the effect of salt crust on the thermal conductivity of one sample of fluvial particulate materials under martian atmospheric pressures 1 a line heat source apparatus was used to measure thermal conductivities of a lightly cemented fluvial sediment salinity 1 1 g kg 1 and the same sample with the cement bonds almost completely disrupted under low pressure carbon dioxide atmospheres the thermal conductivities of the cemented sample were approximately 3 higher over the range of atmospheric pressures tested than the thermal conductivities of the same sample after the cement bonds were broken a thermal conductivity derived particle size was determined for each sample by comparing these thermal conductivity measurements to previous data that demonstrated the dependence of thermal conductivity on particle size actual particle size distributions were determined via physical separation through brass sieves when uncemented 87 of the particles were less than 125 m in diameter with 60 of the sample being less than 63 m in diameter as much as 35 of the cemented sample was composed of conglomerate particles with diameters greater than 500 m the thermal conductivities of the cemented sample were most similar to those of 500 m glass beads whereas the thermal conductivities of the uncemented sample were most similar to those of 75 m glass beads this study demonstrates that even a small amount of salt cement can significantly increase the thermal conductivity of particulate materials as predicted by thermal modeling estimates by previous investigators

valles marineris dune sediment provenance and pathways abstract although low albedo sand is a prevalent component of the martian surface sources and pathways of the sands are uncertain as one of the principal present day martian sediment sinks the valles marineris vm rift system hosts a diversity of dune field populations associated with a variety of landforms that serve as potential sediment sources including spur and gully walls interior layered deposits ilds and landslides here we test the hypothesis that vm dune fields are largely derived from a variety of local and regional intra rift sediment sources results show several dune fields are superposed on ancient wall massifs and ilds that are topographically isolated from extra rift sand sources spectral analysis of dune sand reveals compositional heterogeneity at the basinal dune field and dune scales arguing for discrete relatively unmixed sediment sources in coprates and melas chasmata mapping is consistent with the principle sand source for dunes being noachian aged upper and lower wall materials composed of primary igneous minerals and glasses some of which show evidence for alteration in contrast dune fields in capri juventae and ganges chasmata show evidence for partial sediment derivation from adjacent early hesperian aged hydrated sulfate bearing ild units this finding indicates that these ilds act as secondary sand sources dunes containing soft secondary minerals e g monohydrated sulfate are unlikely to have been derived from distant sources due to the physical weathering of sand grains during transport isolated extra rift dune fields sand sheets and sand patches are located on the plateaus surrounding vm and the adjoining areas but do not form interconnected networks of sand pathways into the rift if past wind regimes with respect to directionality and seasonality were consistent with more recent regimes inferred from morphological analysis i e dune slip faces wind streaks and were sufficient in strength and duration small dune populations within aurorae chaos and north of eastern vm might have resulted from extended sand pathways into vm however we favor local and regional derivation of dune sand from a variety of intra rift lithologic sources for most cases dune sand sources and the mechanism by which the sand is liberated are discussed in the context of findings described herein but are broadly applicable to analysis of sediment production elsewhere on mars

mechanism of arrested charnockite formation at nemmara palghat region southern india abstract the formation of arrested charnockite is an excellent example of structurally controlled channellised fluid flow along specific sites accompanied by selective elemental mobility and mineralogical changes the present paper recognises and focuses study on three types of arrested charnockite formation from palghat region namely shear controlled foliation parallel and boudin neck types and address their spatio temporal relations to regional scale charnoenderbite the shear controlled and foliation parallel types post date deformation and migmatisation the boudin neck type on the contrary is coeval with partial melting and followed the path of cooling and decreasing water activity in the gneiss k feldspar veining around plagioclase and quartz symplectitic intergrowth of biotite quartz after orthopyroxene and k feldspar and fluid inclusion data suggests the presence of alkalic supercritical brine and low density co2 rich fluid during charnockite formation charnockite domains developed following the breakdown of hornblende biotite and quartz are characterised by a more or less pronounced depletion of fe ca mg and ti and trace elements y and zr compared to their counterpart gneiss ree spectra indicate a subtle depletion in the hree near the centre of the charnockite domain although close pair samples of gneiss charnockite are isochemical on a scale of a few millimetres bi directional element movement related to the formation of new mineral was noted it is postulated that arrested charnockite formation developed in situ on local scale within the granitic domains of the hornblende biotite gneiss in the presence of co2 rich fluids and alkalic supercritical saline brine this process post dated the time of regional granulite charnoenderbite and large regional scale retrogression and migmatisation

deucalionis regio mars evidence for a new type of immobile weathered soil unit abstract a small equatorial region south of sinus meridiani deucalionis regio has been found spectrally distinct from other regions as seen in a high spectral resolution telescopic image of mars interpretations from a variety of other observations including infrared radiometric data historical occurrences of localized dust storms and general circulation wind modeling also suggest that the surface of deucalionis regio has properties that are different than those of nearby regions arabia acidalia sinus meridiani and oxia in terms of expression of color crystalline hematite content and perhaps pyroxene abundance and mineralogy the thermophysical and aeolian observations indicate that the soils in deucalionis regio are relatively immobile despite the likely occurrence of winds strong enough to move unconsolidated materials we propose that the soils in this region are indurated or crusted we predict that a mars observer class thermal emission spectrometer and gamma ray spectrometer will show the presence of crust forming minerals and elements in the soils of this region the spatial correlation between areas that have been previously proposed to be regional exposures of crust and areas that are spectrally similar to deucalionis regio may suggest a possible genetic relationship between the composition and the physical properties

ground truth from the opportunity rover for mars thermal inertia data 1 the temperature of the martian surface has been measured by a number of spacecraft and numerical models of the surface thermal response constrain the near surface physical properties the results allow inferences regarding the surface layer and help determine potential hazards for landed spacecraft however thermal models generally do not incorporate the degree of surface complexity that is seen from landers here we examine potential contributions to the thermal response along the opportunity rover s traverse by using ground truth in conjunction with orbiter data from the themis instrument on mars odyssey we show that the size distribution of the ubiquitous hematite spherules varies in a way that is consistent with expectations from orbiter data secondly exposures of bedrock along opportunity s traverse have no observable effect on the bulk thermal response seen from orbit these field observations are an important step toward improving understanding of the physical composition of the martian surface

seismic source modeling seismic source modeling is taken to mean the modeling of seismograms to investigate kinematic properties of the earthquake source current trends such as the use of other data types e g geodetic measurements of coseismic deformation and the explicit consideration of source dynamics when modeling seismograms are beginning to blur this definition but i will adhere to it in this review i have divided seismic source modeling into teleseismic regional and near source modeling teleseismic modeling has the advantage of global coverage for earthquakes of magnitude 5 5 and larger but does not provide much more than point source parameters regional distance modeling has the advantage of a more rapid assessment of earthquake source properties but is complicated by relatively complex wave propagation the coverage is also limited to areas of broadband regional networks typically continental areas of developed countries near source modeling has the potential for detailed imaging of source properties but very few earthquakes occur in regions with sufficient instrumentation to allow this i have also included a section on historical earthquakes because of the additional issues that seismologists face in working with pre wwssn data and because of the important issues such as earthquake recurrence that require historical data in addition to reviewing the progress in seismic source modeling during the last four years i have also briefly reviewed some of the progress in understanding earthquake physics and hazards that has come about because of basic research in earthquake source modeling

analysis of the 4 february 1976 chino valley arizona earthquake abstract this m b 4 9 earthquake was located about 20 km north of prescott in the transition zone between the basin and range and colorado plateau provinces several lines of approach were used to determine the focal mechanism p wave first motions surface wave amplitude and phase spectra and synthetic seismograms the preferred focal mechanism displays northwest trending nodal planes with predominantly normal movement the inferred fault plane strikes 120 dips 40 sw with a slip of 100 and a depth of 10 to 15 km the seismic moment is 1 0 10 23 dyne cm the azimuth of least horizontal stress is inferred to be 37 lithostatic stress generated by variations in elevation and density between the crusts of the southern basin and range and colorado plateau may contribute to the inferred stress orientations uplift and resultant extension in this zone of thin lithosphere and relatively high heat flow may also be important microearthquake studies in the chino valley during the summers of 1978 and 1979 indicate a microseismicity rate of 0 3 events per day this is an order of magnitude less than that observed in the intermountain seismic belt

long period regional wave moment tensor inversion for earthquakes in the western united states source parameters of moderate to large size mw 4 5 earthquakes in the western united states from 1992 to 1994 are determined by point source moment tensor inversion of complete long period t 35 50 s ground motions recorded at regional distances 1 12 stable long period signals are obtained by low pass filtering records from the very broadband seismometers recently deployed in several networks in the western united states these signals are dominated by fundamental mode rayleigh and love waves which have very simple waveforms due to the limited dispersion on the short paths to regional stations since long period motions are relatively insensitive to the attenuation model and crustal structure used in the inversion they provide robust constraints on the seismic moment and faulting geometry as long as adequate azimuthal coverage is available comparisons of solutions for 21 events with results of other regional and teleseismic wave inversions are made to assess the model dependence and uncertainties of our regional centroid moment tensor rcmt solutions rcmt inversion has limited source depth resolution for shallow crustal events but the focal mechanism and seismic moment determinations prove quite stable over a range of source depths in the crust as well as over a range of crustal propagation models simultaneous waveform inversion of shorter period body wave signals can improve the source depth resolution by applying path corrections for heterogeneous crustal structure shorter period surface wave energy can also be inverted allowing the methodology to be extended to lower magnitude regional events as well the rcmt procedure requires minimal signal processing only a sparse broadband network and a simple laterally homogeneous propagation model thus it can readily be automated and applied in near real time to events in the magnitude range from 4 5 to 7 5 distributed over an area as large as the western united states

partial high grade alteration of monazite using alkali bearing fluids experiment and nature recent advances in the dating of monazite using the electron microprobe indicate that thsio 4 and or cath po 4 2 enriched intergrowths in monazite can give ages younger than the original monazite the morphology of the intergrowths suggests that the original monazite grain has been partly altered by a fluid in which th si and ca are mobile this hypothesis has been tested in the piston cylinder apparatus at 1000 mpa and 900 c utilizing a natural unzoned th and pb bearing monazite ce and na 2 si 2 o 5 h 2 o during the experiment a subset of the monazite grains acquired thsi0 4 enriched areas with sharp compositional boundaries devoid of pb and show evidence of being a pseudomorphic partial replacement of the monazite rather than an overgrowth of the monazite these experiments support the hypothesis that similar th enriched or th depleted patches with sharp compositional boundaries observed in natural monazite could be the result of fluid induced alteration via coupled dissolution reprecipitation if so such altered regions would yield information concerning the nature of the fluid responsible for their formation as well as allow for the dating of single or multiple metasomatic events assuming that all pre existing radiogenic pb is removed during alteration

experimental partitioning of rb and k between phlogopite and a concentrated k rb cl brine implications for the role of concentrated kcl brines in the depletion of rb in phlogopite and the stability of phlogopite during charnockite genesis in this study phlogopite synthesis experiments were carried out at 800 c and at 1000 and 2000 mpa for low concentrations of rb xrb rb rb k 0 1 in a concentrated k rb cl brine rb k cl salt xh2obulk 0 3 for each experiment solid run products consisted of approximately 70 80 phlogopite xrb 0 03 0 12 with both a minor celadonite component 10 as well as a cl component in the order of 5 12 m relative to oh the remaining 20 30 consisted of approximately equal amounts of newly grown sanidine and quartz there is no physical evidence that any of these phases are metastable rb fractionated strongly into the phlogopite whereas for the k feldspar rb was almost equally distributed between the feldspar and fluid salt at 800 c the derived distribution coefficients kdphlg fluid rb k and kdsnd fluid rb k for rb henry s law are 1 88 0 12 and 0 86 0 14 respectively at 2000 mpa and 1 52 0 05 and 0 6 0 4 respectively at 1000 mpa several conclusions may be drawn from these experimental results in conjunction with observations in the field the first is that phlogopite with a minor celadonite component and 5 12 m cl relative to oh can form in a relatively dry system consisting of a concentrated rb k cl brine k rb cl salt xh2obulk 0 3 at high temperature and pressures i e 800 c and 1000 2000 mpa the presence of celadonite and cl apparently stabilises the phlogopite in the presence of quartz at low h2o activities as compared to end member oh phlogopite which breaks down to enstatite k feldspar in the presence of quartz a second conclusion is that in concentrated kcl brines rb is preferentially partitioned into the phlogopite under these p t and h2o conditions this agrees with similar studies involving 1 and 2 m k rb cl salt solutions as well as a simple k rb exchange experiments between end member oh phlogopite and a concentrated k rb cl brine xh2ofluid 0 6 xrb 0 05 at 800 c and 1000 mpa

rapid source mechanism analysis of the april 29 1993 cataract creek mw 5 3 northern arizona earthquake abstract the source mechanism of two moderate size normal faulting earthquakes located slightly south of the grand canyon in arizona are studied using several near real time seismic wave analysis procedures the events are found to have source depths near 10 to 15 km and the smaller of the two events m b 4 8 is used to provide empirical green9s functions to analyze the rupture directivity of the larger m w 5 3 mainshock these events indicate complexity in the crustal stress environment on the western margin of the colorado plateau

the chemical composition of martian soil and rocks returned by the mobile alpha proton x ray spectrometer preliminary results from the x ray mode the alpha proton x ray spectrometer apxs on board the rover of the mars pathfinder mission measured the chemical composition of six soils and five rocks at the ares vallis landing site the soil analyses show similarity to those determined by the viking missions the analyzed rocks were partially covered by dust but otherwise compositionally similar to each other they are unexpectedly high in silica and potassium but low in magnesium compared to martian soils and martian meteorites the analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of earth s crust addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition

rapid source mechanism determination of large mw 5 earthquakes in the western united states inversion of complete long period ground motions is used for rapid determination of source mechanisms of mw 5 earthquakes in the western united states the first few minutes of ground motions on local and regional distance waveforms are inverted for point source centroid moment tensors waveforms recorded at regional distances 300 1500 km can be adequately modeled at periods longer than 50 s using the laterally homogeneous prem model dziewonski and anderson 1981 at closer distances 300 km waves with periods as short as 35 s can be analyzed using prem best double couple focal mechanisms for 18 recent large western u s earthquakes compare very well with those obtained by other methods our procedure interfaced with automated data retrieval and source location methods is a viable tool for reliable determination of seismic moment and fault mechanism within 30 minutes after an earthquake

surface and subsurface sedimentary structures produced by salt crusts the growth and subsequent dissolution of salts on or within sediment may alter sedimentary structures and textures to such an extent that it is difficult to identify the depositional origin of that sediment and as a result the sediment may be misinterpreted to help to overcome such problems with investigating ancient successions results are presented from a comprehensive study of the morphology and fabrics of three large areas of modern salt flats in se arabia the sabkhat matti inland region and the at taf coastal region both in the emirate of abu dhabi and the umm as samim region in oman these salt flats are affected by tidal marine alluvial and aeolian depositional processes and include both clastic and carbonate dominated surficial sediments the efflorescent and precipitated salt crusts in these areas can be grouped into two main types thick crusts with high relief 10 cm and a polygonal or blocky morphology or thin crusts with low relief 10 cm and a polygonal or blister like appearance the thin crusts may assume the surface morphology of underlying features such as ripples or biogenic mats a variety of small scale textures were observed pustular growths hair like spikes and irregular wrinkles evolution of these crusts over time results in a variety of distinctive sedimentary fabrics produced by salt growth sediment deformation salt solution sediment collapse sediment aggradation and compound mixtures of these processes salt crust processes produce features that may be confused with aeolian adhesion structures an example from the lower triassic ormskirk sandstone formation of the irish sea basin demonstrates how this knowledge of modern environments improves the interpretation of the rock record a distinctive wavy laminated facies in this formation had previously been interpreted as the product of fluvial sheetfloods modified by soft sediment deformation and bioturbation close inspection of laminations seen in core reveals many of the same sedimentary fabrics seen in se arabia associated with salt crusts this facies is the product of salt growth on aeolian sediment and is not of fluvial origin

microseismicity of the kaibab plateau northern arizona and its tectonic implications abstract a microearthquake investigation of the kaibab plateau in northern arizona revealed swarms of small to very small magnitude earthquakes a 12 station network of portable seismographs recorded 296 events with magnitudes from 0 5 m l t axes from these fault plane solutions yields an average least principal horizontal stress direction of ene wsw the inferred orientation of principal stresses found in this study indicates the kaibab plateau lies within a region of predominantly normal faulting which extends from central arizona northward into southwestern utah although data are sparse in the region surrounding the kaibab plateau evidence for the location of a basin range colorado plateau stress boundary through the kaibab plateau is not supported by the results of this study

a model of thermal conductivity for planetary soils 2 theory for cemented soils 1 a numerical model of heat conduction through particulate media made of spherical grains cemented by various bonding agents is presented the pore filling gas conductivity volume fraction and thermal conductivity of the cementing phase are tunable parameters cement fractions 0 001 0 01 in volume have small effects on the soil bulk thermal conductivity a significant conductivity increase factor 3 8 is observed for bond fractions of 0 01 to 1 in volume in the 1 to 15 bond fraction domain the conductivity increases continuously but less intensely 25 100 conductivity increase compared to a 1 bond system beyond 15 of cements the conductivity increases vigorously and the bulk conductivity rapidly approaches that of bedrock the composition of the cements i e conductivity has little influence on the bulk thermal inertia of the soil especially if the volume of bond 10 these results indicate that temperature measurements are sufficient to detect cemented soils and quantify the amount of cementing phase but the mineralogical nature of the bonds and the typical grain size are unlikely to be determined from orbit on mars a widespread surface unit characterized by a medium albedo 0 19 0 26 and medium high thermal inertia 200 600 j s 0 5 m 2 k 1 has long been hypothesized to be associated with a duricrust the fraction of cement required to fit the thermal data is less than 1 5 by volume this small amount of material is consistent with orbital observations confirming that soil cementation is an important factor controlling the thermal inertia of the martian surface

the influence of local topography for wind direction on mars two examples of dune fields in crater basins in this work we perform an analysis of large dark dunes within moreux crater and herschel crater on mars using high resolution imaging science experiment hirise and context camera ctx data sets these data allow us to conduct a detailed analysis of dune morphology and slip faces concluding that the studied dune fields are influenced by topographically controlled complex wind directions our morphological analysis reveals that inside moreux crater in particular the topographic setting dominates the wind flow direction leading to the development of a sand transport pathway encircling the central peak of the crater the dune fields in herschel crater are also affected by winds controlled by variable topography as suggested by the presence of complex dunes and dune fields our analysis indicate that the studied dune systems is not the result of paleo wind regimes furthermore we perform thermal inertia measurements using thermal emission spectrometer tes data which indicate that the studied dune fields consist of medium sand 250 500 mm in diameter

ion microprobe u pb age determinations on zircon from the late archean granulite facies transition zone of southern india abstract the southern dharwar craton of karnataka and tamil nadu states in south india exposes a depth profile of late archean crust amphibolite facies felsic to intermediate peninsular gneiss of protolith ages 3 4 2 9 ga with subordinate infolded supracrustal relics and the large closepet granite body give way southward to granulite facies orthopyroxene bearing gneisses over a transition zone about 40 km wide with mineralogic pressure indicators increasing from about 4 kbar corresponding to about 15 km paleodepth to about 7 kbar corresponding to near 25 km paleodepth previous whole rock and zircon geochronology have established that amphibolite facies metamorphism migmatization and granite intrusion took place in the latest archean at 2 53 2 51 ga however some workers have considered the foliated granulites as products of an earlier metamorphism distinct from the terminal archean events this work presents whole rock geochemical studies coupled with ion microprobe 207pb 206pb ages and th u

global duricrust on mars analysis of remote sensing data global remote sensing data for mars are analyzed to obtain a simple self consistent model for the surface layer the data sets discussed include radar cross section measurements at several wavelengths radio whole disk thermal emission observations at two wavelengths the global distribution of thermal inertia deviations of diurnal temperatures from those of a homogeneous model and thermal spectral estimates of surface rock abundance and of the thermal inertia of the nonrocky component of the surface the data sets which most constrain the interpretation are the rock abundance map and the correlation of thermal inertia with radar cross section these require the rock abundance to not vary significantly from place to place and simultaneously require the density and thermal inertia of the fines to vary in a consistent manner the simplest model which can explain all of the data involves a global case hardened crust duricrust which varies spatially in its degree of formation in general low thermal inertia regions have a poorly developed crust and highinertia regions have a well developed crust there are however regions that consist of coarse particles and which do not fit this model e g chryse this model is consistent with the ages of low inertia regions and with aeolian mechanisms for their development the duricrust is thought to form via the mobilization of salt ions within a layer of water adsorbed within the regolith and its formation may be associated with the exchange of water between the regolith and atmosphere which occurs on the 105 and 106 year time scale

analysis of the 2009 earthquake swarm near sunset crater volcano arizona abstract a swarm of microearthquakes occurred on october 31 2009 within 5 km of the sunset crater arizona volcano a detailed study of the swarm was warranted because of its location near a young volcanic construct and its proximity to the population center of flagstaff arizona the question posed in this study was whether the swarm was the result of tectonic stress release during fault slip or due to stresses driven by magmatic processes this question was addressed by analyzing and comparing the physical and seismic characteristics of the swarm to the regional tectonic environment and to the characteristics of tectonic swarms in arizona and magmatic volcanic swarms elsewhere this analysis included swarm duration frequency of events b value focal depths and epicentral pattern of the swarm the comparison of the salient features of the 2009 sunset crater swarm to both magmatic and tectonic swarms indicates that the sunset crater swarm has features similar to magmatic swarms and is a potential magmatic swarm candidate

directivity detection and source properties of the 11 may 2011 mw 5 2 lorca spain earthquake a kinematic finite source study of the 11 may 2011 m w 5 2 lorca spain earthquake has been performed using broadband data from the spanish national network the nodal plane ambiguity of the double couple solution was resolved from finite source analysis and a rupture velocity of 1 8 km s 1 and the northeast southwest striking northwest dipping plane was found to best fit the data this fault plane corresponds to the central sector of the alhama de murcia fault amf the resulting slip distribution has a maximum of 19 3 cm and a total seismic moment of 6 25 1016 n m a jackknife test has been performed to estimate the fault plane errors and their consequences in the slip distribution also synthetic tests have been performed to evaluate the errors in the finite source modeling from this model a prediction of the strong ground motion near the fault corrected for soil amplification is given in terms of peak ground velocity pgv which fits with the observed value at the accelerograph in the city of lorca we also compared the pgv converted to modified mercalli intensity at the surface with the intensity distribution also showing good agreement finally we extracted the directivity pulse from the strong ground motion record at lorca with 0 5 s period in the transverse component to the amf direction and 33 cm s 1 pgv to further analyze the directivity effect we estimate the duration and azimuthal amplitude distribution of the source time functions finding them to be shorter and of greater amplitude in the direction of rupture and longer and smaller in amplitude in the opposite direction

determining source parameters of moderate size earthquakes from regional waveforms abstract waveform modeling of the teleseismic long period body wave phases of shallow earthquakes has proven quite effective in determining source parameters for events of magnitude larger than six unfortunately these teleseismic phases become too weak for smaller events and regional data must be used which are generally much more complicated this is because the crust mantle system acts as a leaky waveguide and a large number of rays are required to model the observations in this report we review a procedure for the systematic determination of source parameters from regional body waves a least squares inversion technique is used which is based on a cross correlation of the data and a synthetic seismogram the synthetic waveforms are a linear combination of those for the three fundamental types of fault a set of profiles of the synthetic waveforms is presented although the synthetic waveforms are generated for a model developed for the western united states this model seems to be adequate for most continental regions the inversion is parameterized in terms of fault strike dip and rake these parameters are relatively insensitive to small changes in crustal structure several examples are presented

physical properties of the mars exploration rover landing sites as inferred from mini tes derived thermal inertia 1 the miniature thermal emission spectrometer mini tes on board the two mars exploration rovers provides the first opportunity to observe thermal properties from the martian surface relate these properties to orbital data and perform soil conductivity experiments under martian conditions the thermal inertias of soils bedforms and rock at each landing site were derived to quantify the physical properties of these features and understand geologic processes occurring at these localities the thermal inertia for the gusev plains rock target bonneville beacon 1200 j m 2 k 1 s 1 2 is consistent with a dense basaltic rock but the rocks at the columbia hills have a lower thermal inertia 620 j m 2 k 1 s 1 2 suggesting that they have a volcaniclasic origin bedforms on the floors of craters at both landing sites have thermal inertias of 200 j m 2 k 1 s 1 2 consistent with a particle diameter of 160 m this diameter is comparable to the most easily moved grain size in the current atmosphere on mars suggesting that these bedforms may have formed under current atmospheric conditions along the meridiani plains the thermal inertia is lower than that derived from tes and thermal emission imaging system themis orbital data this discrepancy is not well understood mini tes derived thermal inertias at gusev along a 2 5 km traverse follow trends in thermal inertia measured from orbit with tes and themis however along the traverse there are variability and mixing of particle sizes that are not resolved in the orbital thermal inertia data due to meter scale processes that are not identifiable at larger scales

post peak fluid mediated modification of granulite facies zircon and monazite in the trivandrum block southern india the quarry at kottavattom in the trivandrum block of southern india contains spectacular examples of fluid assisted alteration of high grade metamorphic rocks garnet biotite gneiss has undergone a change in mineral assemblage to form submetre scale orthopyroxene bearing patches later retrogressed to form an amphibole bearing lithology these patches often referred to as arrested or incipient charnockite crosscut the original metamorphic foliation and are typically attributed to passage of a low ah2o fluid through the rock whilst this conversion is recognised as a late stage process little detailed chronological work exists to link it temporally to metamorphism in the region zircon and monazite analysed from kottavattom not only record metamorphism in the trivandrum block but also show internal lobate textures crosscutting the original zoning consistent with fluid aided coupled dissolution reprecipitation during formation of the orthopyroxene bearing patches high grade metamorphism at the quarry occurred between the formation of metamorphic monazite at 585 ma and the growth of metamorphic zircon at 523 ma the fluid assisted alteration of the garnet biotite gneiss is poorly recorded by altered zircon with only minimal resetting of the u pb system whereas monazite has in some cases undergone complete u pb resetting and records an age for fluid infiltration at 495 ma the fluid event therefore places the formation of the altered patches at least 25 myr after the zircon crystallisation in the garnet biotite gneiss the most likely fluid composition causing the modification and u pb resetting of zircon and monazite is locally derived hypersaline brine

upper proterozoic evaporites in the amadeus basin central australia and their role in basin tectonics the amadeus basin an isolated intracratonic basin in the center of the australian continent contains an upper proterozoic to mid paleozoic stratigraphic succession of shallow marine sediments that in places exceeds 14 km in thickness the gillen member of the bitter springs formation which occur toward the base of the upper proterozoic succession includes evaporites which are among the world9s earliest 0 8 to 0 7 ga because of their age the evaporites have been cited in discussions of sea water chemistry and have been the focus of scrutiny for early life forms in spite of their importance the evaporites are poorly known particularly from the viewpoint of their depositional and tectonic setting in an attempt to rectify this deficiency more than 6 000 km of seismic data were analyzed in conjunction with a field and well log study of the unit the late proterozoic amadeus basin appears to have consisted of two major poorly circulated anoxic sub basins which perhaps opened to the ocean to the southeast through the adelaide geosyncline data relating to facies are limited but suggest that deposition of the evaporites was cyclic and followed the patterns identified in other major evaporite basins the carbonates and sulfates being closer to the basin margins and later stage halite and possibly potassium salts being toward the basin center the evaporites were deposited in a shallow marine setting at the time of a relative sea level high stand the apparent sea level high may relate to basin dynamics whereas the cyclicity of the evaporites may be due to eustatic sea level controls acting on the barrier to allow intermittent inflow of sea water salt tectonism began shortly after the evaporites were deposited and continued throughout basin development consequently most of the major anticlinal structures have salt cores the geometry of the salt structures suggests that during their growth the mean strain rate was 10 16 s 1 a rate typical of large salt structures growth on these salt structures has played an important role in controlling later sedimentation particularly during the cambrian

rapid estimation of rupture directivity application to the 1992 landers ms 7 4 and cape mendocino ms 7 2 california earthquakes using empirical green functions with regional and teleseismic surface waves it is possible to resolve fault finiteness effects in many cases uniquely defining the fault plane for relatively large earthquakes the technique requires very little data processing and can be applied in near real time with the current distribution of seismic stations the landers strike slip earthquake was dominated by two sub events with predominantly north northwestward rupture the second sub event was 1 5 times larger and rotated in strike by 12 counterclockwise relative to the first the cape mendocino thrust event had a relatively smooth rupture that propagated to the southwest on a shallow dipping fault

terrestrial analogues of the surface rocks of mars the pathways of chemical weathering processes on earth and the virtual absence of them on the moon are well characterized because we have direct access to samples of primary igneous rocks their upper mantle sources and derivative sedimentary rocks and soil forming the regolith tracing chemical changes on the surface of mars however is more difficult because of limited access to samples from mars terrestrial rocks and minerals are continually being sought which might serve as analogues for martian materials evidence presented here suggests that hisingerite iddingsite and several ferric sulphate minerals derived from deuteric alteration of iron rich basalts may provide clues to the evolutionary history of the surface of mars

recent large earthquakes near cape mendocino and in the gorda plate broadband source time functions fault orientations and rupture complexities the northward migration of the mendocino triple junction is associated with complex faulting within the gorda plate and in the convergent zone between the gorda and north american plates this region has experienced substantial recent large earthquake activity and quantification of these faulting processes is essential for understanding the evolution of the triple junction using an empirical green function deconvolution method for teleseismic and regional surface waves and body waves we obtain relative source time functions for the april 25 1992 cape mendocino thrust earthquake m w 7 2 its two large strike slip aftershocks on april 26 1992 m w 6 5 6 6 and two large strike slip events in the gorda plate that occurred july 13 1991 m w 6 8 and august 17 1991 m w 7 1 the removal of propagation effects using empirical green functions provides unusually detailed source rupture information and indicates that all the ruptures are less than 16 s in duration analyzing the directivity effects observed in the source time functions we resolve rupture directions and corresponding fault orientations for the four largest events and place some constraints on the smaller aftershock significant differences in the rupture duration and stress drop are observed between the cape mendocino mainshock and its two largest aftershocks the mainshock which ruptured westward on a shallow dipping plane either on or paralleling the interplate contact between the gorda and north american plates had a smooth 9 s long rupture with a 0 9 4 6 mpa static stress drop the two largest aftershocks occurred within the uppermost mantle of the gorda plate and have more complex ruptures with total durations of 14 15 s and static stress drops of less than 0 3 mpa perhaps reflecting a difference between mantle and crustal earthquakes in this region the aftershocks appear to have ruptured conjugate strike slip faults accounting for differences in their damage patterns the august 17 1991 gorda plate event ruptured a southwest striking fault while the july 13 1991 event ruptured a southeast striking fault with both events relieving north south compression within the deforming gorda plate the existence of multiple active faults in the region constitutes a significant earthquake hazard associated with the complex stress environment of the migrating triple junction

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

soil like deposits observed by sojourner the pathfinder rover most of the soil like materials at the pathfinder landing site behave like moderately dense soils on earth with friction angles near 34 39 and are called cloddy deposits cloddy deposits appear to be poorly sorted with dust sized to granule sized mineral or rock grains they may contain pebbles small rock fragments and clods thin deposits of porous compressible drifts with friction angles near 26 28 are also present drifts are fine grained cohesions of both types of deposits are small there may be indurated soil like deposits and or coated or crusted rocks cloddy deposits may be fluvial sediments of the ares tiu floods but other origins such as ejecta from nearby impact craters should be considered drifts are probably dusts that settled from the martian atmosphere remote sensing signatures of the deposits inferred from rover observations are consistent with those observed from orbit and earth

nature and distribution of surficial deposits in chryse planitia and vicinity mars color images of bright red dust deposits at the mutch memorial station were acquired at variable incidence angles during sol 611 subsolar longitude 70 northern spring season after removing effects due to atmospheric scattering and absorption the data were used to estimate the independent variables in the hapke 1986 photometric function in blue green and red coordinates the vector representing the space radiance factor of the landing site extracted from viking orbiter images acquired on sol 609 is separated by a euclidean distance of only 0 022 units and an angle of only 1 5 from the vector estimated from the station data for the orbiter lighting and viewing geometries this result implies that light reflected from dust exposures dominates the orbiter signal multiplicative and additive atmospheric terms cancel one another and surface roughness is a second order effect in the orbiter data dust radiance factors computed from station data are most like laboratory spectra for fine grained hawaiian palagonite and are indistinguishable from earth based spectra of classical bright areas color composites of orbiter images show that the dust is found immediately south of acidalia planitia and in association with topographic barriers such as craters and cliffs examination of viking infrared thermal mapper data shows that the dust deposits typically do not have distinctive thermal inertia signatures implying that the deposits are optically thick hundreds of micrometers but thinner than the diurnal thermal skin depth centimeters dark gray material with thermal inertia values 8 12 10 3 cal cm 2 s 1 2 k 1 indicative of sand grain sizes 0 5 1 5 mm dominates the acidalia planitia lowlands and parts of kasei vallis this material also occurs as dark streaks extending from craters in xanthe terra and oxia palus space radiance factors of dark gray material are similar to spectra of mafic rock mixed with a minor amount of palagonitelike material material that is darker than but just as red as the dust deposits occurs in lunae planum xanthe terra and oxia palus areas of intermediate elevation multiple phase angle orbiter images suggest that the dark red exposures are a mixture of bright red and dark gray materials with the dark red exposures being relatively rough at a subpixel scale as compared to exposures of the other two materials thus only two types of materials can be detected in the data covering the study area palagonitelike dust and mafic rock fragments thermal inertia values 4 8 10 3 cal cm 2 s 1 2 k 1 for the dark red material are consistent with the presence of fine to medium sand size particles 0 10 0 5 mm such material should be easily moved by winds the lack of aeolian features implies that the dark red deposits are not composed of loose material rather they are probably more eroded versions of blocky soil or duricrust cemented dust and rock fragments exposed at the station both bright red dust aeolian suspension load and dark gray materials saltation traction loads migrate over the dark red substrate the overall distribution of the surficial units is controlled by topography at a variety of length scales lower wind threshold friction velocities associated with higher atmospheric densities in lowlands keep dust from accumulating and duricrust from forming while higher threshold velocities in highlands lead to net accumulation of dust local topographic obstacles craters walls ridges perturb wind flow and lead to local accumulation or erosion at a variety of elevations in addition the bright red dust ubiquitously found between exposures of dark gray and dark red materials may accumulate as the wind velocity gradient decreases at the transition from smoother dark gray exposures to rougher dark red exposures the distribution of the materials must also be modulated by climatic variations induced by quasi periodic oscillations in obliquity eccentricity and spin axis direction constraining these surficial deposits to be 1 ma

active faulting and seismicity in a prefractured terrane grand canyon arizona structural and seismic data for the eastern grand canyon were analyzed to determine the relationship between basement fractures surface faulting and seismicity published structural data were compared with the results of focal mechanism analysis of tremors occurring in the eastern canyon region during the period 1989 2004 previous studies of the geology of this area indicate that the fault and joint trends exposed in the surface rocks and through the entire sedimentary section were first established with predominant northeast and northwest trends in precambrian time the northwest trends of this prefractured terrane correlate with a dominant northwest trend of nodal planes in the seismic data suggesting that the present stress system in the region is favoring the reactivation of the preferentially oriented pre existing northwest trending fractures

source pulse enhancement by deconvolution of an empirical green s function observations of the earthquake source time function are enhanced if path recording site and instrument complexities can be removed from seismograms assuming that a small earthquake has a simple source its seismogram can be treated as an empirical green s function and deconvolved from the seismogram of a larger and or more complex earthquake by spectral division when the deconvolution is well posed the quotient spectrum represents the apparent source time function of the larger event this study shows that with high quality locally recorded earthquake data it is feasible to fourier transform the quotient and obtain a useful result in the time domain in practice the deconvolution can be stabilized by one of several simple techniques in this paper the method is implemented and tested on high quality digital recordings of aftershocks of the jan 9 1982 miramichi new brunswick earthquake in particular seismograms from a jan 17 aftershock 017 13 33 gmt local mag 3 5 exhibit path or site effects which complicate the determination of source parameters after deconvolution the apparent far field source of this event is a simple pulse in displacement with duration 0 07 second for both p and s

the water content of recurring slope lineae on mars observations of recurring slope lineae rsl from the high resolution imaging science experiment have been interpreted as present day seasonally variable liquid water flows however orbital spectroscopy has not confirmed the presence of liquid h2o only hydrated salts thermal emission imaging system themis temperature data and a numerical heat transfer model definitively constrain the amount of water associated with rsl surface temperature differences between rsl bearing and dry rsl free terrains are consistent with no water associated with rsl and based on measurement uncertainties limit the water content of rsl to at most 0 5 3 wt in addition distinct high thermal inertia regolith signatures expected with crust forming evaporitic salt deposits from cyclical briny water flows are not observed indicating low water salinity if any and or low enough volumes to prevent their formation alternatively observed salts may be preexisting in soils at low abundances i e near or below detection limits and largely immobile these rsl rich surfaces experience 100 k diurnal temperature oscillations possible freeze thaw cycles and or complete evaporation on time scales that challenge their habitability potential the unique surface temperature measurements provided by themis are consistent with a dry rsl hypothesis or at least significantly limit the water content of martian rsl

localized solid state dehydration associated with the varberg charnockite intrusion sw sweden the mineralogy petrology and fluid inclusion chemistry of two charnockite patches within a distance of 4 5 km of the varberg magmatic charnockite intrusion sw sweden are investigated and described utilizing sem empa and fluid inclusion microthermometry garnet clinopyroxene 890 930 degrees c garnet amphibole 600 800 degrees c and garnet biotite 670 860 degrees c fe mg exchange thermometry indicates high temperatures for charnockite patch i compared to relatively lower garnet orthopyroxene garnet amphibole and garnet biotite temperatures of 500 to 600 degrees c for charnockite patch ii plagioclase in the charnockitic patches tends to be more anorthitic and less albitic x an 0 20 x ab 0 76 than in the surrounding regional granitic gneiss x an 0 13 x ab 0 84 replacement antiperthite is commonly found in unrelated plagioclase grains from either patch compared to the regional granitic gneiss where it is relatively rare in either patch k feldspar is considerably less albitic x kfs 0 90 0 92 x ab 0 05 0 10 compared to k feldspar from the regional granitic gneiss it can also be found as micro veins along quartz grain rims both patches are dominated by clinopyroxene as opposed to orthopyroxene garnet biotite and amphibole and in both charnockite patches tend to have lower fe and correspondingly higher mg values compared with garnet biotite and amphibole from the surrounding regional granitic gneiss fluorapatite tends to be relatively enriched in cl and depleted in y ree compared with fluorapatite from the regional granitic gneiss fluid inclusions in charnockite patches i and ii are dominantly carbonic similar to what is seen for the varberg charnockite in addition to quartz relatively high density carbonic inclusions are also preserved in garnet and in fluorapatite it is presumed that pure carbonic fluids must have once coexisted with relic magmatic h2o co2 nacl fluids at peak metamorphic conditions the most likely scenario suggests that charnockite patches i and ii were formed during the later stages of crystallization of the varberg charnockite magmatic body during which copious amounts of co2 rich fluids with a brine cacl2 dominated component were expelled into the country rock via pegmatoid segregations both within and in the immediate surroundings of the charnockite body patch i appears to represent the extension of a pegmatoid segregation whereas patch ii appears to represent fluid induced lower temperature solid state dehydration transport was facilitated via a system of tectonic fissures and fractures generated in the regional migmatized granitic gneiss during its emplacement within the scope of what is known these two charnockite patches fall into the generally observed parameters for localized dehydration zones in general c 2014 elsevier b v all rights reserved less

incipient charnockite characterization at the type localities abstract fifty years after the discovery of incipient charnockite orthopyroxene bearing granitic rocks partially replacing amphibole biotite gneiss in southern india this phenomenon has been found in transitional amphibolite facies to granulite facies terrains on every continent and may be a characteristic feature of progressive deep crustal metamorphism the alteration is essentially a metasomatic transformation mass balance calculations for localities in southern india and sri lanka for which analytic data are most comprehensive show that the main reaction producing orthopyroxene in orthogneiss is breakdown of hornblende by reaction with biotite with loss of feo mgo tio 2 and cao as well as h 2 o from the host rock there is concomitant gain of sio 2 no significant change of alkalis can be demonstrated as essential to the transformation though advanced charnockitic alteration at the type locality of kabbal karnataka may also show large increase of k 2 o with removal of mafic constituents very similar orthopyroxene bearing veins in garnet biotite gneiss at the ponmudi type locality in kerala show definite but more subtle metasomatism with loss of feo and mgo and increase of sio 2 and alkalis both the kabbal and ponmudi alterations occurred at mid crustal levels 5 6 kbar and 700 750 c it is postulated that both types of charnockitic alteration may have been produced as open system processes by much the same kind of metasomatizing fluids nearly coeval co 2 rich and ultrasaline fluids based on fluid inclusion evidence the paragneiss alteration is mainly biotite breakdown with some involvement of garnet and leads to a distinct metamorphic facies type the presence of graphite in some of the garnet biotite gneisses at ponmudi would have resulted in lower oxygen fugacity and probably lower h 2 o activity than in the similar kabbal type metamorphism the fluid rock ratios for both types were small about 10 mass percent of the rocks and the fluids whatever their origin were largely rock governed the source of the metasomatizing fluids has not been definitely identified carbon isotopes of fluid inclusions seem to show an igneous or primitive mantle source at both type localities but ultrasaline fluids may be more plausibly explained by metasedimentary sources and calcareous metasediments have been identified as a source of co 2 in some occurrences much remains to be learned about incipient charnockite and its significance in processes of crustal evolution

seismicity and active faulting of the kanab fredonia area of the southern colorado plateau 1 detailed study of the historic seismicity of the kanab fredonia area adds information to the location of the colorado plateau tectonic boundary in this area and to the nature of contemporary seismicity and faulting on this part of the colorado plateau historic seismicity over 45 years 1959 2004 defines a band of activity which extends through fredonia arizona and into southern utah around kanab the area is dominated by north trending high angle normal faults the spatial distribution of epicenters consists of clusters associated with the west kaibab big springs and toroweap sevier faults indicating that these faults may be active four focal mechanism solutions show basin range style high angle normal faulting on north to north northwest trending surfaces that are parallel to subparallel in most cases to mapped quaternary faults this suggests a present east west extension occurring on the southern colorado plateau for the kanab fredonia area and an expansion of the adjacent basin range province eastward into the plateau as far as the west kaibab big springs faults the west kaibab big springs faults are proposed to be the tectonic boundary of the southern colorado plateau in this area since they mark the limit of significant seismic activity that is combined with basin range type faulting

jarosite and hematite at meridiani planum from opportunity s mossbauer spectrometer mossbauer spectra measured by the opportunity rover revealed four mineralogical components in meridiani planum at eagle crater jarosite and hematite rich outcrop hematite rich soil olivine bearing basaltic soil and a pyroxene bearing basaltic rock bounce rock spherules interpreted to be concretions are hematite rich and dispersed throughout the outcrop hematitic soils both within and outside eagle crater are dominated by spherules and their fragments olivine bearing basaltic soil is present throughout the region bounce rock is probably an impact erratic because jarosite is a hydroxide sulfate mineral its presence at meridiani planum is mineralogical evidence for aqueous processes on mars probably under acid sulfate conditions

discovery of a widespread low latitude diurnal co2 frost cycle on mars while the detection of co2 ice has only been reported outside the martian polar regions at very high elevation i e elysium olympus mons and the tharsis montes nighttime surface observations by the mars climate sounder on board the mars reconnaissance orbiter document the widespread occurrence of atmospherically corrected ground temperatures consistent with the presence of extensive carbon dioxide frost deposits in the dusty low thermal inertia units at middle low latitudes thermal infrared emissivities interpreted in conjunction with mass balance modeling suggest micrometer size co2 ice crystals forming optically thin layers never exceeding a few hundreds of microns in thickness i e 10 2 kg m 2 locally which is insufficient to generate a measurable diurnal pressure cycle 0 1 of the martian atmosphere atmospheric temperatures at middle low latitudes are not consistent with precipitation of co2 ice suggesting that condensation occurs on the surface the recurring growth and sublimation of co2 ice on martian dusty terrains may be an important process preventing soil induration and promoting dynamic phenomena soil avalanching and fluidization and regolith gardening maintaining a reservoir of micrometer size dust particles that are mobile and available for lifting the discovery of this diurnal co2 cycle represents an important step forward in our understanding of the way the martian atmosphere interacts with the surface

the neoarchean gt 34 ni deposit carajas mineral province brazil an atypical iocg related ni sulfide mineralization abstract the gt 34 deposit located 12 km to the sw of the sossego copper gold mine in the carajas province northern brazil represents an unusual ni sulfide mineralization the deposit occurs along a ne sw trending sub vertical shear zone marked by progressive mg alkalic alteration zones predominantly hosted in granitic and locally in granodioritic to tonalitic orthogneisses initial alteration zones result in unique scapolite orthopyroxene assemblage which is partially preserved within pervasive hornblende chlorapatite plagioclase replacement zones nickel mineralization occurs mainly as matrix supported breccias characterized by a pentlandite pyrrhotite rich matrix and rounded fragments chiefly of hornblende and chlorapatite irregular stockworks and net textured veins containing chalcopyrite pentlandite are less common phlogopite talc actinolite alteration and late stage veinlets crosscut the previous alteration zones and the mineralization the phlogopite talc actinolite alteration occurs as irregular veins and chalcopyrite pyrrhotite magnetite are commonly observed where such alteration intersects the ni mineralization late stage veinlets are represented by k feldspar epidote chlorite calcite and quartz albite chlorite calcite epidote veins both containing minor amounts of millerite pyrite and f oh apatite high resolution sims u pb zircon geochronology obtained for the gt 34 deposit revealed an age of 2828 4 ma for zircon grains inherited from the host orthogneisses the timing of the mineralization altered zircon grains from the scapolite orthopyroxene and phlogopite talc actinolite alteration zones is attributed to an age interval between 2751 and 2720 ma although poorly constrained the geochronological data corroborate a neoarchean age for the gt 34 ni mineralization similar to that of other iocg deposits in the carajas province and coeval with the bimodal magmatism in the area the atypical orthopyroxene marialite mineral chemistry support a metasomatic crystallization at high temperatures 700 c low ah2o

multiphase inclusions in peritectic garnet from granulites of the athabasca granulite terrane canada evidence of carbon recycling during neoarchean crustal melting abstract in the last decade the study of fluid and melt inclusions in partially melted rocks has become a key tool to acquire unprecedented information about crustal anatectic processes in this study we report the results of the microstructural and microchemical investigation on multiphase inclusions trapped within peritectic garnet of a neoarchean felsic granulite from the upper deck domain of the athabasca granulite terrane canada inclusions have been studied by sem eds fib sem serial sectioning and raman microspectroscopy and classified in terms of size and hosted phases type i multiphase inclusions are small 15 m primary in origin and do not show evidence of decrepitation their multiphase assemblage is made of ferroan magnesite quartz and graphite in association with minor amounts of corundum pyrophyllite and zn spinel calcite dolomite and zinc bearing sulphide may also be present the coexistence of quartz and corundum in these inclusions is interpreted as the product of metastable growth within pores of extremely small size the fluid phase of type i inclusions always present in amounts 40 vol is co2 rich 96 5 mol with traces of n2 3 3 mol and ch4 0 2 mol these carbon rich type i inclusions coexist in the same cluster with primary melt inclusions nanogranitoids type ii these are large up to 50 m and composed of k feldspar quartz and plagioclase with minor amounts of graphite biotite and aluminosilicate because nanogranitoids are droplets of anatectic silicate melt formed and trapped during incongruent melting of crustal rocks the coexistence of type i multiphase inclusions proves the presence of a carbon rich fluid during the neoarchean anatexis 800 950 c 0 6 1 4 gpa of this portion of continental crust in a likely situation of melt fluid immiscibility according to phase equilibria modelling the uncommon multiphase assemblage within type i inclusions is here interpreted as the result of a post entrapment carbonation reaction between an original co2 bearing fluid and the garnet host during rock cooling from uht conditions

ferric sulfates on mars evidence is presented for the possible formation and existence of ferric sulfato complexes and hydroxo ferric sulfate minerals in the permafrost on mars acidic groundwater derived from atmospheric oxidation of volcanogenic h2s to h2so4 aerosols promoted chemical weathering of fayalitic olivines iron rich pyroxenes plagioclase feldspar and pyrrhotite pentlandite mineral assemblages in crustal ultramafic and basic igneous rocks the acidic groundwater entered into electrochemical reactions with the iron sulfides yielding dissolved feso4 fe so4 2 and feoh2 complex ions and the precipitation of basic ferric sulfate minerals such as those belonging to the roemerite copiapite botryogen and jarosite alunite groups these phases are stabilized at low temperatures and ph in martian permafrost the occurrence of jarosites in terrestrial arid regions suggests that they could also survive on the surface of mars melting of the permafrost and raising of the ph may have initiated the hydrolysis of dissolved ferric sulfato complex ions and led to the precipitation of feooh which reacted with precipitated silica to form phyllosilicates alternatively degradation of the hydrolysate feooh to fe2o3 during sublimation of permafrost exposed on mars surface may account for the presence of eolian maghemite suspected to be the magnetic mineral observed on the viking landers

internal differentiation of the archean continental crust fluid controlled partial melting of granulites and ttg amphibolite associations in central finland fault bound blocks of granulite and enderbite occur within upper amphibolite facies migmatitic tonalitic trondhjemitic granodioritic ttg gneisses of the iisalmi block of central finland these units record reworking and partial melting of different levels of the archean crust during a major tectonothermal event at 2 6 2 7 ga anhydrous mineral assemblages and tonalitic melts in the granulites formed as a result of hydrous phase breakdown melting reactions involving amphibole at peak metamorphic conditions of 8 11 kbar and 750 900 c a nominally fluid absent melting regime in the granulites is supported by the presence of carbonic fluid inclusions the geochemical signature of light rare earth element lree depleted mafic granulites can be modelled by 10 30 wt partial melting of an amphibolite source rock leaving a garnet bearing residue the degree of melting in intermediate granulites is inferred to be less than 10 wt and was restricted by the availability of quartz pressure temperature estimates for the ttg gneisses are significantly lower than for the granulites at 660 770 c and 5 6 kbar based on the p t conditions melting of the ttg gneisses is inferred to have occurred at the wet solidus in the presence of an h 2 o rich fluid a hydrous mineralogy abundant aqueous fluid inclusions and the absence of carbonic inclusions in the gneisses are in accordance with a water fluxed melting regime low ree contents and strong positive eu anomalies in most leucosomes irrespective of the host rock composition suggest that the leucosomes are not melt compositions but represent plagioclase quartz assemblages that crystallized early from felsic melts furthermore similar plagioclase compositions in leucosomes and adjacent mesosomes are not a migmatite paradox as both record equilibration with the same melt phase percolating along grain boundaries

mossbauer mineralogy of rock soil and dust at meridiani planum mars opportunity s journey across sulfate rich outcrop basaltic sand and dust and hematite lag deposits additonal co authors p gutlich e kankeleit t mccoy dw mittlefehldt f renz me schmidt b zubkov sw squyres re arvidson

sulfate deposition in subsurface regolith in gusev crater mars excavating into the shallow martian subsurface has the potential to expose stratigraphic layers and mature regolith which may hold a record of more ancient aqueous interactions than those expected under current martian surface conditions during the spirit rover s exploration of gusev crater rover wheels were used to dig three trenches into the subsurface regolith down to 6 11 cm depth road cut the big hole and the boroughs a high oxidation state of fe and high concentrations of mg s cl and br were found in the subsurface regolith within the two trenches on the plains between the bonneville crater and the foot of columbia hills data analyses on the basis of geochemistry and mineralogy observations suggest the deposition of sulfate minerals within the subsurface regolith mainly mg sulfates accompanied by minor ca sulfates and perhaps fe sulfates an increase of fe2o3 an excess of sio2 and a minor decrease in the olivine proportion relative to surface materials are also inferred three hypotheses are proposed to explain the geochemical trends observed in trenches 1 multiple episodes of acidic fluid infiltration accompanied by in situ interaction with igneous minerals and salt deposition 2 an open hydrologic system characterized by ion transportation in the fluid subsequent evaporation of the fluid and salt deposition and 3 emplacement and mixing of impact ejecta of variable composition while all three may have plausibly contributed to the current state of the subsurface regolith the geochemical data are most consistent with ion transportation by fluids and salt deposition as a result of open system hydrologic behavior although sulfates make up 20 wt of the regolith in the wall of the boroughs trench a higher hydrated sulfate than kieserite within the boroughs or a greater abundance of sulfates elsewhere than is seen in the boroughs wall regolith would be needed to hold the structural water indicated by the water equivalent hydrogen concentration observed by the gamma ray spectrometer on odyssey in the gusev region copyright 2006 by the american geophysical union

moment tensor inversion for offshore earthquakes east of taiwan and their implications to regional collision reliable determination of source parameters for offshore earthquakes east of taiwan with mb 5 5 was a difficult task because of the poor azimuthal coverage by local network and the lack of signals at teleseismic distances we take advantage of the recently established broadband array in taiwan for seismology bats to invert seismic moment tensors for 7 such events occurred in 1996 to cope with different patterns of background noise and unknown structural details we utilize variable frequency bands in the inversion and adapt a two step procedure to select best velocity models for individual epicenter station paths our results are consistent with the overall patterns of regional collision and indicate that the resulting compressive stress has caused significant intraplate deformation within the philippine sea plate simulation of the region s geological evolution and orogenic processes should take this factor into account and allow the philippine sea plate to deform internally

fast and accurate depth and source mechanism estimation using p waveform modeling a tool for special event analysis event screening and regional calibration we have developed validated and applied a fast and accurate interactive easy to use tool for estimating seismic event depth and mechanism by modeling the initial p wave bundle significant features of this tool include its applicability over a broad band of frequencies f 2 hz and magnitudes mb 4 5 its ability to provide accurate high resolution depth estimates and its ability to provide constraints on event mechanism including isotropic contributions it also provides estimates of random and model errors and can be used to test hypotheses and investigate sensitivity to and trade offs between model parameters we validated this tool and its algorithms by showing that our estimated depths and mechanisms are in excellent agreement with ground truth depths and mechanisms based on local and regional data we find that depth can usually be estimated to an accuracy of a few km with a small number of stations although complete mechanisms are sometimes poorly resolved we find that two out of three of the mechanism parameters strike dip rake are usually well constrained we illustrate the potential of this technique for regional calibration special event analysis and event screening by comparing estimated depths and mechanisms of events in the middle east and north africa with those of the national earthquake information center neic and by comparing our depth and mechanism estimates for the may 11 1998 india nuclear explosion and a november 8 1991 earthquake that occurred in the same region

temperatures of granulite facies metamorphism constraints from experimental phase equilibria and thermobarometry corrected for retrograde exchange this study assesses temperatures of formation of common granulites by combining experimental constraints on the p t stability of granulite facies mineral associations with a garnet orthopyroxene grt opx thermobarometry scheme based on al solubility in opx corrected for late fe mg exchange we applied this scheme to 414 granulites of mafic intermediate and aluminous bulk compositions our findings suggest that granulites are much hotter than traditionally assumed and that the p t conditions of the amphibolite granulite transition portrayed in current petrology textbooks are significant underestimates by over 100 c for aluminous and intermediate granulites mean corrected temperatures based on our method are 890 17 and 841 11 c respectively uncertainties reported as 95 confidence limits on the mean consistent with minimum temperatures for orthopyroxene production by fluid absent partial melting in these bulk compositions in contrast mean temperatures based on grt opx fe mg exchange equilibria using the same thermodynamic data are 732 22 and 723 11 c respectively well below the minimum temperatures for opx stability for mafic granulites the mean corrected temperature using our method is 816 12 c similar to the mean temperature of 793 13 c from fe mg exchange reasons for the differences between the mafic granulites and aluminous intermediate granulites are unclear but may be due to the lower al concentrations in opx in the mafic rocks and possible deficiencies in the thermodynamic modelling of these low concentrations we discuss a number of well known granulite terrains in the context of our findings including the adirondacks the acadian granulites of new england the incipient charnockites of southern india and sri lanka and the kerala khondalite belt our findings carry implications for thermotectonic models of granulite formation a computer program to perform our thermobarometry calculations rclc is available from the journal of petrology website at http www petrology oupjournals org or from the authors at http www geo ucalgary ca pattison drm pattison rclc htm

interaction of biotite amphibole gneiss with h2o co2 k na cl fluids at 550 mpa and 750 and 800 с experimental study and applications to dehydration and partial melting in the middle crust to constrain effects of chloride bearing h2o co2 fluids on complex natural assemblages during high grade metamorphism and anatexis we report the results of experiments on the interaction of biotite hornblende tonalitic gneiss from the sand river formation limpopo complex south africa with h2o co2 h2o co2 kcl h2o co2 nacl and h2o co2 k na cl fluids at 550mpa 750 and 8008c and varying chloride h2o co2 ratios with molar co2 co2 h2o 1 4 0 5 heating of solid cylinders of gneiss at both temperatures in the absence of a free fluid phase produced no changes in the gneiss phase assemblage the equimolar h2o co2 fluid at 7508q also did not significantly influence the phase assemblage addition of kcl to the fluid at 7508q resulted in formation of the clinopyroxene k feldspar ilmenite titanite assemblage after biotite hornblende and plagioclase orthopyroxene accompanied by amphibole appeared only at 8008c as a result of biotite breakdown in the presence of h2o co2 and low salinity h2o co2 kcl fluids increase in the kcl content in the fluid at 8008q resulted in the production of a clinopyroxenebearing assemblage increase of the nacl content stabilized amphibole in an assemblage with either orthopyroxene at low nacl concentrations or clinopyroxene nevertheless clinopyroxene albite is stable only at high salt concentrations comparison of the experimental results with the results of thermodynamic modeling using the gibbs free energy minimization method perple x software showed that mineral reactions and assemblages in the run products were governed by the activities of alkali components imposed by kcl and nacl in the h2o co2 fluids and decrease of the water activity served as an additional factor stabilizing anhydrous assemblages no melts formed at 7508c in the presence of the h2o co2 kcl fluids these fluids provoked melting only at 8008c with formation of rhyolitic melts with increasing kcl content of the fluid the melt composition changed to potassic rhyolitic with al2o3513 5 wt cao52 wt k2o na2o47 wt feo feo mgo 40 8 k2o na2o41 and moderate enrichment in cl 0 2 0 6 wt increasing nacl content caused melting at 7508q and shifted the melt composition towards trachytic and trachyandesitic compositions at both 750 and 8008q the experiments support a model for the formation of ferroan a type granite syenite complexes via crustal melting in the presence of h2o co2 salt fluids in extensional tectonic settings they demonstrate a possible link between a type granitoids and mid crustal dehydration zones in amphiboliteto granulite facies terrains and allow a new interpretation of mineral assemblages within these zones in terms of variations in fluid salinity

fluid mediated partial alteration in monazite the role of coupled dissolution reprecipitation in element redistribution and mass transfer monazite ce lree th u ca p si o4 with complex zoning in th and other elements is commonly observed in metamorphic and igneous rocks the hypothesis that this alteration is a product of fluid mediated element mass transfer has been tested in the piston cylinder press caf2 assembly cylindrical graphite oven at 1 000 mpa and 900 c and in cold seal autoclaves on a hydrothermal line at 500 mpa and 600 c experiments included a relatively homogeneous monazite ce 7 8 wt tho2 from a heavy mineral sand plus a series of alkali bearing fluids including 2n naoh 2n koh and na2si2o5 h2o experiments were conducted using bse imaging emp analysis and both tem and hrtem a subset of monazite grains from each experiment show evidence of partial alteration in the form of areas enriched in th si with sharp curvilinear compositional boundaries extending from the grain rim into the monazite interior these thsio4 enriched textures are similar to those commonly seen in natural examples of metasomatised monazite in both magmatic and metamorphic rocks in the na2si2o5 h2o experiments scarce inclusions of britholite formed in the altered monazite the altered monazite is also characterised by strong depletion in pb ca and y thorium and si mobility coupled with the formation of britholite inclusions during partial alteration in the monazite grain is considered to be the product of fluid aided coupled dissolution reprecipitation as opposed to solid state diffusion since other fluids including nacl and kcl brines do not result in the formation of these textures the experimental replication of thsio4 enriched areas in the monazite strongly suggests that similar textures in monazite observed in nature are fluid induced specifically by alkali bearing fluids if true complex metasomatically induced textures in monazite could yield information concerning the nature of the fluid responsible for their formation as well as allow for the dating of the metasomatic event presuming that all the original radiogenic pb has been removed

saltation threshold on earth mars and venus new formulations valid for wide ranges of particle diameter and density and gas density are presented for prediction of saltation threshold speed for small particles a low air density wind tunnel was used to extend the range of previous investigations and to separate the effects of reynolds number and interparticle forces of cohesion the new formulations are used to predict saltation threshold for atmospheric conditions on the surface of the earth mars and venus

first report of paleoproterozoic incipient charnockite from the north china craton implications for ultrahigh temperature metasomatism abstract the assembly of crustal blocks within the north china craton ncc at the terminal stage of craton building during paleoproterozoic witnessed major subduction collision events here we illustrate a case where hot and anhydrous magmas emplaced in the lower crust during the early paleoproterozoic subduction realm in the ncc led to the formation of orthopyroxene bearing dehydrated zones of incipient charnockites within the adjacent ttg tonalite trondhjemite granodiorite suite the coarse greenish anhydrous zones of incipient charnockite show an assemblage of antiperthitic plagioclase orthopyroxene k feldspar quartz with minor clinopyroxene ilmenite magnetite and secondary biotite the peak p t conditions of the incipient charnockite are estimated as 890 970 c and 3 5 6 5 kbar based on mineral chemical analysis and pseudosection modeling in the system nckfmashto suggesting ultra high temperature metasomatism and the hottest incipient charnockites so far reported zircons from the massive charnockite show oscillatory zoned magmatic cores with high th u values rimmed by unzoned and luminescent thin metamorphic overgrowths a concordant group of magmatic zircons yields weighted mean 207 pb 206 pb age of 2401 29 ma and a lower intercept age of ca 1834 81 ma a similar concordant group of zircons from the ttg yields a weighted mean 207 pb 206 pb age of 2446 18 ma and a weighted mean lower intercept age of 1834 47 ma the ca 2 45 ga age from the ttg and 2 40 age from the charnockite are taken to represent the magma emplacement ages and the identical 1 83 ga from zircons in both rocks denoting the timing of late paleoproterozoic metamorphism lu hf analysis of magmatic cores of the zircons from the charnockite and the ttg show clear positive hf t values 1 2 5 9 suggesting juvenile sources the formation of incipient charnockite zones close to the contact with the charnockite pluton is consistent with the quantitative numerical models that predict co 2 migration in anhydrous silicate melt and metasomatic fluid from a rapidly cooling pluton the ultra high temperature metasomatism and solid state reaction generating the incipient charnockites provide important insights on co 2 advection from lower crustal magmas during paleoproterozoic orogeny in the north china craton

fluids and h2o activity at the onset of granulite facies metamorphism abstract evidence is accumulating from experimental petrology and thermodynamic calculations based on detailed descriptions of key natural occurrences that h2o activity at the regional amphibolite facies granulite boundaries in high grade precambrian gneiss terranes coincident with the orthopyroxene isograd is considerably higher 0 3 0 6 than previously thought 0 15 0 3 this revision provides insight into the significance of fluid inclusions in minerals of the incipient charnockites characteristic of the granulite facies transitions in several precambrian gneiss terranes observations on nacl dominated brine inclusions in minerals including some new data in this paper in rocks from such places as the kabbal satnur halagur area of the archean shield of south india have salt concentrations consonant with the stabilization of orthopyroxene relative to calcic amphibole and biotite closely associated co2 dominated fluid inclusions can have substantial h2o contents at typical incipient granulite facies conditions 700 750 c and 0 5 0 7 gpa and can thus have been in equilibrium with the associated brines as immiscible metamorphic fluids observed densities of the best preserved co2 rich fluid inclusions in quartz are consistent with those expected from the equation of state of co2 at incipient granulite facies pressure temperature conditions it seems likely that the role of fluids in granulite facies metamorphism of the deep crust has been considerably underemphasized in discussions still prevalent which concentrate on the role of fluid deficient partial melting as the primary agent to the exclusion of a possible role of metamorphic fluids and metasomatism

mineralogy at meridiani planum from the mini tes experiment on the opportunity rover the miniature thermal emission spectrometer mini tes on opportunity investigated the mineral abundances and compositions of outcrops rocks and soils at meridiani planum coarse crystalline hematite and olivine rich basaltic sands were observed as predicted from orbital tes spectroscopy outcrops of aqueous origin are composed of 15 to 35 by volume magnesium and calcium sulfates a high silica component modeled as a combination of glass feldspar and sheet silicates 20 to 30 and hematite only minor jarosite is identified in mini tes spectra mini tes spectra show only a hematite signature in the millimeter sized spherules basaltic materials have more plagioclase than pyroxene contain olivine and are similar in inferred mineral composition to basalt mapped from orbit bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites bright wind streak material matches global dust waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering

aeolian fluvial interaction evidence for late quaternary channel change and wind rift linear dune formation in the northwestern simpson desert australia in central australia the most easterly extent of the macdonnell ranges border the simpson desert dunefield where widely spaced strike ridges intercept and isolate pockets of broad crested linear dunes that reflect regional changes in late quaternary climate flow regime and channel avulsion an energetic todd river reworked the eastern part of camel flat basin from 75 65 ka until the last glacial maximum lgm when it shifted eastwards but with some flows persisting through the basin until about 10 ka resulting desert surfaces of different age facilitate temporal comparisons of linear dune formation fine grained red dunes 75 65 ka in age occur on the western floor of the basin and are ramped against the foot slopes of the range after the lgm and especially during the holocene the river s departure enabled small pale coloured closely spaced coarser textured linear dunes to form on the abandoned floodplain in the eastern basin their orientation 20 farther west than the larger and older red dunes this realignment indicates that the australian wind whorl shifted southwards some 160 km or 1 5 after the lgm linear dunes in the northwestern simpson desert were formed by wind rifting involving vertical accretion of sand from a proximal source not by long distance sand transport with linear extension the blocking ranges have caused negligible downwind sediment accumulation over the past 75 ka

contemporary seismicity faulting and the state of stress in the colorado plateau the contemporary seismicity of the colorado plateau based on seismic monitoring in the past 30 yr can be characterized as being of small to moderate magnitude and contrary to earlier views of a low to moderate rate of occurrence with earthquakes widely distributed concentrations of earthquakes have been observed in a few areas of the plateau the most seismically active area of the colorado plateau is the eastern wasatch plateau book cliffs where abundant small magnitude seismicity is induced by coal mining the largest earthquakes observed to date of estimated richter magnitude m l 5 6 have generally occurred in northern arizona although very few earthquakes can be associated with known geologic structures or tectonic features in the colorado plateau seismicity appears to be the result of the reactivation of pre existing faults lacking surficial expression but favorably oriented to the tectonic stress field the small to moderate size of the earthquakes and their widespread distribution are consistent with a highly faulted precambrian basement and upper crust and a moderate level of differential tectonic stress earthquakes in the plateau generally occur in the upper crust from the near surface to a depth of 15 20 km although events have been observed in both the lower crust and uppermost mantle in areas of low to normal heat flow the latter suggests that temperatures are sufficiently low at these depths that brittle failure and hence earthquakes are still possible the predominant mode of tectonic deformation within the plateau appears to be normal faulting on northwest to north northwest striking faults with some localized occurrences of strike slip faulting on north west or northeast striking planes at shallow depths the contemporary state of stress within the plateau is characterized by approximate northeast trending extension in contrast to the previous belief that the plateau was being subjected to east west tectonic compression one area of the plateau the eastern wasatch plateau and book cliffs may still be characterized by compressive stresses however the nature of these stresses is not well understood

mobility of components in metasomatic transformation and partial melting of gneisses an example from sri lanka reaction textures fluid inclusions and metasomatic zoning coupled with thermodynamic calculations have allowed us to estimate the conditions under which a biotite hornblende gneiss from the kurunegala district sri lanka hornblende nmg 38 42 biotite nmg 42 44 plagioclase quartz k feldspar ilmenite magnetite was transformed into patches of charnockite along shear zones and foliation planes primary fluid inclusion data suggest that two immiscible fluids an alkalic supercritical brine and almost pure co2 coexisted during the charnockitisation event and subsequent post peak metamorphic evolution of the charnockite these metasomatic fluids migrated through the amphibolite gneiss along shear zones and into the wallrock under peak metamorphic conditions of 700 750 c 5 6 kbar and aflh2o 0 52 0 59 this resulted in the formation of charnockite patches containing the assemblage orthopyroxene nmg 45 48 k feldspar or70 80 quartz plagioclase an28 in addition to k feldspar microveins along quartz and plagioclase grain boundaries remnants of the co2 rich fluid were trapped as separate fluid inclusions the charnockite patches show the following metasomatic zonation patterns

iron sulfur mineralogy of mars magmatic evolution and chemical weathering products models for the evolution of sulfide minerals on mars and reaction pathways to their oxidative weathering products in martian regolith have been proposed based on petrogenetic associations between komatiitic rock types viking geochemical data snc meteorites and terrestrial fe ni sulfide deposits to test the weathering model komatiitic pyrrhotites and olivines were exposed to sulfuric acid solutions with and without dissolved ferric iron added to simulate deep weathering processes and the reaction products were identified by mossbauer spectroscopy secondary fes sub 2 pyrite or marcasite feooh goethite and possibly jarosite were formed from pyrrhotite while olivine was oxidized to nanophase goethite these results suggest that on mars acidic groundwater induced pyrrhotite yields fes sub 2 yields feooh jarosite oxidative weathering reactions particularly in the presence of dissolved fe sup 3 such gossaniferous materials occurring in martian regolith were derived mainly from fe ni sulfides associated with komatiitic basalts and not from sulfides occurring in calc alkaline porphyry copper deposits granitic hydrothermal veins sediment hosted pbs zns ores etc which presumably did not evolve on mars due to the virtual lack of plate tectonic activity there

fluids in granulites since the discovery of co2 fluid inclusions in granulites the role of fluids in the formation of these rocks has been widely studied owing to the complexity of the tectono metamorphic history of granulite terrains fluid inclusion data alone are not sufficient they need to be integrated with geochemical and mineralogical studies done on the same rock samples a clear understanding of the tectono metamorphic history of granulite terranes is also indispensable the widespread occurrence of co2 and the later discovered high salinity aqueous fluid inclusions support the idea that the lower crust underwent fluid flow and that both carbonic and brine fluids played a role in its formation both low h2o activity fluids play a similar role in destabilizing hydrous mineral phases furthermore experimental studies have shown that brine fluids have a much larger geochemical effect on granulites than initially expected these fluids are far more mobile in the lower crust compared with co2 and also have the capability for dissolving numerous minerals as in the example of the limpopo complex fluid inclusions and many metasomatic features observed in granulite terranes can thus be explained only by large scale movement of high salinity aqueous fluids and to a lesser extent co2 implying that lower crustal granulites are not as dry as previously assumed similar brines and co2 rich fluids are also found in mantle material most likely derived from deeply subducted supracrustal protoliths

seismic and tectonic analysis of the 2014 2015 flagstaff arizona earthquake sequence abstract the 1 december 2014 moment magnitude m w 4 7 arizona earthquake occurred 13 km southwest of the city of flagstaff arizona flagstaff is located within the northern arizona seismic belt and the san francisco volcanic field the flagstaff area is subject to infrequent moderate magnitude earthquakes such as the 1993 cataract creek m w 5 3 and the 1912 surface wave magnitude m s 6 2 events the epicenter of the m w 4 7 earthquake lies 2 km to the east of the oak creek normal fault this is the most proximal event to the fault in the last 40 years since the seismographic networks were first deployed the earthquake was recorded throughout northern arizona by stations of the arizona integrated seismic network data were also acquired by the network from two foreshocks of duration magnitude m d 3 2 and 2 8 and 27 aftershocks m d 1 4 3 0 locations were obtained using hypoinverse 2000 and epicenters were accurate in most cases to within 3 0 km or less fault plane solutions were obtained from the mainshock and from seven of the other events of the sequence analysis of the data indicates that release of the stress was controlled by the presence of pre existing structures including the oak creek fault and prominent fractures in the hanging wall block of the fault this is the first well documented fault slip sequence in northern arizona that has shown 1 active northeast ne trending fracture and 2 a pattern of alternation of stress release on ne and northwest nw trending fractures the alternation of stress release accommodates southeast se directed slip on both ne and nw trends the reactivation of the oak creek fault in northern arizona appears to be the result of the westward motion of the colorado plateau producing a strain rate field that implies nw se extension

evidence for episodic alluvial fan formation in far western terra tyrrhena mars a late noachian aged alluvial fan complex within harris crater in far western terra tyrrhena mars is comprised of two well defined source regions and associated discrete depositional lobes three fan units were recognized based on common morphological characteristics thermal properties and spectral signatures although the entire fan complex has been subjected to extensive erosional degradation the preserved morphologies record episodic fan formation and indicate the type of flow processes that occurred the bulk of the fan surface has morphology consistent with fluvial emplacement while one fan unit exhibits a rugged surface texture with boulders consistent with a debris flow this transition from fluvial to late stage debris flow s suggests a decline in available water and or change in sediment supply the thermal inertia values obtained for all three fan surface units mean values ranged from 318 to 344 j m 2 k

temperature dependent thermal inertia of homogeneous martian regolith 1 past studies of the thermophysical properties of the martian surface layer have assumed temperature independent thermal inertia which is a function of the material density specific heat and bulk conductivity in this paper we evaluate the temperature driven variations of these quantities for particulated and cemented material under martian conditions of atmospheric pressure and temperature temperature driven density variations are negligible the specific heat of a basaltic material is strongly influenced by the temperature 75 increase from 150 to 315 k inducing significant variations of the thermal inertia the thermal conductivity of uncemented martian regolith is weakly controlled by the solid phase conductivity and strongly controlled by the gaseous phase conductivity as a result the conductivity of the solid phase i e composition temperature is unimportant whereas medium to large variations 30 50 of the bulk conductivity are associated with temperature induced fluctuations of the pore filling gas conductivity overall the thermal inertia of uncemented martian soils is predicted to vary significantly 80 throughout the range of the observed surface temperatures in the case of cemented soils the contribution of the gas conductivity is generally small and the solid phase i e grains and cement conductivity i e composition temperature becomes more important consequently the magnitude of the thermal inertia change for cemented soils is variable and smaller than that predicted for uncemented materials 10 50 large diurnal and seasonal temperature variations only occur within the top material and most of the near surface regolith does not experience large thermal inertia variations the shapes of modeled diurnal temperature curves are not significantly modified e g the 0200 lt martian local time apparent thermal inertia of uncemented regolith is up to 15 lower than the average daily inertia of the top material thermally derived grain sizes are usually based on conductivity measurements operated at room temperature or above where the thermal inertia and specific heat are higher than on mars implying that grain size predictions for mars are currently underestimated however in situ observations by the mars exploration rovers and thermal conductivity modeling suggest that this underestimation is not significant

fluid assisted granulite metamorphism a continental journey abstract lower crustal granulites which constitute the base of all continents belong to two series high pressure granulites generated by crustal thickening subduction and ultra high temperature granulites associated with crustal extension fluid inclusions and metasomatic features indicate that the latter were metamorphosed in the presence of low water activity fluids high density co2 and brines which have invaded the lower crust at peak metamorphic conditions fluid assisted granulite metamorphism high pressure and ultra high temperature granulites commonly occur along elongated paired belts they were formed from the early proterozoic onwards during a small number of active periods lasting a few hundreds of m y these periods were separated from each other by longer periods of stability each period ended with the formation of a supercontinent whose amalgamation coincided with low to medium pressure ultra high temperature granulite metamorphism immediately before continental break up it is proposed that large quantities of mantle derived co2 stored in the lower crust at the final stage of supercontinent amalgamation are released into the hydro and atmosphere during breakup of the supercontinent fluid assisted granulite metamorphism therefore appears to be an important mechanism for transferring deep mantle fluids towards the earth s surface possible consequences were for example the sudden end of proterozoic glaciations as well as the post cambrian explosion of life

the nagercoil charnockite a magnesian calcic to calc alkalic granitoid dehydrated during a granulite facies metamorphic event the paleoproterozoic nagercoil charnockite massif in southern india consists of garnet absent and garnet bearing varieties with garnet occurring only in those areas where the charnockite incorporates supracrustal lithologies there is a late neoproterozoic cambrian granulite facies metamorphic overprint on the charnockite massif this study examines whether orthopyroxene in the charnockites crystallized during the original magmatic stage or formed during the later high grade metamorphic event the textural association of orthopyroxene and relic garnet grains and reaction intergrowths of garnet and or biotite with orthopyroxene similar to those reported in dehydration zones within the gneisses surrounding the charnockite massif show that orthopyroxene in the charnockite massif formed during the late high grade metamorphic event from dehydration reactions and is not part of the original igneous assemblage metasomatic textures such as thin k feldspar rims together with the presence of co2 rich fluid inclusions in these rocks suggest that co2 metasomatism widely prevalent in the gneisses surrounding the massif probably resulted in the low water activity necessary to form orthopyroxene during the metamorphic overprint an oxygen isotope traverse along a metapelite enclave charnockite contact within the massif shows a distinct variation in d 18 o values with the charnockite away from the contact having the lowest d 18 o value 8 9o similar to that of typical metaluminous granitic rocks the charnockite at the contact shows an intermediate d 18 o value 10 3o and the surrounding metapelite has the highest d 18 o value 12o the intermediate d 18 o value indicates partial assimilation of metapelite with a high d 18 o value into the charnockite with a low d 18 o value both the garnet absent and garnet bearing charnockites have similar compositional ranges to tonalite granodiorite granite ttg suites irrespective of whether garnet is present or not the sr contents of the charnockites show a bimodal distribution a high sr group which is magnesian calcic to calc alkalic metaluminous showing ttg affinities and a low sr group which is dominantly ferroan calcic to calc alkalic metaluminous showing similarities to the orthopyroxene bearing dehydration zones petrogenetic characterization suggests that the protoliths of the nagercoil charnockites were high temperature melts of hydrous basalt

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

nature and origin of materials exposed in the oxia palus western arabia sinus meridiani region mars abstract mars observer will map physical elemental and mineralogical properties of surface materials a key to understanding the regional variations in crustal composition will be the extent to which in situ debris produced from bedrock can be separated from laterally mixed eolian sediments viking orbiter image and thermal data covering equatorial cratered terrain in western arabia eastern oxia and sinuses sabaeus and meridiani were evaluated to test whether local materials related to bedrock could be identified characterized and mapped crater obliteration models imply that kilometers of debris have been produced locally although obliteration rates for the past few billion years have been less than 8 10 3 m year fluvial and eolian landforms clearly indicate lateral transport and mixing of tens of meters of debris six sets of calibrated violet green and red viking images covering the study area were mosaicked and examined in combination with block abundance and fine component inertias from irtm data three major color thermal units can be discerned bright red dust storm deposits brown materials that are probably indurated and dark less red materials that are probably composed of lithic fragments in the medium sand size range the unit boundaries are independent of bedrock geology and erosional landforms the brightest red material apparently mixes with each of the darker units the presence of dark splotches streaks and dunes associated with large craters in oxia indicates that the dark less red material is also mobile the surficial units exposed over the 6 10 6 km 2 study area are therefore likely to represent mixed eolian deposits predominantly decoupled from the underlying bedrock unraveling the mixtures and assignment of components to local bedrock origins will be a major challenge for mars observer