chemical and boron isotopic compositions of tourmaline from the paleoproterozoic houxianyu borate deposit ne china implications for the origin of borate deposit abstract the houxianyu borate deposit in northeastern china is one of the largest boron sources of china hosted mainly in the paleoproterozoic meta volcanic and sedimentary rocks known as the liaohe group that are characterized by high boron concentrations the borate ore body has intimate spatial relationship with the mg rich carbonates silicates of the group with fine grained gneisses meta felsic volcanic rocks as main country rocks the presence of abundant tourmalinites and tourmaline rich quartz veins in the borate orebody provides an opportunity to study the origin of boron the nature of ore forming fluids and possible mineralization mechanism we report the chemical and boron isotopic compositions of tourmalines from the tourmaline rich rocks in the borate deposit and from the tourmaline bearing fine grained gneisses tourmalines from the fine grained gneisses are chemically homogeneous showing relatively high fe and na and low mg with 11b values in a narrow range from 1 22 to 2 63 tourmalines from the tourmaline rich rocks however commonly show compositional zoning with an irregular detrital core and a euhedral overgrowth and have significantly higher mg ree and more pronounced positive eu anomalies v 229 1852 ppm and sr 208 1191 ppm than those from the fine grained gneisses they show varied b isotope values ranging from 4 51 to 12 43 which plot intermediate between those of the terrigenous sediments and arc rocks with low boron isotope values as represented by the 11b 1 22 to 2 63 of the fine grained gneisses of this study and those of marine carbonates and evaporates with high boron isotope values in addition the rim of the zoned tourmaline shows notably higher mg ti v sn and pb and ree particularly lrees but lower fe co cr ni zn mn and lower 11b values than the core these data suggest that 1 the sources of boron of the borate ore body are mainly the paleoproterozoic meta volcanic and sedimentary rocks and 2 the ore forming fluids should be the high temperature metamorphic fluids related to the amphibolite facies metamorphism of the paleoproterozoic foldbelt which leach boron from the boron rich meta volcanic and sedimentary rocks of the liaohe group and the boron rich metamorphic fluids subsequently interacted with the marine mg rich carbonates and evaporates forming borate deposit the tourmaline overgrowth in the rim and the tourmaline rich rocks

palaeoproterozoic meta rhyolite and meta dacite of the liaohe group jiao liao ji belt north china craton petrogenesis and implications for tectonic setting abstract whole rock major and trace element geochemistry along with zircon u pb ages and lu hf isotope data are reported for palaeoproterozoic meta rhyolites and meta dacites of the liaohe group in the northern segment of the jiao liao ji belt north china craton these data are used to constrain the petrogenesis of the rocks and the palaeoproterozoic tectonic evolution of the jiao liao ji belt zircons from these rocks are euhedral subhedral display oscillatory growth zoning and have high th u ratios 0 26 1 21 implying a magmatic origin la icp ms zircon u pb age data indicate that the silicic metavolcanic rocks formed during the palaeoproterozoic 2184 2127 ma the zircons yield ehf t values of 9 7 to 8 9 and tdm2 model ages of 2205 3313 ma geochemically the silicic metavolcanic rocks are metaluminous to weakly peraluminous and belong to the calc alkaline i type series the rocks are characterized by enrichment in large ion lithophile elements and depletion in high field strength elements e g nb ta p and ti and have affinities with igneous rocks that form in an active continental margin setting the geochemical and isotopic data suggest that the rocks were derived mainly from partial melting of meso neoarchaean juvenile lower crust with a possible contribution from older materials the present results combined with the regional geology further demonstrate that an oceanic plate was subducted northward beneath the longgang block during the palaeoproterozoic

tectonics of the paleoproterozoic jiao liao ji orogenic belt in the liaodong peninsula north china craton a review abstract a global collisional orogenic event that formed the columbia supercontinent occurred during 2100 1800 ma in the eastern north china craton ncc the paleoproterozoic jiao liao ji orogenic belt jljob composed of metamorphosed volcanic sedimentary rocks and intrusions may have preserved records of the collisional event tectonics of the jljob thus becomes the key to the understanding of the tectonic evolution of the ncc and may provide important information on assembly of the columbia supercontinent two classical models i e the rift closure model and arc continent collision model have been widely cited for the tectonic evolution of the jljob the former is based on occurrence of a type granites and bimodal volcanics within the orogenic belt and comparable archean blocks to the south and north of it while the latter is supported by occurrence of calc alkaline volcanics i type granites paired metamorphic belts and detrital zircon age constraints integration of literature results and our data we suggest that the jljob was formed by closure of a back arc basin at an active continental margin tectonic evolution of the jljob is subdivided into four stages i e pre orogenic stage at 2200 2060 ma transitional stage at 2060 1940 ma orogenic stage at 1940 1860 ma and post orogenic stage after 1860 ma

is the paleoproterozoic jiao liao ji belt north china craton a rift as a typical example of the paleoproterozoic crust in the eastern block of the north china craton the paleoproterozoic jiao liao ji belt consists principally of the liaohe group and its equivalents liaoji granites and mafic intrusions previous studies indicate that the evolution of the jiao liao ji belt has been mainly attributed to the opening and closing of an intracontinental rift along the eastern continental margin of the north china craton here we synthesize the paleoproterozoic magmatism sedimentation metamorphism and metallogeny against the rift model and propose a process of arc continent collision between the northern longgang and the southern nangrim blocks this conclusion is consistent with the observations including that a the 2 0 to 2 2 ga magmatism shows a typical subalkaline series rather than a bimodal distribution since the mafic rocks mostly have arc affinities and the acidic intermediate rocks belong to the calc alkaline series b the main source of the 1 9 to 2 0 ga sedimentary rocks is the paleoproterozoic arc materials indicating a fore arc or back arc basin setting c a couple of big borate deposits occur in the boron rich volcanic rocks that were formed in convergent continental margins d the north and south liaohe groups show different rock associations and metamorphic histories p t paths and e the nangrim and longgang blocks vary in lithological units geochronology and metamorphic features thus an arc continent collision tectonic scenario for the paleoproterozoic jiao liao ji belt is involved a a southward subduction in the period 2 0 2 2 ga b sedimentation during the period 1 9 2 0 ga c arc continent collision at ca 1 9 ga and d post collisional extension at 1 82 1 87 ga marking the end of the paleoproterozoic tectonothermal event

petrochemistry and sr pb and nd isotopic geochemistry of the paleoproterozoic kuandian complex the eastern liaoning province china abstract a geochemical and isotopic study has been carried out on the paleoproterozoic kuandian complex and some associated granitoids in the eastern liaoning province china the kuandian amphibolite and granite give an imprecise 1 9 0 4 ga all errors are 2 rb sr errorchron with 87 sr 86 sr o 0 711 0 006 a 2 11 0 06 ga pb pb isochron with a first stage growth 8 43 and a 2 31 0 10 ga smnd isochron with 143 nd 144 nd o 0 50970 0 00009 or nd t 1 1 nd depleted mantle model dates tdm of amphibolite are 2 75 to 2 46 ga those of granite are 2 53 to 2 36 ga zircons from the kuandian granite give a minimum 2 14 0 05 ga upper intercept date the kuandian amphibolite is chemically similar to the high mg member of columbia river basalts and the kuandian granite is an anorogenic granite they are genetically related and formed 2 4 to 2 3 ga ago fractional crystallization of olivine pyroxene and plagioclase from precursor magma of the kuandian amphibolite can produce magma with composition of the kuandian granite the paleoproterozoic mantle source in the eastern liaoning province is less depleted than that inferred from the average mantle evolution curve in contrast with the archean mantle in the sino korean craton which is more depleted than the average this study also reveals that the lishan granite of the eastern liaoning province is older than 3 ga and that some granites and dykes previously mapped as proterozoic are of mesozoic age

boron isotope fractionation between tourmaline and fluid an experimental re investigation the fractionation of boron isotopes between synthetic dravitic tourmaline and fluid was determined by hydrothermal experiments between 400 and 700 c at 200 mpa and at 500 c 500 mpa tourmaline was crystallized from an oxide mix in presence of water that contained boron in excess in one series of experiments b fluid b tour was 9 after the run in another series it was 0 1 all experiments produced tourmaline as the sole boron bearing solid along with traces of quartz and talc powder xrd and rietveld refinements revealed no significant amounts of tetrahedrally coordinated boron in tourmaline 11b always preferentially fractionated into the fluid for experiments where b fluid b tour was 9 a consistent temperature dependent boron isotope fractionation curve resulted approximated by 11b tour fluid 4 20 1 000 t k 3 52 r2 0 77 and valid from 400 to 700 c no pressure dependence was observed the fractionation 2 7 0 5 at 400 c and 0 8 0 5 at 700 c is much lower than that previously presented by palmer et al 1992 experiments where b fluid b tour was 0 1 showed a significant larger apparent fractionation of up to 4 7 in one of these runs the isotopic composition of handpicked tourmaline crystals of different size varied by 1 3 this is interpreted as resulting from fractional crystallization of boron isotopes during tourmaline growth due to the small boron reservoir of the fluid relative to tourmaline thus indicating larger fractionation than observed at equilibrium the effect is eliminated or minimized in experiments with very high boron excess in the fluid we therefore suggest that values given by the above relation represent the true equilibrium fractionations

trace and rare earth element geochemistry in tourmaline and cassiterite from the yunlong tin deposit yunnan china implication for migmatitic hydrothermal fluid evolution and ore genesis abstract yunlong tin deposit is a medial sized hydrothermal deposit in western yunnan province of china this deposit is unusual because the tin mineralization occurs exclusively within the migmatite bodies the genesis of the ore deposit has been hotly debated and various models have been proposed including granite related magmatic hydrothermal and migmatitic hydrothermal origins this paper reports a systematic trace and rare earth elements ree geochemical study in tourmaline and cassiterite from the orebodies and associated migmatites from the yunlong tin deposit tourmaline and cassiterite from this deposit show light ree lree enriched patterns with variable eu and ce anomalies consistent with hydrothermal fluids being derived from local high grade metamorphism and migmatization the data suggest that tourmaline and cassiterite were likely precipitated from migmatitic hydrothermal fluids and indicate that the yunlong tin deposit was probably formed during migmatitic hydrothermal process the high concentrations of transition metals e g sc ti v cr mn and zn in tourmalines are also consistent with this model the high concentrations of sn sr and especially sc v and cr in tourmalines can be used to discriminate tourmaline from barren deposits relative to those associated with economic tin mineralization

the palaeoproterozoic boron deposits in eastern liaoning china a metamorphosed evaporite abstract we have carried out a field study of the palaeoproterozoic borate deposits of eastern liaoning province china the borates are hosted within mg silicate and mg carbonate rocks and have previously been interpreted as either skarns or metamorphosed volcanogenic exhalative deposits the deposits contain textures that are compatible with a sedimentary origin of the borates and there is a lack of the associated mineralization that is characteristic of magnesian skarns in addition preliminary boron isotope data indicate that the boron within the borates was not derived from the footwall rocks that have been proposed as the source of the skarn fluids a purely exhalative model can be dismissed on the basis of geochemical arguments and comparison with modern environments which show that borates are too soluble to precipitate directly from hydrothermal fluids the geology and field relationships show a number of similarities with recent non marine evaporite settings and young continental rifts in arid environments we conclude therefore that the liaoning deposits are metamorphosed evaporites in which the boron was originally present as primary evaporite borate minerals this model places the liaoning borates in the same category as the majority of other economic borate deposits in the world

recent earth oblateness variations unraveling climate and postglacial rebound effects earth9s dynamic oblateness j2 has been decreasing due to postglacial rebound pgr however j2 began to increase in 1997 indicating a pronounced global scale mass redistribution within earth9s system we have determined that the observed increases in j2 are caused primarily by a recent surge in subpolar glacial melting and by mass shifts in the southern pacific and indian oceans when these effects are removed the residual trend in j2 2 9 x 10 11 year 1 becomes consistent with previous estimates of pgr from satellite and eclipse data the climatic significance of these rapid shifts in glacial and oceanic mass however remains to be investigated

deformation history of the paleoproterozoic liaohe assemblage in the eastern block of the north china craton the paleoproterozoic liaohe assemblage and associated liaoji granitoids represent the youngest basement in the eastern block of the north china craton various structural elements and metamorphic reaction relations indicate that the liaohe assemblage has experienced three distinct deformational events d1 to d3 and four episodes of metamorphism m1 to m4 the earliest greenschist facies event m1 is recognized in undeformed or weakly deformed domains wrapped by the s1 schistosity suggesting that m1 occurred before d1 the d1 deformation produced small mostly meter scale isoclinal and recumbent folds f1 an associated penetrative axial planar schistosity s1 a mineral stretching lineation l1 and regional scale ductile shear zones concurrent with d1 was m2 metamorphism which occurred before d2 and produced low to medium pressure amphibolite facies assemblages regionally divergent motion senses reflected by the asymmetric f1 folds and other sense of shear indicators together with the radial distribution of the l1 lineation surrounding the liaoji granitoids imply that d1 represents an extensional event the d2 deformation produced open to tight f2 folds of varying scales s2 axial crenulation cleavages and ene ne striking thrust faults involving broadly nw se compression following d2 was m3 metamorphism that led to the formation of sillimanite and cordierite in low pressure type rocks and kyanite in medium pressure rocks the last deformational event d3 formed nw wnw trending folds f3 axial planar kink bands spaced cleavages s3 and strike slip and thrust faults which deflect the earlier d1 and d2 structures d3 occurred at a shallow crustal level and was associated with or followed by a greenschist facies retrograde metamorphic event m4 the liaohe assemblage and associated liaoji granitoids are considered to have formed in a paleoproterozoic rift the late spreading of which led to the occurrence of the early extensional deformation d1 and the m1 and m2 metamorphism and the final closing of which was associated with the d2 and d3 phases of deformation and m3 and m4 metamorphism

impact of terrain attributes parent material and soil types on gully erosion abstract gully erosion is a worldwide matter of concern because of the irreversible losses of fertile land which often have severe environmental economic and social consequences while most of the studies on the gullying process have investigated the involved mechanisms either overland flow incision seepage or piping erosion only few have been conducted on the controlling factors of gully wall retreat an important if not the dominant land degradation process and sediment source in river systems in a representative 4 4 km 2 degraded area of the drakensberg foothills south africa the main objective of this study was to evaluate the relationship between the rate of gully bank retreat gbr and parent material soil types and selected terrain attributes elevation specific drainage area mean slope gradient slope length factor stream power index compound topographic index and slope curvatures the survey of gully bank retreat was performed during an entire hydrological year from september 2007 to september 2008 using a network of pins n 440 from 110 pits both the gully contours and pin coordinates were determined using a gps with a 0 5 m horizontal accuracy n 20 120 the information on the parent material and the soil types was obtained from field observations complemented by laboratory analysis while terrain attributes were extracted from a 20 m dem generated from 5 m interval contour lines the average gbr value for the 6512 m of gully banks found in the area was 0 049 0 0013 m y 1 which considering bank height and soil bulk density corresponded to an erosion rate of 2 30 ton ha 1 y 1 there was no significant difference in gbr between sandstone and dolerite and between acrisols and luvisols despite a weak one to one correlation with the selected terrain attributes r gbr was the highest at hillslope inflexion points profile and plan slope curvatures close to zero in the vicinity of the head cuts and for drainage areas up to 500 m 2 as both situations experience a high removal rate of the soil material produced from the gully bank collapse and protecting gullies from laterally retreating these results could be used to digitally map the more active gully banks for the improved implementation of preventive measures of gully growth if high resolution dems are available there remained however a certain amount of unexplained variability in the data that further research studies on the mechanisms and associated factors of control of gbr could help to address

hydrology of a forested hillslope during storm events abstract subsurface flow from a 0 47 ha hillslope subcatchment at the upper most reach of the west fork 38 ha of walker branch watershed was monitored throughout 1988 stormflow in the first order stream draining the west fork responded simultaneously with the initiation of subsurface flow through 0 to 2 5 m depth from the hillslope subsurface flow from the upper hillslope was only 1 3 of total precipitation for 1988 however individual storms yielded as much as 12 5 of precipitation as subsurface flow the west fork had 10 4 of precipitation observed as storm flow with an additional 29 as baseflow individual storms exhibited up to 71 of precipitation as storm flow in the west fork illustrating the significant increase in percent rain converted to subsurface flow in lower landscape positions as compared to upper hillslopes peak subsurface flow preceded peak streamflow and occurred primarily through the 1 0 2 5 m depth bt2 horizons due to perched water tables preferential flow from hillslopes through macro and mesopores was concluded to be the predominant stormflow mechanism the contributions of the various size pores was reasoned to be dependent upon the position within the soil profile and the stage of the hydrograph preferential flow occurred at extreme soil water conditions with the response due to perched water tables under wet conditions and believed to be due to hydrophobic conditions under extremely dry conditions intermediate soil water conditions resulted in infiltration into soil matrix pores precluding subsurface stormflow

origin and significance of tourmaline rich rocks in the broken hill district australia tourmaline rich rocks are widespread minor lithologies within the early proterozoic willyama supergroup in the broken hill district australia tourmaline concentrations occur in strata bound and local stratiform tourmalinites clastic metasedimentary rocks quartz gahnite lode rocks stratiform pb zn ag sulfide ores garnet quartzites strata bound scheelite deposits quartz tourmaline nodules discordant quartz veins and granitic pegmatites most of the tourmaline rich rocks are within the broken hill group that hosts the main pb zn ag ores at the globe mine along the northeast end of the main lodes tourmalinites are closely associated with pb zn ag mineralization and in places are interbedded with mn rich garnet quartzites galena and other ore minerals occur locally in the cores of recrystallized tourmaline grains in these tourmalinites indicating that tourmaline and sulfides were present together prior to deformation and high grade metamorphism electron microprobe analyses of tourmalines intergrown with fe sulfides at the globe mine show mg rich compositions relative to tourmalines in sulfide free assemblages from the same area suggesting early premetamorphic introduction of boron and mg enrichment of tourmaline by sulfide silicate reactions during metamorphism combined field and geochemical data indicate that the district tourmalinites represent normal clastic sediments that were metasomatically altered by boron rich hydrothermal fluids at or below the sediment water interface whole rock chemical analyses of 33 tourmaline rich rocks show linear trends of data for major and trace elements that closely resemble the trends observed for unmineralized elastic metasedimentary rocks of the district average fe al mg al na al and ti al molar ratios of the tourmaline rich rocks and clastic metasediments are very similar the average k al molar ratio of the tourmaline rich rocks is significantly lower than that of the clastic metasediments reflecting the loss of k during tourmalinite formation chondrite normalized patterns of rare earth elements ree in the quartz rich tourmalinites are generally similar to those of the clastic metasediments except for minor depletions of light ree local positive and negative ce anomalies suggest tourmalinite formation in the presence of seawater or a seawater derived pore fluid the geochemical data imply relative immobility of al ti cr and heavy ree during hydrothermal alteration and later metamorphism boron isotope analyses of 52 tourmaline separates show a total range of delta 11 b values from 26 8 to 17 0 per mil fine grained euhedral nonpoikilitic tourmalines from tourmalinites in the andalusite muscovite zone in the northern part of the district e g black prince mine have delta 11 b values from 21 to 17 per mil whereas coarse granoblastic and poikilo blastic tourmalines from the sillimanite and two pyroxene granulite zones in the southern part of the district e g globe mine have delta 11 b values of 24 to 19 per mil tourmalines in strongly retrogressed tourmalinites have delta 11 b values from about 27 to 20 per mil the observed variations in delta 11 b are consistent with prograde and retrograde metamorphic fractionation of boron isotopes in which the fluid phase is preferentially enriched in the heavier isotope 11 b premetamorphic hydrothermal fluids that deposited the black prince tourmalinites had delta 11 b values of 8 to 5 per mil at 200 degrees to 300 degrees c suggesting a boron source from nonmarine evaporite borates tourmalinites in the broken hill district apparently formed by the same submarine hydrothermal processes as the main pb zn ag lodes and the siliceous ferromanganese protoliths of the garnet quartzites in our model the hydrothermal system s acquired abundant boron by leaching evaporitic borates within the thackaringa group the stratigraphic sequence that underlies the broken hill group and most of the tourmaline concentrations we suggest that evaporites of the thackaringa group provided a source of readily extractable boron for formation of the tourmalinites and also the source of the fluoride sulfur and perhaps the carbonate in the main lodes such evaporites may have been critical for increased metal chloride complexing and transport necessary for deposition of the high grade pb zn ag ores the broken hill deposit may have formed contemporaneously with the mount isa and mcarthur river pb zn ag deposits in similar evaporite bearing sequences during widespread early proterozoic continental rifting

exploration of driving mechanisms of equilibrium boron isotope fractionation in tourmaline group minerals and fluid a density functional theory study abstract the equilibrium boron isotope fractionations 3 4 11b tur fluid between tourmaline mineral groups and fluids at 0 5 gpa 600 1000 k are investigated using density functional theory calculations the first solvent shell controls boron isotope fractionation in solution where the values of both h3bo3 and b oh 4 decrease with increasing numbers of hydrogen bonds in supercritical fluids the weakening of hydrogen bonds and the diversity in configurations of hydrated boron species both contribute to variations in the vibrational frequencies the 1000ln tur fluid value increases with increasing mg fe mg ratios in the dravite schorl solid solution series this effect together with the crystallization sequence predicted from the gibbs free energies of tourmaline formation accounts well for the association of boron isotope and chemical zonation observed in zoned tourmaline grains the dependence of boron isotope fractionation on the b o bond length in tourmaline group minerals reflects the changes in relevant molar volumes caused by differences in the mass and charge of the atoms occupying the x y and z sites of tourmalines this study suggests that the chemical composition of the tourmaline plays an important role in controlling the boron isotope composition in tourmalines crystallized from hydrothermal systems

understanding soil pipe flow and its role in ephemeral gully erosion the role of soil pipeflow in ephemeral gully erosion is not well understood experiments were conducted on continuous soil pipes to better understand the role of internal erosion of soil pipes and its relation to ephemeral gully development soil beds of 140 cm length 100 cm width and 20 cm depth had a single soil pipe of different initial sizes 2 4 6 8 and 10 mm diameter extend from a water reservoir to the outlet experiments were run on providence silt loam and smithdale loam soils under a constant head of 15 cm established for 30 min either the tunnel collapsed or the head could not be maintained soil pipes that were initially 2 and 4 mm clogged instantaneously at their mouth and did not exhibit flow whereas pipes initially 6 mm enlarged by 268 397 and 699 on average for the 6 8 and 10 mm diameters respectively critical shear stress values were found to be essentially zero and erodibility values gave erosion indexes that were extremely high the rapid internal erosion resulted in erratic flow and sediment concentrations with periods of no flow as pipes were temporarily clogged followed by surges of high flow and high sediment concentrations tensiometers within 6 cm of the soil pipes did not exhibit pressure increases typically associated with pipe clogging flow through 10 mm diameter soil pipes exhibited tunnel collapse for both soils tested tunnel collapse typically occurred within minutes of flow establishment suggesting that ephemeral gullies could be misinterpreted as being caused by convergent surface flow if observations were made after the runoff event instead of when flow is first established through soil pipes copyright 2011 john wiley sons ltd

global geodetic signatures of the antarctic ice sheet four scenarios of present day antarctic ice sheet mass change are developed from comprehensive reviews of the available glaciological and oceanographic evidence the gridded scenarios predict widely varying contributions to secular sea level change ranging from 1 1 to 0 45 mm yr and predict polar motion and time varying low degree gravitational coefficients that differ significantly from earlier estimates a reasonably linear relationship between the rate of sea level change from antarctica a and the predicted antarctic is found for the four scenarios this linearity permits a series of forward models to be constructed that incorporate the effects of ice mass changes in antarctica greenland and distributed smaller glaciers as well as postglacial rebound assuming the ice 3g deglaciation history with the goal of obtaining optimum reconciliation between observed constraints on and sea level rise numerous viable combinations of lower mantle viscosity and hydrologie sources are found that satisfy observed in the range of 1 to 2 2 5 mm yr and observed for degrees 2 3 and 4 in contrast rates of global sea level rise above 2 5 mm yr are inconsistent with available observations the successful composite models feature a pair of lower mantle viscosity solutions arising from the sensitivity of to glacial rebound the paired values are well separated at mm yr but move closer together as is increased and in fact merge around 2 2 5 mm yr revealing an intimate relation between and preferred lower mantle viscosity this general pattern is quite robust and persists for different solutions for variations in source assumptions and for different styles of lower mantle viscosity stratification tighter constraints for l 2 may allow some viscosity stratification schemes and source assumptions to be excluded in the future for a given total observed the sea level rise from antarctica a is tightly constrained and ranges from 0 to 1 mm yr corresponding to an ablating ice sheet as estimates of are raised from 1 to 2 5 mm yr however when the degree 3 zonal harmonic constraint is removed the solutions show little sensitivity to antarctic mass balance emphasizing the need for a well determined odd degree secular zonal harmonic for determining polar ice mass balance

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

empirical sediment transport function predicting seepage erosion undercutting for cohesive bank failure prediction summary seepage erosion is an important factor in hillslope instability and failure however predicting erosion by subsurface flow or seepage and incorporating its effects into stability models remains a challenge limitations exist with all existing seepage erosion sediment transport functions including neglecting the three dimensional geometry of the seepage undercut and the cohesive nature of soils the objective was to develop an empirical sediment transport function that can predict seepage erosion and undercutting with time based on three dimensional soil block experiments covering a wide range of hydraulic soil type slope and bulk density combinations the transport function was represented by an excess gradient equation r2 0 54 the critical gradient was predicted by the soil cohesion based on laboratory experiments using a three dimensional gaussian function the geometric relationships between the maximum distance and lateral and vertical dimensions of the undercut were then derived the proposed empirical relationships reasonably predicted the observed volume per unit area of undercut erosion rate and time at which a given amount of undercut developed the flow gradient can be used with the derived sediment transport function the first ever relationship proposed for predicting the dimensions and the geometry of the undercut to predict the impact of seepage erosion undercutting on hillslope stability users only need to input the seepage layer s cohesion bulk density and the hydraulic gradient over time in the near bank ground water system

observing the pole tide with satellite altimetry 1 almost 9 years of sea surface height observations from the topex poseidon t p satellite altimetry mission are used to observe the geocentric pole tide deformations of the sea surface if the oceans are assumed to have an equilibrium response then satellite altimeters effectively observe the equipotential surface that is associated with the solid earth and ocean pole tide deformations the long wavelength component of the geocentric pole tide deformations at the chandler wobble period is observed from t p altimetry to be consistent with the theoretical self consistent equilibrium response of the ocean pole tide the geocentric pole tide explains 70 of the variance in the degree 2 order 1 spherical harmonic component of the residual sea surface heights that are observed by t p after removing the seasonal inverse barometer and lunisolar tidal effects if the long wavelength component of the ocean pole tide is assumed to have an equilibrium response at the chandler wobble period then satellite altimetry proves to be another geodetic technique that can be used to estimate the love number k2 at that period

geochemistry and boron isotopic compositions of tourmaline from the paleoproterozoic amphibolites ne china implications for the origin of borate deposit abstract the paleoproterozoic metasediments and metavolcanics in the jiao liao ji belt northeastern china host a large number of borate deposits to trace the source of boron in these borate deposits we carried out in situ chemical and boron isotopic studies on tourmalines of amphibolites from the lieryu formation of the liaohe group in the jiao liao ji belt the petrology and the chemical compositions of tourmalines of amphibolites show that these tourmalines formed by influx of b rich fluids during different stages of metamorphism the 11b values of tourmaline continue to decline during the successive metamorphism tourmalines that formed during the prograde metamorphism show higher 11b values 9 52 10 18 than those formed during the peak metamorphism of amphibolite facies 7 22 9 43 subsequently tourmalines with lower 11b values formed during the retrograde metamorphism of greenschist facies which have slightly different boron isotopic compositions in cores 4 18 5 50 and rims 2 66 4 66 mainly due to the temperature effect the boron isotopic variations of tourmalines of amphibolites match well with our modeling study of boron isotope the results suggest that tourmalines may be precipitated from fluids released from dehydration of marine sediments with relative high 11b values 9 during prograde metamorphism in the same way the borate deposits formed from the liberated b rich fluids that interacted with the mg rich carbonates and or silicates

the liaohe group an insight into the paleoproterozoic tectonic evolution of the jiao liao ji belt north china craton abstract the jiao liao ji belt represents one of the largest exposed regions of paleoproterozoic rocks along the eastern margin of the north china craton paleoproterozoic basement material in this area is dominated by deformed and metamorphosed volcano sedimentary successions with minor amounts of granitic and mafic intrusions this study presents the results of a systematic zircon u pb geochronological whole rock geochemical and sm nd isotopic analysis of the volcano sedimentary successions within the liaohe group of the jiao liao ji belt these data provide insights into the multiple paleoproterozoic tectonothermal events that have affected the belt as well as the petrogenesis of the paleoproterozoic meta volcanics and metasedimentary rocks on the liaodong peninsula accurate u pb age and trace element determinations of zircons from the meta volcanics in this region using laser ablation inductively coupled plasma mass spectrometry indicate that these units formed at ca 2 2 ga and were metamorphosed at ca 1 9 ga respectively these data indicate that the paleoproterozoic geochronological framework of this region is dominated by 2 2 2 0 ga magmatic 1 98 1 90 ga sedimentary ca 1 90 ga metamorphic and 1 87 1 82 ga post tectonic magmatic events the meta volcanics can be split into basalt basaltic andesite andesite dacite and rhyolite units that define a continuous calc alkaline dominated magmatic sequence that is similar to the sequences commonly found within phanerozoic magmatic arcs the meta basalts are enriched in the light rare earth elements cr co and ni and are depleted in the heavy rare earth elements and the high field strength elements e g nb ta and ti indicating that they formed from magmas generated by the partial melting of lithospheric mantle material that was previously metasomatized by subduction zone derived fluids melts the large geochemical and isotopic variations within the metamorphosed andesite dacite and rhyolite units all provide evidence of magma mixing between felsic melts generated by the partial melting of paleoarchean neoarchean basement material and the mafic melts that may also formed the meta basalts within the liaohe group or evolve via fractional crystallization prior to mixing the geochemistry of the metasedimentary rocks indicate that the pre metamorphism sedimentary units ranged from being compositionally mature to being immature and poorly sorted and were weakly to moderately weathered these sediments were derived primarily from metamorphosed felsic volcanics within the liaohe group as well as the paleoproterozoic liaoji granites they also contain archean continental crustal material that is derived mainly from ancient intermediate mafic basement units the combined geochronological geochemical and geological data indicate that a paleoproterozoic arc continent collision model can well explain the nature and formation of the jiao liao ji belt

soil pipe collapses in a loess pasture of goodwin creek watershed mississippi role of soil properties and past land use little is known about the association of soil pipe collapse features with soil properties or land use history three loess covered catchments in northern mississippi usa were characterized to investigate these relationships soil pipe collapses were characterized for their size type feature and spatial location along with soil properties across the three catchments although mapped as the same soil one of the catchments did not contain pipe collapse features while the other two had 29 4 and 15 4 pipe collapses per hectare these loess soils contained fragipan layers that are suspected of perching water thereby initiating the piping processes pipe collapses associated with subsurface flow paths were not always consistent with surface topography the surface layer tended to be non erodible while layers below even the upper fragipan layers were susceptible to erosion by pipeflow soil properties of the lowest fragipan layer were highly variable but tended to prevent further downward erosion of soil pipes and thus formed a lower boundary for gullies middle to lower landscape positions in one of the piped catchments contained anthropic soils that were highly erodible these anthropic soils were previously gullies that were filled in in the 1950s when forested areas assumed to have been established when land was previously converted from crop to forest land were converted to pasture three decades after this land use change from forest to pasture pipe collapses became evident in contrast the adjacent catchment that does not exhibit pipe collapse features experienced severe sheet and rill erosion prior to the 1930s while in cotton production the surface horizons above the lower fragipan layer were completely removed during this period thus the top soil layer that tends to form a bridge above soil pipes in the more erodible subsoil layers was removed this study showed that knowledge of soil characteristics or topography alone do not explain the distribution of soil pipe collapses as past land use can play a definitive role copyright 2015 john wiley sons ltd

ephemeral gully erosion by preferential flow through a discontinuous soil pipe abstract subsurface flow through soil pipes can contribute to ephemeral gully erosion but these soil pipes are cut off when tillage fills in the gully the objective was to determine the effect of flow through discontinuous soil pipes on ephemeral gully erosion experiments were conducted on 150 cm long by 100 cm wide soil beds with an artificial soil pipe at the upper end that extended 50 cm into the soil immediately above a water restricting horizon the combination of rainfall with pipe flow produced extensive 63 kg soil losses by mass wasting the mode of mass wasting appeared to be sudden cataclysmic pop out failures total soil loss by sheet erosion with rainfall and pipe flow combined 13 6 kg was four times higher than by rainfall alone 3 4 kg under rainfall with pipe flow soil loss by mass wasting was nearly 20 times higher than sheet erosion from rainfall alone soil conservation practices that treat surface runoff process alone may be ineffective if subsurface flow is contributing

sediment detachment and transport processes associated with internal erosion of soil pipes subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping the development of perched water tables in duplex soils fosters lateral flow that can result in seepage at the surface of hillslopes and or formation of soil pipes by internal erosion of lateral preferential flow paths continued internal erosion of soil pipes can lead to gullies dam and levee failures however the processes involved in particle and aggregate detachment from soil pipe walls and transport processes within soil pipes have not been well studied or documented this paper reviews the limited research on sediment detachment and transport in macropores and soil pipes and applies the knowledge learned from the much more extensive studies conducted on streams and industrial pipes to hydrogeologic conditions of soil pipes knowledge gaps are identified and recommendations are made for future research on sediment detachment and transport in soil pipes

la icp ms u pb zircon ages of the liaohe group in the eastern block of the north china craton constraints on the evolution of the jiao liao ji belt abstract as a major lithostratigraphic unit of the palaeoproterozoic jiao liao ji belt in the eastern block of the north china craton the liaohe group consists of an assemblage that is transitional from a lower arkose and volcanic rich sequence langzishan li eryu and gaojiayu formations through a middle carbonate rich sequence dashiqiao formation to an upper argillaceous sequence gaixian formation tectonically associated with the liaohe group are large volumes of granitoid rocks named the liaoji granite whose emplacement age has been dated at about 2 1 2 2 ga regionally the liaohe group and the associated liaoji granite extend along a nee trending belt that is flanked by 2 45 2 55 ga basement gneisses u pb zircon data and cathodoluminescence cl imaging are used to constrain the maximum depositional and metamorphic ages of the liaohe group which are critical in understanding the tectonic setting and history of the jiao liao ji belt cathodoluminescence images reveal that most detrital zircon grains from the liaohe group are characterized by concentric oscillatory zoning with comparatively low luminescence and high th u ratios suggesting magmatic origin but minor zircon grains have structureless overgrowth or recrystallization rims that are characterized by low th u ratio indicating metamorphic origin results of this study show that the detrital zircon grains of the langzishan formation the lowest sequence of the liaohe group have concordant u pb ages ranging from 2 05 to 2 24 ga suggesting that the liaohe group was deposited at some time after 2 05 ga although most overgrowth or recrystallization rims are too narrow to be analyzed some rims yield concordant or upper intercept ages around 1 93 ga interpreted as the peak metamorphic age of the liaohe group detrital zircon grains from the dashiqiao formation in the middle sequence of the liaohe group have concordant u pb ages ranging from 2 25 to 2 53 ga some of which are similar to those of the basement gneisses in the area this study indicates that the liaohe group was deposited after the emplacement of the liaoji granite and the latter may be a major component of the provenance for the langzishan formation in contrast the protoliths of the middle sequence of the liaohe group were most probably derived from the basement gneisses these new zircon ages for the liaohe group and recent data for the liaoji granite combined with lithological structural and metamorphic considerations support a rifting model for the evolution of the jiao liao ji belt

consideration of ocean tides in an ogcm and impacts on subseasonal to decadal polar motion excitation ocean induced changes of earth s rotation are attributed either to tides or to variations of the general circulation analogously numerical world ocean models can still be divided into ocean general circulation and tidal models although a neglect of nonlinear interactions in favor of a linear superimposition of both components of motion is questionable by means of a simultaneous simulation of the ocean s circulation and tides we estimate the importance of two oceanic effects with respect to excitation of polar motion nonlinearities between circulation and long period tides and the circulation induced potential due to loading and self attraction of a baroclinic ocean comparing the linear superimposition of separate model simulations with the simultaneous calculation of circulation and tides it turns out that these second order effects contribute about 8 to ocean induced changes in earth s orientation

shrimp u pb zircon geochronology of the liaoji granitoids constraints on the evolution of the paleoproterozoic jiao liao ji belt in the eastern block of the north china craton abstract the paleoproterozoic jiao liao ji belt lies at the eastern margin of the eastern block of the north china craton and is composed mainly of the liaohe group and the liaoji granitoids the liaoji granitoids are divisible into pre tectonic magnetite and hornblende biotite monzogranitic gneisses and post tectonic or anorogenic porphyritic monzogranites and alkaline syenites shrimp u pb zircon geochronology combined with cathodoluminescence cl imaging has enabled for resolution of magmatic and metamorphic events that can be directed towards understanding the history of the paleoproterozoic jiao liao ji belt shrimp u pb zircon analyses reveal that the pre tectonic magnetite monzogranitic gneisses were emplaced in the period 2176 2166 ma and metamorphosed at 1914 ma and the pre tectonic hornblende biotite monzogranitic gneisses were emplaced at 2150 2143 ma these data demonstrate that the pre tectonic monzogranitic gneisses of the liaoji granitoids were not younger than the deposition of the liaohe group as previously considered since the latter contains a large amount of 2100 2000 ma detrital zircons in contrast the pre tectonic monzogranitic gneisses of the liaoji granitoids or similar aged granitoids may have been an important component of the provenance for the liaohe group shrimp u pb zircon analyses also reveal that the post tectonic porphyritic monzogranites and granites in the jiao liao ji belt were emplaced at 1875 10 and 1856 31 ma respectively simultaneously with the emplacement of the alkaline syenites that was dated at 1857 20 and 1843 23 ma similar post tecotnic or anorogenic granites are not only limited to the jiao liao ji belt but are also found in the north and south korea suggesting that the 1 85 ga post tectonic or anorogenic granitic magmatic event may have occurred in both the korean peninsula and the eastern block of the north china craton the shrimp zircon ages of this study combined with lithological structural metamorphic and geochemical data is consistent with a rift closure model which suggests that the archean complexes on the northern and southern sides of the jiao liao ji belt were originally situated on a single continental block that underwent paleoproterozoic rifting associated with the formation of the liaohe group and liaoji granitoids and closed upon itself at 1 9 ga

anthropogenic impact on global geodynamics due to reservoir water impoundment water impounded in artificial reservoirs since 1950 is by far the largest anthropogenic hydrological change in terms of the mass involved this mass redistribution contributes to geodynamic changes in the earth s rotation and gravitational field that have been closely monitored by modern space geodetic techniques we compute the effect of 88 major reservoirs on length of day polar motion and low degree gravitational coefficients on an individual basis much smaller than geophysical signals in scale and magnitude these anthropogenic effects prove to be non negligible cumulatively especially when considering the fact that our results represent underestimates of the reality in particular reservoir water has contributed a significant fraction in the total observed polar drift over the last 40 years

chemical and stable isotopic compositions of proterozoic metamorphosed evaporites and associated tourmalines from the houxianyu borate deposit eastern liaoning china an integrated major element trace and rare earth element and stable isotope b si o and s study has been carried out on the houxianyu borate deposit eastern liaoning china the present day mineralogy of the deposit is closely similar to that of magnesian skarn deposits and the borates are underlain by granite however the geochemical and isotopic evidence does not favour a skarn type origin in particular the boron isotopic compositions of the borate minerals and associated tourmalines preclude their origin from fluids derived from the granite rather the data are compatible with the borate deposit being a metamorphosed evaporite the mineralogy and chemistry of the deposit are most compatible with a non marineorigin although the high 34s and 11b values suggest that there may have been some marine components to the evaporitic brines overall the premetamorphic origin of the houxianyu borate deposit is similar to that of the tertiary non marine evaporite borate deposits of western turkey there are also similarities with other proterozoic early rifting environments e g the upper proterozoic damaran orogen of south africa that have implications for the structural evolution and mineral potential of the region

boron isotopic composition of marine and nonmarine evaporite borates abstract here we present the results of the boron isotopic analysis of borates from some well known marine and nonmarine evaporite deposits combining new analyses with analyses from the literature yields a mean 11 b value for nine marine evaporite borate analyses of 25 4 permil 11 b 10 b 4 15 0 02 and a mean for twenty five nonmarine evaporite borates of 7 10 permil 11 b 10 b 4 02 0 04 previous studies have shown that the boron isotopic composition of seawater 11 b 40 permil 11 b 10 b 4 20 is about four percent heavier than the boron isotopic composition of most crustal rocks and minerals we suggest that our results for marine and nonmarine evaporite borates reflect this difference thus it should be possible to use boron isotopic composition as a tracer for boron of marine evaporitic origin applications include borate bearing evaporite deposits and perhaps borate and or borosilicate bearing metamorphic rocks

variations in the earth s oblateness during the past 28 years 1 analysis of satellite laser ranging slr data indicates that the earth s dynamic oblateness j2 has undergone significant variations during the past 28 years the dominant signatures in the observed variations in j2 are 1 a secular decrease with a rate of approximately 2 75 10 11 yr 1 2 seasonal annual variations with a mean amplitude of 2 9 10 10 3 significant interannual variations with timescales of 4 6 years and 4 a variation with period of 21 years and an amplitude of 1 4 10 10 with minimum in december 1988 two large interannual variations are related to the strong el nino southern oscillation events during the periods of 1986 1991 and 1996 2002 and it appears that another interannual cycle may have started in late 2002 the superposition of the decadal variation on the interannual signal makes the j2 fluctuation appear to be anomalously large during the 1996 2002 period contemporary models of the mass redistributions in the atmosphere ocean and surface water can explain a major part of the 4 to 6 year fluctuations however the cause of the decadal variation remains unknown

boron isotope geochemistry of metasedimentary rocks and tourmalines in a subduction zone metamorphic suite abstract in order to understand the behavior of boron b and its isotope fractionation during subduction zone metamorphism b contents and isotopic compositions together with major element compositions were determined for metasedimentary rocks and tourmalines from the sambagawa metamorphic belt central shikoku japan no systematic changes in whole rock b content and isotope composition of the metasediments were observed among the different metamorphic grades indicating the lack of a bulk fluid rock b isotope fractionation as a result of devolatilization both modal abundance and grain size of tourmaline increase with increasing metamorphic grade in contrast b contents in muscovite and chlorite decrease with increasing metamorphic grade these observations combined with mass balance calculations of b suggest the formation of tourmaline during progressive metamorphism from metamorphic fluids containing b mainly derived from muscovite and subordinately from chlorite without allowing significant net removal of b from the metasedimentary rocks tourmalines in the higher grade metasedimentary rocks have zonal structure of b isotope and major element composition with decreasing 11 b and increasing mg mg fe from the inner rim core to the outer rim the change of mg mg fe in the tourmalines with increasing grade is paralleled by similar variation in chlorite these observations suggest that the growing tourmalines record the progressive evolution of the b isotopic composition of the metamorphic fluid in the outermost rims preserving the isotope signature of peak metamorphic p t fluid conditions based on the above observations the 11 b of the tourmaline is thought to have been nearly identical to that of the metamorphic fluid resulting in the apparent b isotopic fractionation factor between metamorphic fluid and whole rock 11 b 10 b fluid 11 b 10 b whole rock which decreases from 1 007 0 003 to 1 001 0 003 from chlorite to biotite zone metamorphism such results together with the formation of tourmaline from and sequestering of b in metamorphic fluids may lead to less b isotopic fractionation as a result of subduction zone devolatilization than noted in suites containing less tourmaline this therefore makes it possible to transport b isotopic signatures which ultimately reflect earth s surface materials to the deep mantle perhaps resulting in mantle b isotope anomalies near convergent margins

paleoproterozoic structural evolution of the southern segment of the jiao liao ji belt north china craton abstract the paleoproterozoic jiao liao ji belt separates the eastern block of the north china craton into two small sub blocks the northern longgang and the southern rangrim blocks however it still remains unknown or controversial about the subduction polarity collisional deformation and kinematics between two sub blocks the southern segment of the belt consists of the paleoproterozoic fenzishan and jingshan groups and paleoproterozoic high pressure mafic granulites and serpentinites blocks which are located in the jiaodong complex all of which are separated from the jiaodong complex of neoarchean ttg gneisses by stz1 ductile shear zones structural analysis in this study indicates that most of the rocks in all the units of the southern segment of the jiao liao ji belt underwent three distinct episodes of folding d1 to d3 and two stage of ductile thrust shearing stz1 coeval to d1 and d2 stz2 between d2 and d3 the d1 deformation formed penetrative axial planar foliations s1 bedding parallel ductile shear zone mineral stretching lineations l1 and rarely preserved small isoclinal d1 folds in the jingshan and fenzishan groups in the jingshan group however penetrative deformational transposition resulted in stacking of sedimentary compositional layers which are separated by bedding parallel ductile shear zones stz1 at a period of about 1956 ma to 1914 ma the kinematic indicators of stz1 in the jingshan group with resultant prograde peak metamorphism up to granulite facies grade and the fenzishan group with peak metamorphism up to amphibolite facies grade indicate nw directed compression d2 resulted in crustal thickening with retrograded medium pressure granulite facies grade at about 1914 1893 ma the d2 deformation produced nw verging asymmetric and recumbent folds interpreted to have resulted from basement involved thicken skin structures the jiaodong complex was also involved into the development of wnw verging asymmetric tight folds associated with d2 in the jingshan and the fenzishan groups ongoing collision led to the development of transpressional ductile shearing stz2 forming the transpressional taipingzhuang dextral ductile shear zone between the jingshan group and the southern archean complex and the transpressional tading xiadian sinistral ductile shear zone between the jingshan group and the northern archean complex all three lithotectonic units were superposed during the late d3 deformation with amphibolite facies metamorphism the d3 deformation developed wnw trending open to tight upright folds at about 1893 1875 ma the structural pattern resulting from superimposition of d2 and d3 is a composite synform in the fenzishan and jingshan groups the structural events of d1 and stz1 and d2 and stz2 deformation were possibly responsible for fast syn collisional exhumation of the high pressure mafic granulites the structural patterns and deformational history of the fenzishan and jingshan groups suggest a southeastward directed oblique subduction beneath the northwestern margin of the rangrim block and that the final scissor shaped closure of the rift led to collision between the two blocks to form the coherent basement of the eastern block of the north china craton

tourmaline at diagenetic to low grade metamorphic conditions its petrologic applicability article i nfo tourmaline developed under low temperature conditions b 300 c typically has distinctive morphological and chemical characteristics that reveal significant information about the environments in which they crys tallize under diagenetic conditions tourmaline can develop as overgrowths on detrital tourmaline cores or as new authigenic crystals tourmaline as monopolar crystal overgrowths is found in sandstones shales conglomerates dolostones and limestones nucleating exclusively at the positive end of the c axis cpole on the detrital grain a feature related to the mineral s polar nature these overgrowths tend to have compo sitions dominated by x site vacant tourmaline species e g foitite and can be linked to growth in aqueous environments low in na with other chemical characteristics related to the host rocks as temperature in creases tourmaline overgrowths develop at both the cpole andc pole but continue to exhibit a signif icant degree of morphological and chemical asymmetries these differences at either pole diminish as a function of increasing temperature such that it can be used as an intramineral geothermometer authigenic tourmalines without detrital tourmaline nuclei are found in many sedimentary or weakly meta morphosed metasedimentary rocks as well as fluid dominated geothermal systems here tourmalines are commonly foititic but have mg fe contents influenced by the host rock composition low temperature tour malines developed in hypersaline environments e g salt domes have distinct chemical characteristics high na fe 3 and w o and follow a trend between oxy dravite and povondraite o p trend this composi tional trend can be used as a guide to indicate tourmaline development within low temperature hypersaline environments and appears to be diagnostic of an oxidizing environment with high na in the fluid and high sa linity with the resulting reduction of the activity of h2o the o p trend is retained in some meta evaporite de posits that are relatively high grade and is found in tourmaline from some types of economically important metal deposits although tourmalines in low temperature environments are largely overlooked they have po tential to be a useful indicator of the chemical and thermal environments in a regime largely absent of such indicators

mechanisms of ephemeral gully erosion caused by constant flow through a continuous soil pipe ephemeral gully erosion is considered to be driven by convergent surface flow while the role of subsurface flow is often overlooked this study sought to characterize and quantify the soil erosion mechanisms associated with ephemeral gully erosion by pipe flow a soil pipe 1 cm o d was formed in a 10 cm soil bed immediately above a 5 cm water restricting layer flow into the soil pipe was established at steady state rates of 190 and 284 l h 1 experiments were performed for pipe flow alone and with rainfall despite a constant flow rate into soil pipes pipe flow was highly unstable due to internal mass wasting clogging soil pipes until pressure increases forced the debris plug out of the pipe short 10 20 seconds periods of negligible flow were followed by surges in flow with high sediment concentrations that included a high proportion of aggregates increases in soil water pressures associated with these debris flows were observed but were likely not representative of the pressures inside the soil pipes due to hydraulic non equilibrium between the soil pipe and soil matrix hydraulic non equilibrium resulted in hydraulic gradients in the opposite direction of flow through the soil pipe during early stages of pipe flow pipe flow rates and sediment concentrations during debris flow periods were likely more extreme than observed due to integration over the three minute sample collection interval the slot erosion test set was extended to conditions of constant flow rate through an internal soil pipe that was observed at the front face of a soil bed the modified set provided estimates of shear stress between 2 2 to 5 3 kg m 1 s 2 however the technique did not prove effective for estimation of the soil erodibility coefficient published in 2009 by john wiley sons ltd

the gravity recovery and climate experiment mission overview and early results 1 the grace mission is designed to track changes in the earth s gravity field for a period of five years launched in march 2002 the two grace satellites have collected nearly two years of data a span of data available during the commissioning phase was used to obtain initial gravity models the gravity models developed with this data are more than an order of magnitude better at the long and mid wavelengths than previous models the error estimates indicate a 2 cm accuracy uniformly over the land and ocean regions a consequence of the highly accurate global and homogenous nature of the grace data these early results are a strong affirmation of the grace mission concept

secular boron isotope variations in the continental crust an ion microprobe study abstract tourmalines of various chemical compositions hosted in magmatic rocks with ages ranging from 3 8 ga to the present were analysed for 11 b by ion microprobe a large range of 11 b values from 2 to 30 1 5 was observed the 11 b values are correlated with the chemical composition of the tourmalines the li rich tourmalines being enriched in 11 b compared to fe and or mg rich tourmalines this may reflect mixing in the continental crust between a marine reservoir characterized by high li contents and 11 b values and a continental reservoir characterized by low li contents and 11 b values no relationship between the age and the 11 b values is observed for the fe or for the mg rich tourmalines in contrast the 11 b values of the li rich tourmalines show a tendency to regularly decrease with increasing age this pattern is consistent with a simple model of constant boron isotopic fractionation between seawater and the continental crust during the progressive extraction of the continents a variation in the mean 11 b value of the continental crust from 20 ga ago to 7 at present is predicted by the model the largest variation occurred during the first 2 5 ga

assessment of grass root effects on soil piping in sandy soils using the pinhole test abstract soil piping is an important land degradation process that occurs in a wide range of environments despite an increasing number of studies on this type of subsurface erosion the impact of vegetation on piping erosion is still unclear it can be hypothesized that vegetation and in particular plant roots may reduce piping susceptibility of soils because roots of vegetation also control concentrated flow erosion rates or shallow mass movements therefore this paper aims to assess the impact of grass roots on piping erosion susceptibility of a sandy soil the pinhole test was used as it provides quantitative data on pipeflow discharge sediment concentration and sediment discharge tests were conducted at different hydraulic heads i e 50 mm 180 mm 380 mm and 1020 mm results showed that the hydraulic head was positively correlated with pipeflow discharge sediment concentration and sediment discharge while the presence of grass roots expressed as root density was negatively correlated with these pipeflow characteristics smaller sediment concentrations and sediment discharges were observed in root permeated samples compared to root free samples when root density exceeds 0 5 kg m 3 piping erosion rates decreased by 50 compared to root free soil samples moreover if grass roots are present the positive correlation between hydraulic head and both sediment discharge and sediment concentration is less pronounced demonstrating that grass roots become more effective in reducing piping erosion rates at larger hydraulic heads overall this study demonstrates that grass roots are quite efficient in reducing piping erosion rates in sandy soils even at high hydraulic head 1 m as such grass roots may therefore be used to efficiently control piping erosion rates in topsoils

boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites boron isotope ratios 11b 10b have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings the coverage of these localities is global 5 continents and includes the giant ore bodies at kidd creek and sullivan canada broken hill australia and ducktown usa overall the tourmalines display a wide range in 11b values from 22 8 to 18 3 possible controls over the boron isotopic composition of the tourmalines include 1 composition of the boron source 2 regional metamorphism 3 water rock ratios 4 seawater entrainment 5 temperature of formation and 6 secular variations in seawater 11b the most significant control appears to be the composition of the boron source particularly the nature of footwall lithologies variations in water rock ratios and seawater entrainment are of secondary importance the boron isotope values seem especially sensitive to the presence of evaporites marine and non marine and carbonates in source rocks to the massive sulfide deposits and tourmalinites

timing of metamorphism in the paleoproterozoic jiao liao ji belt new shrimp u pb zircon dating of granulites gneisses and marbles of the jiaobei massif in the north china craton abstract the paleoproterozoic jiao liao ji belt lies in the eastern block of the north china craton with its southern segment extending across the bohai sea into the jiaobei massif high pressure pelitic and mafic granulites have been recently recognized in the paleoproterozoic jingshan group jiaobei massif new shrimp u th pb geochronology combined with cathodoluminescence cl imaging of zircon has been applied to the determination of the timing of the metamorphism of the high temperature and high pressure granulites and associated gneisses and marbles metamorphic zircons in these high pressure granulites gneisses and marbles occur as either single grains or overgrowth or recrystallization rims surrounding and truncating oscillatory zoned magmatic zircon cores metamorphic zircons are all characterized by nebulous zoning or being structureless with high luminescence and relatively low th u values metamorphic zircons from two high pressure mafic granulites yielded 207pb 206pb ages of 1956 41 ma and 1884 24 ma one metamorphic zircon from a garnet sillimanite gneiss also gave an apparent 207pb 206pb age of 1939 15 ma these results are consistent with interval of ages of c 1 93 1 90 ga already obtained by previous studies for the north and south liaohe groups and the laoling group in the northern segment of the jiao liao ji belt metamorphic zircons from a high pressure pelitic granulite and two pelitic gneisses yielded weighted mean 207pb 206pb ages of 1837 8 ma 1821 8 ma and 1836 8 ma respectively two diopside olivine phlogopite marbles yielded weighted mean 207pb 206pb ages of 1817 9 ma and 1790 6 ma these paleoproterozoic metamorphic ages are largely in accordance with metamorphic ages of c 1 85 ga produced from the ji an group in the northern segment of the jiao liao ji belt and c 1 86 1 80 ga obtained for the high pressure pelitic granulites from the jingshan group in the southern segment as this metamorphic event was coeval with the emplacement of a type granites in the jiao liao ji belt and its adjacent areas it is interpreted as having resulted from a post orogenic or anorogenic extensional event

ore controlling factors and metallogenesis of borate deposits in eastern liaoning and southern jilin from the viewpoint of regional ore forming theory the authors analyzed boron bearing rock sequence magnesian host rocks regional metamorphism migmatitization and tectonism and the result shows that the boron bearing rock sequence and the magnesian rocks constituted the basis for the formation of the borate deposits whereas regional metamorphism migmatitization and tectonism made up the necessary conditions the ore forming mechanism of the borate deposits in eastern liaoning and southern jilin lies in the enrichment of boron in primary volcanic sedimentary rocks and the metamorphic hydrothermal reaction between the boron bearing fluid and the magnesian rocks during regional metamorphism migmatitization and tectonism

boron isotope systematics of tourmaline formation in the sullivan pb zn ag deposit british columbia canada abstract we report here the results of 54 boron isotope analyses of tourmaline associated with the giant sullivan pb zn ag deposit in southeastern british columbia canada the 11 b values range from 11 1 to 2 9 which is almost as great as the range found worldwide in tourmalines from 33 massive sulfide deposits and tourmalinites in dominantly clastic metasedimentary terranes the major control on the overall 11 b values of the sullivan tourmalinites is the boron source potential controls over the large range of the data also include 1 differences in formation temperatures of the tourmalinites 2 different stages of tourmaline formation 3 variations in the proportions of dissolved boron incorporated into the tourmaline rayleigh fractionation 4 seawater entrainment and 5 post depositional metamorphism the boron isotope data at sullivan are consistent with boron derivation from leaching of footwall clastic sediments however the great abundance of tourmaline in the sullivan deposit suggests that the local clastic sediments were not the sole source of boron and we argue that non marine evaporites buried deep below the orebody are the most viable source of this additional boron it is likely that some of the variation in tourmaline 11 b values reflect mixing of boron from these two sources comparison of the potential effects of these controls with geologic and other geochemical evidence suggests that major causes for the wide range of 11 b values measured at sullivan are seawater entrainment and rayleigh fractionation although in places post depositional alteration and thermal metamorphism were important in determining 11 b values of some of the recrystallized tourmalinites

deceleration in the earth s oblateness 1 for over three decades satellite laser ranging slr has recorded the global nature of the long wavelength mass change within the earth system analysis of the most recent time series of 30 day slr based estimates of earth s dynamical oblateness characterized by the gravitational degree 2 zonal spherical harmonic j2 indicates that the long term variation of j2 appears to be more quadratic than linear in nature the superposition of a quadratic and an 18 6 year variation leads to the unknown decadal variation reported by cheng and tapley 2004 although the primary trend is expected to be linear due to global isostatic adjustment there is an evident deceleration j 2 18 1 10 13 yr2 in the rate of the decrease in j2 during the last few decades likely due to changes in the rate of the global mass redistribution from melting of the glaciers and ice sheets as well as mass changes in the atmosphere and ocean

source composition and distribution of the fluid in the kurile mantle wedge constraints from across arc variations of b nb and b isotopes b and nb concentrations and b isotope composition were determined for lavas covering the entire length of the kurile arc b nb and 11b of these lavas show clear across arc variations in which both are highest at the trench side and continuously decrease as the slab depth increases b nb in the volcanic front lavas 8 25 is significantly higher than those of morb and oib indicating that the mantle wedge is extensively metasomatized by b rich fluid derived from the subducting slab the frontal 11b values are also out of the range of morb and oib and systematic difference exists between northern kurile nk 5 4 0 5 and central and southern kurile csk 4 3 0 3 however these two parameters approach or coincide with mantle values at the most back arc side the 11b and 87sr 86sr linearly correlate with nb b suggesting control by simple mixing of two isotopically homogeneous components that is slab derived fluid and mantle wedge the estimated 11b and 87sr 86sr of the fluid are 7 0 0 6 and 0 70326 0 00005 for nk and 6 3 0 3 and 0 7033 for csk respectively these fluid compositions are consistent with a source constituted by 95 altered oceanic crust and 5 oceanic sediment with the slight difference between nk and csk resulting from the different lithologies of subducting sediments the mantle wedge beneath the kurile arc has b sr and nd isotope compositions identical with morb but shows significantly higher b nb the above trends bear a close resemblance to those observed in the izu arc strongly suggesting their universality in the arc system the across arc decline of b nb observed both in kurile and izu implies that the fluid flux from the slab continuously decreases as the slab depth increases however this relates only to a final stage of slab dehydration since most of the volatile components are lost at the fore arc region in contrast to b k is uniformly enriched across the arc this requires control by a k bearing mineral phase either in the slab phengite or the mantle wedge phlogopite although such a mineral is responsible for only a small part of the whole fluid transport

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

grace era secular trends in earth rotation parameters a global scale impact of the global warming process 1 recent trends in the two primary anomalies in the rotational state of the planet are analyzed in detail namely those associated with the speed and direction of polar wander and with the non tidal acceleration of the rate of axial rotation via the measurement of the changing oblateness of the earth s shape it is demonstrated that a significant change in the secular trends in both of these independent parameters became evident subsequent to approximately 1992 it is suggested that both parameters might have come to be substantially influenced by mass loss from both the great polar ice sheets and from the very large number of small ice sheets and glaciers that are also being influenced by the global warming phenomenon the modern values for the secular drifts in those parameters that we estimate are appropriate to the period during which measurements have been made by the satellites of the gravity recovery and climate experiment grace thesechangesinsecularratesmightgreatly assist in understanding why the grace inferred values of the time derivatives of the degree two and order one stokes coefficients differ so significantly from those associated with late quaternary ice age influence citation roy k and w r peltier 2011 grace era secular trends in earth rotation parameters a global scale impact of the global warming process geophys res lett 38 l10306 doi 10 1029 2011gl047282

rare earth element cycling in the pore waters of the bering sea slope iodp exp 323 abstract we studied the diagenetic behavior of rare earth elements rees in a highly productive passive margin setting of the bering sea slope site u1345 was drilled during the integrated ocean drilling program expedition 323 at a water depth of 1008 m currently in the center of an oxygen minimum zone pore water concentrations of fourteen rees were determined down to 140 meters below the seafloor mbsf the ree concentrations were higher in the pore water than the deep seawater indicating that there was significant liberation from the sediments during diagenesis there was a major peak at 10 mbsf that was more pronounced for the heavy ree hree this peak occurred below the sulfate methane transition zone 6 3 mbsf and coincided with high concentrations of dissolved iron and manganese at 2 mbsf there was a minor peak in ree and mn contents below 40 mbsf the ree concentration profiles remained constant the ce anomaly was insignificant and relatively constant paas normalized ce ce 1 1 0 2 throughout the depth profile showing that the ce depleted in seawater was restored in the pore water hree enrichment was observed over the entire 140 m except for the upper 1 m where a middle ree mree bulge was apparent ree release in shallow depths 2 4 mbsf is attributed to the release of light rees lrees and mrees during the organoclastic reduction of mn oxides in anoxic sediments the high hree concentrations observed at 10 mbsf can be attributed to the reduction of fe and mn minerals tied to anaerobic oxidation of methane or less significantly to ferromagnesian silicate mineral weathering the upward diffusion flux across the sediment water interface was between 3 for tm and 290 for ce pmol m 2 y 1

petrogenesis and tectonic implications of two types of liaoji granitoid in the jiao liao ji belt north china craton abstract two types of granitoid monzogranite and granodiorite are recognized within the paleoproterozoic liaoji granitoids of the jiao liao ji belt jljb in the hupiyu and simenzi areas north china craton we conducted zircon u pb geochronological geochemical and hf isotopic analyses of these granitoids zircon u pb dating indicates an emplacement age of 2180 14 ma for the monzogranite hupiyu granitoids and ages of 2130 24 and 2173 11 ma for the fangjiaweizi and dadingzi granodiorites at simenzi respectively the hupiyu monzogranite samples are enriched in zr ga and y and depleted in nb and ti low nb y ratios and high zr saturation temperatures 849 884 c indicate that the hupiyu monzogranites have an affinity with a2 subtype granitoids the fangjiaweizi and dadingzi granodiorites have high sr y and low k2o na2o ratios indicating an affinity with adakitic rocks geochemical compositions and wide variation in ehf t values suggest that the monzogranites and granodiorites were derived from thinned and thickened lower crust respectively and that magmatism was accompanied by input of mantle material this study represents the first identification of pre tectonic adakitic rocks in the jljb the assemblage of pre tectonic a2 type granitoids and adakitic rocks indicates a continental back arc basin as the initial tectonic setting of the jljb these new data combined with results of previous studies support an arc continent collision model for the jljb

recent changes in the earth s oblateness driven by greenland and antarctic ice mass loss 1 we use temporal gravity variations from grace to investigate changes in a 34 year time series of earth s oblateness j2 observed by satellite laser ranging slr we use 2002 2010 grace data to compute the effects of greenland and antarctic ice mass variations on j2 2 0 and 1 7 10 11 year respectively their combined effect on the j2 trend during the grace mission is 3 7 10 11 year which agrees well with the gia corrected slr j2 trend over the same time period the results suggest that at least since 2002 ice loss from greenland and antarctica has been the dominant contributor to the current gia corrected j2 trend which apparently began sometime in the 1990s

geochronology and geochemistry of the paleoproterozoic meta basalts from the jiao liao ji belt north china craton implications for petrogenesis and tectonic setting abstract geochronology geochemical and isotopic studies were carried out on the paleoproterozoic meta basalts and related rocks from the jiao liao ji belt north china craton to understand the mantle source characteristics and the geodynamic setting u pb isotopic dating using the la icpms method on zircons from the metamorphosed volcanic rocks reveals that they formed at ca 2204 2158 ma and were metamorphosed at ca 1895 1919 ma respectively the meta basalts are of calc alkali affinity and have arc like geochemical compositions they are enriched in lrees la yb n 3 5 5 1 and liles sr ba rb depleted in hfses nb ta zr hf ti and show variable high nd t values 2 4 to 4 5 the basaltic rocks experienced significant fractional crystallization and minor crustal contamination during magma evolution modeling suggests that the parent magma of the meta basalts was derived from 20 partial melting of spinel garnet lherzolites that were previously metasomatized by subduction zone fluids melts in the late archean petrological geochronological and geochemical data suggest that the paleoproterozoic volcanic rocks formed in an active continental margin setting and were subsequently deformed and metamorphosed to amphibolite facies due to the arc continental collision at ca 1 9 ga rather than in a continental rifting setting as previously thought by most workers

redistributing earth s mass since the end of the last glaciation postglacial rebound of earth9s crust has resulted in a net transfer of mass from the equatorial regions to high latitudes this small mass transfer has been monitored for 25 years but a report by cox and chao suggests that since 1998 the mass transfer has changed direction in their perspective cazenave and nerem discuss possible mechanisms that may have caused this change

determination of long term changes in the earth s gravity field from satellite laser ranging observations temporal changes in the earth s gravity field have been determined by analyzing satellite laser ranging slr observations of eight geodetic satellites using data spanning an interval of over 20 years the satellites used in the analysis include starlette lageos 1 and 2 ajisai etalon 1 and 2 stella and be c geophysical parameters related to both secular and long period variations in the earth s gravity field including the geopotential zonal rates and and the 18 6 year tide parameter were estimated the estimated values for these parameters are centimeters and s18 6 20 0 1 0 2 centimeters the amplitude and phase for the 18 6 year tide are in general agreement with the effects predicted by the earth s mantle anelasticity the solution accuracy was evaluated by considering the effects of errors in various non estimated dynamical model parameters and by varying the data span and data sets used in the solution estimates for from individual lageos 1 and starlette slr data sets are in good agreement the lumped sum values for and are very different for lageos 1 and starlette the zonal rate determination is limited to degree 6 with the current slr data sets analysis of the sensitivity of the solution for the zonal rates to the satellite tracking data span suggests that the temporal extension of the current slr data sets will enhance the solution of zonal rates beyond degree 6

laboratory soil piping and internal erosion experiments evaluation of a soil piping model for low compacted soils mechanistic models have been proposed for soil piping and internal erosion on well compacted levees and dams but limited research has evaluated these models in less compacted more erodible soils typical of hillslopes and streambanks this study utilized a soil box 50 cm long 50 cm wide and 20 cm tall to conduct constant head soil pipe and internal erosion experiments for two soils clay loam from dry creek and sandy loam from cow creek streambanks packed at uniform bulk densities initial gravimetric moisture contents prior to packing were 10 12 and 14 for dry creek soil and 8 12 and 14 for cow creek soil a 1 cm diameter rod was placed horizontally along the length of the soil bed during packing and carefully removed after packing to create a continuous soil pipe a constant head was maintained at the inflow end flow rates and sediment concentrations were measured from the pipe outlet replicate submerged jet erosion tests jets were conducted to derive erodibility parameters for repacked samples at the same moisture contents flow rates from the box experiments were used to calibrate the mechanistic model the influence of the initial moisture content was apparent with some pipes 8 moisture content expanding so fast that limited data was collected the mechanistic model was able to estimate equivalent flow rates to those observed in the experiments but had difficulty matching observed sediment concentrations when the pipes rapidly expanded the jets predicted similar erodibility coefficients compared to the mechanistic model for the more erodible cases but not for the less erodible cases 14 moisture content improved models are needed that better define the changing soil pipe cross section during supply and transport limited internal erosion especially for piping through lower compacted more erodible soils as opposed to more well compacted soils resulting from constructing levees and dams copyright 2013 john wiley sons ltd

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

chemical and boron isotopic variations of tourmaline in the hnilec granite related hydrothermal system slovakia constraints on magmatic and metamorphic fluid evolution multi stage formation of tourmaline occurs in the hnilec granite related hydrothermal tin mineralisation system from the western carpathians slovakia the tourmalines belong to the schorl dravite series and have two major stages of formation the majority crystallized during the first stage defined as m stage forming zoned tourmaline crystals with the cores being generally more fe al and mn rich than the rims during the second stage defined as l stage tourmaline formed as small veins or irregular patches along fractures and cracks in the m stage tourmaline grains in the contact metapelites near the granite body the l stage tourmalines are more mg rich and fe al mn depleted than the m stage tourmalines in the granites the l stage tourmalines have generally similar compositions to those of the m stage tourmaline rims the boron isotopic compositions of the m stage tourmalines vary from 10 3 to 15 4 with no clear variation between the cores and the rims however some of the tourmaline grains from the contact metapelites show a slightly higher 11b in the cores than in the rims the l stage tourmalines have lower 11b value of 16 0 to 17 1 we suggest that these trends reflect a changing fluid source from a dominant magmatic hydrothermal fluid derived from the granites to a late stage metamorphic fluid derived from the regional metamorphism chlorite and biotite zone in the metapelites the significantly higher fe3 in the l stage than the m stage tourmalines reflect changing redox conditions towards a more oxidising environment this redox condition change may have important implications for the hydrothermal tin mineralisation in the area

a multi isotope approach towards constraining the origin of large scale paleoproterozoic b fe mineralization in ne china the final publication is available at elsevier via https doi org 10 1016 j precamres 2017 01 030 2017 this manuscript version is made available under the cc by nc nd 4 0 license http creativecommons org licenses by nc nd 4 0

early proterozoic tectonic styles and associated mineral deposits of the north china platform abstract the remarkable change in tectonic style from archean granite greenstone belts and high grade terrains to linear sedimentary basins marks the beginning of the early proterozoic in china the different evolutionary histories of and accumulations in the early proterozoic basins result in different archean early proterozoic boundaries two time limits 2 8 and 2 5 ga are significant for the boundary in eastern china early proterozoic basins displaying different tectonic styles contain different mineral deposits the liaodong peninsula type of early proterozoic basin contains the most abundant mineral resources and deposit types including stratabound b fe and pb zn deposits in the eugeosynclinal facies of the liaojitite suite and pyrite p and magnesite deposits in miogeosynclinal facies rocks the magnesite deposits in liaodong peninsula are the largest in the world and were formed in a unique geological setting

simultaneous estimation of global present day water transport and glacial isostatic adjustment global water transport between oceans and continents during the transition from glacial to interglacial times has been enormous the viscoelastic solid earth has been responding to this unloading of large ice masses with a rise of the land masses in a process termed glacial isostatic adjustment in addition significant changes in the land ocean water distribution occur at present as both present day changes in the ice water thickness and glacial isostatic adjustment affect space geodetic measurements it is difficult to untangle the relative contributions of these two processes here we combine gravity measurements and geodetic data of surface movement with a data assimilating model of ocean bottom pressure to simultaneously estimate present day water transport and glacial isostatic adjustment we determine their separate contributions to movements in the geocentre which occur in response to changes in the earth s mass distribution with uncertainties below 0 1 mm yr 1 according to our estimates mass losses between 2002 and 2008 in greenland alaska yukon and west antarctica are 104 23 101 23 and 64 32 gt yr 1 respectively our estimates of glacial isostatic adjustment indicate a large geocentre velocity of 0 72 0 06 mm yr 1 in the polar direction we conclude that a significant revision of the present estimates of glacial isostatic adjustments and land ocean water exchange is required present day changes in the thickness of ice sheets and glacial isostatic adjustment both affect space geodetic measurements a combination of gravity measurements and geodetic data of surface movement with a data assimilating model of ocean bottom pressure allows the simultaneous estimation of present day water transport and glacial isostatic adjustment

glaciers dominate eustatic sea level rise in the 21st century ice loss to the sea currently accounts for virtually all of the sea level rise that is not attributable to ocean warming and about 60 of the ice loss is from glaciers and ice caps rather than from the two ice sheets the contribution of these smaller glaciers has accelerated over the past decade in part due to marked thinning and retreat of marine terminating glaciers associated with a dynamic instability that is generally not considered in mass balance and climate modeling this acceleration of glacier melt may cause 0 1 to 0 25 meter of additional sea level rise by 2100

boron isotopic composition of subduction zone metamorphic rocks abstract many arc lavas contain material derived from subducted oceanic crust and sediments but it remains unresolved whether this distinctive geochemical signature is transferred from the subducting slab by aqueous fluids silicate melts or both boron isotopic measurements have the potential to distinguish between slab transfer mechanisms because 11 b fractionates preferentially into aqueous fluids whereas little fractionation may occur during partial melting previous studies have shown that 11 b values of island arc lavas 6 to 7 overlap the range of 11 b values for altered oceanic crust 5 to 25 and pelagic sediments and turbidites 7 to 11 secondary ion mass spectrometry sims analyses of minerals in subduction zone metamorphic rocks yield 11 b 11 to 3 suggesting that slab dehydration reactions significantly lower the 11 b values of subducted oceanic crust and sediments in order to explain the higher 11 b values reported for arc lavas as compared to subduction zone metamorphic rocks the b bearing component derived from the metamorphosed slab must be enriched in 11 b relative to the slab favoring an aqueous fluid as the slab transfer mechanism