franciscan subduction off to a slow start evidence from high precision lu hf garnet ages on high grade blocks lu hf analyses of garnet from metabasic amphibolite glaucophane schist and eclogite facies blocks from the franciscan complex give highly precise ages that allow us to place new constraints on the early thermal history of the franciscan subduction zone garnets yield 176 lu 177 hf ratios ranging from 1 5 to 28 with the highest ratios from garnets with high spessartine pyrope ratio sulphuric acid leaching sal of garnets revealed the presence of inclusions with significantly higher lu hf ratios than those of garnet itself most likely apatite their removal by sal brings the 176 lu 177 hf ratios in garnets down by as much as 40 this suggests that 176 lu 177 hf ratios of apparently pure garnets can be greatly overestimated due to the presence of such inclusions sm nd garnet analyses were dominated by inclusions mainly sphene and failed to provide precise and accurate age information the oldest lu hf ages are 168 7f0 8 and 162 5f0 5 ma on plagioclase bearing garnet amphibolite from panoche pass and the berkeley hills respectively which suggests initiation of the subduction zone at about 169 ma coeval with the formation of the tectonically overlying coast range ophiolite relatively high temperature conditions persisted for about 14 ma as indicated by 153 4f0 8 ma garnet growth recorded in epidote amphibolite and 157 9f0 7 in eclogite from ring mountain and jenner respectively a 146 7f0 7 ma age was obtained from garnet glacuophane schist metamorphosed at around 400 jc the sequence of ages from central and northern california shows a younging trend with decreasing metamorphic grade which supports previous suggestions that the high grade metamorphic blocks and slices resulted from progressive underthrusting and underplating in a cooling subduction system combining geothermometry with geochronological data allow us to estimate cooling rate along the subduction zone interface from amphibolite to blueschist facies conditions as ca 15 jc ma the thermal history requires high initial geothermal gradients within both the footwall and the hangingwall of the subduction zone and a relatively slow subduction rate of the order of 10 km ma during the initial stages of franciscan subduction such conditions are consistent with initiation of the subduction zone at or close to an oceanic spreading centre the data also suggest slow exhumation rates and significant residence time at depth of the earliest franciscan rocks

interplay between subduction retreat and lateral extrusion tectonics of the western carpathians 1 analysis of brittle microstructures reveals three tertiary deformation events in the western carpathians 1 late paleogene bedding parallel extension 2 oligocene to middle miocene nne ssw compression and ese wnw extension 3 post mid miocene nw se extension these regional deformations applied to crustal blocks in the intra carpathian region resulted from forces which were induced by the coupled plate tectonic processes of subduction retreat beneath the carpathian arc and lateral extrusion from the eastern alps toward the carpathian region material flow from the alps spread toward east and ne guided by sinistral strike slip zones along the ne trending continental margin subduction retreat was terminated by mid miocene soft collision of the inner western carpathians with the european foreland ongoing subduction retreat beneath the eastern carpathians caused post mid miocene back arc extension forming the pannonian basin extension spread into the western carpathians by reactivating the extrusion related strike slip faults as normal faults

simulated effect of soil depth and bedrock topography on near surface hydrologic response and slope stability this paper explores the effect of hillslope hydrological behavior on slope stability in the context of transient subsurface saturation development and landslide triggering we perform a series of virtual experiments to address how subsurface topography affects the location and spatial pattern of slip surface development and pore pressure dynamics we use a 3d darcy richards equation solver hydrus 3 d combined with a cellular automata slope stability model to simulate the spatial propagation of the destabilized area our results showed that the soil bedrock interface and in particular bedrock depressions played a key role in pore pressure dynamics acting as an impedance for the downslope drainage of perched water filling and spilling of depressions in the bedrock surface microtopography induced localized zones of increased pressure head such that the development of pore pressure fields not predictable by surface topography lead to rapid landslide propagation our work suggests that landslide models should consider the subsurface topography in order to include a connectivity component in the mathematical description of hydrological processes operating at the hillslope scale copyright 2012 john wiley sons ltd

post collisional tertiary quaternary mafic alkalic magmatism in the carpathian pannonian region a review mafic alkalic volcanism was widespread in the carpathian pannonian region cpr between 11 and 0 2 ma it followed the miocene continental collision of the alcapa and tisia blocks with the european plate as subduction related calc alkaline magmatism was waning several groups of mafic alkalic rocks from different regions within the cpr have been distinguished on the basis of ages and or trace element compositions their trace element and sr nd pb isotope systematics are consistent with derivation from complex mantle source regions which included both depleted asthenosphere and metasomatized lithosphere the mixing of dmm himu emii mantle components within asthenosphere derived magmas indicates variable contamination of the shallow asthenosphere and or thermal boundary layer of the lithosphere by a himu like component prior to and following the introduction of subduction components various mantle sources have been identified lower lithospheric mantle modified by several ancient asthenospheric enrichments source a young asthenospheric plumes with oib like trace element signatures that are either isotopically enriched source b or variably depleted source c old upper asthenosphere heterogeneously contaminated by dm himuemii emi components and slightly influenced by miocene subduction related enrichment source d old upper asthenosphere heterogeneously contaminated by dm himu emii components and significantly influenced by miocene subduction related enrichment source e melt generation was initiated either by i finger like young asthenospheric plumes rising to and heating up the base of the lithosphere below the alcapa block or ii decompressional melting of old asthenosphere upwelling to replace any lower lithosphere or heating and melting former subducted slabs the tisia block d 2004 published by elsevier b v

major risk from rapid large volume landslides in europe eu project runout abstract project runout has investigated methods for reducing the risk from large volume landslides in europe especially those involving rapid rates of emplacement using field data from five test sites bad goisern and kofels in austria tessina and vajont in italy and the barranco de tirajana in gran canaria spain the studies have developed 1 techniques for applying geomorphological investigations and optical remote sensing to map landslides and their evolution 2 analytical numerical and cellular automata models for the emplacement of sturzstroms and debris flows 3 a brittle failure model for forecasting catastrophic slope failure 4 new strategies for integrating large area global positioning system gps arrays with local geodetic monitoring networks 5 methods for raising public awareness of landslide hazards and 6 geographic information system gis based databases for the test areas the results highlight the importance of multidisciplinary studies of landslide hazards combining subjects as diverse as geology and geomorphology remote sensing geodesy fluid dynamics and social profiling they have also identified key goals for an improved understanding of the physical processes that govern landslide collapse and runout as well as for designing strategies for raising public awareness of landslide hazards and for implementing appropriate land management policies for reducing landslide risk

assessing mutuality of change in soil and vegetation patch pattern characteristics by means of cellular automata simulation mutual variations in soil and vegetation pattern characteristics have not received much attention despite their role in the evolution of eco geomorphic systems five landscape metrics were employed to characterize complementary soil and vegetation patterns of patches over a wide range of densities number density size heterogeneity shape and dominance these metrics were calculated for a large number of modeled patterns based on a cellular automata technique employing four separate vegetation spread strategies at different adhesive growth levels as indicated by the data mutual variations in the soil and vegetation metrics allow differentiation between the pattern evolution stages such as perforation dissection fragmentation shrinkage and attrition of one surface type due to the spread expansion and aggregation of a complementary surface type such information may be indicative of the hydro geomorphological processes taking place

potassium rich magmatism in the western outer carpathians magmagenesis in the transitional zone between the european plate and carpathian pannonian region abstract miocene igneous rocks of the western outer carpathians in poland and moravia czech republic were emplaced in a tectonic setting transitional between the european foreland and the carpathian pannonian arc system they form medium to high k calc alkaline suites which are compositionally different to each other and to other calc alkaline sequences in the region geographically and compositionally the moravia rocks can be seen as transitional between the rift related alkaline magmatism of the foreland and the dominantly calc alkaline magmatism of the carpathian pannonian region certain moravia rocks are unusually enriched in incompatible trace elements e g nb 122 ppm and th 31 ppm the primary magmas of both suites were formed in metasomatised lithosphere mantle of the european plate but the enrichment mechanism differed in poland it was by ancient subduction related events whereas in moravia metasomatism was mainly by melts and or fluids from deeper mantle sources partial melting was promoted by impingement of rising asthenosphere on the base of the lithosphere possibly related to reactivation of trans lithospheric nw se trending fault zones

geochemistry and tectonic development of cenozoic magmatism in the carpathian pannonian region this review considers the magmatic processes in the carpathian pannonian region cpr from early miocene to recent times as well as the contemporaneous magmatism at its southern boundary in the dinaride and balkans regions this geodynamic system was controlled by the cretaceous to neogene subduction and collision of africa with eurasia especially by adria that generated the alps to the north the dinaride hellenide belt to the east and caused extrusion collision and inversion tectonics in the cpr this long lived subduction system supplied the mantle lithosphere with various subduction components the cpr contains magmatic rocks of highly diverse compositions calc alkaline k alkalic ultrapotassic and na alkalic all generated in response to complex post collisional tectonic processes these processes formed extensional basins in response to an interplay of compression and extension within two microplates alcapa and tisza dacia competition between the different tectonic processes at both local and regional scales caused variations in the associated magmatism mainly as a result of extension and differences in the rheological properties and composition of the lithosphere extension led to disintegration of the microplates that finally developed into two basin systems the pannonian and transylvanian basins the southern border of the cpr is edged by the adria microplate via sava and vardar zones that acted as regional transcurrent tectonic areas during miocene recent times major trace element and isotopic data of post early miocene magmatic rocks from the cpr suggest that subduction components were preserved in the lithospheric mantle after the cretaceous miocene subduction and were reactivated especially by extensional tectonic processes that allowed uprise of the asthenosphere changes in the composition of the mantle through time support geodynamic scenarios of post collision and extension processes linked to the evolution of the main blocks and their boundary relations weak lithospheric blocks i e alcapa and western tisza generated the pannonian basin and the adjacent styrian transdanubian and z rand basins which show high rates of vertical movement accompanied by a range of magmatic compositions strong lithospheric blocks i e dacia were only marginally deformed where strike slip faulting was associated with magmatism and extension at the boundary of adria and tisza dacia strike slip tectonics and core complex extension were associated with small volume miocene magmatism in narrow extensional sedimentary basins or granitoids in core complex detachment systems along older suture zones sava and vardar accommodating the extension in the pannonian basin and afterward pliocene quaternary inversion magmas of various compositions appear to have acted as lubricants in a range of tectonic processes

strontium isotope composition of middle miocene primary gypsum badenian of the polish carpathian foredeep basin evidence for continual non marine inflow of radiogenic strontium into evaporite basin strontium isotope compositions of ancient sulphate deposits not only provide chemostratigraphic information but also offer insight into the system in which the evaporites precipitated primary gypsum from two middle miocene badenian sections in southern poland shows steadily higher 87sr 86sr ratios than those expected from a marine derived formation the ratios are interpreted as the result of increasing inflow into the basin at the time of gypsum precipitation palaeogeographic reconstructions suggest that riverine runoff sources were situated in the west and east european platforms to the north and east respectively and the carpathians to the south which are mostly composed of mesozoic sedimentary rocks their dissolution cannot be responsible for the higher 87sr 86sr ratios recorded we conclude that archaean and palaeoproterozoic igneous and supracrustal rocks of the ukrainian shield were the source of the higher 87sr 86sr ratios recorded in the badenian primary gypsum a distinctive decreasing trend of 87sr 86sr ratios from western ukraine to southern poland is explained by a consistent direction of brine inflow during gypsum crystallization typical cyclonic circulation controlled by the coriolis effect

the pieniny klippen belt in the western carpathians of northeastern slovakia structural evidence for transpression abstract the pieniny klippen belt represents a 600 km long but only a few kilometers wide suture zone in the carpathian orogenic belt based on a quantitative analysis along a part of its nw trending segment in northeastern slovakia we present structural data supporting transpression the continuous interaction of strike slip shearing horizontal shortening and vertical lengthening as a major deformation style in its polyphase deformation history dextral transpression is expressed in the map scale and outcrop fault pattern the oblique orientation of fold axes to the faults bounding the klippen belt and extension parallel to the fold axes the transpression related strain field is described and quantified by the analysis of 1 orientation of rotated fold axes displaying an acute angle to the margins of the klippen belt 2 orientation and geometry of paleostress derived from mesoscale fault striae analysis e trend of 3 trajectories and flattening geometry and 3 the deformation history indicated by extension veins non coaxial regime different techniques using fault striae data quantify paleostress and subdivide heterogeneous data sets mathematically into homogeneous subsets the observed deformation history is modelled as a homogeneous transpression deformation the best fitting model requires a nw trending present day orientation external contraction direction e g plate slip vector and predicts 16 fold axes parallel extension and 23 axial plane normal shortening

dating of detrital zircons and tracing the provenance of quartzites from the bystrzyckie mts implications for the tectonic setting of the early palaeozoic sedimentary basin developed on the gondwana margin we studied the petrographical characteristics and bulk chemical composition along with the age of detrital zircon grains from quartzites exposed in the western part of the orlica nieznik dome in the saxothuringian zone age spectra of detrital zircons were obtained by u pb laser ablation inductively coupled plasma mass spectrometry dating the zircon ages define a few clusters of which the most numerous are cambro ordovician and neoproterozoic and less frequent are paleoproterozoic and archean a distinctive feature of the investigated samples is the lack of mesoproterozoic zircon grains the youngest age cluster documented in the investigated quartzites points to a late cambrian maximum depositional age and detritus derivation from erosion of cambro ordovician metagranitoids bulk chemical composition of the quartzites indicates that they originated owing to erosion of granite within sedimentary basins developed on a passive continental margin presented data prove the similarity of the examined rocks to quartzites known from the eastern part of the orlica nieznik dome and quartz metasandstones documented in other parts of the variscan belt of europe known as the armorican quartzites or their equivalents exposed in the saxothuringian zone our results support the suggestion that the orlica nieznik dome has an affinity to the west african craton of the gondwana margin and represents a fragment of the saxothuringian zone

neogene quaternary magmatism and geodynamics in the carpathian pannonian region a synthesis in the carpathian pannonian region in neogene times westward dipping subduction in a land locked basin caused collision of two lithospheric blocks alcapa and tisia with the southeastern border of the european plate calc alkaline and alkaline magmatism was closely related to subduction rollback collision and extension from the spatial distribution of the magmatic activity four segments can be defined western segment magmatism occurring on the alcapa block central segment magmatism occurring on both alcapa and the tisia blocks south eastern segment and interior segment both on the tisia block most calc alkaline magmatism in the region resulted from melting of a heterogeneous asthenospheric mantle source modified by addition of fluids and sediment assimilation and fractionation processes at shallow crustal levels occurred in most of the segments strongly masking the deeper source processes long term subduction rollback and or delamination led to contamination of the asthenosphere beneath the western segment here large volume partial melts of the contaminated mantle caused underplating and crustal anatexis leading to mixing of mantle derived calc alkaline magmas with crustal melts in the central segment calc alkaline magmas were formed by subduction and rollback followed by back arc extension and slab breakoff avariable mantle source is indicated in the back arc setting and larger amount of fluid induced metasomatism source enrichment and assimilation nearer to the trench in the interior segment evolution from typical calc alkaline magmas to adakite like ones was related to extension due to fast rotations and transtensional tectonics here calc alkaline magmas formed by decompression melting of a heterogeneous crust mantle lithosphere while adakite like melts resulted from fliud dominated melting of the lithosphere along the south eastern segment slab breakoff was responsible for the generation of typical calcalkaline magmas but in the extreme south of the segment shallow level tearing of the slab followed breakoff strike slip tectonics allowed the rise of hot asthenosphere and generation of adakite like magmas via slab melting along the torn edge of the east european plate alkalic basaltic volcanism with an oib like asthenosphere source followed the calc alkaline stage

late cretaceous deformation of the pieniny klippen belt west carpathians abstract the late cretaceous position and dynamics of the pieniny klippen belt of the west carpathians which lies behind the palaeogene flysch accretionary prism are reconstructed as shown by the reconstruction based on structural sedimentological and palaeomagnetic data the pieniny klippen belt occupied a wnw ese to nw se trending zone during the late cretaceous which acted as an oblique convergent boundary between the ancestral west carpathians and the oceanic lithosphere attached to the north european platform sediments of the pieniny klippen belt were part of both the mountain belt and foredeep at that time known change from pelagic micritic limestone to a flysch sequence is progressively younger seawards in the thrust slice stack forming the pieniny klippen belt the syn sedimentary record includes flysch olistostrome and wildflysch sediments both the nw se thrusting along the ne sw striking faults and dextral strike slip faulting along the wnw ese to nw se striking faults were active in the late cretaceous in the area of the current pieniny klippen belt

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

gis based cell model for simulating debris flow runout on a fan summary a gis based cell model based on a kinematic approach is proposed to simulate debris flow routing on a fan the sediment water mixture is modeled as a monophasic continuum and the flow pattern is discretized by square cells 1 m in size that coincide with the dem cells flow occurs from cells with a higher mixture free surface to those with a lower mixture free surface a uniform flow law is used if the elevation of the former cell is higher than that of the latter otherwise the flow is simulated using the broad crested weir law erosion and deposition are simulated using an empirical law that is adjusted for a monophasic continuum the sediment concentration in the routing volume is computed at each time step and controls both erosion and deposition the cell model is used to simulate a debris flow that occurred on the rio lazer dolomites north eastern italian alps on november 4th 1966 furthermore the hydrologic and the hydraulic conditions for the initiation of debris flow are simulated providing the solid liquid hydrograph of the resulting debris flow a number of simulations has been carried out with physically reasonable parameters the results are compared with the extension of the debris flow deposition area and the map of observed depths of deposited sediments this comparison shows that the proposed model provides good performance the analysis of sensitivity carried out by systematically varying the model parameters shows that lower performances are associated with parameter values that are not physically reasonable the same event is also simulated using a cellular automata model and a finite volume two dimensional model the results show that the two models provide a sediment deposition pattern less accurate than that provided by the present cell model

cellular automata as analysis and synthesis engines at the geomorphology ecology interface abstract the linkages between ecology and geomorphology can be difficult to identify because of physical complexity and the limitations of the current theoretical representations in these two fields of study deep divisions between these disciplines are manifest in the methods used to simulate process such as rigidly physical deterministic methods for many aspects of geomorphology compared with purely stochastic simulations in many models of change in landcover practical and theoretical research into ecology geomorphology linkages cannot wait for a single simulation schema which may never come as a result studies of these linkages often appear disjointed and inconsistent the grid based simulation framework for cellular automata ca allows simultaneous use of competing schemas ca use in general geographic studies has been primarily limited to urban simulations models of change for land cover both highly stochastic and or expert rule based in the last decade however methods for describing physically deterministic systems in the ca framework have become much more accurate the possibility now exists to merge separate ca simulations of different environmental systems into unified multiautomata models because cas allow transition rules that are deterministic probabilistic or expert rule based they can immediately incorporate the existing knowledge rules in ecology and geomorphology the explicitly spatial nature of ca provides a map like framework that should allow a simple and deeply rooted connection with the mapping traditions of the geosciences and ecological sciences

burial and exhumation history of the polish outer carpathians discriminating the role of thrusting and post thrusting extension abstract several tectonic processes have been proposed to be important in the alpine to the recent evolution of the polish outer carpathians i e paleogene neogene thrusting post thrusting extension quaternary reactivation of compression this work tests the effect of these processes on exhumation of the wedge in order to verify their timing and relative role in shaping the polish outer carpathians aft ahe and zhe analyses were performed on samples collected along the study region this allowed the reconstruction of their post depositional minimum heating depth of burial and timing of cooling and exhumation after deposition samples from the innermost units were heated up to temperatures of ca 60 120 c ca 4 9 km whereas samples from the outer units were heated to temperatures lower than 60 c ca 4 km cooling and exhumation occurred progressively later from west to east between ca 25 and 10 ma in the western sector between ca 15 and 5 ma in the eastern sector these results have been put in relationship with single structural features to understand the relative role of thrusts and normal faults in the eastern sector of the study region samples at the footwall of significant normal faults show a higher degree of reset and younger ages than samples located at the hangingwall this implies that in this sector extensional tectonics played an important role in exhumation however proper tectonic exhumation only had a minor role the major exhumation mechanism being erosion which is enhanced in the footwalls and reduced in the hangingwalls in the western sector of the polish outer carpathians only in few cases evidence of enhanced erosion to the footwall of major normal faults could be observed based on the present data in this region the wedge exhumed mainly as a response to thrusting and normal faulting only played a minor role locally modifying the pattern of erosion finally no major exhumation events occurred after miocene pointing to a minor relevance of recent compression unreset zhe dates were used to estimate exhumation of source rocks through the zhe prz and to outline the provenance of sediments forming the polish outer carpathians exhumation occurred both in response to the variscan late devonian to triassic and alpine late jurassic to early paleocene orogeneses suggesting sedimentary provenance both from the southern margin and from the basement heights within the outer carpathian basin

the early paleozoic huangtupo vms cu zn deposit in kalatag eastern tianshan implications from geochemistry and zircon u pb geochronology of volcanic host rocks abstract the tianshan in china forms the southern part of the central asian orogenic belt caob and also hosts important polymetallic resources here we investigate the huangtupo medium size copper zinc deposit located in the central part of the kalatag copper polymetallic belt with a view to evaluate the nature and genesis of the early paleozoic volcanogenic massive sulfide vms cu zn deposits this deposit is correlated to intermediate felsic volcano sedimentary sequences of the early paleozoic daliugou formation which are mainly composed of andesite dacite and rhyolite with minor basalt as well as their pyroclastic equivalents the ore bodies are hosted in the contact zone between andesitic volcanic breccia and tuff representing an eruptive hiatus between the two volcanic cycles with massive sulphide lens at the top and stockwork zone at lower part of the daliugou formation we report new zircon u pb data major and trace element geochemistry and sr nd isotopes from the andesite dacite and andesitic tuff in the huangtupo deposit zircon from the dacite and the andesite occurring above the ore bodies yield and age of 440 1 1 2 ma and 439 7 0 95 ma and that from the andesitic tuff in footwall shows and age of 442 0 1 1 ma all samples show typical geochemical signatures of subduction related calc alkaline magmas with slight enrichment in lile and lree but depletion in nb and ti content relative to primitive mantle the andesites are characterized by high mgo 7 6 10 8 wt contents and mg values 64 72 with low sr y and la yb ratios belonging to sanukite both dacite and tuff have low mgo

comagmatic granophyre and dacite from karymsky volcanic center kamchatka experimental constraints for magma storage conditions abstract despite a 30 000 years difference in age two caldera forming eruptions at karymsky volcanic center kamchatka karymsky 7900 yr bp and academy nauk ca 40 000 yr bp produced two pyroxene dacites with the same composition and mineralogy granophyric xenoliths of the identical whole rock chemistry were found in basalts erupted within academy nauk caldera in 1996 unlike the dacites however the granophyres are holo crystalline and contain biotite and amphibole large amphibole phenocrysts contain rare inclusions of clinopyroxenes which compositionally overlap with clinopyroxenes in the dacites the al content of the amphibole suggests it grew at a pressure of about 100 mpa results of hydrothermal experiments and petrologic observations indicate that academy nauk and karymsky dacites were last equilibrated at 883 19 c 100 15 mpa and 871 19 c 85 18 mpa respectively both at water saturated conditions the mineral assemblage of granophyre is reproduced by isobaric crystallization of the dacite at 100 mpa implying that the granophyres were sampled from the crystallized silicic reservoir that produced the caldera forming eruption of academy nauk similar chemical compositions of karymsky and academy nauk dacites indicate that both were derived from the same crustal level source the eruptive history of the calderas can best be explained by two 10 12 km 3 dacitic batches that detached from a parental body situated in the lower crust then ascended to 3 4 km depth re equilibrated and erupted

hf nd isotopic evolution of the lower crust we report hf isotopic data for over 50 well studied lower crustal samples from three proterozoic and phanerozoic regions in southwest europe eastern australia and southern mexico we use these data to characterize the lu hf isotopic composition of the lower crust and in combination with existing sm nd data to constrain coupled hf nd isotopic behavior and evolution within this reservoir although most of these samples have present day parent daughter p d ratios consistent with hf nd evolution within the terrestrial hf nd array some samples have divergent p d ratios that would evolve out of the terrestrial array in 1 ga or less the present day 176hf 177hf and 143nd 144nd isotopic compositions of all samples with one lone exception plot within the terrestrial array this indicates that 1 some present day p d ratios may be a relatively recently acquired characteristic through magmatic or metamorphic processes not related to the time integrated sm nd and lu hf ratios of their sources and or 2 the lu hf and sm nd p d variations exist on a small hand size scale but not necessarily on a larger scale the lower crust from this initial data set is broadly similar to the upper crust in terms of both its present day p d values and time integrated lu hf and sm nd evolution as a result the lower crust appears to have a hf and nd isotopic composition similar to that of all other crust and mantle reservoirs so far characterized

calcic cores of plagioclase phenocrysts in andesite from karymsky volcano evidence for rapid introduction by basaltic replenishment calcic cores in plagioclase of karymsky andesite of the 1996 2000 eruptive cycle texturally and compositionally both trace and major elements mimic the plagioclase phenocrysts of basalt erupted 6 km away at the onset of the cycle these observations support the view that simultaneous eruption of andesite and basalt at karymsky in the beginning of the cycle represents an example of replenishment and eruption triggering of an andesitic reservoir homogeneity of andesitic output occurred within two months this suggests to us that blending of injected basalt into reservoir magma was thorough and rapid

u pb zircon geochronology and anomalous sr nd hf isotope systematics of late orogenic andesites pieniny klippen belt western carpathians south poland abstract late orogenic andesites and basaltic andesites in the pieniny klippen belt pkb in the western carpathians display atypical isotope systematics strongly departing from those observed among other neogene quaternary calc alkaline rocks in the carpathian pannonian region low end values 10 6 to 5 2 and low ehf values 19 6 to 5 2 are accompanied by unusually low 87 sr 86 sr ratios 0 7052 to 0 7059 major trace element isotope and geochronological data presented in this study indicate two magma sources evolving with low rb sr ratio from which the pkb calc alkaline rocks originated basaltic andesites showing less enriched signature and wider range of isotope compositions end 7 7 to 5 2 ehf 11 3 to 5 2 and 87 sr 86 sr 0 7052 0 7059 are interpreted as having originated from the partial melts derived from an ancient metasomatized sub continental lithospheric mantle which during emplacement were contaminated by the upper crustal material andesites whose precise timing of emplacement was constrained by in situ la icp ms u pb zircon dating at 11 2 0 2 to 12 1 0 3 ma show more enriched signature and narrow range of nd and hf isotope compositions end 10 6 to 10 1 ehf 19 6 to 18 3 accompanied by low 87 sr 86 sr 0 70531 0 70541 u pb dating of the inherited domains in zircons revealed the presence of late paleozoic precambrian and archean age components which support crustal origin of the pkb andesites in situ hf isotope analyses of zircons suggest that andesites could have been derived from enriched initial ehf 13 to 10 permian igneous domains in the lower crust generation of the calc alkaline magmas in the upper lithospheric mantle and in the thickened crust was triggered by decompression or crustal delamination following middle miocene collision of the alcapa block with southern margin of the european platform the pkb fault zone and its splays acted as conduits which enabled ascent of small volumes of andesitic magmas into the upper crust of the western carpathians

comment on evidence for long residence times of rhyolitic magma in the long valley magmatic system the isotopic record in precaldera lavas of glass mountain by a n halliday g a mahood p holden j m metz t j dempster and j p davidson comment and replies on the paper of a n halliday g a mahood p holden j m metz t j dempster and j p davidson 1989 earth planet sci lett 94 274 290

comagmatic a type granophyre and rhyolite from the alid volcanic center eritrea northeast africa vermicular to cuneiform barker 1970 typically the granophyric blocks within late pleistocene pyroclastic flow ejecta from the alid volcanic center northeast africa are the rapidly groundmass feldspars radiate off pre existing feldspar crystallized intrusive equivalent of pumice from the pyroclastic flow phenocrysts with which they are in optical continuity phenocryst compositions and geochemical characteristics of the dunham 1965 some workers prefer the term pumice and granophyre are virtually identical silicate melt inclusions micrographic for highly regular interlocking arand other geochemical and geological constraints reveal those processes rangements of quartz and feldspar as in the coarser leading to development of the granophyric texture rhyolitic agraphic granite fenn 1986 lentz fowler 1992 type magma with 2 6 wt dissolved h2o and a temperature though schloemer 1964 has shown that some graphic near 870 c was intruded to within 2 4 km of the surface causing textures can grow by replacement see also augustithis deformation and structural doming of shallow marine and subaerial 1973 most workers agree that phenocryst bearing strata eruptions of crystal poor rhyolite from this shallow magma granophyres typically form by rapid and simultaneous chamber caused degassing which forced undercooling and consequent crystallization of quartz and feldspar from a melt smith granophyric crystallization of some of the magma remaining in the 1974 such crystallization is generally believed to be due intrusion the most recent eruption from alid excavated the cryto pronounced undercooling of the silicate liquid vogt stallized granitic wall of the magma chamber bringing the grano1930 dunham 1965 not necessarily at eutectic temphyric clasts to the surface peratures or compositions fenn 1986 london et al 1989 lentz fowler 1992 granophyric textures are common in epizonal granitic bodies particularly those associated with volcanic rocks buddington 1959 dunham 1965 on occasion they erupt as comagmatic ejecta in pyroclastic deposits e g

cummingtonite and the evolution of the mount st helens washington magma system an experimental study hydrothermal experiments have been conducted on the 3 5 ka cummingtonite bearing yn tephra from mount st helens washington to determine the stability field of cummingtonite in volcanic rocks and to gather additional data on the evolutionary history of the mount st helens magmatic system cummingtonite is not stable in experiments conducted at or above 810 c at pressures 2 o analyses of melt inclusions that yield preeruption melt h 2 o contents of 6 4 wt the yn tephra belongs to a series of cummingtonite bearing dacites that erupted early in the history of mount st helens these early dacites have relatively homogeneous compositions and are characterized by low temperature 800 c high water pressure and high oxygen fugacity nno 1 phenocryst crystallization silicic magmas that erupted after eruption of basaltic andesite at mount st helens 2 3 ka are more heterogeneous in composition and last equilibrated under higher temperatures 900 c lower water pressures and lower oxygen fugacities than the early dacites these changes in the magma chamber conditions appear to have been related to the intrusion of mafic magma into an upper crustal dacitic magma chamber

phase equilibria constraints on pre eruptive magma storage conditions for the 1956 eruption of bezymianny volcano kamchatka russia abstract phase equilibria experiments were performed on andesites from the catastrophic 1956 eruption of bezymianny volcano kamchatka russia to determine pre eruptive magma storage conditions fifteen experiments were conducted under water saturated conditions with oxygen fugacity equal to the ni nio oxygen buffer at temperatures between 775 and 1100 c and pressures between 50 and 200 mpa simultaneous amphibole and plagioclase crystallization is reproduced at 850 c and 200 mpa the simultaneous crystallization temperature range of the plagioclase clinopyroxene orthopyroxene fe ti oxide assemblage increases with decreasing pressure from 840 to 940 c at 150 mpa to 940 1020 c at 50 mpa melt inclusion compositions in plagioclase phenocrysts and matrix glass match experimental melt compositions reproduced at 50 100 mpa and 50 mpa respectively presence of the silica phase in groundmass and mature amphibole breakdown rims suggests that magma has been stored at ca 3 km depth prior to the final ascent for at least 40 days syn eruptive ascent led to decompression driven crystallization which caused a temperature increase from 850 900 c to 950 1000 c

paleoenvironmental conditions source and maturation of neogene organic matter from the siliciclastic deposits of the orava nowy targ basin abstract the orava nowy targ basin ontb is an intramontane depression filled with neogene and quaternary deposits located at the junction of the inner and outer carpathians the neogene infill of the basin consists mainly of siliciclastic rocks with very common lignite intercalations and is mostly of fluvial or lake origin the organic matter molecular analysis of seventeen neogene samples confirmed the terrigenous origin of organic matter with a predominance of higher plant input in most samples based on the distribution of n alkanes and steranes as well as the presence of tri and tetracyclic diterpenoids and triterpenoids representing oleanane ursane lupane chrysene and picene derivatives high concentrations of compounds originating from both angiosperms and gymnosperms suggest the presence of mixed forests additionally important input of mosses into the primary organic matter is indicated by the high concentration of n c 23 and presence of hop 17 21 enes in most samples a high average aromatic ring and conifer wood degradation index 0 7 indicate high activity of bacteria and wood degrading fungi in the sedimentary environment there was no evidence of weathering and scarce signs of biodegradation were identified all samples were subjected to water washing huminite reflectance and biomarker based parameters as well as the presence of unsaturated pentacyclic triterpenoids and steroids indicate an immature organic matter a trend of decreasing maturation of sediments from east to the west was observed as was a similarity of thermal maturity between the podhale synclinorium and the ontb although the latter seems to be coincidental a thermal gradient value of 35 c km was assumed for calculating the maximum thickness of eroded strata resulting in 1 1 6 km for the se area and a maximum temperature of the deepest buried samples equal to 45 65 c

tectonic significance of changes in post subduction pliocene quaternary magmatism in the south east part of the carpathian pannonian region the south eastern part of the carpathian pannonian region records the cessation of convergence between the european platform moesia and the tisza dacia microplate plio quaternary magmatic activity in this area in close proximity to the vrancea zone shows a shift from normal calc alkaline to much more diverse compositions adakite like calc alkaline k alkalic mafic na alkalic and ultrapotassic suggesting a significant change in geodynamic processes at approximately 3 ma we review the tectonic setting timing petrology and geochemistry of the post collisional volcanism to constrain the role of orogenic building processes such as subduction or collision on melt production and migration the calc alkaline volcanism 5 3 3 9 ma marks the end of normal subduction related magmatism along the post collisional c limani gurghiu harghita volcanic chain in front of the european convergent plate margin at ca 3 ma in south harghita magma compositions changed to adakite like calc alkaline and continued until recent times 0 03 ma interrupted at 1 6 1 2 ma by generation of na and k alkalic magmas signifying changes in the source and melting mechanism we attribute the changes in magma composition in front of the moesian platform to two main geodynamic events 1 slab pull and steepening with opening of a tear window adakite like calc alkaline magmas and 2 renewed contraction associated with deep mantle processes such as slab steepening during post collisional times na and k alkalic magmas contemporaneous post collisional volcanism at the eastern edge of the pannonian basin at 2 6 1 3 ma was dominated by na alkalic and ultrapotassic magmas suggesting a close relationship with thermal asthenospheric doming and strain partitioning related to the adriatic indentation similar timing magma chamber processes and volume for k alkalic shoshonitic magmas in the south apuseni mountains 1 6 ma and south harghita area at a distance of ca 200 km imply a regional connection with the inversion tectonics

eruptive history of karymsky volcano kamchatka ussr based on tephra stratigraphy and 14c dating eruptions of the active karymsky stratovolcano began about 5300 6100 14c b p from within a pre existing caldera which formed 7700 14c b p as indicated by 32 14c determinations on buried soils and charcoal the volcano has gone through two major cycles of activity separated by a 2300 year period of repose the first cycle can be divided into two stages 6100 5100 and 4300 2800 b p the earlier stage began with especially intense eruptions of basaltic andesite to dacite the later stage was characterized by moderate strength eruptions of andesite the second cycle which is characterized by weak to moderate intermittent eruptions of andesite started 500 b p and continues to the present eruptive patterns suggest that this cycle may continue for at least another 200 years with an eruptive character similar to that of the recent past

phases of compression during the evolution of the pannonian basin and its bearing on hydrocarbon exploration abstract progress in understanding the structural evolution of the pannonian basin is reported this has been driven by the application of seismic stratigraphy constrained by magnetostratigraphic data and the recent release of a great amount of hydrocarbon exploration data this has led to a redefinition and better understanding of the syn rift period and style of rifting in addition a complex structural evolution history during the post rift phase has been recognized two compressive events are defined one in the early stage and another in the late stage of evolution the importance of these findings for hydrocarbon exploration includes an improved knowledge of the timing of trap formations and a possible explanation for remarkably variable reservoir pressures in pools of the great hungarian plain

applying genetic algorithms for calibrating a hexagonal cellular automata model for the simulation of debris flows characterised by strong inertial effects abstract in modelling complex a centric phenomena which evolve through local interactions within a discrete time space cellular automata ca represent a valid alternative to standard solution methods based on differential equations flow type phenomena such as lava flows pyroclastic flows earth flows and debris flows can be viewed as a centric dynamical systems and they can therefore be properly investigated in ca terms sciddica s4a is the last release of a two dimensional hexagonal ca model for simulating debris flows characterised by strong inertial effects s4a has been obtained by progressively enriching an initial simplified model originally derived for simulating very simple cases of slow moving flow type landslides using an empirical strategy in s4a the inertial character of the flowing mass is translated into ca terms by means of local rules in particular in the transition function of the model the distribution of landslide debris among the cells is obtained through a double cycle of computation in the first phase the inertial character of the landslide debris is taken into account by considering indicators of momentum in the second phase any remaining debris in the central cell is distributed among the adjacent cells according to the principle of maximum possible equilibrium the complexities of the model and of the phenomena to be simulated suggested the need for an automated technique of evaluation for the determination of the best set of global parameters accordingly the model is calibrated using a genetic algorithm and by considering the may 1998 curti sarno southern italy debris flow the boundaries of the area affected by the debris flow are simulated well with the model errors computed by comparing the simulations with the mapped areal extent of the actual landslide are smaller than those previously obtained without genetic algorithms as the experiments have been realised in a sequential computing environment they could be improved by adopting a parallel environment which allows the performance of a great number of tests in reasonable times

hydrothermal systems of the karymsky volcanic centre kamchatka geochemistry time evolution and solute fluxes abstract karymsky volcanic centre kvc at the middle of the frontal volcanic chain of the kamchatka arc consists of two joined calderas akademii nauk and karymsky volcano and hosts two hydrothermal systems akademii nauk an and karymsky k the an is a typical boiling system with na cl waters tds 1 g l low gas content co2 n2 with deep calculated temperatures of 200 c in contrast springs of the k system have lower temperatures up to 42 c strong gas bubbling tds 2 5 g l and are enriched in hco3 and so42 with mg2 as the main cation there are two intriguing characteristics of the k field i their co2 rich gas 97 mol has the highest 3he 4he ratios ever measured for hydrothermal systems in kamchatka of 8 ra where ra 1 4 10 6 and ii their thermal waters have an unusual cation composition mg na ca after the 1996 sublimnic eruption within an caldera new hot springs appeared close to the eruption site in this paper we synthesize all published and new geochemical data sets the karymsky lake and post 1996 new thermal springs demonstrate exponential decreases in their main dissolved species with a characteristic time of 5 to 8 years the chemistry of an and k springs did not change after the eruption however the concentration of chloride in the lake water approached 35 mg l compared with a background of 8 11 mg l revealing a possible new source of hot water within the karymsky lake all thermal fields of the kvc are drained by the karymsky river with an outflow rate at the source of 2 m3 s flowing out from karymsky lake and at the exit from the karymsky caldera of 4 5 m3 s using the measured solute fluxes at the source an springs and at the exit an k springs the natural heat flux from the two systems can be estimated as 67 mw and 120 mw respectively and 20 t d for the chloride output from both systems

tertiary extension development and extension compression interplay in the west carpathian mountain belt abstract this paper describes palaeostresses calculated from fault striae data the inferred palaeostrain patterns and determines the inter relation of the compression and extension during the tertiary development of the west carpathians the calculated stress and inferred strain patterns for the palaeogene burdigalian indicate that the ancestral west carpathians formed a more or less straight orogenic belt this belt underwent contraction and uplift in its narrow frontal zone stretching along its strike during the paleocene chattian and regional contraction and uplift during the chattian burdigalian the strain stress pattern is similar to the collision related pattern known from the eastern alps for the paleocene burdigalian during the burdigalian tortonian the calculated and inferred west carpathian stress and strain patterns indicate narrow frontal contractional and lateral sinistral transpressional zones in the orogenic front and broad extensional and dextral transtensional zones in the orogenic interior the stress strain pattern is similar to the subduction related pattern known from areas such as the hellenic or sunda banda arcs

experimental constraints on degassing of magma isothermal bubble growth during continuous decompression from high pressure numerical models predict that rapid ascent of hydrous magma can lead to supersaturation of dissolved volatile constituents possibly leading to explosive eruption we have performed controlled decompression experiments to investigate the ascent rates required to maintain bubble melt equilibrium high silica rhyolitic melts were saturated with water at 200 mpa and 825 c decompressed to lower pressures at constant rates of 0 025 0 25 0 5 and 1 0 mpa s 1 and then rapidly quenched isobarically other samples were saturated with water over the pressure range investigated to determine equilibrium water solubility in order to quantify degassing efficiency during decompression at a decompression rate of 0 025 mpa s 1 melt vapor equilibrium was maintained over the entire pressure range examined 200 to 17 5 mpa a single bubble nucleation event occurred in response to decompression and quenched bubble sizes can be modeled by a equilibrium bubble growth model that takes into account the number density of bubbles at decompression rates of 0 25 0 5 and 1 0 mpa s 1 rhyolitic melts could not degas in equilibrium when pressure decreased from 200 mpa to 140 mpa and water supersaturation p in the melt reached up to 60 mpa with higher values at faster decompression rates further pressure release resulted in near equilibrium degassing and p dropped significantly in each case p decreased when bubbles exceeded 10 vol a single heterogeneous bubble nucleation event occurred in each experiment when p 20 mpa no other bubbles nucleated despite p reaching 60 mpa which is probably too low to trigger homogeneous nucleation compared to estimates for magma decompression rates during lava dome eruptions our results indicate that magmas can degas efficiently throughout their ascent to the surface in explosive eruptions decompression rates may exceed those of this study and hence melts may become supersaturated with water such fast decompressions are expected however only when magma is highly vesicular which would aid approach to equilibrium degassing

u pb zircon and titanite systematics of the fish canyon tuff an assessment of high precision u pb geochronology and its application to young volcanic rocks a large data set of single and multi grain zircon and titanite analyses from a sample of the oligocene fish canyon tuff fct a voluminous ash flow from the san juan mountains of colorado and widely used 40ar 39ar geochronological standard has been used to evaluate the influence of various sources of analytical and geological uncertainty on the calculated age of this tuff by the isotope dilution u pb zircon method twenty three single zircon grains and seven small multi grain fractions of the fct yield an inverse variance weighted mean 206pb 238u date of 28 402 0 023 ma 2 mswd 0 93 and a slightly older weighted mean 207pb 235u date of 28 529 0 030 ma mswd 0 74 which are insensitive to common pb corrections initial 230th disequilibria calculated from a newly measured th u 2 2 for fct pumice shards indicate th deficiency for these zircons its correction brings the weighted mean 206pb 238u date to 28 478 0 024 mswd 0 97 minimizing the discordance of the fct zircon analyses these calculations culminate in concordia ages ludwig 1998 for the crystallization of the fct zircons of 28 476 0 029 ma mswd 1 50 without propagating decay constant errors or 28 498 0 035 ma mswd 1 03 with propagated decay constant errors these results are in close agreement with a previous single grain 206pb 238u zircon date of 28 41 0 05 ma for the fct oberli et al 1990 however they do not corroborate the discordia lower intercept date of 27 52 0 09 put forth by lanphere and baadsgard 2001 the 28 476 0 064 ma concordia age for fct zircons including systematic decay constant errors and uncertainty in pb u tracer calibration is substantially older than all published 40ar 39ar sanidine ages which range from 27 5 to 28 05 ma lanphere and baadsgaard 1997 renne et al 1998 a lengthy period 400 k y of zircon residence in the magma chamber before eruption is commonly called upon to explain the age discrepancy however fct titanite which may remain open to pb diffusive exchange until quenching upon eruption yield a minimum 230th disequilibrium corrected weighted mean 206pb 238u age of 28 395 0 049 ma 0 078 with tracer uncertainty weakening residence time arguments and supporting recent calls for re evaluation of the 40k decay constant and the accepted ages for commonly used 40ar 39ar mineral standards the fct zircon concordia age also provides an empirical constraint on the decay constants of the u isotopes indicating the relative accuracy of the currently accepted decay constants to within the original counting statistic errors of jaffey et al 1971

holocene eruptive history of ksudach volcanic massif south kamchatka evolution of a large magmatic chamber the combination of geological tephrochronological and geochemical studies is used to reconstruct the holocene eruptive history of ksudach volcanic massif south kamchatka and to trace the evolution of its magma ksudach is located in the frontal volcanic zone of kamchatka from early holocene till ad 240 the volcano had repetitive voluminous caldera forming eruptions later they gave way to frequent moderate explosive effusive eruptions that formed the shtyubel stratovolcano inside the nested calderas and then to frequent larger explosive eruptions holocene eruptive products are low k2o two pyroxene plagioclase basaltic andesite to rhyodacite mineralogical geochemical and isotopic data suggest that all the rock varieties originated as a result of fractionation of an initial mafic melt with insignificant contamination and assimilation intensive mixing of the fractionating melts prior to and during the course of the eruptions is ubiquitous the eruptions might have been triggered by repetitive injections of new mafic melt into the silicic chamber crystallization of the andesitic and rhyodacitic melts is estimated to have occurred at temperatures of 970 1010 c and 890 910 c respectively ph2o 1 5 2 0 kbar and fo2 close to the nno buffer according to the experimental data such ph2o corresponds to 4 5 5 5 of water in the melt that is close to the content of water in the silicic hornblende bearing magmas of the rear zone of the kuril kamchatka arc hence we suggest that the transition from pyroxene phenocryst associations of the frontal zone to the hornblende bearing ones of the rear zone might be interpreted as reflecting higher temperatures of crystallization of the melts from the frontal zone rather than increasing water content in the rear zone magmas

geochemistry of the 1989 1990 eruption of redoubt volcano part i whole rock major and trace element chemistry the 1989 1990 eruption of redoubt volcano produced medium k calc alkaline andesite and dacite of limited compositional range 58 2 63 4 sio2 and entrained quenched andesitic inclusions 55 sio2 which bear chemical similarities to the rest of the ejecta the earliest december 15 magmas are pumiceous often compositionally banded and the majority is relatively mafic 59 sio2 the most silicic magmas of the eruption are the late december to early january domes up to 63 4 sio2 subsequent magmas formed domes and rare pumices which converge on 60 sio2 chemical variations among ejecta comprise tight linear two component arrays for all elements for which the analytical uncertainty is much less than the compositional range the two component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent additionally the felsic endmember cannot be easily related to the mafic endmember by normal high temperature igneous processes e g the silicic endmember has higher zr yet lower hf than the mafic endmember also relative enrichments of highly incompatible elements are dramatically different across the arrays the mixing event must have preceded eruption by a significant yet unspecified amount of time because groundmass glass compositions are homogeneous for all post december samples swanson et al 1994 this volume in spite of the whole rock chemical diversity this implies time for additional crystallization after the mixing event swanson et al 1994 this volume discuss evidence for a potentially different mixing event recorded only in december 15 magmas cognate cumulate xenoliths composed of pl cpx opx hb mt melt were recovered from january and april deposits these blocks differ from local batholithic country rock in their low concentrations of incompatible elements e g rb 60 wt they have mg cr ni sc and v contents higher than the andesites but lower than redoubt basalts and basaltic andesites thus they may be crystallization products of andesites but do not represent the cumulate residue of basalt fractionation the xenoliths were probably derived from a shallow or intermediate crustal chamber

evolution of the pannonian basin system 2 subsidence and thermal history analysis of sedimentation and thermal data indicates that for most parts of the pannonian basin observed heat flow thermal gradients rates of thermal subsidence and vitrinite reflectance are about twice those predicted by assuming a uniform extension model for basin formation in late miocene time a modified extension model whereby large amounts of heat are added to the uppermost mantle during extension roughly equivalent to replacing the entire sub crustal lithosphere by asthenosphere produced results in good agreement with observation and could also account for periods of uplift observed during extension crustal extension beneath most parts of the basin is estimated to have been about 80 to 170 1 8 to 2 7 although in the deepest parts of the basin deeper than 4 km crustal extension could have been much greater analysis of extension within the danube and zala basins indicates that the late miocene extension in these basins involved the entire lithosphere but subsidence and heat flow data are not well enough constrained to determine if extra heating is required during extension on the basis of tectonic and structural data the vienna basin has been interpreted as the result of thin skinned extensional tectonics above a shallow detachment surface within the upper crust royden et al this issue analysis of thermal and subsidence data from the northern vienna basin suggests that little or no heating occurred during basin extension these data are consistent with a thin skinned extensional origin for the vienna basin and are in better agreement with this interpretation than with the assumption of a uniformly extended lithosphere beneath the basin this study emphasizes the need for good thermal subsidence and structural data in making reconstructions of extensional and thermal histories of sedimentary basins when such data are available it is found that a simple uniform extension model does not explain very well the evolution of some sedimentary basins such as the vienna and pannonian basins in the first instance the basin is thought to be the result of upper crustal extension only due to its special tectonic setting in the second instance the extra heating during extension is due to some unknown processes in the lower lithosphere that may be a general feature of lithospheric extension thus lithospheric extension and associated heating may be distributed in a variety of ways not all extensional sedimentary basins form in the same way application of a uniform subsidence model to basins for which good thermal subsidence and structural data are not available or not properly analysed can lead to reconstructions of thermal histories in error by a factor of 2 or more

first simulations of the sarno debris flows through cellular automata modelling abstract cellular automata ca can be efficiently applied in the simulation of complex natural processes they represent an alternative approach to classical methods based on the resolution of differential equations in this paper the general frame and the latest developments of the cellular automata model sciddica simulation through computational innovative methods for the detection of debris flow path using interactive cellular automata for simulating debris flow phenomena are presented landslides characterised by a dominant flow type e g earth flows debris flows debris avalanches can be considered as dynamical systems subdivided into elementary parts that evolve exclusively as a consequence of local interactions in sciddica space and time are discrete in particular the space in which the phenomenon evolves is represented by square cells whose states describe the considered physical characteristics time is implicit in the steps of model computation the peculiarities of the structure permitted to extend sciddica first release in order to progressively account for more complex phenomenological aspects of the considered landslides in this paper examples of application of sciddica to three real landslide events are presented after briefly describing earlier simulations of the 1992 tessina italy earth flow and of the 1984 mt ontake japan debris avalanche first attempts at modelling a debris flow that occurred in 1998 at sarno italy are discussed the model has been validated through the reconstruction of the initial topographic and geomorphological conditions of a selected typical phenomenon which occurred at chiappe di sarno curti on may 1998 and by successively comparing the simulation results with the actually observed debris flow path even though improvements to the algorithms are still needed and further testing of parameters on a more representative sample of phenomena desirable first simulations of the curti landslide have demonstrated the reliability of sciddica in the assessment of debris flow susceptibility

comagmatic granophyric granite in the fish canyon tuff colorado implications for magma chamber processes during a large ash flow eruption the 27 8 ma fish canyon tuff a vast ash flow sheet 5000 km 3 of uniform phenocryst rich dacite is representative of monotonous intermediate eruptions from a magma chamber that lacked compositional gradients sparse small fragments of comagmatic granophyre in late erupted tuff and postcaldera lava having mineral compositions indistinguishable from phenocrysts in the tuff and precaldera lava like rocks record complex events in the fish canyon chamber just prior to eruption sanidine phenocrysts in the granophyre preserve zoning evidence of mingling with andesitic magma then shattering by decompression and volatile loss accompanying early fish canyon eruptions before overgrowth by granophyre the textural and chemical disequilibria indicate that the eruption resulted from batholith scale remobilization of a shallow subvolcanic chamber contrary to previous interpretations of magma storage and phenocryst growth in the lower crust

phenocrysts versus xenocrysts in the youngest toba tuff implications for the petrogenesis of 2800 km3 of magma the petrogenesis of the 2800 km 3 of magma erupted as the youngest toba tuff has been investigated using experimental petrology and 40 ar 39 ar dating of biotite sanidine hornblende and plagioclase from the tuff we find that hornblende does not crystallize experimentally from the magma at temperatures and pressures indicated by the natural mineral assemblage hornblende is also not in isotopic equilibrium with biotite and sanidine both of which grew experimentally hornblende thus appears xenocrystic despite being a major phase in the tuff some plagioclase is also xenocrystic on the basis of ar isotopes but others are probably phenocrystic because plagioclase grew experimentally crystal clots of hornblende plagioclase observed in the tuff suggest that the xenocrysts came from a common source which was at least 1 5 ma the oldest hornblende 40 ar 39 ar age our results suggest that the toba tuff magma resided at nearly water saturated pressures of 100 150 mpa and that xenocrysts were entrained as recently as 10 yr before the eruption the ubiquitous presence of hornblende in the tuff indicates that entrainment occurred throughout the 2800 km 3 of magma