3 d high speed imaging of volcanic bomb trajectory in basaltic explosive eruptions imaging in general and high speed imaging in particular are important emerging tools for the study of explosive volcanic eruptions however traditional 2 d video observations cannot measure volcanic ejecta motion toward and away from the camera strongly hindering our capability to fully determine crucial hazard related parameters such as explosion directionality and pyroclasts absolute velocity in this paper we use up to three synchronized high speed cameras to reconstruct pyroclasts trajectories in three dimensions classical stereographic techniques are adapted to overcome the difficult observation conditions of active volcanic vents including the large number of overlapping pyroclasts which may change shape in flight variable lighting and clouding conditions and lack of direct access to the target in particular we use a laser rangefinder to measure the geometry of the filming setup and manually track pyroclasts on the videos this method reduces uncertainties to 10 in azimuth and dip angle of the pyroclasts and down to 20 in the absolute velocity estimation we demonstrate the potential of this approach by three examples the development of an explosion at stromboli a bubble burst at halema uma u lava lake and an in flight collision between two bombs at stromboli

trace elements in titanite a potential tool to constrain polygenetic growth processes and timing abstract the petrological information preserved in the trace element signature of titanite is a valuable complement to in situ u pb geochronology and can be used to refine interpretations on the growth of this mineral we present trace element and u pb isotopic compositions of titanite grains in five amphibolite to granulite facies samples from the east albany fraser orogen of western australia chondrite normalised rare earth element ree abundance patterns discriminate between titanite populations and correlate with backscatter electron bse zonation in two samples titanite ree composition correlates with proximity to garnet and in one sample titanite composition correlates with gneissic compositional banding the dy yb ratio can be used as a geochemical indicator to link titanite growth to garnet growth titanite that crystallised in a garnet bearing assemblage is hree depleted with dy yb 2 whereas titanite that crystallised in a garnet free assemblage typically has flat hree patterns with dy yb by integrating the ree signatures with u pb data the five new titanite u pb ages can be linked to a range of processes magmatic titanite crystallisation metamorphic titanite growth garnet growth and or cooling through the closure temperature for pb diffusion in titanite

multistage zircon and titanite growth and inheritance in an archean gneiss complex winnipeg river subprovince ontario abstract the paper presents results from a u pb isotopic investigation of zircon and titanite from three phases of the archean sioux lookout gneiss complex at the margin of the gneissic plutonic winnipeg river subprovince wrs of the superior province the data reveal an intricate data pattern caused by inheritance and multistage crystallization and record the timing of two major orogenic events followed by a protracted post metamorphic evolution a zircon age of 2889 3 ma for a foliated pink granite correlates with that of similar units elsewhere in the superior province and reflects one of the first major episodes of crustal assembly in the pre kenoran evolution of the region tonalite and diorite from the same site yield zircon and titanite ages of 2704 2 and 2705 5 ma which correspond to the timing of major magmatism related to kenoran collision of the wrs with the adjacent wabigoon volcanic domains tonalite and diorite both contain abundant xenocrystic zircon moreover the late kinematic diorite also includes xenocrystic titanite which has a minimum age of 2730 ma and coexists with younger ca 2705 ma titanite and zircon two generations of titanite are also present in both the tonalite and the granite the earliest one reflects the 2704 ma plutonic metamorphic event whereas the second one indicates post metamorphic crystallization at 2650 and 2627 ma caused by superimposed hydrothermal activity and retrogression the data support the concept that the titanite can remain a closed system to pb diffusion at elevated temperatures as long as the crystals escape magmatic or metamorphic recrystallization conversely they also show that titanite can easily be produced by low temperature processes hence generalized interpretation of titanite ages in terms of regional cooling can be inappropriate

in situ la icp ms u pb dating of metavolcanics of norrbotten sweden records of extended geological histories in complex titanite grains in situ u pb dating of a variety of mineral phases is an important goal in petrology this study reports data chiefly from titanite but also from rutile and apatite obtained using the laser ablation la icp ms methodology on polished thick sections in order to retain as much petrologic information as possible and allowing trace element analyses from adjacent areas to the u pb analyses the samples analysed come from svecofennian intermediate to acid volcanic rocks of the porphyry group within the major iron ore province of norrbotten northern sweden where titanite is a common phase associated with the mineralisation using a laser beam of 30 45 m in diameter accurate and relatively precise 2 3 2 on 206pb 238u ratios data can be obtained on titanite similar precision on pb u ratios can be obtained in rutile but accuracy cannot be assessed because of the lack of well characterised standards however the data are a priori accurate as they are geologically reasonable apatite shows reverse discordance which could be explained by a number of scenarios however the 207pb 206pb ages are fairly precise 1 3 2 and the calculated age is geologically reasonable suggesting that the data may be accurate the titanite grains studied show complex internal structures rare earth element ree analysis by la icp ms demonstrates that the core and rim zones are distinct and supports a model for two stage evolution in two out of three samples with the rims in these samples being enriched in total ree and particularly in lree in one sample and displaying a positive y anomaly in contrast to the cores in situ u pb analysis reveals that core zones from all samples retain distinct older ages of c 2050 ma whereas the reworked rims have either distinct younger or strongly reset ages the older cores are interpreted as representing the first alteration metamorphism of the volcanic pile titanite rims record a u pb age of 1870 24 ma 2 at luossavaara and 1826 15 ma 2 at the smaller fe oxide apatite body at gruvberget in both cases the ages are consistent with previous age determinations from the fe oxide apatite deposits a sample from malmberget records a slightly different scenario where u pb ages spread along concordia from c 1920 to 1708 ma we attribute this pattern to metamorphic reworking of primary metasomatic titanite rutile ages from inclusions within the core of gruvberget titanite essentially mimic the ages obtained from the surrounding titanite and suggest that they have undergone the same history apatite inclusions within titanite at malmberget record a younger age of 1584 12 ma 2 which we attribute to later events known to have affected the area these data indicate that the porphyry group volcanics must be at least c 2050 ma in age in contrast to previous age determinations from zircon which suggested a deposition age of c 1960 to 1880 ma the large grain size of the titanites studied coupled with the ability for the first time to obtain in situ u pb ages from small areas has allowed probing of this hitherto unrecognised event smaller zircon grain size coupled with extremely saline hot pressurised high p t metasomatic fluids relating to regional magnetite apatite mineralisation in the period 1900 to 1800 ma may have resulted in resetting of zircon u pb systematics 2007 elsevier b v all rights reserved

ash plume dynamics and eruption source parameters by infrasound and thermal imagery the 2010 eyjafjallajokull eruption during operational ash cloud forecasting prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate mer which is typically inferred from plume height uncertainties for plume heights are large especially for bent over plumes in which the ascent dynamics are strongly affected by the surrounding wind field here we show how uncertainties can be reduced if mer is derived directly from geophysical observations of source dynamics the combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained a dipole in this case and for the plume exit velocity to be calculated 54 142 m s based on the acoustic signal recorded during the 2010 eyjafjallajokull eruption from 4 to 21 may exit velocities are converted into mer using additional information on vent diameter 50 10 m and mixture density 5 4 1 1 kg m3 resulting in an average 9 105 kg s mer during the considered period of the eruption we validate our acoustic derived mer by using independent measurements of plume heights icelandic meteorological office radar observations acoustically derived mer are converted into plume heights using field based relationships and a 1d radially averaged buoyant plume theory model using a reconstructed total grain size distribution we conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real time determination of eruption source parameters this could improve substantially the forecasting of volcano related hazards with important implications for civil aviation safety

effects of explosion energy and depth to the formation of blast wave and crater field explosion experiment for the understanding of volcanic explosion we made field explosion experiments as an analogue of volcanic explosion to understand the relationship between the explosion condition and the resultant surface phenomena the main parameters we employed were explosion depth and explosion energy through the experiments we confirmed that scaled depth which is the depth divided by cube root of energy is the main parameter determining the properties of explosive volcanism the energy assigned to blast wave decreased exponentially against the scaled depth the scaled crater diameter became maximum when the scaled depth was about 4 10 3 m j scaled crater diameters by nuclear chemical subsurface and some volcanic explosions were almost the same from the scaling law the overpressure at crater rim was estimated to be several mpa which corresponded to typical rock strength probably the ground forming materials were broken inside the area where overpressure exceeded their strength

inferring compressible fluid dynamics from vent discharges during volcanic eruptions observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency crf emissions the source of this radiation however has remained elusive until now through experiments and the analysis of field data we show that crf originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions blasts produce flows that expand supersonically generating regions of weakened dielectric strength in close proximity to the vent as erupted materialcharged through fragmentation friction or other electrification processtransits through such a region pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge discharge is maintained as long as overpressured conditions at the vent remain beyond describing the mechanism underlying crf we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating crf sources

infrasonic crackle and supersonic jet noise from the eruption of nabro volcano eritrea the lowermost portion of an explosive volcanic eruption column is considered a momentum driven jet understanding volcanic jets is critical for determining eruption column dynamics and mitigating volcanic hazards however volcanic jets are inherently difficult to observe due to their violence and opacity infrasound from the 2011 eruption of nabro volcano eritrea has waveform features highly similar to the crackle phenomenon uniquely produced by man made supersonic jet engines and rockets and is characterized by repeated asymmetric compressions followed by weaker gradual rarefactions this infrasonic crackle indicates that infrasound source mechanisms in sustained volcanic eruptions are strikingly similar to jet noise sources from heated supersonic jet engines and rockets suggesting that volcanologists can utilize the modeling and physical understandings of man made jets to understand volcanic jets the unique distinctive infrasonic crackle from nabro highlights the use of infrasound to remotely detect and characterize hazardous eruptions and its potential to determine volcanic jet parameters key points nabro volcano produced sound similar to supersonic jet engines and rockets volcanic and man made jets have similar sound source mechanisms infrasound can remotely detect and characterize volcanic eruptions and jets 2013 american geophysical union all rights reserved

campaign style titanite u pb dating by laser ablation icp implications for crustal flow phase transformations and titanite closure abstract u pb dates of titanite from 150 samples of chiefly quartzofeldspathic gneiss and leucosomes were measured across the western gneiss region of norway to understand deformation and metamorphism of typical crustal rocks during ultrahigh pressure uhp subduction and exhumation titanite is unstable at these high temperatures and pressures and indeed most of the titanite yielded post uhp dates a modest number of titanites sampled across large areas however have pre uhp u pb dates indicating that they survived their excursion to and return from mantle depths metastably this has three important implications 1 titanite grains can remain closed to complete pb loss during regional metamorphism at temperatures as high as 750 c and pressures as high as 3 gpa 2 phase transformations in quartzofeldspathic rocks can be inhibited at the same conditions 3 quartz bearing rocks can remain undeformed even at high temperature and pressure both of the latter were previously recognized the present study simply presents a new method for evaluating both using titanite u pb dates

the decompression of volcanic jets in a crater during explosive volcanic eruptions during explosive volcanic eruptions fragmented silicic magma and volatiles exit the vent with pressures typically in the range 10 100 atm and at the speed of sound of the mixture we show that for magmatic volatile contents no in the range 0 03 no 0 06 this has the approximate value 0 95 0 05 nort 12 where r is the gas constant and t is the eruption temperature this speed is nearly independent of the vent pressure and vent radius by assuming there is negligible mixing with the air we have modelled the decompression of such jets following eruption from the vent for free decompression into the atmosphere the velocity of the decompressed jet has the approximate value 1 85 0 05 nort 12 this is nearly independent of the eruption rate for decompression into a crater the process is more complex at low eruption rates with low vent pressure the material becomes underpressured as it rises in the crater a shock then forms in the crater this recompresses the magma volatile mixture which then issues from the crater as a relatively slow subsonic jet at atmospheric pressure as the eruption rate increases such shocks move towards the top of the crater and ultimately cannot form in the crater instead the material issues from the crater as a high speed supersonic jet the upward thrust provided by the crater walls on this high pressure jet then increases the upward velocity above that of a freely decompressing jet the presence of a crater may therfore cause collapse in relatively small eruptions whereas it may promote formation of buoyant eruption columns at higher eruption rates if a crater grows through erosion during an eruption column collapse will typically ensue even if the mass flux remains steady

nd isotope re equilibration during high temperature metamorphism across an orogenic belt evidence from monazite and garnet abstract monazite is a powerful u th pb geochronometer commonly used to determine the tempo of orogenic processes as a light rare earth element lree enriched mineral monazite also records key information for understanding the behavior of sm nd isotope systematics during tectonothermal events however sm nd isotope studies of monazite have received far less attention than its use as a u pb geochronometer here we investigate coupled u pb ages and sm nd isotopic compositions of monazite from partially melted metasedimentary rocks in the jiao liao ji orogenic belt jljb north china craton to provide insight into sm nd isotope behavior during high temperature metamorphism and crustal melting we utilize several complementary dating systems in the same sample including garnet lu hf and sm nd zircon u pb and monazite u pb geochronology to gain precise time constraints on the p t evolution of the jljb garnet lu hf isochron dates of 1 97 1 94 ga are interpreted to represent prograde garnet growth consistent with the prograde metamorphic zircon dates of 1 96 1 90 ga garnet sm nd dates agree with retrograde metamorphic zircon dates and all monazite u pb dates define a relatively narrow age range of 1 86 1 83 ga interpreted to represent retrograde cooling the lack of older monazite grains matching zircon or garnet dates suggests the dissolution of pre existing monazites into partial melt monazite in all samples irrespective of occurring as garnet inclusions or in the matrix yields homogenous nd isotope compositions end 5 at 1 85 ga which are consistent with the garnet and bulk rock values thus nd isotope re equilibration between bulk rock and minerals occurs synchronously across the orogenic belt during high t metamorphism 750 c where melting was involved with no evidence of a pre metamorphic isotope signature this suggests mobility in the sm nd isotope system during high grade metamorphism and melting where the nd isotope signature of monazite likely represents the most recent tectonothermal event

a synthesis and review of historical eruptions at taal volcano southern luzon philippines abstract the philippines is an area of persistent volcanism being located in one of the most tectonically active regions in the world taal volcano in southern luzon is the second most frequently erupting volcano of the 24 active volcanoes in the philippines a comprehensive and critical review of published and unpublished references describing the 33 known historical eruptions of taal may provide answers to knowledge gaps on past eruptive behavior processes and products that could be utilized for hazard and risk assessment of future eruptions data on the prehistoric eruptions and evolution of taal caldera and subsequent deposits are limited only four caldera forming events were identified based on four mapped ignimbrite deposits from oldest to youngest these are the silicic alitagtag ali and caloocan cal pumice flow deposits the dacitic sambong ignimbrite sam and the basaltic andesitic taal scoria flow renamed scoria pyroclastic flow sfl except for sfl with 14c dating yielding 5380 70 to 6830 80 ky there are no age constraints or estimates of extent for the three older deposits a comprehensive review of the historical eruptions of taal volcano is the central element of this paper and includes all eruptions from ad1572 the first known historic event to ad1977 eruption styles and the interplay between processes and products for each eruption are reinterpreted based on the narrative descriptions from all available accounts a change of classification of eruption styles and eruptive products is undertaken for some events at least nine reported eruptions were deemed uncertain including the ad1605 ad1611 event more likely seismic swarms the ad1634 ad1635 and ad1645 may simply be solfataric or hydrothermal activity events and the ad1790 ad1825 ad1842 ad1873 and ad1903 events that were listed in recent published and unpublished documents but do not provide any details to describe and confirm the eruptions except for listing a default vei of 2 pyroclastic density currents brought devastating impacts to the communities around taal during the ad1749 ad1754 ad1911 and ad1965 eruptions and remain the biggest threat in the case of renewed volcanic activity significant implications for aviation are implied by the narrative of tephra fall dispersal towards manila the central gateway of international aviation operation in the philippines during the ad1754 eruptions the dispersal of tephra in the event of an explosive eruption at taal towards metro manila would have catastrophic effects to transport utilities and business activity potentially generating enormous economic losses hazards from earthquake events associated with future volcanic activity may also have localized impacts occurrences of liquefaction phenomena as a consequence of severe ground shaking are interpreted during the ad1749 ad1754 and ad1911 eruptions more work needs to be done to develop a comprehensive understanding of the hazards and risks associated with an explosive eruption at taal volcano especially related to the older quaternary caldera forming eruptions that produced large volume pyroclastic deposits that are extensively distributed and exposed we acknowledge that there may be additional prehistoric eruptions where the eruptive products have not been preserved recognized or reported events that cannot be verified or do not have sufficient details to confirm the eruption have been downgraded to uncertain eruptions that are confirmed with identified dispersal and emplacement of tephra fall and other eruptive deposits as interpreted from narrated records could provide crucial information that may be utilized in hazard assessment

rapid cooling and exhumation in the western part of the mesoproterozoic albany fraser orogen western australia abstract the albany fraser orogen of southwestern australia is an understudied orogenic belt which is interpreted to record the mesoproterozoic suturing of the yilgarn craton of western australia to the mawson craton of east antarctica during rodinia assembly previous u pb geochronology has dated peak amphibolite to granulite facies metamorphism in the orogen at ca 1180 ma here we report the first 40ar 39ar thermochronology of hornblende biotite and muscovite grains from a 360 km transect across the western albany fraser orogen and uncover a record of strikingly fast syn orogenic cooling and exhumation to the north muscovites from the northern foreland record cooling at ca 1159 ma in the central and southern domains of the orogen the biranup and nornalup zones hornblende yields ca 1169 ma cooling ages and biotite yields ca 1172 1144 ma cooling ages the new cooling ages imply that the three domains were exhumed rapidly following peak metamorphism at ca 1180 ma attained a similar structural level by ca 1159 ma and have experienced a uniform exhumation history since that time to constrain mineral closure temperatures and post peak metamorphic cooling rates we conducted a monte carlo simulation which fully propagates uncertainty and minimises error correlations modelling of cooling from hornblende to biotite closure temperatures ca 585 c and 365 c respectively in the nornalup and biranup zones yields fast cooling rates of 33 9 17 c ma and 22 5 7 c ma respectively these fast cooling rates imply rapid exhumation in an active tectonic setting undergoing peak metamorphism although the structural evolution of the albany fraser orogen remains poorly constrained the transpressional tectonic activity associated with deformation in the western part of the albany fraser orogen may have been an active driver of this fast exhumation this is distinctly different from exhumation models for granulite facies domains in other mesoproterozoic orogens which typically experience post orogenic slow 1 5 c ma cooling driven by mechanisms such as orogenic collapse and erosion we consider that the observed differences reflect the interpreted syn tectonic transpressional exhumation history of the albany fraser orogen which is an underrepresented tectonic regime in the mesoproterozoic cooling record

dating shear zones with plastically deformed titanite new insights into the orogenic evolution of the sudbury impact structure ontario canada abstract the sudbury structure is a mineralized impact crater that hosts different families of ore controlling shear zones with poorly known orogenic affinities discriminating whether these deformation events relate to the 1 85 ga crater modification stage or later regional tectonism that collapsed the impact structure is important both for crustal and mineral exploration studies we have combined underground mapping with isotopic and microstructural analysis of titanite and host minerals in a benchmark ore controlling mylonitic shear zone of the mining camp the six shaft shear zone from the creighton mine three growth stages of chemically and microstructurally characterised titanite grains were identified related with the pre syn and late deformation stages in situ u pb age dating of the syndeformational grains demonstrates that a shearing event took place at 1645 54 ma during the mazatzalian labradorian orogeny 1 7 1 6 ga this event led to the plastic deformation and local scale remobilization of primary ni cu pge sulphides in creighton mine sudbury south range the adopted novel petrochronological approach can reveal the age significance of syn deformational processes and holds promise for the untangling of complex syn orogenic processes in precambrian terranes globally

assessing the mechanisms of common pb incorporation into titanite abstract common pb the portion of non radiogenic pb within a u bearing mineral needs to be accurately accounted for in order to subtract its effect on u pb isotopic ratios so that meaningful ages can be calculated the propensity to accommodate common pb during crystallization or later is different across the range of u bearing minerals used for geochronology titanite frequently accommodates significant amounts of common pb however the most appropriate method to correct for this requires knowledge on the mechanism and timing of common pb incorporation information that is commonly difficult to extract in this study the spatial and compositional distribution of trace elements including pb in metamorphic titanites from a greenland amphibolite is investigated on the grain to nano scale titanites have an isotopically similar signature for both common and radiogenic pb in all grains but significantly different quantities of the non radiogenic component microstructural and compositional examination of these grains reveals undeformed but high common pb f207 titanites have homogeneous element distributions on the atomic scale suggesting common pb is incorporated into titanite during its growth and not during later processes in contrast deformed titanite comprising low angle boundaries formed by subgrain rotation recrystallization comprise networks of dislocations that are enriched in mg al k and fe smaller cations may migrate due to elastic strain in the vicinity of the dislocation network yet the larger k cations more likely reflect the mobility of externally derived k along the orientation interface the absence of pb enrichment along the boundary indicates that either pb was too large to fit into migrating lattice dislocations or static low angle boundaries and or that there was no external pb available to diffuse along the grain boundary as the common pb composition is distinctly different to regional pb models the metamorphic titanite grew in a homogeneous pb reservoir dominated by the break down of precursor u bearing phases the different quantity of common pb in the titanite grains indicates a mineral driven element partitioning in an isotopically homogeneous metamorphic reservoir consistent with low u low total ree and flat lree signatures in high f207 analyses these results have implications for the selection of appropriate common pb corrections in titanite and other accessory phases

trace element incorporation in titanite constraints from experimentally determined solid liquid partition coefficients titanite liquid partition coefficients for most of the trace elements relevant in petrogenetic studies are provided for titanite saturated liquids equilibrated at 1 5 gpa and 850 c starting from lamproitic compositions the high compatibility observed for ree hfse sr v and sc and the strong incompatibility observed for actinides large ion lithophile and light elements are discussed in terms of available crystal chemical mechanisms for incorporation and crystal structure control the exchange vectors na1ca 1 and al1ti 1 allow local charge balance to be achieved after incorporation of ree3 and r5 at the ca and ti site respectively the significant amounts of h measured are also relevant in this regard the exchange mechanism being oh 1o 1 at the o1 site the incorporation of u4 and th4 at the ca site is scarce and is likely balanced by that of mg2 at the ti site both these substitutions are responsible for strong structural strain titanite can thus be considered an important repository for ree and hfse in metamorphic and igneous rocks and its role must be accounted for when modelling trace element residence during metamorphic reactions and late magmatic crystallisation history due to the measured differences in compatibility titanite crystallisation increases the values of nb ta and lree hree ratios in residual liquids the similar compatibility of u and pb makes titanite suitable for u pb geochronology of igneous rocks only after common pb correction finally this study confirms that the titanite end member is not suitable for radioactive waste disposal due to the discussed crystal chemical constraints and that titanite based waste forms should contain high amounts of na and mg2

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

inherited pb components in magmatic titanite and their consequence for the interpretation of upb ages abstract the occurrence of inherited radiogenic pb components in 35 ma old magmatic titanite is reported here for the first time the about 810 ma age of the inherited components is identical to that contained in zircon from the same amphibole bearing syenite sample in both minerals the precambrian components were not totally reset during magmatic new growth at 35 ma this age pattern substantiates that the u pb chronometer in titanite is resistant to temperatures in excess of 712 c as is already known for zircon and monazite in consequence u pb ages from crystalline titanites have to be interpreted as the age of mineral formation or re crystallization rather than the time of u pb system closure during cooling of the rock

in situ u pb and trace element analysis of accessory minerals in the kiruna district norrbotten sweden new constraints on the timing and origin of mineralization northern norrbotten sweden is a key part of baltic shield and provides a record of magmatic tectonic and related superimposed fe oxide apatite and iron oxide copper gold iocg mineralization during the svecokarelian orogeny titanite and allanite from a range of mineral deposits in the area have been analysed for u pb isotope systematics and trace element chemistry using laser ablation quadrupole inductively coupled plasma mass spectrometry la icp ms analyses of a single sample from the regional scapolite albite alteration give an age of 1903 8 ma 2 and may be contemporaneous with the early stages of fe mineralization 1890 1870 ma analyses of titanite and allanite from undeformed iocg deposits indicate initial alteration at 1862 16 ma in many deposits subsequent metamorphic effects reset titanite isotope systematics from 1790 to 1800 ma resulting in a spread of u pb isotope analyses along concordia in some instances core regions may record evidence of early thermal events at around 2050 ma titanite and allanite from deformed iocg deposits on major shear zones record ages from 1785 21 ma to 1777 20 ma corresponding to deformation metamorphism and secondary hydrothermal alteration as a result of late orogenic movements the lack of intracrystalline variations in titanite and allanite trace element chemistry suggests that hydrothermal fluid chemistry and metal source were the main controls on mineral trace element chemistry titanite from undeformed fe oxide apatite and iocg deposits is typically light rare earth element lree enriched and shows low u th ratios and low ni in both intermediate to acid and basic volcanic hosted deposits this is consistent with a granitic source for metals minor variations in trace element patterns are consistent with the influence of aqueous complex formation on relative ree solubility deposits related to the nautanen deformation zone have relatively heavy ree hree enriched titanite and lree depleted allanite with high u th ratios and elevated ni contents consistent with leaching of metals from the local basic volcanic rocks all hydrothermal titanites are high field strength element enriched nb ta zr indicating their transport as a result of either high salinities or high f contents or both the data overall support models of iocg type mineralization as a result of regional circulation of saline hydrothermal fluids in association with major crustal structures with at least some metallic components derived from the granitoid rocks of the area all the deposits here show evidence of subsequent metamorphism although penetrative fabrics are restricted to regional scale deformation zones

preserved zr temperatures and u pb ages in high grade metamorphic titanite evidence for a static hot channel in the himalayan orogen abstract titanite grains from 800 c gneisses of the c 6 km thick greater himalayan sequence of central nepal were analyzed for zr in titanite temperatures and u pb ages to investigate the formation and evolution of a former weak mid crustal channel in the himalaya laser ablation icp ms depth profiles and spot analyses of titanite zr and u pb isotopic compositions are inconsistent with diffusional reequilibration on scales greater than 1 2 m and instead data appear to faithfully record both temperature and age titanite records protracted heating from 700 750 c at 37 ma to 775 c at 24 ma and possibly slight cooling to 765 c at 20 ma such temperatures exceed partial melting reactions in associated metapelites and imply profoundly weak rheologies i e a hot channel yet predate initiation of the bounding main central thrust and south tibetan detachment systems by as much as 15 myr evidently thick but weak crustal channels may remain stationary with respect to the convergence direction for 10 myr even during one of earth s biggest continent continent collisions

pyroclast tracking velocimetry illuminates bomb ejection and explosion dynamics at stromboli italy and yasur vanuatu volcanoes a new image processing technique pyroclast tracking velocimetry was used to analyze a set of 30 high speed videos of strombolian explosions from different vents at stromboli italy and yasur vanuatu volcanoes the studied explosions invariably appear to result from the concatenation of up to a hundred individual pyroclast ejection pulses all these pulses share a common evolution over time including 1 a non linear decrease of the pyroclast ejection velocity 2 an increasing spread of ejection angle and 3 an increasing size of the ejected pyroclasts these features reflect the dynamic burst of short lived gas pockets in which the rupture area enlarges while pressure differential decreases we estimated depth of pyroclast release to be approximately 1 and 8 m below the surface at stromboli and yasur respectively in addition explosions featuring more frequent pulses also have higher average ejection velocities and larger total masses of pyroclasts these explosions release a larger overall amount of energy stored in the pressurized gas by a combination of more frequent and stronger ejection pulses in this context the associated kinetic energy per explosion ranging 103 109 j appears to be a good proxy for the explosion magnitude differences in the pulse defining parameters among the different vents suggest that this general process is modulated by geometrical factors in the shallow conduit as well as magma specific rheology indeed the more viscous melt of yasur compared to stromboli is associated with larger vents producing fewer pulses but larger pyroclasts

geometry of isograds thermodynamic constraints on inversion abstract inverted isograds have been reported from metamorphic terrains ranging in age from precambrian to tertiary most of the workers believe that metamorphic inversion was caused by an inverted temperature gradient associated with large scale thrusting however isograds are not isotherms and the former may develop at large angles to the latter it is shown here that the orientation of isograds depends not only on the orientation of isotherms but also on the value of t p of an isograd reaction and that of the temperature gradients accordingly four different sets of conditions for inversion are recognised two for inverted temperature gradients one for a horizontal temperature gradient and one for a normal temperature gradient these conditions have been worked out for four different isograds staurolite in staurolite out muscovite breakdown and partial melting of granitic compositions it is shown that isograds may be in normal or inverted attitudes depending on the orientation and magnitude of the temperature gradient and also on the slope t p of an isograd reaction published accounts of metamorphic inversion do not provide all of these data but explain them in terms of only an inverted temperature gradient which may not be correct and may need re investigation

shocked titanite records chicxulub hydrothermal alteration and impact age abstract hydrothermal activity is a common phenomenon in the wake of impact events yet identifying and dating impact hydrothermal systems can be challenging this study provides the first detailed assessment of the effects of shock microstructures and impact related alteration on the u pb systematics and trace elements of titanite catisio5 focusing on shocked granite target rocks from the peak ring of the chicxulub impact structure mexico a 1 mm long shock twinned titanite grain preserves a dense network of irregular microcracks some of which exploit shock twin interfaces secondary microcrystalline anatase and pyrite are heterogeneously distributed along some microcracks in situ laser ablation multi collector inductively coupled plasma mass spectrometry la mc icpms analysis reveals a mixture of three end member pb components the pb components are 1 common pb consistent with the pb isotopic signature of adjacent alkali feldspar 2 radiogenic pb accumulated since magmatic crystallization and 3 a secondary younger pb signature due to impact related complete radiogenic pb loss the youngest derived ages define a regression from common pb that intersects concordia at 67 4 ma in agreement with the established age of 66 04 0 05 ma for the chicxulub impact event contour maps of la mc icpms data reveal that the young ages are spatially restricted to microstructurally complex domains that correlate with significant depletion in trace elements ree y zr nb mo sn th and reduction in magnitude of the eu eu anomaly mapping by time of flight secondary ion mass spectrometry tof sims show that patterns of localised element depletion in titanite are spatially related to microcracks which are enriched in al the spatial correlation of ages and trace element abundance is consistent with localised removal of pb and other trace elements from a pervasive network of fast fluid pathways in fractured domains via a fluid mediated element transport process associated with the impact event here we interpret the 67 4 ma u pb age to represent hydrothermal pb loss in the chicxulub peak ring in the wake of the impact event these results highlight the potential of our analytical approach using titanite geochronology and geochemistry for dating post impact hydrothermal activity in impact structures elsewhere

geochemical and u pb age constraints on the occurrence of polygenetic titanites in uhp metagranite in the dabie orogen abstract relict magmatic titanite was identified in the core of a few titanite grains with the overgrown rim of metamorphic titanite in uhp metagranite in the dabie orogen la icpms u pb dating gave neoproterozoic ages for the magmatic titanite but triassic ages for the metamorphic titanite the magmatic and metamorphic titanites are clearly distinct by differences in petrological and geochemical compositions the magmatic titanite occurs as residual cores that show bright bse the presence of allanite and quartz inclusions low contents of cao al2o3 and tio2 but high contents of fe2o3 and mgo in trace elements the magmatic titanite exhibits high ree and hfse contents distinctly negative eu anomalies with flat mree hree patterns and high th u ratios in contrast the metamorphic titanite occurs as rims and grains of homogeneously dark bse that contain inclusions of epidote quartz k feldspar rutile biotite and phengite and have relatively high contents of cao al2o3 and tio2 but low contents of fe2o3 and mgo and relatively low ree and hfse contents slightly negative eu anomalies with hree depletion relative to mree and low th u ratios the zr in titanite thermometry yields 727 to 877 c at 0 5 to 1 0 gpa for the magmatic titanite and 729 to 870 c at 1 5 to 2 0 gpa for the metamorphic titanite the neoproterozoic u pb chronometric system of magmatic titanite survived the triassic continental subduction zone hp uhp metamorphism this suggests a relatively high closure temperature of 800 c for the titanite u pb system the metamorphic titanite is principally a product of retrograde metamorphism during decompression exhumation at the transition from hp eclogite facies to amphibolite facies therefore titanite holds a great potential to geochronological and petrogenetic studies of continental subduction zone metamorphic rocks

hazard predictions for volcanic explosions we have developed a method of producing hazard maps for volcanic eruptions using three dimensional numerical simulations numerical simulations of shock wave interactions with terrain were carried out assuming the volcanic explosion is analogous to point source explosions the point source explosion model is coupled with scaling distances for pyroclastic surge and ballistic fragments to produce hazard maps of the damage done both by shock waves and volcanic debris the numerical method is applied to iwatesan volcano which recently became active we demonstrate that the present method of producing hazard maps is useful for establishing better safety countermeasures for volcanic eruptions

modeling shock waves generated by explosive volcanic eruptions atmospheric shock waves induced by explosive volcanic eruptions can provide valuable information about eruption characteristics shock waves are manifested as pressure density gradients that can be remotely observed with relatively little noise field measurements of expanding shock waves can be directly recorded by pressure transducers or imaged under the proper illumination and atmospheric conditions in this paper an open ended shock tube was used to generate weak shock waves in the laboratory that are representative of explosive volcanic eruptions they indicate that strong shock wave theory can be used for modeling moderate volcanic eruptions based on that finding we use strong shock theory to estimate the sudden explosive energy released from several explosive eruptions our energy calculations are well correlated with total energy estimates derived from plume height or erupted mass

estimates of eruption velocity and plume height from infrasonic recordings of the 2006 eruption of augustine volcano alaska abstract the 2006 eruption of augustine volcano alaska began with an explosive phase comprising 13 discrete vulcanian blasts these events generated ash plumes reaching heights of 3 14 km the eruption was recorded by a dense geophysical network including a pressure sensor located 3 2 km from the vent infrasonic signals recorded in association with the eruptions have maximum pressures ranging from 13 111 pa eruption durations are estimated to range from 55 350 s neither of these parameters however correlates with eruption plume height the pressure record however can be used to estimate the velocity and flux of material erupting from the vent assuming that the sound is generated as a dipole source eruptive flux in turn is used to estimate plume height assuming that the plume rises as a buoyant thermal plume heights estimated in this way correlate well with observations events that exhibit strongly impulsive waveforms are underestimated by the model suggesting that flow may have been supersonic

the effect of pre existing craters on the initial development of explosive volcanic eruptions an experimental investigation most volcanic eruptions occur in craters formed by previous activity the presence of a crater implies specific confinement geometries variably filled by loose fragmental deposits which are expected to exert a strong yet poorly studied control on the violent gas expansion that drives the eruption here we analyze patterns of ejection from buried explosions in analog experiments in order to investigate how the presence of a crater and changes in explosion depth and intensity may affect the formation of eruptive ejecta jets results show that scaled depth charge burial depth divided by the cubic root of charge energy controls the velocity and partly spread angle of eruptive jets independently of the presence of a pre existing crater conversely for a fixed scaled depth the presence of a pre existing crater limits the development of a laterally expanding annulus of the jet these results are directly applicable to interpretation of volcanic explosions key points analysis of ejection patterns from intra and extra crater buried explosions velocity and spread angle of ejecta jet are sensitive to explosion scaled depth radially expanding annulus of the jet is sensitive to pre existing crater

u pb geochronology of the grenville orogen of ontario and new york constraints on ancient crustal tectonics based on lithological structural and geophysi cal characteristics the proterozoic grenville orogen of southern ontario and new york has been divided into domains that are separated from each other by ductile shear zones in order to constrain the timing of meta morphism u pb ages were determined on metamorphic and igneous sphenes from marbles calc silicate gneisses amphibolites granitoids skarns and pegmatites in addi tion u pb ages were obtained for monazites from meta pelites and for a rutile from an amphibolite these mineral ages constrain the timing of mineral growth the duration of metamorphism and the cooling history of the different domains that make up the southern part of the exposed grenville orogen based on the ages from metamorphic minerals regional and contact metamorphism occurred in the following intervals central granulite terrane

constraints on pb closure temperature in titanite based on rocks from the ungava orogen canada implications for u pb geochronology and p t t path determinations on the basis of multiequilibrium metamorphic pressure temperature p t estimates we have determined that 660 700 c is a reasonable minimum estimate of the closure t of pb diffusion in titanite a temperature significantly higher than previously suggested activity corrected reactions that produce titanite define narrow t stability fields 40 c that correspond closely to metamorphic p t determinations derived for coronitic garnet clinopyroxene hornblende samples growth of titanite occurring between 1789 and 1814 ma in the underthrust archean basement of the paleoproterozoic ungava orogen northern quebec is associated with retrograde metamorphism during underthrusting of the archean basement approx 1 b y after formation of the original granulitic assemblages

common lead corrected laser ablation icp ms u pb systematics and geochronology of titanite u pb geochronology using laser ablation icp ms is a fairly recently introduced technique and thus far its development has centred on zircon dating using titanite as an example the application of laser ablation icp ms to u pb dating of common pb bearing accessory phases is presented a simple analytical set up comprising a 213 nm nd yag laser coupled to a quadrupole based icp ms instrument is used it is demonstrated that accurate and precise pb u ratios 2 3 at 2 for 206pb 238u can be obtained on small volumes of analysed material using the zircon geostandard 91500 as an external calibration standard a robust common pb correction necessitating the measurement of the stable 204pb isotope is detailed the isobaric 204hg background interference in icp ms is lowered to a level where it does not dominate the total 204 amu signal using in line gold traps on the carrier gas lines the remaining 204hg is stripped from the 204pb signal mathematically by applying a natural hg isotope ratio common pb correction using this method is demonstrated to work well in analyses with elevated u pb signal intensity where this correction fails an alternative method is required and a novel approach using three dimensional u pb concordia is adopted this approach is shown to be extremely powerful in assessing age precision and common pb composition correction the technique is applied to the well characterised fish canyon tuff demonstrating that accurate 7 8 at 2 compared to reference age and precise 2 4 at 2 on 206pb 238u ratios u pb age data can be obtained from titanite even as young as oligocene

burst conditions of explosive volcanic eruptions recorded on microbarographs explosive volcanic eruptions generate pressure disturbances in the atmosphere that propagate away either as acoustic or as shock waves depending on the explosivity of the eruption both types of waves are recorded on microbarographs as 1 to 0 1 hertz n shaped signals followed by a longer period coda these waveforms can be used to estimate burst pressures and gas concentrations in explosive volcanic eruptions and provide estimates of eruption magnitudes

apatite monazite and xenotime in metamorphic rocks this chapter focuses on phosphates that are significant in metamorphic rocks a quick survey of phosphate mineral descriptions at a commercial mineral web site revealed over 500 phosphate mineral names remarkably only three are common in metamorphic rocks apatite monazite and xenotime and this chapter is restricted to discussion of these minerals apatite monazite and to a lesser extent xenotime have enjoyed intensive study during the previous half century following world war ii considerable study was made of minerals that contain fissionable materials and the sometimes large concentrations of u and th in monazite culminated in a number of seminal papers on the occurrence of that mineral e g overstreet 1967 during the 1970s and early 1980s the study of apatite and monazite turned towards their role as a sink for rees and other trace elements in rocks e g watson 1980 watson and capobianco 1981 throughout this period monazite and to some extent xenotime enjoyed attention as a geochronometer e g parrish 1990 and through today this attention has continued to grow accessory minerals such as monazite xenotime and apatite have come to the forefront of research in metamorphic petrology in recent years for two reasons first it has recently been recognized that trace elements in metamorphic rocks and especially trace element zoning in garnet and other major phases contain considerable detailed information about the reaction history a rock has experienced coupled with the fact that diffusion of many trace elements in metamorphic minerals is in general considerably slower than diffusion of major elements in those same minerals the possibility has recently emerged of recovering details of metamorphic petrogenesis that were previously unattainable inasmuch as accessory minerals play a dominant role in the mass budget of many trace elements attention has naturally turned to their paragenesis it has also recently been discovered that

wind entrainment in jets with reversing buoyancy implications for volcanic plumes explosive volcanic eruptions commonly undergo a transition from stable plume to collapsing fountain with associated destructive pyroclastic density currents a major goal in physical volcanology is to predict quantitatively the limit between the flow regimes as a function of the source and environmental conditions atmospheric winds influence the dynamics and stability of the column causing bending and enhancing turbulent air entrainment however the predictions made with 1 d models of volcanic plumes accounting for the presence of wind strongly depend on the wind entrainment coefficient a parameter whose value varies in the literature here we present a new theoretical model to identify an analytical criterion for column collapse in windy conditions we then present new laboratory experiments on turbulent jets with reversing buoyancy rising in a crossflow in order to better constrain our results show that a single value of 0 5 can be used to describe the behavior of laboratory jets with arbitrary buoyancy the results allow us to parameterize our 1 d model of volcanic plumes ppm and to show the crucial importance of wind gradient and profile on volcanic column dynamics through the use of the 1991 mt hudson eruption as a case study finally we propose a new transition diagram between the stable plume and collapsing fountain regimes as a function of wind speed and mass discharge rate only which can be used for the rapid assessment of major hazards during an explosive eruption

element and sr isotope signatures of titanite as indicator of variable fluid composition in hydrated eclogite abstract the trace element signature sr common pb u th ree and hfse of titanite gives important information about the formation process of metamorphic titanite we investigated titanite from different textural positions of a strongly retrogressed eclogite from the tromso norway high p area it shows characteristic titanite rims around partially absorbed rutile interpreted as grown during retrogression and hydration of the high p assemblage the titanite rims around rutile are polycrystalline and in contact with the plagioclase amphibole matrix large idioblastic single crystal titanite grew in veins without relics of precursor rutile compositional zoning of al ti f in titanite of both textural positions is irregular and not related to core or rim position in the crystals there is no evidence for systematic growth sequences or diffusion reflecting changing p t conditions or systematic changes of fluid composition trace element patterns of titanite la icp ms data however show systematic variations in the coupling and decoupling behaviour of strongly fluid mobile sr u moderately fluid mobile ree and little fluid mobile nb ta zr hf elements the trace element signatures of titanite from the two different fabric positions reflect contrasting characteristic fluid compositions single crystal titanite equilibrated with fluid that was channelled in the vein polycrystalline titanite on rutile records the composition of a fluid that had migrated along grain boundaries in the amphibole plagioclase matrix fluid from the matrix also contributed to the geochemical signature of vein titanite whereas influence of fluid from the vein on the composition of polycrystalline titanite in the matrix is not evident 87sr 86sr isotope ratios of the different titanite types support the inference from trace elements of spatially and temporally variable fluid sources

a global study of volcanic infrasound characteristics and the potential for long range monitoring abstract volcanic infrasound from explosive eruptions is detectable at distances up to 1000 s of km and is often recorded on the international monitoring system ims infrasound network though infrasound produced by individual volcanoes has previously been studied more general relationships between infrasound characteristics and eruption parameters remain unclear therefore using a dataset comprising 110 events at 39 globally distributed volcanoes we assess the ability of the ims to monitor remote volcanoes and investigate whether volcanic infrasound exhibits consistent trends across a range of eruption styles and intensities acoustic pressure amplitude and frequency content of the volcanic infrasound were measured and acoustic energy was also calculated these were compared along with the maximum distance of detection for each event to the maximum plume height reported for the event which was used as a proxy for event intensity of the events investigated 62 were detected by at least one infrasound station the maximum distance at which an event was detected generally increased with the plume height and infrasound produced during the eruption of manam png in january 2005 which produced a plume which rose over 20 km above the summit was detected at a distance of 10 671 km total acoustic energy and acoustic pressure amplitude corrected for geometrical spreading increased with plume height whilst the lowest frequency present in the volcanic infrasound decreased additionally relationships seen between infrasound characteristics and eruption plume height indicate that analyses of this data alone could constrain vital estimates of plume heights for otherwise un observed eruptions taken together these findings indicate that if made available for this purpose in the future the ims infrasound network could complement existing monitoring techniques by detecting and characterising eruptions at remote volcanoes which often have no local monitoring networks

titanite petrochronology of the southern brasilia orogen basement effects of retrograde net transfer reactions on titanite trace element compositions abstract combining u pb geochronology and trace element characteristics of accessory minerals more reactive during metamorphism and deformation than zircon such as titanite catisio5 is a powerful tool for elucidating pressure temperature time p t t evolution of orogenic basement complexes this study reports in situ titanite u pb and trace element data from upper amphibolite facies metatexitic orthogneisses of the pouso alegre complex in the basement of the neoproterozoic southern brasilia orogen se brazil the titanite data is combined with thermodynamic modeling major phase compositions and u pb zircon dating and used to constrain the p t t path of the complex during the neoproterozoic orogenesis the investigated garnet amphibole gneisses record peak metamorphic conditions of 750 775 c and 10 5 12 5 kbar associated with partial melting and dated at ca 630 620 ma based on u pb analyses of hree y depleted titanite cores inferred to have crystallized in the presence of garnet near the peak p t conditions extensive melt crystallization at ca 616 ma is constrained by u pb dating of leucosome zircons the exhumation of the complex and re equilibration to ca 550 625 c at 6 9 kbar led to widespread generation of biotite epidote clinozoisite partially replacing amphibole garnet along the main foliation trace element signatures of these retrograde net transfer reactions are recorded in the titanite rims which are hree y enriched strontium depleted and were dated at 605 7 6 2 ma the average zirconium contents of the titanite rims are higher than cores suggesting disequilibrium partitioning of zirconium into titanite during the retrograde path resulting in overestimated zr in titanite temperatures for the rims the exhumation of the complex was concomitant with the intrusion of folded and recrystallized leucogranite dykes dated at 607 0 5 7 ma attesting the persistence of deformation after their intrusion assuming that the pouso alegre complex is part of the sao francisco paleocontinent reworked during the brasilia orogeny the data constrain the minimum age for the collision between the sao francisco paleocontinent and the paranapanema block at ca 620 630 ma and agree with the idea of long lived metamorphism and deformation in the southern brasilia orogen