convectively forced internal gravity waves results from two dimensional numerical experiments two dimensional numerical simulations were performed to investigate the nature of tropospheric internal gravity waves of the type which are observed to occur above active thermal convection over an unstable boundary layer these gravity waves are believed to be excited by a combination of pure thermal forcing and by the boundary layer eddies and cumulus clouds acting as obstacles to the flow in the presence of mean environmental wind shear large amplitude internal gravity waves were obtained in the simulations with amplitudes and horizontal scales similar to the 12 june 1984 aircraft observations over western nebraska this was a day with strong wind shear in the lowest 3 km above the ground and with scattered cumulus clouds topping the boundary layer the simulations show that there is significant difference between the early time solutions as might be predicted by linear theory and late time solutions for the boundary layer eddy structure a layer interaction occurs in which gravity waves of the stable layer are excited by the boundary layer convection there is evidence to suggest that this layer interaction occurs both with and without shear but that it is stronger in the presence of low level shear results indicate that shear or the obstacle effect is a more efficient generator of gravity waves than is the pure thermal forcing the simulations show that the gravity waves initially forced by the boundary layer eddies lead to a feedback mechanism that acts to organize the boundary layer eddies and the cumulus convection the solutions suggest that the character of fair weather convection moist or dry is a non local problem involving at times the full depth of the troposphere the clouds produced in the simulations have very little influence on the wave field or boundary layer eddy structure as they are relatively small cumuli on the other hand the clouds are strongly influenced by the interactions between the wave and eddy fields upshear growth of cumulus clouds similar to that which is frequently observed in nature is reproduced in the simulations the development of feeder feeder is used here in a dynamical sense only clouds on typically the upshear side of the cloud is found to be a result of the interaction between the gravity wave field and the dry and moist convection the relative phase velocity between the gravity waves and the cloud plays a crucial role in determining the character of the cumulus cloud growth in the present simulations these simulations suggest that the dynamics both internal and external to the boundary of a cumulus cloud is a complicated mix between wave dynamics and the usually considered convection dynamics a brief discussion of the implications of the present results to cloud boundary baroclinic instability dynamics is also presented

geochemistry and stratigraphic correlations application to the investigation of geothermal and mineral resources of tuscany italy contribution to the knowledge of the ore deposits of tuscany ii abstract major element geochemistry 364 analyses is used to obtain quantitative information on the initial mineralogical composition and the depositional environment of paleozoic more or less metamorphic rocks from tuscany and elba furthermore this method can be used to improve stratigraphic correlations by comparing the chemical compositions of the metamorphic rocks and their possible non metamorphic counterparts of known stratigraphic position the stratigraphic units were divided into two sets the first includes the units of known stratigraphic or tectonic position taken as reference groups permian red porphyries carboniferous rocks buti group l s porphyritic schists porphyroids lower phyllites and metabasites from the apuan alps and elba the second set comprises the units of uncertain position metapelites and metapsammites from outcrops mines and boreholes from the boccheggiano niccioleta area calamita schists and metabasites associated with these two units micaschists gneisses and associated amphibolites the main results are 1 1 the porphyroids and porphyritic schists differ strongly from the permian red porphyries thus confirming that they belong to two different volcanic episodes 2 2 all the reference units consist of shales sandstones s s or graywackes differing by their degree of maturity increasing from the lower phyllites to the buti group and to the carboniferous formations 3 3 the carboniferous rocks the buti group and the lower phyllites have distinct chemical compositions 4 4 the boccheggiano formation l s and the calamita schists are similar and include rocks chemically equivalent to the lower phyllites the buti group and the carboniferous formations 5 5 the micaschists and gneisses derive from shales and graywackes respectively and chemically recall the lower phyllites 6 6 the metabasites from the apuan alps and from niccioleta are within plate basalts whereas the amphibolites interlayered within the micaschists and gneisses seem ocean floor basalts

evidence for li rich brines and early magmatic fluid rock interactionin the larderello geothermal system abstract the geochemical features of fluids accompanying the first stages of geothermal activity linked to magmatic intrusions have been documented for the larderello geothermal system italy deep drilling has provided samples which preserve evidence of this early geothermal activity four wells san pompeo 2 monteverdi 7 sasso 22 and serrazzano vc 11 penetrated the deeper parts of the larderello system located in a metamorphic basement underlying the tertiary nappe complex which constitutes the main aquifer at larderello the drill holes terminated close to the inferred roof of a granitic complex thought to be responsible for geothermal activity fluid inclusion data were obtained from recrystallized quartz lenses and quartz veins in samples displaying high temperature assemblages plagioclase actinolite biotite tourmaline clinopyroxene andradite wollastonite and also from magmatic quartz in a leucogranite dike the inclusions are mainly secondary in origin oriented in fluid inclusion planes fip related to hydrothermal circulation in the larderello system several generations of high temperature fluids were trapped and include 1 1 h2o co2 dominated vapors displaying variable but significant contents of ch4 and n2 2 2 aqueous vapors containing licl with variable salinity 3 3 aqueous licl brine often oversaturated with respect to halite at room temperature 4 4 complex brine always oversaturated at room temperature with respect to two halite and sylvite or more n 4 salts the presence of licl was confirmed by identification of the salt hydrate licl 5h2o at very low temperature using raman spectroscopy bulk salinities could be roughly estimated at around 30 wt eq licl for the licl brine geometric and chronologic relationships between fip reveal close relationships and mutual contamination between the h2o co2 vapors and licl brine indicating synchronism in their trapping these fluids were generated and trapped at pressures of 100 130 mpa nearly 23 mpa above the estimated present day lithostatic pressure this implies a denudation rate between 0 2 and 0 5 mrn a 1 since the onset of hydrothermal activity compatible with the setting of larderello in a young tortonian collision belt fluid inclusion trapping temperatures 425 650 c show a monotonous increase towards the inferred granite and are around 100 200 c higher than the highest present day temperatures the results are interpreted as recording the interaction between magmatic and contact metamorphic fluids in the early larderello system the h2o co2 vapors resulted from the reheating of the basement metamorphic series often c rich under relatively high temperatures during contact metamorphism lirich fluids expelled from an underlying li rich leucogranite migrated through the metamorphic series and the already cooled granite dikes and experienced local boiling the fluid inclusion data demonstrate the involvement of magmatic fluids during the initial development of this high energy geothermal field

geological structure of a long living geothermal system larderello italy we have examined the data of 600 geothermal wells and re interpreted approximately 500 km seismic profiles through the field of larderello italy we conclude that the two main seismic reflectors present below the geothermal area host two different fluids 1 superheated steam in the upper h horizon reached by drillholes and 2 supercritical fluid in the deeper k horizon reached by few unproductive or damaged wells the superheated steam has the physical and chemical connotation of the geothermal fluid exploited so far at larderello whereas the supercritical fluid represents a potential unconventional deep seated resource still to be assessed the high temperatures existing in correspondence of the k horizon suggest that the silica rich rocks are close to a plastic state and the fluids should remain confined in a medium sealed to the confining rocks unless occasional fluid overpressure and abrupt high strain rates occur

pegmatite wallrock interactions black hills south dakota progressive boron metasomatism adjacent to the tip top pegmatite abstract interaction between country rock and fluids derived from the tip top pegmatite has resulted in a series of boron enriched assemblages between unaltered quartz mica schist to the pegmatite contact is a succession of four mineral assemblages 1 1 quartz biotite potassium feldspar assemblage q b k which consists essentially of the original metamorphic silicate assemblage plus anomalously high amounts of modal tourmaline 2 2 quartz biotite tourmaline assemblage q b t 3 3 tourmaline quartz muscovite assemblage t q m 4 4 tourmaline quartz assemblage t q alkali elements cs rb k li sio 2 and ba show a decrease from the q b k assemblage to the t q assemblage a1 2 o 3 ga b total fe and zn increase moderately from the q b k assemblage to the t q assemblage the mineral chemistries also change considerably the mg mg fe 2 ratios in biotites range from 0 54 to 0 50 in samples from the q b k assemblage to 0 39 in the q b t assemblage the range in tourmaline end member components from the q b k assemblage to the t q assemblage is as follows q b k dravite 63 schorl 23 elbaite 05 buergerite 09 t q dravite 23 schorl 37 elbaite 17 buergerite 23 observed variations in mineral assemblage and whole rock chemistry within the alteration zone appear to a first approximation to be a function of b 2 o 3 boron metasomatism and k 2 o alkali leaching the breakdown of feldspar and biotite may be approximated by reactions 2hcl 2 k na alsi 3 o 8 ai 2 k na cl al 2 sio 5 5sio 2 h 2 o and 2 annite sio 2 5al 2 sio 5 2nacl 6h 3 bo 3 ai 2 tourmaline 2kcl 7h 2 o the alteration zone may represent either a single episode b cs li rb enriched fluid or multiple episodes b zn mn fluid and cs li rb fluid of pegmatite fluid schist interactions in both situations b in the aqueous fluid from the pegmatite reacts with the schist breaking down sheet silicate traps for cs rb li and k and forming tourmaline rich assemblages

doppler ducting of atmospheric gravity waves atmospheric gravity waves are subject to horizontal ducting in a stably stratified atmosphere that contains levels of wind maximum or minimum quite apart from any superimposed consequences of vertical variation of stability and quite apart from the existence or otherwise of critical levels the process doppler ducting is examined here for two prototype cases an isolated wind maximum and a wind minimum at ground level and for two more realistic model cases a strong tropospheric jet and a nocturnal boundary layer jet the wave structure modal behavior and dispersion curves of all four are very similar it is argued that doppler ducting is available to a part of the gravity wave spectrum in all real circumstances and that it should be considered as a possible candidate whenever observations indicate that some ducting process is operative one particular wave event is discussed in some detail and it is shown that doppler ducting in its simplest form provides a plausible alternative to a more complicated ducting process which involved critical levels and energy leakage previously inferred doppler ducting is available equally to gravity waves in the oceans when background currents vary with depth

sericitic alteration at the la crocetta deposit elba island italy interplay between magmatism tectonics and hydrothermal activity the la crocetta mine near porto azzurro elba island tuscany italy is an important producer of raw material for the ceramic industry exploitation focuses on a pervasively sericitized porphyritic aplite of the tuscan magmatic province locally known as eurite which underwent significant potassium enrichment during sericitic alteration eurites are located along the hanging wall of the elba centrale fault a low angle extensional lineament of regional significance a later carbonatization stage apparently associated with high angle extensional tectonics locally overprinted the sericitized facies it is expressed by carbonate pyrite quartz veins with adverse effects on ore quality sericitization was accompanied by addition of potassium and loss of na ca fe rubidium was not enriched along with potassium during sericitization contrary to what would be expected for interaction with late magmatic fluids new 40ar 39ar data from eurites provide an isochron age of about 6 7 ma for the sericitization whereas the age of the unaltered protolith is ca 8 8 ma field evidence indicates the elba centrale fault to be the main channel for the hydrothermal fluids on the other hand the involvement of heat and or fluids contributed by the porto azzurro pluton which crops out in the la crocetta area is ruled out by field geochemical and geochronological data 40ar 39ar age of porto azzurro 5 9 ma i e significantly younger than the sericitization event fluid inclusion studies suggest that sericitization was associated with a low temperature 250 c hydrothermal system fluids were locally boiling of variable salinity 4 17 wt nacl equiv and contained some co2 xco2 0 027 their ultimate source is not unequivocally constrained meteoric and or magmatic contributions may be possible low salinity 2 6 wt nacl equiv low temperature 250 c fluids are associated with the late carbonate veining they are considered to be of dominantly meteoric nature because of their low salinity in summary sericitization at la crocetta is regarded as the product of a detachment fault related low temperature hydrothermal system resulting from the structurally controlled focusing of meteoric and possibly magmatic fluids hence potential targets for exploration for similar resources are represented by aplitic bodies located in the hanging wall of elba centrale fault electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 002 0279 2

ebsd microfabric study of pre cambrian deformations recorded in quartz pebbles from the sierra de la demanda n spain abstract we describe a new method for the reorientation of lattice preferred orientation data in the absence of a pre constrained kinematic reference frame the method enables us to present conventional quartz fabric diagrams after measurements taken from rock sections with a general orientation with respect to foliation and lineation a microstructural and electron back scattered diffraction ebsd study of quartz pebbles in early cambrian conglomerates following this method permit us to recognize a variety of fabrics that resulted from syn metamorphic ductile deformation under variable temperatures up to 650 c the likely source area of the conglomerates was a proterozoic basement candidates for source rock correlations include neoproterozoic units similar to those outcropping in the northern iberian massif neoproterozoic medium to high grade metamorphic rocks as those outcropping in sw iberia or a neoarchean to mesoproterozoic concealed basement

crustal models of the geothermal areas of southern tuscany italy abstract geological and geophysical data gathered in the geothermal areas of southern tuscany located in the inner part of the northern apennines indicate the presence of granite intrusions the most relevant data are 1 regional asthenospheric ascent to a depth of 40 50 km 2 granitic dykes as old as 3 8 2 9 ma and a widespread contact aureole found in several deep geothermal wells 3 very high heat flow values interpreted as the result of convective circulation of hot fluids above shallow magmatic bodies 4 the presence of low density bodies inferred from low gravity values often correlated with positive heat flow anomalies 5 the occurrence of a highly reflective horizon named k in a depth range of 3 12 km in the geothermal areas as shown by seismic reflection data 6 a 30 40 km wide low velocity body below the k horizon whose existence is supported by local earthquake tomography and teleseismic studies 7 the presence of a conductive body which correlates well with the anomalous tomographic and teleseismic body as revealed by magnetotelluric surveys the goal of the paper is to test different alternative crustal models by using these data the models are 1 granite intrusion 2 geopressurized fluids below impervious layers 3 contact metamorphic aureole 4 mylonite layers at the upper lower crust transition and 5 some combination of the four the occurrence of shallow intrusive bodies still partially molten and associated with saline brines is considered the most tenable model

multiple hydro fracturing by boron rich fluids in the late miocene contact aureole of eastern elba island tuscany italy in eastern elba island tuscany italy a shallow crustal level felsic tourmaline bearing dyke sill swarm of late miocene age is associated with abundant tourmaline quartz hydrothermal veins and metasomatic masses development of these veins and masses in the host rocks demonstrates multiple hydro fracturing by magmatic boron rich saline fluid tourmalines in felsic dykes are schorl whereas in veins and metasomatic masses tourmaline composition ranges from schorl dravite through dravite to uvite this compositional shift is evidence for an increasing contribution to the magmatic boron rich fluids by a mg ca ti rich external component represented by biotite rich and amphibolite host rocks this system can be envisaged as an exposed proxy of the high temperature hydrothermal system presently active in the deepest part of the larderello travale geothermal field tuscany

enhanced co2 mineral sequestration by cyclic hydraulic fracturing and si rich fluid infiltration into serpentinites at malentrata tuscany italy abstract the magnesite deposits of malentrata tuscany italy were derived from serpentinite silicification carbonation of the ligurian ophiolite and represent a natural analogue of in situ co 2 mineral sequestration carbonation of magnesium silicate minerals e g serpentine olivine at temperatures below 200 c is an exothermal process involving incorporation of carbon dioxide into stable carbonates e g magnesite dolomite serpentinites at malentrata were transformed to a brownish friable rock characterized by the occurrence of opal chromian montmorillonite fe rich magnesite and minor iron sulfides and oxides widespread lenses of cohesive rocks occur within the altered serpentines resulting from the complete silicification of the protolith the pervasive alteration of serpentinite was accompanied by the formation of a network of magnesite and dolomite veinlets and large magnesite dolomite veins along major structures field observations petrography and mineral chemistry define the following crystallization sequence in the major veins i early microgranular fe poor magnesite ii comb textured fe rich magnesite and dolomite cementing the early brecciated magnesite vein infill and iii late quartz chalcedony and rare opal in the cavities the mineral assemblage observed both in veins and in host rock is indicative of low temperature hydrothermal alteration driven by si and co 2 rich fluids under relatively low ph conditions pervasive and cyclic hydraulic fracturing maintained a high structural permeability during the whole hydrothermal event creating conduits for the input and output fluids the concomitant presence of co 2 and silica in the fluid enhanced the congruent dissolution of serpentine and hampered immediate carbonate deposition the mg bearing solutions were focused out of the reactor zone and promoted massive carbonate veining along the main structural discontinuities this two steps reaction dissolution of serpentinite followed by carbonate precipitation outside the reacting volume seems to be very efficient and provide new insights on in situ and ex situ induced mineral carbonation and its industrial applications

evolution of shear zones through the brittle ductile transition the calamita schists elba island italy abstract a network of shear zones that evolved through the brittle ductile transition is exposed in the calamita schists elba island italy the shear zones formed during late miocene contractional deformation coeval with high grade contact metamorphism 650 c related to the emplacement of plutonic rocks at shallow crustal levels 7 10 km an early stage high metamorphic grade foliation was overprinted by mylonitic deformation that progressively localized on low metamorphic grade shear bands producing s c mylonites during cooling of contact aureole localization of deformation on shear bands was driven by temperature decrease that triggered strain partitioning between hard high grade relics and soft shear bands softening of shear bands occurred likely due to fluid influx and retrograde growth of fine grained phyllosilicates the interconnection of anastomosing shear bands and passive rotation of the relic high grade foliation caused widening of the shear bands producing mylonites with a composite mylonitic foliation and c shear bands an estimate of the vorticity number wk of the flow of 0 3 0 5 was obtained from the orientation of c shear bands measured at the meso and thin section scale close to the brittle ductile transition the growth of soft phyllosilicates allowed c shear bands to act as precursory structures to brittle deformation localized into an array of low angle faults and shear fractures

boron metasomatism of the alta stock contact aureole utah evidence from borates mineral chemistry and geochemistry geochemical study of the alta stock and adjacent contact aureole rocks provides information concerning the source composition and physical chemical conditions of infiltrating fluids special emphasis was given to boron b as a tracer of fluid rock interactions due to the occurrence of borate minerals ludwigite kotoite and szaibelyite in skarn deposits around the stock in addition thin section alpha track mapping implies significant b enrichments in fluid altered minerals within the stock stockwork veins and related selvages igneous sills near the stock contact skarns and in marbles up to 500 m from the stock forsterite clinohumite lizardite and malachite contain between 50 and 1200 ppm b diopside calcite clintonite phlogopite brucite hedenbergite tremolite and other minerals host b to a lesser extent aureole b enrichments correlate well with major and other trace element enrichments and support existing models of element transport in magmatic fluids with lateral down temperature flow large variations in mineral b concentrations reflect changes in b concentrations of these fluids through time mass balance calculations indicate that magmatic fluids emanating from the alta pluton could supply most b in the alta aureole it is estimated that the emplaced magma had an initial b concentration between 7 10 ppm indicated exhalative losses of b from the pluton are on the order of 50 we estimate that the exsolved fluids had a time integrated b concentration of 160 40 ppm although much higher concentrations may have attended local borate mineralization

lateral extrusion of a thermally weakened pluton overburden campiglia marittima tuscany the ascent and emplacement of magmas in the upper crust modify the local pre existing thermal and rheological settings such changes have important effects in producing anomalous structures mass extrusion rock fracturing and in some conditions hydrothermal mineralizations in the campiglia marittima area detailed field mapping led to the reconstruction of a local deformation history that overlaps chronologically and spatially with regional extension this local deformation was triggered at the miocene pliocene boundary by the intrusion of a monzogranitic pluton beneath a carbonate sedimentary sequence the emplacement of the pluton produced a perturbation in the rheological behaviour of the carbonate host rocks producing transient ductile conditions in the very shallow crust the carbonate rocks were thermally weakened and flowed laterally accumulating downslope of the pluton roof mainly toward the east as the thermal anomaly was decaying the brittle ductile boundary moved progressively back towards the pluton and large tension gash shaped volumes of fractured marble were generated these fractured volumes were exploited by rising hydrothermal fluids generating sigmoidal skarn bodies and ore shoots this work presents the campiglia marittima case study as a prime example of structural interference between regional extensional structures and local lateral mass extrusion in a transient ductile rheological regime triggered by pluton emplacement

two stage growth of laccoliths at elba island italy at elba island italy nine shallow level late miocene granite porphyry layers connected by feeder dikes built up three nested christmas tree laccoliths detailed mapping and reconstruction of tectonic history led to restoration of the original 5 km thick sequence and determination of the dimensional parameters of each intrusive layer the laccolith layers were emplaced at depths between 1 9 and 3 7 km exploiting physical discontinuities that served as crustal magma traps inside a stack of nappes the intrusive layers are 50 700 m thick with diameters between 1 6 and 10 km length to thickness relationships for individual laccolith layers show a power law correlation that does not fit the known dimensional distribution for laccoliths but instead fits a line with a slope typical of the theoretical vertical inflation stage of laccolith development this is interpreted as the first reported natural example of the occurrence of a vertical inflation stage during laccolith growth the dimensional data for elba intrusive layers also suggest that laccoliths and plutons commonly form by amalgamation of smaller sheet like bodies while multilayer laccoliths form when coalescence fails possibly owing to the large availability of crustal magma traps

propagating mesoscale cloud bands abstract banded cloud patterns are an often observed mesoscale phenomenon which may be produced under a variety of physical conditions and for a variety of reasons this paper concerns a detailed analysis of a propagating pattern which was observed with the noaa 2 satellite following a period of severe thunderstorm activity in the southwestern united states we review the local atmospheric conditions existing at the time the disturbance was observed and address the question concerning its mechanism of initiation and propagation we first test the hypothesis that the banded cloud formation could simply be a manifestation of a freely propagating packet of internal waves launched by earlier convective activity this hypothesis is shown to be unsatisfactory we next consider the modal structure of the atmosphere in the vicinity of the cloud bands and show that the slowest spatially decaying mode of the mean state has a horizontal wavelength and phase speed which match those of observed disturbance

episodic hydrothermal alteration recorded by microscale oxygen isotope analysis of white mica in the larderello travale geothermal field italy abstract microscale oxygen isotope analysis 18o 16o of minerals can identify distinct events of fluid rock interaction this method is however still limited to a few major and accessory minerals of which most are anhydrous minerals we present the systematic study of oxygen isotope distribution in white mica by secondary ion mass spectrometry sims texturally and chemically distinct white mica populations in granitic and contact metamorphic rocks from the larderello travale geothermal field ltgf italy record stages of magmatic crystallization metamorphic hydrothermal replacement and fluid rock interaction the large range in intra and inter grain white mica 18o values between 1 and 14 reflects varying protoliths and degrees of fluid mineral interaction at variable temperatures 180 450 c present day temperatures p d t this variability reflects the large scale circulation of both 1 magmatic syn intrusive to early contact metamorphic hydrothermal fluids with high 18o values and 2 meteoric fluids with 18o values of 7 during a post intrusive late hydrothermal stage metasedimentary rocks from the upper reservoir contain distinct white mica populations occurring in close proximity m scale including detrital grains 18o 12 14 high na low mg partially altered white mica 18o 8 9 and late hydrothermal white mica 1 6 low na mid mg the late hydrothermal white mica has similar 18o values to other secondary minerals and is in equilibrium with meteoric dominated fluids with a 18o of 6 to 0 5 which circulated in the late hydrothermal stage downhole towards the lower reservoir white mica from two contact metamorphic micaschist samples shows either 1 homogeneous 18o values of ca 9 likely due to recrystallization in the contact metamorphic hydrothermal stage t ca 600 c or 2 a large spread in 18o from 2 to 12 within and across grains of variable texture and chemistry in the host rock and a cross cutting quartz white mica vein ca 300 c present day temperature hereafter p d t this contrasting 18o signature of white mica is also recorded in granite cored at up to 4 6 km depth the carboli granite contains white mica with a homogeneous magmatic 18o of 10 0 6 whereas older granite samples from radicondoli have magmatic to hydrothermal white micas that vary in 18o from 4 to 10 a pronounced intra grain 18o variability of up to 6 occurs in white mica domains with higher fe mg ti halos around inclusions of chloritized biotite as a result of interaction with dominantly meteoric fluids that infiltrated to depths of at least 4 6 km in the porto azzurro granite on elba italy altered white mica has 18o values of 2 6 down from 10 in unaltered grains the distribution of oxygen isotope ratios in white mica is thus firstly a result of pervasive versus selective fluid alteration at depth sample and grain scale secondly the actual preservation of these m scale variabilities indicates that volume diffusion is not detectable at microscale at p d t at or below 350 c where most of the heterogeneous white mica is found selective sample and grain scale fluid penetration occurs episodically and anisotropically on micro and megascale along faults fractures and cleavages producing lower 18o white mica at various times in zones of higher secondary permeability and active hydrothermal fluid circulation

variation in fracture patterns in damage zones related to strike slip faults interfering with pre existing fractures in sandstone calcione area southern tuscany italy abstract this paper deals with the effects of pre existing fractures on the development of damage zones related to meter and decameter strike slip faults which affected late oligocene early miocene sandstone in the calcione area southern tuscany italy strike slip faults dissected rock masses locally affected by pervasive pre existing fractures related to previous deformational events two different domains were identified rock masses affected and unaffected or relatively unaffected by pre existing fractures strike slip faults affecting the two domains made it possible to compare the different configurations of fracture patterns related to isolated or interacting fault segments new data is provided on scaling relations between i fault length and the length of related fractures ii mean step length and width for overstepping fault segments iii angular values at the intersection of the fault plane and related fractures scaling relations obeyed a positive power law for faults dissecting sandstone unaffected by pre existing fractures on the contrary no scaling relations were recognized for faults dissecting sandstone affected by pre existing fractures the development of strike slip faults on rock masses affected by pre existing fractures can simulate splays apparently related to faulting three main points were categorized for detecting deceptive cases there is a real chance of a deceptive fracture pattern if i the angular values at the intersection of the fault and its fractures mode i opening fracture exceed 50 in the wall damage zone ii the scaling relation between fault length and maximum fracture length does not fit a power law iii fractures acted as shear fractures the resulting framework provides additional data for understanding the development and architecture of strike slip faults

a multivariate spatial interpolation of airborne γ ray data using the geological constraints in this paper we present maps of k eu and eth abundances of elba island italy obtained with a multivariate spatial interpolation of airborne ray data using the constraints of the geologic map the radiometric measurements were performed by a module of four nai tl crystals of 16 l mounted on an autogyro we applied the collocated cokriging ccok as a multivariate estimation method for interpolating the primary under sampled airborne ray data considering the well sampled geological information as ancillary variables a random number has been assigned to each of 73 geological formations identified in the geological map at scale 1 10 000 the non dependency of the estimated results from the random numbering process has been tested for three distinct models the experimental cross semivariograms constructed for radioelement geology couples show well defined co variability structures for both direct and crossed variograms the high statistical correlations among k eu and eth measurements are confirmed also by the same maximum distance of spatial autocorrelation combining the smoothing effects of probabilistic interpolator and the abrupt discontinuities of the geological map the results show a distinct correlation between the geological formation and radioactivity content the contour of mt capanne pluton can be distinguished by high k eu and eth abundances while different degrees of radioactivity content identify the tectonic units a clear anomaly of high k content in the mt calamita promontory confirms the presence of felsic dykes and hydrothermal veins not reported in our geological map although we assign a unique number to each geological formation the method shows that the internal variability of the radiometric data is not biased by the multivariate interpolation

structural and lithological control on fluid circulation dilation and ore mineralization rio albano mine island of elba italy abstract we present the results of geological and structural investigation documenting the interaction between hydrothermal fluids and host rock leading to a vein type ore mineralization at shallow crustal depths

boiling and fluid mixing in the chlorite zone of the larderello geothermal system abstract the geochemical features of the geothermal fluids produced within the boiling zone in the relatively shallow parts of the larderello geothermal system italy have been documented as a result of deep drilling which provided samples from 1480 to 2500 m depth four wells monteverdi 1 monteverdi 2a sasso 22 and capannoli 2b have been sampled in the intermediate parts of the larderello aquifer located in a metamorphic basement underlying the tertiary nappe complex which constitutes the shallow aquifer at larderello fluid inclusions from recrystallized quartz lenses and quartz veins in samples displaying a predominant quartz chlorite epidote adularia paragenesis have been studied by microthermometry and raman spectroscopy the inclusions are primary and pseudo secondary in origin when formed in authigenic quartz or of secondary origin when located in fluid inclusion planes related to microfracturing of metamorphic quartz lenses several generations of fluids are present and include h 2 o co 2 dominated vapours and liquids and a series of aqueous liquids for the most part of relatively low salinity the t m ice of both early and late inclusions are mostly between 0 0 and 4 5 c indicating that the salinities of the hydrothermal fluid were very low to moderate however rare fluid inclusions with lower t m ice from 4 9 to 25 0 c were also observed these inclusions may record the occasional input of saline fluids which may be derived from the interaction of the hydrothermal waters with the evaporites present in the shallow part of the larderello field at capannoli 2b earliest h 2 o co 2 liquids were trapped under minimal pressures of 610 645 bars which bracket the estimated present day lithostatic pressure 640 bars in all other samples the main stage of quartz chlorite crystallization occurs under boiling conditions attested by the presence of liquid and vapour rich inclusions that in some instances can be texturally interpreted to be coeval their trapping conditions 350 375 c 160 215 bars are higher than the present day temperatures at the same depth later fluid inclusions attest to a significant cooling of the fluids down to temperatures similar to the present day temperatures during this time pressures were close to hydrostatic conditions most fluid inclusions were trapped within the liquid field this indicating that a significant pressure drop has since affected the main aquifers or fractured zones which are at present under vaporstatic conditions

sensitivity of the subpolar atlantic climate to local winds 1 the mild climate of northern europe is thought to be in part maintained by the deep water formation in the northern north atlantic and the associated meridional overturning circulation it has been argued that this circulation is controlled by the wind stress in the southern ocean using a coupled climate model it is shown that the subpolar atlantic wind stress also plays an important role a partial or a complete suppression of this wind stress results in the low salinity arctic waters filling the subpolar atlantic interior as a result the regions of deep water sinking shift southward and the associated overturning circulation convective activity and oceanic heat loss in the northern north atlantic strongly weaken the sea ice advances southward and the north atlantic climate including over much of europe becomes colder