arid to humid serpentine soils mineralogy and vegetation across the klamath mountains usa abstract ultramafic rocks are extensive in the klamath mountains of california and oregon and there is a great diversity of climate soils and vegetation soils were sampled and vegetation described over serpentinized peridotite at sixteen low altitude well drained sites from arid to humid parts of the mountains receiving from 400 to 3200 mm year of precipitation the soils are dry mollisols and alfisols moist alfisols ultisols and a moist mollisol all of the soils have subsoil exchangeable ca mg ratios

outburst floods from glacial lake missoula abstract the pleistocene outburst floods from glacial lake missoula known as the spokane floods released as much as 2184 km3 of water and produced the greatest known floods of the geologic past a computer simulation model for these floods that is based on physical equations governing the enlargement by water flow of the tunnel penetrating the ice dam is described the predicted maximum flood discharge lies in the range 2 74 106 13 7 106 m3 sec 1 lending independent glaciological support to paleohydrologic estimates of maximum discharge

ni speciation in a new caledonian lateritic regolith a quantitative x ray absorption spectroscopy investigation abstract changes in ni speciation in a 64 m vertical profile of a new caledonian saprolitic lateritic regolith developed over ultramafic rocks under tropical weathering conditions were investigated by exafs spectroscopy quantitative analysis of the exafs spectra by linear combination least squares fitting lc lsf using a large set of model compound spectra showed that ni hosted in primary silicate minerals olivine and serpentine in the bedrock is incorporated in secondary phyllosilicates serpentine and fe oxides goethite in the saprolite unit and mainly in goethite in the laterite unit a significant concentration of ni up to 30 of total ni is also hosted by mn oxides in the transition laterite i e the lowest part of the laterite unit which contains large amounts of mn oxides however the amount of ni associated with mn oxides does not exceed 20 of the total ni in the overlying laterite unit this sequence of ni species from bedrock to laterite yields information about the behavior of ni during tropical weathering of ultramafic rocks the different ni distributions in phyllosilicates in the bedrock randomly distributed and in the saprolite unit clustered indicate two generations of ni bearing phyllosilicates the first which formed at higher temperature is related to serpentinization of oceanic crust whereas the second one which formed at lower temperature is associated with post obduction weathering of ultramafic rocks in addition the observed decrease in the proportion of ni hosted by mn oxides from the transition laterite to the upper lateritic horizons indicates dissolution of mn oxides during the last stages of differentiation of the lateritic regolith i e lateritization finally the ubiquitous occurrence of ni bearing goethite emphasizes the major role of this phase in ni speciation at the different weathering stages and suggests that goethite represents the major host for ni in the final tropical weathering stages of new caledonian ultramafic rocks

effect of mineralogy and pedoclimatic variations on ni and cr distribution in serpentine soils under temperate climate abstract part of the soils occurring in the serpentinite szklary massif sw poland have developed in quaternary under temperate climate on the parent rock not affected by chemical weathering in studied parent ultrabasite ni occurs in cr magnetite up to 0 96 wt of nio forsterite up to 0 55 wt of nio iddingsite up to 0 99 wt of nio and serpentine up to 0 55 wt of nio while cr is bounded with cr magnetites up to 21 77 wt of cr 2 o 3 and clinochlores up to 1 68 wt of cr 2 o 3 cr magnetites are highly resistant to weathering while other primary minerals more susceptible to weathering release parts of ni and cr which are trapped in authigenic phases the latter however contain less ni and cr than corresponding primary minerals clayous matrix 0 37 wt of nio and 0 08 wt of cr 2 o 3 smectites 0 30 wt of nio and 0 07 wt of cr 2 o 3 and mixture of oxy hydroxides and clay minerals 0 36 wt of nio and 0 14 wt of cr 2 o 3 at the mineral scale smectite plays an important role in the trapping of ni at the profile scale ni and cr are moderately diluted upwards the soil profile and cr is generally less mobile than ni the soil formed in szklary is chemically different than the analogous serpentine soils occurring more to the south in europe french massif central vosges mountains and ligurian apennines nw italy the difference is due to participation of fluvioglacial material produced by quaternary continental glaciacion in poland however similar vertical relative variations of ni and cr were found in all compared soils in spite of differences in parent rock composition allogenic contaminations and degree of soil development comparison with other well drained pedons located in similar uphill positions shows a climatic control of the cr and ni vertical distribution in serpentine soils humid mountainous variant of temperate climate induces leaching of mg and subsequent lack in smectite neoformation which lead to the release of ni ni is less mobile in the colder and dryer climate of poland moreover some primary minerals which are generally considered as not stable under soil conditions olivine serpentine and chlorite are still present even in the a horizon of the studied polish pedon their resistance is due to slower rates of weathering related to the climate but also due to former hydrothermal processes affecting the parent rock fabric

mechanisms of faulting in and around caloris basin mercury 1 the distribution of faulting in and around the caloris basin on mercury provides constraints on the planet s early lithosphere and tectonic history by means of a series of finite element models we test a range of ideas regarding lithospheric structure surface loading and shallow flow proposed to account for early contractional features and younger extensional features on the basin floor as well as contractional tectonic features exterior to the basin early stage thrust faults within the basin are well matched by the stress field accompanying flexural subsidence in response to partial infilling of a broad basin floor while younger normal faulting can be the result of flexural uplift in response to later stage emplacement of an exterior annulus of smooth plains deposits a proposed scenario in which later stage inward flow of the lower crust induces uplift of the basin floor can under some conditions yield extension in the basin but not in a manner consistent with the observed distribution of normal faults thrust faulting on the exterior smooth plains can be the result of local subsidence accompanying the emplacement of these units but may also have been influenced by global contraction our results lead to the prediction that the gravity anomaly associated with the caloris basin and surroundings should consist of a central positive anomaly mascon and an annular gravity high separated by a ring of lower gravity gravity and topography measurements to be made by the messenger mission will provide a test of this prediction and more generally of the models developed here

large values of hydraulic roughness in subglacial conduits during conduit enlargement implications for modeling conduit evolution hydraulic roughness accounts for energy dissipated as heat and should exert an important control on rates of subglacial conduit enlargement by melting few studies however have quantified how subglacial conduit roughness evolves over time or how that evolution affects models of conduit enlargement to address this knowledge gap we calculated values for two roughness parameters the darcy weisbach friction factor f and the manning roughness coefficient n using dye tracing data from a mapped subglacial conduit at rieperbreen svalbard values of f and n calculated from dye traces were compared with values of f and n calculated from commonly used relationships between surface roughness heights and conduit hydraulic diameters roughness values calculated from dye tracing ranged from 75 0 97 for f and from 0 68 0 09 s m 1 3 for n equations that calculate roughness parameters from surface roughness heights underpredicted values of f by as much as a factor of 326 and values of n by a factor of 17 relative to values obtained from the dye tracing study we argue these large underpredictions occur because relative roughness in subglacial conduits during the early stages of conduit enlargement exceeds the 5 range of relative roughness that can be used to directly relate values of f and n to flow depth and surface roughness heights simple conduit hydrological models presented here show how parameterization of roughness impacts models of conduit discharge and enlargement rate we used relationships between conduit relative roughness and values of f and n calculated from our dye tracing study to parameterize a model of conduit enlargement assuming a fixed hydraulic gradient of 0 01 and ignoring creep closure it took conduits 9 25 days to enlarge from a diameter of 0 44 m to 3 m which was 6 7 fold longer than using common roughness parameterizations copyright 2013 john wiley sons ltd

the 1994 jokulhlaup at farrow creek british columbia canada abstract an ice dammed lake at the margin of goddard glacier in the southern coast mountains of british columbia drained suddenly in july 1994 producing a jokulhlaup that travelled 11 km down farrow creek to chilko lake the jokulhlaup transported and deposited large quantities of sediment destroyed tracts of forest and severely modified the channel of farrow creek the flood had a peak discharge of between 100 and 300 m3 s 1 and judging from its geomorphic effects was much larger than normal rainfall and snowmelt generated floods in the basin the lake drained via a subglacial tunnel at the base of goddard glacier following a lengthy period of glacier downwasting and retreat drainage occurred when a passageway developed at the base of the weakened dam the escaping waters rapidly enlarged this passageway producing a large tunnel which has not resealed since the jokulhlaup goddard lake is similar to other short lived glacier dammed lakes in western canada that have developed near the toes of glaciers since the end of the little ice age and have disappeared after one or a few outbursts it contrasts with other glacier dammed lakes commonly located farther from glacier termini that have lengthy stable pre jokulhlaup phases and long periods of cyclic or sporadic jokulhlaup activity

cooling fractures in impact melt deposits on the moon and mercury implications for cooling solely by thermal radiation we study the distribution morphology and geometrical properties of fractures in several young impact melt deposits on the moon and mercury and the ways that these fractures may form from cooling by thermal radiation in each impact melt complex the topography of the underlying terrain determines the orientation of cooling fractures such that interior fractures that formed in the relatively thick interior areas of the melt unit are wider and have a larger spacing than marginal fractures that formed in the relatively thin areas near the unit s margins solid debris entrained in molten deposits provides prefracture flaws that can seed cooling fractures but too much solid debris prevents cooling fractures from growing to macroscopic sizes the appearance of subparallel fractures is mainly caused by subsidence of the deposits during the process of cooling and solidification tensile stresses caused by thermal radiation are large enough to initiate cooling fractures on both the moon and mercury which may represent the initial stage of columnar joints formation but the cooling rate caused solely by thermal radiation is not large enough to form well organized columnar joints that feature polygonal colonnades we therefore propose that thermal conduction and convection are the major contributors in the formation of columnar joints on planetary bodies

understanding the genesis of ultramafic soils and catena dynamics in niquelândia brazil this study focuses on the fate of chromium during ultramafic weathering under tropical conditions three soils were studied along a characteristic catena on the ultramafic outcrop of niquel ndia brazil in these soils the cr bearing minerals are inherited chromites 15 4 26 8 wt cr and magnetites 0 4 4 8 wt cr and secondary minerals such as iron oxides 0 2 wt cr or ni smectites 0 6 8 wt cr indeed during weathering cr liberated from primary minerals can first be incorporated into ni smectites garnierite or fe oxides as the weathering continues smectites become unstable and cr liberated into the soil solution and incorporates in fe oxides in this oxidized environment fe and mn are oxidized and oxides can incorporate elements like cr ni and al two types of chromites were distinguished i e a vein type vc and a rock type rc according to their composition chromites could be used as tracer of pedogenesis processes due to the distinct composition of vc and rc types they allow us to show that the upper part of some soil profile results exclusively from colluvial processes and the lower part of the profile results from the ultramafic bedrock weathering the chromite tracer allows us to propose a model of the catena evolution

simulation of the august 1979 sudden discharge of glacier dammed flood lake british columbia in august 1979 a glacier outburst from flood lake british columbia released 150 106 m3 of water the resulting flood was routed through the stikine river and yielded a maximum discharge rate of 1200 m3 s 1 at a gauging station 90 km downstream from the glacier dam we have used a computer model to simulate this outburst in order to test the usefulness of the model as a predictor of flood magnitude the predicted peak discharge is 2160 m3 s 1 at the outlet tunnel of the ice dam and 1700 m3 s 1 at the gauging station

on the clague mathews relation for jokulhlaups in the empirical study of jokulhlaups the peak discharge q max and water volume drained by the ice dammed lake during the floods v t appear to follow a power law relation q max kv t b where k are b are constants determined from field data first identified by clague and mathews 1973 this relation is a useful reference for predicting flood magnitude but its physical origin remains unclear here we develop the theory that connects it to contemporary models for simulating the flood hydrograph we explain how the function q max f v t arises from nye s 1976 theory of time dependent water flow in a subglacial channel coupled to a lake and we describe how discharger volume data record the monotonically increasing form of this function so long as the lake is not emptied in the floods the grimsvotn jokulhlaups present an example where because of partial draining of the lake agreement between the model derived f and data is excellent it is documented that other lake systems drain completely but we explain how the exponent b 2 3 observed for them collectively is due primarily to a scaling effect related to their size modified by other factors such as the flood initiation process

the global distribution of giant radiating dike swarms on venus implications for the global stress state magellan radar data of venus reveal 163 large radial lineament systems composed of graben fissure and fracture elements on the basis of their structure plan view geometry and volcanic associations at least 72 are interpreted to have formed primarily through subsurface dike swarm eraplacement the remainder through uplift or a combination of these two mechanisms the population of swarms is used to determine regional and global stress orientation the stress configura tion recorded from 330 210oe aphrodite terra is best ex plained by isostatic compensation of existing long wave length topography or coupling between mantle flow and the lithosphere the rest are correlated with concentrations of rifting and volcanism in the beta atla themis region the global stress field on venus is different than that of earth where plate boundary forces dominate from their surroundings where domical topography occurs the ra dius of the associated lineament system is on average 2 5 times greater than that of the dome some 53 of the radiat ing systems are associated with concentric structures ranging from central depression bounding scarps 25 km wide to tec tonic rings 575 km in diameter in 51 of these cases the ra dial pattern originates within but also extends significantly beyond the annulus only 9 of the radiating systems are confined completely leaving 40 located outside but focused upon a central annular structure finally the radial geometry is usually quite pronounced near the center of each structure 52 of the time radial lineaments occupy 270 o of azimuth and 80 exceed 180 o figure 2c in their distal regions how ever only 72 of the radiating systems retain a purely radial geometry as the remaining 28 gradually develop a non radial unidirectional lineament configuration all but seven of the radiating systems exhibit volcanism figure 2d lobate flows emerging from individual linea ments or many such flows strongly correlated with multiple radial lineaments occur for 45 of the systems clusters of small shields occur 72 of the time and in 75 of these in stances distinctive alignment of small shields and or pits along radiating lineaments is seen finally 65 are associ ated with some other form of centralized volcanism including multiple forms of edifice construction limited extrusions and sheet like flows which extend into the surrounding terrain

formation and interpretation of dilatant echelon cracks the relative displacements of the walls of many veins joints and dikes demonstrate that these structures are dilatant cracks we infer that dilatant cracks propagate in a principal stress plane normal to the maximum tensile or least compressive stress arrays of echelon crack segments appear to emerge from the peripheries of some dilatant cracks breakdown of a parent crack into an echelon array may be initiated by a spatial or temporal rotation of the remote principal stresses about an axis parallel to the crack propagation direction near the parent crack tip a rotation of the local principal stresses is induced in the same sense but not necessarily through the same angle incipient echelon cracks form at the parent crack tip normal to the local maximum tensile stress further longitudinal growth along surfaces that twist about axes parallel to the propagation direction realigns each echelon crack into a remote principal stress plane the walls of these twisted cracks may be idealized as helicoidal surfaces an array of helicoidal cracks sweeps out less surface area than one parent crack twisting through the same angle thus many echelon cracks grow from a single parent because the work done in creating the array as measured by its surface area decreases as the number of cracks increases in cross sections perpendicular to the propagation direction echelon cracks grow laterally each crack overlapping its neighbors until the mechanical interaction of adjacent cracks limits this growth dilation of each crack pinches the tips of adjacent cracks into an asymmetrical form and introduces local stresses that can cause lateral growth along a curving sigmoidal path sigmoidal echelon cracks may link at tip to plane intersections leaving a step in the through going crack wall the geometry of dilatant echelon cracks may be used to infer spatial or temporal changes in the orientation of principal stresses in the earth

control of nickel availability by nickel bearing minerals in natural and anthropogenic soils the aim of this paper was i to determine the ni bearing minerals and localize ni in natural and contaminated ni rich soils ii to characterize ni availability with isotopic exchange kinetics iek and iii to study its interactions with soil mineralogy and characteristics along a gradient of weathering intensity we sampled 16 soils varying from a recently exposed surface serpentinite in cold regions to ferralsols laterites from a humid tropical climate including two highly contaminated soils ni industry the minerals identified ranged from primary minerals to secondary phyllosilicates and lastly to mn fe oxides according to weathering intensity primary minerals inherited from the parent materials and secondary phyllosilicates formed in low leaching conditions had concentrations of ni similar to the rock 0 2 0 3 when compared to other secondary minerals fe oxides displayed slight ni enrichment in moderate leaching conditions 0 4 0 8 up to 10 fold enrichment in highly weathered ferralsols 4 6 full characterization of the three factors of ni availability in soils the intensity cni the quantity et and the capacity cf factors was achieved with iek for most of the soils cni and et varied conjointly elevated values of these two parameters were found in soils dominated by both phyllosilicates and amorphous fe oxides high exchange capacity low values were found in soils with significant amounts of well crystallized fe oxides high retention capacity in the case of anthropogenic origin control of soil ni availability also depends on the type of ni bearing minerals

mobility of metals in nickel mine spoil materials abstract an understanding of the biogeochemical behaviour of metals in mine spoil materials is a prerequisite to rehabilitate ni mining sites the objective of this study was to characterize the fate of metals in different ni ore spoil materials as influenced by hydrological conditions and fertilisation practices in tropical ultramafic complexes the different stages of lateritic weathering lead to two types of ores and therefore to two spoil types they are mainly either a clay rich saprolite so called garnierite enriched in phyllosilicates or a limonitic material enriched in fe oxides lysimeter columns were designed to monitor leaching waters through both spoil materials the garnieritic spoil released higher concentrations of mg mean 2 25 mg l 1 ni 0 39 mg l 1 and cr 1 19 mg l 1 than the limonitic spoil mg 0 5 mg l 1 ni 0 03 mg l 1 and cr 0 25 mg l 1 chromium was mainly in an anionic form in leaching solutions as exchangeable pools of cr vi in limonite 980 mg kg 1 of kh 2 po 4 extractable cr are considerable its release in water may still occur in the case of a ph increase in mixed spoil metal concentrations were almost as low as in the limonitic one the effect of mineral n fertilisation was a strong release of cations ni mg into the leachate phosphate amendment did not affect the soil solution composition under experimental conditions

influence of rainfall and temperature on dtpa extractable nickel content of serpentine soils in turkey article i nfo influence of rainfall and temperature on dtpa diethylene triamine pentaacetic acid extractable nickel dni and fractional dni total ni f dni concentrations of soils derived from ultramafic serpentine rock under temperate semiarid continental and mediterranean climates were studied all serpentinite areas in western anatolia and the east thrace ca 400 000 km 2 areas were targeted meteorological data from 185 stations versus so called phytoavailable ni concentrations of 192 serpentine soil samples were examined digital elevation model dem anusplin and arc gis 8 1 software packages for generation of climatic surfaces and analysis were employed for extrapolation of the weathering conditions in preparing comparative maps total ni concentrations tni were in the range of 25 7 2680 mg kg 1 whereas dni were between 0 08 and 143 mg kg 1 t he correla tion between ni extractability and the ph was weak r 2 0 175 this restricted effect may be attributed to the soil ph varying between neutral and slightly alkaline average dni concentrations of the soil samples grouped within the province borders indicated that both precipitation and air temperature might be effective on the amount of dni in the serpentine soils studied the combined effect of annual precipitation and mean atmospheric temperature were significant p b 0 01 ondni thedifferencesbetweentheclimaticzonesweredistinctandgen erally increasing with the increase of annual rainfall and mean air temperature

pedogenesis in a soil catena on serpentinite in north western italy serpentinite is a fairly common parent material for soils of the alps and apennines in italy in the apennines these soils may show very different degrees of development even over small areas this work was undertaken to study the pedogenesis on a soil catena occurring on a very small hill with a particular attention to the clay mineral transformations the catena is only 100 m long but four orders of the soil taxonomy were represented ranging from entisols to alfisols in the clay fraction of the entisol and of the inceptisol located respectively at the summit and at the backslope positions we found that serpentine is the main mineral in the clay fraction and that traces of some interstratified low charge vermiculites are present in the surface horizon the two alfisols at the footslope positions have different clay minerals one of them shows some low charge vermiculites in the surface horizons and smectites in the deepest ones while in the other one smectites were found in the surface horizon too these two profiles have different drainage regimes as seen in the field and from laboratory determination of water content and porosity significant differences p 0 01 of porosity were found in the catena between the horizons with smectites and those with low charge vermiculite in the mollisol located at the toeslope position a trend towards acidification was found in the surface horizon but the presence of serpentine acts as a continuous magnesium source thus preventing the base saturation to become 50 the main pedogenic processes in this catena are lessivage of clays formation of different 2 1 phyllosilicates depending probably on the porosity acidification caused by organic materials in some horizons an enrichment of organic matter is possible but the acidification is hindered by the parent rock no clear evidence of chlorite formation from serpentine was found the weathering of serpentine minerals seems to give rise to a low charge vermiculite in upper and drier horizons or to a smectite in poorly drained conditions vermiculite in turn may transform into smectite under a moister environment

observations of englacial water passages a fracture dominated system to test models of the hydraulics and geometry of englacial conduits 48 holes 3900 m of ice were drilled into storglaciaren sweden in search of conduits about 79 of the holes intersected a hydraulically connected englacial feature a video camera was used to examine the features and measure local water flow rates because of the extremely clear ice that surrounded most features their geometry could not be discerned of the remaining features 80 36 were fracture like 16 6 were of complex geometry and 4 2 exhibited a conduit like geometry the fracture like features exhibited steep plunges 708 narrow openings 40 mm and slow water flow speeds 10 mm s 1 we argue that these fracture like features are indeed englacial fractures of unknown origin the depth to fractures intersection varied from near the glacier surface to 96 of local ice depth with a maximum depth of 131 m few hydraulically connected fractures exhibited water motion indicating some preferential flow pathways exist we found one traditional englacial conduit after an intentional search in a field of moulins these results suggest that englacial water flow is conveyed through a ubiquitous network of fractures and that conduits are relatively rare

volcanism on mercury evidence from the first messenger flyby the origin of plains on mercury whether by volcanic flooding or impact ejecta ponding has been controversial since the mariner 10 flybys 1974 75 high resolution images down to 150 meters per pixel obtained during the first messenger flyby show evidence for volcanic vents around the caloris basin inner margin and demonstrate that plains were emplaced sequentially inside and adjacent to numerous large impact craters to thicknesses in excess of several kilometers radial graben and a floor fractured crater may indicate intrusive activity these observations coupled with additional evidence from color images and impact crater size frequency distributions support a volcanic origin for several regions of plains and substantiate the important role of volcanism in the geological history of mercury

ecological implications of pedogenesis and geochemistry of ultramafic soils in kinabalu park malaysia abstract in sabah malaysia ultramafic rock outcrops are widespread totalling 3500 km 2 one of the main outcrops in the tropical zone and predominantly of the peridotite type however strongly serpentinised peridotite is also locally common particularly along fault lines in the mt kinabalu area this study aimed to determine the extent of chemical variation in ultramafic soils in relation to the degree of serpentinisation and the weathering intensity and consequent potential ecological implications linked to resulting soil chemical fertility it was hypothesized that young soils and soils derived from bedrock with a significant degree of serpentinisation strongly differ from typical geric ferralsols and result in soil chemistries with more adverse properties to plant life e g low availability of the essential nutrients n p k and ca and high concentrations of potentially phytotoxic mg and ni ultramafic soil diversity linked to the age of the soil or the degree of serpentinisation would thus be a main factor of plant diversity and distribution the diverse topography of kinabalu park ultramafic soils present between 400 and 2950 m asl has given rise to high pedodiversity with the broad overall ultramafic soil types being i deep laterite soils geric ferralsols ii moderately deep montane soils dystric cambisols with mor humus iii shallow skeletal soils at high altitude eutric cambisols hypermagnesic and iv bare serpentinite soils hypereutric leptosols hypermagnesic at low altitude 200 700 m asl leptosols on serpentinite and eutric cambisols have the most extreme chemical properties in the whole kinabalu park area both with very high mg ca molar quotients with either high available ni cambisols or high ph leptosols these soils host specific and adapted vegetation high level of endemism that tolerates geochemical peculiarities including ni hyperaccumulators geric ferralsols present far less chemical constraints than hypermagnesian cambisols soils to the vegetation and host a tall and very diverse rainforest not so different than that on non ultramafic soils it therefore appears that altitude soil age and degree of bedrock serpentinisation are the main determining factors of soil properties the qualifier ultramafic alone is not sufficient to define soil geochemical and ecological conditions in the kinabalu park area probably more than in any other ultramafic region in the world

magnetic properties of surface sediments as proxies of recent anthropogenic pollution in the anllons riverbed nw spain a study of surface sediments from the anllons riverbed northwestern spain was conducted to assess the use of their magnetic properties as proxies of recent trace element contamination i e as zn pb cr ni and cu thermomagnetic curves hysteresis parameters specific magnetic susceptibility frequency dependent magnetic susceptibility fd magnetic remanence and saturation isothermal remanent magnetization ratios i e s and sirm reveal the presence of mostly fine grained magnetite and maghemite in these samples the tomlinson pollution load index pli as well as the magnetic parameters fd sirm and s ratios vary more or less in agreement to each other when they are sequentially arranged throughout a 30 km long transect that goes from the town of carballo to the river mouth in ponteceso from that profile it is possible to identify an anomaly of that lies between two small peaks of the pli and seems to define a contaminated area probably linked to a diffuse low impact source of pollution there is also a conspicuous peak of the pli that is likely associated to a nearby gold mine the variations of the fd s along the transect are the ones that best reflect the changes in the pli values regardless of the level of contamination this result suggests that adsorption is the main mechanism of trace elements removal by fe oxides in these samples direct signal analyses used to decompose the isothermal remanent magnetization curves reveal the presence of four magnetic fractions with varying relative concentrations all over the profile namely single domain magnetite close to the superparamagnetic threshold sd sp and or maghemite log b 1 2 ca 1 2 single domain magnetite log b 1 2 ca 2 hematite log b 1 2 ca 2 5 and goethite log b 1 2 ca 3 5 integrating all the available information it was sketched out a likely sequence of events that included magnetic minerals neoformation in parent soils their subsequent chemical transformations and the contamination episodes that affected the region

new insights into partial oxidation model of magnetites and thermal alteration of magnetic mineralogy of the chinese loess in air summary new rock magnetic data including low and high temperature thermomagnetic runs and hysteresis loops as well as x ray diffraction measurements are presented from the chinese loess palaeosols at jiuzhoutai on the northwestern margin of the chinese loess plateau to provide sound constraints on the partial oxidation model of magnetites and variations in magnetic mineralogy grain size and oxidation states of loess samples during thermal treatments from room temperature up to 700 c the results show that the partially oxidized magnetites in samples are first reduced probably as a result of the burning of organic matter below 300 c and then reoxidized above that however even after heating to 700 c the highly diminished in size magnetite core still remains stoichiometric as revealed by the 120 k verwey transition we conclude that the diffusion of fe2 from the magnetite core to the surrounding maghemite rim is confined to the oxidation front magnetite core maghemite rim boundary and has less effect on the stoichiometry of the magnetite core the new results also reveal that the absolute number of superparamagnetic grains magnetite maghemite remains relatively stable during heating furthermore the left downward shift in the data points of day plots mainly between 25 and 150 c is caused by a decrease in the oxidation gradient in contrast the right upward mainly between 500 and 650 c shift of the day plots corresponds to a much higher degree of oxidation resulting in the increase of a new oxidation gradient between the magnetite core or the residual maghemite mantle and the newly developed haematite outer rim which is transformed from maghemite by heating these new results place strong constraints on the fidelity of palaeomagnetic results from the chinese loess constructed by thermal demagnetization and provide a more accurate interpretation of the day plot and low temperature magnetic behaviours for these partially oxidized magnetites furthermore this study provides robust lines of evidence for the core rim coupling model between different magnetic phases magnetite maghemite and haematite

trace metals distribution from a serpentinite weathering at the scales of the weathering profile and its related weathering microsystems and clay minerals the distribution of four trace metals nickel ni chromium cr manganese mn and cobalt co and some major elements is studied in a soil profile derived from a natural trace metals bearing rock serpentinite at the scales of 1 the weathering profile c and b horizons and 2 its related weathering microsystems and clay minerals all trace elements are relatively enriched in weathered horizons compared to the rock in the same way as iron and aluminium whereas magnesium is largely leaching an evolutive sequence of trace metals host phases is formed along the weathering profile from magnesian at the bottom to iron rich clay minerals and then aluminous clay minerals and oxy hydroxides at the top different chemical forms of trace metals in weathering profile have been quantified by chemical extractions ni and cr remain mainly in the silicates in contrast mn and co are mainly distributed into amorphous oxy hydroxides in addition trace metals contents are measured using electron microprobe in individual rock forming minerals and in their specific weathering microsystem each with its specific clay mineral each rock forming mineral serves as the host phase for a specific trace metal silicates serpentine and clinochlore contain cr ni and mn whereas oxides concentrate co and cr in the first weathering stages ni and cr are concentrated in secondary clays especially in fe montmorillonite derived from mesh serpentine minerals and in trioctahedral vermiculite derived from chlorite respectively whereas mn and co are mainly used to constitute secondary oxides at the top of the profile mn co and ni host secondary oxy hydroxides have developed due to iron segregation

dike induced faulting in rift zones of iceland and afar geodetic data and field observations demonstrate that the emplacement of dikes in volcanic rift zones frequently generates normal faulting and graben subsidence at the earth9s surface elastic modeling of the vertical ground surface displacements above dikes and faults indicates that the extent of graben subsidence can be achieved only if fault slip extends virtually to or beyond the dike plane at depth a mechanical model that includes dikes and frictional faults shows that dike opening tends to compress and lock faults located to either side of the dike therefore slip extending into or beyond the dike cavity must occur either 1 on faults that intersect the dike near its top above the zone of dike induced compression or 2 on faults that slip ahead of the dike as it propagates laterally data from iceland indicate that slip occurred on deep faults that presumably slipped in advance of the laterally propagating dike

spectroscopic properties of explosive volcanism within the caloris basin with messenger observations volcanism on mercury has been indisputably identified at various locations on the surface by means of both effusive and explosive volcanism its characterization is crucial to understand the evolution of the planet in particular the thermal evolution of the mantle and the volatile content of the planet this analysis presents a detailed view of the pyroclastic deposits of the caloris basin observations from the mercury atmospheric and surface composition spectrometer mascs are used to understand the spectral characteristics of the pyroclastic deposits both in the visible and near infrared additional calibration steps are proposed to reconcile the difference of absolute reflectance between the visible vis and near infrared nir detectors these calibration steps allow the use of the full spectral range of the mascs instrument pyroclastic deposits exhibit a redder spectral slope in the vis and nir this spectral slope diminishes toward the edge of the deposits to match that of mercury s average surface spectral properties in the ultraviolet uv also change as a function of distance to the vent only the uv properties unambiguously separate the pyroclastic deposits from mercury s average spectra the spectral variations are consistent with a lower iron content of the pyroclastic deposits with respect to the average surface of mercury similar to what has been proposed for pyrolcastic deposits on the lunar surface nonetheless given the limited illumination conditions diversity of the mascs instrument other causes such as grain size space weathering and bulk composition could also be accounted for the spectral variations variability of the pyroclastic deposits properties within the entire basin are potentially identified between the three main clusters and could be related to space weathering of deposits of different ages

subglacial jokulhlaup deposition jotunheimen norway abstract the aim of this paper is to discuss the origin of a linear boulder deposit near the mjolkedalsbreen jotunheimen norway subglacial fluvial deposition is suggested by palaeoflow indicators showing flow directions uphill along the axis of a ridge like deposit and the close association of this deposit with an ice contact boulder delta peak discharges of repeated jokulhlaups from the former ice dammed ovre mjolkedalsvatn were estimated at 1188 m3 s 1 using evidence derived from the proglacial jokulhlaup routeway former ice tunnel dimensions and flow conditions associated with the ridge like deposit were derived from a simple pipe flow equation flow velocities of 9 8 11 6 m s 1 and shear stresses of 1440 2018 n m2 were reconstructed for a tunnel less than 3 m in average height and 45 m wide such flows would have been capable of transporting boulders of greater than 3 m in diameter as traction load and material of gravel cobble size in suspension material of this size has been deposited downflow as an ice contact delta linear ridges of boulder gravel with up slope gradients found in association with ice contact deposits in other formerly glaciated areas may similarly be of jokulhlaup origin

geology of the caloris basin mercury a view from messenger the caloris basin the youngest known large impact basin on mercury is revealed in messenger images to be modified by volcanism and deformation in a manner distinct from that of lunar impact basins the morphology and spatial distribution of basin materials themselves closely match lunar counterparts evidence for a volcanic origin of the basin s interior plains includes embayed craters on the basin floor and diffuse deposits surrounding rimless depressions interpreted to be of pyroclastic origin unlike lunar maria the volcanic plains in caloris are higher in albedo than surrounding basin materials and lack spectral evidence for ferrous iron bearing silicates tectonic landforms contractional wrinkle ridges and extensional troughs have distributions and age relations different from their counterparts in and around lunar basins indicating a different stress history

evidence for intrusive activity on mercury from the first messenger flyby images from messenger s first flyby of mercury have shown convincing evidence for surface volcanism here we report on evidence in the new data for several features that are characterized by fractures and graben rare features on a planet dominated by contractional deformation that may be linked to intrusive activity these features include 1 a floor fractured crater interpreted to have been the site of laccolith like sill intrusions the feature is similar to some floor fractured craters on the moon and shows evidence for individual fractured dome like uplifts on the floor 2 a concentric complex of graben observed inside the peak ring on the floor of the 250 km diameter raditladi basin and associated with dark plains and possibly embayed by them the feature may represent an unusual type of floor fracturing associated with deeper intrusions and related ring dikes or cone sheets or the graben may instead be the product of non magmatic uplift of the basin floor 3 a large radial graben swarm pantheon fossae located near the center of the caloris basin thus far unique on mercury and characterized by hundreds of individual graben segments ranging from 5 km to 110 km in length in the nexus graben crosscut one another and produce a local polygonal pattern others curve away from the center as the nexus is approached two scales of graben length are observed the radius of the dense radially symmetric plexus of graben is 175 km and a few graben extend to greater radial distances to the north and southwest out to distances that intersect with a ring of generally concentric graben around the outer basin floor two width scales of graben are observed a large graben about 8 km wide emerges from the nexus and extends for 100 km most graben are less than half this width some graben walls appear cuspate with convex outward wall segments that resemble crater chain segments one crater chain with distinctive raised rims parallels nearby graben locally some graben appear in en echelon patterns and smaller graben sometimes show cross cutting superposition relationships abundant impact craters the most prominent being apollodorus and secondary crater clusters and chains are superposed on the graben system there is little evidence that craters greater than 5 km in diameter have been cut by a graben this relation implies that the graben swarm formed soon after the emplacement of the caloris floor plains these graben are interpreted to be the surface expression of a radial dike swarm emanating from a subsurface magma reservoir similar features in which the dikes contribute to a near surface stress field that favors radial graben are known on the earth venus and mars the location of pantheon fossae in the center of the caloris basin suggests that formation of the radial graben structure is linked to basin evolution

extensional troughs in the caloris basin of mercury evidence of lateral crustal flow thirty years ago mariner 10 revealed extensional troughs that form giant polygons in the floor material of the caloris impact basin mercury the polygonal troughs occur in the interior of the basin and overprint wrinkle ridges formed in an earlier stage of compression in contrast lunar and martian basins exhibit extensional troughs that are circumferential and confined to basin margins loading by basin filling material can explain the extensional and compressional features seen in deformed lunar and martian basins but not the existence of the caloris polygonal troughs here we suggest that the caloris troughs formed from late stage basin uplift and extension due to lateral flow of a relatively thick crust toward the basin center if such lateral flow occurs the resulting timing location and magnitude of the extensional stresses predicted by our model are consistent with those inferred from the polygonal troughs these results are not strongly dependent on the degree of lateral flow or the assumed crustal rigidity for a dry plagioclase rheology and likely radiogenic heat fluxes the crustal thickness around caloris is 90 140 km similar late stage uplift and extension probably do not occur in basins on the moon and mars because their crusts are too thin to allow analogous lateral flow

an integrated study of the grain size dependent magnetic mineralogy of the chinese loess paleosol and its environmental significance 1 to investigate the grain size dependent properties of the magnetic minerals in chinese loess paleosol samples touxiangdao xining qinghai province china magnetic extracts were divided into two size fractions by gravitational settling on the basis of hysteresis measurements thermal demagnetization of low temperature saturation isothermal remanent magnetization and nonmagnetic studies sem and xrd we identified magnetic phases both in the grain size fractions of the magnetic extracts and in the less magnetic residues to provide more accurate and complete descriptions of all the magnetic components in the bulk natural samples the results show that the oxidation degree nonstoichiometry of magnetic minerals is strongly affected by both grain size and the paleoclimatic environment in which they were deposited and altered in ascending order of the oxidation degree of our samples we find 1 loess coarse particles lc are multidomain md magnetite with slight oxidation 2 paleosol coarse pc particles are also md magnetite but with a higher oxidation degree compared to lc 3 loess fine lf particles are pseudo single domain psd magnetite with a high oxidation degree and 4 paleosol fine pf particles are psd maghemite single domain sd and superparamagnetic sp maghemite mainly stay in the residues further thermomagnetic analysis of pf psd maghemite revealed that this natural maghemite has a curie temperature identical to that of magnetite and that the conversion efficiency of transformation from maghemite to hematite is only about 50 after a 700 c heating cooling cycle these new results identify the sources of multicomponent nrm in chinese loess sequences as well as clarify the paleoenviromental and paleoclimatic controls on the remanence components

emplacement and tectonic deformation of smooth plains in the caloris basin mercury abstract messenger s first flyby of mercury provided the first complete view of the caloris basin and its interior smooth plains multispectral imaging shows that the interior plains are spectrally distinct from surrounding terrain with a reflectance about 15 20 higher and a steeper spectral slope than the global average the caloris basin rim massifs and hummocky material in contrast have lower reflectance and a shallower spectral slope than the global average and extend around the entire basin isolated relatively red patches along the margins of caloris each surround irregularly shaped scalloped edged rimless depressions that are interpreted to be volcanic vents some with associated pyroclastic deposits a nearly continuous annulus of smooth plains exterior to the basin displays spectral characteristics that contrast sharply with those of the basin interior smooth plains the exterior smooth plains are lower in reflectance and spectrally similar to the caloris rim massifs and the hummocky materials the rims and floors of larger impact craters in the interior plains expose low reflectance material there is widespread evidence of contractional and extensional tectonic deformation of the caloris interior smooth plains a set of linear radial graben pantheon fossae radiates outward from a zone near the basin center and some of these graben extend to and intersect a set of generally basin concentric graben distributed along the outer margin of the caloris basin floor the average areal extensional strain expressed by the mapped system of graben is 0 08 wrinkle ridges also deform the interior smooth plains and predate both basin radial and basin concentric graben the average areal contractional strain expressed by the mapped wrinkle ridges is 0 07 the density of wrinkle ridges on the western interior smooth plains is less than on the eastern interior plains in contrast to the more even distribution of graben a similar difference is seen between the density of wrinkle ridges on the western and eastern exterior smooth plains with far fewer wrinkle ridges per unit area on the western annular plains superposition relations spectral contrast and the occurrence of volcanic vents and possible pyroclastic deposits all support a volcanic origin for the caloris interior plains crater counts indicate that the caloris exterior plains and hummocky material are younger than the caloris rim and interior plains and are therefore also likely volcanic in origin the contrast in spectral properties between the interior and exterior plains indicates a difference in the composition of the two expanses of volcanic material models for extensional tectonic deformation of the caloris basin interior inferred from the distribution of graben viewed by mariner 10 must be reevaluated to account for the discovery of pantheon fossae

estimates of the magnitude of glacier outburst floods from lake donjek yukon territory canada lake donjek was a large reservoir formed when donjek glacier dammed donjek river although the basin is empty at present a minor advance of donjek glacier could again dam the river and impound app

the tectonics of mercury the view after messenger s first flyby article i nfo during its first flyby of mercury messenger imaged many tectonic landforms most of which are contractional in nature and include lobate scarps high relief ridges and wrinkle ridges wrinkle ridges are found on the smooth plains that partially fill the interior and surround the exterior of the caloris basin and also on smooth plains that fill the interiors of smaller impact basins and larger craters messenger revealed a radial graben complex pantheon fossae nearlyco centered with the caloris basin pantheon fossae and a network of mostly basin concentric graben intheouterportionsofthecalorisbasininteriorformapatternofextensionnotseenelsewhereonmercury the first clear example of extensional faults outside of the caloris basin has been documented on smooth plains inside the peak ring of the relatively young raditladi basin a map of the distribution of tectonic landforms imaged by messenger and mariner 10 shows that lobate scarps are the most widespread type of feature estimates of the horizontal shortening associated with lobate scarps that crosscut and overthrust small impact craters imaged by messenger range from 1 to 3 km previously unrecognized lobate scarps detected in areas imaged by mariner 10 indicate thatearlierestimatesof contractional strainarelow anewestimate of theaverage arealcontractionalstrain 0 06 accommodated byscarps is at leastonethirdgreater thancomparableprevious estimates andcorresponds to a decrease in mercury s radius of at least 0 8 km since the end of heavy impact bombardment of the inner solar system these figures are lower bounds because of the likelihood that not all lobate scarps have been identified even in areas imaged to date crosscutting and embayment relations revealed by messenger suggest that lobate scarps formed before the end of smooth plains emplacement and continued to be active after the emplacement of the youngest smooth plains deposits relatively recent activity on lobate scarps may be the expression of slow but continuous radial contraction that accompanied cooling of mercury s interior and the growth of the planet s solid inner core published by elsevier b v

mobility of ni cr and co in serpentine soils derived on various ultrabasic bedrocks under temperate climate abstract serpentine soil is a common name for soils derived either from igneous peridotites or metamorphic serpentinites however differences in mineralogy of these rocks are responsible for some differences between soils occurring on peridotites and serpentinites in this study we analyze the mobility of ni cr and co in six serpentine sites derived from a variety of parent substrates from partially serpentinized peridotites through serpentinites containing relics of primary minerals and textures to proper serpentinites the mobility of ni cr and co determined using the edta extraction is the highest for ni whereas cr is the least mobile element in all soils studied no relationship between type of parent rock and cr mobility is found the lowest proportions of edta extractable fractions of ni and co up to 7 and 4 of total concentrations respectively are observed in soils derived from proper serpentinites devoid of primary minerals e g olivine pyroxene and having non pseudomorphic texture the highest proportions of edta extractable ni and co are noted in soils derived from partially serpentinized peridotite hornblende peridotite and serpentinite having typical pseudomorphic texture containing primary al rich magnesiochromite up to 18 and 16 of total concentration respectively it is therefore justified that type and origin of ultrabasic parent rock affect metal mobility at least in the case of ni and co in serpentine soils furthermore several soil characteristics such as ph total organic c soil mineralogy also play an important role in the mobility of ni cr and co however relationships between soil properties and metal availability are more pronounced for soils developed on proper serpentinites than for soils deriving from rocks that experienced less advanced serpentinization

geochemical assessment of metal transfer from rock and soil to water in serpentine areas of sabah malaysia the mobility of metals in ultramafic rock soil systems and metal contamination in serpentine soils were investigated from the ranau area in sabah east malaysia metal concentrations were analysed after division into seven operationally defined fractions by selective sequential extraction sse geochemical studies showed that the soils are exceptionally high in cr 95 residing in refractory residual fractions metal speciation studies will shed further light on toxicities in the malaysian ultramafic tropical environment reconciled against elemental metal tenure adopted by common standards

a model for radial dike emplacement in composite cones based on observations from summer coon volcano colorado usa we mapped the geometry of 13 silicic dikes at summer coon an eroded oligocene stratovolcano in southern colorado to investigate various characteristics of radial dike emplacement in composite volcanoes exposed dikes are up to about 7 km in length and have numerous offset segments along their upper peripheries surprisingly most dikes at summer coon increase in thickness with distance from the center of the volcano magma pressure in a dike is expected to lessen away from the pressurized source region which would encourage a blade like dike to decrease in thickness with distance from the center of the volcano we attribute the observed thickness pattern as evidence of a driving pressure gradient which is caused by decreasing host rock shear modulus and horizontal stress both due to decreasing emplacement depths beneath the sloping flanks of the volcano based on data from summer coon we propose that radial dikes originate at depth below the summit of a host volcano and follow steeply inclined paths towards the surface near the interface between volcanic cone and basement which may represent a neutral buoyancy surface or stress barrier magma is transported subhorizontally and radially away from the center of the volcano in blade like dikes the dikes thicken with increasing radial distance and offset segments and fingers form along the upper peripheries of the intrusions eruptions may occur anywhere along the length of the dikes but the erupted volume will generally be greater for dike fed eruptions far from the center of the host volcano owing to the increase in driving pressure with distance from the source observed eruptive volumes vent locations and vent area intrusions from inferred post glacial dike fed eruptions at mount adams washington usa support the proposed model hazards associated with radial dike emplacement are therefore greater for longer dikes that propagate to the outer flanks of a volcano

caloris basin mercury history of deformation from an analysis of tectonic landforms abstract the 1640 km diameter caloris basin is the largest impact basin on mercury and hosts three distinct suites of tectonic structures in its substantially deformed smooth plains indicative of the basin s complex history these structures i e radial graben comprising pantheon fossae concentric graben troughs arranged in an irregular pattern and wrinkle ridges are found at various regions throughout the basin and occasionally interact we document the locations orientations and cross cutting relationships of these structures using high resolution messenger images we suggest that caloris shows a history of continuous deformation resulting from the contemporaneous formation of sets of strain compatible tectonic structures rather than discrete stages of deformation producing each suite independently in temporal sequence we propose that radial graben formed continuously in the basin s early deformational history following initial wrinkle ridge formation possibly representative of a multi ring basin structure overlapping with continued wrinkle ridge formation and persisting with the formation of concentric graben after contraction ceased

explosive volcanism on mercury analysis of vent and deposit morphology and modes of eruption abstract the messenger mission revealed for the first time conclusive evidence of explosive volcanism on mercury several previous works have cataloged the appearance and location of explosive volcanism on the planet using a variety of identifying characteristics including vent presence and deposit color as seen in multispectral image mosaics we present here a comprehensive catalog of vents of likely volcanic origin our classification scheme emphasizes vent morphology we have analyzed the morphologies of all vents in our catalog and recognize three main morphologies simple vent pit vent and vent with mound the majority of vents we identify are located within impact craters the spatial distribution of vents does not correlate with the locations of volcanic smooth plains deposits in contrast to the moon nor do vents correlate with the locations of large impact basins except for the caloris and tolstoj basins using the degradation state of the vent host crater as a proxy for maximum age we suggest that vent formation has been active through the mansurian and into the kuiperian periods although the majority of vents were likely formed much earlier in mercurian history the morphologies and locations of vents are used to investigate a set of plausible formation geometries we find that the most likely and most prevalent formation geometry is that of a dike stalled at depth which then explosively vents to the surface we compare the vent and deposit size of mercurian pyroclastic deposits with localized and regional lunar pyroclastic deposits and find a range of possible eruption energies and corresponding variations in eruption style localized lunar pyroclastic deposits and the majority of mercurian pyroclastic deposits show evidence for eruption that is consistent with the magmatic foam at the top of a dike reaching a critical gas volume fraction a subset of mercurian vents including the prominent copland rachmaninoff vent to the northeast of the rachmaninoff basin indicates eruption at enhanced gas volume fractions this subset of vents shows a similar eruptive behavior to the lunar orientale dark mantle ring deposit suggesting that the dikes that formed these vents and deposits on mercury underwent some form of additional volatile build up either through crustal volatile incorporation or magma convection within the dike there also exists a population of mercurian vents that no longer retain a visible associated pyroclastic deposit we hypothesize that the visible signature of the pyroclastic deposit has been lost through space weathering and regolith mixing processes together these results provide a comprehensive analysis of explosive volcanism on mercury and inform continued research on the thermal history of mercury and magma composition and evolution

igneous dikes on mars revealed by mars orbiter laser altimeter topography the origin of martian grabens has remained controversial for decades given the nonuniqueness of graben morphology and conflicting interpretations of dike induced or faultingbased formation processes we use measurements from the mars orbiter laser altimeter to identify the characteristic topographic signature at the surface of an igneous dike beneath a martian graben our results suggest that this subtle but diagnostic signature can be used to test competing interpretations of the formation of grabens and associated fissures and collapse depressions

evaluation of the origin hypotheses of pantheon fossae central caloris basin mercury the origin of pantheon fossae a complex structure consisting of radial graben in the center of the caloris basin mercury has been debated since the structure was first imaged by the messenger spacecraft three different formation hypotheses have been suggested i e an origin associated with the apollodorus impact into a previously domed caloris basin floor graben formation as surface expressions of dike intrusions and basin interior uplift alone in order to test the scenarios detailed observations from the currently available imagery were compared to the proposed formation mechanisms we evaluate these origin hypotheses by means of detailed interpretations of the graben characteristics and patterns by comparing to radial structures from earth and venus and by mechanical analyses for each formation hypothesis results indicate that the formation of pantheon fossae as the result of doming in the central part of the caloris basin is more likely than it having formed in association with a radially symmetric stress field centered at or near the apollodorus crater that would have been created by a magma chamber or been superimposed on a pre existing dome due to impact mechanics

weathering and vegetation controls on nickel isotope fractionation in surface ultramafic environments albania abstract the dissolved nickel ni isotopic composition of rivers and oceans presents an apparent paradox even though rivers represent a major source of ni in the oceans seawater is more enriched in the heavier isotopes than river water additional sources or processes must therefore be invoked to account for the isotopic budget of dissolved ni in seawater weathering of continental rocks is thought to play a major role in determining the magnitude and sign of isotopic fractionation of metals between a rock and the dissolved product we present a study of ni isotopes in the rock soil plant systems of several ultramafic environments the results reveal key insights into the magnitude and the control of isotopic fractionation during the weathering of continental ultramafic rocks this study introduces new constraints on the influence of vegetation during the weathering process which should be taken into account in interpretations of the variability of ni isotopes in rivers the study area is located in a temperate climate zone within the ophiolitic belt area of albania the serpentinized peridotites sampled present a narrow range of heavy ni isotopic compositions ni 60 0 25 0 16 2sd n 2 at two locations horizons within two soil profiles affected by different degrees of weathering all presented light isotopic compositions compared to the parent rock 60nisoil rock up to 0 63 this suggests that the soil pool takes up the light isotopes while the heavier isotopes remain in the dissolved phase by combining elemental and mineralogical analyses with the isotope compositions determined for the soils the extent of fractionation was found to be controlled by the secondary minerals formed in the soil the types of vegetation growing on ultramafic derived soils are highly adapted and include both ni hyperaccumulating species which can accumulate several percent per weight of ni and non accumulating species whole plant isotopic compositions were found to be isotopically heavier than the soil 60niwhole plant soil up to 0 40 fractions of ni extracted by dtpa diethylenetriaminepentaacetic acid presented isotopically heavy compositions compared to the soil 60nidtpa soil up to 0 89 supporting the hypothesis that the dissolved ni fraction controlled by weathering has a heavy isotope signature the non hyperaccumulators n 2 were inclined to take up and translocate light ni isotopes with a large degree of fractionation 60nileaves roots up to 0 60 for ni hyperaccumulators n 7 significant isotopic fractionation was observed in the plants in their early growth stages while no fractionation occurred during later growth stages when plants are fully loaded with ni this suggests that i the high efficiency translocation process involved in hyperaccumulators does not fractionate ni isotopes and ii the root uptake process mainly controls the isotopic composition of the plant in ultramafic contexts vegetation composed of hyperaccumulators can significantly influence isotopic compositions through its remobilization in the upper soil horizon thereby influencing the isotopic balance of ni exported to rivers

outburst floods from glacier dammed lakes the effect of mode of lake drainage on flood magnitude published accounts of outburst floods from glacier dammed lakes show that a significant number of such floods are associated not with drainage through a tunnel incised into the basal ice the process generally assumed but rather with ice marginal drainage mechanical failure of part of the ice dam or both non tunnel floods are strongly correlated with formation of an ice dam by a glacier advancing from a tributary drainage into either a main river valley or a pre existing body of water lake or fiord for a given lake volume non tunnel floods tend to have significantly higher peak discharges than tunnel drainage floods statistical analysis of data for floods associated with subglacial tunnels yields the following empirical relation between lake volume v and peak discharge qp qp 46v0 66 r2 0 70 when qp is expressed in metres per second and v in millions of cubic metres this updates the so called clague mathews relation for non tunnel floods the analogous relation is qp 1100v0 44 r2 0 58 the latter relation is close to one found by costa 1988 for failure of constructed earthen dams this closeness is probably not coincidental but rather reflects similarities in modes of dam failure and lake drainage we develop a simple physical model of the breach widening process for non tunnel floods assuming that 1 the rate of breach widening is controlled by melting of the ice 2 outflow from the lake is regulated by the hydraulic condition of critical flow where water enters the breach and 3 the effect of lake temperature may be dealt with as done by clarke 1982 calculations based on the model simulate quite well outbursts from lake george alaska dimensional analysis leads to two approximations of the form qp vqf hi 0 where q 0 5 to 0 6 hi is initial lake depth 0 is lake temperature and the form of f hi 0 depends on the relative importance of viscous dissipation and the lake s thermal energy in determining the rate of breach opening these expressions along with the regression relations should prove useful for assessing the probable magnitude of breach type outburst floods

dissolution rate of antigorite from a whole rock experimental study of serpentinite dissolution from 2 ph 9 at 25 c implications for carbon mitigation via enhanced serpentinite weathering serpentinite rock dissolution experiments at 25 c and 2 ph 9 were used to retrieve antigorite dissolution rates as its high abundance and comparatively fast dissolution dominate element release from the rock retrieved antigorite dissolution rates at ph 2 02 and 3 06 are similar to previous literature data for serpentine minerals at corresponding ph in contrast retrieved rates at higher ph are considerably lower than corresponding literature data nonetheless the retrieved rates at ph 5 76 and 7 28 are consistent with the linear log rate ph relationship of orlando et al 2011 suggesting that rates follow a single acidic mechanism to a ph of at least 7 3 the relatively low dissolution rates of serpentine minerals found in this study suggests that significantly more time is required for serpentine weathering than that estimated using the dissolution rates of these solids reported by marini 2006 based on a review of literature data as such using enhanced serpentine weathering as a carbon capture storage strategy may be less efficient than previously assumed

postglacial crustal doming stresses and fracture formation with application to norway abstract postglacial doming of fennoscandia is estimated to have reached a maximum uplift value of 850 m vertical uplift of this magnitude generates stresses that affect the tectonic activity in the domed area using a simple model of a circular elastic plate subject to deflection it is shown that the maximum tensile stresses generated by this uplift occur in the centre of the dome and at the surface reach a numerical value of nearly 30 mpa this tensile stress is an order of magnitude greater than the typical in situ tensile strength of the uppermost part of the crust so that tension fractures are easily generated by this stress tension fractures can under certain conditions reach crustal depths of several hundred metres but if they propagate to greater depths they change into normal faults the tensile stresses at the surface decrease in magnitude with distance from the centre of the dome and become compressive in the marginal parts of the uplifted crustal plate at the surface of these parts the maximum shear stress exceeds 10 mpa because the inferred driving stresses stress drops in earthquakes are commonly only several mpa it follows that the driving shear stress in these marginal parts is large enough to initiate or reactivate seismogenic faults these model results are in broad agreement with data on the current seismotectonics of fennoscandia the formation and reactivation of tensile and shear fractures in fennoscandia as a result of postglacial uplift is likely to increase the hydraulic conductivity of the solid rocks that constitute the uppermost part of the crust this conclusion is supported by reported observations which indicate that the production of groundwater in wells in many areas in norway varies positively with the maximum postglacial uplift

an assemblage of lava flow features on mercury 1 in contrast to other terrestrial planets mercury does not possess a great variety of volcanic features its history of volcanism instead largely manifest by expansive smooth plains however a set of landforms at high northern latitudes on mercury resembles surface flow features documented on earth the moon mars and venus the most striking of such landforms are broad channels that host streamlined islands and that cut through the surrounding intercrater plains together with narrower more sinuous channels coalesced depressions evidence for local flooding of intercrater plains by lavas and a first order analysis of lava flow rates the broad channels define an assemblage of flow features formed by the overland flow of and erosion by voluminous high temperature low viscosity lavas this interpretation is consistent with compositional data suggesting that substantial portions of mercury s crust are composed of magnesian iron poor lithologies moreover the proximity of this partially flooded assemblage to extensive volcanic plains raises the possibility that the formation of these flow features may preface total inundation of an area by lavas emplaced in a flood mode and that they escaped complete burial only due to a waning magmatic supply finally that these broad channels on mercury are volcanic in nature yet resemble outflow channels on mars which are commonly attributed to catastrophic water floods implies that aqueous activity is not a prerequisite for the formation of such distinctive landforms on any planetary body

behavioural properties of trace metals in soils abstract the speciation and spatial distribution of trace metals in soils are closely related to their behaviour in multiphase and dynamic soil systems the surface reactions at soil solution root interfaces are the key to the determination of the amounts of mobile and plant available metals the behaviour of trace metals in the soil environment depends to some extent on their origin lithogenic metals are associated mainly with primary minerals and may be phytoavailable under specific conditions in the soil plant system anthropogenic metals show great diversity but in most cases they are likely to be very mobile and easily available to plants forms of the metals of both origins may be transformed due to pedogenic processes and they become pedogenic metals greatly controlled by soil properties in order to assess the phytoavailability and to accept proper guidelines for permissible trace metal loading their behaviour in the specific soil environments has to be defined

effect of tensile stress concentration around magma chambers on intrusion and extrusion frequencies what controls the intrusion and extrusion frequencies associated with volcanoes is still poorly understood i propose that for volcanoes at divergent plate boundaries these frequencies may be largely determined by the tensile stress concentration around the magma chambers that feed them this stress concentration is mainly a function of the applied tensile stress associated with spreading and the aspect height width ratios of the chambers high spreading rates and or aspect ratios lead to high rates of tensile stress concentration around the chambers and to an increase in their intrusion frequencies it is found that for chambers at the same depth in a volcanic zone the one of the highest aspect ratio will normally intrude magma most frequently also if the chambers are of equal aspect ratios the one at the greatest depth will intrude magma most frequently because the extrusion frequency of a volcano is a fraction of its intrusion frequency the extrusion frequency may also be largely determined by the rate of tensile stress concentration around the magma chamber that feeds the volcano these results are applied to the divergent plate boundary in iceland where many of the volcanoes appear to be fed by double chambers that is shallow chambers fed by deep seated chambers it is found that except when the aspect ratio of the deep seated chamber is much less than that of the shallow chamber the intrusion frequency of the shallow chamber is normally largely controlled by that of the deep seated chamber it is concluded that whereas the short term i e 103 yrs extrusion frequencies of volcanoes at the plate boundary in iceland may be similar to the dike intrusion frequencies of the source chambers the long term i e 104 yrs extrusion frequencies may be about ten times lower than the intrusion frequencies

could pantheon fossae be the result of the apollodorus crater forming impact within the caloris basin mercury abstract the 40 km diameter apollodorus impact crater lies near the center of pantheon fossae a complex of radiating linear troughs itself at the approximate center of the 1500 km diameter caloris basin on mercury here we use a series of finite element models to explore the idea that the apollodorus crater forming impact induced the formation of radially oriented graben by altering a pre existing extensional stress state graben in the outer portions of the caloris basin which display predominantly circumferential orientations have been taken as evidence that the basin interior was in a state of horizontal extensional stress as a result of uplift if the apollodorus crater formed at the time of such a stress state impact induced damage to basin fill material would have caused basin material to move radially outward leading to a decrease in the radial extensional stress and an increase in the circumferential stress if this change in differential stress was sufficient to induce failure the predicted style of faulting would be radial graben extending outward from the exterior crater rim the 230 km radial extent of pantheon fossae implies by this scenario that the apollodorus impact generated a large damage zone extending to perhaps three crater radii 60 km or more the calculations also suggest under this scenario that the caloris basin fill had greater strength than the surrounding crust and that the basin uplift and extensional stress field prior to the apollodorus impact were close to azimuthally symmetric the location of pantheon fossae very near the center of the caloris basin appears to be coincidental any crater similar in size to apollodorus and located within 300 km of the basin center could have produced a radiating set of graben by the mechanism explored here

surface deformation and shallow dike intrusion processes at inyo craters long valley california the inyo craters are the two largest of four phreatic craters that lie within a 2 5 km long 500 to 700 m wide n s trend of faults and fissures at the south end of the inyo volcanic chain in eastern california the alignment of these features with dike fed silicic volcanic centers of the same age a few kilometers to the north suggests that they were produced during intrusion of a dike at about 650 550 yr b p e w extension south of south inyo crater is ten to several tens of meters suggesting that the dike is at least that thick to understand how the faults and fissures developed we mapped and studied the fault and fissure pattern used a theoretical boundary element model to determine the surface strain profile above a shallow dike in a purely elastic medium and conducted physical model experiments of fault and fissure growth results of the field studies and experiments indicate that deformation develops according to the following sequence 1 extension fractures and perhaps other inelastic deformation develop immediately above the dike top and on the limbs of a shallow syncline which forms above the dike 2 fissures form along two parallel trends at the surface on opposite sides of the dike plane leaving a relatively unfractured region in between 3 dip slip movement on subsurface fractures and linkage of these fractures with surface fissures produces inward facing normal fault scarps that bound a nested graben above the dike experimental graben widths are up to several times narrower than predicted from the locations of theoretical strain maxima above a dilating crack in a linearly elastic medium this fact is apparently due to the growth of a zone of inelastic deformation above the experimental dike top in the subsurface if the ratio between the depth to the dike top and the distance between the outermost surface fissures at inyo craters is within the range of ratios measured experimentally then the depth to the dike top is between 250 m and several times that a slant hole drilled in the summer of 1987 by the department of energy office of basic energy sciences intersected three breccia bodies of possibly intrusive origin directly below the center of south inyo crater between 550 m and 610 m below the crater rim no intact juvenile igneous rock was intersected suggesting that the hole passed above the magma filled dike top perhaps passing through the zone of inelastic deformation which is inferred to exist from our model results

deformation associated with ghost craters and basins in volcanic smooth plains on mercury strain analysis and implications for plains evolution 1 since its insertion into orbit about mercury in march 2011 the messenger spacecraft has imaged most previously unseen regions of the planet in unprecedented detail revealing extensive regions of contiguous smooth plains at high northern latitudes and surrounding the caloris basin these smooth plains thought to be emplaced by flood volcanism are populated with several hundred ghost craters and basins nearly to completely buried impact features having rims for which the surface expressions are now primarily rings of deformational landforms associated with some ghost craters are interior groups of graben displaying mostly polygonal patterns the origin of these graben is not yet fully understood but comparison with numerical models suggests that the majority of such features are the result of stresses from local thermal contraction in this paper we highlight a previously unreported category of ghost craters quantify extensional strains across graben bearing ghost craters and make use of graben geometries to gain insights into the subsurface geology of smooth plains areas in particular the style and mechanisms of graben development imply that flooding of impact craters and basins led to substantial pooling of lavas to thicknesses of 1 5 km in addition surface strains derived from groups of graben are generally in agreement with theoretically and numerically derived strains for thermal contraction