regimes of magma recharge and their control on the eruptive behaviour during the period 2001 2005 at mt etna volcano mount etna volcano italy during the period 2001 2005 has undergone a period of intense eruptive activity marked by three large eruptions 2001 2002 2003 and 2004 2005 these eruptions encompassed diverse eruptive styles and regimes from intensely explosive during 2001 and 2002 2003 eruptions to exclusively effusive in the 2004 2005 event in this work we put forward the idea that these three eruptions are the response of the progressive arrival into the uppermost segment of the open conduit system of a new magma which was geochemically distinct in terms of trace element and sr nd pb isotope signature from the products previously emitted by the etnean volcano the magma migrated upwards mainly through a peripheral tectonic system which can be considered as eccentric in spite of its relative proximity to the main system the ingress of the new magma and its gradual displacement from the eccentric system into the uppermost sector of the open conduit gave rise to different eruptive behaviours at the beginning the ascent of the undegassed magma able to exsolve a gas phase at depth and its interaction with closed system magma reservoirs less than 10 km deep gave rise to the explosive events of 2001 and 2002 2003 later when the same magma entered into the open conduit system it took part in the steady state degassing and partially lost its volatile load leading to a totally effusive eruption during the 2004 2005 event one further consideration highlighted here is that in 2001 2005 migration of the feeding axis from an eccentric and peripheral position towards the main open conduit has led to the development of a new vent south east crater 2 located at the eastern base of the south east crater through which most of the subsequent etnean activity occurred

constraints on the nature and evolution of the magma plumbing system of mt etna volcano 1991 2008 from a combined thermodynamic and kinetic modelling of the compositional record of minerals maren kahl sumit chakraborty massimo pompilio and fidel costa school of earth and environment university of leeds leeds ls2 9jt uk institut fur geologie mineralogie und geophysik ruhr universit at bochum bochum 44780 germany istituto nazionale di geofisica e vulcanologia sezione di pisa pisa 56126 italy and earth observatory of singapore nanyang technological university singapore 639798 singapore

ice pumps and their rates an ice pump is a heat engine driven by the change of freezing point with pressure which will melt ice at depth in the ocean and deposit it at a shallower location it is self starting calculations of the maximum magnitude of this effect are made which show good agreement with field data available for sea and lake ice the discussion is applied to the general case of a moving pack ice sheet with a well mixed surface layer and to floating ice shelves the rate of melt from an 11 m deep pressure ridge keel due to ice pumping is estimated as 26 cm year and that from the front of the ross ice shelf at mcmurdo sound antarctica is estimated as 5 m year for the level of water movement noted in the authors field observations far from the ice front pumping between shelf areas of different thickness will still occur with tidal motion providing the necessary water exchange but its magnitude is now limited by the ability to remove the potentially stable layer of melt water out of the system it is important to realize that the pumping does not depend on the availability of sensible heat in the water column and its effects are additional to any melting caused by the advection of warmer water to the ice water interface

volatile induced magma differentiation in the plumbing system of mt etna volcano italy evidence from glass in tephra of the 2001 eruption mount etna volcano was shaken during the summer 2001 by one of the most singular eruptive episodes of the last centuries for about 3 weeks several eruptive fractures developed emitting lava flows and tephra that significantly modified the landscape of the southern flank of the volcano this event stimulated the attention of the scientific community especially for the simultaneous emission of petrologically distinct magmas recognized as coming from different segments of the plumbing system a stratigraphically controlled sampling of tephra layers was performed at the most active vents of the eruption in particular at the 2 100 m cal and at the 2 550 m lag scoria cones detailed scanning electron microscope and energy dispersive x ray spectrometer sem eds analyses performed on glasses found in tephra and comparison with lava whole rock compositions indicate an anomalous increase in ti fe p and particularly of k and cl in the upper layers of the lag sequence mass balance and thermodynamic calculations have shown that this enrichment cannot be accounted for by classical differentiation processes such as crystal fractionation and magma mixing the analysis of petrological features of the magmas involved in the event integrated with the volcanological evolution has evidenced the role played by volatiles in controlling the magmatic evolution within the crustal portion of the plumbing system volatiles constituted of h2o co2 and cl complexes originated from a deeply seated magma body dbm their upward migration occurred through a fracture network possibly developed by the seismic swarms during the period preceding the event in the upper portion of the plumbing system a shallower residing magma body abt had chemical and physical conditions to receive migrating volatiles which hence dissolved the mobilized elements producing the observed selective enrichment this volatile induced differentiation involved exclusively the lowest erupted portion of the abt magma due to the low velocity of volatiles diffusion within a crystallizing magma body and or to the short time between volatiles migration and the onset of the eruption furthermore the increased amount of volatiles in this level of the chamber strongly affected the eruptive behavior in fact the emission of these products at the lag vent towards the end of the eruption modified the eruptive style from classical strombolian to strongly explosive

relationship between petrologic processes in the plumbing system of mt etna and the dynamics of the eastern flank from 1995 to 2005 abstract mt etna volcano is located in a complex tectonic setting with large sectors of its eastern flank sliding seaward at different rates according to recent petrologic studies the etna s plumbing system has a multifaceted geometry variable in space and time and consisting of storage zones at different depths where magma ascending to the surface undergoes various processes mainly fractional crystallization and mixing in this framework we investigated a possible cause effect relationship between the flank displacement and pre eruptive magmatic processes in the shallow plumbing system furthermore a comparison between petrologic data and deformative patterns evidences that from 1995 to july 2001 the aforementioned pre eruptive magmatic processes did not significantly influence the volcano eastern flank dislocation which stayed slow and fairly regular by contrast the onset of the 2001 flank eruption leads to an acceleration of the movement as a consequence of the ascent of a primitive volatile rich sub aphyric basaltic magma from a deeper about 10 km b s l reservoir during the 2001 and 2002 03 activity at least for the decade 1995 2005 pre eruptive magmatic processes in the shallow portion

frazil ice formation in an ice shelf water plume 1 we present a model for the growth of frazil ice crystals and their accumulation as marine ice at the base of antarctic ice shelves the model describes the flow of buoyant water upward along the ice shelf base and includes the differential growth of a range of crystal sizes frazil ice formation starts when the rising plume becomes supercooled initially the majority of crystals have a radius of similar to0 3 mm and concentrations are below 0 1 g l depending on the ice shelf slope which controls the plume speed frazil crystals increase in size and number typically crystals up to 1 0 mm in radius are kept in suspension and concentrations reach a maximum of 0 4 g l the frazil ice in suspension decreases the plume density and thus increases the plume speed larger crystals precipitate upward onto the ice shelf base first with smaller crystals following as the plume slows down in this way marine ice is formed at rates of up to 4 m yr in some places consistent with areas of observed basal accumulation on filchner ronne ice shelf the plume continues below the ice shelf as long as it is buoyant if the plume reaches the ice front its rapid rise produces high supercooling and the ice crystals attain a radius of several millimeters before reaching the surface similar ice crystals have been trawled at depth north of antarctic ice shelves but otherwise no observations exist to verify these first predictions of ice crystal sizes and volumes

macro and micro factors affecting coal seam quality and distribution in southern africa with particular reference to the no 2 seam witbank coalfield south africa abstract petrographical and palynological coal quality investigations relating to variations in one of the best known and well researched coalfields in africa the witbank coalfield and one of the most commercially important seams within this coalfield the no 2 seam are highlighted in this paper the investigations were based on 14 channel samples covering a 40 20 km 2 area in the witbank coalfield the results indicate that the coals in the no 2 seam were formed at the stage of major change over from dwyka to ecca floras as illustrated by the progressive dying out of dwyka pollens and spores and the introduction of ecca floral elements this also suggests a rapid amelioration of climate over the period of peat accumulation following a period of continental glaciation furthermore it is proposed that the in seam horizons reflect fluctuating of cyclic environments probably due to changing water level and plant communities due to changing growth environments saccate pollens appear to occur in association with vitrinite rich microlithotypes trilete spores with inertodetrite and carbominerite rich microlithotypes and plicates with inertite semifusite inertodetrite microlithotypes acritarchs nonspinose are present in parts of the seam where inertodetrite is common and in association with unusual suites of trace and major elements possibly indicating changing geochemical environments in high groundwater conditions petrographic results indicate that the coals are medium rank hypobituminous and show wide variations in maceral mineral and microlithotype compositions both vertically and laterally on the basis of microlithotype and mineral group analyses investigations were undertaken to establish vertical subdivisions by the study of historical patterns and possible lateral correlations of these subdivisions in the area under investigation these methods were then compared with distribution of selected chemical and geochemical parameters the evidence suggests that a common sequence of major events and some minor events occurred during the accumulation of the no 2 seam as manifested by petrographic and palynological facies three major periods or zones are recognized these tepresent periods of relatively stability quiescence separated by major in seam disruptive events namely flood deposits bearing high proportions of detrital organic material or minor clastic sedimentation these zones are subdivided into several subzones representing periods of reworking local flooding or rise in ground water levels and or changing geochemical environments these events can be recognized throughout the area under investigation but the manifestation of these events varies from area to area depending upon topographic situation proximity to river channels valley flanks or palaeoshorelines degree of subsidence and compaction geochemical environment and length of time under a specific set of conditions thus channels in close proximity to one another or in similar positions relative to valley flanks or axes appear to be remarkably similar to one another direct correlation of stratigraphic zones and sub zones from sample site of sample site was therefore possible although the methods to achieve this are complex and require the support of several supplementary complementary interpretative techniques coal quality variations and distribution within the original seam are therefore explicable in terms of the detailed factors listed above

eruptive processes leading to the most explosive lava fountain at etna volcano the 23 november 2013 episode the 23 november 2013 lava fountain at etna volcano was the most explosive of the last 44 episodes that have occurred at etna in 2011 2013 we infer the total magma volume erupted by thermal images analysis and show that it was characterized by a very high time averaged discharge rate tadr of 360 m3 s 1 having erupted 1 6 106 m3 of dense rock equivalent magma volume in just 45 min which is more than 3 times the tadr observed during previous episodes two borehole dilatometers confirmed the eruption dynamics inferred from the thermal images when compared to the other lava fountains this episode can be considered as the explosive end member however the erupted volume was still comparable to the other lava fountain events we interpret that the 23 november explosive end member event was caused by more primitive and gas rich magma entering the system as demonstrated by the exceptional height reached by the lava fountain

long and short term magma differentiation at mt etna as revealed by sr nd isotopes and geochemical data abstract mt etna in sicily italy produces effusive and explosive eruptions from summit craters and flanks petrology of erupted products has proved fundamental to explore the relationship between magma dynamics within the plumbing system and eruptive styles data of sr nd isotopes are quite scarce if compared with the great number of chemical analyses carried out in products of last decades we measure sr nd isotopes major and trace elements in products emitted from 2001 to 2012 and consider also published analyses of the 1995 2001 eruptions because carried out in the same laboratories of 2001 2012 ones furthermore we take into account other published analyses extending back to the 14th century even if performed by different facilities based on this dataset magma dynamics operating at different timescales inside the volcano s plumbing system have been explored our analyses evidence that from 2001 2012 three magma types are present in the volcano s plumbing system i a deep and poorly evolved basaltic and k trachybasaltic magma enriched in radiogenic sr and lile erupted during the 2001 and 2002 03 flank activity ii a shallower more evolved k trachybasaltic magma less enriched in radiogenic sr feeding both summit and flank eruptions and iii an uncommon and scarcely radiogenic hawaiitic magma lile poor emitted exclusively from a small sector of the 2002 03 eruptive fissures by considering a broader time scale from 14th to 21st century we conclude that i different magmatic components are present in the deep volcano s plumbing system at about 10 12 km b s l ii a decoupling of geochemical and isotopic features in magmas stored at different depths is observed after the 1974 flank eruption up to date iii mixing between different magmas is an efficient magmatic process to produce magma differentiation at mt etna regardless of the investigated temporal scale

spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas the eruption of mount etna in 2000 was notable for an exceptional series of 64 periodic lava fountains propelling lava fragments to heights of up to 900 metres it has been difficult to determine which of two suggested sources of power gas release from the magma itself during its rapid ascent or a build up of pressure from gas accumulated at depth is the driving force for these dramatic jets but one of the etna fountains provided volcanologists with the opportunity to use remote sensing not that remote see picture on the following page to determine the infrared spectra of the gas phase this revealed the chemical composition of the gas that powered this fountain as consistent with an origin in an accumulated gas layer lava fountains are spectacular continuous gas jets propelling lava fragments to heights of several hundred metres which occasionally occur during eruptions of low viscosity magmas1 2 3 4 5 whether they are generated by the effervescent disruption of fast rising bubbly melt2 3 4 5 or by the separate ascent of a bubble foam layer accumulated at depth6 7 still remains a matter of debate8 no field measurement has yet allowed firm discrimination between these two models a key insight into the origin of lava fountains may be gained by measuring the chemical composition of the driving gas phase this composition should differ markedly depending on whether the magma degassing occurs before or during eruption9 10 here we report the analysis of magmatic gas during a powerful 250 600 m high lava fountain measured with fourier transform infrared spectroscopy11 12 13 14 on mount etna sicily the abundances of volcanic gas species determined from absorption spectra of lava radiation reveal a fountain gas having higher co2 s and s cl ratios than other etnean emissions14 15 16 17 18 and which cannot derive from syn eruptive bulk degassing of etna basalt19 20 instead its composition suggests violent emptying of a gas bubble layer previously accumulated at about 1 5 km depth below the erupting crater

compositionally zoned crystals and real time degassing data reveal changes in magma transfer dynamics during the 2006 summit eruptive episodes of mt etna one of the major objectives of volcanology remains relating variations in surface monitoring signals to the magmatic processes at depth that cause these variations we present a method that enables compositional and temporal information stored in zoning of minerals olivine in this case to be linked to observations of real time degassing data the integrated record may reveal details of the dynamics of gradual evolution of a plumbing system during eruption we illustrate our approach using the 2006 summit eruptive episodes of mt etna we find that the history tracked by olivine crystals and hence most likely the magma pathways within the shallow plumbing system of mt etna differed considerably between the july and october eruptions the compositional and temporal record preserved in the olivine zoning patterns reveal two mafic recharge events within months of each other june and september 2006 and each of these magma supplies may have triggered the initiation of different eruptive cycles july 14 24 and august 31 december 14 correlation of these observations with gas monitoring data shows that the systematic rise of the co2 so2 gas values is associated with the gradual pre and syn eruptive supply of batches of gas rich mafic magma into segments of etna s shallow plumbing system where mixing with pre existing and more evolved magma occurred

magmatic hydrothermal evolution and devolatilization beneath merapi volcano indonesia abstract at merapi volcano indonesia explosive eruptions lasting several months result from injections of reduced mafic magmas and are interspersed by periods of lava dome growth and collapse quiescent degassing assimilation of wall rock and fractional crystallization lasting a few years silicate melt inclusions and volcanic gases were analyzed to study processes of magmatic volatile exsolution and volcanic degassing during periods of quiescent degassing at merapi volcanic gases were sampled at merapi in 1994 during a phase of quiescent degassing and in 2006 at the end of a dome growth and collapse explosive eruption silicate melt inclusions were collected and analyzed from lavas and scorias for their major element and volatile components solubility relationships between h 2 o and co 2 in melt inclusions demonstrate that melt was being trapped beneath merapi to depths reaching 19 km host amphibole geobarometry indicates crystallization pressures reaching up to 26 km hence there is evidence of deep pooling and crystallization of magma beneath merapi at appreciable depths using a mass balance model of magmatic volatile exsolution we demonstrate that the magma degassing from 19 km to the surface approaches closed system behavior compared to the bulk magmatic volatiles analyzed in melt inclusions volcanic gases had similar amounts of co 2 were enriched in h 2 o and s and depleted in cl and f we thus propose that the magmatic volatile phase was initially exsolved from the magma as a supercritical fluid and that it subsequently exsolved into a h 2 o cl f rich brine and co 2 s rich vapor according to the h 2 o nacl model brine vapor exsolution occurred at 5 km in depth for a 5 wt nacl 900 c to 1000 c fluid although the presence of h 2 s so 2 and co 2 may cause the supercritical fluid to unmix at greater depths magma at shallower depths exsolved a brine and a vapor directly from the melt the volcanic gases at merapi thus represent the vapor fraction of a magmatic volatile phase as brine ponded below the surface we further suggest that carbon dioxide liberated by the magmatic assimilation of limestone as proposed by other studies fluxed the melt thereby promoting co 2 enrichment of the melt and h 2 o degassing finally we propose that merapi volcanic gases are enriched in sulfur compared to the modeled volatile phase composition because deep reduced mafic magma supplies sulfur to the shallow magmatic plumbing system

coal depositional models and the distinction between alluvial and delta plain environments abstract the distinction between coal bearing upper and lower delta plain deposits in the rock record may be based on the presence or absence of features indicative of basinal influence and on the geometry of coal seams discriminating between alluvial plain and upper delta plain sequences is more difficult but is considered possible on coal seam geometry and coal seam splitting patterns other features such as the cross sectional shape of channel deposits may also be useful

no evidence for thermogenic methane release in coal from the karoo ferrar large igneous province abstract the early jurassic toarcian oceanic anoxic event t oae and concurrent negative carbon isotope 13 c excursion have recently been attributed to either the release of methane ch 4 clathrates or thermogenic ch 4 gas associated with the karoo ferrar large igneous province lip into coals and organic rich shales 12 c enriched thermogenic ch 4 production associated with the karoo ferrar would result in residual material being 12 c depleted nearer the intrusions in this study geochemical analyses carbon isotopes volatile matter vm vitrinite reflectance r o are reported for two coal transects associated with dykes intruding the no 4l coal in the highveld coalfield karoo basin south africa vm decreases from over 35 to around 15 in one transect and the second transect shows a less pronounced decrease from 25 to 16 accompanying the decrease in vm content is an increase in r o from background levels of around 0 7 to over 4 adjacent to the dyke used as a palaeo geothermometer r o values indicate background temperatures of 100 c increasing to 300 c close to the contact despite changes in vm and r o there are no significant changes in 13 c certainly not of the magnitude that would be expected associated with large scale thermogenic ch 4 generation these and other gondwanan coals have low vitrinite and liptinite contents components more prone to ch 4 generation in part explaining the modest decreases in vm adjacent to the dykes this combined with the relatively narrow metamorphic aureole surrounding the intrusions and the likelihood that at least some of the volatiles generated by the intrusion were trapped as coalbed ch 4 or condensed as pyrolytic carbon suggests only limited ch 4 release in addition based on original estimates of moisture contents in these coals and the depth at time of intrusion 1 000 2 000 m the dykes would have lost most of their energy heating and evaporating water thus having very little remaining energy to generate thermogenic ch 4

hydrogen in the gas plume of an open vent volcano mount etna italy 1 we report here on the first hydrogen determinations in the volcanic gas plume of mount etna in italy which we obtained during periodic field surveys on the volcano s summit area with an upgraded multigas using a specific ezt3hyt electrochemical sensor we resolved h2 concentrations in the plume of 1 3 ppm above ambient background atmosphere and derived h2 so2 and h2 h2o plume molar ratios of 0 002 0 044 mean 0 013 and 0 0001 0 0042 mean 0 0018 respectively taking the above h2 so2 ratios in combination with a time averaged so2 flux of 1600 gg yr 1 we evaluate that etna contributes a time averaged h2 flux of 0 65 gg yr 1 suggesting that the volcanogenic contribution to the global atmospheric h2 budget 70 000 100 000 gg yr 1 is marginal we also use our observed h2 h2o ratios to propose that etna s passive plume composition is at least partially representative of a quenched temperatures between 750 c and 950 c equilibrium in the gas magma system at redox conditions close to the nickel nickel oxide nno mineral buffer the positive dependence between h2 so2 h2 h2o and co2 so2 ratios suggests that h2 is likely supplied at least in part by deeply rising co2 rich gas bubbles fluxing through a co2 depleted shallow conduit magma

conduit convection magma mixing and melt inclusion trends at persistently degassing volcanoes abstract magmas progressively exsolve volatiles as they ascend towards the earth s surface such that their volatile content is a function of pressure water and carbon dioxide concentrations measured in melt inclusions from degassing volcanoes rarely coincide with modelled degassing trends i show that observed melt inclusion trends can be reproduced through mixing of magmas either during convection within the volcanic conduit or within a subterranean magma reservoir no fluxing gas phase or post entrapment loss of water need be invoked a permeable network allowing gas transport is still required to avoid fragmentation of magma at shallow depths

forecasting etna eruptions by real time observation of volcanic gas composition it is generally accepted but not experimentally proven that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data by discussing the results of two years of real time observation of h2o co2 and so2 in volcanic gases from mount etna volcano we unambiguously demonstrate that increasing co2 so2 ratios can allow detection of the pre eruptive degassing of rising magmas quantitative modeling by the use of a saturation model allows us to relate the pre eruptive increases of the co2 so2 ratio to the refilling of etna s shallow conduits with co2 rich deep reservoir magmas leading to pressurization and triggering of eruption the advent of real time observations of h2o co2 and so2 combined with well constrained models of degassing represents a step forward in eruption forecasting

new insights into magma dynamics during last two eruptions of mount etna as inferred by geochemical monitoring from 2002 to 2005 two distinct eruptive events characterize the volcanic activity at mount etna during the 2002 to 2005 period we identified signals of magma ascent preceding these eruptions by geochemical monitoring of both chemical composition and he isotope ratio of gas emissions from five locations in the peripheral area of the volcano the geochemical signals are interpreted using the models proposed by caracausi et al 2003a 2003b and allow identification of episodes of magma ascent and estimation of the pressures of degassing magma as observed for the 2001 eruption caracausi et al 2003b magma ascent probably triggered the onset of the 2002 2003 eruption and minor events of magma ascent were observed between may and december 2003 in contrast to the previous two eruptions the 2004 2005 eruption was not preceded by significant geochemical signals of volcanic unrest suggesting that this eruption was mainly triggered by the failure of the upper portion of the volcanic edifice under the magmatic hydrostatic pressure in the conduits high 3he 4he ratio revealed new volatile rich magma accumulation the 2002 2003 eruption was preceded by a much shorter period of new magma accumulation from deep levels of the feeding system few minor signals of magma migration were detected at some of the sites during the months preceding the 2004 2005 eruption suggesting that the degassed 3he depleted magma resident in the volcanic conduits was not replaced by new volatile rich magma this is in agreement with the lack of explosive activity during the 2004 2005 eruption and with petrologic observations that the parent magma probably erupted in 2000 and 2001 new geochemical signals of magma ascent from the deep reservoir have been identified since june 2005 indicating that the volcanic activity of mount etna is evolving toward new pre eruptive conditions

the 1989 1990 activity of etna magma mingling and ascent of h2oclsrich basaltic magma evidence from melt inclusions abstract the melt inclusions in olivine phenocrysts from basaltic tephra erupted by etna volcano during the 1989 1990 eruptive period were investigated for major elements cl and s by electron microprobe fluorine by pigme particule induced gamma ray emission and h 2 o by sims the results indicate the ascent of basaltic magmas with different k 2 o concentrations possibly related to different feeding dykes lk basaltic melt inclusions rich in cl s and h 2 o are trapped in olivine fo 84 from the 1990 tephra and represent the early crystallization stage their composition in major elements is quite similar to those of most of the historic and even pre etnean alkali basalts but significantly lower in k 2 o compared with the 1989 1990 lavas only scarce hk basaltic melt inclusions were observed in the outer rim fo 79 6 of reversely zoned olivine phenocrysts and correspond to late crystallization stage at low pressure high sulfur concentration s 0 3 wt is a general characteristic of the etnean basaltic magmas with h 2 o s ratio as high as 7 the volatile abundances of the etna primitive basalts were computed at 1 45 wt for h 2 o 0 17 wt for cl and 0 047 wt for f with a high cl f ratio close to 3 6 the 1989 lava samples with cl at 660 90 ppm and f at 770 30 ppm have suffered a significant cl loss the possible behaviour of the volatile phase as co 2 h 2 o even cl is discussed with h 2 o and chlorine late degassing and an active role of h 2 o during the lava fountaining activity

impact of antarctic ice shelf basal melting on sea ice and deep ocean properties 1 an approximation of antarctica s rocky and icy coastline normally forms the southern boundary in global climate models such a configuration neglects extensive ice shelf areas where ocean ice interaction initiates a net freshwater flux to the circumpolar continental shelf equal to 75 of the annual mean net precipitation in coastal seas the results of a numerical model for the southern ocean using two contrasting configurations with and without caverns beneath major antarctic ice shelves are compared they show that the freshwater flux due to deep basal melting significantly stabilizes the shelf water column in front of an ice shelf as well as downstream due to advection by the coastal current if the freshwater from the caverns is absent sea ice is thinner shelf waters are warmer and saltier and the southern ocean deep basins are flushed by denser waters

facies development in the lower freeport coal bed west central pennsylvania u s a abstract the lower freeport coal bed in west central pennsylvania is interpreted to have formed within a lacustrine mire environment conditions of peat formation caused by the changing chemical and physical environments produced five coal facies and two mineral rich parting facies within the coal bed the coal bed facies are compositionally unique having developed under varying conditions and are manifested by megascopic petrographic palynologic and quality characteristics the initial environment of the lower freeport peat resulted in a coal facies that is relatively high in ash yield and contains large amounts of lycopod miospores and moderate abundances of cryptotelinite crypto gelocollinite inertinite and tree fern miospores this initial lower freeport peat is interpreted to have been a topogenous body that was low lying relatively nutrient rich mesotrophic to eutrophic and susceptible to ground water and to sediment influx from surface water the next facies to form was a ubiquitous clay rich durain parting which is attributed to a general rise in the water table accompanied by widespread flooding following formation of the parting peat accumulation resumed within an environment that inhibited clastic input development of doming in this facies restricted deposition of the upper shale parting to the margins of the mire and allowed low ash peat to form in the interior of the mire because this environment was conducive to preservation of cellular tissue this coal facies also contains large amounts of crypto telinite this facies development is interpreted to have been a transitional phase from topogenous planar peat formation to slightly domed oligotrophic nutrient poor peat formation as domed peat formation continued fluctuations in the water table enabled oxidation of the peat surface and produced high inertinite concentrations toward the top of the coal bed tree ferns became an increasingly important peat contributor in the e upper facies based on the palynoflora this floral change is interpreted to have resulted from the peat surface becoming less wet or better drained a condition that inhibited proliferation of lycopod trees accumulation of the peat continued until rising water levels formed a freshwater lake within which clays and silts were deposited the development of the lower freeport peat from a planar mire through transitional phases toward domed peat formation may be an example of the type of peat formation of other upper middle and upper pennsylvanian coal beds

magma transport and storage at mt etna italy a review of geodetic and petrological data for the 2002 03 2004 and 2006 eruptions abstract a detailed reconstruction of magma movements within the plumbing system of mt etna volcano has been made by reviewing the eruptions occurring during the october 2002 december 2006 period the availability of continuous gps data allowed detecting at least ten different ground deformation stages highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion these data have been coupled with the available petrological datasets including major trace elements and sr nd pb isotope compositions for the volcanic rocks erupted in the 2002 2006 period we identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano the former is located at a depth of 7 km bsl and fed the 2001 and 2002 03 eruptions while the latter located from 3 5 to 5 5 km bsl fed the 2004 05 and 2006 eruptions petrological characteristics of emitted products have been correlated with the inflation vs deflation cycles related to the identified sources providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature finally we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002 03 eruption as a consequence of the major seaward motion of the eastern flank of the volcano

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

comment on conduit convection magma mixing and melt inclusion trends at persistent degassing volcanoes by fred witham published in earth planetary science letters 2011 301 345 352 we discuss the influence of magma mixing on the co 2 h 2 o behavior in magmas witham s model does not fit our melt inclusion data set for mt etna and stromboli magma fluxing by a deep derived co 2 rich gas better explains the co 2 h 2 o evolution

geochemical evidence for mixing between fluids exsolved at different depths in the magmatic system of mt etna italy abstract a 4 year geochemical survey of some fumaroles at the voragine summit crater of mt etna was performed in combination with synchronous monitoring of peripheral gas emissions at the base of the volcano this was the first geochemical study at mt etna to have included the abundances of ar he and c isotopes once the effects of postmagmatic shallow processes were identified and quantitatively removed the he ar co 2 systematics of the voragine crater fumaroles and peripheral gas emissions described the same degassing path combining the carbon isotope composition with information about noble gases provided evidence that the crater fumaroles are fed from a two endmember mixture composed of a deep member coming from pressures between 200 and 400 mpa depending on time and a shallower one exsolved at 130 mpa similar mixing processes probably also occur in gases from peripheral vents the simultaneous assessment of 13 c co2 and he ar values of crater fumaroles over time has identified simple changes in the mixing proportion between the two endmembers and moreover periods during which the exsolution pressure of the deep fluid increased these periods seem to be linked to pre eruptive phases of the volcano the identified open system degassing processes are indicative of efficient bubble melt decoupling at depth whereas the mixing process requires a convective transfer of the deeply exsolved fluids toward shallower levels of magma where further vapor is exsolved in agreement with the most recent geophysical and petrological data from mt etna these observations allow inferences about a deep portion of the plumbing system 5 to 12 km b s l comprising sill like reservoirs connected by small vertical structures and a main reservoir at 2 3 km b s l that is probably fluxed by magmatic volatiles

solidification and turbulence non laminar during magma ascent insights from 2d and 3d analyses of bubbles and minerals in an etnean dyke

melt inclusion record of the conditions of ascent degassing and extrusion of volatile rich alkali basalt during the powerful 2002 flank eruption of mount etna italy 1 two unusual highly explosive flank eruptions succeeded on mount etna in july august 2001 and in october 2002 to january 2003 raising the possibility of changing magmatic conditions here we decipher the origin and mechanisms of the second eruption from the composition and volatile h2o co2 s cl content of olivine hosted melt inclusions in explosive products from its south flank vents our results demonstrate that powerful lava fountains and ash columns at the eruption onset were sustained by closed system ascent of a batch of primitive volatile rich 4 wt basaltic magma that rose from 10 km depth below sea level bsl and suddenly extruded through 2001 fractures maintained opened by eastward flank spreading this magma the most primitive for 240 years probably represents the alkali rich parental end member responsible for etna lavas evolution since the early 1970s few of it was directly extruded at the eruption onset but its input likely pressurized the shallow plumbing system several weeks before the eruption this latter was subsequently fed by the extrusion and degassing of larger amounts of the same but slightly more evolved magma that were ponding at 6 4 km bsl in agreement with seismic data and with the lack of preeruptive so2 accumulation above the initial depth of sulphur exsolution 3 km bsl we find that while ponding this magma was flushed and dehydrated by a co2 rich gas phase of deeper derivation a process that may commonly affect the plumbing system of etna and other alkali basaltic volcanoes

microanalysis of cl br and i in apatite scapolite and silicate glass by la icp ms constraining the abundance and distribution of halogens in geological materials has the potential to provide novel insights into a broad range of earth system processes e g metasomatism melting volatile cycling and ore formation in this contribution we develop analytical protocols for the in situ measurement of cl br and i in widely distributed standard reference materials apatite scapolite silicate glass using readily available laser ablation icp ms instrumentation ablations were performed at a range of square spot sizes 30 80 m using a high repetition rate 25 hz and extended analyte dwell times up to 250 ms to improve sensitivity and signal stability a comparison of la icp ms results with published halogen data was used to calculate the following theoretical limits of quantification cl 360 g g br 8 g g i 0 75 g g a detailed assessment of raw signal intensities for different matrices with known halogen contents combined with high resolution mass scans provides new constraints on the origin of apparent halogen signals on mass cl signal excesses are likely ooh and or oo br is influenced by peak shoulder overlap from arar a diargon cation ar and a matrix based interference tb for samples with br tb 0 6 i signals are similar for all but the highest i materials analysed here suggesting the presence of ubiquitous gas based interferences the observation that false positive halogen signals only occur during sample ablation suggests that they are either matrix derived or related to the process of sample introduction during ablation matrix loading may reduce plasma energy resulting in a greater proportion of polyatomic interferences in the system for cl we provide a new time dependent excess apparent cl spline correction defined by analysis of halogen free olivine via a modified version of the iolite data reduction scheme x trace elements is the correction improves the limit of linearity to 100 g g for cl in glasses down to a 38 m spot size we test our methodology on apatite from permian alkaline lamprophyres in the pyrenees spain and quartz hosted melt inclusions from rhyolitic deposits at the taupo volcanic zone new zealand obtaining results comparable to electron microprobe and sims data we provide recommendations for analytical best practice and highlight the need for well characterised matrix matched srms spanning a broad range of concentrations to allow for the identification and removal of non analyte related contributions to measured signals

conditions of magma storage degassing and ascent at stromboli new insights into the volcano plumbing system with inferences on the eruptive dynamics stromboli is known for its persistent degassing and rhythmic strombolian activity occasionally punctuated by paroxysmal eruptions the basaltic pumice and scoria emitted during paroxysms and strombolian activity respectively differ in their textures crystal contents and glass matrix compositions which testify to distinct conditions of crystallization degassing and magma ascent we present here an extensive dataset on major elements and volatiles co2 h2o s and cl in olivine hosted melt inclusions and embayments from pyroclasts emplaced during explosive eruptions of variable magnitude magma saturation pressures were assessed from the dissolved amounts of h2 oa nd co2 taking into account the melt composition evolution both pressures and melt inclusion compositions indicate that 1 ca basaltic melts entrapped in high mg olivines fo89 90 generate stromboli basalts through crystal fractionation and 2 the stromboli plumbing system can be imaged as a succession of magma ponding zones connected by dikes the 7 10 km interval where magmas are stored and differentiate is periodically recharged by new magma batches possibly ranging from ca basalts to basalts with a co2 rich gas phase these deep recharges promote the formation of bubbly basalt blobs which are able to intrude the shallow plumbing system 2 4 km where co2 gas fluxing enhances h2o loss crystallization and generation of crystal rich dense degassed magma chlorine partitioning into the h2o co2 bearing gas phase accounts for its efficient degassing 69 under the open system conditions of strombolian activity paroxysms however are generated through predominantly closed system ascent of basaltic magma batches from the deep storage zone in this situation crystallization is negligible and sulfur exsolution starts at 170 mpa chlorine remains dissolved in the melt until lower pressures only 16 being lost upon eruption finally we propose a continuum in explosive eruption energy from strombolian activity to large paroxysmal events ultimately controlled by variable pressurization of the deep feeding system associated with magma and gas recharges

stochastic modelling of coalbed methane resources a case study in southeast qinshui basin china this paper presents a stochastic analysis of coalbed methane cbm resources for a coal seam in southeast qinshui basin china log and laboratory data are used to predict the coal thickness coal ash content and coal gas content using reservoir modelling the distributions of the karst collapse column kcc coal seam thickness coal quality and coal gas content are generated the convergent interpolation and sequential gaussian simulation methods are used to model the surface and structure of the coal seam the structural models are determined by the surface structure and coal seam thickness based on the structural models the coal and kcc are converted to two facies and their distributions are obtained using object modelling the coal density distributions are simulated based on each facies model using the sequential gaussian simulation finally different realisations are used to study cbm resources the results show that the heterogeneities in coal seam thickness and coal quality lead to significant uncertainty in estimating cbm resources a model with lower heterogeneity gives a greater cbm resource the distributions of kcc coal seam thickness coal quality and gas content are the main sources for uncertainty in cbm resource estimation the density variogram and top structure contribute less to the uncertainty in cbm resources

transfer of volatiles and metals from mafic to felsic magmas in composite magma chambers an experimental study abstract in order to determine the behavior of metals and volatiles during intrusion of mafic magma into the base of silicic upper crustal magma chambers fluid rock partition coefficients dfluid rock of li b na s cl k mn fe rb sr ba ce cu zn ag cd mo as se sb te w tl pb and bi were determined experimentally at 2 kbar and 850 c close to the solidus of mafic magma in a first step volatile bearing mafic glasses were prepared by melting a natural basaltic trachyandesite in the presence of volatile bearing fluids at 1200 c 10 kbar in piston cylinder presses the hydrous glasses were then equilibrated in subsequent experiments at 850 c 2 kbar in cold seal pressure vessels which caused 80 90 of the melt to crystallize after 0 5 2 0 days of equilibration the exsolved fluid was trapped by means of in situ fracturing in the form of synthetic fluid inclusions in quartz both the mafic rock residue and the fluid inclusions were subsequently analyzed by laser ablation icp ms for major and trace elements reverse experiments were conducted by equilibrating metal bearing aqueous solutions with rock powder and then trapping the fluid in two additional experiments information on relative element mobilities were obtained by reacting fluids that exsolved from crystallizing mafic magma with overlying silicic melts the combined results suggest that under the studied conditions s cl cu se br cd and te are most volatile dfluid rock 10 followed by li b zn as ag sb cs w tl pb and bi dfluid rock 1 10 less volatile are na mg k ca mn fe rb sr mo and rb dfluid rock 0 1 1 and the least fluid mobile elements are al si ti zr ba and ce dfluid rock

modeling the transport of passive tracers in sea ice 1 a model for the vertical transport of passive tracers in sea ice is presented two reynolds flux closure approximations are proposed for the tracer velocity dispersion term in the new ice tracer model icet the schemes enhanced molecular diffusion emd and mixing length diffusion mld are suggested parameterizations of gravity drainage the dominant mechanism of desalination in growing sea ice the performance of icet using each parameterization is tested against two experimental studies simulations i compare profiles of brine salinity with passive tracer concentrations during sea ice growth and melt and simulations ii compare bottom boundary salt and brine volume fluxes with passive tracer fluxes and bottom diffusivities icet behavior is evaluated under three salinity forcing prescriptions both schemes successfully reproduce expected tracer concentrations in simulations i when the salinity forcing evolves logarithmically however in simulations ii the mld scheme outperforms emd in two significant ways 1 growth rate trends in the mld diffusivity parallel measurements of brine volume flux while emd bottom diffusivities remain almost constant and 2 mld bottom tracer concentrations decrease with ice growth rate similar to excluded brine salinity while emd trends are contrary hence enhanced molecular diffusion is highly questionable for implementation in models of reactive passive tracers the icet mixing length diffusivity is a viable choice in sea ice biogeochemical modeling it remains a challenge to assess whether mld can provide quantitative estimates of desalination at each time step for use in forcing icet or for implementation in a model of sea ice salinity

observation and modeling of platelet ice fabric in mcmurdo sound antarctica 1 during the annual growth of landfast ice in mcmurdo sound antarctica an episodic flux of platelet ice crystals from the ocean contributes to the build up of a porous subice platelet layer which is steadily incorporated into the sea ice cover as it thickens over winter in november 2007 we examined the spatial variability of these processes by collecting sea ice cores with simultaneous oceanographic observations along an east west transect in the sound previously identified draped and bladed platelet ice types were observed in addition we identify resumed columnar growth which appears to be a result of geometric selection from the subice platelet layer after the arrival of new platelet crystals from the ocean has ceased a numerical model of mechanical platelet ice processes is developed that predicts crystal texture and c axis distributions producing virtual incorporated platelet ice with known growth history this model demonstrates how a disordered subice platelet layer arises from an initially flat interface and suggests that such a layer is more likely to form later in the growth season the model also suggests how the grain boundary density in incorporated platelet ice responds to changes in the flux of loose platelet crystals from the ocean application of this result to our 2007 platelet ice observations indicates that sea ice in western mcmurdo sound is subject to larger and more persistent platelet fluxes than the ice in the east this is consistent with the pattern of in situ supercooling just beneath the ocean surface

glacier fed sandstone sheets in the weller coal measures permian allan hills antarctica abstract the upper member of the weller coal measures permian at allan hills victoria land antarctica consists of repetitive coal layers separated by sheetlike bodies of predominantly sandstone and subordinate siltstone and conglomerate all of fluvial origin investigation of the lowermost inter coal sheet wc1 reveals abrupt planar basal contacts persistent upward fining and a strong westward palaeocurrent trend three lithofacies are recognized in the wc1 sheet a small scale cross bedded pebbly sandstone which occupies most of the basal portions of the sheet b large scale cross bedded medium coarse sandstone confined to a linear ne sw belt overlying or locally replacing facies a and c siltstone and rippled fine grained sandstone which drapes and overlaps facies a and b and contains glossopteris leaves and vertebraria root traces facies distribution patterns indicate the wc1 body initiated as an abrupt sheetlike incursion of coarse sediment over a low lying mire facies a followed by entrenchment and confinement of flow as the sheet extended distally facies b facies c represents low energy floodplain sedimentation co existing with and later succeeding facies b as deposition evolved toward abandonment and eventual renewal of peat deposition relatively rapid deposition of the sandstone sheet is implied by the lack of any significant hiatus markers outsized clasts up to 45 cm in diameter one observed to display prominent striations occur sporadically throughout the wc1 including within siltstone beds of facies c these are inferred to be ice rafted deposits which together with other evidence suggest meltwater influence possibly glacial on sediment transport and deposition preliminary examination of other sandstone sheets in the upper weller indicates attributes similar to the wc1 including abrupt bases upward fining character and predominantly westward palaeocurrent patterns the allan hills exposures are believed to represent a succession of low lying mire complexes interrupted by abrupt but infrequent incursions of coarse sediment possibly by extreme meltwater floods

2001 flank eruption of the alkali and volatile rich primitive basalt responsible for mount etna s evolution in the last three decades abstract since the early 1970s enhanced eruptive activity of mount etna has been accompanied by selective geochemical changes in erupted lavas among which a gradual increase of alkalis whose origin is still debated here we provide further insight into the origin of this recent evolution based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase poor primitive basalt that was extruded during a highly explosive flank eruption in july august 2001 two types of lava were erupted simultaneously along a n s fracture system trachybasalts from the upper vents 2950 2700 m were simply drained out by fracturing of the central volcanic conduit they are identical to summit crater lavas and contain mg poor olivines fo 70 72 with evolved and volatile poor melt inclusions that represent late stage crystallisation during shallow open conduit degassing in contrast plagioclase poor basalt 80 of total extruded through the lower vents 2550 2100 m derived from lateral dyke intrusion of a more primitive and volatile rich magma across the sedimentary basement this primitive melt is best preserved in rare fo 82 4 80 5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent its high dissolved contents of h 2 o 3 4 wt co 2 0 11 to 0 41 wt s 0 32 wt cl 0 16 wt and f 0 094 wt point to its closed system ascent from 400 to 250 mpa 12 to 6 5 km depth b s l however the predominance of euhedral olivine phenocrysts with common reverse zoning cores fo 76 78 and rims fo 78 80 and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting the few preserved inclusions in these olivines indicate pre eruptive storage of that magma body at about 5 km depth b s l in coherence with seismic data we propose that the 2001 flank eruption resulted from gradual overpressuring of etna s shallow plumbing system due to the influx of volatile rich primitive basalt that may have begun several months in advance we find that this basalt is much richer in alkalis 2 0 wt k 2 o and has higher s cl 2 0 but lower cl k and cl f ratios than all pre 1970s etnean lavas 1 4 wt k 2 o s cl 1 5 as further exemplified by melt inclusions in entrained olivine xenocrysts combining these new observations with previously published data we argue that the 2001 basalt represents a new alkali rich basic end member feeding mt etna only few amount of which had previously been extruded during a 1974 peripheral eruption and more recently during brief paroxysmal summit events over the last three decades this new magma has progressively mixed with and replaced the former k poorer trachybasalts filling the plumbing system leading to extrusion of gradually more primitive and alkali richer lavas its geochemical singularities cannot result from shallow crustal contaminations instead they suggest the involvement of an alkali richer but cl poorer arc type component during recent magma genesis beneath etna

simulation of the crystal growth of platelet sea ice with diffusive heat and mass transfer antarctic coastal sea ice often grows in water that has been supercooled by interaction with an ice shelf in these situations ice crystals can form at depth rise and deposit under the sea ice cover to form a porous layer that eventually consolidates near the base of the existing sea ice the least consolidated portion is called the sub ice platelet layer congelation growth eventually causes the sub ice platelet layer to become frozen into the sea ice cover as incorporated platelet ice in this study we simulate these processes in three dimensions using voronoi dynamics to govern crystal growth kinetics platelet deposition in situ growth and incorporation into the sea ice cover are integrated into the model heat and mass transfer are controlled by diffusion we extract and compare spatial temporal distributions of porosity salinity temperature and crystallographic c axes with observations from mcmurdo sound antarctica the model captures the crystallographic structure of incorporated platelet ice as well as the topology of the sub ice platelet layer the solid fraction which has previously been poorly constrained is simulated to be 0 22 in good agreement with an earlier estimate of 0 25 0 06 this property of the sub ice platelet layer is important for biological processes and for the freeboard thickness relationship around antarctica

chemical heterogeneity of mt etna magmas in the last 15 ka inferences on their mantle sources abstract primitive basaltic magmas are crucial in the study of the geochemical heterogeneity documented in etna magmas and their inferred mantle sources we undertook a systematic sampling of the less evolved basalts mg 50 erupted over the last 15 ka a time period which corresponds to the activity of the youngest volcanic edifice of mt etna complex i e mongibello volcano we focused on lava flows and pyroclastites emplaced during deep dyke fed ddf eruptions which were driven by the rapid ascent of deeply rooted magma intrusions that bypassed the shallow plumbing system of the volcano all the samples were analyzed by the same laboratory to avoid analytical bias to build a comprehensive dataset on their major and trace element compositions and to propose a coherent framework for interpreting the geochemical fingerprints of present day etna basalts trace element modeling together with literature data for sr isotopes gave insight into long term magmatic processes related to different melting degrees of the heterogeneous mantle beneath mt etna ddf magma batches provide good snapshots of their mantle source heterogeneities that point to the variable involvement of clinopyroxenitic lithology rb 87 sr cl rich fluid component s possibly controlled by their source mineralogy and slab derived fluids selectively enriched in alkalis rb k the ongoing alkali rb k enrichment of the present day magmas well manifest since the 1970s is decoupled from that of sr and cl we propose that this process is linked to mantle source composition and is concomitant with changes in both volcanological and seismotectonic patterns of the volcano there is no time evolution of ddf magma chemistry

rates of carbon dioxide plume degassing from mount etna volcano 1 we report here on the real time measurement of co2 and so2 concentrations in the near vent volcanic gas plume of mount etna acquired by the use of a field portable gas analyzer during a series of periodic field surveys on the volcano s summit during the investigated period september 2004 to september 2005 the plume co2 so2 ratio ranged from 1 9 to 10 8 with contrasting composition for northeast and voragine crater plumes scaling the above co2 so2 ratios by uv spectroscopy determined so2 emission rates we estimate co2 emission rates from the volcano in the range 0 9 67 5 kt d 1 average 9 kt d 1 about 2 kt of co2 were emitted daily on average during quiescent passive degassing whereas co2 emission rates from etna s summit were 10 40 times larger during the 2004 2005 effusive event with a cumulative co2 release of 3800 kt during the 6 months of the eruption such a syneruptive increase ascribed to the replenishment of the shallow 6 km volcanic plumbing system by co2 rich 0 25 wt more primitive magmas supports the potential of co2 output rates as key parameters for volcanic hazard assessment

evolution of a supercooled ice shelf water plume with an actively growing subice platelet matrix we use new observations in western mcmurdo sound combined with longitudinal hydrographic transects of the sound to identify a northward flowing ice shelf water isw plume exiting the cavity of the mcmurdo ross ice shelf we estimate the plume s net northward transport at 0 4 0 1 sv carving out a corridor approximately 35 km wide aligned with the victoria land coast basal topography of the mcmurdo ice shelf is such that the plume is delivered to the surface without mixing with overlying warmer water and is therefore able to remain below the surface freezing temperature at the point of observation beneath first year ice thus the upper ocean was supercooled by up to 50 mk at the surface due to pressure relief from recent rapid ascent of the steep basal slope the 70 m thick supercooled layer supports the growth and maintenance of a thick semirigid and porous matrix of platelet ice which is trapped by buoyancy at the ice ocean interface continued growth of individual platelets in supercooled water creates significant brine rejection at the top of the water column which resulted in convection over the upper 200 m thick homogeneous layer by examining the diffusive nature of the intermediate water between layers of isw and high salinity shelf water we conclude that the isw plume must have originated beneath the ross ice shelf and demonstrate that it is likely to expand eastward across mcmurdo sound with the progression of winter

no slab derived co2 in mariana trough back arc basalts implications for carbon subduction and for temporary storage of co2 beneath slow spreading ridges the southern mariana trough is particularly well suited to study mass balance in subduction zones because the flux of material recycled from the subducted slab has been shown to diminish to negligible levels in the southernmost part of the area we present new he and ar concentration and isotopic data for 16 back arc basaltic glasses and combine these with previously published co2 and h2o concentration and 13c data to explore the recycling of carbon and light noble gases in the mariana back arc degassing has affected all samples and is particularly extensive in more water rich samples i e those containing the largest recycled component the degassing history features three stages 1 deep degassing which commenced when the melt reached saturation of co2 and noble gases in the mantle 2 preeruptive degassing during storage in the crust mantle transition zone which involved addition of extraneous co2 to the vapor phase and 3 eruption co2 released during stage 1 was at least partially incorporated into wall rock and subsequently remobilized during stage 2 degassing of later magma batches reconstructed parental values for 3he 4he 13c co2 3he and co2 40ar are indistinguishable from those of mid ocean ridge basalt this implies that there is negligible recycling of subducted carbon helium or argon into the source of mariana trough basalt

delineation of the distinctive nature of tertiary coal beds abstract floral character in mires has changed progressively through time in the carboniferous pteridophytes sphenophytes and lycophytes were dominant but by the permian gymnosperms were an important component of mire flora during the early mesozoic gymnosperms remained the characteristic mire vegetation together with pteridophytes and conifers became dominant during the jurassic cretaceous and paleocene vegetation are similar with taxodiaceous flora being important in mire vegetation from the eocene onwards however angiosperms were increasingly dominant in mire communities and in the miocene herbaceous vegetation began to play a significant role together with these changes in floral character at least three aspects of coal character also appear to vary sequentially with time and are distinctive in the tertiary 1 proportions and thickness of vitrain banding 2 coal bed thickness and 3 proportions of carbonised material a compilation has been made of data from the coal literature comparing older coals with those of the tertiary in order to give a perspective in which to examine tertiary coals it was found that only tertiary coals contain significant proportions of coal devoid of vitrain bands in addition tertiary coals are the thickest recorded coal beds and generally contain low percentages of carbonised material many less than 5 as compared to older coals it is interesting to note that paleocene coal beds are similar to cretaceous coals in that they tend to be thinner and contain higher proportions of carbonised material than do younger tertiary coals the absence of vitrain bands in some tertiary coal beds is thought to result from the floras dominated by angiosperms which are relatively easily degraded as compared to gymnosperms the thickness of tertiary coals may be related to an increase in biomass production from the carboniferous through to the tertiary as plants made less investment in producing lignin an energy intensive process in addition with less lignin in plants easier degradation of biomass may have facilitated nutrient recycling which in turn led to greater biomass production increased biomass production may have also diluted the carbonised material present in some tertiary peats leading to lower proportions in the coal another possible cause of decreased carbonised components in tertiary coal is that decreasing lignin content resulted in decreased charring during fires as lignin is particularly prone to charring a third possibility is that the carbonised component of peat may be concentrated during coalification so that tertiary coals generally of lower rank than mesozoic or paleozoic coals contain a smaller fraction of carbonised plant material it is not at present clear which of these mechanisms may have affected carbonised material in peat and coal but it is clear that lignin type and content has had an important role in determining peat and coal character since the paleozoic

influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the ross sea antarctica 1 satellite imagery shows that there was substantial variability in the sea ice extent in the ross sea during 2001 2003 much of this variability is thought to be due to several large icebergs that moved through the area during that period the effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model it would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs here sea ice concentration is specified from satellite observations to examine the effects of changes in sea ice due to iceberg c 19 simulations were performed using either climatological ice concentrations or the observed ice for that period the heat balance around the ross sea polynya rsp shows that the dominant term in the surface heat budget is the net exchange with the atmosphere but advection of oceanic warm water is also important the area average annual basal melt rate beneath the ross ice shelf is reduced by 12 in the observed sea ice simulation the observed sea ice simulation also creates more high salinity shelf water another simulation was performed with observed sea ice and a fixed iceberg representing b 15a there is reduced advection of warm surface water during summer from the rsp into mcmurdo sound due to b 15a but a much stronger reduction is due to the late opening of the rsp in early 2003 because of c 19

measurements of 220rn and 222rn and co2 emissions in soil and fumarole gases on mt etna volcano italy implications for gas transport and shallow ground fracture this work was funded by the istituto nazionale di geofisica e vulcanologia s g m n and by the dipartimento per la protezione civile italy projects v3 6 28 etna m n and v5 08 diffuse degassing in italy s g and nsf ear 063824101 k w w s

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

melt inclusions track pre eruption storage and dehydration of magmas at etna at mount etna italy vigorous gas rich eruptions in a d 2001 2002 and 2003 were followed by gas poor eruptions in 2004 2006 and 2007 analyses of volatile co2 h2o s cl f semivolatile cu and involatile nb la elements trapped in olivine hosted melt inclusions from these latest eruptions reveal the effects of the sustained interaction between a percolating gas phase and the stored magma melt inclusion compositions indicate that magmas erupted from 2004 to 2007 were residual from the 2001 2003 eruptions and show significant evolution in the volatile content of the melt these melt inclusion observations and variations in the c s of volcanic gases can be accounted for if melts reequilibrated with co2 rich gases during storage and prior to entrapment as melt inclusions sustained gas percolation caused loss of water and enhancement of co2 in the evolving melt and may strongly influence the behavior of cu which potentially partitions into the gas phase vapor melt interactions during magma storage are important controls on magma evolution at persistently degassing volcanoes

a new view of the he ar co2 degassing at mid ocean ridges homogeneous composition of magmas from the upper mantle abstract deep sea exploration is rapidly improving our understanding of volatiles geochemistry in mid ocean ridge igneous products it is also placing greater constraints on degassing processes of the earth s mantle with the result that degassing models based on vapour melt equilibrium are no longer able to explain the increasing number of data in fact such models force to postulate an upper mantle strongly heterogeneous at any scale and cannot account for the widespread carbon supersaturation of the recovered igneous products here we review the global he ar co 2 dataset of fluid inclusions in mid ocean ridge glasses using the framework of advanced modelling of multicomponent bubble growth in magmas we display that non equilibrium fractionations among he ar and co 2 driven by their different diffusivities in silicate melts are common in most of the natural conditions of magma decompression and their signature strongly depends on pressure of degassing due to the comparable ar and co 2 diffusivity magma degassing at low pressure fractionates both the he ar and he co 2 ratio by a similar extent while the slower co 2 diffusion at high pressure causes early kinetic effects on ar co 2 ratio and dramatically changes the degassing path on this ground the very different geochemical signatures among suites of data coming from different ridge segments mainly depend on the depth of the magma chamber where the melt was stored besides the variations inside a single suite highlight variable ascent speed and cooling rate of the emplaced lava the large variations in both the he co 2 and ar co 2 ratios at almost constant he ar displayed in glasses coming from the mid atlantic ridge 24 30 n segment and the rodriguez triple junction are therefore interpreted as a high pressure signature in contrast the simultaneous increase in both he co 2 and he ar of the east pacific rise pito seamount and south east indian ridge data sets suggests the dominance of low pressure fractionation implying that the shallow magma chambers are at a lower depth than those of the mid atlantic ridge 24 30 n and rodriguez triple junction our conclusions support the presence of a relationship between spreading rate and depth of high temperature zones below ridges and are consistent with the depth of magma chambers as suggested from seismic studies non equilibrium degassing explains the volatile systematics of mid ocean ridge basalts by starting from a single mantle derived magma dispensing with the supposed need for heterogeneities in abundance ratios of volatiles in the mantle below oceanic ridges

rapid oxidation of mercury hg at volcanic vents insights from high temperature thermodynamic models of mt etna s emissions a major uncertainty regarding the environmental impacts of volcanic hg is the extent to which hg is deposited locally or transported globally an important control on dispersion and deposition is the oxidation state of hg compounds hg 0 is an inert insoluble gas while hg ii occurs as reactive gases or in particles which deposit rapidly and proximally near the volcanic vent using a new high temperature thermodynamic model we show that although hg in etna s magmatic gases is almost entirely hg 0 i e gaseous elemental mercury significant quantities of hg ii are likely formed at etna s vents as gaseous hgcl2 when magmatic gases are cooled and oxidised by atmospheric gases these results contrast with an earlier model study and allow us to explain recent measurements of hg speciation at the crater rim of etna without invoking rapid 1 min low temperature oxidation processes we further model hg speciation for a series of additional magmatic gas compositions compared to etna hg ii production i e hg ii hgtot is enhanced in more hcl rich magmatic gases but is independent of the hg hbr and hi content of the magmatic gases hg ii production is not strongly influenced by the initial oxidation state of magmatic gases above nno although production is hindered in more reduced magmatic gases the model and results are widely applicable to other open vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature hg speciation in volcanic plumes

observations of platelet ice growth and oceanographic conditions during the winter of 2003 in mcmurdo sound antarctica 1 platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice water interface related to the proximity of ice shelves it is known to form in supercooled seawater this study details the conditions for its growth during the austral winter of 2003 in mcmurdo sound antarctica a key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column monitored using the strength of the backscattered signal from an acoustic doppler current profiler as a proxy generally these crystals appeared from mid may as water near the interface became supercooled this near surface supercooling appears to be related to a simultaneous abrupt change in the structure of the upper 250 m of the water column from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature near surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density over the course of winter of the surface mixed layer created by salt rejection during ice growth these processes allowed cold water trapped by buoyancy in a band at the base of the mixed layer in early winter to gain access to the ice water interface by midwinter this band of cold water probably had its origin beneath the mcmurdo ice shelf

antimoniferous vein type mineralization of the berga antiform eastern thuringia germany a fluid inclusion study abstract the antimoniferous vein mineralization in the schleiz and greiz area eastern thuringia are bound to ne sw striking variscan fault zones along the margins of the berga antiform the sb pb zn ores form massive sulfide sulfosalt quartz carbonate veins breccias or stockworks within ordovician and silurian metasedimentary units devonian metabasalts and metagranitoids mineralogical investigations from several sb mines and hard rock quarries near schleiz and greiz germany show that the sb pb zn sulfides are texturally in close association with quartz and carbonates stibnite is the major sb bearing mineral minerals of the sb pb zn sulfide assemblage replace an earlier zn fe as sulfide quartz assemblage quartz i named the ore stage i mineralization stibnite and quartz ii overgrow these early sulfides accounting for the ore stage ii lead dominated sb sulfides e g zinkenite plagionite semseyite represent the ore stage iii phase followed by sphalerite ii galena and quartz iii accounting for ore stage iv fluid inclusion studies on ore and gangue minerals of the different ore stages give insights into the composition and temperature of the mineralizing fluid s primary fluid inclusion assemblages in ore stage ii stibnite and co genetic quartz ii show variable vapor fractions within fluid inclusion assemblages heterogeneous trapping of co2 at constant salinities of fluid inclusions of the same assemblage indicates the influx of a buoyant pure co2 fluid into an aqueous fluid phase the presented data demonstrates the first example of co2 influx into an aqueous fluid identified by fluid inclusion analyses during this ore stage ii a h2o co2 nacl fluid with eq w nacl of 1 to 2 7 at 220 226 c prevails in contrast fluid inclusions in ore stage iii minerals boulangerite contain a homogeneously trapped h2o nacl cacl2 fluid with eq w nacl up to 8 1 at temperatures 146 c ore stage iv minerals sphalerite ii quartz iii contain a homogeneously trapped h2o nacl cacl2 fluid with eq w nacl of 20 and homogenization into the liquid phase at around 120 c fluid inclusion data suggest p t conditions at the onset of mineralization at around 220 c at 0 70 to 0 75 kbar fluid pressure the mechanisms of sb ore precipitation were induced by the influx of co2 fluid cooling quartz ii stibnite boulangerite and late stage mixing with a high salinity fluid resulting in the precipitation of sphalerite ii galena and quartz iii the unique opportunity to analyze fluid inclusions in many different subsequently precipitating ore and gangue minerals enables the reconstruction of the temporal evolution of the sb veins the distinct change of the ore forming processes from the influx of co2 into an aqueous fluid and cooling ore stage i ii to mixing ore stage iii iv as the dominant precipitation mechanisms are also accompanied by a drastic change in the mineralogy from sb sulfides to pb zn sulfides late orogenic granitic intrusions served as a potential heat metal and sulfur source variscan wrench and thrust tectonics and associated metamorphism account for the ore stage i mineralization hydrothermal sb pb zn assemblages ore stages ii iii and iv precipitated during the latest part of the variscan orogeny most likely around the carboniferous permian boundary although fluid composition and formation temperatures of the greiz and schleiz mineralization are on the first view quite similar to those of other variscan sb mineralization the observation of co2 influx and fluid mixing with a high salinity fluid is unique for european sb occurrences

the miocene costa giardini diatreme iblean mountains southern italy model for maar diatreme formation on a submerged carbonate platform in this paper we present a model for the growth of a maar diatreme complex in a shallow marine environment the miocene age costa giardini diatreme near sortino in the region of the iblei mountains of southern sicily has an outer tuff ring formed by the accumulation of debris flows and surge deposits during hydromagmatic eruptions vesicular lava clasts accretionary lapilli and bombs in the older ejecta indicate that initial eruptions were of gas rich magma abundant xenoliths in the upper late deposited beds of the ring suggest rapid magma ascent and deepening of the eruptive vent is shown by the change in slope of the country rock the interior of the diatreme contains nonbedded breccia composed of both volcanic and country rock clasts of variable size and amount the occurrence of bedded hyaloclastite breccia in an isolated outcrop in the middle lower part of the diatreme suggests subaqueous effusion at a low rate following the end of explosive activity intrusions of nonvesicular magma forming plugs and dikes occur on the western side of the diatreme and at the margins close to the contact between breccia deposits and country rock they indicate involvement of volatile poor magma possibly during late stages of activity we propose that initial hydromagmatic explosive activity occurred in a shallow marine environment and the ejecta created a rampart that isolated for a short time the inner crater from the surrounding marine environment this allowed explosive activity to draw down the water table in the vicinity of the vent and caused deepening of the explosive center a subsequent decrease in the effusion rate and cessation of explosive eruptions allowed the crater to refill with water at which time the hyaloclastite was deposited emplacement of dikes and plugs occurred nonexplosively while the breccia sediment was mostly still soft and unconsolidated locally forming peperites the sheltered low energy lagoon filled with marine limestones mixed with volcaniclastic material eroded from the surrounding ramparts ultimately lagoonal sediments accumulated in the crater until subsidence or erosion of the tuff ring caused a return to normal shallow marine conditions

magma and volatile supply to post collapse volcanism and block resurgence in siwi caldera tanna island vanuatu arc v24c 04 allen s r 2005 complex spatterand pumice rich pyroclastic deposits from an andesitic caldera forming eruption the siwi pyroclastic sequence tanna vanuatu bulletin of volcanology 67

unravelling the processes controlling gas emissions from the central and northeast craters of mt etna abstract we measured volcanic gas emissions from the northeast crater nec and central crater cc of mount etna on 21st july 2008 and 3rd and 31st august 2009 using a novel lightweight open path fourier transform infrared spectrometry op ftir in active mode with a portable infrared lamp contemporaneously we measured the so2 flux of the total gas emission released by the combined summit craters 14 km downwind and the so2 flux emitted by the nec measured at the summit combining these data we determined the flux of the major volcanic components h2o co2 so2 hcl and hf emitted individually from cc and nec craters the results reveal similar so2 hcl ratios but distinct co2 so2 ratios 1 3 and 10 9 for nec and cc respectively and an order of magnitude greater co2 flux from the cc compared with the nec a simple model in which the nec branches from a central feeding conduit at a depth of 2 km can reproduce these observations we highlight that in such a system short term variations in co2 so2 ratios at each crater can occur due to minor variations in the magma gas flux entering each conduit at the branch without an overall change in magma supply co2 so2 variations measured at individual craters may therefore be unrepresentative of the volcanic system and require cautious interpretation monitoring of the total co2 and so2 fluxes emitted from each crater is on the contrary an optimal monitoring strategy and can be achieved using a combination of co2 so2 instruments and so2 imaging cameras

evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at mount etna italy assessment of the magmatic reservoir pressure 1 five gas discharges in the area of mount etna volcano italy and in the near hyblean plateau have been monitored since 1996 all the emissions displayed low contributions from crustal fluids whereas magmatic gases were the main component selective dissolution of these gases into hydrothermal aquifers has been recognized and modeled allowing us to calculate the original composition of the magma released gases the inferred composition of the magmatic gases exhibits synchronous variations of he ne and he co2 ratios which are coherent with the magma degassing process on the basis of numerical simulations of volatile degassing from etnean basalts we have computed the initial and final pressures of the magma batches feeding the emissions we thus can define the levels of the etna plumbing system where magmas are stored pressure values were around 360 and 160 mpa for initial and final stages respectively meaning related depths of about 10 and 3 km below sea level matching those obtained by geophysical investigations for the deep and shallow magma reservoirs in addition we have been able to recognize episodes of magma migration from the deeper reservoir toward the shallow one an important magma injection into the shallow storage volume was detected during the onset of the 2001 eruption 17 july no further injection had taken place during this period until september 2001 providing a possible reason for the quick exhaustion of the eruption in view of this we suggest that the sampled emissions are a powerful geochemical tool to investigate the etna s plumbing system and its magma dynamics as well as the development of eruptive events

atmospheric sources and sinks of volcanogenic elements in a basaltic volcano etna italy abstract this study reports on the first quantitative assessment of the geochemical cycling of volcanogenic elements from their atmospheric release to their deposition back to the ground etna s emissions and atmospheric depositions were characterised for more than 2 years providing data on major and trace element abundance in both volcanic aerosols and bulk depositions volcanic aerosols were collected from 2004 to 2007 at the summit vents by conventional filtration techniques precipitation was collected from 2006 to 2007 in five rain gauges at various altitudes around the summit craters analytical results for volcanic aerosols showed that the dominant anions were s cl and f and that the most abundant metals were k ca mg al fe and ti 1 5 50 g m 3 minor and trace element concentrations ranged from about 0 001 to 1 g m 3 from such analysis we derived an aerosol mass flux ranging from 3000 to 8000 t a 1 most analysed elements had higher concentrations close to the emission vent confirming the prevailing volcanic contribution to bulk deposition calculated deposition rates were integrated over the whole etna area to provide a first estimate of the total deposition fluxes for several major and trace elements these calculated deposition fluxes ranged from 20 to 80 t a 1 al fe si to 0 01 0 1 t a 1 bi cs sc th tl and u comparison between volcanic emissions and atmospheric deposition showed that the amount of trace elements scavenged from the plume in the surrounding of the volcano ranged from 0 1 to 1 for volatile elements such as as bi cd cs cu tl and from 1 to 5 for refractory elements such as al ba co fe ti th u and v consequently more than 90 of volcanogenic trace elements were dispersed further away and may cause a regional scale impact such a large difference between deposition and emission fluxes at mt etna pointed to relatively high stability and long residence time of aerosols in the plume

the effect of depositional environment on coal distribution and quality parameters in a portion of the highveld coalfield south africa abstract eight successive lithofacies associations are identified and described they are each laterally continuous and represent a certain depositional phase throughout the study area these are related to sedimentary processes from which a three dimensional paleoenvironmental model is derived subsequently coal distribution and coal quality characteristics are linked to the depositional features of the model the identified depositional phasescommenced with subglacial glaciofluvial and glaciolacustrine settings with associated gilbert type deltas these are followed by meandering and minor braided fluvial settings characterized by laterally and vertically highly variable lithofacies in which the main coal bearing strata were formed coal distribution and quality parameters ash and volatile matter content calorific value are closely related to paleoenvironmental characteristics major changes of coal distribution and quality parameters are mainly associated with active and abandoned channels and these parameters are less variable in floodplain settings

direct observations of degassing induced crystallization in basalts magma degassing can trigger crystal growth by increasing the magma liquidus temperature as crystallization greatly increases magma viscosity this process can strongly influence eruptive dynamics we use a microscope and heated stage to obtain the first direct observations of degassing driven crystal growth in natural basaltic melts at magmatic temperatures samples from mount etna italy 0 39 wt h2o and kilauea volcano hawaii 0 18 wt h2o were heated in air at 1 bar and held isothermally for 0 5 17 h between 1190 c and 1270 c before cooling to solidus temperatures on heating bubble growth at 900 c indicated volatile exsolution in the hydrous etna sample isothermal conditions produced numerous new plagioclase crystals that grew to 160 m at maximum rates of 5 2 18 10 6 cm s 1 growth rates and crystal morphologies tabular to spherulitic depended on dwell temperature growth slowed dramatically after 20 min as equilibrium was approached in the h2o poor kilauea sample few new crystals appeared they grew at maximum rates of 1 7 6 5 10 6 cm s 1 on cooling crystal nucleation and growth were strongly influenced by preexisting crystal textures highlighting the importance of studying natural samples our results document rapid crystal growth triggered by melt devolatilization when the h2o content of the glass is sufficiently high resultant swift substantial changes in magma texture are a key control on lava rheology at etna and elsewhere

discussion on magma storage region processes of the soufriere hills volcano montserrat geological society london memoirs 39 361 381 the recent study by devine rutherford 2014 magma storage region processes of the soufriere hills volcano montserrat published as chapter 19 of the geological society of london memoir volume 39 focused primarily on updating the record of magmatic temperatures recorded by fe ti oxides in the andesite erupted from soufriere hills volcano however a key result of the paper was that the compositions of some plagioclase hosted melt inclusions indicate mixing of mafic magma components into the host andesite and trapping of the mixed melts within phenocrysts this interpretation is consistent with our earlier work on the chemistry of melt inclusions humphreys et al 2010 and of microlite crystal populations humphreys et al 2009 a 2013 humphreys et al 2010 proposed this interpretation by showing that a subset of soufriere hills melt inclusions and matrix glasses has anomalous concentrations of k2o and or tio2 as have mafic inclusion matrix glasses see humphreys et al 2010 fig 2 however in their appendix devine rutherford 2014 suggest that enrichment in k2o can result only from decompression crystallization and not from magma mingling they also assert that our melt inclusion dataset is fundamentally flawed and subject to faulty corrections for post entrapment correction and that our melt inclusions were actually matrix glasses finally devine rutherford 2014 doubt whether or not one can look at melt inclusion analyses and distinguish the effects of decompression crystallization from the effects of mingling with components derived from the injected mafic magma here we address the criticisms of the devine rutherford 2014 appendix drawing on additional published data to support our arguments and explanations we were unable to reproduce some of the key figures of devine rutherford 2014

high resolution reconstruction of the hoei eruption ad 1707 of fuji volcano japan abstract the hoei eruption of mount fuji in 1707 caused the worst ashfall disaster in japanese history despite the availability of numerous historical documents describing the eruption the detailed eruption sequence has not been verified because the correlation between these descriptions and geological sequences remains unclear in this study we reconstruct the sequential change in the column height using newly established stratigraphy and a detailed timeline obtained from historical documents the eruptive deposit was subdivided into 17 units on the basis of their facies with the mass of each unit established using isopach maps the eruption column height is a function of the magma discharge rate hence the column height of each unit was estimated from its erupted mass and duration which were inferred from the historical documents the correlation of each unit with the actual time was based on the tephra color and grain size an unconformity caused by rainfall and ashfall distribution while reconstructing the unit boundaries we found that not all of them represented a hiatus or relenting phase of ashfall we detected only six obvious quiet intervals from the historical documents therefore many of the unit boundaries may represent a hiatus or relenting phase that was too subtle to have been recorded in the historical documents we define an eruptive pulse as a period of continuous ashfall followed by an obvious quiet interval we divided the 17 units of the hoei eruption into 6 pulses and into 3 stages on the basis of the patterns of the eruptive pulses the characteristics of the three stages are described as follows stage 1 had two energetic eruptive pulses pulses 1 and 2 at least 20 km high column each showing an intense initial outburst followed by a decrease in intensity the eruption sequence indicates ruptures of highly overpressured dacite and andesite magma chambers the initial silicic eruption was followed by basaltic magma withdrawal from a deep and voluminous magma chamber stage ii consisted of discrete subplinian pulses of relatively degassed basaltic magma although the eruption rate throughout the stage decreased the magma supply from depth appears to have been sustained because extensive intrusion near the surface created the mt hoei cryptodome near the vent stage iii was principally characterized by sustained column activity without a clear repose time during this stage the column height appears to have been more than 13 km and we recognized at least two distinct periods of increased activity in which the column height is presumed to have exceeded 16 km the cu rich vesicular scoria and continuous eruption in stage iii indicate a stable supply of volatile rich magma from depth no significant decay was observed in the magma discharge rate hence the eruption could have been halted by a sudden process such as conduit collapse rather than decompression of the magma chamber

maceral distributions in illinois coals and their paleoenvironmental implications abstract for purposes of assessing the maceral distribution of illinois u s a coals analyses were assembled for 326 face channel and drill core samples from 24 coal members of the pennsylvanian system the inertinite content of coals from the missourian and virgilian series averages 16 1 mineral free compared to 9 4 for older coals from the desmoinesian and older series this indicates there was generally a higher state of oxidation in the peat that formed the younger coals this state probably resulted from greater exposure of these peats to weathering as the climate became drier and the water table lower than was the case for the older coals although oxidation during allochthonous deposition of inertinite components is a genetic factor that needs further study to confirm the importance of the climate regional variation of the vitrinite inertinite ratio v i on a mineral and micrinite free basis was observed in the springfield no 5 and herrin no 6 coal members to be related to the geographical position of paleochannel river deposits known to have been contemporaneous with the peats that formed these two coal strata the v i ratio is highest generally 12 27 in samples from areas adjacent to the channels and lower 5 11 some 10 20 km away we interpret the v i ratio to be an inverse index of the degree of oxidation to which the original peat was exposed high v i ratio coal located near the channels probably formed under more anoxic conditions than did the lower v i ratio coal some distance away from the channels the low v i ratio coal probably formed in areas of the peat swamp where the watertable was generally lower than the channel areas

carbon dioxide transport in crustal magmatic systems abstract the volatile chemistry of juvenile volcanic glasses has suggested that shallow stored crustal magmas often suffer the open system addition of a carbon dioxide rich fluid from below probably from a mantle derived basaltic source carbon dioxide fluxing however the actual mechanism of such a fluid transport is poorly understood to constrain the volatile transport mechanism we formulated this phenomenon as a reactive transport process and clarified the fundamental characteristics of chemical exchange in the system the model assumes that a carbon dioxide rich fluid is introduced into a water rich rhyolitic magma column from below and ascends at a constant velocity whilst a volatile exchange takes place between the fluid and melt two types of exchange modes were examined one is the equilibrium mode where the volatile exchange is instantaneously achieved at all column depths the second is the diffusive mode where the volatile exchange is rate limited by diffusion in the equilibrium mode the extent of re equilibration of the entire column is controlled solely by the mass ratio of the integrated fluid to the melt in the diffusive mode the extent of re equilibration is controlled by the damkohler number a dimensionless parameter representing the ratio of the advection time to the diffusion time when the damkohler number for carbon dioxide exceeds 10 the diffusive exchange becomes indistinguishable from the equilibrium exchange both exchange modes produce a negative correlation between the concentrations of carbon dioxide and water in the melt which cannot be explained by conventional degassing models without significant crystallisation the fluid emitted from the column as a volcanic gas changes its composition from carbon dioxide rich to water rich and the emission rate decreases monotonically during fluxing the simulation enables us to constrain the mechanism of fluid transport for the melt inclusion data from the bishop tuff wallace et al 1999 anderson et al 2000 fluid velocity in this magma was estimated to be 10 6 10 7 m s the corresponding mechanism of fluid transport may include permeable flow with a permeability of 10 15 m 2 or a buoyant ascent of individual bubbles with a radius of 4 7 mm

s cl f degassing pattern of water rich alkali basalt modelling and relationship with eruption styles on mount etna volcano abstract our knowledge of the degassing pattern of sulphur chlorine and fluorine during ascent and eruption of basaltic magmas is still fragmental and mainly limited to water poor basalts here we model and discuss the pressure related degassing behaviour of s cl and f during ascent differentiation and extrusion of h2o co2 rich alkali basalt on mount etna sicily as a function of eruptive styles our modelling is based on published and new melt inclusion data for dissolved volatiles co2 h2o s cl f in quenched explosive products from both central conduit 1989 2001 and lateral dyke 2001 and 2002 eruptions pressures are obtained from the dissolved h2o and co2 concentrations and vapour melt partition coefficients of s cl and f are derived from best fitting of melt inclusion data for each step of magma evolution this allows us to compute the compositional evolution of the gas phase during either open or closed system degassing and to compare it with the measured composition of emitted gases we find that sulphur chlorine and fluorine begin to exsolve at respective pressures of 140 mpa 100 mpa and 10 mpa during etna basalt ascent and are respectively degassed at 95 22 55 and 15 upon eruption pure open system degassing fails to explain gas compositions measured during either lateral dyke or central conduit eruptions instead closed system ascent and eruption of the volatile rich basaltic melt well accounts for the time averaged gas composition measured during 2002 type lateral dyke eruptions s cl molar ratio of 5 1 35 bulk cl loss extensive magma fragmentation during the most energetic fountaining phases enhances cl release 55 and produces a lower s cl ratio of 3 7 as actually measured comparatively slower magma rise in the central conduits of etna favours both sulphide saturation of the melt and greater chlorine release 55 resulting in a distinct s cl evolution path and final ratio in eruptive gas in both eruption types any previous bubble melt separation at depth leads to increased s cl and s f ratios in emitted gas high s cl ratios measured during some discrete eruptive events can thus be explained by transitions from closed deep to open shallow system degassing with differential gas transfer extending down to 2 km depth below the vents this depth coincides with the base of the volcanic pile where structural discontinuities and the high magma vesicularity 60 may favour separate gas flow finally the excess s cl f gas discharge through etna summit craters during non eruptive periods requires a mixed supply from shallow magma degassing in the volcanic conduits and deeper derived so2 rich bubbles from the sub volcano plumbing system our modelling provides a useful reference framework for interpreting the monitored variations of s cl and f in mount etna gas emissions as a function of volcanic activity more broadly the observations made for s cl and f degassing on etna may apply to other basaltic volcanoes with water rich magmas such as in arcs

patterns in the recent 2007 2008 activity of mount etna volcano investigated by integrated geophysical and geochemical observations 1 seismic deformation and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment in spite of their wide use there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques here we combine seismic volcanic tremor and long period seismicity deformation gps and geochemical volcanic gas plume co2 so2 ratios measurements in an attempt to interpret trends in the recent 2007 2008 activity of etna volcano we show that each eruptive episode occurring at the southeast crater sec was preceded by a cyclic phase of increase decrease of plume co2 so2 ratios and by inflation of the volcano s summit captured by the gps network these observations are interpreted as reflecting the persistent supply of co2 rich gas bubbles and eventually more primitive magmas to a shallow depth of 1 2 8 km asl magma storage zone below the volcano s central craters ccs overpressuring of the resident magma stored in the upper ccs conduit triggers further magma ascent and finally eruption at sec a process which we capture as an abrupt increase in tremor amplitude an upward 2800 m asl and eastward migration of the source location of seismic tremor and a rapid contraction of the volcano s summit resumption of volcanic activity at sec was also systematically anticipated by declining plume co2 so2 ratios consistent with magma degassing being diverted from the central conduit area toward sec

south africa s coalfields a 2014 perspective abstract for well over a century and a half coal has played a vital role in south africa s economy and currently bituminous coal is the primary energy source for domestic electricity generation as well as being the feedstock for the production of a substantial percentage of the country s liquid fuels it furthermore provides a considerable source of foreign revenue from exports based on geographic considerations and variations in the sedimentation origin formation distribution and quality of the coals 19 coalfields are generally recognised in south africa this paper provides an updated review of their exploration and exploitation histories general geology coal seam nomenclature and coal qualities within the various coalfields autocyclic variability is the norm rather than the exception whereas allocyclic variability is much less so and allows for the correlation of genetically related sequences during the mid jurassic break up of gondwana most of the coal bearing successions were intruded by dolerite these intrusions are important as they may cause devolatilisation and burning of the coal create structural disturbances and related seam correlation problems and difficulties in mining operations whilst many of the coalfields have been extensively explored and exploited those in the north of the country have until recently received much less attention four coalfields occur partly or wholly within the limpopo province of south africa and these may contain as much as 70 of south africa s remaining coal resources these coalfields in particular have been the focus of recent exploration due to the presence of large coking and thermal coal resources as well as for their coal bed methane potential and these resources need to be unlocked with regards to creating maximum benefit and minimal environmental degradation south africa s coals have also been recently addressed as palaeoclimate archives recording gondwana s postglacial climate amelioration by major changes in land plant communities and proving high resolution palyno stratigraphy as a crucial tool to decipher climate change during the permo carboniferous this aspect of the coals of south africa is also reviewed

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

degassing driven crystallisation in basalts abstract syn eruptive crystallisation can drastically increase magma viscosity with profound implications for conduit dynamics lava emplacement and volcanic hazards there is growing evidence that crystallisation is not only cooling driven but can also occur almost isothermally during decompression induced degassing on ascent from depth here we review field and experimental evidence for degassing driven crystallisation in a range of magma compositions we then present new results showing for the first time experimental evidence for this process in basaltic magma our experiments use simultaneous thermogravimetric analysis and differential scanning calorimetry coupled with mass spectrometry tga dsc ms to monitor degassing patterns and thermal events during heating and cooling of porphyritic basaltic samples from mt etna italy the partly degassed samples which contained 0 39 0 81 wt total volatiles in the glass fraction were subjected to two cycles of heating from ambient to 1250 c on the first heating tga data show that 30 60 of the total volatiles degassed slowly at

chemically driven growth and resorption of bubbles in a multivolatile magmatic system abstract a carbon dioxide rich fluid from a deep source fluxes in a water rich shallow stored magma and causes a volatile exchange with the melt we carried out hydrothermal experiments on both bubble free and bearing rhyolitic melts in an h 2 o co 2 system to explore the kinetics of chemical re equilibration between the fluid and the magma in the bubble free experiment a water saturated rhyolitic melt was first synthesized at 800 c and 100 mpa and this interacted with a carbon dioxide rich fluid under the same pt conditions for a period of 3 h the melt temporarily became undersaturated upon the volatile exchange as water quickly diffused out of the melt while dissolution of the carbon dioxide was much slower in the bubble bearing experiments the rhyolitic melt was saturated with h 2 o co 2 fluids at 800 c and 100 mpa decompressed to 50 mpa and then kept for up to 5 56 h water rich bubbles were generated by decompression and initially grew but then dissolved in the melt during the retention time this bubble resorption was attributed to water depletion of the melt upon re equilibration with the carbon dioxide rich surrounding fluid such water depletion and resulting bubble resorption are specific to multivolatile systems such as h 2 o co 2 in which the diffusivity and solubility differ among the end components the bubble resorption occurring in this mechanism may explain the genesis of carbon dioxide rich bubble poor obsidian pyroclasts which are considered to have undergone carbon dioxide rich fluid fluxing we also discuss possible consequences of this effect on the bulk magma density the dissolution of a small amount of carbon dioxide may cause expulsion of a much larger amount of water from the hydrous melt which may increase fluid fraction and thus decrease the bulk density by up to 188 and 104 kg m 3 at 100 and 200 mpa respectively for rhyolitic melts we suggest that such a process has the potential to trigger a volcanic eruption

open path ftir spectroscopy of magma degassing processes during eight lava fountains on mount etna in june july 2001 a series of 16 discrete lava fountain paroxysms occurred at the southeast summit crater sec of mount etna preceding a 28 day long violent flank eruption each paroxysm was preceded by lava effusion growing seismic tremor and a crescendo of strombolian explosive activity culminating into powerful lava fountaining up to 500 m in height during 8 of these 16 events we could measure the chemical composition of the magmatic gas phase h2o co2 so2 hcl hf and co using open path fourier transform infrared op ftir spectrometry at 1 2 km distance from sec and absorption spectra of the radiation emitted by hot lava fragments we show that each fountaining episode was characterized by increasingly co2 rich gas release with co2 so2 and co2 hcl ratios peaking in coincidence with maxima in seismic tremor and fountain height whilst the so2 hcl ratio showed a weak inverse relationship with respect to eruption intensity moreover peak values in both co2 so2 ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval 2 6 days between lava fountains these observations together with a model of volatile degassing at etna support the following driving process prior to and during the june july 2001 lava fountain sequence the shallow 2 km magma reservoir feeding sec received an increasing influx of deeply derived carbon dioxide likely promoted by the deep ascent of volatile rich primitive basalt that produced the subsequent flank eruption this co2 rich gas supply led to gas accumulation and overpressure in sec reservoir generating a bubble foam layer whose periodical collapse powered the successive fountaining events the anti correlation between so2 hcl and eruption intensity is best explained by enhanced syn eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

multidisciplinary investigation on a lava fountain preceding a flank eruption the 10 may 2008 etna case a multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of the erupted products to volcanic tremor long period events and tilt and gravity signals is used to investigate the source depth and magma dynamics of the 10 may 2008 lava fountain at southeast crater sec of mount etna the investigation was undertaken in the framework of the previous 2007 explosive activity as well as the subsequent effusive eruption beginning 13 may 2008 and lasting up to july 2009 all the data concur in indicating that the 10 may lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir about 1500 1700 m below the summit of sec the shift from the episodic strombolian lava fountain activity occurring in 2007 at sec to the more powerful 10 may 2008 lava fountain is explained by the intrusion of a new more primitive magma into the shallow reservoir data also indicate that an attempted magma intrusion east of the summit area occurred during the 10 may fire fountain this event caused the fracturing and weakening of the surrounding rocks and created a preferential pathway for the penetration of the magma that only 3 days later started to feed the 2008 2009 effusive eruption

magma mixing during the 2001 event at mount etna italy effects on the eruptive dynamics abstract during the 2001 eruptive episode three different magmas were erupted on the southern flank of mount etna volcano from distinct vent systems major and minor element chemistry of rocks and minerals shows that mixing occurred and that the mixed magma was erupted during the last eruptive phases the space time integrated analysis of the eruption supported by geophysical data together with major and trace element bulk chemistry xrf icp ms and major and trace mineral chemistry epma lam icp ms support the following model 1 trachybasaltic magma rises through a nnw sse trending structure connected to the main open conduit system 2 ascent of an amphibole bearing trachybasaltic magma from a 6 km deep eccentric reservoir through newly open n s trending fractures 3 just a few days following the eruption onset the two tectonic systems intersect at the laghetto area 4 at the laghetto vent a mixed magma is erupted mixing occurred between the amphibole bearing trachybasaltic magma and an inferred deep more basic end member the most relevant aspect in the eruptive dynamics is that the eruption of the mixed magma at the laghetto vent was highly explosive due to volatile content in the magma the gas phase formed mainly because of the decreased volatile solubility due to rapid fractures opening and increased t related to mixing and partially because of the amphibole breakdown

impact of geological modeling processes on spatial coalbed methane resource estimation spatial coalbed methane cbm resource estimation is based on spatial distributions of coal coal adsorbed gas content and coal density however the spatial distribution of gas content can be generated via two different geological modeling processes 1 the gas content distribution is generated by geological modeling based on the interpreted gas content at boreholes 2 distributions of gas content related logs or coal properties are generated firstly then the gas content distribution is calculated based on the spatial distributions of logs or coal properties by the relationship between the gas content and logs or coal properties this paper presents a study to compare the impact of these two processes on cbm resource estimation for coal seam no 3 cs 3 in southeast qinshui basin china well logs from 22 wells laboratory data from five wells and well tops from 131 wells for cs 3 are used in log interpretation and geological modeling the simple kriging sk is used to build the structural model and the coal distribution weighted and unweighted omni directional variograms for structural residual and coal thickness are calculated using an in house program logs of gamma ray gr and density den or rhob are distributed in 3d by using sequential gaussian simulation sgs with sk algorithm artificial neural network ann is used to build the relationship of the measured raw gas content rgc gas content in raw coal basis with the logs of gr den and measured depth md then the rgc is distributed in 3d by the two geological modeling processes cbm resources are calculated in 3d based on the cells volume coal density and rgc results show that rgc increases with an increase in burial depth total cbm resources for the study area calculated by these two processes are similar for cs 3 but the distribution probability of high gas content is highly different which is important for locating wells