the significance of phenocryst diversity in tephra from recent eruptions at popocatepetl volcano central mexico tephra lapilli from six explosive eruptions between april 1996 and february 1998 at popocatepetl volcano popo in central mexico have been studied to investigate the causes of magma diversification in thick crusted volcanic arcs the tephra particles are sparsely porphyritic 5 vol magnesian andesites sio2 58 65 wt mgo 2 6 5 9 wt that contain phenocrysts of nio rich up to 0 67 wt nio magnesian olivine fo89 91 cores with inclusions of cr spinel cr 59 70 orthopyroxene mg 63 76 clinopyroxene mg 68 86 intermediate to sodic plagioclase an33 66 and traces of amphibole major and trace element systematics indicate magma mixing the liquid mg melt ratios inferred from the ferromagnesian phenocrysts suggest the existence of a mafic mg melt 72 76 and an evolved component magma mg melt 35 40 these component magmas form a hybrid magnesian andesite with an intermediate range of mg melt 50 72 the mafic end member mg melt 72 75 is saturated with olivine and spinel and crystallizes at temperatures 1170 1085 c with oxygen fugacities close to the fayalite magnetite quartz buffer and elevated water contents of several wt h2o a likely location of crystallization is at lower crustal levels possibly at the moho olivine is followed by high mg clinopyroxene which could start to crystallize during magma ascent at depths of 4 to 13 km the mafic magma mixes with an evolved composition containing low mg clino and orthopyroxene and plagioclase at a temperature of 950 c the repetitive ascent of batches of mafic magmas spaced days to weeks apart implies multiple episodes of crystallization and magma mixing the tephra is similar to the popo magnesian andesites suggesting similar generic processes for the common lavas of the volcano the advantage of the tephra is that it can be used to reconstruct the composition of the mafic magma building on the elemental systematics of the tephra and a comparison to the near primary basalts from the surrounding monogenetic fields we infer that the popo mafic end member is a magnesian andesite with variable but high sio2 contents of 55 62 wt and near primary characteristics such as high mg melt of 72 75 feo mgo ratios 1 if extrapolated to an mg melt of 72 75 and high ni contents 200 ppm ni this model implies that the typical elemental signature of the popo andesites such as the low cao al2o3 feo high na2o contents and the depletion in high field strength elements e g p zr ti are mantle source phenomena thus determining the elemental budget of the magnesian andesite as it is prior to the modifications by crustal differentiation is central to quantifying the subcrustal mass fluxes beneath popo

gas and aerosol emissions from lascar volcano northern chile insights into the origin of gases and their links with the volcanic activity abstract this study focuses on the chemical compositions of volcanic gases and aerosols emitted by lascar volcano northern chile the sustained volcanic plume was sampled in april 2009 april 2011 and november 2012 through filter packs and analyzed for major gaseous species so 2 hcl and hf and trace elements during fieldwork so 2 flux measurements were also performed by uv spectrometry doas the lascar volcano is a significant and sustained emitter of so 2 between 150 and 940 t d hcl between 170 t d and 210 t d and hf up to 100 t d combining the so 2 normalized trace element concentrations and the so 2 emission rates we evaluate that the quiescent degassing of lascar is an important local source of trace metals to the atmosphere with contributions to global volcanic fluxes generally less than 2 our data were used to infer the origin of the gas emitted at lascar two major degassing sources were identified a deep magmatic reservoir and a shallow hydrothermal system the variable interaction between these two sources is the most likely scenario for explaining the compositional ranges in acid gases but also in a volatile and fluid mobile trace element such as b these variations are related to changes in volcanic activity an extensive interaction between the hot ascending magmatic gases and the shallow aquifer occurred in 2009 possibly due to a long period of quiescence before magmatic activity renewed in 2011 and 2012 our study highlights therefore that filter pack measurements may be used to study changes in subsurface processes that probably play a key role in triggering volcanic eruptions

laboratory calibration of chemical volcanic gas sampling techniques using an artificial fumarole abstract we have constructed an artificial laboratory fumarole to calibrate the most common chemical volcanic gas sampling techniques and obtain a quantitative measure of their efficacy we have also developed and tested a new rugged and portable venturi spray gas sampler the venturi sampler reproduced the output gas composition most accurately followed by the giggenbach bottles filter packs and lastly alkaline traps passive alkaline traps however did better than filter packs when sampling more concentrated fumarole gases under ideal conditions the accuracy of the giggenbach bottles was identical to the venturi sampler although there was slightly more scatter the giggenbach sampler was more susceptible to problems with condensation on the input train even in a laboratory setting and this technique was only effective in relatively concentrated gas streams filter packs are also effective but extreme care must be exercised to maintain strong undersaturation with respect to the acid gas if strong undersaturation high ph is not maintained the filter packs return erroneously low s cl and s f ratios use of a ph indicator is an effective way of avoiding this problem the passive alkaline traps also under sample sulfur resulting in low reported s cl and s f ratios it appears that the overall sampling efficiency of all techniques was not strongly affected by oxygen fugacity over the limited range tested when detecting sulfate and sulfite simultaneously we found no difference in total sulfur before and after oxidation this suggests that all sulfur from the gas regardless of oxidation state was absorbed as sulfite or sulfate and or was quickly oxidized in solution this conclusion is supported by ic hs reference samples

infrared satellite monitoring at popocatepetl explosions exhalations and cycles of dome growth 1 since december 1994 activity at popocatepetl has evolved through two main phases the first was characterized by elevated seismic activity degassing and emissions of predominantly lithic ash however in march 1996 the volcano entered a magmatic phase which has involved the emplacement of at least eight lava domes within its summit crater we have used infrared radiance data acquired by the goes meteorological satellite alongside ground based geophysical data sets to analyze aspects of this activity we develop a technique to identify magmatic activity at the volcano in the absence of a volcanic heat source the radiance emitted from the hottest pixel pr contained within a 10 10 pixel goes subscene centered on popocatepetl s summit is well correlated with the average radiance emitted by the remaining pixels br because at any given time all pixels within the target box have similar temperatures varying as a function of season cloud cover and solar irradiance however during periods of heightened volcanic activity the radiance emitted by the hottest pixel varies as a function of a time independent volcanic heat source and changes in pr and br become decorrelated allowing volcanic activity to be identified exhalations intermittent ash emissions cannot be identified by routine analysis of goes data because of the low intensity of the associated thermal anomalies explosions however produce distinctive radiance signatures and can be reliably documented two dome growth episodes occurred during our study period one in november december 1998 and the other during february 2000 although the techniques we describe identified the 1998 dome event the 2000 dome went undetected this is explained in terms of their contrasting emplacement styles the 1998 dome was apparent to goes due to the explosions that disrupted its cool carapace scattered hot bombs around the summit cone and exposed its hotter interior to the satellite sensor in contrast the february 2000 dome was not apparent because elevated explosive activity did not accompany its emplacement

the effect of wind stress over the eastern mediterranean on deep water formation in the adriatic sea abstract we investigate the effect of interannual variability of the wind stress over the eastern mediterranean on adriatic deep water adw formation using an oceanic general circulation model of the mediterranean sea driven by monthly era interim wind stress of the years 1979 2014 this is done by using climatological annual cycle of the surface temperature and freshwater flux but interannually varying wind stress a connection between the wind stress magnitude over the rhodes gyre region and adw outflow is found in association with the formation of levantine intermediate water liw 720 years artificially generated wind stress fields were constructed based on the first 50 empirical orthogonal functions eofs of the wind stress monthly anomalies this simulation strengthen the connection that was found and also reveal a centennial internal variability of both the liw and the adw outflow it is also found that the intensity of the rhodes gyre is almost linearly related to the wind stress amplitude however the adw outflow is non monotonically related to the wind stress amplitude there is an optimal wind stress amplitude for which the adw formation is maximal when the wind stress amplitude is more than 50 the climatological mean wind stress amplitude the adw outflow is weakened this implies a different balance between the saline liw and the fresh atlantic water entering the eastern mediterranean from sicily strait under stronger than present wind stress amplitude

impact of the eruptive activity on glacier evolution at popocatepetl volcano mexico during 1994 2004 abstract distribution rate and magnitude of the glacier changes caused by eruptive activity over 1994 2001 at popocatepetl volcano were determined digital elevation models computed by scanned photographs within a digital photogrammetric workstation and the subsequent dem comparison allowed the determination of glacial changes the results show that drastic changes occurred in glacier geometry and morphology over 1996 2001 53 of the glacier surface area was lost due to melting processes the most important loss occurred over 2000 2001 when 19 of the glacier covered area disappeared the glacier volume losses increased over time during 1999 2000 the largest loss was observed however in february 2001 the glacier showed an apparent small increase in volume volcanic processes disturbed the mass balance of the glacier thereby accelerating the ablation processes the eruptive behavior of popocatepetl was characterized during this time by alternating periods of explosive events and low activity pyroclastic flow generation ejection of incandescent material and tephra fall affected the glacier the tephra volume distribution and remobilization produced considerable changes on glacier evolution tephra deposition on the glacier surface was the most frequent process the irregular distribution and thickness of tephra provoked differential ablation and tephra remobilization processes took place on the glacier surface together these processes incised the glacier surface over time based on these results and observations a model of glacier evolution is proposed involving an adjustment phase thinning phase areal retreat phase and fragmentation phase a complex interplay of factors and processes took place between eruptive activity and the glaciers at popocatepetl volcano the glacier evolution and subsequent extinction were induced by the eruptive behavior over the years while not the only process at work eruptive activity played the primary role in accelerating retreat and as a consequence in glacier extinction

spatially correlated anomalous 40ar 39ar age variations in biotites about a lithologic contact near simplon pass switzerland a mechanistic explanation for excess ar forty four biotite samples collected about a lithologic contact between pelite and amphibolite were analyzed for 40ar 39ar and demonstrate the importance of bulk ar diffusivity and system geometry factors not usually considered in the interpretation and collection of 40ar 39ar age data the resulting 40ar 39ar apparent ages range from 11 30 0 05 ma to 17 90 0 10 ma the ages and excess argon contents are spatially and lithologically correlated the pelite samples all yield ages clustering around 12 ma the age expected for cooling through biotite closure 360 c in this region of the alps ages in the amphibolite biotites are older showing a smooth trend between 15 ma at the contact with the pelite to 18 ma 34 cm from the contact this data shows that characterization of the ar closure age for biotite in a given system should not rest on a single sample as otherwise irresolvable differences in age between samples within the same outcrop can exist a generalized mechanistic model for excess argon is presented the presence or absence of excess ar depends on an intrinsic system parameter t the transmissive timescale which is the characteristic time for 40ar to escape through the local intergranular transporting medium itm to some sink for argon to prevent buildup of geochronologically significant excess 40ar t must be very short relative to the true closure age of the mineral a fortran code including radiogenic ar production diffusive loss of ar from biotite and bulk ar diffusion through the itm has been developed application of numerical modeling suggests that the time averaged effective bulk diffusivity deffar in the biotite amphibolite rock during early retrograde cooling is 2 2 1 0 10 8 m2 yr assuming steady state conditions the first such measurement available numerical modeling also provides information about the transmissivity and geologic history specific to the field site including a drop in deffar at 15 5 1 0 ma the timing of this drop is related to coincident rheological changes and the onset of rapid exhumation of the nappe stack

remote determination of sif4 in volcanic plumes a new tool for volcano monitoring sif4 is probably a common trace component of fumarole gases on volcanoes arising from interactions between magmatic hf and wall rocks it is not distinguished from hf in conventional analyses a strong absorption band at 1032 cm 1 makes sif4 well suited to remote open path ftir spectroscopic techniques we report the first measurements of sif4 in volcanic gases at etna and vulcano sicily sif4 concentrations were low at etna but higher at vulcano where the so2 sif4 ratio was consistently around 1 7 10 2 1 thermodynamic considerations show that the hf sif4 ratio increases sharply with increasing temperature thus remote measurements of sif4 may offer a qualitative way of constraining fumarole temperatures we use our ftir measurements of hcl sif4 in combination with conventional measurements of hcl hf to infer an hf sif4 ratio for vulcano of 10 1 consistent with gas temperatures in the range 200 450 c

trace element degassing and enrichment in the eruptive plume of the 2000 eruption of hekla volcano iceland during its last eruption in february 2000 hekla volcano iceland emitted a sub plinian plume that was condensed and scavenged down to the ground by heavy snowstorms offering the unique opportunity to study the chemistry of the gaseous plume released during highly explosive eruptions in this paper we present results on trace element and minor volatile species sulfates chlorides and fluorides concentrations in snow samples collected shortly after the beginning of the eruption the goal of this study is to better constrain the degassing and mobility of trace elements in gaseous emissions trace element volatility at hekla is quantified by means of enrichment factors ef relative to be well known volatile trace elements e g transition metals heavy metals and metalloids are considerably enriched in the volcanic plume of hekla their abundances are governed by the primary magmatic degassing of sulfate and or halide compounds which are gaseous at magmatic temperature their volatility is however slightly lower than in basaltic systems most likely because of the lower magma temperature and higher magma viscosity at hekla more surprisingly refractory elements e g ree th ba and y are also significantly enriched in the eruptive plume of hekla where their apparent volatility is two orders of magnitude higher than in mafic systems in addition ree patterns normalized to the hekla 2000 lava composition show a significant enrichment of hree over lree suggesting the presence of ree fluorides in the volcanic plume such enrichments in the most refractory elements and ree fractionation are difficult to reconcile with primary degassing processes since ree fluorides are not gaseous at magma temperature ree enrichments at hekla could be attributed to incongruent dissolution of tephra grains at low temperature by f rich volcanic gases and aerosols within the eruptive plume this view is supported by both leaching experiments performed on hekla tephra and thermodynamic considerations on ree mobility in hydrothermal fluids and modeling of glass dissolution in f rich aqueous solutions tephra dissolution may also explain the observed enrichments in other refractory elements e g th y and ba and could contribute to the degassing mass balance of some volatile trace elements provided they are mobile in f rich fluids it thus appears that both primary magmatic degassing and secondary tephra dissolution processes govern the chemistry of eruptive plumes released during explosive eruptions

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

constraints on kimberlite ascent mechanisms revealed by phlogopite compositions in kimberlites and mantle xenoliths abstract kimberlite magmas are of economic and scientific importance because they represent the major host to diamonds and are probably the deepest magmas from continental regions in addition kimberlite magmas transport abundant mantle and crustal xenoliths thus providing fundamental information on the composition of the sub continental lithosphere despite their importance the composition and ascent mechanism s of kimberlite melts remain poorly constrained phlogopite is one of the few minerals that preserves a history of fluid migration and magmatism in the mantle and crust and is therefore an invaluable petrogenetic indicator of kimberlite magma evolution here we present major and trace element compositional data for phlogopite from the bultfontein kimberlite kimberley south africa i e the kimberlite type locality and from entrained mantle xenoliths phlogopite macrocrysts 0 3 0 5 mm and microcrysts between 0 1 and 0 3 mm in the bultfontein kimberlite display concentric compositional zoning patterns the cores of these phlogopite grains exhibit compositions typical of phlogopite contained in peridotite mantle xenoliths however the rims of some grains show compositions analogous to kimberlite groundmass phlogopite i e high ti al and ba low cr whereas other rims and intermediate zones between cores and rims exhibit unusually elevated cr and lower al and ba concentrations the latter compositions are indistinguishable from matrix phlogopite in polymict breccia xenoliths considered to represent failed kimberlite intrusions and from ti rich overgrowth rims on phlogopite in other mantle xenoliths consequently it is likely that these phlogopite grains crystallized from kimberlite melts and that the high ti cr zones originated from earlier kimberlite melts at mantle depths we postulate that successive pulses of ascending kimberlite magma progressively metasomatised the conduit along which later kimberlite pulses ascended producing progressively decreasing interaction with the surrounding mantle rocks in our view these processes represent the fundamental mechanism of kimberlite magma ascent our study also indicates that in addition to xenoliths xenocrysts and magmatic phases kimberlite rocks incorporate material crystallized at various mantle depths by previous kimberlite intrusions mantle derived antecrysts

a synthesis of the levantine basin circulation and hydrography 1985 1990 abstract the levantine basin circulation derived from recent data consists of a series of sub basin scale to mesoscale eddies interconnected by jets the basin scale circulation is masked by eddy variability that modulates and modifies it on seasonal and interannual time scales long term qualitative changes in the circulation are reflected in the bifurcation pattterns of ther mid basin jets relative strengths of eddies and the hydrographic properties at the core of these eddies confinement within the basin geometry strongly influences the co evolution of the circulation features surface measurements satellite images and the mass field indicate an entire range of scales of dynamical features in the region the complexity of the circulation is consistent with the basin wide and mesoscale heterogeneity of the hydrographic properties the interannual variability of liw levantine intermediate water formation in the region appears correlated with the changes in the circulation wintertime convective overturning of water masses reach intermediate depths and constitute a dominant mechanism of liw formation especially in anticyclonic eddies and along the coasts of the northern levantine basin

the 23 500 y 14 c bp white pumice plinian eruption and associated debris avalanche and tochimilco lava flow of popocatepetl volcano mexico abstract the white pumice wp is one of the thickest and most voluminous plinian fallouts produced by popocatepetl volcano in central mexico during the late pleistocene holocene its eruption 23 500 14 c y bp 27 800 cal bp was triggered by the catastrophic failure of the sw flank of the volcano the resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction l h of 0 06 the deposit covers an area of 1200 km 2 and has a volume of 10 4 km 3 this gigantic landslide characterized by exceptionally large proximal hummocks 400 m provoked the sudden decompression of the hydrothermal and magmatic systems which produced an initial blast followed by the rise of a plinian column that reached an altitude of 33 km the isopach map allows the recognition of a dispersal axis pointing toward the south where an area of 2490 km 2 was covered by 10 cm of pumice and ash the total volume of the pumice fallout was estimated at 1 9 km 3 dre dense rock equivalent pumice clasts are dacitic 62 66 wt sio 2 anhydrous basis highly vesicular 55 88 vol and display a seriate texture with phenocrysts of plagioclase hornblende augite hypersthene oxides ti magnetite and ilmenite apatite as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by rain induced lahars that reached great distances from the volcano at the same time more degassed andesitic dacitic 61 65 wt sio 2 magma was erupted effusively 4 4 km 3 dre in the new horseshoe shaped 5 km wide crater from which the tochimilco lava flow descended toward the sse where it inundated an area of 68 km 2 and reached as far as 22 km from its source since then multiple eruptions have reconstructed the summit cone almost completely obliterating the horseshoe shaped crater during the course of this catastrophic eruption vei 5 a total volume of 6 3 km 3 dre of juvenile magma pumice and lava were emitted and at least an additional 10 km 3 of pre existing rocks debris avalanche mobilized it surpasses in magnitude most other known plinian eruptions from popocatepetl and can be envisaged as an example of a worst case scenario for hazard evaluation purposes it dramatically changed the morphology of the volcano and had profound and far reaching effects beyond its immediate vicinity along rivers draining surrounding plains as well as on the lacustrine basins e g chalco to the ne a repeat of such an eruption in this densely populated area would certainly cause a major calamity of unprecedented dimensions

40ar 39ar ages in mantle xenolith phlogopites determining the ages of multiple lithospheric mantle events and diatreme ascent rates in southern africa and malaita solomon islands kimberlites are extraordinary natural phenomena ascending through the earth s lithosphere entraining xenoliths to erupt at the surface within hours to days of their inception deep within the lithospheric mantle with the realization that some ar ar phlogopite grain core ages may be indicative of geological events we have undertaken high spatial resolution ar ar dating of phlogopites in xenoliths and megacrysts from kimberley monastery and letseng in southern africa and malaita in the solomon islands to est whether other mantle phlogopite cores may yield meaningful ages modelling of ar diffusive loss profiles from phlogopite grain boundaries to cores provides information on both the eruption age and the duration of outgassing within the kimberlite magma and hence yields estimates on diatreme ascent rates the ascent durations are very similar for all of the southern african pipes studied yielding durations of 0 9 6 9 days assuming an average kimberlite magma temperature of 1000 c these can be compared to estimates from phlogopite xenoliths from siberian diamond bearing kimberlites yielding ascent durations of 2 15 hours assuming the same magma temperature

source mechanism of vulcanian degassing at popocatepetl volcano mexico determined from waveform inversions of very long period signals 1 the source mechanism of very long period vlp signals accompanying volcanic degassing bursts at popocatepetl is analyzed in the 15 70 s band by minimizing the residual error between data and synthetics calculated for a point source embedded in a homogeneous medium the waveforms of two eruptions 23 april and 23 may 2000 representative of mild vulcanian activity are well reproduced by our inversion which takes into account volcano topography the source centroid is positioned 1500 m below the western perimeter of the summit crater and the modeled source is composed of a shallow dipping crack sill with easterly dip of 10 intersecting a steeply dipping crack northeast striking dike dipping 83 northwest whose surface extension bisects the vent both cracks undergo a similar sequence of inflation deflation and reinflation reflecting a cycle of pressurization depressurization and repressurization within a time interval of 3 5 min the largest moment release occurs in the sill showing a maximum volume change of 500 1000 m3 pressure drop of 3 5 mpa and amplitude of recovered pressure equal to 1 2 times the amplitude of the pressure drop in contrast the maximum volume change in the dike is less 200 300 m3 with a corresponding pressure drop of 1 2 mpa and pressure recovery equal to the pressure drop accompanying these volumetric sources are single force components with magnitudes of 108 n consistent with melt advection in response to pressure transients the source time histories of the volumetric components of the source indicate that significant mass movement starts within the sill and triggers a mass movement response in the dike within a few seconds such source behavior is consistent with the opening of a pathway for escape of pent up gases from slow pressurization of the sill driven by magma crystallization the opening of this pathway and associated rapid evacuation of volcanic gases induces the pressure drop pressure recovery in the magma filling the sill is driven by diffusion of gases from the resulting supersaturated melt into bubbles assuming a penny shaped crack at ambient pressure of 40 mpa the observed pressure and volume variations can be modeled with the following attributes crack radius 100 m crack aperture 5 m bubble number density 1010 1012 m 3 initial bubble radius 10 6 m final bubble radius 10 5 m and net decrease of gas concentration in the melt 0 01 wt

popocatepetl s crater filled to the brim significance for hazard evaluation abstract after 67 years of quiescence popocatepetl volcano reawoke on december 24 1994 emitting vigorous ash plumes juvenile magma appeared for the first time on march 29 1996 with the emplacement of a dacitic lava dome inside the crater since then more than 25 dacitic domes have been extruded and destroyed by subsequent explosions on january 22 2001 the activity peaked with a strong explosion that produced pyroclastic flows that reached the timberline and ignited fires at a distance of 4 5 km from the crater these pyroclastic flows were contained within the red zone of the volcano hazards map after 10 years of discontinuous activity popocatepetl s crater is almost completely filled with lava dome rock this scenario poses a new threat to the populations settled in the orange zone intermediate hazard level because future explosions will not be contained by the crater walls and pyroclastic flows will probably reach greater distances from the crater

diamonds through time diamonds form in the upper mantle during episodic events and have been transported to the earth s surface from at least the archean to the phanerozoic small diamonds occur as inclusions in robust minerals in tectonically activated ultrahigh pressure metamorphosed crustal rock establishing an association with subduction processes and recycled carbon but providing no economic deposits diamonds in economic deposits are estimated to be mainly 99 derived from subcontinental lithospheric mantle and rarely approx 1 from the asthenosphere harzburgite and eclogite are of roughly equal importance as source rocks followed by lherzolite and websterite diamonds which provide evidence of extensive residence time in the mantle are with minimal exceptions smooth surfaced crystalline diamonds scd with potential commercial value the oldest prolific scd formation event documented on the world s major diamond producing cratons occurs in archean lithospheric mantle harzburgite metasomatized by likely subduction related potassic carbonatitic fluids disaggregation of the diamondiferous carbonated peridotite on decompression during volcanic transit gives rise to the association between diamonds g10 garnets and diamond inclusion type chromites well used in diamond exploration within the mantle domains of diamond stability there have been repeated episodes of further diamond crystallization and or growth these are associated with old often proterozoic subduction related melt generation metasomatic fluid migration and reaction with preexisting mantle eclogite websterite and peridotite using improved methods of isotope analysis diamond formation ages can be correlated with specific major processes such as craton accretion craton edge subduction and magmatic mantle refertilization fibrous cuboid diamond and fibrous coats on scd are rough surfaced diamonds with abundant fluid inclusions they have low mantle residence time forming rapidly from late stage metasomatic fluids in diamond stable domains that may already contain scd the symbiotic relationship between formation of fibrous diamond and magmatic sampling and transport of diamonds into the crust suggest that the associated fluids contribute diamond friendly volatile loading of the deep lithospheric mantle shortly before the triggering of a volcanic eruption continuing a process of volatile enrichment in the lithospheric mantle already identified in the archean harzburgite diamond event mantle derived scd commonly shows evidence of resorption illustrating that diamond unfriendly processes including lamproite and kimberlite generation are also active and may have a substantial negative effect in extreme cases on scd crystal size exposure of scd to a long period of changing conditions during mantle residence contributes to the difficulty of assigning specific parageneses and ages to individual inclusion free diamonds with our current state of knowledge

high and low k granites and adakites at a palaeoproterozoic plate boundary in northwestern australia the lamboo complex is one of several palaeoproterozoic terrains in northern australia that is intruded by high k i type granites the oldest granites in the complex consist of the high k 1865 1850 ma paperbark supersuite with initial e nd values between 2 7 and 4 0 tonalite sheets of the c 1850 ma dougalls suite have high al 2 o 3 na 2 o sr sr y and la yb and low y and hree and initial e nd values between 1 4 and 0 7 the rocks have compositions similar to adakites that form by melting of mafic rocks in the deep crust with garnet in the residue granites of the 1835 1805 ma sally downs supersuite range from high k types through to crustally derived adakites all with initial e nd values between 0 1 and 1 2 the two supersuites and the dougalls suite were intruded into different tectonic settings previously all of the granites in the lamboo complex were interpreted as partial melts of a chemically and isotopically uniform underplate beneath a rifted archaean craton however their spatial and temporal distribution and their varied compositions are best explained by large scale horizontal plate motions and subduction of oceanic crust

tectonic implications of palaeoproterozoic post collisional high k felsic igneous rocks from the kimberley region of northwestern australia abstract palaeoproterozoic high k i type granites high level porphyry intrusions and felsic volcanic rocks of the whitewater volcanics dominate the hooper and lamboo complexes in the kimberley region of northwestern australia the granites porphyries and volcanic rocks are gradational into each other in the field and they have the same mineralogy similar major and trace element abundances and indistinguishable shrimp u pb zircon ages of 1865 1850 ma there is evidence of widespread mingling between the granites and coeval gabbros magma mixing may be important in the formation of some of the mafic granites but most of the rocks probably formed from felsic parent magmas that underwent variable degrees of fractional crystallization the felsic igneous rocks may have formed by partial melting of intermediate to felsic calc alkaline rocks along the southern and eastern margins of the kimberley craton following accretion of various earlier palaeoproterozoic terranes to the craton therefore models for palaeoproterozoic high k granites in northern australia that invoke intracratonic rifting of a stable archaean craton may need to be revised

chemical variations of tephra fall deposit leachates for three eruptions from popocatepetl volcano abstract leachates from ash samples of the popocatepetl eruptions of april 30 1996 may 12 1997 and october 17 1998 settled at different distances from the crater were analyzed for anions so 4 2 cl f and some metals this study is aimed at determining the causes of the compositional variations of the leachates to assist the assessment of water soil and crop contamination due to ash deposits different behavior was observed in the ion concentrations with distance for the three eruptions on april 30 1996 so 4 2 and f concentrations increased with distance and cl remained almost constant on may 12 1997 concentrations of the three anions decreased with distance on october 17 1998 f cl and so 4 2 increased more than three fold with distance tephra size distributions were also different for the three eruptions the observed trends of the leachates anion concentrations may have different causes the type and intensity of the eruptions the distribution of the tephra sizes the degree of interaction of the tephras with volcanic gases humidity static charge the original characteristics of the solid material the transport time from the crater to the site of settling and the relative angle between the wind direction and the sampling line enrichment factors and concentration trends for metals with distance suggest that co ni cu and pb in the leachates resulted mostly from volcanic gas adsorption

passive infrared remote sensing evidence for large intermittent co2 emissions at popocatepetl volcano mexico abstract passive infrared ftir and correlation spectrometer cospec measurements were conducted at popocatepetl volcano during february 10 to 26 1998 from sites 4 to 17 km distant from the summit volcano behavior was relatively quiet and so 2 flux averaged 1670 1420 t day 51 measurements relatively small for popocatepetl concurrent hcl so 2 and hf so 2 ratios were 0 17 0 01 and 0 031 0 003 respectively about the same as ratios measured from 1994 to 1997 the amount of co 2 in the volcanic plume was quantified using fascode in which atmospheric co 2 is numerically subtracted from the total infrared spectrum to obtain the residual magmatic co 2 surprisingly co 2 so 2 mass ratios rose dramatically to values as high as 140 about 30 times higher than typical values of 2 to 8 measured from 1994 to 1996 these excursions in high co 2 so 2 ratios were short lived lasting no longer than about 0 5 to 3 0 h but co 2 flux occasionally exceeded 100 000 t day we estimate that the average co 2 so 2 ratio for the period was about 23 yielding an average co 2 flux of roughly 38 000 t day chemical and petrographic analyses of lava and pumice erupted during explosions on june 30 1997 and january 1 1998 show conclusively that popocatepetl produces mixed products formed by injection of mafic magma into a more silicic chamber at temperatures and pressures of roughly 1040 c and 5 kbar in addition popocatepetl eruptive products include xenoliths of metamorphosed carbonate rocks containing wollastonite and other calc silicate minerals indicating reaction of magma with cretaceous limestone underlying the volcano using a normal co 2 so 2 ratio of 4 for reference we calculate an average excess co 2 production of 32 000 t day for 17 days this would require assimilation of only 5 10 4 km 3 of limestone an amount easily accessible in the 3 km thick cretaceous section beneath the volcano we also examine two scenarios in which excess co 2 is produced by degassing of subjacent basalt magma but these explanations seem less plausible to us because many other volcanoes are underlain by carbonate sequences short duration bursts of co 2 flux and increased co 2 so 2 ratio might be observed at other sites if simultaneous real time measurements of major gas species are made

an empirical evaluation of the argon diffusion geometry in muscovite the temperature time significance of 40ar 39ar muscovite ages is difficult to evaluate quantitatively because of ambiguities in the choice of an appropriate model diffusion geometry the effective diffusion dimension and large uncertainties in experimentally determined diffusion parameters laser 40ar 39ar studies of natural 40ar concentration gradients suggest that argon loss in muscovite occurs primarily via cylindrical volume diffusion commonly with an effective diffusion dimension equal to the crystal diameter the present study tests the cylinder model geometry and the control of physical grain size on the effective diffusion dimension by measuring the anisotropy of a natural40ar diffusion gradient parallel and perpendicular to 001 in a single euhedral muscovite phenocryst the new data combined with previous studies clearly indicate loss of 40ar via cylindrical volume diffusion and strongly suggest that loss of 40ar across the 001 sheets slab diffusion geometry is minimal in undeformed crystals

downwelling along the northeastern coasts of the eastern mediterranean abstract the most prominent winter storms in the eastern part of the eastern mediterranean are known as cyprus cyclones the surface wind speed is between 15 30 m s 1 and about five such cyclones occur in a typical winter the cyclone radius is between 500 and 1500 km the evolution of the sea structure under such atmospheric forcing is examined with a two dimensional numerical model in the vertical cross section perpendicular to the shore line two distinct regions result in the sea a downwelling zone near the coast about 100 km wide and a horizontally homogeneous zone in the open sea where vertical mixing is the important dynamical process in the open sea the final profiles turn out to be similar to those observed in the levantine intermediate water liw in their formation region we suggest that the liw forms in the region under the influence of these cyprus cyclones in the downwelling zone the 14 17 c isotherms decline by more than 250 m this water has the same t s properties as the water in

new geochemical insights into volcanic degassing magma degassing plays a fundamental role in controlling the style of volcanic eruptions whether a volcanic eruption is explosive or effusive is of crucial importance to approximately 500 million people living in the shadow of hazardous volcanoes worldwide studies of how gases exsolve and separate from magma prior to and during eruptions have been given new impetus by the emergence of more accurate and automated methods to measure volatile species both as volcanic gases and dissolved in the glasses of erupted products the composition of volcanic gases is dependent on a number of factors the most important being magma composition and the depth of gas melt segregation prior to eruption this latter parameter has proved difficult to constrain in the past yet is arguably the most critical for controlling eruptive style spectroscopic techniques operating in the infrared have proved to be of great value in measuring the composition of gases at high temporal resolution such methods when used in tandem with microanalytical geochemical investigations of erupted products are leading to better constraints on the depth at which gases are generated and separated from magma a number of recent studies have focused on transitions between explosive and effusive activity and have led to a better understanding of gas melt segregation at basaltic volcanoes other studies have focused on degassing during intermediate and silicic eruptions important new results include the recognition of fluxing by deep derived gases which buffer the amount of dissolved volatiles in the melt at shallow depths and the observation of gas flow up permeable conduit wall shear zones which may be the primary mechanism for gas loss at the cusp of the most explosive and unpredictable volcanic eruptions in this paper i review current and future directions in the field of geochemical studies of volcanic degassing processes and illustrate how the new insights are beginning to change the way in which we understand and classify volcanic eruptions

elemental mercury at submarine hydrothermal vents in the bay of plenty taupo volcanic zone new zealand hot springs in active geothermal areas such as yellowstone national park the geysers geothermal field in california and the taupo volcanic zone in new zealand are notably enriched in the trace metals au ag as sb and hg such near surface hot springs have formed many of the world s important deposits of gold and silver and some of the largest deposits of mercury the majority of these are associated with continental geothermal systems in subaerial environments here we report the discovery of active mercury depositing hot springs in a submarine setting at nearly 200 m water depth within the offshore extension of the taupo volcanic zone of new zealand these vents contain the first documented occurrence of elemental mercury on the sea floor and provide an important link between offshore hydrothermal activity and mercury depositing geothermal systems on land the discovery has implications for mercury transport in sea floor hydrothermal systems and underscores the importance of submarine volcanic and geothermal activity as a source of mercury in the oceans

remote detection of hcl and so2 in volcanic gas from unzen volcano japan a telescope attached ft ir spectral radiometer was applied for remote measurement of chemical composition of the volcanic gas of unzen volcano japan which started erupting in november 1990 the observations were carried out at the site about 1 3 km away from the gas emitting region of the volcano in march and july 1992 absorption features of so2 vl and hcl were identified and column amounts of so2 and hcl of the volcanic gas plume were estimated using a nonlinear least squares method the so2 hcl ratio was in the range between 0 7 and 1 8 for both march and july observations this is the first remote ground based observation of hcl in volcanic gas

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

a new method for sampling fumarolic gases analysis of major minor and metallic trace elements with ammonia solutions abstract a new method using ammonia solutions in pre evacuated quartz bottles has been experimented for volcanic gas sampling and analysing various tests reproducibility variability and comparison with known methods such as naoh pre evacuated bottles and acid condensates have been performed to check for their efficiency by using ammonia solutions acid gases st hcl hf carbon dioxide noncondensible gases n 2 ar and metallic trace elements mte can be measured with standard methods hplc gc titrimetry icp ms results show that acid gases co 2 and noncondensible gases are sampled and analysed with similar efficiency in nh 4 oh bottles than by using the known and accurate naoh method moreover a key point is that nh 4 oh solutions after undergoing adequate processing oxidation and acidification allow also precise mte measurements by using standard icp ms methods such mte measurements appear much more reliable than those performed on acid condensates pre evacuated ammonia bottles appear therefore as an optimum tool to collect volcanic gases and to obtain their complete chemical composition

a new collector for sampling volcanic aerosols abstract a new apparatus venturi effect system ves designed for sampling volcanic plumes is described and tested at vulcano italy this device together with purified basic nh 4 oh solutions supplies optimal conditions to obtain reliable s total cl f ratios and enrichment factors for metallic trace elements mte good concordance for acid gas ratios and metal enrichment factors in both the gas phase and the related plume allows the procedure to be validated the ves appears in vulcano conditions as a simple robust and easily portable apparatus that allows reliable collection of both acid gases and mte within a single sample and the analysis with current chemical methods high pressure liquid chromatography inductively coupled plasma mass spectrometry this apparatus may be suitable for more difficult volcanoes where only the plume can be sampled

dynamics of the ca 4965 yr 14c bp ochre pumice plinian eruption of popocatepetl volcano mexico abstract the ochre pumice op plinian fallout was produced by popocatepetl volcano in central mexico during a major plinian eruption that occurred 4965 65 14 c yr bp 3700 bc the op is part of the ochre pumice sequence ops that consists of surge fall and pyroclastic flow deposits the op plinian fallout shows a bimodal grain size distribution with poor to moderate sorting that improves progressively towards the upper beds the juvenile component is mainly pumice 83 wt whereas the accidental components consist of igneous sedimentary and metamorphic clasts from the walls of the magma chamber and or conduit the vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal and glass contents increase this suggests increasing magma degassing prior and during the eruption the chemical composition of the pumice varies insignificantly at the base it is less evolved sio 2 61 wt and it becomes slightly more silicic towards the top sio 2 63 wt pumice clasts have a crystallinity index that ranges between 10 and 25 vol and display a seriate texture with phenocrysts of euhedral plagioclase pl clinopyroxene cpx orthopyroxene opx olivine ol oxide ox apatite ap the size of the maximum lithic 2 5 cm at a horizontal distance of 19 km indicates an eruption column height of 37 41 km the isopach map allows the recognition of a dispersal axis that points towards the nne where an area of 300 km 2 was covered by 6 cm of pumice and ash a minimum volume for the op plinian fallout deposit was calculated using a minimum thickness of 6 cm found at distal outcrops and was estimated at 4 9 km 3 which corresponds to 2 km 3 of dense rock equivalent dre stratigraphic relations indicate that the entire ops was emplaced during a short time interval of a few days to weeks and consisted of three main different phases phreato magmatic plinian and vulcanian it started violently with the emplacement of surges and then culminated with the eruption of the op fallout deposit as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by the growth of domes in the crater and the emplacement of block and ash flows generated by vulcanian explosions

reactive halogens bro and oclo detected in the plume of soufriere hills volcano during an eruption hiatus volcanic plumes are sites of dynamic chemistry involving halogen gases here we present new data on the relative abundances of so2 bro and oclo gases emitted from soufriere hills volcano shv they were collected during an eruptive hiatus but during sustained degassing at this halogen rich volcano by comparison with data from a previous study during an eruptive phase and application of the data and modeling of villemant et al 2008 we suggest that after consideration of errors either the rate of hbr conversion to bro is variable ranging from 30 to 15 and or the relative partitioning of cl and br into the gas phase from the melt changes according to eruptive activity we examine the potential implications of this for fluid melt partitioning and compare our results with data from the experimental literature our work contributes toward understanding the controls on the bro so2 ratio for volcano monitoring purposes the changes in plume chemistry with regard to bromine at the onset of lava extrusion may be large and rapid oclo was detected in the plume at shv for the first time this species has only previously been detected in emissions from mount etna using ground based methods and from puyehue cordon caulle using satellite based methods no hcho or noy species were detected in the spectra

the origin of high hydrogen content in kimberlitic olivine evidence from hydroxyl zonation in olivine from kimberlites and mantle xenoliths abstract olivine macrocrysts in kimberlites are the most h rich natural olivines known their xenocrystic provenance makes unclear whether h enrichment occurred in the mantle prior to entrainment in kimberlite magma or during ascent we present a fourier transform infrared ftir spectroscopy based study of h zonation in kimberlite derived olivine macrocrysts and or olivine in xenoliths from the kimberlites jericho nunavut canada beartooth northwest territories canada and pipe 200 and matsoku lesotho the objective of the study was to determine whether changes in the concentration or speciation of h defects in proximity to the host kimberlite could yield insights into the origin of h enrichment within the group 1 region of the ftir spectrum 3420 3700 cm 1 we find that olivines within xenoliths and macrocrysts show weak zonation or significant h depletions in rims peaks in the group 2 region 3260 3420 cm 1 in beartooth olivines show marked decrease in the crystal margins in comparison to group 1 peaks we find no preserved evidence for kimberlite related h enrichment in our dataset we ascribe h depletion to diffusive h loss to infiltrating kimberlitic media diffusion models using coefficients previously applied to dehydrogenation of olivine and assuming a dry environment produce extremely short ascent durations incompatible with the results of other geospeedometers this mismatch suggests that the poorly developed zonation in jericho and beartooth olivines indicates water enrichment and or faster ascent of these melts in comparison to pipe 200 and matsoku resulting in greater retention of mantle derived h a further significant factor in the mismatch is the differing speciation of h in most natural mantle derived olivines in comparison to those used in diffusion experiments we argue that the presence of presumably mantle derived group 2 h in olivine macrocrysts indicates rapid ascent of magma exsolving water rich fluid permitting preservation of these faster diffusing defects only in particularly rapidly ascending kimberlite magmas this interpretation explains empirical correlations between the presence of group 2 bands water derived diamond resorption features and volcaniclastic kimberlite facies

excess argon evolution in hp lt rocks a uvlamp study of phengite and k free minerals nw turkey excess argon is a common problem in high pressure metamorphic rocks here we present 40ar 39ar data from metabasite metachert and metapelite lithologies and a range of minerals the results allow us to discuss the origin of the excess argon and processes leading to its incorporation during high pressure metamorphism samples were derived from blueschist and low temperature eclogite facies rocks from the tavsanli zone of nw turkey samples were analysed using the 40ar 39ar ultra violet laser ablation microprobe uvlamp and yield ages ranging from 72 3 to 154 7 ma detailed intra grain profiling of phengites in situ and analyses of sodic amphibole lawsonite quartz and garnet present a detailed picture of the spatial distribution of excess argon within different minerals in the same hand samples revealing that they acted as near closed systems where excess argon was preferentially partitioned into phengite whole rock xrf data indicates a scattered relationship between bulk k2o content of the rock and the concentration of excess argon in phengite we conclude that excess argon was derived in situ in a relatively closed fluid absent system rather than introduced by fluids

plume chemistry provides insights into mechanisms of sulfur and halogen degassing in basaltic volcanoes abstract this paper deals with sulfur chlorine and fluorine abundances in the eruptive volcanic plume of the huge october 2002 january 2003 eruption of mount etna aiming at relating the relevant compositional variations observed throughout with changes in eruption dynamics and degassing mechanisms the recurrent sampling of plume acidic volatiles by filter pack methodology revealed that during the study period s cl and cl f ratios ranged from 0 1 6 8 and 0 9 5 6 respectively plume s cl ratios increased by a factor of 10 as volcanic activity drifted from paroxysmal lava fountaining mid and late november to passive degassing and minor effusion early january and then decreased to the low values s cl 0 1 typical of the final stages of the eruption parallel variations in chlorine to fluorine ratios were also observed a theoretical model is proposed for quantitative interpretation of these changes in plume composition the model calculates the composition of a volatile phase exsolving from an ascending etna magma based on knowledge of solubilities and abundances in the undegassed melt of sulfur and halogens t m gerlach eos 72 1991 249 254 255 according to this model degassing of etnean basaltic melt at high pressures and depths 100 mpa 3 km is likely to release a co2 h2o rich vapor phase with s cl molar ratios 1 extensive sulfur and chlorine degassing from the melt would take place at shallower depth p

volcanic emissions of metals and halogens from white island new zealand and erebus volcano antarctica determined with chemical traps abstract volcanic emission rates of as sb pb hg se cl and f were determined at erebus volcano antarctica and white island new zealand using chemical traps the trace metal fluxes were determined by combining the species to s ratios in the solutions with so2 emission rates measured by correlation spectrometry at the two volcanoes at erebus volcano fluxes for the metals pb and hg were 2 0 10 4 and 8 1 10 6 kg s 11 respectively fluxes for cl f as sb and se 0 35 0 15 2 5 10 4 1 2 10 5 and 4 5 10 6 kg s 1 respectively agreed within error limits for values determined previously by the lioh impregnated filter method zreda gostynska g kyle p finnegan d prestbo k 1997 volcanic gas emissions from mount erebus and their impact on the antarctic environment journal of geophysical research 102 b7 15039 15055 demonstrating the utility of the chemical trap method a fall in the as s ratio from 7 10 4 in 1997 1999 to 3 10 4 in 2000 at erebus coincided with a change in the frequency and style of eruptive activity that may have been due to injection of magma into the system at white island chemical trap data indicated fluxes of cl 0 90 f 0 0079 pb 2 7 10 4 hg 1 1 10 5 as 1 3 10 4 sb 1 9 10 5 and se 1 5 10 5 kg s 1 samples collected 600 m downwind of the active crater were comparable to samples collected adjacent to the main gas vent showing that this method can still be used at some distance from a degassing vent

geochemical evidence of magma intrusion inferred from diffuse co 2 emissions and fumarole plume chemistry the 2010 2011 volcanic unrest at taal volcano philippines we report herein significant increases in the diffuse co2 emission through the lake and soils of the taal volcano main crater philippines during a volcano seismic unrest period in april 2010 june 2011 monitoring of co2 emissions from the taal main crater lake and soils in the fumarole areas started in 2008 with a collaborative project between iter and phivolcs in august 2010 the total diffuse co2 emission from the taal main crater lake increased almost three times from a previously measured baseline emission value 1 000 t day 1 to 2 716 54 t day 1 this increase occurred during anomalous seismic activity which started in april 2010 the highest co2 emission value in the crater lake was measured in march 2011 at 4 670 159 t day 1 when the volcano was still showing signs of unrest significant changes in the co2 so2 co2 h2o and so2 h2s ratios in the fumarole gases suggest the occurrence of a magmatic injection several weeks before the onset of the volcano seismic unrest period these observed changes in the co2 emission rate and the fumarole gas composition as the result of magmatic activity were likely caused by magma moving from a deep reservoir to a shallow reservoir

atmospheric expansion wave simulations of popocatepetl explosions 1 we present a compressible gasdynamic numerical model that utilizes a three dimensional adaptive grid to provide high spatial resolution of an expanding compression wave we apply this model to recent explosions of popocatepetl volcano in mexico by incorporating both high resolution topography for a lower boundary and atmospheric stratification based upon climatological thermodynamic soundings explosions are simulated by the instantaneous release of an overpressure in a prescribed volume over the volcano s crater the results show a compression wave that propagates as a supersonic shock close to the explosion transforming into a sonic compression wave at larger distances we validate the model predictions by comparing them to pressure time series measured by a microbarograph located 11 km away from the crater with the model validation we estimate the equivalent initial internal energy of the explosions to range from 2 1013 j to 1 1 1015 j

chemical monitoring of volcanic gas using remote ft ir spectroscopy at several active volcanoes in japan abstract chemical compositions of volcanic gases of several japanese active volcanoes have been monitored from distant safe places since the beginning of the 1990s using an ft ir spectral radiometer for absorption measurements an infrared light source behind volcanic gas emissions is necessary in a volcanic environment in the early observations infrared radiation from hot lava domes unzen volcano and hot ground heated by high temperature fumaroles usu aso and satsuma iwojima volcanoes were used as infrared light sources however these sources were not available in many cases this remote ft ir method became more commonly applied to chemical monitoring of volcanic gases emitted from the summit or slopes of active volcanoes using scattered solar infrared light as infrared light sources sakurajima miyakejima and asama volcanoes to date eight species have been measured using this method so2 hcl hf co co2 cos sif4 and h2o the observations indicate that volcanic gases for each volcano have different chemical composition on a so2 hcl hf ternary diagram in spite of similar tectonic settings suggesting that vapor melt volume ratios during volcanic gas formation differ among volcanoes during more than 15 years of monitoring chemical changes in volcanic gases attributable to ascent of magma were observed only at asama where hcl so2 and hf hcl ratios in the eruptive period were higher than those in non eruptive period because of scrubbing of more soluble components in surface hydrothermal systems in the non eruptive stage or solubility controlled fractionation processes results show that these parameters are the most prospective ones among the various parameters measured using the remote ft ir method to monitor volcanic activities

degassing patterns of tungurahua volcano ecuador during the 1999 2006 eruptive period inferred from remote spectroscopic measurements of so2 emissions this paper presents the results of 7 years aug 1999 oct 2006 of so2 gas measurements during the ongoing eruption of tungurahua volcano ecuador from 2004 onwards the operation of scanning spectrometers has furnished high temporal resolution measurements of so2 flux enabling this dataset to be correlated with other datasets including seismicity the emission rate of so2 during this period ranges from less than 100 to 35000 tonnes day t d with a mean daily emission rate of 1458 t d and a standard deviation of 2026 t d average daily emissions during inferred explosive phases are about 1 75 times greater than during passive degassing intervals the total amount of sulfur emitted since 1999 is estimated as at least 1 91 mt mostly injected into the troposphere and carried westwards from the volcano our observations suggest that the rate of passive degassing at tungurahua requires so2 exsolution of an andesitic magma volume that is two orders of magnitude larger than expected for the amount of erupted magma two possible and not mutually exclusive mechanisms are considered here to explain this excess degassing gas flow through a permeable stagnant magma filled conduit and gas escape from convective magma overturning in the conduit we have found that real time gas monitoring contributes significantly to better eruption forecasting at tungurahua because it has provided improved understanding of underlying physical mechanisms of magma ascent and eruption

major and trace element compositional variation of phlogopite from kimberlites and carbonatites as a petrogenetic indicator abstract ferromagnesian trioctahedral micas are a common macrocryst phenocryst phase in kimberlites and carbonatites we explored the possibility of using the chemistry of ferromagnesian micas to discriminate between these rocks in order to assess their economic potential we determined the extent of major and trace element variations of micas from 14 selected kimberlite and carbonatite localities worldwide representing several different kimberlite fields and alkaline carbonatite provinces phlogopite macrocrysts from kimberlites follow two principal evolutionary trends primary macrocrystic involving an increase in ba al ti cr zr nb and sr contents at decreasing mg towards the rim and transitional macrocryst groundmass trend involving an increase in kinoshitalite component at decreasing fe ti and cr contents micas from dolomite calcite carbonatites cover a much greater compositional range than those from kimberlites defining evolutionary trends towards annite tetra ferriphlogopite and kinoshitalite our data confirm that macrocrystic micas from kimberlites cannot be reliably distinguished from carbonatitic phlogopite on the basis of their major element compositions exceptions are fe al rich fe fe mg 0 2 and na rich 0 3 wt na 2 o micas that seem to be virtually restricted to carbonatites the generally higher levels of na in carbonatitic micas relative to those from kimberlites can be explained by the lower na abundances in the latter relative to carbonatites our data indicate that the trace element composition of mica determined by la icp ms can be used as a reliable petrogenetic indicator kimberlitic phlogopite is characteristically enriched in cr up to 12030 ppm ni up to 1600 ppm and co 40 70 ppm and depleted in mn 280 ppm nb 28 ppm sr 55 ppm sc 8 ppm zr 12 ppm and to some extent cs 7 ppm and ta 3 ppm with respect to carbonatitic micas 315 ppm cr 470 ppm ni 34 ppm co up to 17200 ppm mn 1080 ppm nb 830 ppm sr 80 ppm sc 105 ppm zr 27 ppm cs and 19 ppm ta with the exception of zr the observed differences in trace element composition of mica probably reflect the contrasting trace element geochemistry of kimberlitic and carbonatitic magmas the depletion of kimberlitic phlogopite in zr and possibly nb ta can be explained by sequestration of these elements in the earlier crystallized ilmenite variations in ba rb and v contents are similar in mica from both rock types and cannot be used as a petrogenetic indicator

intercomparison of volcanic gas monitoring methodologies performed on vulcano island italy 1 volcanic gas emissions from fumaroles on the rim of la fossa crater vulcano island italy were measured simultaneously using direct sampling for h2o co2 total sulfur hcl and hf filter packs for so2 hcl hf and short path active mode ftir measurements for h2o co2 so2 hcl and hf in an intercomparison study in may 2002 the results show that cl f ratios were in good agreement between all three methods and that ftir and direct sampling determined comparable proportions of co2 and h2o amounts of total s observed in direct sampling data were approximately double the amounts of so2 measured with filter packs and ftir this difference could be attributed either to the fact ftir and filter packs do not measure reduced sulfur species e g h2s or to sublimation of elemental s upon exit from the fumarole after collection by direct sampling but before detection with ftir and filter packs

thermal effects of magma degassing abstract the thermodynamics of diffusive bubble growth is dominated by latent heat of water exsolution vaporization and the work of gas expansion p dv work a numerical assessment of the effects of these on cooling of bubbly magma water in albite indicates that a magma can exsolve volatiles at equilibrium or with varying degrees of oversaturation depending on decompression history and degassing kinetics heat of water exsolution vaporization from magmatic melts has not previously been experimentally or analytically determined and we have evaluated it from others thermodynamic functions known for the albite water system heat of exsolution is small for pressures over 100 mpa but can reach 20 kj mole at 1 2 mpa 10 20 bar oversaturation degassing at 10 20 bar can cause cooling of albite by 8 k wt of exsolved water the thermal effect of equilibrium degassing depends on the starting pressure of decompression because it follows the solubility curve for a saturated melt at 100 mpa 4 wt water it can cool a magma at least by 35 k before it disrupts into spray as gas volume fraction exceeds 0 8 although we do not specifically consider the dynamics of bubble interactions in this study our results suggest that the dynamic cooling rate could be significant at the vent of an erupting magma column and under extreme eruption conditions can lead to glass formation around fast growing bubbles of magmatic foam this could cause fragmentation into fine ash by brittle failure conversely bubble wall cooling even before glass formation can serve to reduce diffusive volatile flux into bubbles decreasing the overall cooling of the system and lead to solidification of oversaturated magmas as occasionally observed in eruption products

magmatic evolution and ascent history of the aries micaceous kimberlite central kimberley basin western australia evidence from zoned phlogopite phenocrysts and uv laser 40ar 39ar analysis of phlogopite biotite the neoproterozoic aries kimberlite was emplaced in the central kimberley basin western australia as a n nne trending series of three diatremes infilled by lithic rich kimberlite breccias the breccias are intruded by hypabyssal macrocrystic phlogopite kimberlite dykes that exhibit differentiation to a minor high na si olivine phlogopite richterite kimberlite and late stage macrocrystic serpentine diopside ultramafic dykes mineralogical and geochemical evidence suggests that the high na si olivine phlogopite richterite kimberlite was derived from the macrocrystic phlogopite kimberlite as a residual liquid following extended phlogopite crystallization and the assimilation of country rock sandstone and that the macrocrystic serpentine diopside ultramafic dykes formed as mafic cumulates from a macrocrystic phlogopite kimberlite chemical zonation of phlogopite biotite phenocrysts indicates a complex magmatic history for the aries kimberlite with the early inheritance of a range of high ti phlogopite biotite xenocrysts from metasomatized mantle lithologies followed by the crystallization of a population of high cr phlogopite phenocrysts within the spinel facies lithospheric mantle a further one to two phlogopite biotite overgrowth rims of distinct composition formed on the phlogopite phenocrysts at higher levels during ascent to the surface ultra violet laser 40ar 39ar dating of mica grain rims yielded a kimberlite eruption age of 815 4 4 3 ma 95 confidence 40ar 39ar laser profiling of one high ti phlogopite biotite macrocryst revealed a radiogenic 40ar diffusive loss profile from which a kimberlite magma ascent duration from the spinel facies lithospheric mantle was estimated assuming an average kimberlite magma temperature of 1000 c yielding a value of 0 23 2 32 days for the north extension lobe of the aries kimberlite

chemistry of ash leachates to monitor volcanic activity an application to popocatepetl volcano central mexico abstract monitoring volcanic activity and assessing volcanic risk in an on going eruption is a problem that requires the maximum possible independent data to reduce uncertainty a quick relatively simple and inexpensive method to follow the development of an eruption and to complement other monitoring parameters is the chemical analysis of ash leachates particularly in the case of eruptions related to dome emplacement here the systematic analysis of so 4 2 cl and f concentrations in ash leachates is proposed as a valuable tool for volcanic activity monitoring however some results must be carefully assessed as is the case for s cl ratios since eruption of hydrothermally altered material may be confused with degassing of incoming magma sulfur isotopes help to identify so4 produced by hydrothermal processes from magmatic so2 lower s isotopic values correlated with higher f percentages represent a better indicator of fresh magmatic influence that may lead to stronger eruptions and emplacement of new lava domes additionally multivariate statistical analysis helps to identify different eruption characteristics provided that the analyses are made over a long enough time to sample different stages of an eruption

depositional age and provenance of the marboo formation from shrimp u pb zircon geochronology implications for the early palaeoproterozoic tectonic evolution of the kimberley region western australia abstract the marboo formation is the oldest rock unit in the hooper complex in the west kimberley region of western australia the complex forms an elongate belt 350 km long and at least 100 km wide of deformed and metamorphosed palaeoproterozoic low to high grade metasedimentary rocks and mafic and felsic igneous rocks the marboo formation consists of a sequence of turbiditic metasedimentary rocks derived from the northwest an area of crust now buried beneath the unconformably overlying speewah and kimberley basins shrimp u pb dating of detrital zircons from a low grade quartz wacke indicate that the provenance terrain contributed zircons dated at around 2500 to 2400 ma 2300 ma 2200 to 2050 ma 1970 ma and 1910 ma the mount joseph migmatite formed by in situ melting of the marboo formation and zircons interpreted as detrital in origin give ages of 2500 to 2000 ma a maximum depositional age is provided by a population of zircon cores dated at 1872 9 ma growth of rims on zircons is dated at 1861 5 ma and is interpreted as the age of high grade metamorphism a minimum age for deposition is provided by the richenda microgranodiorite which forms a high level intrusive stock into the marboo formation and is dated at 1858 5 ma comparison with recent shrimp ages from the halls creek group in the east kimberley indicates that the turbidites of the marboo formation were deposited deformed metamorphosed and intruded by granitoid before the majority of the turbiditic metasedimentary rocks in the olympio formation were deposited this is not consistent with deposition of the turbiditic rocks in the same basin the assumption of contemporaneous turbidite deposition throughout the kimberley region has been taken as evidence of intracratonic palaeoproterozoic orogeny however these results provide support for plate tectonic models and the recognition of tectonostratigraphic terranes within the kimberley region detrital zircons from the marboo formation suggest that unexposed crust beneath the speewah and kimberley basins is largely early palaeoproterozoic in age rather than archaean as previously assumed the spread in ages indicates that the time period between formation of late archaean basement in northern australia and the formation of palaeoproterozoic orogens was marked by ongoing crust formation and was not a period of quiessence

laser interference and nomarski interference imaging of zoning profiles in plagioclase phenocrysts from the may 18 1980 eruption of mount st helens washington

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

an ftir study of hydrogen in anorthoclase and associated melt inclusions high resolution fourier transform infrared ftir spectroscopy has been used to document the presence of hydrogen to estimate its concentration and to document its oxygen speciation in anorthoclase crystals and associated melt inclusions from mount erebus antarctica synchrotron generated infrared radiation 100 to 1000 times brighter than globar generated infrared radiation permits rapid collection of maps that depict relative intensities of a chosen ftir band across the mapped area spectra and or compositional maps showing variations in water concentration were collected from anorthoclase megacrysts and melt inclusions in the megacrysts studies of anorthoclase megacrysts involved collection of spectra from three mutually perpendicular sections cut from the crystals ftir spectra of anorthoclase crystals are characterized by a broad absorption band at approximately 3200 cm sup 1 in the mid ir range the universal mass absorption coefficient for mid ir range feldspar spectra established by johnson and rossman 2003 was used for quantitative estimates of water concentrations in the feldspar crystals based on integrated area under the 3200 cm sup 1 band water concentration in the anorthoclase sample was approximately 126 ppm with an overall error of approximately 30 ftir spectra of melt inclusions are characterized by a broad asymmetric absorption band at approx 3550 cm sup 1 that was used tomore calculate total water concentration the absence of a band at 1630 cm sup 1 suggests that water in the melt inclusions occurs as oh sup rather than as molecular h sub 2 o absorption coefficients established by mandeville et al 2002 for h species in glass were used to calculate water concentrations in the melt inclusions melt inclusions in the mt erebus anorthoclase have water concentrations ranging from 0 12 to 0 39 wt with an overall error of approximately 15 the ratio of water in anorthoclase crystals to water in the melt from which the crystals formed based on this study and at these low melt water concentrations is approximately 1 10 however water concentration varies significantly from one melt inclusion to another possibly suggesting initial melt water heterogeneity maps of water concentration show that variations in water concentration within melt inclusions are associated with fractures that cut the melt inclusions and in some cases do not extend out into surrounding crystals or into crystal inclusions thin approx 50 micro m thick zones of elevated water concentrations on the boundaries of the crystals in contact with melt inclusions suggest that water has diffused into the crystals from the melt inclusions less

excess 40ar transport scale and mechanism in high pressure phengites a case study from an eclogitized metabasite of the dora maira nappe western alps application of the bulk separate furnace heating laser step heating and in situ laser agemapping 40ar 39ar techniques reveals that high pressure phengites from an alpine eclogite of the dora maira basement nappe western alps were pervasively contaminated with excess 40ar to yield ages 130 ma spot fusion dating of individual grains with the 40ar 39ar laserprobe reveals concentric radial patterns with core ages as high as 320 ma showing that this excess component was trapped at an early stage and subsequently remobilized by volume diffusion during a late greenschist thermal pulse the single grains and population from this hand sample retain major differences in apparent ages indicating that the extent of the excess 40ar contamination varies from grain to grain attempt to model these differences in terms of grain size dependent fractional loss falls short and demonstrates that strong cm scale argon isotopic gradients locally prevailed during syn kinematic high pressure metamorphism on petrostructural grounds a model of internal isotopic buffering is outlined whereby the excess 40ar is argued to have been internally derived from within the eclogite protolith itself low intergranular ar diffusion rates due to reduced water activity buffered below unity by the phengite assemblage resulted in the local segregation and partitioning of the excess 40ar along grain boundaries during ongoing ductile deformation supporting evidence for this model comes from the recent literature on fluid and stable isotope behaviour in alpine eclogites and very high pressure metasediments which shows that volatile recycling during high pressure metamorphism may occur on a very limited scale

continuous measurements of sif 4 and so 2 by thermal emission spectroscopy insight from a 6 month survey at the popocatepetl volcano abstract the processes linked with the emplacement and growth destruction of a lava dome are of prime importance to understand the stability of such extrusions and assess the associated risks for local populations during the last couple of decades ground and space based spectroscopic techniques have been developed to monitor such processes from a safe distance such approaches significantly improved our knowledge about the relationship between the chemical composition of the volcanic gas plumes and both the deep and shallow volcanic processes leading to the different types of explosive activity the potential of the ground based thermal emission fourier transform infrared spectroscopy ftir remained under exploited due to the difficulty to properly handle the radiative transfer phenomena despite the drawbacks in the complex analytical requirements this method enables to continuously monitor day and night with a high temporal resolution 1 meas 3 min relevant gas species such as so 2 and sif 4 in the volcanic plumes previous studies have related the temporal variations of the sif 4 so 2 ratio in volcanic plumes to the onset of vulcanian explosions this study reports a 6 month so 2 sif 4 and sif 4 so 2 time series from january to june 2015 of the popocatepetl s gas plume obtained from ftir thermal emission spectroscopic measurements the infrared spectra were analyzed using the sfit4 radiative transfer and inverse model which we have adapted for this application we obtained highly variable sif 4 so 2 ratios with a mean value of 3 6 10 4 with the highest values around 3 10 3 measured during the final phase of a lava dome growth february march 2015 the rapid sif 4 so 2 variations were more carefully explored and compared for the first time with the seismic activity a remarkable coincidence between sharp sif 4 so 2 rises and the seismic events are evidenced here

mafic magma recharge supplies high co2 and so2 gas fluxes from popocatepetl volcano mexico since late 1994 open vent eruptive activity and degassing at popocatepetl volcano mexico have released large masses of co2 and so2 tephra and lava produced by these eruptions show evidence for mixing of mafic and silicic magmas shortly before eruption we present the first measurements of dissolved co2 in the mafic magma end member based on analyses of olivine hosted melt inclusions that were trapped at pressures as high as 400 mpa 15 km depth beneath the volcano we combine our data with thermodynamic models to show that degassing of mafic magma at 150 350 mpa pressure can explain the co2 so2 mass ratios 1 8 of volcanic gases released from the volcano during 1995 1997 our results demonstrate that mafic magma recharge was responsible for the high measured fluxes of co2 and so2 from 1995 to 1997 the total so2 emission of 9 mt during this period requires intrusion and degassing of a minimum of 0 8 km3 of mafic magma only 0 3 of this new mafic magma has been erupted in the form of mixed hybrid lava and tephra our results suggest that the ongoing eruption of popocatepetl is essentially an intrusive event more generally we suggest that intrusion and deep degassing may explain the high gas fluxes at some other open vent volcanoes rather than convection of magma in the uppermost parts of subvolcanic conduits

mammoth bones embedded in a late pleistocene lahar from popocatepetl volcano near tocuila central mexico the accidental discovery in july 1996 of the tocuila mammoth site in the eastern valley of mexico was followed by intensive scientific excavation which yielded remains of at least seven individuals of mammuthus columbi in an area measuring only 28 m 2 the high density of mostly disarticulated mammoth bones identified 3 m below the surface in a massive 130 cm thick lahar deposit of sandy ash and rounded pumice fragments is unusual and suggests a high energy depositional environment samples of charcoal found within this deposit yielded radiocarbon ages ranging between 10 220 75 and 12 615 95 yr b p the lahar was studied in greater detail in order to establish its provenance determination of grain size distribution and magnetic properties of the deposit as well as petrographical mineralogical and geochemical analyses of pumice clasts all indicate that the lahar was derived from volcanic fallout deposits that originated at popocatepetl volcano located 50 km south southeast of the site popocatepetl underwent a major phreato plinian eruption dated ca 14 000 yr b p at the end of the last major glaciation dispersal of the fallout was mostly toward the northwest and north deposits were found on the slopes of tlaloc mountain 4150 m 20 km southeast of tocuila at the beginning of deglaciation and the onset of more humid conditions 3000 yr later lahars derived from the fallout deposits picked up the bones of already dead animals and then deposited them on the shores of lake texcoco and or simply covered bones without major displacement

isotopic chemical and dissolved gas constraints on spring water from popocatepetl volcano mexico evidence of gas water interaction between magmatic component and shallow fluids abstract geochemical research was carried out on cold and hot springs at popocatepetl popo volcano mexico in 1999 to identify a possible relationship with magmatic activity the chemical and isotopic composition of the fluids is compatible with strong gas water interaction between deep and shallow fluids in fact the isotopic composition of he and dissolved carbon species is consistent with a magmatic origin the presence of a geothermal system having a temperature of 80 100 c was estimated on the basis of liquid geothermometers a large amount of dissolved co 2 in the springs was also detected and associated with high co 2 degassing

re os isotopic evidence for archean lithospheric mantle beneath the kimberley block western australia we report sm nd and the first re os isotopic data as well as platinum group element concentrations for two of the highest grade diamond deposits in the kimberley block of western australia whole rock sm nd isotopic data for the 1200 ma argyle olivine lamproite and an argyle peridotite xenolith yield unradiogenic initial isotopic compositions nd 3 2 to 6 0 and depleted mantle model ages of 1750 to 2000 ma these data indicate that shallow mantle light rare earth element enrichment of the argyle lamproite source probably occurred during the proterozoic hooper orogeny sm nd isotopic data for the 800 ma seppelt kimberlite yield a radiogenic initial isotopic composition nd 1 8 and a t dm model age of 1200 ma isotopic features consistent with worldwide group i kimberlite occurrences re os isotopic data yield unradiogenic initial isotopic compositions for the argyle lamproite and peridotite xenoliths os 2 to 6 and seppelt kimberlite and kimberlitic chromites os 7 to 8 whereas data for a picroilmenite megacryst from the 800 ma maude creek kimberlite yield a radiogenic initial os isotopic composition os 27 our modeling suggests that the os isotopic composition of the argyle lamproite and peridotites may be explained as mixtures of a ca 3000 ma refractory mantle component as represented by the kimberlitic chromites and a ca 1500 ma enriched mantle component as represented by the picroilmenite megacryst the xenoliths and chromites yield an imprecise re os isochron age of 3400 ma giving a strong indication that the kimberley block is underlain by archean continental lithospheric mantle and that this mantle was largely unaffected during early proterozoic orogenesis

mineralogy of the tk1 and tk4 kimberlites in the timmasamudram cluster wajrakarur kimberlite field india implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres abstract a mineralogical study of the hypabyssal facies late cretaceous macrocrystic pulse of tk1 intrusion and the mesoproterozoic aphanitic pulse of tk4 intrusion in the wajrakarur kimberlite field of southern india shows that the rocks contain macrocrysts of forsteritic olivine phenocrysts and microphenocrysts of al na poor diopside and phlogopite set in a groundmass mainly of al na poor diopside and phlogopite other groundmass minerals are spinel perovskite and fluorapatite in tk1 and spinel titanite chlorite calcite and gittinsite in tk4 k richterite and perovskite occur only as inclusions in phlogopite and titanite respectively in tk4 late stage deuteric phases include pyrite and barite in tk1 and strontianite chalcopyrite galena and pentlandite in tk4 diopside microphenocrysts in tk4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth tk1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite whereas tk4 spinels are less evolved with magnesiochromite composition only tk1 phlogopites show a simple compositional trend that is typical of lamproite micas while four distinct growth zones are observed in tk4 phlogopites with the following compositional characteristics zone i high cr 2 o 3 and tio 2 and low bao zone ii low cr 2 o 3 zone iii low tio 2 and high bao zone iv low bao forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for tk1 olivines mineralogically both tk1 and tk4 are classified as diopside phlogopite lamproites rather than archetypal kimberlites the two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions with elevated content of fe 3 in phlogopite spinel and perovskite tk1 appears to have crystallised in a relatively high oxygen fugacity environment multiple growth generations of phlogopite spinel and fluorapatite in tk4 indicate a complex evolutionary history of the magma close spatial and temporal associations of mesoproterozoic kimberlites and lamproites in southern india can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting

thermal maturity evaluation of dispersed organic matter inclusions from kimberlite pipes lac de gras northwest territories canada abstract dispersed organic matter dom inclusions have been recovered from crater diatreme and diatreme xenoliths within hypabyssal facies of diamondiferous kimberlite pipes in the lac de gras region of northwest territories canada incident white and fluorescent light microscopy has been used to study vitrinite and liptinite dom xenoliths in the pipes percent reflectance in oil ro of wood derived vitrinite visible light region fluorescence properties of sporinite cutinite and resinite and changes in maceral morphology have been used to evaluate thermal alteration within the kimberlite pipes temperature estimates for different thermal zones in the kimberlite pipes have been inferred by comparing vitrinite reflectance with data from rapid pyrolysis experiments conducted on low rank vitrinites crater facies dom consists of very low reflecting 20 to 200 c to a maximum of 650 c the presence of petroleum derived cokes are consistent with estimates of 400 450 c for samples recovered close to and within hypabyssal dykes and macrocrystic breccia and massive hypabyssal facies below this zone tuffisitic kimberlites are marked by a reduction in vitrinite reflectance 0 5 to 1 8 ro and a lower inferred alteration temperature estimated at 200 to 450 c anomalous populations of very low reflecting partially devolatilized vitrinite 0 50 to 0 84 ro in this zone may have suppressed reflectance possibly a consequence of liquefaction like conditions and impregnation by oily bitumens produced during pyrolysis of associated liptinite macerals

degassing of halogens from basaltic volcanism insights from volcanic gas observations abstract the currently available data set of s cl f abundances in volcanic gas plumes and high temperature fumarolic gas samples from basaltic volcanism is reviewed here in the attempt to derive constraints on the modes of halogen degassing from mafic silicate melts apart from large volcano to volcano variations reflecting remarkable differences in volatile abundances in the source magmas each of the explored volcanoes displays large changes of so2 hcl and so2 hf ratios with the style of volcanic activity with hcl hf staying fairly constant halogen abundances are low and so2 hcl and so2 hf are high when fresh volatile rich magmas sustain degassing as during explosive eruptions at the onset of eruptive cycles or shortly before paroxysmal events low so2 hcl and so2 hf ratios are instead characteristic of late stages of volcanic degassing typically being observed in the concluding stages of basaltic eruptions or during periods of reduced magma supply at persistently degassing volcanoes these observations are taken as evidence of halogens being less keen to enter the gas phase relative to s during degassing of basaltic magmas and quantitatively interpreted in light of a rayleigh type open system degassing model the model though simple quantitatively reproduces the range of volcanic gas compositions observed at basaltic volcanoes worldwide and allows prediction of vapour melt partitioning contrasts of factors 9 and 36 for the volatile couples s cl and s f respectively these predictions require validation from appropriately designed experiments of halogen partitioning between magmatic vapours and silicate melts over a range of p t x conditions

gas composition of popocatepetl volcano between 2007 and 2008 ftir spectroscopic measurements of an explosive event and during quiescent degassing abstract on december 1 2007 the solar absorption infrared spectra of the popocatepetl volcanic plume was recorded during an eruptive event and complementarily on november 17 2008 the passive quiescent degassing was measured from the same site a portable ftir spectrometer with a scanning mirror for fast tracking of the sun provided the flexibility quality and simplicity needed for field deployment slant columns of the gases so 2 hcl hf and sif 4 were retrieved and strong differences could be observed when comparing gas ratios in both time periods during the explosive eruption the so 2 hcl ratio was three times greater and the hf hcl ratio was slightly smaller than during passive degassing while the ratios among so 2 hcl hf and sif 4 describe the chemical composition of the volcanic gas mixture the sif 4 hf ratio provides information about the equilibrium temperatures of the stored gases which in this study were calculated at 150 and 185 c for the explosive and quiescent degassing episodes respectively we conclude that cooling of lava domes in the crater precedes vulcanian explosions as suggested by schaaf et al 2005 based on so 2 flux grutter et al 2008 and measurements and data from the november 2008 event the average fluxes for hcl hf sif 4 and f through quiescent degassing are estimated to be 204 22 7 9 8 and 31 7 tons day respectively these values are similar to those reported by love et al 1998 more than 10 yrs ago

geochemical surveillance of magmatic volatiles at popocatepetl volcano mexico surveillance of popocatepetl volcanic plume geochemistry and so 2 flux began in early 1994 after fumarolic and seismic activity increased significantly during 1993 volatile traps placed around the summit were collected at near monthly intervals until the volcano erupted on december 21 1994 additional trap samples were obtained in early 1996 before the volcano erupted again emplacing a small dacite dome in the summit crater abundances of volatile constituents ppm day of cl s total f co 2 hg and as varied but most constituents were relatively high in early and late 1994 however ratios of these constituents to cl were highest in mid 1994 34 s s total in trap solutions ranged from 1 5 to 6 4 lowest values generally occurred during late 1994 13 c co 2 of trap solutions were greatly contaminated with atmospheric co 2 and affected by absorption kinetics when trap data are combined with so 2 flux measurements made through november 1996 popocatepetl released about 3 9 mt so 2 16 mt co 2 0 75 mt hcl 0 075 mt hf 260 t as 2 6 t hg and roughly 200 mt h 2 o near vent gas concentrations in the volcanic plume measured by correlation spectrometer cospec and fourier transform infrared ftir commonly exceed human recommended exposure limits and may constitute a potential health hazard volatile geochemistry combined with petrologic observations and melt inclusion studies show that mafic magma injection into a preexisting silicic chamber has accompanied renewed volcanism at popocatepetl minor assimilation of cretaceous wall rocks probably occurred in mid 1994

k ar age of the east peripheral kimberlite at de beers mine kimberley r s a summary the kimberlite pipe at de beers mine kimberley is a complex multiple structure three concordant argon 40 argon 39 age spectra have been obtained from samples from the 720 m level in the east peripheral kimberlite each spectrum is dominated by a major plateau feature between 84 and 89 ma and none shows significant evidence of either excess argon or argon loss discrepancy the available evidence suggests that the k ar age of normal magmatic emplacement cooling of the east peripheral kimberlite at de beers mine was close to 86 2 ma

viscosity of high k basalt from the 5th april 2003 stromboli paroxysmal explosion abstract the 5th april 2003 paroxysmal event was the strongest explosion that has occurred at stromboli in the last 50 years this event lasted only few minutes and was characterised by two violent explosions followed by gas and pyroclast emission in order to constrain models of the dynamics of the paroxystic event the viscosity of anhydrous and hydrous stromboli high potassium hk basaltic melts have been measured viscosity has been investigated in the low viscosity range with the falling sphere method at superliquidus temperatures 1423 to 1673 k and 0 5 gpa and in the high viscosity range with micropenetration near the glass transition temperature 723 to 1035 k at atmospheric pressure falling sphere experiments were performed in a piston cylinder apparatus with melts whose water content varies from nominally anhydrous 0 02 wt h 2 o to 4 16 wt h 2 o the combination of high and low viscosity data permits a general description of the viscosity as a function of temperature and water contentusing a modified tamman vogel fulcher equation using these new viscosity data an estimation of the flow regime and magma velocity is performed our data suggest that the ascent of magma from the 7 8 km deep reservoir to a shallower reservoir located at about 3 km of depth may occur within minutes moreover we infer a turbulent flow regime finally our estimates of the ascent velocity agree qualitatively with results from petrological studies e g bertagnini a metrich n landi p rosi m 2003 stromboli volcano aeolian archipelago italy an open window on the deep feeding system of a steady state basaltic volcano journal of geophysical research 108 2336 2350 which indicate a turbulent flow regime and rapid ascent velocities such to inhibit volatile loss induced crystallization we conclude that hazard evaluation at stromboli island should incorporate the likelihood of very rapid ascent of less evolved melts from depth

volcanic plume monitoring at mount etna by diffusive passive sampling 1 this paper reports the use of diffusive tubes in determining hf hcl and so2 in the volcanic plume of mount etna in an attempt to highlight the potential of this method in studying volcanoes in a first application a network of 18 diffusive tubes was installed on etna s flanks aimed at evaluating the atmospheric dispersion of the volcanic plume on a local scale results showed a monotonic decrease in volatile air concentrations with distance from the craters hf from 0 15 to 0 003 mol m 3 hcl from 2 to 0 01 mol m 3 and so2 from 11 to 0 04 mol m 3 revealing the prevalently volcanic contribution matching of so2 hcl and hcl hf volatile ratios with contemporaneous measurements at the summit craters validated the use of diffusive tubes in tracing the chemical features of a volcanic plume from remote locations a first tentative assessment of dry deposition rates of volcanogenic acidic gases was also made yielding 2 5 74 t d 1 so2 0 6 17 t d 1 hcl and 0 02 0 6 t d 1 hf and revealing the potential environmental impact of gas emissions in a second experiment carried out during the recent october 2002 to february 2003 eruption of etna diffusive tubes provided a continuous record of the chemical composition of the eruptive plume from a safe distance of 1 km from the vents thus considerably decreasing the risks involved in sampling this highlighted a clear time decrease in so2 concentrations and so2 hcl ratios which was interpreted as due to progressive exhaustion of volatile degassing and eruption energy

amphiboles in the igneous environment the time is ripe for a fresh inventory of occurrences of amphibole group minerals in igneous rocks here i build on the available resources for example on the review of wones and gilbert 1982 in volume 9b of the rimg series they entitled their chapter amphiboles in the igneous environment i adopt the same title but intend to make the scope of my review somewhat broader by including non igneous rocks formed in the igneous environments much has been written about occurrences of amphibole group minerals over the last quarter of a century much of it ably summarized by deer et al 1997 and it is quite impossible to do more here than to summarize representative findings concerning the textural development and broad compositional features of minerals of the amphibole group that are important in igneous contexts amphibole group minerals are widespread in igneous rocks produced in zones undergoing extension as well as in rocks associated with subduction systems each setting may be associated with specific late stage metasomatic phenomena in which amphibole group minerals play a key role metasomatic overprints involving an amphibole also are widespread in the mantle and act as an essential step in the fertilization of sterile mantle if it is to produce alkali basaltic magmas by partial melting finally selected findings are summarized here on amphibole group minerals in igneous environments in other parts of the solar system amphibole group minerals have generally been underutilized in petrological studies reasons are not hard to find the full characterization of an amphibole presents serious challenges so much so that most investigators have been constrained to examine only those major elements that can be assessed in routine electron microprobe analyses as hawthorne and oberti 2006 pointed out in their essay on the future of schemes of classification it has become abundantly clear that progress is within

volcanic emissions from popocatepetl volcano mexico quantified using moderate resolution imaging spectroradiometer modis infrared data a case study of the december 2000 january 2001 emissions abstract during december 2000 and january 2001 an increase in activity at popocatepetl volcano mexico was observed in both ground based correlation spectrometer cospec data and in imagery from various satellite sensors including the moderate resolution imaging spectroradiometer modis total ozone mapping spectrometer toms advanced very high resolution radiometer avhrr and geostationary satellite 8 goes 8 fine ash abundances detected by modis ranged between 6000 and 255 000 metric tons and fine ash abundances detected by avhrr measured at different times ranged between 4000 and 76 000 metric tons the difference in ranges of ash mass detected by these two sensors depends largely on the difference in data acquisition time between the two sensors in detecting popocatepetl s ash clouds however the difference could also be partly attributed to differences in spatial resolution and band sensitivity which are believed to be significantly more favorable for modis mean effective radii for the two sensors images were typically within 10 of each other values ranged from 5 to 8 m and were strongly a function of residence time two types of infrared retrieval were used for the detection and quantification of so2 masses one based on the 7 3 m so2 absorption feature and the other on the 8 6 m absorption feature so2 values were attainable using the 8 6 m retrieval for most images but were problematic using the 7 3 m retrieval only one so2 cloud was successfully measured by the 7 3 m retrieval january 23rd 2001 04 50 utc this cloud was at an altitude of approximately 12 km the highest cloud in the suite of images analyzed and yielded an so2 mass of 16 500 metric tons this suggests that elevated heights above 10 km are required to negate the effects of atmospheric water vapor upon the 7 3 m retrieval at tropical latitudes so2 clouds for which the 8 6 m retrieval was successful but 7 3 m was not were at heights between 6 and 10 km comparison of so2 retrievals obtained from modis images directly to cospec measurements was achieved by taking cross sections of the plume in the modis so2 maps wind data at the appropriate altitude can then be used to calculate fluxes comparable to those measured by cospec in units of tons day 1 the fluxes calculated from the plume transects fell within the range of fluxes measured by the cospec at 5 32 kt day 1 and suggest more emissions in mid to late december and lower emission rates throughout january the modis data also complement a ground based study on magnetic anomalies in which it was observed that more magma was extruded in the january 23 2001 eruption than in the eruptions in december of 2000 ash quantification from modis imagery suggests that the majority of fine ash was erupted in january of 2001