morphotectonics in the central east region of south brazil implications for catchments of the lava tudo and pelotas rivers state of santa catarina abstract the catchments of the lava tudo and pelotas rivers are located on the eastern edge of the parana sedimentary basin central east of the brazilian state of santa catarina this region comprises mesozoic volcanic rocks from the parana large igneous province lip deformed by cenozoic joints and faults morphometric analysis carried out using remote sensing and structural data showed the influence of tectonics on the geomorphological framework of the target catchments which therefore provided a morphological characterization of the area deformation of the topography was determined from changes in topographic surface drainage basin asymmetries disturbances on longitudinal profiles and anomalies in drainage patterns associated with ne sw and nw se faults derived from reactivation of the proterozoic basement as well as other neotectonically formed structures trending mainly n s and e w the asymmetry recognized in the studied catchments results from tectonic tilting marked by oblique ne sw faults the deformation pulses resulted in the dismantlement of an extensive local paleogene planation surface also known as the sul americana surface in the southeastern and southern regions of brazil morphotectonic evolution has been associated with tectonic pulses that took place between the upper cretaceous and upper pleistocene

tectonic geomorphology of the southeastern mississippi embayment in northern mississippi usa we analyzed drainage basin geometry in part of the southeastern mississippi embayment near the new madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism toward this goal a field of drainage basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure lithofacies seismicity remotely sensed lineaments and major drainage divides transverse topographical drainage basin asymmetry t index results define geomorphic domains in northern mississippi 33 to 35 n 88 5 to 90 25 w that may reflect deep crustal blocks bounded by active faults or flexures t index measurements a proxy for lateral stream migration of more than 4500 second order drainage basins produced a two dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains some domain boundaries correspond to mapped faults of two paleozoic fault systems in our study area the northeast striking mississippi valley graben system and the northwest striking ouachita thrust belt and foreland faults several other prominent domain boundaries may be previously unmapped faults flexures parallel to these systems this interpretation is supported by satellite image analysis of the northeastern study area which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain

brazilian structural provinces an introduction abstract the territory of brazil coincides almost entirely with the south american platform the crystalline core of the continent its basement is composed of ancient metamorphic and igneous rocks and it has not suffered any tectonic regeneration since the beginning of the phanerozoic sedimentary rocks with almost horizontal bedding cover this crystalline basement this latter shows ages as old as early precambrian although ages between 500 and 1000 m y are conspicuously frequent the cratonic areas became consolidated more than 1700 m y ago whereas the fold belts formed essentially between 500 and 1700 m y ago the sedimentary cover accumulated from the early silurian in three large intracratonic basins until the platform became completely stabilized a late jurassic to early cretaceous reactivation caused by the break up of the ancient gondwana continent created another basin sequence chiefly along the atlantic continental margin based on the nature of the crystalline basement rocks and the sedimentary cover ten structural provinces can be distinguished 1 rio branco province in the north of the country occupied by the guyana shield and still only poorly known with an important fold belt developed during the so called transamazonian cycle 2000 200m y with high grade metamorphic rocks and only slight influence of later events 2 tapajos province in central brazil corresponding to the amazonas or guaporecraton showing chiefly precambrian crystalline rocks and behaving as an cratonic area during the phanerozoic 3 sa o francisco province located on the atlantic shield with its basement covered by rocks of different ages chiefly affected by the brasiliano cycle between 1000 and 500 m y and constituting another cratonic area 4 tocantins province between the amazonas and sa o francisco cratons with the oldest rocks in its centre ages over 2600 m y and at the eastern and western borders metamorphic sequences of various fold belts and almost no phanerozoic deposits 5 mantiqueira province located along the southern part of the atlantic coast affected chiefly by the brasiliano folding cycle 6 borborema province in the northeast brazilian fold belt affected by the brasiliano cycle in a very complex way and with important faulted zones it was reactivated in phanerozoic times when also sedimentary covers accumulated 7 amazonas province represented by the amazonas sedimentary basin syneclise and subdivided into four parts by three important arcs 8 parnaiba province coinciding with the piauf maranha o syneclise and filled with a rather thick sedimentary sequence 9 paranaprovince the sedimentary basin of southern brazil in which the well known late paleozoic glaciation features are found and which possesses an extensive cover of basaltic rocks of late jurassic to early cretaceous age 10 coastal province and continental margin the youngest structural unit developed during the separation of the continent and represented by rift valleys and coastal basins filled with mesozoic cenozoic deposits of various kinds

nature of the lithosphere across the variscan orogen of sw iberia dense wide angle seismic reflection data 1 two wide angle seismic transects have been acquired across the sw iberian massif they crossed three major geological zones south portuguese zone ossa morena zone and central iberian zone with their tectonic contacts and the pyrite belt being of greatest interest a total of 690 digital seismic recording instruments 650 texans and 40 reftek 3 component units from the iris passcal instrument pool were used the transects a and b are each approximately 300 km long and consist of 3 and 6 shot points respectively with an approximately 60 km shot point interval the charge sizes range from 1000 kg at the edges to 500 kg at the center these recently acquired experiments were designed to provide velocity constraints on the lithosphere and to complement the previously acquired normal incidence seismic profile iberseis both data sets are part of the sw iberia project which was developed within the europrobe program and designed to address fundamental questions about the nature and dynamics of the variscan lithosphere the acquisition parameters provide closely spaced wide angle seismic images of the lithosphere beneath sw iberia in transect a the station spacing was on average 400 m while along transect b the receiver spacing was approximately 150 m because of this close trace spacing the lateral continuity of the seismic arrivals is greatly improved frequency analysis revealed that the recorded events feature relatively low frequencies 6 25 hz after processing the shot records show high amplitude and well defined arrivals the interpreted pmp arrival located at approximately 11 s normal incidence traveltime is characterized by high amplitude and relatively low frequency 6 12 hz a well defined pn arrival appears at offsets beyond 120 km at far offsets greater than 180 km an upper mantle reflection is observed furthermore within the upper crust the shots records feature a relatively high velocity arrival located at 4 5 s normal incidence traveltime the analysis of this arrival indicates that it probably corresponds to the top of the iberian reflective body identified in the iberseis deep seismic profile the velocity models obtained by forward modeling show a complex crust especially in the middle crust the velocity models are the most detailed ones that have been produced in the area and contain a large amount of new features that are relevant to the understanding of the composition of the crust and upper mantle beneath the zone the velocity depth functions derived from the velocity models have higher middle crustal velocities than the average in other continental areas a comparison between laboratory seismic velocity measurements and the velocities of the models was carried out in order to estimate the crustal and the upper mantle composition results indicate that the high middle crust velocities correspond to rocks of a mafic composition the combined data set reveals new aspects related to the lithospheric evolution of this transpressive orogen and allows us to attempt an interpretative cross section of the upper lithosphere in sw iberia

migration of contaminants in groundwater at a landfill a case study 3 tritium as an indicator of dispersion and recharge abstract since the beginning of the era of major atmospheric tests of nuclear weapons in 1953 rain and snow has contained concentrations of 3 h that have been above the natural levels that existed prior to 1953 as a consequence 3 h now serves as an identifier or tracer of post 1952 water in groundwater flow systems in this study the distribution of 3 h in and near the contaminant plume at the borden landfill was determined by analysis of samples from multilevel point samplers and from bundle piezometers the contaminant plume which was delineated using cl and so 2 4 patterns was found to contain a large zone of tritiated water and a smaller zone with no detectable 3 h much of the zone of untritiated water exists in the frontal segment of the plume this is consistent with the fact that landfilling operations at the site began in 1940 and that as the plume developed in the period from 1940 to 1952 any natural 3 h that may have existed in the plume during this period is now below the detection level an estimate of the 3 h concentrations in water that has recharged the aquifer beneath the landfill was developed using the nearly continuous record for 3 h in precipitation at ottawa ontario with comparisons to less frequent data from other sampling stations the ottawa record indicates that during the years in the 1960 s in which peak 3 h concentrations occurred values of thousands of tu in precipitation were common and levels of many hundreds of tu or higher existed almost continuously in the zone of tritiated water in the plume and in the tritiated zone in the natural groundwater up and downgradient of the plume all of the sample points except three in the plume had concentrations below 150 tu two of these three have concentrations below 290 tu the general occurrence in the aquifer of 3 h levels that are much below the high levels that existed in precipitation prior to the 1970 s is attributed to radioactive decay and to the effect of longitudinal hydrodynamic dispersion that has caused mixing of the tritiated groundwater with older untritiated water an analytical solution to the one dimensional form of the advection dispersion equation was used with the method of superposition to simulate the distribution of 3 h along the central flow path in the contaminant plume simulated 3 h distributions using longitudinal dispersivity values in the range of 30 60 m gave 3 h distributions similar to the field values although the longitudinal dispersivity range of 30 60 m is far above the range reported from laboratory experiments on sand and although it is much above the range obtained in a small scale tracer test at the borden site it is within the range reported in the literature based on the calibration of models to regional contaminant migration patterns in glaciofluvial or alluvial aquifers the strong longitudinal dispersion is believed to be caused by mixing between the ubiquitous layers of fine and medium grained sand and silty sand that comprise the aquifer an estimate of the average annual rate of recharge that has contributed to the groundwater zone beneath the landfill during the bomb tritium period was obtained by comparing the input of 3 h to an area segment of the landfill with the 3 h contained within a groundwater flow tube leading from the specified area along the centerline of the contaminant plume this approach yielded a minimum average annual recharge rate of 50 with the main cause of uncertainty being the extent of the area in which recharge occurs

world class ni cu pge deposits key factors in their genesis magmatic ni cu sulfide deposits form as the result of segregation and concentration of droplets of liquid sulfide from mafic or ultramafic magma and the partitioning of chalcophile elements into these from the silicate melt sulfide saturation of a magma is not enough in itself to produce an ore deposit the appropriate physical environment is required so that the sulfide liquid mixes with enough magma to become adequately enriched in chalcophile metals and then is concentrated in a restricted locality so that the resulting concentration is of ore grade the deposits of the noril sk region have developed within flat elongate bodies 15 2 0 2 km that intrude argillites evaporites and coal measures adjacent to a major trans crustal fault and immediately below the centre of a 3 5 km thick volcanic basin studies of the overlying basalts have shown that lavas forming a 500 m thick sequence within these have lost 75 of their cu and ni and more than 90 of their pge overlying basalts show a gradual recovery in their chalcophile element concentrations to reach normal values 500 m above the top of the highly depleted zone the ore bearing noril sk type intrusions correlate with those basalts above the depleted zone that contain normal levels of chalcophile elements the high proportion of sulfide 2 10 wt associated with the noril sk type intrusions the high pge content of the ores the extensive metamorphic aureole 100 400 m around the bodies and the heavy sulfur isotopic composition of the ores 8 12 34s are explicable if the ore bearing bodies are exit conduits from high level intrusions along which magma has flowed en route to extrude at surface the first magma to enter these intrusions reacted with much evaporitic sulfur at a low r value and thus gave rise to sulfides with low metal tenors successive flow of magma through the system progressively enriched the sulfides in the conduits losing progressively less of their chalcophile metals and thus accounting for the upward increase in metals in successive lava flows above the highly depleted flows the voisey s bay deposit lies partly within a 30 100 m thick sheet of troctolite interpreted as a feeder for the 1 334 ga voisey s bay intrusion and partly at the base of this intrusion where the feeder adjoins it studies of olivine compositions indicate that an early pulse of magma through the feeder and into the intrusion was ni depleted but that subsequent pulses were much less depleted trace element re os and s and o isotope data and mineralogical studies indicate that the magma pulses interacted with country gneiss probably principally in a deeper level intrusion extracting sio2 na2o k2o and possibly sulfur form the gneiss which accounts for the magma becoming sulfide saturated the jinchuan deposit of north central china occurs within a 6 km long dyke like body of peridotite the compositions of olivine within the dyke the igneous rocks themselves and the ore are all inconsistent with derivation of the body from ultramafic magma as originally supposed and indicate that the structure forms the keel of a much larger intrusion of magnesian basalt magma flow of magma into the intrusion has resulted in olivine and sulfide being retained where the keel was widening out into the intrusion the west australian komatiite related deposits occur in thermal erosional troughs which have developed due to the channelisation of magma flow and the resulting thermal erosion of underlying sediments and basalt by the hot komatiite magma the sediments are sulfide rich and may have contributed substantially to the sulfide of the ores the mineralisation in the duluth complex occurs in troctolitic intrusions along the western margin of the complex as a result of magma interacting with and extracting sulfur from the underlying graphite and sulfide bearing sediments no magma flow channels have been identified so far and the lack of magma flow subsequent to the development of sulfide immiscibility is regarded as the reason why these deposits are not of economic grade when most major ni cu sulfide deposits are compared they prove to have a number of features in common olivine rich magma proximity to a major crustal fault sulfide bearing country rocks chalcophile element depletion in related intrusive or extrusive rocks field and or geochemical evidence of interaction between the magma and the country rocks and the presence of or proximity to a magma conduit the features are thought to explain the three key requirements sulfide immiscibilty adequate mixing between sulfides and magma and localisation of the sulfides discussed and have important implications with respect to exploration

a new scenario for related iocg and ni cu mineralization the relationship with giant mid crustal mafic sills variscan iberian massif both magmatic ni cu and hydrothermal iron oxide copper gold mineralization coexist in ancient belts but their relationship remains poorly known geochronology and field geology evidence show that in sw iberia both styles of mineralization were coeval with widespread metaluminous to peraluminous variscan magmatism 350 330 ma we propose that mineralization was probably related to a hidden large layered mafic ultramafic layered complex recently inferred from geophysics that was emplaced in a mid crustal decollement zone contamination of a primitive mantle derived magma with continental crust in the layered complex led to fractional crystallization accompanied by high t low p metamorphism and the incorporation of volatiles into the melt hot hypersaline co2 ch4 bearing brines were subsequently released and focused along major thrusts and strike slip faults to produce the iocg mineralization assimilation of continental crust also led to the formation of sulphide magmas that were tectonically injected high into the crust leading to the formation of pipe like breccia hosted ni cu ore bodies all these processes took probably place as a consequence of oblique ridge and or continent continent collision

seismicity around the mahendragarh dehradun basement fault in the western ganga plain india a neotectonic perspective the ne sw trending mahendragarh dehradun fault mdf is a basement fault in the western ganga plain the earthquake 4 7 mb epicentered on this fault on 2nd june 2017 was focused around 10 km depth and does not show any surface rupture ground penetrating radar gpr survey around the epicenter detects few shallow depth subsurface normal faults parallel to the mdf however it is unclear whether these normal faults are linked with the 2017 earthquake or other previous earthquakes seismic record usgs since 1975 to 2017 suggests occurrence of 22 earthquakes 5 mb around the mdf and majority 63 of these are clustered around delhi and rohtak following the 2017 earthquake frequency of earthquakes occurence sharply increased than previously recorded instrumentation period from 1975 to 1995 majority of the seismicity is focused around 10 km depths shallowing to depths of 25 207 km recorded from 1975 to 2004 earthquakes clustered along the main himalayan thrust mht shows similar temporal trend as near the mdf southward thrust movement of the himalaya orogenic wedge predicts to impose strike slip motion on the orthogonal oriented steep basement faults which is consistent with geologic and geomorphic field relations and seismicity focal mechanisms along the mdf the observed upper crustal deformation associated with such fault deformation pattern may be partly influenced by the mdf and partly by the foreland bulge seismicity potential tectono geomorphic parameters and soil chronosequence may suggest the surface deformation is active through the holocene

seismic imaging and modelling of the lithosphere of sw iberia abstract data from a closely spaced wide angle transect has been used to study the middle to lower crust and the moho in sw iberia a low fold wide angle stack image reveals a highly heterogeneous seismic signature at lower crustal levels changing laterally along the profile the lower crust features an irregular distribution of the reflectivity that can be explained by a heterogeneous distribution of physical properties the moho discontinuity also features a high variability in its seismic character that correlates with the different tectonic terranes in the area a 2d finite difference code was used for solving the elastic wave equation and to provide synthetic wide angle shots relatively simple layer cake model derived from conventional refraction interpretation generates the main events of the shot records however these models cannot account for the lateral variability of the seismic signature in order to obtain more realistic simulations the velocity model was modified introducing stochastic lensing at different levels within the crust the moho was modelled as a 3 km thick layered structure the resulting average velocity models include a high velocity layer at mid crustal depth a highly reflective lower crust and a relatively thin horizontal moho this heterogeneous model can be achieved by lensing within the crust a layered mafic intrusion and a strongly laminated lower crust and moho

river gradient anomalies reveal recent tectonic movements when assuming an exponential gradient decrease along a river course abstract high resolution digital models combined with gis or other terrain modelling software allow many new possibilities in geoscience in this paper we develop describe and test a novel method the gla method to detect active tectonic uplift or subsidence along river courses it is a modification of hack s sl index method in order to overcome the disadvantages of the latter the core assumption of the gla method is that over geological time river profiles quickly adjust to follow an exponential decrease in elevation along the river course any large deviation can be attributed to active tectonic movement or to disturbances in erosion sedimentation processes caused by an anthropogenic structure e g artificial dam during the testing phase the locations of identified deviations were compared to the locations of faults identified on a 1 100 000 geological map results show that higher magnitude deviations are found within a maximum radius of 200 m from the fault and the majority of detected deviations within a maximum radius of 600 m from faults or thrusts however these results are not the best that could be obtained because the geological map that was used and the only one available for the area is not of the appropriate scale and was therefore not precise enough comparison of deviation magnitudes against psinsar measurements of vertical displacements in the vicinity revealed that in spite of the very few suitable points available a good correlation between both independent methods was obtained r 2 0 68 for the e research area and r 2 0 69 for the w research area the gla method was applied to the three test sites where previous studies have shown active tectonic movements it shows that deviations occur at the intersections between active faults and river courses as well as also correctly detected active uplift attributed to the increased sedimentation rate above an artificial hydropower dam and an increased erosion rate below the method gives promising results and it is acknowledged that the gla method needs to be tested in other locations around the world

hydrological characteristics of slope deposits in high tropical mountains cordillera real bolivia abstract the hydrological processes within slope deposits are not well known particularly for high tropical mountains with climatic conditions giving seasonal contrasts in the hydrological cycle measurements have been taken in a high andean valley of the cordillera real bolivia with the aim to determine the role of the slope deposits in the framework of a hydraulic modelling different transfer time measurements combined with morphometrical and sedimentological analysis were carried out on three talus slopes and two moraines during the rainy season after injection of salt the electrical conductivity of the water in slope deposits springs is monitored to estimate transfer velocities the hydrological behaviour of these slope deposits depends on the season in the dry season all the water infiltrates and there is no visible outlet during the wet season one part soaks in and gives springs down slope the lag times estimated by the measurement of tracer velocity demonstrate that these slope deposits delayed the flow depending on the type of deposit the delay is at least 24 h in the case of the talus slopes and more than 48 h in the case of lateral moraines

tritium as an indicator of recharge and dispersion in a groundwater system in central ontario the detailed distribution of tritium 3h in the recharge area of a shallow unconfined sand aquifer near sturgeon falls ontario is described at this forested shallow water table site bomb tritium has penetrated uniformly to a depth of 8 12 m indicating recharge of 15 cm year which is 16 of precipitation the zone of bomb tritium contains 3h concentrations of from 16 to 269 tritium unit tu whereas much lower values 1 tu are observed in groundwaters recharged only a few years prior to 1953 the year when significant fallout of bomb tritium began tritium distribution is accurately simulated using one and two dimensional models when the ottawa record is used for the post 1953 tritium input function when dispersion is low and when a prebomb tritium input value of 3 tu is used this prebomb value is slightly lower than that suggested by kaufman and libby 1954 based on precipitation and surface water samples from the early 1950s the simulations indicate and field data corroborate that in 1986 3h levels of more than 100 tu occur only in groundwaters recharged between 1957 and 1971 while levels in excess of 200 tu occur only in groundwaters recharged during 1961 1967 the 1960s tritium peak is observed within a narrow distinct depth zone at all locations along the flow section investigated

the aguablanca ni cu pge deposit sw spainossa morena zone lat 37 57 n long 6 11 w

integration of spectral spatial and morphometric data into lithological mapping a comparison of different machine learning algorithms in the kurdistan region ne iraq abstract lithological mapping in mountainous regions is often impeded by limited accessibility due to relief this study aims to evaluate 1 the performance of different supervised classification approaches using remote sensing data and 2 the use of additional information such as geomorphology we exemplify the methodology in the bardi zard area in ne iraq a part of the zagros fold thrust belt known for its chromite deposits we highlighted the improvement of remote sensing geological classification by integrating geomorphic features and spatial information in the classification scheme we performed a maximum likelihood ml classification method besides two machine learning algorithms mla support vector machine svm and random forest rf to allow the joint use of geomorphic features band ratio br principal component analysis pca spatial information spatial coordinates and multispectral data of the advanced space borne thermal emission and reflection radiometer aster satellite the rf algorithm showed reliable results and discriminated serpentinite talus and terrace deposits red argillites with conglomerates and limestone limy conglomerates and limestone conglomerates tuffites interbedded with basic lavas limestone and metamorphosed limestone and reddish green shales the best overall accuracy 80 was achieved by random forest rf algorithms in the majority of the sixteen tested combination datasets

geophysical evidence of a mantle derived intrusion in sw iberia 1 deep seismic reflection data acquired as part of the sw iberia europrobe project across the transpressional variscan orogen sample three tectonic terranes the south portuguese zone the ossa morena zone and the central iberian zone the seismic data reveal the existence of a mid crustal reflective body 140 km long and of variable thickness up to 5 km the iberian reflective body the conductivity image provided by coincident mt soundings the amplitude characteristics of the seismics mineralization studies related to magmatic ore deposits and the surface geology suggest that the irb is a mantle derived mafic intrusion the geophysical geological and petrological data suggest that the irb is most probably an early carboniferous approximately at 350 340 ma mantle derived intrusion possibly linked to plume activity that took place in europe in the carboniferous and permian

comparison of basin morphometry analyses derived from different dems on two drainage basins in turkey morphometric analyses provide important data about basins and their drainage networks many data sources which are produced from different techniques can be used in this analysis two areas which have similar areal and formal features but have different vegetation density were selected as study areas kabisre and koyunluyusufozu basin selected parameters were implemented to both basins using five different datasets aster gdem srtm dem alos dsm 30 m and topo dems 30 m and 10 m the topo dems were produced from 1 25 000 scaled digitized topographical maps the morphometric analyses result of topo dems 10 m resolution was used as the benchmark data for comparing the results of the other data sources as a result srtm dems gave the most compatible results with the results of reference data for the study area of kabisre basin that has heavy vegetation and the alos dsms gave the closest results to the reference data in study area on koyunluyusufozu basin that is deprived of vegetation

hydrological characteristics of an alpine glacial valley in the north italian dolomites abstract hydrogeological characteristics of alpine regions generally are determined to a large extent by the geomorphological development during the quaternary period pleistocene and holocene this development and the hydrogeological characteristics were studied for a glacial trough valley san vigilio developed in a dolomite limestone complex in the alps of north italy geo electrical soundings were successful for detecting the shape of the glacial valley bottom and to interpret the depth and sediment type distribution of the glacial valley fill composed of ground moraine fluvio glacial deposits fluvial fans talus cones and lake deposits hydrochemical analyses and environmental isotopes 3 h and 18 o were used to further interpret the groundwater flow systems

multivariate analysis and interpretation of the hydrochemistry of a dolomitic reef aquifer northern italy regionalization based on multivariate statistical analyses of hydrochemical data and environmental isotopes proved most successful in differentiating groundwater of different hydrogeological origins within the sasso lungo dolomitic mountain stock northern italy the approach used chemical and isotopic data to evaluate hydrologic properties normally determined by more traditional techniques from field and laboratory studies of 19 hydrochemical variables measured at 46 sampling points three distinct groups of water types were differentiated in close agreement with hydrogeological evidence namely 1 pure sciliar dolomite water 2 water from volcanic deposits and 3 mixed water from sciliar dolomite and volcanic deposits environmental isotopes are used to support hydrogeological observations arid the hydrochemical analyses and also to provide valuable additional information for further distinction between hydrogeological subsystems the data show that the dolomite aquifer discharges from two main subsystems 1 relatively young shallow to moderately deep waters in the central part of the reef stock and 2 older groundwater discharging at the rims of the reef

crustal structure of the transpressional variscan orogen of sw iberia sw iberia deep seismic reflection profile iberseis 1 iberseis a 303 km long 20 s deep seismic reflection profile was acquired across the variscan belt in sw iberian peninsula the acquisition parameters were designed to obtain a high resolution crustal scale image of this orogen the seismic profile samples three major tectonic terranes the south portuguese zone the ossa morena zone and the central iberian zone which were accreted in late paleozoic times these terranes show a distinctive seismic signature as do the sutures separating them late strike slip movements through crustal wedges are apparent in the seismic image and have strongly modified the geometry of sutures the upper crust appears to be decoupled from the lower crust all along the seismic line but some deformation has been accommodated at deeper levels a sill like structure is imaged in the middle crust as a 1 2 s thick and 175 km long high amplitude conspicuous reflective band it is interpreted as a great intrusion of mafic magma in a midcrustal decollement taking into account surface geological data and the revealed crustal architecture a tectonic evolution is proposed for sw iberia which includes transpressional collision interacting during early carboniferous with a mantle plume the moho can be identified along the entire transect as subhorizontal and located at 10 to 11 s indicating a 30 35 km average crustal thickness its seismic signature changes laterally being very reflective beneath the south portuguese zone and the central iberian zone but discontinuous and diffuse below the ossa morena zone

migration of contaminants in groundwater at a landfill a case study 2 groundwater monitoring devices abstract six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the borden landfill these include standpipe piezometers water table standpipes an auger head sampler suction type and positive displacement type multilevel point samplers and bundle piezometers with the exception of the first two each of these devices provides a means of obtaining vertical sample profiles of groundwater from a single borehole the auger head sampler which is a device that is attached to the cutting head of conventional continuous flight hollow stem augers yields samples from relatively undisturbed aquifer zones as the augers are advanced downward in the borehole from one depth of sampling to another this method is a rapid means of aquiring water quality profiles for mapping the distribution of a contaminant plume the other three profiling devices can be used to establish permanent networks for groundwater quality monitoring a suction type multilevel sampler consists of twenty or more narrow polyethylene or polypropylene tubes contained in a pvc casing that is capped at the bottom each tube extends to a different depth and is attached to a small screened sampling point that extends through the casing to draw water from the aquifer when suction is applied a positive displacement multilevel sampler is similar except that each sampling point is connected to a positive displacement pumping device located inside the pvc casing adjacent to the screen use of the suction type multilevel sampler is limited to zones where the water table is less than the suction lift depth of 8 or 9 m the positive displacement sampler can be used even if the water table is at a much greater depth a bundle piezometer consists of 1 2 cm o d flexible polyethylene tubes each with a short screened section at the bottom fastened as a bundle around a semi rigid center piezometer constructed of thick walled 2 cm o d pvc pipe in shallow water table areas water is withdrawn from each of the tubes and from the pvc piezometer by suction in areas with a deep water table samples are obtained by bailing with a narrow tube with a check valve on the bottom or by displacement using a double or triple tube gas drive sampler the positive displacement multilevel sampler or use of the gas drive samplers in the bundle piezometers provide the best opportunities for collecting samples that can be filtered and have preservatives added without the water being influenced excessively by degassing or by oxygen invasion networks of these three types of devices for multilevel groundwater monitoring were installed in the borden aquifer by means of hollow stem augers the devices are particularly well suited for use in aquifers composed of cohesionless sand or gravel that have little or no clay and groundwater flow that is primarily horizontal when 8 cm diameter hollow stem augers are used as many as eight polyethylene tubes are included conveniently in each bundle piezometer if augers with a larger hollow stem are used more tubes can be assembled in each bundle

calibration of a mass transport model using environmental tritium abstract tritium profiles of groundwater were obtained by detailed vertical sampling of a 20 m thick aquifer comprising fluvioglacial sediments in the central part of the netherlands using the known environmental tritium input time series since 1951 these profiles were used to calibrate the random walk model of t a prickett et al to perform this procedure the model was modified to allow vertical use and a time dependent non instantaneous input of a decaying radioactive tracer during this calibration the following parameters were varied 1 geological geometry position and extent of a clay lens 2 permeability variations 3 ratio of net precipitation and effective porosity and 4 longitudinal and transverse dispersivity the calibrated model was hence use to predict the flushing of manure contamination from the aquifer the applied calibration technique has proved useful to test and roughly calibrate the hydraulic properties estimated from the logs of a limited number of borings with the accuracy needed for mass transport modelling compared with the very detailed drilling program that is usually required to obtain such detailed information this tritium based calibration seems competitive for shallow phreatic aquifers

migration of contaminants in groundwater at a landfill a case study 6 hydrogeochemistry multilevel point samplers located on a longitudinal cross section through the plume of contaminated groundwater in the sand aquifer at the abandoned borden landfill were used to obtain a suite of small volume samples for analysis of major ions and of minor and trace level inorganic constituents calcium is the dominant cation and sulphate and bicarbonate are the dominant anions in the contaminant plume with maximum concentrations of 400 2000 and 1200 mg l 1 respectively beneath the landfill the most highly contaminated water in the aquifer has total dissolved solids of 4000 mg l 1 sulphate and iron are the only inorganic constituents that exceed the recommended limits for drinking water the plume contains above background concentrations of dissolved zinc and manganese no heavy metals or other hazardous inorganic trace elements occur at levels above the maximum limits for drinking water the plume contains levels of total dissolved organic carbon that are above background levels ranging from 30 mg l 1 beneath the landfill to 5 mg l 1 near the front of the plume the landfill which is almost entirely above the water table contains high partial pressures of carbon dioxide and methane the high carbon dioxide levels induce substantial dissolution of calcite which occurs in sand layers in the landfill and in the aquifer immediately below the landfill calcite dissolution is the origin of much of the dissolved inorganic carbon and some of the calcium in the plume most of the sulphate and much of the calcium in the plume appears to be derived from gypsum in construction debris in the landfill groundwater beneath the landfill is saturated with respect to gypsum and slightly supersaturated with respect to calcite some of the dissolved iron in the plume results from the release under reducing conditions of iron from ferric iron coatings on sand grains located in the aquifer beneath the landfill and in the layers in the refuse dissolved iron concentrations appear to be limited by the solubility of siderite dissolved sulphide is present at only very low concentrations and is probably controlled by ferrous sulphide solubility exchange of cations between the aquifer material and the leachate contaminated groundwater is an apparent cause of calcium release and subsequent precipitation of calcite in the plume as much of 80 of the k 20 of the mg2 and 15 of the na in the plume exists on the exchange sites the effects of dispersive and geochemical attenuation were evaluated from the ratios of chloride to other species along a central flow path from the landfill to the front of the plume platinum electrode measurements and electrochemical potentials calculated from equilibrium speciation of analysed constituents varied over a wide range of values and provided poor agreement among methods for the same sample only potentials derived from the iron redox couples and pt electrode measurements exhibited fair agreement for any one sample the rather narrow range of pt electrode potential values along the central flow line through the plume suggest that the electrochemical potentials are buffered apparently as a result of fe oh 3 s ag feco3 s equilibria

application of morphometry in neotectonic studies at the eastern edge of the parana basin santa catarina state brazil article i nfo the neotectonic evolution of the eastern edge of the parana basin in the santa catarina state brazil was investi gated using field data and detailed morphometric analysis along an east west section analysis included gener ation of maps of isobase hydraulic gradients hypsometry incision of drainage basins drainage asymmetry and anomalous morphological features all these maps generated results that agreed with field data and helped define recent faults in directions close to n s and e w both probably reactivated faults of the parana basin and the basement geomorphological features identified in topographic maps possibly related to neotectonism have a close agreement with our observations in the field the asymmetry of basins as analysed by the t index method proved to be compatible with the influence of a e w compressive tectonic regime and showed a move ment from w to e application of the hypsometric integral technique helped establish a correlation between the younger basins with structures trending n s 30 the n s faults were related to a compressional stress field shmax close to e wa nd shmin stress minimum around n s thereby establishing a tectonic context of structures developed in a transpressive regime the compressional field was caused by the subduction of the nazca tectonic plate below the south american plate whereas the transcurrent component exploited pre existent e w structures when the atlantic ocean was opening

magma generation and sulfide saturation of permian mafic ultramafic intrusions from the western part of the northern tianshan in nw china implications for ni cu mineralization compared to permian magmatic ni cu sulfide deposits in the eastern part of the northern tianshan such as huangshan and huangshandong those in the western part e g baixintan and lubei are poorly documented zircon id tims u pb age data 279 7 0 2 ma of lherzolite and la icpms u pb age data 277 8 3 4 ma of a hornblende gabbro suggest the lubei intrusion was emplaced in the early permian the baixintan and lubei mafic ultramafic intrusive rocks are characterized by enrichments of large ion lithophile elements and th and u relative to the high field strength elements as well as depletion of nb and ta relative to mid ocean ridge basalt the 87sr 86sr t 0 70354 0 70713 end t 2 80 to 7 05 and ehf t 2 50 18 4 values for the intrusions indicate that they have assimilated tianshan basement rocks whereas the se s ratios 181 10 6 418 10 6 and 34scdt values 0 13 to 0 90 of the sulfides suggest that crustal sulfur has not been incorporated into the magma the decrease in pd zr with increasing th nb pm indicates that sulfide saturation accompanied crustal contamination the olivine compositions and whole rock chalcophile elements of the baixintan and lubei intrusions imply that the parental magma of the intrusive rocks in the west contains higher chalcophile elements than those in the east which suggests that the mafic ultramafic intrusions in the western part of the northern tianshan should be regarded as favorable ni cu sulfide exploration targets

migration of contaminants in groundwater at a landfill a case study 4 a natural gradient dispersion test abstract a natural gradient tracer test using a chloride solution with an initial injection volume of 0 7 m 3 was performed in the sandy aquifer at the borden site the solution was injected into five well points set 1 m below the water table in an uncontaminated zone situated above the contaminant plume at a location 450 m downflow from the landfill under conditions of natural groundwater flow the tracer slug was monitored for a period of 4 months by withdrawing small volume samples from points in a three dimensional array of bundle type multilevel samplers measurements of hydraulic head were obtained from a network of miniature piezometers soon after injection the tracer slug gradually split into two halves one half moving horizontally at an average velocity of 2 9 10 6 ms 1 and the other horizontally at 8 2 10 7 ms 1 although the split has been attributed to local lateral heterogeneity the nature of the heterogeneity and its influence on the hydraulic head distribution were not clearly distinguishable in the field data obtained before during or after the test the chloride patterns for each of the two halves of the tracer slug evolved into gaussian forms although the patterns demonstrated some irregularity at early time the relatively smooth gaussian forms were unexpected because the aquifer has numerous small scale heterogeneities observed in vertical cores obtained from the tracer zone and because the glaciofluvial origin of the aquifer suggests that heterogeneities are not laterally continuous simulated chloride distributions from a three dimensional analytical solution to the advection dispersion equation were fitted to the field data to obtain best fit estimates of the values of longitudinal transverse horizontal and transverse vertical dispersivity at various travel distances for each of the two halves of the tracer zone this is the first known field test that has permitted the estimation of three principal dispersion coefficients in layered media the longitudinal dispersivity was found to increase from 0 01 m at a distance of 0 75 m from the source to 0 08 m at 11 0 m the transverse horizontal dispersivity increased also to a value of 0 03 m at 11 0 m transverse vertical dispersion was very weak and was accounted for by molecular diffusion the relative lack of vertical dispersion is consistent with the shape of the plume of leachate contamination from the landfill it was concluded that the observed increase in dispersivity along the path of migration is likely caused by heterogeneities information on the dispersion controlling heterogeneities is not yet available as practical field methodologies for their identification and description have not yet been developed until such information is incorporated into mass transport models a realistic solution of the dispersion problem in heterogeneous media will remain elusive

sulfide silicate textures in magmatic ni cu pge sulfide ore deposits massive semi massive and sulfide matrix breccia ores abstract much of the value of magmatic ni cu pge sulfide orebodies is contained within massive or semi massive ores that show a wide variety of textural relationships to included or adjacent silicate rocks we identify five mutually gradational textural types 1 pure inclusion free massive sulfide ores 2 sulfide matrix ore breccias of sharp wall soft wall or mixed character 3 emulsion textured ores formed by frozen mixtures of molten silicate and sulfide most commonly developed as melt films at thermal erosion contacts 4 vein hosted sulfides formed at late magmatic or high temperature post emplacement deformation stage close to the brittle ductile transition in the country rocks or host igneous bodies and 5 tectonic durchbewegung breccias formed by mechanical inter shearing of less ductile silicate inclusions and more ductile solid sulfides some deposits the moran shoot at kambalda being the type example record the invasion of country rock footwall by downward or sideways percolating superheated molten sulfide liquid generating vertical sequences of pure massive sulfide emulsion textured ores and finely spaced invasive sulfide veins these are referred to as sulfide melting infiltration fronts and may provide a clue to the mechanism of formation of sulfide rich magmatic ores as whole sulfide matrix ore breccias are particularly well developed in the voisey s bay and aguablanca deposits where they developed by flooding of percolating sulfide melt through the silicate matrix of magmatic intrusion breccias displacing silicate melt the lithology of the silicate or carbonate rock inclusions determines the nature of the inclusion matrix relationships non refractory inclusions typically disaggregate along original grain boundaries to leave coherent inclusions surrounded by clouds of inclusion derived or matrix derived crystals with the low melting silicate component preferentially displaced by sulfide liquid whereas refractory inclusions retain sharp boundaries zonation of inclusions and overgrowths preserves reaction between inclusion and silicate matrix that pre dates invasion of the intrusion breccia by sulfide liquid the process of percolation of dense low viscosity sulfide liquid into pore space and fractures within partially molten or melting silicate rock is a unifying theme that links sulfide matrix ore breccias and emulsion textured ores with distinctive textures in less sulfide rich rocks such as net texture matrix ore texture leopard texture poikilitic net texture and interspinifex ore vein hosted massive sulfides may be emplaced under magmatic conditions where the excess pressure of the sulfide liquid column drives or enhances fracturing of the country rock and injection of sulfide into the cracks such veins are commonly referred to as remobilised a term which may obscure process understanding and should be reserved for cases where tectonic solid state mobilisation of sulfide can be demonstrated on textural and structural grounds the tendency of sulfide liquids to invade country rocks and potentially to drive the propagation of their own magmatic containers may be a critical feedback loop in the development of magmatic sulfide mineral systems

4 transpressional tectonics lower crust decoupling and intrusion of deep mafic sills a model for the unusual metallogenesis of sw iberia abstract sw iberia is interpreted as an accretionary magmatic belt resulting from the collision between the south portuguese zone and the autochthonous iberian terrane in variscan times 350 to 330 ma in the south portuguese zone pull apart basins were filled with a thick sequence of siliciclastic sediments and bimodal volcanic rocks that host the giant massive sulphides of the iberian pyrite belt massive sulphides precipitated in highly efficient geochemical traps where metal rich but sulphur depleted fluids of dominant basinal derivation mixed with sulphide rich modified seawater massive sulphides formed either in porous reactive volcanic rocks by sub seafloor replacement or in dark shale by replacement of mud or by exhalation within confined basins with high biogenic activity crustal thinning and magma intrusion were responsible for thermal maturation and dehydration of sedimentary rocks while magmatic fluids probably had a minor influence on the observed geochemical signatures the ossa morena zone was a coeval calc alkaline magmatic arc it was the site for unusual mineralization particularly magmatic ni cu and hydrothermal fe oxide cu au ores iocg most magmatism and mineralization took place at local extensional zones along first order strike slip faults and thrusts the source of magmas and iocg and ni cu deposits probably lay in a large mafic ultramafic layered complex intruded along a detachment at the boundary between the upper and lower crust here juvenile melts extensively interacted with low grade metamorphic rocks inducing widespread anatexis magma contamination and further exsolution of hydrothermal fluids hypersaline fluids 18 o fluid 5 4 to 12 were focused upward into thrusts and faults leading to early magnetite mineralization associated with a high temperature 500 c albite actinolite salite alteration and subsequent copper gold bearing vein mineralization at somewhat lower temperatures assimilation of sediments by magmas led in turn to the formation of immiscible sulphide and silicate melts that accumulated in the footwall of the layered igneous complex further injection of both basic and sulphide rich magmas into the upper crust led to the formation of ni cu rich breccia pipes younger 330 to 280 ma peraluminous granitoids probably reflect the slow ascent of relatively dry and viscous magmas formed by contact anatexis these granitoids have w sn and pb zn related mineralization that also shows geochemical evidence of major mantle crust interaction late epithermal hg cu sb and pb zn ag mineralization was driven by convective hydrothermal cells resulting from the high geothermal gradients that were set up in the zone by intrusion of the layered igneous complex in all cases most of the sulphur seems to have been derived from leaching of the host sedimentary rocks 34 s 7 to 20 with only limited mixing with sulphur of magmatic derivation the metallogenic characteristics of the two terranes are quite different in the ossa morena zone juvenile magmatism played a major role as the source of metals and controlled the styles of mineralization in the south portuguese zone magmas only acted as heat sources but seem to have had no major influence as sources of metals and fluids which are dominated by crustal signatures most of the magmatic and tectonic features related to the variscan subduction and collision seem to be masked by those resulting from transpressional deformation and deep mafic intrusion which led to the development of a metallogenic belt with little resemblance to other accretionary magmatic arcs

crystallographic preferred orientations and microstructure of a variscan marble mylonite in the ossa morena zone sw iberia the mylonitic marbles of the cherneca shear zone a variscan sinistral strike slip structure developed in the ossa morena zone sw iberia related to the emplacement of the santa olalla igneous complex were studied in detail different mylonites from protomylonites to ultramylonites were analyzed by electron back scattering diffraction ebsd in order to determine the crystallographic preferred orientation cpo of calcite the cpos show very good agreement with experimental torsion work giving suitable interpretations of the operative slip systems and strain quantifications thus the obtained natural cpos validate the experimental approaches a wide range of observed textures and microstructures are mainly controlled by the amount of shear strain the presence of secondary phases and the development of antithetic subsidiary shears the effect of secondary phases and the nucleation of antithetic shear bands on texture development are discussed

tilting neotectonics of the guadiamar drainage basin sw spain the guadiamar river ows from the southern iberian massif to the guadalquivir foreland basin sw spain its drainage basin displays asymmetries in the stream network the arrangement of alluvial terraces and the con guration of the trunk river valley the stream network asymmetry was studied using morphometric measures of transverse topographic sym metry asymmetry factor and drainage basin shape the alluvial terraces were studied through the lithologic logs of more than a hundred boreholes and eld mapping the morphometric methods demonstrate a regional tectonic tilting toward the sse causing both the migration of the guadiamar river toward the east and the migration of the guadiamar tributaries toward the southwest as a consequence of the guadiamar river migration an asymmetric valley developed with a steep eastern margin caused by river dissection and a gentle western margin where the main alluvial deposits are found the ages obtained using the 14c analysis of samples from several alluvial deposits show that the river migration and thus tilting has occurred during the holocene as well as earlier in the quaternary this interpretation revises the guadiamar longitudinal fault assumed by previous studies copyright 2003 john wiley sons ltd

identification of possible quaternary deformation in the northeastern mississippi embayment using quantitative geomorphic analysis of drainage basin asymmetry to investigate neotectonism in the mississippi embayment east of the new madrid seismic zone we identified geomorphic domains that show evidence of ground tilting during quaternary time transverse basin profiles were converted to two dimensional vectors that denote channel position with respect to basin divides these basin asymmetry vectors record the net direction and degree of lateral migration of trunk streams more than 2500 vectors were measured and spatially averaged within 400 km 2 bins this field of 300 mean vectors delineates several domains that show preferred directions of stream migrations possibly driven by ground tilting the timing of stream migration was interpreted using across valley distributions of quaternary alluvial terraces comparison of our mean vector field with subsurface structures suggests that some domain boundaries may be related to reactivated faults late quaternary activity is suggested for two northeast striking faults of the southeastern reelfoot rift margin we acquired two seismic profiles showing near surface faulting beneath scarps that follow the domain boundary associated with one of these northeast striking faults big creek fault zone reelfoot thrust seismicity ends on the south against this fault suggesting that the rift margin has dextral slip accommodating northeastward movement of the thrust hanging wall our vector field also suggests late quaternary movement on the reelfoot thrust and on two other northwest striking faults here termed the hatchie river fault and the wolf river fault several other weak domains may imply minor elements of neotectonism our results demonstrate that morphometric analysis of drainage basin asymmetry can be an effective reconnaissance tool within neotectonic settings

u pb age constraints on variscan magmatism and ni cu pge metallogeny in the ossa morena zone sw iberia new u pb zircon ages from the santa olalla igneous complex have been obtained which improve the knowledge of the precise timing of variscan magmatism in the ossa morena zone sw iberia this complex has a special relevance as it hosts the most important ni cu platinum group element pge mineralization in europe the aguablanca deposit u pb zircon ages have been obtained for seven samples belonging to the santa olalla igneous complex and spatially related granites with the exception of the cala granite 352 4 ma which represents an older intrusion the bulk of samples yield ages that cluster around 340 3 ma the santa olalla tonalite 341 5 3 ma the sultana hornblende tonalite 341 3 ma a mingling area at the contact between the aguablanca and santa olalla stocks 341 1 5 ma the garrote granite 339 3 ma the teuler granite 338 2 ma and dioritic dykes from the aguablanca stock 338 6 0 8 ma the bodonal cala porphyry which has also been dated 530 3 ma comprises a group of sub volcanic rhyolitic intrusions belonging to the bodonal cala volcano sedimentary complex which hosts the igneous rocks the knowledge that emplacement of the aguablanca deposit was related to episodic transtensional tectonic stages during the variscan orogeny will be fundamental in future mineral exploration in the ossa morena zone

paleoenvironmental dynamics of low order paleovalleys in the late quaternary palmas cacador summit surface southern brazil abstract the quaternary dynamics of landscapes in the subtropical continental region of brazil is not still well understood pedostratigraphic records of low order paleovalleys paleovalley heads and 1st and 2nd order paleovalleys of the palmas cacador summit surface serve as important resources for the identification of landscape component responses relief soil sediment and vegetation of plateau areas of southern brazil in the light of environmental changes driven by climatic variations of the late quaternary we integrated litho pedo allo and chronostratigraphic descriptions with carbon stable isotope analysis phytoliths indices and 14c and osl dating we found that at 44 86 ky bp there was a change in the hydrodynamics of 2nd order perennial channels humid climate controlled possibly by tectonics at 28 35 to 23 69 to 28 ky bp regressive pedogenesis in dry climate began with a predominance of erosion by overland flows at 2 60 to 23 69 ky bp full regressive pedogenesis occurred under a continuous climate regime of drier characteristics punctuated by millenary climatic fluctuations to a wetter regime of between 4 60 and 19 77 ky bp echoing the results postulated by the knox s model during this period the most pronounced modifications to the landscape were made with a change in vegetation from campo cerrado to campo limpo with changes in erosion patterns caused first by overland flows and then earthflows debris flows and with the gradual silting filling and burying of gullies valley heads and 1st and 2nd order valley bases since 2 60 ky bp the area returned to a predominance of progressive pedogenesis in wet and cold climates finally we found that at the local scale low order basins

erratum to a new style of ni cu mineralization related to magmatic breccia pipes in a transpressional magmatic arc aguablanca spain the aguablanca deposit represents a new style of magmatic ni cu mineralization in discordant sulfide rich pyroxenitic breccia pipes the orebody is hosted by variscan calc alkaline diorites and gabbros which intruded during an oblique subduction collision event transpressional transtensional left lateral structures facilitated the intrusion of primitive magmas to shallow depths in the crust a two stage genetic model is proposed in the first stage a transitional deep magma chamber formed the primitive magma interacted at depth with wall rocks resulting in extensive crustal contamination concomitant sulfide magma immiscibility and settling of orthopyroxene clinopyroxene and sulfide rich cumulates to form a layered magmatic complex geochemical and mineralogical evidence including the virtual disappearance of olivine heavy 34s values 7 4 distinctive nd sr and pb signatures high au contents and the presence of spinel and graphite indicate a major interaction with the upper crust probably with pyrite rich carbonaceous slates of late proterozoic age the second stage was related with the emplacement of residual calc alkaline gabbroic to noritic melts and the development of an intrusive breccia containing fragments of the consolidated layered complex rocks and associated disseminated to massive sulfides

the evolution of troctolitic and high al basaltic magmas in proterozoic anorthosite plutonic suites and implications for the voisey s bay massive ni cu sulfide deposit the voisey s bay massive ni cu sulfide deposit is contained within troctolitic plagioclase olivine intrusions of the 1 34 to 1 29 ga nain plutonic suite coastal labrador canada and represents a new setting for magmatic sulfide deposits proterozoic anorthosite plutonic suites consist of vast quantities as much as 20 000 km 2 of cumulate anorthosite leucotroctolite leuconorite intrusions of troctolite and fe enriched dioritic rocks and large granitic batholiths crystallization ages span nearly 1 200 m y within the middle proterozoic 2 12 0 92 ga many proterozoic anorthosite plutonic suites were emplaced into relatively young proterozoic crust and some were intruded along archean proterozoic boundaries e g nain labrador laramie wyoming korosten ukraine nearly all of the largest plutonic suites contain significant areas thousands of km 2 of plagioclase rich cumulate rocks that are olivine bearing olivine anorthosite leucotroctolite troctolitic rocks 20 30 modal olivine occur in proterozoic anorthosite plutonic suites principally as cumulates in layered or massive intrusions e g kiglapait hettasch jonathon nain intruded into anorthositic rocks with the notable exception of the voisey s bay deposit nearly all troctolitic rocks crystallized late in the evolution of individual plutonic suites many of the troctolitic intrusions have fine grained olivine rich marginal rocks that closely represent parental magma compositions numerous fine grained olivine normative dikes with high al basaltic compositions also occur within many plutonic suites nain harp lake laramie adirondack and share compositional characteristics with the troctolitic magmas these olivine normative high al basaltic magmas record the least evolved compositions in proterozoic anorthosite plutonic suites mg 0 43 0 64 an 45 60 have high al 2o 3 15 19 wt and feo total 9 15 wt contents and typically show the least contaminated sr and nd isotope compositions in a given plutonic suite many dikes and marginal rocks have strong positive eu anomalies a feature of the melt composition that is not related to plagioclase accumulation except at laramie the least evolved troctolitic magmas appear to have about 8 wt percent mgo and corresponding ni and s concentrations between 100 to 150 ppm and 0 02 to 0 05 wt percent respectively based on closed system fractionation in the kiglapait intrusion sulfide saturation occurs late in the crystallization history of troctolitic magmas after ni concentrations have been severely depleted by protracted olivine fractionation the optimal conditions for formation of a ni cu sulfide deposit associated with a proterozoic anorthosite plutonic suite require a relatively high mgo parental magma that has not crystallized much prior olivine and an external source of s to promote early sulfide saturation probably through desulfurization reactions as hot troctolitic magmas ascend through the crust an economically important massive ni cu sulfide deposit on the scale of voisey s bay clearly requires large volumes of magma probably involving continuous replenishment of relatively ni rich unfractionated parental magma in staging chambers or mixing between magmas in conduits during ascent a model for the formation of troctolite associated massive ni cu sulfide deposits is proposed depending on the relative degrees of sulfide saturation and fractionation of the mixed magmas mixing between troctolitic magmas in a conduit or magma chamber may either poison the system stopping sulfide segregation or enhance sulfide segregation

multi stream order analyses in basin asymmetry a tool to discriminate the influence of neotectonics in fluvial landscape development madrid basin central spain morphometric analysis of the tajo drainage network using a dem was carried out in order to determine neotectonic influence on the development of the madrid basin since the pliocene statistical analysis of digitally derived transverse topographical drainage basin asymmetry t factor was used to infer directions of ground tilting a crustal block pattern was interpreted from a mean basin asymmetry vector field that was computed using a new approach based on a gridded running average of the raw vector field measurement of r factor for different order channels allows investigation of evolution rates of different order rivers and at the same time reveals possible factors controlling basin evolution the vector data show clear differences between high and low orders high order asymmetry is consistent with fluvial terrace distribution as it reflects channel migration and incision within the main valleys and shows a general trend toward a central basin axis running sw ne a sw ne trend is also defined by other morphographical approaches such as drainage density and relief analysis both approaches point toward the presence of two uplifted areas running sw ne and a subsided zone between them which is in agreement with previous crustal flexure models in contrast low order asymmetry shows a clear trend indicating eastward tilting which could be driven by recent changes in maximum principal stress direction and its influence on fault reactivations in general large rivers generating fluvial terraces are controlled by basement structure with positive and negative crustal flexures driving their migration direction and thus controlling the spatial distribution of terraces because the position of main streams is controlled by large tectonic lineaments that favor groundwater flow convergence on the other hand small tributaries have low capabilities to attain equilibrium and t factor values of low order basins may reflect more recent block tectonics due to variations in stress fields or may reflect local controls like lithology

acadian synorogenic mafic intrusions in the maine appalachians two belts of syn acadian mafic intrusions the central maine belt is progressively more altered and metamorphosed toward the southwest at the northeast end the moxie pluton represents the least altered and most important example in the belt forsterite contents of the most primitive olivines are consistent with the derivation of the earliest magma from a largely unfractionated mantle melt the coastal maine belt is spatially associated with the siluro devonian coastal volcanics the age difference however between the volcanics and plutonics suggests that they may not be directly related the important pocomoonshine gabbro appears to represent the well layered roof zone of a major fractionated body mineral compositions are similar to those in the moxie pluton and suggest a similar primary magma intrusions in both belts have complex contacts pronounced contact aureoles and were all deformed by late acadian deformation modified journal abstract

re os sm nd and pb isotopic constraints on mantle and crustal contributions to magmatic sulfide mineralization in the duluth complex abstract previous petrologic and stable isotopic studies of sulfide mineralization in the duluth complex have led to the premise that sulfide genesis is strongly linked to the interaction between mantle derived magmas and sedimentary country rocks in a rift zone environment in order to more fully evaluate the nature of this interaction and to gain an insight into the possible importance of externally derived metals in the ore forming process pb sm nd and re os isotopic studies of the babbitt cu ni deposit were initiated rock types examined include low sulfide troctolite that show very little petrologic evidence for contamination disseminated sulfide bearing troctolitic to gabbroic rocks that occur close to the basal contact with country rocks and contain metasedimentary xenoliths and massive sulfide lead isotopic values of whole rocks plagioclase mineral separates and massive sulfides show only subtle differences and are compatible with 3 to 5 contamination of a mantle derived melt with a proterozoic crustal contaminant e nd 1 1 ga values of the troctolite and gabbro samples are chondritic and only the massive sulfides show strong evidence for contamination based on sm nd isotopic values massive sulfides tend to be more sensitive indicators of contamination in the sm nd system because of late stage incorporation of a light rare earth element rich fluid into a ca po 4 apatite component of the immiscible sulfide liquid os 1 1 ga values are also strongly anomalous and range from 500 to 1200 in disseminated sulfide bearing troctolites and massive sulfides these values are also consistent with from 1 to 3 contamination by c rich and strongly radiogenic proterozoic sedimentary rocks elemental and isotopic mass balance calculations suggest that up to 50 of the pb and at least 35 of the os in the sulfide mineralization have been derived from external sources a corollary is that other metals may also be in part derived from external sources which would aid in explaining the compositional diversity of the sulfide mineralization selective assimilation of country rocks by mantle derived magmas may occur in crustal staging chambers during ascent to shallower levels or in situ as a result of devolatilization reactions and partial melting

magma emplacement in transpression the santa olalla igneous complex ossa morena zone sw iberia the santa olalla igneous complex a late variscan group of intrusions located in the ossa morena zone sw iberia has been the focus of a gravity and structural study the structure outlined by the foliation map is complex showing two different structural domains one characterized by vertical and the other by horizontal magmatic foliations the vertical fabrics are restricted to the ne half of the complex which is in direct contact with a variscan sinistral strike slip fault cherneca fault whereas the horizontal fabrics are developed in the sw half of the complex which is characterized by a horizontal tabular geometry gravity modeling indicates that the deeper floor of the plutons is closely related to the ne margin and the cherneca fault an emplacement and structural evolution model for this igneous complex is proposed following these structural and gravity results 1 magma ascent was favored by releasing bends in the trace of the cherneca fault 2 when magma reached the present level it intruded to the sw with a horizontal sheet geometry generating the subhorizontal foliation domain 3 after emplacement the ne half of the complex suffered the external tectonic stress field provoked by sinistral motion along the cherneca fault subsequently generating the subvertical magmatic foliation domain

is unique scaling of aquifer macrodispersivity supported by field data spreading of conservative solutes in groundwater due to aquifer heterogeneity is quantified by the macrodispersivity which was found to be scale dependent it increases with travel distance stabilizing eventually at a constant value however the question of its asymptotic behavior at very large scale is still a matter of debate it was surmised in the literature that macrodispersivity scales up following a unique scaling law attempts to define such a law were made by fitting a regression line in the log log representation of an ensemble of macrodispersivities from multiple experiments the functional relationships differ among the authors based on the choice of data our study revisits the data basis used for inferring unique scaling through a detailed analysis of literature marcodispersivities in addition values were collected from the most recent tracer tests reported in the literature we specified a system of criteria for reliability and reevaluated the reliability of the reported values the final collection of reliable estimates of macrodispersivity does not support a unique scaling law relationship on the contrary our results indicate that the field data can be explained as a collection of macrodispersivities of aquifers with varying degree of heterogeneity where each exhibits its own constant asymptotic value our investigation concludes that transport and particularly the macrodispersivity is formation specific and that modeling of transport cannot be relegated to a unique scaling law instead transport requires characterization of aquifer properties e g spatial distribution of hydraulic conductivity and the use of adequate models

textural development in sulfide matrix ore breccias in the aguablanca ni cu deposit spain revealed by x ray fluorescence microscopy abstract the intrusion hosted ni cu sulfide deposit at aguablanca in south western spain contains a high proportion of ores in the form of sulfide matrix ore breccias these are polymict comprising autoliths and xenoliths in sulfide rich and or sulfide poor matrices inclusion lithologies include calc silicate skarn rocks from the adjacent marbles ultramafic and mafic cumulates and remelted and recrystallized mafic rocks containing spinifex like textures breccia textures have been investigated at mm to cm scale using desk top and synchrotron based microbeam xrf mapping which reveal a number of distinctive common features disaggregation of inclusions into adjacent sulfide along original silicate grain boundaries complex reverse and oscillatory zoning in cr content of clinopyroxene grains within sulfide and inside inclusions narrow reaction rims between country rock clasts and enclosing silicates and preferential disposition of pyroxene crystals within pyrrhotite pentlandite aggregates original mss relative to inclusion poor chalcopyrite the observed range of textures is explained by a model of percolation of molten sulfide through a pre existing silicate matrix intrusion breccia preferentially displacing a cotectic or eutectic plagioclase pyroxene melt the process is analogous to that believed to have formed interspinifex ore in komatiite hosted deposits and also to that responsible for superficially similar sulfide matrix ore breccias at voisey s bay the preserved range of textures is interpreted as being due to late stage gravity driven percolation of sulfide liquid from above into a pre existing partially molten intrusion breccia this intrusion breccia itself may have been emplaced into the neck of the aguablanca stock in the waning stages of magma flow

scale dependence of hypsometric integrals an analysis of southeast african basins abstract previous studies have shown that the hypsometry of individual drainage basins is sensitive to both tectonic uplift rates and variations in erosional resistance of different lithological units however basin hypsometry has also been found to be related to the size the shape and relief of the sampled area as well as factors such as the type of dominant erosional process this study extends the evaluation of the controls on a basin s hypsometry by assessing factors that might influence the spatial distribution of hypsometric integrals at different scales the method is applied to catchments draining the southeast margin of southern africa kwazulu natal region because of the region s rather uniform runoff a rather well constrained denudational history and a relatively simple coastward sequence of bedrock geology several sets of basins were extracted from an srtm derived 90 m resolution dem one set of main basins those that have outlets at sea level and six sets of sub basins of different size based on strahler order the mean area of the sub basins sampled ranged from 9 km2 for strahler order 2 through to 3215 km2 for strahler order 6 in contrast to previous studies data from this study fail to show a correspondence between hypsometric integral and indices of basin dimension such as basin area and basin relief rather basin hypsometry in se africa varies spatially and with scale in particular a mountain range scale positive hypsometric integral anomaly situated between 10 and 100 km of the coast line was observed but only in basins of strahler order 5 and less this anomaly is compatible with moderate crustal displacement focussed midway between the coast and the drakensburg escarpment some intermediate scale positive hypsometric integral anomalies in basins of strahler order 4 and less was also observed in some cases these anomalies correspond to differences in erosional resistance among major lithological groups finally numerous local basin scale positive hypsometric integral anomalies in basins of strahler order 3 and less were also observed in many cases these latter anomalies are related to local differences in lithological resistance e g the presence of dolerite sills and dikes the analysis of the spatial variation of hypsometric integrals in basins of different size ranges is therefore a useful first step in assessing factors that control landscape development

a morphotectonic map of the northern arava in israel derived from isobase lines abstract in areas characterized by flat and weakly incised relief built of young and lithologically uniform sediments structural and tectonic maps are often non existent or of no great avail under such conditions the regional morphotectonic analysis of the study area may be a most useful tool to produce the required basic hydrogeological information it consists basically of two consecutive steps i e definition of stream orders and the preparation of isobase maps in the research of quaternary geology isobase surface analysis is regarded as a means for identifying young tectonic processes the morphotectonic map is the final derivative of isobase maps it portrays the basic lineaments or dislocation lines derived by analysing deviations in the directions of isobase lines of their spreading or compression and of deviations between axes of valleys the morphotectonic map presented in this paper portrays several major morphostructural units within the arava graben in the area between the dead sea and nahal paran

analysis of drainage basin symmetry as a rapid technique to identify areas of possible quaternary tilt block tectonics an example from the mississippi embayment there is a coincidence of seismicity and major river valleys in the southwestern mississippi embayment that suggests control of the drainage pattern by northwest trending faults pleistocene river terraces reveal a strong southwestward preferred river migration in this region that may be a result of fault block tilting a rapid new technique of drainage basin analysis is herein presented that quantifies transverse topographic basin symmetry these data permit discrimination of random stream migrations and regionally preferred stream migrations and identify the direction of maximum migration if bedrock dip can be shown to be a negligible influence on stream migration then the direction of regionally preferred migration implies a period of ground tilting in that direction drainage basin asymmetry vectors bearing and degree of asymmetry calculated from transverse topographic profiles of 271 4 km basin segments in the study area suggest preferred stream migration in response to west southwest ward ground tilting bearing 259 the eastward regional dip of bed rock horizons only locally influences migration river terrace distributions reveal a chronology of stream migration episodes southwestward migration in the ouachita saline and arkansas river basins occurred during early to middle pleistocene time in the southwestern mississippi embayment a wisconsin early holocene southwestward migration episode is evidenced along southeast flowing reaches of the ouachita and arkansas rivers but not along the southeast flowing reach of the intervening saline river suggesting that these rivers overlie separate northwest trending tilt blocks although this technique does not provide direct evidence of ground tilting it provides a quick look method of identifying possible tilting elements in neotectonic regions using only topographic maps this technique is of greatest utility where active faults are concealed or poorly exposed such as in the mississippi embayment

isotopical differentiation of groundwater of different hydrogeologic origin abstract variations in the values from 14c 3h and 13c analyses can be used to differentiate young groundwater which was recharged in limestone from that recharged in sandstone areas this is due to the fact that the process of isotopic maturation of groundwater occurs at different rates in different geologic environments

morphotectonics of a high plateau on the northwestern flank of the continental rift of southeastern brazil abstract integration of landform and structural analysis allowed the identification of late pleistocene holocene pulses of tectonic activity in the campos do jordao plateau with ages and regimes similar to the ones from the continental rift fault reactivation along precambrian shear zones give rise to a series of conspicuous morphotectonic features determine the formation of stream piracy phenomena and divide the plateau into smaller blocks recognition of these tectonic pulses as well as of their effects in landform development particularly clear on the campos de sao francisco at the highest area of the se edge of the plateau show that besides the climate related quaternary environmental changes significant neotectonic instability should be considered in the geomorphic evolution of the campos do jordao plateau

origin and emplacement of the aguablanca magmatic ni cu pge sulfide deposit sw iberia a multidisciplinary approach a model is proposed for the origin and emplacement of the ca 341 ma aguablanca magmatic ni cu platinum group element pge sulfi de deposit sw iberia integrating petrological geochemical structural and geophysical data the aguablanca deposit occurs in an unusual geodynamic context for this ore type an active plate margin as an exotic magmatic subvertical breccia located at the northern part of the coeval gabbronorite aguablanca stock 341 1 5 ma structural and gravity data show that mineralized breccia occurs inside the inferred feeder zone for the stock adjacent to the cherneca ductile shear zone a variscan sinistral transpressional structure the orientation of the feeder zone corresponds to that expected for tensional fractures formed within the strain fi eld of the adjacent cherneca ductile shear two distinctive stages are established for the origin and emplacement of the deposit 1 initially the ore forming processes are attributed to magma emplacement in the crust assimilation of crustal s and segregation and gravitational settling of sulfi de melt a scenario similar to most plutonic ni cu sulfi de ores and 2 fi nal emplacement of the ni cu sulfi de bearing rocks by multiple melt injections controlled by successive opening events of tensional fractures related to the cherneca ductile shear zone

geochemistry of the kalatongke ni cu pge sulfide deposit nw china implications for the formation of magmatic sulfide mineralization in a postcollisional environment the kalatongke also spelt as karatungk ni cu platinum group element pge sulfide deposit containing 33 mt sulfide ore with a grade of 0 8 wt ni and 1 3 wt cu is located in the eastern junggar terrane northern xinjiang nw china the largest sulfide ore body which occupies more than 50 vol of the intrusion y1 is dominantly comprised of disseminated sulfide with a massive sulfide inner zone economic disseminated sulfides also occur at the base of the intrusions y2 and y3 the main host rock types are norite in the lower part and diorite in the upper part of each intrusion enrichment in large ion lithophile elements and depletion in heavy rare earth elements relative to mid ocean ridge basalt indicate that the mafic intrusions were produced from magmas derived from a metasomatized garnet lherzolite mantle the average grades of the disseminated ores are 0 6 wt ni and 1 1 wt cu whereas those of the massive ores are 2 wt ni and 8 wt cu the pge contents of the disseminated ores 14 69 ppb pt and 78 162 ppb pd are lower than those of the massive ores 120 505 ppb pt and 30 827 ppb pd however on the basis of 100 sulfide pge contents of the massive sulfides are lower than those of the disseminated sulfides very high cu pd ratios 4 5 104 indicate that the kalatongke sulfides segregated from pge depleted magma produced by prior sulfide saturation and separation a negative correlation between the cu pd ratio and the pd content in 100 sulfide indicates that the pge content of the sulfide is controlled by both the pge concentrations in the parental silicate magma and the ratio of the amount of silicate to sulfide magma the negative correlations between ir and pd indicate that the massive sulfides experienced fractionation

polymineralic orientation analysis of magmatic rocks using electron back scatter diffraction implications for igneous fabric origin and evolution abstract electron back scatter diffraction ebsd which provides an easy way of acquiring large numbers of individual crystallographic orientation data from different phases has been applied to the study of magmatic fabrics using this technique the crystallographic preferred orientation cpo of plagioclase biotite orthopyroxene hornblende and quartz in natural tonalites and quartzdiorites from the santa olalla igneous complex sw iberia deformed during the magmatic stage have been determined plagioclase is the coarser phase defining the main fabric in each sample whereas biotite can display either the same fabric as plagioclase or a completely different one the differences between these two phases occur because 1 smaller phases interact with the larger ones to produce more random orientations 2 under simple shear finer phases can completely rotate giving a girdle included in the xz plane 3 finer phases can more easily preserve relict fabrics while the coarser phases are completely reoriented by the last stress tensor the last phases to crystallize show weak to completely random cpos hornblende or completely random distributions quartz the study was completed with a shape preferred orientation analysis using the intercept method in order to detect weak magmatic lineations and numerical modelling simulations of theoretically equivalent simple shear situations for each sample

metamorphic degassing of carbonates in the contact aureole of the aguablanca cu ni pge deposit spain analysis of magmatic and sedimentary rocks of several large igneous provinces has demonstrated that the release of gas during plutonic metamorphic processes may be linked to global climate change and mass extinctions aguablanca one of the largest cu ni pge deposits in europe formed during the variscan orogeny when a mafic magma intruded limestones and shales creating a contact aureole composed of marble skarn and hornfels our petrological and geochemical investigation of the aureole provides evidence that a combination of the two processes led to the formation of the ore deposit the assimilation of terrigenous sediments supplied s to the magma while the assimilation of carbonates changed the oxygen fugacity and decreased the solubility of sulfur in the magma the metamorphic assemblages in the contact aureole are directly related to heterogeneity of the protolith and particularly to the original proportions of calcite and clay we modeled carbon dioxide degassing during contact metamorphism and showed that pure limestone is relatively unproductive because of its high reaction temperature the presence of clay however leads to the formation of calc silicates and significantly enhances co2 degassing our estimations suggest that degassing of the aguablanca contact aureole released about 74 8 mt of co2 a relatively low volume that we attribute to the composition of the host rock mainly a pure limestone a far larger volume of carbon dioxide was emitted by the contact metamorphism of dolostones in the contact aureole of panzhihua part of emeishan large igneous province sw china we propose that the level of emission of carbon dioxide depends strongly on the nature of the protolith and has to be considered when predicting environmental impact during the emplacement of large igneous provinces

seismicity and stresses in the brazilian passive margin abstract seismicity and stresses along the brazilian continental margin show different patterns between the northeastern and southeastern regions in the northeastern margin earthquakes tend to occur onshore under a strike slip regime with horizontal compression parallel to the northern coast line in the southeastern margin higher seismicity is observed offshore in areas where the continental crust was highly extended during the south atlantic rifting in the mesozoic three new events in the southeast continental shelf are shown to have reverse faulting mechanisms from waveform modeling of short period teleseismic p waves multiple depth phases reflections from the top and bottom of the water layer and double reflections in the water layer could be identified and better constrained the hypocenters to middle and upper crustal depths in south america models of intraplate stresses caused by plate boundary forces and spreading effects due to the continental oceanic crustal transition indicate higher compressional stresses in the se offshore area as compared with the continental area in agreement with the observed higher seismicity and reverse faulting mechanisms the combination of regional stresses local flexural effects from thick sedimentary loads and a presumably weaker crust from mesozoic thinning explains the main patterns of seismicity in the northeastern and southeastern brazilian margins

3d gravity modelling of the aguablanca stock tectonic control and emplacement of a variscan gabbronorite bearing a ni cu pge ore sw iberia the aguablanca stock is a variscan mafic pluton located in the ossa morena zone southern iberian massif hosting an unusual ni cu pge mineralization associated with magmatic breccia pipes which intruded its northern part the emplacement of the aguablanca stock and the mineralized breccia pipes are related to the activity of the cherneca ductile shear zone a variscan sinistral shear zone that favoured magma ascent through the upper crust a detailed gravity study has been carried out in order to investigate the 3d geometry of the aguablanca intrusion and to get insights about the emplacement mechanism and tectonic controls of the mineralization the three dimensional gravity modelling shows that the stock has an inverted drop geometry with a feeder zone in contact with the cherneca ductile shear zone the inferred orientation of the feeder zone suggests that the emplacement probably took place along an open tensional crack formed within the strain field of the adjacent cherneca ductile shear zone the modelling of the breccia pipes hosting the ni cu pge ore shows that they are included inside the feeder zone thus their emplacement is probably controlled by successive opening events of this tensional crack

migration of contaminants in groundwater at a landfill a case study 1 groundwater flow and plume delineation abstract a landfill derived contaminant plume with a maximum width of 600 m a length of 700 m and a maximum depth of 20 m in an unconfined sand aquifer was delineated by means of a monitoring network that includes standpipe piezometers multilevel point samplers and bundle piezometers the extent of detectable contamination caused by the landfill which began operation in 1940 and which became inactive in 1976 was determined from the distributions of chloride sulfate and electrical conductance in the sand aquifer all of which have levels in the leachate that are greatly above those in uncontaminated groundwater the maximum temperature of groundwater in the zone of contamination beneath the landfill is 12 c which is 4 5 c above background the thermal plume in the aquifer extends 150 m downgradient from the centre of the landfill a slight transient water table mound exists beneath the landfill in the late spring and summer in response to snowmelt and heavy rainfall beneath the landfill the zone of leachate contamination extends to the bottom of the aquifer apparently because of transient downward components of hydraulic gradient caused by the water table mound and possibly because of the higher density and lower viscosity of the contaminated water values of hydraulic conductivity which show variations due to local heterogeneity were obtained from slug tests of piezometers from pumping tests and from laboratory tests because of the inherent uncertainty in the aquifer parameter values the 38 yr frontal position of the plume calculated using the darcy equation with the assumption of plug flow can differ from the observed frontal position by many hundreds of metres although the use of mean parameter values produces a close agreement the width of the plume is large relative to the width of the landfill and can be accounted for primarily by variable periods of lateral east and westward flow caused by changes in water table configuration due to the variable nature of recharge northward from the landfill the vertical thickness of the plume decreases and the top of the plume is farther below the water table the thickness of the zone of uncontaminated groundwater above the plume increases northward as the area of recharge of uncontaminated water downflow from the landfill increases because dispersion in the vertical direction is weak there is very little mixing between the overlying zone of recharge water and the contaminant plume concentration profiles are irregular beneath and near the landfill and become smooth downgradient where the maximum concentrations are much less than those beneath landfill these features are attributed to a strong influence of longitudinal dispersion the plume passes beneath a small shallow stream near the landfill without significant influence on the stream

landscape evolution and deduction of surface deformation in the soan dun nw himalaya india abstract the consequence of strain accumulation along various himalayan thrusts is manifested in shaping the topography and present day lanscape features of the himalaya consequently the strain accomodation is attributed to the occurrence of various devastating earthquakes in the himalayan domain including 1905 kangra earthquake mw 7 8 which occurred along the kangra valley fault in the present study we analyzed and estimatedsss fault related parameters gradient length anomaly gla analysis together with interferometric synthetic aperture radar in sar measurements to understand the landscape evolution and deformation pattern within the soan dun piggy back basin in the northwest himalayan front we combined the results of geodetic geological geomorphology and insar to constrain the uplift and subsidence between himalayan frontal thrust hft and main boundary thrust mbt zones the estimated results of fault parameters reveal that the horizontal shortening of northwest himalaya is higher than the vertical uplift the computed values of gla magnitude analysis for the uplifted region vary from 9 21 to 0 77 whereas these range from 5 48 to 26 60 for the subsided region the depicted range of vertical deformation observed from the insar measurements ranges from 3 13 to 3 14 mm y where the positive and negative value of phases are correlated with the ground uplift and subsidence the rate of deformation observed from persistent scatterer interferometry psi phase velocity and gla magnitude is positively supported by the chronologically constrained uplift rates as 3 4 0 3 mm y the geomorphic evidences such as folded tilted and truncated alluvial fan surfaces offsetting of channels fault scarps and displaced sedimentary sequences indicate active nature of the soan dun the study would be eventually useful for seismic hazard assessment and future infrastructure development in the seismotectonically active regions like soan dun of nw himalayan front

neotectonics in the south american passive margin evidence of late quaternary uplifting in the northern paraiba basin ne brazil abstract the relief evolution of several areas of northeastern brazil has been increasingly related to tectonic events this is the case for the paraiba basin where an abundance of faults and folds were recorded in neogene and even late pleistocene holocene deposits we tested whether dome like morphologies in the northern sector of this basin where geological exposures are scarce were also formed by tectonic deformation the work combined limited geological data with qualitative and quantitative analyses of the relief applying the 1 arc second digital elevation model provided by the shuttle radar topography mission the geomorphic indices of basin asymmetry factor af swath topographic profiles enhanced transverse hypsometry index thi and normalized river long profiles were used for validating a neotectonic origin for the dome like morphologies this interpretation was also supported by other morphological evidence of the dome relief including recurving channels featured in radial to recurved trellis patterns tectonically controlled drainage sub basins high relative relief values related to increased fluvial incision and anomalous river long profiles indicative of ungraded rivers the domic structures were attributed to fault and fold related strike slip deformation during the late quaternary this record supports the proposal that the south american passive margin remained under tectonic stress long after the main rifting in the late jurassic early cretaceous

the mechanism of runoff generation from an alpine glacier during a storm traced by oxygen 18o16o abstract as a result of progressive fractionation and seasonal effects in snow accumulation on a glacier 18 o 16 o ratios of glacier meltwater differ significantly from those of summer precipitation 18 o 16 o ratios of precipitation and runoff have been used to separate pluvial and glacial runoff components from an alpine glacier during one single storm it was found especially during the rising limb of the hydrograph that the bulk of runoff consisted of pre storm meltwater stored in the glacier body on the basis of the results a better insight could be gained into the storage push through process in the glacier body active during the storm this leads to a distinction between recharge and discharge zones on the glacier the discharge zone being the main source area for quick response on rainfall thus the mechanism of runoff generation of the alpine glacier studied is comparable with that found in normal headwater catchments

petrology and geochemistry of mafic ultramafic fragments from the aguablanca ni cu ore breccia southwest spain aguablanca southwest spain is the first economic ni cu pge deposit found in southern europe two features make it an unusual example of magmatic sulfide ore it is related to the development of an andean type continental magmatic arc and it is hosted by a subvertical magmatic breccia the structural style and the geodynamic context of the deposit contrast with most plutonic ni cu pge deposits elsewhere which occur at specific levels of layered mafic intrusions in rift environments the ni cu deposit is hosted by the aguablanca intrusion a mafic body composed of gabbronorite and minor quartz diorite gabbro and norite sulfides are concentrated in a gabbronorite matrix along a subvertical dip of 70 80 n funnel like magmatic breccia that contains barren or slightly mineralized ultramafic mafic cumulate fragments modal compositions of the fragments reflect a wide variety of rock types including peridotite hornblende rich werhlite dunite and hornblende rich harzburgite pyroxenite ortho and clinopyroxenite gabbro gabbro gabbronorite and hornblende gabbro and anorthosite the primary silicate assemblage includes olivine fo91 fo79 orthopyroxene mg no 0 85 0 73 clinopyroxene mg no 0 93 0 62 plagioclase an99 an38 amphibole mg no 0 87 0 68 and phlogopite mg no 0 89 0 64 the wide range of rock types and the fe enrichment trends in the primary ferromagnesian silicates suggest magmatic differentiation processes from the parent melts with the fragments representing different stages of cumulate formation the ore bearing breccia contains both semimassive and disseminated sulfides in the gabbronorite matrix textures vary between meso and orthocumulate and the rock forming magmatic silicates are orthopyroxene mg no 0 83 0 74 clinopyroxene mg no 0 89 0 78 plagioclase an50 an77 and intercumulus amphibole mg no 0 86 0 70 phlogopite 0 84 0 69 and minor quartz the gabbronorite in the matrix of the breccia is petrographically and chemically very similar to that of the unmineralized parts of the main aguablanca intrusion and exhibits a similar differentiation trend suggesting that the matrix of the ore bearing breccia and the unmineralized rocks belong to a same magmatic suite the local presence of mafic ultramafic fragments in the barren aguablanca intrusion supports this suggestion the presence of highly ni depleted olivine whole rock cu zr ratios below 1 and the local occurrence of disseminations of magmatic sulfides in the peridotite fragments point to sulfide segregation before and or during the formation of the peridotite cumulates mantle normalized incompatible trace element patterns of the fragments along with published sulfur isotope data are consistent with crustal contamination suggesting that addition of crustal sulfur from pyrite bearing black slates led to sulfide saturation these results support a model in which sulfides segregated and settled during the differentiation of an unexposed mafic ultramafic complex now sampled as fragments in the breccia whereas the overlying silicate magma most probably fed by successive fresh magma injections underwent fractional crystallization giving rise to this cumulate sequence the emplacement of the ore breccia took place at temperatures above the monosulfide solid solution mss solidus but below the olivine and pyroxene solidus likely owing to the explosive injection of a new pulse of magma into the chamber which mingled with the sulfide liquid and disrupted the overlying cumulate sequence as a consequence fragments reached their current position in the breccia injected along with the sulfide and the silicate melts which subsequently formed the sulfide rich gabbronorite

shear wave modeling and poisson s ratio in the variscan belt of sw iberia in 2003 two wide angle reflection refraction seismic transects were acquired in the variscan belt of sw iberia the approximately 250 and 300 km long dense trace spacing transects revealed clear s wave arrivals in the shot gathers recorded by vertical component sensors in both transects first s wave arrivals sg and moho reflections sms are the most prominent phases that can be correlated from shot to shot sg is observed up to relatively large offsets and constrains the upper and middle crust s wave velocities the sms is seen from offset 0 18 s twtt to 150 km offset where it intercepts first s wave arrivals sg the upper mantle refracted phase sn is difficult to recognize although pms smp converted phases can be identified using a 2 d ray tracing approach two s wave velocity models for the crust of sw iberia were obtained these s wave velocity models complement the previous p wave velocity models and provide us with relatively well resolved poisson s ratio crustal sections for sw iberia the resulting poisson s ratio models present differences between tectonic zones at upper and middle crustal depths thus supporting the existence of different tectonic zones prior to the variscan collision the most noteworthy feature is the high poisson s ratio value over 0 28 coincident with high p wave velocity areas over 6 8 km s at midcrustal depths in order to constrain the possible crustal composition p wave velocities and poisson s ratios have been compared with published laboratory measurements on different crustal rock types this comparison indicates that the high p wave velocity and poisson s ratios are compatible with a mixture of mafic to ultramafic rock types alternating with felsic ones this result is consistent with the existence of mafic layered bodies in the middle crust in the same way that has been suggested by previous works in this area

the use of tritium in groundwater to determine fluid mean residence times of valles caldera hydrothermal fluids new mexico usa abstract naturally and artificially produced 3 h in precipitation is used to place limits on mean residence times of fluids associated with the valles caldera geothermal reservoir the 3 h concentrations in precipitation are used to calculate fluid mean residence times using two end member cases piston flow and well mixed reservoirs these simplified models using 3 h yield relative fluid mean residence times in different portions of the system in situ 3 h production in the reservoir through neutron interaction with 6 li is considered and only very low levels of 3 h 0 01 t u are contributed to the waters by this process calculations using the end member cases at valles caldera indicate that mean residence times of geothermal waters in the reservoir are between 3000 and 10 000 years the results also show that the two distinct subsystems of the main reservoir are associated with different fluid mean residence times waters in the redondo creek subsystem are older 4300 to 10 000 years than waters in the sulphur springs subsystem 2000 4400 years comparison of the results of the end member cases with those obtained using more sophisticated methods indicates that the two end member cases with the use of 3 h can provide acceptable limits order of magnitude on a fluid s mean residence time and volumes within a reservoir

plumbotectonic evolution of the ossa morena zone iberian peninsula tracing the influence of mantle crust interaction in ore forming processes the ossa morena zone in the variscan belt of the iberian peninsula is characterized by a complex geotec tonic evolution it hosts a neoproterozoic paleozoic sequence that records the existence of two orogenic events cadomian and variscan separated by rift and stable platform stages middle cambrian to late devonian volcanogenic and sediment hosted massive sulfides skarns magmatic ni cu deposits synmetamorphic and intragranitic and perigranitic veins and replacement bodies are related to different magmatic hydrothermal systems ranging in age from 650 ma to about 250 ma the lead isotope signatures from 26 different mineral deposits show variable ratios of 206pb 204pb 17 49 18 44 207pb 204pb 15 47 15 67 and 208pb 204pb 37 37 38 78 that have low average values 9 7 but high values 38 3 as a whole the lead isotope data define an irregular cluster that plots around the stacey and kramers 1975 growth curve but clearly marks the existence of two main ore forming events during cadomian and variscan times the most radiogenic samples are from some minor zn pb stratiform sedimentary exhalative mineralization they are interpreted as having a dominantly crustal derivation 10 1 in which most of the lead was leached from a pre cadomian continental basement with a long crustal history this basement has strong geochemical affinities with the oldest rocks of the iberian terrane however most of the ore samples investigated plot below the stacey and kramers 1975 reference curve indicating polyphase but variable mixing of lead from upper crustal and mantle lead reservoirs at the terrane scale clear mixing lines between the two end member reser voirs are evident only in the oldest volcanic rock and sedimentary rock hosted massive sulfide deposits related to the cadomian late neoproterozoic early cambrian magmatic arc in the other deposit types lead isotopes have more restricted values the crustal lead is interpreted as having been derived from ancient crust 2 1 2 5 ga and the derived shales montemolin formation that predated the cadomian orogeny the mantle derived lead may have been derived from three different sources neoproterozoic tholeiitic orthoamphibolite syn cadomian calc alkaline andesite or calc alkaline metaluminous plutonic rocks intruded during the variscan orogeny the first two sources probably controlled the lead isotope signatures of the cadomian massive sulfide deposits and the variscan synmetamorphic veins the input of primitive lead is especially significant during variscan times 350 300 ma and is interpreted as having been related to the existence of a large primitive reservoir that controlled the variscan magmatic metallogenic and hydrothermal evolution of the ossa morena zone this primitive lead is recognized in most of the magmatic hydrothermal deposits including the typically crust derived w and pb bearing perigranitic hydrothermal systems likewise associated plutonic rocks have more primitive lead isotope signatures than their counterparts in other iberian terranes the lead isotope evolution of the region is consistent with recent geophysical data that suggest that a deep large mafic sill was intruded below the ossa morena zone during variscan times this sill was a likely key factor in the different pb isotope evolution of the ossa morena zone compared with the nearby iberian terranes and the entire western mediterranean province which are char acterized by lengthy crustal histories with very little input of primitive lead the extensive mantle crust inter action probably explains the wide variety and the unusual metallogenic features of the ossa morena zone

alteration of platinum group minerals and dispersion of platinum group elements during progressive weathering of the aguablanca ni cu deposit sw spain the distribution mineralogy and mobility of the platinum group elements pge in the surface environment are poorly understood this study of the lower less altered and upper more altered gossan overlying the aguablanca ni cu pge magmatic deposit spain has shown that the platinum group minerals pgm are progressively oxidised and dispersed into iron oxides that form the gossan a combination of the characterization of pge in host pgm using a scanning electron microscope and measurement of pge at lower concentrations in host iron oxides using laser ablation inductively coupled plasma mass spectrometry la icp ms has for the first time allowed the total distribution of the pge within a gossan to be documented this study has revealed a complete in situ alteration and dispersion sequence of the pgm including 1 breakdown of both the more stable pt arsenides pt pd tellurides and the less stable bismuthotellurides 2 formation of partially oxidised pgm 3 development of a wide range of oxidised pt and pd bearing phases 4 subsequent formation of fe pge oxides and pge hydroxides 5 incorporation of pge into ferruginous supergene products and lastly 6 concentration of pge at the edges of veins and iron oxides dispersion of pd is greater than for the other pge with pd being widely distributed throughout the iron oxides this oxidising environment produced pge oxides rather than pge alloys also commonly found in the surface environment especially in placers these results provide critical evidence for the stages of mineralogical change from pge host mineralogy in magmatic ores to surface weathering producing pge oxides