variable parent magmas and recharge regimes of the parinacota magma system n chile revealed by fe mg and sr zoning in plagioclase abstract zoning patterns of an content and fe mg and sr concentrations in plagioclase phenocrysts in andesites from parinacota volcano n chile reflect alternating recharge events with two chemically distinct mafic magmas these magmas are characterized by low and high sr contents similar to two recent mafic flank eruptions one end member basaltic andesite shows large sr enrichment and heavy rare earth depletions and thus equilibrated with lower crustal rocks at depth where plagioclase high sr is unstable and garnet high hree y is stable a second end member magma is lower in sr ba contents and has ree patterns typical for parent magmas elsewhere in the central andes the number of recorded recharge events increases after a catastrophic sector collapse and during the subsequent rebuilding of the stratocone variations of an fe and mg contents and morphology of zones suggest also changes in water pressure including decompression under water under saturated and water saturated conditions evidence for decompression is more present in post collapse samples suggesting that the change in the volcano dynamics involves changes in magma chamber location this shows the importance of the cone collapse event in the volcano s magmatic evolution we propose that both end members are only seen at the surface of parinacota volcano because of the particular dynamics of this volcanic system and that similar processes might occur in other volcanic centres of the central volcanic zone

reconciling heterogeneity in crystal zoning data an application of shared characteristic diagrams at chaos crags lassen volcanic center california isotope trace element and textural crystal zoning patterns record heterogeneity in magmatic systems not resolved by whole rock analyses these zoning data are used to infer crystal residence times magma mixing and other magmatic processes in many magmatic systems we present the shared characteristic diagram scd as an organizational framework for crystal zoning data that compares information from different phases and chemical tracers in a common framework an example from chaos crags in the cascade arc produces three main results 1 anorthite zoning profiles in plagioclase have fewer shared characteristics in mafic inclusions than in the host rhyodacite 2 single crystal 87sr 86sr data from previous studies tepley et al 1999 are consistent with more shared history between crystals than in anorthite profiles this difference reflects a more homogeneous distribution of 87sr 86sr than the intensive parameters controlling plagioclase composition 3 the chaos crags system exhibits a layer of heterogeneity in crystal populations that is not represented in whole rock analyses that indicate only simple binary mixing the inconsistency between 87sr 86sr and anorthite zoning data highlights decoupling between compositionally controlled and temperature water controlled zoning in plagioclase from chaos crags

a new method to quantify the real supply of mafic components to a hybrid andesite the eruption of soufriere hills volcano montserrat has been ongoing since 1995 the volcano is erupting a crystal rich hornblende plagioclase andesite with ubiquitous mafic inclusions indicating mixing with mafic magma this mafic magma is thought to be the driving force of the eruption supplying heat and volatiles to the andesite resident in the magma chamber as well as producing macroscopic mafic inclusions the magma mixing process involves incorporation of phenocrysts from the andesite into the mafic magma these inherited phenocrysts show clear disequilibrium textures e g sieved plagioclase rims and thermal breakdown rims on hornblende approximately 25 of all phenocrysts in the andesite show these textures indicating very extensive mass transfer between the two magma types fragments of mafic inclusions down to sub mm scale are found in the andesite together with mafic crystal clusters which are commonly found adhered to the rims of phenocrysts with disequilibrium features mineral chemistry also points to the transfer of microlites or microphenocrysts initially formed in the mafic inclusions into the andesite this combined evidence suggests that some of the mafic inclusions disaggregate during mingling and or ascent possibly due to shearing and raises the question what proportion of the andesite groundmass actually originated in the mafic inclusions and thus what is the true amount of mafic magma in the magmatic system we present a new method for quantifying the relative proportions of groundmass plagioclase derived from mafic and andesitic magma based on analysis of back scattered electron images of the groundmass preliminary results indicate that approximately 16 of all groundmass plagioclase belongs genetically to the mafic inclusions together with the crystal clusters disequilibrium phenocryst textures and mm scale inclusions there is a cryptic mafic component in the andesite of approximately 6 by volume this is significant compared with the proportion of macroscopic mafic inclusions typically 1 5 the new method has the potential to allow tracking of the mafic fraction through time and thus to yield further insights into magma hybridisation processes

paleoseismic evidence from trench investigation along hajipur fault himalayan frontal thrust nw himalaya implications of the faulting pattern on landscape evolution and seismic hazard abstract the study area falls within the mesoseismal zone of 1905 kangra earthquake mw 7 8 two parallel nnw sse striking active fault scarps named as hajipur faults hf1 and hf2 along the northwestern end of the janauri anticline in the foothill zone have displaced floodplain sediments of the beas river the hf1 and hf2 represent the imbricate faults of the himalayan frontal thrust hft and are the result of lateral propagation of deformation from two fold segments i e jf1 and jf2 respectively in northwest direction along the strike ground penetrating radar gpr profiles and trenching across the hf2 reveal two low angle thrust fault strands f1 and f2 displacements of 7 5 m on f2 and 1 5 m on the associated branching faults f a f b and f c were observed total four stratigraphic units unit a gravel with a lens of medium sand unit a is the oldest overlain by units b medium to coarse sand unit c with fine to medium sand and unit d fine to medium sand with scattered gravel were observed in trench radiocarbon ages of the charcoal samples from unit b and unit d optical ages of sediments from units a b and c gpr data and trench log suggest two major events along f1 and f2 strands event i along f1 occurred during 2600 800 yr bp and event ii along f2 around 400 yr bp and before 300 yr bp given the uncertainty in dates it is suggested that the latest event occurred during 1500 1600 ad considering the oldest unit unit a exposed in trench with vertical displacement of 7 5 8 m age of 2600 500 yr bp and net displacement of 9 m during single event along low angle fault 25 implies slip rate 7 6 1 7 mm yr uplift rate 3 2 0 6 mm yr shortening rate 6 9 1 4 mm yr and recurrence interval 1160 250 yr for large magnitude event with mw 7 0 with the recurrence of 1100 yr the penultimate event probably occurred at around 1400 1500 yr bp given the recent gps based slip rate of 14 1 mm yr in kangra reentrant baneerjee and burgman 2002 the present study suggests that about half of this slip is consumed along the hft and that this fault is more active compared to those in the hinterland

seismotectonics of the san andreas fault system between point arena and cape mendocino in northern california implications for the development and evolution of a young transform the northernmost and relatively youthful segment of the san andreas fault system is situated within a 100 km wide zone of northwest trending strike slip faults that includes from west to east the san andreas maacama and bartlett springs faults although the san andreas fault is the principal strike slip fault in this system it has been virtually aseismic since the 1906 earthquake moderate levels of seismicity locate to the east along the maacama fault and to a lesser extent the bartlett springs fault at focal depths typical of other strike slip faults within the san andreas fault system in central california north of the san andreas fault system within the cape mendocino area earthquakes occur at depths of up to 40 km and primarily reflect internal deformation of the subducting gorda slab and slip along the mendocino fracture zone seismicity along the maacama and bartlett springs faults is dominated by right lateral to oblique reverse slip along fault planes that dip 50 75 to the northeast the northern extent of seismicity along these faults terminates near the surface projection of the southern edge of the gorda slab the onset of seismicity along these faults may be related to the abrupt change in the elastic thickness of the north american plate as it enters the asthenospheric window the maacama and bartlett springs faults are strike parallel with active reverse faults within the forearc region of the cascadia subduction zone this preexisting structural fabric of northwest trending reverse faults in the forearc area appears to have strongly influenced the initial slip and complexity of these faults continuation of the moderately dipping maacama fault to the southeast along the steeply dipping healdsburg and rodgers creek fault zones and the near vertical hayward and calaveras fault zones in the san francisco bay area suggests that these faults evolve toward a more vertical dip to minimize the shear stresses that tend to resist plate motion

geochemical and isotopic zoning patterns of plagioclase megacrysts in gabbroic dykes from the gardar province south greenland implications for crystallisation processes in anorthositic magmas chemical and sr isotopic zoning patterns in plagioclase megacrysts from gabbroic dykes in the gardar province can be used to elucidate magma chamber and emplacement processes the megacrysts occur either as single crystals or assembled as anorthosite xenoliths the size of the megacrysts varies from 1 cm to 1 m they consist of a large core with variable zonation an58 39 and a relatively small 600 m normally zoned rim an62 27 the contact between core and rim is sharp and marked by a sharp increase in anorthite content which can reach 11 mol an this gap is interpreted as having formed during dyke emplacement due to a sudden pressure release some of the megacryst cores show a fairly constant composition whereas others exhibit an unusual wavy oscillatory zoning which has not been reported elsewhere to our knowledge the oscillatory zoning has wavelengths of up to 2 500 m and a maximum amplitude of 7 mol an it is interpreted as reflecting movements of the crystals in the magma reservoir the sr isotopic composition of one crystal shows a radiogenic inner core 87sr 86sr i 0 7044 and a less radiogenic outer core 87sr 86sr i 0 7039 0 7036 the lack of a significant change between outer core and rim 87sr 86sr i 0 7037 is consistent with formation of the more an rich rim due to pressure release variations in the core may be related to movements of the crystal and or magma mixing a trace element profile across a megacryst shows a small increase in sr and small decreases in ba and la contents of the recalculated melt composition across the core rim boundary whereas p ce nd and eu remain constant melt compositional changes upon emplacement are therefore considered to be of minor importance constant ratios of incompatible trace elements in the megacryst cores indicate a dominant influence of a lower crustal source on trace element budgets

a cross correlation method for chemical profiles in minerals with an application to zircons of the kilgore tuff usa magmatic crystals are characterised by chemical zonation patterns that reflect the thermal and chemical conditions within magma reservoirs in which they grew crystals that exhibit similar patterns of zonation are often interpreted to have experienced similar conditions of growth these patterns of zonation may represent continuous processes such as cooling or more instantaneous events such as magma injection and provide an insight into the structure and evolution of a magmatic system both temporally and spatially we have developed an algorithm that is objectively able to quantify the similarity within and between suites of magmatic crystals from different samples significantly the algorithm is able to identify correlation that occurs between the interiors of two crystals but does not extend to the rim which provides an opportunity to understand the long term evolution of magmatic systems we develop and explain the mathematical basis for our algorithm and introduce its application using cathodoluminescence images of zircons from the kilgore tuff usa the results allow us to correlate samples from two different outcrops that are found over 80 km apart

high resolution quantitative imaging of plagioclase composition using accumulated backscattered electron images new constraints on oscillatory zoning oscillatory zoning in plagioclase is investigated at small scale 10 m using accumulated backscattered electron bse images as high resolution imaging method combined with electron microprobe quantitative analysis gray value profiles across these images can be calibrated for an content with a resolution of 0 5 mol an applied to oscillatory zoned crystals this new application of bse imaging allows better characterization of zoning patterns along a profile and quantification of wavelength amplitude and shape of the oscillations we also obtain high resolution information on the morphology of growth zones boundaries this approach allows us to better classify the different types of oscillations and concentric zoning dissolution is more frequent than usually recognized major resorption surfaces crosscut several growth zones irregular 5 10 m saw tooth zones are delimited by faint wavy dissolution surfaces and must be distinguished from small scale oscillations 1 3 m with straight boundaries this suggests at least two mechanisms for the formation of these zoning patterns faint oscillations are probably caused by local kinetic control whereas wavy dissolution surfaces involve magma chamber dynamics

wavelet based correlation wbc of zoned crystal populations and magma mixing magma mixing is a common process and yet the rates kinematics and numbers of events are difficult to establish one expression of mixing is the major trace element and isotopic zoning in crystals which provides a sequential but non monotonic record of the creation and dissipation of volumes of distinct chemical potential we demonstrate a wavelet based correlation wbc technique that uses this zoning for the recognition of the minimum number of mixing or open system events and the criteria for identifying populations of crystals that have previously shared a mixing event when combined with field observations of the spatial distribution of crystal populations wbc provides a statistical link between the time varying thermodynamic and fluid dynamic history of the magmatic system wbc can also be used as a data mining utility to reveal open system events where outcrop is sparse an analysis of zoned plagioclase from the tuolumne intrusive suite provides a proof of principle for wbc 1 2002 elsevier science b v all rights reserved

palaeolimnological approaches to climate change with special regard to the biological record abstract lakes systems respond physically chemically and biologically to changes in climate and these responses are registered in many various ways in lake sediment records this paper focuses principally on the biological record and describes recent research that aims to reconstruct i past variability in effective moisture and ii past variability in temperature changes in effective moisture are manifested especially by changes in lake water level in closed lake basins water level change can cause significant changes in water salinity that is registered in sediments by changes in the composition of fossil assemblages especially diatoms in open freshwater lake basins changes in water level are best reconstructed from the aquatic macrofossil record and potentially from the ratio of open water to littoral species of cladocera ostracods and diatoms the most promising biological method for reconstructing past temperature is chironomid analysis and a range of new chironomid temperature transfer functions are being developed however biological responses to changing temperature are usually indirect as a result of temperature effects on water column stratification nutrient cycling and alkalinity generation and in most cases a correct interpretation of the climatic significance of changes in the fossil record requires an understanding of the processes that are operating in the water column a multi proxy whole lake approach is advocated as the best way forward not only as a means of reconstructing past climate but also as a means of assessing the impact of climate change on lake systems

how a complex basaltic volcanic system works constraints from integrating seismic geodetic and petrological data at mount etna volcano during the july august 2014 eruption the petrological part of this study was supported by the fir 2014 research grant to marco viccaro from the university of catania italy grant number 2f119b title of the project dynamics of evolution ascent and emplacement of basic magmas case studies from eruptive manifestations of eastern sicily

a high resolution late glacial and early holocene diatom record from baffin island eastern canadian arctic an interval of late glacial to early holocene sedimentation spanning the period 12 9 8 4 ka bp 14c dated by accelerator mass spectrometry is contained within 15 cm of gyttja in a core from a small lake on southwestern cumberland peninsula baffin island this sediment was subsampled in continuous 2 5 mm increments for diatom analysis extremely low sediment accumulation rates 1 8 cm ka 1 are characteristic of the initial phase of organic sedimentation but they increase rapidly to 14 2 cm ka 1 after 9 ka bp the first 0 5 cm of gyttja contained an acidophilous diatom flora resembling that of underlying mineral sediments thereafter and throughout the late glacial and earliest holocene diatom floras were dominated by alkaliphilous and circumneutral species of fragilaria around 9 ka bp shifts to acidophilous floras dominated by brachysira brebissonii and later eunotia rhomboidea and frustulia rhomboides vars saxonica and crassinervia suggest a period of natural lake acidification high dia

timescales of pre eruptive magmatic processes at vulcano aeolian islands italy during the last 1000 years abstract an integrated petrological and geochemical study on plagioclase crystals erupted at vulcano island aeolian islands southern italy over the past 1000 years allowed us to draw a detailed model of the internal structure of the volcanic system in which modes of magma interaction and timescales of storage at crustal depth are shown the integration of compositional textural and temporal record preserved in plagioclase crystals provides evidence for an articulated plumbing system constituted by several reservoirs connected at the crust mantle boundary here a basaltic shoshonitic magma resides and is thought to feed the shallow magma reservoir of both la fossa and vulcanello centers finally triggering eruptions throughout injections from depth textural and micro compositional data on plagioclase crystals suggest the presence of three main magma levels located between ca 17 and 2 km of depth beneath la fossa cone which were intermittently reactivated over the whole period of activity considered plagioclase textures and compositional zoning indicate that the shallow

tof sims and electron microprobe investigations of zoned magmatic orthopyroxenes first results of trace and minor element analysis with implications for diffusion modeling zoned phenocrysts in volcanic rocks potentially provide an archive of magmatic processes as a crystal grows and comes into contact with different melt batches the chemical and textural signature of this journey is recorded within its crystal lattice the timescale of some magmatic processes can be investigated through the relaxation of chemical gradients across crystal growth zones through the application of diffusion modeling techniques one of the current limitations to diffusion modeling is the spatial and analytical resolution of the chemical profile that conventional techniques such as electron probe microanalyzer epma dynamic secondary ion mass spectrometry sims and laser ablation inductively coupled plasma mass spectrometry la icpms can achieve here for the first time we present time of flight tof sims tof sims data for zoning of orthopyroxene crystals from the may 1982 eruption of mount st helens volcano u s a and cross calibrate these data between backscattered electron images and epma tof sims has the advantage of being able to achieve micrometer to nanoscale spatial resolution of major elements as well as analyses of light elements such as li and trace and minor elements na k and ni at concentrations that cannot be achieved by epma provided that convolution overlap effects and polyatomic mass inferences are carefully considered with tof sims analyses we identified zoning of li on a spatial scale ca 5 10 m that would be inaccessible to most other conventional analytical techniques preliminary results indicate that li a fast diffusing element may be introduced to the crystals in the minutes hours or days prior to eruption and may provide insights into pre eruptive magmatic processes thus tof sims has the potential to be a powerful tool for obtaining minor and trace element profiles across compositional interfaces within crystals at high spatial resolution

semiautomated georadar data acquisition in three dimensions under favorable conditions georadar techniques can provide vivid images of the shallow subsurface 10 50 m although the significant advantages of 3 d georadar surveying strategies are well documented they generally require much greater expenditures than traditional 2 d approaches we introduce an efficient semiautomated 3 d georadar acquisition and processing scheme that does not jeopardize data quality a standard georadar acquisition unit is integrated with an innovative self tracking laser theodolite with automatic target recognition capabilities georadar and coordinate data are recorded simultaneously as the georadar antennae are transported steadily across a survey area while tracking a target prism mounted between the antennae the theodolite provides real time coordinate information with high accuracy in all directions at 1 m s moderate walking speed the coordinates are determined to better than 0 04 m and at 3 m s they are better than 0 07 m subsequent to acquisition semiautomati

unusual magma storage conditions at mt etna southern italy as evidenced by plagioclase megacryst bearing lavas implications for the plumbing system geometry and summit caldera collapse at mt etna volcano the emission of plagioclase megacryst bearing lavas known locally as cicirara has occurred rarely and generally in association with unusual volcanological phenomena in this work we interpret the magma chamber processes and the structural features of the plumbing system that led to the production of these peculiar volcanic rocks based on a detailed study of plagioclase megacrysts including their oscillatory zoning sieve textures and fluid inclusions patchy zoning suggests limited ascent in the deep levels of the plumbing system based on the plagioclase nucleation threshold and the volatile saturation depth at intermediate water undersaturated levels of the plumbing system ascent is faster as indicated by crystals with coarse sieve textures storage at shallow water saturated levels less than 6 km deep is associated with oscillatory zoning with very small changes in an slightly larger an variations coupled with different wavelengths provide evidence of convection of crystals across distinct zones of the chamber stripes of melt inclusions formed at steps of magma ascent and volatile loss whereas layers of fluid inclusions may be related to episodes of volatile flushing into the magma chamber in contrast strongly sieve textured envelopes with an increase and constant feo may be related to mixing with more volatile rich magmas of similar composition we interpret the repeated occurrence of cicirara lavas as evidence that the shallow portion of the plumbing system underwent a progressive coalescence of a complex network of dykes and sills in response to increasing rates of magma supply from depth major magma withdrawals from this larger reservoir may be linked to episodes of summit instability associated with major caldera collapses

inter and intracrystalline isotopic disequilibria techniques and applications in the last 20 years we have seen a significant expansion of techniques related to geochemical and isotopic microsampling of materials in the earth sciences from constraining pre eruptive histories of flood basalt magmas to identifying the natal rivers of origin of anadromous fishes these techniques have had significant impacts in a wide variety of scientific fields nowhere has the impact been greater than in identifying the sources processes and timing of processes involved in igneous magmatic systems both technique refinements and the development of new technologies have aided in advancing microsampling applications thus allowing for a better understanding of the sources and mechanisms responsible for changing geochemical and isotopic signatures in natural systems in this chapter we focus on the techniques and technologies associated with radiogenic isotope microsampling and review applications of these techniques as utilized in scientific investigations isotope microsamping is a logical extension of earlier studies that evaluated individual components of magmas and magma systems including melts and minerals from the use of petrographic microscopes and the later introduction of the electron microprobe the focus on internal chemical variations in melts and minerals is critical to assessing the petrogenetic histories of igneous rocks even today these technologies are used to ensure that further trace element and isotopic analyses are undertaken in a textural and major element context for trace elements and isotopes early studies e g cortini and van calsteren 1985 confirmed variations in the melt and mineral components of many igneous rocks but focused on mineral or glass separates potential information associated with isotopic variations retained by individual crystals or internal variations within individual crystals was lost later studies such as geist et al 1988 focused on isotope variations within single megacrysts to constrain mixing scenarios between basaltic andesitic and rhyolitic magmas and davidson et al 1990 used

repeated recharge assimilation and hybridization in magmas erupted from el chichon as recorded by plagioclase and amphibole phenocrysts abstract compositional and isotopic zoning patterns in plagioclase and amphibole phenocrysts from el chichon record multiple cycles of country rock assimilation magma injection hybridization and mixing laser ablation icp ms and electron microprobe analyses of plagioclase crystals from 7 eruptions spanning 3100 years reveal four types of zoning these compositional and isotopic zones are often associated with textural changes observed in the crystals in thin section e g sieved or patchy regions amphiboles are frequently zoned in al and si and in two magmas may have clinopyroxene rims interestingly most plagioclase show multiple and repeated zoning patterns moreover all magmas contain all zoning patterns and textures and crystals with substantially different sequences of zones occur within mm of one another the most reasonable explanation for the origin of these textures is a frequently recharged chamber plagioclase zones with increasing anorthite contents an and decreasing 87sr 86sr ratios record injection by a hotter possibly wetter and more primitive magma lower 87sr 86sr ratio zones with decreasing an and increasing 87sr 86sr ratios record assimilation of country rock and or hybridization of the host and injected magmas injection of hot magma may provide the heat for country rock assimilation changes in an without corresponding changes in 87sr 86sr ratio likely record slight variations in pressure or temperature during crystallization or the far field thermal effects of magma injection variations in 87sr 86sr ratio unaccompanied by anzoning record assimilation of country rock amphibole zoning patterns also record periodic heating events amphibole with clinopyroxene rims record episodes where the magma was heated beyond the amphibole stability field bulk compositional homogeneity and the juxtaposition of many crystals with disparate zoning patterns in single pumice require the magmatic system to be well mixed strontium diffusion rates indicate that the plagioclase zoning patterns cannot have persisted at magmatic pressures and temperatures for more than 500 years thus cycles of injection and assimilation occur on timescales equal to or shorter than the eruption recurrence interval long term compositional and isotopic homogeneity indicate that there is a balance between recharge assimilation and crystallization

unraveling the presence of multiple plagioclase populations and identification of representative two dimensional sections using a statistical and numerical approach many plagioclase phenocrysts from volcanic and plutonic rocks display quite complex chemical and textural zoning patterns understanding the zoning patterns and variety of crystal populations holds clues to the processes and timescales that lead to the formation of the igneous rocks however in addition to a true natural complexity of the crystal population the large variety of plagioclase types can be partly artifacts of the use of two dimensional 2d petrographic thin sections and random cuts of three dimensional 3d plagioclase crystals thus the identification of the true number of plagioclase populations and the decision of which are representative crystal sections to be used for detailed trace element and isotope analysis is not obvious and tends to be subjective here we approach this problem with a series of numerical simulations and statistical analyses of a variety of plagioclase crystals zoned in 3d we analyze the effect of increasing complexity of zoning based on 2d chemical maps e g backscattered electron images bse we first analyze the random sections of single crystals and then study the effect of mixing of different crystal populations in the samples by quantifying the similarity of the compositional histogram of about a hundred 2d plagioclase sections it is possible to identify the so called reference and ideal sections that are representative of the real 3d crystal populations these section types allow filtering out the random cut effects and explain more than 90 of the plagioclase compositional data of a given sample our method allows the identification of the main crystal populations and representative crystals that can then be used for a more robust interpretation of magmatic processes and timescales

acquisition and processing strategies for 3d georadar surveying a region characterized by rugged topography efficiently performing 3d ground penetrating radar gpr or georadar surveys across rugged terrain and then processing the resultant data are challenging tasks conventional approaches using unconnected gpr and topographic surveying equipment are excessively time consuming for such environments and special migration schemes may be required to produce meaningful images we have collected gpr data across an unstable craggy mountain slope in the swiss alps using a novel acquisition system that records gpr and coincident coordinate information simultaneously undulating topography dips of 8 to 16 and boulders with diameters up to about 2 m complicated the field campaign after standard processing the data were found to be plagued by time shifts associated with minor coordinate inaccuracies uneven antenna ground coupling and numerous small gaps in data coverage these problems were resolved by passing the data sequentially through an adaptive f xy deconvolution routine and f kx and f ky filters this filtering also reduced incoherent noise finally the data were migrated using a 3d algorithm that accounted for the undulating topography the nonmigrated and migrated images contained gently and moderately dipping reflections from lithological boundaries and actively opening fracture zones a suite of prominent diffraction patterns was generated at a steeply dipping fracture zone that projected to the surface through this case history we introduce a general strategy for 3d gpr studies of topographically rugged land

lake sediment studies of holocene glacial activity in the karsa valley northern sweden contrasts in interpretation a multidisciplinary study of lake sediments deposited in lake basins in the karsa valley northern sweden suggests the complete disappearance of the karsa glacier during the early and mid holocene glacier reformation indicated by the deposition of sediment with a fine particle size distribution and low organic content in the three lakes took place at c 3000 14 c years bp this interpretation contrasts with a study based on the weight loss on ignition of the same sediments which suggests several glacier advances throughout the entire holocene the contrasting interpretation is due to different methodological approaches single core site studies should be avoided in the future and only features that are consistently reproducible and can be dated in spatially distributed cores should be interpreted in terms of variations in glacial activity environmental conditions and ultimately climate

igneous layering fractional crystallization and growth of granitic plutons the dolbel batholith in sw niger this study reassesses the development of compositional layering during the growth of granitic plutons with emphasis on fractional crystallization and its interaction with both injection and inflationrelated deformation the dolbel batholith sw niger consists of 14 kilometre sized plutons emplaced by pulsed magma inputs each pluton has a coarse grained core and a peripheral layered series rocks consist of albite an 11 k feldspar or96 99 ab1 4 quartz edenite xmg1 4 0 37 0 55 augite xmg1 4 0 65 0 72 and accessories apatite titanite and fe ti oxides whole rock compositions are metaluminous sodic k2o na2o1 4 0 49 0 62 and iron rich feotot feotot mgo 1 4 0 65 0 82 the layering is present as size graded and modally graded sub vertical rhythmic units each unit is composed of three layers which are towards the interior edenite plagioclase ca p edenite plagioclase augite quartz cq and edenite plagioclase augite quartz k feldspar ck all phases except quartz show zoned microstructures consisting of external intercumulus overgrowths a central section showing oscillatory zoning and in the case of amphibole and titanite complexly zoned cores ba and sr contents of feldspars decrease towards the rims plagioclase crystal size distributions are similar in all units suggesting that each unit experienced a similar thermal history edenite characteristic of the basal ca p layer is the earliest phase to crystallize microtextures and phase diagrams suggest that edenite cores may have been brought up with magma batches at the site of emplacement and mechanically segregated along the crystallized wall whereas outer zones of the same crystals formed in situ the subsequent cq layers correspond to cotectic compositions in the qz ab or phase diagram at ph2o1 4 5 kbar each rhythmic unit may therefore correspond to a magma batch and their repetition to crystallization of recurrent magma recharges microtextures and chemical variations in major phases allow four main crystallization stages to be distinguished 1 open system crystallization in a stirred magma during magma emplacement involving dissolution and overgrowth core of edenite and titanite crystals 2 in situ fractional crystallization in boundary layers ca p and cq layers 3 equilibrium en masse eutectic crystallization ck layers 4 compaction and crystallization of the interstitial liquid in a highly crystallized mush e g feldspar intercumulus overgrowths it is concluded that the formation of the layered series in the dolbel plutons corresponds principally to in situ differentiation of successive magma batches the variable thickness of the ck layers and the microtextures show that crystallization of a rhythmic unit stops and it is compacted when a new magma batch is injected into the chamber therefore assembly of pulsed magma injections and fractional crystallization are independent but complementary processes during pluton construction

transient uprise of gas and gas rich magma batches fed the pulsating behavior of the 2006 eruptive episodes at mt etna volcano volcanic rock samples were systematically collected during the 2006 eruptive episodes at mt etna major and trace elements together with sr pb isotope ratios were then obtained on the whole rocks for different times of emission and vent locations on the same samples selected plagioclase crystals were investigated through high contrast bse images and core to rim compositional profiles for an and feo wt were obtained the major element variation through time suggests the involvement of a more basic magma because mgo feotot and cao al2o3 ratios tend to increase from the beginning to the end of the eruption this more basic magma was characterized by a peculiar geochemical and isotopic signature this is testified by the negative trend of lrees some hfses e g nb zr y and lead isotopes together with increase of some incompatible element ratios e g rb la zr nb with respect to products erupted before concerning the plagioclase crystals four main texture types were recognized at the core and rim which indicate either near equilibrium crystallization or disequilibrium accompanied by strong destabilization these textures were attributed to i crystallization at equilibrium conditions at depth or within the open conduit two types of oscillatory zoning ii magma decompression at variable ascent rates coarsely sieve textures and dissolution at the core iii inputs of more basic magma sieve textured rims all the available data coupled with co2 so2 molar ratio measured in the gas plume obtained from literature support the idea that the pulsating regime observed for the volcanic phenomena at the surface during the period july december 2006 reflects the transient rapid ascent of several co2 bubble fluxes and or co2 rich magma batches from the deep to the shallow levels of the plumbing system this integrated study has also led to the identification of the replenishment event during the eruption that allowed the ingress of the magma with distinct geochemical isotopic signature

combining csd and isotopic microanalysis magma supply and mixing processes at stromboli volcano aeolian islands italy integrating isotopic microanalysis with other analytical techniques creates powerful new methodologies for understanding the evolution of rock samples at the sub grain scale here we present crystal size distribution csd data for a 26 000 year old sample from stromboli volcano and accompanying isotopic microanalysis of the phenocrysts a technique called the icsd plot is introduced which given stated assumptions allows the integration of both sets of data to generate timelines of isotopic evolution through the volcanic system the combined approach is powerful allowing investigation of the magma supply mixing crystallisation and contamination processes prior to eruption of a volcanic sample for stromboli volcano the combined analysis suggests that the change in magma type following a cone collapse took roughly five years to complete similar to the timescale of changes seen in recent decades

chemical evolution of intercumulus liquid as recorded in plagioclase overgrowth rims from the skaergaard intrusion the intercumulus liquid of a crystal mush fills pore spaces and typically solidifies to form overgrowths on cumulus grains and poikilitic post cumulus minerals if the liquid is immobile solidification produces zoned intercumulus minerals as a result of progressive fractionation of the residual liquid convection within the mush results in buffering of the liquid composition and thus limits mineral zonation for fully solidified cumulates fossil changes in liquid composition or porosity are difficult to identify however detailed study of immobile minor components of plagioclase overgrowth rims can provide information about the progressive solidification of intercumulus material ti contents of plagioclase overgrowths in samples from the lowermost parts of the skaergaard intrusion show strong variations with anorthite content with decreasing xan ti concentrations first rise and then fall consistent with changing tio2 contents of the intercumulus liquid during solidification tio2 in plagioclase decreases sharply at an55 reflecting local saturation of fe ti oxides ti in clinopyroxene oikocrysts also falls rimward but zoning in faster diffusing species fe mg is limited other than slight reverse zones that may occur on the plagioclase margins xan falls continuously during crystallization the reverse zoning is interpreted as the result of compaction driven dissolution and reprecipitation of plagioclase the continual decrease in xan is exploited together with back scattered electron images of the cumulates to produce calibrated images showing regions of progressive crystallization this allows the regions crystallizing at each stage of solidification to be visualized these images show that the final remnants of interstitial melt were present in triangular pockets and as thin grain boundary melt films this approach can provide information about the progressive reduction of porosity during cumulate solidification

the mixing of magmas in plutonic and volcanic environments analogies and differences abstract magma mixing processes have been widely recognized in both the plutonic and volcanic environments but the quality and quantity of information that can be extracted from the two environments are substantially different understanding the advantages and limits associated with the study of plutonic and volcanic rocks is essential to establish precise methodological approaches to build the most complete conceptual model by merging information from these two complementary igneous environments in this work we review magmatic interaction processes in the plutonic and volcanic environments by considering several aspects of these geological phenomena in particular we first briefly report on the structural and geochemical evidence for magma mixing in both plutonic and volcanic rocks with the aim to provide a general picture of this natural phenomenon successively we discuss some recent results about magma mixing achieved using the concepts from chaos theory and discuss their potential impact on magma differentiation finally we attempt to build a general picture of this igneous process by merging present day information from both the plutonic and volcanic environments it emerges from the general picture that the time spent by the magmatic system in the molten or partially molten state is the crucial factor for the preservation of the fingerprints of magma mixing in the two environments we propose a conceptual model that may be useful to understand what kind of information we can obtain from volcanic and plutonic rocks and ultimately to maximize our knowledge about magma mixing

strange attractors in plagioclase oscillatory zoning petrological implications oscillatory zoning in plagioclase crystals from different mixed lava flows cropping out on the island of capraia italy has been investigated an calibrated profiles from back scattered electron images are used as compositional time series of oscillatory zoning they are analyzed by a qualitative visual method that allows to appreciate at first sight the global structure of the time series and by a quantitative method to reconstruct the attractors associated to the oscillatory patterns and to calculate the fractal dimension of attractors results show that attractors have fractional dimensions indicating that series are chaotic in addition it is evidenced that there is a wide variation in oscillatory zoning in crystals from the same lava flow and that plagioclase populations from the different lava flows differ in the shape of frequency histograms of attractor dimension the development of oscillatory zoning is simulated by considering a chemically inhomogeneous magmatic mass governed by chaotic flow fields coupled with chemical diffusion in which plagioclase crystals grow according to the availability of nutrients in their neighborhoods results show that in such a dynamical system plagioclase crystals develop chaotic zoning patterns analogous to those observed in natural plagioclases this approach allows us to explain the differences observed in plagioclase crystals from the same lava flow and the differences in the shape of frequency histograms of attractor dimensions in the four lava flows

the holocene vegetation history of the khibiny mountains implications for the post glacial expansion of spruce and alder on the kola peninsula northwestern russia

gas burst vs gas rich magma recharge a multidisciplinary study to reveal factors controlling triggering of the recent paroxysmal eruptions at mt etna abstract since january 2011 mt etna volcano has been affected by more than forty paroxysmal eruptions at the summit new south east crater nsec on the basis of their very variable duration seven eruptions have been selected among the twenty five of 2011 2012 in order to decipher potential differences in their triggering mechanism paroxysms have been investigated through a multidisciplinary approach that integrates data from volcanic tremor and petrology textures and micro analysis on plagioclase crystals our results lead to the conclusion that close relationships exist between the duration of the eruptions and the temporal evolution of the volcanic tremor amplitude especially during the strombolian phase preceding the paroxysmal activity in this regard we distinguished 1 paroxysms preceded by long lasting initial strombolian phases characterized by low rate of volcanic tremor amplitude increase and 2 eruptions preceded by short initial strombolian phases showing high rate of volcanic tremor amplitude increase based on the pattern of volcanic tremor amplitude increase the former mainly showed a ramp shaped morphology while the latter a bell shaped trend location of the volcanic tremor centroid during the quiescent intervals between the paroxysmal eruptions has highlighted the presence of a magmatic volume at 1 2 km a s l beneath the north east crater nec during the syn eruptive strombolian and lava fountaining phases the centroid of volcanic tremor migrates below the nsec this leads to the consideration that the magma batch residing beneath nec played an important role in the volcanic activity at nsec during the considered period also the textures and compositional zoning anorthite and iron variations in selected plagioclase crystals of the analyzed lavas suggest relations between duration of the paroxysms and dynamics of pre eruptive magmatic processes at depth particularly two mechanisms have been accounted for triggering of eruptions at the nsec on the basis of the concordant or discordant behavior of anorthite and iron in plagioclase coupled with disequilibrium textures at the rim concordant anorthite and iron increases in plagioclase crystals with sieve textured rims indicate recharge by more mafic gas rich magma this textural compositional behavior has been related to long lasting eruptions whose volcanic tremor amplitude evolution produced ramp shaped increase of the volcanic tremor amplitude before the paroxysmal phase on the contrary crystals with sieve textures at the rim characterized by increasing iron at rather constant or decreasing anorthite suggest the prominent role of gas injections into the residing system in this instance the compositional behavior has been linked with short lasting eruptions whose volcanic tremor amplitude evolution led to a sudden increase of the seismic amplitude before the climax of the eruption thus our work put forward the idea that the evolution and duration of the strombolian phase preceding the paroxysmal eruptions of 2011 2012 at mt etna are strongly controlled by the eruption triggering mechanism which can be either gas burst or gas rich magma recharge

zoned orthopyroxenes in the ni co sulfide ore bearing xiarihamu mafic ultramafic intrusion in northern tibetan plateau china implications for multiple magma replenishments abstract the xiarihamu mafic ultramafic intrusion is situated in the east kunlun orogenic belt e kob northern tibetan plateau china with ni co sulfide mineralization mainly in orthopyroxenite and olivine orthopyroxenite whole rock and mineral compositions show cyclic variations in drill hole intersections through the xiarihamu mafic ultramafic intrusion microbeam x ray fluorescence xrf mapping shows reverse zoning cr poor core cr rich rim and oscillatory zoning cr poor core cr rich mantle and cr poor rim in orthopyroxene of olivine orthopyroxenite and orthopyroxenite zoned orthopyroxenes are euhedral or subhedral and there are relatively sharp interfaces between zones with distinct cr contents crystal size distribution csd curves of orthopyroxenes in olivine orthopyroxenite show concave upward curvature at size larger than 3 0 mm and larger orthopyroxenes commonly display zoning implying a secondary recrystallization and grain growth of larger orthopyroxenes quantitative analyses show that cr and enstatite contents of cores are relatively lower but incompatible element e g ti zr ga and sr contents of cores are higher than rims in reverse zoned orthopyroxenes and chemical profiles of unzoned orthopyroxenes resemble those of rims but different from those of cores in reverse zoned orthopyroxenes chemical profiles of orthopyroxenes indicate that cr zoning is not due to the change in cr partitioning behavior between orthopyroxene and silicate melt which shows significant temperature and redox dependence textural feature and crystal size distribution of orthopyroxenes suggest the formation of cr rich zones attests to the multi stage growth in the process of magma replenishment rather than a reactive liquid flow model or in situ trapped liquid overgrowth orthopyroxene zoning together with compositional variation and intrusive relationship between olivine orthopyroxenite and orthopyroxenite imply that the xiarihamu mafic ultramafic intrusion was formed by multiple magma replenishments with magma varying roughly from a more evolved to a more primitive composition

a multi methodological re evaluation of the volcanic events during the 1580 ce and 1808 eruptions at sao jorge island azores archipelago portugal abstract among all eruptions that took place on the azores archipelago since the portuguese settlement in the xvi century those of 1580 and 1808 in the island of sao jorge were unusual the magma erupted in 1580 ascended from at least 23 km and ponded at a minimum depth of 16 km here residual magma fractionated mafic phases and plagioclase during 228 years before erupted again in 1808 magma emission occurred from numerous fissures active at the same time and opening for several kilometres following a local tectonic trend hydro volcanic outbursts and hot rock fall over steep slopes caused casualties and injuries and lava flows and heavy tephra fallout affected the local economy despite of all these dramatic consequences the memory of these eruptions is almost vanished representative geosites and morphological landforms if not hindered by lush vegetation have been reshaped by diffuse quarries and reworked to recover croplands and pastures aiming at a better comprehension of the multiple hazards associated with volcanic eruptions at sao jorge island we retraced the volcanic events of these two eruptions by matching our re interpretation of historic reports with field data and photogrammetry and with fluid inclusions petrography and geochemical data of erupted products

structure and dynamics of the laacher see magma chamber eifel germany from major and trace element zoning in sanidine a cathodoluminescence and electron microprobe study microtextures and zoning patterns in sanidine phenocrysts from the phonolitic laacher see tephra germany were investigated in order to constrain processes occurring in the magma chamber before eruption the laacher see tephra unit is chemically zoned and has been inferred to represent the product of eruption of an inverted layered magma chamber samples from various levels in the deposit were investigated we used a combination of textural studies optical microscopy and back scattered electron bse imaging electron microprobe emp analysis of major minor and trace elements ca na k al si ba sr fe and ti and element mapping the samples studied contain two feldspar phases and the ternary composition of the sanidine thus constrains the temperature of crystallization whereas its trace element content reflects the melt composition the large diversity in textures found in the sanidine crystals can be classified into three types composite c type pseudooscillatory po type and resorbed patchy r type trace elementpoor lamellar composite alkali feldspars c type are found in samples inferred to represent the top and the middle part of the magma chamber they grew as composite crystals from the melt at temperatures as low as 650 c in a highly differentiated and volatilerich boundary layer at the magma chamber roof or wall pseudooscillatory zoning with resorption surfaces po type is found in sanidinesfromsamplesinferredtorepresentthemiddlepartandthebase of the magma chamber repeated large an variations 1 4 mol reflect temperature variations of 100 300 ca ssociated with changes in water content variations of minor and trace elements ba sr and ti in sanidine decoupled from the pseudo oscillations of the major elements reflect chemical changes in the melt and are damped by chemicaldiffusioninthemelt bothmajorandminorelementvariations inpo typecrystalsareinterpretedastheprogressiveinfluenceofamore mafic hotter melt this may be partly explained by the settling of crystals through the thermal and chemical gradient existing in the magma chamber however the additional role of magma recharge may be required to explain the large temperature variations resorbed patchy zoned crystals r type found mainly in samples corresponding to the middle part of the magma chamber reflect early growth in a differentiated boundary layer followed by resorption and overgrowthinthemainmagmabody manyofthelaacherseesanidine crystals did not crystallize for the most part in the melt in which they were erupted in the presence of preserved major and trace element zonation in the magma this observation indicates crystal dispersion within a layered magma chamber without large scale mixing and overturn

variable regimes in magma systems documented in plagioclase zoning patterns el misti stratovolcano and andahua monogenetic cones abstract magmas may experience closed or open system evolution during their ascent and evolution in the upper crust chemically closed system processes can involve heat transfer from underplating mafic magmas or decompression due to magma ascent on the other hand newly injected magmas can mix with the residing magma and hybridize plagioclase zonation patterns and electron microprobe major and trace element analysis constrain these contrasting scenarios for andesites from the 80 km3 el misti stratovolcano 5822 m and a field of relatively small monogenetic andahua scoria cones both in southern peru in particular fe concentration in plagioclase reveals valuable information within a magmatic system to explore the dominance of closed vs open system processes large and correlated anorthite fe contrasts at resorption zones identify compositional mixing related to recharge subhorizontal an fe variations record thermal or water induced effects el misti volcano a large but still relatively youthful stratovolcano is dominated during most of its approx 120 ka history by closed system effects during its evolution recharge and mixing mostly occurred cryptically as it is not recorded in drastic compositional changes in magmas or their phenocrysts a small volume erupted at el misti however is affected by strong open system behaviour as reflected in strongly correlated variations in an and fe contents of plagioclase compositions its crystal population is texturally and chemically very similar to lavas of the monogenetic cinder cones of the andahua volcanic field for the el misti magma reservoir resorption events caused by thermal effects or magma ascent are more frequent in comparison to the actual eruption frequencies many cycles of closed system evolution heat transfer and decompression therefore occurred without resulting in an eruption plagioclase zonations from lavas of the monogenetic andahua field indicate that any mafic batch that intruded the much smaller reservoirs immediately triggered an eruption by contrast a large magma system that feeds el misti volcano can easily accommodate a new batch without causing eruption

formation of cordierite bearing lavas during anatexis in the lower crust beneath lipari island aeolian arc italy cordierite bearing lavas cbl 105 ka erupted from the mt s angelo volcano at lipari aeolian arc italy are high k andesites displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and or processes cbl consist of megacrysts of ca plagioclase and clinopyroxene euhedral crystals of cordierite and garnet microphenocrysts of orthopyroxene and plagioclase set in a heterogeneous rhyodacitic rhyolitic groundmass containing abundant metamorphic and gabbroic xenoliths new petrographic chemical and isotopic data indicate formation of cbl by mixing of basaltic andesitic magmas and high k peraluminous rhyolitic magmas of anatectic origin and characterize partial melting processes in the lower continental crust of lipari crustal anatectic melts generated through two main dehydration melting peritectic reactions of metasedimentary rocks 1 biotite aluminosilicate quartz albite garnet cordierite k feldspar melt 2 biotite garnet quartz orthopyroxene cordierite k feldspar melt their position into the petrogenetic grid suggests that heating and consequent melting of metasedimentary rocks occurred at temperatures of 725 t 900 c and pressures of 0 4 0 45 gpa anatexis in the lower crust of lipari was induced by protracted emplacement of basic magmas in the lower crust 130 ky crustal melting of the lower crust at 105 ka affected the volcano evolution impeding frequent mafic magma eruptions and promoting magma stagnation and fractional crystallization processes

constraints on crystal storage timescales in mixed magmas uranium series disequilibria in plagioclase from holocene magmas at mount hood oregon abstract uranium series crystal ages interpreted within a textural and geochemical framework can provide insight into crystal storage timescales especially in cases where crystals may derive from multiple sources we report here 230 th 226 ra model ages of two distinct populations of plagioclase from low silica dacites from mount hood oregon a volcano where previous studies show that the compositions of erupted magmas are controlled by magma recharge mixing and incorporation of plagioclase derived from mafic and silicic end member magmas we have measured trace element concentrations and 238 u 230 th 226 ra disequilibria in four plagioclase size fractions from the timberline 1500 a and old maid 215 a eruptive sequences after correction for groundmass and apatite contamination average 230 th 226 ra model ages of large 500 m plagioclase are 4 5 ka timberline and 5 5 ka old maid with ages of cores that are 10 ka in each case indicating that plagioclase derived from silicic magmas crystallized thousands of years before eruptions these model ages are longer than timescales of repose between eruptions indicating that these crystals resided in the sub surface over multiple eruptions likely stored in a silicic crystal mush zone that periodically interacts with mafic recharge magmas remobilizing a fraction of the large plagioclase crystals during each eruptive event after correction for large plagioclase contamination small 226 ra ba relative to equilibrium with liquid proxies groundmass and mafic inclusion leading to 230 th 226 ra model ages that are 230 th 226 ra disequilibria require that the majority of crystals in the separate are young 226 ra ba could potentially be explained by rapid crystallization immediately prior to and or during mixing events consistent with evidence of rapid crystallization of rims rapid crystallization of mafic intrusions may trigger eruption at mount hood by producing a partially crystalline mafic magma capable of mixing with a reheated silicic crystal mush

plagioclase zoning as an indicator of magma processes at bezymianny volcano kamchatka back scattered electron bse derived zoning patterns of plagioclase phenocrysts are used to identify magma processes at bezymianny volcano kamchatka based on the 2000 2007 sequence of eruptive products the erupted magmas are two pyroxene andesites which last equilibrated at 915 c temperature 77 87 mpa pressure and a water content of 1 4 wt textural and compositional zoning of individual plagioclase phenocrysts typically includes a repeated core to rim sequence of oscillatory zoning an50 60 truncated by a dissolution surface followed by an abrupt increase in an content up to an85 which then gradually decreases rimward this zoning pattern is interpreted to be the result of frequent replenishments of the magma chamber which cause both thermal and chemical interaction between resident and recharge magmas the outermost 70 to 150 m wide zoning patterns of plagioclase phenocrysts are composed of dissolution surface with a subsequent increase in an and fe contents zoning patterns of the rims exhibit correlation among plagioclase phenocrysts within one eruption rims are interpreted as a result of crystallization of a batch of magma in the conduit after recharge event

flower structures and riedel shears at a step over zone along the alpine fault new zealand inferred from 2 d and 3 d gpr images 1 high resolution gps and ground penetrating radar gpr data are used to detect and identify hidden faults along a stretch of the transpressional alpine fault south island new zealand immediately north of its junction with the hope fault at this location the alpine fault emerges from the basement into a sequence of variably thick late holocene gravel deposits geomorphology and trenching already mapped three principal fault strands and two distinct step over zones at the study site our gpr images reveal numerous additional secondary fault strands throughout the region only some of which are obvious at the surface or in the trench walls according to the gpr data the main fault generated disturbance zone has a width ranging from 40 to 200 m the secondary fault strands outside of the step over zones likely represent the branches of positive flower structures whereas the faulting pattern around the step over zones is best explained in terms of linked riedel shears systematic northeastward increases in the width of the main fault generated disturbance zone and corresponding increases in principal fault scarp height are the likely consequences of older terraces in the northeast being disrupted and offset by more earthquakes than younger terraces in the southwest the pattern of complex faulting in this region is distinct from the system of alternating strike slip and reverse faults characteristic of the alpine fault to the south and from the rather simple sequence of faults mapped to the north gpr surveying has added new information on the distribution and nature of faulting at our study site

mapping the architecture of glaciofluvial sediments with three dimensional georadar three dimensional 3 d ground penetrating radar georadar mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units to investigate the potential of this high resolution technique and at the same time study the architecture of quaternary glaciofluvial deposits georadar data have been collected on a dense grid established across a sequence of braided river gravels and sands in northeastern switzerland results of this survey are striking 3 d images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of approx 15 m clearly defined are the dominant flow direction of the ancient braided river system the boundaries between different sedimentary facies and the level of the ground water table trough fill sediments and subhorizontal channel deposits observed on 7 m high quarry walls can be followed confidently in the subsurface the orientation shape and size of the troughs and the strike and dip of the cross bedding are all well resolved

magma storage ascent and recharge history prior to the 1991 eruption at avachinsky volcano kamchatka russia inferences on the plumbing system geometry article i nfo textural and compositional features of plagioclase phenocrysts of the 1991 eruption lavas at avachinsky volcano kamchatka russia were used to investigate the feeding system processes volcanics are porphyritic basaltic andesites and andesites with low k affinity a fractionation modeling for both major and trace elements was per formed to justify the development of these evolved compositions the occurrence of other magma chamber pro cesses was verified through high contrast bse images and core to rim compositional profiles an and feo wt on plagioclase crystals textural types include small and large scale oscillation patterns disequilibrium textures at the crystal core patchy zoning coarse sieve textures dissolved cores disequilibrium textures at the crystal rim sieve textures melt inclusion alignments at the rim disequilibrium textures at the cores may testify episodes of destabilization at various decompression rates under water undersaturated conditions which suggests different pathways of magma ascent at depth at shallower water saturated conditions plagioclase crystallization continues in a system not affected by important chemical physical perturbations oscillatory zoning develops strongly sieve textured rims along with an increase at rather constant feo are evidence of mixing before the 1991 eruption between a residing magma and a hotter and volatile richer one the textural evidence implies that crystals underwent common histories at shallow levels supporting the existence of a large magma reservoir whose top is at 5 5 km of depth distinct textures at the outer rims in a hand size sample are evidence that crys

resolution of fault slip along the 470 km long rupture of the great 1906 san francisco earthquake and its implications data from all available triangulation networks affected by the 1906 earthquake have been combined to assess the trade off between slip resolution and its uncertainty and to construct a conservative image of coseismic slip along the rupture because of varying network aperture and station density slip resolution is very uneven although slip is determined within uncertainties of 1 0 m along 60 of the fault constraints are poor on the remaining mostly offshore portions of the rupture slip decreases from maxima of 8 6 and 7 5 m at shelter cove and tomales bay to 4 5 m near mount tamalpais and 2 7 m at loma prieta the geodetically derived slip distribution is in poor agreement with estimates based on analysis of s wave seismograms probably because these waves register only 20 30 of the total seismic moment obtained from longer period surface waves consideration of a range of fault geometries for 1906 slip near loma prieta indicates right lateral motions lie between 2 3 and 3 1 m these values are considerably greater than the 1 5 m of measured surface slip on which several assessments of high earthquake hazard for this fault segment were based this factor along with the absence of 1989 slippage where 1906 surface slip was used to make the forecasts casts doubt on some claims of success in predicting the 1989 m 6 9 loma prieta earthquake

stratigraphic architecture and fault offsets of alluvial terraces at te marua wellington fault new zealand revealed by pseudo 3d gpr investigation 1 past earthquake slips on faults are commonly determined by measuring morphological offsets at current ground surface because those offsets might not always be well preserved we examine whether the first 10 m below ground surface contains relevant information to complement them we focus on the te marua site new zealand where 11 alluvial terraces have been dextrally offset by the wellington fault we investigated the site using pseudo 3d ground penetrating radar and also produced a high resolution digital elevation model dem of the zone to constrain the surface slip record the gpr data reveal additional information 1 they image the 3d stratigraphic architecture of the seven youngest terraces and show that they are strath terraces carved into graywacke bedrock each strath surface is overlain by 3 5 m of horizontally bedded gravel sheets including two pronounced and traceable reflectors 2 thanks to the multilayer architecture terrace risers and channels are imaged at three depths and their lateral offsets can be measured three to four times constraining respective offsets and their uncertainties more reliably and 3 the offsets are better preserved in the subsurface than at the ground surface likely due to subsequent erosion deposition on the latter from surface and subsurface data we infer that te marua has recorded six cumulative offsets of 2 9 7 6 18 23 2 26 and 31 m 1 2 m large earthquakes on southern wellington fault might produce 3 5 m of slip slightly less than previously proposed pseudo 3d gpr thus provides a novel paleoseismological tool to complement and refine surface investigations

results of 3 d georadar surveying and trenching the san andreas fault near its northern landward limit abstract as part of a program to determine the location and geometry of the san andreas fault saf buried beneath shallow sediments near its northern landward limit three 20 m long parallel trenches were constructed at positions distributed over a distance of 55 m the majority of excavated material comprised unconsolidated fluvial sediments deposited in a number of paleochannels single zones of active faulting identified in each of the trenches were initially interpreted in terms of a solitary strand of the saf to map the saf between and beyond the trenches and to detect other active fault zones hidden by the young sedimentary cover we collected a dense ground penetrating radar georadar data set across a 23 2 72 m area the data were recorded using a semi automated acquisition system that included a conventional georadar unit coupled to a self tracking laser theodolite with automatic target recognition capabilities since these data were plagued by system ringing as a result of the moderate to high electrical conductivities of the surficial sediments an extensive data processing scheme was required to extract meaningful subsurface information the final processed georadar volume cuboid contained numerous subhorizontal and trough shaped reflections that originated from the fluvial paleochannels using the geological interpretation of the trench walls as a guide to pick semi automatically the times of the most important reflecting horizons we discovered that alignments of the nearly linear boundaries of these horizons defined two nw se trending strands of the saf within the survey area the georadar expression of the eastern saf strand could only be traced over a distance of 38 m it had been intersected in the northern trench in contrast the western saf strand extended over the entire length of the georadar volume and had been intersected in the central and southern trenches prominent reflections on georadar cross sections were found to be vertically displaced by 0 2 0 3 m across both saf strands a conspicuous linear trending feature observed on horizontal sections at 3 3 3 6 m depth was laterally offset by 4 5 5 5 m along the eastern saf strand the interpreted vertical and horizontal offsets could have been generated by the 1906 san francisco earthquake and or earlier events undetermined amounts of aseismic slip may also have occurred along the newly defined saf strands

magmatic residence times of zoned phenocrysts introduction and application of the binary element diffusion modelling bedm technique this paper describes a general technique binary element diffusion modelling bedm for determining single crystal residence times in magmas that relies on modelling the diffusion of two or more elements in the crystal bedm has the advantage over other diffusion based models in that it does not need a precisely defined initial compositional profile for the crystal at zero time and instead requires that the concentrations of the two elements are correlated during crystallisation any differences subsequently observed between the two elements are caused by intracrystalline diffusion during residence in hot magma these differences are removed by artificially ageing the slower diffusing of the two elements and the amount of time taken to undo the difference between the elements is simply related to the crystal residence time decoupling time at high temperatures the bedm principle is demonstrated using artificial data and is then applied to literature data for sr and ba in a zoned sanidine crystal from the bishop tuff anderson et al in j petrol 41 3 449 473 2000 for this crystal the method gives a residence time estimate of 114 ka at 800 c which is then compared with estimates from other methods in theory the method can be further expanded for use as a geothermometer as well as geochronometer however this is not easily possible with the diffusivity data currently available

a temporal record of magma accumulation and evolution beneath nevado de toluca mexico preserved in plagioclase phenocrysts plagioclase crystals from the 8 km 10 5 ka upper toluca pumice utp eruption from nevado detoluca provide a detailed temporal record of pre eruptive magmatic processes the crystals display a range of textures and major and trace element concentrations a distinct feature of the crystals is the presence of several sharp increases in mgo feo andtio2 which occur at some of the numerous resorption horizons and coincide with increases in xan and in some cases ce and la these abrupt compositional peaks and the associated textural variations reflect recharge events of more mafic melt three distinct recharge events can be recognized the general compositional trends suggest that crystallization occurred within a common chamber however the crystal cores display a range of textures and a wide range of compositions suggesting that they are relics of earlier crystallization episodes within the upper crust the temporal record of sr and ba melt contents recorded by the crystals calculated using partition coefficients fluctuates significantly within single crystals overall two trends of sr ba variation in the melt are apparent the first trend involves decreasing sr and slightly increasing ba consistent with plagioclase crystallization the second trend involves an increase in both sr and ba that is not consistent with crystallization of plagioclase alone this trend is ascribed to chemical variations within the deeper magma reservoirs from which the various magma batches entering the utp shallow reservoir were ultimately sourced the magmatic system under nevado de toluca was open and received intermittent but relatively small pulses of magma from a deeper source dacite was the predominant recharge composition although some pulses were distinctly more mafic and hotter these processes led to the accumulation of a large volume of dacitic magma in the upper crust one of the more mafic pulses appears to have triggered the eruption

cooling of a magmatic system under thermal chaotic mixing the cooling of a basaltic melt undergoing chaotic advection is studied numerically for a magma with a temperature dependent viscosity in a two dimensional 2d cavity with moving boundary different statistical mixing and energy indicators are used to characterize the efficiency of cooling by thermal chaotic mixing we show that different cooling rates can be obtained during the thermal mixing of a single basaltic magmatic batch undergoing chaotic advection this process can induce complex temperature patterns inside the magma chamber the emergence of chaotic dynamics strongly modulates the temperature fields over time and greatly increases the cooling rates this mechanism has implications for the thermal lifetime of the magmatic body and may favor the appearance of chemical heterogeneities in the igneous system as a result of different crystallization rates results from this study also highlight that even a single magma batch can develop under chaotic thermal advection complex thermal and therefore compositional patterns resulting from different cooling rates which can account for some natural features that to date have received unsatisfactory explanations including the production of magmatic enclaves showing completely different cooling histories compared with the host magma compositional zoning in mineral phases and the generation of large scale compositional zoning observed in many plutons worldwide

application of ground penetrating radar to investigation of near surface fault properties in the san francisco bay region abstract in many geologic environments ground penetrating radar gpr provides high resolution images of near surface earth structure gpr data collection is nondestructive and very economical the scale of features detected by gpr lies between those imaged by high resolution seismic reflection surveys and those exposed in trenches and is therefore potentially complementary to traditional techniques for fault location and mapping sixty two gpr profiles were collected at 12 sites in the san francisco bay region results show that gpr data correlate with large scale features in existing trench observations can be used to locate faults where they are buried or where their positions are not well known and can identify previously unknown fault segments the best data acquired were on a profile across the san andreas fault traversing pleistocene terrace deposits south of olema in marin county this profile shows a complicated multi branched fault system from the ground surface down to about 40 m the maximum depth for which data were recorded

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

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

localization and characterization of an active fault in an urbanized area in central guatemala by means of geoelectrical imaging article i nfo article history the polochic and motagua faults define the active plate boundary between the north american and caribbean plates in central guatemala a splay of the polochic fault traverses the rapidly growing city of san miguel uspantan that is periodically affected by destructive earthquakes this fault splay was located using a 2d electrical resistivity tomography ert survey that also characterized the fault damage zone and evaluated the thickness and nature of recent deposits upon which most of the city is built ert images show the fault as a 50 m wide near vertical low resistivity anomaly bounded within a few meters by high resistivity anomalies forward modeling reproduces the key aspects of the observed electrical resistivity data with remarkable fidelity thus defining the overall location geometry and internal structure of the fault zone as well as the affected lithologies our results indicate that the city is constructed on a 20 m thick surficial layer consisting of poorly consolidated highly porous water logged pumice this soft layer is likely to amplify seismic waves and to liquefy upon moderate to strong ground shaking the electrical conductivity as well as the major element chemistry of the groundwater provides evidence to suggest that the local aquifer might at least in part be fed by water rising along the fault therefore the potential threat posed by this fault splay may not be limited to its seismic activity per se but could be compounded its potential propensity to enhance seismic site effects by injecting water into the soft surficial sediments the results of this study provide the basis for a rigorous analysis of seismic hazard and sustainable development of san miguel uspantan and illustrate the potential of ert surveying for paleoseismic studies

three years 2011 2013 of eruptive activity at mt etna working modes and timescales of the modern volcano plumbing system from micro analytical studies of crystals abstract tracking magma dynamics at active volcanoes by using the compositional and textural records of minerals is becoming an important aspect of modern volcanology to solve key issues such as temporal relationships between magma recharge and eruption duration of magma storage and final ascent upward to the surface these issues are relevant at mt etna where the style of volcanic activity during the last years showed drastic variations in duration and intensity the paroxysmal activity between 2011 and 2013 at the volcano summit has given the opportunity to investigate the chemical physical processes driving the activity and to fix their spatial temporal relationships into the plumbing system an extensive compositional dataset of plagioclase and olivine crystals from lavas emitted between the 2011 and 2013 at mt etna has been used to constrain modes and timescales of magma storage and transfer to the surface plagioclase crystals display either near equilibrium or disequilibrium textures at the core and rim that indicate complex histories of magma crystallization under variable chemical and physical conditions crystals with different textures have been characterized for major an minor fe and mg and trace elements sr ba textural relationships at the plagioclase cores support the idea that crystals undergo variable decompression rates in the deep parts of the plumbing system fe and mg zoning vs anorthite in correspondence of plagioclase sieve textures at the rim suggest that processes of gas flushing have a dominant role in triggering paroxysmal eruptions determining a sudden intensification of the eruptive activity up to the fountaining phase the sr ba ratio in oscillatory zoned plagioclase revealed the dominant presence into the plumbing system of high sr magma volumes coexisting with low sr magma batches that preserve a geochemical signature similar to that of magmas feeding the pre 1971 activity through sr diffusion modeling in plagioclase the maximum time of magma storage during the considered eruptive period has been evaluated timescales of crystal residence in the plumbing system are short five years to three decades suggesting limited magma storage and faster transfer dynamics to the surface chemical zoning of olivine crystals highlights processes of multi step magma transfer and residence at different levels of the plumbing system the upward migration of magmas occurred primarily through multiple episodes of injection and mixing between five compositionally distinct magmatic environments m i whose p t o 2 characteristics and concentrations in dissolved volatiles were constrained by thermodynamic modeling on the basis of the forsterite contents found at the olivine cores from a deepest reservoir located at depth of 600 mpa the most primitive magma m00 fo 84 moved along dominant pathways intercepting the m0 fo 80 82 at 390 mpa and or m1a fo 78 250 mpa m1b fo 75 140 mpa and finally the shallow m2 fo 70 73 40 mpa storage zones for some eruptive episodes olivine zoning highlights a preferential route of transfer connecting the m00 and m2 storage zones that facilitated the fast migration of primitive magma at shallow depth fe mg diffusion modeling on olivine normal and reverse zoning defines the timescales of magma transfer and storage across these magmatic environments which vary from 1 to 18 months whereas intrusion and mixing by more basic magma into the shallowest reservoir occurred always within 5 months before the eruption relevance of this study mainly relies on the quantification of volcanic processes at depth that may have considerable consequences in development of unusual high energy eruptions at basaltic volcanoes generally acknowledged for their weak to mild explosive activity

finding the buried record of past earthquakes with gpr based palaeoseismology a case study on the hope fault new zealand in places where sedimentation and erosion compete at fast rates part of the record of past earthquakes on faults may be buried hence hidden in the first few metres below the surface we developed a novel form of palaeoseismology of geophysical type based on the use of a dense pseudo 3 d ground penetrating radar gpr survey to investigate such possible buried earthquake traces on a long fast slipping strike slip fault hope fault new zealand at a site terako where marked alluvial conditions prevail we first used lidar data to analyse the ground surface morphology of the 2 km2 site at the greatest resolution nineteen morphological markers were observed mainly alluvial terrace risers and small stream channels that are all dextrally offset by the fault by amounts ranging between 3 and 200 m the measurements document about 10 past earthquake slip events with a mean coseismic slip of 3 3 1 m with the most recent earthquake event having a slip of 3 0 5 m we then investigated a detailed area of the site 400 x 600 m2 with pseudo 3 d gpr we measured 56 similar to 400 m long 510 m spaced gpr profiles 250 mhz parallel to the fault and evenly distributed on either side the analysis revealed the existence of a palaeosurface buried at about 3 m depth corresponding to the top of alluvial terraces of different ages that buried surface is incised by a dense network of stream channels that are all dextrally offset by the fault we measured 48 lateral offsets in the buried channel network more than twice than at the surface these offsets range between 6 and 108 m as observed at the surface yet provide a more continuous record of the fault slip the similarity of the successive slip increments suggests a slip per event averaging 4 4 1 m fairly similar to that estimated from surface data from the total surface and buried 67 offset collection we infer that a minimum of 30 large earthquakes have broken the hope fault at the terako site in the last about 67 kyr with an average coseismic slip of 3 2 1 m a minimum average recurrence time of about 200 yr and a magnitude of at least mw 7 07 4 our study therefore confirms that part of the record of past earthquakes may indeed reside in the first few metres below the surface where it may be explored with geophysical gpr based palaeoseismology developing such a new palaeoseismological tool should provide rich information that may complement surface observations and help to document the past earthquakes on faults

mineral textures and zoning as evidence for open system processes investigations of mineral textures and zoning as evidence for open system processes during magmatic evolution have always been a centerpiece of petrological studies and have provided some of the best evidence for magma mixing and crustal contamination for many decades e g milch 1905 kuno 1936 eichelberger 1975 sato 1975 anderson 1976 in fact evidence from mineral studies was instrumental in the acceptance of magma mixing as important petrological process ever since it was initially proposed by bunsen 1851 in recent years mineral studies are invigorated by the development of high precision high resolution analytical instruments and techniques through which textural information and compositional data are combined e g jerram and davidson 2007 as minerals respond texturally and compositionally to changing magmatic environments they preserve in their crystal growth stratigraphy a wealth of information regarding their past history of magmatic processes and compositions cf ginibre et al 2007 on the other hand magmatic liquids melts are snapshots of current magmatic states and provide less direct evidence of the processes responsible for their evolution in addition liquids may crystallize thereby destroying the direct evidence they provide with an appropriate set of observations and measurements we can correlate textures with mineral compositions and thus produce a richer composite picture of magmatic evolution than compositional data of minerals alone this contribution reviews the zoning and textures of minerals frequently encountered in volcanic rocks many of which apply equally to plutonic rocks and the interpretations ascribed to these features in terms of open system magmatic processes first i will address the analytical tools that are used to acquire textural and compositional data followed by a brief review of open system processes and a summary of the relevant textures from that point on i will address some mineral specific aspects followed by a discussion

crystallization and resorption in plutonic plagioclase implications on the evolution of granodiorite magma gesiniec granodiorite strzelin crystalline massif sw poland abstract granodiorite from the gesiniec intrusion strzelin crystalline massif sw poland contains complexly zoned plagioclases five chemically and structurally distinct zones can be correlated among crystals cores 25 35 an inner mantles 40 45 an outer mantles 40 25 an resorption zones 35 50 an and rims 35 30 an good structural and chemical major and trace elements correlation of zones between crystals indicates that zonation was produced by changes in conditions of crystallization on a magma chamber scale plagioclase being the liquidus phase records a time span from the beginning of crystallization to emplacement and rapid cooling of granodiorite as thin dykes crystallization began with the formation of inner mantles the paucity and different sizes of inner mantles suggests slow crystallization in high temperature magma normally zoned inner mantles were formed under increasing undercooling compositional trends in mantles suggest closed system crystallization the major resorption zones were caused by injection of less evolved magma as indicated by the strontium increase in plagioclase the injection triggered a rapid rise of magma and plagioclase crystals facilitating mixing but also inducing fast kinetically controlled growth of complex multiple oscillatory zonation within resorption zones the ascent of magma caused decompression melting of plagioclase and produced melt inclusions within inner mantles the cores the decompression range is estimated at a minimum of 2 kbar emplacement of granodiorite as thin dykes allow rapid cooling and preservation of magmatic zonation in plagioclases melt inclusions crystallized completely during post magmatic cooling the zonation styles of plutonic plagioclase differ markedly from volcanic ones suggesting different magma evolution zones in plutonic plagioclase are well correlated indicating crystallization in quiescent magma where crystals accumulation and compositional magma stratification may occur crystals probably did not travel between different regimes resorption occurred but as single albeit complex episodes good correlation of zones in plutonic plagioclases allows a distinction between the main processes controlling zonation and superimposed kinetic effects

crustal forensics in arc magmas abstract the geochemical characteristics of continental crust are present in nearly all arc magmas these characteristics may reflect a specific source process such as fluid fluxing common to both arc magmas and the continental crust and or may reflect the incorporation of continental crust into arc magmas either at source via subducted sediment or via contamination during differentiation resolving the relative mass contributions of juvenile mantle derived material versus that derived from pre existing crust of the upper plate and providing these estimates on an element by element basis is important because 1 we want to constrain crustal growth rates 2 we want to quantitatively track element cycling at convergent margins and 3 we want to determine the origin of economically important elements and compounds traditional geochemical approaches for determining the contributions of various components to arc magmas are particularly successful when applied on a comparative basis studies of suites from multiple magmatic systems along arcs for which differentiation effects can be individually constrained can be used to extrapolate to potential source compositions in the lesser antilles arc for example differentiation trends from individual volcanoes are consistent with open system evolution however such trends do not project back to a common primitive magma composition suggesting that differentiation modifies magmas that were derived from distinct mantle sources we propose that such approaches should now be complemented by petrographically constrained mineral scale isotope and trace element analysis to unravel the contributing components to arc magmas this innovative approach can 1 better constrain true end member compositions by returning wider ranges in geochemical compositions among constituent minerals than is found in whole rocks 2 better determine magmatic evolution processes from core rim isotopic or trace element profiles from the phases contained in magmas and 3 constrain rates of differentiation by applying diffusion controlled timescales to element profiles an example from nguaruhoe volcano new zealand underscores the importance of such a microsampling approach showing that mineral isotopic compositions encompass wide ranges that whole rock isotopic compositions are consequently simply element weighted averages of the heterogeneous crystal cargo and that open system evolution is proved by core rim variations in sr isotope ratios nguaruhoe is just one of many systems examined through microanalytical approaches the overwhelming conclusion of these studies is that crystal cargoes are not truly phenocrystic but are inherited from various sources the implication of this realization is that the interpretation of whole rock isotopic data including the currently popular u series needs careful evaluation in the context of petrographic observations

relationship between kamen volcano and the klyuchevskaya group of volcanoes kamchatka data on the geology petrography mineralogy and geochemistry of rocks from kamen volcano central kamchatka depression are presented and compared with rocks from the neighbouring active volcanoes the rocks from kamen and ploskie sopky volcanoes differ systematically in major elemental and mineral compositions and could not have been produced from the same primary melts the compositional trends of kamen stratovolcano lavas and dikes are clearly distinct from those of klyuchevskoy lavas in all major and trace element diagrams as well as in mineral composition however lavas of the monogenetic cones on the southwestern slope of kamen volcano are similar to the moderately high mg basalts from klyuchevskoy and may have been derived from the same primary melts this means that the monogenetic cones of kamen volcano represent the feeding magma for klyuchevskoy volcano rocks from kamen stratovolcano and bezymianny form a common trend on all major element diagrams indicating their genetic proximity this suggests that bezymianny volcano inherited the feeding magma system of extinct kamen volcano the observed geochemical diversity of rocks from the klyuchevskaya group of volcanoes can be explained as the result of both gradual depletion over time of the mantle n morb type source due to the intense previous magmatic events in this area and the addition of distinct fluids to this mantle source

understanding crystal populations and their significance through the magma plumbing system crystals are rarely composed of a single crystal population that have grown solely from the batch of magma in which they are resident on emplacement either by eruption or shallow intrusion close investigation of the majority of crystal populations reveal that they comprise up to four main components phenocrysts crystals co genetic with their magmatic host xenocrysts crystals wholly or in part foreign to the magmatic host and magma system antecrysts crystals which are recycled one or several times before inclusion in the host magma but have an origin within the magmatic system and microlites which represent small co genetic crystals which nucleate and grow rapidly on decompression and eruption textural analysis techniques are employed to quantify key aspects of the crystal population including crystal shape crystal size distributions spatial distribution patterns and textural modification using dihedral angles santorini provides a case study of an active volcanic system where a combined textural analysis study has been developed highlighting how the crystal population is being continuously modified by a series of replenishment and mixing events developing textural and microgeochemical techniques provides the next stage in the interrogation of crystal populations linking textures to isotopic heterogeneities and providing fingerprints of where crystals are sourced and re cycled

dynamics of magma mixing in partially crystallized magma chambers textural and petrological constraints from the basal complex of the austurhorn intrusion se iceland the tertiary austurhorn intrusive complex in se iceland represents an exhumed magma chamber that has recorded an extensive history of magma mixing and mingling the basal part of the intrusion consists predominantly of granophyres that have been intensively and repeatedly intruded by more mafic magma this association of granophyres basic and hybrid rocks at austurhorn is referred to in the literature as a net veined complex but field relations suggest a much more complex emplacement history here we present petrological and physical constraints on the various processes that resulted in magma mixing and mingling and the formation of different generations of hybrid rocks at austurhorn the complexity of the mixing and mingling processes increases towards the inferred centre of the intrusion where chaotic hybrid rocks dominate the exposed lithology complex cross cutting relations between different hybrid generations strongly suggest multiple magma injection and reheating events in the basal part of the shallow magma chamber model calculations employing distribution coefficients based on rare earth element concentrations reveal that early stage hybrid magma generations formed by pure endmember mixing between felsic and mafic magma with about 10 mafic fraction in the hybrids with repeated injections of mafic magma into the base of the magma chamber the intruding magma interacted to a greater extent with pre existing hybrids this led to the formation of hybrid magma compositions that are shifted towards the mafic endmember over time with up to 30 of the mafic fraction in the hybrids these mixing processes are recorded in the zonation patterns of clinopyroxene and plagioclase phenocrysts the latter have been divided into four main groups by cross correlation analysis melt viscosity calculations were performed to constrain the possible conditions of magma mixing and the results indicate that the interaction of the contrasting magmas most probably occurred at temperatures of approximately 1000 c up to 1120 c this suggests that the initiation of effective magma mixing requires local superheating of the felsic magmas thereby confining the process to areas of localized substantial mafic magma injection

shallow geometry and displacements on the san andreas fault near point arena based on trenching and 3 d georadar surveying 1 to characterize buried portions of the san andreas fault saf near its northern extremity in california three trenches were excavated perpendicular to it and a 3 d georadar data set was acquired similar sequences of unconsolidated fluvial sediments franciscan serpentinite and active fault zones were observed in the three trenches fault traces in the trenches were initially assumed to be part of a single saf strand however the georadar data demonstrated the existence of two saf strands one of which was exposed in the central and southern trenches and the other in the northern trench offset of a linear trending georadar feature possibly a fluvial paleochannel suggests that 4 5 5 5 m of horizontal displacement occurred across the eastern saf strand either during the 1906 san francisco earthquake or earlier georadar reflections from flat lying and trough shaped sedimentary boundaries are vertically offset by 0 2 0 3 m along both fault strands

location and geometry of the wellington fault new zealand defined by detailed three dimensional georadar data 1 earthquakes with surface wave magnitudes of 7 3 7 9 are estimated to be associated with the rupture of the wellington fault at relatively regular intervals of 500 770 years the last such earthquake probably happened between ad 1510 and 1660 along its southern segment the wellington fault passes through wellington new zealand s capital and the densely populated hutt valley it is considered to be a highly hazardous structure to map the shallow geometry of the wellington fault we have collected 3 d ground penetrating radar georadar data at two sites along the fault in the hutt valley at one site the first ever georadar fault plane reflections from an active strike slip fault are observed they coincide with conspicuous diffractions generated by abrupt truncations of structures against the fault plane these georadar data provide the most vivid shallow images of any active fault surveyed to date at the second site apparent offsets of lineaments in the sedimentary sections on either side of the fault are consistent with 20 m of dextral displacement estimated from the offset of a nearby terrace riser the dips and minimum depth extents of the primary zones of fault displacement at the two sites are 55 75 se and 20 m and 72 84 se and 12 m respectively although the georadar defined zones of faulting are a few meters wide prominent reflection fabrics suggest that shearing fracturing and crushing extend for several tens of meters on either side of the fault

constraints on the pre eruptive magmatic history of the quaternary laacher see volcano germany ba zonation patterns in sanidine phenocrysts from mafic and intermediate phonolite and crystal rich cumulates from the laacher see volcano 12 9 ka in western germany document diffusion times suggestive of periodic recharge events throughout the magma reservoir s entire lifespan of 24 ky phenocrysts analysed from samples that formed late at the base of the compositionally zoned magma reservoir by mixing and mingling between a resident phonolite magma and recharging basanite show resorption and thin 2 10 m late stage ba rich overgrowth short diffusion profiles across these boundaries give diffusion times of 1 5 3 years at most which are interpreted to be the maximum duration between the most recent recharge by the basanite and eruption the lack of such late overgrowth in samples from other parts of the phonolite reservoir suggests that effect of this mixing and mingling was limited to the crystal rich base sanidines in the cumulates by contrast are generally devoid of zoned crystals only rare cumulate crystals with resorbed outer boundaries and very thin overgrowths a few microns with very sharp compositional changes imply the remobilization of cumulates only months before eruption based on the diffusion timescales and storage temperatures obtained in a previous study we present a genetic model for the conditions and timing of storage and re activation of the magma system prior to the eruption of laacher see which is the largest volcanic event in central europe since the last glaciation

role of magma mixing in the petrogenesis of tephra erupted during the 1990 98 explosive activity of nevado sabancaya southern peru the nevado sabancaya in southern peru has exhibited a persistent eruptive activity over eight years following a violent eruption in may june 1990 the explosive activity consisted of alternated vulcanian and phreatomagmatic events followed by declining phreatic activity since late 1997 the mean production rate of magma has remained low 106 107 m3 per year

gpr measurements to assess the emeelt active fault s characteristics in a highly smooth topographic context mongolia to estimate the seismic hazard the geometry dip length and orientation and the dynamics type of displacements and amplitude of the faults in the area of interest need to be understood in this paper in addition to geomorphologic observations we present the results of two ground penetrating radar gpr campaigns conducted in 2010 and 2011 along the emeelt fault in the vicinity of ulaanbaatar capital of mongolia located in an intracontinental region with low deformation rate that induces long recurrence time between large earthquakes as the geomorphology induced by the fault activity has been highly smoothed by erosion processes since the last event the fault location and geometry is difficult to determine precisely however by using gpr first a non destructive and fast investigation the fault and the sedimentary deposits near the surface can be characterized and the results can be used for the choice of trench location gpr was performed with a 50 mhz antenna over 2 d lines and with a 500 mhz antenna for pseudo 3 d surveys the 500 mhz gpr profiles show a good consistency with the trench observations dug next to the pseudo 3 d surveys the 3 d 500 mhz gpr imaging of a palaeochannel crossed by the fault allowed us to estimate its lateral displacement to be about 2 m this is consistent with a right lateral strike slip displacement induced by an earthquake around magnitude 7 or several around magnitude 6 the 2 d 50 mhz profiles recorded perpendicular to the fault show a strong reflection dipping to the ne which corresponds to the fault plane those profiles provided complementary information on the fault such as its location at shallow depth its dip angle from 23 to 35 and define its lateral extension central asia is known for its high level of seismic hazards especially mongolia which has been one of the most seismically active intracontinental regions in the world with four large earthquakes magnitude around 8 along its active faults in the western part of the country during the last century khilko et al 1985 the deformation in mongolia is located between compressive structures related to the collision and penetration of the indian plate into the eurasian plate and extensive structures in the north of the country related with the baykal rift tapponnier molnar 1979 baljinnyam et al 1993 schlupp 1996 bayasgalan jackson 1999 the seismic activity observed in the vicinity of ulaanbaatar ub capital of mongolia is relatively low compared to the activity observed in western mongolia nevertheless since 2005 the seismic activity around ub not only has increased but is also organized see fig 1 at the west of ub along two perpendicular directions which determine two active faults emeelt fault discovered in 2008 nnw sse direction 25 km long minimum and situated about 10 km w of ub and hustai fault wsw ene direction 80 km long with its ne tip at less than 20 km west of ub their length and morphology indicate that they can produce earthquakes of magnitude 6 5 7 5 schlupp et al 2012 most of the mongolian population 1 2 million over 3 million is concentrated at ub which is the main political and economical centre of the country hence the study of seismic hazard and the estimation of the probability of future destructive earthquakes are of primary importance for the country dugarmaa et al 2006 since the last large earthquake the faults geomorphology has been highly smoothed by erosional processes and the exact location of the fault plane surface rupture is thus hidden within a several metre wide strip the gpr method has been proven to give good and useful results to characterize faults by identifying offsets of radar reflections malik et al 2007 christie et al 2009 yalciner et al 2013 and

a la icp ms study of minerals in the rocche rosse magmatic enclaves evidence of a mafic input triggering the latest silicic eruption of lipari island aeolian arc italy the volcanic products of lipari island aeolian arc italy younger than 10 ka are mostly aphyric rhyolitic pumices and obsidians emitted during unusual strombolian type eruptions which ended with the emplacement of lava flows the last volcanic activity on the island dates back to 1230 40 ad with the extrusion of rocche rosse rr obsidian lava flow recently mafic enclaves of latitic to trachytic composition have been identified and an evolution process between these enclaves and the rhyolitic magma has been documented in detail davi m 2007 the rocche rosse rhyolitic lava flow lipari aeolian islands magmatological and volcanological aspects plinius supplement to the european journal of mineralogy 33 1 8 in this work textural and trace element investigation of mineral phases of the rr enclaves such as crystals of clinopyroxene olivine plagioclase alkali feldspar and biotite was carried out to delineate the most recent feeding system of the island since such a reconstruction could be significant in terms of hazard forecasting the results indicate that most of the mineral phases are reversely or oscillatory zoned with respect to both major and trace elements suggesting an early crystallization under low f o 2 conditions from melts of intermediate composition followed by a later growth from a more mafic presumably shoshonitic basaltic magma than that from which their cores crystallized crystals of magnesium rich pyroxene and forsteritic rich olivine are indicative of the presence of this shoshonitic basaltic magma based on microanalytical data it is suggested here that the feeding system of recent lipari volcanic activity was characterized by a shoshonitic basaltic magma originating from a deep reservoir which may have evolved and stopped in the crust generating zoned magma chambers at different depths in which latitic and rhyolitic magmas reside the sudden arrival of a new input of mafic melt may have interacted with these resident fractionated magmas and triggered the eruption a plumbing system of this type has been shown to be active in the southern sector of the aeolian islands since the last 42 ka gioncada a mazzuoli r milton a 2005 magma mixing at lipari aeolian islands italy insights from textural and compositional features of phenocrysts j volcanol geotherm res 145 97 118 peccerillo a frezzotti m l de astis g ventura g 2006 modeling the magma plumbing system of vulcano aeolian islands italy by integrated fluid inclusion geobarometry petrology and geophysics geology 34 17 20 it is concluded that the hazard assessment of lipari island should take into account the arrival of deep and never erupted mafic melts as eruption triggers of more evolved shallower magma bodies

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

origin of crosscutting dissolution surfaces in magmatic plagioclase crosscutting dissolution surfaces dss are rare features observed in magmatic plagioclase crystals in this study crosscutting dss of dacitic plagioclase crystals from the shirahama group izu peninsula japan were investigated using a nomarski differential interference contrast imaging microscope and chemical compositional data crosscutting ds slopes were examined by tracing digitized images the following features of crosscutting dss are reported for the first time 1 traces of the crosscutting dss showed parabolic like shapes 2 crosscutting dss were found on select adjacent or opposite faces of the crystals suggesting a preferential dissolution of a limited area of the plagioclase 3 projecting points were observed with directional characteristics and 4 square or angular patterns were found in the less dissolved parts of the crystals the formation of crosscutting features is controlled by dissolution and crystal settling into hotter magma process velocities depend on the physical properties of the magma such that a description of crosscutting features can reveal valuable information about the magmatic environment and the dynamic behavior of crystals

modeling of gas driven magmatic overturn tracking of phenocryst dispersal and gathering during magma mixing 1 we present a combined multiphase numerical and crystal tracking approach that provides a framework to investigate the transport and zoning of crystals associated with a gas driven mixing event mixing in compositionally intermediate to silicic magmatic systems is often initiated by gas exsolution in the recharging magma causing a density inversion and subsequent overturn the overturn is simulated for a range of bubble volume fractions bubbles and therefore indirectly for a range of reynolds numbers re all simulations show chaotic flow dynamics with fast overturn timescales of minutes to hours the large scale mixing is inefficient during a single overturn resulting in a continuously stratified system with respect to bubble volume fraction the crystal tracking algorithm provides us with information on the small scales i e 10 cm on this length scale we observe gathering of different crystals during the overturn that typically ranges on the order of tens of meters thus a complex crystal population may arise within a single overturn this gathering and dispersal of crystals is strongest and most uniform for high re for low re crystal populations are characterized by less gathering of crystals that originated from distal portions of the magma body during the overturn the crystals pass through environments of changing chemical potential we apply the damkohler number da which compares the crystallization or dissolution to the advection timescale results show an asymmetry between crystallization and dissolution crystallization times are too slow during gas driven overturn to record transient changes in chemical potential crystals most likely only record their initial as well as their final chemical environment in contrast dissolution and advection rates are of similar order suggesting potential dissolution during the overturn on the basis of the results for gas driven overturn we expect that slower physical mixing processes may be continuously recorded in the zonation pattern of the crystal phases as long as the changes in chemical potential produce crystal growth

a multiproxy record of holocene environmental changes in the central kola peninsula northwest russia a sediment core from chuna lake kola peninsula northwest russia was studied for pollen diatoms and sediment chemistry in order to infer post glacial environmental changes and to investigate responses of the lake ecosystem to these changes the past ph and dissolved organic carbon doc of the lake were inferred using diatom based transfer functions between 9000 and 4200 cal yr bp slow natural acidification and major changes in the diatom flora occurred in chuna lake these correlated with changes in regional pollen the arrival of trees in the catchment changes in erosion sediment organic content and doc during the past 4200 yr diatom based proxies showed no clear response to changes in vegetation and erosion as autochthonous ecological processes became more important than external climate influences during the late holocene the pollen stratigraphy reflects the major climate patterns of the central kola peninsula during the holocene i e a climate optimum between 9000 and 5400 5000 cal yr bp when climate was warm and dry and gradual climate cooling and an increase in moisture during the past 5400 5000 yr this agrees with the occurrence of the north south humidity gradient in fennoscandia during the holocene copyright 2002 john wiley sons ltd

nanoscale characterisation of crystal zoning abstract advances in analytical techniques are fundamental to the enhanced understandings of many geological processes zoned volcanic crystals have been analysed by low 5 kv field emission gun electron probe micro analyser feg epma and nanosims to obtain sub micrometre chemical profiles and compared to time of flight sims tof sims and high 15 20 kv epma profiles plagioclase and orthopyroxene crystals have been analysed by feg epma at accelerating voltages of 5 kv providing a spatial resolution step size of 350 nm the resolution of the lowest energy x ray for orthopyroxene crystals using a 30 nm beam and ca 750 nm for plagioclase crystals which at low voltages are unstable and require a 500 nm defocused beam step sizes are comparable in size to interaction volumes analytical protocols are detailed that permit quantitative major and minor element compositions to be acquired at similar precision and accuracy as traditional epma analyses at 15 20 kv nanosims analysis of the same crystals provides a greater spatial resolution of up to 200 nm and allows the measurement of li also the nanosims profiles however cannot currently be quantified the ability to analyse crystals at sub micrometre scales is demonstrated by the good agreement between nanosims feg epma conventional epma and tof sims data feg epma nanosims and tof sims techniques have broad applications within the earth sciences in petrologic studies for example these methods have the ability to analyse small crystals in experimental charges and provide chemical profiles of crystal zoning at a spatial resolution of ca 200 300 nm such profiles are important in crystal forensics and diffusion chronometry studies the implications for the latter application are that timescales of volcanic processes that occur in the days years immediately prior to the eruption can now be studied

high k mafic plinian eruptions of volcan de colima mexico the last plinian type eruption of volcan de colima mexico occurred in 1913 this resulted in the removal of the top 100 m of the edifice and the deposition of a tephra layer that blanketed the slopes of the colima volcanic complex cvc road cuts on the flanks of the nearby nevado de colima edifice expose pre 1913 air fall tephra pyroclastic flow and ash rich surge deposits resulting from numerous highly explosive events throughout the holocene the majority of the pumice and scoria fallout deposits are medium k subalkaline basaltic andesite and andesite in composition defining a clear major element differentiation trend in contrast three newly discovered scoria fallout deposits are high k subalkaline transitional to alkaline basaltic andesite in composition and are characterized by the presence of phlogopite these deposits have high mgo up to 7 9 wt k2o up to 2 6 wt and p2o5 up to 0 67 wt contents they are also strongly enriched in fluid and melt mobile large ion lithophile elements lile rb ba k sr and th and light ree lree la ce pr and nd relative to the majority of the colima tephra fallout deposits strontium and nd isotope systematics reveal that the high k mafic scoria have more radiogenic sr 87sr 86sr 0 70365 0 70408 and less radiogenic nd 143nd 144nd 0 51279 0 51294 compared with the majority of the subalkaline tephras 87sr 86sr 0 70338 0 70371 and 143nd 144nd 0 51290 0 51295 two component mixing models using whole rock geochemical data indicate the importance of magma mixing in the petrogenesis of the colima magmas with addition of up to 50 by volume of an alkaline mafic magma component in the most potassic magmas this is supported by mineral chemistry and textural data which reveal multiple episodes of decompression and magma mingling within a shallow crustal magma storage region the presence of these potassic tephra fall deposits among the otherwise prevailing medium k subalkaline stratigraphy indicates that pulses of k rich alkaline mafic magmas periodically enter the cvc plumbing system on timescales of a few thousand years and may trigger plinian explosive eruptions

crystal residence times from trace element zoning in plagioclase reveal changes in magma transfer dynamics at mt etna during the last 400 years abstract trace element zoning in plagioclase of selected alkaline lavas from the historic 1607 1892 ad and recent 1983 2013 ad activity of mt etna volcano has been used to explore the possible role that volcano tectonics exert on magma transfer dynamics the observed textural characteristics of crystals include near equilibrium textures i e oscillatory zoning and textures with variable extent of disequilibrium patchy zoning coarse sieve textures and dissolved cores historic crystals exhibit lower k concentrations at lower anorthite contents a feature in agreement with the general more potassic character of the recent lavas if compared to the historic products historic plagioclases have statistically higher ba and lower sr concentrations than the recent crystals which result in different sr ba ratios for the two suites of plagioclase variations in the anorthite content along core to rim profiles obtained on crystals with different types of textures for both the historic and recent eruptive periods were evaluated particularly versus sr ba at comparable average an contents crystals characterized by oscillatory zoning which are representative of near equilibrium crystallization from the magma display distinct sr ba ratios we suggest that these features are primarily related to recharge of a new geochemically distinct magma into the storage and transport system of the volcano in addition to distinct trace element and textural characteristics of plagioclase sr diffusion modeling for plagioclase suggests that residence times are generally shorter for crystals found in recently erupted lavas 25 77 years average 43 years compared to those of the historic products 43 163 years average 99 years shorter residences times correlate with gradual increases in eruption volume and eruption frequency rates through time we attribute these features to an increasing influence since the 17th century of extensional tectonic structures within the upper 10 km of the etnean crust which have promoted shorter residence times and higher eruption frequency

deciphering textural and chemical zoning of k feldspar megacrysts from mt amiata volcano southern tuscany italy insights into the petrogenesis and abnormal crystal growth abstract this study reports the complex textural and chemical features of k feldspar megacrysts up to 5 cm long hosted in trachydacitic lava flows lava domes and coulees from mt amiata volcano tuscan magmatic province central italy backscattering and cathodoluminescence imaging coupled with core to rim major and trace elements patterns reveal complex zoning and resorption surfaces associated with sharp chemical variations e g sr and ba these zoning patterns originated by disequilibrium and re equilibration events related to the repeated influx of mafic magmas or convective motions in the trachydacitic magma reservoir multiple mafic magma refilling occurences are also supported by the field record of abundant microgranular magmatic enclaves in the studied products our results highlight that the abnormal dimension of the studied k feldspars originates by the interplay between petrological and kinetic processes involving i extensive dissolution ii heterogeneous nucleation iii alternation of spasmodic growth events in disequilibrium and near equilibrium crystallization the repeated influx of hotter magmas and reheating can determine the thermal condition to the growth of few large k feldspar megacrysts also the strong textural and chemical similarities observed in the k feldspar megacrysts from mt amiata volcanic rocks and mt capanne monzogranite elba island central italy support the hypothesis of a phenocrystic origin of intrusive k feldspar megacrysts

minor and trace element zoning in plagioclase implications for magma chamber processes at parinacota volcano northern chile textural and compositional zoning in plagioclase phenocrysts in a sample from parinacota volcano chile was investigated using backscattered electron images and electron microprobe analysis of major and trace elements large 2 mm oscillatory zoned crystals type i with resorption surfaces of moderate an discontinuities 10 an and decreasing trace element contents sr mg ti towards the rim reflect melt differentiation and turbulent convection in the main magma body early recharge with a low sr mafic magma is seen in the core small scale sr variations in the core indicate limited diffusion and thus residence and differentiation times of the magma shorter than a few thousand years smaller crystals type ii with low trace element an ratio reflect the influence of an h2o rich melt probably from a differentiated boundary layer closed system in situ crystallisation mafic magma recharge and the role of a water rich differentiated boundary layer can be distinguished from the an trace element relationships crystals apparently move relatively freely between different parts and regimes in the magma chamber evidence for convective crystal dispersion high sr type ii crystals indicate an earlier input of sr rich mafic magma recharge of two distinct mafic magma types is thus identified high sr and low sr which must have been present at increasing recharge rates with time in the plumbing system throughout the volcano s history

characterization of the shallow structures of active fault zones using 3 d ground penetrating radar data 1 where they can be correlated with geological exposures and trenches 3 d ground penetrating radar gpr data can contribute critical subsurface information to paleoseismic investigations because active faults are typically characterized by complicated near surface structures that vary with the styles of faulting and the types of rock that are ruptured gpr data can be difficult to interpret we have acquired 3 d gpr data sets across three active fault zones within new zealand that have different deformation styles the strike slip wellington fault zone reverse faults of the ostler fault zone and normal faults of the maleme fault zone to improve our interpretation of the processed gpr volumes we employed two suites of geometric attributes the first suite was computed using a coherence based algorithm it provided estimates of the coherency azimuth and dip of reflections the second suite quantified the volumetric textures of reflections which allowed different reflection facies to be defined objectively we have demonstrated how some attributes were more successful at visualizing certain structural or depositional characteristics than others for example the coherency attribute was an excellent tool for highlighting normal faults within volcanic deposits of the maleme fault zone whereas the texture based attributes were most useful for discriminating between the gravel and metasediment units juxtaposed by the wellington fault zone our gpr data sets and associated attribute volumes showed details of near surface fault geometry that were not obvious from surface mapping and they revealed evidence of off fault deformation gravitational collapse and topple structures

anorthite calibrated backscattered electron profiles trace elements and growth textures in feldspars from the teide pico viejo volcanic complex tenerife abstract magma chamber dynamics at the phonolitic to basanitic teide pico viejo volcanic complex on tenerife canary islands have been investigated using feldspar zonation and chemistry backscattered electron image grey value profiles obtained by electron microprobe and calibrated on anorthite content allow the investigation of much better spatially resolved zonation profiles than quantitative point analysis alone on the basis of these zonation patterns and trace element analyses by electron microprobe magma chamber processes such as magma recharge and mingling as well as whole chamber overturn events can be identified and characterized in more detail samples from all investigated eruption centres contain feldspars which have experienced growth in a deep reservoir followed by ascent resorption and growth of mantles in more shallow levels in the crust just prior to eruption two pico viejo samples exhibit feldspars with a characteristic drop in anorthite content which is not accompanied by resorption trace element behaviour in these samples shows that cores and mantles have grown from the same magma reservoir the conclusion from these data is that there occurred complete overturn events in layered magma chambers presumably induced by cold plumes from the cupola layers a mass balance calculation shows that the proportions of the layers are 75 wt lower part and 25 wt cupola layer correlations between zonation patterns of single crystals in different rocks show that the teide magma chambers are larger and chemically buffered compared with the smaller pico viejo system feldspars from pico viejo exhibit rather complex anorthite profiles and more frequently display disturbances likely to be caused by arrival of new magma batches