interaction of magmatic fluids and silicate melt residues with saline groundwater in the footwall of the sudbury igneous complex ontario canada new evidence from bulk rock geochemistry fluid inclusions and stable isotopes abstract along the northern margin of the 1 85 ga sudbury igneous complex sic canada a volumetrically minor rock type known as the footwall granophyre fwgp preserves evidence of the interaction of magmatic fluid and groundwater the fwgp comprises veins dikes and irregular bodies of a quartz alkali feldspar plagioclase intergrowth that are most abundant near footwall style cu ni platinum group element mineralization textures and cross cutting relations show that the emplacement of the fwgp created favourable sites for the later deposition of sulfides geochemical and physical evidence show that the fwgp did not form by in situ partial melting of the archean country rocks in the footwall beneath the sic it represents a mobilized injected silicate residue from either the contact between partially melted country rocks and the sic or from the crystallizing sic itself its bulk composition can be modeled as the product of fractional crystallization of a liquid with an initial composition equivalent to granophyric matrix trapped liquid in the lowermost units of the sic norite and sublayer primary fluid saline h 2 o poor and melt silicate h 2 o rich inclusions hosted in quartz from the fwgp have bulk and trace element compositions consistent with those hosted in quartz from the granophyric matrix of the lower units of the sic norite sublayer fluid inclusions contain mixtures of a high salinity 44 70 wt nacl equivalent n 39 na fe rich aqueous magmatic fluid and a lower salinity ca and sr rich groundwater the magmatic end member is thought to be an sic derived volatile phase estimates of the mixing proportions show that primary and secondary inclusions in the fwgp contain 60 100 and 30 80 of the magmatic end member by mass respectively fluids responsible for the remobilization of ore metals represent mixtures containing a much higher proportion of the groundwater end member not less than 70 by mass compared to the fluids trapped in the fwgp at considerable distance 400 m from the sic the chlorine isotope composition of biotite in the fwgp is enriched in 37 cl 37 cl 0 98 to 1 61 scapolite from the high temperature veins and the interstices of rock types in the main mass of the sic shows similar enrichment in 37 cl up to 1 34 whereas biotite from the archean country rocks 37 cl 0 88 to 0 53 and associated groundwater are 37 cl depleted the results of this study lead to two important conclusions concerning genetic and exploration models for the footwall ore zones first magmatic end member fluid introduced into the footwall with the melt from which the fwgp crystallized contained very little cu rarely 100 ppm the main ore metal in the footwall ores this result questions hydrothermal models for footwall ore formation that hypothesize that cu and other ore metals were remobilized from sulfide deposits along the sic contact by magmatic hydrothermal fluids and redeposited in the footwall it is more likely that ore metals were only locally remobilized in the footwall ore zones when metal poor hybrid fluids interacted with pre existing sulfide veins of magmatic origin second inclusions containing the hybrid fluid occur in the fwgp rock type throughout the footwall in both mineralized and unmineralized areas therefore although the fwgp preserves stable cl isotope and fluid inclusion evidence that magmatic fluid was introduced into the footwall detection of this magmatic component alone will not serve as a useful exploration method in contrast mapping the distribution and abundance of fwgp may be ore predictive since fwgp emplacement and its higher abundance in mineralized areas appears to have been a structural and textural prerequisite for footwall ore emplacement

chlorine cycling during subduction of altered oceanic crust eclogitic rocks that have experienced devolatilization with little or no interaction with external fluid sources can be viewed as analogues of crustal material which may be transferred back into the mantle during subduction thus they can be used to evaluate the extent of the recycling of volatile elements such as chlorine we report new oxygen isotope ratios of omphacite and fluid inclusion data determined from eclogitic metagabbros of the rocciavre massif italian alps the data are compared with those obtained for the monviso cyclades and the franciscan complex high pressure rocks in all localities relics of early dehydration fluids are preserved as primary fluid inclusions in the cores of omphacite megacrysts rocciavre monviso and franciscan complex or garnet cyclades salinity estimates of the inclusion fluids range from 32 to 45 wt nacl in rocciavre 17 to 21 wt nacl in monviso and are similar to seawater in other areas omphacite and bulk rock 18o values of rocciavre 5 1 6 8 and monviso 3 0 5 3 metagabbros are markedly lower than those of cyclades 6 8 14 3 and the franciscan 6 7 13 1 metabasites the fluid salinity 18o systematics of eclogitic rocks is similar to that documented along a typical section of the altered oceanic crust and unmetamorphosed ophiolites this suggests that high pressure metamorphism and associated processes did not modify significantly the variability in chlorine concentrations and oxygen isotope ratios inherited from a stage of sea floor hydrothermal alteration under low basaltic layer and high temperature gabbroic layer conditions respectively extrapolating the estimated h2o and cl contents of eclogitic rocks to a representative section of the subducted oceanic crust indicates that a minimum of 100 to 200 ppm cl could be recycled into the mantle during subduction this yields a cl h2o ratio of 3 6 to 7 5 10 2 for the subducted oceanic crust which is similar to e morb on the basis of available cl isotopic data we infer that a large proportion 70 of the cl stored in the altered crust should be recycled to the mantle to generate an isotopic composition of the subducted crust equivalent to the source of unaltered mid ocean ridge basalt 37cl 4 7

sedimentological features of sabellaria spinulosa biocontructions abstract sedentary polychaete sabellaria spinulosa leukhart 1849 is a suspension feeder that builds tubes by cementing together terrigenous particles under a set of environmental conditions s spinulosa can form reefs consisting of hundreds or thousands of worm tubes that can vary greatly in thickness size and patchiness the more developed reefs form in areas with a large and continuous supply of sand turbulent water nutrient availability and rocky seafloor recently for the first time in the mediterranean area a large reef of s spinulosa has been discovered along the northern gargano coast at torre mileto adriatic sea southern italy in this paper we will detail the main sedimentological data of this worm reef in order to evaluate the kind of terrigenous particles involved in the worm tube constructions detailed grain size and petrographic analyses were carried out on both reef and soft sediment substrate samples it is demonstrated that s spinulosa selects sands on the basis of their grain size and shape and not their composition it is also shown that some seasonal variations of these parameters are the result of the interplay between reef growth and degradation periods mainly related to physical processes in particular the degradation stages seem to be induced mainly by storm wave action while the reef growth is the result of the complex interaction between ecological and physical processes

criteria for differentiating microbial caddisfly bioherms from those of marine polychaetes in a lacustrine setting paleocene second member funing formation subei basin east china abstract paleogene carbonate successions from lacustrine basins across east china yield microbial bioherms containing abundant agglutinated fossil tubes historically these have been interpreted as the dwellings of polychaetes introduced by marine incursions this is problematic because these tubes are associated with abundant non marine fauna and algae diverse and exceptionally well preserved fossil tubes from carbonate microbial bioherms were studied in outcrops and drill cores of the second member of the paleocene funing formation subei basin east china detailed macro meso and micro structural investigations of these tube dominated bioherms reveal that the putative marine polychaete tubes better fit the morphologies and construction styles of lacustrine caddisfly insecta trichoptera larval cases eliminating the need for a marine influence on this lacustrine setting individual caddisfly cases are commonly 10 25 mm in length and 1 2 5 mm in diameter and form slightly curved tapered tubes or coiled spirals twelve tubular case construction styles were further identified based on caddisfly case wall structures and dominant grain types caddisfly cases are commonly single walled with rarer nested instar cases comprising double or triple walls of different sizes most cases are fully agglutinated with neatly arranged similarly sized and closely connected particles of clastic grains carbonate particles plant fragments and phosphatic fish bones sparsely agglutinated cases are also present but much rarer and conform to the silk larval cases of caddisflies the caddisfly cases appear as gregarious aggregations within carbonate microbial bioherms the microbial caddisfly bioherms in this study are commonly developed on carbonate hardground or mudstone within the wave washed high energy shallow lacustrine littoral zone and can be traced along the western paleolake margin of the jinhu depression of the subei basin for up to 60 km the bioherms are composed of repeated microbial caddisfly couplets made up of randomly arranged and similarly sized caddisfly cases encrusted by domed planar columnar or cauliflower like microbial layers cyclic microbial caddisfly couplets fit well with caddisfly biology but are not known to occur with marine polychaetes this is the first report of microbial caddisfly bioherms in cenozoic strata of china and is the oldest cenozoic record of caddisflies in china

using airborne laser altimetry to estimate sabellaria alveolata polychaeta sabellariidae reefs volume in tidal flat environments abstract this study has exploited aerial photographs and lidar digital elevation model to quantify intertidal complex landforms volume a first volume estimation of the main sabellariid polychaete reef complex of the bay of mont saint michel france is presented the sabellaria alveolata is an engineering species that heavily modifies its environment this gregarious tube building annelid forms dense and solid reefs of bioclastic coarse sand which can reach several km 2 since 1970 a very strong decline of reefs has been observed the authorities have curbed fishing activities without any noticeable changes in reef health status the s alveolata reef volume is estimated to be 132 048 m 3 96 301 m 3 for sainte anne reef and 35 747 m 3 for champeaux reef further lidar data surveys will be needed to be able to understand and quantify the accretion erosion processes in play in the reef dynamic because of the internal variability of topographic complexity of the reef characterized by crevices cracks and holes rather than whole blocks further studies are needed to calculate more accurately the volume of the reef

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

segmentation and configuration of subducted lithosphere in italy an important control on thrust belt and foredeep basin evolution the apennine foredeep basin system located on continental crust consists of four roughly parallel basin segments each containing a flexural outer rise and an inner trough that deepens continuously toward the thrust belt flexural modeling of subsidence data across the basin indicates that this foredeep basin results mainly from deep subsurface loads acting on the subducted slab from within the subduction zone rather than from the topographic load of the apennine mountains the geometry of the four basin segments observed within the apennine foredeep is thus inferred to reflect subduction of segmented lithosphere where each lithospheric segment corresponds to a segment of the foredeep basin beneath the basin and in the foreland the lithosphere is continuous segmentation occurs only at depth beneath the thrust belt this pattern olf segmentation of the subducted lithosphere at depth is reflected in the large scale geometry of the outer part of the apennine thrust belt and appears to control it similarly the pattern of segmentation also appears to control the position of the eastern limit of back arc type extension in western italy these relations strongly suggest a genetic relation between subduction zone processes foredeep basin geometry and thrust belt evolution in which the configuration of the subducted lithosphere largely controls the large scale surface deformation observed in the apennine system

chlorine isotopic compositions of high temperature hydrothermal vent fluids over ridge axes abstract we present chlorine stable isotope compositions of high temperature hydrothermal vent fluids from two mid oceanic ridges the six hydrothermal fluids come from sites along the slow spreading mid atlantic ridge menez gwen at 37 50 n lucky strike at 37 17 n and rainbow at 36 14 n and the ultrafast spreading east pacific rise from three contiguous segments centered respectively at 17 25 s 18 15 s and 18 26 s these samples exhibit a large range in temperature ph chlorinity and mg content reflecting various geological settings and substrata nature basaltic or ultramafic although showing a large range of chlorinity from 251 to 821 mmol kg the fluids display homogeneous chlorine isotope signatures 37 cl smoc 0 03 0 06 indistinguishable from that of seawater this homogeneity contrasts with the large range of 37 cl previously observed in continental or off axis oceanic fluids this study explores possible processes that may change cl concentration during fluid genesis and discusses their theoretical isotopic effects the 37 cl homogeneity implies that at the p t conditions of the ridge axis the process of phase separation at sub or super critical conditions that explains most of chlorinity variations does not significantly fractionate chlorine isotopes this study shows that the physical and chemical processes that likely alter cl concentrations in ridge axis systems i e transport processes mixing or water rock interaction contribute to minimize the range of 37 cl around the seawater 37 cl value

dehydration of subducting serpentinite implications for halogen mobility in subduction zones and the deep halogen cycle we investigated the halogen cl f br and i chemistry of serpentinites that record progressive dehydration during subduction from shallow oceanic environments via increased pressure and temperature conditions to complete breakdown of antigorite the aim is to evaluate the relevance of serpentinites for halogen recycling in subduction zones and for deep mantle recharge of these elements the halogen compositions of the analyzed samples indicate input from seawater and sedimentary sources during initial serpentinization of either subducting lithospheric mantle during slab bending or forearc mantle by uprising slab fluids during the first dehydration stage antigorite brucite olivine h2o fluids with high br cl and i cl ratios are released resulting in residual serpentinites with lower br cl and i cl ratios veins associated with this event and with the final antigorite breakdown antigorite olivine orthopyroxene h2o show higher halogen ratios compared to their adjacent wall rocks and they are similar to those found in arc volcanoes f cl and i cl between ca 0 083 1 5 and ca 0 00038 0 0013 respectively all measured deserpentinization samples show a narrow range in 37cl values between 0 42 and 0 92 overlapping the 37cl values of seafloor serpentinites and confirming that no significant cl isotope fractionation occurs during subduction dehydration of serpentinites our findings document the conservative behavior of halogens during subduction mass balance constraints reveal that serpentinites strongly control the halogen chemistry of deep subduction zone fluids and that descent of rock residues after deserpentinization strongly affects the halogen budget of the mantle

development of a brine dominated hydrothermal system at temperatures of 400 500 c in the upper level plutonic sequence troodos ophiolite cyprus abstract microthermometric analyses of quartz hosted fluid inclusions in fresh and epidotized plagiogranites from the troodos ophiolite cyprus indicate that brine rich fluids 46 56 wt nacl equivalent at temperatures 400 500 c were pervasive throughout many of the plagiogranite bodies high salinity fe bearing inclusions along healed microfractures homogenize by halite dissolution at temperatures of 400 500 c liquid dominated low salinity 2 7 wt nacl secondary fluid inclusions are ubiquitous in all plagiogranite and gabbro samples studied homogenization of the low salinity inclusions occurs at uncorrected temperatures of 200 400 c the quartz hosted high salinity fluids represent either phase separation of hydrothermal seawater or an exsolved magmatic aqueous phase at uncorrected temperatures of 400 500 c migration and segregation of brine and vapor phases into fractures near the margins of the crystallizing plagiogranite bodies resulted in preferential entrapment of the fe rich brines in the deep seated high temperature portions of the hydrothermal system subsequent fracturing of the upper plutonic rocks at temperatures of 200 400 c allowed penetration by seawater which pervasively altered the plagiogranites hydration reactions involving formation of secondary minerals and or mixing with phase separated fluids resulted in fluid salinities two times that of seawater

investigating the effects of micro texture and geo mechanical properties on the abrasiveness of volcanic rocks abstract the abrasiveness of rocks is a fundamental rock property that affects sawing and cutting performance wear of tunnel boring machine tbm heads the cerchar abrasiveness index cai test is a commonly used procedure to define rock abrasivity this paper investigates the relationship between quantitative mineralogical and petrographic data and cai values for some selected volcanic rocks in addition the research examines the relationship between physical e g effective porosity and p wave velocities and mechanical e g uniaxial compressive strength ucs brazilian tensile strength bts young s modulus e properties including brittleness values and cai values quantitative mineralogical and petrographic analyses reveal the variations in micro textural properties as defined by different groundmass phenocryst ratios analyses also suggest that the dimensions of opaque minerals and plagioclase feldspar apparently have individual effects on cai values additionally the combined effects of grain size and primary types of constituent minerals have a significant on cai values additionally results of physical and mechanical tests indicate that as p wave velocities increase cai values increase the increasing values of ucs bts and e cause cai values to increase significantly however only one of three brittleness values was found to have a considerable relationship with cai values this research demonstrates the importance of evaluating the micro textural variations and the combined effects of micro texture physical properties and mechanical properties on the cai values of volcanic rocks

landscape response to tectonic and climatic forcing in the foredeep of the southern apennines italy insights from quaternary stratigraphy quantitative geomorphic analysis and denudation rate proxies we present new data about the morphological and stratigraphic evolution and the rates of fluvial denudation of the tavoliere di puglia plain a low relief landscape representing the northernmost sector of the pliocene pleistocene foredeep of the southern apennines the study area is located between the easternmost part of the southern apennine chain and the gargano promontory and it is characterized by several orders of terraced fluvial deposits disconformably overlying lower pleistocene marine clay and organized in a staircase geometry which recorded the emersion and the long term incision history of this sector since mid pleistocene times we used the spatial and altimetric distribution of several orders of middle to late pleistocene fluvial terraces in order to perform paleotopographic reconstruction and gis aided eroded volumes estimates then we estimated denudation rates on the basis of the terraces chronostratigraphy supported by published osl and aar dating middle to upper pleistocene denudation rates estimated by means of such an approach are slightly lower than 0 1 mm yr 1 in good agreement with short term data from direct and indirect evaluation of suspended sediment yield the analysis of longitudinal river profiles using the stream power erosion model provided additional information on the incision rates of the studied area middle to late quaternary uplift rates about 0 15 mm yr 1 calculated on the basis of the elevation above sea level of marine deposits outcropping in the easternmost sector of the study area are quite similar to the erosion rates average value thus suggesting a steady state fluvial incision the approach adopted in this work has demonstrated that erosion rates traditionally obtained by quantitative geomorphic analysis and ksn estimations can be successfully integrated to quantify rates of tectonic or geomorphological processes of a landscape approaching steady state equilibrium copyright 2014 john wiley sons ltd

the influence of rock strength and abrasive mineral content on the cerchar abrasive index abstract the cerchar abrasive index is based on a simple test and is widely used to assess the abrasiveness of rocks detailed examination of the test has shown that the index is largely influenced by the rock strength and only partially by the rock abrasiveness the standard test was found to be incapable of providing accurate indices for rocks of low relative abrasiveness and a modification to the test is presented to overcome this problem the interpretation of the test results has been extended to enable calculation of the specific wear rate which is a more precise measure of the abrasiveness of materials

changing brine inputs into hydrothermal fluids southern cleft segment juan de fuca ridge author s wheat cg zierenberg ra paduan jb caress dw clague da chadwick ww abstract 2020 the authors in 2016 temperature recorders were recovered temperatures were measured and fluid samples were collected from vent 1 a high temperature 338 c hydrothermal discharge site on the southern cleft segment of the juan de fuca ridge coupled with previous sampling efforts this collection represents a 32 year record of discharge from a single chimney structure the longest record to date remarkably the fluid has remained brine dominated for more than three decades this brine formed during phase separation and segregation prior to initial observations in 1984 although the chloride concentration of the discharging fluid has decreased with time the fluid temperature has remained nearly constant for at least 3 3 years and probably for 15 or even 22 years compositions of the discharging fluids are consistent with inputs from a deep sourced brine which was last equilibrated at g400 c at a depth consistent with the base of the sheeted dikes and the brittle ductile transition this brine mixed diffusion or dispersion with a likely non phase separated hydrothermal fluid prior to discharge a survey of hydrothermal endmember fluids with chlorinities in excess of 700 mmol kg shows with the exception of fe a single trend between major ion concentrations and chlorinity even though data are from a range of crustal compositions spreading rates and water and magma depths calculated deep sourced brines from hydrothermal fluid data are similar to data based on fluid inclusions and estimates of brine assimilation in magmas a better understanding of brines is required given their potential duration of discharge and capacity for mobilizing metals

chlorine stable isotope composition of the oceanic crust implications for earth s distribution of chlorine abstract this first investigation of the cl stable isotope composition of seafloor rocks reveals systematic variations in 37 cl 35 cl of the oceanic crust and its mantle source s relative to seawater chlorine isotopic measurements expressed as 37 cl relative to the seawater 37 cl 35 cl ratio of fresh morb glass hydrothermally produced amphibole containing whole rocks and smectite veins are presented all the samples analyzed are isotopically enriched 0 2 7 5 relative to seawater 0 uptake of cl into amphibole during axial hydrothermal alteration fractionates cl relative to seawater the isotopic compositions of morb glasses are between 0 2 and 7 2 this range appears to be partially due to the assimilation of cl from hydrothermally altered wallrock into morb magmas samples which are unaffected by assimilation have 37 cl between 3 and 7 2 overall the data imply that cl is isotopically fractionated between the surface and mantle reservoirs of earth calculations based on the degree of fractionation suggest that approximately 40 of the cl originally in the degassed mantle now resides on earth s surface

chlorine isotopic composition in seafloor serpentinites and high pressure metaperidotites insights into oceanic serpentinization and subduction processes bulk rock chlorine content and isotopic composition 37 cl were determined in oceanic serpentinites high pressure metaperidotites and metasediments in order to gain constraints on the global chlorine cycle associated with hydrothermal alteration and subduction of oceanic lithosphere the distribution of insoluble chlorine in oceanic serpentinites was also investigated by electron microprobe the hydrothermally altered ultramafic samples were dredged along the south west indian ridge and the mid atlantic ridge the high pressure metamorphic samples were collected in the western alps metaperidotites in the erro tobbio unit and metasediments in the schistes lustres nappe oceanic serpentinites show relatively large variations of bulk rock cl contents and 37 cl values with mean values of 1105 596 ppm and 0 7 0 4 o respectively n 8 1 serpentines formed after olivine meshes show lower cl content than those formed after orthopyroxene bastites in bastites of two different samples cl is positively correlated with al 2 o 3 and negatively correlated with sio 2 these relationships are interpreted as reflecting preferential cl incorporation into the bastite structure distorted by al substituted for si rather than different alteration conditions between olivine and orthopyroxene minerals high pressure metaperidotites display relatively homogeneous cl contents and 37 cl values with mean values of 467 88 ppm and 1 4 0 1 respectively n 7 1 a macroscopic high pressure olivine bearing vein formed from partial devolatilization of serpentinites at 2 5 gpa and 500 600 c shows a cl content and a 37 cl value of 603 ppm and 1 6 o respectively metasediments n 2 show low whole rock cl contents 15 ppm cl that did not allow cl isotope analyses to be obtained the range of negative 37 cl values observed in oceanic serpentinites is likely to result from water rock interaction with fluids that have negative 37 cl values the homogeneity of 37 cl values from the high pressure olivine bearing vein and the metaperidotite samples implies that progressive loss of cl inherited from oceanic alteration throughout subduction did not significantly fractionate cl isotopes chlorine recycled in subduction zones via metaperidotites should thus show a range of 37 cl values similar to the range found in oceanic serpentinized peridotites

chlorine isotope composition of volcanic gases and rocks at mount etna italy and inferences on the local mantle source abstract we present the first chlorine isotope compositional data for gases and lavas from mount etna italy and to our knowledge of active mediterranean volcanism we investigated lavas erupted and gases discharged during 2008 2011 from a high temperature fumarole ht 300 c and plume gases from both north east and central craters most of the samples vary in a narrow range of chlorine isotope composition 37 cl values 0 0 7 with gases partially overlapping with rocks only ht gases sampled in 2009 have been clearly affected by secondary processes 37 cl values 15 9 resulting in partial removal of chlorine and isotopic fractionation producing a 37 cl enrichment in the residual gaseous hcl these secondary processes also affect although to a lesser extent plume gases from north east crater nec although post magmatic processes are able to modify the chlorine isotope composition 37 cl values are not affected by magma degassing for residual fractions 0 3 in the melt or any effect is within our data variability finally 37 cl values and cl k ratios of magmatic chlorine constrain the etnean source to be compatible with depleted mantle dmm contaminated by altered oceanic crust aoc in agreement with indications from more common isotopic tracers of mantle processes

a study of rock abrasivity and tool wear in coal measures rocks this paper examines the relations between cerchar abrasivity index cai and petrographic properties of coal measures rocks in the zonguldak coal basin turkey in this study petrographic properties and abrasivity indices of 29 sedimentary rock samples were determined and the values of cai and petrographic analysis results were compared a good linear relationship between cai and average quartz grain size parameters was found the test results also showed that abrasivity was affected by the mineralogical composition cement type degree of cementation quartz content and average quartz grain size it was found that abrasivity of rock was decreased by the low grade of cementation between abrasive minerals cai values and petrographic properties were used to estimate tool consumption in underground works in the zonguldak coal basin it was observed that when cai values increased tool consumption increased

stable isotopic and trace element evidence for restricted fluid migration in 2 gpa eclogites mineral stable isotopic and trace element studies in 2 gpa banded eclogites of the tauern window eastern alps record mm to cm scale heterogeneities that reflect compositional variations in the accompanying metamorphic fluids a close correlation between dolomite mode and dolomite 18o is consistent with equilibrium partitioning among coexisting minerals and fluids small variations in dolomite 13c values correspond with 18o variations but an overall decrease in dolomite 13c by c 1 o across a 12 cm sample is a relict feature that pre dates eclogite equilibration garnet omphacite and clinozoisite rims show little systematic mineral mineral partitioning behaviour for ti v cr y sr or zr major elements however are well equilibrated among these same minerals despite the apparent lack of mineral mineral trace element equilibration most of the trace elements vary systematically with water activity calculated in each layer trace element behaviour during the eclogite metamorphism thus appears to have been controlled largely by mineral fluid interactions along grain boundaries shallow structural levels in other subduction complexes c 10 45 km typically exhibit fracture controlled permeability and extensive metasomatism but there is no field or geochemical evidence for extensive fluid advection during high pressure metamorphism in the tauern eclogites because most dewatering and devolatilization during tectonic burial occurs prior to eclogite conditions the volumetric fluid rock ratio in eclogites should generally be low low fluid rock ratios coupled with the possible non wetting nature of the fluids permits the production and preservation of fine scale chemical heterogeneities in deeply subducted eclogites and associated fluids however the eventual breakdown at greater depth of volatile bearing dolomite phengite clinozoisite zoisite or amphibole could lead to renewed fracture controlled fluid release from the subducted rocks to regions appropriate for arc magma generation

the systematics of boron isotopes in izu arc front volcanic rocks the process of fluid release from the subducting slab beneath the izu arc volcanic front izu vf was examined by measuring b concentrations and b isotope ratios in the neogene fallout tephra odp site 782a both were measured by secondary ion mass spectrometry in a subset of matrix glasses and glassy plagioclase hosted melt inclusions selected from material previously analyzed for major and trace elements glasses and radiogenic isotopes sr nd pb bulk tephra these tephra glasses have high b abundances 10 60 ppm and heavy 11b values 4 5 to 12 0 extending the previously reported range for izu vf rocks 11b 7 0 to 7 3 the glasses show striking negative correlations of 11b with large ion lithophile element lile nb ratios these correlations cannot be explained by mixing two separate slab fluids originating from the subducting sediment and the subducting basaltic crust respectively model a two alternative models models b and c are proposed model b proposes that the inverse correlations are inherited from altered oceanic crust aoc which shows a systematic decrease of b and lile with increasing depth from basaltic layer 2a to layer 3 paralleled by an increase in 11b from 1 to 10 to 24 in this model the contribution of sedimentary b is insignificant 4 of b in the izu vf rocks model c explains the correlation as a mixture of a low 11b 1 composite slab fluid a mixture of metasediment and metabasalt derived fluids with a metasomatized mantle wedge containing elevated b 1 2 ppm and heavy 11b 14 the mantle wedge was likely metasomatized by 11b rich fluids beneath the outer forearc and subsequently down dragged to arc front depths by the descending slab pb b isotope systematics indicate that at arc front depths 53 of the b in the izu vf is derived from the wedge this implies that the heavy 11b values of izu vf rocks are largely a result of fluid fractionation and do not reflect variations in slab source provenance i e subducting sediment vs basaltic crust since the b content of the peridotite at the outer forearc 7 58 ppm b mean 24 16 ppm is much higher than beneath the arc front 1 2 ppm b the hydrated mantle wedge must have released a b rich fluid on its downward path this wedge flux can explain 1 the across arc decrease in b and 11b e g izu kuriles without requiring a progressive decrease in fluid flux from the subducting slab and 2 the thermal structure of volcanic arcs as reflected in the b and 11b variations of volcanic arc rocks

piggyback tectonics long term growth of kilauea on the south flank of mauna loa abstract compositional and age data from offshore pillow lavas and volcaniclastic sediments along with on land geologic seismic and deformation data provide broad perspectives on the early growth of kilauea volcano and the long term geometric evolution of its rift zones sulfur rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater growth of a large compositionally diverse alkalic edifice the alkalic rocks yield 40ar 39ar ages as old as about 275 ka transitional composition lavas which mark beginning of the shield stage while most or all the edifice remained below sea level probably first erupted after about 150 ka and tholeiitic lavas of present day type are probably younger than 100 ka breccia clasts from papau seamount and along the lower southwest corner of the hilina bench are derived from subaerial mauna loa requiring that mauna loa s flank underlies western parts of kilauea at shallow depth the volume of the kilauea edifice is therefore smaller 10 000 km3 than previous estimates 15 40 000 km3 lava thickness accumulation rates appear to have remained nearly constant during edifice growth as effusion rates increased from 25 106 m3 yr at end of the alkalic stage to the present day tholeiite rate of 100 106 m3 yr seismic and gravity data show that the deep plumbing system for kilauea s magma supply extends nearly vertically through the oceanic crust at least to mantle depths of 30 35 km directly below its present day caldera proximity of kilauea s caldera to the surface boundary with mauna loa and the presence of mauna loa rocks at shallow depth beneath the south flank are difficult to reconcile with a submarine origin for early kilauea alkalic lavas unless geometric relations between the two volcanoes have changed substantially during growth of the kilauea shield seismic and ground deformation data suggest seaward spreading of the entire south flank of hawaii island independently of the boundary between kilauea and mauna loa along a landward dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying oceanic crust current steady state horizontal displacements increase seaward at rates of 1 5 cm yr on the lower flank of mauna loa and reaching 5 8 cm yr at the kilauea coastline infrequent 100 yr large earthquakes generate similar geometries but 102 larger displacements per event present day kilauea is the more dynamic edifice but prior to inception of kilauea and during its early growth mauna loa is inferred to have undergone intense volcano spreading involving the kaoiki honuapo fault system considered a geometric analog of the hilina system on kilauea cumulative deformation of mauna loa s south flank during growth of kilauea since 200 300 ka is estimated to have involved 10 km of seaward spreading displacing the rift zones of k lauea while its deep plumbing system and summit magma reservoir remained nearly fixed in space kilauea s rift zones rather than migrating southward with time solely due to dike emplacement preferentially on the mobile seaward side alternatively are interpreted to have been transported passively southward piggyback style during shield stage growth of kilauea as a blister on the still mobile south flank of mauna loa such an evolution of kilauea accounts for the arcuate geometry of the present day rift zones proximity of the summit magma supply to the exposed flank of mauna loa initial submarine growth of the ancestral edifice and present day location of mauna loa rocks at shallow depth beneath the south flank of kilauea

holocene coastal dune development and environmental changes in apulia southern italy abstract the coastal area of southern apulia is characterised by marine deposits of pleistocene and holocene ages it shows the effects of different phases of coastal morphology evolution during the middle and upper pleistocene a number of marine terraces were shaped in some places they are characterised by thin beach deposits along with a dune belt and relative back dune deposits two important morphogenetic phases occurred during the holocene the former was characterised by deposition of beach deposits placed slightly above present mean sea level and by formation of dune belts which were radiometrically aged about 6000 years bp this event marks the end of the rapid postglacial transgression that occurred during the holocene climatic optimum during the younger phase dated at about 2500 years bp deposition of aeolian sands occurred archaeological and morphological evidences suggest that this phase should be related to a low sea level stand followed by a slow sea level rise up to the present position and by humid temperate climatic conditions the collected data about the holocene dune belts occurring along the apulian coastline suggest that main phases of dune development could be related to the effects of sea level changes climatic conditions and in a subordinate way to human activity

water storage in the mantle the origins of the oceans and earth s volatile atmosphere are major unsolved problems in earth sciences the recent study by finger et al of the crystal chemistry of a water bearing mineral phase cryptically named phase b and grown under conditions equivalent to a depth in the earth of 360 km dramatically demonstrates that several times the earth s visible water budget could be stored in the mantle

chlorine isotope and cl br fractionation in fluids of poas volcano costa rica insight into an active volcanic hydrothermal system abstract halogen rich volcanic fluids issued at the surface carry information on properties and processes operating in shallow hydrothermal systems this paper reports a long term record of cl br concentrations and 37cl signatures of lake water and fumaroles from the active crater of poas volcano costa rica where surface expressions of magmatic hydrothermal activity have shown substantial periodic changes over the last decades both the hyperacid water of its crater lake laguna caliente and subaerial fumaroles show significant temporal variability in cl br concentrations br cl ratios and 37cl reflecting variations in the mode and magnitude of volatile transfer the 37cl signatures of the lake covering the period 1985 2012 show fluctuations between 0 02 0 06 and 1 15 0 09 condensate samples from adjacent fumaroles on the southern shore collected during the interval 2010 2012 with strong changes in gas temperature 107 763 c display a much larger range from 0 43 0 09 to 14 09 0 08 most of the variations in cl isotope br cl and concentration signals can be attributed to interaction between magma derived gas and liquid water in the volcanic hydrothermal system below the crater the 37cl were lowest and closest to magmatic values in 1 fumarolic gas that experienced little or no interaction with subsurface water and followed a relatively dry pathway and 2 water that captured the bulk of magmatic halogen output so that no phase separation could induce fractionation in contrast elevated 37cl can be explained by partial scavenging and fractionation during subsurface gas liquid interaction hence strong cl isotope fractionation leading to very high 37cl in poas fumaroles indicates that they followed a wet pathway highest 37cl values in the lake water were found mostly in periods when it received a significant input from subaqueous fumaroles or when high temperatures and low ph caused hcl evaporation it is concluded that combined monitoring of 37cl and br cl in laguna caliente and adjacent fumaroles provides valuable information on activity in the subsurface hydrothermal system with significant relevance for volcanic surveillance of poas

growth history of kilauea inferred from volatile concentrations in submarine collected basalts abstract major element and volatile h2o co2 s compositions of glasses from the submarine flanks of kilauea volcano record its growth from pre shield into tholeiite shield stage pillow lavas of mildly alkalic basalt at 2600 1900 mbsl on the upper slope of the south flank are an intermediate link between deeper alkalic volcaniclastics and the modern tholeiite shield lava clast glasses from the west flank of papau seamount are subaerial mauna loa like tholeiite and mark the contact between the two volcanoes h2o and co2 in sandstone and breccia glasses from the hilina bench and in alkalic to tholeiitic pillow glasses above and to the east were measured by ftir volatile saturation pressures equal sampling depths 10 mpa 1000 m water for south flank and puna ridge pillow lavas suggesting recovery near eruption depths and or vapor re equilibration during down slope flow south flank glasses are divisible into low pressure co2 0 5 wt s 1000 1700 ppm and high pressure groups co2 40 ppm s 1000 ppm corresponding to eruption sea level at moderate water depths 300 1000 m or shallower but in disequilibrium and in deep water 1000 m saturation pressures range widely in early alkalic to strongly alkalic breccia clast and sandstone glasses establishing that early k lauea s vents spanned much of mauna loa s submarine flank with some vents exceeding sea level later south flank alkalic pillow lavas expose a sizeable submarine edifice that grew concurrent with nearby subaerial alkalic eruptions the onset of the tholeiitic shield stage is marked by extension of eruptions eastward and into deeper water to 5500 m during growth of the puna ridge subaerial and shallow water eruptions from earliest kilauea show that it is underlain shallowly by mauna loa implying that mauna loa is larger and kilauea smaller than previously recognized

halogens in volcanic systems the transport degassing and atmospheric release of halogens from active volcanism on earth have been the focus of increasing interest over the last few decades and have recently been the subject of the 1st workshop on halogens in volcanic systems and their environmental impacts that was held in december of 2007 at yosemite lodge in yosemite national park california as an introduction to this chemical geology special issue collecting contributions from many of the participants at the workshop we review here recent advances in this field including experimental and theoretical investigations of halogen behaviour in volcanic and related magmatic systems we discuss previous research on several aspects of halogen geochemistry including halogen abundances in the mantle and magmas on earth the effects of halogens on phase equilibria and melt viscosities their partitioning between melt and fluid phase s upon decompression cooling and crystallisation of magmas in the earth s crust and their final atmospheric release as volcanic gases the role of halogens in the genesis of hydrothermal systems and in the transport of ore forming metals is also reviewed and we discuss our current understanding of atmospheric processing of volcanic halogens in both the troposphere and stratosphere and their consequent impacts in spite of these recent advancements our current understanding of halogen geochemistry at active volcanoes is still far too fragmentary and the key questions that require answers from future research are summarised in our conclusions

u series isotope data on lau basin glasses the role of subduction related fluids during melt generation in back arc basins new thermal ionization mass spectrometry u series disequilibrium data are presented for 24 basaltic to dacitic glasses from active spreading centres in the back arc lau basin sw pacific together with additional inductively coupled plasma mass spectrometry trace element analyses and sr nd pb isotope data valu fa ridge samples adjacent to the arc front have high u th and 230th 238u 1 implying a recent 350 ka addition of a u rich slab derived fluid the valu fa data can be combined with existing 230th 238u data for the central tonga arc to infer a fluid addition event at 50 ka the similar sources and time scales for fluid transfer beneath the valu fa ridge and beneath the arc itself suggest that the valu fa ridge is propagating into the arc front region central lau basin samples further behind the arc have lower u th and 230th 238u 1 similar to typical mid ocean ridge basalts morb within the central lau basin a water rich subduction component is seen only in samples closest to the arc and this fluid does not have the high u th composition of the fluid at valu fa melt generation in the central lau basin appears to be dominated by normal ridge type processes but the relatively low 230th 238u for these shallow ridges compared with global morb could be a consequence of increased melt productivity as a result of the elevated water contents the transition from 238u to 230th excesses within the back arc basin is not a smooth function of decreasing addition of a u rich fluid moving away from the arc front but also reflects the complex dynamics between two major mantle domains within the mantle wedge pacific beneath valu fa ridge indian beneath the central lau basin

a temperate reef builder an evaluation of the growth morphology and composition of sabellaria alveolata l colonies on carbonate platforms in south wales sabellaria alveolata linne polychaeta sabellariidae is a sedentary polychaete that builds wave resistant reefs from sand sized particles reefs are formed in areas with a large continuous supply of sand sized sediment and turbulent water such as the bristol channel uk although several studies have documented the extent growth form and geological importance of sabellariidae their bioconstructive role has not been adequately assessed s alveolata occurs rarely in the uk and is classified as a distinct ecological unit by the marine nature conservation review yet it has been little studied thus there is a need for greater understanding of the species role in uk coastal ecology and geomorphology an evaluation of reef development in terms of composition growth and extent of s alveolata constructions on carbonate shore platforms in south wales is presented here results indicate that s alveolata is a fast growing species capable of juvenile settlement tube formation and growth of 2 5 5 0 cm in as little as two months after installation of exposure blocks of artificial substrata particle size analysis of 24 randomly selected reefs and ten adjacent sand samples shows a significant difference in mean grain size with worms consolidating particles of a coarser size distribution than the mean particle size of surrounding sand preliminary scanning electron microscope observations indicate preferential use of flat platy and elongate particles in the worm tubes this research forms part of a larger study concerned with quantifying the bioconstructive capability of s alveolata

a preliminary investigation of chlorine xanes in silicate glasses 1 chlorine speciation in silicate melts affects volatile exsolution rheology and thermodynamic properties of the melt but is poorly known x ray absorption near edge structure xanes spectra have been used to investigate cl speciation in 26 silicate glasses and to test the hypothesis that cl in silicate melts is hosted by species that combine cl and network modifying cations such as ca and mg results indicate that cl in cmas cao mgo al2o3 sio2 plus na2o k2o or mno silicate glasses exists as a combination of ca clx and mg clx species or possibly as mixed ca mgy clx species the geometry and stoichiometry of the proposed species is unknown but there are similarities between spectra from ca bearing melts and the spectra of hydrated cacl2 2h2o suggesting that the ca clx species could have a salt like atomic arrangement and ionic bonding further investigations using xanes alternative spectroscopic techniques and forward modeling approaches are required to distinguish between these possibilities

chlorine isotope variations along the central american volcanic front and back arc volcanic outputs ash tephra and lava samples of 23 volcanic centers from the volcanic front secondary front and back arc in central america were analyzed for their 37cl values with the goal of using chlorine isotopes as a tracer of fluids sourced from the subducting cocos slab 37cl values range from 2 6 to 3 0 with systematic variations along the length of the front values from the northernmost guatemala and el salvador and southernmost costa rica ends of the front have mantle like signatures in contrast 37cl values are both positive and negative in the center of the front nicaragua implying a sediment and or serpentinite derived component geophysical observations are consistent with extensive hydration of the cocos plate offshore of nicaragua in support of a serpentinite derived fluid source fluids from dehydrating serpentinites may also incorporate cl from overlying sediments resulting in a multiple source chlorine signature

chlorine isotope variations across the izu bonin mariana arc chlorine isotope ratios were determined for volcanic gas geothermal well ash and lava samples along the izu bonin mariana volcanic front serpentinite clasts and muds from serpentine seamounts conical south chamorro torishima basalts from the guguan cross chain and sediments from ocean drilling program odp sites 800 801 802 and 1149 there is no systematic variation in 37 cl values along the volcanic front in either gas or ash samples in contrast distinct variations occur across the arc implying variations in the fluid source at different depths within the subduction zone serpentinite clasts and serpentine muds from the seamounts tap a source of 30 km depth and have 37 cl values of structurally bound chloride of 0 4 0 4 n 24 identical to most seafloor serpentinites suggesting a serpentinite chrysotile and or lizardite to antigorite transition fluid source tapping deeper levels of the subduction zone 115 130 km depth volcanic gases and ashes have 37 cl values averaging 1 1 1 0 n 29 precisely overlapping the range measured in sediments from odp cores 1 1 0 7 n 11 and limited altered oceanic crust aoc both sediments and aoc are possible cl sources in the volcanic front the guguan cross chain basalts come from the greatest depths and have an average 37 cl value of 0 2 0 2 n 3 suggesting a second serpentine derived source in this case from antigorite breakdown at 200 km depth

the critical point and two phase boundary of seawater 200 500 c abstract the two phase boundary of seawater was determined by isothermal decompression of fully condensed seawater in the range of 200 500 c the pressure at which phase separation occurred for each isotherm was determined by a comparison of the refractive index of fluid removed from the top and bottom of the reaction vessel the critical point was determined to be in the range of 403 406 c 285 302 bar and was located by the inflection in the two phase boundary and by the relative volume of fluid and vapor as a function of temperature the two phase boundary of 3 2 nacl solution was found to coincide exactly with that of seawater over the range tested in the present study the boundary for both is described by a single seventh order polynomial equation the two phase boundary defines the maximum temperature of seawater circulating at depth in the oceanic crust thus the boundary puts a limit of about 390 c for seawater circulating near the seafloor at active ocean ridges 2 5 km water depth and about 465 c at the top of a magma chamber occurring at 2 km below the seafloor

interactions between magma chambers and hydrothermal systems oceanic and ophiolitic constraints a compilation of published exit temperatures and salinities for seafloor hydrothermal fluids along with fluid inclusion data on oceanic and ophiolitic rocks shows that ridge axes hydrothermal systems are generally characterized by maximum temperatures around 300 360 c thus clearly being in the one phase field they overlie a lower system marked by the generation of highly saline brines at high temperatures the brines may have originated either when seawater approached the top of the magma chamber or more probably as exsolution products of the differentiated melts that typify the roof of oceanic magma chambers in ophiolites the brines typically occur within the transition zone between the sheeted dike complex and the plutonic sequence i e on top of magma chambers this transition zone relatively well known from ophiolite studies oman troodos bay of islands josephine is characterized by mutually intrusive relationships between gabbro plagiogranite and dikes and xenoliths of altered diabase within plagiogranite and gabbro in fast to medium spreading ophiolites oman it is the locus of a major downward decrease in the density of hydrothermal veins and alteration the vein system is strongly anisotropic and shows a well marked preferred vertical along strike orientation the underlying cumulates are almost unaltered and exhibit only a diffuse net of amphibole veins while the overlying sheeted dike complex is densely veined and pervasively altered this zone is marked by major gradients in the physical parameters over short distances temperature several degrees celsius per meter pressure several hundred kilopascals transition from brittle to ductile in steady state systems direct interactions between the magma chamber and the hydrothermal system are restricted to this zone characterized by exsolution of magmatic volatiles into the hydrothermal system and the incorporation of hydrothermal fluids into the magma chamber by digestion of altered roof rocks complications to this steady state model resulting from a non steady state magma chamber e g josephine ophiolite are mainly the development of late stage faulting and more pronounced retrogressive alteration

δ37cl systematics of a backarc spreading system the lau basin determinations of 37 cl in glasses and melt inclusions from backarc basin basalts of the lau basin southern pacific ocean constrain the effects of mantle source subduction and shallow assimilation in sections of the lau basin not heavily affected by subduction input central and eastern lau spreading centers cl derived from unfractionated seawater via assimilation in shallow crustal environments is the predominant source of excess cl and moderates 37 cl to near zero values in contrast low cl glasses from the mangatolu triple junction have distinctly negative 37 cl compatible with recent estimates for 37 cl of the depleted mantle source along the valu fa ridge subduction input manifests as 37 cl that is variable but dispersed toward more negative values in both lavas and melt inclusions these values are compatible with a second source of lighter cl within a slab derived flux derived from altered ocean crust sediments and or serpentinized mantle wedge

phase relations and adiabats in boiling seafloor geothermal systems abstract observations of large salinity variations and vent temperatures in the range of 380 400 c suggest that boiling or two phase separation may be occurring in some seafloor geothermal systems consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed system conditions salinity and temperature of boiling vents can be used to estimate the pressure temperature point in the subsurface at which liquid seawater first reached the two phase boundary data are reviewed to construct phase diagrams of coexisting brines and vapors in the two phase region at pressures corresponding to those of the seafloor geothermal systems a method is developed for calculating the enthalpy and entropy of the coexisting mixtures and results are used to construct adiabats from the seafloor to the p t two phase boundary results for seafloor vents discharging at 2300 m below sea level indicate that a 385 c vent is composed of a brine 7 nacl equivalent in equilibrium with a vapor 0 1 nacl brine constitutes 45 by weight of the mixture and the fluid first boiled at approximately 1 km below the seafloor at 415 c 330 bar a 400 c vent is primarily vapor 88 wt 0 044 nacl with a small amount of brine 26 nacl and first boiled at 2 9 km below the seafloor at 500 c 520 bar these results show that adiabatic decompression in the two phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor

chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity the evaluation of the status of shallow magma body i e from the final intrusion stage to quiescence and back to activity one of the key parameters that trigger and sustain volcanic eruptions has been challenging in modern volcanology among volatile tracers chlorine cl uniquely exsolves at shallow depths and is highly hydrophilic consequently cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities however such enrichment could also result from numerous other processes e g water evaporation dissolution of old chloride mineral deposits seawater contamination that are unrelated to magmatic activity here based on stable isotope compositions of chloride and dissolved inorganic carbon as well as previous published 3he 4he data obtained in thermal springs from two recently erupted volcanoes la soufriere in guadeloupe and montagne pelee in martinique in the lesser antilles arc we show that the magmatic cl efficiently trapped in thermal springs displays negative 37cl values 0 65 0 65 consistent with a slab derived origin but distinct from the isotope compositions of chloride in surface reservoirs e g seawater local meteoric waters rivers and cold springs displaying common 37cl values of around 0 using this 37cl difference as an index of magmatic cl we further examined thermal spring samples including a 30 year archive from two thermal springs in guadeloupe covering samples from its last eruption in 1976 1977 to 2008 and an island wide sampling event in martinique in 2008 to trace the evolution of magmatic cl in the volcanic hydrothermal systems over time the results show that magmatic cl can be rapidly flushed out of the hydrothermal systems within 30 to 80 years after the eruption much quicker than other volatile tracers such as co2 and noble gases which can exsolve at greater depths and constantly migrate to the surface because arc volcanoes often have well developed hydrothermal systems where magmatic cl is easily transferred to the surface following its exsolution from shallow magma body we suggest that 37cl has great potential to be a unique proxy to monitor the cessation and revival of infrequent arc volcanoes particularly at centennial time scales

stable cl isotopes in subduction zone pore waters implications for fluid rock reactions and the cycling of chlorine stable cl isotope ratios measured in marine pore waters associated with the barbados and nankai subduction zones extend significantly to 8 the range of 37 cl values reported for natural waters these relatively large negative values together with geologic and chemical evidence from barbados and nankai and recent laboratory data showing that hydrous silicate minerals i e those with structural oh sites are enriched up to 7 5 in 37 cl relative to seawater strongly suggest that the isotopic composition of cl in pore waters from subduction zones reflects diagenetic and metamorphic dehydration and transformation reactions these reactions involve clays and or other hydrous silicate phases at depth in the fluid source regions chlorine therefore cannot be considered geochemically conservative in these systems the uptake of cl by hydrous phases provides a mechanism by which cl can be cycled into the mantle through subduction zones thus stable cl isotopes should help in determining the extent to which cl and companion excess volatiles like h 2 o and co 2 cycle between the crust and mantle

volatiles in glasses from mauna loa volcano hawai i implications for magma degassing and contamination and growth of hawaiian volcanoes glasses from mauna loa pillow basalts recent subaerial vents and inclusions in olivine were analyzed for s cl f and major elements by electron microprobe select submarine glasses were also analyzed for h2o and co2 by infrared spectroscopy the compositional variation of these tholeiitic glasses is dominantly controlled by crystal fractionation and they indicate quenching temperatures of 1 115 1 196 c submarine rift zone glasses have higher volatile abundances except f than nearly all other submarine and subaerial glasses with the maximum concentrations increasing with water depth the overwhelming dominance of degassed glasses on the submarine flanks of mauna loa implies that much of volcano s recent submarine growth involved subaerially erupted lava that reached great water depths up to 3 1 km via lava tubes anomalously high f and cl in some submarine glasses and glass inclusions indicate contamination possibly by fumarolic deposits in ephemeral rift zone magma chambers the relatively high co2 but variable h2o k2o and s k2o in some submarine rift zone glasses indicates pre eruptive mixing between degassed and undegassed magma within mauna loa s rift system volatile compositions for mauna loa magmas are similar to other active hawaiian volcanoes in s and f but are less cl rich than l ihi glasses however cl k2o ratios are similar mauna loa and l ihi magmas have comparable but lower h2o than those from kilauea thus kilauea s source may be more h2o rich the dissimilar volatile distribution in glasses from active hawaiian volcanoes is inconsistent with predictions for a simple concentrically zoned plume model

incorporation of seawater into mid ocean ridge lava flows during emplacement evidence for the interaction between seawater and lava during emplacement on the deep seafloor can be observed in solidified flows at a variety of scales including rapid quenching of their outer crusts and the formation of lava pillars through the body of the flow recently an additional interaction incorporation of heated seawater vapor into the body of a flow has been proposed large voids and vesicles beneath the surface crusts of mid ocean ridge crest lobate and sheet lava flows and lava drips found within those cavities have been cited as evidence for this interaction the voids resulting from this interaction contribute to the high porosity of the shallow ocean crust and play an important role in crustal permeability and hydrothermal circulation at mid ocean ridges and thus it is important to understand their origin we analyze lava samples from the fast spreading east pacific rise and intermediate spreading galapagos spreading center to characterize this process identify the source of the vapor and investigate the implications this would have on submarine lava flow dynamics we find that lava samples that have interacted with a vapor have a zone of increased vesicularity on the underside of the lava crust and a coating of precipitate minerals i e crystal fringe that are distinct in form and composition from those crystallized from the melt we use thermochemical modeling to simulate the reaction between the lava and a vapor and find that only with seawater can we reproduce the phase assemblage we observe within the crystal fringes present in the samples model results suggest that large scale contamination of the lava by mass exchange with the vapor is unlikely but we observe local enrichment of the lava in cl resulting from the incorporation of a brine phase separated from the seawater we suggest that high eruption rates are necessary for seawater incorporation to occur but the mechanism by which seawater enters the flow has yet to be resolved a persistent vapor phase may be important in inhibiting the collapse of lava flow roofs during natural waxing and waning of lava levels during emplacement allowing lava pathways to be maintained during long lived eruptions in addition we illustrate the potential for a persistent vapor layer to increase local flow rates within submarine flows by up to a factor of three thereby influencing how lava is distributed across the ridge crest

geochemistry of lau basin volcanic rocks influence of ridge segmentation and arc proximity side scan sonar imaging of the central lau basin sw pacific has revealed a central lau spreading centre clsc propagating southwards at the expense of an eastern lau spreading centre elsc with a small intermediate lau spreading centre ilsc forming a relay between the two volcanic rocks sampled along these spreading centres and from two adjacent seamounts are glassy to fine grained pillow lavas and sheet flows of basalts ferrobasalts and andesites the evolved rocks are mostly confined to the propagating tip of the clsc and can be explained by a high rate of cooling relative to magma supply as invoked for magma genesis at propagating ridges elsewhere compared with equivalent rocks from the eastern pacific the most evolved members of the clsc suite require similarly high degrees 90 of fractional crystallization from their basaltic parents fractional crystallisation cannot however account for the compositional differences between clsc and elsc lavas whereas the composition of the clsc lavas lies just within the compositional spectrum of typical n morb the elsc lavas are distinctly enriched in alkali and alkaline earth elements reach oxide and apatite saturation at lower fe ti and p concentrations and generally show greater vesicularity despite slightly greater depths of eruption all indicative of a water rich subduction component they also have lower contents of ni sc na and fe and higher contents of si at a given mgo concentration that indicate a more depleted and more hydrous mantle beneath the elsc compared with the clsc these results provide further evidence that beneath the central lau basin the source composition changes progressively from morb type to island arc tholeiite type as the subduction zone is approached both eastwards from the clsc to elsc and southwards along the elsc to the valu fa ridge they also indicate that the composition of the subduction component may vary systematically away from the arc with th lree ba rb and h as h2o all present close to the arc only ba rb and h2o present at intermediate distances and just h2o perceptible at the furthest distances

focused fluid flow during subduction oxygen isotope data from high pressure ophiolites of the western alps abstract during subduction hydrothermally altered oceanic crust undergoes extensive dehydration the water released migrates upwards and may escape along the slab mantle interface or continue rising to hydrate the mantle overlying the subducting slab oxygen isotope ratios from eclogitic ophiolites of the western alps correlate closely with lithology samples with little altered basalt as a protolith have 18 o values of 5 1 6 0 material representing low temperature alteration zone rocks have 18 o values of 5 9 6 6 and rocks orginating in high temperature alteration zones have 18 o values of 4 6 5 3 these isotopic values closely approach those of the ocean crust and unmetamorphosed ophiolites these data suggest that the alpine rocks have not experienced significant fluid flow during metamorphism implying that the escape of fluid from subducted ocean crust is highly focused probably along structurally controlled pathways to the top of the slab the fluid may then continue largely along the slab mantle interface although a portion of it rises further to hydrate the overlying mantle

the source of halogens in geothermal fluids from the taupo volcanic zone north island new zealand abstract forty seven samples of deep geothermal well fluids and hot springs from 14 geothermal sites in the taupo volcanic zone tvz north island new zealand were analyzed for cl br and li concentrations and 37cl 7li 18o and d values the main purpose of this study was to identify the sources of salinity in the tvz fluids and to assess the processes that control stable chlorine isotopic fractionation in the geothermal waters the samples were obtained from deep wells in the mokai ohaaki wairakei rotokawa kawerau ngatamariki and tauhara geothermal fields and from the hot springs at rotorua waiotapu lake taupo waimangu waikite orakei korako and tokaanu two main meteoric recharge areas were identified in the central tvz one located to the ne with 18o and d values of 5 5 and 35 respectively and the other to the sw with a 18o value of 6 7 and d value of 43 water rock interactions in most of the geothermal fluids resulted in a 18o shift to more positive values up to 1 for mokai and over 3 for kawerau the 7li values range from 2 9 to 2 0 and suggest that the deep geothermal fluids have interacted with rocks with low 7li values the highest 7li values 1 4 in the reservoir fluids were found at kawerau where the low quartz content of the greywacke may result in the depletion of 6li the 37cl values of the samples ranged from 1 0 to 0 8 the 37cl values of 0 2 0 1 and 0 0 were measured in samples from orakei korako waiotapu and waimangu respectively and these are interpreted to have been affected by surface evaporation and distillation processes excluding these data most waters with high cl br ratios had positive 37cl values the cl br molar ratios in well samples ranged from 659 to 1664 and the 37cl values from 1 0 to 0 8 the hot springs had cl br molar ratios ranging from 858 to 1611and 37cl values from 0 8 to 0 7 overall the cl br molar ratios of the fluids are comparable with published data on basaltic magmas and these magmas are inferred to be the main source of halogens in the geothermal fluids however the geothermal fluids can be separated into two main groups one associated with rhyolitic magmas characterized by positive 37cl values and high cl br molar ratios and other related to andesitic magmas with negative 37cl values and lower cl br molar ratios we suggest therefore that the isotopic fractionation of the stable cl isotopes is related to the difference in water contents of andesitic and rhyolitic magmas and that the fluid phase is enriched in 37cl during magmatic evolution there is no evidence of isotopic fractionation during the transit of the geothermal fluids from the reservoir to the surface but evaporation and distillation processes at the surface can affect the 37cl values

alteration of oceanic crust and geologic cycling of chlorine and water we report new estimates of transport rates for h2o and cl between the mantle and surface reservoirs our estimates take into consideration alteration of oceanic crust especially that of plutonic rocks and possible subduction of sediments the effect of hydrothermal alteration on the cl budget seems to be negligible but the effect on the h2o budget is significant altered oceanic crust excluding sediments contains about 10 times as much h2o as the unaltered crust and its subduction may result in a net transport of h2o to the upper mantle in subduction zones however the rate of expulsion of h2o from the mantle by subduction zone magmatism is comparable to the amount released by ridge magmatism and is only about 10 of the amount subducted therefore about 90 of the subducted h2o must be returned to the mantle or returned to the crust by other processes in addition subduction of oceanic sediments to mantle depths will result in 1 1 a further increase in the return rate of h2o to the mantle reservoir 2 2 possible net transfer of cl to the mantle depending on the rate of pore water expulsion

seismic anisotropy indicates ridge parallel asthenospheric flow beneath the eastern lau spreading center seismic anisotropy beneath the eastern lau spreading center elsc is investigated using both rayleigh waves and shear waves using data from the 2009 2010 elsc ocean bottom seismograph experiment phase velocities of rayleigh waves determined by ambient noise cross correlation are inverted for azimuthally anisotropic phase velocity maps splitting of s waves from five intermediate and deep focus earthquakes was determined by waveform analysis taken together rayleigh wave and s wave data indicate that significant 2 anisotropy extends to at least 300 km depth both data sets indicate a fast direction aligned within a few degrees of the n10 e striking elsc and somewhat oblique to the n25 e strike of the neighboring volcanic arc we therefore describe the fast direction as spreading perpendicular not convergence perpendicular and interpret it as due to ridge parallel flow of the asthenosphere however the region arcward east of the elsc has the stronger anisotropy suggesting that the strongest flow gradients may occur in the region between the spreading center and the arc in contrast to being centered beneath the elsc fluids released from the underlying plate may produce anisotropic hydrous materials but more importantly lower the viscosity thus enhancing along strike flow both could contribute to an along strike fast direction signature seafloor spreading diminishes south of the seismic array ceasing altogether south of latitude 25 s 500 km south of the array center a region dominated by much slower tectonic extension suggesting that asthenosphere is inflowing from the north to accommodate the increase in asthenospheric volume associated with the seafloor spreading

ultra high chlorine in submarine kilauea glasses evidence for direct assimilation of brine by magma basaltic glass grains from the submarine south flank of kilauea hawai i have cl concentrations of 0 01 1 68 wt the latter being the highest cl content yet recorded for a hawaiian glass the high cl glass grains are products of brine assimilation by tholeiite magma the glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of kilauea s submarine midslope bench the clast contains two distinct suites of glass grains abundant degassed tholeiites perhaps derived from subaerial lavas of mauna loa that shattered upon ocean entry and a smaller population of kea type tholeiite n 17 analyzed that erupted subaqueously based on elevated s 780 1050 ppm h2o 0 42 1 27 wt and co2 1000 ppm six 5000 ppm and two grains have 10 000 ppm dissolved cl abundances of h2o na2o k2o and several trace elements increase regularly with cl concentration and we estimate that cl enrichment was due to up to 13 wt addition of a brine consisting of 78 h2o wt 13 cl 4 4 na 2 6 k 2 6 ca 620 ppm ba 360 ppm sr 65 ppm rb and 7 ppm pb the large amounts of brine addition argue against bulk assimilation of low porosity brine bearing rock the brine s composition is appropriate for a seawater derived hydrothermal fluid that reacted with basaltic wall rocks at t 100 c losing mg and s and gaining k ca rb ba sr and pb followed by phase separation near 500 c and 50 mpa 5 km below sea level at hydrostatic pressure brine was assimilated at or near the depth it formed as estimated on petrologic grounds but under lithostatic conditions the highest extents of assimilation either forced volatile saturation of the magma or enriched already coexisting magmatic vapor in h2o possible mechanisms for assimilation are 1 forcible injection of brine into magma during bursting of overpressured pockets heated by new dikes or 2 intrusion of magma into lenses or sills occupied by trapped brine

long term event stratigraphy of the apulia platform margin upper jurassic to eocene gargano southern italy abstract the upper jurassic to eocene apulia platform margin and the eastward transition to the adjacent basinal deposits are well exposed in the gargano promontory southern italy a carbonate block that is part of the slightly deformed foreland of the southern apennine thrust belt the long term stratigraphy of this margin and slope transect is punctuated by five major dynamic phenomena that subdivide the succession into six second order sequences these events include 1 a valanginian drowning unconformity 2 an early aptian albian drowning and demise of the platform 3 late albian cenomanian platform margin failures 4 a santonian campanian retreat of the platform margin and 5 eocene uplift and platform margin collapse the first event is documented worldwide and is probably eustatic in origin the second is concomitant with some oceanic anoxic events oae the last three processes are probably related to foreland reaction to subduction and collision in the dinarides and hellenides thrust belts the ultimate cause of the albian cenomanian failures is more problematic a worldwide eustatic regression is documented at this time but regional geology seems to favor tectonic uplift

coastal lava flows from mauna loa and hualalai volcanoes kona hawaii a major carbonate reef which drowned 13 ka is now submerged 150 m below sea level on the west coast of the island of hawaii a 25 km span of this reef was investigated using the submersiblemakali i the reef occurs on the flanks of two active volcanoes mauna loa and hualalai and the lavas from both volcanoes both underlie and overlie the submerged reef most of the basaltic lava flows that crossed the reef did so when the water was much shallower and when they had to flow a shorter distance from shoreline to reef face lava flows on top of the reef have protected it from erosion and solution and now occur at seaward projecting salients on the reef face these relations suggest that the reef has retreated shoreward as much as 50 m since it formed a 7 km wide shadow zone occurs where no hualalai lava flows cross the reef south of kailua these lava flows were probably diverted around a large summit cone complex a similar shadow zone on the flank of mauna loa volcano in the kealakekua bay region is downslope from the present mauna loa caldera which ponds mauna loa lava and prevents it from reaching the coastline south of the mauna loa shadow zone the 150 m reef has been totally covered and obscured by mauna loa lava the boundary between hualalai and mauna loa lava on land occurs over a 6 km wide zone whereas flows crossing the 150 m reef show a sharper boundary offshore from the north side of the subaerial transition zone this indicates that since the formation of the reef hualalai lava has migrated south mantling mauna loa lava more recently mauna loa lava is again encroaching north on hualalai lava

contamination of basaltic lava by seawater evidence found in a lava pillar from axial seamount juan de fuca ridge a lava pillar formed during the 1998 eruption at axial seamount exhibits compositional and textural evidence for contamination by seawater under magmatic conditions glass immediately adjacent to anastomosing microfractures within 1 cm of the inner pillar wall is oxidized and significantly enriched in na and cl and depleted in fe and k with respect to that in glassy selvages from the unaffected outer pillar wall the affected glass contains up to 1 wt cl and is enriched by 2 wt na2o relative to unaffected glass consistent with a nearly 1 1 molar incorporation of nacl glass bordering the cl enriched glass in the inner pillar wall is depleted in na but enriched in k the presence of tiny 10 m grains of cu fe sulfides and fe sulfides as well as elemental ni ag and au in the na depleted k enriched glass of the inner pillar wall implies significant reduction of this glass presumably by hydrogen generated during seawater contamination and oxidation of lava adjacent to microfractures we interpret the compositional anomalies we see in the glass of the interior pillar wall as caused by rapid incorporation of seawater into the still molten lava during pillar growth probably on the time scale of seconds to minutes only one of seven examined lava pillars shows this effect and we interpret that seawater has to be trapped in contact with molten lava inside the lava pillar in this case to produce the effects we see thus under the right conditions seawater contamination of lavas during submarine eruptions is one means by which the oceanic crust can sequester cl during its global flux cycle however since very few recent lava flows have been examined in similar detail the global significance of this process in effecting earth s cl budget remains uncertain

constraints on cooling and degassing of pumice during plinian volcanic eruptions based on model calculations during explosive volcanic eruptions pumice clasts are transported into the atmosphere and their thermal and degassing histories determine how much volatiles are lost syneruptively this process is studied by combining a steady state eruption column model with a model for the cooling and degassing of pumice in the model we investigate the impact of various parameters e g mass eruption rate biot number eruption temperature and geometry on the cooling and degassing of pumice and find that the biot number and the eruption temperature are the most influential during typical risetimes of pumices inside eruption columns 200 300 s those smaller than 0 5 cm in diameter are found to lose little of their volatiles syneruptively and remain in thermal equilibrium with the plume in the case of larger pumices the ratio of the cooling timescale r p 2 where rp is the pumice radius and is the thermal diffusivity to the degassing timescale w 2 d 0 where w is the vesicle wall thickness and d 0 is the species diffusivity controls degassing if this ratio is larger than 50 degassing of the pumice will be nearly complete with a few percent of the original volatiles left in the outer rind of the pumice for a ratio of less than 0 1 no volatiles escape the pumice typical values for thermal and species diffusivity as well as vesicle wall thickness indicate that in the case of degassing cl and h 2 o the transition from 0 1 to 50 will be in the pumice size range of 1 10 cm here volatile concentration is a strong function of position inside the pumice suggesting that values for volatile contents measured on picked matrix glass from crushed samples may not be the best way to estimate the volatile content of matrix glass a number which is frequently used to estimate the total volatile input of volcanic eruptions this effect is even more pronounced when looking at hydrogen isotopic fractionation with larger pumices tending toward d 80

salinity of oceanic hydrothermal fluids a fluid inclusion study abstract an extensive microthermometric study of quartz epidote plagioclase anhydrite and sphalerite hosted fluid inclusions from ophiolitic semail oman and trinity california ophiolites and oceanic east pacific rise hydrothermal vents gorringe bank odp leg 111 hole 504b crust has been carried out in order to constrain a model accounting for wide salinity variations measured in the oceanic hydrothermal fluids recorded salinities in fluid inclusions vary between 0 3 and 52 wt nacl eq however more than 60 of the mean standard deviation salinities of the samples are within the range 3 2 0 3wt nacl eq microthermometric error and the mean salinity of all fluid inclusions without the brines is 4 0 wt nacl eq with a standard deviation of 1 6 wt nacl eq whereas most samples display slightly higher salinities than seawater several samples exhibit very high salinities more than two times that of seawater these high salinities are restricted to the plagiogranites semail and trinity ophiolites which mark the top of the fossil magma chamber in the transition zone between the plutonic sequence and the sheeted dyke complex the fluid inclusion population studied in the plagiogranites is characterized by the occurrence of four major fluid inclusion families 1 low to medium salinity liquid vapor fluid inclusions which homogenize into the liquid phase 2 low salinity liquid vapor fluid inclusions with pseudocritical homogenization 3 low to medium salinity liquid vapor fluid inclusions which homogenize into the vapor phase and 4 high salinity liquid vapor halite fluid inclusions which homogenize into the liquid phase by halite dissolution and exhibit salinities as high as 52 wt nacl eq these fluid inclusion families are interpreted as resulting from phase separation occurring in hydrothermal or magmatic fluids within the transition zone between the hydrothermal system and the magma chamber at temperatures higher than 500 c very low salinities less than half that of seawater have been found only in one dioritic sample from the gorringe bank mineralogical and petrological data from the semail ophiolite shows the absence of cl rich minerals furthermore hydration of the crust although very important cannot account for the large salinity variations thus the large salinity variations measured are interpreted as resulting from phase separation and generation of brine rich fluids at the top of the magma chamber this phase separation and subsequent phase segregation and brine accumulation may result in a double diffusive convection of the fluids in the hydrothermal system

fluid inclusion and mineral isotopic compositions hco in eclogitic rocks as tracers of local fluid migration during high pressure metamorphism eclogite facies metagabbros from the monviso ophiolitic complex italian western alps provide a unique opportunity to trace fluid migration processes in a portion of the oceanic crust that has undergone subduction at a depth of 40 km we have determined the omphacites 18o and the abundance d and 13c of hydrous and carbonaceous compounds present in whole rocks which are believed to trace the residual phases of what was mobilized in the original rocks during subduction prograde dehydration reactions and eclogitization of hydrothermally altered oceanic metagabbros was accompanied by approximately 90 fluid loss the remaining fluid was trapped as primary water rich fluid inclusions in omphacite megacrysts that developed at the expense of the precursor magmatic pyroxene deformation of the eclogitic rocks resulted in continuous recycling of fluid between mylonites and omphacite veins without further fluid loss from the host ductile shear zone oxygen isotopes of omphacite omp and hydrogen isotopes of water in the fluid inclusions fi analyzed in low strain rocks mylonites and undeformed deformed veins show marked variations 18oomp and dfi values ranging from 3 0 to 5 3 and from 31 to 93 respectively detailed isotopic analysis of several individual vein wallrock pairs show that the scale of isotopic equilibration is of the order of one centimeter therefore the eclogitic minerals and fluids filling the veins are concluded to be locally derived our results argue against recent models which suggest large scale mass flushing of isotopically homogeneous fluids during subduction zone metamorphism on average the h2o contents and dfi value are within the upper mantle range the carbon has been inherited from the metamorphic transformation of the original carbon present in the oceanic crust and has a mean 13c value of 24 2 1 2 two carbonaceous components can be recognized condensed carbon which represents the major carbon species and carbonate daughter crystals present in fluid inclusions 18oomp values are significantly lower than those reported for mantle minerals and are similar to pyroxene and whole rock values from hydrothermally altered oceanic crust it is suggested that the isotopic imprint of the monviso eclogitic minerals and fluids represents the signature of mid ocean ridge hydrothermal alteration and subduction zone eclogitization processes the rocks studied could be the missing link between altered oceanic gabbros and eclogitic xenoliths in addition the range in 18oomp values recorded in the different microstructural domains covers most of the 18o values reported in type a b and c eclogitic xenoliths implying that caution must be exercised when using oxygen isotopes as an indicator of the origin of eclogitic xenoliths

response of two phase fluids to fracture configurations within submarine hydrothermal systems submarine hydrothermal systems at mid ocean ridges evolve within a region of brittle deformation overlying a region of ductile deformation the interplay between brittle and ductile modes of deformation and the geometry of fracture systems within the brittle zone can exert a significant influence on fluid flow especially under conditions leading to aqueous two phase separation within the brittle region fractures vary between large conduits directly open to the seafloor and small veins and microcracks with constricted or indirect connections to the seafloor in the ductile region fluids may be trapped under near lithostatic pressure while fluids within throughgoing veins in the brittle region will experience hydrostatic pressure in a narrow transition zone between these two extremes a steep pore fluid pressure gradient must exist in the brittle region itself fluid pressures will vary between lithostatic and hydrostatic as fluid occupies interstices varying from isolated pores through tortuous microcracks to channels directly connected to the main upflow conduits a hydrostatic gradient modified by the decreased density of hot fluid and the effects of the flow itself should be applicable in major conduits open to the seafloor fluctuating pressure conditions in the transition zone may induce phase changes in a fluid remaining at constant depth as a result of the large volume increase that accompanies two phase separation a two phase fluid must either accelerate upward or exert an increased pressure on its surroundings possibly leading to enhanced fracturing the fracture configuration will also affect the behavior of the mixed fluid after phase separation a two phase fluid experiencing rapid turbulent flow in a large open conduit is more likely to remain a well mixed suspension of vapor and liquid whereas a two phase mixture in a constricted branching series of channels moving more slowly in a laminar flow regime is more likely to undergo physical isolation of the phases leading to venting of a vapor phase and retention of a saline brine phase at depth we propose a possible configuration for the fracture pattern within a submarine hydrothermal system consisting of a feeder zone comprised of anastomozing microcracks and veinlets progressively increasing in diameter and decreasing in abundance feeding into a main upflow stockwork zone in which flow directly to the surface takes place in relatively large unconstricted conduits fluid movement within a feeder zone may be modified by capillary flow tortuous channelways disconnected fractures blocking of cracks by mineral deposition and opening of new fractures

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

variety and origin of magmas on shatsky rise northwest pacific ocean 1 shatsky rise consists of thick 30 km maximum basaltic crust with various geochemical compositions geochemistry data indicate that four magma types exist on the plateau namely normal low ti high nb and u1349 types the normal type is the most abundant in volume and appears on all three large edifices of the plateau tamu ori and shirshov massifs composition of the normal type is similar to normal mid ocean ridge basalt n morb composition but with slight relative enrichment of the more incompatible elements the low ti type is distinguished from the normal type basalt by slightly lower ti content at a given mgo composition of the high nb type is characterized by distinctively high contents of incompatible trace elements u1349 type basalts are composed of more primitive and depleted compositions compared with the others the normal type basalts constitute 94 of the lava units of the oldest tamu massif and non normal types i e the other three types basalts comprise 57 on the younger ori massif implying that geochemical compositions may have become heterogeneous with time petrological examination demonstrates that compositions of the normal low ti and high nb type basalts evolved through fractional crystallization of olivine plagioclase and augite in shallow magma chambers 200 mpa model calculations of immobile trace elements estimate that the normal type basalt can be formed by 15 melting of a depleted mantle source in the presence of residual garnet this degree of melting is similar to n morb but the larger effect of residual garnet during petrogenesis implies that a greater depth of melting

deformation processes in eclogitic rocks evidence for the rheological delamination of the oceanic crust in deeper levels of subduction zones the deformation mechanisms and associated growth processes operating in omphacite during foliation development and veining have been studied in a km scale eclogitic ductile shear zone from the monviso meta ophiolitic complex italian western alps dislocation creep due to multiple slip and or climb is the dominant deformation mechanism whereas 100 and 001 twinning fracturing and intergranular fluid phase diffusional creep are subordinate active slip systems include 110 001 12 110 110 100 001 and 12 010 100 fracturing is interpreted in terms of brittle instabilities arising from strain and pore fluid pressure partitioning between adjacent omphacite domains the transition from plastic to brittle behaviour of rocks is cyclic in nature as the internally generated fluids can be released and trapped repetitively during progressive deformation the significance of the eclogitic shear zone is discussed in terms of a mechanically weak zone that developed during burial or at least prior to the peak of temperature at a minimum depth of 40 km in a subduction zone and which subsequently acted as a zone of detachment during a late stage of the alpine orogeny a rheological model for oceanic crust delamination in deeper levels of subduction zones is presented

widespread assimilation of a seawater derived component at loihi seamount hawaii many tholeiitic and transitional pillow rim and fragmental glasses from loihi seamount hawaii have high cl contents and cl k 2o ratios and ratios of cl to other incompatible components such as p 2o 5 h 2o etc relative to other hawaiian subaerial volcanoes e g mauna loa mauna kea and kilauea we suggest that this results from widespread contamination of loihi magmas by a cl rich seawater derived component assimilation of high cl phases such as saline brine or cl rich minerals halite or iron hydroxychlorides with high cl h 2o ratios can explain the range and magnitude of cl contents in loihi glasses as well as the variations in the ratios of cl to other incompatible elements brines and cl rich minerals are thought to form from seawater within the hydrothermal systems associated with submarine volcanoes and loihi magmas could plausibly have assimilated such materials from the hydrothermal envelope adjacent to the magma chamber our model can also explain semiquantitatively the observed contamination of loihi glasses with atmospheric derived noble gases provided the assimilant has concentrations of ne and ar comparable to or slightly less than seawater this is more likely for brines than for cl rich minerals leading us to favor brines as the major assimilant cl br ratios for a limited number of loihi samples are also seawater like and show no indication of the higher values expected to be associated with the assimilation of cl rich hydrothermal minerals although cl enrichment is a common feature of lavas from loihi submarine glasses from other hawaiian volcanoes show little kilauea or no mauna loa mauna kea evidence of this process suggesting that assimilation of seawater derived components is more likely to occur in the early stages of growth of oceanic volcanoes summit collapse events such as the one observed at loihi in october 1996 provide a ready mechanism for depositing brine bearing rocks from the volcanic edifice into the top of a submarine summit magma chamber

the contributions of biogeomorphology to the emerging field of geobiology biogeomorphology has developed into a well established research field over the past 15 years with studies examining a range of two way interrelations between organisms and geomorphology in a variety of terrestrial and marine environments this paper starts by defining the core biogeomorphological processes bioerosion bioprotection and bioconstruction particular emphasis is placed on the study of bioconstructional forms providing a clear definition examples of bioconstructions and crucially examining important interactions between bioconstruction and bioerosion three key areas where biogeomorphological research can directly contribute to the emerging field of geobiology are identified 1 the use of biogeomorphological approaches combined with palaeoecological investigations and predictive modelling in the growing field of carbon sequestration and climate change mitigation 2 providing geomorphological expertise to support the emerging field of astrobiology and 3 the potential contributions of biogeomorphology to the blossoming field of bio geoengineering some key research directions and challenges for future biogeomorphological research include exploring how biogeomorphological studies can contribute to and benefit from collaborations with other fields of geobiology and assisting in the development of a useful effective interdisciplinary toolbox of methods to improve quantification of geobiological processes importantly suggestions are made for potentially fruitful collaborations with geomicrobiologists geochemists and palaeoecologists

a chlorine isotope study of dsdp odp serpentinized ultramafic rocks insights into the serpentinization process abstract eight dsdp odp cores were analyzed for major ion concentrations and 37cl values of water soluble chloride 37clwsc and structurally bound chloride 37clsbc in serpentinized ultramafic rocks this diverse set of cores spans a wide range in age temperature of serpentinization tectonic setting and geographic location of drilled serpentinized oceanic crust three of the cores were sampled at closely spaced intervals to investigate downhole variation in cl concentration and chlorine isotope composition the average total cl content of all 86 samples is 0 26 0 16 wt 0 19 0 10 wt as water soluble cl xwsc and 0 09 0 09 wt as structurally bound cl xsbc structurally bound cl concentration nearly doubles with depth in all cores there is no consistent trend in water soluble cl content among the cores chlorine isotope fractionation between the structurally bound cl site and the water soluble cl site varies from 1 08 to 1 16 averaging to 0 21 samples with negative fractionations may be related to reequilibration of the water soluble chloride with seawater post serpentinite formation six of the cores have positive bulk 37cl values 0 05 to 0 36 the other two cores 173 1068a leg hole and 84 570 have negative bulk 37cl values 1 26 and 0 54 the cores with negative 37cl values also have variable cl so42 ratios in contrast to all other cores the isotopically positive cores 153 920d and 147 895e show no isotopic variation with depth the isotopically negative core 173 1068a decreases by 1 with depth for both the water soluble and structurally bound cl fractions non zero bulk 37cl values indicate cl in serpentinites was incorporated during original hydration and is not an artifact of seawater infiltration during drilling cores with positive 37cl values are most likely explained by open system fractionation during hydrothermal alteration with preferential incorporation of 37cl from seawater into the serpentinite and loss of residual light cl back to the ocean fluid rock ratios were probably low as evidenced by the presence of water soluble salts the two isotopically negative cores are characterized by a thick overlying sedimentary package that was in place prior to serpentinization we believe the low 37cl values of these cores are a result of hydration of ultramafic rock by infiltrating aqueous pore fluids from the overlying sediments the resulting serpentinites inherit the characteristic negative 37cl values of the pore waters chlorine stable isotopes can be used to identify the source of the serpentinizing fluid and ultimately discern chemical and tectonic processes involved in serpentinization

processes of brine generation and circulation in the oceanic crust fluid inclusion evidence from the troodos ophiolite cyprus detailed temporal thermal and compositional data on aqueous fluid inclusions from a suite of plutonic and diabase samples from the troodos ophiolite cyprus provide the first documentation that generation of high temperature brines may be common at depth in the oceanic crust anastomosing arrays of fluid inclusions in rocks of the upper intrusive sequence record episodic fracturing events the earliest fracturing event at temperatures 450 600 c resulted in entrapment of brine rich aqueous fluids with salinities of 36 61 wt nacl equivalent homogenization of the brine inclusions by haute dissolution the virtual absence of vaporrich fluid inclusions throughout the upper level plutonic sequence and the restriction of brine inclusions to the most evolved plutonic rocks suggests that exsolution of brines off of the late stage gabbro and plagiogranite melts played a significant role in generating the quartz hosted high salinity inclusions cooling of the fluids during pulses of fluid migration associated with episodic fracturing events resulted in entrapment of the brines in the deep seated high temperature portion of the hydrothermal system in localized areas the high temperature brines nacl kcl cacl2 caused extreme alteration of the plagiogranite bodies and in the formation of podiform epidosites arrays of low temperature low salinity fluid inclusions which in some samples crosscut fractures dominated by brine inclusions indicate downward propagation of a cracking front subsequent to collapse of the high temperature magmatic system resulting in penetration of seawaterlike fluids into the plutonic sequence at temperatures 200 400 c hydration reactions under greenschist facies conditions or limited mixing with brine rich fluids may have resulted in salinity variations from 70 below to 200 above seawater concentrations temperatures and compositions of the low salinity inclusions are similar to those found in stockwork systems beneath troodos ore deposits and to those of fluids exiting active submarine hydrothermal vents at mid ocean ridge spreading centers the low temperature fracture networks may represent an extensive deep seated feeder system which coalesced to form zones of concentrated hydrothermal upflow

the sources and evolution of mineralising fluids in iron oxide copper gold systems norrbotten sweden constraints from br cl ratios and stable cl isotopes of fluid inclusion leachates we have analysed the halogen concentrations and chlorine stable isotope composition of fluid inclusion leachates from three spatially associated fe oxide cu au mineralising systems in norrbotten sweden fluid inclusions in late stage veins in fe oxide apatite deposits contain saline brines and have a wide range of br cl molar ratios from 0 2 to 1 1 10 3 and 37cl values from 3 1 to 1 0 leachates from saline fluid inclusions from the greenstone and porphyry hosted cu au prospects have br cl ratios that range from 0 2 to 0 5 10 3 and 37cl values from 5 6 to 1 3 finally the cu au deposits hosted by the nautanen deformation zone ndz have br cl molar ratios from 0 4 to 1 1 10 3 and 37cl values that range from 2 4 to 0 5 although the bulk of the data fall within 0 0 5 the br cl ratios of leachates are consistent with the derivation of salinity from magmatic sources or from the dissolution of halite most of the isotopic data from the fe oxide apatite and greenstone deposits are consistent with a mantle derived source of the chlorine with the exception of the four samples with the most negative values the origin of the low 37cl values in these samples is unknown but we suggest that there may have been some modification of the cl isotope signature due to fractionation between the mineralising fluids and cl rich silicate assemblages found in the alteration haloes around the deposits if such a process has occurred then a modified crustal source of the chlorine for all the samples cannot be ruled out although the amount of fractionation necessary to generate the low 37cl values would be significantly larger the source of cl in the ndz deposits has a crustal signature which suggests the cl in this system may be derived from meta evaporites or from input from crustal melts such as granitic pegmatites of the lina suite