magma extraction from the mantle wedge at convergent margins through dikes a parametric sensitivity analysis 1 we address under what conditions a magma generated by partial melting at 100 km depth in the mantle wedge above a subduction zone can reach the crust in dikes before stalling we also address under what conditions primitive basaltic magma mg 60 can be delivered from this depth to the crust we employ linear elastic fracture mechanics with magma solidification theory and perform a parametric sensitivity analysis all dikes are initiated at a depth of 100 km in the thermal core of the wedge and the moho is fixed at 35 km depth we consider a range of melt solidus temperatures 800 1100c viscosities 10 100 pa s and densities 2400 2700 kg m 3 we also consider a range of host rock fracture toughness values 50 300 mpa m 1 2 and dike lengths 2 5 km and two thermal structures for the mantle wedge 1260 and 1400c at 100 km depth and 760 and 900c at 35 km depth for the given parameter space many dikes can reach the moho in less than a few hundred hours well within the time constraints provided by u series isotope disequilibria studies increasing the temperature in the mantle wedge or increasing the dike length allows additional dikes to propagate to the moho we conclude that some dikes with vertical lengths near their critical lengths and relatively high solidus temperatures will stall in the mantle before reaching the moho and these may be returned by corner flow to depths where they can melt under hydrous conditions thus a chemical signature in arc lavas suggesting partial melting of slab basalts may be partly influenced by these recycled dikes alternatively dikes with lengths well above their critical lengths can easily deliver primitive magmas to the crust particularly if the mantle wedge is relatively hot dike transport remains a viable primary mechanism of magma ascent in convergent tectonic settings but the potential for less rapid mechanisms making an important contribution increases as the mantle temperature at the moho approaches the solidus temperature of the magma

boninitic and tholeiitic dykes in the lewis hills mantle section of the bay of islands ophiolite implications for magmatism adjacent to a fracture zone in a back arc spreading environment a detailed integrated field petrographic and geochemical study of the springers hill area of the bay of islands ophiolite exposed in the lewis hills was undertaken to explain the anomalously high abundance of veins and dykes of chromitite orthopyroxenite and clinopyroxenite and their associated dunites hosted by a refractory harzburgite dunite mixture a geodynamic situation is presented which is constrained by previous studies requiring formation of the springers hill mantle section at a ridge fracture zone intersection and the whole of the bay of islands ophiolite within a back arc spreading environment the veins and dykes formed during magmatism at the ridge fracture zone intersection and along the fracture zone as progressively hotter more fertile richer in clinopyroxene asthenosphere ascended and was channelled up and along the fracture zone wall shallow melting of refractory harzburgite in the presence of subduction derived hydrous fluids produced light rare earth element lree enric

dehydration melting of amphibolite at 10 kbar the effects of temperature and time we have simulated the dehydration melting of a natural low k calcic amphibolite 67 4 hornblende 32 5 anorthite in piston cylinder experiments at 10 kbar and 750 1000 c for 1 9 days the solidus temperature is lower than 750 c garnet appears at 850 c the overall reaction is hb p l cpx al hb ca hb ga opx three stages of reaction are 1 melting dominated by the growth of clinopyroxene and garnet with little change in composition of liquid or garnet 2 a reversal of this reaction between 875 c and 900 c with decreases in the amounts of liquid and garnet and 3 a large increase in liquid along with the loss of hornblende and decrease of plagioclase while clinopyroxene and garnet increase garnet is enriched in pyrope and zoned from fe cores to mg edges range 3 mol pyrope liquid composition is enriched first in an to 950 c and then in ab the liquids are more calcic and aluminous than natural tonalites which is attributed to the plagioclase composition an90 the formation of peraluminous liquid from the metaluminous amphibolite is caused by anorthite not h2o saturated conditions the results are consistent with an amphibolite phase diagram with relatively high solidus temperatures in the garnet absent field 900 1000 c but with a solidus backbend at 7 9 kbar coincident with the garnet in boundary hornblende breakdown due to garnet formation in a closed system must make h2o available for h2o undersaturated melting right down to the h2o saturated solidus below 700 c which defines a large low temperature pt area where hydrous granitoid melts can be generated with residual garnet and hornblende

origin of podiform chromitite a new model based on the luobusa ophiolite tibet abstract podiform chromitites have been interpreted as the result of melt rock reaction and related melt mixing in upper mantle sections of ophiolites however the discovery of ultrahigh pressure uhp minerals especially diamond and coesite in many podiform chromitites and host peridotites raises fundamental questions about the validity of this model chromitites in the luobusa ophiolite of tibet range from massive to nodular to disseminated chromite grains in both the chromitites and peridotites have variable but relatively high mgo and are classified as magnesiochromite many magnesiochromite grains in the massive chromitites contain inclusions of forsterite and pyroxene as well as diamonds and other unusual minerals forsterite inclusions have fo numbers of 97 99 and nio contents of 1 11 1 29 wt mg s 100 mg mg fe of clinopyroxene inclusions are 96 98 and those of orthopyroxene are 96 97 x ray studies show that the olivine inclusions have very small unit cells and short cation oxygen bond distances suggesting crystallization at high pressure in contrast magnesiochromite grains in nodular and disseminated chromitites lack pyroxene inclusions and their olivine inclusions have lower fo numbers of 94 96 and lower nio contents of 0 35 0 58 wt in addition magnesiochromite in massive ores has higher fe3 fetotal 0 42 than that in nodular and disseminated ores which have ratios of 0 22 disseminated chromitites also show systematic changes in olivine and magnesiochromite compositions from the dunite envelope to the massive ore indicating melt rock reaction these observations suggest that the formation of podiform chromitites is a multi stage process magnesiochromite grains and perhaps small bodies of chromitite crystallize deep in the mantle under low ambient o2 from partial melts of peridotite uhp minerals and highly magnesian olivine and pyroxene inclusions are trapped in these magnesiochromite grains when oceanic crustal slabs are trapped in suprasubduction zones ssz they are modified by island arc tholeiitic and boninitic magmas which change the magnesiochromite compositions and deposit chromitite ores in melt channels

successive estimation of a tsunami wavefield without earthquake source data a data assimilation approach toward real time tsunami forecasting we propose a tsunami forecasting method based on a data assimilation technique designed for dense tsunameter networks rather than using seismic source parameters or initial sea surface height as the initial condition of for a tsunami forecasting it estimates the current tsunami wavefield tsunami height and tsunami velocity in real time by repeatedly assimilating dense tsunami data into a numerical simulation numerical experiments were performed using a simple 1 d station array and the 2 d layout of the new s net tsunameter network around the japan trench treating a synthetic tsunami calculated by the finite difference method as observed data the data assimilation reproduced the assumed tsunami wavefield before the tsunami struck the coastline because the method estimates the full tsunami wavefield including velocity these wavefields can be used as initial conditions for other tsunami simulations to calculate inundation or runup for real time forecasting

oblique slip on the puysegur subduction interface in the 2009 july mw 7 8 dusky sound earthquake from gps and insar observations implications for the tectonics of southwestern new zealand summary the mw 7 8 dusky sound earthquake of 2009 july 15 was the largest earthquake in new zealand in the past 80 yr and is the only major subduction interface earthquake in the new zealand historical record we have estimated the coseismic and early post seismic slip distribution in the earthquake by inversion of gps and differential interferometric synthetic aperture radar dinsar observations we show that slip during the earthquake was highly obliqueandessentiallyintheaustralia pacificrelativeplatemotiondirection failureoccurred onaca 80by50kmpatchofthesubductioninterfacewithmaximumslip5 6m inthisregion the offshore alpine fault carries up to 30 mm yr 1 of slip before terminating at resolution ridge near the southern end of the 2009 slip patch the southernmost part of the alpine fault trace lies near the up dip end of the 2009 slip patch and the fault probably exists only within the crust of the over riding plate in this region terminating at shallow depth where it meets the subduction interface there is no evidence for rupture of the alpine fault during the 2009 event however coulomb stress changes from the subduction earthquake have brought this section of the alpine fault closer to failure in contrast to many subduction zones undergoing oblique subduction where the slip in major earthquakes is partitioned into more or less pure thrustearthquakesonthesubductioninterfaceandstrike slipearthquakesinthebackarc thisis a case where the majority of the subduction interface slip is not partitioned with only a shallow convergence zone west of the strike slip alpine fault undergoing contraction approximately normal to subduction zone strike north of the 2009 earthquake region the alpine fault lies further east relative to the subduction interface and partitioning between strike slip on the alpine fault and trench normal thrusting on the subduction interface takes place in a more typical fashion our results provide the first clear demonstration of non partitioned oblique slip between the australian and pacific plates offshore of southern new zealand

amazonia during the last glacial abstract new data on the vegetational history and quaternary geology of amazonia permit an improved reconstruction of past environments in amazonia during the last glacial period although limited data from rondonia carajas and guyana show that in certain areas savanna type vegetation and savanna forest had replaced the rain forest during the late pleniglacial ca 22 000 13 000 yr b p the amazonian forest may have been split up into one major west amazonian and several other medium size forest areas this suggests a decline in rainfall of 500 to 1000 mm a reduction of 25 to 40 temperatures may also have been 2 to 6 c 4 2 c lower than today possibly substancially influencing amazonian vegetation during the humid middle pleniglacial 55 000 26 000 yr b p rivers carried a lot of water and sediment resulting in the deposition of lower terrace sediments with one dry interruption around 40 000 yr b p carajas and katira in carajas there is evidence of dry periods ocurring at about 40 000 yr b p and during the early pleniglacial ca 60 000 yr b p rivers carried little water and incised into the low terrace sediments during the dry late pleniglacial water levels rose during the late glacial 13 000 10 000 yr b p or at the beginning of the holocene 10 000 yr b p sedimentation in and of the present inundation valleys commenced after that

alpine and pacific styles of phanerozoic mountain building subduction zone petrogenesis of continental crust a broad continuum exists between two distinct end member types of mountain building alpine type orogenic belts develop during subduction of an ocean basin between two continental blocks resulting in collision they are characterized by an imbricate sequence of oceanward verging nappes some alpine belts exhibit superimposed late stage backthrusting sediments are chiefly platform carbonates and siliciclastics in some cases associated with minor amounts of bimodal volcanics pre existing granitic gneisses and related continental rocks constitute an autochthonous parautochthonous basement metamorphism of deeply subducted portions of the orogen ranges from relatively high pressure hp to ultrahigh pressure uhp calcalkaline volcanic plutonic rocks are rare and have peraluminous s type bulk compositions in contrast pacific type orogens develop within and landward from long sustained oceanic subduction zones they consist of an outboard oceanic trench accretionary prism and an inboard continental margin island arc the oceanic assemblage consists of first cycle in part melanged volcaniclastics and minor but widespread cherts deep water carbonates intimately mixed with disaggregated ophiolites the section recrystallized under hp conditions recumbent fold vergence is oceanward a massive slightly older to coeval calcalkaline arc is sited landward from the trench complex on the stable non subducted plate it consists of abundant dominantly intermediate metaluminous i type volcanics resting on old crust both assemblages are thrown into open folds intruded by comagmatic i type granitoids and metamorphosed locally to regionally under high t low p conditions in the subduction channel of collisional and outboard circumpacific terranes combined extension above and subduction below allows buoyancy driven ascent of ductile thin aspect ratio slices of hp uhp complexes to midcrustal levels where most closely approached neutral buoyancy exposure of rising sheets caused by erosion and gravitational collapse results in moderate amounts of sedimentary debris because exhumed sialic slivers are of modest volume at massive sialic buildups associated with convergent plate cusps syntaxes tectonic aneurysms may help transport hp uhp complexes from mid to upper crustal levels the closure of relatively small ocean basins that typify many intracratonic suture zones provides only limited production of intermediate and silicic melts so volcanic plutonic belts are poorly developed in alpine orogens compared with circumpacific convergent plate junctions generation of a calcalkaline arc mainly depends on volatile evolution at the depth of magma generation phase equilibrium studies show that under typical subduction zone p t trajectories clinoamphibole ca al hydrous silicates constitute the major hydroxyl bearing phases in deep seated metamorphic rocks of morb composition other hydrous minerals are of minor abundance ca and na clinoamphiboles dehydrate at pressures of above approximately 2 gpa but low temperature devolatilization may be delayed by pressure overstepping thus metabasaltic blueschists and amphibolites expel h2o at melt generation depths and commonly achieve stable eclogitic assemblages partly serpentinized mantle beneath the oceanic crust dehydrates at roughly comparable conditions for reasonable subduction zone geothermal gradients however white micas biotites remain stable to pressures 3 gpa accordingly attending descent to depths of 100 km mica rich quartzofeldspathic lithologies that constitute much of the continental crust fail to evolve substantial amounts of h2o and transform incompletely to stable eclogite facies assemblages underflow of amphibolitized oceanic lithosphere thus generates most of the deep seated volatile flux and the consequent partial melting to produce the calcalkaline suite along and above a subduction zone where large volumes of micaceous intermediate and felsic crustal materials are carried down to great depths volatile flux severely diminishes thus continental collision in general does not produce a volcanic plutonic arc whereas in contrast the long continued contemporaneous underflow of oceanic lithosphere does

quasi real time fault model estimation for near field tsunami forecasting based on rtk gps analysis application to the 2011 tohoku oki earthquake mw 9 0 1 real time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales because the measured permanent displacement directly gives the true earthquake size seismic moment mw information which in turn provides tsunami forecasting we have developed an algorithm to detect estimate static ground displacements due to earthquake faulting from real time kinematic gps rtk gps time series the new algorithm identifies permanent displacements by monitoring the difference of a short term average sta to a long term average lta of the gps time series we assessed the noise property and precision of the rtk gps time series with various baseline length conditions and orbits and discerned that the real time ephemerides based on the international gnss service igs are sufficient for crustal deformation monitoring with long baselines up to 1 000 km we applied the algorithm to data obtained in the 2011 off the pacific coast of tohoku earthquake mw 9 0 to test the possibility of coseismic displacement detections and further we inverted the obtained displacement fields for a fault model the inversion estimated a fault model with mw 8 7 which is close to the actual mw of 9 0 within five minutes from the origin time once the fault model is estimated tsunami waveforms can be immediately synthesized using pre computed tsunami green s functions the calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights suggesting that the rtk gps data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations

accuracy of timescales retrieved from diffusion modeling in olivine a 3d perspective diffusion modeling in olivine is a useful tool to resolve the timescales of various magmatic processes practical olivine geospeedometry applications employ 1d chemical transects across sections that are randomly sampled from a given 3d crystal population but the accuracy and precision with which timescales can be retrieved from this procedure are not well constrained here we use numerical 3d diffusion models of fe mg to evaluate and quantify the uncertainties associated with their 1d counterparts the 3d diffusion models were built using both simple and realistic olivine morphologies and incorporate diffusion anisotropy as well as different zoning styles the 3d model crystals were sectioned along ideal or random planes which were used to perform 1d models and timescale comparisons results show that the timescales retrieved from 1d profiles are highly inaccurate and can vary by factors of 0 1 25 if diffusion anisotropy is not taken into account even when anisotropy is corrected for timescales can still vary between 0 2 10 times the true 3d diffusion time due to crystal shape and sectioning effects simple grain selection procedures are described to reduce the misfit between calculated and actual diffusion times and achieve an accuracy and precision of 5 and 15 25 relative respectively provided that the grains are carefully selected about 20 concentration profiles and associated 1d models suffice to achieve this accuracy

water in h2o saturated magma fluid systems solubility behavior in k2o al2o3 sio2 h2o to 2 0 gpa and 1300 c abstract the distribution of h 2 o alkali silicate and alkali aluminosilicate components between coexisting h 2 o saturated melt and silicate and aluminosilicate saturated aqueous fluids has been determined in the pressure and temperature range 0 8 2 0 gpa and 700 1300 c respectively the solubility of silicate and aluminosilicate materials in aqueous fluid is between 1 and 12 mol this solubility is a positive function of both pressure and temperature the solubility increases with increasing alkali content and diminishes as the system becomes more aluminous the h 2 o solubility in coexisting h 2 o saturated peralkaline silicate and aluminosilicate melt ranges between 10 and 50 mol the h 2 o solubility is a positive and near linear function increasing pressure and of decreasing temperature the h 2 o saturation values are marginally sensitive to aluminum content the si k and al k ratios in the aqueous fluid are less than those of the coexisting aluminosilicate melt the partial molar volume of h 2 o in the melts v h 2 o melt is 14 cm 3 mol and decreases slightly with increasing temperature at the same temperature v h 2 o melt decreases as the melts become more aluminous the partial molar volume of h 2 o in the silicate and aluminosilicate saturated aqueous fluids v h 2 o fluid 16 7 22 cm 3 mol generally is less than that of pure h 2 o at the same pressure and temperature the v h 2 o fluid is insensitive to pressure in the 0 8 to 2 0 pressure range the v h 2 o fluid p t is much smaller than that of pure h 2 o in the 0 8 2 0 gpa pressure range the partial molar volumes of h 2 o in silicate melts and silicate saturated aqueous solutions were combined with published data to estimate the energy release during exsolution of h 2 o from h 2 o saturated magma in shallow magma chambers such as those feeding explosive dacitic eruptions 0 2 gpa and 800 1000 c about 1 9 10 9 ergs g h 2 o were obtained at 800 c and 0 2 gpa this value decreases by about 10 between 0 2 gpa and ambient pressure thus the exact pressure during such eruptions is not needed to evaluate the effect of exsolved h 2 o on the energy budget the energy contribution from exsolved h 2 o appears to be 2 to 4 of the total energy budget of such volcanic eruptions

slow slip near the trench at the hikurangi subduction zone new zealand the range of fault slip behaviors near the trench at subduction plate boundaries is critical to know as this is where the world s largest most damaging tsunamis are generated our knowledge of these behaviors has remained largely incomplete partially due to the challenging nature of crustal deformation measurements at offshore plate boundaries here we present detailed seafloor deformation observations made during an offshore slow slip event sse in september and october 2014 using a network of absolute pressure gauges deployed at the hikurangi subduction margin offshore new zealand these data show the distribution of vertical seafloor deformation during the sse and reveal direct evidence for sses occurring close to the trench within 2 kilometers of the seafloor where very low temperatures and pressures exist

magmatic differentiation at an island arc caldera okmok volcano aleutian islands alaska okmok volcano is situated on oceanic crust in the central aleutian arc and experienced large 15 km caldera forming eruptions at 12 000 years bp and 2050 years bp each caldera forming eruption began with a small plinian rhyodacite event followed by the emplacement of a dominantly andesitic ash flow unit whereas effusive interandpost caldera lavashavebeenmorebasaltic phenocryst assemblages are composed ofolivine pyroxene plagioclase fe ti oxides and indicate crystallization at1000 11008cat 0 1 0 2gpa in thepresence of 0 4 h2o the erupted products follow a tholeiitic evolutionary trend and calculated liquid compositions range from 52 to 68 wt sio2 with 0 8 3 3 wt k2o major and trace element models suggest that the more evolved magmas were produced by 50 60 in situ fractional crystallization around the margins of the shallow magma chamber oxygen and strontium isotope data o 4 4 4 9o sr sr 0 7032 0 7034 indicate interaction with a hydrothermally altered crustal component which led to elevated thorium isotope ratios in some caldera forming magmas this compromises the use of uranium thorium disequilibria th u 1 4 0 849 0 964 to constrain the time scales of magma differentiation but instead suggests that the age of the hydrothermal system is 100 ka modelling of the diffusion ofstrontiuminplagioclase indicates thatmanyevolved crystal rims formed less than 200 years prior to eruption this addition of rim material probably reflects the remobilization of crystals from the chamber margins following replenishment basaltic recharge led to the expansion of the magma chamber which was responsible for the most recent caldera forming event

method to determine appropriate source models of large earthquakes including tsunami earthquakes for tsunami early warning in central america large earthquakes such as the mw 7 7 1992 nicaragua earthquake have occurred off the pacific coasts of el salvador and nicaragua in central america and have generated distractive tsunamis along these coasts it is necessary to determine appropriate fault models before large tsunamis hit the coast in this study first fault parameters were estimated from the w phase inversion and then an appropriate fault model was determined from the fault parameters and scaling relationships with a depth dependent rigidity the method was tested for four large earthquakes the 1992 nicaragua tsunami earthquake mw7 7 the 2001 el salvador earthquake mw7 7 the 2004 el astillero earthquake mw7 0 and the 2012 el salvador nicaragua earthquake mw7 3 which occurred off el salvador and nicaragua in central america the tsunami numerical simulations were carried out from the determined fault models we found that the observed tsunami heights run up heights and inundation areas were reasonably well explained by the computed ones therefore our method for tsunami early warning purpose should work to estimate a fault model which reproduces tsunami heights near the coast of el salvador and nicaragua due to large earthquakes in the subduction zone

zoned olivine xenocrysts in a late mesozoic gabbro from the southern taihang mountains implications for old lithospheric mantle beneath the central north china craton zoned olivine grains are abundant in the late mesozoic shatuo gabbro southern taihang mountains central north china craton olivine cores are rich in mgo and nio rims are rich in feo and mno and both cores and rims have very low cao contents the cores invariably have a high mg no 92 94 similar to olivine xenocrysts from palaeozoic kimberlites in eastern china the compositional features of these olivines imply that they are xenocrysts rather than phenocrysts namely disaggregates of mantle peridotites at the time of intrusion the compositional similarity of olivine cores to xenocrysts from palaeozoic kimberlites suggests that the lithospheric mantle beneath the central north china craton is ancient and refractory in nature and quite different from eastern china where the mantle is mainly composed of newly accreted materials resulting from large scale lithospheric removal and replacement the contrasting features of the lithospheric mantle beneath the eastern and central north china craton imply that the large scale lithospheric removal in phanerozoic times was mainly confined to the eastern north china craton

palaeoenvironmental changes during the last ca 8590 calibrated yr 7800 radiocarbon yr in the dry forest ecosystem of the patia valley southern colombian andes a multiproxy approach two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the patia valley colombia the 500 cm long core el patia 1 was analysed using diatoms pollen lithostratigraphy geochemistry charcoal and radiocarbon dates the 270 cm long core patia 2 was analysed using pollen lithostratigraphy and radiocarbon dates the environmental reconstruction includes the local development and history of the patia 1 swamp and the regional vegetation history of the two swamps the environmental reconstruction shows a fluvial system in the area before 7830 14c yr bp ca 8590 cal yr bp after this date the river gradually moved away leading to the formation of the swamp patia 1 open vegetation with patches of dry forest surrounded the swamp between 7670 and 6860 14c yr bp 8350 7690 cal yr bp the swamp become partially isolated from the river and was a permanent water body which was alkaline and mesotrophic during this period the surroundings were covered by dry forest from 6860 to 5870 14c yr bp 7690 6690 cal yr bp the swamp was totally isolated from the river and suffered from frequent periods of desiccation and erosion from 5870 to 3570 14c yr bp 6690 3890 cal yr bp the swamp turned into a marsh terrestrial environment and in the surrounding area the dry forest alternated with open vegetation it is possible that there were human impacts on the environment during this period between 3570 and 1990 14c yr bp 3890 2000 cal yr bp unstable conditions prevailed after 1990 14c yr bp 2000 cal yr bp swamp conditions of permanent water were re established open vegetation surrounded the swamp agriculture and human activities were present and have continued since then the climatic reconstruction suggests an increase in humidity at ca 7670 14c yr bp 8350 cal yr bp and a dry climate between 6860 and 5870 14c yr bp 7690 6690 cal yr bp

globally scattered 2011 tohoku tsunami waves from a seafloor sensor array in the northeast pacific ocean modeling of tsunami wave propagation for forecasting focuses on the arrival time and amplitude of the earliest tsunami waves reaching coastlines the complex later tsunami wavefield in which scattering is predominant poses additional hazards due to possible constructive interference of coherent packets of wave energy however almost no datasets exist to characterize the geographical sources and temporal evolution of the scattered waves here we show how recordings of the 2011 tohoku tsunami by an array of pressure gauge sensors in the northeastern pacific ocean reveal coherent waves that are produced by scattering from distant coastlines including south america and antarctica as well as multiple seafloor fracture zones ridges and island chains multiple signal classification analysis and backward propagation ray tracing provide tight constraints on the origin of each scattered phase and resolve simultaneous wave arrivals from different scatterers incoming waves from constant back azimuths occur over time durations of several hours revealing the time persistence of specific geographical scatterers the results can advance numerical predictions of tsunami wave impact because they provide direct evidence for the necessity of incorporating both local and distant bathymetry over a range of length scales and for long time durations to account for the azimuthal dependence of scatterer strength

fault slip distribution of the 2014 iquique chile earthquake estimated from ocean wide tsunami waveforms and gps data we applied a new method to compute tsunami green s functions for slip inversion of the 1 april 2014 iquique earthquake using both near field and far field tsunami waveforms inclusion of the effects of the elastic loading of seafloor compressibility of seawater and the geopotential variation in the computed green s functions reproduced the tsunami traveltime delay relative to long wave simulation and allowed us to use far field records in tsunami waveform inversion multiple time window inversion was applied to tsunami waveforms iteratively until the result resembles the stable moment rate function from teleseismic inversion we also used gps data for a joint inversion of tsunami waveforms and coseismic crustal deformation the major slip region with a size of 100 km 40 km is located downdip the epicenter at depth 28 km regardless of assumed rupture velocities the total seismic moment estimated from the slip distribution is 1 24 1021 n m mw 8 0

asthenospheric injection and back arc opening isotopic evidence from northeast japan nd and sr isotopic compositions were determined for the tertiary volcanics from the back arc side of the ne japan arc sr isotopes show a linear trend through time from an enriched signature 87sr86sr 0 705437 to a depleted signature 87sr86sr 0 70270 in a complementary fashion nd isotopes start at low value nd 0 80 and show a gradual increase nd 8 3 with decreasing age isotopic change of nd and sr from the enriched signature to the depleted one is synchronous with the opening of the japan sea at 15 ma this synchronism indicates that the opening of the japan sea was initiated by the injection of the asthenosphere during the pre opening stage the mantle wedge was composed of a two layered structure the sub continental lithosphere and the underlying asthenosphere the volcanics of this stage characterized by an enriched isotopic signature were derived from a source with a higher proportion of sub continental lithosphere the sub continental lithosphere of the back arc side was thinned by the injection of the depleted asthenosphere which accelerated the growth of the morb source within the mantle wedge of the back arc side and resulted in magma generation with the depleted isotopic signature of nd and sr at the post opening stage

the arc lavas of the shirahama group japan sr and nd isotopic data indicate mantle derived bimodal magmatism new sr and nd isotopic data are presented and integrated with previous data for the shirahama group mio pliocene mediumk volcanic arc suite of south central honshu japan main results are 1 the shirahama lavas range in sr sr from 0 70315 to 0 70337 and in mnd 144nd from 0 51298 to 0 51306 the sr and nd isotopic data cluster tightly within the mantle array and all lie within an overlapping field of midocean ridge basalt and ocean island basalt 2 small differences exist among the shirahama tholeiitic series calc alkaline series and mixed lavas the present isotopic data are consistent with a previously published model which proposes that chemical variations in magmas of coexisting tholeiitic and calc alkaline series are produced through crystal fractionation from mantlederived magmas of basalt and magnesian andesite respectively moreover the tholeiitic series and the calc alkaline series are isotopically identical thus both magma series can be derived from a source mantle with the same isotopic composition supporting the hypothesis of simultaneous generation of basalt and magnesian andesite magmas from a single diapir rising through the mantle wedge above the subduction zone the differences of water content and temperature within the diapir are again thought to have been produced through dehydration and heating of an isotopically homogeneous hydrous diapir the isotopic data show that the high sio lavas have the same isotopic compositions as more mafic lavas these data and liquid lines of descent of the shirahama magmas suggest that even rhyolites can be produced by differentiation from mantle derived magmas without crustal contamination analyses from 38 other arc volcanoes have been compiled to investigate the intravolcano variability of sr sr twelve of these display no intravolcano strontium isotopic variability as is the case with the shirahama group but others show greater variation of sr 86sr from individual volcanic centers presumably reflecting crustal contamination most of the latter volcanoes are underlain by thick continental crust it is noteworthy however that the greater variations of sr sr correlate with sio2 content andesites or dacites not basalts from the same volcano have the lowest sr sr and these rocks are calc alkaline in terms of feo mgo and sio theoretically assimilation of continental crust by the isotopically uniform shirahama magmas could produce these relationships given that mantle derived basalt and magnesian andesite both encounter continental crust on their ascent to the surface the hotter basalt magma would assimilate more crustal wallrocks than the cooler andesite resulting in the basalt being more radiogenic fractional crystallization magma mixing and or assimilation fractional crystallization of these magmas in crustal magma chambers could produce large compositional variations but the derivatives of the hotter basaltic magmas tholeiitic series in the broad sense would display greater contamination than those derived from the cooler andesitic magmas calc alkaline series

aleutian terranes from nd isotopes nd isotope ratios substantiate the identification of oceanic crustal terranes within the continental crustal basement of the aleutian island arc the oceanic terranes are exposed in the westernmost aleutians but to the east they are completely buried by isotopically distinct arc volcanic rocks analogous oceanic terranes may be important components of the terrane collages that comprise the continents

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

upper mantle seismic anisotropy at a strike slip boundary south island new zealand new shear wave splitting measurements made from stations onshore and offshore the south island of new zealand show a zone of anisotropy 100 200 km wide measurements in central south island and up to approximately 100 km offshore from the west coast yield orientations of the fast quasi shear wave nearly parallel to relative plate motion with increased obliquity to this orientation observed farther from shore on the eastern side of the island fast orientations rotate counterclockwise to become nearly perpendicular to the orientation of relative plate motion approximately 200 km off the east coast uniform delay times between the fast and slow quasi shear waves of nearly 2 0 s onshore continue to stations approximately 100 km off the west coast after which they decrease to 1 s at 200 km stations more than 300 km from the west coast show little to no splitting east coast stations have delay times around 1 s simple strain fields calculated from a thin viscous sheet model representing distributed lithospheric deformation with strain rates decreasing exponentially to both the northwest and southeast with e folding dimensions of 25 35 km approximately 75 of the deformation within a zone 100 140 km wide match orientations and amounts of observed splitting a model of deformation localized in the lithosphere and then spreading out in the asthenosphere also yields predictions consistent with observed splitting if at depths of 100 130 km below the lithosphere typical grain sizes are 6 7 mm

wet and dry basalt magma evolution at torishima volcano izu bonin arc japan the possible role of phengite in the downgoing slab the arc front volcanoes of sumisu 31 58n 1408e andtorishima 30 58n 140 38e in the central izu bonin arc are similar in size and rise as relatively isolated edifices from the seafloor together they provide valuable along arc information about magma generation processes the volcanoes have erupted low k basalts originating from both wet and dry parental basaltic magmas low zr basalts and high zr basalts respectively based on models involving fluid immobile incompatible element ratios la sm the parental basalts appear to result from different degrees of partial melting of the same source mantle 20 and 10 for wet and dry basalt magmas respectively assuming that the wet basalts contain greater abundances of slab derived components than their dry counterparts geochemical comparison of these two basalt types permits the identification of the specific elements involved in fluid transport from the subducting slab using an extensive set of new geochemical data fromtorishima where the top of the downgoing slab is about 100 km deep we find that cs pb and sr are variably enriched in the low zr basalts which cannot be accounted for by fractional crystallization or by differences in the degree of mantle melting these elements are interpreted to be selectively concentrated in slab derived metasomatic fluids variations in k high field strength element and rare earth element concentrations are readily explained by variations in the degree of melting between the lowand high zr basalts these elements are not contained in the slab derived fluids rb and ba exhibit variable behaviour in the low zr basalts ranging from immobile similar to k to mildly enriched in some low zr basalts we suggest that the k rich mica phengite plays an important role in determining the composition of fluids released from the downgoing slab in arcfront settings where slab depth is 100 km phengite is stable and the fluids released from the slab contain little k in back arc settings however where the slab is at 100 140 km depth phengite is unstable and k rich fluids are released we conclude that cross arc variations in the k content of arc basalts are probably related to differing compositions of released fluids or melts rather than the widely held view that such variations are controlled by the degree of partial melting

vertical deformation measurements on the submerged south flank of kīlauea volcano hawai i reveal seafloor motion associated with volcanic collapse 1 a four year seafloor geodetic study was conducted to measure vertical deformation of the submerged south flank of k lauea volcano on the active hilina slump the hilina slump is a site of significant deformation major earthquakes with ground cracking and associated tsunami a new technique was developed to measure vertical deformation on the seafloor using pressure sensors in campaign style surveys the data revealed the midslope bench of the offshore slump is uplifting at 9 0 2 4 cm a but transitions to no significant deformation on the outer bench and slump toe elastic half space inverse modeling of these data show that the observed deformation can be fit by seaward slip of 28 1 7 3 cm a extending from the east rift zone 27 0 0 5 km on a gently island dipping decollement fault plane at a depth of approximately 7 km modeling suggests that the outer bench is not currently deforming because the majority of k lauea is submerged these offshore measurements are necessary to constrain the seaward extent of fault slip and the motion of the outer bench

partial melting of mantle wedge and evolution of island arc crust evolution of the crust in the northeast honshu arc is discussed on the basis of the melting experiments of a peridotite under hydrous conditions and the crustal compositions estimated from deep crustal xenoliths and seismic velocity data the chemical compositions of melts formed by partial melting of a hydrous peridotite within the pressure temperature conditions for shallow parts of the mantle wedge 1 2 2 0 gpa have been experimentally determined with the sandwich experiment technique the melts range from olivine tholeiitic to magnesian andesitic compositions sio2 48 56 wt mgo 9 14 wt beneath the volcanic front in the northeast honshu arc and are slightly less silicic beneath the coast of the sea of japan the crustal compositions of the volcanic zone in the northeast honshu arc estimated from deep seated crustal inclusions in volcanic rocks and the velocity structures of the crust are andesitic in the central zone and high alumina basaltic near the coast of the sea of japan the compositions of possible primary melts formed in the mantle wedge are significantly more mafic than these crustal compositions consequently if the major part of the crustal materials in the volcanic zone was formed by magmas generated in the mantle wedge thick up to 30 km ultramafic cumulates including olivine pyroxenite must have been formed beneath moho during fractional crystallization and would constitute the upper part of the mantle wedge the volume of the mantle wedge consisting entirely of even fertile peridotite was not sufficient to produce crustal materials and cumulates in the volcanic zone by such processes in the northeast honshu arc a static mantle wedge model is therefore not satisfactory for the growth of the crust in northeast honshu arc a dynamic model is suggested in which the mantle materials have been supplied into the mantle wedge from the back arc side by a convective flow

crystal capture sorting and retention in convecting magma the mystery of producing strong compositional diversity among suites of comagmatic igneous rocks is investigated by considering the dynamic evolution of basaltic magma in a sheet like chamber a central conclusion is that inward progressing crystallization produces strong viscosity and temperature gradients that promote convection only near the leading edge of the upper thermal boundary layer convection is apparently confined to an essentially isoviscous isothermal region that hugs the downward growing roof zone strong changes in viscosity with crystallization divide the upper and lower thermal boundary layers into regions of decreasing viscosity and crystallinity n called rigid crust n 0 5 mush 0 5 n 0 25 and suspension n 0 25 the strong increase in viscosity near the mush suspension interface acts as a capture front that overtakes and traps slowly settling crystals initial phenocrysts mostly escape capture but crystals nucleated and grown in the suspension zone can escape only if the capture front slows to a critical rate attainable only in bodies thicker than about 100 m escaping crystals are redistributed and sorted by convection driven by the advance of the capture front itself crystal laden plumes traverse the central hot core of the body and deposit partially resorbed and sorted crystals within the lower suspension zone convection is never vigorous but is part of an overall intimate balance between roofward heat loss rigid crust growth crystallization kinetics and transport and sorting of sinking escaped crystals there is a strong similarity between these processes and those producing both varves and saline pan deposits it is clear that lavas lava lakes and sills are indeed examples of true magma chambers strongly exhibiting certain aspects of this over all process these aspects commonly also characterize the large mafic magmatic bodies because strong compositional changes in the residual melt occur largely outward that is at lower temperatures and higher crystallinities of the capture front which is immobile and mostly within rigid crust the possible range in comagmatic compositions available for eruption anywhere within the active magma is very limited this is in broad agreement with the compositional range observed in basaltic lava lakes sills and plutons like skaergaard the tuning of convection crystallization kinetics and phase equilibria in chambers of this type can produce a variety of textures and layering but not a diversity of compositions

time scales of magma transport and mixing at kīlauea volcano hawai i modeling of volcanic processes is limited by a lack of knowledge of the time scales of storage mixing and final ascent of magmas into the shallowest portions of volcanic plumbing systems immediately prior to eruption it is impossible to measure these time scales directly however micro analytical techniques provide indirect estimates based on the extent of diffusion of species through melts and crystals we use diffusion in olivine phenocrysts from the a d 1959 k lauea iki hawai i usa eruption to constrain the timing of mixing events in the crustal plumbing system on time scales of months to years before eruption the time scales derived from zonation of fe mg in olivines combined with contemporaneous geophysical data suggest that mixing occurred on three time scales 1 as much as 2 yr prior to eruption in the deep storage system 2 in a shallow reservoir between incoming hot melts and resident melt for several weeks to months prior to eruption and 3 in the conduit and summit reservoir between the resident magma and cooled surface lava draining back into the vent on time scales of hours to several days during pauses between episodes synchronous inflation of the shallow reservoir with deep earthquake swarms and mixing suggests an intermittently open transcrustal magmatic system

paleoenvironmental insights into the quaternary evolution of the southern brazilian coast based on fossil and modern diatom assemblages abstract diatom assemblages provide a strong basis for detailed interpretations of paleoceanography and diatom paleoecology of the southern brazilian coast nine cores obtained in the coastal plain shelf and continental slope and thirteen surface sediment samples of the patos lagoon provide an excellent opportunity to use a paleoecological approach to study detailed quaternary environmental changes in the southern coasts in the interval studied the basin sedimentation occurred in a marine dominated environment related to humid periods prior to 43 500 year bp abundant diatom taxa are highlighted as excellent indicators of environmental changes including salinity sediment composition and transport by incised valleys providing additional insights into coastal evolution paralia sulcata is dominant in all analyzed cores occurring continuously from late pleistocene to holocene but is rare in the modern sediments non marine diatom assemblages occurred continuously but in very low densities in periods before and after the last glacial maximum abrupt changes in sedimentation have been recorded related to shifts from marine dominated to shallow estuarine deposition during the holocene sea level rose rapidly which is responsible for the progressive coastal flooding prior to 8420 7930 year bp the holocene barrier system became more continuous and patos lagoon developed consequently the secondary former inlets from the jacui and camaqua rivers are closed and only one single inlet rio grande channel remains active the spatial distribution of modern assemblages is controlled by salinity gradient wind action and climate forcing the bottom sediments of patos lagoon are dominated by freshwater diatom aulacoseira veraluciae aulacoseira sp 2 and marine estuarine species of cyclotella litoralis

pn anisotropy beneath the south island of new zealand and implications for distributed deformation in continental lithosphere pn travel times from regional earthquakes recorded both by stations on new zealand and by ocean bottom seismographs deployed offshore indicate anisotropy in the uppermost mantle beneath the region the largest anisotropy of 8 2 1 lies beneath the deforming part of the south island to just off its west coast a zone roughly 100 200 km wide the fastest propagation is aligned n60 e 3 essentially parallel to the largely strike slip relative plate motion since 20 ma also n60 e the magnitude of anisotropy decreases abruptly northwest and southeast of this zone and on the southeast side of the island the orientation of fastest propagation is between n32 w and n s the n60 e orientation of fast propagation is consistent with finite strain within the uppermost part of the mantle lithosphere if the measured 850 km of displacement of the pacific plate past the australia plate is spread over a region with a width of 100 200 km the agreement of this orientation of fast propagation with the orientation or relative plate motion suggests the possibility of but does not require some dynamic recrystallization in rock as cold as 500 800 c where peierls creep seems to be the likely deformation mechanism such a strain distribution matches deformation of a thin viscous sheet that obeys a constitutive relationship of the form e n where e is the average strain rate and is the operative deviatoric stress with an average value of n 3 10 presumably the nw se fast propagation in the region southeast of the island results from strain that precedes the cenozoic deformation that has shaped the island

a 2860 year high resolution pollen and charcoal record from the cordillera de talamanca in panama a history of human and volcanic forest disturbance late holocene vegetational disturbance by human and volcanic activity in the lower montane rain forest region of cordillera de talamanca province of chiriqui in panama have been studied on the sedimentary archive from laguna volcan 1500 m elevation the pollen and charcoal record dated by four radiocarbon ams dates provides evidence of amerindian occupation and strong impact on the lower montane rain forest region since the beginning of the record at 2860 14c yr bp there is evidence of at least three eruptions of volcan baru which affected the study region at 1800 1000 and 500 14c yr bp the first two events had apparently relatively little effects while the latest volcanic eruption which deposited a 20 cm thick tephra layer in the studied lake had a catastrophic impact amerindian life and culture of the study area was destroyed after the last eruption the montane rain forest recovered markedly fires were rare and agriculture activity stopped in the surroundings of the lake suggesting that

scaling relations of earthquake source parameter estimates with special focus on subduction environment abstract earthquake rupture length and width estimates are in demand in many seismological applications earthquake magnitude estimates are often available whereas the geometrical extensions of the rupture fault mostly are lacking therefore scaling relations are needed to derive length and width from magnitude most frequently used are the relationships of wells and coppersmith 1994 derived on the basis of a large dataset including all slip types with the exception of thrust faulting events in subduction environments however there are many applications dealing with earthquakes in subduction zones because of their high seismic and tsunamigenic potential there are no well established scaling relations for moment magnitude and length width for subduction events within this study we compiled a large database of source parameter estimates of 283 earthquakes all focal mechanisms are represented but special focus is set on large subduction zone events in particular scaling relations were fitted with linear least square as well as orthogonal regression and analyzed regarding the difference between continental and subduction zone oceanic relationships additionally the effect of technical progress in earthquake parameter estimation on scaling relations was tested as well as the influence of different fault mechanisms for a given moment magnitude we found shorter but wider rupture areas of thrust events compared to wells and coppersmith 1994 the thrust event relationships for pure continental and pure subduction zone rupture areas were found to be almost identical the scaling relations differ significantly for slip types the exclusion of events prior to 1964 when the worldwide standard seismic network was established resulted in a remarkable effect on strike slip scaling relations the data do not show any saturation of rupture width of strike slip earthquakes generally rupture area seems to scale with mean slip independent of magnitude the aspect ratio l w however depends on moment and differs for each slip type

generation and polybaric differentiation of east greenland early tertiary flood basalts major element trace element isotope and petrographic studies of magma diverentiation mantle melting the basal volcanics in the kangerdlugssuaq fjord region of the east greenland margin provide constraints on the generation and subsequent diverentiation and contamination histories of magmas during the early stage of continental rifting creating the north atlantic ocean basin most primitive lavas of the succession are introduction shown to have accumulated olivine corrections for crystal ac the distinctive geochemical features of continental flood cumulation yield estimates for erupted primitive liquids with mgo basalts cfbs are strongly controlled by the composition contents between 9 and 13 wt the occurrence of suspended and structure of the continental lithosphere and underfo88 olivine phenocrysts further requires the existence of parental lying mantle significant controversy remains concerning magmas with mgo contents up to 17 wt and feo contents up the balance of contributions from the lithosphere and to 14 wt quantitative modeling of fractionation indicates the mantle and the mechanisms by which the various that kangerdlugssuaq magmas primarily diverentiated at moderate source components contribute to basalt petrogenesis pressures 8 kbar to form dunitic and wehrlitic cumulates at how are basalt compositions influenced by generation depths of 25 km evolved east greenland flood basalts from the in anomalous regions in the deep mantle plumes by scoresby sund region record a more complex fractionation history interaction between rising magmas and the continental involving olivine clinopyroxene fractionation in the lower crust lithospheric mantle and by contamination with conas found for the lower basalts followed by olivine plagioclase tinental crust how are the diverentiation con clinopyroxene fractionation at shallow crustal levels cor tamination magma mixing and storage histories of cfbs relations between sio2 incompatible elements and sr nd isotopic controlled by the structure of the continental lithosphere ratios for the lower basalts are consistent with bulk assimilation and how do the thermal and chemical features of the of up to 15 20 archean leucogneiss with unradiogenic sr and mantle and the extensional history of the continental nd isotopic ratios characteristic of lewisian type lower crust lithosphere avect mantle melting and compositions of comparisons between inferred magma types for lower basalts and primary liquids estimated primary liquids from elsewhere in the north atlantic these questions are best addressed in the context of show complex relationships among feo mgo tio2 contents a geologically and geochemically well constrained cfb and cao al2o3 ratios that relate to regional and temporal changes province such as the north atlantic tertiary province in mantle temperatures lithospheric thickness and involvement of separation of east greenland from northern europe in at least two end member mantle sources we postulate that the the early tertiary at 60 myr ago was accompanied by lower basalts of east greenland were derived from iron poor voluminous volcanic activity the blosseville coast of mantle depleted by prior melt extraction and distinct from morb east greenland extending from kangerdlugssuaq fjord source mantle that was enriched in tio2 and lrees by a to scoresby sund fig 1 contains spectacularly exposed metasomatic event shortly before early tertiary magmatism we sections of lavas these sections begin at the basal contact associate this depleted mantle source with the ancestral iceland of the lavas with underlying cretaceous tertiary sediments and archean basement and continue to the plume anomaly

chemical zoning and homogenization of pasamonte type pyroxene and their bearing on thermal metamorphism of a howardite parent body we studied thermal metamorphism in the surface layer of a eucrite parent body by examining pyroxene zoning ca mg fe zoning of pyroxenes in the pasamonte eucrite can be classified into three types type 1 with a core composition of ca5mg62fe32 and rim of ca41mg20fe4o type 2 with core of ca5mg62fe32 and rim of ca25mg34fe41 and type 3 with core of ca5mg66fe29 and rim of ca7mg32fe61 type 1 typically occurs adjacent to a mesostasis type 2 typically occurs adjacent to a surrounding plagioclase and type 3 is common in pyroxenes in the matrix pasamonte is less metamorphosed than previously believed because of the wide range of composition of zoned pyroxenes on the basis of ca mg fe variation data we have calculated the degree of homogenization of zoned pyroxenes by numerically solving the diffusion equation a pasamonte type pyroxene may yield a juvinas type pyroxene by thermal metamorphism the homogenization of juvinas pyroxene could not have taken place during initial cooling and may be related to reheating events although our calculation rests upon some assumptions

element zoning trends in olivine phenocrysts from a supposed primary high magnesian andesite an electron and ion microprobe study electron and ion probe microanalysis have been used to obtain zoning profiles for major and trace elements in olivine phenocrysts from a high magnesian andesite from shodo shima island southwest japan this rock was previously thought to represent undifferentiated primary magma some crystals have unzoned cores while others show cores which are reversely zoned with respect to mg mg fe ni mn and cr in addition some ni profiles show a normally zoned hump at the most central portions of the reversely zoned crystals all crystals show normally zoned rims the li concentrations are constant throughout the cores of all crystals studied but rise sharply by a factor of up to at least six in the rims the ca and co concentrations are essentially constant throughout all the crystals mechanisms for producing the observed zoning profiles are discussed and it is concluded that the reverse zoning was produced by the introduction of crystals into a less differentiated magma than that in which they grew the reversely zoned crystals could therefore represent xenocrysts which were introduced into an undifferentiated magma or phenocrysts introduced into a more primitive magma by a magma mixing process the ni profiles are used to estimate the residence time of these crystals in the more primitive magma the following trace element partition co efficients have been estimated for the olivine groundmass system in this rock dni 16 dmn 1 1 dco 4 2 dca 0 02 dti 0 005 dv 0 05 dsc 0 2 dna 0 0002 studies of trace element zoning will become increasingly important as the new generation of trace element microprobes become available but a larger database of experimentally determined values for trace element partition coefficients and diffusion coefficients in crystals and magmas and a better understanding of other disequilibrium processes are required to fully exploit the new data

short time scales of magma mixing processes prior to the 2011 eruption of shinmoedake volcano kirishima volcanic group japan we estimated time scales of magma mixing processes just prior to the 2011 sub plinian eruptions of shinmoedake volcano to investigate the mechanisms of the triggering processes of these eruptions the sequence of these eruptions serves as an ideal example to investigate eruption mechanisms because the available geophysical and petrological observations can be combined for interpretation of magmatic processes the eruptive products were mainly phenocryst rich 28 vol andesitic pumice sio2 57 wt with a small amount of more silicic pumice sio2 62 63 wt and banded pumice these pumices were formed by mixing of low temperature mushy silicic magma dacite and high temperature mafic magma basalt or basaltic andesite we calculated the time scales on the basis of zoning analysis of magnetite phenocrysts and diffusion calculations and we compared the derived time scales with those of volcanic inflation deflation observations the magnetite data revealed that a significant mixing process mixing i occurred 0 4 to 3 days before the eruptions pre eruptive mixing and likely triggered the eruptions this mixing process was not accompanied by significant crustal deformation indicating that the process was not accompanied by a significant change in volume of the magma chamber we propose magmatic overturn or melt accumulation within the magma chamber as a possible process a subordinate mixing process mixing ii also occurred only several hours before the eruptions likely during magma ascent syn eruptive mixing however we interpret mafic injection to have begun more than several tens of days prior to mixing i likely occurring with the beginning of the inflation december 2009 the injection did not instantaneously cause an eruption but could have resulted in stable stratified magma layers to form a hybrid andesitic magma mobile layer this hybrid andesite then formed the main eruptive component of the 2011 eruptions of shinmoedake

petrology of arc volcanic rocks and their origin by mantle diapirs abstract calc alkalic chemical trends characteristic of arc volcanic rocks mainly result from three mechanisms which act additively 1 fractional crystallization involving separation of titanomagnetite 2 selective concentration of plagioclase phenocrysts and selective depletion of titanomagnetite phenocryst compared with the actually fractionated proportion and 3 mixing of magmas on continuous fractionation trends the association of calc alkalic and tholeiitic trends in a single composite volcano may not represent different fractional crystallization processes or different chemistries of primary magmas but the calc alkalic chemical trend can be considered as a mixing trend resulting from mixing of various magmas on associated tholeiitic chemical trends chemical variations of most arc volcanic rocks including calc alkalic ones can accordingly be essentially accounted for by the low pressure fractional crystallization of phenocrystic phases from primary basaltic magmas crystallization sequences of arc magmas which are strongly dependent on water content in magmas are deduced from the phenocryst assemblages the crystallization sequence changes laterally across arc suggesting increasing water contents in magmas toward the back arc side as is also seen for other incompatible elements such as k and rb systematic differences in the characteristic crystallization sequence are also observed among arcs roughly correlating with the crustal thickness water content in magma like other incompatible elements tends to increase with increasing crustal thickness the variation of incompatible elements including water roughly represents that of the degree of partial melting of the upper mantle which is broadly controlled by the crustal thickness the variation of water content indicates that arc magmas are not saturated with water during differentiation to late differentiates such as dacite or rhyolite this strongly constrains the maximum water contents in primary basaltic magma at most 2 5 wt this value suggests that magma generation beneath arcs is dependent on dry solidus of peridotite diapiric uprise of the hot deeper mantle and associated adiabatic decompression would be necessary for mantle peridotite to attain the temperature as high as dry solidus diapirs that begin to rise from the subduction zone may stop at or near the crust mantle boundary because of the surrounding density change and their degree of partial melting is roughly controlled by their stopped depth assuming their similar temperature across arc variation is also explained by the stopped depth of diapirs but is not controlled by crustal thickness

crustal contamination of late neogene basalts in the dien bien phu basin nw vietnam some insights from petrological and geochronological studies early pliocene zanclean basalts in the dien bien phu pull apart basin in nw vietnam associated with the presently sinistral dien bien phu fault zone have been dated by the k ar method at 4 4 4 9 and 5 4 5 2 ma rapid migration of basaltic magma to the surface in the dien bien phu fault zone may be due to pliocene transtension of the crust in this region resulting from asthenospheric upwelling induced by lateral displacement of the mantle the basalts are moderately phyric 10 and consist of olivine hyalosiderite plagioclase bytownite labradorite and orthopyroxene bytownite labradorite phenocrysts and a fine grained crystalline matrix olivine hortonolite plagioclase labradorite clinopyroxene pigeonite and augite k feldspar the presence of fe rich olivine and orthopyroxene phenocrysts indicates that the basalts are sio2 saturated oversaturated olivine tholeiites which formed under water undersaturated conditions the dien bien phu basalts contain both mantle derived pyroxenites dunites gabbros and crustal sillimanite mullite mg fe spinel wallrock xenoliths indicative of crustal contamination during the ascent of the basaltic magma the basalts show selective enrichment in some mobile elements k rb sr and th a feature considered to be a result of metasomatism these rocks classified on the basis of their normative composition as quartz tholeiites could represent primary olivine tholeiites basalts in which the geochemical signatures were modified by the processes of contamination 2006 elsevier ltd all rights reserved

petrogenic implications of ree and ba data on mafic and ultramafic inclusions from itinome gata japan ultramafic and mafic inclusions from itinome gata in japan were studied systematically from a viewpoint of earth element ree and barium abundances mineral separates from lherzolites and their host basalt as well as andesite from an adjacent volcano were also analyzed for ree and ba garnet lherzolites which are believed to have formed at a depth of 50 to 70 km have a convex upwards chondrite normalized ree patterns similar to those of alpine type lherzolites spinel lherzolites which are believed to be derived from shallower depths than garnet lherzolites have various ree patterns and negative eu anomalies spinel lherzolites that are high in basaltic components have convex upwards ree patterns as do garnet lherzolites whereas mg rich strongly basalt depleted spinel lherzolites have v shaped ree patterns the ree variation among spinel lherzolites reflects the differing degrees of liquid phase extraction of basaltic components in times past the ree pattern of the liquid phase extracted from t

reaction rim growth on olivine in silicic melts implications for magma mixing finely crystalline amphibole or pyroxene rims that form during reaction between silicic host melt and cognate olivine xenocrysts newly introduced during magma mixing events can provide information about the timing between mixing and volcanic eruptions we investigated rim growth experimentally by placing forsteritic olivine in rhyolitic and rhyodacitic melts for times between 25 and 622 h at 50 and 150 mpa h2o saturated at the ni nio buffer rims of orthopyroxene microlites formed from high silica rhyolite and rhyodacite melts at 885 c and 50 mpa and in the rhyolite at 150 mpa and 885 c rims of amphibole with lesser orthopyroxene formed in the rhyolite at 150 mpa and 800 c and in the rhyodacite at 150 mpa and 885 c irregular convolute olivine edges and mass balance between olivine melt and rim phases show that olivine partly dissolved at all conditions iron rich zones at the exteriors of olivines which increased in width parabolically with time show that fe mg interdiffusion occurring in olivines was not outpaced by olivine dissolution linear increases of the square of rim widths with time suggest that diffusion within the melt is the rate controlling process for olivine dissolution and rim growth rims grew one half to one order of magnitude faster when melt water contents were doubled unless conditions were far above the liquidus rim growth rate in rhyolite increases from 0 055 0 01 m2 h at 885 c and 50 mpa to 0 64 0 13 m2 h at 800 c and 150 mpa melt composition has a lesser effect on rim growth rates with growth rate increasing as melt sio2 content decreases pyroxene rims on olivines in andesite erupted from arenal volcano costa rica grew at a rate of 3 0 0 2 m2 h over an eleven year period this rate is faster than those of the experiments due to lower melt viscosity and higher temperatures and suggests that a magma mixing event preceded the start of the eruption by days

tsunami data assimilation of cascadia seafloor pressure gauge records from the 2012 haida gwaii earthquake we use tsunami waveforms recorded on a dense array of seafloor pressure gauges offshore oregon and california from the 2012 haida gwaii canada earthquake to simulate the performance of two different real time tsunami forecasting methods in the first method the tsunami source is first estimated by inversion of recorded tsunami waveforms in the second method the array data are assimilated to reproduce tsunami wavefields these estimates can be used for forecasting tsunami on the coast the dense seafloor array provides critical data for both methods to produce timeliness 30 min lead time and accuracy in both timing and amplitude 94 confidence tsunami forecasts real time tsunami data on dense arrays and data assimilation can be tested as a possible new generation tsunami warning system

zoning of phosphorus in igneous olivine we describe p zoning in olivines from terrestrial basalts andesites dacites and komatiites and from a martian meteorite p2o5 contents of olivines vary from below the detection limit 0 01 wt to 0 2 0 4 wt over a few microns with no correlated variations in fo content zoning patterns include p rich crystal cores with skeletal hopper or euhedral shapes oscillatory zoning structures suggesting replacement of p rich zones by p poor olivine and sector zoning melt inclusions in olivines are usually located near p rich regions but in direct contact with low p olivine crystallization experiments on basaltic compositions at constant cooling rates 15 30 c h reproduce many of these features we infer that p rich zones in experimental and natural olivines reflect incorporation of p in excess of equilibrium partitioning during rapid growth and zoning patterns primarily record crystal growth rate variations occurrences of high p phenocryst cores may reflect pulses of rapid crystal growth following delayed nucleation due to undercooling most cases of oscillatory zoning in p likely reflect internal factors whereby oscillating growth rates occur without external forcings but some p zoning in natural olivines may reflect external forcings e g magma mixing events eruption that result in variable crystal growth rates and or p contents in the magma in experimental and some natural olivines al cr and p concentrations are roughly linearly and positively correlated suggesting coupled substitutions but in natural phenocrysts cr zoning is usually less intense than p zoning and al zoning weak to absent we propose that olivines grow from basic and ultrabasic magmas with correlated zoning in p cr and al superimposed on normal zoning in fe mg rapidly diffusing divalent cations homogenize during residence in hot magma al and cr only partially homogenize and delicate p zoning is preserved because p diffuses very slowly this interpretation is consistent with the fact that zoning is largely preserved not only in p but also in al cr and divalent cations in olivines with short residence times at high temperature e g experimentally grown olivines komatiitic olivines groundmass olivines and the rims of olivine phenocrysts grown during eruption p zoning is widespread in magmatic olivine revealing details of crystal growth and intra crystal stratigraphy in what otherwise appear to be relatively featureless crystals since it is preserved in early formed olivines with prolonged residence times in magmas at high temperatures p zoning has promise as an archive of information about an otherwise largely inaccessible stage of a magma s history study of such features should be a valuable supplement to routine petrographic investigations of basic and ultrabasic rocks especially because these features can be observed with standard electron microprobe techniques

w phase inversion and tsunami inundation modeling for tsunami early warning case study for the 2011 tohoku event centroid moment tensor solutions for the 2011 tohoku earthquake are determined by w phase inversions using 5 and 10 min data recorded by the full range seismograph network of japan f net by a scaling relation of moment magnitude to rupture area and an assumption of rigidity of 4 1010 n m 2 simple rectangular earthquake fault models are estimated from the solutions tsunami inundations in the sendai plain minamisanriku rikuzentakata and taro are simulated using the estimated fault models then the simulated tsunami inundation area and heights are compared with the observations even the simulated tsunami heights and inundations from the w phase solution that used only 5 min data are considerably similar to the observations the results are improved when using 10 min of w phase data these show that the w phase solutions are reliable to be used for tsunami inundation modeling furthermore the technique that combines w phase inversion and tsunami inundation modeling can produce results that have sufficient accuracy for tsunami early warning purposes

traveltime delay and initial phase reversal of distant tsunamis coupled with the self gravitating elastic earth systematic tsunami traveltime delays of up to 15 min relative to the numerically simulated long waves from the 2010 chilean and 2011 tohoku oki earthquakes were widely observed at deep ocean tsunamimeters enigmatic small negative phases appearing before the main peak were commonly found only at the trans oceanic locations the frequency dependence of the measured tsunami phase velocities shows reverse dispersions at long periods i e the tsunami speed becomes slower at periods beyond 1000 s this is consistent with the phase velocities of a tsunami mode coupled with a self gravitating elastic earth suggesting that the effects of compression and dilatation of seawater elastic tsunami loadings on a solid earth and the geopotential variations associated with the motion of mass during tsunami propagation are responsible for the traveltime delays and the initial negative phases simple 1 d tsunami propagation tests confirm that the reverse dispersion creates a small negative phase that precedes the main peak at large distances a new method to simulate tsunami waveforms on real ocean bathymetry that takes into account seawater compressibility the elasticity of the earth and geopotential perturbations has been developed by applying a phase correction to the simulated long waves the simulated waveforms in which phase corrections are applied for the dispersion effects accurately reproduce the observed waveforms including a small initial negative phase that appears at distant locations the traveltime difference between the observed and simulated waveforms has been decreased to less than 5 min and the waveform difference between them remarkably diminishes

holocene history of the choco rain forest from laguna piusbi southern pacific lowlands of colombia abstract a high resolution pollen record from a 5 m long sediment core from the closed lake basin laguna piusbi in the southern colombian pacific lowlands of choco dated by 11 ams14c dates that range from ca 7670 to 22014c yr b p represents the first holocene record from the choco rain forest area the interval between 7600 and 610014c yr b p 500 265 cm composed of sandy clays that accumulated during the initial phase of lake formation is almost barren of pollen fungal spores and the presence of herbs and disturbance taxa suggest the basin was at least temporarily inundated and the vegetation was open the closed lake basin might have formed during an earthquake probably about 440014c yr b p from the interval of about 600014c yr b p onwards 200 different pollen and spore types were identified in the core illustrating a diverse floristic composition of the local rain forest main taxa are moraceae urticaceae cecropia melastomataceae combretaceae acalypha alchornea fabaceae mimosa piper protium sloanea euterpe geonoma socratea andwettinia little change took place during that time interval compared to the pollen records from the rain forests of the colombian amazon basin and adjacent savannas the choco rain forest ecosystem has been very stable during the late holocene paleoindians probably lived there at least since 346014c yr b p evidence of agricultural activity shown by cultivation ofzea maissurrounding the lake spans the last 1710 yr past and present very moist climate and little human influence are important factors in maintaining the stable ecosystem and high biodiversity of the choco rain forest

the eagle and east eagle sulfide ore bearing mafic ultramafic intrusions in the midcontinent rift system upper michigan geochronology and petrologic evolution 1 the eagle and east eagle intrusions are small subvertical dike like mafic ultramafic bodies that cut proterozoic sedimentary strata in the baraga basin in northern michigan the eagle intrusion hosts a newly discovered magmatic ni cu pge deposit the nearby east eagle intrusion also contains sulfide mineralization but the extent of this mineralization has yet to be determined by further drilling both intrusions contain olivine bearing rocks such as feldspathic peridotite melatroctolite and olivine melagabbro sulfide accumulations range from disseminated at both eagle and east eagle to semimassive and massive at eagle u pb baddeleyite dating gives a crystallization age of 1107 2 5 7 ma for the eagle intrusion coeval with eruption of picritic basalts at the base of the volcanic succession in the midcontinent rift system mrs the fo contents of olivine cores in the eagle and east eagle intrusions vary between 75 and 85 mol higher than those of olivine in larger layered intrusions in the mrs such as the duluth complex the feo mgo ratios and al2o3 contents of the parental magmas for the eagle and east eagle intrusions inferred from olivine and spinel compositions are similar to those of picritic basalts in the base of the mrs volcanic succession these petrochemical data suggest that the eagle and east eagle intrusions are the intrusive equivalents of high mgo basalts that erupted in the early stages of continental magmatism associated with the development of the rift variations in mineral compositions and incompatible trace element ratios suggest that at least three major pulses of magmas were involved in the formation of low sulfide rocks in the eagle intrusion lower fo contents of olivine associated with semimassive sulfides as compared to that of olivine in low sulfide rocks suggest that the magma associated with the semimassive sulfide was more fractionated than the parental magmas of the low sulfide rocks in the eagle intrusion accumulation of suspended olivine crystals and sulfide droplets from ascending magmas as they passed through wide parts of the conduits at eagle and east eagle played a critical role in the genesis of olivine rich rocks and sulfide ores in the intrusions the eagle ni cu pge deposit typifies the conduit style of magmatic sulfide deposition that is associated with continental basaltic magmatism

slip distribution of the 2007 bengkulu earthquake inferred from tsunami waveforms and insar data 1 joint inversion study using tsunami waveforms and insar data provides a new way to understand the magnitude and spatial extent of subduction zone earthquakes a great earthquake mw 8 5 occurred on 12 september 2007 off the west coast of bengkulu indonesia the tsunami generated by the event was recorded by tide gauge stations around the indian ocean and by two bottom pressure sensors in the deep sea the ground surface displacements produced by the earthquake on pagai islands and on sumatra island were observed by interferometric synthetic aperture radar insar we estimated the slip distribution of the earthquake by joint inversion incorporating a spatial smoothness constraint using tsunami waveforms and insar data the total released seismic moment calculated from the slip distribution is 6 7 1021 n m mw 8 5 consistent with the seismic moment of the global cmt solution 6 71 1021 n m the maximum observed tsunami heights along the coast of bengkulu agree with those computed from the slip distribution the slip amount of the 2007 earthquake is smaller than the amount of potential slip that has been accumulated since after the 1797 and 1833 events the premise is that averaged over long periods of time the entire fault must slip equal amounts therefore the 2007 great earthquake could be followed by several great earthquakes that will rupture the plate interface until the potential slip that has been accumulated is completely released

dynamic plumbing system beneath volcanoes revealed by kinetic modeling and the connection to monitoring data an example from mt etna abstract our ability to monitor volcanoes using seismic signals ground deformation gas fluxes or other ground and satellite based observations as well as our understanding of melt reservoirs that feed eruptions have evolved tremendously in recent years the complex plumbing systems that are thought to feed eruptions are however difficult to relate to the monitoring signals here we show that the record preserved in compositional zoning of erupted minerals may be used to reconstruct sections of the plumbing system kinetic modeling of such zoning can yield information on the residence time of magma in different segments of the plumbing systems this allows a more nuanced evaluation of the link between observed monitoring signals or eruption styles and the magmatic processes and movement of batches of melts at depth the approach is illustrated through a study of the compositional zoning recorded in olivine crystals from the 1991 1993 se flank eruption products of mt etna sicily the zoning patterns in crystals reveal that the plumbing system of the volcano consisted of at least three different magmatic environments between which magma was transported and mixed in the year or two preceding the start of eruption quantification of this history indicates that two main pathways of melt migration and three timescales dominated the dynamics of the system combination of this information with the timing of observation of various monitoring signals allows a reconstruction of the dynamic evolution of this section of the plumbing system during the early stages of the 1991 1993 eruption it is seen for example how the migration of melt through the same sections of the plumbing system can cause pre eruptive triggering enhance strombolian activity and through the ensuing eruption cleanse and flush the plumbing system different kinds of mixing occur simultaneously at different sections of the plumbing system on different timescales a few days up to two years

decadal time gaps between mafic intrusion and silicic eruption obtained from chemical zoning patterns in olivine abstract intrusion of mafic magma in a silicic crustal reservoir has been reported in numerous studies of subduction related volcanoes and is considered a main process for triggering explosive eruptions and for transferring geochemical signatures from the mantle to the crust here we determine the timescales between mafic silicic encounters and eruption by exploiting the fact that during such interactions magmas exchange crystals and their mineral compositions will strive to equilibrate to the new environmental conditions specifically we model the fe mg zoning patterns of olivine found in the dacites andesite and quenched mafic inclusions of the holocene zoned eruption of volcan san pedro 36 s chilean andes the san pedro eruption is an example where mixing between silicic and mafic magmas produced intermediate compositions e g andesite at depth in the magma reservoir for modeling the compositional profiles we took into account the anisotropy of fe mg diffusion in olivine and also the effects of diffusion in multiple dimensions aspects that have been largely neglected in previous works the retrieved timescales for olivine melt equilibration by diffusion display an array ranging from 1 year for the most silica rich dacite to 50 years for the andesite this array of timescales rather than a single value provides new insight into the details of mafic silicic mixing at depth they reveal processes that occur on a longer timescale than the days to weeks time gap for cases where the mafic intrusion triggered the eruption and they might be associated with the instances where seismic activity or significant inflation of the volcanic edifice was not immediately followed by eruption on the other hand the year to decade timescales that we report for producing magmas of intermediate composition e g andesites are much shorter than the 10 3 10 5 years inferred from u series disequilibria data for igneous differentiation by closed system fractionation to produce similar magma compositions at subduction zones

palaeoenvironmental dynamics and underlying climatic changes in southeast amazonia serra sul dos carajas brazil during the late pleistocene and holocene abstract pollen fern spore micro charcoal sediment and mineral analyses have been carried out on a 466 cm long sediment core from the serra sul dos carajas swamp in southeastern amazonia ten ams radiocarbon dates suggest that the sediment covers at least the last 73 000 years shifts between tropical forests and savanna changes in species composition as well as changes in fire frequency indicate several wet and dry periods during this time interval during the assumed early pleniglacial 73 50 ka the dominance of savanna vegetation reflects drier conditions whereas vegetation changes in the mid pleniglacial 50 40 ka suggest alternating wet and dry phases under generally cool conditions the recorded next period before the last glacial maximum lgm shows a transition to wetter and cooler conditions followed by a cold and dry lgm and late glacial at the beginning of the holocene between 11 4 and 10 2 cal ka tropical forest expanded reflecting stable and very humid conditions during the early to mid holocene an increasingly seasonal generally warm and dry climate established dry seasons were longer than at present during mid holocene times with a pronounced dry phase from 9 to 3 4 cal ka only after 3 4 cal ka did modern tropical rainforests became established under present day climatic conditions comparison with other palaeoecological studies in the amazon basin and eastern andean regions suggests that environmental changes in serra sul were strongly coupled with large scale climatic changes and sea surface temperature variability in the tropical atlantic

olivine phenocrysts of hawaiian olivine tholeiite and oceanite olivine phenocrysts of hawaiian tholeiites display a variety of textures and a variation in composition which is due to supercooled crystallization the highest forsterite content measured is 91 and the highest magnesia content estimated for a tholeiitic liquid is 17 using the olivine geothermometer the liquid of this composition may be either a primary magma or a primitive magma it is not yet possible to specify any particular composition range for the primary hawaiian tholeiites

island arc magmatism in relation to the evolution of the crust and mantle abstract one aspect of the evolution of the earth s mantle is the development through geologic time of the continental crust a popular hypothesis is that the earth s crust has developed through the magmatic events associated with plate movements a two stage melting process involving generation of ocean ridge basalts followed by subduction and partial remelting of the oceanic lithosphere to form andesitic suites has been invoked as the major continental crust forming magmatic cycle however there is chemical and isotopic evidence for the composition of continental crust and arcs that is in conflict with the broad consequences predicted by this hypothesis the average composition of the upper continental crust has been fairly readily determined as granodioritic but the composition of the lower crust is less certain seismological and petrological evidence suggest that a substantial portion of the lower crust is basaltic in character therefore it cannot be concluded that the bulk average crust corresponds to andesite again the rock type most frequently collected in many arcs is andesite but the conclusion that the whole arc pile is of this composition is illogical and not supported by much field and petrologic evidence the peripheral accretion of arcs to continents is well documented for post palaeozoic epochs so that the nature of arc magma sources is critically relevant to the processes of continental crustal growth a large body of data on arc magmas can be explained by the hypothesis that the superjacent upper mantle wedge rather than the subducted lithosphere itself is the major source of arc erupted melts for many oceanic arcs isotopic evidence 87 sr 86 sr 143 nd 144 nd rules out the possibility that they constitute appropriate bulk crustal additions for the development of continents continental crustal growth may therefore either have changed in essential chemical isotopic character since the cambrian or arc magmas derived from chondritic type or lil enriched sources may be the only volumetrically significant additions to continental crust

intracrustal controls on the coexistence of tholeiitic and calc alkaline magma series at aso volcano sw japan aso caldera sw japan was formed incrementally over a period of 300 kyr by the eruption of four basaltic to dacitic pyroclastic flow and fall deposits aso 1 4 these units are collectively referred to as the aso pyroclastic flow deposit apfd in which tholeiitic and calc alkaline magmas have been erupted in close temporal and spatial proximity detailed petrological and geochemical studies indicate that a major shift in magmatic composition occurred between aso 1 and 4 as the caldera forming stage evolved changing from a predominantly tholeiitic to a calc alkaline signature the mineralogical and geochemical characteristics of aso 1 4 suggest that magmatic evolution within each unit is controlled by fractional crystallization associated with magma mixing crustal assimilation by altering the fractional crystallization mineral assemblage as well as the relative amounts of fractional crystallization magma mixing and crustal assimilation the systematic shifts in differentiation trends and magmatic series observed between the four eruptive units can be reproduced this suggests that the coexistence of tholeiitic and calc alkaline magma series can be attributed to shallow level intracrustal processes

on the lateral variations in chemical composition and volume of quaternary volcanic rocks across japanese arcs the fe mg fe ratios xfe of the quaternary basalts sio2 53 wt in the japanese arcs were examined the xxfe of relatively magnesian basalts decreases from the volcanic front toward the japan sea across the arcs based on the partition coefficient of mg fe2 between olivine and liquid it is suggested that all the basalts near the volcanic front which are mostly tholeiitic basalts are significantly fractionated whereas many basalts near the japan sea which are mostly alkali basalts are little fractionated the k2 o content in the primary basalt magmas increases toward the japan sea combining the xfe and k2 o data it is suggested that relatively large amounts of tholeiitic magmas are produced near the volcanic front but they fractionate during their ascent whereas smaller amounts of alkali basalt magmas are formed near the japan sea but they can ascend with less fractionation the density of primary tholeiite magma is significantly larger than that of primary alkali basalt magmas it is most likely that primary tholeiite magmas cannot ascend beyond the upper crust and would fractionate to produce less dense tholeiitic magmas near the volcanic front whereas primary alkali basalt magmas can ascend through the upper crust without fractionation as far as buoyancy is the principal ascending force in the japanese arcs the stress field may be less compressional near the japan sea than near the volcanic front so that magmas can ascend more rapidly in the latter region than in the former these two factors may be responsible for the above mentioned chemical variations of basalt magmas across the arcs the variation in volume of the quaternary volcanic rocks across the arcs can be explained by the presence of a melt rich zone above but nearly parallel to the subducted slab

evaluation of the 15 july 2009 fiordland new zealand tsunami in the source region we undertake detailed near field numerical modelling of the tsunami generated by the 15 july 2009 earthquake mw 7 8 in fiordland new zealand high resolution bathymetry and topography data at breaksea and dusky sounds and chalky and preservation inlets are derived mostly from digitised new zealand nautical charts shuttle radar topographic mission srtm 3 arc second data and general bathymetric chart of the ocean gebco 30 s data a combination of continuous and campaign global positioning system gps satellite radar alos palsar insar images and seismology data are used to constrain the seafloor deformation for the initial tsunami condition this source model derived independently of dart observations provides an excellent fit to observed tsunami elevations recorded by dart buoy 55015 the model results in the near field show maximum tsunami elevations in the range 0 5 2 0 m inside the sounds and inlets with maximum flow speeds of 3 0 m s along the open coast maximum tsunami elevations reach 2 0 m the high flow speeds through the inlets may change the inlet stratifications and water mass inside the sounds media reports and field reconnaissance data show some tsunami evidence at cormorant cove duck and goose coves and passage point

variation of al2o3 content in late cenozoic japanese basalts a re examination of kuno s high alumina basalt al2o3 variation in late cenozoic japanese basalts is re examined using the mg value as the differentiation index there exist no apparent differences in al2o3 among three postulated parental basalt magma types low alkali tholeiite high alumina basalt and alkali olivine basalt when the undifferentiated basalts with high mg values 55 are compared the al2o3 content of each type of basalt increases with decreasing mg value at mg values 55 and most basalts lack phenocryst plagioclase this feature is indicative of al2o3 increase by predominant mafic mineral fractionation and the absence of significant plagioclase fractionation among the differentiated basalts mg value 55 systematic differences of al2o3 content are observed the more alkalic basalt has the higher al2o3 content the origin of this variation is considered to result from a systematic difference in timing of the first appearance of plagioclase during crystallization from tholeiite through high alumina basalt to alkali basalt the progressive delay of plagioclase crystallization relative to mafic silicates may be explained by the gradual increase in h2o content in basalt magmas from tholeiite to alkali basalt

retrieving timescales of oceanic crustal evolution at oceanic core complexes insights from diffusion modelling of geochemical profiles in olivine abstract the building of oceanic crust at oceanic core complexes occ has been described as a complex process involving multiple intrusions of magma over a protracted period of time the migration of primitive magmas i e mid ocean ridge basalts morbs can lead to melt rock interactions during reactive porous flow processes through the lithosphere the timescales of these reactive processes and the subsequent cooling of the modified crystal matrix remain unconstrained diffusion modelling has been widely used to retrieve timescales of magmatic processes in this study we use diffusion models to constrain i the minimum timescales of melt rock interactions and ii the cooling rates of the gabbroic sequence forming the oceanic crust at an occ we chose samples of the most primitive olivine rich troctolites from the gabbroic sequence sampled in iodp hole u1309d atlantis massif occ mid atlantic ridge 30 n olivine rich troctolites were interpreted as marking local partial assimilation of mantle intervals into the oceanic crust and thus allowed to understand the dynamics of mantle assimilation and the formation of slow spreading oceanic crust at the atlantis massif occ olivines in olivine rich troctolites represent relicts of pre existing mantle olivine while clinopyroxenes and plagioclases are crystallized during reactive percolation olivine chemical compositions show that olivine rich troctolites inherit chemical heterogeneity from the mantle precursor flat geochemical profiles in olivine indicate complete chemical re equilibration of olivine crystals with the locally modified percolating melt exception is made for most ca profiles that show lower ca contents at the olivine rim compared to the relative crystal core as the result of subsolidus cooling three dimensional 3d diffusion models at magmatic conditions t 1210 1300 c and p 2 kbar reveal that complete chemical re equilibration of 4 mm size mantle derived olivine with percolating morb type melts can be attained within durations of less than 300 yr the ca in olivine geospeedometer reveal that cooling rates from 1200 c to 1050 c are constant downhole and on average 0 004 c yr they are comparable with lower temperature cooling rates 850 c 250 c estimated at the atlantis massif occ the minimum timescales from 3d models point to rather fast re equilibration of olivine the downhole chemical heterogeneity inherited from the precursor mantle coupled with the timescales of diffusive re equilibration suggest that the partial assimilation of the upwelling mantle and its incorporation into the oceanic crust occurred in the time frame of a single melt input our cooling data are consistent with building of the oceanic crust at occs controlled by continuous uplift in turn governed by long lived detachment faults the latter contribute to the rapid cooling of the assimilated mantle intervals and the magma bodies diffusion models of geochemical profiles in olivine from a single crustal section allow to reconstitute the early magmatic processes leading to mantle assimilation and early crystallization of gabbros and the cooling history of the oceanic crust at occ from magmatic conditions to hydrothermalism

real time inversion of gps data for finite fault modeling and rapid hazard assessment 1 responses to recent great earthquakes and ensuing tsunamis in sumatra chile and japan with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic regional gps networks such as those in western north america and japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time we report on rapid modeling of two large earthquakes the 2003 mw 8 3 tokachi oki earthquake 100 km offshore hokkaido island using 356 geonet stations and the 2010 mw 7 2 el mayor cucapah earthquake in northern baja california using 95 crtn stations in southern california about 75 km northwest of the epicenter working in a simulated real time mode we invert for finite fault slip in a homogeneous elastic half space using green s functions obtained from okada s formulation we compare two approaches the first starts with a catalog of pre defined faults while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane in either case we are able to characterize both earthquakes in less than two minutes reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude

the significance of unusual zoning in olivines from famous area basalt 527 1 1 major element ni mn and ca electron microprobe analyses of olivine phenocrysts in one of the most primitive basalts from the famous area of the mid atlantic ridge 527 1 1 reveal two different olivine populations distinguished by their zoning characteristics the often skeletal group i olivines have zoning profiles with high forsterite high ni low mn and low ca cores these profiles can be explained by low pressure crystallization from the 527 1 1 magma on cooling the equant often megacrystic group ii olivines also have high forsterite low mn cores but the cores have low ni compared to rims thus they are normally zoned with respect to mg fe and mn but reversely zoned with respect to ni for example ni ranges from 1 700 ppm at fo90 5 in the core to 2 100 ppm at fo89 5 at the rim in view of the published whole rock and mineral data of le roex et al 1981 the most likely explanation for these data is that the group ii olivines are xenocrysts assimilated from solidified plagioclase pyroxene basalts through which the 527 1 1 basalt ascended the diffusion rate of ni and size of the xenocrystic olivines are used to calculate the residence time of the assimilated olivines in the magma an alternative hypothesis would be a high pressure origin for the group ii olivines this would be possible if future experiments show that with increasing pressure the partition coefficient for ni decreases relative to the partition coefficient for mg for a given bulk composition current evidence suggests this is unlikely the data from 527 1 1 and other samples from the famous area require magmas with distinct ni mgo feo characteristics in general morb from different ridge segments fall on distinct trends on plots of mgovs ni as well as mgovs feo calculation of the mgo and ni contents of primary magmas suggests a mechanism by which such distinct trends could come about

green s function based tsunami data assimilation a fast data assimilation approach toward tsunami early warning we propose a new tsunami data assimilation approach based on green s functions to reduce the computation time for tsunami early warning green s function based tsunami data assimilation gftda forecasts the waveforms at points of interest pois by superposition of green s functions between observation stations and pois unlike the previous assimilation approach gftda does not require the calculation of the tsunami wavefield for the whole region during the assimilation process because the green s functions have been calculated in advance the forecasted waveforms can be calculated by a simple matrix manipulation the application to the tsunami waveforms recorded by the bottom pressure gauges of the cascadia initiative from the 2012 haida gwaii earthquake reveals that gftda achieves the same accuracy as the previous assimilation approach while reducing the time required to issue a valid tsunami warning

late glacial and holocene environmental and climatic changes from a limnological transect through colombia northern south america abstract we present a synthesis of the palaeolimnological and palaeoclimatic reconstructions of four sites in colombia the record from lake el caimito the westernmost site on the pacific coast dates from the late holocene and shows lacustrine sedimentation frequently interrupted by fluvial pulses these pulses probably reflect periods of increased precipitation related to la nina phases east of el caimito site is the patia swamp situated between the western and central andean cordilleras the patia records the dynamics of forest expansion reduction and changes in water levels although the climatic signal of the patia core is difficult to reconstruct there is a clear increase in humidity in the mid holocene the fuquene lake record on the eastern andean cordillera records dry and cold conditions during the late pleistocene very humid conditions for the early mid holocene and dry conditions during the mid late holocene las margaritas site on the eastern savannas records dry conditions during the early holocene and overall humid conditions for the mid and late holocene climate conditions from the fuquene and las margaritas sites seem to reflect the holocene movements of the intertropical convergence zone itcz the latter site being more affected by humidity coming from the amazon region

chronometry and speedometry of magmatic processes using chemical diffusion in olivine plagioclase and pyroxenes the magmatic processes that fuel volcanism crustal growth ore formation and discharge of volcanic gases and aerosols to the atmosphere occur across a range of timescales from millions of years to just a few seconds for example the production of new oceanic crust at mid ocean ridges is a near continuous process that can operate in any one ocean basin on timescales of more than 100 m y however the driving force for such processes is the spreading of the ocean plates that happens on a cm yr timescale at the other end of the spectrum explosive volcanic eruptions involve the ascent and fragmentation of magma at velocities of the order of 100 m s such that the journey from a magma chamber to an ash cloud may take place in a matter of minutes in this case the driving force is the rapid expansion of magmatic gas in response to changes in pressure at intermediate timescales magmatic processes may give rise to hydrothermal ore deposits on timescales of less than a million years for an individual deposit while growth of giant granite batholiths may require piecemeal assembly of magma batches on timescales of a few million years although each of these processes has a characteristic time averaged timescale on which it operates this is typically the end result of one or more natural processes that operate on much shorter timescales for example mid ocean ridges do not extrude magma continuously onto the ocean floor mineralising fluids do not discharge continuously through the shallow crust and granitic magmas do not dribble continuously into evolving batholithic chambers in some cases it is the long term timescales that are important for example the spreading rate of ocean basins in others it is the short term timescales that are important for example the episodic growth of lava domes at active volcanoes although

late quaternary vegetation and climate change in the panama basin palynological evidence from marine cores odp 677b and tr 163 38 abstract the late quaternary paleoenvironmental history from pacific slopes of the western andes is reconstructed by pollen analysis of 32 samples from two marine sediment cores from the panama basin eastern equatorial pacific core odp 677b 83 44 2200 w 1 12 1440 n 3473 m water depth is 185 cm long and spans the last 39 410 years core tr 163 38 81 583 w 1 337 n 2200 m water depth is 103 cm long and covers the last 17 380 years six ecological groups were established mangrove brackish and fresh water swamps terra firma lowland forests broad range taxa andean forests and open vegetation a good correspondence was found between the changes of these ecological groups in the two cores the records evidence the continuous presence of all vegetation types during the last 39 410 years and specially the uninterrupted occurrence of tropical rain forest they record a development from 1 a cold and humid phase 39 410 28 120 yr cal bp with moderately high sea levels 2 the coldest and driest phase in the record 28 120 14 500 yr cal bp accompanied by the lowest sea levels 3 a transitional phase when sea level rose and humid conditions dominated 4 a stage 11 300 5600 yr cal bp of the highest sea levels and moisture conditions including a drier period 7000 yr bp to 5 a final period 5600 yr cal bp present when sea level reached its present height humidity persisted and indicators of disturbance expanded peaks in pollen and spore concentration associated with high river discharge periods indicate periods of higher precipitation around 33 500 28 000 and 12 000 9000 yr cal bp although main vegetation responses seem to reflect rainfall and moisture variations a good correspondence was found between 18o values and percentages of andean and lowland pollen suggesting that vegetation also responded to tempearture changes

time scales of magmatic processes from modeling the zoning patterns of crystals the advent of polarized light microscopy in the middle of the 19th century allowed mineralogists and petrologists interested in igneous rocks to recognize the widespread occurrence of fine scale heterogeneities in the optical properties of minerals e g see young 2003 for details the interpretation of mineral zoning patterns as archives of magmatic processes has been with us for some time e g larsen et al 1938 tomkeieff 1939 the development of the electron microprobe in the 1960 s allowed mineral zoning profiles to be quantitatively analyzed and modeled e g bottinga et al 1966 moore and evans 1967 enhanced textural observations permitted recognition of many kinds of detailed structures during the growth and dissolution of magmatic minerals fig 1 e g anderson 1983 pearce and kolisnik 1990 and these processes were also explored using experimental and numerical models e g albarede and bottinga 1972 lofgren 1972 kirkpatrick et al 1976 loomis 1982 major element zoning patterns are routinely measured and with the arrival of the ion microprobe the identification of heterogeneous distribution of trace elements opened the window for more realistic and sophisticated scenarios and models fig 1 e g kohn et al 1989 blundy and shimizu 1991 singer et al 1995 we now measure abundances of naturally occurring isotopes at the scale of tens of micrometers e g davidson et al 2007a ramos and tepley 2008 and this allows in situ dating of crystals e g cooper and reid 2008 figure 1 a nomarski dic image of a plagioclase crystal from a gabbroic xenolith of volcan san pedro costa et al 2002 the crystal shows a well defined core and a rim separated by an oscillatory zoned interval ion microprobe analysis pits and the trace of the electron microprobe traverse between the pits are evident b major

melting experiments on a high magnesian andesite abstract melting experiments were conducted on a high magnesian bronzite olivine andesite teraga ike andesite which is considered to be a primary andesite the high magnesian andesite magma is in equilibrium with both olivine and orthopyroxene at about 15 5 kbar and 1080 c under h2o saturated conditions and at lower pressure and higher temperature under h2o undersaturated conditions this suggests that high magnesian andesites could be generated by the partial melting of upper mantle peridotite containing a small amount of h2o

boron partitioning in the upper mantle an experimental and ion probe study piston cylinder experiments were performed on two natural spinel lherzolites from lherz french pyrenees and kilbourne hole usa in order to determine the distribution coefficients of boron between minerals and melt for upper mantle conditions additionally a morb glass and its phenocrysts were taken as a low pressure analogue boron concentration measurements were made by ion probe the only technique suitable for in situ 10 m boron concentration measurements in the range 0 1 1 ppm the two starting peridotites samples have low bulk boron concentrations of 0 96 and 0 81 ppm boron distribution coefficients were determined from 1 direct measurement of melt and crystals in contact and 2 calculations from profiles of several tens of measurements made using 10 m diameter spots containing variable proportions of crystals and melt distribution coefficients between minerals and melt decrease in the following order dcpx melt 0 117 dsp melt 0 08 dol melt 0 034 dopx melt 0 027 the limited ranges of composition pressure and temperature investigated mimic natural conditions for basalt genesis but sharply limit the present data for determining variations of partition coefficients with p t and x however boron behavior seems to follow roughly that of aluminum since the al richest minerals are the ones with the highest boron distribution coefficients the dol melt values increase with pressure which is similar to what has been observed for the distribution coefficient of aluminum between olivine and melt boron is therefore strongly incompatible during partial melting in the mantle using these distribution coefficients and assuming that morb have been produced by 5 20 partial melting the depleted mantle source of morb is estimated to contain 0 05 0 3 ppm b these values correspond to the lower limit for the mean boron content of chondrites 0 55 0 3 ppm but are in accordance with a simple budget of boron between mantle crust and seawater in fact a simple mass balance calculation where all the boron hosted in the crust and in seawater is presumed to have been extracted from an upper mantle of chondritic original boron content yields a boron content for the depleted upper mantle of 0 3 ppm at present because in situ boron concentration measurements under the ppm level at the m scale are now possible with the ion probe and because of its strong partitioning in melts and possible partitioning in fluids boron is a potentially very powerful geochemical tracer for the study of mantle processes such as basalt genesis or metasomatism

a petrologic perspective of kīlauea volcano s summit magma reservoir two hundred years of magmatic history are documented by the lavas and tephra sampled from k olauea s historical summit eruptions this paper presents detailed petrographic and geochemical data for a comprehensive suite of samples erupted within or near k olauea s summit caldera since the 17th century our results elucidate the range of magmatic processes that operate within the volcano s summit magma reservoir and document two compositional trends that span nearly the entire known range for the volcano prior to the 1924 summit crater collapse a trend of increasing incompatible element and cao and decreasing sio2 abundances at a constant mgo prevailed thereafter the trend reversed direction and has persisted for the rest of the 20th century including during the current puau a oa o eruption the rapid and systematic nature of these temporal geochemical variations indicates that the summit reservoir is a single relatively small body rather than a plexus of dikes and sills olivine fractionation is the dominant petrologic process within this reservoir petrographic observations and olivine and whole rock geochemical data suggest that the summit reservoir has a crown of aphyric more evolved low density magma differentiation within this crown involving clinopyroxene and plagioclase is more extensive than previously recognized in k olauea summit lavas the effects of crystal fractionation are superimposed upon an evolving hybrid magma composition produced by mixing new mantle derived magmas with more fractionated reservoir magma frequent eruptions of these hybrid reservoir magmas document the rapid variation in parental magma composition these compositional variations correlate with magma supply rate both are thought to be influenced by the degree of melting of small scale source heterogeneities within the hawaiian plume however k olauea s source compositions and partial melting processes have varied only within a narrow range over the past 350 kyr

development of an automatic volcanic ash sampling apparatus for active volcanoes we develop an automatic system for the sampling of ash fall particles to be used for continuous monitoring of magma ascent and eruptive dynamics at active volcanoes the system consists of a sampling apparatus and cameras to monitor surface phenomena during eruptions the sampling apparatus for time series unmanned monitoring of ash satsuma i and satsuma ii is less than 10 kg in weight and works automatically for more than a month with a 10 kg lead battery to obtain a total of 30 to 36 samples in one cycle of operation the time range covered in one cycle varies from less than an hour to several months depending on the aims of observation allowing researchers to target minute scale fluctuations in a single eruptive event as well as daily to weekly trends in persistent volcanic activity the latest version satsuma ii also enables control of sampling parameters remotely by e mail commands durability of the apparatus is high our prototypes worked for several months in rainy and typhoon seasons at windy and humid locations and under strong sunlight we have been successful in collecting ash samples emitted from showa crater almost everyday for more than 4 years 2008 2012 at sakurajima volcano in southwest japan

petrogenesis of mafic inclusions in rhyolitic lavas from narugo volcano northeastern japan mafic inclusions present in the rhyolitic lavas of narugo volcano japan are vesiculated andesites with diktytaxitic textures mainly composed of quenched acicular plagioclase pyroxenes and interstitial glass when the mafic magma was incorporated into the silicarich host magma the cores of pyroxenes and plagioclase began to crystallize 1000 c in a boundary layer between the mafic and felsic magmas phenocryst rim compositions and interstitial glass compositions average 78 wt sio2 in the mafic inclusions are the same as those of the phenocrysts and groundmass glass in the host rhyolite this suggests that the host felsic melt infiltrated into the incompletely solidified mafic inclusion and that the interstitial melt composition in the inclusions became close to that of the host melt c 850 c infiltration was enhanced by the vesiculation of the mafic magma finally hybridized and density reduced portions of the mafic magma floated up from the boundary layer into the host rhyolite we conclude that the ascent of mafic magma triggered the eruption of the host rhyolitic magma

residence time and crystallization history of nickeliferous olivine phenocrysts from the northern yatsugatake volcanoes central japan application of a growth and diffusion model in the system mg fe ni abstract the chemical zoning of nickeliferous olivine phenocrysts in calc alkaline andesites from the northern yatsugatake volcanoes central japan is examined by a growth and diffusion model in the system mg fe ni nickeliferous olivine phenocrysts are included in the high alumina basaltic end member magma which forms the mixed calc alkaline andesites in the northern yatsugatake volcanoes the olivine phenocrysts can be divided into three types on the basis of chemical composition zoning profile and occurrence type 1 olivine is rich in ca and mg and the zoning profile of type 1 forms a slightly more fe rich trend than the maximum fractionation trend in the nio versus forsterite content fo diagram the most mg and ni rich and mn poor core of type 1 fo 91 5 mol nio 0 40 wt mno 0 13 wt can be in equilibrium with peridotite in the upper mantle by contrast type 2 olivine is ca poor and rich in fe and ni compared to type 1 the zoning patterns of type 2 are more variable the nio content in fe rich type 2 phenocrysts decreases rapidly from core to rim within a narrow range of fo the maximum nio content of type 2 is 0 53 wt the transitional type olivine has an intermediate composition between type 1 and type 2 and a similar zoning profile as that of type 1 type 1 olivine mainly occurs as isolated phenocrysts while fe rich type 2 occurs as crystal clots the growth and diffusion calculation in the system mg fe ni revealed that the composition of normally zoned olivine is enriched in fe by diffusion without a marked depression in the ni content due to a larger fe mg interdiffusion coefficient than the ni tracer diffusion coefficient in olivine the zoning patterns of both type 1 and type 2 can be reproduced by calculation the residence time of type 1 olivine in the magma is estimated to be less than 10 0 5 1 y at 1150 1050 c whereas the residence time of fe enriched type 2 olivine is from ten to one hundred times longer than that of type 1 the long residence time and occurrence as crystal clots suggest that the fe enriched type 2 olivine phenocrysts were captured and crystallized in the crystal mush at the roof and bottom of a magma chamber

the petrology and geochemistry of high magnesium andesites at the western tip of the setouchi volcanic belt sw japan k ar ages and petrographical and geochemical characteristics of high magnesium andesites and plagioclase phyric andesites from the ne kyushu region japan are presented k ar ages range from 10 7 0 3 to 14 4 0 4ma overlapping those reported for lavas of the setouchi volcanic belt in other regions 11 16ma this together with major and incompatible trace element and sr nd pb isotopic characteristics confirms that the setouchi volcanic belt which is characterized by the occurrence of high magnesium andesites extends for 600 km along the sw japan arc thus it may be suggested that the unusual tectonic setting required for high magnesium andesite magma generation was attained only for this limited region possibly in association with subduction of the young hence hot lithosphere of the shikoku basin two types of high magnesium andesite possessing identical bulk rock compositions are recognized one contains olivine phenocrysts with chromian spinel inclusions showing compositional characteristics consistent with their crystallization as liquidus phases whereas the other contains niand fe rich olivine and fe3 rich spinel one of the possible causes for such unusual mineral compositions could be effective elemental diffusion within and through olivine crystals associated with a long residence time in a crustal magma chamber and the slow rate of cooling of the host magma the compositions of liquidus chromite and olivine as well as whole rock major element compositions suggest that the ne kyushu highmagnesium andesite magmas were produced by higher degrees of partial melting than those in other regions of the setouchi volcanic belt

island arc processes relevant to crustal and mantle evolution abstract recycling of continental crust occurs at convergent plate margins recycling must be investigated at several structural levels and time scales shallow intermediate and deep surface recycling sedimentary igneous and structural redistribution of crustal mass is not included in this hierarchy although it controls the composition of the recycled crust crustal growth structural and geochemical evolution is directly tied to the larger less complex mantle crustal recycling at the deepest structural level must be understood better in order to choose between alternative interpretations of the isotopic evolution of the mantle crustal recycling at intermediate structural levels by subduction of crust and its subsequent reappearance as a component of volcanic arc magmas has important implications for the question of long term crustal growth crustal recycling at shallow structural levels is important in understanding the development of forearc regions the mass flux at present day convergent plate margins has been diagramed in order to systematize future investigations and to clarify the distinction between the recycling at different levels and the observable quantities in the present day earth that are relevant to recycling disputes

diffusion coupling between trace and major elements and a model for calculation of magma residence times using plagioclase residence times of plagioclase crystals in magma reservoirs can be determined by modeling the compositional zoning of trace elements in these crystals we present a formulation to model diffusion of trace elements in plagioclase paying special attention to certain thermodynamic and kinetic aspects in particular we account for the compositional dependence on anorthite content of the chemical potential and diffusion coefficients of trace elements e g mg the choice of suitable boundary conditions and potential effects of diffusion in more than one dimension we show that contrary to intuition diffusive fluxes of trace elements may be coupled to major element concentration gradients and ignoring such coupling can lead to incorrect estimates of timescales we illustrate application of the model using plagioclase crystals from a suite of gabbroic xenoliths from a holocene dacitic lava flow of volcan san pedro chilean andes 36 s the inferred timescale for metasomatism of the xenoliths by evolved liquids is on the order of 100 30 to 148 yr and serves to illustrate how trace element zoning in plagioclase provides a window into timescales of magmatic processes inaccessible by isotopic or other methods

life time of a stratified magma chamber recorded in ultramafic xenoliths from ichinomegata volcano northeastern japan variations in major element chemistry and modal compositions of the mantle xenolith bearing calc alkalic ejecta from ichinomegata volcano are inferred to be due to mixing of three magmatic end members basalt i sio2 51 wt mgo 8 5 wt basalt ii sio2 54 wt mgo 5 wt and dacite sio2 65 wt mgo2 wt ultramafic xenoliths are found in mafic mixtures of dacite basalt i and dacite basalt ii the thermal histories of the xenoliths in both mixtures are compared with each other chemical compositions of olivine and orthopyroxene in xenoliths suggest that xenoliths in basalt i were equilibrated at about 800 c while those in basalt ii were also equilibrated originally at about 800 c but were subsequently annealed at about 1000 c for more than 102 3 years prior to the eruption