predictive modeling of slope deposits and comparisons of two small areas in northern germany abstract methods for correct quantitative comparison of several terrains are important in the development and use of quantitative landscape evolution models and they need to introduce specific modeling parameters we introduce such parameters and compare two small terrains with respect to the link slope valley for the description of slope deposits colluvium in them we show that colluvium accumulation in small areas cannot be described by linear models and thus introduce non linear models two small areas perdoel 0 29 ha and bornhoved 3 2 ha are studied slope deposits in the both are mainly in dry valleys with a total thickness m total up to 2 0 m in perdoel and up to 1 2 m in bornhoved parent materials are mainly pleistocene sands aged 30 kyr bp exponential models of multiple regression that use a 1 m lidar dem digital elevation model explained 70 93 of spatial variability in m total parameters dh 12 and dv 12 of horizontal and vertical distances are introduced that permit to characterize and compare conditions of colluvium formation for various terrains the study areas differ 3 7 times by the parameter dh 12 that describes a horizontal distance from thalwegs at which m total diminishes 2 72 times dh 12 is greater in bornhoved 29 7 m than in perdoel 8 12 m we relate this difference in dh 12 to the distinction between types of the link slope valley a regional type if catchment area of a region outside a given small area plays an important role and a local type when accumulation of colluvium from valley banks within a small area is of more importance we argue that the link slope valley is regional in perdoel and local in bornhoved peaks of colluvium thickness were found on thalwegs of three studied valleys by both direct measurements in a trench and model surfaces of m total a hypothesis on the formation mechanism of such peaks is discussed the parameter dv 12 describes a vertical distance from a peak of colluvium thickness along valley bottom at which m total diminishes 2 72 times values of this parameter differ 1 4 times for the study areas dv 12 is greater in perdoel 3 0 m than in bornhoved 2 1 m thus indicating more sharp peaks of m total in bornhoved exponential models allow construction of predictive maps of buried pleistocene surfaces for both the terrains and calculate colluvium volumes with an error 4 2 for perdoel and 7 1 for bornhoved comparisons of buried and present surfaces showed that the latter are more smoothed more strongly in valleys where flow branching is increased

changes in sulfides and platinum group minerals with the degree of alteration in the roby twilight and high grade zones of the lac des iles complex ontario canada the lac des iles complex hosts pd deposits with unusually high pd pt and pd ir ratios these high ratios have been attributed to the introduction of pd by late magmatic hydrothermal fluids the presence of hydrous silicates and low temperature sulfide mineral assemblages has been advanced as evidence for fluid overprint this idea has been investigated by documenting the change in silicate sulfide and platinum group mineralogy and texture in samples from the deposit ranging from fresh gabbronorite to extensively altered chlorite actinolite schist in addition whole rock analysis combined with laser ablation analysis of the sulfides was used to determine which phase controlled each of the pge in fresh gabbronorite the sulfide assemblage is igneous pyrrhotite pentlandite chalcopyrite and pd is present mainly in pentlandite and kotulskite pdte inclusions associated with the sulfide minerals all other pge except pt are present in solid solution in pyrrhotite and pentlandite platinum is present as sperrylite ptas2 and montcheite ptte2 inclusions associated with the sulfide minerals these observations suggest that the pge in the fresh gabbronorite were all collected by magmatic sulfide liquid in the chlorite actinolite schist the sulfide assemblage is a low temperature assemblage consisting of chalcopyrite pyrite millerite a minor amount of palladium is present in millerite but most is present as bismuth rich kotulskite and pd arsenides both of which are associated with hydrous silicate all other pge except pt are hosted by pyrite a minor amount of pt is present in pyrite but most is found as sperrylite and montcheite associated with hydrous silicate minerals the pyrite could have formed by fe loss from pyrrhotite resulting in the pyrite inheriting os ir ru and rh and fe loss from pentlandite to form millerite resulting in the millerite inheriting some pd the pge concentrations of the whole rock show there is no direct correlation between the sulfide assemblage the degree of alteration of the silicate minerals and ore grade thus although fluids have clearly altered the sulfide silicate and platinum group mineralogy and their textures it is not clear that these fluids have changed the pge content of the rocks

investigations on buried soils and colluvial layers around bronze age burial mounds at bornhoved northern germany an approach to test the hypothesis of landscape openness by the incidence of colluviation the idea of open landscapes around prehistoric burial mounds is founded on their topographical position and findings of plaggen clots within the hills at some sites we have investigated the surroundings of four bronze age burial mounds at bornhoved northern germany to test whether this assumed landscape openness enabled soil erosion and colluviation or not the soils and colluvia within a watershed below the burial mounds were investigated in six large exposures and additional auger cores the chronology is based on 21 ams radiocarbon dates complemented by charcoal analysis and the content of selected heavy metals in the sediments colluvia were deposited in the late neolithic 2500 2200 cal bc roman emperor times 250 400 cal ad mediaeval times ad 600 1400 and modern times ad 1800 2000 our findings indicate that the soil surfaces were protected against soil erosion during the phase of bronze age funeral use cal 1800 600 bc either the prehistoric gravediggers practised a well suited form of pasturing to keep the scenery open or the surroundings of the burial mounds were forested at the time of funeral use the results of charcoal analysis reflect the known succession of woody taxa in the region and underline the great potential of anthracology on colluvial layers for palaeoenvironmental reconstructions apart from traditional archives such as lakes or mires bulk radiocarbon dating of organic matter overestimated the time of burial of a buried soil as well as the time of deposition of colluvial layers considerably

formation and modification of metastable intermediate sodium potassium mica paragonite and muscovite in hydrothermally altered metabasites from northern wales

on the mechanisms for low sulfide high platinum group element and high sulfide low platinum group element mineralization in the eastern gabbro coldwell complex canada evidence from textural associations s se values and platinum group element concentrations of base metal sulfides

systematic variations in magmatic sulphide chemistry from mid ocean ridges back arc basins and island arcs abstract immiscible sulphide liquids preserved as magmatic sulphide globules are hosted in igneous rocks of highly variable composition formed during magmatic processes at different tectonic settings here we report on compositional in situ data of magmatic sulphides from mid ocean ridge back arc and island arc magmatic systems iron ni rich monosulphide solid solutions mss that mainly consist of pyrrhotite and pentlandite are the dominant phases in magmatic sulphide globules in subduction related magmas mss are most abundant in relatively evolved melts and characterised by low ni and high fe contents as well as low ni cu ratios 1 thus mss chemistry varies systematically in lavas from the different tectonic settings in terms of their fe ni distribution and ni cu ratio the observed mineralogical and chemical variations between mss from the different settings reflect early s saturation accompanied by olivine fractionation along mid ocean ridges compared to later stage s saturation in arc systems associated with fe ti oxide fractionation these systematics are probably related to the relatively oxidised character of subduction zone magmas opposed to more reduced mid ocean ridge melts large ni cu variations in mss from the same locality and in individual samples suggest that s saturation is a multistage or continuous process leading to inclusions of magmatic sulphides that represent different fractionation stages in the ascending magma

platinum group element gold silver and base metal distribution in compositionally zoned sulfide droplets from the medvezky creek mine noril sk russia concentrations of ag au cd co re zn and platinum group elements pge have been determined in sulfide minerals from zoned sulfide droplets of the noril sk 1 medvezky creek mine the aims of the study were to establish whether these elements are located in the major sulfide minerals pentlandite pyrrhotite chalcopyrite and cubanite to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution mss nickel cu ag re os ir ru rh and pd were found to be largely located in the major sulfide minerals in contrast less than 25 of the au cd pt and zn in the rock was found to be present in these sulfides osmium ir ru rh and re were found to be concentrated in pyrrhotite and pentlandite palladium and co was found to be concentrated in pentlandite silver cd and zn concentrations are highest in chalcopyrite and cubanite gold and platinum showed no preference for any of the major sulfide minerals the enrichment of os ir ru rh and re in pyrrhotite and pentlandite exsolution products of mss and the low levels of these elements in the cubanite and chalcopyrite exsolution products of intermediate solid solution iss support the mss crystal fractionation model because os ir ru rh and re are compatible with mss the enrichment of ag cd and zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid gold and pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides bismithides and alloys during pentlandite exsolution pd appears to have diffused from the cu rich portion of the droplet into pentlandite

the formation of pt ir alloys and cu pd rich sulfide melts by partial desulfurization of fe ni cu sulfides results of experiments and implications for natural systems abstract we propose a model of high temperature formation of platinum group element pge alloys from base metal sulfides subjected to decreasing sulfur fugacity f s 2 for this purpose we experimentally investigated the effect of partial desulfurization of monosulfide solid solution mss with variable ni and cu contents on the distribution behaviour of pt ir and pd at 1000 c we partially removed sulfur from the pge bearing mss using the tube in tube technique and pyrrhotite as an f s 2 buffer we found that mss undergoing s loss can produce 1 pt and ir exsolution from the mss matrix in the form of pge bearing alloys 2 partial melting of the cu ni bearing mss to form fe rich mss cu ni pd rich sulfide liquid and fe ir pt alloy both of these processes are geologically important the partial melting of the s depleted sulfides could explain the presence of two types of sulfides found in the mantle mss dominated sulfides and s poor sulfides consisting mainly of pentlandite and chalcopyrite we also suggest that the cu ni pd rich liquid formed by partial melting of the sulfides could migrate away from the mss and fe ir pt alloys thus spatially decoupling ir pt and cu pd as observed in reefs and mantle nodules in addition the formation of pge alloys in response to the desulfurization processes potentially could occur 1 after pressure falls during transport of the basalt magma with entrained sulfide droplets 2 after sulfur removal by s undersaturated melts or fluids from pge enriched sulfide proto ore 3 after degassing of the sulfide droplets occurring in a sub volcanic chamber and 4 as a result of sulfide interaction with chromite

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

detection of land surface memory by correlations between thickness of colluvial deposits and morphometric variables abstract some morphometric variables store information about past land surfaces longer than others this property of morphometric variables is recognised as land surface memory slope deposits soils and vegetation also have this memory in this study a memory effect was quantitatively detected by spearman correlations between thickness of colluvium and morphometric variables of the modern land surface during long term sedimentation the sign of horizontal curvature kh may be inverted from minus to plus suggesting that locations with positive kh values are not accumulation zones however the thickness of colluvial deposits at such locations in our study area indicates sediment accumulation the sign of minimal curvature kmin tends to be more stable and remains negative this difference provides the stronger correlation of colluvial layer thickness with kmin than with kh the strongest correlation was found for total thickness of the colluvial deposits of the neolithic and iron age with kmin 0 84 the correlation with kh was weaker 0 71

palaeoclimatic indicators in soils buried under archaeological monuments in the eurasian steppe a review the russian experience of the local reconstruction of the eurasian steppe climate during the last 5000 years based on geoarchaeological approaches is reviewed examples of traditional palaeoclimatic reconstructions in russia based on organic matter highly soluble salts and gypsum content and location of salts and gypsum horizons in the profile of buried soils are given pedogenic carbonate as a palaeoclimatic indicator is considered the possibilities of the quantitative reconstruction of the palaeoprecipitation based on magnetic properties of buried soils are observed the innovative approach of palaeoclimatic reconstruction based on soil microbiology methods is reviewed the problem of temporary transformation of palaeoclimatic indicators in buried soils is shown a methodology for the interpretation of palaeoclimatic indicators of buried soils for a local palaeoclimatic reconstruction is given

geology sulfide mineralogy and petrogenesis of the angstberg ni cu pge sulfide mineralization lausitz block bohemian massif germany a potential ni cu exploration target in central europe abstract germany s largest known magmatic ni cu pge sulfide enrichment is associated with the gabbroic angstberg intrusion that is one of several small scaled ni cu sulfide bearing intrusions in the northern bohemian massif central european variscan belt the intrusions are part of a middle devonian to early carboniferous mafic ultramafic magmatic system that emplaced within cadomian granodiorites of the lausitz block the angstberg intrusion represents an exposed sub vertical dike like body 320 60 m in plan view and comprises olivine gabbronorite olivine gabbro gabbro olivine hornblende gabbro and hornblende pyroxene gabbro the hornblende bearing and hornblende free lithologies originate from at least two variably fractionated basaltic parental magma batches which differ in their ti lree hree and volatile contents fractionation probably took place in deeper seated sections of the magmatic system possibly within staging magma chamber s overall enriched incompatible trace element patterns suggest that the angstberg lithologies are linked with intra plate magmatism likely associated with a transtensional setting in the course of the variscan orogeny the previously suggested devonian age of the intrusion is confirmed by an 40ar 39ar biotite age of 373 4 0 9 ma for the olivine gabbro the magmatic sulfide mineralization is predominated by disseminated sulfides that are hosted in the olivine richest parts of the olivine gabbronorite and olivine hornblende gabbro lithologies in addition some sulfide matrix breccias up to 70 modal sulfides occur directly on the footwall contact of the intrusion to granodiorite both mineralization types are characterized by a predominance of pyrrhotite over pentlandite and chalcopyrite with minor secondary violarite and pyrite and accessory pge au and ag phases nickel rich bismuthotellurides of the melonite merenskyite solid solution series and froodite are the most common platinum group minerals disseminated sulfides are characterized by high ni moderate cu and low pt and pd tenors 4 9 wt ni 2 6 wt cu 200 800 ppb pt 200 1000 ppb pd sulfide matrix breccias feature comparable ni but lower cu pt and pd tenors 4 6 wt ni 0 3 1 wt cu 10 100 ppb pt 40 200 ppb pd fractional crystallization and wall rock assimilation of granodiorite are regarded as key factors for sulfide saturation in the magmas associated with the angstberg intrusion sulfur isotope compositions of pyrrhotite pentlandite chalcopyrite assemblages 1 4 to 0 2 vcdt propose a mantle origin of s whereas addition of crustal s cannot be completely ruled out as the s isotope values of the sulfides overlap with those of the granodiorite 7 to 4 vcdt olivine and sulfide textures suggest that disseminated sulfides likely originate from sulfide melts that were entrained in an olivine rich crystal mush during magma rise to upper levels the sulfide matrix breccias also resulted from entrained sulfide melts or from gravity driven downward percolation of sulfide melts from stratigraphically higher now eroded levels in both cases the formation of sulfide matrix breccias most likely was amplified by in situ thermomechanical erosion of the granodioritic wall rock caused by flash boiling of thermally dehydrating biotite despite spatial limitations of the mineralized zones and limited information about the architecture of the intrusions in the northern bohemian massif the angstberg intrusion as well as other neighboring magmatic sulfide occurrences may represent a new exploration target for ni and cu in central europe

mineralogy of the hse in the subcontinental lithospheric mantle an interpretive review abstract the highly siderophile elements hse os ir ru rh pt pd re au exist in solid solution in accessory base metal sulfides bms as well as nano to micron scale minerals in rocks of the subcontinental lithospheric mantle sclm the latter include platinum group minerals pgm and gold minerals which may vary widely in morphology composition and distribution the pgm form isolated grains often associated with larger bms hosted in residual olivine located at interstices in between peridotite forming minerals or more commonly in association with metasomatic minerals pyroxenes carbonates phosphates and silicate glasses in some peridotite xenoliths the pgm found inside residual olivine are mainly os ir and ru rich sulfides and alloys in contrast those associated with metasomatic minerals or silicate glasses of peridotite xenoliths consist of pt pd and rh bonded with semimetals like as te bi and sn nanoscale observations on natural samples along with the results of recent experiments indicate that nucleation of pgm is mainly related with the uptake of hse by nanoparticles nanominerals or nanomelts at high temperature 900 c in both silicate and or sulfide melts regardless of the residual or metasomatic origin of their host minerals a similar interpretation can be assumed for gold minerals our observations highlight that nanoscale processes play an important role on the ore forming potential of primitive mantle derived magmas parental to magmatic hydrothermal deposits enriched in noble metals the metal inventory in these magmas could be related with the physical incorporation of hse bearing nanoparticles or nanomelts during processes of partial melting of mantle peridotite and melt migration from the mantle to overlying continental crust

textural and compositional evidence for the formation of pentlandite via peritectic reaction implications for the distribution of highly siderophile elements the distribution of highly siderophile elements is used in the study of a wide variety of geological topics from planet formation and evolution to the formation of ore deposits under mantle and crustal conditions these elements behave as highly chalcophile elements and pentlandite pn is an important host for most of these elements therefore understanding how pn forms is important to understanding the processes that control these elements the classic model for the formation of pn is that below 650 c the high temperature sulfides monosulfide solid solution mss and intermediate solid solution iss are no longer stable and exsolve into pyrrhotite po pn and chalcopyrite ccp however pn has been shown to be the main host of pd in many ore deposits and given that pd is incompatible with both mss and iss this observation is inconsistent with the exsolution model furthermore experimental work has shown that pn can form by peritectic reaction between mss and fractionated sulfide liquid to date this type of pn has not been reported in natural samples in our study of chalcophile element concentrations in pn from iconic magmatic ni cu platinum group element deposits we observed three textures of pn contact pn in between po and ccp granular pn included within ccp or po and flame pn included within po the contact pn shows zonation in mo rh ru re os and ir with these elements being enriched toward the po contact and depleted toward the ccp contact in some cases pd displays a zonation antithetical to that of these elements in this contribution we propose that the contact pn formed via the peritectic reaction described above and inherited mo ru rh re os and ir from the mss whereas pd was contributed from the fractionated sulfide liquid we expect that this type of pn should be present wherever mss and fractionated sulfide liquid remained in contact

the geology and geochemistry of the waterfall gorge section of the insizwa complex with particular reference to the origin of the nickel sulfide deposits the jurassic aged mafic rocks from the waterfall gorge section of the insizwa layered complex transkei range in composition from olivine gabbro and picrite basal zone through a series of gabbros central zone to monzonites roof zone the compositional data for the mineral phases olivine plagioclase bronzite and augite show significant features in the basal gabbro the trend in compositional variation is the reverse of that seen in the central zone of the intrusion and olivines from the picrite unit are the most forsteritic in the intrusion but they are depleted in ni compared to olivines from the basal gabbro and central zone the data for olivines from the picrite unit at tabankulu exhibit a similar but more significant degree of depletion mineral compositional and whole rock geochemical data for the basal olivine gabbro suggest that olivine control is primarily responsible for the compositional variation in this unit at insizwa however to account for the upward increase in the forsterite content of the cumulus olivine at the base the intrusion of successively less fractionated batches of a low mgo magma is suggested we suggest that the depletion of the olivines in ni can be attributed to the equilibration of the parent magma with sulfide and we show that these data are consistent with experimental distribution coefficient data for ni between olivine and sulfide permitting broad constraints to be placed on the grade as well as the tonnage and location of the ore extrapolation of these conclusions to the tabankulu intrusion suggest that the highly ni depleted olivines of the picrite have equilibrated with a magma from which a particularly high proportion of sulfide has segregated geophysical data fail to detect a massive orebody at the base of the intrusion though several small bodies may exist it is suggested that saturation may have occurred at depth and only a small amount of sulfide has been transported to the surface in the picrite and concentrated in depressions at the base of the intrusion massive and disseminated magmatic ni sulfide mineralization is confined to the lower basal zone and shows a consistent fractionation into pyrrhotite pentlandite rich ore at the base and chalcopyrite rich ore at the top in both massive sheets and globular ore the cause of sulfur saturation cannot be attributed to the reduction of the solubility of sulfur in the magma by increasing the sio 2 concentration contamination despite the close association of the ore with granophyric segregations in the basal olivine gabbro indeed the major and trace element data argue strongly against wholesale assimilation of crust at any stage in the production of the basal gabbro

experimental evaluation of liquid immiscibility in a portion of the system fe ni cu s using high gravitational acceleration experimental results reported by ballhaus et al 2001 suggest there may be some natural sulfide liquid compositions in equilibrium with primitive mafic magmas that encounter a field of immiscibility at superliquidus conditions in this communication we present results of static and high acceleration experiments done using one of the bulk compositions for which immiscibility is reported their ms 11 as well as mixtures of the alleged conjugate melts at all conditions investigated melts quenched to a homogeneous distribution of quench phases with no evidence for compositional separation over the length scale of the sample these results indicate that the ms 11 composition produced a homogeneous liquid during the experiment and therefore we could not verify the two phase field reported by ballhaus et al 2001 we suggest caution when evoking sulfide liquid immiscibility as a differentiation mechanism during magmatic sulfide evolution

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

petrology and crystallization history of multiphase sulfide droplets in a mafic dike from uruguay implications for the origin of cu ni pge sulfide deposits sulfide blebs in a mafic dike belonging to the uruguayan dike swarm replicate at a small scale many features observed in larger platinum group element enriched nickel copper sulfide deposits such as in sudbury and noril sk these blebs formed by the crystallization of droplets of immiscible sulfide liquid form 1 cm sized ovoid geopetal structures with pyrrhotite and pentlandite at the base chalcopyrite and cubanite at the top and titaniferous magnetite at the margins magnetite crystallized first followed by nickel and iron rich monosulfide solid solution which sank to the bottom of the droplets and from which pyrrhotite and pentlandite subsequently exsolved the remaining copper rich liquid in the upper part of the droplets crystallized to form an intermediate solid solution from which chalcopyrite and cubanite subsequently exsolved the final extremely evolved cu fe s rich pd sn pb mo ag bi te and sb bearing liquid crystallized as 10 to 20 sized veinlets filling fractures in the magnetite and adjacent silicate minerals the veinlets crossing the magnetite often terminate in 100 m sized subrounded globules at the contact of the magnetite and the surrounding silicate minerals indicating a direction of veinlet filling away from the center of the blebs textural evidence in the blebs illustrates that as crystallization proceeded and the immiscible sulfide liquid droplets within the dike sank a distance of less than 1 mm relative to the adjacent silicate onto already partially crystallized silicate minerals the sulfide liquid surrounded and resorbed the already solid magnetite grains at the top of the blebs magnetite grains were isolated above the sulfide liquid and partially surrounded by quartz plagioclase and amphibole an assemblage representing a late stage magma that had been drawn into the space created above the droplets as they sank and which is more evolved than that of the surrounding host dike the location of the blebs within the dike isolated from influences external to the dike indicates both that the fracture filling by evolved immiscible cu rich sulfide liquid is related to crystallization processes rather than later tectonic events and that the bismuth tellurium and antimony have a late magmatic origin associated with crystallization of the immiscible sulfide liquid

sulphide mineral evolution and metal mobility during alteration of the oceanic crust insights from odp hole 1256d fluxes of metals during the hydrothermal alteration of the oceanic crust have far reaching effects including buffering of the compositions of the ocean and lithosphere supporting microbial life an