thermal decay of carbonate dimension stones fabric physical and mechanical changes this paper deals with the effects of thermal stresses on selected carbonate rocks used as dimension stones they are mesozoic calcareous and dolomitic rocks cropping out in apulia southern italy that for their physico mechanical and aesthetic properties have always been finding a large application both as ornamental stones and as simple construction materials their use is attested not only in italy in works of archaeological historical and artistic interest too the cause effect relationships of thermal degradation were studied by means of an artificial accelerated ageing test in order to provide a perspective about the decay of carbonate stones due to diurnal and seasonal temperature fluctuations as well as thermal shocks during events of fire development the stone samples were subjected to thermal cycles in a muffle furnace ranging from 100 to 700 c after each cycle several non destructive and semi destructive tests were carried out mass and volume measurements mercury intrusion porosimetry sclerometer tests ultrasonic tests thin section observations and determination of chromatic alterations through image analysis and munsell charts method in this way the qualitative and quantitative modifications induced in fabric physical and mechanical properties were discussed the results highlight the fundamental role of depositional and diagenetic fabric that together with mineralogical composition represents the most significant discriminating factor in the response of the stone to thermal stresses

igneous microstructures in migmatites clear differences between the microstructures of leucosomes and mesosomes occur in some nebulitic migmatites in the proterozoic arunta block central australia the leucosomes show crystal faces of k feldspar microcline microperthite cordierite andalusite and plagio clase against quartz indicating crystallization of a melt in contrast the mesosomes show predominantly polygonal grain shapes modified by 001 crystal faces of biotite and rare crystal faces in some porphyroblasts of garnet cordierite and orthopyroxene indicating re crystallization in the solid state the occurrence of abundant crystal faces in minerals such as feldspar cordierite and andalusite which typically grow crystal faces in magmas but generally not in metamorphic rocks is evidence of former melt therefore igneous microstructures can be preserved in leucosomes that have not undergone penetrative subsolidus deformation and recrystallization the cores of many of the crystals of cordierite and k feldspar have small locally oriented inclusions similar to those in the same minerals in the mesosomes these indicate that the cores remained solid during crystallization of the leucosome which produced inclusion free euhedral rims these crystals provide criteria for recognizing possible restite in granitoid magmas

ig mapper a new arcgis toolbox for the geostatistics based automated geochemical mapping of igneous rocks abstract this work introduces a user friendly fast and effective tool for the automated geochemical mapping of igneous rocks to provide a geospatial representation of petrological parameters through the application of either deterministic or stochastic interpolation techniques the geostatistical approach allows mapping to be extended to areas where igneous rocks are hidden under sedimentary cover also introducing an estimate of the interpolation reliability this new gis based automated procedure which is mostly constructed with the arcgis model builder as a graphical code designer can generate three main types of outputs 1 interpolation maps of major and trace elements isotopic compositions and derived parameters to provide valuable geospatial information regarding the genetic and structural relationships between magmatic bodies 2 lithological maps that are based on the geostatistical interpolation of major element data and mirror the main geochemical classification diagrams of plutonic rocks and 3 interpolation checking maps which provide an estimate of the geostatistical interpolability for one specific parameter at a time this last output is expressed in the form of an empirical index stochastic interpolation index which highlights the randomness level of a specific value distribution this automated lithological mapping function is an entirely new tool based on five original python scripts which makes it possible to interpolate on a georeferenced map the compositions deriving from the most used geochemical classification diagrams this new tool package is presented here by using a portion of the serre batholith in central calabria southern italy to illustrate the potential of this method to open new research perspectives in igneous petrology

multisensor profiling of a concentric gravity wave event propagating from the troposphere to the ionosphere in this paper we present near simultaneous observations of a gravity wave gw event in the stratosphere mesosphere and ionosphere over the south central united states and track it from its convective source region in the troposphere to the ionosphere where it appears as a traveling ionospheric disturbance tid on 4 april 2014 concentric gw ring patterns were seen at stratospheric heights in close proximity to a convective storm over north texas in the atmospheric infrared sounder data on board the nasa aqua satellite concentric gws of similar orientation and epicenter were also observed in mesospheric nightglow measurements of the day night band of the visible infrared imaging radiometer suite on the suomi national polar orbiting partnership satellite concentric tids were seen in total electron content data derived from ground based gps receivers distributed throughout the u s these new multisensor observations of tids and atmospheric gws can provide a unique perspective on ionosphere atmosphere coupling

fabric transitions in the saxony granulite terrain abstract quartz fabric transitions reported from the saxony granulite terrain and from the nearby ore mountains are interesting because of the changes in the pattern types and the variation in the opening angles of the fabric skeletons a short summary is presented of salient features in research documented in the east german literature between 1961 and 1978 the changes in fabric skeleton with decreasing metamorphic grade are proposed as mainly consequent to the deactivation of prism c glide systems as temperature decreases fabrics indicative of the appearance of the c burgers vector might be diagnostic for deformation in regimes of comparatively high temperatures or low strainrates or for deformation under conditions such that there is a relatively high kinetically effective hydroxyl content in the quartz structure

dislocation creep regimes in quartz aggregates abstract using optical and tem microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates depending on the relative rates of grain boundary migration dislocation climb and dislocation production within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization at lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion controlled dislocation climb to be an effective recovery mechanism in this regime recovery is accommodated by strain induced grain boundary migration recrystallization with an increase in temperature or decrease in strain rate the rate of dislocation climb becomes sufficiently rapid to accommodate recovery in this regime dynamic recrystallization occurs by progressive subgrain rotation with a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery however in this regime grain boundary migration is rapid thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation the identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers in addition the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred

microstructural evolution of the serido belt ne brazil the effect of two tectonic events on development of c axis preferred orientation in quartz the polyphase evolution of the serido belt ne brazil includes d crust formation at 2 3 2 1 ga d 2 thrust tectonics at 1 9 ga and crustal reworking by d 3 strike slip shear zones at 600 ma microstructural investigations within mylonites associated with d 2 and d 3 events were used to constrain the tectono thermal evolution of the belt d 2 shear zones commenced at deeper crustal levels and high amphibolite facies conditions 600 650 degreesc through grain boundary migration subgrain rotation and operation of quartz q prism slip continued shearing and exhumation of the terrain forced the re equilibration of high t fabrics and the switching of slip systems from c prism to positive and negative a rhombs during d 3 enhancement of ductility by dissipation of heat that came from syn d 3 granites developed wide belts of amphibolite facies mylonites continued shearing uplift and cooling of the region induced d 3 shear zones to act in ductile brittle regimes marked by fracturing and development of thinner belts of greenschist facies mylonites during this event switching from a prism to a basal slip indicates a thermal path from 600 to 350 degreesc therefore microstructures and quartz c axis fabrics in polydeformed rocks from the serido belt preserve the record of two major events which includes contrasting deformation mechanisms and thermal paths c 2003 elsevier ltd all rights reserved

concentric traveling ionosphere disturbances triggered by super typhoon meranti 2016 concentric traveling ionosphere disturbances ctids in total electron content tec triggered by super typhoon meranti on 13 september 2016 are detected using the ground based global navigation satellite system gnss network in taiwan the ctids emanated outwards before the typhoon landfall and lasted for more than 10 hours the characteristics of ctids agree with the gravity wave theory and exhibit spatial and temporal scales in wave periods of 8 30 minutes horizontal wavelengths of 160 200 km and horizontal phase velocities of 106 220 m s we also observe the ctids showing the stationary wave character broad spectra of ctids are excited after the rainbands of typhoon impinged on central mountain range cmr of taiwan the ray tracing technique confirms that the ctids were excited by convective clouds spiral rainbands and the eyewall of typhoon meranti this study provides new evidence of typhoon induced concentric gravity waves in the ionosphere

assessment of the european standard for the determination of resistance of marble to thermal and moisture cycles recommendations for improvements the bowing phenomenon is so relevant that two projects eu funded from 1999 studied it and a european standard to assess the resistance to thermal and moisture cycles influencing bowing has been recently adopted in particular according en 16306 2013 measurements of bowing and flexural strength should be performed before and at the end of the ageing cycles additional non destructive tests are recommended but are not compulsory for the standard moreover annex a of en 16306 contains guidance on the limit values for the selection of marble types suitable for outdoor uses especially facade applications eleven varieties of marble have been tested by means of this laboratory ageing test non destructive tests such as the measurements of ultrasonic pulse velocity upv adjacent grains analysis open porosity and water absorption have been executed together with the conventional flexural strength test the results obtained from image analysis on thin sections indicate that the aga index may not always be correlated with the other tests amount of bowing loss of flexural strength or loss of upv some consideration of the decrease in mechanical resistance and the bowing in relation to the variety of marble tested and the limit values indicated in annex a of en 16306 can be noted it is known that bowing and rapid strength loss occur in some varieties of marble when used as exterior cladding and other exterior applications additional conclusions have been drawn bowing and flexural strength correlate well and can be used to assess the suitability of the marble to be employed in outdoors

quartz preferred orientation in naturally deformed mylonitic rocks montalto shear zone italy a comparison of results by different techniques their advantages and limitations in the geologic record the quartz c axis patterns are widely adopted in the investigation of crystallographic preferred orientations cpo of naturally deformed rocks to this aim in the present work four different methods for measuring quartz c axis orientations in naturally sheared rocks were applied and compared the classical universal stage technique the computer integrated polarization microscopy method cip the time of flight tof neutron diffraction analysis and the electron backscatter diffraction ebsd microstructural analysis and cpo patterns of quartz together with the ones obtained for feldspars and micas in mylonitic granitoid rocks have been then considered to solve structural and geological questions related to the montalto crustal scale shear zone calabria southern italy results obtained by applying the different techniques are discussed and the advantages as well as limitations of each method are highlighted importantly our findings suggest that patterns obtained by means of different techniques are quite similar in particular for such mylonites a subsimple shear 40 simple shear vs 60 pure shear by shape analysis of porphyroclasts was inferred a general tendency of an asymmetric c maximum near to the z direction normal to foliation suggesting dominant basal slip consistent with fabric patterns related to dynamically recrystallization under greenschist facies is recognized rhombohedral slip was likely active as documented by pole figures of positive and negative rhombs tof which reveal also potential mechanical dauphine twinning results showed that the most complete cpo characterization on deformed rocks is given by the tof from which also other quartz crystallographic axes can be obtained as well as various mineral phases may be investigated however this use is restricted by the fact that a there are very few tof facilities around the world and b there is loss of any domainal reference since tof is a bulk type analysis ebsd is a widely used technique which allows an excellent microstructural control of the user covering a good amount of investigated grains cip and us are not expensive techniques with respect the other kind of investigations and even if they might be considered obsolete and or time consuming they have the advantage to provide a fine and grain by grain first round inspection on the investigated rock fabric

displacement and strain patterns from naturally occurring shear zone terminations abstract strain distribution patterns are described from several naturally occurring ductile shear zone terminations and a two fold classification is suggested type i termination patterns show a symmetrical decrease in strain area and intensity and are associated with very low shear strain values in the main shear zone the more common type ii termination patterns show a symmetrical increase in strain area with decrease in strain intensity some brittle ductile examples of type ii terminations contain secondary shears that resemble splay faults all the available evidence suggests that the deformation near the terminations of these shear zones is not plane strain nor do the observed strain patterns readily fit the existing theoretical models

strain and shape fabric variations associated with ductile shear zones abstract the foliated and compositionally banded granitic orthogneisses in the central core of the maggia nappe a lower pennine basement nappe of the central swiss alps are shown to be the sheared equivalent of late hercynian age granitic intrusions these ductile shear zones show mineral assemblages in amphibolite facies are alpine in age and form an anastomosing network enclosing remnant lozenge shaped pods of relatively undeformed rock the foliation developed within the shear zones concomitantly with a change in shape of quartz grain aggregates from initially equidimensional through tear drop shapes to ribbon like aggregates these shape changes occurred by intracrystalline glide together with intercrystalline slip on deformation induced planar surfaces

the rheology of polymineralic rocks an approach deduced from empirical and theoretical work a model is proposed for the rheology of bi and polyphase rocks based on the rheology of the components their volume fractions and their geometrical distribution the model is formulated for the common case where some minerals deform by crystall plasticity at steady state and others stronger ones deform in the vincinity of the brittle ductile transition

microfabric study on the deformational and thermal history of the alpi apuane marbles carrara marbles italy marbles from different geometrical and structural positions within the alpi apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure c axis orientation and temperature analysis statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80 100 m to 250 300 m this is correlated with an equilibration calcite dolomite temperature from 360 380 c to 420 430 c two kinds of dynamically recrystallized microstructures have been investigated a first one exhibiting coarse grains 150 200 m with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size 40 50 m and predominantly straight grain boundaries these microstructural types associated with localized post thermal peak shear zones and meter to kilometer scale folds are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms dislocation creep associated with predominant grain boundary migration type b1 or subgrain rotation recrystallization type b2 these differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type b1 390 c than in type b2 370 340 c we have been able to relate the development of the different microfabric types to the successive stages of deformation of the alpi apuane metamorphic complex

quantitative microstructural analysis of mylonites formed during alpine tectonics in the western mediterranean realm abstract quantitative microstructural investigations involving new gis based tools are applied to three different types of mylonitic rocks these techniques enable mineral shape distribution maps to be produced thereby allowing the nature and relative percentage of the weakening vs hardening layers as well as their kinematics to be obtained within a statistically meaningful dataset selected rock types are derived from shearing associated with the meso alpine strike slip tectonics of the western mediterranean realm which since the paleocene has involved skarn migmatitic paragneiss and tonalites these rocks belong to a deep seated portion of the original southern european variscan chain known as the calabrian pelortani orogen microstructural maps reveal porphyroclastic domains represented alternatively by feldspar amphibole pyroxene or scapolite that can be distinguished from weakening phase areas characterised by quartz biotite plus quartz or alternatively by calcite when the weakening layer is controlled predominantly by skarns image elaboration of porphyroclastic domains was employed to estimate the dominant shear type with rigid grain analysis indicating a pure shear component of 66 68 for the mylonitic tonalites 62 66 for the mylonitic paragneisses and 58 62 for the mylonitic skarn grain boundary mapping of the quartz rich domains also permits an estimate of shear strain rate which ranges from 1 14 10 12 1 s for mylonitic paragneiss to 5 91 10 12 1 s for mylonitic tonalite and is in accord with high strain zones in natural settings finally our results opened up new perspectives in the interpretation of the kinematics and rheology of this exhumed sector of the southern european variscan chain reflecting the deep seated meso alpine strike slip tectonics of the western mediterranean realm

concentric gravity waves in the mesosphere generated by deep convective plumes in the lower atmosphere near fort collins colorado 1 gravity waves in the mesopause region 80 105 km may induce perturbations in oh meinal band emissions at 87 km these perturbations can be observed by ground based oh airglow imagers in this paper we present observations of concentric gravity waves cgw by the all sky oh imager at yucca ridge field station 40 7 n 104 9 w near fort collins colorado we find that expanding rings of concentric gravity waves were observed on 9 out of 723 clear nights from 2003 to 2008 in particular on 11 may 2004 concentric rings were observed for 1 5 h with nearly perfect circular rings entirely in the field of view during the first 30 min the centers of the concentric rings occurred at the geographic locations of two strong convective plumes which were active in the troposphere 1 h earlier we measured the horizontal wavelengths and periods of these gravity waves as functions of both radius and time these results agreed reasonably well with the internal boussinesq gravity wave dispersion relation with an assumed zero background wind similarly for the other 8 cases strong convective plumes occurred prior to the cgw observations near the apparent center of each of the arcs or rings for the 7 out of the 9 cases radiosonde data were available up to z 30 35 km these data showed that the wind speeds from the tropopause to 30 35 km were smaller than 20 30 m s because 8 of the 9 cases occurred when the total horizontal mean winds were weak and because the horizontal winds below 87 km were less than 20 m s on 11 may 2004 according to radiosonde and time gcm model data we postulate that weak background horizontal winds are likely a necessary condition for gravity waves excited from convective overshooting to be observed as concentric arcs or rings in the oh layer

medium scale traveling ionospheric disturbances triggered by super typhoon nepartak 2016 two remarkable typhoon induced traveling ionospheric disturbances tids with concentric and northwest southeast nw se alignments respectively associated with concentric gravity waves cgws and ionosphere instabilities possibly seeded by cgws were observed in total electron content tec derived from ground based gnss networks in taiwan and japan when the category 5 super typhoon nepartak approached taiwan on 7 july 2016 the concentric tids ctids first appear with horizontal phase velocities of 161 200 m s horizontal wavelengths of 160 270 km and periods of 15 22 min during 08 00 11 20 ut following the ctids the nw se aligned nighttime medium scale tids mstids are formed on the west edge of the ctids over the taiwan strait during 11 30 14 00 ut it is suggested that the mstids are produced by the electrodynamical coupling of perkins instability and cgw induced polarization electric fields this study proposes connections of typhoon induced ctids and subsequently occurring mstids in the low latitude ionosphere

anelastic processes and stress transfer from shallow to deep fault regions abstract post seismic displacement and strain fields after a major strike slip earthquake are studied in terms of the stress taking place at depth over localized mylonitized shear belts the coseismic stress field produced by the earthquake is represented in terms of crack theory and its post seismic relaxation is studied in terms of a crack model for creep processes recently proposed in the geophysical literature the existence of a sequence of relaxation times which are roughly reciprocal integer numbers and the faster relaxation of stronger stress heterogeneities are shown to be responsible for features of the deformation field observed at the free surface in the post seismic phase deformation becomes progressively slower as to relaxation times and its wavelength becomes accordingly longer similar features are also shown by viscoelastic models of the lithosphere asthenosphere system in which anelastic processes are entirely due to transient post earthquake flow in the asthenosphere the two possibilities are discussed and a major role of intracrustal stress relaxation in the postseismic phase is proposed

turbulent upwelling of the mid latitude ionosphere 2 theoretical framework in a companion paper data from the mu radar have been presented which show that during sunspot minimum conditions in japan the mid latitude ionosphere is sometimes characterized by regions of rapid and turbulent upwelling in this paper we explore possible mechanisms for these events the most likely process seems to be the instability of the equilibrium which occurs when the mid latitude plasma is supported against gravity either by an eastward electric field component or by a southward neutral wind as was proposed by perkins 1973 we show for example that the growth rate determined by perkins is considerably higher in sunspot minimum conditions than at sunspot maximum for comparable altitudes of the ionospheric f layer the growth rate is not very large however and we argue here that the observed structures must evolve from preexisting undulations of the bottomside of the f region which are generated by gravity waves that is the gravity waves create finite amplitude structures which are amplified by the plasma instability an intriguing feature of the gravity wave role in this process is that the echoing patches detected by the mu radar and the height bands detected by the arecibo radar which we believe to be related phenomena all seem to propagate to the west this is the same direction reported for the angle of arrival measurements of classic mid latitude spread f by a number of researchers using ionosonde techniques since the mu radar detects the upwelling regions from nonthermal 3 m irregularities there must be mechanism to create such tracers we propose that secondary structures are created at intermediate scales via the e b instability operating on the dome of the upwelling structure and by the neutral wind driven process on either the west or the east wall of the structure depending on the direction of the zonal wind the 3 m waves are then created in a cascade process which brings energy into a range of k space in which the structures are linearly damped finally we discuss the fine structure of the echoing patches and suggest several plausible mechanisms two of which involve e region coupling and one which deals with the vertical structure of the gravity wave seeding process

discontinuous grain growth in recrystallised vein quartz implications for grain boundary structure grain boundary mobility crystallographic preferred orientation and stress history abstract grain growth is a process driven by the reduction of interfacial free energy leading to an increase in grain size and a reduction of the number of grains in a given volume of a single phase polycrystalline material discontinuous grain growth dcgg as opposed to normal grain growth ngg involves just a few grains blasts growing at the expense of a matrix that itself undergoes much slower modification in grain size hence producing a bimodal grain size distribution as a transient state prior to impingement of the blasts such a transient state has been found in a quartz layer in metamorphic rocks of the sesia zone western alps there large strain free quartz grains occur that reveal concave outward grain boundaries against a matrix of small grains with a pronounced crystallographic and a weak dimensional preferred orientation the misorientation of the blasts with respect to the matrix grains systematically exceeds 30 this finding suggests that the mobility of high angle grain boundaries in a natural quartzite depends on the degree of their misorientation among other factors as known for metals and alloys the width of the grain boundaries must be sufficiently small to allow for this effect dcgg is promoted by a pronounced crystallographic preferred orientation cpo that leaves only a few grain boundaries with sufficient misorientation to be mobile in contrast to ngg dcgg wipes out any pre existing cpo and information on activated glide systems or kinematics during the preceding stage of flow is lost after dcgg has gone to completion a complementary new cpo could even develop that could be difficult to interpret with respect to tectonic history interfacial free energy driven grain growth reflects a period of low stress annealing and thus constitutes a first order signal

the effects of a meso alpine collision event on the tectono metamorphic evolution of the peloritani mountain belt eastern sicily southern italy

simultaneous observations of convective gravity waves from a ground based airglow imager and the airs satellite experiment 1 we report the first joint observations of convectively generated gravity waves gws using an oh airglow imager in colorado and the atmospheric infrared sounder airs onboard the aqua satellite convective gws appearing as concentric rings are observed over the western great plain regions of north america in the evening of 3 june 2008 in the airglow images inspecting both weather radars and airs radiances at 8 1 m strong convective clouds are found near the center of the concentric rings the airs data at 4 3 m show semicircular gws with horizontal wavelengths of 60 80 km at 0900 ut whereas the airglow imager observed circular gws with horizontal wavelengths of 44 km and airglow emission perturbation of 6 at the same geographic location at 0910 ut large scale gws horizontal wavelengths greater than 100 km emanating northwestward can be seen in both airs data and airglow images at different times the imager observed small scale ripples associated with unstable concentric gws in the mesopause in the early evening given that the brightness temperature perturbation of the gws in the airs data is about 0 16 k and assuming that the gws propagate without dissipation from the stratosphere to the upper mesosphere the expected airglow emission perturbation caused by the gws would be 4 17 ray tracing simulations are performed to demonstrate that the gws seen in airs and in the imager were likely excited by the same convective system

microstructural investigation of naturally deformed leucogneiss from an alpine shear zone southern calabria italy in order to reveal any correlation between the preferred orientation of quartz and progressive intensity of strain a suite of deformed leucogneiss collected within a ductile shear zone outcropping in calabria southern italy was investigated based on the microstructural approach and matrix clast relationships the method applied here may be useful for appraising the connection between deformation mechanisms of constituent minerals and bulk textural properties of naturally sheared rocks accordingly quartz c axis orientation patterns were determined by image assisted analysis results revealed a correlation between finite strain and textural features as strain increases the matrix develops at the expense of the clast counterpart which is instead progressively reduced in both size and amount

nucleation growth and structural development of mylonitic shear zones in granitic rock abstract well exposed shear zones in granitic rock of the sierra nevada are preserved in various degrees of development facilitating interpretation of the mechanisms of shear zone nucleation and growth field relations suggest that these shear zones formed by shear localization within pre existing aplite dikes that served as tabular zones of inherent weakness crossing dikes provide a measure of the offset at several points along the shear zones apparently the shear zones grew in width as they accumulated offset and propagated longitudinally by end to end linkage of approximately coplanar aplite dike segments propagation caused discontinuous dikes or dike segments to be joined giving the shear zones a forked or eye shaped trace pattern some shear zones have developed opening fractures at their tips analogous to the splay fractures that form near the tips of small faults these shear zones provide an excellent opportunity to study the processes involved in natural shear zone formation in granitic rocks where shear is localized along pre existing zones of inherent weakness they may serve as useful analogs for the growth and development of larger scale faults that involve ductile shearing

flame perthite in metapelitic gneisses at cooma se australia flame perthite occurs locally in high grade migmatitic gneisses of pelitic composition at cooma se australia it is developed best in leucosomes and rocks in which cordierite is largely unaltered such rocks are inferred to have been stronger than more altered rocks causing local stress concentrations sufficient to promote the nucleation of flames the variability in the abundance of flames could be due to variability in stress concentrations in relation to orientation of the microperthite grains if the pryer robin model for flame perthite is applicable to these rocks possible sources of na are 1 release of na as cordierite and potassium feldspar were replaced by biotite andalusite quartz symplectite at upper amphibolite facies conditions and 2 release of na as microperthite was replaced by muscovite both these reactions appear to have occurred at amphibolite facies conditions because late fibrous sillimanite has replaced all minerals including myrmekite albite flames and much of the muscovite conceivably some muscovite that has not been replaced by sillimanite may have formed at greenschist facies conditions alteration of plagioclase does not appear to have been a major source of na for the flames because plagioclase is absent from many of the cooma metapelitic rock and where present is unaltered

observations of electric fields associated with internal gravity waves 1 at the jicamarca radio observatory the vertical drift component yields a very accurate measure of the eastward electric field occasionally this drift component displays a downward phase progression evidence for a relationship to a gravity wave we examined the jicamarca database for events of this type and made an attempt to determine the properties of the associated waves the only measurables we have are the amplitudes the frequency in the earth fixed frame and the vertical wavelength in order to avoid shorting by the current along magnetic field lines we argue that the propagation must be close to pure zonal we then use measurements or models of the zonal plasma drift and argue that the zonal wind should be in the same direction and about 15 higher using this estimate we then determine the frequency in the wind frame by solving the dispersion relation for gravity waves and the doppler shift equation simultaneously typical values for the horizontal wavelength vertical wavelength and period in the wind frame are 600 km 350 km and 25 min respectively the typical gravity wave induced vertical drift perpendicular to b in these events is a few meters per second this is marginal at best for seeding the rayleigh taylor instability however larger amplitude events may be masked by the development of the plumes themselves all but two events found thus far occurred at night but the daytime cases are fascinating since the e region is expected to short out such fields

evolution of c axis pole figures and grain size during dynamic recrystallization results from experimentally sheared quartzite 1 quartzite samples experimentally sheared at conditions where subgrain rotation and grain boundary migration recrystallization are active show a striking change in the c axis crystallographic preferred orientation cpo with increasing shear strain up to 8 and degree of recrystallization up to 100 we used optical methods to determine the c axis cpo for the bulk samples and for porphyroclasts and recrystallized grains separately and to track the strengths of the cpos in five different orientation domains with increasing the c axis pole figure evolves from a broad peripheral maximum indicative of basal a slip to an inclined single girdle with two maxima indicative of rhomb a slip and finally an elongate single maximum at the girdle center indicative of prism a slip throughout this sequence the fabric skeleton rotates with the sense of shear the bulk preferred c axis orientation results from growth and shrinkage of differently oriented crystallographic domains grain boundary density analysis indicates that the size of prism a recrystallized grains is 1 5 times that of average and 2 times that of rhomb grains indicating that prism a slip is significantly easier at our experimental conditions this inference is supported by autocorrelation function analysis of the various orientation domains and how they evolve with strain similar progressive changes in c axis cpo are observed in quartzites naturally sheared at conditions where grain boundary migration recrystallization operates these results indicate that achievement of microstructural and mechanical steady state requires high strain and complete recrystallization

prism and basal plane parallel subgrain boundaries in quartz a microstructural geothermobarometer empirical data on quartz subgrain patterns from various metamorphic rocks show that at least up to 10 kbar in the stability field of low quartz prismatic subgrain boundaries are dominant whereas basal subgrain boundaries are not developed in the high quartz stability field both prismatic and basal subgrain boundaries occur and form typical rectangular chessboard patterns the likely reason behind the different occurrence of these subgrain patterns is that in high quartz prismatic glide becomes as easy as or probably even easier than basal glide the two types of subgrain patterns can be clearly distinguished by optical microscopy consequently the occurrence of chessboard subgrain patterns in quartz represents a practicable geothermobarometer the possibilities of its application are far reaching and include the specification of deformation conditions at high grade metamorphism the recognition of syntectonic intrusions and the distinction between pluton emplacement at lower and at higher crustal levels

timescales and mechanisms of batholith construction constraints from zircon oxygen isotopes and geochronology of the late variscan serre batholith calabria southern italy abstract the late variscan serre batholith in central calabria represents the middle portion c 13 km thick of a tilted crustal section continuously exposed from lower crustal granulites to upper crustal phyllites the batholith is zoned consisting of several granitoid types that were emplaced at depths ranging from c 23 to c 6 km deep strongly foliated quartz diorites and tonalites were emplaced into migmatitic metapelites the intermediate level granitoids are weakly foliated to unfoliated porphyritic granodiorites and monzogranites and the shallowest bodies are two mica granodiorites and granites grading upward to biotite amphibole granodiorites emplaced into paragneisses and phyllites five samples representative of the main granitoid types in terms of both composition and emplacement depth have been dated by shrimp zircon from a lower crustal quartz diorite gave an emplacement age of 297 3 3 1 ma two middle crustal strongly peraluminous k feldspar megacrystic granites were emplaced at 296 1 1 9 ma and 294 9 2 7 ma a middle to upper crustal two mica monzogranite was emplaced at 294 2 2 6 ma and finally an upper crustal weakly peraluminous granodiorite from the batholith roof was emplaced at 292 2 2 6 ma these results are consistent with the development of the batholith by incremental multipulse overaccretion each granitoid body being in a dominantly rigid state before intrusion of the next with little or no possibility of magma mixing the difference in age between the oldest and youngest granitoids from the batholith floor and roof respectively is 5 1 4 0 ma providing an upper limit of about 9 ma on the time taken for batholith construction the presence in the c 296 294 ma granitoids of c 305 302 ma anatectic zircon with varied th u and oxygen isotope compositions indicates a time interval of 8 9 ma between incipient partial melting in the lower crust and magma emplacement in the middle crust the emplacement of the first granitoid bodies into the top of the lower crust was controlled tectonically by the activation of a deep seated shear zone the shallowest granodiorites were emplaced during the waning stages of the shear zone activity producing late to post tectonic contact metamorphism in the upper crustal phyllites and mylonitic paragneisses

concentric waves and short period oscillations observed in the ionosphere after the 2013 moore ef5 tornado 1 we detected clear concentric waves and short period oscillations in the ionosphere after an enhanced fujita scale ef 5 tornado hit moore oklahoma u s on 20 may 2013 using dense wide coverage ionospheric total electron content tec observations in north america these concentric waves were nondispersive with a horizontal wavelength of 120 km and a period of 13 min they were observed for more than 7 h throughout north america tec oscillations with a period of 4 min were also observed to the south of moore for more than 8 h a comparison between the tec observations and infrared cloud image from the goes satellite indicates that the concentric waves and short period oscillations are caused by supercell induced atmospheric gravity waves and acoustic resonances respectively this observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere

medium scale traveling ionospheric disturbances induced by typhoon chan hom over china this paper reports the ionospheric response to typhoon chan hom using global positioning system network data from china combined with observations of an ionosonde chain two medium scale traveling ionospheric disturbances mstids were observed around the two landing times of typhoon chan hom the mstid with a phase fronts aligned in the north south direction was detected on the east coast of china at 16 50 18 40 ut on 11 july 2015 and moved westward with a mean horizontal phase velocity of 268 m s and period of 56 min then the concentric mstid appeared on the northeast of china at 01 50 05 10 ut on 13 july 2015 and propagated in the radial direction with average horizontal phase velocity of 143 m s and period of 45 min there may be some connections between the north south aligned mstid and the electrodynamical coupling of the sporadic e layer and the f layer while the concentric mstid may be caused by the concentric gravity waves resulting from the bodyforces related with the typhoon

hydrogeochemical study of an ophiolitic aquifer a case study of lago southern italy calabria a hydrogeochemical survey was carried out in the area of lago calabria region southern italy and outcropping geological units were classified from the hydrogeological point of view to explain the evolution of local groundwaters in addition reaction path modeling was performed to simulate the evolution of groundwaters upon interaction with local metabasalts phyllites and serpentinites by means of the eq3 6 software package version 8 0 simulations were carried at constant temperature of 14 1 c which reproduces the average temperature of local groundwaters three different simulations have been performed for the average metabasalt fixing the fugacity of co2 at either 10 2 4 bar mean value 10 2 0 bar mean value 1 or 10 2 9 bar mean value 1 the simulation for the average serpentinite and phyllite was carried out at the mean value of the fugacity of co2 10 2 4 bar all evidences acquired in this study namely the hydrogeological framework the chemical analysis of local groundwaters and the results of reaction path modeling consistently point out that groundwater circulation under ordinary hydraulic gradient primarily occurs in the ophiolitic sub complex and that dissolution of metabasalts and serpentinites controls the chemical characteristics of the groundwaters from the study area

engineering geological properties of leitha limestone from historical quarries in burgenland and styria austria abstract this research has focused predominantly on assessing the most important physical and mechanical properties of leitha limestone rock samples and of a separate oolitic limestone sample in conjunction with sedimentological and microfacies analyses the microfacies characteristics of these samples together with their other technical properties help to explain why the leitha limestone is an important material for monuments and for restoration work rock samples for laboratory tests were collected from 12 sites located within alpine neogene basins samples for the assessment of rock properties were taken from abandoned quarries in the kaisersteinbruch bruckneudorf military area from abandoned and active quarries at st margarethen and from the aflenz underground quarry to broaden the scope of the investigations previous research results from quarries at st margarethen mannersdorf wolfsthal and hundsheim were also included thin sections were made from one of the drill cores from each quarry the microfacies analysis of the leitha limestone samples indicated a spectrum from encrusting coralline algae boundstones to coralline algae grainstones and rudstones and also included variable quantities of other bioclasts and siliciclasts the detailed results revealed considerable differences between the various samples which are considered to be from a shallow marine intertidal to subtidal paleoenvironment with variable hydrodynamic conditions the rock quality and durability were assessed through laboratory testing of physical and mechanical properties including measurements of real and apparent density porosity water absorption capacity uniaxial compressive strength ucs for both dry and water saturated rock samples and for samples following repeated freeze thaw cycles the coefficient of softening and the coefficient of freezing all investigated rock samples had different porosities and absorption capacities they also differed in their ucs values which were very variable but mostly belonged to the weak rock category ucs below 50 mpa five of the tested rock samples had higher ucs values and were consequently ranked in the firm rock category the microfacies investigation proved to be a valuable tool for interpreting the measured engineering geological properties in particular the porosity and rock strength

structural analysis of mylonitic rocks in the cougar creek complex oregon idaho using the porphyroclast hyperbolic distribution method and potential use of sc type extensional shear bands as quantitative vorticity indicators abstract mylonitic rocks of the cougar creek complex of northeastern oregon and west central idaho provide an opportunity to document the deformational structures produced during general non coaxial shear within quartz feldspar mylonites and to explore the potential role of sc type extensional shear bands in vorticity analysis well developed feldspar porphyroclasts within six mylonite zones were utilized to estimate bulk kinematic vorticity w k using the porphyroclast hyperbolic distribution phd method w k values for the cougar creek mylonites range from w k 0 26 to w k 0 37 synthetic and antithetic shear band inclinations were measured relative to observed shear zone boundaries within five mylonite zones with estimated w k values and compared to the non coaxial flow field geometries and eigenvector orientations in each mylonite zone synthetic sc type shear band populations exhibit a range of inclination with maximum inclination lying approximately parallel to the acute bisector ab of the eigenvectors similarly antithetic shear band populations show a range of inclination near the obtuse bisector ob of the eigenvectors we infer that sc type extensional shear bands form initially parallel to ab and ob and rotate towards the flow plane with progressive deformation decreasing their inclination relative to the shear zone boundary ab and ob have significance in the strain field in that they represent orientations of maximum angular strain rate thus planes perpendicular to ab and ob are mechanically favorable for small zones of localized simple shear shear bands within the heterogeneous bulk strain of the mylonite orientation analysis of populations of sc type shear bands may provide a direct quantitative means of estimating w k

late cretaceous age of fractures in the sierra nevada batholith california regional sets of steeply dipping joints and faults are common throughout the sierra nevada batholith yet relatively little is known about how or when they formed within some east northeast striking left lateral fault zones in the mount abbot quadrangle of the central sierra nevada the host granodiorite is hydrothermally altered to a lower greenschist assemblage that contains muscovite the muscovite yields a mean k ar and sup 40 ar sup 39 ar age of 79 ma which provides a minimum age for the faulting field relations show that these faults developed from earlier formed mineralized joints so these ages also provide a minimum age for the jointing published ages of biotite hornblende and zircon from the host granodiorite of lake edison are 80 ma k ar 85 ma k ar and 90 ma u pb respectively the geochronology field relations and hydrothermal mineral assemblages together suggest that the mineralized joints and faults all formed between 85 and 79 ma soon after the host pluton was emplaced

microstructural compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone rhodope core complex greece at the southern boundary of the rhodope massif ne greece the kavala shear zone ksz represents an example of the eastern mediterranean deep seated extensional tectonic setting during miocene time extensional deformation favoured syntectonic emplacement and subsequent exhumation of plutonic bodies this paper deals with the strain related changes in macroscopic geochemical and microstructural properties of the lithotypes collected along the ksz comprising granitoids from the pluton aplitic dykes and host rock gneisses moreover we investigated the evolution of seismic anisotropy on a suite of granitoid mylonites as a result of progressive strain isotropic compressional and shear wave velocities v p v s and densities calculated from modal proportions and single crystal elastic properties at given pressure temperature p t conditions are compared to respective experimental data including the directional dependence anisotropy of wave velocities compared to the calculated isotropic velocities which are similar for all of the investigated mylonites average values v p 5 87 km s 1 v s 3 4 km s 1 v p v s 1 73 and density 2 65 g cm 3 the seismic measurements give evidence for marked p wave velocity anisotropy up to 6 92 at 400 mpa in the most deformed rock due to marked microstructural changes with progressive strain as highlighted by the alignment of mica chlorite minerals and quartz ribbons the highest p and s wave velocities are parallel to the foliation plane and lowest normal to the foliation plane importantly v p remains constant within the foliation with progressive strain but decreases normal to foliation the potential of the observed seismic anisotropy of the ksz mylonites with respect to detectable seismic reflections is briefly discussed

mesospheric concentric gravity waves generated by multiple convective storms over the north american great plain 1 we report on six continuous hours of oh airglow imager observations at z 87 km of convectively generated gravity waves gws near fort collins colorado on the evening of 08 september 2005 these gws appeared as nearly concentric rings and had epicenters near the locations of deep convection in three thunderstorms in colorado nebraska and south dakota using goes satellite and weather radar observations we show that the gws closely follow the thunderstorms using the background wind from a nearby radar the intrinsic wave parameters and vertical wavelengths are calculated the temperature perturbations are estimated to be t t 1 3 for gws with horizontal wavelengths h 20 40 km and horizontal phase speeds 40 60 m s the horizontal wavelengths of gws from a convective cluster decreased in time from 30 to 15 km we employ convective plume and ray trace models to simulate the gw induced oh intensity perturbations from convective plumes clusters and complexes we find that the results using the background model wind radiosonde time gcm agree well with the late time observations when the images are dominated by southwestward short wavelength high frequency gws these late time gws propagate against the background wind and have h 30 40 km and periods of 20 30 min the oh intensity perturbations are enhanced because the vertical wavelengths z increased t t increased and the vertical velocity perturbations w decreased because the gws were near their reflection levels we also find that these short wavelength gws were created 5 h earlier by an extremely energetic deep convective plume in south dakota thereby showing that small scale convective gws directly link the troposphere and mesopause region

statistical study of nighttime medium scale traveling ionospheric disturbances using midlatitude airglow images 1 we have investigated statistical characteristics of the nighttime medium scale traveling ionospheric disturbances mstids observed in 630 nm airglow images at two stations rikubetsu 43 5 n 34 8 mlat and shigaraki 34 9 n 25 4 mlat in japan for 1998 2000 near the solar maximum period most of the observed mstids propagate southwestward in the images the typical wavelength velocity period and amplitude are 100 300 km 50 100 m s 0 5 1 5 h and 5 15 respectively seasonal variations in these parameters are not clear the occurrence rate has a major peak 50 60 in summer that appears 2 months earlier at lower latitudes and a minor peak in winter similar occurrence characteristics are obtained from midlatitude spread f signatures using multipoint ionosonde data in japan though the coincidence of the spread f and the mstids in airglow images is only 10 15

medium scale traveling ionospheric disturbances detected with dense and wide tec maps over north america 1 nighttime and daytime medium scale traveling ionospheric disturbances mstids are detected with dense and wide detrended total electron content tec maps over north america using multiple gps receiver networks the tec maps cover a wide region of 60 130 w and 24 54 n 30 65 n in geomagnetic latitude and have a spatial resolution of 1 05 1 05 in latitude and longitude 0 15 0 15 with 7 7 pixel smoothing and a temporal resolution of 30 seconds the tec maps reveal for the first time that the nighttime mstids propagate southwestward with 200 500 km wavelengths over north america and have wavefronts longer than 2 000 km we also observe that daytime mstids with 300 1 000 km wavelengths propagate southeastward until mid afternoon and southwestward in the late afternoon in the mid to late afternoon these mstids propagating in the different directions are superimposed the tec maps can be a new powerful tool to investigate the mstids

postseismic rebound due to creep of the lower lithosphere and asthenosphere postseismic surface deformations are attributed to the inelastic flow of the subcrustal regions of the earth following an earthquake a multilayer representation of the earth s rheological properties is used in conjunction with a finite element computational scheme to calculate time dependent displacements and strains subsequent to a strike slip earthquake the deviatoric stress strain relation for the uppermost layer is assumed elastic lower layers are assumed to be in order of increasing depth a standard linear three element viscoelastic solid a linear viscoelastic fluid and another elastic solid physically these layers correspond to the upper lithosphere lower lithosphere asthenosphere and lower mantle respectively elastic dilatational properties are assumed throughout appreciable postseismic displacements possibly approaching meters for large earthquakes arise from the viscoelastic relaxation following the sudden coseismic slip furthermore compared to the simpler case of an elastic lithosphere over a viscoelastic asthenosphere the near fault postseismic shear strain is increased by a factor of two or more in some cases by the presence of a viscoelastic lower lithosphere also the duration of postseismic straining is increased if the viscosity of the lower lithosphere is greater than that of the underlying asthenosphere

nighttime medium scale traveling ionospheric disturbances at low geomagnetic latitudes 1 nighttime medium scale traveling ionospheric disturbances mstids are a commonly observed structure in the middle latitude ionosphere during the months surrounding the solstices and low solar flux conditions mstids consist of one or more narrow bands exhibiting uplift in f region electron density which are elongated from northwest to southeast in the northern hemisphere and southwest to northeast in the southern hemisphere these electrified structures propagate westward and toward the equator in a direction perpendicular to their long dimension previously this type of mstid was not thought to occur at magnetic latitudes equatorward of the equatorial anomalies or approximately 15 geomagnetic latitude here we present observational evidence from a field aligned narrowfield imaging system of mstids existing very close to the magnetic equator we discuss the implications of this observation in terms of the development and propagation of mstids