late cretaceous volcanic rocks and associated granites in gyeongsang basin se korea their chronological ages and tectonic implications for cratonic destruction of the north china craton abstract the gyeongsang basin is the largest exclusively non marine sedimentary basin in korean peninsula located in southeastern part of the peninsula its sedimentary setting magma source tectonic nature and formation age are important to understand the mesozoic tectonic evolution of not only the sino korea craton but also the entire northeast asia the gyeongsang supergroup the basin fill is divided into the sindong hayang and yucheon groups in ascending order the sindong and hayang groups are composed of sandstone shale minor amounts of conglomerate and marl deposited in a non marine environment whereas the yucheon group is characterized by the dominance of volcanic rocks precise isotopic ages and geochemical analyses are scarce for the volcanic elements of this basin restricting our understanding of its geodynamic setting and evolution in this study we present new u pb zircon ages from the volcanic rocks of the yucheon group and associated granites in the gyeongsang basin thirteen volcanic samples yielded ages ranging from 94 4 to 78 4 ma and four granite samples give ages 72 ma these data confirm that a major magmatic event occurred during late cretaceous and the gyeongsang volcano sedimentary complex represents a rock association representing a late cretaceous island arc in comparison with the sambagawa metamorphic belt the jurassic chichibu accretionary complex ac with cretaceous strike slip basin sediments and the cretaceous shimanto melange zone in southwest japan it is likely that above motioned complexes constitute the trace of a continuous subduction related island arc system in se korea extending from sw japan although the peak ages of the magmatic rocks in the eastern part of the north china craton ncc are 130 10 ma indicating an important time of continental lithospheric thinning under the ncc the ages of the gyeongsang magmatic rocks are markedly younger late cretaceous magmatism was very weak in the eastern ncc therefore it is probable that early middle mesozoic lithospheric thinning beneath the eastern ncc is triggered by multiple tectonic factors not only by the subduction of the pacific plate suggested by some previous studies in addition 20 inherited xenocrystic zircons from these volcanic rocks give archean ages ranging from 2 5 to 2 6 ga suggesting the existence of late archean rocks in the yeongnam massif the yeongnam massif is predominated by the latest archean crustal growth at 2 50 ga consistent with the characteristics of the north china craton

long term atmospheric deposition as the source of nitrate and other salts in the atacama desert chile new evidence from mass independent oxygen isotopic compositions abstract isotopic analysis of nitrate and sulfate minerals from the nitrate ore fields of the atacama desert in northern chile has shown anomalous 17 o enrichments in both minerals 17 o values of 14 21 in nitrate and 0 4 to 4 in sulfate are the most positive found in terrestrial minerals to date modeling of atmospheric processes indicates that the 17 o signatures are the result of photochemical reactions in the troposphere and stratosphere we conclude that the bulk of the nitrate sulfate and other soluble salts in some parts of the atacama desert must be the result of atmospheric deposition of particles produced by gas to particle conversion with minor but varying amounts from sea spray and local terrestrial sources flux calculations indicate that the major salt deposits could have accumulated from atmospheric deposition in a period of 200 000 to 2 0 m years during hyper arid conditions similar to those currently found in the atacama desert correlations between 17 o and 18 o in nitrate salts from the atacama desert and mojave desert california indicate varying fractions of microbial and photochemical end member sources the photochemical nitrate isotope signature is well preserved in the driest surficial environments that are almost lifeless whereas the microbial nitrate isotope signature becomes dominant rapidly with increasing moisture biologic activity and nitrogen cycling these isotopic signatures have important implications for paleoclimate astrobiology and n cycling studies

influence of pore pressure on the event size distribution of induced earthquakes 1 during an enhanced geothermal system egs experiment fluid is injected at high pressure into crystalline rock to enhance its permeability and thus create a reservoir from which geothermal heat can be extracted the fracturing of the basement caused by these high pore pressures is associated with microseismicity however the relationship between the magnitudes of these induced seismic events and the applied fluid injection rates and thus pore pressure is unknown here we show how pore pressure can be linked to the seismic frequency magnitude distribution described by its slope theb value we evaluate the dataset of an egs in basel switzerland and compare the observed event size distribution with the outcome of a minimalistic model of pore pressure evolution that relates event sizes to the differential stress d we observe that the decrease of b values with increasing distance of the injection point is likely caused by a decrease in pore pressure this leads to an increase of the probability of a large magnitude event with distance and time

chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

archean basement components and metamorphic overprints of the rangnim massif in the northern part of the korean peninsula and tectonic implications for the sino korean craton abstract the geology of the korean peninsula s northern part is little known to the international community even though this area is a critical link between various eastern asia terranes its tectonic architecture and geochronological framework are still gaps in knowledge this study reports integrated field geochemical and geochronological characteristics of the precambrian gneissic rocks from this region focusing on the rangnim massif the studied samples are divisible into three groups according to their field occurrence as granitic gneiss fine grained biotite gneiss and leuco veins the essential mineralogy of all these rocks is biotite bt muscovite mu plagioclase pl k feldspar kf and quartz the analyzed samples show high sio2 65 92 77 63 wt and al2o3 10 23 to 17 56 wt contents low mgo and cao their k2o contents is mostly higher than na2o sims secondary ion mass spectrometry zircon u pb dating of the eleven samples yields magmatic protolith ages of 2454 2567 ma and multiple metamorphic overprintings during the earliest paleoproterozoic 2 45 ga paleoproterozoic 1 87 1 93 ga and jurassic 160 ma the presence of these potassic granitoids in different locations indicate the high extent maturation of neoarchean continental crust in the rangnim massif zircon lu hf isotopic results of these samples show large variations mostly plotting between the depleted mantle linear model line and chondritic uniform reservoir chur line but some have negative ehf t values considering that their protoliths are all crust melting products it can be concluded that the neoarchean magmatism incorporated both juvenile crustal components as well as a reworking of older crust this is supported by the detection of rare early archean xenocrysts based on juvenile crust having ehf values of 0 before 3500 3600 ma it is concluded that the reworked components were eoarchean in age not hadean magmatic as well as precambrian metamorphic pulses of the rangnim massif show broad similarities with the eastern north china craton gyeonggi and yeongnam massifs and southwest japan which seem to suggest that they might share a coherent precambrian basement and evolutionary history at least before the end of late paleoproterozoic

early permian peak metamorphism recorded in u pb system of black slates from the ogcheon metamorphic belt south korea and its tectonic implication abstract we report pb pb whole rock and uraninite chemical th u total pb isochron method chime ages of carbonaceous black slates from the ogcheon metamorphic belt south korea the pb isotopic data of whole rock samples yield 207 pb 206 pb ages of 283 33 and 291 13 ma for two outcrops from the northeastern part of the belt the uraninite chime age is estimated at 283 26 and 281 27 ma for the northeastern and the middle part of the belt respectively all of the above ages are identical within error ranges and represent the timing of peak metamorphism after the late precambrian intraplate rifting on the other hand the 207 pb 206 pb whole rock age for the southwestern part of the belt is estimated at 194 27 ma probably representing the timing of contact thermal metamorphism associated with the intrusion of jurassic granitic plutons rb sr isotopic data of the black slates do not define any meaningful isochron the early permian metamorphic age of this study does not support any tectonic scheme in favor of major tectonometamorphism at either the silurian devonian or the triassic time instead it corroborates the probability that the two zones in the ogcheon belt the ogcheon metamorphic belt and the taebaegsan zone were separated from each other before the development of major structural framework in the former our data do not support an idea that the ogcheon belt corresponds to the continuation of the triassic collision belt in east central china

tracking paleozoic evolution of the south korean peninsula from detrital zircon records implications for the tectonic history of east asia abstract the southern part of the korean peninsula preserves important records of the paleozoic evolutionary history of east asia here we present shrimp u pb ages of detrital zircon grains from paleozoic metasedimentary successions okcheon and joseon supergroups yeoncheon group taean formation and pyeongan supergroup that are incorporated into the major phanerozoic mountain belts okcheon and hongseong imjingang belts in south korea providing new insights for provenances and paleotectonic evolution of the south korean peninsula during paleozoic time the zircon ages from our samples display two distinct spectra patterns in their presence absence of neoproterozoic and or paleozoic populations our results together with the available data from the korean peninsula suggest that 1 the early to middle paleozoic successions in the okcheon belt were deposited in continental margin setting s formed by neoproterozoic intracratonic rifting 2 the middle paleozoic metasedimentary rocks in the imjingang belt can be interpreted as molasse and flysch sediments along an active continental margin 3 the late paleozoic to early triassic taean formation along the western gyeonggi massif represents a syn to post collision deltaic complex of a remnant oceanic basin and 4 the late paleozoic to possibly early triassic pyeongan supergroup in the okcheon belt might represent a wedge top and or foreland basin the spatial and temporal discrepancy between the south korean peninsula and the central china orogenic belt during paleozoic might reflect lateral variations in crustal evolution history along the east asian continental margin during the paleo tethyan ocean closure

geodynamics of the ogcheon belt south korea abstract the ogcheon belt is a stack of synmetamorphic southeastward verging nappes resulting from the deformation of a volcanosedimentary sequence deposited in an early palaeozoic rift which was affected by polyphase tectonics its pre cretaceous structure results from three main orogenic events the ogcheon late silurian devonian indosinian late permian triassic and yenshanian middle jurassic early cretaceous tectonic phases the external autochthonous or para autochthonous units represent platform zones with shallow water deposits whereas rift facies characterize the internal domain the yeongweol sequence forming an outer shelf on the southeastern margin of the rift displays affinities with the jiangnan basin of south china it is in wrench fault contact with the easternmost duwibong sequence correlated with the north china north korea platform in the internal metamorphic units post cambrian early ordovician pelitic and turbiditic rift metasediments overlie a thin cambrian or cambrian ordovician early platform sequence two subdomains are distinguished the upper units chung ju and pibaryeong units representing the deep axial part of the basin contain distal flyshoids and large olistoliths derived from the northwestern narrow margin the lower units turung san poeun and iwharyeong are related to the wide margin located between the deep rift domain and the stable southeastern platform the latter transitional domain is characterized by thick submarine debris flows and volcanics of alkali or transitional tholeiitic affinity the volcanic activity and mass gravity flow sedimentation are closely related to the crustal thinning and subsequent rifting and tilting lithostratigraphic evidence allows the correlation of the unfossiliferous rift metasediments with the cambrian ordovician platform sequence in one single basin the post middle silurian pre mid carboniferous ogcheon ensialic orogeny resulted in the closure of the rift with relatively minor effects in the platform area it gave rise to an intracontinental fold thrust belt without ophiolites this tectonic event may have been contemporaneous with early palaeozoic tectonism in the quinling belt in central china and in the southeast china fold belt the definitive constitution of the sino korean craton took place before the mid carboniferous and molasse sedimentation was initiated on a single platform located on the western edge of the yakuno oceanic basin of southwest japan in late permian and early triassic times the closure of the oceanic area and the subsequent westward collision of the honshu block are marked in korea by the intracratonic indosinian tectonism since late triassic times predominantly transcurrent movements have occurred along nne ssw faults associated with syntectonic intermontane troughs and important granitization

deep crustal carbonate rocks exposed by meteor impact on mars mars may have once had a co2 rich atmosphere but carbonate rocks that could provide evidence for such conditions are sparse spectral analyses of rocks exposed from deep within an impact crater reveal that carbonate deposits may be extensive on mars but are buried under layers of younger volcanic rocks

indosinian dextral ductile fault system and synkinematic plutonism in the southwest of the ogcheon belt south korea reply abstract the structure of the mylonite belt in the southwestern part of the ogcheon belt has been investigated and interpreted in the light of recent radiometric data the shear belt is composed of several en echelon dextral shear zones relayed by compressional or extensional tectonic bridges the dextral displacement along the fault system which may be extended to the hida zone of japan is of the order of 200 km it has brought into contact the ryeongnam block and its cambrian middle ordovician cover of north china affinity with the southwestern margin of the ogcheon belt characterized by cambrian middle silurian rift facies and shelf deposits of south china affinity synkinematic plutons are emplaced within the shear belt which is postdated by uppermost triassic unfoliated granitoids at the surface the shear belt generated elongated intermontane coal basins initiated as transtensional half grabens because of its post permian pre early jurassic age and its dextral kinematics we correlate the shear belt with the late stages of the akyioshi indosinian collisional orogeny of the east asian margin the synkinematic plutonism that accompanied the shear zone may be due to post collisional crustal stretching and subsequent anatexis at the mantle crust interface

formation of alunite jarosite and hydrous iron oxides in a hypersaline system lake tyrrell victoria australia abstract alunite kal 3 so 4 2 oh 6 and jarosite kfe 3 so 4 2 oh 6 are common weathering products of aluminosilicates and pyrite long range transport of the constituents forming these minerals and the subsequent deposition of alunite and jarosite in an evaporite setting have not been previously documented such conditions for the occurrence of alunite and jarosite were investigated in a hypersaline system where acid groundwater enriched in k al fe iii and so 4 enter a saltplaya lake sediment cores were studied by thin section xrd and sem eds groundwater and pore water chemistries were also analyzed the results show that alunite and jarosite occur together or as individual layers and cements within the top 20 cm of the sediments where the groundwater is most concentrated due to evaporation hydrous fe oxides also occur as cements or vein fillings with the alunite and jarosite but are distributed throughout the 70 cm sediment column studied the results are consistent with a model in which alunite and jarosite precipitate as a result of the evaporation of water thermodynamic modeling indicates that the pore water in the playa sediments maybe in equilibrium with alunite jarosite and hydrous fe oxides

setting constraints on the nature and origin of the two major hydrous sulfates on mars monohydrated and polyhydrated sulfates monohydrated mg sulfate mgso4 h2o and polyhydrated sulfate are the most common and abundant hydrous sulfates observed thus far on mars they are widely distributed and coexist in many locations on the basis of results from two new sets of experiments in combination with past experimental studies and the subsurface salt mineralogy observed at a saline playa dalangtan dlt in a terrestrial analogue hyperarid region on the tibet plateau we can now set new constraints on the nature and origin of these two major martian sulfates starkeyite mgso4 4h2o is the best candidate for polyhydrated sulfate mgso4 h2o in the form of lh 1w generated from dehydration of mg sulfates with high degrees of hydration is the most likely mineral form for the majority of martian monohydrated mg sulfate two critical properties of mg sulfates are responsible for the coexistence of these two phases that have very different degrees of hydration 1 the metastability of a substructural unit in starkeyite at relatively low temperatures and 2 catalytic effects attributed to coprecipitated species sulfates chlorides oxides and hydroxides from chemically complex brines that help overcome the metastability of starkeyite the combination of these two properties controls the coexistence of the lh 1w layer and starkeyite layers at many locations on mars which sometimes occur in an interbedded stratigraphy the structural h2o held by these two broadly distributed sulfates represents a large h2o reservoir at the surface and in the shallow subsurface on current mars

field investigation of dried lakes in western united states as an analogue to desiccation fractures on mars potential desiccation polygons pdps tens to hundreds of meters in size have been observed in numerous regions on mars particularly in ancient 3 gyr old terrains of inferred paleolacustrine playa geologic setting and in association with hydrous minerals such as smectites therefore a better understanding of the conditions in which large desiccation polygons form could yield unique insight into the ancient climate on mars many dried lakebeds playas in western united states display large 50 m wide desiccation polygons which we consider to be analogues for pdps on mars therefore we have carried out fieldwork in seven of these dried lakes in san bernardino and the death valley national park regions complemented with laboratory and spectral analysis of collected samples our study shows that the investigated lacustrine playa sediments have a a soil matrix containing 40 75 clays and fine silt by volume where the clay minerals are dominated by illite muscovite followed by smectite b carbonaceous mineralogy with variable amounts of chloride and sulfate salts and significantly c roughly similar spectral signatures in the visible near infrared vis nir range we conclude that the development of large desiccation fractures is consistent with water table retreat in addition the comparison of the mineralogical to the spectral observations further suggests that remote sensing vis nir spectroscopy has its limitations for detailed characterization of lacustrine playa deposits finally our results imply that the widespread distribution of pdps on mars indicates global or regional climatic transitions from wet conditions to more arid ones making them important candidate sites for future in situ missions

neoproterozoic bimodal volcanism in the central ogcheon belt korea age and tectonic implication abstract u pb zircon ages were determined for a metavolcanic rock from the munjuri formation in the central ogcheon belt korea four zircon fractions were analyzed of which three are nearly concordant the data define a discordia with an upper intercept at 755 8 1 3 ma and a lower intercept at 160 19 ma mswd 0 72 the upper intercept age is interpreted to indicate the timing of bimodal volcanism and the lower intercept age is interpreted to reflect jurassic thermal metamorphism this is the first definite evidence supporting the existence of a formation in the ogcheon belt that is at least in part late precambrian nd isotope and trace element geochemistry of the amphibolites and felsic metavolcanics suggests that they originated from a mantle source in a continental rift environment the rift does not appear to have matured enough to develop oceanic crust since rocks indicating deep sea environments are absent the possibility that the ogcheon belt is an extension of the east chinese collision belt as suggested by several authors is not supported by the available evidence

isotopic evidence for the source of ca and s in soil gypsum anhydrite and calcite in the atacama desert chile abstract the origin of pedogenic salts in the atacama desert has long been debated possible salt sources include in situ weathering at the soil site local sources such as aerosols from the adjacent pacific ocean or salt encrusted playas salars and extra local atmospheric dust to identify the origin of ca and s in atacama soil salts we determined 34 s and 87 sr 86 sr values of soil gypsum anhydrite and 87 sr 86 sr values of soil calcite along three east west trending transects our results demonstrate the strong influence of marine aerosols on soil gypsum anhydrite development in areas where marine fog penetrates inland results from an east west transect located along a breach in the coastal cordillera show that most soils within 90 km of the coast and below 1300 m in elevation are influenced by marine aerosols and that soils within 50 km and below 800 m in elevation receive 50 of ca and s from marine aerosols 34 s values 14 and 87 sr 86 sr values 0 7083 in areas where the coastal cordillera is 1200 m in elevation however coastal fog cannot penetrate inland and the contribution of marine aerosols to soils is greatly reduced most pedogenic salts from inland soils have 34 s values between 5 0 to 8 0 and 87 sr 86 sr ratios between 0 7070 and 0 7076 these values are similar to average 34 s and 87 sr 86 sr values of salts from local streams lakes and salars 5 4 2 34 s and 0 70749 0 00045 87 sr 86 sr in the andes and atacama suggesting extensive eolian reworking of salar salts onto the surrounding landscape ultimately salar salts are precipitated from evaporated ground water which has acquired its dissolved solutes from water rock interactions both high and low temperature along flowpaths from recharge areas in the andes therefore the main source for ca and s in gypsum anhydrite in non coastal soils is indirect and involves bedrock alteration not surficially on the hyperarid landscape but in the subsurface by ground water followed by eolian redistribution of ground water derived salar salts to soils the spatial distribution of high grade nitrate deposits appears to correspond with areas that receive the lowest fluxes of local marine and salar salt supporting arguments for tropospheric nitrogen as the main source for soil nitrate

earthquake clusters in southern california i identification and stability 1 we use recent results on statistical analysis of seismicity to present a robust method for comprehensive detection and analysis of earthquake clusters the method is based on nearest neighbor distances of events in space time energy domain the method is applied to a 1981 2011 relocated seismicity catalog of southern california having 111 981 events with magnitudes m 2 and corresponding synthetic catalogs produced by the epidemic type aftershock sequence etas model analysis of the etas model demonstrates that the cluster detection results are accurate and stable with respect to 1 three numerical parameters of the method 2 variations of the minimal reported magnitude 3 catalog incompleteness and 4 location errors application of the method to the observed catalog separates the 111 981 examined earthquakes into 41 393 statistically significant clusters comprised of foreshocks mainshocks and aftershocks the results reproduce the essential known statistical properties of earthquake clusters which provide overall support for the proposed technique in addition systematic analysis with our method allows us to detect several new features of seismicity that include 1 existence of a significant population of single event clusters 2 existence of foreshock activity in natural seismicity that exceeds expectation based on the etas model and 3 dependence of all cluster properties except area on the magnitude difference of events from mainshocks but not on their absolute values the classification of detected clusters into several major types generally corresponding to singles burst like and swarm like sequences and correlations between different cluster types and geographic locations is addressed in a companion paper

calibrating the late ordovician glaciation and mass extinction by the eccentricity cycles of earth s orbit a process based sedimentological analysis of upper ordovician glacial marine rocks in africa suggests that full glaciation of the continental shelf started in the late extraordinarius zone of the hirnantian two cycles of ice sheet growth are represented during full glaciation initial terrestrial ice sheet growth in the early extraordinarius zone influenced the first event of the late ordovician mass extinction retreat of the ice sheet from the shelf ended by the persculptus zone when the second event of the late ordovician mass extinction began eccentricity controlled ice sheet growth is assumed periodicity 0 1 m y hence two cycles of full glaciation lasted 0 2 m y the duration of the extraordinarius zone is estimated as 0 5 m y therefore the minimum duration of the first extinction event was 0 3 m y

history of the clay rich unit at mawrth vallis mars high resolution mapping of a candidate landing site the mawrth vallis region is covered by some of the largest phyllosilicate rich outcrops on mars making it a unique window into the past history of mars in terms of water alteration potential habitability and the search for past life a landing ellipse had been proposed for the curiosity rover this area has been extensively observed by the high resolution imaging science experiment and the compact reconnaissance imaging spectrometer for mars offering the possibility to produce geologic structural and topographic maps at very high resolution these observations provide an unprecedented detailed context of the rocks at mawrth vallis in terms of deposition alteration erosion and mechanical constraints our analyses demonstrate the presence of a variety of alteration environments on the surface and readily accessible to a rover the presence of flowing water at the surface postdating the formation of the clay rich units and evidence for probable circulation of fluids in the rocks at different depths these rocks undergo continuous erosion creating fresh outcrops where potential biomarkers may have been preserved the diversity of aqueous environments over geological time coupled to excellent preservation properties make the area a very strong candidate for future robotic investigation on mars like the nasa mars 2020 mission

timing of mylonitization in the funatsu shear zone within hida belt of southwest japan implications for correlation with the shear zones around the ogcheon belt in the korean peninsula abstract the funatsu shear zone is an early mesozoic dextral ductile shear zone located in the hida belt of southwest japan consisting mainly of granite mylonites the jurassic funatsu granites intrude the hida metamorphic rocks and the granite mylonites the shrimp u pb zircon ages of granite mylonites in the funatsu shear zone around the tateyama area are 250 2 2 ma and 240 2 ma shrimp u pb zircon age of the okumayama granodiorite which is a member of the funatsu granites and which intrudes the granite mylonite is 191 3 ma we interpret that the timing of mylonitization in the funatsu shear zone to be after 240 ma and prior to 191 ma triassic to early jurassic and possibly around 215 211 ma late triassic corresponding to the k ar ages of hornblende in basic inclusions of the granite mylonite in the korean peninsula dextral ductile shear movement occurred in the cheongsan shear zone of south central ogcheon belt during middle to late triassic time accompanied by the intrusion of jurassic daebo granites which are correlated to the funatsu granites the similarities in geology deformation characteristics timing of mylonitization and paleogeographic location suggest that the funatsu shear zone can be correlated to the cheongsan shear zone

coordinated spectral and xrd analyses of magnesite nontronite forsterite mixtures and implications for carbonates on mars 1 mineral detection on mars largely relies on laboratory data of minerals and mineral mixtures the objective of this study is to provide reflectance spectra in the visible near infrared vnir and mid ir regions x ray diffraction xrd data and mossbauer spectra of a suite of carbonate phyllosilicate and olivine mixtures in order to facilitate identification and characterization of these minerals on mars remote sensing observations indicate that combinations of these minerals are present in ancient rocks on mars around the isidis basin and in gusev crater magnesite nontronite and forsterite size fractions 125 m were selected for this study results of the vnir reflectance analyses illustrate the complexity of vnir spectra of mixtures analyses of the nir band depths near 2 3 2 5 3 4 and 4 m showed clear trends with carbonate abundance although the data are not linear mixtures of magnesite and nontronite exhibited a band near 2 3 m much closer to that observed for nontronite than that for magnesite vnir analyses of the mixtures indicated that a small amount of forsterite in any of the mixtures contributed a large increase in the broad 1 m band and hence the red slope characteristic of fe2 bearing minerals mid ir mixture spectra were dominated by magnesite and forsterite and nontronite was much more difficult to detect by mid ir spectra in the mixtures this could be related to why phyllosilicates are detected in many locations on mars using data collected by the compact reconnaissance imaging spectrometer for mars but not detected using data collected by the thermal emission spectrometer mossbauer spectroscopy is well suited for analyses of fe2 and fe3 bearing minerals and modeling of the peak areas gave well correlated trends for nontronite and forsterite abundances where abundant fe was present xrd full pattern fitting analyses were performed on the magnesite forsterite series giving results within 6 wt of the actual values with a mean difference between actual and calculated values of 2 4 wt this study provides important laboratory data for characterizing the spectral and xrd properties of mineral mixtures that will facilitate mineral identification on mars carbonates in particular have been primarily observed at low abundances and in small outcrops and they are frequently found mixed with other minerals through analyses of mineral mixtures using multiple data sets this study seeks to provide ground truthing that will enable better coordination of carbonate detections in the dust and rocks of mars

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

surface and subsurface composition of the life in the atacama field sites from rover data and orbital image analysis 1 the life in the atacama project examined six different sites in the atacama desert chile over 3 years in an attempt to remotely detect the presence of life with a rover the remote science team using only orbital and rover data sets identified areas with a high potential for life as targets for further inspection by the rover orbital data in the visible near infrared vnir and in the thermal infrared tir were used to examine the mineralogy geomorphology and chlorophyll potential of the field sites field instruments included two spectrometers vnir reflectance and tir emission and a neutron detector this project represents the first time a neutron detector has been used as part of a science blind rover field test rover based spectroscopy was used to identify the composition of small scale features not visible in the orbital images and to improve interpretations of those data sets the orbital and ground based data sets produced consistent results suggesting that much of the field sites consist of altered volcanic terrains with later deposits of sulfates quartz and iron oxides at one location site a the ground based spectral data revealed considerably greater compositional diversity than was seen from the orbital view one neutron detector transect provided insight into subsurface hydrogen concentrations which correlated with life and surface features the results presented here have implications for targeting strategies especially for future mars rover missions looking for potential habitats paleohabitats

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

deep alteration between hellas and isidis basins abstract recent investigations of alteration of martian crustal outcrops suggest putative crustal hydrothermal systems which are favorable environments for the emergence of life in this study we perform an analysis of the crism targeted observations covering crustal outcrops in the region between the hellas and isidis basins with the goal of investigating the alteration phases over the wide studied region we detect the presence of possible serpentines chlorites smectites and carbonates these detections occur within ejecta blankets crater walls and central uplifts of impact craters we investigate the relation between the observed associations of minerals and the ages of the impact craters assessed by crater count no clear relation is observed we also investigate the relationship between the group of detected mineral and the pre impact depth of the studied outcrops assessed from the size of the impact craters this method allows us to reconstruct the pre impact cross section we suggest that alteration of the first 7 km of the crust between the hellas and isidis basins may have undergone alteration processes

magmatism along the southeast margin of the yangtze block precambrian collision of the yangtze and cathysia blocks of china the time and the environment of formation of igneous rocks along the southern margin of the yangtze continental block in southern anhui province and northeastern jiangxi province china are discussed sm nd dating for samples from two ophiolite suites give ages of about 1 ga late proterozoic granodiorites in the study area have ages of about 0 9 ga and have normal intrusive relations against banxi group metamorphic country rocks trace element abundances and initial nd isotope ratios for ophiolite and proterozoic granodiorites are consistent with formation in an island arc environment in contrast sr and nd isotopes for mesozoic granitoids of the region suggest that they are products of remelting of crustal sources similar to the basement of the yangtze block these relations do not support a recently proposed mesozoic overthrust tectonic model for southeast china but rather favor a late precambrian collision history for the yangtze and cathysia blocks

late palaeozoic to early mesozoic geodynamic evolution of the circum pacific orogenic belt in south korea and southwest japan abstract a review of the overall features of the late palaeozoic early mesozoic orogen of southwest japan and its korean hinterland allows a new geodynamic model for the building of the east asian margin to be proposed during middle carboniferous to early permian times an oceanic basin formed in a passive margin environment at a moderate spreading rate as the honshu continental block drifted away from the sino korean continent during that period paralic platform conditions and extensional synsedimentary tectonics prevailed in korea in middle permian times the closure of the oceanic area was responsible for yakuno ophiolite obduction and high pressure metamorphism while highly subsiding coal basins developed in the emerged korean hinterland thereafter in late permian times when the honshu block collided with the asian margin akiyoshi orogeny locally derived terrestrial clastic sedimentation in korea has succeeded coal measure deposition with local unconformity in early triassic times the collision was completed and regional uplift of the thickened crust resulted in the deposition of thick distal siliciclastic rocks in rapidly subsiding hinterland troughs korea and flyschoid deposition in the tamba foreland basin outer zone of southwest japan middle to late triassic medium to low pressure metamorphism large scale transcurrent tectonics and associated calc alkaline synkinematic plutonism in the hida and ogcheon belts represent a post collisional feature of the akiyoshi orogenic event post tectonic intrusives and terrestrial deposits post date intracratonic tectonics at ca 200 ma thus the akiyoshi orogeny of southwest japan is a result of continental drift and ensuing collisional rewelding of a fragment of sino korea the honshu microcontinent

terrestrial analogs for interpretation of infrared spectra from the martian surface and subsurface sulfate nitrate carbonate and phyllosilicate bearing atacama desert soils 1 hyperarid 6 5 m was not suited for salt and phyllosilicate detection because of overlapping spectra from primary silicates e g feldspar water and carbon dioxide the visible near infrared 0 35 2 5 m region was suited for detecting carbonate nitrate gypsum water of hydration and phyllosilicate hydroxyls without interference from primary silicates however gypsum water of hydration features can obscure phyllosilicate hydroxyl carbonate and nitrate features if gypsum levels are high overtone combination absorption features in the midinfrared were determined to be the best indicators of sulfate 4 48 4 70 m nitrate 4 12 m and carbonate 3 98 m because interferences from overlapping primary silicate and water features are not present in this region interferences from co2 and thermal emission effects in the overtone combination region are possible but may be minimized by corrective techniques infrared analysis of atacama desert soils can provide insight into the spectral search of sulfate nitrate carbonate and phyllosilicate containing soils on mars

tectonometamorphic evolution of the permo triassic songrim indosinian orogeny evidence from the late paleozoic pyeongan supergroup in the northeastern taebaeksan basin south korea the deformed and metamorphosed middle pennsylvanian to early triassic rocks of the pyeongan supergroup occurring in northeastern flank of the paleozoic taebaeksan basin east central south korea record the impact of the late permian triassic songrim indosinian collisional orogeny in the eastern eurasia margin analysis of meso and microstructures and their relationship with porphyroblast growth has revealed that these metasedimentary rocks were affected by four deformation events d1 d4 during the polyphase deformations successive foliations with alternately steep s1 and s3 and flat lying s2 and s4 orientations were produced with growth of chloritoid andalusite and kyanite porphyroblasts during d1 and d2 and growth of garnet staurolite and andalusite porphyroblasts during d3 and d4 shrimp u pb detrital zircon ages 330 310 ma from metapelites in the oldest unit of the pyeongan supergroup in the study area combined with the previous data on sandstone compositions indicate magmatic activity that was contemporaneous with the initial deposition of the pyeongan supergroup this also suggests that the pyeongan supergroup was deposited in an arc related foreland basin at an active continental margin during the late carboniferous and permian time two contractional deformation events d1 and d3 and two events related to gravitational flattening d2 and d4 along with barrovian type medium pressure regional metamorphism may have resulted from the late permian triassic songrim orogeny related to collision between the north and south china blocks and or collision between the eastern eurasia margin and the proto japan terrane

hydrodynamic and suspended sediment transport controls on river mouth morphology 1 river mouths building into standing bodies of water have strikingly varied growth habits this presents a compelling pattern formation problem that is also of great practical relevance for subsurface prediction and managing coastal wetlands here we present a generalized 2 5 dimensional potential vorticity pv theory that explains sedimentation patterns of a sediment laden stationary jet by coupling an understanding of vorticity with suspended sediment concentration fields we explore the physical meaning of this new sediment pv definition and its impact on outflow depositional patterns by analyzing data from a shallow wall bounded plane jet experiment and by discussing new theoretical insights a key result is that lateral advection and diffusion of suspended sediment are directly proportional to jet vorticity a feature that reveals the mechanistic process that forms elongated channels by focused levee deposition the new pv theory constitutes a more generalized mathematical framework that expands the rouse theory for the equilibrium of suspended sediment

martian polar and circum polar sulfate bearing deposits sublimation tills derived from the north polar cap previous spectroscopic studies have shown the presence of hydrated minerals in various kinds of sedimentary accumulations covering and encircling the martian north polar cap more specifically gypsum a hydrated calcium sulfate has been detected on olympia planum a restricted part of the circum polar dune field to further constrain the geographical distribution and the process of formation and accumulation of these hydrated minerals we performed an integrated morphological structural and compositional analysis of a key area where hydrated minerals were detected and where the main polar landforms are present by the development of a spectral processing method based on spectral derivation and by the acquisition of laboratory spectra of gypsum ice mixtures we find that gypsum bearing sediment is not restricted to the olympia planum dunes but is also present in all kinds of superficial sediment covering the surface of the north polar cap and the circum polar dune field spectral signatures consistent with perchlorates are also detected on these deposits the interpretation of landforms reveals that this gypsum bearing sediment was released from the ice cap by sublimation we thus infer that gypsum crystals that are now present in the circum polar dune field derive from the interior of the north polar cap gypsum crystals that were initially trapped in the ice cap have been released by sublimation of the ice and have accumulated in the form of ablation tills at the surface of the ice cap these gypsum bearing sublimation tills are reworked by winds and are transported towards the circum polar dune field comparison with sulfates found in terrestrial glaciers suggests that gypsum crystals in the martian north polar cap have formed by weathering of dust particles either in the atmosphere prior to their deposition during the formation of the ice cap and or in the ice cap after their deposition

spectral properties of ca sulfates gypsum bassanite and anhydrite this study of the spectral properties of ca sulfates was initiated to support remote detection of these minerals on mars gypsum bassanite and anhydrite are the currently known forms of ca sulfates they are typically found in sedimentary evaporites on earth but can also form via reaction of acidic fluids associated with volcanic activity reflectance emission transmittance and raman spectra are discussed here for various sample forms gypsum and bassanite spectra exhibit characteristic and distinct triplet bands near 1 4 1 5 m a strong band near 1 93 1 94 m and multiple features near 2 1 2 3 m attributed to h2o anhydrite bassanite and gypsum all have so4 combination and overtone features from 4 2 5 m that are present in reflectance spectra the mid ir region spectra exhibit strong so4 3 and 4 vibrational bands near 1150 1200 and 600 680 cm 1 8 5 and 16 m respectively additional weaker features are observed near 1005 1015 cm 1 10 m for 1 and near 470 510 cm 1 20 m for 2 the mid ir h2o bending vibration occurs near 1623 1630 cm 1 6 2 m the visible near infrared region spectra are brighter for the finer grained samples in reflectance and emission spectra of the mid ir region the 4 bands begin to invert for the finer grained samples and the 1 vibration occurs as a band instead of a peak and has the strongest intensity for the finer grained samples the 2 vibration is a sharp band for anhydrite and a broad peak for gypsum the band center of the 1 vibration follows a trend of decreasing frequency increasing wavelength with increasing hydration of the sample in the transmittance raman and reflectance spectra anhydrite forms at elevated temperatures compared to gypsum and at lower temperature salt concentration and ph than bassanite the relative humidity controls whether bassanite or gypsum is stable thus distinguishing among gypsum bassanite and anhydrite via remote sensing can provide constraints on the geochemical environment

a large sedimentary basin in the terra sirenum region of the southern highlands of mars abstract different lines of evidence point to hydrological cycling in the martian past the extent duration and magnitude of this cycling remains unclear as well as the magnitude of aqueous processes on the surface here we provide geomorphic and mineralogic evidence of a large inter crater sedimentary basin located in the terra sirenum region which was once covered by a body of liquid water with an areal extent of at least 30 000 km 2 and a depth of approximately 200 m the topographic basin which is modified by a number of large impact craters is partly controlled by ancient impact and tectonic structures as a result of evaporation of the large body of water salt flats formed in the lowest topographic reaches of the basin hydrated phyllosilicates occur in close proximity to the salt flats and in the ejecta and rim materials of small impact craters with stratigraphic relations that suggest that they underlie the evaporite deposits crater statistics place the maximum age of aqueous activity during the late noachian epoch the relatively pristine mineral deposits in the basin have a high potential to yield information of the geochemistry and water activity during the ancient noachian period when conditions were seemingly more conducive to life

hydrochemistry of two adjacent acid saline lakes in the andes of northern chile numerous closed basins in central andes contain saline lakes and salt crusts salars almost all of them are neutral or alkaline lakes only two lakes out of 84 studied in bolivia and chile are acid lakes they are located in two adjacent intravolcanic basins in northern chile the origin of acidity is due to the juxtaposition of two factors the very strong hydrothermal alteration of volcanic rocks in the drainage basins and the high sulfur content in the whole area primary minerals are replaced by amorphous silica limonite chlorite white mica and elemental sulfur the buffer capacity of the volcanic rocks has been considerably lowered and is no longer sufficient to neutralize the sulfuric acid generated by oxidation of native sulfur dissolution modeling of chlorite white mica and sulfur in a neutral inflow water leads to a composition very much like that of the acid inflows the modeled acid solution is oversaturated with respect to alunite by several orders of magnitude exactly as observed in natural acid inflows some of the alunite reported in the altered zones of the drainage basins could be supergene in origin the simulation of evaporation of acid inflows shows a good agreement between salar brines and computed brines indicating that the acidic brines do not originate in the past hydrothermal activity but result from recent supergene processes the leaching of the severely altered volcanic rocks and the direct evaporation of the resulting acidic waters aluminium shows a conservative behavior in both salars reflecting the drastic lowering of the saturation index of al sulfate minerals in evaporating acid brines which is confirmed by the lack of detection of alunite within both salars

evidence for significant clockwise rotations of the korean peninsula during cretaceous abstract in an effort to evaluate the cretaceous magnetostratigraphy for the korean peninsula and to establish the tectonic coherence of its various elements we collected paleomagnetic data from 121 samples from 20 sites within the chilgok formation 108 3 109 9 ma in the gyeongsang basin together with previously published data we evaluate the results from a total of 163 sites in the basin we combine our age model with results from recent stratigraphic paleomagnetic and radiometric geochemical studies in this study we found that two distinct declination shifts decrease with younging direction indicating two clockwise rotational events of the korean peninsula with respect to the eurasia continent the earlier event took place during 130 100 ma phase i newly termed goguryeo disturbance and a later one during 80 50 ma phase iii belonging to bulguksa orogeny the mean rotation rate in the interval from 115 2 to 103 8 ma phase i is about 0 74 ma while the rate from 90 9 to 79 8 ma phase ii is 0 19 ma based on paleolatitude change during phase i we infer that the korean peninsula eastern part of the sino korea block migrated southward about 300 km after the complete amalgamation of the sino korea block into the eurasian continent resulting in n s compression within the korean peninsula and manchuria large scale strike slip faults e g tan lu fault okcheon boundary fault were probably rejuvenated in the sino korea block during phase i

spectral reflectance and morphologic correlations in eastern terra meridiani mars the mars express observatoire pour la mineralogie l9eau les glaces et l9activite omega hyperspectral image data covering eastern terra meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite bearing plains explored by the opportunity rover identification of crystalline water in kieserite mgso4 h2o is linked to materials exposed in a valley and plateau to the north of hematite bearing plains the mineralogical similarities between the etched terrain deposits examined with omega data and the layered rocks examined by opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales

mineralogy of juventae chasma sulfates in the light toned mounds mafic minerals in the bedrock and hydrated silica and hydroxylated ferric sulfate on the plateau 1 juventae chasma contains four light toned sulfate bearing mounds denoted here as a d from west to east inside the trough mafic outcrops at the base of the mounds and in the wall rock and light toned layered deposits of opal and ferric sulfates on the plateau hyperspectral visible near infrared compact reconnaissance imaging spectrometer for mars crism spectra were used to identify monohydrated and polyhydrated sulfate phs outcrops of layered material on the bright mounds most of the monohydrated sulfate signatures closely resemble those of szomolnokite feso4 h2o characterized by a water band near 2 08 m while some areas exhibit spectral features more similar to those of kieserite mgso4 h2o with a band centered closer to 2 13 m the largest phs outcrops occur on the top of mound b and their spectral features are most consistent with ferricopiapite melanterite and starkeyite but a specific mineral cannot be uniquely identified at this time coordinated analyses of crism maps mars orbiter laser altimeter elevations and high resolution imaging science experiment images suggest that mounds a and b may have formed together and then eroded into separate mounds while mounds c and d likely formed separately mafic minerals low ca pyroxene high ca pyroxene and olivine are observed in large 2 10 km wide outcrops in the wall rock and in smaller outcrops 50 500 m across at the floor of the canyon most of the wall rock is covered by at least a thin layer of dust and does not exhibit strong features characteristic of these minerals the plateau region northwest of juventae chasma is characterized by an abundance of light toned layered deposits one region contains two spectrally unique phases exhibiting a highly stratified terraced pattern crism spectra of one unit eroded into swirling patterns with arc like ridges exhibit a narrow 2 23 m band assigned to hydroxylated ferric sulfate a thin layer of a fractured material bearing an opaline silica phase is observed at the contact between the older plateau unit and the younger hydroxylated ferric sulfate bearing light toned layered deposits hydrothermal processes may have produced an acidic environment that fostered formation of the hydrated silica and hydroxylated ferric sulfate units

possible eastward extension of chinese collision belt in south korea the imjingang belt structural petrological and geochronological data from the middle korean peninsula indicate that the qinling dabie sulu collisional belt of east central china crosses the yellow sea and extends into the imjingang belt the yeoncheon complex first identified as the western imjingang belt comprises primarily north dipping metamorphic sequences 1 the northern jingok unit consisting of barrovian type metapelites and 2 the southern samgot unit consisting of calc silicate and amphibolitic rocks south vergent structures with reverse sense shearing are dominant in the jingok unit whereas late normal sense shearing is pervasive in the samgot unit and the deformed granitoid to the south these structural patterns are interpreted to correspond to extensional deformation associated with uplift following compression in a collisional belt pressure temperature p t estimates from the amphibolites suggest a high p amphibolite facies metamorphism 8 13 kbar and 630 790 c possibly evolving from eclogite facies conditions along a clockwise p t path sm nd and rb sr geochronological data suggest that the amphibolites emplaced in late proterozoic time were metamorphosed during permian triassic time

detrital zircon u pb geochronology and tectonic implications of the paleozoic sequences in western south korea abstract the middle paleozoic metasedimentary sequences of the western gyeonggi massif taean formation and wolhyeonri complex imjingang belt and southwestern okcheon belt provide clues to the successive tectonic events that occurred during the evolution of the korean peninsula in this study we present shrimp u pb ages of detrital zircon grains from the metasandstones of the taean formation and yeoncheon group of the imjingang belt and from quartzites in three paleozoic formations of the southwestern okcheon belt the zircon grains from all of the samples yielded similar u pb age spectra of paleoarchean neoarchean to middle paleozoic with a dominant age population within the paleozoic the maximum ages of deposition estimated from the youngest dominant concordant detrital zircons were 431 457 ma for the western gyeonggi massif and imjingang belt and 380 355 ma for the southwestern okcheon belt permian metamorphic zircon overgrowths correlated with subduction prior to the triassic collision were also found middle paleozoic metamorphic zircon overgrowths that can be compared to those of the yunkai wuishan orogenic belt of the cathaysia block were indentified in the wolhyeonri complex the dominant zircon populations of this study and the available data for the korean peninsula compare well with those from the yangtze block cathaysia block and qilian qinling orogenic belt which were located at the northeastern margin of eastern gondwana during the early paleozoic

two years at meridiani planum results from the opportunity rover the mars exploration rover opportunity has spent more than 2 years exploring meridiani planum traveling 8 kilometers and detecting features that reveal ancient environmental conditions these include well developed festoon trough cross lamination formed in flowing liquid water strata with smaller and more abundant hematite rich concretions than those seen previously possible relict hopper crystals that might reflect the formation of halite thick weathering rinds on rock surfaces resistant fracture fills and networks of polygonal fractures likely caused by dehydration of sulfate salts chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergone substantial chemical alteration from a precursor basaltic composition observations from microscopic to orbital scales indicate that ancient meridiani once had abundant acidic groundwater arid and oxidizing surface conditions and occasional liquid flow on the surface

new lu hf and pb pb age constraints on the earliest animal fossils abstract the neoproterozoic doushantuo formation south china preserves a unique assemblage of early multicellular fossils and overlies rocks which are thought to have formed during an ice age of global extent the age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the proterozoic eon until now direct dating of sedimentary formations such as the doushantuo has been difficult and associated with large uncertainties here we show that dating of doushantuo phosphorites by a novel lu hf dating method and conventional pb pb geochronometry independently yield ages of 584 26 ma and 599 3 4 2 ma respectively these ages are in agreement with bio and chemostratigraphical observations and show that the doushantuo animal remains predate diverse ediacaran fossil assemblages making them the oldest unambiguous remains of metazoans currently known furthermore the pb pb age for the post glacial doushantuo rocks suggests that the neoproterozoic glaciation in china might predate glacial rocks in eastern north america commonly associated with the younger marinoan of two major neoproterozoic glaciations the combination of lu hf and pb pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on proterozoic biological and environmental history

lower silurian hot shales in north africa and arabia regional distribution and depositional model abstract lowermost silurian organic rich hot shales are the origin of 80 90 of palaeozoic sourced hydrocarbons in north africa and also played a major role in petroleum generation on the arabian peninsula in most cases the shales were deposited directly above upper ordovician peri glacial sandstones during the initial early silurian transgression that was a result of the melting of the late ordovician icecap deposition of the main organic rich shale unit in the north african arabian region was restricted to the earliest silurian rhuddanian stage acuminatus atavus and probably early cyphus graptolite biozones during this short period 1 2 m y a favourable combination of factors existed which led to the development of exceptionally strong oxygen deficiency in the area in most countries of the study area the post rhuddanian silurian shales are organically lean and have not contributed to petroleum generation the distribution and thickness of the basal silurian hot shales have been mapped in detail for the whole north african region using logs from some 300 exploration wells in libya tunisia algeria and morocco in addition all relevant accessible published and unpublished surface and subsurface data of the lower silurian shales in north africa and arabia have been reviewed including sedimentological biostratigraphic and organic geochemical data the lowermost silurian hot shales of northern gondwana are laterally discontinuous and their distribution and thickness were controlled by the early silurian palaeorelief which was shaped mainly by glacial processes of the late ordovician ice age and by pan african and infracambrian compressional and extensional tectonism the thickest and areally most extensive basal silurian organic rich shales in north africa occur in algeria tunisia and western libya while on the arabian peninsula they are most prolific in saudi arabia oman jordan and iraq the hot shales were not deposited in egypt which was a large palaeohigh at that time the depositional model presented may help in better understanding the source potential of the basal silurian shales in less explored regions of north africa and arabia including morocco northern niger and the kufra basin in southeast libya

structural characteristics of the central ogcheon belt south korea orogen parallel tectonic transport model abstract the rocks in the central ogcheon belt south korea underwent three deformational phases d1 d2 and d3 during the mesozoic era in the study area nw and ne trending geological structures such as thrusts and folds are juxtaposed the nw and ne trending folds deform isoclinal folds f1 with axial planar slaty cleavage s1 and have axial planar crenulation cleavage all of these folds are overprinted by brittle faults d3 it is inferred from field data that the nw and ne trending structures are products of a single deformational phase d2 a very large scale inclined ne vergent isoclinal fold f1 produced an irregular boundary of precambrian basement and a basement promontory which acted as a structural obstacle against subsequent deformational phases during the e vergent phase d2 deformation partitioning occurred due to the irregular block boundary and orogen parallel and orthogonal structures were produced the d3 phase is recognized as large scale e w trending structures including folds and faults thus the structural evolution of the central ogcheon belt is related to the clockwise rotation of the maximum compressive stress axis from ne sw to n s during the mesozoic era this study shows that the shape of colliding boundary is a very important factor in controlling the structural pattern and evolution in the study area

hydrochemistry on the yilgarn block western australia ferrolysis and mineralisation in acidic brines abstract in the southeastern part of western australia internal drainage and a semi arid climate have resulted in extensive development of playas the brines beneath the playas wedge outwards and force local infiltration to crop out at playa margins as discharge zones the discharging water contains dissolved fe2 oxidation and hydrolysis ferrolysis of which generates very acidic water ph 2 8 at least some of the alkalinity generated by the original reduction of fe3 has been sequestered as subsurface calcrete within local soils the acidity causes the dissolution of kaolinite which is abundant in playa sediments and as a thick capping on weathered bedrock giving water with a low ph and high concentrations of dissolved al and si evaporation and mixing with playa brines containing high concentrations of k and so4 causes alunite to precipitate as ph rises from a minimum of 2 8 at chlorinities of 1 to 2 m to 6 at chlorinities of 4 8 m the alunite deposits formed by this process are many orders of magnitude larger than occurrences elsewhere in the world the large scale mobilisation of si during this process may be one mechanism for the formation of silica cemented rocks silcrete that are widespread in the australian regolith

petrogenesis of paleoproterozoic 2 02 1 96 ga metagranitoids in the southwestern yeongnam massif korean peninsula and their significance for the tectonic history of northeast asia insights from zircon u pb hf isotope and whole rock geochemical compositions abstract the jangsu gokseong area is located in the southwestern part of the yeongnam massif and mainly consists of precambrian metagranitoids metagranite metaleucogranite and metagranodiorite with minor migmatite and marble sensitive high resolution ion microprobe shrimp zircon u pb dating shows that the metagranitoids emplaced during ca 2 02 1 96 ga and metamorphosed at ca 1 89 1 87 ga the metagranitoids show calc alkaline trends enrichment in large lithophile elements and negative nb and ta anomalies with low sr y

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

metamorphic evolution of the baekdong metabasite in the hongseong area south korea and its relationship with the sulu collision belt of china abstract ultramafic rocks in the hongseong area southwest gyeonggi massif south korea occur as lenses within precambrian granitic gneiss the ultramafic bodies contain metabasite boudins that have undergone at least three stages of metamorphism the first stage mineral assemblage is garnet augite x jd aeg 0 06 0 11 hornblende plagioclase rutile titanite and represents a transitional condition between the eclogite eg high pressure granulite hg and amphibolite facies am the second stage is characterized by an assemblage of garnet augite x jd aeg 0 01 0 06 hornblende plagioclase titanite representing the transitional condition between low pressure granulite facies lg and am a third stage is identified by an am assemblage of hornblende plagioclase garnet in symplectites formed during garnet breakdown the p t conditions of the first second and third stages are 11 8 16 3 kb 690 780 c 8 2 8 7 kb 660 820 c and 4 0 6 3 kb 490 610 c respectively cores and rims of two garnets in the country rock granitic gneiss give p t estimates of 8 9 13 5 kb 640 815 c and 5 5 6 3 kb 575 680 c indicating a retrograde p t path similar to that of the metabasite boudins ti zr y data indicate that the baekdong metabasites probably had an island arc paleotectonic setting while it may be concluded that the hongseong area in the gyeonggi massif is a possible extension of the sulu collision belt in china sm nd whole rock garnet isochron ages of the baekdong metabasites 268 297 ma are significantly older than the age of uhp metamorphism 208 245 ma in the dabie sulu collision belt hence collision between the north and south china blocks may have occurred earlier in the korean peninsula than in china

spectral reflectance of carbonate minerals in the visible and near infrared 0 35 2 55 microns calcite aragonite and dolomite

the origin of brines and salts in chilean salars a hydrochemical review abstract northern chile is characterized by a succession of north south trending ranges and basins occupied by numerous saline lakes and salt crusts collectively called salars fossil salt crusts are found to the west in the extremely arid central valley while active salars receiving permanent inflows fill many intravolcanic basins to the east in the semiarid cordillera sea salts and desert dust are blown eastward over the cordillera where they constitute an appreciable fraction of the solute load of very dilute waters salt content evaporative concentration of inflow waters leads to sulfate rich or calcium rich near neutral brines alkaline brines are almost completely lacking the alkalinity calcium ratio of inflow waters is lowered by the oxidation of native sulfur reducing alkalinity and the deposition of eolian gypsum increasing ca concentration theoretically so4 rich inflow waters and their derived so4 rich brines should be found in the intravolcanic basins of the cordillera because of the ubiquity of native sulfur while ca rich brines should prevail in sedimentary basins where ca rich minerals are abundant this relation is perfectly observed in the salar de atacama the largest in chile however several salars located within the volcanic cordillera belong to the ca rich group inflows and brines may have acquired their ca rich composition in pleistocene time when their drainage basins were mainly sedimentary later on recent lava flows and ignimbrites covered the sedimentary formations underground waters may have kept their early sedimentary signature by continuous recycling however the weathering of volcanic rocks tend to slowly shift the water compositions from the ca rich to the so4 rich type

distribution and formation of chlorides and phyllosilicates in terra sirenum mars 1 the terra sirenum region of mars located in the noachian southern highlands is mineralogically diverse providing unique insight into ancient aqueous processes analyses of remote sensing data over the region indicate the presence of both fe or mg rich phyllosilicates and a spectrally unique deposit interpreted to be rich in chloride salts the stratigraphic relationships indicate that the phyllosilicates are part of the ancient highland crust and that the salts were deposited at a later time in some instances there is clear morphological evidence that salts were mobilized and deposited by near surface waters

is the ogcheon metamorphic belt of korea the eastward continuation of the nanhua basin of china abstract the ogcheon metamorphic belt in central korea has been interpreted to be the eastward extension of the nanhua basin aulacogen of southeast china in this paper comparisons are made between the two regions based on stratigraphic thermal tectonic and other considerations from this comparison correlation of geological events between the nanhua basin and ogcheon metamorphic belt are at best equivocal the closest similarity is the presence in both regions of two major diamictite units of glacial origin and neoproterozoic age 750 690 ma range in china but of controversial origin and uncertain age in korea volcanic rocks in both regions appear to have similar petrological and geochemical traits and are interpreted to be rift related however their ages are different mostly 795 780 ma in the nanhua basin and c 750 ma in central korea so correlation remains uncertain more isotopic data from both regions may shed light on this comparison correlation between other pre carboniferous stratigraphic units in the two regions is hampered by the uncertainty about the stratigraphic age and succession in the ogcheon metamorphic belt stemming mainly from the absence of fossils and the strong tectonic metamorphic overprint both regions appear to have undergone deformation and metamorphism during the middle triassic indosinian songrim in some uncertain way related to the collision between the north and south china plates in the ogcheon metamorphic belt there has been no confirmation of a mid palaeozoic event but in the nanhua basin that event is recorded by stratigraphic and palaeogeographic evidence in the nanhua basin there is no evidence for an early permian metamorphic event that appears on isotopic grounds to have affected the ogcheon metamorphic belt this apparent difference has been interpreted as a result of diachronous deformation during late palaeozoic early mesozoic plate collisions that took place earlier in the east in korea than in the west in china

near infrared spectroscopy of lacustrine sediments in the great salt lake desert an analog study for martian paleolake basins the identification and characterization of aqueous minerals within ancient lacustrine environments on mars are a high priority for determining the past habitability of the red planet terrestrial analog studies are useful both for understanding the mineralogy of lacustrine sediments how the mineralogy varies with location in a lacustrine environment and for validating the use of certain techniques such as visible near infrared vnir spectroscopy in this study sediments from the pilot valley paleolake basin of the great salt lake desert were characterized using vnir as an analog for martian paleolake basins the spectra and subsequent interpretations were then compared to mineralogical characterization by ground truth methods including x ray diffraction automated scanning electron microscopy and several geochemical analysis techniques in general there is good agreement between vnir and ground truth methods on the major classes of minerals present in the lake sediments and vnir spectra can also easily discriminate between clay dominated and salt dominated lacustrine terrains within the paleolake basin however detection of more detailed mineralogy is difficult with vnir spectra alone as some minerals can dominate the spectra even at very low abundances at this site the vnir spectra are dominated by absorption bands that are most consistent with gypsum and smectites though the ground truth methods reveal more diverse mineral assemblages that include a variety of sulfates primary and secondary phyllosilicates carbonates and chlorides this study provides insight into the limitations regarding the use of vnir in characterizing complex mineral assemblages inherent in lacustrine settings

the pyeongan supergroup upper paleozoic lower triassic in the okcheon belt korea a review of stratigraphy and detrital zircon provenance and its implications for the tectonic setting of the eastern sino korean block abstract the tectonic setting of the okcheon belt in the korean peninsula has long been regarded as one of the important topics in discussing east asian tectonics the controversial tectonic setting of the okcheon belt before the triassic collision between north and south china limits proper understanding of the late paleozoic tectonics of east asia focusing on the upper paleozoic to lower triassic pyeongan supergroup coeval sedimentary records in different parts of the okcheon belt are reviewed this study has a clear advantage over previous assessments that build upon comparison between meta sedimentary units of unknown age in the region the pyeongan supergroup sediments show high similarity in both stratigraphy and detrital zircon u pb ages throughout the okcheon belt they are distinct from their age equivalents in south china while sharing characteristics with those in north korea and north china critical criteria include marine influence and enrichment of organic materials at each time period and relative proportion of mesoproterozoic silurian components in detrital zircon age population the combined results agree with the view that the entire okcheon belt was a single tectonic unit at least by the late carboniferous the results of this study favor the idea of the sino korean block encompassing the whole korean peninsula and cast doubts on the tectonic models that attribute the southern part of the korean peninsula to the south china block a retroarc foreland basin setting of the okcheon belt with detritus mainly provided from a subduction related orogen in the continent sided japan is inferred from the provenance characteristics of the detrital zircons

extensional tectonics within a subduction type orogen the case study of the wugongshan dome jiangxi province southeastern china abstract in southeastern china the wugongshan massif consists of metamorphic rocks and granites generally considered as basement rocks formed during an early paleozoic orogeny our structural and radiometric reappraisal of this massif shows that it results from a mesozoic doming in the metamorphic rocks the foliation defines an e w elliptical shape and bears a n s stretching lineation the axial zone of the dome is occupied by oriented plutons the outer part of the dome consists of devonian quartzite carboniferous permian limestone and triassic jurassic sandstone ductile deformation observed in the permian carbonates and older units develops contrasting kinematics the northern and southern flanks present top to the north and top to the south motions respectively the same divergent pattern of motion is recorded from brittle structures up to the jurassic sandstone the late cretaceous red beds are undeformed in the axial zone coaxial flow indicated by symmetric pressure shadows and quartz fabrics predominates along the n and s flanks of the dome post folial recumbent folds are symmetrically overturned to the n and s respectively but at the two extremities of the dome the fold axes are parallel to the stretching lineation 40 ar 39 ar ages of biotite and muscovite from mylonite and granite suggest a late triassic age for the ductile deformation and an early cretaceous age for the final doming the wugongshan dome is similar to a metamorphic core complex formed in an extensional tectonic regime a model which emphasizes plutonism is discussed from permian to early cretaceous southeastern china was a subduction type orogen the crust of which was thickened by accretion of mantle derived magmas the emplacement of a large amount of mesozoic granitoids in southeastern china promoted thermal softening and gravitational instability that allowed the crust to extend the formation of the wugongshan dome and other metamorphic core complexes appears to be a the direct consequence of plutonic activity and crust rheology

crustal structure of the gunsan basin in the se yellow sea from ocean bottom seismometer obs data and its linkage to the south china block abstract two major tectonic units in ne asia are the sino korean or north china and south china blocks that collided in the permo triassic periods the south china block is suggested to extend eastward to the korean peninsula across the southern yellow sea the gunsan basin is a well defined fault bounded sedimentary basin in the se yellow sea and is regarded as a structural link of the south china block to the korean peninsula we collected deep seismic sounding data recorded on ocean bottom seismometers to investigate how the crustal structure and nature of the south china block vary in the gunsan basin toward the middle part of the korean peninsula the main part of the gunsan basin is underlain by relatively thin 10 km thick upper and much thicker 20 km thick lower crustal layers indicating a close affinity to the south china block whereas it shows distinction from the korean peninsula underlain by upper and lower crustal layers with equal 15 km thickness a change in crustal structure is recognized under the eastern margin of the gunsan basin toward the korean peninsula that features a transition to the korean peninsula the thick lower crustal layer in the gunsan basin appears to be inherited from the evolution of the south china block including crustal shortening associated with the assembly of rodinia in the neoproterozoic before the collision between the sino korean and south china blocks

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

middle precambrian detrital monazite and zircon from the hida gneiss on oki dogo island japan their origin and implications for the correlation of basement gneiss of southwest japan and korea abstract monazite and zircon from seven paragneiss samples of the upper amphibolite facies grade from oki dogo island in the hida terrane western japan were analyzed for th u and pb on an electron microprobe most monazite grains are chronologically unzoned and give unequivocal chime chemical th u total pb isochron ages of 250 ma but some grains show a distinct core overgrowth relationship the cores retain evidence of pre 250 ma ages and are interpreted to be of detrital origin suggesting that monazite can be more immune to diagenetic and low grade metamorphic decompositions than had been thought previously zircon grains rounded to nearly euhedral give chime ages ranging from 3000 to 350 ma of particular interest are several rounded 3000 ma recycled zircons which perhaps originated from an archean terrain in the sino korean craton the youngest age of detrital zircons constrains that the gneiss protolith deposited after the 350 ma event the chime monazite and zircon ages for the paragneisses from oki dogo island and from the main part of the hida terrane reveal that the gneisses formed from permo carboniferous clastic sediments during a single metamorphism at ca 250 ma the results are in marked contrast to the current view that 1 the hida gneiss is a polymetamorphosed precambrian complex 2 the central part hida gneiss region and the eastern marginal part unazuki schist region of the hida terrane are correlative with the precambrian kyonggi massif and the paleozoic okchon zone in the korean peninsula respectively instead we consider that the okchon zone alone can be correlatable with the paleozoic hida terrane

hydrous minerals on mars as seen by the crism and omega imaging spectrometers updated global view 1 the surface of mars has preserved the record of early environments in which its basaltic crust was altered by liquid water these aqueous environments have survived in the form of hydrological morphologies and alteration minerals including clays and hydrated salts because these minerals probe on earth aqueous environments compatible with biotic activity understanding their formation processes on mars is of great exobiological relevance and also offers insight into earth s now erased ancient water environments using remote sensing we conducted a large scale investigation of the distribution composition age and geomorphic settings of hydrous minerals on mars providing a sharpened global view of the early aqueous environments and their evolution with time aqueous alteration seems to have produced clays on a planetary scale but these are found to be restricted to the oldest observable terrains on mars 4 gyr however very diverse aqueous environments have also been found which suggest widespread complex aqueous settings from the surface to kilometric depths and spanning over 1 gyr by building a robust statistical sample of detections the global trends inferred here attempt to provide a broad view of our current understanding of hydrous minerals on mars and provide context for more localized in depth analyses collectively these trends suggest that at least transient conditions have existed on mars which may have been favorable for pre biotic to biotic activity

characteristics of seismicity inside and outside the salton sea geothermal fieldcharacteristics of seismicity inside and outside the salton sea geothermal field

on developing thermal cave detection techniques for earth the moon and mars abstract the purpose of this study is to 1 demonstrate the viability of detecting terrestrial caves at thermal infrared wavelengths 2 improve our understanding of terrestrial cave thermal behavior 3 identify times of day when cave openings have the maximum thermal contrast with the surrounding surface regolith and 4 further our understanding of how to detect caves on earth the moon and mars we monitored the thermal behavior of two caves in the atacama desert of northern chile through this work we identified times when temperature contrasts between entrance and surface were greatest thus enabling us to suggest optimal overflight times the largest thermal contrast for both caves occurred during mid day one cave demonstrated thermal behavior at the entrance suggestive of cold trapping while the second cave demonstrated temperature shifts suggestive of airflow we also collected thermograms without knowing optimal detection times these images suggest both caves may also be detectable during off peak times we suggest cave detection using thermal remote sensing on earth and other planetary objects will be limited by 1 capturing imagery in the appropriate thermal wavelength 2 the size of cave entrance vs the sensor s spatial resolution 3 the viewing angle of the platform in relation to the slope trajectory of the cave entrance 4 the strength of the thermal signal associated with the cave entrance and 5 the time of day and season of thermal image capture through this and other studies we will begin to identify the range of conditions under which caves are detectable in the thermal infrared and thus improve our detection capabilities of these features on earth the moon and mars

compression to extension switch during the middle triassic orogeny of eastern china the case study of the jiulingshan massif in the southern foreland of the dabieshan abstract the jiulingshan massif is an e w trending anticlinorium in the south china block scb that forms the southern foreland of the qinling dabie orogen the jiulingshan consists of middle proterozoic ca 1 ga 800 ma metamorphic and plutonic rocks unconformably overlain by sinian to triassic rocks in these cover rocks two episodes of deformation of pre late triassic age are recognized namely a n s compressional phase characterized by south verging thrusts upright folds and vertical cleavage followed by an extensional phase characterized by layer parallel slip collapse folds and extensional allochthons of proterozoic slate on top of carboniferous to middle triassic carbonates the extensional tectonics appears to be a mechanical consequence of the compressional tectonics on a regional scale the jiulingshan massif forms one of the domed crustal scale shear zones of the scb that accommodated the continuing convergence that immediately followed the qinling dabie collision

comparison of the ordovician carboniferous boundary between korea and ne china implications for correlation and tectonic evolution abstract there is a great hiatus between ordovician and carboniferous strata in the northeast china and korean peninsula in order to understand geology and tectonic evolution and to find out the similarities and differences in both regions two sections in the western hill near beijing in ne china and several sections in the korean peninsula were selected to examine their geologic boundaries between lower and upper paleozoic strata to compare their characteristic features at four sites in the two sections in the western hill near beijing were examined their contact relations the hui yu section is the same horizon where one site is top of a quarry hill and the other of down hill mid carboniferous qingshuijian formation rests on the ordovician majiagou formation limestone beds are more commonly intercalated with shale and sandstone at site 2 of the hui yu section while at site 1 conglomerate beds are dominant site 1 of the se shu fen section shows eroded and concealed karst topography and conglomerate beds are intercalated within shale beds silurian and devonian strata are absent in these areas in the korean peninsula most o c contacts occur between ordovician limestone formation and carboniferous strata although silurian strata occur beneath the carboniferous strata in the jeongseon area and pyeongnam basin most contact relations are parallel unconformity and angular unconformity is rarely seen the o c relations in both regions are similar to each other and these indicate that the korean peninsula was located near or belonged to the sino korean paraplatform during paleozoic time

different sulfate sources and their post depositional migration in atacama soils abstract sulfate is one of the major salts accumulated in the hyperarid atacama desert chile its origin has been attributed to local weathering volcanic source sea salt and atmosphere deposition previous studies concluded that atmospheric sulfate is present in the desert but this term was poorly defined in terms of chemical origin and its contribution to the total sulfate budget in soil is debated the contribution of each potential sulfate source is expected to vary geographically due to different source locations efforts to quantify the contribution from each source have been hampered by the lack of well defined isotopic compositions for its end members in this study we discard the vague term of atmospheric sulfate by recognizing two major sulfate sources on the basis of their formation pathways primary and secondary sulfate primary sulfate including those from rock weathering sea salt and volcanic ash leachates do not have an 17o anomaly secondary sulfate derived from the oxidation of reduced sulfur gases biological or volcanic emissions by atmospheric ozone or hydrogen peroxide however has an 17o anomaly we developed a method to extract water soluble anions sequentially or entirely from bulk soil samples and analyzed the sulfate concentrations and 17o anomalies for four geographically representative soil profiles in the central atacama desert 23 s to 25 5 s we found that sequential sulfate extractions on the same soil sample produce sulfate with decreasing 17o values except for a positive bulge at 20 to 50 cm in depth there is a general increase in the 17o value for total sulfate with soil depth for all the four soil profiles that we examined these findings are consistent with the hypothesis that secondary sulfates 17o anomalous sulfates are more soluble and thus preferentially leached in liquid water than primary sulfate the finding also warns that incomplete sulfate extraction from sulfate rich soils yields unpredictable results we infer a 17o value of 4 6 for secondary sulfate based on data from partial sulfate extraction experiments total contribution of secondary sulfate in the central atacama desert is estimated to range from 9 to 24 with the highest percentage in the central depression

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

detection of hydrated silicates in crustal outcrops in the northern plains of mars the composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early mars we present an analysis of the composition of large craters in the martian northern plains based on data from spaceborne imaging spectrometers nine of the craters have excavated assemblages of phyllosilicates from ancient noachian crust buried beneath the plains cover the phyllosilicates are indistinguishable from those exposed in widespread locations in the southern highlands demonstrating that liquid water once altered both hemispheres of mars

linking the sulu uhp belt to the korean peninsula evidence from eclogite precambrian basement and paleozoic sedimentary basins abstract considerable debate on whether and how the sulu orogenic belt extends eastward to the korean peninsula has remained over the past decade new results reported here include the following 1 an eclogite and retrograded eclogite bearing complex hongseong complex is discovered in south korea in which the eclogite occurs as lenses in circa 810 820 ma granitic gneiss shrimp zircon dating of the eclogite yields 230 ma for the metamorphic age and 880 ma for the protolith age 2 the basement of the rangnim gyeonggi and yeongnam massifs have affinities to the basement of the north china block ncb however the gyeonggi massif encloses a minor amount of large or small slabs of the hongseong complex that are similar to the rocks of the sulu belt 3 two main paleozoic basins within the rangnim and gyeonggi massifs have a similar paleozoic tectono stratigraphy to the ncb 4 the imjingang and ogcheon belts do not exhibit any metamorphic characteristics of collisional orogenic belts based on these facts we propose a crustal detachment and thrust model and suggest that the collision belt between the yangtze block yb and ncb sino korea craton is preserved along the western margin of the korean peninsula the lower part of the uhp metamorphosed lithosphere of the yb was subducted under the korean peninsula and not uplifted to the surface the lower crust of the yb the hongseong complex was detached from the subducted lithosphere and thrust over the korean peninsula and inserted into the basement rocks of the gyeonggi massif the upper crust of the yb possibly was detached from the lower crust and overthrusted along the honam and chugaryong shear zones the imjingang and ogcheon belts possibly represent the detached upper crust of yb and their present occurrences are controlled by a mesozoic strike slip shear structure all these detached lower and upper crustal slabs were strongly deformed during the late jurassic and early cretaceous tectonic event leading to their present geological distribution and characteristics

coupled tectonic evolution of andean orogeny and global climate abstract the largest tectonic relief breaking the earth s surface 13 km vertically is at the subduction margin of the andes which generates routinely megathrust earthquakes mw 8 5 and drives the paradigmatic andean orogen here we present key geologic evidence to reassess first order features of geomorphology and tectonics across the central andes where the orogen includes the altiplano plateau and attains its maximum integrated height and width the andean subduction margin has a stepped morphology dominated by the low relief atacama bench which is similar to a giant uplifted terrace slopes gently over a width of 60 100 km from the andes to the pacific and runs over more than 1000 km of coastal length we find that the genesis of stepped morphology at the andean seaboard is due to concomitant development of large west vergent thrusts parallel to the subduction interface and increasing aridity in the atacama desert which keeps an unprecedented large scale record of interplaying tectonics and cenozoic climate change incorporating our results with published geological knowledge demonstrates that andean orogeny is characterized by trench perpendicular bivergent and trench parallel bilateral growth over the past 50 myr associated with positive trench velocity toward the continent trench advance and subduction of a wide slab under south america we hypothesize that a global plate tectonic reorganization involving long lasting viscous mantle flow has probably forced both andean orogeny and global climate cooling since 50 ma in contrast two important stepwise pulses of increasing aridity and trench perpendicular andean growth appear to be results of changes in erosion rates due to global late eocene and middle miocene cooling events

modeling flow and reactive transport to explain mineral zoning in the atacama salt flat aquifer chile geochemical processes are typically neglected when modeling groundwater flow in highly saline systems in the atacama salt flat northern chile field data indicate that the main aquifer presents a mineralogical zoning consisting of carbonates sulfates and halite which is a result of precipitation and or dissolution reactions when precipitation and or dissolution of minerals are active processes in the aquifer physical properties that control groundwater flow such as porosity and permeability would also change until now groundwater flow in the atacama salt flat has been simulated with conventional constant or variable density flow models this study for the first time investigated the importance of incorporating geochemical processes in modeling the atacama salt flat aquifer in particular the impact of mineral precipitation dissolution on aquifer s physical properties and flow patterns was studied to this end the shemat code was utilized to develop a two dimensional numerical groundwater flow model in the eastern border of the atacama salt flat the shemat code solves the classic groundwater flow equation coupled to the reactive transport of ions and mineral precipitation with variable density viscosity porosity and permeability when geochemical processes were included in the simulations the model reproduced reasonably well the mineral zoning evidenced by field observations mineral precipitation was responsible of a strong permeability reduction in areas of the aquifer associated with halite and calcite formation permeability alterations were responsible of changes in the equivalent freshwater head that resulted in significant flow pattern variations compared to variable density flow models these results highlight the importance of considering geochemical processes that modify the aquifer s physical properties when modeling groundwater flow in highly saline aquifers such as the atacama salt flat aquifer

orbital evidence for more widespread carbonate bearing rocks on mars carbonates are key minerals for understanding ancient martian environments because they are indicators of potentially habitable neutral to alkaline water and may be an important reservoir for paleoatmospheric co 2 previous remote sensing studies have identified mostly mg rich carbonates both in martian dust and in a late noachian rock unit circumferential to the isidis basin here we report evidence for older fe and or ca rich carbonates exposed from the subsurface by impact craters and troughs these carbonates are found in and around the huygens basin northwest of hellas in western noachis terra between the argyre basin and valles marineris and in other isolated locations spread widely across the planet in all cases they cooccur with or near phyllosilicates and in huygens basin specifically they occupy layered rocks exhumed from up to 5 km depth we discuss factors that might explain their observed regional distribution arguments for why carbonates may be even more widespread in noachian materials than presently appreciated and what could be gained by targeting these carbonates for further study with future orbital or landed missions to mars

detrital modes of the pyeongan supergroup late carboniferous early triassic sandstones in the samcheog coalfield korea implications for provenance and tectonic setting abstract medium to coarse sandstones of the carboniferous to early triassic pyeongan supergroup in the samcheog coalfield korea were studied to infer the provenance and tectonic settings of the source areas sandstone detrital modes change upwards stratigraphically sandstone types from the manhang to dosagog formations low to middle in the sequence are quartzarenite and sublitharenite to litharenite whereas sandstones of the gohan and donggo formations high in the sequence are feldspathic litharenite and arkose respectively using various ternary diagrams the provenance of the manhang to gohan formations is suggested to be a recycled orogen setting some gohan formation sandstones plot within the arc related setting field and the donggo formation sandstones plot within both continental block and recycled orogen fields results of quartz grain petrography are consistent with those of detrital modes quartz in sandstones of all units except the donggo formation indicates derivation from low rank metamorphic sources quartz in donggo sandstones was derived from medium to high rank metamorphic and plutonic source rocks considering the sandstone composition and palaeocurrent data the pyeongan supergroup probably was deposited in a molasse foreland basin and was derived from a synbasinal orogenic belt probably the akiyoshi orogen located in southwest japan

remote sensing and in situ mineralogic survey of the chilean salars an analog to mars evaporate deposits abstract the identification and characterization of hydrated minerals within ancient aqueous environments on mars are high priorities for determining the past habitability of the planet few studies however have focused on characterizing the entire mineral assemblage even though it could aide our understanding of past environments in this study we use both spaceborne and field vnir spectroscopy analyses to study the mineralogy of various salt flats salars of the northern region of chile as an analog for martian evaporites these data are then compared to laboratory based raman and xrd analyses for a complete overview on mineral assemblages central core and marginal zones within the salars are easily distinguished on the landsat 8 band color composites these areas host different mineral assemblages that often result in different landscapes the lower elevation salar de atacama located in the andean pre depression is characterized by a unique thick halite crust at its center whereas various assemblages of calcium sulfates gypsum bassanite anhydrite and sodium sulfates mirabilite thenardite blodite glauberite borates ulexite pinnoite al fe clays and carbonates calcite aragonite were found at its margin sulfates form the main crust of the andean salars to the east although various compositions are observed these compositions appear controlled by the type of feeder brine ca so4 or mixed a result of the local geology among other factors sulfate crusts were found to be generally thin

the origin and distribution of salts on alluvial fans in the atacama desert northern chile the atacama desert has been predominantly hyperarid since the middle miocene combined ionic and x ray diffraction analysis shows that calcium sulphate is prevalent on three similar alluvial fans in salar basins across a transect of different environments in antofagasta province northern chile differences between the fans were largely due to the effect of local factors on salt input secondary redistribution and deposit preservation thus carbonate was notable in the high andes fan c and pre cordillera fan b whereas in the central valley fan a greater qualities of the more soluble salts chlorides and nitrates probably reflect the higher level of aridity and an oceanic source the camanchaca calcium sulphate distribution on the alluvial fans and on adjacent hilltops indicates an aeolian origin evidence from the pre cordillera fan b however suggests that salt input may have been episodic related to changes in conditions within the general aridity and possibly to stone pavement and soil development calcium sulphate sources range from an input in andean precipitation and the camanchaca to abundant regional evaporite deposits it is probable however that products of andean volcanism constitute the dominant primary source of calcium sulphate and that the salt has subsequently been distributed widely within the endoreic basins of the region by a combination of groundwater surface flow and the wind 1997 john wiley sons ltd

multiple mineral horizons in layered outcrops at mawrth vallis mars signify changing geochemical environments on early mars abstract refined calibrations of crism images are enabling identification of smaller deposits of unique aqueous materials on mars that reveal changing environmental conditions at the region surrounding mawrth vallis through characterization of these clay sulfate assemblages and their association with the layered phyllosilicate units of this region more details of the aqueous geochemical history can be gleaned a stratigraphy including five distinct mineral horizons is mapped using compositional data from crism over ctx and hrsc imagery across 100s of km and from crism over hirise imagery across 100s of meters transitions in mineralogic units were characterized using visible near infrared vnir spectral properties and surface morphology we identified and characterized complex doublet type spectral signatures with two bands between 2 2 and 2 3 m at one stratigraphic horizon based on comparisons with terrestrial sites the spectral doublet unit described here may reflect the remnants of a salty evaporative period that existed on mars during the transition from formation of fe rich phyllosilicates to al rich phyllosilicates layered outcrops observed at mawrth vallis are thicker than in other altered regions of mars but may represent processes that were more widespread in wet regions of the planet during its early history the aqueous geochemical environments supporting the outcrops observed here include i the formation of fe3 rich smectites in a warm and wet environment ii overlain by a thin ferrous bearing clay unit that could be associated with heating or reducing conditions iii followed by a transition to salty and or acidic alteration phases and sulfates characterized by the spectral doublet shape in an evaporative setting iv formation of al rich phyllosilicates through pedogenesis or acid leaching and v finally persistence of poorly crystalline aluminosilicates marking the end of the warm climate on early mars the doublet type units described here are likely composed of clay sulfate assemblages formed in saline acidic evaporative environments similar to those found in western australia and the atacama desert despite the chemically extreme and variable waters present at these terrestrial saline lake environments active ecosystems are present thus these doublet type units may mark exciting areas for continued exploration important to astrobiology on mars

neoproterozoic 900 ma sariwon sills in north korea geochronology geochemistry and implications for the evolution of the south eastern margin of the north china craton article the sariwon sills are distributed in the pyongnam basin at the center of the korean peninsula eastern part of the north china craton these sills are up to 150 m in thickness and up to more than 10 km in length baddeleyite grains separated from a 50 m thick sill give a sims 206 pb 207 pb age of 899 7 ma mswd 0 34 n 14 which is interpreted to be the crystallization age of this sill zircon grains from the same sill gives a lower intercept u pb age of 400 ma which is likely a close estimation of the greenschist facies metamorphism of this sill the sariwon sills are dolerites and have tholeiitic compositions they show enrichment of light rare earth element concentrations la ybn 1 4 2 8 and are slightly depleted in high field strength elements e g nb zr and ti in comparison to neighboring elements on the primitive mantle normalized spidergram the whole rock endt t 900 ma values are around 2 whereas in situ ehft t 900 ma values from zircon grains vary from 25 to 8 they are similar to the coeval sills in other parts of the north china craton e g the chulan sills xu huai basin shandong peninsula and the dalian sills lv da basin liaodong peninsula these sills possibly originated from a depleted mantle source e g asthenosphere rather than from the ancient lithospheric mantle of the north china craton and have experienced significant assimilation of lithospheric materials the strata and sills in the xu huai lv da and pyongnam basins are comparable moreover the three basins are geographically correlatable based on neoproterozoic geographical reconstruction we therefore propose that there is a xu huai lv da pyongnam rift system along the south eastern edge of the north china craton during neoproterozoic 900 ma with the closure of the rift at 400 ma as a result of a continent margin process it is possible that this southeastern margin of the ncc did not face the inland in the configuration of the supercontinent rodinia

identification distribution and possible origins of sulfates in capri chasma mars inferred from crism data crism is a hyperspectral imager onboard the mars reconnaissance orbiter mro nasa 2005 which has been acquiring data since november 2006 and has targeted hydrated minerals previously detected by omega mars express esa 2003 the present study focuses on hydrated minerals detected with crism at high spatial resolution in the vicinity of capri chasma a canyon of the valles marineris system crism data were processed and coupled with mro and other spacecraft data in particular hirise high resolution science experiment mro images detections revealed sulfates in abundance in capri especially linked to the interior layered deposits ild that lie in the central part of the chasma both monohydrated and polyhydrated sulfates are found at different elevations and are associated with different layers monohydrated sulfates are widely detected over the massive light toned cliffs of the ild whereas polyhydrated sulfates seem to form a basal and a top layer associated with lower albedo deposits in flatter areas hydrated silicates phyllosilicates or opaline silica have also been detected very locally on two mounds about a few hundred meters in diameter at the bottom of the ild cliffs we suggest some formation models of these minerals that are consistent with our observations