the scheelite skarn deposit of salau ariege french pyrenees between 1971 and 1986 the scheelite deposit of salau located in the french hercynian pyrenees produced 930 000 metric tons of ore with 1 50 percent wo 3 13 950 metric tons of wo 3 the skarn deposit is hosted in a devonian carbonate and partly detrital series intruded by a late carboniferous stock in the devonian series the lithostratigraphy and geochemistry of which is described in some detail a unit of so called barregiennes i e rythmic alternations of limestones and silts appears to be very favorable for extensive development of skarns and overprinted ores the hercynian orogeny involved polyphase deformation regional metamorphism of greenschist facies and late intrusions of granite granodiorite deformation included two coaxial stages of tight isoclinal folding and one important later stage which partly controlled the intrusion of the granodiorite stock followed by three stages of brittle deformation ore deposition is related to faulting stages 0 and 1 and orebodies are cut into slices by stage 2 reverse faults the salau intrusion includes various rock types belonging to two slightly different calcalkaline trends one of these trends characterized by its low k contents is unusual in the pyrenees the local shapes of the intrusion apophyses and embayments are important controls of the orebodies after isochemical contact metamorphism the skarns and ores developed in two main stages related to the infiltration of two quite different types of fluids during the first stage 540 degrees 450 degrees c anhydrous skarn formation was followed by an intergranular development of pyrrhotite scheelite quartz calcite in equilibrium with the earlier hedenbergite the resulting tungsten grade is uneconomic the associated fluids probably of magmatic origin had a high salinity in the second stage 450 degrees 350 degrees c no new skarn formed transformations of the silicate rocks are observed a first substage of epidotization was followed by the development of intermediate grossularite almandine spessartite garnet and finally by the main ore stage with scheelite pyrrhotite arsenopyrite and other sulfides with some gold two types of fluid inclusions are found in this stage one is similar in composition to the first stage the other is characterized by low salinity and high co 2 and ch 4 contents

petrologic and stable isotope constraints on the source and evolution of skarn forming fluids at pine creek california a detailed geochemical analysis of the well exposed multistage pine creek california tungsten deposit has constrained the roles of magmatic metamorphic and meteoric fluids in the development of the zoned scheelite ore and calc silicate skarn metamorphic conditions of p 2 kb t 600 degrees c and x sub co 2 0 25 are recorded in the metasedimentary rocks of the septum metamorphism yielded calcite diopside graphite and calcite dolomite periclase brucite forsterite assemblages in the variably dolomitic siliceous carbonate rocks of the pine creek septurn following intrusion of the morgan creek quartz monzonite metasomatism developed the zoned endoskarn exoskarn at the contact the massive garnet andradite sub 20 50 pyroxene hedenbergite sub 20 80 or quartz skarn assemblage carries most of the scheelite calculated t x sub co 2 equilibria corrected for solid solution effects restrict skarn formation to x sub co 2 0 2 at t 500 degrees or 50 degrees c calculated f sub o 2 f sub f 2 f sub s 2 diagrams indicate f sub o 2 values near quartz fayalite magnetite and f sub s 2 values well below pyrrhotite pyrite during skarn formation slightly falling temperatures were accompanied by increased f sub s 2 and hydration of the skarn assemblages stable isotope data for calcites show a mixing trend from unaltered marble delta 18 o 24ppm delta 13 c 3 5 degrees to values in equilibrium with magmatic fluids delta 18 o 8ppm delta 13 c 6ppm biotite quartz thermometry for the quartz monzonite yields temperatures of 410 degrees to 460 degrees c well below the solidus and suggesting later reequilibration pyroxene quartz analyses suggest that these minerals equilibrated at temperatures of 460 degrees to 560 degrees c the delta 18 o values measured for garnets suggest disequilibrium for the garnet quartz and garnet pyroxene pairs d h results for epidote and biotite suggest that meteoric water influx became more important with time sulfur isotope data are consistent with a reduced magmatic source

rugged crater ejecta as a guide to megaregolith thickness in the southern nearside of the moon the southern highlands of the moon comprise superposed ejecta layers individually as thick as a few kilometers from the major basins smaller 1 16 km diameter impact craters that penetrate this layered megaregolith and excavate material from depth have radar properties that provide insight into the variability of megaregolith thickness above a postulated basement of large crustal blocks we observe a significant difference in the population of radar bright craters 1 16 km and larger in diameter between regions of the southeastern near side highlands north and south of lat 48 s there are about one third more radar bright craters north of this line than to the south broadly coincident with the mapped boundary between southern deposits mapped as pre nectarian age and those of nectarian imbrian age to the north the radar bright crater population is consistent with a megaregolith thickness of 1 5 km in the north and 2 5 km in the south a difference we attribute to south pole aitken basin ejecta

constriction in a transpressive regime an example in the iberian branch of the ibero armorican arc abstract detailed strain analyses in the armorican quartzites have been performed in various places within the centro iberian zone of western europe the observed strain pattern shows that in the inner ibero armorican arc as well as near the hinge zone sinistral transpression produces constrictive ellipsoids in the outer arc away from the hinge zone the deformation regime produces plane strain to oblate strain ellipsoids some of these data clearly contradict existent kinematical models which associate constriction with transtension and consider transpression zones to generate oblate strain ellipsoids however newly developed models show that it is possible to obtain a wide range of finite strain ellipsoids in transpression zones if one takes account of lateral escape axial depression and volume change the geodynamic implications of the strain analyses suggest generation of constriction in a transpressive regime caused by lateral expulsion in front of the cantabrian indenter that produced the ibero armorican arc this mechanism was responsible for the variscan wrench component in western europe which was mainly sinistral in iberia and dextral in britanny in iberia the displacement by lateral escape was easily accommodated by subduction of the south portuguese terrane under the ossa morena zone of the iberian terrane

physicochemical study of skarn formation in pelitic rock costabonne peak area eastern pyrenees france the costabonne skarn complex was emplaced in the lower part of the cambrian canaveilles formation eastern pyrenees in contact with a hercynian granitic stock skarns have developed from calcium poor 0 99 with minor co2 ch4 n2 h2 o2 h2s hcl and hf ca na and k were the most abundant cations temperature and pressure conditions are estimated to be at least 550 c and 1 7 to 2 0 kb respectively the totality of the observed transformations may be described in the system cao k2o sio2 al2o3 mgo h2o with the minerals quartz muscovite phlogopite tremolite diopside grossular k feldspar and anorthite with cao and k2o taken as perfectly mobile components sio2 al2o3 and mgo as determining inert components and h2o as excess component the reactions leading to the skarn formation can be represented in a mu cao mu rm k 2 o diagram the succession of zones is shown to take place with increasing cao from the schist z0 up to the garnet zone z4 the nature of the feldspar plagioclase or k feldspar depends on the value of mu rm k 2 o relative to cao

a scheelite mineralization in calc silicate rocks of the moldanubicum bohemian massif in austria in the moldanubicum bohemian massif of austria a tungsten mineralization bound to calc silicate rocks was discovered in the so called bunte serie a metasedimentary geologic unit now in amphibolite to higher amphibolite facies the main constituents of the scheelite bearing rocks are ferro salite meionite rich scapolite and quartz the average tungsten content is estimated to be 1500 ppm no further elements that would be characteristic for an exoskarn formation are enriched conspicuously the whole series of calc silicate rocks is intercalated in sillimanite gneisses this series could be traced for about 5 km the mineralization seems to be strata bound contacts with intrusive rocks were not observed the field evidence is therefore easiest to reconcile with a synsedimentary origin but the geology of the region is not known in sufficient detail to make this interpretation conclusive

lunar surface roughness derived from lro diviner radiometer observations abstract sunlit and shaded slopes have a variety of temperatures based on their orientation with respect to the sun generally greater slope angles lead to higher anisothermality within the field of view this anisothermality is detected by measuring changing emitted radiance as a function of viewing angle or by measuring the difference in brightness temperatures with respect to observation wavelength thermal infrared measurements from the lunar reconnaissance orbiter diviner radiometer were used to derive lunar surface roughness via two observation types 1 nadir multispectral observations with full diurnal coverage and 2 multiple emission angle targeted observations measurements were compared to simulated radiance from a radiative equilibrium thermal model and gaussian slope distribution model nadir observations most closely match a 20 rms slope distribution and multiple emission angle observations can be modeled using 20 35 rms slope distributions limited sampling of the lunar surface did not show any clear variation in roughness among surface units two dimensional modeling shows that surfaces separated by distances greater than 0 5 5 mm can remain thermally isolated in the lunar environment indicating the length scale of the roughness features non equilibrium conditions are prevalent at night and near sunrise and sunset preventing the use of the equilibrium thermal model for roughness derivations using data acquired at these local times multiple emission angle observations also show a significant decrease in radiance at high emission angles in both daytime and nighttime observations and hemispherical emissivity is lower than is apparent from nadir observations these observations and models serve as a basis for comparison with similar measurements of other airless bodies and as an initial template for the interpretation of tir measurements acquired under a variety of geometric conditions

a compositional study of the aristarchus region of the moon using near infrared reflectance spectroscopy newly obtained near infrared reflectance spectra for features on or near the aristarchus plateau demonstrate the diversity of compositions in the region highland units are of three probable compositions a feldspar and clinopyroxene assemblage a probable clinopyroxene olivine and possibly feldspar assemblage and an assemblage composed of olivine or olivine and feldspar the feldspar clinopyroxene assemblage is tentatively correlated with the major th anomaly centered on aristarchus crater the regional pyroclastic deposits on the plateau are composed of greater than 90 fe2 bearing glass the aristarchus cratering event fully penetrated any mare or pyroclastics in the target evidence for mare related material is found in the ejecta on the mare side of the mare plateau contact

seismicity and subsidence following the 2011 nabro eruption eritrea insights into the plumbing system of an off rift volcano nabro volcano situated to the east of the afar rift zone erupted on 12 june 2011 eruptions at such off rift volcanoes are infrequent and consequently the plumbing systems are poorly understood we present posteruption synthetic aperture radar sar images from the terrasar x satellite and posteruption continuous seismic activity from a local seismic array interferometric analysis of sar data reveals a circular 12 km wide signal subsiding at 200 mm yr we inverted for the best fit mogi source finding a 4 1 107 m3 yr volume decrease at 7 1 km depth between 31 august and 7 october 2011 we located 658 and relocated 456 earthquakes with local magnitudes between 0 4 and 4 5 seismicity beneath the se edge of nabro at 11 km depth is likely associated with high strain rates from deep magma flow into the modeled reservoir this suggests that magma is supplied through a narrow conduit and then stored at 7 km depth we interpret seismicity at 4 6 km depth as brittle fracturing above the inferred magma reservoir focal mechanisms delineate a thrust fault striking ne sw and dipping 45 to the se across the caldera floor we propose that the crustal response is to slip on this fault which crosscuts the caldera rather than to deform on ring faults the ne sw fault plane is not associated with measurable surface deformation indicating that it does not contribute much to the caldera deformation we show that subsidence of the caldera is controlled by magma chamber processes rather than fault slip

the geochemistry of zoning in skarn minerals at the king island dolphin mine trends of chemical zoning in crystals of garnet pyroxene scheelite and amphibole in 34 samples collected from the pluton9s contact updip to 500 m from the contact in the main ore horizon at the king islnd scheelite dolphin mine show systematic variations garnet cores up to 400 m from the contact are the most andradite rich reaching values of 98 mole percent nearest the contact andradite values decrease systematically both for a particular part of the garnet crystals away from the contact and across individual grains to the outer edges the mole percent andradite in core and outer core zones decreases to the 500 m mark while in the midsection and edge zones the values decrease to 400 m and then increase a similar relationship occurs in pyroxenes which nearest the contact contain hedenbergite values of 98 mole percent scheelite occurring as inclusions in garnet reach values of scheelite 65 powellites 34 for core zones nearest the pluton while scheelite interstitial to garnet have maximum values of scheelite 72 powellite 27 powellite contents decrease both toward the edges of individual grains and along the traverse to the 400 m mark where a reversal of trend occurs continuing to 500 m from the contact amphibole compositions show a linear decrease of the ratio fe super 2 fe super 2 mg mn from 98 nearest the contact to 88 at 390 and then decreasing abruptly to 65 at 500 m fluid inclusion filling temperatures vary systematically in time and distance from the pluton with a maximum near 800 degrees c for garnet midsections nearest the pluton to temperatures as low as 180 degrees c for interstitial calcite and quartz the salinities decrease from near 65 weight percent total dissolved salts in the early formed minerals i e garnet nearest the pluton to less than 3 weight percent for later formed minerals farthest from the contact i e calcite these decreases occur out from the contact and progressively toward the end of the paragenetic sequence scheelite initially crystallized at higher temperatures but interstitial scheelite precipitation occurred from a concentrated na k ca cl solution approximately 10 molal total dissolved salts at temperatures of approximately 500 degrees c at the pluton9s contact to 300 degrees c at a distance of 500 m from the contact chemical variations of fluid compositions for all but garnet core zones beyond 400 m from the contact occurred due to mixing of solutions derived from the northern boundary fault the interface between solutions which have permeated through and reacted with the developing skarn unit and those derived from the fault marks the maximum outward edge from the pluton of boiling of the solutions the highest concentrations of w ore reversals or inflection points in mineral composition profiles and changes in the elemental ratios of constituents in the brine solutions hot saline solutions initially cooled to approximately 380 degrees c on entering the colder marble horizon flow along this horizon caused the loss of heat dilution and chemical change of the solution this latter in response to both reactions with the marble and hornfelsic units as well as the precipitation of the skarn permeability was produced by the dissolution of caco 3 to produce cacl sub 2 aq and faulting with time thermal equilibrium was reached between the evolving fluid and the contact rocks until boiling of the solution occurred with the loss of a co sub 2 rich vapor during this event the northern boundary fault was tectonically active so that primary fluid now entered the forming skarn both from the fault and the contact of the pluton mo rich scheelite began to precipitate at the time of boiling subsequent to garnet pyroxene crystallization after the boiling event and contemporaneous with the crystallization of amphibole some quartz mo rich scheelite not armored in garnet was dissolved redistributed and redeposited as mo poor scheelite and molybdenite this type of scheelite forms most of the ore being mined

apollo 17 landing site topography photometric corrections and heterogeneity of the surrounding highland massifs 1 a high resolution digital elevation model for the apollo 17 landing site 20 n 31 e and surrounding region is used to correct the photometry of clementine ultraviolet visible multispectral data to standard viewing and illumination geometry on a pixel by pixel basis feo and tio2 concentrations were derived from these topographic photometrically corrected data and steep sloped highland massifs are used to assess the magnitude of the effects of the correction the effects are significant yielding errors as high as 5 wt feo and 4 wt tio2 absolute on 30 slopes the magnitude of the correction varies for sun facing versus anti sun slopes with greater changes on anti sun slopes because most of the apollo 17 sample stations were on surfaces with low slope values 5 the topography has only a small effect on the use of the apollo 17 site for calibration of feo and tio2 parameters topographically corrected data and derived compositional information are used to show accurately the variation in composition of the highland units such as the massifs and the sculptured hills on a fine scale massif compositions are consistent with mixtures of noritic impact melt and feldspathic granulitic material plus variable amounts of high ti basalt on flanks at low elevations and pyroclastic deposits at high elevations as surmised from previous studies an unexpected enrichment in feo at intermediate elevations in some places where massif surfaces have not been covered by mass wasting of impact melt rich material signals an older volcanic component not previously recognized this component may be correlative with an old high plains volcanic unit exposed northeast of the landing site and north of the sculptured hills downslope movement of regolith on steep slopes appears to have resulted in compositional or grain size sorting leading to an apparent enrichment in feo and tio2 from volcanic glass in valleys and draws the sculptured hills have highly variable compositions ranging from feldspathic patches to exposures of mafic rocks a strong but localized mafic anomaly within the sculptured hills may be a small postbasin volcanic feature consisting of very low ti basalt

a revised algorithm for calculating tio2 from clementine uvvis data a synthesis of rock soil and remotely sensed tio2 concentrations 1 investigating mare basalt compositions at both the sample and remote sensing level for the apollo and luna mare sites reveals the need for a more complex regression procedure than previously proposed in order to extract accurate tio2 concentrations from clementine spectral reflectance csr data the tio2 algorithm of lucey and coworkers is modified by using two different sets of regression parameters to relate measured regolith compositions from sampling locations to the csr properties of these sites one regression trend fits the majority of apollo data and the second regression is a fit to the apollo 11 luna 16 and luna 24 data which were considered to be anomalous in previous tio2 calibrations these three sites have unusually low albedo compared to other mare landing sites and some 32 of nearside mare regions appear to share this characteristic possible reasons for these differences related to proximity of the other sites to mare highland boundaries are discussed using the dual regression method we find 1 that tio2 concentrations calculated for the basaltic landing sites faithfully reproduce a bimodal distribution as seen in the sample data 2 that when coupled with the effects of other thermal neutron absorbers ti concentrations are more consistent with observed epithermal to thermal neutron flux ratios than are previous clementine based derivations of tio2 for basaltic regions and 3 that basalts of intermediate tio2 concentrations occur most frequently in the oceanus procellarum region and that these intermediate concentrations appear to be inherent to the flows underlying the regolith and presumably to the basalt source regions

buried stratigraphic relationships along the southwestern shores of oceanus procellarum implications for early lunar volcanism the composition of mare highland boundaries is investigated in the region of southwestern oceanus procellarum using multispectral images from the galileo solid state imaging system the data are analyzed using a linear image based spectral mixture model to map the distribution and abundance of spectral end members representing mare basalt mature highland soils and fresh crater materials the fraction images that result from the mixture modeling are then integrated into a geographic information system database to analyze the relationship between the compositional gradients and regional geologic and geomorphic units within this framework three basic types of mixing gradients are recognized narrow mixing zones broad mixing zones and complex mixing zones the narrow zones appear to be the result of simple postformation lateral mass transport of surface materials due to the time averaged effects of impact cratering and regolith gardening the broad or moderate mixing zones exhibit evidence for significant incorporation of basalt into the distal basin ejecta of orientale and thus are interpreted to indicate that pre orientale volcanism and volcanic deposits were widespread in the procellarum region this is further corroborated by the mare rich ejecta blanket observed for the 100 km diameter impact crater letronne the complex mixing zones show evidence for extensive pre orientale and perhaps pre imbrium cryptomare as well as some volcanism extending into the late imbrian period these results indicate that mare highland boundaries frequently contain a convolved geologic record that allows insight into the geologic events prior to the final one apparently recorded by surface deposits for this region of the moon we now recognize that volcanism was well established and widespread in early imbrian time but had become more focused to a few major volcanic regions humorum procellarum by the late imbrian

mars mapping with delay doppler radar mars radar imaging results from arecibo 12 6 cm observations are presented the images were derived from delay doppler mapping using a coded long pulse technique to mitigate the effects of echo overspreading images of the depolarized echo are used to identify regions of high decimeter scale roughness some of the strongest echo features are located on the major shield volcanoes or on relatively young off shield flows such as the olympus and pavonis lava aprons the shields themselves have highly irregular radar signatures suggesting complex volcanic histories some mars radar features have twice the depolarized brightness of the roughest terrestrial lava flows apparently due to higher levels of multiple scattering from surfaces of spectacular roughness or from volume scattering low brightness smooth areas are associated with older surfaces such as fractured and highland terra as well as with terrain interpreted to be debris lobes ash flows and aureoles in particular a close connection was found between the 12 6 cm counterpart of the stealth feature and the medusae fossae formation postulated to be deep ignimbrite deposits marte valus is anomalous in being the only outflow channel showing strongly enhanced echoes which supports the idea that this channel and the elysium basin that it drained are filled with lava flows a weak radar feature was found for the south polar residual ice cap comparisons with goldstone 3 5 cm data show that the south polar enhancement is much weaker at 12 6 cm than at 3 5 cm indicating that the southern ice cap becomes optically thin at the longer wavelength a north polar enhancement has also been found which is comparable in strength to the 12 6 cm south polar feature

a frequency dependent description of propagating sea level signals in the kuroshio extension region abstracthilbert empirical orthogonal function analysis is used to provide a frequency dependent description of observed sea level variability in the kuroshio extension region 1993 2012 inclusive the dominant high frequency mode periods between 140 and 350 days describes signals that propagate westward with the largest amplitudes in the vicinity of the shatsky rise and emperor seamounts based on the close correspondence between the variance of the high frequency variability and the underlying bathymetry it is speculated that this mode is driven by jet bathymetry interactions the dominant low frequency mode periods longer than 350 days is explained in terms of wind forced jet trapped rossby waves that propagate along the mean kuroshio extension jet one of the most surprising findings of this study is that sea level changes north of the jet in the meander region anticipate changes south of the jet by about 3 yr based on correlations of observed sea level with the pacific decadal oscillation and

regolith composition and structure in the lunar maria results of long wavelength radar studies radar measurements at 70 cm and 7 5 m wavelengths provide insight into the structure and composition of the upper 5 100 m of the lunar regolith and crust we combine high resolution 3 5 km 70 cm radar data for the nearside with earlier calibrated full disk observations at the same wavelength to provide a reasonable estimate of the lunar backscatter coefficient these data are tested against models for echoes from a buried substrate and mie scattering from surface and buried rocks these mechanisms are expected to dominate the 70 cm radar echo with their relative importance determined by the rock population regolith depth substrate roughness and the loss tangent of the soil results indicate that the 70 cm radar echo for the maria comes largely from mie scattering by rocks buried within the fine soil radar scattering from a buried substrate is not likely to greatly affect the observed return we also compared the 70 cm and 7 5 m radar images to infrared eclipse temperature maps crater population age estimates for the maria and to tio2 and feo abundances inferred from earth based telescopic and clementine multispectral observations these data imply that 1 the tio2 ilmenite content of the regolith controls variations in 70 cm depolarized echo strength among mare units with higher titanium abundance leading to lower echoes 2 changes in the average 70 cm return for a given tio2 abundance between maria of different ages do occur but uncertainties in the current radar data do not allow us to uniquely distinguish between variations in rock population with age and calibration effects 3 the 7 5 m radar echoes are controlled by the age of the mare basalt flows with older deposits having a greater degree of fracturing and higher backscatter future mapping at 12 6 cm and 70 cm wavelengths will help to resolve some of the issues raised here

alignments of volcanic features in the southern hemisphere of mars produced by migrating mantle plumes abstract mars shows alignments of volcanic landforms in its southern hemisphere starting from the equatorial regions and converging towards the south pole and visible at global scale these composite alignments of volcanoes calderas shields vents heads of valley networks and massifs between the equatorial regions and the southern polar region define twelve different lines fitted by rhumb lines loxodromes that i propose to be the traces of mantle plumes the morphology of the volcanic centres changes along some of the alignments suggesting different processes of magma emplacement and eruptive style the diameters of the volcanic centres and of the volcanic provinces are largest at tharsis and elysium directly proportional to the number of alignments starting from them a minor presence of unaligned volcanic features is observed on the northern lowlands and on the highlands outside the 12 major alignments the heads of channels commonly interpreted as fluvial valleys are aligned with the other volcanic centres unaltered olivine is present along their bed floors raising severe doubts as to their aqueous origin several hypotheses have tried to explain the formation of tharsis with the migration of a single mantle plume under the martian lithosphere but the discovery of twelve alignments six starting from tharsis favours the hypothesis of several mantle plumes as predicted by the model of the southern polar giant impact spgi and provides a new view on the formation of the volcanic provinces of mars

radar images of mars full disk images of mars have been obtained with the use of the very large array vla to map the radar reflected flux density the transmitter system was the 70 m antenna of the deep space network at goldstone california the surface of mars was illuminated with continuous wave radiation at a wavelength of 3 5 cm the reflected energy was mapped in individual 12 minute snapshots with the vla in its largest configuration fringe spacings as small as 67 km were obtained the images reveal near surface features including a region in the tharsis volcano area over 2000 km in east west extent that displayed no echo to the very low level of the radar system noise the feature called stealth is interpreted as a deposit of dust or ash with a density less than about 0 5 gram per cubic centimeter and free of rocks larger than 1 cm across the deposit must be several meters thick and may be much deeper the strongest reflecting geological feature was the south polar ice cap which was reduced in size to the residual south polar ice cap at the season of observation the cap image is interpreted as arising from nearly pure co 2 or h 2o ice with a small amount of martian dust less than 2 percent by volume and a depth greater than 2 to 5 m only one anomalous reflecting feature was identified outside of the tharsis region although the elysium region was poorly sampled in this experiment and the north pole was not visible from earth

geologic context of the mars radar stealth region in southwestern tharsis stealth is a region on mars that has no distinguishable radar return stealth was discovered in 1988 by muhleman et al 1991 in 3 5 cm earth based radar images and it was found to extend 2000 km along the martian equator west of arsia and pavonis montes stealth was proposed to be a deposit of unconsolidated granular material with a minimum thickness of several meters with the most likely explanation being that stealth is a volcanic tephra deposit muhleman et al 1991 1995 stealth overlies some of the youngest geologic units on mars including lava flows and a giant curvilinear ridged lobate unit on the west flank of arsia mons stealth also overlies part of a region of smooth and wind scoured materials called the medusae fossae formation examination of high resolution viking orbiter images suggests that stealth is the youngest of several discontinuous wind worked mantles of fine grained 1 cm sediment older deposits of fine sediment appear to be interbedded with lava flows and show evidence of aeolian deposition dunes and deposits in the lee of topographic obstacles and erosion yardangs and pedestal craters the geologic context supports a volcanic ash origin for stealth if stealth is composed of tephra then its extent and the nature of landforms in the region indicate that it resulted from multiple eruptions that occurred relatively late in martian history possible source vents include linear depressions flanked by constructive volcanic landforms that are located on the lower western slopes of arsia and pavonis montes

radar probing of planetary regoliths an example from the northern rim of imbrium basin 1 imaging radar measurements at long wavelengths e g 30 cm allow deep up to tens of meters probing of the physical structure and dielectric properties of planetary regoliths we illustrate a potential application for a mars orbital synthetic aperture radar sar using new earth based 70 cm wavelength radar data for the moon the terrae on the northern margin of mare imbrium the montes jura region have diffuse radar backscatter echoes that are 2 4 times weaker at 3 8 cm 70 cm and 7 5 m wavelengths than most other lunar nearside terrae possible geologic explanations are 1 a pyroclastic deposit associated with sinuous rilles in this region 2 buried mare basalt or a zone of mixed highland basaltic debris cryptomaria or 3 layers of ejecta associated with the iridum and plato impacts that have fewer meter sized rocks than typical highlands regolith while radar data at 3 8 cm to 7 5 m wavelengths suggest significant differences between the montes jura region and typical highlands the surface geochemistry and rock abundance inferred from clementine uv vis data and eclipse thermal images are consistent with other lunar terrae there is no evidence for enhanced iron abundance expected for basaltic pyroclastic deposits near the source vents of the sinuous rilles radial to plato the regions of low 70 cm radar return are consistent with overlapping concentric haloes about iridum and plato and do not occur preferentially in topographically low areas as is observed for radar mapped cryptomaria thus we suggest that the extensive radar dark area associated with the montes jura region is due to overlapping rock poor ejecta deposits from iridum and plato craters comparison of the radial extent of low radar return crater haloes with a model for ejecta thickness shows that these rock poor layers are detected by 70 cm radar where they are on the order of 10 m and thicker a sar in orbit about mars could use similar deep probing to reveal the nature of crater and basin related deposits

scheelite mineralization in central east greenland numerous scheelite mineralized areas have been located in the caledonian fold belt of central east greenland 70 74 1 2 n the fold belt comprises archaean and proterozoic metamorphic complexes flanked by late proterozoic and lower palaeozoic sediments and intruded by upper proterozoic and caledonian granitic rocks scheelite mineralization occurs in marble skarns in upper proterozoic metasediments often spatially associated with caledonian or older granitic intrusives skarns and quartz veins in late proterozoic sediments lower ebg quartzite up to 7 km from outcropping caledonian granites veins in fault zones cutting late proterozoic sediments upper ebg limestones in this paper the three types are described with emphasis on structural setting mineralogy and trace element chemistry it is concluded that most scheelite mineralization is associated with caledonian igneous activity either at or near granite contacts or as mineralization distal to granites at depth of the various types described the scheelite veins in late proterozoic limestone are considered to be of the best economic potential

earth based radar data reveal extended deposits of the moon s orientale basin we present new earth based radar observations of ejecta associated with the lunar orientale impact basin we can distinguish 1 a block poor ejecta facies composing a concentric halo of mantling material 10 m or greater in thickness that extends more than 1000 km from the basin center and 2 a melt rich deposit that forms a discontinuous but areally extensive stratigraphic marker across the southern highlands the melt rich component likely extends well into the south pole aitken basin a key target for future landed and sample return missions the observation of these two ejecta facies and their distribution across the southern nearside yields new insight into the types and distribution of material contributed by large basin forming impacts to the highlands megaregolith

geologic setting petrology and geochemistry of zoned tungsten bearing skarns at the strawberry mine central sierra nevada california the strawberry mine 90 km northeast of fresno california occurs on the margin of a small roof pendant of early jurassic metasedimentary rocks and middle cretaceous metaigneous rocks middle cretaceous granitic intrusions surround and intrude the roof pendant adjacent to one granodiorite intrusion several subvertical marble layers are replaced by scheelite bearing skarns the skarns form spears that project as much as 300 m upward and into the marble layers between the marble and granodiorite the skarns comprise a metasomatic column and are subdivided into four zones 1 wollastonite skarn adjacent to and replacing marble and containing wollastonite grossularite idocrase and diopside 2 garnet skarn containing andradite grossularite diopside hedenbergite and scheelite 3 pyroxene skarn containing hedenbergite diopside plagioclase magnetite and scheelite and 4 hornblende skarn adjacent to granodiorite and containing hornblende plagioclase microcline magnetite and scheelite important features of the skarn zonation are sharp contacts between skarn zones relative constancy of whole rock mineral and modal compositions within each skarn zone major changes in whole rock mineral and modal compositions across contacts between skarn zones and systematic replacement between skarn zones with any given skarn zone replaced by the next lower and adjacent skarn zone toward the granodiorite volume remained approximately constant in the replacement of marble by various skarn zones marble and skarn exhibit uniformly low porosity data on mineral paragenesis and mineral composition indicate that in the replacement of any skarn the most calcic mineral is consumed and the residual calc silicate minerals in the replacing skarn increase in abundance and are richer in total fe and mno this mineral paragenesis can be related to systematic variations in whole rock composition from the marble to the granodiorite skarns are progressively depleted in cao and co 2 and progressively enriched in sio 2 total fe mgo mno al 2 o 3 na 2 o k 2 o and wo 3 the skarns probably formed when an aqueous fluid containing a solute fraction relatively depleted in ca and co 2 and relatively enriched in si fe mg mn al na k and w was expelled from a granitic magma into country rock the tendency toward local equilibrium between fluid and marble resulted in formation of skarns with systematic stepwise changes in mineral and rock composition at contacts between skarns achievement of local equilibrium occurred mainly by infiltration metasomatism with a possible minor component of diffusion metasomatism

compositional analyses of lunar pyroclastic deposits abstract the 5 band clementine uvvis data at 100 m pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits lpds and these were compared to representative lunar maria and highlands deposits results show that the albedo spectral color and inferred composition of most lpds are similar to those of low titanium mature lunar maria these lpds may have consisted largely of fragmented basalt with substantial components of iron bearing mafic minerals pyroxenes olivine and smaller amounts if any of volcanic glass several smaller lpds also show substantial highland components three classes of very large deposits can be distinguished from most lpds and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components one class has spectral properties that are dominated by high titanium crystallized black beads e g taurus littrow a second consists of a mixture of high titanium glasses and beads with a higher glass bead ratio sulpicius gallus than that of taurus littrow and a third has a significant component of quenched iron bearing volcanic glasses aristarchus with possible moderate titanium contents although areally extensive these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied 27 and eruption of such materials was thus likely to have been less frequent on the moon

imaging of lunar surface maturity the physical evolution of the lunar surface with exposure to the space environment is termed maturation and maturity is the degree to which a particular lunar soil possesses quantitative characteristics consistent with that exposure several quantitative measures or indices of maturity have been proposed and employed including the abundance of solar wind gas abundance of various types of agglutinates various measures of grain size and is feo among the changes attendant with space exposure are striking changes in the optical characteristics of soils mature lunar soils are dark red and exhibit reduced spectral contrast relative to immature soils this paper presents an optical maturity index that quantifies the spectral effects of maturation we show that this optical maturity index correlates with other maturity indices about as well as the accepted maturity indices correlate among themselves and is only weakly coupled to composition the modest correlations among maturity indices suggest important controls on individual maturity indices other than age uncorrelated variations in the rates of accumulation of individual indicators or variations in depths over which indicators are emplaced in addition to mixing these effects conspire to reduce the equivalence of maturity and duration of surface exposure optical maturity illustrates some of these effects showing that ejecta of large and small craters mature at different rates and that the interiors and ejecta of large craters exhibit systematically different optical maturities the same or analogous effects are likely to influence other maturity indices

earth based observations of radar dark crater haloes on the moon implications for regolith properties 1 earth based radar can be used in conjunction with other data sets collected remotely or in situ to characterize the physical and chemical properties of the lunar regolith we use previously existing and newly acquired earth based radar measurements at 70 cm wavelength to investigate the properties of distinctive low return haloes surrounding 39 nearside impact craters these haloes are distinct from the well known optically dark haloes associated with volcanic craters or with impacts into cryptomare deposits we examine two possible mechanisms for formation of radar dark haloes 1 excavation of high tio2 high loss tangent basalt and 2 deposition of a mantling layer produced in the impact process that is depleted in meter sized blocks comparison of the radar data with apollo and lunar orbiter images indicates a general spatial correspondence between radar dark crater haloes and radial ridged ejecta facies distal to the radar bright crater rims comparison with clementine uv vis multispectral data indicates no apparent spatial correlation between regions of enhanced tio2 content and radar dark haloes though variations in tio2 content may play a role for some mare craters they are insufficient to account for the observed offsets in radar echo power we conclude that the radar dark haloes result from a block poor ejecta deposit that disappears over time with meteoroid bombardment a more detailed and comprehensive analysis of ejecta degradation processes and rates following acquisition of additional high resolution radar data could lead to a refinement of the lunar geologic timescale

detectability of subsurface interfaces in lunar maria by the lrs selene sounding radar influence of mineralogical composition 1 the lunar radar sounder lrs of the selene mission has detected horizontal subsurface features at depths of a few hundreds of meters within all major lunar maria we have mapped these features at global scale and found a heterogeneous geographical distribution which correlates negatively with the maps of tio 2 and feo obtained from uv vis measurements by the clementine probe high concentration of ilmenite fetio 3 in the basaltic mare lava can explain this correlation this mineral being a strong absorber for low frequency electromagnetic waves thus absence of detection of subsurface interfaces by lrs on a large portion of lunar maria does not necessarily imply that these interfaces are actually absent

mars orbital synthetic aperture radar obtaining geologic information from radar polarimetry 1 radar penetration of mantling layers and scattering from buried objects or interfaces is a topic of current interest in both terrestrial and planetary remote sensing we examine the behavior of surface and subsurface scattering interfaces and the types of information that may be obtained from observations in different polarizations and wavelengths these results are applied to the design of a future mars orbital synthetic aperture radar sar for which we draw the following conclusions 1 mapping of buried geologic features is best accomplished using vv polarization at an optimal wavelength determined by the competing effects of antenna gain attenuation in the dust and the reduction in effective surface roughness with wavelength p band frequencies 1 ghz or less offer the best opportunity for detection of moderately rough buried features 2 the relative roles of surface and subsurface scattering may be determined using measurements in hh and vv polarization with a channel gain calibration better than 0 5 db 3 the thickness of a mantling layer or ice mass cannot be directly inferred from multiwavelength observations layer thickness may be inferred from the interferometric correlation of backscatter measurements collected on suitably spaced orbital passes though the required phase measurement accuracy is challenging while additional information may be gained by collecting scattering data in more polarizations or wavelengths we suggest that the primary science goals of a mars orbiting radar could be accomplished by a single wavelength system capable of collecting vv and hh polarizations with the calibration and orbit control needed to permit interferometric analysis

radar mapping of lunar cryptomaria east of orientale basin 1 lunar cryptomare deposits represent early basaltic volcanic material that has been mantled by or incorporated into highland rich ejecta from basin or crater forming impacts mapping these buried basalts is important for understanding regional stratigraphy and the history and extent of lunar volcanism we use new 70 cm wavelength radar images collected using arecibo observatory and the green bank telescope and clementine data to study cryptomaria east of orientale basin earlier multispectral analyses showed that mare material is mixed with the highland terrain along the western margin of oceanus procellarum leading to a detectable increase in the feo and tio2 abundance of the regolith surface the highland margin of western procellarum is also characterized by low 70 cm radar returns consistent with an increased regolith loss tangent due to ilmenite in the mare derived material the low 70 cm radar echo however persists well to the west of the mixed zone evident in multispectral data and includes the region surrounding cruger crater it is likely that mare basalt or a mixed zone of mare and highland material exists at depth across the region and only reaches the visible surface near the western procellarum margin the plausible depth to this mixed zone is dependent upon the loss tangent of the overlying pure highland ejecta if orientale ejecta is primarily low loss anorthosite then the mixed zone could lie at depths of up to several tens of meters we propose that pre orientale mare deposits flooded the region between cruger grimaldi and oceanus procellarum and also patches west and northwest of humorum basin the total area of these deposits represents 178 103 km2 or an additional 0 5 of the lunar surface covered by mare basalts

stratabound tungsten mineralization in regional metamorphic calc silicate rocks from the austroalpine crystalline complex austria stratabound tungsten mineralization in regional metamorphic calc silicate rocks of probably lower paleozoic age is described from the polymetamorphic austroalpine crystalline complex acc of the eastern alps scheelite bearing calc silicate rocks which are often associated with marbles and tourmalinites are intercalated conformably with metaclastic rocks alkalipoor calc silicate rocks with high amounts of clinozoisite zoisite grossular quartz plagioclase etc are the most important host rocks for tungsten mineralization these unusual calc silicate rocks are products of regional metaorphism and are interpreted as reaction skarns they have formed in the presence of a water dominated fluid phase with very low xco2 in the koralpe estimated p t conditions are 650 700 c at 5 7 kb the mineralogical composition and the mineral zoning of the calc silicate rocks is controlled by the degree of the hercynian and eoalpine metamorphism there are no signs of graniteelated skarn formation tungsten preconcentration is thought to be syngenetic syndiagenetic it is genetically linked to exhalative hydrothermal processes in other lower paleozoic terrains of the eastern alps

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

tungsten skarn mineralizations in a regional metamorphic terrain in northern norway a possible metamorphic ore deposit scheelite and molybdenite bearing scapolite skarn and plagioclase skarn occur as stratabound mineralizations in a terrain which has suffered regional metamorphism scapolite skarn formed as replacement skarns in plagioclase bearing hornblendic gneiss whereas plagioclase skarn precipitated in fractures as vein skarn mineralizations the genesis of these skarn deposits are closely connected to an episode of boudinage on the limbs of a large scale dome shaped fold fluid inclusion studies revealed that the ore forming fluids were composed of co2 with 2 to 17 mole ch4 which formed due to decarbonation reactions during peak metamorphism at the end of the caledonian orogenesis thermodynamic considerations indicate that scapolite and plagioclase formed above 550 c and 2 kbar pressure and were followed by precipitation of scheelite between 400 and 570 c

remote sensing of lunar pyroclastic mantling deposits abstract mantling deposits on the moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining these pyroclastic units are characterized as having low albedos having smooth fine textured surfaces and consisting in part of homogeneous febearing volcanic glass and partially crystallized spheres mantling units exhibit low returns on depolarized 3 8 cm radar maps indicating an absence of surface scatterers in the 1 to 50 cm size range a number of reflectance spectra from several regional pyroclastic deposits are presented for the first time these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant fe bearing volcanic glass component the rima bode region is discussed as an example of an area in which several types of remote sensing data including 3 8 cm radar spectral reflectance and multispectral vidicon data were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit the recognition of numerous varieties of volcanic glass samples especially relatively high albedo e g green yellow glasses suggests the existence of additional unrecognized mantling deposits with albedos higher than those studied to date on the basis of the remote sensing data summarized and presented five new areas have been identified which may represent higher albedo regional pyroclastic deposits

remote sensing studies of the terrain northwest of humorum basin we have used near infrared reflectance spectra and earth based radar data to investigate the composition and origin of the various geologic units northwest of humorum basin as well as the stratigraphy of the humorum pre impact target site the results of our spectral analysis indicate that at least a portion of the inner mare bounding ring is composed of pure anorthosite other highlands units in the region are dominated by noritic anorthosite the anorthosites on the inner ring may have been derived from a layer of anorthosite that exists at depth beneath a more pyroxene rich unit both gassendi g and f craters expose mare material from beneath a highlands rich surface unit that was emplaced as a result of the letronne gassendi and other impact events this ancient basalt unit was emplaced after the formation of humorum basin but prior to the orientale impact

mineralogy and metasomatic evolution of distal strata bound scheelite skarns in the riba de alva mine northeastern portugal the metasediment hosted distal scheelite skarns from the riba de alva mine barca de alva escalhao region northeastern portugal consist of three main levels of strata bound boudin shaped 0 5 to 4 m thick bodies having a total resource of 380 000 tons t with an average grade of 0 51 percent wo3 the boudinage of the cambrian metasedimentary rocks of the slate greywacke complex occurred early during the hercynian orogeny prior to the granitic complex intrusion and the skarn forming process the granitic complex corresponds to reduced highly evolved and metallogenically specialized s type leucogranites comparable to those commonly associated with mo poor w f skarns four different skarn types were recognized pyroxene skarn with fe diopside anorthite amphibole epidote skarns with actinolite clinozoisite bytownite phlogopite ore skarn with clinozoisite scheelite fluorite calcite labradorite apatite fe axinite armenite scapolite and late stage veins with quartz or fluorite or calcite clinozoisite andesine or albite adularia clinopyroxene ranges from di80hd20 to di60hd40 amphibole compositions range from actinolite to mg hornblende and are f rich 0 5 1 9 wt clinozoisite often zoned with fe poor cores shows little compositional variation in the skarn types having a low pistacitic component 5 13 ps plagioclase compositions grade from anorthite in pyroxene skarn through andesine and albite in late stage veins phlogopite as amphibole is f rich 2 45 4 70 wt an extremely pure mo free scheelite the only ore mineral present is restricted to the ore skarn type the riba de alva skarns were formed after intrusion of the hercynian granitic complex by selective infiltrative metasomatic alteration of argillaceous dolomitic limestone an early stage of prograde alteration led to the formation of the pyroxene skarn through reaction with an si rich and fe bearing fluid scheelite mineralization occurred during retrograde alteration which was mainly fracture controlled and is characterized by a pervasive infiltration metasomatism with minor diffusion in the skarn walls this alteration started with hydration reactions to form amphibole epidote skarns probably under lower xco2 conditions ore skarn formation with scheelite deposition took place later during this retrograde stage mainly along veins within the strata bound boudins as the result of a decrease in temperature and or significant changes in the activity of some fluid components such as w f na mn p and b and particularly an increase in aca monomineralic late stage veins represent the waning stage of the skarn forming process