mobility and fractionation of rare earth elements in argillaceous sediments implications for dating diagenesis and low grade metamorphism abstract we report sm nd and rb sr data for the fine fractions of lower paleozoic argillaceous rocks from wales uk and new york usa spanning the range of low grade metamorphic conditions from the diagenetic zone zeolite facies to the epizone greenschist facies in all cases leaching of the fine fractions results in a high 147 sm 144 nd 0 09 0 29 acid soluble component and a complementary low 147 sm 144 nd 0 05 0 14 residual component the observed fractionation is an ancient feature related to diagenesis burial and metamorphism the magnitude of sm nd fractionation between leachates and residues as well as the resulting sm nd ages vary as a function of grain size and metamorphic grade uncleaved welsh mudrocks of the diagenetic zone yield sm nd leachate residue ages of 453 484 ma in agreement with their llanviian to caradocian biostratigraphic ages whereas higher grade rocks of the anchizone and epizone yield sm nd ages as young as 413 ma these ages are transitional between the time of deposition and the time of regional deformation related to the acadian orogeny at 390 ma distinct convex upward rare earth element ree patterns of the leachates suggest that the precipitation of early diagenetic apatite controls the trace element budget of the rock forcing a depletion of middle rees on the subsequently formed diagenetic phyllosilicates the amount of organic matter present and the extent of later prograde reactions are probable modifiers of this fractionation process ordovician and devonian clastic rocks associated with the trenton and onondaga limestones of new york yield single sample and multi sample sm nd isochron ages that agree well with their biostratigraphic ages of 454 ma and 390 ma respectively the ree fractionation observed in shale leachates of the ordovician utica formation is related to ca mg of the bulk rock and hence to the composition of the diagenetic carbonate cement in all cases the sm nd system remained closed subsequent to the peak of diagenesis or metamorphism including the north american rocks that show no evidence of being isotopically reset during widespread remagnetization of the subjacent limestone units in the late paleozoic

behavior of rare earth elements in a paleoweathering profile on granodiorite in the front range colorado usa abstract a paleoweathering profile on the boulder granodiorite in northern colorado provides an opportunity to trace the behavior of rees from parent rock through a weathering profile into unconformably overlying permian sediments with progressive upward weathering of the granodiorite na2o cao sio2 ta hf co th cr sc cr th zr hf la sc zr y and la th decrease al2o3 and fe2o3t increase and tio2 mgo k2o p2o5 rb zr sc cr co hf nb ta y th u ree ti nb and zr nb increase to maximum values and then either level off or decrease lree enrichment is less in the weathering profile than in the parent granodiorite and although the parent does not have an eu anomaly or only a slight positive anomaly all samples from the weathering profile and overlying sediments have significant negative eu anomalies this observation is especially important in that it shows conclusively that a negative eu anomaly can be produced during chemical weathering of granitoids we suggest these eu anomalies are due to relative enrichment of the other rees and partial loss of eu during the breakdown of plagioclase the boulder weathering profile also has a very minor negative ce anomaly that is within error of a ce anomaly in the parent in the unweathered parent 50 of the ree are contained in sphene and in the case of la also in allanite from 10 20 of the ree are contained in apatite and biotite hornblende and from 7 10 of the hrees are in zircon with exception of eu for which feldspars contribute about 8 negligible amounts of rees occur in the feldspars in weathered samples 75 of the rees are contained in clay minerals the crossover between sphene and clay control of rees occurs over a distance of 1 m near the contact with fresh rock except for their small negative eu anomalies the clay minerals have ree patterns very similar to those of the parent rock isocon plots suggest apparent enrichments of many elements in the boulder weathering profile result from losses of na ca and si during plagioclase weathering in addition variable amounts of sr eu ta nb p and ba were lost during weathering although th u zr y th sc zr hf lu hf and ti zr may have been transferred relatively unchanged from granodiorite parent to the bulk weathering profile most other element ratios and ree distributions were significantly changed during weathering this observation implies that caution needs to be exercised when using ree patterns and element ratios to trace sediment provenance the fact that most element ratios and ree distributions also differ between fountain sediments and the bulk weathering profile may be related to one or a combination of four factors listed in order of probable decreasing importance contribution of other sources to the fountain sediments sorting of minerals during sediment deposition remobilization of elements during diagenesis and leaching of elements by water flow through the upper meter of the weathering profile

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

chemical processes affecting the mobility of major minor and trace elements during weathering of granitic rocks abstract the behaviour of 38 major and trace elements as well as changes in the mineralogy have been examined in 10 weathering profiles developing on some portuguese granitic rocks element mobilities are calculated from geochemical data normalized with respect to ti in the fresh parent rock chemical elements are divided into two groups immobile and mobile on the basis of their geochemical distribution during weathering elements that are immobile during weathering are zr hf fe al th nb sc and the ree very mobile are ca na p k sr ba rb mg and si mobile elements are derived mainly from leachable minerals such as feldspars micas and apatites whereas immobile elements are either concentrated in resistate phases or strongly adsorbed by secondary minerals the geochemical behaviour of mn cr v fe and ce is very dependent on redox conditions redox transformations of these elements can be used to set limits on the oxidation state of a weathering suite the ree are mobilized or fractionated during late stages of weathering but not during moderate stages of weathering this fractionation is caused by selective leaching of rocks composed of both stable and unstable minerals containing ree

rare earth element and mineralogic changes in holocene soil and stream sediment a case study in the wet mountains colorado u s a size fractions of soil and stream sediment developed on plutonic metamorphic or mixed plutonic metamorphic sources in the wet mountains colorado have been analyzed for ree rare earth elements and mineralogy the clay sized fractions 0 5 m and 0 5 2 m or 2 m have ree contents that are similar to more enriched than the source eu sm ratios that are similar to the source and la lu ratios that are higher than their corresponding source the 0 5 m fractions have lower ree contents than the corresponding 0 5 2 m fraction in every stream sediment for example unweathered san isabel batholith near the sampled stream sediment contains ree 511 712 ppm and eusmratio 0 17 0 19 and lalu cn 9 8 10 3 the corresponding 0 5 and 0 5 2 m fractions of sediment formed from san isabel batholith are enriched in the ree ree 1135 and 2225 ppm respec are slightly lower in eu sm ratios 0 16 and 0 14 respec and are higher in la lu ratios 12 2 and 16 3 respec than the unweathered rocks the silts have lree light ree contents and eu sm ratios very similar to the source due to similar mineralogy but silts have hree heavy ree contents higher than the source due to high zircon for example silt sized fractions in stream sediment draining the san isabel batholith contain ree 808 ppm eusmratio 0 18 and lalu cn 7 4 in contrast the sands contain lower ree contents similar to higher eu sm ratios and lower la lu ratios than the corresponding source due to depletion in heavy minerals concentrated in the ree and containing lower eu sm ratios relative to quartz and feldspar depleted in the ree and containing higher eu sm ratios for example the sand fraction from stream sediment from the san isabel batholith has ree 206 ppm eusmratio 0 17 and lalu cn 5 6 small variations of accessory minerals concentrated in the ree like allanite or sphene may cause drastic variation in ree content in the sand fraction clays and silts derived only from the plutonic rocks have higher ree and similar to lower eu sm ratios than corresponding fractions derived only from migmatites e g ree of silt fractions from migmatites 224 ppm and from plutons 375 808 ppm eu sm ratios from migmatites 0 17 and from plutons 0 11 0 18 the ree content and the eu sm ratio of clays and silts derived from migmatites are much more similar to the average of mcps mid continent platform sediment than corresponding fractions derived from the plutons mcps has ree 192 ppm eusm 0 19 lalu 8 0 the eusm ratio of sands derived from plutons and migmatite are lower to mostly higher than the mcps the ree content of sands from plutons are not necessarily higher than the mcps due to variation in heavy minerals like allanite or sphene concentrated in the ree sediments derived from mixed sources have ree contents in fine fractions that may not necessarily reflect the ree content of the nearest source for example 0 5 2 m and silt fractions developed on the san isabel batholith with a migmatite upstream have the high ree content of the batholith ree in 0 5 2 m fraction 1100 ppm silt 573 ppm while the corresponding 0 5 m fraction has the very low ree content of the migmatites ree 110 ppm these results suggest fine grained material near the source may sample a much larger area than coarser material near the source thus analysis of fine grained sediment associated with coarse grained material near the source may give a much different impression of the source than would determination of the source using classic petrographic examination of the sand or gravels

a perturbation solution for bingham plastic mudflows an analytical solution is proposed for laminar mudflows and debris flows that can be modeled by a bingham plastic law two dimensional unsteady nonuniform bingham flows released from a point source or a source of finite size dam break problem or mudslide problem on a steep slope are considered the method of matched asymptotic expansions was implemented to get a first order solution for the dam break problem the proposed model is found to be valid when the shock wave has advanced three reservoir lengths downstream also it is found that the bingham flow only propagates a finite distance downstream with the shock depth asymptotically approaching the yield depth and the shock velocity asymptotically falling to zero the hydrograph produced by a bingham flow is seen to have a slower and lower flood peak and a longer and higher flow tail than that produced by newtonian flow having the same dynamic viscosity comparison of the model predictions with laboratory observations shows reasonable agreement

mobilization and redistribution of rees and thorium in a syenitic lateritic profile a mass balance study abstract ree th geochemistry and mineralogy have been studied in a lateritic profile derived from a syenite at akongo in sw cameroon ree and th mass balance calculations for the host rock minerals show that at least 70 of the lree s and 50 of the hrees are contained in allanite apatite titanite and epidote and at least 50 of the th is controlled by the same accessory minerals which represent about 2 wt of the unaltered syenite these accessory phases are destroyed during the first stages of weathering causing most of the rees and th to be rapidly released into the soil comparison of the variation in the zr ti and th content as a function of the apparent density of the different zones of the saprolite shows that th is the least mobile element the presence of secondary thorianite tho2 the etched surface on zircon grains and the presence of ti in secondary cerianite support this geochemical interpretation the concentration of thorium was therefore chosen as invariant relative to the concentration of the other elements especially the rees in mass balance calculations most of the rees are leached in the iron rich upper horizons loose nodular horizon iron crust and top of mottled clay horizon where the groundwater table moves saprolite and bottom of the mottled clay horizon the rees are fractionated and redistributed there is a juxtaposition of leached and accumulation zones with precipitation of lree aluminous hydrated phosphates this study supports the existence of two different cycles for the redistribution of elements in the soil 1 1 as dissolved ions in the saprolite horizon and 2 2 as individual particles in the upper part of the profile

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

ree geochemistry of recent clastic sediments from the kaveri floodplains southern india implication to source area weathering and sedimentary processes abstract the kaveri river drains through archean gneissic and charnockitic terranes in south india the rare earth element ree chemistry of the floodplain sediments along with their major and trace element composition in different size fractions are discussed we observe a strong coherence between ree and tio2 contents in the sediments which is suggestive of strong control by titanite or its weathered products on the ree chemistry ree concentrations also show a general increase with decreasing size of bulk sediments different size fractions and of light and heavy mineral fractions this suggests the presence of ree in the fe oxy hydroxide surface coatings on clastic grains formed by the weathering of hornblende and titanite in the granodioritic to dioritic protoliths we also interpret the data as showing that ree patterns of clastic sediments notably eu anomaly are affected by the degree of source rock weathering as well as by the fluvial processes of sorting and mineral differentiation therefore for provenance study sediments having all granulometric grades such as the floodplain sediments are preferable because they most closely represent the source particularly when the source region suffered little chemical weathering in the present case the sediments were derived from the high standing hills of archean charnockites because of their recent uplift and physical denudation

open channel flow of bingham fluids applications in debris flow research the results of a numerical simulation of open channel flow of bingham fluids provide improved capabilities for analyzing muddy debris flows and their depositis and for routing debris flows because of limitations of the phenomenonological bingham model results are deemed applicable to mud rich debris flows only most published field estimates of debris flow rheological bingham properties depend on application to natural channels of analytical solutions for flow through channels with either circular or very wide channel cross sections lack of a general solution for flow of bingham fluids in channels with realistic shapes has restricted capabilities in debris flow modeling and field data analysis numerical solutions permit generalization and extension of analytical solutions to channels of arbitrary cross sectional form without loss of accuracy the numerical model fidap utilizes a well established finite element formulation of the non newtonian fluid flow problem and reproduces available analytical

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

cerium anomalies in lateritic profiles the ree geochemistry and mineralogy have been studied in four lateritic profiles one derived from a syenite akongo sw cameroon the others being developed on a gneissic basement and located along a soil toposequence goyoum e cameroon there is a fractionation between lree and hree in the lateritic samples during weathering the weathered residual products being enriched in lree from la to eu and depleted in hree from gd to lu sampled waters are enriched in hree in relation to the syenite host rock a positive ce anomaly has been found systematically at the top of the saprolite beneath a zone of iron oxide accumulation in the laterite up to 2000 ppm ce may be present in the akongo profile cerianite ceo2 is present as very fine coatings in non ferruginous clayey domains primary ree bearing accessory minerals are weathered at the bottom of the profile specifically allanite and apatite are transformed into florencite and rhabdophane but these phases have no ce anomaly all the data are interpreted as the result of the following processes 1 1 ree leaching in a reducing environment 2 2 oxidation of ce3 to ce4 in an oxidizing environment 3 3 deposition of cerium as cerianite whereas the other ree remain in solution

geochemical evolution of archean shales from south africa i the swaziland and pongola supergroups abstract the fig tree group and moodies group part of the swaziland supergroup are exposed in the barberton mountain land and are 3 3 3 5 ga old shales from the fig tree group are characterized by variable rare earth element ree patterns with lan ybn 5 5 1 8 95 confidence and eu eu 0 97 0 18 shales from the moodies group have more fractionated ree patterns lan ybn 8 7 2 0 and less variable eu anomalies eu eu 0 92 0 02 both groups are characterized by very high abundances of cr and ni modelling of those trace elements which are relatively unfractionated during sedimentary processes ree th sc is consistent with the derivation of these sedimentary rocks from a mixture of the archean bimodal igneous suite mafic volcanics tonalites trondhjemites felsic volcanics with the moodies group requiring a larger percentage of the felsic end member the data for shales from the swaziland supergroup support models suggesting that the archean exposed crust was of more mafic composition than the post archean upper crust and that intracrustal melting was relatively unimportant in differentiating the archean crust the pongola supergroup is younger than the swaziland supergroup but older than 2 9 ga shales and mudstones from the nsuze and mozaan groups show ree characteristics intermediate between the older shales of the swaziland supergroup and typical post archean shales one quartzite sample from the witwatersrand supergroup ca 2 6 ga has a ree pattern virtually parallel to average post archean shales but with much lower abundances the change from typical archean to post archean sedimentary trace element patterns has been documented in early proterozoic successions from canada and australia this change has been related to a short interval of intense growth and chemical differentiation of the continental crust during the late archean 2 7 2 5 ga in southern africa this change appears to have taken place much earlier 3 2 2 9 ga but can be related to similar processes thus the period of crustal evolution related to the archean proterozoic boundary while virtually episodic regionally occurred over a protracted period world wide during the period ca 3 2 2 5 ga

weathering plants and the long term carbon cycle the chemical weathering of ca mg silicate rocks is the principal process whereby co2 is removed from the atmosphere on long or multimillion year time scales at present vascular land plants exert an important influence on weathering by recycling water and by bringing about the secretion of acids and the buildup of high levels of co2 in soils before the spread of vascular plants on the continents during the mid paleozoic chemical weathering must have been achieved by higher levels of atmospheric co2 and or by the intercession of primitive land biota such as lichens and cyanobacteria from examination of several pre vascular weathering scenarios it is concluded that in order to prohibit unreasonably high levels of atmospheric co2 weathering during the precambrian and early paleozoic must have taken place under essentially closed system abiotic conditions linear feedback or via strong regulation by primitive biota preliminary examination of modern weathering by lichens over tens to thousands of years militates against the latter possibility however much more work needs to be done on the quantitative effect of both primitive biota and vascular plants on the rate of weathering and their response to changes in atmospheric co2 before anything more definitive can be said

another look at rare earth elements in shales linear correlation and mass balance considerations indicate that clays are more important than zircon or other heavy minerals in hosting both light and heavy ree in cratonic shales considering the uniformity of the eu anomaly and ree distributions in cratonic shales it seems likely that detritus is thoroughly mixed during weathering and sediment transport and that the ree patterns in shales reflect the average ree pattern of the sources regardless of the ratio of clays to heavy minerals in the shales shales suspended river loads and near shore marine sediments all have broadly similar ree patterns and reported hree depletions in the latter two groups may reflect incomplete dissolution of heavy minerals during sample preparation ree distributions in shales and suspended river loads determined by inna are similar to those in average upper continent crust and ree distributions in shale averages nasc and paas seem to be reasonably representative of the average composition of post archean upper continental crust

influence of flow resistance stresses on debris flow runout the hydrodynamic modeling of debris flows is challenged by the complicated mechanism of debris flow and the large variability of material composition therefore in the dynamic continuum modeling of debris flows it is essential to select suitable rheological and associated friction parameters the quadratic rheological model is the most comprehensive approach because it considers the effects of viscous behavior solid particle resistance turbulent properties and friction characteristics of debris flow therefore this study adopted the quadratic model as the governing flow resistance stress and analyzed the influence of various flow resistance stresses to evaluate the runout performance the shallow water equations with modified bottom friction were discretized and the developed model was validated against a dam break flow and a spreading of circular cone problem then to investigate the relationship between the flow resistance relations and the bottom shear stresses exerted by the cones and dry bed the model was applied to runout in a rectangular domain with three cone shaped obstacles an actual field runout event that occurred in korea in 2011 was replicated and the runout paths and flow patterns were analyzed according to the various resistance stresses by considering both the extremely rapid runout velocity and the striking run up height the results obtained by the quadratic stress relation achieved the best performance however for the successful application of the quadratic approach three parameters had to be adjusted with consideration to locality

effect of bed sediment entrainment on debris flow resistance entrainment of sediment from hillslope and channel usually has a significant influence on resistance of debris flow this effect is studied by flume experiments of debris flow over rigid and erodible beds fifty contrast flume tests show that the flow resistance over the erodible bed is significantly larger than that over the rigid bed because of higher energy consumption resulting from sediment transport a new formula of debris flow resistance involving the entrainment effect is obtained from the erodible bed data by nondimensional multiple regression analysis

1d modeling of mud debris unsteady flows the national weather service 1d dynamic flood routing model fldwav is enhanced to include capability of modeling mud debris unsteady flows by including an additional friction slope term in the momentum equation of the saint venant equations three techniques are incorporated into the model to determine the mud debris related friction slope term due to the internal viscous dissipation of non newtonian fluids and granular sliding friction of coarse grained debris surges these techniques are tested and some computational results are compared with observed field data and experimental data

geohazards of slope mass movement and its prevention in hong kong rapid urban development in hilly terrain coupled with tropical storms with heavy rainfall has led to the frequent occurrence of disastrous landslides in hong kong this paper outlines several case histories of such disastrous landslides in hong kong and the major efforts that have been made to mitigate landslide hazards in hong kong since the mid 1970s factors that contributed to such landslides and their causative mechanisms are analyzed methods of predicting the runout distance and lateral extent of rainfall induced slope failures are summarized slope maintenance requirements and stabilization measures are delineated including the stabilization of loose fill slopes

evaluation of approaches to calculate debris flow parameters for hazard assessment abstract many different runout prediction methods can be applied to estimate the mobility of future debris flows during hazard assessment the present article reviews the empirical analytical simple flow routing and numerical techniques all these techniques were applied to back calculate a debris flow which occurred in 1982 at la guingueta catchment in the eastern pyrenees a sensitivity analysis of input parameters was carried out while special attention was paid to the influence of rheological parameters we used the voellmy fluid rheology for our analytical and numerical modelling since this flow resistance law coincided best with field observations the simulation results indicated that the basal friction coefficients rather affect the runout distance while the turbulence terms mainly influence flow velocity a comparison of the velocity computed on the fan showed that the analytical model calculated values similar to the numerical ones the values of our rheological parameters calibrated at la guingueta agree with data back calculated for other debris flows empirical relationships represent another method to estimate total runout distance the results confirmed that they contain an important uncertainty and they are strictly valid only for the conditions which were the basis for their development with regards to the simple flow routing algorithm this methods could satisfactorily simulate the total area affected by the 1982 debris flow but it was not able to directly calculate total runout distance and velocity finally a suggestion on how different runout prediction methods can be applied to generate debris flow hazard maps is presented taking into account the definition of hazard and intensity the best choice would be to divide the resulting hazard maps into two types final hazard maps and preliminary hazard maps only the use of numerical models provided final hazard maps because they could incorporate different event magnitudes and they supplied output values for intensity calculation in contrast empirical relationships and flow routing algorithms or a combination of both could be applied to create preliminary hazard maps the present study only focussed on runout prediction methods other necessary tasks to complete the hazard assessment can be looked up in the guidelines for landslide susceptibility hazard and risk zoning included in this special issue

weathering of gneissic rocks in the upper reaches of cauvery river south india implications to neotectonics of the region in the upper reaches of the cauvery catchment area in southern india the archean peninsular gneisses exhibit a greater degree of weathering in the field relative to the massive charnockites and granites although the gneisses have been physically broken down along foliation planes fractures and compositional discontinuities secondary mineral such as chlorite smectite kaolinite and fe oxyhydroxide formation is insignificant consequently there is little chemical change even up to the stage of saprolite development only in the regolith there is some loss of ca na sr ba mg and sio2 other elements such as fe mn al cr ni and ree all show enrichment relative to tio2 in areas which have developed profiles by in situ weathering the chondrite normalized ree patterns however show little change excepting a slight flattening of the patterns because of greater hree mobility during weathering clay minerals also have flattened ree patterns because of relative hree enrichment the depletion and the enrichment of different elements appear to be related to mild leaching of primary mafic minerals by meteoric water rather than by mineral breakdown this and the extent of variation in chemical index of alteration values suggest that that the gneisses have suffered only incipient chemical weathering for the extent of physical weathering undergone by them it is likely that this contrasting weathering extents of these 2500 ma rocks is due to their exposure to surface geological processes only recently because of ongoing periodic uplift and physical erosion of this region

major element ree and other trace element behavior in amphibolite weathering under semiarid conditions in southern india abstract a body of komatiitic amphibolite an enclave within the archean high grade orthogneisses in southern india shows mild chemical weathering under semiarid conditions along fractures chemical weathering has advanced chemical index of alteration documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm cia 53 end document cia of fresh documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage

geochemistry and petrogenesis of granitoids around the kolar schist belt south india constraints for the evolution of the crust in the kolar area the peninsular gneiss surrounding the n s trending kolar schist belt in the dharwar craton includes several components of granitic rocks that range in composition from tonalite to granite on the west the different phases are referred to as the dod the dosa and the banded gneiss and the patna granite the gneisses on the east are dominantly of one type and are referred to as the kambha gneiss the champion gneiss occurring within the eastern part of the belt is compositionally similar to the plutonic dod gneiss and probably represents a near surface intrusion late aplites are present on both sides of the belt the banded gneiss was formed by partial melting of tonalitic rocks and the aplites were formed by the action of aqueous fluids during amphibolite grade metamorphism excepting these two rocks all other granitoids seem to have been formed from silica oversaturated parent magmas derived from lile enriched mantle sources by fractionation processes including liquid immiscibility and fractional cry

mineralogical and chemical changes of soil and stream sediment formed by intense weathering of the danburg granite georgia u s a abstract a series of soil and stream sediments developed during intense weathering on the metaluminous danburg granite northeastern georgia u s a have been analyzed mineralogically and chemically the concentrations of ba na rb and cs in the silt and coarser fractions are controlled mainly by feldspars and biotite hf is controlled by zircon and the ree rare earth elements and th are largely controlled by sphene variations in feldspar sphene and zircon may produce small variations in eu sm and la lu ratios ferromagnesian minerals control ta fe co sc and cr concentrations the mineralogical and chemical composition of the danburg granite is more closely reflected in the silt than in the sand or gravel fractions of stream sediments in the silt the contents of rb ree th ta fe co and sc and the ratios of la sc th sc la co th co eu sm and la lu are similar to those in the unweathered granite in contrast these element contents or ratios in the sands and gravels are 0 05 3 the concentration in the unweathered granite ta and ba contents are an exception to the above the ta and ba contents of the sands and gravels are similar to those of the granite in the kaolinite halloysite clays the content of na is depleted relative to the source rb cs ba hf and ta are depleted or enriched in the clays relative to the source while the ree th fe co sc and cr are enriched the eu sm eu anomaly size and la lu ratios and the ree patterns of the clays are similar to those of the source thus the mineralogy and element contents of a siltstone developed from metaluminous granitic sources during intense weathering would be expected to be more similar to the source rock than the sandstones and conglomerates claystones should contain similar ree patterns and eu sm ratios as the source rock but such fine grained sediments might represent much larger areas of source rocks than the more locally derived sandstones or conglomerates

geochemical signature of provenance in sand size material in soils and stream sediments near the tobacco root batholith montana u s a abstract trace element geochemistry of sandstones are being used to determine provenance we have conducted preliminary and limited experiments to determine to what extent daughter sands retain the geochemical signature of parent rocks six sets of first order stream sediments soils from adjacent slopes and a variety of parent rocks were collected from southwestern montana u s a sampling in a low relief area ensured that climate and residence time of soils on slopes could be eliminated as variables sand size fractions of stream sediments and soils and the corresponding parent rocks granodiorite quartz monzonite granite gneiss biotite tonalite gneiss and amphibolite were analyzed for most major elements and selected trace elements petrologic modal analysis of the parent rocks and the 0 25 0 50 mm fraction of each sand was done to monitor major mineralogic control if any on chemical compositions of the samples our data show that the abundances of the si and al in sediments do not discriminate provenance abundances of ca mg fe and ti may broadly distinguish between sands derived from metamorphic and igneous source rocks at least in the area studied differences in abundances of the ba and th and the ratio of la lu between granitic tonalitic and amphibolitic parent rocks are preserved in the daughter sediments that we studied however the size of the eu anomaly in the ree patterns of different daughter sediments is not diagnostic of parent rocks abundances of co and sc distinguish between sediments derived from felsic and mafic rocks a better provenance discrimination is obtained if the ratios la sc th sc la co ba sc and ba co are used petrologic modal data show that mineral contents and chemical compositions of parent rocks are compatible with each other the chemical composition of the sands may be roughly correlated to the petrological modal data but the abundances of some minor and trace elements of sediments cannot be inferred from modal mineralogy this is expected because these elements may concentrate in accessory minerals and or may weather out into aqueous or clay mineral fractions it is also compatible with conclusions of previous studies that some of these elements do not reside in sand size fractions of siliciclastic sediments

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

distribution of ree and trace elements in size and mineral fractions of high purity quartz sands eight sample sets raw quartz sand quartz fraction 2 m clay fraction 2 20 m fraction and heavy minerals of the cretaceous quartz sand deposits of haltern and weferlingen central germany and the tertiary quartz sand of frechen western germany were studied to characterize the distribution of ree and trace elements and to get genetic information about provenance and sedimentologic history of the sediments the quartz sand samples from different localities have rather similar trace element distribution and ree patterns with enriched lree and negative eu anomalies however these relations can be modified by local changes in syn or postsedimentary geochemical conditions adsorption of ree and trace elements on humic substances under reducing conditions and postsedimentary weathering in the quartz sand of weferlingen resulted in significantly modified element abundances the concentration of trace elements is most important in the 2 m fraction and in the heavy mineral fraction where they may be enriched by a factor of up to 100 the chondrite normalized ree distribution of the 2 m fraction is quite similar to those in the north american shale nas with average eu sm ratios of 0 21 and layb cn of 6 1 low trace element abundances in the 2 and 2 20 m fractions were attributed to quartz dilution and quantified among the common minerals in the heavy mineral fractions especially zircon and the fe 1bti oxides rutile ilmenite magnetite influence the trace element distribution investigations concerning the provenance of the quartz sands illustrate that the host sediments have a rather homogeneous geochemical signature due to their sedimentological history taking into account th ta variations the quartz sands of weferlingen and haltern can be distinguished from the frechen quartz sand additionally discriminations based on element ratios within the quartz fraction th sc ba sc ba co cs sc or li sc seem to be promising

comparison between computed and experimentally generated impulse waves large water waves caused by massive slide impacts are a potential hazard along waterways coastal areas and alpine regions experimental research has been conducted at the swiss laboratory of hydraulics to assess the risk from landslide generated impulse waves analogously the centro elettrotecnico sperimentale italiano performed numerical simulations of initial landslide and consequent impulse wave propagation using two mathematical models based on the conservative shallow water equations this paper presents the experimental test results and numerical predictions of impulse waves in a flume for a range of stillwater depths landslide volumes and impact velocities at laboratory scale the comparison between the measured and predicted wave free surface profiles generally produced corresponding wave heights although the initial wave peak is too steep and arrives too early excluding spurious random effects the relative differences between measured and numerically computed maximum wave heights ranged wi

case study numerical simulations of debris flow below stoze slovenia in november 2000 a landslide debris flow with a volume of 1 2 106 m3 slid down from sto e mountain in nw slovenia it partly or totally destroyed 23 buildings in the village of log pod mangartom a

promotion of chemical weathering by higher plants field observations on hawaiian basalts abstract an electron microprobe and petrographic microscope were used to study the biota rock interface beneath higher plant communities and lichens as well as unvegetated surfaces on hawaiian basalt flows ranging from a few years to several thousand years in age and currently receiving moderate to extremely high annual rainfall we find dramatic order of magnitude minimum acceleration of weathering rates beneath vascular plants on the youngest flows relative to adjacent non or primitively vegetated controls notably rocks colonized by the common fruticose lichen stereocaulon uulcani bulk dissolution of plagioclase accounts for most of the weathering observed beneath higher plants on these young basalts analysis of older flows under mature forests reveals that chemical weathering beneath vascular plant communities continues unabated for thousands of years after initial colonization moreover such weathering is not limited to exterior basalt surfaces but is commonly found adjacent to joints and vesicles within the rock where it is often associated with fine sub 2 mm diameter plant roots plagioclase dissolution was also observed on lichen encrusted and unvegetated flows a few hundred to thousands of years in age but it was typically much less advanced than beneath higher plants and rarely extended more than several millimeters from exterior rock surfaces chemical denudation rates on older flows with higher plants are at minimum ten times greater than those with only lichens or microbiota in the environments studied if s uulcani and associated microflora resemble the terrestrial precursors to vascular plant communities then the results of studies such as this have implications for the history of atmospheric co 2 and the earth s climate

paleomagnetism of paleogene rocks of the central east kamchatka and komanorsky islands tectonic implications abstract paleomagnetic investigation of paleocene eocene to miocene rocks has been carried out at five localities in the eastern kamchatka and komandorsky islands after thermal and af cleanings consistent paleomagnetic directions were isolated for a number of formations data from the kronotsky peninsula and medny island passed both the fold and reversal tests and thus can be considered as reliable other results are of lower quality all the results were derived from sedimentary rocks and thus the corresponding paleolatitudes may be biased due to inclination errors a limited collection of basalts yielded inclination values systematically lower than those in sediments this anomaly was tentatively explained by shape anisotropy the correctness of paleolatitude estimations was thus left unproved several models of the northern pacific tectonic evolution were suggested and analyzed but the authors failed to find a model that was fully compatible with paleomagnetic kinematic and geological data

numerical modeling of anhui debris flow a mathematical model is fonnulated to simulate dam break transient debris flows in which the debris and water mixture is assumed to be isotropic and continuous in terms of its viscoelastoplasticity a three dimensional 3d rheologic model for bingham body is used to describe the relationship between the stress tensor and the rate of strain only the defonnation caused by the deviatoric stress tensor is taken into account under the prior considerations the governing equations for two dimensional 2d depth averaged transient debris flows are obtained by integrating the equation of continuity and equations of motion over depth for 3d flows to deal with the transient and high speed features of dam break debris flows the derived governing equations are discretized and solved using the method of characteristics the model is applied to simulate the dam break debris flow of april 30 1986 for the jinshan debris reservoir in anhui china the debris and water mixtures reach as far as 900 m downstream from the initial tailings dam site with a depth of 1 7 m near the tailings dam and 1 0 m at 900 m downstream these model results are in good agreement with the available observations

analysis of debris wave development with one dimensional shallow water equations the objective of this contribution is to analyze the formation of debris waves in natural channels numerical simulations are carried out with a 1d code based on shallow water equations and on the weighted averaged flux method the numerical code represents the incised channel geometry with a power law relation between local width and flow depth and accounts for all source terms in the momentum equation the debris mixture is treated as a homogeneous fluid over a fixed bottom whose rheological behavior alternatively follows herschel bulkley bingham or generalized viscoplastic models the code is first validated by applying it to dam break tests on mudflows down a laboratory chute and verifying its efficiency in the simulation of rapid transients then following the analytical method developed by trowbridge the stability of a uniform flow for a generalized viscoplastic fluid is examined showing that debris flows become unstable for froude numbers well below 1 applications of the code to real debris

rare earth elements in the sedimentary cycle a pilot study of the first leg the effects of source rock composition and climate on the natural abundances of rare elements ree in the first leg of the sedimentary cycle are evaluated using a study with holocene fluvia sands the medium grained sand fraction of samples collected from first order streams exclusively draining granitic plutons in montana semi arid georgia humid and south carolina humid are analyzed it is found that the ree distribution patterns but not the total absolute abundances of the daughter sands are very similar despite compositional differences between parent plutons averages of the three areas are determined to have a la lu ratio of about 103 showing a depletion of heavy ree with respect to an average granite la lu 79 or the composition of north american shales la lu 55 however the eu sm ratio in sands from these areas is about 0 22 which is very close to this ratio in north american shales 0 21 although the overall ree distribution of these sands is not similar to that of the north american shales in any way it is concluded that the major rock type but neither its minor subdivisions nor the climate controls the ree distribution patterns in first cycle daughter sands although the total and the parent rock normalized abundances of ree in sands from humid areas are much lower than those in sands from arid areas

arrested charnockite formation at kottavattam southern india at kottavattam southern kerala india late proterozoic homogeneous leptynitic garnet biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation charnockitization post dates the polyphase deformation regional high grade metamorphism and anatexis and evidently occurred at a late stage of the pan african tectonothermal history geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar p lith t conditions 650 700 degrees c 5 6kbar in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases x co2 0 7 0 6 x h2o 0 2 0 3 x n2 0 1 logf o2 l7 5 mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow outward migrating transition zones adjacent to the gneiss followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone compared to the host gneiss the charnockite shows higher concentrations of k na sr ba and zn and lower concentrations of mg fe ti v y zr and the hree with a complementary pattern in the narrow transition zones of biotite breakdown the p lith t x h2o data and chemical zonation patterns indicate charnockitization through subsolidus dehydration reaction in an open system subsequent residence of the carbonic fluids in the charnockite resulted in low grade alteration causing modification of the syn charnockitic elemental distribution patterns and the properties of entrapped fluids we favour an internally controlled process of arrested charnockitization in which during near isothermal uplift the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from fluid absent in the gneiss to fluid present in the fracture zones and to the development of an initial fluid pressure gradient triggering the dehydration reaction