polar vortices on earth and mars a comparative study of the climatology and variability from reanalyses polar vortices on mars provide case studies to aid understanding of geophysical vortex dynamics and may help to resolve long standing issues regarding polar vortices on earth due to the recent development of the first publicly available martian reanalysis dataset macda for the first time we are able to characterise thoroughly the structure and evolution of the martian polar vortices and hence perform a systematic comparison with the polar vortices on earth the winter atmospheric circulations of the two planets are compared with a specific focus on the structure and evolution of the polar vortices the martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on earth during winter while on earth this residual circulation is very different from the eulerian circulation on mars it is found to be very similar unlike on earth it is found that the martian polar vortices are annular and that the northern hemisphere vortex is far stronger than its southern counterpart while winter hemisphere differences in vortex strength are also reported on earth the contrast is not as large distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices in that the martian polar vortices are observed to decrease in size at higher altitudes whereas on earth the opposite is observed finally it is found that the martian vortices are less variable through the winter than on earth especially in terms of the vortex geometry during one particular major regional dust storm on mars martian year 26 an equatorward displacement of the vortex is observed sharing some qualitative characteristics of sudden stratospheric warmings on earth

geographic and seasonal distributions of brunt vaisala frequency and rossby radii in the north pacific and north atlantic abstract long term mean temperature and salinity profiles computed from an edited set of historical hydrographic data have been used to calculate mean profiles of density and brunt vaisala seasonal variations in internal rossby radii are everywhere surprisingly small

geology and metallogenic evolution of the polymetallic deposits of the alcudia valley mineral field eastern sierra morena spain the alcudia valley is intensely mineralized with a large number of pb zn ag cu deposits hosted by neoproterozoic and paleozoic sedimentary rocks five distinct types of deposits have been recognized the most significant mineralizing events were related to the two major phases of deformation hd1 hd2 and granite emplacement during the hercynian orogeny stable isotope and lithogeochemical data demonstrate that the metals as well as sulfur and carbon were sourced from the local sedimentary rocks type a deposits are minor occurrences of strata bound mineralization with zn pb occurring as disseminations and small veins in late ordovician limestone a syndiagenetic origin is suggested by the limited stratigraphic distribution of the mineralization and anomalous base metal contents of late ordovician early silurian black shales overlying the mineralized limestone minor remobilization of disseminated sulfides into joints took place during late diagenesis or early hercynian deformation types b c and d are syntectonic deposits with zn pb type b deposits are strongly deformed veins in hd1 fractures in ordovician rocks a process involving local mobilization of metals by a surface derived fluid is indicated by depleted metal contents of host rocks adjacent to the veins the similarity of 34s values of ore sulfides with disseminated pyrite in the host rocks and the 18oh2o values type c deposits exhibit a greater variation in morphology and degree of deformation compared to other types and are found in both hd1 and hd2 fractures in late ordovician and silurian rocks the stratigraphic distribution and 34s values of sulfides are similar to type a deposits suggesting that localized hydrothermal systems either remobilized type a mineralization or derived metals and sulfur from the same source type d deposits occur in hd2 shear fractures in neoproterozoic rocks the 13c values of carbonate gangue and the similarity of 34s values of ore sulfides and disseminated pyrite in the host rocks indicate that black shales of the neoproterozoic sequence are the major source of sulfur and carbon mixing of a metamorphic fluid with a surface derived fluid is suggested by fluid inclusion and oxygen isotope data type e deposits the most abundant and economically most important type are post tectonic pb zn veins occupying hd2 fractures and are widely distributed through the district in rocks ranging from neoproterozoic to late ordovician mineral assemblages and ag contents of the veins show a zonal relationship with respect to monzogranite outcrops indicating that late hercynian magmatism was the source of heat driving fluid migration through the fracture system fluid inclusion and oxygen isotope data are typical of basinal brines reaction of the fluid with black shales of the neoproterozoic sequence is suggested by 34s values of sulfides and 13c values of carbonates of the main stages of the paragenetic sequence the final paragenetic stage consists of barite calcite and pyrite which may have been deposited during a later hydrothermal event probably in the early triassic

geology of a vigorous hydrothermal system on the endeavour segment juan de fuca ridge a high precision high resolution geologic map explicitly documents relationships between tectonic features and large steep sided sulfide sulfate silica deposits in the vigorously venting endeavour hydrothermal field near the northern end of the juan de fuca ridge water depth in the vent field varies from 2220 to 2200 m location of the most massive sulfide structures appears to be controlled by intersections of ridge parallel normal faults and other fracture fissure sets that trend oblique to and perpendicular to the overall structural fabric of the axial valley the fractured basaltic substrate is primarily composed of well weathered pillow and lobate flows as presently mapped the field is about 200 by 400 m on a side and contains at least 15 large 1000 m3 sulfide edifices and many tens of smaller commonly inactive sulfide structures the larger sulfide structures are also the most vigorously venting features in the field they are commonly more than 30 m in diameter and up to 20 m in height actively venting sulfide structures in the northern portion of the field stand higher and are more massive than active structures in the southern portion of the field which tend to be slightly to distinctly smaller maximum venting temperatures of 375 c are associated with the smaller structures in the southeastern portion of the field highest temperature venting fluids from the more massive structures in the northern portion of the field are consistently 20 30 c lower hydrothermal output from individual active sulfide features varies from no flow in the lower third of the edifice to vigorous output from fracture controlled black smoker activity near the top of the structures a different type of high temperature venting takes place from the upper sides of the structures in the form of overflow from fully exposed quiescent pools of buoyant 350 c vent water trapped beneath overhanging sulfide sulfate silica ledges or flanges these flanges are attached to the upper outer walls of the large sulfide edifices two types of diffuse venting in the endeavour field include a lower temperature 8 15 c output through colonies of large tubeworms and 25 50 c vent fluid that seems to percolate through the tops of overhanging flanges the large size and steep walled nature of the these structures evidently results from sustained venting in a mature hydrothermal system coupled with dual mineral depositional mechanisms involving vertical growth by accumulation of chimney sulfide debris and lateral growth by means of flange development

the relative effect of particles and turbulence on acoustic scattering from deep sea hydrothermal vent plumes revisited the relative importance of suspended particles and turbulence as backscattering mechanisms within a hydrothermal plume located on the endeavour segment of the juan de fuca ridge is determined by comparing acoustic backscatter measured by the cabled observatory vent imaging sonar covis with model calculations based on in situ samples of particles suspended within the plume analysis of plume samples yields estimates of the mass concentration and size distribution of particles which are used to quantify their contribution to acoustic backscatter the result shows negligible effects of plume particles on acoustic backscatter within the initial 10 m rise of the plume this suggests turbulence induced temperature fluctuations are the dominant backscattering mechanism within lower levels of the plume furthermore inversion of the observed acoustic backscatter for the standard deviation of temperature within the plume yields a reasonable match with the in situ temperature measurements made by a conductivity

40ar 39ar illite dating of late caledonian acadian metamorphism and cooling of k bentonites and slates from the welsh basin u k the vacuum encapsulation laser 40ar39ar technique allows extremely small 10 6 g samples of fine grained materials such as diagenetic clays to be dated here we show that the method can be extended to higher grade clay minerals the integration of transmission electron microscopic tem characterization with 40ar39ar dating of vacuum encapsulated samples permits the resolution of the timing of metamorphic growth cooling from the time of diagenesis we have applied this technique to well characterized lower paleozoic slates and k bentonites from the welsh basin which span the transition from anchizonal to epizonal grade which had been previously studied using rbsr and smnd dating tem observations of epizonal k bentonites and slate showed that illite in these samples is of 2m1 polytype of muscovite like composition and oriented parallel to cleavage suggesting that they are of metamorphic origin total gas ages equivalent to conventional kar ages for encapsulated epizonal k bentonites and slate 340 408 ma are considerably variable the ar retention ages calculated from 39ar and 40ar atoms retained in the sample after irradiation are more consistent 383 411 ma the 39ar recoil losses are minor for illites from whole rock samples of epizonal k bentonites but very significant for clay separates of epizonal slate plateaus in age spectra were observed in epizonal k bentonites and slate the plateau ages 414 421 ma and retention ages 383 411 ma can be correlated with the onset of acadian metamorphism and culmination of uplift and inversion of the welsh basin respectively these ages are significantly younger than the 450 ma ages previously reported for diagenetic clays using the same method suggesting that diagenetic history has been lost in these epizonal k bentonites and slate tem observations of anchizonal slates showed that there are two modes of illite the first mode is similar to that observed in epizonal samples suggesting a metamorphic origin the second mode consists of the 1md polytype has typical diagenetic illite composition and is oriented parallel to bedding suggesting a diagenetic origin total gas ages for encapsulated anchizonal slates vary considerably 361 422 ma the retention ages are more consistent 413 432 ma than the total gas ages the 39ar recoil losses are more significant than those for epizonal k bentonites and slate plateaus in age spectra are generally not observed however the consistent retention ages for the anchizonal slates correspond to the plateau ages for the epizonal samples and are inferred to represent the onset of acadian metamorphism these data when combined with our previously published results for diagenetic shales suggest that thermal conditions near the boundary of anchizonal and epizonal grades are necessary to completely reset ar systems in shales and slates

the structure of mars lower atmosphere from mars express radio science mars occultation measurements 1 the mars express radio science experiment mars investigates the lower and middle atmosphere of mars between the surface and about 40 km with a very high vertical resolution more than 600 profiles of temperature pressure and neutral number density were retrieved between 2004 and 2011 covering four martian years mys 27 30 radio occultation experiments provide the unique possibility to retrieve geopotential height information to supplement temperature values the temperature field in the northern winter hemisphere displays strong temperature inversions indicating a pronounced polar warming in the northern polar night my 27 the temperature and geopotential fields imply the presence of a strong zonal jet with peak wind speeds of more than 170 m s at an altitude of about 30 km 15 pa and a latitude of 60 65 n the longitudinal temperature and geopotential fields in the southern winter of martian year 30 at latitudes between 49 and 69 s are dominated by a stationary zonal wave s 1 structure in the lower atmosphere associated meridional wind fields retrieved by assuming geostrophic balance have amplitudes up to 12 m s at the 200 pa level an investigation of small scale atmospheric waves reveals enhanced gravity wave activity in the daytime atmosphere above elevated terrain and in the winter extratropics radio occultation experiments also provide unique insight into the structure of the planetary boundary layer the deepest convective boundary layers up to 10 km are found over elevated terrain

possible effects of breaking gravity waves on the circulation of the middle atmosphere of mars a simplified quasi geostrophic beta plane dynamical model of the zonal mean flow is used to investigate the possible effects of breaking internal gravity waves on the circulation in the middle atmospheric region 10 100 km altitude of mars the gravity wave parameterization employed is basically the saturation parameterization of lindzen 1981 which has been utilized in several terrestrial modeling studies numerical simulations are performed for a range of plausible values of the gravity wave parameters and for different representations of the mean flow thermal forcing with a focus on the effects of topographically forced stationary gravity waves on the winter hemisphere circulation the results of the model simulations show that breaking gravity waves of intermediate horizontal scales 100 1000 km wavelengths could act to close off the winter westerly circumpolar jet in the 40 80 km altitude region and induce strong high latitude warming at these levels the latter could explain recent thermal measurements indicating that martian winter polar latitudes may be very warm far above radiative equilibrium in this middle atmospheric region deming et al 1986 for the most plausible range of parameter values breaking gravity waves do not induce much warming below 40 km consistent with available data showing that winter high latitudes are normally very cold at lower levels several dust storm cases indicate that breaking gravity waves possibly could act to induce a very large polar warming at relatively low altitudes such as was observed during the 1977 winter solstice dust storm however quite large gravity wave amplitudes and or relatively long horizontal wavelengths are required for such strong low level effects thermal forcing associated with dust heating might be a source for such anomalous gravity wave activity during a global dust storm summer simulations indicate that breaking gravity waves might alter the mean flow at somewhat higher levels than in the winter hemisphere as a consequence of the presence of westerlies in the lower atmosphere this could explain the presence of a warm summer pole in the recent 50 80 km thermal measurements of deming et al several aspects of the results relating to the middle atmospheric circulation and the polar warming phenomenon are discussed the possible importance of breaking gravity waves for constituent transports in the middle atmosphere of mars is also briefly considered

the latest post variscan fluids in the spanish central system evidence from fluid inclusion and stable isotope data abstract the spanish central system has been subjected to repeated fluid incursions which were responsible for a variety of mineralizing episodes including w sn cu zn pb as ag f ba and barren quartz veins these hydrothermal fluids occurred over a 200 ma time period and the latest hydrothermal event is recorded in barren quartz veins this study is a multidisciplinary approach leading to the characterization of the hydrothermal fluids preserved in barren quartz veins which are spatially but not temporally related to hercynian upper crustal granites the veins were dated by the 39 ar 40 ar method and the fluids were examined using petrographic microthermometric chemical and isotopic methods fluid inclusions in barren quartz veins indicate that two fluids were related to this hydrothermal event the main part of the quartz veins were formed from an early low salinity 2 o nacl fluid this fluid was trapped at around 270 25 c and 0 1 1 kbar under sublithostatic to hydrostatic conditions 18 o 9 to 2 and d 70 to 34 5 values indicate a meteoric origin for water with significant water rock interactions the latest h 2 o nacl cacl 2 fluid is found in two types of fluid inclusions a primary liquid vapour type 16 24 wt nacl and 1 12 wt cacl 2 and secondary hypersaline type 7 15 wt nacl and 21 27 wt cacl 2 significant li concentrations in this fluid were confirmed this late ca bearing fluid formed quartz crystals in the central part of the veins and was trapped at 70 140 c at a maximum pressure of 0 5 kbar the low 18 o 20 to 6 and d 137 to 116 values suggest a meteoric origin for this fluid however its high salinity probably requires a source from triassic evaporite basins located in the ne tip of the spanish central system anomalously low isotopic values have been previously reported from kaolinites of lower cretaceous age anomalous climatic conditions during the cretaceous appear to be the main reason to explain this very negative meteoric water strong isotopic depletion in meteoric water has been observed in modern areas with monsoonal climates the hydrothermal evolution of barren quartz veins in the spanish central system is comparable to other hydrothermal post variscan events in central and south western europe related to the opening of the north atlantic during cretaceous time

recent developments in dating ancient crustal fluid flow several isotopic techniques have recently been developed or substantially improved allowing the accurate determination of the timing of fluid related processes these include k ar rb sr and sm nd dating of diagenetic minerals in clastic rocks u pb dating of carbonates sm nd dating of fluorite and uraninite re os and rb sr dating of sulfides 40ar 39ar and rb sr dating of fluid inclusions and u pb dating of ilmenite magnetite sphene and rutile while many of these techniques require further evaluation some have already resulted in new constraints on a variety of crustal fluid flow models

a newly dated cretaceous hydrothermal event in the iberian ranges eastern spain and its significance within the mesozoic thermal history in the iberian peninsula abstract the iberian peninsula hosts the world class hg mining district of almaden besides pre hercynian ore bodies alpine cycle hg bearing veins are also present in the eastern iberian ranges espadan deposits we present both the first absolute ages 84 4 and 85 3 ma for a post hercynian hg deposit in spain obtained from primary muscovites and a complete compilation of published mesozoic radiometric absolute ages of the iberian peninsula we deduce that there are three main thermal episodes that affected the iberian peninsula which have been revealed after the comparison among the magmatic metamorphic and hydrothermal ages moreover the espadan hydrothermal system was active when both the cretaceous alkalic magmatism took place in southern portugal and in the pyrenees and during the opening of the bay of biscay

surface generated mesoscale eddies transport deep sea products from hydrothermal vents atmospheric forcing which is known to have a strong influence on surface ocean dynamics and production is typically not considered in studies of the deep sea our observations and models demonstrate an unexpected influence of surface generated mesoscale eddies in the transport of hydrothermal vent efflux and of vent larvae away from the northern east pacific rise transport by these deep reaching eddies provides a mechanism for spreading the hydrothermal chemical and heat flux into the deep ocean interior and for dispersing propagules hundreds of kilometers between isolated and ephemeral communities because the eddies interacting with the east pacific rise are formed seasonally and are sensitive to phenomena such as el nino they have the potential to introduce seasonal to interannual atmospheric variations into the deep sea

ore lead and sulphur isotope pattern from the low temperature veins of the catalonian coastal ranges ne spain the lead isotopic composition of galenas from low temperature veins of the catalonian coastal ranges ne spain displays a small but distinct range of values 18 318 206pb 204pb 18 678 15 678 207pb 204pb 15 767 and 38 534 208pb 204pb 39 189 the data define a linear trend in the 208pb 204pb versus 206pb 204pb diagram that can be interpreted in terms of mixing of lead from different reservoirs the lead appears to be derived from a solution that preferentially leached granites of late hercynian age sulphur isotopic compositions of the galenas range from 8 5 to 7 3 but variations in a single deposit are small 1 2 pointing to different sources of sulphur in a 34s versus 206pb 204pb plot no clear correlation trends appear lead isotope data from deposits of similar characteristics situated within the hercynian orogenic belt as the linares la carolina district s spain and the inglesiente sulcis area sardinia show slight differences indicating a source area of similar lead isotopic composition in the ccr and linares la carolina districts the main source of lead is related to the hercynian granites of each area although small contributions from metasediments cannot be ruled out the contribution of lead from metasedimentary rocks is particularly seen in the sardinian hercynian vein type ores

deep sea hydrothermal plumes and their interaction with oscillatory flows 1 the acoustic scintillation method is applied to the investigation and monitoring of a vigorous hydrothermal plume from dante within the main endeavour vent field mef in the endeavour ridge segment a 40 day time series of the plume s vertical velocity and temperature fluctuations provides a unique opportunity to study deep sea plume dynamics in a tidally varying horizontal cross flow an integral plume model that takes into account ambient stratification and horizontal cross flows is established from the conservation equations of mass momentum and density deficit using a linear additive entrainment velocity in the model e um u that is a function of both the plume relative axial velocity um and the relative ambient flow perpendicular to the plume u gives consistent results to the experimental data suggesting entrainment coefficients 0 1 and 0 6 also from the integral model the plume height in a horizontal cross flow ua is shown to scale as 1 8b1 3ua 1 3n 2 3 for 0 01 ua 0 1 m s where b is the initial buoyancy transport and n is the ambient stratification both of which are assumed constant

the martian zonal mean circulation angular momentum and potential vorticity structure in gcm simulations abstract analysis of simulations performed with the nasa ames mars gcm shows that under dusty conditions the northern hemisphere winter solstice circulation becomes characterized by a zonally averaged state in which the potential vorticity at upper levels is very small outside of high latitudes the available observational data in particular the 15 m observations obtained by the viking irtm during the 1977 winter solstice global dust storm provide evidence for changes in the martian circulation that are basically like those found in the gcm in the mars gcm simulations for dusty solstice conditions an extremely intense and approximately angular momentum conserving hadley circulation is responsible for creating the low potential vorticity configuration this can be contrasted with the venus titan numerical simulations discussed by allison et al in which quasi barotropic eddies appear to be largely responsible for the existence of low potential vorticity in lower and midlatitudes at a near equinox seaso

olivine dolerite intrusionsin the fastnet basin sills of olivine microgabbro and olivine dolerite 0 5 180 m thick intrude lower liassic hettangian sinemurian sediments in the fastnet basin a sw extension of the n celtic sea basin about lat 50 n long 10 w the evidence of 3 wells and 2300 km of seismic reflection profiles indicates 6 major sills and sill complexes and 3 possible igneous centres or plugs a high level sill may intrude lower cretaceous sediments and one plug apparently deforms cretaceous reflectors k ar ages on separated biotites from a thick sill intruding liassic sediments gave 170 4 ma bajocian this sill contains 30 olivine fo 70 73 20 clinopyroxene magnesian salite 45 plagioclase an 60 78 with accessory magnetite ilmenite edenitic hornblende ti phlogopite apatite zircon spinel in olivine and sulphides alteration to serpentine minerals chlorite sericitic mica and leucoxene is sporadic the magmatism in the fastnet province thus appears to have been active from the mid jurassic to the early tertiary related initially to the time of initial rifting between the european and american plates and subsequently to their final separation between greenland and rockall and associated thulean magmatism

models of single stage concomitant potassium argon exchange an interpretation of discordant whole rock k ar data from hydrothermally altered igneous rocks of the south pennine orefield u k abstract a model of single stage concomitant potassium and argon exchange is advanced to explain the existence of rectilinear isochrons in potassium argon correlation diagrams produced from suites of altered rocks negative isochron intercepts are shown to be a consequence of fractional argon loss which exceeds potassium loss and it is demonstrated that no information of immediate geological significance can be obtained from the gradient of such an isochron bounds to the primary formation age and age of exchange event may be established using extreme values of the observed potassium content and from estimates based on the inferred petrology and chemistry of the unaltered rock and or its alteration products ten carboniferous igneous units from the south pennine orefield involving thirty eight independent samples are investigated by means of the model and eight of the units are consistent with a model of potassium and argon exchange occurring in earliest mesozoic times ca 200 ma it is argued that this conclusion augments the already substantial body of evidence for an identifiable widespread igneous and hydrothermal province associated with early rifting processes in the north atlantic

winter polar warmings and the meridional transport on mars simulated with a general circulation model abstract winter polar warmings in the middle atmosphere of mars occur due to the adiabatic heating associated with the downward branch of the cross equatorial meridional circulation thus they are the manifestation of the global meridional transport rather than of local radiative effects we report on a series of numerical experiments with a recently developed general circulation model of the martian atmosphere to examine the relative roles of the mechanical and thermal forcing in the meridional transport the experiments were focused on answering the question of whether the martian circulation is consistent with the thermally driven nearly inviscid hadley cell as was pointed out by some previous studies or it is forced mainly by zonally asymmetric eddies it is demonstrated that under realistic conditions in the middle atmosphere the meridional transport is maintained primarily by dissipating large scale planetary waves and solar tides this mechanism is similar to the extratropical pump in the middle atmosphere on earth only in the run with artificially weak zonal disturbances was the circulation reminiscent of thermally induced hadley cells in the experiment with an imposed dust storm the modified atmospheric refraction changes the vertical propagation of the eddies as the result the eliassen palm fluxes convergence increases in high winter latitudes of the middle atmosphere the meridional transport gets stronger and the polar temperature rises additional numerical experiments demonstrated that insufficient model resolution increased numerical dissipation and especially neglect of non lte effects for the 15 m co2 band could weaken the meridional transport and the magnitude of polar warmings in gcms

in situ measurement of dissolved chloride in high temperature hydrothermal fluids abstract the ability to continuously monitor chemical properties of hydrothermal vent effluents for extended periods of time is essential to understanding dynamic processes responsible for the temporally variable nature of mid ocean ridge hydrothermal systems although instruments do exist for some parameters there has been no sensor capable of measuring the chloride concentration an indicator of possible phase separation on a real time and long term basis in this article we discuss the construction of a novel instrument which measures solution resistance as a proxy for chloride concentration the sensor consists of four gold electrodes embedded in a cylindrical zro 2 ceramic housing it has been successfully deployed in several high temperature vents at the main endeavour field mef on the juan de fuca ridge in the ne pacific and calibrated under simulated hydrothermal conditions ranging up to 380 c and 300 bar the in situ data clearly demonstrate a tidal influence on the effluent from some high temperature vents possibly relating to a subsurface mixing process involving non seawater end members non tidal changes are used to constrain the sequence and type of controls operating on fluids circulating within the subsurface

tectonothermal evolution of the northeastern margin of iberia since the break up of pangea to present revealed by low temperature fission track and u th he thermochronology a case history of the catalan coastal ranges abstract the catalan coastal ranges ccr form part of the northeastern iberian mediterranean margin this margin typifies the transition zone between the thickened crust of the pyrenees and ebro basin 32 to 40 km and the extremely thinned continental crust of the offshore valencia trough 8 km despite intensive geological research in recent decades the issue of the unsolved thermochronological history has hardly been addressed for the catalan margin this study provides for the first time a continuous low temperature thermochronological dataset covering the period from late paleozoic to present day more than 100 analyses have been performed in an area less than 200 km long by 50 km wide zircon and apatite fission track zft and aft results of the hercynian basement yield cooling ages between 254 41 104 16 ma and 223 27 16 3 ma respectively apatite u th he ages range between 58 3 and 2 0 0 2 ma these thermochronological data provide evidence for a very active geothermal past revealing above all an important thermal period coeval with the triassic early jurassic break up of pangea hereby we discuss and suggest various mechanisms responsible for the elevated crustal temperatures detected this new dataset also provides new constraints on the allocation of areas where exhumation uplift occurred synchronous with some tectonic phases the widespread presence of hydrothermal mineralizations and the present day overmaturity state of the mesozoic sediments with regard to oil potential in the ccr despite the local scale of the catalan margin the very detailed study here presented sheds some light on the geological implications of results from other more regional thermochronological studies on the iberian microplate studies that yield similar mesozoic thermochronological record for areas that also experienced extensional fracturing and subsidence during the break up of pangea

a review of molybdenite and fluorite mineralisation in caledonian granite basement western ireland incorporating new field and fluid inclusion studies and re os and u pb geochronology abstract the recent discovery of late magmatic quartz vein hosted molybdenite and exceptional gem quality vein fluorite in the caledonian galway granite complex ggc has prompted a review of these contrasting styles of mineralisation in the late caledonian granite basement connemara western ireland existing published u pb and re os chronometry and fluid inclusion microthermometry are combined with new a geological field observations b u pb zircon and re os molybdenite geochronometry and c fluid inclusion microthermometry to generate a new pressure temperature time model p t t of mineralisation for the ggc re os chronometry molybdenite indicates that granite related molybdenite mineralisation extended from 423 to 380ma overlapping with the ggc emplacement history determined by u pb zircon chronometry the p t t model reflects initial granite emplacement and mo mineralisation at 423ma followed by lower p and t granite emplacement and related quartz vein hosted mo mineralisation at 410ma carna pluton 400ma kilkieran pluton and at 380ma costelloe murvey granite the gem quality fluorite veins in the ggc represent late triassic hydrothermal mineralisation these veins form part of a regional n atlantic european triassic jurassic hydrothermal mineralisation province vein emplacement was triggered by the rifting of the n atlantic facilitating crustal thinning and subsidence of continental crust and initiating hydrothermal activity at the margins of mesozoic basins

the path to covis a review of acoustic imaging of hydrothermal flow regimes abstract acoustic imaging of hydrothermal flow regimes started with the incidental recognition of a plume on a routine sonar scan for obstacles in the path of the human occupied submersible alvin developments in sonar engineering acoustic data processing and scientific visualization have been combined to develop technology which can effectively capture the behavior of focused and diffuse hydrothermal discharge this paper traces the development of these acoustic imaging techniques for hydrothermal flow regimes from their conception through to the development of the cabled observatory vent imaging sonar covis covis has monitored such flow eight times a day for several years successful acoustic techniques for estimating plume entrainment bending vertical rise volume flux and heat flux are presented as is the state of the art in diffuse flow detection

hydrothermal fluids during mesozoic reactivation of the st lawrence rift system canada c o sr and pb isotopic characterization calcite veins with accessory galena sphalerite barite and fluorite are abundant within the ottawa bonnechere and the charlevoix saguenay failed arms of the st lawrence rift system which developed during early paleozoic times within gneisses of the grenville province of canada the mineral assemblages paragenesis and precipitation temperatures of the veins resemble the mississippi valley deposits crosscutting relationships with carbonate rocks of the st lawrence lowlands and deformed carbonate rock slivers of the charlevoix astrobleme show that the ottawa graben and saguenay graben veins are younger than mid ordovician or post devonian respectively 18o and 13c values for vein calcite are positively correlated and range from 11 to 24 and 9 to 3 respectively 87sr86sr in calcite and barite range from 0 7129 to 0 7081 the fluids that precipitated calcite were part of a hydrothermal system dominated by meteoric water enriched in 18o by exchange with silicate minerals and deep seated carbon either from mantle outgassing deep seated brines of the canadian shield or from oxidation of reduced carbon in high grade metamorphic rocks veins cutting marbles of the grenville supergroup have lower 87sr86sr and higher 18o and 13c values than those hosted in quartzofeldspathic gneisses of the grenville province showing that the fluids were modified by interaction at depth with the marbles stable and sr isotope compositions are also correlated with layb ratios in calcite supporting the fact that the veins formed within similar hydrothermal systems in both the ottawa and saguenay grabens the pb isotopic compositions of vein galena are radiogenic 206pb204pb 18 0 19 7 207pb204pb 15 5 15 7 208pb204pb 37 9 41 0 and positively correlated in conventional pb pb diagrams pb isotope and ree data strongly suggest that the fluids leached selectively at the mineral scale gneisses of the grenville province the basinal fluids within the shelf sequence of the western appalachians had 208pb204pb ratios in the lower paleozoic significantly lower than those of vein galena this excludes the basin brine model of formation for the vein deposits like suggested for the mississippi valley deposits the veins rather formed in the mesozoic in response to the rifting of northeastern north america and the reactivation of the st lawrence rift

characteristics of 4 day oscillations trapped by the juan de fuca ridge current meter observations from different studies along the crest of the juan de fuca ridge have been combined to show new features of the relatively large broad spectral peak centered near a period of about 4 days the coherence range of the 4 day oscillations has been extended to the extreme ends of the ridge and the trapped waves appear to propagate northward along the entire length of the ridge at about 1 m s spectral amplitudes are about double on the south end compared to the north end and a recent model for bottom trapped subinertial waves over topography shows this may be due to variations in ridge width allen and thomson 1993 new observations show coherence between temperatures and currents near the south cleft vent field and suggest 4 day oscillations can play a major role in the local advection of hydrothermal plumes these observations combined with earlier results demonstrate that 4 day oscillations are a significant ridge trapped feature and they suggest that other ridges may be important in transmitting energy over much longer distances

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

constrained circulation at endeavour ridge facilitates colonization by vent larvae understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid ocean ridge system remains a major challenge in oceanic research1 2 among the factors considered important in the recruitment of deep sea larvae are metabolic lifespan the connectivity of the seafloor topography and the characteristics of the currents3 here we use current velocity measurements from endeavour ridge to examine the role of topographically constrained circulation on larval transport along ridge we show that the dominant tidal and wind generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest and that hydrothermal plumes rising from vent fields in the valley drive a steady near bottom inflow within the valley extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid ocean ridges shields larvae from cross axis dispersal into the inhospitable deep ocean this effect augmented by plume driven circulation within rift valleys having active hydrothermal venting helps retain larvae near their source larvae are then exported preferentially down ridge during regional flow events that intermittently over ride the currents within the valley

a global view of gravity waves in the martian atmosphere inferred from a high resolution general circulation model global characteristics of the small scale gravity wave gw field in the martian atmosphere obtained from a high resolution general circulation model gcm are presented for the first time the simulated gw induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km the model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of gws mountainous regions and the meandering winter polar jet orographic gws are filtered while propagating upward and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities wave fluxes are directed mainly against the local wind gw dissipation in the upper mesosphere generates body forces of tens of m s 1 per martian solar day sol 1 which tend to close the simulated jets the results represent a realistic surrogate for missing observations which can be used for constraining gw parameterizations and validating gcm simulations

high resolution thermal inertia mapping from the mars global surveyor thermal emission spectrometer abstract high resolution thermal inertia mapping results are presented derived from mars global surveyor mgs thermal emission spectrometer tes observations of the surface temperature of mars obtained during the early portion of the mgs mapping mission thermal inertia is the key property controlling the diurnal surface temperature variations and is dependent on the physical character of the top few centimeters of the surface it represents a complex combination of particle size rock abundance exposures of bedrock and degree of induration in this work we describe the derivation of thermal inertia from tes data present global scale analysis and place these results into context with earlier work a global map of nighttime thermal bolometer based thermal inertia is presented at 1 4 per pixel resolution with approximately 63 coverage between 50 s and 70 n latitude global analysis shows a similar pattern of high and low thermal inertia as seen in previous viking low resolution mapping significantly more detail is present in the high resolution tes thermal inertia this detail represents horizontal small scale variability in the nature of the surface correlation with albedo indicates the presence of a previously undiscovered surface unit of moderate to high thermal inertia and intermediate albedo this new unit has a modal peak thermal inertia of 180 250 j m 2 k 1 s 1 2 and a narrow range of albedo near 0 24 the unit covering a significant fraction of the surface typically surrounds the low thermal inertia regions and may comprise a deposit of indurated fine material local 3 km resolution maps are also presented as examples of eolian fluvial and volcanic geology some impact crater rims and intracrater dunes show higher thermal inertias than the surrounding terrain thermal inertia of aeolian deposits such as intracrater dunes may be related to average particle size outflow channels and valleys consistently show higher thermal inertias than the surrounding terrain generally correlations between spatial variations in thermal inertia and geologic features suggest a relationship between the hundred meter scale morphology and the centimeter scale surface layer

martian great dust storms interpretive axially symmetric models abstract the simplified theory of steady nearly inviscid thermally forced axially symmetric atmospheric motions developed by schneider 1977 is applied to the study of the problem of the martian great dust storms a highly idealized calculation of the atmospheric response to heating concentrated in a small latitude band is carried out qualitatively different local and global response regimes are identified as the heating is increased from zero some critical value is reached at which the response jumps from local to global it is suggested that this transition from local to global response may be related to the observed explosive growth of great dust storms results from the idealized model indicate that subtropical latitudes are favored for the initiation of a dust raising global dust storm as the meridional scale of the response to a heat source of fixed intensity is largest for the heat source located close to the equator but the surface stress in the zonal direction produced by the response increases as the heat source is moved towards the poles also the steady axially symmetric martian response to solar forcing is examined modification to the solar forced response due to an added latitudinally localized heat source is briefly discussed and it is indicated that similar transition behavior to that obtained in the more idealized model is to be expected in this case also implications of the dynamical model for the dependence of the occurence of great dust storms on orbital parameters are remarked on

dating of alteration episodes related to mercury mineralization in the almaden district spain the almadin mercury deposits represent one of the largest geochemical anomalies on earth but the mode and timing of their formation remains a matter of controversy there are two main possibilities hydrothermal solutions associated with alkali basalt volcanism in the silurian and devonian or regional hydrothermal activity during later hercynian metamorphism although these models can be distinguished by determining the age of ore deposition no suitable isotopic method had been applied to the problem prior to this study we report here on vacuum encapsulated and more traditional laser ar ar dating performed on illite concentrates and cr rich micas that are intimately associated with mercury mineraiization in both devonian and silurian host rocks illite is associated with a later stage of hg mineralization cinnabar kaolinite pyrophyllite chlorite which locally replaces an earlier episode associated with carbonates and cr mica the dating results from illite separates suggest that the later stages of hg mineralization or remobilization occurred about 360 ma which is about 20 ma younger than any mercury hosting rocks in the district and coincides with the onset of regional deformation during the hercynian orogeny cr mica ages are variable and range from 365 ma to 427 ma this age range spans the period between the deposition of the criadero quartzite the oldest sedimentary unit hosting mercury and the later episode of mineralization this suggests that mineralization started at least by the mid to lower silurian and the younger argon ages for cr mica could represent partial to nearly total argon loss caused by the hercynian metamorphic event it appears that both postulated styles of mercury mineralization occurred separated in time by up to 80 million years

entrainment and bending in a major hydrothermal plume main endeavour field juan de fuca ridge 1 we measure expansion rate and bending in a 23 hour time series of acoustic images of the lower 25 m section of a buoyant hydrothermal plume rising from grotto vent in the main endeavour field juan de fuca ridge we then calculate entrainment coefficient the constant of proportionality relating mean inflow velocity at the plume edge to maximum mean upward velocity within the plume the plume section alternately bends southwest at relatively high inclinations 37 and northeast at lower inclinations at irregular intervals twice during this time period apparently driven by current reversals in the mixed semi diurnal tidal cycle the measured expansion rates 0 11 0 25 m m and calculated entrainment coefficients 0 07 0 18 are directly proportional to the degree of bending r2 0 75 the loss of buoyancy flux related to enhanced mixing in a stratified environment during bending may contribute to reduction of potential rise height consistent with predicted 400 m and measured 300 350 m plume tops

a turbulent convection model with an observational context for a deep sea hydrothermal plume in a time variable cross flow 1 a turbulent convection model for a hydrothermal fluid discharging into a tidally modulated stratified cross flow is used to investigate time variable conditions in plumes such as the one rising from dante a sulfide mound at 2175 m depth on the endeavour segment of the juan de fuca ridge that plume is the consequence of the coalescence of 10 or more small individual plumes from chimneys discharging hot salt diminished fluid into the near bottom ocean at dante the discharge encounters ambient horizontal currents with speeds oscillating from near zero to a maximum of 7 cm s 1 speeds which can bend a plume more than 45 from the vertical model results are compatible with field measurements of the plume footprint size and vertical velocity both 20 m above the source when earlier estimates for dante s heat flux of 50 mw drive the convection the small scale short period variability of velocities and properties distributions observed in the field is mimicked in model results plumes pool above a source during periods of weak cross flows but stream away from the source with more diluted concentrations and lower rise heights at other times plume distributions at identical cross flow speeds differ whether the flow is accelerating or decelerating small changes in background hydrographic profiles create differences in rise heights comparable to those caused by large changes in source buoyancy flux if put into an entrainment context results suggest an entrainment coefficient eff that varies from 0 11 to 0 025 with increasing height 2 76 m above the source

fluid inclusions in pre ore minerals from the carbonate hosted mercury deposits in the espadan ranges eastern spain abstract the fluids associated with pre ore minerals in the carbonate hosted mercury veins from the espadan ranges eastern spain have been studied using microthermometry cryo sem eds raman spectroscopy and crush leach analyses in order to determine their origin and the processes responsible for mineralization three primary fluid inclusion types have been found in quartz and dolomite 1 type s composed of liquid vapour mainly co 2 halite 2 type s v composed of liquid high density co 2 double bubble halite and 3 type v composed of high density co 2 n 2 mixtures type s fluid inclusions are preferentially trapped in betxi type veins characterized by the presence of hydrothermal dolomite whereas type v fluid inclusions are trapped almost exclusively in eslida type veins which were without dolomite from these data two different fluids can be inferred to occur during the period of formation of the veins 1 a complex polysaline brine of nacl kcl cacl 2 mgcl 2 so 4 2 h 2 o composition with a salinity of up to 33 eq wt nacl and a 2 co 2 n 2 rich fluid the brine halogen composition points to its secondary origin caused by the dissolution of underlying marine evaporites it is thought that these deposits were formed during jurassic or cretaceous rifting periods as a consequence of fluid mixing between a high salinity secondary brine and connate waters the generation of a co 2 n 2 rich phase caused the pressure increase of the fluids that favoured the hydraulic fracturing of the enclosing rock dolostone the origin of this volatile rich phase probably occurred due to the oxidation and thermochemical breakdown of the organic matter contained in the host rock this event is recorded by the coetaneous trapping of both aqueous and carbonic fluids in quartz crystals the formation conditions for the hypogene sulphide paragenesis are obscure but the coincidence between the preferential trapping of type v fluid inclusions the absence of hydrothermal dolomite and the major abundance of mercury in eslida type veins is thought to be linked to a mercury fractionation event to the vapour phase during the release of the volatiles

a fluid inclusion and stable isotope study of 200 ma of fluid evolution in the galway granite connemara ireland fluid inclusions in granite quartz and three generations of veins indicate that three fluids have affected the caledonian galway granite these fluids were examined by petrography microthermometry chlorite thermometry fluid chemistry and stable isotope studies the earliest fluid was a h2o co2 nacl fluid of moderate salinity 4 10 wt nacl eq that deposited late magmatic molybdenite mineralised quartz veins v1 and formed the earliest secondary inclusions in granite quartz this fluid is more abundant in the west of the batholith corresponding to a decrease in emplacement depth within veins and to the east this fluid was trapped homogeneously but in granite quartz in the west it unmixed at 305 390 c and 0 7 1 8 kbar homogeneous quartz 18o across the batholith 9 5 0 4 n 12 suggests v1 precipitation at high temperatures perhaps 600 c and pressures 1 3 kbar from magmatic fluids microthermometric data for v1 indicate lower temperatures suggesting inclusion volumes re equilibrated during cooling the second fluid was a h2o nacl kcl low moderate salinity 0 10 wt nacl eq moderate temperature 270 340 c high d 18 2 low 18o 0 5 2 0 fluid of meteoric origin this fluid penetrated the batholith via quartz veins v2 which infill faults active during post consolidation uplift of the batholith it forms the most common inclusion type in granite quartz throughout the batholith and is responsible for widespread retrograde alteration involving chloritization of biotite and hornblende sericitization and saussuritization of plagioclase and reddening of k feldspar the salinity was generated by fluid rock interactions within the granite within granite quartz this fluid was trapped at 0 5 2 3 kbar having become overpressured this fluid probably infiltrated the granite in a meteoric convection system during cooling after intrusion but a later age cannot be ruled out the final fluid to enter the granite and its host rocks was a h2o nacl cacl2 kcl fluid with variable salinity 8 28 wt nacl eq temperature 125 205 c d 17 to 45 18o 3 to 1 2 13cco2 19 to 0 and 34ssulphate 13 23 that deposited veins containing quartz fluorite calcite barite galena chalcopyrite sphalerite and pyrite v3 correlations of salinity temperature d and 18o are interpreted as the result of mixing of two fluid end members one a high d 17 to 8 moderate 18o 1 2 2 5 high 13cco2 4 low 34ssulphate 13 high temperature 205 230 c moderate salinity 8 12 wt nacl eq fluid the other a low d 61 to 45 low 18o 5 4 to 3 low 13c 10 high 34ssulphate 20 23 low temperature 80 125 c high salinity 21 28 wt nacl eq fluid geochronological evidence suggests v3 veins are late triassic the high d end member is interpreted as a contemporaneous surface fluid probably mixed meteoric water and evaporated seawater and or dissolved evaporites whereas the low d end member is interpreted as a basinal brine derived from the adjacent carboniferous sequence this study demonstrates that the galway granite was a locus for repeated fluid events for a variety of reasons from expulsion of magmatic fluids during the final stages of crystallisation through a meteoric convection system probably driven by waning magmatic heat to much later mineralisation concentrated in its vicinity due to thermal tectonic and compositional properties of granite batholiths which encourage mineralisation long after magmatic heat has abated

permian clockwise rotations of the ebro and corso sardinian blocks during iberian armorican oroclinal bending preliminary paleomagnetic data from the catalan coastal range ne spain abstract paleomagnetic investigations of early permian and triassic magmatic rocks from catalan coastal ranges provide three magnetic directions which are interpreted as primary magnetizations and partly as overprints the succession of magnetic directions is interpreted in terms of a succession of large scale clockwise rotations which bring the whole assembly of pyrenees catalonia corsica sardinia and maures esterel massifs from the southeast of the massif central to the west during permian this major movement is associated with clockwise rotation of northern limb of the iberian orocline during latest carboniferous and early permian 305 290 ma subsequently permian large scale dextral transtensional extensional shearing operated along aquitanian shear belt between the massif central in the northeast and the iberian variscan massifs in the southwest the latest phase of the rotation in the late permian early triassic is associated with alkaline magmatism probably linked to neo tethys opening activity in western europe

magnitude and variance of near bottom horizontal heat flux at the main endeavour hydrothermal vent field 1 we characterize hydrothermal plumes and hydrography within the axial valley of the endeavour segment juan de fuca ridge northeast pacific using data from an autonomous underwater vehicle a lowered ctd and two current meter moorings our survey of the main endeavour hydrothermal vent field mef shows hydrographic variability on scales as short as 20 m and 10 min within the 100 m deep axial valley the mean flow is 1 5 cm s to the north and tidal oscillations have 5 cm s amplitude combining the mean flow with an estimate of the difference in average temperature observed north and south of mef we find that the net along axis horizontal heat flux has a mean magnitude of 8 42 mw an advection diffusion model forced by local current records explains the observed temporal hydrographic variability and shows that mean horizontal flux variance is correspondingly high standard deviation 63 mw a steady state mef heat budget constrained by the observed horizontal flux and measurements of vertical fluxes from other studies has two implications the mef heat flux is partitioned about equally between diffuse and focused vents and about 85 of the flux from diffuse plumes is entrained by focused plumes

dusty deep convection in the mars year 34 planet encircling dust event dusty convection convective activity powered by radiative heating of dust is a ubiquitous phenomenon in mars s atmosphere but is especially deep that is impactful on the middle atmosphere and widespread during planet encircling dust events pede that occur every few mars years my yet the relative roles of dusty deep convection and global dynamics such as the principal meridional overturning cell pmoc and the radiative tides in dust storm development and the vertical transport of dust and water are still unclear here observations from the mars climate sounder on board mars reconnaissance orbiter mro mcs are used to study dusty deep convection and its impact on middle atmospheric water content during the my 34 pede commenced june 2018 additional context is provided by mro mcs observations of the my 28 pede commenced june 2007 this investigation establishes that a few localized centers of dusty deep convection in the tropics formed in the initial phases of both pede simultaneously with a substantial increase in middle atmospheric water content the growth phase of the my 34 pede was defined by episodic outbreaks of deep convection along the acidalia and utopia storm tracks as opposed to less episodic more longitudinally distributed convective activity during the my 28 pede the most intense convection during both pede was observed in southern eastern tharsis where mro mcs observed multiple instances of deep convective clouds transporting dust to altitudes of 70 90 km these results suggest that martian pede typically contain multiple convectively active mesoscale weather systems

chronology of magmatism and mineralization in the kassandra mining area greece the potentials and limitations of dating hydrothermal illites abstract various geochronological methods u pb rb sr and k ar have been applied to constrain the timing of magmatism and polymetallic mineralization in the kassandra mining district northern greece these data provide the first geochronological evidence that porphyry copper mineralization proximal copper skarns and distal high temperature carbonate hosted pb zn ag au replacement ores formed contemporaneously and probably within less than 2 million years polymetallic mineralization is temporally related to the emplacement of granodioritic to quartz dioritic porphyries 24 25 ma that postdate the largest post tectonic intrusion of the area the stratoni granodiorite 27 9 1 2 ma andesite porphyry dikes which crosscut the pb zn ag au ores and associated alterations represent the last magmatic phase in the area 19 1 0 6 ma and did not contribute to metal concentration the combination of k ar rb sr and oxygen isotope studies of hydrothermal illite rich clays and careful granulometric analysis constrains the reliability of these geochronological methods and emphasizes the importance of characterizing the post formational history of the sample we identify various processes which partly disturbed the k ar and rb sr system of some clays such as retrograde alteration by heated meteoric waters superimposed supergene illitization and resetting of both isotopic systems due to a hydrothermal overprint related to the intrusion of the andesite porphyry our data however suggest that diffusive ar loss from the finest clay fractions k ar system conventional k ar ages of 200 c therefore do not give reliable formation ages the loss of ar may be used to model the cooling history of the hydrothermal system applying the concept of closure temperatures dodson 1973 40k 40arrad isochrons of natural coarser grained 0 6 m size fractions of illites from single samples even when slightly contaminated with feldspars may yield meaningful ages either of the formation or of a reheating event the rb sr dating of hydrothermal clays is sensitive to contamination by adsorbed strontium which may not be cogenetic with the clay as well as feldspars which may not have been homogenized isotopically by the illitization process

near inertial motions over a mid ocean ridge effects of topography and hydrothermal plumes we investigate the spatial structure of near inertial motions in the vicinity of the endeavour segment of juan de fuca ridge approximately 48 n 129 w in the northeast pacific ocean on the basis of time series current and water property data collected from september 1984 to september 1987 near inertial motions are ubiquitous features of the 2200 m water column with root mean square rms current speeds comparable to those of the dominant m2 tidal currents within the lower 1000 m of the water column where most of the observations were obtained near inertial oscillations have rms current speeds of o 1 cm s and vertical isotherm displacements of o 10 m the fluctuations are confined to the frequency band 0 966 1 079 f f is the local coriolis parameter and have characteristic event durations of 1 week although the spectra of subsurface motions are dominated by the blue shifted superinertial band significant spectral peaks are found also in the subinertial and inertial frequency bands marked alteration of the near inertial current amplitudes occurs over two well defined depth zones within the study region within the 200 m zone immediately above the 2100 m ridge crest current amplitudes are amplified by a factor of 1 2 1 7 because of bottom reflection and or scattering of the downward propagating energy evidence that the amplification may be linked to bottom reflection rather than to scattering is provided by flattening and cross slope rotation of the near inertial current ellipses with increased proximity to the top of the ridge reflection would occur at grazing angles of less than 1 and would be associated with surface generated waves originating at distances of over 100 km from the observational site in contrast to the enhanced amplitudes immediately above the top of the ridge near inertial currents within the 1600 to 1800 m depth range undergo pronounced attenuation and frequency alteration amplitude attenuation is especially pronounced for motions in the superinertial band and may arise through critical layer absorption of downward propagating waves as they encounter increased vertical shear in the background flow the increased shear is most likely associated with buoyancy induced flow formed by the extensive hydrothermal plume emanating from vent sites in the axial valley along the ridge crest but it could also be related to bottom trapped oscillations over the steep ridge topography near inertial motions are estimated to have vertical coherence scales of the order of 10 100 m while horizontal coherence scales exceed the 50 km separation between the mooring locations minimum vertical and horizontal coherences are found for the depth zone 1600 1800 m while maximum correlation occurs for near bottom motions immediately above the crest of the ridge weak near inertial motions are observed within the 100 m deep axial valley

thermal structure and dust loading of the martian atmosphere during late southern summer mariner 9 revisited the temperature structure and dust loading of the martian atmosphere are investigated using thermal emission spectra recorded by the mariner 9 infrared interferometer spectrometer iris the analysis is restricted to a subset of the iris data consisting of approximately 2400 spectra in a 12 day period extending from ls 343 to ls 348 corresponding to late southern summer on mars simultaneous retrieval of the vertical distribution of both atmospheric temperature and dust optical depth is accomplished through an iterative procedure which is performed on each spectrum the inclusion of dust opacity in the retrieval algorithm causes the retrieved temperatures to change by more than 20 k in some atmospheric layers the largest column integrated 9 m dust optical depths 0 4 occur over the equatorial regions the highest atmospheric temperatures 260 k are found at low altitudes near the subsolar latitude 6 s while the coldest temperatures 150 k are found at levels near 1 0 mbar over the winter pole a comparison of temperature maps for 1400 lt and 0200 lt indicates diurnal temperature variations as large as 80 k at low altitudes near the subsolar latitude whereas diurnal temperature changes at pressures less than 1 0 mbar are typically about 10 k both dayside and night side temperatures above about 0 1 mbar 40 km are warmer over the winter north polar region than over the equator or the summer south polar region this thermal structure suggests the existence of a net zonally averaged meridional circulation with rising motion at low latitudes poleward flow at altitudes above 40 km and subsidence over the poles because a meridional circulation transports atmospheric constituents as well as heat it has significant implications for the net flux of dust and water into the polar regions

a method for doppler acoustic measurement of black smoker flow fields 1 a method is developed for using multibeam sonar to map the flow velocity field of black smoker plumes the method is used to obtain two dimensional cross sectional maps of vertical velocity but is capable of mapping velocity in three dimensions this is in contrast to conventional current meters which measure only at several points and acoustic doppler current profilers whose diverging beams cannot readily map the interior of a plume geometric corrections are used to estimate the vertical component of velocity compensating for ambient current the method is demonstrated using data from the main plume at the grotto vent complex in the main endeavour field juan de fuca ridge and the errors due to noise signal fluctuations and fluctuations in plume structure are estimated

numerical simulation of hydrothermal vent induced circulation at endeavour ridge hydrothermal venting at endeavour ridge is focused at five major vent fields spaced at 2 km intervals along a narrow 1 km wide north south trending rift valley a princeton ocean model with an axially symmetric rift valley centered within a rotating full depth 2400 m stratified ocean is used to simulate the circulation and associated temperature and salinity fields generated by vertical heat fluxes from the five vent fields steady seafloor heat fluxes are introduced instantaneously to a quiescent ocean using the model provision for boundary fluxes the model achieves a quasi steady state in about 80 days results are consistent with observation in particular buoyant plumes emanating from the larger vent fields rise to trapping depths as shallow as 1850 m 350 m above bottom and spread laterally with the vent induced circulation plume anomalies remain confined to within several kilometers of the ridge except to the west where anomalies extend more than 10 km off axis as with observations modeled currents within the valley consist of a strong 10 cm s 1 poleward inflow within roughly 75 m of the bottom and an equally strong equatorward counterflow above that depth weak 1 cm s 1 equatorward flow develops over the flank of the west ridge and weak poleward flow over the flank of the east ridge cyclonic relative vorticity dominates the model circulation within the valley while anticyclonic vorticity prevails above the depth of neutral plume buoyancy findings support the notion that turbulent entrainment by buoyant plumes forces a mean poleward flow within the confines of the endeavour ridge axial valley

discrete and diffuse heat transfer atashes vent field axial volcano juan de fuca ridge abstract heat fluxes of discrete and diffuse components of hydrothermal discharge are estimated from submersible measurement in the ashes vent field located in the caldera of axial volcano on the central juan de fuca ridge the discrete component comprises discharge from individual vents and the diffuse component comprises seepage from large areas of the seafloor the investigation centered on the high temperature portion of the field a 100 100 m area of fractured lobate and sheet lava flows encompassing discrete discharge 326 c from seven individual vents and diffuse flow from intervening areas a total of 4 4 2 10 6 w was estimated for the discrete heat flux based on measurements of effluent temperature flow rate and orifice diameter at all the known individual vents by d s v alvin in september 1987 a total of 15 75 10 6 w was calculated with a standard plume model for the diffuse flux based on a grid of temperature measurements at altitudes of 1 m and 20 m above the study area using a 1 m long vertical array of temperature sensors mounted at the front of alvin s instrument platform the study indicates that 1 the diffuse component rises separately from the discrete component of hydrothermal discharge and is laterally advected by a prevailing current below the discrete component and that 2 the diffuse component of convective heat flux is approximately an order of magnitude greater than the discrete component in the high temperature portion of the ashes vent field

dynamical modeling of a planetary wave mechanism for a martian polar warming abstract a dynamical mechanism for the martian atmospheric polar warming observed by the viking irtm during the 1977 winter solstice dust storm and a similar one possibly observed by mariner 9 in 1971 is proposed and investigated using a simplified nonlinear model the model is of a type previously used to successfully simulate the essential aspects of terrestrial sudden stratospheric warmings the dynamical mechanism is in part very similar fundamentally to that responsible for these warmings involving planetary scale waves a number of numerical experiments have been conducted to assess the basic viability of such a mechanism for the martian polar warming and to examine its sensitivity to several factors these experiments demonstrate that a planetary wave mechanism can produce a polar warming with the magnitude and suddenness of that observed a planetary wave mechanism must primarily involve wavenumber 1 as wavenumber 2 is too strongly vertically trapped to produce a warming like that observed the necessary wave forcing in the present model can be topographic mechanical or thermal and nonstationary and is relatively large but certainly plausible the strong radiative damping in the mars atmosphere acts to substantially inhibit a warming through its effects on both the zonal flow and the wave dissipation plays a greater role relative to transience in a model martian warming of the type studied here than in a sudden stratospheric warming increasing radiative damping during a warming due to higher temperatures and greater dust loading may play a role in yielding a relatively rapid cooling phase for the mars warming event the residual mean meridional circulation during a model warming entails strong poleward and downward flow into high northern latitudes throughout a very deep region this probably indicates similar transport of atmospheric dust as well as water such transports are of considerable potential significance for both the dust and water cycles on mars

gravity waves and high altitude co2 ice cloud formation in the martian atmosphere we present the first general circulation model simulations that quantify and reproduce patches of extremely cold air required for co2 condensation and cloud formation in the martian mesosphere they are created by subgrid scale gravity waves gws accounted for in the model with the interactively implemented spectral parameterization distributions of gw induced temperature fluctuations and occurrences of supersaturation conditions are in a good agreement with observations of high altitude co2 ice clouds our study confirms the key role of gws in facilitating co2 cloud formation discusses their tidal modulation and predicts clouds at altitudes higher than have been observed to date

a late triassic 40ar 39ar age for the el hammam high ree fluorite deposit morocco mineralization related to the central atlantic magmatic province el hammam is the only fluorite mine in morocco production 100 000 t year the fluorite mineralization is in an array of fluorite calcite veins and is characterized by unusually high ree content in carbonate minerals 1 400 ppm in calcite up to 2 000 ppm in siderite and in fluorite about 600 ppm since the 1960s the genesis of the deposit has been attributed to a mesothermal hydrothermal event connected with late variscan granitic intrusions precise 40ar 39ar dating of hydrothermal k feldspar yields an age of formation of the el hammam deposit at 205 1 ma its genesis is therefore associated in time and space with the development of the triassic jurassic basins and the associated anorogenic continental flood basalts of the moroccan mesetian middle atlas the source of the hydrothermal mineralization magmatic and or metamorphic is discussed

estimates of gravity wave drag on mars indication of a possible lower thermospheric wind reversal spectral gravity wave parameterization suitable for planetary thermospheres applied to wind and temperature from mars climate database reveals enormously strong drag incompatible with the wind distribution it points out to a possible wind reversal in the 110 140 km layer similar to the one in the earth s lower thermosphere

modeling the effects of tidal loading on mid ocean ridge hydrothermal systems 1 tidal signals are observed in numerous time series measurements obtained from mid ocean ridge hydrothermal systems in some instances these tidal signals are clearly the result of ocean currents but in other instances it appears that the signals may originate in the subseafloor formation in order to explore the effect of ocean tidal loading on mid ocean ridge hydrothermal systems we apply a one dimensional analytical model of tidal loading on a poroelastic half space and develop a two dimensional numerical model of tidal loading on a poroelastic convection cell the one dimensional models show that for a reasonable range of fluid elastic and hydrological properties the loading efficiency may vary from near zero to near unity and the diffusive penetration depth for tidal pressure signals may vary from tens of meters to kilometers the two dimensional models demonstrate that tides may generate significant vertical and horizontal pressure gradients in mid ocean ridge hydrothermal systems as a result of spatial variations in fluid temperatures and the elastic and hydrological properties of the crust these continuum models predict that outflow temperature perturbations will be very small 10 4 c but in real systems where the continuum hypothesis does not always apply the perturbations may be on the order of 0 1 c the models predict relatively large perturbations to fluid velocity at the seafloor for high temperature vents the outflow perturbations normalized to the mean flow velocity increase as the permeability decreases flow reversals at the seafloor are predicted in some regions of net low temperature outflow and net inflow during the tidal cycle in the subseafloor tidally induced flow perturbations are likely to significantly enhance mixing and fluid exchange below the seafloor in regions of slow flow and in regions where there are strong gradients in temperature or in the mechanical and hydrological properties of the crust tidally enhanced mixing and fluid exchange may significantly influence the extent and character of microbial production in the subseafloor

the age of the latest thermal overprint of tin and polymetallic deposits in the erzgebirge germany constraints from fluorite u th sm he thermochronology the erzgebirge region of germany records two major episodes of hydrothermal activity which includes a late carboniferous to early permian event associated with significant sn w mineralization that is related to late variscan granite magmatism and a mesozoic episode of polymetallic vein mineralization in contrast to the first event the age of the younger hydrothermal activity is poorly constrained for the latter various geochronological methods yielded a wide age range from permian to early tertiary here we apply fluorite u th sm he thermochronology fhe on both types of mineralization with a twofold goal 1 to investigate the sensitivity and applicability of the new fhe method evans et al 2005 and 2 to constrain the thermal history of ore deposits in the erzgebirge region two hundred and thirty three aliquots from seven mineralization localities have been dated fluorite from six deposits yielded cretaceous fhe ages between 112 to 79 ma which are independent of their paragenesis in contrast fluorite from the sadisdorf sn w deposit yielded an age of 234 ma the younger ages are interpreted as cooling ages indicating the time of the last thermal overprint including possible hydrothermal activity in the erzgebirge the oldest triassic fhe ages at sadisdorf indicate that the mesozoic thermal overprint only partially reset the u th sm he system of the late variscan mineralization thermal modeling based on fhe ages and he diffusion parameters in fluorite results in thermal histories comparable to the results from the well established apatite based thermal modeling this study emphasizes the applicability of fluorite u th sm he thermochronology which is especially suited for ore deposits where apatite is lacking

paleomagnetism and potassium argon age of the messejana dike portugal and spain angular limitation to the rotation of the iberian peninsula since the middle jurassic abstract a paleomagnetic and potassium argon dating investigation has been carried out on a 530 km long dike system which transects the western iberian peninsula in a northeasterly direction the k ar age determinations were made on mineral separates exclusively they range between 160 and 200 ma and the authors suppose that this reflects the actual time interval of the intrusion in accord with previous results the paleomagnetic pole derived from 12 sites regularly distributed along the dike 71 n 236 e coincides well with other mesozoic paleomagnetic poles from the western africa a contemporaneous pole from stable europe is tentatively deduced from african and north american late triassic early jurassic poles using different reconstruction models around the north atlantic ocean the divergence between this pole and the iberian pole corresponds to the result obtained for permian poles

observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar 2 we present a 26 day time series october 2010 of physical properties volume flux flow velocity expansion rate of a vigorous deep sea hydrothermal plume measured using our cabled observatory vent imaging sonar covis which is connected to the northeast pacific time series underwater experiment canada cabled observatory at the main endeavour field on the juan de fuca ridge covis quantitatively monitors the initial buoyant rise of the plume from 5 m to 15 m above the vents the time series exhibits temporal variations of the plume vertical volume flux 1 93 5 09 m3 s centerline vertical velocity component 0 11 0 24 m s and expansion rate 0 082 0 21 m m these variations have major spectral peaks at semidiurnal 2 cycle day and inertial oscillation 1 5 cycle day frequencies the plume expansion rate average 0 14 m m is inversely proportional to the plume centerline vertical velocity component coefficient of determination r2 0 5 this inverse proportionality as well as the semidiurnal frequency indicates interaction between the plume and ambient ocean currents consistent with an entrainment of ambient seawater that increases with the magnitude of ambient currents the inertial oscillations observed in the time series provide evidence for the influence of surface storms on the dynamics of hydrothermal plumes

u th he evidence of jurassic continuous hydrothermal activity in the schwarzwald basement germany abstract u th he model and isochron ages of 21 botryoidal hematites collected from the hohberg base metal vein system in the triberg granite complex mittelschwarzwald germany cover most of the jurassic period the possibility of quantitative 4 he loss triggered by successive hydrothermal events although conceivable for individual hematites based on a 4 he retentivity study and calculated opening temperatures of hematite for 4 he of 90 180 c can largely be ruled out thus the range of model and isochron ages indicates that the majority of the hematites are not cogenetic this is supported by a broad range of pb total concentrations in the hohberg botryoidal hematites 150 2700 ppm by comparison with virtually identical pb total concentrations found in cogenetic hematites from four different vein systems in the schwarzwald the th u ratios of the hematites vary by a factor of 700 0 01 7 25 mainly as a result of the range of th concentrations 0 1 74 ppm the incorporation of substantial amounts of th in hematite is thought to result from increased th transport mobility possibly caused by association with colloids and or complexing in the ore solution 18 o analyses of a 160 ma old cogenetic hematite quartz pair indicate that precipitation occurred from a fluid of magmatic origin at a temperature of 180 c the regional temperature peak in the basement at the present erosional surface during the jurassic 130 c provides a lower temperature limit of hematite formation this implies that hematite emplacement occurred at temperatures roughly ranging between 130 and 180 c the jurassic continuous hydrothermal activity suggests that the pre rifting european craton is characterized by local thermal fluxes during a long time span

kar ages of clay size concentrates from the mineralisation of the pedroches batholith spain and evidence for mesozoic hydrothermal activity associated with the break up of pangaea abstract the k ar ages of 32 clay concentrates extracted from samples of ore gangue and wallrock associated with mineralisation in the pedroches batholith lie in the range 119 285 ma although some of the mineralisation is of permian age more than half of the ages lie between 210 and 230 ma and indicate a hydrothermal event at this triassic time a comparison with age data for mineralisation and certain anorogenic magmatism in other areas of the north atlantic reveals a consistent pattern of a major event at ca 210 230 ma and a minor event at ca 160 ma with little cretaceous or tertiary activity it is proposed that the ca 210 230 ma event was related to an initial rapid fracturing of the crust associated with the break up of pangaea which was related with an increase in the geothermal gradient and penetration of the deep crust by surface waters which returned via both new and rejuvenated fissure systems

semi brittle deformation within the alpine fault zone new zealand abstract this paper reports the results of an attempt to identify the deformation micromechanisms in the brittle ductile transition zone of the alpine fault new zealand characterization of sequentially developed microstructures was carried out using optical microscopy hvem and stem analysis it was found that the transition zone corresponds to a broad zone of retrogression produced initially by microcracking and fluid infiltration the non catastropic nature of the fracturing indicates that fluid enhanced sub critical cracking is a significant crustal deformation mechanism after the initial phase of retrogression both ductile and brittle processes coexist and cyclically alternate in response to stress cycling the relative importance of macroscopic brittle processes may decrease with time as more ductile minerals especially phyllosilicates develop during continued retrogression

global and seasonal distribution of gravity wave activity in mars lower atmosphere derived from mgs radio occultation data 1 temperature profiles from mars global surveyor mgs radio occultation measurements reveal vertical wave structures assumed to be atmospheric gravity waves in mars lower atmosphere for each vertical temperature profile derived from a radio occultation measurement wave energy density is calculated and results are locally averaged to derive a global distribution of gravity wave activity global distributions are determined for all values of solar longitude and for solar longitudes corresponding to northern summer and winter to show seasonality and for vertical wavelengths less than 10 km to remove the contribution from thermal tides which dominate in the martian tropics at larger vertical wavelengths the global energy density patterns show significant wave activity over the tropics and the mountainous tharsis region averaged over all seasons and enhanced activity in northern summer compared to winter for the most part the observed data does not correlate well with the orographic forcing schemes used to model gravity waves in general circulation models for mars suggesting that wave sources other than orography play an important role on mars

solstitial temperature inversions in the martian middle atmosphere observational clues and 2 d modeling abstract the possible existence of stable warming at middle altitudes in the martian atmosphere was first examined by j r barnes j geophys res 95 1401 1990 in one dimensional modeling of the effect of breaking gravity waves on the general circulation this work was motivated by infrared observations of d deming m j mumma f espenak t kostius and d zipoy icarus 66 366 1986 which suggested temperatures far from radiative equilibrium above polar regions at solstice new observational evidence was obtained from heterodyne measurements of the j 2 1 12 co and 13 co transitions made during the 1988 opposition at this date corresponding to southern summer solstice these lines were mapped as a function of the position on the martian disk with the iram 30 m telescope wind velocities near 50 km altitude and vertical thermal profiles were derived from the doppler shift and the line profiles respectively at various locations on mars the northern winter hemisphere profiles indicate the presence of a warm layer in the 40 60 km altitude range with a relative warming of 5 k compared to smoothly decreasing temperature profiles such as those found in the southern hemisphere this may be interpreted in terms of a temperature inversion in the northern middle atmosphere such a phenomenon may be similar to the stable inversion layers observed in the terrestrial mesosphere which are believed to be a response to the gravity wave activity we show that a zonally averaged model of the martian middle atmosphere using the parametrization of gravity waves effects propounded by r s lindzen j geophys res 86 9707 1981 is able to produce both a plausible zonal wind field consistent with the measurements of e lellouch j j goldstein s w bougher g paubert and j rosenqvist astrophys j 383 401 1991 and a thermal field in good agreement with the observations the 2 d modeling further indicates that weak equatorial thermal inversions may occur due to the penetration of the summer hemisphere retrograde jet into the winter hemisphere

geothermal heat flux from hydrothermal plumes on the juan de fuca ridge thesis m s massachusetts institute of technology dept of ocean engineering and woods hole oceanographic institution 1991

plumbotectonic evolution of the ossa morena zone iberian peninsula tracing the influence of mantle crust interaction in ore forming processes the ossa morena zone in the variscan belt of the iberian peninsula is characterized by a complex geotec tonic evolution it hosts a neoproterozoic paleozoic sequence that records the existence of two orogenic events cadomian and variscan separated by rift and stable platform stages middle cambrian to late devonian volcanogenic and sediment hosted massive sulfides skarns magmatic ni cu deposits synmetamorphic and intragranitic and perigranitic veins and replacement bodies are related to different magmatic hydrothermal systems ranging in age from 650 ma to about 250 ma the lead isotope signatures from 26 different mineral deposits show variable ratios of 206pb 204pb 17 49 18 44 207pb 204pb 15 47 15 67 and 208pb 204pb 37 37 38 78 that have low average values 9 7 but high values 38 3 as a whole the lead isotope data define an irregular cluster that plots around the stacey and kramers 1975 growth curve but clearly marks the existence of two main ore forming events during cadomian and variscan times the most radiogenic samples are from some minor zn pb stratiform sedimentary exhalative mineralization they are interpreted as having a dominantly crustal derivation 10 1 in which most of the lead was leached from a pre cadomian continental basement with a long crustal history this basement has strong geochemical affinities with the oldest rocks of the iberian terrane however most of the ore samples investigated plot below the stacey and kramers 1975 reference curve indicating polyphase but variable mixing of lead from upper crustal and mantle lead reservoirs at the terrane scale clear mixing lines between the two end member reser voirs are evident only in the oldest volcanic rock and sedimentary rock hosted massive sulfide deposits related to the cadomian late neoproterozoic early cambrian magmatic arc in the other deposit types lead isotopes have more restricted values the crustal lead is interpreted as having been derived from ancient crust 2 1 2 5 ga and the derived shales montemolin formation that predated the cadomian orogeny the mantle derived lead may have been derived from three different sources neoproterozoic tholeiitic orthoamphibolite syn cadomian calc alkaline andesite or calc alkaline metaluminous plutonic rocks intruded during the variscan orogeny the first two sources probably controlled the lead isotope signatures of the cadomian massive sulfide deposits and the variscan synmetamorphic veins the input of primitive lead is especially significant during variscan times 350 300 ma and is interpreted as having been related to the existence of a large primitive reservoir that controlled the variscan magmatic metallogenic and hydrothermal evolution of the ossa morena zone this primitive lead is recognized in most of the magmatic hydrothermal deposits including the typically crust derived w and pb bearing perigranitic hydrothermal systems likewise associated plutonic rocks have more primitive lead isotope signatures than their counterparts in other iberian terranes the lead isotope evolution of the region is consistent with recent geophysical data that suggest that a deep large mafic sill was intruded below the ossa morena zone during variscan times this sill was a likely key factor in the different pb isotope evolution of the ossa morena zone compared with the nearby iberian terranes and the entire western mediterranean province which are char acterized by lengthy crustal histories with very little input of primitive lead the extensive mantle crust inter action probably explains the wide variety and the unusual metallogenic features of the ossa morena zone