performances of ground penetrating radars in arid volcanic regions consequences for mars subsurface exploration a gpr field experiment in the republic of djibouti provides evidence for very low radar penetration in arid volcanic materials in the range 100 500 mhz this phenomenon is attributed to the high iron oxide and evaporite concentration in soils which significantly increases the conductivity thus leading to poor subsurface imaging performances the geologic context in djibouti is shown to provide a good terrestrial analogue to mars geology results of this study show that the future sounding radar missions to mars may not reach the penetration depths previously anticipated

low frequency radar sounding investigations of the north amargosa desert nevada a potential analog of conductive subsurface environments on mars 1 theoretical estimates of low frequency radar sounding performance and its potential for mapping moist subsurface interfaces in conductive environments on mars are controversial with predictions of ultimate penetration depth ranging from a few meters to kilometers to address this issue we conducted a broadband electromagnetic field survey in which we combined ground penetrating radar gpr operating at multiple low frequencies with the transient electromagnetic method tem to investigate the dependence of radar penetration depth on ground resistivity surveys were performed in the frequency range 16 100 mhz at two locations on the northwest margin of the amargosa desert nevada where numerous mars analog investigations have been performed the surveys were conducted on a 20 m high homogenous sand dune and on the flanks of a 20 m high scoria cone and above a buried lava flow a wet alluvial interface was located at the bottom of each structure gpr detected the wet alluvium contact at the base of the sand dune but failed to penetrate to the same depth at the scoria cone under similar residual moisture content depths of investigation for both the scoria cone and the buried lava flow were limited to approximately 10 m owing to the presence of conductive inclusions in the first few meters which are below the radar resolution but dramatically decreased the dynamic of the radar backscattered echoes and hence the penetration depth absorption models constrained by the tem data are in good agreement with these observations depths of investigation varied weakly with frequency owing to substantial frequency independent absorption

re os dating of molybdenite from tongchanggou mo polymetallic deposit in northwest yunnan and its metallogenic environment the tongchanggou mo polymetallic deposit lies in the western margin depression belt of the yangtze landmass and is adjacent to yidun island arc and garze litang suture zone it is a representative ore deposit in studying yanshanian mineralization and shows bright future for further prospecting some intrusions or apophyses have been wholly mineralized and hydrothermal metasomatism in the upper part mainly displays skarn type and hydrothermal vein type mineralization in wall rocks forming a porphyry minerogenetic series the ore deposit is a large size or even a superlarge deposit re os isotopic dating technique was applied and six molybdenite samples were analyzed for re os isotopic compositions and the model ages obtained are from 82 34 1 28 to 88 27 1 23 ma with the isochron age being 85 10 ma the result suggests that mo mineralization occurred in yanshanian period during which zhongza block and yangtze landmass collided intensively and gradually turned into post collision stage because of the thickening of the crust crustal melting or crustal mantle melting resulted in the formation of s type granite and granite porphyry accompanied by molybdenum polymetallic mineralization the re content of the molybdenite is 6 440 43 530 ng g suggesting that the metallogenic material originated from a source mixed with crust and mantle components field investigation shows that concealed granite intrusions may exist in the depth and mineralization was related to magmatic intrusion acid intrusions in the area extend from north to south and the belt passes through yidun arc and enters the western margin of yangtze landmass in northwestern yunnan a number of large middle molybdenum polymetallic deposits were formed in the belt accordingly they are scattered from north to south represented by xiuwacu relin hongshan and tongchanggou the research on metallogenic background and ore prognosis is of great significance for ore exploration in this area

geochronology and geochemistry of late cretaceous igneous intrusions and mo cu w mineralization in the southern yidun arc sw china implications for metallogenesis and geodynamic setting abstract the sanjiang tethyan metallogenic domain stmd is an important part of the tethyan giant metallogenic belt the yidun arc is a part of the stmd in the eastern tibetan plateau recently four newly discovered mo cu w ore deposits related to granitic intrusions were found distributed along the north south strike in the southern yidun arc which are identified as the xiuwacu relin hongshan and tongchanggou deposits herein these four deposits formed along high angle north northwest or north west strike slip faults with vein type and porphyry type mo cu mineralization developed in the intrusions molybdenite re os and zircon u pb dating together with zircon hf isotopes and whole rock geochemistry of the intrusions were studied to discern the relationship between mineralization and magmatism metallogenesis and tectonic settings molybdenite from skarn type mineralization at the hongshan deposit has a re os isochron age of 81 2 2 6 ma mswd 1 3 n 5 consistent with previously published zircon u pb ages and re os ages of porphyry type mo mineralization these results indicate that the hongshan is a late cretaceous porphyry skarn cu mo deposit zircon u pb ages of the granitic intrusions in the xiuwacu relin and tongchanggou deposits varying from 87 4 ma to 82 7 ma combined with published molybdenite re os age spectrum 85 ma to 81 2 ma it is proposed that the mo cu w mineralization in the shangri la region is spatially temporally and probably genetically related to the late cretaceous granitic intrusions the relin hongshan and tongchanggou intrusions have high sio 2 65 2 70 0 wt sr 363 905 ppm sr y 22 72 and la yb 37 69 ratios and low y 11 6 17 0 ppm and yb 0 97 1 59 ppm which displayed adakitic affinities their low mgo 0 66 1 44 wt mg 25 46 variable negative zircon e hf t values 7 9 to 2 3 and proterozoic two stages hf model ages t dm2 1 13 1 62 ga suggest that they were probably dominantly derived from partial melting of thickened lower continental crust according to the tectonic evolution of the bangong meso tethys ocean during the late mesozoic the late cretaceous igneous event and mineralization in the yidun arc likely formed under a late or post collision extensional environment probably related to the collision between the lhasa and qiangtang terranes during the late cretaceous

late quaternary sedimentary environments and landforms in the ganges delta abstract late quaternary sediments deposited since the lowest stand of sea level during the last glacial maximum in the ganges delta and its surrounding region were classified into five units according to their sedimentary facies these are the lowest unit of sandy gravels the lower unit of sand with a few gravels and the middle upper and uppermost units consisting mainly of sand and silt with occasional peat layers the contact between the lower and middle units is fairly sharp and the upper part of the lower unit is oxidized in some places this suggests a period of subaerial exposure after the deposition of the lower unit during the low stand of sea level about the time of the last glacial maximum rivers in the ganges delta and its surrounding region dissected the surfaces of the region and deposited the lowest unit on the valley floors the lower unit was deposited over the lowest unit during an early stage of the post glacial transgression between ca 12 000 yr bp and 10 000 yr bp the surface of the delta was slightly dissected and the top of the lower unit was weathered and oxidized following this period the middle and upper units of alluvial or deltaic sand and silt with occasional peat were deposited the coastline in the early holocene retreated towards the central part of the present ganges delta in the middle and late holocene the silt and clay with occasional peat layers of the uppermost unit indicate that the lowland gradually became marshy and poorly drained as the rate of transgression became slower

sharad radar sounding of the vastitas borealis formation in amazonis planitia 1 amazonis planitia has undergone alternating episodes of sedimentary and volcanic infilling forming an interleaved sequence with an upper surface that is very smooth at the kilometer scale earlier work interprets the near surface materials as either young rough lava flows or ice rich sediment layers overlying a basement comprising the vastitas borealis formation and earlier hesperian plains sounding radar profiles across amazonis planitia from the shallow radar sharad instrument on the mars reconnaissance orbiter reveal a subsurface dielectric interface that increases in depth toward the north along most orbital tracks the maximum depth of detection is 100 170 m depending upon the real dielectric permittivity of the materials but the interface may persist at greater depth to the north if the reflected energy is attenuated below the sharad noise floor the dielectric horizon likely marks the boundary between sedimentary material of the vastitas borealis formation and underlying hesperian volcanic plains the sharad detected interface follows the surface topography across at least one of the large wrinkle ridges in north central amazonis planitia this conformality suggests that vastitas borealis sediments at least in this region were emplaced prior to compressional tectonic deformation the change in radar echo strength with time delay is consistent with a loss tangent of 0 005 0 012 for the column of material between the surface and the reflector these values are consistent with dry moderate density sediments or the lower end of the range of values measured for basalts while a component of distributed ice in a higher loss matrix cannot be ruled out we do not find evidence for a dielectric horizon within the vastitas borealis formation that might suggest an abrupt change from an upper dry layer to an ice rich lower deposit

the fluvial geochemistry of the rivers of eastern siberia i tributaries of the lena river draining the sedimentary platform of the siberian craton abstract the response of continental weathering rates to changing climate and atmospheric pco 2 is of considerable importance both to the interpretation of the geological sedimentary record and to predictions of the effects of future anthropogenic influences while comprehensive work on the controlling mechanisms of contemporary chemical and mechanical weathering has been carried out in the tropics and to a lesser extent in the strongly perturbed northern temperate latitudes very little is known about the peri glacial environments in the subarctic and arctic thus the effects of climate essentially temperature and runoff on the rates of atmospheric co 2 consumption by weathering are not well quantified at this climatic extreme to remedy this lack a comprehensive survey has been carried out of the geochemistry of the large rivers of eastern siberia the lena yana indigirka kolyma anadyr and numerous lesser streams which drain a pristine high latitude region that has not experienced the pervasive effects of glaciation and subsequent anthropogenic impacts common to western eurasia and north america the scale of the terrain sampled in terms of area is comparable to that of the continental united states or the amazon orinoco and includes a similarly diverse range of geologic and climatic environments in this paper the chemical fluxes from the western region the very large ancient and geologically stable sedimentary basin precambrian to quaternary of the siberian platform will be presented and compared to published results from analogous terrains in the tropical basins of china while the range in the chemical signatures of the various tributaries included here 60 sampled is large this mainly reflects lithology rather than the weathering environment the areal chemical fluxes are comparable to those of the chinese rivers being dominated by the dissolution of carbonates and evaporites the net consumption of atmospheric co 2 by aluminosilicate weathering is minor as it is in the tropical basins it is much smaller than in active orogenic belts in similar latitudes e g the fraser and yukon but comparable to those of the mackenzie tributaries that drain the eastern slope of the rockies lithology exerts the dominant influence in determining the weathering yield from sedimentary terrains and for a largely carbonate evaporite terrain climate does not have a direct effect

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

electrically conducting ca rich brines rather than water expected in the martian subsurface 1 if mars ever possessed a salty liquid hydrosphere which later partly evaporated and froze down then any aqueous fluids left near the surface could have evolved to become dense eutectic brines eutectic brines by definition are the last to freeze and the first to melt if cacl2 rich such brines can remain liquid until temperatures below 220 k close to the average surface temperature of mars in the martian subsurface in intimate contact with the ca rich basaltic regolith nacl rich early brines should have reacted to become ca rich fractional crystallization freezing and partial melting would also drive brines toward cacl2 rich compositions in other words eutectic brine compositions could be present in the shallow subsurface of mars for the same reasons that eutectic magma compositions are common on earth don juan pond antarctica a cacl2 rich eutectic brine provides a possible terrestrial analog particularly because it is fed from a basaltic aquifer owing to their relative density and fluid nature brines in the martian regolith should eventually become sandwiched between ice above and salts beneath a thawing brine sandwich provides one explanation among many for the young gullies recently attributed to seepage of liquid water on mars whether or not brine seepage explains the gullies phenomenon dense cacl2 rich brines are to be expected in the deep subsurface of mars although they might be somewhat diluted temperatures permitting and of variable salt composition in any case they should be good conductors of electricity

extensive valley glacier deposits in the northern mid latitudes of mars evidence for late amazonian obliquity driven climate change understanding spin orbital parameter driven climate change on mars prior to 20 ma ago requires geological evidence because numerical solutions for that period are chaotic and non unique we show geological evidence that lineated valley fill at low midlatitudes in the northern hemisphere of mars 37 58 n originated through regional snow and ice accumulation and underwent glacial like flow breached upland craters and theater headed valleys reveal features typical of erosion in association with terrestrial glaciers parallel converging and chevron like lineations in potentially ice rich deposits on valley floors indicate that flow occurred through constrictions and converged from different directions at different velocities together these martian deposits and erosional landforms resemble those of intermontaine glacial systems on earth particularly in their major morphology topographic shape planform and detailed surface features an inferred late amazonian age combined with predictions of climate models suggest that the obliquity of mars exceeded a mean of 458 for a sustained period during this time significant transfer of ice occurred from icerich regions e g the poles to mid latitudes causing prolonged snow and ice accumulation there and forming an extensive system of valley glaciers d 2005 elsevier b v all rights reserved

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

on water detection in the martian subsurface using sounding radar several radar experiments are planned to map the martian subsurface down to several kilometers searching for subsurface liquid water reservoirs using different concepts and techniques all based on the penetration property of radio frequency waves in arid soils the penetration depth of low frequency radar is mainly related to the electromagnetic properties of the investigated medium thus a good knowledge of the martian subsurface dielectric profile along the first few kilometers is necessary for future water identification and data interpretation in this work we have investigated the electrical and magnetic properties of the martian surface and subsurface using terrestrial laboratory analogues in the frequency range 1 500 mhz covering the frequency domain of the mars advanced radar for subsurface and ionosphere sounding marsis experiment on board the mars express mission esa 2003 the netlander ground penetrating radar gpr cnes 2007 and future sounding radar that may be updated to the mars exploration program in the follow the water strategy in our approach we constructed experimentally the most common dielectric profile representative of the martian subsurface by measuring the electric permittivity and magnetic permeability of well defined mixtures of basaltic volcanic and sedimentary materials that have been reported for mars we also considered iron oxides hematite and maghemite and evaporites that may be present such as gypsum and their mixtures with representative amounts of the martian geological context under the most common petrophysical and geophysical conditions along the subsurface profile this led to synthetic representative samples of the martian subsurface materials under adequate conditions of porosity and temperature that should exist in the first 2 5 km of the upper crust dielectric measurements show that the first layers of the martian subsurface a few hundred meters which are mainly composed of volcanic iron rich materials could dramatically decrease the radar penetration depth initially foreseen thus limiting deep subsurface exploration we also investigated the constraints on subsurface water detectability in a radar lossy medium and its dielectric identification among surrounding geological materials

shallow radar sharad sounding observations of the medusae fossae formation mars the sharad shallow radar sounding radar on the mars reconnaissance orbiter detects subsurface reflections in the eastern and western parts of the medusae fossae formation mff the radar waves penetrate up to 580 m of the mff and detect clear subsurface interfaces in two locations west mff between 150 and 155 e and east mff between 209 and 213 e analysis of sharad radargrams suggests that the real part of the permittivity is 3 0 which falls within the range of permittivity values inferred from marsis data for thicker parts of the mff the sharad data cannot uniquely determine the composition of the mff material but the low permittivity implies that the upper few hundred meters of the mff material has a high porosity one possibility is that the mff is comprised of low density welded or interlocked pyroclastic deposits that are capable of sustaining the steep sided yardangs and ridges seen in imagery the sharad surface echo power across the mff is low relative to typical martian plains and completely disappears in parts of the east mff that correspond to the radar dark stealth region these areas are extremely rough at centimeter to meter scales and the lack of echo power is most likely due to a combination of surface roughness and a low near surface permittivity that reduces the echo strength from any locally flat regions there is also no radar evidence for internal layering in any of the sharad data for the mff despite the fact that tens of meters scale layering is apparent in infrared and visible wavelength images of nearby areas these interfaces may not be detected in sharad data if their permittivity contrasts are low or if the layers are discontinuous the lack of closely spaced internal radar reflectors suggests that the mff is not an equatorial analog to the current martian polar deposits which show clear evidence of multiple internal layers in sharad data

hydrochemical evaluation of shallow groundwater aquifers a case study from a semiarid himalayan foothill river basin northwest india this paper describes the hydrochemical characteristics and ion exchange process in the groundwater of a semiarid climatic condition river basin located at himalayan foothill northwest india chemical testing results on ph ec tds hardness major cations and anions revealed that the groundwater quality is suitable for potable use high concentrations of ca2 so4 2 and cl are observed in the alluvial plain while low so4 2 and cl concentrations are confined to the piedmont zone low and high concentrations of hco3 are distributed in the alluvial plain and in the piedmont zone respectively aquifer panel diagram revealed that piedmont zone is dominated by gravelly sand layers while alluvial plain is dominated by fine and medium sand layers the scatter diagrams of so4 2 hco3 versus ca2 mg2 and cl versus na show predominance of the ion exchange process the scatter plot of ca2 mg2 versus total cations tz indicates that ca2 and mg2 are resulted from the weathering of silicate minerals stiff diagrams suggest that the alluvial plain has more concentration of ions than the piedmont area suggesting longer evolutionary period of groundwater in the alluvial plain than in the piedmont area groundwater in the alluvial plain is characterized by ca2 mg2 hco3 na2 ca2 hco3 and na2 hco3 water types while it is characterized by ca2 mg2 hco3 type in the piedmont area the result of correlation matrices of groundwater suggests that the variations of ion relations are due to the impact of lithological and groundwater level variations in the alluvial plain and in the piedmont area

ground penetrating radar sounding in mafic lava flows assessing attenuation and scattering losses in mars analog volcanic terrains we conducted low frequency 16 to 100 mhz ground penetrating radar surveys on the eroded lava flows at craters of the moon idaho usa volcanic field to evaluate the potential of future radar sounding investigations on mars to map shallow subsurface features radar sounding profiles were obtained from three locations above a lava tube across a volcanic rift and over a scoria cone results were combined with laboratory permittivity and magnetic permeability measurements of field collected samples to deconvolve the electromagnetic attenuation and scattering losses from the total losses and therefore separately quantify both effects on the radar penetration depth our results demonstrate a constrained performance for low frequency sounding radars to characterize mafic arid volcanic terrains that contain a significant amount of ferro oxides 14 mainly in the form of olivine and magnetite penetration depths of 35 m were achieved at a frequency of 100 mhz and depths of 80 m were achieved at 16 mhz with an effective dynamic range of 60 db results indicate that for frequencies below 100 mhz the electromagnetic attenuation dominated the signal losses while above this frequency threshold the volume scattering dominated the losses over our frequency range the observed electromagnetic attenuation and penetration depths were strongly dependent on the magnetic losses ground porosities and degree of heterogeneity rather than the sounding frequency in light of these results we suggest average attenuation and scattering losses measured in terms of db m and discuss the expected penetration depth for the mars orbital radar sounding instruments sharad and marsis in mafic volcanic terrains

mesozoic multiple magmatism and porphyry skarn cu polymetallic systems of the yidun terrane eastern tethys implications for subduction and transtension related metallogeny abstract most mineralized porphyries associated with large to giant oxidized porphyry cu deposits show an affinity with relatively high sr y features the mesozoic porphyry skarn cu polymetallic systems of the yidun terrane hosted by the late triassic and late cretaceous intrusions provide chances to investigate the spatial and genetic relationships between subduction and transtension related magmatism and mineralization and determine the petrogenesis and fertility of magmatic rocks zircon u pb ages indicate that the late triassic pre ore quartz diorite porphyries and syn ore quartz monzonite porphyries were emplaced at 225 and 215 ma respectively the late cretaceous syn ore monzogranite porphyries were emplaced at 83 78 ma our new data combined with previously published geochronological data show the spatially overlapping distribution of the multiple mesozoic porphyry systems in the yidun terrane although all the late triassic intrusive rocks share similar geochemical characteristics the pre ore quartz diorite porphyries have normal arc related chemical features with low sr y and la yb n ratios high y and yb abundances while the syn ore quartz monzonite porphyries exhibit high sr y and la yb n ratios low y and yb abundances all samples show similar sr nd hf isotopic compositions 87sr 86sr i 0 7060 0 7117 end t 6 7 to 0 0 zircon ehf t 4 0 to 3 0 suggesting that they were probably derived from partial melting of juvenile lower crust trace element patterns and partial melt modeling indicate that the quartz diorite porphyries were likely formed by partial melting of normal thick lower crust while the causative quartz monzonite porphyries were probably formed by partial melting of eclogitized thickened lower crust we propose that pre ore quartz diorite porphyries were probably generated earlier via the subduction of garze litang oceanic crust and syn ore quartz monzonite porphyries were formed later by partial melting of sulfide enriched thickened juvenile lower crust thus these high sr y quartz monzonite porphyries host several economically important porphyry cu deposits such as pualng xuejiping and songnuo however the late cretaceous syn ore monzogranite porphyries have lower ehf t values 8 4 to 2 9 and end t values 7 5 to 3 8 than the late triassic porphyries indicating that the former mainly originated from ancient crustal materials new dataset and previous studies suggest that the late cretaceous post collisional transtension triggered the asthenospheric upwelling and the underplating of mafic magmas induced the partial melting of garnet bearing amphibolite and thus caused the emplacement of monzogranite porphyries and associated porphyry skarn cu mo deposits

multiple mesozoic porphyry skarn cu mo w systems in yidun terrane east tethys constraints from zircon u pb and molybdenite re os geochronology abstract porphyry cu mo au deposits typically formed in volcanoplutonic arcs above subduction zones however there is increasing evidence for the occurrence of porphyry deposits related to magmas generated after the underplating arc has ceased post subduction lithospheric thickening lithospheric extension or mantle lithosphere delamination could trigger the remelting of subduction modified arc lithosphere and lead to the formation of post subduction porphyry deposits the nnw trending yidun terrane located in the eastern tethys experienced subduction of garze litang oceanic plate a branch of the paleotethys in the late triassic and witnessed two mineralization events respectively associated with the ca 215 ma arc related intermediate felsic porphyries and the 88 79 ma mildly alkaline granitic porphyries it is therefore an ideal place to investigate the genetic linkage between the subduction related porphyry deposits and post subduction porphyry deposits our new in situ zircon u pb dating of the two granitic intrusions biotite granite 213 4 0 9 ma monzogranite porphyry 86 0 0 4 ma in the xiuwacu district the molybdenite re os age 84 7 0 6 ma of the mineralization and previously published geochronological data together show the spatially overlapping distribution of the multiple mesozoic porphyry systems in the late triassic yidun arc system furthermore the arc like elemental signatures and the mixed sr nd hf isotopic signatures of the late cretaceous ore related porphyries i e originating from a mixed components between the 215 ma juvenile arc crust and the mesoproterozoic mafic lower crust indicate a genetic linkage between the late triassic and late cretaceous porphyry systems this suggests that the remelting of underplated arc related mafic rocks formed during the subduction of the garze litang ocean could be responsible for the mixing between the mantle derived components and the mesoproterozoic lower crustal materials when post subduction transtension occurred in the late cretaceous the formation of the late cretaceous porphyry skarn cu mo w deposits could most likely be related to the remelting of late triassic residual sulfide bearing cu rich cumulates in the subduction modified lower crust that triggered by the late cretaceous transtension

antarctic dry valleys microclimate zonation variable geomorphic processes and implications for assessing climate change on mars the antarctic dry valleys adv are generally classified as a hyper arid cold polar desert the region has long been considered an important terrestrial analog for mars because of its generally cold and dry climate and because it contains a suite of landforms at macro meso and microscales that closely resemble those occurring on the martian surface the extreme hyperaridity of both mars and the adv has focused attention on the importance of salts and brines on soil development phase transitions from liquid water to water ice and ultimately on process geomorphology and landscape evolution at a range of scales on both planets the adv can be subdivided into three microclimate zones a coastal thaw zone an inland mixed zone and a stable upland zone zones are defined on the basis of summertime measurements of atmospheric temperature soil moisture and relative humidity subtle variations in these climate parameters result in considerable differences in the distribution and morphology of 1 macroscale features e g slopes and gullies 2 mesoscale features e g polygons including ice wedge sand wedge and sublimation type polygons as well as viscous flow features including solifluction lobes gelifluction lobes and debris covered glaciers and 3 microscale features e g rock weathering processes features including salt weathering wind erosion and surface pitting equilibrium landforms are those features that formed in balance with environmental conditions within fixed microclimate zones some equilibrium landforms such as sublimation polygons indicate the presence of extensive near surface ice identification of similar landforms on mars may also provide a basis for detecting the location of shallow ice landforms that today appear in disequilibrium with local microclimate conditions in the adv signify past and or ongoing shifts in climate zonation understanding these shifts is assisting in the documentation of the climate record for the adv a similar type of landform analysis can be applied to the surface of mars where analogous microclimates and equilibrium landforms occur 1 in a variety of local environments 2 in different latitudinal bands and 3 in units of different ages documenting the nature and evolution of the adv microclimate zones and their associated geomorphic processes is helping to provide a quantitative framework for assessing the evolution of climate on mars

dielectric properties of asteroid vesta s surface as constrained by dawn vir observations abstract earth and orbital based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces as well as potentially explore some of their shallow subsurface physical properties if the dielectric and topographic properties of asteroid s surfaces are defined one can constrain their surface textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter to achieve this objective we establish the first dielectric model of asteroid vesta for the case of a dry volatile poor regolith employing an analogy to the dielectric properties of lunar soil and adjusted for the surface densities and temperatures deduced from dawn s visible and infrared mapping spectrometer vir our model suggests that the real part of the dielectric constant at the surface of vesta is relatively constant ranging from 2 3 to 2 5 from the night to day side of vesta while the loss tangent shows slight variation as a function of diurnal temperature ranging from 6 10 3 to 8 10 3 we estimate the surface porosity to be 55 in the upper meter of the regolith as derived from vir observations this is 12 higher than previous estimation of porosity derived from previous earth based x and s band radar observation we suggest that the radar backscattering properties of asteroid vesta will be mainly driven by the changes in surface roughness rather than potential dielectric variations in the upper regolith in the x and s band

mars north polar deposits stratigraphy age and geodynamical response the shallow radar sharad on the mars reconnaissance orbiter has imaged the internal stratigraphy of the north polar layered deposits of mars radar reflections within the deposits reveal a laterally continuous deposition of layers which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice the packet interpacket structure can be explained by approximately million year periodicities in mars obliquity or orbital eccentricity the observed 100 meter maximum deflection of the underlying substrate in response to the ice load implies that the present day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers alternatively the response to the load may be in a transient state controlled by mantle viscosity both scenarios probably require that mars has a subchondritic abundance of heat producing elements

periglacial landforms at the phoenix landing site and the northern plains of mars 1 we examine potentially periglacial landforms in mars orbiter camera moc and high resolution imaging science experiment hirise images at the phoenix landing site and compare them with numerical models of permafrost processes to better understand the origin nature and history of the permafrost and the surface of the northern plains of mars small scale 3 6 m polygonal patterned ground is ubiquitous throughout the phoenix landing site and northern plains larger scale 20 25 m polygonal patterns and regularly spaced 20 35 m rubble piles localized collections of rocks and boulders are also common rubble piles were previously identified as basketball terrain in moc images the small polygon networks exhibit well developed and relatively undegraded morphology and they overlay all other landforms comparison of the small polygons with a numerical model shows that their size is consistent with a thermal contraction origin on current day mars and are likely active in addition the observed polygon size is consistent with a subsurface rheology of ice cemented soil on depth scales of about 10 m the size and morphology of the larger polygonal patterns and rubble piles indicate a past episode of polygon formation and rock sorting in thermal contraction polygons while the ice table was about twice as deep as it is presently the pervasive nature of small and large polygons and the extensive sorting of surface rocks indicates that widespread overturning of the surface layer to depths of many meters has occurred in the recent geologic past this periglacial reworking has had a significant influence on the landscape at the phoenix landing site and over the martian northern plains

application of a ramp flat fault model to interpretation of the naga thrust and possible implications for petroleum exploration along the naga thrust front the assam arakan thrust belt extends along the india myanmar border from the chinese border on the north to the bay of bengal on the south tertiary nonmarine sediments dominate the stratigraphy within the frontal zone of this fold and thrust belt thrust fault flats occur in the upper barail group coaly interval and ramps are localized by preexistent normal faults and stratigraphic discontinuities as a result the frontal zone of the thrust belt is characterized by multiscale imbricate structures the jaipur anticline occurs at the foreland edge of the naga thrust imbricate zone at the northeastern end of the assam valley application of flat ramp geometric models with a limited data set from the jaipur anticline allows creation of geometrically viable models for interpreting the general structure of the jaipur anticline and for developing hydrocarbon exploration leads the results of this method indicate that 1 the proven productive foreland trend extends several kilometers beneath the naga thrust and 2 zones of high dip in the thrust belt mark the location of prospect leads probably related to local thrust imbrication the method provides a testable process of identifying prospective areas therefore it can minimize exploration expense and optimize exploration planning

geomorphic analysis of lobate debris aprons on mars at mars orbiter camera scale evidence for ice sublimation initiated by fractures 1 lobate debris aprons known to be geomorphic landform indicators of the presence of ground ice are of special interest for future missions devoted to the research of water on mars lobate debris aprons in fretted terrains of deuteronilus and protonilus mensae 35 50 n show typical convex shapes interpreted to be the result of viscous deformation at the scale of mars orbiter camera moc high resolution images the surface of these debris aprons shows complex patterns with small pits and buttes these patterns can be explained by the mantling of dust the accumulation of interstitial ice and the subsequent removal of ice by sublimation the sublimation of the ground ice is especially initiated and accelerated by subsurface heterogeneities like fractures theoretical quantification of sublimation rates therefore minimizes sublimation which is not a homogeneous process at least over the landforms studied crater counts show that the sublimation occurred in the last tens of millions of years up to the recent past in the point of view of future searching of subsurface ice only surface layers are submitted to sublimation favoring the conservation of ground ice in deeper layers since the formation of the landform the geophysical survey of lobate debris aprons would give interesting insights into the subsurface distribution of ice and its seasonal variations especially in order to measure current sublimation of ground ice

radar probing of jovian icy moons understanding subsurface water and structure detectability in the juice and europa missions abstract radar probing of jovian icy satellites is fundamental for understanding the moons origin and their thermal evolution as potential habitable environments in our solar system using the current state of knowledge of the geological and geophysical properties of ganymede europa and callisto we perform a comprehensive radar detectability study to quantify the exploration depth and the lower limit for subsurface identification of water and key tectonic structural elements to achieve these objectives we establish parametric dielectric models that reflect different hypotheses on the formation and thermal evolution of each moon the models are then used for fdtd radar propagation simulations at the 9 mhz sounding frequency proposed for both esa juice and nasa europa missions we investigate the detectability above the galactic noise level of four predominant subsurface features brittle ductile interfaces shallow faults brine aquifers and the hypothesized global oceans for ganymede our results suggest that the brittle ductile interface could be within radar detectability range in the bright terrains but is more challenging for the dark terrains moreover understanding the slope variation of the brittle ductile interface is possible after clutter reduction and focusing for europa the detection of shallow subsurface structural elements few kilometers deep such as fractures faults and brine lenses is achievable and not compromised by surface clutter the objective of detecting the potential deep global ocean on europa is also doable under both the convective and conductive hypotheses finally for callisto radar waves can achieve an average penetration depth of 15 km although the current understanding of callisto s subsurface dielectric properties does not suggest sufficiently strong contrasts to produce unambiguous radar returns

comparison of geophysical investigations for detection of massive ground ice pingo ice 1 six different geophysical investigations 1 ground penetrating radar 2 dc resistivity sounding 3 seismic refraction 4 very low frequency vhf electromagnetic 5 helicopter borne electromagnetic hem and 6 transient electromagnetic tem techniques were employed to obtain information on the ice body properties of pingos near fairbanks alaska the surface nuclear magnetic resonance nmr data were also compared from similar sites near one of the study pingos the geophysical investigations were undertaken along with core sampling and permafrost drilling to enable measurement of the ground temperature regime drilling ground truthing results support field geophysical investigations and have led to the development of a technique for distinguishing massive ice and overburden material of the permafrost the two dimensional dc resistivity sounding tomography and ground penetrating radar profiling are useful for ice detection under heterogeneous conditions however the dc resistivity sounding investigation required high quality ground contact and less area coverage the active layer thickness and the homogeneous horizontal structure of the overburden material are important parameters influencing detection of massive ice in permafrost for most methods such as seismic tem or surface nmr

absorption and scattering in ground penetrating radar analysis of the bishop tuff 1 ground penetrating radar gpr signals are attenuated by both absorption and scattering we performed low frequency 100 mhz gpr surveys at the volcanic tableland of the bishop california tuff to evaluate the factors that control gpr depth of investigation and to develop insight into the capabilities of such radars for mars the subsurface reflection character was very different for two different commercial systems used together they revealed both internal welding contacts in the tuff and an abundance of discrete scatterers attenuation coefficients were computed from profiles that showed distributed scattering the semilogarithmic signal decay is directly analogous to seismic coda the absorption intrinsic loss was determined to be 1 db m from low frequency vertical electric soundings the residual attenuation that is the attenuation in the absence of absorption is attributed to scattering scattering attenuation of 1 db m at 25 50 mhz corresponds to mean free paths as short as 4 m a fraction of the two way propagation distances of 20 40 m therefore the bishop tuff is formally a strong scatterer to gpr the mean free path is also comparable to the subsurface radar wavelength in this case maximizing scattering loss the scatterers themselves likely originate as welding heterogeneities contrasts in dielectric constant due to density differences may be supplemented by moisture variations on mars scattering is likely to contribute significant losses to gpr signals in all but the most uniform materials and unfrozen thin films of water in the lower cryosphere could influence both absorption and scattering

human impact on regional groundwater composition through intervention in natural flow patterns and changes in land use schot p p and van der wal j 1992 human impact on regional groundwater composition through intervention in natural flow patterns and changes in land use j hydrol 134 297 313 the relations between groundwater composition land use soil conditions and flow patterns on a regional scale are studied for the gooi and vechtstreek area in the netherlands this densely populated area consists of a glacier created ridge with dry sand soils bordered by the vecht and eem river plains with wet peat and clay soils r mode factor analysis and q mode cluster analysis were applied to a set of 1349 groundwater analyses to determine the factors controlling groundwater composition and the main resulting water types the results indicate that groundwater composition in the study area is affected on a regional scale by human activities through changes in land use and intervention in natural flow patterns on the ridge ground water is recharged by precipitation which dissolves carbonates from the matrix of the sandy aquifer increased solute concentrations in shallow ground water especially of nitrate sulphate and potassium indicate increased pollution resulting from urbanization and increasingly intensive agricultural activity over the past decades in the vecht river plain infiltration occurs as a result of drainage of polders and groundwater extraction on the ridge recharge occurs by precipitation and from polluted surface water to which ammonium organic complexes and carbonic acid are added through decomposition of organic matter in the peat and clay soils the carbonic acid results in enhanced dissolution of carbonates present in the soil and the underlying sandy aquifer oxygen depletion and subsequent low redox potentials result in denitrification dissolution of manganese and iron oxides and sulphate ro duction the flow of ground water from high level to low level polders causes displacement of a former stagnant brackish groundwater body under the vecht river plain accompanied by increased mixing of fresh and brackish ground water

radar sounding of temperate permafrost in alaska analogy to the martian midlatitude to high latitude ice rich terrains 1 radar detection of subsurface ice on mars has been widely debated in part because the dielectric signature of ice as deduced from the dielectric constant can be confused with dry silicate rich materials to identify the ice dielectric signature it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss unfortunately the latter remains poorly quantified at both mars advanced radar for subsurface and ionospheric sounding marsis and shallow subsurface radar sharad frequencies to address this ambiguity we conducted multiple frequency ground penetrating radar and resistivity investigations in well characterized temperate permafrost in fairbanks alaska the area shows several geomorphologic similarities to midlatitude and high latitude terrains on mars this approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 mhz frequency band at 20 mhz our results suggest an average dielectric loss rate of 0 25 0 03 db m whereas the corresponding average scattering loss rate is 0 94 0 37 db m the scattering loss was found to represent 69 of the total signal attenuation considering this result and the study by heggy et al 2006a in volcanic environments we revised the interpretation of the attenuation coefficient calculated from sharad data over the deuteronilus mensae region and amazonis planitia we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity our results suggest that even if deuteronilus mensae deposits and the vastitas borealis formation may have similar dielectric constants their imaginary parts are different this implies that the two regions have different bulk compositions with the former being ice rich sediments and the latter being nonconsolidated volcanic deposits

tropical to mid latitude snow and ice accumulation flow and glaciation on mars images from the mars express hrsc high resolution stereo camera of debris aprons at the base of massifs in eastern hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice rich glacier like viscous flow and sublimation together with new evidence for recent ice rich rock glaciers at the base of the olympus mons scarp superposed on larger late amazonian debris covered piedmont glaciers we interpret these deposits as evidence for geologically recent and recurring glacial activity in tropical and mid latitude regions of mars during periods of increased spin axis obliquity when polar ice was mobilized and redeposited in microenvironments at lower latitudes the data indicate that abundant residual ice probably remains in these deposits and that these records of geologically recent climate changes are accessible to future automated and human surface exploration

geographic variations in the thermal and diffusive stability of ground ice on mars to investigate the stability of ground ice within the top several meters of the martian regolith time dependent models of the thermal and diffusive behavior of the regolith have been developed the geographic distribution of thermal inertia and albedo as well as the latitudinal variation in insolation have been included in calculations of surface and subsurface temperatures between 60 latitude ground ice was found to be stable where the annual mean surface and subsurface temperatures were below the atmospheric frost point this generally occurs poleward of the mid latitudes the latitude poleward of which ground ice is stable varies by about 20 to 30 from one longitude to another geographic variations in thermal inertia and albedo are the primary factors controlling regional variations in ice stability calculations of temperatures at high and low obliquity suggest that ground ice would be stable globally at high obliquity and would not be stable between 60 latitude at low obliquity thermally driven diffusion of atmospheric water vapor within the regolith was modeled accounting for both ordinary molecular and knudsen transport and equilibrium between ice vapor and adsorbed phases atmospheric water vapor was found to be able to supply the top few meters of the regolith with ice in regions where the annual mean surface temperature was below the atmospheric frost point ice was found to begin condensing in as short as 1000 martian years rapid accumulation of ice in the pore space of the upper layers of the regolith acted to choke transport to lower layers and slow the diffusion process even so after 105 martian years in some cases as much as 30 to 40 of the available pore space accumulated ice the total amount of subsurface ice ranged from a few to more than 25 g cm2 within the top few meters in regions of stability ground ice was found to form below a depth where the annual average vapor pressure over ice was equal to the annual average atmospheric vapor pressure near the surface atmospheric vapor was not found to accumulate as ice below a depth where the seasonal temperature oscillations gave way to the geothermal gradient the time scales for condensation of ground ice were found to be comparable to that of orbital oscillations suggesting that the present geographic distribution of ground ice may depend on the orbital history of mars

seismic imaging of the naga thrust using multiscale waveform inversion this case study images the structural features related to the naga thrust fault northeast india using a combination of multiscale waveform inversion and prestack depth migration psdm the waveform model and the psdm image complement each other the former provides a physical property map p wave velocity model and the latter provides a structural image the velocity model encompassing the starting model for waveform inversion is constructed using joint inversion of first and reflected traveltimes the 4 8 hz data are inverted consecutively in 1 hz bandwidths to yield the final waveform model which in turn is used for psdm the psdm image and the waveform model are consistent with the lithological interpretation of an inline exploratory well when interpreted jointly the psdm image and the waveform model reveal the presence of a conjugate fault system in the naga thrust and fold belt

geochronology of the hongniu hongshan porphyry and skarn cu deposit northwestern yunnan province china implications for mineralization of the zhongdian arc abstract the hongniu hongshan porphyry and skarn copper deposit is located in the triassic zhongdian island arc northwestern yunnan province china single zircon laser ablation inductively coupled plasma mass spectrometry u pb dating suggests that the diorite porphyry and the quartz monzonite porphyry in the deposit area formed at 200 ma and 77 ma respectively a re os isotopic date of molybdenite from the ore is 78 9 ma which indicates that in addition to the known triassic cu au porphyry systems a late cretaceous porphyry cu mo mineralization event also exists in the zhongdian arc the quartz monzonite porphyry shows characteristics of a magnetite series intrusion with a high concentration of al k rb ba and pb low amount of ta ti y and yb and a high ratio of sr y average 26 42 the cretaceous porphyry also shows a strong fractionation between light and heavy rare earth elements average la yb n 37 9 which is similar to those of the triassic subduction related diorite porphyry in the hongniu hongshan deposit and the porphyry hosting the pulang copper deposit however in contrast to the older intrusions the quartz monzonite porphyry contains higher concentrations of large ion lithophile elements and co and lesser sr and zr therefore whereas the triassic porphyry cu au mineralization is related to slab subduction slab in an arc setting the quartz monzonite porphyry in the hongniu hongshan deposit formed by the remelting of the residual oceanic slab combined with contributions from subduction modified arc lithosphere and continental crust which provided the metals for the late cretaceous mineralization

characteristics and origin of polygonal terrain in southern utopia planitia mars results from mars orbiter laser altimeter and mars orbiter camera data giant polygons on mars with several kilometers in diameter were first observed in mariner 9 and viking orbiter images and their origin formation and evolution have remained enigmatic since that time new data obtained by the mars orbiter laser altimeter mola and the mars orbiter camera moc on board the mars global surveyor spacecraft now permit analysis of topography and morphology of the polygonal terrain in unprecedented detail mola data show that 1 giant polygonal terrain in utopia is located at the lower slopes of a basin structure that is the utopia basin 2 the onset of polygonal terrain in utopia is close to the same elevation in several profiles and lies at about the same elevation as a terrace which was interpreted as a shore line of an ancient body of standing water within the utopia basin proper 3 polygonal terrain occurs over a wide range of elevations on regional slopes of 0 1 4 the depths of the troughs range from 5 m to 115 m averaging about 30 m and tend to be greater toward the center of the utopia basin 5 the mean width of polygonal troughs is of the order of 2 km ranging from 0 5 to 7 5 km data from the mars orbiter camera moc indicate that 1 the troughs are generally broad graben like features with varying morphologies i e terraces and lobateness and dimensions widths and depths 2 trough morphology has been modified by aeolian processes 3 polygonal troughs are weakly interconnected at moc resolutions and there are no smaller polygons observed within the giant polygons 4 circular depressions which are probably related to subsurface collapse sometimes occur at the bottoms of polygonal troughs 5 small scale polygonal terrain on the ejecta blankets of young craters with fluidized ejecta in the investigated area exhibits different characteristics i e smaller size presence of rims greater degree of interconnections than giant polygons in the viking images we see that 1 old impact craters are increasingly buried with younger materials toward the basin center and that 2 a large number of superposed impact craters on polygonal terrain exhibit distinctive ejecta morphologies such as rampart ejecta blankets and single and double lobate ejecta blankets mola and moc observations are consistent with the formation of polygonal terrain in the area of a former standing body of water but polygon size seems too large to be readily accounted for by desiccation or freezing processes alone on the basis of the observed characteristics we propose that the giant polygons are primarily of tectonic origin being caused by uplift of the floor of the utopia basin there are several candidates for the cause of uplift 1 the removal of the load representing former standing bodies of water water thickness estimated for the utopia basin is about 1 km in this scenario removal of this load comparable to loads placed on terrestrial continental lithosphere by the laurentide and scandinavian ice sheets by loss of the water or ice could cause uplift of the floor and polygon formation 2 the freezing and expansion of residual water buried by sediments or in the near subsurface or 3 a combination of these from the discussion of alternative models in the light of the mola and moc data we conclude that formation of giant polygons by tectonic uplift of the basin floor is most likely and deserves further investigation

high latitude patterned grounds on mars classification distribution and climatic control patterned grounds such as polygonal features and slope stripes are the signature of the presence of ground ice and of temperature variations in cold regions on earth identifying similar features on mars is important to understand its past climate as well as the ground ice distribution in this study young patterned grounds are classed and mapped from the systematical analysis of mars observer camera high resolution images these features are located poleward of 55 latitude which fits the distribution of ground ice found by the neutron spectrometer onboard mars odyssey thermal contraction due to seasonal temperature variations is the predominant process of formation of polygons formed by cracks which sizes vary from 15 to 300 m the small 40 m widespread polygons are very recent and degraded by the desiccation of ground ice from the cracks which enhances the effect of ice sublimation the large polygons 50 to 300 m located only around the south co2 polar cap indicate the presence of ground ice and thus outline the limit of the co2 ice cap they could be due to the blanketing of water ice deposits by the advances and retreats of the residual co2 ice cap during the last thousand years large 50 250 m and homogeneous polygons similar to ice wedge polygons hillslope stripes and solifluction lobes may indicate that specific environments such as crater floors and hillslopes could have been submitted to freeze thaw cycles possibly related to higher summer temperatures in periods of obliquity higher than 35 these interpretations must be strengthened by higher resolution images such as those of the hirise mission of the mars reconnaissance orbiter because locations with past seasonal thaw could be of major interest as potential landing sites for the phoenix mission

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

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

geomorphic evidence for the distribution of ground ice on mars high resolution viking orbiter images show evidence for quasi viscous relaxation of topography the relaxation is believed to be due to creep deformation of ice in near surface materials the global distribution of the inferred ground ice shows a pronounced latitudinal dependence the equatorial regions of mars appear to be ice poor while the heavily cratered terrain poleward of 30 latitude appears to be ice rich the style of creep poleward of 30 varies with latitude possibly due to variations in ice rheology with temperature the distribution suggests that ice at low latitudes which is not in equilibrium with the present atmosphere has been lost via sublimation and diffusion through the regolith thereby causing a net poleward transport of ice over martian history

spatial relationships between patterned ground and ground ice detected by the neutron spectrometer on mars 1 patterned grounds like polygonal features are the signature of climatic effects in periglacial regions on earth identifying similar features on mars is important for an understanding of the past martian climate in this study we mapped fresh patterned landforms from the systematic analysis of mars orbiter camera high resolution images we show that most of them are distributed at latitudes poleward of 55 making a climatic control likely this distribution correlates to the distribution of ground ice detected by the neutron spectrometer aboard mars odyssey this correlation is likely the consequence of the neutron spectrometer detecting ice no deeper than about 1 m patterned ground formation requires ice in this range of depth because these features are triggered by the propagation of a thermal wave that is driven by seasonal or diurnal changes in insolation which affect the temperature in the uppermost ground layers sublimation seems to play a role in the shaping of many of the small patterns observed at latitudes between 55 and 70 no widespread polygonal features are correlated to the equatorial regions where hydrogen is detected by the neutron spectrometer

complex permittivity and clay mineralogy of grain size fractions in a wet silt soil we determined the complex permittivity and clay mineralogy of grain size fractions in a wet silt soil we used one clay size fraction and three silt size fractions measured permittivity with low error from 25 mhz to 2 4 ghz with time domain spectroscopy and estimated mineral weight percentages using x ray diffraction xrd the volumetric water contents were near 30 and the temperature was 25 c for the whole soil standard fractionation procedures yielded 2 4 clay size particles by weight but xrd showed that the phyllosilicate clay minerals kaolinite illite and smectite made up 17 and were significantly present in all fractions above approximately 500mhz all real parts were similar below approximately 500 mhz the real and imaginary permittivities increased with decreasing grain size as frequency decreased and the imaginary parts became dominated by direct current conduction similarly below approximately 500 mhz the measured permittivity of montmorillonite a common smectite dominate

comparative analysis of reflection characteristics of lunar penetrating radar data using numerical simulations abstract the moon and most extraterrestrial objects are lacking in water thus electromagnetic waves can penetrate deep into the ground and bring some structural information about the regolith and surrounding rocks as an important assistant to the existing payloads ground penetrating radar gpr is particularly suitable for deep space exploration which is feasible and necessary for detecting the subsurface structures mainly associated with the dielectric permittivity variations of extraterrestrial objects unfortunately there are not enough reference gpr profiles or drills on the extraterrestrial objects to constrain the acquired data here we construct some typical models and perform numerical simulations to make the results reasonable various factors are considered including the type scale and location of the abnormal bodies then we review the reflecting phenomenon under the ground and perform comparative analyses on the reflection characteristics of different models finally we present some criteria for identifying different reflectors using critical patterns of reflections the configuration of our numerical experiments is comparable to that of the lunar penetrating radar onboard the yutu 1 and 2 thus the results would be reliable to support the geological interpretation of detected records as well as possible gpr detection on extraterrestrial objects in the future this work is helpful for recognizing the reflection characteristics of the observed gpr data and would be beneficial to uncovering more critical details of subsurface structures

the state of toxicity and cause of elevated iron and manganese concentrations in surface water and groundwater around naga thrust of assam arakan basin northeastern india an alarming situation of exceedingly high fe and mn concentrations in both surface water and groundwater has been identified in a tectonically active region located in assam arakan basin of northeast india cross plots pearson correlation principal component analysis and flow net methods were applied to elucidate the present state and possible sources of fe and mn contamination out of 32 water samples collected for the study all of them found exceeding 28 times more for fe and 136 times more for mn than epa limit correlation and cross plots of ph tds ec fe mn cu zn suggest the reduction of both fe hydroxides and mn oxides in redox condition into dissolve states leading to fe and mn elevations in groundwater principal component analysis exhibits three pc factors in which pc1 and pc3 reflected oxidized condition and pc2 reflected reducing environment that controlled fe and mn concentrations the study also revealed that source of high fe and mn contaminations was controlled by groundwater flows water table contour flow net suggests that the chathe river acts as influent stream and supplies elevated fe and mn water into the shallow aquifers baseflow from the discharge areas into low lying areas causes accretion of fe and mn in pond oxbow lake backswamp and shallow aquifers

hydrologic and geologic factors controlling surface and groundwater chemistry in indian wells owens valley area southeastern california usa the indian wells owens valley area is located in the semi arid basin and range province which is characterized by alternating mountains and alluvial basins surface water resources are limited in this arid region and water demand is mainly met by groundwater pumpage in a classic basin and range groundwater system water flows from recharge areas in the mountains to discharge areas in adjacent valleys discharge areas are generally occupied by playas where large amounts of salt deposition occur due to evaporating groundwater hydrochemical data from a total of 1368 spring surface and well water samples collected over an 80 year period were used to evaluate water quality and to determine processes that control water chemistry q mode hierarchical cluster analysis hca was employed for partitioning the water samples into hydrochemical facies also known as water groups or water types five major water groups resulted from the hca analysis the samples from the area were classified as recharge area waters ca na hco3 water and na ca hco3 water transition zone waters na hco3 cl water and discharge area waters na cl water and more concentrated na cl water spatial plots of the major statistical groups show that the samples that belong to the same group are located in close proximity to one another suggesting the same processes and or flowpaths inverse geochemical models of the statistical groups were developed using phreeqc to elucidate the chemical reactions controlling water chemistry the inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into four categories 1 silicate weathering reactions 2 dissolution of salts 3 precipitation of calcite amorphous silica and clay minerals and 4 ion exchange

volcano ground ice interactions in elysium planitia mars abstract the occurence within elysium planitia of meltwater deposits possible pseudocraters collapse features within troughs and outflow channels indicates that a layer of subsurface volatiles existed at the time of volcanic activity within this area the pseudocraters are interpreted to be indicators of near surface volatiles while meltwater deposits and the degree of preservation of trough walls and floors are thought to signify greater volatile depths a latitudinal variation in the distribution of these features indicates either that the depth to the volatile layer increased from less than about 50 m at 35 n to greater than 600 m at 24 n or that an ice wedge that existed at 35 n thinned to nonexistence at 24 n braided distributary channel systems within the chaotic terrain north of elysium planitia show that ephemeral lakes were repeatedly created and drained at this locality the existence of volatiles contemporaneous with volcanic activity permits a search to be made for explosively generated landforms predicted to exist by previous theoretical models morphological evidence for strombolian vulcanian and plinian eruptions is lacking within western elysium planitia there are no identifiable cinder cones pyroclastic flow deposits or mantled areas indicative of large airfall deposits at an image resolution of 50 150 m pixel however the pseudocraters indicate that small scale phreatomagmatic activity may have taken place

global distribution and migration of subsurface ice on mars a thermal diffusive model of h2o kinetics and equilibrium was developed to investigate the long term evolution and depth distribution of subsurface ice on mars the model quantitatively takes into account 1 obliquity variations 2 eccentricity variations 3 long term changes in the solar luminosity 4 variations in the argument of subsolar meridian in planetocentric equatorial coordinates 5 albedo changes at higher latitudes due to seasonal phase changes of co2 and the varying extent of co2 ice cover 6 planetary internal heat flow 7 temperature variations in the regolith as a function of depth time and latitude due to the above factors 8 atmospheric pressure variations over a 104 year time scale 9 the effects of factors 1 through 5 on seasonal polar cap temperatures and 10 knudsen and molecular diffusion of h2o through the regolith the migration of h2o into or out of the regolith is determined by two boundary conditions the h2o vapor pressure at the subsurface ice boundary and the annual average h2o concentration at the base of the atmosphere these are controlled respectively by the annual average regolith temperature at the given depth and seasonal temperatures at the polar cap starting from an arbitrary initial uniform depth distribution of subsurface ice h2o fluxes into or out of the regolith are calculated for 100 selected obliquity cycles each representing a different epoch in mars history the h2o fluxes are translated into ice thicknesses and extrapolated over time to give the subsurface ice depth as a function of latitude and time the results show that obliquity variations influence annual average regolith temperatures in varying degrees depending on latitude with the greatest effect at the poles and almost no effect at 40 lat insolation changes at the pole due to obliquity argument of subsolar meridian and eccentricity variations can produce enormous atmospheric h2o concentration variations of 6 orders of magnitude over an obliquity cycle superimposed on these cyclic variations is a slow monotonic change due to the increasing solar luminosity albedo changes at the polar cap due to seasonal phase changes of co2 and the varying thickness of the co2 ice cover are critically important in determining annual average atmospheric h2o concentrations despite the strongly oscillating character of the boundary conditions only small amounts of h2o are exchanged between the regolith and the atmosphere per obliquity cycle 10 g cm2 the net result of h2o migration is that the regolith below 30 40 lat is depleted of subsurface ice while the regolith above 30 40 lat contains permanent ice due to the depth of penetration of the annual thermal wave this result is supported by recent morphological studies the rate of migration of h2o is strongly dependent on average pore capillary radius for which we have assumed values of 1 and 10 m we estimate that the h2o ice removed from the regolith would produce a permanent ice cap with a volume between 2 106 and 6 106 km3 this generally agrees with estimates deduced from deflationary features at lower latitudes depositional features at higher latitudes and the mass of the polar caps

garnets in porphyry skarn systems a la icp ms fluid inclusion and stable isotope study of garnets from the hongniu hongshan copper deposit zhongdian area nw yunnan province china abstract the late cretaceous hongniu hongshan porphyry skarn copper deposit is located in the zhongdian area of northwestern yunnan province china garnets from the deposit have compositions that range from adr14grs86 to almost pure andradite adr98grs2 and display two different styles of zoning the garnets are predominantly of magmatic hydrothermal origin as is evidenced by their 18ofluid 5 4 6 9 and low dfluid 142 to 100 values both of which likely result from late stage magmatic open system degassing three generations of garnet have been identified in this deposit 1 al rich garnets grt i adr22 57grs78 43 are anisotropic have sector dodecahedral twinning are slightly enriched in light rare earth elements lrees compared with the heavy rare earth elements hrees have negative or negligible eu anomalies and contain high concentrations of f fluid inclusions within these al rich garnets generally have salinities of 12 39 wt nacl eq and have liquid vapor homogenization temperatures th of 272 331 c the grt i are most likely associated with low to medium salinity fluids that were generated by the contraction of an ascending vapor phase and that formed during diffusive metasomatism caused by pore fluids equilibrating with the host rocks at low w r water rock ratios these garnets formed as a result of the high f activity of the system which increased the solubility of al within the magmato hydrothermal fluids in the system 2 fe rich garnets adr75 98grs25 2 have trapezohedral faces and are both anisotropic with oscillatory zoning and isotropic these second generation fe rich garnets grt ii have high ree concentrations are lree enriched and hree depleted and generally have positive but variable eu anomalies all of the fe rich garnets contain high salinity fluid inclusions with multiple daughter minerals with salinities of 33 80 wt nacl eq some of them show higher temperatures of halite dissolution 465 591 c than liquid vapor homogenization temperatures 319 473 c and several fe rich garnets contain inclusion groups indicative of boiling the grt ii are associated with high temperature hypersaline fluids that were segregated from magma at a depth of at least 5 6 km and reacted with carbonates at depths shallower than 2 0 km 3 al rich garnet veins adr14 60grs86 40 contain allotriomorphic crystals have lower hfse high field strength element and ree concentrations than the other garnets and have hree enriched and lree depleted patterns with small eu anomalies that are typical of the majority of garnets the grt iii most likely formed from residual metasomatic fluids

natural organic matter in sedimentary basins and its relation to arsenic in anoxic ground water the example of west bengal and its worldwide implications in order to investigate the mechanism of as release to anoxic ground water in alluvial aquifers the authors sampled ground waters from 3 piezometer nests 79 shallow 80 m wells in an area 750 m by 450 m just north of barasat near kolkata calcutta in southern west bengal high concentrations of as 200 1180 mug l 1 are accompanied by high concentrations of fe 3 13 7 mgl 1 and po4 1 6 5 mg l 1 ground water that is rich in mn 1 5 3 mg l 1 contains 50 mug l 1 of as the composition of shallow ground water varies at the 100 m scale laterally and the metre scale vertically with vertical gradients in as concentration reaching 200 mug l 1 m 1 the as is supplied by reductive dissolution of feooh and release of the sorbed as to solution the process is driven by natural organic matter in peaty strata both within the aquifer sands and in the overlying confining unit in well waters thermotolerant coliforms a proxy for faecal contamination are not present in high numbers 10 cfu 100 ml in 85 of wells showing that faecally derived organic matter does not enter the aquifer does not drive reduction of feooh and so does not release as to ground water arsenic concentrations are high much greater than50 mug l 1 where reduction of feooh is complete and its entire load of sorbed as is released to solution at which point the aquifer sediments become grey in colour as feooh vanishes where reduction is incomplete the sediments are brown in colour and resorption of as to residual feooh keeps as concentrations below 10 mug l 1 in the presence of dissolved fe sorbed as released by reduction of mn oxides does not increase as in ground water because the as resorbs to feooh high concentrations of as are common in alluvial aquifers of the bengal basin arise because himalayan erosion supplies immature sediments with low surface loadings of feooh on mineral grains to a depositional environment that is rich in organic mater so that complete reduction of feooh is common c 2004 published by elsevier ltd

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

late cretaceous granitic intrusions and associated deposits in the yidun arc of the eastern tibetan plateau abstract the yidun arc is an important tectonic unit and polymetallic metallogenic belt in the sanjiang tectono magmatic belt in which many cretaceous 138 75 ma granites and associated polymetallic deposits are distributed along a nw trending belt the queershan cuomolong rongyicuo and genie granitic intrusions and the associated sn pb zn ag polymetallic deposits are distributed in the changtai and xiangcheng arcs whereas the xiuwacu relin hongshan and tongchanggou granitic intrusions and the associated cu mo w deposits are mainly distributed in the geza arc this study presents new zircon u pb hf o isotopic data for the queershan cuomolong rongyicuo genie xiuwacu and tongchanggou granitic intrusions combined with the structural analysis of the xiuwacu granitic complex to discuss the differences in the petrogenesis and metallogenesis of these granitic intrusions as well as the geodynamic processes that controlled the formation of the late cretaceous intrusions and related deposits hf o isotopic characteristics indicate that the highly fractionated granites hfg in the changtai and xiangcheng arcs were mainly derived from the partial melting of metasedimentary crustal materials with a minor input from mantle components while the i type granites ig in the geza arc were predominantly derived from the partial melting of ancient lower crustal material the spatial distributions of the different types of deposits in the yidun arc were probably controlled by the magma sources reduced magmas produced by the partial melting of the sedimentary crust in the changtai and xiangcheng arcs are favorable for w sn pb and zn mineralization whereas oxidized magmas produced by the partial melting of the lower crust in the geza arc are conducive to the enrichment of cu au and mo the geochronological data indicate that the emplacement ages of the late cretaceous granites in the yidun arc gradually decrease from north to south ranging from 106 to 73 ma reflecting the southward lateral tectonic migration the structural analysis of the xiuwacu w mo deposit in combination with previous studies demonstrated that the late cretaceous granites in the yidun arc were likely formed in a regional extensional setting which was probably related to the slab break off of the bangong nujiang oceanic slab or the subduction of the yarlung zangbo oceanic slab

terrane boundary and spatio temporal distribution of ore deposits in the sanjiang tethyan orogen insights from zircon hf isotopic mapping abstract the sanjiang tethyan orogen sjto of the eastern tethyan tectonic belt in china records a transition from late paleozoic tethys realm to cenozoic continental collision associated with the formation of large metallic mineral deposits this contribution combines geological and hf isotopic data for igneous rocks from the sjto together with the salient features associated with mineralization to gain insights into the crustal architecture and metallogeny integrating the available information from tectonic events sedimentary successions paleobiogeography and paleolatitude based on paleomagnetic data the hf isotopic maps that we construct highlight the changning menglian suture as an important tectonic boundary between the gondwana and cathaysian continents the changning menglian suture separates two distinct hf isotopic domains with an old reworked crustal block to the southwestern part of the sjto and a juvenile crustal block with significant mantle derived components to the northeastern part of the orogen the hf isotopic mapping of the sjto also provides important indications on the location of different deposits the jinshajiang ailaoshan suture appears to have exerted a first order control on the localisation of cenozoic magmatism and intrusion related mineral systems the magmatic source for intrusions in the eastern high ehf low tdmc domain is dominated by mantle components and gave rise to porphyry and porphyry skarn cu mo mineralization in contrast the magma sources for intrusions in the low ehf high tdmc domains contain an old and reworked crustal component and gave rise to granite related sn w mineralization those for the intrusions characterized by variable ehf and tdmc are dominantly reworked older crustal components together with subordinate juvenile material which generated the granite related pb zn cu ag mineralization

the fluvial geochemistry and denudation rate of the guayana shield in venezuela colombia and brazil abstract the guayana shield is composed of early to mid precambrian igneous and metamorphic basement rocks with a quartzitic platform cover the complete absence of limestones and evaporites allows a clear chemical expression in the stream data of the primary weathering of the basement in a humid tropical environment total erosion rates are extremely slow 10 m m y with equal contributions from the dissolved and suspended loads however the former is largely silica with ratios of si to total cation equivalents si tz ranging to in excess of three weathering is complete to kaolinite and gibbsite i e the environment is one of active laterisation with a penetration rate of the weathering front into the fresh substrate about twice the denudation rate in basins of relatively homogeneous lithology rb sr isochrons constructed from the river data agree with the whole rock ages from the drainages thus all the common refractory rb containing minerals k feldspar mica are completely dissolved the thick lateritic regolith that is accumulating as a result of this intense weathering is a common relict feature on other southern hemisphere shields in the absence of active tectonics or greatly accelerated mechanical erosion the weathering rates of these basement rocks must be quite insensitive to environmental change

tethys tectonic evolution and its bearing on the distribution of important mineral deposits in the sanjiang region sw china abstract the sanjiang region in se tibet plateau and nw yunnan is known to have formed by amalgamation of gondwana derived continental blocks and arc terranes as a result of oceanic subduction followed by continental collision from paleozoic to mesozoic in this paper we provide a synthesis of tectonic evolution magmatism and metallogeny in the region based on data from literatures early paleozoic ophiolites 473 439 ma in the changning menglian belt indicate the existence of a proto tethys ocean in this region two episodes of subduction related magmatism in the early paleozoic one occurred in the baoshan and tengchong blocks at 502 455 ma and the other occurred in the simao block at 421 401 ma are regarded as evidence for two different events of subduction of the proto tethys ocean at different locations the proto tethys was succeeded in early devonian by the paleo tethys which comprised the main ocean and three branches ailaoshan jinshajiang and garze litang the changning menglian main ocean existed from middle devonian to middle triassic the remnants of the oceanic crust are preserved in a few places in the longmu tso shuanghu suture as well as in the changning menglian ophiolite belt the eastward subduction of the main oceanic plate from early permian to early triassic formed a prominent arc terrane stretching 1500 km from yunnan to eastern tibet from the waning stage of subduction to post subduction numerous s type granite plutons with ages varying between 230 and 219 ma such as the lincang batholith in yunnan were emplaced at or close to the suture this event produced several hydrothermal w sn deposits in the region the tectonic evolution and associated magmatism of the jinshajiang and ailaoshan branch oceans are generally comparable to those of the main ocean however the branch oceans were subducted westward instead the garze litang branch ocean also underwent westward subduction from middle devonian to late triassic arc related high sr y porphyry intrusions and associated porphyry skarn cu mo au deposits are common in the jinshajiang ailaoshan region especially in the yidun arc which formed prior to jurassic the vms deposits in the sanjiang region formed in diverse tectonic settings including middle silurian back arc basins carboniferous oceanic islands paleozoic subduction zones and triassic post subduction rifting environments the mesozoic and early cenozoic evolution of the baoshan and tengchong blocks was largely influenced by eastward oceanic subduction of the meso and neo tethys from late permian to middle cretaceous and from late cretaceous to 50 ma respectively abundant early cretaceous granitoids and associated skarn type pb zn and sn fe deposits in the baoshan and tengchong blocks were produced in the background of the shan boundary oceanic slab subduction to the west and the break off of the nujiang bitu oceanic slab to the north the subduction of the neo tethys oceanic plate beneath the tengchong block from late cretaceous to paleogene formed abundant s type granitoids and many skarn type and greisen type sn w deposits granitoids formed at 105 to 81 ma and contemporaneous hydrothermal w mo ag and au deposits which temporally coincided with the subduction of the neo tethys are common in the yidun arc terrane

major ion chemistry of renuka lake and weathering processes sirmaur district himachal pradesh india renuka lake in the lesser himalaya himachal pradesh is in a valley surrounded by mountains comprised of highly crumpled shattered crushed folded and dislocated rocks consisting of carbonaceous shales slates often pyrite ferrous limestone quartzites boulder beds etc a detailed and systematic study of the major ion chemistry of the lake clay mineral composition of the bed and core sediments and the pb210 isotope estimation in the latter was conducted the chemistry is dominated by carbonate weathering and ca mg and hco3 so4 accounts for about 90 of the cations and anions the so4 content is almost the same as the hco3 the low contribution of na k to the total cations and the ca mg and hco3 data tends to indicate that silicate weathering has not been the potential source of major ions to the lake waters this difference may be related to the increasing susceptibility to weathering of carbonate over silicate rocks exposed in the catchment and also seepage of water at the bottom the high sulphate content in waters is derived from dissolution of pyrite ferrous reduced black shales which constitute a significant lithology in the catchment the chemical index of alteration cia value in core sediments is on an average 76 which is comparable with average shale 70 75 and the rate of sedimentation 3 3 mm year based on measurement of pb210 indicating a fairly high weathering rate in the catchment illite is the dominant clay mineral 52 90 in the bed and core sediments chlorite constitutes 7 48 and the kaolinite chlorite mixed silicate layer is l 2 this is consistent with the shale slate sandstone lithology in the valley

late cretaceous metallogeny in the zhongdian area constraints from re os dating of molybdenite and pyrrhotite from the hongshan cu deposit yunnan china abstract the zhongdian area in yunnan southwestern china located at the southern end of the yidun volcano magmatic arc that was formed during the triassic westward subduction of the gaze litang ocean hosts numerous triassic large porphyry and skarn deposits the arc suffered jurassic to cretaceous arc continental orogenic collision and cenozoic intracontinental strike slip shearing the hongshan cu mo pb zn deposit is potentially a large deposit and contains two ore types 1 predominant layered skarn cu pb zn ores along marble hornfels contacts and 2 minor crosscutting vein type cu mo mineralization previous research forwards a two stage genetic model without sufficient dating evidence supposing the skarn mineralization is related to the triassic calc alkalic intrusions and the vein type mineralization related to cretaceous quartz monzonite porphyries re os dating of molybdenite from vein type ores and quartz monzonite porphyries and that of pyrrhotite from skarn ores are presented here to constrain the mineralization age and rebuild the genetic model analyses of eight molybdenite samples yield an isochron age of 79 7 3 1 ma mswd 9 2 for the vein type mineralization and a model age of 81 9 1 1 ma for the quartz monzonite porphyries isotope data on seven pyrrhotite samples from the skarn ores yield an isochron age of 79 16 ma z mswd 8 4 the re os ages for the two ore types are concordant within analytical errors indicating that the hongshan deposit was formed in the late cretaceous elevated re contents in molybdenite 13 65 to 63 91 g g and extremely radiogenic initial 187 os 188 os ratios in pyrrhotite 0 7673 to 0 8184 weighted average 0 796 0 038 together with elevated os values in pyrrhotite 507 to 547 average 528 imply a significant crustal component in the ore forming materials that was likely derived from a lower crustal reservoir combined with the tectonic evolution of the zhongdian area and geochemical characteristics of corresponding intrusions the ages of mineralization obtained in this study indicate that the hongshan deposit was formed in a post collision setting with a genetic relationship to the emplacement of the quartz monzonite porphyry these results provide significant new information for the study and exploration of the late cretaceous metallogeny in the zhongdian area

outwash plains and thermokarst on mars abstract the spatial distribution of different types of rampart craters on mars suggests a hemispheric asymmetry in the distribution of ground ice the northern plains especially major topographic depressions near the terminations of outflow channels have high percentages of rampart craters two of these basins acidalia and utopia planitiae received extraordinarily large amounts of water and sediment from the chryse and elysium outflow channels in both regions the analysis of high resolution viking pictures 12 m pixel indicates a concentration of kilometer scale depressions that are similar in size and form to thermokarstic features in yakutia siberia and parts of the arctic coastal plain of north america accordingly we infer that 1 utopia planitia and acidalia planitia may contain thick laterally continuous ice rich sedimentary deposits related to outflow channel forming floods and 2 these areas of mars may have experienced thermokarstic processes similar to modern thermokarstic processes in some periglacial regions of earth

geology geochronology and geochemistry of granitic intrusions and the related ores at the hongshan cu polymetallic deposit insights into the late cretaceous post collisional porphyry related mineralization systems in the southern yidun arc sw china abstract the hongshan cu polymetallic deposit is located in the southern yidun arc in southwestern china where both subduction related late triassic and post collisional late cretaceous porphyry skarn epithermal mineralization systems have been previously recognized in this study two distinct magmatic events represented by diorite porphyry and quartz monzonite porphyry have been revealed in the hongshan deposit with zircon shrimp u pb ages of 214 2 ma and 73 4 0 7 ma respectively the 73 ma age is comparable to the re os ages of 77 to 80 ma of ore minerals from the hongshan deposit indicating that the mineralization is related to the late cretaceous quartz monzonite porphyries rather than late triassic diorite porphyries the late triassic diorite porphyries belong to the high k calc alkaline series and show arc magmatic geochemical characteristics such as enrichment in rb ba th and u and depletion in hfses indicating that they were formed during the westward subduction of the garze litang ocean in contrast the late cretaceous quartz monzonite porphyries show shoshonitic i type geochemical characteristics with high sio 2 k 2 o lile low hree y and yb contents and high lree hree and la yb ratios these geochemical characteristics together with the sr nd pb isotopic compositions average 87 sr 86 sr i 0 7085 e nd t 6 0 206 pb 204 pb 19 064 207 pb 204 pb 15 738 208 pb 204 pb 39 733 suggest that the quartz monzonite porphyries originated from the partial melting of the ancient lower crust in response to underplating of mafic magma from subduction metasomatized mantle lithosphere possibly triggered by regional extension in the post collisional tectonic stage the s isotopic compositions 34 s v cdt 3 81 to 5 80 and pb isotopic compositions 206 pb 204 pb 18 014 to 18 809 207 pb 204 pb 15 550 to 15 785 and 208 pb 204 pb 38 057 to 39 468 of ore sulfides indicate that the sulfur and metals were derived from mixed mantle and crustal sources it is proposed that although the late triassic magmatic event is not directly related to mineralization it contributed to the late cretaceous mineralization system through the storage of large amounts of sulfur and metals as well as water in the cumulate zone in the mantle lithosphere through subduction metasomatism re melting of the mantle lithosphere including the hydrous cumulate zone and ancient lower crust during the post collisional stage produced fertile magmas which ascended to shallow depths to form quartz monzonite porphyries hydrothermal fluids released from the intrusions resulted in porphyry type mo cu ores in and near the intrusions skarn type cu mo ores in the country rocks above the intrusions and hydrothermal pb zn ores in the periphery

radar evidence for ice in lobate debris aprons in the mid northern latitudes of mars 1 subsurface radar sounding data indicate that lobate debris aprons found in deuteronilus mensae in the mid northern latitudes of mars are composed predominantly of water ice the position in time delay and the relatively low amount of signal loss of the apparent basal reflectors below the debris aprons indicate that aprons contain only a minor component of lithic material the current presence of large ice masses at these latitudes has important implications for the climate evolution of mars and for future targets for in situ exploration

temperature distribution and its relation to hydrocarbon accumulation in upper assam valley india well log temperatures have been recorded in more than 400 wells drilled so far by oil india ltd in its concessions in the upper assam tertiary sedimentary basin at the northeastern corner of the indian subcontinent subsurface temperatures presented in the form of isogeothermal maps show 1 a general increase with the rise of basement configuration and 2 maximum values over the crests of local highs with gradual decrease toward the flanks the difference being on the order of 15 c geothermal gradients in the areas studied decrease with depth within argillaceous sediments but increase in the arenaceous group the geothermal gradients obtained for different areas of this sedimentary basin can be used in the hydrocarbon liquid window concept for oil exploration the study reveals that in the eastern part of this basin theoretically a considerable thickness of potentially hydrocarbon bearing section could be down to a depth of about 9 150 m which is yet to be explored by deep drilling

scalloped terrains in the peneus and amphitrites paterae region of mars as observed by hirise abstract the peneus and amphitrites paterae region of mars displays large areas of smooth geologically young terrains overlying a rougher and older topography these terrains may be remnants of the mid latitude mantle deposit which is thought to be composed of ice rich material originating from airfall deposition during a high obliquity period less than 5 ma ago within these terrains there are several types of potentially periglacial features in particular there are networks of polygonal cracks and scalloped shaped depressions which are similar to features found in utopia planitia in the northern hemisphere this area also displays knobby terrain similar to the so called basketball terrains of the mid and high martian latitudes we use recent high resolution images from the high resolution imaging science experiment hirise along with data from previous mars missions to study the small scale morphology of the scalloped terrains and associated polygon network and knobby terrains we compare these with the features observed in utopia planitia and attempt to determine their formation process while the two sites share many general features scallops in peneus amphitrites paterae lack the diverse polygon network i e there is little variation in the polygon sizes and shapes and large curvilinear ridges observed in utopia planitia this points to a more homogeneous ice content within the substrate in the peneus amphitrites paterae region and implies that scallop formation is independent of polygon formation this work shows that as in utopia planitia sublimation of interstitial ice is a likely process explaining the formation of the scalloped depressions in the region of peneus amphitrites paterae therefore we provide a simplified scallop formation model based on sublimation of interstitial ice as proposed for utopia planitia we also show that the differences in scallop morphologies between the two regions may be explained by differences in near surface ice content sublimation rates and age of formation of the scalloped terrains

characterisation of organic matter in a shallow reducing arsenic rich aquifer west bengal abstract elevated arsenic in groundwaters extensively exploited for irrigation and drinking water in west bengal and bangladesh is causing serious impacts on human health a key mechanism for the genesis of arsenic as in these waters is microbially mediated reductive transformation of arsenic bearing fe iii hydrated oxides the role of organic c in this process whether from in situ organic matter om i e om from within the sediment or from other sources is widely recognised despite this there is a paucity of data about the characteristics of om in these as rich aquifers extraction and analysis of the polar and apolar fractions from seven different sediments from a known groundwater as hotspot in west bengal revealed om characteristic of the original terrestrial depositional environment however this was overprinted by abundant hydrocarbons with thermally mature e g petroleum distributions these hydrocarbons included abundant high molecular weight n alkanes and unresolved complex mixtures ucms as well as thermally mature distributions of hopanes and steranes additionally at certain depths surface sands 8 and 13 m deeper sands 25 m the om appeared to be biodegraded with the preferential removal of petroleum sourced n alkanes suggesting that indigenous microbes within the aquifer can utilise this carbon source the presence of this previously unreported source of bioavailable organic carbon is of importance as it has the potential to promote microbial activity and subsequent as release in the aquifers

stratigraphic profiling with ground penetrating radar in permafrost a review of possible analogs for mars 1 we review our past and ongoing use of ground penetrating radar to investigate permafrost in alaska and in the dry valleys of antarctica the results may be relevant to radar efforts on mars because of arid conditions and the presence of ice the pulses were centered at 50 100 and 400 mhz we interpret profiles from two sites in the eastern taylor valley to show glaciolacustrine and glaciofluvial stratigraphy the maximum depth of stratigraphy profiled there was about 33 m near fairbanks alaska the depth of penetration at 50 mhz was near 80 m in marginally frozen and stratified alluvial sands at the fairbanks sites supplementary drilling was required to differentiate between reflections from conductive bedrock a graphitic schist and those from the water table at depths of 20 25 m at a site on the north slope of alaska we profiled present and remnant freezing fronts in an alluvial floodplain the relative permittivity at most sites ranged between about 4 and 5 5 which is consistent with dry conditions the mineralogy and low ice content weak interface reflectivity or the lack of further interfaces may have limited the interpretation of maximum penetration where no water table was present because signal absorption should have been low and scarce diffractions imply that scattering was weak the interface reflectivities beneath taylor valley may be a function of only density contrasts since free water and possibly ice is absent

review of mesozoic multiple magmatism and porphyry cu mo w mineralization in the yidun arc eastern tibet plateau abstract the yidun arc was formed in response to the westward subduction of garze litang ocean a branch of paleotethys in the late triassic where abundant porphyry cu mo deposits 221 213 ma developed along the regional nw se sinistral faults and emplaced in the southern portion of the arc the ore related porphyries are mostly metaluminous or slightly peraluminous belonging to shoshonitic high potassium calc alkaline i type granites with ehf t values of 6 64 to 4 12 the ore bearing magmas were probably derived from the partial melting of subduction metasomatic enriched mantle with the contamination of underplated mafic materials the late cretaceous 88 80 ma highly fractionated i type granite belt and related porphyry cu mo deposits and magmatic hydrothermal cu mo w deposits occur along approximately n s trending faults in the yidun arc this belt extended across the yidun arc and garze litang suture zone to the north and across the yangtze craton to the south intruding the late triassic porphyry belt the ore related porphyries are characterized by high silica and high total alkalis with enrichment in large ion lithophile elements liles rb u and k and depletion in high field strength elements hfse nb ta p and ti and ba they have lower ehf t values varying from 9 55 to 2 75 and significant negative eu anomalies indicating that the ore bearing porphyritic magmas originated from ancient middle upper crust two stage magmatism and mineralization were superimposed in the xiangcheng shangri la district some ore deposits comprise two episodes of magmatism and associated mineralization such as both 207 3 0 ma granodiorite and 82 1 1 2 ma monzogranite intruded in the xiuwacu deposit causing cu mo w polymetallic mineralization to date 11 late triassic porphyry cu deposits e g the pulang giant deposit with 5 1 mt cu and five late cretaceous porphyry cu mo w deposits e g tongchanggou mo deposit with 0 59 mt mo have been evaluated in the xiangcheng shangri la district the continuity and inheritance of multiphase magmatism and the new understanding of superimposed mineralization will help to guide future exploration

earthquake recurrence and rupture dynamics of himalayan frontal thrust india the black mango fault is a structural discontinuity that transforms motion between two segments of the active himalayan frontal thrust hft in northwestern india the black mango fault displays evidence of two large surface rupture earthquakes during the past 650 years subsequent to 1294 a d and 1423 a d and possibly another rupture at about 260 a d displacement during the last two earthquakes was at minimum 4 6 meters and 2 4 to 4 0 meters respectively and possibly larger for the 260 a d event abandoned terraces of the adjacent markanda river record uplift due to slip on the underlying hft of 4 8 0 9 millimeters per year or greater since the mid holocene the uplift rate is equivalent to rates of fault slip and crustal shortening of 9 6 3 5 7 0 millimeters per year and 8 4 3 6 7 3 millimeters per year respectively when it is assumed that the hft dips 30 10

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

thermal contraction crack polygons on mars classification distribution and climate implications from hirise observations morphology is shown to be consistent with thermal contraction cracking of an ice rich mantling unit consistent with observations of sediment wedge thermal contraction crack polygons forming in ice cemented sediment at the phoenix landing site polygon groups are distributed symmetrically in both northern and southern hemispheres suggesting strong climate controls on polygon morphology northern hemisphere polygonally patterned surfaces are found to decrease in age from low to high latitude spanning surface ages from 1 to 0 1 ma suggesting more recent deposition of ice rich material at high latitudes than at low latitudes six of the seven classes of polygons are interpreted to be capable of forming because of the combined effects of thermal contraction cracking and differential sublimation suggesting that sublimation and sand wedge polygons dominate martian high latitudes gully polygon systems present at midlatitudes suggest that small amounts of liquid water may have been involved in thermal contraction crack polygon processes producing composite wedge polygons no evidence is found for the presence of pervasive small scale ice wedge polygons

petroleum geochemistry of a part of upper assam basin india a brief overview abstract the upper assam tertiary sedimentary basin is an important petroleum province with reservoir rocks ranging in age from upper paleocene to miocene the bulk of the oil production is from the barail oligocene and tipam miocene formations promising hydrocarbon pools have been discovered recently in upper paleocene lower eocene formations prolific source rocks occur within the barail oligocene formation langpar formation upper paleocene and lakadong theria member of sylhet formation of upper paleocene lower eocene age the source rocks contain predominantly type ii organic matter and are thermally immature to early mature biomarker ratios indicate the dominance of land plant derived kerogen the barail and tipam oils have moderate gravity and significant wax contents the physical and chemical characteristics of the paleocene eocene crude oil is similar to that produced from younger horizons within the basin with the exception of minor quantities of heavy viscous crude oils observed in a few wells multivariate analysis including principal components analysis and factor analysis of fluorescence data and principal components analysis of biomarker data indicate that the barail oligocene and tipam miocene oil have been derived from barail source rocks with a possible contribution from eocene source rocks these preliminary studies have not provided conclusive evidence for the source of the eocene oils although geological factors indicate that the source rocks are probably the interbedded shales coals occurring within the upper paleocene lower eocene sediments

design and field experiments of a ground penetrating radar for mars exploration 1 we developed a wideband low power lightweight prototype ground penetrating radar gpr for subsurface exploration for mars the transmitter and receiver subsystems were constructed using a commercially available radio frequency rf and digital integrated circuits connectorized components and evaluation boards the transmit receive system antennas laptop controller and batteries are all accommodated on a 2 5 m sled field experiments were conducted in kansas and alaska the experiments in kansas tested the operation of the system the primary objective of the alaska experiments was to investigate the ability of a gpr to detect and distinguish between subsurface deposits of ice and ice cemented soils the investigation depths of these experiments ranged from 1 m to 30 m and the subsurface geology included near surface thaw discontinuous permafrost water saturated soils and lenses of pure ice dielectric contrasts within the ground were detected with near meter resolution however identifying the geologic context of an interface was difficult due to ambiguities associated with reflection data these investigations demonstrate some of the difficulties associated with inverting reflection data to obtain dielectric properties of the subsurface fortunately previous geophysical investigations such as drilled cores and seismic surveys helped to constrain the geology and numerical simulations provided an additional resource for the interpretations on mars additional geological context will be limited and numerical simulations will become extremely important for data interpretation due to these difficulties we demonstrate in one experiment how dielectric information can be obtained directly from bistatic measurements with a fixed transmitter and mobile receiver finally a comparison with a commercially available geophysical survey systems inc gssi radar system is presented and we discuss how the system can be modified and improved for future exploration on mars

the distribution and behavior of martian ground ice during past and present epochs mars undergoes significant oscillations in its orbit which will have a pronounced effect on its climate and in particular on the behavior of subsurface water ice we explore and map the behavior of ice in the martian near surface regolith over the past 1 m y using a diffusion and condensation model presented in an earlier paper with two primary modifications to include orbitally induced variations in insolation and atmospheric water abundance we find that the past behavior of ground ice differs significantly from that at the present epoch primarily the result of high amplitude oscillations in obliquity presently 25 in midlatitude and equatorial regions ground ice will condense from atmospheric water during times of higher obliquity filling the top few meters of the regolith with significant amounts of ice at an obliquity of 32 ground ice becomes stable globally during times of lower obliquity ground ice will sublime and diffuse back into the atmosphere dessicating the regolith to a depth of about 1 to 2 m equatorward of 60 to 70 latitude in the high latitude regions these oscillations are considerably subdued below this depth of cyclic saturation and dessication a long term stability of ice exists in some geographic regions we present a map of the distribution of ice expected at the present epoch cyclic exchange of water between the global regolith and polar regions will have significant implications for surface geology and the polar layered deposits

a hydrogeochemical approach to evaluate the occurrence and source of salinization in the shallow aquifers of the southeastern imphal valley in the indo myanmar range of northeast india the imphal valley is an intramontane basin confined within an anticlinorium of several anticlines and synclines in the disang group of rocks of tertiary age this valley of more than 2 million people is occupied by fluvio lacustrine deposits of quaternary age and is located in the central part of the indo myanmar range of northeast india the hydrogeochemical parameters of temperature ph orp tds na cl br ba b sr li 18o hco3 k mg ca no3 po4 so4 in 173 samples using ion chromatograph icp aes icp oes icp ms and 37 dugwells were studied to understand the occurrence and origin of salinization process for the first time the order of abundance of ions is identified as hco3 na cl ca mg k no3 po4 sr br b ba li so4 five hydrochemical facies na cl ca mg hco3 na hco3 ca mg hco3 cl and ca mg cl represent the types of waters the saline dominated water types na cl and na hco3 represent piedmont and the rest of the facies represent alluvial plain and flood plain groundwaters durov s diagram reveales initial and intermediate stages of groundwater evolution isotope 18o gibbs diagram and ions scatter plots suggest evaporation and crystallization processes leading to halite encrustation in the disang shales negative eh low no3 and the absence of so4 indicates reduced condition coupled with rich dissolve organic matters leading to elevation of salts in soils around piedmont where the rock type is exclusively of the disang shales trilinear plot correlation matrix and water table flow analysis suggest salinization of groundwater originates in piedmont groundwater and disseminates towards alluvial plain and flood plain along the flow path

hydrochemical characteristics of aquifers near sutherland in the western karoo south africa the western karoo depends entirely on groundwater for domestic and agricultural use an understanding of the chemical evolution of the groundwater provides insight into the interaction of water with the environment and contributes to better resource management descriptive statistics correlation matrices and factor analysis together with stable isotope data were used to gain an understanding of the hydrochemical processes of the groundwaters in the fractured rocks around sutherland in the western karoo the main processes influencing the groundwater chemistry are salinisation mineral precipitation and dissolution cation exchange and human activity the stable isotope data indicate that the infiltration of evaporated water is partly responsible for the occurrence of saline subsurface waters the ionic oxygen and hydrogen stable isotope composition of the groundwaters suggests that the effects of localised topography are one of the overriding factors controlling the groundwater chemistry in higher lying areas ca hco3 2 type waters are prevalent while in topographical flat areas nacl type waters dominate in areas where water collects close to or at the surface saline soils are formed from these areas salts are leached to the subsurface during significant recharge periods these findings are important in that they contribute to the identification of suitable locations for developing groundwater resources that could yield a relatively better quality water q 2001 elsevier science b v all rights reserved

an assessment of evidence for pingos on mars using hirise pingos are small hills with cores of ice formed by injection and freezing of pressurized water the possibility of pingos on mars is of particular interest because of the associated implications for liquid water we have systematically searched for candidate pingos using images from the high resolution imaging science experiment hirise camera since pingos are expected to develop surface fractures due to extension of the frozen ground over the ice core we have searched for fractured features and identified a variety of mounds these features are confined to the martian mid latitudes in the bands where gullies are also most common the observed fractured mounds have a variety of morphologies and are likely of multiple origins isolated fractured mounds found on the floors of gullied craters in the southern hemisphere match the general morphologic characteristics of terrestrial pingos and are the best candidates for martian pingos but there is currently no direct evidence for presence of ice cores and it is difficult to produce the necessary water volumes so these features should still be interpreted with caution other fractured mounds appear more likely to be erosional remnants of an unusual mantling layer or possibly thermokarst structures flat topped mounds in utopia have some characteristics fracture pattern and latitudinal distribution consistent with pingos but differ in other aspects such as shape and setting while we do not rule out a pingo origin we prefer an erosional model for these enigmatic features

properties of the 67p churyumov gerasimenko interior revealed by consert radar the philae lander provides a unique opportunity to investigate the internal structure of a comet nucleus providing information about its formation and evolution in the early solar system we present comet nucleus sounding experiment by radiowave transmission consert measurements of the interior of comet 67p churyumov gerasimenko from the propagation time and form of the signals the upper part of the head of 67p is fairly homogeneous on a spatial scale of tens of meters consert also reduced the size of the uncertainty of philae s final landing site down to approximately 21 by 34 square meters the average permittivity is about 1 27 suggesting that this region has a volumetric dust ice ratio of 0 4 to 2 6 and a porosity of 75 to 85 the dust component may be comparable to that of carbonaceous chondrites

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

stable isotope and fluid inclusion constraints on the source and evolution of ore fluids in the hongniu hongshan cu skarn deposit yunnan province china the hongniu hongshan cu skarn deposit 77 8 mt at 1 8 cu is located in the central part of the zhongdian porphyry and skarn cu belt in southwestern china skarn and orebodies occur mainly between the different units of the upper triassic qugasi formation or within altered limestone adjacent to late cretaceous intrusions 78 76 ma three main paragenetic stages of skarn formation and ore deposition have been recognized on the basis of petrographic observations 1 pre ore stage hornfels with diopside di87 72hd12 7 small scale endoskarn with reddish grossular adr22 57gr78 43 diopside di83 92hd7 15 vesuvianite and abundant exoskarn with red brown andradite adr75 98gr2 22 sahlite di28 41hd58 71 and wollastonite 2 syn ore stage retrograde minerals sulfides pyrite chalcopyrite pyrrhotite molybdenite galena and sphalerite quartz and calcite and 3 post ore stage calcite veins sulfur isotope values of sulfides are relatively high with an average 34s 4 9 n 40 suggesting that the ore forming fluid was magmatic and that the sulfides precipitated from a relatively reducing ore fluid the coexistence of silicate melt and primary fluid inclusions in quartz phenocrysts of the mineralization related quartz monzonite porphyry indicates the simultaneous entrapment of fluid and melt and records the process of the aqueous fluid exsolving from the crystallizing melt the initial single phase fluid has a salinity of 8 8 to 12 7 wt nacl equiv and homogenization temperatures of 566 to 650 c corresponding to pressures of 680 to 940 bar and lithostatic depth of 2 5 to 3 5 km the primary fluid inclusions in the pre ore stage garnet and pyroxene composed of coeval vapor rich v type and halite bearing s i and s ii types containing sylvite inclusions 32 79 total wt salts share similar homogenization temperatures 450 550 c indicative of the occurrence of fluid unmixing under lithostatic pressures of 550 to 780 bar 2 0 km depth primary fluid inclusions trapped in syn ore quartz calcite and epidote show the common development of s type inclusions 37 3 wt nacl equiv with coexisting v type liquid rich l type and co2 bearing c i type inclusions all of which have homogenization temperatures of 300 to 400 c and trapping pressures of 100 to 400 bar 1 5 km depth brine inclusions homogenized by halite dissolution after vapor disappearance in both the pre and syn ore stages are interpreted to have been trapped under overpressured conditions 1 520 bar oxygen isotope analyses were conducted on garnet wollastonite epidote quartz and calcite the pre ore stage garnet and wollastonite have 18ofluid values of 5 6 to 8 1 whereas the syn ore stage epidote quartz and calcite have more variable 18ofluid values in the range of 3 9 to 17 5 the 18ofluid values of the post ore stage vein calcite 15 2 21 3 are much higher than both the pre and syn ore stages the vapor phase of inclusions contains h2s ch4 and c2h6 in the syn ore stages all these observations reveal that 1 the formation of the cu skarn deposit was dominated by a magmatic hydrothermal system 2 multiple fluid pulses contributed to the formation of the pre and syn ore stage skarn minerals and sulfides and 3 the increase in ph due to the neutralization of the acidic fluid could be the main factor controlling the large scale ore deposition in hongniu hongshan

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

thermokarst processes and the origin of crater rim gullies in utopia and western elysium planitia abstract we have identified a number of gullies that could be aqueous in origin near or at the rim of several impact craters in utopia planitia and western elysium planitia 30 0 59 0 n 241 0 291 0 w based on the sharpness of their incisions and the general absence of superposed craters we ascribe a relatively recent origin to the gullies scalloped depressions are commonplace throughout the region as well as on the crater walls rims and floors near the areas of gully issuance occasionally the depressions cross cut the gully debris aprons suggesting that the formation of some depressions is even more recent than that of the gullies previous research has proposed that the depressions are collapse basins formed by thermokarst processes on earth thermokarst landforms occur in areas of low gradient topography where the permanently frozen ground permafrost is ice rich and has undergone a change in thermal equilibrium this change can be triggered by long term or episodic cyclic climate change and accompanying rises in mean temperatures towards 0 c as well as by rises in seasonally sustained summer temperatures well above 0 c in order to explain the origin of the rim or near rim gullies we invoke high obliquity and the possibility that this region of mars experienced obliquity driven rises in temperature atmospheric pressure and humidity sufficient to keep surface water and near surface ground ice stable for extended periods of time we propose that gully formation is closely related to local freeze thaw processes that in turn generate a thermokarst landscape of which the gullies are a part this geological and climatological scenario comprises the following steps 1 an inundation of meltwater at high obliquity due to the thawing of an atmospherically deposited snowpack or ice sheet and the subsequent saturation of the underlying regolith to tens of metres of depth 2 loss of water on the surface perhaps as obliquity decreases slightly followed by the progressive freezing of the saturated regolith this creates an aggrading mass of ice rich regolith 3 obliquity induced temperature rises that engender the thaw drainage and partial evaporation of the near surface ice rich regolith 4 localised formation of thermokarst collapse basins alases as water is evacuated from these basins 5 formation of gullies near or at some impact crater rims as the result of meltwater migration from nearby alases through the thawed regolith to the areas of gully issuance although the plains materials in this region are in part very old possibly hesperian or even noachian the mantling deposits and their deformation by thermokarst processes appears to be relatively young this suggests that recent climatic conditions could have been episodically warmer and wetter than had been previously thought

origin of the polygons and the thickness of vastitas borealis formation in western utopia planitia on mars 1 many middle scale about 100m cracking space polygons are located between the area of the giant polygons and the thumbprint terrains in western utopia planitia most of the patterns are located on vastitas borealis formation the polygonal patterns have frequently been associated with collapsed features such as a covered trough like features the width of the underground crack is approximately 400 500 m the thickness of the surface materials 6 12 m where polygonal patterns occur was calculated based on the space of cracking relationship polygonal networks with strongly oriented features and parallel to the contour line are likely caused by structural geological origin as well as bending forces from the center of the basin