late stage water eruptions from ascraeus mons volcano mars implications for its structure and history abstract ascraeus mons was one of the first of the martian volcanoes to be imaged by the high resolution stereo camera hrsc experiment onboard the esa mars express spacecraft these images show much of the volcano at a higher resolution than previously and details of its lava flows sinuous rilles flank vents and tectonic features indicate an unexpected origin for some of these features we establish the time stratigraphic sequence for these features and use a numerical model on hrsc stereo dtms of the sinuous rilles and conclude that they were formed by water erosion terrestrial analogues for such features are found at reunion island and other volcanoes we then examine the overall structure of the volcano which is dissimilar to that of large terrestrial volcanoes in important respects and perform laboratory analogue experiments of its deformation concluding that the tectonic features were formed by sinking of the volcano into a substratum that was much weaker than the volcanic edifice an ice rich substratum melted by a combination of pressure melting and magmatic heating seems the most likely mechanism analogous water escape structures in a similar volcanic situation have been identified at mt haddington in the antarctic the possible role of a hydrological cycle and a hydrothermal system within the volcano are discussed based on field evidence we propose that much of the broad aprons of lobate flows issuing from the ne and ssw foot of ascraeus mons are composed of mudflows rather than lava flows these different approaches are linked into a coherent history of this volcano the similarity of ascraeus mons to pavonis mons and arsia mons though ascraeus is younger suggests that some of our conclusions may apply to these volcanoes too

ice lubricated gravity spreading of the olympus mons aureole deposits abstract gravity sliding and spreading at low strain rates can account for the general morphology and structure of the aureoles and basal scarp of olympus mons detachment sliding could have occurred around the volcano if either pore fluid pressures were exceptionally high greater than 90 or the rocks had very low resistance to shear about 1 105 pa or 1 bar because of the vast areal extent and probable shallow depth of the detachment zone development of ubiquitous high pore fluid pressures beneath aureole forming material was unlikely however a zone of sufficiently weak material consisting of about 10 interstitial or interbedded ice could have been present if so a simple rheologic model for the aureole deposits can be applied that consists of a thin ductile layer overlain by a thicker brittle layer according to this model extensional deformation would have occurred near the shield and compressional deformation in its distal parts proximal grabens and distal corrugations on aureole surfaces support this model a submarine slide at kitimat arm british columbia is a valid qualitative analogy for the observed features and inferred emplacement style of the aureole deposits ground ice processes have been considered the cause of many geologic features on mars a 3 average concentration of ground ice in the regolith is predicted by theoretical models for the ice budget and cryosphere ice may have been deposited in higher concentrations below the aureole forming material the source of the ice could have been juvenile water circulated hydrothermally by olympus mons volcanism the basal scarp of olympus mons apparently demarcates the transition between the upper stable part of the shield and its lower part that decoupled and formed the aureole deposits this transition may reflect a change in the bulk shear strength of the shield caused either by a radial dependence in the abundance of ice or fluid in the shield materials or by the concentration of intrusive dikes within the volcano other martian volcanoes exhibit virtually no evidence of similar large scale gravity spreading and basal scarps perhaps such evidence if it existed has been buried by lava flows or perhaps the smaller size of other volcanoes did not permit the development of these features

composite model with fractional flow dimensions for well test analysis in fractured rocks abstract the represented analytical model is addressed to fracture zone aquifers in which well test responses can be commonly matched with models involving fractional flow dimensions the model assumes a composite structure representing the fractures opening into the pumping well and the fracture system comprising the actual aquifer the aim is to assess the hydraulic properties for the near well zone and the aquifer in terms of concrete parameters even if flow dimensions have fractional values dimensionless drawdown in pumping and observation wells was solved by applying laplace transforms the early time approximation for the pumping well can be used to assess the transmissivity t 1 if the flow dimension in the inner zone n 1 is greater than about 1 7 the long time solutions indicate that the inner zone induces a pseudo skin effect that can be estimated by comparing the pumping well and observation well data if k 1 is known the extent of the inner zone r can be estimated from the pseudo skin factor the responses tend to form log log straight lines with slopes of 1 n 2 by plotting drawdown vs t 1 n 2 on the double logarithmic scale the product of the hydraulic conductivity and the through flow area at the wellbore radius ka 2 and the hydraulic diffusivity d 2 of the aquifer can be estimated from the slope and the intercept the hydraulic conductivity of the aquifer k 2 is estimated by considering the through flow area as a projection of an n 2 dimensional sphere with a radius of r wb through three dimensional space by an amount r 3 n 2 the analyzed field example comprises a pumping test of a fracture zone aquifer in south central finland for the pumping well simultaneous matching of drawdown and derivative type curves with observed responses can be used to verify the results of the early time analysis and the proposed straight line procedure in addition type curve matching yields estimates of the hydraulic diffusivity ratio and a value of the dimensionless wellbore storage the analyzed observation wells are considered to be sufficiently far from the inner zone consequently type curves are produced based on the dimensionless drawdown solution that is identical to generalized radial flow model type curve matching of the observation well responses produces estimates for ka 2 k 2 and d 2 the obtained values are similar to previous studies that included models relying on integer flow dimensions however models relying on the fractional flow dimensions are capable to simulate the observed responses more accurately

chemically striking regions on mars and stealth revisited 1 the mars odyssey gamma ray spectrometer suite has yielded global chemical information for mars in this work we establish regions of unusual chemical composition relative to average mars primarily on the basis of ca cl fe h k si and th using data from mars odyssey the mars exploration rovers the mars reconnaissance orbiter imaging and 3 5 cm and 1 35 cm radar observations from earth we examine a chemically striking 2 e6 km2 region and find it to overlap significantly with a radar stealth region on mars it is remarkably enriched in cl and depleted in fe and si along with minor variations in h k and th relative to average mars surface dust observed at the two rover sites mixed with and indurated by ca mg bearing sulfate salts would be a reasonable chemical and physical analog to meter scale depths we describe potential scenarios that may have contributed to the unique properties of this region the bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ hydrothermal acid fog reactions on the flanks of nearby volcanoes may have generated sulfates with subsequent deflation and transport alternatively sulfates may have been produced by low temperature regional scale activity of ground ice driven brine and or regional scale deposition of acidified h2o snowfall

further evidence for a mass movement origin of the olympus mons aureole analysis of the ridge graben and fracture patterns on the aureole material surrounding olympus mons lends further support to an origin by gravity sliding of the outer flanks of the shield the patterns provide evidence of the nature of sliding especially in the last stages of emplacement no part of the slide need have traveled the whole extent of the aureole for the slides to occur on a shallow slope reduction of shear strength of the materials involved is required possibly by melting of ground ice triggering mechanisms could be volcanically related marsquakes and possibly stresses induced on the surrounding area by the growing olympus mons volcano

provenance of glacial marine conglomerates in the permian lagar formation of southern tibet evidence for affinity of the lhasa terrane with australia abstract paleogeographic reconstructions of the lhasa terrane of the southern tibetan plateau are uncertain in paleozoic and investigating the paleogeographic location of the terrane via the current geographical configuration is difficult however gravels contained within glacial sediments offer an opportunity to solve this problem the lagar formation in the central lhasa sub terrane contains glacial marine deposits that incorporate gravel clasts composed of granitoids sandstone quartzite limestone and rhyolite these diamictites were derived from continental glaciation and were deposited mainly near a grounding line or ice front in littoral neritic to neritic environments we present new zircon u pb isotopic and whole rock geochemical data for the tonalitic conglomerates of the lagar formation the results indicate that the tonalites crystallized during the paleoproterozoic 1 76 ga and show a geochemical affinity with i type granite the tonalites typically have negative eu anomalies eu 0 31 0 37 high concentrations of rare earth elements depletion in high field strength elements enrichment in th marked positive zircon ehf t values 6 46 14 68 end t values of 1 24 to 1 76 and tdm2 ages of 2 37 2 13 ga all of these data indicate that the tonalites were produced by the partial melting of modified mafic crust or underplate in a subduction related environment on the basis of a comprehensive analysis of all 1 8 1 7 ga magmatism in east gondwana we propose that the most likely provenance of the tonalitic conglomerates is southern arunta and mt isa in northern australia therefore the central lhasa sub terrane may have been located near australia during the paleozoic

proterozoic stratigraphy and tectonic history of the georgetown inlier northeastern queensland the proterozoic sequence in the central part of the georgetown inlier has been divided into the etheridge langlovale croydon and inorunie groups the early to middle proterozoic etheridge group consists of shallow water fine grained clastic metasedimentary rocks and minor basaltic lavas and related dolerite intrusions it was deposited in a uniformly subsiding basin in a continental setting sometime between 2400 and 1570 ma it was first deformed at 1570 ma d1 and again at 1470 ma d2 by major folding events accompanied by low to intermediate pressure metamorphism mainly in the greenschist and amphibolite facies but ranging into the granulite facies in places during d2 the grade of metamorphism increases from west to east extensive s type plutonic magmatism accompanied d2 in the west the langlovale group a fluviatile to marine pro deltaic facies post dates d1 and was deposited before d2 it is moderately folded but not regionally metamorphosed post orogenic magmatism also s type is represented in the western part of the inlier by the subaerial felsic ignimbrite of the croydon volcanic group and related subvolcanic granitoids the volcanic rocks are overlaim by the fluviatile inorunie group which is of uncertain age neither the croydon volcanic group nor the inorunie group is appreciably deformed or metamorphosed in the eastern quarter of the inlier a largely metavolcanic andesitic to felsic sequence may be an allochthonous terrain of early palaeozoic age but it could be proterozoic known proterozoic rocks thought to have been thrust over this sequence crop out on the eastern edge of the inlier they are the halls reward metamorphics and maficultramafic rocks including the boiler gully complex their relationship to the etheridge group is uncertain convective mantle upwelling could account for the extension of the continental crust which allowed deposition of the etheridge group no rifting is apparent and only the sag phase of the model of etheridge et al may be represented underplating of the crust could account for the metamorphism and felsic magma generation during the middle proterozoic the etheridge group shows characteristics of both tectonostratigraphic cycles recognized elsewhere in nothern australia and without better radiometric control correlation is difficult

a sagging spreading continuum of large volcano structure gravitational deformation strongly infl uences the structure and eruptive behavior of large volcanoes using scaled analog models we characterize a range of structural architectures produced by volcano sagging and volcano spreading these arise from the interplay of variable basement rigidity and volcano basement de coupling from comparison to volcanoes on earth la reunion and hawaii and mars elysium and olympus montes the models highlight a structural continuum in which large volcanoes throughout the solar system lie

dust and ice deposition in the martian geologic record abstract the polar layered deposits of mars demonstrate that thick accumulations of dust and ice deposits can develop on the planet if environmental conditions are favorable these deposits appear to be hundreds of millions of years old and other deposits of similar size but of greater age in nonpolar regions may have formed by similar processes possible relict dust deposits include from oldest to youngest noachian intercrater materials including arabia mantle deposits noachian to early hesperian south polar pitted deposits early hesperian hellas and argyre basin deposits late hesperian electris deposits and the amazonian medusae fossae formation these deposits typically are hundreds of meters to a couple kilometers thick and cover upward of a million or more square kilometers the apparent persistence of dust sedimentation at the south pole back to the early hesperian or earlier and the early growth of tharsis during the late noachian and perhaps earlier indicates that extensive polar wandering is unlikely following the middle noachian a scenario for the overall history of dust and perhaps ice deposition on mars includes widespread voluminous accumulations perhaps planetwide during the noachian as impacts volcanism and surface processes generated large amounts of dust the arabia deposits may have formed as ice availability and dust accumulation waned during the early hesperian thick dust sedimentation became restricted to the south pole and the deep hellas and argyre basins the north polar sedimentary record prior to the amazonian is largely obscured deposits at electris and medusae fossae may have resulted from local sources of fine grained material perhaps volcanic eruptions

topography of the shield volcano olympus mons on mars olympus mons one of the largest known shield volcanoes in the solar system covers an area of 3 2 105 km2and has a diameter of 600 km excluding its vast aureole deposits the structure is five times larger than the largest shield volcano on the earth it is situated on the north west flank of the tharsis volcanic region a broad topographic rise on the martian surface the volcano has three physical subdivisions the summit caldera the terraced upper flanks and the lower flanks which terminate in a scarp 2 10 km high that nearly surrounds the structure a large block of images of the tharsis region including olympus mons was obtained by the viking mission1 here we present a topographic map of olympus mons compiled using various combinations of stereo pairs of these images together with stereoscopic perspective views generated by image processing techniques

characterization of the hydrogeological experimental site of poitiers france by stochastic well testing analysis summary we assess the applicability and performance of the stochastic well testing methodology of neuman et al neuman s p guadagnini a riva m 2004 type curve estimation of statistical heterogeneity water resources research 40 w04201 doi 10 1029 2003wr002405 neuman s p blattstein a riva m tartakovsky d m guadagnini a ptak t 2007 type curve interpretation of late time pumping test data in randomly heterogeneous aquifers water resources research 43 w10421 doi 10 1029 2007wr005871 to provide a geostatistical characterization of the transmissivity distribution of a heterogeneous aquifer we use cross hole pumping test information also referred to as interference testing collected during two extensive and detailed experimental campaigns performed in 2004 and 2005 in a limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the methodology we use is based on stochastic type curves of mean drawdown and associated variance and is aimed at revisiting the results of routine pumping tests within a stochastic framework it allows estimating the geometric mean integral scale and variance of local log transmissivities on the basis of quasi steady state head data when a randomly heterogeneous confined aquifer is pumped at a constant rate the results are discussed by comparison against a previous deterministic analyses performed at the site using the same dataset and b information obtained by geostatistical analysis of existing geophysical data the estimated values of integral scales and variance of log transmissivity are viewed in light of multiscale theories which conceptualize the heterogeneity of porous and fractured systems as hierarchical random processes distributed across a multiplicity of scales the scale dependence observed for the estimated variogram parameters of log transmissivity at the hes site is consistent with the behavior of published worldwide data

hydraulic testing of low permeability formations a case study in the granite of cadalso de los vidrios spain abstract in recent years the study of low permeability geological formations has undergone considerable development this is mainly due to the use of natural geological barriers to confine waste disposals preventing leaking water from bringing contaminants into contact with the biosphere and the groundwater resources in that context the spanish geological survey igme spanish acronym supported by the national radioactive waste management agency enresa spanish acronym and with the technical advice of the swedish nuclear fuel and waste management company skb designed and built a mobile hydrogeological unit umh spanish acronym for low permeability formations characterization which has been operational since 1997 and has been used for different purposes among other possibilities the umh allows conducting constant transient state flow rate injection tests constant head transient state injection tests pseudo stationary state injection tests pressure fall off tests slug tests and pulse tests the main objectives of this article are to describe the hydraulic characterization methodology used by igme to carry out hydraulic tests in low permeability environment to compare different testing methods and to summarize the results that have been obtained when characterizing the leucogranites of cadalso de los vidrios in spain the study area presents an increasing interest for granite production inside the community of madrid the petrological and structural characteristics of the granite rocks and the core samples extracted from a 200 m deep borehole investigation are described the packer tests are conducted with the mobile hydrogeological unit the tests are interpreted with the help of analytical solutions the main software used is hytool an open source matlab toolbox that provides a library of analytical solutions and a set of routines to facilitate hydraulic tests interpretation the results allow the elaboration of a comparative analysis of the applied hydraulic tests and to define the hydraulic conductivity optimum application interval most suited for each of the used methods hydraulic conductivity values obtained varies from 3 20 10 7 m s for the upper weathered layer to 2 80 10 12 m s for the test section from 97 36 to 116 15 m depth finally the hydraulic conductivity values obtained in this area are compared with other case studies of granite formations around the world

mars and earth comparison of cold climate features abstract on earth glacial and periglacial features are common in areas of cold climate on mars the temperature of the present day surface is appropriate for permafrost and the presence of water is suspected from data relating to the outgassing of the planet from remote sensing measurements over the polar caps and elsewhere on the martian surface and from recognition of fluvial morphological features such as channels these observations and the possibility that ice could be in equilibrium with the atmosphere in the high latitudes north and south of 40 latitude suggest that glacial and periglacial features should exist on the planet morphological studies based mainly on viking pictures indicate many features that can be attributed to the action of ice among these features are extensive talus aprons debris avalanches flows that resemble glaciers or rock glaciers ridges that look like moraines various types of patterned ground scalloped scarps and chaotically collapsed terrain that could be attributed to thermokarst processes and landforms that may reflect the interaction of volcanism and ice

crustal evolution in the georgetown inlier north queensland australia a detrital zircon grain study abstract the use of in situ hf isotope analysis of zircon allows a more detailed evaluation of magma generation processes than the analysis of whole rock isotopic systems and is a powerful tool for studying crustal evolution detrital zircon grains have been analysed by in situ lam icpms and lam mc icpms for u pb ages trace element patterns and hf isotope composition to evaluate patterns of magma genesis and crustal evolution in the central part of the precambrian georgetown inlier north queensland australia archean zircons and low hf in proterozoic and phanerozoic magmatic zircons provide direct evidence for the existence of archean crustal components in the georgetown inlier although the surface geology is dominated by mesoproterozoic basement rocks and palaeozoic granitoids crustal evolution in the georgetown inlier has involved at least three stages of heating and granitoid magmatism possibly associated with basaltic magma underplating and or overplating 1545 1585 ma 420 ma and 340 ma in general granitoids with high hf are typical of the percyvale area closest to the phanerozoic tasman fold belt and may reflect thinner and younger crust granitoids with less radiogenic hf isotope compositions are typical of the einasleigh and mount surprise areas in the central part of the inlier and may reflect the presence of older and thicker crust the most significant juvenile additions to the crust after archean time occurred in the einasleigh and mount surprise areas during mesoproterozoic time and in the percyvale area during carboniferous time in the mount surprise area resorbed zircon cores of mesoproterozoic age are overgrown by magmatic rims of siluro devonian age similarities in the hf isotope composition of core rim pairs suggest that the large range in hf observed in zircons from siluro devonian granitoids reflects remelting of a heterogeneous 1545 1585 ma old crust rather than mixing between juvenile and crustal sources crustal remelting has been the main process responsible for the production of granitoid magmas in the georgetown inlier however minor addition of mantle derived material may have occurred during both mesoproterozoic and carboniferous time similarities and differences in the crustal evolution of the mt isa broken hill and georgetown blocks suggest that the proterozoic history of the australian continental margin involved the accretion and subsequent dispersal of individual originally archean microcontinents

carboniferous and permian granites of the northern tasman orogenic belt queensland australia insights into petrogenesis and crustal evolution from an in situ zircon study in situ u pb dating and lu hf systematics of zircon in granites of the hodgkinson province in the northern tasman orogenic belt queensland australia reveal input of isotopically more evolved crustal magmas and larger ranges in 176hf 177hf in the carboniferous i type granites 0 28219 0 28269 weighted average 0 28245 than in the permian s type granites 0 28249 0 28280 weighted average 0 28262 and permian i type granites 0 28253 0 28274 weighted average 0 28260 the wide range in the hf isotope compositions of zircons in the carboniferous and permian granites can be explained by remelting of a heterogeneous mesoproterozoic crustal source whereas a narrow range reflects the subsequent dissolution of inherited grains cores and magma homogenisation before zircon crystallisation alternatively mixing between the most radiogenic and unradiogenic magmas can produce the isotopic variation seen in other carboniferous granites remelting of neoproterozoic average crust or mafic younger crust can produce the more radiogenic hf isotope compositions of zircons in the permian s type granites an overlap between the hf isotope signatures of the carboniferous i type granites in the southwestern hodgkinson province and the northeastern australian craton 0 28211 0 28254 and evidence for major magmatic events at 1 585 1 545 and 345 300 ma imply that the southwestern province is underlain by cratonic crust which wedges out towards the northeast the more radiogenic hf isotope signature of the permian granites and a lack of evidence for these major magmatic events in the southeastern and central hodgkinson province imply that these parts are characterised by different crustal sources and crustal evolution histories

debris covered piedmont glaciers along the northwest flank of the olympus mons scarp evidence for low latitude ice accumulation during the late amazonian of mars we use viking and new mgs and odyssey data to characterize the lobate deposits superimposed on aureole deposits along the west and northwest flanks of olympus mons mars these features have previously been interpreted variously as landslide pyroclastic lava flow or glacial features on the basis of viking images the advent of multiple high resolution image and topography data sets from recent spacecraft missions allow us to revisit these features and assess their origins on the basis of these new data we interpret these features as glacial deposits and the remnants of cold based debris covered glaciers that underwent multiple episodes of advance and retreat occasionally interacting with extrusive volcanism from higher on the slopes of olympus mons we subdivide the deposits into fifteen distinctive lobes typical lobes begin at a theater like alcove in the escarpment at the base of olympus mons interpreted to be former ice accumulation zones and extend outward as a tongue shaped or fan shaped deposit the surface of a typical lobe contains moving outward from the basal escarpment a chaotic facies of disorganized hillocks interpreted as sublimation till in the accumulation zone arcuate ridged facies characterized by regular subparallel ridges and interpreted as the ridges of surface debris formed by the flow of underlying ice and marginal ridges interpreted as local terminal moraines several lobes also contain a hummocky facies toward their margins that is interpreted as a distinctive type of sublimation till shaped by structural dislocations and preferential loss of ice blocky units are found extending from the escarpment onto several lobes these units are interpreted as evidence of lava ice interaction and imply that ice was present at a time of eruptive volcanic activity higher on the slopes of olympus mons other than minor channel like features in association with lava ice interactions we find no evidence for the flow of liquid water in association with these lobate features that might suggest 1 near surface groundwater as a source for ice in the alcoves in the lobe source region at the base of the scarp or 2 basal melting and drainage emanating from the lobes that might indicate wet based glacial conditions instead the array of features is consistent with cold based glacial processes the glacial interpretations outlined here are consistent with recent geological evidence for lowlatitude ice rich features at similar positions on the tharsis montes as well as with orbital dynamic and climate models indicating extensive snow and ice accumulation associated with episodes of increased obliquity during the late amazonian period of the history of mars

late paleoproterozoic sedimentary and mafic rocks in the hekou area sw china implication for the reconstruction of the yangtze block in columbia abstract the paleoproterozoic hekou group in the western yangtze block is a volcano sedimentary succession that is intruded by gabbroic plutons sedimentary rocks in the group include slates marble and meta siltstones interlayered with felsic metavolcanic rocks metabasalts and metatuffs both the volcanic rocks of the hekou group and gabbros have undergone upper greenschist to lower amphibolite facies metamorphism metatuff samples from different layers have average zircon u pb ages of 1697 ma slightly older than the intruding gabbroic plutons with zircon u pb ages of 1684 ma both metabasalts and metagabbros have similar elemental and isotopic compositions indicative of a co magmatic origin they are rich in tio2 mostly 2 5 wt zr 94 5 347 ppm ta 0 48 3 00 ppm and th 1 05 7 61 ppm with high nb y ratios mostly 0 6 and lree enriched chondrite normalized ree patterns resembling within plate mafic rocks their positive whole rock nd t 0 2 to 3 4 and zircon hf t values 3 3 to 8 4 suggest contributions from a depleted mantle source the large range of nd t and hf t values and variable degrees of nb ta anomalies ta lapn 0 17 1 75 are indicative of crust contamination during magma ascending both the metabasalts and metagabbros are considered to have formed in a continental rift setting detrital zircon grains from meta siltstones in the hekou group have u pb age populations mainly at 2070 1880 ma 2330 2250 ma and 2900 2700 ma these age populations are comparable to those of the north australian and north china cratons in the columbia supercontinent however in terms of geochemical features the 1 7 ga within plate mafic rocks at hekou are similar to those from the 1 7 ga leichhardt and calvert superbasins of the north australian craton but different from those from the 1 7 1 2 ga zhaertai bayan obo rift zone of the north china craton it is thus suggested that the yangtze block was more likely linked with the north australian craton in columbia during the late paleoproterozoic these rifting basins and mafic rocks may record the initial break up of the columbia supercontinent

flow bearing structures of fractured rocks insights from hydraulic property scalings revealed by a pumping test abstract a long duration pumping test conducted over 151 days in a fractured sandstone and shale formation displays a nonstandard drawdown response and anomalous pressure diffusion which cannot be properly interpreted using existing frameworks e g homogeneous double porosity boundary conditions and fractal models an alternative framework with simple geometry and more complex hydraulic properties is thus proposed to interpret such kind of drawdown responses the analytical development allows first to demonstrate all scaling relations in this interpretation framework then and most importantly the multi scale hydraulic test provides consistent scalings of transmissivity t to storativity s over distances ranging from 83 to 383 m in a faulted area drawdown analysis in several monitoring wells shows persistent decrease of transmissivity in highly channelized fracture flow structures in one structure the cubic dependency of transmissivity to storativity identifies a well defined fault and also demonstrates the validity of poiseuille flow at a scale rarely investigated in the other structure the linear dependency of transmissivity to storativity indicates that the flow bearing structure is the surrounding fracture network well designed pumping tests combined with scaling analysis driven by geological evidence thus provide essential information on flow bearing structures for site characterization and modeling tasks at least for moderate to low permeable fractured rocks the scaling of transmissivity to storativity appears to be more informative than any separate interpretation of hydraulic property scaling exponents

dual porosity fractal models for transient flow analysis in fissured rocks a dual porosity fractal model is derived that considers transient flow from block to fissure skin between the fissure and the block and storage capacity and skin effect on the pumping well type curves for different flow dimensions are provided they concern the pumping well and observation wells located either in the fissure system or in a matrix block the interpretation of a field case using this model shows good agreement between the theoretical drawdown and the observed data with consistent results from the pumping well and the observation well a flow dimension of 1 45 is obtained

crustal architecture and geodynamics of north queensland australia insights from deep seismic reflection profiling abstract a deep crustal seismic reflection and magnetotelluric survey conducted in 2007 established the architecture and geodynamic framework of north queensland australia results based on the interpretation of the deep seismic data include the discovery of a major west dipping paleoproterozoic or older crustal boundary considered to be an ancient suture zone separating relatively nonreflective thick crust of the mount isa province from thinner two layered crust to the east farther to the east a second major crustal boundary also dips west or southwest offsetting the moho and extending below it and is interpreted as a fossil subduction zone across the region the lower crust is mostly highly reflective and is subdivided into three mappable seismic provinces but they have not been tracked to the surface in the east the greenvale and charters towers provinces part of the thomson orogen have been mapped on the surface as two discrete provinces but the seismic interpretation raises the possibility that these two provinces are continuous in the subsurface and also extend northwards to beneath the hodgkinson province originally forming part of an extensive neoproterozoic cambrian passive margin continuation of the thomson orogen at depth beneath the hodgkinson and broken river provinces suggests that these provinces which formed in an oceanic environment possibly as an accretionary wedge at a convergent margin have been thrust westwards onto the older continental passive margin the tasman line originally defined to represent the eastern limit of precambrian rocks in australia has a complicated geometry in three dimensions which is related to regional deformational events during the paleozoic overall the seismic data show evidence for a continental margin with a long history paleoproterozoic to early mesozoic but showing only limited outward growth by crustal accretion because of a repeated history of overthrust shortening during repeated phases of orogenesis

ignimbrites of amazonis planitia region of mars a series of postulated ignimbrite units is mapped in the amazonis memnonia and aeolis quadrangles of mars the units cover about 2 2 106 km2 within a broad but discontinuous and irregular belt trending east west along the highland lowland boundary the ignimbrites overlie parts of the western and southern aureole materials of olympus mons but are embayed in places by the lava plains of the lowlands stratigraphic relations between the basalt flows from the tharsis montes region and the ignimbrites are not clearly defined crater counts suggest that the younger ignimbrites postdate the lava flows crater counts per square kilometer for the ignimbrites range from 7 29 1 95 10 4 to 6 36 2 01 10 5 for craters larger than 1 km in diameter the ignimbrite materials form thick 100 m extensive relatively flat sheets that are smooth to grooved or gently undulating grooved surfaces appear to be yardangs and in most places are not alined with prevailing wind directions the seven mapped ignimbrite units are characterized by morphologic expression stratigraphic position and crater counts similarities to ignimbrites in the pancake range of central nevada include 1 rounded patches of smooth high albedo nonwelded material superposed on jointed low albedo welded material 2 local complementary joint sets in welded materials and 3 thick flow sheets of great areal extent that follow but subdue underlying topography four major eruptive centers occur in areas where units are thickest and where a dominant nnw sse structural trend is expressed locally by unit margins elongate collapse features and normal faulting a minimum volume of 3 85 106 km3 for the deposits has been calculated from thickness estimates based on shadow measurements and crater rim height relations

the history of a continent from upb ages of zircons from orinoco river sand and smnd isotopes in orinoco basin river sediments abstract we report shrimp u pb ages of 49 zircons from a sand sample from the lower orinoco river venezuela and nd model ages of the fine sediment load from the main river and tributaries the u pb ages reflect individual magmatic or metamorphic events the sm nd model ages reflect average crustal residence ages of the sediment sources together they allow delineation of the crust formation history of the basement precursors of the sediments the u pb ages range from 2 83 to 0 15 ga and most are concordant or nearly so discrete age groupings occur at 2 8 2 1 and 1 1 ga the oldest group contains only three samples but is isolated from its closest neighbors by a 600 ma age gap larger age groupings at 2 1 and 1 1 ga make up about a third and a quarter of the total number of analyses respectively the remaining analyses scatter along concordia and most are younger than 1 6 ga the 2 8 and 2 1 ga ages correspond to periods of crust formation of the imataca and trans amazonian provinces of the guyana shield respectively and record intervals of short but intensive continental growth these ages coincide with 2 9 and 2 1 ga nd model ages of sediments from tributaries draining the archean and proterozoic provinces of the guyana shield respectively indicating that the u pb ages record the geological history of the crystalline basement of the orinoco basin zircons with ages corresponding to the major orogenies of the north atlantic continents the superior at 2 7 ga and hudsonian at 1 7 1 9 ga were not found in the orinoco sample the age distribution may indicate that south and north america were separated throughout their history nd model ages of sediments from the lower orinoco river and andean tributaries are 1 9 ga broadly within the range displayed by major rivers and dusts this age does not coincide with known thermal events in the region and reflects mixing of sources with different crust formation ages the igneous and metamorphic history of these sources as recorded by the detrital zircons is that of the orinoco basin basement this implies that despite evidence of fast sedimentary recycling global similarities in nd crustal residence ages and the probability of cross continent mixing through continental drift the sedimentary material carried by individual rivers is mainly derived from the crystalline basement in the basin the global semblance in nd isotope ratios in major river sediments and atmospheric dusts results from the averaging effect of large scale sampling of the continents which are heterogeneous in age on smaller regional scales a large portion of the continental crust in the orinoco basin formed during the trans amazonian orogeny at 2 0 2 1 ga and smaller portions formed both earlier at 2 8 ga and later after 1 6 ga these observations which are consistent with the relative sizes of crustal age provinces in the orinoco basin indicate that sediments from the lower orinoco and andean tributaries contain 25 35 of material added to the crust since trans amazonian times nd model ages of these sediments underestimate the average crust formation age of the basement of the orinoco basin by only about 10 if this relationship holds in other river basins then nd model ages of major rivers and wind blown particulates indicate that the mean age of the continental crust is 1 9 2 ga

fault propagation folds induced by gravitational failure and slumping of the central costa rica volcanic range implications for large terrestrial and martian volcanic edifices long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress in contrast the ridges bordering the central costa rica volcanic range ccrvr are the topographic expression of hanging wall asymmetric angular anticlines overlying low angle thrust faults at the base of the range these faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20 000 years the thrust fault underlying alajuela ridge rises from a depth of 700 m at a dip of 15 over a distance of a few kilometers it ramps up at 600 m depth on a 40 slope and terminates in the axis of the forward syncline 400 m below the surface the hanging wall of this fault has been thrusted about 200 m away from the volcanic range axis thrusting on the lower flanks of the ccrvr is compensated by extension on the range axis with formation of summit grabens shallow seismicity in the volcanic range suggests that thrusting is still active we postulate that at kilauea volcano hawaii the gravity and magma induced slumping of the southern flank on low angle thrust faults generates hanging wall anticlines similar to those observed in costa rica these anticlines are hypothesized to occur along the base of the volcano where the thrust faults ramp up toward the sea bottom ridges and scarps between 2000 and 5000 m below sea level are interpreted as the topographic expression of these folds we further suggest that the scarps of the ccrvr and kilauea are valid scaled terrestrial analogs of the perimeter scarp of the martian volcano olympus mons we suggest that the crust below olympus mons has failed under the load of the volcano triggering the radial slumping of the flanks of the volcano on basal thrusts the thrusting would have in turn formed the anticlinal ridges and scarps that surround the edifice the thrusting seems to be preferential toward the northwest and southeast and a northeast southwest rift zone seems to have developed perpendicular to the regional topographic gradient the thrust faults may extend all the way to the base of the martian crust about 40 km and they may have been active until almost the end of the volcanic activity we suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices in the ccrvr and at kilauea this slumping of the flanks is a slow intermittent process but it could evolve to rapid massive avalanching leading to catastrophic eruptions thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards

flow behavior in a dual fracture network a model that incorporates a pseudo random process controlled by mechanical rules of fracturing is used to generate 3d orthogonal joint networks in tabular stratified aquifers the results presented here assume that two sets of fractures each with different conductivities coexist this is the case in many aquifers or petroleum reservoirs that contain sets of fractures with distinct hydraulic properties related to each direction of fracturing constant rate pump tests from partially penetrating wells are simulated in synthetic networks the transient head response is analyzed using the type curve approach and plots as a function of time of pressure propagation in the synthetic network are shown the hydrodynamic response can result in a pressure transient that is similar to a dual porosity behavior even though such an assumption was not made a priori we show in this paper that this dual porosity like flow behavior is in fact related to the major role of the network connectivity especially around the well and to the aperture contrast between the different families of fractures that especially affects the earlier hydrodynamic response flow characteristics that may be interpreted as a dual porosity flow behavior are thus related to a lateral heterogeneity large fracture or small fault accordingly when a dual porosity model matches well test data the resulting reservoir parameters can be erroneous because of the model assumptions basis that are not necessarily verified finally it is shown both on simulated data and well test data that such confusion in the interpretation of the flow behavior can easily occur well test data from a single well must therefore be used cautiously to assess the flow properties of fractured reservoirs with lateral heterogeneities such as large fractures or small faults

lithospheric flexure and gravity spreading of olympus mons volcano mars the structural architecture of large volcanoes is governed substantially by gravity driven deformation that is manifest as distinct processes such as basement flexure or volcanic spreading temporal effects and the mutual interplay of these processes have been investigated only to a limited extent and so we present novel numerical models of the time dependent deformation associated with them the models simulate the combined effects of lithospheric flexure and volcanic spreading during growth increments of an elastoplastic volcanic cone different spreading scenarios are considered by a variable coupling decoupling behavior at the interface between volcano and basement we apply our models to olympus mons on mars which is characterized by upper to middle flank terraces on the shield is encircled by a basal scarp that has an average slope of 30 and is surrounded by distant deposits that resemble large scale slumping features on earth our results are consistent with the interpretation that terraces on olympus mons flanks form by thrust faulting that results from lithospheric flexure the presence and expression of terraces depend on the coupling of volcano and basement on the time of volcano growth relative to mantle relaxation and on the cohesion of the edifice the encircling scarp may be related to a very low friction detachment at the edifice base which leads to a normal fault regime on the lowermost flanks with time and volcano growth predicted stress and faulting regimes migrate only slightly indicating that the structural architecture of volcanoes is largely set in the very early stages of formation

volcanic plutonic connections and metal fertility of highly evolved magma systems a case study from the herberton sn w mo mineral field queensland australia abstract understanding the connection between the highly evolved intrusive and extrusive systems is essential to explore the evolution of high silicic magma systems which plays an important role in discussions of planetary differentiation the growth of continents crustal evolution and the formation of highly evolved magma associated sn w mo mineral systems to discern differences between fertile and non fertile igneous rocks associated with sn w mo mineralization and reveal the genetic links between coeval intrusive and extrusive rocks we integrate whole rock geochemistry geochronology and hf isotope signatures of igneous zircons from contemporaneous plutonic and volcanic rocks from the world class herberton mineral field of queensland australia the 310 300 ma intrusive rocks and associated intra plutonic w mo mineralization formed from relatively oxidized magmas after moderate degrees of crystal fractionation the geochemical and isotopic features of the coeval volcanic succession are best reconciled utilizing the widely accepted volcanic plutonic connection model whereby the volcanic rocks represent fractionated derivatives of the intrusive rocks older intrusions emplaced at 335 315 ma formed from relatively low fo2 magmas that fractionated extensively to produce highly evolved granites that host sn mineralization coeval volcanic rocks of this suite are compositionally less evolved than the intrusive rocks thereby requiring a different model to link these plutonic volcanic sequences in this case we propose that the most fractionated magmas were not lost to volcanism but instead were effectively retained at the plutonic level which allowed further localized build up of volatiles and lithophile metals in the plutonic environment this disconnection to the volcanism and degassing may be a crucial step for forming granite hosted sn mineralization the transition between these two igneous regimes in herberton region over a 30 m y period is attributed to a change from an early compressive tectonic environment with a thickened crust to conditions of crustal thinning and lithospheric extension due to progressive slab rollback such tectonic transitions may provide favorable conditions for intrusion related mineralization given the common occurrence of volcanic and plutonic rocks associated with sn w mo mineralization worldwide we suggest that a combined understanding of temporal tectonic evolution and plutonic volcanic connections can assist in assessment of regional scale mineralization potential which in turn can aid strategies for future ore deposit exploration

early crustal evolution in the western yangtze block evidence from u pb and lu hf isotopes on detrital zircons from sedimentary rocks abstract in situ u pb and lu hf data on detrital zircons from paleo to neoproterozoic sediments have been used to gain a clearer picture of the regional tectonic background and crustal evolution in the western part of the yangtze block the youngest concordant zircon ages for sedimentary units suggest maximum depositional ages of 1014 ma for the kunyang group 750 649 ma for the sinian sequences and 525 ma for the cambrian sediments the yinmin formation previously assigned to the middle part of the kunyang group was actually deposited after 1667 ma and contains zircons whose ages are dominantly from late archean to paleoproterozoic 2 8 2 7 ga 2 5 2 3 ga and 1 85 ga the heishantou formation in the lower part of the kunyang group has two major age populations of 1 0 ga and 1 8 1 6 ga the sinian and cambrian sedimentary rocks are dominated by neoproterozoic zircons with age peaks at 760 ma and 825 ma consistent with the ages of widespread igneous rocks around the yangtze block the lu hf isotope data suggest that a significant juvenile input took place during archean and neoproterozoic times respectively while crustal reworking was dominant during the paleoproterozoic time the archean paleoproterozoic detritus is isotopically distinct from the archean paleoproterozoic basement exposed in the northern part of the yangtze block suggesting that a subarea of old crust lies beneath the young sediments covering the craton the presence of abundant 1 85 ga zircons suggests that the yangtze block was probably part of the columbia supercontinent during paleoproterozoic time comparisons to the other parts of columbia suggest that the yangtze block could have been adjacent to the north china craton and or australia

the pristine shape of olympus mons on mars and the subaqueous origin of its aureole deposits abstract the tallest volcano in the solar system olympus mons on mars is bordered by at least ten enormous sub circular hummocky deposits forming a welded halo termed the aureole the aureole units or simply aureoles which are the deposits of landslides from olympus mons have dramatically transformed the pristine size and shape of the volcanic edifice topographic data are used to determine the amount of collapsed material and so reconstruct the original outline of olympus mons before the landslides took place under the assumption that the edifice did not start failing until it had reached this maximum size due to post aureole deposition on the eastern and southern flanks and to the uncertainty of the slippage level on the northern side the reconstruction is sufficiently precise along the western and north western olympus mons flank it is more uncertain for the northern flank while it is not feasible around the rest of the volcano it appears that the radius along the western and north western olympus mons before the collapse of the aureole landslides was approximately 200 km longer or more the results show that the volume of the aureoles even if enormous is insufficient to fill the ideal conical edifice which would be obtained prolonging the olympus mons flanks with present slope angles thus an overhang remains in the pre aureole reconstructed olympus mons which would also explain the onset of instability that led to the aureole collapse further a drape deposit blanketing the southern acheron fossae ridge just at the front of the western w aureole landslide deposit and a fan channel system carved on the same w aureole are investigated and it is suggested that these morphologies have been emplaced in subaqueous setting while the drape may indicate a landslide thrust water splash akin to a tsunami deposit caused by the fast travelling w aureole landslide the fan channel system is similar to certain morphologies in the terrestrial oceans a numerical model of the collapse of the western aureole unit in water shows final runouts on both acheron ridge and amazonis planitia compatible with observations provided that the friction angle is extremely small of the order of a tenth of degree simulations indicate that the w aureole could have reached acheron fossae ridge with velocities in excess of 100 m s which would explain the several tens of km long distance reached by the landslide thrust tsunami deposit in short morphological and numerical lines of evidence would indicate a subaqueous origin for the largest w aureole landslide

skin effect in generalized radial flow model in fractured media summary a generalized radial flow model treating the flow dimension as an arbitrary number and taking into account the well skin effect is presented to describe the transient head distribution in a fractured medium under the robin condition during constant head tests the laplace domain solution for the head distribution is first developed via the laplace transforms and the corresponding time domain solution in terms of the hydraulic head is then obtained using the bromwich integral method in addition based on the head solution and darcy s law the solution for the wellbore flux is further developed to investigate the skin effect it is found that the skin effect on the wellbore flux is significant at early times under this circumstance it would not be appropriate to neglect the skin effect in the model in determining the hydraulic parameters from the analysis of field data our solutions will be useful for the predictions of the spatial and temporal head distribution and wellbore flux or in investigating the skin effect on the head distribution and wellbore flux for flow with various dimensions in fractured media

generation of martian chaos and channels by debris flows abstract a debris flow mechanism is proposed to account for the formation of chaos and the large channels debouching into chryse planitia from the adjacent southern uplands of mars the debris is thought to have originated through a mechanism of collapse in the chaotic terrains which exist at the head of these channels as well as locally along the channels this proposition is based on the detailed morphologic similarities between martian channel source areas and the heads of both subaerial and subaqueous terrestrial debris flows the downslope movement of the debris produced the channels through a modification of earlier collapse areas b active bed erosion and c loading induced collapse the large scale channel geometry and the assemblage of related morphologic features on mars correspond tto that observed in subaqueous debris flow chutes on the mississippi delta front through various mechanisms of strain dependent viscosity decrease the debris flow gained mobility downstream turned into a debris avalanche and moved onto chryse planitia at very high velocities this high velocity avalanche eroded a series of streamlined remnants near the channel mouths and deposited its load as a thin blanket over a large area of the basin creating virtually no depositional relief

rheological constraints on martian landslides we use a dynamic finite difference model to simulate martian landslides in the valles marineris canyon system and olympus mons aureole using three different modal rheologies frictional bingham and power law the frictional and bingham modes are applied individually fluidized rheology is treated as a combination of frictional and power law modes general fluidization can include pore pressure contributions whereas acoustic fluidization does not we find that general fluidization most often produces slides that best match landslide geometry in the valles marineris this implies that some amount of supporting liquid or gas was present in the material during failure the profile of the olympus mons aureole is not well matched by any landslide model suggesting an alternative genesis in contrast acoustic fluidization produces the best match for a lunar slide a result anticipated for dry crust with no overlying atmosphere the presence of pressurized fluid during valles marineris landsliding may be due to liquid water beneath a thin cryosphere 1 2 km or flash sublimation of co2

amazonis planitia the role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on mars 1 amazonis planitia located between the two main volcanic provinces on mars tharsis and elysium is characterized by extremely smooth topography at several scale lengths as smooth as oceanic abyssal plains topography on earth we use mars global surveyor mgs data primarily very high resolution mars orbiter laser altimeter mola topography and derivative slope maps gradient maps and detrended maps to examine the surface morphology of amazonis planitia and the stratigraphic relationships among previously mapped and newly defined units these new data reveal the presence of a 1300 km diameter noachian impact basin in northwest amazonis planitia and an extensive late hesperian lava flow unit that appears to have originated from the olympus mons source area prior to aureole formation the presence of this previously unrecognized flow unit strongly suggests that olympus mons activity dates back to at least the hesperian as did activity on the tharsis montes emplacement of this 100 meter thick flow unit formed a barrier along the northern margin of amazonis planitia which had a profound influence on the subsequent geologic history of the region formation of olympus mons aureole deposits created an eastern topographic barrier and subsequent tharsis montes lava flows entered the basin from the south flowing around the aureole these three barriers degraded noachian crater rim protoolympus mons flow unit and olympus mons aureole caused subsequent lava flows and outflow channel effluents primarily from the elysium region to the west to pond on the floor of amazonis planitia preferentially smoothing the terrain there mars orbiter camera moc images substantiate that at least two very fluid lava flows alternated with fluvial episodes from elysium planitia flowing through marte valles onto the floor of the amazonis planitia basin within amazonis planitia moc images show flow like textures heavily mantled by sediments and radar data reveal the presence of rough lava flow surfaces underlying the sedimentary debris these data thus suggest that the unique smoothness of amazonis planitia is the result of deposition of thin fluid lava flows and fluvial sediments in an enclosed basin crater counts suggest that the most recent resurfacing may have occurred in the latest amazonian period in the last 1 of the history of mars in light of its unique history it is somewhat ironic to note that amazonis planitia was originally thought to be a typical young martian surface and therefore used to name the amazonian era index terms 6225 planetology solar system objects mars 5415 planetology solid surface planets erosion and weathering 5470 planetology solid surface planets surface materials and properties 5480 planetology solid surface planets volcanism 8450 4267 oceanography general paleoceanography keywords mars water amazonis planitia marte vallis volcanism amazonian citation fuller e r and j w head iii amazonis planitia the role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on mars j geophys res 107 e10 5081 doi 10 1029 2002je001842 2002

volcanic spreading and lateral variations in the structure of olympus mons mars the olympus mons volcano on mars is notable not only for its immense height and width but also for substantial asymmetries in its structure the gently sloped northwest flank extends to a much greater distance from the central caldera complex than the more steeply sloped southeast flank furthermore the northwest flank exhibits lower flank extensional faults whereas the southeast shows upper flank compressional terraces and lower flank upthrust blocks however both the northwest and southeast flanks exhibit characteristic concave upward profiles and steep bounding scarps in contrast to other sectors the nw se asymmetries are aligned with the regional slope from the tharsis rise but an understanding of the underlying causes has remained elusive we use particle dynamics models of growing spreading volcanoes to demonstrate that these flank structures could reflect the properties of the basement materials underlying olympus mons we find that basal slopes alone are insufficient to produce the observed concave upward slopes and asymmetries in flank extent and deformation style that are observed at olympus mons instead lateral variations in basal friction are required these variations are most likely related to the presence of sediments transported and preferentially accumulated downslope from the tharsis rise such sediments likely correspond to ancient phyllosilicates clays recently discovered by the mars express mission

granite a planetary point of view the telluric planets and the asteroid belt display the same internal structure with a metallic inner core and a silicate outer shell experimental data and petrological evidence in silicate systems show that granite can be produced through all types of magmatic processes on moon 4 4 3 9 ga granite clasts displaying dry mineral assemblages correspond to discrete intrusive events large k ca enrichment and low ree abundances in granite relative to kreep are consistent with silicate liquid immiscibility a process observed in melt inclusions within olivine of lunar basalts on mars black and white rhythmic layers observed on the tharsis rise along the flanks of valles marineris and the peripheral scarps of the tharsis montes giant volcanoes suggest the eruption of possibly felsic pyroclastites samples analysed in the mars pathfinder landing site yield basic to intermediate 45 to 62 wt sio2 compositions though no granites were found so far in the martian snc meteorites a component close to terrestrial continental granitic crust is inferred from trace element and isotope systematics like the martian northern hemisphere venus has suffered extensive volcanic resurfacing whereas folded and faulted areas resemble terrestrial continents the hypothesis of a granitic component is again tantalizing finally extra terrestrial granite is also found as enclaves within iron meteorites and ordinary chondrites granite a major component of the earth s crust can be generated in all geodynamic settings the low density of granite favours continental accretion thus the occurrence or absence of granite and of associated silicic volcanism within the other telluric planets is not a trivial question granite is generally thought to be produced through wet processes lunar evidence shows that dry conditions may apply as well in venus a large planet with high rates of magma production it is speculated that significant volumes of granite can develop

aureole deposits of the martian volcano olympus mons the aureole of grooved terrain that surrounds the large shield volcano olympus mons consists of several overlapping roughly circular sheets each 0 5 to 1 5 km thick the surfaces of these materials bear abundant curvilinear ridges and troughs 10 to 100 km long and 1 to 5 km wide which form anastomosing patterns that vary in length and width over the aureole the aureole is asymmetric to olympus mons extending almost 1000 km northwest from the center of the volcano but only 600 km southeast the lobate form of the deposits the pressure ridges on their surfaces and the deflection of aureole material around barriers indicate that the deposits were emplaced as viscous flows high resolution viking orbiter pictures show the aureole material to be unstratified and it is inferred to contain randomly distributed large dark blocks whose weathering products form dark streaks in the talus on the flanks of ridges a pyroclastic origin is proposed for the aureole the following sequence is suggested at least six great pyroclastic eruptions occurred prior to the construction olympus mons they formed very fluid ash flows that became viscous during late stages of emplacement and pressure ridges formed on the surfaces of the deposits before they finally came to rest the oldest and most extensive aureole deposit finely grooved terrain was considerably modified by erosion prior to being partly covered by later eruptions a positive gravity anomaly over the olympus mons area may define the site of a near surface magma chamber that was the source of the pyroclastic eruptions

the aureole of olympus mons mars as the compound deposit of submarine landslides abstract the enigmatic deposits building up the olympus mons aureole on mars are likely among the largest landslide remnants in the solar system these deposits exhibit an extraordinary run out distance up to nearly 700 km in spite of a fall height some 100 times smaller after quantifying the mobility of the olympus mons aureole lobes it is suggested based on dynamical considerations and morphological analysis that the aureole could be the consequence of a series of gigantic subaqueous landslides in order to bring evidence in favor of this interpretation comparisons are drawn between the different landslide deposits on earth and mars emphasizing the similarity with the rock avalanches of the canary islands and the hawaii the results of experimental subaqueous debris flows are also analyzed and numerical calculations are introduced to simulate the dynamics of flow in analogy with certain subaqueous landslides on earth it is possible that the outstanding run out of the aureole lobes was a consequence of hydroplaning a natural lubrication by water during flow

mars paleostratigraphic restoration of buried surfaces in tharsis montes volcanism in the tharsis province of mars occurred in several different areas and was generally continuous without large time intervals between eruptive episodes major lava flow units are numerous and extensive but relatively thin in many places impact craters on buried surfaces project above younger flows that overlie them a new application of crater dating methods has been developed to aid in the identification of these buried surfaces and to determine their lateral extent the technique is especially adaptable to the tharsis region where the stratigraphic succession of major flow units has been established by detailed geologic mapping knowledge of the overall stratigraphy allows correlations to be made between known and unknown surfaces by comparing their crater frequencies at diameters large enough to insure their recognition on the buried unit the method has been applied to aid in the restoration of buried rock units and to construct a series of paleostratigraphic maps showing the sequence of major eruptive events in the tharsis region

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

can electrical conductivity data from a single pumping test provide information about the location of a neighboring mixing zone between two aquifers an example from aix les bains marlioz savoie france summary pumping tests were first developed to interpret observed drawdown in wells analyses of drawdown and temperature profiles now help petroleum geologists and geothermal energy specialists improve production rates and numerous hydrogeological studies have combined drawdown data with measures of electrical conductivity or a chemical parameter often a pollutant the present study used electrical conductivity data from a pumping test in a single well to obtain information about the position of the hydrothermal plume that feeds aix les bains thermes de marlioz spa applying this data to a 3d model of an equivalent porous medium showed that the plume at the bottom of the subsurface aquifer must be downstream from the well in the present study combining drawdown data for a single well with electrical conductivity measurements provided an efficient method for determining the position of a mixing zone near pumped wells this method may well be generalizable to other situations

state of stress faulting and eruption characteristics of large volcanoes on mars the formation of a large volcano loads the underlying lithospheric plate and can lead to lithospheric flexure and faulting in turn lithospheric deformation affects the stress field beneath and within the volcanic edifice and can influence magma transport modeling the interaction of these processes is crucial to an understanding of the history of eruption characteristics and tectonic deformation of large volcanoes we develop models of time dependent stress and deformation for the tharsis volcanoes on mars by means of a finite element code we calculate stresses and displacements due to a volcano shaped load emplaced on an elastic plate overlying a viscoelastic mantle models variously incorporate growth of the volcanic load with time and a detachment between volcano and lithosphere the models illustrate the manner in which time dependent stresses induced by lithospheric plate flexure beneath the volcanic load may affect eruption histories and the derived stress fields can be related to tectonic features on and surrounding martian volcanoes as a result of flexure there are three regions where stresses become sufficiently large to cause failure by faulting according to the mohr coulomb criterion at the surface of the plate just outward of the volcano near the base of the elastic lithosphere beneath the center of the volcano and on the upper flanks of the volcano early in its growth history normal faulting is the dominant mode of failure predicted for the first region consistent with circumferential graben observed around the tharsis montes and with the scarp at the base of olympus mons interpreted as a large offset listric normal fault normal faulting mostly radially oriented is predicted for the second region failure in the third region is predicted to consist of thrust faulting circumferentially oriented on the upper and middle flanks and radially oriented on the lower flanks in models simulating a growing volcano this portion of the edifice is subsequently covered by later units which exhibit lower stresses and are not predicted to fail this volume of early failure remains the most highly stressed area in the edifice concentric terraces interpreted by some workers as thrust faults on the upper flanks of olympus mons may correspond to the predicted circumferential thrust features if the most recent increments of volcano growth were relatively large or in the presence of local material property or stress field variations for volcanoes detached from the plate predicted failure in the edifice takes the form of radial normal faulting near the volcano base the addition of a local extensional stress arising from the regional topographic slope yields a pattern of predicted faulting which closely matches that observed on the tharsis montes including the development of radial rifts on the lower volcano flanks to the northeast and southwest and the asymmetric formation of circumferential flank graben this stress state is also consistent with an interpretation of the aureole deposits of olympus mons as the result of gravity sliding along a basal detachment our models also suggest an explanation for the lack of strike slip features predicted by previously published flexural models around the tharsis volcanoes for a given load increment the first mode of near surface failure for most of the area immediately outward of the load is circumferential normal faulting and graben formation as the volcano grows and the flexural response to the increasing load proceeds the predicted failure mode in a portion of this annular region surrounding the volcano changes to strike slip faulting because normal faulting has been predicted to have taken place earlier however it is likely that release of later stresses will occur by reactivation and growth of these normal faults and graben rather than by the formation of new strike slip faults

geologically recent water flow inferred in channel systems in the ne sulci gordii region mars a series of fluid carved channels in the sulci gordii region of mars were investigated numerous channel networks exist in sulci gordii part of the olympus mons aureole and this area comprises some of the youngest volcanic terrain on mars the channels ranged in length from 43 to 155 km with widths of 128 288 m the morphology of the channels was analysed assuming both lava and water as possible agents for three of the four channels studied water appears to be the likely agent while one channel is probably lava formed for the water formed channels discharge rates were estimated at 8000 36 000 m3 s 1 the lava channel was probably formed from short lived episodic activity by a low viscosity lava the age of the channels and surrounding area was estimated using crater counting to be 100 ma water has appeared to have flowed for almost 150 km under the climatic conditions at this time there is some evidence for later tectonic activity possibly as recent as 10 ma but crater dating accuracy was limited by the lack of high resolution images of some areas sulci gordii is therefore a dynamic site with evidence of hydrological and volcanic activity extending into the recent geological past

olympus mons aureole deposits new evidence for a flank failure origin 1 the origin of the rough textured aureoles that surround the immense olympus mons volcano on mars is controversial we present data from the mars global surveyor and mars odyssey missions to demonstrate that at least two of the aureole lobes are derived from the volcano s flanks in large and probably catastrophic mass movement events leaving behind headwalls that constitute the basal scarp this evidence stems from the morphology and internal structure of aureole blocks which exhibit remnants of volcanic flow units on their surfaces our claim is supported by plausible reconstructions of the prefailure flanks structural analogs to known flank failure events at hawaiian volcanoes suggest that repeated cycles of flank growth and collapse at olympus mons allow generation of the observed aureoles from a protoedifice similar in size and shape to the present one

fractal patterns of fractures in granites abstract fractal measurements using the cantor s dust method in a linear one dimensional analysis mode were made on the fracture patterns revealed on two dimensional planar surfaces in four granites this method allows one to conclude that 1 the fracture systems seen on two dimensional surfaces in granites are consistent with the part of fractal theory that predicts a repetition of patterns on different scales of observation self similarity fractal analysis gives essentially the same values of d on the scale of kilometres metres and centimetres five orders of magnitude using mapped surface fracture patterns in a sierra nevada granite batholith mt abbot quadrangle calif 2 fractures show the same fractal values at different depths in a given batholith mapped fractures main stage ore veins at three mining levels over a 700 m depth interval of the boulder batholith butte mont show the same fractal values although the fracture disposition appears to be different at different levels 3 different sets of fracture planes in a granite batholith central france and in experimental deformation can have different fractal values in these examples shear and tension modes have the same fractal values while compressional fractures follow a different fractal mode of failure the composite fracture patterns are also fractal but with a different median fractal value compared to the individual values for the fracture plane sets these observations indicate that the fractal method can possibly be used to distinguish fractures of different origins in a complex system it is concluded that granites fracture in a fractal manner which can be followed at many scales it appears that fracture planes of different origins can be characterized using linear fractal analysis

a volcanotectonic survey of ascraeus mons mars 1 ascraeus mons is one of the largest volcanoes on mars it is replete with well preserved features that can be used to understand its volcanotectonic evolution previous studies of this volcano focused on specific features and were limited by the quality and coverage of contemporary data our objective is to review and enhance the existing developmental model for ascraeus by considering all endogenic surface features on the volcano we surveyed the volcano s caldera complex flank terraces pit structures sinuous rilles arcuate grabens and small vents we report the spatial and temporal distributions of these features appraise their proposed formation mechanisms in light of our mapping results and propose a detailed geological history for ascraeus mons an initial shield building phase was followed by the formation of a summit caldera complex and small parasitic cones while compression due to flexure of the supporting basement led to extensive terracing of the shield flanks an eruptive hiatus followed ending with the construction of expansive rift aprons to the northeast and southwest against later extensive flank resurfacing in the late amazonian continued flexure formed arcuate grabens concentric to the edifice localized eruption and surface flow of a fluid agent lava and or water from within the volcano then produced a population of rilles on the lower flanks finally in a change of flank tectonic regime from compression to extension pit crater chains and troughs developed on the main shield and rift aprons eventually coalescing to form large embayments at the northeast and southwest base of the volcano

mars a water rich planet abstract mars had outgassed at least 0 5 to 1 km of water 10 to 20 bar of co2 and 0 1 to 0 3 bar of n2 the volatiles that have been retained are mostly in the cratered uplands terrain softening fretted channels debris flows and closed depressions indicate that at least the upper 2 km of the cratered uplands at high latitudes 30 contain ice in amounts that exceed the porosity estimated to be 10 20 theoretical studies and lack of these features in the cratered uplands at low latitudes suggest that the upper 1 km of the uplands at low latitudes is ice poor however valley networks indicate that water was present near the surface early in the planet s history although in amounts smaller than at high latitudes the entire upper 1 km planetwide is estimated to have contained 75 125 m of water at the end of heavy bombardment the largest sink for water is the megaregolith below 1 km episodic eruption of water from the deep megaregolith cut many of the large outflow channels from the volume of water needed to cut the circum chryse channels and assuming uniform planetwide distribution of water the deep megaregolith is estimated to have contained at least 350 m of water at the end of heavy bombardment thereby giving a total minimum inventory of 424 475 m planetwide most of the water lost from the low latitude uplands by diffusion and in cutting the valley networks is now believed to be in the polar layered terrains most of the water involved in cutting the outflow channels is in the low lying northern plains where a variety of features that have been attributed to ground ice is present a large fraction of the planet s surface has been overplated with water poor volcanics of which we have samples in the snc meteorites the younger volcanics have reacted extensively with the old volatile rich basement some of the co2 and n2 outgassed was lost during heavy bombardment by impact erosion of the atmosphere and other processes the remaining was fixed carbonates and folded deep into the megaregolith during heavy bombardment

flank vents and graben as indicators of late amazonian volcanotectonic activity on olympus mons previous studies have focused on large scale features on olympus mons such as its flank terraces the summit caldera complex and the basal escarpment and aureole deposits here we identify and characterize previously unrecognized and unmapped small scale features to help further understand the volcanotectonic evolution of this enormous volcano using context camera ctx high resolution imaging science experiment hirise thermal emission imaging system themis high resolution stereo camera digital terrain model hrsc dtm and mars orbiter laser altimeter mola data we identified and characterized the morphology and distribution of 60 flank vents and 84 graben on olympus mons we find that effusive eruptions have dominated volcanic activity on olympus mons in the late amazonian explosive eruptions were rare implying volatile poor magmas and or a lack of magma water interactions during the late amazonian the distribution of flank vents suggests dike propagation of 100 s of km and shallow magma storage small graben not previously observed in lower resolution data occur primarily on the lower flanks of olympus mons and indicate late stage extensional tectonism based on superposition relationships we have concluded two stages of development for olympus mons during the late amazonian 1 primarily effusive resurfacing and formation of flank vents followed by 2 waning effusive volcanism and graben formation and or reactivation this developmental sequence resembles that proposed for ascraeus mons and other large martian shields suggesting a similar geologic evolution for these volcanoes

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

rejuvenation vs recycling of archean crust in the gawler craton south australia evidence from u pb and hf isotopes in detrital zircon abstract zircon grains from modern and ancient drainages of the gawler craton south australia have been analysed to define the relative contributions of juvenile sources and recycled crust to magmatic activity as a function of time and to constrain the role of mantle inputs during the proterozoic rejuvenation of the archean gawler craton the integration of hf isotope data with u pb age spectra shows that the crustal evolution was dominated by long periods of crustal reworking and that crust generated in the paleoarchean 3 2 3 5 ga was largely reworked during proterozoic time four periods of juvenile mantle input can be recognised at ca 2540 ma 1853 ma 1595 ma and 1169 ma the 1169 ma event is not previously recognised in the gawler craton but the absence of other important age peaks argues against the transport of these zircons from the musgrave block only minor proportions of the magmatic zircons with paleoproterozoic to mesoproterozoic ages have strongly juvenile signatures e hf 4 indicating that crustal reworking was the dominant process with relatively minor mantle input comparison of the crustal evolution with that of nearby australian terranes suggests that although the gawler craton shows some similarities with the mount isa block and the georgetown inlier in neoarchean paleoproterozoic time it evolved independently between ca 1800 and 1550 ma

kilometer scale roughness of mars results from mola data analysis the mars orbiter laser altimeter mola data are used to characterize the kilometer scale surface roughness of mars the median absolute value of the differential slope at a given baseline is proposed as a data derived measure of the surface roughness at this scale study of the scale dependence of roughness for the smoothest terrains gives an independent estimate of 20 cm for mola ranging accuracy the baseline lengths from 0 6 to 20 km are used and kilometer scale roughness is mapped for the entire surface the maps show that different geological units have distinctive roughness characteristics scale dependence of roughness for a number of geological units is presented and discussed the southern polar cap is rougher than the northern at kilometer and subkilometer scale which suggests differences in the sublimation condensation balance the vastitas borealis formation has a distinctive 3 km scale background surface topography which suggests a nonvolcanic origin for its upper layer young volcanic plains in amazonis planitia and the eastern part of elysium planitia are very similar to each other in their roughness characteristics and differ from other volcanic plains on mars which suggests a distinctive eruption style there are systematic latitudinal variations of roughness in both the southern highlands and the northern lowlands terrains at high latitude are smoother at short baselines the characteristic vertical scale related to this difference is several meters processes that could be responsible for formation of this trend include creep of ice rich near surface material at high latitudes treatment of the surface with repetitive deposition and sublimation of seasonal frost climate controlled deposition and or cementation of dust at high latitudes and repetitive sublimation and accumulation of subsurface ice at low latitudes with climate variations all mechanisms of origin could operate more effectively under different climate conditions relevant morphological observations favor mechanisms involving deposition of smooth blankets at high latitudes

a change in the geodynamics of continental growth 3 billion years ago models for the growth of continental crust rely on knowing the balance between the generation of new crust and the reworking of old crust throughout earth s history the oxygen isotopic composition of zircons for which uranium lead and hafnium isotopic data provide age constraints is a key archive of crustal reworking we identified systematic variations in hafnium and oxygen isotopes in zircons of different ages that reveal the relative proportions of reworked crust and of new crust through time growth of continental crust appears to have been a continuous process albeit at variable rates a marked decrease in the rate of crustal growth at 3 billion years ago may be linked to the onset of subduction driven plate tectonics

flank tectonics of martian volcanoes on the flanks of olympus mons is a series of terraces concentrically distributed around the caldera their morphology and location suggest that they could be thrust faults caused by compressional failure of the cone in an attempt to understand the mechanism of faulting and the possible influences of the interior structure of olympus mons we have constructed a numerical model for elastic stresses within a martian volcano in the absence of internal pressurization the middle slopes of the cone are subjected to compressional stress appropriate to the formation of thrust faults these stresses for olympus mons are 250 mpa if a vacant magma chamber is contained within the cone the region of maximum compressional stress is extended toward the base of the cone if the magma chamber is pressurized extensional stresses occur at the summit and on the upper slopes of the cone for a filled but unpressurized magma chamber the observed positions of the faults agree well with the calculated region of high compressional stress three other volcanoes on mars ascraeus mons arsia mons and pavonis mons possess similar terraces extending our analysis to other martian volcanoes we find that only these three and olympus mons have flank stresses that exceed the compressional failure strength of basalt lending support to the view that the terraces on all four are thrust faults

ground ice on mars inventory distribution and resulting landforms abstract most 90 of the estimated original volume of outgassed water on mars cannot be satisfactorily accounted for by exospheric escape or storage in the atmosphere as frost or in the permanent north polar ice cap the balance may be stored as ground ice in the martian cryosphere a zone of permanently frozen ground that is protected from the atmosphere by a debris cover ground ice can exist throughout the entire cryosphere but it need not fill it if the ground ice does fill the cryosphere then excess water can exist in a confined aquifer the theoretical distribution of ground ice can be tested by identification of forms on the martian surface that may be related to the presence of subsurface ice the observed features that are most likely to reflect ground ice are thermokarst like pits and debris flows landforms with ambivalent origins include polygonally patterned ground lobate ejecta blankets craters with central pits and curvilinear features the most persuasive morphologic evidence for ground ice is thermokarst pits and debris flows the thermokarst pits are primarily located in the volcanic regions of tharsis and elysium the association of ice related features with these volcanic areas suggests that these forms are not directly latitude dependent activation by orbital variations could produce periodic multiple episodes of melting that are dependent upon latitude the presence of ice related features in both hemispheres and the equatorial region of mars indicates that ground ice may be or have been present over the entire planet as predicted by the cryosphere model

resurfacing history of the northern plains of mars based on geologic mapping of mars global surveyor data 1 geologic mapping of the northern plains of mars based on mars orbiter laser altimeter topography and viking and mars orbiter camera images reveals new insights into geologic processes and events in this region during the hesperian and amazonian periods we propose four successive stages of lowland resurfacing likely related to the activity of near surface volatiles commencing at the highland lowland boundary hlb and progressing to lower topographic levels as follows highest elevations indicated stage 1 upper boundary plains early hesperian 2 0 to 2 9 km stage 2 lower boundary plains and outflow channel dissection late hesperian 2 7 to 4 0 km stage 3 vastitas borealis formation vbf surface late hesperian to early amazonian 3 1 to 4 1 km and stage 4 local chaos zones early amazonian 3 8 to 5 0 km at acidalia mensa stage 2 and 3 levels may be lower 4 4 and 4 8 km respectively contractional ridges form the dominant structure in the plains and developed from near the end of the early hesperian to the early amazonian geomorphic evidence for a northern plains filling ocean during stage 2 is absent because one did not form or its evidence was destroyed by stage 3 resurfacing remnants of possible amazonian dust mantles occur on top of the vbf the north polar layered deposits appear to be made up of an up to kilometer thick lower sequence of sandy layers early to middle amazonian in age overlain by late amazonian ice rich dust layers both units appear to have outliers suggesting that they once were more extensive

groundwater recharge in a hard rock aquifer a conceptual model including surface loading effects knowledge about the groundwater recharge is essential for the prediction of impacts of groundwater withdrawal and underground construction recharge in the bedrock is however difficult to estimate the objectives of this thesis were to increase the understanding of groundwater recharge in crystalline bedrock to investigate how the recharge could be estimated and to develop new models to describe the recharge the study was based on three approaches groundwater dating using chlorofluorocarbons cfcs geohydraulic field measurements and mathematical modelling low concentrations of cfc 11 and cfc 113 were found in the bedrock groundwater which in combination with low dissolved oxygen levels indicated anaerobe degradation the cfc 12 and tritium concentrations agreed fairly well which means that apparent ages could be true ages the results suggest that cfc dating may not be reliable at forested humid sites covered by fine grained soil a quick response in hydraulic head to precipitation was observed in the studied bedrock despite the 10 m thick till cover a substantial portion of observed head variations was found to be loading effects involving no storage changes or water flow the loading efficiency of the bedrock was estimated from the air pressure response to be 0 95 the surface loading was calculated from measurements of air pressure water in the soil and snow about 20 of the seasonal variation of the hydraulic head was estimated to be related to loading changes only a simple conceptual model could be used to simulate the observed hydraulic heads the loading effect had to be included to properly describe individual recharge events numerical experiments were performed with a soil bedrock profile when the rock was modelled as a heterogeneous continuum unsaturated zones developed at high hydraulic gradients the phenomenon appeared in areas where low conductive zones were located upstream of high conductive zones decreasing the effective hydraulic conductivity of the material

granitic magmatism basement ages and provenance indicators in the malay peninsula insights from detrital zircon u pb and hf isotope data abstract the malay peninsula lies on two continental blocks sibumasu and east malaya which are intruded by granitoids in two provinces the main range and eastern previous models propose that permian triassic granitoids are subduction related and syn to post collisional we present 752 u pb analyses that were carried out on zircons from river sands in the malay peninsula of these 243 grains were selected for hf isotope analyses our data suggest a more complex sibumasu east malaya collision history 176hf 177hfi ratios reveal that permian triassic zircons were sourced from three magmatic suites a permian crustally derived granitoids b early middle triassic granitoids with mixed mantle crust sources and c late triassic crustally derived granitoids this suggests three permian triassic episodes of magmatism in the malay peninsula two of which occurred in the eastern province although the exact timing of the sibumasu east malaya collision remains unresolved current data suggest that it occurred before the late triassic probably in late permian early triassic our data also indicate that sibumasu and east malaya basements are chronologically heterogeneous but predominantly of proterozoic age some basement may be neoarchaean but there is no evidence for basement older than 2 8 ga finally we show that hf isotope signatures of triassic zircons can be used as provenance indicators

reconstruction of groundwater flows and chemical water evolution in an amagmatic hydrothermal system la lechere french alps summary a detailed picture of the hydrogeochemistry of an alpine thermal area la lechere french alps was drawn up from new and complete analyses of shallow and deep groundwater including major and trace elements gases and stable 18 o d 13 c 34 s and radiogenic isotopes 14 c combined with data on the trace and stable isotope 18 o 34 s contents of the aquifer rocks three different groundwater facies were recognized 1 the shallow groundwater in the carbonate and crystalline rocks presents a poorly mineralized ca hco 3 facies 2 the shallow groundwater from the evaporitic fault zone presents a mineralized ca mg so 4 facies 3 and the deep thermal water presents a highly mineralized ca na so 4 facies the evolution from facies 2 to facies 3 is controlled by three phenomena i the presence or absence of evaporitic deposits along the fault which governs whether or not the water can interact with carbonates and dolomites ii interactions with micaschists and permo carboniferous rocks which lead to ca na exchanges and enrichment in some trace elements and gases co 2 ch 4 and h 2 s and iii the long residence time several thousand years and high temperature 90 c of the thermal water

the olympus mons aureole formation by gravitational spreading new observations of the aureole deposits of olympus mons are in agreement with previous suggestions that the aureole lobes could have been formed by movement under gravity away from the observed scarps the characteristic corrugated morphology of the aureole is probably secondary formed by erosion along structural inhomogeneities geometries of the corrugations and translational faults in the aureole deposits favor a mechanism of emplacement that involves material with substantial shear strength rather than viscous flow estimates of the aspect ratios of terrestrial landslides nappes and ash flows suggest that the aureole deposits are more similar in overall shape to slide emplaced bodies than to pyroclastic flows although martian physical conditions permit the formation of ash flows there is no positive evidence for their existence a gravitational spreading mechanism is proposed that involves imbricate thrusting in distal regions analogous with terrestrial thrust sheets corrugations in the aureole developed by erosion along imbricate or listric faults basal shear stresses on the decoupling surface may have been of the order of 106 pa 10 bars the nature of the decoupling surfaces in the proximal regions is uncertain but is likely to have been the topographic surface in distal parts the aureole deposits were probably emplaced as a series of sheets by spreading under gravity from an ancestral olympus mons which extended farther to the northwest than does the present volcano as a result of the accumulation of lavas under the then prevailing stress conditions recent lava eruptions from the volcano have been concentrated in northeast and southwest sectors indicating a changed stress regime since aureole emplacement

a new method of characterizing fissured media by pumping tests with observation wells abstract an analogy has been defined between the relation s r t at n and the elementary solution derived from the general flow equation describing fluid flow in fissured media assuming a non integer flow dimension that analogy can be used to characterize a fissured medium by parameters that are similar to those describing a porous reservoir if at least two observation wells are available and if flow involves a sufficient number of fractures the flow system behaves as a fractal object with observation wells located along axes in several directions anisotropy can be characterized two field applications illustrate the proposed method

discrete element simulations of gravitational volcanic deformation 1 deformation structures and geometries 1 we have carried out two dimensional particle dynamics simulations of granular piles subject to frictional coulomb failure criteria to gain a first order understanding of different modes of gravitational deformation within volcanoes under uniform basal and internal strength conditions granular piles grow self similarly developing distinctive stratigraphies morphologies and structures piles constructed upon cohesive substrates exhibit particle avalanching forming outward dipping strata and angle of repose slopes systematic decreases in basal strength lead to progressively deeper and steeper internal detachment faults and slip along a basal decollement landslide forms grade from shallow slumps to deep seated landslide and finally to axial subsidence and outward flank displacements or volcanic spreading surface slopes decrease and develop concave up morphologies with decreasing decollement strength depositional layers tilt progressively inward spatial variations in basal strength cause lateral transitions in pile structure stratigraphy and morphology this approximation of volcanoes as coulomb granular piles reproduces the richness of deformational structures and surface morphologies in many volcanic settings the gentle slopes of hawaiian volcanoes and olympus mons on mars suggest weak basal decollements that enable volcanic spreading high angle normal faults favored above weak decollements are interpreted in both settings and may explain catastrophic sector collapse in hawaii and broad aureole deposits surrounding olympus mons in contrast steeper slopes and shallow detachment faults predominate in the canary islands thought to lack a weak decollement favoring smaller more frequent slope failures than predicted for hawaii the numerical results provide a useful predictive tool for interpreting dynamic behavior and associated geologic hazards of active volcanoes

a note on the drawdown diffusive behavior of fractured rocks 1 transients in fractured media are described using a model in which permeability depends on space and time the motivation for the differential equation used here draws on recent results for diffusion on fractals in the asymptotic regime the solution proposed is consistent with the scaling arguments for diffusion on fractal structures known results for transients in fractured rocks may be extracted from the solution given here