calcic amphibole equilibria and a new amphibole plagioclase geothermometer there is currently a dearth of reliable thermobarometers for many hornblende and plagioclase bearing rocks such as granitoids and amphibolites a semi empirical thermodynamic evaluation of the available experimental data on amphibole plagioclase assemblages leads to a new thermometer based on the aliv content of amphibole coexisting with plagioclase in silica saturated rocks the principal exchange vector in amphiboles as a function of temperature in both the natural and experimental studies is left na square 1 right a left alsi 1 right t1 we have analysed the data using 3 different amphibole activity models to calibrate the thermometer reactions 1 edenite 4 quartz tremolite albite 1 2 pargasite 4 quartz hornblende albite 2 the equilibrium relation for both 1 and 2 leads to the proposed new thermometer t frac 0 677p 48 98 y 0 0429 0 008314 ln k and k left frac si 4 8 si right x ab plag where si is the number of atoms per formula unit in amphiboles with p in kbar and t in k the term y represents plagioclase non ideality rtln ab from darken s quadratic formalism dqf with y 0 for xab 0 5 and y 8 06 25 5 1 xab 2 for xab 0 5 the best fits to the data were obtained by assuming complete coupling between al on the t1 site and na in the a site of amphibole and the standard deviation of residuals in the fit is 38 c the thermometer is robust to ferric iron recalculation procedures from electron probe data and should yield temperatures of equilibration for hornblende plagioclase assemblages with uncertainties of around 75 c for rocks equilibrated at temperatures in the range 500 1100 c the thermometer should only be used in this temperature range and for assemblages with plagioclase less calcic than an92 and with amphiboles containing less than 7 8 si atoms pfu good results have been attained on natural examples from greenschist to granulite facies metamorphic rocks as well as from a variety of mafic to acid intrusive and extrusive igneous rocks our analysis shows that the pressure dependence is poorly constrained and the equilibria are not suitable for barometry

intense sub kilometer scale boundary layer rolls observed in hurricane fran high resolution observations obtained with the doppler on wheels dow mobile weather radar near the point of landfall of hurricane fran 1996 revealed the existence of intense sub kilometer scale boundary layer rolls that strongly modulated the near surface wind speed it is proposed that these structures are one cause of geographically varying surface damage patterns that have been observed after some landfalling hurricanes and that they cause much of the observed gustiness bringing high velocity air from aloft to the lowest observable levels high resolution dow radar observations are contrasted with lower resolution observations obtained with an operational weather radar which underestimated peak low level wind speeds

evidence for early aragonite in paleo lacustrine sediments abstract distinct pseudomorphs of displacive pseudohexagonal aragonite crystals are found in organic rich lake deposits of the rift basins of the east coast of north america triassic jurassic these crystals developed while the sediments were relatively uncompacted and soft and hence are displacive readily mistaken for molds and casts of pre existing halite and or thinolite ikaite a second form of early aragonite is found in more evaporative sediments of the newark basin passaic formation developed as pseudomorphic replacement of precursor more soluble minerals such as glauberite and or gypsum that formed during deposition in all instances the aragonite is now replaced by calcite and dolomite but still preserves much of the original and unusual crystal form and associated inter al structure this aragonite is probably formed due to release of co2 by bacterial breakdown of organic matter in bottom sediments elevated mg ca in the pore waters may also have promoted preferential formation of aragonite over calcite

the significance of the reaction path in synthesizing single phase amphibole of defined composition amphiboles are common and very complex rock forming minerals knowledge of their physical chemical and thermodynamic properties allows us to understand rock forming and geodynamic processes amphiboles also possess distinctive physical properties that make them potentially attractive in applied fields certainly millions of dollars rubles etc were spent 30 40 years ago to optimize techniques of amphibole synthesis and ironically comparable sums have been or are still being spent to remediate asbestos danger in short for whatever purpose be it basic research or applied mineralogy the task of synthesizing amphiboles of defined composition and crystal chemical nature has been a challenge for a very long time however even a cursory review of the literature on amphiboles converges on one often recognized and much discussed dilemma e g hawthorne 1983b 1995 maresch and czank 1983b graham et al 1989 raudsepp et al 1991 compositions of amphibole products most often depart from the nominal experimental target is it then possible to synthesize single phase amphibole products and if not why not ideally synthesizing single phase hydroxyl amphibole from a given bulk composition would be the most accurate way to proceed to a well characterized amphibole product simply in terms of chemical composition a bulk starting material can be prepared with greater accuracy than a multi grain product can be characterized analytically what goes in must come out however reality is more sobering various states of disorder are possible at constant bulk composition e g oberti et al 2007 hawthorne and della ventura 2007 above all the necessity to introduce h2o as a fluid both as an intrinsic component of the structure and as a means of transmitting pressure in the experiment introduces new and difficult to control degrees of freedom changes in valence states become possible the target stoichiometry of the amphibole may be changed

sedimentary facies distribution and genesis of a recent carbonate rich saline lake gallocanta lake iberian chain ne spain abstract the study focuses on the holocene sedimentary infill of the gallocanta lacustrine basin in the iberian chain ne spain the gallocanta lake is a saline wetland with a maximum length of 7 5 km and a maximum width of 2 85 km the water depth varies significantly from a maximum depth of 2 m to completely dry in the central areas central subenvironment sapropels and salts develop with halite gypsum anhydrite dolomite aragonite calcite magnesite and lesser amounts of quartz and clay minerals cyanobacteria filaments are related to the aragonite and dolomite crystals the marginal subenvironment either has a gradual or a sharp change from that of the central subenvironment an inner area with desiccated light grey lutites is present in this marginal subenvironment in sem and x ray diffraction analyses quartz clay minerals aragonite calcite and small quantities of dolomite gypsum anhydrite and halite can be identified this inner area is surrounded by an external fringe composed of light brown lutites and a high concentration of salicornia meadwod and microbial mats this zone is only occasionally submerged and contains sandy and conglomerate islets active palustrine areas are flood zones where grey lutites with a significant quantity of vegetation such as reeds are common in general this entire sector is being modified by human action five sedimentary facies have been defined and this has enabled the identification of three distinct stages in the general evolution of the basin the first stage is an alluvial period developing during an arid climate after this a more humid stage facilitated the installation of a shallow carbonate rich lake a reduction of the water level probably due to a more arid stage induces a salinity increase of the lacustrine brine and the change to the third stage which corresponds to the present conditions the water level experienced frequent oscillations and alternations between humid conditions with a high production of organic matter which favors carbonate formation and water level dropdowns even to total dryness with saline sedimentation

bacterially mediated formation of diagenetic aragonite and native sulfur in zechstein carbonates upper permian central germany abstract neoformed diagenetic aragonite associated with organic rich aggregations and native sulfur occur within cavities of the ca2 and ca3 zechstein carbonates in central germany the cavities were formerly filled with gypsum bacterial sulfate reduction favored the precipitation of the carbonate phase this can be attributed to an increase in alkalinity accompanied with sulfate reduction the high sr concentrations of the neoformed aragonites compared to the low concentrations in the carbonate host rocks point to sulfate dissolution as the cation supplying process for the precipitation of aragonite low 13c values 10 pdb of the aragonite indicate that some of its carbon is derived from organic matter that has been oxidized by bacterial sulfate reduction aragonite inclusions bear rhomb shaped crystals of calcite replacing former dolomite elevated mg ca ratios due to this dedolomitization may have promoted the precipitation of aragonite instead of calcite the aragonite precipitated in the near surface meteoric vadose zone in recent times aragonite crystals display a platy habit sem analyses show that two types of micro rods are associated with these plates the mineralized micro rods are interpreted to be fossilized bacteria aragonite inclusions most of which contain organic rich aggregations yield a distinctive biomarker pattern high concentrations of specific unsaturated fatty acids are clearly indicative of newly produced organic matter and reflect the presence of a discrete microbial community being associated with the formation of the aragonite at one of the studied localities the aragonite is accompanied by native sulfur the formation of sulfur was mediated by h2s oxidizing bacteria this is corroborated by the presence of densely packed curved rods representing permineralized bacterial cells on and within the sulfur

ultramafic rocks of a fracture zone ophiolite north cascades washington abstract the ingalls complex was deformed in a late jurassic oceanic fracture zone an unusually diverse group of ultramafic tectonites comprise three units in this ophiolite unit 1 consists mostly of poorly to moderately foliated harzburgite and dunite characterized by porphyroclastic textures irregular shaped and tabular dunite bodies probably represent intrusive bodies or residues of partial melting voluminous unit 2 consists mostly of poorly to strongly foliated iherzolite and clinopyroxene bearing harzburgite plagioclase peridotite is present locally olivine and enstatite generally define equigranular mosaics or weakly porphyroclastic textures clinopyroxene however in some samples displays only weak deformation compositional zoning simple growth twins and interstitial commonly poikilitic texture clinopyroxene and plagioclase in these samples probably formed from a melt after recrystallization of olivine and enstatite indicating that these iherzolites are impregnated peridotites other iherzolites and clinopyroxene bearing harzburgites may represent weakly depleted mantle pods of metagabbroic gneiss within unit 2 probably are small intrusions that were deformed as they cooled unit 3 represents a major high temperature 700 900 c shear zone that separates units 1 and 2 and consists of strongly foliated commonly mylonitic iherzolites and hornblende peridotites the latter are the most strongly foliated ultramafites and olivine in them records stresses as high as 275 mpa the abundance of hornblende implies a genetic relationship between mylonitization and the hydration and metasomatism necessary to form such rocks from iherzolites mineral chemistry and geothermometry are typical of mantle tectonites in many ophiolites and oceanic fracture zones there is a particularly strong similarity between the spinels in the ingalls complex and the spinels from the owen and vema fracture zones hornblende in unit 3 ranges from edenite to edenitic hornblende calculated temperatures from cpx opx pairs in unit 2 range from 950 to 1000 c these data are best explained by horizontal and vertical displacements in oceanic fracture zones which may juxtapose lithosphere formed at different structural levels and with different petrologic histories unit 1 represents a block of upper mantle which probably experienced convective upwelling and partial melting beneath a spreading ridge near its intersection with a fracture zone during convective upwelling at least parts of the upper mantle represented by unit 2 were impregnated by a melt the impregnated iherzolite may be accounted for by the edge effect at a fracture zone or reduced melt production at a fracture zone due to ribbon spreading the mylonite zone of unit 3 reworks iherzolites and harzburgites which were originally part of the block represented by unit 2 and probably records deformation in the active segment of the fracture zone these observations document the complexities that may occur in ultramafic rocks within oceanic fracture zones they also suggest that impregnation metasomatism and high stresses are important in these zones

alteration mineralization and radiometric ages of the source pluton at the sangan iron skarn deposit northeastern iran abstract the world class sangan iron skarn deposit with a proven reserve of 1000 mt iron ore 53 fe is located in the khaf kashmar bardaskan volcano plutonic metallogenic belt kkb vpmb of northeastern iran along the e w trending regional doruneh fault north of the lut block skarn mineralization occurs at the contact of the 39 1 0 6 ma to 38 3 0 5 ma middle eocene syenite to syenogranite porphyry source pluton with cretaceous carbonate rocks the source pluton is part of an i type calcalkaline granitoid series with potassium to shoshonitic affinity metaluminous to slightly peraluminous character the granitoids are enriched in lile cs rb ba k th and u and lree la and ce are depleted in hfse nb y ta and ti hree yb and lu and eu which together with the low sr 96 to 362 ppm and la yb n contents suggest a metasomatized slab derived mantel source within the cenozoic volcanoplutonic continental arc of northeaster iran the location of the skarn orebodies is controlled by the regional e w doruneh fault structure and the spatial distribution and the two calcic and magnesian skarns is controlled by the composition of the carbonate protolith that consists of limestone in the west and dolomite in the east the chemistry of the skarn minerals reflects the composition of the protoliths the western skarn is dominated by ca rich calcsilicates that consist of prograde ca rich garnet adr 50 97 grs 0 45 sps alm 2 7 ca fe rich pyroxene hd 75 6 di 20 jo 4 5 k cl f bearing fe ca rich amphibole ferrohastingsite fe 4 4 ca 2 mg 0 5 k 0 4 na 0 3 si 6 5 al 1 8 o 22 cl f oh 2 in endoskarns and retrograde ferroactinolite fe 4 2 ca 2 mgmn 0 04 na 0 1 k 0 06 si 7 8 al 0 2 o 22 f cl oh 2 and fe rich chlorite ripidolite fe 4 3 mg 1 1 ca 0 06 mn 0 01 al 2 8 si 3 o 10 oh 8 in the exoskarns wollasonite plagioclase and k feldspar have been additionally formed together with ferrohastingsite in the endoskarns the eastern magnesian skarn is typically phlogopite rich k 0 9 mg 2 7 fe 0 2 na 0 02 si 2 9 al 1 2 o 10 oh f 2 and consists of prograde forsterite fo 97 0 fa 2 7 diopsidic pyroxene hd 0 2 di 0 88 and retrograde mg rich actinolite mg rich chlorite clinochlore mg 4 5 fe 0 1 k 0 05 al 1 8 si 2 7 o 10 oh 8 serpentine and talc iron mineralization overprints the calcsilicate skarns in both the western and the eastern skarns and is magnesian in the eastern orebodies 3 65 wt mgo the iron ore consists of a number of high grade replacement and magnetite orebodies with minor amounts of pyrrhotite chalcopyrite and pyrite indicating a large scale metasomatic transfer of iron bearing fluids during middle eocene magmatic activity at the kkb vpmb

microgranitoid enclaves in the felsic looanga monzogranite new england batholith australia pressure quench cumulates abstract sparse microgranitoid enclaves mge in the leucocratic i type looanga monzogranite near bendemeer n s w australia range from microdiorite to micromonzogranite and all have fine to medium grainsize igneous microstructures the enclaves that vary from sio 2 53 to 69 wt are all less silicic than the host monzogranite 71 76 wt although compositionally diverse the enclaves and host monzogranite pluton share a common mineralogy of quartz oligoclase ferro edenitic hornblende iron rich mg 35 biotite fluor apatite and k feldspar except for the core of one double enclave the enclaves have the same 87 sr 86 sr initial ratio as the host pluton a characteristic of the enclaves is high mno mno mgo feo ratios with mno abundances of the more mafic enclaves up to 0 8 wt higher than any common magma the enclaves have a wide range of na 2 o k 2 o ratios 0 5 to 2 8 and in common with the host pluton contain hornblendes with na 2 o k 2 o ratios varying from 1 5 to 2 3 the hornblendes in two enclaves have lower na 2 o k 2 o ratios than their host enclave making it unlikely that the hornblende could have crystallised from a melt of the same composition as these enclaves chemically and mineralogically the more mafic enclaves have characteristics expected of cumulates formed from a magma of similar composition as the host pluton in that they contain the same minerals but are enriched in the near liquidus phases hornblende plagioclase and biotite and depleted in the near solidus phases quartz and k feldspar except for some minor replacement of pyroxene by hornblende the minerals do not show microstructural evidence of being made over from other minerals it is argued that the mineral chemistry of these enclaves is also a primary feature rather than the result of mineralogical equilibration with the host monzogranite magma the two most felsic enclaves are medium grained monzogranites sio 2 68 and 70 wt and are considered to be compositionally little different from the magmas from which they crystallised these two exhibit hydrothermal alteration and are considered to be fragments of an earlier roof phase of the intrusion the quench microstructure and cumulate chemistry of the more mafic enclaves are argued to result from p h 2 o reduction events within the upper parts of the magma chamber due to roof fracture brought on by the pressure increase imparted to the magma by the fluid release from a water saturated magma the sudden reduction in fluid pressure results in an increase in the liquidus and solidus temperatures of the water saturated magma and this rather than a drop in temperature produces quench conditions the reduction in p h 2 o shifts the cotectic compositions in the q ab or system closer to k feldspar and quartz and this and the heat of crystallisation restrict the amount of these two near solidus minerals that crystallise the enclaves form as crystal cluster cumulates around minerals already in the magma and or any other solid substrate available including the magma chamber roof this pressure quench cumulate mechanism explains why the looanga enclaves are mineralogically similar to the host granite and we suggest that this process may be more widely applicable to enclaves in granitic rocks

a new hyper calcic amphibole with ca at the a site fluor cannilloite from pargas finland electron microprobe analysis of amphiboles from pargas finland shows up to 2 42 ca apfu atoms per formula unit far in excess of the usual maximum value of 2 00 ca apfu observed in amphiboles the most ca rich composition is ko 12nao 35cao 52 cal 92mn6 65 fe6 63 mg3 73 fe6 t3 tio o2alo 82 si5 63ai2 37 022 oh 0 46f 1 54 fluor cannilloite ideally caca2 mg4ai si5ai3 022f2 is a new amphibole species in which ca is dominant at the a site fluor cannilloite occurs as isolated anhedral grains and small granular aggregates in a marble together with calcite muscovite anorthite aluminous diopside pyrope and fluorite it is grayish green with a grayish white streak brittle h 6 dmeas 3 05 g cm3 and shows perfect 110 cleavage in plane polarized light it is pale greenish gray to almost colorless rather cloudy and mottled in appearance and is not pleochroic fluor cannilloite is biaxial positive a 1 611 2 3 1 616 2 l 1 633 2 2 v 49 2 dispersion weak r v it is monoclinic space group c21m a 9 826 4 b 17 906 9 c 5 301 3 a 3 105 41 4 v 899 2 a3 z 2 the ten strongest x ray diffraction lines in the

coherent turbulence in the boundary layer of hurricane rita 2005 during an eyewall replacement cycle abstractthe structure of coherent turbulence in an eyewall replacement cycle in hurricane rita 2005 is presented from novel airborne doppler radar observations using the imaging wind and rain air

dehydration melting of tonalites part ii composition of melts and solids dehydration melting of tonalitic compositions phlogopite or biotite plagioclase quartz assemblages is investigated within a temperature range of 700 1000 c and pressure range of 2 15 kbar the solid reaction products in the case of the phlogopite plagioclase an45 quartz starting material are enstatite clinopyroxene and potassium feldspar with amphiboles occurring occasionally at 12 kbar zoisite is observed below 800 c and garnet at 900 c the reaction products of dehydration melting of the biotite ann50 plagioclase an45 quartz assemblage are melt orthopyroxene clinopyroxene amphibole and potassium feldspar at pressures 8 kbar and temperatures below 800 c epidote is also formed almandine rich garnet appears above 10 kbar at temperatures 750 c the composition of melts is granitic to granodioritic hence showing the importance of dehydration melting of tonalites for the formation of granitic melts and granulitic restites at pressure temperature conditions within the continental crust the melt compositions plot close to the cotectic line dividing the liquidus surfaces between quartz and potassium feldspar in the haplogranite system at 5 kbar and ah2o 1 the composition of the melts changes with the composition of the starting material temperature and pressure with increasing temperature the melt becomes enriched in al2o3 and feo mgo potash in the melt is highest just when biotite disappears the amount of cao decreases up to 900 c at 5 kbar whereas at higher temperatures it increases as amphibole clinopyroxene and more an component dissolve in the melt the na2o content of the melt increases slightly with increase in temperature the composition of the melt at temperatures 900 c approaches that of the starting assemblage the melt fraction varies with composition and proportion of hydrous phases in the starting composition as well as temperature and pressure with increasing modal biotite from 20 to 30 wt the melt proportion increases from 19 8 to 22 3 vol 850 c and 5 kbar with increasing temperature from 800 to 950 c at 5 kbar the increase in melt fraction is from 11 to 25 8 vol the effect of pressure on the melt fraction is observed to be relatively small and the melt proportion in the same assemblage decreases at 850 c from 19 8 vol at 5 kbar to 15 3 vol at 15 kbar selected experiments were reversed at 2 and 5 kbar to demonstrate that near equilibrium compositions were obtained in runs of longer duration

estimation and mapping of hurricane turbulent energy using airborne doppler measurements abstract hurricane turbulent kinetic energy tke was computed using airborne doppler measurements from the noaa wp 3d tail radars and tke data were retrieved for a variety of storms at different stages of their life cycle the geometry of the radar analysis coupled with the relatively small beam resolution at ranges 8 km allowed for the estimation of subkilometer turbulent processes two dimensional profiles of tke were constructed and revealed that the strongest turbulence was generally located in convective regions such as the eyewall with magnitudes often exceeding 15 m2 s 2 and in the boundary layer with values of 5 10 m2 s 2 in the lowest kilometer a correlation analysis showed that the strong turbulence was generally associated with strong horizontal shear of vertical and radial wind components in the eyewall and strong vertical shear of horizontal wind in the boundary layer mean vertical profiles of tke decrease sharply above the hurricane boundary layer and level off at low magnitude for al

prevalence of tornado scale vortices in the tropical cyclone eyewall analyses of datasets from manned research flights that penetrated hurricane eyes and tropical cyclone tc damage surveys strongly suggest the existence of tornado scale vortices in the turbulent boundary layer of the tc eyewall however their small horizontal scale their fast movement and the associated severe turbulence make the tornado scale vortex very difficult to observe directly to understand tornado scale vortices in the tc eyewall and their influence on the tc vortex mesoscale rainbands and convective clouds a numerical experiment including seven nested domains with the smallest horizontal grid interval of 37 m is conducted to perform a large eddy simulation les with the advanced weather research and forecast wrf model we show that most of the observed features associated with tornado scale vortices can be realistically simulated in the wrf les framework the numerical simulation confirms the existence of simulated tornado scale vortices in the turbulent boundary layer of the tc eyewall our numerical experiment suggests that tornado scale vortices are prevalent at the inner edge of the intense eyewall convection

stratigraphic record of the early mesozoic breakup of pangea in the laurasia gondwana rift system rift basins of the central atlantic margins cam of north america and morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early mesozoic the best known is the newark basin of new jersey new york and pennsylvania where an astronomically calibrated magnetic polarity time scale is developed lacustrine cycles of milankovitch origin are commonly present in cam basins with the period changing from 10 ky paleoequator with coals to 20 ky 4 10n to perhaps 40 ky northward with evaporites cycles of100 ky 413 ky and2 my are also important four mostly unconformity bounded tectonostratigraphic sequences are present the anisian ts i is fluvial and eolian ts ii ts iv late triassic to early jurassic consist of tripartite lacustrine sequences caused by extension pulses the newark basin accumulation rate history allows comparison with quantitative rift basin models the north american plate s slow northward drift resulted in a relative shift of climate although the rapid humidification during the latest triassic and early jurassic is associated with a sea level rise the triassic jurassic mass extinction is of independent origin plausibly impact related

diagenesis of the newark rift basin eastern north america late triassic nonmarine strata in the newark rift basin eastern north america accumulated in a subsiding half graben prior to opening of the atlantic ocean these strata consist in ascending order of the stockton lockatong and passaic formations although different in specific lithology these formations all exhibit diagenetic fabrics dominated by authigenic albite and analcime these same minerals have a similar presence in late triassic newark supergroup strata of other rift related basins to the north suggesting that related authigenesis is not simply a result of local diagenetic factors the basal deposit the stockton formation is composed of fluvial sandstones and overbank mudstones with nodular pedogenic calcite calcrete during burial original micrite was first recrystallized into sparry calcite and then later subjected to partial replacement by authigenic albite which is also present as overgrowths and void fillings in overbank mudstones the lockatong formation contains organic rich shales carbonates and evaporative mudstones deposited under cyclic conditions in laterally extensive lacustrine environments analcime comprises up to 40 of these strata by volume occurring within the matrix as a replacement of original carbonates and evaporites and as fillings in macrovoids the overlying passaic formation is made up of massive red mudstones evaporites and local calcareous lacustrine sequences evaporites are replaced by coarse grained anhydrite together with some authigenic albite a central question concerns the source for the na si and al required for albite and analcime authigenesis it is suggested that in addition to alteration of primary siliciclastic material sodium in particular was supplied in two ways 1 from high concentrations in original evaporative brines and groundwaters lockatong and passaic formations and 2 from dissolution of associated sodium bearing evaporites lockatong and passaic formation during diagenesis it is proposed here that basin sourced na enriched brines circulated through the section over time as albite is more stable at elevated temperatures relative to analcime it developed in the lowermost strata of the basin stockton formation analcime is more prevalent in the overlying lockatong formation

the evolution of latera caldera central italy in the light of subsurface data subsurface geothermal exploration has considerably added to our knowledge of the latera volcanic complex a syenitic body is located about 2 km below the present day surface k ar data point a 0 9 ma age the primary magma was a silica saturated trachyte undersaturated hauyne bearing products are found near the carbonatic wall rocks and have been interpreted as reaction products subsurface data from deep drilling and geophysical surveys suggest that the latera caldera resulted from three main successive collapse phases i formation of an old caldera now buried related to the eruption of ignimbrites from the syenitic magma chamber ii sinking of the eastern sector as a consequence of the formation of the nearby bolsena caldera 0 3 ma iii multistage formation of the present latera caldera 0 16 ma

an estimation of turbulent characteristics in the low level region of intense hurricanes allen 1980 and hugo 1989 this study analyzes the flight level data collected by research aircraft that penetrated the eyewalls of category 5 hurricane hugo 1989 and category 4 hurricane allen 1980 between 1 km and the sea surface estimates of turbulent momentum flux turbulent kinetic energy tke and vertical eddy diffusivity are obtained before and during the eyewall penetrations spatial scales of turbulent eddies are determined through a spectral analysis the turbulence parameters estimated for the eyewall penetration leg are found to be nearly an order of magnitude larger than those for the leg outside the eyewall at similar altitudes in the low level intense eyewall region the horizontal length scale of the dominant turbulent eddies is found to be between 500 and 3000 m and the corresponding vertical length scale is approximately 100 m the results suggest also that it is unwise to include eyewall vorticity maxima evm in the turbulence parameter estimation because the evms are likely to be quasi two dimensional vortex structures that are embedded within the three dimensional turbulence on the inside edge of the eyewall this studyis afirstattempt at estimatingthe characteristics of turbulent flow in the low leveltroposphereof an intense eyewall using in situ aircraft observations the authors believe that the results can offer useful guidance in numerical weather prediction efforts aimed at improving the forecast of hurricane intensity because of the small sample size analyzed in this study further analyses of the turbulent characteristics in the high wind region of hurricanes are imperative

transition of the hurricane boundary layer during the landfall of hurricane irene 2011 abstractthe hurricane boundary layer hbl has been observed in great detail through aircraft investigations of tropical cyclones over the open ocean but the coastal transition of the hbl has been

interstellar hydroxyl in meteoritic chondrules implications for the origin of water in the inner solar system abstract ion probe determinations of water concentrations and d h ratios have been performed on different phases pyroxene olivine and mesostasis of chondrules from the bishunpur and semarkona ll3 chondrites mean water concentrations average 1290 ppm in olivine 500 to 2100 ppm 2400 ppm in pyroxene 400 to 9800 ppm and up to 3950 ppm in the mesostasis 1000 to 16500 ppm in one chondrule an iron oxide phase exhibits a mean water concentration of 1 70 wt 1 21 to 2 15 wt hydrogen isotopic measurements reveal the presence of two water sources with high and low d h ratios pyroxenes range from 74 to 479 10 6 with a mean value of 186 10 6 n 54 the mesostasis from 124 to 203 10 6 with a mean value of 152 10 6 n 8 olivines from 63 to 209 10 6 with a mean value of 130 10 6 n 13 the iron oxide phase from 157 to 360 10 6 with a mean value of 219 10 6 n 7 hydroxyls in pyroxenes have been identified as submicroscopic poorly crystallized amphibole lamellae through high resolution transmission electron microscopy considering the broad range of d h ratios in pyroxene chondrules alteration in a unique meteoritic parent body seems to be excluded an early hydroxylation of the pyroxene occurring during chondrule formation due to the presence of water bearing minerals among chondrule precursors seems the only possible interpretation of the data accordingly the distribution of d h ratios in chondrules reflects that of their precursors such a distribution is quite similar to that found in matrix minerals as recorded by water concentration and d h ratio the mesostasis has been subjected to hydrothermal alteration after the incorporation of the chondrules into the meteoritic parent body this alteration took place with water having a mean d h ratio reflecting the mixing of the d depleted and d rich sources the d rich component is interpreted as a preserved interstellar source while the low d h ratio reflects a water component that underwent isotopic exchange with protosolar molecular hydrogen

alteration and mass transfer in cataclasites and mylonites in 6 6 km of granitic crust at the siljan impact structure central sweden granitic rocks deformed by cataclasis and mylonitization on macro a few meters and micro thin section scales are found at depths down to 6 6km in the siljan impact structure in central sweden granites near fault planes exhibit 1 fracturing kinking fragmentation and recrystallization of feldspars into pure k and na endmember varieties 2 fragmentation polygonization and development of undulose extinction in quartz and 3 kinking appearance of wavy extinction and alteration of biotite chlorite amphibole and alteration of ilmenite and magnetite whole rock chemical analyses of deformed and undeformed rocks show that deformed rocks are enriched in sio2 by about 5 wt and depleted in other oxides by variable percentages apart from rb and co the concentrations of other trace elements including ba sr zn zr pb cd cu cr ni v u th la and li are lower in deformed relative to undeformed rocks mass balance calculations for a 1000 cm3 model granite which were based on modal mineralogy whole rock chemistry and mineral analyses suggest that the break down of primary biotite chlorite and amphibole in deformed zones released elements to circulating fluids these calculations also indicate liberation of water and a doubling of porosity from 1 to 2 during the deformation episodes later precipitation of minerals in shear and tension fractures reduced this porosity within the upper 2000 m of the gravberg 1 well the formation of fracture filling minerals smectite calcite hematite chlorite and albite is impact related and was favored by active circulation of meteoric water fracture filling minerals in the upper 2000 m of the borehole formed at temperatures of 70 to 200 c between depths of 2000 and 3500 m fracture filling mineral assemblages dominated by fe mg chlorite sphene and epidote suggest formation temperatures in the range of 150 to 300 c occurrence of pumpellyite and prehnite in some altered biotite and chlorite of the deformed zones between 3500 and 5500 m suggest preimpact metamorphism and formation temperature above 150 c below 5500 m the mineral assemblages in the fractures are dominated by quartz sphene epidote and some muscovite and chlorite indicating a temperature range between 300 and 450 c one of the possible origins for the ch4 and h2 gases detected in the gravberg 1 well is a combination of hydrogen ions released by decomposition of hydrated silicates biotite chlorite hornblende with carbon the presence of iron in the deformed granitic rocks prevented the resulting ch4 from being oxidized

cataclastic rocks of the san gabriel fault an expression of deformation at deeper crustal levels in the san andreas fault zone the san gabriel fault a deeply eroded late oligocene to middle pliocene precursor to the san andreas was chosen for petrologic study to provide information regarding intrafault material representative of deeper crustal levels cataclastic rocks exposed along the present trace of the san andreas in this area are exclusively a variety of fault gouge that is essentially a rock flour with a quartz feldspar biotite chlorite amphibole epidote and fe ti oxide mineralogy representing the milled down equivalent of the original rock anderson and osborne 1979 anderson et al 1980 likewise fault gouge and associated breccia are common along the san gabriel fault but only where the zone of cataclasis is several tens of meters wide at several localities the zone is extremely narrow several centimeters and the cataclastic rock type is cataclasite a dark aphanitic and highly comminuted and indurated rock the cataclastic rocks along the san gabriel fault exhibit more comminution than that observed for gouge along the san andreas the average grain diameter for the san andreas gouge ranges from 0 01 to 0 06 mm for the san gabriel cataclastic rocks it ranges from 0 0001 to 0 007 mm whereas the san andreas gouge remains particulate to the smallest grain size the ultra fine grain matrix of the san gabriel cataclasite is composed of a mosaic of equidimensional interlocking grains the cataclastic rocks along the san gabriel fault also show more mineralogiec changes compared to gouge from the san andreas fault at the expense of biotite amphibole and feldspar there is some growth of new albite chlorite sericite laumontite analcime mordenite and calcite the highest grade of metamorphism is laumontite chlorite zone zeolite facies mineral assemblages and constrained uplift rates allow temperature and depth estimates of 200 30 c and 2 5 km thus suggesting an approximate geothermal gradient of 50 c km such elevated temperatures imply a moderate to high stress regime for the san andreas which is consistent with experimental rock failure studies moreover these results suggest that the previously observed lack of heat flow coaxial with the fault zone may be the result of dissipation rather than low stress much of the mineralogy of the cataclastic rocks is still relict from the earlier igneous or metamorphic history of the protolith porphyroclasts even in the most deformed rocks consist of relict plagioclase oligoclase to andesine alkali feldspar quartz biotite amphibole epidote allanite and fe ti oxides ilmenite and magnetite we have found no significant development of any clay minerals illite kaolinite or montmorillonite for many sites the compositions of these minerals directly correspond to the mineral compositions in rock types on one or both sides of the fault whole rock major and trace element chemistry coupled with mineral compositions show that mixing within the zone of cataclasis is not uniform and that originally micaceous foliated or physically more heterogeneous rock units may contribute a disproportionally large amount to the resultant intrafault material as previously found for the gouge along the san andreas chemical mobility is not a major factor in the formation of cataclastic rocks of the san gabriel fault we see only minor changes for si and alkalies however there is a marked mobility of li which is a probable result of the alteration and formation of new mica minerals the gouge of the san andreas and san gabriel faults probably formed by cataclastic flow there is some indication presently not well constrained that the fine grained matrix of the cataclasite of from the san gabriel fault formed in response to superplastic flow

formation of the jurassic south china large granitic province insights from the genesis of the jiufeng pluton abstract the magma source and thermal regime for the formation of large granitic provinces lgps have been the subjects of much debate as mineralogical geochemical and isotopic variations of plutonic rocks preserve records of crustal thermal evolution the jiufeng pluton was comprehensively studied to gain insights into material and heat sources and tectonic process in the formation of the south china lgp sims zircon u pb analyses of a biotite granite 158 9 1 3 ma three two mica granites stage i 159 7 1 2 ma stage ii 158 6 1 2 ma and 156 8 1 2 ma and a muscovite granodiorite 159 0 4 4 ma of the jiufeng pluton suggest that they are coeval and were emplaced in a short period of no more than 5 3 m y limited variations in whole rock nd isotope end t 12 6 to 9 5 and zircon hf o isotopes ehf t 12 0 to 6 3 18 o 6 8 9 4 suggest that the jiufeng pluton was mainly derived from melting of a common metasedimentary source possibly with a minor basaltic contribution we consider the geochemical variations of the jiufeng pluton are primarily a result of incremental assembly of magma batches produced from rapid step like transition from fluid saturated to fluid absent melting of the source the muscovite granodiorite with high na 2 o 3 80 wt k 2 o na 2 o 1 is interpreted to have been produced by fluid saturated melting at low temperature 650 c high p 2 o 5 0 09 0 17 wt zircon saturation temperature t zr 769 816 c and la yb ratios 8 4 55 8 of the stage ii two mica granite support its formation from high temperature 800 c biotite dehydration melting whereas lower p 2 o 5 zr 685 742 c and la yb

petrogenesis of late jurassic two mica granites and associated diorites and syenite porphyries in guangzhou se china abstract the south china block scb is considered to have undergone extensive reworking of continental crust however the mechanisms of this crustal reworking are unclear here we report on late jurassic 162 155 ma two mica granites and associated diorites and syenite porphyries from the huolushan longyandong area of guangzhou city southeastern china the two mica granites have high sio2 contents 69 6 73 6 wt and weakly peraluminous to strongly peraluminous compositions these rocks have enriched sr nd hf isotopic compositions 87sr 86sr i 0 7094 0 7145 end t 10 5 to 9 3 ehf t 12 7 to 4 2 the huolushan two mica granites have variable zircon o isotopic compositions 18o 6 8 10 4 whereas the longyandong two mica granites have homogeneous compositions 18o 8 6 9 9 the huolushan syenite porphyries have moderate sio2 59 6 60 1 wt and high alkaline k2o na2o 9 4 9 8 wt contents their sr nd hf o isotopic compositions 87sr 86sr i 0 7105 0 7119 end t 9 9 to 9 8 ehf t 14 1 to 5 9 18o 6 5 10 6 are similar to those of the huolushan two mica granites the huolushan diorites have moderate sio2 contents 59 9 60 4 wt and are high k calc alkaline and metaluminous with mg values of 43 2 43 8 their sr nd isotopic compositions 87sr 86sr i 0 7106 0 7109 end t 8 8 to 8 6 are less enriched than those of the two mica granites and syenite porphyries in addition the diorites have high zircon 18o values 7 8 8 9 and a wide range of zircon ehf t values 13 4 to 5 6 we propose that the huolushan two mica granites were derived from a metagreywacke dominated hybridized source with minor juvenile crustal rocks and that the longyandong two mica granites were generated by partial melting of metagreywackes the huolushan syenite porphyries were formed by the mixing of metasedimentary rock derived felsic magmas and minor enriched mantle derived alkaline magmas the huolushan diorites were most likely derived by partial melting of mafic lower crust with the dioritic magmas undergoing assimilation and fractional crystallization afc during ascent all of these intrusive rocks were likely formed in an extensional intraplate setting the mantle derived magmas which could have been triggered by lithospheric extension underplated the middle lower crust and provided heat for crustal reworking and materials for late mesozoic crustal growth

asbestos fibre identification vs evaluation of asbestos hazard in ophiolitic rock melanges a case study from the ligurian alps italy in recent years the high incidence of harmful health effects through inhalation of airborne asbestos from amphibole bearing rock melanges has been thoroughly documented here we present a field based multi scale geological approach aimed at illustrating the occurrence of amphibole fibrous mineralisation in an ophiolitic suite from the ligurian alps italy and discussing the implication on in situ determination of the asbestos hazard the rock melange is composed of plurimetre sized blocks of different lithotypes metagabbro serpentinite chloritoschist juxtaposed by the meaning of tectonic structures the geological structural survey revealed that the fibrous mineralisation is localised in specific structural sites of the rock volume including veins and schistosity both micro chemical and crystal structure analyses on selected fibrous samples revealed that actinolite fibres grow in veins within the metagabbro and in chloritoschists while fibrous tremolite occurs in serpentinite schistosity the morphological features of these amphibole fibres have been analysed in tem images and used for classifying them as asbestiform or non asbestiform the results show that the asbestos hazard determination is not unequivocally identified when different procedures for asbestos fibre identification and classification are applied this may have impact on normatives and regulations in defining environmental hazards due to asbestos occurrence

the cabo de la vela mafic ultramafic complex northeastern colombian caribbean region a record of multistage evolution of a late cretaceous intra oceanic arc ophiolite related rocks accreted to caribbean plate margins provide insights into complex intra oceanic evolution of the plate and its interaction with continental margins of the americas petrologic geochemical and isotope k ar sr and nd data were obtained in poorly known serpentinites gabbros and andesite dykes of the cabo de la vela mafic ultramafic complex from the guajira peninsula north colombia field relations metasomatic alteration patterns and whole rock mineral geochemistry combined with juvenile isotope signatures of the different units suggest that gabbros and serpentinites formed in a slow spreading supra subduction zone that was brought to shallower depths and subsequently evolved to an arc setting where andesitic rocks formed with little sediment input the tectonomagmatic evolution of the cabo de la vela mafic ultramafic complex involved an intra oceanic arc that evolved from pre campanian time to 74 ma relationships with other units from the guajira peninsula show either the existence of a mature arc basement or a series of coalesced allocthonous arcs juxtaposed before accretion onto the passive continental margin of south american in pre eocene times correlations with ophiolite related rocks of the southern caribbean and diachronism in the accretionary process are compatible with a wsw ese advancing caribbean plate front ophiolitic rocks are fundamental to understanding of the complex dynamics and evolution of oceanic crust and its interaction with continental margins to form so called cordilleran type orogens shervais 2001 beccaluva et al 2004 in the caribbean area studies of ophiolitic complexes have identified remnants of rift margins ocean plateaux and arc systems formed in oceanic domains that evolved since the mesozoic following the break up of pangea giunta et al 2002 2006 however different models show lack of concensus testing of regional models through local relationships has often not been successful possibly due to lack of detailed information iturralde vinent lidiak 2006 for discusions a few ophiolite related rocks have been described from the colombian caribbean macdonald 1964 lockwood 1965 alvarez 1967 however their formation setting and their implications for the geotectonic models of the caribbean have not been discussed we present integrated petrological mineral chemistry whole rock geochemistry nd and sr isotopes and k ar geochronology data from the cabo de la vela mafic ultramafic complex of the southwestern caribbean they allow reconstruction of a late cretaceous arc related magmatic system that was accreted to the continental margin of south america in pre eocene times the implication of this and other available regional data is discussed within the framework of the caribbean plate tectonic evolution

metamorphic amphiboles composition and coexistence amphiboles have long been key players in metamorphic petrology the concept of facies was developed for rocks of basaltic composition eskola 1920 1939 fyfe et al 1958 and within this concept amphiboles had a leading role the first appearance of amphiboles the presence of amphiboles of certain compositions or last appearance of amphiboles that are replaced by pyroxene bearing assemblages mark a number of major facies boundaries the transition from greenschist to amphibolite facies is marked in part by hornblende replacing actinolite and the granulite facies is defined by the breakdown of hornblende to orthopyroxene bearing assemblages the blueschist facies is defined by the appearance of glaucophane while the transition from blueschist facies to eclogite facies conditions is indicated by the breakdown of glaucophane to omphacitic pyroxene bearing assemblages references to amphibole names actinolite glaucophane or rocks characterized by certain amphiboles amphibolite hornblende figure prominently in six facies names turner 1981 liou et al 1985 oh et al 1988 evans 1990 peacock 1993 a large part of the literature that is devoted to metamorphic petrology of amphiboles concerns reactions which produce amphiboles from more hydrated mafic igneous rocks or lead to the destruction of amphiboles as they break down to form anhydrous or nearly anhydrous mineral assemblages consequently amphiboles can be thought of as occupying the wide intermediate portion of p t xfluid space in which metamorphic rocks are found the number of citations of the published amphibole nomenclature serves as a yardstick meterstick of the interest in amphiboles and a minimum estimate of the amount of literature devoted to this mineral two versions of the nomenclature of amphiboles have appeared 1978 and 1997 leake 1978 leake et al 1997 and they have been cited a over 2300 times in the past 28 years this works out to a minimum

a comment on calcic amphibole equilibria and a new amphibole plagioclase geothermometer by j d blundy and t j b holland contrib mineral petrol 1990 104 208 224 the calibration by blundy and holland is not a calibration of the reaction albite tremolite edenite 4quartz because the aliv content of amphiboles is a combined result of vec tk text vec ed text and vec pl substitutions

tremolite and h 2 o activity attending metamorphism of hornblende plagioclase garnet assemblages estimation of the activity of tremolite component atr in calcic amphiboles is an important problem in igneous and metamorphic petrology because equilibria involving tremolite are used in the estimation of the activity of h2o attending crystallization of igneous and metamorphic rocks estimated values of atr from hornblende analyses using both ionic and coupled substitution crystalline solution models can be compared to values of atr calculated from vapor absent mineral equilibria in addition these values of atr can be used in calculations of ah2o for rocks for which there is an independent estimate of ah2o the values of atr calculated from vapor absent equilibria are generally consistent with those estimated from the different crystalline solution models but uncertainties in the calculations preclude choosing a preferred solution model from computed mineral equilibria it is clear that mineral assemblages with low values of atr can be in equilibrium with high values of ah2o consequently the low values of ah2o estimated from hornblende bearing high grade rocks with low values of atr may be real rocks from mica creek british columbia probably achieved extremely low values of ah2o by vapor absent metamorphism

why rolls are prevalent in the hurricane boundary layer recent remote sensing observations show that the hurricane boundary layer flow although energetic is not a region of homogeneous turbulence in fact the observations convincingly demonstrate that a large fraction of the turbulent flow in the regions away from the deep convective rainbands is highly organized into intense horizontal roll vortices that are approximately aligned with the mean wind and span the depth of the boundary layer these observations show that rolls strongly increase the flux of momentum between the underlying surface and the main body of the storm compared to an equivalent hurricane boundary layer flow without rolls the linear and nonlinear dynamics of hurricane boundary layer roll formation are outlined and it is shown why rolls are in fact the expected basic hurricane boundary layer state the model presented here explains the hurricane roll features currently documented in field programs and makes predictions that can be tested in future experiments the primary effects of rolls on the boundary layer fluxes are inherently nonlocal and nongradient and hence cannot be captured by standard downgradient turbulence parameterizations used in hurricane simulations however the nonlinear theory is the proper starting point for developing boundary layer parameterizations that include roll modification of the turbulent fluxes

genesis of the goshen county wyoming tornado on 5 june 2009 during vortex2 abstractthe genesis of a strong and long lived tornado observed during the second verification of the origins of rotation in tornadoes experiment vortex2 in goshen county wyoming on 5 june 2009 is studied mobile radar mobile mesonet rawinsonde and photographic data are used to produce an integrated analysis of the evolution of the wind precipitation and thermodynamic fields in the parent supercell to deduce the processes that resulted in tornadogenesis several minutes prior to tornadogenesis the rear flank downdraft intensifies and a secondary rear flank downdraft forms and cyclonically wraps around the developing tornado kinematic and thermodynamic analyses suggest that horizontal vorticity created in the forward flank and hook echo is tilted and then stretched near the developing tornado tilting and stretching are enhanced in the developing low level circulation as the secondary rear flank downdraft develops intensifies and wraps around the circulation center shortly thereafter the to

mesozoic alkaline rocks of the averill plutonic complex the 150 ma averill alkaline plutonic complex is situated in southern british columbia within the intermontane belt of the canadian cordillera it comprises concentrically arranged phases of pyroxenite monzogabbro monzodiorite monzonite and syenite gradational changes in the modal composition of the phases contrast with an abrupt change in crystallinity from euhedral mafic minerals in the ultramafic mafic phases to an anhedral interstitial habit for mafic minerals in the syenite whole rock compositions have clear alkaline affinities e g feldspathoid normative and indicate a chemical discontinuity between the ultramafic mafic phases and the late syenite phases melanite garnet is an important accessory mineral of the syenite and is characteristic of silica undersaturated alkaline intrusions clinopyroxene feldspar amphibole biotite melanite and titanite compositions compare closely with those of other alkaline complexes in the western cordillera

the role of evaporating showers in the transfer of sting jet momentum to the surface the most damaging winds in a severe extratropical cyclone often occur just ahead of the evaporating ends of cloud filaments emanating from the so called cloud head these winds are associated with low level jets lljs sometimes occurring just above the boundary layer the question then arises as to how the high momentum is transferred to the surface an opportunity to address this question arose when the severe st jude s day windstorm travelled across southern england on 28 october 2013 we have carried out a mesoanalysis of a network of 1 min resolution automatic weather stations and high resolution doppler radar scans from the sensitive s band chilbolton advanced meteorological radar camra along with satellite and radar network imagery and numerical weather prediction products we show that although the damaging winds occurred in a relatively dry region of the cyclone there was evidence within the llj of abundant precipitation residues from shallow convective clouds that were evaporating in a localized region of descent we find that pockets of high momentum were transported towards the surface by the few remaining actively precipitating convective clouds within the llj and also by precipitation free convection in the boundary layer that was able to entrain evaporatively cooled air from the llj the boundary layer convection was organized in along wind rolls separated by 500 to about 3000 m the spacing varying according to the vertical extent of the convection the spacing was greatest where the strongest winds penetrated to the surface a run with a medium resolution version of the weather research and forecasting wrf model was able to reproduce the properties of the observed llj it confirmed the llj to be a sting jet which descended over the leading edge of a weaker cold conveyor belt jet

thermobarometric and40ar 39ar geochronologic constraints on eohimalayan metamorphism in the dinggye area southern tibet mineral assemblages in the dinggye area of southern tibet 28 n 88 e provide new insights regarding the poorly understood eohimalayan metamorphic event in the eastern himalayan orogen major element partitioning thermobarometry of pelitic rocks indicates temperatures of 750 830 k at depths of 14 3 km consistent with the presence of kyanite sillimanite and andalusite schists in the area laser and resistance furnace40ar 39ar analyses of hornblendes from intercalated amphibolites yield closure ages of 25 ma overlap between the probable range of ar closure temperatures for these hornblendes and the metamorphic temperatures estimated through thermobarometry suggests that eohimalayan metamorphism in the dinggye area occurred in late oligocene time no more than about 10 million years before the main or neohimalayan phase of metamorphism in early to middle miocene time muscovite biotite and k feldspar40ar 39ar ages indicate an important episode of rapid cooling between 16 and 13 ma which is interpreted as a signature of tectonic denudation related to movement on n dipping extensional structures of the south tibetan detachment system

paleoenvironmental reconstruction of a saline lake in the tertiary evidence from aragonite laminae in the northern tibet plateau abstract the origin of aragonite has long been debated because it is precipitated and preserved under specific conditions aragonite laminae first found from eocene to miocene strata in the western qaidam basin northern tibet plateau contain much information on paleolake signatures mineralogical and geochemical analyses were conducted on alternating yellowish and grayish aragonite layers the yellowish layers are mainly composed of aragonite crystals while the grayish layers contain less aragonite and fewer organic remnants that accumulate among debris with sporadic framboidal pyrite the 13c values of yellowish layers are remarkably positive by approximately 4 01 vpdb and the 18o values are slightly negative compared with base data of the qaidam basin considering the 12co2 absorption of algal blooms positive excursions of 13c shown in aragonite indicate high 13c values in depositional water therefore a seasonal algal influenced inorganic origin is proposed to explain the formation of aragonite laminae during warm seasons mg ca ratios are elevated because of evaporation effects the algal blooms decrease the co2 content leading to high ph values these conditions promote the rapid crystal growth of aragonite instead of other carbonate minerals slightly negative 18o values in yellowish layers are interpreted as the result of intense inflow during warm seasons which leads to less precipitation of organic matter and debris the grayish layers in cold seasons are the opposite from the eocene to oligocene the progressively decreasing 18o values of aragonite reflect global cooling during this time a conspicuously positive step in 18o values indicates an arid environment coinciding with the uplift of the himalaya from the oligocene to lower miocene the results from this study show that understanding of aragonite in the qaidam basin is essential to reconstruct the high resolution paleoenvironment and to reveal the tertiary evolution of paleoclimates in the northern tibet plateau

simulation and parameterization of the turbulent transport in the hurricane boundary layer by large eddies 1 hurricane boundary layer hbl processes especially the structure of the coherent large eddy circulations lecs and their induced vertical transport are not well understood this paper introduces a large eddy simulation les framework in a weather hindcasting mode developed from a multiple scale nested weather research and forecasting wrf model using the wrf les this study investigated the structure of the hbl lecs and the associated vertical transport during the landfall of hurricane ivan 2004 the simulation shows that the hbl lecs exist in a mean stable environment and consist of well defined updraft and downdraft statistically the hbl lecs are only slightly skewed with the updrafts and downdrafts relatively evenly distributed spatially the inversion base basically envelopes the upper boundary of lecs the trough in between two adjacent lecs is where most entrainment takes place whereas the crest of the lecs is where boundary layer air detrains out of the hbl in such a way lecs directly connect the surface the hbl and the main body of a hurricane vortex and enhance the exchange of energy moisture and momentum between them it is found that the current boundary layer schemes significantly underestimate the resolved turbulent fluxes due to the fact that the effects of lecs have not been included in the parameterizations on the basis of the statistical structure of lecs simulated by the wrf les this paper proposes a conceptual updraft downdraft model that can potentially be implemented in weather forecasting models to parameterize the fluxes induced by the hbl lec transport

finescale dual doppler analysis of hurricane boundary layer structures in hurricane frances 2004 at landfall abstracttwo doppler on wheels dow mobile radars collected fine spatial scale dual doppler data in the right front quadrant and eye of hurricane frances 2004 as it made landfall near stuart florida a 5 7 km dual doppler baseline established a dual doppler domain south and east of fort pierce florida encompassing a 5 5 km 5 5 km horizontal area with a grid spacing of 20 m allowing for the resolution of subkilometer scale horizontal structures and associated kinematics three dimensional vector wind analyses of the boundary layer revealed the presence of linear coherent structures with a characteristic wavelength of 400 500 m near the surface that increased in size and became more cellular in shape with increasing height average horizontal perturbation winds were proportional to average total horizontal winds within the eye of the hurricane the features lost linear coherency despite a high mean wind speed possibly due to changes in stability a slight decrease in the characteristic wavelength

paleomagnetic and geobarometric study of the mid cretaceous whitehorse pluton yukon territory this is the first of several lithoprobe paleomagnetic studies underway to examine geotectonic motions in the northern canadian cordillera except for one controversial study estimates for terranes underlying the intermontane belt in the yukon have been extrapolated from studies in alaska southern british columbia and the northwestern united states the whitehorse pluton is a large unmetamorphosed and undeformed tonalitic body of mid cretaceous age 112 ma that was intruded into sedimentary units of the whitehorse trough in the stikinia terrane geothermobarometric estimates for eight sites around the pluton indicate that postmagnetization tilting has been negligible since cooling through the hornblende crystallization temperature and that the pluton is a high level intrusion paleomagnetic measurements for 22 of 24 sites in the pluton yield a well defined characteristic remanent magnetization chrm direction that is steeply down and northwards the chrm direction gives a paleopole of 285 5 e 81 7 n

multilevel tower observations of vertical eddy diffusivity and mixing length in the tropical cyclone boundary layer during landfalls abstractthis study analyzes the fast response 20 hz wind data collected by a multilevel tower during the landfalls of tropical storm lionrock 1006 typhoon fanapi 1011 and typhoon megi 1015

using amphibole phenocrysts to track vapor transfer during magma crystallization and transport an example from mount st helens washington abstract in order to evaluate and further constrain models for volatile movement and vapor enrichment of magma stored at shallow levels amphibole phenocrysts from 2004 2005 mount st helens dacite were analyzed for major and selected trace elements li cu zn mn and ree and li isotopes several recent studies have examined fluid mobile trace element abundances in phencryst phases and melt inclusions as a means of tracking volatile movement within subvolcanic magmatic systems and high li contents in plagioclase phenocrysts from 1980 and 2004 mount st helens dacites have been interpreted as evidence that shallow magma was fluxed by a li bearing vapor phase prior to eruption in amphibole phenocrysts zn and mn behave compatibly correlating to feo and al 2 o 3 and show no systematic change with time in contrast li and cu abundances in amphibole vary by up to 3 orders of magnitude 7 6 1140 g g and 1 7 to 94 g g respectively and do not generally correlate with either major or trace elements however they do correlate moderately well r 2 0 54 95 confidence with each other and show systematic temporal variations that are opposite to those observed for plagioclase precluding a simple 1 step diffusion model for li enrichment we propose a diffusion crystallization multi stage dcms model to explain the temporal variations and co variations of li and cu in early erupted dacite october december 2004 profiles of li isotopes in conjunction with measured 7 li intensities and core to rim increases in li concentration are characteristic of li diffusion into the amphiboles consistent with prior models of plagioclase enrichment in amphiboles from 2005 dacite average li and cu concentrations are high 260 660 g g and 29 45 g g respectively and in contrast to amphiboles from earlier erupted dacite correlate weakly with al 2 o 3 wt amphibole al 2 o 3 concentrations are an indicator of pressure with high al amphiboles crystallizing at higher pressures and we suggest that li and cu are partitioned into a fluid phase during ascent and crystallization of the magma so that amphiboles crystallizing at lower pressure have correspondingly lower li and cu concentrations however low li and cu in amphiboles from the dacite at the start of the eruption also require crystallization from a low li cu bearing melt or residence times long enough for amphiboles to re equilibrate with a li cu depleted melt estimated residence times suggest that amphiboles in early dacite could have been present since the end of the 1980 1986 eruptive episode at mount st helens

authigenesis of native sulphur and dolomite in a lacustrine evaporitic setting hellin basin late miocene se spain abundant sulphur is present in the late miocene evaporitic sequence of the lacustrine hellin basin in se spain weathering of triassic evaporites controlled the chemical composition of the miocene lake the lacustrine deposits comprise gypsum marlstones diatomites and carbonate beds sulphur bearing carbonate deposits predominantly consist of early diagenetic dolomite abundant dolomite crystals with a spheroidal habit are in accordance with an early formation and point to a microbial origin the carbon isotopic composition of the dolomite 13 c values between 10 and 4 indicates mixing of lake water carbonate and carbonate derived from the remineralization of organic matter by heterotrophic bacteria dolomite precipitated syngenetically under evaporitic conditions as indicated by high oxygen isotope values 18 o between 6 and 11 nodules of native sulphur are found in gypsum carbonate beds and marlstone layers sulphur formed in the course of microbial sulphate reduction as reflected by its strong depletion in 34 s 34 s values as low as 17 near to the surface many of the sulphur nodules were in part or completely substituted by secondary gypsum which still reflects the sulphur isotopic composition of native sulphur 18 to 10 this study exemplifies the role of bacterial sulphate reduction in the formation of dolomite and native sulphur in a semi enclosed lacustrine basin during late miocene time

nd isotopic study of the neoproterozoic mara rosa arc central brazil implications for the evolution of the brasilia belt abstract the goias magmatic arc is a 0 9 0 64 ga island arc underlying large areas of the western part of the brasilia belt in central brazil it is exposed in two separate sections known as the arenopolis arc in the south and the mara rosa arc in the north it is made of island arc volcanic sedimentary sequences forming narrow nne to nnw belts separated from each other by tonalitic granodioritic granitic orthogneisses all rocks are metamorphosed under upper greenschist to amphibolite facies conditions but have kept major geochemical and isotopic features indicating the juvenile nature of the igneous protoliths the meta igneous and metasedimentary rocks are intruded by a number of late to post orogenic granites e nd 850 ranging from 1 5 to 4 6 with t dm values between 1 0 and 1 1 ga metasedimentary rocks in the mara rosa supracrustal belts display geochemical features suggesting that they represent first cycle immature sediments which preserve chemical characteristics of their igneous sources their nd isotopic characteristics support this interpretation t dm model ages for detrital metasediments are mostly in the interval between 0 9 and 1 2 ga indicating that they are a product of erosion of the arc rocks the absence of older contributions to these sediments seems to indicate an intraoceanic setting this is also suggested by the nd isotopic composition of the 0 8 ga old tholeiitic amphibolites which display positive initial e nd 4 9 indicating derivation from a depleted mantle source syn orogenic deformed granites forming small intrusions within the supracrustal belts have t dm ages ranging from 0 77 to 2 54 ga the older model age values indicate the presence of hidden fragments of ancient crust which were probably tectonically interleaved with younger rocks during accretion of the arc the post orogenic granites are moderately peraluminous and the nd model ages between 1 0 and 1 3 ga indicate that their parental magmas were predominantly re melts of the arc rocks their peraluminous nature reflects the incorporation of substantial amounts of arc sediments in the original magma garnet whole rock sm nd ages for the metasediments may be interpreted to refer to two metamorphic events an older event at 0 76 0 73 ga and a younger event at 604 610 ma mineral chemistry indicate that the older episode was characterized by higher p t and the younger by lower p t the older metamorphic event is interpreted preliminarily as the result of the accretion of island arc terranes to the western edge of the orogen and the younger event as a result of final ocean closure and continental collision between the amazon and sao francisco continents the goias arc formation and accretion is partially coeval with rodinia break up suggesting that the western margin of the sao francisco congo was peripheral in that supercontinent and faced a wide oceanic basin during most of the neoproterozoic

coeval migmatites and granulites muskoka domain southwestern grenville province ontario we present new field observations and petrologic and geochronological data from the muskoka domain in the southwestern grenville province of ontario in an attempt to constrain the relationship between amphibolite facies and granulite facies gneisses in areas of transitional metamorphic grade and to examine their implication for tectonometamorphic models for the grenville province of ontario the predominant medium grained amphibolite facies migmatitic orthogneisses of the muskoka domain contain several generations of leucosome some of which are related to southeast directed extensional structures the amphibolite facies granitoid gneisses contain numerous mafic enclaves with granulite facies assemblages recrystallized from anhydrous precursors during grenvillian metamorphism other associated granulites are characterized by their patchy occurrence and gradational contacts similar to the charnockites in southern india patchy granulites leucocratic vein networks in mafic enclaves and crosscutting leuc

an observational study of hurricane boundary layer small scale coherent structures abstract data with high temporal and spatial resolution from hurricanes isabel 2003 and frances 2004 were analyzed to provide a detailed study of near surface linear structures with subkilometer wavelengths of the hurricane boundary layer hbl the analysis showed that the features were omnipresent throughout the data collection displayed a horizontal and vertical coherency and maintained an average orientation of 7 left of the low level wind a unique objective wavelength analysis was conducted where wavelength was defined as the distance between two wind maxima or minima perpendicular to the features long axis and revealed that although wavelengths as large as 1400 m were observed the majority of the features had wavelengths between 200 and 650 m the assessed wavelengths differ from those documented in a recent observational study to evaluate the correlation between the features and the underlying near surface wind field time and spectral analyses were completed and ground relative freque

characteristics of asbestiform and non asbestiform calcic amphiboles abstract in terms of morphology there are four major types of calcic amphibole massive prismatic finely acicular and asbestos representatives of each of these types have been examined by optical microscopy x ray diffraction scanning and transmission electron microscopy and electron probe microanalysis massive specimens nephrite consist of randomly oriented clusters of fine roughly lath shaped sub microscopic crystals within each cluster the lath lengths z are approximately aligned but neighbouring laths are rotated with respect to one another finely acicular specimens byssolites have well formed crystals bounded mainly by 110 100 and 010 faces and characteristically have striations parallel to their lengths asbestiform varieties range from finer flexible to coarser more brittle specimens and many specimens contain a mixture of fine and coarse fibrils the fibrils in a bundle are aligned parallel to z but are in a range of azimuthal orientations it is inferred that they are formed by multiple independent nucleation and growth parallel to z rather than through parting or cleavage on 110 planes 100 defect or twin planes or on 010 planar defects the 110 cleavage in amphiboles is well reported but 100 features are rarely mentioned in the literature our observations reveal the importance of 100 as a cleavage or parting as well as the tendency in nephrites byssolites and asbestos towards a lath like parallel to z morphology with flattening on 100 in the latter varieties therefore the y direction is that of second fastest crystal growth after z when subjected to moderate grinding the comminution of asbestos fibres proceeds more by separation of fibrils and less by fracturing to shorter lengths as compared with prismatic and byssolite specimens prolonged grinding does however shorten lengths of even the least brittle asbestos transmission electron microscopy revealed extensive sub grain boundaries and dislocation networks suggesting a deformation history in all prismatic and nephrite specimens fine multiple 100 twinning was observed in asbestos but not in other varieties although chain width defects on 010 with visibility enhanced by beam damage were most abundant in nephrites and fibrous tremolites there appears to be no completely consistent relationship between such features and morphological type electron probe analyses showed that specimens that contain more than a very small amount of aluminium do not have asbestiform habit asbestos specimens also have lower contents of mn na and k and have formulae closer to the ideal ca2 mg fe 5si8o22 oh 2 small departures from this in asbestos involve na in the a site compensated by na for ca rather than al for si whereas the reverse is true in byssolites chemical substitutions in prismatic specimens are much less constrained the characteristics of the four morphological sub groups correlate reasonably well with what is known of their geological environments

metasomatism titanian acmite and alkali amphiboles in lithic wacke inclusions within the coyote peak diatreme humboldt county california

on the use of advection correction in trajectory calculations abstractan advection correction procedure is used to mitigate temporal interpolation errors in trajectory analyses constructed from gridded in space and time velocity data the procedure is based on a technique introduced by gal chen to reduce radar data analysis errors arising for the nonsimultaneity of the data collection experiments are conducted using data from a high resolution cloud model 1 cm1 numerical model simulation of a supercell storm initialized within an environment representative of the 24 may 2011 el reno oklahoma tornadic supercell storm trajectory analyses using advection correction are compared to traditional trajectory analyses using linear time interpolation backward trajectories are integrated over a 5 min period for a range of data input time intervals and for velocity pattern translation estimates obtained from different analysis subdomain sizes box widths and first guess options the use of advection correction reduces trajectory end point position errors for a large m

rapid exhumation and mountain building in the western alps petrology and 40ar 39ar geochronology of detritus from tertiary basins of southeastern france 1 tertiary convergence high pressure low temperature hp lt metamorphism and subsequent exhumation in the internal western alps were concurrent with detrital deposition in foreland basins at the external periphery of the orogen in the present work we have probed the geochronology and chemistry of white mica grains and metamorphic pebbles from the foreland basins of se france in order to gain additional perspective on exhumation rates and mountain building processes in the internal domain of the tertiary orogen our data indicate that throughout the tertiary these basins were mainly fed from a relatively low pressure source dominated by si poor micas yielding pre alpine 40ar 39ar ages small amounts of detritus composed of high pressure minerals and pebbles are first detected in early oligocene 30 32 ma strata of the barreme basin the 40ar 39ar geochronology of phengites from garnet blueschist pebbles from these strata yielded 34 3 ma ages indicating rapid ascent and exposure of hp lt rocks in the internal part of the orogen shortly after metamorphism to explain the preponderance of pre alpine micas alongside the rare presence of alpine hp lt detritus we suggest that the general architecture of the western alps whereby inner hp lt metamorphic units are cut off from the se france basins by a low grade lid of brianconnais back thrusts was rapidly built in the early oligocene and did not change significantly since then

an observational case for the prevalence of roll vortices in the hurricane boundary layer abstract doppler velocity data from weather surveillance radar 1988 doppler wsr 88d radars during four hurricane landfalls are analyzed to investigate the presence of organized vortices in the hurricane boundary layer hbl the wavelength depth magnitude and track of velocity anomalies were compiled through analysis of doppler velocity data the analysis reveals alternating bands of enhanced and reduced azimuthal winds closely aligned with the mean wind direction resulting statistics provide compelling evidence for the presence of organized secondary circulations or boundary layer rolls across significant areas during four hurricane landfalls the results confirm previous observations of the presence of rolls in the hbl a potential limitation of the study presented here is the resolution of the wsr 88d data in particular analysis of higher resolution data e g from the doppler on wheels is needed to confirm that data aliasing has not unduly impacted the statistics reported here momentum flux

multiscale analysis of tropical cyclone kinematic structure from airborne doppler radar composites abstractthe multiscale inner core structure of mature tropical cyclones is presented via the use of composites of airborne doppler radar analyses the structure of the axisymmetric vortex and the convective and turbulent scale properties within this axisymmetric framework are shown to be consistent with many previous studies focusing on individual cases or using different airborne data sources on the vortex scale these structures include the primary and secondary circulations eyewall slope decay of the tangential wind with height low level inflow layer and region of enhanced outflow radial variation of convective and stratiform reflectivity eyewall vorticity and divergence fields and rainband signatures in the radial wind vertical velocity vorticity and divergence composite mean and variance fields statistics of convective scale fields and how they vary as a function of proximity to the radius of maximum wind show that the inner eyewall edge is associated with stronger updrafts and higher refl

glendonites in neoproterozoic low latitude interglacial sedimentary rocks northwest canada insights into the cryogenian ocean and precambrian cold water carbonates stellate crystals of ferroan dolomite in neritic siliciclastic and carbonate sedimentary rocks between sturtian and marinoan glaciations in the mackenzie mountains are interpreted as replaced glendonites these pseudomorphs after ikaite indicate that shallow seawater at that time was near freezing stromatolites verify that paleoenvironments were in the photic zone and physical sedimentary structures such as hummocky cross bedding confirm that the seafloor was repeatedly disturbed by storms glendonites within these low latitude continental shelf to coastal sedimentary deposits imply that global ocean water during much of cryogenian time was likely very cold such an ocean would easily have cooled to yield widespread sea ice and through positive feedback growth of low latitude continental glaciers in this situation gas hydrates could have formed in shallow water cold shelf sediment but would have been particularly sensitive to destabilization as a result of sea level change co occurrence of pisolites and glendonites in these rocks additionally implies that some ooids and pisoids might have been unlike phanerozoic equivalents characteristic of cold water sediments