the origin of jadeitite forming subduction zone fluids cl guided sims oxygen isotope and trace element evidence jadeitite a rare high p t rock is associated spatially with blueschist and or eclogite terranes scanning electron microscope sem and cathodoluminescence cl petrography of jadeitite samples from several major occurrences in burma myanmar guatemala japan kazakhstan and the u s a show that grains were deposited from s uids jadeite grain compositions indicate these s uid compositions changed with time cl imagery guided the acquisition of oxygen isotope and trace element analyses with the ion microprobe jadeite grains in each rock grew in cycles that began with red and or blue luminescent and ended with green luminescent zones the cl images were used to order the data into crystallization sequences these data and electron microprobe major element analyses document the association of green cl with increases in ca mg and cr 1 toward grain exteriors 2 in ne grained matrix around porphyroblasts 3 in shear zones that cut grains 4 in former open spaces now lled with jadeite or 5 in veins abundances of many trace elements are greater in green cl jadeitite compared with the red or blue cl zones some of these elements in particular li rb sr ti hf zr y and ree are unlikely to have been derived from serpentinite although crystal chemical effects may explain some of the trace element systematics e g preferential incorporation of ree into ca richer jadeite some kinetic control is suggested by sector zoned rhythmically zoned grains the oxygen isotope data suggest that jadeitite depositing s uids either had multiple sources or evolved in composition along their s ow paths or both

alteration of hyaloclastites in the hsdp 2 phase 1 drill core 1 description and paragenesis this is the publisher s version copyright 2003 by chinese geophysical society all rights reserved

in situ determination of long term basaltic glass dissolution in the unsaturated zone abstract maximum in situ weathering rates of basaltic glass measured at the el malpais national monument in new mexico are on the order of 2 5 10 19 mol cm 2 s rates were calculated from backscattered electron bse imaging of weathered porosity and are equivalent to 1 7 5 of the surface per 1000 years weathering is independent of glass composition but appears to increase with flow elevation at el malpais measured rates represent weathering over 3000 years and are substantially lower than glass dissolution rates measured in the laboratory over much shorter time spans basaltic glass is a close chemical analogue to glass hosts proposed for encapsulation of high level nuclear wastes radionuclide release rates predicted from the basis of in situ field rates are substantially less than those predicted from short term laboratory experiments

zeolite compositions as proxies for eruptive paleoenvironment we report chemical compositions of authigenic alteration minerals in subglacially erupted hyaloclastite breccias from james ross island antarctica which provide a geochemical proxy for paleoenvironment analyses of zeolites phillipsite and chabazite from several lava fed deltas on the island were compared with published compositions of zeolites from known freshwater and marine environments using values of na k ca 3 0 for phillipsites and 1 0 for chabazites the data successfully distinguish between marine and freshwater alteration however our study also suggests that volcanic breccias may not be sealed to fluids even when the pore spaces are completely filled the james ross island data show that at higher elevations in lava fed deltas the zeolites preserve their original freshwater influenced i e glacial compositions whereas at lower elevations na k ca ratios are generally higher and indicate a later marine influence we suggest that water may penetrate several kilometers into the volcanic pile by movement along fractures and or grain boundaries

post eruptive morphological evolution of island volcanoes surtsey as a modern case study abstract surtsey is a small volcanic island in the vestmannaeyjar archipelago off the south coast of iceland the eruption leading to the island s emersion lasted for 3 5 yr 1963 1967 while destructive forces have been active for over 50 yr 1963 present day during which surtsey has suffered rapid subaerial and submarine erosion and undergone major morphological changes surtsey is a well documented modern example of the post eruptive degradational stage of island volcanoes and has provided the unique opportunity to continuously observe and quantify the effects of intense geomorphic processes in this paper we focus on coastal and marine processes re shaping the shoreline and shallow water portions of the surtsey complex since its formation and on the related geomorphological record analogies with the post eruptive morphological evolution of recently active island volcanoes at the emerging stage encompassing different climatic conditions wave regimes and geological contexts are discussed

influence of alteration on the mechanical behaviour and failure mode of andesite implications for shallow seismicity and volcano monitoring volcanoes often host hydrothermal systems that alter the host rock to understand the influence of alteration on mechanical behaviour of edifice forming rock we performed a series of triaxial deformation experiments on variably altered andesite from mt ruapehu new zealand under constant effective pressure under the imposed conditions andesite with intermediate argillic alteration deforms in a brittle manner forming fractures by contrast andesite with advanced argillic alteration deforms in a ductile manner with sample failure driven by distributed cataclastic pore collapse we consider this the result of an increase in porosity and clay content with increasing alteration ancillary experiments highlight that the brittle ductile transition occurs at lower effective pressure i e at shallower depths in andesites with advanced argillic alteration relative to unaltered andesites of comparable porosity we conclude that advanced argillic alteration can create an anomalous shallow ductile zone which has important implications for fluid flow and pre eruptive seismicity

ice volcano interaction of the 1996 gjalp subglacial eruption vatnajokull iceland volcanic eruptions under glaciers can cause dangerous floods and lahars1 2 3 and create hyaloclastite fragmented glassy rock mountains4 5 6 7 8 but processes such as the rate of heat transfer between ice and magma edifice formation and the response of the surrounding glacier are poorly understood because of the lack of data here we present observations from the fissure eruption at vatnajokull ice cap iceland in october 1996 in the 13 days of the eruption 3 km3 of ice were melted and the erupted magma fragmented into glass forming a hyaloclastite ridge 6 7 km long and 200 300 m high under 500 750 m of ice meltwater of temperatures of 15 20 c flowed along a narrow channel at the glacier bed into the grimsvotn subglacial lake for five weeks before draining in a sudden flood or jokulhlaup subsidence and crevassing of the ice cap occurred over the eruptive fissure and the meltwater path whereas elsewhere the glacier surface remained intact suggesting that subglacial eruptions do not trigger widespread basal sliding in warm based glaciers

insights into crustal assimilation by icelandic basalts from boron isotopes in melt inclusions from the 1783 1784 lakagigar eruption abstract the boron isotope system has great potential for tracing alteration and assimilation in basaltic systems due to the very low concentrations of b in mantle derived melts and the strong isotopic contrast between the mantle and surface materials however variability in b concentrations and isotope ratios in basalts can also be interpreted to reflect inputs from enriched regions of the mantle as the extent of mantle heterogeneity with respect to boron remains poorly delineated we have determined boron concentrations and isotope ratios in fresh glassy plagioclase hosted melt inclusions and unaltered scoriaceous matrix glasses from four localities associated with the 1783 1784 lakagigar laki fissure eruption iceland boron concentrations range from 0 59 to 1 25 ppm in the melt inclusions and from 1 25 to 1 65 ppm in the matrix glasses while 11 b nbs 951 ranges from 7 8 to 16 5 in the melt inclusions and 10 5 to 16 9 in the matrix glasses in contrast to previous studies of boron in basaltic melt inclusions from other fissure swarms in iceland gurenko and chaussidon 1997 chem geol 135 21 34 the lakagigar melt inclusions display a significant range of boron concentrations and isotope ratios at constant k 2 o wt which is more consistent with b addition by assimilation of altered basalt than it is with mixing between depleted and enriched mantle sources assimilation of freshwater altered crustal materials at depth may impart a light 11 b signature such as that observed in the lakagigar melt inclusions and tephra host glasses considering boron concentrations and isotope ratios in the lakagigar glasses and previously studied altered icelandic basalts together with volatile equilibration depths of the lakagigar melt inclusions we propose that a mantle derived magmas formed beneath lakagigar assimilated 5 20 altered crust at a depth of 3 4 km or more probably during magma accumulation in sills formed at the boundaries of low density hyaloclastite layers and b the magma subsequently underwent extensive mixing and homogenization prior to eruption quite possibly within the magma chamber beneath the grimsvotn central volcano assimilating an additional 10 of altered crust at that time for a total of up to 30 crustal assimilation we hypothesize that volatiles including h 2 o co 2 s f and cl which were responsible for the majority of the considerable casualties attributed to the lakagigar eruption were added together with isotopically light b by assimilation of hydrothermally altered crustal materials

the geological history of geysir iceland a tephrochronological approach to the dating of sinter the vertical succession through the discharge apron of geysir up to 3 5 m thick is formed of five lithological units a e units a b c and e are formed of siliceous sinters whereas unit d is a brown ash bed tephra grains in units c d and e came from katla hekla and vei ivotn katla tephra in unit d has been largely altered to palagonite integration of tephrochronological ages historical records and geological and geomorphological relationships shows that the geysir succession developed in four main phases during phase i c 10 000 4000 years ago laminated sinters formed from hot spring waters phase ii initiated c 3300 years ago saw the termination of sinter formation and blanketing of the area with tephra from katla and hekla phase iii c 3000 900 years ago represented by the boundary between units d and e was characterized by weathering and little sinter deposition phase iv was initiated with the re birth of geysir 800 900 years ago sinter deposited from the discharged waters has however been largely confined to the southern part of the discharge apron only limited opal a precipitation has occurred since 1916 because of a decline in geysir9s eruptions

hydrothermal alteration at mururoa atoll french polynesia abstract petrological study of altered aerial basaltic flows submarine pillow lavas and oceanitic basalts of a rift zone sampled in two drill cores in the mururoa atoll viviane 1000 m depth fuchsia 550 m depth shows that during hydrothermal alteration processes the secondary clay minerals evolve the following three different trends controlled by permeability of the rocks and by rock fluid interaction mg saponite al saponite and al montmorillonite in the basaltic pillow lavas first celadonite saponite assemblage crystallizes in fresh glass rich rocks in altered and brecciated rocks the latter mineral assemblage is followed by fe saponite and mg saponite in breccias the glass is replaced by fe saponite the residual voids are sealed by zeolites mainly phillipsite apophyllite or gypsum indicating an upper temperature limit of 65 c in the aerial basaltic flows massive rocks are affected by celadonite and random mixed layer chlorite saponite crystallizations in the strongly altered rocks veined or brecciated the primary minerals and glass are partly replaced by al saponites and locally by chabazite the same al saponite fills up the veins and constitutes the major part of the cement as rock fluid interaction increases the si al and ca content in the solution increases inducing the late precipitation of aluminous smectite and chabazite in the oceanitic basalts sampled in the rift zone massive rocks are affected by crystallization of secondary clay minerals which is governed by local equilibrium femg clay minerals talc mg saponite celadonite partly replace the olivine phenocrysts and al saponite replaces the glass in veined and brecciated rocks the paragenesis is dioctahedral al smectite silica amorphous for a temperature range 2 content in the solution

occurrence of zeolites in sedimentary rocks an overview zeolites have been known since the mid 1750s but prior to the early 1950s most reported occurrences of zeolites were in fracture fillings and amygdules in igneous rocks particularly basaltic lava flows indeed most of the large attractive zeolite specimens in museum collections were obtained from lavas in recent years zeolites have been recognized as important rock forming constituents in low grade metamorphic rocks and in a variety of sedimentary rocks most zeolites in sedimentary rocks are finely crystalline that is they occur as microscopic or submicroscopic crystals and they are therefore of little appeal to mineral collectors however deposits of this type are voluminous and have great geologic significance and economic potential zeolites are among the most common authigenic silicate minerals that occur in sedimentary rocks and they form in sedimentary rocks of diverse lithology age and depositional environment about twenty species of zeolites have been reported from sedimentary rocks but only eight zeolites commonly make up the major part of zeolitic rocks these are analcime chabazite clinoptilolite erionite heulandite laumontite mordenite and phillipsite this chapter will consider chiefly the zeolites in sedimentary rocks with emphasis on volcaniclastic deposits which contain the largest concentrations of zeolites the occurrence of zeolites in lava flows is mentioned only briefly journal articles on the occurrence and origin of natural zeolites have multiplied at a rapid rate since the mineralogy and geology of natural zeolites was first published in 1977 as volume 4 of the mineralogical society of america s reviews in mineralogy the present review will highlight areas of more recent research on the occurrence and origin of zeolites and some of the coexisting minerals a wide variety of zeolites has been identified in sedimentary deposits with the most common being clinoptilolite analcime heulandite laumontite and phillipsite less abundant zeolites include chabazite erionite mordenite natrolite

geochemical and mineralogical analyses of palagonitic tuffs and altered rinds of pillow basalts in iceland and applications to mars samples of altered pillow lavas and hyalotuffs were collected from a volcanic tuya and hyaloclastite ridge in western iceland altered basaltic material from regions such as hloudufell tuya and thorolfsfell ridge may be similar to the surface fines on mars which are thought to contain altered basaltic components as well geochemical and mineralogical analyses have been performed on the icelandic samples in order to characterize the properties that distinguish palagonitization from other forms of low temperature alteration in this environment major elements were measured using an electron microprobe and mineralogy was determined through x ray diffraction and visible infrared reflectance spectroscopy the primary focus in this study was on the less than 2 microns size fractions of the hloudufell altered pillow and thorolfsfell palagonitic tuff samples the palagonitic tuff contained more crystalline clay minerals and has a higher al fe ratio the altered pillow lava contained higher abundances of nanophase iron oxides oxyhydroxides the extended visible region spectra of the less than 2 microns fractions of both icelandic samples are similar to bright martian soils measured by pathfinder

a natural analogue of nuclear waste glass in compacted bentonite abstract a marine based argillaceous rock containing volcanic glass shards has been investigated to infer the long term durability of vitrified nuclear waste in compacted bentonite which is a candidate for buffer material constituting the engineered barrier system for nuclear waste disposal fission track ages indicate that the volcanic glass shards andesitic scoria have been buried in the argillaceous rock for about 1 ma neither glass matrix dissolution nor precipitation on the surface was seen under an optical microscope little leaching of any element has been recognized by analyses using an electron microprobe analyzer secondary ion mass spectrometry analysis however indicates significant hydration which may dominantly be a permeation of molecular water as an indicator of durability of glass against groundwater a normalized mass loss of si nl si has been evaluated for the volcanic glass based on free energy for hydration the difference between estimated nl si of the volcanic glass and that of a simulated waste glass is within one order so that the volcanic glass may be analogous to a waste glass with respect to durability to water the argillaceous rock is analogous to the compacted bentonite with respect to physical properties such as dry density unconfined compression strength porosity and hydraulic conductivity the ambient physical and chemical conditions surrounding the volcanic glass have been also investigated temperature was in the range from 4 to 30 c due to the burial history of the volcanic glass over most of the past 1 ma the volcanic glass has been in contact with groundwater originating from seawater thermodynamic calculations indicate 1 ph 7 74 7 94 of the groundwater has mainly been controlled by dissolution of carbonate minerals 2 the redox potential eh 34 73 mv of the groundwater has dominantly been controlled by decomposition of organic materials to produce ch 4 g and 3 activity of aqueous silica of the groundwater was in equilibrium with sio 2 amorphous because of the equilibrium between aqueous silica and sio 2 amorphous the volcanic glass did not dissolve during the burial vitrified nuclear waste sealed in compacted bentonite therefore will not dissolve significantly if buried in an environment as mentioned above

progressive cooling of the hyaloclastite ridge at gjalp iceland 1996 2005 abstract in the subglacial eruption at gjalp in october 1996 a 6 km long and 500 m high subglacial hyaloclastite ridge was formed while large volumes of ice were melted by extremely fast heat transfer from magma to ice repeated surveying of ice surface geometry measurement of inflow of ice and a full stokes 2 d ice flow model have been combined to estimate the heat output from gjalp for the period 1996 2005 the very high heat output of order 10 6 mw during the eruption was followed by rapid decline dropping to 2500 mw by mid 1997 it remained similar until mid 1999 but declined to 700 mw in 1999 2001 since 2001 heat output has been insignificant probably of order 10 mw the total heat carried with the 1 2 10 12 kg of basaltic andesite erupted 0 45 km 3 dre is estimated to have been 1 5 10 18 j about two thirds of the thermal energy released from the 0 7 km 3 edifice in gjalp occurred during the 13 day long eruption 20 was released from end of eruption until mid 1997 a further 10 in 1997 2001 and from mid 2001 to present only a small fraction remained the post eruption heat output history can be reconciled with the gradual release of 5 10 17 j thermal energy remaining in the gjalp ridge after the eruption assuming single phase liquid convection in the cooling edifice the average temperature of the edifice is found to have been approximately 240 c at the end of the eruption dropping to 110 c after 9 months and reaching 40 c in 2001 although an initial period of several months of very high permeability is possible the most probable value of the permeability from 1997 onwards is of order 10 12 m 2 this is consistent with consolidated palagonitized hyaloclastite but incompatible with unconsolidated tephra this may indicate that palagonitization had advanced sufficiently in the first 1 2 years to form a consolidated hyaloclastite ridge resistant to erosion no ice flow traversing the gjalp ridge has been observed suggesting that it has effectively been shielded from glacial erosion in its first 10 years of existence

evidence of volcanic and glacial activity in chryse and acidalia planitiae mars abstract chryse and acidalia planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water ice rich geologic history these landforms include giant polygons bounded by kilometer scale arcuate troughs bright pitted mounds and mesa like features to investigate the significance of the last we have analyzed in detail the region between 60 n 290 e and 10 n 360 e utilizing hirise high resolution imaging science experiment images as well as regional scale data for context the mesas may be analogous to terrestrial tuyas emergent sub ice volcanoes although definitive proof has not been identified we also report on a blocky unit and associated landforms drumlins eskers inverted valleys kettle holes consistent with ice emplaced volcanic or volcano sedimentary flows the spatial association between tuya like mesas ice emplaced flows and further possible evidence of volcanism deflated flow fronts volcanic vents columnar jointing rootless cones and an extensive fluid rich substratum giant polygons bright mounds rampart craters allows for the possibility of glaciovolcanic activity in the region landforms indicative of glacial activity on chryse acidalia suggest a paleoclimatic environment remarkably different from today s climate changes on mars driven by orbital obliquity changes or giant outflow channel activity could have resulted in ice sheet related landforms far from the current polar caps

maar diatreme volcanoes a review maar diatreme volcanoes are produced by explosive eruptions that cut deeply into the country rock a maar is the crater cut into the ground and surrounded by an ejecta ring while the diatreme structure continues downward and encloses diatreme and root zone deposits here we attempt an evenhanded review of maar diatreme volcanology that extends from mafic to kimberlitic varieties and from historical maar eruptions to deeply eroded or mined diatreme structures we conclude that maar diatreme eruptions are episodic ejecta rings provide invaluable insight into eruption processes and sequence but are incomplete records of diatreme formation deposits within the diatreme structure include in varying proportions lower unbedded deposits sometimes typified by subvertical contacts among domains of debris emplaced sequentially and upper bedded deposits formed by sedimentation on surfaces open to the atmosphere a basal root zone comprises the transition from coherent magmatic feeder dike to clastic deposits formed by fragmentation of magma and enclosing country rock root zones are irregular in form and the clastic deposits are typically intruded by contorted dikes irregular root zone like chaotic breccias cut by contorted dikes are also present within diatreme deposits where they represent intra diatreme fragmentation zones and record changes in the location of the explosion locus during eruption

eruption dynamics at pahvant butte volcano utah western usa insights from ash sheet dispersal grain size and geochemical data shallow to emergent subaqueous basaltic explosive eruptions here referred to as surtseyan are a source of pyroclastic material expelled from subaqueous vents and transferred to the water column and atmosphere they can threaten coastal communities in different ways and one of these is through the generation of pyroclastic density currents travelling over water once the eruption becomes subaerial these may be preceded or accompanied by eruption fed currents moving along the sea lake floor one approach for studying these eruptions is through analysis of their deposits but these are commonly either inaccessible under water or poorly preserved by the time they are exposed subaerially the site selected for this work pahvant butte ut usa avoids these limitations the volcano was formed at 18 600 cal year b p in the giant pleistocene lake bonneville by an eruption initiated at a relatively shallow water depth 85 m the water is now drained and deposits of the edifice and of the ash sheet at medial distances on the old lake floor medial lake are accessible and well preserved the ash sheet deposits allow us to investigate dispersal of ash from a surtseyan eruption including the subaqueous phase of edifice building by comparing edifice deposits with ash sheet deposits correlated using geochemistry and textural analysis results suggest that medial deposited ash from pahvant butte travelled at least 25 km from the vent in eruption fed pyroclastic density currents moving along the lake floor this transport began early in the eruption apparently prior to the volcano s subaerial emergence

the nanophase iron mineral s in mars soil a series of surface modified clays containing nanophase np iron oxide oxyhydroxides of extremely small particle sizes with total iron contents as high as found in mars soil were prepared by iron deposition on the clay surface from ferrous chloride solution comprehensive studies of the iron mineralogy in these mars soil analogs were conducted using chemical extractions solubility analyses ph and redox x ray and electron diffractometry electron microscopic imaging specific surface area and particle size determinations differential thermal analyses magnetic properties characterization spectral reflectance and viking biology simulation experiments the clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron which slowly converts to more stable fully oxidized iron minerals the clay acted as an effective matrix both chemically and sterically preventing the major part of the synthesized iron oxides from ripening i e growing and developing larger crystals the precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1 10 nm having large specific surface area the noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate lepidocrocite gamma feooh was detected by selected area electron diffraction it is formed from a double iron fe ii fe iii hydroxy mineral such as green rust or ferrosic hydroxide magnetic measurements suggested that lepidocrocite converted to the more stable maghemite gamma fe2o3 by mild heat treatment and then to nanophase hematite alpha fe2o3 by extensive heat treatment after mild heating the iron enriched clay became slightly magnetic to the extent that it adheres to a hand held magnet as was observed with mars soil the chemical reactivity of the iron enriched clays strongly resembles and offers a plausible mechanism for the somewhat puzzling observations of the viking biology experiments their unique chemical reactivities are attributed to the combined catalytic effects of the iron oxide oxyhydroxides and silicate phase surfaces the reflectance spectrum of the clay iron preparations in the visible range is generally similar to the reflectance curves of bright regions on mars this strengthens the evidence for the predominance of nanophase iron oxides oxyhydroxides in mars soil the mode of formation of these nanophase iron oxides on mars is still unknown it is puzzling that despite the long period of time since aqueous weathering took place on mars they have not developed from their transitory stage to well crystallized end members the possibility is suggested that these phases represent a continuously on going extremely slow weathering process

exploring the human nature dynamics of hunga tonga hunga ha apai earth s newest landmass abstract this paper examines the human nature dynamics of volcanic eruptions through a multidisciplinary exploration of the recently formed hunga tonga hunga ha apai hthh landmass in the kingdom of tonga hthh was formed in early 2015 in the ha apai island group in southwestern tonga this landmass has persisted longer than expected providing a rare opportunity to examine pathways of erosion and biological colonization and offering a glimpse into the cultural dynamics of a continuously changing polynesian seascape in 2018 and 2019 a collaborative partnership between the kingdom of tonga sea education association sea and the united states national aeronautics and space administration nasa ran expeditions to hthh to calibrate satellite observations via field ship and drone based measurements in accessing hthh via sea s sailing school vessel ssv the robert c seamans a team of scientists and students combined fieldwork in anthropology oceanography and physical volcanology to study micro and macro scale dynamics of this classical surtseyan eruption site in this pathfinding paper we discuss the value of involving students in the process of real time scientific discovery with on the fly adaptive hypothesis testing this collaborative project provided mutual benefit to initiatives in science and education by offering robust data collection while expanding environmental and cultural literacy additionally we integrate collaborative research on hthh with ethnographic research to understand how this ever changing sea of islands or intimately interconnected island spaces impact social cultural relations within oceania we emphasize the importance of such multidisciplinary research in understanding the complexity of human nature relations in a rapidly changing world

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

a radiometric age for the cretaceous tertiary boundary based upon k ar rb sr and u pb ages of bentonites from alberta saskatchewan and montana bentonites associated with coal seams at the north american cretaceous tertiary k t boundary in the red deer valley of alberta in the frenchman valley of saskatchewan and near hell creek montana were dated by the k ar rb sr and u pb methods based upon palynological stratigraphic correlation and the presence of a sharp iridium anomaly the three sampled bentonite horizons all occur less than 1 m above the established k t boundary there is evidence of possible systematic errors giving dating results outside nominal statistical error values despite possible constant errors the weighted mean of nine average dates is calculated as 64 3 1 2 ma 2 standard deviation an unweighted averaging produces a grand mean age of 64 4 1 2 ma

authigenic mineral texture in submarine 1979 basalt drill core surtsey volcano iceland author s jackson md couper s stan cv ivarsson m czabaj mw tamura n parkinson d miyagi lm moore jg abstract 2019 american geophysical union all rights reserved micrometer scale maps of authigenic microstructures in submarine basaltic tuff from a 1979 surtsey volcano iceland drill core acquired 15 years after eruptions terminated describe the initial alteration of oceanic basalt in a low temperature hydrothermal system an integrative investigative approach uses synchrotron source x ray microdiffraction microfluoresence micro computed tomography and scanning transmission electron microscopy coupled with raman spectroscopy to create finely resolved spatial frameworks that record a continuum of alteration in glass and olivine microanalytical maps of vesicular and fractured lapilli in specimens from 157 1 137 9 and 102 6 m depths and borehole temperatures of 83 93 9 and 141 3 c measured in 1980 respectively describe the production of nanocrystalline clay mineral zeolites and al tobermorite in diverse microenvironments irregular alteration fronts at 157 1 m depth resemble microchannels associated with biological activity in older basalts by contrast linear microstructures with little resemblance to previously described alteration features have nanocrystalline clay mineral nontronite and zeolite amicite texture the crystallographic preferred orientation rotates around an axis parallel to the linear feature raman spectra indicating degraded and poorly ordered carbonaceous matter of possible biological origin are associated with nanocrystalline clay mineral in a crystallographically oriented linear microstructure in altered olivine at 102 6 m and with subcircular nanoscale cavities in altered glass at 137 9 m depth although evidence for biotic processes is inconclusive the integrated analyses describe the complex organization of previously unrecognized mineral texture in very young basalt they provide a foundational mineralogical reference for longitudinal time lapse characterizations of palagonitized basalt in oceanic environments