauea s rift zones rather than migrating southward with time solely due to dike emplacement preferentially on the mobile seaward side alternatively are interpreted to have been transported passively southward piggyback style during shield stage growth of kilauea as a blister on the still mobile south flank of mauna loa such an evolution of kilauea accounts for the arcuate geometry of the present day rift zones proximity of the summit magma supply to the exposed flank of mauna loa initial submarine growth of the ancestral edifice and present day location of mauna loa rocks at shallow depth beneath the south flank of kilauea

magma supply and storage at kilauea volcano hawaii 1956 1983 abstract shallow crustal magma reservoirs beneath the summit of kilauea volcano and within its rift zones are linked in such a way that the magma supply to each can be estimated from the rate of ground deformation at the volcano s summit our model builds on the well documented pattern of summit inflation as magma accumulates in a shallow summit reservoir followed by deflation as magma is discharged to the surface or into the rift zones magma supply to the summit reservoir is thus proportional to summit uplift and supply to the rift zones is proportional to summit subsidence the average proportionality constant is 0 33 10 6 m 3 rad this model yields minimum supply estimates because it does not account for magma which escapes detection by moving passively through the summit reservoir or directly into the rift zones calculations suggest that magma was supplied to kilauea during july 1956 april 1983 at a minimum average rate of 7 2 10 6 m3 month roughly 35 of the net supply was extruded the rest remains stored within the volcano s east rift zone 55 and southwest rift zone 10 periods of relatively rapid supply were associated with the large kapoho eruption in 1960 and the sustained mauna ulu eruptions in 1969 1971 and 1972 1974 bursts of harmonic tremor from the mantle beneath kilauea were also unusually energetic during 1968 1975 suggesting a close link between kilauea s deep magma supply region and shallow storage reservoirs it remains unclear whether pulses in magma supply from depth give rise to corresponding increases in shallow supply or if instead unloading of a delicately balanced magma transport system during large eruptions or intrusions triggers more rapid ascent from a relatively constant mantle source

ups and downs on spreading flanks of ocean island volcanoes evidence from mauna loa and kīlauea submarine flank deposits of hawaiian volcanoes are widely recognized to have formed largely by gravitationally driven volcano spreading and associated landsliding observations from submersibles show that prominent benches at middepths on flanks of mauna loa and k lauea consist of volcaniclastic debris derived by landsliding from nearby shallow submarine and subaerial flanks of the same edifice massive slide breccias from the mature subaerial tholeiitic shield of mauna loa underlie the frontal scarp of its south kona bench in contrast coarse volcaniclastic sediments derived largely from submarine erupted preshield alkalic and transitional basalts of ancestral k lauea underlie its hilina bench both midslope benches record the same general processes of slope failure followed by modest compression during continued volcano spreading even though they record development during different stages of edifice growth the dive results suggest that volcaniclastic rocks at the north end of the kona bench interpreted by others as distal sediments from older volcanoes that were offscraped uplifted and accreted to the island by far traveled thrusts alternatively are a largely coherent stratigraphic assemblage deposited in a basin behind the south kona bench

volcanic spreading on mauna loa volcano hawaii evidence from accretion alteration and exhumation of volcaniclastic sediments a transect of submersible dives across the submarine west flank of mauna loa volcano yields compelling evidence for volcanic spreading and associated hydrothermal circulation during volcano growth a frontal bench at the toe of the flank formerly thought to be a downdropped block of mauna loa contains a mix of volcaniclastic lithologies including distally derived siltstone mudstone and hyaloclastite the bench is overlain by bedded gravels and subaerially erupted pillow flows derived from local shoreline crossing lava flows the volcaniclastic strata in the bench were offscraped uplifted and accreted to the edge of the flank as it plowed seaward into the surrounding moat the accreted strata underwent significant diagenesis through deep burial and circulation of hydrothermal fluids expelled from porous sediments beneath the volcano timing constraints for bench growth and breakup suggest that catastrophic failure of the subaerial edifice ca 250 200 ka triggered volcanic spreading by reducing stresses resisting basal sliding and rift zone inflation increased eruptive activity and westward migration of mauna loa9s southwest rift zone gradually rebuilt the massive flank arresting slip prior to detachment of the alika 2 debris avalanche ca 120 ka

mining induced seismicity in faulted geologic structures an analysis of seismicity induced slip potential relationships between the locations of mining induced seismic events local fault structure and mine geometry were examined in a deep hard rock mine in northern idaho stopes experiencing rock bursts and other large seismic events were found to fall into two structural regimes the silver vein and the n48 w trend a steeply dipping plane of seismic activity that is subparallel to major local steeply dipping faults which bound blocky structures the n48 w trend also intersects a shaft that was seriously damaged when fault gouge was expelled into the opening during a 3 month period of high seismic energy release models of stress interaction are used to support the hypothesis that mining induced deformation was mobilized along a 1 5 km length of the n48 w trend specifically numerical models are used to simulate rupture of seismic events and estimate induced changes in the quasi static stress field a coulomb failure criterion is used with these results to estimate the spatial variation in potential for slip on planes parallel to local faulting increases in the potential for slip on fault planes subparallel to the n48 w trend are consistent with activation of deformation along its 1 5 km length for events with constant seismic moment stress drop is shown to be far more important than source dimension in elevating slip potential along the observed plane of seismic activity

diverse basalt types from loihi seamount hawaii loihi seamount is the southeasternmost active volcano in the hawaiian emperor volcanic chain the seamount is considered representative of the early phase of hawaiian volcanism because of its youth small size and location near the melting anomaly seventeen dredge stations recovered transitional basalt alkalic basalt and basanite in addition to the expected tholeiitic basalt four flows of alkalic basalt contain common small dunite xenoliths the recovered samples have thin palagonite rinds and almost no manganese on the glassy surfaces we estimate that the lavas are less than about 4 000 yr old and many are less than 1 000 yr old loihi seamount is apparently in a transitional growth phase between the early eruption of alkalic lavas and the commonly observed subaerial tholeiitic eruptive phase previously thought to dominate hawaiian volcanism from inception until the postcaldera collapse alkalic stage

argon geochronology of kilauea s early submarine history submarine alkalic and transitional basalts collected by submersible along kilauea volcano s south flank represent early eruptive products from earth s most active volcano strongly alkalic basalt fragments sampled from volcaniclastic deposits below the mid slope hilina bench yield 40 ar 39 ar ages from 212 38 to 280 20 ka these ages are similar to high precision 234 9 and 239 10 ka phlogopite ages from nephelinite clasts in the same deposits above the mid slope bench two intact alkalic to transitional pillow lava sequences protrude through the younger sediment apron samples collected from a weakly alkalic basalt section yield 138 30 to 166 26 ka ages and others from a transitional basalt section yield 138 115 and 228 114 ka ages the ages are incompatible with previous unspiked k ar studies from samples in deep drill holes along the east rift of kilauea the submarine birth of kilauea volcano is estimated at 300 ka if the weakly alkalic sequence we dated is representative of the volcano as a whole the transition from alkalic to tholeiitic basalt compositions is dated at 150 ka

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

overthrusting and sediment accretion along kilauea s mobile south flank hawaii evidence for volcanic spreading from marine seismic reflection data a large intermittently active submarine landslide known as the hilina slump has been interpreted along the south flank of kilauea volcano seaward dipping faults on land mark its headwall and an offshore bench may define its uplifted toe geodetic data show that the entire south flank is also moving seaward by a process referred to as volcanic spreading this provides an alternative explanation for the bench i e overthrusting along the edge of the sliding flank the latter interpretation is consistent with new seismic reflection data across the submarine flank a prominent reflection near the top of the oceanic plate suggests the decollement upon which the mobile flank slides landward dipping reflections rise from this horizon and bound packages of bedded strata faulted and imbricated within the bench the absence of correlative seaward dipping faults and rotated strata on the upper flank suggests that the bench is not coupled to a slump moreover kinematic reconstructions of the bench indicate that it has accommodated 15 24 km of displacement this value is consistent with estimates for rift zone extension but too high for shortening at the toe of a slump we interpret the bench to result from overthrusting and accretion of volcaniclastic sediments to the edge of the mobile flank and suggest that morphologic benches develop preferentially where landslide debris has accumulated near the base of the volcano and can be accreted to its sliding edifice

two dimensional reactive transport modeling of the alteration of a fractured limestone by hyperalkaline solutions at maqarin jordan abstract two dimensional reactive transport modeling of the maqarin eastern springs site a natural analogue for the alteration of a fractured limestone by high ph portland cement waters has been performed using the crunchflow code these 2d calculations included transport by advection dispersion diffusion along a single fracture and diffusion in the wall rock solute transport was coupled to mineral dissolution and precipitation a limited sensitivity analysis evaluated the effect of different values of primary mineral surface areas flow velocity and sulfate concentration of the inflowing high ph solution major secondary minerals include ettringite thaumasite c s h c a s h and calcite c s h c a s h precipitation is controlled by the dissolution of primary silicates ettringite precipitation is controlled by diffusion of sulfate and aluminum from the wall rock to the fracture with aluminum provided by the dissolution of albite calcite precipitation is controlled by diffusion of carbonate from the wall rock extents of porosity sealing along the fracture and in the fracture wall rock interface depend on assumptions regarding flow velocity and composition of the high ph solution the multiple episodes of fracture sealing and reactivation evidenced in the fracture infills were not included in the simulations results can qualitatively reproduce the reported decrease in porosity in the fractures and in the wall rock next to the fractures instances of porosity increase next to fractures caused by carbonate dissolution were not reproduced by the calculations

ultra high chlorine in submarine kilauea glasses evidence for direct assimilation of brine by magma basaltic glass grains from the submarine south flank of kilauea hawai i have cl concentrations of 0 01 1 68 wt the latter being the highest cl content yet recorded for a hawaiian glass the high cl glass grains are products of brine assimilation by tholeiite magma the glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of kilauea s submarine midslope bench the clast contains two distinct suites of glass grains abundant degassed tholeiites perhaps derived from subaerial lavas of mauna loa that shattered upon ocean entry and a smaller population of kea type tholeiite n 17 analyzed that erupted subaqueously based on elevated s 780 1050 ppm h2o 0 42 1 27 wt and co2 1000 ppm six 5000 ppm and two grains have 10 000 ppm dissolved cl abundances of h2o na2o k2o and several trace elements increase regularly with cl concentration and we estimate that cl enrichment was due to up to 13 wt addition of a brine consisting of 78 h2o wt 13 cl 4 4 na 2 6 k 2 6 ca 620 ppm ba 360 ppm sr 65 ppm rb and 7 ppm pb the large amounts of brine addition argue against bulk assimilation of low porosity brine bearing rock the brine s composition is appropriate for a seawater derived hydrothermal fluid that reacted with basaltic wall rocks at t 100 c losing mg and s and gaining k ca rb ba sr and pb followed by phase separation near 500 c and 50 mpa 5 km below sea level at hydrostatic pressure brine was assimilated at or near the depth it formed as estimated on petrologic grounds but under lithostatic conditions the highest extents of assimilation either forced volatile saturation of the magma or enriched already coexisting magmatic vapor in h2o possible mechanisms for assimilation are 1 forcible injection of brine into magma during bursting of overpressured pockets heated by new dikes or 2 intrusion of magma into lenses or sills occupied by trapped brine

structure of the mobile south flank of kilauea volcano hawaii how do huge landslides occur in hawaii we can begin to address this question by examining an incipient landslide structure on the mobile south flank of kilauea volcano between 1970 and 1989 this part of the south flank moved in a southeast direction seaward by 4 m on its eastern end and by 10 m on its western end parallel to the western boundary of a large oifshore topographic bench we show that abrupt decreases in cumulative flank movement correspond to abrupt decreases in hypocenter concentration most of the earthquakes occur in a 7 to 10 km deep band beneath the south flank and relative relocation of a subset of these events shows that they are derived from a single horizontal plane which appears to be a decollement focal mechanisms for this deep seismicity are dominated by thrust fault mechanisms with the overlying block moving seaward a comparison of south flank bathymetry with decollement structures on other volcanoes suggests that the distal end of this decollement coincides with the distal end of the offshore topographic bench 30 50 km from shore and 5 km below sea level the fault system forming the hilina pali is connected with this decollement so that slip on the hilina pali s normal faults coincides with slip of the decollement and with reverse faulting of the distal end of the bench this interpretation is supported by studies of the events associated with the m7 2 kalapana earthquake in 1975 when the hilina pali is connected to the outer bench with a decollement inferred from seismicity a wedge 8 km thick adjacent to kilauea s magma system and 1 2 km thick along the edge of the outer bench an area over 3000 km2 is defined the thickness adjacent to the magma system decreases eastward along kilauea s east rift zone and southwestward from kilauea caldera whereas the thickness of the lip of the outer bench decreases only eastward geologic observations and geophysical studies of the subaerial flank reveal an extensive magma system beneath the koae fault system as well as beneath kilauea caldera and its east rift zone we infer that the boundary of the proximal end of the mobile flank is the southern boundary of this magma system and that this boundary coincides with the southern boundaries of both the koae fault system and kilauea s east rift zone

aeromagnetic study of the island of hawaii an aeromagnetic study of the island of hawaii provides new insight on magnetic properties of subsurface rock and geologic structure on a regional scale spectral depth analysis delineates two shallow magnetic zones each roughly 1 5 km thick lying at a depth of 1 km one zone of unknown origin lies in the center of the island and correlates with a regional magnetic high the other zone coincides with pronounced magnetic lows paralleling kilauea s active east rift zone these magnetic lows probably depict rocks chemically altered by hydrothermal fluids in which titanomagnetite has been destroyed analysis of magnetic terrain effects indicates that magnetization also decreases with depth within mauna kea and mauna loa we estimate that magnetization is reduced by about half at a depth of 1 km the magnetic method is particularly useful in delineating the lateral extent of local shield structures such as rifts summit calderas pit craters and vent fissures rifts possess characteristic magnetic patterns primarily long wavelength linear magnetic low zones we propose alteration processes reduce magnetizations along the flanks of rifts on the other hand along young rifts e g kilauea s east rift zone short wavelength magnetic anomalies probably reflect slowly cooled unaltered intrusions altered rock may also produce magnetic lows that help define buried summit calderas

models of hawaiian volcano growth and plume structure implications of results from the hawaii scientific drilling project the shapes of typical hawaiian volcanoes are simply parameterized and a relationship is derived for the dependence of lava accumulation rates on volcano volume and volumetric growth rate the dependence of lava accumulation rate on time is derived by estimating the eruption rate of a volcano as it traverses the hawaiian plume with the eruption rate determined from a specified radial dependence of magma generation in the plume and assuming that a volcano captures melt from a circular area centered on the volcano summit the timescale of volcano growth is t 2 r plate where r is the radius of the melting zone of the circular plume and plate is the velocity of the pacific plate the growth progress of a volcano can be described by a dimensionless time t t plate 2r where t 0 is chosen to be the start of volcano growth and t 1 approximates the end of shield growth using a melt generation rate for the whole plume of 0 2 km 3 yr a plume diameter of 50 km and a plate velocity of 10 cm yr we calculate that the lifetime of a typical volcano is 1000 kyr for a volcano that traverses the axis of the plume the standard dimensions are a volume of 57 000 km 3 a summit thickness of 18 km a summit elevation of 3 6 km and a basal radius of 60 km the volcano first breaches the sea surface at t 0 22 when it has attained only 5 of its eventual volume 80 of the volume accumulates between t 0 3 and t 0 7 typical lava accumulation rates start out over 50 m kyr in the earliest stages of growth from the seafloor and level out at 35 m kyr from t 0 05 until t 0 4 from t 0 4 to t 0 9 the submarine lava accumulation rates decrease almost linearly from 35 m kyr to 0 subaerial accumulation rates are about 30 lower the lava accumulation rate is a good indicator of volcano age a volcano that passes over the plume at a distance 0 4r off to the side of the plume axis is predicted to have a volume of about 60 of the standard volcano a lifetime about 8 shorter and lava accumulation rates about 15 20 smaller the depth age data for mauna kea lavas cored by the hawaii scientific drilling project are a good fit to the model parameters used given that mauna kea appears to have crossed the plume about 15 20 km off axis the lifetime of mauna kea is estimated to be 920 kyr mauna loa is predicted to be at a stage corresponding to t 0 8 kilauea is at t 0 6 and loihi is at t 0 16 the model also allows the subsurface structure of the volcanoes the interfaces between lavas from different volcanoes to be modeled radial geochemical structure in the plume may be blurred in the lavas because the volcanoes capture magma from a sizeable cross sectional area of the plume this inference is qualitatively born out by available isotopic data the model predicts that new hawaiian volcanoes are typically initiated on the seafloor near the base of the next older volcano but generally off the older volcano s flank

native gold in a hawaiian alkalic magma native gold found in fresh basanite glass from the early submarine phase of kilauea volcano hawaii may be the first documented case of the transport of gold as a distinct precious metal phase in a mantle derived magma the gold bearing glass is a grain in bedded volcanic glass sandstone japan marine science and technology center jamstec sample s508 r3 collected by the submersible shinkai 6500 at 3879 m depth off kilauea south flank extensive outcrops there expose debris flow breccias and sandstones containing submarine erupted alkalic rock fragments and glasses from early kilauea precipitation of an immiscible gold liquid resulted from resorption of magmatic sulfides during crystallization differentiation with consequent liberation of sulfide hosted gold elevated whole rock gold concentrations to 36 ppb for fresh lavas and clasts from early kilauea further show that some magmas erupted at the beginning stages of hawaiian shield volcanoes were distinctly gold rich most likely owing to limited residual sulfide in their mantle source alkalic magmas at other ocean islands may also be gold rich and oceanic hot spot provinces may contain underappreciated gold resources

high ph plume from low alkali cement fracture grouting reactive transport modeling and comparison with ph monitoring at onkalo finland grouting of water conducting fractures with low alkali cement is foreseen for the potential future repository for spent nuclear fuel in finland onkalo site a possible consequence is the formation of high ph solutions which will be able to react with the host rock calculations have been performed including the hydration and simultaneous leaching of the grout the effect of different possible groundwater compositions has been studied the results show that after grouting the duration of the initial high ph peak is short 0 5 a which compares well with observations at a test borehole magnesium in the groundwater induces the precipitation of brucite at the grout fracture interface which consumes oh in the longer term the results show a gradually decaying ph tail ph 9 controlled by the precipitation of calcite at the grout fracture interface the duration of this tail correlates inversely with the carbonate content of the inflowing groundwater a major finding of this study is that mineral precipitation controls the formation of a potential high ph plume by consuming alkalinity and limiting diffusive solute exchange between the grout and the circulating groundwater as a consequence assumption of long term interaction between rocks or engineering barrier materials with flowing high ph 12 solutions may not be very realistic

geology of the ostrava karvina coalfield upper silesian basin czech republic and its influence on mining abstract the ostrava karvina coalfield represents the czechoslovak part of the upper silesian basin which is one of the most important european coal deposits it is an exception in europe as the major part of the coal reserves are of namurian age the formation of the upper silesian basin resulted largely from the tectonism that occurred during three periods these were the origin of the cadomian variscan and alpine structural stages the variscan evolution comprises the platform development middle devonian early carboniferous the period of marine molasse latest visean namurian a paralic molasse namurian a and terrigenous molasse namurian b and c westphalian two major basinal tectonic units with contrasting facies and tectonic structures originated in the latest visean as a result of the variscan mobilization the variscan foredeep along the western margin of the basin with thick coal bearing carboniferous and complicated fold and fault structures and the upper silesian stable block an extensive platform in the eastern part of the basin with a reduced thickness of sediments and simple tectonic structure the alpine tectonic movements rejuvenated the older major faults influenced the origin of a very sharply marked pre tertiary paleorelief formed on the top of carboniferous deposits and led to the nappe structure of the mesozoic and tertiary rocks which cover southern parts of the ostrava karvina coalfield the paralic ostrava formation namurian a is up to 3000 m thick with individual cycles varying from 6 to 20 m in thickness reflecting the broad variation in depositional environments it contains more than 170 coal seams with an average thickness of 73 cm about 80 marine and brackish horizons more than 100 freshwater horizons 16 coal tonsteins and 30 layers of whetstone rocks serve for correlation the continental karvina formation namurian b c and westphalian a deposited after tectonic inversion is up to 1000 m thick it contains up to 90 coal seams 180 cm thick on average maximum up to 16 m the cycles are thicker and laterally less stable than those in the ostrava formation and contain frequent layers of conglomerates and coarse grained sandstones only 25 freshwater horizons are known the typical feature of both formations is the frequent occurrence of tuffogenous layers whetstone rocks and tonsteins which are important strategraphic key horizons the coal seams mainly comprise bituminous coal at the lower boundary of the limnic karvina formation there is an abrupt increase in the abundance of inertinite up to 80 of the coal the majority of coals are of a high quality and can be used for coke production the sulphur and phosphorus content is very low less than 0 7 and 0 02 0 11 respectively the geological reserves are estimated to be about 16 000 million t of coal the variegated barren rocks the so called red beds have been recorded over the entire southwestern part of the basin the genesis of this rocks is discussed the following geological phenomena complicate the deep mining activity irregular development and distribution of the coal seams complex tectonic structure erosion wash outs the effect of the formation of red beds on coal beds gas rock and water bursts anomalous geomechanic features and the complicated paleorelief of the coal bearing carboniferous these phenomena and their influence on the mining activity are described