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

tourmalinite from northern guangxi china the extensive development of tourmalinite is a feature that distinguishes the northern guangxi polymetallic tin province of china from similar metallogenic provinces elsewhere two types of tourmalinite occur in the province the first type in the lower part of the early proterozoic sibao group is bedded stratiform or lenticular tourmalinite that shows well developed laminated gel and degelatinized structures its mineral assemblage is very simple and the grain size ranges from 2 to 8 m this tourmaline is relatively rich in mg with an fe fe mg ratio of 0 25 0 50 the second type of tourmalinite occurs as lodes distributed in the exocontact zone of late proterozoic biotite granite intrusions its mineral assemblage is relatively complex the tourmaline is present as euhedral or subhedral crystals ranging from 0 1 to 3 5 mm mostly from 0 5 to 1 mm this tourmaline commonly exhibits a radiating zoned structure with fe fe mg ratios of 0 64 0 79 it is suggested that the bedded tourmalinite formed by exhalation in an early proterozoic spreading ridge environment whereas the vein tourmalinite formed in a plate convergence setting genetically associated with emplacement of late proterozoic biotite granite as the tourmalinites themselves are related to mineralized rocks and orebodies their origin and the related boron cycle of the region reflect to some extent the formation and evolution of the associated polymetallic tin deposits of the region

detritic tourmalines with complex zonation in the cretaceous exotic flysches of the western carpathians where did they come from abstract the period of the cretaceous marked a time of convergence in the tethyan realm characterized by both collisions and local ophiolitic obduction sedimentary records from this period are full of detritic materials of unknown provenance so called exotics among these exotic rocks and minerals was tourmaline with complex zonation which began to appear in considerable amounts research conducted in albian to senonian exotics of the western carpathians has shown that there are two kinds of complex zoned grains 1 grains with a fabric consisting of several tourmaline phases which are chaotically arranged as laths and 2 grains displaying a fine intergrowth of tourmaline and quartz the first type of tourmaline shows a continuous trend of al and its substitution by fe3 at the y and z sites thus shifting from a schorl dravitic composition to a bosiite one the second type consists of a dominant presence of schorl dravitic tourmaline however with a scarce occurrence of al enriched oxy dravitic foititic and magnesio foititic compositions tourmaline with complex zonation occurs in metamorphics which include hp and uhp facies evaporitic complexes and hydrothermal deposits they also appear locally in granites and pegmatites in most of the rocks saline and boron rich fluids played a substantial role in the high pressure metamorphics there was an influx of fluids during their exhumation because the examined exotics are rich in ophiolitic material including hp to uhp rock pebbles it is substantiated to assume that the also represented the main source of the complex zoned tourmaline they may have also combined with permian lower triassic evaporites where the dismembered ophiolites are often embedded hydrothermal veins and granitoids did not represent a regionally significant and widespread source at that time

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

direct and indirect evaluation of denudation rates in central italy abstract this paper presents the main results of a series of geomorphological studies aimed to the quantitative direct and indirect evaluation of denudation processes in central italy these studies which started in some sample areas since long ago were further deepened and extended to a wider number of drainage basins representative of a variety of morphostructural conditions the complex cause effect relationships among factors influencing both the morphogenesis and the plano altimetric configurations of drainage basins resulted in a large variability in the values of the denudation index tu which ranged from 200 to 2500 t km2 year very high values tu 10 000 t km2 year were obtained for small catchments belonging to the wider basins of ombrone river and tevere river where fast morphological modifications occur due to the action of surface running waters and gravity in the drainage basins affected by the most powerful denudation processes direct measurements of denudation were performed several monitoring stations were equipped with iron stakes and disks to record the local modifications of the topographic surface with time whereas some of these stations have been working continuously since 1993 some others have been running only periodically direct measurements pertinent to periods longer than a decade indicated that mean annual values of denudation range between 1 and 2 5 cm year for slopes affected by sharp edged and or rounded edged badlands higher denudation rates 3 4 cm year were obtained for shorter observation periods still higher rates were recorded for short periods at the gully bottom or in coincidence with mass movements before bench marks were turned up or damaged denudation processes are likely to occur discontinuously they show a step like trend with time and are triggered by rainfall events distributed over a number of consecutive days though not greatly intense particularly their amount should overcome the threshold of 60 mm per 5 consecutive days below this threshold the surface runoff does not seem to reach the power necessary to induce significant modifications of the topographic surface in the study area

origin and petrogenetic implications of tourmaline rich rocks in the sierra nevada betic cordillera southeastern spain tourmaline rich rocks up to 60 tourmaline associated with low medium grade metamorphic assemblages occur in the sierra nevada area betic cordillera southeastern spain tourmaline appears in a variety of forms 1 stratiform tourmalinites 2 quartz tourmaline nodules 3 porphyroclasts in felsic orthogneisses and 4 disseminations in psammopelitic metasediments and gneisses tourmaline within these lithologic groups exhibits textural and chemical variations that reflect complex premetamorphic growth under open system conditions and subsequent changes due to alpine regional metamorphism microprobe analyses of the tourmalines reveal a wide compositional variation between schorl and dravite end members with variable contents of x site vacancies av 0 084 0 225 apfu ca av 0 095 0 269 apfu and excess of al up to 6 588 apfu compared with the theoretical value of 6 in ideal schorl and dravite the amount of ca may be significant in porphyroclasts from the gneisses fe fe mg ratios for tourmalines in tourmalinites metasediments and gneisses range from 0 34 to 0 95 0 16 to 0 92 and 0 28 to 0 97 respectively na na ca ratios are also variable mostly ranging from 0 5 to 0 9 many of the tourmalines have complex chemical and colour zoning patterns including significant fluctuations in al fe mg na ca ti and f based on petrographic and chemical data three generations of tourmaline have been established the first generation corresponds to magmatic postmagmatic tourmaline that is represented by tourmaline porphyroclasts within the orthogneisses the second generation of tourmaline formed during tourmalinization of psammopelitic rocks giving rise to tourmalinites the third generation of tourmaline is represented by cellular textures pale reaction rims and overgrowths developed during the alpine regional metamorphic overprint d 2002 elsevier science b v all rights reserved

evaluation of different machine learning models for predicting and mapping the susceptibility of gully erosion abstract gully erosion constitutes a serious problem for land degradation in a wide range of environments the main objective of this research was to compare the performance of seven state of the art machine learning models svm with four kernel types bp ann rf and brt to model the occurrence of gully erosion in the kashkan poldokhtar watershed iran in the first step a gully inventory map consisting of 65 gully polygons was prepared through field surveys three different sample data sets s1 s2 and s3 including both positive and negative cells 70 for training and 30 for validation were randomly prepared to evaluate the robustness of the models to model the gully erosion susceptibility 12 geo environmental factors were selected as predictors finally the goodness of fit and prediction skill of the models were evaluated by different criteria including efficiency percent kappa coefficient and the area under the roc curves auc in terms of accuracy the rf rbf svm brt and p svm models performed excellently both in the degree of fitting and in predictive performance auc values well above 0 9 which resulted in accurate predictions therefore these models can be used in other gully erosion studies as they are capable of rapidly producing accurate and robust gully erosion susceptibility maps gesms for decision making and soil and water management practices furthermore it was found that performance of rf and rbf svm for modelling gully erosion occurrence is quite stable when the learning and validation samples are changed

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

a gis based approach for gully erosion susceptibility modelling a test in sicily italy the aim of this study is to analyze the susceptibility conditions to gully erosion phenomena in the magazzolo river basin and to test a method that allows for driving the factors selection the study area is one of the largest 225 km2 watershed of southern sicily and it is mostly characterized by gentle slopes carved into clayey and evaporitic sediments except for the northern sector where carbonatic rocks give rise to steep slopes in order to obtain a quantitative evaluation of gully erosion susceptibility statistical relationships between the spatial distributions of gullies affecting the area and a set of twelve environmental variables were analyzed stereoscopic analysis of aerial photographs dated 2000 and field surveys carried out in 2006 allowed us to map about a thousand landforms produced by linear water erosion processes classifiable as ephemeral and permanent gullies the linear density of the gullies computed on each of the factors classes was assumed as the function expressing the susceptibility level of the latter a 40 m digital elevation model dem prepared from 1 10 000 scale topographic maps was used to compute the values of nine topographic attributes primary slope aspect plan curvature profile curvature general curvature tangential curvature secondary stream power index topographic wetness index ls usle factor from available thematic maps and field checks three other physical attributes lithology soil texture land use were derived for each of these variables a 40 m grid layer was generated reclassifying the topographic variables according to their standard deviation values in order to evaluate the controlling role of the selected predictive variables one variable susceptibility models based on the spatial relationships between each single factor and gullies were produced and submitted to a validation procedure the latter was carried out by evaluating the predictive performance of models trained on one half of the landform archive and tested on the other large differences of accuracy were verified by computing geometric indexes of the validation curves prediction and success rate curves roc curves drawn for each one variable model in particular soil texture general curvature and aspect demonstrated a weak or a null influence on the spatial distribution of gullies within the studied area while on the contrary tangential curvature stream power index and plan curvature showed high predictive skills hence predictive models were produced on a multi variable basis by variously combining the one variable models the validation of the multi variables models which generally indicated quite satisfactory results were used as a sensitivity analysis tool to evaluate differences in the prediction results produced by changing the set of combined physical attributes the sensitivity analysis pointed out that by increasing the number of combined environmental variables an improvement of the susceptibility assessment is produced this is true with the exception of adding to the multi variables models a variable as slope aspect not correlated to the target variable the addition of this attribute produces effects on the validation curves that are not distinguishable from noise and as a consequence the slope aspect was excluded from the final multi variables model used to draw the gully erosion susceptibility map of the magazzolo river basin in conclusion the research showed that the validation of one variable models can be used as a tool for selecting factors to be combined to prepare the best performing multi variables gully erosion susceptibility model

sub millimeter heterogeneity of yttrium and chromium during growth of semi pelitic garnet x ray maps of yttrium and chromium in two garnets from a semipelitic schist from central nepal reveal parallel spiraling bands of high and low concentration 10 30 m wide this zoning mimics similar concentration bands defined by foliation in the matrix outside the garnets the garnets apparently incorporated the matrix zoning intact during growth at conditions up to lower amphibolite facies these observations and interpretations indicate that yand cr concentrations remained heterogeneous at the scale of tens of micrometers during breakdown of matrix minerals and growth of garnet this conclusion extends results of previous work which showed that y and cr do not homogenize at the centimeter to millimeter scale during metamorphism to amphibolite facies the width of the concentration bands in the garnets places a constraint on the maximum effective intracrystalline diffusion coefficient for both y and cr in garnet of about 10 21 cm 2 s for peak metamorphic conditions of about 9 kbar at 5708c different concentrations of yand cr at different positions around the rim of each garnet indicate disequilibrium for these elements between garnet and matrix phases the presence of an internal foliation defined by the yand cr concentration bands rules out pre kinematic garnet growth most useful in conjunction with other indicators zoning of these elements in garnet is thus a tool for deciphering the relative timing of deformation and garnet growth

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

assessment of calanchi and rill interrill erosion susceptibilities using terrain analysis and geostochastics a case study in the oltrepo pavese northern apennines italy

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

chemical and boron isotope compositions of tourmaline in the hadamiao porphyry gold deposit inner mongolia china abstract the hadamiao porphyry gold deposit in inner mongolia china is located in the northern margin of the north china craton ncc tourmaline is a common mineral in hydrothermal veins and granitic rocks contemporaneous with the mineralized granite porphyry in this deposit the tourmaline can be divided into six types including magmatic tourmaline tur m1 in granite porphyry dikes magmatic hydrothermal transitional tourmaline tur m2 in nodular granitic rocks and hydrothermal tourmalines in early tourmaline veins tur v1 gold bearing quartz tourmaline chalcopyrite veins tur v2 breccia cements tur v3 and late carbonate quartz veins tur v4 the gold mineralization is closely related to the occurrence of tur v2 almost all the tourmalines from the hadamiao deposit belong to the alkali group and show a schorlitic dravitic composition except for some tur m1 belonging to uvite the concentrations of most elements in different tourmaline types overlap tur m1 has higher ca w th u pb mn and zr contents than other types and the hydrothermal tourmalines v1 v4 show slightly higher ba cu and y contents than tur m1 and tur m2 the concentration of au in tur m1 and tur m2 can reach up to 80 ppb and is higher than that in tur v1 the au content in tur v2 is an order of magnitude higher than that in other stages of tourmaline systematic contrasts in major and trace element compositions between magmatic and hydrothermal tourmalines are attributed to the assimilation of the country rock by the magmatic hydrothermal system the six types of tourmaline exhibit variable 11b values ranging from 8 7 to 21 2 tur m1 shows the highest 11b values of 15 1 to 21 2 and tur v2 yields the lowest values ranging from 8 7 to 5 4 the boron probably came from two sources with different isotopic compositions one with high positive 11b values and the other with negative 11b values magmatic hydrothermal fluids could have provided isotopically light boron for hydrothermal tourmalines whereas the heavy boron in magmatic tourmaline was probably derived from marine carbonates that are widespread in the study area the magma related to the mineralization and the one containing magmatic tourmaline may have experienced different degrees of interaction with wall rocks resulting in the diversity of 11b values in hadamiao tourmaline

boron isotope variations in tourmaline from hydrothermal ore deposits a review of controlling factors and insights for mineralizing systems abstract tourmaline group minerals are typically the predominant host of boron in hydrothermal mineral deposits boron is a fluid mobile element whose isotopic composition reflects many factors that are relevant to understanding mineralizing processes including fluid source s fluid rock interaction and formational temperature a new compilation of 2622 published 11b values for tourmaline from diverse types of hydrothermal ore deposits is presented here with the focus 2215 analyses on seven main types porphyry cu mo au deposits granite related sn w deposits iocg deposits orogenic au deposits stratabound vms and sedex deposits and sediment hosted u deposits the total range of 11b values for the seven types is 26 8 to 35 0 four granite sn w orogenic au stratabound vms and sedex have median 11b values close to the continental crustal average of about 10 the median values for iocg and porphyry cu mo au deposits are higher 3 9 and 2 1 respectively whereas sediment hosted u deposits have distinctly high 11b median 25 3 importantly a considerable range of 11b values exists for tourmaline within each deposit type the smallest 17 8 for granite sn w deposits and the largest 48 0 for iocg deposits the boron isotope variations in tourmaline from different deposits are suggested reflect three levels of controlling factors and how these factors operated is illustrated with selected number of case studies the primary factor is the composition of the boron source secondary effects relate to fluid tourmaline fractionation equilibrium or rayleigh there are commonly also tertiary factors that depend on evolution of the specific deposit these include fluid mixing changing water rock ratio and or depositional temperature influences of other boron bearing minerals and where relevant post ore metamorphism separating the effects of these factors is rarely possible from boron isotopes alone however the growth of multi isotope studies of tourmaline and coexisting phases such as mica as well as developments in modelling experimentation of boron isotopes and element partitioning suggest that this limitation will be overcome

digital terrain modelling a review of hydrological geomorphological and biological applications the topography of a catchment has a major impact on the hydrological geomorphological and biological processes active in the landscape the spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems furthermore topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology digital elevation models are the primary data used in the analysis of catchment topography we describe elevation data sources digital elevation model structures and the analysis of digital elevation data for hydrological geomorphological and biological applications some hydrologic models that make use of digital representations of topography are also considered

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

major and trace element geochemistry of tourmalines from archean orogenic gold deposits proxies for the origin of gold mineralizing fluids abstract orogenic style gold mineralizations in the archean hattu schist belt e finland are present in all major host rock lithologies including epiclastic sedimentary and volcanogenic rocks as well as felsic intrusives the gold mineralizations occur as dissemination in altered wall rocks and within hydrothermal quartz veins hydrothermal tourmalines are often associated with the gold mineralizations occurring in the quartz veins as alteration minerals in contacts of the metasedimentary host rocks and quartz veins but also within mineral assemblages of the metasedimentary and magmatic rocks we characterize and compare the major trace and rare earth element chemistry of these tourmalines in order to evaluate their suitability as a petrogenetic tool for tracing the fluid sources of the hydrothermal system by comparing the chemistry of tourmalines from gold mineralization with those from metamorphic and magmatic host rocks we test whether tourmaline composition can be used to identify the source rocks of the gold transporting hydrothermal fluids all analyzed tourmalines belong to the alkali super group and plot along the schorl dravite join the hydrothermal tourmalines have li sr and v concentrations comparable to metamorphic tourmalines and clearly distinct from magmatic tourmalines because the concentrations of ni pb cr mn ga zn and sn show a wide overlap between magmatic metamorphic and hydrothermal tourmalines these elements do not permit to discriminate between different source rocks the co variations of many elements in hydrothermal tourmalines when plotted against li show more similarity to metamorphic tourmalines and the whole rock compositions of metasedimentary and metavolcanic host rocks than to their magmatic counterparts this indicates that the major and trace element composition of hydrothermal tourmalines in the hattu schist belt is predominantly controlled by the host rocks and local fluid rock interactions and does not reflect the distal fluid sources the effect of local fluid rock interaction is also manifested by the ree patterns of tourmalines the magmatic tourmalines have distinct lree enriched patterns resembling the whole rock ree patterns of granitic intrusives while the metamorphic and hydrothermal tourmalines have flat or weakly fractionated patterns similar to metavolcanic and metasedimentary host rocks taken together the tourmaline data suggest that hydrothermal tourmalines associated to gold mineralizing fluids are most likely genetically related to metamorphic rock sources without important contributions of magmatic fluids and that local fluid rock interaction exerted a major control on tourmaline chemistry

micropiping processes and biancana evolution in southeast tuscany italy abstract biancane badlands consisting of small domes dissected by rills and micropipes with rough disordered microrehef can be found along the apennines in italy the dominant processes forming biancane differ from those of badlands formed on smectite rich mudrocks as micropipes associated with pseudokarstic enlargement of pores and cracks predominate and form the main routes for evacuation of eroded material biancana evolution is controlled by water infiltration into intact bedrock producing an erodible weathering rind which is more porous than intact rock this rind is easily removed by rill or micropipe flow and erosion is therefore weathering controlled depending on rind production by infiltrating water infiltration is initially slow and stepped due to slow water movement through very small capillary pores in intact rock alternating with rapid filling of macropores and cracks this occurs due to rapid matrix pore enlargement by dispersion and or dissolution the infiltration pattern is accurately reproduced by a model built on progressive development of weathering layers by moisture penetration model results are consistent with weathering rind depths and erosion observed in the field and show that a pipe network can be generated on newly exposed rock by the rainfall of one year propagation of the pipe network diverts a progressively larger proportion of runoff into micropipes expanding weathering rind production within the biancana as well as on the surface internal weathering and flow progressively dominate with few unweathered corestones and the biancana gradually collapses into a penultimate souffle like form

tourmaline in the central swedish ore district more than 40 recently discovered tourmaline occurrences have been investigated in the mid proterozoic bergslagen ore district of central sweden some are spatially associated with ores others with zones of leaching remobilization and migmatization among the tourmaline bearing ore deposits are the dammberg znpb fe sulphide deposit the sala pb zn ag deposit the dalkarlsberg pershyttan and haksberg fe oxide deposits the leja cu deposit and the zinkgruvan zn pb ag deposit tourmaline has been recorded a as tourmalinites and tourmaline bearing chemical sediments b in tourmaline bearing skarns c in tourmaline quartz veins d as disseminations along the foliation in schists e in tourmaline pegmatites f in tourmalinized haloes in metavolcanites along tourmaline pegmatites and g in late joints tourmalinites tourmaline bearing chemical sediments and tourmaline bearing skarns are spatially associated with sulphide and oxide mineralizations the dravite components in these tourmalines are proportional to the size of zn pb sulphide mineralizations tourmalines from quartz veins close to and within ore deposits contain high zr and cr contents with increasing distance away from these deposits the zr and cr contents fall significantly tourmalines from pegmatites have inherited a number of trace element enrichments through partial melting and assimilation of volcaniclastic sediments into granitic melts despite magmatic homogenization zn contents in these tourmalines reflect the proximity of zn pb sulphide deposits decreasing away from them tourmalines from late joints with zn contents above the 100 ppm level are also indicative for the proximity of zn pb sulphide mineralizations thus some trace elements in these tourmalines may represent suitable exploration tools

origin and significance of tourmalinites and tourmaline bearing rocks of menderes massif western anatolia turkey abstract in the western central portion of anatolia lies the menderes massif a large metamorphic crystalline complex made of neoproterozoic to precambrian basement rocks overlain by palaeozoic to early tertiary metasedimentary rocks and with a multistage metamorphic evolution developed from the late neo proterozoic to eocene we have undertaken a study of the petrology geochemistry and boron isotope composition of these tourmaline occurrences aiming to constrain the processes responsible for the enrichment of boron and other fluid mobile elements in the menderes massif the dispersed tourmaline has chemical and boron isotope compositions typical of a continental crust setting but while some of the tourmalinites display similar signatures others have heavier boron isotope compositions up to 7 5 we suggest that the tourmalinites with continental characteristics formed part of the original pan african basement rocks whereas those with heavier 11b signatures formed by later metamorphism during the alpine orogeny possibly through interaction with subduction like fluids this proposed process may also have been coincident with metasomatism of the lithospheric mantle beneath the massif which is known to have experienced multistage metasomatism and enrichment history up to neogene time

chemical and boron isotope compositions of tourmaline from the jaduguda u cu fe deposit singhbhum shear zone india implications for the sources and evolution of mineralizing fluids abstract the proterozoic jaduguda u cu fe deposit in the singhbhum shear zone eastern india hosts the oldest and most productive uranium mine in india the polymetallic ores in jaduguda are hosted in altered sheared and metamorphosed volcano sedimentary rocks and this complexity has lead to a confusion in ore genetic models for the deposit a characteristic of the mineralization is the presence of abundant tourmaline locally exceeding 50 vol which is spatially associated with u and cu mineralization in all rock types and its chemical and b isotopic variations provide important constraints on fluid source s and ore deposit affinity we examined tourmaline from the u cu ore zone and adjacent footwall and hanging wall meta sedimentary rocks tourmaline grew in three different stages pre kinematic tourmaline 1 represented by fractured and porphyroblastic grains is ubiquitous in the wall rocks and the u cu zone syn kinematic tourmaline 2 and post kinematic tourmaline 3 are found exclusively in the u cu zone where intense shear deformation has focussed fluid flow alteration and metamorphism all tourmalines belong to the alkalic group and most are dravitic systematic contrasts in major element compositions between tourmaline 1 and tourmaline 2 are attributed to the influence of high fluid rock ratios in the u cu ore zone tourmaline from the jaduguda deposit exhibits a wide overall range of 11b values from 6 8 to 17 2 positive values of tourmaline 1 are irrespective of host rock and ore association u or u cu and range between 2 3 to 17 2 n 44 the calculated 11b values of fluid in equilibrium with this tourmaline for mineralization temperatures of 300 450 c range from 4 to 20 the 11b values of syn kinematic tourmaline 2 are much lower than tourmaline 1 between 6 8 and 4 n 7 and the corresponding fluid 11b values are 4 8 6 the high values of 11b for tourmaline 1 and early fluid suggest a marine evaporite or basinal brine was the source of boron and this fits with abundant mineralogical and geochemical evidence for highly saline fluids during mineralization we propose that the isotopically lighter fluid associated with tourmaline 2 and related syn kinematic mineralization mobilization was derived from the metamorphic volcano sedimentary rocks at high fluid rock ratios in and around the shear zone post kinematic tourmaline 3 is compositionally and isotopically 11b 4 to 11 1 n 5 similar to tourmaline 1 in the same samples suggesting it formed by local recrystallization of the early tourmaline or from a renewed influx of saline fluids similar to those which formed the pre kinematic mineralization integrating the results of this tourmaline study with the geological and geochemical characteristics of the jaduguda u cu fe mineralization suggests that it is best regarded as a variant of the fe oxide cu u ree or iocg class of deposits

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

tourmalinization related to late proterozoic early palaeozoic lode gold mineralization in the bin yauri area nigeria three types of tourmaline occurrence have been identified in the area of bin yauri nigeria mesothermal lode gold mineralization these are 1 stratabound tourmalinites in pelitic metasediments 2 tourmaline in a hydrothermal alteration assemblage within hornfelsed wall rocks 3 tourmaline in auriferous quartz and quartz carbonate veins although the tourmaline occurrences are all within or close to the contact aureole of a granodiorite intrusion geochemical characteristics of the tourmalines are broadly similar and reflect a common metasedimentary source two stages of tourmalinization are envisaged the earlier ca 1100 ma involved syngenetic diagenetic formation of tourmalinites while the later ca 500 ma involved epigenetic hydrothermal tourmaline gold mineralization possibly derived by dehydration and devolatilization of metasedimentary sequences containing tourmaline rich rocks or tourmalinites electron microprobe analyses indicate that the tourmalines are intermediate members of the schorl dravite solid solution series plots involving feo mgo and or al2o3 from these analyses are used to constrain the sources and processes of tourmalinization two metallogenic implications are derived from this study one is that although the tourmalinites are barren of gold and base metal mineralization their occurrences nevertheless encourages exploration for syngenetic exhalative massive sulphide deposits in the region the other implication applies to the potential use of tourmaline in deciphering the physico chemical conditions of gold mineralizing fluids in the bin yauri area

geochronological constraints on tourmaline formation in the western fold belt of the mount isa inlier australia evidence for large scale metamorphism at 1 57 ga boron metasomatism during two deformational events resulted in tourmaline formation in parts of late palaeoproterozoic eastern creek volcanics of the western fold belt of the mount isa inlier despite low u pb ratios 1 as measured by laser ablation icp ms when the step leaching process was applied to the tourmaline it process extracted pb fractions with 206 pb 204 pb up to 76 illustrating the method s ability to efficiently separate radiogenic and common pb that are hosted in different crystal lattice sites tourmaline from two syn d2 metamorphic hydrothermal veins at anderson s lode and eldorado yield similar pb step leaching ages of 1573 12 and 1577 48 ma respectively tourmaline from a post d2 but pre d3a vein at king was dated at 1528 51 ma although there is evidence to suggest some contribution from u rich inclusions i e zircon and monazite to some leach steps the isochrons are thought to provide robust ages for hydrothermal tourmaline formation during two discrete thermal events this is supported by estimates of pb closure temperatures in tourmaline derived from ionic porosity models the 1575 ma ages for d2 also reflect the main metamorphic event in the western fold belt but are 40 myr older than accepted age estimates for this episode the revised timing for peak metamorphism tectonism in the western fold belt corresponds with the age of metamorphism in the eastern fold belt suggesting broadly coeval tectonic histories across the entire inlier from at least 1600 ma

a rare garnet tourmaline sillimanite biotite ilmenite quartz assemblage from the granulite facies region of south central massachusetts a rare lithology consisting of garnet tourmaline sillimanite biotite ilmenite quartz has been found within the granulite facies region of south central massachusetts the homogeneous ti rich oxy dravitic tourmaline x mg mg mg fe 0 72 0 77 falls into the alkali group and is similar in composition to lower grade tourmaline found in corresponding metapelitic rocks in maine charge balancing calculations and binary diagrams suggest that like biotite in the region tourmaline has undergone deprotonation by means of the exchange vectors alor 1 oh 1 and tio 2 r 1 oh 2 where r represents fe mg the restriction of a concordant tourmaline rich horizon in otherwise tourmaline free rocks of this granulite facies region suggests that either 1 b released during prograde fluid absent dehydration reactions of muscovite and biotite was locally available in a fluid phase or melt for later crystallization near the peak of granulite facies metamorphism along pathways that provided a conduit for fluid migration or 2 that this is simply a b rich compositional horizon tourmalinite that survived anatexis and granulite facies metamorphism and that records the incipient conditions of tourmaline breakdown and subsequent recrystallization near or post peak metamorphism

water erosion susceptibility mapping by applying stochastic gradient treeboost to the imera meridionale river basin sicily italy abstract soil erosion by water constitutes a serious problem affecting various countries in the last few years a number of studies have adopted statistical approaches for erosion susceptibility zonation in this study the stochastic gradient treeboost sgt was tested as a multivariate statistical tool for exploring analyzing and predicting the spatial occurrence of rill interrill erosion and gully erosion this technique implements the stochastic gradient boosting algorithm with a tree based method the study area is a 9 5 km 2 river catchment located in central northern sicily italy where water erosion processes are prevalent and affect the agricultural productivity of local communities in order to model soil erosion by water the spatial distribution of landforms due to rill interrill and gully erosion was mapped and 12 environmental variables were selected as predictors four calibration and four validation subsets were obtained by randomly extracting sets of negative cases both for rill interrill erosion and gully erosion models the results of validation based on receiving operating characteristic roc curves showed excellent to outstanding accuracies of the models and thus a high prediction skill moreover sgt allowed us to explore the relationships between erosion landforms and predictors a different suite of predictor variables was found to be important for the two models elevation aspect landform classification and land use are the main controlling factors for rill interrill erosion whilst the stream power index plan curvature and the topographic wetness index were the most important independent variables for gullies finally an roc plot analysis made it possible to define a threshold value to classify cells according to the presence absence of the two erosion processes hence by heuristically combining the resulting rill interrill erosion and gully erosion susceptibility maps an integrated water erosion susceptibility map was created the adopted method offers the advantages of an objective and repeatable procedure whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

boron isotopic constraints on the nb and ta mineralization of the syenitic dikes in the 260 ma emeishan large igneous province sw china abstract both nb ta mineralized and nb ta poor syenitic dikes in the panxi region sw china are spatially and temporally associated with syenitic plutons which are part of the 260 ma emeishan large igneous province these syenitic dikes are nw striking and have width varying from 1 to 5 m and length from 50 to 300 m the dikes are mainly composed of k feldspar albite aegirine and arfvedsonite however mineral modes are different in the nb ta mineralized and nb ta poor syenitic dikes the major nb ta bearing mineral in the dikes is pyrochlore which is closely associated with albite and occurs in places with intensive albitization rocks of the nb ta mineralized syenitic dikes contain more albite and less k feldspar than the nb ta poor dikes and have compositions more evolved than the nb ta poor dikes indicating that the nb ta mineralized syenitic dikes formed from a highly evolved magma we analyzed the b concentrations and b isotopic compositions of the samples of both nb ta mineralized and nb ta poor syenitic dikes and associated syenitic pluton using a single column purification method and icp aes and mc icp ms techniques the samples of the nb ta mineralized syenitic dikes have whole rock b concentrations ranging from 11 4 to 23 9 ppm and 11b values from 17 95 to 14 54 whereas the samples of the nb ta poor dikes and syenitic plutons have b concentrations varying from 3 32 to 16 5 ppm and 11b values from 13 45 to 10 02 the high b concentration of the nb ta mineralized dikes relative to the nb ta poor dikes is consistent with that b is incompatible and tends to be rich in more evolved magma the relatively low 11b values of the nb ta mineralized dikes indicate that the b isotopes may have fractionated between fluids and rocks in a transitional magmatic hydrothermal stage we propose that the highly evolved magmas in a transitional magmatic hydrothermal stage may have nb and ta fluorine complexes dissolved in the hydrothermal fluids in the presence of na albite crystallization due to intensive albitization in this stage resulted in the decrease of na in the fluids decomposing the nb and ta fluorine complexes the released nb and ta from the complexes were then dissolved in the fluids and finally entered the lattice of pyrochlore crystals in the stage of albitization

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

geochemistry of hydrothermal tourmaline from iocg occurrences in the great bear magmatic zone implications for fluid source s and fluid composition evolution abstract tourmaline crystallized during iron oxide and alkali calcic alteration and iocg mineralization in the great bear magmatic zone canada within the samples analyzed tourmaline occurs as small crystals in the groundmass of hydrothermal breccias southern breccia and contact lake or as large prismatic crystals in quartz ore mineralogy veins contact lake devries lake and nico the tourmaline from these localities is predominantly shorlitic in composition with minor dravitic uvitic and feruvitic components the boron isotopic composition ranges from 15 to 5 with the majority of values between 15 and 10 the lack of variation among samples supports a common fluid source across the belt for the metasomatic hydrothermal systems these results are isotopically similar to global magmatic and non marine evaporitic reservoirs and lighter than seawater and marine sedimentary rocks the 11b results support a single fluid iocg deposit model for the systems studied wherein metasomatic hydrothermal fluids derived by magmatism ascend and evolve over time through fluid rock interactions

cryptocrystalline permian tourmalinites of possible metasomatic origin in the orobic alps northern italy strata bound tourmaline rich rocks or tourmalinites are relatively rare but important rock types that locally are associated with base metal gold tungsten cobalt and uranium deposits e g ethier and campbell 1977 slack 1982 slack et al 1984 plimer 1986 1987 bone 1988 sun and ge 1989 nie et al 1990 modreski and connor 1991 bhattacharya et al 1992 bandyopadhyay et al 1993 although their significance as guides to strata bound mineral deposits is well established the origin of most tourmalinites is still controversial see slack et al 1993 nearly all documented tourmalinites are of proterozoic or early paleozoic age and have undergone at least lower greenschist facies metamorphism that hampers interpretations of their origin because of changes in texture mineralogy and chemistry this paper describes an important occurrence of finegrained tourmalinites from the orobic alps northern italy in which metamorphic onditions did not exceed prehnite pumpellyite grade the orobic tourmalinites are believed to be permian and represent the youngest and most fine grained examples of such rocks known to date

major and trace element chemistry of gahnite as an exploration guide to broken hill type pb zn ag mineralization in the broken hill domain new south wales australia gahnite bearing rocks are common throughout the proterozoic broken hill domain new south wales australia where they are spatially associated with broken hill type pb zn ag mineralization including the supergiant broken hill deposit in the past such rocks have been utilized as exploration guides to ores of this type but their presence has had mixed success in discovering new occurrences of sulfide mineralization major element chemistry of gahnite has previously been used to define a compositional range associated with metamorphosed massive sulfides deposits including broken hill type deposits but it fails to distinguish sulfide rich from sulfide poor occurrences major and trace element data from la icp ms and electron microprobe analyses were obtained for gahnite from twelve broken hill type deposits to determine whether or not gahnite chemistry may be used to distinguish prospective exploration targets from nonprospective occurrences major and trace element data were discriminated using a principal component analysis and in a bivariate plot of zn fe versus ni cr v to distinguish gahnite associated with the broken hill deposit from that associated with sulfide poor lode pegmatite and sillimanite gneiss bivariate plots of zn fe versus trace element contents e g ga co mn co ni v cd suggest gahnite from the broken hill deposit has a relatively restricted compositional range that overlaps with some minor broken hill type occurrences based on the ore grade wt pb zn of rocks hosting gahnite at each locality gahnite in the highest grade mineralization from minor broken hill type deposits possess compositions that plot within the field for gahnite from the broken hill deposit which suggests that major and trace element chemistry e g zn fe 2 4 vs co 10 110 ppm ga 110 400 ppm mn 500 2 250 ppm and co 25 100 ppm vs ga 125 375 ppm may be used as an exploration guide to high grade ore

the geology and mineralogy of the loulo mining district mali west africa evidence for two distinct styles of orogenic gold mineralization loulo is a world class orogenic gold mining district in the birimian terrane of western mali orebodies are located along second or higher order shears associated with the senegal mali shear zone with gold mineralization largely linked to a transtensional event the mine camp is divided into two distinct styles of gold deposit on the basis of differing geologic characteristics one group is typified by the gara deposit whereas the other by the yalea deposit both deposit styles are hosted by similar rock types calcareous graywackes and calciticdolomitic marbles gara style orebodies occur as sulfide disseminations or ankerite rich shear vein stockworks hosted in folded tourmalinized sandstones and breccias mainly within 2 km of the senegal mali shear zone these deposits are characterized by intense multi stage albitization and tourmalinization pre syn and postmineralization gold lodes are fe rich dominated by nickeloan pyrite contain cu ni co minor and trace sulfides e g chalcopyrite gersdorffite pentlandite cobaltite millerite and show consistently high levels of p ree w bearing phases apatite monazite xenotime and scheelite base metal concentrations show a marked increase in marble host rocks with the formation of nickeloan pyrite cobaltite clausthalite ores in contrast yalea style deposits are associated with quartz ankerite vein lodes and disseminated sulfide stringer zones mineralization occurs along highly altered tourmaline absent brittle ductile shears up to 8 km away from the senegal mali shear zone wall rock alteration is characterized by addition of k 2 o cao co 2 h 2 o and sio 2 with mineral assemblages consisting of chlorite sericite carbonate quartz albite ore paragenesis is enriched in as mainly as multistage growth of arsenopyrite and arsenian pyrite base metal sulfides scheelite and ree phosphates are extremely rare the diversity in the ore paragenesis is controlled by a dynamic hydrothermal system that sourced fluids and metals from different reservoirs within the region the as rich yalea style deposits have characteristics typical of birimian gold mineralization in ghana and auriferous fluids are likely derived from the dewatering of sedimentary rocks during regional metamorphism on the other hand the polymetallic fe b rich gara style orebodies show atypical features for birimian gold mineralization instead field relations and the mineralogy and geochemistry of the gara style lodes indicate a strong hydrothermal influence from surrounding intrusive stocks with possible links between gold mineralization and iron oxide skarn development in the region the data collected at loulo highlight the diverse nature of orogenic gold deposits especially in west africa this style of ore deposit can form from a variety of fluid sources both metamorphic and magmatic

detrital metamorphic and metasomatic tourmaline in high pressure metasediments from syros greece intra grain boron isotope patterns determined by secondary ion mass spectrometry the boron isotopic composition of zoned tourmaline in two metasediments from the island of syros determined by secondary ion mass spectrometry sims reflects the sedimentary and metamorphic record of the rocks tourmaline from a silicate bearing marble contains small 20 m detrital cores with highly variable 11b values 10 7 to 3 6 pointing to a heterogeneous protolith derived from multiple sources the sedimentary b isotopic record survived the entire metamorphic cycle with peak temperatures of 500 c prograde to peak metamorphic rims are homogeneous and similar among all analysed grains 11b 0 9 the varying 11b values of detrital cores in the siliceous marble demonstrate that in situ b isotope analysis of tourmaline by sims is a potentially powerful tool for provenance studies not only in sediments but also in metasediments a meta tuffitic blueschist bears abundant tourmaline with dravitic cores of detrital or authigenic origin 11b 3 3 and prograde to peak metamorphic overgrowth zones 1 6 fe rich rims formed during influx of b bearing fluids under retrograde conditions show strongly increasing 11b values up to 7 7 towards the margins of the grains the 11b values of metamorphic tourmaline from syros formed in mixed terrigenous marine sediments reflect the b signal blended from these two different sources and was probably not altered by dehydration during subduction

boron isotopic composition of tourmaline prismatine and grandidierite from granulite facies paragneisses in the larsemann hills prydz bay east antarctica evidence for a non marine evaporite source a unique assemblage of b rich rocks 2 wt b containing the borosilicate minerals tourmaline tur prismatine prs and grandidierite gdd is exposed in the ca 1000 ma brattstrand paragneiss in the larsemann hills east antarctica the b isotope composition of these three minerals in 21 paragneisses and 6 anatectic pegmatites were measured in situ using secondary ion mass spectrometry 11b ranges from 2 8 to 14 4 in tourmaline from 9 6 to 17 8 in prismatine and from 2 8 to 8 7 in grandidierite weighted uncertainties mostly 1 2 per sample in most cases average 11b increases in a given sample prs tur gdd whether the observed b isotope distribution has attained equilibrium were assessed using two criteria microstructural equilibrium and regular distribution of mg and fe in samples for which the two criteria are met we assume the measured distribution of isotopes 11ba b 11ba 11bb represents equilibrium 11btur prs 5 0 1 4 5 of 12 pairs 11btur gdd 3 3 0 8 3 of 5 pairs and 11bgdd prs 7 2 1 3 2 of 2 pairs consistent with the preference of 10b for tetrahedral sites prismatine and 11b for trigonal sites tourmaline grandidierite ab initio computations of b isotope fractionation factors 11btur prs 6 4 1 3 11btur gdd 1 8 1 1 and 11bgdd prs 8 2 1 1 provide confirmation of the measured fractionations the computed relaxed ionic structure of grandidierite gave a shorter 1 368 a b o bond length than in case of dravite 1 385 a which explains the measured enrichment of grandidierite in 11b relative to tourmaline the precursor of the b rich rock least changed by metamorphism tourmaline metaquartzite 11b tur 8 6 to 5 9 is interpreted to be a product of pre metamorphic hydrothermal b metasomatism boron sources consistent with this 11b range include oceanic crust clastic sediments volcanic rocks and non marine evaporite borate but not marine evaporite however dominance of metasediments in the brattstrand paragneiss major and trace element compositions of the b rich rocks and presence of abundant b are consistent with non marine evaporite being the most important source of b for the b rich lithologies of the larsemann hills a possible scenario for precursors of these rocks is a succession of clastic sediments in part tuffaceous intercalated with b rich evaporite deposits in a continental rift basin in which circulating hydrothermal fluids leached b from the evaporite and precipitated it as tourmaline in the associated clastic rocks to form the precursors to the tourmaline metaquartzites

assessment of calanchi and rill interrill erosion susceptibility in northern liguria italy a case study using a probabilistic modelling framework abstract soils are a vital part of the natural environment and one of the most important natural resources the european mediterranean regions are particularly sensitive to soil degradation especially in italy many landscapes are prone to water related soil erosion processes such as rill interrill erosion sheet erosion gullies and complex processes forming calanchi corresponding to the english term badlands calanchi develop preferentially on plio pleistocene deposits which are highly susceptible to aquatic erosion processes this study focusses on the assessment of rill interrill erosion as well as calanchi erosion forms and features in previously none or very little studied areas of the langhe roero and monferrato located in the liguria and piedmont region northern apennines italy in this study we assess the driving factors and the spatial distribution of rill interrill and calanchi erosion processes using a geostatistical geostochastic modelling framework therefore a maximum entropy model a generalized linear model and a boosted regression tree approach were applied as independent environmental variables we selected dem based morphometric information as well as pedologic and geologic input data moreover we explore remote sensing techniques to derive information on the vegetation density and vitality the stochastic models applied show that the two very different soil erosion phenomena can be differentiated well with the chosen stochastic techniques the main drivers controlling the spatial distribution of aquatic soil erosion in the study area are soil type slope elevation and topographic wetness index the results of the maxent and brt model were confirmed by the glm application in terms of the significance of predictor variables generally the models show an acceptable to excellent performance with brt and glm outperforming maxent the single independent variable response curves gave valuable insights into the process triggering the erosion forms we were able to clearly differentiate between the processes looking at the response curves that show reasonable characteristics with all applied models

on the occurrence and boron isotopic composition of tourmaline in ultra high pressure metamorphic rocks abstract the extensive p t stability and the high chemical variability of tourmaline tur together with its common occurrence in metasediments proves its high potential for petrological and isotope geochemical studies on fluid rock interaction in subduction and collision related rocks this paper reviews the occurrence major element chemistry and boron isotopic composition of tur in high and ultrahigh pressure metamorphic uhpm rocks in addition it presents a new discovery of coesite bearing tur schorl from the erzgebirge germany as well as tur dravite related to the retrograde history of coesite and diamond bearing rocks from the erzgebirge and the kokchetav massif kazakhstan the scarce data on worldwide occurrences of u hpm tur reveal a high occupation of the crystallographic x site dominated by na and the possible presence of excess b with little further distinctiveness in its major element composition when compared with tur from medium grade rocks high k 2 o contents in tur are probably not related to uhp growth or equilibration the b isotopic composition of u hpm tur ranges in 11 b from 16 to 1 with many samples in or below the range of continental crust in contrast tur formed during retrograde fluid influx typically shows high 11 b values up to 28 suggesting heavy b fluids infiltrating the exhuming u hpm units coesite inclusions in tur characterized by raman spectroscopy are regarded as the best indicator for its uhp stability supplementary material analytical methods tourmaline compositions and boron isotope values are available at http www geolsoc org uk sup18354

long and short term evolution of several mediterranean denudation hot spots the role of rainfall variations and human impact abstract severe slope denudation is one of the most important environmental problems in the mediterranean region in particular badlands are widespread in central italy as a result of extensive clayey outcrops current climatic conditions and rapid quaternary uplift human activity may significantly affect the development and evolution of these denudation hot spots especially through changes in land use this work is focused on a badland site that has developed over the last 30 years on a gently sloping area of cropland in central italy the site named bargiano underwent cropland abandonment in 1980 and was selected to evaluate the effects of external forcing such as human impact and rainfall variations on the development of water erosion processes the remnants of the 1980 cropland surface and the present eroded surface were sampled using differential global positioning system techniques to perform a volumetric estimation of the eroded material and to calculate the average erosion rate for fairly large time spans the dgps survey was coupled with a 2 year monitoring with erosion pins in the region which permitted comparisons between long and short term average erosion rates in addition the analysis of the rainfall series recorded at the orvieto pluviometric station allowed us to assess and evaluate the role of critical rainfall events on denudation intensity finally a further comparison of the measured and estimated erosion rates from the bargiano site with the data recorded at other long lasting monitoring stations that are set up in certain key areas of central italy the tevere river and ombrone river basins revealed that the bargiano experimental hillslope experienced considerably higher erosion rates than were noted at the other sites our investigations demonstrated that cropland abandonment caused an increase in the erosion rate relative to what happened in natural areas characterized by similar physiographic conditions this finding is consistent with previously reported results for other badlands found in the mediterranean area moreover the results obtained suggest that after the abandonment of its cropland the bargiano site evolved in a cyclical manner that was driven by intrinsic thresholds to a greater extent than it was affected by external climatic changes

tourmaline in proterozoic massive sulfide deposits from rajasthan india we have analyzed the chemical composition and boron isotope composition of tourmaline from tourmalinites granite and a quartz tourmaline vein from the deri ore zone and from a pegmatitic band in the rampura agucha ore body these two proterozoic massive sulfide deposits occur in the aravalli delhi orogenic belt rajasthan northwest india tourmaline from stratiform tourmalinites closely associated with the massive sulfides in the deri deposit have preserved their original chemical compositions despite regional and thermal metamorphism in the area these tourmalines have low fe fe mg ratios 0 19 0 30 mean 0 26 that suggest formation close to the sediment sea water interface the 11b values 15 5 and 16 4 are compatible with boron derived from leaching of argillaceous sediments and or felsic volcanics underlying the original massive sulfide deposit during its formation boron isotope compositions measured in tourmaline from a post ore granite and quartz tourmaline vein in the deri deposit indicate that boron in these tourmalines was derived from the tourmalinites produced during ore formation the boron isotope systematics of a coarse brown tourmaline crystal from a pegmatitic band on the hanging wall contact of the rampura agucha deposit indicate that 45 25 of the boron within the original tourmaline was lost during upper amphibolite facies regional metamorphism

insight into diagenetic processes from authigenic tourmaline an example from carboniferous and permian siliciclastic rocks of western poland abstract authigenic tourmaline is a rare and minor component of siliciclastic rocks however once it occurs it can be used to interpret a number of subsurface parameters and processes such as fluid composition redox state salinity ph and fluid migration paths notwithstanding the conditions of tourmaline authigenesis still need to be recognize with greater clarity carboniferous and permian siliciclastic rocks in the subsurface of western poland in the vicinity of the dolsk fault show unusually high boron contents at places surpassing 1000 g g which are associated with the presence of authigenic tourmaline the mineral forms fine elongated crystals of nano to micrometer width grouped in radiating or semi parallel aggregates which are dispersed in the clay matrix of shales and graywackes coat grain surfaces and line secondary pores in porous sandstones replace some grains in volcaniclastic breccia and overgrow detrital tourmalines in quartzarenites regardless of host rock compositions the tourmaline is si deficient moderately al rich and shows significant x site vacancies and highly variable mg mg fetot ratios in rare zoned tourmaline the mg mg fetot ratios distinctly decrease and vacancies slightly increase towards the growth direction the results suggest that the tourmaline nucleated rapidly under a strong driving force at high boron concentration and high temperature the fluids which enabled the process were acidic reducing b and mg bearing and of low na and ca contents the tourmaline grew primarily at the expense of kaolinite possibly of other clay minerals and k feldspar in the temperature range 150 200 c its crystallization was a short episode in the diagenetic history of the host rocks tourmaline authigenesis across the carboniferous permian unconformity in the proximity of a prominent fault zone is evidence for fluid and heat migration along faults and for temporarily open geochemical system during late diagenesis the source of boron has been unproven yet the circulation of bitterns originated from upper permian evaporites was highly probable

chemical and boron isotopic compositions of tourmaline from the archean big bell and mount gibson gold deposits murchison province yilgarn craton western australia abstract tourmaline is a commonly found gangue mineral in archean greenstone belt lode gold deposits worldwide in this paper we report major trace and rare earth element ree and boron isotopic compositions of tourmaline from two major amphibolite grade archean gold deposits big bell and mount gibson murchison province yilgarn craton western australia in an attempt to better understand the hydrothermal gold formation processes that were also responsible for tourmalinization tourmalines in these two major deposits all belong to the dravite schorl series and tend to be mg rich where closely associated with gold and sulfide ores the ore related tourmalines also contain high concentrations of ore metals such as au ag pb and cu in the big bell deposit tourmalines occur along the foliation in lode schists and show low fe fe mg ratios of 0 11 0 30 tio 2 contents of 0 15 0 73 wt and negligible mno 11 b values of 17 7 to 15 0 in the mount gibson deposit the tourmalines closely associated with the sulfide ores are the most mg rich with low fe fe mg ratios of 0 19 0 22 while tourmalines from garnet bearing biotite muscovite schists that overly the lode gold orebody are more fe rich fe fe mg 0 30 0 63 tourmalines from an amphibolite schist are mg rich with fe fe mg ratios 0 27 0 34 that lie between the above two groups of tourmalines the compositional trend from fe rich tourmalines in the sulfide poor schists to mg rich in the sulfide ores at mount gibson is similar to that observed in massive sulfide ore deposits worldwide alternatively the mg rich nature of the sulfide related tourmalines may be due to metamorphic reactions that are accompanied by fe incorporation into sulfides leaving coexisting silicates more mg rich the ree geochemistry of the tourmalines from the mount gibson ore zone schists displays strong hree enrichments and positive eu anomalies with eu eu ratios up to 2 4 which are similar to tourmalines associated with massive sulfide deposits the ore related tourmalines disseminated in the host schists show 11 b values of 18 6 to 17 0 whereas one coarse grained tourmaline vein has a lower 11 b value of 21 9 to 21 4 these data support hypotheses which suggest that the schists that host the gold mineralization are the metamorphosed equivalents of a base metal rich hydrothermally altered seafloor horizon that is typical of vms style mineralization with the boron possibly derived from leaching of footwall sedimentary and volcanic rocks during hydrothermal circulation

simulation of soil erosion and deposition in a changing land use a modelling approach to implement the support practice factor abstract using the usped unit stream power erosion deposition model three land use scenarios were analysed for an italian small catchment 15 km 2 of high landscape value the upper orme stream catchment located in the chianti area 30 km south of florence has a long historical agriculture record information on land use and soil conservation practices date back to 1821 hence offering an opportunity to model impacts of land use change on erosion and deposition for this study a procedure that takes into account soil conservation practices and potential sediment storage is proposed the approach was to calculate and model the flow accumulation considering rural and logging roads location of urban areas drainage ditches streams gullies and permanent sediment sinks this calculation attempts to assess the spatial variability especially the impact of support practices p factor weather data from 1980 2003 were taken into account to calculate the r factor however to consider the intense pluviometric conditions in terms of the erosivity factor the 0 75th quantile was used while the lowest erosivity was modelled using the 0 25th quantile results of the usped model simulation show that in 1821 the mean annual net erosion for the watershed was 2 8 mg ha 1 y 1 in 1954 it was 4 2 mg ha 1 y 1 and in 2004 it was 5 3 mg ha 1 y 1 conservation practices can reduce erosion processes by 20 mg ha 1 y 1 when the 1821 practices are introduced in the present management on the other hand if the support practices are not considered in the model soil erosion risk is overestimated field observation for the present day simulation confirmed that erosion and associated sediment deposition predicted by the model depend as expected on geomorphology and land use the model shows limitations that are mainly due to the input data a high resolution dem is essential for the delineation of reliable topographic potential to predict erosion and deposition especially in vineyards

tourmalinites from the eastern sierras pampeanas argentina abstract in the eastern sierras pampeanas central argentina tourmalinites and coticules are found in close association with stratabound scheelite deposits in metamorphic terranes in sierra grande agua de ramon and ambul districts and sierra de altautina tourmalinites are associated with stratabound scheelite deposits related to orthoamphibolites in the pampa del tamboreo area tourmalinites are located in biotite schists stratigraphically related to acid to intermediate metavolcanic rocks and scheelite bearing quartzites the mineral chemistry and boron isotopic compositions of tourmalinite hosted and vein hosted tourmalines are investigated overall the tourmalines belong to the dravite schorl series and are generally aluminous fe fe mg ranges from 0 33 to 0 85 al al fe mg from 0 66 to 0 76 and the amount of x site vacancy 0 12 0 48 indicates significant foitite components their boron isotopic compositions 11 b are from 24 0 to 15 0 similar mineral chemistries and boron isotopic values for tourmaline in tourmalinites related to stratabound scheelite mineralisation and in tungsten bearing quartz veins suggest a common source for the boron and probably the tungsten the field chemical and isotopic relationships are consistent with tungsten and boron in quartz vein deposits being remobilised from stratabound scheelite and tourmalinite dominantly by liquid state transfer associated with regional shear zones tungsten and boron in the original sedimentary sequence now meta exhalites are ascribed to volcanogenic exhalations

boron metasomatism and behaviour of rare earth elements during formation of tourmaline rocks in the eastern arunta inlier central australia tourmaline rocks of previously unclear genesis and spatially associated with w cu bearing calc silicate rocks occur in palaeoproterozoic supracrustal and felsic intrusive rocks in the bonya hills in the eastern arunta inlier central australia tourmalinisation of metapelitic host rocks postdates the peak of regional low pressure metamorphism m1 d1 500 c 0 2 gpa and occurred synkinematically between the two main deformation events d1 and d2 coeval with emplacement of late strangways 1 73 ga tourmaline bearing leucogranites and pegmatites tourmaline is classified as schorl to dravite in tourmaline quartz rocks and surrounding tourmaline rich alteration zones and as fe rich schorl to foitite in the leucogranites boron metasomatism resulted in systematic depletion of k li rb cs mn and enrichment of b and in some samples of na and ca in the tourmaline rocks compared to unaltered metasedimentary host rocks whole rock ree concentrations and patterns of unaltered schist tourmalinised schist and tourmaline quartz veins the latter were the zones of influx of the boron rich hydrothermal fluid are comparable to those of post archaean shales thus the whole rock ree patterns of these rocks are mostly controlled by the metapelitic precursor in contrast ree concentrations of leucogranitic rocks are low 10 times chondritic and their flat ree patterns with pronounced negative eu anomalies are typical for fractionated granitic melts coexisting with a fluid phase ree patterns for tourmalines separated from metapelite hosted tourmaline quartz veins and tourmaline bearing granites are very different from one another but each tourmaline pattern mirrors the ree distribution of its immediate host rock tourmalines occurring in tourmaline quartz veins within tourmalinised metasediments have lree enriched lan ybn 6 3 55 shale like patterns with higher ree 54 108 ppm in contrast those formed in evolved leucogranites exhibit flat ree patterns lan ybn 1 0 5 6 with pronounced negative eu anomalies and are lower in ree 5 6 30 ppm we therefore conclude that ree concentrations and patterns of tourmaline from the different tourmaline rocks studied are controlled by the host rock and not by the hydrothermal fluid causing boron metasomatism from the similarity of the ree pattern of separated tourmaline with the host rock we further conclude that incorporation of rees in tourmaline is not intrinsically controlled i e by crystal chemical factors tourmaline does not preferentially fractionate specific rees or groups of rees during crystallisation from evolved boron and fluid rich granitic melts or during alteration of clastic metasediments by boron rich magmatic hydrothermal fluids

the impact of the farming practice of remodelling hillslope topography on badland morphology and soil erosion processes abstract badland landforms created in plio pleistocene clay landscapes of the basilicata region of southern italy form marginal features in a semi arid landscape dominated by the widespread cultivation of subsidised cereals these badland features are high relative relief forms exhibiting a high drainage density and steep slopes with slope angles typically in excess of 35 economic incentives to increase agricultural productivity have resulted in the practice of remodelling these marginal areas using heavy earth moving equipment remodelling the badland features creates longer slopes at lower angles which can be cultivated using conventional farm machinery these changes in hillslope morphology have altered the degree to which soil erosion processes operating in these areas are spatially coupled in the badland areas erosion and deposition are strongly localised with minimal sediment delivery to ephemeral or perennial channel systems the economically driven change in land use from visually striking badland areas to newly remodelled fields for agricultural use results in an increase in the coupling of drainage networks and a net increase in soil erosion

assessment of susceptibility to earth flow landslide using logistic regression and multivariate adaptive regression splines a case of the belice river basin western sicily italy abstract in this paper terrain susceptibility to earth flow occurrence was evaluated by using geographic information systems gis and two statistical methods logistic regression lr and multivariate adaptive regression splines mars lr has been already demonstrated to provide reliable predictions of earth flow occurrence whereas mars as far as we know has never been used to generate earth flow susceptibility models the experiment was carried out in a basin of western sicily italy which extends for 51 km 2 and is severely affected by earth flows in total we mapped 1376 earth flows covering an area of 4 59 km 2 to explore the effect of pre failure topography on earth flow spatial distribution we performed a reconstruction of topography before the landslide occurrence this was achieved by preparing a digital terrain model dtm where altitude of areas hosting landslides was interpolated from the adjacent undisturbed land surface by using the algorithm topo to raster this dtm was exploited to extract 15 morphological and hydrological variables that in addition to outcropping lithology were employed as explanatory variables of earth flow spatial distribution the predictive skill of the earth flow susceptibility models and the robustness of the procedure were tested by preparing five datasets each including a different subset of landslides and stable areas the accuracy of the predictive models was evaluated by drawing receiver operating characteristic roc curves and by calculating the area under the roc curve auc the results demonstrate that the overall accuracy of lr and mars earth flow susceptibility models is from excellent to outstanding however auc values of the validation datasets attest to a higher predictive power of mars models auc between 0 881 and 0 912 with respect to lr models auc between 0 823 and 0 870 the adopted procedure proved to be resistant to overfitting and stable when changes of the learning and validation samples are performed in conclusion the highly acceptable predictive skill of the statistical models confirms the reliability of the procedure adopted to reconstruct the pre failure topographic conditions such a method solves the conceptual problem arising when post failure elevation data are the only source of topographic information available to model landslide susceptibility furthermore with respect to other solutions proposed in the past which identify as unstable the conditions of landslide surroundings our approach allows for more accurate measurement of those variables e g curvature convergence index topographic position index that depend on the relative position of a cell with respect to its nearby pixels

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

predicting the susceptibility to gully initiation in data poor regions permanent gullies are common features in many landscapes and quite often they represent the dominant soil erosion process once a gully has initiated field evidence shows that gully channel formation and headcut migration rapidly occur in order to prevent the undesired effects of gullying there is a need to predict the places where new gullies might initiate from detailed field measurements studies have demonstrated strong inverse relationships between slope gradient of the soil surface s and drainage area a at the point of channel initiation across catchments in different climatic and morphological environments such slope area thresholds s a can be used to predict locations in the landscape where gullies might initiate however acquiring s a requires detailed field investigations and accurate high resolution digital elevation data which are usually difficult to acquire to circumvent this issue we propose a two step method that uses published s a thresholds and a logistic regression analysis lr s a thresholds from the literature are used as proxies of field measurement the method is calibrated and validated on a watershed close to the town of algiers northern algeria where gully erosion affects most of the slopes the gullies extend up to several kilometres in length and cover 16 of the study area first we reconstruct the initiation areas of the existing gullies by applying s a thresholds for similar environments then using the initiation area map as the dependent variable with combinations of topographic and lithological predictor variables we calibrate several lr models it provides relevant results in terms of statistical reliability prediction performance and geomorphological significance this method using s a thresholds with data driven assessment methods like lr proves to be efficient when applied to common spatial data and establishes a methodology that will allow similar studies to be undertaken elsewhere

a functional entity approach to predict soil erosion processes in a small plio pleistocene mediterranean catchment in northern chianti italy abstract in this paper we evaluate different methods to predict soil erosion processes we derived different layers of predictor variables for the study area in the northern chianti italy describing the soil lithologic complex land use and topographic characteristics for a subcatchment of the orme river we mapped erosion processes by interpreting aerial photographs and field observations these were classified as erosional response units eru i e spatial areas of homogeneous erosion processes the eru were used as the response variable in the soil erosion modelling process we applied two models i bootstrap aggregation random forest rf and ii stochastic gradient boosting treenet tn to predict the potential spatial distribution of erosion processes for the entire orme river catchment the models are statistically evaluated using training data and a set of performance parameters such as the area under the receiver operating characteristic curve auc cohen s kappa and pseudo r2 variable importance and response curves provide further insight into controlling factors of erosion both models provided good performance in terms of classification and calibration however tn outperformed rf similar classes such as active and inactive landslides can be discriminated and well interpreted by considering response curves and relative variable importance the spatial distribution of the predicted erosion susceptibilities generally follows topographic constraints and is similar for both models hence the model based delineation of eru on the basis of soil and terrain information is a valuable tool in geomorphology it provides insights into factors controlling erosion processes and may allow the extrapolation and prediction of erosion processes in unsurveyed areas

assessment of land degradation susceptibility by scenario analysis a case study in southern tuscany italy abstract in the mediterranean area land degradation phenomena are becoming more and more important due to future climate change and increasing climate variability as highlighted in recent global assessment projects such as the millennium ecosystem assessment or the dialogue on water and climate thus there is consistent evidence that extreme events such as droughts and floods are more frequent than before on the other hand the mediterranean area is strongly influenced by human activities such as cultivation over hundreds of years however in the last decades the cultivation methods and techniques are subject to profound changes such as mechanization use of fertilizers and pesticides remodellation of entire hillslopes etc this particular situation leads to and aggravates the existing stress on land resources as a result land degradation and soil erosion phenomena are leading to decreasing soil productivity or the loss of fertile top soil and related water quality and quantity issues the centre for soil erosion studies cres in grosseto tuscany recently started a study to identify and monitor changes of land use in southern tuscany italy the aim of this study is to assess land degradation sensitivity by scenario analysis as a proxi for land degradation surface wash erosion processes such as rill and interill erosion processes are chosen these present day processes are identified by aerial photo interpretation and subsequently modelled with a simple rusle approach on a monthly basis in this study boundary conditions such as future precipitation were taken from the a2 future climate scenario published by the international panel on climate change ipcc special report on emission scenarios sres moreover current land use was identified from aerial photographs and future land use scenarios were developed considering ecological and socio economical issues for present day conditions of the test area subsequently the different climate and land use scenarios were analysed to study soil erosion susceptibility on the landscape scale the study shows that even with a decline in precipitation volume until 2070 in some months higher erosion rates occur due to higher rainfall erosivity furthermore land use changes play an important role for soil erosion susceptibility as shown the various scenarios can effectively reduce or enhance soil erosion

clastic metasediments of the early proterozoic broken hill group new south wales australia geochemistry provenance and metallogenic significance whole rock analyses of samples of pelite psammite and psammopelite from the early proterozoic broken hill group willyama supergroup in the broken hill block new south wales australia reveal distinctive geochemical signatures major element data show high al2o3 and k2o low mgo and na2o and relatively high fe2o3tmgo ratios compared to average early proterozoic clastic metasediments high field strength elements hfse are especially abundant including nb most 15 27 ppm ta most 1 0 2 2 ppm th 17 36 ppm hf 4 15 ppm and zr most 170 400 ppm y 33 74 ppm is also high concentrations of ferromagnesian elements are generally low sc 20 ppm ni 62 ppm co 26 ppm cr most 100 ppm data for rare earth elements rees show high abundances of light rees lacn 116 250 chondrite lacn 437 in one sample high lacnybcn ratios 5 6 13 9 and large negative eu anomalies eueu 0 32 0 57 the geochemical data indicate derivation of the metasedimentary rocks of the broken hill group by the erosion mainly of felsic igneous or meta igneous rocks high concentrations of hfse y and rees in the metasediments suggest a provenance dominanted by anorogenic granites and or rhyolites including those with a type chemistry likely sources of the metasediments were the rhyolitic to rhyodacitic protoliths of local quartz feldspar biotite garnet gneisses e g potosi type gneiss that occur within the lower part of the willyama supergroup or chemically similar basement rocks in the region alternative sources may have included early proterozoic anorogenic granites and or rhyolites in the mount isa and or pine creek blocks of northern australia or in the gawler craton of south australia metallogenic considerations suggest that the metasediments of the broken hill block formed enriched source rocks during the generation of pegmatite hosted deposits and concentrations of la ce nb ta th and sn in the region li be b w and u in pegmatite minerals of the district may have been acquired during granulite facies metamorphism of the local metasediments

mass wasting triggered by the 2008 wenchuan earthquake is greater than orogenic growth shallow earthquakes lead to the uplift of mountain ranges but also trigger landslides that remove mass an analysis of the 2008 wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift

classification of slope processes based on multitemporal dinsar analyses in the himalaya of nw bhutan abstract slope deformation in mountainous terrain can be driven by different processes the nature of which is either gravitational and irreversible or seasonal and reversible the latter induced by permafrost variations or by hydromechanical or thermomechanical effects the importance of identifying such deformations is not only related to the hazard they can pose but also to the understanding of changes that permafrost or local hydrological conditions undergo here we carry out a multi temporal insar analysis over a mountainous area 8000 km2 large straddling north western bhutan and southern tibet we propose a methodology to separate locally deforming areas from the effects of long wavelength signals through the analysis of the spatio temporal behaviour of 4 years long time series of surface displacements we present the mapping of hundreds of small scale features that appear to be actively deforming as well as several examples of reversible deformation rarely detected at this scale in such a challenging and vast region the analysis of the multi annual trend of ground deformation shows a relatively small number of irreversible gravitational movements clearly related to rock slides which attests a low level of recent activity of large rock slope instabilities in the region in the southernmost lower elevation parts of the study area we quantify reversible surface displacements with amplitudes ranging between 5 and 17 mm and showing maximum displacements towards the satellite in summer months thus compatible with hydro mechanical effects related to groundwater table variations in addition the ground movement induced by the active layer s response to thawing and freezing over the gentler slopes and high elevation permafrost regions of bhutan and southern tibet is on average around 10 mm with maxima up to 28 mm the localised displacements appear to be largely associated to braided stream plains glacier outwash plains or low angle fine sediment covered slopes

exploiting maximum entropy method and aster data for assessing debris flow and debris slide susceptibility for the giampilieri catchment north eastern sicily italy this study aims at evaluating the performance of the maximum entropy method in assessing landslide susceptibility exploiting topographic and multispectral remote sensing predictors we selected the catchment of the giampilieri stream which is located in the north eastern sector of sicily southern italy as test site on 1 october 2009 a storm rainfall triggered in this area hundreds of debris flow avalanche phenomena causing extensive economical damage and loss of life within this area a presence only based statistical method was applied to obtain susceptibility models capable of distinguishing future activation sites of debris flow and debris slide which where the main source of failure mechanisms for flow or avalanche type propagation the set of predictors used in this experiment comprised primary and secondary topographic attributes derived by processing a high resolution digital elevation model corine land cover data and a set of vegetation and mineral indices obtained by processing multispectral aster images all the selected data sources are dated before the disaster a spatially random partition technique was adopted for validation generating 50 replicates for each of the two considered movement typologies in order to assess accuracy precision and reliability of the models the debris slide and debris flow susceptibility models produced high performances with the first type being the best fit the evaluation of the probability estimates around the mean value for each mapped pixel shows an inverted relation with the most robust models corresponding to the debris flows with respect to the role of each predictor within the modelling phase debris flows appeared to be primarily controlled by topographic attributes whilst the debris slides were better explained by remotely sensed derived indices particularly by the occurrence of previous wildfires across the slope the overall excellent performances of the two models suggest promising perspectives for the application of presence only methods and remote sensing derived predictors copyright 2016 john wiley sons ltd

the paleoproterozoic dorlin gold deposit french guiana genetic constraints of the stable isotope geochemistry abstract this paper reports on oxygen hydrogen carbon and sulphur isotopic compositions of silicates carbonates and sulphides from the dorlin gold deposit in the paleoproterozoic greenstone belt of central french guiana the dorlin orebodies result from the polydeformation of a large tourmalinite bearing stratabound sulphide deposit hosted by volcanic and sedimentary rocks of the paramaca series metamorphosed in the greenschist facies the mineralizing envelope would initially have consisted of an inner zone of tourmaline sulphide bearing ores m2 surrounded by a zone of chlorite sulphide bearing mineralization m1 the stratabound sulphide deposit was locally cut by a muscovite sulphide quartz stockwork m3 the 18 o values of quartz and chlorite from the chlorite sulphide mineralization are 12 2 and about 5 5 smow respectively those of quartz and tourmaline from the tourmaline sulphide mineralization are about 14 and 8 5 smow and those of quartz and muscovite from the discordant stockwork are 12 4 and 6 9 smow d values of the chlorite tourmaline and muscovite are about 45 28 and 38 smow respectively carbonates calcite dolomite ankerite and siderite in the mineralizations have 18 o values between 10 8 and 15 7 relative to smow and 13 c values of 5 2 to 0 8 relative to pdb 34 s values of samples from the three mineralizations range between 0 5 to 2 6 cdt with two exceptions at 2 8 and 2 9 the data support the existence of a zoned hydrothermal system largely controlled by a network of paleofractures and slightly reworked by a late muscovite sulphide quartz stockwork the isotopic geothermometers record temperatures of ore deposition in the range of 200 300 c the d and 18 o values of the chlorites tourmalines and muscovites would indicate a large input of seawater in the dorlin hydrothermal fluids whereas the 18 o and 13 c of the carbonates and 34 s of pyrite provide evidence of a magmatic component resulting probably for a large part from leaching of the volcanic host rocks

global patterns of loss of life from landslides global loss of life from landslides is poorly quantifi ed a global data set of fatalities from nonseismically triggered landslides that resulted in loss of life between a d 2004 and 2010 permits for the fi rst time proper quantifi cation of impacts and spatial distributions in total 2620 fatal landslides were recorded worldwide during the 7 yr period of the study causing a total of 32 322 recorded fatalities these total numbers of landslides and victims are an order of magnitude greater than other data sets have indicated but analysis of the data suggests that it may still slightly underestimate the true human costs the majority of human losses occur in asia especially along the himalayan arc and in china this geographical concentration dominates the annual landslide cycle which peaks in the northern hemisphere summer months finally numbers of fatalities per event show a fat tailed power law distribution with the density of landslides being moderately correlated with the population density on a national basis

regional scale modelling of shallow landslides with different initiation mechanisms sliding versus liquefaction abstract rainfall induced landslides can result from different soil failure mechanisms each leading to slope instabilities characterized by varying times and depths of occurrence this paper discusses the performance of a physically based model for the spatially distributed analysis of landslide susceptibility the model allows the simultaneous assessment of two failure modes frictional slips and liquefaction induced flowslides the underlying mechanical formulation relies on stability principles for unsaturated soils while infiltration is treated as a transient process described by the richards equation the model has been applied to a series of landslides occurred in 1998 in campania italy using laboratory data to constrain the input parameters the analyses provide spatial and temporal patterns of landslide initiation consistent with field evidences in that they capture most of the affected landslide source areas and predict a temporal evolution of instabilities in agreement with reported failure times similar to available regional inventories the computed fraction of flowslides corresponds to 75 of the total unstable area while the resulting ratio between success and error indices is twice as large as those reported in other studies for the same site parametric analyses conducted by varying the hydraulic conductivity ks have pointed out a strong interplay between the dynamics of infiltration the mode of slope instability and the depth of failure in particular it has been found that low values of ks promote shallow flowslides due to moisture perching and high saturation at the surface while larger values of ks favor deeper infiltration fronts and frictional slips initiating at higher suction the comparison between these scenarios showed that simulations based on calibrated hydraulic properties encompass the widest distribution of failure depths thus reproducing more accurately the typical landslides of the site

tourmaline as a recorder of contrasting boron source and potential tin mineralization in the mopanshan pluton from inner mongolia northeastern china abstract abundant tourmaline occurs in the mopanshan pluton in inner mongolia of ne china and can be classified by its occurrence into four types nodular tourmalines nd type pegmatite pocket tourmalines pp type stockwork tourmalines sw type and vein tourmalines vt type all these tourmalines belong to the alkali group and are dravite schorl petrography and major elements data suggest that the nd and pp type tourmalines crystallized during the transition from late magmatic to early hydrothermal evolution of granite with all the components derived from the magma petrography and trace elements especially sr v cr ni ti data suggest that the sw and vt type tourmalines may form by the mixing of magmatic and country rocks components in the post magmatic hydrothermal environment due to the similar 11b of the sw type with the nd and pp type tourmalines variation

gully erosion susceptibility assessment by means of gis based logistic regression a case of sicily italy article i nfo article history this research aims at characterizing susceptibility conditions to gully erosion by means of gis and multivariate statistical analysis the study area is a 9 5 km 2 river catchment in central northern sicily where agriculture ac tivities are limited by intense erosion by means of field surveys and interpretation of aerial images we prepared a digitalmap of thespatial distribution of 260 gulliesinthestudy area inaddition fromavailable thematicmaps a 5 m cell size digital elevation model and field checks we derived 27 environmental attributes that describe the variability of lithology land use topography and road position these attributes were selected for their potential influence on erosion processes while the dependent variable was given by presence or absence of gullies within two different types of mapping units 5 m grid cells and slope units average size 2 66 ha the functional re lationships between gully occurrence and the controlling factors were obtained from forward stepwise logistic regression to calculate the probability to host a gully for each mapping unit in order to train and test the predictive models three calibration and three validation subsets of both grid cells and slope units were randomly selected results of validation based on roc receiving operating characteristic curves attest for acceptable to excellent accuracies of the models showing better predictive skill and more stable performance of the susceptibility model based on grid cells

badlands denudation hot spots the role of parent material properties on geomorphic processes in 20 years monitored sites of southern tuscany italy abstract some monitoring stations have been recording for 20 years the geomorphic processes acting on calanchi and biancane badlands located in the tyrrhenian side of central italy field monitoring was aimed at studying the dynamics of surface processes such as sheet rill and gully erosion shallow landsliding piping and tunneling considering their space time variability as a consequence of both natural factors and human pressure this paper shows the results of grain size geochemical and mineralogical composition of parent materials from upper orcia valley sites southern tuscany to further elucidate the role of their properties on processes acting on both bare and vegetated surfaces parent materials properties are discussed with respect to the initiation and development of different badlands processes in particular clay dispersivity at different depths in the sample sites is examined as a well known controlling factor of accelerated erosion thus providing some interesting clues for understanding the spatial variability of denudation rates in the considered badlands sites

talc mineralisation associated with soft hematite ore gongo soco deposit minas gerais brazil petrography mineral chemistry and boron isotope composition of tourmaline talc mineralisation occurs as hematite talc schist between soft hematite ore and dolomitic itabirite at gongo soco quadrilatero ferrifero of minas gerais brazil the hematite talc schist and soft hematite have a prominent tectonic foliation of tabular hematite tabular hematite without preferential orientation is superimposed on the tectonic foliation the talcose schist is enriched in f and has a constant fe s ratio electron microprobe analyses indicate trace amounts of s in different generations of hematite the whole rock fe s ratio possibly represents sulfate s from hematite hosted fluid inclusions fluid inclusions in foliation overprinting hematite and chlorite geothermometry from talcose rocks suggest respectively temperatures from 200 c to 300 c tourmaline a rarely observed mineral in the hematite talc schist belongs to the alkali group and falls in the dravite compositional field boron isotope determinations of tourmaline crystals using secondary ion mass spectrometry vary from 20 to 12 11b this compositional isotopic range and the tourmaline chemical composition suggest a meta evaporitic origin a non marine evaporitic setting is the most likely source of acidic highly oxidising fluids which resulted in the abundant f bearing talc and the presence of otherwise immobile ti in hematite oxidising brines were channelled along shear zones and converted dolomitic itabirite into the gongo soco soft hematite and the talc mineralisation the latter is envisaged as the hydrothermal wall rock alteration of dolomitic itabirite which gave rise to the soft hematite ore

correlation of satellite image time series for the detection and monitoring of slow moving landslides abstract slow moving landslides are widespread in many landscapes with significant impacts on the topographic relief sediment transfer and human settlements their area wide mapping and monitoring in mountainous terrain however is still challenging the growing archives of optical remote sensing images offer great potential for the operational detection and monitoring of surface motion in such areas this study proposes a multiple pairwise image correlation mpic technique to obtain a series of redundant horizontal displacement fields and different multi temporal indicators for a more accurate detection and quantification of surface displacement the technique is developed and tested on a series of monoscopic and stereoscopic pleiades satellite images at a test site in the south french alps empirical tests confirm that mpic significantly increased detection accuracy f measure 0 85 and that the measurement error can be reduced by averaging velocities from all pair combinations covering a given time step i e when stereo pairs are available for at least one date the derived inventory and displacement fields of 169 slow moving landslides show a positive relationship between the landslide size and velocities as well as a seasonal acceleration of the largest landslides in response to an increase in effective precipitation the processing technique can be adapted to better exploit increasingly available time series from a variety of optical satellites for the detection and monitoring of landslide displacement

modeling sediment yields in italian catchments abstract sediment yield observations derived from 40 long term sedimentation records in italian reservoirs were used to calibrate and validate the spatially distributed sediment delivery model watem sedem using the best data available at national scale the sediment yield data set includes records from semi natural catchments in northern italy as well as agricultural and semi natural basins in central and southern italy the average size of the catchments is 150 km2 with mean annual sediment yields ranging from 0 20 to 20 t ha 1 year 1 watem sedem estimates mean annual sediment fluxes to permanent river channels depending on the local transport capacity the sediment flux is detachment limited or transport limited the optimal transport capacity parameters for italian conditions were derived via automatic calibration procedures a global model calibration procedure taking into account all catchments in the dataset led to an overestimation of the sediment yield for the mountain catchments and an underestimation for the non mountain catchments sediment yield estimates are more reliable when calibration procedures are applied separately for mountain and non mountain catchments the model performance of watem sedem is rather poor in the mountain catchments r 0 25 which suggests that the model structure is too simplified to come to an adequate description of the sediment fluxes the model performance for the non mountain catchments which are more important from a management point of view is significantly better r 0 51 considering the fact that data layers with a 75 75 m resolution were used the results are encouraging the further development and application of spatially distributed sediment yield models at regional and national scale levels

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

spatial and temporal analysis of a global landslide catalog abstract landslide inventories are critical to support investigations of where and when landslides have happened and may occur in the future however there is surprisingly little information on the historical occurrence of landslides at the global scale this paper presents a new publicly available global landslide catalog glc which is based on media reports online databases and other sources this database is currently available at http ojo streamer herokuapp com the 5741 points in the glc provide a foundation for evaluating spatial and temporal trends in landslide activity from 2007 to 2013 globally landslides were reported most frequently from july to september most events occurred in asia north america and southeast asia in contrast fewer than 5 of the fatalities were reported in north america suggesting a significant amount of under reporting in other regions as well as potential discrepancies between developing and developed regions reported landslide events were also compared to satellite based precipitation estimates from the tropical rainfall measuring mission trmm to evaluate the co occurrence of extreme precipitation and landslide activity of the 3550 points considered in a subset of the glc approximately 60 of the reported landslides have daily precipitation exceeding the 95th percentile of precipitation calculated over a 14 year trmm record for the same location this study also investigated how the recurrence interval of extreme precipitation corresponded to some of the most catastrophic landslide events in spite of several reporting and cataloging biases spatial and temporal analysis of the glc suggests that it is a valuable database for characterizing global patterns of landslide occurrence and evaluating relationships with extreme precipitation at regional and global scales