a new indicator of movement direction during orogenesis measurement technique and application to the alps the orientation of axes of sigmoidal staircase or spiral inclusion trails within porphyroblasts provides an indicator of the direction of movement during deformation that is synchronous with metamorphism a simple technique is presented in detail to find this axis in 3d by radially sectioning a horizontal slab cut from an oriented sample when viewed from one direction the switch in asymmetry of the porphyroblast inclusion trails in these sections defines the trend of the axis further radial sectioning of a vertical slab cut parallel to this trend determines the plunge of this axis this technique is independent of the model adopted for the formation of sigmoidal or spiral shaped inclusion trails and can be used to evaluate the mechanism by which they form it can also be used to evaluate theories of folding and orogenesis measurements of spiral and sigmoid axes in garnet porphyroblasts from the european alps show that they reflect the movement of the african plate relative to europe better than linear indicators preserved within the same rocks

influences of reaction history and chemical diffusion on p t calculations for staurolite schists from the littleton formation northwestern new hampshire geothermometry from staurolite grade pelitic assemblages may fail to reflect peak temperatures of metamorphism because of 1 prograde gamet consuming reactions and 2 diffusional reequilibration during cooling in response to retrograde reactions gamet dissolution during staurolite formation leads to sharp compositional gradients within a few micrometers of garnet rims these gradients may then be modified by diffusion on cooling and lead to anomalous temperature estimates calculated from thermo barometers involving garnet numerical simulations of mineral growth and diffusion were used to examine these effects for a prograde metamorphic sequence from the salmon hole brook syncline northwestern new hampshire in higher grade assemblages mineral textures indicate that staurolite grew by the consumption of gamet and gamet biotite temperature estimates fall in the range 515 t 30 c interbedded layers containing garnet and biotite but not staurolite yield temperature estimates of 565 t 25 c in the eastern portion of the syncline rocks containing kyanite staurolite garnet biotite assemblages indicate temperatures of 550 t 25 c hypothetical growth and reaction histories that adhere to the modal mineralogical and known geochronological constraints were developed using a thermodynamically rigorous treatment of mineral modes and compositions incorporating calculations for multicomponent diffusion in garnet these models demonstrate that temperature estimates from staurolite schists may underestimate actual thermal maxima by more than 50 c gamet growth accompanying the reaction staurolite kyanite biotite garnet can lead to higher absolute temperature estimates but these may still be at least 50 c lower than actual peak temperatures simulations also demonstrate that fe enrichment in biotite accompanying retrograde production of chlorite may lead to calculated temperatures that are 10 50 c higher than would occur where only diffusional exchange operated on cooling evidence from additional metamorphic terranes suggests that this reaction model has wide applicability

major and trace element zoning in garnets from calcareous pelites in the nw shelburne falls quadrangle massachusetts garnet growth histories in retrograded rocks

improved remote sensing estimates of lava flow cooling a case study of the 1991 1993 mount etna eruption infrared radiance data acquired by the landsat thematic mapper tm provide information regarding the thermal state of active lavas which can be used to estimate flow surface temperatures and thus lava cooling saturation of one or both of tm s short wave infrared swir wavebands has meant however that previous studies of lava flow cooling have approximated what is almost certainly an n thermal component flow surface temperature distribution where n 1 with a single pixel integrated temperature pit we show that the high sensitivity of tm s swir wavebands to the small amount of high temperature e g 1000 c material exposed in hot fractures within the flows cooler e g 200 c surface crust results in the calculation of pits that are higher than the temperature of this crust which is usually the dominant radiative component this causes heat loss from such pixels to be overestimated we present adaptations that allow more realistic heat loss estimates to be produced using tm data by assuming that a second high temperature component contributes to the radiance measured from saturated pixels and by defining an appropriate range for the temperature of the lava crust by analyzing a suite of five tm images acquired during the 1991 1993 eruption of mount etna we present more realistic estimates of how this flow cooled as well as results that show how the flow regime of the lava evolved over time the methods we present will continue to be of use as although the next generation of high spatial resolution sensors such as the landsat 7 enhanced thematic mapper plus etm and the terra advanced space borne thermal emission and reflection radiometer aster will be less susceptible to saturation than tm the problem will still persist

three dimensional imaging of garnet porphyroblast sizes and chemical zoning nucleation and growth history in the garnet zone the three dimensional 3 d growth history of two garnet zone samples grt chl bt ms pl qtz ilm from southwestern maine was examined by serial sectioning and 3 d reconstructions of compositional zoning from backscatter images and x ray maps mn fe mg and ca zoning is broadly concentric the concentration of mn in garnet cores generally correlates with size d 50 to 750 micrometers indicating progressive nucleation in detail all elements show irregular patchy zoning in the cores assuming constancy of mn on the rims of all garnet crystals in a rock volume plus no subsequent diffusional modification mn concentration can be used as a time line for garnet growth examination of the evolution of individual garnet crystals reveals that multiple nuclei formed simultaneously in the core regions and that nuclei expanded by growth in amoeba shape forms along preexisting mineral grain boundaries primarily quartz and plagioclase dissolving the interior grains until the grains were either gone or encapsulated at which time dissolution ceased amoeba shaped garnet crystals coalesced as they grew and simultaneously new nuclei appeared in the nearby matrix the net result was a single garnet porphyroblast that formed by the growth and coalescence of multiple nuclei radius rate plots constructed by counting pixels in 2 d images reveal that crystals grew at the same radial rate regardless of size the observation of continuous nucleation in the vicinity of preexisting crystals plus the radius rate plots rule out diffusion over length scales on the order of the garnet radius or greater as the rate limiting step and are consistent with either diffusion over shorter length scales or interface control as rate limiting to garnet growth the strong clustering of garnet nuclei requires clustering of favorable nucleation sites which may have been caused by favorable orientation of garnet precursor minerals i e chlorite quartz

sigmoidal inclusion trails punctuated fabric development and interactions between metamorphism and deformation porphyroblast inclusion fabrics are consistent in style and geometry across three proterozoic metamorphic field gradients comprising two pluton related gradients in central arizona and one regional gradient in northern new mexico garnet crystals contain curved sigmoidal inclusion trails in low grade chlorite schists these trails can be correlated directly with matrix crenulations of an older schistosity s1 the garnet crystals preferentially grew in crenulation hinges but some late crenulations nucleated on existing garnet porphyroblasts at higher grade biotite staurolite and andalusite porphyroblasts occur in a homogeneous s2 foliation primarily defined by matrix biotite and ilmenite biotite porphyroblasts have straight to sigmoidal inclusion trails that also represent the weakly folded s1 schistosity staurolite and andalusite contain distinctive inclusion rich and inclusion poor domains that represent a relict s2 differentiated crenulation cleavage together the inclusion relationships document the progressive development of the s2 fabric through six stages garnet and biotite porphyroblasts contain stage 2 or 3 crenulations staurolite and andalusite generally contain stage 4 crenulations and the matrix typically contains a homogeneous stage 6 cleavage the similarity of inclusion relationships across spatially and temporally distinct metamorphic field gradients of widely differing scales suggests a fundamental link between metamorphism and deformation three end member relationships may be involved 1 tectonic linkages where similar p t time histories and similar bulk compositions combine to produce similar metamorphic and structural signatures 2 deformation controlled linkages where certain microstructures particularly crenulation hinges are favourable environments for the nucleation and or growth of porphyroblasts and 3 reaction controlled linkages where metamorphic reactions particularly dehydration reactions are associated with an increase in the rate of fabric development a general model is proposed in which 1 garnet and biotite porphyroblasts preferentially grow in stage 2 or 3 crenulation hinges and 2 chlorite consuming metamorphic reactions lead to pulses in the rate of fabric evolution the data suggest that fabric development and porphyroblast growth may have been quite rapid of the order of several hundreds of thousands of years in these rocks these microstructures and processes may be characteristic of low pressure first cycle metamorphic belts

age and genesis of the pusangguo skarn cu dominated polymetallic deposit gangdese metallogenic belt tibet abstract the pusangguo skarn cu polymetallic deposit is a newly discovered deposit in the western gangdese porphyry copper belt gpcb the orebodies are hosted along the contact between limestone of the early cretaceous takena formation and a biotite granodiorite intrusion the mineralization is associated with the biotite granodiorite intrusion and is divided into four stages 1 a prograde skarn stage 2 a pre ore retrograde skarn stage 3 a quartz sulfides stage and 4 a post ore carbonate stage these skarns have the characteristics of both calcareous and manganese skarns the mineral compositions of the garnets and pyroxenes indicate that the ore forming environment gradually evolved from a high temperature oxidative and alkaline environment into a low temperature and reductive environment the sulfur and lead isotopic compositions of the ore sulfides suggest a magmatic source for the sulfur and a crust dominated source for the ore forming metals the hydrogen and oxygen isotopic compositions of the quartz and garnets in the ores indicate that the ore forming fluids may have originated from a mixture of magmatic and meteoric fluids the geochronological data show that both the magmatism 14 8 0 4 ma and mineralization 13 2 0 7 ma occurred during the miocene in a post collisional tectonic setting the ore forming biotite granodiorite is a high k calc alkaline i type granite and has an adakitic geochemical affinity similar to the gangdese miocene adakites which were generated from thickened lower crust in a post collisional tectonic setting the low positive ehf t values 0 to 2 6 young two stage hf model zircon ages and whole rock geochemical and lead isotopic compositions indicate that the magma of the ore related biotite granodiorite may have originated from the thickened lower crust in the lhasa terrane

an overgrowth model to explain multiple dispersed high mn regions in the cores of garnet porphyroblasts the central portions of garnet porphyroblasts from harpswell neck maine exhibit small discrete regions of high mn content dispersed in three dimensions orientation contrast imaging oci and quantitative crystallographic orientation measurements from electron backscatter diffraction ebsd patterns show that most garnet porphyroblasts contain no variations in crystallographic orientation it is difficult to reconcile these data with a model in which each high mn region represents a discrete garnet nucleus an alternative hypothesis invokes a model of garnet growth in which precursor phases rich in mn are overgrown and their mn is incorporated locally into the garnet structure although this model requires length scales for equilibration of mn during the early stages of garnet growth that are shorter than any previously documented that inference is consistent with the very low temperatures of garnet nucleation in these rocks and with compositional evidence for progressively larger scales of equilibrium as reaction progressed very short length scales for equilibration of mn identified in this study for the lowest grade portion of the history of the rocks call into question the common assumption of rock wide equilibrium for mn during garnet growth at low temperature the absence of rock wide equilibrium for mn at low grade has potential negative implications for all common interpretive methods based in phase equilibria including thermobarometric studies and thermodynamic analysis of the origin and meaning of zoning in low grade garnet

lava lake surface characterization by thermal imaging erta ale volcano ethiopia the project sviluppo di sistemi di monitoraggio dipartimento di protezione civile di regione sicilia ingv catania section italy the leverhulme trust the bbc and the ethiopian air force

ground based thermal imaging of lava lakes at erebus volcano antarctica abstract mount erebus a large intraplate stratovolcano dominating ross island antarctica hosts the world s only active phonolite lava lakes the main manifestation of activity at erebus volcano in december 2004 was as the presence of two convecting lava lakes within an inner crater the long lived ray lake 1400 m2 in area was the site of up to 10 small strombolian eruptions per day a new but short lived 1000 1200 m2 lake formed at werner vent in december 2004 sourced by lava flowing from a crater formed in 1993 by a phreatic eruption we measured the radiative heat flux from the two lakes in december 2004 using a compact infrared ir imaging camera daily thermal ir surveys from the main crater rim provide images of the lava lake surface temperatures and identify sites of upwelling and downwelling the radiative heat outputs calculated for the ray and werner lakes are 30 35 mw and 20 mw respectively we estimate that the magma flux needed to sustain the combined heat loss is 250 710 kg s 1 that the minimum volume of the magma reservoir is 2 km3 and that the radius of the conduit feeding the ray lake is 2 m

distinguishing and correlating multiple phases of metamorphism across a multiply deformed region using the axes of spiral staircase and sigmoidal inclusion trails in garnet schists from the appalachian orogen in south east vermont have undergone multiple phases of garnet growth these phases can be distinguished by the trend and relative timing of foliation inflexion or intersection axes fias of foliations preserved as inclusion trails in garnet porphyroblasts the relative timing of different generations of fias is determined from samples containing porphyroblasts with two or three differently trending fias developed outwards from core to rim multi fia porphyroblasts schists from south east vermont show a consistent pattern of relative clockwise rotation of fia trends from oldest to youngest four populations or sets of fias can be distinguished on the basis of their relative timings and trends from oldest to youngest the four sets have modal peaks trending sw ne w e nnw sse and ssw nne these peaks show that each of the four fia sets has a statistically consistent trend at all scales across a 35 125 km area containing numerous mesoscopic and macroscopic folds the fias of set 4 are defined by inclusion trails that are continuous with matrix foliations have trends subparallel to most folds and are inferred to have developed contemporaneously with these structures conversely sets 1 to 3 are oblique to and pre date most matrix foliations and folds all four fia sets occur in siluro devonian rocks and must have formed in the acadian orogeny the lack of statistically significant differences in the distribution of fia trends across the study area and their consistent relative timings in multi fia porphyroblasts despite a complex regional deformation history involving numerous phases of folding at all scales suggest the porphyroblasts have not rotated relative to one another the change in fia trend with time resulted from rotation of the kinematic reference frame of bulk flow possibly as a consequence of the reorganization of lithospheric plates responsible for acadian orogenesis recognition of distinct generations of fias provides a means of distinguishing different phases of porphyroblast growth four periods of garnet porphyroblast growth occurred in the schists of south east vermont this growth was heterogeneously distributed on the cm2 m2 scale no single porphyroblast records all stages of growth and adjacent samples from the same or dissimilar rock types commonly contain porphyroblasts that preserve different sequences of growth factors that may have been responsible for switching porphyroblast growth on and off at this scale include i subtle differences in bulk chemical composition ii oscillating levels of heat owing to the buffering effect of endothermic garnet forming reactions iii channelized infiltration of fluids with localized fluid buffering of bulk composition and iv cyclic controls on the rates of diffusion and material transport of reactants either by channelized fluid flow or by a changing pattern of microfracturing during foliation development consistency in fia trend and relative timing provide a new method for potentially distinguishing and correlating successive metamorphic events or even phases of metamorphism within a progressive tectonothermal event along and across orogens using a consistent pattern of core to rim changes in fia trend multiple phases of growth of a single porphyroblastic mineral can be quantitatively distinguished allowing correlation of different phases of growth around and across macroscopic folds the relative timing of growth of different porphyroblastic minerals can also be quantitatively determined using fia data and correlated around and across macroscopic folds conceptually the paragenetic history preserved in each generation of porphyroblast growth in the form of chemical zoning and the minerals in inclusion trails could be combined to produce a more detailed p t t deformation path than previously determined

characterization of volcanic thermal anomalies by means of sub pixel temperature distribution analysis the simultaneous solution of the planck equation involving the widely used dual band technique using two shortwave infrared swir bands allows for an estimate of the fractional area of the hottest part of an active lava flow f h and the background temperature of the cooler crust t c the use of a high spectral and spatial resolution imaging spectrometer with a wide dynamic range of 15 bits dais 7915 in the wavelength range from 0 501 to 12 67 m resulted in the identification of crustal temperature and fractional areas for an intra crater hot spot at mount etna italy this study indicates the existence of a relationship between these t c and f h extracted from dais and landsat tm data when the dual band equation system is performed on a lava flow a logarithmic distribution is obtained from a plot of the fractional area of the hottest temperature vs the temperature of the cooler crust an entirely different distribution is obtained over active degassing vents where increases in t c occur without any increase in f h this result indicates that we can use scatter plots of t c vs fh to discriminate between different types of volcanic activity in this case between degassing vents and lava flows using satellite thermal data

in situ major and trace elements of garnet and scheelite in the nuri cu w mo deposit south gangdese tibet implications for mineral genesis and ore forming fluid records abstract garnet and scheelite are common hydrothermal silicate mineral and metal mineral in skarn or porphyry skarn deposits and can aid in constraining the composition of ore forming fluid based on in situ major and trace element analyses of garnet and scheelite from the nuri cu w mo deposit we discuss the factors and mechanisms controlling the incorporation of rare earth elements rees into the garnet and scheelite and investigate the associated hydrothermal fluid characteristics the garnets from the nuri deposit belong to the grossular andradite grandite solid solution series and range in composition from adr64grs34 to adr91grs8 the ree patterns of garnet are enriched in light rare earth elements lrees and depleted in heavy rare earth elements hrees the rees characteristics indicates that the incorporation of rees into the nuri garnet was controlled by the surface adsorption and element substitution in the mineral structure based on the cathodoluminescence cl images of scheelite two growth stages early and late stages are identified these two stages of scheelite belong to the scheelite powellite series and are enriched in lrees and depleted in hrees however the early scheelite exhibits negative or no eu anomalies 0 34 0 95 whereas the late scheelite presents positive eu anomalies 1 25 2 89 the mo content in the early scheelite is positively correlated with the eu value while the mo content in the late scheelite is negatively correlated with eu these characteristics indicate that the redox state of the ore forming fluid gradually changed from the oxidized state to the reduced state the preferred ree3 substitution for ca2 in the nuri scheelite is 3ca2 2ree3 ca where ca is a ca site vacancy the ree features of the scheelite are mainly controlled by the ree nature of the ore forming fluid according to the characteristics of trace elements in garnet and scheelite we suggest that the ore forming fluid of the nuri deposit is a magmatic fluid mixed with a slightly acidic external fluid chloride complexes may be the main transport ligand of the rees and the oxygen fugacity of the ore forming fluid gradually decreased

centrifugal modeling of seismic behavior of large diameter pipe in liquefiable soil this study focused on the behavior of a large diameter burial pipe with special reference to its stability against flotation subject to soil liquefaction centrifugal modeling technique was used where the results are presented for a total of eight shaking table tests conducted on the burial pipe in a laminar box under 30g gravitational field the ground was prepared with nevada sand at a relative density of 38 and shaken with a sinusoidal wave at an amplitude of 0 5g the use of a viscous fluid in a saturated soil deposit satisfied the time scaling relationships of both dynamic and dissipation phenomena the centrifugal modeling technique simulated flotation of pipeline as the soil liquefied a technique that used gravels and geosynthetic material was used to mitigate flotation the response of the soil deposit in terms of acceleration and excess pore pressure was investigated the uplifting of the pipe earth pressure response and ground surface deformation were also presented based on the test results a design procedure was proposed for the burial pipe in resisting flotation due to soil liquefaction the deadweight and stiffness of the gravel unit which was confined by geosynthetic were important items in design

three dimensional patterns of garnet nucleation and growth three dimensional compositional zoning patterns in garnet zone garnets from harpswell neck maine united states suggest complex patterns of nucleation and growth compositional zoning is often asymmetric and core compositions do not always coincide with the geometric center of the garnet in detail garnet zoning patterns show multiple isolated high mno areas that we interpret as sites of garnet nucleation if it is assumed that garnet growth is close to equilibrium and the mn zoning is not significantly modified by diffusion then the mno contours or isosurfaces can serve as a proxy for patterns of garnet nucleation and growth computer generated three dimensional animations of these patchwork mno zoning patterns reveal that many garnets contain multiple nuclei that grew and coalesced to form a single crystal new nuclei often appeared next to preexisting porphyroblasts and became incorporated into the growing crystal contrary to the widely held idea that garnets grow radially outward from a single nucleus we propose that many of the garnets examined in this study grew by the coalescence of multiple nuclei

age and setting of the bronson hill magmatic arc a re evaluation based on u pb zircon ages in southern new england new u pb zircon ages of selected rocks from the bronson hill anticlinorium in southern new england are as follows microcline gneiss of the dry hill gneiss in the pelham dome believed to be metamorphosed alkali rhyolite is confirmed as late proterozoic yielding an age of 613 3 ma another sample shows strong evidence of zircon inheritance with a minimum mean age of 1402 ma plagioclase rich gneisses with associated amphibolites swanzey pauchaug monson and fourmile gneisses now believed to represent metamorphosed intrusive igneous rocks yield ages from 454 to 442 3 2 ma thus ranging from early late through latest ordovician consistent with other absolute ages of the oliverian plutonic series in the region quartz phyric rhyolite from the upper member of the ammonoosuc volcanics and rhyolite tuff from the partridge formation are dated at 453 2 ma and 449 3 2 ma respectively indicating that eruption of felsic lavas in the overlying volcanic section spanned an interval of approximately 4 m y additional zircon ages are reported from a crosscutting but deformed tonalite dike in the swanzey gneiss 381 3 ma and a coarse grained gabbro from the prescott intrusive complex 407 3 2 ma intrusive into the partridge formation metamorphic overprinting of the region during both the acadian and alleghanian orogenies is indicated by u pb titanite ages of 357 5 ma and 292 5 ma from a tonalite gneiss on prescott peninsula and the dry hill gneiss respectively the above ages and other zircon ages as well as petrography and geochemistry of the fourmile monson swanzey pauchaug and other plagioclase rich gneisses of the bronson hill anticlinorium suggest that they represent the plutonic root of a calc alkaline magmatic arc at least 250 km long that was produced partly or entirely on a continental margin in late ordovician time ca 454 442 ma the physically overlying cover sequence of chemically different tholeiitic arc volcanic and sedimentary rocks of the ammonoosuc volcanics and partridge formation previously thought to rest unconformably on the plagioclase rich plutonic gneisses is now shown to have had a magmatic history overlapping with them the zircon ages in the plutonic gneisses and the cover sequence indicate that both are the same age or slightly younger than the late ordovician caradocian emplacement of the giddings brook slice of the taconian allochthons and too young to have formed above an early and medial ordovician subduction zone

porphyroblast nucleation growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development in regional metamorphic rocks the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain rate gradients across the boundaries between the partitioned zones these generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain because of their uniquely layered crystal structure however most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients and hence are susceptible to dissolution and solution transfer as a consequence zones of progressive shearing become zones of dissolution of most minerals and of concentration of phyllosilicates and graphite exceptions are mylonites where strain rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing as they would be dissolved by the effects of shearing strain on their boundaries however they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation this includes a build up of stored strain energy relative to zones of progressive shearing in which dissolution is occuring porphyroblast growth is generally syndeformational and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account porphyroblasts in a contact aureole do not grow statically either as microfracturing associated with emplacement allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening the criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning reactivation of deforming foliations and a general lack of rotation of porphyroblasts with the spectacular exception of genuinely spiralling garnet porphyroblasts

contrasting triggering mechanisms of the 2001 and 2002 2003 eruptions of mount etna italy abstract mount etna produced two significant eruptions in 2001 and 2002 2003 which we have analysed using geological seismic and deformation data these eruptions showed some similarities such as the activating of two magmatic plumbing systems central lateral and eccentric but they differed in their triggering mechanisms while the 2001 eruption was largely the result of the emplacement of a n s eccentric dike independent from the central conduits consistent with e w regional extension the 2002 2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano this is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions during the months prior to the 2001 eruption most epicenters were concentrated on the southern flank at depths of 5 15 km below sea level during the 4 days before the eruption earthquake hypocenters migrated to shallower levels from 5 km bsl upward indicating the emplacement of the eccentric dike this is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements edm in contrast the months before the 2002 2003 eruption were characterised by shallower seismicity mainly concentrated along the active faults bordering the slipping flank sector flank slip accelerated in september 2002 and a second more vigorous acceleration of flank slip occurred on 26 27 october 2002 accompanying the opening of eruptive vents the very short 2 h seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption subsequently flank slip deformation extended all over the eastern and southeastern flanks of the volcano causing serious damage in this sector the events of 2001 2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics magma accumulation and eruption and flank instability in this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip which in turn facilitated the 2002 2003 eruption this sequence of events points to a long term feedback mechanism between magmatism and flank instability at etna

ductility of garnet as an indicator of extremely high temperature deformation discoidal shaped garnets alm63 prp33 grs3 sps1 occur in the foliation plane of lineated quartzofeldspathic mylonites of the morin shear zone located along the eastern boundary of the morin anorthosite complex grenville province quebec the flattened shape of garnets records a component of coaxial strain x y z different from the dominant rotational shear strain x y z in this mylonite tem observations indicate dislocation slip and recovery to be the main mechanism for the deformation of garnet extrapolation of available experimentally determined flow laws to natural strain rates shows an inversion of flow strength between quartz feldspar and garnet garnet much stronger than quartz and feldspar at temperatures below 700 c becomes weaker than quartz and feldspar above 900 c the coaxial ductile strain recorded by the garnets could be produced by a local uncharacterized deformation under extremely high temperature conditions at the roof of the rising anorthositic diapir 1155 ma subsequent lower temperature rotational deformation is related to strike slip movement along the morin shear zone 1020 ma

a review of algorithms for detecting volcanic hot spots in satellite infrared data since the 1980s application of thermal infrared satellite data for volcano monitoring has rapidly evolved to become a proven operational tool due to the large quantities of data provided by sensors in polar and geostationary orbits as well as the sheer number of active volcanoes on earth processing and managing such data sets requires an enormous amount of workforce a number of algorithms have been developed to facilitate detection location and tracking of hot spots of active volcanoes a collation and review of hot spot detection algorithms developed and applied by the volcanological community reveals three main types which have been applied to date contextual fixed threshold and temporal the founding algorithms for these three classes are vast modvolc and rst respectively through comparison with manually based detections the performance of each algorithm was tested for sustained lava flows etna and stromboli strombolian activity stromboli lava dome growth and collapse augustine and fumarole fields vulcano it is shown that as the number of correctly identified anomalies increases so too does the number of false positives although each of the algorithms operates well within the limits and criteria of their design requirements and application under current data restraints no algorithm can be expected to perform perfectly

low stress deformation of garnet by incongruent dissolution precipitation creep abstract microstructures indicating incongruent dissolution precipitation creep of garnet in eclogite facies graphitic micaschist tauern window eastern alps are investigated garnet dissolution is observed where garnet poikiloblasts grown at eclogite facies metamorphism approached each other as a consequence of progressive deformation during exhumation with estimated p t conditions between 570 c 1 7 gpa and 470 c 0 9 gpa the poikiloblasts are separated by a dissolution seam and flanked by strain shadows filled with quartz white mica and chlorite there is no evidence for crystal plastic deformation of garnet two cases are investigated a stylolitic contact zone b smooth contact zone in both cases internal fabrics of the poikiloblasts and concentric chemical zoning are truncated material previously forming inclusions in the garnet poikiloblasts is now passively enriched in a dissolution seam the original microstructure of fine grained mica graphite aggregates remaining preserved though microstructures suggest that garnet dissolution was driven by local stress concentration the level of differential stress remained too low for plastic deformation of the fine grained white mica graphite aggregates set free from the stress supporting garnet incongruent dissolution precipitation creep appears to be a particularly effective deformation mechanism at low stress in a subduction channel

the distribution style and intensity of alleghanian metamorphism in south central new england petrologic evidence from the pelham and willimantic domes abstract alleghanian metamorphism in south central new england is characterized by late pennsylvanian documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm kyanite mathrm muscovite mathrm staurolite end document grade heterogeneous reconstitution of migmatitic documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepack

deformation induced garnet zoning compositional zoning patterns in garnet porphyroblasts from kyanite bearing samples of the devonian littleton formation north central massachusetts reveal complex patterns of growth that are related to multiple deformation and metamorphic events garnet porphyroblasts exhibit asymmetrical and irregular zoning patterns in xmn xca and fe fe mg zoning reversals in mn and fe fe mg and patch distribution in ca appear to occur around the boundaries of the textural zones also the compositions of the garnet at the textural boundaries are variable for all traverses these observations suggest that the garnet zoning was not only modified from diffusion processes but was also influenced by pre existing microfabrics through the effects of preferential dissolution and resorption in partial disequilibrium relationships between chemical and textural truncations indicate that the zoning patterns of garnet were strongly modified from preferential dissolution and precipitation during the development of successive foliations that occurred in zones of high strain stress cleavage seams and zones of low strain stress respectively

disequilibrium for ca during growth of pelitic garnet compositional zoning in hundreds of almandine rich garnets in amphibolite by facies micaceous quartzites from the picuris range north central new mexico usa indicates that although mn mg and fe achieve chemical equilibrium at hand sample scale during garnet growth ca does not instead ca concentrations at the surface of growing garnets appear to depend strongly on kinetic factors that govern the local chemical environment yielding disequilibrium for ca at scales larger than the region immediately surrounding an individual porphyroblast detailed zoning profiles were obtained for 371 garnet crystals in a small volume of a single sample of garnetiferous quartzite and core analyses were made of 97 additional crystals each analysis was made on a section that passed precisely through the morphological centre of the crystal located by means of 3 d imagery from computed x ray tomography the data reveal strong correlations between crystal size and concentrations of mn mg and fe but not ca in garnet cores a relationship between crystal size and isolation rigorous cross correlations among concentrations of mn mg and fe but not ca and systematic variations in ca concentrations as a function of crystal size and core composition that are anomalous in comparison to the behaviour of the other divalent cations we interpret these observations as the result of thermally accelerated diffusion controlled garnet growth in circumstances that promoted rapid intergranular diffusion and thus rock wide equilibration of mn mg and fe but that prevented equilibration at similar scale for ca because of its more sluggish intergranular diffusion the anomalous behaviour of ca is made evident in these garnets by the presence of sharp spikes in ca concentration which are demonstrably not a consequence of any simultaneous rock wide event such as a change in pressure temperature or some other intensive parameter instead ca concentrations probably reflect the local extent of reaction in the immediate vicinity of each porphyroblast to the degree that such kinetic factors introduce departures from chemical equilibrium for ca thermobarometric estimates that involve grossular contents of pelitic garnet will be in error

rheology of the plate interface dissolution precipitation creep in high pressure metamorphic rocks abstract subduction zone models invoke deformation to be concentrated along the plate interface in a region of particularly low temperature geophysical observations do not provide constraints on temperature stress and deformation patterns with desired resolution in contrast the record of high pressure metamorphic rocks exhumed from subduction zones provides details on p t history deformation mechanisms and stress state albeit not readily correlated with the former dynamic situation on larger scale here we review available information on dissolution precipitation creep dpc in high pressure metamorphic rocks which if representative for subduction zones in general can pose constraints on conditions rheology and flow patterns along the plate interface the key observations and conclusions are that 1 deformation is typically highly inhomogeneous and localized into shear zones 2 stresses are generally too low to drive crystal plastic deformation 3 microfabrics suggest dissolution precipitation creep to be the predominant deformation mechanism 4 an aqueous fluid at quasi lithostatic pressure is available throughout allowing for tensile fracturing and crack healing or sealing 5 low stress combined with high strain rates required for localized deformation at typical subduction rates implies low viscosity and 6 contribution of shear heating to the thermal budget of subduction zones should be moderate the dominant deformation mechanism dpc is reviewed in some detail including experimental and theoretical approaches various examples of dpc in high pressure metamorphic rocks are illustrated emphasizing the role of interphase boundaries as sites of dissolution rheology governed by dpc is proposed to control interplate coupling and development of a subduction channel with return flow being a likely candidate for rapid exhumation of high pressure metamorphic rocks

combining compositional zoning and foliation intersection axes fias in garnet to quantitatively determine early p t t paths in multiply deformed and metamorphosed schists north central massachusetts usa quantitative compositional and microstructural analysis of garnet porphyroblasts in kyanite staurolite garnet grade rocks from the northeastern flank of the pelham dome north central massachusetts distinguishes the effects of acadian deformation and metamorphism from extensive overprinting alleghanian shearing the p t conditions and the metamorphic path during the acadian were determined using samples preserving well defined stages in a lengthy tectonic history revealed by a succession of five foliation intersection axis trends preserved within porphyroblasts fias this acadian succession extends at least 120 km to the north into rocks where no evidence has been found of an alleghanian overprint for each sample where garnet first nucleated during one of these stages in the tectonic history the pt of core growth was determined by plotting the intersection of the mn fe and ca isopleths calculated for the core composition on a p t pseudosection for that sample using thermocalc combining the pt data from all these samples indicates that the temperature and pressure increased throughout acadian orogenesis causing episodic garnet growth during the alleghanian locally intense shearing especially against the margin of the pelham dome formed the dominant schistosity which truncated all foliations defined by inclusion trails in porphyroblasts and obliterated all remains of acadian deformation and metamorphism in the rock matrix shearing was accompanied by near complete homogenization of the compositional zoning in garnet porphyroblasts and an associated apparent increase in the temperature of the matrix to 700 c in those rocks lying directly adjacent to the pelham dome and resulted from the rocks of the northfield syncline being thrust a large distance southwards over the gneisses in the dome

exploring the limits of identifying sub pixel thermal features using aster tir data abstract understanding the characteristics of volcanic thermal emissions and how they change with time is important for forecasting and monitoring volcanic activity and potential hazards satellite instruments view volcanic thermal features across the globe at various temporal and spatial resolutions thermal features that may be a precursor to a major eruption or indicative of important changes in an on going eruption can be subtle making them challenging to reliably identify with satellite instruments the goal of this study was to explore the limits of the types and magnitudes of thermal anomalies that could be detected using satellite thermal infrared tir data specifically the characterization of sub pixel thermal features with a wide range of temperatures is considered using aster multispectral tir data first theoretical calculations were made to define a thermal mixing detection threshold for aster which quantifies the limits of aster s ability to resolve sub pixel thermal mixing over a range of hot target temperatures and pixel areas then aster tir data were used to model sub pixel thermal features at the yellowstone national park geothermal area hot spring pools with temperatures from 40 to 90 c and at mount erebus volcano antarctica an active lava lake with temperatures from 200 to 800 c finally various sources of uncertainty in sub pixel thermal calculations were quantified for these empirical measurements including pixel resampling atmospheric correction and background temperature and emissivity assumptions

la icp ms trace element geochemistry of garnets constraints on hydrothermal fluid evolution and genesis of the xinqiao cu s fe au deposit eastern china abstract the xinqiao cu s fe au deposit in the tongling ore district an important part of the middle lower yangtze river valley metallogenic belt in eastern china is located along the northern margin of the yangtze block the deposit consists of two major mineralization types stratiform and skarn the genesis of the former is disputed the more important stratiform orebody 90 of the total cu s and fe reserves has abundant garnet as the main gangue mineral similar to the skarn orebody hosted in the intrusive contact garnets from the xinqiao stratiform orebody range from pure andradite and 100 to and 50 gro 46 and can be divided into the early grt1 and late grt2 generation both generations contain low mno 0 19 0 89 wide range of y ho 39 0 40 7 for grt1 29 8 67 9 for grt2 and do not contain melt or fluid melt inclusions indicative of a magmatic hydrothermal replacement origin grt1 and the grt2 cores are grandite whilst the grt2 rims are mainly andradite with some grandite zones grandite is enriched in heavy rare earth elements hrees and displays low lree hree la n yb n and u concentrations with negative eu anomalies whereas andradite is hree depleted and displays high lree hree la n yb n ratios and u concentrations with positive eu anomalies the distinct trace element features suggest that the hydrothermal fluids for grt1 and the grt2 cores were of nearly neutral ph relatively oxidized and hree enriched whereas those for the grt2 rims had experienced episodic inflections between a mildly acidic relatively reduced and hree depleted fluid and a nearly neutral relatively oxidized and hree enriched fluid meanwhile they also reveal that grt1 and the grt2 cores may have formed by diffusive metasomatism in a closed system whereas the grt2 rims may have formed by infiltration metasomatism in an open fracture system possibly related to the unconformity that hosts the xinqiao stratiform orebody we propose that the xinqiao stratiform orebody may have formed from early cretaceous magmatic hydrothermal fluids associated with the jitou stock similar to the skarn type orebodies in the district

volcano monitoring using short wavelength infrared data from satellites data from remote sensing satellites operating in the short wavelength infrared can be used to measure temperatures of about 150 c and above the gain settings of the landsat thematic mapper tm sensors are such that to record pixel integrated temperatures from 150 c to over 1000 c requires the use of several spectral bands if the radiant source occupies less than a whole pixel as is the case for fumaroles or a crusted lava surface with incandescent cracks then the pixel integrated temperature is less than the actual surface temperature of the hot areas and appears to be different at each wavelength by determining pixel integrated temperature in two spectral bands we can estimate both the temperature and size of hot areas which occupy less than a complete pixel in some cases our observations provide the only available data on the state of activity of a particular volcano in others they support and refine field observations our landsat tm data reveal otherwise unobserved precursor and subsequent activity related to the september 1986 eruption of lascar volcano chile and supplement other data on the march 1986 eruption of augustine volcano alaska they also indicate the continued presence of lava lakes at erta ale ethiopia in the absence of any ground based observations and document minor eruptive activity at mount erebus antarctica landsat multispectral scanner data have been used to measure the variation in temperature along a lava flow on sierra negra galapagos islands which occurred in 1979

prograde retrograde p t t deformation path of austroalpine micaschists during variscan continental collision eastern alps a complete prograde p t path defined by 10 calculated p t fields in succession is recognized from metapelites by using geothermobarometry on garnet bearing assemblages with microstructural control overstacking of several tectonic units during an early variscan continental collision explains the complex prograde p t history isostatic uplift and deformation controlled the retrograde p t path deformation with changing character acted continuously during all stages of the evolution of the austroalpine basement complex after the intrusion of caledonian granitoids metapelites and magmatic rocks suffered a shearing deformation d1 d2 which produced sheath folds as well as the main foliation s2 spessartine rich first generation garnets situated in microlithons enclosed by s2 record the onset of shearing under increasing high pressure low temperature conditions 7 kbar 380 c geothermobarometry on second generation garnets which have been rotated during growth indicates isothermal decompression from 9 kbar to 5 kbar 500 c and subsequent recompression heating during continuing shearing this is explained by overthrusting of a tectonic unit unit 2 from ne to sw upon the micaschist unit unit 1 followed by isostatic uplift and further overstocking of a third unit unit 3 the resulting pmax of 12 kbar at 650 c and further increasing temperatures up to 680 c accompanied by decompression have been calculated using a third generation of garnets these high pressure high temperature conditions may explain the occurrence of eclogitic metabasites in adjacent regions staurolite and kyanite first appeared under decreasing pressures at the last stage of prograde p t evolution shortening deformation d3 and simultaneous growth of typical amphibolite facies minerals staurolite 2 kyanite 2 sillimanite andalusite occurred during the retrograde path a final step of variscan evolution was marked by an oppositely directed shearing d4 at t 300 c and p 3 kbar possibly indicating backthrusting or extension apart from acid intrusions no signs of a previous caledonian thermotectonic history were found in the area to the south of the defereggen antholz vals line

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

diffusion control of garnet growth harpswell neck maine usa a detailed analysis of chemical zoning in two garnet crystals from harpswell neck maine forms the basis of an interpretation of garnet nucleation and growth mechanisms garnet apparently nucleates initially on crenulations of mica and chlorite and quickly overgrows the entire crenulation giving rise to complex two dimensional zoning patterns depending on the orientation of the thin section cut contours of ca zoning cross those of mn fe and mg indicating a lack of equilibrium among these major garnet constituents zoning of fe mg and mn is interpreted to reflect equilibrium with the rock matrix whereas ca zoning is interpreted to be controlled by diffusive transport between the matrix and the growing crystal image analysis reveals that the growth of garnet is more rapid along triple grain intersections than along double grain boundaries moreover different minerals are replaced by garnet at different rates the relative rate of replacement by garnet along double grain boundaries is ordered as muscovite chlorite plagioclase quartz flux calculations reveal that replacement is limited by diffusion of si along double grain boundaries to or from the local reaction site it is concluded that multiple diffusive pathways control the bulk replacement of the rock matrix by garnet with si and al transport being rate limiting in these samples

lava flow thermal analysis using three infrared bands of remote sensing imagery a study case from mount etna 2001 eruption abstract infrared remotely sensed data can be used to estimate heat flux and thermal features of active volcanoes the model proposed by crisp and baloga crisp j baloga s 1990 a model for lava flows with two thermal components journal of geophysical research 95 1255 1270 for active lava flows considers the thermal flux a function of the fractional area of two thermally distinct radiant surfaces the larger surface area corresponds to the cooler crust of the flow the smaller one to fractures in the crust in this model the crust temperature t c the temperature of the cracks t h and the fractional area of the hottest component f h represent the three unknowns to work out the simultaneous solution of the planck equation dual band technique for two distinct shortwave infrared swir bands allows to estimate any two of the parameters t c t h f h if the third is assumed dozier j 1981 a method for satellite identification of surface temperature fields of subpixel resolution remote sensing environment 11 221 229 the airborne sensor mivis was flown on mount etna during the july august 2001 eruption this hyperspectral imaging spectrometer offers 72 bands in the swir range and 10 bands in thermal infrared tir region of the spectrum which can be used to solve the dual band system without any assumptions therefore we can combine three spectral mivis bands to obtain simultaneous solutions for the three unknowns here the procedure for solving such a system is presented it is then demonstrated that a tir channel is required to better pinpoint solutions to the 2 components model finally the spatial and statistical characteristic of the resultant mivis derived temperature and flux distributions are introduced and statistics for each hot spot investigated

thirty years of satellite derived lava discharge rates at etna implications for steady volumetric output 1 we present a 30 year long data set of satellite derived time averaged lava discharge rates tadr for mount etna volcano sicily italy spanning 1980 2010 and comprising 1792 measurements during 23 eruptions we use this to classify eruptions on the basis of magnitude and intensity as well as the shape of the tadr time series which characterizes each effusive event we find that while 1983 1993 was characterized by less frequent but longer duration effusive eruptions at lower tadrs 2000 2010 was characterized by more frequent eruptions of shorter duration and higher tadrs however roughly the same lava volume was erupted during both of these 11 year long periods so that the volumetric output was linear over the entire 30 year period increasing at a rate of 0 8 m3 s 1 between 1980 and 2010 the cumulative volume record can be extended back in time using data available in the literature this allows us to assess etna s output history over 5 centuries and to place the current trend in historical context we find that output has been stable at this rate since 1971 at this time the output rate changed from a low discharge rate phase which had characterized the period 1759 to 1970 to a high discharge rate phase this new phase had the same output rate as the high discharge rate phase that characterized the period 1610 1669 the 1610 1669 phase ended with the most voluminous eruption of historic times

effects of viewing geometry on avhrr observations of volcanic thermal anomalies abstract we investigate the influence of viewing geometry and dynamic range of the advanced very high resolution radiometer avhrr sensor on detecting eruptions on poorly monitored volcanoes numerical models of sunwarmed flows and typical active features associated with hawaiian eruptions overturning lava lakes surface flows of three different sizes and lava tubes with skylights show that new lava flows at 1000 c can be identified at all scan angles if the area of the activity exceeds 60 m 2 given a background temperature of 20 c more difficult is the detection of small breakouts of lava flows or tube fed flows when these features lie towards the edge of the swath because of the dynamic range and gain setting of the sensor bands 3 4 and 5 saturate at 49 c it is possible that similar thermal signatures may be produced when inactive flows are heated by the sun the ability of the avhrr to detect on going activity in hawaii in july 1991 is tested by comparing landsat thematic mapper and nadir avhrr scenes obtained within 3 5 hours of each other for an active pahoehoe flow field with a well developed tube system this comparison shows that within the area of thermally alarmed avhrr pixels

thermal distributions of hot volcanic surfaces constrained using three infrared bands of remote sensing data infrared remote sensing provides a means for radiometry of hot volcanic features previously two spectral band measurements have been combined to solve simple 2 component models of lava surface temperatures however pixel dimensions often exceed the widths of lava bodies in such cases 3 component models are more realistic here a procedure for solving such a model from three infrared observations is presented it is then demonstrated using thematic mapper simulator data recorded over mount etna italy in 1991 by constraining temperatures and pixel filling fractions of the three different thermal components in this way improved estimates of radiant emittance can be obtained the techniques described could be applied to satellite data of volcanic and other hot spots including fires

retrogressive dissolution of garnet effect on garnet biotite geothermometry cation exchange geothermometry is predicated on the basis of chemical equilibration between phases involved in ion exchange reactions if chemical equilibrium is attained between the phases at any temperature and subsequently locked in temperature determinations should be consistent throughout a given sample the attainment of chemical equilibrium is commonly inferred where phases used for thermobarometry are in mutual contact or where sharp straight grain boundaries exist between grains thermometric determinations on garnet biotite pairs in a metapelite from the cheyenne belt wyoming illustrate the problem of using these criteria to infer chemical equilibrium in one example garnet biotite pairs from different parts of a single zoned garnet grain yield apparent temperatures that range over 150 c and are anomalously higher than documented metamorphic conditions almandine garnets from low to intermediate grade pelitic rocks commonly show strong compositional zoning retrograde modification coupled with strain induced dissolution of garnet may result in meaningless temperatures because of nonequilibration of phases used for geothermometry apparent textural equilibrium or mutual contact of grains may not be indicative of chemical equilibrium dissolution of garnet under conditions of biotite stability can produce garnet biotite pairs with sharp straight grain boundaries suggestive of textural equilibrium in the absence of visible truncation of compositional zones compositional maps or microprobe traverses both parallel and normal to schistosity are necessary to evaluate the possibility of dissolution failure to do so may result in the incorrect interpretation of t p determinations

sequential porphyroblast growth and crenulation cleavage development during progressive deformation abstract six stages of crenulation cleavage development during a single deformation event d2 can be recognised in both matrix and porphyroblast inclusion trails in the robertson river formation n e australia these stages progress from undeformed to crenulation and differentiated crenulation of s1 through development of differentiated crenulation cleavage s2 and differentiated schistosity s2 to homogeneous foliation s2 these rocks underwent prograde metamorphism during d2 and chloritoid garnet staurolite andalusite and sillimanite isograds have been mapped most rocks are rich in porphyroblasts which commonly contain well defined inclusion trails the geometry of these trails varies from one mineral type to the next depending on the timing of porphyroblast growth relative to the stage of crenulation cleavage development in the schistose matrix the deformation history involved progressive bulk inhomogeneous shortening and the strain is very heterogeneous on all scales partly as a consequence of this hence each of the six stages of crenulation cleavage development formed locally at various times during d2 therefore if a porphyroblast grew late in the deformation it could overgrow all stages of crenulation cleavage development including the very early ones the temperature increased during metamorphism in any one locality and consequently some porphyroblasts overgrew others that were unstable in the new conditions preserving them from destruction hence the precise timing of mineralogical reactions deduced from isograds and mineral chemistry relative to the stages in schistosity development can also be determined in the andalusite zone the sequence of porphyroblasts in decreasing order of age is biotite garnet biotite staurolite andalusite dissolution of garnet occurred during growth of staurolite and especially andalusite and dissolution of staurolite accompanied andalusite growth

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

the internal inclusion trail geometries preserved within a first phase of porphyroblast growth the inclusion trail geometry within a first phase of porphyroblast growth can differ significantly from that preserved by further enlargement because the porphyroblast forms a rigid mass up against which the rock preferentially strains during ensuing events the geometry of the first overgrown inclusion trails is affected by their primary orientation including any pre existing curvature combined with any heterogeneous rotation of this foliation about the developing stretching lineation this can impact the apparent timing of foliation intersection inflection axes preserved within porphyroblasts fias that nucleated during the development of a sub horizontal foliation but is readily resolved 3 d computer analysis of sigmoidal inclusion trails reveals that the asymmetry method for fia determinations is unaffected by the cut location relative to the porphyroblast core significantly perfect spiral inclusion trail geometries can be produced from a sigmoidal shape in cuts up 30 away from the fia therefore since fias in most porphyroblasts bear no relation to matrix structures there is a 17 chance that thin sections cut relative to the foliation lie within 30 of a fia and could contain such an apparent spiral fias maintain consistent trends for the first phase of porphyroblast growth accompanying horizontal bulk shortening but may vary in plunge fias have sub horizontal plunges for porphyroblasts nucleating during gravitational collapse but may vary in trend for all periods of porphyroblast regrowth the data available indicates that fias remain consistently trending and sub horizontal until the relative direction of plate motion causing orogenesis changes

partitioning of deformation along an orogen and its effects on porphyroblast growth during orogenesis an identical succession of foliation inflection intersection axis trends in porphyroblasts fias is present in three separate areas affected by acadian deformation and metamorphism along 130 kms of the appalachians from east central vermont to north central massachusetts the fias trend successively nw se sw ne w e nnw sse and ssw nne and appear to have formed during the same succession of deformations which have been dated in se vermont as follows not yet dated pre 425 ma 425 to 404 ma 404 to 385 ma and 385 to 360 ma respectively the two areas that are furthest apart in east central vermont and north central massachusetts have strikingly similar total distributions of fias in garnet porphyroblasts that show a somewhat inverse relationship to those observed in the chester athens dome area of se vermont that separates them that is the number of samples containing the first formed fia set is greatest for the two regions lying furthest apart and decreases in younger sets whereas the number of samples containing the first fia set is the least in the central region and increases for more recently developed sets partitioning of deformation into zones of progressive shearing and shortening has been demonstrated to control the sites of development of differentiated crenulation cleavage versus porphyroblast growth and sites of porphyroblast growth on one limb of a regional fold versus the other we argue that partitioning of the deformation around competent feldspathic gneiss bodies at an orogen scale produced the variation in the number of samples containing the various fia sets between the central and outer areas described above porphyroblasts most commonly grew during sw ne directed shortening to the north and south of the chester athens dome region of the appalachians but only rarely grew in the latter region this suggests that deformation at this time partitioned around an outlier of competent basement feldspathic gneiss that underlies the chester athens dome region and this protected the rocks above and in the strain shadow to the nw and se from the effects of the great bulk of the deformation that occurred over the period of time during which nw se trending fias formed we attribute the increase in the number of samples containing progressively younger fias in the chester athens dome area during subsequent periods of nw se n s wsw ene and wnw ese directed shortening to the rise in temperature and pressure recorded in the rocks above the chester athens dome with peak conditions occurring during the development of the nnw sse oriented fia set between 404 and 385 ma as the temperature and pressure increased the gneiss below would have become less competent allowing the deformation associated with the succession of fia sets to partition more pervasively through the dome core this provided more sites for porphyroblast nucleation and growth and hence the number of samples recording these fia sets increased the concomitant decrease in the number of samples in which porphyroblasts grew in the rock within the areas to the north and south with successive fias possibly resulted from a progressive increase in competency of these rocks as the number of porphyroblasts increased

scales of disequilibrium and rates of equilibration during metamorphism mounting evidence suggests that partial disequilibrium meaning disequilibrium for some elements but not for others may be a common but rarely detected phenomenon during metamorphic mineral growth even in ordinary prograde reactions that progress to completion detailed examination of compositional variations in garnet crystals over a range of metamorphic grade suggests distinctly different scales of equilibration for common elements with strong temperature dependence under lower greenschist facies conditions fe and mg may equilibrate at hand sample scale whereas mn and ca may not equilibrate even at millimeter scale although mn may achieve hand sample scale equilibration under upper greenschist facies conditions ca and many trivalent cations e g rees may not do so until temperatures exceed those of the middle amphibolite facies even in the lower granulite facies some elements e g y yb show indications of disequilibrium at sub centimeter scales during garnet growth analysis and numerical modeling of undisputed disequilibrium textures demonstrate that the most common impediment to equilibration during metamorphism is the sluggishness of intergranular diffusion the same mechanism known to govern porphyroblast crystallization in many metamorphic environments despite this importance to petrology few quantitative determinations exist of inter granular diffusion rates under metamorphic conditions using numerical simulations of coupled intergranular and intracrystalline diffusion processes in coronal textures around partially resorbed garnet crystals from the llano uplift u s a a very precise and relatively accurate estimate is obtained for the rate of intergranular diffusion of al in fluid undersaturated systems this result and an earlier estimate for fluid saturated systems provide bracketing values for al diffusivity during metamorphism

an emergent strategy for volcano hazard assessment from thermal satellite monitoring to lava flow modeling abstract spaceborne remote sensing techniques and numerical simulations have been combined in a web gis framework lav hazard to evaluate lava flow hazard in real time by using the hotsat satellite thermal monitoring system to estimate time varying tadr time averaged discharge rate and the magflow physics based model to simulate lava flow paths the lav hazard platform allows timely definition of parameters and maps essential for hazard assessment including the propagation time of lava flows and the maximum run out distance we used lav hazard during the 2008 2009 lava flow forming eruption at mt etna sicily italy we measured the temporal variation in thermal emission up to four times per hour during the entire duration of the eruption using seviri and modis data the time series of radiative power allowed us to identify six diverse thermal phases each related to different dynamic volcanic processes and associated with different tadrs and lava flow emplacement conditions satellite derived estimates of lava discharge rates were computed and integrated for the whole period of the eruption almost 14 months showing that a lava volume of between 32 and 61 million cubic meters was erupted of which about 2 3 was emplaced during the first 4 months these time varying discharge rates were then used to drive magflow simulations to chart the spread of lava as a function of time tadrs were sufficiently low 3 s that no lava flows were capable of flowing any great distance so that they did not pose a hazard to vulnerable agricultural and urban areas on the flanks of etna

analysis of volcanic activity patterns using modis thermal alerts we investigate eruptive activity by analysis of thermal alert data from the modis moderate resolution imaging spectrometer thermal infrared satellite instrument detected by the modvolc modis volcano alert algorithm these data are openly available on the internet and easy to use we show how such data can plug major gaps in the conventional monitoring record of volcanoes in an otherwise generally poorly documented region melanesia including characterising the mechanism of lava effusion at pago demonstrating an earlier than realised onset of lava effusion at lopevi extending the known period of lava lake activity at ambrym and confirming ongoing activity at bagana langila and tinakula we also add to the record of activity even at some generally better monitored volcanoes in indonesia but point out that care must be taken to recognise and exclude fires